Growth regime map for liquid-bound granules: further development and experimental validation

Iveson, Simon M., Wauters, Philippe A. L., Forrest, Sarah, Litster, James D., Meesters, Gabrie M. H. and Scarlett, Brian (2001) Growth regime map for liquid-bound granules: further development and experimental validation. Powder Technology, 117 1-2: 83-97. doi:10.1016/S0032-5910(01)00317-5

Author Iveson, Simon M.
Wauters, Philippe A. L.
Forrest, Sarah
Litster, James D.
Meesters, Gabrie M. H.
Scarlett, Brian
Title Growth regime map for liquid-bound granules: further development and experimental validation
Journal name Powder Technology   Check publisher's open access policy
ISSN 0032-5910
Publication date 2001-06-04
Sub-type Article (original research)
DOI 10.1016/S0032-5910(01)00317-5
Volume 117
Issue 1-2
Start page 83
End page 97
Total pages 15
Editor J. P. K. Seville
Place of publication Amsterdam, The Netherlands
Publisher Elsevier
Collection year 2001
Language eng
Subject C1
290699 Chemical Engineering not elsewhere classified
670499 Other
670601 Chemical fertilisers
Abstract An attempt was made to quantify the boundaries and validate the granule growth regime map for liquid-bound granules recently proposed by Iveson and Litster (AlChE J. 44 (1998) 1510). This regime map postulates that the type of granule growth behaviour is a function of only two dimensionless groups: the amount of granule deformation during collision (characterised by a Stokes deformation number, St(def)) and the maximum granule pore saturation, s(max). The results of experiments performed with a range of materials (glass ballotini, iron ore fines, copper chalcopyrite powder and a sodium sulphate and cellulose mixture) using both drum and high shear mixer granulators were examined. The drum granulation results gave good agreement with the proposed regime map. The boundary between crumb and steady growth occurs at St(def) of order 0.1 and the boundary between steady and induction growth occurs at St(def) of order 0.001. The nucleation only boundary occurs at pore saturations that increase from 70% to 80% with decreasing St(def). However, the high shear mixer results all had St(def) numbers which were too large. This is most likely to be because the chopper tip-speed is an over-estimate of the average impact velocity granules experience and possibly also due to the dynamic yield strength of the materials being significantly greater than the yield strengths measured at low strain rates. Hence, the map is only a useful tool for comparing the granulation behaviour of different materials in the same device. Until we have a better understanding of the flow patterns and impact velocities in granulators, it cannot be used to compare different types of equipment. Theoretical considerations also revealed that several of the regime boundaries are also functions of additional parameters not explicitly contained on the map, such as binder viscosity. (C) 2001 Elsevier Science B.V. All rights reserved.
Keyword Engineering, Chemical
Growth Regime Map
High-shear Mixer
Granulation Mechanisms
Q-Index Code C1

Document type: Journal Article
Sub-type: Article (original research)
Collection: School of Chemical Engineering Publications
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Created: Tue, 14 Aug 2007, 16:26:47 EST