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Tuesday, March 8, 2011

CEMENT !!! Part II

Well , as already said ... preparation of cement is a two step process .
Firstly , Beneficiation of cement rock , and
then the actual method of preparation of cement .



BENEFICIATION OF  CEMENT ROCK :- 

What is " Beneficiation" in the first place ?? 
Simply , It is the process of improving the physical and chemical properties of the raw materials so that we can recover the final product with more efficiency , and thus , more profit !!! It is the process of separating the gangue from the required ore . It is also known as "mineral dressing" . These beneficiation methods  are based on the properties of fluid mechanics and adsorption . 
The limestone obtained from the mines is not pure and efficient enough for use in the production of cement , hence the need to beneficiate it . 
The operations used can be grinding , classification , flotation , thickening and much more accordingly , keeping the quality of the ore in mind .  

The beneficiation can be done by two methods - wet and dry methods . Dry methods are more efficient preventing wastage , but more care has to be taken in separation . Nowadays , wet processes are more in vogue . 


The process consists of the following steps : 
1) Firstly , the ore is examined , magnetic impurities are removed easily by respective methods and the ore is  then pulverized to a fine mixture . Pulverizers are mechanical devices , including ball mills , tube mills , etc , which are used for grinding the mixture into a fine powder . 
A TYPICAL PULVERIZER

2) If the ore is usable enough , then it is directly sent into the "Hydro separator" . The part of the ore which is not so suitable enough is further processed , they are sent into "Rake Classifiers" .
Hydro separators are devices in which solids in suspension are agitated by hydraulic pressure or stirring devices , thus separating the ore . It is normally used to separate the ore from water . Speaking in common sense terms - HYDRO = water , SEPERATOR = device to separate . :P
Rake Classifiers are a type of mechanical classifier which utilize reciprocal rakes on an inclined plane to separate coarse particles from the fine ore . The fine material is overflowed , while the coarse waste material is discharged by means of the inclined plane . 
A TYPICAL HYDRO-SEPARATOR


3) The over-flown product from the rake classifier is then sent into a "Homogenizer" , which allows only one part of the ore , for us , the useful part and from there , it is sent into 3 Flotation Cells - namely Beater , Enriching and Stripping cells . 
A TYPICAL FLOTATION CELL
 Froth Flotation method takes place at these flotation cells . 
The BEATER cell is the place at which the cross-currents of the ore and the Frothing agent meet .
Then , the STRIPPING cell removes the sedimented ore .
The  ENRICHING cell enriches the ore with the froth and thus we obtain pure ore particles in the ore . For more efficiency , the froth reagent water is continuously recovered . 


4)  This product meets the already sent pure product at the hydro-separator , where the suspended ore particles in water are recovered , thus obtaining pure limestone slurry which can be used for cement production .
Note that in wet process we obtain a slurry , while in the dry process we get a powdery mixture itself . 




The reagent water is removed by the hydro-separator , thus giving us PURE BENEFICIATED LIMESTONE ROCK SLURRY , which is ready to be used in the next stage .........Keep logged in !!!