Preliminary evaluation of vacuum desorption efficiency and the influence of vacuum port configuration in a calf-20 VPSA system for CO

Vacuum Pressure Swing Adsorption (VPSA) is a promising, energy-efficient technology for post-combustion CO? capture; however, mass-transfer resistance during regeneration often limits its performance. To address this, this study evaluates the CO? capture performance of the Metal-Organic Framework (MOF) CALF-20 and optimizes vacuum desorption processes. Breakthrough experiments were conducted on an adsorption column (90 cm in height, 2 cm in diameter) containing 244 g of adsorbent using a gas mixture of 15% CO?/85% N? at 5 NLPM. CALF-20 exhibited a breakthrough time of 374 s, with a saturation adsorption capacity of 1.37 mol CO?/kg. Furthermore, the influence of vacuum port configuration was investigated using three ports located at 11, 50, and 79 cm from the column bottom. The results demonstrate that switching from the conventional single-bottom port configuration (desorption efficiency, nDES = 79.77%) to the optimized 2-port configuration at the bottom and middle (2-M&B) significantly increased nDES to 93.24%. These findings confirm that strategic port positioning effectively mitigates mass-transfer resistance, providing a critical engineering solution for scaling up high-efficiency MOF-based VPSA systems.