| In response to the national call to promote clean energy, energy saving and emissions reduction, liquefied natural gas (LNG) as the representative of the new energy has been large-scale application. To make full use of the ammonia synthesis tail gas resources such as methane, ammonia, hydrogen,frozen ammonia method of eliminating ammonia, membrane separation technology and cryogenic rectification technology isolate various valuable components one by one, methane make LNG, which achieve maximize the value of the use of synthetic ammonia tail gas, while successfully achieve zero emissions of synthetic ammonia exhaust.Frozen ammonia method is used to remove milligram ammonia, which avoids ammonia in tail gas at the late stage of deep cooling gradually forming accumulation on the heat exchanger or pipe blockage. By three plate-fin heat exchangers combined device, the ammonia content in the tail gas is reduced to less than 20ppm (V/V) successfully, and the efficient use of plate-fin heat exchanger greatly reduces the hot and cold fluid temperature difference, which greatly improves the cooling efficiency of the refrigeration units.Using hollow fiber membrane separation hydrogen for hydrogen purity of 94% or more, hydrogen content in the tail gas is reduced to 5% at the same time, which avoid the tail gas in the late of cryogenic liquefied section appeared in thermal throat, and ensure the smooth running of nitrogen expander; In cryogenic liquefied and cryogenic rectification process by using nitrogen expansion refrigeration and liquid nitrogen wash two ways to provide cooling capacity, can reduce the methane content in the tail gas after treatment to less than 1%. Including nitrogen expansion as raw materials for the supply of cold energy of high temperature side liquefied gas, using liquid nitrogen wash as the supply of cold energy of low temperature side cryogenic rectification, reduced the power consumption, the combination of the two cooling ways completely feasible and the energy consumption is low.In the process of Nitrogen gas expansion and tail gas expansion, the expansion of the reflux method significantly improves the refrigeration efficiency.Using 5 channels efficient plate-fin heat exchanger improves the cooling efficiency, and achieves the maximum amount of cold recycling, and reduces the irreversible degree in the process of sewing equipment. The raw gas material of the high pressure is bubbled into rectifying column reboiler, which provides the heat for the rectification, and the high pressure gas material itself due to liquefaction, realized the amount of cold and heat recovery, reducing energy consumption.Using aspen plus 10.2 software of process simulation software to simulate the liquefaction and cryogenic rectification sections throughout, reduces the risk of the whole set of device putting-in-service proactively. With the simulation datas of comprehensive recovery technology has carried on the material balance, the heat balance, equipment calculations and selections, map the process flow diagram, floor-plans and equipment drawings. In the device commissioning phase, the device running statuses of the whole device are analyzed.Device experiments show that this process route is feasible. The product liquefied natural gas contains CH4 98.5%～99.6%, which surpasses CH4 of 75% or more GBT19204-2003 requirement, the methane extraction rate is 99.9%or more; By-product of ammonia contains NH3 98.4%～99.0.The hydrogen contains H2 94% ～95%.The utilization rate of feed gas is≥99.9%.The success of the device throws with symbolizing the tail gas of synthetic ammonia can use the method that many technologies unify, recycles waste, successfully the separation and purification is LNQ simultaneously by-product liquid ammonia and hydrogen at the same time. Namely reduced the pollution of synthetic ammonia enterprises to the environment, increased the income, and raised the production efficiency of the synthetic ammonia. The economic and social benefits are remarkable. |
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