Prediction of just suspended speed for mixed slurries at high solids loadings


Ayranci İ., Ng T., Etchells A. W. , Kresta S. M.

CHEMICAL ENGINEERING RESEARCH & DESIGN, vol.91, no.2, pp.227-233, 2013 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 91 Issue: 2
  • Publication Date: 2013
  • Doi Number: 10.1016/j.cherd.2012.08.002
  • Journal Name: CHEMICAL ENGINEERING RESEARCH & DESIGN
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Page Numbers: pp.227-233
  • Keywords: Just suspended speed, Stirred tank, Power model, Momentum model, Mixture, High solids loading, MIXING CHARACTERISTICS, COMPLETE SUSPENSION, LIQUID, CLEARANCE, PARTICLES, MODERATE
  • Middle East Technical University Affiliated: Yes

Abstract

One design heuristic used to determine the just suspended speed, N-js, for mixed slurries assumes that the mixture N-js is dominated by the particle phase with the maximum N-js. This approach does not incorporate the effect of the second solid phase. Two new models are proposed to predict the mixture N-js: the power model and the momentum model. These models determine the mixture N-js using the sum of the power or the sum of the momentum required to suspend the individual solid phases. The models were tested using experimental data for two impellers, a Lightnin A310 impeller and a 45 degrees pitched-blade turbine. A range of off-bottom clearances, and six mixtures of solids up to 27 wt% solids loading completed the data set. The power model accurately predicts mixture N-js for both impellers over the full range of clearances and up to 27 wt% mixtures. (c) 2012 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.