Mohanarangam, Krishna; Stephens, Darrin W CFD Modeling of floating and settling phases in settling tanks Conference Seventh International Conference on CFD in the Minerals and Process Industries, 2009. Abstract | Links | BibTeX | Tags: ASM, Cenospheres, Floating, Modelling, Multiphase, Oil, Phases, PVC, SST, Tanks @conference{mohanarangam2009cfd,
title = {CFD Modeling of floating and settling phases in settling tanks},
author = {Krishna Mohanarangam and Darrin W Stephens},
doi = {10.13140/RG.2.1.5078.7686},
year = {2009},
date = {2009-01-01},
booktitle = {Seventh International Conference on CFD in the Minerals and Process Industries},
journal = {Seventh International Conference on CFD in the Minerals and Process Industries},
pages = {9--11},
abstract = {A Computational Fluid Dynamics (CFD) model for modelling a floating phase has been developed and tested on a settling tank. The current model used for settling tanks is able to predict the settling of solids and the formation of a higher density layer of solids at the bottom of the vessel. Due to the widespread use of settling tanks in water and other chemical industries, floating phases (cenospheres, oil, PVC, etc) form a major part of the separation process. With this in mind, a model has been developed to incorporate both the settling as well as the floating of the secondary phases. The simulations were performed by customizing the commercially available software ANSYS-CFX (release 10.0). Multi-phase simulations were performed with clay, sand and a floating solid (density less than the continuous phase) as the secondary phases. Numerical instability was encountered in the volume fraction of the floating phase at the top boundary, where the floating phase collected, when using the unmodified version of ANSYS-CFX. This was mainly due to the volume fraction tending towards unity without any gradient at the top boundary. To prevent this happening, an extra term that is ignored in the CFX implementation was included in the slip velocity calculation. This essentially sets up a volume fraction gradient of the floating phase. Two variants of particle sizes for the floating phase were used to access this phenomenon. Contour plots of the floating phase volume fraction are presented within the feedwell as well in the cross-section of the tank to depict the preferential concentration of the phase. Further results are also shown for the settling solids. NOMENCLATURE C D drag co-efficient C µ k-ε turbulence model constant C ε1-2 k-ε turbulence model constant d diameter g acceleration due to gravity k Turbulence Kinetic Energy (T.K.E) p pressure r solids fraction Re Reynolds number Sc t Turbulent Schmidt number S1-S2 Diameter of floating species t time U velocity Y mass fraction x,y,z cartesion co-ordinate system ε turbulence dissipation rate μ dynamic viscosity eff},
keywords = {ASM, Cenospheres, Floating, Modelling, Multiphase, Oil, Phases, PVC, SST, Tanks},
pubstate = {published},
tppubtype = {conference}
}
A Computational Fluid Dynamics (CFD) model for modelling a floating phase has been developed and tested on a settling tank. The current model used for settling tanks is able to predict the settling of solids and the formation of a higher density layer of solids at the bottom of the vessel. Due to the widespread use of settling tanks in water and other chemical industries, floating phases (cenospheres, oil, PVC, etc) form a major part of the separation process. With this in mind, a model has been developed to incorporate both the settling as well as the floating of the secondary phases. The simulations were performed by customizing the commercially available software ANSYS-CFX (release 10.0). Multi-phase simulations were performed with clay, sand and a floating solid (density less than the continuous phase) as the secondary phases. Numerical instability was encountered in the volume fraction of the floating phase at the top boundary, where the floating phase collected, when using the unmodified version of ANSYS-CFX. This was mainly due to the volume fraction tending towards unity without any gradient at the top boundary. To prevent this happening, an extra term that is ignored in the CFX implementation was included in the slip velocity calculation. This essentially sets up a volume fraction gradient of the floating phase. Two variants of particle sizes for the floating phase were used to access this phenomenon. Contour plots of the floating phase volume fraction are presented within the feedwell as well in the cross-section of the tank to depict the preferential concentration of the phase. Further results are also shown for the settling solids. NOMENCLATURE C D drag co-efficient C µ k-ε turbulence model constant C ε1-2 k-ε turbulence model constant d diameter g acceleration due to gravity k Turbulence Kinetic Energy (T.K.E) p pressure r solids fraction Re Reynolds number Sc t Turbulent Schmidt number S1-S2 Diameter of floating species t time U velocity Y mass fraction x,y,z cartesion co-ordinate system ε turbulence dissipation rate μ dynamic viscosity eff |