The presentation is based on Mass Transfer the major subject of Chemical Engineering. It includes Separation Technologies Typical Applications Industries Distillation vs. Extraction LLE Extraction LLE extraction Principle Solvent Operation Condition Mode of Operation Extractor Type Design Criteria Equipment for extraction

2. Liquid-Liquid Extraction
Mass Transfer

3. Physical Separations
Decantation, Coalescing, Filtration, Demisting
Evaporation
Single Effect, Multiple Effect
Distillation
Simple, Azeotropic, Extractive, Reactive
Extraction
Simple, Fractional, Reactive
Adsorption
Pressure Swing, Temperature Swing
Crystallization
Melt, Solvent
Membranes
MF, UF, NF, RO
Easy
Difficult
Difficulty
Of
Separation
Separation
Technologies

4. Typical Applications
•Remove products and pollutants from dilute aqueous streams
•Wash polar compounds or acids/bases from organic streams
•Heat sensitive products
•Non-volatile materials
•Azeotropic and close boiling mixtures
•Alternative to high cost distillations

5. Chemical •Washing of acids/bases, polar compounds from organics
Pharmaceuticals
• Recovery of active materials from fermentation broths
• Purification of vitamin products
Effluent Treatment
• Recovery of phenol, DMF, DMAC
• Recovery of acetic acid from dilute solutions
Polymer Processing
• Recovery of caprolactam for nylon manufacture
• Separation of catalyst from reaction products
Petroleum
• Lube oil quality improvement
• Separation of aromatics/aliphatics (BTX)
Petrochemicals
• Separation of olefins/parafins
• Separation of structural isomers
Food Industry
• Decaffeination of coffee and tea
• Separation of essential oils (flavors and fragrances)
Metals Industry
• Copper production
• Recovery of rare earth elements
Inorganic Chemicals • Purification of phosphoric acid
Nuclear Industry • Purification of uranium
Industries

6. Distillation vs. Extraction
Organic Compound BP [°C]
Water Solu.
[%]
Azeotrope
B.P. [°C]
Azeotrope
Water [%]
Typical Reduction Level
Methylene Chloride 40 2.0 38.1 1.5 < 50 ppb
Acetone 56.2 Infinite Non Azeotropic < 50 ppb
Methanol 64.5 Infinite Non Azeotropic < 50 ppb
Benzene 80.1 0.18 69.4 8.9 < 50 ppb
Toluene 110.8 0.05 85.0 20.2 < 50 ppb
Formaldehyde -21 Infinite Non Azeotropic < 1,000 ppm
Formic Acid 100.8 Infinite 107.1 22.5 < 500 ppm
Acetic Acid 118.0 Infinite Non Azeotropic < 500 ppm
Pyridine 115.5 57 92.6 43 < 10 ppm
Aniline 181.4 3.60 99.0 80.8 < 10 ppm
Phenol 181.4 8.20 99.5 90.8 < 10 ppm
Nitrobenzene 210.9 0.04 98.6 88.0 < 10 ppm
Dinitrotoluene (2,4) 300.0 0.03 99 – 100 > 90 < 10 ppm
Dimethyl Formamide 153.0 Infinite Non Azeotropic < 10 ppm
Dimethyl Acetamide 166.1 Infinite Non Azeotropic < 10 ppm
n-Methylpyrrolidone 202.0 Infinite Non Azeotropic < 10 ppm
ExtractionDistillation

9. LLE extraction Principle
The separation of the components of a liquid mixture by treatment with a solvent in
which one or more of the desired components is preferentially soluble is known as
liquid-liquid extraction.
(a) Bringing the feed mixture and the solvent into intimate contact,
(b) Separation of the resulting two phases, and
(c) Removal and recovery of the solvent from each phase.
The Solute present in the aqueous phase gets partitioned or distributed in both the
phases
If the solute has solubility in the organic solvent, more of the solute would be present
in the organic phase at equilibrium and extraction is said to be more efficient
LLE Extraction

11. A – 99
B – 0
C – 1
100
Feed (F)
A – 0
B – 50
C – 0
50
Solvent (S)
A – 0
B – 50
C – 0.8
50.8
Extract (E)
A – 99.0
B – 0
C – 0.2
99.2
Raffinate (R)
      4.07.92
99
50M
F
SE
7.92
99
0.2
50
0.8
RaffinateinSoluteConc.
ExtractinSoluteConc.
M
0.2
1.0
0.2
FeedinSolute
RaffinateinSolute
U


Fraction Unextracted
Distribution Coefficient
Extraction Factor

12. Stage 1 Stage 2
1 2
1 2
Modes of Operations
• Co-current contact
• Cross flow
• Counter-current flow

13. Multiple-contact system with fresh solvent

15. Parameters of LLE Process
• Solvent
• Operation Condition
• Mode of Operation
• Extractor Type
• Design Criteria

16. Points need to be considered
1. Higher the partition coefficient greater will be the extraction efficiency
2. Large density differences between the extractant and raffinate = better
separation if the separation is by gravity alone
3. High viscosity of solvent affect the phase separation.
4. Should have negligible miscibility/ solubility in the aqueous feed to minimize
solvent loss
5. Easily recovered and purified for recycling after extraction.
6. Should be easily available and cost effective
7. Low interfacial tension between the phases facilitates the dispersion of phases
and improves mass transfer
8. Physio-chemical properties such as boiling point, density, interfacial tension,
viscosity, corrosiveness, flammability, stability compatibility with product,
availability should be satisfactory

17. Equipment for extraction
• A high degree of turbulence facilitates intimate contact between the
two liquid phases and allows a high rate of mass transfer.
Two main types of equipment are used in solvent extraction
1. Vessels in which mechanical agitation facilitates mixing.
2. Vessels in which mixing is done by the counter-current flow of the
two liquids themselves.

18. Batch extractor Continuous Column Extractor
(a)Design for heavy solvent (b)Design for light solvent
(a) (b)

19. (a) Static Bubble column
(b) Sieve plate column
(c) Agitated column
(d) Spray column
(e) Packed column
(f) Rotating Disc

20. (a) Kuhni column (a) Scheibel column (a) Karr column

21. Types of
equipment
Stages Flow Rate Resident
Time
Physical
properties
of fluid
Floor Area
Occupied
Mixer
Settler
L H H L-H H
Centrifugal L L L L-M M
Static
Column
M M M L-M L
Agitated
column
H M M L-H L
*L= LOW
H= HIGH
M= MEDIUM

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