METHOD OF PRODUCTION OF MAGNESIUM FROM ASH OF BURNT BROWN COAL Russian patent published in 2007 - IPC C22B7/00 C22B26/22 

FIELD: production of magnesium from ash of burnt brown coal by electrolysis of dehydrated chlorides; utilization of ash of burnt brown coal at electric power plants.

SUBSTANCE: ash is leached-out at two stages: at the first stage leaching-out is carried out with water at addition of hydrochloric acid to pH of about 8.0 at the solid-to-liquid ratio of 1:(8-10) and temperature of 20°C; at the second stage leaching-out is carried out with 15- 20-% hydrochloric acid at temperature of 60-100°C and continued for 0.5 h. Magnesium chloride solution is cleaned from admixtures by caustic magnesite and/or brucite in stepwise manner: first to pH of 3.5-4.5, after which sodium hypochlorite is introduced and again caustic magnesite is introduced to pH 6.0-6.5. Caustic magnesite is introduced in liquid state or in form of suspension. Cleaned magnesium chloride solution is boiled-down to 400-450 g/dm³ of MgCl₂ and is cleaned from calcium compounds by treatment with magnesium sulfate taken at ratio of Ca⁺²:SO₄ ⁺²=1:0.9. Synthesis of carnallite is carried out at temperature of 110-115°C by dissolving the waste electrolyte and/or potassium chloride in magnesium chloride solution for forming carnallite, crystallization, dehydration at dose of sodium chloride in finished product no less than 12% and electrolysis for obtaining magnesium, chlorine and waste electrolyte.

EFFECT: extended sources of raw materials; low cost of process; enhanced ecological safety.

7 cl, 1 tbl, 1 ex