sedimentation and filtration

kayakjokeMechanics

Feb 22, 2014 (3 years and 3 months ago)

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Effect of cluster size in
sedimentation and filtration

Bruno A. Di Giovanni
, Richard G.
Holdich

and Victor M.
Starov

Department of Chemical
Engineering



Cluster

formation



Experimental

conditions



Particle

size

analysis



Permeability

in

sedimentation

and

filtration



Prediction

of

filtration

and

sedimentation

data

from

size

analysis

INTRODUCTION

Introduction

AGGREGATION

Destabilization

Transport

Coagulation

Flocculation

Perikinetic

Orthokinetic

Destabilization

Stable suspension

(TiO
2

in Distilled water)

Unstable suspension

(TiO
2

in Tap water)

TiO
2

TiO
2

Destabilization

Distilled water

NaNO
3
(1
mM
)

+

MgSO
4

(1
mM
)

TiO
2

Particle size analysis: transport

0
1
2
3
4
5
6
7
8
9
10
11
12
0
60
120
180
240
300
360
420
480
540
Mean Diameter [µm]

Time [sec]

Primary particle size = 20nm

Orthokinetic

transport

0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
0
120
240
360
480
600
720
840
960
1080
1200
Mean Diameter (micron)

Time (sec)

Continuous ultrasonic

Particle size analysis: shear fields

Low shear

D
cluster

= 11 µm

High shear

Breakages

0
1
2
3
4
5
6
7
8
9
10
11
12
0
60
120
180
240
300
360
420
480
540
600
Mean Diameter [µm]

Time [sec]

Pump speed 1





Pump speed 2


Pump speed 3

Pump speed 4

Pump speed 5

Filtration test

o

Plexiglass

cylinder with inner diameter of 7.75 cm

o

Cellulose filter medium

o

Constant temperature

o

Constant initial mixing technique

o

Recycled suspensions

o

Four different initial solid concentrations: 0.7 % v/v,
1.0% v/v, 1.5% v/v, 2.0% v/v, 3.0% v/v.

Filtration system

A

C

B

Cake

Suspension

(Supernatant)

Filter
medium

Metal perforated
plate

Connections:

(A)

Peristaltic pump

(B)

Pressure transducer

(C)

Pressure gauge

Filtration equations

(1) Constant pressure filtration:

(2) Constant rate filtration:

0
2
2
2





t
V
P
A
R
V
P
A
c
m


At
V
R
V
t
A
V
c
P
m






2
Filtration
-
Permeation



av
S
s
c
k








1
1
1
Specific cake resistance









dt
dV
P
A
L
k

For Permeation:

For Filtration:

Sedimentation test

o

Different size
of vessels

o

Constant temperature

o

Constant mixing technique

o

Recycled suspensions

o

Four different initial solid concentrations: 0.5 % v/v, 0.7
% v/v, 1.0 % v/v, 1.5% v/v.

Sedimentation

0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
0
2000
4000
6000
8000
10000
12000
Interface Height (
-
)

Time (sec)



k
u
g
c
x
p
s
s








k
Initial period

Solid concentration:
0.7 % v/v.

Permeability relationships

-

Kozeny
-
Carman:

-

Happel
-
Brenner:



2
2
3
1
v
S
Kc
c
k























3
5
2
2
3
5
3
1
2
3
12
2
3
3
2
c
c
x
c
c
c
k
sd
Results

0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
Solid cake concentration (v/v)

Pressure (bar)

Filtration
Permeation
Results

1.0E-16
1.0E-14
1.0E-12
1.0E-10
1.0E-08
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
0.16
0.18
0.20
Permeability (m
2
)

Final solid concentration (v/v)

Filtration
Permeation
Sedimentation




Results

1.E-02
1.E-01
1.E+00
1.E+01
1.E-16
1.E-15
1.E-14
1.E-13
1.E-12
1.E-11
1.E-10
1.E-09
Size (
μ
m)

Permeability (m
2
)

Filtration
Permeation
Sedimentation




Results

0.01
0.10
1.00
10.00
1.E-17
1.E-16
1.E-15
1.E-14
1.E-13
1.E-12
1.E-11
1.E-10
1.E-09
Size (
μ
m)

Permeability (m2)

Experimental
Predicted
CONCLUSIONS



Cluster

formation

is

an

important

process

in

solid
-
liquid

separation
.



The

best

parameters

such

as

ionic

strength,

pH,

temperature

have

to

be

identified

in

order

to

have

a

good

control

of

the

process
.



High

values

of

permeabiity

occurred

at

low

solid

concentrations

and

high

particle

size

as

expected
.



Pressure

values

did

not

have

any

effect

in

the

cake

concentration

for

the

permeation

process
.



Happel

and

Brenner

equation

allowed

to

calculate

the

cluster

size

with

a

fair

match

with

the

data

from

size

measurement

.

THANK YOU

FOR YOUR ATTENTION