Biogas upgrading using membrane contactor process: Pressure-cascaded stripping configuration

In this paper, we present a novel pressure-cascaded stripping configuration for membrane contactor biogas upgrading processes. The work clearly illustrates that optimizing the stripping unit for the biogas upgrading process is crucial to maximize the plant productivity. Employing polypropylene (PP) hollow fiber membrane modules and water as physical absorbent, the effects of absorption pressure, gas liquid flowrate, and vacuum mode were systematically studied. In addition, exploiting the solubility difference between CO2 and CH4, as well as the preferential absorption of CO2 in water, a pressure-cascaded stripping tank was implemented to recover and recycle the absorbed CH4 in high purity. The proposed configuration simultaneously enhanced the biomethane yield (90%) and purity (97%), high enough to be linked to the natural gas pipeline. A preliminary analysis showed that the proposed configuration offers cost benefits for large-scale biogas upgrading plants, and a significant reduction of global warming potential (GWP) compared to conventional configuration. The process developed in this work will be implemented in a biogas pilot-plant site to assess its overall feasibility. (C) 2017 Published by Elsevier B.V.