Cement is produced with fine grinding of clinker and plaster. Clinker is a product made by steady burning of a homogenous special mixture of limestone and clay with predominance of calcium silicate till its baking.
Presently Russia produces about 60 mln tons of different brands of cement per year thus holding the 7th place in the world after China (2.5 billion tons/year), India (260 mln tons/year), the USA, Iran, Vietnam and Japan (80 mln tons/year each).
The grinding equipment is used for four processes starting from producing source raw material and finishing with the end product release.
Regardless of the production method, wet, dry, semidry or combined, the following 4 grinding processes are used for cement production:
Process 1. Raw material procession.
Carbonate rock (limestone, marlstone, or chalk) and clay is grinded with powerful grinders (see Picture) making a blended mass which is later burned.
Process 2. Fuel procession.
If coal is used for burning, it shall be crushed in hammer mills. Recently appeared a tendency to use different fuel domestic waste, mainly used car tyres processed with ring crosses or rotor-type impeller breaker mill, in order to reduce prime costs of the product release (See Recycling).
Process 3. Clinker grinding.
The product of burning, clinker, is crushed in hammer mills and grinded in mills to the powder of thousand times less than 1 millimeter.
Process 4. Grinding additives.
In order to improve quality of produced cement, it is supplemented with plaster for adjusting setting time and with active mineral additives (pyrites cinder, flue dust, bauxite, sand, gaize, tripoli) for improving certain properties and reducing the cost of cement.
Most common domestic raw material grinders. 1 – SMD-97A (manufactured by OJSC “Volgatsemmash”, city of Togliatti; 2 – SMD-75A (manufactured by OJSC “Drobmash”, city of Vyksa).
In the present time all new cement plants commissioned into operation in the past few years use today the most cost efficient production method and are almost fully equipped with foreign equipment (Denmark, China, Germany), which refers to grinders as well. Highly efficient grinders for raw materials and clinker are completed, as a rule, with hammers of increased wear resistance of such top-world manufacturers as Magotteaux (Belgium), Hardtop (Germany) and Sinoma (China).