Rotary Kilns & Calciners | Optimized Rotary Kilns

Rotary kiln can be either of the direct-fired type, or the indirect-fired type. In a direct-fired kiln, a fuel is burnt in the drum, and the material is processed through direct contact with the flue gas. In an indirect-fired kiln, material is processed in an inert environment, and is heated through contact with the shell of the kiln, which is heated from the outside to maintain an inert environment.

The furnace walls (normally lined) make intermittent contact with the flue gas and the charge. Heat required for the various physical and chemical processes is delivered to the charge by lifting and overturning the charge as it moves through the interior of the rotary kiln

The shell of the kiln is made of mild steel plate. Mild steel is the only viable material for the purpose, but presents the problem that the maximum temperature of the feed inside the kiln is over 1400°C, while the gas temperatures reach 1900°C. The melting point of mild steel is around 1300°C, and it starts to weaken at 480°C, so considerable effort is required to protect the shell from overheating.

Professional Rotary Kiln Manufacture.pdf

Rotary kilns (sometimes called calciners or rotary furnaces) are used for thermal treatment processes such as calcination, sintering, pyrolysis and firing, as well as for oxidation and reduction. These treatments can be applied to powders, granulates, suspensions and green bodies. A rotary kiln consists of a cylindrical, rotating body mounted between stationary material feed and outlet housings. The constant turning of the kiln body mixes the material, ensuring that it is processed homogeneously. Rotary kilns are heated either directly (inside the kiln chamber) or indirectly (from outside), depending upon the requirements of the application.