On the development of Vacuum Swing adsorption (VSA) technology for post-combustion CO₂ capture

A metal-organic framework, UiO-66, has been evaluated as adsorbent in a post-combustion vacuum swing adsorption (VSA) process. Equilibrium isotherms of the most relevant gases (CO₂ and N2) as well as breakthrough curves measured using synthetic flue gas containing 15 mol% CO₂ without and with 9 mol% water vapor are reported. Based on the breakthrough data, a six step one-column VSA cycle is designed and the effects of adsorption and CO₂ rinse times used on the CO₂ recovery and CO₂ purity are examined. With the chosen process configuration and cycle design CO₂ purities around 60% and CO₂ recoveries up to 70% are achieved. 50 cycle adsorption-desorption experiments show that the cyclic CO₂ capacity is reduced by approximately 25% in the presence of water vapor. No reduction in cyclic capacity is observed with increased cycle number; there is rather a slight increase in cyclic capacity with cycle number indicating that a cyclic steady state still not has been reached after 50 cycles.