Introduction
Mullite insulation bricks are lightweight refractory materials primarily composed of the mullite mineral (chemical formula: 3Al₂O₃·2SiO₂). They are typically manufactured using high-alumina bauxite and industrial alumina through sintering or fusion processes. With an Al₂O₃ content generally ≥45%, combined with a small amount of SiO₂, these bricks offer high-temperature resistance, low thermal conductivity, and excellent thermal shock resistance.
Advantage
High Refractoriness: The melting point of mullite crystals (3Al₂O₃·2SiO₂) reaches 1,850°C. Finished bricks generally exhibit a refractoriness of ≥1,700°C, allowing for long-term use in high-temperature environments ranging from 1,200–1,500°C.
High-Temperature Structural Stability: Mullite crystals resist melting and phase transformation at elevated temperatures, maintaining the integrity of the brick structure. Suitable for continuous high-temperature equipment such as heating and cracking furnaces.
Low Thermal Conductivity: Room-temperature thermal conductivity is ≤0.25 W/(m·K)-only 1/3 to 1/5 that of traditional clay bricks-significantly reducing heat loss and energy consumption in furnaces.
Lightweight Porous Structure: With a typical density of 0.8–1.2 g/cm³, the closed-pore or micro-porous structure effectively blocks heat conduction pathways, offering both "lightweight" and "thermal insulation" benefits.
Low Thermal Expansion Coefficient: Mullite crystals exhibit a thermal expansion coefficient of approximately 5.3×10⁻⁶/°C, which helps prevent cracking during rapid temperature changes. Ideal for kilns with frequent start/stop cycles, such as ceramic sintering and annealing furnaces.
Micro-Crack Self-Cushioning: The porous structure helps absorb thermal stress, preventing rapid propagation of micro-cracks and extending service life.
Acid Corrosion Resistance: Provides strong resistance to acidic flue gases (e.g., SO₂, NOx), making it suitable for petrochemical cracking furnaces, coal-fired boilers, and other corrosive environments.
Weak Alkali Erosion Resistance: Resists chemical reactions in mildly alkaline media (e.g., K₂O, Na₂O).
Strong Slag Resistance: Withstands erosion from metallurgical slags, glass melts, and other molten substances, making it an effective protective layer in kiln linings.
Raw Materials
High-alumina bauxite, industrial alumina (Al₂O₃), and siliceous raw materials (SiO₂).
Physical and Chemical Specifications
| Grade / Specifications |
JM-23 |
JM-26 |
JM-28 |
JM-30 |
|
Al2O3 % |
40 |
55 |
65 |
70 |
|
Fe2O3 % |
1.0 |
0.9 |
0.7 |
0.6 |
|
Bulk Density (g/cm3) |
0.55 |
0.85 |
0.95 |
1.05 |
|
Cold Crushing Strength (Mpa) |
1.0 |
2.0 |
2.5 |
3.0 |
|
Reheating Linear Change (%) °C*12 hr |
1230°C |
1400°C |
1510°C |
1620°C |
|
Thermal conductivity 350°C (W/m.k) |
0.20 |
0.30 |
0.39 |
0.45 |
|
Refractoriness under Load ºC @0.05MPa |
1080 |
1250 |
1360 |
1470 |
Process
Raw Material Pretreatment → Batching & Mixing → Molding & Drying → High-Temperature Sintering → Post-Treatment & Quality Inspection
Sintering Regime Control
Sintering Regime:
Heating Stage:
0–600°C: Raise temperature slowly (5–10°C/h) to allow for complete volatilization of pore-forming agents and prevent blistering.
600–1,200°C: Heat at 10–15°C/h. Mullite phase formation begins, and the binder forms a glass phase.
Holding Stage:
Hold at peak temperature (e.g., 1,550°C) for 8–12 hours to promote mullite crystal growth (grain size: 5–10 μm) and enhance brick strength.
Cooling Stage:
Cool down with the furnace to below 100°C at ≤15°C/h to prevent thermal stress-induced cracking.
Application
Heating and Heat Treatment Furnaces
Used for wall and roof insulation, reducing heat loss and improving temperature uniformity while withstanding high-temperature flue gas erosion and thermal cycling (e.g., reheating furnaces, annealing furnaces).
Blast Furnaces and Hot Blast Stoves
Functions as insulation for furnace linings to minimize heat transfer and improve thermal efficiency, especially in regenerator sections.
Ladles and Tundishes
Serves as an inner lining to prevent rapid temperature loss of molten steel and resist slag corrosion.
Ceramic Kilns
Used in tunnel and shuttle kiln walls and roofs, providing insulation, reducing energy use, and supporting high-temperature sintering (≥1,200°C).
Glass Melting Furnaces
Applied for kiln insulation, often in combination with other refractories, to reduce heat loss and extend kiln lifespan (e.g., breast walls, regenerator partitions).
High-Temperature Reaction Furnaces
Insulates cracking furnaces and gasifiers, preventing heat leakage and maintaining reaction efficiency under high-temperature conditions.
Heat Treatment Equipment
Protects the chambers of high-temperature roasters and calciners in the chemical industry from corrosive gases and maintains temperature stability.
Circulating Fluidized Bed Boilers (CFB)
Provides insulation in furnace beds and cyclone separators, resisting erosion by fly ash and high-temperature gases while reducing heat loss.
Waste Incinerators
Used for lining insulation in combustion chambers, withstanding complex chemical erosion (e.g., chlorine, sulfur-containing gases) while maintaining operational temperatures.
Refractory Production Kilns
Provides self-insulation during production, supporting a sustainable process (e.g., mullite kiln insulation).
Aerospace & Military Industry
Temporary thermal protection in high-temperature test equipment or spacecraft ground facilities, often in combination with other high-performance materials.
Typical Application Scenarios
| Application Area | Specific Equipment | Core Function of Mullite Insulation Bricks |
|---|---|---|
| Metallurgical Furnaces | Continuous Steel Reheating Furnaces | Roof insulation to reduce heat loss and stabilize furnace temperature |
| Ceramic Kilns | High-Temperature Sintering Zone Walls | Thermal insulation to reduce energy consumption and maintain sintering quality |
| Chemical Cracking Furnaces | Radiant Section of Naphtha Cracking Units | Resists high-temperature oil-gas corrosion and maintains high reaction efficiency |
| Circulating Fluidized Beds | Water-cooled Furnace Walls | Resists fly ash erosion and reduces heat dissipation for improved efficiency |
Summary of Application Advantages
Dual High-Temperature Resistance and Insulation:
Maintains structural stability in 1,200–1,600°C environments while offering low thermal conductivity (0.15–0.3 W/(m·K)), resulting in notable energy savings.
Erosion and Thermal Shock Resistance:
Excellent resistance to acidic and neutral slags, as well as flue gas corrosion, with strong adaptability to sudden temperature changes.
Lightweight and Structurally Adaptable:
With low density (0.8–1.5 g/cm³), it reduces equipment load and can be customized into shaped bricks for complex furnace geometries.
Why chooes us?
01/Customized dimensions and shapes
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Customized Brick Shape
Provide Sample Sheets--Mold Opening & Quotation--Mold Opening & Sample Making--Bulk Production Quotation--Contract Signing--Bulk Production
02/Delivery cycle and logistics
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Sea freight, land freight. Determine the mode of transportation according to the needs
About 30 days, customized products delivery time depends on the actual situation.
03/Customized packaging
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Customize your brand
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Take your brand to the next level, contact us today to discuss your project!
04/Purchase ZINFON refractory Bricks at Reasonable Prices
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The price of refractory bricks is a known key factor influencing customers' purchasing decisions. Therefore, we offer affordable refractory bricks for sale. Here are several reasons why ZINFON provides refractory bricks at competitive prices:
01
Factory price
02
Low raw material cost
03
Mass production
It is worth noting that while price is an important factor, it should not be the sole determinant of your purchasing decision. When buying refractory bricks from ZINFON, quality, reliability, and technical support are equally important considerations.
By choosing ZINFON as your supplier, you can access high-quality refractory bricks, a wide range of other refractory materials, and comprehensive support. Contact ZINFON Refractories immediately to discuss your specific requirements and obtain customized solutions!
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