Bauxite is the main raw material for producing brown corundum, and high alumina clinker with 88% and 90% Al2O3 content is the main raw material for sub-white corundum.
Production of white corundum, compact corundum with alumina as raw material.
Bauxite is also called high bauxite or bauxite, the main minerals are alumina (Al2O3 H2O) and alumina (Al2O33H2O).
Our reserves of bauxite are extremely rich: it is produced in shanxi, Hebei and Shandong provinces north of the Yellow River, through Henan and Guangxi provinces in the middle, and in Guizhou and Yunnan provinces in the southwest.
At present the main producing areas of high bauxite clinker are shanxi, Henan and Guizhou.
There are also smaller mines under development in Hunan.
The main minerals of bauxite in China are boehmite, kaolinite and pyrophyllite. According to its mineral composition, it can be divided into three types: boehmite – kaolinite type (DK);
Boehmite kaolinite type (BK);
Boehmite – pyrophyllite type (DP).
At present, DK type high bauxite is the most widely used, DK type high bauxite clinker is divided into S, ⅰ, ⅱ A, ⅱ B, ⅲ and so on according to its Al2O3 content.
Artificial production of corundum is made of industrial alumina or high bauxite as the main raw material by melting in an electric arc furnace.
In addition, corundum plate alumina can also be prepared by sintering.
This method is still based on industrial alumina powder as the main raw material, calcination, fine grinding, pelletization and firing.
This method is difficult to produce, but the product has high strength, strong erosion resistance and good thermal shock stability.
The so-called "sub-white corundum" is actually high bauxite based dense fused corundum, Al2O3 content is greater than 98%, apparent porosity is less than 4%;
It is made of high bauxite by electric melting under reductive atmosphere and controlled conditions.
Corundum crystal is granular, generally 115mm;
The main impurities are rutile, aluminum titanate and its solid solution.
Mullite is a refractory material mainly composed of 3Al2O32SiO2 crystalline phase.
Mullite is divided into natural mullite and synthetic mullite.
Natural mullite is rare, and artificial synthesis is generally used.
Mullite is stable and insoluble in hydrofluoric acid.
It has good mechanical and thermal properties at high temperature. Therefore, synthetic mullite and its products have the advantages of high density and purity, high structural strength at high temperature, low creep rate at high temperature, low thermal expansion rate, strong chemical erosion resistance and thermal shock resistance.
Sillimanite minerals are kyanite, andalusite, sillimanite, commonly known as "three stones".
The chemical composition of three stone is the same, but the crystal structure is different, is homogenous heterocrystal.
When heated to high temperature, all are converted to mullite, generating a small amount of molten SiO2, accompanied by volume expansion.
Because the size of three stone heating expansion is different, its direct utilization degree is not the same.
Because the volume of andalusite changes little, whether it is used to make bricks, or as an additive, are directly used raw materials.
However, sillimanite and kyanite are often added into the ingredients in the form of expansion agent, especially for more amorphous refractories.
To make bricks, the clinker must be calcined, especially the mature material must be calcined for kyanite.
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