Efficient biogas upgrading by a novel membrane-cryogenic hybrid process: Experiment and simulation study

As a promising renewable fuel, biogas has been given widely attention. Upgrading raw biogas into high purity biomethane via a cost-effective route could facilitate the enhancement of heating value and combustion efficiency. In this study, biogas upgrading performance of a novel membrane-cryogenic hybrid system was investigated. The separation properties of two kinds of hollow fiber membranes (polyimide and polysulfone) were tested at different operating temperature, and then process simulation was conducted based on the experimental data. The experiment results indicated that operating membrane at the low temperature condition could be a potential method to improve biomethane purity (increased by 6.0% and 6.8% via polyimide and polysulfone, respectively), which was beneficial for combining membrane with cryogenic in the hybrid process. In addition, the simulation results showed that the total energy consumption of (polyimide) membrane-cryogenic hybrid process could be reduced to 0.8 MJ/kg-CH4, when the cold energy was recuperated from liquefied biomethane (bio-LNG). It could be observed that the proposed novel membrane-cryogenic hybrid process could be a competitive alternative for the conventional biogas upgrading technologies to produce high quality (up to 98%) biomethane.