Cement is manufactured from limestone and clay or shale. These raw materials are extracted from the quarry crushed to a very fine powder and then blended in the exact proportions.
Manufacturing of cement includes 4 stages:
1. Mixture of raw materials
2. Burning of raw materials
3. Grinding of clinkers
4. Storage and packaging
Stage 1 - Mixture of raw materials:-
Calcium, Silicon, Iron, and Aluminum are the major raw materials utilized in the manufacture of cement.
Mixing procedure is done in 2 methods that is dry process and wet process.
Dry process:
The raw materials like calcareous and argillaceous are crushed within the gyratory crushers to urge 2-5cm size pieces separately.The crushed materials are grinded again to get fine particles into ball or tube mill.Once screening is done,each finely grinded material is kept in hopper. Now,these powdered materials are combined in needed proportion to get dry raw mix that is then kept in silos and ready to be sent into rotary kiln.
Wet Process:
Firstly, the raw materials are crushed and created into a fine kind and stored in silos.The clay is then washed in washing mils to get rid of adhering organic matter found in clay.The fine stone and water washed clay are sent to flow within the channels and transfer to grinding mills where they are completely mixed and also the paste are created,i.e., called as slurry. The grinding procedure is an often ball or tube mill or maybe both. Then the slurry is junction rectifier gathered basin wherever composition is often adjusted.The slurry contains around 38-40% water that is kept in storage tanks and stored ready for the rotary kiln.
Stage 2 - Burning of Raw Materials:
The burning materials are taken out in the rotary kiln where as the raw materials are turned at 1-2rpm at its longitudinal axis. The rotary kiln is generated of steel tubes having the diameter of 2.5-3.0 meter and also the length differs from 90-120 meter. The inner portion of the kiln is lined with refractory bricks. The kiln is given support on the columns of masonry or concrete and lively on ball bearing in slightly inclined position at a gradient of 1 in 25 to 1 in 30. The temperature of oxidation zone is around 10000C, wherever the decomposition of limestone takes place.The remaining material is in the shape of little lumps called nodules once the CO2 is discharged.
Stage 3 - Grinding of Clinkers:
The cooled clinkers are received from the cooling pans and sent into mills. The clinkers are grinded finely into powder in a ball mill or tube mill. The powdered mineral is side around 2-3% as retarding agent throughout the ultimate grinding. The ultimate obtained product is the cement which doesn’t settle quickly once comes connected with water. Therefore the mineral delays the dissolution of tri - calcium aluminates by forming tri calcium sulfoaluminate that is insoluble and prevents too early more reactions of setting and hardening.
Stage 4 - Storage and packaging:
The grinded cement is kept in silos, from that it is marketed whether in container load or 50kg bags.
