Light burnt magnesia powder



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Composition, Structure and Properties of Medium-grade Magnesia

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Composition, Structure and Properties of Medium-grade Magnesia

Date:2017-03-11 author:Hongkai Fire Resistance click:

Medium-grade magnesia is widely used in the production of magnesia-carbon bricks, alumina-magnesia-carbon bricks, magnesia-alumina spinel bricks and other alkaline magnesia products because of its good corrosion resistance to alkaline slag. By studying and analyzing the volume density, apparent porosity and microstructures of sintered magnesia, the relationship between the microstructures and macroscopic properties of sintered magnesia can be systematically understood. China produces 18 million tons of magnesite and 10 million tons of magnesite annually, accounting for about 80% of the world's magnesite output. The main methods of producing magnesite from magnesite are sintering and electrofusion. Magnesite decomposes into MgCO3 MgO + CO2 after calcination. The reaction began at 350 C, and was intense at 550 650 C, and decomposed completely at 1000 C. At this time, the texture of MgO is loose and its chemical activity is very high. It is called light burning MgO (active MgO). It is also called light-burned MgO powder because it changes from bulk to powder after calcination. As the temperature continues to rise, the MgO crystal grows, the lattice defects are corrected, the chemical activity decreases, the volume shrinks, and the structure is compact. At this time, the temperature ranges from 1500 C to 1600 C, which is called sintered MgO or "dead burning" MgO. It is called magnesia in industry. The sintering condition of magnesia can be judged by density, reburning shrinkage, Hydration Performance and burning reduction. Magnesia produced by fluidized bed furnace and suspension furnace is generally of high activity, while that produced by tunnel kiln and reverberation kiln is of low activity, and that produced by rotary kiln is between the former two. At present, the classification of magnesia is as follows: sintered magnesia is divided into ordinary magnesia, intermediate magnesia, high purity magnesia, fused magnesia is divided into ordinary fused magnesia, large crystalline fused magnesia. In addition, there are seawater magnesia and brine magnesia. Properties of magnesia. The expansion coefficient of periclase is larger (14 *10-6~15 *10-6 (-1), and its chemical properties are stable. It does not react with various refractories (except silica brick) below 1540 (-1). It has excellent resistance to alkaline slag containing CaO and FeO. Magnesium is easily volatilized (melting point 2800 C) when it is higher than 2300 C. Magnesium is easily reduced to metallic magnesium by carbon at high temperature. Magnesium (OH) 2 is easily hydrated in air, especially in moist air. The crystalline size of magnesia. The crystalline size of magnesia is general. The crystalline sizes of all kinds of magnesia are as follows: light burnt magnesia powder is less than 3 micron, sintered magnesia is 40 micron to 200 micron, fused magnesia is 200 micron to 1500 micron (or more than 5000 micron).

Medium grade magnesia