Method for producing high-purity anhydrous magnesium chloride by using bischofite

Abstract

The invention provides a method for producing high-purity anhydrous magnesium chloride by using bischofite. The method comprises the following steps: preparing an aqueous solution from the bischofite, and carrying out centrifugal spray drying to prepare magnesium chloride dihydrate powder; mixing and calcining the magnesium chloride dihydrate powder and ammonia chloride, and respectively collecting a anhydrous magnesium chloride coarse product and an ammonia chloride product; mixing and distilling the anhydrous magnesium chloride coarse product and sulfoxide chloride, and respectively collecting sulfoxide chloride and high-purity anhydrous magnesium chloride solids. In the whole technological process, no exogenous impurities are introduced, and the production cost is low; the purity of the prepared anhydrous magnesium chloride is up to 99.98 percent or above, the moisture content is 0.003 percent or below, and the content of magnesium oxide which is a harmful impurity is 0.02 percent or below, so that the prepared anhydrous magnesium chloride completely meets the raw material standard of electrolytic metal magnesium. Furthermore, the method passes through the pilot test, and is relatively low in requirements for corrosion property and sealing property of technological equipment, easy to operate and suitable for industrial large-scale production.

Description

technical field [0001] The invention relates to a method for producing anhydrous magnesium chloride, in particular to a method for producing high-purity anhydrous magnesium chloride by utilizing bischofite. Background technique [0002] Magnesium metal is an important non-ferrous metal, which is widely used in aviation, electronics, mobile communications, automobiles, metallurgical chemical reagents and many other fields. At present, the main method of producing metal magnesium is the anhydrous magnesium chloride molten electrolysis method, which has low energy consumption, little pollution, and no carbon emissions. It is in line with the concept of low-carbon economic development and is also the development trend of magnesium smelting in the future. [0003] Bischofite is one of the main raw materials for preparing anhydrous magnesium chloride. my country has abundant sea salt brine and salt lake brine resources, which contain rich magnesium chloride. It is a cheap and wide...

AI Technical Summary

Problems solved by technology

[0005] The gas-solid phase reaction method is to remove water molecules by thermally decomposing bischofite in a calciner. In order to inhibit the hydrolysis of magnesium chloride and control the content of magnesium oxide to ≤0.2%, it is necessary to feed a sufficient amount of hydrogen chloride. The circulation of hydrogen chloride is large and the reaction time is long. The requirements for sealing and corrosion resistance of reaction equipment are very high. Central South University, Guizhou Magnesium Aluminum Design Institute, and Shantou Electrochemical Plant have all done a lot of research, but the problem of serious equipment corrosion has not been effectively solved.

For example, in the patent application CN101734693A, in this method, magnesium chloride hexahydrate is added to ethylene glycol to form a solution, water molecules are removed by distillation, and then ammonia gas is introduced into the alcohol solution to generate magnesium chloride hexaamine, and magnesium chloride hexahydrate is calcined to obtain anhydrous magnesium chloride. In this method, a small amount of magnesium chloride will be hydrolyzed to generate magnesium oxide during dehydration, thereby reducing the quality of anhydrous magnesium chloride, and the amount of ammonia gas introduced into the alcohol solution is large, and 30mol of ammonia molecules can produce 1mol of magnesium chloride. The productivity is low, the process route is long, and The use of a large amount of organic solvents is harmful to the human body and the environment

[0008] In summary, the anhydrous magnesium chloride prepared by the existing method contains high magnesium oxide impurities, which is difficult to meet the requirements of electrolysis. In addition, the gas-solid phase reaction method has a large amount of hydrogen chloride circulation, serious corrosion, and high air tightness requirements; the ammonium carnallite method High impurity content and poor quality; ammonia complexation method has low purity, large amount of ammonia circulation, and uses a large amount of organic matter to cause pollution

The existence of these problems makes the preparation of high-purity anhydrous magnesium chloride still exist very big challenge

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