Investigation of control strategies for adsorption-based CO2 capture from a thermal power plant under variable load operation

Abstract

This work considers the closed-loop behavior of a moving bed temperature swing adsorption process designed to capture CO2 from a coal-fired power plant. Four decentralized control strategies were studied based on step changes and ramps of flue gas feed flow rate and controller setpoint changes. A proportional-integral (PI) control configuration, where CO2 purity was controlled by hot fluid velocity to the desorption section and CO2 recovery was controlled by the sorbent flow rate, demonstrated the overall best performance. The 99% settling time for higher-level control variables varied from 0 to 13 min for most control configurations and the settling time for CO2 purity was generally longer than for CO2 recovery. The simulations show that using ratio controllers lead to larger offsets but can give around 10 times faster purity response compared to PI-control. All investigated control combinations were able to keep the controlled variables relatively close to the setpoints and the largest relative steady state setpoint offset was 2%.