What are the main aspects of damage caused by refractory materials used in glass kilns

1. Erosion
Powder, liquid glass, and flame gases in the kiln can corrode refractory materials at high temperatures.
The erosion effect of the powder on the refractory material is mainly manifested in the erosion of the refractory material by the alkali vapor evaporated by the powder at high temperature, such as the erosion of the surface of the silica brick, the "rat hole" inside, and the anti nephelinization effect in the checkered brick. In addition, the fly ash of ultra-fine powder in the powder accumulates in the grid body of the heat storage chamber, forming tumors and blocking the grid holes. In severe cases, the grid bricks may collapse and be damaged, forcing thermal repair. The erosion effect increases with increasing temperature, and the melting temperature increases by 50? 60 ℃ will shorten the service life by about one year. Parts such as the front face wall, the charging port, the front space of the melting section, the pool wall, the small furnace, and the upper grid of the regenerator can be corroded by the powder.
The corrosive effect of liquid glass on refractory materials is much smaller than that of powder, and the phase reaction between liquid glass and the interface layer of refractory materials is complex. The glass liquid first dissolves the free SiO2 in the refractory. The dissolution rate of mullite is relatively small, and it accumulates at the interface between glass liquid and refractory materials. Although the small crystalline mullite dissolves, the large crystalline mullite even increases during use. After the refractory material is eroded, SiO2 and Al2O3 are added to the molten substance in contact with it. The molten substance will diffuse into the rest of the glass liquid. During the diffusion process, the composition of the molten substance changes, SiO2 and alkali liquor increase, and a change occurs at the interface β- Due to the aggregation effect of Al2O3 crystals, on the contact surface between the refractory and liquid glass, there is first a layer of mullite, followed by a layer of mullite β- The Al2O3 layer is followed by a non corroding refractory material. After the refractory is dissolved, the viscosity of the glass liquid increases, promoting the formation of a more difficult to move protective layer on the surface of the refractory, reducing the effect of continued erosion.
The corrosive effect of glass liquid on refractory materials depends on its physical properties such as viscosity and surface tension. Glass liquid with low viscosity and low surface tension is easy to soak the refractory material and absorb it from its surface pores, causing strong erosion of the entire refractory material. High alkali glass has a lower viscosity, and borosilicate glass has a low surface tension, so their corrosive action is intense. Increasing the melting temperature will reduce the viscosity and surface tension of the molten glass, thereby accelerating the erosion effect. Liquid glass containing boric acid, phosphoric acid, fluorine, aluminum, and barium compounds has a strong corrosive effect on refractory materials. Strong convection of liquid glass and unstable liquid surface will wash away the protective layer, accelerating corrosion. For refractory materials themselves, the degree of corrosion is mainly related to their chemical composition, mineral composition, and structural state. Irregularity and cracks in the surface of refractory materials can exacerbate erosion. The pool wall bricks at the liquid level and the pool wall brick masonry joints are located in places prone to erosion by glass liquid. The erosion of horizontal joints is more severe than that of vertical joints, so it is required that the masonry surface be smooth, the masonry joints be small, and the entire block should be erected.
The combustion products of coal gas and heavy oil (containing corrosive gases such as so2 and V2O5) and the volatiles of individual batch components can also corrode refractory materials in flame spaces, small furnaces, heat storage chambers, and other places. Under high temperatures, different furnace building materials may react with each other, resulting in damage. For example, 1600? At 1650 ℃, clay bricks and silica bricks will react violently, high alumina bricks and silica bricks will react moderately, and fused zirconia corundum bricks and silica bricks will react violently, resulting in severe co melting. The fused zirconium corundum bricks react moderately with quartz bricks and white foamed stones, while react in contact with corundum bricks. Therefore, corundum bricks can be used as transition materials.
The lattice used in the heat storage chamber is also damaged due to the action of the redox atmosphere. The damage mechanism is mainly due to the different valence states and coordination states of the variable valence ions in the oxidation and reduction states, resulting in volume changes, resulting in reduced strength and cracking of the product.
2. Burn out
Under the action of high temperature for a long time, refractory materials can be damaged by melting (also known as burning flow) or softening and deformation. "If a part of the kiln is locally overheated or the refractory material is not sufficiently refractory, the refractory material will be burned and melted.". Sometimes, if the fire resistance is qualified, but the load softening temperature is low, the refractory material will also soften and deform during long-term use, affecting the stability and service life of the entire masonry. The severity of burn loss depends on temperature and the nature of the refractory. Small furnace spout arches, small furnace legs, tongues, regenerator arches, melter arches, and breast walls are vulnerable to burns.
3. Crack damage
Cracking mainly occurs during the baking stage. During kiln baking, a certain temperature difference occurs inside the refractory bricks, resulting in corresponding mechanical stress. If the heating rate is too fast and exceeds the allowable ultimate strength of the refractory material, cracks will appear, even breaking into fragments. Electrically fused, highly sintered, dense refractory materials * are easily damaged. In addition to the stress caused by temperature difference, the expansion or contraction caused by the change of crystal form of refractory materials also produces stress. When the temperature rises too fast, the crystal form changes quickly and the volume changes too much, resulting in excessive stress and cracking of the refractory material. Therefore, the temperature must be raised according to the predetermined baking curve during baking. After baking, refractory materials are exposed to high temperatures for a long time, and the mechanical strength of refractory materials at this operating temperature is much lower than at room temperature. If the mechanical load applied to the refractory material is too large, the refractory material will undergo inelastic deformation (similar to the flow of highly viscous liquids), resulting in damage.
4. Wear
When glass liquid flows along the refractory material, it has the effect of dripping water through the stone, grinding the refractory material into grooves, which is mechanical wear. The main wear area is at the glass level. In addition, it is also evident at the locations where circulating fluid flows, especially where fluid flow is turbulent. When the liquid level fluctuates and the liquid flow changes (such as affected by temperature fluctuations), wear increases.