01
Main structure and working environment of glass kiln
The glass kiln is mainly composed of three parts: the melting part of the pool furnace, the cooling part and the regenerator. Among them, the melting department is responsible for the melting, clarification and homogenization of batch materials. It consists of the upper structure of the melting part (big wall, breast wall, small furnace mouth, etc.) and the pool kiln (pool wall, pool bottom, etc.).
The flame ejected from the small furnace fills the flame space in the upper structure, and the flame space has a very high working temperature, so that the batch material is forcibly melted. In a soda-lime glass kiln, this temperature can reach 1649°C. Therefore, the refractory materials used for the upper structure of the melting part must not only withstand higher working temperatures, but also must have the ability to resist alkali vapor, flying material erosion, and small furnace flames to the material.
Usually, the glass phase in the refractory material will be precipitated from the structure and enter the glass liquid under the action of high temperature and the erosion of saturated alkali vapor. On the one hand, pores are left to become channels for foreign substances to invade; on the other hand, defects such as stones, streaks, and bubbles are formed, which seriously affect the quality of glass. The pool wall tiles are in direct contact with the molten glass and are eroded by the melt. After being eroded, the surface of the cast refractory produces a highly viscous liquid phase layer. At this time, the service life of the refractory material is closely related to the protective effect of the layer. For example, if there are eddy currents on the surface of the refractory, the highly viscous liquid phase layer will be quickly lost, exposing new surfaces, and the molten glass will continue to attack these surfaces. Therefore, it will be destroyed very quickly. In contrast, pool wall tiles are more susceptible to erosion by glass liquid than pool bottom tiles. For example, the area most prone to erosion of pool wall tiles is the “liquid line” of the glass. This area is located at the interface of gas, liquid, and solid phases. Since it cannot be protected by the high-viscosity liquid phase flowing down from the upper part, the erosion rate in this area is very fast, and it is often necessary to use cooling or binding bricks to maintain its life. After the glass liquid penetrates into the brick joints, it first erodes the areas with weaker erosion resistance in the brick tissue. If the erosion products cannot adhere to the brick joints, but are lost into the glass liquid, severe erosion grooves will be produced.
The cooling zone is a place to cool down the temperature of the molten glass, and the gradually lowered molten glass enters the tin bath through the lip brick. Compared with the melting part, this area suffers less chemical erosion, thermal erosion, and mechanical erosion. However, molten glass has no ability to melt defects such as small stones and streaks in the glass. Therefore, “clean” refractory materials such as fused-cast α-β alumina bricks, β alumina bricks, etc. are required.
The regenerator is used in the glass kiln to recover the waste heat in the exhaust gas, preheat the combustion air and intensify the combustion. The regenerator mainly relies on checker bricks to undertake the function of heat exchange. When heated, the checker brick cools the exhaust gas and heats itself; after the airflow is reversed, the checker brick preheats the exhaust gas itself to be cooled. On the one hand, checker bricks are subject to frequent alternating changes of cold and heat; on the other hand, the checker body not only bears the impact and abrasion of high-temperature exhaust gas, but also is eroded by waste materials and alkali steam. In particular, after using petroleum coke as an alternative fuel, the content of harmful substances such as S0₂ and V₂0₅ in kiln gas and fly materials increased greatly. service life.
In short, the working environment of the glass kiln is quite harsh, which makes the corrosion of the refractory material very serious. For the key parts of the glass kiln, it is necessary to select materials with suitable properties according to the erosion mechanism, so as to effectively prolong the service life of the kiln.
02
A new type of fused cast refractory used in the flame space – low glass phase exudation fused cast AZS refractory
The ambient temperature in the flame space of the glass kiln is relatively high. Excessively high temperature will significantly reduce the service life of materials in this area. According to data records, every time the melting temperature in the kiln pool increases by 50-60°C, the service life of refractory materials will be shortened by 1/ 2.
In order to improve the service life of glass furnaces, in the 1990s, cast refractory materials were widely used in the upper structure of glass furnaces. Fused cast AZS materials are mainly composed of baddeleyite phase, corundum phase, and silicate glass phase. However, with the continuous improvement of the equipment level of my country’s glass industry and the comprehensive promotion of oxy-fuel combustion technology, the melting temperature of the glass furnace has been greatly increased compared with the previous one. When the temperature of the furnace exceeds the melting temperature of the glass phase, the glass phase will become liquid and carry finely divided oblique chromite to the surface of the brick body. On the one hand, it produces a large number of pores, allowing the intrusion of erosive substances, which intensifies the corrosion of the brick body; on the other hand, the glass phase seeping out of the material drops into the glass solution, causing a large number of defects in the produced glass, which affects the quality of the glass. quality. Therefore, in order to adapt the material to this high-temperature, high-alkali environment, ensure the normal operation of the kiln, and improve the pass rate of the product, the researchers developed a low glass exudation AZS casting material for this phenomenon.
The chemical composition of the material: the proportion of SiO2 is 13%, the proportion of Zr02 is 17%, and the proportion of Na02 is 1.7%. It can be seen that the material contains a relatively high chemical composition that forms a glass phase. In addition, petrographic analysis also shows that the amount of glass phase in the material has reached 21%, which is equivalent to the glass phase content of ordinary AZS fused cast bricks. Therefore, the reason for the low glass exudation property of this material is not entirely due to the composition of the material, but also to the special structure of the material.
Through a large number of experiments, it is concluded that because the low glass phase material has the excellent characteristics of “zero” exudation at high temperature, it effectively solves the problem of contaminating the glass liquid due to the glass phase exuded from the upper flame space casting material in a high temperature environment. problems, and because of its lower glass phase composition, the material has higher creep resistance, the material can withstand higher operating temperatures, and the high temperature performance of the material has been improved, especially suitable for use in kilns with severe erosion In the superstructure of the furnace charging area.
