Concentration separation method for methane in low-concentration coal-bed gas

The invention discloses a concentration separation method for methane in low-concentration coal-bed gas. The concentration separation method comprises the following steps: the low-concentration coal-bed gas is compressed and purified sequentially, and then subjected to primary pressure swing adsorption deoxidation treatment and secondary pressure swing adsorption denitrification concentration treatment to realize concentration separation of the methane in the low-concentration coal-bed gas. For the pressure swing adsorption concentration separation method for the methane in the low-concentration coal-bed gas, the low-concentration coal-bed gas is taken as the raw material and firstly compressed and purified, then the methane in the low-concentration coal-bed gas is subjected to separation concentration with two-stage pressure swing adsorption methods according to the concentration of a gas source, so that the concentration of the methane in the coal-bed gas is increased to 80%-90% from 20%-40% in feed gas. According to the concentration separation method, purposes of CH4 concentration and deoxidation are achieved only through one carbon molecular sieve which is a BM-1 carbon molecular sieve, the concentration separation efficiency is increased greatly, and the concentration separation method has significance and high application value in the aspect of industrial popularization of the coal-bed gas.