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      Cement ball mill (2 compartments) sizing with Bond method      
      Warning: This calculator gives a rough and initial idea for sizing a cement ball mill.    
      To go ahead, a deeper study is necessary with ball mills suppliers.      
                 
      Date         
      Company/Plant
                 
      Mill size calculation is for
           
    1 Fresh feed characteristics:          
      Warning: It is always necessary to take into account the coarsest cement, that to say the cement   
      giving the most important production for sizing a ball mill!        
      Composition: Name: Percent: Work index: Specific gravity:  
          % kWh/t kg/dm3  
       
     
       
     
       
     
       
     
       
     
        Total:  
                 
      Fresh feed 80% of passing: Name: F80:      
        mm    
        mm    
        mm    
        mm    
        mm    
        Total: mm      or µm
                 
    2 Fineness target:          
      Fineness Blaine cm2/gr      
      Fineness Blaine corrected (*) cm2/gr      
      (*) In case of pozzolana, limestone or trass          
      Fineness on a sieve
    µm residue %
      (*) For raw meal, 90µ is generally used          
      Sieve for 80% of Passing µm      
    3 Production target: t/h      
    4 Bond formula for cement ball mills:          
     
     
           
             
             
             
     
     
             
               
      where C1 is a correction for dry grinding,        
      C2 is a correction for open circuit, not used here        
      C3 is a correction for mill diameter,          
      C4 is a correction for feed size,          
      C5 is a correction for product fineness.          
      C6 is a correction for high-efficiency separators.        
     
     
             
               
     
     
     
       
     
     
           
     
     
           
             
             
     
     
       
         
         
         
         
         
     
     
           
             
             
     
     
         
           
    5 Efficiency factors:          
      Type of process (C1)
       C1 =  
      Open or closed circuit (C2)
       C2 =  
      Choose a temporary diameter m C3 =  
      Diameter inside liners m      
      Correction for feed size     C4 =  
      Correction for product fineness size     C5 =  
      Correction for HE separators
      C6 =  
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    6 Estimated mill specific energy: kWh/t at the shaft    
    7 Absorbed power required: kW      
      Type of transmission
    gives an efficiency of  
      Absorbed power to the terminals kW      
      Real mill specific energy kWh/t at motor terminals    
    8 Ball mill sizing (2 compartments) calculation:        
      Length/Diameter Ratio        
     
     
              
               
               
               
               
      Usefull length  m      
      Critical speed rpm      
      Mill speed (*) rpm or of the critical speed
      (*) Modern mills have a speed of rotation between 70 and 75% of the critical speed!    
      First compartment:          
      Required specific power kWh/t (Respect the usual values)  
     
     
           
             
             
             
             
             
             
      Real specific power (*) kWh/t      
      (*) Taking into account slag, fly ash and filler         
      Required power for Chamber 1 kW      
      Estimated filling degree (*) %      
      (*) usually between 27% and 33%           
      Length of the first chamber m (*)      
      (*) If DIN configuration, choose the closest value taking into account: 0 - 0,25 - 0,50 - 0,75 m    
      Length of the first chamber (DIN) m      
      New absorbed power of Chamber 1 kW at motor terminals    
      New specific power kWh/t      
      Length of the second chamber m (*)      
      (*) If DIN configuration, choose the closest value taking into account: 0 - 0,25 - 0,50 - 0,75 m    
      Length of the 2nd chamber (DIN) m      
      Estimated filling degree (*) %      
      (*) usually between 25% and 33%          
      Absorbed power of Chamber 2 kW at motor terminals    
      Mill absorbed power kW at motor terminals (*)  
      Precision with the absorbed power required by the Bond formula (*) --->
      (*) If this value is much different (more than ± 2%) than the value found in the point 5, begin again the  
      calculation by changing the diameter value in point 5, the L/D ratio, the mill speed, the filling degree,  
      and respecting the usual values!          
    9 Other power correction factors:          
      50% or more slag in the fresh feed        
      Alumina cement        
      Retention rings in chamber 2
           
      Cylpebs in chamber 2
           
      New chamber 1 absorbed power kW at motor terminals    
      New chamber 2 absorbed power kW at motor terminals    
      New mill absorbed power kW at motor terminals    
    10 Ball mill final dimensions:          
      Width of the internals:          
      Feed end liners mm      
      Intermediate diaphragm (*) mm      
      (*) In case of central discharge mill (double rotator), it becomes the central discharge diaphragm!          
      Outlet diaphragm (*) mm      
      (*) In case of central discharge mill (double rotator), it becomes the feed end liners of chamber 2!    
      Final dimensions:          
      Shell Diameter m      
      Inside diameter m      
      Liners thickness average mm (*)      
      (*) In reality, thickness of first compartment liners is higher and of second compartment liners is lower!    
      Total mill length flange to flange m      
      Mill speed  rpm      
      Chamber 1:          
      Useful Length m of the total length
      Ball charge tons or % Volume load
      Chamber 2:          
      Useful Length m      
      Ball charge tons or % Volume load
    11 If necessary, drying chamber (for raw mill):        
      Drying chamber?
           
        Name: Moisture:      
      Maximum moisture of the fresh feed %H2O    
        %H2O    
        %H2O    
        %H2O    
        %H2O    
        Total moisture %H2O   or liters/h
      Diameter of the drying chamber (*) m       
      (*) is generally the same as the grinding section or slightly lower        
      Required volume m3      
      Required length m       
      (*) If DIN configuration, choose the closest value taking into account: 0 - 0,25 - 0,50 - 0,75 m    
      Chosed DIN length m      
      Drying chamber absorbed power kW      
    12 Required installed power:          
      Total Mill absorbed power kW      
      Installed power kW      
                 
      Warning: This calculator gives a rough and initial idea for sizing a cement ball mill.    
      To go ahead, a deeper study is necessary with ball mills suppliers.      
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    All rights reserved © 2012-2015 The Cement Grinding Office