The main materials used in cement production are minerals containing calcium oxide, silex, alumina and iron oxide.
These components are rarely found in one type of raw material; therefore, for the cement production the raw mix is selected for the following components:
CARBONATE COMPONENT (rich in calx) is contained in the raw mix in a quantity of 76-80%:
- Limestone. Mohs hardness is 1.8-3.0. The older the geological fraction, the firmer. One of the varieties of lime spar is marble.
- Unlike limestone, it has a looser, earthy structure; therefore, it refers to specifically designed raw materials for wet production. Chalk is soft raw material, it does not require crushing.
- Marl is a limestone with admixtures of silex and clay substances, as well as iron oxide.It is a transitional stage to clay. The hardness of marl is lower than the hardness of limestone The more clay substances, the lower its hardness. This is an excellent raw material for cement production.
Each of these materials has different grinding coefficient. The higher grinding coefficient, the more grinding of this material. The grinding factors for base raw materials in cement production are given in table below.
| Grind material | Grinding coefficient |
| Rotary kiln clinker | 1.00 |
| Shaft furnace clinker | 1.15-1.25 |
| Granulated blast-furnace slag | 0.55-1.10 |
| Chalk | 3.70 |
| Clay | 3.00-3.50 |
| Marl | 1.40 |
| Limestone | 1.20 |
| Quartz sand | 0.60-0.70 |
CLAY COMPONENT (contains little lime)
Clay minerals have a fine-grained structure; the grain size does not exceed 2 microns.
CORRECTIVE ADDITIVES
Corrective additives are added in cases where the chemical composition of the raw mix does not meet the established requirements. For example, sand, tripoli are used to increase silica. With a lack of iron oxide to reduce the clinker sintering temperature and increase the saturation coefficient, add pyrites cinder, iron ore. This results in saving gas during burning. Carbonate and clay components are used to provide the necessary content of CaCO3. They have different carbonate components of CaCO3 (titer).The carbonate component contains up to 97% CaCO3, clay contains about 10%. It is necessary to achieve, for example, a titer of 80%. Therefore, there are sludge pools with high and low titer content on cement plants. The sludge from pools is mixed in certain proportions.
In this connection, each cement plant has its own, unique composition of raw materials for production of finished goods. For example, a mixture of materials used by some cement plants in Ukraine.
– limestone, clay, slag;
– marl, chalk; cinder 2.5%;
– limestone, clay + loam, corrective additives;
– limestone-coquina; reddish clay;
– coal washing, cake, cinder;
– marl, loam, pyrite cinder.
The choice of composition of materials mixture with useful components generally is determined by plant’s geographical location and delivery of raw materials.
The only common feature in all cement production plants is the difficulty of grinding the source material as the material is hard enough and has high abrasiveness.
That is why high quality grinding balls with high hardness over the entire section are used during grinding materials in tube mills in this industry. During 10 years Company Energosteel has been supplying grinding balls to cement plants not only in Ukraine, but also abroad.