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Optimal Combination of Refractory Brick Types for Various Sections of Glass Furnaces
2026-06-27
Selection of Operating Conditions and Types of Refractory Bricks for Key Sections of Melting Furnaces
Crowns
The crowns (including the skewbacks) of the melting and cooling sections of glass melting furnaces operate at temperatures of 1600°C. Refractory materials used in these areas must withstand high temperatures and structural loads while also resisting the erosive effects of alkali vapors and batch materials. Consequently, these materials require extremely high refractoriness, a high load-softening temperature, and excellent creep resistance. Additionally, they must possess low thermal conductivity, avoid contaminating the molten glass, have a relatively low bulk density, and exhibit good high-temperature strength. High-performance, high-purity silica bricks possess precisely these characteristics:
1. High load-bearing temperature, approaching the material's refractoriness;2. Good stability at high temperatures and high compressive strength;
3. As the primary component is SiO₂ (content >96%)—sharing the same major elemental composition as glass—contaminants resulting from high-temperature erosion pose virtually no risk of polluting the molten glass;
4. Low cost. Consequently, high-purity, high-quality silica bricks have become the preferred choice for the crowns of various glass furnaces.
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https://www.skrefractory.com/high-quality-silica-brick-use-for-industry-furnace-product/
The primary causes of crown brick degradation include chemical erosion resulting from high-temperature reactions between refractory materials and batch carryover or alkali vapors, as well as changes in structural density and crystalline transformations driven by phase migration and temperature fluctuations. Research indicates that the alteration process of high-quality silica bricks used in glass furnace crowns under high-temperature conditions is driven primarily by impurity migration and phase transformations, while the effects of chemical erosion and dissolution are negligible. Through phase transformation and self-purification mechanisms, the properties of the bricks in the active furnace zone gradually evolve, resulting in enhanced high-temperature performance.
Tank Walls
(1) Sections in contact with molten glass: These are the parts of the melting and cooling section tank walls that come into direct contact with the molten glass. They are subjected to high temperatures, chemical corrosion from the glass melt, and mechanical/physical erosion caused by the flow of the glass. The primary requirement for refractory materials in this area is excellent resistance to glass corrosion, combined with the necessity of not contaminating the glass melt.
In China, fused-cast zirconia-corundum bricks, α-β corundum bricks, and β-corundum bricks are commonly used to construct glass furnace tank walls. Fused-cast zirconia-corundum bricks offer excellent high-temperature performance and resistance to glass corrosion; this is due to the formation of a eutectic structure of baddeleyite and α-Al₂O₃—a structure providing corrosion resistance unattainable by sintered refractories—making them highly suitable for tank wall bricks in the melting section. The primary crystalline phase of α-β corundum and β-corundum bricks is corundum, with a glass phase content of only 1%–2%, resulting in good corrosion resistance. However, compared to fused-cast zirconia-corundum bricks, they lack ZrO₂ crystals; consequently, the reaction layer has low viscosity and is less stable at high temperatures, leading to a higher rate of diffusion between the brick surface and the glass melt, and thus faster wear of the furnace lining. Nevertheless, at operating temperatures below 1350°C, α-β corundum and β-corundum bricks exhibit better corrosion resistance than fused-cast zirconia-corundum bricks. Therefore, they are ideal refractory materials for sections such as the cooling zone when temperatures remain below 1350°C.
(2) Sections not in direct contact with molten glass: These are the parts of the melting and cooling section tank walls that do not touch the molten glass (also known as breastwalls). This area is primarily subjected to the erosive effects of alkali vapors and batch materials. Depending on the specific design, either corundum-based materials or silica bricks are used; both types meet the necessary requirements. Consequently, hooked bricks and straight bricks are frequently employed in this section.
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https://www.skrefractory.com/fused-casting-azs33-36-41-block-product/
Regenerator
(1) Regenerator Crowns and Side Walls: The inner surfaces of the regenerator crowns and side walls are subjected to erosion from high temperatures, dust, and alkali vapors; the severity of this erosion decreases from top to bottom. The selection of refractory materials is determined by the specific temperatures and erosion levels experienced by the crown and the upper, middle, and lower sections of the side walls. Silica bricks and high-quality silica bricks are generally recommended for the crown and side walls, while low-porosity fireclay bricks and high-alumina bricks are typically recommended for the middle section of the side walls; standard fireclay bricks and low-porosity fireclay bricks are generally used for the lower section of the furnace. Depending on the specific design, ordinary and direct-bonded magnesia-chrome bricks have commonly been used for the upper and middle sections of the side walls in recent years, and basic bricks—such as magnesia-alumina bricks—have also demonstrated good performance.
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(2) Checkerwork: Because the entire brick structure of the checkerwork is subjected to high temperatures and structural loads, as well as the effects of dust and alkali vapors, it experiences more severe erosion than the crowns and side walls, resulting in much harsher operating conditions. Clogging and collapse of the checkerwork are often major reasons for shutting down glass furnaces for cold repairs. Therefore, the refractory materials used in the checkerwork must possess high physical strength and low creep rates; they must also exhibit strong resistance to alkali erosion and fluctuations in furnace temperature and atmosphere, resist dust adhesion, and demonstrate a slow rate of degradation.
Top of the checkerwork: Temperatures here are highest, reaching 1400–1540°C, and the material is subject to the most severe erosion from alkali vapors and dust; consequently, fused-rebonded magnesia bricks are typically selected. Because fused-rebonded magnesia bricks contain fewer silicate phases and feature large periclase crystals with direct bonding between them, the rate of periclase crystal growth induced by alkali vapors is retarded or inhibited, making the bricks resistant to cracking and pulverization.
Upper section of the checkerwork: Temperatures range from 1100°C to 1430°C; "95#" grade rebonded magnesia bricks are generally sufficient for this zone.
Middle section of the checkerwork: Temperatures range from 800°C to 1100°C. Within this range, alkali metal sulfates condense, causing severe erosion and chemical reactions in magnesia- or calcia-based checker bricks; this leads to significant brick expansion and serious damage. Therefore, magnesia bricks are unsuitable here; instead, materials such as magnesia-alumina spinel bricks, direct-bonded magnesia-chrome bricks, magnesia-zirconia bricks, or forsterite bricks should be used.
Lower section of the checkerwork: This section operates at lower temperatures and bears a heavy load, with minimal alkali erosion; however, its proximity to the flue exposes it to direct cold air impact. The material must withstand rapid thermal cycling (thermal shock), and cost-effectiveness is a priority. Consequently, low-porosity fireclay bricks—which are relatively inexpensive—are typically used.
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