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- Title
The effect of off-wall clearance of a side-entering impeller on the mixing of pulp suspensions in a cylindrical stock chest.
- Authors
Bhole, Manish R.; Hui, Leo K.; Gomez, Clara; Bennington, Chad P. J.; Dumont, Guy A.
- Abstract
For a side-entering impeller of diameter D, the clearance from the off-wall ( E) is characterised by E/ D and it affects the mixing quality attained in a pulp stock chest. For agitation of pulp suspensions, mixing can be characterised by the size of cavern produced by the impeller. In this work, we have investigated cavern size as a function of the impeller off-wall clearance in a laboratory-scale cylindrical stock chest. Hardwood pulp suspensions of Cm = 2%, 3%, and 4% (fibre mass concentration) were agitated using an axial flow impeller with E/ D varied from 0.14 to 0.68. Cavern size was measured using electrical resistance tomography (ERT) in batch operation and dynamic mixing tests in continuous operation, with cavern size increasing with increasing E/ D. At E/ D = 0.14, throttling of the impeller suction occurred which reduced cavern size. Computational fluid dynamic (CFD) simulations for steady state operation under-predicted the cavern size, but correctly captured the trend in cavern size variation with E/ D. The measured cavern volumes compared well with predictions of an axial force model that accounted for interaction between the cavern and the vessel walls only when impeller throttling was absent.
- Subjects
IMPELLERS; MIXING; PULPWOOD; COMPUTATIONAL fluid dynamics; COMPUTER simulation
- Publication
Canadian Journal of Chemical Engineering, 2011, Vol 89, Issue 5, p985
- ISSN
0008-4034
- Publication type
Article
- DOI
10.1002/cjce.20503