The reasonable refractory matching of glass wool melting furnace is the key to achieve high efficiency. Of course, the selection of refractory materials needs to comprehensively consider factors such as kiln age, investment, current status of refractory materials and production cycle, so as to make the operation of the melting furnace most efficient and economical.
The design principle of melting furnace refractory materials is: within a kiln period, strive to make the erosion of refractory materials in various parts of the melting furnace basically synchronized. This is the most economical and reasonable.
The configuration analysis of refractory materials in various parts is as follows:
1. Melting pool wall
Due to the low melting temperature, generally below 1400℃, and the viscosity of glass liquid is large, the reaction diffusion rate is small, so the erosion of the pool wall is small, and generally 33# oxidation method electric melting zirconium corundum bricks are used. For horizontal flame melting furnaces, in order to achieve a longer kiln age, the melting pool wall needs to use chromium zirconium corundum bricks with a chromium content of 30%. Regardless of the material of refractory materials used, no insulation is done near the liquid level line of the pool wall, and air blowing cooling is used to extend the service life of the pool wall.
2. Melting breast wall
The melting breast wall is in the flame space of the melting furnace. Due to the high-temperature hot air flow, a large amount of alkali and boron volatiles adhere to the surface and gaps of the breast wall bricks, and react chemically with the breast wall bricks to cause erosion. Therefore, breast wall bricks generally choose neutral refractory materials or alkaline refractory materials with stable high-temperature chemical properties and resistance to alkali and boron. For breast walls with low kiln age, 33# fused zirconium corundum bricks are the best choice, but for breast walls with long kiln age, sintered zircon bricks or chromium zirconium corundum bricks with a chromium content of 30% are better.
3. Melting pool bottom paving bricks
Because the heat dissipation area of the melting pool bottom is large, in addition to strengthening insulation, it is also necessary to consider the increased erosion caused by the increase in pool bottom temperature caused by insulation. Fused zirconium corundum brick paving is the first choice for the bottom of glass wool melting furnace pool. For most glass wool melting furnaces, the stability of this material is fully matched with the life of the melting furnace.
When the glass liquid depth of the melting furnace is less than 500mm and bubbling is used, the high temperature of the glass liquid at the bottom of the pool and the strong convection of the glass liquid generated by bubbling greatly aggravate the mechanical scouring and erosion of the glass liquid on the refractory material at the bottom of the pool. If the traditional electric fused zirconium corundum brick pavement layer is used, it is difficult to meet the long kiln life (more than 5 years), so it is more appropriate to choose chromium zirconium corundum bricks containing 15% chromium.
4. Melting part of the large crown
For horseshoe flame glass wool melting furnace, most of the crown tops use silica bricks. Although alkaline bricks are suitable for alkaline glass liquid, silica bricks are cheap and have poor resistance to alkaline vapor erosion. Due to the high boron and alkali content in the glass wool composition, when the glass glaze on the surface of the brick is lost, the silica bricks are easily eroded by boron and alkali vapor, thus affecting the life of the melting furnace.
At present, the silica brick crown tops of domestic horseshoe flame glass wool melting furnaces generally produce rat holes after 9 months to 1 year, and need frequent maintenance and repairs, and can barely last for 3 years. Repairing the crown is not only a heavy hot repair operation, but also has an impact on production. If the kiln life is more than 5 years, the crown material of the glass wool melting furnace is not suitable for silica bricks, but chromium-zirconium corundum bricks containing 30% chromium or special sintered mullite bricks should be used.
5. Liquid hole
The liquid hole is the most easily eroded part of the glass wool melting furnace, and it cannot be repaired in hot state. Therefore, the service life of the liquid hole refractory directly determines the life of the melting furnace.
At present, the liquid hole of most glass wool melting furnaces uses 41# non-shrinkage pore fused zirconium corundum bricks. Since the glass liquid temperature of the glass wool melting furnace is relatively low, generally below 1250℃, the erosion of the liquid hole refractory material is mainly mechanical scouring. For small-tonnage glass wool melting furnaces, 41# non-shrinkage pore fused zirconium corundum bricks can fully meet the requirements of kiln age, but for large-tonnage and long-kiln-age glass wool melting furnaces, it is more reasonable to use chromium-zirconium corundum bricks containing 50% chromium for the liquid hole bricks.
6. Checker bricks
Glass wool contains high alkali and low boron, which corrodes magnesia bricks severely. Moreover, alkali vapor and boron vapor are easy to crystallize in the medium temperature zone (810~940℃), and the crystallized material has a high viscosity and adheres to the uneven surface of the checker brick after erosion, thus causing the checker brick to be blocked.
At present, the checker bricks of glass wool melting furnaces generally use alkaline bricks, 97 magnesia bricks or 98 magnesia bricks on the upper layer, 95 magnesia bricks or 96 magnesia bricks on the middle layer, and magnesia chrome bricks and low-porosity clay bricks on the lower layer. The checker bricks configured in this way have a lower cost, but because alkali and boron vapor crystallize and adhere to the checker bricks, the checker bricks need to be replaced after about one and a half years of use. For checker bricks with a long kiln age, cross-shaped fused zirconium corundum bricks are the first choice.
7. Forehearth
For the upper structure of the flame kiln passage, 33# fused zirconium corundum bricks or sintered zircon bricks are generally used. For the upper structure of the electric melting furnace forehearth, sintered mullite bricks can be used.
For the forehearth in contact with the glass liquid, either 33# fused zirconium corundum bricks or chromium zirconium corundum bricks containing 30% chromium can be used.
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