A tunnel kiln is a continuous firing device typically used for sintering and drying materials such as ceramics, bricks, pottery, gypsum, and asbestos. It is structured as a long and narrow tunnel, lined with refractory bricks or other high-temperature resistant materials to withstand high temperatures and chemical corrosion. Tunnel kilns are typically divided into several zones including pre-heating, firing, and cooling zones, where materials are sequentially heated, sintered, and cooled to complete the required processing. They can be categorized based on structure into pusher kilns, roller kilns, and shuttle kilns.