Sedimentation Course Pack
SEDIMENTATION
According to Brown (1950), sedimentation is the separation of a suspension into a supernatant clear fluid and a rather dense slurry containing a higher concentration of solid.
According to Perry (), sedimentation is the partial separation or concentration of suspended solid particles from a liquid by gravity settling. This field may be divided into the functional operations of thickening, whose purpose is to increase the concentration of suspended solids in a feed stream; and clarification whose purpose is to remove a relatively small quantity of suspended particles and produce a clear effluent.
Classification of Settleable Solids
There are different factors to be consider in choosing the type of sedimentation to be used, some of it are particle size, viscosity, solid and solution densities as well as the characteristics of the particles within the slurry.
In this figure, it illustrates the relationship between solid concentration, interparticle cohesiveness and the type of sedimentation that may exist. Totally discrete particles include many mineral particles, salt crystals and similar substances that have little tendency to cohere. The flocculent particles generally include those smaller than 20 micrometer, metal hydroxides, chemical precipitates and most organic substances other than true colloids.
Sedimentation Tests
Determination of Clarification-Zone Requirements
In the treatment of solids suspensions which are in the particulate-settling regime, the usual objective will be the production of a clear effluent and test methods limited to this type of settling will be the normal sizing procedure, although the area demand for thickening should be verified.
Long-Tube Method
A transparent tube 2 to 4 m long and at least 100 mm in diameter (preferably larger), fitted with sampling taps every 200 to 300 mm, is used in this test. The tube is mounted vertically and filled with a representative sample of feed suspension. At
According to Brown (1950), sedimentation is the separation of a suspension into a supernatant clear fluid and a rather dense slurry containing a higher concentration of solid.
According to Perry (), sedimentation is the partial separation or concentration of suspended solid particles from a liquid by gravity settling. This field may be divided into the functional operations of thickening, whose purpose is to increase the concentration of suspended solids in a feed stream; and clarification whose purpose is to remove a relatively small quantity of suspended particles and produce a clear effluent.
Classification of Settleable Solids
There are different factors to be consider in choosing the type of sedimentation to be used, some of it are particle size, viscosity, solid and solution densities as well as the characteristics of the particles within the slurry.
In this figure, it illustrates the relationship between solid concentration, interparticle cohesiveness and the type of sedimentation that may exist. Totally discrete particles include many mineral particles, salt crystals and similar substances that have little tendency to cohere. The flocculent particles generally include those smaller than 20 micrometer, metal hydroxides, chemical precipitates and most organic substances other than true colloids.
Sedimentation Tests
Determination of Clarification-Zone Requirements
In the treatment of solids suspensions which are in the particulate-settling regime, the usual objective will be the production of a clear effluent and test methods limited to this type of settling will be the normal sizing procedure, although the area demand for thickening should be verified.
Long-Tube Method
A transparent tube 2 to 4 m long and at least 100 mm in diameter (preferably larger), fitted with sampling taps every 200 to 300 mm, is used in this test. The tube is mounted vertically and filled with a representative sample of feed suspension. At
References: Brown, George G., et al. Unit Operations. New York: John Wiley & Sons, Inc., 1971. Foust, Alan S., et al. Principles of Unit Operations. 2nd ed. New Jersey: John Wiley & Sons, Inc., 1980. Geankoplis, C.J. Principles of Transport Processes and Separation Processes. 4th edition. New Jersey: Pearson Education, Inc. 2003. McCabe, W.L., and Smith, C. Unit Operations of Chemical Engineering, 5th edition. New York: McGraw-Hill Book Company, 1993. Perry, Robert H. et.al. Perry’s Chemical Engineering Handbook. 7th edition. New York: McGraw-Hill Book Company.1997.