What are the raw materials and synthesis methods of magnesium oxide production？

Production raw materials.

(a), magnesite is one of the main sources of magnesium oxide, (MgO) content of about 47%, MgCO3 after light calcination (400 ~ 600 ℃) calcined and then ground into a solid powder (MgO). The source is widely distributed in Liaoning, Xinjiang, Sichuan, Shandong, Tibet and other provinces and autonomous regions, with reserves of 2.8 billion tons, accounting for 30% of the world’s mineral sources.

(b), dolomite ore [CaMg(CO3)2] is also the main source of magnesium oxide, and the reserves are larger and more widely distributed, MgO content of about 22%. CaO content of about 30%, the rest is 48%, MgCO3 and CaO theoretical structure of the two is one to one. Dolomite delineation line is to MgCO3 content in 25% or more shall prevail, otherwise can not be used as the production of magnesium oxide ore, also can not be called dolomite.

(c), serpentine [Mg6(Si4O10)(OH)2] is also the raw material for the production of magnesium oxide, mainly water magnesium silicate (3MgO-2SiO2-2H2O).

(d), smelting light magnesium alloy slag is also the raw material for the production of magnesium oxide.

Preparation process.

1. brine a lime method: the brine which has been purified and refined in advance and the lime milk made by digestion and de-slagging treatment are subjected to precipitation reaction in the precipitation tank, flocculant is added to the obtained slurry, and after thorough mixing, it enters the settling tank for separation, and then filtered, washed, dried and crushed to produce finished magnesium oxide.

2. brine – ammonia method: to remove sulfate, carbon dioxide, a small amount of boron and other impurities by purification treatment of brine as raw material, ammonia as a precipitant in the reaction kettle for precipitation reaction, before the reaction into a certain amount of crystal species, for full stirring. The ratio of brine to ammonia is 1:(0.9~0.93), and the temperature is controlled at 40℃. Flocculant was added at the end of the reaction, and the precipitate was filtered, washed, dried and crushed to produce finished magnesium oxide. The test method to improve the yield, shorten the washing cycle, improve and perfect the production process.

3. rhodochrosite – hydrochloric acid – ammonia method: magnesite and anthracite or coke in the vertical kiln calcination, to generate magnesium oxide and carbon dioxide. Bitter earth powder with water into a slurry after the reaction with the prescribed concentration of hydrochloric acid to prepare magnesium chloride solution. Its magnesium chloride solution reacts with a certain concentration of ammonia in the reactor, and the products are washed, settled, filtered and separated, dried and crushed to get magnesium oxide products. According to the need can add surface treatment agent for surface treatment.

4. microcrystalline magnesium oxide at room temperature when the preparation of saturated MgCl2-6H2O solution, at 70 ℃ under stirring pass into the excess of concentrated ammonia, then magnesium oxide slowly precipitate precipitation. Note 1: The distilled water and ammonia used must not contain CO2, distilled water needs to be fully boiled, and CO2 in NH3 needs to be removed by KOH. Preparation of magnesium oxide device Note 2: The reaction vessel should be made of hard glass to avoid the reaction between Mg(OH)2 and silicic acid. The obtained precipitate is left in the mother liquor for two days, during which it can be heated several times, each time to 70°C, and then the precipitate is decanted and washed. It is then placed in a nickel beaker coated with paraffin and washed by centrifugation with CO2-free distilled water. Precipitation and decantation operation can be carried out in the device, the magnesium oxide obtained first on the potassium oxide vacuum drying, and then on the phosphorus pentoxide vacuum drying.

5. Large grain magnesium oxide. Add 243mL of water to a wide-mouth platinum container, then add 1375g of KOH and 485g of MgCl2-6H2O, heated to 210℃ on an electric furnace and clarified after about half an hour. Then it was cooled slowly to room temperature in 18h, that is, about 0.2mL diameter crystals precipitated, dried at 100 ℃ for 2h, that is, large crystals of magnesium oxide.