Classification, Performance and Application of High Alumina Bricks

High-alumina bricks are aluminosilicate refractory materials with an Al2O3 content of over 48% by mass. Due to their high alumina content, they are called high-alumina refractory materials.

They can be classified according to their mineral content as follows:

1. Mullite-silica bricks, with an Al2O3 content of 40%~70%.

2. Mullite-corundum bricks, with an Al2O3 content of 79%~95%.

3. Corundum bricks, with an Al2O3 content of 95%~100%.

They can also be classified according to Al2O3 content, such as:

• Grade I: Al2O3 > 75%.

• Grade II: Al2O3 60%~75%.

• Grade III: Al2O3 48%~60%.

Rongsheng High-Performance High Alumina Bricks

Performance of High-Alumina Bricks

High-alumina bricks are made from bauxite or other raw materials with high alumina content through forming and calcination. Generally, high-alumina bricks are made from high-quality bauxite clinker, supplemented with binding clay and additives. Certain processes are added during the production of high-alumina refractory bricks to amplify their advantages. The main performance characteristics of high-alumina bricks are as follows:

• ① High refractoriness. Due to the high Al2O3 content, the refractoriness is generally between 1750 and 1790℃.

• ② High softening point under load. Due to the low impurity content, the softening point under load is high. The high-temperature performance of high-alumina bricks is related to the microstructure of the material. The high-temperature resistance of the matrix is ​​much lower than that of the granular part; during use, slag first melts the matrix. Therefore, the high-temperature performance of the material can be improved by modifying and adjusting the matrix and structure.

• ③ Good slag resistance. High-alumina bricks have a high Al2O3 content, making them nearly neutral materials. The slag resistance of high-alumina materials increases with increasing Al2O3 content. However, its resistance to alkaline slag is lower than that of alkaline refractories. Reducing the impurity content helps improve slag resistance. Simultaneously, increasing the material's density and reducing its porosity are also effective measures to improve its slag resistance.

• ④ Good thermal stability and a small coefficient of thermal expansion. High-alumina bricks have poorer thermal shock resistance than clay bricks, which is closely related to the mineral composition of the material. Grades I and II high-alumina bricks are even worse than Grade III high-alumina bricks. In production, thermal shock resistance is often improved by modifying the particle structure characteristics of the material or by adding a certain amount of synthetic cordierite (2MgO·2Al2O3·SiO2) and other minerals to the batch.

What are the application scenarios for high-alumina refractory bricks?

The application scenarios for high-alumina refractory bricks, i.e., their application areas, are:

• 1. Steel Manufacturing Industry: Blast furnaces, hot blast stoves, electric furnaces, ladles, tundishes, heating furnaces, refining furnaces, annealing furnaces, cupola furnaces.

• 2. Non-ferrous Metals Industry: Smelting furnaces, refining furnaces, reverberatory furnaces, converters.

• 3. Building Materials Industry: Cement kilns, glass kilns, ceramic kilns, lime kilns, kiln cars, tunnel kilns.

• 4. Energy and Incineration: Coke ovens, circulating fluidized bed boilers, carbon roasting furnaces, incinerators.

Application of High-Alumina Refractory Bricks in Metallurgical Furnaces

Taking metallurgical furnaces as an example, the operating environment of lead smelting furnaces is extremely complex. This requires refractory bricks to possess not only sufficient high-temperature resistance but also resistance to slag and molten lead corrosion, as well as resistance to slag and flue gas erosion. In the selection of refractory bricks, lead metallurgical furnaces primarily use magnesia-chrome bricks, high-alumina bricks, and high-alumina refractory ramming materials. High-alumina bricks and high-alumina refractory ramming materials are mainly used in the permanent lining area of ​​the furnace bottom.

In the design of lead metallurgical furnace linings, the selection of durable materials varies depending on the location within the furnace body. Taking a fixed horizontal metallurgical furnace body as an example, the furnace bottom generally uses magnesia-chrome bricks, high-alumina bricks, aluminum-chrome spinel, high-alumina ramming material, and magnesia ramming material. Some sections use high-strength anti-seepage ramming material, whose composition also belongs to the Al2O3-SiO2 system, with an Al2O3 content >75%. The proportion of liquid lead reaches 10.6 g/cm3, exhibiting strong permeability. Therefore, the refractory material at the furnace bottom must possess both heat dissipation capabilities and high lead penetration resistance. Currently, a widely used method is to first lay high-alumina bricks on the furnace bottom steel plate. These bricks have high compressive strength (40-60 MPa at room temperature) and a thermal conductivity (2.09 + 1.861 × 10⁻³ t) higher than magnesia-chrome bricks (1.28 + 0.407 × 10⁻³ t), making the furnace bottom a suitable bedding layer. A layer of lead-penetration-resistant refractory material should be placed on top of the furnace bottom bedding layer.

To purchase high-quality high-alumina refractory bricks, please contact RS High-Alumina Refractory Materials Manufacturer for free samples and quotations.