Analysis of the Application of Refractory Materials in Various Sections of Glass Tank Furnaces

The application of refractory materials in various sections of horseshoe-flame and float glass furnaces is described below.

① Furnace Sidewall Bricks

For tank furnaces melting soda-lime-silica batches or boron-containing batches, the ideal material for the sidewall bricks is electrofused zirconia-corundum. When melting alkali-free or low-alkali glass fibers—where acidic corrosion is severe—the sidewall bricks should preferably be made of AZS bricks or dense zircon bricks; fused silica bricks may also be used. At the interface between the furnace sidewall and the main arch, zircon bricks are commonly employed as a transitional layer to prevent chemical reactions between the electrofused sidewall bricks and the ordinary silica bricks situated above the transition zone.

② Furnace Bottom Bricks
Furnace bottom bricks are required to be abrasion-resistant and possess structural integrity. Currently, a multi-layer composite furnace bottom structure is widely adopted. This multi-layer configuration typically involves installing an insulation layer beneath the main structural layer—large clay bricks. A protective layer and an abrasion-resistant layer are then positioned above the large clay bricks. The protective layer is constructed using rammed mixes composed of zircon sand or electrofused corundum. The abrasion-resistant layer sits atop the protective layer; it serves to protect the rammed furnace bottom and comes into direct contact with the molten glass. For this layer, electrofused AZS bricks—known for their excellent corrosion and abrasion resistance—are commonly used.

The two-dimensional structural layout is as follows:
Glass-Contact Layer:       Electrofused AZS bricks
Protective Layer:       Sintered zircon bricks, zircon rammed mix
Main Structural Layer:       Large clay bricks
Insulation Layer / Reinforcement Structure
The practical benefits of this composite furnace bottom structure include reduced heat loss and an extended service life for the furnace bottom. When melting glass containing heavy metal elements (such as lead glass) or highly corrosive glass (such as opal glass), an additional protective layer and abrasion-resistant layer may be added atop the original layers to prevent glass leakage. These original protective and abrasion-resistant layers are also referred to as the "secondary paving layers," for which sintered AZS bricks or zircon bricks may be utilized.

③ Furnace Roof
The characteristic forms of brick deterioration in this section are corrosion (primarily caused by the condensation of alkaline sulfates, resulting in a honeycomb-like texture) and thermal erosion. Consequently, the materials used here must exhibit exceptional stability against alkaline vapors at high temperatures, in addition to possessing a high refractoriness under load and excellent creep resistance. Suitable material choices include silica bricks, high-grade silica bricks, and electrofused AZS bricks.
④ Breastwall Bricks
For the sections of the breastwall that come into direct contact with the molten glass, high-density electrofused AZS bricks are required. However, in high-temperature environments, electrofused bricks are prone to reacting with the silica bricks of the main arch. Therefore, to prevent chemical reactions resulting from the direct contact between the electrofused bricks of the furnace wall and the standard silica bricks of the main arch, sintered zircon bricks are frequently installed between the breastwall and the main arch to serve as a protective barrier.

⑤ Bricks for the Front and Rear Walls
These constitute the front and rear walls enclosing the melting zone. Both walls exhibit two primary characteristics of deterioration: corrosion and thermal erosion. Furthermore, the front wall is subjected to abrasion and corrosion from the batch materials, as well as scouring by escaping flames; consequently, it is considered one of the most vulnerable sections of a tank furnace. Currently, electrofused AZS-33 bricks are the standard choice; however, composite structures—such as L-shaped suspended walls—that combine high-quality silica bricks with sintered AZS bricks are also employed. When high-quality silica bricks are utilized for the front wall, they must be supplemented with air cooling.
⑥ Bricks for the Port Structure
The refractory bricks used in the port structure can be categorized and considered according to their specific sections: the burner arch, the port neck, and the nozzle blocks. Bricks in the port area are required to withstand high temperatures, chemical corrosion, and mechanical scouring, while also possessing adequate thermal shock resistance. When firing producer gas (which entails a lower thermal load), silica bricks—or even large-format kaolin bricks—may be utilized. Conversely, when firing high-calorific-value fuels (which entail a higher thermal load), electrofused AZS-33 bricks are specified for critical components such as the burner arch bricks, side wall bricks, hearth bricks, skewback bricks, tongue bricks, and nozzle blocks; in this high-load scenario, the hearth may also be constructed using dense, sintered corundum bricks. Depending on the specific reactive environment within the furnace, sintered chrome-corundum refractories are also frequently employed in this area to extend the overall service life of the furnace.

⑦ Regenerator

Within budgetary constraints, the selection of refractory bricks for the furnace regenerator is highly diverse; however, the primary objective is to ensure—at a reasonable cost—that the checkerwork within the regenerator possesses the requisite characteristics: high-temperature resistance, corrosion resistance, thermal shock resistance, high heat capacity, and high thermal conductivity. Furthermore, this selection aims to guarantee that, throughout the furnace's operation, the surfaces of the checker bricks remain smooth and non-porous, thereby preventing dust accumulation, inhibiting the absorption of condensing gases, and eliminating the potential for clogging.

Here are two proposed solutions:

High-End Option:

Top Layer:33% Content — Sintered Zirconium Corundum
Second Layer: 33% Content — Sintered Zirconium Corundum
Third Layer: 33% Content — Sintered Zirconium Corundum
Fourth Layer: 18% Content — Sintered Zirconium Corundum / Zirconium-bearing Mullite
Bottom Layer: High-Quality, Low-Porosity Clay Bricks

Advantages: During furnace operation, the surface of the checker bricks remains smooth and non-porous; they do not trap dust, do not absorb condensing gases, and present no risk of clogging. The regenerator chamber offers a minimum service life of 7 years—a truly "install-and-forget" solution.

Disadvantages: The cost is relatively high.

Mid-Range, High Cost-Effectiveness Solution:

Top Layer: Chrome-Zirconium Corundum
Second Layer: Chrome Corundum / Chrome-Zirconium Corundum
Third Layer: Zircon-Mullite
Fourth Layer: Fused Mullite / Sintered Mullite
Bottom Layer: High-Quality Low-Porosity Clay Brick / Sillimanite (Low-Porosity)
Advantages: While keeping construction costs in check, this solution effectively preserves the service life of the regenerator chamber, offering excellent cost-effectiveness.

Depending on the specific operating conditions of the furnace—including the composition of the molten glass, flame temperature, and choice of fuel—the aforementioned recommendations may be subject to adjustment. With the ultimate objective of safeguarding the glass furnace in mind, there is no single "best" refractory material; rather, there are only choices that are "better" suited to the specific circumstances.