Reburned magnesite It is calcined by magnesite, bischofite or magnesium hydroxide extracted from seawater at high temperature. It is a general term for the products of magnesite and other magnesia raw materials that have been treated at high temperature to reach the sintering process. The magnesia produced by the magnesia manufacturer with natural magnesite as raw material is called sintered magnesia by using the one-step or two-step calcination process of high-temperature equipment such as shaft kiln and rotary kiln; Seawater magnesia is produced by extracting magnesium oxide from seawater after magnesite and other raw materials are melted in an electric arc furnace and cooled.
Magnesite is one of the most important raw materials for refractories, which is used to manufacture various magnesia bricks, magnesia alumina bricks Ramming material , furnace mending materials, etc., which contain more impurities, are used to pave the bottom of the steelmaking furnace, etc. The high-purity magnesite is produced by flotation purification of natural super grade magnesite ore, light burning, fine grinding, ball pressing and ultra-high temperature oil shaft kiln calcination. It is a high-quality raw material for brick making refractory.
The properties of magnesia are divided into chemical properties and physical properties. The chemical properties of magnesia mainly refer to that magnesia is mainly composed of periclase MgO. periclase is one of the common minerals in cement clinker. periclase can coexist with the four main minerals C3S, C2S, C3A and C4AF in cement clinker. Therefore, periclase has extremely good corrosion resistance for cement clinker.
Periclase is an equiaxed mineral, which can form complete solid solution with FeO, NiO and MnO. Mohs hardness 6, relative density 3.58, melting point up to 2800 ° C, 0? The thermal expansion coefficient at 1000 ° C is 13.5X10-6/K, 100? The thermal conductivity at 1000 ° C is 3.39? 4.19W/(m?K)。
These physical properties make magnesia refractories in cement rotary kiln often show the following phenomena:
① Periclase has a high melting point, so many magnesia refractories have good high temperature resistance;
② The periclase has good thermal conductivity. When high MgO refractory materials are used and the kiln skin cannot be hung, the surface temperature of the kiln body rises. At this time, not only the heat loss is great, but also the cylinder is easy to burn out;
③ The high coefficient of thermal expansion of periclase leads to the lack of thermal shock resistance of magnesia refractories.
