Magnesium is calcined at high temperature from magnesite, hydromagnesite or magnesium hydroxide extracted from sea water. Magnesite is the general term for the products of magnesite materials which are processed at high temperature to the sintering process. With high temperature equipment such as shaft kiln and rotary kiln calcination or two-step calcination process, tubular magnesia brick, magnesia produced by firing natural magnesite as material is called sintered magnesia; Magnesite and so on as the material by arc furnace melting to melt state after cooling is called from the extraction of magnesium oxide from sea water is called seawater magnesia.
Magnesia is one of the refractory materials, used for manufacturing all kinds of magnesia brick, magnesia aluminum brick, ramming material, filling furnace material, containing more impurities, used for paving steelmaking furnace bottom, etc. High purity magnesite is produced by flotation purification of natural magnesite and calcined by light burning, fine grinding, ball temperature and oil shaft kiln. It is a kind of refractory material for brick making.
The properties of magnesia are divided into chemical properties and physical properties. The chemical properties of magnesia mainly refers to that magnesia is mainly composed of magnesite MgO. Magnesite is one of the common minerals in cement. Magnesite can coexist with the four main minerals C3S, C2S, C3A and C4AF in cement. Therefore, magnesite has good corrosion resistance on cement clinker. Physical properties make magnesium refractories in cement rotary kilns often show the phenomenon:
Magnesite melting point is very high, so that many magnesium refractories have good high temperature resistance;
Magnesite has good thermal conductivity. When high MgO refractories are used and cannot be hung on the kiln skin, the surface temperature of the kiln body rises. At this time, not only the heat loss is great, but also the simple burning of the cylinder body.
High thermal expansion coefficient of magnesite, resulting in the lack of thermal shock resistance of magnesium refractories, in use, magnesium refractories often fall off.