Dissolved
Dissol
ed Gas Flotation –
Bubble Benefits
EnviroArabia 2007
Dr. Michael Howdeshell
Edward Godeaux
For internal use only / Copyright © Siemens
Protection
AG 2006.
noticeAll
/ Copyright
rights reserved.
notice
Page 1
M. Howdeshell
Water Technologies
I t d ti / Contents
Introduction
C t t
Floatation technology is one of the
main methods for removing
contaminants from waste streams
resulting from remediation
remediation,
stimulation, completion and
workover fluid activities. Not only is
th
there
a need
d tto increase
i
th
the
efficiency of these systems; there is
also a need to reduce the size and
weight of the equipment.
Contents
ƒ What is Flotation
ƒ Available Technologies
ƒ Results of Field Testing
ƒ Summary
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M. Howdeshell
Water Technologies
Fl t ti Process
Flotation
P
ƒ Float solids, oils, and other contaminants
ƒ The floated contaminates are skimmed and removed
ƒ Attachment of gas bubbles to oil droplets is the key factor
°•
•°°↑
°••°↑° °••° ↑ °•°↑°
•↑
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M. Howdeshell
Water Technologies
Fl t ti Process
Flotation
P
– Stokes
St k L
Law
Vs=
Vs
r
g
ρp
ρf
η
-
2 r2g(ρp – ρf)
9
η
Oil settling
g velocity
y ((cm/sec))
Stokes radius of the oil droplet (cm)
Standard gravity (cm/sec2)
D
Density
it off the
th oilil ((g/cm
/ 3)
Density of the water (g/cm3)
Fluid viscosity
y (dyne
( y sec/cm2)
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M. Howdeshell
Water Technologies
Fl t ti Process
Flotation
P
– Stokes
St k L
Law
Vs≈
Vs
ρp
ρp
- Oil settling
g velocity
y ((cm/sec))
- Density of the oil (g/cm3)
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Page 5
M. Howdeshell
Water Technologies
Fl t ti Systems
Flotation
S t
ƒ Dissolved Air Flotation (DAF)
ƒ Induced Gas Flotation (IGF)
ƒ Sparging System
ƒ Dissolved Gas Flotation (DGF)
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M. Howdeshell
Water Technologies
Di
Dissolved
l d Air
Ai Flotation
Fl t ti (DAF)
ƒ Air is compressed and dissolved into the water stream
ƒ Bubble size is very small and results in good separation
ƒ System
S t
requires
i
a compressor and
d saturation
t ti tank
t k
ƒ Not suited to off-shore applications due to large
f t i t/ i ht and
footprint/weight
d high
hi h maintenance
i t
requirements
i
t
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M. Howdeshell
Water Technologies
I d
Induced
d Gas
G Flotation
Fl t ti
ƒ System can be Mechanical or Hydraulic
ƒ Mechanical
ƒ Uses motor and paddle to shear gas out of the water
ƒ As the paddle spins in the water, it agitates the cell with small
b bbl
bubbles
ƒ The mechanical portions require some maintenance
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Page 8
M. Howdeshell
Water Technologies
I d
Induced
d Gas
G Flotation
Fl t ti – Mechanical
M h i lD
Design
i
MECHANICAL
BEARING HOUSING
& SHAFT ASSEMBLY
GAS INLET PATHS
MOTOR
GAS CAVITY
NEGATIVE PRESSURE AREA
LIQUID LEVEL
STAND PIPE
HOOD
2 PHASE
MIXTURER FLOW
LAUDER
DISPERSER
ROTOR
LIQUID VORTEX
LIQUID RECIRCULATION
PATHS
Figure 1a. Mechanical system.
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M. Howdeshell
Water Technologies
I d
Induced
d Gas
G Flotation
Fl t ti
ƒ System can be Mechanical or Hydraulic
ƒ Hydraulic
ƒ Uses a recirculation pump to drive an educator, which induces fine
gas bubbles into the water.
ƒ Each flotation cell is filled with many micro
micro-fine
fine gas bubbles
bubbles.
ƒ The recirculation pump recycles from 25% to 125% depending on
g
the equipment design.
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Page 10
M. Howdeshell
Water Technologies
I d
Induced
d Gas
G Flotation
Fl t ti – Hydraulic
H d
li Design
D i
HYDRAULIC
RECYCLE
WATER
GAS VENTURI
WATER LEVEL
OIL
RECYCLE
WATER
Fi
Figure
1b.
1b Hydraulic
H d li system.
t
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M. Howdeshell
Water Technologies
G Sparging
Gas
S
i
ƒ This system uses a porous stainless steel tube to sparge small gas
bubbles into the water.
ƒ The gas bubbles are very small and provide good results.
ƒ The sparge tubes, however, are prone to plugging with scale and/or
hydrocarbons.
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M. Howdeshell
Water Technologies
Di
Dissolved
l d Gas
G Flotation
Fl t ti
ƒ Back pressure is key to system operation and can be tuned
ƒ Utilizes a dual sided impeller to pull both water and gas
g very
y fine bubbles.
ƒ Gas is dissolved into the water creating
ƒ Gas/water mixture flows across a globe valve creating a pressure drop
ƒ Gas breaks out of solution with pressure drop
ƒ Discharge from globe valve is sent to a gas floatation unit
ƒ Fine bubbles produced by the dissolved gas aid in oil separation
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Page 13
M. Howdeshell
Water Technologies
S t
System
C
Comparison
i
System
Prone to
Fouling
Suited to Off
OffShore Operation
No
No
Yes
Yes
No
Yes
No
Yes
DAF
Sparging
S
i
System
IGF
DGF
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M. Howdeshell
Water Technologies
B bbl Formation
Bubble
F
ti
DGF
Bubble Density
y
IGF
DGF >> IGF
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M. Howdeshell
Water Technologies
DGF Bubble
B bbl Formation
F
ti
DGF Pump Off
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M. Howdeshell
Water Technologies
DGF Bubble
B bbl Formation
F
ti
DGF Pump On 5 Seconds
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Page 17
M. Howdeshell
Water Technologies
DGF Bubble
B bbl Formation
F
ti
DGF Pump On 30 Seconds
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Page 18
M. Howdeshell
Water Technologies
DGF Bubble
B bbl Size
Si Control
C t l
50 PSI
55 PSI
60 PSI
Data collected with a Microtrac S3500 Particle Size Analyzer
Siemens Water Technologies DGF pump used for testing
DGF technology
gy can create gas
g bubbles
from 1 to 175 microns
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Page 19
M. Howdeshell
Water Technologies
DGF Flexibility
Fl ibilit
ƒ Ability to adjust to changing water chemistry in real time
ƒ Ability to adapt to varying oil droplet sizes in a matter of
minutes
DGF Efficiency Optimization
Measure Influent
Oil and Grease
Measure Effluent
Oil and Grease
Adjust DGF
Back Pressure
Repeat Until
Optimized
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M. Howdeshell
Water Technologies
DGF Flexibility
Fl ibilit
DGF Oil & Grease Removal Efficiency
120
Efficiency (%
E
%)
100
80
60
40
20
0
35
40
45
50
55
60
65
70
DGF Pressure (PSI)
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Page 21
M. Howdeshell
Water Technologies
S t
System
C
Comparison
i
System
Prone to
Fouling
Suited for Mechanical
Off-Shore
Parts
Bubble
Density
Flexible
Operation
DAF
No
No
Several
Moderate
No
Sparging
System
Yes
Yes
Few
Low
No
IGF
No
Yes
Many
Low
No
DGF
No
Yes
Few
High
Yes
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Page 22
M. Howdeshell
Water Technologies
C t t
Contact
Dr. Michael Howdeshell
Dr
Research & Development Director
Siemens Water Technology
Edward Godeaux
Produced Water Manager
Siemens Water Technology
301 W Military Rd
Rothschild, WI 54474
411 Commercial Parkway
Broussard, LA 70518
Phone: (715) 355-3450
Phone: (337) 837-3071
[email protected]
@
edward,[email protected]
,g
@
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Page 23
M. Howdeshell
Water Technologies
Th k you for
Thank
f your attention!
tt ti !
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Page 24
M. Howdeshell
Water Technologies