POSSIBILITY TO RETURN TO THE CYCLE OF HYDROGEN CHLORIDE CAPTURE WITH CAUSTIC SODA BY CONCENTRATING IT AND COMPLETE EXTRACTION OF COMMERCIAL SODIUM CHLORIDE
Authors:   Kazan National Research Technological University, DUBROVINA K.R. , SHAKIROV T.R. , SULEYMANOVA A.Z. , KHATSRINOV A.I. ,   Kazan National Research Technological University
Published: December 2024

The chlorine industry does not lose its relevance and serves as a valuable raw material for the production of organochlorine compounds and inorganic products. The main products in demand in the chlorine industry are vinyl chloride, methylene chloride, chlorinated paraffin, chlorine-containing pesticides, hydrochloric acid, chlorine gas, potassium chloride, ammonium chloride, calcium chlorate, and alkali metal perchlorates. The production of commercial organic and inorganic products generates significant hydrogen chloride waste, causing serious technical, economic and environmental problems. Therefore, the relevance of the rational use of waste hydrogen chloride, in particular the production of hydrochloric acid solutions or its conversion into valuable inorganic products, is obvious. In the literature, very little attention has been paid to the issue of neutralization of hydrogen chloride vapors. The petrochemical industry processes petroleum into marketable products using organochlorine compounds. During the synthesis, gas-free hydrogen chloride is formed. Hydrogen chloride is collected in an alkaline scrubber. Irrigation is carried out with a 10% sodium hydroxide solution. The irrigated solution after absorption is represented by a predominant content of sodium chloride with a small amount of sodium hydroxide and the presence of traces of petroleum products. In terms of the degree of mineralization, the spent alkali is comparable to standard brines for the chemical industry TU 2152-008-00204872-2012 Crude sodium chloride brine. One of the optimal options for possible processing of waste alkali from petrochemical synthesis is the separation of sodium chloride in the form of commercial sodium chloride. The material composition of waste alkali is represented by the following salt composition: 270 g/l NaCl, 33 g/l NaOH and 0.58 mg/dm3 of petroleum products. At the first stage of the work, adsorption purification of waste alkali with activated carbon from petroleum products was carried out. The reduction in petroleum products decreased by 86% from 0.57 to 0.08 mg/dm3. At the second stage of the work, experimental research was carried out on the possible separation of sodium chloride by introducing solid reactive sodium hydroxide into the waste alkali. The optimal ratio at which sodium chloride is extracted in the form of a solid phase is observed at the ratio of solid sodium hydroxide: spent alkali T: L = 1: 0,4. The resulting suspension is evaporated and centrifuged. The solid phase after centrifugation is sent for drying and can be used as commercial sodium chloride. The liquid phase is represented primarily by sodium hydroxide, which can be returned to the cycle with dilution in accordance with the technological regulations. Thus, the absorption capture of exhaust hydrogen chloride in an alkaline scrubber and its conversion into commercial sodium chloride makes it possible to organize a waste-free closed-cycle production.