Which refractory brick is more suitable for glass furnace

The so-called "electric fusion" refers to a manufacturing process for refractory bricks, in which the batch materials are heated and melted in an electric arc furnace, poured into a mold in a liquid state, and cured to achieve ceramic bonding. Compared with sintered bricks, it has the characteristics of dense structure, very low porosity, high bulk density, high mechanical strength and high-temperature structural strength, and strong resistance to glass liquid erosion.

The main varieties on the market at present are: fused mullite bricks, fused zirconium corundum bricks, fused chrome zirconium corundum bricks, fused quartz bricks, fused corundum bricks, etc.

Which of these electric-fused refractory materials is more suitable for use in glass melting furnaces?

1. Fused mullite brick
   Fused mullite brick uses high-alumina bauxite as raw material, and different bauxites are mixed into the composition of mullite (3Al2O3·2SiO2, with mass fractions of Al2O372%, SiO228%). It melts at around 2300℃, is poured into a sand mold at 1850℃, and then annealed to eliminate stress. The main crystal phases are mullite and corundum, and the glass phase is filled between the crystal phases. Its resistance to glass liquid erosion is stronger than that of sintered refractory materials, but not as good as other fused refractory materials. Adding a small amount of zirconium dioxide (7%-8.5%) can make the mullite crystals smaller and the brick structure dense, and the amount of mullite increases to 60%-70%, which relatively reduces the content of the glass phase and reduces the cracks of the product. Fused mullite bricks are gradually replaced by fused zirconium bricks.
2. Fused zirconium corundum bricks
   Fused zirconium corundum bricks are divided into three grades according to the content of ZrO2, and the corresponding grades are: AZS-33 (containing ZrO2 33%), AZS-36 (containing ZrO2 36%), and AZS-41 (containing ZrO2 41%).
   Fused zirconium corundum bricks are made of zircon and industrial alumina as the main raw materials, and a small amount of zircon-rich sand (in order to increase the content of ZrO2), soda ash and borax are added. According to the different atmospheres during melting, there are two methods: reduction melting method and oxidation melting method. At present, the oxidation method is mainly used. The oxidation melting method can eliminate the pollution caused by graphite electrodes in the molten liquid, and the carbon content is low (0.005%-0.02%), which can reduce the bubble content in the glass and improve the quality of the glass liquid.
3. Fused corundum bricks
   Fused corundum bricks are made of high-purity alumina as raw materials, and a small amount of soda ash is introduced, and melted at 2000-2200℃. The production process is similar to that of high-alumina products. There are fused α-corundum bricks, fused α, β-corundum bricks, fused β-corundum bricks, etc. Fused α-corundum bricks are mainly suitable for melting borosilicate glass, opal glass and melts containing sulfates. Fused α, β-corundum bricks contain only a small amount of glass phase in their composition. They will not seep out during use, and have little pollution to the glass liquid. Direct contact with the glass liquid will not color the glass liquid, and they have good corrosion resistance. They are ideal materials for the cooling pool wall of the glass melting furnace, the bottom of the kiln, and the launder of the float glass melting furnace. Fused corundum bricks are suitable for the upper structure of the working pool of the melting furnace, the burner at the rear of the melting zone, and the breast wall and small furnace flat near it.
4. Fused chrome-zirconia-corundum bricks
   10%-30% Cr2O3 is introduced into AZS-33 bricks, and fused chrome-zirconia-corundum bricks (abbreviated as AZCS bricks, French brand ER2161) are produced by non-shrinkage cavity casting method. The surface and interior of the bricks are dark green. The bricks contain 4.5% shrinkage pores and no connected pores. Due to the formation of aluminum-chromium spinel solid solution, the viscosity of the glass phase is increased, and the ability to resist glass liquid corrosion is greatly improved. It is 3.4 times that of fused AZS-33 bricks and 2.6 times that of fused AZS-41 bricks.
5. Fused quartz bricks
   The production process of fused quartz bricks is the same as that of quartz glass. High-purity quartz sand (SiO2 content above 99.5%) is used as raw material, a small amount of Na20 is added as a mineralizer, and melted in a graphite resistance furnace (1750-1800℃). After melting, the entire molten material is quickly taken out, rolled into bricks, and then mechanically processed after cooling in the air. The thermal expansion coefficient is extremely small and the thermal shock resistance is good. It has strong resistance to the erosion of boron glass liquid, but not to the erosion of sodium-lime-silicon glass liquid.

Through the above introduction, do you have a deeper introduction to several commonly used fused refractory materials in glass kilns? If you have other opinions and insights, please feel free to communicate with us.