In this work two different types of coal fired power generation cycles are thermodynamically analysed and benchmarked to each other. First, different configurations of an integrated gasification combined cycle (IGGC) are investigated. Second, different configurations of a lignite fired boiler (LFB) cycle are studied. For both types of power generation cycles, appropriate configurations without CO2 capture are analysed and are used as reference cycles for the appropriate power generation cycles with CO2 capture. Furthermore, membrane reactors are integrated into these power generation cycles in addition to CO2 capture. One goal of the present work is to show the thermodynamic potential of these power generation cycles with CO2 capture and integrated membrane reactor in comparison to the appropriate cycle without membrane reactor. Another goal is to investigate how the operating conditions of the membrane reactor induce the overall power generation cycles in terms of power output and net efficiency.
Oxygen transport membrane (OTM) reactors have been integrated into those power generation cycles to generate the require oxygen instead of a conventional air separation unit (ASU). The OTM reactor is integrated into the gas turbine cycle and separates oxygen from preheated air and thus the ASU becomes redundant. For the IGCC, additionally a configuration with integrated hydrogen-selective membrane reactor is analysed to compare its thermodynamic potential to the one of the OTM reactor.
The IGCC without CO2 capture achieves a net efficiency of 45.1%. If CO2 capture is applied to the IGCC, the net efficiency drops by 10.0%-pts. In case of the OTM reactor it is found that the net efficiency is determined by the operating conditions of the OTM reactor. In case of challenging operating conditions, meaning a large difference in total pressure across the membrane, the IGCC with integrated OTM reactor achieves a net efficiency of 35.5%. This shows that the thermodynamic potential of the IGCC with integrated OTM reactor is limited because the net efficiency can only be slightly higher, by 0.4%-pts. If the difference in total pressure has to be smaller to limit the mechanical load on the membrane material, the net efficiency reduces to 31-33%. In this case the cycle becomes less attractive compared to the IGCC with CO2 capture. The thermodynamic potential of the IGCC with integrated hydrogen-selective membrane reactor is higher, obtaining a net efficiency of 36.7%.