Proportion Pressure Swing Adsorption for Low Concentration Coal Mine Methane Enrichment

Abstract

Using traditional Pressure Swing Adsorption (PSA) with a single adsorbent for low concentration coal mine methane (LCCMM) at a concentration of 30% or less can result in a final CH4 concentration very close to the explosion limit, increasing the risk of explosion. Proportion Pressure Swing Adsorption (PPSA) is a new and safer enrichment method suggested for LCCMM enrichment that uses a mixture of active carbon (AC) and carbon molecular sieves (CMS) as adsorbents. With this method, CH4 and O2 in LCCMM can be adsorbed simultaneously because CH4 is mostly adsorbed by active carbon and O2 is mostly adsorbed by the CMS. Therefore, the concentration of CH4 and O2 is well controlled and does not exceed the explosive limit during the adsorption and desorption processes. We have demonstrated the safety and feasibility of PPSA for obtaining 30% CH4 from LCCMM, with 20% CH4 in air as a feed stock. Our results show that the O2 concentration can be controlled well and does not exceed the explosive limit in both adsorption and desorption, and the CH4 concentration in the desorption gas can be increased to more than 30% by adjusting the bed length and mass ratio of the AC and CMS. Taking these results together, it appears that PPSA is a safe method for LCCMM enrichment.