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      Blaine Specific Surface Area - First part            
                             
      1 Introduction:                  
        - Cement fineness is expressed either in terms of Particle Size Distribution (PSD) with residues (or passing) on reference
          sieves or by its specific surface area in Blaine.            
        - In this presentation, we will develop the Blaine method which is the most widely used in the world of cement.  
        - As we know, cement contains grains (particles) of very different sizes and shapes.      
        - The diameter can vary between less than 1 μ up to approximately 100 μ.        
        - Of these particles, it is the smallest ones that offer the largest area in relation to the volume.    
        - It is therefore these small particles which, during the concrete mixing, present the greatest number of contacts with water and
          participate most actively to the phenomena of setting and hardening.        
        - It can also be said that the total surface area of the cement particles is inversely proportional to their diameter.  
        - If the following two conditions are met:            
          * All particles have the same diameter              
          * All particles are spheric                
        - We have the following table:              
         
     
     
           
           
           
           
           
           
           
        - The following table gives the diameter for usual Blaine values (always with the 2 hypotheses above):    
         
     
                 
                       
                       
                       
                       
                       
                       
                       
        - The calculation below gives you the diameter of the spherical particles as a function of Blaine:    
        - Put the Blaine:                
          Blaine cm2/g              
        - Calculation of the diameter of the particle:            
          Diameter microns              
                             
      2 Usual Blaine values inside the cement ball mill:            
      2.1. Mill in open circuit:                
        - Cement fineness: 3000 Blaine              
        - The sheet below gives a good idea of the Blaine value in the finished compartment (*)      
          (*) Blaine analysis of the first compartment are generally not realized due to the too coarse product      
         
     
                     
                             
                             
                             
                             
                             
                             
                             
                             
                             
                             
                             
                             
                             
                             
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        - The sheet below gives a good idea of the Blaine value evolution in the circuit        
         
     
                     
                             
                             
                             
                             
                             
                             
                             
                             
                             
        - The mill ventilation in open circuit is limited and the product of the filter is normally very fine.    
        - The quantity of the filter product in the finished product is calculated with the following formulas:    
         
     
             
                   
          Or:                  
         
     
                   
                         
         
     
     
           
           
          Or:                  
         
     
               
                     
          And finally:                  
         
     
                 
                       
                       
         
     
                   
                         
        - In this case:                  
         
     
           
                 
                 
         
     
               
                     
        - Small calculator, enter the values:              
              Blaine              
          Mill product              
          Filter product              
          Finished product              
          Mill product in %  %            
          Filter product in % %            
        - A fineness till to 3500 Blaine is possible with an acceptable energy consumption in open circuit.    
      2.2. Mill in closed circuit -inside the mill:              
        - For all finenesses, the evolution of the Blaine is similar in the second chamber because the final fineness of the cement is given 
          by the separator.                
        - The sheet below gives a good idea of the Blaine value in the finished compartment:      
         
     
                     
                             
                             
                             
                             
                             
                             
                             
                             
                             
                             
                             
                             
                             
                             
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      2.3. Mill in closed circuit - separator of the first generation - 3200 Blaine cement target :      
        - See a typical flow-sheet with the Blaine of the samples taken in the circuit:        
         
     
         
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
        - Names of the samples are:               
         
     
                 
                       
                       
                       
                       
                       
                       
                       
        - The Blaine value of the separator rejects is high.            
        - It means that a lot of very fines particles goes back to the mill.          
        - This is generally the situation with a separator of the first generation which doesn't have a good efficiency.  
        - The Blaine value of the filter is lower than the separator fines because there is more air from the mill.    
        - Calculation of the circulation factor with Blaine value:          
         
     
                 
                       
                       
        - With:                  
          c  =  circulation factor                
          Blainep = Blaine of the separator fines              
          Blainef = Blaine of the separator feed              
          Blainer = Blaine of the separator rejects            
        - In this case:                  
         
     
                 
                       
                       
        - Small calculator, enter the values:              
              Blaine              
          Separator feed              
          Separator rejects              
          Separator fines              
          Circulation factor              
                             
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