Unveiling the critical role of biogas compositions on carbon dioxide separation in biogas upgrading using pressure swing adsorption

Biogas upgrading is an important technique for biomethane production, a renewable source of energy with low carbon footprint. The presence of even small concentrations of impurities in biogas influences its properties at different levels. The effect of the individual component species on the biogas upgrading performance has not been fully evaluated and closely understood. In this work, biogas component species, including the typical binary biogas mixture (CH4/CO2) and one impurity with maximum concentration, flowing over silica gel bed are modelled and analyzed to study their effects on the biogas upgrading process. The model is built using Aspen Adsorption (TM) and Aspen Hysys version 10 and validated using experimental data reported previously. The effect of each component species is reported, and the deviation from the typical binary biogas mixture is marked. From our analyses, the presence of all the component species causes an adverse implication on the biogas upgrading performance. The presence of 20% nitrogen, for example, brings about the highest increase in viscosity and density of the biogas mixture, resulting in the highest friction factor between gas molecules and bed surface. Ten percent of moisture content causes the highest pressure drop during adsorption. Interestingly, 5% oxygen, 3% hydrogen, and 1% ammonia enhance the recovery of methane by 1.48%, 0.93%, and 0.56%, respectively. This study can be used to predict the biogas mixing behavior during the biomethane upgrading using pressure swing adsorption. The proposed model possesses a great competence for making prediction of biomethane upgrading performance of PSA process with impressive ability to disclose the influence of the common impurities on upgrading performance and biogas properties.