Simulated Process Evaluation of Synthetic Natural Gas Production Based on Biomass Gasification and Potential of CO2 Capture Using Membrane Separation Technology

Synthetic natural gas (SNG) production using biomass gasification has recently become important as SNG has been suggested as an alternative to fossil fuels. In the process, CH4 synthesis (methanation) must be considered in addition to biomass gasification. By integrating exothermic methanation and endothermic gasification, the required heat energy can be lowered in an autothermal process. In this study, the performances of autothermal SNG production were estimated from process simulations. In this process, CO2 separation after methanation is inevitably energy-intensive. Therefore, feasibility analysis was conducted on the autothermal SNG production process with CO2/CH4 membrane separation, which is expected to achieve drastically lower energy consumption. These assessments can determine whether membrane separation has the potential as an alternative to the conventional separation unit. Using a membrane process, CH4 loss can become less than 2 %, if the separation factor of CO2 over CH4 exceeds 50. Therefore, we conclude that this value should be set as the minimal target value for the CO2/CH4 separation factor. Achievement of this goal will probably facilitate widespread use of SNG production by biomass gasification.