Real adsorbed solution theory model for the adsorption of CO2 from humid gas on CALF-20

CALF-20 is a metal organic framework which acts as a physical adsorbent for CO2. A potential benefit of CALF-20 over more traditional zeolite physical adsorbents is that CALF-20 exhibits a strong Type I adsorption behavior for CO2, while water exhibits S shaped Type V adsorption. As a result, CALF-20 maintains most of its CO2 capacity for up to 50% relative humidity modelling and predicting the multi-component adsorption of water and CO2 on CALF-20 is a prerequisite for accurate process modeling. In this work a real adsorbed solution theory (RAST) model is developed to predict the non-ideal multi-component adsorption in H2O – CO2 – N2 gas mixtures. We demonstrate that RAST can accurately represent the non-ideal adsorption. The RAST model is then applied to predict the adsorption from ternary mixtures of water, nitrogen, and CO2. It is shown that co-adsorption of water has a more negative effect on CO2 adsorption at lower partial pressures of CO2. This fact has significant implications on adsorption process design for low pressure flue gas sources such as coal boiler and natural gas combined cycle flue gas.