What are the commonly used lightweight insulating bricks for glass melting furnaces?

1. Lightweight Clay Bricks
Lightweight clay bricks are typically produced by incorporating sawdust and utilizing the plastic molding method. The raw batch consists of clay (30–40%), grog (15–25%), and hardwood sawdust (30–45%), to which specific quantities of syrup and waste sulfite liquor are added. Following mixing, aging, and molding, the bricks undergo drying (until residual moisture is less than 10%) and are then fired (at a temperature of 1250–1350°C) with a 4-hour holding period. Alternatively, lightweight bricks can be produced by blending clay with porous or hollow materials (such as fly ash cenospheres or diatomaceous earth). Since the bricks undergo significant deformation during the drying and firing processes, the finished products require post-firing shaping and processing. The bulk density of lightweight clay bricks ranges from 0.4 to 1.3 g/cm³.

2. Lightweight Silica Bricks
The manufacturing method for lightweight silica bricks is similar to that of lightweight clay bricks. Ordinary silica is ground to a particle size of less than 1 mm, and then mixed with 30% to 45% anthracite (with an ash content of less than 10% and a particle size of 0.2–1 mm) or coke. A small amount of lime or gypsum, along with waste pulp liquor, is also added to the mixture. After forming and drying, the bricks are fired at a temperature of 1270–1300°C. Lightweight silica bricks have a bulk density ranging from 0.9 to 1.1 g/cm³; their thermal conductivity is only half that of ordinary silica bricks. They also exhibit superior thermal shock resistance. The initial temperature of softening under load can reach 1600°C—significantly higher than that of lightweight clay bricks. Consequently, the maximum service temperature for lightweight silica bricks can reach 1550°C. Furthermore, they do not undergo shrinkage at high temperatures; instead, they exhibit a slight expansion.

3. Lightweight High-Alumina Bricks
Lightweight high-alumina bricks are typically produced using the foam method. A slurry is prepared using high-alumina clinker, clay, and a small amount of sawdust (added to increase the viscosity of the batch). A specific quantity of electrolyte—such as Al₂(SO₄)₃—is also added to stabilize the slurry. A foaming agent with low surface tension (e.g., rosin soap) is then added to the slurry in appropriate proportions to induce foaming. The resulting foamed slurry is prepared in a mixer and cast into molds. The green bricks, while still in their molds, are initially dried at a low temperature (approximately 40°C); after demolding, they undergo further drying at 80–95°C. Upon completion of the drying process, the residual moisture content should be between 3% and 5%. Finally, the bricks are fired at 1300–1350°C and held at this temperature for 4–6 hours. Lightweight high-alumina bricks possess a bulk density ranging from 0.4 to 1.0 g/cm³ and a porosity level reaching 66–67%.

4. Lightweight Insulation Boards and Insulation Wool
Optimizing the thermal insulation design of glass furnaces is essential for elevating the overall standard of furnace design, thereby achieving the dual objectives of energy conservation and extending the furnace's service life. As key thermal equipment within the glass industry, glass furnaces account for a significant portion of energy consumption; consequently, utilizing ceramic fiber boards as lightweight insulation liners for the furnace backing helps to maintain the furnace's airtightness and thermal insulation efficiency.