Magnesite can be divided into natural magnesia and seawater magnesia or synthetic magnesia. Natural magnesia mainly comes from natural magnesite, but it is difficult to obtain high purity and high quality products due to the quality of raw ore, and the magnesium sand has become the main source of magnesite in industrialized countries. Magnesite in MgO style theory content is 47.3%, the rest of the classification of CaO, SiO2, iron impurities, magnesite heated to 700 ℃ ~ 800 ℃ in air decomposition, known as the "light burned magnesia, further becomes inactive when it is heated to above 1530 ℃ periclase become hard burned magnesia, referred to as the" dead burned magnesite ". The synthetic seawater magnesia produced by industrial production is made from seawater and digesting dolomite. The deposited Mg(OH)2 was calcined, and MgO was obtained. The calcium and silica ratio in the synthetic magnesia, which was not burned into bricks, was 0.3~0.5, and the calcium silicate ratio of the high purity seawater magnesia was higher than 1.7, and its high temperature intensity was the highest.
Magnesia manufacturing
According to the sintering characteristics of raw materials and different technical requirements of magnesia products, one step of calcining or two-step calcining technology can be adopted in the process of magnesia production. In order to produce high purity and high density magnesia, the main crystal phase can be directly combined.
Step calcining process as follows: raw materials (have a certain particle size requirements of magnesite stone) - calcining (in shaft kiln and rotary kiln using coke or ash-free fuel, calcination temperature above 1600 ℃) to finished product check, sintered magnesia. Due to the pollution of SiO2 in coke ash, the amount of SiO2 in magnesia increased by about 2%.
Two-step calcining process as follows: raw materials (if there is a requirement for a certain particle size magnesite stone or purification of ore concentrate) - > light burning (in rotary kiln, suspension calcining kiln, multi-layer, fluidized bed furnace and reverberatory furnace, ash-free fuel used by about 1000 ℃ (calcined)) - fine grinding fineness (the more the higher the density of fine magnesia) - calcining (in shaft kiln and rotary kiln with ash-free fuel burning, temperature above 1800 ℃) and sintered magnesia.