LCA Final (1).docx

PULP AND PAPER INDUSTRY

A Life Cycle Assessment

Presented to Aileen D. Nieva,

Professor, School of Chemical Engineering,

Chemistry, Biological Engineering and

Material Science Engineering

In Partial Fulfillment of the Requirements

for CHE 185-1 Industrial Waste Management

And Control

By

Hayag, Christine Aira

Jacobe, Lanz

Landingin, Junard

Macalino, Angelo

Salen, Vladimir

March 2016

IntroductionThe concept of sustainable development involves LCA of products, efficient resource utilization, energy conservation, limitation of wastes from households and industries. The pulp and paper industry is also seeking to embrace the benefits that come with sustainable development by striking a balance between economic, social and environmental aspects of development. The main purpose of carrying out the study was the identification and assessment of the environmental impacts that are a result of the production of paper.

The industry is also improving its environmental performance through improved waste treatment systems. This study determines the different hotspot on the process and recommend different control and management on each hotspots. One management and control method was designed to make it sustainable enough to be used in the manufacturing process. Life Cycle Assessment (LCA) is thus an appropriate method to get a global overview of the pulp and paper industry and therefore be able to identify opportunities for raw material and energy optimization as well as improving the efficiency of waste treatments systems.

Goal and Scope of the Study

As part of company continuous environmental performance improvement efforts, technical teams have to assess the potential environmental impacts of paper and to identify the top management and control methods for different hotspots that should reduce the products impacts on the environment.

The organization now wishes to quantify the perceived potential improvement and establish whether there are still other opportunities that could be exploited to optimize the environmental performance of the product.

The range of actions, alternatives and impacts that are to be examined is defined to allow stakeholders to make their concerns known and ensures the issues and potential impacts are addressed.

Objectives of the Company

Our company target to be the most sustainable manufacturer of paper within our vicinity and nearby areas, providing a high quality and eco-friendly paper for daily writing and printing use or purposes.

To be the most trusted paper producing company that supports the improvement and development of the communities within our vicinity and nearby areas through the use of sustainable high quality made paper.

To be the best business partner of big companies to promote sustainability, improvement and development of environment.

System Boundary

The system boundary includes the (1) raw material acquisition, (2) manufacturing, (3) emission to air, water and land and (4) treatment and disposal of waste. Raw material acquisition involves the growth, management and harvesting of the tree. Manufacturing involves the process concerned in paper production. Emissions to air, water and land from raw materials acquisition and manufacturing of paper are also involved. Lastly, proper treatment and disposal of emission and waste are needed before releasing it to the environment. The system boundary is shown in the figure below.

Energy

Water

Materials:

NaOH, Na2S, Cl2, NaClO2, CaCO3, Starch, Aklyl Ketone Dimer

(AKD), Packaging Material

Container

Raw Materials Acquisition:

Harvesting of Tree

Manufacturing:

Debarking, Chipping, Screening, Digesting, Bleaching,

Washing, Refining, Filtering, Forming,

Clarifying, Pressing, Drying,

Coating, Calendar, Reeling, Winding,

Packaging

Emission:

Air Emission: CO2, PM, NOX, SOX,

VOC

Waste Water

Solid Waste

Treatment and Disposal

Transportation

WITHIN THE BOUNDARY:

\

INVENTORY ANALYSIS:

Life Cycle Inventory Analysis (LCIA) is a thorough procedure accounting for the environmental loads during the product’s life cycle (Babu and Ramkrishna, 2003). Inventory Analysis is a systematic, objective, stepwise procedure for quantifying energy and raw materials requirement, atmospheric emissions, water borne emissions, solid wastes, and other releases for the entire life cycle of a product, package process, material or activity (Manjare and Babu, 2005). It is a process of data collection and calculations intended to quantify the inputs and outputs of a product system. These inputs and outputs may include resources used, as well as release to air, water, or land (SAIC, 2006). This data was made available by the pulp and paper industry in San Ildefonso, Bulacan. Some of the data was collected through databases.

INPUTRaw Materials: wood, water and chemicalsEnergy: coal, diesel and electricity

Raw Materials and Energy Acquisition

Wood, energy, water, chemicals

Manufacturing and Processing:

Pulping, papermaking and

packaging

Distribution and Transportation

Use, reuse, maintenance

Recover, Recycle

OUTPUTTreatment and Disposal

Usable Products:Newsprint paperBy-products: paper and wood

Environmental Impacts: Airborne Emissions: CO2, SO2,

NOx Water Effluent: BOD, COD,

metals Solid Waste: bark, sludge,

paper, etc. Other environmental releases

The system starts with wood harvesting that involves felling, cutting and truck loading. Data was collected for the transportation of the wood to the pulp mills. Transportation of raw materials such as coal was also considered in the study. Energy use data was also collected. The pulp and paper industry purchases electricity from the national grid and data was collected for the production of electricity from coal, which is the main fossil fuel, used for the production of electricity. The pre-combustion effects of the fuels used in the other paper life cycle stages were explored. The main fuel used is coal.

INPUTS: (in kg/hr)

Stream Water O2 N2 Wood Chip

0 - 13,536.98 50,924.82 -

1 - - - 35,156.10

2 - - 50,924.82 -

3 54,431.04 - - -

4 54,431.04 - - -

5 54,431.04 - - -

6 54,431.04 - - -

INDIVIDUAL PARAMETERS AND ITS EFFECTS

Energy Consumption

The pulping processes and the paper making process at the mills are the most important consumer of non-renewable energy in the form of coal. This is followed by the production of electricity that is used in the production of the paper. The production of chemical pulp also consumes a significant amount of energy even. Transportation also accounts for a significant amount energy consumed in the life cycle.

Water Emissions

The pulping processes at the pulp mill are the most important contributor as far as the chemical oxygen demand is concerned. The generation of electricity and the extraction of coal are also significant contributors to the emissions to water systems.

Air Emissions

The major source of carbon dioxide is onsite energy use at the pulp mills where pulping and papermaking is carried out. Transportation generates most of the NOx during the transportation of wood from the forest to the pulp mill and also transportation of coal to the pulp and paper mills. Wood harvesting is also an important contributor to air emissions and the pulp mill also contributes significantly to air emissions. Sulphur dioxide is mainly produced during production processes at the pulp mills. The production of the electricity that is used at the mills is also an important contributor to air emissions.

Global Warming

As seen in the figure above, the pulping and paper making process has about 72-73% contribution to the global warming potentials for 100 years. The extraction of coal accounts for close to 10% contribution to this impact category. Transportation and generation of electricity from coal have almost equal contributions of about 5% each to global warming.

Figure3. Global Warming Potentials in 100 years

Figure 4.Damage assessment

Acidification

As seen on the graph above, the pulp and the paper is the greatest contributor to acidification with a contribution of about 42%. This is due to the sulphur dioxide that is emitted into the atmosphere during the combustion of coal for steam production. Transportation is the second in contribution at about 35%, due to the release of NOx from transportation of wood and coal to the pulp mills.

Eutrophication

Pulp and paper is also the largest contributor to eutrophication as observed in figure 4. This has a contribution of 42 % followed by transportation, which accounts for about 35% contribution. The reason for such a scenario is mainly due to the release of nitrates into the water from the mechanical pulping that takes place at the pulp mills.

Climate Change

The pulp mills contribute more than 70% to climate change which is mainly the result of emissions. Extraction of coal is the second largest contributor with close to 10% contribution. Transportation and the production of electricity have very little contribution to this parameter.

Ozone Depletion

Transportation takes account in ozone depletion since it produces much of carbon monoxide. Transportation accounts for approximately 50% contribution to this impact category. Chemical pulp contributes about 23% to this impact category.

Eco-toxicity

Pulp and paper industry contributes much to the toxicity of ecosystem because of the chemicals that are used during the production of pulp and these include defoamers, biocides and dyes. This stage accounts for slightly above 65% contribution to this impact category. Chemical pulp also contributes significantly to this impact category followed by transportation, which has a relatively low contribution to this impact category about 7%.

Characterizations and Environmental Impacts

Air Emissions

Air Emission Table 1. Characterization of air emissions Outputs Source General Impact Specific Impact Carbon Dioxide (CO2) From combustion of

fuel Climate Effect Air Resources

Global warming

Sulfur Oxides (SOx) From combustion of fuel

Human Health Climate Effect Ecotoxicity Air Resources

Acid Rain, Respiratory Damage, Corrosion

Nitrogen Oxides (NOx)

From combustion of fuel


Photochemical Smog, Eutrophication, Acid Rain

Particulate Matter (PM)

Fine particles from the paper manufacturing process


Respiratory Disease, Retard Plant Growth, Climate Cooling Effect

Carbon Monoxide (CO)

Incomplete combustion of fuel

Climate Effect Human Health Air Resources

Ground level ozone formation, Asphyxiation

Waste Water Waste Water Table 2. Characterization of waste water Outputs Source General Impact Specific Impact Waste Water: Turbidity

From Maintenance Water resources Human health Ecotoxicity

Water quality effects: TSS Public – Chronic Aquatic - Chronic

Waste Water: Heavy Metals


Water quality effects: BOD Public – Acute

Aquatic – Acute Waste Water: Total Dissolved Solids


Nutrient enrichment/Water quality effects: TDS Public – Chronic Aquatic - Chronic

Waste Water: Total Suspended Solid


Nutrient enrichment/Water Quality effects: BOD Public- Chronic Aquatic- Chronic

Waste Water: DO From Maintanance Water Resources Ecotoxicity

Nutrient enrichment/Water Quality effects: BOD Public- Chronic Aquatic- Chronic

Solid Waste Solid Waste Table 3. Characterization of solid wastes Outputs Source General Impact Specific Impact Sludge Sludge from waste

water pretreatment. contains fillers, ink particles, fibers

Landfill space use Solid waste

Used Sacks From wood chips Landfill space use Solid waste Rejected plastic Packaging

Packaging with defects to be sent back to the supplier

Landfill space use Solid waste

Process Flow Diagram

Environmental Impacts on Main Processes

Process: Debarker

Wastewater Air Emission

Process: Chipper

Wastewater

Air Emission

Process: Screening


Process: Digester


Process: Bleaching


Process: Bleaching


Process: Chloro-alkali Reactor


Process: Reactor

Wastewater

Air Emission

Process: Washing


Process: Refiner


Process: Forming


Process: Presser

Wastewater

Air Emission

Process: Dryer


Process: Coating

WastewaterAir Emission

Process: Calendering


Process: Reeling


Process: Winder

Wastewater

Air Emission

Process: Quality Control


Process: Packaging


Process: Multi effect Evaporator


Process: Recovery Furnace


Process: Smelt Dissolving Tank


Process: Green Liquor Clarifier


Process: Dreg Washing

Wastewater

Process: Slaker/Causticizer


Solid Waste

Process: White Liquor Clarifier


Process: Lime Mud Washing


Process: Filter


Process: Lime Kiln


Hotspots

Bleaching

includes multiple steps which consumes a lot of material and produces a lot of waste and power utilizes chlorine dioxide

Control and Management Method

1. Dry Debarking Process water is used only for log washing and de-icing and is recirculated effectively

with minimum generation of wastewater and water pollutant Creates bark with a lower water content, which will result in a better energy balance for

the mill Less water is needed in the debarking and the dissolved amount of organic substance is

reduced.

2. Extended modified cooking to a low kappa Balance between kappa reduction in cooking and in oxygen delignification since the

selectivity is much higher in the latter system Decrease the lignin content (lower kappa numbers) in the pulp entering the bleach plant

so as to reduce the use of the expensive bleaching chemicals Reduction in lignin content will reduce the amount of pollutants discharged while

increasing the amount of organic substances going to the recovery boiler3. Closed Screening

Contributes to the reduction of organic compounds in the effluents Recovery and incineration in the recovery boiler Bring the clean counter-currently through the fibreline, which gradually increases the dry

solid content of the liquor

Chemical Pulping

Required to convert wood chips into paper Chemicals used in the pulping process, namely: sodium hydroxide and hydrogen sulphide,

produces harmful chemical compound.


1. Combined Heat and Power in Chemical Recovery Using an extraction back pressure and/or extraction condensing turbine, the heat content

of the black liquor can be converted both to electricity and heat Significantly increase the amount of useful energy extracted from black liquor, thereby

helping reduce the need for electricity or fuel purchase.2. Collection of Spillages

Carry out on-site measures to minimize the discharged of process chemicals Pulping liquor can escape the seals on brown stock washers, pumps and valves Liquor spill can cause process interruption, tank overflows, mechanical breakdowns and

other errors3. Lime Kiln Modifications

Calcination of the CaCO3 in lime mud to generate CaO Modifications are possible to decrease energy consumption in the kiln Evaporation energy can be reduced by installing high efficiency filters to decrease the

water content of the kiln intake Higher efficiency refractory insulation bricks can be fitted to increase heat transfer in the

kiln Heat energy can be recovered from the lime and from the kiln-off gas to preheat input

lime and combustion air Furthermore, such improvements may also improve the rate of the recovery of lime from

green liquor, thus reducing a mill’s requirement for additional purchased lime

Chemical Recovery

In Kraft Process, chemicals used in the pulping process are recovered

Energy and material extensive utilizing and produces a considerable amount of waste, greatly dregs and grits which is of importance in terms of solid waste.


1. Partial Closure of the Bleach Plant Substantial further reductions in discharges to water of organic substances, nutrients and

metals Recycling of filtrates to the chemical recovery Reduce the volumetric flow through the bleach plant Leading the liquids counter-currently from the last bleach stage through the sequence via

the oxygen stage washing apparatus to the brown stock washer.2. Total Chlorine Fee (TCF) Bleaching Technique

Bleaching process carried out without any chlorine containing chemicals Hydrogen peroxide together with ozone or peracetic acid are the most commonly used

chemical Possible to attain full market brightness with peroxide as the sole bleaching chemical

with low kappa content Dose-response curve for brightness versus peroxide consumption is quite shallow at top

brightness3. Ozone Bleaching

Provide more delignification power Ozone activates the fibres towards peroxide and this result in higher brightness nad lower

peroxide consumption Ozone is generated by means of silent electrical discharges in a stream of oxygen gas Since the ozone concentration will be only 14-16% in oxygen, fairly large volumes of

oxygen are required Ozone bleaching (O3) has very investment costs due to the high costs of ozone generators

and auxiliary equipment for ozone generators

Dimensions of Sustainable Development for Treatment on Hotspots

Treatment on Chemical Pulping

Control for Chemical Pulping

Dimensions of Sustainable Development

Economic Ecological Social

Advantage Disadvantage Advantage Disadvantage Advantage Disadvantage

Dry Debarking 1. Same equipment investment compared to wet debarking2. Improves energy efficiency

1. Decrease wastewater amount2. Decreases TSS, BOD and COD load as well as organic compounds

1. Requires fresh wood2. High energy consumption

1. Mitigation of heal risks

Extended modified cooking to a low kappa

1. Bleaching chemicals needed decreases2. No loss in strength properties

1. Consumption of active alkali (NaOH and Na2S) may slightly increase2. Amount of dissolved substances going to the recovery system increases3. Heat generation in the recovery boiler increases

1. Lower lignin content meaning fewer discharges of organic substances and nutrients2. Lower pollutant load in the wastewater from bleaching3. Reduction of emissions to water

1. Increase wood consumption

1. Mitigation of heal risks2. Safer working conditions

Closed Screening 1. Energy consumption increases due to increased need for evaporation

1. Significant reduction of organic compounds in the effluents2. Screening plant has no discharges to water3. Reduction of emission to water

1. Safer working conditions

Treatment on Chemical Recovery

Control for Chemical Recovery




Combined Heat and Power in Chemical Recovery

1. High energy yield2. Extract energy from black liquor

1. Savings dependable on the price and of electricity and fuels in the country

1. Reduce CO2 release rate by half

1. Electricity generation

Collection of Spilages

1. Energy savings due to collected spills

1.The investment cost for spill-liquor handling systems producing 1500 ADt/d pulp mill is estimated to be EUR 0.8 – 1.5 million

1. Reduction of wastewater from chemical recovery process2. Reduce wasted pulping liquor

1. Better publicity

Lime kiln modifications

1. Lime kiln energy savings up to 5%2. Reduce lime usage

1. Investment cost of about $2.5/t pulp has been assumed

1. Reduction of wastewater from lime kiln

1. Safer working conditions

Treatment on Bleaching

Control for Bleaching




Partial Closure of the Bleach Plant

1. Additional capacity

1. Total rebuild of the water distribution system including extra storage for internal waters2. Control strategy for the water management3. Additional energy consumption

1. Reduction of wastewater2. Reduction of BOD and COD loads3. Less sludge generation

1. Less job Opportunities

TCF Bleaching Tecnique

1. No significant differences in chemical and energy consumption in ECF and TCF alternative

1. No AOX and chloro organic compounds formation

1. Mitigation of health risks

Ozone Bleaching 1. Result in the same papermaking properties

1. High investment and operating cost

1. Reduction of emission to water (AOX)

1. Mitigation of health risks

Treatment Design

Combined Heat and Power in Chemical Recovery

Principle of CHP:

The energy losses from power generation and from heat production can be reduced by combined generation of both, heat and power (CHP, also called cogeneration). Cogeneration plants raise the conversion efficiency of fuel use from around one-third in conventional power stations to around 80% (or more). Thus, for many paper mills it is possible to increase the overall energy efficiency of the process by making use of the cogeneration thus reducing fuel consumption and air emissions. The energy requirement and the heat-power ratio in the paper and board industry is very appropriate for the use of CHP [Pröger, 1996]. The characteristics of the processes as high and balanced electricity and heat needs, and regularity of operation over the year are also favourable.

Many paper mills have installed different kinds of cogeneration processes. For instance, for boiler houses fired with gas one or several gas turbines prior to the existing supplementary fired steam generator can be installed to reach a higher output of electricity from the plant. If a steam turbine is already in operation a gas turbine can be installed before the steam generator to generate a higher yield of power.

There are different schemes for combined cycle power plants on the market. Which system is applied depends mainly on the existing power plants already in operation and on local conditions.

To verify the literature efficiency (80% > η) of CHP, the overall efficiency of the cycle is computed using the formula:

η=|W T+W P+QS|

QBx100 %=

|−2885.89+130.6755−(2935.01 )(54431.043600 )|

56308.34578x 100 %

η ≈ 84 %

Based from the computed efficiency of the cycle (84%), the literature efficiency of CHP processes is valid and higher compared to conventional power stations where energy loss/waste is high.

Emissions per unit of generated heat or power drop significantly as a result of the increased thermal efficiency of CHP. Overall thermal efficiencies can reach 93% thus reducing the carbon dioxide release rate by about 50% compared to conventional power generation combustion systems with an electrical efficiency of about 38%. In contrast, emissions to air on the site will increase.

The following reduction rates are achieved by the application of combined co-generation relative to using coal-fired utilities for electricity generation (Biberach, 2001):

• Fuel consumption: 29 % reduction,

• NOx: 38 % reduction,

• CO: 97 % reduction,

• SO2: 100 % reduction,

• CO2, fossil: 46 % reduction.

In bigger co-generation plants NOx and CO content of the exhaust gas is controlled continuously. Other mills may have periodic measurements of NOx and CO.

In conjunction with the greenhouse effect, cogeneration power plants based on gas turbines in combined cycle application are regarded as being an important option for the reduction of CO2 because of their comparatively high thermal efficiency also for relatively small capacity units (from some MW upwards). The high electricity/heat ratio and the high efficiency of the conversion of fuels to power and heat reduces significantly the specific CO2 emission per kWh produced compared to conventional power plants. The overall emissions for power generation decrease due to higher thermal efficiency.

Process Flow Diagram

Summary of Material Balances: (Flows in kg/hr)

Stream Water O2 N2

Wood Chip CO2 Nox

Sox PM Total

0 -

13,536.98

50,924.82

-

-

-

-

-

64,461.79

1 -

-

-

35,156.10

-

-

-

-

35,156.10

2 -

-

50,924.82

-

18,613.34

10.1

4

4.05

10.1

4 69,562.49

3 54,431 -

-

-

-

-

-

-

54,431.04

.04

4 54,431

.04 -

-

-

-

-

-

-

54,431.04

5 54,431

.04 -

-

-

-

-

-

-

54,431.04

6 54,431

.04 -

-

-

-

-

-

-

54,431.04

Hypothetical Material Balances:

A typical Kraft Pulp and Paper plant would require about 120,000 lb/hr of low pressure steam for heating purposes in chemical recovery. (Source: CHP Feasibility Analysis, EPA)

Basis: 120,000 lb/hr of steam

S 6=120,000 lbhr (0.453592 kg

lb )=54,431.04 kgsteam

Assuming no loss in water during whole process:

S 6=S5=S 4=S 3=54,431.04 kg steam

Wood Chip Properties (Source: Engineeringtoolbox.com)

Heating Value 9,000 kj/kgMoisture Content 50%

Energy per Weight Unit 62%

HeatingValue of Woodchip=(9,000 kJkg ) (0.62 )=5,766 kJ /kg

Woodchip Input in Boiler:

From Energy Balance:

Qb=56,308.34578 kW

S 1=56,308.34578 kJ

s

5,766 kJkg

(3600 shr )=35,156.09518 kg

For theoretical air requirement:

Air Required = 318 kg/GJ (Source: Boiler Plant Systems)

S 2=(318 kgGJ )(202.71 GJ

hr )=64,461.79kg /s

Air Composition:

Component Mass Flow (kg/hr)N2 50,924.82O2 13,536.98

Total 64,461.79

Flue Gas:

Assumptions:

All O2 in air is converted to CO2

N2 feed is equal to N2 in flue gas

Other emissions are based on typical emission levels based on boiler duty.

(Data from: biomassenergycentre.org.uk)

CO 2=13,536.98 kg(4432 )=18,613.34 kg/hr

N 2=50,924.82 kg /hr

Component mg/MJNOx 50PM 50SOx 20

Qb=(56,308.35 kJs )(3600 s

hr )(1 MJ1000 kj )=202,710.0448 MJ /hr

NOx=(202,710.0448 MJhr )( 50 mg

MJ )( 1kg106 mg )=10.13550224 kg/hr

PM=(202,710.0448 MJhr )(50 mg

MJ )( 1kg106mg )=10.13550224 kg /hr

SOx=(202,710.0448 MJhr )( 20 mg

MJ )( 1 kg106 mg )=4.054200896 kg /hr

Equipment: Combined Heat and Power (CHP) Generation from Chemical Recovery

Hypothetical Material Balance

Basis: Steam requirement of 120000 lb/hr

Converting basis to kg/hr:

Steamrequirement=S 6=(120000lbhr )( 0.453592 kg

lb )=54431.04 kghr

At TB101:

S5=S 6

S 5=54431.04 kghr

At BO101:

No mixing of water (S4) & biomass/wood (S1), therefore:

S4=S5

S4=54431.04 kghr

At PM101:

S3=S 4

S 3=54431.04 kghr

Hypothetical Energy Balance

At TB101:

For superheated steam @ 250°C & 1200 kPa:

H 6=2935.01 kJkg s6=6.8293 kJ

kg−K v6=0.19235 m3

kg

For superheated steam @ 400°C & 6000 kPa:

H 5=3177.17 kJkg s5=6.5407 kJ

kg−K v5=0.04739 m3

kg

For the power recovered from the turbine:

Since m5 = m6,

W T=m5 ( H 6−H 5 )

W T=(54431.04 kghr )( hr

3600 s ) (2935.01−3177.17 ) kJkg

=−3661.395 kW

Since the turbine has an efficiency of 78%, computing for the capacity:

W T=(0.78 ) (−3661.395 kW )≈−2800 kW

At PM101:

For saturated liquid water @ 10 kPa:

H 3=191.79 kJkg s3=0.6492 kJ

kg−K v3=0.00101 m3

kg

For the power requirement of the pump:

Assumptions:

Incompressible fluid (v3 = v4)

Pressure of water at BT101 is constant (P4 = P3)

Since m3 = m4,

W p=m3(H 4−H 3)=m3 v3(P4−P3)

W p=(54431.04 kghr )( hr

3600 s )(0.00101 m3

kg ) (6000−10 ) kPa=91.47288 kW

Rearranging the equation to solve for H4:

H 4=H3+W p

m3=191.79 kJ

kg+(91.47288 kJ

s )( 3600 shr )

54431.04 kghr

=197.8399 kJkg

Since the pump has an efficiency of 70%, computing for the capacity:

W p=91.47288 kW

0.70≈ 131 kW

At BO101:

For the heat added to the pumped water:

Since m4 = m5,

Qh=m4 ( H 5−H4 )

Qh=(54431.04 kghr )( hr

3600 s )(3177.17−197.8399 ) kJkg

=45046.67662 kW

For the heat requirement of the boiler:

Assume a boiler efficiency of 80%:

Qb=Qh

η=45046.67662 kW

0.8≈57000 kW

Equipment Data SheetPM101

Volumetric Flow Rate (m3/s) 0.01512Type of Pump Centrifugal

Efficiency 70%Capacity (kW) 131

BO101Efficiency 80%

Capacity (kW) 57000

TB101Type of Turbine Steam

Efficiency 78%Capacity (kW) 2800

Possible Innovations/Improvements on CHP design:

Based on the generated material balances, combustion of wood chips produces particulate matter (PM), NOx, SOx, Carbon dioxide (CO2) and Carbon monoxide (CO).

These pollutants are mainly found in the flue gases in the boiler, thus the design improvement shall focus on methods to reduce the pollutants from the flue gas generated.

Emission Abatement Technologies

(Based from: Biomass heating: a guide to medium scale wood chip and wood pellet systems)

Technology Advantages DisadvantagesCyclone grit arrestor -Will take out most particulates

down to about 20micron.

-Will not take out a significant proportion of PM10 and smaller. -Will not take out any gas including NOx.

Bag filter -Will take out most particulates down to about 1 micron (0.001mm) diameter. -Will take out almost all PM10 and PM2.5 particulates.

-Regular filter cleaning required.-Will not take out any gas including NOx.-Unlikely to be commercially viable if flue gas temperatures exceed 200oC.

Electrostatic filter -Will take out almost all particulates down to ultrafineparticles, i.e. smaller than PM2.5.

-Must be used in series with a cyclone.-Will not take out any gas including NOx.

Wet scrubber -Will take out almost all particulates down to ultrafineparticles, i.e. smaller than PM2.5.-Will dissolve gases including CO2 and (less effectively)NO2. -Enables a high degree of heat recovery from the boiler flue gases.

-Must be used in series with a cyclone.-Weak acid produced as gases dissolve; requiresneutralisation and the removal of salts from thescrubber water.-Significantly reduces flue gas buoyancy

Ceramic filter -Able to remove most particulates from high temperature flue gas.-Long life expectancy

-Will not remove any gas including NOx.-Must be used in series with a cyclone.-High cost.

Reference:

1. C .T Mbohwa1, L. Mashoko. Application of Life Cycle Assessment in the Zimbabwean Pulp and Paper industry from http://www.lcm2007.org/paper/Mbohwa.pdf

2. Gavrilescu D. (2004). Management of Pulp and Paper Mill Waste. Switzerlan: Springer International Publishing

3. The EIA in the Pulp and Paper Industry, Forestry Department. from http://www.fao.org/docrep/005/v9933e/V9933E03.htm#ch3.2.1

http://www.lcm2007.org/paper/Mbohwa.pdf

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