Portland Cement Clinker Grinding Plants
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cement clinker processing plant
cement is typically made 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 correct proportions.This blended raw material is called the ‘raw feed’ or ‘kiln feed’ and is heated in a rotary kiln where it reaches a temperature of about 1400 C to 1500 C. In its simplest form, the rotary kiln is a tube up to 200 metres long and perhaps 6 metres in diameter, with a long flame at one end. The raw feed enters the kiln at the cool end and gradually passes down to the hot end, then falls out of the kiln and cools down.
The material formed in the kiln is described as ‘clinker’ and is typically composed of rounded nodules between 1mm and 25mm across. After cooling, the clinker may be stored temporarily in a clinker store, or it may pass directly to the cement mill. The cement mill grinds the clinker to a fine powder. A small amount of gypsum – a form of calcium sulfate – is normally ground up with the clinker. The gypsum controls the setting properties of the cement when water is added
Cement Clinker’s Wet Process
In the wet process, each raw material is proportioned to meet a desired chemical composition and fed to a rotating ball mill with water. The raw materials are ground to a size where the majority of the materials are less than 75 microns. Materials exiting the mill are called “slurry” and have flow ability characteristics. This slurry is pumped to blending tanks and homogenized to insure the chemical composition of the slurry is correct. Following the homogenization process, the slurry is stored in tanks until required.
Cement Clinker’s Dry Process
In the dry process, each raw material is proportioned to meet a desired chemical composition and fed to either a rotating ball mill or vertical roller mill. The raw materials are dried with waste process gases and ground to a size where the majority of the materials are less than 75 microns. The dry materials exiting either type of mill are called “kiln feed”. The kiln feed is pneumatically blended to insure the chemical composition of the kiln feed is well homogenized and then stored in silos until required.
cement clinker vertical roller mill for sale
In recent years, cement clinker plants are increasingly looking to vertical roller mill technology for their finish grinding needs. Vertical roller mills present a compact and efficient grinding method. Clinker and gypsum is ground on a rotating table that passes under large rollers. Material is forced off the table by centrifugal force, where it is then swept up into an air stream to a classifier immediately above. Just as with a ball mill, material that is too coarse is returned to the table for additional grinding while material that is fine enough is collected as product. The compact design of a vertical roller mill allows it to dry, grind, and classify, all within one piece of equipment and all in a relatively compact space. Vertical roller mill technology allows: (1) power consumption savings; (2) consistent product quality and (3) process simplification.