The erosion of fused AZS bricks is mainly divided into physical action and chemical action. The physical action means that the wall of the glass melting furnace is repeatedly subjected to the impact of rapid cold and rapid heat during the long-term operation, and its surface must undergo a process of contraction and expansion. Due to excessive fatigue, the structure of the
fused AZS brick is damaged, resulting in an increase in surface cracks and a loose structure. Therefore, it will crack and peel off under the action of airflow, material and glass liquid, and this process will be repeated continuously.
The chemical effect on fused AZS bricks is more complicated and severe, which can be divided into four aspects:
(1) Precipitation of glass phase
The fused AZS bricks on the wall of the pool are subjected to high temperature molten glass for a long time (>1500℃). On the one hand, the glass phase in the brick will gradually melt and precipitate (the minimum precipitation temperature is about 1150℃); on the other hand, the alkali glass containing Na2O The liquid will penetrate into the brick along the pores and cracks of the brick body, and diffuse and interpenetrate with the precipitated glass phase, thus reducing the viscosity of the precipitated glass liquid and improving the fluidity, thereby intensifying the corrosion behavior and expanding in depth.
(2) Damaged skeleton
As the corrosion of the molten glass increases in depth, the skeleton minerals constituting the brick body are gradually infiltrated and surrounded by the molten glass containing Na2O, and the skeleton begins to be corroded. The first dissolved mullite decomposes into α-Al2O3 and SiO2, which in turn promotes the conversion of α-Al2O3 to β-Al2O3. As the temperature increases, β-Al2O3 is completely dissolved in the molten glass, and the crystal lattice of oblique zircon and corundum is also destroyed, and then fragmented, disintegrated, and partially melted. β-Al2O3 gradually dissolves in the glass at high temperature and is rarely retained. With the continuous diffusion and penetration of the glass, the oblique zircon crystallites become free, some of which are taken away with the glass liquid, and may become glass stones. save. Although oblique zircon can dissolve into glass, its solubility is very small. As the temperature fluctuates, ZrO2 crystallizes rapidly from molten glass to form skeleton or beaded oblique zircon crystals.
(3) Crystallization of new minerals
Because the skeleton mineral of the brick body is partially melted in the molten glass, the composition of the original molten glass is changed. Therefore, when the ratio of SiO2-Al2O3-Na2O in the molten glass is close to the theoretical composition of nepheline, a large amount of nepheline crystals will precipitate.
Al2O3+2SiO2+Na2O→2NaAlSiO4 (nepheline)
(4) Invasion of nepheline
Since the density of nepheline is less than the density of the brick body, while nepheline crystals are precipitated, the brick body structure becomes loose with the larger volume expansion. Although the melting of part of the crystalline phase in the brick will increase the viscosity of the glass liquid and have a certain protective effect on the loose structure, it still cannot completely block the airflow in the kiln, the scouring of the material and the glass liquid and the action of gravity, and cracks, Peel off into the molten glass and form glass stones. The wound surface after peeling continued to be eroded and washed by the glass liquid and continued to peel off. The result will inevitably lead to the erosion and disintegration of fused AZS bricks.
