c28420-lecture4-2009 - Course 28420: Lecture 4 Part A...

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Course 28420: Lecture 4 Part A Topics to be covered: Introduction to solvent based liquid-liquid extraction (parts of chapter 8). Single-equilibrium stage (chapter 4 – sections 4.5 and 4.6) and cascades (chapter 5 – section 5.3). Part B will cover mainly sections 8.3 to 8.5 1 C28420: Separation Process Principles - Lecture 4 (2009)
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Introduction to Liquid-Liquid Extraction Main Features: Two liquid phases Use of solvents Recovery of solvents Used when V-L separation is not feasible Usually operated at low pressures (around tmospheric) atmospheric) C28420: Separation Process Principles - Lecture 4 (2009) 2 Figure 8.1 Typical liquid-liquid extraction process.
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How to find suitable solvents? See lecture2 notes. Compare the selection by checking the table on slide 4. A good solvent should lower the activity coefficient of the solute. Why? Are there exceptions? C28420: Separation Process Principles - Lecture 4 (2009) 3
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List of typical solute- carrier-solvent systems. Note that phenol- water-benzene ontradicts the table contradicts the table on slide 3. C28420: Separation Process Principles - Lecture 4 (2009) 4
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Graphical Design Technique Liquid, L1 Feed, Z T, P oncept of an equilibrium stage Liquid, L2 Concept of an equilibrium stage Choice of independent variables Model for equilibrium curve (phase equilibrium) Model for operating line (mass balance) 5 C28420: Separation Process Principles - Lecture 4 (2009)
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LLE phase diagrams: Different ways to draw them Equilateral triangular diagram Right triangular diagram ne liquid phase Tie-lines One liquid phase Two liquid phases Figure 4.14 Liquid-Liquid equilibrium, ethylene glycol-furfural-water, 25ºC, 101 kPa Note: The equilibrium data corresponds to constant T and P C28420: Separation Process Principles - Lecture 4 (2009) 6
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Other types of LLE phase diagrams (a) Type I, one inmiscible pair Figure 8.10 Most common classes of ternary systems (b) Type II, two inmiscible pairs C28420: Separation Process Principles - Lecture 4 (2009) 7
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Effect of solvents on the type of LLE phase diagrams Maximum solvent-free feed composition of A Feed mixture must be between C-F Good solvent Not so good solvent C28420: Separation Process Principles - Lecture 4 (2009) 8 Figure 8.11 Effect of solubility on range of feed composition that can be extracted.
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Model for an equilibrium stage (Fig 4.13) omponents A and C mutually insoluble omponents A and C partially soluble Components A and C mutually insoluble Components A and C partially soluble X B (F) F A = X B (E) S + X B (R) F A solute mass balance (4-21) X B (E) = K´ DB X B (R) equilibrium distribution (4-22) X (R) / X (F) = 1/(1 + E ) fraction of B extracted (4-25) C28420: Separation Process Principles - Lecture 4 (2009) 9 B B B
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Draw the ternary LLE diagram Locate F (feed) & S (solvent) treams & join them in a streams & join them in a straight line Locate any point M that etermines the mixing point determines the mixing point between F and S.
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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-lecture4-2009 - Course 28420: Lecture 4 Part A...

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