Method for recovering methyl chloride from methyl chloride waste gas

Abstract

The invention discloses a method for recovering methyl chloride from methyl chloride waste gas. The method comprises the steps that absorbing liquid and the waste gas are in reverse contact in an absorbing tower, most of the waste gas is absorbed by the absorbing liquid, extracted from the bottom of the absorbing tower and then separated through rectification to collect the methyl chloride with amass percentage of 99.9% or above and the absorbing liquid, the rest of the waste gas is extracted from the top of the absorbing tower, and a solvent is recovered after cooling and flashing are conducted. Glyphosate is a common herbicide, and the preparation process of the gherbicide produces methyl chloride waste gas byproducts. According to the method, the absorbing liquid used for recovering the methyl chloride waste gas is the composition with any proportion of one or more than two of benzene, ethanol and dichloroethane. By means of the method, high purity methyl chloride is recovered fromthe methyl chloride waste gas, the consumption amount of the absorbing liquid in the whole operation process is less, the absorbing liquid can be recycled, the obtained high purity methyl chloride can be sold as byproducts, and the waste gas processing amount and the harm on the environment are greatly reduced.

Description

technical field [0001] The invention belongs to the field of waste gas treatment in chemical production, and relates to a method for recovering methyl chloride from waste gas of methyl chloride. Background technique [0002] Glyphosate is a herbicide commercialized by Monsanto Company in the United States in 1974. Because of its high efficiency, low toxicity, low residue, broad spectrum, and good environmental compatibility, glyphosate has become the most widely used herbicide in the world. Broad range of herbicides. Since the 1980s, most glyphosate manufacturers in China have adopted the alkyl ester synthesis process with glycine, dimethyl phosphite, and paraformaldehyde as the main raw materials. Although this process has the advantages of stable process and high yield, However, its production process produces waste gas rich in methyl chloride, which requires additional treatment. [0003] The main components of exhaust gas are methyl chloride, methanol, methylal, air, e...

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Problems solved by technology

[0004] At present, the production scale of glyphosate in my country reaches one million tons per year, and more than 60,000 tons of methyl chloride are discharged into the atmosphere every year. The commonly used methods for recovering glyphosate by-product methyl chloride include condensation method, membrane separation method, absorption method, and adsorption method. etc., the invention patent CN201610168438.X discloses a recycling process of washing water with methyl chloride, and there are also documents disclosing different treatment methods such as water washing, alkali washing, concentrated sulfuric acid drying process, compression condensation-pressure swing adsorption coupling process, etc., these methods It usually needs to go through several operating units, which has the disadvantages of high energy consumption and cumbersome operation. However, the process of recovering methyl chloride in glyphosate tail gas with benzene, ethanol, and methylene chloride as the absorbing liquid has not yet appeared in the prior art.

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