Comprehensive experimental and theoretical insights into the performance of polysulfone hollow-fiber membrane modules in biogas purification process

Abstract

This study experimentally and theoretically explores the separation characteristics of polysulfone hollow fiber membranes for removing carbon dioxide and sulfur compounds from biogas and provides insights into the effects of various operating conditions on the separation characteristics of polysulfone membranes. The experiments to determine the effects of the stage cuts, feed pressure, and sulfur compounds on the membrane separation performance under dry conditions were performed using both binary gas (70% CH4, 30% CO2) and simulated biogas (30% CO2, 1900 ppm H2S, 100 ppm COS, and 100 ppm CS2, balance gas CH4). In addition, detailed theoretical investigations were conducted to understand the separation phenomena of the multicomponent gas through the hollow fiber membrane in conjunction with the experimental data for model validation; the model incorporated the mass transfer across the membrane and a concentration boundary layer adjacent to the membrane. The proposed model was in good agreement with the experimental results, which showed a relative error of < 5%, compared to the model that did not consider the concentration polarization and that based on the conventional mass transfer correlation. The removal efficiency of the sulfur compounds was 70-80% in the feed pressure range of 2.3-2.6 bar. Furthermore, the presence of sulfur compounds had a negligible effect on the separation performance of the polysulfone membrane.