Low Concentration Coal Mine Methane Concentrated by Vacuum Pressure Swing Adsorption

Abstract

In order to solve the current situation that low-concentration oxygen-bearing coal mine methane can’t be concentrated and utilized, the vacuum pressure swing adsorption process was employed to concentrate the oxygen-bearing coal mine methane gas with the methane concentration of 20%. To ensure the safety of the enrichment process, mixed adsorbents consist of active carbon and carbon molecular sieve was used innovatively, which can adsorb methane and oxygen simultaneously. So that the oxygen and methane concentration of both effluent gas and product gas of the process are both in safe range. The separation process of coal mine methane gas was carried out at room temperature under adsorption pressure no more than 320 kPa abs., and desorption pressure about 25 kPa abs. The effects of adsorber adsorption time, adsorbent’s quality ratio, adsorption pressure, purge time, purge time on the process were investigated. When the quality ratio of carbon molecular sieve and active carbon was 3.4, the methane can be concentrated to upper than 33% the concentration of methane and oxygen in effluent gas are lower than 2.4% and 10.8% respectively. When we added a purge step with a purge time of 5s, the product methane concentration decreased to 31%, and the concentration of methane and oxygen in effluent decreased to 1.6% and 9.5% respectively. This study shows that the low-concentration coal mine methane gas can be concentrated and utilized for industrial applications.