Refractory materials, as the primary component of glass furnaces, have a decisive impact on glass quality, energy consumption, and product cost. The future of glass melting technology depends, to a certain extent, on advancements in refractory manufacturing technology and improvements in product quality.

Glass Furnace Structure

For large float lines, a glass furnace typically consists of an L-shaped ceiling (typically made of silica bricks), a melting section (areas in direct contact with the molten glass are made of fused-metal bricks, with silica bricks or fused-metal bricks near the top), a neck section (typically made of silica bricks), a cooling section including the ear sump (areas in direct contact with the molten glass are typically made of corundum, with areas not in direct contact using silica bricks or corundum), an annealing lehr, and a regenerator (made of high-alumina bricks, clay bricks, or directly bonded magnesia-chrome bricks).

Application Conditions and Type Selection of Refractory Bricks for Key Furnace Parts

01

Cone

The crown (including the corners) of the melting and cooling sections of a glass furnace operates at temperatures of 1600°C. The refractory materials used in these areas must withstand high temperatures, heavy loads, and the erosion of alkali vapor and batch materials. Therefore, the refractory material used for the crown must possess extremely high refractoriness, a high refractoriness under load, and good creep resistance. Furthermore, it must have low thermal conductivity, be non-contaminating at high temperatures, and possess a low bulk density and excellent high-temperature strength. High-performance, high-quality, high-purity silica bricks precisely meet these requirements:

1. High load temperatures approach their refractoriness; 2. Excellent stability at high temperatures and high compressive strength; 3. Because the primary component, SiO2, is >96%, the same elemental composition as glass, corrosive substances at high temperatures rarely contaminate the glass; 4. Affordable price. Therefore, high-purity, high-quality silica bricks are the preferred choice for various glass crowns in glass production processes.

Chemical attack caused by the high-temperature chemical reaction between fly ash and alkali vapor and the refractory material, as well as changes in crystal form and structural density caused by phase migration and temperature, are the primary causes of damage to arch roof bricks. Research results indicate that the corrosion process of high-quality glass kiln silica bricks used in arch roofs under the high temperatures of the kiln is primarily caused by impurity migration and phase transformation, with chemical attack and dissolution essentially negligible. Phase transformation and self-purification gradually alter the kiln's operating performance, improving its high-temperature performance.

02

Pool Walls

1. Areas in Contact with Molten Glass: The areas of the melting and cooling tank walls that come into direct contact with the molten glass are subject to high temperatures, chemical attack from the molten glass, and mechanical erosion caused by its flow. The most critical requirements for the refractory material in these areas are excellent resistance to molten glass corrosion and the avoidance of contamination.

Domestic glass kilns generally utilize fused zirconium corundum bricks, α-β corundum bricks, and β-corundum bricks for masonry. Fused zirconium-corundum bricks offer excellent resistance to high temperatures and molten glass. This is due to their eutectic combination of baddeleyite zircon and α-Al₂O₃, which offers exceptional corrosion resistance not found in sintered refractories. Therefore, they are ideally suited for use as lining bricks in the melting tank of glass furnaces. α-β and β-corundum bricks are primarily corundum, with a glass phase content of only 1%-2%. They exhibit excellent corrosion resistance, but compared to fused zirconium-corundum bricks, their reaction layer lacks ZrO₂ crystals, resulting in lower viscosity and less stability at high temperatures. This results in a higher diffusion rate between the brick surface and the molten glass, leading to faster damage to the kiln lining. However, at kiln temperatures below 1350°C, α-β and β-corundum bricks offer superior corrosion resistance compared to fused zirconium-corundum bricks. Therefore, α-β and β-corundum bricks are ideal refractory materials for cooling areas and other applications below 1350°C.

2. Areas Not in Direct Contact with Molten Glass: The areas of the melting and cooling tank walls that are not in direct contact with the molten glass (also called breast walls) are primarily subject to erosion from alkali vapor and batch materials. Depending on the design, either corundum or silica bricks are used; both materials meet the requirements. Therefore, hook-type and straight bricks are often used in this area.

03

Regenerator

1. Regenerator Arch and Side Walls: The inner surfaces of the regenerator arch and side walls are subject to erosion from high temperatures, dust, and alkali vapor. The degree of erosion decreases from top to bottom. The choice of refractory material is determined by the temperature and erosion levels experienced by the top, side walls, upper, middle, and lower sections of the glass furnace regenerator. Silica bricks and high-quality silica bricks are generally recommended for the top and side walls. Low-porosity clay bricks and high-alumina bricks are generally recommended for the middle side walls. Standard clay bricks and low-porosity clay bricks are generally used for the lower section of the furnace. Depending on the design, in recent years, the upper portion of the sidewalls has generally been constructed with ordinary magnesia-chrome bricks and directly bonded magnesia-chrome bricks. Alkaline bricks such as magnesia-alumina bricks have also achieved good results.

2. Cellular: Because the entire cellar is exposed to high temperatures, dust, and alkali vapor, it is subject to more severe corrosion than the arches and sidewalls, and therefore faces more stringent operating conditions. Cellular blockage and collapse are often a major cause of glass furnace shutdowns and cold repairs. Therefore, cellar refractory materials must possess high physical strength, low creep rate, strong resistance to alkali corrosion caused by changes in furnace temperature and atmosphere, and resistance to dust adhesion, resulting in slow damage.

At the top of the cellar, where temperatures are highest, reaching 1400-1540°C, alkali vapor and dust erosion are the most severe. Therefore, fused-melted and bonded magnesia bricks are generally used. Because fused rebonded magnesia bricks contain relatively few silicates, the periclase crystals have already grown, forming direct bonds between the periclase. This slows and prevents the gradual growth of the periclase crystals under the action of alkali vapor, making the brick less susceptible to cracking and pulverization.

Upper lattice: The temperature here can reach 1100-1430°C, and 95# rebonded magnesia bricks are generally sufficient.

Middle lattice: The temperature is 800-1100°C. Within this range, alkali sulfates condense, and the magnesium and calcium lattice is severely corroded by SO₃ and Na₂O, resulting in chemical reactions. This can cause significant brick expansion and damage. Therefore, magnesia bricks are not suitable for this area. Instead, magnesia-alumina spinel bricks, directly bonded magnesia-chrome bricks, magnesia-zirconium bricks, and forsterite bricks should be used.

The lower part of the grid body: This section has a low operating temperature, heavy load, and is less susceptible to alkali corrosion. However, it is close to the flue and is directly affected by cold air. The required material should be able to withstand rapid cooling and heating, and the price should be low. Therefore, low-porosity clay bricks are generally used.