(122d) A Post-Combustion CO2 Capture Rapid Pressure/Vacuum Swing Adsorption Process and Its Application for Decarbonizing a Coal-Fired Power Plant
Up to now, relatively less attention has been paid to adsorption-based carbon capture research than conventional amine processes and other promising alternatives, such as solid- or chemical- looping and oxy-combustion, when it is aimed to achieve 90+% CO2 recovery and 95+% CO2 purity for decarbonising fossil fuel-based power plants. However, both numerical simulation studies and lab- and pilot- scale experimental campaigns has been demonstrating that a well-designed CO2 capture adsorption process can spend less energy than a conventional amine process for post-combustion carbon capture. There is still a concern with practicality of a commercial-scale CO2 capture adsorption process lingering on due to its requiring a huge volume of adsorbents relating to the performance of currently available best CO2-selective adsorbents. But this issue can be overcome to some extent by process design given the fact that the size of the adsorption column can be drastically reduced by operating the adsorption process in a fast cyclic mode.
In this study, a simple one-column Rapid Pressure/Vacuum Swing Adsorption (RPSA) process was designed and its performance was evaluated by a high-fidelity adsorption process simulation using gPROMS. The mathematical model contains a rigorous energy balance incorporating temporal and spatial changes of the kinetic energy of a gas flow on a fixed-bed adsorption column. The effects of the kinetic energy terms are in most cases deemed negligible in simulating conventional cyclic adsorption processes for gas separation. However, the terms relating to the kinetic energy change become influential in case of a cyclic adsorption process experiencing an abrupt velocity change during the pressure-varying steps, i.e. RPSA. The simulation of the CO2-enriching RPSA unit demonstrated that the use of the rigorous energy balance in combination with a full momentum balance could generate the bed temperature and concentration profiles that are different from what commonly used simplified energy balances predict, leading to different CO2 purity and recovery.
In addition, a novel strategy to configure the CO2 capture RPSA unit will be presented in order to achieve the aggressive CO2 capture target, i.e. 95+% CO2 purity and 90+% CO2 recovery at the same time.