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School of Environment, RAsian Institut
Bangkok
RAW MATERIALPREPARATION
Energy Flow
PULPING
Χ Chemical Pulping � Alkaline
- Kraft or sulfate √- Soda pulping
� Acidic or sulfiteΧ Mechanical - GWP - RMP - TMP - CTMPΧ Semi-chemical Pulping - Neutral sulfite
Raw Materials(Conventional: Wood
Others: Grass,Bagasse, Straw etc.)
Debarked Wood / Woodchips
Screening &Washing
Crude Pulp
Thickening
Paper Machine
Finished PaperProducts
Fine Purified Pulp
Unbleached Pulp
Bleached pulp
Pulp DigesterSteam(180°C,
12-13 GJ/t)
Electricity
StockPreparation
Electricity
Drying &Finishing
Steam(8 GJ/t)
Electricity
ChipperElectricity
BLEACHING
PAPER MAKING
Electricity
400-520 kWh/t
220-300 kWh/t
Effluents & Emissions
Raw Materials(Conventional: Wood
Others: Grass,Bagasse, Straw etc.)
Debarked Wood / Woodchips
Screening &Washing
Crude Pulp
Thickening
Paper Machine
Finished PaperProducts
Fine Purified Pulp
Unbleached Pulp
Bleached pulp
Chipper
Pulp Digester
Bleaching Plant
StockPreparation
Drying &Finishing
White water,Fiber, Fillers,
Broke, etc.
Evaporator
Chemicalrecovery boiler
to Treatment plants
Condensate
Chemical reuse
Weak black liquor
Strong black liquortoCombustion
toAnaerobictreatment
Sedimentation &Aerobic
treatmentEffluent
to pulp digester
Evaporative emission
Sludge,Bleach water
Refining
Waste paper(secondary
intake)
Refining
Waste paper(secondary
intake)
Gaseseousemission
Fiber & inksludge
Heat emission
Liquid clean-up,Broke, Coatings
etc.
BleachingSteam(5 GJ/t)
Steam(5-6 GJ/t)
Pulp & Paper Industry
School of Environment, Resources and Development Asian Institute of Technology
Bangkok - Thailand
TECHNOLOGY, ENERGY EFFICIENCY AND
ENVIRONMENTAL EXTERNALITIES IN THE PULP
AND PAPER INDUSTRY
ASIA
NIN
STITUTE
19 5 9
OF TECH
NO
LOG
Y
TECHNOLOGY, ENERGY EFFICIENCY AND ENVIRONMENTAL EXTERNALITIES IN THE PULP
AND PAPER INDUSTRY
Brahmanand Mohanty
School of Environment, Resources and Development Asian Institute of Technology
Bangkok - Thailand
RAW MATERIALPREPARATION
Energy Flow
PULPING
Χ Chemical Pulping � Alkaline
- Kraft or sulfate √- Soda pulping
� Acidic or sulfiteΧ Mechanical - GWP - RMP - TMP - CTMPΧ Semi-chemical Pulping - Neutral sulfite
Raw Materials(Conventional: Wood
Others: Grass, Bagasse,Straw etc.)
Debarked Wood / Woodchips
Screening &Washing
Crude Pulp
Thickening
Paper Machine
Finished PaperProducts
Fine Purified Pulp
Unbleached Pulp
Bleached pulp
Pulp DigesterSteam
(180°C,12-13 GJ/t)
Electricity
StockPreparation
Electricity
Drying &Finishing
Steam(8 GJ/t)
Electricity
ChipperElectricity
BLEACHING
PAPER MAKING
Electricity
400-520 kWh/t
220-300 kWh/t
Effluents & Emissions
Raw Materials(Conventional: Wood
Others: Grass, Bagasse,Straw etc.)
Debarked Wood / Woodchips
Screening &Washing
Crude Pulp
Thickening
Paper Machine
Finished PaperProducts
Fine Purified Pulp
Unbleached Pulp
Bleached pulp
Chipper
Pulp Digester
Bleaching Plant
StockPreparation
Drying &Finishing
White water,Fiber, Fillers,
Broke, etc.
Evaporator
Chemicalrecovery boiler
to Treatment plants
CondensateChemical reuse
Weak black liquor
Strong black liquorto Combustion
to Anaerobictreatment
Sedimentation &Aerobic trea tment Effluent
to pulp digester
Evaporative emission
Sludge,Bleach water
Refining
Waste paper(se condary intake)
Refining
Waste paper(secondary intake)
Gaseseous emission
Fiber & inksludge
Heat emission
Liquid clean-up,Broke, Coatings etc.
BleachingSteam(5 GJ/t)
Steam(5-6 GJ/t)
Pulp & Paper Industry
Technology, Energy Efficiency and Environmental Externalities in the Pulp and Paper Industry © Asian Institute of Technology, 1997 Edited by Brahmanand Mohanty Published by School of Environment, Resources and Development Asian Institute of Technology P.O. Box 4, Pathumthani 12120 Thailand e-mail: [email protected] NOTICE Neither the Swedish International Development Cooperation Agency (Sida) nor the Asian Institute of Technology (AIT) makes any warranty, expressed or implied, or assume any legal liability for the accuracy, completeness, or usefulness of any information, appratus, product, or represents that its use would not infringe privately owned rights. Reference herein to any trademark, or manufacturer, or otherwise does not constitute or imply its endorsement, recommendation, or favoring by Sida or AIT. ISBN 974 - 8256 - 72 - 3 Printed in India by All India Press, Pondicherry.
FOREWORD The use of fossil fuels leads to the emission of so-called "Green House Gases (GHG)", a concept which comprises carbon dioxide, nitrous oxides, sulfur oxides, etc. In recent years, a good deal of research has provided enough material to put forward the claim that a big increase in the concentration of carbon dioxide in the atmosphere would lead to a rise in the average global temperature, with negative consequences for the global climate. This claim has been confirmed by the United Nations Intergovernmental Panel on Climate Change (IPCC) in its second scientific assessment published in 1996. Global warming can have catastrophic impact on human and global security: island nations and low lying coastal regions would be permanently drowned by the rise in the level of the oceans brought on by the melting of polar ice; drought would become widespread; and desertification would expand and accelerate. Persistent famines, mass migrations and large-scale conflict would be the result. Agriculture, food and water security, and international trade would come under severe strain. Until recently, industrialized countries have accounted for most of the emission of the GHG, in particular carbon dioxide, because their economic development has been very strongly based on the use of fossil fuels. However, the same dynamic has also led to a situation where the newly industrializing countries of Asia and Latin America (the strong South) are today contributing significantly to the emission of carbon dioxide. This tendency will spread to and encompass an increasing number of developing countries unless both the industrialized and the developing countries jointly agree on implementing the measures to halt and then reverse the global trend towards a rapid rise in the emission of carbon dioxide. That is the central purpose of the IPCC, which has succeeded in obtaining commitments from most of the industrialized countries to reduce their emissions of carbon dioxide. At the 1995 meeting in Berlin of the Conference of the Parties (CoP) to the United Nations Climate Convention, it was decided to initiate negotiations to strengthen the emission-reduction measures by the industrialized countries, as well as countries of Eastern Europe and the Former Soviet Union. The final negotiations are planned to take place at the December 1997 meeting in Kyoto of the CoP, which ought to result in legal instruments to ensure that the agreed measures are being fulfilled. The fossil fuel generated climate problem is very complex, with strong vested interests and special alliances. There is still considerable skepticism in the developing world about the need for measures to counter global warming, in particular in the strong South, which in no way wants to jeopardize its own rapid economic development. It is therefore imperative to find innovative solutions, both technical and institutional, to the climate problem, which are acceptable to both the North and the South. Meeting this challenge calls for inter alia research programs that tackle the technological, techno-economic and policy problems in
promoting the transition to decreasing use of fossil fuels, increasing energy efficiency and fuel substitution, and carbon recycling systems of energy production and use. The Asian Regional Research Programme on Energy, Environment and Climate (ARRPEEC) is part of this global effort, which Sida is very pleased to have initiated and is fully supporting. The ARRPEEC comprises technological, techno-economic and policy research on energy efficiency, fuel substitution and carbon recycling in the principal economic sectors of East, Southeast and South Asian countries. M R Bhagavan Senior Research Adviser, Department for Research Cooperation Swedish International Development Cooperation Agency, Sida
PREFACE Industries have always played a crucial role in the socio-economic development of a country. They have contributed primarily to increased prosperity, greater employment and livelihood opportunities. On the other hand, industries are accused of accelerating the consumption of scarce fossil fuels and of polluting the local, regional, and global environment by releasing solid, liquid and gaseous pollutants to their surroundings. Experiences gained worldwide have shown that these impacts of industries on resource use and the environment can be contained through more efficient production processes and adoption of cleaner technologies and procedures. Thus, fossil fuel consumption can be cut down drastically and waste generation can be avoided or minimized to the lowest possible level. Regulatory regimes introduced in several countries have led the industries to adopt appropriate measures. Some countries have adopted economic instruments to reflect the true cost of goods and services by internalizing the environmental costs of their input, production, use, recycling and disposal. The improvement of production system through the use of technologies and processes that utilize resources more efficiently and achieve “more with less” is an important pathway towards the long-term sustenance of industries. It is in this context that a research project was undertaken by the Asian Institute of Technology (AIT), with the support of the Swedish International Development Cooperation Agency (Sida). The project entitled “Development of Energy Efficient and Environmentally Sound Industrial Technologies in Asia” was launched with the specific objective to enhance the synergy among selected Asian developing countries in their efforts to grasp the mechanism and various aspects related to the adoption and propagation of energy efficient and environmentally sound technologies. Three energy intensive and environmentally polluting industrial sub-sectors (cement, iron & steel, and pulp & paper) and four Asian countries of varying sizes, political systems and stages of development (China, India, Philippines, Sri Lanka) were selected in the framework of this study. To enhance in-country capacity building in the subject matter, collaboration was sought from reputed national institutes who nominated experts to actively participate in the execution of the project. The activities undertaken in the first phase of the project were the following:
- Evaluation of the status of technologies in selected energy intensive and environmentally polluting industries;
- Identification of potential areas for energy conservation and pollution abatement in these industries;
- Analysis of the technological development of energy intensive and polluting industries in relation with the national regulatory measures;
- Identification of major barriers to efficiency improvements and pollution abatement in the industrial sector.
Based on the initial guidelines prepared at AIT under the leadership of Dr. X. Chen, discussions were held with the experts from the national research institutes (NRIs) of the four participating countries. The outcomes of these meetings were used as a basis for the preparation of country reports which were presented at two project workshops held at Manila in May 1995 and at Bangkok in November 1995. On the basis of the reports submitted, cross-country comparison reports were prepared at AIT and additional relevant information was sought from the NRIs to bridge some of the gaps found in their respective reports. This is the third of the four volumes of documents which have resulted from this interactive research work between AIT and the NRIs. This volume on “Technology, energy efficiency and environmental externalities in the pulp and paper industry” covers a description of the paper manufacturing process, and the energy and environmental aspects associated with it. Then there is a cross-country comparison of the pulp and paper sector in the four countries, followed by individual country reports prepared by the four NRIs. The first five chapters were prepared by Dr. B. Mohanty and Dr. Uwe Stoll with the assistance of research associates figuring in the Project Team. Sincere thanks are extended to all the members of the Project Team including the supporting staff, past and present, for their active participation and contribution to the project. The enthusiasm and dynamism of Dr. X. Chen during the execution of the first phase and the understanding and leadership provided by Dr. C. Visvanathan in the crucial completion period of the project are acknowledged here. The project would have never seen the light of the day without the support of Sida. Finally, appreciations are due to two individuals who have actually conceived the Asian Regional Research Programme on Energy, Environment and Climate (ARRPEEC) and provided constant support and encouragement to this specific project under the overall program: Dr. M.R. Bhagawan, Senior Research Adviser at Sida, and Dr. S.C. Bhattacharya, Professor at AIT. Brahmanand Mohanty Asian Institute of Technology June, 1997
PROJECT TEAM Faculty Members (Asian Institute of Technology - School of Environment, Resources and Development)
- Dr. Xavier Chen, Energy Program (Until February 1996) - Dr. Brahmanand Mohanty, Energy Program - Dr. Uwe Stoll, Environmental Engineering Program (Until January 1996) - Dr. C. Visvanathan, Environmental Engineering Program (From January 1996)
Research Associates (Asian Institute of Technology - School of Environment, Resources and Development)
- Ms. Nahid Amin - Ms. Lilita B. Bacareza - Mr. Z. Khandkar - Mr. Aung Naing Oo - Mr. K. Parameshwaran
National Research Institutes
- Institute for Techno-Economics and Energy System Analysis, Tsinghua University, Beijing, China (Prof. Qiu Daxiong)
- Energy Management Centre, Ministry of Power, New Delhi, India (Mr. S. Ramaswamy)
- Department of Energy, Manila, Philippines (Mr. C.T. Tupas) - Energy Conservation Fund, Ministry of Irrigation, Power and Energy, Colombo,
Sri Lanka (Mr. U. Daranagama) Research Fellows
- Dr. Wu Xiaobo, School of Management, Zhejiang University, China (January-June 1996)
- Ms. Wang Yanjia, Tsinghua University, China (May-November 1996) - Mr. Anil Kumar Aneja, Thapar Corporate R&D Centre, India (May-November
1996) - Ms. Marisol Portal, National Power Corporation, Philippines (May-November
1996) - Mr. Gamini Senanayake, Industrial Services Bureau of North Western Province,
Sri Lanka (May-November 1996)
CONTENTS FOREWARD
PREFACE
PROJECT TEAM
1. GENERAL........................................................................................................................................ 1
2. PRODUCTION PROCESSES ......................................................................................................... 2
2.1 PULPING PROCESSES .................................................................................................................................................2 2.1.1 Sulfite pulping process .............................................................................................................................................4 2.1.2 Kraft (sulfate) pulping process..................................................................................................................................4 2.1.3 Semi-chemical pulping process ..................................................................................................................................5 2.1.4 Mechanical pulping process ......................................................................................................................................6
2.2 CHEMICAL PROCESSING LINE ..................................................................................................................................6 2.3 FIBER PROCESSING LINE ...........................................................................................................................................9 2.4 BLEACHING OF PULP .................................................................................................................................................9 2.5 CHEMICAL PLANT ................................................................................................................................................... 11 2.6 MANUFACTURING PROCESS OF PAPER ............................................................................................................... 11
3. ENERGY ISSUES IN PULP AND PAPER INDUSTRY...............................................................13
3.1 TYPICAL ENERGY CONSUMPTION PATTERNS ................................................................................................... 13 3.2 ENERGY EFFICIENT MEASURES ........................................................................................................................... 15
3.2.1 Short term measures ............................................................................................................................................. 15 3.2.2 Medium term measures......................................................................................................................................... 15 3.2.3 Long term measures ............................................................................................................................................. 17
3.3 NEW ENERGY EFFICIENT TECHNOLOGIES FOR PAPERMAKING .................................................................. 19 3.4 CONCLUDING REMARKS ON ENERGY ISSUES ................................................................................................... 20
4. SOURCES OF POLLUTION AND ITS MANAGEMENT.......................................................... 22
4.1 SOURCES AND CHARACTERISTICS OF POLLUTANTS ......................................................................................... 22 4.1.1 Sources of wastewater generated ............................................................................................................................ 22 4.1.2 Characteristics of wastewater generated ................................................................................................................. 23 4.1.3 Sources and characteristics of gaseous emissions ..................................................................................................... 25 4.1.4 Sources and characteristics of solid wastes ............................................................................................................. 25
4.2 CURRENT POLLUTION ABATEMENT STRATEGIES AND TECHNOLOGIES..................................................... 25 4.2.1 Water pollution control......................................................................................................................................... 25 4.2.2 Solid waste disposal.............................................................................................................................................. 29
4.3 POSSIBILITIES FOR APPLICATION OF ALTERNATIVE TECHNOLOGIES FOR POLLUTION CONTROL ....... 29 4.3.1 Anaerobic treatment of wastes .............................................................................................................................. 29 4.3.2 Membrane technology ........................................................................................................................................... 29 4.3.3 Dissolved air floatation for fiber recovery............................................................................................................... 30 4.3.4 Ozone bleaching ................................................................................................................................................... 30 4.3.5 Modified continuous cooking process (MCC) ........................................................................................................ 31 4.3.6 DARS in soda pulping of bagasse ....................................................................................................................... 32 4.3.7 Dry forming of paper web ..................................................................................................................................... 32
4.4 CONCLUDING REMARKS ON POLLUTION MANAGEMENT...................................................................................
5. CROSS COUNTRY REPORT ON THE PULP AND PAPER INDUSTRY................................ 34
5.1 INTRODUCTION ....................................................................................................................................................... 34 5.2 OVERVIEW OF THE INDUSTRY .............................................................................................................................. 34
5.2.1 Role in the national economy ................................................................................................................................ 34 5.2.2 Share in total energy consumption......................................................................................................................... 34 5.2.3 Production trends ................................................................................................................................................. 35 5.2.4 Mills and their capacities...................................................................................................................................... 36
5.3 CHARACTERISTICS OF THE PARAMETERS AFFECTING ENERGY EFFICIENCY ............................................. 38 5.3.1 Raw material mix................................................................................................................................................ 39 5.3.2 Level of waste paper utilization ............................................................................................................................ 39 5.3.3 Energy consumption by type.................................................................................................................................. 39 5.3.4 Awareness about energy conservation .................................................................................................................... 40
5.4 CHARACTERISTICS OF THE PARAMETERS AFFECTING POLLUTION ABATEMENT MEASURES..................... 41 5.4.1 Causes of pollution ............................................................................................................................................... 42 5.4.2 Current water pollution control strategies .............................................................................................................. 42 5.4.3 Current air pollution control strategies .................................................................................................................. 44 5.4.4 Current solid waste control strategies..................................................................................................................... 44 5.4.5 Comparison of effluent and emission characteristics ............................................................................................... 44
5.5 POTENTIAL FOR ENERGY EFFICIENCY IMPROVEMENT .................................................................................. 46 5.5.1 Structure of the industry ....................................................................................................................................... 46 5.5.2 Raw materials...................................................................................................................................................... 46 5.5.3 Potential for energy conservation............................................................................................................................ 46
5.6 POTENTIAL FOR POLLUTION ABATEMENT ......................................................................................................... 46 5.7 CONCLUSION............................................................................................................................................................ 49
6. PROFILE OF THE PULP AND PAPER INDUSTRY IN SELECTED ASIAN COUNTRIES…………………………………………………………………………………………….50
6.1 COUNTRY REPORT: CHINA.................................................................................................................................... 50 6.1.1 Introduction.......................................................................................................................................................... 50 6.1.2 Technological trajectory of China’s paper industry ................................................................................................. 54 6.1.3 Evolution of energy efficiency in Chinese pulp & paper industry ........................................................................... 61 6.1.4 Environmental externalities of the pulp & paper industry in China..................................................................... 67 6.1.5 Potential for energy efficiency improvement and pollution abatement through technological changes.......................... 70 6.1.6 Status of application of new technologies................................................................................................................ 75 6.1.7 Conclusions .......................................................................................................................................................... 77
6.2 COUNTRY REPORT: INDIA............................................................................................................................ 79 6.2.1 Introduction.......................................................................................................................................................... 79 6.2.2 Technological trajectory of the Indian paper industry ............................................................................................. 79 6.2.3 Evolution of energy efficiency in Indian pulp and paper industry ........................................................................... 87 6.2.4 Environmental externalities of technological development in the pulp and paper industry ....................................... 89 6.2.5 Potential for energy efficiency improvement and pollution abatement through technological change ........................... 93 6.2.6 Status of the application of new technologies .......................................................................................................... 99
6.3 COUNTRY REPORT: PHILIPPINES............................................................................................................ 100 6.3.1 Introduction........................................................................................................................................................ 100 6.3.2 Technological trajectory of the paper industry in the Philippines........................................................................... 100 6.3.3 Evolution of energy efficiency in the pulp and paper industry of the Philippines.................................................... 106
6.3.4 Environmental externalities of the pulp and paper industry of the Philippines..................................................... 109 6.3.5 Potential for energy efficiency improvement and pollution abatement through technological changes........................ 111 6.3.6 Status of application of new technologies.............................................................................................................. 113 6.3.7 Concluding remarks ........................................................................................................................................... 114
6.4 COUNTRY REPORT: SRI LANKA................................................................................................................ 115 6.4.1 Introduction........................................................................................................................................................ 115 6.4.2 Technological trajectory of the Sri Lankan pulp and paper industry.................................................................... 115 6.4.3 Evolution of energy efficiency in the pulp and paper industry of Sri Lanka ......................................................... 117 6.4.4 Environmental externalities in the pulp and paper industry of Sri Lanka.......................................................... 117 6.4.5 Potential for energy efficiency improvement and pollution abatement through technological changes........................ 118
7. BIBLIOGRAPHY ..........................................................................................................................120
General 1
1. GENERAL
With paper being an essential commodity of today’s society, the pulp and paper industry has been growing rapidly all over the world. The industry rates among the highest energy consumers in many countries. Theoretically, the pulp and paper industry should not require any purchased energy, because waste materials generated can be re-used as fuels. However, most pulp and paper mills normally purchase 20-50% of their total energy, mostly as electricity. Although the specific energy consumption values of paper products have been decreasing steadily, there is still potential for energy saving by employing advanced technologies and by modifying the current energy use practices. One of the distinguishing characteristics of the pulp and paper industry is the enormous generation of wastes. Therefore, an integrated approach towards energy and environment could be highly beneficial for the future betterment of the industry. Environmental pollution caused by industries is closely related to the technologies used and to the pattern of energy consumption by the technologies. The key to the success of pollution abatement in industrial sector will depend on the approach of regulations, promotion of new technologies in the production and waste minimization activities (clean technologies), and improvement of industrial energy efficiency. Energy efficiency improvement and environmental pollution reduction can only be achieved by either retrofit measures (modification of the existing technology and equipment) or by installation of clean technologies, or both. This document describes the production processes and technologies in use (Sec. 2), the energy saving opportunities and potential in light of both the existing and new technologies (Sec. 3), as well as the issues of sources of pollution and pollution abatement measures including the possibilities for pollution abatement in the pulp and paper industry in future (Sec. 4). It also provides a cross country comparison of the sector (Sec. 5) followed by individual country reports on the pulp and paper industry of four Asian industrializing nations (Sec. 6).
2 Technology, Energy Efficiency and Environmental Externalities in the Pulp and Paper Industry
2. PRODUCTION PROCESSES
Raw materials primarily considered for commercial scale production of pulp and paper include pine, bamboo, rubber wood, mixed tropical hardwood, bagasse, Burma grass and rice straw. These raw materials consist mainly of cellulose, hemicellulose and lignin. Cellulose and hemicellulose are polysaccharides as starch. Target of the pulping process is to crack and remove this matrix and separate out the pure cellulose as a natural and resistant raw product. Lignin, hemicellulose and the extracts are separated by cooking in a digester. Lignin becomes dissolved by sulfonization, hemicellulose gets hydrolyzed and the extracts get partly dissolved under acidic conditions. In the ensuing procedural steps (bleaching process), the remaining lignin gets oxidized, both in acidic and alkaline phase, whereas the hemicellulose and extracts get dissolved mainly in the alkaline phase. Only about 40% of the raw material input is represented in the solid yield. The environmental problem with the pulp and paper industry is evidently the other 60%, which is the liquid by-product and has to be treated further. General flowchart of the pulp and paper making process is given in Figure 2.1. The pulp may be broadly classified as follows:
- High quality pulp - Sulfite pulp (SP) - Kraft / Sulfate pulp (KP)
- Low quality pulp (wood fibric) - Semichemical pulp (SCP) - Ground or Mechanical pulp (GP)
2.1 Pulping Processes
The main manufacturing processes of pulp production are: - Sulfite Pulping (SP): chemical pulping, acidic process, cooks the chips with acid
sulfite solution at a high temperature for half a day. - Kraft or Sulfate Pulping (KP): chemical pulping, alkaline process, cooks the chips
with caustic soda and sodium sulfate at a high temperature (160°C) for several hours. Bleached Kraft pulp can be processed into papers of high grade.
- Semichemical Pulping (SCP): combination of chemical and mechanical pulping processes. - Ground or Mechanical Pulping (GP): involves mechanical grinding of wood,
generates less pollution. However, this process is not suitable for products with quality requirements, because of less durability and poor color.
Production Processes 3
RAW MATERIALPREPARATION
Process Flow (includingRaw Materials & By-Products) Energy Flow
PULPING
Χ Chemical Pulping � Alkaline
- Kraft or sulfate√- Soda pulping
� Acidic or sulfiteΧ Mechanical - GWP - RMP - TMP - CTMPΧ Semi-chemical Pulping - Neutral sulfite
Raw Materials(Conventional: Wood
Others: Grass, Bagasse,Straw etc.)
Debarked Wood / Woodchips
Screening &Washing
Crude Pulp
Thickening
Paper Machine
Finished PaperProducts
Fine Purified Pulp
Unbleached Pulp
Bleached pulp
Chipper
Pulp DigesterSteam / Hot waterChemicals
- Alkaline sulfate liquor (Kraft)- Acid sulfite liquor (Acidic)
- Neutral sulfite liquor (Semi-chemical)
White water(Reuse water),or Fresh water
Bleaching Plant
BleachingChemicals
White water orFresh water
StockPreparation
Fillers, Dye,Alum, Starch
White water orFresh water
Fresh water orWhite water
Drying &Finishing
Steam
CoatingChemicals
Figure 2.1. Process flow chart of the pulp and paper industry
Raw Materials(Conventional: Wood
Others: Grass, Bagasse,Straw etc.)
Debarked Wood / Woodchips
Screening &Washing
Crude Pulp
Thickening
Paper Machine
Finished PaperProducts
Fine Purified Pulp
Unbleached Pulp
Bleached pulp
Pulp DigesterSteam
(180°C,12-13 GJ/t)
Electricity
StockPreparation
Electricity
Drying &Finishing
Steam(8 GJ/t)
Electricity
ChipperElectricityWood wastes, barks etc.to Waste Boiler
Evaporator
Chemicalrecovery boiler
to Treatment plants
CondensateChemical reuse
BLEACHING
PAPER MAKING
Electricity
400-520 kWh/t
220-300 kWh/t
Weak black liquor
Strong black liquorto Combustion
to Anaerobictreatment
Sedimentation &Aerobic treatment
Effluents & Emissions
Raw Materials(Conventional: Wood
Others: Grass, Bagasse,Straw etc.)
Debarked Wood / Woodchips
Screening &Washing
Crude Pulp
Thickening
Paper Machine
Finished PaperProducts
Fine Purified Pulp
Unbleached Pulp
Bleached pulp
Chipper
Pulp Digester
Bleaching Plant
StockPreparation
Drying &Finishing
White water,Fiber, Fillers,
Broke, etc.
Evaporator
Chemicalrecovery boiler
to Treatment plants
CondensateChemical reuse
Weak black liquor
Strong black liquorto Combustion
to Anaerobictreatment
Sedimentation &Aerobic treatment Effluent
to pulp digester
Evaporative emission
Sludge,Bleach water
Refining
Waste paper(secondary intake)
Refining
Waste paper(secondary intake)
Refining
Waste paper(secondary intake)
Gaseseous emission
Fiber & inksludge
Heat emission
Liquid clean-up,Broke, Coatings etc.
BleachingSteam(5 GJ/t)
Steam(5-6 GJ/t)
4 Technology, Energy Efficiency and Environmental Externalities in the Pulp and Paper Industry
It is estimated that the proportion of pulp produced in the world using these major processes are: 75% chemical pulp (mostly Kraft), 20% mechanical pulp, and the remaining 5% other pulps (RAO et al, 1995). 2.1.1 Sulfite pulping process
The fiber binding lignin is softened and dissolved to a considerable extent in a solution containing dissolved SO2, hydrogensulfite (bisulfite) ion (HSO3
-), or sulfite ions, producing acid sulfite or bisulfite chemical pulps. The HSO3
- reacts in the digester with the phenolic group on the lignin, forming sulfonic acids. The yield varies from 45 to 65% depending on the cooking degree, usually the yield is about 50% for standard non-bleached pulps. If the pulp is bleached, another 4 to 5% of the original wood may be lost in the process. This sulfite method is one of two major wood-pulping processes. The cellulose fiber obtained from the sulfite process is less strong compared to the Kraft process. 2.1.2 Kraft (sulfate) pulping process
The soda process has been largely replaced by the sulfate or (Kraft) process. This process includes not only NaOH, but also Na2S in the cooking liquor. The presence of caustic soda in the cooking liquor makes this pulping process suitable for use with all wood species. Sodium sulfate plays a buffering role that allows digestion to be possible at lower pH, thus reducing damage to the fibers and producing pulp with high strength property. In water solution, the sulfide ion (S2-) hydrolyzes to form hydroxide ions (OH-) and hydrogen sulfide ions (HS-) according to the formula :
S2-- + H 2 O → HS- + OH-
The initial high concentration of NaOH (hence OH- ions) forces the equilibrium to the left, according to Le Chatelier’s principle. The net result being that delignification occurs at a more steady rate and HS- can also react with the lignin to enhance its solubility. The residual liquor is very dark, and is called the “Black liquor”. The flowchart of Kraft or sulfate process is shown in Figure 2.2. As another alkaline pulping process, soda pulping process is used in which the cooking liquor is sodium hydroxide, obtained by adding a mixture of soda ash (Na2CO3) and lime [Ca(OH)2] to the digester. The digestion phase is in operation for about 10 hours under high pressure and temperature. The digestion decomposes or separates the binding, non-cellulose materials such as lignin and resins, from the fibers and consequently, weakens them. This method is rarely used at present and has been largely replaced by the Kraft pulping process.
Production Processes 5
Make-Up Caustic(NaOH)
Make- Up Saltcake ( Na2SO4)
Wood Chios
Digester
Water
BrownstackWashers
Pulp to BleachPlant
Weak BlackLiquor
Evaporator
EvaporatorCondensates
NaOH /Na2S
LimeMud
Washer
White LiquorClarifier
Green LiquorClarifier
White LiquorStorage
Slaker andCaustizers
Na2SO4 +organicsStrong
Black Liquor
RecoveryBoiler Smelt
DissolvingTank
Lime Kiln
DregsWasher
Weak Wash
LimeStone
Na2S / Na2CO3
Smelt
Water
Lime MudThickener
Figure 2.2. Kraft (sulfate) pulping process
2.1.3 Semi-chemical pulping process
In this process, hardwood and soft wood pulp is obtained by a series of chemical and mechanical wood treatments, none of which by itself is sufficient to make fibers separate readily. Unlike chemical pulping, this process enables more of the lignin and hemicellulose constituents of wood to be retained in the pulp and thus the pulp yield is often very high (about 75-80%, based on dried wood). The process involves cooking of chips (hardwood) for 10-20 minutes at a temperature of 175-1850C with an aqueous solution of sodium sulfite and sodium carbonate. The amount of pulping chemical required is about 9-19% Na2CO3 and 4-7% SO2 per ton of dried wood. The pulp is defiberized mechanically in disc refiners and washed by a counter-current method on rotary drums (Kleppe and Rogers, 1970).
6 Technology, Energy Efficiency and Environmental Externalities in the Pulp and Paper Industry
2.1.4 Mechanical pulping process
Mechanical pulp is produced by grinding or shredding raw materials to free fibers. In addition, heat under pressure may be applied to assist the process. It consists of two principal physical methods of producing ground wood pulp. The older technology involves grinding the logs and stone grinding on large grind stones, whereas the modern technology employs chip refining or refined ground-wood. Bleaching may be done by adding a small amount of sodium peroxide and/or hydrogen sulfite. Mechanical pulping provides low grade pulps with high color and relatively short fibers, but produces a high yield, converting about 95% of the wood into pulp; minimal on-site air pollution is produced and relatively low water loads are generated (Anonymous 1981). The modern mechanical pulping process is illustrated in Figure 2.3. 2.2 Chemical processing line
Recovery of pulping chemicals is, in fact, limited to sodium and magnesium-based liquors, since calcium cannot be recovered economically and there is only limited experience on recovery of ammonia (Anonymous, 1982). In the chemical processing, high-efficiency recovery of chemicals is achieved. Maximum recovery of the chemicals may result in a relatively cleaner effluent in which chemical toxicants are no longer a significant factor as far as stream pollution is concerned. In the sulfite pulping process, magnesium bisulfite is recovered. Dissolved wood substances are 99% in the weak black liquor obtained from cooking after pulp separation. This weak black liquor has about 13% of dry solids (DS). After evaporation, the weak black liquor is converted to a strong liquor containing about 45% of DS. The black liquor from the evaporation plant is led to the recovery boiler. This liquor is further evaporated in a cascade evaporator in the recovery boiler up to 60% total solids before being burnt in the boiler. Ash from gas cleaning consists mainly of magnesium oxide. It gets hydrolyzed to magnesium hydroxide which, in turn, is used for flue gas cleaning. Final product is magnesium bisulfite solution to which SO2 and MgO are added for its reuse in the cooking process. The treatment of black liquor from Kraft mills involves evaporation and incineration in order to recover the chemicals and to utilize the heating value of the dissolved wood substance. During the recovery process, Na2SO4 (with or without added sulfur) is added to make up the relatively small proportion of chemicals lost in various steps of the process, and to form the green liquor. The chemical compounds in this green liquor are converted to desired cooking chemicals by the addition of lime so as to form the white liquor and a lime-mud consisting chiefly of CaCO3. The white liquor is returned to the pulping operation as the cooking liquor. Lime mud is calcined to form CaO which is reused by converting other green liquor to white liquor. By-product recovery of turpentine, resin and fatty acids also aids in reducing the strength of Kraft pulp waste water.
Production Processes 7
Wood
Grinder RoomStorage
Grinder
Coarse Screen
Fine Screen
CentrifugalCleaners
Deckers
Bleaching
Storage
Paper MachineSaveall
White WaterTank
Refiners
Water
Sewer
Sewer
Paper
Water
0.6 - 0.8 % Consistency
2 % Consistency
Figure 2.3. Flow chart of the mechanical pulping process
8 Technology, Energy Efficiency and Environmental Externalities in the Pulp and Paper Industry
Special Issues Related to Chemical Processing Line
A. Chemical recovery of black liquor from rice straw pulping
Rice straw contains 8-14 % of silica (SiO2). For chemical pulp produced from rice straw, about half of this silica gets dissolved in the black liquor. This causes problems in all stages of the chemical recovery process. For a pulp mill that depends on non-wood fiber, silica must be eliminated from black liquor to produce pulp economically and to meet environmental restrictions. The chemical recovery in this application is relatively new and there is only limited information and experience today. Following is an example of such a recovery method: Investigations on desilication of rice straw black liquor started in the 1970s and a pilot plant was started in 1985 (UNEP IE/PAC, 1992). In the proposed chemicals recovery and desilication process, black liquor coming from the washing unit is filtered in a drum-filter. The out-flowing black liquor is fed through a buffering tank to the four-effect evaporator plant. For low concentrations, evaporation takes place in three long-tube falling film evaporators. Higher concentrations are attained in a forced circulation evaporator, which pre-concentrates the black liquor to a DS content of between 8 and 14% - the optimum for effective desilication. The forced-circulation stage further concentrates the desilicated black liquor. Next, a stream of pre-concentrated black liquor is fed to a draft-tube reactor equipped with stirrer and foam breaker, where it is brought into intimate contact with a continuous stream of flue gas from the power station stack. Here, soluble sodium silicates are converted into sodium carbonate and largely insoluble SiO2. This two-phase mixture is routed through an intermediate tank to a decanter which separates the precipitates from the clean liquor. For final clarification, the liquor is passed through a separator ,where the residual insoluble particles are removed. Subsequently, this desilicated black liquor is then burned in the conventional way. The optimum pH value is between 9 and 10. The corresponding specific flue gas rate at a CO2 concentration of 6-8% is in the range of 50 to 150 m3 gas (at NTP) per m3 of black liquor. Irrespective of the silica content of the incoming black liquor, which typically is of the order of 1% (by weight), total silica contents of 0.05% by weight were attained downstream of the separator. The silica extracted from the black liquor, together with some alkali and organic matter, forms a sludge which is discharged from the decanter at a DS content of 30-40%, and burnt in a fuel-oil-fired incinerator. Elution of the alkali from the ash with water, followed by filtering and drying, yields almost white silica granulates, which can be used as a filler in paper making.
Production Processes 9
B. Use of black liquor as fertilizers
Potassium fertilizer
A potassium alkaline sulfite process can be used to produce the chemical pulp. The pulping black liquor as well as bleaching effluent of alkaline or neutral sulfite may be collected and evaporated to obtain a salable liquid fertilizer product, (UNEP IE/PAC, 1992). Solid organo-potassium fertilizer can also be prepared (ANONYMOUS , 1982).
Ammonia fertilizer
Another new process of ammonium bisulfite straw pulp has been popularized in many small size paper mills. By this process, its wastewater can be directly used for farm irrigation as ammonia fertilizer (WANG YANJIA, 1995). 2.3 Fiber processing line
The fiber processing line employs washing of the fibers and separation of contaminants from the raw fibers in a cascaded counter-current process to produce the concentrated pulp. The remaining liquid is called the weak black liquor. 2.4 Bleaching of pulp
Chemical pulping, especially the Kraft process, produces dark colored pulp owing to a number of factors, among which are: remaining lignin, wood components which make paper turn yellow and brittle, and resinous bark as well as knot particles which leave tiny dark spots on the paper. In order to obtain white and strong paper, these constituents should be removed further by bleaching operations. Bleaching is a successive process involving multiple steps (normally 4-6) consisting of several oxidation stages (one or two alkaline). It utilizes various chemical agents, such as chlorine, sodium hydroxide, sodium hypochlorite and chlorine dioxide. Sulfite pulp needs less bleaching agents than sulfate pulp. According to S DERGREN (1993), there are two types of bleaching sequences: conventional and modern bleaching processes (Figure 2.4). The conventional bleaching technique consists of six stages in which chlorine gas is the dominating delignifying agent whereas chlorine dioxide is used only in the final bleaching stage. The amount of chlorine in the first bleaching stage is about 50 to 70 kg per ton of pulp. The modern bleaching technique has been developed since the mid 1970’s in Sweden. It aims to avoid the discharge of chlorinated organic matter from the bleaching plant. In modern bleaching technology, oxygen delignification is used; the charge of chlorine in the first bleaching stage has gradually been reduced by the introduction of low multiple chlorination and by a gradual substitution of chlorine by chlorine dioxide to totally eliminate the use of elemental chlorine as the bleaching agent.
10 Technology, Energy Efficiency and Environmental Externalities in the Pulp and Paper Industry
Figure 2.4 Scheme of conventional and modern bleaching sequence
Production Processes 11
2.5 Chemical Plant
Many pulp and paper mills have their own chemical plants where caustic soda and chlorine are produced through electrolysis in diaphragm cells, and calcium hypochlorite is produced from lime, H2O, and Cl2. 2.6 Manufacturing Process of Paper
In this process the pulp is converted into paper. The first stage of paper making operation is the stock preparation. The fibers to be included in the stock are heated and mixed. Different chemicals and fillers such as aluminum sulfate, clay and starch are also added to the pulp stock for enhancement of certain properties of the paper or board. The stock is then pumped to the paper machine system where it is screened and finally brought to the paper-forming machine itself. In the paper machine, the pulp sheet is dewatered on a fine mesh wire, pressed in several roll presses and air-dried in a semi-heated pulp dryer section. The paper making process is illustrated in Figure 2.5.
Figure 2.5 Overall paper making process
12 Technology, Energy Efficiency and Environmental Externalities in the Pulp and Paper Industry
Recovery processes in the paper mill attempt to recover the washed out fibers and fillers. These processes are based on sedimentation and floatation principles. Conical or other sedimentation tanks are used to separate the suspended solid. Floatation devices are revolving, cylindrical, perforated screens or filters to remove the suspended solid in the form of a mat which is subsequently scraped off the drum and returned to the paper making stock system. The use of wastepaper as a raw material for paper production is being emphasized nowadays. This process requires the de-inking of the waste paper. The de-inking process has two main steps (the flotation process and the washing process) and employs various equipment, like pulp shredder, drum screen, high density cleaner, floatater (closed injection floatater, Sweetmark floatater, and Lamort floatater), pressurized screen and washer. When waste newsprint paper is stored for a short period, the ink carrier on the wastepaper is not sufficiently dried. However, it is absorbed by the fiber only. Under the action of chemical reagents and under conditions of suitable temperature and consistency, the carrier is saponified. The ink is dispersed easily and the pigment is also released easily. The pigment, which consists of carbon black, usually forms good particles under the treatment of pulp shredder. If waste paper has been stored for a long time, the ink carriers are solidified due to drying and aging. In this case, an increased quantity and density of de-inking chemical (such as NaOH) must be added and reaction temperature and reaction time should be increased so that the ink can be saponified. Shredding of the wastepaper and putting it in the de-inking chemical are done in high density pulp shredder, in which the waste newsprint paper is soaked, osmosed, absorbed and expanded by the solution of de-inking chemicals. The main chemicals used in de-inking process are NaOH and formic acid (HCOOH).
Energy Issues in the Pulp and Paper Industry 13
3. ENERGY ISSUES IN PULP AND PAPER INDUSTRY
3.1 Typical Energy Consumption Patterns
The primary energy sources used in the pulp and paper industry are thermal energy in the form of steam and mechanical energy converted from electricity. The thermal energy accounts for about 70-80% of the total primary energy and is mainly used in pulping and drying processes. The process steam is generated from waste raw materials, concentrated black liquor and other fuels such as coal, fuel oil and gas. In the pulp and paper mills, on-site electricity generation typically ranges from 0-60% of the total power consumption. The energy consumption of a pulp and paper mill depends on the raw materials used, type of pulping process and the degree and type of final products. The typical specific energy consumption values of different paper-making processes are shown in Figure 3.1.
0
5
10
15
20
25
30
35
Aci
d S
ulfit
e
Kra
ft
Sem
i-C
hem
ical
Gro
und-
woo
d
Ther
mo-
mec
hani
cal
GJ/
ton
of P
aper
Pro
duct
s
Pulping Bleaching Paperforming Drying and finishing Others
45%
8.5%
17.5%
25%
4%
39%
15.5%
17%
24.5%
4%
45.5%
10.5%
16.5%
24%
3.5%
50%
17.5%
3.5%
25.5%
3.5%
48%
4%
18%
26.5%
3.5%
Figure 3.1 Typical energy consumption of paper-making processes
From Figure 3.1, it can be seen that the highest energy consumer in a pulp and paper mill is the pulping process. The average specific energy consumption of pulping process is low in industrialized countries because of the higher percentage of waste-paper pulp in total pulp produced. The specific energy consumption of waste-paper pulp is about 3 times less than that of wood pulp.
14 Technology, Energy Efficiency and Environmental Externalities in the Pulp and Paper Industry
The average specific electricity consumption of pulp and paper industry is 1000-1300 kWh per ton of paper products. The percentage of total electrical power consumed in different stages of a typical paper manufacturing process is shown in Figure 3.2.
40%22%
11%
13% 12%2%
Paperforming Pulping Chemical plantBoiler house Water treatment Others
Figure 3.2 Breakdown of electricity consumption in an integrated mill
The temperature level of process steam of a pulp and paper mill is normally below 200°C. The typical specific steam requirement is 8-12 tons per ton of paper products. The breakdown of process steam is given in Figure 3.3.
40%21%
5%
33%1%
Pulping BleachingHot watermaking DryingOthers
Figure 3.3 Breakdown of process steam in an integrated mill
Energy Issues in the Pulp and Paper Industry 15
3.2 Energy Efficient Measures
As mentioned earlier, the overall energy requirement of a pulp and paper mill can be theoretically met by waste materials and concentrated black liquor. Therefore, the objectives of energy conservation measures in the pulp and paper industry are to reduce the purchased energy and to recover as much energy from the internal waste fuels as possible. 3.2.1 Short term measures
The immediate actions which can be taken without substantial investment to achieve a certain level of energy savings in pulp and paper industry are:
- inspection to encourage conservation activity - excess air and flue gas temperature control - recovery of heat from boiler blowdown - proper insulation of steam lines - power factor improvement of electric motors - ensuring an efficient washing (to minimize the dilution of black liquor) - recovery of heat from extracted black liquor after cooking - recovery of heat from condensate of drying process (about 5% of fuel can be
saved) 3.2.2 Medium term measures
The medium term measures include modifications in processes and materials, recovery of waste heat and self power generation with moderate to large investments. 3.2.2.1 Measures on processed materials
(i) Higher percentage of waste-paper pulp
The recycling of more waste paper in pulping can lead to not only energy saving but also conservation of forest and environment. An increase in the percentage of waste-paper pulp by 10% can save about 6.5% of energy required for pulping process. (ii) Recovery of chemicals
The amount of chemicals recovered in pulping process has an effect on the overall specific energy consumption of the pulp and paper industry. Although the chemical recovery rate is usually high in the larger mills (over 90%), that of medium and small mills are low, typically 50-70%. Therefore, proper chemical recovery systems should be installed in the pulp and paper mills.
16 Technology, Energy Efficiency and Environmental Externalities in the Pulp and Paper Industry
The recovery of chemical products by a membrane process, particularly using mineral membrane through ultrafiltration, can result in higher recovery rate and less pollution. Although the membrane process consumes electricity required by the pumps to pressurize the liquid and to circulate it, cogenerated electricity (elaborated later) can support the case for ultrafiltration. 3.2.2.2 Self energy production
(i) Cogeneration
Cogeneration is a promising technology for better utilization of energy sources if process steam demand is high. Therefore, the pulp and paper industry has a high potential for application of cogeneration. For the high pressure steam systems (60-80 bar), it is possible to generate excess electricity by as much as 600 kWh per ton of paper, which could be sold to the grid. The generation of surplus electricity is of no interest to the industry if the regulation in the country does not permit the selling of this electricity to the grid. As a consequence of such a case, the upper limit is an electrical-match process: the maximum amount of electricity generated is the same as that needed by the factory. The pay-back period of cogeneration system is around 3-5 years. (ii) Methanogenesis
The technology of methane generation from organic wastes through anaerobic digestion permits at the same time energy recovery and reduction in environmental pollution. The methanogenesis can compete with other waste treatment processes because of its potential for energy production. As an example, the anaerobic digestion process can produce energy of the order of 6.4 GJ per ton of paper and the pay-back period is about 4 years.
3.2.2.3 Modifications in the sub-processes
(i) Conversion of batch to continuous digester
Up to 40% of steam consumption can be saved by converting the pulping process from batch to continuous. The continuous pulping can also offer steady recovery of heat from the outgoing materials of the digester.
(ii) Mechanical vapor compression
Large amounts of energy (in the form of steam) are required for concentration of black liquor from 10 to 60% before firing in a heat recovery boiler. This is achieved conventionally in a multi-effect evaporator where the vapors from last effect are finally condensed in a surface condenser. Energy thus transferred to cooling water cannot normally be put to useful purpose, especially in the hot tropical climate, due to its lower heat content.
Energy Issues in the Pulp and Paper Industry 17
The use of mechanical vapor recompression (MVR) is suitable for partial concentration (up to about 23%) of black liquor by replacing the first stages of multi-effect evaporators. The energy demand of black liquor concentration process can be reduced by 70-80% by practically replacing the direct distillation with MVR. The installation of MVR would be economically more attractive with the availability of cogenerated electricity. The pay-back period of MVR installation is site specific and varies from 1.5 to 6 years. (iii) Vacuum pump in paperforming
The replacement of vacuum pump in paperforming can save about 25% of electricity consumed. (iv) Change in pressing
The use of longer nips or hot press which is heated by waste streams can save the steam consumption of drying process by 15-20%. 3.2.2.4 Waste heat recovery
(i) Heat pump hot water system
In the drying process, the water contained in the paper is evaporated and is normally rejected to the atmosphere. The energy content of evaporated water can be recovered by a heat pump to produce hot water for washing of the pulp. This system can save about 1.3 MJ per ton of paper. (ii) Flash steam recovery in drying process
The typical pressure of steam used in the drying process is 3-4 bar. The condensate coming from the dryers is returned to the condensate tank where some amount is flashed into the environment. The flash steam can be recovered for further use in the processes by one of the following systems:
- absorption heat transformer (energy saved = 200 MJ/ton of paper) - vapor compression heat pump (energy saved = 600 MJ/ton of paper) - ejecto-compressor (energy saved = 600 MJ/ton of paper)
3.2.3 Long term measures
The long term measures include better site arrangement of the industry, excess power generation for the grid, adaptation of the new emerging processes and computerization of the manufacturing processes.
18 Technology, Energy Efficiency and Environmental Externalities in the Pulp and Paper Industry
(i) Interconnected factories: sugar mills and pulp mills
The sugar industry, due to its generation of bagasse, is a very important source of raw material for pulping. By employing cogeneration, a well-designed sugar plant is normally able to produce its electricity while a considerable amount of excess bagasse still remains. This bagasse can be burnt in order to produce electricity if its buy-back by the grid is permitted. But bagasse can be used for pulping too. The coupling of a paper mill and a sugar plant is therefore interesting. There are several modes of coupling the two plants. Some possibilities are:
- The sugar plant produces its electricity and sells excess bagasse to the pulp plant. The latter produces electricity through cogeneration and combustion of black liquor.
- Several sugar plants providing extra bagasse to one pulp plant; the sugar mills and
the pulp mill are completely independent as far as energy use is concerned. - A pool is formed in order to manage the energy usage jointly by the sugar and
pulp mills with any surplus electricity eventually sold back to the grid.
This kind of management is very attractive from the point of view of appropriate use of raw material and energy, and regional development, but several constraints must be taken into account:
- Seasonal working conditions of the sugar industry - Competition between the buy-back rate of electricity by the grid (if allowed)
and the benefit of producing paper (with additional investment) - Technical problems related to pulping from bagasse, etc.
(ii) Excess power generation
The pulp and paper industry offers the practice of industrial cogeneration since the demand of process steam is high. Since decentralization of power sector is beneficial both at the macro and micro levels, excess power generation from the pulp and paper industry should be a long term objective for better utilization of energy sources. (iii) Adaptation of new emerging processes
The pulp and paper industry is one of the most pollution producers in the industrial sector. New pulping processes are still emerging (mentioned in the following section) as clean technologies. Therefore adaptation of new emerging processes will enhance the integrated approach to energy and environment.
Energy Issues in the Pulp and Paper Industry 19
(iv) Computerization
Like other industries, computer-control of processes in the pulp and paper industry can result in a better management of all the resources. The computerization will lead to the reduction in fuel cost, chemicals, electrical charge and personnel services, etc., and guarantee a better quality pulp. As an example, the pay-back period of the computer-controlled system in a Kraft pulp mill with a capacity of 300 tons of pulp per day was estimated as less than 6 years. 3.3 New Energy Efficient Technologies for Papermaking
Among the new emerging processes, ozonation, BG-TAG-LAMORT process and organocell process are the three most promising options. (i) Ozonation
Ozone has a very high oxidizing and disinfecting power. Its use in water treatment is well established and is gradually increasing. The development of integrating an ozonizing stage into the bleaching sequences in the pulp and paper industry, however, is new and has been driven by environmental, economic and energy-related considerations. Energy requirement for ozone production has been consistently reduced during the last ten years. Only 10 kWh is now needed for the production of 1 kg of ozone instead of the 20 kWh required in the past. Ozone is an oxide but it is a clean one. It can be used anytime there is a requirement of an oxidizer. Its uses for the pulp industry can be through at least three options:
- by replacing chlorine as an environmentally safe bleaching agent in the chemical process. The reaction can be carried out at room temperature and atmospheric pressure; 1% of ozone increases the brightness of the pulp from 45 up to 75 ISO in a single stage.
- by reacting with lignin in the thermomechanical process and modifying its
structure. About 2% of ozone appears to be able to keep a high yield of the thermomechanical process (around 90%) providing a strength comparable to that of the chemical pulp.
- in the pollution abatement process, a specific quality of ozone for oxidizing at
different levels can be used for classical type of water treatment, but it can also contribute to help in rapid flocculation or the deterioration of microorganisms, for example.
20 Technology, Energy Efficiency and Environmental Externalities in the Pulp and Paper Industry
An oxygen recycled process is also available, permitting considerable decrease in oxygen requirement. Oxygen process, however, requires to be carried out at high pressure and temperature. (ii) BG-TAG-LAMORT process
One of the main sources of pollution of the pulp industry lies in the cooking process as it needs chemical agents and a large quantity of water. The BG-TAG-LAMORT process uses a dry cooker to avoid this problem. The raw material is soaked in a minimum amount of solution, so that the volume of black liquor is reduced and its concentration is high. The volume of water required can in fact be reduced 5 folds. The black liquor can be transferred directly to the furnace of a boiler for combustion. This process is particularly suitable for small and medium size production plants and is well suited for raw materials such as bagasse. A plant producing 60,000 t/year of pulp costs about 80 million US dollars. The process is based on a 50 t/day module. (iii) Organocell process
The objective is the same as for the other processes: reducing the pollution as a result of the presence of sulfur in wastes. The organocell process extracts the lignin by alcohol, and sodium hydroxide. The advantage is a non-degradation of lignin. The interest lies in the possibility of using lignin for producing chemical products such as polymers and derivatives. This process can be seen in the light of a new biomass chemistry. The energy consumption is at the level of solvent regeneration. 3.4 Concluding Remarks on Energy Issues
The management practices to obtain better energy efficiency in the pulp and paper industry are illustrated in Figure 3.4. The regular energy conservation practices such as insulation maintenance of steam lines, excess air control, checking of steam leakage, etc., can save certain amount of energy consumption, since the pulp and paper industry consumes a large amount of steam. The temperature levels of processes are normally below 200°C. Therefore, application of thermal upgrading systems can offer significant energy savings, especially in the large mills. The higher recovery rate of chemicals and materials is also an important issue in the pulp and paper industry for the preservation of resources. Since the full utilization of internal energy sources is the major goal for higher energy efficiency, cogeneration and methane production would be beneficial both at the plant and macro levels.
Energy Issues in the Pulp and Paper Industry 21
MethaneProduction
MembraneSeperation
Ozonation
ThermalUpgrading
Fuel(external + internal)
Effluent
ToGrid
Electricity
- Rational use of energy sources
- Energy recovery
- Depollution
- Fibre recovery- Waterrecycling- Depollution
- Chemical saving- Energy recovery- Water saving- Depollution
- Energy Saving
Management Practices Benefits
Cogeneration
Figure 3.4. Management practices for better energy efficiency
22 Technology, Energy Efficiency and Environmental Externalities in the Pulp and Paper Industry
4. SOURCES OF POLLUTION AND ITS MANAGEMENT
4.1 Sources and Characteristics of Pollutants
The major environmental problems in the pulp and paper industry come from the production of pulp. Different methods are used for pulp production. The specific environmental effects vary depending upon the pulping process used. Mechanical pulping requires relatively small quantities of water for chipping and milling of the fibers and this water is only slightly polluted. On the other hand, chemical pulping requires large quantities of water and causes severe water pollution. The use of chemical pulping is, therefore, restricted to areas where a large receiving water body is available to absorb the contaminants remaining after the treatment of wastewater. Water-, air-, solid- and indirect pollutants are generated from the different processes. Suspended solids and dissolved organic substances (including lignin) that are not readily biodegradable are the major pollutants. Most air pollution problems are related to sulfur and sulfur dioxide and other sulfur compounds. 4.1.1 Sources of wastewater generated
The sources and characteristics of wastewater in the pulp and paper industry are as follows: (i) Chipping
Wastewater from the chipping process contains coarse materials, i.e. barks and chips. (ii) Black liquor
Black liquor is the wastewater from the digestion and the rinsing process. (iii) Evaporator condensate
The condensate from the evaporator in the chemical recovery process contains odorous alkyl sulfides, which is treated by steam stripping before being transferred to the treatment plant. This wastewater is rich in acetate and methanol and is usually treated with other wastewater. (iv) Wastewater from bleaching
The most problematic wastewater generated in bleached Kraft pulp (BKP) production is from the bleaching process, especially in the initial bleaching stages. It contains hard-biodegradable organics (such as lignin and hemicellulose), chlorinated organics and dioxin, and 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) compounds. Furthermore, it is highly colored with brown substances. The effluents not only have negative impact on plant and animal life in the receiving areas, but are also “persistent”, i.e., they bio-degrade very slowly.
Sources of Pollution and its Management in the Pulp and Paper Industry 23
(v) White water
Wastewater from the paper making process contains fine fibers and other solids such as fillers. The excess white water after fiber recovery is treated by coagulation/flocculation process and is discharged to the treatment plant. 4.1.2 Characteristics of wastewater generated
The wastewater of pulp and paper effluents may contain dissolved organic compounds and chemicals used in the process, fibers, fillers and additives, color, bark, ash and lime sludge. The dissolved compounds originate in pulping process, suspended solids are present in effluents from practically all stages and parts of the industry. The suspended matter consists generally of fibers and bark residue, ash lime and clay. Dissolved organic substances include lignin, carbohydrates, organic acids and alcohol which, with the exception of lignin, are readily biodegradable. Conventional parameters to quantify the pollution load are biochemical oxygen demand (BOD5), dry solids (DS) and pH. Toxic pollutants present are pentachlorophenol (PCP), trichlorophenol (TCP), zinc, chloroform, bleach plant derivatives, PCB-1 2 4 2, other pollutants, ammonia, color, resin, and acids. The effluent characteristics of different bleached Kraft pulp mills in Sweden and Finland are shown in Table 4.1.
Table 4.1. Effluent from bleached Kraft pulp mills prior to external treatment
Type of wood and Technology BOD7 kg/t
COD kg/t
SS kg/t
TOCl kg/t
Soft wood Technology in Finland & Sweden 1970 Technology in Finland 1988 Technology in Sweden 1988 Hard wood Technology in Finland & Sweden 1970 Technology in Finland 1988 Technology in Sweden 1988
55 24 19
60 25 25
190 85 65
180 75 75
15 11 8
28 12 9
>6 5
3.5 4
2.5 2.5
Source: Adapted from BONSOR et al, 1988 The characteristic of de-inking wastewater from paper industry where waste paper is used as raw material is given in Table 4.2.
24 Technology, Energy Efficiency and Environmental Externalities in the Pulp and Paper Industry
Table 4.2. Characteristics of de-inking wastewater from waste paper mill
Country Flow rate m3 / t
TSS kg / t
BOD kg / t
COD kg / t
Product
Philippine paper mill 26 10.0 5.0 Newsprint German paper mill 10.5 4.7 10.5 Carton German paper mill 4.2 5.9 13.4 Testliner paper
Source: Adapted from C. T. Tupas, 1995 Characteristics of combined effluent of pulp and paper mills, and distribution of pollution load from different sections of pulp and paper mills are shown in Table 4.3.
Table 4.3. Characteristics of combined effluent of pulp and paper mills and distribution of pollution load from different sections of a mill
Item Small mill (Sastry et al.)
Large mill (Subrahmanyam et al.)
Produces 20 tons of paper per day
Produces 2000 tons of paper per day
Flow per day Color pH Total solids, mg /l Suspended solids mg /l COD mg /l BOD mg /l COD/BOD ratio
330 m3 / t -
8.2-8.5 -
900-2000 4300-5780 680-1250
3.9-5
222 m3 / t 7800 units
8.5-9.5 4410 3300 716 155 4.6
Item Digester section
Bleaching section
Paper mill section
Flow % Small Large BOD % Small Large Suspended Solid % Small Large
45.5 9.75
66
32.5
60 3
16.2 27.8
18.4 32.5
14.5 1.35
10.8 16.7
2
1.43
7.75 3.4
Sources of Pollution and its Management in the Pulp and Paper Industry 25
4.1.3 Sources and characteristics of gaseous emissions
Gaseous emissions of concern are the discharges of those components considered as air pollutants and odorous components. These pollutants of the pulping industry, especially from chemical pulping, are hydrogen sulfides, organic sulfide, SOx and NOx. The release of sulfur containing gases during Kraft digestion and burning of black liquor generates H2S, a highly malodorous gas, SO2, and various methyl derivatives such as methyl mercaptan (CH3SH), dimethyl sulfide (CH3)2S, and dimethyl disulfide (CH3-S-S-CH3). Odorous components as phenols and turpenes are liberated from all other pulping processes. 4.1.4 Sources and characteristics of solid wastes
The pulp and paper industry produces solid wastes which, depending on the pulping process and the chemical processing, consist of waste water sludge, ash, bark, woodwaste and paper. These wastes have high pollution potential and should be disposed of in controlled landfills to avoid leaching of the sub-soil. 4.2 Current Pollution Abatement Strategies and Technologies
4.2.1 Water pollution control
Pulp and paper mill wastes are treated by the following processes: - Recovery processes. - Sedimentation and floatation to remove suspended matter. - Chemical precipitation to remove color and suspended and colloidal particulate
matter. - Biological treatment to remove oxygen demanding matter/dissolved organic
matter. The treatment of waste water may consist of all or a combination of some of these processes. (i) Recovery processes
The recovery of the process chemicals and fibers reduces the pollution load to a great extent. Where the economy permits, the color bearing ‘black liquor’ is treated for the recovery of chemicals. However, in this process the lignin is destroyed. The lignin may be recovered from the black liquor by precipitation and by acidulation with either carbon dioxide or sulfuric acid. These recovered lignins have got various uses in other industries. The alkali lignins of Kraft process may be used as a dispersing agent in various suspensions. Lignins may be used as raw materials for various other substances, e.g. dimethyl sulfur oxide, which is used as spinning solvent for polyacrylonitrile fibers. Activated carbon may also be manufactured from the lignin recovered from black liquors.
26 Technology, Energy Efficiency and Environmental Externalities in the Pulp and Paper Industry
The fibers in the white water from the paper mills are recovered either by sedimentation or by floatation using forced air in the tank. The recovery of lime from the lime mud can be achieved by the process of calcination. (ii) Chemical treatment for color removal
The chemical coagulation for the removal of color is found to be uneconomical. Attempts have been made to recover color from the waste using the lime sludge; the results are not at all encouraging. “Massive Lime Treatment” process, developed by the National Council for Stream Improvement in the USA is said to be capable of removing about 90% of color and 40 to 60% of BOD from the waste. In this process, the entire quantity of lime, normally required for the re-causticization of green liquor into white liquor, is allowed to react with the colored waste effluent first. The color is absorbed by the lime, and the sludge after settling is used in recausticizing the green liquor. The treatment of green liquor with colored lime sludge results in the formation of dark brown liquor, containing both desired cooking chemicals and color-producing components, like lignin. The lignin-bearing liquor is used as digested liquid, and then is destroyed along with the fresh lignins in the subsequent operations of concentration and incineration in the process of chemical recovery. In a study conducted by NEERI, it has been observed that acidic activated carbon can remove up to 94% of the color from the pulp mill waste. However, pH of the waste is required to be reduced to 3.0 before this activated carbon treatment. (iii) Physical treatment for clarification
Mechanically cleaned circular clarifiers alone are capable of 70-80% removal of the suspended solids from the combined mill effluent. About 95 to 99% removal of settleable solids can be accomplished in the clarifiers. However, the BOD reduction is comparatively small and of the order of 25-40% only. A surface loading in the order of 30 to 31 m3/m2/day is found to be adequate for up to 79% removal of suspended solids and 52% removal of COD at a detention time of 30 minutes. The primary sludge produced in the clarifiers can be thickened to such a consistency in the clarifier itself that it can be easily dewatered mechanically. (iv) Biological treatment of the waste
Considerable reduction of BOD from the waste can be accomplished in both conventional and low cost biological treatment processes. Some are also effective in the reduction of color from the waste.
Sources of Pollution and its Management in the Pulp and Paper Industry 27
If sufficient area is available, the waste stabilization ponds offer the cheapest means for treatment. Depth of these ponds vary from 0.9 m to 1.5 m; the detention period may vary from 12 to 30 days. A minimum of 85% removal of BOD is achievable, with a loading rate of up to 56 kg/hectare/day. Aerated lagoons are the improved forms of the stabilization ponds. They can be adopted to upgrade the performance of already present quiescent stabilization ponds that have become inadequate because of the increased loading or more stringent receiving water criteria. The mechanical surface aerators are the most satisfactory oxygen transfer device. BOD reduction up to 50 to 95% can be achieved in the aerated lagoons by varying nutrients feed, air supply and detention time (3 to 20 days), at the loading range of 670 to 1340 kg of BOD per hectare per day. Aerated lagoons are employed, either when the effluent BOD is moderate (where a partial chemical recovery from the black liquor is practiced), or as a polishing device. In one particular case, a detention period of 5 days was found adequate for 90% BOD removal; the system rate constant was found to be 0.21/day. It may be noted that the pulp and paper mill waste does not contain necessary nutrients for the bacterial growth, and hence nitrogen and phosphorous are to be added into the lagoons in the form of urea or ammonia and phosphoric acid in a BOD:N:P ratio of 100:5:1. The nutrient addition is not necessary when a detention period of more than 10-15 days are provided. Segregated strong waste or combined wastes may be well treated in Anaerobic lagoons with nutrient supplement. A BOD loading of 0.048 kg/m3/day and a detention time of 20 days were found to be adequate for 72.5% removal of BOD in a particular case. In another case, 77.5% removal of BOD was reported at a detention time of 6-8 days and a loading of 0.017 kg of BOD/m3/day. Aerated lagoons may be employed after the anaerobic lagoons where a high effluent quality is required. The system rate constant in the aerated lagoons, preceded by the anaerobic lagoons may be taken as 0.15-0.17 per day. A detention period of 7 days in these aerated lagoons are adequate. Activated sludge process is the most satisfactory and sophisticated system for the effluent treatment. Instead of porous diffusers, the surface aerators are often suggested as the oxygen transfer device in the aeration tanks treating pulp and paper mill effluent. It is reported that about 80 to 90% BOD removal can be achieved with a loading rate of 0.2 to 0.3 kg of BOD per kg of MLSS for a detention time of 3 to 9 hours, MLSS concentration of 2000-4000 mg/l, recirculation ratio of 0.3-0.5, and a nutrient supplement at the BOD:N:P ratio of 100:5:1. While designing the secondary settling tank in an activated sludge process, it should be borne in mind that a large portion of the fine fibers is not biodegradable and also does not settle easily. Flow diagram for the treatment of waste from a typical pulp mill is given in Figure 4.1.
28 Technology, Energy Efficiency and Environmental Externalities in the Pulp and Paper Industry
Limetreatment Clarifier Cooling
TowerAnaerobic
Lagoon
AeratedLagoon
AeratedLagoon
StabilizationTankGrift Cham Clarifier
Lime
BlackLiquor
Calcium Hypochloride
OtherWaste
Colour reduction=70%BOD reduction=40-50%Detention time=4 Hrs
Detention Time= 3 Days
Effluent
BOD reduction 87%Detention Time 1.5 days
Nutrients
Figure 4.1 Flow diagram of wastewater treatment of a typical pulp mill
Trickling filter has got a limited use in the treatment of the pulp and paper mill effluent, due to the greater chances of clogging of the media with fibrous material. Also the trickling filter system is not capable of providing a high degree of treatment even with the new plastic media. With greater specific surface area, the BOD removal is found to be only 40-50%. (vi) Land treatment method
Some types of soil are capable of removing color from the waste. The waste is stored and allowed to be absorbed in such a soil. The capability of the soil in removing the color depends on the cation exchange capacity of the soil. In addition to cation exchange capacity, the soil should be sufficiently permeable to accept the entire volume of waste. (vii) Disposal of waste by irrigation
The pulp mill effluent may be utilized for irrigation. No adverse effect on crops are reported for crops like maize, paddy, jowar and kenaf. Yields almost identical to those with conventional irrigation practices are reported for wheat and sugarcane (RAO & DATTA, 1987).
Sources of Pollution and its Management in the Pulp and Paper Industry 29
4.2.2 Solid waste disposal
Application of incineration furnace for heat/energy recovery from combustion of fibers, barks, wood residues, other organic materials and wastewater sludge is practiced today but still needs more attention. 4.3 Possibilities for Application of Alternative Technologies for Pollution Control
Since it is impossible to completely eliminate the waste coming out of the production process, it is always necessary to have some sort of end-of-the-pipe treatment to meet the stringent environmental discharge regulations. There have been numerous developments towards cleaner production opportunities in the industry. In this section some of the recent technological developments on both end-of-the-pipe treatment and production process modification as well as raw material changes for waste reduction are discussed. 4.3.1 Anaerobic treatment of wastes
In recent years, the trend in the industry has changed from resource-destroying aerobic to resource-conserving anaerobic wastewater treatment. By anaerobic treatment, a combination of energy-efficient wastewater purification and energy recovery in the form of biogas production can be achieved. Such a full-scale application of anaerobic process is widespread in the developed countries. Originally, conventional anaerobic treatment in an economic manner required highly concentrated wastewater. The development of anaerobic process-technology during recent years has drastically reduced this requirement. Pulp and paper industries discharge large quantities of fibers and different types of sludge. These wastes correspond to large quantities of energy consumed by the treatment and disposal process and large amounts of potential energy stored in the materials. Because of the savings in processing energy and the recovery of potential energy, the demand for using anaerobic treatment of these wastes has greatly increased. 4.3.2 Membrane technology
Several membrane processes (reverse osmosis, electrodialysis, and ultrafiltration) have recently been developed to treat the wastewater. Electrodialysis procedures have been successfully used to treat bisulfite spent liquor generated in a sulfite pulping process. In electrodialysis process, an imposed electric current is used to cause selective movement of charged ions. A traditional electrodialysis system can be modified for this particular application by placing sulfurous acid (H2SO3) in several compartments and the spent liquor (containing large amounts of lignosulfonic acid sodium salt and small amounts of non-ionizable sugars) in another set of compartments. The compartments and membranes are arranged such that the sodium and bisulfite ions combine in a third set of compartments, forming sodium bisulfite (NaHSO3). This NaHSO3 can be recycled as cooking liquor. In
30 Technology, Energy Efficiency and Environmental Externalities in the Pulp and Paper Industry
addition, the remaining mixture of sugars and lignosulfonic acid can be sold as plywood adhesives. One difficulty with the process is high power requirement. The greater amount of dilute wastes, arising primarily from the washing of pulp for further lignin removal, also constitutes a serious waste problem. Typically, this wastewater may contain about 1% dissolved solids. These dilute streams can be treated by a combination of ultra-filtration followed by reverse osmosis, or by just the reverse osmosis step. The purified water can be returned to the system; the small-volume concentrated wastes can then be treated as digester wastes. 4.3.3 Dissolved air floatation for fiber recovery
This process is based on the fact that, addition of air to the waste stream could enhance the natural propensity of the fibers to float, thereby separating them from the water. Initially, polymeric flocculating agents are added, causing the suspended fibers to coagulate together into flocs. The stream is then mixed with water in which air has been dissolved under pressure. When the pressure is released, air comes out of solution as small bubbles which attach themselves to the flocs, bringing them to the surface from where they can be readily skimmed off. The success of the technology is due to:
- its versatility and ease of operation. - the economic returns associated with fiber recovery. - substantially reduced residence times, which removes the possibility of any
organic material becoming contaminated by microorganisms, and speedy re-circulation, thereby limiting the loss of process heat.
- levels of clarification superior to what can be achieved with traditional methods. 4.3.4 Ozone bleaching
The 5-stage bleaching sequence (CEDED process) is the most common and one of the most economical bleaching processes for the pulp. For each stage, the dissolved organics and the inorganic bleaching chemicals must be washed out of the pulp before entering the next stage. Although the amount of wash water and the resulting effluent could be minimized by reuse of the washings as wash water for the prior stage in a counter-current feedback fashion, eventually it is necessary to sewer all the washings for treatment in the plant’s effluent treatment system. The result is a high BOD, high COD, high color and highly chlorinated solution of organics, which are formed principally from the reaction of chlorine with pulp. The replacement manufacturing process is a 4-stage bleaching sequence, using oxygen with caustic as the bleaching agents in the first stage (O), followed by ozone treatment in the second stage (Z), caustic extraction augmented by oxygen in the third stage (EO), and a final chlorine dioxide stage (D). Since there is no use in the O, Z, or EO stages of chemicals that are incompatible with recycle and recovery in the mill’s existing pulping
Sources of Pollution and its Management in the Pulp and Paper Industry 31
liquor closed-cycle system, virtually all of the washings from these three stages are recovered without sewering. The only significant effluent from the bleach plant is the small amount of contaminated washings coming out of the final chlorine dioxide stage. This process is successfully used in the USA. Since essentially all the caustic used in the oxygen stage treatment of the OZ(EO)D bleaching is recovered and recycled back to the cooking liquor closed recycle system, one is able to use it as the caustic for the oxygen stage when caustic makeup is needed for the cooking liquor cycle, disposing of the cost for purchasing additional caustic. However, when no caustic make-up is required, one can oxidize with oxygen the product from the cooking liquor recycle (white liquor) and use the oxidized white liquor for the alkali requirement. This results in an extra load (regeneration load of about 5% more cooking liquor for the pine pulp) on the cooking liquor recycle equipment’s capacity. The recovery and recycle of organic and inorganic solids, purged in the bleach plant effluents, give about 7% more solids than normal for pine pulp production. While it is true that this is an extra use of recovery capacity, it also results in extra solids which may be used as fuel for producing steam in the recovery boiler. About 6% more steam per ton of pine pulp can be produced. 4.3.5 Modified continuous cooking process (MCC)
MCC adapts the principles of extended delignification to continuous pulping and rectifies the drawbacks of a conventional, continuous Kraft cook. The effective alkali concentration through the duration of cooking is evened out by decreasing it at the beginning of cooking and increasing it at the end. In a conventional cooking, the high bulk lignin concentration at the end hinders diffusion of dissolved lignin out of the chips, causing re-precipitation. The MCC process has been accomplished through the modification of 2-vessel Kamyr continuous digesters to allow both the introduction of white liquor at several points and counter-current flow of the liquor during the final cooking phase. Moreover, a nonchlorine fiber line which is used in the mill, consists of a digester for medium-consistency cooking and a medium consistency oxygen-delignification stage, followed by an efficient post-oxygen washing stage with pressure diffuser and a wash press. Kappa number reductions of 8 units for softwood and 4 to 5 units for hardwood have been accomplished without loss of strength properties. About 20-25% less total active chlorine is needed to bleach the pulp to about 90% ISO brightness compared to the conventional Kraft pulp. The MCC fiber line can be regarded as one of the most advanced in the world today, meeting current and future requirements for the environment while still producing fully competitive pulp. It is possible to produce bleached pulp without using chlorine, achieving brightness even above 90% ISO, the level required for the most demanding market pulps.
32 Technology, Energy Efficiency and Environmental Externalities in the Pulp and Paper Industry
4.3.6 DARS in soda pulping of bagasse
The basic principle of the DARS process involves the production of sodium ferrite by auto-causticization of sodium carbonate with ferric oxide and subsequently to obtain sodium hydroxide by hydrolyzing the sodium ferrite. Silica is an undesirable element in all the spent liquors from pulping of agricultural residues. Extensive studies on the effect of silica impurity in the recovery loop revealed that only a minor proportion of silica passes into white liquor during ferrite auto-causticization process. This is an advantage of the process and, unlike conventional recovery, it may not be necessary to go for additional stages of desilication of spent liquor prior to recovery operation. Among the benefits of the process are operational flexibility, compact and simple operation, less space requirement, most economic use of fuel by way of minimized quantity of high cost fuels, non-requirement of a high degree of process automation. Unlike the smelt in conventional recovery, the combustion product is solid, so the process is safe. 4.3.7 Dry forming of paper web
The dry forming method can, in principle, be divided into the following phases: defibration of raw materials, forming, binder application, curing, and finishing. The main raw material, mostly wood pulp, is defiberized in a hammer mill. After this, the fibers are transported by means of a fan to the forming section. Each former consists of two perforated drums rotating inside the forming head. The fibers circulate horizontally between the drums. The accepted fiber material is formed onto the moving forming wire by suction. After forming, the web is led through heated compactor and embosser rolls. In the third phase, a binder solution is sprayed onto the web. The application is made separately on both sides of the web, each application being followed by thorough-drying. Full strength is achieved during the curing as the binder is cross-linked. The curing is also performed in a through-dryer. To improve the final properties, the web is led through a finishing calendar. In the dry forming process, the fresh water demand is only 0.8 liters per kilogram of produced material (air dry). It is totally used to dilute the binder. The dry forming process creates neither waste water nor effluent gases. Dry formed materials have unique absorption and wet strength properties. They are non-abrasive, soft, and feel like textile. The products are suitable for different kinds of toweling and wiping, in health-care, hygiene and for table settings. The process is non-polluting, there are no waste water problems, and the mill can be located either close to consumers in an urban location or near the sources of raw materials.
Sources of Pollution and its Management in the Pulp and Paper Industry 33
4.4 Concluding Remarks on Pollution Management
The most significant environmental issue is the use of chlorine in bleaching. Industrial developments demonstrate that totally chlorine-free bleaching is feasible for many pulp and paper products, but it cannot produce certain grades of paper. Implementation of cleaner production process and pollution prevention measures can provide both economic and environmental benefits. Wherever feasible, use of a total wastewater recycling system along with a total chlorine-free pulp bleaching system is, therefore, recommended. As a minimum, total elemental chlorine-free pulp bleaching system may be employed. Sulfur oxide emissions are scrubbed with slightly alkaline solutions. Electrostatic precipitators are used to control the release of particulate matter to the atmosphere. Effluent treatment typically includes neutralization, primary treatment to remove suspended solids, and biological/secondary treatment to reduce BOD5 and toxicity. Flocculation to assist in the removal of suspended solids is also sometimes necessary. Biological treatment systems, such as activated sludge and anaerobic treatment, can reduce BOD5 by over 95 percent. Tertiary treatment may be performed to remove toxicity, color, and coliform. Solid waste treatment steps include de-watering and combustion in an incinerator, bark boiler, or a utility boiler along with fossil fuels. If a mechanical clarifier is used in primary treatment, the sludge is dewatered and may be incinerated; otherwise it is land filled. The uses of ozone for partial degradation of lignin, solvent, or dry cooking result from another consideration of how to achieve a “clean process”. The future of the pulp and paper industry rests with an objective of avoiding or reducing the waste instead of treating it. Therefore, the adoption of emerging clean technologies along with the computerization of processes will guarantee a cleaner and highly energy efficient pulp and paper industry in the future.
34 Technology, Energy Efficiency and Environmental Externalities in the Pulp and Paper Industry
5. CROSS COUNTRY REPORT ON THE PULP AND PAPER INDUSTRY
5.1 Introduction
The pulp and paper industry has been growing very rapidly in the developing countries. As an essential commodity for the society and the consumption of paper being normally parallel with the economic growth of a particular country, the production of paper products are expected to increase in the future, especially in the developing countries. The pulp and paper industry is capital, energy and pollution intensive; however, the profits from this industry are usually marginal. Therefore, many developing countries have avoided investment risks and have been importing the pulp and high quality paper products. Along with the rapid industrialization, the developing countries have been trying to increase their domestic productions to meet the higher share of national demands. Considering the competitiveness with the outside world, the energy consumption which is one of the major inputs to the pulp and paper industry has become an important issue in the developing countries. This section presents a comparative study of the pulp and paper industries of China, India, the Philippines and Sri Lanka. The production trends and the role of the industry are presented for each country. A comparison has been done in order to understand the major causes of inefficiency in energy use and pollution abatement in the industry. The possible improvements are identified and the potential for the introduction of energy efficient and environmentally sound technologies is assessed. 5.2 Overview of the industry
To have an overview of the pulp and paper industries of the countries under study, comparisons have been made on the role of the industry in each country, shares in industrial and total national energy consumption, production trends and number of mills and their capacities. 5.2.1 Role in the national economy
In 1993, the Chinese pulp and paper industry accounted for 1.54% of the total industrial sector’s gross output value. 5.2.2 Share in total energy consumption
In China, the pulp and paper industry is the largest energy consumer among all light industries. In 1992, the energy consumption of Chinese pulp and paper industry accounted for 3.25% and 1.74% of total industrial and national energy consumptions, respectively. In India, the pulp and paper industry is ranked as the sixth largest energy consumer in the country.
Cross Country Comparison of the Pulp and Paper Industry35
In 1992, the Philippines’ pulp and paper industry accounted for 8.45% of industrial sector’s energy consumption and 2.5% of total national energy consumption. 5.2.3 Production trends
Among the countries under this study, China ranked as the world’s third largest paper and paper board producer in 1992 after USA and Japan. The trends of pulp and paper and paper board productions are shown in Figure 5.1.
0
2
4
6
8
10
12
1980 1985 1990 1992
Mill
ion
Tons
China
India
Pulp Production
0
2
4
6
8
10
12
14
1980 1985 1990 1992
Milli
on T
ons
China
India
Paper & Paper Board Production
0
100
200
300
400
500
1980 1981 1982 1983 1984 1985 1986 1987 1988
Thou
sand
Ton
s
Philippines' Paper & Paper Board Production
0
5
10
15
20
25
30
1980 1990 1992
Thou
sand
Ton
s
Pulp
Paper Products
Sri Lankan Pulp and Paper & Paper Board Production
Figure 5.1 Production trends of pulp, paper & paper board The pulp and paper industry is growing very rapidly in China with an average growth rate in paper and paper board production of about 14% in the last decade, the highest value in the world. However, China is still importing pulp and paper products to meet the national demand. In 1992, net imported paper and paper board was 2.34 million tons and commercial pulp was 0.6 million tons. With low per capita consumption of 16.7 kg per year (world average per capital consumption is 45.3 kg per year), the demand and production of paper products are expected to increase in China.
36 Technology, Energy Efficiency and Environmental Externalities in the Pulp and Paper Industry
From Figure 5.1, it can be seen that Indian pulp and paper and paper board production had a significant increase in the last decade. The pulp production remained nearly constant from 1990 to 1992 while the paper products had been increasing along with the increase in imported commercial pulp. In Philippines, the production of paper and paper board was greatly fluctuating in the last decade and has been achieving significant growth since 1985. Sri Lankan paper industry has become more dependent on the imported commercial pulp. 5.2.4 Mills and their capacities
The average plant capacity of the pulp and paper industries in the countries under study are shown in Figure 5.2.
'000
Ton
s pe
r yea
r
0
5
10
15
20
25
30
China India Philippines Sri Lanka
2.5
10.166
15
25.5
Figure 5.2 Average plant capacity (paper and paper board production) At the end of 1992, there were 11,940 enterprises in Chinese pulp and paper industry. The pulp and paper board capacity of the biggest mill is 150,000 tons per year. The breakdown of the Chinese mill by annual plant capacity is given in Figure 5.3. Therefore, the small mills dominate in China, contributing to about 57% of the total production. In India, there are 325 mills, 26 integrated mills and 297 small paper mills in the pulp and paper industry. The number of small mills has been increasing more rapidly than the large mills so that average plant capacity has decreased from 12,222 tons of paper products in 1980 to 10,166 tons in 1992. With the increasing paper demand and shortage of forest based raw material, the Government of India has formulated a policy of promoting small mills based on straw and bagasse.
Cross Country Comparison of the Pulp and Paper Industry37
2%10%
88%
>30,000 10,000-30,000 <10,000
Figure 5.3 Breakdown of the Chinese pulp and paper mills by plant capacity (tons/year)
There are 32 mills in operation in the Philippines. These are 26 non-integrated paper mills, 2 integrated pulp and paper mills and 4 purely pulp manufacturers. There are two pulp and paper mills in Sri Lanka. However, as the sections of the older plants have become unavailable for production, the total installed capacity has been decreasing and only one mill was effectively in operation in 1992. The capacity utilization factors of the pulp and paper industries in the countries under this study are given in Figure 5.4. In China and the Philippines, the installed capacities are fully utilized and the Indian pulp and paper industry has low capacity utilization factor due to older equipment.
110.45
67.7
96.64
0
20
40
60
80
100
120
China India Philippines
%
Figure 5.4 Capacity utilization factor (paper and paper board)
38 Technology, Energy Efficiency and Environmental Externalities in the Pulp and Paper Industry
5.3 Characteristics of the Parameters Affecting Energy Efficiency
The specific energy consumption of the pulp and paper industry depends on the following: - Raw material mix - Share of imported pulp - Pulping process mix - Share of waste-paper pulp - Level of black liquor recovery - Share of cogenerated electricity - Product mix, etc.
The overall specific energy consumption of the pulp and paper industries of the selected countries and world average are given in Figure 5.5.
GJ/
Ton
of P
aper
Pro
duct
s
0
10
20
30
40
50
60
70
80
China India Philippines Japan WorldAverage
Figure 5.5 Specific energy consumption of the pulp and paper industry It can be seen that the specific energy consumption of Indian pulp and paper industry is significantly too high. In comparison with Japan, the Chinese pulp and paper industry consumes more than double the energy to produce the same amount of paper products. The low specific energy consumption of the industry in the Philippines is due to the high share of imported pulp. The trends of specific energy consumption in China and India are given in Figure 5.6. One can observe a gradual reduction of specific energy consumption of the order of 5.33% in China in the last decade. However, the specific energy consumption of Indian pulp and paper industry did not reduce significantly in the last decade; it has only started decreasing since 1990. In order to understand the major causes of the inefficiency in energy use, some parameters affecting the energy efficiency are compared in this section.
Cross Country Comparison of the Pulp and Paper Industry39
GJ/
Ton
of P
aper
Pro
duct
s
0
10
20
30
40
50
60
70
80
90
1980 1981 1984 1985 1990 1992
ChinaIndia
Figure 5.6 Trends of specific energy consumption in China and India
5.3.1 Raw material mix
The major difference between the developing countries and the industrialized countries in raw material mix is the share of wood pulp in paper making. The share of wood pulp in national total is given in Figure 5.7. The higher the share of wood pulp, the lower is the overall specific energy consumption of the pulp and paper industry. In China, straw-material-made pulp holds a dominant share in the mix, accounting for 63% of the total pulp. In India, bamboo pulp accounted for 43.42% and bagasse and straw pulp together had a share of 33.38% of the total pulp produced. 5.3.2 Level of waste paper utilization
Greater level of waste paper utilization in pulping leads to resources conservation, energy saving and environmental protection. Developing countries however tend to use lower percentage of waste paper in comparison with the developed countries. The level of waste paper utilization is shown in Figure 5.8 for selected countries. This is found to be quite low in China and India, leading to the higher specific energy consumption of the industry. 5.3.3 Energy consumption by type
The breakdown of specific energy consumption by type is given in Table 5.1. The major steam consumers in the pulp and paper industry are digesters and dryers. It can be seen in this table that the specific steam consumption of Indian pulp and paper mills is too high, reflecting the inefficiency of digesters and dryers. The higher steam consumption in digesters is due to the non-wood pulping. The high electricity consumption can be reduced by replacing/modifying outdated paper-making machines which are the major electricity consumers.
40 Technology, Energy Efficiency and Environmental Externalities in the Pulp and Paper Industry
23.9 23.2
47.63
23.03
95.199.3 99.1
0
20
40
60
80
100
China India Philippines Sri Lanka Japan US France
% o
f Tot
al P
ulp
Figure 5.7 Share of wood pulp in selected countries
22.5
29
51.2 52.5750 48
0
10
20
30
40
50
60
China Philippines Japan
% o
f Tot
al P
ulp
* % of total installed capacity
Figure 5.8 Level of waste paper utilization
Table 5.1 Specific energy consumption by type
China India Philippines Developed Countries
Steam Consumption (Tons/ton paper) N/A 10-16 6-7 4-6.5 Electricity Consumption (kWh/ton Paper) 1100-1800 1200-1700 1000-1100 500-1100
5.3.4
5.3.5 Awareness about energy conservation
With increasing energy cost and international competitiveness, some energy conservation measures that have been undertaken in the selected countries are summarized in Table 5.2.
Cross Country Comparison of the Pulp and Paper Industry41
Table 5.2 Energy conservation measures undertaken in different countries
Country Energy Conservation Measures China - Holding energy management training workshops
- Improving efficiency of boilers and condensate recovery - Enhancing thermal insulation performance - Popularizing energy saving electrical appliances - Increasing level of chemicals recovery - Conversion of cylindrical to Fourdrinier paper machines - Conversion of batch to continuous digesters - Installation of on-line moisture monitoring and control systems - Installation of efficient press - Installation of jump-proof energy-saving pumps - Employment of heat pump in dryer section - Enhancing black liquor recovery - Installation of computer-controlled cooking - Practicing cogeneration
India - Installation of condensate recovery systems - Conversion of batch to continuous digesters - Conversion of cylindrical to Fourdrinier paper machines - Enhancing chemical recovery - Installation of falling film type evaporators - Employing process automation - Replacement of disc chippers by drum chippers - Conversion of pneumatic conveyors to mechanical types - Conversion of spreader stoker to fluidized bed combustion boilers
Philippines - Installation of computerized moisture control system - Taking energy audits - Installation of cogeneration systems - Power factor improvements
Therefore, it can be seen that some advanced energy efficient technologies have been already installed in the developing countries. However, the dissemination rate of these technologies is very limited in comparison with the industrialized countries. 5.4 Characteristics of the parameters affecting pollution abatement measures
There is great potential for resources recovery in this industry through pollution abatement measures. But less attention was paid in this direction mainly due to limited dissemination of those technologies and high capital share for the industry which is categorized as small scale in these developing countries. However, some local environmental regulations and public awareness due to growing industrialization in the region has forced the industries to introduce some pollution
42 Technology, Energy Efficiency and Environmental Externalities in the Pulp and Paper Industry
abatement programs. The obsolete machinery and technologies generally in use in this region further weaken the already deteriorated environment. The type and quantity of pollutants produced vary from industry to industry depending on the process employed. 5.4.1 Causes of pollution
The causes of pollution from pulp and paper industries in the countries studied are attributed to the following:
- Type of raw material in use (predominantly agro-residue based industry) - Type of fuel in use to meet energy demand - Obsolete technology and machinery in use - Lower production capacities of the mills, using inferior technical equipment - No strict enforcement of environmental regulations - thinking that it is an extra expenditure without any return - A marginal profit making industry
As shown in the Figure 5.7, the share of wood pulp in the countries under study is about one fourth of the production except in the Philippines where it is nearly 50%. But in developed countries the share is almost 100% which implies that more research and development are under way to eliminate pollution problem by wood pulping. The agro-residue based raw materials cause more pollution problems than the wood. In India, China and Sri Lanka straw dominates the share of the raw material for pulping. Among all the non-woody raw materials, straw poses the most serious environmental pollution problem because of the difficulties in chemical recovery from black liquor due to its high silica content. The use of waste paper as raw material reduces both energy consumption and pollution problems. As seen in Figure 5.8 the utilization levels of waste paper in Sri Lanka and Philippines are the same as the industrialized countries (about 50% of the pulp production), whereas it is only 25% of total pulp production in India and China. 5.4.2 Current water pollution control strategies
As pulp and paper is a serious water polluting industry, some measures are under way to abate pollution problems whose potential for improvements is very high. Current practices to abate water pollution in these countries are reported as below. 5.4.2.1 In China
During the period of 1980 to 1988 - BOD discharge decreased by 33% - Suspended solids decreased by 36% - Alkali recovery increase at the rate of 5.3%
These reductions were achieved by
- Integrated exploitation of digested wastewater
Cross Country Comparison of the Pulp and Paper Industry43
- White water recycling - Fiber recovery - Alkali recovery
However those developments are mainly reported for the large and medium scale pulp and paper industries. In 1990, alkali recovery rate in the wood pulp mills is reported as more than 60% whereas the recovery rate in straw pulp mill is around 6%. This should be mainly because of the high silica content in the black liquor of rice straw for which there have been limited technological developments. In 1989 - 1990:
- 13% of the total discharged wastewater met the local regulatory standards - for the first time a regulation was set up for wastewater disposal - no regulation related to air pollution existed - average alkali recovery percentage 34% - average alkali recovery rate in large scale enterprise was 80 -90% - average alkali recovery rate in medium scale enterprise was 75 - 80% - wastewater treated and recycling ratio was 30 - 50%
5.4.2.2 In India
- small mills generate more pollutants due to the absence of chemical recovery system - Production process control to reduce wastewater volume and pollutants - Wastewater treatment technologies to reduce the pollution strength - Use of oxygen and peroxide as bleaching agents - Chemical recovery
During the period of 1985 to 1993
- Alkali recovery per year increased from 285,000 to 455,000 tons - Wastewater treated and recycled per year increased from 1520 to 520 million m3 - Material recovery and recycling per year increased from 1,520,000 to 2,550,000 tons
5.4.2.3 In Philippines
- Most of the old mills only have filters for fiber recovery - Chemical recovery is practiced to certain extent
In Sri Lanka, of the only two pulp and paper mills, one has no chemical recovery facilities. Though the second plant has the facility, it was never commissioned because of the higher silica content in the black liquor. As a remedial measure, raw material for pulping was changed to waste paper from rice straw.
44 Technology, Energy Efficiency and Environmental Externalities in the Pulp and Paper Industry
5.4.3 Current air pollution control strategies
The major sources of air pollution are burning of fuels for power generation and dedusting of raw materials. Since air pollution in this industry is not serious as water pollution, much less attention is paid in this area. To give an example, no air emission regulations were enacted in China until 1990. But in India, the air pollution act was enacted in 1981; cyclones and Electrostatic precipitators are mainly used as air pollution control equipment whose share of 20% in 1960 increased to 60% in 1992. 5.4.4 Current solid waste control strategies
In all these countries, solid wastes generated from the process itself and secondary wastes derived from pollution control measures such as dust collection equipment and wastewater treatment, are dumped at landfill sites without any pretreatment. In some plants the solid waste which can be used as fuel is recycled to replace the boiler fuels. 5.4.5 Comparison of effluent and emission characteristics
In general, the information provided in the country reports are quite diverse and use different basis. As some of them are given for per ton production basis whereas others in ambient standards, it is not possible to make any comparison in some cases. For the purpose of comparison it is preferable to have the amount of pollutant released per ton of product than in ambient standards. It is mainly because the allowable limit of pollutant discharge to the surrounding in different countries depends on the geographical location, climatic condition and overall intensity of pollutants released from all other sources. A comparison of fresh water consumption, quantity and characteristics of wastewater with German standards is presented in Table 5.3. Even though a number of parameters are tabulated, most of them cannot be compared due to the limitation of data availability. Also, as seen from Table 5.3, no data are available for the Philippines and Sri Lanka, may be due to the minor share of these industries in their national economy. A similar comparison for air emission are shown in Table 5.4. As said earlier the comparison was not possible in most of the cases because of non-availability of data from any of the countries under study. It implies that none of the countries pays any attention to air pollution abatement.
Cross Country Comparison of the Pulp and Paper Industry45
Table 5.3 Quantity and characteristics of wastewater released
Parameters Germany * China India Philippines
Sri Lanka
Water consumption (ton/ton bleached pulp produced) (ton/ton paper produced)
70 - 130
220
30
Wastewater discharged (ton/ton bleached pulp produced) (ton/ton paper produced)
7 - 12
70-380**
PH Suspended solids (mg/l) 50 151*** 10*** Settleable solids (ml/l) DS (mg/l) BOD5 (kg/ton pulp) (kg/ton paper)
5 1-6
10-270
COD (kg/ton pulp) (kg/ton paper)
70 3-12
150
50-1100** 5
Oil and Grease (mg/l) Total N (mg/l) Wastewater reuse rate (%) 68.6 90-95 Treatment rate of wastewater (%) Proportion reaching discharge standards (%)
Hydro carbons (kg/ton pulp) (kg/ton paper)
1.0 0.01-0.04
* The German regulatory standard; BOD & COD based on 24 hour sample ** Depending on the raw material; waste paper lowest & rice straw etc. high *** in kg/ton paper
Table 5.4 Quantity and characteristics of air pollutants released
Parameters Germany
China* India
Philippines
Sri Lanka
Dust discharged (TSP) (mg/m3) 30 260,000 SO2 (mg/m3) 100 270,000 NOx (mg/m3) 500 CO (mg/m3) 100 Organics (mg/m3) Treatment rate of waste gas (%) Rate of treated waste gas discharged which meet standards (%)
* in tons
46 Technology, Energy Efficiency and Environmental Externalities in the Pulp and Paper Industry
5.5 Potential for Energy Efficiency Improvement
5.5.1 Structure of the industry
One of the major reasons for the high specific energy consumption in China and India is the small scale of the mills. Taking macro economic consideration into account, the expansion of small mills based on non-wood materials might be suitable for some countries. In such a case, the expansion of small mills should be planned ensuring that they incorporate energy efficient technologies and chemical recovery systems. In the case of India, the capital utilization factor is too low, therefore, closure of inefficient small mills would improve the overall energy efficiency of the industry. Finally, the future expansion of the industry should be based on the large-scale mills so that cogeneration facilities and thermal upgrading systems can be employed economically. 5.5.2 Raw materials
The specific energy consumption of the pulp and paper industry can be reduced by increasing the share of wood pulp. However, this is a question of macro economics and the concern for the preservation of forest resources. The current level of waste paper recycling in the developing countries is lower than that in industrialized countries. Therefore, increasing the share of recycled paper could improve the overall energy efficiency of the industry. 5.5.3 Potential for energy conservation
The potential for major energy conservation in the countries under this study is summarized in Table 5.5. 5.6 Potential for pollution abatement
Use of non-wood raw materials are identified as one of the major source of pollutant in this region. Due to the economic level and availability of non-wood raw material in plenty, it is impossible to eliminate its use. Since in developed countries wood covers almost all the raw material requirements, the developing countries which use non-wood products as raw material must have their own research and development facilities to develop environmentally sound technologies. As a serious water polluting industry, its future expansion in this region should be well planned to abate pollution load on the environment. As seen earlier, the pollution abatement measures in these countries are in their infancy. So as a first step, records should be maintained about pollution loads and water consumption.
Cross Country Comparison of the Pulp and Paper Industry47
Table 5.5 Potential for energy conservation#
Energy Conservation Measures China India Philippines Sri Lanka
Short Term Measures - Management practices - Boiler efficiency improvement - Insulation improvement - Power factor improvement
** ****1 *** ***
**** ***2 **** ****
**** *** **** ***
**** *** *** ***
Medium Term Measures - Chemical recovery - Condensate recovery - Cogeneration - Methanogenesis - Conversion of batch to continuous digesters - Mechanical vapor compression of black liquor - Vacuum pump installation - Installation of efficient press - Heat pump hot water system - Flash steam recovery in dryers - Process automation
***3
*** ***5 **** **** **** **** ****7
**** **** ****
****4
**** ****6 **** **** **** **** ****8
**** **** ***9
*** **** **** **** *** *** **** **** **** **** ****
*** *** *** **** *** *** **** **** **** **** ****
Long Term Measures - Interconnected factories (with sugar mills) - Excess power generation - Adaptation of new pulping processes - Computerization
*** **** **** ****
**** **** **** ****
** **** *** ****
- **** *** ****
# For each energy conservation measure, the relative scope of application is shown by the number of asterisks. For instance, the measure of connecting with sugar mills has a higher scope in India, where the share of bagasse-pulp is significant, than in China where straw-pulp is more important.
1 Most of the Chinese mills have boiler efficiencies below 60% 2 Boiler efficiency in small mills is 50-60%, however, most of the medium and large mills
employ fluidized boilers with an efficiency of 70-80% 3 Alkali recovery rate in China was 36.66% of total consumption in 1988 4 Nearly all agro-based paper mills have no chemical recovery system 5 Almost all mills have cogeneration systems but they could meet only 10.5% of electricity
demand 6 Only 40% of Indian large mills have cogeneration facilities 7 Dryness of wet paper from paper machine is about 30% in China 8 Dryness of wet paper from paper machine is 35-38% (50% in developed countries) 9 About 25% of Indian mills have installed electronic automation systems
48 Technology, Energy Efficiency and Environmental Externalities in the Pulp and Paper Industry
The source reduction and waste minimization measures rather than end of pipe treatment not only lead to cost saving in waste treatment but also save the depleting natural resources. Recovering and recycling of fibers seems to be the most promising of all the measures. Larger the mill, lesser is the specific treatment cost, both in terms of capital as well as operation and maintenance costs. But due to the nature of the industry and availability of raw materials, it is difficult to control the growth of the small scale industries in this region. Therefore, the optimum level of mill capacity should be estimated on the basis of various considerations to plan the future expansion of the industry. The potentials for major pollution abatement options based on the available technologies are summarized in the Table 5.6.
Table 5.6 Potentials for pollution abatement measures #
Pollution Abatement Measures China India Philippines Sri Lanka Short Term Measures - Management practices - Good house keeping - Operating at optimized parameters - Full capacity utilization - Prevention of leakage, spills, overflows et. - Resource recovery and recycling - Improving water recycle utilization ratio (e.g. white
water recycling for washing of pulp) - Implementation of environmental regulations
strictly
*** *** *** *** *** ***
****
***
**** *** *** *** *** ***
****
***
**** *** *** *** *** ***
****
***
**** *** *** *** *** ***
****
***
Medium Term Measures - Improved chemical recovery - Substitution for Chlorine with ozone, oxygen and
hydrogen peroxide in bleaching - Increased rate of waste paper utilization - Removal of silica before evaporation process (for
rice straw) - Efficient air pollution control equipment - Advance wastewater treatment
***
*** ****
**** **** ****
***
*** ****
**** *** ****
*****
**** ***
*** **** ****
****
**** ***
**** **** ****
Long Term Measures - Prohibiting new small scale mill development
wherever possible - Process monitoring and control by expert system
****
****
****
****
***
****
***
****
# For each pollution abatement measure, the relative scope of application is shown by number of asterisks as in Table 5.5.
Cross Country Comparison of the Pulp and Paper Industry49
5.7 Conclusion
The energy saving potential in the pulp and paper industry for the European Community as a whole was estimated as 20-30% of the current energy consumed. Therefore, the potential of energy saving in the developing countries where outdated technologies dominate, could be substantially higher. Since the industry generates waste materials which can be used as fuel, self-power generation in cogeneration mode could be one of the most promising measures to improve the overall energy efficiency of the industry. Major energy savings could also accrue from the application of thermal upgrading systems. The pulp and paper industry is a favorable candidate for excess power generation and supply to the grid. Therefore, encouragement from the governmental institutions by means of regulations and incentives would not only improve the energy efficiency of the industry but also be economically beneficial to the country. To achieve better energy efficiency in the pulp and paper industry, the type of useful support the government institutions can extend are setting target for dissemination of each promising energy efficient technology, spreading knowledge about new technologies, organizing energy conferences and workshops, and encouraging research and development activities. Energy efficient and environmentally sound pulping processes have been mainly developed for wood pulp which currently accounts for 90% of the world’s pulp. Therefore, for countries like China and India where non-wood pulps dominate, it is necessary to carry out research work on energy efficient and environmentally sound pulping for non-wood materials. For countries where limited or no energy conservation measures have been undertaken, installation of measuring equipment in the processes and data acquisition could help to plan and take actions in improving energy efficiency and reducing pollution from the industry. As this industry is an important water polluter, serious consideration should be given to recycle and reuse the water within the plant as much as possible. Due to the chemical content of pulp washing water, it is toxic for aquatic lives; therefore improved chemical recovery methods should be practiced to recover as much chemicals as possible, which does not only reduce the pollution load but also the amount of chemical required for the process. Burning fuels for power generation and in the boilers is a source of air pollution. Any measure taken for energy efficiency improvement ultimately leads to reduction in air pollution loads.
50 Technology, Energy Efficiency and Environmental Externalities in the Pulp and Paper Industry
6. PROFILE OF THE PULP AND PAPER INDUSTRY IN SELECTED ASIAN COUNTRIES
This section evaluates the current status and technological trajectory of the pulp and paper industry in four Asian countries, namely China, India, the Philippines and Sri Lanka. 6.1 COUNTRY REPORT: CHINA
6.1.1 Introduction
The pulp and paper industry is one of the most energy-intensive and polluting industries in China. In 1993, it accounted for 9.8% of the total industrial waste water discharge and 38.2% of the total BOD discharge from the industrial sector. Serious environmental pollution becomes increasingly unacceptable as it harms the health of local residents and destroys the local ecology. The Chinese government has been trying to tighten environmental regulations in order to reduce the pollution level from paper mills. Implementation of these regulations, however, has encountered numerous difficulties due to the complexities of the industry. Low energy efficiency and high environmental pollution from the pulp and paper industry are not only caused by the backwardness of technological facilities, they are also consequences of the industry’s organization in terms of plant distribution and ownership. Problems in the industry should therefore by analyzed in a systematic manner to take into consideration various interactive factors that determine energy efficiency and environmental pollution. The objective of this section is to find out the determining factors and major causes of environmental pollution in the pulp and paper industry. In what follows, an analysis of the evolution of energy efficiency and environmental pollution in relation to its technological evolution is presented. Firstly, the technological trajectory of the pulp and paper industry is laid out, and secondly, an analysis of the evolution of energy efficiency and assessment of the environmental externalities is done. Then the potential for energy efficiency improvement and pollution abatement through technological changes is analyzed. Finally, the status of the application of new technologies is presented and some recommendations for further studies are proposed. 6.1.1.1 Evolution of China’s pulp and paper industry
It is well known that the ancient paper making technology was one of the four famous ancient inventions of China. It is also acknowledged that China's ancient paper making technology had played a great role in the global paper making industry, and in the progress and dissemination of human science and culture across countries in the history of human development.
Profile of the Pulp and Paper Industry in Selected Asian Countries 51
The sole process used in the pulp and paper mills in China, however, was the simple manual operation method. Not until 1884, when Shanghai Huazhang Paper Mill was put into operation in East China, was the machine-made paper production technology introduced. The technology was invented in Europe in the year 1799. The country’s pulp and paper industry developed slowly due to various internal as well as external reasons. By 1949, the national machine-made paper and paperboard production was only 108 thousand tons compared to the manual production of 120 thousand tons. Generally, the features of Old China's paper making industry can be summarized as follows:
- From the point of view of paper making, manually operated paper production accounted for two thirds, while machine-made paper production accounted for only one-third of the total paper output.
- From the point of view of paper consumption, domestic mechanical paper production
met just less than one third of the national demand. The rest was met by imports. - As for the local distribution of the industry across China, mechanized paper making
plants were found mainly in a few coastal provinces, while manually operated paper making mills were located mainly in several southern provinces abundant in bamboo resources.
- As far as mechanical paper making technology is concerned, most key machine
components needed for the industry were imported from abroad because of the severe lack of industrial infrastructure.
6.1.1.2 Major achievements in China’s pulp and paper industry
Since P.R. China was founded in 1949, a drastic change has occurred in its booming pulp and paper industry. By the year 1992, China's pulp production, paper & paperboard production and national paper & paperboard consumption ranked third in the world, after USA and Japan. China's current pulp and paper industry has developed since 1952, when its total mechanical paper & paperboard output was only 372,000 tons, to 17.25 million tons by the year 1992 with a consistent annual growth rate of 10%. Particularly during the last decade, the average growth of paper & paperboard production reached 14%, a high value in the history of world paper industry. Its gross output in 1993 reached 61.12 billion Yuan, or 1.54% of the total industry gross output value. Its net output of 15.1 billion Yuan accounted for 1.18% of the national industry value. Table 6.1.1 shows the contribution of China's pulp, paper & paperboard production to the world total. Table 6.1.2 gives the situation of paper production and consumption in the world and in the country as well.
52 Technology, Energy Efficiency and Environmental Externalities in the Pulp and Paper Industry
Table 6.1.1 Status of China's mechanical pulp, paper & paperboard productions
Year 1985 1986 1987 1988 1989 1990 Share of pulp production in the world output, %
4.5 4.5 4.8 5.2 5.68 5.91
Ranked position worldwide 7 7 7 7 6 5 Share of the world paper & paperboard production, %
4.7 4.9 5.3 5.6 5.70 5.75
Ranked position worldwide 6 5 4 4 4 4 Sources: [1,2,3,10]
Table 6.1.2 Global paper industry production and consumption in 1990
Item Number of Factories
Production capacity (103 ton)
Per capita consumption
(kg)
Superficial consumption
(103 ton)
Production (103 ton)
(1) (2) (1) (2) (1) (2) (1) (2)
China 250* 176* 15500 11000 12.6 14429 9838 13719 9500 World 4372 1352 266253 183503 44.8 237107 160577 238781 160649China’s share in the world (%)
5.7 13 5.8 6.0 ~6.09 5.98 ~ 6.13
5.70 ~ 5.75
5.91
Notes: (1) Paper & paperboard; (2) Pulp * The factories counted here refer only to those with a capacity of more than 30,000 ton/year. Source: [10]
Figures 6.1.1 and 6.1.2 show China's pulp, paper & paperboard production. Though a considerable achievement has been made in China's Pulp & Paper Industry since 1949, there still exists a strong impetus to boost China's pulp & paper industry to meet its immense market demand for paper consumption by more than 1.2 billion people. It can be seen from Table 6.1.2 that the 1990 average paper & paperboard consumption per capita in China was still only a quarter of world average level. China's paper & paperboard consumption accounted only for 6% of the world’s total volume, while its population accounted for some 20% of the global population. In 1992, net imports of paper & paperboard reached 2.34 million tons, and imported commercial pulp also reached 600,000 ton to fill the gap between domestic production and demand. Self-sufficiency rate for paper demand has decreased recently in line with China's escalating economic development. It is predicted by other relevant research that China’s economy will maintain current aggressive growth trend in a foreseeable period. By the turn of the century, its growth rate will be maintained at 7-9%. According to a synchronous growth principle of paper & paperboard consumption with GDP, the growth rate of domestic paper demand will also be maintained at 7-9%. This means that the market demand for paper in 2000 will reach 331 million tons.
Profile of the Pulp and Paper Industry in Selected Asian Countries 53
0
200
400
600
800
1000
1200
1400
1600
1800
1940 1950 1960 1970 1980 1990 2000
Prod
uctio
n 10
,000
tonn
e
totalmanualmechanical
Figure 6.1.1 Production of paper & paperboard in China since 1949
Prod
uctio
n 10
,000
tonn
e
0
100
200
300
400
500
600
700
800
900
1000
1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 Figure 6.1.2 Machine-made pulp production in China since 1949
54 Technology, Energy Efficiency and Environmental Externalities in the Pulp and Paper Industry
Though paper & paperboard consumption of China was at number 3 in the world in 1992, its average consumption per capita was only 16.7 kg per person, or less than one half of the world average value of 45.3 kg per person. If this indicator for China is to reach one half of the world average level by 2000, a production increment of more than 10 million tons from 1992's 17.25 million tons will then be required. Considering therefore the impossibility of too much dependence on imports to meet the domestic paper market demand, China’s pulp and paper industry in the foreseeable future calls for a fast and sustainable development. 6.1.2 Technological trajectory of China’s paper industry
6.1.2.1 Pulp and paper production and development
In 1949, machine-made paper output accounted only for 47% of total volume. By 1985, the share of mechanical paper to the total output rose to 97.9%. Manually operated paper production (less than 366,000 tons, the peak volume in 1932) is reserved for some special kinds of traditional papers such as the most famous Xuanzi. Figure 6.1.3 illustrates the evolution of China's mechanical paper making capability.
Prod
uctio
n C
apac
ity m
illio
n to
n
0
2
4
6
8
10
12
14
16
18
20
1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 Figure 6.1.3 Production capacities of China's paper & paperboard
Profile of the Pulp and Paper Industry in Selected Asian Countries 55
Before 1949, the types of mechanical papers were only several dozens, with some common kinds for printing, writing, packaging, etc. The key reason for this was the severe lack of mechanical manufacturing capability. Along with the rapid growth of mechanical pulp and paper production capacity, the number of types of various paper & paperboard has also increased to a great extent. Within the first five-year planning period, for instance, newly-added types of paper reached 79, including paper sack, condenser paper, blue print base paper, pictorial paper, fax paper, etc. By the end of 1985, the total number of paper & paperboard products in China increased to more than five hundred, a number which could meet all sectoral basic demands. The types of pulp also increased simultaneously with the increased demand for diverse kinds of paper products during the same period. The share of various paper & paperboard products in China in 1992 is shown in Table 6.1.3.
Table 6.1.3 Composition of types of paper and paperboard in China in 1992
Type Press & printing
Writing paper
Packing paper
Industrial paper
Paperboard Living &
other Share(%) 25 10.6 11 3.0 42 8.4
The quality of the different paper & paperboard products has also been improving gradually. By 1985, six products were honored as the State Golden Quality Products, 46 products as State Silver Quality Products and other 176 products as Light Industry Excellent Quality Products. For example, a paper for computer use made by the Shandong Paper Mill General, is regarded to be of good quality from all major technical performance indicators, and is reckoned to catch up with and/or exceed international levels of paper of the same kind. Another example is the Chinese-made toilet papers which held a 90% share of the market in the Hong Kong area in 1986. The much increased number of product types as well as the much improved quality of paper product embody the rise of the technical level in the Chinese paper industry. 6.1.2.2 Development of pulp & paper enterprises
In the context of China, pulp and paper mills can be classified into three categories in terms of their capacity of production: large mills with a capacity of more than 30,000 tons/year; medium size mills with a capacity of 10,000 to 30,000 tons/year; and small mills with a capacity of less then 10,000 tons/year. In 1949, there were only little more than 100 mills across the country. By the end of 1992, however, the number of paper mills increased to more than 9,000 [13]. From Chinese statistics [11], the number of total enterprises was 11,940. The production of the biggest scale paper mill increased from 30,000 to more than 150,000 tons/year. Among them, 1665 paper mills belonged to the China Light Industry Commission (CLIC, i.e., the former Light Industry Ministry of China)
56 Technology, Energy Efficiency and Environmental Externalities in the Pulp and Paper Industry
with an average enterprise scale of around 4700 tons/year. The other mills belonged to the agriculture, forest or rural township systems with an average enterprise scale of only 1842 tons/year. Thus, the national average paper mill capacity was only about 2500 tons/year. In comparison, the average pulp mill capacity in some industrialized countries is 170,000 tons/year, with the average output being 61 thousand tons per unit paper and paperboard mill. The large number of dispersed paper making enterprises with smaller capacities is considered to be the main reason for bad scale-benefit, low management level, lagging behind technical level as well as severe environmental pollution. In most cases, China’s paper enterprises are integrated pulp and paper mills, while those which solely produce commercial pulp number a few. Only a minority of paper mills located in urban areas use commercial pulp or waste paper for production.
2%10%
88%
large scale medium scale small scale
28%
57% 15%
large scale medium scale small scale
Figure 6.1.4 Composition of paper mills and their contribution to the total production Not all paper enterprises belong to the China Light Industry Commission (CLIC) or the professional management ministry for light industrial products such as paper, sugar, glass, wine, etc. The agricultural sector (including rural township and reclamation systems), forest sector and military systems have their own paper mills. In township paper mills, the dominant process is either the lime-based yellow strawboard production or packaging-paper production by recovery of waste paper. Most mills belonging to the forest system mainly use timber materials to produce unbleached pulp and/or paperboard. Those belonging to the agricultural reclamation and military systems are usually straw-based integrated mills. This complex mix creates a barrier for the professional management of the pulp and paper industry.
Profile of the Pulp and Paper Industry in Selected Asian Countries 57
6.1.2.3 Technological progress in China’s pulp and paper industry
a. Technological events
In the course of the paper industry’s technological development, two aspects were equally focused and combined. One, it deeply depended on domestic R&D capability and diffusion of domestic advanced experiences and technologies. Second, much efforts were placed on introducing foreign advanced technologies and equipment as well as learning and digesting internationally advanced expertise. Some important milestones in the progress of the paper making technology in China can be briefly depicted as follows:
- During the 1950s, a series of Fourdrinier paper machines and auxiliary facilities, each with a capacity of 50 tons/day, were designed and manufactured by domestic R&D experts for some key expansion projects.
- In 1957, the first ejection furnace made in China for alkali recovery was installed in
Jiamusi Paper Mill. - In the meantime, some large capacity paper making machines of 100, 150, or 200
tons/day capacity were imported. Log-milling machines of international standards were also imported.
- Around 1970, some key imported foreign equipment included continuous digester of
straw pulp, pressurized pulp bleaching machines, ejection furnaces for alkali recovery, 150 tons/day heat wood-chip milling machines, etc.
- Some domestically developed technologies, such as on-line moisture control system,
paper fold-pressing technology & mill pulp making were popularized in national paper mills.
- Alkali recovery capability from pulp making black liquor increased from a trifle in 1957
to 362,200 ton/year in 1988 or 36.66% of the total alkali consumption for the year. In Qingzhou Paper Mill, Nanping Paper Mill and Jiamusi Paper Mill, production-needed alkali can approximately be provided by their alkali recovery systems. Electrostatic precipitators were also disseminated to large and medium size paper mills, which proved beneficial both for alkali recovery and for dust prevention. Figure 6.1.5 illustrates the growth curve of alkali recovery from 1979.
- The capability of integrated exploitation of sulfite pulp wastewater for production of
some by-products was also boosted
58 Technology, Energy Efficiency and Environmental Externalities in the Pulp and Paper Industry
- Since 1968, the new process of utilizing ammonium bisulfite straw pulp has been popularized in many small paper mills in Shandong, Sichuan and other provinces. Using this process, wastewater can be directly used for farm irrigation.
- Since 1978, new systems for loop or cycle utilization of clean water in paper mills were
created, e.g. tilt-plate precipitating method in Tianjing Paper Mill, tilt-tube precipitating method in Shanghai Vanguard Paper Mill, and air buoyancy method in Suzhou Huashen Paper Mill.
Year
1000
ton
0
50
100
150
200
250
300
350
400
1979 1980 1982 1984 1986 1988
CapacityProduction
Figure 6.1.5 Growth curves of alkali recovery from 1979 to 1988
b. Technological advances with imported foreign technologies, facilities and equipment
Since the early 1980s, the scale of technology import has been increasing step by step so as to narrow the technical gap between the paper industry of China and the developed countries. From 1980 to 1988, about US$ 300 million had been spent to update the pulp and papermaking technologies and equipment in the country. It is also estimated that more than US$ 1 billion had been spent for importing technologies and equipment from 1989 to 1995. The technology processes adopted together with the import of equipment are listed below:
- Technological transformation, upgrading and/or overhauling in some state-owned key enterprises: 150 t/d paper machine transformation at the Qinzhou Paper Mill, combined with the installation of advanced equipment from Beloit Corp. (the project proved to be very successful and brought about 50% increment in production capacity, better quality of paper sack product and new type of elastic paper sack); 200 t/d paper machine transformation at the Jiamusi Paper Mill; 100 t/d paper machine transformations at the
Profile of the Pulp and Paper Industry in Selected Asian Countries 59
Yueyang and Liujiang Paper Mills; and Nanpin No. 1 paper machine transformations which was a typical case of optimum adoption of imported equipment to match with the local situation.
- Installation of new and advanced technology and equipment, including exhausted heat
recovery equipment from Sweden for a 150 t/d TMP production line at Jilin Pulp & Paper Mill, enabling it to produce CTMP and make newsprint paper; 60 t/d sulfofication CMP line imported from Finland at the Shiyan Pulp and Paper Mill; horizontal continuous digesters of Sunds Defibration Corp. of Sweden installed at Jiaozuo, Dezhou, Fuzhou and Jihe, etc.; the first set of Swedish Kamyr’s Vertical Continuous Digester installed at Yibin Paper Mill; plank-style membrane vaporizer and concentrator from Finland Ahlstrom Corp. installed at the Jiamusi and Liujiang paper mills; white silt kiln imported from the same corporation for Jilin Paper Mill; horizontal belt-style vacuum washer for spent sulfite liquor (so-called red liquor) from English Black Clawson Corp. installed at Kaisan Pulp Mill and Guangzhou Paper Mill; de-inking equipment of the same corporation at Beijing’s No. 1 Paper Mill; nearly 50 sets of constant moisture-control systems for paper making from Measurex Corp. and Accupay Corp. of USA and Lippka Corp. of Germany, etc., which can stabilize paper moisture and paper mass; coated paper machine and coating material process line imported from France and Germany at Shanghai Jiangnan Pulp & Paper Mill. Besides the above-mentioned state-of-art technological equipment from the industrialized countries, a number of second-hand paper machines and paperboard machines were also purchased at costs of about one fifth to one tenth that of the brand-new ones.
c. Recent developments in the domestic production process and equipment
Some dominant home-developed technological advances since 1990 include:
- Large-size alkali recovery furnaces with capacities of 200 and 300 t/d have been built at Jiamusi and Jilin paper mills, respectively. Furthermore, a set of alkali recovery furnace with the biggest pulp-dealing capacity of 1000 t/d was exported to Indonesia.
- Small-size whole system equipment of 30 t/d CTMP capacity has been successfully
manufactured in Shanghai and put into operation in Fujian Province. - Several sets of locally made horizontal-tube continuous digester of 50 t/d straw pulp
making capacity have been made and put into operation in China, after importing and adapting relative technologies from Swedish Sunds Corp.
- New jam-proof energy-saving pump for pulp transport was designed successfully with an
energy conservation benefit of 20% compared to conventional pumps. These pumps
60 Technology, Energy Efficiency and Environmental Externalities in the Pulp and Paper Industry
were installed at a dozen paper mills, proving additional compact, low-noise and little oscillation features.
- Locally made new vacuum pulp washers with 35 m2 area were used at some newly built
paper projects. - As an advancement in the black liquor vaporization system, a whole set of plate-style
membrane vaporizer systems (with 50% higher efficiency than the old ones and bigger load) have been commissioned at the Qinzhou Pulp & Paper Mill.
- Small-size domestic-made waste paper disposing and de-inking systems have been put
into operation at Xingshi Paper Mill. - High intensity press and polyester dry net for replacement of conventional dry canvas in
the process of papermaking. - Heat pump systems for the paper machine’s dryer section were used at Minfen Pulp &
Paper Group, Tianjing Paper Mill and Qiqihar Pulp & Paper Mill. Their operations showed that specific steam consumptions per ton of paper were reduced by 29.4%, 28.3% and 36.6%, respectively. The heat pump-based technology can substitute conventional two- or three-stage cascade system, making full use of steam thermal energy and available energy to remove condensate smoothly.
During the last four decades, China’s researchers in the paper field have made many more achievements, including the development of new types of raw materials for pulp making, development of new types of paper & paperboard, retrofitting or improvement of pulping processes, R&D for some key equipment, integrated utilization of digested wastewater, development and utilization of emulsion materials, filling materials and other chemical agents in the paper producing processes, as well as some basic academic researches in universities and research institutes. As for wastewater pollution abatement, eight key achievements have also been made concerning chemical agents recovery, sulfite pulping wastewater integrated exploitation, bio-chemical treatment of pulping wastewater, etc. 6.1.2.4 Two prominent technological characteristics
In the mixes of pulp production, there exists an eminent characteristic for China's paper industry, i.e., straw-material-made pulp holds a dominant share in the mix (grass-straw pulp 63%), while wood pulp accounted for as low as 26% in the mix. It is well known that using wood as a pulping raw material is better than using straw from the point of view of pulp production efficiency, environmental protection, or from wood material's economical utilization. At present, wood material accounts for more than 90% of the global pulp production.
Profile of the Pulp and Paper Industry in Selected Asian Countries 61
Another problem existing in China’s paper industry is the very low level of waste paper recycling. In 1988, waste-paper pulp (including imported waste paper) accounted for 22.5% only, while the same indicators for Japan and European Union were 50% and 48%, respectively. A higher percentage of waste paper pulp in the total pulp production is beneficial for resource conservation, energy savings and environmental protection. Generally, China’s pulp & paper industry has made a great technological achievement, though some problems should be solved when facing the next century. 6.1.3 Evolution of energy efficiency in Chinese pulp & paper industry
6.1.3.1 General situation of energy consumption
The pulp & paper industry of China is the biggest energy consuming industry among all light industries. Table 6.1.4 shows the overall energy consumption of the industry, while Table 6.1.5 and Figure 6.1.6 show the unit energy consumption of its major products. Table 6.1.6 shows the unit energy consumption for 870 paper mills belonging to the CLIC from 1985 to 1990.
Table 6.1.4 Overall energy consumption by the industry from 1985 to 1992
Indicator Coal 10,000 ton
Electricity billion kWh
Total 10,000 toe
Year 1985 1990 1992 1985 1990 1992 1985 1990 1992Data 1251 1640 1787 8.09 11.98 13.97 847.5 1109 1240Share in national total %
1.53
1.55
1.57
1.96
1.92
1.84
1.69
2.13
1.74
Source: [11]
Table 6.1.5 Unit product energy consumption in the paper industry
Item Unit 1980 1985 1988 1989 1990 Electricity consumption for wood pulp
KWh/ton
1522 1588 1560 1566
SOE consumption for total pulp toe/ton 0.419 0.406 0.445 Electricity for newsprint KWh/to
n 556 565 568 583
SOE for paper & paperboard toe/ton 0.99 0.60 0.57 Integrated energy consumption toe/ton 1.257 0.910 0.805
Source: [6,12], both SOE and oe are standard oil equivalent
62 Technology, Energy Efficiency and Environmental Externalities in the Pulp and Paper Industry
Table 6.1.6 Specific energy consumption of major products for 870 paper mills of CLIC
Indicator Unit 1985 1988 1989 1990 Integrated specific energy consumption
toe/t 1.07 1.01 1.01
Mechanical wood pulp kWh/t 1522 1588 1560 1566 Newsprint kWh/t 556 565 568 583
Source: [1, 3] Though integrated unit energy consumption has decreased in recent years, the unit electricity consumption for mechanical wood pulp and newsprint increased on the contrary. For the same paper & paperboard products, specific energy consumption values of non-CLIC paper mills are generally higher than that of CLIC ones, except for the township case. The reason for the very low specific energy consumption of the latter is the low quality of its products and the simple, crude equipment being employed. Table 6.1.7 gives a comparison of the unit energy consumption of paper mills among various sectors.
0
0.5
1
1.5
2
2.5
1981 1984 1985 1990 1992
Year
ton
ce/to
n(pa
per &
pap
erbo
ard)
Figure 6.1.6 Integrated energy consumption of the paper industry in China
Table 6.1.7 Specific energy consumption by various owners (1990)
Item National CLIC Agricultural system Forest Military total Reclamation Township system system Production, Mt 13.72 7.71 0.38 5.23 0.10 0.30 Energy consumption (103 toe) 11086 7330 377 2982 99 299 Specific energy consumption of paper & paper board, toe/t
0.805
0.949
0.995
0.569
0.995
0.995
Source: [1]
Profile of the Pulp and Paper Industry in Selected Asian Countries 63
From 1985 to 1990, energy consumption per 10,000 Yuan gross output volume (in 1980 fixed price) of paper industry within CLIC system decreased from 3.93 toe/10,000 Yuan to 3.01 toe/10,000 Yuan. The energy consumption elasticity was 0.28, and the annual average energy saving rate was 5.33% during the period. It should be noted that the decrease of energy consumption cannot be fully attributed to direct energy conservation via technology or process advances. Two aspects can be highlighted for the decrease. One is the change in product mix and the emergence of new high value-added paper products. The other is the change in raw material mix, i.e., growth of imported commercial pulp and waste paper as secondary fibrous raw material. These two factors enable the paper industry to augment its production and output without any proportional increase in energy demand. 6.1.3.2 Major endeavors for the progress in energy efficiency
From the above tables and Figure 6.1.6, it can be seen that the integrated energy consumption indicator decreased by 42.7% from 1981 to 1992 with an average annual reduction rate of 5.2%. Therefore, much energy conservation was obtained throughout this period. The main causes can be attributed to the following:
- Enhancement of enterprise energy management from all aspects including setting up a national energy conservation network, holding energy management/saving training workshops, issuing rated energy consumption norms for special paper products in August 1985 (four grades for a paper product: Testing Norm, Average Advanced Norm, Domestic Professional Advanced Norm and International Advanced Norm).
- Retrofitting some old and low efficiency boilers, remolding a batch of oil-fired boilers
into coal-fired boilers (under the stringent oil energy supply situation) and improving technical skills of operators.
- Enhancement of thermal insulating performance of steam tubes and digester equipment. - Popularizing and disseminating some energy saving equipment such as Electric Loci
Vacuum Fans, Pan mills and double-paned mills, speed-adjustable electrical fans, electricity-saving appliances, etc..
- By 1991, more than sixty large scale pulp & paper mill cogeneration plants were installed
with a total power capacity of 473 MW. Of these, 422 MW capacity belonged to thirty key enterprises. For comparison, cogeneration capacity in 1949 was only 10 MW. In 1990, power generation by cogeneration plants amounted to 1.65 billion kWh. At the same time, newly-built large and/or medium scale paper mills had their own cogeneration plants [5].
64 Technology, Energy Efficiency and Environmental Externalities in the Pulp and Paper Industry
- A number of technological transformations for paper making machine parts had been implemented, including white liquor recovery, dryer condensate recovery, three-stage steam feed, etc..
- Minicomputer-based systems had been primarily used for the cooking process and
automation control for constant moisture content of paper in the paper making process. - Since 1980, much efforts have been made to popularize and disseminate energy-saving
spray nozzles as well as white liquor circulation recovery. This has led to the decrease in specific water consumption in the paper making process. For example, utilization of a fan-pattern spray nozzle can bring about water savings of 18-20%. Adoption of white liquor circulating loop can enable specific water consumption to decrease from 200-300 m3 to 50 m3 of water per ton of paper.
6.1.3.3 Comparison of the energy consumption of Chinese pulp & paper industry with
other countries
The overall energy consumption level in China’s pulp and paper industry is much higher when compared to its foreign counterparts in spite of the above achievements in energy conservation during the last years. As for the integrated unit energy consumption of paper & paperboard product, the indicator in the United States had decreased to 1.17 tce/ton of paper and paperboard (0.766 toe/t) as early as the mid-70s[12], which means that China's energy level lags some 20 years behind that of the USA. By the end of the 1970s, the same indicator in industrialized countries generally went down to the level of 1.15 - 1.22 tce/t (0.753-0.798 toe/t), which was only 64% or even less than China's value at the same time.[12] In 1989, integrated energy consumption for Japanese pulp & paper industry was 14.5 GJ/ton* or 0.495 tce/ton (0.324 toe/t), which was only 40% that of China. A comparison of the unit energy consumption of China and some developed countries, and the world average level are shown in Figure 6.1.7 and Table 6.1.8.
* 1 tce = 0.654 toe = 29.31 GJ and 1 toe = 44.76 GJ
Profile of the Pulp and Paper Industry in Selected Asian Countries 65
ton
ce/to
n(pa
per &
pap
erbo
ard)
0
0.2
0.4
0.6
0.8
1
1.2
1.4
Advanced inNorthEurope
Australianewsprint
Englandnewsprit (low
limit)
Englandnewsprint(up limit)
USAnewsprint
Japan P.R.China
Figure 6.1.7 Comparison of integrated energy consumption among various countries
Table 6.1.8 Domestic and international integrated product energy consumption
Minimum energy consumption
toe/t
Maximum energy consumption toe/t
Average level toe/t
China 0.818 1.113 1.010 World 0.330 0.779 0.556
6.1.3.4 Main reasons for the low efficiency energy situation in the paper industry
There are many complex reasons for the low energy efficiency in China. The most prominent among them are identified as follows. First, there are more than 10,000 paper enterprises, most of which are small in size (with an average per enterprise scale of 2550 ton/year), owned by diverse sectors and township industries. Most of these small paper mills use straw as raw material without any recovery of either valuable chemicals or thermal energy. Such small scale pulp and paper mills are reputed not to be adopting alkali recovery processes, cogeneration, as well as other high-energy, high efficiency technologies. These mills are also not easily monitored for their energy consumption due to the severe lack of technical strength. Moreover, many entrepreneurs do not care about their factories' energy efficiency for some complex reasons.
Newsprint (low limit)
66 Technology, Energy Efficiency and Environmental Externalities in the Pulp and Paper Industry
Second, with regard to large size paper mills, there still exists a big gap between the most energy efficient enterprises and the lowest ones. A survey conducted in 1986 in 32 key enterprises showed that the average integrated energy consumption was about 1.48 tce/t (0.969 toe/t). The indicator for the most energy efficient enterprise was 0.78, which can compete with internationally advanced levels, while the same for the lowest one was 2.6 tce/t (1.70 toe/t), or three times higher than the former.[12] Third, as mentioned above, there were only 60 large size paper mills with cogeneration power plants among the ten thousand paper mills nationwide in 1990. For the total 4500 MW power capacity of electric equipment in the sector, self-generation of power could only meet 10.5% of electricity demand. It has been proven that a cogeneration plant can do the paper mill itself much good due to its greater and stable combined thermal and power load. Once again, the size of small paper mills is blamed for the non-installation of cogeneration systems. [5] Fourth, perhaps the root cause of the problem of low energy efficiency is the low efficiency of boilers used in the paper mills. Despite some medium-pressure boilers installed in a few large size paper enterprises with a thermal efficiency of 80%, those installed in myriad small paper mills have efficiencies as low as 60%[4]. On the contrary, the efficiency for industrial boilers in developed countries is within the range of 80-85%. Often, heat loss rates of thermal network exceed 10%. Therefore, overall thermal efficiency for China's pulp & paper enterprises might be lower than 30%, some even less than 25%.[4] Fifth, most of the high calorific wastewater and other associated energy carriers (bark, sawdust etc.) are abandoned without recovery of relevant chemicals and for energy supply. For the time being, there are only three paper mills (Jilin Pulp & Paper Mill, Jiamusi Pulp & Paper Mill and Wufu Eastern Pulp & Paper Mill) installed with waste recovery boilers in which bark, sawdust and wood chips are fired. Beside the loss of energy, the environment is polluted. In comparison, some Western European paper mills can provide 87% of energy for their whole pulping process by fully exploiting waste materials such as bark and black liquor. Sixth, energy consumed for the digestion process usually accounts for 45% of the total pulping and paper making process. Usually, continuous digestion process can save 40% of the amount of steam compared with the intermittent digestion process, whereby much thermal energy savings can be obtained. Unfortunately, most digestion processes in China are intermittent ones except in rare cases. At present, the best figure for pulping process in China is about 1.6 ton steam/ton of pulp. The same indicator for foreign countries is just 0.4-0.6 ton steam/ton of pulp. Most equipment used for cooking in foreign countries are either the continuous digestion process or the low-energy-consuming intermittent digestion (RDH). Seventh, cylinder machines for paper making in China’s paper mills account for only 83% of the total number of paper machines with speeds of lower than 200 m/min and widths of 1m to 2m. In
Profile of the Pulp and Paper Industry in Selected Asian Countries 67
comparison, the width of Fourdrinier machine is generally between 5-10m, with machine speeds of 800-1200 m/min. Finally, as for the fuel mix pertaining to the pulp & paper industry of China, coal is the dominant fuel accounting for 95% of the total. Most types of coal used are of low grade. 6.1.4 Environmental externalities of the pulp & paper industry in China
6.1.4.1 Liquid, gaseous and solid pollutants
The pulp & paper industry is a typical pollution intensive industry among all industries. The most serious externality is the water pollution due to the highly concentrated organic wastewater effluents. Table 6.1.9 shows the amount of wastewater discharged from 2282 pulp & paper mills counted in 1993. BOD (biochemical oxygen demand) discharge by the paper mills was 2.716 billion tons, accounting for 38.2% of national BOD discharge, holding the first position among all industries in China. If all pulp & paper mills were taken into account, the total wastewater amount discharged from the industry would have reached as high as 3 billion tons in 1992, accounting for about one eighth of national total wastewater amount, ranking third after the chemical and ferrous industries.
Table 6.1.9 Wastewater discharge and treatment by Chinese paper industry in 1993 (Mt)
Number of enterprise counted
Total wastewater discharged
Discharged directly to inland
water body
Discharged directly to
sea
Discharged through treatment
plant
Wastewater under State Discharge Standards
2282 pulp & paper mills 2158 1713 18 21.4 314 All industries 21949 NA NA 17934 12049 Share of pulp & paper industry
9.8% – – 1.2‰ 2.6%
Besides slag (coal combustion cinders and white silt from alkali recovery), dust and ash, pungent smell and noise have also their environmental impacts. In 1992, slag and cinder discharged by the paper industry rose to 4.8 million tons, 296,000 tons of SO2, 267,000 tons of soot and dust, and 2.34 million tons of CO2. Table 6.1.10 shows some gaseous emissions from the industry. It can be found that two-thirds of the gaseous emissions are from fuel combustion in industrial boilers, and one-third is from the production processes.
68 Technology, Energy Efficiency and Environmental Externalities in the Pulp and Paper Industry
Table 6.1.10 Gaseous emissions by pulp & paper industry in China in 1993
Indicator
Total gaseous emissions billion
m3
Emissions from fuel
combustion billion
m3
Emissions from
production process
billion m3
SO2 emissions
104 t
Soot discharged
104 t
Dust discharge
d
104 t Pulp & Paper industry
173.1 117.1 56.0 28.177 28.7497 3.9332
All industries 9342 6004 3338 1292 880 617 National 10960 1795 1416
From Table 6.1.11, which shows the water pollution discharge loads in China from 1980 to 1988, it can be seen that specific water pollution loads (including BOD and SS) decreased by 33% to 36%. The reduction stemmed from alkali recovery, integrated exploitation of digested wastewater, use of recycled white water as well as fiber recovery which were popularized and used in some large and medium scale pulp & paper mills. Nevertheless, total water pollution amounts escalated gradually.
Table 6.1.11 Estimation of the total amount of water pollution and discharge load[9]
Year Wastewater discharged
BOD SS
Unit 108 m3/year
m3/ton paper
10,000 ton/year
kg/ton paper
10,000 ton/year
kg/ton paper
1980 27.6 516 125.5 235 120.3 225 1985 33 362 143 157 146 160 1988 40 315 190 150 192 151
Note: BOD – Biochemical or Biological Oxygen Demand, SS – fiber, fillings suspensions 6.1.4.2 Pollution from paper mill: a case of Qiqihar pulp & paper mill
Considering the 33 key large size pulp & paper mills belonging to the China Light Industries Commission (CLIC), not all of them are environmentally sound. For example, Qiqihar pulp & paper mill,[7,14] famous for its newsprint paper production, accounted for 11.5% of the national total newsprint paper production from 1954 to 1991. In 1991, its wastewater discharge was 70344 - 77446 tons/day, from which the COD (Chemical Oxygen Demand) discharge was 40.125 - 41.029 tons/day, BOD discharge was 6.836 tons/day, SS was 25.821 - 3.3821 tons/day, emitted gaseous pollutant soot and dust was 4112 tons/year, SO2 was at 1133 tons/year, total amount of solid waste was 63331 tons/year, and the strongest noise intensity was at 110 - 136 dB(A). A more detailed pollution situation of the paper mill is shown in Table 6.1.12-a & b and Table 6.1.13.
Profile of the Pulp and Paper Industry in Selected Asian Countries 69
Table 6.1.12-a Status of water pollution in Qiqihar pulp & paper mill (summer)
Pollution source Pollutants Unit Amount Receptacle water effluent m3/d 51631
White liquor COD cr kg/d 30101 oxidizing outlet BOD5 kg/d 4698 pond
SS kg/d 19973 water effluent m3/d 19815
Black liquor CODcr kg/d 10106 oxidizing outlet BOD5 kg/d 2140 pond
SS kg/d 9348 water effluent m3/d 6000
Ash outlet CODcr kg/d 822 oxidizing BOD5 kg/d - pond SS kg/d 4500
Table 6.1.12-b Status of water pollution in Qiqihar pulp & paper mill (winter)
Pollution source Pollutants Unit Amount Receptacle water effluent m3/d 44529
White liquor CODcr kg/d 39197 oxidizing outlet BOD5 kg/d 4698 pond
SS kg/d 11973 water effluent m3/d 19815
Black liquor CODcr kg/d 10106 oxidizing outlet BOD5 kg/d 2140 pond
SS kg/d 9348 water effluent m3/d 6000
Ash outlet CODcr kg/d 822 oxidizing BOD5 kg/d pond SS kg/d 4500
Table 6.1.13 Gaseous and solid pollution by Qiqihar pulp & paper mill
Pollution source Pollutants Unit Amount Receptacle Cogeneration smoke & soot t/year 3558-1015 atmosphere Kilns TSP t/year. 555 atmosphere SO2 t/year 119 Alkali recovery workshop H2S mg/m3 ~90 near the workshop Cogeneration Slag & Ash m3/year 50000 ash storage field Wood preparing bark m3/year 54 filler or workshop residential fuel Alkali recovery white silt and t/d 32.8 to lime kiln for workshop alkaline ash lime recovery
70 Technology, Energy Efficiency and Environmental Externalities in the Pulp and Paper Industry
According to the wastewater discharging norm for pulp & paper industry (GB3544-92), its total wastewater discharged was about two times greater than the set quota; COD was 1.7 - 2.0 times greater and SS was 1.5 - 2.9 times greater than the set quota. Much reductions should be achieved if all the paper mills abide by the set regulation. [7] 6.1.4.3 Major causes of the increasing pollution
Recently, pulp & paperboard production rose rapidly. This could be attributed mainly to the high increase in production of many small size straw-based township enterprises. This change resulted in both average unit enterprise scale decrease and overall technical level fall, because most of them were furnished with low-technical-level equipment. Other reasons are summarized as follows:
- Indifference to environmental pollution from enterprises leaders to workers. - The share of non-wood fiber raw material is too large. For the prevailing straw pulp
pollution in China, there are no technically mature and economically feasible clean production and/or environment-protecting technologies available.
- As for the vast capital investment demand for clean production and environmental
treatment in China's various paper mills, there are no special and definite financial channels as yet.
- No stern environmental assessment is stipulated as an indispensable prerequisite to the
plant before the construction of many new pulp and paper mills, especially those in rural townships.
6.1.5 Potential for energy efficiency improvement and pollution abatement through
technological changes
From the above analysis, it can be concluded that there exists great potential for energy savings as well as environmental alleviation. The potentials identified can be summarized as follows: 1. Adjustment of the present structure of the enterprises (scale), and development of a scale-economy of large capacity enterprises and/or groups. There is a worldwide development trend in pulp & paper industry for the time being: many pulp & paper mills ally together to pursue stronger market competitive ability. In Japan, two leading pulp & paper companies, each of which had a capacity more than 1 million tons per year have merged into a super-enterprise recently. As mentioned above, China's average size per enterprise is much lower compared to its foreign counterparts, which results in a series of problems that encumber its energy efficiency as well as environment-friendly development. It is a common consensus among Chinese paper experts that
Profile of the Pulp and Paper Industry in Selected Asian Countries 71
construction of large size paper mills installed with modern technological equipment is of great importance. Many township mills and other little enterprises should be merged into bigger ones for higher productivity, higher energy efficiency and more sound environmental compatibility. Moreover, larger scale paper mills will pave the way for a series of subsequent measures to deal with existing problems. 2. Changing raw material composition of China's current pulp production, raising the share of wood pulp and waste-paper pulp. According to statistics on straw pulp production, China has been the first in the world for years. It had been found, however, that the dominant fraction of straw pulp production is also a barrier to energy efficiency improvement and pollution abatement. In the United States and Japan, wood pulp's fraction in the total pulp production was more than 99% (Table 6.1.14):
Table 6.1.14 Global pulp production capacity and share of wood pulp (FAO, 1987)
Country Total production capacity (103 ton)
Wood pulp's share in national total (%)
USA 53,677 99.3 Japan 12,675 95.1 former USSR 12,408 99.9 China 10,679 23.9 Brazil 4,375 93.4 India 2,790 26.9 France 2,310 99.1
Exploitation of wood resources for boosting wood pulp production will not only raise the quality of the final paper products, it will also create a favorable condition for “associated biomass energy” recovery utilization. Moreover, all kinds of mature pollution abatement technologies pertaining to the wood pulp process can be implemented easily. To reduce fiber raw material consumption in pulp production, an effective way is to enhance waste paper recovery. It has been proven that wastepaper-derived pulp uses only around 1/4 or 1/3 of the energy claimed by the wood-derived pulp. In 1988, China's waste-paper pulp (including imported waste paper) accounting for 22.5% of the total pulp production, implied a big potential when compared to the same indicators of Japan and the European Union (50% and 48% respectively). Exploitation of waste paper for pulp production not only reduces consumption of energy and other resources, but also improves the quality of the environment.
72 Technology, Energy Efficiency and Environmental Externalities in the Pulp and Paper Industry
3. Technological reform and renovation on outdated boilers. There are many old industrial coal-fired boilers with a total capacity of more than 14,000 tons/h in the Chinese paper industry, and most of them have efficiencies lower than 60% or even 50%. This status indicates a great potential for energy savings through the improvement of the boiler efficiency. Combining technical renovation of some appropriate boilers and simple elimination of some is a better approach for efficiency improvement. There exist many mature and technical-economically feasible processes which can be used for boiler renovation. For example, the efficiency of small boilers with a capacity of less than 1 ton/h can be upgraded from 45% to 60% by a series of renovations. For boilers with a capacity between 1-4 tons/h, the efficiency can be raised even to 75% by technical renovation at a lower cost. Besides this, boosting workers’ operational skill is also important. 4. Development of cogeneration
Cogeneration is a very useful technology for efficiency improvement in a pulp & paper mill, which can provide thermal energy and electricity for its various processes. Compared to separate heat and power generation, it can get a prominent energy conservation effect of more than 20%. As a rule, any paper mill which owns two or more sets of boilers with unit capacity of more than 10 t/h should build its corresponding cogeneration plant. Chinese experts estimated that [8] total cogeneration installed capacity in the paper industry may be as much as 1600 MW by the year 2000. In 1991, total cogeneration capacity was just 473 MW. The energy saving potential by cogeneration in the Chinese paper industry will reach more than 2 million tce (1.31 million toe) by 2000 if 1600 MW installed cogeneration capacity can be realized. The potential for cogeneration, therefore, is great. 5. Recovery of waste liquors and other associated energy carriers such as digested black liquor, bark, and sawdust. Recovery of associated energy carriers such as black liquor is of great benefit both for energy savings and for environmental protection. A ton of dried solid remnant of black liquor in the process of sulfate pulping can provide thermal energy of 0.43~0.49 tce (0.28 toe ~ 0.32 toe). In the paper industry of developed countries, energy supply from associated energy carriers such as black liquor and bark account for a remarkable share. For instance, black liquor and bark supplied 37.3% and 4.3%, respectively, of the total paper industry energy demand in the USA in the early 1980s. In Finland and Sweden, the two items together could meet more than 50% of the total energy demand. In some cases, even the total energy demand by all processes can be met fully by recovery of black liquor and bark.
Profile of the Pulp and Paper Industry in Selected Asian Countries 73
It is estimated that the total black liquor of the industry can provide at least 3 million toe based on 1990’s conditions. In comparison, the level of wastewater recovery and utilization in China lags behind. At present, alkaline pulp capacity with black liquor recovery is only 1.2 million tons, accounting for 41% of the total alkaline pulping capacity nationwide. Most of the paper mills do not have the facilities to exploit either black liquor or bark to recover chemicals and thermal energy. It is projected by CLIC that if 1.2 million newly-added alkaline pulp capacity with black liquor recovery is realized by 2000, then 130,000 toe energy can be saved, and 450,000 tons caustic soda can be recycled while reducing BOD discharge by 250,000 tons. Combustible waste residue from large scale wood pulp mills alone amounts to 240,000 ton/year. As only three mills are installed with waste boilers firing these waste solid, there is an immense potential for energy efficiency improvement and environmental protection. 6. To adopt advanced pulp and paper making technologies both for paper mills modernization and for building new large scale paper mills. Generally, the energy consumed is distributed among all production processes as follows: 2% for wood material preparation, 46% for pulping (digestion, cleansing and alkali recovery), 4% for bleaching, 43% for paper shaping, 5% for paper processing. Among the pulping processes, digestion accounts for 97% of energy demand. Attention should be given therefore to the two energy-consuming processes, digestion and paper making. There exist two digestion processes: continuous digestion process and intermittent digestion. Compared to the latter, the former can avoid steam load fluctuation, thus reducing steam consumption by 40%. Continuous digestion process should be recommended to replace intermittent one. At present, medium or small size continuous digestion equipment can be made in China, and a number of such equipment have already been commissioned. Moreover, a new low-energy, cold-spouting intermittent digestion process (RDH) invented abroad is found to save 50% or more steam while raising productivity by 10-15% when compared to the conventional intermittent digestion process. This new process can therefore find a promising market in China, though the use of such technology is not yet realized in the country. Additionally, the direct heating process for digestion should be substituted by the indirect heating process since the former consumes 15-20% more energy than the latter. Another process which should also be given attention for energy savings is the paper making stage. There are a number of feasible technological transformation methods for comprehensive energy-related improvement of the paper machines. Medium speed Fourdrinier machines can substitute existing cylinder machines. The drying ability of the machines can also be boosted by polyester former, new pulp feeder and new drying apparatus. High intensity multi-press can be used in machine press parts to raise wet paper dryness from the current 32%-38% to 48%-50%. It has been proven that reduction of 1% of moisture content of wet paper before drying can save 5% of the steam consumption for drying. The dryness of wet paper in Chinese paper mills is usually
74 Technology, Energy Efficiency and Environmental Externalities in the Pulp and Paper Industry
around 30%, while that of western countries is more than 50%. Some technical measures to raise thermal efficiency for drying include multi-stage steam feed, whole-sealed cover, recovery of exhaust heat from its cover, etc. Computer-controlled steam feed for dry oven in some foreign countries also proved to be a useful way to save steam consumption. Computer-based constant moisture control systems should be disseminated in large or medium-size key paper mills. It is estimated that specific energy consumption of paper machines would be reduced by 30% through the above-mentioned technologies. If 20% of the existing paper machines are retrofitted by the year 2000, 650,000 toe can be conserved. 7. Application of electricity-saving equipment for technical renovation, replacement of outmoded appliances and dissemination of computer-controlled automation processes. The performance of electrical equipment directly affects the electricity consumption of the whole paper mill. Some available low-electricity-consuming equipment such as double-panned mill, Loci electric fan, axial-flow fan and speed-adjustable electric motor have better electricity saving effects compared to their respective old generation equipment. For instance, the replacement of variable frequency- speed-adjustable electric motor could save electricity by some 30% in most cases, while its cost could be paid back in a few years. Here, existing barriers in the Chinese case are mainly incentives and initial investments. On the other side, computer controlled automation process may bring 10% steam reduction for the process of pulping and 15% energy savings for paper shaping process in the Chinese context.[12] 8. For environmental protection, especially water pollution control, challenges and opportunities exist together. Potential for pollution abatement includes:
- For the alkali pulping process, alkali recovery rates of various raw material-based mills can be increased to various levels: 90% alkali recovery rate for wood pulp, 80% for bamboo/bagasse pulp, and 70% for wheat straw pulp can be reached.
- For the acid process, efforts should be made to integrate exploitation of wastewater to
produce adhesives, alcohol by products, etc. - For ammonium bisulfite pulp, wastewater can be used for agricultural irrigation & farm
fertilizer. Recovery exploitation rate of wastewater for this process can increase to 60% or higher.
9. There is still a great potential for water conservation by improving water recycle utilization rate. Current white liquor recovery rate of paper machine is 30%, while the dryer condensate recovery rate is 50%
Profile of the Pulp and Paper Industry in Selected Asian Countries 75
10. Enhancement of pulp & paper industry professional management, effective implementation of existing regulations relevant to energy consumption and environmental protection issues. 6.1.6 Status of application of new technologies
Because most paper mills in China do not belong to the CLIC, there is no strong authority or administrative department responsible for the professional management of the pulp & paper industry. Much data concerning the status of the application of new technologies are not available. Following is an example of application of Alkali Recovery (AR) process in China: This technology is reckoned by the industry to be the key approach for environmental control. By the end of 1992, there were 63 paper mills installed with alkali recovery facilities. Total alkali recovery capacity hit 450,000 tons/year, while actual alkali recovery amount was 380,000 tons/year. By the AR process, about 400,000 tons of organic pollutants were refined. The AR rates in large size wood pulp mills reached 90%, and in medium capacity wood pulp mills, 75-80%. AR rate in large size straw pulp mills was 70% or so, medium size straw ones, 50-60%. There was about 1.2 million tons/year pulping capacity matched with alkali recovery facilities in 1992, accounting for 41.4% of the total 2.9 million tons/year pulping capacity which needed the technology (Table 6.1.15). Figure 6.1.8 shows the alkali recovery evolution during the decade from 1980 to 1990. It can be found that overall alkali recovery and wood pulp alkali recovery kept similar increasing trends, with annual growth rates of 5.3% and 5.9%, respectively. Meanwhile, recovery of straw pulp alkali increased from 54,200 tons to 73,000 tons.
Table 6.1.15 Status of AR utilization in China in 1992
Alkali-based pulp Wood pulp Straw pulp Pulping capacity with AR, Mt 1.2 0.80 0.40 Pulping capacity demanding AR, Mt 2.9 0.90 2.00 Diffusion rate % 41.4 88.9 20 AR rate % 22.6 70 6
With regards to the total amount of alkali recovery, the wood pulp mills’ situation was generally better than that of the straw pulp mills. Figure 6.1.9 shows the alkali recovery rates of the situation in the two pulp mills. Alkali recovery rate in the wood pulp mills exceeded 60% in 1990. In the straw pulp case, the indicator was maintained at lower than 10%. If those straw pulp mills outside the CLIC (which often consumed alkali without recovery ) were taken into account, however, the real indicator of alkali recovery for whole straw pulp case should be lower than 6% (Figure 6.1.9).
76 Technology, Energy Efficiency and Environmental Externalities in the Pulp and Paper Industry
Year
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1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1992
Total ARWood Pulp ARStraw Pulp AR
Figure 6.1.8 Alkali recovery by wood pulp and straw pulp from 1980 to 1990
Year
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ent
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1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990
Total AR rateWood Pulp ARrateStraw pulp ARrate
Figure 6.1.9 National macro alkali recovery rates vs. year
Since 1980, some important alkali recovery projects had been completed in large or medium size wood pulp mills such as the Jiamusi Paper Mill, Jilin Paper Mill, Zhalandun Pulp & Paper Mill, Helongjiang Paper Mill, Yalujiang Paper Mill, Nanping Paper Mill and Qingzhou Paper Mill. At the same time, technical transformations to large size straw pulp mills had also been made successfully. For instance, plate membranous concentrating vaporizers had been added into alkali recovery systems in Zhenjing Pulp & Paper Mill, Yueyang and Liujing Paper Mills. In a few cases, technical transformation and capacity extension for alkali recovery in medium or small size straw pulp mills had been made with satisfying techno-economic effects, as in the case of the Guigang, Shanghai Songjiang Pulp & Paper Mills, etc.
Profile of the Pulp and Paper Industry in Selected Asian Countries 77
Unfortunately, alkali recovery situation for most medium and small size straw pulp mills (with capacity of 15-35 tons pulp/day) was problematic due to reasons such as small economies of scale, low technical equipment installation, poor operation management as well as immature technologies available for black liquor treatment in straw pulp mills. By the end of 1994, there were 73 AR projects with a total AR capacity of 370,000 tons/year. Of these, 37 projects with a total AR capacity of 120,000 tons/year were built but not commissioned, and 36 projects of total AR capacity of 250,000 ton/year were under construction. By the end of 1995, there will be a total of 30 paper mills installed with AR facilities with a total AR capacity of 820,000 tons/year. During the last decades, the AR capacity with an annual growth rate of 5.3% still lagged behind that of the paper & paperboard at 15% and the pulp growth rate of 13.7% during the same period. This therefore suggests that more alkali is to be consumed to meet faster demand. For improvement of the AR rate and wastewater integrated exploitation, wastewater abstraction is the primary process to be solved. Several hundreds of domestically-developed belt pulp scrubbers have been built since the 1970s. Some large size paper mills also imported new high-efficiency pulp scrubbers. In a Guangzhou paper mill, where an imported advanced pulp scrubber was installed, the AR was boosted to more than 80%. As for many AR processes concerning straw pulp production and other digested wastewater recovery technologies, an eminent problem in the Chinese situation is how to commercialize and/or disseminate the results of the studies in paper mills. 6.1.7 Conclusions
From the above discussion, some main conclusions concerning the pulp & paper industry in China can be briefly summarized as follows:
- The pulp & paper industry of China is a fast developing industry, and currently ranks third in the world. It could probably catch up with Japan to become the second largest producer in the world by 2000.
- The pulp & paper industry of China is a highly energy-intensive and polluting industry,
and is particularly blamed for water pollution. - China's integrated energy consumption indicator in the pulp & paper industry is 2.45
times as high as that of Japan, 1.45 times as high as that of USA. Therefore, its energy efficiency is much lower.
78 Technology, Energy Efficiency and Environmental Externalities in the Pulp and Paper Industry
- Due to the lack of wastewater recovery, exploitation and treatment technologies and/or measures, the industry is responsible for 1/8 of the national wastewater discharge, and more than 1/3 of the national BOD discharge. Thus, it is urgent to curb the rampant environmental damaging behavior of the pulp & paper industry.
- There exists a great potential for energy efficiency improvement and environmental
pollution mitigation from the industry through a number of technical measures, including technological renovation and substitution for existing processes; transformation of existing paper mills; improvement of boiler efficiency; installation of cogeneration; recovery of wastewater and other associated energy carriers (bark, sawdust); digestion process replacement; computed-based automation etc.
- From the viewpoint of national macro-system, enhancement of waste paper recycling,
reshaping of enterprise scales, as well as the change of raw materials for pulping should help in further improvement and pollution abatement.
- Consolidating pulp & paper professional management and tightening the
implementation of existing pollution control regulations, as well as even legislating appropriate laws for discharge norm from paper mill are urgently needed.
Profile of the Pulp and Paper Industry in Selected Asian Countries 79
6.2 COUNTRY REPORT: INDIA
6.2.1 Introduction
The paper industry in India has been established for over a century, with four paper manufacturing units initially in operation with an annual output of 20,000 tons. From an installed capacity of 137,000 tons in the year 1951, the paper industry has grown during the last four decades to an installed capacity of 3,463,000 tons of paper and paperboard, and 300,000 tons of newsprint. The development of India’s paper industry centered on bamboo for raw material, rather than wood as in other countries. With bamboo resources falling short of the requirement due to the short term planning adapted then, the use of tropical hardwood started in the 1960s. Until the start of the 70s, the paper industry had been forest-based and industrial units were integrated with pulp, paper and chemical recovery systems. Being highly capital-intensive, new investments were not forthcoming at the desired levels. Anticipating a shortage of paper in the 1960s, a crash program for the expansion of the industry was devised, under which, second-hand plants and machinery were allowed to be imported. The number of units in the process increased from 25 in 1960-1961 to the current 340 units. Most of the small paper mills are either agro-based or waste paper-based. At present, 29 units with a capacity of 1,485,000 tons, representing 43% of the installed capacity for paper and paper board, rely on forest-based raw materials. Eighty-nine units with a capacity of 974,000 tons, representing 28% of the installed capacity, are based on agricultural residues. These units use imported pulp and recycled fiber as well. Added to these are some 22 units with a capacity of 1,004,000 tons, representing 29% of the installed capacity, which are largely dependent on imported recycled fibers. The effective capacity utilization of bamboo and wood-based units is 95%, 80% for agro-based units, 63% for recycled fiber-based units, with an average effective capacity utilization of 82% (Figure 6.2.1). The overall capacity utilization in relation to installed capacity is 62%. The demand for paper and paperboard by the turn of the century shall be reckoned in terms of the development phase which has already started. The per capita consumption of newsprint paper, currently at 2.4 kg, shall increase to 4.5 kg by the year 2000 (Figure 6.2.2). The demand for paper and paperboard products would vary from the packaging to newsprints, and others. 6.2.2 Technological trajectory of the Indian paper industry
6.2.2.1 Structure of the paper industry
At the start of the 1950s, the average production size of the paper mills was only 8,000 t/year. Integrated paper mills based on forest raw materials set up during 1955-1960 resulted in an increase in the average unit size to 16,000 t/year. In the next decades, additional capacity was
80 Technology, Energy Efficiency and Environmental Externalities in the Pulp and Paper Industry
mostly due to the expansion of existing mills and commissioning of small paper mills, but the average size declined to 13,500 t/year. During 1970-1980, although 8 large integrated mills with production sizes of 20,000 t/year were commissioned, the added capacity was mainly in the form of small units and the average size remained at 12,500 t/year. From 1980-1985, an increase in the number of units by more than 100% was realized, with small paper mills registering a growth of 129% and capacity increase of 50%. However, only one large integrated mill (the Nagaland Pulp and Paper Mill with a capacity of 33,000 t/year) was commissioned during the period, while four other large mills effected expansion for a total of 44,500 tons. A small pulp mill (the Century Pulp and Paper Mill with a capacity of 20,000 t/year) was commissioned in 1981 and the average unit size came down to about 9,400 t/year.
Figure 6.2.1 Installed capacity and production of India’s pulp & paper industry
Figure 6.2.2 Per capita paper consumption in India In 1988, only one large integrated pulp and paper mill (the Cachar Paper Project of Hindustan Paper Corporation, with a capacity of 100,000 tons) was commissioned. The rest of the additions to the existing capacity was by way of expanding a few small paper mills. After the commissioning of the Cachar project, there has been no further commissioning of integrated pulp and paper mills based on forest raw materials.
1960 1970 1980 1990 1992Installed Capacity
4000
3500
3000
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1500
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0
Ton
/ Yea
r
Production
Profile of the Pulp and Paper Industry in Selected Asian Countries 81
The number of large mills went up to 25 in 1990, and in 1992, three large mills (Pudumjee Pulp and Paper Mill, Balkrishna Papers, and Tribeni Tissues, Ltd.) were added as a result of expansion from the small category. Similarly in 1993, two large mills have been added through expansion and two new agro-residues-based units have been set up. During the last five years, only three new units were set up in the large paper mill category. The trend of setting up small paper mills accounting for about 50% of the total capacity is continuing. The average unit has also remained at about 10,000 tons. The growth of the paper industry in India is shown in Figure 6.2.3.
1960 1970 1980 1990 19920
50
100
150
200
250
300
# of
mill
s
1960 1970 1980 1990 1992
Year
Small Paper MillsIntegrated Paper Mills
Figure 6.2.3 Growth of the paper industry in India (1960 to 1992)
6.2.2.2 Raw materials scenario
Twenty years ago, the Indian paper industry started with bamboo as the sole major raw material. The restricted availability of the material, however, has curtailed its usage to about 40% at present. Because of this, there has been a considerable shift towards the use of tropical hardwood, eucalyptus, and other non-conventional raw materials. Today, depending on the source of raw material, the paper industry is classified as follows:
- Forest-based: bamboo & hardwood (plantation-grown raw materials: mainly Eucalyptus and Subabul)
- Unconventional raw materials (agro-residues, jute, grass straw, bagasse, etc.)
- Waste paper-based Segment wise, effective installed capacities in the paper industry are as follows:
Forest-based raw material: 43% Agro-based 28% Waste paper-based 29%
82 Technology, Energy Efficiency and Environmental Externalities in the Pulp and Paper Industry
Today, the large gap between the demand and supply for paper is basically for the newsprint type while future requirements for paper and paper board are expected to register a sharp increase. There is therefore a need to substitute scarce forest resources with non-conventional raw materials as an immediate measure to meet raw material requirements in the pulp & paper industry. Plantations on long-term basis by using modern silviculture practices and other technologies like tissue culture for improving the productivity of the forest-based raw materials should be considered. 6.2.2.3 Technological advancement
Since its establishment, the paper industry in India underwent a lot of changes by way of equipment and process development. A hundred years ago, the machinery and equipment available for pulping, bleaching and papermaking, limited the size of the mills to about 50 t/d. Apart from constraints such as the availability of energy, raw materials and other inputs, one reason for the low capacity utilization of the mills is the fact that productive assets are often not at optimum levels of efficiency due to the lack of modernization and renovation of old equipment. Furthermore, the Indian paper industry has adopted equipment primarily designed for the processing of indigenous softwood materials, such as bamboo, but these are used for hardwood as well. Consequently, operating efficiencies are low and processes require modernization of techniques to ensure better yields, reduce costs and conserve raw materials. In view of the increasing paper demand and shortage of forest-based raw materials, the government has drawn up a policy to promote small mills based on straw and bagasse. The size of the mill has to be restricted due to the seasonal availability of the raw materials, and technical problems involved. These agro-based paper mills produce almost all kinds of paper and boards for writing and printing. In the absence of a chemical recovery system and high cost of alkali, these mills use low amounts of chemicals at the cooking stage and excess amounts of chlorine in the bleaching stage. Second-hand paper machines which are used for papermaking are energy deficient, and since these mills do not have chemical recovery units, the discharge of spent liquor, and excess consumption of chlorine are major causes of water and environmental pollution. On the other hand, the large integrated mills which mainly produce writing and printing grade papers are equipped with full-fledged chemical recovery systems and effluent treatment plants. Developments in the pulp and paper industry has been gradual, though systematic and elaborate research activities in the fields of fiber chemistry, morphology, engineering, have been continuing. Today, advanced knowledge in morphology and structure of fibers, chemical reactions of wood components such as carbohydrates and lignin during pulping and bleaching, has led to several technological innovations in the field of pulping. The spectrum of fibrous raw materials which was initially limited to wood, has widened to non-wood fibrous raw materials.
Profile of the Pulp and Paper Industry in Selected Asian Countries 83
The papermaking process involves three main stages: raw material preparation, pulping and bleaching, and papermaking. A. Raw material preparation Wood and bamboo are felled at the forests. Wood is debarked at the felling or mill site. The fiber losses in handling is more than 10%. Agricultural residues like straws & bagasse are stored in bales. Being seasonal crops, their storage for long periods are prone to microbial degradation which often affects the quality of pulp produced. Chipping
The wood is chipped in disc chippers which are also used for bamboo chipping, though the Palman Drum type is nowadays commonly used for bamboo. About 53% of the total number of chippers (accounting for 58% of the total installed capacity) were installed since 1975, and are mostly of the drum types. While the aggregate capacity of chippers for individual units range between 35 to 168 t/h, most units fall between 45-50 t/h capacity. Straws are cut by chop cutters, which are not power efficient, while bagasse is de-pithed before digestion. B. Pulping and bleaching Indian mills predominantly use the alkaline pulping process. Large mills based on forest raw materials use the Kraft process, whereas agro-based mills use the soda process. Newsprint mills use mechanical, chemical, chemi-mechanical and chemi-thermomechanical (CTMP) processes. Digestion
The predominant practice for digestion is the use of batch digesters. Two large mills use continuous digesters for bamboo and wood, whereas some of the agro-based mills use Pandya digesters. The reasons for not using continuous digesters in agro-based mills include:
- higher outlays for machinery replacement in the existing units
- lack of flexibility in the continuous digester process system to accept varying raw material mix
- the relatively small size of the mills makes it uneconomical to use continuous digesters more efficiently
Bleaching
Most Indian mills use chlorine-based bleaching chemicals with barometer drop leg or displacement type of washers. Common bleaching sequences are CEHH, CEH, and CHHH, of which CEHH is most commonly used in order to achieve a brightness level of over 75%. Some large mills have
84 Technology, Energy Efficiency and Environmental Externalities in the Pulp and Paper Industry
started using chlorine dioxide and peroxide partially, i.e., CE(p)HH, while many paper mills propose to go for oxygen bleaching. Pulp Washing
Small mills without chemical recovery systems normally employ the poacher-type washer followed by one or two drum washers. The fresh water consumption is as high as 20-50 m3/t (paper) in these mills. Integrated mills have 3-4 drum washers with counter-current washing. Stock Preparation
Most of the units have replaced conical and wide angle refiners with the relatively energy efficient double disc refiners. C. Paper machines Three types of paper machines are commonly employed in the industry: cylinder molds, Fourdrinier formers, and twin wire formers The cylinder molds are commonly used for small mills engaged in the manufacture of multi-layered boards. The Fourdrinier machines are most commonly employed both in small and big mills for the manufacture of varieties of paper. About 81% of the total paper machines have Fourdrinier formers and 84% have speeds of 150 to 300 meters per minute (mpm). Only 5 machines have operating speeds of more than 400 mpm. Twinformers that are commonly employed in the newsprint industry, have high speeds and can accept weaker pulp. However, their application in small units is not economically viable. Other data regarding paper machines used in the industry are as follows: 56% of the total number of paper machines have thyrister control drives; 30% have sectorial drives, and 33% have line/pulley drives; 48% have open type of head boxes; 52% have closed-type head boxes; 62% have suction processes; 39% are equipped with size presses while 69% are equipped with calendars. The condensate recovery in most of the mills is between 60% to 90%. D. Chemical recovery system While all wood-based paper mills have chemical recovery systems, most of the small mills do not have one, and the efficiency attained in the recovery units are below 90%. Impressive developments, however, have been made in the evaporation and combustion of spent liquor. From the 60s to the 80s mills have installed either short-tube or long-tube variety types of evaporators. Since spent liquor exhibit very high viscosity, this restricts the evaporator outlet concentration to 40-45% solids. Scaling tendencies and colloidal instability of spent liquor are also the common problems faced in evaporator units. Recently, the use of the falling-film type of
Profile of the Pulp and Paper Industry in Selected Asian Countries 85
evaporator has been favored. Experience with these evaporators have shown clean benefits like high-end concentration, maximum steam economy and improved condensate quality. Boilers used in the industry are the coal-fired types. About 11% of the total installed capacity, mainly fluidized bed boilers, are 5 years of age. Prior to 1975, the capacity was 20 t/h of steam generated at 20-30 kg/cm2 pressure and 380oC to 400oC temperature, with a thermal efficiency of 50-60%. From 1975 onwards, the steam generation capacity increased to 25-27 t/h at 40-60 kg/cm2 pressure and 400oC to 480oC temperature. Thermal efficiency has increased to 70-80%. The Central Pulp and Paper Research Institute (CPPRI) is engaged in developing the Direct Alkali Recovery System (DARS) for agro-based mills. Organizations like ESVIN Technologies and Amrit Banaspati Company are also engaged in R&D work for chemical recovery. CPPRI has made breakthroughs in the desilication of black liquor that will improve performance of the recovery unit in non-wood-based paper mills, while opening the option for lime sludge reburning. E. Other machinery and equipment The manufacture of paper from raw materials storage & transport to the packing and handling of the finished product requires utilization of a wide range of equipment. In addition, various auxiliary items such as steam boilers, power generation equipment, effluent treatment equipment, etc., are also required. India has now developed its capability to manufacture and supply almost the entire range of equipment for the paper industry, specifically for the pulping plant and stock preparation; equipment such as paper machines, steam and power generation equipment, chemical recovery equipment, etc. Figure 6.2.4 shows the general distribution of process automation in the paper industry of India. 6.2.2.4 Human resource in the Indian paper industry
Despite the growth of the paper industry, industrial performance has been unsatisfactory due to the poor management of materials, money, and manpower, of which manpower planning and training is most neglected. For a sustained performance, the industry should have the ability to adopt appropriate technology to conserve energy and raw materials, and to cut down costs. This challenge can be faced only through a competent and skilled manpower at all levels. On the average, the industry utilizes 78 persons in the production line per 1,000 annual tons of production. The technical manpower components are 35-40 and 40-60 for every 1,000 annual tons in the large and small mills, respectively. For the whole Indian paper industry, professional and technical manpower comprise 13% of the total manpower; administrative/executive and managerial personnel constitute 23%; 12% are clerical personnel, 7% are service workers, and 45% are production-related workers.
86 Technology, Energy Efficiency and Environmental Externalities in the Pulp and Paper Industry
To meet the challenges of technical upgrading and productivity improvement, the industry will strive for a reduction in its manpower usage with an associated rise in workers’ competence. For the next 10-12 years, it is estimated that the average manpower utilization in the country will be 35 persons per 1,000 annual tons in the paper & paper board sector, and 15-20 persons per 1,000 annual tons in the newsprint sector. Training programs in the pulp and paper industry will be modified to fit into the national pattern for degree/polytechnic diploma levels. The entire strategy of manpower development will involve training competent/skilled personnel to move the industry to perform at its best level.
1985 1990 1991 1992 19930
10
20
30
40
50
60
70
Sta
tus
(% o
f Fac
torie
s)
1985 1990 1991 1992 1993
Computerization Electronic AutomationElectro Mechanical Regulation Manual Operation
Figure 6.2.4. Status of process automation in the paper industry
6.2.2.5 Current status of the pulp and paper industry in Indian national economy
The paper industry constitutes the core of industries directly linked to the national economy. Current per capita consumption of paper is 2.5 kg, and is expected to grow to 4.2 kg by the end of the century. Efforts to build additional capacity to meet the future requirements of various grades of paper are on-going. In fact, the country has attained self-sufficiency in most varieties of industrial paper. Newsprint, though, is still imported at 40% levels, implying a considerable outflow of foreign exchange. Considering the huge amount of non-conventional raw materials available for pulp and paper manufacture, there exists a big export potential in the pulp and paper sector. In 1994-1995 alone, nearly 200,000 tons of paper had been exported to third world countries.
Profile of the Pulp and Paper Industry in Selected Asian Countries 87
6.2.3 Evolution of energy efficiency in Indian pulp and paper industry
Pulp and paper being an energy intensive industry, is ranked the sixth largest energy consumer in the country. Fuels from external sources comprise 70% of the total used, as compared to 30-40% for those in developed countries. The energy component in the Indian paper industry is as high as 30% of the total cost of production, consuming about 7% of the country’s coal and approximately 3% of the electrical energy requirements of the whole manufacturing sector. Unlike other industries, the paper industry requires large quantity of low grade energy (200oC). Of the total energy requirements, about 15-25% is of high grade (electrical energy), and the rest is constituted by low grade energy. In terms of thermodynamic efficiency, the industry is lowest among the energy intensive manufacturing units of the steel and cement industries. The industry was greatly affected by the energy crisis in the early 1970s, which led to the adoption of energy conservation methods. Most of the mills installed before the 1970 crisis however, were not energy conserving in design and technology. Even though the concept of energy savings intensity had already been identified in the 80s, consumption patterns remained the same, brought about by the following:
- lack of modernization - use of obsolete technology - lack of process control system - change in fibrous raw material mix
The estimated energy consumption in the pulp and paper industry is 2.42 tons of oil equivalent per ton of paper. The major energy-consuming plants are the chippers, digesters, refiners, paper machines and evaporation plants. The present specific energy consumption patterns show higher variations in the integrated pulp and paper mills. The specific steam consumption varies from 10.2 to 17.4 tons/ton of paper produced, while the specific power consumption varies from 1,300 to 1,940 kWh/ton of paper. Water consumption also varies from 225 m3 to 450 m3/ton of paper. In the last decade, the cost of coal and electricity has increased by 500% and fuel oil by 1000%. Based on the industry’s 4.25 million tons of total installed capacity and capacity utilization for all products, the projected consumption of the paper industry by year 2000 would require an additional 3.0 million tons of coal and about 1.82 million kWh electricity. This means a 76% increase in coal requirements and 139% increase in electricity requirements. With rising energy costs, ways and means to conserve energy now becomes a major thrust in the industry.
Energy consumption patterns in developed countries and in India
Between 1975-1983, the Japanese paper industry has reduced its specific energy consumption from 0.662 toe to 0.437 toe per ton of paper, accounting for a 34% reduction in specific energy
88 Technology, Energy Efficiency and Environmental Externalities in the Pulp and Paper Industry
consumption. This could be attributed to the country’s heavy investments in fossil fuel substitution energy programs. European oil consumption has also been cut down from 37% to 8%. The Swedish paper industry managed to cut its oil fuel consumption by over 70% between 1973 and 1983. In the USA, energy from residual fuel and self-generating sources now accounts for an estimated 57-58 percent. Clearly, most of the developed countries have made significant progress to conserve energy, and are presently depending only on 30-40% of fuels from external sources. India however, is still 70% dependent on external fuels. The industry’s specific energy consumption varies between 0.76 to 1.325 toe per ton of paper. Table 6.2.1, Table 6.2.2 and Figure 6.2.5 show a comparison between mills in India and the developed countries, and energy consumption patterns in the country. It is worthwhile to note that some Indian paper mills have already taken some in-plant energy conservation measures.
Table 6.2.1 Comparison of energy consumption of developed countries and India
Particulars Developed countries India Total specific steam consumption, t/t paper 6.5-8.5 10-16 Digester 1.9-2.3 2.3-3.9 Evaporator 1.5-2.2 2.5-4.0 Paper machine 1.9-2.0 3.0-4.0 S/R plant 0.3-0.5 0.5-1.1 Bleach plant 0.2-0.25 0.35-0.40 Steam generator per ton of black solids 3.0-3.5 1.5-2.5
Table 6.2.2 Electricity consumption of paper in Developing countries and India (kWh/t)
Particulars Developed countries India Total Consumption 1150-1250 1200-1700 Chipper 92-98 112-128 Digester 43-46 58-62 Washing and screening 116-122 145-155 Bleaching plant 66-69 88-92 Stock preparation 164-175 275-286 Paper machine 410-415 465-475 S/R plant 127-135 170-190 Utilities & others 160-165 246-252 Total specific energy (Gcal/t) 4.14-4.50 4.32-6.12
Profile of the Pulp and Paper Industry in Selected Asian Countries 89
Figure 6.2.5 Energy consumption pattern in the Indian paper industry
6.2.4 Environmental externalities of technological development in the pulp and paper
industry
The pulp and paper industry is essentially a chemical process industry with a distinctive impact on the environment. It is estimated that about 41.8% of wood is recovered as bleached pulp, roughly 4.2% of the remaining wood ends up as solid waste, as 5.25% goes into waste waters as dissolved organic matter, and 2.3% ends up as suspended solids also in wastewater. The potential pollutants from a pulp and paper mill fall into four categories as follows:
- effluents - air pollutants - solid wastes - noise pollution
1960 1970 1980 1990 19920
0.5
1.0
1.5
2.0
2.5
Specific electricity, MWh / ton PaperSpecific coal, toe / ton PaperSpecific fuel oil, toe / ton PaperSpecific non-conventional energy, toe / ton PaperIntegrated specific energy, toe / ton Paper
90 Technology, Energy Efficiency and Environmental Externalities in the Pulp and Paper Industry
6.2.4.1 Effluents
Waste water is discharged from almost all unit operations. Large paper mill waste waters are generally segregated into streams, namely, colored streams (due to lignin from pulp washing, caustic extraction and chemical recovery sector), and colorless stream (chipper house, chlorination, hypochlorite and paper machines). Bleach plant effluents constitute nearly 65% of the total BOD and 90% of the total color load of combined effluents in large mills. Small mills generate ostensibly higher pollution than larger mills mainly due to the absence of chemical recovery systems. Major pollution loads come from spent pulping liquor, of which 90% of the color and 50% of the COD is due to lignin which is almost completely bio-refractory. Tables 6.2.3 and 6.2.4 show the effluent characteristics and the pollution loads of black liquor and organics in Indian pulp and paper mills.
Table 6.2.3 Characteristics of effluents from the pulp and paper mills
Integrated pulp & paper mills
Newsprint mills
Agro-based small paper mills
Waste paper mills
Raw material bamboo, hardwood bamboo, hardwood
rice straw, wheat straw, bagasse, etc.
waste paper
waste water, m3/ton 230-250 200 200-380 70-150 PH 6.0-9.0 7.2-7.3 6.0-8.5 6.0-8.5 Pollution load, kg/ton paper:
Suspended solids 100-150 100 90-240 50-80 BOD5 35-50 45 85-270 10-40 COD 150-200 135 500-1100 50-90
Table 6.2.4 Pollution loads of black liquor and organics
Parameters Bagasse Rice straw COD, kg/t pulp 1075 1247 BOD, kg/t pulp 216 234 Black liquor COD/BOD
Color, kg/t pulp (PCU) 5.0
1394 5.3
1514 Acid precipitation COD, kg/t pulp 530 628 Lignin separated BOD, kg/t pulp
Color, kg/t pulp (PCU) was not biodegradable
1283 was not biodegradable
1444
Supernatant free from lignin
COD, kg/t pulp BOD, kg/t pulp
COD/BOD Color, kg/t pulp (PCU)
417 197 2.1 82
381 247 1.5
1113
Profile of the Pulp and Paper Industry in Selected Asian Countries 91
Although the spent pulping liquor is the major source of pollution in terms of depleting oxygen conditions, the toxicity of the effluents in terms of Total Organic Chlorine (TOCl) originates from the bleaching plant of the large and small mills. The amount of TOCl produced is dependent on the amount of free Cl2 used during bleaching operations and is roughly calculated by the following equation:
TOCl = K(C+D/5 +H/2) kg TOCl/air dried ton of pulp, where C, D, & H are doses of Cl2, ClO2 and hypochlorite.
In India, the situation due to these chloro compounds becomes more alarming in the small paper mills. Increasing caustic soda prices and increasing gap between caustic soda and chlorine prices indicate a tendency to decrease alkali charge in cooking, thereby increasing lignin content and chlorine consumption. 6.2.4.2 Solid wastes
Solid wastes constitute a complex problem in the industry due to the varying nature and enormity of the wastes generated. Table 6.2.5 shows the solid waste generation from the small and large paper mills. The main sources of solid wastes are:
- The raw material handling/preparation - The effluent sludge from the combined mills effluent treatment plant - Flue dust from coal-fired boilers and fines in the coal - Coal cinders from coal-fired boilers - Lime sludge from the chemical recovery plant - Hypo mud from the hypo plant - Pith generation from the de-pithing plant.
Wastes from raw materials handling are burnt, discharged as effluent, or dumped in barren lands. Burning of lime sludge from causticizers and hypochlorite preparation plants in India, however, is unsuccessful due to the high silica content. Hence, the desilication of the black liquor is essential. Moreover, sludge from water treatment or effluent treatment plants contains nearly 72% organic compounds and has 45-50% water content. Therefore, dewatering of the sludge, and stabilizing the water is necessary before its final disposal. Coal ash which accounts for 30-32% of the total coal burnt also adds to the solid waste disposal problem. Most of it is used as landfill, although its disposal is still a cause for concern. From the foregoing discussion, the seriousness of the problems due to wastes generated from the pulp and paper industry is not something to be taken for granted. The pressure on land is already high, and unless long term plans are made to either reburn the lime sludge, to separate and re-use fibrous wastes, and to use coal ash for building materials, the mills will face serious problems for
92 Technology, Energy Efficiency and Environmental Externalities in the Pulp and Paper Industry
solid waste disposal in the coming years. The rising consciousness for a clean, healthy environment and the implementation of stringent measures for solid waste disposal will force the industry to make decisions in order to stop environmental degradation.
Table 6.2.5 Solid waste generation in paper mills
Waste source Large paper mills (kg dry solids / ton
paper)
Small paper mills (kg dry solids / ton
paper) Raw material handling/preparation
45 210*
Hypochlorite preparation grit 20 nil Recausticizing lime mud 593 nil Power plant/boiler ash** 656 1300 Waste treatment plant*** 1. Primary sludge 159 105 2. Secondary sludge 34 105 TOTAL 1507 1731
% inorganic solids 84 75 % organic solids 16 25
6.2.4.3 Air pollution
Particulate and gaseous pollutants from the pulp and paper mills are discharged through the following:
- Digester relief - Brown stock washers - Washer-bleach liquor preparation plant - Multi-effect evaporators for black liquor - Direct contact evaporators like cascades, cyclones, etc. - Chemical recovery furnace - Smelt dissolving and slaking tanks - Lime kilns - Boiler flue gases
* When bagasse is used in place of straw in SPM, solid waste generated from raw materials handling will
be 550 kg/ton paper and total solid wastes will be 2071 kg/t with 65% inorganic solids. ** Ash generation depends on % ash in coal and the amount of power/steam generation. *** Estimated (assuming 0.5 kg mixed liquor suspended solids produced / kg BOD removed in activated
sludge treatment plant.
Profile of the Pulp and Paper Industry in Selected Asian Countries 93
Air pollutants are generally controlled by the dust-collecting equipment. Chemical particulates emitted from recovery furnaces, smelt dissolving tanks and lime kilns, mostly of sodium sulfate and sodium carbonate, are controlled to a considerable extent by the use of venturi scrubbers, electrostatic precipitators, and other effective dust-collecting devices. Emitted gases which are a variable mixture of hydrogen sulfide, methyl mercaptans, dimethyl sulfide and sulfur dioxide, originate mainly from the sulfate pulping process. Table 6.2.6 shows the main emissions of reduced sulfur compounds from the sulfate pulping process.
Table 6.2.6 Main emissions of sulfur compounds from the sulfate pulping process
Emission rate, kg/t90 Emission source H2S *MM
CH3SH *DMS
CH3SCH3 *DMDS CH3SSC
H3 Batch digester 0-0.15 0-1.3 0.05-3.3 0.05-2.0 Continuous digester 0-0.10 0.5-1 0.05-0.5 0.05-0.4 Washing 0-0.10 0.05-1 0.1-1.0 0.1-0.08 Evaporation 0.05-1.5 0.05-0.8 0.05-1.0 0.05-1.0 Recovery Furnace (with DCE)
0-2.50 0-2 0-1 0.03
Smelt dissolving tank 0-1.0 0-0.08 0-0.5 0.03 *MM: Methyl-mercaptan; DMS: Dimethyl sulfide; DMDS: Dimethyl Disulfide 6.2.4.4 Noise pollution
The major contribution to noise pollution comes from the chipper house, vacuum pumps and compressors. Mufflers are necessary to reduce noise in vacuum pumps; and in the paper machine drive, changing the material of construction not only reduces noise, it also has the additional advantage of self-lubrication. Wherever possible, the paper machine drive gears are made of polypick or nylon material to serve the purpose of reducing noise. 6.2.5 Potential for energy efficiency improvement and pollution abatement through
technological change
6.2.5.1 Energy saving potential
It is estimated that the energy bill of the pulp and paper industry is about Rs 10 billion with a savings potential of at least 20% or Rs 2 billion, if a proper impetus is given to energy management. Technological renovations can play a significant role in improving the energy efficiency of the processes and lead to a reduction in specific energy consumption, improvement of energy and productivity and product quality. These may include major modifications of the existing plants and changes in the operating practices or process controls and equipment.
94 Technology, Energy Efficiency and Environmental Externalities in the Pulp and Paper Industry
The industry can achieve better energy performance in a number of ways: - short-term schemes with small investments and improved housekeeping measures
estimated to reduce the energy bill by 5% - medium-term schemes with attractive pay-back periods can reduce the energy bill by 10-
15% - long-term schemes with major investments can cut the energy bill by 5-10%.
6.2.5.2 Energy and environmental audits, process modifications, optimization and control,
and energy generation
A. Energy and environmental audits Energy audit is used as a tool in defining and pursuing comprehensive energy management programs. Its primary objective is to determine ways of reducing energy consumption per unit of product output. The process is conducted in two ways: preliminary audit and the detailed audit. The preliminary audit is conducted in a limited span of time, focusing on the major energy supply and demand aspects which account for 70% of the total energy requirements. The detailed audit goes beyond the quantitative estimates to cost savings. Environmental audits also help in identifying areas of high pollution loads which can be useful for the management to come up with measures to reduce pollution discharges. In general, Indian paper mills adopt pollution abatement strategies of two types:
- Internal measure: production process control aimed at reducing waste water volume and pollutant discharge load from the mill
- External measure: waste water treatment technologies or end-of-pipe treatment systems aimed at reducing discharges of pollutants to the environment.
B. Process modifications, optimization and advanced controls Through the combination of modifying existing processes and the development of new ones, the objective of improving energy efficiency can be achieved. Considerable energy savings in the industry has been reported brought about by such measures:
- Digester: 10-20% - Bleaching 5-10% - Evaporator 3-5% - Recovery boiler 20-50% - Paper machines 10-20%
Following are some latest technologies that are applied in the pulp and paper industry of India:
Profile of the Pulp and Paper Industry in Selected Asian Countries 95
Raw Materials Handling
1. Replacement of disc chippers by drum chippers
In some of the mills, it has been observed that the replacement of large numbers of disc-type low capacity chippers with high capacity chippers made it possible to reduce energy consumption from 35 kWh to as low as 7 kWh/ TBD1 chips.
Table 6.2.7 Comparative energy consumption of different chippers used
Type of chippers Capacity TBD Energy consumption kWh/ton of BD chip
1. Drum type 20-25 7 2. Disc type 6-10 30
(Status: already in use in three large mills) 2. Conversion of pneumatic conveyor to the mechanical type
80% of the mills in India have resorted to the mechanical type of conveying, and a reduction of 4-5 tons energy consumption had been realized. Performance-wise, the cleated conveyor belts offer an excellent alternative to the pneumatic conveyors. Due to layout restrictions, however, the other mills are not able to likewise do conversions. Pulping
1. Installation of continuous digesters in place of batch digesters
In some of the large integrated mills mainly in the public sector units, the old conventional batch digesters are now being replaced by continuous digesters, and are found to be energy efficient (Table 6.2.8). Advantages brought about by the latter are:
- uniform cooking and better pulp quality - low specific energy consumption - less alkali charge - shorter cooking cycle - higher liquor concentration for recovery
2. RDH/Cold Blow System
This technological innovation has been introduced for energy conservation of 20-25%, and are ideally suited for stationary digesters.
1 TBD : Ton Bone Dry
96 Technology, Energy Efficiency and Environmental Externalities in the Pulp and Paper Industry
Table 6.2.8 Comparative performance of different digesters used
Batch Continuous Steam/ton of pulp 1.6 1.0 Power units/ton of pulp 150 56 Alkali (%) 16 14
(Status: HPC units (Nawgaon, Cachar) have Kamyr digesters whereas Seshashayee Paper Boards and Tamilnadu News Print Ltd. have Pandia continuous digesters.)
Bleaching
1. Oxygen bleaching
This process is being used in paper mills which go for a low kappa number pulping. The introduction of oxygen delignification before bleaching reduces the bleach consumption, making the bleach effluent less toxic towards the environment with the added advantage of being able to generate additional steam from extracted organics at the oxygen stage. Another recently introduced bleaching technique is the use of peroxide in the conventional systems, which has already been adopted in one of the paper mills in the country. 2. Stock preparation
Most of the Indian integrated and non-integrated paper mills are replacing the conventional conical and wide angle refiners with disc refiners, which are found to be comparatively highly energy efficient (Table 6.2.9).
Table 6.2.9 Comparative power consumption of different refiners used
Type Specific energy consumption (kWh / sr / ton of pulp)
Wide angle refiner 14-18 Conical refiner 9-13
Double disc refiner 7-9 Triple disc refiner 6
Chemical Recovery
1. Evaporators
The type of evaporators being used in the Indian paper industry has been the long & short tube evaporators. These are currently being replaced by the 7-effect free falling film type evaporators which reduce steam consumption by 25-30% in the evaporator section. Increasing the number of effects of falling film evaporators can achieve a steam economy as high as 8.0.
Profile of the Pulp and Paper Industry in Selected Asian Countries 97
Recently, high pressure pumps have also been installed in some of the paper mills which help to improve steam economy from 4.2 to 4.8. 2. Energy cogeneration through boiler modifications
A number of improvements in the paper industry are needed with regards to the following: configuration of recovery boilers with respect to liquor firing, efficient three zone air distribution, auxiliary fuel furnace construction corrosion, protection and steam pressure. Earlier, boilers were giving steam pressures of 20 kg/cm2 but mills are now able to produce steam pressures of 40-60 kg/cm2. With new designs, boilers can now produce high pressure steam of 100 kg/cm2. By incorporating the above-mentioned improvement, the West Coast Paper Mills in India is now going for recovery with steam pressure of 80 kg/cm2. 3. Introduction of on-line measurement and control system
On-line measurements and control systems have lately been introduced in Indian paper machines in the Tribeni and HNL paper mills. Other mills are following suit. The introduction of such systems aids in the following:
- high fiber savings - improved and consistent quality of paper - optional moisture content - reduction in energy consumption due to high % of moisture in paper.
Digesters
It has been observed that the use of low liquor to material ratio is quite effective in reducing the energy consumption in the digester section. In small agro-based pulp mills, this is achieved by the constant monitoring of low moisture in the raw material, maintaining a high concentration of the cooking liquor (100g/li) and a high temperature or shorter cooking cycle. Installation of screw press for efficient washing of pulp
In conventional washing systems, non-woody raw materials are more difficult to wash compared to woody raw materials. The usual equipment being used is the counter current multistage vacuum drum filters. It is observed, however, that for every percent increase in solids, a savings potential of 25 tons of steam per day in a 100 tons per day pulp mill is possible. Table 6.2.10 shows how the steam requirement in evaporators is reduced with an increase in inlet solid concentrations. In one of the straw-based mills, it was observed that the installation of the screw press before the vacuum washer increased the specific loading rate and initial concentration of weak black liquor to the evaporator. This reduced the steam requirement during the evaporation process. Table 6.2.11 shows the effects of process modification.
98 Technology, Energy Efficiency and Environmental Externalities in the Pulp and Paper Industry
Table 6.2.10 Steam requirements with varying inlet and outlet concentrations
White black liquor Final concentration (%)
Steam requirement (t/t of pulp)
6 40 10.6 42 10.7 45 10.8
8 40 7.5 42 7.6 45 7.7
10 40 5.6 42 5.7
45 5.8
Table 6.2.11 Conventional and screw pressing followed by conventional washing
Mode Specific loading rate
BDMT/m
Black liquor solids
%
Chemical loss kg NaOH/t
Conventional washer (3-stage)
1.46 10 18
Screw press followed by conventional washer (3-stage)
1.73 12 12
High solids evaporation through thermal depolymerization
The energy in terms of steam that can be generated per ton of black liquor solids is dependent on the concentration of black liquor that is fired in the recovery boiler. Since it is difficult to handle highly viscous black liquor from non-woody materials in the evaporator, heat treatment of black liquor at temperatures higher than the cooking temperature could reduce the viscosity of black liquor tremendously, making it possible for the black liquor to evaporate, leaving behind some 70% solids. The advantages of the black liquor treatment are the following:
- Instead of a 50-55% thermal efficiency for 55% black liquor solids, the net thermal efficiency is likely to reach 70% in cases of 65% solid concentration.
- The use of direct contact evaporator is eliminated, thereby reducing gaseous pollution. C. Energy generation With regards to energy generation, small paper plants operating with lower capacity boilers consume waste fuels such as rice husk, bagasse, etc., and depend greatly on purchased power. Large mills on the other hand, generate part of their own power through cogeneration.
Profile of the Pulp and Paper Industry in Selected Asian Countries 99
Commonly-used boilers are the stoker-fired boilers which may either be the chain grate or spreader-stoker type, with capacities ranging from 6-80 t/h. Most medium and large-size mills currently have installed fluidized bed combustion (FBC) boilers or are in the process of converting spreader stoker to FBC boilers. 6.2.6 Status of the application of new technologies
The extent of employment of energy-efficient and environmentally sound technologies (EEESTs) in the pulp and paper mills of India is summarized in Table 6.2.12.
Table 6.2.12 EEESTs in the pulp and paper mills of India
Technology No. of mills using the technology Palman chippers 7 Kamyr continuous digesters 2 Pandia continuous digesters 3 Oxidative extraction (OE) 4 Elemental chlorine-free bleaching 3 Double disk refiners 50% of the mills Twin wire machines 5 Free flowing falling film evaporators 3 Long tube vertical type evaporators most integrated mills have LTV
evaporators High pressure boilers (40-60 kg/cm) 5 Electrostatic precipitator 70% of the integrated mills Lime sludge reburning 5 Full fledged effluent treatment system 80-90% of the integrated mills and some
selected medium and small-sized mills Despite the changes occurring with regards to environmental consciousness, public concerns and customer preferences in the country, the pulp and paper industry is still in a difficult position to impose total environmental management and undergo environmental control modifications in the facilities. Nevertheless, some new trends are currently being realized in a number of paper mills in the country in order to combat environmental problems (see Table 6.2.12).
100 Technology, Energy Efficiency and Environmental Externalities in the Pulp and Paper Industry
6.3 COUNTRY REPORT: PHILIPPINES
6.3.1 Introduction
All industrial processes generate waste. Since no production system can transform all input resources completely into end-products, waste generation is inevitable. Problems arise when these wastes are discharged in excess of what the environment can absorb. The industrial sector which accounts for a large share in the country’s energy consumption, is also a major source of environmental pollution. Industrial pollution has earlier been considered a local problem but is today recognized as regional as well as global. Common sources of industrial pollution are the waste water used in the manufacturing process and the emissions from combustion of fossil fuel. There is a wide array of technically feasible abatement measures ranging from efficiency improvement in the process to the more common and usually more expensive end-of-pipe pollution abatement technologies. The pulp and paper industry is one of the industrial sector’s high energy consumers and major contributors in pollution. Attention to the pulp and paper industry, therefore, deserves a high priority. This section looks into the technological status of the pulp and paper industry of the Philippines with regards to energy efficiency and environmental soundness. Through the historical and present techno-economic data of the industry, the potential for improving the current status of technologies for energy and environmental management is analyzed. 6.3.2 Technological trajectory of the paper industry in the Philippines
6.3.2.1 Structure of the paper industry
Pulp and paper production in the Philippines was pioneered by Compania de Cellulosa de Filipinas when it established an integrated pulp and paper mill in 1948 in Bais, Negros Occidental. The mill which produced 10 tons of bond paper per day using bagasse as raw material is still in operating condition. Another pioneer in the paper industry was established in 1950 in Metro Manila to operate a second-hand board machine. This machine is still operational and currently produces chipboard. A number of paper mills were established during the 1950s and the early 1960s when the industry had to contend with two sets of import duty levels - a lower rate for pulp and a higher rate for finished paper and brand products. This encouraged the mills to utilize the cheaper imported raw materials. In effect, plans to build pulping facilities for most of the mills never materialized. Several non-integrated paper mills were established during the 1970s and 1980s but these were based mainly on imported and local recycled waste paper. The list of paper mills in the country and their dates of establishment are shown in Annex 1.
Profile of the Pulp and Paper Industry in Selected Asian Countries 101
From 1978 to 1991, paper production in the Philippines remained flat. Consumption on one hand increased from 440,000 tons in 1978 to 753,000 tons in 1993 (Table 6.3.1). To meet increasing demand, the country had to rely on imports. In contrast, production of paper and board in other ASEAN countries rose from 820,000 to 2,100,000 tons with marginal increase in net imports during the same ten-year period. Despite the problem of power shortages in the last two years, the industry managed to continue operations and, aided by resilient domestic market, was able to post moderate gains. Total production of the country’s operating mills reached 490,000 tons in 1992 and increased by 6% to 518,000 tons in 1993.
Table 6.3.1 Evolution of paper industry: total paper and paperboard (103 tons)
Year Installed Capacity
Production Consumption Imports
1987 439 319.5 475.0 200.8 1988 506 341.0 493.9 193.0 1989 564 345.0 554.6 216.4 1990 579 325.0 481.6 205.3 1991 579 392.0 626.0 245.2 1992 635 489.0 743.1 279.5 1993 650 517.5 753.1 279.5
Source: Aragon, P.M., Country Focus. A. Production capacity
From a 1989 survey, the industry coverage was 33 pulp and paper mills, with 4 integrated mills (shown in Table 6.3.2) and 5 pulp manufacturers (Table 6.3.3). The remaining 24 are non-integrated paper mills. Exclusive of two non-operating mills, the total production capacity of the integrated mills is 410,000 tons per annum. The total pulp capacity of the Philippines is about 289,000 tons per annum while aggregate paper capacity is approximately 611,000 tons per year. In view of several closures, the average annual operating capacities for pulp and paper production are 223,000 tons and 526,000 tons, respectively (Table 6.3.4). The industry structure is very small compared to international standards. Of the 28 paper mills, only 3 have a capacity of over 50,000 tons per annum (Table 6.3.5). The average size of mills ranges from 10,000 to 15,000 tons per annum. The industry structure is also outmoded and as a result, suffers from lengthy machine downtime due to difficulties in obtaining outdated replacement parts.
102 Technology, Energy Efficiency and Environmental Externalities in the Pulp and Paper Industry
Table 6.3.2 Integrated pulp and paper mills in the Philippines, 1989
Company/Mill Pulp Paper Capacity
(103 t/year)Materials Capacity
(103 t/year)Main Grades
PICOP 180 Mech, UKP, BKP
150 Newsprint, Linerboard, Corrugated Medium
Central Azucarera 9 Bagasse 14 Printing United Pulp & Paper 16 Bagasse 31 Sack Kraft, Corrug.
Medium, Linerboard Menzi Dev’t. Corp. 3 Abaca 7 Printing & Writing
Table 6.3.3 Pulp mills in the Philippines, 1989
Company/Mill Capacity (103 t/year) Materials Albay Agro-Ind’l. Dev’t. Corp. 1 Abaca Canlubang Pulp Mfg. Company 4.5 Abaca Cellophil Resources Corporation 66 Wood Pulp Isarog Pulp and Paper Co. 4.5 Abaca PICOP 5 Abaca
Table 6.3.4 Total pulp and paper mill capacities in the Philippines, 1989
Mill Categories Capacity (103 t/year) Pulp Paper
Integrated mills 208 202 Pulp mills 81 - Paper mills - 409 Total capacities 289 611 Operational capacities 223 536
Table 6.3.5 Philippine paper mills categorized by rated capacity (t/year)
Rated Capacity Number of paper mills Below 10,000 10
10,000 to 20,000 10 20,000 to 50,000 5 50,000 & above 3
B. Paper machines There are currently 45 paper machines in the country with a total capacity of 540,000 tons per annum, or an average of 12,000 tons annually (Table 6.3.6).
Profile of the Pulp and Paper Industry in Selected Asian Countries 103
Table 6.3.6 Paper machine structure in the Philippines in terms of capacity (103 t/year), trim width per cm, and start-up year
PM capacity Operating machines
Total paper capacity
% Share
below 10 33 166 31.0 10 - 19 7 102 19.0 20 - 29 1 27 5.0 30 - 39 1 31 5.8 40 - 49 - - - 50 - 59 - - - 60 - 69 2 128 23.9 over 69 1 82 15.3 Total 45 536 100.0
PM trim/cm below 201 22 132 24.6 201 - 300 16 118 22.0 301 - 400 5 144 26.9 401 - 500 - - - 501 - 600 1 60 11.2 over 600 1 82 15.3
Total 45 536 100.0 Start-up Year before 1960 7 57 10.6
1960s 19 132 24.6 1970s 10 240 44.8 1980s 9 107 20.0 Total 45 536 100.0
As can be seen in Table 6.3.6, only three of the machines operate at a minimum of 60,000 tons per year, representing less than 40 percent of the total industry capacity. Most of the machines were bought second-hand and are very small both in terms of capacity and width. Only two have a width greater than 5 meters. The machines are also very old. However, it is quite difficult to establish the exact age of these machines because almost all have been bought second-hand. Twenty machines have reportedly been installed during the past 20 years. Of the 45 operating machines, 5 can easily absorb 50 percent of the total annual production capacity. In fact, the 2 biggest machines (with a trim exceeding 500 cm) have a combined capacity constituting 26.5 percent of total. Essentially, the country’s aggregate paper requirements may be supplied by only ten medium-sized (not necessarily modern) paper machines. Table 6.3.7 presents the status of the country’s paper machines in 1989, relative to that of the other ASEAN countries.
104 Technology, Energy Efficiency and Environmental Externalities in the Pulp and Paper Industry
Table 6.3.7 Total capacities of paper machines in ASEAN countries by mill capacity, age, and width, 1989 (103 t/year)
Distribution Indonesia Malaysia Philippines Singapore Thailand TotalPM Capacity below 20,000 455 136 294 42 330 125721,000-40,000 464 - 103 77 161 805 41,000-60,000 155 - 60 60 50 325 61,000-80,000 285 130 72 - 220 707 over 80,000 225 - 82 - 200 507 Total 1584 266 611 179 961 3601# of machines 90 27 52 13 78 260 Average capacity 17.6 9.9 11.8 13.8 12.3 13.9 Start-up year before 1950s 375 82 160 38 116 771 1950s 10 - 55 - 6 71 1960s 156 13 111 1 162 443 1970s 281 26 238 47 287 879 1980s 762 145 47 93 390 1437Total 1584 266 611 179 961 3601Median age (yr.) 10 8 21 9 12 13 Wire width (m) below 3 602 121 301 64 540 16283 - 5 617 15 168 115 351 12665 - 7 140 130 142 - 70 482 over 7 225 - - - 225 Total 1584 266 611 179 961 3601Median width (m) 3.35 3.80 3.06 3.46 2.25 3.02
Local mills lack the simplest instrumentation and process control systems. The speed of most machines is quite slow and consumption of energy is high. They are also ill-equipped in terms of environmental protection. Prolonged shutdowns have become common due to lack of spare parts and inadequate engineering/consulting companies. Safety standards are generally low and fatal accidents frequently occur. 6.3.2.2 Technology
Standard manufacturing technology is being used in the industry. Given the papermaking equipment and facilities available and the flexible requirements of the domestic market, this is found to be adequate for the industry. There appears to be an adequate supply of trained technicians and skilled personnel. Some big mills also engage foreign technicians as needed.
Profile of the Pulp and Paper Industry in Selected Asian Countries 105
Based on the study commissioned by the Development Bank of the Philippines (DBP) in 1992, it was observed that the technological framework of the pulp and paper industry is essentially structured as follows:
- Only 5 of the country’s operating mills are integrated with pulp production, representing 36% of total production capacity.
- The industry is heavily dependent on imported raw materials, particularly virgin pulp,
waste paper, and papermaking chemicals. - Existing paper machines are generally small and do not have economies of scale to
compete with foreign products. Even the 3 biggest machines representing 40% of the total production capacity do not have the economies of scale to be internationally competitive. Of the 45 operating machines, 40 have production capacities below 20,000 tons.
- Most of the paper machines are old and obsolete. Many were bought second-hand and
were already outmoded on start-up. - One reason for the industry’s low operating efficiency is the difficulty to find spare parts
for the outmoded machines. Shutdowns due to lack of spare parts are common among local mills.
- High energy consumption is also an effect of obsolete machinery. Only a handful of the
local machines have some sort of heat recovery system. - High energy costs, in turn, result in high production costs. To compare, a modern
newsprint paper mill based on waste paper consumes about 900 to 1,000 kWh per ton, while a standard Philippine mill consumes 1,275 kWh per ton.
- Modern integrated process control devices which are standard equipment for all machines
in Western countries are not available in Philippine mills. Local mills are basically equipped with conventional pneumatic instrumentation, only 3 machines use computerized weight and moisture control systems, and a few operate without any kind of instrumentation at all.
- Most machines operate at speeds below 500 m/min. The fastest newsprint machine runs
at 760 m/min, slower than the speed of modern machines, which is 1,000 m/min. - Faulty process designs result from lack of engineering and technical expertise specific to
the pulp and paper sub-sector. Extra operation costs are thus incurred, further aggravating the low operating efficiency of the industry.
106 Technology, Energy Efficiency and Environmental Externalities in the Pulp and Paper Industry
- Safety standards in most mills are very low and fatal accidents frequently occur. Unprotected rotating parts, roll nips and pulpers are safety hazards in many mills.
6.3.3 Evolution of energy efficiency in the pulp and paper industry of the Philippines
6.3.3.1 Energy profile
The pulp and paper industry is an energy-intensive industry where energy consumption varies with respect to the manufacturing operations and processes involved. From 1984 to 1992, figures show an increasing trend in the total consumption of energy for the pulp and paper sector. (Figure 6.3.1). Oil, non-oil and electricity consumption comprise 40%, 35% and 25%, respectively, of the total energy consumption in the industry.
toe
050000
100000150000200000250000300000350000400000450000
1984 1985 1986 1987 1988 1989 1990 1991 1992
Oil Non-oil Electricity Total Energy
Figure 6.3.1 Historical energy consumption of the pulp and paper sector in the Philippines
(koe, 1984 to 1992)
The industry is also considered one of the high fuel oil consuming sectors among the Philippine industries with a share of 2.5% of the total industrial fuel oil consumption. The profile on energy use as is described below was based on six mills studied (Table 6.3.8 and Figure 6.3.2). A. Energy consumption
Total annual energy consumption in six plants is 182,258 toe. This is broken down into 141,154 toe (77%) bunker fuel and 284,64 toe (16%) electricity, and 12,640 toe (7%) for others. The energy requirement is used mainly as heat for steam generation/process heating and as mechanical power to run the plants’ electrical motors. Consumption of energy depends largely on the type of machine, its process design, operating efficiency, and production rate. Normally, smaller machines consume less energy because they
Profile of the Pulp and Paper Industry in Selected Asian Countries 107
involve simpler processes with less automation. However, specific energy consumption is higher in smaller production units. As a result, energy utilization of local mills is 20 to 40% higher than standard levels. B. Energy source mix
The energy use pattern in the six mills is based mainly on electricity and oil sources. One firm uses non-oil energy sources in the form of waste wood and black liquor. More than half of the energy input in the industry is used to generate steam for process heating. Supply of electricity differs among the plants. Most companies utilize electricity which is entirely supplied from outside, while one company internally generates a small portion of its electricity requirements.
Table 6.3.8 Annual energy consumption of six mills of the Philippine paper industry
Bunker Fuel Electricity Others Total Company 103 liters toe MWh toe GJ toe toe
A 2224 2202 11197 955 3157 B 20700 20500 45528 3884 24384 C 1104 1093 1877 160 1253 D 10490 10388 84530 7211 17599 E 4056 4016 14853 1267 5283 F 10971 102955 175680 14987 533398 12640 130582
Total 142544 141154 333665 28464 533398 12640 182258 77.45% 15.62% 6.93% 100.00% Average 23757 28231 55611 5693 36452
Bunker Fuel77%
Electricity16%
Others7%
Figure 6.3.2 Distribution of annual energy consumption of six Philippine paper mills
C. Energy application
About 72% of energy input goes for process heating. The use of electricity, mostly in electric motors, accounts for 23%. Other small applications such as materials handling and transportation, which utilizes petroleum products, account for 5% (Table 6.3.9).
108 Technology, Energy Efficiency and Environmental Externalities in the Pulp and Paper Industry
Table 6.3.9 Energy utilization profile of 3 energy-intensive industries in the Philippines
Energy Applications (%) Paper Industry
Cement (Dry) Steel/Metal
Mechanical Power Drive 23% 24% 30.3% Process Heating 72% 74.5% 66.0% Transport/Handling 5% 0.5% 1.5% Lighting/Air-conditioning
1.0% 2.2%
Total 100.00% 100.00% 100.00% D. Specific Energy Consumption
On the average, energy consumed in six mills in the country is about 475.6 kgoe/t of paper produced. This ratio can be broken down into 364.5 kgoe (bunker fuel) per ton paper and 1,084 kWh of electricity inputs per ton (Table 6.3.10).
Table 6.3.10 Specific energy consumption of the six paper mills in the Philippines
Company SFC in kgoe/t SELC in kWh/t SEC in kgoe/t A 310.9 1,580.0 445.6 B 512.9 1,139.0 612.5 C 239.2 410.8 274.3 D 131.2 1,067.3 240.1 E 306.5 1,133.5 403.2 F 686.3 1,171.2 877.0
Average 364.5 1,083.6 475.6
E. Energy cost
A previous survey revealed that from 1983 to 1986, fuels purchased accounted for 48% of the total of the sector, while electricity accounted for 52% (Table 6.3.11). The average cost of fuels and electricity purchased during the same period was P728,669 and P804,813, respectively. At present, the cost of bunker fuel oil which is the main source of energy for the industry, ranges from P2.65 to P2.99 per liter. Electricity cost varies between P1.275 to P2.86 per kWh.
Profile of the Pulp and Paper Industry in Selected Asian Countries 109
Table 6.3.11 Historical energy cost data of the Philippine paper industry (103 US$)
Year Fuels Purchased Electricity Purchased Total 1983 31937 25162 58377 1984 50786 33440 86258 1985 17614 28594 46913 1986 16250 41574 58473
Average 29147 32193 62505 % of Total 48% 52% 100%
Source: National Statistics Office, Annual Survey of Establishments 6.3.4 Environmental externalities of the pulp and paper industry of the Philippines
6.3.4.1 Environmental concerns
The industry is heavily concentrated in Metro Manila with strong pressure to establish adequate pollution control measures. No mill can be expected to comply with the required environmental protection standards due to the high investment needed for proper pollution control measures. A. Water pollution
The mills in the Philippines are mostly old and obsolete with limited pollution control facilities. The problem of pollution is more pronounced in the Metro Manila area where most of the mills are located. To worsen matters, Metro Manila has no common sewer system to ensure adequate waste water treatment. The main pollutants for the pulp and paper industry are the biological oxygen demand (BOD5) and the total suspended solids (TSS). Water pollution in Metro Manila has become very alarming. Both the industrial sector and private individuals are guilty of contributing to the city’s pollution problem. The huge influx of people from the provinces who do not have adequate sanitary facilities aggravates the situation. Meanwhile, most of the old paper mills only have filters for fiber recovery. Effluent water standards in the Philippines are set as ambient combinations. In contrast, other pulp and paper producing countries base their standards on the kilogram of pollutant discharged per ton of pulp and paper produced. There is no point, therefore, in comparing the two standards. The ambient water concentration applied in the Philippines is, however, close to the standard set in developed countries, particularly in the USA. B. In-plant measures and external effluent water treatment
Aside from minimized water consumption, recovery of fiber, energy and chemicals is equally important for paper mills. The most common measures to effect this include the following:
110 Technology, Energy Efficiency and Environmental Externalities in the Pulp and Paper Industry
- collection and recirculation of clean, cool water - installation of a vacuum sealing water system equipped with its own cooling tower and
cooling water recirculation system - minimized flow of fresh water shower - use of mechanical seals to minimize sealing water consumption of pumps, agitators, and
refiners - sufficient white water storage to equalize water flow and make operations more stable - use of effective fiber filters (fiber save all) or other equally effective recovery equipment
to minimize fiber content in white water overflow The introduction of the above measures is expected to enable paper mills in areas with insufficient fresh water supply to further reduce water consumption to 10 m3 per ton. In the Philippines, average water consumption is higher, at 30 m3 per ton. This is because most of the mills are old and small, and it is very expensive to undertake a total rebuild. Also, waste paper is used as furnish in many mills and fresh water consumption is vital in the operation of these mills to ensure better quality of paper produced. In-plant measures alone cannot adequately control the presence of effluents and pollutants in water. It is necessary to undertake further treatment of effluents before final discharge is made. Before discharge, effluents must first be externally treated. A primary clarifier can reduce TSS by as much as 70 to 95 percent but BOD can only be reduced marginally by this method. A secondary treatment in an aerated lagoon or an activated sludge plant is necessary to shrink BOD by about 50 to 90 percent TSS can be minimized further by a secondary clarifier. Primary treatment should be compulsory for all pulp and paper mills starting from 1994. Secondary treatment including sludge handling should be obligated by the year 2000 or earlier. Also, new paper mills are encouraged to be built outside Metro Manila. A 1992 DBP study showed that environmental protection cost for the projected paper capacity in the year 2000 is estimated to be about US$ 70 million. This includes in-plant measures, primary and secondary treatment, and sludge handling. Project financing could come from grants and long-term loans sourced from international financing institutions. The total investment for installing environmental control measures for the five mills in 1992 is summarized in Table 6.3.12. C. Emissions to the atmosphere
Practically all paper mills in the country have power boilers using Bunker C oil as fuel. Only one mill has a recovery boiler. The power boilers in most paper mills are generally small and medium-sized. When oil is burned, particulate matter and sulfur compounds are formed. The amount of sulfur compound depends on the amount of sulfur in oil.
Profile of the Pulp and Paper Industry in Selected Asian Countries 111
Table 6.3.12 Investment for environmental control measures in 5 paper mills (103 US $)
Case In-plant measures
Primary treatment
Secondary treatment
Sludge handling
Total
A 190 1650 6100 1590 9530 B 100 710 2210 860 3880 C 85 370 860 760 2075 D 100 660 1940 910 3610 E 80 280 590 730 1680
Reducing sulfuric emission may be realistically effected by the use of sulfur-free fuel or fuel with low sulfuric content and, treatment of flue gas after combustion. Using oil with low sulfur content is very effective in regulating sulfuric emissions. This kind of oil, however, is more expensive than the normal heavy oil. Electrostatic precipitators and scrubbers used for external treatment of flue gas are likewise effective but expensive. Particulate matter is practically eliminated (99 percent) with the application of the electrostatic precipitator. To reduce the sulfuric compounds H2S and SO2, it is necessary to wash the gases in scrubbers. This process reduces sulfur emission by as much as 90 to 95 percent. 6.3.5 Potential for energy efficiency improvement and pollution abatement through
technological changes
6.3.5.1 Energy conservation opportunities
The following are the general observations and identified technologies with potentials for conserving energy for the industry on the basis of previous sectoral studies, surveys and energy audits conducted in the pulp and paper industry.
- Combustion tests conducted during recent energy audits showed that majority of boilers were operating well within or near the optimum operating condition with boiler efficiencies varying from 72.4% to 87.7%.
Four of the six companies surveyed, have, in one time or another, purchased and used a
portable or on-line flue gas analyzer to monitor the combustion performance of their boilers and adjust/fine tune the air-fuel ratio. Of these four companies, only two have a functioning flue gas analyzer, one portable and one on-line. In the other two companies, the analyzers had not been operational for quite some time due to exhausted oxygen absorbent/cell. Most of the companies get a free boiler efficiency testing from the bunker fuel and/or fuel additive supplier on a monthly basis, while one company never had its boiler tested.
- Boiler feedwater treatment is generally adequate, except in at least 3 companies where
about 1/8 inch thick scale was found inside the boiler tubes during descaling.
112 Technology, Energy Efficiency and Environmental Externalities in the Pulp and Paper Industry
- Fuel oil metering is usually done via day tank level monitoring. Only half of the companies surveyed are maintaining boiler operation logsheets.
- Condensate recovered from the paper machines and returned back to the boiler house
varied from as low as 30% to as high as 85%. - Leaks were often noted on the steam and condensate lines. Steam and condensate lines
were also commonly observed to be inadequately insulated in most of the plants visited. Insulation usually consists of wool blanket or asbestos with aluminum cladding.
- There is at least one opportunity to investigate the feasibility of installing waste heat
recovery system in the form of economizer to recover heat from boiler flue gas and a heat exchanger to recover heat from boiler blowdown.
- Historical data is not always available to show the distribution of electrical energy to the
paper machines and other consumers. Furthermore, there is often a lack of watt-hour sub-metering system for the major process areas/equipment. Electrical power distribution in a paper mill goes mainly to the paper machine to provide motive power, the balance goes to the boiler house, lighting, air conditioning, office equipment and miscellaneous loads.
- Natural lighting is effectively utilized in most of the companies surveyed. However, most
installed skylights need to be cleaned/replaced. The installation/retrofitting of reflectors on existing fluorescent fixtures is uncommon in the industry. The rapid start type ballasts are still commonly used. Indoor lighting is predominated by fluorescent fixtures. A typical fixture is surface-mounted and consists of two 4-watt fluorescent tubes, without reflectors or diffusers but only a casing for the ballast.
- Motor loads account for the largest portion of the total electrical load. This is an
indication that there are energy conservation opportunities in the system. - The electrical power factor of five plants ranged between 83.75% and 99.5%. In one
plant, however, the monthly metered power factor of the plant’s electrical system averages at a very low 72.58%. As a result of this very low power factor, a power factor adjustment or penalty is added to the electricity bill.
- To ensure a reliable supply of electricity, at least two paper mills are seriously considering
to install 12 to 20 MW cogeneration systems. Assuming that 50% of the industry will install cogeneration systems to be self-sufficient in its thermal and electrical requirements, a considerable amount of savings in annual fuel consumption can be realized.
Profile of the Pulp and Paper Industry in Selected Asian Countries 113
- Air intake in compressed air systems is often from the same enclosed area/surroundings where the compressors are located.
- Pumps and refiners utilized by the paper industry are quite inefficient. Pumps normally
consume 25 to 35% of electrical energy, while refiners use up 15 to 25%. The low efficiency of these machines may be attributed to design capacity and actual process requirements. Other factors which significantly influence power consumption and refining results are the types of refiner, plate pattern, and speed.
- Paper drying consumes the biggest share of the process steam. An increase of about 2 to
35% of paper web dryness after press may be achieved if a typical press part is improved. This alone would reduce steam consumption of paper drying by 8 to 12%. It could also improve the machine’s efficiency.
6.3.5.2 Energy conservation program
Majority of the companies in the industry do not have formal energy conservation committee at present. Some used to be very active in energy conservation earlier and have, in the past, implemented a number of energy conservation measures or are still carrying out energy conservation activities but in a much less aggressive manner. 6.3.6 Status of application of new technologies
In spite the opportunities for energy conservation in the industry, there are barriers to their effective implementation. These include technical, financial, institutional and other related issues as perceived by the industry. The technical barriers in the implementation of energy conservation technologies are mostly due to existing plant layout, support facilities and services offered by suppliers. For waste fuel utilization and coal conversion, problems on pollution, safety, and effects on quality of products were noted. These barriers include the lack of information on reliable suppliers and services offered, lack of expertise regarding operation, maintenance and servicing of equipment/system, and other operation-related problems. The financial/economic viability of energy conservation technologies is a major concern of every industry, and the most common financial barriers include the unavailability of funds for energy conservation projects and the lack of skill, both of plant personnel and financial institution personnel, in the packaging and evaluation of energy conservation projects. There is also a need to enhance the existing institutional framework that promotes and encourages energy conservation. A more aggressive information/dissemination campaign should be emphasized to encourage the industry to practice energy conservation.
114 Technology, Energy Efficiency and Environmental Externalities in the Pulp and Paper Industry
6.3.7 Concluding remarks
The pulp and paper industry in the Philippines has been described as small, outmoded, and highly protected. It is generally inefficient and internationally non-competitive, with bleak long-term prospects. Most of the machines in the pulp and paper sector are old and replaceable. It is believed that 10 reasonably-sized paper machines can easily produce 600,000 to 700,000 tons of the required one million tons projected for the year 2000. Operating fewer but bigger units will take advantage of economies of scale and benefit from modern process technologies. In the face of existing conditions, expansion is not recommended for the local industry. The increasing pressure to install environmental protection facilities in all mills and the required dislocation of plants outside the densely populated metropolis likewise demand a major structural change. Millers are, therefore, encouraged to relocate outside the densely populated metropolis with the high cost of environmental protection necessitating relocation in areas which are less populated. Since the industry has not yet reached the ultimate limits of resource-use efficiency, reducing waste generation should be high on the industry’s agenda, not only because of concern for the environment, but for the more fundamental reason of improving profitability. After all, whatever the industry discharges as waste are essentially the very resources it buys and pays for in the first place. Nothing comes free. Yet in the past, waste reduction never received the priority it deserved. It is important, therefore, to reflect and analyze why.
Profile of the Pulp and Paper Industry in Selected Asian Countries 115
6.4 COUNTRY REPORT: SRI LANKA
6.4.1 Introduction
The current gross domestic product of Sri Lanka is estimated to be increasing at 6.9%. Manufacturing, wholesale and retail trade and agriculture are the most important contributory sectors to the growth. In 1993, the GDP at current market price was estimated to be Rs. 150.8 billion, with agriculture, forestry and fishing contributing 21.2% share of the GNP, mining and quarrying 2.5%, manufacturing 19.4%, wholesale and retail trade 21.8% and construction 7%. The population of Sri Lanka in 1993 has been estimated at 17.62 million. The per capita GNP at current factor cost prices is estimated at US$ 526 in 93, an increase of 16.5% over previous year. Pulp and paper industry in Sri Lanka was introduced in the 1950’s by the state and was managed by the state until very recently. The machinery and the technologies are generally old. Though it has been realised that improvements in energy efficiency and environmental standards are very desirable, the lack of finances has impeded this development. 6.4.2 Technological trajectory of the Sri Lankan pulp and paper industry
6.4.2.1 Capacity, production, raw material and process mix
There are two paper mills in Sri Lanka. The pulp manufacturing techniques of these mills are soda pulping and neutral sulfite semi-chemical processes. Both these plants are designed to use straw as the raw material. Figure 6.4.1 shows the pulp production and Figure 6.4.2 shows the raw material mix for pulp production. The second plant was commissioned in the late seventies thus increasing the total installed capacities. However, as sections of the older plants become unavailable for production, the total installed capacity gradually decreased. This is reflected in Figure 6.4.1. The extent of production of pulp from rice straw gradually decreased due to the environmental effect of discharges from this process. To make up for these losses, the production from waste paper increased proportionately. The productivity reported is shown in Table 6.4.1.
Table 6.4.1 Reported productivity in Sri Lankan pulp and paper industry
Year Productivity (ton/employee) 1960 7.7 1980 5.4 1990 6.2 1992 9.2
The shortfall between the demand for pulp and local production were met by gradual increase of imported pulp from large pulp manufacturers, as these became economically attractive.
116 Technology, Energy Efficiency and Environmental Externalities in the Pulp and Paper Industry
1970 1980 1990 19920
2000400060008000
100001200014000
Pul
p P
rodu
ctio
n
1970 1980 1990 1992
YearInstalled Capacity From Straw & Wood From Waste Paper
Figure 6.4.1 Sri Lanka’s pulp production capacity by source (tons)
1970 1980 1990 19920
5000
10000
15000
20000
25000
30000
35000
Raw
mat
eria
l
1970 1980 1990 1992Year
Wood Straw
Figure 6.4.2 Raw material mix for pulp production (tons)
6.4.2.2 Role of the pulp and paper industry in the national economy
Paper is a direct input to other economic activities like printing and service sectors and remains very important in Sri Lankan economy although its relative importance in terms of production is not very significant. The contribution of the pulp and paper industry to the Sri Lankan national economy is
Profile of the Pulp and Paper Industry in Selected Asian Countries 117
demonstrated by its high value added and employment and profitability ratios. The percentage of value added to GDP and the value of output has been increasing over the years. Table 6.4.2 shows some key economic indicators of the sector.
Table 6.4.2 Economic indicators of the pulp and paper industry
Year 1985 1993 Value Added to GDP (Million Rs.)
200.235 416.347
No. of Direct Employees 3953 3167 Sector employment as a ratio of:
Industrial EmploymentTotal Employment
1.26% 0.08%
0.4% 0.06%
Direct employment in the pulp and paper sector declined by about 19% between the years 1985 and 1993. This was caused mainly by the closure of the Valachchenai plant owing to terrorism in the Eastern part of Sri Lanka since 1985. 6.4.3 Evolution of energy efficiency in the pulp and paper industry of Sri Lanka
Figure 6.4.3 shows the specific energy consumption of the two processes. These factories have been operating on varying raw material and technological mixes over the years. Whenever imported pulp or waste paper was cheaper, the imported component increased substantially. Thus over the years, these plants have been operating with varying degrees of integration, giving non-consistent values for specific energy consumption. 6.4.4 Environmental externalities in the pulp and paper industry of Sri Lanka
The paper mill which was commissioned in the 1950's, does not have a chemical recovery plant and the black liquor was directly discharged into a natural water stream. This has caused a severe environmental problem in the area. The stream became dead due to oxygen depletion and the deposition of fibrous material along the banks. The lagoon which receives the water stream which was rich in prawns and other varieties of fish also became dead. This has led to some serious social problems in the fishing villages of the area.
118 Technology, Energy Efficiency and Environmental Externalities in the Pulp and Paper Industry
1980 1990 19920
0.10.20.30.40.50.60.70.80.9
Spe
cific
Ene
rgy
Con
sum
ptio
n
1980 1990 1992Year
Soda Pulping Sulfite Process
Figure 6.4.3 Specific energy consumption for soda and sulfite pulping processes (toe/t of pulp)
In the eighties the use of straw as raw material was reduced and recycling of waste paper was increased in this factory. In the early 90s, pulp production from straw was completely stopped. Since then the environmental issue of discharging effluent into the lagoon has been satisfactorily resolved. The second plant which was commissioned in the 1970's was equipped with a chemical recovery plant. Unfortunately this plant has never been commissioned due to the high silica content in the black liquor. Since the inception of the plant the effluents from the mill have been discharged into a main river. As the effluents are discharged without chemical recovery, the pollution caused to the river is appreciable. The users of the river water are agitating for remedial action. 6.4.5 Potential for energy efficiency improvement and pollution abatement through
technological changes
The following options may be examined to resolve the high energy cost and the environmental problems caused: (a) Change Raw Material
- By changing the raw material from rice straw to bagasse, the silica problem in the black liquor could be overcome. With minor modification to the chemical recovery plant, chemicals in the effluent could be recovered. Adequate bagasse is available in the locality.
Profile of the Pulp and Paper Industry in Selected Asian Countries 119
- The use of wood as raw material for the manufacture of pulp will have similar advantages as
above. The resources needed for growing of trees for this purpose are available. (b) Change of Chemical
By the use of potassium hydroxide instead of sodium hydroxide for cooking of rice straw, the effluent could be collected and marketed as potassium based fertilizer. (c) Change of Fuel
As the paper factories are located in the rice growing and processing areas, adequate quantities of rice husk is available to be used as fuel for the production of steam for heat and electricity.
120 Technology, Energy Efficiency and Environmental Externalities in the Pulp and Paper Industry
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The Asian Institute of Technology (AIT) is an autonomous international academic institution located in Bangkok, Thailand. It’s main mission is the promotion of technological changes and their management for sustainable development in the Asia-Pacific region through high-level education, research and outreach activities which integrate technology, planning and management. AIT carried out this Asian Regional Research Programme in Energy, Environment and Climate (ARRPEEC), with the support of the Swedish International Development Cooperation Agency (Sida). One of the projects under this program concerns the Development of Energy Efficient and Environmentally Sound Industrial Technologies in Asia. The objective of this specific project is to enhance the synergy among selected developing countries in their efforts to adopt and propagate energy efficient and environmentally sound technologies. The industrial sub-sectors identified for in-depth analysis are iron & steel, cement, and pulp & paper. The project involves active participation of experts from collaborating institutes from four Asian countries, namely China, India, the Philippines, and Sri Lanka. The technological trajectories, energy efficiency and environmental externalities of the pulp and paper industry in the four Asian countries are presented in this document (Volume III). Other related publications based on this research finding include: Volume I Technology, Energy Efficiency and Environmental Externalities in the
Cement Industry Volume II Technology, Energy Efficiency and Environmental Externalities in the
Iron & Steel Industry Volume IV Regulatory Measures and Technological Changes in the Cement, Iron
& Steel, and Pulp & Paper Industries An assessment of the implementation of energy efficient and environmentally sound industrial technologies among the selected countries is presented in a separate “Cross-Country Comparison” Report.
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