A thermodynamic analysis of biogas-to-methanol conversion with CH4 recycling and CO2 utilization using Aspen HYSYS

Hydrocarbon reforming routes are renowned for producing a multitude of energy-effective renewable fuels and/or chemicals. In this study, Aspen HYSYS simulation software was employed to assess the feasibility of a biogas-to-methanol conversion process via coupling CH4 recycling and CO2 sequestration with the dry reforming of biogas. The results revealed that CH4 conversion dramatically enhanced via the recycling of unreacted CH4, followed by CO2 mitigation to a more considerable extent. Simulation runs were performed while varying the reactor pressure and temperature in the ranges of 1.0 to 2.5 bar and 700 to 900 °C, respectively. It was observed that the CO2 conversion decreased continuously as the pressure increased, while there were negligible differences in terms of CH4 conversion using the recycling loop, especially at temperatures of ≥800 °C. At 900 °C and 1 bar, the stoichiometric product (H2/CO) ratio, with CH4 conversion of 83.7% and CO2 conversion of 99.9%, was achieved. An increase in temperature did not significantly affect the WGSR, and 96.6% reactor conversion, with a H2/CO ratio of 1.98, was obtained at a temperature of 150 °C and a pressure of 1.0 bar. The reported study inferred that methanol can be produced at a rate of 24.7 kg h−1 using a biogas molar flow of 1.0 kg mol h−1 under the optimal conditions of 200 °C (temperature) and 100 bar (pressure), with a net thermal efficiency of 67.3%. Overall, it is concluded that biogas dry reforming could allow a sustainable methanol synthesis process with CO2 mitigation at a potentially lower cost, especially in rural areas.