Production process

Cement factories are usually located closely either to hot spots in the market or even more often to areas with sufficient quantities of raw materials of adequate quality. The aim is to keep transport cost low. 

Basically, cement is produced in two steps: firstly, clinker is produced from raw materials. Secondly, cement is produced from cement clinker.

Main processes in cement manufacturing are: crushing, grinding and burning clinker at high temperatures. It begins in the quarries where the main raw material is exploiting a mixture of limestone with small amounts of clay with mining and transporting. The next stage in the process is crushing; crushed material is homogenized and then milled to fine powder like cement. During the milling, different additives are used to achieve appropriate composition of the raw mill for the production of clinker.

Clinker burning is a part of the cement manufacturing process which is the most energy intensive, as it is performing at temperatures from 1450 to 1500°C and with temperature from 1900 to 2000°C in the flame or in the gas phase. During the process, clinker minerals form three calcium silicates C3S – alit, di dicalcium silicate C2S – belit, three calcium aluminate C3A in tetra calcium aluminate ferit C4AF. These substances are “guilty” for the main characteristic properties of concrete, which are well known to all of us. These are solidity, stability and durability.   Clinker is then milled with additives such as blast furnace slag, limestone, natural and artificial pozzolana, silica and calcium fly ash, silica fume and alternative raw materials, to a fine homogenized powder – cement. During the milling an addition of about 5% of natural or artificial gypsum is necessary to regulate the setting time of cement. Without this, cement material would set too fast.

The final stage is dispatching to consumers or to the dispatch centres in bulk or in bags, by trucks or by railway.

To provide the high temperatures in the kiln different fuels can be used: natural sources like natural gas, coal, crude oil or pet coke, different type of wastes could be used as alternatives fuels.