Chapter 4

Supercritical Fluids Extraction From Solids-II

time

am

oun

t of e

xtra

ct in

so

lid p

ha

se

steady

unsteady

starting

P, T = const.

total amount of extract in feed

amo

unt o

f ext

ract steady unsteady

starting

time

Course of the extraction process

Remaining extract in feed Accumulated extract in sc solvent

Composition of extract changes with conditions of extraction and time

CaffeineTheobromine

Decaffeination of green coffee beans

Lack and Seidlitz 1993

Decaffeination of green coffee beans

Lack and Seidlitz 1993

Flow scheme of decaffeination plant

Schoeller-Bleckmann design

Lack and Seidlitz 1993

Comparison of extraction behaviour

Zwiefelhofer 1990

Composition of liquid CO2 hop extract

Gardner 1993

Rossi et al., 1989

1: Liquor, 40 MPa, 80 oC, 5 h

2: Liquor, 40 MPa, 50 oC, 5 h

3: Nibs, 40 MPa, 80 oC, 5 h

4: Nibs, 40 MPa, 50 oC, 5 h

5: Shells, 30 MPa, 80 oC, 6 h

Fat extraction from cocoa

Standard design

Extractor

Heat exchanger

Cycle gas compressor

Precipitator

Total number of pressure vessels for SFE

Gehrig 1998

100 1000 10000 100000

Throughput feed [t/a]

Batch process

Continuous process

Biggest plant 60 000 t/a

Cost per ton of solid feed [DM]

10000

1000

100

Economy of scale: CO2-extraction from solids

0 500 1000 1500 2000 2500 3000 3500 40000

1

2

3

4

5

6

7

8

mass flow: 18.4 g/min mass flow: 25.8 g/min gradient of the extraction curve; 18.4 g/min; y =0. 00665 gradient of the extraction curve; 25.78 g/min;yyy y

=0 .00663

oil[g]

CO2 [g]

extraction at 300 bar444eeeend4040

Franca, Reber, Meireles, Machado, Brunner, J. Supercritical Fluids 1998

Extraction of Buriti

0 1000 2000 3000 4000 5000-10000

-5000

0

5000

10000

15000

20000

25000

CO2 (g)

Caro

tene

con

cent

ratio

n (p

pm)

0

20

40

60

80

Soxhlet

Am

ount of carotene (mg)

Carotene

Franca, Reber, Meireles, Machado, Brunner, J. Supercritical Fluids 1998

Extraction of Buriti

0,00

0,01

0,02

0,03

0,04

0,05

0 10 20 30 40 50 60g CO2 / g Vorlage

g ASester / g Vorlage

200 bar 60° C

300 bar 60° C

400 bar 60° C

400 bar 70° C

300 bar 40° C

400 bar 40° C

Arachidonic acid from fermentation

Arachidonic acid as methylester extracted from dried filter cakegAAE / gcake

g CO2 / g cake

Extraction of meat products

Effect of varying pressure on the accumulated yield of lipid( left ) and water (right) extracted with supercritical CO2 at 50 oC

R.R. Chao, 1996

Extraction of beef tallow

Cumulative weight of beef tallow extracted by CO2 varying the pressure and temperature

R.R. Chao et al., 1993

Cholesterol concentration in extract

scCO2

Lipid and cholesterol extract from beef tallow.

CO2 and CO2 - ethanol

R. R. Chao et al., 1993

Extraction of beef tallow

Brunner XVII CBCTA - Fortaleza 2000 19

Percent oil removed as a function of volume of CO2 . Feed: Type I: unsalted, Type II: x salted.Extraction P = 408 +/- 6.8 bar, T = 55 +/- 1 oC. Separation: P 2 bar; T = 30 +/-3 oC.

Extraction of oil from chips

S. Vijayan et al., 1994

Extraction of mustard seed oils

300 bar, 40 oC

total amount oil water myrosinase activity

Taniguchi et al. 1987

Extraction of oil from peanuts

CO2

25 oC

Goodrum 1996

Extraction of theobromine from cocoa seed shells

Simon 1990

50 kgCO2/(kgFh) 93 183 304

0 100 200 300 4000

20

40

60

80

1006h

2h

1h

28s

semibatch 25 MPa, 653 K [6] continuous 24 MPa, 663 K

de

gre

e o

f e

xtra

ctio

n

[%]

solvent to soil ratio [kgH

2O

/kgdry soil material

]

Cleaning of Soil

Semibatch and continuous extraction results versus solvent to soil ratio

0 1 2 3 40,0

0,2

0,4

0,6

0,8

1,0

exper i mental data 25 MPa, 650 K, 2.2 kg H2O/ h

degr

ee o

f ex

trac

tion

E

t i me [hour s]

Cleaning of Soil

Course of an extraction of hydrocarbon contaminants rom soil with supercritical water.

Temperature Loading Residence O2 excess Degree of time conversion U

___________________________________________________________________ [°C] [ghc/LH2O] [s] [mol O2/ mohc-mhc)/ mhc

mol O2,min]___________________________________________________________________

290 6.7 135 1.68 0.963

330 0.7 107 26 0.999998

385 3.0 68 6.99 0.9376

Reaction results at 25 MPa, 88 cm3 reactor

SCWO of extracted organic waste from soil

Unterschiedliche Behandlungsmethoden des CND- Bodens:

Wasser ist org. Lösemitteln überlegen

TO

C [

g C

/kg

TS

]Vergleich TOC nach Extraktionen

als Schicht

am Rand

als Kohlenwasser-

stoffpartikel

in den Poren

adsorbiert

im Innern gelöst

Kontaminationsverteilung

ab

c

d

e

f

g

hCO2

2H O

Festbettextraktionsanlage

ac

b

e

d

f

g

Kontinuierlicher Rohrreaktor

Flow sheme of continuous extaction apparatus: Fließbild der kombinierten Anlage: a Vorlagebehälter mit Rührwerk, b Pufferautoklav, c Wirbelbettheizer -Vorwärmer- d Extraktionsstrecke, e Elektrolysezelle im Schutzbehälter, f Doppelrohrwärmetauscher, g Sammelgefäß, h Gasanalysegerät, i evakuierter Glasbehälter

a magnetic stirrer, b  membrane pump, c feed vessel, d buffer vessel, e pump, f preheater (28 ml), g extraction pipe (38 ml), h cooler, i flask, j CO2-meter, k evacuated glas vessel.

0.0 2.5 5.0 7.5 10.0 12.5 15.00

20

40

60

80

100

Kohlendioxid50-100°C, 20 MPa

Wasser 380°C, 25 MPa

Lösungsmittelverhältnis [kg LM/kg Boden]

Ext

rakt

ions

grad

[%

]

Realgealterte (20 Jahre) Kontamination (Schluff)

kann mit Wasser vollständig gereinigt werden.

Lösungsmittelvergleich

• Porendiffusion aus

Mikro- in Mesoporen

• Diffusion im Porenfluid

oder Lösungsmittel

• Stofftransport durch

Strömungsgrenzschicht

• konvektiver Stofftransport

mit Lösungsmittelstrom

Transportmechanismen

Kontamination am Feststoff

Partikelporen

Fluidphase

)c

c1(Xk

t

Xpmax

pS1

S

r

c

r

2

r

cD

t

c p2p

2

effp

p

)cc(

1

d

6)cc(

V

VA

t

cfRrp

f

f

pfRrp

f

PartPartf

Strömungsform durch berücksichtigen

Auflösung als Reaktion 1. Ordnung

Modellierung Extraktion

• Suspension als Strähne/Einzel-korn betrachtet

• Dodecan bildet Bezug

0 50 100 150 200 250 300 350 4000

20

40

60

80

100

P = 24 MPa, = 23-49 s, T = 378 - 393 °C

experimentell kombiniertes Modell

Ext

rakt

ions

grad

[%

]

Lösungsmittelverhältnis [kg H2O/kg Boden]

Modellierungsergebnisse

0 50 100 150 2000

20

40

60

80

100

2. Extraktion

1.

3. Extraktion

2.

1.

experimentell (2 Gew.%) simuliert (2 Gew.%) experimentell (3 Gew.%) simuliert (3 Gew.%)

Ext

rakt

ions

grad

[%]

Verweilzeit [s]

P = 24 MPa

T = 381 - 389°C

P = 24 MPa

T = 361 - 381°C

Modellierungsparameter

zur Simulation geeignet

Simulation der Extraktion

0 2 4 6 8 10 12 14 16 18 200

50

100

150

200

250

300

350

CSB° 4502 mg/l

CSB° 2250 mg/l

CSB° 2668 mg/l

t [Tage]

BS

B [

mg/

l]

Extraktionsbedingungen 400°C 3 MPa 380°C 25 MPa 320°C 25 MPa

Beurteilung der biologischen Abbaubarkeit mittels akkumu-lierten Sauer-stoffverbrauchs von Belebt-schlamm

Bruchteil von CSB° wird erreicht

Biologische Abbaubarkeit

25 50 75 100 125 15010

20

30

40

50

60

Verweilzeit [s]

Ext

rakt

ions

grad

Ble

i [%

]

T = 50 °C pH = 3 pH = 4 CO

2

P = 25 MPa

Extraktionsver-mögen liegt im Bereich niedrigerer Temperaturen in Abhängigkeit von der Verweilzeit im Bereich von Essigsäure

Zugabe von Essigsäure zur Einstellung des pH-Wertes

Vergleich mit Essigsäure

100 200 300 400 500 600 7000

20

40

60

80

100

Verweilzeit [s]

Ext

rakt

ions

grad

KW

S [

%] P = 25 MPa

T = 25 °C T = 300 °C T = 340 °C T = 370 °C

Langes Spülen bewirkt Reinigung

Trotz relativ hoher Verweilzeit Reinigung nicht vollständig, trotz nahe-/ überkritischen Bedingungen

Bezug:

60.000 mg/kg

(40.000 mg/kg)

Extraktion der KWSt. (Mischkontamination)

0 50 100 150 200 250 300

2.8

2.9

3.0

3.1

3.2

3.3

3.4

3.5

3.6

P = 25 MPa P = 20 MPa (Toews, 1995) P = 15 MPa (Toews, 1995)

pH-v

alue

temperature [°C]

Lowering pH by dissolution of CO2 in H2O

Calculated pH-value of water for carbon dioxide saturated solutions at a pressure of 25 MPa. Equilibrium data from Wiebe (1941), Takenouchi (1964)

Nowak 1995

Solubilities of real hydrocarbon contaminations in water

Water in lubricating oil

EthylbenzeneDimethylcyclohexane

Real weathered extracted contamination

G.M. Schneider

Phase equilibrium:Hydrocarbons in carbon dioxide

Solubility of n-decane in water

0 50 100 150 200 250 300 350

2.5

2.6

2.7

2.8

2.9

3.0

3.1

3.2

3.3

Messungen (T oews) P = 10 MPa P = 15.1 MPa P = 20.2 MPa

Berechnung nach Messdaten(Takenouchi)

P = 20 MPa P = 25 MPa P = 30 MPa

Berechnung nach Messdaten (Wiebe) P = 20.2 MPa P = 30.3 MPa

pH

-We

rt

Temperatur [°C]

Abgeschätzter pH-Wert für Kohlensäure, 1. Dissoziationsstufe

Toews et al., 1995

CO2 - H2O

100 150 200 250 300 3500,00

0,02

0,04

0,06

0,08

0,10

0,12

0,14

0,16

0,18

0,20

0,22

200 bar

250 bar

300 bar

400 bar

Lösl

ichk

eit [

g C

O2

/ g H

2O]

Temperatur [°C]Temperature [°C]

So

lub

ilit

y [

gC

O2/g

H2O

]

The solubility of carbon dioxide in liquid water

Biopolymers: Acid catalysis

20 40 60 80 100 1200.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.16

0.18

150 °C

200 °C

250 °C

270 °C

275 °C300 °C

Mo

lan

teil

Ko

hle

nd

ioxi

d in

Wa

sse

r [-

]

Druck [M Pa]

Löslichkeiten von CO2 in Wasser

Takenouchi und Kennedy, 1964

CO2 - H2O

10 20 30 40 50 60 70 80

0.005

0.010

0.015

0.020

0.025

0.030

0.035

Mo

lan

teil

Ko

hle

nd

ioxi

d in

Wa

sse

r [-

]

Druck [MPa]

T = 12°C T = 35°C T = 40°C T = 50°C T = 75°C T =100°C

CO2 - H2O

Gleichgewichtslöslichkeiten von CO2 in Wasser

Wiebe und Gaddy, 1940, Wiebe, 1941

Incentives:

Unrestricted use of site

Remove risk for environment

(water, air, persons, ...

?

Quantities:

Site: 100 m x 100 m

2 m depth

20 000 m3

40 000 t

Remediation II

Solvent ratio kg CO2 / kg soil

De

gre

e o

f ex

tra

cti

on

, % Artificially contaminated

Real contamination,

weathered

Soil extraction with carbon dioxide

Solvent ratio kg CO2 / kg soil

De

gre

e o

f ex

tra

cti

on

, %

Soil extraction

Comparison of CO2 and H2O

25 50 75 100 125 15010

20

30

40

50

60

Verweilzeit [s]

Ext

rakt

ions

grad

Ble

i [%

]

T = 50 °C pH = 3 pH = 4 CO

2

P = 25 MPa

Extraktionsver-mögen liegt im Bereich niedrigerer Temperaturen in Abhängigkeit von der Verweilzeit im Bereich von Essigsäure

Zugabe von Essigsäure zur Einstellung des pH-Wertes

Vergleich mit Essigsäure

Soilmaterial

Washing

Low contaminated fractionreutilization

High contaminatedfraction (smallparticles)

Cleaning Dumping

Thermal(incineration)

SCWSCWO

Othersolvents

biological

Destruction, total oxidation !

Direct route tocleaning

Soil Remediation Method

1 2 3 4Type of contamination diesel

artificialDiesel/lubricat

ing oil;weathered

diesel/lubricating oil;

weathered

diesel/lubricating oil;

weatheredAmount of contamination[mg hc/kg dry solidmaterial]

24418 136587 20231 35066

Age [years] 0.5 20 2 45Type of soil material weak

loamy sandstrong clayey

loamsand strong clayey

sandParticle mean diameter(sphere of equivalentvolume) [mm]

182 18 211 213

Pretreatment - sieved at 710 mm

from washingprocess

sieved at 710 mm

Table 2: Extraction results of real contaminated soil materials (adapted from 7 ).

Soil material from: Petrol Station Industrial Site Old Barrel DepotSauter diameter (m) 30 7 14Contamination lubricating oil

aged 1 yearlubricating oil

aged > 20 yearsPAH

aged > 45 yearsInitial concentration(mg hydrocarbons/ kgdry substance)

20 200 103 500 11 050

ExtractionFinal concentrationmg hydrocarbons/ kgdry substance)

< 20 < 100 < 10

Amount extracted, % > 99.9 > 99.9 > 99.9Temperature , K 663 655 665Pressure , MPa 24 24 25Solvent/soil ratio,kg water/kg drymatter

6 6 12

0 1 2 30

20

40

60

80

100

2

80 °C, 0,32 l/h 80 °C, 0,48 l/h 80 °C, 0,63 l/h 100 °C, 0,77 l/h

Ext

rakt

ions

grad

[%

]

Lösungsmittelverhältnis [kg CO /kg Boden]

TIR

c

TIR

d

TIRTIR

PI

a

M b

TIR TIR

TIC

2COPIRC

fV

N2

g

TICe

h

i

Figure 10: Flow sheme of continuous extaction apparatus: Fließbild der kombinierten Anlage: a Vorlagebehälter mit Rührwerk, b Pufferautoklav, c Wirbelbettheizer -Vorwärmer- d Extraktionsstrecke, e Elektrolysezelle im Schutzbehälter, f Doppelrohrwärmetauscher, g Sammelgefäß, h Gasanalysegerät, i evakuierter Glasbehälter

a magnetic stirrer, b feed vessel, c membrane pump, d buffer vessel, e , f preheater (28 ml), g extraction pipe (38 ml), h cooler, i flask, j CO2-meter, k evacuated glas vessel.

0 100 200 300 4000

100

200

300

400

500

concentration of soil material in water [wt%]

10 0,250,51h

ydro

carb

on

s so

lve

nt

[m

g/l]

solvent to soil ratio [kgH2O

/kgsoil material

]

Figure 12: Concentration of hydrocarbons in the fluid aqueous phase versus concentrationof soil material in water (solvent to soil ratio)at 663 K and 24 MPa.

0 2 4 6 8 100

20

40

60

80

100 E

xtra

ktio

nsgr

ad [%

]

Konzentration Bodenmaterial in der Suspension [Gew%]

Figure 13: Degree of extraction in dependence on the amount of soil material in the solvent (solvent to soil ratio). This diagram corresponds to the left branch of Fig. 12, i.e. up to solvent to soil ratios of 100.T = 663 K, P = 24 MPa, residence time: 28 s.

580 600 620 640 66060

70

80

90

100

de

gre

e o

f e

xtra

ctio

n

[%]

temperature [K]

Figure 14: Extraction results versus temperature at 24 MPa, residence time: 45 s; 1 wt.-%soil in water.

0.0 0.2 0.4 0.6 0.8 1.0 1.255

60

65

70

75

80

85

Bodenkonzentration [Gew.%]

Ext

rakt

ions

grad

Ant

imon

[%

] T = 50 °C T = 100 °C T = 200 °C

Figure 17: Degree of extraction for antimony. P = 25 MPa, material “GKSS”.

1 . D e s o r p t i o n :

maxAgg

AggBodenDe

Boden

X

XCk

tC

1

2 . D i f f u s i o n :

r

Xrr

XD

X

XCk

t

XAg gAg g

effAg g

Ag gBo d enBo d enDe

Ag gAg g

212

2

max

3 . C o n v e c t i o n :

FluidAggSuspensionAgg

FluidSuspension

XXdt

Xr R

16

C o m b i n a t i o n o f s i n g l e p a r t i c l e a n d f i l a m e n t m o d e l :

SträhneEinzelkorn

komb

EEE

)(

Soil Remediation Modelling