Study On Enrichment Of Low-concentration Methane By Adsorption

The utilization of coal-bed gas plays an important role both in energy conservation and environmental protection. The bottleneck for solving the use of coal bed gas lies in effective separation of CH4 and N2. Adsorption method is a preferable technology in separating CH4 in CH4/N2 system and the selection of adsorbents is the core of the process. The adsorption behaviors of methane in a simulated coal-bed gas on two kinds of adsorbents, i.e. activated carbon and micropore zeolites with different pore structures are compared. The experiment results show that adsorbed CH4 amount on different adsorbents exhibits great difference, which was closely related to pore structures, rather than the BET specific surface area. Suitable pore size with 0.5-0.7nm is extremely important for CH4 concentration.Compared with micropore zeolites, the activated carbon which was prepared by using KOH and H3PO4 as activators in the experiment has the larger methane capacity. The different activators need different activation conditions in order to obtain the activated carbon with large methane adsorption amount. When KOH is used as activator, the optimized activation conditions were as follows, the ratio between alkali and carbonization coconut shell is 3:1, the activation time is 2h and the activation temperature is 600℃and the CH4 adsorption capacity was up to 6.54ml/g. When H3PO4 is used as activator, the optimized activation conditions were as follows, the concentration of H3PO4 is 1mol/L, the activation time is 2h and the activation temperature is 500℃and the CH4 adsorption capacity was up to7.15 ml/g.