Method for preparing anhydrous sodium sulfate from chromium-containing mirabilite

Abstract

The invention relates to the field of a chemical industry and particularly relates to a method for preparing anhydrous sodium sulfate from chromium-containing mirabilite as a by-product in the production process of sodium dichromate. The method comprises dissolving a certain concentration of chrome-containing mirabilite in chromium-containing waste water, adding quantitative sodium thiosulfate into the waste water to promote reduction of hexavalent chromium into trivalent chromium under 0.1-1 Mpa at 80-190 DEG C, wherein the trivalent chromium in a form of chromium trioxide hydrate is precipitated, adding a small amount of sulfuric acid to neutralize, filtering to acquire the chromium trioxide hydrate, removing impurities, carrying out decoloration, evaporating to precipitate anhydrous sodium sulfate crystals, and carrying out continuous centrifugal separation and drying. The method is simple and easy, utilizes cheap raw materials, has low energy consumption and a high automation degree and is suitable for large-scale production. The quality of the industrial anhydrous sodium sulfate product obtained by the method meets the requirements of class I products in the GB / T 6009-2014 industrial anhydrous sodium sulfate standard.

Description

technical field [0001] The invention relates to the field of chemical industry, in particular to a method for preparing anhydrous sodium sulfate by utilizing chromium-containing Glauber's salt, a by-product in the production process of sodium dichromate. Background technique [0002] Before 2000, the total annual production of sodium dichromate in my country's chromium salt enterprises was less than 100,000 tons, and the total amount of by-product chromium-containing Glauber's salt was about 130,000 tons. Sodium sulfate water, but due to the small production scale of sodium dichromate and the low output of by-product chromium-containing Glauber's salt, the cost of using chromium-containing Glauber's salt to prepare industrial anhydrous sodium sulfate is higher than the cost of directly using natural Glauber's salt to produce anhydrous sodium sulfate. This kind of research was terminated, and the dried chromium-containing Glauber's salt was used as a cement accelerator instead....

AI Technical Summary

Problems solved by technology

[0002] Before 2000, the total annual production of sodium dichromate in my country's chromium salt enterprises was less than 100,000 tons, and the total amount of by-product chromium-containing Glauber's salt was about 130,000 tons. Sodium sulfate water, but due to the small production scale of sodium dichromate and the low output of by-product chromium-containing Glauber's salt, the cost of using chromium-containing Glauber's salt to prepare industrial anhydrous sodium sulfate is higher than the cost of directly using natural Glauber's salt to produce anhydrous sodium sulfate. This kind of research was terminated, and the dried chromium-containing Glauber's salt was used as the cement accelerator instead. Since the hexavalent chromium in the chromium-containing Glauber's salt has not been reduced, the cement accelerator made will pollute the environment

In the end, most chromium salt manufacturers choose to use chromium-containing Glauber's salt to produce soda sulfide, because the hexavalent chromium in chromium-containing Glauber's salt will be reduced to detoxify during the production of soda sulfide, but the waste gas and slag generated during the production of soda sulfide are still in polluted environment

[0003] After 2000, research on the reuse of chromium-containing Glauber's salt gradually emerged. Sichuan Anxian Yinhe Jianhua Group Co., Ltd. developed a method for preparing potassium sulfate from chromium-containing Glauber's salt (CN200610000019.1), but due to high energy consumption, It is difficult to achieve continuous production, resulting in high production costs of potassium sulfate, unable to form market competitiveness

In recent years, Li Xianrong, Hu Yihua and others of Sichuan Yinhe Chemical Co., Ltd. have developed a method for refining sodium sulfate by chromium-containing Glauber's salt (CN201310533304.X). This method uses the crystal slurry method to produce sodium sulfate, but Due to the problem of hexavalent chromium wrapped in crystal slurry, the hexavalent chromium in the produced sodium sulfate exceeds the standard, sometimes as high as 100ppm; and because the process does not remove impurities and decolorize, the whiteness of the product cannot meet GB / T 6009-2014 Industrial anhydrous sodium sulfate standard requirement; In addition, the reducing agent that adopts in this method is sodium sulfite, and neutralizing agent is caustic soda, and these two kinds of raw materials are too expensive for low-value product sodium sulfate, cause the cost of sodium sulfate produced Too high, patented technology cannot form actual productivity