The erosion of fused zirconium corundum bricks is mainly divided into physical effects and chemical effects. The physical effect means that during long-term operation of the glass furnace wall, it is repeatedly subjected to the impact of rapid cooling and rapid heating, and its surface layer must undergo a shrinkage-expansion process. Due to excessive fatigue, the structure of the fused zirconium corundum bricks is damaged, resulting in increased surface cracks and loose structure. Therefore, it will crack and peel under the erosion of air flow, materials and glass liquid, and this process will be repeated continuously.
The corrosion of fused zirconium corundum bricks by chemical effects is more complex and severe, and can be divided into four aspects:
1. Precipitation of glass phase
The fused zirconium corundum bricks on the pool wall have been exposed to high-temperature glass liquid for a long time (>1500℃). On the one hand, the glass phase in the bricks will gradually melt and precipitate (the minimum precipitation temperature is about 1150℃); on the other hand, the alkaline glass containing Na2O The liquid will invade into the brick along the pores and cracks of the brick body, diffuse and interpenetrate with the precipitated glass, thus reducing the viscosity and improving fluidity of the precipitated glass liquid, which in turn will intensify the corrosion behavior and extend to depth.
2. The skeleton is damaged
As the erosion of the glass liquid intensifies in depth, the skeleton minerals that make up the brick body are gradually infiltrated and surrounded by the Na2O-containing glass liquid, and the skeleton also begins to be eroded. First, the dissolved mullite decomposes into α-Al2O3 and SiO2, which in turn promotes the conversion of α-Al2O3 into β-Al2O3. As the temperature increases, all β-Al2O3 is dissolved in the glass liquid, and the baddeleyite and corundum lattice is also damaged, resulting in fragmentation, disintegration, and partial melting. β-Al2O3 gradually dissolves in the glass at high temperatures and rarely remains. With the continuous diffusion and penetration of the glass, baddeleyite microcrystals become free, part of which is taken away with the glass liquid and may become glass stones, and part of which is absorbed by the glass. Keep it. Although baddeleyite can be dissolved into glass, its solubility is very small. As the temperature fluctuates, ZrO2 quickly crystallizes from the glass liquid to form skeleton or beaded baddeleyite crystals.
3. Crystallization of new minerals
Since the skeleton minerals of the bricks are partially melted into the glass liquid, the composition of the original glass liquid is changed. Therefore, when the ratio of SiO2-Al2O3-Na2O in the glass liquid is close to the theoretical composition of nepheline, a large amount of nepheline crystals will precipitate.
Al2O3+2SiO2+Na2O→2NaAlSiO4 (nepheline)