Enrichment of coal-bed methane by PSA complemented with CO2 displacement



A PSA cycle complemented with CO2 displacement was studied for enriching coal-bed methane (CBM). The column was first pressurized to the adsorption pressure with feed gas, and then N2 was produced at column top in step 2. The feed gas switched to CO2 at the end of step 2, and the adsorbed CH4 was displaced and pushed to column top by CO2 becoming the second column-top product in step 3. The CO2 stream was shut off before it broke through the sorption bed. Then bed regeneration followed. A series of CH4/N2 mixtures containing 17.62 to 51.33% CH4 was used for feed gas. It was experimentally shown that the product concentration was higher than 90%, and methane recovery was higher than 98% even for the feed of low-methane concentration. Displacement at ambient pressure was shown more efficient than the displacement at adsorption pressure for the enrichment. © 2010 American Institute of Chemical Engineers AIChE J, 2011