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      Pre-grinding systems        
                   
      3   Roller Press (suite 4)        
         3.10 Particle size results of the press:        
        - Here below is an example of particle size at the roller press output for clinker:    
         
     
           
                 
                 
                 
                 
                 
                 
                 
                 
                 
                 
        - Here below, the RRSB diagram of the product leaving the press and the feed:    
         
     
           
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
        - It may be observed that the product leaving the press has a high proportion of fine particles,  
          35% smaller than 90μ.        
        - This is confirmed by the reduction rate:        
         
     
       
             
             
             
             
             
             
             
             
             
        - The reduction ratio is inversely proportional to the particle size.      
         3.11 Elements of sizing considerations:        
         3.11.1 Density of the cakes        
        - It is known that the density of the cakes at the output of the roller press is greater than the density of the fresh
          material feeding the press.        
        - One can know that density by applying the following formula:      
         
     
           
                 
                 
          With:        
          ρ is the density in t/m3        
          T is the throughput of the press in t/h        
          T is the output U in t/h multiplied by the circulation factor c      
          l is the width of the rollers in m        
          e is the distance (gap) between rollers or thickness of cakes in m      
          v is the peripheral speed in m/s        
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        - Example of calculation:        
          * Output U = 160 t/h        
          * Circulation factor c = 2,5        
          * Width of rollers l = 0,9 m        
          * Thickness of cakes e = 0,035 m        
          * Rollers speed v = 1,50 m/s        
          Calculation and result:        
          * Throughput of the press T = 160.2,5 = 400 t/h      
          * Density of the cakes:        
         
     
         
               
               
        - Usual density values:        
          * Limestone: 2,2 - 2,4 t/m3        
          * Clinker: 2,3 - 2,6 t/m3        
          * Slag: 2,1- 2,3 t/m3        
         3.11.2 Typical values of working angles        
        - Working angles of the mobile and fixed rolls are respectively αc1 and αc2.    
        - These two angles are equal and depend on the type of material.      
        - One can also define the angle δ which is related to the above two angles by the equation:  
         
     
           
                 
        - See figure below:        
         
     
           
                 
                 
                 
                 
                 
                 
                 
        - The usual values of these angles are:        
         
     
       
             
             
             
             
             
         3.11.3 Absorbed power of the press        
        - The absorbed power of the roller press is directly proportional to the friction angle αf.  
        - The usual values generally accepted for this angle are:      
         
     
           
                 
                 
                 
                 
        - The formula to calculate the absorbed power is as follows:      
         
     
         
               
               
          With:        
          P is the absorbed power in kW        
          F is the applied force in kN        
          αf is the friction angle in degrees        
          v is the peripheral speed in m/s        
          η is the efficiency of the transmission and motor      
        - Example of calculation:        
          * Rollers speed v = 1,50 m/s        
          * RP force F = 9700 kN        
          * Angle αf = 2°        
          * Efficiency η = 0,96        
          Calculation and result:        
         
     
       
             
             
                   
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