Methane separation from coal mine methane gas by vacuum pressure swing adsorption

The findings were presented from laboratory investigations and computer calculations for the VPSA (vacuum pressure swing adsorption) process employed to recover methane from coal mine methane gas. The separation process of coal methane gas was carried out at temperature of 278 K under adsorption pressure equal 300 kPa abs., and desorption pressure equal 25 kPa abs. Coal mine methane gas with the CH 4 content of 55.2 vol% was enriched into methane-rich gas which contained 96–98 vol% CH 4 . The methane recovery efficiency reached 86–91% with the ratio for re-circulated methane to that introduced with the feed falling within P/F = 1.8–2.12. The methane content in the adsorption effluent gas was 11–15 vol% under those conditions while nitrogen and oxygen were removed at 96–98% from the methane-rich gas. That separation level of the coal mine gas can be achieved when the methane sorption wave is brought to the outlet point of the sorption bed at the adsorption phase, and then the methane sorption wave is brought to the entry point of the sorption bed at the counter-current purge phase.