Small-scale biomass CHP technologies Situation in Finland, Denmark and Sweden

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European Commission (Directorate-General for Energy and Transport) Contract no. NNE5/2002/52: OPET CHP/DH Cluster

Small-scale biomass CHP

technologies

Situation in Finland, Denmark and

Sweden

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Author(s): Miikka Kirjavainen (VTT), Kari Sipilä (VTT), Tuula Savola (HUT), Marianne Salomón (Royal Institute of Technology, Sweden), Eija Alakangas (VTT)

Organisation: VTT Processes

Address: P.O. Box 1601, FIN-02044 VTT (Biologinkuja 5, Espoo) Tel.: +358-9-4561

Fax: +358-9-456 5005

E-mail: Contact [email protected] or [email protected] Web: www.vtt.fi (report available at www.opet-chp.net)

Cover photos: Left Ristiina CHP plant (Kvaerner Power Oy) and Vilppula CHP (Wärtsilä Biopower)

The project "OPET CHP/DH Cluster" has obtained financial support from the European Commission (Directorate-General for Energy and Transport) under the contract no. NNE5/2002/52 for Community Activities in the Field of the specific programme for RTD and demonstration on "Energy, Environment and Sustainable Development - Part B: Energy programme"

The responsibility for the content on this publication lies solely with the authors. The content does not necessarily represent the opinion of the European Community and the Community is not responsible for any use that might be made of data appearing herein.

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Small-scale biomass CHP technologies

Situation in Finland, Denmark and Sweden

OPET Report 12

Miikka Kirjavainen, Kari Sipilä & Eija Alakangas VTT Processes

Tuula Savola

Helsinki University of Technology Marianne Salomón

Royal Institute of Technology, Sweden

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Preface

This study is a part of a three-year research project ”Small scale biomass CHP and district heat”. The project is coordinated by the Finnish District Heat Association (SKY) and is funded by the National Technology Agency (Tekes) and several Finnish companies. The aim of the project is to find improved solutions for small-scale biomass CHP production.

This report is a final report of a subproject ”State-of-the-Art small scale CHP Technologies” and describes the main technical solutions for small scale biomass CHP in Finland, Sweden and Denmark. The purpose of this subproject was to identify the best available technologies currently used.

The scope of the study was chosen to include present biomass CHP technologies with electric power output between 1 – 20 MWe. Also included is a narrow review of emerging technologies that have not yet reached commercial and technical maturity. However, a detailed analysis of gasification technologies was excluded from this study. This subproject was carried out by Technical Research Centre of Finland (VTT) and Helsinki University of Technology (HUT). Mr Miikka Kirjavainen from VTT Processes was responsible for the review of the Finnish situation. Mr Kari Sipilä from VTT Processes wrote the analysis of CHP potential in Finland. Ms Tuula Savola from the Helsinki University of Technology, Laboratory of Energy Engineering and Environmental Protection wrote the review of the situation in Sweden and Denmark in cooperation with Ms Marianne Salomón from Royal Institute of Technology (Sweden). OPET CHP/DHC is the main dissemination source of this report. Ms Eija Alakangas from VTT Processes has edited the report for OPET CHP/DH publication. Report is available on OPET CHP-website at www.opet-chp.net as pdf-file.

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1. Small scale biomass CHP technologies

1.1 General

The main technology for small scale CHP production continues to be the Rankine cycle. New technologies like gasification of biomass, stirling engines and organic rankine cycle (ORC) are being developed but most of those have yet to reach the technical and commercial maturity.

Due to economic reasons, small scale CHP plants are often simplified and pre-engineered modular units. Annual operating hours typically vary between 4000 – 5000 h, most of which is on partial load. Small physical size of the plant, fast delivery (8 – 20 months) and the general uncertainty in the energy market all work in favour of a simplified, cheaper plant and therefore advanced process alternatives like feedwater preheating in several stages is usually not applied as the small increase in efficiency would not compensate the increased cost of the plant.

1.2 Combustion technologies

1.2.1 Grate combustion

Grate combustion is the traditional technology for burning solid fuels. Grates are still widely used for both hot water boilers and steam production in small scale plants. Grates are less tolerant for fuel quality variations than fluidised bed boilers but they have been able to compete with modern combustion technologies due to continuous research and development.

The new improved grate firing technologies make it possible to burn very wet fuels like sawdust and bark residue. With simple construction, grate firing can offer a competitive alternative in the small scale. In Finland, companies like Wärtsilä Biopower and Thermia Oy have developed new competitive grate boiler types. Especially the underfeed rotating grate boiler developed by Wärtsilät has proved to be successful.

1.2.2 Fluidised bed combustion

Fluidised bed combustion technologies have been developed since the late 60’s. The first concepts were based on bubbling fluidised beds (BFB) and the development of

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circulating fluidised bed (CFB) technology started in early 70’s. Finnish boiler suppliers Foster Wheeler and Kvaerner are among the leading companies in the world.

Fluidised bed combustion has mainly been used in recent CHP plants with the exception of a few small (<3 MWe) plants. Also a number of old grate-fired boilers or recovery boilers have been converted to fluidised bed boilers. The BFB boiler type is considered to be a better option for small-scale plants due to its simplifier construction and therefore lower investment. The new enhanced CFB technologies, Foster Wheeler Compact and Kvaerner Cymic offer an alternative for low-grade fuels and different wastes. In Finland, however, the Kuhmo power plant is the only small scale biomass CHP plant utilizing a CFB boiler.

1.2.3 Gasification

Gasification technologies for biomass CHP production have been researched intensively. However, few of these have been demonstrated in the small scale. A pilot plant of 6 MWe demonstrating IGCC (Integrated Gasification Combined Cycle) technology has been built in Värnamo, Sweden, but it is currently out of operation. Generally IGCC technology is more suitable in larger scale (over 50 MWe) due to the complexity of the plant and therefore high specific investment costs.

Entimos Oy has built a pilot plant and first commercial application of their patented biomass gasifier in the town of Tervola. There are some problems left but the concept looks promising. The Tervola plant is described in more detail in chapter 4.1.

A detailed analysis of gasification technologies was not included in the scope of this study. OPET Finland has published earlier review of gasification technology in Finland. An estimation of the suitability of different gasification technologies for different power plant sizes is presented in figure 1.

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Fixed-bed gasifier + microturbine Fixed-bed gasifier + Stirling engine Fixed-bed gasifier + gas / diesel engine

Fixed-bed gasifier + steam cycle

Atmospheric-pressure gasifier + indirect gas turbine cycles

Fixed/fluidised-bed gasifier & co-firing in natural gas engines

Fluidised-bed gasifier connected to existing coal- or oil-fired boilers Gasification + fuel cell +

gas turbine and/or steam cycle

Simplified IGCC based on pressurised gasification

Long-term

Power, MW

0.1 1 5 10 50 100 200

2000

Power production from biomass

Gasification-based systems for different size classes

Figure 1. Gasification technologies for different power plant size classes.

1.2.4 Internal combustion engines

Both Otto and Diesel engines are widely utilised for CHP production. ICE based power plants have a relatively low specific investment cost and the construction time of a plant is short. Other advantages are flexible operation parameters like fast start-up and shutdown times, high efficiency on partial loads, relatively easy maintenance and often also multi-fuel capability.

ICE’s can use a wide variety of fuels, including gaseous and liquid bio- and fossil fuels. Possible biofuels include biogas from waste treatment plants and landfills or from gasification of waste or biomass, and pyrolysis oil. More research is still needed regarding the fuel properties and modification of the ICE’s as the currently available ICE models are typically optimized for natural gas or oil.

1.2.5 Steam engines

The steam engine is the traditional technology in using steam for electrical or mechanical power production. In electricity produnction, steam engines have largely

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been replaced by the more effective steam turbines. Recently, however, steam engine based plants have been built to utilize locally some low-greed biofuels. High degree of superheating is not necessary or even desirable. therefor resulting in small size and competitive overall economy of the plant.

The main drawback of steam engines is the low power-to-heat ratio. Swedish company Ranotor have announced plans to increase the ratio up to 0.3 – 0.35 but the recently built steam motor based CHP plants have power-to-heat ratios as low as 0.1 – 0.15.

1.3 Technologies under R&D

1.3.1 Stirling engine

Research concerning Stirling engines is carried out more in Denmark and in Sweden than in Finland. Equipment suppliers have announced plans to increase the available plant sizes up to several hundred kWe:s but so far the commercially available units have been very small, typically under 100 kWe. A figure of a Stirling engine power plant is shown in figure 2. Chimney District heating Stirling engine T=80 CO T=60 CO T=1200 CO T=600 CO T=764 CO Air preheater Secondary air Primary air

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1.3.2 Organic Rankine Cycle

Organic Rankine Cycle (ORC) process is based on using an organic fluid like toluene instead of water as a working fluid in a rankine process. Lappeenranta University of Technology have been researching the ORC process and feasibility studies have been carried out to integrate an ORC plant with a natural gas fired engine power plant. However, no commercial applications of ORC processes have been announced yet. A figure of an ORC process is shown in figure 3.

Turbine Generator Condenser Cooler Pre feedpump Main feedpump Recuperator Fluegas Heat exhanger Frequency inverter

Figure 3. ORC process.

1.3.3 Air Bottoming Cycle

Air Bottoming Cycle (ABC) process is a combined cycle where the heat of exhaust gases from a gas turbine is used as heat source for another turbine. This arrangement increases the electric output by some 25% as well as reduces the CO2 and NOx emissions by 25% compared with a single gas turbine. The main drawback of the ABC process is the high cost of the plant. The use of high-speed technology in order to cut the investment costs is under further research.

1.3.4 Evaporative gas turbine

In an evaporative gas turbine (EvGT) process, water is added into the GT cycle in a humidifier before combustion. The main components of an EvGT plant are a gas turbine, humidifier, recuperator and a flue gas condenser. The cost of electricity

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production in an EvGT plant is estimated to be about 30% less than in a conventional combined cycle, as the expensive steam turbine, steam condenser and related accessories and pipings are not needed.

A 600 kWe pilot EvGT plant using natural gas as fuel has been built in Lund Tekniska Högskolan. The plant has an electrical efficiency of about 55% and overall efficiency of 94%. The EvGT process is estimated to be commercially available by 2010.

1.3.5 Externally fired gas turbine

Externally fired gas turbine (EFGT) is a gas turbine where the combustion chamber is replaced by a heat exchanger. The combustion takes place in f.ex. an external CFB boiler and therefore the working fluid of the EFGT is entirely clean, thus resulting in radically reduced risk of GT blade corrosion.

Some coal-fired EFGT plants are already in operation, but generally more research is needed especially regarding the use of heat exchangers in high temperatures. EFGT technology is estimated to be commercially available for small-scale applications by 2010.

1.3.6 Pulverized wood-fired gas turbine

The pulverized wood-fired gas turbine (PWFGT) uses wood powder as fuel for a gas turbine. The main problems of this technology are corrosion, erosion and incrustation in the gas turbine blades. Research regarding this technology is carried out at least in Luleå Tekniska Högskolan in Sweden and by Bioten company in the USA. A pilot plant of 3 MWe has already been built in Luleå, and it is expected this technology would reach commercial stage by 2010.

1.3.7 Powdered fuel combustion engine

The use of wood powder as fuel for a diesel engine has been researched in Sweden. The first tests however have not been encouraging as the combustion chamber of the tested unmodified diesel engine melted after just 28 hours of test runs. Ceramic cylinder components and other modifications of the engine would be needed before this technology could break through.

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2. CHP potential in Finland

2.1 CHP potential including all fuels

CHP (Combined Heat and Power production) has long traditions in Finland. First CHP plants were built in 1960s and big coal and peat fired CHP plants were built in 1970s. Building of CHP plants were based on large enough district heating activities in towns, where CHP plants are locating.

In 2000 there were 48 places in Finland, which have CHP production connected to DH-network. The total capacity was 4128 MW electricity and 5671 MW heat. The capital Helsinki of Finland has the biggest CHP capacity 1017 MW in electricity and 1300 MW in heat. CHP plants produce about 76 % of Finnish district heating energy.

CHP extra potential in Finland has been evaluated to be 941 MW of electricity and 1670 MW of heat with 6000 hours annual peak load time based on district heat energy consumption in 2000. The CHP potential is evaluated to be 3685 MW electricity and 5020 MW heat with 2000 hours annual peak load time. The total amount of possible CHP units is 194 divided in seven categories. The deviation of the amount of CHP units is shown in figure 4 categorised by the unit size.

Figure 4. Number of the extra potential CHP plants in Finland.

In evaluating the CHP potential CHP plants have to be able to drive 6 000 h/a or 2 000 h/a based on heat load in 2000. The same principle is used in those places, where CHP production already exists. The potential of the heat capacity is evaluated based on the rest of heat load after CHP production already existing. The share of existed CHP production can not be more than 80% of total annual heat demand.

MINI CHP POTENTIAL IN FINLAND

33 82 36 25 11 5 ₂ 0 20 40 60 80 100 1 THERMAL OUTPUT NU M B E R O F P O W E R P L ANT S <=1 MW 1-5 MW 5-10 MW 10-20 MW 20-40 MW 40-80 MW > 80 MW

Total amount = 194 tpeak= 6000 h/a

MINI CHP POTENTIAL IN FINLAND

9 40 42 51 25 15 ₁₂ 0 10 20 30 40 50 60 1 THERMAL OUTPUT NU M B E R O F P O W E R P L A N T S <=1 MW 1-5 MW 5-10 MW 10-20 MW 20-40 MW 40-80 MW > 80 MW Total amount = 194 tpeak= 2000 h/a

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The potential capacity of CHP is calculated based on the power to heat ratio (black line) shown in figure 5. Maximum and minimum of the power to heat ratio are shown also base on today's technology. Potential capacity of CHP plants is shown in figure 6 divided in seven categories.

POWER TO HEAT RATIO OF CHP PLANT

0,0 0,2 0,4 0,6 0,8 1,0 1,2 <=1 1-5 5-10 10-20 20-40 40-80 > 80 THERMAL OUTPUT OF CHP [MW] P O W E R T O HE AT RA T IO ( P /Q minimum maximum

Figure 5. Power to heat ratio of CHP plant as a function of heat capacity.

a) b)

Figure 6. CHP potential categorised in thermal output of the plants. MINI CHP POTENTIAL IN FINLAND

17 22 9 22 8 33 1 30 4 29 7 264 3 80 87 13 2 ₁₅₂ 223 264

0

100

200

300

400

<=1 1-5 5-10 10-20 20-40 40-80 > 80 THERMAL OUTPUT [MW] CA P A C IT Y [ M W

] Thermal capacity_{Power capacity}

Total capacity: electricity 941 MW, heat 1670 MW tpeak= 6000 h/a

MINI CHP POTENTIAL IN FINLAND

4 10 8 338 748 762 848 2202 1 38 128 299 381 636 2202 0 500 1000 1500 2000 2500 <=1 1-5 5-10 10-20 20-40 40-80 > 80 THERMAL OUTPUT [MW] CAP ACI T Y [ M W ] Thermal capacity Power capacity

Total capacity: electricity 3685 MW, heat 5010 MW tpeak= 2000 h/a

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2.2 CHP potential including bio fuels, peat and natural gas

CHP potential has been evaluated to be 611 MW of electricity and 1044 MW of heat with 6000 hours of annual peak load time based on district heat energy consumption produced on bio fuel, peat and natural gas in 2000. The CHP potential is evaluated to be 3685 MW electricity and 5010 MW heat with 2000 hours of annual peak load time. The total amount of possible CHP units is 116. If the peat fuel is not included, the amount of CHP plants is 85 and total heat capacity is 481 MWe/822 MWth. The deviation of the amount of CHP units is shown in figure 7 categorised by the unit size. The fuels are presented in table 1.

MINI CHP POTENTIAL IN FINLAND

Fuel: jtu, ptu, mka,popu,tept, bio, kipa

13 56 23 13 5 4 1 0 10 20 30 40 50 60 1 THERMAL OUTPUT NUM BE R O F C H P P L ANT S ] <=1 MW 1-5 MW 5-10 MW 10-20 MW 20-40 MW 40-80 MW > 80 MW

Total amount = 116 tpeak=6000 h/a

a) b)

Figure 7. Number of the potential CHP plants using bio fuels, peat or natural gas in

Finland.

Table 1. Acronyms for fuels.

Fuels

jtu milled peat

ptu sod peat

mka natural gas

popu forest fuel

tept industrial wood waste pjät wood industrial liquid waste

bio biogas

kipa renewable fuel

We see that 91% of potential CHP plants exist in category less than 20 MW of thermal effect, if 6 000 h/a of peak load demand is required. The range 1 – 5 MW covers the

MINI CHP POTENTIAL IN FINLAND

Fuel: jtu, ptu, mka,popu,tept, bio, kipa

4 20 26 36 15 6 8 0 5 10 15 20 25 30 35 40 1 THERMAL OUTPUT N U MB E R O F C H P PL A N T S ] <=1 MW 1-5 MW 5-10 MW 10-20 MW 20-40 MW 40-80 MW > 80 MW

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most part of the CHP amount having proportion of 48%. Correspondingly the proportion in the thermal size of 20 MW or less is 74%, if 2 000 h/a peak load time is demanded including biggest proportion of 31% in the category of 10 – 20 MW.

The potential capacity of CHP is calculated based on the power to heat ratio shown in figure 5. Potential capacity of CHP plant is shown in figure 8 divided in seven categories. CHP plants need gas or gasified fuels in power to heat ratio ranges over 40 MW.

MINI CHP POTENTIAL IN FINLAND Fuel: jtu, ptu, mka,popu,tept, bio, kipa

8 160 14 6 165 15 0 231 18 3 2 56 55 66 75 174 18 3 0 50 100 150 200 250 <=1 1-5 5-10 10-20 20-40 40-80 > 80 THERMAL OUTPUT [MW] CA P ACI T Y [ M W ] Thermal capacity Power capacity

Total: electricity 611 MW, heat 1044 MW tpeak= 6000 h/a

a) b)

Figure 8. CHP potential categorised in thermal output of the CHP plants, if bio fuels, peat or natural gas is used.

2.3 CHP potential including only biofuels

CHP potential has been evaluated to be 80 MW of electricity and 214 MW of heat with 6000 hours of annual peak load time based on district heat energy consumption produced on bio fuel in 2000. The CHP potential is evaluated to be 293 MW electricity and 641 MW heat with 2000 hours of annual peak load time. The total amount of possible CHP units is 51. The deviation of the amount of CHP units is shown in figure 9 categorised by the unit size.

We see that 90% of potential CHP plants exist in category less than 10 MW of thermal effect, if 6000 h/a of peak load demand is required. The range 1-5 MW covers the most part of the CHP amount having proportion of 53%. Correspondingly the proportion in the thermal size of 20 MW or less is 82%, if 2000 h/a peak load time is demanded including biggest proportion of 31% in the category of 10 – 20 MW.

MINI CHP POTENTIAL IN FINLAND Fuel: jtu, ptu, mka,popu,tept, bio, kipa

2 64 210 514 449 326 156 6 0 22 80 206 225 245 156 6 0 200 400 600 800 1000 1200 1400 1600 1800 <=1 1-5 5-10 10-20 20-40 40-80 > 80 THERMAL OUTPUT [MW] CAP AC IT Y [ M W ] Thermal capacity Power capacity

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a) b)

Figure 9. Number of the potential CHP plants using bio fuels in Finland.

The potential capacity of CHP is calculated based on the power to heat ratio shown in figure 5. The potential capacity of CHP plants is shown in figure 10 divided in seven categories.

a) b)

Figure 10. CHP potential categorised in thermal output of the CHP plants, if biofuel are used.

The potential capacity of biofuel CHP is located on Finnish map in figures 11 and 12. The total demand of fuel is about 2 TWh, when peak load time is 6 000 or 2 000 hours a year. Difference of the estimated fuel production and existing demand in 2010 before those extra CHP installations has been evaluated also in figure 11 (the column on the right side). The four columns from the left side are number of new CHP plants, heat

MINI CHP POTENTIAL IN FINLAND

Fuel: popu,tept, bio, kipa

8 27 11 5 0 0 0 0 5 10 15 20 25 30 1 THERMAL OUTPUT NU M B E R O F CHP P L ANT S ] <=1 MW 1-5 MW 5-10 MW 10-20 MW 20-40 MW 40-80 MW > 80 MW

Fuel: popu,tept, bio, kipa

2 14 10 16 8 1 ₀ 0 5 10 15 20 1 THERMAL OUTPUT N U M B E R O F CHP P L ANT S <=1 MW 1-5 MW 5-10 MW 10-20 MW 20-40 MW 40-80 MW > 80 MW

Fuel: popu,tept, bio, kipa

6 73 74 61 0 0 0 1 26 28 ₂₄ 0 0 0 0 10 20 30 40 50 60 70 80 <=1 1-5 5-10 10-20 20-40 40-80 > 80 THERMAL CAPACITY [MW] C A P ACI T Y [ M W ] Thermal capacity Power capacity

Total: electricity 80 MW, heat 214 MW

tpeak= 6000 h/a

MINI CHP POTENTIAL IN FINLAND

Fuel: popu,tept, bio, kipa

2 45 82 22 5 239 48 0 0 16 31 90 11 9 36 0 0 50 100 150 200 250 300 <=1 1-5 5-10 10-20 20-40 40-80 > 80 THERMAL CAPACITY [MW] CA P A C IT Y [ M W

] Thermal capacity_{Power capacity}

Total: electricity 293 MW, heat 641 MW

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production, electricity production and annual fuel demand of the CHP plants. As we can see in figure there are four main areas, where biofuel installations are possible.

1. South Savo, Finnish Karelia North and Kainuu: 10 possible CHP plants with fuel demand of 304 GWh a year when the estimated fuel production will be 38,1 TWh in 2010. Main part of the fuel will be forest fuels.

2. Lapland and Middle Ostrobothnia: 5 possible CHP plants with fuel demand of 163 GWh a year when the estimated fuel production will be 57.8 TWh in 2010. Main part of the fuel will be peat.

3. South coast and Häme-Uusimaa: 8 possible CHP plants with fuel demand of 454 GWh a year when the estimated fuel production will be 1.8 TWh in 2010. Main part of the fuel will be renewables.

4. Ahvenanmaa: 1 possible CHP plant with fuel demand of 300 GWh a year when the estimated fuel production will be 0.5 TWh in 2010. Main part of the fuel will be renewable.

There would be possible to build 24 small-scale CHP plants with total capacity of 136 MWe/306 MWth and annual fuel demand of 1.22 TWh. If district heat energy market will increase 2% a year in those four areas, the market potential after 10 years will be about 22% higher than in 2000.

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Figure 11. Areal potential of bio-CHP production and biofuel resources in Finland. 3 30,2 14,4 0,95 46,70 0 5 10 15 20 25 30 35 40 45 50 LAPLAND nr., MW, 100*GWh Number [kpl] Heat [MW] Electricity [MW] Bio fuel demand [100*GWh] v. 2010 Bio fuel dem.-cons. [100*GWh] 1 9,6 3,7 0,30 0,50 0 2 4 6 8 10 12 AHVENANMAA nr. , M W , 100*G W h 4 82,6 39,7 2,59 -22,20 -40 -20 0 20 40 60 80 100 NORTH POHJANMAA n r., MW , 100*G W h 2 7,6 2,7 0,24 24,40 0 5 10 15 20 25 30 KAINUU nr. , M W , 100*GWh 1 47,8 35,8 1,76 -40,00 -50 -40 -30 -20 -10 0 10 20 30 40 50 60 WEST COAST nr ., MW , 100* GW h 2 22,7 8,9 0,68 11,10 0 5 10 15 20 25 MIDDLE POHJANMAA nr ., M W , 100* G W h 4 40,2 15,8 1,21 -4,20 -10 -5 0 5 10 15 20 25 30 35 40 45 NORTH SAVO n r., M W , 100*G W h 3 35,3 14,0 1,06 -5,30 -10 -5 0 5 10 15 20 25 30 35 40 SOUTH POHJANMAA nr., M W , 100*G W h 4 41,6 16,3 1,25 4,40 0 5 10 15 20 25 30 35 40 45 SOUTH SAVO nr., M W , 1 0 0 *GW h 4 51,7 20,6 1,55 13,30 0 10 20 30 40 50 60 NORTH KARJALA n r. , M W , 100* GWh 2 11,4 4,2 0,35 -15,60 -20 -15 -10 -5 0 5 10 15 PIRKANMAA nr. , M W , 100*GW h 4 50,8 22,6 1,57 -4,40 -10 0 10 20 30 40 50 60 MIDDLE FINLAND n r., M W , 100* GW h 6 108,4 51,7 3,399,00 0 20 40 60 80 100 120 HÄME-UUSIMAA nr ., MW, 100* G W h 7 57,1 22,2 1,72 0,00 0 10 20 30 40 50 60 SOUTH-WEST FINLAND nr ., MW , 100* GW h 2 36,4 17,6 1,15 9,00 0 5 10 15 20 25 30 35 40 SOUTH COAST n r., M W , 100*G W h 2 7,1 2,5 0,22 -26,60 -30 -25 -20 -15 -10 -5 0 5 10 KYMI nr ., MW , 100* GW h

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2.3.1 CHP potential if oil is replaced by biofuel

CHP potential has been evaluated to be 501 MW of electricity and 776 MW of heat based on district heat energy consumption, if production by oil fuel and coal fired heat only boilers could be replaced by biofuels in 2000. Criteria for evaluation are the same as mentioned earlier in this chapter. The total amount of possible CHP units is 61. The deviation of amount of potential CHP plants is shown in figure 13 in seven categories. The capacity of CHP plants is shown in figure 14. The power to heat –ratio is shown in figure 5.

a) b)

Figure 13. Number of the potential CHP plants; if production by oil fuel and coal fuel in coal fired heat only boilers could be replaced by biofuel.

a) b)

Figure 14. CHP potential categorised in thermal output of the plants, if production by oil fuel and coal fuel in coal fired heat only boilers could be replaced by biofuel.

MINI CHP POTENTIAL IN FINLAND

Fuel: kpö,rpö and kihi-heating ==> bio fuel

11 19 12 8 6 3 ₂ 0 5 10 15 20 1 THERMAL OUPUT NUM BE R O F CH P P L ANT S <=1 MW 1-5 MW 5-10 MW 10-20 MW 20-40 MW 40-80 MW > 80 MW

Total amont = 61 tpeak=6000 h/a

Fuel: kpö,rpö and kihi-heating ==> bio fuel

5 50 77 11 4 154 18 5 191 1 18 29 46 77 13 9 191 0 50 100 150 200 250 <=1 1-5 5-10 10-20 20-40 40-80 > 80 THERMAL OUTPUT [MW] CA P A CI T Y [ M W ] Thermal capacity Electric capacity

MINI CHP POTENTIAL IN FINLAND

Fuel: kpö,rpö and kihi-heating ==> bio fuel

3 12 11 13 7 10 5 0 2 4 6 8 10 12 14 1 THERMAL OUPUT N U M BE R O F CH P P L A N T S <=1 MW 1-5 MW 5-10 MW 10-20 MW 20-40 MW 40-80 MW > 80 MW Total amont = 61 tpeak=2000 h/a

Fuel: kpö,rpö and kihi-heating ==> bio fuel

1 29 88 206 208 59 1 745 0 10 34 82 104 44 3 745 0 100 200 300 400 500 600 700 800 <=1 1-5 5-10 10-20 20-40 40-80 > 80 THERMAL OUTPUT [MW] CA PA CI T Y [ M W ] Thermal capacity Electric capacity

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2.3.2 Recapitulate

Summarising of the results is presented in table 2. The real peak load time was in 2000 for electricity 2893 hours and for heat 3627 hours. CHP plants were driven also only in heat production mode passing the turbine. If the annual peak load time is 6000 h, the electricity production increases more than double and heat production 66%. When annual peak load is 2000 h, on the contrary electricity production is 31% and heat production 45% less than it was in 2000.

If peat, bio fuels and natural gas increase CHP capacity the electricity will be increased by 15% and the heat by 18%. Correspondingly production of electricity and heat increases 31%, when the annual peak load is 6000 h. If peak hours is 2000 h/a, the CHP capacity will be increased 57% in electricity and 55% in heat and correspondingly production of electricity will be increased 39% and heat 31%.

If energy production by oil fuel and coal fired heat only boilers will be changed to bio fuel, the capacity will be increased 12% in electricity and 14 % in heat with annual peak load of 6000 hours. Correspondingly the capacity will be increased 35 and 33% with annual peak load of 2000 hours. The production will be increased 25% in electricity and 23% in heat with peak load of 6000 h/a and correspondingly 24 and 18% with 2000 h/a. Together the extra use of biofuel and changing oil fuels to bio fuel used in new CHP units the capacity of CHP could be increased 30% compared to CHP capacity in 2000. The CHP production will be increased 54% with 6000 hours of peak load time. If 2000 hours peak load is required, extra CHP capacity of 90% could be built and production could be increased 55%.

Table 2. Evaluation of extra CHP capacity compared to existing capacity in 2000, if CHP capacity will be installed based on bio fuels and changing oil fired CHP production to biofuel.

CHP energy production

tpeak = 6000 h 2000 h

e 2893 Electricity Heat Electricity Heat OBS. !

h 3617 MW GWh MW GWh MW GWh MW GWh

Existing CHP s 4 128,1 11 944,0 5 670,8 20 512,9 4 128,1 11 944,0 5 670,8 20 512,9tabl4/tabl1, SKY Existing CHP s 4 128,1 24 768,6 5 670,8 34 024,8 4 128,1 8 256,2 5 670,8 11 341,6calculated t peak Extra potential; all fuels 941,3 5 647,9 1 670,1 10 020,7 3 685,2 7 370,5 5 010,3 10 020,7

Extra potential: bio fuels 610,9 3 665,5 1 044,0 6 263,9 2 343,8 4 687,6 3 132,0 6 263,9

Extra pot.: loil,hoil,coal =>bio 500,8 3 005,0 778,8 4 673,1 1 422,8 2 845,6 1 878,3 3 756,7 % incresing compared to basic case

CHPs, changing p.h. time 1,000 2,074 1,000 1,659 1,000 0,691 1,000 0,553calculated t peak Extra potential; all fuels 0,228 0,473 0,295 0,489 0,893 0,617 0,884 0,489

Extra potential: bio fuels 0,148 0,307 0,184 0,305 0,568 0,392 0,552 0,305

Extra pot.: loil,hoil,coal =>bio 0,121 0,252 0,137 0,228 0,345 0,238 0,331 0,183

Two last rows total 0,269 0,558 0,321 0,533 0,912 0,631 0,884 0,489

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3. Overview of small scale biomass CHP plants

in Finland

3.1 General

There are some 40 small CHP plants with electric powers less than 20 MW connected to district heating networks in Finland. Ten of these plants utilize oil or coal as fuel while the others use either natural gas, biomass or peat. During the last 10 years, no new coal or oil fired plants have been built while 10 new biomass plants and several gas fired units have started operation.

Most of the small CHP plants using biomass also use peat as fuel. In some plants, peat is the main fuel and the share of biomass is less than 30%. Table 3 below summarises the recent biofueled CHP plants in Finland.

Table 3. Properties of selected Finnish biomass CHP plants.

Power plant Power output MWe Heat output MWdh Fuel input MWf Electric eff.

Total eff. Power-to-heat ratio Steam values Fuel Technology °C/bar/kgs-1 Tervola 0,47 1,13 2,0 0,24 0,815 0,42

-/-/-wood residue gasification+ gas engine Kiuruvesi 0,9 6 8,1 0,11 0,852 0,15 350/25/2,8 bark, sawdust, wood chips grate+steam engine Karstula 1 10 12,9 0,85 0,850 0,10 350/24/?

bark, sawdust grate+steam engine Kuhmo 4,8 12,9 20,1 0,24 0,881 0,37 490/81/? wood residue CBF Kuusamo 6,1 17,6 27,6 0,22 0,860 0,35 510/61/8

peat, wood chips, sawdust

BFB Kankaanpää 6 17 26,0 0,23 0,885 0,35 510/60/7,9 peat, wood BFB Lieksa 8 22 33,9 0,24 0,885 0,36 510/61/8 peat, wood residue CFB Iisalmi 14,7 30 48,0 0,31 0,931 0,49 515/93/17,5 wood chips, wood residue, REF BFB Forssa 17,2 48 71,7 0,24 0,909 0,36 510/62/22,8 wood chips, wood residue, REF BFB Kokkola 20 50 78,7 0,25 0,890 0,40 482/80/27 peat, wood chips BFB

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The investment costs of the plants vary remarkably depending on the selected technology and on the scale of the delivery if an outside contractor is used (as usually is the case). The Ministry of Trade and Industry (MTI) admit investment subsidies for biofuelled power plants. The upper limit of the subsidy is 25 – 30% of the investment, but typically the subsidy has only amounted 14 – 16% of the total investment. The investment costs and subsidies from MTI are shown in table 4.

Table 4. Cost data of the recent small scale CHP plants in Finland.

Power plant Power output Investment Subsidy Investment Start up year

MWe MEUR MEUR EUR/kWe

Tervola 0,5 1,3 0,3 2720 2002 Kiuruvesi 0,9 5,0 ? 5556 1999 Karstula 1,0 4,7 ? 4709 2000 Kuhmo 4,8 12,4 2,0 2583 1992 Kuusamo 6,1 8,4 1,7 1379 1993 Kankaanpää 6,0 8,1 1,2 1346 1992 Lieksa 8,0 10,1 2,0 1261 1994 Iisalmi 14,7 21,0 2,7 1429 2002 Forssa 17,2 17,1 1,7 994 1996 Kokkola 20,0 26,9 - 1346 2002

3.2 Comparison

Each plant is built for a specific purpose and location, and therefore a generic comparison of the plants may seem unnecessary or misleading. However, in order to choose the most promising CHP concepts for further analysis, it was necessary to compare the plants with each other.

The plants are graded on the basis of power-to-heat ratio, total efficiency, investment cost and an estimate of the technical ”goodness” of the plant. Table 5 below shows the comparison table of the selected power plants. The comparison criteria are explained in more detail in the footnotes of the table.

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Table 5. Comparison of recent small scale biomass CHP plants in Finland.

Power plant Power Heat Overall Power- Startup Invest-output MWe output MWdh eff. to-heat ratio year ment cost MEUR α * Tot.eff.1 invest-ment factor2 technically up-to-date3 Average grade4 Tervola 0,47 1,13 0,815 0,42 2002 1,3 0,34 0,53 3 2,3 Kiuruvesi 0,9 6 0,852 0,15 1999 5,0 0,13 0,56 1,5 1,5 Karstula 1 10 0,850 0,10 2000 4,7 0,09 0,35 2,5 1,8 Kuhmo 4,8 12,9 0,881 0,37 1992 12,4 0,33 0,47 1 1,7 Kuusamo 6,1 17,6 0,860 0,35 1993 8,4 0,30 0,24 0,5 1,8 Kankaanpää 6 17 0,885 0,35 1992 8,1 0,31 0,24 1 2,0 Lieksa 8 22 0,885 0,36 1994 10,1 0,32 0,23 0,5 1,8 Iisalmi 14,7 30 0,931 0,49 2002 21,0 0,46 0,30 2,5 2,8 Forssa 17,2 48 0,909 0,36 1996 17,1 0,33 0,18 2 2,3 Kokkola 20 50 0,890 0,40 2002 26,9 0,36 0,26 2,5 2,5

Estimation of the power plant

1 _{Calculated as (Power to heat -ratio) x (Total efficiency)}

2 _{Calculated as (Total investment) / (2.5 x Power production + 1.1 x Heat production). The coefficients for} power and heat are derived from the mean efficiencies of condensing power plant and heat distribution central respectively.

3 _{Estimated on the basis of start up year (1990-94 : 1 point, 1995-1999 : 2 points, 2000}_→_{: 3 points), the} boiler technology (fluidized bed is the state-of-art technology, grate -0.5 points) and used fuels (is also peat used -0.5 points). Also flue gas condensing is seen as an advantage (+0.5 points).

4_{Average state-of-the-art grade for the power plant from 1 (fair) to 3 (very good). The}_α_{x Tot.eff.}_is graded from 1-3 , so that the α x Tot.eff ratio of 0.20-0.39 is 1 point, 0.30-0.40 gives 2 points and >40 gives 3 points. The investment factor is transferred into grades so that the factor <0.39 gives 3 points, 0.40-0.55 gives 2 points and >0.55 gives 1 point.

As a conclusion, in the smallest scale with electric power near 1 MW, the Tervola power plant is the most interesting case. The problem with the other plants in this size class is the very low power-to-heat ratio, due to low steam values and the use of a cylindral steam engine instead of steam turbine. However, the Tervola plant is the first commercial application of the Entimos gasifier and there still are some unsolved problems (see chapter 4.1).

In the 5 – 10 MW scale, all the Finnish recent CHP plants are relatively old and they get average grades with the grading system applied here. In the larger 10 – 20 MW scale, the new Iisalmi power plant receives the highest grades (investment cost not taken into account).

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4. Descriptions of some biomass CHP plants in

Finland

4.1 Tervola 0.5 MW

e

/1.1 MW

dh

4.1.1 Background

Tervola combined heat and power plant produces electricity and district heat for the municipality of Tervola. The plant produces about 90% of the district heat and about 10% of the electric power needed by Tervola. The electric power of the Tervola plant is less than 1 MWe which was selected for lower limit of the scope of this study. The plant manufacturer Entimos Oy however aims to offer modular packages of 2 MWfuel/0,5 MWe which can be combined to each other.

The Tervola power plant is supplied by a family company Entimos Oy. The gasifier is developed and patented by the Saares family and the Tervola plant is the first commercial application. Previously a pilot plant was built in 1996.

The total investment in the plant was about 1.3 MEUR in 1999-2001, which gives a specific investment of 2 720 EUR/kWe for electric power. The investment decision was made in 1999 and the plant was supposed to be in operation by April 2001. However, there have been some problems with the gas cleaning before the gas engine and the start-up of continuous electric power production has delayed. More research and measurements is needed that developers can start electric power production.

4.1.2 Process description

Using wood residues like bark and sawdust from sawmills as fuels, the plant produces 0.47 MW electricity and 1.13 MW district heat with an overall efficiency of 81.5%. The main components of the plant are a fuel gasifier, a gas engine with a heat recovery unit and a separate gas boiler. The gasifier is a combined counter flow/forward flow process. The dirtier product gas from the counter flow is burned in a separate gas boiler. The cleaner product gas from forward flow is cleaned in cyclones and bag filters before it is burned in a spark-ignited gas engine supplied by Jenbacher AG. The process diagram of the Tervola power plant is shown in figure 15.

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Figure 15. Process diagram of Tervola power plant. Summary: Electricity: 0.47 MWe District heat: 1.13 MWdh Electrical efficiency: 0.25 Power-to-heat ratio: 0.42 Overall efficiency: 81.5%

Fuel input: 2.0 MWfuel

Fuels: wood residue from sawmills

Boiler: gasifier + gas engine (Jenbacher)

Start up year: 2002

4.2 Kiuruvesi, Iisalmen Sahat Oy,

0,9 MW

e

/6 MW

dh

4.2.1 Background

The plant produces electricity for the Kiuruvesi sawmill and district heat for the town of Kiuruvesi. The plant is owned by Iisalmen Sahat Oy and produces about 75% of the electricity needed by a sawmill. The heat is sold to Savon Voima Oy which operates the district heat network in the town of Kiuruvesi. The Kiuruvesi plant was the first Sermet BioPower plant. Year 2000, another quite similar plant was built in the town of Karstula.

The total investment in the power plant was 2.7 MEUR in 1999 which gives an 3000 EUR/kWe specific investment for electric power. The plant started commercial operation in the autumn 1999.

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The plant uses bark, sawdust and forest chips as fuels. The moisture content of the fuel is usually between 50 – 65%. The wet fuel is burned in an underfeed rotating grate fired boiler supplied by Sermet Oy. Steam values after the boiler are 350°C and 24 bar and the live steam flow is 2.8 kg/s. The steam is led into a 6-cylinder engine turbine producing 0.9 MW electric power. After the engine the steam is led to a heat exchanger to produce district heat. Condensed water is then pumped back to the boiler. Currently Wärtsilä Biopower is suppling CHP plants with steam turbine. First plant is in operation in Kiuruvesi town, owned by the energy company Atro Oy, from Kuopio. Further CHP plants have been commissioned at sawmills in Renko and Vilppula in Finland. The production of electricity is 1.3 MWe at the Renko plant and 2.9 MWe at the Vilppula plant.

The process diagram of a new Wärtsilä BioPower plant is shown in figure 16.

Figure 16. Process diagram of Wärtsilä Biopower power plant (2.3 MW electricity).

Summary: Electricity: 0.9 MWe District heat: 6 MWdh Electrical efficiency: 0.11 Power-to-heat ratio: 0.15 Overall efficiency: 85%

Fuels: sawdust, bark, wood chips

Boiler: underfeed rotating grate

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4.3 Kuhmo 4.9 MW

e

/12.9 MW

dh

Kuhmo power plant produces district heat for the town of Kuhmo and process heat for Kuhmo Sawmill. The plant covers about 80 – 90% of the annual district heat demand and about one third of the power need of the town of Kuhmo.

The plant uses industrial wood residues from the nearby sawmill as well as forest chips as fuels. The plan has an electric power of 4.9 MW and district heat power of 12.9 MW. The power plant started commercial operation in 1992.

The boiler was the first Pyroflow Compact circulating fludized bed boiler supplied by Foster Wheeler (Ahlstrom at the time). This boiler type represents the second generation of Pyroflow boilers. After the initial problems with the dust separator, the boiler has performed excellently. mg/MJ CO 26 NOx 56 N2O 3 SO2 5 CxHy 0 Dust 7

The total investment in the power plant was 12,4 MEUR in 1992 which gives a 2540 EUR/kWe specific investment for electric power.

Summary: Electricity: 4.9 MWe District heat: 12.9 MWdh Electrical efficiency: 0.24 Power-to-heat ratio: 0.37 Overall efficiency: 88%

Fuel input: 20 MWfuel

Fuels: sawdust, bark, wood chips

Boiler: circulating fluidised bed

Steam values: 6.3 kg/s, 490°C, 81 bar

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4.4 Kankaanpää, Kankaanpään Kaukolämpö Oy,

6 MW

e

/17 MW

dh

4.4.1 Background

Kankaanpään Kaukolämpö is a joint venture of the town of Kankaanpää and a local electric company Vatajankosken Sähkö Oy. The power plant produces district heat for the town of Kankaanpää and for the nearby garrison of Niinisalo. Kankaanpään Kaukolämpö owns the power plant but Vatajankosken Sähkö Oy has full control of the electric power production. The district heat power of the plant is about 50% of the peak demand and the plant produces about 90% of the annual district heat energy demand. The annual power production is about 22 000 MWh which is about 25% of the electric power consumption of the town of Kankaanpää.

The decision to build the plant was made in July 1990, building work started in June 1991 and the plant started commercial production in September 1992.

The main fuels of the plant are peat and wood. The fuel is burned in a Ahlstrom Termoflow boiler. The live steam flow is 7.9 kg/s in 510°C temperature and 60 bar pressure. After the boiler steam is led into a high speed (12 000 r/min) steam turbine supplied by Blohm&Voss. The turbine has one extraction for the feedwater tank. The generator is a 8 MVA/1500 r/min by ABB Strömberg. The flue gases are cleaned in an electrostatic precipitator.

The total investment in the power plant was 8.4 MEUR in 1992 which gives a 1 346 EUR/kWe specific investment for electric power.

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Summary: Electricity: 6 MWe District heat: 17 MWdh Electrical efficiency: 0.23 Power-to-heat ratio: 0.35 Overall efficiency: 0.885 Fuel input: 26 MW

Fuels: peat, wood chips

Boiler: BFB

Steam values: 7.9 kg/s, 510°C, 60 bar Emission control: electrostatic precipitator

Crew: 1

Start up year: 1992

4.5 Kuusamo, Fortum Oyj, 6.1 MW

e

/17.5 MW

dh

4.5.1 Background

Kuusamo Power Plant produces power and district heat for the town of Kuusamo. The plant is owned by Fortum Oyj and operated by Koillis-Pohjan Sähkö and Kuusamon Vesiosuuskunta. The district heat produced in the plant is sold to Kuusamon Vesiosuuskunta and electric power to Koillis-Pohjan Sähkö Oy. The plant is located on the same site with an older heating plant of Kuusamon Vesiosuuskunta and the plants share a common oil tank and a fuel receiving station.

Normally the plant produces all the district heat needed by the town of Kuusamo. If the need for heating power is higher than the district heat power of the plant, it is possible to run the old heating plant in parallel with the power plant.

The plant was designed and constructed as a turnkey delivery by Fortum Engineering (IVO International Ltd at the time). The project started in September 1992 and the plant started commercial operation in January 1994.

The total investment in the power plant was 8.4 MEUR in 1992 which gives a 1400 EUR/kWe specific investment for electric power. Fortum received an investment subsidy of about 1.7 MEUR (20%) for the building of the plant.

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4.5.2 Process description

The main fuels are peat (both milled and sod peat are used) and wood residues. Heavy fuel oil is used as a backup and start-up fuel.

Milled peat is dryed in a flash dryer which uses hot sand from the BFB boiler as heat source. The dryer is developed and patented by Fortum Oyj. The drying takes place in a vertical tube. The milled peat and sand from the boiler are conveyed through the dryer by circulating steam. After the dryer, peat and sand are separated from the steam and are led back to the boiler. The steam is led to a condenser which is connected to district heat network. The heating power of the fuel dryer is 3.5 MW. Before the dryer, the moist content of the fuel is typically 40 – 60% and after drying 8 – 20%.

Fuel is burned in a bubbling fluidized bed boiler supplied by FosterWheeler. The live steam flow is 8 kg/s, temperature of the superheated steam is 510°C and pressure 61 bar. After the boiler the steam is led into a single case high-speed (12 000 r/s) steam turbine running an 1500 r/s generator. After the turbine is one district heat exchanger and district heat temperatures normally 50/87.5°C. The turbine has one extraction for feedwater tank. The feedwater temperature before the boiler is 105°C. An electrostatic precipitator is used for flue gas cleaning.

Normally the district heating system is used in series so that the main heat exchanger (after the turbine) is first and the heat exchanger of the peat dryer is second. If the need for higher district heat temperature is higher than 95°C, the order of the heat exchangers is changed in order to maximize the electric power output of the plant. Drying section of the plant is not in utilisation currently.

Summary

Electricity: 6.1 MWe

District heat: 17.5 MWdh (21,2 with dryer) Electrical efficiency: 0.22

Power-to-heat ratio: 0.35

Overall efficiency: 86%

Fuel input: 27.6 MW

Fuels: milled peat, sod peat, wood residue

Boiler: bubbling fluidised bed

Steam values: 8 kg/s, 510°C, 61 bar Emission control: electrostatic precipitator

Crew: 1 + 1 daytime

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4.6 Lieksa, Vapo Oy, 8 MW

e

/14 MW

dh

/8 MW

process heat

4.6.1 Background

Lieksa power plant produces electricity and district heat for the Town of Lieksa and process heat for the Vapo Kevätniemi sawmill. The plant is owned and operated by Vapo Oy. The district heat is sold to Lieksan Lämpö Oy and electric power to Lieksan Sähkö Oy. The plant produces about 90% of the district heating energy need of Lieksa and about one third of the electric power supply of Lieksan Sähkö.

The plant was designed and constructed as a turnkey delivery by Fortum Engineering. The contract to build the plant was signed in April 1993 and the plant started commercial operation in November 1994. The total investment in the power plant was 10 MEUR in 1992 which gives a 1260 EUR/kWe specific investment for electric power. An investment aid of about 2 MEUR (20%) for the building of the plant was admitted.

The main fuel of the plant is milled peat. Also wood residues like bark and sawdust from the nearby sawmill are used. The fuel is burned in a Kvaerner (Tampella Power at the time) CYMIC® circulating fluidized bed boiler. The plant was the first commercial application of the CYMIC (Cylindrical Multi-Inlet Cyclone) boiler type. The aim of this boiler type is to combine the benefits of the traditional BFB and CFB boilers: to reach low NOx and SOx emissions with low operating and maintenance costs. An additional benefit is the compact size of the boiler which helps the on-site installation work. Several this type of fluidised bed boiler are in operation in Finland and in Europe.

The fuel power of the boiler is 33.9 MW and steam values after the boiler are 510°C and 61 bar. Live steam flow is 10.5 kg/s. After the boiler the steam is led into a high-speed steam turbine supplied by ABB Lang. The turbine is equipped with one extraction for process heat exchanger and feedwater tank. The process diagram of the Lieksa plant is shown in figure 17.

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Figure 17. Process diagram of Lieksa power plant.

Summary

Electric power: 8 MWe

District heat: 14 MWdh + 8 MW process heat for Kevätniemi sawmill

Electrical efficiency: 24% Power-to-heat ratio: 0.36

Overall efficiency: 88%

Fuel input: 33.9 MW

Fuels: peat (120000 loose m3/a), wood residue (100000 loose m3/a)

Boiler: CYMIC® circulating fluidised bed Steam values: 8 kg/s, 510°C, 61 bar

Emission control: electrostatic precipitator

Startup year: 1994

4.7 Iisalmi, Salmi Voima Oy, 14.7 MW

e

/30 MW

dh

4.7.1 Background

The new Iisalmi power plant will produce electricity to Atro Oy’s (previously Savon Voima Oy) grid and district heat for the Salmi Voima’s district heat network for the

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the Atro Group. The plant was built to replace the old Parkatti heating plant which includes a 15 MWdh fluidized bed boiler using peat and sawdust as well as two boilers using heavy fuel oil as fuel. The old plants will remain as backup boilers for exceptional conditions. The new plant has a fuel power of 48 MW, electric power of 14.7 MW and district heat power of 30 MW. Annual operating time is planned to be about 5000 h, annual power production 60 – 70 GWhe and district heat production 150 – 185 GWhdh. The plant started commercial operation in October 2002.

The total investment in the power plant was 21 MEUR, which gives a 1429 eur/kWe specific investment for electric power. An investment subsidy of 2.7 MEUR (13%) for the building of the plant was granted by MTI.

The plant uses milled peat (70 – 100%), wood based fuels like wood chips, sawdust and bark (0 – 27%) and REF (0 – 3%) as fuels. Light fuel oil is used as start-up and backup fuel. The share of wood based fuels could be increased up to 70% without modifications in the future, availability permitting.

The fuel is burned in a bubbling fluidized bed boiler supplied by FosterWheeler. The live steam flow is 17.5 kg/s, steam temperature 515°C and pressure 93 bar. The steam turbine is a new single casing 2-stage model with double flow district heating tail. This construction results in power to heat –ratio of 0.49 which is considerably higher than usual in this size class. The turbine supplier is B&V Industrietechnik GmBh. Process diagram is presented in figure 18.

Particles are removed with an electrostatic precipitator. The particle emissions will be 25 mg/MJ, SO2 emissions 140 mg/MJ, NOx emissions 150 mg NO2/MJ and CO2 emissions 80 – 113 g/MJ, depending on the fuel mix.

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G TURBINE 190 Co DISTRICT HEAT 30 MW 70/55/70 Co 15 MW Steam 17.3 kg/s, 93 bar/515o_C 120/55/70 Co

Figure18. Process diagram of Iisalmi Plant (Salmi Voima Oy).

Summary: Electricity: 14.7 MWe District heat: 30 MWdh Electrical efficiency: 31% Power-to-heat ratio: 0.49 Overall efficiency: 93%

Fuels: wood chips, sawdust, bark, peat, REF

Steam values: 17.5 kg/s, 513°C, 93 bar Emission control: electrostatic precipitator

Startup year: 2002

4.8 Forssa, Forssan Energia, 17.2 MW

e

/48 MW

dh

4.8.1 Background

Forssa power plant produces electricity and district heat for the town of Forssa. Year 1999 the plant produced 41.2 GWh of electricity, 26.6% of all electricity supply of Forssan Energia, and 147.1 GWh of district heat, which is about 93% of the district heat used in the town. Forssa power plant started commercial operation in October 1996 and it is the first district heating power plant in Finland which is fuelled only by wood biomass.

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The total investment in the power plant was 17.1 MEUR in 1996, which gives a 994 EUR/kWe specific investment for electric power. The investment subsidy received from the Ministry of Trade and Industry was about 1.7 MEUR. The annual maintenance costs are estimated to vary between 50 000 – 67 200 EUR/a.

The relatively low specific cost of the plant were achieved as Forssan Energia themselves acted as contractor, even though Osmo Kaulamo Engineering had an important role in the project. The estimated saving compared to a turnkey delivery was about 20%.

The main fuels used are industrial wood residues (54%) and forest chips (34%). The plant also uses building wastes and some other wood-containing substances as well as REF fuels (4%).

The fuel is burned in a BFB furnace. The live steam flow is 22.8 kg/s, temperature 510°C and pressure 62 bar. After the boiler, live steam is led into a 17.2 MWe back pressure steam turbine. Turbine is equipped with two extractions, one for feedwater tank and one for second district heat exchanger. The process diagram of the plant is shown in figure 19. The use of REF fuels has caused corrosion problems with the boiler and has resulted in yearly need of repair work.

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Summary: Electricity: 17.2 MWe District heat: 48 MWdh Electrical efficiency: 24% Power-to-heat ratio: 0.36 Overall efficiency: 91%

Fuels: wood chips, industrial wood residue, REF

Steam values: 22.8 kg/s, 510°C, 62 bar

Start up year: 1996

4.9 Kokkola, Kokkolan Voima Oy, 20 MW

e

/50 MW

dh

4.9.1 Background

Kokkola power plant produces electricity and district heat for the town of Kokkola. Kokkolan Voima Oy is a member of Pohjolan Voima (PVO) group, but the town of Kokkola owns the series of shares which gives the town full control of all the power and heat produced in the plant.

The plant was planned and built by PVO-Engineering, also part of the PVO Group. The final decision to build the plant was made in early 2000, construction work started during the spring 2000, the boiler and the turbine were installed during spring and summer of 2001, test runs were made in October-November 2001 and the plant has been in commercial operation since December 2001.

The total investment in the plant was about 26.9 MEUR in 2001. The specific investment for electric power is therefore about 1346 EUR/kWe. The town of Kokkola has been a minor shareholder of PVO Group since 1992, and has been self-sufficient with regard to electric power. The new power plant will result in increased power sales to the spot market by the town.

At present, about 60% of the building stock in the town is connected to the district heating network and the annual demand of district heating energy is about 200 GWh. In the near future the share of district heating is expected to rise to 65% which would mean a demand of 280 GWhdh/a. The planned annual operating time for the new power plant is 5000 – 6000 h, of which 4000h will be on partial load.

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4.9.2 Process description

The plant uses wood chips, bark, sawdust and peat (50%) as fuels. According to Juhani Paananen, Energy Manager of Kokkolan Energia, it is technically possible to increase the share of wood based fuels up to 80% if their prices remain competitive.

The fuel is burned in a 70 MWst bubbling fluidised bed boiler supplied by Kvarner Pulping Oy. The live steam flow is 27 kg/s, the temperature of live steam is 482°C and pressure 80 bar. The relatively low live steam temperature was chosen in order to avoid chloride corrosion which would accelerate at temperatures around 500°C. After the boiler live steam is led to a 21 MW back pressure steam turbine supplied by Siemens AG. The turbine is a single case reaction turbine with extractions to feedwater tank, low pressure feedwater preheater and two district heat exchangers.

There is also a heat accumulator with height of 45 m and volume of 3200 m3 and discharge power of 50 MWdh. The accumulator makes it possible to run the plant with full power in daytime when the price of electric power is higher.

The power plant is located near a sulphur acid factory owned by Kemira Chemicals. The hot sulphur acid has previously been cooled with sea water but when the new power plant was built, the cooling process was renovated and equipped with three heat exchangers and connected to the district heating network. The power of the heat recovery system is 15 MWdh and it can be run either in series or in parallel with the power plant. Also a backup boiler of 12 MWdh utilising oil as fuel is installed.

Process diagram of the Kokkola CHP plant including biofuel handling system at plant is shown in figure 20.

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G 20 MWe 4x250 m3 100 m3/h 50 MWDH Turbine Stack KOKKOLAN VOIMA OY Fly ash Bottom ash

Fuel receiving Screening

and crushing Ash

ESP

27 kg/s, 80 bar, 482 Co

Fuel storage at plant

Figure 20. Process diagram of Kokkola CHP plant including biofuel fuel handling system at the plant.

Summary: Electricity: 20 MWe District heat: 50 MWdh Electrical efficiency: 0.25 Power-to-heat ratio: 0.4 Overall efficiency: 89%

Fuels: wood chips, sawdust, bark, peat

Steam values: 27 kg/s, 482°C, 80 bar

Crew: 1

Start up year: 2001

4.10 Recent small scale industrial CHP plants

4.10.1 Savonlinna, Järvi-Suomen Voima Oy

17MWe /33 MWdh/20 MW ph

The new Savonlinna CHP plant will produce 17 MW electric power and 33 MW district heat for the local energy company Suur-Savon Sähkö Oy and 20 MW process heat for

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nearby UPM Schauman Wood Oy plywood mill. The plant is owned by Järvi-Suomen Voima Oy, which is owned by Pohjolan Voima Oy and Suur-Savon Sähkö Oy.

The plant uses mainly wood residues from the plywood factory and other wood processing industry within the area. Other possible fuels are forest chips, peat and HFO.

4.10.2 Ristiina, Järvi-Suomen Voima Oy, 10 MWe/65 MWph

The Ristiina CHP plant produces 10 MWe electric power and 64 MW process steam for the Pellosniemi plywood mill. This plant too is owned by Järvi-Suomen Voima Oy. All the energy produced by the plant is used by the plywood mill.

The plant uses wood residues from the mill as fuels and it replaced the old HFO boilers. The fuels are burned in a BFB boiler supplied by Kvaerner Power Oy. Kvaearner has patented a new sand material which is quartz-free and enables efficient combustion of alkali-rich fuels such as plywood residue.Steam values are: 482°C, 84 bar and 30 kg/s. The plant started commercial operation in May 2002.

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5. Summary of the situation in Finland

Several small scale CHP plants using biomass have been built in Finland during the last ten years. The majority of these plants are based on the conventional rankine process where superheated steam from the boiler is led to a high speed back-pressure steam turbine running a generator through a reduction gear. The only exceptions are the smallest plants with electric powers between 0.5 – 1 MWe. The 0.5 MWe Tervola plant is based on biomass gasification where the biogas is burned in a gas engine. The Karstula and Kiuruvesi plants (0.9 – 1.0 MWe) utilize a grate boiler and a steam engine instead of a steam turbine for power production. All the other plants examined, with capacities between 4.8 – 20 MWe, use a fluidised bed boiler to produce superheated steam and a conventional back pressure steam turbine for power production.

Many of the plants described in this report use also peat as fuel. In Lieksa and Kokkola, peat is the main fuel while the wood based biofuels only possess a minor share between 0 – 30% of the fuels used. However, it is technically possible to increase the share of wood based fuels up to 70% in these plants, but the availability and price of biofuels within the economic transportation distance from the plants restrict the possibilities to increase their share. In the larger scale, the new Iisalmi plant receives the highest grades and should be examined in more detail.

The most interesting case for further research in the smallest size class is the Entimos power plant based on biomass gasification and a gas engine. The benefit of this concept is the high power-to-heat ratio. The Entimos power plant still has some unsolved problems.

No CHP plants have been built recently in the scale of 2 – 4 MWe in Finland. The first full-size small-scale CHP plant based on Novel fixed-bed gasification will be constructed at the plant in 2004. The plant will be equipped with a complete gas-cleaning train consisting of a gas reformer, filter and acid/base scrubber for residual nitrogen compounds removal. Three 0.6 MWe Jenbacher engines will be installed for power production and a gas boiler for heat recovery.

The Novel gasifier, developed by Condens Oy and VTT, is a new type of fixed-bed gasifier based on forced fuel flow, which also makes it suitable for low-bulk-density fibrous biomass fuels. The gasifier can be operated with a wide range of biomass residues with moisture content from 0 to 55% and a particle size from sawdust to large chips.The main process alternatives available would be a grate boiler or a small BFB boiler with a small steam turbine.

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References

Alakangas, E. & Flyktman, M. 2001. Biomass CHP technologies. VTT Energy Reports 7/2001. VTT Energy. 54 p. + 8 p (available at http://www.inf.vtt.fi//pdf/)

Carlsen, H., Status and prospects of small-scale power production based on Stirling engines – Danish experiences. In: Seminar on Power Production from Biomass 3 1998 Espoo Power production from biomass III gasification and pyrolysis, R&D&D for industry, Espoo, Finland, 14-15 September, 1998

De Vries, R., Meijer, R., Hietanen, L., Lohiniva, E. & Sipilä, K., 2000, Evaluation of the Dutch and Finnish situation of energy recovery from biomass and waste. Technology Review 99/2000. Tekes, National Technology Agency. 113 p.

Energia 1/2002. Separate pull-out, 16s.

Forssa CHP plant – Finland, The Analysis report of plant – Cofiring of biomass – evaluation of fuel procurement and handling in selected existing plants and exchange of information. Jyväskylä 2000 (available at http://eubionet.vtt.fi).

Helynen S., Flyktman M.i, Mäkinen T., Sipilä K. & Vesterinen P., 2002, The possibilities of bioenergy in reducing greenhouse gases. VTT Research Notes 2145, 110 p. + app. 2 p.( Finnish, English abstract), 951-38-6055-8 (available at http://www.inf.vtt.fi//pdf/ ).

IEA workshop on Biomass Energy 2 1998 Paris Biomass energy: data, analysis and trends Paris, France, 23-245th March 1998 conference proceedings.

Major, G., Learning from experiences with small-scale cogeneration. CADDET analyses series

Review of Finnish biomass gasification technologies. OPET Report 4. VTT Processes, Espoo 2002 (available at http://www.tekes.fi/opet/pdf/OPET_Report4_2002.pdf).

Statistic of District Heating in Finland, Finnish District Heating Association, 2000, 70 p. (Finnish)

Vanhanen, J. & Loimaranta, O. 1999. Mikro- ja MiniCHP: Teknologiaselvitys. Helsinki, Finland. 42 s.

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http://www.vyh.fi/ympsuo/luvat/psa/salmivoi.htm http://www.vn.fi/vn/ktm/6ktm_etu.htm

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6. Biomass CHP plants in Sweden

6.1 CHP production in Sweden

Sweden has a well-developed district heating network with only a small share of combined heat and power (CHP) plants. In the year 2000 the contribution of the district heat coming from the CHP plants was about 10 % of the total 41 TWh district heat production [Fjärrvärmeföreningen, 2000]. For example, in Finland the same share has been about 80 % [Finnish District Heating Association, 1998]. Major reason for the low share of the CHP plants in Sweden has been the large amount of nuclear and hydropower available.

The CHP plants had about 7 % share of the Swedish electricity production in the year 2001 [Swedish National Energy Administration, 2001a]. From this share about 5.5 TWhe came from the CHP plants connected to the district heating n

Small-scale biomass CHP technologies Situation in Finland, Denmark and Sweden

Small-scale biomass CHP

Small-scale biomass CHP technologies

Contents

1. Small scale biomass CHP technologies

1.2.1 Grate combustion

1.2.3 Gasification

Power production from biomass

1.2.4 Internal combustion engines

1.3 Technologies under R&D

1.3.1 Stirling engine

1.3.3 Air Bottoming Cycle

1.3.5 Externally fired gas turbine

1.3.7 Powdered fuel combustion engine

2. CHP potential in Finland

MINI CHP POTENTIAL IN FINLAND

POWER TO HEAT RATIO OF CHP PLANT

0

MINI CHP POTENTIAL IN FINLAND

MINI CHP POTENTIAL IN FINLAND

Fuels

MINI CHP POTENTIAL IN FINLAND

2.3 CHP potential including only biofuels

MINI CHP POTENTIAL IN FINLAND

MINI CHP POTENTIAL IN FINLAND

2.3.1 CHP potential if oil is replaced by biofuel

MINI CHP POTENTIAL IN FINLAND

Fuel: kpö,rpö and kihi-heating ==> bio fuel

MINI CHP POTENTIAL IN FINLAND

Fuel: kpö,rpö and kihi-heating ==> bio fuel

CHP energy production

3. Overview of small scale biomass CHP plants

3.2 Comparison

4. Descriptions of some biomass CHP plants in

4.1.1 Background

4.2 Kiuruvesi, Iisalmen Sahat Oy,

4.2.1 Background

4.3 Kuhmo 4.9 MW

4.4 Kankaanpää, Kankaanpään Kaukolämpö Oy,

4.4.1 Background

4.5 Kuusamo, Fortum Oyj, 6.1 MW

4.5.1 Background

4.5.2 Process description

4.6 Lieksa, Vapo Oy, 8 MW

4.6.1 Background

4.7 Iisalmi, Salmi Voima Oy, 14.7 MW

4.7.1 Background

4.8 Forssa, Forssan Energia, 17.2 MW

4.8.1 Background

4.9 Kokkola, Kokkolan Voima Oy, 20 MW

4.9.1 Background

4.9.2 Process description

4.10 Recent small scale industrial CHP plants

4.10.1 Savonlinna, Järvi-Suomen Voima Oy

4.10.2 Ristiina, Järvi-Suomen Voima Oy, 10 MWe/65 MWph

5. Summary of the situation in Finland

References

6. Biomass CHP plants in Sweden