Upgrade Of Low Content Of Methane In Coal Mine Ventilation Air By Pressure Swing Adsorption

Currently, most coal mines around the world discharge ventilation air methane (VAM) into the air directly,which cause a tremendous environmental problem and lead to inadvertent loss of valuable energy source. Upgrade of low content of methane in VAM is a tough work because the separation of methane and nitrogen is difficult. In this paper, we use a mixture of CH4 and N2 as a model gas, investigated the adsorption selectivity for CH4 of 13X zeolite molecular sieve and activated carbons.The results showed that the adsorption selectivity for CH4 on activated carbons was better than 13X zeolite molecular sieve。The separation factors for methane/nitrogen system were 3.485～3.657 on AC-1 and 3.080～3.388 on AC-2 at 0.2-0.5Mpa; Pore diameter was the factor that determines whether the activated carbon could selectively adsorb methane. With AC-1 and AC-2 as adsorbents, the influence of temperature on separation factor was tested, the result showed, when temperature was changed between 20 and 30℃, the change of separation factor was not obvious.Using AC-1 and AC-2 as adsorbents, the study on upgradeing of low concentration of methane in simulated VAM gas (CH4 concentration is 0.503%) was carried out via pressure swing adsorption (PSA) process at room temperature. The influence of adsorption time and pressure equalization time on concentration of methane in desorption gas and vent gas at different pressure were tested. Under the premise of concentration of methane in vent gas is lower than 0.001%,the concentration of CH4 in desorption gas can be upgraded to 1.162% by AC-1,with pressure 0.4Mpa, flow rate 700ml/min,While the concentration of CH4 can be upgraded to 1.138%,with the pressure 0.3Mpa,flow rate 600ml/min.The concentration of CH4 in desorption gas can be upgraded to 1.132% by AC-2,with pressure 0.4Mpa, flow rate 500ml/min,While the concentration of CH4 can be upgraded to 1.112%,with the pressure 0.3Mpa,flow rate 400ml/min.