Techno-economic evaluation of biogas upgrading process using CO2 facilitated transport membrane

The biogas upgrading by membrane separation process using a highly efficient CO2-selective polyvinylamine/polyvinylalcohol (PVAm/PVA) blend membrane was investigated by experimental study and simulation with respect to process design, operation optimization and economic evaluation. This blend membrane takes advantages of the unique CO2 facilitated transport from PVAm and the robust mechanical properties from PVA, exhibits both high CO2/CH4 separation efficiency and very good stability. CO2 transports through the water swollen membrane matrix in the form of bicarbonate. CO2/CH4 selectivity up to 40 and CO2 permeance up to 0.55 m3(STP)/m2 h bar at 2 bar were documented in lab with synthesized biogas (35% CO2 and 65% CH4). Membrane performances at varying feed pressures were recorded and used as the simulation basis in this work. The process simulation of an on-farm scale biogas upgrading plant (1000 Nm3/h) was conducted. Processes with four different membrane module configurations with or without recycle were evaluated technically and economically, and the 2-stage in cascade with recycle configuration was proven optimal among the four processes. The sensitivity of the process to various operation parameters was analyzed and the operation conditions were optimized.