Briefly describe several high alumina bricks commonly used in high temperature industrial kilns

In industrial kilns, commonly used high alumina bricks have the following five categories.

1. Ordinary high alumina brick

  The main mineral composition of the brick is mullite, corundum and glass phase. With the increase of alumina content in the product, mullite and corundum also increase, the glass phase will decrease accordingly, and the refractoriness and high temperature performance of the product will be improved. Ordinary high-alumina bricks have a series of better refractory properties than clay products, and are widely used materials with good application effects and are widely used in various thermal kilns. Compared with clay products, it can effectively improve the service life of the kiln.

2. High-load soft high-alumina brick

   Compared with ordinary high-alumina bricks, high-load soft high-alumina bricks are different in the matrix part and the binder part: in addition to adding three stone concentrates, the matrix part is reasonably introduced according to the theoretical composition that the chemical composition after burning is close to mullite. For high-aluminum materials, such as corundum powder, high-alumina corundum powder, etc., the binder is selected from high-quality clay, etc., depending on the variety, different clay and composite binders or mullite binders are used. Through the above method, the load softening temperature of high alumina bricks can be increased by about 50-70 °C.

3. Low creep high alumina brick

  The creep resistance of high alumina bricks is improved by employing the so-called unbalanced reaction. That is to say, according to the operating temperature of the kiln, add three-stone minerals, activated alumina, etc. to the matrix, so that the composition of the matrix is close to or completely composed of mullite, because the mullite of the matrix will definitely increase the mullite content of the material. , reducing the glass phase content, and the excellent mechanical and thermal properties of mullite are beneficial to the improvement of high temperature properties of the material. To fully mullite the matrix, control of alumina/silica is key. Low creep high alumina bricks are widely used in hot blast stoves, blast furnaces and other thermal kilns.

4. Phosphate bonded high alumina brick

  Phosphate bonded high alumina bricks are made of dense super or first grade high alumina bauxite clinker as the main raw material, phosphate solution or aluminum phosphate solution as binder, after semi-dry press molding, heat treatment at 400-600 ℃ The chemical binder refractory products made are non-burning bricks. In order to avoid large shrinkage of the products during use, it is generally necessary to introduce heat-expandable raw materials, such as kyanite and silica, into the ingredients. Compared with ceramic-bonded fired high-alumina bricks, it has better spalling resistance, but its softening temperature under load is lower and its corrosion resistance is poor. Therefore, it is necessary to add a small amount of fused corundum, mullite, etc. to strengthen the matrix. . Phosphate-bonded high-alumina bricks are widely used in cement rotary kilns, electric furnace roofs and other kiln parts.

5. Micro-expanded high alumina brick

The brick is mainly made of high-alumina brick bauxite as the main raw material, adding three-stone concentrate, according to the production process of high-alumina brick. In order to make the high-alumina bricks expand properly during use, the key is to select the three-stone concentrate and its particle size, and control the firing temperature, so that part of the selected three-stone mineral is mullite, and part of the three-stone mineral remains. The residual three-stone minerals are further mulliteized in the process of use, accompanied by volume expansion, the selected three-stone minerals are preferably composite materials. Due to the different decomposition temperatures of the three-stone minerals, the expansion produced by mulliteization also varies. Using this feature, the high alumina brick has a corresponding expansion effect due to different working temperatures, squeeze the brick joints, improve the overall compactness of the lining body, and thus improve the resistance to slag penetration of the brick.