Liquid-Liquid Extraction
Hierarchy of Separation Technologies
Physical Separations
Decantation, Coalescing, Filtration, Demisting
Easy
Evaporation
Single Effect, Multiple Effect
Distillation
Simple, Azeotropic, Extractive, Reactive
Extraction
Simple, Fractional, Reactive
Difficulty
Of
Separation
Adsorption
Pressure Swing, Temperature Swing
Crystallization
Melt, Solvent
Membranes
MF, UF, NF, RO
Difficult
Typical Applications
• Remove products and pollutants from dilute aqueous streams
• Wash polar compounds or acids/bases from organic streams
• Heat sensitive products
• Non-volatile materials
• Azeotropic and close boiling mixtures
• Alternative to high cost distillations
Extraction is Used in a Wide
Variety of Industries
Chemical
•Washing of acids/bases, polar compounds from organics
Pharmaceuticals
• Recovery of active materials from fermentation broths
• Purification of vitamin products
Effluent Treatment
• Recovery of phenol, DMF, DMAC
• Recovery of acetic acid from dilute solutions
Polymer Processing
• Recovery of caprolactam for nylon manufacture
• Separation of catalyst from reaction products
Petroleum
• Lube oil quality improvement
• Separation of aromatics/aliphatics (BTX)
Petrochemicals
• Separation of olefins/parafins
• Separation of structural isomers
Food Industry
• Decaffeination of coffee and tea
• Separation of essential oils (flavors and fragrances)
Metals Industry
• Copper production
• Recovery of rare earth elements
Inorganic Chemicals
• Purification of phosphoric acid
Nuclear Industry
• Purification of uranium
Removal of Organics From Water
Distillation vs. Extraction
BP [°C]
Water
Solu. [%]
Azeotrope
B.P. [°C]
Azeotrope
Water [%]
40
2.0
38.1
1.5
Acetone
56.2
Infinite
Non Azeotropic
< 50 ppb
Methanol
64.5
Infinite
Non Azeotropic
< 50 ppb
Benzene
80.1
0.18
69.4
8.9
< 50 ppb
Toluene
110.8
0.05
85.0
20.2
< 50 ppb
-21
Infinite
Formic Acid
100.8
Infinite
Acetic Acid
118.0
Infinite
Pyridine
115.5
57
92.6
43
< 10 ppm
Aniline
181.4
3.60
99.0
80.8
< 10 ppm
Phenol
181.4
8.20
99.5
90.8
< 10 ppm
Nitrobenzene
210.9
0.04
98.6
88.0
< 10 ppm
Dinitrotoluene (2,4)
300.0
0.03
99 – 100
> 90
< 10 ppm
Dimethyl Formamide
153.0
Infinite
Non Azeotropic
< 10 ppm
Dimethyl Acetamide
166.1
Infinite
Non Azeotropic
< 10 ppm
n-Methylpyrrolidone
202.0
Infinite
Non Azeotropic
< 10 ppm
Distillation
Organic Compound
Methylene Chloride
Extraction
Formaldehyde
Non Azeotropic
107.1
22.5
Non Azeotropic
Typical
Reduction Level
< 50 ppb
< 1,000 ppm
< 500 ppm
< 500 ppm
Simple Extraction Single Stage
Extract (E)
A–0
B – 50
Feed (F)
C – 0.8
50.8
A – 99
B–0
C–1
100
A–0
Raffinate (R)
B – 50
A – 99.0
B–0
C – 0.2
C–0
99.2
50
Solvent (S)
Fraction Unextracted
Distribution Coefficient
Extraction Factor
U
Solute in Raffinate 0.2

 0.2
Solute in Feed
1.0
0.8
Conc. Solute in Extract
50  7.92
M

Conc. Solute in Raffinate 0.2
99
E  S M   50 7.92   4.0
F
99
 


Cross Flow Extraction
E1
E2
B+C
E3
B+C
E4
B+C
B+C
A+B
F
R1
R2
C
F + S = M1
R3
C
R1 + S = M 2
R4
C
B
C
R2 + S = M 3
R3 + S = M 4
F
R2
A
R3
R4
R1
M1
M2
M3
M4
E1
E2
E3
E4
C
A
Countercurrent Flow Extraction
E1
B+C
C
E3
B+C
A+B
F
R1
R2
B+C
R3
E2
R4
B+C
A
E4
B
Equations
F+S=M
E1 + R 4 = M
F + S = E1 + R4
F – E1 = R4 – S = D
F
R1
R2
R3
R4
A
E1
M
E2
E3
E4
S C
D
Countercurrent Extraction
B+C
Feed (F)
A+B
Extract (E):
Solute Rich Stream
Primary Interface
Continuous Phase
Dispersed Phase
Solvent (S)
C
A
Raffinate (R):
Solute Lean Stream
Bench Scale Test Apparatus
Variable Speed Drive
Baffle
Thermometer
Tempered
Water Out
1 – Liter Flask
Tempered
Water In
Drain
Simple Extraction
Process
Scheme
Solute Free
Basis
EI
E
F
xAS
xBF
1.0
N
yAE
yBE
yCE
1.0
FI
XBF = xBF
xAF
S
SI
yAS
yBS
yCS
1.0
YBS = yBF
yAS+ yCS
R
xAR
xBR
xCR
1.0
Graphical
Solution
N
YBE = yBE
yAR+ yCE
YBE
Y
RI
XBR = xBR
xAR+ xCR
FI=F(xAR)
SI=S(yAS+yCS)
EI=E(yAE+yCE)
RI=R(xAR+xCR)
YBS
XBR
m = YB*
XB*
X
XBF
Distribution Coefficient
on Solute Free Basis
Extract Composition (Wt Fract., Solute Free)
Typical LLE Equilibrium Curve
0.09
0.08
0.07
0.06
0.05
0.04
0.03
0.02
0.01
0.00
0.000
0.005
0.010
0.015
Raffinate Composition (Wt Fract., Solute Free)
0.020
Graphical Determination of Theoretical Stages
Extract Composition (Wt Fract., Solute Free)
95% Solute Extraction, S/F = 1.0 mass basis
(0.136, 0.114)
0.12
0.10
1
0.08
0.06
0.04
0.02
2
0.00
0.000
3
0.020
0.040
0.060
0.080
0.100
Raffinate Composition (Wt Fract., Solute Free)
0.120
Graphical Determination of Theoretical Stages
Extract Composition (Wt Fract., Solute Free)
98% Solute Extraction, S/F = 1.0 mass basis
(0.136, 0.118)
0.12
0.10
1
0.08
0.06
0.04
4
0.02
6
0.00
0.000
5
2
3
0.020
0.040
0.060
0.080
0.100
Raffinate Composition (Wt Fract., Solute Free)
0.120
Kremser Equation
n
Where: n
xf
xn
ys
m
E
=
=
=
=
=
=
ys 


x




m 1 1   1 
LOG f
ys   E  E 
 xn  m 


LOG E
Number of theoretical stages required
Conc. of solute in feed on solute free basis
Conc. of solute in raffinate on solute free basis
Conc. of solute in solvent on solute free basis
Distribution coefficient
Extraction factor = (m)(S/F)
Engineering Calculations
Kremser Type Plot
YBE
E1
E = 0.3
1.0
0.8
0.6
F1
XBF
S1
YBS
XB
R1
R Factor
E = Extraction
E = m (S1/F1)
XBR/XBF = Fraction Unextracted
0.4
0.3
0.2
0.1
0.08
0.06
0.04
0.03
0.02
0.01
0.008
0.006
0.004
0.003
0.002
0.001
0.0008
0.0006
0.0005
1
2
3
4 5
6
7 8 10 15 20
Number of Ideal Stages
Typical Extraction System
Feed
B+C+(A)
A+B
Solvent
Recovery
Raffinate
Stripping
C
(A+B)
Extraction
Solvent
C
(A)
A+(B+C)
A (B+C)
B (C)
C
(A+B)
Removal of Phenol from Wastewater
Extract
Wastewater Feed
0.1 – 8 % Phenol
Solvent
Recovery
Raffinate
Stripping
Extraction
Recycled
Solvent
Raffinate
< 1 ppm Phenol
Biological Treatment
Or
Carbon Adsorption
ppb Phenol
Phenol
Recovery of Acetic Acid from Water
Using a Low Boiling Solvent
Extract
Aqueous Feed
20 - 40 %
Acetic Acid
Solvent
Recovery
Raffinate
Stripping
Extraction
Recycled
Solvent
Typical Solvents:
Ethyl Acetate
Butyl Acetate
Raffinate
Aqueous Raffinate
Acetic Acid
Recovery of Carboxylic Acids from Wastewater
Using a High Boiling Point Solvent
Formic Acid
99%+ Purity
Water
Water Feed
0.1 – 5 %
Mixed Acids
Acid
Recovery
Solvent
Recovery
Dehydration
Extraction
Raffinate
< 1,000 ppb
Mixed Acids
Recovered Solvent
Clean Up
Acetic Acid
99%+ Purity
Neutralization/Washing of Acid or Base
or Polar Compounds from Organic Stream
Organic
Water
Extraction
Caustic (Mild)**
Feed (Organic + Acid) **
Water + Salts
** Organic Feed could
contain caustic. MidFeed would be mild acid.
Series Extraction
Extract
Solvent 1
B+C
C
Feed
Solvent 2
A+B
D
Extractor 1 & 2 May Differ By:
- Temperature
- pH
- Solvent
Extractor #2
Extractor #1
Raffinate
A
Product
B+D
Recovery of Caprolactam
Extract
Lactam Oil Phase
65 – 70% Caprolactam
Water
Ammonium Sulphate Phase
2 – 3% Caprolactam
Raffinate
AQ Waste
to
Discharge
Re-Extraction
Reaction
Section
Am. Sulphate Ext.
Lactam Oil Ext.
Feed From
Am. Sulph.
Waste to
Discharge
Lactam Oil
to
Recovery
Solvent
Phosphoric Acid Purification via Extraction
Recycle
Re-Extraction
Scrub Extraction
Feed
Extraction
HCL
Phosphate
Rock
Digester
Water
Scrub Solv.
Raffinate
to Disposal
Solvent
Phosphoric
Acid to
Recovery
Organo-Metallic Catalyst Recovery
Organic
Cobalt
Catalyst
Preparation
Extraction
Feed
Organo-Metallic
Catalyst
Reactor
Slipstream
Makeup
Organic
Separator
Water Effluent
(200 ppm Cobalt)
Product
Water Effluent
(1 ppm Cobalt)
Fractional Extraction
Process Scheme
EI
YAE,YBE
SI2
XAS2,XBS
2
(A-Rich)
NR
F1I
XAF,XBF
NS
S 1I
XAS1,XBS1
RI
(B-Rich)
XAR,XBR
Extraction of Flavors and
Aromas
Typical Products:
Orange Oil
Lemon Oil
Peppermint Oil
Cinnamon Oil
Aqueous Alcohol
Solvent 2
Distillation
Solvent 1
Distillation
Extraction
Essential Oil
Hydrocarbon
Oil
Essential Extract
Separation of Structural
Isomers
pH Adjust
(Optional)
Solvent 1 Recycle
Typical Applications:
m. p. - Cresol
Xylenols
2 , 6 - Lutidine
3 , 4 - Picoline
Solvent 2 Recycle
pH Adjust
(Optional)
Aqueous
Recycle
Solvent 2
Distillation
Extraction
Isomer
Feed
Solvent 1
Distillation
Extraction
Mixed
Aqueous
Raffinate
Reflux
Isomer 1
Isomer 2
Major Types of Extraction Equipment
Mixer
Settlers
Column
Contactors
Used primarily in the metals
industry due to:
- Large flows
- Intense mixing
- Long Residence time
- Corrosive fluids
- History
Spray
Packed
Static
Tray
Agitated
Pulsed
Centrifugal
Used primarily in the
pharmaceutical industry due to:
- Large flows
- Intense mixing
- Long Residence time
- Corrosive fluids
- History
Rotary
Reciprocating
Rarely used
Used in:
Used in:
Used in:
- Refining
- Refining
- Nuclear
- Petrochemicals
- Petrochemicals
- Inorganics
- Chemicals
Example:
- Random
- Structured
- SMVPTM
Example:
- Sieve
Example:
- Packed
- Tray
- Disc & Donut
Used in:
- Chemicals
- Petrochemicals
- Refining
- Pharmaceutical
Example:
- RDC
- Scheibel
Example:
- Karr
Mix / Decant Tank
Characteristics
Feed Inlet
• Mix – Settle – Phase separate in a single
tank
• Batch Processing only
• Requires multiple solvent additions for
more than one stage (crossflow operation)
• Typically used for small capacity
operations or intermittent processing
Sight Glass
Outlet
Mixer / Settlers
Characteristics
• Handle very high flowrates
Light Phase In
• Good for processes with
relatively slow reactions
(residence time required)
• Provide intense mixing to
promote mass transfer
• Require large amount of
floor space
Heavy Phase Out
• Suitable when few theoretical
stages required
• Large solvent inventory (and
losses)
Centrifugal Extractor
Characteristics
• Countercurrent flow via centrifugal
force
• Low residence time ideally suited for
some pharmaceutical applications
• Handles low density difference
between phases
• Provide up to several theoretical
stages per unit
• High speed device requires
maintenance
• Susceptible to fouling and plugging
due to small clearances
Packed Column
Extract (E)
Characteristics
• High capacity:
20-30 M3/M2-hr (Random)
500-750 gal/ft2-hr (Random)
40-80 M3/M2-hr (Structured)
1,000-2,000 gal/ft2-hr (Structured)
Feed (F)
• Poor efficiency due to backmixing and
wetting
• Limited turndown flexibility
• Affected by changes in wetting
characteristics
• Limited as to which phase can be
dispersed
Solvent (S)
Raffinate (R)
• Requires low interfacial tension for
economic usefulness
• Not good for fouling service
Sieve Tray Column
Feed (F)
Extract (E)
Primary
Interface
Characteristics
• High capacity: 30-50 M3/M2-hr
750-1,250 gal/ft2-hr
• Good efficiency due to minimum
backmixing
• Multiple interfaces can be a problem
• Limited turndown flexibility
• Affected by changes in wetting
characteristics
• Limited as to which phase can be
dispersed
Solvent (S)
Raffinate (R)
RDC Extractor
Characteristics
Drive Motor
Gearbox
• Reasonable capacity:
20-30 M3/M2-hr
• Limited efficiency due to
axial backmixing
Light
Phase Out
Heavy
Phase In
• Suitable for viscous materials
Vessel
Walls
• Suitable for fouling materials
Shaft
• Sensitive to emulsions due to
high shear mixing
• Reasonable turndown (40%)
Stators
Light
Phase In
Interface
Heavy
Phase Out
Interface
Control
Rotors
Scheibel Column
Characteristics
• Reasonable
capacity:
15-25 M3/M2-hr
350-600 gal/ft2-hr
Gearbox
Variable Speed
Drive
Light
Phase Out
Heavy
Phase In
Rotating
Shaft
Horizontal
Vessel
Outer Baffle
Walls
• High efficiency due
to internal baffling
• Good turndown
capability (4:1) and
high flexibility
• Best suited when
many stages are
required
• Not recommended
for highly fouling
systems or systems
that tend to emulsify
Turbine
Impeller
Light
Phase In
Interface
Heavy
Phase Out
Interface
Control
Horizontal
Inner Baffle
Scheibel Column Internal Assembly
Karr Reciprocating Column
Drive
Assembly
Seal
Characteristics
• Highest capacity:
30-60 M3/M2-hr
750-1,500 gal/ft2-hr
Heavy
Phase Inlet
• Good efficiency
• Good turndown capability (4:1)
• Uniform shear mixing
• Best suited for systems that
emulsify
Light
Phase Out
Spider Plate
Sparger
Center Shaft
& Spacers
Metal Baffle
Plate
Tie Rods
& Spacers
Perforated
Plate
Teflon
Baffle Plate
Light
Phase Inlet
Sparger
Interface
Heavy
Phase Out
Interface
Control
Karr Column Plate Stack Assembly
Pulsed Extractor
Characteristics
• Reasonable capacity:
20-30 M3/M2-hr
Light
Phase Out
Heavy
Phase In
• Best suited for nuclear
applications due to lack of seal
Timer
Solenoid
Valves
• Also suited for corrosive
applications since can be
constructed out or non-metals
Air
• Limited stages due to
backmixing
• Limited diameter/height due
to pulse energy required
Compressed
Air
Exhaust
Liquid
Light
Phase In
Pulse
Leg
Interface
Heavy
Phase Out
Interface
Control
Comparison Plot of Various
Commercial Extractors
20
Efficiency / Stages per Meter
Scheibel
10
6
RZE
Key
Kuhni
Graesser
Karr
PFK
4
PSE
RDC
2
FK
MS
1
SE
.06
0.4
0.2
1
2
4 6 10
20
40 60 100
Capacity M3/(M2 HR)
Graesser = Raining Bucket
MS = Mixer Settler
SE = Sieve Plate
FK = Random Packed
PFK = Pulsed Packed
PSE = Pulsed Sieve Plate
RDC = Rotating Disc Contactor
RZE = Agitated Cell
Karr = Karr Recipr. Plate
Kuhni = Kuhni Column
Scheibel = Scheibel Column
Column Selection Criteria
Static Column
A static column design may be appropriate when:
• Interfacial tension is low to medium: up to 10-15
dynes/cm
• Only a few theoretical stages are required, and
reduction in S/F is not an economic benefit
• No operational flexibility required
• There is a large difference in solvent to feed
rates
Column Selection Criteria
Agitated Column
Agitated columns are generally more economical when:
• More than 2-3 theoretical stages are required
• Interfacial tension is moderate to high, although
low interfacial tensions may also be economical
• A reduction in solvent usage is beneficial to the
process economics
• The process requires a wide turndown as well as
the ability to handle a range of S/F ratios
Column Selection Criteria
Rotating Disc Contactor (RDC)
• Systems with moderate to high viscosity, i.e. >
100 cps
• Systems that are residence time controlled, for
example, slow mass transfer rate with few
theoretical stages required
• Systems with a high tendency towards fouling
Column Selection Criteria
Scheibel Column
• Systems that require a large number of stages
due to either theoretical stage requirements or
low mass transfer rates
• Low volume applications in which a relatively
small column is required
• Systems that process relatively easily, without a
tendency to emulsify and/or flood
Column Selection Criteria
Karr Reciprocation Plate Column
• Difficult systems that tend to emulsify and/or
flood easily
• Systems in which the hydraulic behavior varies
significantly through length of the column
• Sometimes requiring non-metallic internals, such
as Teflon due to wetting characteristics or
corrosive materials
• Fouling applications that may have tars
formations and/or solids precipitation
The Three Cornerstones of Successful
Extraction Applications
Successful
Application
Proper Solvent
Selection
Meaningful
Pilot Tests
Accurate
Scale-Up
Selection Based on:
Testing Based on:
Scale-Up Based on:
•
•
Actual feed stocks
•
Proven techniques
•
Full process including
solvent recovery
•
Proper safety factors
•
Wide range of operating
conditions
•
•
Sound thermodynamic
principles
Sound economic
principles
• Availability
• Recoverability
Sound environmental
principles
• Toxicity
• Safety
Organic Group Interactions
Solvent Class
Solute Class
1
2
3
4
5
6
7
8
9
10
11
12
1
Phenol
0
0
-
0
-
-
-
-
-
-
+
+
2
Acid, thiol
0
0
-
0
-
-
0
0
0
0
+
+
3
Alcohol, water
-
-
0
+
+
0
-
-
+
+
+
+
4
Active H on multihalogen
0
0
+
0
-
-
-
-
-
-
0
+
5
Ketone, amide with no H on N,
sulfone, phosphine oxide
-
-
+
-
0
+
+
+
+
+
+
+
6
Tertiary amine
-
-
0
-
+
0
+
+
0
+
0
0
7
Secondary amine
-
0
-
-
-
+
+
0
0
0
0
+
8
Primary amine, ammonia, amide,
with 2H on N
-
0
-
-
+
+
0
0
+
+
+
+
9
Ether, oxide, sulfoxide
-
0
+
-
+
0
0
+
0
+
0
+
10
Ester, aldehyde, carbonate,
phosphate, nitrate, nitrite, nitrile
-
0
+
-
+
+
0
+
+
0
+
+
11
Aromatic, olefin, halogen, aromatic
multihalogen, paraffin without
active H, manahalogen paraffin
+
+
+
0
+
0
0
+
0
+
0
0
Paraffin, carbon disulfide
+
+
+
+
+
0
+
+
+
+
0
0
12
1 - 4 = H donor groups
5 – 12 = H acceptor groups
12 = Non-H bonding groups
Liquid-Liquid Extraction Scale-Up
• Theoretical scale-up is difficult
• Complexity of processes taking place within an extractor
 Droplet Breakup
 Coalescence
 Mass Transfer
 Axial and radial mixing
 Effects of impurities
• Best method of design:
Pilot testing followed by empirical scale-up
Pilot Plant Configuration
•
Determine type of column to be used based on process considerations
•
Use the same kind of equipment for the production unit
•
Determine diameter and height of pilot column based on experience
Type of Column
Diameter
Height
Packed
3” to 4”
3’ to 6’ per Theoretical Stage (TS)
Tray
4” to 6”
4’ to 5’ Trays per TS
Karr
1”
1’ to 3’ per TS
Scheibel
3”
3 to 6 Actual Stages per TS (Approx. 3” to 6”)
Continuous Extraction Pilot Plant
Arrangement
Variable Speed Drive
Extract
Hot Oil
Raffinate
Feed
Solvent
KMPS Pilot Plant Services Group
KMPS maintains a pilot
plant dedicated to extraction
R & D and applications
testing
Possible Extraction Column
Configurations
Solvent is Light Phase
E
B+C
E
B+C
F
F
Primary
Interface
A+B
Solvent
Dispersed
S
A+B
Solvent
Continuous
Primary
Interface
S
C
C
A
Solvent is Heavy Phase
R
R
A
A
A
R
S
R
S
C
C
Solvent
Dispersed
Primary
Interface
F
Primary
Interface
Solvent
Continuous
F
A+B
E
B+C
A+B
E
B+C
Factors Effecting which Phase is
Dispersed
Flow Rate
•
•
For Sieve Tray and Packed Columns – disperse the higher flowing phase
For all other columns – disperse lower flowing phase
Viscosity
•
For efficiency – disperse less viscous phase
Viscous drop
Diffusion rate inside the drop is
inhibited by viscosity
•
For capacity – disperse more viscous phase
Viscous continuous phase
Drop rise or fall
will be inhibited
Factors Effecting which Phase is
Dispersed
Surface Wetting
•
Want the continuous phase to preferentially set the internals – this minimizes
coalescence and therefore maximizes interfacial area.
Droplets coalesce.
Interfacial area lost.
Droplets retain shape.
Maximizes interfacial area.
Importance of maintaining droplets
Assume – 30% holdup of dispersed phase in 1 M3 of solution
Droplet
Diameter
[m]
Droplet
Volume
[M3]
Number
Droplets
Droplet
SA [M2]
Interfacial
Area
[M2/M3]
100
0.3
7.16x1010
1.26x10-7
9022
300
0.3
2.65x109
1.13x10-6
2995
500
0.3
5.73x108
3.14x10-6
1796
Factors Effecting which Phase is
Dispersed
Marangoni Effect
•
Coalescence is enhanced by mass transfer from
droplets
continuous phase
A+B
C
Mass Transfer Direction
A+B
C
A+B
C+B
Continuous
c)
• Droplets tend to coalesce
• Must be counteracted by additional energy
A
C
Dispersed
(d
C+B
Continuous
(c
Dispersed
d)
• Droplets tend to repel each other
• Less energy required to maintain dispersion
Interface Behavior
Actions to control unstable interface
As extraction proceeds, interface normally
grows in thickness and forms a “rag” layer
that stabilizes at some thickness
Light Phase
Dispersed
Rag
Layer
If rag layer continues to grow, some action
must be taken
1.
2.
Rag Draw
Continuously withdraw a portion of the
interface and pass through a filter to
remove interfacial contamination
Reverse Phases
Often a stable interface can be controlled
by reversing which phase is dispersed
Heavy Phase
Dispersed
Growing
Uncontrolled
Interface
Filter
1
2
Entrainment
Entrainment involves carrying over a small portion of one phase out the wrong end
of the column.
Entrainment is controlled by:
1.) Increased settling time inside the column
2.) Coalescer inside the column
3.) Coalescer external to the column
E
E
E
F
1
S
F
F
F
OR
2
OR
R
3
S
S
S
E
R
R
R
Flooding
Flooding – the point where the upward or downward flow of the dispersed phase
ceases and a second interface is formed in the column.
Flooding can be caused by:
• Increased continuous phase flow rate which increases drag on droplets
f
Primary Interface
F2 > F1
f
Primary Interface
E
F1
E
F2
Second
Interface
S
S
R
R
Flooding
Flooding can be caused by:
• Increased agitation speed which forms smaller droplets which cannot
overcome flow of the continuous phase
• Decreased interfacial tension – forms smaller drops – same effect as
increased agitation
f1
Primary Interface
f2 > f 1
f
Primary Interface
2
E
F1
E
F2
Second
Interface
S
S
R
R
Pilot Tests
Static Columns
Agitated Columns
(Packed, Tray)
(Scheibel, Karr)
Process Factors
Column Variable
Variable
N, S/F
D, H
(F+S)
N, S/F
D, H
(F+S),f
f
F
F
H
S
H
D
Flood
HETS
S
D
F+S
F+S
MIN
HETS
HETS
f
F+S
Extractor Flow Patterns
Ideal Plug Flow
Y
Actual Flow
Y
X
X
This “axial” or “back” mixing causes
concentration gradients that decrease driving
force and therefore increase HETS
Generalized Scale-up Procedure
Pilot Scale
Commercial Scale
f2
f1
Q1
Q2
Feed Rate
Feed Rate
H1
H2
D1
Basic Scale-up Relationships:
D2/D1 = K1(Q2/Q1 )^M1
H2/H1 = K2(D2/D1 )^M2
f2/f1 = K3(D2/D1)^M3
D2
Where:
K1, M1 = Capacity Scale-up Factors
K2, M2 = Efficiency Scale-up Factors
K3, M3 = Power Scale-up Factors
Application – Scheibel Column
• Extraction of nitrated organics from spent acid stream
using an organic solvent
• Reduce nitrated organic compounds from 3.9% to less
than 50 ppm
• S/F ratio fixed by process at 3.9
• Equilibrium data indicated that 4.5 theoretical stages
required
• Commercial design: 3,900 lb/hr (270 GPH) spent acid
feed
Scheibel Column Pilot Plant Setup
Nitrated Organics Extraction
Interface
Variable
Speed Drive
Hot Oil
Organic
Extract
Spent Acid
Feed
MCB
Solvent
Aqueous
Raffinate
Scheibel Column Pilot Plant Test Results
Nitrated Organics Extraction
Run
# of
Acid Feed MCB Feed
Stages [cc/min]
[cc/min]
Column
Temp [°C]
Agitation
Speed
[RPM]
Raffinate - Nit.
Org. Conc.
[PPM]
1
18
300
185
82
400
856
2
18
300
185
80
500
776
3
18
300
185
84
600
328
4
18
380
235
43
500
963
5
18
380
235
91
600
159
6
18
380
235
73
500
563
7
18
380
235
74
700
148
8
36
380
235
78
500
16
9
36
380
235
78
600
11
10
36
300
185
70
600
15
11
36
300
185
83
650
13
12
36
240
150
54
600
47
Scheibel Column Scale-up Procedure
Nitrated Organics Extraction
530
Column Capacity
For Dia. < 18”
[GPH/FT2]
Rate in Commercial Column
For Dia. ≥ 18”
[GPH/FT2]
600
157
14” Dia. = 430 GPH/FT2
300
100
5
[GPH/FT2]
Rate in 3” Dia. Pilot Scheibel
Column
10
15
[IN]
Scheibel Column
Diameter
20
Scheibel Column Pilot Plant Scale-up
Nitrated Organics Extraction
• Diameter = 14” (D1)
• Expanded Head Diameter = 20” (D2)
• Bed Height = 9’-6” (A)
• Overall Height = 16’-4” (B)
D1
A
D2
B
Application – Karr Column
Alcohol Extraction from Acrylates
• Extraction of methanol from an acrylate stream using
water as the solvent
• Reduce methanol from 2.5% to less than 0.1%
• S/F ratio specified by client as 0.32 wt. basis
• Equilibrium data: distribution coefficient generated by
KMPS, with average value of 5.3
• Commercial design: 36,900 lb/hr (4,660 GPH) acrylate
feed
Karr Column Pilot Plant Setup
Alcohol Extraction from Acrylates
Karr Column
1” Dia. x 8’ Plate Stack
Plate Spacing from Top:
6’ of 2”
1’ of 4”
1’ of 6”
316SS Shaft, Plates
& Spacers
Variable
Speed Drive
Hot Oil
Raffinate
(Acrylate Phase)
Water
Feed
Extract
(H2O + Alcohol)
Acrylate Feed
(methyl or ethyl)
Interface
Karr Column Pilot Plant Test Results
Methanol Extraction from Acrylate
Run
Plate
Stack
Feed Rate
[cc/min]
Water Feed
Rate
[cc/min]
Agitator
Speed
[SPM]
Interface
Raffinate
Conc.
Alcohol
Raffinate
Conc.
Water
1
1
150
45
100
Bottom
0.124
2.55
2
1
150
45
75
Bottom
0.165
2.83
3
2
150
45
110
Bottom
0.169
2.78
4
2
150
45
140
Bottom
0.112
2.72
5
2
180
54
100
Bottom
0.203
2.90
6
2
180
54
125
Bottom
0.146
3.08
7
2
180
54
150
Bottom
0.118
2.66
8
2
180
54
200
Bottom
0.078
2.73
9
2
210
63
175
Bottom
0.084
2.65
Notes:
Karr column with 1” dia. X 6’ plate stack height.
Plate stack #1 is constant 2” plate spacing.
Plate stack #2 has variable spacing, from top: 4’ of 2”, 1’ of 4”, 1’ of 6” spacing.
Feed is acrylate with approximately 2.5% methanol
Karr Column Pilot Plant Scale-up Procedure
Methanol Extraction from Acrylate
• Select optimal run from test results
* Run 8:
Feed Rate = 150 cc/min
Solvent Rate = 45 cc/min
Specific Throughput (Q) = 560 GPH/FT2
• Production column design
* Diameter – direct scale-up based on specific throughput
* Height – HCOMM = ƒ (H)PILOT
* Agitation Speed – SPMCOMM = ƒ (SPM)PILOT
Karr Column Pilot Plant Scale-up Procedure
Methanol Extraction from Acrylate
• HCOMM = (DCOMM / DPILOT)0.38 x HPILOT
• HCOMM = (45/1)0.38 x (6 feet) = 26 feet
• SPMCOMM = (DPILOT / DCOMM)0.14 x SPMPILOT
• SPMCOMM = (1/45)0.14 x (200 SPM) = 117 SPM
• Where:
* HCOMM = Height Commercial Column
* HPILOT = Height Pilot Column
* DCOMM = Diameter Commercial Column
* DPILOT = Diameter Pilot Column
* SPMCOMM = Commercial Strokes Per Minute
* SPMPILOT = Pilot Strokes Per Minute
Karr Column Pilot Plant Scale-up
Methanol Extraction from Acrylate
• Diameter = 45” (D1)
• Expanded Head Diameter = 68” (D2)
• Plate Stack = 26’-0” (A)
• Overall Height = 36’-8” (B)
D1
A
D2
B
Extraction Experience
KMPS has supplied over
300 extraction columns.
Questions?