Post-combustion CO2 capture using exchanger type vacuum temperature swing adsorption: Cycle design and performance analysis

Carbon capture and storage (CCS) is a critical technology in mitigating greenhouse gas emissions and achieving carbon peaking and carbon neutrality goals. Currently, there is a great challenge to effectively utilize and transfer the extensive waste heat from large emission point sources to capture CO2 in a cost-effective way. In this study, we demonstrate and simulate a novel multi-columns-in-column exchanger type adsorption unit (ETAU) employing activated carbon as the adsorbent for the post-combustion vacuum temperature swing adsorption (VTSA) process. Advanced heat management strategies are proved feasible to minimize heat and power consumption. After the validation of the model using 1-bed 5-step experimental results, 4-bed 7-step and 4-bed 9-step cycles were developed in Aspen Adsorption. Results confirm that both cycles are effective in improving CO2 purity. In the 4-bed 7-step cycle, when the recycle time is 300 s, the CO2 product with a purity of 88.4%, a recovery of 98.8%, and a productivity of 0.975 mol/kgads/hr can be obtained under an adsorption temperature of 283 K, desorption temperature of 383 K, and vacuum pressure of 0.09 bar. Parameters analysis shows that raising the desorption temperature leads to more specific heat consumption, and by decreasing the vacuum pressure the specific power consumption will increase. Lower adsorption temperatures and vacuum pressures are found beneficial to the exergy efficiency through response surface analysis. Our evaluation indicates that the novel VTSA cycles with the ETAU design can achieve excellent CO2 purity and recovery, and the low desorption temperature allows partial insertion of ultra-low-grade heat.