Question: What is a tunnel kiln? In which industries are tunnel kilns commonly used? How much do you know about the refractories commonly adopted for tunnel kilns?
A tunnel kiln is a continuous high-temperature heat treatment equipment that uses a conveyor belt or track inside the kiln to move products through preheating, firing, and cooling processes.
I,Core Definition of Tunnel Kiln
A tunnel kiln is essentially a long, enclosed tunnel-shaped furnace.
Structural Features:The kiln body is fixed, with kiln cars, conveyor belts, or roller tables inside for transporting products.
Working Principle:Products enter from the kiln head (low-temperature end) with the transport equipment, pass through the preheating zone, firing zone, and cooling zone in sequence, and finally exit from the kiln tail (low-temperature end), realizing continuous production.
Core Advantages:Compared with intermittent kilns, it significantly improves production efficiency, ensures uniform product quality, and reduces energy consumption.
II,Main Application Industries of Tunnel Kilns
With the advantages of continuity and large-scale production, tunnel kilns are widely used in industries requiring high-temperature firing.
Building Materials Industry: As the most important application field, it is used to produce ceramic wall and floor tiles such as ceramic tiles, floor tiles, and split bricks, as well as refractory bricks, hollow bricks, and aerated concrete blocks.
Domestic and Artistic Ceramics Industry: It fires ceramic products such as tableware, tea sets, vases, and sculptures, ensuring the color and texture of products through precise temperature control.
Metallurgical and Chemical Industry: It is used for roasting metal ores, sintering metal powders, and high-temperature treatment of chemical raw materials (such as alumina and magnesium oxide).
Special Materials Industry: It produces electronic ceramics (such as ceramic substrates), structural ceramics, and high-temperature refractory materials that have strict requirements on temperature and atmosphere.
III,Recommended Refractories for Tunnel Kilns
The selection of refractories depends on the temperature and working conditions of different zones in the kiln, with the core being to ensure high-temperature resistance, corrosion resistance, and thermal shock resistance.
| Kiln Zone | Common Refractories | Recommended Reasons |
| Preheating Zone (low temperature,with moisture) | High-alumina bricks (low alumina content, e.g.,LZ-48), fire clay bricks | Moderate price, can withstand medium and low temperatures, and has strong resistance to moisture corrosion |
| Firing Zone (highest temperature, up to 1200-1800°C) | High-alumina bricks (high alumina content, e.g.,LZ-65/LZ-75), corundum bricks, mullite bricks | Excellent high-temperature resistance, resistance to high-temperature gas scouring and material corrosion, and can work stably at high temperatures for a long time |
| Cooling Zone (abrupt temperaturedrop, frequent thermal shocks) | Thermal shock-resistant high-alumina bricks,cordierite bricks, silicon carbide bricks | Small thermal expansion coefficient, strong thermal shock resistance, can withstand severe temperature changes during cooling, and is not easy to crack. |
| Kiln Cars/Kiln Furniture (carryproducts, need load-bearing and high-temperature resistance) |
Cordierite-mullite kiln furniture, silicon carbideshelves, high-alumina kiln car bricks | High strength, high-temperature resistance, and thermal shockresistance, can be reused without deformation, ensuring safe transportation |
