Method and device for purifying, absorbing and recycling chlorinated gas in benzene chlorination process

Abstract

The invention discloses a method and device for purifying, absorbing and recycling chlorinated gas in a benzene chlorination process. The method comprises the steps that end gas produced in benzene chlorination reaction is led to a buffer tank, the gas from the buffer tank directly flows into a cascade reaction unit containing solid ferrous chloride for dechlorination and debenzolization, the end gas subjected to dechlorination and debenzolization enters a primary low-temperature heat exchange system, the cooled end gas enters a cascade dryer containing concentrated sulfuric acid for drying, the dried end gas enters a secondary low-temperature heat exchange system, the hydrogen chloride gas from the secondary low-temperature heat exchange system enters a finished product tank with a demister. The method utilizes the ferrous chloride to absorb chlorine gas in the end gas and convert the chlorine gas into ferric trichloride, the ferric trichloride catalyzes benzene and chlorine gas reaction to generate chlorinated benzene, a reactant is directly fed into a chlorinated benzene workshop for reuse, the end gas subjected to dechlorination and debenzolization is dried and purified by the concentrated sulfuric acid, sulfuric acid obtained through drying can be directly reused for disperse dye synthesis, efficient utilization of the chlorinated end gas is achieved, and the green, low-carbon and cyclic development requirements are met.

Description

technical field [0001] The invention relates to the technical field of waste gas treatment, in particular to a method and device for purification, absorption and recycling of chlorination tail gas in a benzene chlorination process. Background technique [0002] Chlorinated benzene and dichlorobenzene are generally produced through the chlorination reaction of benzene and chlorine, so the chlorination tail gas usually contains a large amount of hydrogen chloride, as well as non-condensable gases such as benzene, chlorine, nitrogen, and hydrogen. A large amount of hydrogen chloride gas produced in the production process of chlorinated benzene and dichlorobenzene will not only cause waste of resources, but also cause serious harm to the environment. Therefore, for the tail gas produced by the chlorination process of benzene, it is of great practical significance to research and develop a method that can effectively recover hydrogen chloride and other useful components. It can n...

AI Technical Summary

Problems solved by technology

In addition, the use of water and alkali washing directly removes chlorine and hydrogen chloride gas in the tail gas, which does not realize the effective utilization of hydrogen chloride, and is accompanied by the generation of organic acids and salty wastewater

[0005] Patent document CN 101077466A discloses a method for recovering and recycling the tail gas containing benzene and hydrogen chloride in the production of chlorinated benzene. The benzene gas is condensed, gas-liquid separated, and the captured benzene is sent to the chlorinated benzene workshop. The concentrated hydrochloric acid produced is analyzed by the desorption tower and then enters the low-temperature condenser for condensation. The concentrated sulfuric acid is dried, and the dried hydrogen chloride gas is sent to the polyvinyl chloride VCM The synthesis production line has achieved that almost all the benzene and hydrogen chloride entrained in the chlorinated benzene tail gas are recovered and recycled, but the captured chlorinated benzene is acidic chlorinated benzene, which needs to be neutralized before returning to the chlorinated benzene production system Therefore, it is bound to be accompanied by the generation of organic wastewater and high-salt wastewater; in addition, the tail gas containing hydrogen chloride is absorbed by water or low-concentration acid, and the organic matter will inevitably enter the hydrochloric acid solution, and the hydrogen chloride gas obtained by the analysis of concentrated hydrochloric acid with organic matter must be Contains organic matter, and whether the organic matter contained will affect the subsequent PVC products. The inventor has no experimental data to verify. At the same time, it increases the number of processing steps and increases the processing cost to a certain extent.

[0006] Another patent document CN 102849681A realizes the removal of chlorine gas contained in the by-product hydrogen chloride gas in the organic chloride production process, but the method needs to be equipped with a purification liquid, and does not remove the by-product hydrogen chloride gas generated in the organic by-product process. Organic matter works, therefore, the hydrogen chloride gas produced should contain organic matter, the patent does not explicitly mention

Images