Final Report Summary - ENCAP (Enhanced Capture of CO2)
The goal for the ENCAP project has been to develop and validate a number of CO2 precombustion technologies that in large power Plants meet the target 90% CO2 capture rate and 50% capture cost reduction - from a level of EUR 50-60 per tonne of CO2 avoided.
The ENCAP project has included development and validation of a large number of CO2 precombustion capture technologies and concepts.
Significant development of concepts of pre-combustion decarbonisation - integrated gasification combined cycle (IGCC) for hard coal and lignite and integrated reforming combined cycle (IRCC) for natural gas were initiated in the beginning of the project. Further development and validation of H2-rich fuel combustion concepts gas turbines based on lean premixed technology have successful performed test rigs. The development and validation of the IGCC concept and the OxyFuel concept within ENCAP has generated results that put them as candidates for near future actions.
The project has performed development and research on components for a chemical looping combustion using coal and pet coke. The results indicate a promising concept. A number of oxygen carriers have been tested. Tests with different coals has been performed in prototype scale Two innovative prospective concepts based on the chemical looping principle using natural gas has been studied and tested in laboratory scale.
The OxyFuel concept and the IGCC concept use oxygen in the process. The ENCAP project has developed three high-temperature oxygen generation concepts including integration of the concepts into power plants in order to investigate their competitiveness to the established cryogenic technique. The project has investigated a number of prospective emerging technologies and further developed OxyFuel combustion cycles for natural gas and Pre-combustion capture cycles for natural gas and hard coal.
The project was structured in six sub-projects (SPs), set out below.
-SP1: Process and power systems
The SP1 work has covered the comparison between the power plants with different precombustion decarbonisation, oxy-fuel technologies and other pre-combustion technologies developed in the ENCAP subprojects. A great number of technical descriptions of such concepts and cost data exist in international sources and the development inside and outside Europe was followed. However, these data are based on different presumptions and cannot easily be compared with each other. No directly relevant model was found for the comparison and recommendation that SP1 is making in ENCAP.
Altogether, the development of uniform guidelines for the description of relevant power plant performance and cost calculations was necessary to meet the objective of the ENCAP project.
-SP2: Pre-combustion decarbonisation technologies
In this sub-project the target has been the process development for IGCC/IRCC based on hard coal, lignite and natural gas to confirm the feasibility of these concepts with integrated CO2 capture. In addition, capture-free cases for hard coal and lignite were deemed necessary to develop as reference cases, whereas the reference case for the IRCC is a natural gas fired combined cycle. Since both manufacturers and utilities have been involved in the work, this has enabled duly taking into account the user's perspective in the development work.
Power plant concepts with pre-combustion capture of CO2 for natural gas, hard coal and lignite were developed and evaluated, and also used in the benchmarking work in SP1. A capture rate higher than the predefined minimum of 90% was obtained for hard coal and natural gas, whereas the capture rate for lignite was 85%, due to the chosen gasification process. CO2 avoidance cost was around 25 EUR/tonne CO2 for the bituminous case, around 18 EUR/tonne CO2 for the lignite case and around 35 EUR/tonne CO2 for the IRCC case, meaning that the coal-fired cases meet the ENCAP cost target, but not the natural-gas fired case.
-SP3: Oxyfuel combustion technologies
The principle of OxyFuel combustion (a.k.a oxycombustion) is that a (carbon-containing) fuel is burnt in the presence of oxygen but without the presence of nitrogen. Part of the resulting flue gas (mainly consisting of CO2 and H2O) is recirculated back to the furnace for temperature control. The remaining flue gas is cleaned, including condensation of water, and the remaining CO2 is compressed for further transport.
The power process studies carried out in SP3 are based on state-of-the-art technology. Further near-term improvements in efficiency of the PF and CFB OxyFuel plants can be expected through further optimisation of gas separation technology (ASU and CPU) as well as increasing the steam parameters (700 degrees Celsius power plants). Capture rates met the ENCAP target of 90% and investment costs were found to increase with 45- 60% based on net power output, compared to the reference air-fired power plants. Cost of electricity was found to have an increase of 38-45%, whereas CO2 avoidance cost was found to be around 20 EUR/ton CO2 avoided for all cases.
-SP4: Chemical looping combustion
The potential of the CLC combined cycle was to some extent proven to be very important in terms of efficiency already prior to ENCAP, as it has a small energy penalty compared with other CO2 capture technologies applied to gas turbines. Nevertheless, it could by no means be said that power cycles with CLC for CO2 capture were fully investigated at that period in time, and further work on cycle simulations was judged necessary, both for gaseous and solid fuels.
Altogether in SP4, promising results were obtained but technical maturity is not there yet for chemical looping combustion. Additional development effort of stable and cost effective oxygen carriers is required in the scale-up of CLC reactors and to demonstrate the full operability of the CLC process. The concept studied is in the 450 MW size. Thus this concept is not available in the near future or for larger power plants. Among the process applications considered within ENCAP, the CFB boiler application has a more advanced development status compared to the Gas Turbine Power Cycle application.
-SP5: High-temperature oxygen generation for power cycles
The objectives for SP5 were to identify and develop low-cost advanced high-temperature oxygen separation process options for use in the power plant processes developed in ENCAP SP2 and SP3.
In-depth investigations were made on the CAR material and on the integration of the CAR process in a lignite-fired PF oxyfuel boiler power plant. Thermal efficiency for this option is better when using flue gas than when using steam as purge medium. If using flue gas, however, current CAR materials have insufficient resistance to CO2 and SO2 exposure. These results confirmed again that additional, relevant efforts in the material stability and performance and in the process integration are needed in order to improve the competitiveness and attractiveness of CAR technology.
-SP6: Novel pre-combustion capture concepts
The objectives for SP6 were to investigate prospective emerging pre-combustion decarbonisation and OxyFuel capture technologies that are estimated to have a high potential for capture cost reduction while maintaining a high capture rate.
A large number of cycles were analysed, the most critical components of the most interesting cycles were studied to considerable level of detail and a full economic assessment of these cycles was made on a consistent basis. Out of seventeen cycles studied in SP6, eight cycles for natural gas and three cycles for coal exceed the target of 90% CO2 capture. The work of SP6 has thus well achieved the ENCAP objective of at least 90% capture. Out of eight IGCC systems studied in SP6, six cycles have shown CO2 avoidance costs of less than EUR 30 per ton of CO2. As to the four natural gas oxy-fuel cycles studied in SP6, the CO2 avoidance cost varied from 40 to 47 Euros per ton of CO2.
So the work of SP6 achieved the cost reduction target of ENCAP on coal IGCC systems with pre-combustion but showed that difficulties exist to achieve the cost reduction target for natural gas oxy-fuel systems. The work in SP6 showed, however, as mentioned above, that IGCC systems based on membranes are still not at short distance from practical realisation.
The project has performed development and research on concepts and components for chemical looping combustion technology. A design concept for a 455 MWe supercritical coal CLC-CFB (circulating fluidised bed) boiler operating with coal and pet coke has been developed and sized. The work shows that the CLC CFB is a feasible concept, close to conventional CFB processes. The ENCAP project has developed three high-temperature oxygen generation concepts; Oxygen separator membrane for power plant cycles; High temperature oxygen adsorbent (CAR) and Oxygen-transport membrane systems for power production.
The CAR concept with cyclic oxygen adsorption/desorption was found to be the most mature of three investigated high-temperature oxygen generation options. The two other was found interesting but need significant more time for further development. Due to the ENCAP project time frame the further work then focused on the CAR process and further experimental work was performed in order to find the optimum CAR material and geometry. One material could be selected based on a trade-off between chemical stability and performance (i.e. oxygen storage capacity) under dynamic conditions.
ENCAP has investigated a number of prospective emerging pre-combustion decarbonisation and OxyFuel capture technologies that are estimated to have a high potential for capture cost reduction while maintaining a high capture rate. An important result is a structured two-step evaluation of 17 novel process concepts for precombustion decarbonisation and OxyFuel combustion revealed the natural gas fired OxyFuel Combustion Cycles as the most promising novel concepts, showing an acceptable thermal efficiency and without requiring any significant scientific breakthrough (in e.g. combustion engineering and aerodynamic design) for their realisation.
These options generally can be described as less mature than the other concepts developed in ENCAP, (most are at the conceptual level). CO2 avoidance cost for these cycles, however, was estimated to be EUR 40-47 /ton CO2 avoided, meaning that they do not meet the CO2 cost target of ENCAP.
The further development of CO2 pre-combustion by the ENCAP consortium has been carried out during an important period when the interest of the overall CCS concept has gradually increased. The knowledge generated and that is in the hand of the ENCAP consortium and several partners in the consortium have already been activated in further development of CO2 capture technologies in new CO2 capture projects in FP7 and the EC RFCS programme.
CO2 Capture influence on the European power situation and the possibility to meet specified CO2 reduction targets has been studied in different scenarios. The results from the study on CO2 capture influence on the European power situation show that it is possible to meet an 85% CO2 reduction target by 2050, requiring a large contribution from CCS, with a steep ramp-up post 2020, which imposes challenges for timely investments in corresponding CCS infrastructure. The results should not be seen as predictions of energy futures but rather a quantitative analysis investigating the possible roles and limits for different technologies, including CCS.
The ENCAP project has included development and validation of a large number of CO2 precombustion capture technologies and concepts.
Significant development of concepts of pre-combustion decarbonisation - integrated gasification combined cycle (IGCC) for hard coal and lignite and integrated reforming combined cycle (IRCC) for natural gas were initiated in the beginning of the project. Further development and validation of H2-rich fuel combustion concepts gas turbines based on lean premixed technology have successful performed test rigs. The development and validation of the IGCC concept and the OxyFuel concept within ENCAP has generated results that put them as candidates for near future actions.
The project has performed development and research on components for a chemical looping combustion using coal and pet coke. The results indicate a promising concept. A number of oxygen carriers have been tested. Tests with different coals has been performed in prototype scale Two innovative prospective concepts based on the chemical looping principle using natural gas has been studied and tested in laboratory scale.
The OxyFuel concept and the IGCC concept use oxygen in the process. The ENCAP project has developed three high-temperature oxygen generation concepts including integration of the concepts into power plants in order to investigate their competitiveness to the established cryogenic technique. The project has investigated a number of prospective emerging technologies and further developed OxyFuel combustion cycles for natural gas and Pre-combustion capture cycles for natural gas and hard coal.
The project was structured in six sub-projects (SPs), set out below.
-SP1: Process and power systems
The SP1 work has covered the comparison between the power plants with different precombustion decarbonisation, oxy-fuel technologies and other pre-combustion technologies developed in the ENCAP subprojects. A great number of technical descriptions of such concepts and cost data exist in international sources and the development inside and outside Europe was followed. However, these data are based on different presumptions and cannot easily be compared with each other. No directly relevant model was found for the comparison and recommendation that SP1 is making in ENCAP.
Altogether, the development of uniform guidelines for the description of relevant power plant performance and cost calculations was necessary to meet the objective of the ENCAP project.
-SP2: Pre-combustion decarbonisation technologies
In this sub-project the target has been the process development for IGCC/IRCC based on hard coal, lignite and natural gas to confirm the feasibility of these concepts with integrated CO2 capture. In addition, capture-free cases for hard coal and lignite were deemed necessary to develop as reference cases, whereas the reference case for the IRCC is a natural gas fired combined cycle. Since both manufacturers and utilities have been involved in the work, this has enabled duly taking into account the user's perspective in the development work.
Power plant concepts with pre-combustion capture of CO2 for natural gas, hard coal and lignite were developed and evaluated, and also used in the benchmarking work in SP1. A capture rate higher than the predefined minimum of 90% was obtained for hard coal and natural gas, whereas the capture rate for lignite was 85%, due to the chosen gasification process. CO2 avoidance cost was around 25 EUR/tonne CO2 for the bituminous case, around 18 EUR/tonne CO2 for the lignite case and around 35 EUR/tonne CO2 for the IRCC case, meaning that the coal-fired cases meet the ENCAP cost target, but not the natural-gas fired case.
-SP3: Oxyfuel combustion technologies
The principle of OxyFuel combustion (a.k.a oxycombustion) is that a (carbon-containing) fuel is burnt in the presence of oxygen but without the presence of nitrogen. Part of the resulting flue gas (mainly consisting of CO2 and H2O) is recirculated back to the furnace for temperature control. The remaining flue gas is cleaned, including condensation of water, and the remaining CO2 is compressed for further transport.
The power process studies carried out in SP3 are based on state-of-the-art technology. Further near-term improvements in efficiency of the PF and CFB OxyFuel plants can be expected through further optimisation of gas separation technology (ASU and CPU) as well as increasing the steam parameters (700 degrees Celsius power plants). Capture rates met the ENCAP target of 90% and investment costs were found to increase with 45- 60% based on net power output, compared to the reference air-fired power plants. Cost of electricity was found to have an increase of 38-45%, whereas CO2 avoidance cost was found to be around 20 EUR/ton CO2 avoided for all cases.
-SP4: Chemical looping combustion
The potential of the CLC combined cycle was to some extent proven to be very important in terms of efficiency already prior to ENCAP, as it has a small energy penalty compared with other CO2 capture technologies applied to gas turbines. Nevertheless, it could by no means be said that power cycles with CLC for CO2 capture were fully investigated at that period in time, and further work on cycle simulations was judged necessary, both for gaseous and solid fuels.
Altogether in SP4, promising results were obtained but technical maturity is not there yet for chemical looping combustion. Additional development effort of stable and cost effective oxygen carriers is required in the scale-up of CLC reactors and to demonstrate the full operability of the CLC process. The concept studied is in the 450 MW size. Thus this concept is not available in the near future or for larger power plants. Among the process applications considered within ENCAP, the CFB boiler application has a more advanced development status compared to the Gas Turbine Power Cycle application.
-SP5: High-temperature oxygen generation for power cycles
The objectives for SP5 were to identify and develop low-cost advanced high-temperature oxygen separation process options for use in the power plant processes developed in ENCAP SP2 and SP3.
In-depth investigations were made on the CAR material and on the integration of the CAR process in a lignite-fired PF oxyfuel boiler power plant. Thermal efficiency for this option is better when using flue gas than when using steam as purge medium. If using flue gas, however, current CAR materials have insufficient resistance to CO2 and SO2 exposure. These results confirmed again that additional, relevant efforts in the material stability and performance and in the process integration are needed in order to improve the competitiveness and attractiveness of CAR technology.
-SP6: Novel pre-combustion capture concepts
The objectives for SP6 were to investigate prospective emerging pre-combustion decarbonisation and OxyFuel capture technologies that are estimated to have a high potential for capture cost reduction while maintaining a high capture rate.
A large number of cycles were analysed, the most critical components of the most interesting cycles were studied to considerable level of detail and a full economic assessment of these cycles was made on a consistent basis. Out of seventeen cycles studied in SP6, eight cycles for natural gas and three cycles for coal exceed the target of 90% CO2 capture. The work of SP6 has thus well achieved the ENCAP objective of at least 90% capture. Out of eight IGCC systems studied in SP6, six cycles have shown CO2 avoidance costs of less than EUR 30 per ton of CO2. As to the four natural gas oxy-fuel cycles studied in SP6, the CO2 avoidance cost varied from 40 to 47 Euros per ton of CO2.
So the work of SP6 achieved the cost reduction target of ENCAP on coal IGCC systems with pre-combustion but showed that difficulties exist to achieve the cost reduction target for natural gas oxy-fuel systems. The work in SP6 showed, however, as mentioned above, that IGCC systems based on membranes are still not at short distance from practical realisation.
The project has performed development and research on concepts and components for chemical looping combustion technology. A design concept for a 455 MWe supercritical coal CLC-CFB (circulating fluidised bed) boiler operating with coal and pet coke has been developed and sized. The work shows that the CLC CFB is a feasible concept, close to conventional CFB processes. The ENCAP project has developed three high-temperature oxygen generation concepts; Oxygen separator membrane for power plant cycles; High temperature oxygen adsorbent (CAR) and Oxygen-transport membrane systems for power production.
The CAR concept with cyclic oxygen adsorption/desorption was found to be the most mature of three investigated high-temperature oxygen generation options. The two other was found interesting but need significant more time for further development. Due to the ENCAP project time frame the further work then focused on the CAR process and further experimental work was performed in order to find the optimum CAR material and geometry. One material could be selected based on a trade-off between chemical stability and performance (i.e. oxygen storage capacity) under dynamic conditions.
ENCAP has investigated a number of prospective emerging pre-combustion decarbonisation and OxyFuel capture technologies that are estimated to have a high potential for capture cost reduction while maintaining a high capture rate. An important result is a structured two-step evaluation of 17 novel process concepts for precombustion decarbonisation and OxyFuel combustion revealed the natural gas fired OxyFuel Combustion Cycles as the most promising novel concepts, showing an acceptable thermal efficiency and without requiring any significant scientific breakthrough (in e.g. combustion engineering and aerodynamic design) for their realisation.
These options generally can be described as less mature than the other concepts developed in ENCAP, (most are at the conceptual level). CO2 avoidance cost for these cycles, however, was estimated to be EUR 40-47 /ton CO2 avoided, meaning that they do not meet the CO2 cost target of ENCAP.
The further development of CO2 pre-combustion by the ENCAP consortium has been carried out during an important period when the interest of the overall CCS concept has gradually increased. The knowledge generated and that is in the hand of the ENCAP consortium and several partners in the consortium have already been activated in further development of CO2 capture technologies in new CO2 capture projects in FP7 and the EC RFCS programme.
CO2 Capture influence on the European power situation and the possibility to meet specified CO2 reduction targets has been studied in different scenarios. The results from the study on CO2 capture influence on the European power situation show that it is possible to meet an 85% CO2 reduction target by 2050, requiring a large contribution from CCS, with a steep ramp-up post 2020, which imposes challenges for timely investments in corresponding CCS infrastructure. The results should not be seen as predictions of energy futures but rather a quantitative analysis investigating the possible roles and limits for different technologies, including CCS.
