How to use fused cast AZS sidewall blocks correctly?

At present, the sidewall blocks of the melting zone of ordinary glass furnaces generally adopt an overall sidewall shallow tank structure with a thickness of 250 mm and a height of about 1,350 mm. The sidewall blocks are made of fully oxidized void free cast fused cast AZS blocks. Generally, fused cast AZS # 36 blocks is used in the melting zone, fused cast AZS # 33 blocks is used in the clarification zone, and fused cast AZS # 41 blocks is used in the corners. Under the same quality conditions, high-grade blocks have stronger corrosion resistance, but when the erosion residue is less than 50 mm, high-grade blocks are prone to bursting. There are also designs with layered structures or deep tank structures. With the increase of furnace age and the use of lower-layer insulation and bubbling, the erosion of the lower sidewall is large and difficult to check. Some manufacturers have very thin lower sidewalls when releasing water, so the quality of the lower sidewalls should also be taken seriously. In order to gradually extend the service life of glass furnaces, the production technology of fused cast AZS blocks has been improved, and it is also crucial to use sidewall blocks well.

►Conclusion

I Characteristics of fused cast AZS blocks

There are many companies producing fused cast AZS blocks (fused zirconium corundum blocks) for glass furnaces at home and abroad, and the product quality level and price vary greatly. Many manufacturers at home and abroad have a lot of room for improvement in appearance quality, composition design, casting process and dimensional accuracy. The quality of blocks directly affects the service life of the sidewall, especially the crystal structure, glass phase content and processing accuracy of blocks.
Due to its dense structure and low porosity, the fused refractory material has an extremely high Young’s modulus below 800 ℃, is very brittle, has a large cold compressive strength of more than 350 MPa, but has a tensile strength of only about 20 MPa. When subjected to thermal shock and uneven heating, the tensile stress caused by the temperature difference is too large and the volume changes too fast, and there is no pore to buffer, so it is very easy to burst.
The figure below shows the physical and chemical properties of fused cast AZS #33 blocks：

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II.Heating up of sidewall blocks

During the heating process of the fused cast AZS sidewall block in the glass furnace,
When the temperature is between 0 and 1 100 ℃, the block gradually expands linearly with the increase of temperature, and the linear expansion of this process is about 0.8%.
When the temperature is between 1 100 and 1 200 ℃, the monoclinic ZrO₂ in the block body transforms into tetragonal ZrO₂, accompanied by the change of volume, the block body shrinks, and the total expansion rate drops from about 0.8% to about 0.6%;
when the temperature is higher than 1 200 ℃, the block starts to expand again with the increase of temperature;
Below 1 600 ℃, the overall expansion of the sidewall block is not large, and the average expansion coefficient is about 7×10^-6/℃