ACC Limited (Formerly the Associated Cement Companies Limited) one of the largest producers of cement in India. The company is only Cement Company to get Super brand status in India. Established in 1936, ACC has been a pioneer and trend-setter in cement and concrete technology. Among the first companies in India to include commitment to environment protection as a corporate objective, the ACC has won accolades for environment friendly measures taken at its plants and mines, and has also been felicitated for its acts of good corporate citizenship. Cement has 4 types of manufacturing process they are, Wet, Semi wet, Dry and Semi Dry. The plant which we visited was using a semi wet process. It is quite an old process which takes more time and raw materials. But the wet and the semi wet process give the best quality of cement as they use water for mixing. In the dry process air is used as the medium for mixing. The raw materials used in making the cement are limestone, silica, iron, alumina, fly ash, gypsum, red soil and slag. They procure lime stone from their own quarry and all others from different areas.
At the first limestone is crushed into fine powder, number of crushing stages depends on the bond index (hardness) of the material, sometimes floatation (where they use water to crush) is also used and mixed with all the raw materials. This is pulverized to the size of 100 microns. The mixture of raw materials is called as the clinker.
Now the clinker is send through the pre heaters then to kiln where the materials are heated to 1800O Celsius and it is passed through the coolers and they get cold. From the coolers the heat is transferred back to the pre heaters and the waste heat is released to the atmosphere. This total system is called as Pyro system.
The materials got from the Kiln process is now let into the ball mill where it comes out as slurry and then it is smashed into a very fine powder. Then this product is subject to the final grinding where they add fly ash, slag and gypsum for different grades of cement. Gypsum is added in all the grades of cement because it will retard the setting time.
They have 3 different varieties of cement they are, PPC, OPC and Coastal Plus. In PPC there is 60% of Clinker, 35% of ash and 5% of gypsum. In coastal plus they use slag as an extra material which is got from the steel plants as a waste. OPC is the best grade cement which is used for building foundation and the PPC is used for the other building parts. Coastal Plus is used for construction near the sea shore. It was a fantabulous field visit where we were astonished by the size of the plant and we gained the basic knowledge on the working of the cement industry and the process involved in making of the cement.