Device and method for producing magnesium hydroxide, hydrogen and chlorine with magnesium chloride solution

Abstract

A device and method for producing magnesium hydroxide, hydrogen and chlorine from a magnesium chloride solution. The device includes an electrolytic cell, an anode and a cathode; the anode electrode plate of the anode is parallel to the anode working surface and fixed together through a connecting plate; the cathode electrode plate of the cathode It is parallel to the cathode working surface and fixed with the cathode working surface through the connecting plate. The bottom of the cathode chamber is connected with the inside of the electrolytic cell. The method is: (1) Add magnesium chloride solution to the electrolytic cell and anode chamber; (2) Apply electricity to perform electrolysis, and control the current density at 0.01~0.20A / cm2; (3) Collect the chlorine and hydrogen produced by electrolysis; (4) Supplement New magnesium chloride solution; (5) The generated Mg(OH)2 is deposited or enriched on the cathode working surface, and the Mg(OH)2 is scraped off by a scraper. The method of the invention has the advantages of high electrolysis efficiency, high product purity, low production cost, simple device structure and convenient operation, and is suitable for large-scale industrial production.

Description

technical field [0001] The invention belongs to the technical field of electrolysis, and in particular relates to a device and a method for preparing magnesium hydroxide, hydrogen and chlorine from a magnesium chloride solution. Background technique [0002] Magnesium hydroxide and its magnesia produced by calcination at high temperature are important chemical materials, metallurgical materials and refractory materials; magnesium is usually known as bischofite MgCl 2 ·6H 2 O, MgCl 2 , brucite (mainly composed of Mg(OH) 2 ), magnesite and dolomite, carnallite (KCl MgCl 2 ) in the form of minerals, among which bihalite and carnallite are soluble minerals, mainly found in seawater and salt lakes, while magnesite, dolomite and brucite are mainly in the form of MgCO 3 , CaCO 3 · MgCO 3 Carbonate and Mg(OH) 2 exist in mineral form. Magnesite, dolomite and brucite are insoluble minerals, which can generate MgO and CaO MgO compounds after calcination, and these compounds are...

AI Technical Summary

Problems solved by technology

If such a huge amount of bicholorite resources is not developed and utilized in time, it will not only waste resources, but also cause serious damage to the local ecological environment, forming the so-called "magnesium damage"; with the continuous expansion of potassium fertilizer production, by-products There are more and more bischofites, and the development and utilization of magnesium resources has become more and more urgent

[0005] In order to make rational use of these magnesium resources, people have been continuously researching their application, and have explored several comprehensive utilization methods of bischofite: one is to use bischofite MgCl 2 ·6H 2 The water of crystallization in O is taken off, and anhydrous magnesium chloride is made, and anhydrous magnesium chloride is used as molten salt electrolysis to produce the raw material of metal magnesium, but this method has its shortcoming, although this method is technically feasible, cost and The energy consumption is high, and the dosage is limited; another method to utilize bischofite is to use ammonia water or other alkaline solutions, such as lime water and ammonia water, to neutralize the magnesium chloride aqueous solution, and convert magnesium chloride into Mg(OH) 2 , and then the Mg(OH) 2 It is filtered and separated from ammonium chloride or calcium chloride solution, but these methods are not only difficult to precipitate and filter, but also cause a large amount of waste liquid of calcium chloride, which cannot be treated, resulting in secondary pollution problems; there is also a treatment of water magnesium chloride The method of bischofite is to change magnesium chloride into magnesium hydroxide product by aqueous solution electrolysis and by-product hydrogen and chlorine to realize the full utilization of bischofite. This method is undoubtedly a good method, but this method has not yet been developed. It can be successful in industry because during the electrolysis process, the magnesium hydroxide precipitate generated at the cathode is not easy to separate from the cathode, and it is easy to adhere to the cathode, which increases the resistance of the cathode. In the past, someone used a vibrating cathode Technology and the method of constantly scraping out the cathode product by using a special device can solve this problem, but it has not been applied in industry because of its complicated operation; so far, the structural problem of the electrolyzer has not been solved well, and the cathode cannot be used The product is taken out from the cathode chamber; another problem is that the resistance of the magnesium chloride aqueous solution is relatively large, the cell voltage is relatively high, and the current efficiency is low.

Although the addition of alkali metal chloride can reduce the resistance of the magnesium chloride aqueous solution, the concentration of alkali metal chloride is too high, which will make the magnesium hydroxide precipitate produced thinner, which is not easy to separate from the cathode, and its process operating conditions are difficult to master. The electrolysis of magnesium chloride aqueous solution to produce magnesium hydroxide technology has not been successfully applied in industry

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