Glass industry
A glass melting furnace is a thermal processing equipment constructed from refractory materials and used for melting glass. When selecting refractory materials for glass furnaces, it is essential to take into account comprehensively factors such as the type of furnace, the specific location of use, the mechanisms of material degradation, as well as the type of glass being melted and the kinds of colorants added. The appropriate refractory materials for glass furnaces must be able to withstand the corrosive effects of molten glass and furnace gases, while also possessing a high softening temperature under load and excellent thermal stability.
Glass melting furnaces can be classified into crucible furnaces, batch tank furnaces, and continuous tank furnaces. Currently, the mainstream approach is to combine flame-based and electric melting technologies. All such furnaces comprise four core components: glass melting, heat source supply, waste heat recovery, and flue gas and air supply. In flame-based melting furnaces, the flame carries substantial waste heat as it exits the furnace chamber. This waste heat can be utilized to preheat combustion air and fuel gas, thereby raising the flame temperature and reducing fuel consumption. The key equipment for waste heat recovery is typically a heat-storage chamber or a heat exchanger.
Operating characteristics of glass melting furnaces
The kiln pool can operate at a maximum working temperature of 1600℃, with temperature fluctuations in various zones ranging from 100 to 200℃. The glass melt contains silica, is acidic, and exhibits corrosive properties. At the same time, the flow of molten glass exerts intense mechanical erosion on the kiln structure.
Refractory Materials for Various Parts of Glass Melting Furnaces
Arch-top insulation: The structure consists of three layers—the wear-resistant layer is made of silicon-based sealing material, the insulation layer is composed of lightweight silica bricks, and the thermal barrier layer is 100 mm thick ceramic fiber castable.
Pool wall insulation: Use electrofused zircon-corundum bricks, AZS bricks, or dense zirconium silicate bricks.
Bottom insulation for the pool: A highly integrated composite insulation structure is employed. The wear-resistant layer consists of electrofused AZS bricks combined with zircon sand ramming material or electrofused corundum ramming material. The insulation layer is made of clay bricks, and the thermal barrier layer comprises two 30-mm-thick ceramic fiber boards laid in a staggered pattern.
Refractory insulation for the heat-storage chamber: The checker bricks are selected in three layers—upper, middle, and lower—using magnesia bricks, medium-grade magnesia bricks, and low-porosity clay bricks. For areas such as the vault roof, side walls, small furnaces, feeding pits, molten-metal outlets, cooling pools, and forming pools, refractory bricks of different grades are chosen according to specific requirements, including silica bricks, electrofused zircon-corundum bricks, AZS-33 bricks, and α-Al₂O₃ bricks.
Float Glass Tin Bath Insulation: The tin bath has a high temperature of 1100℃ at the front end and 600℃ at the rear end. The insulation system consists of a combination of high-density refractory bricks/heavy-duty castables, clay insulating bricks, and ceramic fiber boards (thermal insulation layer).
The application of unshaped refractory materials in glass kilns is becoming a mainstream trend. For example, in England, prefabricated refractory concrete blocks are used to construct parts such as the heat-storage chamber, grid brick arches, flues, small furnace supports, and burners, significantly reducing the number of joints in the kiln structure. This not only enhances furnace construction efficiency but also shortens the downtime required for cold repairs.
There are also well-established solutions for selecting thermal insulation materials in foreign glass kilns. Commonly used materials include high-alumina bricks, lightweight silica bricks, and fiber-based materials, with aluminum-silicate fiber-based materials being the most prevalent. Among these, Germany not only uses diatomaceous earth, aluminum-silicate fibers, and silicate fiber materials but also extensively employs lightweight thermal insulation products based on calcium silicate.
Float Glass Annealing Furnace: The high temperature for float glass annealing is 540–570℃, and the glass must be held at this temperature for 2 minutes. The annealing furnace does not have a dedicated insulation structure; instead, temperature control is primarily achieved through natural heat dissipation from the steel shell.
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