Brown Aluminum Oxide 250 Grit Wholesale Russia

Bauxite contains high Fe2O3. Although most of it can be removed, it has a certain impact on brown fused alumina product quality. A series of physical and chemical changes occur during the bauxite heating process. Studying it is not only of great significance for the production of alumina, the distribution of its super-grade ore is not concentrated, smelting green silicon carbide, sub-white corundum, but also the basis for manufacturing high-alumina refractories.

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At the same time as the second mullite reaction, Fe2O3, TiO2 and other impurities in the bauxite form a liquid phase with Al2O3 and SiO2. The brown aluminum oxide crystals of mullite and corundum grow up, and the stomata shrink and disappear. China is a country with abundant bauxite resources in the world, but due to the natural law of ore deposit formation, the black silicon carbide mechanized mining is severely mixed, and the natural type of ore is complex and difficult to strictly classify.(brown aluminum oxide 250 grit wholesale russia)

Above 1200 ° C, free brown aluminium oxide reacts with free SiO2 (cristobalite) to form mullite, which is called secondary mullite and has a volume expansion of about 10% at the same time. The reaction formula is as follows: secondary mullite The petrochemical reaction starts at 1200 ° C, and its completion temperature varies depending on the ratio of Al2O3 / SiO2 in bauxite. The larger the ratio, the lower the completion temperature, aluminum oxide abrasive which is generally around 1400 ~ 1500 ° C.

(brown aluminum oxide 250 grit wholesale russia)The more secondary mullite is produced, and the white alumina beneficiation products of iron removal, the larger the volume expansion is, and the more difficult the sintering is. The phases formed after calcination of bauxite are mainly corundum, mullite and glass phases. When the aluminum oxide grit content of Al2O3 is 65% ~ 70% and the ratio of Al2O3 / SiO2 is close to 2.55, the total amount of mullite reaches the highest point, and the amount of secondary mullite is the largest. 

Recrystallization (sintering) stage. Above 1400 ~ 1500 ° C, the secondary mullite transformation in bauxite has been completed and entered the black corundum recrystallization stage. The impurities in it form a liquid phase and fill the pores in the block. Due to the dissolution and crystallization of the solid phase in the liquid phase, and the diffusion of molecules between the solid phase, the synthetic corundum block gradually becomes denser with time at high temperatures. Into.(brown aluminum oxide 250 grit wholesale russia)

The change of bauxite during pink corundum heating can be divided into three stages, namely the decomposition stage, the secondary mullite stage, and the recrystallization and sintering stage. In summary, the physical and chemical changes in the bauxite calcination process are restricted by various factors, among which the Al2O3 content, mineral composition and distribution, and the level of the emery abrasive calcination temperature determine the sintering characteristics of the bauxite. 

(brown aluminum oxide 250 grit wholesale russia)In recent years, the Yangquan bauxite mine in Shanxi has adopted a flotation process, titanium reduction, classification and purification have significantly improved the quality of silicon carbide abrasive unpurified products. Guizhou uses washed coal as fuel, uses a rotary kiln to calcinate bauxite, adopts measures such as stabilizing the calcination temperature and lengthening the garnet abrasive firing zone, so that the high-grade bauxite clinker contains Al2O3 above 88.2%, up to 91.3% .