A parametric study of a PSA process for pre-combustion CO2 capture

Abstract

A PSA process for pre-combustion capture within an IGCC power plant is presented. The process specifications are a high purity and recovery of CO2, i.e. the more adsorbable component, which is not standard in PSA and requires the development of a new PSA cycle. In order to determine its separation performance, a multi-objective optimization is carried out having the CO2 purity and recovery as objectives. The results of this optimization are presented graphically as sets of optimal operating points, i.e. the so-called Pareto set. Moreover, the CO2 productivity is calculated for each point on the Pareto set, representing a further performance indicator. Different process configurations and conditions are optimized and the obtained Pareto sets are compared. The process configuration investigated in this study are the direction of the flow during the depressurization steps and the number of pressure equalization steps. It is shown that a co-current depressurization is beneficial in terms of CO2 purity and capture rate, and that increasing the number of pressure equalization steps leads to a higher CO2 purity, but has a negative impact on the specific adsorbent productivity. The separation performance was found to depend on the operating temperature, on the adsorption pressure, at which H2 is produced, and on the desorption pressure, at which CO2 is produced. It improves for decreasing temperature and decreasing desorption pressure, whereas changing the adsorption pressure does not affect it though leading to lower productivity.