Modelling and optimization of hybrid PSA/membrane separation processes

The present work proposes a modelling and optimization framework for hybrid pressure swing adsorption (PSA) and membrane processes for gas separations. The hybrid PSA/membrane scheme has been applied on the process of hydrogen production from steam methane reformer off gas. Three different hybrid separation schemes have been considered and analyzed. Maximum overall hydrogen recovery has been achieved for given minimum requirements in product purity, while optimizing various PSA and membrane operating and design parameters: the number of adsorption columns, PSA cycle configurations, the number of pressure equalizations/co-current depressurization steps, multiple adsorbent layers, PSA and membrane feed pressure, purge-to-feed ratio, bed length, carbon-to zeolite ratio, membrane area, thickness, and support thickness. The optimization results have been compared to the optimization results of the PSA only case and the benefits of hybrid separation systems have been assessed in terms of the improvements in the overall hydrogen recovery (similar to 2 %), reduction of adsorption beds size (up to 46 %), concentration of the carbon dioxide and carbon monoxide captured in a separate stream (up to 76 %), and reduction of the carbon dioxide content in the waste gases (up to 74 %).