An Integrated Two-Stage P/VSA Process for Postcombustion CO2 Capture Using Combinations of Adsorbents Zeolite 13X and Mg-MOF-74

Abstract

An integrated two-stage pressure/vacuum swing adsorption (P/VSA) process for postcombustion CO2 capture from dry flue gas has been simulated and optimized. In the first stage CO2 is concentrated to 40–60% at almost atmospheric pressure, and in the second stage it is further concentrated to 95%. A two-bed six-step cycle configuration was employed in the first stage, while a two-bed five-step cycle configuration was used in the second stage. All possible combinations of two different types of adsorbents (zeolite 13X and Mg-MOF-74) have been employed to study the effect of adsorbent type on key process performance indicators of the process under consideration. The results from systematic comparative simulations demonstrate that the combination of adsorbents zeolite 13X–Mg-MOF-74 has the best process performance, in terms of CO2 purity and CO2 recovery, followed by the use of zeolite 13X at both stages of the process. Furthermore, process optimization studies employing the above combinations of adsorbents have been performed to minimize energy consumption for specified minimum requirements in CO2 purity and in CO2 recovery. The optimization results indicate that the minimum target of 95% in CO2 purity and 90% in CO2 recovery is met for the integrated two-stage P/VSA process, for both combinations of adsorbents at different operating conditions, resulting in different energy requirements and CO2 productivities.