Analysis of Commonly Used Refractory Insulation Materials and Their Characteristics in Glass Melting Kilns
As the core equipment in glass manufacturing, the glass melting kiln operates at temperatures exceeding 1600℃, placing extremely high demands on the performance of refractory insulation materials. Traditional materials rely on increased thickness to achieve thermal insulation, while new materials such as aluminosilicate fiber blankets achieve "thin over thick" insulation through structural optimization. These have become a key direction in the industry's technological upgrading.
This paper analyzes the technical characteristics and development trends of refractory insulation materials commonly used in glass kilns from three dimensions: material classification, performance characteristics, and application scenarios.
01. Material Classification: Four Systems to Build the Kiln "Shield"
Refractory insulation materials used in glass kilns are mainly divided into four categories: cast refractories, sintered refractories, unshaped refractories, and insulating refractories. Each category offers a differentiated solution tailored to specific working conditions.
1. Fused Refractories: The "Ultimate Defense" Against High-Temperature Erosion
Represented by electrofused zirconia-corundum bricks (AZS bricks) and electrofused alumina bricks, these materials are melted at high temperatures in electric arc furnaces and then cast to form a dense, defect-free crystalline structure. Their core advantages include:
Erosion resistance: AZS bricks with 33%–41% zirconium content can withstand continuous erosion from molten glass at 1700 °C for up to 10 years, with a bubble precipitation rate of less than 0.05 bubbles/cm²·h, ensuring the purity of the glass melt.
Thermal shock stability: After 100 cycles of water quenching from 1200 °C to room temperature, the strength retention rate exceeds 90%, far surpassing the 35-cycle standard for sintered bricks.
Application scenario: Primarily used in the areas most exposed to molten glass erosion, such as the walls of the melting tank, throat area, feeder spouts, and similar zones. For example, after using AZS bricks with 41% zirconium content in a float glass production line, the service life of the tank wall was extended from 5 to 12 years, with annual refractory cost savings exceeding RMB 2 million per production line.
2. Sintered Refractories: The "Economic Choice" for Diversified Formulations
This category includes silica bricks, high-alumina bricks, mullite bricks, and others, which are produced through powder pressing and sintering processes. Their typical properties include:
Cost-effectiveness: Silica bricks (SiO₂ ≥ 94%) cost only one-third the price of AZS bricks and are suitable for use in areas not in direct contact with molten glass, such as large crowns and breast walls.
Alkali resistance: Magnesia bricks (MgO ≥ 97%) are resistant to erosion by alkaline frit at 1800 °C and are commonly used in the upper layers of regenerator checkers.
Structural optimization: Electrofused mullite bricks (Al₂O₃ ≥ 75%) achieve a reduced thermal conductivity of 1.2 W/(m·K) through directional crystallization technology, resulting in 15% energy savings compared to traditional sintered bricks.
3.Amorphous Refractories: The "Liquid Guardian" for Flexible Repair
Refractory castables and plastic refractories, though accounting for only 3%–4% of total usage, play a crucial role in extending kiln service life:
Construction adaptability: These materials can be cast on-site to repair erosion damage to the tank walls. After repair, they can restore up to 85% of the original brick strength.
Spalling resistance: Castables reinforced with steel fibers can withstand thermal shock at 1400 °C without spalling, extending the service life by up to three times compared to standard castables.
Typical case: A photovoltaic glass melting kiln used low-cement bonded castables to repair the tank wall, reducing annual maintenance downtime by 48 hours and increasing production capacity by 8%.
4.Thermal Insulation Refractory Materials: The "Invisible Champion" of Energy Saving and Consumption Reduction
Centered on aluminosilicate fiber blankets and lightweight insulating bricks, these materials achieve high-efficiency insulation through optimized pore structures:
Ultra-thin insulation: A 10 mm thick aluminosilicate fiber blanket has a thermal conductivity of just 0.035 W/(m·K), equivalent to the insulation performance of a 50 mm rock wool board. This reduces the surface temperature of the kiln from 320 °C to 110 °C.
Thermal shock resistance: Zirconium-containing fiber blankets can undergo 200 cycles of water quenching from 1000 °C to room temperature without cracking, meeting the demands of frequent kiln start-up and shutdown operations.
System-wide energy savings: After a full insulation upgrade of a float glass production line, annual natural gas consumption was reduced by 3.2 million m³, with CO₂ emissions reduced by 6,800 tonnes.
02 Performance Comparison: Data Reveal the Technological Generation Gap
Using kiln wall insulation as an example, this section compares the performance differences between traditional rock wool boards and the new aluminosilicate fiber blankets
| Index | Aluminosilicate Fiber Blanket (10mm) | Rock Wool Board (50mm) | Improvement Degree |
|---|---|---|---|
| Thermal Conductivity at Room Temperature | 0.035W/(m·K) | 0.042W/(m·K) | -16.7% |
| Thermal Conductivity at 1000°C | 0.098W/(m·K) | 0.185W/(m·K) | -47.0% |
| Tensile Strength | ≥21MPa | 0.08MPa | +26150% |
| Weight per Unit Area | 1.2kg/m² | 10kg/m² | -88% |
| Linear Shrinkage at 1200°C | ≤1.5% | 8% | -81.3% |
| Chemical Stability | Resistant to pH 2 - 12 Solutions | Resistant to pH 5 - 9 Solutions | +60% |
03 Application Scenarios: From Extreme Environments to Daily Operation and Maintenance
1.Key Areas of the Melting Section
Pool wall: The composite structure of "41% AZS bricks + 10 mm aluminosilicate fiber blanket" not only resists erosion from molten glass but also reduces heat loss.
Swan: The combination of silica insulating bricks (density ≤ 1.3 g/cm³) and fiber blankets reduces the temperature at the top of the swan from 350 °C to 120 °C, saving 1.8 million yuan in annual fuel costs.
2.Energy-saving Optimization of the Heat Storage Chamber
Lattice body: Magnesium bricks (MgO ≥ 97%) are used in the upper layer to resist alkaline erosion, while high-alumina insulating bricks (thermal conductivity ≤ 0.2 W/(m·K)) are used in the middle and lower layers, reducing the exhaust temperature from 420 °C to 280 °C.
Wall thermal insulation: Nanoporous calcium silicate boards (20 mm thick) replace traditional diatomaceous earth, reducing wall heat loss by 65%.
3. Repair and Emergency Treatment
Rapid repair: Zirconium-containing refractory slurry (ZrO₂ ≥ 30%) enables repair of pool wall cracks in less than 2 hours, restoring productivity.
Partial replacement: The modular design of fiber blanket assemblies allows rapid replacement within 4 hours, reducing furnace downtime by 80% compared to traditional brick structures.
04 Conclusion
From 50 mm rock wool boards to 10 mm aluminosilicate fiber blankets, glass kiln insulation is undergoing a paradigm shift from "thickness stacking" to "structural optimization." Data show that kilns using the new insulation system can reduce energy consumption per unit of molten glass to 1250 kcal/kg, achieving 22% greater energy efficiency than traditional processes.
With the advancement of the "dual carbon" goals, thin, lightweight, intelligent, and systematic refractory insulation materials will become the industry standard, accelerating the transformation of glass manufacturing toward greener, low-carbon production.