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Liquid Liquid Extraction

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Jaydeep Vakil
Jaydeep Vakil

This PPT contains Basics and Detail study of Liquid Liquid Extraction.....one of the unit operation in Mass Transfer. Also contains solvent selection criteria.

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TOPIC : LIQUID-LIQUID EXTRACTION Branch: B.E.Chemical
Separation Techniques Distillation Crystallization Salting Out Solvent Extraction
Why liquid-liquid extraction ï‚— When difference in Boiling Point of two component is very low. ï‚— For azeotropic mixtures. ï‚— To avoid thermal decomposition. ï‚— It consumes Lower Energy than the distillation. ï‚— If proportion of one component is very less then other and it have high boiling point. 1- Separation is done according to different in solubility . 2- Problem with L-L extraction that we mix then we separate. IMP Notes:
What is liquid-liquid extraction Solvent Feed Raffinate Extract SeparationContact
What is liquid-liquid extraction As Inlet:  Solute + Inert  Solvent As Outlet: • Extract • Raffinate Each stage contain:  Contact  Separation
Equilateral Triangular Co- Ordinates
Equilateral Triangular Co- Ordinates
Types of ternary systems 1) Formation of one pair of partially soluble liquids. [closed ternary diagram] 2) Formation of two pair of partially soluble liquids. [open ternary diagram]
Formation of one pair of partially miscible liquids ï‚¢ AC&BC are completely soluble. ï‚¢ AB is partially soluble. ï‚¢ M will be separated to two compositions; N & L ï‚¢ If C is solvent for A so as C increases, L goes up till P(Plait Point) at which A,B & C become one phase. This is done due to the increase in mutual solubility between A&B. C BA P II I M N L
Formation of one pair of partially miscible liquids ï‚— Equilibrium relation. Effects: 1) Effect of TEMPERATURE 2) Effect of PRESSURE x y P
Formation of two pair of partially miscible liquids ï‚— A-B & C-B are partially soluble. ï‚— A is completely soluble in C.
Formation of two pair of partially miscible liquids Effects: 1) Effect of TEMPERATURE 2) Effect of PRESSURE
Multi Component System ï‚— In this type of system there are >=4 components in which 2 are solute and 2 are solvents. So it is known as multi component system. ï‚— E.g: the distribution of formic acid and acetic acids between the partly soluble solvents water and carbon tetrachloride. But this type of system representation requires 3D graph which is very difficult to understand. So Generally it is not used.
Choice Of Solvent 1) Selectivity 2) Distribution Co-efficient 3) Insolubility of solvent 4) Recoverability 5) Density 6) Interfacial Tension 7) Chemical Reactivity 8) Viscosity, Vapor Pressure, Freezing Point 9) Non Toxic, Non Flammable, & low cost.
Stage definition ï‚— It is a mechanical device or series that allow the solvent & solution to contact and separate. So; stage is:
SINGLE STAGE
1 V0, y0 L1, x1L0, x0 V1, y1 V0+L0=V1+L1=M V0y0+L0x0=V1y1+L1x1=MxM are on the same straight line y0, x0, xM are on the same straight line y1, x1, xM SINGLE STAGE
Multi stage cross current
Multi stage cross current 1 2 L0, x0 L1, x1 L2, x2 V0, y0 V0, y0 V2, y2V1, y1 y0, x0, xM1 are on the same straight line are on the same straight line y1, x1, xM1 y0, x1, xM2 are on the same straight line are on the same straight line y2, x2, xM2
MULTI STAGE COUNTER CURRENT 1 n L0, x0 L1, x1 Ln, xn V1, y1 Vn, yn Vn+1, yn+1 Vn+1+L0=V1+Ln=M Vn+1yn+1+L0x0=V1y1+Lnxn=MxM L0-V1=Ln-Vn+1=R No. of stages = n+(a/a+b) But get a & b from AB line
EQUIPMENT: ï‚— Different mechanical devices are used in liquid-liquid extraction such as: 1. The simplest is a mixer/settler, or decanter, in which the two liquid phases are separated. 2. Plate towers, packed towers, and mechanically agitated mixers (rotating disk contactors)
Extractor/stripper process
1. Mixer/ Settler Mixing vessel with variable-speed turbine agitator Horizontal gravity-settling vessel
Types of Impeller In Mixer
2. Spray column
3. Packed column
4. Tray Column:
Liquid Liquid Extraction

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Liquid Liquid Extraction

  • 3. Why liquid-liquid extraction ï‚— When difference in Boiling Point of two component is very low. ï‚— For azeotropic mixtures. ï‚— To avoid thermal decomposition. ï‚— It consumes Lower Energy than the distillation. ï‚— If proportion of one component is very less then other and it have high boiling point. 1- Separation is done according to different in solubility . 2- Problem with L-L extraction that we mix then we separate. IMP Notes:
  • 4. What is liquid-liquid extraction Solvent Feed Raffinate Extract SeparationContact
  • 5. What is liquid-liquid extraction As Inlet: ï‚— Solute + Inert ï‚— Solvent As Outlet: • Extract • Raffinate Each stage contain: ï‚— Contact ï‚— Separation
  • 8. Types of ternary systems 1) Formation of one pair of partially soluble liquids. [closed ternary diagram] 2) Formation of two pair of partially soluble liquids. [open ternary diagram]
  • 9. Formation of one pair of partially miscible liquids ï‚¢ AC&BC are completely soluble. ï‚¢ AB is partially soluble. ï‚¢ M will be separated to two compositions; N & L ï‚¢ If C is solvent for A so as C increases, L goes up till P(Plait Point) at which A,B & C become one phase. This is done due to the increase in mutual solubility between A&B. C BA P II I M N L
  • 10. Formation of one pair of partially miscible liquids ï‚— Equilibrium relation. Effects: 1) Effect of TEMPERATURE 2) Effect of PRESSURE x y P
  • 11. Formation of two pair of partially miscible liquids ï‚— A-B & C-B are partially soluble. ï‚— A is completely soluble in C.
  • 12. Formation of two pair of partially miscible liquids Effects: 1) Effect of TEMPERATURE 2) Effect of PRESSURE
  • 13. Multi Component System ï‚— In this type of system there are >=4 components in which 2 are solute and 2 are solvents. So it is known as multi component system. ï‚— E.g: the distribution of formic acid and acetic acids between the partly soluble solvents water and carbon tetrachloride. But this type of system representation requires 3D graph which is very difficult to understand. So Generally it is not used.
  • 14. Choice Of Solvent 1) Selectivity 2) Distribution Co-efficient 3) Insolubility of solvent 4) Recoverability 5) Density 6) Interfacial Tension 7) Chemical Reactivity 8) Viscosity, Vapor Pressure, Freezing Point 9) Non Toxic, Non Flammable, & low cost.
  • 15. Stage definition ï‚— It is a mechanical device or series that allow the solvent & solution to contact and separate. So; stage is:
  • 17. 1 V0, y0 L1, x1L0, x0 V1, y1 V0+L0=V1+L1=M V0y0+L0x0=V1y1+L1x1=MxM are on the same straight line y0, x0, xM are on the same straight line y1, x1, xM SINGLE STAGE
  • 18. Multi stage cross current
  • 19. Multi stage cross current 1 2 L0, x0 L1, x1 L2, x2 V0, y0 V0, y0 V2, y2V1, y1 y0, x0, xM1 are on the same straight line are on the same straight line y1, x1, xM1 y0, x1, xM2 are on the same straight line are on the same straight line y2, x2, xM2
  • 20. MULTI STAGE COUNTER CURRENT 1 n L0, x0 L1, x1 Ln, xn V1, y1 Vn, yn Vn+1, yn+1 Vn+1+L0=V1+Ln=M Vn+1yn+1+L0x0=V1y1+Lnxn=MxM L0-V1=Ln-Vn+1=R No. of stages = n+(a/a+b) But get a & b from AB line
  • 21. EQUIPMENT: ï‚— Different mechanical devices are used in liquid-liquid extraction such as: 1. The simplest is a mixer/settler, or decanter, in which the two liquid phases are separated. 2. Plate towers, packed towers, and mechanically agitated mixers (rotating disk contactors)
  • 23. 1. Mixer/ Settler Mixing vessel with variable-speed turbine agitator Horizontal gravity-settling vessel
  • 24. Types of Impeller In Mixer