Magnesium oxide (chemical formula: MgO) is an oxide of magnesium, an ionic compound. It is a white solid at room temperature. Magnesium oxide exists in the form of periclase in nature and is a raw material for magnesium smelting. 
Magnesium oxide has a high degree of refractory insulation properties. It can be converted into crystals by burning at a temperature above 1000 ° C. When it is raised to 1500 - 2000 ° C, it is a dead magnesium oxide (also known as magnesia) or sintered magnesia. 
Magnesium oxide is commonly known as bitter soil, also known as magnesium oxide. Magnesium oxide is a basic oxide and has the property of a basic oxide. It is a gelling material. White powder (light yellow is magnesium nitride), odorless, tasteless, non-toxic, is a typical alkaline earth metal oxide, chemical formula MgO. A white powder having a melting point of 2852 ° C, a boiling point of 3600 ° C and a relative density of 3.58 (25 ° C). Soluble in acid and ammonium salt solution, insoluble in alcohol. The solubility in water is 0.00062 g / 100 mL (0 ° C) 
0.0086 g / 100 mL (30 ° C). Exposure to the air, easy to absorb water and carbon dioxide and gradually become basic magnesium carbonate, lighter products are faster than heavy products, combined with water to form magnesium hydroxide under certain conditions, slightly alkaline reaction, pH of saturated aqueous solution It is 10.3. Soluble in acid and ammonium salts are insoluble in water, and the solution is alkaline. Do not dissolve in ethanol. Strong refraction in the visible and near-ultraviolet range. Magnesite (MgCO3), dolomite (MgCO3·CaCO3) and seawater are the main raw materials for the production of magnesium oxide. Thermal decomposition of magnesite or dolomite gives magnesia. The seawater is treated with slaked lime to obtain magnesium hydroxide precipitate, and the magnesium hydroxide is burned to obtain magnesium oxide. The magnesium chloride halide block obtained by comprehensive utilization of seawater or the brine after bromine extraction may be used as a raw material, and sodium hydroxide or sodium carbonate may be added to form magnesium hydroxide or basic magnesium carbonate precipitate, and then calcined to obtain magnesium oxide. China mainly uses magnesite, dolomite, brine or halogen blocks as raw materials.

classification
Magnesium oxide is divided into light magnesium oxide and heavy magnesium oxide, magnesium oxide (light) CAS: 1309-48-4  GB : HG/T 2573-2012
Lightweight is mainly used as ceramic, loose in volume and white amorphous powder. Odorless, tasteless and non-toxic. Density 3 . 58g/cm3. Hard to dissolve in pure water and organic solvents, the solubility in water increases due to the presence of carbon dioxide. Soluble in acid, ammonium salt solution. It is converted into crystals by high temperature burning. In the case of carbon dioxide in the air, it forms a double salt of magnesium carbonate.

index
Mgo ≥ 93% 
Fe203 ≤ 0.5% 
S ≤ 0.03% 
CI ≤ 0.05% 
Ca ≤ 0.5% 
activity (iodine absorption value): 90-180 
hydrochloric acid insoluble matter ≤ 0.05% 
particle size range ( D50 ): 2-10 micron 

Preparation: light Magnesium oxide is generally made from magnesium chloride, magnesium sulfate, or magnesium hydrogencarbonate, and becomes a water-soluble product, which is chemically converted into a water-insoluble product, and then calcined into magnesium oxide. 
More widely used

Magnesium oxide (heavy) CAS : 1309-48-4 GB: HG/T2679-2006
Generally referred to as magnesium oxide is heavy magnesium oxide, alias lamp powder. White or beige powder. It is easy to absorb moisture and carbon dioxide in the exposed air, and it is easy to gel and harden when mixed with magnesium chloride solution. The heavy volume is compact, easy to combine with water, and it is easy to absorb water and carbon dioxide in the exposed air. It is easy to gel and harden with magnesium chloride solution. 
Packing 50 Kg/bag of 

heavy magnesium oxide is divided into light burning and reburning.

The magnesite building material is used for the light burning of heavy magnesium oxide.
Light burning, reburning difference
The so-called light burning and re-burning are mainly distinguished by the sintering temperature. When the sintering temperature is below 1200 °C, the magnesium oxide produced generally belongs to light-burned magnesia. When the sintering temperature reaches 1200 °C or higher, it is fired. Magnesium oxide is called calcined magnesium. 

Preparation : Magnesite, magnesite is directly calcined.
Application: Heavy light burnt magnesia is used in the rice milling industry for firing and semi-roller; the construction industry is used to manufacture artificial chemical flooring, artificial marble, heat-proof panels, sound insulation panels; the plastics industry is used as a filler; Can be used to produce other magnesium salts. 
85 powder magnesium chloride building materials external wall insulation 
90 yellow powder for water treatment, desulfurization 
90 light white powder for magnesium fertilizer. 
Heavy light burning powder contains 85 light burning powder, 90 light yellow powder, 90 light white powder, the size is about 200 mesh

Preparation method (summary)

Magnesium oxide

Double reduction carbonization
In order to increase the extraction rate of magnesium oxide and reduce the energy consumption of the product. To improve product quality and increase product variety, the double-reduction carbonization process mainly changes the carbonization conditions and subtracts the high-energy production process. The purified lime emulsion is subjected to a carbonization reaction under specific conditions to dissolve 80-90% of MgO, and a supersaturated solution of light magnesium carbonate containing 20 to 30 g/liter of MgO is formed. After rapid pressure filtration, the basic magnesium carbonate is resolved under a specific condition by a saturated solution of light magnesium carbonate at 20-30 degrees. The basic magnesium carbonate filter cake has a moisture content of only 50-60%. Calcined to obtain a light magnesium oxide product. 
Double reduction carbonization method 
Features of the process: (see process flow diagram for details) 
(1) The extraction rate of magnesium oxide is increased by 20-30%. 
(2) The compression and pyrolysis process is subtracted, and the moisture content of the basic magnesium carbonate filter cake is reduced by 25-30%. 
Therefore, the coal consumption per ton of light magnesium oxide product is reduced by 75% and the power consumption is reduced by 65%.

Magnesium oxide

Gas phase method
The high-purity magnesium metal and oxygen are reacted to form crystal nuclei, and then the particles are further grown to obtain high-purity fine powder magnesia. The crude raw material containing 80% by weight or more of magnesium oxide is dissolved with a mineral acid (sulfuric acid, hydrochloric acid, nitric acid) at a molar ratio of 1:2 to obtain a magnesium salt of a mineral acid. The impurities are removed by purification, and subjected to pressure heat treatment in an oxygen atmosphere, followed by washing with water, dehydration, and drying, and heating at 1100 ° C for 1 hour to obtain high-purity magnesium oxide. 
The magnesium hydroxide calcination method uses the magnesium sulfate solution for purification and purification as a raw material, and the Mg(OH)2 is precipitated by adding pure ammonia water as a precipitant to the magnesium liquid, and the solid-liquid separation is carried out by a plate and frame filter press, and the filter cake is washed high. The purity of Mg(OH) 2 is further dried and calcined to obtain high-purity magnesium oxide. 
The calcined bituminous powder is subjected to water selection to remove impurities and precipitated into a magnesium slurry, which is then dehydrated to form magnesium oxide by digestion, drying and calcination. Its MgO+H 2 O→Mg(OH) 2 Mg(OH) 2 →MgO+H 2 O;

Magnesium oxide

Calcination method
The magnesite is calcined in a calciner at 950 ° C, cooled, sieved, and pulverized to obtain light burned magnesia. 
The soda ash method firstly dilutes the bitter brine with water to about 20 °Be, and then adds a soda clarified solution of about 20 ° Be under stirring, and reacts at 55 ° C to form heavy magnesium carbonate, which is rinsed and centrifuged. The calcination is carried out at 700 to 900 ° C, and the light magnesium oxide product is obtained by pulverization and air separation. It is 5Na2CO3+5MgCl2+6H2O→4MgCO3·Mg(OH)2·5H2O+10NaCl+CO2↑ 
4MgCO3·Mg(OH)2·5H2O→5MgO+4CO2↑+6H2O

Magnesium oxide

Carbonization
The dolomite is calcined, digested and carbonized to obtain basic magnesium carbonate, which is then thermally decomposed, calcined, pulverized and air-selected to obtain light magnesium oxide. Its MgCO3·CaCO3→MgO+CaO+2CO2↑ 
(MgO+CaO)+2H2O→Mg(OH)2 +Ca(OH)2 
Mg(OH)2+Ca(OH)2+3CO2→Mg(HCO3)2+ CaCO3+H2O5 
Mg(HCO3)2+H2O→4MgCO3·Mg(OH)2·5H2O+6CO2↑4MgCO3 
Mg(OH)2·5H2O→5MgO+4CO2↑+6H2O Ammonium Solution The ion content is about 50g/L. After removing impurities, it is mixed with ammonium hydrogencarbonate in an appropriate ratio to carry out precipitation reaction, and then centrifugally dehydrated, dried, calcined, pulverized and classified, and packaged to obtain a light magnesium oxide finished product. 5MgCl2+10NH4HCO3+H2O→4MgCO3·Mg(OH)2·5H2O+10NH4CI+6CO2↑ 
4MgCO3·Mg(OH)2·5H2O→5MgO+4CO2+6H2O;

Magnesium oxide

Carbonation
Activated magnesium oxide can be obtained by using dolomite or magnesite, calcination, water digestion, carbonation, calcination and pulverization. The brine dolomite lime method uses seawater or brine as a raw material to precipitate with lime or dolomitic ash, and the obtained magnesium hydroxide precipitate is filtered, dried and calcined to obtain active magnesium oxide. The bitter soil powder-sulfuric acid-carbon ammonium method reacts the magnesium-containing raw material such as bitter soil powder with sulfuric acid to form a magnesium sulfate solution, and the MgO+H2SO4→MgSO4+H2O magnesium sulfate solution reacts with ammonium hydrogencarbonate to form magnesium carbonate precipitate, and the MgSO4 is formed. +NH4HCO3+NH3→MgCO3↓+(NH4)2SO4 The precipitate is then separated by filtration, washed, dried, calcined and pulverized to obtain active magnesium oxide.

Magnesium oxide

Sintering method
The fused magnesium block is used as a raw material. After being selected, crushed and sieved, it is thoroughly mixed with a certain proportion of liquid titanium dioxide, and then washed, dried and sintered to select a particle size of 40-150, which is the finished high-temperature electrical grade magnesium oxide.

Magnesium oxide

Halogen ammonium carbonate method

The brine is reacted with ammonium hydrogencarbonate to form basic magnesium carbonate, which is then aged, washed, dehydrated, dried, calcined, pulverized, purified, and heat treated to obtain silicon steel grade magnesium oxide.

Magnesium oxide

Electrofusion method
The high-purity magnesium oxide is used as a raw material, and the finished product is obtained by electrofusion.

Magnesium oxide

Hydrochloric acid method
The waste material for producing heavy magnesium oxide is sent to the reactor, and hydrochloric acid is added to carry out a reaction to form magnesium chloride hexahydrate, and then sodium carbonate is added to carry out a reaction to form basic magnesium carbonate, which is washed with water, and the basic magnesium carbonate is calcined at a high temperature and cooled. After pulverization, magnetic magnesium oxide is obtained. 2MgO+4HCI+4H 2 O→2MgCl 2 ·6H 2 O·5MgCl 2 +5Na 2 CO 3 +6H 2 O→4MgCO 3 ·Mg(OH) 2 ·5H 2 O+CO 2 ↑+10NaCl 4 MgCO 3 · Mg(OH) 2 ·5H 2 O

application
Used in the chemical industry to produce raw 
materials such as magnesium sulfate, magnesium hydroxide, magnesium chloride, building materials industry, magnesium mobile houses, magnesium fertilizer production materials, waste acid water neutralizers, heavy metal ion adsorbents, 
industrial oxidase: also known as light magnesium oxide . It plays an important role in many inorganic salt products. 
It is mainly used in the production of enamel, ceramics, refractory materials, etc. 
as a filler 
in the manufacture of polishing agents, adhesives, and paints. It is used as a promoter and catalyst 
in rayon, rubber (chloroprene rubber, fluororubber). Antacids and laxatives for the treatment of hyperacidity, stomach and duodenal ulcers 
. Degassing agents used by food processors as a sugar refining agent. Ph conditioners for ice cream powders, etc. 
In the construction industry, magnesium oxide can produce magnesium-containing special cements and insulation boards: 
the largest use in agriculture is as feed for fertilizers and livestock, and is a major element in the metabolism of plants and animals. Used as a feed for dairy cows to prevent nervous system dysfunction caused by magnesium deficiency, the so-called pasture rickets; 
in the chemical industry, the use of magnesium and magnesium chemicals such as magnesium sulfate, magnesium oxide and other industrial products; 
In addition, it is also used in water treatment, flue gas washing and in the glass, dye, cable, silicon steel industry, uranium processing electronics industry, insulation materials industry, as well as in petroleum additives, casting, phenolic plastics and other industries.