Method and device for recovering hydrogen on purge gas in synthetic ammonia and gas stored in tank

Abstract

The invention discloses a method and a device for recovering hydrogen on purge gas in synthetic ammonia and gas stored in a tank. The method comprises the following steps that: firstly, the purge gas and the gas stored in the tank are subjected to ammonia washing treatment; the purge gas subjected to ammonia washing is sent to a precise filter for removing water fog, is subjected to temperature adjustment by a preheater and sent to a hydrogen film separator; hydrogen in the purge gas is returned by excess pressure to a synthesis compressor at the permeable side of the hydrogen film separator; gas at the permeable excess side of the hydrogen film separator is subjected to pressure reduction, and then is mixed with low-pressure gas stored in the tank subjected to ammonia washing; the gas stored in the tank is mixed and sent to a molecular sieve adsorber and a dust filter for removing residual ammonia and water, and then is sent to a cold box system; and gas exhausted from the cold box is used as a hydrogen product and fuel gas. The invention utilizes the self high pressure of the purge gas, reclaims the hydrogen by a film separation method, the hydrogen at the permeable side of the film is returned to the synthesis compressor by the excess pressure, and overcomes the defects of complicated equipment, high manufacturing and maintenance cost and low recovery rate of usable gas such as hydrogen and the like caused by independent recovery of hydrogen on the prior purge gas and the gas stored in the tank.

Description

technical field [0001] The invention relates to a method and a device for recovering synthetic ammonia purge gas and storage tank gas, in particular to a method for recovering hydrogen from synthetic ammonia purge gas and storage tank gas. Background technique [0002] Synthetic ammonia is a pillar industry of the national economy, and its output ranks first among various chemical products. At the same time, it is also a big energy consumer. About 10% of the world's energy is used for ammonia synthesis. With the aggravation of the double crisis of energy and environment, it is imperative to save energy and reduce emissions of synthetic ammonia plants. The tail gas of ammonia synthesis mainly includes purge gas (part of the recycle gas extracted from the ammonia synthesis tower) and storage tank gas (gas decompressed and flashed out of the liquid ammonia storage tank). The main components of ammonia synthesis tail gas are ammonia, hydrogen and nitrogen raw materials, and in...

AI Technical Summary

Problems solved by technology

It is specifically reflected in: due to the large pressure difference between the release gas and the storage tank gas, at present, the ammonia synthesis plant or only recovers the hydrogen in the release gas, and the storage tank gas is only used as fuel after recovering ammonia, thus greatly reducing its utilization value; Or separate the purge gas from the storage tank gas for hydrogen recovery, which greatly increases the equipment investment, and the total recovery rate of these methods from the tail gas of ammonia synthesis is still relatively low.

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