Optimizing membrane module for biogas separation

Biogas as a sustainable energy source produced via different fermentation technologies needs upgrading prior use as fuel or for heat and electricity productions. Today, membrane technology is becoming more and more accepted to compete with other conventional biogas separation methods. We develop a membrane optimization model to find optimal values of operating parameters and the most effective layout while minimizing annual separation cost. To design a hollow fiber module, this model is also used to specify the optimal values of module packing fraction and dimensions while minimizing the required module number for a separation process. We also propose a new modeling approach to select membrane characteristics by which effects of CO2 permeance and CO2/CH4 selectivity on optimal process layouts are investigated. This approach provides a practical guideline for experimentalists to quickly verify the effect of modification techniques on membranes prior to using in a realistic process. The results show that the separation cost is less sensitive to the CH4 recovery ( < 95%). For the same CO2/CH4 selectivity, not only the separation cost reduces by increasing the CO2 permeance by a factor of 2 but this also result in a 40% reduction in the total membrane area. The techno-economic analysis finally reveals that the membrane technology has a high potential either to displace the conventional methods or to be used in a hybrid process.