Centrifugal sedimentation types

Characteristics of the performance of the main types of commercial SLS equipment are summarized in Table 11.3. The completeness of the removal of liquid from the solid and of solid from the liquid may be important factors. In some kinds of equipment residual liquid can be removed by blowing air or other gas through the cake. When the liquid contains dissolved substances that are undesirable in the filter cake, the slurry may be followed by pure water to displace the residual filtrate. Qualitative cost comparisons also are shown in this table. Similar comparisons of filtering and sedimentation types of centrifuges are in Table 11.19. 

Characteristics of centrifugal filters and sedimentation centrifuges are in Table 11.19. The filtering types are made to handle from less than 5 tons/hr to more than 100 tons/hr of solids, with g-levels ranging from 30 to 3000. For sedimentation types, theg-levels listed... 

This entry has presented a brief description of sedimenting and filtering centrifuges. The types of separation, separation duties, and modes of operation have been discussed. The basic common and distinct mechanical elements have also been dealt with. References are included for those readers seeking a more in-depth historical, theoretical, as well as practical background on the subject. 

Sedimentation centrifuge disc type drop diameter >20 and <200 pm feed concentration 6 to 60% v/v suited for low surface tension, density differences >0.02 Mg/m. Solids contamination <0.1% v/v. Use differential type for drop diameter >200 pm feed concentration 6 to 60% v/v suited for low surface tension, density differences >0.05 Mg/m. Solids contamination <0.1% v/v. 

Equation 8 provides the basis of comparison for the performance of various bottle centrifuges having the same material, and also, under certain circumstances, of other types of sedimentation centrifuges, if geometric dissimilarities are also considered. 

The Z-concept permits scale-up between sinulat centrifuges solely on the basis of sedimentation performance. Other criteria and limitations, however, should also be investigated. Scale-up analysis for a specified sohds concentration, for instance, requires knowledge of sohds residence time, permissible accumulation of sohds in the bowl, G level, sohds conveyabihty, flowabihty, compressibihty, limitations of torque, and sohds loading. Extrapolation of data from one size centrifuge to another calls for the apphcation of specific scale-up mechanisms for the particular type of centrifuge and performance requirement. 

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