Pretreatment method and system of syngas for synthetic ammonia

Abstract

The invention discloses a pretreatment method and system of syngas for synthetic ammonia. The system comprises a dehydration device, a mercury removal device and a cryogenic separation device; the dehydration device is used for cooling and dehydrating the syngas; the mercury removal device is used for mercury removal and purification of the dehydrated syngas output by the dehydration device; the cryogenic separation device comprises a plate-fin heat exchanger group and is used for cooling the purified syngas output by the mercury removal device and outputting low-temperature purified syngas; and the cryogenic separation device further comprises a gas-liquid separation unit, the gas-liquid separation unit is used for carrying out gas-liquid separation on the low-temperature purified syngasoutput by the plate-fin heat exchanger unit to output low-temperature purified gas, and the low-temperature purified gas is heated by the plate-fin heat exchanger unit to obtain purified syngas for synthetic ammonia. Through reasonable arrangement of part structures, impurities in the syngas for synthetic ammonia are efficiently removed, and the impurity gas is made into a CNG product in a rectification and purification mode to be output, so the additional value of the product is increased; and meanwhile, circulating nitrogen is adopted for pressurization and expansion, so the energy efficiency is improved, and the overall device transformation cost and operation consumption are reduced.

Description

technical field [0001] The invention belongs to the technical field of coal chemical industry, and in particular relates to a method and system for pretreatment of feed gas for synthetic ammonia. Background technique [0002] The ammonia synthesis reaction in the ammonia synthesis plant is the core section of the whole plant, and it is also an important section that determines the energy consumption of the entire plant. The ammonia synthesis reaction has strict requirements on the N / H ratio and content of the raw material gas for ammonia synthesis. Impurity gases and inert gases such as methane and argon in the components will reduce the reaction efficiency of the ammonia synthesis unit and increase the energy consumption. [0003] At present, in the process of updating and eliminating the traditional normal-pressure coal gasification method in the country, the main components of the ammonia synthesis raw material gas produced by the new alternative coal gasification are: hy...

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Problems solved by technology

[0002] The ammonia synthesis reaction in the ammonia synthesis plant is the core section of the whole plant, and it is also an important section that determines the energy consumption of the entire plant. The ammonia synthesis reaction has strict requirements on the N / H ratio and content of the raw material gas for ammonia synthesis. Impurity gases and inert gases such as methane and argon in the components will reduce the reaction efficiency of the ammonia synthesis unit and increase the energy consumption

[0003] At present, in the process of updating and eliminating the traditional normal-pressure coal gasification method in the country, the main components of the ammonia synthesis raw material gas produced by the new alternative coal gasification are: hydrogen (67%-72% by mole), nitrogen (22% by mole ~24%), methane (4% to 10% by mole), argon (0.4% to 0.6% by mole), water (saturated state), methane and argon do not participate in the reaction as inert gases in the ammonia synthesis section. The compression and reaction process of the system will consume a lot of useless work, which will increase the energy consumption of the system and reduce the net ammonia value of ammonia synthesis, which poses a severe challenge to the ammonia synthesis section of the ammonia synthesis plant

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