1. COUNTERCURRENT MULTISTAGE EXTRACTION
Chapter 6
COUNTERCURRENT MULTISTAGE EXTRACTION II
More Applications
HETP, HTU,
Capacity

2. Tocopherol - Separation

3. Structure of Tocochromanols

4. Solubility of Tocopherols in sc-CO2

5. Squalene - Tocopherol - Sterol - Separation

6. Top Product of Tocopherols

7. Binary Analysis of the Separation Process

8. Separation Factor Squalene- Tocopherol

9. Squalene - Tocopherol/Sterol-separation with CO2
99 wt-% squalene
90 wt-% squalene
Saure 1996

10. Squalene/Tocopherols From Distillates
Gas, liquid
Squalene
Tocopherols
Sterols
Feed
Saure 1996
Equilibrium stages

11. Separation of FFA
C16/C18-FFA -CO2
Machado 1998

12. Purification of Synthetic Tocopherolacetate
Calculation of number of theoretical stages (Jänecke). 333 K, 24 MPa CO2. U. Fleck. Tocopherolacetate.

13. Purification of Synthetic Tocopherolacetate
Determination of nth in dependence on reflux ratio for different purities. (McCabe-Thiele and Jänecke); 333 K, 16 MPa CO2. . U. Fleck.

14. Purification of Synthetic Tocopherolacetate
Concentration profiles along column length; 333 K, 20 MPa CO2. U. Fleck.

15. Free fatty acids (FFA) -/- Squalene- FA-esters
Buß 1999

16. Separation Factor: Influence of Concentration
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

17. Separation Analysis: FFA, Toco - Triglycerides, Carotene
Solvent ratio
 / (kg reflux / kg extract

18. Separation Analysis: FAME - Carotenes

19. Orange Peel Oil
Representation of an improved separation factor model at 333 K. M. Budich

20. Orange Peel Oil: Removal of Terpenes
Budich 1998

21. No Aceotrope in Ethanol - Water
Budich, 1998

22. Calculation of the theoretical number of stages. M. Budich.
Ethanol - Water
Calculation of the theoretical number of stages. M. Budich.

23. Mixer-Settler (5 Stages)
Flow Scheme of Mixer-Settler. M. Jungfer, Design: Trepp, ETH-Zürich

24. Mixer-Settler, Single Stage
Mixer-Settler-Module No. n. M. Jungfer, Design: Trepp, ETH-Zürich

25. Countercurrent Separation
Solvent Cycle: Solvent to Feed Ratio of SFE Processes
Countercurrent Separation
V/L v S / F
FAEE, FAME (5 %)   125
FFA (fatty acids) (2 %)  50
Squalene (1.5 %)   50
Tocopherol-Purif. (2.5 %)   45
Solvent ratio V/L, kg/kg
Reflux ratio v, -
Solvent to feed ratio S/F, kgF /kgF
Basis:
Solvent: Carbon dioxide
MPa, 350 K

26. Solubility and Solvent to Feed Ratio
Relationship between loading and solvent-to-feed ratio.
M. Budich. Orange peel oil.

27. Means for reducing costs
Enhance solubility in solvent:
Pressure, temperature
other solvent (C3H8 vs. CO2)
Reduce energy for solvent cycle:
low p for extract recovery

28. Purification of Tocopherol: CO2-Propane
Temp Solubility Selectivity
10 % Propane
initial feed mixture
Solubility
Selectivity
Density
Fleck 1998

29. Purification of tocopherol: CO2-Propane
Propane,10 MPa
Propane, 9 MPa
Solvent ratio = 30
Solvent ratio = 70
Reflux ratio
Fleck, 1999

30. Some Data on Solvent Cycle Costs
High vacuum distillation: 100 %
p Solvent: CO %
Solvent: CO2 + C3H %
Adsorption:
Solvent: CO %
Solvent: CO2 + C3H %

31. HETP, HTU
FA-ethyl esters - CO2
Riha 1996

32. HETP: Tocopherol
HETP (Jänecke) vs solvent ratio in stripping section. Saure, 1996

33. HETS for aqueous mixtures
M. Budich

34. Pressure drop, flooding
log  p
log (gas loading)
flooding mG
Different packings, systems
log mL
log (gas/liquid loading)

35. Raschig- Olive oil- Dist.
Flooding
CY-Water
CY- Toco
Raschig-Water
Raschig- Olive oil- Dist.
EX-Water
Stockfleth
1999
Billet-diagram

36. Flooding: Tocopherol Feed Mixture (55 % Toco)
Flooding diagram for tocopherol feed mixture (T155/CO2), Packing Sulzer CY ; Operating points (BP) and observed flooding points (FP). C. Saure, 1996

37. Density of Phases
Densities of the coexisting phases of the system PFAD + CO2. N. Machado

38. Flooding: PFAD
Hydraulic capacity diagram of packed columns. FV = f (y). N. Machado

39. Density of coexisting phases: CO2–Squalene.
Density of Phases
Density of coexisting phases: CO2–Squalene.
Flüssig-/Gasphase: / = 333,15 K, / = 353,15 K ▲/▲ = 373,15 K. D. Buß

40. Flooding: Squalene
Hydraulic capacity diagram of packed columns: Squalene - CO2. N. Machado

41. Flooding: CPO
Flooding Diagram, Crude Palm Oil - Carbon Dioxide, M. Jungfer, 2000

42. Flooding: Olive Oil Deodorizer Distillate
Flooding diagram CO2–OODD; Packing “Sulzer EX 35 mm”. Exp. Flooding Data: Stockfleth , o = Data of separation column. D. Buß, 2001.

43. Purification of Synthetic Tocopherolacetate
Loading limits for a 35 and 50 mm column. CO2. U. Fleck.

44. Pressure-drop curves. M. Budich. Orange peel oil.

45. Flooding: Orange Peel Oil
velocity of vapor phase inside an empty tube
Overall correlation of flooding lines for CO2+orange peel oil. M. Budich

46. Flooding: Orange Peel Oil
Median lines: B=52.7 for CO2+terpenes; B=77.5 for CO2+5-fold concentrate.
A = 8.0.
Comparison of flooding behavior of different mixtures. M. Budich.

47. Density of Phases
Densities of coexisting phases of CO2+ethanol+water mixtures. M. Budich.

48. Flooding point data for CO2+ethanol+water
M. Budich, 1999

49. Flooding: Ethanol - Water - CO2
Flooding point of CO2+ ethanol + water. M Budich.

50. Flooding point 100 000 kgCO2/(m2h): Column diameter Throughput
Capacity of Columns
Flooding point kgCO2/(m2h):
Column diameter Throughput
[mm] [kgCO2/h]
Linear velocity: 46 mm/s

51. Column diameter
FA-ethyl esters - CO2
Riha 1996

52. Flowsheet of the experimental Apparatus
HYDRODYNAMIC BEHAVIOUR IN PACKED COUNTERCURRENT COLUMNS FOR SUPERCRITICAL FLUID EXTRACTION
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

53. Regular Structured Column Packings
Structure of flow channels in regular packings

54. Flow of liquid film against countercurrent gas flow:
a) negigible, b) strong, c) very strong influence of gas flow.

55. Increasing flow velocity
Shape of liquid film:
smooth, rippled (waves), with noses, drops are formed.

56. A Falling Film At High Pressures
Flow Regimes
a. – Waves. b. – Crests. c. – Drop formation. d. – Flooding. T = 338 K, P = 20.6 MPa.

57. Film-Thickness: Nusselt’s Theory
Corn germ oil - CO2, 338 K , 7.6 MPa  P 20,6 MPa, : Nusselt (1916)

58. Flow Regimes: Influence of Gas Flow
From the figure it is obvious that the gas flow has a significant impact on the flow regime of the liquid film.
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

59. 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. ,
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:
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:

60. Influence of Gas Flow
Rating the pressure drop to the impact pressure of the gas flow yields the dimensionless gas resistance factor G:
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.

61. 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.

62. Flooding Correlation of the flooding points according to Wallis [10]:
G. B Wallis, (1969), One-Dimensional Two-Phase Flow, McGraw-Hill, New York
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.
For the correlation of the data displayed, the values K1=0,4222 and K2=1,1457 with a standard deviation of 19%.

63. General Flooding Diagram
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.
Very similar to:
T. K. Sherwood, G. H. Shipley and F. A. L. Holloway (1938), Ind. Eng. Chem., 7, ,
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.