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Keywords:

  • bladed mixer;
  • agitated drying;
  • wet granular flow and particle agglomeration

Abstract

The flow and agglomeration of wet particles in a bladed mixer was studied experimentally using particle image velocimetry and computationally using the discrete element method. The experimental and computational work showed that particle beds at low moisture contents are characterized by enhanced convective and diffusive particle motion as well as enhanced mixing kinetics when compared to dry particle beds. This behavior is attributed to the development of small particle agglomerates which behave like rough, nonspherical particles and enable the transfer of energy from the blades to the particle bed. At higher moisture contents, a different behavior was observed. Particle convective and diffusive motion was hindered by the presence of moisture at higher levels leading to a decrease in mixing performance. This occurs as large agglomerates are formed and are not broken apart by shear leading to poor mixing. Pressure and shear stress profiles were shown to be affected by the amount of moisture in the system. The extent of agglomeration at different moisture contents was quantified via the discrete element simulations. Agglomerate size distributions and morphology were shown to be strong functions of moisture content. © 2012 American Institute of Chemical Engineers AIChE J, 2012