Site trials of methane capture from low-concentration coalbed methane drainage wells using a mobile skid-mounted vacuum pressure swing adsorption system

Abstract

Coalbed methane (CBM) emissions account for a large part of methane (CH4) emission in the fossil energy area, and vacuum pressure swing adsorption (VPSA) is an effective method to recover low-concentration CBM. However, CBM supply can fluctuate in quality or quantity because of the constantly changing geological conditions, thus permanent large-scale factory mode is economically inappropriate. In this work, a highly integrated mobile skid-mounted prototype VPSA system was designed and installed, and site trials of low-concentration CH4 capture were, for the first time, carried out in a coal mine site of Huayang New Material Technology Group Co. Ltd in China. Site trials including breakthrough tests and VPSA experiments were conducted in a fluctuating range of CH4 (16–30%). The effects of flow rate, adsorption pressure, and feed concentration on the separation process were revealed using a breakthrough process, and their effects on the dynamic parameters were also analyzed. After purification, the CH4 content in product gas was increased from 16–30% to 43.3–70.7% which all meet the requirements of 4T grade city gas in China, and maximum CH4 productivity of 43.6 × 10−3 m3/(kg·h) can be achieved. More importantly, multicycle breakthrough tests demonstrated that superhydrophobic zeolite TUTJ-1 is more resistant to the effects of water and has more potential for capturing CH4 under humid conditions than activated carbon.