Method for preparing refining agent from dechlorinated light salt brine

Abstract

The invention discloses a method for preparing a refining agent from dechlorinated light salt brine. The method comprises the following steps of: mixing free chlorine-containing light salt brine which is generated after electrolyzing ultrapure saline in an ionic membrane electrolytic cell with free chlorine-containing condensed water from a chlorine system, and then subjecting the mixed light salt brine to vacuum dechlorination and chemical dechlorination to obtain the dechlorinated light salt brine. The dechlorinated light salt brine is suitable for directly preparing sodium sulfite and sodium carbonate, and can also be used for preparing ferric trichloride after being acidized in stead of production water. According to the invention, the refining agent preparation in brine purification in the chlor-alkali industry widely adopted at present is improved, and the dechlorinated light salt brine in the system is directly used for preparing the refining agent in stead of external production water or purified water.

Description

technical field [0001] The invention relates to a process for producing chlor-alkali, in particular to a process for producing chlor-alkali by electrolyzing sodium chloride. Background technique [0002] At present, chlor-alkali enterprises usually adopt the electrolytic sodium chloride production process, and the production water for preparing sodium chloride solution generally comes from surface water such as rivers and lakes or underground well water. This kind of production water generally has a pH of 7-8, high hardness, and contains a large amount of Calcium, magnesium ions. In order to remove calcium and magnesium ions, it is necessary to prepare refined preparations during production. The refined preparations include sodium carbonate, ferric chloride and sodium sulfite solutions. At the same time, production water or pure water is also used to prepare the refined preparations. The defects brought by this process Yes: First, after the refined preparation solution is a...

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Problems solved by technology

In order to remove calcium and magnesium ions, it is necessary to prepare refined preparations during production. The refined preparations include sodium carbonate, ferric chloride and sodium sulfite solutions. At the same time, production water or pure water is also used to prepare the refined preparations. The defects brought by this process Yes: First, after the refined preparation solution is added to the production system, it is equivalent to diluting the brine, which is not conducive to the stability of the brine concentration, especially in the process of all-halogen soda production, which is not conducive to the increase of the brine concentration; Iron, in the case of PH=7-8, the following reaction FeCL is easy to occur 3 +3OH - =Fe(OH) 3 +CL - , and ferric hydroxide is a colloid, which has the properties of colloid, and is easy to absorb impurity ions to form precipitates, block the pipeline, and need to pickle the pipeline regularly; the third is that when the production water is used to prepare sodium carbonate, the carbonic acid Sodium pipelines are prone to freezing and need to be defrosted with steam

Furthermore, pure water is needed when preparing sodium sulfite, and pure water needs to be produced by reverse osmosis process, generally 12-15 yuan / ton, causing economic burden to chlor-alkali enterprises

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