Sintered magnesia is divided into ordinary magnesia, medium-grade magnesia, high-purity magnesia!

Sintered magnesia is divided into ordinary magnesia, medium-grade magnesia, high-purity magnesia, electrofused magnesia is divided into ordinary electrofused magnesia, large crystal electrofused magnesia. In addition, there are sea water magnesia and brine magnesia.

Properties of magnesia. Magnesite has a large expansion coefficient (14×10-6 ~ 15×10-6℃-1), stable chemical properties, and does not react or react slightly with various refractory materials (except silicon bricks) below 1540℃. It has a good resistance to alkaline slag containing CaO and FeO. When the temperature is higher than 2300℃, the magnesite is volatile (melting point 2800℃). It is easy to be reduced to magnesium by carbon at high temperature. In air, especially in humid air, magnesite readily hydrates to form Mg(OH)2.

The decomposition reaction of magnesite after calcination is MgCO3→MgO+CO2. The reaction started at 350℃, and the reaction was intense at 550℃~650℃, and decomposed completely at 1000℃. At this time, the texture of MgO is loose and the chemical activity is high, which is called light burning MgO (active MgO). It is also called lightly burnt MgO powder because it changes from block to powder after calcination. As the temperature continues to rise, MgO crystals grow up, lattice defects are corrected, chemical activity decreases, volume shrinks, and the structure is compact. At this time, it is about 1500℃~1600℃, known as sintered MgO or "dead burn" MgO. It is called magnesia in industry.

The sintering condition of magnesite can be measured by density, refiring shrinkage, hydration property and burning. The activity of the fluidized bed furnace and suspension furnace is generally higher than that of tunnel kiln and reflection kiln, and the activity of rotary kiln is between the first two.

Production process of reburned magnesia: The reburned magnesia is mainly made of natural magnesite with 46% content, calcined by high temperature kiln.

USES of refired magnesia: refired magnesia is mainly used to make magnesia brick and raw materials for producing unshaped refractory materials. The finished products are used for steelmaking, electric furnace bottom and ramming furnace.

The refracturing magnesia is mainly made of 46.5% magnesite, which is calcined by shaft kiln at 1500℃ to 800℃ or so.