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

Ayrancı Tansık, İnci
Ng, Theodore
Etchells, Arthur W.
Kresta, Suzanne M.
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.