Alumina is an important refractory material, widely used in various industrial fields for its excellent high-temperature, chemical stability, and mechanical strength.

I. Refractory Properties of Alumina

The main component of alumina is alumina (Al₂O₃) which usually contains more than 48%, and some high-purity products can have an alumina content of more than 85%. Its refractoriness is extremely, generally reaching above 1700℃, and even some high-alumina products can have a refractoriness of up to 1890℃. high refractoriness allows it to maintain structural stability in high-temperature environments and is not prone to thermal expansion or contraction.

Alumina also has good chemical stability, able maintain stability in both acidic and alkaline environments and is not easily corroded. In addition, its low thermal conductivity and high mechanical strength make it perform well in high- furnaces, effectively reducing heat loss and withstanding mechanical pressure in high-temperature environments.

II. Application Fields of Alumina

(1) Metallurgical Industry

Alumina is widely used in the lining and insulation layer of high-temperature smelting equipment such as blast furnaces, converter, and electric furnaces. Its high refiness and corrosion resistance can effectively protect the furnace body and extend the service life of equipment.

In the Bayer process for aluminum production, alumina is one of the main raw, requiring an Al₂O₃ content ≥ 55%, consuming 4-5 tons of high-quality alumina for every 1 ton of metal aluminum produced

(2) Building Materials

Alumina is used to produce high-alumina refractory bricks, refractory castables, and refractory mortars etc. These materials are widely used in the lining of blast furnaces, kilns, and industrial furnaces, able to withstand high temperatures and chemical corrosion.

High-alina refractory bricks are divided into ordinary high-alumina bricks (48%-75%), first-class high-alumina bricks (above 75, mullite bricks, and corundum bricks according to their Al₂O₃ content.

(3) Chemical Industry

Alumina is used in petrochemical, chemical furnaces, and catalyst carriers, etc. Its excellent refractory performance and chemical stability make it an ideal material choice.

Alumina can also be used assts, adsorbents, etc., in chemical production.

(4) Glass Industry

Alumina is used in the lining and insulation layer of glass melting furnaces able to resist the corrosion of molten glass.

(5) Ceramics Industry

Alumina is used in the production of high-temperature ceramics and refory ceramics, giving ceramic products good strength and wear resistance.

High-purity alumina powder can also be used in sapphire crystal growth, lithium battery separator, and other high-tech fields.

(6) Precision Casting

Fine powder of sintered alumina can be used for precision casting molds, with the characteristics no deformation at high temperatures and strong wear resistance.

III. Processing and Quality Control of Bauxite

The production process of bauxite includes crushing, grinding, classification, sintering,. The sintering temperature is generally between 1200-1700℃, and the specific temperature is adjusted according to the grade and use of baux. In terms of quality control, bauxite needs to be tested for indicators such as Al₂O₃ content, bulk density, and refractoriness. According to the GBT 24483-2009 national standard, bauxite is divided into special grade (Al₂O₃≥75%), first grade (0%-75%), and second grade (60%-70%) according to its composition.

IV. Future Development Trends

With the advancement of technology and the development industry, the application fields of bauxite are still expanding. For example, its deep processing technology is extending towards nano-functionalization to meet the needs of lightweight materials in new vehicles, aerospace, and other fields. In addition, the application of bauxite in environmental engineering is also increasing, such as using its adsorption performance to treat industrial waste.

In summary, bauxite, with its high refractoriness, chemical stability, low thermal conductivity, etc., has shown superior performance and broad application potential in the of refractory materials, and it is an indispensable important raw material in modern industry.