Method for preparing high-purity liquefied natural gas from ammonia synthesis tail gas

Abstract

The invention discloses a method for preparing high-purity liquefied natural gas from ammonia synthesis tail gas. The method includes filling the ammonia synthesis tail gas in a molecular sieve absorber to perform purification treatment for the ammonia synthesis tail gas, sequentially delivering the purified tail gas into a main heat exchanger and an evaporator to cool the tail gas, filling the cooled tail gas in a dehydrogenation rectifying tower to perform rectification separation for the tail gas; exhausting oxygen-rich gas from the top of the tower after the separation and obtaining methane-rich liquid from the bottom of the tower; and delivering the methane-rich liquid into a product rectifying tower to perform further rectification separation for the methane-rich liquid and obtaining a high-purity liquefied natural gas LNG product at the bottom of the product rectifying tower after the rectification separation. By the method, resources such as methane and hydrogen in the tail gas can be effectively recycled, so that the resources are recycled, waste of the resources is reduced, the waste resources are turned into wealth, and environmental pollution and waste of energy are avoided. Accordingly, the method has remarkable economical benefit and social benefit.

Description

technical field [0001] The invention relates to the technical field of recovery and comprehensive utilization of synthetic ammonia tail gas, in particular to a method for preparing high-purity liquefied natural gas (LNG) by using synthetic ammonia tail gas. Background technique [0002] The tail gas discharged from the ammonia synthesis plant contains methane (about 40%), nitrogen (about 39.2%), hydrogen (about 20%), argon (about 0.8%) and ammonia, etc. resources, while the production of ammonia also emits carbon dioxide. For the tail gas emitted by synthetic ammonia, most domestic manufacturers send part of the tail gas to the boiler for combustion and recycling, which is neither economical nor environmentally friendly. Combusting or directly venting the tail gas of synthetic ammonia not only wastes energy and pollutes the environment, but also reduces the economic benefits of the nitrogen fertilizer plant. The beneficial methane and argon contained therein cannot be recy...

AI Technical Summary

Problems solved by technology

The technical scheme of the invention can effectively solve the problems of polluting the environment, wasting energy, and aggravating the greenhouse effect caused by the combustion or venting of the tail gas of synthetic ammonia, and prepares high-purity liquefied natural gas (LNG)

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