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Matters needing attention in the use of fused zirconium corundum brick

Release time:

2021-11-12 11:01

Electric fused zirconium corundum brick is a kind of zirconium corundum brick, mainly used in glass melting furnace, electric fused zirconium corundum brick commonly known as white iron brick, also known as corundum-oblique zircon brick. The main chemical composition is AI203 50%-70%,ZrO2 20%-40%, and the rest is SiO2. The main mineral composition is oblique zircon (ZrO2), corundum (a-AI2O3) and glass phase. The crystallization of oblique zircon forms the backbone of the brick body, ZrO2 has a high melting point (2715 ℃) and good chemical stability, and has a strong resistance to acid medium, especially glass liquid.

Electro-fused zirconium corundum bricks are used in industrial furnaces such as glass furnaces. The parts used in glass furnaces are the upper pool wall, small furnace flat arch, small furnace stack, tongue arch and breast wall. The following problems should be paid attention to in the use of fused zirconium corundum brick:

(1) Irregular changes in thermal expansion

The expansion curve of fused-cast zirconium corundum brick has an anomaly near 1000 ℃, and its internal ZrO2 crystal undergoes reversible crystal transformation and has a large volume change. Therefore, products containing ZrO2 should not be used in parts with sharp fluctuations in temperature at about 1000 ℃. When baking the kiln, the temperature change should not be too large at 900-1150 ℃, generally not more than 15 ℃/h, and the temperature should be raised steadily. Some parts to prevent blowing cold air, need to use other brick protection, to prevent burst.

(2) Shrinkage

During pouring and molding, shrinkage cavities often appear at the casting mouth, with many pores in the brick body and poor density. Therefore, when building the pool wall of the glass melting part, the shrinkage cavities will all face the inner direction of the kiln. If the casting mouth faces outward, when the brick body erodes to a very thin thickness, it will cause leakage of glass liquid. When used in the upper flame space of the pool kiln, the service life is very long, and the problem of running glass liquid will not occur, so the casting mouth is used outward to extend the service life.

(3) Eutectic

Contact masonry of fused-cast zirconium corundum bricks and clay bricks will cause eutectic phenomenon at a high temperature of 1300 ℃. Therefore, when selecting refractory materials, contact masonry of two refractory materials with serious eutectic phenomenon should be avoided. For example, silica bricks are vulnerable to erosion of fused-cast zirconium corundum bricks under fused-cast zirconium corundum bricks.

Application of fused corundum brick in float glass melting furnace

The glass melting furnace is a thermal equipment for melting glass composed of refractory materials. The service efficiency and service life of glass melting furnace depend on the variety and quality of refractory materials to a great extent. The development of glass production technology depends to a large extent on the improvement of refractory manufacturing technology. Therefore, the rational selection and use of refractory materials is a very important content in the design of glass melting furnaces. To do this, we must master the following two points, one is the characteristics and applicable parts of the selected refractory materials, and the other is the use conditions and erosion mechanism of each part of the glass furnace.

Process Improvement of Electro-fused Zirconium Corundum Pavement Brick

Electrically fused zirconium corundum brick is made of industrial alumina powder and zircon sand (containing 66% of zirconium oxide and 34% of silicon dioxide) melted at high temperature in an electric furnace. After melting, it is cast into a shape (the casting temperature is 1780-1840 ℃), injected into the model and cooled to form a solid close to white. Its petrographic structure consists of the eutectoid body and glass phase of corundum and zirconium clinite, it is a eutectoid body of corundum phase and zirconium clinoptilite phase, and the glass phase is filled between their crystals.

How to overcome the defects produced in the casting and annealing of fused zirconium corundum bricks

Electrofused zircon corundum brick in the production will produce a variety of defects, resulting in the use of poor quality products. The physical and chemical inhomogeneity of zirconium corundum bricks is often the main reason for the defects of the products. Particles that are not melted through in the batch and gas inclusions that have not been discharged from the melt in time are all physical inhomogeneities. The difference in the composition of the melt along the depth of the furnace is a chemical inhomogeneity.

Causes of Serious Erosion of Zirconium Corundum Brick in Glass Electric Melting Furnace

The erosion of fused zirconium corundum brick is mainly divided into physical action and chemical action. Physical action refers to the glass melting furnace wall in the long-term operation process, repeatedly subjected to the impact of rapid cooling and rapid heat, the surface must undergo a contraction of the expansion of the change process. Due to excessive fatigue, the structure of fused zirconium corundum brick is damaged, resulting in increased surface cracks and loose structure. Therefore, under the action of air flow, material and glass liquid washing, cracking and peeling, and this process will be repeated.