Theoretical and experimental study of CO2 removal from biogas employing a hollow fiber polyimide membrane

In the present work, the efficient removal of CO2 from CH4 for biogas upgrade is investigated, employing a commercial polyimide (PI) membrane (UBE Industries Ltd., Japan). The goal is to meet the requirements of high purity biomethane (>95%) for effective energy use (e.g., by connecting the CH4-rich gaseous stream into the natural gas grid) with simultaneous CO2 capture, for potential reuse. The separation process is studied experimentally employing a commercial hollow fiber polyimide membrane module at laboratory scale conditions, while mathematical process models of various complexity in terms of the flow conditions are employed and compared with the experiments. The results demonstrate that, among the different flow models, the crossflow model is in much better agreement with the experimental results and can be further employed to design more complex membrane module configurations, such as two- and three-stage processes, recycle, etc.