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IGCC demonstration plant for peat
Bioresource lechnolog)' 46 (1993) 119-123
IGCC DEMONSTRATION PLANT FOR PEAT Martti Aijiil~i & Erkki Huuskonen Imatran Voima Oy, R &D, PO Box 112, FIN O1601 Vantaa, Finland
Abstract Gasification combined cycle technology (1GC() for power production using low-rank fuels is under development in bTnland. In this study, the possibilities to demon,strate the air blown gasification technology in Finland art" studied. The work includes different greenJield and retrofit applications using peat as fuel. The processes have been planned and calculated using three different gas turbines and different type of fuel dryer inte,gration to the process. The results show' that the demonstration of the new technology is expensive and needs extensive support to the investment. The complete integration of the fuel dryer, ~'here the dryer operates at process pressure, turns out to he the most profitable case compared with other dr)'ing applications. The retrofit plant should be pre[~rred as demonstration plant because it decreases the needJi,financial support, and the risks are also smaller.
In studying costs and profitability, it is important to bear in mind that these factors represent the costs of a technology to be demonstrated, i.e. an immature technology.
2 SELECTION OF APPLICATION PROJECTS AND TECHNOLOGY 2.1 Selected projects The following projects were studied:
(1) a gasification gas turbine to be built in front of the Haapavesi 170-MWe condensing power plant; (2) a gasification gas turbine to be built at the Outokumpu works in the city of Kokkola; (3) a gasification gas turbine producing district heat and electric power to be built in an unspecified, medium-sized town; (4) a gasification gas turbine to be built close to the sawmill of Lieksa, supplying the sawmill and the population centre with energy for heating.
Key wo,'ds: Gasification, power plant, peat, biofuels.
At the Haapavesi Power Plant, the study was carried out on the basis of two different turbines. A variety of different process connections was further studied in most of their applications. The gasification technology was assessed as a demonstration power plant for various applications, i.e. as an immature technology to be demonstrated. In all applications, except in the Haapavesi Power Plant, the gasification concept was compared with an optional power-plant concept, i.e. a conventional steam process. The Haapavesi power plant was compared with the evaluation of IVO's electric-power-acquisition system. The larger amount of electric power typically generated in a gasification process, compared with a conventional plant, was valued according to the valuation of IVO's electric-power-acquisition system. The changes in generation of district-heat energy were valued according to the present, alte,rnative mode of generation.
1 BACKGROUND
Imatran Voima Oy (IVO) has been developing and assessing a power-plant technology based on gasification and related processes since 1985. The project now under way aims to study the costs and the prospects of a demonstration of a power-plant technology based on air-blown gasification and hot-gas cleanup. The study is financed by the J A L O Research Programme of the Ministry of Trade and Industry, Vapo Oy, and IVO. The study is in two stages: in the first stage, a feasibility study based on preliminary price quotations was worked out for four different application objects, giving altogether ten different options; in the second stage, the economically most beneficial of the abovementioned options was selected to provide a basis for an assessment in more detail of the costs of the power plant. I'he first stage is now completed, and this paper provides a report on its results. The second stage is still in preparation.
Bioresource Technology 0960-8524/93/S06.00 © 1993 Elsevier Science Publishers Ltd, England. Printed in Great Britain
119
2.2 Common technology selections The pressurized air-blown gasification technology provides the basis in all cases. Prior to gasification, the fuel is dried to a moisture content of 15%. The dryin technologies and connections applied in various cases are introduced later in the text. In addition to air and
M. Jtijiild, E. Huuskonen
120
fuel, some steam is also fed to the gasifier. After the gasifier, coarse dust is separated with cyclones and returned back to the fluidized bed. The gas generated in the gasifier is cooled to the temperature required by the control valve of the gas turbine and the combustion chamber. Saturated steam is produced with the energy generated in cooling. The ash and coal particles with alkalis condensed on their surface are removed from the gas at this reduced temperature. The separated dust is removed from the process. The ash is also removed from the fluidized bed, if needed. Sand can also be fed to the gasifier to maintain the bed. The air required by the gasifier is taken from the compressor, and it is compressed into the gasifier after cooling. After the gas turbine, there is the heatrecovery boiler, where either steam or hot water is generated, depending on the situation. Low-temperature energy is used for district heating or, in the case of Haapavesi, to replace the extractions of the steam turbine.
2.3 Emission requirements In all cases, the same requirements were imposed on the emissions: NOx level below 140 mg/MJ; no desulphurization (desulphurization to a minor extent in principle should be feasible by feeding lime to the gasifier); no separate need for dedusting after the ceramic hot filter.
2.4 The Haapavesi power plant In the Haapavesi case, two different types of gas turbine were studied: the Siemens K W U 64.3 and the
GE Frame 6 (Fig. 1). In both cases, the waste heat of the gasification process (heat-recovery boiler and gas cooling) was used to generate additional steam that was fed to the existing steam turbine's intermediate-pressure section after the second superheating of the steam. The waste heat present at a lower temperature is used to replace the extraction steam required by the lowpressure peheater. The gasification plant is a retrofit (Fig. 2) and the investment consists of the gasifier, the dryer, the gas turbine, and the heat-recovery boilers, including auxiliary equipment. The steam-turbine process already exists. Several different process connections were studied with both gas-turbine alternatives. The one that was economically most favourable was selected. The process cost was calculated, for example, by applying three different dryer connections: (a) complete integration of the pressurized steam dryer (Hulkkonen et al., 1991 a,b); the surplus steam produced during the drying process is fed to the gasification gas fow; it expands in the gas turbine to produce additional electricity; furthermore, the integration offers the benefit of feeding fuel in a simpler way and at a cheaper cost; (b) partial integration of the dryer, an atmospheric condensing-steam dryer; the condensing energy of the steam is used to replace the extraction steam required by the low-pressure preheater; (c) a non-integrated dryer: a separate peat drum dryer based on a separate drying-power supply. The calculations were made on the assumption that peat with a moisture content of 50% is used as fuel. The additional electric power was valued according to the valuation of optional power in IVO's electricpower-acquisition system.
"I !
i
i
°~o~.~ ......
Fig. 1.
L I
Process of the power plant for a town with complete integration of the dryer.
IGCC demonstration plant for peat
121
! !
! I i
i i '
!
Fig. 2.
I L !
Process of the Haapavesi retrofit with complete integration of the dryer.
2.5 T h e city of K o k k o l a The application for the city of Kokkola was calculated on the basis of a Frame 6 turbine and on the use of indirect steam drying by using its condensing energy for the production of district heat (partially integrated dryer). Owing to the existing steam turbines and the steam generation of the zinc works, the process will be rather complicated. In this connection, the heatrecovery boiler generates 60-bar steam for the existing back-pressure turbine, 5"5-bar steam as process steam. Furthermore, the heat-recovery boiler is used to superheat the saturated steam from the zinc works. The gasification plant is a retrofit and the investment consists of gasifier, dryer, gas turbine, and heatrecovery boiler, including auxiliary equipment. The steam process already exists. In the Kokkola case, the alternative application to be built was a fluidized-bed boiler. 2.6 P o w e r plant for a city The power plant to be constructed in a medium-sized city was calculated on the basis of a Frame 6 gas turbine. In the city, a district-heat network was assumed to be already connected to a peat boiler. This application consisted in building practically a whole new power plant. A small-scale power plant built in the city of Mikkeli was used as comparison basis for pricing. The city-power-plant application was calculated on the basis of a plant producing district heat with a partially integrated dryer and, separately, with a completely integrated dryer connection. The calculations were made on the assumption that peat with a moisture content of 50% is used as fuel.
2.7 T h e L i e k s a sawmill The application for the Lieksa sawmill was calculated on the basis of a Ruston Tornado turbine. The process would not include a steam turbine, but all the generated waste heat would be used by the sawmill and in the heating of the urbain centre. A fully integrated dryer is used in this application. In case all the heat produced in the plant is not needed in the sawmill or in the town, the surplus heat is used to produce injection steam for the gas turbine. The fuels to be used are peat with a moisture content of 50% and wood waste with the same moisture content, and the calculations were carried out accordingly. The Lieksa case was compared with a small-scale poewr plant based on a steam process being planned in Lieksa.
3 ECONOMIC STUDY 3.1 Calculation basis The calculations were based on the following items: real interest rate 8%; operation time 20 years or, in the case of Kokkola, 15 years; peak operating time (design value) at Haapavesi 6500 h; in other applications according to the need for heat; profitability calculation based on the present value method; unschedule non-availability during operation: first 50%; later, for the town-power-plant application 90%, and for others 85%; repair costs for the gas-turbine and steam-turbine processes the same as those for a conventional
M. Aijiilii, E. Huuskonen
122
natural-gas combined-cycle plant; the gasifier has higher repair costs than a conventional boiler, though; operating properties with part-load according to the gas turbine. the actual fuel price of the region in question; larger manning than in a conventional technology, i.e. one more worker per shift compared with a conventional process; normal stand-by power rates; the actual value of additional electricity or district heat in the case in question; comparison with an optional, local-power-generation investment made in each case (valuation according to IVO's electric-power-acquisition system at Haapavesi); pricing of major components of the gasification section according to Enviropower (U-gas technology); otherwise according to IVO's standard pre-feasibility pricing; pricing based on a technology according to which the power plant could be built today, considering its nature as a demonstration plant; and technical risks related to the demonstration plant were not considered in the cost study, nor were all development-related costs caused by the demonstration. 3.2 T h e results o f the d e m o n s t r a t i o n plant
All the alternatives studied above result in a negative current value of more than FIM 100 million, even more than FIM150 million, when applying the calculation
criteria referred to above. Taken all together, the situation seems to be that the investment cost of a demonstration IGCC plant is considerably greater than an optional power-generation investment. In spite of the more favourable operation economy of the IGCC plant, it is hard to catch up with the difference in price during the operation. The Frame 6 gas turbine to be more profitable than the K W U 64.3 turbine at Haapavesi. The most important reason for that was that it was not possible to feed all the steam generated with the K W U 64.3 turbine to the steam turbine. According to the calculations, the economy of the process in the applications studied can be substantially improved by completely integrating a dryer to the process so that all the surplus steam generated can be mixed with the gasifier's product gas. The application of Lieksa seems to be the most attractive option according to Table 1. The loss generated in this application is the smallest one, as is its riskbearing investment. For a demonstration plant, however, it was considered too small. A clear disadvantage of the town-power-plant application is that it requires a relatively large investment, i.e. in this case, the steam process also needs to be built, which in turn increases the investment associated with the risks of demonstration. According to the present study, a Frame 6 gas turbine with a fully integrated dryer was chosen for the Haapavesi plant to be studied in the second stage of the project. Obvious advantages of Haapavesi include relatively cheap fuel and a minor investment need at the steam-process side.
Table 1. Profitability of a demonstration plant in various cases and with various dryer-connection applications
Additional power (MWe) Haapavesi Frame 6 partially integrated drying non-integrated drying completely integrated drying KWI 64.3 partially integrated drying completely integrated drying Kokkola Frame 6 partially integrated drying City-power-plant application Frame 6 partially integrated drying completely integrated drying Lieksa Ruston Tornado completely integrated drying "Difficult to separate. bEfficiencies of heat.
59 61 64
Additional heat (MWth)
m
m
m
91 97
60
60 62
6-7
m
a
Efficiency of power increase (%)
Present value compared with the option (FIM million)
39 37 43
-215 -210 - 150
41 45
- 300 - 200
m t J
-220
70 53
41 (89) o 41 (76) °
-215 - 170
13
27 (80) h
-115
IGCC demonstration plant for peat 3.3 Economy of a commercial plant The estimates presented above show the profitability and need of support for a gasification demonstration plant. On the basis of the previous calculations, estimates on the competitiveness of the air-blown gasification technology compared with optional technologies, as the gasification technology has been adopted for commercial use, have been worked out at IVO. The study is not yet completed, and to carry out such a study in an adequate way is difficult, but some general conclusions may be introduced at this stage. The economy of the gasification power plant could be substantially improved if: the NO, SCR plant were eliminated, which would reduce the investment costs and eliminate catalystreplacement an ammonium costs, and pressure losses would also be smaller; feeding of fuel to the pressure could be arranged in a more economical way; the amount of inertization gas could be reduced, or it could be totally eliminated; the complete integration of the dryer were used. Furthermore, a strong doubt has arisen that the gasification power plant equipped with a hot-gas cleanup as a process today represents a technology so complicated that it is not competitive in very small-scale applications as compared with optional power-plant technology. 4 CONCLUSIONS A sufficiently extensive demonstration plant is needed to have the technology adopted for commercial use and introduced as plausible. The following conclusions can be drawn from the studies performed: the gasification technology needs extensive support to be implemented; in addition to the support, readiness to take risks is required;
123
the demonstration should be carried out on a plant to be retrofitted, not on a new plant; from the viewpoint of plausibility of the demonstration, it needs to be large-scale enough, in particular as the range of applications does not include very small-scale plants; internal integration of the process (e.g. the integration of a dryer) can yield substantial savings; the gasification process provides distinct objectives that, if developed, yield savings; even if further developed, the gasification technology is not expected to complete the profitability in very small units; with regard to district-heat loads, a disadvantage of the competitiveness of the technology is its low adjustability and dependence of the plant size on the choice of gas turbine; and an advantage of the technology compared with optional technologies is the prospect of generating additional electric power with high efficiency and small specific emissions offered by the increase in thermal loads. The work now goes on to concentrate on specifying the case of Haapavesi in more detail to establish the prospects of demonstration. A further goal of the specified calculations is to find out the costs arising from the complementary effect of introducing biomass to the concept.
REFERENCES Hulkkonen, S., Raiko, M. & Aij~l~i, M. (1991a). High efficiency power plant processes for moist fuels. In IGTI -Vol. 6, 1991 ASME CoGen-Turbo. Budapest, ttunga~; 3-5 Sept. Hulkkonen, S., Raiko, M. & J~ij~il/i, M. (1991 b). New power plant concept for moist fuels, IVOSDIG. 36th International (;as Turhine and Aeroengine Congress and Exposition, Orlando, FE, USA, 3-6 June.
IGCC DEMONSTRATION PLANT FOR PEAT Martti Aijiil~i & Erkki Huuskonen Imatran Voima Oy, R &D, PO Box 112, FIN O1601 Vantaa, Finland
Abstract Gasification combined cycle technology (1GC() for power production using low-rank fuels is under development in bTnland. In this study, the possibilities to demon,strate the air blown gasification technology in Finland art" studied. The work includes different greenJield and retrofit applications using peat as fuel. The processes have been planned and calculated using three different gas turbines and different type of fuel dryer inte,gration to the process. The results show' that the demonstration of the new technology is expensive and needs extensive support to the investment. The complete integration of the fuel dryer, ~'here the dryer operates at process pressure, turns out to he the most profitable case compared with other dr)'ing applications. The retrofit plant should be pre[~rred as demonstration plant because it decreases the needJi,financial support, and the risks are also smaller.
In studying costs and profitability, it is important to bear in mind that these factors represent the costs of a technology to be demonstrated, i.e. an immature technology.
2 SELECTION OF APPLICATION PROJECTS AND TECHNOLOGY 2.1 Selected projects The following projects were studied:
(1) a gasification gas turbine to be built in front of the Haapavesi 170-MWe condensing power plant; (2) a gasification gas turbine to be built at the Outokumpu works in the city of Kokkola; (3) a gasification gas turbine producing district heat and electric power to be built in an unspecified, medium-sized town; (4) a gasification gas turbine to be built close to the sawmill of Lieksa, supplying the sawmill and the population centre with energy for heating.
Key wo,'ds: Gasification, power plant, peat, biofuels.
At the Haapavesi Power Plant, the study was carried out on the basis of two different turbines. A variety of different process connections was further studied in most of their applications. The gasification technology was assessed as a demonstration power plant for various applications, i.e. as an immature technology to be demonstrated. In all applications, except in the Haapavesi Power Plant, the gasification concept was compared with an optional power-plant concept, i.e. a conventional steam process. The Haapavesi power plant was compared with the evaluation of IVO's electric-power-acquisition system. The larger amount of electric power typically generated in a gasification process, compared with a conventional plant, was valued according to the valuation of IVO's electric-power-acquisition system. The changes in generation of district-heat energy were valued according to the present, alte,rnative mode of generation.
1 BACKGROUND
Imatran Voima Oy (IVO) has been developing and assessing a power-plant technology based on gasification and related processes since 1985. The project now under way aims to study the costs and the prospects of a demonstration of a power-plant technology based on air-blown gasification and hot-gas cleanup. The study is financed by the J A L O Research Programme of the Ministry of Trade and Industry, Vapo Oy, and IVO. The study is in two stages: in the first stage, a feasibility study based on preliminary price quotations was worked out for four different application objects, giving altogether ten different options; in the second stage, the economically most beneficial of the abovementioned options was selected to provide a basis for an assessment in more detail of the costs of the power plant. I'he first stage is now completed, and this paper provides a report on its results. The second stage is still in preparation.
Bioresource Technology 0960-8524/93/S06.00 © 1993 Elsevier Science Publishers Ltd, England. Printed in Great Britain
119
2.2 Common technology selections The pressurized air-blown gasification technology provides the basis in all cases. Prior to gasification, the fuel is dried to a moisture content of 15%. The dryin technologies and connections applied in various cases are introduced later in the text. In addition to air and
M. Jtijiild, E. Huuskonen
120
fuel, some steam is also fed to the gasifier. After the gasifier, coarse dust is separated with cyclones and returned back to the fluidized bed. The gas generated in the gasifier is cooled to the temperature required by the control valve of the gas turbine and the combustion chamber. Saturated steam is produced with the energy generated in cooling. The ash and coal particles with alkalis condensed on their surface are removed from the gas at this reduced temperature. The separated dust is removed from the process. The ash is also removed from the fluidized bed, if needed. Sand can also be fed to the gasifier to maintain the bed. The air required by the gasifier is taken from the compressor, and it is compressed into the gasifier after cooling. After the gas turbine, there is the heatrecovery boiler, where either steam or hot water is generated, depending on the situation. Low-temperature energy is used for district heating or, in the case of Haapavesi, to replace the extractions of the steam turbine.
2.3 Emission requirements In all cases, the same requirements were imposed on the emissions: NOx level below 140 mg/MJ; no desulphurization (desulphurization to a minor extent in principle should be feasible by feeding lime to the gasifier); no separate need for dedusting after the ceramic hot filter.
2.4 The Haapavesi power plant In the Haapavesi case, two different types of gas turbine were studied: the Siemens K W U 64.3 and the
GE Frame 6 (Fig. 1). In both cases, the waste heat of the gasification process (heat-recovery boiler and gas cooling) was used to generate additional steam that was fed to the existing steam turbine's intermediate-pressure section after the second superheating of the steam. The waste heat present at a lower temperature is used to replace the extraction steam required by the lowpressure peheater. The gasification plant is a retrofit (Fig. 2) and the investment consists of the gasifier, the dryer, the gas turbine, and the heat-recovery boilers, including auxiliary equipment. The steam-turbine process already exists. Several different process connections were studied with both gas-turbine alternatives. The one that was economically most favourable was selected. The process cost was calculated, for example, by applying three different dryer connections: (a) complete integration of the pressurized steam dryer (Hulkkonen et al., 1991 a,b); the surplus steam produced during the drying process is fed to the gasification gas fow; it expands in the gas turbine to produce additional electricity; furthermore, the integration offers the benefit of feeding fuel in a simpler way and at a cheaper cost; (b) partial integration of the dryer, an atmospheric condensing-steam dryer; the condensing energy of the steam is used to replace the extraction steam required by the low-pressure preheater; (c) a non-integrated dryer: a separate peat drum dryer based on a separate drying-power supply. The calculations were made on the assumption that peat with a moisture content of 50% is used as fuel. The additional electric power was valued according to the valuation of optional power in IVO's electricpower-acquisition system.
"I !
i
i
°~o~.~ ......
Fig. 1.
L I
Process of the power plant for a town with complete integration of the dryer.
IGCC demonstration plant for peat
121
! !
! I i
i i '
!
Fig. 2.
I L !
Process of the Haapavesi retrofit with complete integration of the dryer.
2.5 T h e city of K o k k o l a The application for the city of Kokkola was calculated on the basis of a Frame 6 turbine and on the use of indirect steam drying by using its condensing energy for the production of district heat (partially integrated dryer). Owing to the existing steam turbines and the steam generation of the zinc works, the process will be rather complicated. In this connection, the heatrecovery boiler generates 60-bar steam for the existing back-pressure turbine, 5"5-bar steam as process steam. Furthermore, the heat-recovery boiler is used to superheat the saturated steam from the zinc works. The gasification plant is a retrofit and the investment consists of gasifier, dryer, gas turbine, and heatrecovery boiler, including auxiliary equipment. The steam process already exists. In the Kokkola case, the alternative application to be built was a fluidized-bed boiler. 2.6 P o w e r plant for a city The power plant to be constructed in a medium-sized city was calculated on the basis of a Frame 6 gas turbine. In the city, a district-heat network was assumed to be already connected to a peat boiler. This application consisted in building practically a whole new power plant. A small-scale power plant built in the city of Mikkeli was used as comparison basis for pricing. The city-power-plant application was calculated on the basis of a plant producing district heat with a partially integrated dryer and, separately, with a completely integrated dryer connection. The calculations were made on the assumption that peat with a moisture content of 50% is used as fuel.
2.7 T h e L i e k s a sawmill The application for the Lieksa sawmill was calculated on the basis of a Ruston Tornado turbine. The process would not include a steam turbine, but all the generated waste heat would be used by the sawmill and in the heating of the urbain centre. A fully integrated dryer is used in this application. In case all the heat produced in the plant is not needed in the sawmill or in the town, the surplus heat is used to produce injection steam for the gas turbine. The fuels to be used are peat with a moisture content of 50% and wood waste with the same moisture content, and the calculations were carried out accordingly. The Lieksa case was compared with a small-scale poewr plant based on a steam process being planned in Lieksa.
3 ECONOMIC STUDY 3.1 Calculation basis The calculations were based on the following items: real interest rate 8%; operation time 20 years or, in the case of Kokkola, 15 years; peak operating time (design value) at Haapavesi 6500 h; in other applications according to the need for heat; profitability calculation based on the present value method; unschedule non-availability during operation: first 50%; later, for the town-power-plant application 90%, and for others 85%; repair costs for the gas-turbine and steam-turbine processes the same as those for a conventional
M. Aijiilii, E. Huuskonen
122
natural-gas combined-cycle plant; the gasifier has higher repair costs than a conventional boiler, though; operating properties with part-load according to the gas turbine. the actual fuel price of the region in question; larger manning than in a conventional technology, i.e. one more worker per shift compared with a conventional process; normal stand-by power rates; the actual value of additional electricity or district heat in the case in question; comparison with an optional, local-power-generation investment made in each case (valuation according to IVO's electric-power-acquisition system at Haapavesi); pricing of major components of the gasification section according to Enviropower (U-gas technology); otherwise according to IVO's standard pre-feasibility pricing; pricing based on a technology according to which the power plant could be built today, considering its nature as a demonstration plant; and technical risks related to the demonstration plant were not considered in the cost study, nor were all development-related costs caused by the demonstration. 3.2 T h e results o f the d e m o n s t r a t i o n plant
All the alternatives studied above result in a negative current value of more than FIM 100 million, even more than FIM150 million, when applying the calculation
criteria referred to above. Taken all together, the situation seems to be that the investment cost of a demonstration IGCC plant is considerably greater than an optional power-generation investment. In spite of the more favourable operation economy of the IGCC plant, it is hard to catch up with the difference in price during the operation. The Frame 6 gas turbine to be more profitable than the K W U 64.3 turbine at Haapavesi. The most important reason for that was that it was not possible to feed all the steam generated with the K W U 64.3 turbine to the steam turbine. According to the calculations, the economy of the process in the applications studied can be substantially improved by completely integrating a dryer to the process so that all the surplus steam generated can be mixed with the gasifier's product gas. The application of Lieksa seems to be the most attractive option according to Table 1. The loss generated in this application is the smallest one, as is its riskbearing investment. For a demonstration plant, however, it was considered too small. A clear disadvantage of the town-power-plant application is that it requires a relatively large investment, i.e. in this case, the steam process also needs to be built, which in turn increases the investment associated with the risks of demonstration. According to the present study, a Frame 6 gas turbine with a fully integrated dryer was chosen for the Haapavesi plant to be studied in the second stage of the project. Obvious advantages of Haapavesi include relatively cheap fuel and a minor investment need at the steam-process side.
Table 1. Profitability of a demonstration plant in various cases and with various dryer-connection applications
Additional power (MWe) Haapavesi Frame 6 partially integrated drying non-integrated drying completely integrated drying KWI 64.3 partially integrated drying completely integrated drying Kokkola Frame 6 partially integrated drying City-power-plant application Frame 6 partially integrated drying completely integrated drying Lieksa Ruston Tornado completely integrated drying "Difficult to separate. bEfficiencies of heat.
59 61 64
Additional heat (MWth)
m
m
m
91 97
60
60 62
6-7
m
a
Efficiency of power increase (%)
Present value compared with the option (FIM million)
39 37 43
-215 -210 - 150
41 45
- 300 - 200
m t J
-220
70 53
41 (89) o 41 (76) °
-215 - 170
13
27 (80) h
-115
IGCC demonstration plant for peat 3.3 Economy of a commercial plant The estimates presented above show the profitability and need of support for a gasification demonstration plant. On the basis of the previous calculations, estimates on the competitiveness of the air-blown gasification technology compared with optional technologies, as the gasification technology has been adopted for commercial use, have been worked out at IVO. The study is not yet completed, and to carry out such a study in an adequate way is difficult, but some general conclusions may be introduced at this stage. The economy of the gasification power plant could be substantially improved if: the NO, SCR plant were eliminated, which would reduce the investment costs and eliminate catalystreplacement an ammonium costs, and pressure losses would also be smaller; feeding of fuel to the pressure could be arranged in a more economical way; the amount of inertization gas could be reduced, or it could be totally eliminated; the complete integration of the dryer were used. Furthermore, a strong doubt has arisen that the gasification power plant equipped with a hot-gas cleanup as a process today represents a technology so complicated that it is not competitive in very small-scale applications as compared with optional power-plant technology. 4 CONCLUSIONS A sufficiently extensive demonstration plant is needed to have the technology adopted for commercial use and introduced as plausible. The following conclusions can be drawn from the studies performed: the gasification technology needs extensive support to be implemented; in addition to the support, readiness to take risks is required;
123
the demonstration should be carried out on a plant to be retrofitted, not on a new plant; from the viewpoint of plausibility of the demonstration, it needs to be large-scale enough, in particular as the range of applications does not include very small-scale plants; internal integration of the process (e.g. the integration of a dryer) can yield substantial savings; the gasification process provides distinct objectives that, if developed, yield savings; even if further developed, the gasification technology is not expected to complete the profitability in very small units; with regard to district-heat loads, a disadvantage of the competitiveness of the technology is its low adjustability and dependence of the plant size on the choice of gas turbine; and an advantage of the technology compared with optional technologies is the prospect of generating additional electric power with high efficiency and small specific emissions offered by the increase in thermal loads. The work now goes on to concentrate on specifying the case of Haapavesi in more detail to establish the prospects of demonstration. A further goal of the specified calculations is to find out the costs arising from the complementary effect of introducing biomass to the concept.
REFERENCES Hulkkonen, S., Raiko, M. & Aij~l~i, M. (1991a). High efficiency power plant processes for moist fuels. In IGTI -Vol. 6, 1991 ASME CoGen-Turbo. Budapest, ttunga~; 3-5 Sept. Hulkkonen, S., Raiko, M. & J~ij~il/i, M. (1991 b). New power plant concept for moist fuels, IVOSDIG. 36th International (;as Turhine and Aeroengine Congress and Exposition, Orlando, FE, USA, 3-6 June.