Post on 01-Jan-2016
MODELLING OF HYDROCYCLONESMODELLING OF HYDROCYCLONES
CFD Modelling GroupDepartment of Mechanical EngineeringUniversity of British Columbia
Process Simulations Limited
OBJECTIVES
Feed
Reject
Accept
HYDROCYCLONESHYDROCYCLONES
Investigate the flow, particle, and fiber Investigate the flow, particle, and fiber separation occurring in hydrocyclones separation occurring in hydrocyclones
Use suitable turbulence models for Use suitable turbulence models for high swirl fluid flowshigh swirl fluid flows
Develop mathematical models to Develop mathematical models to compute fiber trajectories in complex compute fiber trajectories in complex flowsflows
Model separation and fractionation Model separation and fractionation according to properties in hydro-according to properties in hydro-cyclonescyclones
HYDROCYCLONESHYDROCYCLONES
3-D turbulent flow is solved in 3-D turbulent flow is solved in hydrocyclones using k - hydrocyclones using k - turbulence model turbulence model with curvature correctionwith curvature correction
Lagrangian method for tracking spherical Lagrangian method for tracking spherical particles three-dimensionally in particles three-dimensionally in hydrocyclones to obtain separation curveshydrocyclones to obtain separation curves
Spherical particles are replaced in Spherical particles are replaced in lagrangian model with rigid fibre, able to lagrangian model with rigid fibre, able to swell, and ignoring fibre rotationswell, and ignoring fibre rotation
MODEL CHARACTERISTICS
HYDROCYCLONES HYDROCYCLONES NUMERICAL METHODSNUMERICAL METHODS
Develop 3D method using cylindrical curvilinear gridDevelop 3D method using cylindrical curvilinear grid
- combination of cylindrical co-ordinates and non-orthogonal grids
Take advantage of the cylindrical co-ordinates to calculate Take advantage of the cylindrical co-ordinates to calculate the physical geometrical quantities and curvature source the physical geometrical quantities and curvature source terms accuratelyterms accurately
Circular co-ordinates are used to account for the curved Circular co-ordinates are used to account for the curved surface of each control cell in the calculation of surface of each control cell in the calculation of geometrical quantitiesgeometrical quantities
The centrifugal force is used to replace the curvature The centrifugal force is used to replace the curvature source term in the angular momentum equationsource term in the angular momentum equation
The standard k-The standard k- model fails to produce model fails to produce reasonable solutionreasonable solution
Use modified k-Use modified k- model proposed by Launder model proposed by Launder
- model adds correction term in dissipation equation
HYDROCYCLONESHYDROCYCLONES
Rit = Turbulent Richardson number
u = tangential velocity
r = radial
TURBULENCE MODEL
HYDROCYCLONESHYDROCYCLONES
Traced by numerical integration of the particle Traced by numerical integration of the particle velocity calculated from the fluid velocity and velocity calculated from the fluid velocity and particle slip velocityparticle slip velocity
Particle slip velocity is solved from the dynamic Particle slip velocity is solved from the dynamic force balance in radial, tangential & axial directionsforce balance in radial, tangential & axial directions
u = tangential velocities
Us = settling velocities
Vp= particle volume
Ap= projected area
Particle Trajectory
pDxslplp ACUgV 2
2
1)(
HYDROCYCLONESHYDROCYCLONES
Turbulence model is proven to be criticalTurbulence model is proven to be critical
Modified k-Modified k- model is identified as a good model is identified as a good alternative for high swirl flowsalternative for high swirl flows
Model is accurate for both flow simulation Model is accurate for both flow simulation and separation predictionand separation prediction
Model can be used to analyse performance Model can be used to analyse performance of industrial hydrocyclonesof industrial hydrocyclones
- design, separation, optimisation
3 Different Hydrocyclones3 Different Hydrocyclones
Dimensions(in mm)
Cyclone 1 Cyclone 2 Cyclone 3
Cyclone Diameter 76 75 75
Inlet Diameter 21 25 25
Cylindrical Length 51 75 75
Vortex Finder Diameter 26 25 22
Vortex Finder Length 30 50 50
Spigot Diameter 12 15 11
Cone Angle 11 20 20
COMPARISON (PARTICLES)COMPARISON (PARTICLES)
FIBER FRACTIONATIONFIBER FRACTIONATION
x
r
0 0.1 0.2 0.3 0.40
0.005
0.01
0.015
0.02
0.025
0.03
0.035
0.04
(a)
x
r
0 0.1 0.2 0.3 0.40
0.005
0.01
0.015
0.02
0.025
0.03
0.035
0.04
p1.52431E+071.42361E+071.32292E+071.22222E+071.12153E+071.02083E+079.20135E+068.1944E+067.18745E+066.1805E+065.17355E+064.1666E+063.15965E+062.1527E+061.14575E+06
(b)
x
r
0 0.1 0.2 0.3 0.40
0.005
0.01
0.015
0.02
0.025
0.03
0.035
0.04sw
2.845312.655632.465942.276252.086561.896881.707191.51751.327811.138130.9484380.758750.5690630.3793750.189688
(c)
(a) Velocity vectors, (b) pressure contours, and (c) swirl velocity contours in a hydrocyclone
FIBER FRACTIONATIONFIBER FRACTIONATION
10
20
30
40
50
60
70
0
20
40
60
80
100
carr
ied
ove
r(%
)
5
0
20
40
60
80
100
carrie
do
ver
(%)
5
10
20
30
40
50
60
70
cov89.62577.67565.72553.77541.82529.87517.9255.975
densityrel = 1.04
densityrel = 1.14
densityrel = 1.42
densityrel
carr
ied
ove
r(%
)
1
1
1.1
1.1
1.2
1.2
1.3
1.3
1.4
1.4
0 0
10 10
20 20
30 30
40 40
50 50
60 60
70 70
80 80
90 90
100 100
A densityrel
B densityrel
*
*
Fiber B
Fiber A
Influence of the particle density on fractionation
Separation on diameter and length as function of the particle density
FIBER FRACTIONATIONFIBER FRACTIONATION
diameter (microns)
carr
ied
ove
r(%
)10
10
20
20
30
30
40
40
50
50
60
60
70
70
0 0
10 10
20 20
30 30
40 40
50 50
60 60
70 70
80 80
90 90
100 100
A diameterB diameter
Fiber A
*
*
Fiber B
20
40
60
0
50
100
carr
ied
ove
r(%
)
1.2
1.4
0
50
100
carrie
do
ver
(%)
1.2
1.4
20
40
60
cov22.220.385718.571416.757114.942913.128611.31439.57.685715.871434.057142.242860.428571-1.38571-3.2
10 20 30 40 50 60 70
diameter (microns)
10 20 30 40 50 60 70
diameter (microns)
1.1
1.2
1.3
1.4
de
nsi
tyre
l
1.1
1.2
1.3
1.4
de
nsi
tyre
l
1.1
1.2
1.3
1.4
de
nsi
tyre
l
10 20 30 40 50 60 70
diameter (microns)
The difference between particles carried over at t = 20°C and t = 45°C. The yellow grid represents particles carried over at t = 20°C
Influence of the particle diameter on fractionation
FIBER FRACTIONATIONFIBER FRACTIONATION
The combined influence of coarseness and specific surface on separation
Influence of the particle coarseness on separation based on specific surface
0
10
20
30
40
50
60
00.1
0.20.3
0.4200
400
600
800
1000
57.754.350.847.444.040.637.133.730.326.923.420.016.613.29.8
Coarseness and Specific surface influence on separation
coarseness (mg/m)
specific surface (m2/kg)
carried over (%)carried over (%)
specific surface (m2/kg)ca
rrie
do
ver
(%)
200 400 600 800 10000
10
20
30
40
50
60
70
80
90
100
coarseness = 0.1 mg/mcoarseness = 0.2 mg/mcoarseness = 0.3 mg/mcoarseness = 0.4 mg/mcoarseness = 0.5 mg/m
Influence of coarsenesson separation based on specific surface
Particle length = 2 mmShape factor s3 = 1.5
FIBER FRACTIONATIONFIBER FRACTIONATION
Influence of particle length on separation based on diameter
Influence of the particle length on fractionation
diameter (m)
carr
ied
un
de
r(%
)
2E-05 4E-05 6E-05 8E-05 0.00010
10
20
30
40
50
60
70
80
90
100
density = 1100 kg/m3, L = 1 mmdensity = 1100 kg/m3, L = 6 mmdensity = 1050 kg/m3, L = 1 mmdensity = 1050 kg/m3, L = 6 mm
Influence of particle length on separation based on diameter
length (mm)ca
rrie
do
ver
(%)
1 2 3 4 5 60
10
20
30
40
50
60
70
80
90
100
Influence of particle length on fractionation
Reference data:
Fiber A: L = 3.1 mm; density = 1050 kg/m3; d = 48 micronsFiber B: L = 3.5 mm; density = 1100 kg/m3; d = 39 microns
Reference lines:
(a) density = 1050 kg/m3; d = 48 microns(b) density = 1100 kg/m3; d = 39 microns(c) density = 1140 kg/m3; d = 12 microns(d) density = 1140 kg/m3; d = 45 microns
Fiber A
**
Fiber B
FIBER FRACTIONATIONFIBER FRACTIONATION
Influence of entry particle position on separation and fractionation (Fibre A - Early Wood, Fibre B - Late Wood) for an entry feed at the top of hydrocyclone (z = 0)
ytangential (mm)
x axi
al(m
m)
0 10 20 30 400
5
10
15
20
downward
upward
Separation as function of entry position for fiber B (z = 0 mm)- Tangential feed -
ytangential (mm)
x axi
al(m
m)
0 10 20 30 400
5
10
15
20
downward
upward
Separation as function of entry position for fiber A (z = 0 mm)- Tangential feed -
ytangential (mm)
x axi
al(m
m)
0 10 20 30 405
10
15
20
25
downward
upward
Separation as function of entry position for fiber A (z = 5 mm)- Tangential feed -
ytangential (mm)x a
xia
l(m
m)
0 10 20 30 405
10
15
20
25
downward
upward
Separation as function of entry position for fiber B (z = 5 mm)- Tangential feed -
Influence of entry particle position on separation and fractionation (Fibre A - Early Wood, Fibre B - Late Wood) for a 5 mm downward entry feed (z = 5 mm)
BENEFITSBENEFITS
Increase operating efficiency for hydrocyclonesIncrease operating efficiency for hydrocyclones
Optimize the hydrocyclones designOptimize the hydrocyclones design
Evaluate the influence on fractionation of fiber Evaluate the influence on fractionation of fiber wet density, fiber diameter, fiber length, and wet density, fiber diameter, fiber length, and fiber specific surfacefiber specific surface
Evaluate the influence of the fluid temperature on Evaluate the influence of the fluid temperature on fractionationfractionation
Predict the fractionation performance of a hydro-Predict the fractionation performance of a hydro-cyclone for given fiber propertiescyclone for given fiber properties
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