Manufacturing Process - Grey Cement
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.
All JK 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 to a vertical roller mill/Ball 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 mechanical transport /FK pumps. In the preheaters the material is heated to 750ºC. 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 1,450ºC and 1,500ºC. 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 , for producing Portland [Pozzolana] Cement ("PPC"), clinker, gypsum and fly ash are used and for producing Portland Slag Cement (PSC), cement uses clinker , gypsum and slag.