Lecture 36. the Phase Rule

Total Page:16

File Type:pdf, Size:1020Kb

Lecture 36. the Phase Rule Lecture 36. The Phase Rule P = number of phases C = number of components (chemically independent constituents) F = number of degrees of freedom xC,P = the mole fraction of component C in phase P The variables used to describe a system in equilibrium: x11, x21, x31,...,xC −1,1 phase 1 x12 , x22 , x32 ,..., xC−1,2 phase 2 x1P , x2P , x3P ,...,xC−1,P phase P T,P Total number of variables = P(C-1) + 2 Constraints on the system: m11 = m12 = m13 =…= m1,P P - 1 relations m21 = m22 = m23 =…= m2,P P - 1 relations mC,1 = mC,2 = mC,3 =…= mC,P P - 1 relations 1 Total number of constraints = C(P - 1) Degrees of freedom = variables - constraints F=P(C- 1) + 2 - C(P - 1) F=C- P+2 Single Component Systems: F = 3 - P In single phase regions, F = 2. Both T and P may vary. At the equilibrium between two phases, F = 1. Changing T requires a change in P, and vice versa. At the triple point, F = 0. Tt and Pt are unique. 2 Four phases cannot be in equilibrium (for a single component.) Two Component Systems: F = 4 - P The possible phases are the vapor, two immiscible (or partially miscible) liquid phases, and two solid phases. (Of course, they don’t have to all exist. The liquids might turn out to be miscible for all compositions.) 3 Liquid-Vapor Equilibrium Possible degrees of freedom: T, P, mole fraction of A xA = mole fraction of A in the liquid yA = mole fraction of A in the vapor zA = overall mole fraction of A (for the entire system) We can plot either T vs zA holding P constant, or P vs zA holding T constant. Let A be the more volatile substance: * * PA >PB and Tb,A <Tb,B Pressure-composition diagrams Fix the temperature at some value, T. Assume Raoult’s Law: * * P=PA xA +PB xB * * * * * P=PA xA +PB (1 - xA)=PB + (PA - PB )xA 4 Composition of the vapor P x P* y = A = A A > x A * + ()* − * A P PB PA PB x A P x P* y = B = B B < x B * + ()* − * B P PB PA PB xA Point a: One phase, F = 3 (T, P, xA) Point b: Liquid starts to vaporize, F = 2 (T,P; xA not free.) xA = zb,yA = yb” Vapor is rich in A. Point c: Liquid has lost so much A that its composition is xA = xc’. The vapor is now poorer in A, yA = yc” Ratio of moles in the two phases is given by the lever rule: n ′′ liq = cc ′ nvap cc 5 Pointd:Liquidisalmostallgone,xA = xd’,yA = yd =zA For points below d, only the vapor is present (F=3). Numerical example: benzene-toluene at 20 C Exercise 8.4b. Let B = toluene and A = benzene. * * Given: PA = 74 Torr, PB = 22 Torr, zA =0.5 Q. At what pressure does the mixture begin to boil? A. At point b, P = 0.5x22 + 0.5x74 = 48 Torr. Q. What is the composition of the vapor at this point? A. PB = 0.5x22 = 11, PA = 0.5x74 = 37, yA = 37/48 = 0.77 Q. What is the composition and vapor pressure of the liquid when the last few drops of liquid boil? A. Point d. 74x y = z = 0.5 = A A A + − 74xA 22(1 xA ) xA = 0.229, xB =0.771 P = 0.229x74 + 0.771x22= 33.9 Torr 6 Lecture 37. Construction of the Temperature- Composition Diagram Fix the total pressure at some chosen value, P. Boiling does not occur at a unique temperature, but rather over a range of temperatures. (Contrast with a pure substance.) The vapor pressure curve is determined by the liquid composition: P=PA(T) + PB(T) PA(T) is the vapor pressure of pure A at temperature T. 7 Assume Raoult’s Law: = * + * P xA PA (T) xB PB (T) = * + − * xAPA (T) (1 xA )PB (T) = * + * − * PB (T ) xA (PA (T ) PB (T )) The vapor pressure pure liquid A at any temperature T is given by the Clapeyron-Clausius equation: * ∆H PA (T) = − vap,A 1 − 1 ln * PA (T0 ) R T T0 * PA (T0 ) =1atm,T0 = normal boiling point of A. The same reasoning applies to substance B. * * Once we have PA (T ) and PB (T ) , Raoult’s Law gives us xA as a unique function of T and P. This allows us to construct the liquid curve. 8 Composition of the vapor: P x P* (T) y = A = A A A P P ∆H 1 1 * − vap − y P (T ) RT T T A = A = e b, A xA P This result is equivalent to µ * + = µ * + A,vap RT ln y A A,liq RT ln xA This last result is the starting point for the boiling point elevation formula, except that there we assume yA =1. 9 Recipe for construction of the phase diagram: 1. Calculate Tb,A and Tb,B at the pressure of the diagram. 2. Choose a temperature Tb,A <T<Tb,B * * 3. Calculate PA (T ) and PB (T ). P − P* (T ) x = B 4. A * − * PA (T ) PB (T ) = * 5. y A x APA (T)/P. 10 Cooling of a vapor mixture Point a. Pure vapor, yA =zA Point b. Vapor begins to condense at xA =zb’,yA =zA =zb Point c. Comparable amounts of the two phases are n ′ vapor = cc present. Lever rule: ′′ nliquid cc Point d. Vapor is almost all gone; xA =zd’ =zA,yA =zd” Point e. Only liquid is present. 11 Distillation Point a. Mixture starts to boil, with xA =zA,yA =zb Points b-c. Vapor is condensed to form a liquid with xA=zb =zc Point c. The liquid that was collected in the previous step is boiled to form a vapor with xA=zd Condensation of the last bit of vapor produces a liquid very rich in either A (if Tb,A <Tb,B on the left) or B (if Tb,A >Tb,B on the right). 12 Non-ideal solutions Left: Impossible phase diagram, because at Pmax,where the liquid of this composition just starts to boil, there is no corresponding point on the vapor curve. (There is no tie line.) The vapor should always lie below the liquid in a pressure-composition diagram. At an extremum they must touch. Center: Vapor pressure reaches a maximum because of repulsion between A and B. This is an azeotrope, where the liquid and vapor have the same composition. (Note an error in the drawing: The vapor curve does not have a cusp, but rather is tangent to the liquid curve.) Right: Vapor pressure reaches a minimum because of attraction between A and B. This is also an azeotrope. 13 Distillation of non-ideal solutions Left diagram: low boiling azeotrope. A solution of composition za first boils at Ta. The vapor comes off with composition zb. It is condensed and then boils at Tc The final vapor to come off has the azeotropic composition, and the remaining liquid is enriched in B (or A, depending on which side of the azeotrope the process started). Right diagram: high boiling azeotrope. As before, za first boils at Ta The final vapor to come off is enriched in B (or A), and the remaining liquid has the azeotropic composition. 14 Equilibrium between immiscible liquids Upper Critical Lower Critical Double Critical Temperature Temperature Temperature The two phase region is always described by a tie line. It is a “no man’s land.” 15 Boiling of immiscible liquids Melting of immiscible solids Mixture of non-reactive Solids A and B react to solids. form compound AB. 16 Lecture 38. Equilibrium Constants Consider the following reaction: H2 +Cl2 Ø 2HCl Does it occur spontaneously? Let’s calculate DG for one mole of reaction. ∆ 0 = G f (H 2 ) 0 ∆ 0 = G f (Cl2 ) 0 ∆ 0 = − G f (HCl) 95.30kJ / mol ∆ 0 = − Gr 190.6 It seems that the reaction occurs spontaneously. But what if we start with pure HCl. Shouldn’t some of it react to form H2 and Cl2? 17 To determine when the reaction occurs spontaneously, we must take the partial pressures into account: P ∆G (Cl ) = 0 + RT ln Cl2 f 2 P o Cl2 P ∆ = − + HCl G f (HCl) 95.30 RT ln o PHCl P 2 P P ∆ = − + HCl − H 2 − Cl2 Gr 190.6 RT ln RT ln RT ln P0 Po Po At equilibrium, DGr =0.Thatis, 2 PHCl (P o ) 2 P 2 190.6 = −∆G o = RT ln = RT ln HCl r P P H 2 Cl2 PH PCl 2 2 P o P o = −∆ 0 RT ln K P Gr ln KP = 76.93 at 298 K 33 KP =2.57x10 18 So what happens if we start with pure HCl? P P = P = 0 Suppose that initially HCl =1barand H2 Cl2 P = 1− 2z P = P = z At equilibrium, HCl and H 2 Cl2 ()1− 2z 2 = 2.57x1033 z2 1 ≈ 2.57x1033 z2 z=1.97 x 10-17 This reaction goes nearly to completion. But this won’t be the case at higher T. 19 Another example: N2O4 F 2NO2 ∆ 0 = G f 97.89 and 51.31 kJ/mol ∆ 0 = − = Gr 2x51.31 97.89 47.30 ln KP = -4.730/RT = 1.909 2 PNO 2 Po P2 = = = NO2 K P 0.148 o PN O P P 2 4 N2O4 Po What is the composition of 2 bar of this material? Let x be the mole fraction of NO2.
Recommended publications
  • Thermodynamics
    TREATISE ON THERMODYNAMICS BY DR. MAX PLANCK PROFESSOR OF THEORETICAL PHYSICS IN THE UNIVERSITY OF BERLIN TRANSLATED WITH THE AUTHOR'S SANCTION BY ALEXANDER OGG, M.A., B.Sc., PH.D., F.INST.P. PROFESSOR OF PHYSICS, UNIVERSITY OF CAPETOWN, SOUTH AFRICA THIRD EDITION TRANSLATED FROM THE SEVENTH GERMAN EDITION DOVER PUBLICATIONS, INC. FROM THE PREFACE TO THE FIRST EDITION. THE oft-repeated requests either to publish my collected papers on Thermodynamics, or to work them up into a comprehensive treatise, first suggested the writing of this book. Although the first plan would have been the simpler, especially as I found no occasion to make any important changes in the line of thought of my original papers, yet I decided to rewrite the whole subject-matter, with the inten- tion of giving at greater length, and with more detail, certain general considerations and demonstrations too concisely expressed in these papers. My chief reason, however, was that an opportunity was thus offered of presenting the entire field of Thermodynamics from a uniform point of view. This, to be sure, deprives the work of the character of an original contribution to science, and stamps it rather as an introductory text-book on Thermodynamics for students who have taken elementary courses in Physics and Chemistry, and are familiar with the elements of the Differential and Integral Calculus. The numerical values in the examples, which have been worked as applications of the theory, have, almost all of them, been taken from the original papers; only a few, that have been determined by frequent measurement, have been " taken from the tables in Kohlrausch's Leitfaden der prak- tischen Physik." It should be emphasized, however, that the numbers used, notwithstanding the care taken, have not vii x PREFACE.
    [Show full text]
  • The Separation of Three Azeotropes by Extractive Distillation by An-I Yeh A
    The separation of three azeotropes by extractive distillation by An-I Yeh A thesis submitted in partial fulfillment of the requirement for the degree of Master of Science in Chemical Engineering Montana State University © Copyright by An-I Yeh (1983) Abstract: Several different kinds of extractive distillation agents were investigated to affect the separation of three binary liquid mixtures, isopropyl ether - acetone, methyl acetate - methanol, and isopropyl ether - methyl ethyl ketone. Because of the small size of the extractive distillation column, relative volatilities were assumed constant and the Fenske equation was used to calculate the relative volatilities and the number of minimum theoretical plates. Dimethyl sulfoxide was found to be a good extractive distillation agent. Extractive distillation when employing a proper agent not only negated the azeotropes of the above mixtures, but also improved the efficiency of separation. This process could reverse the relative volatility of isopropyl ether and acetone. This reversion was also found in the system of methyl acetate and methanol when nitrobenzene was the agent. However, normal distillation curves were obtained for the system of isopropyl ether and methyl ethyl ketone undergoing extractive distillation. In the system of methyl acetate and methanol, the relative volatility decreased as the agents' carbon number increased when glycols were used as the agents. In addition, the oxygen number and the locations of hydroxyl groups in the glycols used were believed to affect the values of relative volatility. An appreciable amount of agent must be maintained in the column to affect separation. When dimethyl sulfoxide was an agent for the three systems studied, the relative volatility increased as the addition rate increased.
    [Show full text]
  • Development of a Process for N-Butanol Recovery from Abe
    937 A publication of CHEMICAL ENGINEERING TRANSACTIONS VOL. 74, 2019 The Italian Association of Chemical Engineering Online at www.cetjournal.it Guest Editors: Sauro Pierucci, Jiří Jaromír Klemeš, Laura Piazza Copyright © 2019, AIDIC Servizi S.r.l. ISBN 978-88-95608-71-6; ISSN 2283-9216 DOI: 10.3303/CET1974157 Development of a Process for N-Butanol Recovery from Abe Wastewater Streams by Membrane Technology * Marco Stoller , Marco Bravi, Paola Russo, Roberto Bubbico, Barbara Mazzarotta Sapienza University of Rome, Dept. of Chemical Materials Environmental Engineering, Via Eudossiana 18, 00184 Rome, Italy [email protected] The aceton-butyl-ethanolic fermentation process (ABE) is a biotechnological process that leads to the production of acetone, n-butanol and ethanol (ABE compounds) from glucose sources and amides by use of certain biomasses. The process was developed initially during the middle of the last century and suffers from decline due to the greater petrochemical production of products and the lowering of the costs of the sector. Nowadays, the ABE process is regaining great interest because the fraction with the highest concentration, i.e. n-butanol, is an excellent constituent for biofuels. The ABE process has been optimized over time to obtain maximum yields of n-butanol, but the problem of separating and concentrating the butanol in the outlet stream of the ABE process persists. To allow an adequate use, often distillation by use of more columns is required. Moreover, the contained biomasses and suspended solids, in high quantity, must be eliminated, leading to overall high treatment costs. This work will report the main idea and some preliminary experimental results for the development and application of a process based on membrane technologies, to separate and concentrate the butanol from ABE process streams to sensibly reduce the difficulty to perform a final distillation.
    [Show full text]
  • Evaluation of Azeotropic Dehydration for the Preservation of Shrimp. James Edward Rutledge Louisiana State University and Agricultural & Mechanical College
    Louisiana State University LSU Digital Commons LSU Historical Dissertations and Theses Graduate School 1969 Evaluation of Azeotropic Dehydration for the Preservation of Shrimp. James Edward Rutledge Louisiana State University and Agricultural & Mechanical College Follow this and additional works at: https://digitalcommons.lsu.edu/gradschool_disstheses Recommended Citation Rutledge, James Edward, "Evaluation of Azeotropic Dehydration for the Preservation of Shrimp." (1969). LSU Historical Dissertations and Theses. 1689. https://digitalcommons.lsu.edu/gradschool_disstheses/1689 This Dissertation is brought to you for free and open access by the Graduate School at LSU Digital Commons. It has been accepted for inclusion in LSU Historical Dissertations and Theses by an authorized administrator of LSU Digital Commons. For more information, please contact [email protected]. This dissertation has been 70-9089 microfilmed exactly as received RUTLEDGE, James Edward, 1941- EVALUATION OF AZEOTROPIC DEHYDRATION FOR THE PRESERVATION OF SHRIMP. The Louisiana State University and Agricultural and Mechanical College, PhJD., 1969 Food Technology University Microfilms, Inc., Ann Arbor, Michigan Evaluation of Azeotropic Dehydration for the Preservation of Shrimp A Dissertation Submitted to the Graduate Faculty of the Louisiana State University and Agricultural and Mechanical College in partial fulfillment of the requirements for the degree of Doctor of Philosophy in The Department of Food Science and Technology by James Edward Rutledge B.S., Texas A&M University, 1963 M.S., Texas A&M University, 1966 August, 1969 ACKNOWLEDGMENT The author wishes to express his sincere appreciation to his major professor, Dr, Fred H. Hoskins, for the guidance which he supplied not only in respect to this dissertation but also in regard to the author’s graduate career at Louisiana State University, Gratitude is also extended to Dr.
    [Show full text]
  • FUGACITY It Is Simply a Measure of Molar Gibbs Energy of a Real Gas
    FUGACITY It is simply a measure of molar Gibbs energy of a real gas . Modifying the simple equation for the chemical potential of an ideal gas by introducing the concept of a fugacity (f). The fugacity is an “ effective pressure” which forces the equation below to be true for real gases: θθθ f µµµ ,p( T) === µµµ (T) +++ RT ln where pθ = 1 atm pθθθ A plot of the chemical potential for an ideal and real gas is shown as a function of the pressure at constant temperature. The fugacity has the units of pressure. As the pressure approaches zero, the real gas approach the ideal gas behavior and f approaches the pressure. 1 If fugacity is an “effective pressure” i.e, the pressure that gives the right value for the chemical potential of a real gas. So, the only way we can get a value for it and hence for µµµ is from the gas pressure. Thus we must find the relation between the effective pressure f and the measured pressure p. let f = φ p φ is defined as the fugacity coefficient. φφφ is the “fudge factor” that modifies the actual measured pressure to give the true chemical potential of the real gas. By introducing φ we have just put off finding f directly. Thus, now we have to find φ. Substituting for φφφ in the above equation gives: p µ=µ+(p,T)θ (T) RT ln + RT ln φ=µ (ideal gas) + RT ln φ pθ µµµ(p,T) −−− µµµ(ideal gas ) === RT ln φφφ This equation shows that the difference in chemical potential between the real and ideal gas lies in the term RT ln φφφ.φ This is the term due to molecular interaction effects.
    [Show full text]
  • Phase Diagrams
    Module-07 Phase Diagrams Contents 1) Equilibrium phase diagrams, Particle strengthening by precipitation and precipitation reactions 2) Kinetics of nucleation and growth 3) The iron-carbon system, phase transformations 4) Transformation rate effects and TTT diagrams, Microstructure and property changes in iron- carbon system Mixtures – Solutions – Phases Almost all materials have more than one phase in them. Thus engineering materials attain their special properties. Macroscopic basic unit of a material is called component. It refers to a independent chemical species. The components of a system may be elements, ions or compounds. A phase can be defined as a homogeneous portion of a system that has uniform physical and chemical characteristics i.e. it is a physically distinct from other phases, chemically homogeneous and mechanically separable portion of a system. A component can exist in many phases. E.g.: Water exists as ice, liquid water, and water vapor. Carbon exists as graphite and diamond. Mixtures – Solutions – Phases (contd…) When two phases are present in a system, it is not necessary that there be a difference in both physical and chemical properties; a disparity in one or the other set of properties is sufficient. A solution (liquid or solid) is phase with more than one component; a mixture is a material with more than one phase. Solute (minor component of two in a solution) does not change the structural pattern of the solvent, and the composition of any solution can be varied. In mixtures, there are different phases, each with its own atomic arrangement. It is possible to have a mixture of two different solutions! Gibbs phase rule In a system under a set of conditions, number of phases (P) exist can be related to the number of components (C) and degrees of freedom (F) by Gibbs phase rule.
    [Show full text]
  • By a 965% ATT'ys
    July 19, 1960 A. WATZL ETAL 2,945,788 PROCESS FOR THE PURIFICATION OF DIMETHYLTEREPHTHALATE Filed Nov. 19, l956 AZEOTROPE DISTILLATE CONDENSER CONDENSED WACUUM DISTILLATE DRY DISTILLATION MXTURE N2 COLUMN MPURE - SOD WACUUMFILTER ETHYLENE DMETHYL DMETHYL GLYCOL TEREPHTHALATE TEREPHTHALATE ETHYLENE GLYCOL INVENTORS: ANTON WATZL by aERHARD 965% SIGGEL ATT'YS 2,945,788 Patented July 19, 1960 2 phthalate is immediately suitable for reesterification or Subsequent polycondensation to polyethylene terephthal 2,945,788 ate. There are gained polycondensates of high degree of PROCESS FOR THE PURIFICATION OF viscosity with K values from 50 to 57. DMETHYLTEREPHTHALATE The best mode contemplated for practicing the inven Anton Watz, Kleinwallstadt (Ufr), and Erhard Siggel, tion involves the use of ethylene glycol as the aliphatic Laudenbach (Main), Germany, assignors to Vereinigte glycol. The following is a specific illustration thereof. Glanzstoff-Fabriken A.G., Wuppertal-Elberfeld, Ger Example many Thirty grams of crude dimethylterephthalate are mixed Filed Nov.19, 1956, Ser. No. 622,778 in a flask with 270 grams of ethylene glycol and azeo tropically distilled with the introduction of dry nitrogen 4 Claims. (C. 202-42) in a column of 30 cm. at about 44 Torr (1 Torr equals 1 mm. Hg). The azeotrope goes over at about 120° C. i This invention, in general, relates to production of into a cooled condenser. The dimethylterephthalate dimethylterephthalate and more particularly to the puri 5 separated from the glycol by vacuum filtering can be fication thereof. used immediately for reesterification or for polyconden The purification of dimethylterephthalate can be car sation. This process is illustrated in the flow sheet of ried out either by distillation or by recrystallization from the accompanying drawing.
    [Show full text]
  • Heterogeneous Azeotropic Distillation
    PROSIMPLUS APPLICATION EXAMPLE HETEROGENEOUS AZEOTROPIC DISTILLATION EXAMPLE PURPOSE This example illustrates a high purity separation process of an azeotropic mixture (ethanol-water) through heterogeneous azeotropic distillation. This process includes distillation columns. Additionally these rigorous multi- stage separation modules are part of a recycling stream, demonstrating the efficiency of ProSimPlus convergence methods. Specifications are set on output streams in order to insure the required purity. This example illustrates the way to set "non-standard" specifications in the multi-stage separation modules. Three phase calculations (vapor-liquid- liquid) are done with the taken into account of possible liquid phase splitting. ACCESS Free-Internet Restricted to ProSim clients Restricted Confidential CORRESPONDING PROSIMPLUS FILE PSPS_EX_EN-Heterogeneous-Azeotropic-Distillation.pmp3 . Reader is reminded that this use case is only an example and should not be used for other purposes. Although this example is based on actual case it may not be considered as typical nor are the data used always the most accurate available. ProSim shall have no responsibility or liability for damages arising out of or related to the use of the results of calculations based on this example. Copyright © 2009 ProSim, Labège, France - All rights reserved www.prosim.net Heterogeneous azeotropic distillation Version: March, 2009 Page: 2 / 12 TABLE OF CONTENTS 1. PROCESS MODELING 3 1.1. Process description 3 1.2. Process flowsheet 5 1.3. Specifications 6 1.4. Components 6 1.5. Thermodynamic model 7 1.6. Operating conditions 7 1.7. "Hints and Tips" 9 2. RESULTS 9 2.1. Comments on results 9 2.2. Mass and energy balances 10 2.3.
    [Show full text]
  • Introduction to Phase Diagrams*
    ASM Handbook, Volume 3, Alloy Phase Diagrams Copyright # 2016 ASM InternationalW H. Okamoto, M.E. Schlesinger and E.M. Mueller, editors All rights reserved asminternational.org Introduction to Phase Diagrams* IN MATERIALS SCIENCE, a phase is a a system with varying composition of two com- Nevertheless, phase diagrams are instrumental physically homogeneous state of matter with a ponents. While other extensive and intensive in predicting phase transformations and their given chemical composition and arrangement properties influence the phase structure, materi- resulting microstructures. True equilibrium is, of atoms. The simplest examples are the three als scientists typically hold these properties con- of course, rarely attained by metals and alloys states of matter (solid, liquid, or gas) of a pure stant for practical ease of use and interpretation. in the course of ordinary manufacture and appli- element. The solid, liquid, and gas states of a Phase diagrams are usually constructed with a cation. Rates of heating and cooling are usually pure element obviously have the same chemical constant pressure of one atmosphere. too fast, times of heat treatment too short, and composition, but each phase is obviously distinct Phase diagrams are useful graphical representa- phase changes too sluggish for the ultimate equi- physically due to differences in the bonding and tions that show the phases in equilibrium present librium state to be reached. However, any change arrangement of atoms. in the system at various specified compositions, that does occur must constitute an adjustment Some pure elements (such as iron and tita- temperatures, and pressures. It should be recog- toward equilibrium. Hence, the direction of nium) are also allotropic, which means that the nized that phase diagrams represent equilibrium change can be ascertained from the phase dia- crystal structure of the solid phase changes with conditions for an alloy, which means that very gram, and a wealth of experience is available to temperature and pressure.
    [Show full text]
  • Enhanced Distillation • Use of Triangular Graphs
    Lecture 15. Enhanced Distillation and Supercritical Extraction (1) [Ch. 11] • Enhanced Distillation • Use of Triangular Graphs - Zeotropic mixture -Mixture forming one minimum-boiling azeotrope - Mixture forming two minimum-boiling azeotropes • Residue-Curve Maps • Distillation-Curve Maps • Product-Composition Regions at Total Reflux Enhanced Distillation • Cases when ordinary distillation is not economical - Boiling point difference between components is less than 50℃ - Relative volatility is less than 1.10 - Mixture forms an azeotrope • Enhanced distillation - Extractive distillation : adding a large amount of solvent - Salt distillation : adding a soluble , ionic salt - Pressure-swing distillation : operating at two different pressures - Homogeneous azeotropic distillation : adding an entrainer - Heterogeneous azeotropic distillation : adding an entrainer - Reactive distillation : adding a separating agent to react selectively and reversibly with feed component(s) Zeotropic vs. Azeotropic Systems Binary zeotropic system Binary azeotropic system P = constant AtAzeotrope C T-y T-x Pure B xA, yA Pure A Use of Triangular Graphs • Triangular vapor-liquid diagram for ternary mixture - Too complex to understand • Plot with only equilibr ium liquid composition fofoatenayr a ternary mixture - Easy to understand -Convenient to use - Provide useful information in distillation of ternary components . Residue curve . Distill ati on curve Distillation Curves for Ternary Systems Each curve in each diagram is the locus of possible equilibrium liquid-phase
    [Show full text]
  • Separation of Dimethyl Carbonate and Methanol Mixture by Pervaporation Using Hybsi Ceramic Membrane
    Separation of dimethyl carbonate and methanol mixture by pervaporation using HybSi ceramic membrane Dissertation presented by Antoine GOFFINET for obtaining the master's degree in Chemical and Materials Engineering Supervisors Patricia LUIS ALCONERO Readers Iwona CYBULSKA, Denis DOCHAIN, Wenqi LI Academic year 2017-2018 Abstract In the current context of high biodiesel production, some by-products are created partic- ularly glycerol. Glycerol has a wide range of applications however its market is supersatu- rated as its production is very high. A solution found is the production of a value added com- ponent from glycerol. This value added component is the glycerol carbonate (GC) produced by transesterification reaction of glycerol with dimethyl carbonate (DMC). The reaction in- cludes four components: glycerol, DMC, GC and methanol. As methanol and DMC make up an azeotropic mixture, it is not possible to separate them by distillation. Pervaporation is a solution for this separation as it can break the azeotrope mixture and have other advantages especially energy saving. The pervaporation using polymeric membrane presents disadvan- tages as the low thermally and chemically resistance. Therefore another kind of membrane is needed. As ceramic membrane resistance is higher, the commercial HybSi ceramic is se- lected for this thesis experiments. This study aim to analyse the separation of DMC and methanol by pervaporation. The separation performance of HybSi membrane is evaluated at 40-50-60◦C with binary mixture of different concentrations. The permeation through the membrane is analysed by the solution-diffusion model. h kg i The results showed low permeate flux between 0 and 0.86 hm2 .
    [Show full text]
  • Partial Separation of an Azeotropic Mixture of Hydrogen Chloride and Water and Copper (II) Chloride Recovery for Optimization of the Copper-Chlorine Cycle
    Partial Separation of an Azeotropic Mixture of Hydrogen Chloride and Water and Copper (II) Chloride Recovery for Optimization of the Copper-Chlorine Cycle by Matthew P. Lescisin A Thesis Submitted in Partial Fulfillment of the Requirements for the Degree of Master of Applied Science in The Faculty of Engineering and Applied Science Mechanical Engineering University of Ontario Institute of Technology September 2017 © Matthew P. Lescisin, 2017 Contents Contents ii Abstract v Acknowledgments vi List of Figures vii List of Tables viii Nomenclature ix Quantities...................................... ix Greek Letters.................................... x Subscripts...................................... xi Acronyms...................................... xi 1 Introduction1 2 Background4 2.1 Boiling in the Subcooled Liquid Region .................. 4 2.2 Vapor-Liquid Equilibrium (VLE)...................... 5 2.3 Phase Diagrams................................ 5 2.3.1 Tie-Lines ............................... 6 2.4 Distillation .................................. 6 2.5 Azeotropes .................................. 8 3 Literature Review9 3.1 Azeotropic Distillation............................ 9 3.2 Extractive Distillation............................ 10 3.3 Pressure-Swing Distillation .......................... 11 3.4 Batch Mode.................................. 13 3.5 Heat-Integrated Distillation Columns.................... 13 3.5.1 Heat-Integrated PSD......................... 14 ii CONTENTS iii 3.6 Reflux Ratio ................................. 15
    [Show full text]