Device and process for preparing natural gas through closed-loop circulation comprehensive utilization of synthesis ammonia tower rear gas

Abstract

The invention relates to a device and a process for preparing natural gas through closed-loop circulation comprehensive utilization of synthesis ammonia tower rear gas. Low-pressure methane synthesis system tower rear gas generated by a low-pressure methane synthesis system is fed into a low-pressure cold box, and meanwhile, nitrogen is injected into the low-pressure cold box; after being compressed by a six-section high-pressure machine, the residual gas is fed into a synthetic ammonia system to react to generate synthetic ammonia, and meanwhile, synthetic ammonia tower post-gas containing 3% of ammonia and 24% of methane, which is formed by combining purge gas and circulating gas, is generated, the synthetic ammonia tower post-gas is fed into a first high-pressure cold box, and the rest synthetic ammonia tower post-gas is fed into a second high-pressure cold box; meanwhile, nitrogen and methane injected into the second high-pressure cold box are fed into a natural gas storage tank to be stored, and residual gas is fed into a synthetic ammonia system through a circulator to produce synthetic ammonia. The design is reasonable, the conception is ingenious, and the design purpose of one tower with two products is achieved.

Description

technical field [0001] The invention relates to the technical field of synthetic ammonia, in particular to a process for preparing natural gas by comprehensive utilization of closed circulation of gas behind a synthetic ammonia tower. Background technique [0002] China's synthetic ammonia industry started from Nanjing Yonglining Plant, and has gone through nearly a hundred years of history. Synthetic ammonia industry is one of the basic inorganic chemicals. Ammonia is the main raw material for fertilizer industry and basic organic chemicals. It can be processed from ammonia into nitric acid. , the production of nitric acid is often attributed to the synthetic ammonia industry. The synthetic ammonia industry was formed in the early 20th century, and began to use ammonia as a raw material for rocket fuel and explosives industry to serve the war; after the end of the First World War, it turned to serve agriculture and industry. With the development of science and technology, ...

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Problems solved by technology

[0004] China's existing coal-based synthetic ammonia, medium-pressure combined alcohol, and combined urea (national standard) production lines, in which the post-column gas of the low-pressure one-step synthetic natural gas system is sent to the synthetic ammonia system to prepare synthetic ammonia, because there is methane in the post-column gas, which cannot be removed , the synthetic ammonia system synthesizes ammonia and produces methane-containing after-column gas at the same time, and the presence of methane affects NH 3 The synthesis rate can only reach 11.5%, and there is only one product in one tower, that is, synthetic ammonia

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