Silica bricks are refractory materials made primarily from quartzite or other high-silica raw materials. Containing more than 93% silica (SiO₂), they are widely recognized for their excellent resistance to high temperatures, thermal shock at elevated ranges, and acidic slags. Silica bricks are an essential component in various high-heat industrial processes, particularly in furnaces used for glass, steel, and coke production.
What Are Silica Bricks?
Silica bricks are formed from selected quartzites and a small amount of lime (CaO) as a binder. These materials are shaped, fired at temperatures above 1400°C, and undergo a critical transformation where quartz converts into tridymite and cristobalite, the key mineral phases responsible for the brick’s thermal behavior.
Key Properties of Silica Bricks
- High refractoriness: Can withstand temperatures above 1650°C
- Volume stability: Excellent dimensional stability at high temperature
- Resistance to acidic slags: Ideal for acidic environments
- Thermal conductivity: Suitable for heat-transfer zones
- High strength at elevated temperatures: Maintains structural integrity in hot conditions
Typical Composition
- Silica (SiO₂): 93–96%
- Alumina (Al₂O₃): <1%
- Iron Oxide (Fe₂O₃): 1–1.5%
- Calcium Oxide (CaO): 1–2%
Applications of Silica Bricks
Silica bricks are used in a range of high-temperature industrial applications:
- Glass industry: Furnace crowns, regenerators, and combustion chambers
- Metallurgy: Coke ovens, hot blast stoves, and open hearth furnaces
- Ceramics: Kilns and high-temperature lining structures
- Chemical industry: Acid-reactor linings and incinerators
Advantages of Silica Bricks
- Excellent thermal resistance in high-heat zones
- Stable expansion behavior at elevated temperatures
- Long service life in acidic environments
- Good cost-efficiency for high-volume applications
Limitations
- Poor resistance to thermal shock at low temperatures: Not ideal for rapidly changing temperatures
- Incompatibility with basic slags: Should not be used in basic furnace zones
- Brittleness: More fragile than alumina-based bricks
Selection Considerations
Choosing silica bricks depends on operational conditions, such as:
- Working temperature range
- Presence of acidic or basic materials
- Mechanical wear and abrasion level
- Thermal cycling frequency
Maintenance and Installation Tips
- Use silica-based mortar for compatibility
- Preheat gradually to avoid thermal stress
- Install with minimal joint spacing to reduce heat loss
- Monitor expansion joints to avoid structural deformation
Conclusion
Silica bricks are a fundamental material in many high-temperature industrial processes due to their ability to withstand extreme heat and acidic environments. While they require careful installation and are less suitable for dynamic thermal cycles, their advantages in terms of thermal stability and resistance make them a trusted solution in furnace design, especially in the glass, coke, and steel sectors.
