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Tuesday, March 5, 2013

CONINUOUS FILTRATION

CONTINUOUS FILTRATION
Since testing and scale-up are different for batch and continuous filtration, discussion in this section will be limited to continuous filtration.
It is both convenient and reasonable in continuous filtration, except for precoat filters, to assume that the resistance of the filter cloth plus filtrate drainage is negligible compared to the resistance of the filter cake and to assume that both pressure drop and specific cake resistance remain constant throughout  the filter cycle. Equation  (18-54), integrated  under these conditions, may then be manipulated  to give the following relationships:



where  W  is the  weight of dry filter cake solids/unit  area, Vf is the volume of cake formation filtrate/unit area, Vw     is the volume of cake wash filtrate/unit area, Θf  is the cake formation time, Θw is the cake wash time, and N is the wash ratio, the volume of cake wash/volume of liquid in the discharged cake.
As long as the suspended solids concentration  in the feed remains constant, these equations lead to the following convenient correlations:

There are two other useful empirical correlations as follows:

where R is percent remaining—the percent of solute in the unwashed cake that remains after washing.

Genk, Wayne J., dkk. 2008. Perry’s chemical engineers handbook,  Section 18: Liquid-solid Operations and equipment. New York: The McGraw-Hill Companies, Inc

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