Carbon Dioxide is a greenhouse gas naturally found as a component in natural gas, biogas and landfill gas and is also generated whilst flaring or burning the waste methane/gases. For CO2 capture and CO2-CH4 separation, we have investigated the membrane-based technology which offers high energy efficiency, simple modules and process design, reduced footprint, and enhanced energy content of the product gas whilst reducing pipeline corrosion problems and minimising greenhouse gas (GHG) emission. Gas separation membranes require not only materials with excellent separation performance such as selectivity and permeability but also resistant to high temperatures and pressures.
In this work, we have examined the performance of advanced polymeric membranes made from the high-performance intrinsic polyimide material for the recovery of methane and subsequent reduction of GHG emission in natural gas and biogas upgrading applications. Pressure-driven gas separation simulations were performed using the intrinsic parameters of hollow-fibre membranes. It was found that employing the advanced polyimide membrane allows a wider range of operating temperatures (up to 80 °C) and pressures (500 kPag to 100,000 kPag) whilst achieving performance and GHG emission reduction goals. Thus, we employed an innovative concept by combining the advanced membrane materials with a novel multi-stage separation process to recover the CH4 up to 95%-99% in the product (retentate) and CO2 concentration of up to 95%-98% in off-gas (permeate).
Subsequent field-tests for the membranes durability, stability and relative capacity and separation performance compared to cellulose acetate (CA) based membrane systems. These tests have found that the polyimide hollow-fibre membranes are resistant to degradation from hydrogen sulphide (H2S), heavy hydrocarbons (HHCs), and are less susceptible to time effected degradation of permeance and selectivity.