The tunnel kiln is generally a long straight channel, with fixed kiln walls and kiln roofs on both sides and at the top (the top is divided into flat roofs and vaults). The kiln car runs on the track laid at the bottom. The kiln car is loaded with fired products, and the kiln car enters the car in turn, and the kiln tail leaves the car. The kiln body constitutes a fixed preheating zone, a cooling zone, usually called the "three belts" of the tunnel kiln. The high-temperature flue gas generated by combustion flows along the tunnel to the kiln head in the front chimney of the tunnel kiln or under the action of an induced draft fan, and at the same time gradually preheats the products entering the kiln. This section constitutes the preheating zone of the tunnel kiln. The middle of the tunnel kiln is the firing zone. Cold air is bulged at the end of the tunnel kiln to cool the products in the tunnel kiln. After the bulging cold air is heated by the products, it is pumped out and sent to the drying kiln as a heat source for drying the green body. This section constitutes the cooling zone of the tunnel kiln. The fuel used in the fired brick tunnel kiln is solid, liquid and gas. At present, most tunnel kilns in China have replaced coal with gas as the combustion raw material.
Tunnel kiln is a continuous production, there is no interruption period in the middle, the firing cycle is short and the output is large, it is not affected by natural weather, and it saves fuel. It mainly uses the countercurrent principle to work, so the heat utilization rate is high, and the heat utilization rate is as high as 50% compared with the conventional wheel kiln. Tunnel kiln production can save labor, improve the working environment, reduce environmental pollution, and is easy to operate. Loading and unloading products is easy to realize mechanization. Reduce the labor intensity of workers. In terms of improving product quality, compared with the wheel kiln, it reduces the secondary backhaul of workers, and the firing temperature is controllable and adjustable. It is easy to control its firing law, and the crushing rate is low. The tunnel kiln and the supporting equipment in the kiln are more durable, because the tunnel kiln is not affected by sudden cooling and sudden heating compared with the wheel kiln, so the service life of the kiln body is longer, and the tunnel kiln has 2 | 3 less floor space than the wheel kiln with the same output and specifications. The masonry materials and equipment used in the tunnel kiln and the wheel kiln are different. Therefore, the investment cost is higher than that of the wheel kiln, but the later production cost is lower than that of the wheel kiln.