Materials are milled and dried in a roller mill. Heavy rollers are held over a rotating table and the coarse materials are milled until fine enough to be carried by air to the homogenizing silo.
At the exit of the homogenization silo, the material is transported through a pneumatic system to the preheater. The preheater consists of a series of cyclones of 4 stories and allows for the pre-heating of the material before it goes to the pre-calcinator. The precalcinator allows the calcification of the material to 90% . Once calcification is done, the material is ready to be “cooked” in the rotating kiln. The preheating process increases the energy efficiency of the kiln as the material is calcined at the point of entry into the kiln.
7) Rotating kiln
The kiln has the shape of a rotating tube with a 4% inclination. The kiln is designed to maximize the efficiency of heat transfer from fuel burning to the raw material. The material entering the kiln at 1000oC, is heated until it reaches a temperature of 1450oC. In the kiln, temperature reaches up to 2000oC. As such, minerals fuse together to form new mineral combinations, mainly calcium silicate crystals: cement clinker.