Green Hydrogen Recovery from Natural Gas Grids by Vacuum Pressure Swing Adsorption

This study focuses on the development of a conceptual vacuum pressure swing adsorption process (VPSA) for green hydrogen (GH) recovery from natural gas grids (NGGs). Accordingly, the kinetics-based separation of H2 from NGG was achieved by using a commercial carbon molecular sieve (CMS-3K-172) adsorbent. To develop the VPSA cycle, the CMS-3K-172 was characterized, single- and multicomponent breakthrough curves for H2 and CH4 were performed, and adsorption isotherms were collected between 195 and 273 K and pressures up to 18 bar. To separate H2 (20%) from CH4 (80%), three different VPSA cycle configurations were designed and simulated by using Aspen Adsorption. The operational variables, such as step times, intermediate-to-high-pressure ratio, purge-to-feed ratio, and H2 initial concentration, were evaluated for maximum values of purity, recovery, and adsorbent productivity. The results show that the VPSA processes can enrich H2 in the product stream by up to 68% with a recovery of 92%.