Ammonia recovery method for gas mixture in hydrogen cyanide production

Abstract

The invention discloses an ammonia recovery method from the mixing gas produced in the process of hydrogen cyanide production, comprising ammonia absorption process, decyanation process, desorption process and rectifying process for solving the technical problem. The invention is characterized in that decyanation process is set separately to recovery hydrogen cyanide gas, avoiding the loss of hydrogen cyanide caused by a large amount of acid gas like hydrocyanic acid contained in the ammonium phosphate solution directly steamed in Versum method, reducing production cost of hydrogen cyanide, reducing the emission of the harmful acid gas like hydrogen cyanide, and avoiding the serious pollution of peripheral enviroment. Besides, the ammonium phosphate solution contains a much smaller amout of hydrocyanic acid after hydrogen cyanide is recovered, which can not influence production process and make the production process more safety.

Description

technical field [0001] The invention relates to a method for recovering ammonia, in particular to a method for recovering ammonia from mixed gas in hydrogen cyanide production. Background technique [0002] The production method of hydrogen cyanide is mostly based on methane, ammonia and air as raw materials in industry, and it is produced by reaction at 800°C-1000°C with platinum, aluminum, and rhodium mesh catalysts. Due to the occurrence of side reactions in the mixed gas from the reactor during the production of hydrogen cyanide, the composition of the mixed gas is relatively complicated, which contains a large amount of unreacted ammonia and the product water generated by the reaction, so whether it is hydrogen Whether the cyanic acid product is involved in the next reaction, the ammonia and water in the mixed gas must be removed. The current industrial methods for removing ammonia from cyanide-containing mixtures mostly use the Fossum method for purifying gas in the c...

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Problems solved by technology

[0003] In this process flow, the following reasons are mainly due to the fact that the Forsum method cannot be directly applied to the ammonia recovery process of the mixed gas produced in the production of hydrogen cyanide: 1. Since the content of hydrogen cyanide gas in the coal gas is only 0.6g / m 3 -0.7g / m 3 , while the hydrogen cyanide content in the mixed gas produced in the production of hydrogen cyanide reaches 85.48g / m 3 , the content of hydrogen cyanide in phosphoric acid rich solution is different, and the recovery effect of ammonia is poor

2. In the decyanation part, the Fossum method adopts the method of directly distilling out a large amount of acid gases such as hydrocyanic acid contained in the ammonium phosphate solution, which will increase the production cost of hydrogen cyanide and cause serious damage to the surrounding environment. Pollution

The high concentration of hydrocyanic acid in the ammonium phosphate solution will also generate hydrocyanic acid polymers, which can cause blockage or even explosion of the tray, posing a safety hazard

3. The mixed gas produced in the production of hydrogen cyanide contains a lot of water vapor, and a large amount of water will be condensed during the process of absorbing ammonia, which will cause the expansion of water in the system

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