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Direct Dry Air Capture of CO2 Using VTSA with Faujasite Zeolites

The capture and concentration of CO₂ from a dry ambient air stream by temperature vacuum swing adsorption (TVSA) have been experimentally demonstrated on a small scale by using a single bed system packed with 20 g of zeolite X. Initially seven different commercially available type X zeolites were investigated, and one of them was chosen for a more comprehensive study. Breakthrough experiments were carried out by perturbing the He saturated bed with compressed ambient air with CO₂ of around 410–440 ppm. In the process studied, a basic four-step TVSA cycle was investigated first, comprising the following steps: pressurization, adsorption, blowdown, and desorption. Four different regeneration temperatures were tested along with four different gas space velocities. With this cycle configuration, CO₂ was concentrated to 95% from 400 ppm with total capture fractions as high as 81%. The energy consumption per ton of CO₂ captured in the system is discussed for the different process configurations. The results from this study are discussed on how to improve the possibility of using low Si/Al ratio faujasite-structured zeolites in direct air capture of CO₂.