RU99101660A - METHOD OF PREPARING MAGNESIUM - Google Patents

Claims (1)

1. The method of obtaining magnesium, including the preparation of carnallite from a solution of magnesium chloride released during the processing of magnesium-containing raw materials and waste (sea water, brine of salt lakes, carbonates, magnesites, etc.) chlorides, potassium, sodium separation by settling and / or centrifugation returned to the head the process of mother liquor from the solid phase, dehydration of the solid phase with heated gases obtained by burning fuel with primary air, and then cooling the combustion products with secondary air, gas cleaning and electrolysis to obtain magnesium, chlorine and spent electrolyte, returning the whole or part of the latter to the process, preparing carnallite, characterized in that the chlorine obtained during electrolysis is fully or partially preliminarily reduced to hydrogen chloride, feeding chlorine into the high-temperature furnace in the flame of hydrogen-containing fuel, and after cooling the superheated more than usual coolant with secondary air and dehydrate the resulting mixture with synthetic carnallite in a fluidized bed due to the heat of the mixture or additionally supplying part of the heat to carnallite using a contact method from heated devices placed in a layer or in contact with it, and then either absorbing hydrogen chloride from waste gases of dehydration with an aqueous solution circulating in a gas cleaning to obtain hydrochloric acid of a given concentration and oxygen or calcium compounds with it separately or together / or magnesium, or directly absorbing hydrogen chloride from dehydration waste gases by pulp containing the above oxygenated calcium compounds and / or magnesium to produce calcium and / or magnesium chloride solutions; however, all of the original components are introduced into the process in ratios that provide the following contents of the components in synthetic carnallite entering the dehydration, wt.%:
Potassium chloride - 21-25
Magnesium chloride - 30-32
Sodium chloride - 3.5-9.0,
Calcium chloride - 0.3 - 2.0,
Water - The Rest
2. The method according to paragraphs. 1 and 2, characterized in that the molar ratio of potassium chloride to magnesium chloride in synthetic carnallite, fed to dehydration, is maintained within 0.9-1.05.  3. The method according to p. 1 or 2, characterized in that obtained during the synthesis of the solid phase is washed with a solution of calcium chloride.  4. Method according to any one of claims. 1-3, characterized in that calcium chloride, obtained by neutralizing hydrogen chloride from dehydration exhaust gases with oxygenated calcium compounds (lime milk), is returned to the stage of preparation of synthetic carnallite for purifying magnesium chloride solution from sulphates and / or purifying synthetic carnallite from impregnating the latter stock solution containing magnesium chloride.  5. The method according to p. 1, characterized in that obtained by dehydration of synthetic carnallite in a current of heated gases containing hydrogen chloride, solid deeply dehydrated low hydrolyzed carnallite is loaded into a melt of electrolyzers of the production line for electrolytic production of magnesium, chlorine and spent carnallite.  6. The method according to p. 1, characterized in that in case of accumulation of calcium chloride in the cycle, sodium or magnesium sulfates are introduced into the solution of magnesium chloride before the synthesis and precipitated solid calcium sulfate is precipitated from the solution.  7. The method according to p. 1, characterized in that with insufficient content of sodium chloride in the feedstock, this chloride, necessary to increase the electrolyte conductivity and a corresponding reduction in electricity consumption for electrolysis, is added directly to the melt intended for electrolysis.