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VTT RESEARCH NOTES

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W1KSTERCarl Wilen & Esa Kurkela

Gasification of biomass for energy productionState of technology in Finland and global market

perspectives

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VTT TIEDOTTEITA - MEDDELANDEN - RESEARCH NOTES 1842

Gasification of biomass for energy production

State of technology in Finland and global market perspectives

Carl Wilen & Esa Kurkela

VTT Energy

■tyrrTECHNICAL RESEARCH CENTRE OF FINLAND

ISBN 951-38-5126-5 ISSN 1235-0605

Copyright © Valtion teknillinen tutkimuskeskus (VTT) 1997

JULKAISIJA - UTGIVARE - PUBLISHER

Valtion teknillinen tutkimuskeskus (VTT), Vuorimiehentie 5, PL 2000, 02044 VTT puh. vaihde (09) 4561, faksi (09) 456 4374

Statens tekniska forskningscentral (VTT), Bergsmansvagen 5, PB 2000, 02044 VTT tel. vaxel (09) 4561, fax (09) 456 4374

Technical Research Centre of Finland (VTT), Vuorimiehentie 5, P.O.Box 2000, FIN-02044 VTT, Finland phone internal. + 358 9 4561, fax + 358 9 456 4374

VTT Energia, Energian tuotantoteknologiat, Biologinkuja 3-5, PL 1601, 02044 VTT puh. vaihde (09) 4561, faksi (09) 460 493

VTT Energi, Energiproduktionsteknologi, Biologgranden 3-5, PB 1601, 02044 VTT tel. vaxel (09) 4561, fax (09) 460 493

VTT Energy, Energy Production Technologies, Biologinkuja 3-5,P.O.Box 1601, FIN-02044 VTT, Finlandphone internal. + 358 9 4561, fax + 358 9 460 493

Technical editing Leena Ukskoski

VTT OFFSETPAINO, ESPOO 1997

Wilen, Carl & Kurkela, Esa. Gasification of biomass for energy production. State of technology in Fin­land and global market perspectives. Espoo 1997, Technical Research Centre of Finland, VTT Tiedotteita - Meddelanden - Research Notes 1842. 64 p.

UDC 620.9:621.311.23Keywords gasification, biomass, bioenergy, energy production

AbstractThis report reviews the development of the biomass gasification technology in Finland over the last two decades. Information on Finnish biomass resources and use, energy economy and national research policy is provided as background. Global biomass re­sources and potential energy from biomass markets are also assessed based on available literature, to put the development of the gasification technology into a wider perpective of global biomass utilisation for energy production.

The increasing use of biomass and other indigenous forms of energy has been part and parcel of the Finnish energy policy for some twenty years. Biomass and peat account for almost 20% of the production of primary energy in Finland. As the consumption of biofuels is significantly lower than the annual growth or renewal, the use of bioenergy is considered to be an important measure of reducing carbon dioxide emissions.

Research and development on thermal gasification of solid fuels was initiated in the late 1970s in Finland. The principal aim was to decrease the dependence of Finnish energy economy on imported oil by increasing the utilisation potential of indigenous fuels. De­velopment in the early 1980s focused on simple atmospheric-pressure fuel gas applica­tions including a gasification heating plant. Eight Bioneer updraft gasifiers (abt 5 MWJ were constructed in 1982 - 1986, and a new Bioneer gasifier was commissioned in east­ern Finland in 1996. A Pyroflow circulating fluidised-bed gasifier was also commer­cialised in the mid-1980s; four gasifiers (15-35 MWJ were commissioned.

In the late 1980s the interest in integrated gasification combined-cycle (IGCC) power plants, based on pressurised air gasification of biomass and hot gas cleanup, increased in Finland and in many other countries. The utilisation potential for indigenous fuels is mainly in medium-scale combined heat and electricity production (20 - 150 MWe). Foster Wheeler Energia Oy, Carbona Inc. and Imatran Voima Oy are the main gasifica­tion technology developers in Finland. In 1993, a biomass IGCC demonstration plant based on Foster Wheeler gasification technology and owned by the Swedish utility company Sydkraft was commissioned in Sweden. The plant is the first combined-cycle plant for generating electricity from fuel gas produced entirely from biomass.

Atmospheric-pressure gasification of biomass fuels is a simpler and cheaper technology than pressurised gasification. Co-combustion is a promising new alternative, in which the biomass gasification is integrated to a pulverised coal-fired boiler. The concept will be demonstrated by Foster Wheeler Energia Oy and a municipal power company.

3

Preface

This review on activities concerning biomass gasification in Finland over the two last decades and on global biomass resources and market potential has been prepared within the Gasification and Advanced Combustion Research Group of VTT Energy.

The technical part of the study was conducted within the framework of the EC concerted action project “Analyses and coordination of the activities concerning a gasification of biomass” led by the University of Stuttgart. This AIR Programme project was co­ordinated by Martin Kaltschmidt of IER'Stuttgart. This review is based on reports and publications of Finnish companies, research organisations and authorities active in the area of energy production and use. The work was mainly conducted in late 1995. Hence, the chapters on biomass resources and use describe the situation in 1994 - 1995 in Fin­land, with some reflections to later dates. Gasification technology is updated to repre­sent the situation in 1996.

The global biomass resources and the market potential for electricity production from biomass were assessed on the basis of existing literature. This study was carried out to support the extensive biomass gasification research work carried out at VTT Energy. The work was conducted within several gasification projects financed primarily by Technology Development Centre Finland (TEKES) through its research programmes BIOENERGY and LIEKKI2, as well as by VTT Energy and the industry.

Espoo, April 1997

Authors

4

Contents

ABSTRACT 3

PREFACE 4

1 INTRODUCTION 7

2 BIOMASS RESOURCES AND NATIONAL POLICY IN FINLAND 82.1 Primary energy consumption 82.2 Biomass sources and use in Finland 92.3 Taxation and deregulation 11

COMMERCIAL GASIFICATION PROJECTS 133.1 Background 133.2 Fixed-bed updraft gasification 14

3.2.1 Process development 143.2.2 Process description 143.2.3 Commercial plants 163.2.4 Evaluation and conclusions 17

3.3 Circulating fluidised-bed gasification 183.3.1 Process description 183.3.2 Commercial plant 193.3.3 Operational experience 19

3.4 Peat-based HTW gasification plant 203.4.1 Choice of the gasification process 203.4.2 Process description 213.4.3 Experiences and conclusions 22

DEMONSTRATION PROJECTS 234.1 Background 234.2 Carbona Inc. 23

4.2.1 Company profile 234.2.2 Gasification pilot plant 244.2.3 IGCC demonstration 26

4.3 Foster Wheeler Energia Oy 264.3.1 Bioflow Energy System 264.3.2 Vamamo IGCC plant 274.3.3 Commissioning and experiences 294.3.4 Technology development 304.3.5 CFB gasification connected to boiler 30

5

4.4 IVOSDIG Process 314.4.1 General 314.4.2 Process description 314.4.3 Process performance 34

5 RESEARCH ACTIVITIES 355.1 General 355.2 Gasification research at VTT Energy 35

5.2.1 Pressurised fluidised-bed gasification 355.2.2 Atmospheric-pressure gasification 38

6 FUTURE PERSPECTIVES OF BIOMASS GASIFICATION IN FINLAND 40

7 GLOBAL MARKET POTENTIAL OF BIOMASS-FUELLEDPOWER PLANTS 437.1 Global biomass use 437.2 Supply of biomass for energy 447.3 Electricity demand and biomass supply scenarios 467.4 Biomass-based electricity production scenario 507.5 European projections 547.6 European electricity prices 577.7 Conclusions 58

REFERENCES 59

6

1. Introduction

Intensive development work on the gasification technology of solid fuels was initiated in the early 1980s in Finland, the aim being to replace imported fuels (and raw materials) by gas produced from indigenous fuels, peat and wood wastes. The most significant industrial-scale projects in the 1980s were

• development of the Bioneer heating station based on an updraft gasifier (size class 1 - 15MWJ,

. development of the Pyroflow circulating-bed gasifier for lime kiln applications,

• peat ammonia proj ect of Kemira Oy,

• gasification-diesel tests by A. Ahlstrom Corporation and Wartsila Diesel.

Since the late 1980s, the main object of interest has been in the development of the so- called simplified IGCC. The driving force in the research and development work is to develop systems with a considerably higher power-to-heat ratio than that achievable in conventional combined heat and power plants (CHP) based on direct combustion and a steam cycle. The main potential of CHP in Finland is in medium-size power plants (30 - 150 MW, where oxygen-blown gasification is not economically attractive. This is why the R&D work in Finland was focused on the development of simplified IGCC processes based on air gasification and hot gas cleanup. In the 1990s this technology was brought to the demonstration level mainly by Finnish companies Foster Wheeler Energia Oy (former Ahlstrom Pyropower) and Carbona Inc. (former Enviropower).

However, the economical feasibility of the simplified IGCC technology requires as large a size class (>30 - 50 MWJ, that this technology cannot be applied to all potential biomass and peat applications due to a limited availability of low-priced biomass. Atmospheric-pressure gasification of biomass fuels is of simpler and cheaper technol­ogy than pressurised gasification. Consequently, it is more suitable to smaller size classes. A promising new alternative is co-combustion, in which biomass gasification is integrated to a pulverised coal-fired boiler. The concept will be demonstrated by Foster Wheeler Energia Oy and Lahden Lampdvoima Oy, a power company owned by the city of Lahti.

This report reviews the development of biomass gasification technology in Finland over the last two decades. Information on biomass resources and use, energy economy and national research policy is provided as background. Global biomass resources and po­tential energy from biomass markets are also assessed on the basis of available litera­ture, to put the development of gasification technology into a wider perpective of global biomass use for energy production.

7

2. Biomass resources and national policy in Finland

2.1 Primary energy consumption

Finland’s total energy consumption amounted to 31.7 Mtoe (1 289 PJ) in 1995 (Figure 1). After the drop in consumption during the first half of the decade, there has been a return during the past two years to levels comparable to those at the late 1980s. In 1994 the energy consumption rose by about 4%, largely due to an increase in the output of the export industry [1],

The biggest energy consumer is the manufacturing industry, accounting for 46% of Finland’s total energy consumption. The forest industry accounts for about 60% of the industrial energy demand. Space heating excluding industrial installations accounts for 22%, transport for 13%, and other forms of energy consumption for 19% of the total energy consumption.

Over the years 1970 - 1995 there has been a clear decrease in the dependency of im­ported oil in favour of a versatile energy palette. This makes the Finnish energy market less vulnerable to fluctuations in energy prices and disruptions in supplies. In recent years there has been a marked increase in the use of peat and industrial waste fuels in the form of black liquor and wood wastes, i.e., mainly bark.

Net electric imports 7%

Natural gas 9% HydroPower 10%

Total primary energy consumption 31.7 Mtoe (1995)

Figure 1. Consumption ofprimary energy by source of energy in Finland 1995.

8

In 1995, Finland’s electricity consumption was 69 TWh. Electricity use by primary en­ergy source is shown in Figure 2. In 1995, Finland’s available electricity supply capac­ity was 15 700 MW: hydropower 2 200 MW, nuclear power 2 300 MW, other con­densing power 3 600 MW, and back-pressure power 4 000 MW. The remainder con­sisted of peak power and imports. According to the Finnish Ministry of Trade and In­dustry [43] the electricity demand is expected to rise to about 85 TWh by the year 2000 and to 96 TWh by 2005. This would require an additional generation capacity of 4 400 MW by 2005. The heat load is expected to grow very moderately over the same time period both in district heating and in industrial applications. Consequently, the devel­opment of CHP processes with high power-to-heat ratios (IGCC) is very important in

Net electric imports 12%

Coal 14%

Natural gas 9%

Xuc:?ar power 26%

Peat 8%

..cod fuel 10%Hydro Power 19%

Total electricity production 69 TWh (1995)

Finland.Figure 2. Electricity use in Finland by primary energy source in 1995.

2.2 Biomass sources and use in Finland

The increasing use of bioenergy and other indigenous forms of energy has been part and parcel of the Finnish energy policy for some twenty years. Biomass and peat account for about 20% of the production of primary energy in Finland. Of this, 15 percentage units comprise wood-derived biomass (spent pulping liquors, wood waste, firewood) and 6 percentage units peat (Figure 1). The proportion of wood in Finland’s total energy use is highest among all industrialised countries. Biofuelled power plants have been built for combined electricity and heat generation in most of the cities, towns and manufacturing establishments where it has been found economically feasible.

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When the consumption of biomass fuels is significantly lower than the annual growth, they are superior to fossil fuels also from the viewpoint of sustainable development. In addition to energy saving, the increasing use of bioenergy is considered to be one of the measures of reducing carbon dioxide emissions.

The consumption of biomass exceeded slightly 6 Mtoe (244 PJ) in Finland in 1994 [43, 44]. The consumption of wood-derived fuels was equal to 4.6 Mtoe (187 PJ) and that of peat 1.6 Mtoe (65 PJ). The biomass resources, annual growth and use are presented in Table 1.

Table 1. Biomass resources, annual growth and use in Finland in 1994, Mtoe.

Resources Growth Energy usePeat 550 2.5 1.6Wood 600 24 4.6Straw 0.6 0Energy crops* 1 0MSW 0.6 0Total 6.2

* Reed canary grass

The production potential of biomass fuels exceeds substantially the current use [43]. The surplus potential of unmarketable forest residues is estimated at about 2 Mtoe (83 PJ), which is classified as an annual harvestable energy reserve. Agricultural wastes are at this moment of no economic significance in energy production. Straw could, however, be combusted together with other biomasses. The annual potential of cereal straw is 0.2 - 0.6 Mtoe (8 - 24 PJ). Another 1 Mtoe/a (41 PJ/a) of energy crops could be produced on set-a-side agricultural land as non-food production. The annual amount of combustible municipal waste is estimated to be equal to about 0.6 Mtoe (24 PJ).

The Finnish Government announced a special bioenergy programme in 1994. The goal is to increase the use of bioenergy by 25% over the next 10 years. This corresponds to an increase of about 1.5 Mtoe/a by the year 2005. The programme includes numerous measures to increase the use of biomass in the energy sector. These include:

• Resources for bioenergy R & D will be increased.

• Demonstration of new technologies will be supported.

• Increased power production at pulp mills will be supported.

• Electricity grid will be opened for small producers.

It has been estimated that the biomass resources in Finland could technically maintain a considerably larger use than presently, in spite of the fact that the share of biomass in

10

the energy sector is already now one of the highest within the OECD countries. The high cost of biomass fuel remains the largest obstacle to increasing its use. Peat is com­petitive in cogeneration in Central and Northern Finland due to tax policy. Wood is available at competitive cost within forest products industries, while beyond that wood remains too expensive as a fuel.

The objective of supporting biomass use is to give a positive initiative for an activity that is considered competitive in the long run. Eventually also the fuel use of biomass has to be economically sound. Therefore, the thrust in the Government’s support for biomass will be related to developing new utilisation technology and to providing pos­sibilities to bring new products into the market.

2.3 Taxation and deregulation

Finland was the first country to impose a carbon-based environmental tax in 1990. Re­newable energy resources, including wood fuels, were taxffee. The environmental taxes were restructured in 1994 and increased in 1995. At the end of 1996 the Parliament ap­proved a new taxation bill, which transfers the taxation in the power production sector from input fuels to the end product, electricity.

The new energy taxes became effective at the beginning of 1997. The taxes on electric­ity was divided into two categories. Higher taxes (category I) are to be paid by private consumers, service sector, farmers and public sector. Category II imposes lower taxes on industry and greenhouses (Table 2) [2].

Table 2. Electricity taxes since 1 January 1997, FIM/MWh (FIM1 = ECU 0.175).Category Electricity tax Supply security

feeTotal

FIM/MWhTotal

ECU/MWhCategory I * 31 0.75 31.8 5.6Category II * 16.75 0.75 17.5 3.0* Electricity tax was FIM 24/MWh on 1 January - 31 March 1997, and FIM 33/MWh in category I and FIM 14.5 in category II since 1 April 1997.

Taxation of fuels for heat generation remains virtually on the same level as in previous years. The tax is determined only on the carbon content of the fuel, and it is FIM 70 (ECU 12.3) per tonne of C02, except for a considerably lower tax on fuel peat (Table 3) [2, 58].

The tax has divided the fuels used for combined electricity and heat generation into two groups. The fuels used for heat generation are taxed on the basis of the amount of heat

11

produced. The consumption of fuels is calculated by multiplying the heat amount gener­ated by factor 1.05. Hence, the percentage of heat recovered from fuels is estimated to

Table 3. Energy taxes in heat production on 1 January 1997, FIM/MWh (FIM 1 -

Energy tax, total Fuel price, inch taxes and VATFIM/MWh ECU/MWh FIM/MWh ECU/MWh

Coal 24.8 4.4 73 12.8Fuel peat1 4.2 0.74 58 10.2Wood chips 0 0 67 11.7Natural gas 2 14.7 2.6 89 15.6Light fuel oil 31.3 5.5 188 32.9Heavy fuel oil 22.4 3.8 111 19.41 Taxable if the annual consumption is more than 15 GWh.2 Deduction for natural gas is 50% since 1 January 1997.

be 95%. The biomass-fuelled CHP plants (electricity output < 40 MWe), wind power plants and small hydropower plants (electricity output < 1 MWJ obtain a production support of FIM 16/MWh (ECU 2.7/MWh) over the next five years. The support is based on the electricity amount delivered to the grid.

The deregulation of the electricity market was introduced in Finland in 1995 and will be fully implemented in 1997. As the deregulation also proceeds in Sweden and Norway, the Nordic countries will probably develop towards a more integrated electricity market. This is expected to lead to a more efficient use of resources. The effect on the electricity price is still unforeseeable.

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3. Commercial gasification projects

3.1 Background

Research and development on thermal gasification of solid fuels was initiated at the end of the 1970s in Finland. The principal aim of the work was to decrease the dependence of Finnish energy economy on imported oil by increasing the utilisation potential of indigenous fuels. Since peat and biomass are the only indigenous fuels in Finland, the gasification R & D activities were focused on the utilisation of these feedstocks. The Energy Department of the Finnish Ministry of Trade and Industry has intensively sup­ported this research since the beginning of the 1980s.

The development work in the early 1980s was related to simple atmospheric fuel gas applications including a gasification heating plant, lime kilns and other lose-coupled end uses, where no specific gas cleaning was required [3,4], Nine Bioneer updraft gasifiers, developed initially at the Technical Research Centre of Finland (VTT) in co-operation with an equipment manufacturer, were constructed over the years 1982 - 1986, then- outputs being about 5 MW&. In 1996 a new Bioneer gasifier was taken into operation in Ilomantsi, eastern Finland. These gasifiers are coupled to small district heating boilers and drying kilns [5, 6], A Pyroflow circulating fluidised-bed gasifier (developed by A. Ahlstrom Corporation) was also commercialised in the mid-1980s; four gasifiers in the range of 15 - 35 MW& were commissioned. The product gas of these gasifiers is used for fuelling lime-rebuming kilns at pulp mills [7,8], Both the Pyroflow and the Bioneer gasifiers have operated very successfully, and all these plants are still in commercial operation. However, the economical feasibility of small-scale gasification plants was decreased by the decline of the oil price in the mid-1980s. Consequently, the activity in this field has been rather negligible since 1986.

In the late 1980s the interest in integrated gasification combined-cycle (IGCC) power plants increased in Finland as well as in many other countries. Government-funded re­search also focused mainly on the utilisation of indigenous fuels, wood wastes and peat. The utilisation potential for these fuels is mainly in medium-scale combined heat and electricity production from 20 to 150 MWe, where oxygen gasification and cold gas cleanup are economically not as attractive as in large-scale power production from coal. This is why the Finnish experimental research and development work was focused on the development of simplified IGCC processes based on air gasification and hot gas cleanup. The driving force of this development is the need of higher power-to-heat ra­tios in cogeneration, since the heat loads in district heating and process industry are no more increasing significantly while the consumption of electricity is still growing. The IGCC process seems to be the most promising candidate for meeting this requirement in short and medium-term scale.

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3.2 Fixed-bed gasification

3.2.1 Process development

The development of an updraft gasifier for peat and wood was initiated at VTT in the late 1970s. The aim was to replace imported fuels by low-Btu gas derived from indige­nous fuels: wood and peat. After an extensive experimental programme carried out on a 1.5 MW test gasifier of VTT, a demonstration plant of 5.2 MW was commissioned in 1982. This plant is located in the town of Kankaanpaa and is integrated to a boiler, which produces district heat [6, 9].

In 1984 - 1986 VTT and Bioneer carried out experimental research on a new 1.5 MW pilot plant located at the Hameenlinna Works of Bioneer Company. This research was related to the utilisation of municipal solid waste and other waste materials and to ther­mal cracking of updraft gas [10].

3.2.2 Process description

The Bioneer gasifier is of updraft fixed-bed type, producing low-Btu tarry gas. A sche­matic diagram of the gasifier integrated to a boiler is shown in Figure 3. The gasifier comprises a gas-tight feeding system, a refractory-lined shaft reactor and a rotating cone-shaped grate. The fuel is fed into the upper part of the gasifier, wherefrom it flows downwards through drying, pyrolysis, gasification and combustion zones. The ash re­maining after combustion is removed from the bottom of the reactor. The temperature of the combustion zone is regulated by humidifying gasification air. Air and steam are fed through the rotating grate into the lower part of the reactor. In the existing Bioneer plants, the gas is burnt close to the gasifier.

Gasification experiments and extensive experiences from commercial operation have verified that the method of updraft gasification can be applied to a wide variety of solid fuels. To ensure reliable operation of the gasifier and good combustion of the product gas, the feedstock should meet the following requirements:

• mainly piece-like, maximum content of fines 30-50 wt%

• moisture content less than 50 - 55%

• ash fusion temperature >900 °C

• no caking tendency.

Typical product gas compositions for different solid fuels are given in Table 4 [6,10].

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1 23

1. Fuel storage 6. Ash removers 12. Gas burner2. Fuel conveyor 7. Ash coveour 13. Combustion air fan3. Fuel feeder 8. Ash balette 14. Gas boiler4. Gas generator 9. Humidifier 15. Flue gas fan5. Grate 10. Gasfication air fan 16. Stack

11. Gas pipe

Figure 3. Flowchart of the Bioneer district heating plant.

The dry product gas of wood chips, forest residues and sod peat contains 50 - 100 g/m3n tar. The tar content of municipal waste ranges 10-20 g/m3n and of straw 10-40 g/m3n. Tar and light hydrocarbons contained in the product gas increase the net calorific value by 0.5 - 4 MJ/m3n.

Table 4. Composition of dry gas producedfrom different fuels.

Fuel Moisturecontent% w.b.

CO H2 CH4 CO2 Heat value HHV

MJ/m^nSod peat 42 21.6 16.8 2.4 12.5 5.8Wood chips 41 30.2 10.8 2.5 7.1 6.2Forest waste chips 55 20.0 17.0 1.5 13.0 5.3MSW *, briquette 8 17.8 14.6 2.6 11.0 5.1Straw, chopped 29 18.9 17.6 2.3 13.8 5.5* MSW = municipal solid waste

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3.2.3 Commercial plants

Bioneer gasifiers are in operation at small district heating plants with outputs around 5 MWft. The plants are completely automated and operated with minimum personal costs. All the existing commercial stations were commissioned by Bioneer Company, which was originally part of YIT Corporation, but was bought by A. Ahlstrom Corpora­tion at the end of the 1980s. Most of these plants are still in operation.

A new Bioneer gasification plant was commissioned in the beginning of 1996 by Foster Wheeler Energia Oy, the company that took over the operation of Ahlstrom Pyropower in 1995. The 6.4 MW* plant is located in Ilomantsi, east of Finland. The commercial Bioneer gasifiers are presented in Table 5 [3, 6],

Table 5. Bioneer gasifiers in commercial operation.

Owner Year of construction

OutputMW

Application Main fuel

Kankaanpaan Kaukolampo Oy FIN-38700 Kankaanpaa, Finland

1982 5 Districtheating

Peat

Kempeleen Lampolaitos FIN-90440 Kempele, Finland

1985 5 Districtheating

Peat

Kauhajoen Lampohuolto Oy FIN-61800 Kauhajoki, Finland

1985 5 Districtheating

Peat

Bioneer OyFIN-13111 Hameenlinna, Finland

1985 1.5 Pilot plant Peat

Parkanon Lampo OyFIN-39700 Parkano, Finland

1986 4 Districtheating

Peat

Kiteen Lampo OyFIN-82501 Kitee, Finland

1986 6 Districtheating

Peat & wood chips

Byggelit AB 1986 6 Drying Wood chipsS-830 30 LIT, Sweden 1986 4 Drying Wood chipsAB Vilhelmina VarmeverkS-912 00 Vilhelmina, Sweden

1986 5 Districtheating

Peat

Jalasjarven Lampo OyFIN-61601 Jaiasjarvi, Finland

1986 5 Districtheating

Peat

Ilomantsin Lampo OyFIN-82900 Ilomantsi, Finland

1996 6.4 Districtheating

Peat & wood chips

Information available on the present situation, performance data and cost evaluation is presented in Table 6.

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Table 6. Performance and cost data on Bioneer gasification heating plants.

Heat production in 1994

Kiteen Lampo Oy Jalasjarven Lampo Oy Parkanon Lampo Oy

Nominal effect MW

654

Heat production MWh/a31 80023 00020 800

Time of peak power h/a

5 3004 6005 200

Fuel consump­tion MWh/a

36 80024 60024 000

Average performanceOperation time 8 000 h/aAvailability 95 - 97 %Total personnel 3-4Heat generationSpecific investment costs 350 kECU/MWSpecific operation costs 17 ECU/MWhSpecific heat generation costs 20 ECU/MWh

3.2.4 Evaluation and conclusions

The competitiveness of the Bioneer boiler plant compared to conventional solid fuel boilers is based on the following factors:

• high reliability, automatic operation, high degree of utilisation

• high efficiency even at part-load, 85 - 90%

• low specific emissions, small need of flue gas cleaning

• possibility to employ different feedstocks in the same plant.

Good experiences have been obtained from the operation of the Bioneer updraft gasifi­cation plants during the development period and from the operation of the commercial plants. Practically all solid fuels available in Finland can be gasified. The commercial plants in operation in Finland and Sweden use wood chips, wood wastes and sod peat as fuels. Promising results have also been obtained with straw, municipal waste and coal/wood waste mixtures at the pilot plant.

After the commercialisation of these atmospheric gasifiers the research and develop­ment work has been directed to cleaning gas from tars and other impurities to increase the utilisation potential of gasification technology. One of the greatest advantages of updraft gasification is low particulate loading of unpurified flue gas, which makes fur­ther purification of gas simpler and cheaper than in most combustion processes. Labo­ratory experiments have shown [11] that the tars of the product gas can be cracked com­pletely by using dolomite or nickel-based catalysts. The development of gasification diesel power plants still requires practical technical solutions and long-term experience from the use of catalysts.

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3.3 Circulating fluidised-bed gasification

3.3.1 Process description

The first commercial gasifier employing Ahlstrom Pyroflow circulating fluidised-bed technology was commissioned in 1983 at the With. Schauman Pulp Mill (today Wisa Forest) in Pietarsaari, Finland. The gas is used for fuelling the lime kiln of the mill [8] (Figure 4).

The fuel is crushed with a hammer mill and fed into a flash dryer (0 4.8 x 44.9 m). The energy consumed by the dryer is obtained from hot flue gases (150 °C) of the recovery boilers. After the drying tube, part of fuel can be recirculated back into the drying pro­cess. The fuel is separated from the flue gases by a cyclone and finally with a multi­cyclone.

The Pyroflow gasifier comprises a vertical cylinder and a uniflow cyclone, both refrac­tory-lined. The air wind box, air distribution plate and ash removal equipment are con­nected to the base. Dry biofuel is fed through the side of the reactor. The biofuel is py- rolysed at 750 - 950 °C in the sand circulating in the reactor yielding gas, which is then led to the lime kiln burner at 700 °C. The energy fed into the lime kiln is controlled by the fuel flow, and the gasification temperature is controlled by the air flow.

FUEL DRYING WITH FLUE GASES FROM RECOVERY BOILER

GAS BURNING IN LIME KILN

Figure 4. The Pyroflow gasifier at Wisa Forest Pulp Mill.

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3.3.2 Commercial plant

A. Ahlstrom Corporation commissioned four Pyroflow gasifiers in the output range of 54 - 126 GJ/h (16 - 35 MW) in 1983 - 1986. Two of the plants are located in Sweden and one in Portugal. All these plants are fuelled with wood waste, which is dried in pneumatic dryers to < 15% moisture before gasification. Information on the commercial Pyroflow gasifiers is given in Table 7 [3].

Process design data on the Wisaforest Pyroflow plant is presented in Table 8 [8]. The gasifiers of the Swedish and Portuguese plants are of the same type, but the fuel drying systems differ from each other.

Table 7. Pyroflow gasifiers.

Year of delivery

Customer Application Thermal ca­pacity, MW

1981 Hans Ahlstrom Laboratory, Karhula, Finland Pilot plant 31983 Wisa Forest, Pietarsaari, Finland Lime kiln gasifier 351985 Norrsundet Bruks AB, Norrsundet, Sweden Lime kiln gasifier 251986 Portucel, Rodao Mill, Portugal Lime kiln gasifier 151986 ASSI, Karlsborgs Bruk, Karlsborg, Sweden Lime kiln gasifier 27

Table 8. Wisa Forest Pyroflow plant.

FuelSawdust 70%Bark 30%

Drying gas temperature 150 OCDry matter to gasifier 15%Effect 34 MWFuel flow 1.8kgo.d./sGasifying temperature 750 - 900 °C

A. Ahlstrom Corporation, together with Wartsila Oy, developed a diesel power plant based on the Pyroflow gasifier and Wartsila engines in the early 1980s. The plant was extensively tested in pilot scale, but was never commercialised. The key problem in this project was the removal of condensable tars from the product gas, which has always been the most important barrier to the engine use of gasifier product gases.

3.3.3 Operational experience

At the commercial Wisa Forest Pyroflow plant, the target of replacing 85% of the fuel oil used at Wisa Forest lime kiln was achieved after a few months from the start-up.

19

Since then the gasifier has been operating extremely reliably with only a few interrup­tions. The major reasons for the gasifier shutdowns have been:

• blocking in fuel drying and feeding,

• blocking in ash removal,

• change of hammers in the crushers, and

• maintenance.

The most common reasons for maintenance have been change or turning of hammers in the fuel crusher. Flanges and bellows in the pipe transporting hot gases to the burner have also needed a lot of maintenance. Corrosion and erosion were also observed to some extent in the pipe, but no tar contaminants.

3.4 Peat-based HTW gasification plant

3.4.1 Choice of the gasification process

Kemira Oy modified its existing oil-based ammonia plant to use also peat-derived syn­thesis gas in ammonia production. The decision to build a HTW-gasification plant was made in 1985 after pilot-scale gasification experiments in three different gasification processes.

Before starting the full-scale project, pilot experiments were carried out at oversea plants in order to minimise technical risks. Test runs using the following three processes were carried out with peat delivered from Finland in 1984 - 1985:

• HTW (high-temperature-Winkler) process in Germany

• U-GAS process in the USA-

• MINO process in Sweden.

The choice of the process went in favour of the German HTW process [13]. The HTW licence is owned by Rheinbraun AG, while the engineering was carried out by UHDE GmbH. One strong argument in favour of this choice was the fact that Rheinbraun AG had already constructed a full-scale gasification demonstration plant for brown coal that is in many respects similar to peat.

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3.4.2 Process description

The principle of the drying and gasification process is shown in Figure 5. Crushed peat must be dried to about 15% moisture content prior to the gasification process. Use of wet peat would result in synthesis gas of inferior quality (high C02 content). The supe­rior transport and feed properties of drier peat also increase the operational reliability of the process. In the pressurised MoDo steam dryer, the peat is carried by circulating steam flow in the inner 100 nun-diameter pipes of four tube heat exchangers. Bled steam of 11 bar from the turbine of the power plant is used as drying energy in the jacket of the pipes. Dried sod peat crush is separated in the cyclone and is led into two parallel feed systems of the gasifier. In gasification, the dried sod peat crush is pressur­ised to 10 bar pressure in lock-hoppers and fed by metering screws into the reactor. Oxygen and steam are blown below peat so that the peat bed is fluidised. The gasifica­tion reactions occur in the fluidised bed and in the upper zone of the reactor at 750 - 950 °C. The product gas is synthesis gas that contains hydrogen and carbon monoxide.

Steam from peat fired boiler 11 barSteam

Sod peat42t/h, moisture 40%

Steam 4 barcoverterMoDosteam dryer Hot water

Crusher SteamHTW gasifier

Peat I crush \ moisture 15% ,

Obar 750- 950° C

Waterscrubber

Gas to amisol scrubber 1500kmot/h 29 bar

Oxygen

y SludgeDust separation

Figure 5. Drying ofpeat and production ofsynthesis gas for ammonia production, Ke- mira Oy.

21

3.4.3 Experiences and conclusions

The HTW gasification plant was commissioned in 1988 and was in operation for several thousands of hours in 1988 - 1990. Most of the time the gasifier was operated at partial capacity together with one oil gasifier. The heterogeneous quality of peat feedstock caused operational problems in the pretreatment equipment and in the lock-hopper feeding system, which was designed on the basis of experiences from brown coal use. The high naphthalene content of raw gas also caused operational problems in the early stage of operation. This problem was eliminated by elevating the gasification tempera­ture and by adding a naphthalene removal unit into the gas cleaning line.

During the operation periods subsequent to the first start-up, the following problems besides those caused by naphthalene crystallisation were encountered [12,14]:

• variations in peat quality

• capacity of the peat crusher

• particle size distribution

• troubles with feeding equipment of peat drying, which disturbed smooth operation

• blockages in the 1-cyclone of the gasifier.

All these factors probably contributed to the high naphthalene content as well. During the operating periods, the recycle pipe of the hot cyclone was always blocked up within a few days of operation. This did not prevent the production but affected the naphtha­lene content, carbon conversion rate as well as the yield of synthesis gas.

The technical difficulties with fuel feeding, pretreatment and quality were solved through fuel quality control, by adding a second crusher and by modifying the feeding.

The Kemira peat gasification plant proved the technical feasibility of peat-based synthe­sis gas production. The project also gave valuable information on topics like peat pre­treatment, feeding to pressurised reactors and formation of tars and other impurities in fluidised-bed gasification. This information is also relevant in the development of IGCC power plants.

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4. Demonstration projects

4.1 Background

Research on integrated gasification combined-cycle (IGCC) technology was initiated in the latter half of the 1980s. The government-funded work has focused on the utilisation of indigenous fuels in which case the potential applications are mainly restricted to the area of medium-scale combined heat and electricity production (20 to 150 MWe). The driving force is the need for higher power-to-heat ratios since, in general, heat loads are not increasing whereas the consumption of electricity is. The power-to-heat ratio of an IGCC cogeneration plant is typically twice that of a conventional steam-cycle cogen­eration plant.

Due to the fact that the market for peat and biomass based IGCC plants exists in the medium-size range (20 -150 MWe), the Finnish R & D focuses on the development of simplified IGCC processes based on gasification with air and subsequent hot gas cleanup. Most of the present Finnish research and development activities are related to processes based on fluidised-bed gasification followed by gas filtration with ceramic or metal filters. Several Finnish companies are undertaking significant process develop­ment work related to IGCC technology. This development work is supported by gov­ernment-funded research projects conducted at VTT and at Finnish universities.

4.2 Carbona Inc.

4.2.1 Company profile

Enviropower Inc. was a joint venture of Tampella Power Inc. and a Swedish utility company, Vattenfall, developing an IGCC process based on the U-GAS coal gasifica­tion process, which was originally developed by the Institute of Gas Technology, USA. In 1996 the two owners decided to cease operations of the company as part of an overall streamlining of the operations. Former employees of Enviropower Inc. acquired, through a management buy-out, the rights to Enviropower’s pressurised gasification technology and established a new company, Carbona Inc.

The Carbona process concept incorporates air-blown fluidised-bed gasification and hot gas cleaning. Carbona is developing this technology for biomass and coal feedstocks. Carbona will use the testing facilities of VTT Energy in research and engineering work as well as Enviropower's existing pilot plant in Tampere.

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Enviropower commissioned a 15 MWft pilot plant in autumn 1991 in Tampere, Finland. The first test run was carried out in October 1991. In 1993 - 1995, several wood gasifi­cation tests have been carried out in the pilot plant.

4.2.2 Gasification pilot plant

Carbona’s pressurised fluidised bed gasification pilot plant is based on the U-Gas gasi­fier and includes all essential modules for research, component testing and for complet­ing the development of the U-Gas process for IGCC applications. The maximum ther­mal input of the pilot plant is 15 MW and it can be operated at up to 30 bar pressure and 1 100 °C temperature. The process flow diagram of the pilot is shown in Figure 6 [15].

Provisions have been made to use a variety of feedstocks besides coal, including peat, wood waste and pulp mill sludge. These fuels can be tested separately or as fuel mix­tures. Fuel feeding can be accomplished through lock-hoppers (dry fuel). Dolomite or limestone can be fed to the gasifier for in-bed desulphurisation.

SULPHURREMOVAL FLARE

STACK2nd STAGE CYCLONE

PRODUCT GAS COOLER .

1st STAGE CYCLONE

SORBENTFEED

CRUS­HINGDRYING BIOMASS

FEED

GASIFIER

STEAM

DISTRICTHEATING

ASHREMOVAL

Figure 6. Flow diagram of the Enviropower gasification pilot plant.

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The gasifier is based on the U-Gas process, which is a single-stage pressurised fluidised- bed gasifier. The gasifier produces low-Btu gas suitable for combustion in the gas tur­bine. In coal gasification, the bulk of fuel ash is removed through the bottom of the gasi­fier. The gasification agents, air and steam (provision also made for oxygen), are fed in a certain ratio through the bottom (jet, grid and venturi) of the fluidised bed to maintain proper conditions for simultaneous fluidisation and proper ash removal. The fines elutriated from the fluidised bed are separated from the product gas in two stages of external cyclones. The fines from both stages are returned to the fluidised bed.

The product gas leaving the gasifier cyclones is then cooled in two steps: first to 400 - 650 °C, then after hot gas clean-up to 200 - 350 °C. After the first gas cooling stage the external, the post-gasification sulphur removal system is by-passed when gasifying biomass. The dust particles are removed from the gas stream by ceramic candle filters cleaned by nitrogen pulsing. The pilot plant is equipped with a state-of-the-art data ac­quisition and control system and served by well equipped laboratories.

A total of 3 000 tons of wood-based biomass (as received) was gasified during 900 test hours in 1993 [16]. Long, stable set points were achieved under demo plant operating conditions. The testing conditions and fuels/amounts gasified are presented in Table 9. Some results are shown in Table 10.

Table 9. Biomass pilot test runs, Enviropower pilot plant [16].

Operation pressure 14-18-22 barOperation temperature 800 - 950 ocPlant capacity 15 -17 MJ/s (MWth), 100 t/dayFUELS GASIFIED (1993 - 1995) Amount/tWood chips 1 630Forest residue 1 650Paper mill waste (bark, paper, sludge) 460Straw with coal 20 (+ 1201 coal)

Table 10. Biomass gasification pilot test programme, test results, Enviropower power plant [16].

Forest residue BarkPilot plant fuel input MJ/s 15 15Product gas LHV (dry) MJ/m3 4.5 - 5.6 4.5 - 5.6Fuel conversion % 97-99 97-99Product gas dust content after ceramic filter mg/m^N <5 <5Alkalines (K + Na) ppm(w) 0.01 0.01Product gas H2S content mg/mgN 15-50 -200Product gas NH3 content mg/m^N 500 - 1 500 -2 200

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Fuel testing for the Finnish demonstration project called ’’Summa IGCC Demonstration Project” started in February 1995 and was continued through in May 1995. The ceramic filter unit functioned well with excellent filtration efficiency. Generally the combined dust and tar loading was less than 4 ppm(w) after filtration. This level of dust loading is lower than the dust concentration specified by gas turbine manufacturers and much lower than the limit required by environmental regulations.

4.2.3 IGCC demonstration

The development of the biomass-fuelled simplified IGCC process has achieved the ma­turity for demonstration in full scale. Enviropower had plans to demonstrate this tech­nology on a fast schedule participating in the initiation of demonstration projects both in Europe and in the United States [16]. Presently Carbona Inc. is involved in two IGCC demonstration project, a 55 MWe gasification plant connected to a combined cycle in India and an Alfa-alfa Gas Project in Minnesota, USA.

In Finland, the pulp and paper industry typically utilises all the in-house wood waste (black liquor, bark, etc.). Hence, the repowering of a paper mill power plant gives an excellent opportunity for the demonstration of the biomass-fuelled IGCC process, as was the case in the Summa IGCC Demonstration Project, where the steam turbines of the existing power plant would have been utilised. The aim was to build a 60 MW IGCC plant. However, the amount of available biomass, waste from the mill and forestry resi­dues were not available in sufficient amounts and at a competitive price. The decision to cease operation of Enviropower and the availability of natural gas at the site contributed to the interruption of the demonstration plans.

4.3 Foster Wheeler Energia Oy

4.3.1 Bioflow Energy System

Another large Finnish boiler manufacturer, Ahlstrom Pyropower, was also active in the field of pressurised power plants. In 1995 the company was acquired by Foster Wheeler in USA. The new company Foster Wheeler Energia Oy proceeds with the development of gasification technology.

Ahlstrom Pyropower, today Foster Wheeler Energia Oy, is co-operating with the Swed­ish utility company, Sydkraft. The companies decided in 1991 to start jointly the devel­opment of the Bioflow Energy System based on IGCC technology utilising biomass as fuel. The first step in this co-operation was the decision to build a demonstration plant at Vamamo in southern Sweden [17]. This process is based on the pressurised Pyroflow circulating fluidised-bed gasifier and on hot gas cleaning.

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4.3.2 Varnamo IGCC plant

The capacity of the Vamamo IGCC plant is 6 MW electricity and 9 MW district heat. The Vamamo plant is shown in Figure 7. Typical plant performance data of the Bioflow IGCC plant are presented in Table 11 and general process data of the Vamamo demon­stration plant in Table 12 [18].

The fuel received to the site is dried and crushed in external rotary drum dryer and fuel preparation facilities. Almost two-thirds of the fuel prepared is delivered to other facili­ties in the neighbouring cities. The preparation plant is designed to handle all kinds of wood fuels.

The biomass as well as the bed material are handled with lock-hopper systems. The gasifier including cyclone and return leg is totally refractory-lined. The cyclone is de­signed in such a way that both the solids and the gas are discharged from the bottom of the cyclone and thus saves space and piping work. Operating pressure exceeds 20 atm and the temperature is as high as 950 °C to 1 000 °C to enhance the thermal catalytic cracking effect. Coarser ash generated in the system is discharged from the bottom of the gasifier and is cooled before entering the depressurisation system.

The gas cooler is of fire-tube design and cools the gas to approximately 350 °C before it enters the ceramic filter vessel for particulate clean-up. The clean gas then enters the gas turbine, is combusted and expanded generating 4.1 MWe of electricity in the generator. The flue gas flows into a waste heat steam generator with evaporative and superheating surface. The superheated steam generated enters a steam turbine that generates ap­proximately 2 MWe at 100% MCR. The steam turbine has moderate process perform­ance, but has been included to demonstrate the whole IGCC system. Steam pressure is 40 bar and temperature 470 °C. The major duty in the district heating system is handled in the steam condenser, while some heat is transferred to the net by the district heating economiser, booster air cooling and the cooling water circuit for the gasification train. The percentile duties of these vary with load.

Table 11. Bioflow technical data [18J.

Gasification pressure 24 barLHV of product gas 5 MJ/m^nTotal efficiency 85 - 90 %Electrical efficiency- cogeneration 40 - 45 %- condensing 44 - 50 %Power-to-heat ration (cogeneration processes) 0.8- 1.2Typical plant size 20- 150 MWeNOx < 50 mg/MJfuelSOx < 25 mg/MJfuelParticulates < 10 mg/MJfuel

27

Figure 7. Varnamo CFB gasifier train.

Table 12. Varnamo process data [18].

Plant size FuelGasification pressureGasification temperatureProduct gas heat valuePower productionDistrict heatingSteam temperatureSteam pressurePlant ownerGasifierCeramic filterGas turbineSteam turbineWaste heat steam generatorBooster compressor

18 MW fuel input Wood waste & chips 22 bar950 - 1 000 °C5 MJ/m^n6 MW 9 MW 470 °C 40 bar SydkraftAhlstrom Boilers Schumacher European Gas Turbine Nadrowski Ahlstrom Termoflow Ingersoll-Rand

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4.3.3 Commissioning and experiences

Gasifier commissioning started in late spring 1993 and the first combustible gas at ele­vated pressure was produced at the end of June 1993 [18]. The strategy in the commis­sioning was to raise pressure in steps in order to assure proper operation of the plant and to evaluate the performance. During these steps, however, some problems were experi­enced that prolonged the commissioning phase. These problems were mostly associated with auxiliary equipment. Fuel feeding in the conventional part as well as in the pres­surised parts caused some problems with leaking seals and shaft boxes for the augers. Ash valves also experienced some leakage of gas through the seals. This was found to be caused by too large actuators creating uneven forces on the valves themselves and, hence, misalignment. Although these problems were relatively easy to correct it has taken time due to long delivery times and installation work of some new equipment.

The commissioning and testing within the framework of the demonstration programme are in progress. Gasification to normal operating pressure has been reached, i.e., close to 22 bar(g). Data has been collected at this pressure and at lower pressures as well, and the quality of gas has been evaluated. The heating value of the product gas has typically been approximately 4.6 - 5.5 MJ/m3n. The material and energy balances indicate an ex­tremely high carbon conversion in the system (in excess of 98 - 99%).

Testing activities in the commissioning stage comprised:

• optimisation of the lock-hopper feeding sequence with regard to nitrogen consump­tion

• optimisation of process parameters: gasification temperature, bed pressure, fluidisa­tion velocity, etc.

• testing of different types of bed material.

The ceramic filter has been operated some 700 hours, and the experiences have so far been very good. The ceramic filter has operated well and stable at high pressure and the basic level of pressure difference has been low and stable during the test runs. The dust measurements made after the hot gas filter indicated extremely low dust emissions in the product gas. Despite the problems mentioned above during the first steps of the commissioning, which delayed the commissioning stage, a very good progress was ex­perienced.

Up to September 1996 the gasification plant has been in operation for about 4 500 hours and some 150 hours of fully integrated operation (100% product gas firing of gas tur­bine) has been achieved. Observations during the fuel changeover phase and during the operation of 100% product gas firing showed no adverse effect on either combustion performance or turbine behaviour.

29

After commissioning the plant will initially be in test use to demonstrate the technology as well as for the development of the power plant concept. The demonstration stage will consist of the optimisation of the process performance and control, of improving hard­ware and process design, and of monitoring plant reliability and availability. The dem­onstration programme will be conducted jointly by Foster Wheeler Energia Oy and Sydkraft. Part of the development work will be carried out at national research centres and universities in Finland and Sweden through government and industry-funded re­search programmes.

4.3.4 Technology development

The Vamamo demonstration plant will give an excellent opportunity of developing fur­ther the IGCC technology to increase efficiency, optimise process performance, improve hardware and process design and monitor plant reliability. This work, in addition to other related projects, will further develop and commercialise the technology.

The next unit is expected to be in a larger size range than the Vamamo plant. A scale-up to 20 to 80 MWe is realistic and is very much dependent on the low calorific turbine size available. Commercialisation of the technology to scales from 20 to 120 MWe is also very much dependent on the existence of sufficient amounts of fuel for the lifetime of the plant.

4.3.5 CFB gasification connected to boiler

Lahden Lampovoima Oy, a power company owned by the city of Lahti in southern Finland and Imatran Voima Oy, is planning to build a 40 - 50 MW& CFB gasification plant connected to a 350 MW* steam boiler fired by coal and natural gas. The power plant produces electricity and district heat for the city of Lahti. The new gasifier is of Foster Wheeler atmospheric-pressure CFB design. This demonstration plant will be fired by wood waste, wood chips, peat and recycled fuel (REF). The biomass is gasified and the product gas utilised in the steam boiler to replace fossil fuels. The consumption of fossil fuels is cut with a maximum of 300 GWh/a, equivalent to 45 000 tons of coal. The concept is shown in Figure 8.

30

Bottomash

Figure 8. Biomass CFB gasifier connected to an existing coal boiler plant, Lahden Lampovoima Oy.

4.4 IVOSDIG Process

4.4.1 General

The Finnish utility company Imatran Voima Oy (IVO) is developing an advanced gas turbine power plant process for wet fuels like peat, biomass and lignite. The process is patented and called IVOSDIG (Imatran Voima’s Steam Drying, Injection, Gasification) process. IVO’s R & D work is presently focused on testing components related to the fuel supply and steam drying. The aim of the development work is to reach a commer­cial level for the peat-utilising process towards the end of the 1990s [19,20].

4.4.2 Process description

The IVOSDIG process is a high-efficiency power plant process for moist fuels like peat, biomass and brown coal. The process consists of a steam-injected gas turbine, an air- blown gasifier and a pressurised fuel dryer. The dryer operates in steam atmosphere and is integrated to the process to produce injection steam for the gas turbine. The process can be implemented as a simple gas turbine cycle or as a combined-cycle process.

31

I VO has initiated experimental research on the components unique for the process. The first 1 000 hours of test runs using the pressurised steam drying pilot plant commis­sioned in 1991 have been carried out successfully. The feedstocks used so far have been peat and wood biomass in the form of sawdust and crushed wood chips.

Figure 9 shows the basic version of the IVSODIG process and the principle of the IVOSDIG cycle [18]. In the simple process, power is generated only in the gas turbine, the steam turbine being not used at all. In the example calculation, the process was planned to be operated with peat as fuel, and it was calculated based on the Siemens KWU 64.3 gas turbine giving a power output of about 100 MWC.

The moist fuel is pressurised and fed into the high-pressure steam dryer (23 bar) where it dries in direct contact with superheated drying steam to the final moisture of 15% prior to the gasifier. The dry fuel is then separated from the steam flow and fed into the pressurised gasifier. After the cyclone, a flow is separated from the steam flow and mixed as injection steam with the fuel gas produced in the gasifier. Most of the steam in the dryer circuit is, however, circulated. The injection steam flow separated in the peat con­cept is about 10% of the whole circulating steam flow.

The gasifier is an air-blown fluidised-bed gasifier. The product gas is of low calorific value; the heat value of peat fuel gas is estimated at 4.5 MJ/kg (LHV). The product gas is passed together with the injection steam flow through a ceramic filter into the gas turbine combustion chamber. After the gas turbine, the flue gases flow into the waste heat boiler, which superheats the steam circulating in the dryer circuit.

In the combined cycle application, the IVOSDIG principle is adjusted to a gasification combined-cycle process. This type of integration is suitable in larger plant sizes for fuels with slightly lower initial moisture contents and, in addition, for condensing power gen­eration, when cogenerating power and heat. It is also feasible as a retrofit application. The IVOSDIG combined-cycle process is shown in Figure 10.

The main idea in the combined cycle process is the same as in the simple process. The example process is constructed around the given values for the GE Frame-6 gas turbine producing about 50 MWe with steam injection. The fuel used in the example calculation is brown coal of 60% initial moisture content. The fuel type is of minor significance, while the moisture content of the fuel is more crucial.

32

RECIRCULATIONEXTRACTION STEAMSTEAM BLOWER(EVAPORATED FROM FUEL) ,

GAS CLEAN WG

PRESSU­RIZEDDRYER

PRESSURIZEDCOMBUSTION

BOOSTER

WET FUEL \ /PRESSU- V DRY PUB R1ZATION > k FEEDING

COMPR.

WASTE HEAT

DRYING STEAM SUPERHEATER

ADDITIONALSTEAMGENERATOR

Figure 9. TVOSDIG simple gas turbine cycle.

EXTRACTION STEAM STEAM BLOWER (EVAPORATED FROM FUEL)

Figure 10. IVOSDIG combined-cycle process.

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4.4.3 Process performance

The power-generating efficiency of the 1VOSDIG cycle is high, close to 50% based on the lower heating value of the fuel [19]. When cogenerating power and heat, the high efficiency can be seen as a high power-to-heat ratio, i.e., essentially higher than that of conventional cogeneration power plants. The power-generating efficiency of the largest conventional peat-fired power plant in the world is about 40%.

The IVOSDIG process is suitable for fuels with a high moisture content like peat, bio­mass, and brown coal with initial moisture contents ranging 30 - 70%. Advantages of the process are a high power-generating efficiency with a simple dryer and process. The feeding of wet fuel into high pressure is also easier than that of dry fuel. The need of inert gases in feeding is smaller. These give a competitive cost of electricity compared with that achieved by other processes using such fuels of high moisture content.

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5. Research activities

5.1 General

Research and development on gasification in Finland are focused on the development of integrated gasification combined-cycle cogeneration plants fuelled with biomass and peat. In smaller-scale applications, atmospheric-pressure circulating-bed gasification technology is of current interest in electricity generation based on a gasification-diesel concept. In addition, the co-combustion of wood and waste-derived product gas in PC boilers is the topic of intensive research in Finland.

Public funding for gasification research is channelled mainly through national research programmes. Research is carried out by VTT Energy and by technical universities (projects of basic research type).

5.2 Gasification research at VTT Energy

Gasification research at VTT Energy can be divided into three main fields of activity:

• Pressurised fluidised-bed gasification and the most critical technical questions of the simplified IGCC process

• Atmospheric-pressure gasification for small-scale energy production and for co­combustion in large utility boilers

• Fuel characterisation and fundamentals of gasification and hot gas cleaning.

The unique test facilities and analysing equipment are summarised in Table 13.

5.2.1 Pressurised fluidised-bed gasification

The main objective of VTT Energy’s current activity is to support industrial develop­ment projects by carrying out experimental research on the most critical aspects of the simplified IGCC concept, and in particular, on problems associated with the use of bio­mass feedstocks. The most important research topics are:

• Feedstock pretreatment and feeding into pressure- Technological and safety aspects of peat and biomass handling [21]- Feed of peat and biomass into pressurised reactors [22]

• Pressurised gasification- Test runs with peat and biomass on a pressurised fluidised-bed gasification test rig

[23,24,25,39,41]- Fundamental studies of ash behaviour and char reactivity [26,27]

35

Table 13. Gasification test facilities ofVTT Energy.

PDU/PRU GASIFIERSPressurised fluidised-bed gasification test rig (1988-)

Circulating fluidised-bed gasifier (1995-)

Fixed-bed gasifier and ther­mal cracker(1985-BENCH-SCALE RIGSPressurised fluidised-bed re­actor for fundamental studies . (1993-)

Fluidised-bed reactor and cracking unit (1995-)

Filter testing facility (1993 -)

Fluidised bed reactor for ash sintering studies (1995-)Pressurised honeycomb reactor (1994-)

Entrained flow reactor (1995- .)

LABORATORY FACILITIES

Up to 80 kg/h feed rate Pressure 3-10 bar Temperature 700 - 1 100 °C

Up to 50 kg/h feed rate Atmospheric pressure Temperature 700 - 1 100 °C

Up to 25 kg/h feed rate Atmospheric pressure

Batch/continuos feed id 30 mm, SiC reactor Pressure 2-20 bar, synthetic gas atmosphere1.2 bar, max 1 000 °C Up to 500 g/h feed rate

Synthetic gas, 1-5 bar Temperature 300 - 900 °C

1 bar, up to 1 100 °C Continuous feedUp to lObar, 1 000 <>C

Syn gas or real gasifica­tion gas from PDU gasi­fier1.2 bar, max. 1 100 °C Up to 500 g/h feed rate

• Tests with new feedstocks for IGCC applications

• Gas filtration tests• By-pass testing of secon­

dary gas cleaning catalysts. Tests with waste materials

and biofuels for atmos­pheric-pressure applica­tions

. Development of gas clean­ing for CFB gasifiers

. Tests with waste materials

. Fluidised-bed pyrolysis tests

. Reactivity tests

. Gas cleaning studies

. Pyrolysis in N2

. Preliminary air gasification tests with new feedstocks

. Fate of tars and soot• Corrosion of filter materials• Filtration tests. Sintering tests in real flui­

dised-bed conditions. Catalytic decomposition of

tars and NH3• Other gas cleaning tests

. Air/N2/synthetic gas

. Pyrolysis, reactivity, gasifi­cation

. Ambient pressure and pressurised TGA facilities

. Pressurised heated-grid apparatus

. Pyroprobe pyrolysis GC (AED/MS)• Tube reactor for studies of gas-phase reactions . Pressurised fixed-bed reactor for catalyst testing

36

- Development of sampling and measuring systems for pressurised gasifiers [25, 28]

- Feedstock characterisation and release of different effluents [40]

• Hot gas cleaning- Testing of different ceramic filters under conditions of coal, peat and wood gasifi­

cation [29, 39]- Behaviour of alkali metals in gasification and gas filtration [30, 31,39]- Fundamental studies of ash behaviour and char reactivity [26,27]- Development of sampling and measuring systems for pressurised gasifiers [25,

28]- Feedstock characterisation and release of different effluents [40]- Fundamentals of catalytic tar removal methods [32,33, 34, 39]- Development of a catalytic tar and ammonia decomposition method based on

honeycomb catalysts [11]- Development of methods for removing nitrogen compounds including selective

oxidation of ammonia [33, 34]

• Process simulation [35, 36, 37, 38, 42].

In addition, VTT Energy is participating in industrial development projects of Finnish companies by carrying out confidential test runs on its PDU-scale test rigs and by per­forming special measurements at pilot and demonstration plants of the industry.

The pressurised fluidised-bed test facilities of VTT Energy are illustrated in Figure 11. Technical data and operating experiences are summarised in Table 14.

Table 14. Technical data on the PFG test facility of VTT Energy.

Bed-i.d. 15 cm Feedstocks gasified (by the end of 1994):Freeboard-i.d. 25 cm - Sawdust and wood wastesReactor height 4.2 m - Straw

bed 1.2 m - Different peat productsfreeboard 3.0 m - Rhenish brown coal

Operating pressure 2.5 - 10 bar - Hard coals: Iowa Rawhide, Polish coal,Bed temperature 700 - 1 000 oc Illinois No. 6, Colombian coalFreeboard t (max) 1 100 °C Total gasification test time 2 210 hFluidising velocity 0.5 -1.5 m/s Number of measured set points 152Gasification agents Air, steam Amount of gasified fuels 1041Fuel input Abt 50 kg/h Fuel feed rate (max) 80 kg/h

The test facilities are equipped with two separate feeding systems for different types of solid feedstock. The hearth of the test rig is a refractory-lined reactor. Two different distributor plates can be used depending on the required range of fluidising air flow rate. Secondary air can be introduced from above the fluidised bed. The filter module com-

37

BIOMASS FEEDER

PARTICULATES

PERMANENT GASES LIGHT TARS NH3, HCN H2S, COS HCI, H20

ALKALI VAPOURS

COMBUSTOR

BOTTOM ASH FILTER FINES

Figure 11. Schematic diagram of the PFG test rig ofVTT Energy.

prises five ceramic candle elements cleaned by pressurised nitrogen pulses. A wide vari­ety of process measurements can be carried out, collected by a data logger and proc­essed by a microcomputer. On-line measurements of permanent gases and sampling of tars, alkalis, nitrogen compounds and particulates are indicated on the diagram in Figure 11.

5.2.2 Atmospheric-pressure gasification

Research on atmospheric-pressure gasification is related to small-scale energy produc­tion from biomass and wastes. This concept can be utilised in the following energy pro­duction systems:

• gasification diesel plant

• separate gasification of biomass/wastes and combustion of the purified gas in an ex­isting large coal-fired boiler

• waste gasification followed by efficient gas combustion.

For this purpose, VTT Energy has commissioned a new atmospheric circulating flui- dised-bed gasification rig in 1995 [45]. This CFB gasifier is shown in Figure 12, and the technical data are summarised in Table 15. The most important research topics are:

. Separate gasification of biomass/wastes and combustion of purified gas in large coal- fired utility boilers

38

. CFB gasification of problematic agrofuels and wastes

. Development of gas cleaning technology for gasification diesel power plants

. Application of CFB gasification in other process concepts.

Figure 12. Atmospheric-pressure CFB test rig ofVTT Energy.

Table 15. Technical data of the CFB test rig of VTT Energy.

Reactor i.d. 15 cmReactor height 9 000 cmOperating pressure 1 barTemperature range max 1 000 °CFluidising velocity 1-6 m/sFuel input 10 - 60 kg/h

39

6. Future perspectives of biomass gasification in Finland

The relative use of bioenergy in Finland is about 20%, i.e., highest among industrialised countries. Biomass is mostly used in multifuel boilers applying advanced fluidised-bed combustion technology. Forest residues have the largest potential for additional biomass use, but their competitiveness is often poor compared to that of coal and other fossil fuels.

The development of gasification technology in Finland has focused on the simplified IGCC combined-cycle process. Finland developed, as the first in the world, plans for a full-scale demonstration plant based on IGCC technology in the mid-1990s. However, these plans were not realised, mainly for financial reasons. Simultaneously, a significant reorganisation took place in the Finnish boiler industry. The reforms in the taxation of energy production and consumption, recently ratified by Finland’s Parliament, may also increase the uncertainty about the future role of biomass in combined electricity and heat generation in Finland. The IGCC technology has not lost its great technical poten­tial (high efficiency, high electricity yield in CHP production), but it seems that the first commercial plants will not be realised until after the turn of the year 2000 and even then probably in countries with a more favourable electricity/fuel price ratio than in Finland.

The economic competitiveness of the IGCC technology requires as large a plant size (>30 - 50 MWe), that this technology cannot be applied in all potential objects of bio­mass and peat use in Finland. New gasification-based power plant technologies that are technically suitable for different size classes are shown in Figure 13. Their mutual com­petitiveness is of course dependent on the site. In a small size class, the gasification die­sel technology would primarily be competitive with the conventional steam process. The gasification diesel concept has been demonstrated by Ahlstrom and Wartsila Corpo­rations in Finland in the mid-1980s, when however problems were still caused by gas cleanup.

In addition to diesel power plants, atmospheric gasification technology can be utilised in many other applications. One promising alternative is a method of co-combustion, in which biomass gasification is integrated to a pulverised coal-fired boiler. This process is of great interest in Europe, where a potential of about 50 plants is estimated to exist in the relatively near future. One of the three leading European manufacturer of atmos­pheric circulated-bed gasifiers is Foster Wheeler Energia Oy, Finland.

Advantages of the co-combustion method based on a separate biomass gasifier and on the combustion of gas in an existing boiler are:

40

1 5 10 50 100 200 500 MWelilt

Combustion atSTEAM CYCLE

atmospheric pressure + steam cycle

CO-COMBUSTION Atmospheric CFB gasif. + PC boiler

1GASIFICATION - DIESEL

Unpressurized gasification + cold gas cleaning + diesel engine

iTOPPING CYCLE

Pressurized partial gasification + PFBC

IGCC -1 ATMUnpressurized gasification + cold gas cleaning

+ gas compression + combined cycle

SIMPLIFIED IGCC Pressurized air gasification hot gas

cleaning + combined cycle 1

IGCC - 02Oxygen gasification + wet cleaning +

combined cycle------------------------1' a,3,„8*|

1 5 10 50 100 200 500 MWeSIZE CLASS

Figure 13. Gasification technologies for solidfuels suitable for use in power plants of different size classes.

. Additional costs are caused only by biomass gasification and minor boiler modifica­tions.

. An effective steam cycle of large size class can be utilised.

. Gas can be cleaned, if necessary, from corrosive alkali metals and chlorine prior to leading it into the coal-fired boiler.

. If necessary, biomass ashes can be separated from coal ashes.

Atmospheric-pressure gasification is of simpler and cheaper technology than pressurised gasification. In this respect, the threshold of commissioning this technology is lower than that of pressurised gasification. Successful demonstration projects of atmospheric gasification may also contribute to the commercialisation of pressurised gasification.

The Finnish Government has made a decision to increase the funding of research and development to 2.9% of GNP by the year 2000, i.e. to a level equal to that of the most significant European countries. Of the about 18 milliards FIM channelled for research and development, 40% will come from the Government and 60% from the private sec­tor. The aim is to increase the proportion of bionenergy by about 1.5 Mtoe/a by the year 2005, and this requires an intensive contribution to research and development and to demonstration of novel technologies. The objectives of gasification research are

41

to support demonstration projects of pressurised gasification and to solve the critical problems related to commissioning this technology,

to improve the competitiveness of IGCC plants by developing combined gasification of coal and biomass,

to develop atmospheric gasification and, in particular gasification of problematic agrobiomasses and wastes,

to demonstrate the gasification diesel power plant with engine tests, and to develop catalytic tar removal that presently forms the bottleneck of the work.

42

7. Global market potential of biomass- fuelled power plants

7.1 Global biomass use

Biomass is the world's fourth largest energy source today. The biomass resources com­prise several different types of material including fuelwood and charcoal, agricultural and forestry residues, and industrial and urban wastes.

Due to the fact that a large part of biomass, e.g. fuelwood in most rural areas, is utilised outside the market system as a non-commercial fuel, the role of biomass in the global energy economy is not well-known. Official data published by the Food and Agricul­tural Organisation (FAO) of the United Nations may differ quite significantly from more detailed surveys of individual countries. However, the best estimates [46] suggest that biomass is consumed globally at a rate of about 1 200 Mtoe per year, which is some 13% of the world's energy use (Figure 14). Biomass is the dominant source of energy, 33%, in developing countries, where nearly three-fourths of the world's people live. In some developing countries biomass supplies 80 - 90% of all energy used. In industrial­ised countries the share of biomass is much lower representing on average only 3% of the primary energy consumption. This can be compared to the high biomass (including peat) use in Finland (21%) and Sweden (17%). In the United States, about 4% of the primary energy use is met by biomass.

Industrialised countries Total: 257 EJ, 6131 Mtoe (67 %)

Population 1.3 billion (25 %)

World Biomass 3 %

Hydro 6 %

Oil 36 %Total: 386 EJ, 9205 Mtoe

Population 5.3 billion

Oil 33 %

Nuclear 8 %

Gas 24 <Coal 23 %

Gas 19 %Coal 24 %

Developing countries Total: 129 EJ, 3074 Mtoe (33 %)

Population 4.0 billion (75 %)

Figure 14. Primary energy consumption 1990 [46].

43

7.2 Supply of biomass for energy

Currently, the most important sources of biomass in industrial countries constitute resi­dues from forestry, agriculture and industry, and domestic wastes and sludges. Because the residues are relatively inexpensive and can be used locally, they have been used as a fuel source for centuries and have more recently provided a good feedstock for bio­energy industry in both industrial and developing countries [47]. While the residues provide an important initial feedstock for the bioenergy industry, the development of large-scale energy production from biomass will in the future probably rely on specifi­cally grown energy crops such as sugar cane, rapeseed, switch grass and short rotation forestry [48]. Large-scale production of biomass crop raises many questions about land availability and environmental impacts, which must be addressed if bioenergy is to be accepted by the public. However, in tropical countries there are large amounts of defor­ested and degraded lands that would benefit from the establishment of bioenergy plan­tations. Species with high dry matter yields could ideally be grown on high-quality agri­cultural land, for example, set-aside land in Europe and USA.

Woods & Hall [46] estimate recoverable biomass residues on a country basis in WEC Survey of Energy Resources. The authors have compared data from the FAO, the UN Statistical Office (UNSO) and the Biomass User's Network (BUN). The estimate relies on production data using certain commonly accepted residue coefficients in calculating the recoverable amounts. The logic is presented in Figure 15 together with the coeffi­cients used, and the potential supplies of biomass in Figure 16. It should be noted that these figures do not include dung residues or biomass plantations.

Estimating the land area available for biomass energy plantation is extremely difficult. There are two main categories: surplus agricultural land, and marginal or degraded land. Hislop & Hall [49] have used the present global land use patterns and the present and potential crop land in developing countries (original sources FAO and World Resource Institute) and estimate that 10% of the total land now in forests, woodlands, croplands and permanent pasture would be available for biomass plantation. The overall crop pro­ductivity is estimated at 15 t dry matter per hectare and year, and the energy content at 20 GJ/t. Hislop and Hall also estimated the sustainable recoverable forest and crop resi­dues using the same principles as in the WEC calculations. The total potential supplies of biomass from residues and plantations are summarised in Figure 17.

The global total of energy available including plantations is about 293 EJ (7 000 Mtoe), roughly 75 % of the primary energy consumption. The potential of biomass plantations is fairly significant compared to the recoverable residues. It is clear, that with the current cost structure of fuels and energy the presented energy plantation estimates will not be a reality in the foreseeable future. The authors point out that the figures are neither opti­mistic nor pessimistic. The huge potential at least shows that it is in principle possible to

44

replace fossil fuels by a massive production of renewable energy, should this be consid­ered necessary to avoid, e.g., a climate change.

RECOVERABLE BIOMASS RESIDUES

Energy Statistics Yearbook 1989 Forest Product yearbook 1989

Forestry residues:- "total cut" = 1.67 * roundwood production- site of cutting: 40 % of "total cut"- mills: 50 % of "industrial roundwood"- residues from fuelwood and charcoal: 40 of "total cut"

ENERGY CONTENT OF HARVESTABLE

RESIDUESAgricultural crop residues

Forestry residues

Recoverable residues:25 % of potentially harvestable residues

Figure 15. Recoverable biomass residues, basis of estimate [46J.

RECOVERABLE BIOMASS RESIDUES

Potential Supplies of Biomass for Energy, EJ/a Mtoe/a

EUROPE ex-USSR AFRICAUS/CANADA OCEANIA LATIN AMERICA ASIA incl. CHINA

□ Crop residues ■ Forestry residues

Figure 16. Potential supplies of recoverable biomass [46].

45

POTENTIAL SUSTAINABLE SUPPLY OF BIOMASS FOR ENERGY

Potential Supplies of Biomass for Energy, EJ/a ~ Mtoe/a

EUROPE ex-USSR AFRICA OTHER ASIAUS/CANADA OCEANIA LATIN AMERICA CHINA

■ Plantations D Crop residues ■ Forestry residues

Figure 17. Potential sustainable supply of biomass for energy [49].

7.3 Electricity demand and biomass supply scenarios

Scenarios and forecasts concerning the development of the global demand of electricity and direct fuel use and the role of renewable energy in this, presented in this report, are mainly based on studies by Johansson et al. [50] and Hislop & Hall [49].

The forecasts of electricity consumption were prepared by the Response Strategies Working Group of the Intergovernmental Panel of Climate Change (IPCC) and are based on four demand scenarios, developed to show the effects of different energy and energy related policies in global C02 emissions. General assumptions for OECD coun­tries are a slow energy demand, population and economic growth, but a more rapid grow of electricity demand. In newly industrialised and developing countries the energy and electricity demand is rising more rapidly, but the economic growth is constrained by limited power supplies. The most conservative scenario, the Accelerated Policies Sce­nario, assumes a high rate of energy efficiency improvement, an emphasis on non-fossil (solar and nuclear) technologies in the first half of the 21st century, and a concentration of total greenhouse gases kept below a doubling of pre-industrial levels throughout the 21st century. This scenario predicts a doubling of the world population between 1985 and 2050. The world electricity demand is projected to increase between 1985 and 2025 by 135% (from 8 432 TWh/y to 19 861 TWh/y), and between 1985 and 2050 by 265% (from 8 432 TWh/y to 30 750 TWh/y).

46

To estimate the future market for biomass-based power production two fuel supply sce­narios have been developed by Hislop & Hall [49] and Johansson et al. [50] The first, the Renewable Intensive Global Energy Scenario (RIGES) represents a policy stance heavily based on renewables which leads to an extensive use of biomass residues and the establishment of energy plantations. It requires a radical, global extension of present policies to very large-scale reforestation and to conversion of large areas of degraded marginal land to energy plantations. The RIGES scenario was designed to satisfy the energy demands of the Accelerated Policies scenario of IPCC.

The second scenario, the Existing Policies Scenario (EPS), is a more conservative ap­proach that assumes less ambitious measures based on an extension of current policies. This scenario was derived by taking the biomass resource used for the RIGES scenario and limiting it to what seems realistic given no radical changes to policies already pre­vailing in several regions of the world. It assumes that globally 80% of sugar cane and kraft pulp residues are used except in Africa, where the available resources are only 10% because of political instability. For other residues, 5% of the potential in Africa, 10% in Centrally Planned Europe and 40% in the remaining countries are used. For en­ergy plantations it includes 50% of the potential for US and OECD Europe, where there are highly developed approaches to reforestation and restoration of marginal and set- aside land, 20% of Latin American potential, 10% of that in Centrally Planned Asia and only 5% of the African potential.

The methodology used in deriving the two scenarios for the total biomass supply for energy for the years 2025 and 2050 is summarised in Figure 18. The potential supplies of biomass for energy according to the RIGES scenario are presented in Figures 19 (year 2025) and 20 (year 2050).

By comparing Figures 16, 17, 19 and 20, describing present and future global biomass resources, it seems clear that the largest present biomass supply potential is found in plantations and that the most significant growth of available biomass resources can in the future be found in the developing countries. Regardless of the uncertainties involved in the projected scenarios, it can be concluded that the potential sustainable supply of biomass is huge.

The World Energy Council's International Energy Data Report 1992 [51] includes Na­tional Energy Data Profiles from some 50 WEC Member Committees. In developing the national profiles WEC has striven to harmonise the definitions and reporting techniques, which should result in a better comparability of national energy data. The report pres­ents energy data from 1970 forward and also gives a forecast for 2005 or 2010. The primary energy production from "other” indigenous resources (excluding fossil, nuclear and hydro), in most national profiles defined as wood, pulping liquors, industrial and municipal wastes, peat, bagasse, alcohol fuels, charcoal, etc., are presented for some non-European and European countries in Figures 21 and 22. The countries showing a

47

POTENTIAL MARKETS FOR EfB SYSTEMS, SCENARIOS FOR 2025 AND 2050

FAO statistics

Existing Policies Scenario CEPS')- no radical changes to policies- residues and plantations crops showing lowest risk and highest returns will be used (10-80 % of RIGES supply depending on region and fuel)

Population & product!tity growth

ELECTRICITY (DEMAND SCENARIO ]

IPCC/APS

Intergovernmental Panel on Climat Change (IPCC) Accelerated Policies Scenario (APS):- high economic growth- energy-efficient technologies- emphasis on non-fossil fuels (solar, nuclear)- electricity cosumption increase 265 % 1985 > 2050

Cost funtions

Renewable IntensiveGlobal Energy Scenario(RIGES):

large scale reforestation conversion of large

areas of degraded and marginal land to energy plantations - utilisation of all sustanably and econimically available residues and plantations

Figure 18. Potential biomass supply and markets for energy from biomass systems, sce­narios for 2025 and 2050 [49, 50].

TOTAL BIOMASS SUPPLIES FOR ENERGY RIGES scenario 2025

Potential Supplies of Biomass for Energy, EJ/a Mtoe/a

706050403020100

17501500

EUROPE ex-USSR AFRICA OTHER ASIAUS/CANADA OCEANIA LATIN AMERICA CHINA

Industrialised Developing

------------- 44Jt--------------------------------------

Plantation Crop Forestry □ Fuelwood/charcoal Dung □ Urban

refuse

Figure 19. Total biomass supplies for energy, RIGES scenario 2025 [50].

48

TOTAL BIOMASS SUPPLIES FOR ENERGY RIGES scenario 2050

Potential Supplies of Biomass for Energy, EJ/a70

~ Mtoe/a

605040302010

0

Industrialised

18,5 18,3

EUROPE ex-USSRUS/CANADA OCEANIA

-64£-

Developing

-4376-

~zjj|

AFRICA OTHER ASIA

17501500

1250

1000750

500

2500

LATIN AMERICA CHINA

Plantation Crop Forestry D Fuelwood/charcoal Dung n Urban

refuse

Figure 20. Total biomass supplies for energy, RIGES scenario 2050 [50].

PRIMARY ENERGY PRODUCTION

Energy production [ Mtoe/a ]

200

150

100

50

0

161

i1 !

United States Brazil Mexico Canada Thailand Australia

■ 1990 E3 2005-2010

Figure 21. Primary energy production from indigenous resources, selected non- European countries [51].

49

PRIMARY ENERGY PRODUCTION

Sweden Finland France Germany Italy Poland Spain

■ 1990 ■ 2005-2010

Figure 22. Primary energy production from indigenous resources, selected European countries [51].

high utilisation of renewable fuels or a significant increase of utilisation were selected for this presentation. Data on, i.a., Indonesia and Malaysia are unfortunately not avail­able.

The WEC data estimates a rapid growth in the use of renewables for energy production in USA and Brazil, and in the European countries Germany, Italy, Poland and Spain. This projection shows a much more conservative potential than the estimates presented before by Johanson et. al. [50] and Hislop & Hall [49], based on merely potential sup­plies of biomass for energy.

7.4 Biomass-based electricity production scenario

Renewables can play a major role in the global energy economy in the decades ahead. In the global energy demand scenario adopted for the construction of the RIGES scenario [50], global electricity production would more than double by 2025, and more than tri­ple by 2050. The share of renewable energy generation would increase from 20% in 1985 (mostly hydroelectric power) to about 60% in 2025, with roughly comparable contributions from hydropower, intermittent renewables (wind and direct solar power) and biomass (Figure 23). In 2050 the contributions of intermittent renewables and gas is estimated to be more than 30%, respectively.

50

ELECTRICITY GENERATIONfor the RIGES scenario

Electricity generation, TWh/a40000

30000

20000

10000

0

Year

Figure 23. Electricity generation for the Renewable-Intensive Global Energy Scenario

Hislop & Hall [49] have also considered long-term opportunities for electricity from biomass. They have looked at different sizes of plants likely needed in different sectors of industry, region and type of biomass. The fuel supply scenarios mentioned above, EPS and RIGES, are considered. The electricity demand is assumed to develop accord­ing to the Accelerated Policies Scenario. The logic of estimation is described in the lower part of Figure 18. Hislop and Hall concluded that the potential market for power from biomass under the EPS scenario is 207 GW and under the RIGES scenario 455 GW in 2025 and 687 GW in 2050.

As any dramatic change in the global energy policy is unlikely to occur in the near fu­ture, resulting in vast investments in energy plantations especially in developing coun­tries, it seems rather improbable that the RIGES scenario could be realised as early as 2025. Therefore only the results of the EPS scenario will be considered here. The power production potential was divided by the authors roughly into three size classes repre­senting small, medium and large scale plants, having an electricity output of 0.5 MWe, 7 MWe and 40 MWe, respectively. The potential scale depends significantly on the re­gion and the type of biomass residue. Residues of pulp and sugar industry are mainly produced in fairly large scale. In the sugar cane sector the authors estimate that most of the plants would be 15 MWe and above, and only 10% of the residues would require 1 -

1985 2025 2050

51

15 MWe plants. In the forestry residue sector the plant size is often limited by high transportation costs to medium-size power production. About 25% of the potential for­estry residue supply is assumed to be affected by these considerations. In the plantation sector the position is more complex. There will be a market for large systems, although it may be difficult to produce enough fuel in densely populated areas (e.g. Europe) to justify plants larger than 10-25 MWe. It is estimated that the medium-size systems account for 15% of the available plantation crop. There will also be a market for smaller on farm systems of 100 kWe to 2 MWe, which would account for 15% of the potential plantation land.

The results for different regions of the world as well as for different types of biomass feedstocks are shown in Figure 24. The potential of medium and large scale power plants estimated according to the EPS scenario for 2025 is shown. According to the same scenario the potential of the smallest plants of 0.5 MWe is enormous, over 10 000 plants, but they are excluded from this presentation due to lack of available low cost and reliable operating technologies. Corresponding numbers for the RIGES scenario show a more than four-fold potential of power plants in the plantation section.

Potential markets for EfB systems under Excisting Policies ScenarioNumber and size of plants (MWe) by 2025

NUMBER OF PLANTS

3000

2500

2000

1500

1000

500

07 MWe

40 MWe40 MWe 7 MWe 40 MWe

7 MWe 40 MWe 7 MWeFEEDSTOCK/SIZE OF PLANT

#0 Europe 3 US/Canada 0 ex-USSR Q Australia/N.Zeala nd |0 Latin America 0 Africa Zj Asda |

Figure 24. Potential markets for EfB systems under EPS scenario [49].

52

The message of these figures is clear: despite the inherited uncertainty of the presented scenarios the potential market for all three sizes of plants is very large indeed.

Probably the most realistic short-term potential for large-scale biomass gasification plants (IGCC) is in the combined heat and electricity production in process industry. In Finland and Sweden and also in North America, the pulp and paper industry has at the same time the need for combined heat and electricity production and there often are large quantities of bark and other wood residues available for energy production. The paper and pulp industry is growing very rapidly in the industrialised parts of Asia. Most of the paper and pulp integrates are claimed to use coal for energy generation and burn­ing the wood waste in piles because the waste is not considered an areal energy source. The lack of the national electricity grid is also a reason for the low utilisation of excess biomass sources for power production. The energy demand of pulp and paper integrates is satisfied mostly by diesel power generation and by burning black liquor and coal.

Several countries like India, Pakistan, Russia and China are known to have large bio­mass resources and are likely to become an important market in the future. However, it was impossible to assess the biomass potential of these countries due to lack of reliable information.

The sugar mills are another industrial field, where the growth in power demand is not matched by the growth in capacity, but low-grade biomass resources, usually residues, are under-used and readily available. According to Figure 24 there is a huge potential in medium and large-scale power production especially in Latin America (mainly in Bra­zil) and Asia. The energy requirement of the sugar industry consists predominantly of power for machinery and of heat for evaporation processes. This energy is currently provided by bagasse. Tops and leaves are also potential biomass resources, but currently not widely utilised.

The role and potential of the sugar cane industry is extensively reviewed in references [52, 53] (the ASEAN region, India) and [54, 55] (global potential). Bagasse is currently combusted in boilers having very low steam values and electricity production efficien­cies, the order of 5% being fairly typical of the boilers of the sugar industry. The elec­tricity yield could be increased to about 15% of the bagasse energy content by replacing the present boilers by high-pressure boilers [52]. The use of IGCC and STIG technology could increase the electricity yield easily up to 30 - 35% depending on the size of the plant and on the design of the power cycle [54, 55]. Larson et al. [24] estimated the total global potential of bagasse-based IGCC/STIG plants at 51.5 GW on the basis of the 1985 global cane production using an electricity yield of 33 % and an annual capacity factor of 75% (corresponding to 1 700 plants of 30 MWe). 54% of this potential is in Latin America and 27% in Asia.

53

The average size of typical sugar mills varies depending on region, age and structure of the industry. In India the mills are old and have a small capacity averaging 2 100 TCD (tonnes of cane per day), in Australia and Brazil the average size is 8 000 TCD, in Indo­nesia 5 000 TCD and in Thailand the relatively new mills have an average capacity of 10 000 - 15 000 TCD. The wet (50%) bagasse residues comprise about 30% of the cane production [53] and, considering a 30% electricity yield easily achievable with gasifica­tion systems, this corresponds to a power production potential of about 20 MWe for the smallest mills up to 80 - 120 MWe for the largest ones.

The prospects for gasification systems in the sugar industry depend heavily on local and regional conditions, infrastructure, availability of a national grid and national price poli­cies. The sugar cane production is not necessarily year-around, which calls for other fuels (such as coal) to be used in power production during off-milling seasons.

7.5 European projections

The European Commission has recently prepared a scenario on European energy to 2020 [56]. Four different scenarios were developed to produce a range of energy futures that could apply in the European Community over the next 25 years. In this presentation only the Conventional Wisdom scenario is referred to. This scenario represents the “business as usual” world, the baseline (traditional) projection, with the current struc­tural social and economical problems and a economic growth that gradually weakens in the long term.

In the Conventional Wisdom world, global energy supply is likely to grow from 8 400 Mtoe in 1990 to about 12 600 Mtoe in 2020, an average annual increase of 1.6%. Natural gas is forecast to be the fastest growing fuel of around 2.7%/year. The supply of solid fuels (mainly coal) will grow in the -developing world and the renewable fuels are forecast to grow by about 2.0 %/year.

The primary energy consumption in the European Community grows slowly in all sce­narios, in the Conventional Wisdom scenario by 0.7%/year between 1995 and 2020 (Figure 25). Natural gas shows the greatest volume increase. Demand will at least dou­ble, mainly for power generation. The renewable energy sources also show a significant growth.

Excepting renewable energies, indigenous energy production of the European Commu­nity will peak and ultimately decline, perhaps by one fifth by 2020 (Figure 26). Domes­tic production of solid fuels will fall substantially to 2020, as oil production is unlikely to show any significant decline before 2000 but will fall thereafter. Gas production is ex­pected to peak a little later, and the rate of decline to 2020 is forecast to be slower. The

54

EUROPEAN COMMUNITY, GROSS ENERGY CONSUMPTION Conventional Wisdom scenario 1990-2020

Energy consumption, Mtoe/a

■ Renewable energy sources

[ | Nuclear

gGasgo,g Solids

1990 1995 2000 2005 2010 2015 2020

Figure 25. EC energy consumption, Conventional Wisdom scenario [56],

EUROPEAN COMMUNITY, PRIMARY PRODUCTION Conventional Wisdom scenario 1990-2020

Primary energy production, Mtoe/a

800

600

400

200

■ Wind, hydro, geoth.800 B Biomass

■ Hydro□ Nuclear

- 600 ■ Gas* O#■ Solids

400

200

0 0 1990 1995 2000 2005 2010 2015 2020

Figure 26. EC primary energy production, Conventional Wisdom scenario [56],

55

Conventional Wisdom Scenario expects the renewable energies more than to double. In a world in which significant social shifts are seen as the solution to environmental problems (Forum scenario) renewable energies progress particularly well to achieve three times present day levels. Also the market-oriented scenario (Hypermarket) denotes a substantial growth in the production renewable energies.

In the final energy demand, the prevailing trend is the growing penetration of electricity. In the Conventional Wisdom Scenario electricity is a fast growing sector with an aver­age projected rate of growth at 1.3%/year in 1995 - 2020. The most significant increase of electric generation capacity can be seen in the natural gas combined-cycle plants, rising from 16 GWe in 1995 to 159 GWe in 2020 (Figure 27).

The biomass industry is one of the emerging new activities. A total of 113 Mtoe of bio­mass will be required in 2020 (Table 16). To this 11 Mtoe of waste should be added. The new uses of biomass are mainly in production of biofuels and in power generation.

GWe 700 ■

600 -

500 -

400 ■

300

200

100

0

Conventional Wisdom Electric Generation Capacity

0 Biomass and Fuel Cells D New CHP■ Clean Coal0 Nat. Gas. Comb. Cycle■ Conventional Thermal■ Nuclear■ Renewables

1995 2020

Figure 27. Increase in electricity generation capacity according to Conventional Wis­dom scenario [56],

Table 16. Biomass uses in Mtoe according to Conventional Wisdom scenario [56].1995 2020

Direct combustion 34.4 40.4Electricity generation 4.6 29.2Biofuel production 0.2 43.3Total 39.2 112.9

56

7.6 European electricity prices

International electricity prices in Europe have been surveyed in reference [57]. The comparison of prices is difficult, because the comparison on the basis of bank exchange rates does not reflect the real situation due to different economic factors and purchasing powers in each country. In Figure 28 the electricity prices (including taxes) are pre­sented for small private users, large private users and industry. It may be concluded that the most significant market potential for biomass fuelled power production exist in countries with high electricity prices, like Italy, Spain, Portugal, Great Britain and Ger­many.

Electricity prices in EuropeJanuary 1995

ECU/kWh

Private user Small; 1700 kWh/a ■

Private user [■ IndustryLarge; 7500 kWh/a 10 MW; 7000 h/a

Figure 28. Electricity prices in Europe [57].

The Conventional Wisdom Scenario of the EC energy report mentioned above predicts, that in general the consumer price of electricity remains stable [56]. However, some of the Member States, like Austria, Italy, Portugal, Spain and Sweden, may experience an increase in electricity prices.

57

7.7 Conclusions

Gasification technology is a key conversion technology in designing global Renewable Intensive Energy Policies for avoiding the climate change caused by the use of fossil fuels. The present sustainable recoverable biomass residues constitute an enormous en­ergy reserve. The largest biomass supply potential compromises the plantations, and the most significant growth of available biomass resources can in the future been found in developing countries.

The most realistic potential of biomass-based power production can be found in pulp and paper industry and in sugar industry. The most potential plant size seems to be in the range 20 - 70 MWe. The potential in sugar industry is even larger than in pulp and paper industry, but the location of this industry in areas of unstable economies and poorly developed infrastructure may hamper investments in new technology.

The potential of small-scale electricity production from biomass is also huge and the concepts based on gasification and diesel engines have prospects for competing with conventional boilers.

The EC energy scenarios forecast that the supply of renewable energies will grow quickly as soon as problems of economics and market acceptability are overcome. Starting from a small base, the share of renewables in world energy is likely to exceed 10% by 2020. Biomass appears to be promising. The 2020 scenarios show a consider­able biomass penetration. Gas is expected to be the fastest growing fuel, notably in the power generation market. The environmental disadvantages of solid fuels are largely responsible for the anticipated decline in coal use in European Community. However, coal remains an important fuel for power production.

58

References

1. Energy statistics 1995. Helsinki: Statistics Finland, 1996. (Energy 1996:1.)

2. Lehtonen, A. Uusi energiaverotus. (New energy taxation). Bioenergia - Bioenergy Research Programme, Newsletter, 1997. No. 1, pp. 8 - 9.

3. Kurkela, E. A review of current activities on biomass and peat gasification in Finland. IEA Thermal Gasification Project Meeting, Espoo, Finland 17 - 20 Sept 1991. Background Report.

4. Kurkela, E. & Sipila, K. Power production from biomass and peat by simplified IGCC processes - research activities in Finland. 10th EPRI Conference on Coal Gasification Power Plants, San Francisco, CA, 16-18 Oct 1991.

5. Kurkela, E. Status of peat and biomass gasification in Finland. Biomass, 1989. Vol. 18, pp. 28-29.

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7. Lyytinen, H. Biomass gasification as a fuel supply for lime kilns: description of recent installations. Tappi Journal, 1987. July, pp. 77 - 80.

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11. Simeil, P., Kurkela, E., Stahlberg, P. & Hepola, J. Catalytic hot gas cleaning of gasification gas. Catalysis Today, 1996. Vol. 27, pp. 55 - 62.

12. Koljonen, J., Kurkela, E. & Wilen, C. Peat-based HTW-plant at Oulu. Biore­source Technology, 1993. Vol. 46, pp. 95 -101.

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13. Kurkela, E., Sipila, K. & Koljonen, J. Synthesis gas production from Finnish peat. In: Klass, D. L. (ed.) Energy from biomass and wastes X. Chicago: Institute of Gas Technology, 1986. Pp. 697 -711.

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21. Wilen, C. & Rautalin, A. Handling and feeding of biomass to pressurized reac­tors: safety engineering. Biomass Technology, 1993. Vol. 46, pp. 77- 85.

22. Rautalin, A. & Wilen, C. Feeding biomass into pressure and related safety engi­neering. Espoo: VTT, 1992. 61 pp. (VTT Research Notes 1428.)

23. Kurkela, E. & Stahlberg, P. Air gasification of peat, wood and brown coal in a pressurised fluidized bed reactor. 1. Carbon conversion, gas yields and tar forma­tion. Fuel Processing Technology, 1992. Vol. 31, pp. 1-21.

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24. Kurkela, E. & Stahlberg, P. Air gasification of peat, wood and brown coal in a pressurised fluidized bed reactor. 2. Nitrogen compounds. Fuel Processing Tech­nology, 1992. Vol. 31, pp. 23 - 32.

25. Kurkela, E., Stahlberg, P. & Laatikainen, J. Pressurized fluidized-bed gasification experiments with wood, peat and coal at VTT in 1991 - 1992. Part 1. Test facili­ties and gasification experiments with sawdust. Espoo: VTT, 1993. 55 p. + app. 2 p. (VTT Publications 161.)

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28. Lappi, M., Kurkela, E., Stahlberg, P. & Leppamaki, E. Sampling and analysing strategies for biomass gasifiers. IEA, Biomass Agreement, Task Report. Espoo: VTT Energy, 1990. Unpublished report.

29. Kurkela, E., Stahlberg, P., Laatikainen, J. & Nieminen, M. Removal of particu­lates and alkali metals from the product gas of a pressurized fluid-bed gasifier. Proc. Energy from Biomass and Wastes XV, Washington, D. C., March 1991. Chicago: IGT, 1991.

30. Kurkela, E., Stahlberg, P., Laatikainen, J. & Nieminen, M. Removal of particu­lates and alkali metals from the product gas of a pressurized fluid-bed gasifier. Proc. International Filtration & Separation Conference Filtech Europa 91, Karlsruhe Oct 1991. Horsham: The Filtration Society, 1991. Pp. 449 - 467.

31. Mojtahedi, W., Kurkela, E. & Nieminen, M. Release of sodium and potassium in pressurized fluidized-bed gasification of peat. J. Inst, of Energy, 1991. Vol. 63, No. 456, pp. 95 - 100.

32. Simell, P., Kurkela, E. & Stahlberg, P. Formation and catalytic decomposition of tars from fluidized-bed gasification. In: Bridgwater, A. V. (ed.) Proc. Conf. Ad­vances in Thermochemical Biomass Conversion, Interlaken, 11-15 May 1992. Vol. 1. Glasgow: Blackie Academic & Professional, 1994. Pp. 265 - 279.

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34. Leppalahti, J. Formation and behaviour of nitrogen compounds in an IGCC proc­ess. Bioresource Technology, 1993. Vol. 46, No 1 - 2, pp. 65 - 70.

35. Solantausta, Y., Makinen, T., Kurkela, E. & McKeough, P. Performance of co­generation gasification combined-cycle power plants employing biomass as fuel. In: Bridgwater, A. V. (ed.) Proc. Conf. Advances in Thermochemical Biomass Conversion, Interlaken, 11-15 May 1992. Vol. 1. Glasgow: Blackie Academic & Professional, 1994. Pp. 476 - 494.

36. Solantausta, Y. & Kurkela, E. Feasibility of electricity production from biomass by gasification systems. Espoo: VTT, 1995. 51 p. (VTT Research Notes 1648.)

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Published by Series title, number and report code of publication

—Vuorimiehentie 5, P.O.Box 2000, FIN-02044 VTT, Finland yTT Tiedotteita 1842 VTT-TTED-1842\m 1 i rnone internal. + 600 y 4bb 1 VII Fax+ 358 9 456 4374 Date Project number

June 1997 N6SU00204Authors) Name of project

Wilen, CarlKurkela, Esa

AIR2-CT94-2284

Commissioned by

VTT Energy, European Commission

Title

Gasification of biomass for energy productionState of technology in Finland and global market perspectives

Abstract

This report reviews the development of the biomass gasification technology in Finland over the last two decades. Information on Finnish biomass resources and use, energy economy and national research policy is provided as background. Global biomass resources and potential energy from biomass markets are also assessed based on available literature, to put the development of the gasification technology into a wider perpective of global biomass utilisation for energy production.The increasing use of biomass and other indigenous forms of energy has been part and parcel of the Finnish energy policy for some twenty years. Biomass and peat account for almost 20% of die production of primary energy in Finland. As the consumption of biofuels is significantly lower than the annual growth or renewal, the use of bioenergy is considered to be an important measure of reducing carbon dioxide emissions.Research and development on thermal gasification of solid fuels was initiated in the late 1970s in Finland. The principal aim was to decrease the dependence of Finnish energy economy on imported oil by increasing the utilisation potential of indigenous fuels. Development in the early 1980s focused on simple atmospheric-pres­sure fuel gas applications including a gasification heat­ing plant. Eight Bioneer updraft gasifiers (abt 5 MW,,,) were constructed in 1982-1986, and a new Bioneer

Activity unit

VTT Energy, Energy Production Technologies, Biologinkuja 3-5, P.CXBox 1601, FIN-02044 VTT, Finland

ISSN and series title

1235-0605 VTT TIEDOTTEITA - MEDDELANDEN - RESEARCH NOTES

ISBN Language951-38-5126-5 English

Class (UDC) Keywords

620.9:621.311.23 gasification, biomass, bioenergy, energy production

Sold by VTT Information ServiceP.O. Box 2000, FIN-02044 VTT, Finland Phone internal. + 358 9 456 4404- Fax + 358 9 456 4374

Pages

64 p.

Price group

B

gasifier was commissioned in eastern Finland in 1996. A Pyroflow circulating fluidised-bed gasifier was also commercialised in the mid-1980s; four gasifiers (15-35 MWy,) were commissioned.In the late 1980s the interest in integrated gasification combined-cycle (IGCC) power plants, based on pressu­rised air gasification of biomass and hot gas cleanup, increased in Finland and in many other countries. The utilisation potential for indigenous fuels is mainly in medium-scale combined heat and electricity production (20-150 MWe). Foster Wheeler Energia Oy, Carbona Inc. and Imatran Voima Oy are the main gasification technology developers in Finland. In 1993, a biomass IGCC demonstration plant based on Foster Wheeler gasification technology and owned by the Swedish utility company Sydkraft was commissioned in Sweden. The plant is the first combined-cycle plant for generating electricity from fuel gas produced entirely from bio­mass.Atmospheric-pressure gasification of biomass fuels is a simpler and cheaper technology than pressurised gasifi­cation. Co-combustion is a promising new alternative, in which the biomass gasification is integrated to a pul­verised coal-fired boiler. The concept will be demon­strated by Foster Wheeler Energia Oy and a municipal power company.