How we make cement


Part 1 - raw materials extraction

1. Quarry

  • Extraction of limestone, marl and clays using drilling and blasting techniques
  • Other materials that contain the required proportions of calcium, silicon, aluminium and iron oxides are extracted as well

 

2. Crusher

  • The quarried material is then reduced in size by compression and/or impact in various mechanical crushers
  • Crushed rock is reduced in size from 120 cm to between 1.2 and 8 cm.
  • Drying of raw material may also be necessary for efficient crushing and pre-blending

 

3. Conveyor

  • Raw material is then transported from the quarry
  • using conveyors, rail wagons or other suitable logistics solutions specific to the cement plant




Part 2 - blending and clinkerization

4. Mixing bed

  • The crushed limestone and clay is homogenized by stacking and reclaiming in a long layered stockpile
  • This material is then ready for milling and drying in the kiln

 

5. Raw mill

  • The raw materials are milled and dried in a roller mill
  • Heavy rollers are held over a rotating table and the material is milled until it is fine enough to be carried by air to a homogenizing silo.

 

6. Filter bag

  • Filters comprise filters of either woven fabric or needle felts to remove particles from kiln exhaust
  • The exhaust gas from many kilns is used for drying raw materials
  • improving the energy efficiency of the plant.

 

7. Preheater

  • Cyclone preheaters enable the raw material of cement production to be preheated before entry into the kiln.
  • This increases the energy efficiency of the kiln as the material is 20-40% calcined at the point of entry into the kiln.

 

8. Kiln

  • The kiln is designed to maximize the efficiency of heat transfer from fuel burning to the raw material
  • In the preheater tower the raw materials are heated rapidly to a temperature of about 1000°C, where the limestone forms burnt lime.
  • In the rotating kiln, the temperature reaches up to 2000°C.
  • At this high temperature, minerals fuse together to form predominantly calcium silicate crystals - cement clinker.

 

9. Cooler

  • The molten cement clinker is then cooled as rapidly as possible
  • The ambient air used to cool the clinker is then fed into the kiln as combustion air
  • ensuring high utilization of the heat produced




Part 3 - grinding and distribution

10. Clinker silo

  • Clinker may be either stored on site in preparation for grinding to form cement
  • or transported to other sites

 

11. Cement mill

  • Finish milling is the grinding together of cement clinker, with around 5% of natural or synthetic gypsum
  • Other cementitious materials such as slag, flyash or other pozzolans may also be incorporated into the final cement powder

 

12. Logistics

  • Final cement may be transported pre-bagged or as a bulk powder.
  • The method of transport selected varies according to location 
  • and may include transport via truck, rail or ship