Selective-exhaust gas recirculation for CO2 capture using membrane technology

Membranes can potentially offer low-cost CO2 capture from post-combustion flue gas.
However, the low partial pressure of CO2 in flue gases can inhibit their effectiveness
unless methods are employed to increase their partial pressure. Selective-Exhaust Gas
Recirculation (S-EGR) has recently received considerable attention. In this study, the
performance of a dense polydimethylsiloxane (PDMS) membrane for the separation of
CO2/N2 binary model mixtures for S-EGR application was investigated using a bench-scale
experimental rig. Measurements at different pressures, at different feeding concentrations
and with nitrogen as sweep gas revealed an average carbon dioxide permeability of 2943
± 4.1%RSD Barrer. The bench-scale membrane module showed high potential to separate
binary mixtures of N2 and CO2 containing 5 to 20% CO2. The permeability was slightly
affected by feed pressures ranging from 1 to 2.4 bar. Furthermore, the separation
selectivity for a CO2/N2 mixture of 10%/90% (by volume) reached a maximum of 10.55 at
1.8 bar. Based on the results from the bench-scale experiments, a pilot-scale PDMS
membrane module was tested for the first time using a real flue gas mixture taken from the
combustion of natural gas. Results from the pilot-scale experiments confirmed the
potential of the PDMS membrane system to be used in an S-EGR configuration for capture
of CO2.