There are three major stages in cement manufacturing, irrespective of the adopted technology:
A- Mix and Grind the raw materials (mainly Limestone & Clay)
B- Burn the raw mix at >1280°C to produce clinker
C- Grind the clinker
Each stage contains steps which differ from one technique to other.
Following are the main steps of cement manufacturing (dry process):
1- Quarrying of raw material:
The main raw materials are Limestone & Clay in addition to supplement raw materials; (Iron Ore & bauxite), the quarry is mapped according to the deposit chemical composition; for optimum utilization. The operation blasting and transportation to the Crusher.
2- Crushing & Pre-blending:
The material is shifted from quarry to crusher, then the crushed raw materials are stacked (Horizontally) to the respective piles then reclaimed (vertically) to the respective bin as to achieve the best initial mixing prior feeding to raw mill
3- Raw Mill; Drying, Grinding & Storage:
From the respective raw materials bins the mill feeding proportion percentage is calculated according to the raw materials chemical composition and to the aimed cement properties, after drying and grinding the mill output is diverted to the storage silo where further mixing is taking place to ensure of the raw meal prior to burn it in the kiln.
4- Clinkerization; preheater, kiln & Cooler:
The homogeneous raw meal (kiln feed) is extracted from the storage silo to feed the kiln and heated up gradually up to > 1280°C then cooled down to around 100°C, then diverted to the clinker storage silo/yard.
5- Clinker Grinding; Cement Mill:
5 % of gypsum is ground along with the produced clinker in the form of fine greyish powder; Cement, then diverted to cement storage silo.
Gypsum is added “To control setting time, cement needs a minimum amount of calcium sulfate, mostly in the form of gypsum added to the clinker. On the other hand the maximum allowable SO3-content in cement to prevent “sulfate expansion” is established according to various cement standard, between 2.5 and 4.0% SO3.”
6- Dispatching of Cement:
The cement mostly dispatches by two forms:
The basic layout of a cement plant has been as above since the early nineteenth century. Two raw materials - one high in calcium and one low in calcium - are crushed, then finely ground together in a raw mill to make "rawmix". The rawmix is burned in a kiln with fuel to make clinker. The clinker is finely ground with a small addition of gypsum in a finish mill, producing the fine powder which is called cement.
[(2)Cement Data Book, Duda, 2nd edition]