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.

由于煤矿井下瓦斯抽采技术的限制，大量低浓度煤层气释放到大气中，甲烷浓度低，利用难度较大，造成环境污染和资源浪费。如果能从煤层气中分离出甲烷，液化成液化天然气（LNG）产品，就可以减少资源浪费，实现节能减排。但受煤矿地质条件和瓦斯抽采泵的影响，煤层气的甲烷浓度波动较大，对液化厂来说是一个不利因素。本文介绍了低浓度煤层气低温液体中试装置。根据测试数据，从理论上研究了原料气甲烷浓度的波动对装置性能的影响，结果是：甲烷回收的LNG产品对原料气甲烷浓度的变化更为敏感，甲烷产品纯度随原料气甲烷浓度的变化而变化变化不大。在装置的设计中，应考虑到制冷剂的循环量和原料气的流量是可以调节的。如果原料气中甲烷含量增加，操作者应降低原料气流量，以保持甲烷纯度和回收率，或通过增加制冷剂循环流量来提高LNG产品收率，从而提高装置的经济性. 甲烷回收的LNG产品对原料气甲烷浓度变化较为敏感，产品甲烷纯度随原料气甲烷浓度变化不大。在装置的设计中，应考虑到制冷剂的循环量和原料气的流量是可以调节的。如果原料气中甲烷含量增加，操作者应降低原料气流量，以保持甲烷纯度和回收率，或通过增加制冷剂循环流量来提高LNG产品收率，从而提高装置的经济性. 甲烷回收的LNG产品对原料气甲烷浓度变化较为敏感，产品甲烷纯度随原料气甲烷浓度变化不大。在装置的设计中，应考虑到制冷剂的循环量和原料气的流量是可以调节的。如果原料气中甲烷含量增加，操作者应降低原料气流量，以保持甲烷纯度和回收率，或通过增加制冷剂循环流量来提高LNG产品收率，从而提高装置的经济性. 应考虑到制冷剂的循环和原料气的流量是可以调节的。如果原料气中甲烷含量增加，操作者应降低原料气流量，以保持甲烷纯度和回收率，或通过增加制冷剂循环流量来提高LNG产品收率，从而提高装置的经济性. 应考虑到制冷剂的循环和原料气的流量是可以调节的。如果原料气中甲烷含量增加，操作者应降低原料气流量，以保持甲烷纯度和回收率，或通过增加制冷剂循环流量来提高LNG产品收率，从而提高装置的经济性.