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

Transcription

1 Small-scale biomass CHP technologies Situation in Finland, Denmark and Sweden OPET Report 12 European Commission (Directorate-General for Energy and Transport) Contract no. NNE5/22/52: OPET CHP/DH Cluster Task 2 Small and micro scale CHP & Task 3 Conversion to Biomass CHP

2 Copyright VTT Processes and Finnish District Heating Association, 24 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 161, FIN-244 VTT (Biologinkuja 5, Espoo) Tel.: Fax: Contact or Web: (report available at 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. NNE5/22/52 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. 2

3 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 Espoo, April 24 3

4 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 2 MW e. 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 as pdf-file. 4

5 Contents Preface Small scale biomass CHP technologies General Combustion technologies Grate combustion Fluidised bed combustion Gasification Internal combustion engines Steam engines Technologies under R&D Stirling engine Organic Rankine Cycle Air Bottoming Cycle Evaporative gas turbine Externally fired gas turbine Pulverized wood-fired gas turbine Powdered fuel combustion engine CHP potential in Finland CHP potential including all fuels CHP potential including bio fuels, peat and natural gas CHP potential including only biofuels CHP potential if oil is replaced by biofuel Recapitulate Overview of small scale biomass CHP plants in Finland General Comparison

6 4. Descriptions of some biomass CHP plants in Finland Tervola.5 MW e /1.1 MW dh Background Process description Kiuruvesi, Iisalmen Sahat Oy,,9 MW e /6 MW dh Background Process description Kuhmo 4.9 MW e /12.9 MW dh Kankaanpää, Kankaanpään Kaukolämpö Oy, 6 MW e /17 MW dh Background Process description Kuusamo, Fortum Oyj, 6,1 MW e /17,5 MW dh Background Process description Lieksa, Vapo Oy, 8 MW e /14 MW dh /8 MW process heat Background Process description Iisalmi, Salmi Voima Oy, 14.7 MW e /3 MW dh Background Process description Forssa, Forssan Energia, 17.2 MW e /48 MW dh Background Process description Kokkola, Kokkolan Voima Oy, 2 MW e /5 MW dh Background Process description Recent small scale industrial CHP plants Savonlinna, Järvi-Suomen Voima Oy 17MW e /33 MW dh /2 MW ph Ristiina, Järvi-Suomen Voima Oy, 1 MW e /65 MW ph Summary of the situation in Finland Biomass CHP plants in Sweden CHP production in Sweden Biomass potential and fuel prices in Sweden Energy prices and biofuel taxation Future potential of the small-scale biomass CHP plants in Sweden Listings of <2 MW e biomass CHP plants in Sweden

7 8. Process descriptions of some biomass CHP plants in Sweden Myresjöhus, Vattenfall AB, 2 MW e Process description Växjö (Sandvik II), Vattenfall AB, 38 MWe Process description Nässjö, Vattenfall AB (operated by Nässjö Affärsverken AB), 9 MW e Process description Hallsberg, Sydkraft, 2.5 MW e Process description Härnösand, Härnösand Energi och Miljö, 11.7 MW e Process description Biomass CHP plants in Denmark Current situation Objectives to increase the biomass use Listing of some < 2 MW e biomass CHP plants in Denmark Summary of the Swedish and Danish situation Summary

8 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 preengineered modular units. Annual operating hours typically vary between 4 5 h, most of which is on partial load. Small physical size of the plant, fast delivery (8 2 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 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 Fluidised bed combustion Fluidised bed combustion technologies have been developed since the late 6 s. The first concepts were based on bubbling fluidised beds (BFB) and the development of 8

9 circulating fluidised bed (CFB) technology started in early 7 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 MW e ) 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 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 MW e 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 5 MW e ) 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. 9

10 Fixed-bed gasifier + microturbine Fixed-bed gasifier + Stirling engine Fixed-bed gasifier + gas / diesel engine Fixed-bed gasifier + steam cycle Power production from biomass Gasification-based systems for different size classes Atmospheric-pressure gasifier + indirect gas turbine cycles Fixed/fluidised-bed gasifier & co-firing in natural gas engines Gasification + fuel cell + gas turbine and/or steam cycle Simplified IGCC based on pressurised gasification Fluidised-bed gasifier connected to existing coal- or oil-fired boilers Power, MW Long-term 2 Figure 1. Gasification technologies for different power plant size classes 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 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 1

11 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.3.35 but the recently built steam motor based CHP plants have power-to-heat ratios as low as Technologies under R&D 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 kw e :s but so far the commercially available units have been very small, typically under 1 kw e. A figure of a Stirling engine power plant is shown in figure 2. Chimney District heating T=8 O C Stirling engine T=6 O C Air preheater T=764 O C T=6 O C Secondary air T=12 O C Primary air Figure 2. Arrangement of a 29/14 kw Stirling engine CHP plant. 11

12 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. Recuperator Heat exhanger Turbine Condenser Frequency inverter Generator Fluegas Cooler Main feedpump Pre feedpump Figure 3. ORC process 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 CO 2 and NO x 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 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 12

13 production in an EvGT plant is estimated to be about 3% less than in a conventional combined cycle, as the expensive steam turbine, steam condenser and related accessories and pipings are not needed. A 6 kw e 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 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 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 MW e has already been built in Luleå, and it is expected this technology would reach commercial stage by 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. 13

14 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 196s and big coal and peat fired CHP plants were built in 197s. Building of CHP plants were based on large enough district heating activities in towns, where CHP plants are locating. In 2 there were 48 places in Finland, which have CHP production connected to DHnetwork. The total capacity was 4128 MW electricity and 5671 MW heat. The capital Helsinki of Finland has the biggest CHP capacity 117 MW in electricity and 13 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 167 MW of heat with 6 hours annual peak load time based on district heat energy consumption in 2. The CHP potential is evaluated to be 3685 MW electricity and 52 MW heat with 2 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. MINI CHP POTENTIAL IN FINLAND MINI CHP POTENTIAL IN FINLAND NUMBER OF POWER PLANTS THERMAL 1OUTPUT 5 2 <=1 MW 1-5 MW 5-1 MW 1-2 MW 2-4 MW 4-8 MW > 8 MW NUMBER OF POWER PLANTS THERMAL 1OUTPUT 12 <=1 MW 1-5 MW 5-1 MW 1-2 MW 2-4 MW 4-8 MW > 8 MW Total amount = 194 t peak = 6 h/a Total amount = 194 t peak = 2 h/a 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 h/a or 2 h/a based on heat load in 2. 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 8% of total annual heat demand. 14

15 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 (P/Q 1,2 1,,8,6,4,2, POWER TO HEAT RATIO OF CHP PLANT maximum minimum <= > 8 THERMAL OUTPUT OF CHP [MW] Figure 5. Power to heat ratio of CHP plant as a function of heat capacity. CAPACITY [MW] MINI CHP POTENTIAL IN FINLAND t peak = 6 h/a 17 Thermal capacity Power capacity <= > 8 THERMAL OUTPUT [MW] Total capacity: electricity 941 MW, heat 167 MW CAPACITY [MW] MINI CHP POTENTIAL IN FINLAND t peak = 2 h/a Thermal capacity Power capacity <= > 8 THERMAL OUTPUT [MW] Total capacity: electricity 3685 MW, heat 51 MW a) b) Figure 6. CHP potential categorised in thermal output of the plants. 15

16 2.2 CHP potential including bio fuels, peat and natural gas CHP potential has been evaluated to be 611 MW of electricity and 144 MW of heat with 6 hours of annual peak load time based on district heat energy consumption produced on bio fuel, peat and natural gas in 2. The CHP potential is evaluated to be 3685 MW electricity and 51 MW heat with 2 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 MW e /822 MW th. 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. NUMBER OF CHP PLANTS] MINI CHP POTENTIAL IN FINLAND Fuel: jtu, ptu, mka,popu,tept, bio, kipa THERMAL OUTPUT 1 <=1 MW 1-5 MW 5-1 MW 1-2 MW 2-4 MW 4-8 MW > 8 MW NUMBER OF CHP PLANTS] MINI CHP POTENTIAL IN FINLAND Fuel: jtu, ptu, mka,popu,tept, bio, kipa THERMAL OUTPUT 6 8 <=1 MW 1-5 MW 5-1 MW 1-2 MW 2-4 MW 4-8 MW > 8 MW Total amount = 116 t peak =6 h/a Total amount = 116 t peak =2 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 ptu mka popu tept pjät bio kipa milled peat sod peat natural gas forest fuel industrial wood waste wood industrial liquid waste biogas renewable fuel We see that 91% of potential CHP plants exist in category less than 2 MW of thermal effect, if 6 h/a of peak load demand is required. The range 1 5 MW covers the 16

17 most part of the CHP amount having proportion of 48%. Correspondingly the proportion in the thermal size of 2 MW or less is 74%, if 2 h/a peak load time is demanded including biggest proportion of 31% in the category of 1 2 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 4 MW. CAPACITY [MW] MINI CHP POTENTIAL IN FINLAND Fuel: jtu, ptu, mka,popu,tept, bio, kipa Thermal capacity Power capacity t peak = 6 h/a <= > 8 THERMAL OUTPUT [MW] Total: electricity 611 MW, heat 144 MW CAPACITY [MW] MINI CHP POTENTIAL IN FINLAND Fuel: jtu, ptu, mka,popu,tept, bio, kipa Thermal capacity Power capacity t peak = 2 h/a <= > 8 THERMAL OUTPUT [MW] Total: electricity 2344 MW, heat 3132 MW 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 8 MW of electricity and 214 MW of heat with 6 hours of annual peak load time based on district heat energy consumption produced on bio fuel in 2. The CHP potential is evaluated to be 293 MW electricity and 641 MW heat with 2 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 9% of potential CHP plants exist in category less than 1 MW of thermal effect, if 6 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 2 MW or less is 82%, if 2 h/a peak load time is demanded including biggest proportion of 31% in the category of 1 2 MW. 17

18 NUMBER OF CHP PLANTS] MINI CHP POTENTIAL IN FINLAND Fuel: popu,tept, bio, kipa THERMAL OUTPUT <=1 MW 1-5 MW 5-1 MW 1-2 MW 2-4 MW 4-8 MW > 8 MW NUMBER OF CHP PLANTS MINI CHP POTENTIAL IN FINLAND Fuel: popu,tept, bio, kipa THERMAL OUTPUT 8 1 <=1 MW 1-5 MW 5-1 MW 1-2 MW 2-4 MW 4-8 MW > 8 MW Total amount = 51 t peak =6 h/a Total amount = 51 t peak =2 h/a 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 1 divided in seven categories. CAPACITY [MW] MINI CHP POTENTIAL IN FINLAND Fuel: popu,tept, bio, kipa <= > 8 THERMAL CAPACITY [MW] Total: electricity 8 MW, heat 214 MW Thermal capacity Power capacity t peak = 6 h/a CAPACITY [MW] MINI CHP POTENTIAL IN FINLAND Fuel: popu,tept, bio, kipa <= > 8 THERMAL CAPACITY [MW] 239 Total: electricity 293 MW, heat 641 MW 119 Thermal capacity Power capacity t peak = 2 h/a a) b) Figure 1. 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 or 2 hours a year. Difference of the estimated fuel production and existing demand in 21 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 18

19 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: 1 possible CHP plants with fuel demand of 34 GWh a year when the estimated fuel production will be 38,1 TWh in 21. 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 21. 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 21. Main part of the fuel will be renewables. 4. Ahvenanmaa: 1 possible CHP plant with fuel demand of 3 GWh a year when the estimated fuel production will be.5 TWh in 21. Main part of the fuel will be renewable. There would be possible to build 24 small-scale CHP plants with total capacity of 136 MW e /36 MW th 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 1 years will be about 22% higher than in 2. 19

20 5 46, Number [kpl] nr., MW, 1*GWh ,2 14,4 Heat [MW] Electricity [MW] Bio fuel demand 1 [1*GWh] 5 3,95 v. 21 Bio fuel dem.-cons. [1*GWh] LAPLAND 1 82,6 8 nr., MW, 1*GWh ,3 14, 3 1,6 SOUTH POHJANMAA -5,3 11,4 nr., MW, 1*GWh nr., MW, 1*GWh ,7 11,1 8,9 2,68 MIDDLE POHJANMAA 47,8 35,8 1 1,76 WEST COAST -4, nr., MW, 1*GWh nr., MW, 1*GWh nr., MW, 1*GWh ,7 2,59 NORTH POHJANMAA -22,2 24,4 7,6 2,7,24 KAINUU 51,7 2,6 13,3 4 1,55 NORTH KARJALA nr., MW, 1*GWh ,2,35 PIRKANMAA -15,6 nr., MW, 1*GWh ,2 15,8 1, , NORTH SAVO -4,2 5 nr., MW, 1*GWh ,2 7 1,72, SOUTH-WEST FINLAND 9,6 nr., MW, 1*GWh ,6 16,3 1,25 4,4 SOUTH SAVO nr., MW, 1*GWh ,7 AHVENANMAA,3,5 nr., MW, 1*GWh ,4 17,6 9, 1,15 SOUTH COAST nr., MW, 1*GWh ,4 51,7 6 3,39 9, HÄME-UUSIMAA nr., MW, 1*GWh ,1 2,5,22 KYMI -26,6 nr., MW, 1*GWh ,8 22,6 1,57 MIDDLE FINLAND -4,4 Figure 11. Areal potential of bio-chp production and biofuel resources in Finland. 2

21 21 Figure Small-scale biofuel CHP located on the Finnish map.

22 2.3.1 CHP potential if oil is replaced by biofuel CHP potential has been evaluated to be 51 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 2. 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. NUMBER OF CHP PLANTS MINI CHP POTENTIAL IN FINLAND Fuel: kpö,rpö and kihi-heating ==> bio fuel THERMAL OUPUT Total amont = t peak =6 h/a <=1 MW 1-5 MW 5-1 MW 1-2 MW 2-4 MW 4-8 MW > 8 MW NUMBER OF CHP PLANTS MINI CHP POTENTIAL IN FINLAND Fuel: kpö,rpö and kihi-heating ==> bio fuel THERMAL OUPUT Total amont = 61 5 t peak =2 h/a <=1 MW 1-5 MW 5-1 MW 1-2 MW 2-4 MW 4-8 MW > 8 MW 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. CAPACITY [MW] MINI CHP POTENTIAL IN FINLAND Fuel: kpö,rpö and kihi-heating ==> bio fuel 5 1 Thermal capacity Electric capacity t peak = 6 h/a <= > 8 THERMAL OUTPUT [MW] Total: electricity 51 MW, heat 776 MW MINI CHP POTENTIAL IN FINLAND Fuel: kpö,rpö and kihi-heating ==> bio fuel 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. CAPACITY [MW] Thermal capacity Electric capacity t peak = 2 h/a <= > 8 THERMAL OUTPUT [MW] Total: electricity 1418 MW, heat 1868 MW 22

23 2.3.2 Recapitulate Summarising of the results is presented in table 2. The real peak load time was in 2 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 6 h, the electricity production increases more than double and heat production 66%. When annual peak load is 2 h, on the contrary electricity production is 31% and heat production 45% less than it was in 2. 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 6 h. If peak hours is 2 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 6 hours. Correspondingly the capacity will be increased 35 and 33% with annual peak load of 2 hours. The production will be increased 25% in electricity and 23% in heat with peak load of 6 h/a and correspondingly 24 and 18% with 2 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 3% compared to CHP capacity in 2. The CHP production will be increased 54% with 6 hours of peak load time. If 2 hours peak load is required, extra CHP capacity of 9% could be built and production could be increased 55%. Table 2. Evaluation of extra CHP capacity compared to existing capacity in 2, if CHP capacity will be installed based on bio fuels and changing oil fired CHP production to biofuel. CHP energy production t peak = 6 h 2 h e 2893 Electricity Heat Electricity Heat OBS.! h 3617 MW GWh MW GWh MW GWh MW GWh Existing CHP s 4 128, , 5 67, , , , 5 67, ,9 tabl4/tabl1, SKY Existing CHP s 4 128, ,6 5 67, , , ,2 5 67, ,6 calculated t peak Extra potential; all fuels 941, ,9 1 67,1 1 2, ,2 7 37,5 5 1,3 1 2,7 Extra potential: bio fuels 61, ,5 1 44, 6 263, , , , 6 263,9 Extra pot.: loil,hoil,coal =>bio 5,8 3 5, 778, , , , , ,7 % incresing compared to basic case CHPs, changing p.h. time 1, 2,74 1, 1,659 1,,691 1,,553 calculated t peak Extra potential; all fuels,228,473,295,489,893,617,884,489 Extra potential: bio fuels,148,37,184,35,568,392,552,35 Extra pot.: loil,hoil,coal =>bio,121,252,137,228,345,238,331,183 Two last rows total,269,558,321,533,912,631,884,489 It is noticeable that in evaluation the potential of extra CHP capacity no economical aspects were included. 23

24 3. Overview of small scale biomass CHP plants in Finland 3.1 General There are some 4 small CHP plants with electric powers less than 2 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 1 years, no new coal or oil fired plants have been built while 1 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 3%. 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 MW dh Fuel input MW f Electric eff. Total eff. Powerto-heat ratio Steam values Fuel Technology C/bar/kgs -1 wood residue gasification+ Tervola,47 1,13 2,,24,815,42 -/-/- gas engine Kiuruvesi,9 6 8,1,11,852,15 35/25/2,8 bark, sawdust, wood chips grate+steam engine Karstula ,9,85,85,1 35/24/? bark, sawdust grate+steam engine Kuhmo 4,8 12,9 2,1,24,881,37 49/81/? wood residue CBF peat, wood BFB Kuusamo 6,1 17,6 27,6,22,86,35 51/61/8 chips, sawdust Kankaanpää ,,23,885,35 51/6/7,9 peat, wood BFB peat, wood CFB Lieksa ,9,24,885,36 51/61/8 residue wood chips, BFB wood residue, Iisalmi 14,7 3 48,,31,931,49 515/93/17,5 REF wood chips, BFB Forssa 17, ,7,24,99,36 51/62/22,8 wood residue, REF peat, wood BFB Kokkola ,7,25,89,4 482/8/27 chips 24

25 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 3% 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,5 1,3, Kiuruvesi,9 5,? Karstula 1, 4,7? Kuhmo 4,8 12,4 2, Kuusamo 6,1 8,4 1, Kankaanpää 6, 8,1 1, Lieksa 8, 1,1 2, Iisalmi 14,7 21, 2, Forssa 17,2 17,1 1, Kokkola 2, 26, 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. 25

26 Table 5. Comparison of recent small scale biomass CHP plants in Finland. eff. to-heat Power plant Power Heat Overall Power- Startup Investoutput output year ment MW e MW dh ratio cost MEUR α * Tot.eff. 1 Estimation of the power plant investment up-to-date 3 technically factor 2 Average grade 4 Tervola,47 1,13,815, ,3,34,53 3 2,3 Kiuruvesi,9 6,852, ,,13,56 1,5 1,5 Karstula 1 1,85,1 2 4,7,9,35 2,5 1,8 Kuhmo 4,8 12,9,881, ,4,33,47 1 1,7 Kuusamo 6,1 17,6,86, ,4,3,24,5 1,8 Kankaanpää 6 17,885, ,1,31,24 1 2, Lieksa 8 22,885, ,1,32,23,5 1,8 Iisalmi 14,7 3,931, ,,46,3 2,5 2,8 Forssa 17,2 48,99, ,1,33,18 2 2,3 Kokkola 2 5,89, ,9,36,26 2,5 2,5 1 Calculated as (Power to heat -ratio) x (Total efficiency) 2 Calculated as (Total investment) / (2.5 x Power production 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 ( : 1 point, : 2 points, 2 : 3 points), the boiler technology (fluidized bed is the state-of-art technology, grate -.5 points) and used fuels (is also peat used -.5 points). Also flue gas condensing is seen as an advantage (+.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 is 1 point,.3-.4 gives 2 points and >4 gives 3 points. The investment factor is transferred into grades so that the factor <.39 gives 3 points, gives 2 points and >.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 1 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 1 2 MW scale, the new Iisalmi power plant receives the highest grades (investment cost not taken into account). 26

27 4. Descriptions of some biomass CHP plants in Finland 4.1 Tervola.5 MW e /1.1 MW dh Background Tervola combined heat and power plant produces electricity and district heat for the municipality of Tervola. The plant produces about 9% of the district heat and about 1% of the electric power needed by Tervola. The electric power of the Tervola plant is less than 1 MW e 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 MW fuel /,5 MW e 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 The total investment in the plant was about 1.3 MEUR in , which gives a specific investment of 2 72 EUR/kW e for electric power. The investment decision was made in 1999 and the plant was supposed to be in operation by April 21. 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 Process description Using wood residues like bark and sawdust from sawmills as fuels, the plant produces.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

28 Figure 15. Process diagram of Tervola power plant. Summary: Electricity:.47 MW e District heat: 1.13 MW dh Electrical efficiency:.25 Power-to-heat ratio:.42 Overall efficiency: 81.5% Fuel input: 2. MW fuel Fuels: wood residue from sawmills Boiler: gasifier + gas engine (Jenbacher) Start up year: Kiuruvesi, Iisalmen Sahat Oy,,9 MW e /6 MW dh 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 2, 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 3 EUR/kW e specific investment for electric power. The plant started commercial operation in the autumn

29 4.2.2 Process description The plant uses bark, sawdust and forest chips as fuels. The moisture content of the fuel is usually between 5 65%. The wet fuel is burned in an underfeed rotating grate fired boiler supplied by Sermet Oy. Steam values after the boiler are 35 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.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 MW e at the Renko plant and 2.9 MW e 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:.9 MW e District heat: 6 MW dh Electrical efficiency:.11 Power-to-heat ratio:.15 Overall efficiency: 85% Fuel input: 8.1 MW fuel Fuels: sawdust, bark, wood chips Boiler: underfeed rotating grate Steam values: 2.8 kg/s, 35 C, 25 bar Start up year:

30 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 8 9% 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 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 Dust 7 The total investment in the power plant was 12,4 MEUR in 1992 which gives a 254 EUR/kW e specific investment for electric power. Summary: Electricity: 4.9 MW e District heat: 12.9 MW dh Electrical efficiency:.24 Power-to-heat ratio:.37 Overall efficiency: 88% Fuel input: 2 MW fuel Fuels: sawdust, bark, wood chips Boiler: circulating fluidised bed Steam values: 6.3 kg/s, 49 C, 81 bar Start up year:

31 4.4 Kankaanpää, Kankaanpään Kaukolämpö Oy, 6 MW e /17 MW dh 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 5% of the peak demand and the plant produces about 9% of the annual district heat energy demand. The annual power production is about 22 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 199, building work started in June 1991 and the plant started commercial production in September Process description 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 51 C temperature and 6 bar pressure. After the boiler steam is led into a high speed (12 r/min) steam turbine supplied by Blohm&Voss. The turbine has one extraction for the feedwater tank. The generator is a 8 MVA/15 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 EUR/kW e specific investment for electric power. 31

32 Summary: Electricity: 6 MW e District heat: 17 MW dh Electrical efficiency:.23 Power-to-heat ratio:.35 Overall efficiency:.885 Fuel input: 26 MW Fuels: peat, wood chips Boiler: BFB Steam values: 7.9 kg/s, 51 C, 6 bar Emission control: electrostatic precipitator Crew: 1 Start up year: Kuusamo, Fortum Oyj, 6.1 MW e /17.5 MW dh 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 The total investment in the power plant was 8.4 MEUR in 1992 which gives a 14 EUR/kW e specific investment for electric power. Fortum received an investment subsidy of about 1.7 MEUR (2%) for the building of the plant. 32

33 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 4 6% and after drying 8 2%. 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 51 C and pressure 61 bar. After the boiler the steam is led into a single case high-speed (12 r/s) steam turbine running an 15 r/s generator. After the turbine is one district heat exchanger and district heat temperatures normally 5/87.5 C. The turbine has one extraction for feedwater tank. The feedwater temperature before the boiler is 15 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 MW e District heat: 17.5 MW dh (21,2 with dryer) Electrical efficiency:.22 Power-to-heat ratio:.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, 51 C, 61 bar Emission control: electrostatic precipitator Crew: daytime Start up year:

34 4.6 Lieksa, Vapo Oy, 8 MW e /14 MW dh /8 MW process heat 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 9% 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 The total investment in the power plant was 1 MEUR in 1992 which gives a 126 EUR/kW e specific investment for electric power. An investment aid of about 2 MEUR (2%) for the building of the plant was admitted Process description 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 NO x and SO x 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 51 C and 61 bar. Live steam flow is 1.5 kg/s. After the boiler the steam is led into a highspeed 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

35 Figure 17. Process diagram of Lieksa power plant. Summary Electric power: District heat: Electrical efficiency: 24% Power-to-heat ratio:.36 Overall efficiency: 88% 8 MW e 14 MW dh + 8 MW process heat for Kevätniemi sawmill Fuel input: 33.9 MW Fuels: peat (12 loose m 3 /a), wood residue (1 loose m 3 /a) Boiler: CYMIC circulating fluidised bed Steam values: 8 kg/s, 51 C, 61 bar Emission control: electrostatic precipitator Startup year: Iisalmi, Salmi Voima Oy, 14.7 MW e /3 MW dh 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 town of Iisalmi. The plant is owned and operated by Salmi Voima Oy who belongs to 35