Experimental study on heat transfer caused by feed gas concentration fluctuation in low concentration CBM utilization unit

Due to the restriction of mashgas drainage technology in underground coal mine, a huge number of low concentration coal-bed methane is released into the atmosphere, because of the low methane concentration and the greater difficulty of utilization, causing environmental pollution and waste of resources. If the methane can be separated from coal-bed methane, and liquefied into liquefied natural gas (LNG) product, the waste of resources and realize energy-saving and emission-reduction can be reduced. But affected by the coal mine geological condition and the gas drainage pump, methane concentration of the coal-bed methane has large fluctuation, quite a disadvantage for the liquefaction plant. Low concentration coal-bed gas cryogenic liquid pilot plant is presented in this paper. According to the test data, the fluctuation in raw material gas methane concentrations influence on device performance was studied theoretically, the result is: LNG products of methane recovery is more sensitive to changes in raw material gas of methane concentration, and the product purity of methane with the feed gas methane concentration changed little. In the design of the device, it should be taken into account that the circulation of refrigerant and the flow of raw gas can be adjusted. If the methane content in feed gas increased, operator should reduce the flux of feed gas, in order to maintain methane purity and recovery rate, or increase the yield of LNG product by increasing circulating flux of refrigerant, thereby increasing the economic performance of the device.