Why High Alumina Bricks Are the Essential Refractories For High-Temperature Applications？

Why High Alumina Bricks Are the Essential Refractories For High-Temperature Applications？

Refractory materials are essential lining materials for kilns. Among them, high alumina bricks play a crucial role and are highly recognized in the market. Almost all furnaces require high alumina bricks.

What are High Alumina Bricks?

When we mention high alumina bricks, we must highlight their unique chemical composition. As the name implies, high alumina bricks have a significant aluminum oxide (Al₂O₃) content exceeding 48%, making it one of their main components. Additionally, silicon dioxide (SiO₂) plays an important role, together forming the cornerstone of alumina-silica refractory materials. Among many refractory bricks, high alumina bricks stand out due to their unique advantages.

So, what exactly is a high alumina brick? It is a meticulously designed and crafted high-temperature resistant material with specific shapes and sizes. Chemically, high alumina bricks exhibit neutral properties, meaning they perform excellently in acid and alkali resistance. Even in high-temperature environments, they remain stable and resist corrosion by acids and alkalis. Notably, the higher the aluminum oxide content, the better the corrosion resistance.

Furthermore, as a common refractory material, the physical properties of high alumina bricks, such as refractoriness, high-temperature softening temperature, strength, and porosity, adjust according to their content and structural composition. This adaptability allows high alumina bricks to meet different industrial environments and application needs, making them indispensable in various fields.

Visually, high alumina bricks exhibit diverse characteristics. Depending on the production process and raw materials, different manufacturers’ products may vary in color, such as yellow, off-white, and beige.

Alumina Content in Various Grades of High Alumina Bricks:

Grade 1 High Alumina Bricks: ≥75% Al₂O₃ content

Grade 2 High Alumina Bricks: ≥65% Al₂O₃ content

Grade 3 High Alumina Bricks: ≥55% Al₂O₃ content

Special Grade High Alumina Bricks: ≥80% Al₂O₃ content

Types of High Alumina Bricks

High alumina bricks come in various types, including Grade 1, 2, and 3 high alumina refractory bricks, anti-spalling high alumina bricks, low creep high alumina bricks, phosphate high alumina bricks, low porosity high alumina bricks, and wear-resistant high alumina bricks. In terms of size and specifications, common ones include T3 standard bricks (23011465mm), large and small cutting high alumina bricks, large and small axe high alumina bricks, high alumina arch bricks, high alumina anchor bricks, high alumina hanging bricks, casting high alumina sleeve bricks, steel flow high alumina bricks, stopper high alumina bricks, casting cup high alumina bricks, and many more. Custom-shaped high alumina bricks are also available. Due to their extensive performance and application advantages, high alumina bricks can be customized according to the furnace type requirements.

Characteristics of High Alumina Bricks

Refractoriness: High alumina bricks surpass clay and semi-silica bricks in refractoriness, reaching an impressive 1750-1790 degrees Celsius. This outstanding performance makes high alumina bricks stand out in the field of advanced refractory materials, providing solid assurance for applications in various high-temperature environments.

Load Softening Temperature: Due to the high Al₂O₃ content and low impurities in high alumina products, the formation of fusible glassy materials is relatively low. Therefore, the load softening temperature of high alumina bricks is higher than that of clay bricks, usually above 1420-1550 degrees Celsius. Although the load softening temperature is slightly lower than that of silica bricks, this does not affect their stability and reliability in high-temperature environments.

Slag Resistance: High alumina bricks also perform excellently in slag resistance. They can resist corrosion from acidic slags and, to some extent, from alkaline slags. Although their resistance to alkaline slags is relatively weaker, it is sufficient for most industrial applications.

widely applicable in the chemical and metallurgical industries.

Chemical Resistance: High alumina refractory products excel in resisting chemical corrosion from acidic or alkaline slags, metal liquids, and oxidation-reduction reactions. Moreover, as Al₂O₃ content increases and harmful impurities decrease, their chemical resistance improves further. This characteristic makes high alumina bricks

Applications of High Alumina Bricks in Kiln Linings

Furnace Chambers: High alumina refractory bricks are indispensable for industrial furnace chambers across various industries such as metallurgy, chemical, glass, and ceramics. Their outstanding refractory performance allows them to withstand high temperatures and pressure without retreating, making them ideal for protecting furnace chambers from high-temperature erosion and corrosion. Additionally, their wear resistance ensures stable performance over extended periods, supporting the continuous operation of industrial furnaces. Furthermore, their excellent corrosion resistance in both acidic and alkaline environments ensures the integrity and safety of the furnace chambers.

Kiln Chambers: High alumina refractory bricks are suitable for various kilns, such as rotary kilns, laser kilns, and graphitization kilns. Kilns operating at high temperatures require refractory bricks with high refractoriness. High alumina bricks offer high-temperature stability, wear resistance, and impact resistance, enabling long-term stable operation.

Hot Blast Furnace Chambers: High alumina refractory bricks are suitable for the structure of hot blast furnace chambers, including combustion chambers, burners, and air ducts. Hot blast furnaces operating at high temperatures require refractory materials with high durability. High alumina bricks can work stably in high-temperature and high-pressure environments, maintaining a long service life.

Kiln Linings and Cladding: High alumina refractory bricks are often used as kiln linings and cladding materials to protect kiln walls from high temperatures and corrosion. The selection of kiln linings is crucial to the performance and longevity of kilns. High alumina bricks offer excellent refractory and wear-resistant properties, effectively extending the kiln’s service life.

Furnace Front Equipment: High alumina refractory bricks can also be used in various furnace front equipment, such as the exit, tail, and burners of hot blast furnaces, as well as the combustion chambers and high-temperature flues of boilers. They provide insulation, corrosion resistance, and anti-erosion functions.

Heat Treatment Furnaces: In heat treatment processes, various heat treatment furnaces such as annealing furnaces, quenching furnaces, and equalizing furnaces are indispensable. These furnaces operate in high-temperature environments, requiring refractory bricks with excellent performance. High alumina refractory bricks ensure the refractory performance of furnace chambers under high-temperature conditions. They maintain stable physical and chemical properties during long-term high-temperature exposure and sudden temperature changes, ensuring the stable operation of heat treatment furnaces. Furthermore, their wear resistance and corrosion resistance ensure the integrity and smoothness of furnace chamber walls, extending the service life of heat treatment furnaces.

Electric Furnace Chambers: High alumina refractory bricks are widely used in various electric furnaces such as arc furnaces and induction furnaces. Electric furnaces operating at high temperatures require refractory materials with high temperature stability and electromagnetic properties. High alumina bricks can work stably in electric furnace chambers, protecting the furnace from high-temperature erosion.High alumina bricks are also used in the steel industry (blast furnaces, hot blast furnaces, electric furnaces, ladles, intermediate vessels, heating furnaces, refining furnaces, annealing furnaces, cupola furnaces), non-ferrous metal industries (smelting furnaces, refining furnaces, reflection furnaces, converters), construction materials (cement kilns, glass kilns, ceramic kilns, lime kilns, kiln cars, tunnel kilns), energy and incineration (coke ovens, circulating fluidized bed boilers, carbon roasting furnaces, incinerators), and various high-temperature industrial kilns. High alumina bricks are indispensable in industrial production with high application rates in high-temperature industrial kilns operating at 1300-1500 degrees Celsius.

How to Select High-Quality High Alumina Bricks

Appearance: The quality of high alumina bricks is first reflected in their appearance. The surface should be smooth, usually beige, and may vary slightly with different aluminum oxide content. The higher the content, the whiter the color. The four edges should be neat without broken corners or cracks, and black spots should be minimized. Black spots on the surface often result from iron oxide formation during the calcination process. If there are extensive black spots, it may indicate high iron oxide content, which can affect the brick’s service life.

Sound: A practical way to judge the quality of high alumina bricks is by sound. When two bricks are struck together, high-quality high alumina bricks produce a clear, non-dull sound, indicating dense internal structure and excellent quality.

Weight: Weight is another important indicator. Different grades of high alumina bricks have different weights. Generally, the higher the aluminum oxide content, the heavier the weight. Standard bricks are usually about 4.5 kg each, with small variations based on brick specifications.

Physical and Chemical Indicators: The quality of high alumina bricks also relies on key indicators such as aluminum oxide content, high-temperature load softening temperature, normal temperature compressive strength, high-temperature volume stability, true specific gravity, and bulk density. These indicators ensure that high alumina bricks maintain their integrity and performance in high-temperature environments.