Gas Turbine CO2 Enhancements on Carbon Capture and Storage

The objective of this research was to investigate the impact of increasing the CO2 concentration in the exhaust flue gas in gas turbines via exhaust gas recirculation (EGR) and selective exhaust gas recirculation study (S-EGR). The gas turbine types explored are the micro gas turbine (MGT) and the combined cycle gas turbine (CCGT). Both gas turbines were integrated with a chemical absorption capture plant operated using MEA, in order to determine the reduction in carbon emissions into the atmosphere. Modelling the CCGT, involved a fuel flexibility study as well as a techno-economic analysis carried out to determine the cost of electricity (COE) and cost of CO2 avoided (COA) to ascertain the economic and energy savings involved as well as the emission reductions. The study on the MGT, entailed the experimental and modelling analysis of S-EGR via CO2 injection into the compressor inlet, with a maximum CO2 injection flowrate of 300 kg/h. The experimental campaign carried out on the MGT and capture plant were based at the LCCC, in Sheffield. The performance of the MGT is investigated over a range of power outputs (100 kWe to 60 kWe) and the emission properties are recorded. It was observed that the CO2 flue gas concentration increased from 1.8 mol% to 9.6 mol% and 1.5 mol% to 11.6 mol% at 100 kWe and 60 kWe respectively, which improved the performance of the integrated capture plant, indicating that S-EGR operation in the MGT could reduce the specific reboiler duty by 15% whilst increasing the liquid-gas ratio, at a constant capture rate of 90%, thus, reducing overall energy costs. The CCGT study entailed the modelling of fuel flexibility via increasing the CO2 content in the fuel from a conventional natural gas composition with 1 mol% CO2 to a maximum CO2 content of 10 mol%. Then, an Exhaust Gas Recirculation (EGR) study, involving a 35% EGR ratio stream from the exhaust to the compressor inlet, in which the CO2 content in both the fuel and the air were increased. In both studies, the CCGT is integrated to a capture plant, to reduce the emissions from the power plant. The results indicate that implementing EGR in a CCGT provides better working conditions for the integrated capture plant, when operating with various fuel compositions. The COE and COA associated with EGR implemented CCGT’s are noticeably lower and thus proving its high energy savings and emission reductions.