Effect of Bubble Surface Properties on Bubble–Particle Collision Efficiency in Froth Flotation
Abstract
1. Introduction
2. Theoretical Development
2.1. Schulze Model Theory
2.1.1. The Interceptional Effect
2.1.2. The Gravitational Effect
2.1.3. The Inertial Effect
2.2. GSE Model Theory
3. CFD-based Micro-Scale Modelling Method for Bubble-Particle Collision Efficiency
4. Results and Discussion
4.1. Effects of Bubble Surface Properties on Bubble Near-Wall Flow Field
4.2. Effects of Bubble Surface Properties on Particle-Bubble Relative Motion Behavior
4.3. Particle-Bubble Collision Efficiencies under Mobile and Immobile Bubble Surface Conditions
5. Conclusions
Author Contributions
Funding
Conflicts of Interest
Abbreviations
Roman | |
a | Fitting parameter |
b | Fitting parameter |
Db | Bubble diameter |
Dp | Particle diameter |
Ec | Collision efficiency |
Interceptional component of collision efficiency | |
Interceptional component of collision efficiency as given by Sutherland | |
Gravitational component of collision efficiency | |
Ecin | Inertial component of collision efficiency |
Etot | Total collision efficiency, as the sum of three components |
Collision efficiency as given by the GSE model | |
f | Parameter in the GSE model related to surface fluidity |
Fi | Force on the ith particle |
FD | Drag force on particle |
FG | Gravitational force on particle |
FP | Pressure force on particle |
FA | Added mass force on particle |
g | Acceleration due to gravity |
G | Non-dimensionalized terminal velocity of the particle, Vp/Ub |
K | Ratio of the particle inertial force to the drag force |
K3 | Modified Stokes number |
mp | Mass of particle |
p | Pressure |
r | Radial coordinate (i.e., distance from the center of the bubble) |
Rb | Bubble radius |
Rc | Distance of the critical flow line from vertical at a large distance |
Rp | Particle radius |
Re | Bubble Reynolds number |
xi | Position of the ith particle (vector) |
X | Non-dimensional radial co-ordinate, r/Rb |
u | Fluid velocity (vector) |
Ub | Velocity of bubble relative to surrounding liquid |
vi | Velocity of the ith particle (vector) |
Vp | Terminal velocity of particle |
Greek | |
β | Parameter in the GSE model |
ρ | Liquid density |
ρp | Particle density |
μ | Liquid dynamic viscosity |
ψ | Stokes (axisymmetric) stream-function |
ψc | Value of stream-function for critical (grazing) streamline |
Non-dimensionalized value of stream-function for critical streamline | |
θ | Angular coordinate (angle from the vertical) |
θc | Angle of the collision point of the critical grazing trajectory |
θt | Parameter in the GSE model |
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Model | Bubble Surface Mobility | Fluid Flow | Drawback(s) | |||
---|---|---|---|---|---|---|
Mobile and Immobile | ● | Stokes | It is valid only for particles with large Stokes Number | |||
Mobile | ● | Potential | It is not applicable for fine particles due to neglecting particle interceptional effect Particle inertial effect is entirely ignored | |||
Mobile and Immobile | ● | ● | Intermediate | It’s applicable to bubbles much larger than those used in flotation The hydrodynamic interaction between the particle and the fluid was presumed negligible | ||
Mobile | ● | ● | ● | Intermediate | The model does not take the negative inertial effect into account | |
Mobile | ● | ● | ● | Potential | The model poorly estimates the collision angle It disregards the microhydrodynamics and bubble wall effects It also neglects the higher Stokes numbers | |
Immobile | ● | Intermediate | It presumes a uniform distribution of collision over the entire upper half surface of bubbles It disregards the particle inertial effect | |||
Immobile | ● | ● | Stokes | It is only valid for Stokes flow conditions Drag force of fluid and the inertial forces of particles are ignored | ||
Immobile | ● | ● | Stokes and Potential | Inertial force is neglected No internal circulation and a non-slip condition at the bubble surface are assumed | ||
Immobile | ● | Stokes | It can be used just when the both particle (dp < 20 μm) and bubble sizes (db < 100 μm) are very fine | |||
Immobile | ● | ● | Stokes | The model can only used for small bubbles (db < 100 μm) | ||
Immobile | ● | ● | ● | Intermediate | It disregards the microhydyodynamics and bubble wall effects The impact of particle density along with cell turbulence are missing | |
Immobile | ● | Intermediate | It is only applicable when particle size (dp < 100 μm) and bubble size (db < 1 mm) | |||
Mobile and Immobile | ● | ● | ● | Intermediate | Complexity of the model makes it difficult to be used |
Bubble Diameter (mm) | Mesh Numbers | Particle Numbers | Inlet Velocity (m/s) | Re |
---|---|---|---|---|
0.6 | 5,102,342 | 4000 | 0.0656 | 39 |
0.9 | 6,590,614 | 6000 | 0.1 | 90 |
1.3 | 13,924,728 | 12,000 | 0.156 | 203 |
2.0 | 16,258,560 | 13,333 | 0.248 | 496 |
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Li, S.; Jue, K.; Sun, C. Effect of Bubble Surface Properties on Bubble–Particle Collision Efficiency in Froth Flotation. Minerals 2020, 10, 367. https://doi.org/10.3390/min10040367
Li S, Jue K, Sun C. Effect of Bubble Surface Properties on Bubble–Particle Collision Efficiency in Froth Flotation. Minerals. 2020; 10(4):367. https://doi.org/10.3390/min10040367
Chicago/Turabian StyleLi, Shuofu, Kou Jue, and Chunbao Sun. 2020. "Effect of Bubble Surface Properties on Bubble–Particle Collision Efficiency in Froth Flotation" Minerals 10, no. 4: 367. https://doi.org/10.3390/min10040367
APA StyleLi, S., Jue, K., & Sun, C. (2020). Effect of Bubble Surface Properties on Bubble–Particle Collision Efficiency in Froth Flotation. Minerals, 10(4), 367. https://doi.org/10.3390/min10040367