Transcript Kein Folientitel

Chapter 7
Solvent Cycle,
Methods for Solute Precipitation
Heat and Mass Transfer:
High Pressure chemical Engineering I (WS)
Flow Scheme of a Solvent Cycle
Solvent Cycle
Solvent Cycle Steps:
separate the extract from the solvent (1),
clean the solvent for reuse (2),
remove the solvent from raffinate (3),
adjust composition of solvent mixture (if applicable) (4).
SFE Modes of Operation
Single stage Multiple stage Counter- Chromato(precipitation) current
graphic
Solvent Cycle: Solvent to feed ratio of SFE processes
Extraction From Solids
S
t
S/F
Essential oils
(5 %)
20
<1
> 20
Edible oils
(2 %)
40
<1
 40
Coffee decaffeination (0.01 %)
200
5
 40
Black tea decaff. (0.01 %)
230
 1.5
 150
Total amount of solvent S, kg/kgF
Basis:
Extraction time t, h
Solvent: Carbon dioxide
Solvent to Feed Ratio S/F, kgS /(kgF h)
10 - 30 MPa, 330 K
Solvent Cycle: Solvent to feed ratio of SFE processes
Countercurrent Separation
V/L
 20
FAEE, FAME (5 %)
7.5
v
S/F
 125
50
4.5
 50
(1.5 %)
 20
10
 50
(2.5 %)
35
 20
 45
FFA (fatty acids)
(2 %)
Squalene
Tocopherol-Purif.
Solvent ratio V/L, kg/kg
Basis:
Reflux ratio v, -
Solvent: Carbon dioxide
Solvent to feed ratio S/F, kgF /kgF
10 - 30 MPa, 350 K
Solvent Cycle: Solvent to feed ratio of SFE processes
Chromatographic Separation
Pr
tr
S/F
DHA / DPA
 1.5
15
900 x 103 EM
Phytol-isomers
10- 30
6
 900 EM
 200 SMB
Productivity Pr, gP /(kgStPh h)
Basis:
Retention time, min
Solvent: Carbon dioxide
Solvent to feed ratio S/F, kgF /kgF
10 - 30 MPa, 310 K
Modes For Product Recovery
Reduction of pressure or density
Anti solvent
Membrane separation
Adsorption
Absorption
De-Entrainment
......
Solubility of Caffeine in CO2
Solubility [mg/kg CO 2]
1000
100
T = 313 K
T = 318 K
T = 333 K
10
300
400
Birtigh, Brunner, Johannsen
500
600
700
3
Density [kg/m ]
800
900
Gas Circuit in the Compressor Mode
Compressor Process, Throttling Sub-Critical
Compressor Process, Throttling Super- Critical
Pump Process
Pump Process, Throttling, Sub-Critical
Pump Process, Throttling Super- Critical
Energy Consumption by Various Solvent Cycles
Extraction temperature: 313 K
Energy needed for the gas cycle
for
S/F 125 kg/kg:
Mechanical Energy
Thermal energy in
Thermal energy out
70 kJ/kgCO2
Extraction pressure [MPa]
Pump with heat
recovery
8750 kJ/kgFeed
Pump without heat
recovery
Compressor with
heat recovery
95 kJ/kgCO2
Compressor without
heat recovery
11875 kJ/kgFeed
Energy [kJ/kg]
Modes For Product Recovery
Reduction of pressure or density
(temperature)
Anti solvent
Membrane separation
Adsorption
Absorption
De-Entrainment
Solubility in a Gas With a Modifier (Entrainer)
Influence of temperature
Brunner 1983
Solubility of Caffeine in CO2
Data by:
Gährs 1984
Ebeling, Franck 1984
Johannsen, Brunner 1994
Modes For Product Recovery
Reduction of pressure or density
Anti solvent
Membrane separation
Adsorption
Absorption
De-Entrainment
......
Anti-Solvent: Solubility of Caffeine in CO2
Influence of nitrogen
Gährs 1984
Modes For Product Recovery
Reduction of pressure or density
Anti solvent
Membrane separation
Adsorption
Absorption
De-Entrainment
......
Solvent Cycle With Membrane Separation
Coupling with a Membrane Unit
P = 2 MPa
PC
PC
B1
RV1
RV3
M1
RV2
PC
18 MPa
323 K
WT1
K1
1
WT2
P1
Separation by Membranes
p = 2.0 MPa
Retentate
active dense layer
1.5 mole CO2
OC
kg/(m2 h)
CO2
Permeate
< 0.06 wt.-%
1.86 wt.-%
P = 18 MPa, T = 323 K
GKSS-membrane (organic, active dense layer)
Solvent Cycle in a T,s - Diagram
Compressor mode
CO2
Extraction/
separation
Temperature
Precipitation at
low p
Precipitation at
high p
Entropy
Energy For Different Solvent Cycles
Pump-Cycle
53 kJ/ kgCO2
1
Compressor-Cycle
21 kJ/ kgCO2
2
Membrane-Cycle
Like
Wie in 22
7.6 kJ/ kgCO2
3
Sartorelli 2001
Modes For Product Recovery
Reduction of pressure or density
Anti solvent
Membrane separation
Adsorption
Absorption
De-Entrainment
......
Adsorption of Caffeine on Activated Carbon
0.5
X [kg/kg AC]
0.4
T=318 K
P=13 MPa
P=20 MPa
P=30 MPa
P=13 MPa Langmuir
P=20 MPa Langmuir
P=30 MPa Langmuir
0.3
0.2
0.1
0
0
100 200 300 400 500 600 700 800
Y [mg/kg CO 2]
Recovery of Tocopherolacetate by Adsorption
Silica with 52% loading,
loaded by high pressure
adsorption
Silica with 50% loading,
loaded by mixing,
conventional process
Loading of adsorbate [wt.-%]
Recovery of Tocopherolacetate by Adsorption
60
55
50
autoclave: 333K, 20MPa
fixed bed adsorber: 353K
flow: 20gsolvent/min
45
40
200
feed in autoclave:
TA ca. 97 wt.-%
TA ca. 73 wt.-%
250
300
350
400
450
500
3
Density CO [kg/m ]
2
550
600
Modes For Product Recovery
Reduction of pressure or density
Anti solvent
Membrane separation
Adsorption
Absorption
De-Entrainment
......
Phase Equilibrium Caffeine - Water - CO2
Caffeine Loading in
SCF Phase [mg/kg]
1000
P = 19 MPa
T = 343,1 K
T = 323,1 K
P = 28 MPa
T = 343,1 K
100
10
100
1000
10000
Caffeine Loading in Water Phase [mg/kg]
Modes For Product Recovery
Reduction of pressure or density
Anti solvent
Membrane separation
Adsorption
Absorption
De-Entrainment
......
Solubility in a Gas With a Modifier (Entrainer)
Influence of temperature
Brunner 1983
tocochromanol fraction
in fluid phase [mass%]
De-Entrainment
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
Birtigh
solubility tocochromanol in CO2
0
0.05
0.1
0.15
0.2
0.25
0.3
mwater / m total
Figure 4:Tocochromanol fraction in SCF phase as function of the
total water fraction
Generalization of Precipitation: Membership - Functions
 (x): relative number of statements from people at the pool
1
„Hot“
Too hot
Not yet hot
 (x)
0
25
35
45
Temperature at the Swimming Pool
T [oC]  x
Membership Functions
P
Adsorption Membrane
1.0
1.0
0.5
0.5

Molar weight solute [kg/mol]
0.0
0.1
0.5
0.9
0.0
0.2
0.9
1.6
1
2
0.5
1.0
4
7
1.0

0.5
Inlet loading
Solubility in separator
0.0
1 2
10
100
Loading
fluid phase [wt%]
1.0
1.0
0.5
0.5

0.0
0
1
2
0.0
0
1.0

0.5
Inlet loading
Solubility in extractor
0.0
0.0
1.0
1.0
0.5
0.5

Reduced Pressure
0.0
1
4
7
0.0
1
1.0

Residence time [min]0.5
0.0
0
3
6
Birtigh
Absorption De-Entrain T
1.0
Solubility of solute

in water [g/g] 0.5
0.0
0.0
0.05 0.10
1.0
1.0
0.5
0.5
0.0
0.0
0.0
0.0
0.05
0.1
0.0
0.0
1.0

0.5
0.0
1 2
10
100
1.0

Reduced pressure
1.0

0.5
1.0
1.0
1.0
0.5
0.5
0.0
1 2
10
100
0.0
1 2
10
100
3
6
if only 1 phase in Extractor
0.5
0.0
1
1.0
if 2 phases in Extractor
3
5
0.2
0.4
0.5
0.5
0.0
0.0
0.2
0.4
1.0

Residence time0.5
[min]
0.0
0
Solvent ratio
0.1
Membership
Functions
0.5
Inlet loading
Solubility in Separator
Absorbent
0.05
1.0

TSeparator
TDecomposition

T
3
6
1.0

0.5
0.0
0.0
0.0
0.0
1.0
1.0
1.0
0.5
0.5
0.5
0.0
0
3
6
0.0
0
3
6
0.0
0
1.0
0.5
0.1
0.2
0.0
0.0
Birtigh
0.1
0.2