Most of oxygen-bearing coal-bed methane(CBM)has not been utilized due to the limit in technique for production.The discharged gas leads to not only the waste of resources but also environmental pollution.In this study

a liquefaction process is proposed and designed for the typical CBM.HYSYS software is adopted to simulate the process.The flammability limits are analyzed and calculated based on the flammability limit theory and the simulated results of HYSYS.The results indicate that no flammable hazards exist in the processes of compression

liquefaction and throttling but they may appear at the top of the distillation tower.A method

in which oxygen is first removed from the feed gas with the control of the bottom flowrate(flowrate of the liquid product at column bottom)

is adopted to ensure that the methane content is always higher than the flammability limit in the whole liquefaction and distillation processes

so that the operation safety of the whole process is very high.The methane recovery rate and the purity of liquid product are high with low energy consumption.Furthermore

the liquefaction process has good applicability for other gas resources.The simulation results can offer references for the separation of oxygen from CBM and security analysis of liquefied process.