CO2-enhanced and humidified operation of a micro-gas turbine for carbon capture

Abstract

As greenhouse gas emissions are a key driver of climate change, sources of CO2 must be mitigated, particularly from carbon-intensive sectors, like power production. Natural gas provides an increasingly large percentage of electricity; however its lower carbon intensity is insufficient to make proportional reduction contributions to circumvent 2 °C global warming. The low partial pressure of CO2 in its flue gas makes post-combustion capture more challenging – increasing the CO2 in the exhaust assists in enhancing capture efficiency. This paper experimentally investigates the impact of the combination of humidified air turbines and exhaust gas recirculation to increase CO2 partial pressures, with the aim of evaluating their effects on emissions and turbine parameters at various turndown ratios. It was found that CO2 levels could be increased from 1.5 to 5.3 vol%, meaning more efficient post-combustion capture would be possible. CO2 and steam additions increased incomplete combustion when used together at high levels for low turndown ratios (below 60%), with CO increasing from 49 to 211 ppm and CH4 from 2.5 to 52 ppm; this effect was negated at higher power outputs. Turbine cycle humidification resulted in net improvements to the turbine efficiency, by up to 5.5% on a specific fuel consumption basis.