COUNTERCURRENT MULTISTAGE EXTRACTION II More Applications HETP, HTU, Capacity Chapter 6
Dec 17, 2015
COUNTERCURRENT MULTISTAGE EXTRACTION
II
More Applications
HETP, HTU,
Capacity
Chapter 6
Tocopherol - Separation
Structure of Tocochromanols
Solubility of Tocopherols in sc-CO2
Squalene - Tocopherol - Sterol - Separation
Top Product of Tocopherols
Binary Analysis of the Separation Process
Separation Factor Squalene- Tocopherol
5 10 15 20 25 30 355
10
15
20
25
99 Gew.% Squalen
90 Gew.% Squalen
20 MPa/343 K 23 MPa/353 K 26 MPa/363 K
nth [
-]
[-]
Squalene - Tocopherol/Sterol-separation with CO2
Saure 1996
99 wt-% squalene
90 wt-% squalene
6
5
4
3
2
1
0 20 40 60 80 100
0 20 40 60 80 100
Feedzugabe
Gas-, Flüssigphase: , Squalen , Tocopherole , Sterine
xi' [Mol%]
Ko
lon
nen
stu
fen
[-]
SqualeneTocopherolsSterols
Gas, liquid
Saure 1996
Feed
Equ
ilibr
ium
sta
ges
Squalene/Tocopherols From Distillates
2 3 4 5 6 7 810
15
20
25
30
35
40
45
50
point of minimum
99 % of C16 in extract
99 % of C16 in extract
T = 373 K, P = 29 MPa.
System: PFAD/SC-CO2
Nth
Num
ber o
f Sta
ges
Reflux ratio [-]
60
80
100
120
140
160
Solvent-to-Feed ratio S/F [-]
min
= 2,522, Nmin
= 13.
min
= 3,276, Nmin
= 18
Separation of FFA
C16/C18-FFA -CO2
Machado 1998
0.0 0.2 0.4 0.6 0.8 1.00
20
40
60
80
100
120
140
160
180
NE ; N
R [-]
Anteil LFK + TAGas- bzw. Flüssigphase
[-]
Calculation of number of theoretical stages (Jänecke). 333 K, 24 MPa CO2.
U. Fleck. Tocopherolacetate.
Purification of Synthetic Tocopherolacetate
5 10 15 20 25 30 35
5
10
15
20
25
T = 333 K; P = 16 MPa
Anteil "Rest"8 Gew.-% 6 Gew.-%
McCabe Thiele Jänecke
nth
[-]
Rücklaufverhältnis [-]
Determination of nth in dependence on reflux ratio for different purities. (McCabe-Thiele and Jänecke); 333 K, 16 MPa CO2. . U. Fleck.
Purification of Synthetic Tocopherolacetate
1E-3 0.01 0.1 10.6 0.7 0.8 0.9
I. Stufe V18T = 333 Kp = 20 MPa
Feedzugabe
Extrakt
3. OG
2. OG
1. OG
EG
Raffinat
TA.g TA.fl s1.g s1.fl s2.g s2.fl s3.g s3.fl s5.g s5.fl s6.g s6.fl
Massenanteil [-]
Kol
onne
nhöh
e
Concentration profiles along column length; 333 K, 20 MPa CO2. U. Fleck.
Purification of Synthetic Tocopherolacetate
0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7
1
2
3
4
5
6 Squalene L VFFE L VFFA L VH
eigh
t of
Col
umn
[m]
Concentration, CO2-free [-] Buß 1999
Free fatty acids (FFA) -/- Squalene- FA-esters
0,51,01,52,02,53,03,5
1
2
3
4
5
6
Kolonnenh
öhe [m
]
Ki [-]
0,00,51,01,52,02,53,03,5
1
2
3
4
5
6
Kolonnenh
öhe [m
]
i, Squalen
[-]
Variation of K-factors (left) and separation factors (right) with column length. 370 K; 23 MPa. Left: = Squalen, = FAE, = FFA; Right: = aFAE, Squalen, = aFFA, Squalen. D. Buß, 2001
Separation Factor: Influence of Concentration
10 20 30 40 504
8
12
16
20
24
LMV
/ (k
g C
O2
/ kg
Fee
d)
CPO/CO2 für xLFK,F = 4,6 Ma.%, xLFK,E = 95 Ma.%, xLFK,R = 0,1 Ma.%
n th, J
änec
ke /
-
/ (kg Rücklauf / kg Extrakt)
0
100
200
300
400
500
LMV
nth
20 MPa, 340 K 20 MPa, 370 K 25 MPa, " 30 MPa, "
Separation Analysis: FFA, Toco - Triglycerides, Carotene
/ (kg reflux / kg extract
Solvent ratio
0 1 2 3 4 52
4
6
8
10
12n th
, Jä
ne
cke
/ -
/ (kg Rücklauf / kg Extrakt)
0
10
20
30
40
50 12,5 MPa 320 K
15,0 MPa 320 K
17,5 MPa 340 K
20,0 MPa 340 K
20,0 MPa 360 K
22,5 MPa 360 K L
MV
/ (
kg C
O2
/ kg
Fe
ed
)
FAME/-Carotin/CO2 für x
Caro,F = 500 ppm, x
Caro,E = 10 ppm, x
Caro,R = 10 000 ppm
Separation Analysis: FAME - Carotenes
86 88 90 92 94 98 99 1001.0
1.5
2.0
2.5
3.0
11.4 MPa
11.25 MPa
11.1 MPa
10.8 MPa
10.4 MPa
10.0 MPa
9.0 MPa333 K
10.0 MPa 10.4 MPa 10.8 MPa 11.1 MPa 11.25 MPa Eq. 3
Sep
arat
ion
Fac
tor
T/A
Terpenes in Solvent-Free Liquid Phase [wt %]
Representation of an improved separation factor model at 333 K. M. Budich
Orange Peel Oil
2 4 6 8 10 12 1410
20
30
40
50
60
Sol
vent
-to-
Fee
d R
atio
[kg/
kg]
Num
ber of
The
oret
ical
Sta
ges
Reflux Ratio [kg/kg]
100
200
300
400
50099.8 wt % terpenes in extractfolding ratio = 10
333 K, 10.0 MPa 333 K, 10.7 MPa
Budich 1998
Orange Peel Oil: Removal of Terpenes
0 20 40 60 80 100
1
10
CO2+ethanol+water at 333 K, 10 MPa
ethanol+water at 0.1 MPa (Kirschbaum, 1969)
conventional sampling method modified sampling method
Sep
arat
ion
Fac
tor e
than
ol /
wat
er
Ethanol in Solvent-Free Liquid Phase [wt %]
Budich, 1998
No Aceotrope in Ethanol - Water
0 10 20 30 40 500
10
20
30
40
50
Sol
vent
-to-
Fee
d R
atio
[kg/
kg]
number of theoretical stages
Num
ber
of T
heor
etic
al S
tage
s
Extract Reflux Ratio [kg/kg]
0
20
40
60
80
100Feed: 10 wt % ethanolExtract: 99.0 wt % ethanolRaffinate: 0.1 wt % ethanol
333 K, 10 MPa
solvent-to-feed ratio
Calculation of the theoretical number of stages. M. Budich.
Ethanol - Water
Flow Scheme of Mixer-Settler. M. Jungfer, 2000. Design: Trepp, ETH-Zürich
Mixer-Settler (5 Stages)
Mixer-Settler-Module No. n. M. Jungfer, 2000. Design: Trepp, ETH-Zürich
Mixer-Settler, Single Stage
Countercurrent Separation
V/L v S / F
FAEE, FAME (5 %) 20 7.5 125
FFA (fatty acids) (2 %) 50 4.5 50
Squalene (1.5 %) 20 10 50
Tocopherol-Purif. (2.5 %) 35 20 45Solvent ratio V/L, kg/kg
Reflux ratio v, -
Solvent to feed ratio S/F, kgF /kgF
Basis:
Solvent: Carbon dioxide
10 - 30 MPa, 350 K
Solvent Cycle: Solvent to Feed Ratio of SFE Processes
0 20 40 60 80 100 120 1400
100
200
300
400
500
600 Feed = 100 kg/h orange peel oilFolding Ratio = 10Reflux Ratio = 4
323 K 333 K 343 K
Sol
vent
-to-
Fee
d R
atio
[kg/
kg]
Loading [g Extract/kg CO2]
Relationship between loading and solvent-to-feed ratio. M. Budich. Orange peel oil.
Solubility and Solvent to Feed Ratio
Enhance solubility in solvent:
Pressure, temperature
other solvent (C3H8 vs. CO2)
Reduce energy for solvent cycle:
low p for extract recovery
Means for reducing costs
350 400 450 500 550 600 650 700 750 800 8500
2
4
6
8
10
12
14
0
2
4
6
8
10
12
14
10% PropanAusgangsware
Löslichkeitgas [%]
[k1
-3/k
TA
,5+
6] [-
]
Temp: Löslichkeit 313K 333K 353K
DichteCO
2/Propan
[kg/m3] Density
Se
lect
ivity
So
lub
ility
Temp. Solubility Selectivity
10 % Propane
initial feed mixture
Fleck 1998
Purification of Tocopherol: CO2-Propane
0 1 2 3 4 5 6 7 86
8
10
12
14
16
18
LMV = const = 30
LMV = const = 70
T = 313 K
MW
= 618 kg/m3
07.08.98 15:51:38
10% Propan; 10 MPa 20% Propan; 9 MPa 30% Propan, 9 MPa
n th M
cCab
e-Th
iele
[-]
Rücklaufverhältnis [-]Reflux ratio
Solvent ratio = 30
Solvent ratio = 70
Propane,10 MPa
Propane, 9 MPa
Propane, 9 MPa
Fleck, 1999
Purification of tocopherol: CO2-Propane
High vacuum distillation: 100 %
p Solvent: CO2 200 %
Solvent: CO2 + C3H8 20 %
Adsorption:
Solvent: CO2 50 %
Solvent: CO2 + C3H8 8 %
Some Data on Solvent Cycle Costs
thnhHETP /
.
,d
,
Fak
VHTU
yy
yNTU
NTUHTUh
v
y
y
o
i
FA-ethyl esters - CO2
Riha 1996
HETP, HTU
20 30 40 50 60 700
1
2
3
23 MPa/353 Ky=0,4440+0,0183x
26 MPa/363 Ky=-0,2697+0,0460x
23 MPa/353 K 26 MPa/363 K 26 MPa/353 K
HE
TP
[m
]
LMVa [kg/kg]
HETP (Jänecke) vs solvent ratio in stripping section. Saure, 1996
HETP: Tocopherol
75 80 85 90 95 1000.0
0.5
1.0
1.5
2.0
enriching section
ethanol+water mixtures aqueous aroma mixtures Ikawa et al. (1993)
HETS [m
]
Organic Components in Extract [wt %]
0 20 40 60 80 1000.0
0.5
1.0
1.5
2.0
experiments with liquid CO
2 reflux
stripping section
ethanol+water mixtures aqueous aroma mixtures
HE
TS
[m]
Organic Components in Feed Mixture [wt %]
HETS for aqueous mixtures
M. Budich
log p
log mL
mG
log (gas loading)
log (gas/liquid loading)
Different packings, systems
flooding
Pressure drop, flooding
CY-Water
CY- TocoRaschig-Water
Raschig- Olive oil- Dist.
EX-Water
Stockfleth
1999Billet-diagram
Flooding
10-4 10-3 10-20,1
1
20 MPa, 373 K
30 MPa, 393 K
30 MPa, 373 K
20 MPa, 323 K
30 MPa, 323 K
BP, 23 MPa/353 K BP, 26 MPa/363 K FP, 23 MPa/353 K
QV*
V0,
5 [m
/s*(
kg/m
³)0,
5 ]
QL [m³/m²s]
Flooding diagram for tocopherol feed mixture (T155/CO2), Packing Sulzer CY ; Operating points (BP) and observed flooding points (FP). C. Saure, 1996
Flooding: Tocopherol Feed Mixture (55 % Toco)
14 16 18 20 22 24 26 28 30300
400
500
600
700
800
900
1000
Liquid phase
Gas phase
System: PFAD + CO2
T = 373 KT = 353 KT = 333 K
Den
sity
[kg/
m3 ]
P [MPa]
Densities of the coexisting phases of the system PFAD + CO2. N. Machado
Density of Phases
0,1 10,01
0,1
Loading
Flooding
Gas
Cap
acit
y F
acto
r F V
[m
/s]
Flow Parameter [-]
System: PFAD + CO2
Packing: Sulzer EXD
Kol = 25 mm
T = 373 K, P = 29.3 MPaT = 373 K, P = 25.3 MPaT = 373 K, P = 20.3 MPaT = 353 K, P = 29.2 MPaT = 353 K, P = 24.4 MPaT = 353 K, P = 20.3 MPaT = 333 K, P = 29.0 MPaT = 333 K, P = 24.6 MPaT = 333 K, P = 19.9 MPa
Hydraulic capacity diagram of packed columns. FV = f (y). N. Machado
Flooding: PFAD
14 16 18 20 22 24 26300
400
500
600
700
800
900
Dic
hte
[kg/
m3 ]
Druck [MPa]
Density of coexisting phases: CO2–Squalene. Flüssig-/Gasphase: / = 333,15 K, / = 353,15 K ▲/▲ = 373,15 K. D. Buß
Density of Phases
0,1 10,01
0,1
Flooding
Loading
System: Squalene + CO2
Packing: Sulzer EXD
Col = 25 mm
T = 333 K, P = 20 MPaT = 333 K, P = 25 MPaT = 353 K, P = 20 MPaT = 353 K, P = 25 MPaT = 373 K, P = 20 MPaT = 373 K, P = 25 MPaG
as C
apac
ity
Fac
tor
Fv
[m/s
]
Flow Parameter [-]Hydraulic capacity diagram of packed columns: Squalene - CO2. N. Machado
Flooding: Squalene
0,01 0,1
0,01
Flutpunkte Betriebspunkte
Sulzer EX Gewebedrahtpackung mit CPO / CO2
A / V = 2725 m2/m
3 = 0,86 d
hydr = 2,02 mm
Kap
azitä
tsfa
ktor
F' V
/ (m
/s)
Flussparameter / -
Flooding Diagram, Crude Palm Oil - Carbon Dioxide, M. Jungfer, 2000
Flooding: CPO
0,01 0,1 1
0,01
0,1
Gas
bela
stun
gsfa
ktor
FG [
-]
Strömungsparameter [-]
Flooding diagram CO2–OODD; Packing “Sulzer EX 35 mm”. Exp. Flooding Data: Stockfleth , o = Data of separation column. D. Buß, 2001.
GL
GGG uF
L
G
V
L
Flooding: Olive Oil Deodorizer Distillate
320 325 330 335 340 345
44000
48000
52000
56000
60000
64000
35 mm Kolonne 50 mm Kolonne
= 776 kg/m3
Bela
stung
sgre
nze [k
g CO
2/m2 *h
]
Temperatur [K]
Loading limits for a 35 and 50 mm column. CO2. U. Fleck.
Purification of Synthetic Tocopherolacetate
0 10000 20000 30000 400000
200
400
600
800
1000
1200
40000 30000 20000
Vapor phase cross-section capacity [kg/(m²h)] =
CO2+orange peel oil
at 333 K and 10 MPa
Pre
ssur
e D
rop P
/H [P
a/m
]
Liquid-Phase Cross-Section Capacity [kg/(m²h)]
Pressure-drop curves. M. Budich. Orange peel oil.
Pressure Drop
0.1 10.01
0.1
CO2+orange peel oil
323 K 333 K 343 K
±15%
Capa
city
Fact
or F
V [m
/s]
Flow Parameter [-]
Overall correlation of flooding lines for CO2+orange peel oil. M. Budich
L
V
V
L
m
m
VL
VVV uF
A
mu
V
VV
velocity of vapor phase inside an empty tube
BAFV
1
Flooding: Orange Peel Oil
0.1 10.01
0.1
increasing percentageof aroma components
CO2+terpenes CO2+orange peel oil CO2+5-fold concentrate
Cap
acity
Fac
tor F
V [m
/s]
Flow Parameter [-]
Comparison of flooding behavior of different mixtures. M. Budich.
Median lines: B=52.7 for CO2+terpenes; B=77.5 for CO2+5-fold concentrate.
A = 8.0.
BAFV
1
Flooding: Orange Peel Oil
0 20 40 60 80 100275
300
325
350
375
700
800
900
1000 T = 333 K, P = 10 MPa
derived from VLE measurements
Vapor phase
Liquid phase
Den
sity
[kg/
m³]
Ethanol in Solvent-Free Phase [wt %]
Densities of coexisting phases of CO2+ethanol+water mixtures. M. Budich.
Density of Phases
1000 10000
10000
20000
30000
40000
50000
60000
70000
80000
experiments at theextraction tower
333.2 K, 10 MPa 90.4 56.0 80.1 50.0 69.6 44.6
19.5
Ethanol in Liquid Phase [wt %]
Vap
or P
hase
C
ross
-Sec
tion
Cap
acity
[kg/
(m²h
)]
Liquid Phase Cross-Section Capacity [kg/(m²h)]
Flooding point data for CO2+ethanol+water
M. Budich, 1999
0.01 0.1 1
0.01
0.1Ethanol in an ethanol+water mixture [wt %]
2.1 3.1 19.5
36.140.144.650.056.0
69.6 80.1 90.4 90.6 93.8 96.5
Capaci
ty F
act
or
FV [m
/s]
Flow Parameter [-]
Flooding point of CO2+ ethanol + water. M Budich.
Flooding: Ethanol - Water - CO2
GL
GGG uF
L
G
V
L
Flooding point 100 000 kgCO2/(m2h):
Column diameter Throughput
[mm] [kgCO2/h]
25 49
50 196
100 785
Linear velocity: 46 mm/s
Capacity of Columns
Column diameter
FA-ethyl esters - CO2
Riha 1996
HYDRODYNAMIC BEHAVIOUR IN PACKED COUNTERCURRENT COLUMNS FOR
SUPERCRITICAL FLUID EXTRACTION
DPI1DPI2
FI2
FI1
1
23
4
45
5
1 - Column, 2 - Autoclave, 3 - Differential Pressure Transducers 4 - Gear Pumps, 5 - Flow Meters, Full Line - Liquid Cycle, Dashed Line - Supercritical Fluid Cycle
Flowsheet of the experimental Apparatus
Structure of flow channels in regular packings
Sulze r M e lla p a kSulze r EX
Regular Structured Column Packings
wG
wG
wG
wL , m a x
0
Film
a .
x
Film
x
c .
wL
wL
Film
x
b .
Flow of liquid film against countercurrent gas flow:
a) negigible, b) strong, c) very strong influence of gas flow.
Shape of liquid film: smooth, rippled (waves), with noses, drops are formed.
Increasing flow velocity
Flow Regimesa. – Waves. b. – Crests. c. – Drop formation. d. – Flooding. T = 338 K, P = 20.6 MPa.
A Falling Film At High Pressures
1 100,9
1
2
3
L1/
3 = (
2g L
²/(
L/U
)²)1/
3
ReL = m
L/(
LU)
Corn germ oil - CO2, 338 K , 7.6 MPa P 20,6 MPa, : Nusselt (1916)
Film-Thickness: Nusselt’s Theory
4000
6000
8000
10000
20000
40000
60000
80000
0,70,80,91
2
3
4
5
6
7
Figure 4
Re L = mL/(LU)
KF=L³/(g
L
4)
Flow Regimes: Full Squares: Drop formation without gas flow. Empty Squares: Drop formation with gas flow. Full Triangles: Crest formation without gas flow. Empty Triangles: Crest formation with gas flow. Line: Moser’s correlation
From the figure it is obvious that the gas flow has a significant impact on the flow regime of the liquid film.
Flow Regimes: Influence of Gas Flow
The gas flow exerts a shear force on the liquid film, and this affects the shape of the interface, i. e. the flow regime. ,
Hshear dHF where is the shear stress, H the height of the film and dH its hydraulic diameter.
The gas flow exerts the following force on the liquid surface:
2Hgas dPF
where P is the pressure drop.
If the shear force the gas exerts on the inner wall of the glass tube is neglected, a force balance yields:
H
dPFF H
sheargas
Influence of Gas Flow
Rating the pressure drop to the impact pressure of the gas flow yields the dimensionless gas resistance factor G:
Huu
dP
LGG
HG 2
where uG – uL is the slip velocity.
The influence of the gas flow on the flow regime is now taken into account by using the property ReL(1+G)n instead of ReL.
Influence of Gas Flow
4000
6000
8000
10000
20000
40000
60000
80000
0,70,80,91
2
3
4
5
6
7
Figure 5
Re L(1+ G)1/3
KF=L³/(g
L
4)
Flow Regimes: New Diagram accounting for Shear Stress. Full Squares: Drop formation without gas flow. Empty Squares: Drop formation with gas flow. Full Triangles: Crest formation without gas flow. Empty Triangles: Crest formation with gas flow. Line: Moser’s correlation.
Flooding
Correlation of the flooding points according to Wallis [10]:
GLH
LLL
GLH
GGGLG dg
uj
dg
ujjfj
**** ;;
With uL for the superficial liquid velocity and the fractional void volume which is unity for a falling film column but smaller than unity for packed columns. jG* and jL* are modified Froude-Numbers rating the respective impact pressure to the difference between liquid head and buoyancy.
21
2*2
*1
*
1
K
KjKjKj GLG
For the correlation of the data displayed, the values K1=0,4222 and K2=1,1457 with a standard deviation of 19%.
G. B Wallis, (1969), One-Dimensional Two-Phase Flow, McGraw-Hill, New York
0,01 0,1 10,04
0,1
0,2
0,3
0,4
HP Packings14,15
HP Packings13
NP Mellapak19
This work
Figure 6
j G* =
u G/( G
/(g
d H( L
-G)))0.
5
=uL/u
G(
L/
G)0.5
Flooding Diagram. Thick line: Correlation. Dashed lines: 30% interval. Empty triangles: Structured and random packings at high pressures. Circles: Structured packings at high pressures. Full diamond: MellapakTM at normal pressure. Full triangles: Falling film flooding at high pressures.
Very similar to:T. K. Sherwood, G. H. Shipley and F. A. L. Holloway (1938),
Ind. Eng. Chem., 7, 765 - 769,
Packings: Sulzer CY, Sulzer EX, Sulzer Mellapak, 5x5x0.5 mm Raschig rings, and 4 mm Berl saddles.
Substances: water, air, carbon dioxide, olive oil deodorizer distillate, soybean oil deodorizer distillate, fatty acid methyl esters, and tocopherols.
General Flooding Diagram