Coalbed methane(CBM)is a kind of unconventional natural gas.In China

CBM often contains air when it comes out of the well.Considering issues regarding safety

it is natural that oxygen must be removed firstly.Then

the effective enrichment of methane from methane-nitrogen mixture is one of the most important issues in the utilization of CBM.In this paper

a two-bed pressure swing adsorption(PSA)experimental apparatus was used to separate CH4/N2 mixture on a selected type of carbon molecular sieve(CMS)adsorbent.Owing to the kinetic separation mechanism on CMS

nitrogen is adsorbed on CMS

while methane with certain pressure is delivered out continuously.The influence of adsorption pressure

feed gas velocity and cycle time on the overall performance of the adsorption process was discussed.Feeding a mixture of 50% CH4/50% N2

methane purity of 95.45% was obtained;and 94.89% purity was obtained while feeding a mixture of 30% CH4/70% N2.The results show that all three parameters may affect the separation performance

and the later two have greater influences.It is easier to achieve methane purity above 90% at low adsorption pressure and low feed gas velocity.And the shorter the cycle time

the higher the methane purity is.