A roller kiln is a tunnel kiln with a narrow and elongated cross-section. Unlike car tunnel kilns, it operates not with kiln cars loaded with products but with a series of parallel rollers that span the cross-section of the kiln's working channel, forming the "roller track." Products are placed on the roller track and conveyed into the kiln as the rollers turn, completing the firing process within the kiln, hence the name roller kiln. Roller kilns can be categorized by the combustion structure used, the heating method, or the number of channels. Generally, roller kilns in the building ceramics industry are classified by the combination of fuel and heating methods.

Bright Flame Roller Kiln - The flame enters the upper and lower spaces of the roller track, contacting the products and directly heating them.

(1) Gas-fired flame roller kiln. Common gas fuels include natural gas, blast furnace gas, liquefied petroleum gas, etc., with a requirement for clean gas.

(2) Direct flame roller kilns fueled by light diesel oil. Due to the simpler fuel supply system and lower investment compared to the gas supply system, most of the direct flame roller kilns built domestically in recent years have been fueled by light diesel oil.

2. Flame Retarding Conveyor Kiln - The flame typically enters only the muffle chamber isolated from the kiln chamber, where it radiates heat to the products through flame-retarding plates for heating.

(1) Coal-burning roller hearth kilns burn coal in the firebox, with the flames entering the flame-dividing channel (muffle channel) under the roller, indirectly heating the products. Some domestic coal-burning roller hearth kilns, to stabilize the kiln temperature and reduce the temperature difference between the upper and lower parts, install several electric heating elements (silicon carbide rods) on the rollers to compensate for the heating of the products, which has a certain effect on improving product quality. Such roller hearth kilns can be called coal-electric mixed-firing roller hearth kilns, but they still fall under the category of coal-burning flame-dividing roller hearth kilns.

(2) Oil-burning flame-separating roller kilns use heavy oil or residuum oil as fuel, with flames typically entering the muffle channels beneath the kiln's passageways for indirect heating of products. The oil-burning flame-separating roller kilns constructed in China in the early 1980s, in addition to having muffle channels below the rollers, also had them on top, but these were generally removed later. By the mid to late 1980s, most heavy-oil roller kilns were upgraded to oil-burning semi-flame-separating roller kilns, featuring fire outlets at appropriate locations to allow some combustion products into the working channel. As the semi-flame-separating roller kilns, except for the fire outlets, have similar structures to the full flame-separating roller kilns, they can be categorized together.

3. Electrically heated roller kiln - Heated by electrical heating elements (silicon carbide rods or electric heating wires) installed above and below the rollers, which radiate heat to the products. Suitable for manufacturers with abundant power resources or small-scale roller kilns. Among the aforementioned types of roller kilns, the flameless roller kiln is advantageous for improving heat transfer efficiency, evening out the temperature field within the kiln, and energy conservation, as the combustion products directly contact the products, representing the mainstream of roller kilns. Of course, each region has its own resource characteristics, and other types of roller kilns are also widely used in our country.

The roller kiln can also be categorized by the number of working channels: single-layer, double-layer, triple-layer, and so on. Multi-layer roller kilns can save fuel, shorten the kiln length, reduce land use, and lower investment costs. However, with the increase in layers, it complicates the transport lines for entering and exiting the kiln, the interlock control system, and the kiln structure itself, which also brings considerable difficulties in removing brick fragment debris.

Mostly in China, single-layer roller kilns are used, with some employing double-layer channels. One layer is for baking products, while the other is for drying green bodies. The drying heat source utilizes the waste heat from the baking layer. Generally speaking, it is advisable to use multi-layer kilns when the kiln width is narrow, the working temperature is not too high, and the space is limited, but it is generally not recommended to exceed three layers.