Refractory Materials for Various Sections of Glass Melting Furnaces and Precautions for Their Use

01 Sidewall Blocks
For furnaces melting soda-lime-silica or boron-containing batches, fused-cast AZS (alumina-zirconia-silica) blocks are the ideal material for sidewalls. Specifically, blocks cast using the tilted-casting method (with the gate facing outward) are typically installed in the lower sections. When melting alkali-free or low-alkali glass fibers, which cause severe acidic corrosion, sidewall blocks should be made of AZS, dense zircon, or fused silica.
02 Furnace Bottom Blocks
Furnace bottom blocks must be wear-resistant and ensure structural integrity. Multi-layer composite bottom structures are currently the standard. This design typically involves an insulation layer laid beneath the main structural layer (composed of large fireclay blocks), with a protective layer and a wear-resistant layer placed above the fireclay blocks. The protective layer is formed using rammed zircon sand or fused corundum ramming mix. The wear-resistant layer sits atop the protective layer, shielding the rammed bottom material and coming into direct contact with the molten glass; fused-cast AZS blocks—which offer excellent corrosion and wear resistance—are commonly used for this purpose. This composite structure reduces heat loss and extends the service life of the furnace bottom. When melting glass containing heavy metals (such as lead glass) or highly corrosive glass (such as opal glass), an additional protective layer and wear-resistant layer may be added over the existing ones to prevent leakage. The original protective and wear-resistant layers then serve as a secondary paving layer, utilizing sintered AZS or zircon blocks.

03 Batch-Charging Zone Blocks
Blocks in the batch-charging zone are subject to severe damage due to corrosion by batch powder and molten glass, abrasion from the batch layer, erosion by glass flow, and exposure to flames. Materials with high-temperature resistance to abrasion and corrosion are required; typically, void-free fused AZS-41 blocks (containing 41% ZrO₂) are used, often with increased block thickness and enhanced air cooling. Except for corner blocks, standard cast AZS-33 blocks may be used for other sections; large cast kaolin blocks may also be considered for the lower-layer blocks in this zone.
04 Throat Blocks
The flow velocity of molten glass is highest within the throat of the tank furnace, and convection currents are pronounced, leading to severe abrasion and accelerated corrosion. Therefore, void-free AZS-41 blocks should be used for the throat cover blocks, and the sidewall blocks should ideally be made of the same material—or at the very least, void-free blocks should be employed. Fused silica blocks are used when melting borosilicate glass.

05 Bricks for Cooling and Forming Sections
The glass melt in the cooling and forming sections has already undergone melting and refining and has entered the final stage of the melting process. At this point, it is critical to avoid introducing any defects—such as bubbles, cords, or stones—into the melt. For the cooling section, AZS-33 bricks produced via the oxidation method should be used; these feature a high glass-phase exudation temperature and do not generate bubbles in the melt. For the forming section (such as the forehearth), fused-cast α-β Al₂O₃ or α-Al₂O₃ bricks should be selected.

06 Bricks for the Furnace Crown and Breastwall
The primary modes of deterioration for bricks in these areas are corrosion (mainly caused by the condensation of alkaline sulfates, resulting in honeycomb-like erosion) and burn-off. Materials used here must exhibit exceptional stability against alkali vapors at high temperatures, as well as high load-softening temperatures and creep resistance. Suitable options include silica bricks, high-quality silica bricks, and fused-cast AZS-33 bricks.

07 Bricks for the Front Wall and Lattice

These refer to the front and rear walls enclosing the melting zone. They are subject to two types of deterioration: corrosion and burn-out. In particular, the front wall is exposed to abrasion and corrosion from the batch materials as well as erosion from escaping flames, making it one of the vulnerable sections of the tank furnace. Currently, fused-cast AZS-33 bricks are used, though combinations of high-quality silica bricks and sintered AZS bricks are also employed (such as in L-shaped suspended walls). In addition to the use of high-quality silica bricks, the front wall requires air cooling.

09 Refractories for Port Assemblies
Refractories for port assemblies can be categorized into components such as the port mouth, port neck, and burner block. These bricks must withstand high temperatures, corrosion, and erosion, while also possessing adequate thermal shock resistance. Silica bricks—or even large kaolin blocks—may be used when firing producer gas (low thermal load). However, when firing high-calorific-value fuels (high thermal load), fused-cast AZS-33 bricks are required for components such as port mouth blocks, side wall bricks, bottom plates, intermediate bricks for the sloped arch, tongue bricks, and burner blocks; dense sintered corundum bricks may also be used for the bottom plates.

10 Selection of Refractories for Special Areas

Certain sections of the glass melting furnace masonry—such as bubbler ports, furnace dams, electrode ports, inspection ports, and measurement ports—serve specific functions and exhibit unique wear characteristics. In areas of the furnace not in contact with the molten glass (such as the superstructure crown, walls, ports, and charging system), deterioration is caused by high temperatures, dust erosion, and chemical attack from various volatiles. These volatiles originate from the molten glass, batch materials, and combustion products; their primary constituents include alkali metal oxides and borates, as well as chlorides, fluorides, and sulfur compounds. At high temperatures, these volatiles exist as alkali vapors, but they condense into a liquid phase when temperatures drop.