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