Recovery method for hydrogen chloride gas produced in production process for 3,5-dichloro-4-aminobenzotrifluoride

Abstract

The invention discloses a recovery method for hydrogen chloride gas produced in a production process for 3,5-dichloro-4-aminobenzotrifluoride. The method is characterized by comprising the following steps: pressurizing HCl gas produced in production of 3,5-dichloro-4-aminobenzotrifluoride by using a fan and introducing the pressurized HCl gas into a primary falling film absorber from the bottom of a tower; subjecting the HCl gas to absorption by a spray device and then to separation by a gas-liquid device; allowing separated gas to enter into a secondary falling film absorber for absorption; then allowing tail gas to enter into a two-stage alkali spray tower for absorption; and finally, carrying out evacuation by using a high exhaust pipe, cyclically using falling film absorption liquid and allowing the falling film absorption liquid to flow out from the bottom of the secondary falling film absorber when the concentration of the falling film absorption liquid reaches 30%, wherein the falling film absorption liquid is reused as hydrochloric acid with a mass concentration of 30%. The recovery method has the following advantages: the falling film absorbers have the advantages of high absorption efficiency, corrosion resistance, high absorption strength, high concentration of the product hydrochloric acid, a low outlet temperature, stable operation and convenience in controlling; discharge of HCl exhaust gas is substantially reduced while recovery of useful materials; and a good effect is obtained during multiple cycles of absorption of HCl gas with water.

Description

technical field [0001] The invention relates to a method for recovering hydrogen chloride gas in the process of producing 3,5-dichloro-4-aminotrifluorotoluene. Background technique [0002] For a long time, due to the use of liquid chlorine as raw material, a large amount of hydrogen chloride gas is produced during the reaction and decomposition. The original process only takes simple measures for this and then directly empties it, which not only causes great pollution to the environment, but also wastes a large part of resources ( Hydrogen chloride gas), and in the production process of our company's product tetramisole hydrochloride, there are two-step salt formation reactions that require the use of more hydrochloric acid (30%), but this part of hydrochloric acid has been purchased, which is a waste of money and is harmful to the environment. Pollution is caused, thereby impelling the implementation of this scheme, therefore, in order to solve the above-mentioned problem,...

AI Technical Summary

Problems solved by technology

[0002] For a long time, due to the use of liquid chlorine as raw material, a large amount of hydrogen chloride gas is produced during the reaction and decomposition. The original process only takes simple measures for this and then directly empties it, which not only causes great pollution to the environment, but also wastes a large part of resources ( Hydrogen chloride gas), and in the production process of our company's product tetramisole hydrochloride, there are two-step salt formation reactions that require the use of more hydrochloric acid (30%), but this part of hydrochloric acid has been purchased, which is a waste of money and is harmful to the environment. cause pollution, thereby impelling the implementation of this scheme, therefore, in order to solve the above problems, a new technical scheme is specially provided