1. Extraction Technology

2. Extraction Process
Figure 8.1 Typical liquid-liquid extraction process.

3. Typical Extractor Light Phase Dispersed Heavy Phase Dispersed
Out
Light Phase
Out
Heavy Phase In
Heavy Phase In
Light Phase In
Light Phase In
Heavy Phase
Out
Heavy Phase
Out
Light Phase Dispersed
Heavy Phase Dispersed

4. Typical Extractor Light Phase Dispersed Extract Out Feed In Solvent In
Raffinate
Out
Light Phase Dispersed

5. Liquid-liquid Equilibrium
Phase I
Phase II

6. Design Methods Theoretical Trays Hunter – Nash graphical method Aspen
Packed Tower Height
Seibert et al.
Sieve Tray Efficiency

7. Hunter – Nash Graphical Method
Blender Material Balance
M = F + S = RNp+ E1
M xM = F xF + S yS = RNp xNp + E1y1

8. Hunter – Nash Graphical Method
Figure Location of product point.

9. D “P” Point 100 lbs 181 lbs D = 81 lbs 10 lbs 90 lbs 171 lbs

10. Hunter – Nash Graphical Method
Figure 8.15 Location of operating point.

11. Hunter – Nash Graphical Method
Figure 8.18 Determination of minimum solvent to feed ratio.

12. Hunter – Nash Graphical Method
Figure 8.17 Determination of the number of equilibrium stages.

13. Graphical Method Example
In a continuous counter-current train of mixer settlers, 100 kg/hr of a 40 wt % acetone / 60 wt % water
solution is to be reduced to 10 wt % acetone by extraction with pure 1,1,2 trichloroethane (TCE) at 25 C.
Find:
The minimum solvent rate
At 1.8 times the minimum solvent rate, find the number of mixer settlers required.
Water Phase ( wt %)
TCE Phase ( wt %)
C2H3Cl3
Water
Acetone
0.73
82.23
17.04
73.76
1.10
25.14
1.02
72.06
26.92
59.21
2.27
38.52
1.17
67.95
30.88
53.92
3.11
42.97
1.60
62.67
35.73
47.53
4.26
48.21
2.10
57.00
40.90
40.00
6.05
53.95
3.75
50.20
46.05
33.70
8.90
57.40
6.52
41.70
51.78
26.26
13.40
60.34

14. Acetone
E1min F
Mmin
RNp s
Water
TCE

15. Acetone E1 F M
RNp s
TCE
Water

16. 10 Minute Problem
A feed stream “C” of 100 kg/min containing 30 mass percent solute “A” is being contacted in a single stage stirred contactor with 50 kg/min of pure solvent “S” (equilibrium figure below). Determine the composition and amount of the resulting raffinate and extract streams.

17. Extractor Sieve Tray
Photo of Sieve tray

18. Trayed Extractor Efficiency (Treybal Empirical Model)
Where: Ht = tray spacing (ft)
Ud = superficial dispersed
phase velocity
Uc = superficial continuous
s = interfacial tension (dyne/cm)

19. Interfacial Tension

20. Trayed Extractor Efficiency (Seibert Model)
Kod,r
Kod,f
Seibert, A.F. and Fair, J.R., “Mass-Transfer Efficiency
of a Large-scale Sieve Tray Extractor,” Ind. Eng. Chem.
Res., 32 (10): (1993).

21. Trayed Extractor Efficiency
Correction of k d,r from Seibert Table VI Equation 16

22. Trayed Extractor Efficiency
dVS

23. Trayed Extractor Efficiency

24. Trayed Extractor Hydraulics

25. Packed Liquid-liquid Extraction
IMTP
Pall Rings
Structured

26. Packed Extractor Design (Hydraulics)
Seibert, A.F., Reeves, B.E., and Fair, J.R., “Performance of a
Large-scale Packed Liquid-Liquid Extractor,” Ind. Eng. Chem. Res.
29 (9); (1990).

27. Packed Extractor Design (Hydraulics)

28. Packed Extractor Design (Mass Transfer)

29. Extraction Equipment Selection
Depends on:
- solvent recovery economics
- viscosities, interfacial tension, solids
- product/solvent value
- flowrates
- risk assessment
- operation experience

30. Static Columns
Spray Tower
Packed Tower
(a)

31. Static Columns Sieve Tray Light liquid out Operating interface
Heavy liquid in
Light liquid in
Heavy liquid out
Operating
interface
Perforated
plate
Downcomer
Coalesced
dispersed
Sieve Tray

32. Oldshue-Rushston Column
Develop in 1950s
Many commercial installations
Solids handling
Viscosities to 500 cP
Differential contactor

33. Reciprocating Plate Extractor (Karr)
Developed in 1959
Many commercial installations
V. High Volumetric Efficiency
Vary tray amplitude and frequency
Caution at low interfacial tensions
Tray movement can clean walls
Differential contactor
Scale-up to the 0.38 power on diameter
Other variations (e.g. VPE)

34. Podbielniak Horizontal centrifugal extractor High efficiency
Short residence time
Minimum inventory
Light phase out
Light phase in
Heavy phase in
Heavy phase out

35. Mixer-Settler Wide range of designs Handle wide range of flow ratios
Easy start-up
Easy to clean/inspect
Batch operations
Larger equipment
Handles solids
Low headroom
Occupy much floor space
Can add stages
Interstage pumping often required
High solvent inventory

36. Hollow Fiber Extractor
Solvent Out
Solvent In
Feed In
Feed Out
Developed in 1980s
Modified in 1990s
Stage contactor
Low organic solvent to aqueous feed ratios
Few commercial extraction applications
Many commercial gas/liquid applications

37. Stichlmair (1980)