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Unsuspended mass of solid particles in stirred tanks
Author(s) -
Brucato Alberto,
Brucato Valerio
Publication year - 1998
Publication title -
the canadian journal of chemical engineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.404
H-Index - 67
eISSN - 1939-019X
pISSN - 0008-4034
DOI - 10.1002/cjce.5450760311
Subject(s) - agitator , impeller , rushton turbine , suspension (topology) , mixing (physics) , mechanics , baffle , fraction (chemistry) , mass fraction , turbine , draft tube , materials science , mechanical engineering , engineering , chromatography , physics , chemistry , mathematics , composite material , quantum mechanics , homotopy , pure mathematics
An original technique for the determination of the fraction of unsuspended solid particles at agitation speeds smaller than N js , is proposed. The technique is based on the “twin‐systems” concept and is completed by a suitable tracing and detection technique for the solid phase. Results obtained with a fully baffled tank stirred by a Rushton turbine impeller show that the fraction of solids never leaving the tank bottom can be simply correlated to the ratio between agitation speed and Zwietering's complete suspension speed. It is shown that at agitator speeds of about 80% of Zwietering's complete suspension speed, practically all particles but a few, are already suspended. This finding implies that large energy and installation cost savings can be achieved, with respect to current design practices, without significantly affecting the solid‐liquid mixing performance.