Vacuum-crystallization units for the production of magnesium from serpentinite

Preparation of magnesium from multimillion ton asbestos production dumps, i.e., serpentinite, provides its competitiveness in the world and internal markets due to the low raw material costs, whose price in the net cost of finished metal reaches 30%. Artificial carnallite for magnesium electrolysis is separated by crystallization in multistage vacuum-crystallization units from a solution formed as a result of synthesizing magnesium chloride solution and added potassium chloride. Chromium-magnesium solution forms on leaching serpentinite with hydrochloric acid and separation of impurities, but potassium chloride from the electrolysis bath after dissolution and crystallization is returned again to the technology. Crystallization units for carnallite and potassium chloride are fitted with self-evaporation crystallizers of SverdNIIkhimmash construction, which are used successfully in the production of many inorganic salts. Synthetic carnallite KCl·MgCl 2 ·6H 2 O in magnesium production is separated by crystallization from a hot carnallite suspension, prepared by synthesis [1] of potassium chloride and chromium-magnesium solution. The chromium-magnesium solution forms on leaching serpentinite with hydrochloric acid, and potassium chloride is prepared by crystallization from a solution of exhausted electrolyte. A multi-vessel vacuum-crystallization unit (VCU) is used for crystallizing potassium chloride and carnallite, fitted with double-loop crystallizers [2, 3]. The construction of the crystallizers has been developed in Sverdlovskii Research and Design Institute of Chemical Machine Building (SverdNIIkhimmash) and is recommended in the production of various mineral salts, including carnallite, potassium chloride, and cooking salt. The potassium chloride and carnallite VCU should provide productivity, chemical and grain size composition of crystals separated from a multicomponent solution. As a result of self-evaporation of hot solution under vacuum there is cooling and crystallization from a salt solution