The performance of homogeneous chrome-zircon corundum bricks used in different glass furnaces

In the glass industry, as the core equipment for glass production, the technical level of the furnace is constantly improving, and new technologies such as improving combustion intensity, strengthening heat transfer effect, reducing heat loss, and reducing pollution to products and the environment are widely used. For example, oxy-fuel combustion technology has obvious energy-saving effects and is one of the development directions of melting furnaces. However, the use of these technologies will accelerate the corrosion of refractory materials, so refractory materials are required to withstand higher temperatures and more intense chemical erosion; at the same time, because of different glass compositions, the glass viscosity and the conductivity of the glass liquid will vary greatly at high temperatures. , So the corrosion performance of the refractory materials in contact is also very different. The working conditions of the various parts of the tank kiln are different, and the performance of the refractory materials is required to be different. Only when a variety of high-quality refractory materials are used in combination, can "reasonable matching and synchronization of kiln age" be realized.

1. Excellent corrosion resistance of homogeneous chrome -zircon corundum brick

The performance of chrome corundum bricks  depends on the chemical composition and mineral phase composition. When the chemical composition is similar, the mineral phase composition is a crucial factor affecting the performance. Because the chrome -zircon corundum brick is composed of multiple mineral phases, whether the mineral phase composition is reasonable depends on the chemical composition and production process conditions. In the actual use process, glass manufacturers often only value the chemical composition, but not enough pay attention to the mineral phase. Therefore, there will be a situation where the chemical composition is the same but the performance is far different.

High-quality homogeneous chrome -zircon corundum bricks  should be composed of more than 70% aluminum-chromium solid solution CrxAl2-x03. The rest are: chromium oxide, plagioclase, corundum, and almost no glass phase. The phase of ordinary chrome -zircon corundum bricks  is generally composed of less than 60% aluminum-chromium solid solution CrxA103, and the rest are: chromium oxide, plagioclase, corundum, and glass phase (5T0%). The reason for the glass phase is that the raw materials for the production of chrome -zircon corundum bricks  contain more fused cast AZS bricks, and the quality of these AZS regrinds is uneven, so the quality is difficult to be stabilized and guaranteed.

The homogeneous chromium-zirconium corundum described in this article has undergone laboratory comparison tests and practical use to verify that its corrosion resistance is very excellent. The laboratory comparison test results are shown in Table 1. It has been widely used in the severely corroded parts of the kiln: liquid level line, feed opening corner, flow hole cover, kiln sill, flow opening, bubble brick, electrode brick.

Table 1.Comparison of erosion of various glass by fusion cast AZS-41 and homogeneous chromium zirconium corundum bricks  Unit: mm/24h

It can be seen from Table 1 that for soda lime glass, the corrosion resistance of homogeneous chrome -zircon corundum bricks  at a melting temperature of 1450°C is more than twice that of fused-cast AZS-41 #bricks. When the melting temperature rises above 1500°C, then Its anti-erosion ability is 2.5 times more than that of fused cast AZS-41 # brick. The corrosion resistance of homogeneous chromium zirconium corundum in basalt and steelmaking slag containing high metal oxides is more obvious. The corrosion resistance of AZCS-50B is more than 3 times that of molten cast AZS-41 #brick.

For parts with high temperature, high alkali vapor concentration, low glass viscosity, and serious erosion, the corrosion resistance of homogeneous chrome -zircon corundum bricks  is superior to that of fused-cast AZS bricks. The reason why fused-cast AZS bricks contain plagioclase, corundum and glass phases Three kinds of mineral facies. After the fused cast AZS brick comes into contact with the molten glass, the glass phase in the brick is first replaced by the low-viscosity molten glass, then the corundum phase is dissolved, and then the plagioclase is dissolved. The plagioclase is the mineral phase that is most resistant to the corrosion of molten glass and plays a role in improving the corrosion resistance of refractory materials. The glass phase is the weak link in the refractory material, the high temperature glass liquid is easy to diffuse the channel, which greatly affects the corrosion resistance of the material. The high-quality homogeneous chrome -zircon corundum bricks  do not contain glass phase, and aluminum chromium solid solution CrxAhx03, chromium oxide, plagioclase, corundum, etc. are all mineral phases with good resistance to glass corrosion, and they are fully processed Evenly dispersed, after high-temperature sintering, the microstructure is uniform, and the deterioration layer is very thin when exposed to glass liquid for a long time. The erosion form is micro-planar erosion, while the ordinary chrome -zircon corundum bricks  and fused-cast AZS bricks with uneven structure have relatively more deteriorated layers when used. Thick, the form of erosion is microscopic three-dimensional erosion. The figure below is the comparison of the microstructure of fused cast AZS bricks, homogeneous chromium zirconium corundum bricks, and ordinary chromium zirconium corundum bricks:


Figure 1. SEM image of fused cast AZS-41 brick                 Figure 2. SEM image of homogeneous chromium zirconium corundum brick            Figure 3. SEM image of ordinary chromium zirconium corundum brick

2. Comparison of actual use effect between fusion cast AZS-41 and AZCS-50B

A bottle glass kiln liquid cave cover bricks using AZCS-50B, running for 5.5 years, a total of more than 400,000 Tons of glass, after the furnace is dismantled, the erosion amount of the AZCS-50B cover brick is measured to be 40mm, and the molten cast AZS-41# above the cover brick.The erosion amount of bricks on the brick pool wall is 130mm. It clearly shows that the corrosion resistance of AZCS-50B brick is superior to AZS-41#.

     Figure 4. 2.5-year-old fused cast AZS-41 brick                            Figure 5. Homogeneous chromium zirconium corundum AZCS-50B bricks that have been used for 5.5 years

3. High temperature resistivity

In order to improve the melting rate of glass furnaces, molybdenum electrode auxiliary heating is gradually popularized in glass wool, slag wool, and bottle glass furnaces. Therefore, there are related requirements for the high temperature resistivity of electrode bricks and surrounding refractory materials. The measurement of the rate adopts the method of comparing with the standard resistance at high temperature, and the measurement results are shown in Table 2. The results show that the high temperature resistivity of homogeneous chromium-zirconium corundum AZCS-30B, 50B bricks is significantly higher than that of fused-cast AZS-41 bricks. In addition, the corrosion resistance is better than that of fused-cast AZS-41 bricks, so it can be used for glass wool and slag wool. , Electrode bricks of basalt fiber kiln.

Table 2. High temperature resistivity of fused cast AZS-41 and homogeneous chromium zirconium corundum bricks Unit: ohm•cm

4. Foaming and stone tendency:

The test conditions for evaluating the foaming tendency of refractory materials in contact with high-temperature molten glass are mainly the test temperature and holding time. The foaming rate of refractory materials is closely related to the composition of the molten glass. In this paper, we use glass discs placed on the surface for finishing. The refractory crucible is heated to different test temperatures (1200-1450) in the test electric furnace, and kept at the test temperature for 3-24 hours, and then slowly cooled. Observe the number and size of bubbles per unit area under a magnifying glass. The results show that the higher the chromium oxide content, the lower the foaming tendency. CR90GE shows a very low foaming tendency, which is equivalent to the foaming tendency of high-quality fused-cast AZS-41# materials. It is recommended to choose CR90-GE. CR92-GB. CR94-GA bricks with good corrosion resistance and lower foaming tendency.

For the analysis method of stone tendency, this article uses electron microscope to analyze the microstructure of the interface between the molten glass adhered to the sample surface and the glass erosion interface after the erosion test. The analysis results show that the stone tendency of homogeneous chrome -zircon corundum bricks  is lower than that of traditional fusion-casting AZS-41#. The stone tendency depends on the material phase composition and the uniformity of the microstructure. If the mineral phase composition contains multiple mineral phases with large differences in resistance to glass erosion, and the distribution of the mineral phases is uneven, the stone tendency will be higher.

5. Colorability

The traditional view is that Cr203-containing refractory materials are likely to cause chrome green coloration on glass. However, in Europe, a large number of daily glass furnaces use homogeneous chrome -zircon corundum bricks  and high-content chromium oxide bricks. The corrosion amount of the refractory material is calculated as the proportion of the total molten glass. The average content of Cr203 into the glass is less than 1PPM, which is not affected for ordinary white glass, but for ultra-white glass, you need to carefully choose the appropriate content. Refractory material of chromium oxide.

6. Conclusion

Homogeneous chrome -zircon corundum bricks with uniform microstructure and reasonable mineral phase composition are significantly better than traditional fused-cast AZS bricks in corrosion resistance. They are ideal for the production of glass wool, slag insulation cotton, basalt fiber, daily glass and other key parts of the furnace.