CEMENT MANUFACTURING PROCESS PART (2)

(E)Raw Meal Homogenisation:-After the raw meal powder is collected in dedusting devices they are send to Homogenising Silos(Pneumatic) for better homogenization inorder to produce a uniform kiln feed to avoid process problems.

(F)Pyroprocessing Section:- The homogenized raw meal is then fed into a Suspension Preheater with Precalciner arrangement where they undergo complete dehydration and partial decarbonation(upto 96%) in contact with the hot flue gases originating from the combustion process of fuels(coal,animal meal,plastics etc...) inside the kiln.The flow of material and gas are counter current with respect to each other.The various stages of Preheater tower are called cyclones which are connected by ducts.This partially calcined raw meal enters the kiln which is the heart of the cement manufacturing process and then in the burning zone the material becomes semi liquid and formation of clinker starts at temperatures of 1300-1400°C. The clinker so formed then falls into the clinker cooler where the clinker undergoes sudden cooling(quenching).This sudden cooling of clinker helps to arrest the clinker phases,helps in valuable heat recuperation back into the kiln,avoid formation of large periclase(MgO) crystals which are detrimental to clinker strength.
The various clinker phases are C3S,C2S,C3A & C4AF which are known as Alite,Belite,Aluminate and Ferrite respectively.Alite give early strength,Belite later strength,Aluminate hydration properties and Ferrite provides the colour.The average thermal consumption for the cement manufacturing process with Suspension Preheater and precalciner is about 650-750Kcal/Kg.Clinker.

(G)Clinker Storage and Cement Grinding stage:-The clinker so formed is transported to either clinker silos or a clinker storage shed where the clinker is stored for about 1-2 weeks prior to grinding-this process is called seasoning of clinker and gives better results with respect to cement properties.
The seasoned clinker which has a size of about 1.5-3 cm is transported to Cement mills(horizontal/VRM) where they are ground along with gypsum(set retarder),slag and flyash for making different varieties of cement.The ground cement size is expressed as residue on 90 and 212 micron sieves.

(H)Cement Packing and Despatch Section:-This is the last stage of the cement manufacturing process.The cement powder from the cement mills is collected in dedusting devices like ESP and Bag Filters and then transported to cement silos to be send as bulk cement or send to cement packers to be sold as cement packets.