ISSN:
0930-7516
Keywords:
Chemistry
;
Industrial Chemistry and Chemical Engineering
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Process Engineering, Biotechnology, Nutrition Technology
Notes:
In stirred systems, the presence of solid particles leads to a pronounced lengthening of mixing time, sometimes to over 10 times that for the single-phase state. The mixing behaviour is strongly heterogeneous, since the slurry is mixed comparatively rapidly, while markedly slower homogenization occurs in the solid-free zone. This is the consequence of different fluid velocities in the two regions. For particle settling velocities in excess of 5 cm/s, mixing times assume maximum values on reaching the state of complete suspension. By contrast, at lower settling velocities, maximum mixing times occur before suspension is complete. Mixing times are influenced only be the state of suspension and not by the mode of its generation. Consequently, for the fulfilment of the 90% suspended slurry height criterion, mixing times are independent of stirrer speed, solid concentration, type of agitator or diameter ratio d/D. The effects of particle diameter, viscosity and equipment dimensions on mixing time, when the 90% slurry height criterion is fulfilled, are reflected by the ratio of the vessel diameter to a representative liquid velocity.
Additional Material:
11 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/ceat.270150505
