Experimental demonstration of humid post-combustion CO2 capture by vacuum swing adsorption using CALF-20

Abstract

Calgary Framework 20 (CALF-20) is a metal-organic framework deployed for industrial post-combustion CO₂ capture. This work explores capturing CO₂ from a humid stream using CALF-20. A four-step vacuum swing adsorption (VSA) cycle incorporating a light product pressurization step was examined. Two columns packed with structured CALF-20 were used to perform VSA experiments over a wide range of relative humidity (RH) values (13%, 25%, 45% and 70% RH). Key process performance indicators, purity, recovery and productivity were measured and compared with the dry case basis. At low to intermediate relative humidity (13-45% RH), the difference between the dry and the wet VSA cycle was minimal. The purity and recovery were approximately 95% and 71% in Case Study 1, and 92% and 81% in Case Study 2, respectively. The temperature and composition histories were similar to the dry. At high relative humidity (70% RH), while CALF-20 could still achieve similar purity, recovery and productivity, reaching low pressure during the evacuation step was difficult due to the water condensation. Each experiment was run for several days (hundreds of cycles) to confirm the long-term stability of the material. CALF-20 also showed good cyclic durability; minimal loss in the CO₂ capacity from the used CALF-20 sample (~ 10,000 cycles) was observed.