Experimental quantification and modelling of attrition of infant formulae during pneumatic conveying
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Accepted Version
Date
2011-08
Authors
Hanley, Kevin John
Journal Title
Journal ISSN
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Publisher
University College Cork
Published Version
Abstract
Infant formula is often produced as an agglomerated powder using a spray drying
process. Pneumatic conveying is commonly used for transporting this product within a
manufacturing plant. The transient mechanical loads imposed by this process cause
some of the agglomerates to disintegrate, which has implications for key quality characteristics
of the formula including bulk density and wettability. This thesis used both
experimental and modelling approaches to investigate this breakage during conveying.
One set of conveying trials had the objective of establishing relationships between the
geometry and operating conditions of the conveying system and the resulting changes
in bulk properties of the infant formula upon conveying. A modular stainless steel
pneumatic conveying rig was constructed for these trials. The mode of conveying and
air velocity had a statistically-significant effect on bulk density at a 95% level, while
mode of conveying was the only factor which significantly influenced D[4,3] or wettability.
A separate set of conveying experiments investigated the effect of infant formula
composition, rather than the pneumatic conveying parameters, and also assessed the
relationships between the mechanical responses of individual agglomerates of four
infant formulae and their compositions. The bulk densities before conveying, and the
forces and strains at failure of individual agglomerates, were related to the protein
content. The force at failure and stiffness of individual agglomerates were strongly
correlated, and generally increased with increasing protein to fat ratio while the strain
at failure decreased.
Two models of breakage were developed at different scales; the first was a detailed
discrete element model of a single agglomerate. This was calibrated using a novel
approach based on Taguchi methods which was shown to have considerable advantages
over basic parameter studies which are widely used. The data obtained using this
model compared well to experimental results for quasi-static uniaxial compression of
individual agglomerates. The model also gave adequate results for dynamic loading
simulations. A probabilistic model of pneumatic conveying was also developed; this was
suitable for predicting breakage in large populations of agglomerates and was highly
versatile: parts of the model could easily be substituted by the researcher according to
their specific requirements.
Description
Keywords
Dairy powders , Attrition of agglomerates , Discrete element modelling , Taguchi methods , Pneumatic conveying
Citation
Hanley, K.J. 2011. Experimental quantification and modelling of attrition of infant formulae during pneumatic conveying. PhD Thesis, University College Cork.