Preparation technique for high-purity MgO, Mg(OH)2 and MgCO3 by ammonium salt rotation method

The invention discloses a manufacturing method of high-purity MgO, Mg (OH) 2 and MgCO3, which comprises the following steps: 1. sintering MgO and condensed solution of ammonium sulfate lightly; entering into ammonia-evaporating tower to evaporate NH3; adsorbing water as regenerative ammonia or making with purified CO2 to form regenerative ammonia carbonate; 2. blending SO42- and a little more 1.5% (CaO+MgO) than SO42- before evaporating ammonia; obtaining the residule as MgO; removing slag with Fe, Ca, Al , Mn and heavy metal; filtering; obtaining the purified MgSO4 liquid; 3. Proceeding ionic exchange for filtrate to purify; obtaining pure MgSO4 liquid; 4. Allocating ammonium hydrogen carbonate and ammonia to make high-purity ammonium carbonate solution; 5. Entering high-purity MgSO4 liquid and high-purity (NH4)2CO3 liquid or ammonia into double-circulating metathetical sediment with MgCO3 and Mg (OH) 2; washing; drying; obtaining the high-purity product; heating to decompose MgCO3 and Mg (OH) 2 into MgO; 6. Condensing mother liquid; obtaining the condensed ammonia sulfate liquid; 7. Using ammonia chloride and ammonia nitrate to replace ammonia sulfate.