PRE-TREATMENT TECHNOLOGIES, AND THEIR EFFECTS ON THE INTERNATIONAL

BIOENERGY SUPPLY CHAIN LOGISTICS

Techno-economic evaluation of torrefaction, fast pyrolysis and pelletisation

Ayla Uslu Report number: NWS-I-2005-27 December 2005

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PRE-TREATMENT TECHNOLOGIES

AND THEIR EFFECTS ON THE INTERNATIONAL BIOENERGY

SUPPLY CHAIN LOGISTICS

Techno-economic evaluation of torrefaction, fast pyrolysis and pelletisation

Supervision: Dr. Andre Faaij P.C.A. Bergman

Ayla Uslu This study was concluded in partial fulfilment of the Master of Science program in Sustainable Development- Energy and Resources. Department of Science, Technology & Society Utrecht University, the Netherlands Part of the research was conducted in the Energy research Centre of the Netherlands (ECN). Biomass Department, Petten, the Netherlands

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ACKNOWLEDGEMENT.............................................................................................................6

ABSTRACT ....................................................................................................................................7

1 INTRODUCTION..................................................................................................................8

1.1 GENERAL BACKGROUND...................................................................................................8 1.2 PROBLEM FORMULATION...................................................................................................9 1.3 OBJECTIVES.....................................................................................................................10 1.4 METHODOLOGY AND EVALUATION CRITERIA ..................................................................10 1.5 REPORT STRUCTURE........................................................................................................11

2 TECHNOLOGIES ...............................................................................................................12 2.1 TORREFACTION ...............................................................................................................12 2.2 PYROLYSIS ......................................................................................................................31 2.3 PELLETISATION ...............................................................................................................44 2.4 COMPARISON OF PROCESSES ...........................................................................................52 2.5 SENSITIVITY ANALYSES FOR PRE-TREATMENT TECHNOLOGIES........................................55 2.6 FINAL CONVERSION.........................................................................................................59

3 CHAIN ANALYSIS .............................................................................................................62

3.1 APPROACH AND METHODOLOGY .....................................................................................62 3.2 LOGISTIC OPERATIONS ....................................................................................................63 3.3 DESIGNED CHAINS ..........................................................................................................67 3.4 CHAIN ANALYSIS.............................................................................................................69 3.5 SENSITIVITY ANALYSIS ...................................................................................................81

4 DISCUSSION AND CONCLUSION..................................................................................83

4.1 PRE-TREATMENT TECHNOLOGIES ....................................................................................83 4.2 CHAIN ANALYSIS.............................................................................................................84 4.3 RECOMMENDATIONS .......................................................................................................86

5 REFERENCE LIST .............................................................................................................88

6 APPENDICES ......................................................................................................................92

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LIST OF TABLES Table 1 Net calorific values (LHV) of untreated wood, torrefied biomass, charcoal and coal ................... 15 Table 2 Comparison of the three evaluated reactor types for 150 MWth output torrefaction process........ 20 Table 3 Wood, torrefied biomass, wood pellets and torrefied pellets property comparison. ...................... 22 Table 4 Technical performance of torrefied wood pelletisation for sawdust and green wood chips .......... 22 Table 5 Overall energy balance of the 150 MWth torrefaction process...................................................... 25 Table 6 Local parameters assumed for different world regions .................................................................. 27 Table 7 Total capital investment of a 37. 5 MWth torrefaction plant........................................................... 28 Table 8 Specific investment cost calculations of various capacities. .......................................................... 30 Table 9 Typical properties of wood derived crude bio-oil .......................................................................... 32 Table 10 25 MWth-input capacity pyrolysis process investment cost calculations (sawdust as feedstock)37 Table 11 Economic parameters for a 25 MWth biomass pyrolysis plant.................................................... 38 Table 12 Production cost of a 25 MWth rotating cone pyrolysis plant ....................................................... 38 Table 13 Characteristics of wood pellets (Sawdust, cutter shavings, and wood-grinding dusts as raw

materials.............................................................................................................................................. 46 Table 14 Cost data of pelletisation process ................................................................................................. 50 Table 15 Technical comparison of torrefaction, TOP, pyrolysis and pelletisation pre-treatment processes.

............................................................................................................................................................ 53 Table 16 Economic comparison of torrefaction, TOP, pyrolysis and pelletisation pre-treatment processes

............................................................................................................................................................ 54 Table 17 Main parameters used and ranges for sensitivity analysis............................................................ 55 Table 18 Effects of scale on pellet production costs. .................................................................................. 58 Table 19 Cost figures for final conversion step........................................................................................... 59 Table 20 Characteristics of Latin American energy crops considered in this study (Ranges indicate short

and long term,).................................................................................................................................... 64 Table 21 Logistics of biomass from harvesting to the pre-treatment process point. ................................... 67 Table 22 Designed chains............................................................................................................................ 69 Table 23 Parameter used for sensitivity analysis and ranges ...................................................................... 81 Table 24 Techno-economic comparison of torrefaction, TOP, pelletisation and pyrolysis ....................... 83 Table 25 Costs of chains delivering fuel and power ................................................................................... 85 LIST OF FIGURES Figure 1 Main physico-chemical phenomena during heating of lignocellulosic materials at pre-pyrolytic

conditions (torrefaction). Main decomposition regimes are based on Koukios et al. (1982) ...................13 Figure 2 Stages in the heating of moist biomass from ‘ambient’ temperature to the desired torrefaction

temperature and the subsequent cooling of the torrefied product (Bergman et al, 2005).........................14 Figure 3 Schematic representation of the Pechiney process (Berman et al, 2005)............................................17 Figure 4 General flow diagram of ECN torrefaction process (Bergman at al, 2005)........................................18 Figure 5 Torrefaction process authothermal operation equations .....................................................................19 Figure 6 General flow diagram of torrefaction in combination with pelletisation ............................................21 Figure 7 Net mass flows corresponding with torrefaction of cuttings at 280 oC and 17.5 min reaction time

(HE: Heat exchanger). ..............................................................................................................................24 Figure 8 Net energy flows (in MWth) corresponding with torrefaction of woodcuttings at 280 °C and 17.5

min reaction time (HE: heat exchanger). ..................................................................................................25 Figure 9 Total capital investment cost breakdown Figure 10 Equipment cost breakdown ..................29 Figure 11 State of the art Ensyn RTP plant flow diagram (Source).................................................................34 Figure 12 A schematic presentation of the mass and energy balance of a 5-ton dry feed per hour pyrolysis

plant ..........................................................................................................................................................35 Figure 13 Specific Pyrolysis Plant Investments 1987-2003 (Solantausta, 2001)..............................................40

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Figure 14 Specific Pyrolysis Plant Investments (Historic data from1987 to 2003 (Solantausta, 2001)............40 Figure 15 Fast pyrolysis total plant costs versus feedstock (dry) input (Bridgwater et al, 2002). ....................41 Figure 15 Specific investment cost versus capacity (MWth LHV) data of 5 different pyrolysis plants ..............42 Figure 17 Total capital investment cost versus feedstock (ton dry/hr) of 5 different pyrolysis plants (Graph

uses the same data as Figure 15)...............................................................................................................43 Figure 17 State-of-the-art pellet production process diagram...........................................................................45 Figure 18 Mass balance of the pelletising process ............................................................................................48 Figure 19 Energy balance for a 24000 pellet production process (Cost data is obtained from Thek and

Obernberg (2004)). ...................................................................................................................................48 Figure 20 Cost breakdown of the total capital investment cost of a 24 000 ton pellet process (data from

Thek and Obernberg, (2004) is used)........................................................................................................52 Figure 21 Sensitivity of torrefied biomass production ......................................................................................55 Figure 22 Sensitivity analysis of bio-oil production costs ...............................................................................56 Figure 23 Pellet production sensitivity analysis ................................................................................................56 Figure 24 Effects of scale on torrefaction investment costs..............................................................................57 Figure 25 Effect of scale on the bio-oil production costs..................................................................................58 Figure 26 Biomass transport overview..............................................................................................................63 Figure 27 Schematically presentation of transportation distances ....................................................................66 Figure 28 Modelled bio-energy chains from Latin America to West Europe ...................................................68 Figure 29 Cost data of chains delivering pellets in €/ ton dry delivered. ..........................................................70 Figure 30 Cost of bio-oil delivered to West Europe in €/GJHHV .......................................................................71 Figure 31 Costs of FT liquid for different pre-treated feedstock (Conversion in the graph comprises pre-

treatment and FT processes). ....................................................................................................................72 Figure 32 Cost of the chains delivering electricity by means of BIGCC ..........................................................73 Figure 33 Cost of power obtained by combustion for various bio-energy chains.............................................74 Figure 34 Cost of power obtained by co-firing for various bio-energy chains .................................................74 Figure 35 Energy use of chains delivering biomass to the Rotterdam harbour in GJ/ ton dry delivered. .........75 Figure 36 Energy use of bio-oil delivered to West Europe in GJ/GJHHVbio-oil....................................................76 Figure 37 Energy use of the chains delivering FT liquid ..................................................................................76 Figure 38 Primary energy use of chains delivering energy ...............................................................................76 Figure 39 Primary energy use for chains delivering electricity.........................................................................77 Figure 40 CO2 emission of chains delivering biomass to West Europe in kg CO2/ ton dry delivered..............78 Figure 41 CO2 emission caused by bio-oil delivery from Latin America to West Europe. ..............................78 Figure 42 CO2 emissions of chains delivering FT liquid..................................................................................79 Figure 43 Comparison of the power cost delivery figures for every chain. ......................................................80 Figure 44 CO2 emissions of the chains delivering electricity (conversion in this graph means the pre-

treatment steps and emissions count for the electricity utilised during pre-treatment). ...........................80 Figure 45 Sensitivity analysis for TOP process (OW: harvest operation period) .............................................82 Figure 46 Sensitivity analysis of TOP delivery versus pre-treatment unit scale. ..............................................83 Figure 47: Relation between the MCA and the energy yield of torrefaction. Values are taken from the

main design matrix. The error bars represent the possible inaccuracy in the HHV measurement. ..........95 Figure 48: Size reduction results of various torrefied biomass and feed biomass.............................................95 Figure 49 Bench scale pyrolysis unit flow diagram ........................................................................................100 Figure 50 BioTherm pyrolysis process flow diagram .....................................................................................101 Figure 51 RTI process for production of bio-oil, bubbling fluidised bed type of reactor. ..............................102 Figure 52 Circulating fluid bed reactor. ..........................................................................................................103 Figure 53 schematic diagram of the CFB unit for biomass flash pyrolysis.....................................................103 Figure 54 Rotating cone reactor ......................................................................................................................105 Figure 55 Rotating cone reactor pyrolysis process flow diagram ...................................................................105

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Acknowledgement This research has been performed at Utrecht University and at the Energy Research Centre of the Netherlands (ECN). First, I would like to thank my supervisor Andre Faaij, for his support and guidance. I also thank to Patrick Bergman who has never hesitated to share his valuable knowledge, advice and who has supervised my work during my internship at ECN. Many thanks to Jaap Kiel, who made the internship at ECN possible. Special thanks go to my friends and my family. They give a special colour to my life, which makes it more valuable.

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Abstract The need for supplying sustainable energy resources raises the urgency of finding optimised bioenergy chains. Pre-treatment step is one of the factors, that has a significant influence on the overall chain. Torrefaction, pelletisation and pyrolysis technologies convert biomass into dens energy carriers that ease the transportation and handling. Besides, they influence the final conversion step. In this study, first the technical and economic performances of the pre-treatment technologies are assessed. Next, the economy of scale of each technology is analysed and the impacts of the pre-treated energy carriers on the final conversion stage is evaluated. Finally, several scenarios are produced, where Latin American energy crops are pre-treated and intermediate energy carriers are delivered to Western Europe and converted into power and syn-fuel. In this chain analysis step, not only the technologies but also the different scales are compared with each other. The technology assessment part indicates that torrefaction is a very promising technology due to its high process efficiency compared to pelletising and pyrolysis technologies. Moreover, when torrefaction is combined with pelletisation, the product (TOP pellets) energy content is as high as 20.4-22.7 GJ/ton. For comparison, conventional pellet energy content is 17.7 GJ/ton while pyrolysis oil energy content is 17 GJ/ton. Another important point is that above 40 MWth torrefaction plant capacities, there is no economy of scale. When the economics of the three pre-treatment technologies are compared, pelletisation has the lowest specific capital investment, followed by torrefaction. However, there is a significant variation between the cost figures found in scientific literature for pyrolysis technology. The bioenergy chain analysis indicates that 89% of the biomass initial content can be delivered as cheap as 73.4 €/ton (3.34€/GJ) in the form of torrefied pellets (TOP). In fact, TOP process increases the bulk density 15% compared to conventional pellets, which lowers the first truck transport. When the biomass is converted to pellets and delivered to Rotterdam harbour, the cost is 3.94€/GJHHV, which is very close to TOP pellet delivery. On the other hand when the biomass is delivered to the Rotterdam harbour in the form of pyrolsyis oil, the cost is in the range of 4.7 -6.6 €/GJHHV. Furthermore, this study indicates that electricity can be produced as little as 4.4 €cent/kWhe from an existing co-firing plant, while the electricity cost from a BIGCC facility is 4.6 €cent/kWhe even though it includes high amount of investment costs. Fisher Tropish fuel produced in Europe costs 6.44 €/GJHHV for TOP pellets and 6.97 €/GJ for conventional pellets delivered from Latin America. On the other hand, pyrolysis liquid can be converted into FT liquid with a cost of 9.5 €/GJHHV. In addition, the energy requirement indicates how sustainable the designed chains are. For TOP delivery, the primary energy requirement is as low as 0.05 GJ/GJdelivery, while it is 0.12 GJ/GJdelivery for pellets and 0.08 GJ/GJHHV for pyrolysis oil.

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1 Introduction 1.1 General Background Sustainable development is defined by the Brundtland Commission as “a process of change where the exploitation of resources, the direction of investments, the orientation of technological development and institutional changes are all in harmony and enhance both current and future potential to meet human needs and aspirations.” In this respect sustained energy supply is one of the essential targets to be achieved and depends on secure and reliable energy sources. The current global energy development pattern brings, however, significant danger due to the reliance on fossil fuels. Most of the world’s oil reserves are located in certain countries, which make energy supply vulnerable. Another problem that has emerged is that fossil fuel consumption causes substantial environmental harm. In the IPCC 2nd report, it is mentioned that human activity has caused a rise in atmospheric temperature in the recent years.

In addressing those threats, developed countries increasingly shift towards renewable energy sources. Biomass is one of the renewable energy sources that are available worldwide. It is abundant throughout the planet and can be used as an energy source with no CO2 addition to the environment. Currently, bio-energy contributes 35% of the primary energy consumption in developing countries, which accounts for 9-14% of global energy demand (Hamelinck, 2004). According to some IPCC SRES1 future market scenarios, 30% of the total energy supply is ascribed to biomass in 2100 (Nakicenovic and Swart, 2000). Those figures are the indicators for a future biomass based energy market potential. In fact, in some countries such as Brazil, Sweden and Finland bio-energy markets have already emerged. Moreover, large–scale biomass trade can be the centre of attention due to European legislations concerning climate policies. For example, in the agreement of the Dutch government with Dutch energy sector, it is stated that 6 Mton/year of fossil fuel CO2 reduction needs to be accomplished in 2008-2012 by the coal-fired power stations in the Netherlands. Half of this reduction is planned to be accomplished through replacing coal by biomass (Bergman et al, 2005).

Another phenomenon that triggers the international biomass trade is that some countries have larger biomass resources compared to other countries. For example; Latin America holds high biomass energy production potential (Hoogwijk et al. 2003; Damen and Faaij 2003; Agterberg and Faaij 1998). Several researches have given indications that intercontinental trade of biofuel could be economically feasible (Hamelinck, 2004; Wasser and Brown 1995; Agbert and Faaij, 1998). Hamelinck et al (2003) has conducted a study to assess whether large-scale long distance transport of bio fuel from certain world regions, such as Latin America and Eastern Europe, is economically and energetically feasible and attractive in terms of greenhouse gas (GHG) reduction. International biomass logistics were analysed by conducting several bio energy chains. These studies exposed that the pre-treatment step plays an eminent role in the whole chain since it affects the storage, transport and final conversion steps. Broadly, feedstock costs contribute 1 IPCC SRES; International Panel on Climate Change (IPCC) Special Report on Emissions Scenario (SRES)

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20%-65% of the total delivery cost whereas pre-treatment and transport contribute 20%-25% and 25%-40%, respectively, depending on the location of the biomass resource. When the overall chain is considered, the final conversion contributes roughly to more than 50% of electricity or fuel delivered. Existing research has been conducted mostly to obtain design data, process performance, product properties and the by product composition of the pre-treatment technologies. However, their techno-economic performances on the total bioenergy supply chain require detailed study. In this context, the key technologies, pyrolysis, torrefaction and pelletising need to be analysed in terms of technical performances and economy of scale. Pyrolysis and torrefaction are the thermochemical conversion technologies where bio-oil and torrefied biomass are produced in different temperature ranges respectively. On the other hand in pelletisation biomass is dried and compressed to produce cylindrical pieces. Various bio-energy chains can be designed where these technologies are considered and depending on the economy and impacts on environment in terms of GHG emissions, the optimal chain can be obtained. 1.2 Problem formulation The studies concerning long distance bio-energy transport analysed several cases to perform the biomass delivery and final energy production costs. Hamelinck developed a tool with which different bioenergy chains can be analysed. This tool enables to assess the influence of different pre-treatment technologies on the technical and economic performance of the whole chain. It is clear from the work of Hamelinck (2004) that energy densification of the biomass is crucial. Converting biomass into a densified intermediate can save transport and handling costs. In addition, it can improve the efficiency of the final conversion stage. Subsequently, pre-treatment methods deserve more attention in the positioning of the chain and techno-economic analysis of the treatment processes themselves. Torrefaction, pyrolysis and pelletising are the pre-treatment technologies considered in this study. Currently, the state-of-the-art biomass-to-energy chains are mostly based on energy densification by means of pelletisation. However, commercially available bio pellets are expensive and cannot be produced economically from a wide variety of biomass resources (only sawdust and planer shavings) when the small (smaller than 30 mm) particle sizes are required. New pre-treatment technologies are currently under development. Fast pyrolysis, charcoal production and torrefaction may improve economics of the overall production chain. However, these technologies are still under development and their economic and technical performances are unclear. Moreover, there is no normalised data set, which can give a clear picture of the economic performances. Available information, however, mainly discusses the technology and the intermediate products they produce, rather than their influence on the performance of the whole production chain. Therefore, the key research question in this study is: Which pre-treatment method(s), at what point of the chain, with which conversion technology (ies) would give the optimal power and fuel (syngas) delivery costs for international biomass supply chains?

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1.3 Objectives The main objective of this study is to identify the optimal bioenergy chain design and provide insight in the differences between the torrefaction, pyrolysis and pelletisation pre-treatment technologies. This can be done by performing a techno-economic analysis of the biomass-to-energy production chain that is based on pelletisation, torrefaction and pyrolysis. Moreover, this study focuses on the influence of the pre-treated biomass (intermediates) on transportation. The sub-objectives are: -Analysing the potential and future technical and economic performances of torrefaction, pyrolysis and pelletising in relation to scale. -Evaluating the influence of intermediate products on transportation. -Analysing the impacts of intermediate products on power and syngas conversion technologies. As pelletisation is commercially applied, this technology is considered the state-of-the-art reference (SOTA-system). Hence, the introduction of alternative pre-treatment technologies as pyrolysis and torrefaction are only interesting when they are comparable or better than the economics of this reference. However, the improvement options on pelletisation still need to be investigated even though it is commercially applied. The bio-energy techno-economic analysis is based on biomass resources located in South America (Brazil) and the final conversion to power and fuels is situated in North-West of Europe. 1.4 Methodology and evaluation criteria A technology review is performed where the design data of pre-treatment technologies are collected to determine the current technology status of pyrolysis, torrefaction and pelletisation. The state-of-the-art processes are identified according to their commercial or demonstrated applications. Following the literature survey, mass yields, energy yields and process efficiencies of each technology are presented. Economic evaluation is conducted by calculating the required capital investments and total production costs. The capital costs are based on component level cost data, which are obtained from literature and personal communication. Since the capacities of the components affect the specific cost of a plant, economy of scale is analysed. This is done by identifying the base scales, the base costs and the maximum scales of the equipments. Next, the actual equipment costs are calculated using the scale factor R. R-values per component are obtained from literature (Faaij et al., 1998; Bergman et al, 2005). Finally, the total capital investment requirements are calculated (See Appendix 1). This is followed by the sensitivity analysis of the parameters that influence the production costs The cost data are normalised using the OECD deflator and exchange rates of national currencies per US$(See Appendix 2). In addition, the impacts of the pre-treated intermediates on the final conversion step are assessed. Entrained flow gasification for Fischer Tropsch liquid production, biomass integrated gasification combined cycle (BIGCC), combustion and co firing for power production are considered as final conversion technologies. Since, the final conversion technologies have got specific requirements like the feedstock particle size, shape; compressibility, bulk density, and moisture content,

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intermediate energy carriers can alter the feedstock preparation and feeding system. Moreover, they can influence the gas-cleaning step that takes part in gasification. Therefore, impacts of pre-treated intermediates on conversion technologies are investigated. Following the final conversion stage, several biomass–to-energy chains are designed. In this part, Hamelinck’s (2003) “biomass logistic tool” is used. This tool gives the possibility to set up harvesting, transport, storage, handling, pre-treatment and final conversion steps in many ways. It also enables to visualize the different combinations and scales of operations and carries out techno-economic analysis. Furthermore it allows conducting sensitivity analyses to test the robustness of the study results and assess the variation in fuel/power costs. South American bio-energy crops (eucalyptus) are considered as the source of biomass in this study. The final conversion stage is assumed to be applied in Rotterdam by means of Fischer-Tropsch (FT) and conventional power plants. The transport mediums are chosen to be trucks for local transport and ships for international transport. 1.5 Report structure The report begins with the review of the pre-treatment technologies. Chapter 2 presents the techno-economic analysis and the improvement options for torrefaction, pyrolysis and pelletisation processes. In addition to this, it provides the sensitivity analyses, scale effects and a brief techno-economic data comparison of pre-treatment processes. The influence of the pre-treated intermediate on gasification and combustion in terms of efficiency and economy are also presented in this chapter Chapter 3 describes the approach and methodology used for biomass chain analysis. Moreover, it presents the designed chains and provides the results. Finally, Chapter 4 summarises the main conclusions of this study and presents the discussion and recommendations.

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2 Technologies 2.1 Torrefaction 2.1.1 Process definition Torrefaction is a thermal pre-treatment technology carried out at atmospheric pressure in the absence of oxygen. It occurs at temperatures between 200-300 oC where a solid uniform product is produced. This product has very low moisture content and a high calorific value compared to fresh biomass. The origin of torrefaction comes from roasting of coffee beans. This process however has been done in lower temperatures in the presence of oxygen. Since the 1930’s on, torrefaction has been used in relation to woody biomass. The research outcomes in those years appeared to be favourable at the technical stage; however, torrefied wood did not find the market outlets. In France, torrefaction has been applied to produce a wood that is used as a building material (Bioenergy, 2002). In the 1980s the focus was on using torrefaction technology to produce wood that can be used as a reducing agent in metallurgic applications. A torrefaction plant demonstration with a production capacity of 12000 ton/year was constructed and operated (Bergman et al, 2005). In recent years, torrefaction has gained significant importance for energy applications. Even though it is still in its infancy, several studies have shown that torrefaction upgrades the energy density, hydrophobic nature and grindability properties of biomass (Bergman et al, 2005; Bioenergy 2000; Prins, 2004). Through torrefaction biomass is converted into torrefied biomass which is typically 70% of its initial weight and contains 90% of the original energy content (Bioenergy, 2000; Bergman et al, 2005). 30% of the biomass is converted into torrefaction gas that contains 10% of the initial energy content. The moisture uptake of torrefied biomass is very limited varying from1-6%. Destruction of OH groups in the biomass by dehydration reactions causes the loss of capacity to form hydrogen bonds with water. In addition, non-polar unsaturated structures are formed which makes the torrefied biomass hydrophobic (Bergman et al, 2005). 2.1.1.1 Torrefaction decomposition mechanism The polymeric structure of woody and herbaceous biomass comprises mainly cellulose, hemicellulose and lignin. The most reactive polymer is hemicellulose whereas the cellulose is the thermo stable part. At low torrefaction temperatures decomposition occurs in the hemicellulose structure by means of a limited devolatilisation and carbonisation. In the lignin and cellulose structure however a minor decomposition is expected. When the temperature is raised up to 200- 300 oC, hemicellulose extensively decomposes into volatiles and char-like solid products, whereas limited devolatilisation and carbonisation occur in the lignin and cellulose structure (See Figure 1, Bergman et al, 2005)

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D

drying (A)

ExtensiveDevolatilisation

and

carbonisation(E)

Limiteddevolatilisation

andcarbonisation (D)

depolymerisationand

recondensation(C)

A

E

D

C

E

A

D

C

glass transition/softening (B)

Hemicellulose Lignin Cellulose

100

150

200

250

300

Temp

eratu

re (°

C)

Hemicellulose Lignin Cellulose100

150

200

250

300

Temp

eratu

re (°

C)TORR

EFAC

TION

Figure 1 Main physico-chemical phenomena during heating of lignocellulosic materials at pre-pyrolytic conditions (torrefaction). Main decomposition regimes are based on Koukios et al. (1982) Depending on the torrefaction conditions and the biomass properties, torrefaction products can be classified as solid, liquid and gas at room temperature. The solid phase, so called torrefied biomass, consists of original sugar structures and the reaction products, which are modified sugar structures, newly formed polymeric structures, char and ash fractions. The gas phase consists of mainly CO, CO2, and traces of H2, CH4 and light aromatic components. And in the liquid phase; H2O from biomass thermal decomposition, organics from devolatilisation and carbonisation and lipids consist. Nonetheless, torrefaction conditions; reaction time and torrefaction temperature are fairly important in product specification (Berman et al, 2005). 2.1.1.2 Torrefaction conditions Reaction time and reactor residence time is defined clearly before clarifying the necessary torrefaction temperature and the significance of moisture content in the torrefaction process. In fact, biomass has to be heated through several stages before the real torrefaction regime is reached. In practice, the solid residence time in a reactor is never equal to the time which biomass particles are exposed to torrefaction (Bergman et al, 2005). In Figure 2, temperature-time stages

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for a batch-wise operated torrefaction reactor is illustrated; however, those stages are the same for continuous operations.

Figure 2 Stages in the heating of moist biomass from ‘ambient’ temperature to the desired torrefaction temperature and the subsequent cooling of the torrefied product (Bergman et al, 2005). Temperature-time profile is considered to be typical for a batch-wise operated reactor. Explanation: th = heating time to drying, tdry = drying time, th,int = intermediate heating time from drying to torrefaction, ttor = reaction time at desired torrefaction temperature, ttor,h = heating time torrefaction from 200°C to desired torrefaction temperature (Ttor), ttor,c = cooling time from the desired Ttor to 200 °C, tc = cooling time to ambient temperature. In the initial heating stage, biomass moisture content evaporation is very slow; nonetheless, the biomass temperature increases. In the pre-drying stage, moisture content decreases dramatically while the biomass temperature stays constant. Following this stage, post-drying and intermediate heating occurs. The temperature increases up to 200 oC and the physically bounded water is

100

200

300

ttor

ttor,httor,c

T tor

tdry

th,int

tcth

Biom

ass t

empe

ratu

re (°

C)

tim e

pre-drying

post drying andinterm ediate

heatingin itia l heating torrefaction solids cooling

Moist

ure c

onte

ntMa

ss yi

eld (d

ry)

tim e

Heat

dem

and

(cum

mul

ative

)

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released. Above 200 oC torrefaction reaction occurs. Devolatilisation takes part in this stage. And finally, solid product is cooled to below 200 oC. 2.1.1.3 Product quality During torrefaction biomass loses relatively more oxygen and hydrogen compared to carbon, subsequently the calorific value of the product increases. The net calorific value (LHVdry) of torrefied biomass is in the range of 18-23 MJ/kg or 20-24 MJ/kg when the HHV (dry) is concerned. In Table 1, the comparison of torrified biomass with raw wood, charcoal and coal is presented. Table 1 Net calorific values (LHV) of untreated wood, torrefied biomass, charcoal and coal Untreated

wood Torrefied biomass

Charcoal

Coal

LHVdry (MJ/kg)

17-19 18-23 30 25-30

Source: Bergman et al, 2005 The moisture uptake of torrefied biomass is very limited due to the dehydration reactions that take place during the torrefaction reaction. Those reactions prevent the bonding of biomass hydrogen with water. Another change in the biomass occurs is the volumetric density. The torrefied biomass becomes more porous with a volumetric density of 180 to 300 kg/m3 depending on the initial biomass density and torrefaction conditions. It becomes more fragile as it looses its mechanical strength. As a result, torrefied biomass size reduction becomes easier, which is advantageous in conversion applications since they require biomass in very small sizes such as in the form of powder for entrained flow gasification 2.1.2 Production technology 2.1.2.1 Current status

Torrefaction technology is not commercially available yet. However, torrefaction history dates back to the late 1980’s when the upgrading of wood and briquettes by means of torrefaction was investigated at the Asian Institute of Technology, Bangkok, Thailand. Another study was held in Brazil. The Grupo Combustíveis Alternativos (GCA) at the University of Campinas in Brazil used a bench unit for biomass torrefaction (Bioenergy, 2002). Those studies provided information about the product quality.

The recent studies on torrefaction technology are based on the airless drying concept (Bioenergy, 2002) and the rotating drum concept (Duijn, 2004). In addition to this, at ECN extensive research has been carried out. They designed an optimum integrated process, and studied the impacts of torrefied biomass on co-firing and entrained flow gasification. In addition to this, they have developed a TOP process (Torrefaction and Pelletisation) which aims to bring TOP pellets to the energy market.

The only commercially applied torrefaction plant, PECHINEY, was built up in 1980s in France and was operated for a few years. It was a continuous process which was applied by Le Bois

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Torrefie du Lot, a subsidiary of Pechiney Electrometallurgie in order to produce roasted wood for use in manufacturing silicon steel (Bioenergy, 2002).

2.1.2.2 State-of –the- art-system (SOTA) description PECHINEY has built the first demonstration unit of a torrefaction process that was in operation since early 1987s with a capacity of 12 000 ton/year of torrefied wood as a reduction agent for silicon metal (Girard and Shah, 2005). Since this is the only commercially built process, it is accepted as the state-of-the-art system. However, it should not be forgotten that the process conditions applied were different than it should be to yield a product that can be converted into energy in a later stage. The process applied at Pechniey mainly consisted of a chopper where grinding is done, a drying kiln, and a torrefaction reactor (roaster) (see Figure 3). The received wood was cut into 50 to 80 mm long and 15 mm thick chips at a rate of 20 ton/hr by a drum chopper. The pieces larger than 80 mm were removed at the outlet of the screen to be recycled and the fines that were smaller than 15 mm were sent to the boiler to be combusted. Following this operation the wood chips were transported to a tunnel kiln for drying. The chips, dried to 10%mc, were transported to the roaster (torrefaction reactor) which was a hot mixing device with a double sheath and a rotating shaft with disc sections perpendicular to the axis of the shafts. The reactor was heated by conduction and thermal oil was used as a heat transfer fluid. This fluid was recycled between boiler and the reactor. The gases generated in the roaster were combusted and the fumes were returned to the kiln after being de-dusted. The temperature at the end of the roaster was reduced (Bergman et al, 2005).

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WoodStorage Chopper Wood Screen

Drying kiln Roaster Screen

large rejects

TW fines

TW metallurgy

wood fines toboiler

TWleisure

incinerator

combustibles

TW

flue gas

Boilerwood fines from

wood screen

thermalliquid

Figure 3 Schematic representation of the Pechiney process (Berman et al, 2005) The Pechiney process aimed at a product that has got a fixed carbon content with homogenized moisture content. The operation temperature was in the range of 240 to 280 oC with a residence time of 60 to 90 minutes. Various problems existed with this reactor design when it was considered for bigger scales. The heat exchange area in this reactor was a limiting factor. The feed moisture content was limited to 15% while the reactor through put was limited to 2 ton/hr. Higher moisture contents would drop the reactor throughput. Another disadvantage was that the reactor required free-flowing feed particles (Bergman et al, 2005). The energy efficiency of Pechiney was calculated as 65-75%. The low process efficiency was caused mainly by the feedstock losses during the chipping and sieving steps. 2.1.2.3 Assessment of the Pechiney process The investment cost of Pechiney process was approximately 2.9 M€ in 1985 with a specific investment of 25 €/ton product (Bergman et al, 2005). More than 80% of the total investment cost was arising from the reactor. The torrefied wood production was roughly 100 €/ton when the feedstock costs were excluded. When the feedstock costs were included, the production cost would approximately be around 150-180 €/ton. Process scaling up could reduce the production costs. However, the reactor used in the Pechiney process was poor in scaling up properties and expensive (Bergman et al, 2005). These properties imply the need to search further for a better

18

process technology. In fact, a torrefaction process with a capacity of 150 MWth is designed by ECN. 2.1.2.4 ECN Torrefaction technology The ECN torrefaction process is based on direct heating of the biomass during torrefaction by using the hot gas that is recycled. The torrefaction gas is re-pressurised and heated before it is recycled to the reactor. The necessary heat for drying and torrefaction is produced by combustion of liberated torrefaction gas. In fact, the energy content of the torrefaction gas plays a significant role in providing the energy demand of the dryer and the reactor. When the energy obtained from the torrefaction gas is equal to the energy demand of the dryer and the reactor, the system operates authothermal. On the other hand when the energy content of the gas is not enough, utility energy needs to be used. The moisture content of the feedstock is extremely important since the feedstock property determines the required heat demand. The relationship between the feedstock moisture content and energy yield in ECN process can be summarised by; the wetter the biomass feedstock is the lower the energy yield to be allowed in torrefaction in order to perform authothermal operation. In Appendix 3 the relationship between authotermal operation of the process in relation to the moisture content and energy yield of torrefaction is presented. The energy content of the torrefaction gas is directly related to the solid and energy yield of torrefaction. Therefore, when torrefaction is operated in a different condition that produces less energy yield, there will be surplus of energy in the form of torrefaction gas, in contrast when the energy yield of the process is higher than the optimised conditions this time the energy produced from the gas will not be enough to meet the dryer and reactor demand. This phenomenon is explained in Figure 5. TheECN torrefaction process consists of dryer, reactor, heat exchanger, combustion and cooling (Figure 4).

Drying Torrefaction Cooling

Heat exchange

biomassTorrefiedbiomass

Air

utillity Fuel

Fluegas

Combustion

DP

Torrefactiongases

Fluegas

Fluegas

gasrecycle

Figure 4 General flow diagram of ECN torrefaction process (Bergman at al, 2005)

19

(DP: Pressure Drop recovery)

Figure 5 Torrefaction process authothermal operation equations In this design the torrefaction gas is expected to be combusted so that the energy demand of the dryer can be met without or with a little utility fuel consumption. Thus, this would result in a self supporting, high efficient system. The calorific value of the gas ranges from 5.3 MJ/Nm3 to 16.2 MJ/Nm3 at the temperatures of 265 oC and 290 oC, respectively.

Dryer

Qdryer

Qgas = Qdryer + Q react.

Qgas

Qreact.

Torref.reactor

20

Components of the system Dryer: Directly heated rotating drum technology was selected to dry the biomass from 50% moisture content to the desired 15%. Dryer design was based on flue gas re-circulation and modelled by ECN (Bergman, 2004a). Reactor: During the process design at ECN, three different reactor types are considered. Screw reactor was one of the options since it was used in the SOTA process (Pechiney). The second option was the directly heated rotating drum technology due to its many applications as a dryer and the third option was the directly heated moving bed. Directly heated moving bed gains from its compactness (high fill percentage), simplicity in construction, high heat transfer rates and small reactor size requirement. Another advantage of the moving bed reactor is that there is not a specific feedstock shape requirement. It can handle non-free flowing materials. In fact, design studies in ECN resulted in favour of the moving bed reactor as the most promising technology. The three reactor comparison is summarised in the following table (Table 2). Table 2 Comparison of the three evaluated reactor types for 150 MWth output torrefaction process Heat transfer

coefficient 1 Total residence time

Fill Shape of material input

Costs 2

W/m2/K minutes % Indirectly heated screw

30 34 60-70 Free-moving expensive

Directly heated rotating drum

41 55 10-15 Free-moving medium

Directly heated moving bed

200 20 100 flexible cheap

1 Estimated heat transfer coefficient is based on m2 exchange area for the screw reactor, on m3 reactor volume for the rotating drum and on m2 particle surface area for moving bed. 2 Equipment purchase costs are compared with each other; moving bed reactor is roughly 6 times cheaper than the screw reactor. Source: Bergman et al, 2005. Cooler The torrefied biomass was cooled down to 50 oC by an indirectly heated rotating drum technology. Water was chosen as a coolant. 2.1.2.5 Torrefied biomass densification In the 2.1.1.3 section torrefied biomass is defined as a porous product, with a low density. However, torrefied biomass is fragile which makes it relatively easy to grind. On the other hand decreased mechanical strength and increased dust formation capacity in addition to low volumetric density makes a densification stage necessary. Besides, when the long distance

21

transport is considered, especially the shipment, pelletising the torrefied biomass is inevitable. This subject is discussed further in the biomass supply chain chapter. The mass density of torrefied biomass pellets is about 22 MJ/kg whereas the energy density reaches up to 18 GJ/ m3. Although this energy density is less than that of coal (20.4 GJ/m3), it is still 20% higher than commercial wood pellets (Lipinsky et al, 2002; Bergman et al, 2005). So, torrefaction in combination with pelletising offers significant advantages when the biomass logistics are considered. Densification following torrefaction is considered in several studies (Lipinsky et al, 2002; Reed and Bryant, 1978; Koukios, 1993; Bergman et al, 2005). Those studies indicate that the pressure required for densification could be reduced with a factor of 2 at 225 oC, while the energy consumption of densification could be reduced by a factor of 2 compared to biomass pelletisation. Biomass pelletising consists of drying and size reduction prior to the densification. Steam conditioning is applied to soften the biomass fibres. Following densification bio-pellets are cooled down. However, when torrefaction is considered, steam pre-conditioning is not required since torrefied biomass is fragile. Following torrefaction, size reduction, densification and cooling can be achieved (Figure 6). Figure 6 General flow diagram of torrefaction in combination with pelletisation Size reduction: The power consumption for size reduction following torrefaction is reduces around 70-90 % compared to biomass pelletisation (Bergman, 2005). Besides, production capacity of a chipper increases with a factor 7.5 to 15 compared to biomass. A simpler type of size reduction such as cutting mills, and jaw crushers can be deployed instead of hammer mills, which are used for the conventional pelletising process (Bergman, 2005). The experimental results of size reduction carried out at ECN (Bergman et al, 2005) are presented in Appendix 4. Densification: AT ECN, a piston press has carried out torrefied biomass densification experiments. This press was modified to press in different diameters of various biomass products under different torrefaction conditions. The comparison of torrified pellets with torrefied biomass, wood pellets and fresh wood is shown in Table 3 (Bergman, 2005).

Drying Torrefaction Size Reductio

Densification Cooling Biomass

Torrefied pellets

22

Table 3 Wood, torrefied biomass, wood pellets and torrefied pellets property comparison. Properties Unit Wood Torref.biomass Wood pellets Torref. pellets Low High Low High Moisture content %wt 35% 3% 10% 7% 5% 1% Calorific value (LHV)

Dry MJ/kg 17.7 20.4 17.7 17.7 20.4 22.7 As received MJ/kg 10.5 19.9 15.6 16.2 19.9 21.6 Mass density (bulk) Kg/m3 550 230 500 650 750 850 Energy density GJ/m3 5.8 4.6 7.8 10.5 14.9 18.4 Pellet strength - - Good Very good Dust formation Moderate High Limited Limited Hydroscopic nature Water

uptake Hydro phobic

Swelling/ water uptake

Poor swelling/ Hydro phobic

Biological degradation

Possible Impossible Possible Impossible

Pelletising the torrefied biomass not only increases the mass density but also the energy density. Besides, mechanical strength improves. According to the experiments at ECN, torrefied pellets can withstand 1.5 to 2 times the force exerted on conventionally produced pellets before breakage. The water intake capacity of the product was determined by immersing them into water for 15 hours. A gravimetric measurement device was employed to measure the water intake contents. The results showed that torrefied pellet water intake was very limited (up to 10-20% on mass basis) whereas wood pellets swell rapidly (Bergman, 2005). Technical performance characteristics of torrefied wood pelletising for sawdust and greenwood chips are given below (Table 4). Table 4 Technical performance of torrefied wood pelletisation for sawdust and green wood chips Item Unit Torrefied wood

pelletisation (sawdust)

Torrefied wood pelletisation (green wood chips)

Feedstock capacity Kton/y 170 170 Moisture content Wt. 57% 57% LHVar feed MJ/kg 6.2 6.2 Production capacity Kton/y 56 56 MWth fuel 40 40 Product Moisture content Wt. 3% 3% LHVar product MJ/kg 20.8 20.8 Cooling water m3/ton

product 16.7 16.7

Utility fuel MWth 3.9 4.7

23

Electricity consumption MWe 0.83 1.01 Thermal efficiency 98.5% 96.5% Net efficiency 93.7% 90.8% a.r: as received

24

2.1.3 Technology evaluation 2.1.3.1 Objectives & Methodology The focus in this section is on the technical feasibility of torrefaction process. This technology is not commercialised yet and most of the demonstrations have been done under laboratory condition. As a newly emerging technology, it requires technology analysis. In addition, the exploration of future development options is aimed at. In the analysis, the data obtained from the ASPEN flow sheet simulation package, which was created at ECN, is used. Overall mass and energy balances derived from those studies are used to calculate overall performance of the system. The process conditions are assumed to be the same as in the ECN torrefaction study (Bergman et al, 2005). 2.1.3.2 Mass and energy balances According to the ECN study (Bergman et al, 2005) done under 280 oC temperature and 17.5 min reaction time conditions, the torrefaction reaction mass yield was determined as around 70% (Figure 7) whereas the mass yield of drying was around 60%. This number corresponds to the moisture content loss. In fact the biomass input moisture content was 50% and the biomass moisture content leaving the dryer was 15%.

Figure 7 Net mass flows corresponding with torrefaction of cuttings at 280 oC and 17.5 min reaction time (HE: Heat exchanger). The thermal efficiency of the whole process was calculated as 96% while the net efficiency was approximately 92 %( includes the utility consumption) (Figure 8 and Table 5). The thermal efficiency of the whole process is mainly determined by the efficiency of the drying. The energy flow in dryer increases from 135.7 MWth to 152.8 MWth (See Figure 7). The high torrefaction efficiency takes its roots from the authothermal operation where the produced torrefaction gas is combusted and the energy demand of the dryer and reactor is met.

flue gas(combustables +non combust.)21.97 kg/s

0.01 kg/s ash1.03 kg/s

Combustion

3.62 kg/s

biomass 18.97 kg/s 11.16 kg/s

torref. gas7.54 kg/s

20 kg/s Drying Torrefaction torrefied biomass

HE 14.16 kg/s

flue gas

25

Drying Torrefaction

HE

biomassTorrefiedbiomass

Combustion

Fluegas

Fluegas

156.1 135.7 152.8 150

22.2

21.4

7.97

5.47

27.7

14.7

Cooling

4.10

Torrefactiongas

Figure 8 Net energy flows (in MWth) corresponding with torrefaction of woodcuttings at 280 °C and 17.5 min reaction time (HE: heat exchanger). Table 5 Overall energy balance of the 150 MWth torrefaction process Utility Unit Value Thermal output MWth 150 Thermal input MWth 156 Electricity input Dryer MWth Reactor MWth Fired heater/heat exchanger MWth Axial flow fan MWe 1.28 Product cooler MWe 1 Air turbo blower MWe 0.4 Electricity input MWe 2.68 Thermal equivalent 1 MWth 6.7 Thermal efficiency 2 % 0.96 Net efficiency 3 % 0.92 1 The efficiency of energy conversion is accepted as 0.40 2 Thermal efficiency is calculated as: thermal output/thermal input 3 Net efficiency is calculated as: thermal output/ (thermal input + utility)

26

2.1.4 Economic evaluation 2.1.4.1 Methodology Economic evaluation is based on the estimations of required capital investment and total production costs. Factorial method described by Peters and Timmerhaus (1991) is used as the reference source in the calculation assumptions (See Appendix 1). Direct costs consist of equipments and their installation, buildings, process and auxiliary, service facilities, yard improvements and the cost of land. Indirect costs include engineering & supervision, construction expense/constructer fee and contingencies. Both direct and indirect costs compose the fixed capital investment. The torrefied biomass production costs are calculated by dividing the total annual costs of a system by the produced amount of torrefied biomass. The total annual costs are;

• Annual investment • Operation and maintenance • Biomass feedstock • Electricity demand

The annual investment cost is calculated according to the below equation:

L

annul

rr

ItI

−+−=

=

)1(1

*

α

α

where: Iannual = annual investment cost α = the capital recovery factor It = total investment r = the discount rate L = the life time or depreciation period of the equipment The depreciation period was set to 10 years due to the expected lifetime of dryer and reactor. 8000h/year is assumed to keep the operation continuous. The chain analysis in this thesis is based on the assumption that biomass is imported from Latin America to West Europe and the biomass pre-treatment step is supposed to takes part in the Latin American region. Therefore, the parameters assumed for different world regions and used in the torrefied wood production cost calculation are presented in Table 6. The production cost breakdown estimations are presented in Appendix 5.

27

Table 6 Local parameters assumed for different world regions Latin America Western Europe Electricity price1 €/ MWhe 35 60 Labour price2 €/ Man-hour 6 25 1 Electricity prices are derived from Hamelinck et al (2003), Dutch retail price for industry in The Netherlands are presented by the IEA(2002) and the average Brazilian price for electricity is 34 €(ANEEL, 2003). 2 Average salary for Western Europe is in the range of 14-40 €/man-hour (Bridgwater et al, 2002; Hamelinck et al, 2003), the labour costs in Latin America ranges around 1.37-6.59 US$ in 1998, depending on the contract type (Tokman & Martinez, 1999). Following these steps, the economy of scale is assessed. To do so, 10MWth, 18.7MWth, 37.5MWth, 75MWth, and 150 MWth output capacities are selected. The scale is chosen in the range of 10 to 150 MWth since the only commercial process’ capacity was 10MWth and 150 MWth was designed at ECN. The cost calculations are done using scale factors per component. When the maximum unit is reached, it is assumed that parallel units are built to meet the desired capacity which means that the scale factor is accepted as 1. Cost estimates are done accepting 37.5 MWth process as the base capacity because in ECN 150 MWth plant cost estimates were based on this capacity due to the fact that maximum unit of the process components are reached (Berman, 2005). For the 10 and 18.7 MWth processes R- factors are used, however for 75 and 150 MWth the units are paralleled, so the equipment cost are calculated by doubling each unit’s cost. The R-values (Appendix 6) are obtained from BIG/CC study (Faaij et al, 1998) and from ECN technical experts (Berman, 2005a). 2.1.4.2 Estimation of the total capital investment

The total capital investment is estimated using the combination of capacity factored, equipment-based estimates and vendor quotes of the main plant items. The flow rates, heat duty, power equipment and such as capacity ratios are used in capacity factored estimation. The equipment-based estimations are done according to detailed design calculations (Bergman et al, 2005). Finally, the total investment cost for a 37.5 MWth output torrefaction process including drying is calculated as 6.5 M€ and presented in Table 7 .The major cost is derived from the installation cost. When it concerns the equipment costs, the dryer is the most expensive equipment followed by torrefaction reactor (Figure 9 and Figure 10).

28

Table 7 Total capital investment of a 37. 5 MWth torrefaction plant Costs

1 R-values Base

scale Max. scale

M€ I. Direct cost 1. Purchased Equipment Dryer 2 0,61 0,5 8 25 ton dry/hr Reactor 0,59 0,72 20 20 MWth Axial flow fans 0,10 0,7 1 .. MWe Product cooler 0,48 0,6 3 20 ton dry/hr Air turbo blowers 0,01 0,65 1 .. MWe Burners +heat exchangers 0,24 0,6 2. Installation Main plant items erection 0,14 0,7 Civil 0,20 0,65 Lagging 0,06 0,7 3. Instrumentation and control 0,22 0,3 4. Piping ducting and chutes 0,41 0,7 5. Electrical installation 0,22 0,3 A. continued dryers 0,09 0,65 B. buildings, process and auxiliary 0,45 0,65 C. service facilities and yard improvements - 0,65 service facilities general 0,19 0,7 cooling water system 0,10 0,6 air supply system 0,02 0,65 storage 0,43 0,65 yard improvements 0,07 0,65 D. land 0,06 0,7 II. Indirect costs - A. engineering and supervision 0,80 0,7 B. construction expense/ contractor fee 0,22 0,7 C. contingency 0,55 0,7 - Working capital 0,32 0,7 Total Capital Investment 6,53 Specific investment (euro/ton/year) 14,47 1 Cost calculations are based on the 150 MWth torrefaction plant cost estimate (Bergman et al, 2005). Since the 150 MWth plant consists of 4 parallel lines, purchased costs calculations for 37.5 MWth plant are done by dividing the cost figure into four. 2 Rotary drum dryer is used. According to Calis et al (2002), maximum scale is 25 ton dry/hr.

29

Equipment costs

31%

Instalation costs39%

Indirect costs25%

Working capital5%

Figure 9 Total capital investment cost breakdown Figure 10 Equipment cost breakdown 2.1.4.3 Estimation of the total production costs The total production cost for a 150 MWth capacity torrefaction plant is estimated in the range of 40-58 €/ton product when the feedstock cost is excluded (Bergman et al, 2005) (See Appendix 7). When the operation conditions are optimised, lower production costs can be achieved. In fact natural gas cost is rather high and when biomass is used as fuel instead of natural gas or a drier biomass is processed, the total production cost can be decreased. 2.1.4.4 Economies of scale Usually when the production capacity of a process is increased, a reduction in the average production cost is expected. Thus, economies of scale are defined as decreasing specific investment costs while up-scaling a certain technology as a power function (Dornburg and Faaij, 2001). The relationship between costs and capacities are as follows:

R

SZE

SIZE

SIZESIZE

COSTSCOSTS

=

1

2

1

2

where r is scaling factor ranging between 0 and 1 In this study, economy of scale is based on component level cost data. R-values per component are obtained from literature (Faaij et al, 1998) and ECN study (Bergman et al, 2005) whereas base scales, base costs and maximum scales are obtained from the study done by Bergman et al, (2005). For relatively large capacities (like 150 MWth), multiple units have to be considered. However, this reduces the economy of scale. Even though purchasing multiple units may cause some discount, this option is omitted in this study because the discount rate is vendor related. For the indirect costs, scaling up is not applied since they are the percentages of the capital investment costs and when the scale effect is applied to capital investment, it influences the indirect costs.

Heaters12%

Blowers1%

Product cooler21%

Fans5% Reactor

30%

Dryer31%

30

37.5 MWth capacity process is used as the reference scale because rotary drum dryer which comprises the highest cost compared to other equipments is used in its maximum scale in this process. When the capacity is exceeded 40 MWth, multiple equipment units need to be used. For the smaller scale processes R- Values are used to scale down. Table 8 presents the specific investment cost calculations for different plant scales. Table 8 Specific investment cost calculations of various capacities. Production Capacity (MWth) 150 75 37,5 18,5 10,00 R

values

M€ M€ M€ M€ M€ I. Direct costs 1. Equipment purchase costs Dryer 2,45 1,23 0,61 0,43 0,32 0.50 Reactor 2,34 1,17 0,59 0,29 0,19 0.72 Axial flow fans 0,40 0,20 0,10 0,06 0,04 0.70 Product cooler 1,68 0,89 0,48 0,04 0,17 0.60 Air turbo blowers 0,04 0,02 0,01 0,01 0,00 0.70 Burners +heat exchangers 0,94 0,47 0,24 0,27 0,11 0.60 2. Installation Main plant items erection 0,36 0,22 0,14 0,08 0,05 0.70 Civil 0,50 0,32 0,20 0,13 0,09 0.65 Lagging 0,15 0,09 0,06 0,03 0,02 0.70 3. Instrumentation and control 0,33 0,26 0,22 0,17 0,14 0.30 4. Piping ducting and chutes 1,07 0,66 0,41 0,25 0,16 0.70 5. Electrical installation 0,33 0,26 0,22 0,17 0,14 0.30 A. continued dryers 0,23 0,15 0,09 0,06 0,04 0.65 B. buildings, process and auxiliary 1,10 0,70 0,45 0,28 0,19 0.65 C. service facilities and yard improvements service facilities general 0,50 0,31 0,19 0,12 0,08 0.70 cooling water system 0,24 0,16 0,10 0,07 0,05 0.60 air supply system 0,04 0,03 0,02 0,01 0,01 0.65 storage 1,05 0,67 0,43 0,27 0,18 0.65 yard improvements 0,17 0,11 0,07 0,04 0,03 0.65 D. land 0,15 0,09 0,06 0,03 0,02 0.70 II. Indirect costs A. engineering and supervision 2,10 1,30 0,80 0,49 0,32 0.70 B. const. expense/ contractor fee 0,59 0,36 0,22 0,14 0,09 0.70 C. contingency 1,44 0,89 0,55 0,33 0,22 0.70 Working capital 0,83 0,51 0,32 0,19 0,12 0.70

31

Total Capital Investment 1 19,00 11,05 6,53 3,96 2,77 Specific investment (euro/ton/year)2 11,93 12,36 14,47 17,56 23,19 1Total investment cost is multiplied by the recovery factor (α) to obtain annual investment cost. 2 Specific investment cost is calculated by dividing annual investment cost by the production capacity. 2.2 Pyrolysis 2.2.1 Process definition Pyrolysis can be described as the direct thermal decomposition of biomass in the absence of oxygen (Yaman, 2004). Temperatures employed in pyrolysis are 400 to 800 oC (Bridgwater and Evans, 1993). The products of pyrolysis include gas, liquid and solid char. The relative proportions of products are dependent on the pyrolysis method, the characteristics of the biomass and the reaction parameters (United Nations, 1994). The process can be adjusted in favour of solid, liquid or gas production. Depending on the product demand operation conditions are modified. In the conventional pyrolysis, equal yields of gas, liquid and solid are produced. However, this is not a favourable technology due to the multiplicity of products that are difficult to handle and market. The lower efficiency in gas production and the heat transfer to the reactor are the main problems. Another method that captures a lot of attention is fast pyrolysis where very high heating rates at moderate temperatures and rapid product quenching are employed. The main product is liquid, the so called pyrolysis oil. At high reaction temperature, however, the main product is gaseous. The by-product in both conditions is char. The focus of this study is based on fast pyrolysis since the product aimed at in this study is liquid. Fast pyrolysis technology has received much attention in the last decades as a solution to convert biomass to a liquid fuel. In fact, liquid fraction can be maximized up to 75% wt on a dry biomass feed basis (Bridgwater et al, 2002) 2.2.1.1 Pyrolysis decomposition mechanism As previously mentioned, biomass consists of cellulose, hemicelluloses and lignin. Cellulose and hemicellulose degrades rapidly whereas lignin decomposes over a wider temperature range. Fast pyrolysis occurs around 500 oC in which biomass is rapidly heated in the absence of oxygen. It generates mostly vapours and aerosols where a rapid quenching of the pyrolysis vapours is needed to minimize secondary reactions. The vapour residence time is typically 1 s. Fast pyrolysis technology is in favour of high liquid production. The necessary conditions for fast pyrolysis are:

• High heating and heat transfer rates at the reaction interface; • Finely ground biomass feedstock; • A moderate reaction temperature (around 500 oC); • A vapour phase temperature of 450 –500 oC; • Short vapour residence times (less than 2 seconds) • Rapid cooling of pyrolysis vapour to produce bio-oil

32

2.2.1.2 Products Pyrolysis process yields 3 main products that are liquid, char and gas. Generally, the yields from fast pyrolysis are between 40-65 wt% organic condensate, 10 to 20% char, 10-30% gases and 5-15% water based on dry feed (Diebold and Bridgwater, 1999) depending on the biomass feed characteristics and reaction conditions. The LHV of gases are expected to be around 15 MJ/nm3 (Diebold and Bridgwater, 1999), when the fast pyrolysis reactor operation is in favour of maximum liquid production with a minimum of vapour cracking. When it concerns the LHV of chars, it has been reported to be around 32 MJ/kg (Diebold and Bridgwater, 1999). The char produced in fast pyrolysis is very flammable due to its small size and high volatility, therefore hot char from the process should be properly handled to avoid ignition. Pyrolysis oil, the desired product, is a dark brown liquid with a distinctive odour. The liquid fraction consists of two parts: an aquatic phase and a non-aquatic phase. While the aquatic phase consists of organo-oxygen compounds, the non-aqua phase consists of insoluble organics, mainly aromatics. The general characteristics of this bio-oil is summarised in Table 9. However, the properties of bio-oil depend on the type of process, the feedstock and its moisture content. In their study, Raveendran and Ganesh (1996) indicate the higher heating values for several biomass types (See Appendix 8). Table 9 Typical properties of wood derived crude bio-oil Typical value Unit Moisture content 20-30 % pH 2.5 Specific gravity 1.2 Kg/lt Element analysis C 55-58 % H 5.5-7.0 % O 35-40 % N 0-0.2 % Ash 0-0.2 % HHV as produced 16-19 MJ/kg LHV 15-18 MJ/kg Viscosity (40 C and 25% water)

40-400 Cp

Solid (char) 0.1-0.5 Source: Pyne, 2005

33

2.2.2 Production technology 2.2.2.1 Current status

Fast pyrolysis of biomass is on the verge of development and demonstration stage (in power production). Bio-oil production has been demonstrated in North America at a scale up to 2 ton/hr throughput, whereas pyrolysis plants are being marketed up to 10 ton/hr throughputs in Canada (Ensyn, 2005). Ensyn has started its fundamental fast pyrolysis experiments in 1981 at the University of Western Ontario. The first commercial application of the Ensyn Technology was a 100 kg/hr unit to produce chemicals and fuel oil at Red Arrow Products in Wisconsin, USA. The product yields were 67% bio-oil, 26% gas and 0.8% char (kg/kg feed basis). In 1995 Resource Transforms International Ltd. (RTI) began bench scale production of bio-oil. Dynamotive Corp. has achieved a commercial version of RTI process so named “BioTherm TM Technology”. The pilot plant was operated at a capacity of 2 ton/day on a continuous feed basis and it processed more than 35 tones of feedstock (Dynamotive, 1999) and in 2000 they designed and built a 10-ton/day bio-oil commercial demonstration plant. In 2003 Dynamotive launched the construction of a 100 ton/day plant at Erie Flooring and Wood Products, Ontario. Currently Ensyn has got a fast pyrolysis plant with a capacity of 75 ton/day (wet bases), which is operating commercially. This facility was built in Wisconsin in 1996 and has operated with a commercial availability of over 94 % (Ensyn, 2005).

Europe on the other hand has recently involved in the production of liquid fuels from biomass. However, a commercial pyrolysis demonstration plant was constructed in Edenhausen (Germany) with a capacity of 5000 ton/year and was operational until 1989. The aim in this process was the pyrolysis of plastic wastes, rubber wastes, oil wastes or other organic waste materials (Karminsky, 1985). A second demonstration scale of 600 kg/h plant was built at the Grimma machine factory, East Germany for the extraction of aromatic chemicals from the whole tires but this plant is also not operational (Kaminsky, 1985). In Italy, ENEL have installed a pilot plant, designed and built by Ensyn of Canada, to produce a fuel for co-firing in oil fired power plant. A 500-kg/h pyrolysis plant was planned to be demonstrated in Italy in 1989 with a liquid and char yield of 25% for each (Bridgewater et al, 2000). In fact, Enel Produzino is operating a pilot facility and currently the aim is to improve its operability and the product quality (Bio-energy projects, 2004). In mid 1993 Union Fenosa (Spain) constructed a 200-kg/h fast pyrolysis pilot plant, which is based on the University of Waterloo (Canada) process. Another 200-kg/h pilot plant was demonstrated in Belgium in 1991 and operated until 1992. The bio-oil yield of the plant was 39.9%wt., the gas yield was 16.2% wt. and the char yield was determined as 29%wt (Egemin). The most recent pilot plant was installed in Italy at Bastorda in mid 1996. It was a 15 ton/day Ensyn RTP3 pilot plant.

2.2.2.2 State-of-the-art-technology Ensyn patented Rapid Thermal Processing (RTP™) technology is accepted as the state of the art technology because it is commercialised (Figure 14). In this technology, biomass from the hopper passes through a metering screw and feed screw into the vessel reactor where biomass is contacted with a stream of hot sand. Following this section, sand is separated from the product vapour in a primary cyclone, re-heated and re-circulated to carry the heat to the fresh biomass. A

34

secondary cyclone removes the char and inorganic fines consisting of ash and entrained sand (Bridgwater and Bridge, 1991). Several condensers, filters and demisters are used to condense and recover the liquid product. This process necessitates a feedstock with moisture content less than 10% on wet basis and a particle size less than 5mm, preferably 3mm. The liquid product is 67%, daf, 74% as received

Figure 11 State of the art Ensyn RTP plant flow diagram (Source) 2.2.3 Technology evaluation 2.2.3.1 Methodology Pyrolysis technology requires a lot of interest due to its significant logistical and hence economic advantages. It is possible to obtain detailed technical data for various reactor types but in this study an overall technology assessment which consists of mass and energy balances are presented. When the existing fast pyrolysis technologies with various reactor specifications are considered, fluid bed configurations are the most popular reactors from the commercial point of view due to their ease of operating and ready scale up (Bridgwater, 1999). On the other hand ablative reactors offer the advantage of smaller downstream equipments and more intensive reaction. The overview of current technologies are summarised in Appendix 9. In this study rotating cone pyrolysis process is used as a reference technology due to its being compact and good integration of heat. This technology has been designed and demonstrated by BTG. The detailed data are obtained from BTG Biomass Technology Group BV, The Netherlands (Gansekoele et al, 2000). Even though state-of –the-art-technology is chosen different in the techno-economic calculation steps rotating cone technology is used as the reference process. As seen in the flow diagram, particles are heated rapidly by mixing sand, which is used as a heat carrier. The products are non-condensable gases, bio-oil and char. Char is combusted in a fluid bed together with sand where heat is conveyed to the sand. The produced gas is cleaned in a filter and fed in the condenser.

biomass

gas off gas

Biomass feeder

secondary cyclone

primary cyclone condensor column

bio oil

Reactor char chatchpot packet condenser column

heat for

pyrolysis

gas recirculation

35

Circulating bio-oil is used as a cooling medium, which is cooled down by water from a cooling tower. 2.2.3.2 Mass and energy balances The process diagram of the 5.5 ton/hr rotating cone reactor is given in Figure 12 where the mass and energy balances are demonstrated (Gansekoele et al, 2000). In addition to this, detailed mass balance of a 200 kg/hr pyrolysis plant is presented in Appendix 10. The mass yield of the main product, bio-oil is 70%, where as non-condensable gas mass yield is 20% and char yield is 10%. It is assumed that the gas leaving the condenser can be combusted in a gas engine for electricity generation and flue gases can be used for heating application.

0.7 kg/hrfluegas

bio-oil 4 tons/hr7.5 tons/hr 5.5 tons/hr 5.5 tons/hr 16.5 MWLHV

25 MWLHV 25 MWLHV 25 MWLHV

gas 0.75 tons/hrDryer Hammer mill Pyrolysis unit 2.1MWLHV

ash0.05 tons/hr

Figure 12 A schematic presentation of the mass and energy balance of a 5-ton dry feed per hour pyrolysis plant The char that is created in the pyrolysis plant is combusted and reused in the reactor. Since the char combustion energy is more than what is required to run the reactor, the system works in authotermal mode (Gansekoele et al, 2000). As it can be seen in Figure 12, the energy yield of the pyrolysis technology is approximately 66%. 2.2.4 Economic evaluation When international bio-energy transport is considered, pyrolysis pre-treatment option seems attractive. The liquid product can be either stored or readily transported depending on the requirement. Due to its relatively high energy content and bulk density, it can be economically advantageous compared to pellet transport. In addition to this when the final conversion stage is considered, converting bio-oil into energy or FT liquid is supposed to be easier than pellets. These assumptions are investigated later in the bio-energy chain analysis chapter. Even though the pyrolysis technology attracts a lot of attention and gets more commercialised, it still necessitates a detailed economic evaluation due to lack of publicly available economic data.

36

2.2.4.1 Methodology The economic data obtained in this study for fast pyrolysis technology varies from each other. Therefore, in this section, first the reference pyrolysis plant cost data is presented and compared to the data obtained from Hamelinck et al (2003). Second a literature review (Bridgwater and Evans, 1993; Bridgwater et al, 2002; Calis et al, 2002; Solantausta, 2001; Hamelinck et al, 2003) is conducted and finally the results are compared. 2.2.4.2 Reference case Before biomass is fed to the pyrolysis system, it needs to be prepared. In fact pyrolysis reactors require stringent feedstock particles and moisture content. When the rotating cone reactor is considered it demands a feedstock that has got a 2 mm particle size and moisture content below 12% (Gansekoele et al, 2000). Therefore, the plant consists of dryer, hammermill and storage as preparation phase. Following this process, the feedstock enters the pyrolysis plant. Investment cost of a 25 MWth process is presented in Table 10. In addition to this, another process is designed where mainly Hamelinck et al (2003) data are used.

37

Table 10 25 MWth-input capacity pyrolysis process investment cost calculations (sawdust as feedstock) Item Rotating cone pyrolsysis

plant (Gansekoele et al, 2000)

Reference plant

Costs (M€) Costs (M€) I. Direct costs Rotary dryer 0.36 0.81 1 Hammermill 0.07 0.08 2 Silo 0.10 0.08 3 Installation cost (20%)4 0.11 0.19 Buildings 5 0.12 0.21 Wood yard conditioning 0.03 - Sub-total 0.79 1.58 II. Indirect costs Engineering and supervision (5% of direct costs)

0.04 0.08

Const. expense and contractor’s fee (6% of direct costs)

0.04 0.08

Pyrolysis plant 6 3.5 7 8.5 78 Fixed capital investment 4.37 11.61 1 A 100 ton/hr Van den Broek rotary drum with 5 M€ capital cost is scaled down by the 0.7 scale factor (Hamelinck et al, 2003). 2 50 ton/hr hammermill with 0.37 M€ base capital is scaled down with a 0.7 scale factor (Hamelinck et al, 2003) 3 5000 m3 silo capital cost is mentioned 0.331 M€ (Hamelinck et al; Suurs 2002). 4 Instalation costs are estimated to be the 20% of direct costs 5 Building costs are assumed to be the 22% of purchased equipment costs (Peters and Timmerhaus, 1990). 6 Cost data assumed to include engineering & construction expenses. 6 The rotating cone technology includes biomass feed system, sand circulation system, char combustion, reactor and bio-oil condensing system Pyrolysis plant cost estimation details are confidential. 7 Calculation is based on equation 1.

38

In this study, production cost breakdown (See Table 12) is processed. The economic parameters used in this calculation are shown in Table 11 Economic parameters for a 25 MWth biomass pyrolysis plant Factor Value Unit Biomass type wood Moisture content 50% wt% d.a.f. Ash content 1 wt% d.a.f. Particle size 10 mm Biomass input 5 ton dry/hr Annual availability

7500 Hr/yr

Bio-oil yield 70 % Bio-oil LHV 17.5 MJ/kg Biomass cost 35 €/ton d.a.f Depreciation 6.7 %/year Pyrolysis plant cost

3.5 M€

Pre-treatment cost

0.8 M€

d.a.f.= dry ash free Table 12 Production cost of a 25 MWth rotating cone pyrolysis plant I. MANUFACTURING COSTS M€ A. Direct Product Cost 1. Raw Materials 1.39 2. Operation Labour 0.38 3. Direct Supervisory and clerical labour 0.08 4. Utilities Electricity 0.15 5. Maintenance and Repairs 0.14 6. Operating Supplies 0.02 7. Laboratory Charges 0.15 8. Patents and Royalties B. Fixed Charges 1. Depreciation 0.31 2. Local Taxes 0.14 3. Insurance 0.04 4. Rent 0.01 C. Plant Overhead 0.35 II. GENERAL EXPENSES A. Administrate Costs 0.09 B. Distribution and Selling Costs 0.80 C. Research and Development Cost 0,2

39

III TOTAL PRODUCT COSTS 4.22

112.65 Bio-oil production cost €/ton-feed €/GJ

9.20

The production cost is estimated around 112 €/ton (9 €/GJ) when the feedstock cost is accepted as 35 €/ton d.a.f for the reference case. On the other hand when the feedstock price is accepted as 0, the bio-oil production cost is approximately 75 €/ton (~6 €/GJ). The calculation results are consistent when compared to literature studies (Bridgwater et al, 2002; Solantausta, 2001). 2.2.4.3 Literature review and study comparison Even though there have been many demonstrated pyrolysis plants, the related cost figures are being kept confidential. Therefore, this part of the study is based on literature reviews in combination with the obtained cost figure data evaluations. In Figure 14 and Figure 15 pyrolysis plant investments of several studies are summarised (VTT (Fin), Aston University (UK) & Kemmiinformation AB (Se)).The data used by Aston University is reported as manufacturer’s data whereas VTT used literature with in-house data, and Kemiinformation data used industrial data. In Figure 14, the pyrolysis plant investment cost data between 40- 60 MWth varies substantially, which creates discrepancy. Even though the cost data is from the same source, it differs. For instance, in 2003, the specific investment cost of a 37.5 MWth liquid capacity was estimated around 350 kUS$/MWth, while it was estimated around 410 US$/MWth in 2002 for 48 MWth capacity (See Figure 14). Even for the similar capacities, the ranges of the cost estimates are different. According to the VTT study results, a pyrolysis plant costs around 34.5 € in 1999 with a capacity of approximately 56 MWth, while it costs around 25 M€ for 53 MWth capacity in 2002. Because of lack of information about the estimate details, it is not possible to clarify the variations.

40

Figure 13 Specific Pyrolysis Plant Investments 1987-2003 (Solantausta, 2001)

Figure 14 Specific Pyrolysis Plant Investments (Historic data from1987 to 2003 (Solantausta, 2001) In another study Bridgwater et al, (2002) has compiled a number of fast pyrolysis systems to give a financial scope. 14 data point for fast pyrolysis module was used, and the below figure was obtained (Figure 15).

41

Figure 15 Fast pyrolysis total plant costs versus feedstock (dry) input (Bridgwater et al, 2002). The equation to calculate the cost of fast pyrolysis system was determined from the figure as; TPCconv, pyr, kECU2000 = 40.8× (Q h, pret, dry×1000)0.6194 Equation 1 where, TPCconv, pyr = the total plant cost of the pyrolysis reactor system, Qh, pret, dry = the mass flow rate of prepared wood feed into the reactor, ton dry/hr However, the cost data of this curve could not be obtained. Therefore, a new curve is produced which consists of available cost estimates (Bridgwater and Evans, 1993). Five different pyrolysis plant capital investment cost data are plotted into a graph (Figure 16). The data distribution is reasonable excluding point 3. The data in point 3 (Bridgwater and Evans, 1993) is outside the expected range and this can be interpreted as the result of low process efficiency (30.62%). Detailed information about the cost data is included in Appendix 11. When the graph is compared to the VTT study (Figure 13 and Figure 14), the cost data differ. The reason can be that the cost data in VTT study include drying, which increases the capital cost significantly. However, it is not possible to give further clarification since detailed information related to the investment costs in VTT study is not available.

0

500

1000

1500

2000

2500

3000

3500

0 5 10 15 20

MWth-output (LHV)

Spec

. Inv

estm

ent

(kU

S$,2

004/

MW

th)

42

Figure 16 Specific investment cost versus capacity (MWth LHV) data of 5 different pyrolysis plants When the total capital investment costs versus feedstock amount are plotted in a graph (See Figure 17), an equation (Equation 2), different from Bridgwater et al (2002) is obtained. Different calculation methods may cause this difference. Bridgwater et al, (2002) has collected normalised plant costs for a number of fast pyrolysis and gasification systems to give the same equipment and financial scope while in this study five different pyrolysis plant investment cost data estimation is plotted to the graph. On the other hand, in the Shell study, a simpler approach was followed (Calis et al., 2002). The investment cost for the pyrolysis system was calculated using the scale factor. A scale factor of 0.6 was accepted for pyrolysis plants. As an example, a maximum size of 10 ton/hr plant investment cost was derived from the 2 ton/hr system, which was under design and for which a price of 2.27 M€ was estimated. The installed investment cost of a 10 ton/hr plant was calculated as 5.96 M€ for 2002(6.19M€2004) (Calis et al, 2002). When a 10 ton/hr plant is calculated according to Equation 1 the total plant cost is calculated as 12.25 M€2000(13.36 M€2004) whereas it is calculated as 5.01 M€, 2004 by Equation 2. It is rather difficult to clarify the reasons beneath the cost figure differences without knowing the detailed information related to the data used in those studies. It might be derived from the characteristics of the pyrolysis plant, the reactors used and the definition of the pyrolysis plants. In case the pyrolysis plant cost figures include dryer costs, it is reasonable to obtain such high cost figures. Another point, which needs to be emphasized, is that the total plant cost mentioned in Bridgwater’s study is different than total plant investment. It requires adjustment for interest and inflation.

43

Capital investment cost of pyrolysis plants

y = 94.126x0.4316

R2 = 0.8164

0

1000

2000

3000

4000

5000

6000

0 1000 2000 3000 4000 5000 6000Feed input (kg/hr)

Tota

l Cap

ital I

nves

tmen

t (kE

uro-

200

Figure 17 Total capital investment cost versus feedstock (ton dry/hr) of 5 different pyrolysis plants (Graph uses the same data as Figure 16). TCI, k€2004 = 94.126 *Qdry(kg/hr)0.4316 Equation 2

44

2.3 Pelletisation 2.3.1 Process definition Pelletising can be defined as drying and forming of biomass under high pressure to produce cylindrical pieces of compressed and extruded biomass with a maximum diameter of 25 mm. The aim in pelletising is to densify the biomass to produce a significant smaller volume and a higher volumetric energy density fuel that is more efficient to store, ship and convert into electricity or other chemicals (AEAT, 2003). By pelletising not only a uniform and stable fuel is obtained but also the amount of dust produced is minimized. Another advantage of pelletising is that it enables free flowing2, which facilitates material handling and rate of flow control (Koppejan and Meulman, 2001). In 1880, the first patent for densification was issued in the U.S. (Reed and Bryant, 1978).The sawdust or other wood residues were heated to 150 oF (65.5 oC) and then compacted with a steam hammer. Those processes at first were used to produce animal feed and then it shifted into densified fuel production for energy market. Densification in terms of pelletising has been commercialised. As an example, a 120-ton/day plant has been operating since 1976 in Oregon (Reed and Bryant, 1978). In addition, Finland and Sweden are the two leading countries in pelletising technology in Europe. The pellet production in 2001 exceeded 700,000 tons (Hirsmark, 2002). The production of pellets requires small feedstock particles, maximum 3-20 mm (Pierik and Curvers, 1995) and the moisture content below 10-15 %. However, piston press can compensate for up to 20 % moisture content. Pelletising process consist of the following stages.

• Feedstock reception • Chipping • Final drying • Size reduction (typically to 3 mm) • Pelletising • Cooling • Storage

The flow line of the process depends on the characteristics of the biomass received. For example if the feedstock material is exclusively sawdust there will be no requirement for chipping.

2 Free flowing means that the particles have got the same shape that they can flow through freely.

45

2.3.1.1 Pelletising decomposition mechanism Biomass densification in the form of pelletising occurs around a temperature of 150 oC . Cellulose is stable at temperatures below 250 oC. However, lignin, which holds the cellulose together like glue, begins to soften at 100 oC and permits the moulding of the wood. Water plays an important role in densification. If the feedstock is either too dry or too wet, the pressure required for densification increases dramatically. In fact, moisture content of 10% to 25% is mentioned as optimal (Reed and Brytant, 1978). Thus, the feedstock is heated to 50 to 100 oC to soften the lignin and obtain the desired moisture content and at approximately 150 oC mechanical densification is applied. 2.3.2 Production technology 2.3.2.1 Current status As mentioned above pelletising technology is fully commercialised. The use of wood pellets has increased in the 1990s in Sweden, Finland, Denmark and Austria and earlier in the North America. In the recent years, several pellet production plants have been established and the utilization equipment has improved (Alakangas and Paju, 2002). 2.3.2.2 State of the art system (SOTA) description Pellet production basically consists of at least four steps. These steps are drying, milling (grinding), pelletising and cooling (Figure 18).

Figure 18 State-of-the-art pellet production process diagram Drying: The moisture content of fresh biomass is around 50 %. In the pelletising process biomass is dried to 10-15% moisture content. This not only increases energy density but also eases the handling and transportation since the biomass weight is reduced. Another advantage is that dried biomass is less susceptible to mould and insect attacks during storage (Stahl et al, 2004).

pelletisation

biomass

screening

drying

grindingcooling pellet storage

46

There are many biomass dryer types developed. Drum dryer, steam dryer (direct or indirect) and hot air dryer are the commonly used technologies (Malisius et al, 2000). Grinding: In general hammer mills are used in this step. They grind biomass into fine fractions not bigger than 3mm. However, the screen size depends on the diameter of the pellets to be produced. Grinding is necessary to produce uniform materials for feeding to the pellet mill. The hammer mill is in general powered by an electric motor, which is converted into heat. This heat is also used to extract further moisture from the raw material at this stage. Pelletising: There are two main types of pelletisers: flat die pelletisers or ring die pelletisers (MacMahon and Payne, 1982). Loose materials are fed into pelletising cavity. Die rotation and roller pressure force the material through die, compressing it into pellets. Adjustable knifes cut the pellets to the desired length. To increase the abrasion resistance and bind the biomass, additives or binding agents can be used in this stage. They are usually added at approximately 1 wt% of the pellet mass (MacMohan and Payne, 1982). Cooling: The pressure exerted during the pelletising process can break up the pellets. Therefore, the cooling process is necessary to stabilise, harden and form the pellets (Viak et al, 200). Counter-flow coolers are mostly used for this process. 2.3.2.3 Products The produced pellets have a net calorific heating value in the range of 16.9 - 16 MJ/kg. The actual value depends on the moisture content that varies between 5 to 10%. Table 13 Characteristics of wood pellets (Sawdust, cutter shavings, and wood-grinding dusts as raw materials Variables Unit Value Size diameter length

mm mm

6-10 10-13

Energy content MJ/kg 16.9-18.0 Moisture content % 7-12 Ash content % 2 Bulk density kg/m3 650-700 Space demand m3/ton 1.5 Source: Alakangas and Paju, 2002 2.3.2.4 Improvements in the pelletising technology Currently there are two different processes, which are under development in order to improve the quality of the pellets and to decrease the energy consumption during pelletisation process. One of them is a steam explosion process where experimental pellet production plant is being carried out. The aim is to produce pellets which are much harder, have a higher specific weight (with a bulk density of 850 kg/m3) and are less sensitive to moisture and separation of fines. The research is being carried out in Norway at the Cambi Bioenergi Vestmarka. The raw material is preconditioned in this technology by heating a steam-compression reactor to release the natural

47

lignin. After a certain exposure time, the pressure is reduced, which causes the material to explode. In the literature it is mentioned that the preconditioning process also doubles the pellet production capacity.However, the plant in Norway is a prototype plant and is not yet commercial. The second technology has been developed by the Italian company EcoTre System. The aim of this development was to minimize energy consumption. In this new technology, the electricity consumption ranges between 0.025 kWh/kg-0.045 kWh/kg, depending on the type of wood (in Hamelinck et al (2003) the electricity consumption is mentioned at the range of 15-40 kWhe/ton with a moisture content of 8%). The process operates at low temperatures (55-60 oC) and without any additives. The main advantage of this system is its simplicity and lower investment costs. The pelletiser in this process can handle biomass with 30% to 35% moisture content, which means that a simple dryer can be employed or a dryer might not be required et al. In fact, there is significant energy consumption and investment cost reduction in this technology. Hamelinck et al (2003) mentioned the energy consumption of a rotary drum dryer 20 kWhe/ton. 2.3.2.5 Reliability Even though pellet production technologies are commercialised, the production of sufficiently strong pellets that can endure mechanical wear caused by storage and transport is still a challenge (Alakangas and Paju, 2002). There are various standard values for fuel pellets in Europe and US (AEAT, 2003) (See Appendix 12). However; those standards do not usually define durability or mechanical stability. Pellet standards and the quality marking are important in order to guarantee high quality pellets. 2.3.3 Techno-economic evaluation 2.3.3.1 Objectives & Methodology This part includes a general overview of the technology in relation to the technical and economic data. The aim is to present the data which is used in the chain analysis In the economic evaluation part, an Austrian case study (Thek and Obernberg, 2004) with a 24 000-ton pellet product/year is presented in order to include the recent improvements in the costs figures. The plant is assumed to operate 7884 h/year. The investment cost consists of equipment costs (drying, grinding, pelletisation, cooling, storage and peripheral equipments) and general investment costs, which include electrical installation, and construction costs. The annual capital cost is calculated by multiplying the capital recovery factor with the investment cost. Since the utilization period varies per equipment, annual capital cost is first calculated per item and then added up to find the final capital cost. In the production cost calculations the operation costs differ depending on the location of the plant. This is due to the difference between labour cost in Europe and Latin America and between electricity costs.

48

2.3.3.2 Mass and Energy balance Most of the time the fresh biomass moisture content is around 50%, while the produced pellet moisture content is 10%. Since no volatilisation has occurred during pelletising process, the total mass loss is caused by the moisture content evaporation (Figure 19).

Figure 19 Mass balance of the pelletising process When it concerns the energy balance, not only the energy density of feedstock and the product but also the energy consumed during the process has to be evaluated. A complete energy balance of a 24 000 ton pellet /year process is presented in Figure 20. The thermal efficiency is calculated approximately 94%, whereas net efficiency is 87%. 34000 ton/year Drying Grinding Pelletisation Cooling 24000 tonpellet/year12.66 MWth 12 MWth

0.19 MWth 0.27 MWth 0.58 MWth 0.03 MWth Figure 20 Energy balance for a 24000 pellet production process (Cost data is obtained from Thek and Obernberg (2004)).

44.45 water evaporation

biomass pellets

100 M (50% mc) 55.5 M (10% mc)

49

2.3.3.3 Estimation of total capital investment and production costs In this part, recent studies carried out by Thek and Obernberg (2004) and Hamelinck et al, (2003) are used as reference literatures. The data in Thek and Obernberg (2004) study are based on the already realised plants, questionnaire survey of pellet producers in Austria, South Tyrol and Sweden. On the other hand, the data used in the other study consist of literature survey and manufacturing data. A 24000 ton/year pellet production plant total investment cost is mentioned as 2 M€ (Thek and Obernberg , 2004). Specific investment costs mentioned in those studies are summarised in Table 14. The dryer cost data differs significantly. The tube bundle dryer is given for a 6 ton/hr capacity, whereas rotary drum dryer capacity is mentioned as 100ton/hr (Hamelinck et al, 2003)

50

Table 14 Cost data of pelletisation process Thek and Obernberg, 20041 Hamelinck et al, 2003

Specific Invest Costs 2

O&M

Life time

Energy

Type Specific Invest. Costs

O&M

Life time

Energy-e

Type

k€/MWthinp

ut % year kWhe/to

n k€/MWthinp

ut % years Kwhe/ton

Drying 3 Tube bundle dryer

15.8 4

2.5

15

13

Rotary Drum

29.4 5

3

15

20

Grinding Hammer mill

8.26 18 10 36.67 Hammermill

4.34 20 15 0.26(kwh.√mm/ton)8

Pelletisation7 Ring die pellet mill

40.7

10

10

77.67

Pellet press 8 197 10 28

Cooling Counterflow cooler

1.08

2

15

4

General investments9

48.34

1

Peripheral equipment 10

0.083

2

10

30

Total 100.5 41.74 11 1 The capacity of the plant is 47304 tonfresh/year with a 7884 hr/year operation load. The LHVar is considered as 6.2 GJ/ton, 55% w.b. 2 Specific investment costs are calculated by dividing the total investment cost with the input capacity 3 Tube bundle dryer and the belt dryer are mentioned as the most common dryers in Austria and the specific costs of dryers are in the range of 16.85-26.16

€/tonpellets (Thek and Obernberg, 2004). The capital cost of a dryer with 3 ton/h water evaporation rate is mentioned to be in the range of 40000-55000 €/year (Thek and Obernberg, 2004). The capacity of tube bundle dryer is given as 6 ton/hr. In the table it is scaled up to 100 ton/hr to be comparable with rotary drum dryer.

4 In the literature the investment cost of tube bundle dryer is mentioned as 375 k€ and the input capacity 6 ton/hr (Thek and Obernberg, 2004) 5 In Hamelinck et al, (2003), the rotary drum dryer is assumed to be the most conventional and proven technology for drying. The evaporated water is

calculated as 72.8 ton for a 100 ton/hr capacity dryer. In Bergman (2004), rotary drum dryer for 20 MWth is mentioned as 434 k€. 6 Grinding investment cost is mentioned as 62 000€ for hammermill (Thek and Obernberg, 2004). 7 The biomass moisture content is accepted as 15% before entering the pelletiser.

51

8 The energy consumption of chipping is calculated depending on the diameter of the product. Energy consumption in Hamelinck et al, (2003) is given as a bond index (See details in Hamelinck et al, 2003).

9 General investment costs include mainly construction costs. 10 Peripheral equipment cost consists of conveying systems, intermediate storage, and steel constructions. 11 the total costs can not be compared with each other, since the first column gives the total plant cost, wheras the second coloum gives only the equipment

costs.

52

As shown in Figure 21, the total capital investment costs are dominated by the peripheral equipment costs, general investment costs and the dryer costs.

0

50.000

100.000

150.000

200.000

250.000

Pellet process

Cap

ital c

osts

(Eur

o200

4 /ye

ar)

Perip. Equipm.StorageCoolingPelletisetionGrindingDryingGeneral investment

Figure 21 Cost breakdown of the total capital investment cost of a 24 000 ton pellet process (data from Thek and Obernberg, (2004) is used). The specific pellet production cost is approximately 90.7 €/ton with the 36 €/ton dry raw material cost. The annual operating time is considered as 7884 hr/year and the electricity price is 50.87 €/MWh (Thek and Obernberg, 2004). When biomass cost is considered o, the production cost is approximately 58 €/ton. 2.4 Comparison of processes The technical and economic comparison of the pre-treatment processes mentioned in this study are presented in Table 15 and Table 16.

53

Table 15 Technical comparison of torrefaction, TOP, pyrolysis and pelletisation pre-treatment processes. Unit Torrefaction TOP Process Pyrolysis Pelletisation

Feedstock type Woodcuttings chips Sawdust 1 Green wood chips Clean wood waste2 Sawdust Greenwood chips

Input Cap. MWth 25 25 25 25 25 25

Moist. content %wt 50% 57% 57% -- 57% 57%

LHV a.r MJ/kg 6.2 6.2 6.2 6.2 6.2 6.2

Product type Torr. biomass Pellets Pellets Bio-oil Pellets Pellets

Product m.c. %wt 3 5-1 5-1 20-30 (~22%) 10-7 10-7

Product LHV -a r

MJ/kg 19.9 20 4

19.9-21 6

19.9-21.6 0 20 4 22 7

17 15.8 17 7

15.8 17 7Mass density

(bulk)Kg/m3 230 750-850 750-850 1200 500-650 500-650

Energy density(bulk)

GJ/m3 4.6 14.9-18 4

14.9-18.4 20-303 7.8-10.5 7.8-10.5

Production capacity

MWth 24 24.63 24.12 16.5 23.48 23.05

Thermal efficiency 3

LHV 96.1% 98.5% 96.5% 66% 93.9% 92.2%

Net efficiency4 92.3% 93.7% 90.8% 64% 5 87% 84%

1 Sawdust is generally know with a relatively lower moisture content (around 35%), however in this study the moisture contents and the energy contents are obtained from ECN literature (Bergman et al, 2004) 2 3mm pine wood, sawdust residues from wood waste supplier, poplar, beech, wheat straw, rice husks, beech/oak and several organic waste materials have been successfully converted to bio-oil 3 Thermal efficiency indicates the efficiency where utility use is not included (energy cap. product /energy cap. feedstock) 4 Net efficiency includes the utility consumption 5 Pyrolysis electricity consumption is accepted as 0.0150 Mwe/MWth, in (Shell study-Calis et al, 2003), electricity is assumed to be generated with 40% efficiency.

54

Table 16 Economic comparison of torrefaction, TOP, pyrolysis and pelletisation pre-treatment processes

1 Data is obtained from Bergman, (2005). Cost data includes drying, sizing, pelletisation and cooling equipments. Scale for torrefaction, TOP and Pelletisation are 37.5 MWth input, 44 MWth input, and 44 MWth input, respectively. 2 The cost data is derived form the rotating cone reactor study and from the calculation where equipment costs data is mainly obtained from Hamelinck et al (2003).Details of cost calculations can be found in Pyrolysis section. 3 The production cost assumptions are based on the 0 feedstock cost, 8000 hr load factor and 10 years life time for torrefaction, TOP and pelletisation, and 15 years for pyrolysis. 4 The energy consumption of the Moving Bed torrefaction process is 92 kWh (Bergman, 2005. 5 Data include drying, torrefaction, size reduction and densification; in fact steam for drying is obtained from the torrefaction gas. 6 Calculation is done based on shell study; spec. electricity consumption is accepted as 0.0150 Mwe/MWth, in and the MWth, in is accepted as 25 MWth (Fig.23) or a 5 ton dry/hr pyrolysis plant. This value is accepted as 40 kWh/ton feed in Hamelinck’s study (2004). 7 Data include drying, sizing and densification process. 8 Data is obtained from Hamelinck et al, (2003).

Torrefaction 1

TOP process 1 Pyrolysis Pelletisation 1

Specific Capital investment

M€/MWthinput 0.17 0.13(sawdust) 0.19(greenwood)

0.19-0.42 2

0.09(sawdust) 0.15 (greenwood)

O&M % 5 5 48 5 €/ton

58 45 (sawdust) 50(green wood)

108

41(sawdust) 54(green wood)

Production costs 3

€/GJ 3.2 2.5 5.86 3.4 Energy –e kWh/ton 92 4 91(sawdust)

110(greenwood) 5

75 6 129(sawdust)-201(greenwood) 7

55

2.5 Sensitivity analyses for pre-treatment technologies The parameters that affect the torrefied biomass and bio-oil production costs are analysed. In the total production cost concept, biomass cost, capital cost, load factor, interest rate and depreciation period are the factors that affect the production costs significantly. Therefore, sensitivities of production costs based on these factors are investigated. Table 13 shows the parameters and the ranges these parameters may vary. Table 17 Main parameters used and ranges for sensitivity analysis Torrefied

biomass Bio-oil Pellet

Parameters Value Range Value Range Value Range Biomass costs(€/tondry) 20.4 14-32.5 37 30-43 36 20-45 Capital costs (M€) 25 12.5-43.75 3.5 2.75-4 0.24 50%-150% Discount rate (%) 8 8-18 5 4-10 7 5-15 Load factor (h/year) 8000 7500-8560 7500 7000-8760 7884 7500-8760 Depreciation period(years)

10 6-16 20 10-25 15 10-20

Torrefied biomass production costs are highly sensitive to the capital costs. Increasing capital investment 40 % increases the product cost 17%. Following to capital cost, discount rate influences the production cost. In fact, discount rate determines depreciation of the capital costs.

Sensitivity analysis of torref. biomass production cost

45

50

55

60

65

0 2 4 6 8 10 12

parameter variation

Torre

fied

biom

ass p

rodu

ctio

n co

sts

(eur

o/to

n pr

. -yea

r)

capital costsinterest ratedepreciation periodbiomass costsload factor

Figure 22 Sensitivity of torrefied biomass production

56

Bio-oil production cost is influenced by biomass costs, capital costs and load factor significantly. When the raw materiel is increased from15 €/ton to 50 €/ton, the bio-oil production cost increases around 30%. The bio-oil production cost is hardly affected by the capital investment cost of the pyrolysis plant which is different than torrefied biomass production cost. The reason might be that drying and size reduction is not included in the pyrolysis process which accounts a high percentage in the total capital cost. Increasing load factor from 80% to 100% decreases the production cost approximately 15%. The bio-oil can be produced as cheap as 8 €/GJ in the full load.

Sensitivity analysis of bio-oil production cost

8

8,5

9

9,5

10

1 2 3 4 5 6Variables

Bio

-oil

cost

(Eur

o/G

J

Biomass costs

Capital costs

DepreciationperiodLoad factor

Figure 23 Sensitivity analysis of bio-oil production costs When pelletisation process is considered, load factor can decrease pellet production cost to 83 €/ton. But still the load factor considered is more than 80%.

Pelletisation sensitivity analysis

80

85

90

95

100

1 2 3

Variable

Pelle

t pro

duct

ion

costs

(eur

o/to

n pe

llet)

Biomass costCapital costInt. rateDepreciationLoad factor

Figure 24 Pellet production sensitivity analysis

57

Another important factor that needs further investigation is the scale effect. Economies of scale have a considerable influence on the production costs. The torrefaction and pyrolysis processes are capital-intensive; hence investment costs are key to the establishment of production costs. Unless the maximum scales of the equipments are excesses, cheaper investment cost can be achieved by larger conversion units. In Figure 25, the economy of scale on capital investment costs are displayed. The cost data plotted to the graph can be found in section 2.1.4. After 40 MWth input, the specific investment cost is constant. In this repect, capacities larger than 40 MWth does not decrease the production cost. On the other hand, when the capacity is smaller than 40 MWth, production costs will be more expensive due to higher investment costs

Torrefaction economy of scale

0,00

10,00

20,00

30,00

40,00

50,00

60,00

0,00 50,00 100,00 150,00 200,00

MWth output

Spec

ific

Inve

stm

ent C

osts

(Eur

o/to

n)

Figure 25 Effects of scale on torrefaction investment costs On the other hand, when pyrolysis process is considered, smaller scales are needed. According to Figure 26, capacities larger than 20-25 MWth input don’t benefit much from economies of scale. For the pelletising process, economy of scale increases above 20 MWth input capacities.

58

Pyrolysis economy of scale

0,00

50,00

100,00

150,00

200,00

250,00

300,00

0,00 20,00 40,00 60,00 80,00

MWth

Spec

ific

prod

uctio

n co

s(E

uro/

ton)

Figure 26 Effect of scale on the bio-oil production costs.

Economy of scale

40

50

60

70

80

0 10 20 30 40 50 60

MWth

Spec

ific

prod

uctio

n co

st (E

uro/

ton

pelle

t)

Table 18 Effects of scale on pellet production costs.

59

2.6 Final conversion The objective of this chapter is to identify the effects of torrefied biomass, and pyrolysis oil on the final conversion stage in terms of technology and economy. In this study biomass is eventually assumed to be used for electricity generation and transportation fuel production. Therefore, combustion, co-firing, biomass integrated gasification combined cycle (BIGCC), and Fischer Tropsch technologies are addressed where the final conversion is applied in the chain analysis. The cost data considered in this study is presented in Table 19.System descriptions and information about the cost data can be found Appendix 13. Table 19 Cost figures for final conversion step Unit BIGCC1 FB-

Combustion2 Co-firing 3

EF gasification4

Base scale MWth 105 200 100 1000 Maximum scale MWth 408 200 100 - R factor 0.61 0.77 0.7 0.5 Efficiency % 57 35 40 71% Life time year 25 25 10 25 Total capital req. M€ 90 124 16.7 41-45 Spec. capital req. M€/MWth-

input 0.86 0.62 0.16 0.041-0.045

O&M % 4 4 0 4 1 Cost data is obtained from Faaij et al, 1988 2 Data is based on Dornburg, 1997 3 Data is based on Hamelinck et al, 2003. Extra (non fuel) costs for coal load are mentioned as 13.7 €/MWhLHV for pellets and 6.3 €/MWhLHV for pyrolysis oil. This cost is accepted as capital cost and O&M accepted as 0. The depreciation is done for 10 years. 4 The investment of an entrained flow gasifier includes fuel feeding system and syngas cooler. The investment cost is increased 10% when the feedstock is solid (Calis et al, 2003) Impact of pre-treated biomass on gasification systems When torrefaction is applied to the biomass several advantages are foreseen. In the gasification pre-treatment step, electricity consumption for milling decreases significantly. The fibrous structure and the tenancy of biomass are reduced by hemicelluloses decomposition together with the depolymeristation of cellulose during the torrefaction reaction. The power consumption in size reduction is significantly reduced when the biomass is first torrefied. 85% power reduction can be achieved. According to a study carried out at ECN (van der Drift et al, 2004), milling biomass into 100µm consumes 0.08kWe/kWthdry. However, when torrefaction is applied, the consumption decreases to 0.01-0.02 kWe/kWth. In the same study the relationship between the particle size and chipper capacity are determined for untreated, dried and torrefied willow. The capacity of the mill increases in proportion to the particle size. When the 0.2 mm particle size is

60

considered, the chipper capacity for torrefied willow is up to 6.5 times the capacity of untreated willow. In Appendix 14 the detailed study definitions can be found. In the case of bio-oil, the pre-treatment section needs to be adjusted depending on the bio-oil characteristics. In fact, sizing is not necessary anymore and the feeding system can be similar to the liquid fuel feeding systems instead of the ones that are suitable for solid feed in. Impacts of pre-treated biomass on combustion Combustion reactivity of the torrefied biomass was evaluated at ECN (Bergman et al, 2005). In this study, it was observed that the carbon conversion of torrefied biomass is comparable to that of woodcuttings and significantly higher compared to low- or high volatile coal (Bergman et al, 2005). In the case of bio-oil combustion, the quality of the bio-oil influences the combustion efficiency significantly. In fact, when the oil quality is poor, even the modifications to the burner and boiler cannot be enough. The most important parameters for bio-oil combustion are viscosity, water and particulates content, bio-oil raw material, bio-oil age and amount of methanol addition (up to 10% wt%) (Pyne, 2005). Methanol addition homogenises poor quality oil and decreases particulate emissions. The effects of the pyrolysis-oil quality on combustion is summarised as (Pyne, 2005):

- it may cause blockage in the feed line due to the various reactivity of oil components,

- oil age and/or in homogeneity gives uneven combustion, - methanol edition homogenizes the poor quality pyrolysis oil and improves its

combustion, - solid content affects the amount of incombustibles, - The increase of pyrolysis oil water content causes NOx reduction but on the other

hand it increases the particle and soot emissions. The high viscosity of the bio-oil causes blockages of the burner pipe and the high water content of bio-oil makes it barely possible to ignite (Gansekoele et al, 2000).Therefore the bio-oil needs to be pre-treated before it is combusted. Different than a regular biomass pre-treatment section, which is mainly biomass sizing; the bio-oil pre-treatment step consists of filtering and pre-heating the bio-oil. Filtering The oil is filtered to reach a maximum particle size of 40 µm. The equipment used for filtering needs to be stainless steel, due to the aggressive characteristics of bio-oil. According to a study done by Gansekoele et al, (2000), following remarks regarding filtering are made: 1) The entire system has to be cleaned with methanol after filtering. 2) Bio-oil charges of less than 30 cSt viscosity do not have to be preheated. Pre-heating of bio-oil

61

Following the filtering stage, bio-oil was prepared for combustion at constant temperature in a heating and stirring device in the BTG test study. The pre heat temperature was set to roughly 60 oC, depending on the bio-oil quality. The tests run by BTG showed that the preheating of the flame tunnel to reach wall temperature above 500 oC is very important for a stable combustion of bio-oil. In addition to this, preheating the bio-oil up to 60-70 oC improves the combustion. For a stable combustion of bio-oil, the flame tunnel has to be preheated to reach wall temperatures above 500 oC. Another experimental study was carried out by Juste et al, (2000) to analyse the combustibility of pyrolysis oil. This study also showed that some important modifications need to be done in the injection system of the gas turbine due to the high viscosity of bio-oil.

62

3 Chain analysis 3.1 Approach and methodology In order to achieve sustainable energy targets in terms of bio-energy production, the biomass derived energy production costs have to be competitive. When the international bio-energy trade is considered; there are several factors, which influence the overall production cost. In fact the means of biomass plantation, the transportation type and distances, the pre-treatment methods and their locations, and the final conversion technologies affect the production costs significantly. Hamelinck et al (2003) developed a tool that with which the possible bio-energy chains can be compared and the influence of key parameters can be assessed. However, torrefaction pre-treatment option was not considered in Hamelinck et al (2003) study. This chapter covers performance evaluation and further optimisation of long distance bio-energy supply and final conversion stage with a special focus on the pre-treatment technologies, namely torrefaction and pyrolysis whereas pelletising is used as a reference process. Different pre-treatment scales are applied to the bio-energy chains in order to see their impacts on technical and economic performances of the total chain. Several bio-energy chains are considered to obtain the most efficient transport chain design and the techno-economic evaluation of the overall chain is achieved by using Hamelinck’s logistic tool (Hamelinck et al, 2003). The biomass chains considered in this study generally consist of production, pre-treatment, transport and energy conversion steps. An important parameter in the chain design is the locations where the pre-treatment options are situated. In this study five transfer points are considered. Namely, these are: -Production site -Central gathering point (CGP) -Export terminal -Import terminal -Conversion unit Figure 27 visualises these transfer points.

63

Figure 27 Biomass transport overview 3.2 Logistic operations 3.2.1 Biomass source, storage, sizing and drying Latin American energy crops are chosen as the biomass source in this study since Latin America offers high yield biomass with low production costs (Hamelinck et al, 2003). Argentina, Brazil, and Chile are the countries where biomass plantations exist commonly. In Brazil 6 Mha of plantation area is used for pulpwood and energy production (Damen, 2001). In the northeast part, there is a potential of 8-13 EJ/yr of Eucalyptus energy. Plantations in Argentina amounts up 0.85 Mha whilst it is 2.3 Mha in Chile (Bonita et al, 2002). The characteristics of Latin American energy crops are presented in Table 20.

Bio

mas

s pr

oduc

ttion

Cen

tral

Gat

herin

g Po

int(

CG

P)B

iom

ass

prod

uctti

onB

iom

ass

prod

uctti

on

Expo

rt

Term

inal

(Har

bour

)

Impo

rt

Term

inal

(Har

bour

)

Conversion Unit

Bio

mas

s pr

oduc

ttion

Bio

mas

s pr

oduc

ttion

64

Table 20 Characteristics of Latin American energy crops considered in this study (Ranges indicate short and long term,) Type Logs Position Roadside Biomass (€/tonw.b) (€/GJ)

16.8-10.2 1.8-1

Energy fuel (MJHHV/ton) 60-49 Distribution (ton/km2) 467-583 Avg ps(mm) 1000 Density (kg/m3

bulk) 324 HV (GJHHV/tondry) 19.4 Dm loss/month 0.5% Supply Whole year Source: Hamelinck et al, 2003 w.b: wet bases; Dm: dry matter; Avg ps: Average particle size HV: heating value Harvest bundlers are employed as a harvesting technology because it is assumed that there are dense plantations and a machine which cuts and bundles the stems directly is more efficient, especially for transportation. The harvested biomass is considered to be stored in the field for up to six weeks so that natural drying is achieved without any extra cost. Further in the transport chain several other storage options are applied depending on the biomass type. When the biomass is in the form of pellets, silos, when it is in the form of bio-oil, special lined carbon steel tanks are considered. 3.2.2 Sizing Following to the harvesting operation biomass is cut to the desired feedstock particle size depending on the pre-treatment process type. From bundles (3000 mm) to chips (30 mm), roll crushers are employed. Due to the smaller size requirements for the pre-treatment technologies (2 mm for pyrolysis and 3-10 mm for pellets) hammer mills are required. Costs and other related operational data are based on the Hamelinck et al, (2003) study. 3.2.3 Drying Drying in this study is done to increase the efficiency of pre-treatment technologies, to produce better quality energy carriers, to decrease the capital costs of conversion technologies and to avoid biomass decomposition. A rotary drum dryer is employed in this study due to its commercial availability. In the torrefaction technology, biomass is dried to 15% moisture content whereas in pyrolysis it is done to 7%. The cost data for drying is included in the pre-treatment cost figures because the drying technology is integrated. 3.2.4 Pre-treatment

65

As mentioned before, biomass feedstock is either converted into pyrolysis oil or into torrefied biomass. Following to the torrefaction, feedstock is pelletised due to its low bulk density. In the base case scenario, biomass is directly pelletised without being converted into an intermediate.

66

3.2.5 Final conversion As mentioned in the previous chapter, gasification (FB) combined cycle (BIGCC), EF gasification, combustion and co-firing technologies are applied in the end of the chain with the purpose of either electricity production or syngas production. 3.2.6 Transportation Transport distances are determined depending on the pre-treatment process capacities, the percentage of the land occupied with crops and the biomass yield. In fact, pre-treatment plants are located at the centre of the farming areas in order to provide sufficient amount of feedstock to the process unit. It is assumed that the percentage of the land used for energy farming is between 10 and 30 %( Faaij et al, 1998). In this study, 20% of land under energy cropping and 5.74 tonfresh/ha.yr yield is accepted. Farming areas are assumed as circle areas. The pre-treatment unit is located in the centre of the circle, so that the biomass delivery area provides sufficient amount of biomass to the unit. The first truck transport distance is accepted as the radius of the circle (See Figure 28) (Dornburg and Faaij, 2001; Faaij and Meuleman, 1998; Bothwel 2005). The total transport distance to the harbour is accepted as 100 km. So the second transport distance varies depending on the size of the pre-treatment unit.

Harbour

Biomass delivery area Harbour

R2 R1 XPre-treat. unit

Figure 28 Schematically presentation of transportation distances The first transportation distances from the place of harvesting to the transfer point in relation to the capacity of pre-treatment unit is illustrated in Table 21. Following the pre-treatment step, biomass is transported to the harbour. Shipment distance from Latin America to West Europe is assumed as 11,500 km. Suezmax tanker (125000 ton) is considered for bio-oil shipment and Suzemaks bulk carrier or tank is employed for pellets. Another assumption made is that the distance from the import harbour to the final conversion unit is accepted as 100 km for which a truck is considered.

67

Table 21 Logistics of biomass from harvesting to the pre-treatment process point.

3.3 Designed Chains Depending on the harvesting methods, pre-treatment technologies, pre-treatment capacities and final conversion processes, several bio-energy chains from Latin America to West Europe can be modelled. In Figure 29, chain options that are modelled in this study are illustrated. In the local processing steps, smaller pre-treatment units (19MWth) are assumed whereas in the central gathering points relatively bigger pre-treatment options (150 MWth) are considered. The mentioned pre-treatment processes consist of further sizing, drying, conversion, and cooling. Therefore, these options are not renamed in the designed chains. The 1st and the 2nd chain are considered to show the transport cost differences between torrefied biomass and torrefied + pelletised (TOP) biomass. The last chain is considered as the reference scenario. The chains are analysed assuming that the biomass input is 600MWth.

Pre-treatment Capacity MWth input 19,13 25,00 40,82 76,53 153,06 Biomass LHVdry(MJ/kg) 17,70 17,70 17,70 17,70 17,70 Fuel input plant (kton wet/year) 47,89 61,54 102,17 191,58 383,15 Moisture content 35% 35% 35% 35% 35% Fuel input plant (kton dry/year) 31.13 40.00 66.41 124.52 249.05 Yield (ton /ha/yr) 5,74 5,74 5,74 5,74 5,74 Number of ha energy crops 8343.90 10720.99 17800.32 33375.61 66751.21 Land available for energy farming 20% 20% 20% 20% 20% Number of square km energy crops with 20% occupation

417.20

536.05

890.02

1668.78

3337.56

Distance to transfer point(km, one way) 11.53 13.07 16.84 23.05 32.60 Av. distance to transfer point(km, one way) 8 9 12 16 23

68

Storage Storage Storage StorageOpen air pile (bales) Open air pile (bales) Open air pile (bales) Open air pile (bales)

truck transp. truck transp. truck transp. truck transp.

Chipper ChipperTorrefaction Hammermill HammermillPelletisation Chipper Pyrolysis Chipper PelletisationStorage (Silo) Torrefaction Storage (Tank) Hammermill

Peletisation PyrolysisStorage (Silo) Storage (Tank)

truck transp. truck transp. truck transp. truck transp.

Combustion

truck transp.

truck transp.

truck transp.

ship transport

Import Harbour

truck transp.

Storage

cent

ral

Harvesting (felling)

Chipper

Base Case Scenario

StorageOpen air pile (bales)

truck transp.

Final conversionBIGCCCo-firing

StorageOpen air pile (bales)

Export Harbour

EF-Fischer Tropsch

loca

l

loca

lChipperTorrefactionStorage (Silo)

cent

ral

Storage(silo/tank)Preparation

Figure 29 Modelled bio-energy chains from Latin America to West Europe

69

In the analysis section, every chain is given a name depending on the pre-treatment type, scale and final conversion type. The codes of the chains are shortly summarised in Table 22. Table 22 Designed chains. Code Pre-treatment type Pre-

treatment Scale

Final conversion type

LA1-torr(18.75)-ship Torrefaction 18.75 MWth

LA1-torr+pellet(18.75)-ship

18.75 MWth

LA1-TOP(40)-ship 40 MWth LA1-torr+pellet(75)-ship 75 MWth LA1-torr+pellet(150)-ship

Torref. + Pellet.

150 MWth

LA1-pellet(40)-ship Pelletisation 40 MWth LA1-pyro(rot. cone)-ship 25 MWth LA1-pyro (10)- ship

Pyrolysis 10 MWth

No final conversion, delivery to Rott. harbour

LA1-TOP-ship-FT(EF) Torref. + Pellet. 40 MWth

LA1-pellet-ship-FT(EF) Pelletisation 40 MWth LA1-pyro-ship FT(EF) Pyrolysis 25 MWth

Fischer Tropsh (Entrained flow) in Rotterdam

LA1-TOP-BIGCC Torref. + Pellet. 40 MWth LA1-pellet-BIGCC Pelletisation 40 MWth LA1-pyro-BIGCC Pyrolysis 25 MWth

BIGCC (Fluidised bed)

LA1-TOP-combustion Torref.+pellet. 40 MWth LA1-pellet-combustion Pelletisation 40 MWth LA1-pyro-combustion Pyrolysis 25 MWth

Combustion

LA1-TOP-co-firing Torref. +pellet. 40 MWth LA1-pellet-co-firing Pelletisation 40 MWth LA1-pyro-co-firing Pyrolysis 25 MWth

Co-firing

LA1: Latin American energy crops 3.4 Chain analysis 3.4.1 Cost data 3.4.1.1 Chains delivering solid energy carriers The size of the pre-treatment unit plays a significant role in biomass logistics since it influences both the first truck transport distance, and the costs of the transportation. In Figure 30, the torrefaction pre-treatment option is compared for different scales. At first, the logistics of torrefied biomass for a smaller scale (18.75 MWth) is analysed to see the difference between transporting it as pellets or as torrefied biomass. In fact, the cost difference is significant. The

70

main cause is the shipment. Torrified biomass bulk density is very light (230 kg/ton) compared to torrefied and pelletised biomass (750 kg/ton).Transportation of torrefied biomass in the form of pellets is much cheaper. Therefore, further in the chain design, torrefaction is considered in combination with pelletisation and named as TOP. Second, the different torrefaction scales are compared with each other to estimate the optimum scale of torrefaction unit. When 18,75 MWth-40MWth-75MWth and 150 MWth are compared , it is seen that the delivery costs of smaller scales are relatively cheaper, however, in the 40 MWth system (named as TOP process), the cost can be as cheap as 75,5 €/ton dry delivered. Actually, in the torrefaction technology section 40 MWth is defined as the optimal scale because of economy of scale (See 2.1.4.4). Furthermore, this process is compared to the base case scenario where biomass is converted into pellet and transported. In addition to this, scale effect of pelletisation is also investigated. The analysis shows that the cost of delivering biomass in the form of TOP is very close to the form of pellets. The delivery cost of TOP to pellet is 73.5 €/ton dry delivery to 69.7 €/ton dry delivery. However, when the cost data is considered for the energy content, the TOP delivery cost is cheaper than the pellet (3.34 €/GJLHV to 3.94 €/GJLHV, respectively). The major steps contributing to the overall delivery cost are biomass source, truck transport and pre-treatment step. Pre-treatment step contributes to 26% of the total delivery cost, while truck transport contributes to 24% and biomass to 26 %. Figure 30 Cost data of chains delivering pellets in €/ ton dry delivered. 3.4.1.2 Chains delivering liquid energy carriers 10 and 25 MWth capacity pyrolysis plants are considered in the bio-oil delivery concept in order to see the effect of scale on delivery costs. However, the pyrolysis plant cost data differs significantly in literature, which causes discrepancy. Therefore, in Figure 31, bio-oil delivery cost is analysed for two different cost data obtained for the same scale (See Table 10). In addition to this, pre-treatment scale effect is evaluated by considering a smaller plant scale (10 MWth).

Costs of chains delivering pellets

0

20

40

60

80

100

120

LA1-torr(18,75)-ship LA1-torr+pellet(18,75)-ship LA1-TOP(40)-ship LA1-torr+pell(75)-ship LA1-torr+pell(150)-ship LA1-pellet(40)-ship LA1-Pell(20)-ship

Co

sts

(€

/to

nn

e d

ry d

eli

vere

d) Storage

DryingDensificationSizingShipTrainTruckWireBiomass

Torrefaction+pelletisation Referance (pelletisation)Torrfaction

71

The delivery cost of bio-oil ranges between 4.7 €/GJHHV – 5.3 €/ GJHHV for a cheaper investment cost figure, whereas it increases to 6.6 €/ GJHHV when the investment cost is calculated depending on other references (Hamelinck et al, 2003; Solantausta 2001). As mentioned before, inconsistent pyrolysis plan cost data causes inconsistency in the chain analysis. The cost of bio-oil delivery contributes to biomass, transportation, storage and pre-treatment costs. Approximately 30-50% of the cost counts for pre-treatment. Figure 31 Cost of bio-oil delivered to West Europe in €/GJHHV On the other hand when Fishers Tropsch liquid production is considered, the conversion to FT liquid stage is assumed to be applied in West Europe. The FT liquid cost around 6.44 €/GJHHV for TOP whereas it costs approximately 9.42 €/GJHHV for bio-oil (See Figure 32). However, the liquid cost in the reference case, where pelletisation is considered, is 6.97 €/GJHHV. Fischer Tropsch conversion unit is considered in West Europe with a large scale (1000MWth) since FT liquid production is cost effective at large scales (Hamelinck et al, 2003; Bathdizdai, 2004; Calis et al, 2003).

Cost of chains delivering FT-liquids

0

1

2

3

4

5

6

7

8

9

10

LA1-TOP-ship-FT(EF) LA1-Pellet -ship-FT(EF) LA1-pyro-ship-FT(EF)

Co

sts

(€

/G

JHH

V L

iqu

ids) Conversion

StorageDensificationDryingSizingShipTrainTruckWireBiomass

Referance

Pre-

trea

t.+co

nv.

Cost of chains delivering bio-oil

0

1

2

3

4

5

6

7

8

LA1-pyro(rot .cone)-ship LA1-pyro(10)-ship LA1-pyro(25A)-ship LA1-pyro(10MWt h-A)-ship

Cost

s (€

/GJH

HV

Liq

uid

s)

StorageDensificationShipTruckBiomass

Rot. ConeComparison

25 MWth10 MWth

25 MWth

10 MWth

72

Figure 32 Costs of FT liquid for different pre-treated feedstock (Conversion in the graph comprises pre-treatment and FT processes).

73

3.4.1.3 Chains producing electricity Electricity is assumed to be produced either in BIGCC or in FB combustor –steam turbine or in PC boiler. However, application of bio-oil in BIGCC and FB-combustor is not considered in this study because technical possibility of bio–oil in fluidised bed has not researched. The electricity cost for TOP and pellet chain are 13.05 €/GJ (4.6 €cent/kWhe) and 15.24 €/GJ (5.5 €cent/KWhe) respectively, when BIGCC option is considered (Figure 33). The conversion step contributes approximately 50% of the total power cost while the second major contributor is transportation (~25%). However, the conversion step in Figure 33 not only comprises the BIGCC system but also the biomass pre-treatment steps. The storage costs shown in the figure for TOP process can be omitted since torrefied biomass has got a hydrophobic characteristic, so instead of storing them in silos, they can be stored in open air. Figure 33 Cost of the chains delivering electricity by means of BIGCC In the case of using FB-combustion, cost of chains delivering electricity are; 21.64 €/GJ (7.7 €cent/kWhe) for the TOP chain, and 22.84 €/GJ (8.2 €cent/kWhe) for the reference chain. Similar to the electricity production by BIGCC, the costs of the chains in Figure 34 are mainly influenced by conversion steps followed by transportation and biomass harvesting steps. Conversion step here also includes both pre-treatment and final conversion to electricity step. It accounts for approximately 60% of the total cost.

Costs of chains delivering electricity (BIGCC)

0

2

4

6

8

10

12

14

16

LA1-TOP-BIGCC LA1-pellets-BIGCC

Cost

s (€

/GJ

pow

er d

eliv

ered

)

ConversionStorageDensificationDryingSizingShipTrainTruckWireBiomass

Referance

74

Figure 34 Cost of power obtained by combustion for various bio-energy chains On the other hand, when the chains are analysed assuming the final conversion step as co-firing, the electricity costs are in the range of 12.2 €/GJ (4.4 €cent/kWhe) – 16.2€/GJ (5.8 €cent/kWhe) for TOP chain and pyrolysis chain, respectively. Approximately 10-15% wood pellets can be co-fired by mass (Hamelinck et al, 2003) and the feedstock handling accounts 6.3 €/MWhLHV for bio-oil and 13.7 €/MWhLHV value for pellets (Hamelinck et al, 2003).

Cost of chains delivering electricity (co-firing)

0

2

4

6

8

10

12

14

16

18

LA1-TOP-co-f i r ing LA1-pel let-co-f i r ing LA1-pyr o-co-f i r ing

Cos

ts (€

/GJ

pow

er d

eliv

ered

)

ConversionStorageSizingShipTruckBiomass

Figure 35 Cost of power obtained by co-firing for various bio-energy chains

Costs of chains delivering electricity (FB-combustion)

0

5

10

15

20

25

LA1-TOP-combust ion LA1-pellet-combustion

Cost

s (€

/GJ

pow

er d

eliv

ered

)

ConversionStorageDensificationDryingSizingShipTrainTruckWireBiomass

Referance

75

3.4.2 Energy use 3.4.2.1 Chains delivering solid energy carrier Figure 36 shows the primary energy use for the considered chains in this study. Energy use for chains delivering biomass range from 1.98 GJ/ton dm for TOP process with a relatively small scale (18.75 MWth) to 2.46 GJ/ton dm for torrefied biomass without pelletisation. This difference occurs due to the energy use during shipment. Total energy use of a Suezmak bulk carrier is 4516 MJ/km (Hamelinck et al, 2003) and a ship is filled volumetrically before it is filled down to its load mark by weight due to light load of torrefied wood which explains such a high energy use in torrefied biomass shipment. The primary energy use for TOP delivery is approximately 8.5% of the delivered LHV. On the other hand only torrefied and delivered biomass requires 12% of the delivered LHV. Reference case primary energy requirement for energy is 11% of delivered biomass (LHV). Figure 36 Energy use of chains delivering biomass to the Rotterdam harbour in GJ/ ton dry delivered.

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3.4.2.2 Energy use of chain delivering liquid The energy use in bio-oil delivery to West Europe is approximately 8% of the delivered bio oil HHV. The energy is mainly required in the pre-treatment step and transportation step. Figure 37 Energy use of bio-oil delivered to West Europe in GJ/GJHHVbio-oil On the other hand, the primary energy use of FT liquid production chain is 26 % of the delivered HHV for reference case, whereas it is approximately 16 % for the chain where bio-oil is converted in to FT liquid. TOP process also uses primary energy of its 17% energy content. The pellet chains require further sizing to be fed to the gasifier whereas bio oil does not need to be pulverised Figure 38 Energy use of the chains delivering FT liquid Figure 39 Primary energy use of chains delivering energy

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3.4.2.3 Energy use of chains delivering electricity The primary energy use is in the range of 15% to 25 % to deliver 1 GJ power. The main steps that use primary energy are the energy requirement for densification and fuel consumption. In fact, approximately 40% of the energy use contributes to the pre-treatment (mentioned as densification) step.

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Figure 40 Primary energy use for chains delivering electricity. 3.4.3 CO2 emissions 3.4.3.1 Delivering solid energy carriers CO2 emission for the designed chains follow a similar path as energy use since the CO2 emission is the highest for the chain of 18,75 MWth torrefied biomass and lowest for TOP for the same scale(18.75MWth)process. The amount of emissions of the torrefied biomass reaches 138.16 kg/ton dm, which is mainly caused by the shipment and followed by the electricity consumption for pelletisation. The CO2 emission in biomass harvesting is mainly caused by the electricity consumed for harvesting equipment and the fuel used to forward the harvested biomass. The CO2 caught in the harvested biomass at the beginning of the chain is not considered in the below figures. The lowest CO2 emission (4 kg/GJ) happens in the TOP chain, where a 40 MWth torrefaction and pelletisation pre-treatment is considered

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CO2 emissions of chains delivering biomass

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Figure 41 CO2 emission of chains delivering biomass to West Europe in kg CO2/ ton dry delivered 3.4.3.2 Chains delivering liquids Figure 42 presents the CO2 emissions of each chain in which biomass is converted into bio-oil and delivered to West Europe harbour. CO2 emitted to the atmosphere is mainly because of the electricity used during bio-oil conversion step and the fuel used in transportation. The Latin American electricity mix contains 49% natural gas, which causes 0.056 ton CO2/GJgas. Average CO2 emission is around 4.1 kg per 1 GJ bio-oil delivered to the west Europe harbour. Figure 42 CO2 emission caused by bio-oil delivery from Latin America to West Europe.

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In the case of FT chains, similar to the energy use, reference case CO2 emission is the highest (11.90 kg CO2/GJ liquid). Delivering biomass in the form of TOP and bio-oil and converting them into FT liquid causes approximately 8.5 kg CO2/GJ liquid. Figure 43 CO2 emissions of chains delivering FT liquid. 3.4.4 Comparison of the chains delivering power and chain optimisation One of the aims of this study was to obtain the optimal chain. In this respect, the chain that delivers electricity and FT liquid cheaper with less energy use during the cycle and that emits less CO2 needs to be identified. In order to find this out, all the designed chains delivering power are compared in terms of power delivery cost, FT delivery costs, energy use and CO2 emissions. According to the Figure 44, electricity can be delivered as cheap as 12.2 €/GJ (4.4 €/kWhe) from an existing co-firing plant. On the other hand it costs 13.05 €/GJ (4.6 €cent/kWhe) when the BIGCC is considered. Even with high capital investment cost, BIGCC is compatible to the existing co-firing plants because of its high efficiency.

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Figure 44 Comparison of the power cost delivery figures for every chain. When the greenhouse gas emissions are considered, the least environmental friendly chain is the one with pellet combustion. It emits 22.93 kg CO2/GJ (Figure 45). TOP –BIGCC chain emits 9.5kg CO2/GJ. Figure 45 CO2 emissions of the chains delivering electricity (conversion in this graph means the pre-treatment steps and emissions count for the electricity utilised during pre-treatment).

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However when the FT liquid delivery is considered, TOP chain delivering liquid costs as cheap as 6.44 €/GJHHV. CO2 emission of TOP chain and pyrolysis chain are less compared to pellet chain. However, pyrolysis chain cost is 9.42 €/GJHHV. As a conclusion, the TOP chain with BIGCC and Entrained flow Fischer Tropish liquid production chains are accepted as the optimal chains by means of production costs and environmental factors. BIGCC efficiency is higher (56%) compared to combustion (35%) and co-firing (40%) and it gains from bigger scales (105MWth-408MWth) whereas entrained flow gasification efficiency is considered as 71% with a 1000 MWth capacity. 3.5 Sensitivity Analysis For biomass supply to Western Europe, plantation yield, interest rate, and load factor are determined as the key uncertainties. The base values and the ranges sensitivity analysis done, is presented in Table 23. Table 23 Parameter used for sensitivity analysis and ranges Parameters Base value Range Interest rate 10% 5%-20% Yield (ton/ha.year) 5.74 1.43-11.48 Harvest operation period (OW)(months)

8 3-12

Figure 46 shows the results of sensitivity analysis. Torrefied and pelletsised (TOP) biomass delivery cost is very sensitive to harvest operation period and interest rate. Changing the operation period form 8 months to 6 months increases the TOP delivery cost 14%. On the other hand, when operation period is increased to 12 months, TOP delivery cost decreases about 16%. The cost changes depend on the storage and operational costs. In fact, the number of storage unit increases significantly, when the biomass is harvested for a shorter period of time. And operation cost decreases because the equipment is not fully utilised throughout the year. The cost of TOP delivered is 73.5 €/ton for 8 months harvesting and it decreases to 61.9 €/ton for 12 months harvesting. Interest rate also plays an important role in delivered TOP cost. An increase of interest rate from 10 % to 20 percent, increases the intermediate cost from 73.5€/ton to 90.3 €/ton. The cost difference is related to the capital investment cost of the equipment employed in the chain. When the biomass yield is considered, there is a variation in the transportation costs. When the land yield is increased, the needed biomass harvesting area decreases, which causes a decrease in the first truck transport (the first truck transport calculation is presented in Table 21). The first truck distance decreases 30%, when the biomass yield is doubled. But the cost reduction is as small as 1% since biomass yields in Latin America is high and the first truck transports are

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relatively short. The biomass yield increase logically decreases the biomass costs; however, since the biomass plantation and harvesting is not in this study boundary, this cost difference is not included. According to Batidzirai (2005), changing biomass yield from 60% to 140% of base value results in 21% fuel cost change.

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Figure 46 Sensitivity analysis for TOP process (OW: harvest operation period) The torrefaction process is capital intensive. Therefore, scale effect plays an important role in the fuel delivery cost. When the pre-treatment unit is considered as small as 10 MWth, the delivery cost is 82.9 €/GJ. Increasing the unit scale to 40 MWth, causes 11% delivery cost decrease. On the other hand, when the unit scale exceeds 40 MWth, the delivery cost does not influence from the scale effect. Besides, the delivery cost increases0.28%, mainly because of longer first transport distance.

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4 Discussion and conclusion The main research question in this study was: Which pre-treatment method(s), at what point of the chain, with which conversion technology (ies) would give the optimal power and syn-fuel production costs for the intercontinental biomass supply chain? In this chapter, the main outcomes of this study are discussed and an answer to the research question is presented. 4.1 Pre-treatment technologies The three different pre-treatment technologies, torrefaction, pyrolysis and pelletisation were evaluated in terms of their technical and economic performances. In the following table, the study results are summarized. Table 24 Techno-economic comparison of torrefaction, TOP, pelletisation and pyrolysis Torrefaction TOP Pelletisation Pyrolysis Process efficiency % 92% 90.8% 84%-87% 66%-70% Product Energy content(LHVdry)

MJ/kg 20.4 20.4-22.7

17.7 17

Mass density Kg/m3 230 750-850 1200 500-650 Energy density GJ/m3 4.6 14.9-

18.4 7.8-10.5 20-30

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Specific capital investments

M€/MWth 0.17 0.19 0.15 0.19-0.42

Production costs €/ton 58 50 54 75-104 Table 24 indicates that torrefaction, TOP (torrefaction in combination with pelletisation) and pelletisation process efficiencies are quite high compared to pyrolysis technology. The product energy content of TOP process is also significant. Combining torrefaction with pelletisetion eliminates the low bulk density of torrefied biomass, thereby increasing the energy density of the intermediate product. Energy density of the TOP pellet is approximately 1.75 times higher than conventional pellets and 3 times higher than torrefied biomass. When the economics of the three pre-treatment technologies are compared, pelletisation has the lowest specific capital investment costs. Adding the densification step after the torrefaction process increases the specific investment cost by only 10%, which includes both sizing and pelletisation processes. The reason for such a low extra investment is that torrefied biomass is easily grinded. Thus, the power consumption for sizing decreases by approximately 50%-75 % compared to fresh biomass. When the specific capital investment of pyrolysis technology is considered, there is a significant variation between the cost figures found in scientific literature. This variation could have been explained by assuming that different technologies were used. However, the cost data even from the same source was inconsistent. Therefore, in this study, two scenarios were considered, one each with low and relatively high capital investment costs. Depending on those scenarios, the pyrolysis liquid production cost estimates are in the range of 6-12 €/GJHHV in the Western Europe conditions. Economy of scale plays a significant role in the specific capital investment costs. This study showed that torrefaction plant capacity exceeding 40 MWth did not gain from the economy of scale anymore. A similar conclusion can be reached for the pelletisation process. Pelletisation process exceeding 35-40 MWth, does not gain much from the economy of scale. The detailed information can be found in the economy of scale section. Pyrolysis technology benefits from economy of scale in smaller capacities. Above 25 MWth, economy of scale advantages disappear for pyrolysis. Consequently, this study indicates that torrefaction in combination with pelletisation pre-treatment process is comparable and even more advantageous than pelletisation. The, pyrolysis process, as an alternative, has serious drawbacks in terms of process efficiency and economy, when compared to the other technologies. However, their performances as part of the overall bioenergy chain determines their desirability, which is discussed below. 4.2 Chain analysis In this study, various biomass supply chains were envisioned. Biomass supply chain logistics for torrefied and pelletised (TOP) biomass, pellets and pyrolysis oil included harvesting, storage, pre-treatment, transportation and final conversion. The final conversions considered were to

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Fischer tropsch (FT) fuels and also power production by means of biomass integrated gasification combined cycle (BIGCC), combustion and co-firing. Latin American energy crops (eucalyptus) were assumed to be imported to the Netherlands. In order to investigate the optimal location for the pre-treatment processes, different scales and, parallel to these, different locations were applied in the chains. These chains were then compared with each other. The chains were named depending on the pre-treatment technology applied. The calculation results are summarized in Table 25. Table 25 Costs of chains delivering fuel and power Intermediate

delivered to harbour €/GJHHV

FT-Liquid fuel €/GJHHV

Power (BIGCC) €/kWh

Power (Combustion) €/kWh

Power (Co-firing) €/kWh

TOP 3.34 6.44 4.6 7.7 4.6 Pellet 3.94 6.97 5.5 8.2 4.8 F.Pyrolysis 4.7 -6.6 9.50 5.9 As seen in Table 25, TOP pellets can be delivered as low as 73.5 €/ton (3.34 €/GJ). One of the reason for such a low delivery cost is the approximately 15% higher bulk density compared to conventional pellets, which lowers the first truck transport costs. Another reason is the plant scale applied. As mentioned before, with a 40 MWth plant scale, it was possible to obtain low production costs. In fact, when TOP is considered for smaller scales, such as 18.75 MWth, the delivery cost increased by 16%. On the other hand, when the base scale is increased by 87.7%, the delivery cost increases by 10% because of longer first truck transport. In fact, the truck transport contributes 24 % of the biomass delivery cost. In addition to these, the amount of storage steps is reduced at an optimal scale level. Pyrolysis oil delivery costs are in the range of 4.7 -6.6 €/GJ, depending on the scenarios mentioned above. This study shows that it is possible to deliver 89% of an 17.22 PJ initial amount of biomass to Rotterdam harbor by means of TOP pellets, whereas it is 80% for pellets and 66% for pyrolysis oil. These efficiencies are influenced by the pre-treatment process efficiencies and the dry matter losses during transport. When the final conversion is applied at large centralised facility, Fischer Tropsch fuel production cost can be as low as 6.44 €/GJHHV. The entrained flow gasifier assumed here had a 1000 MWth capacity. When pyrolysis oil is converted into FT liquid, the delivery cost is 9.40 €/GJHHV. The truck transport, the storage and the pre-treatment costs are the major costs in the overall chain. Table 25 indicates that power production costs can be as low as 4.6 €/kWh either with a large scale biomass integrated gasification combined cycle facility or with an existing co-firing plant. BIGCC benefits from its high efficiency, which is assumed to be 57% whereas it is 35% for combustion and 40% for co-firing. As mentioned, cost data for co-firing does not include the facility capital investment cost but it includes extra costs for pellets and pyrolysis oil handling. It means that when a new facility is considered the cost will be higher.

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Energy use and CO2 emissions are the aspects that indicate the sustainability of the chains. The primary energy required to deliver the fuel to the Rotterdam harbour is, 8 % for delivered TOP, 10% for pellet and 8%-9% for pyrolysis oil (HHV) of their initial energy content. Conversion to FT fuels requires 16 to 26% while it is in the range of 15% to 25% for power production. The CO2 emissions are caused mainly by the transportation fuel and the external power used for densification. Latin American power and fuel mixes and efficiencies were used to calculate the CO2 emissions. The study results show that the CO2 emission for TOP supply is 4 kg CO2/GJ

delivered, while it is 5.5 kg CO2/GJ delivered for pellet supply to the Rotterdam harbour. On the other hand, the pyrolysis oil supply chain emits 4.1 kg CO2/GJ delivered. FT chains emits in the range of 8.5 kg CO2/GJ delivered -11.90 kg CO2/GJ delivered, where the former data is for TOP pellet delivery and conversion and the latter for pellet deliver and conversion in the Rotterdam harbour. The CO2 emission for power production is in the range of 9.5 CO2/GJ

power delivered with TOP pellet-BIGCC system and 22.9 CO2/GJ power delivered with pellet combustion. For the comparison, the CO2 emission from coal combustion is 95kg CO2/GJLHV and natural gas combustion is 56 kg CO2/GJLHV. Consequently, according to this study, the following answers to the research question can be given:

• Torrefaction in combination with pelletisation(TOP), in plants with a scale of 40 MWth, is the optimum supply chain,

• TOP supply converted to the FT-liquid is the optimal synfuel production chain and, • TOP supply converted to power either by BIGCC or existing co-firing facility are the

optimal chains. Another striking conclusion of this study is that pyrolysis facility, even with the optimistic data, can not compete with the TOP and pelletisation pre-treatment technologies in the context of intercontinental bioenergy logistics. 4.3 Recommendations This study shows that converting biomass into TOP intermediate decreases the long distance transport costs compared to pellets. The plant capacity considered is 40 MWth. Since there is no current torrefaction plant demonstration, considering such a large scale brings its risks. On the other hand, pelletisation has already been commercialised and there is a room to improve the technology. Pyrolysis technology, on the other hand fell short. Even though pyrolysis technology keeps it is popularity, lack of information is a bottleneck which needs to be overcome. The pre-treatment technologies in this study consider a high load factor to keep the system continuous. However, it creates the risk in meeting the feedstock requirements. This necessitates several storage and extensive biomass production areas. Besides, the bioenergy supply chain is very sensitive to the harvest operation period. In this study, 8 months harvesting is considered, however, investors should keep in mind the risk of shorter harvesting periods, which in return increases the delivery costs.

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Consequently, this study indicates that intercontinental bioenergy transport is economically and energetically feasible, when the pre-treatment is considered in the chain. Furthermore, torrefaction in combination with pelletisation is a very promising technology that requires further interest from investors and policy makers.

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[Koukios et al, 1982] Koukious EG, Mavrokoukoulakis J, Abatzoglou N, “ Energy densification of biomass”, Proc 1st National Conf. on Soft Energy Forms, Thessaloniki, 1982.

[Koukios, 1993] Koukios EG, “Progress in thermochemical, solid-state refining of biofuels- from research to commercialization”, Advances in thermochemical biomass conversion, Vol 2, Bridgwater 2003.

[Lappas et al., 2002] Lappas AA, Samolada MC, Iatridis DK, Voutetakis SS, Vasalos IA, “Biomass pyrolysis in a circulating fluid bed reactor for the production of fuels and chemicals”, Chemical Process Engineering Research Institute (CPERI) and Department of Chemical Engineering, Aristotelian University of Thessaloniki, Greece, 2002.

[Lipinsky et al., 2002] Lipinsky ES, Arcate JR, Reed TB, “Enhanced wood fuels via torrefaction”, Fuel Chemistry division preprints, 2002.

[MacMahon and Payne, 1982] MacMahon, M. J. & Payne J. D. Holmens pelleterings handbok. Holmen Chemicals Limited, 1982.

[Nakicenovic and Swart, 2000] Nakicenovic N. and Swart R., “Intergovernmental panel on climate change, special report on emission scenarios, a special report of IPPS working group III”, Cambridge university press, Cambridge UK,612 pp., 2000.

[Peters and Timmerhaus,1990] Peters MS, Timmerhaus KD, “Plant design and economics for chemical engineers”, 4th edition, MacGrawHill Book Co, Singapore, 1990.

[Pierik and Curvers, 1995] Pierik JTG, Curvers APWM, “ Logistics and pre-treatment of biomass fuels for gasification and combustion”, ECN, the Netherlands, 1995.

[Pyne, 2005] http://www.pyne.co.uk/?_id=73 [Raveedan and Ganesh, 1996] Raveendran K and Ganesh A, “Heating value of biomass and biomass products”,

Energy Systems Engineering, Indian Institute of Technology, Bombay, India, 1996.

[Reed and Bryant, 1978] Reed T, Bryant B, “Densified Biomass a new form of solid fuel”, Solar Energy Research Institute, US department of energy division of solar technology, 1978.

[Scott et al, 1999] Scott DS, Majerski P, Piskorz J, Radlein D,”A second look at fast pyrolysis of biomass-the RTI process”, Journal of Analytical and Applied Pyrolysis 51pp 23-37 , Waterloo, Canada, 1999,

[Solantausta, 2001] Solantausta Y, “Techno-economic assessment, the Finish case study”, COMBIO- A new competitive liquid biofuel for heating, work package 5, project no: NNE5-CT-2001-00604, 2001

[Stahl et al, 2004] Stahl M, Granstro¨ m K, Berghel J, Renstro¨ m R. Industrial processes for biomass drying and their effects on the quality properties of wood pellets. Journal of Biomass and Bioenergy, 2004.

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[Thek and Obernberger, 2004] Thek G, Obernberger I, “Wood pellet production costs under Australian and in comparison to Swedish framework conditions”, Biomass & Bioenergy, V.27, p. 671-693 Graz, Austria, 2004.

[Tokman and Martinez, 1999] Tokman VE, Martinez D, “ Labour costs and competitiveness in the Latin Amerian manufacturing sector, 1990-1998”, Cepal review 69, 1999. http://www.eclac.cl/publicaciones/SecretariaEjecutiva/7/lcg2067I/tokman.pdf

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[Mlisius et al, 2000] Malisius U, Jauschnegg H, Schmidl H, Nilson B, Rapp S, Strehler A, Hartman H, Huber R, Whitfield J, Kessler D, Geislhofr A, Hahn B, “ Wood pellets in Europe-state of the art technologiss, activities, market”, Industrial Netwok on Wood Pellets, Thermie B DIS/ 2043/98-AT, 2000.

[Wagenaar et al., 1994] Wagenaar BM, Prins W, Van Swaaij PM, “Pyrolysis of biomass in the rotating cone reactor: Modelling and experimental justification”, Chemical Engineering Science, Vol. 49 pp. 5109-5126, The Netherlands, 1994.

[Yaman, 2004] Yaman S, “Pyrolysis of biomass to produce fuels and chemical feedstocks”, Chemical and Metallurgical Engineering Faculty, Chemical Engineering Department, Istanbul Technical University, Istanbul, Turkey,2003.

[UNDP, 2005] http://www.undp.org/seed/energy/policy/ch_9.htm http://www.fao.org/docrep/T4470E/t4470e0a.htm

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6 Appendices Appendix 1 Peters MS, Timmerhaus KD, plant design and economics for chemical engineers, fourth edition, university of Colorado, Estimation of capital investment cost (showing individual components) The percentages indicate in the following summary of the various costs constituting the capital investment are approximations applicable to ordinary chemical processing plants. It should be realized that the values given can vary depending on many factors, such as plant location, type of process, complexity of instrumentation, etc. ---------------------------------------------------------------------------------------------------------------------

I. Direct costs = material and labour involved in actual installation of complete facility (70-85% of fixed-capital investment) A. Equipment+installation+instrumentation+piping+electrical+insulation+painting (50-60%

of fixed-capital investment) 1. Purchased equipment (15-40& of fixed-capital investment) 2. Installation, including insulation and painting 3. Instrumentation and controls, installed (6-30% of purchased equipment cost) 4. Piping, installed (10-80% of purchased-equipment cost) 5. Electrical, installed (10-40% of purchase-equipment cost) B. Building, process and auxiliary (10-70% of purchased-equipment cost) C. Service facilities and yard improvements (40-100% of purchased-equipment costs) D. Land(1-2% of fixed-capital investment or 4-8% of purchased-equipment cost)

II. Indirect costs = expenses which are not directly involved with material and labour of actual installation of complete facility (15-30% of fixed-capital investment) A. Engineering and supervision (5-30% of direct costs) B. Construction expense and contractor’s fee (6-30% of direct costs) C. Contingency (5-15% of fixed-capital investment

III. Fixed-capital investment = direct costs +indirect costs IV. Working capital (10-20% of total investment) V. Total capital investment = fixed-capital investment + working capital -------------------------------------------------------------------------------------------------------------- Estimation of total product cost (showing individual components) The percentages indicated in the following summary of the various costs involved in the complete operation of manufacturing plants are approximations applicable to ordinary chemical processing plants. It should be realized that the values given can vary depending on many factors, such as plant location, type of process, and company policies. Percentages are expressed on annual basis. -------------------------------------------------------------------------------------------------------------- I. Manufacturing cost= direct production costs +fixed charges +plant overhead costs A. Direct production costs (about 60% of total product cost)

1. Raw materials (10-50% of total product cost) 2. Operation labour (10-20% of total product cost) 3. Direct supervision and clerical labour (10-25% of operation labour)

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4. Utilities (10-20% of total product cost) 5. Maintenance and repair (2-10% of fixed-capital investment) 6. Operating supplies (10-20% of cost for maintenance and repairs, or 0.5-1% of fixed

capital investment) 7. Labour charges (10-20% of operating labour) 8. Patents and royalties (o-6% of total product cost) B. Fixed charges (10-20% of total product cost) 1. Depreciation (depends on life period, salvage value, and method of calculation-about 10%

of fixed-capital investment for machinery and equipment and 2-3% of building value for buildings)

2. Local taxes (1-4% of fixed-capital investment) 3. Insurance (0.4-1% of fixed-capital investment) 4. Rent (8-12% of value of rented land and buildings) C. Plant overhead costs (50-70% of cost for operating labour, supervision, and maintenance, or 5-15% of total product cost); includes costs for the following: general plant upkeep and overhead, payroll overhead, packaging, medical services, safety and protection, restaurants, recreation, salvage, laboratories, and storage facilities.

II. General expenses= administrative costs+ distribution and selling costs + research and development costs.

A. Administrative costs (about 15% of costs for operating labour, supervision, and maintenance, or 2-6% of total product cost); includes costs for executive salaries, clerical wages, legal fees, office supplies, and communications.

B. Distribution and selling costs (2-20% of total product cost); includes costs for sales offices, salesman, shipping, and advertising

C. Research and development costs (2-5% of every sales dollar or about 5% for total product cost)

D. Financing (interest) 1 (0-10% of total capital investment) III. Total product cost2 = manufacturing cost+ general expenses IV. Gross-earning cost (gross earning = total income – total product cost; amount of gross

earnings cost depends on amount of amount of gross earnings for entire company and income-tax regulations; a general range for gross earning cost is 30-40% of gross earnings)

----------------------------------------------------------------------------------------------------------------- 1 interest on borrowed money is often considered as a fixed charge

2 if desired, a contingency factor can be included by increasing the total product cost by 1-5%.

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Appendix 2 OECD Deflator Deflators for Resource Flows from DAC Donors a (2003 = 100)

1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004

Australia 17.04 17.18 17.31 17.86 18.34 18.84 19.46 20.08 20.82 21.98 22.90 24.87 27.96 37.79 44.98 46.86 49.28 48.99 54.69 58.51 65.49 72.72 71.80 69.30 71.53 59.86 60.94 68.85 83.44 90.45 93.59 95.56 91.29 85.46 92.79 95.64 103.39 99.58 84.54 87.43 81.85 75.46 81.50 100.00 117.45 AustraliaAustria 9.90 10.39 10.83 11.21 11.57 12.19 12.55 12.97 13.27 13.73 14.26 15.73 18.24 23.25 26.69 30.48 31.27 35.77 43.20 48.83 53.02 45.94 45.08 44.25 41.59 41.44 57.75 71.24 73.88 71.14 85.30 86.25 94.89 92.12 96.35 111.25 107.06 92.82 91.79 88.51 77.91 77.03 82.14 100.00 112.22 Austria

Belgium 13.06 13.21 13.45 13.83 14.51 15.30 15.87 16.43 16.78 17.39 18.38 19.83 23.29 28.17 31.71 37.66 38.60 44.69 53.10 59.64 62.20 51.51 45.04 42.51 39.69 40.34 55.16 67.12 69.65 68.13 82.55 83.08 91.31 88.36 93.14 106.96 103.03 90.54 90.68 88.15 77.21 76.35 81.81 100.00 112.46 BelgiumCanada 22.29 21.33 20.53 20.79 21.37 22.14 23.26 24.26 25.19 26.35 28.49 30.47 32.91 35.69 41.85 44.37 49.97 49.49 49.17 52.47 58.29 63.09 66.52 70.19 68.99 67.44 68.31 74.86 84.26 91.59 95.87 100.52 96.55 91.77 87.68 89.23 91.25 90.94 84.54 85.89 89.47 86.77 86.44 100.00 111.35 Canada

Denmark 11.72 11.70 11.71 11.71 11.68 11.69 11.70 12.27 12.24 12.99 14.05 15.36 17.91 22.94 25.85 31.19 32.30 35.74 42.61 48.17 48.83 43.20 41.01 40.51 37.93 38.89 52.96 65.86 68.62 66.48 81.43 80.98 88.22 83.32 86.38 99.76 98.81 88.65 88.31 86.29 76.69 76.07 81.58 100.00 111.93 DenmarkFinland 12.45 13.12 13.64 14.25 15.28 16.05 16.80 16.93 15.46 16.11 16.72 18.00 19.72 24.53 30.48 35.41 38.48 40.23 42.37 48.71 55.87 53.54 52.05 48.80 49.00 50.01 63.66 76.56 87.18 90.44 107.56 104.05 95.57 76.66 85.47 107.04 101.40 91.67 92.07 88.17 78.46 78.60 83.42 100.00 110.80 Finland

France 15.47 15.47 15.49 15.49 16.13 16.57 17.00 17.52 18.15 18.42 18.30 19.52 22.82 28.03 29.04 36.80 36.68 38.99 46.75 54.60 61.18 52.92 48.83 46.07 43.08 44.20 60.27 71.46 74.41 71.73 86.48 85.97 93.43 89.48 92.89 105.10 103.99 92.29 92.08 88.60 77.21 76.29 82.23 100.00 112.03 FranceGermany 10.51 11.42 11.93 12.33 12.75 13.15 13.59 13.85 14.15 14.99 17.38 19.52 22.44 28.56 31.64 35.08 35.56 39.98 48.15 54.69 57.79 48.47 47.28 46.39 42.46 41.95 58.70 72.20 75.00 71.70 86.11 85.48 95.35 93.39 97.52 112.69 108.42 94.70 94.37 90.90 78.42 77.22 82.49 100.00 110.99 Germany

Greece 11.62 11.75 12.30 12.43 12.86 13.38 14.04 14.34 14.56 15.02 15.59 16.05 16.86 20.63 25.03 26.53 27.07 30.54 34.84 41.51 43.01 40.30 42.56 38.93 37.03 35.97 42.32 50.33 56.04 56.08 69.33 72.17 79.20 75.36 79.23 90.99 94.02 88.53 86.13 85.70 74.10 73.66 80.59 100.00 113.22 GreeceIreland 10.07 10.31 10.83 11.09 12.13 12.69 13.24 13.42 12.21 13.30 14.63 16.49 19.12 21.61 21.89 24.89 24.44 26.89 32.67 39.64 45.64 41.96 42.66 41.34 38.35 39.36 53.12 60.27 63.71 62.58 72.50 71.80 78.07 70.63 73.28 80.84 82.30 81.34 81.29 80.20 72.71 74.67 82.07 100.00 113.79 Ireland

Italy 10.15 10.43 11.03 11.95 12.67 13.19 13.50 13.88 14.14 14.62 15.62 16.94 19.04 21.56 23.19 26.91 24.88 27.84 32.86 38.92 45.82 41.10 40.46 41.47 39.97 40.05 55.35 67.56 71.88 72.62 89.95 93.47 98.40 80.16 80.85 84.06 93.43 86.68 87.32 84.74 74.90 74.71 81.03 100.00 113.05 ItalyJapan 7.37 7.93 8.29 8.70 9.20 9.70 10.19 10.75 11.43 12.07 12.90 13.96 16.71 21.36 24.01 25.30 27.35 32.24 43.04 42.45 43.17 46.33 41.91 44.99 46.41 47.28 68.07 79.55 90.48 85.93 83.86 92.94 100.27 114.85 125.08 135.15 116.00 104.60 96.61 109.37 113.30 98.99 94.96 100.00 104.79 Japan

Luxembourg 12.01 11.57 12.05 12.40 13.15 13.55 14.03 14.13 14.76 15.48 17.99 18.24 21.30 27.00 31.59 33.16 35.46 38.65 46.23 52.83 57.14 48.24 43.44 41.47 38.33 38.41 51.04 61.11 63.78 61.92 74.83 74.54 82.17 81.02 86.62 100.55 97.67 86.87 87.91 86.13 77.59 76.84 81.73 100.00 112.38 LuxembourgNetherlands 8.86 9.69 9.84 10.31 11.18 11.89 12.54 13.12 13.61 14.46 15.39 17.21 20.50 25.67 29.12 34.10 35.55 40.85 48.79 54.79 58.34 48.98 48.24 46.09 41.56 40.86 55.48 66.61 68.91 64.95 77.35 77.48 84.31 81.32 84.90 98.19 94.58 83.38 83.37 81.24 73.04 74.68 81.02 100.00 110.80 Netherlands

New Zealand 16.11 16.08 16.10 16.74 17.34 18.08 17.06 18.06 16.18 15.97 17.88 20.55 24.06 30.37 31.18 30.36 30.03 34.25 42.13 47.89 52.80 54.85 53.18 49.48 44.44 44.72 54.50 69.76 83.15 79.80 82.24 80.18 75.61 78.25 86.74 98.33 105.60 101.99 83.54 82.72 72.85 70.56 78.04 100.00 117.55 New ZealandNorway 10.87 11.15 11.68 12.06 12.62 13.23 13.76 14.17 14.81 15.43 17.40 18.83 21.14 26.47 30.36 35.32 36.34 40.36 43.56 47.64 55.26 53.71 52.68 49.83 47.38 47.33 54.53 63.98 69.43 69.23 79.25 78.19 81.08 72.65 72.98 83.58 85.37 80.19 74.61 77.00 79.07 78.22 86.66 100.00 110.95 Norway

Portugal 10.87 11.08 11.08 11.31 11.48 11.94 12.57 13.05 13.30 14.34 14.61 15.55 17.51 21.24 24.37 28.07 27.58 27.49 29.28 31.41 37.14 35.49 33.20 29.65 27.97 29.33 40.52 46.95 51.05 51.69 64.57 70.07 83.63 75.35 78.21 89.58 89.73 81.97 82.72 81.64 73.06 74.09 81.50 100.00 111.90 PortugalSpain 7.70 7.83 8.25 8.90 9.56 10.43 11.28 12.01 11.11 11.68 12.39 13.45 15.78 19.52 22.84 26.78 26.76 29.07 34.76 46.42 49.30 43.05 41.09 35.17 34.80 35.74 48.15 57.80 64.93 68.28 85.11 89.28 96.69 81.34 80.26 90.49 92.19 81.62 81.92 80.52 72.03 72.93 80.20 100.00 113.42 Spain

Sweden 14.50 14.93 15.56 15.89 16.71 17.69 18.73 19.78 20.22 20.91 21.18 23.58 27.37 32.12 33.49 40.53 43.99 48.65 53.34 59.40 68.30 62.49 54.42 49.11 48.96 50.17 64.54 76.03 83.65 85.89 101.77 108.59 113.98 87.82 90.78 101.33 109.05 97.14 93.99 91.24 83.30 75.31 81.33 100.00 111.12 SwedenSwitzerland 9.11 9.11 9.10 9.11 9.11 9.09 9.54 9.96 10.29 10.56 11.08 12.67 14.98 19.53 22.22 27.46 29.14 30.38 42.31 46.40 47.28 42.63 44.10 43.77 40.48 39.62 55.81 69.17 72.48 66.83 82.06 84.00 87.53 85.27 93.57 109.13 104.30 88.79 88.58 86.01 77.18 77.71 85.63 100.00 109.40 Switzerland

United Kingdom 11.45 11.80 12.25 12.38 12.77 13.50 14.07 14.22 12.90 13.59 14.64 16.32 18.03 18.98 20.80 24.99 23.36 25.76 31.62 39.99 52.38 50.38 47.06 43.10 39.52 40.27 47.54 55.82 64.57 63.79 74.52 78.90 81.64 71.73 74.25 78.59 80.23 86.62 90.07 89.95 85.28 82.97 89.18 100.00 114.60 United KingdomUnited States 19.85 20.08 20.35 20.56 20.88 21.26 21.87 22.54 23.50 24.67 25.98 27.27 28.46 30.05 32.76 35.85 37.92 40.33 43.17 46.74 50.98 55.77 59.17 61.52 63.83 65.77 67.22 69.05 71.41 74.11 76.97 79.66 81.50 83.38 85.15 86.89 88.54 90.01 91.01 92.33 94.34 96.60 98.20 100.00 102.04 United States

TOTAL DAC 16.08 16.25 16.74 17.10 17.47 17.83 18.24 18.12 18.93 19.24 20.30 21.53 24.11 26.91 29.96 34.11 35.21 38.27 43.94 48.95 53.24 51.63 50.93 50.72 49.71 50.39 61.38 70.57 75.87 75.23 83.59 86.58 91.61 89.54 93.66 103.85 99.17 92.40 90.53 92.04 88.23 84.50 88.03 100.00 108.76 TOTAL DAC

EC 13.33 13.33 13.33 13.33 13.95 14.53 15.06 15.53 16.04 16.85 17.93 19.15 20.41 22.28 24.98 29.56 27.39 30.70 37.30 43.64 48.86 43.09 41.69 41.02 38.78 39.55 53.80 65.27 69.40 67.41 81.45 82.68 90.35 84.72 88.50 99.92 99.12 89.86 90.21 86.88 76.18 75.79 81.76 100.00 112.03 EC

a) Including the effect of exchange rate changes, i.e. applicable to US dollar figures only.

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Appendix 3 The relationship between authotermal operation of the process in relation to the moisture content and energy yield of torrefaction

0.70

0.75

0.80

0.85

0.90

0.95

1.00

0% 10% 20% 30% 40% 50%

MCA (% wt. Biomass feedstock)

ener

gy yi

eld (L

HVda

f)

Figure 48: Relation between the MCA and the energy yield of torrefaction. Values are taken from the main design matrix. The error bars represent the possible inaccuracy in the HHV measurement. Appendix 4 Size reduction results of various torrified biomass and feed biomass

-

10

20

30

40

50

60

70

80

90

- 0.2 0.4 0.6 0.8 1.0 1.2 1.4

average particle size (mm, volume based)

Powe

r con

sump

tion (

kWe/M

Wth

)

C(270,21)C(280,18)C(290,12)W(290,24)W(260,24)Willow (10-13% moist)Willow (<1% moist)Woodcuttings (14% moist)AU bituminous coalTW borssele rundemolition wood(D,300,10)(D,280,10)(W,265,10)

-

40

80

120

160

200

240

280

320

360

- 0.2 0.4 0.6 0.8 1.0

average particle size (mm, volume based)

chipp

er ca

pacit

y (kW

th)

Net power consumption curves Capacity curves Figure 49: Size reduction results of various torrefied biomass and feed biomass (Bergman et al, 2004)

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Appendix 5 Torrefied biomass production cost breakdown I. MANUFACTURING COSTS 1. Raw Materials 2. Operation Labour 1 25 €/man-hour for Western

Europe 6 euro/man-hour Latin America

60% of the employee is accepted as Latin American employee

3.Direct Supervisory & clerical labour

15% of Operation labour

4. Utilities 5. Maintenance and Repairs 2% of Total capital investment 6. Operating Supplies 15% of Maintenance & repair 7. Laboratory Charges 10% of Operation labour 8. Patents and Royalties 3% of Total capital investment B. Fixed Charges 1. Depreciation 18% of Total capital investment 2. Local Taxes 1% of Total capital investment 3. Insurance 0.5% of Total capital investment 4. Rent C. Plant Overhead 60% of Operation labour II. GENERAL EXPENSES A. Administrate Costs 15% of Operation labour B. Distribution and Selling Costs

3% of Total production cost

C. Research and Development Cost

3% of Total production cost

Source: Peters&Timmerhaus, (1991) fourth edition 1 In the calculations, it is assumed that 40% of the employees are at the management position and they are being paid according to the West European labour cost, 60% of the employees are assumed to work as the general staff and their salaries are calculated on the basis of Latin American labour price. In Hamelinck, Latin American labour price is mentioned as 1 euro/man-hour. In this study this price is increased to 2.5 euro/man-hour taking the labour education level and necessary specialisation for the plant into consideration.

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Appendix 6 Component list relevant for BIG/CC systems and their corresponding R-values.

Source: Faaij et al, 1988

98

Appendix 7 Estimation of the total production costs of the torrefied biomass Cost Items Total production costsI. MANUFACTURING COSTS Meuro/tonA. Direct Product Cost1. Raw Materials2. Operation Operating labour 5.423. Direct Supervisory and cleical labor 0.814. UtilitiesElectricity 5.88Natural Gas 13.44Cooling water 0.665. MaintananMaintenance 2.086. Operating Supplies 0.317. Laboratory Charges 0.548. Patents and Royalties 0.87

B. Fixed Charges1. Depreciation 15.472. Local Taxes 1.043. Insurance 0.524. Rent ..

C. Plant Overhead 3.25

II. GENERAL EXPENSESA, Administrive Costs 0.81B. Distribution and Selling Costs 2.17C. Research and Development Cost 2.17D. Financing 5.46

TOTAL PRODUCT COSTS 58.18 Source: Bergman et al, 2005

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Appendix 8 Higher heating values and energy distributions of raw biomass and pyrolysis products

Source: Raveendran & Ganesh, 1996 Appendix 9 Overview of current fast pyrolysis technologies Fluid bed reactors Fluid bed configurations are the most popular reactors from the commercial point of view due to their ease of operating and ready scale up (Bridgwater, 1999). The liquid production is up to 70% on a dry feed basis. Biomass needs to be grinded to small particles (<2-3 mm) to achieve high heating rates. When the volatiles residence time (net empty reactor volume divided by the inlet gas volume rate at reactor conditions) is in the range of 0.2-0.6 s., it is possible to produce maximum yield of organic liquid at temperatures of 475-525 oC for nearly all biomass feedstock. However, it is difficult to design a reactor capable on a large scale of very high heating rates required for such a short processing time. Besides, it should not be forgotten that the biomass particle residence time in the optimal temperature should be longer than the apparent volatile residence time to achieve the complete conversion unless the biomass particles are extremely fine (around 50 µm). There are 2 types of fluid bed reactors; bubbling fluid bed and circulating fluid bed. Bubbling fluid bed reactors Bubbling bed reactors are easy to construct and operate since they have got a well-understood technology. Temperature control is easy in this reactor and the efficiency of heat transfer to biomass particles is high. The bubbling bed reactor configurations are widely used in laboratory systems. This design produces a good quality bio-oil with minimum char content. Char is eluted from the reactor since char can act as a catalyst to crack the vapour.

100

When the scaling up of this reactor is considered, heat transfer to bed can be a limiting factor. Residence time of solids and vapours are controlled by fluidising gas flow rate and it is higher for char than for vapours. The high gas-to-biomass fed ratio causes thermal efficiency reduction because the re-circulating gas steam in the bio-oil condensation units requires cooling and reheating again to reuse it as a heat source for pyrolyser. The thermal efficiency in this technology ranges from 60 to 70% depending on the design (Scott et al., 1999). The diagram of a bench-scale pyrolysis unit flow diagram operated in the University of Waterloo is shown in figure 1.

Figure 1 Bench scale pyrolysis unit flow diagram According to a study carried on by University of Waterloo and Resource Transform International, short volatile residence times required for the process can also be achieved in a deep fluid bed contrary to the necessary condition mentioned as shallow bed depth by other scientists. They discovered that they could achieve high yields of liquid at relatively low temperatures; moderate heating rates and relatively long solids and gas residence times (Scott et al., 1999). The shallow fluid beds were causing transverse temperature and concentration gradients to develop in the fluid bed, which demanded special design methods, in large sizes. The temperature range applied in this study ranges from 360 to 490 o C with gas residence times greater than 2 s. up to 5 s. The liquid yields and the composition obtained in this study was similar to other fast pyrolysis with higher temperatures and shorter residence times like 0.3 –0.8 s. The experiment results of the RTI process and Waterloo fast pyrolysis process (WFPP) is presented in table 1. The particle size in the RTI study was 1 mm maximum with a moister content of 10%.

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Table 1 Comparison of yields from waterloo fast pyrolysis process and RTI process Source: Dynamotive Corp. has achieved a commercial version of RTI process so named “ BioTherm TM Technology”. The pilot plant was operated at a capacity of 2 tonnes of feedstock per day on the continues feed basis and it has already processed more than 35 tones of feedstock. When pine as the prepared feedstock (10% mc and small particles) was used in BioTherm to produce 72%yield rate of bio-oil, around 2.5 MJ/kg of heat is required (including the radiation and exhaust gas loses). However when the non-condensable gas produced is directly injected into the reactor burner, the required net heat from an external source is only 1.0 MJ/kg, which represents the 5% of the total calorific value of the bio-oil (DynaMotive, 1999). The BioTherm process consists of the following equipments (Fig 2):

Figure 2 BioTherm pyrolysis process flow diagram Storage hopper and feed system; feedstock is conveyed to a storage hopper with an auger and a screw feeder supplies feedstock to a lock hopper consists of a two knife-gate valves that in turn supplies the feed to a metering box. By the help of this metering box, a controlled amount of feedstock is fed through a constant speed injector screw. Pyrolysis reactor; the external jacket, surrounding the reactor shell is heated by a natural gas burner to heat the fluidised sand. The exhaust gas from the jacked is used to preheat the pyrolysis gas by means of a gas to gas heat exchanger before the pyrolysis gas is re-entered the reactor. In

Table X. Comparisen of yields from waterloo fast pyrolysis process and RTI processProcess Experimental yields (wt.%) mf hardwood sawdust feed

Temperature(oC) Char Bio-oil GasWFPP 500 11.8 76.9 5.9RTI process 430 12.5 74.3 10.1RTI process with char converter 430 4.5 73 19

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the reactor the feedstock is rapidly heated to temperatures above 450 oC by fluidised sand, in the absence of oxygen. Cyclone: The products pass through two mechanical cyclones to remove entrained solid char particles. The char is collected under the cyclones. Bio-oil recovery quench system: The gases, vapours and aerosols scrubbed are rapidly cooled down to below 50 oC in the quenching system by a liquid. The bio-oil condensed are collected in a product than while the liquid recovered is cooled in a heat exchanger and recycled to the recovery system. Electrostatic precipitator: The non-condensable gas and residual biooil aerosol droplets enter to the electrostatic precipitator. The clean inert gas is then recycled to the bubbling fluid bed reactor. The excess of the gas is vented from the system. Product tank: Figure 3 RTI process for production of bio-oil, bubbling fluidised bed type of reactor. Circulating fluid bed (CFB) & Transported bed reactors In this technology the residence time for char and vapour are almost the same and the char content of the produced bi-oil is higher which may require a post-treatment to reduce char content. Most circulating fluid beds are dilute phase units; heat transfer rates are not high since they depend only on gas-solid convective transfer. CFB is suitable for large throughputs. In general there exists a char combustor, which delivers the heat to the reactor by re-circulation of

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the heated sand (Figure 4). Ash transfer to the pyrolyser and accumulation in the circulating solids can be a problem that needs to be worked out in this technology. In fact ash can behave like cracking catalysts for organic molecules, which can cause loss of volatile bio-oil yield In this technology either recycling of the partially reacted feed or a very fine particle size is necessary to achieve the necessary biomass residence time since the particle residence time would not be uniform and would only be a little greater than volatile residence time.

Figure 4 Circulating fluid bed reactor. Source: Pyne, 2005

Figure 5 Shematic diagram of the CFB unit for biomass flash pyrolysis Source: Lappas et al, 2002

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Ablative pyrolysis In this technology there is no upper limit in feedstock sizing since the rate of reaction is not limited by the rate of heat transfer through a biomass particle as it is in other pyrolysis technologies. In ablative pyrolysis heat is transferred from the hot reactor walls through the biomass under pressure. Pressure, the reactor surface temperature and the relative velocity of the biomass on the heat exchange surface influence the rate of reaction. The process is limited in heat supply to the reactor rather than heat supply to the biomass particles. However in the cyclonic types, achieving the necessary residence time for the biomass particles can be a problem, therefore partially reacted solids should be recycled. The char abrasion in this technology is significant. The cone types or plate types of ablative reactors are mechanically complex since they require moving parts. Another issue in this type of technology is that there could be high heat losses because the hot surface must be at a higher temperature than the reaction temperature (Scott et al, 1999). On the other hand, even though the process equipments are smaller, the reaction is more intensive. The system scaling is more costly due to process control by surface area. Rotating cone reactor: The schema of a rotating cone reactor demonstrated by BTG is presented below. The wood particles are fed to the bottom of the rotating cone together with the heat carrier particles (sand). The rotation in the reactor both achieves the solid mixing and its’ transport to the upward of the reactor. Since the particles contact to the hot rotating cone wall while being transported, a high heating transfer rate is achieved (Wagenaar et al, 1994). While the biomass is transported to the upper part of the cone, the pyrolysis vapour residence time is kept below 1s. In order to avoid the secondary tar cracking. The ash char and unconverted biomass is being collected in the dead volume of the reactor. One of the advantages mentioned is that pyrolysis product will be formed at high concentration since no carrier gas is needed; this in fact might cause cost reduction. Moreover, gas-phase residence time in the reactor can be reduced due to the possibility of a small gas phase volume in side the rotating cone. In addition, bio-oil cracking reactions can be reduced. An advanced version of rotating cone has been developed, where the cone is partly submerged in a fluid bed. As can be seen from the schematic view of the reactor (Fig. 6) the technology includes an internal circulation of particles where the sand is flown through the upper part of the cone and fell down back to the into the fluidised bed an external circulation where the char and sand are transported through an orifice to the combustor. In the combustor sand is reheated and is recycled to the reactor by means of a standpipe, riser and cyclone. The advantages of this technology are its being compact and good integration of heat.

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Figure 6 Rotating cone reactor

Figure 7 Rotating cone reactor pyrolysis process flow diagram Source: Btgworld.com, 2005 Vortex reactor: In this reactor the particle size enters the reactor is more flexible. 13 mm particle size has been applied in an engineering scale pyrolysis system, where vortex rector was

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Vacuum pyrolysis In vacuum pyrolysis solid heating and mass transfer rates are low and the solid residence time is very high (Bridgwater et al, 2002; Scott et al, 1999). The technology requires large-scale equipment (Scott et al, 1999). Even though a comparable amount of bio-oil yield can be achieved by vacuum pyrolysis, a large capacity of vacuum pump is needed to require the vacuum condition, which makes the system rather expensive (Wagenaar et al, 1994). One of the advantage in this technology is that short volatile residence times is easy to achieve without coupling the biomass particle residence time to that of the volatiles. The general features of the reactors are summarised in the below table. Table 2 Overview of fast pyrolysis reactor characteristics for bio-oil production

Source: Pyne, 2005

Bio-oil Feed Scalewt% size up

Fluid bed Demo 75 Medium Small High Medium EasyCFB Pilot 75 High Medium High Large EasyEntrained None 65 High Small High Large EasyRotating cone Pilot 65 High V small Low Small HardAblative Lab 75 High Large Low Small HardVacuum Demo 60 High Large Low Large Hard

Specific size

# Demo = demonstration (200 – 2000 kg h-1)

# Pilot = pilot plant (200 – 200 kg h-1

# Lab = laboratory (1 – 20 kg h-1)

Property Status# Complexity Inert gas need

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Appendix 10 Mass balance of a 200 kg/hr pyrolysis plant (Source: Gansekoele et al, 2000)

380 kg/hr

6000 kg/hr Non condensable gas 40 kg/hr

Combustor

Biomass200 kg/hr 8640 kg/hr

180 kg/hr Cooling tower 3500 kg/hr

Reactor6020 kg/hr

heat exchanger120 kg/hrAir water

240 kg/hrAir

Oil140 kg/hr

Con

dens

or

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Appendix 11 The pyrolysis plants capital cost and efficiency data

Name Capacity (ton/hr)

Efficiency Total capital costs Year Reactor

technology

Remarks

1 Egemin 0.20 40% 500,000 GBP 1992 Entrained flow

Cost figures include storage, feeding and pyrolysis system

2 Ensyn 1.04 67% 1,600,000 US$ 1992 Transported bed

Cost estimates are in the range of US$800,000-1600,000. These figures don’t include building, land, utilities, feed and product oil storage.

3 ASR 4.00 30.62% 5,030,000 US$ 1992 Vacuum pyrolysis

The aim is to pyrolyse shredder waste. Capital cost includes install., instrumentation, piping, insulation and electricity installation

4 Interchem (NA)Industries

4.17 50% 2,360,000 US$ 1991 Ablative pyrolysis

The cost includes material handling, pyrolysis system, oil handling, char handling and all the storage systems. However it does not include purchase or leasing of land.

5 BTG 5.00 70% 3,500,000 € 2000 Rotating cone

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Appendix 12 Wood pellet quality requirements

Source: AET, 2003

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Appendix 13 Final conversion technologies 1 Biomass Gasification Combined Cycle and Fischer Tropsch Fuel Biomass gasification is the thermochemical conversion of carbonaceous feedstock into a gaseous energy carrier, so called fuel gas by partial oxidation at elevated temperatures (Bridgwater, 1995). In the biomass Integrated Gasification Combined Cycle (BIGCC), the flue gas produced is used to fire a gas turbine. Furthermore, a gas turbine is combined with a steam cycle that offers high electrical efficiencies (Faaij et al, 1998; Bridgwater, 1995). A BIGCC system consists of pre-treatment, gasification, gas cleanup, gas turbine, heat recovery steam generator and steam turbine sections (Figure 1). The gasification technologies assumed in this study are entrained flow gasification and fluid bed gasification. In fact, fluid bed gasification is better suited for larger scales because of the high specific throughput of the reactors (which keeps the vessel size limited) and the flexibility for various fuel types (Faaij et al, 1998).On the other hand entrained flow gasification is one of the most developed and versatile gasification technologies due to its high operation temperature (up to 1500 oC). There have been many commercially operating entrained flow gasifiers in Europe; however, their applications with biomass are very little. Fluidised bed reactor is applied in the BIGCC system while entrained bed gasification is applied in the Fischer Tropsch fuel production. .

Figure 1 Schematic presentation of a BIGCC system Source: Faaij et al, 1988

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Cost data for BIGCC systems and FT fuel The capital costs of BIGCC systems are estimated in several studies (Faaij A and Meuleman B, 1998; Craig and Mann, 1996; Dornburg, 1999). The data collected from those researches are plotted into a graph (Figure ). In Figure 2, the trendline for integrated gasification combined cycle capital costs are presented. The dotes in the figure denote the estimates. In another study carried out by Faaij et al. (1998), the total capital requirement for the BIGCC systems are assumed in the range between 112M€-256M€ for the capacity range of 94 MWLHV-

input-364 MWLHV-input in the base year of 2004. When those cost data are compared with Figure , it can be seen that the cost data for a 94 MWth input is rather consistent whereas for the bigger scales (around 300 MWth input), Figure offers cheaper capital costs. The reason of this difference can depend on the trendline. In fact, the estimated capital cost of a 332 MWth input is around 240 M€ which is also consistent with the study of Faaij et al (1998).

Capital costs of IGCC systems

0

200

400

600

800

1000

1200

1400

1600

1800

19 27 40 66 80 144 140 170 250 310 300

MWth

Eur

o-20

04/k

Wth

Figure 2 Capital costs of IGCC systems According to Calis, et al, (2003), the investment of an entrained flow gasifier including fuel feeding and syngas cooler is estimated using the oil (entrained flow) gasifier 41 €/kWth for a 1000 MWth plant. When the feedstock is solid biomass, a 10% increase on investment is assumed resulting in 45 €/kWth for an entrained flow gasifier including fuel feeding and syngas cooler.

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2 Combustion &Co-firing In general biomass combustion for 100% biomass applications is either stoker-fired or fluid designs (Bridgwater et al, 2002). However in the recent years, small proportions of biomass are being co-fired with coal in large suspension-fired furnaces. In this study fluid bed boiler combined with a steam turbine is selected due to it’s commercially availability in larger scales (at capacities ranging from 15 to 715 MWth input (Bridgwater et al, 2003). Appendix 14 Effects of torrefied biomass on entrained flow gasification Several experiments were carried out in ECN to manifest the torrefied wood size reduction improvements. In those experiments torrefaction was done with the 3-6 kg batch reactor and a heavy-duty cutting mill (1,5kWe) is employed. Figure 1 illustrates the relation between power consumption and particle size for both fresh biomass and torrefied biomass.

Figure 1 Effect of torrefaction on the power consumption of biomass size reduction. Legend: biomass type (T (oC), reaction time (min)) Moisture content of fresh biomass was in the range of 10-13% on mass basis, except for the dried willow (<1%wt). Moisture content of the torrefied biomass ranges from 1.2-6.6%wt. As seen in the figure, the power consumption is significantly reduced when the biomass is first torrefied. 85% power reduction can be achieved. However the type of the feedstock influences the power consumption. For example willow torrifeied decreases the power consumption with about 50% compared to untreated biomass. When the willow untreated, dried and torrefied are compared, the related chemical and physical change can be distinguished. For example when the willow size is cut down to 0.2 mm, the power consumption for torrefied willow is around 8 for dried willow is 30 and for untreated willow is 55 kWe/MWth So around 45% in power

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consumption can be related to the physical change, whereas the 40% can be related to the chemical changes due to torrefaction pre-treatment. Milling biomass into 100µm consumes 0.08kWe/kWth, however when torrefaction is applied the consumption decreases to 0.01-0.02 kWe/kWth (van der Drift et al., 2004). In the same study carried out by ECN the relationship between the particle size and chipper capacity are determined for untreated, dried and torrefied willow (Figure 3). The capacity of the mill increases in proportion to the particle size. When the 0.2 mm particle size is considered the chipper capacity for torrefied willow is up to 6.5 times the capacity of untreated willow. Another positive impact of torrefaction is that it acts as a thermal filter, which abolishes the original differences existing in, untreated biomass and yield a product with similar mechanical properties.

When it concerns the particle size distribution and shape, the experiments indicate that the particles become smaller in the length to diameter ratio. Besides, the length of particles is reduced more compared to their diameter. Thus the particles become more spherical. This is an important feature since it affects the smooth fluidisation. Smooth fluidisation of coal, willow and torrefied willow are measured and it is concluded that a 100µm torrefied biomass can achieve fluidisation. When it concerns the untreated biomass, fluidisation is not possible to achieve due to their needle shape that keeps the particles too large to meet the smooth fluidisation regime. Another positive impact of torrefaction is that it acts as a thermal filter, which abolishes the original differences existing in, untreated biomass and yield a product with similar mechanical properties.

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Appendix 15 Bio-oil production cost figures

Source: Bridgwater et al., 2002