QUALITY CHANGES, DUST GENERATION, AND COMMINGLING ...

In DEM modeling, particle interaction is treated as a dynamic process, which assumes
that equilibrium states develop whenever internal forces in the system balance (Theuerkauf et al.,
2007). Contact forces and displacement of a stressed particle assembly are found by tracking the
motion of individual particles. Motion results from disturbances that propagate through the
assembly. Mechanical behavior of the system is described by motion of each particle and force
and moment acting at each contact.
Newton’s law of motion gives the relationship between particle motion and the forces
acting on each particle, and particles are assumed to interact only at contact points. Thus, their
motion is independent of the other particles. The soft-sphere approach commonly used in DEM
models allows the particles to overlap each other, giving realistic contact areas. Overlaps,
however, are assumed to be small in relation to particle size. Force-displacement laws at the
contacts can be represented by a Hertz-Mindlin no-slip contact model (Mindlin, 1949; Mindlin
and Deresiewicz, 1953; Tsuji et al., 1992; Di Renzo and Di Maio, 2004, 2005). Normal and
tangential forces, velocities, and related parameters are described by appropriate equations from
the mechanics of particles (Tsuji et al., 1992; DEM Solutions, 2009; Remy et al., 2009).
With demand for high-quality grain and feed, research to ensure safety and purity of the
grain and minimize dust emissions during elevator handling is vital. Repeated handling data on
quality and durability of corn-based alternative feed pellets compared with data for shelled corn
is valuable to improve feed handling and transportation procedures. A dust study to fill the gap
where no complete PSD is available for wheat and corn dusts and provide more specific data,
particularly on small particle sizes, is needed. A validated mechanistic model to accurately
predict grain commingling in grain elevators is important for extending the knowledge of grain
commingling beyond the few current experimental studies.
1.4 Research Objectives
The overall objective of this research was to characterize the quality of grain and feed
during handling in a bucket elevator in terms of durability, purity, and safety to improve
transportation and handling practices for grain and feed handlers. Specific objectives were to
(1) determine the effects of repeated handling on the quality of feed pellets and shelled
corn;
(2) characterize the dust generated during corn and wheat handling;
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