Maintenance of refired magnesium oxide protective coating

Main features of refired magnesia products:

Magnesia is mainly made of 46.5% magnesite, calcined by shaft kiln at 1500℃ to 800℃ or so. Products belong to tan color, dead burned magnesia products mainly contain the composition of the magnesium oxide, calcium oxide, silicon oxide, ferric oxide, 3 oxidation 2 aluminium, caustic soda, dead burned magnesia Mgo style magnesium oxide main content are 80%, 82%, 85%, 88%, 90%, 91%, 92%, 93%, calcium oxide composition at about 2.5% of the dead burned magnesia, dead burned magnesia the silica component between 3.5% and 7%, ferric oxide of dead burned magnesia content is between 0.8% and 1.5%, Electrical grade magnesium oxide powder, 97 fused magnesia, fused magnesia 98 3 oxidation 2 aluminium content in about 1% of dead burned magnesia, dead burned magnesia in caustic soda content in 1%, dead burned magnesia is mainly used in brick and main ideal of the amorphous refractory raw material, the other dead burned magnesia products can also be used in steelmaking, electric furnace and furnace bottom ramming furnace lining and other industries use.

Magnesite, also known as sintered magnesite, is composed of magnesite, magnesite or magnesium hydroxide from the reaction of sea water and lime milk. It is formed by calcination at high temperature and has strong hydration ability. It is mainly used for making basic refractory materials, such as magnesia brick and magnesia alumina brick.

The magnesia can be divided into natural magnesia and seawater magnesia or synthetic magnesia. Natural magnesite mainly comes from natural magnesite, but due to the quality restriction of raw magnesite, it is difficult to obtain high-quality products. So far, seawater magnesite has become the main source of magnesite used in industrialized countries.

According to the chemical composition of magnesite, the quality and phase composition of magnesite products can be predicted. When calculating the phase composition, only when the uniformity of magnesite raw material and the calcining temperature of the material are sufficient to balance the phase composition, the calculated phase composition will be consistent with the experimental results, and the higher the purity of the material, the more consistent the phase composition will be.

Calcined to 700℃, magnesite decomposes CO2, and calcined to 1000℃ or so to produce light calcined magnesite (caustic magnesium oxide), commonly known as bitter earth powder, with loose texture and high chemical activity. If the temperature continues to rise to above 1700 ~ 1800℃, the grain size of calcined magnesite will grow gradually, shrink in volume, increase in density, and decrease in chemical activity greatly, that is, calcined magnesite will become sintered magnesite.

There are two kinds of structure forms between the grains of magnesite:

Silicate bond (ceramic bond) : The main crystalline phases are bonded together by low melting point silicate or amorphous silicate, which is sintered in liquid phase.

Direct combination; A bond formed by direct contact of high melting point grains, which belongs to solid sintering and generally does not involve liquid phase in sintering. The directly bonded magnesia products have high mechanical strength, slag resistance and volume stability at high temperature.