Designing of liquid liquid extraction columns

DESIGNING LIQUID-LIQUID
EXTRACTION COLUMNS
An Introduction
September 16th, 2020

Koch Modular at a Glance
Koch Modular is a Joint Venture company, partnered
with , one of the world's most
prominent suppliers of mass transfer equipment. Koch-
Glitsch’s parent company is Koch Industries, one of the
largest privately held corporations in the United States.
Technical Expertise
For over 25 years Koch Modular has successfully
designed and supplied complete modular constructed
process systems for the worldwide Chemical
Processing Industry.
Our customers rely upon us for our technical expertise
and quality systems.

Koch Modular Presenter Biographies
Don Glatz is the Manager of Extraction Technology at Koch
Modular. Don’s activities include the evaluation and
optimization of extraction processes plus scale-up and
design of extraction systems. He has been working in this
field for the past 25 years and has published a number of
papers and articles covering this subject. Don holds a BS in
chemical engineering from Rensselaer Polytechnic Institute
and an MBA from Fairleigh Dickinson University.
Brendan Cross is a Senior Process Engineer at Koch
Modular that works in the Extraction Technology Group.
Brendan is responsible for liquid-liquid extraction application
evaluation, extraction column and pilot test design, and
commissioning and process startup. He has been with Koch
Modular for over 10 years and also has experience in
distillation and process development. Brendan holds a BS in
chemical engineering Columbia University.

Typical Applications
When is it prudent to use extraction?
When you want to:
 Remove high boiling organics from dilute aqueous streams such as
waste water or fermentation broths
 Recovery of non-volatile components which are typically inorganic chemicals
 Extract water soluble components from immiscible organic streams – quite
often referred to as a “water wash”
 Separate multiple component mixtures often utilizing fractional
extraction technique
 Separate heat sensitive products
 Process azeotropic and close boiling mixtures
 Avoid a high cost distillation solution

Industries Using Extraction Technology
Chemical  Recovery of acetic acid from dilute solutions
 Washing of acids/bases, polar compounds from
organics
 Recovery of valuable chemicals from aqueous solutions
Metals/Mining  Copper production
 Recovery of rare earth elements
Polymer Processing  Recovery of caprolactam for nylon manufacture
 Separation of catalyst from reaction products
 Water extraction of water soluble components
Biochemical Processing  Recovery of carboxylic acid from fermentation broths
 Recovery of valuable “oil” from algae broths
Effluent Treatment  Removal and recovery of phenol, DMF, DMAC
 Removal of nitrated organics
 Wastewater processing
Inorganic Chemicals  Purification of phosphoric acid

Simple Extraction Single Stage
U =
Solute in Raffinate
Solute in Feed
=
0.2
1.0
= 0.2
M =
Conc. Solute in Extract
Conc. Solute in Raffinate
=
0.8
50
0.2
99
= 7.92
E = S
F M = 50
99 7.92 = 4.0
Fraction Unextracted
Distribution Coefficient
Extraction Factor
A – 99
B – 0
C – 1
100
Feed (F)
A – 0
B – 50
C – 0
50
Solvent (S)
A – 0
B – 50
C – 0.8
50.8
Extract (E)
A – 99.0
B – 0
C – 0.2
99.2
Raffinate (R)

LEGEND
A, B Components in feed
C Component in solvent
Rx Raffinate from stage x
Ex Extract (made up of components B & C)
Mx Composition of two phase mixture
C C C C
A + B
Feed
E1 E2 E3 E4
F + S = M1 R1 + S = M2 R2 + S = M3 R3 + S = M4
R1 R2 R3 R4
Solvent Solvent Solvent Solvent
R1
R2
R3
R4
E1
E2
E3
E4
M1
M2
M3
M4
B
A C
F
Cross Flow Extraction

Countercurrent Flow Extraction
F + S = M
E1 + R4 = M
F + S = E1 + R4
F – E1 = R4 – S = Δ
Equations
A
C
E1
E2
E3
E4
A + B
Feed R1 R2 R3 R4
Solvent
C
R1
R2
R3
R4
E1
B
A
F
Δ
M E2
E3E4

Countercurrent Extraction
B + C
A + B
Feed (F)
Solvent (S)
Extract (E):
Solute Rich Stream
Raffinate (R):
Solute Lean Stream
Primary
Interface
Continuous
Phase
Dispersed Phase
(Droplets)
A
C

Bench Scale Test Apparatus (Liquid-Liquid Equilibrium Development)
Variable Speed Drive
Thermometer
Baffle
Tempered
Water In
Drain
1 Liter Flask
Tempered
Water Out
Used to:
 Generate distribution coefficients
 Screen solvents
 Perform qualitative observations

LLE Equilibrium and Operating Lines
Solute Free Basis
𝑋 𝐵𝐹 =
𝑋 𝐵𝐹
𝑋𝐴𝐹
𝑌𝐵𝐸 =
𝑦 𝐵𝐸
𝑦 𝐴𝑅 + 𝑦 𝐶𝐸
𝑋 𝐵𝑅 =
𝑥 𝐵𝑅
𝑥 𝐴𝑅 + 𝑥 𝐶𝑅
𝑌𝐵𝑆 =
𝑦 𝐵𝐹
𝑦 𝐴𝑆 + 𝑦 𝐶𝑆 𝐹′
= 𝐹 𝑥 𝐴𝑅
𝑆′
= 𝑆 𝑦 𝐴𝑆 𝑦 𝐶𝑆
𝐸′
= 𝐸 𝑦 𝐴𝐸 𝑦 𝐶𝐸
𝑅′
= 𝑅(𝑥 𝐴𝑅 𝑥 𝐶𝑅
Graphical Solution
Y
X
YBE
YBS
XBR
𝑚 =
𝑌𝐵∗
𝑋 𝐵∗
Distributon Coefficient
on Solute Free Basis
XBFR’
E’
F’
S’

Graphical Determination of Theoretical Stages
98% Solute Extraction, S/F = 1.0 mass basis
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.000 0.020 0.040 0.060 0.080 0.100 0.120
ExtractComp(WtFrac.,SoluteFree)
Raffinate Composition (Wt Frac., Solute Free)
2
3
4
5
6
(0.136, 0.118)
1

Kremser Equation
n = Number of theoretical stages required
xf = Conc. of solute in feed on solute free basis
xn = Conc. of solute in raffinate on solute free basis
ys = Conc. of solute in solvent on solute free basis
m = Distribution coefficient
E = Extraction factor = (m)(S/F)
ELOG
E
1
E
1
1
m
sy
nx
m
sy
f
x
LOG
n 





























1.0
0.8
0.6
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 Theoretical Stages
XBR/XBF=FractionUnextracted
E = 0.3

Recovery of Acetic Acid from Water Using a Low Boiling
Solvent
Aqueous Feed
1 - 30 %
Acetic Acid
Typical Solvents:
Ethyl Acetate
MTBE
Extraction
Raffinate
Stripping
Solvent
Recovery
Raffinate
Recycled
Solvent
Extract
Acetic Acid
Aqueous Raffinate
Steam
14

15
Fractional Extraction of Flavors and Aromas
Oil
Essential
Extract
Extraction
Solvent1
Distillation
Aqueous Alcohol
Solvent2
Distillation
Essential Oil
Hydrocarbon
Typical Products:
Orange Oil
Lemon Oil
Peppermint Oil
Cinnamon Oil

Major Types of Extraction Equipment
Used primarily in the metals
industry due to:
 Large flows
 Intense mixing
 Long Residence time
 Corrosive fluids
 History
Used primarily in the
pharmaceutical industry due to:
 Low Volume
 Short Residence time
 Handles Small Gravity Diff.
 History
Static Agitated
Spray Packed Tray Pulsed Rotary Reciprocating
Rarely used Used in:
 Refining
 Petrochemicals
Example:
 Random
 Structured
 SMVPTM
Used in:
 Refining
 Petrochemicals
Example:
 Sieve
Used in:
 Nuclear
 Inorganics
 Chemicals
Example:
 Packed
 Tray
 Disc & Donut
Example:
 RDC
 SCHEIBEL®
Example:
 KARR®
Used in:
 Chemicals
 Petrochemicals
 Refining
 Pharmaceutical
Mixer Settlers CentrifugalColumn Contactors
Packed ReciprocatingRotary

Packed Column
Feed (F)
Solvent (S)
Extract (E)
Raffinate (R)
Characteristics
 High capacity:
- 500-750 gal/ft2-hr (Random)
- 20-30 M3/M2-hr (Random)
- 1,000-2,000 gal/ft2-hr (Structured)
- 40-80 M3/M2-hr (Structured)
 Limited as to which phase can be dispersed – internals
MOC selection is critical
 Affected by changes in wetting characteristics
 Poor efficiency due to backmixing and wetting
 Not good for fouling service
 Limited turndown flexibility
 Requires low interfacial tension for economic usefulness

SCHEIBEL® Column
Characteristics
 Reasonable capacity:
- 350-600 gal/ft2-hr
- 15-25 M3/M2-hr
 High efficiency due to turbine impellers
and internal baffling
 Best suited when many stages are required
 Good turndown capability (4:1)
and high flexibility
 Not recommended for highly fouling
systems or systems that tend to emulsify
 Typical commercial operating speed: 15-75
RPM
Light
Phase In
Heavy
Phase In
Light
Phase Out
Heavy
Phase Out
Variable Speed
Drive
Interface
Control
Interface
Vessel
Walls
Rotating
Shaft
Turbine
Impeller
Horizontal
Inner Baffle
Horizontal
Outer Baffle

Internals for a 6.5 foot (2 meter) diameter SCHEIBEL® Column
SCHEIBEL® Column Internals
SCHEIBEL® Column internals installation

KARR® Reciprocating Column
Characteristics
 Highest capacity:
- 750-1,500 gal/ft2-hr
- 30-60 M3/M2-hr
 Good efficiency
 Good turndown capability (4:1)
 Uniform shear mixing
 Best suited for systems that have slow phase
separation or emulsify
 Optimal design for systems with suspended solids
 Typical commercial operating speed: 15 – 70 SPM
Heavy
Phase Inlet
Sparger
Light
Phase Inlet
Sparger
Light
Phase Out
Interface
Baffle Plate
Tie Rods
& Spacers
Perforated
Plate
Drive
Assembly
Interface
Control
Heavy
Phase Out

Internals for a 3 foot (1 meter) diameter KARR® Column
KARR® Column Plate Stack Assembly
KARR® internals installation

Comparing Commercial Extractors
1 2 4 6 10 20 40 60 100
0.2
0.4
.06
1
2
4
6
10
20
SCHEIBEL
KARR
RDC
Graesser
Kuhni
RZE
PFK
PSE
FK
MS SE
Efficiency/StagesperMeter
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® Col.
KEY

Preliminary LLE Column Design
Required by Koch Modular:
 Mixing and settling behavior of feed and solvent
 Liquid-liquid equilibrium data
 Feed composition and required raffinate composition
 Design capacity – mass feed flow rate and SG
Koch Modular can provide:
 Selection of optimal column type
 Preliminary design (diameter and height)
 Budget cost for extraction column
 Proposal for pilot plant test (required for process
performance guarantee)

Liquid-Liquid Extraction Scale-Up
Theoretical scale-up is difficult due to complex processes
occurring in an extractor
 Tendency to Emulsify
 Effects of Impurities or Solids
 Coalescing / Wetting Characteristics
 Phase Ratio Variability and Density Gradients
 Axial and Radial Mixing
 Mass Transfer Rate
 Interfacial and Drop Turbulence Effects

Liquid-Liquid Extraction Scale-Up
Best method of design:
Pilot testing followed by empirical scale-up

Which Phase is Continuous?
Solvent is Heavy Phase
Solvent is Light Phase
Primary
Interface
Solvent
Dispersed
Primary
Interface
R
E
F
S
Solvent
Continuous Primary
Interface
E
F
R
S
Solvent
Continuous
Primary
Interface
R
S
E
F
Solvent
Dispersed
S
F
E
R

Surface Wetting
 Want the continuous phase to preferentially wet
the internals – this minimizes coalescence and
therefore maximizes interfacial area
 For aqueous-organic systems, if water is the
continuous phase, use metal internals,
if organic is the continuous phase, use plastic
internals
Marangoni Effect
 Effect of mass transfer on interfacial tension
 For greater efficiency, disperse the solvent
 Droplets tend to repel each other
 Less energy required to maintain dispersion
Determining the Dispersed Phase
Flow Rate (Phase Ratio)
 For Sieve Tray and Packed Columns – disperse
the higher flowing phase
 For Agitated Columns – disperse lower flowing
phase
Viscosity
 For efficiency – disperse less viscous phase
(greater diffusion in less viscous droplet)
 For capacity – disperse more viscous phase (less
drag on droplets)
Droplets
coalesce.
Interfacial
area lost.
Droplets retain
shape.
Maximizes
interfacial area.
Viscous continuous phase
Drop rise or fall
will be inhibited

Interface Behavior – Rag Layers and Emulsion Bands
Emulsion band builds up
at interface due to slow
phase separation
Emulsion
Band
Rag
Layer
Solids build up at the
interface = rag layer
Corrective Actions
1. Reverse Phases
2. For Emulsion Band: slow down capacity or reduce
agitation speed
3. For Rag Layer: circulate liquid through an external filter

Entrainment refers to removing a small portion of one phase out of the wrong end of the column
i.e. where the other phase exits.
Entrainment
E
OR OR
Entrainment is
controlled by:
1. Increased settling
time inside the column
2. Coalescer inside the
column, within the
disengaging section
3. Coalescer external to
the column
R
E
F
S
R
E
F
S
R
E
F
S
R
F
S

Primary Interface
f
F1
S
E
R
Primary Interface
f
F2
S
E
R
Second
Interface
F2 > F1
Flooding
Flooding is 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

Flooding
f1
Primary Interface
f2
F2
S
E
R
Second
Interface
f2 > f1
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
Primary Interface
F1
S
E
R

Generalized Scale-up Procedure
Pilot Scale
f1
Q1
D1
H1
Feed Rate
f2
Q2
Feed Rate
D2
Basic Scale-up Relationships:
D2/D1 = K1(Q2/Q1 )^M1
H2/H1 = K2(D2/D1 )^M2
f2/f1 = K3(D2/D1)^M3
Where:
K1, M1 = Capacity Scale-up Factors
K2, M2 = Efficiency Scale-up Factors
K3, M3 = Power Scale-up Factors
Commercial Scale
“Axial” or “back” mixing increases as an extraction column’s diameter is
increased. This phenomena causes concentration gradients that decrease
driving force and therefore increase HETS.
H2

Koch Modular Pilot Plant Services Group
Koch Modular maintains a pilot plant dedicated to
extraction R & D and applications testing
Pilot Plant Capabilities
• Ability to test liquid-liquid extraction with:
• KARR® columns with a plate stack as high as 20 feet (6
meters)
• SCHEIBEL® columns with up to 150 agitated stages
• Distillation for solvent recovery / downstream
purification
• Analytical capabilities:
• GC
• HPLC
• Titration
• IC
• Karl Fischer
• Outside labs can be used for other types of analysis

Continuous Extraction Pilot Plant Arrangement
Hot Oil
Feed Solvent
Raffinate
Extract
Mass Meter
Mass
Meter

Recovery of Carboxylic Acids from Fermentation Broth
Broth generated from cellulosic materials
– approx. 5% acids
LLE Goal: To achieve >95% recovery (high purity) and
minimize solvent usage
Ethyl acetate selected solvent – but emulsified easily
Preliminary Data in RDC Columns
 Difficult operation due to emulsification
 < 90% acid recovery
 High S/F ratio – 2.0
KARR® Column Required

Pilot KARR® Column for Carboxylic Acids Extraction
1” diameter x 12’ Plate Stack
Hot Oil
Whole Broth Feed
Ethyl Acetate
Variable Speed Drive
Aqueous Out
(Raffinate)
Organic Out (Extract Phase)
Mass Meter
Mass
Meter
Interface

TABLE 1: Pilot Plant Data for Fermentation Broth Extraction
All runs performed in a 25 mm diameter, KARR® Column
RUN Plate Stack Ht. Capacity Temp. S/F Ratio Agitation Acid Recovery
# (feet) GPH/ft2 C SPM %
1 12 700 23 1.7 30 95.0
2 12 700 23 1.7 40 97.5
3 12 700 23 1.7 50 Flooded
4 8 700 23 1.7 30 93.3
5 8 700 23 1.7 40 Flooded
6 10 700 23 1.7 30 96.3
7 12 650 23 1.5 30 96.5
8 12 500 23 1.5 40 97.6
9 12 700 23 1.5 30 94.3
10 12 650 45 1.5 30 98.3
11 12 650 45 1.5 50 98.7
12 12 650 45 1.5 60 Flooded

KARR® Column Pilot Plant Scale-up Procedure
Carboxylic Acid Extraction from Broth
 DCOMM = 22” (1:1 Scale-up Based on Capacity)
 HCOMM = (DCOMM / DPILOT)0.38 x HPILOT
 HCOMM = (22/1)0.38 x (12 feet) = 38 feet | 11.6 M
 SPMCOMM = (DPILOT / DCOMM)0.14 x SPMPILOT
 SPMCOMM = (1/22)0.14 x (50 SPM) = 32 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 Design | Carboxylic Acids Extraction from Broth
 Diameter = 22” | 0.56M (D1)
 Expanded Ends
Diameter = 44” | 1.1M (D2)
 Plate Stack = 38’-0” | 11.6M (A)
 Overall Height = 50’-6” | 15.4M (B)
 Part of complete modular system (LLE +
solvent recovery distillation columns)
designed, fabricated, and installed

Modular System Design | Carboxylic Acids Extraction from Broth

KARR® Column Demonstration Video
Can be viewed on our website or here:
https://www.youtube.com/watch?v=TlJaSK6YEp4
42

Extraction Experience
Koch Modular has supplied over 300 commercial
extraction columns
Koch Modular has also supplied hundreds of pilot
scale extraction columns
We have tested more than 200 different processes
in the pilot plant
QUESTIONS?

Designing of liquid liquid extraction columns

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Editor's Notes