Experimental Humid Post-Combustion CO2 Capture Using a Metal-Organic Framework, Calf-20 By Vacuum Pressure Swing Adsorption

The presence of water in the flue gas from coal power plants makes CO₂ capture processes more difficult. Often, many studies assumed water is removed before entering the CO₂ capture unit. Characterizing the impact of H₂O on the CO₂ separation is essential and challenged due to a high affinity of H₂O onto most solid porous adsorbents. Particularly MOFs are considered to be sensitive to moisture. In this work, CALF-20, a water resistant and water stable metal organic framework, was studied and characterized for humid post-combustion CO₂ capture process. A mathematical model coupled with a process optimizer helped in identifying operating conditions that can guarantee high CO₂ purity and recovery. Two process cycles were experimentally tested in a lab-scale Vacuum swing adsorption rig under both dry and wet condition using a synthetic flue gas with 15% CO₂ and 85% N₂. Under the dry case, it was possible to obtain a CO₂ purity of 95% and a recovery of 90%. To study the impact of H₂O, the humidifier was introduced to create a stable humid stream. Various relative humidity (RH) values were examined: 15%, 25%, 45% and 70%. All wet PVSA experiments were run up to 400 cycles. The MOF demonstrated extraordinary stability and produced exceptional purity and recovery of CO₂.