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

Mingyan Roller Furnace - The flame enters the upper and lower spaces of the roller channel, 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 burning 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 for burning light diesel oil.

2. Flame-retardant roller kiln - The flame generally enters only the muffle channel isolated from the kiln passage, where it is radiated to the products through flame-retardant plates for heating.

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

(2) Oil-burning flame-separating roller kilns use heavy oil or residuum oil as fuel, with the flames typically entering the kiln's muffle channels below, heating the products indirectly. The oil-burning flame-separating roller kilns built in China in the early 1980s, in addition to having muffle channels below the rollers, also had additional ones on top, but these were generally removed later. By the mid to late 1980s, most roller kilns burning heavy oil were improved to oil-burning semi-flame-separating roller kilns, which involved leaving a fire outlet at appropriate locations to allow some combustion products into the working channel. Since the semi-flame-separating roller kilns, apart from the fire outlets, have similar structures to the full flame-separating roller kilns, they can be categorized together.

3. Electric heated roller kiln - Utilizes electric heating elements (silicon carbide rods or electric heating wires) installed above and below the rollers as the heat source for radiant heating of the products. Suitable for manufacturers with abundant electric power resources or small-scale roller kilns. Among the aforementioned types of roller kilns, the flameless roller kiln, with its combustion products directly contacting the products, is beneficial for improving heat transfer efficiency, uniforming the temperature field across the kiln cross-section, and energy conservation, representing the mainstream of roller kilns. Of course, each region has its own resource characteristics, and other types of roller kilns have also been widely applied in our country.

The roller kiln can also be categorized by the number of working channels: single-layer roller kiln, double-layer roller kiln, triple-layer roller kiln, and so on. Multi-layer roller kilns can save fuel, shorten the kiln length, reduce land use, and lower investment costs. However, the increased number of layers complicates the transportation lines for loading and unloading, the interlock control system, and the kiln structure itself, which also makes it more difficult to remove brick fragments.

Mostly in China, single-layer roller kilns are used, with some employing two-pass systems. One layer is used for firing products, while the other dries the green bodies. The drying heat source utilizes the residual heat from the firing 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 land area is limited, but it is usually not recommended to exceed three layers.