Transient CO2 capture for open-cycle gas turbines in future energy systems

Abstract

In complex electricity systems with a varied generation mix, the security of supply is important, and the quick-response nature of gas turbines is invaluable in providing system flexibility. Accompanied with post-combustion capture (PCC) of CO2, gas turbines can support the transition to a future low-carbon electricity system. This study presents the development and validation of a dynamic rate-based model of the benchmark CO2 absorption process, using 30 wt% monoethanolamine (MEA). The model is scaled up from pilot-scale to match the flue gas output from a modern small-scale gas turbine operating in open-cycle configuration. Simulations of various flexible operating scenarios shows the rapid transitioning between full and partial load is beneficial in delivering higher time-averaged CO2 capture rates, compared to the Baseload scenario where the PCC system is operated at full load for 5 h. Maintaining a constant liquid/gas (L/G) ratio results in 90.01% CO2 capture; however, this increases the energy demand due to constant reboiler steam flowrate. To compensate, the steam flowrate is also ramped, resulting in a small decrease in reboiler duty compared to the Baseload scenario. Importantly, no negative energy or capture rate related issues to highly-transient PCC operation are found.