Calcined bauxite is the product of high-temperature calcination treatment of bauxite, widely used in industrial fields such as refractory materials, abrasives, ceramics, etc. The following provides a detailed introduction from the aspects of raw material characteristics, calcination process, performance characteristics, and application fields:
1, Raw material: bauxite
Bauxite, also known as alumina or bauxite, is a soil like mineral mainly composed of trihydrate alumina, monohydrate hard alumina, or monohydrate soft alumina. Its main chemical component is alumina (Al ₂ O3), and it also contains impurities such as silica (SiO ₂), iron oxide (Fe ₂ O3), and titanium oxide (TiO ₂).
-According to the alumina content, it can be divided into high alumina alumina (Al ₂ O ∝>70%), medium alumina alumina (60%~70%), and low alumina alumina (<60%).
-High quality bauxite has the characteristics of high alumina content and low impurities, making it an ideal raw material for producing calcined bauxite.
2, Calcination process
Calcination is the core process of bauxite processing, aimed at removing moisture and volatile matter, restructuring mineral structure, and improving stability and strength.
1. * * Pre processing * *: Crushing and screening of raw ore to remove impurities and produce block or powder materials of a certain particle size.
2. * * Calcination process * *: Calcination is carried out in a rotary kiln, vertical kiln, or tunnel kiln at a high temperature of * * 1200-1800 ℃ * *.
-Low temperature stage (<1000 ℃): Remove adsorbed water and crystal water, and transform monohydrate alumina into corundum phase.
-High temperature stage (>1200 ℃): Impurities (such as SiO ₂, Fe ₂ O3) react with alumina to generate low melting point minerals (such as mullite), promoting sintering and increasing density.
3. Cooling and Processing: After calcination, bauxite is cooled, crushed, and screened to produce products of different particle sizes (blocks, aggregates, fine powders, etc.).
3, Performance characteristics
Compared with the original ore, the properties of calcined bauxite undergo significant changes:
-Chemical stability: Alumina exists in the form of stable corundum or mullite phases, enhancing its ability to resist acid and alkali corrosion.
-High temperature performance: The fire resistance can reach above 1770 ℃, and the thermal shock resistance (not easily broken when the temperature suddenly changes) is excellent.
-* * Physical properties * *: Density increases (3.2-3.6g/cm ³), porosity decreases, and strength increases (compressive strength can reach several hundred MPa).
-High hardness: Mohs hardness of 7-8, close to corundum, with good wear resistance.
4, Main categories
According to the calcination temperature and purpose, calcined bauxite can be divided into:
-* * Ordinary calcined bauxite * *: calcination temperature of 1200-1400 ℃, used for general refractory materials and building materials.
-High alumina calcined bauxite: calcination temperature of 1500-1800 ℃, alumina content>85%, mainly used for advanced refractory products and abrasives.
-Electric melting calcined bauxite: After high-temperature melting in an electric arc furnace and cooling, the purity is higher and the crystallization is more complete. It is used for ultra-high temperature refractory materials or precision ceramics.
5, Application Fields
1. * * Refractory material industry * * (main applications):
-Produce refractory bricks, castables, plastics, etc. for lining kilns in high-temperature industries such as steel, cement, and glass.
-High alumina bauxite clinker is a key raw material for producing shaped/unshaped refractory materials, which can improve the material's high temperature resistance and service life.
2. * * Abrasive industry * *:
-High hardness and good wear resistance, can be made into grinding tools such as grinding wheels and sandpaper, used for grinding and polishing metals and stones.
3. Ceramics and Building Materials:
-As an additive for ceramic bodies or glazes, it improves the strength and heat resistance of ceramics.
-Used for high alumina cement (aluminate cement), it has the characteristics of fast hardening, high strength, and high temperature resistance.
4. * * Other fields * *:
-Used for glass fiber reinforced materials, chemical catalyst carriers, etc.
6, Origin and Market
Global bauxite resources are abundant, with major production areas including China, Guinea, Australia, and others. China is a major producer and consumer of calcined bauxite. High alumina bauxite from Shanxi, Henan, Guizhou and other places has excellent quality and its products are exported to the international market. Our factory is located in Shanxi and we look forward to working with you!
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