Impact of CO₂-enriched combustion air on micro-gas turbine performance for carbon capture

Power generation is one of the largest anthropogenic greenhouse gas emission sources; although it is now reducing in carbon intensity due to switching from coal to gas, this is only part of a bridging solution that will require the utilization of carbon capture technologies. Gas turbines, such as those at the UK Carbon Capture Storage Research Centre's Pilot-scale Advanced CO2 Capture Technology (UKCCSRC PACT) National Core Facility, have high exhaust gas mass flow rates with relatively low CO2 concentrations; therefore solvent-based post-combustion capture is energy intensive. Exhaust gas recirculation (EGR) can increase CO2 levels, reducing the capture energy penalty. The aim of this paper is to simulate EGR through enrichment of the combustion air with CO2 to assess changes to turbine performance and potential impacts on complete generation and capture systems. The oxidising air was enhanced with CO2, up to 6.29%vol dry, impacting mechanical performance, reducing both engine speed by over 400 revolutions per minute and compression temperatures. Furthermore, it affected complete combustion, seen in changes to CO and unburned hydrocarbon emissions. This impacted on turbine efficiency, which increased specific fuel consumption (by 2.9%). CO2 enhancement could therefore result in significant efficiency gains for the capture plant.