Energy-Saving Insulation Materials for Glass Melting Furnaces

01. Principles for Selecting Insulation Materials for Glass Furnaces

Due to the harsh operating environment, insulation materials for glass furnaces should meet the following principles:

1. Excellent thermal insulation performance: thermal conductivity λ ≤ 0.14 W/(m·K) at 350K, such as microporous board.

2. Adequate refractoriness: especially in composite insulation systems, each insulation layer must meet interface temperature requirements to avoid loss of performance or failure.

3. High-temperature stability: materials must resist pulverization and spalling under service temperatures.

4. Good chemical stability: resistant to corrosion and erosion, and capable of bonding firmly to refractory linings.

5. Impact resistance and lightweight.

6. Economic feasibility: since the crown, furnace bottom, and sidewalls account for ~85% of the total heat loss, materials should reduce the surface temperature of the furnace body. The lower the temperature difference between furnace surface and ambient air, the lower the heat loss. Thus, the thermal conductivity of insulation materials is directly correlated with insulation efficiency.

02. Introduction to New Thermal Insulation Materials

Historically, insulation materials for glass furnaces can be divided into traditional and new-generation materials.

• Traditional materials: lightweight clay bricks, ceramic fiber boards, calcium silicate boards, lightweight silica bricks, and high-temperature coatings.

• New-generation materials: high-performance fiber spraying coatings, microporous insulation boards, titania–silica aerogel blankets, and high-emissivity coatings.

2.1 High-Performance Fiber Spray Coatings

Applied on the furnace’s heat-dissipating outer surfaces, they provide excellent sealing and insulation performance with remarkable energy-saving and environmental benefits.

2.2 Microporous Insulation Boards

Made from special inorganic refractory powders forming nanopores smaller than air molecules’ free path. Their thermal conductivity is lower than still air. Boards can be laminated with PE film, aluminum foil, or fiber fabrics.

Working principle:

• Conduction: Nano-scale particle contacts create very high thermal resistance.

• Convection: Nanopores (~20 nm) prevent air convection since free path of air molecules at room temperature is ~60 nm.

• Radiation: Infrared reflective nano-additives minimize radiative heat transfer.

Microporous insulation board

2.3 Titania–Silica Aerogel Blankets

Composite insulation made from ceramic fiber layers and high-efficiency aerogel layers with 3D nano-pore structures.

Key properties:

• Thermal conductivity: 0.012–0.016 W/(m·K)

• Non-combustible (Class A1), stable up to 1050°C

• Excellent compression, vibration, and dimensional stability

• Moisture-proof, aging-resistant

• Very low thermal expansion

• Space-saving, lightweight, flexible, easy to cut and install

2.4 High-Emissivity Energy-Saving Coatings

Unlike conventional insulation, these are sprayed onto the inner surface of the furnace, enhancing internal radiation while reducing external heat loss.

Performance parameters:

• Coating thickness: 0.1–0.2 mm

• Excellent thermal shock resistance and flexibility

• High acid/alkali resistance, suitable for harsh combustion atmospheres

• Not an insulation material itself, but absorbs and re-radiates ~95% of heat, keeping it circulating inside the furnace

• Emissivity remains 0.85–0.95 at high temperatures (vs. 0.2–0.3 for common refractories)

High-Performance Fiber Spray Coatings——Reinforcing Modifier

03. Selection of Insulation Materials

3.1 Material Choice for Different Furnace Zones

• Crown: curved surfaces require spray-applied or blanket-type insulation, not rigid boards.

• Different inner surfaces: since surface temperatures vary, especially in composite systems, interface temperatures between layers must be checked to ensure safe working ranges.

3.2 Insulation System Design

Once the type of material is determined, specifications and quantities should be calculated using a heat transfer model. Furnace heat transfer can be simplified into two processes: from inner wall to outer wall, and from outer wall to ambient environment (neglecting port radiation and regenerator effects).

Calcium Silicate Board

04. Conclusions

1. By modeling an ideal glass furnace, analyzing heat transfer mechanisms and thermal balance equations, insulation parameters can be calculated more accurately.

2. New insulation materials should be selected based on furnace zone morphology and operating temperatures. With properties such as low thermal conductivity, high temperature resistance, and high emissivity, a well-designed composite insulation system can achieve optimal energy-saving results.

3. Compared with traditional materials, new-generation insulation significantly reduces furnace heat loss, improves energy efficiency, and ensures longer-lasting insulation performance.