High Thermal Efficiency And Short Firing Time With Steel Belt Kiln

A tunnel kiln is a long, straight tunnel with fixed walls and a roof on its sides and top, with a track laid on the bottom where kiln cars operate. The combustion equipment is located on both sides in the middle of the tunnel kiln, forming a fixed high-temperature zone called the firing zone. The high-temperature flue gas generated by combustion flows towards the kiln head under the action of the chimney or induced draft fan at the front end of the tunnel kiln, gradually preheating the products entering the kiln. This section constitutes the preheating zone of the tunnel kiln. Cold air is introduced at the end of the tunnel kiln, cooling the products in the last section of the tunnel kiln. The cold air flows through the products and is heated, then extracted and sent to the dryer as a heat source for drying green bodies. This section forms the cooling zone of the tunnel kiln.

Clay bodies are placed on kiln cars, which are continuously pushed slowly from the entrance of the preheating zone, while the kiln cars loaded with fired products are gradually pushed out from the exit of the cooling zone.

Advantages of Tunnel Kiln:

1. Continuous production, short cycle time, large output, and high quality.
2. High thermal efficiency and fuel economy due to the counterflow principle, with excellent heat retention and residual heat utilization, saving about 50-60% fuel.
3. Shorter firing time, taking about 20 hours compared to 3-5 days for conventional large kilns.
4. Labor-saving: Operations are simple, and loading and unloading of the kiln are done outside, improving working conditions and reducing labor intensity.
5. Improved quality: The temperatures of the preheating, firing, and cooling zones are often kept within a certain range, making it easier to control the firing process and resulting in higher quality and lower breakage rates.
6. Durability of kiln and kiln furniture: The kiln body is not subjected to rapid temperature changes, extending its service life to about 5-7 years before requiring maintenance.

However, the materials and equipment required for constructing a tunnel kiln are more substantial, leading to a higher initial investment. Since it is a continuous firing kiln, the firing regime should not be changed arbitrarily, making it generally suitable for large-scale production and products with similar firing requirements. It is less flexible in operation.

Tunnel kilns are used for firing blue bricks and tiles, ceramics, new energy materials, etc. The kiln structure can be built or assembled with steel structures.