c28420-lecture2-2009 - Lecture 2 Lecture 2: Solvent...

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Lecture 2 Lecture 2: Solvent selection & Solvent-based separation C28420: Separation Process Principles - Lecture 2 (2009) 1
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What are Solvents? Why do we need them? olvent: olvent is that constituent of a solution that is Solvent: Solvent is that constituent of a solution that is liquid in the pure state, is usually present in the larger amount and has dissolved the other constituent (a solute) of the solution. The solute may be a solid, a liquid or a gas. The solvent may be a single compound or a mixture of d compounds. When needed: Solvent based separation techniques become necessary when separation or removal of a solute(s) from a mixture become difficult or infeasible by nventional separation techniques such as distillation conventional separation techniques such as distillation. C28420: Separation Process Principles - Lecture 2 (2009) 2
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Mechanism of Separation hase Creation & addition; Barrier; Solid agent; Force field Phase Creation & addition; Barrier; Solid agent; Force field or Gradient (separation is based on differences in properties of phases 1 and 2) Note: Solvents are needed when separation of type (a) is not ossible as in type (b) C28420: Separation Process Principles - Lecture 2 (2009) 3 py p ( )
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Types of Solvent-based Separation Extractive distillation Azeotropic distillation Liquid-liquid traction Crystallization extraction Gas absorption Liquid stripping C28420: Separation Process Principles - Lecture 2 (2009) 4
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Types of Solvent-based Separation Extractive distillation V-L Azeotropic distillation V-L-L Liquid-liquid extraction L-L q q Crystallization S-L Gas absorption G-L Liquid Stripping G-L In each case, the solvent dissolves one or more compounds t h f d i t d t f t h it i from the feed mixture and goes to one of the co-existing phases. The remaining feed compounds go to the other phase! C28420: Separation Process Principles - Lecture 2 (2009) 5
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Types of Solvent-based Separation Extractive distillation V-L distillation + distillation Azeotropic distillation V-L-L distillation (vlle) + distillation Liquid-liquid extraction L-L LL-extraction + distillation Crystallization S-L precipitation + centrifuge b t i Gas absorption G-L absorption + distillation Liquid Stripping stripping + distillation The second distillation column is needed to recover the solvent nd recycle it back to the process. a d ecyc e t bac to t e p ocess. Important properties: Solubility, selectivity, heat of aporization vapor pressure density EHS roperties C28420: Separation Process Principles - Lecture 2 (2009) 6 vaporization, vapor pressure, density, EHS-properties
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Example of solvent-based separation Process Raw Materials Products Solvent Clean Water Clean Water Contaminated Water Extraction Solvent + solute Determine target for solvent f F Problem solution * f = 100 (0.018 – 0.00) * f S = F W (X in,s – X out,s ) Solubility, S = f S /F S S ( ) Solubility, S = 1.8/ F S olvent ID provides * Find solvent to match target S – use data & models Solvent ID provides S F S = 1.8/ S Solvent ID decides extraction process ; solvent-solute relations identify the process parameters Order different solutions according
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This note was uploaded on 11/20/2009 for the course CHME DTU-abroad taught by Professor Rafiqulgani during the Fall '09 term at Rensselaer Polytechnic Institute.

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c28420-lecture2-2009 - Lecture 2 Lecture 2: Solvent...

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