The production process for cement consists of drying, grinding and mixing limestone and additives like bauxite and iron ore
into a powder known as “raw meal”. The raw meal is then heated and burned in a pre-heater and kiln and then cooled in an air
cooling system to form a semi-finished product, known as a clinker. Clinker (95%) is cooled by air and subsequently ground with
gypsum (5%) to form Ordinary Portland Cement (“OPC”). Other forms of cement require increased blending with other raw
materials. Blending of clinker with other materials helps impart key characteristics to cement, which eventually govern its end
use.
There are two general processes for producing clinker and cement in India : a dry process and a wet process.
The basic differences between these processes are the form in which the raw meal is fed into the kiln, and the amount of energy consumed in each of the processes. In the dry process, the raw meal is fed into the kiln in the form of a dry powder resulting in energy saving, whereas in the wet process the raw meal is fed into the kiln in the form of slurry. There is also a semi-dry process, which consumes more energy than the dry process but lesser than the wet process.
There are two general processes for producing clinker and cement in India : a dry process and a wet process.
The basic differences between these processes are the form in which the raw meal is fed into the kiln, and the amount of energy consumed in each of the processes. In the dry process, the raw meal is fed into the kiln in the form of a dry powder resulting in energy saving, whereas in the wet process the raw meal is fed into the kiln in the form of slurry. There is also a semi-dry process, which consumes more energy than the dry process but lesser than the wet process.
The basic steps involved in the production process is set out below:
All J.K. Cement plants are dry process plants. Limestone is crushed to a uniform and usable size, blended with certain additives (such as iron ore and bauxite) and discharged on a vertical roller mill, where the raw materials are ground to fine powder. An electrostatic precipitator dedusts the raw mill gases and collects the raw meal for a series of further stages of blending. The homogenized raw meal thus extracted is pumped to the top of a preheater by air lift pumps. In the preheaters the material is heated to 750°C. Subsequently, the raw meal undergoes a process of calcination in a precalcinator (in which the carbonates present are reduced to oxides) and is then fed to the kiln. The remaining calcination and clinkerization reactions are completed in the kiln where the temperature is raised to between 1,450°C and 1,500°C. The clinker formed is cooled and conveyed to the clinker silo from where it is extracted and transported to the cement mills for producing cement. For producing OPC, clinker and gypsum are used and for producing Portland [Pozzolana] Cement (“PPC”), clinker, gypsum and fly ash are used. In the production of Portland Blast Furnace Stag Cement (“PSC”), granulated blast furnace slag from steel plants is added to clinker.
