含氧煤层气液化HYSYS模拟及安全性分析

HYSYS simulation and security analysis for liquefaction process of oxygen-contained coal-bed methane

设计了一种混合制冷剂和氮节流共同制冷的含氧煤层气液化精馏工艺,模拟结果显示,该工艺可以较为彻底地去除氮气、氧气等,对x(CH_4)为40%的煤层气进料,获得LNG产品纯度高达99.91%,甲烷回收率为97.12%,LNG生产能耗为0.94k W·h/m^3(STP)。对该工艺进行了爆炸安全性分析,表明煤层气仅在精馏塔顶部有爆炸可能性。采用往精馏塔通入氮气降低塔内氧含量的方法来保证操作安全,并对通入氮气的流量和位置进行了优化。结果表明从精馏塔内气体中氧的物质的量分数大于8%的最下层塔板处通入与煤层气同流量的氮气,对氧气稀释效果最好,在保证高纯度LNG产品和甲烷回收率的同时,生产能耗升高30%。

An oxygen-contained coal-bed methane（CBM） liquefaction rectification process using mixed refrigerant and nitrogenthrottle refrigeration was designed and simulation computation ws made with HYSYS. Results showed that for CBM with methane mole fraction of 40%, the nitrogen and oxygen could be completely removed by this process, and LNG purity could reach 99.91%with a methane recovery of 97.12%, while LNG production energy consumption was 0.94 kW·h/m3（STP）. Explosion safety analysis of this process indicated that the explosion probability exists only in the top of rectifying column. Introducing N_2 into the rectifying column to reduce the oxygen concentration was adopted to ensure safe operation, and N_2 flow rate and entering plate position were optimized. Results showed that it＇s best to introduce N2 in the same quantity of CBM into the rectifying column from the bottom plate in which oxygen mole fraction was over 8%, by which the energy consumption increased by 30% to produce high pure LNG product in high recovery of methane.