Screens, separating revolving

The feed-preparation screen between crusher and separately vessel may be of either the revolving or the vibrating type. Wash water is apphed only to the feed end ofthe screen so that the process feed will enter the separator moist but without any free water, which would lower pulp density. In a few instances it has been found advantageous to provide for surge storage between screen and separator to drain off further excess water. 

Size separation of particles. Use a grizzly of spaced, inclined, vibrated parallel bars to remove large particles greater than 2 inches in diameter. Use a revolving cylindrical perforated screen to remove intermediate-size particles in the size range of 0.25 inch to 1.5 inches in diameter. Use flat, inclined woven screens (U.S. standard) that are vibrated, shaken, or impacted with bouncing balls to separate small particles in the size range of 3 to 80 mesh. Use an air classifier to separate fine particles smaller than 80 mesh. 

Revolving screen Trommel particle diameter 3 mm to 50 cm feed solids concentration 5 to 25%. Use separation. 

Revolving screen centrifugal particle diameter 400 to 1200 jtm Use dewater, separate intermediate diameters and use high speed for fines. 

Revolving screen probability particle diameter < 6 mm Use separate intermediate and fines 45 to 4750 rm. 

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