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Reasons for and types of refractory bricks used in different parts of a glass melting furnace.
2026-03-16
As the core equipment in glass production, the glass melting furnace operates in an extremely harsh environment: temperatures reach 1570-1610℃, and multiple factors such as glass liquid flow and erosion, chemical corrosion from raw materials, and alkali vapor attack combine to place stringent demands on the performance of refractory materials. Due to functional differences in different parts of the furnace, specific types of refractory bricks must be selected to balance durability, cost, and glass quality. This article analyzes the logic behind refractory brick selection and the characteristics of typical materials, focusing on the key parts of the melting furnace.
1. Melting section: Subjected to the dual challenges of high temperature and chemical corrosion.
The melting zone is the core area where the glass melt transforms from raw materials into a homogeneous melt. Its tank walls and bottom are in direct contact with the high-temperature glass melt and must withstand both mechanical erosion and chemical corrosion.
① Tank Walls: Balancing Erosion and Abrasion Resistance
Material Selection Logic: The tank walls are the area where glass melt flow is most turbulent. Materials with strong resistance to glass melt corrosion and good thermal shock stability are required. Electrofused zirconia-corundum bricks (AZS bricks), containing 20%-40% ZrO₂, form a corundum-zircon eutectic structure, providing significantly superior corrosion resistance compared to other materials. The high-viscosity sodium feldspar glass layer formed on the surface after erosion effectively prevents further corrosion.
Typical Applications:
• AZS-33/36 bricks: Used in the upper and middle parts of the tank walls, containing 33%-36% ZrO₂, offering moderate corrosion resistance and lower cost.
• AZS-41 bricks: Used in areas with the most severe erosion, such as tank corners and flow channels, containing 41% ZrO₂, providing over 30% improved corrosion resistance.
• Alternative Solutions: In the cooling zone tank walls where temperatures are below 1350℃, α-β corundum bricks or β-corundum bricks are more economical choices due to their low thermal expansion coefficient and good thermal shock resistance.
② Tank Bottom: Dual Requirements of Support and Insulation
Material Selection Logic: The tank bottom must withstand the hydrostatic pressure of the glass melt and the impact of raw materials, while also insulating against heat from the lower regenerator chamber. Electrofused alumina bricks (corundum bricks), with an Al₂O₃ content ≥92%, have extremely strong resistance to glass melt penetration and introduce almost no impurities, making them widely used in critical areas of the tank bottom.
Typical Applications:
• Electrofused α-β corundum bricks: Used in the central area of the tank bottom, providing both corrosion resistance and mechanical strength.
• Clay bricks/high-alumina bricks: Used in the non-directly contacted areas of the tank bottom to reduce costs.
2. Arch Roof: The ultimate challenge of high temperature and structural stability.
The furnace crown is the highest temperature zone of the melting pool (1600-1650℃), and must withstand high temperatures, heavy loads, and alkali vapor corrosion. Therefore, the refractory material requires extremely high refractoriness, load softening temperature, and creep resistance.
① Silica Bricks: The Cost-Effective Choice
Material Selection Logic: Silica bricks have SiO₂ as their main component (≥96%), and their load softening temperature is close to their refractoriness (1690-1730℃). Furthermore, the corrosive substances generated at high temperatures are similar in composition to the glass melt, resulting in almost no glass contamination. Their cost is only 1/3 to 1/2 that of AZS bricks, making them the mainstream material for furnace crowns.
Typical Applications:
• High-quality high-purity silica bricks: Used for the large furnace crown in the melting section, requiring an apparent porosity of ≤22% and a true density of ≤2.35 g/cm³ to reduce alkali vapor penetration.
• L-shaped suspended wall silica bricks: Used for the front wall, in conjunction with a forced air cooling system to resist flame erosion.
② Electrofused Zirconia-Alumina Bricks: A Supplement for Special Scenarios
Material Selection Logic: In areas with concentrated heat load, such as the burner nozzles and tongue arches of small furnaces burning high-calorific value fuels (such as natural gas), AZS-33 bricks with better thermal shock resistance are required. Their thermal shock resistance (ΔT≥300℃) is superior to that of silica bricks (ΔT≤200℃).
3. Regenerative Chamber: The interplay between heat recovery and corrosion resistance
The regenerator recovers heat from flue gas through a checkerwork structure. Its upper walls, arch, and checkerwork are subjected to high temperatures, dust, and alkali vapor corrosion. Material selection must consider both corrosion resistance and cost-effectiveness.
① Walls and Arch: Layered Material Selection Strategy
Selection Logic: The temperature in the regenerator decreases from top to bottom (1400-800℃), and the degree of corrosion weakens, resulting in a gradient distribution of materials.
Typical Applications:
• Upper part (1400-1200℃): Silicon bricks or high-quality high-alumina bricks (Al₂O₃≥60%) are used due to their strong resistance to alkali vapor corrosion.
• Middle part (1200-1000℃): Low-porosity clay bricks (apparent porosity ≤18%) are used to balance corrosion resistance and cost.
• Lower part (1000-800℃): Ordinary clay bricks are used, utilizing their low thermal conductivity (0.5-0.8 W/m·K) to reduce heat loss.
② Checkerwork: Balancing Anti-clogging and Durability
Selection Logic: The checkerwork must withstand high-temperature loads, dust erosion, and alkali corrosion for extended periods. Clogging and collapse are the main failure modes. The material needs to possess high mechanical strength, low creep rate, and resistance to dust adhesion.
Typical Applications:
• Upper part (1400-1300℃): Electrofused magnesia bricks (MgO≥95%) are used because the direct bonding structure of periclase provides strong resistance to alkali corrosion.
• Middle part (1100-900℃): Magnesia-alumina spinel bricks (MgO·Al₂O₃) are used to resist volume expansion caused by Na₂SO₄ condensation.
• Lower part (below 900℃): Low-porosity clay bricks are used, utilizing their thermal shock resistance (ΔT≥250℃) to cope with temperature fluctuations.
4. Special Areas: Function-Oriented Customized Material Selection
① Bubbling Ports and Furnace Hearth: Resistance to Erosion and Thermal Shock
• Material Selection Logic: Due to the vigorous circulation of molten glass, the bubbling ports require AZS-41 bricks with extremely high erosion resistance; the furnace hearth, which bears the static pressure and temperature gradient of the molten glass, commonly uses fused alumina bricks.
② Electrode Ports and Measurement Ports: Dual Requirements of Insulation and Corrosion Resistance
• Material Selection Logic: The electrode ports require fused silica bricks (SiO₂≥99.5%) with high resistivity (≥10⁸Ω·m) to prevent current leakage; the measurement ports use custom-made AZS-33 bricks to withstand long-term flame erosion.
5. Trends and Outlook
As glass melting technology develops towards larger scale and higher melting temperatures, traditional silica bricks are gradually being replaced due to their limited refractoriness (≤1730℃). The application of high-performance materials such as electrofused zirconia-corundum bricks and electrofused alumina bricks is continuously increasing, while new technologies such as nano-modified refractory materials and gradient functional materials are driving the industry towards longer service life and lower energy consumption.
Conclusion
The selection of refractory bricks for glass melting furnaces is a complex interplay of materials science, thermal engineering, and economic considerations. By precisely matching the functional requirements of each section with the characteristics of the materials, it is possible to significantly extend furnace life and reduce energy consumption, providing strong support for the high-quality development of the glass industry.