What is tunnel kiln? | Yingfeng Machinery

A tunnel kiln is a type of kiln used for the continuous firing of materials such as ceramics, bricks, or refractories. It is called a “tunnel kiln” because it has a long, tunnel - shaped structure.

Structure

Firing Zone:

The central part of the tunnel kiln is the firing zone. In this area, the temperature is raised to the required level for the firing process. For example, in a ceramic tunnel kiln, temperatures can reach up to 1,300 - 1,400 degrees Celsius. The length of the firing zone can vary depending on the type of product and the production scale.

Pre - heating Zone:

At the entrance of the tunnel kiln, there is a pre - heating zone. The materials to be fired are gradually heated as they move through this zone. This helps to reduce thermal shock when the materials enter the high - temperature firing zone. The pre - heating is usually achieved by the waste heat from the firing zone, which is a way of energy - saving.

Cooling Zone:

After passing through the firing zone, the products enter the cooling zone. Here, the products are cooled down in a controlled manner. The cooling rate is important as it can affect the quality of the final products. For instance, rapid cooling may cause cracks in ceramics, so a proper cooling curve is designed to ensure the products cool down at an appropriate speed.

Working Principle

The materials to be fired are placed on kiln cars or conveyor belts and are continuously moved through the tunnel kiln at a slow and steady speed. As they move through the different zones, they experience the pre - heating, firing, and cooling processes in sequence. The heat source for the tunnel kiln can be various, such as gas burners, electric heaters, or a combination of both. The hot gases generated in the firing zone flow towards the pre - heating zone, which helps to utilize the waste heat.

Advantages

High Production Efficiency:

Because it is a continuous production process, tunnel kilns can produce a large quantity of products in a relatively short time. Compared to batch - type kilns, the production cycle is more regular and efficient. For example, a well - designed brick - making tunnel kiln can produce thousands of bricks per day.

Good Product Quality Uniformity:

The products in the tunnel kiln experience the same temperature - time curve during the firing process as they move through the kiln at a constant speed. This ensures a high degree of uniformity in product quality. In the production of high - grade ceramics, the tunnel kiln can help to achieve consistent color, density, and strength of the products.

Energy - saving:

The utilization of waste heat in the tunnel kiln is an important feature. The hot gases from the firing zone are used to pre - heat the raw materials, which reduces the energy consumption required for the overall firing process. This makes the tunnel kiln more energy - efficient compared to some other types of kilns.

Applications

Ceramics Industry:

Tunnel kilns are widely used in the production of various ceramic products, including tableware, sanitary ware, and ceramic tiles. For ceramic tile production, the tunnel kiln can ensure that the tiles have a smooth surface, accurate dimensions, and good mechanical properties.

Brick and Tile Industry:

In the brick and tile manufacturing, tunnel kilns play a crucial role. They can fire different types of bricks such as clay bricks, shale bricks, and perforated bricks. The fired bricks have high strength and good durability, meeting the requirements of construction.

Refractories Industry:

For the production of refractory materials, tunnel kilns are used to fire products such as refractory bricks and insulating materials. The high - temperature firing process in the tunnel kiln can improve the refractoriness and thermal insulation performance of these materials, which are essential for applications in high - temperature industrial furnaces.

FAQ

Advantages