The Application and Production Process of High-Aluminum Refractory Materials: A Detailed Explanation
What are high-aluminum refractory bricks? Experts from Yaozhong Refractories provide specific answers: Through the production theory of high-aluminum refractory bricks, it has been proven that strictly selecting and grading high-aluminum clinker before crushing, and storing it by grade, along with adopting a method of fine grinding using bauxite clinker and bonding clay, can improve product quality.
What are high-aluminum refractory bricks? Experts from Yaozhong Refractories provide specific answers: High-aluminum refractory bricks are aluminum-silicate refractory products with an alumina (Al2O3) content exceeding 48%. If the Al2O3 content exceeds 90%, they are referred to as corundum bricks. Due to cost differences, standards vary among countries. For example, European countries set the lower limit for high-aluminum refractory materials at 42% Al2O3. In China, high-aluminum bricks are divided into three grades based on their Al2O3 content: Grade I – Al2O3 content >75%; Grade II – Al2O3 content between 60-75%; Grade III – Al2O3 content between 48-60%.
A neutral refractory material with an alumina content above 48%. It is made by shaping and firing bauxite or other raw materials with a higher alumina content. It has high thermal stability, with a fire resistance of over 1770°C and good slag resistance. Used in the lining of electric steelmaking furnaces, glass melting furnaces, cement rotary kilns, etc.
High-load softening and low creep high-aluminum bricks are advanced refractory materials primarily made from premium-grade bauxite, electric fused corundum, and electric fused mullite. These products have advantages such as minimal high-temperature creep, strong corrosion resistance, and excellent thermal shock stability. They are suitable for large and medium-sized hot blast stoves and have successfully contributed to the domestic production of high-quality, high-end imported refractory materials required for new types of hot blast stoves in China, being listed as a national-level "Spark Program" project.
Raw Materials:
Based on cost conditions and product requirements, the following types of raw materials can be used: Bauxite primarily composed of hydrous aluminum oxide minerals (such as gibbsite, boehmite, etc.), sillimanite group minerals (including kyanite, sillimanite, andalusite, etc.), and synthetic raw materials like industrial alumina, synthetic mullite, and electric fused corundum. China has abundant and high-quality bauxite resources, mainly distributed in Shanxi, Henan, Hebei, Guizhou, Shandong, and other places. The produced bauxite mainly consists of a mixture of two minerals: gibbsite (-Al2O3·H2O) and kaolinite.
Characteristics:
1. What is the fire resistance of high-aluminum refractory bricks? What are its characteristics?
The fire resistance of high-aluminum refractory bricks is higher than that of clay bricks and semi-silica bricks, reaching 1750~1790°C, making them advanced refractory materials.
2. What is the load-softening temperature of high-aluminum refractory bricks?
Since high-aluminum products have a high Al2O3 content and fewer impurities, forming less fusible glassy phases, their load-softening temperature is higher than that of clay refractory bricks. However, due to the absence of a mullite crystal network structure, the load-softening temperature is still not as high as that of silica bricks.
c. Slag resistance: High-aluminum refractory bricks contain more Al2O3, approaching neutral refractory materials, capable of resisting both acidic and basic slags. However, because they also contain SiO2, their ability to resist basic slags is weaker than their ability to resist acidic slags.
Production Process:
The production process of high-aluminum refractory bricks is similar to that of multi-clinker clay refractory bricks. The difference lies in the higher proportion of clinker in the mix, which can reach up to 90~95%. Before crushing, the clinker needs to be strictly selected, graded, screened, and iron removed. The firing temperature is higher; for instance, when firing Grade I and II high-aluminum bricks in tunnel kilns, the typical temperature ranges from 1500~1600°C.
Refractory experts have proven through the production of high-aluminum refractory bricks that strictly selecting, grading, and storing high-aluminum clinker before crushing, and adopting a method of fine grinding using bauxite clinker and bonding clay, can enhance product quality.
Uses of High-Aluminum Refractory Bricks:
Primarily used for constructing blast furnaces, hot blast stoves, electric furnace roofs, blast furnaces, reflecting furnaces, and rotary kiln linings. Additionally, high-aluminum bricks are widely used as checker bricks in regenerative systems, nozzles, and water mouth bricks in casting systems. However, since high-aluminum bricks are more expensive than clay bricks, areas where clay refractory bricks can meet requirements do not need to use high-aluminum bricks.
Reference: http://www.sdyaozhong.com/