Raw material for cement
A) Calcareous materials
- Marine shells
B) Argillaceous Materials
- Blas Furnace Slag
There are three processes of cement manufacturing
- Wet process
- Dry process
- Semi-dry process
Following three distinct operations are involved in the manufacture of cement
- Mixing of raw materials
In the wet process, raw materials are mixed wet in required proportions and slurry is formed. While in the dry process raw materials are mixed in required proportions in dry form and the dry raw mix is formed. The remaining two operations, namely, burning and grinding, are the same for both the process.
The corrected slurry is fed into a rotary kiln from the upper end. As the slurry gradually descends, there is a rise in temperature and small lumps, known as nodules are formed.
These nodules, reach the burning zone, where the temperature is about 1300°C to 1500°C. In the burning zone, the calcined product is formed and nodules are connected to small hard balls, knows as clinkers. The size of clinkers varies from 3mm to 20mm.
Clinkers, as obtained from rotary kiln, are finely ground in ball mills and tube mills. A small quantity of about 2 to 3% of gypsum is added to prevent the flash setting of the cement.
The finely ground cement is stored in silos. It is then weighed and packed in bags by automatic machine. Each bag of cement contains 50kg about 0.035 m3 of cement.
Leading cement manufacturing companies in India
- Associate cement company (ACC)
- Birla group of company
- Ambuja cement company
- Sanghi cement company
- Shree Digvijay cement co. ltd
- Binani cement company
- Hathi cement company
- Grasim cement company