Capture of CO2 from flue gas by vacuum pressure swing adsorption using activated carbon beads

Vacuum pressure swing adsorption (VPSA) for CO2 capture has attracted much research effort with the development of the novel CO2 adsorbent materials. In this work, a new adsorbent, that is, pitch-based activated carbon bead (AC bead), was used to capture CO2 by VPSA process from flue gas. Adsorption equilibrium and kinetics data had been reported in a previous work. Fixed-bed breakthrough experiments were carried out in order to evaluate the effect of feed flowrate, composition as well as the operating pressure and temperature in the adsorption process. A four-step Skarstrom-type cycle, including co-current pressurization with feed stream, feed, counter-current blowdown, and counter-current purge with N2 was employed for CO2 capture to evaluate the performance of AC beads for CO2 capture with the feed compositions from 15–50% CO2 balanced with N2. Various operating conditions such as total feed flowrate, feed composition, feed pressure, temperature and vacuum pressure were studied experimentally. The simulation of the VPSA unit taking into account mass balance, Ergun relation for pressure drop and energy balance was performed in the gPROMS using a bi-LDF approximation for mass transfer and Virial equation for equilibrium. The simulation and experimental results were in good agreement. Furthermore, two-stage VPSA process was adopted and high CO2 purity and recovery were obtained for post-combustion CO2 capture using AC beads.