Influence of Contained Water Vapor on Performance of Simulated Biogas Separation by Pressure Swing Adsorption

Abstract

For the CH₄ enrichment from biogas mainly consisting of CO₂, CH₄ and water vapor, the effect of water vapor on the separation performance by pressure swing adsorption, PSA, was experimentally investigated using three different adsorbents. Zeolite 13X, which has satisfactory adsorption ability for CO₂, SAPO-34, which shows superior water vapor adsorption/desorption characteristics, and the carbon molecular sieve (CMS), which is a hydrophobic adsorbent, were employed as adsorbents. It was found that the separation performance of zeolite 13X significantly decreased when water vapor was contained in the simulated biogas. The separation performance of SAPO-34 also decreased when water vapor was contained in the simulated gas, however, the decay of separation performance was partly inhibited due to its ease of water vapor desorption. CMS showed no separation performance decay even though the water vapor was contained in mixed gas since the amount of adsorbed water onto the CMS was low. From these results, it was suggested that the CMS is suitable as an adsorbent for the biogas separation containing water vapor.