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      Separators in the cement industry              
                               
      7   Third generation separators:              
      7.1   Introduction:                  
          - Also called: Cage separators or High Efficiency Separators.          
          - These separators has been developed in the beginning of the eighties (O'Sepa from Onoda Cement).    
          - As the second generation, the air flow required for the separation is produced by an external fan.    
          - The separator material feed is carried out mechanically by means of suitable continuous conveyors.    
          - Fines are conveyed by air in external cyclones or directly to a bag filter.        
          - The main separating device is a cylindrical rotor. The rotor is like a cage composed of blades closely spaced.  
          - The rotor is operated by a variable speed drive.             
          - The rotor speed determines swirl in the classifying zone and therefore the cut of the separator.    
          - The composition of forces acting in the separating zone is showed in the figure below:      
           
         		        
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
          - Here a non-exhaustive list of High Efficiency separators:           
            - O'Sepa (FLSmidth)              
            - Sepol (Polysius)              
            - Sepax (FLSmidth)              
            - SD (Sturtevant)              
            - Sepmaster (KHD)              
            - QDK (Pfeiffer)              
            - TSV (FCB)                
            - O&K (Orenstein & Koppel AG)            
            - PRESEP VTP (PSP Engineering a.s.)            
            - CTC SERIES (CEMTEC)              
            - Cemag (CMP AG)              
            - Copies from China              
      7.2   Advantages of 3rd generation dynamic separators:            
          - Possibility of mechanical adjustments              
          - Possibility of very large flow rates              
          - Flexibility to produce products of different qualities          
          - Better efficiency than the conventional and cyclones separators          
          - Reduction of mill specific consumption            
          - Increase of the grinding capacity              
          - Reduction of the cement temperature              
          - Better cement quality (Straighter RRB curve giving better 28 days and early strengths)      
      7.3   Disadvantages of 3rd generation dynamic separators:            
          - Difficulty to get the optimum seal system            
          - No constant velocity of flow and no constant centrifugal acceleration of particles can affect the efficiency  
      7.4   General principle of operation:              
          - The material is generally fed at the top of the separator.          
          - There are 2 or more feed chutes in order to improve the dispersion of the material on the distribution plate.  
          - Material falls and is dispersed in the circulating air by the distribution plate.        
          - The feed forms a thin cylindrical curtain of material in the classifying zone.        
          - The air stream is generated by an external fan.            
          - According to the type of circuit, it is possible to have 100% of fresh air, a part of the air recirculated or 100% of the air  
            recirculated.                
          - Often, there are a primary air inlet, a second air inlet and also a tertiary air inlet depending of the design.  
          - The airflow leaves the guide vanes almost tangentially to the outside of the cage.      
          - Material is arriving in the separation zone between the guide vanes (or louvres) and the rotating cage.    
          - The particles are driven by three forces: The centrifugal force due to the dispersing plate      
            * The centrifugal force due to the dispersing plate            
            * The drag force due to the air flow              
            * The gravity due to the mass of the particule            
          - The drag force is trying to pull the material into the rotating cage.        
          - The centrifugal force is trying to push the material toward the guide vanes.        
          - It is the balance of these forces which induces a regular cut size of the separator.      
          - This balance remaining steady because the material in the classifying zone has always the same radius of rotation,  
            then the centrifugal force is the same in all areas.            
          - On the other hand, the air and material are normally distributed uniformly, the air velocity (then, drag force) remains equal.
          - The coarse material doesn't enter in the rotating cage and goes out by gravity up to the bottom device (cone or other).
          - The fine material enters in the cage and exits with the air flow by the upper or lower part of the separator.  
          - See the figure below (from the O'Sepa):            
           
         		      
                 
                 
                 
                 
                 
                 
                 
                 
                 
                 
                 
                 
                 
                 
                 
                 
                 
                 
                 
                 
                 
                 
                 
                 
            Warning:                  
            * Suppliers propose generally a version for raw and cement mill circuits where the gas and the material are going  
            out together of the mill and enter from the bottom of the separator.        
            * Some suppliers propose also special versions for circuits with pre-grinding systems (Roller Press).    
            * Principles of operation described in this page only present the classical version for grinding circuits with  
            bucket elevator for the material feed.              
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      7.5   Principle of operation for each design:              
          O'Sepa (FLSmidth):                
          - The material enters through the top of the separator.          
          - Material falls and is dispersed by the distribution plate.          
          - The primary and secondary air creates a vortex in the separating zone.        
          - The material falls between the rotor and the louvres.          
          - Fines are aspirated.                
          - Coarse particles are accelerated by the rotor and held by the guide vanes, which slide out of the separator through  
            the lower part.                
          - The fine material exits with the airflow through the upper part of the housing.      
          - As a certain number of fines particles are entrained downwards with coarse particles, the tertiary air flow  
            helps to pick up any fines in the rejects.            
          - The fineness of the product is adjusted by the speed of the rotor.        
          - Website of the separator: http://www.flsmidth.com        
          - See the figure above                
          Sepol (Polysius):                
          - The material enters through the top of the separator.          
          - Material falls and is dispersed by the distribution plate.          
          - There is one tangential air inlet.              
          - The material falls between the rotor and the louvres.          
          - Fines are aspirated.                
          - Coarse particles are accelerated by the rotor and held by the guide vanes, which slide out of the separator through  
            the lower part.                
          - The fine material exits with the airflow through the lower part of the housing.      
          - The fineness of the product is adjusted by the speed of the rotor.        
          - Website of the separator: www.polysius.com          
          - See the figure below:                
           
         		            
                       
                       
                       
                       
                       
                       
                       
                       
                       
                       
                       
                       
                       
                       
                       
                       
                       
                       
                       
          Sepax (FLSmidth):                
          - The sepax differs by a body divided into two parts: dispersion and separation parts.      
          - The material enters through the middle of the separator on one side.        
          - Air enters from the bottom of the separator.            
          - Material is carried with the air to the upper part of the separator.        
          - Material enters in the classification area between the rotor and the guide vanes.      
          - Coarse particles are accelerated by the rotor, held by the guide vanes and slide up to the rejects cone.    
          - Fines are aspirated with air flow through the rotating cage and exit through the upper part of the separator.  
          - The fineness of the product is adjusted by the speed of the rotor.        
          - Website of the separator: http://www.flsmidth.com        
          - See the figure below:                
           
         		            
                       
                       
                       
                       
                       
                       
                       
                       
                       
                       
                       
                       
                       
                       
                       
                       
                       
                       
                       
                       
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          SD (Sturtevant):                
          - The material enters through the top of the separator.          
          - Material falls and is dispersed by the distribution plate.          
          - The tangential air inlet is in the upper part of the separator.          
          - Various tangential air inlets can be realized.            
          - The material falls between the rotor and the louvres.          
          - Fines are aspirated.                
          - Coarse particles are accelerated by the rotor and held by the guide vanes, which slide out of the separator through  
            the lower part.                
          - Some models have horizontal louvres.            
          - The fine material exits with the airflow through the upper part of the housing.      
          - The fineness of the product is adjusted by the speed of the rotor.        
          - Website of the separator: sturtevantinc.com          
          - See the figure below:                
           
         		        
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
          Sepmaster (KHD):                
          - The material enters from the top of the separator.            
          - The air stream is generated by an external fan.            
          - The material falls between the rotor and the louvres.          
          - Fines are aspirated.                
          - Coarse particles are accelerated by the rotor and held by the guide vanes, which slide out of the separator through  
            the lower part.                
          - The fine material exits with the airflow through the upper part of the housing.      
          - The fineness of the product is adjusted by the speed of the rotor.        
          - Motor and reducer are on the bottom of the device.          
          - Website of the separator: www.khd.com          
          - See the figure below:                
           
         		        
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
          QDK (Pfeiffer):                
          - The material enters through the top of the separator.          
          - Material falls and is dispersed by the distribution plate.          
          - There is one tangential air inlet.              
          - The material falls between the rotor and the louvres.          
          - Fines are aspirated.                
          - Coarse particles are accelerated by the rotor and held by the guide vanes, which slide out of the separator through  
            the lower part.                
          - The fine material exits with the airflow through the upper part of the housing.      
          - The fineness of the product is adjusted by the speed of the rotor.        
          - Website of the separator: www.christianpfeiffer.net        
          - See the figure below:                
           
         		        
                    
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
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          TSV (FCB):                  
          - The material enters through the top of the separator.          
          - There is one tangential air inlet.              
          - The fine material exits with the airflow through the top of the housing.        
          - The fineness of the product is adjusted by the speed of the rotor.        
          - Website of the separator: www.fivesgroup.com          
          - See the figure below:                
           
         		          
                     
                     
                     
                     
                     
                     
                     
                     
                     
                     
                     
                     
                     
                     
                     
                     
                     
                     
                     
          O&K (Orenstein & Koppel AG):              
          - The material enters through the top of the separator.          
          - Material falls and is dispersed by the distribution plate.          
          - There is one tangential air inlet.              
          - The material falls between the rotor and the louvres.          
          - Fines are aspirated.                
          - Coarse particles are accelerated by the rotor and held by the guide vanes, which slide out of the separator through  
            the lower part.                
          - The fine material exits with the airflow through the lower part of the housing.      
          - The fineness of the product is adjusted by the speed of the rotor.        
          - See the figure below:                
           
         		        
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
          PRESEP VTP (PSP Engineering a.s.):              
          - The material enters through the top of the separator.          
          - Material falls and is dispersed by the distribution plate.          
          - There is one or various tangential air inlets.            
          - The material falls between the rotor and the louvres.          
          - Fines are aspirated.                
          - Coarse particles are accelerated by the rotor and held by the guide vanes, which slide out of the separator through  
            the lower part.                
          - The fine material exits with the airflow through the lower part of the housing.      
          - Website of the separator: www.pspeng.cz          
          - See the figure below:                
           
         		          
                     
                     
                     
                     
                     
                     
                     
                     
                     
                     
                     
                     
                     
                     
                     
                     
                     
                     
                     
                     
                     
                     
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          CTC SERIES (CEMTEC):                
          - The material enters through the top of the separator.          
          - There is one tangential air inlet.              
          - The fine material exits with the airflow through the top of the housing.        
          - The fineness of the product is adjusted by the speed of the rotor.        
          - Website of the separator: http://www.cemtec.at          
          - See the figure below:                
           
         		      
                 
                 
                 
                 
                 
                 
                 
                 
                 
                 
                 
                 
                 
                 
                 
                 
                 
                 
                 
                 
                 
                 
                               
          Cemag (Cement and Mining Processing (CMP) AG)            
          - The material enters through the top of the separator.          
          - Material falls and is dispersed by the distribution plate.          
          - There are two tangential air inlets.              
          - The material falls between the rotor and the guide vanes.          
          - Fines are aspirated inside the rotor.              
          - Coarse particles are accelerated by the rotor and held by the guide vanes, which slide out of the separator through  
            the lower part.                
          - The fine material exits with the airflow through the lower part of the separator.      
          - Website of the separator: ww.cmpag.com          
          - See the figure below:                
           
         		      
                 
                 
                 
                 
                 
                 
                 
                 
                 
                 
                 
                 
                 
                 
                 
                 
                 
                 
                 
                 
                 
                 
                 
                 
                 
                           
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