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CFD-DEM simulations of early turbulent solid–liquid mixing: Prediction of suspension curve and just-suspended speed

Bruno Blais, Olivier Bertrand, Louis Fradette, François Bertrand

Article (2017)

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Abstract

Solid–liquid mixing as a unit operation still faces considerable challenges, notably regarding the prediction of the impeller speed required to suspend the particles (Njs), the fraction of suspended solids and the homogeneity of the suspension at a given speed. In this work, we extend to the turbulent regime, by means of large eddy simulation (LES), a CFD-DEM model developed recently in our group for solid–liquid mixing. The resulting model is used to study the mixing of glass particles in a baffled stirred tank equipped with a down-pumping pitched blade turbine. Various characteristics of the liquid dynamics as well as the distribution and motion of the solids are investigated. The fraction of suspended solid particles predicted by the model is validated against experimental data obtained via the pressure gauge technique (PGT). Two new methods to calculate the fraction of suspended particles in a Euler–Lagrange simulation, the so-called Lagrangian suspended fraction analysis (LSFA) and the decorrelated fraction analysis (DFA) techniques are introduced. The results obtained with these two methods, as well as with many others taken from the literature, are compared to the Zwietering correlation and to the results obtained by the PGT. It is found that some techniques proposed in the literature, namely the local concentration, the power consumption and the transient solids concentration analysis techniques, cannot be applied adequately in this case. On the other hand, the LSFA, DFA and PGT techniques are observed to predict accurately the fraction of suspended solids when compared to experimental PGT data.

Uncontrolled Keywords

Multiphase flow; Solid–liquid mixing; Large-eddy simulation; DEMCFD-DEM

Subjects: 1800 Chemical engineering > 1800 Chemical engineering
Department: Department of Chemical Engineering
Research Center: URPEI - Research Center in Industrial Flow Processes
Funders: CRSNG/NSERC, CRSNG/NSERC - Vanier Scholarship
PolyPublie URL: https://publications.polymtl.ca/9067/
Journal Title: Chemical Engineering Research and Design (vol. 123)
Publisher: Elsevier
DOI: 10.1016/j.cherd.2017.05.021
Official URL: https://doi.org/10.1016/j.cherd.2017.05.021
Date Deposited: 12 Aug 2021 14:05
Last Modified: 16 Nov 2022 23:11
Cite in APA 7: Blais, B., Bertrand, O., Fradette, L., & Bertrand, F. (2017). CFD-DEM simulations of early turbulent solid–liquid mixing: Prediction of suspension curve and just-suspended speed. Chemical Engineering Research and Design, 123, 388-406. https://doi.org/10.1016/j.cherd.2017.05.021

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