c28420-lecture5-2009 - Course 28420: Lecture 5 28420 Topics...

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Course 28420: Lecture 5 Topics to be covered: Separation systems involving solids (sections 4.7 & 4.9) plus ditional notes additional notes 28420: Separation Process Principles - Lecture 5 (2009) 1
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Separation Processes Involving Solids Leaching (non-equilibrium or equilibrium ) Selectively dissolves solids with solvents rystallization ( uilibrium r kinetically controlled) Crystallization ( equilibrium or kinetically controlled) Promotes formation of solids b l i t i & D b l i t i Sublimation & Desublimation Solid vaporizes to gas phase or vice versa without passing rough liquid phase through liquid phase Gas Adsorption One or more of a gas mixture is adsorbed on a solid surface 28420: Separation Process Principles - Lecture 5 (2009) 2
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Graphical Design Technique Liquid, L Feed, Z T, P oncept of an equilibrium stage Solid, S Concept of an equilibrium stage Choice of independent variables Model for equilibrium curve (phase equilibrium) r model for non- uilibrium process or model for non equilibrium process Model for operating line (mass balance) 3 28420: Separation Process Principles - Lecture 5 (2009)
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eaching Leaching X s = solute/(solvent+solute) in the overflow Y s = solute/(solvent+solute) in the underflow Y 1 = carrier/(solvent+solute) in the overflow y = fraction solvent in overflow or underflow x = fraction solute in overflow or underflow Figure 4.20 Leaching stage. 28420: Separation Process Principles - Lecture 5 (2009) 4
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Non-ideal Leaching Solid-liquid phases for Over-flow and under-flow may or ay not be at leaching (Carrier A carries a may not be at equilibrium or ideal leaching compound B that is removed by lectively For ideal leaching, the tie-lines (equilibrium) are selectively dissolving in solvent S parallel and vertical and there Note : The enthalpy- is no change in composition composition curves also look similar 28420: Separation Process Principles - Lecture 5 (2009) 5
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Example 4.9 p 28420: Separation Process Principles - Lecture 5 (2009) 6
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Figure 4.22 1. Construct y-x diagram For ideal system, overflow and underflow lines are parallel; tie- lines pass through the origin For inert carrier, the overflow line is solvent- free 2. Locate solvent (S 0 ) and feed (L 0 );find mixing point M; draw tie-line passing through to locate S nd L 28420: Separation Process Principles - Lecture 5 (2009) 7 M to locate S 1 and L 1
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28420: Separation Process Principles - Lecture 5 (2009) 8
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How to generate SLE phase diagrams? gp g e need model for Solid iquid phase equilibrium We need model for Solid-Liquid phase equilibrium We need model for activity coefficients for compound i in the liquid phase We need the melting points and the heats of fusion of compound i We need to repeat the calculations for different sets of conditions of temperature and/or pressure Note: The above model neglects the effects of pressure and entropy 28420: Separation Process Principles - Lecture 5 (2009) 9
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Phase Equilibrium: Solid-liquid split Liquid, L Feed, Z Solid, S T Typical 2-Phase SLE Calculation S = x L p[ F RT (T - T}] = 1,2,….N s i i x i i exp[ H i /(RT mi ){(T T mi )/T}] i 1,2,….N i x i = i s i = i z i
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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-lecture5-2009 - Course 28420: Lecture 5 28420 Topics...

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