Recovery method of ammonia from vent gas during ammonia synthesis

Abstract

The invention relates to a recovery method of ammonia from vent gas during ammonia synthesis in an ammonia synthesis plant. The method comprises the steps of: moving a vent position to a circulating gas pipeline before the outlet of an ammonia cooler and a third ammonia separator, and moving a refinery gas supplementing port to a circulating gas pipeline after the vent and before the third ammonia separator; additionally installing a small ammonia separator or installing a used ammonia separator for separating and recovering liquid ammonia in the vent gas cooled by the ammonia cooler; connecting a vent gas pipe led from the vent with the gas inlet of the small ammonia separator or used ammonia separator, and connecting the vent gas outlet of the small ammonia separator or used ammonia separator to a hydrogen-extracting ammonia washing tower; and automatically returning liquid ammonia separated and recovered by the small ammonia separator or used ammonia separator to the circulating gas pipeline after the outlet of the ammonia cooler and the vent for recovering, and then entering liquid ammonia into the third ammonia separator together with circulating gas to separate ammonia. According to the method provided by the invention, only one high-pressure device is increased, and the complement investment is not needed or the complement investment is lower.

Description

technical field

[0001] The invention relates to a method for recovering ammonia from air released from ammonia synthesis in an ammonia synthesis plant. Background technique

[0002] In the prior art, there are two vent positions in the ammonia synthesis process of each ammonia synthesis plant, one is after the third ammonia separator, and the gas replenishment position is before the third ammonia separator, which belongs to the vent after gas replenishment. Venting here, the synthetic cycle gas has passed through the ammonia cooler and the third ammonia separator, the ammonia content in the vented air is the lowest, and the ammonia content is generally about 2.5% (volume). The ammonia water generated in the ammonia washing tower is less. However, there is the refined gas that has just been supplemented in the vented air, and the refined gas is also released together, which loses the refined gas that contains about 74% (volume) hydrogen and is refined through multiple proces...

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