Liquid nitrogen washing purified synthetic gas and device for cryogenically separating and recovering LNG (liquefied natural gas) thereof

Abstract

The invention belongs to the technical field of low temperature cryogenic separation and purification and discloses a liquid nitrogen washing purified synthetic gas and a device for cryogenically separating and recovering LNG thereof, comprising a raw material gas pre-processing system, a purifying cryogenic separating cool box and a mixing refrigerant refrigeration cycle system, wherein raw material gas in a cool box system is washed by a nitrogen washing tower to obtain the qualified synthetic gas; the synthetic gas is returned, recycled, cooled and output from a device; high purified LNG liquid is obtained at the bottom of a rectifying tower; and the LNG liquid is served as product and transmitted to a storage system after being cool-throttled. The separation system substitutes former two independent systems of a liquid nitrogen purification system and an LNG single liquefied system, simultaneously achieves to the aims of purifying the synthetic gas and recovering LNG, reduces one-time equipment investment and operation cost, and greatly prolongs the operation period. The liquid nitrogen washing purified synthetic gas and the device have stable operation and outstanding advantage for large-scale device.

Description

technical field [0001] The invention belongs to the technical field of low-temperature cryogenic separation and purification, and in particular relates to a liquid nitrogen washing and purification synthesis gas and a device for cryogenic separation and recovery of LNG. Background technique [0002] Ammonia is one of the important inorganic chemical products and occupies an important position in the national economy. Except that liquid ammonia can be directly used as fertilizer, nitrogen fertilizers used in agriculture, such as urea, ammonium nitrate, ammonium phosphate, ammonium chloride and various nitrogen-containing compound fertilizers, all use ammonia as raw material. Synthetic ammonia is one of the bulk chemical products. The world's annual output of synthetic ammonia has reached more than 100 million tons, of which about 80% is used to produce chemical fertilizers, and 20% is used as raw materials for other chemical products. [0003] The purification of synthetic a...

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Problems solved by technology

[0003] The purification of synthetic ammonia adopts different methods according to the overall process. Most of the current processes use liquid nitrogen washing. In conventional liquid nitrogen washing, the washed backflow gas is used as the fuel gas out of the device, and the fuel gas system is removed, and the components change. Larger, calorific value cannot be guaranteed

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