Available online at (Elixir International Journal) Chemical Engineering. Elixir Chem. Engg. 40 (2011)

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1 5549 D.Krishn/ Elixir Chem. Engg. 40 ( ARTICLE INF O Article history: Received: 1 October 011; Received in revised form: 14 November 011; Acceed: November 011; Keywords Azeotropic mixture, Solvent, Roults lw, Temperture, Pressure, Composition. Avilble online t (Elixir Interntionl Journl Modeling nd simultion of Azeotropic distilltion D. Krishn Deprtment of Chemicl Engineering, M.V.G.R. College of Engineering, Vizingrm, Indi Introduction An zeotropic mixture distills without chnge in composition nd in generl it hs boiling point higher or lower thn tht of ny of its pure constituents. A constnt boiling mixture is n zeotropic mixture. Azeotropes re specil form of non-idel solution. Azeotopes exist in solution becuse of moleculr dissimilrity of the components of the mixture. Ewell et l.,1944 [1] hve published n interesting pproch to predicting zeotropes formtion bsed on the conce of hydrogen bonds. The devition from idelity which results in zeotropes is ttributed to hydrogen bonds or internl pressure, the former being more importnt. The hydrogen bond conce is stted s follows. Hydrogen cn co-ordinte between two molecules of oxygen, nitrogen of fluorine. It cn lso coordinte between one of these donor toms (oxygen, nitrogen, fluorine nd crbon tom, provided sufficient number of negtive toms or groups re ttched to the crbon tom. Hydrogen cn not co-ordinte between two crbon toms, depending upon the toms between which hydrogen is coordinting. Toshihiko et l., 1994 [] hve conducted experiments for isobric vpor-liquid equilibri for cetone+chloroform+methnol nd for the constituent binry systems chloroform+methnol nd chloroform+cetone which were mesured t Kp using liquid-vpor ebullition-type equilibrium still. The experimentl dt were correlted with extended Redlich-Kister nd Wilson equtions. The dt were best correlted nd completely clculted for the ternry nd three binry zeotropic dt using extended Redlich-Kister eqution. Orge B et l., 1995 [3] hve conducted experiments for vpor liquid equilibrium results for the Acetone+Methnol+Chlorobenzene t constnt pressure of Kp. The equilibrium dt hve been compred with those predicted by ASOG, UNIFAC, UNIFAC-Dortmund nd UNIFAC-Lyngby group contribution methods, with lower Chemicl Engineering Elixir Chem. Engg. 40 ( AB STRACT Azeotropic distilltion is specil cse of multicomponent distilltion used for seprtion of binry mixtures which re either difficult or impossible to seprte by ordinry frctiontion. The work is minly focus on the seprtion of zeotropic mixtures. Selection of solvent plys n importnt role in industry to brek the zeotropes in esy wy. The solvent is selected in such wy tht it should brek the zeotropic mixture nd lso should form zeotropic mixture with one of the originl component. Determining the existence of homogeneous zeotropes together with their composition, temperture nd pressure is importnt from both theoreticl nd prcticl stndpoints in the nlysis of phse behvior nd in the synthesis nd design of seprtion system employing distilltion. Different moles of solvent re dded to the existence composition of zeotropic mixtures t constnt temperture nd pressure. Roult s lw is tken in the modeling to get vpor mixture from given liquid mixture clculted fter ddition of the solvent to the originl zeotropic mixture. 011 Elixir All rights reserved. stndrd devitions of the vpor molr frction nd temperture being clculted by the ltter. Stdtherr MA et l., 1999 [4] hve determined the existence nd composition of homogeneous zeotropes together with their composition nd temperture which is importnt from both theoreticl nd prcticl stndpoints in the nlysis of phse behvior nd in the synthesis nd design of seprtion systems employing distilltion. They hve described new method tht relibly loctes ny nd ll homogeneous zeotropes for multicomponent mixtures nd lso verifies the nonexistence of homogeneous zeotropes if none re present. The method is bsed on intervl nlysis, nd provides mthemticl nd computtionl gurntee tht ll zeotropes re locted. The technique is generl purpose nd cn be pplied in connection with ny thermodynmic model describing vpor-liquid equilibrium. An exmple using five-component mixture modeled with the NRTL eqution is presented. Vicente Mrtinez-Sori et l., 1999 [5] hve conducted experiments for vpor-liquid equilibri, which were conducted for binry systems of tert-butyl lcohol with toluene, isooctne nd methylcyclohexne t Kp using recirculting still. Experimentl vlues of the vpor pressure of non-oxygented pure components hve been obtined. The ccurcy of experimentl mesurements ws ±0.01 K in temperture, ±0.001 Kp in pressure, nd ±0.001 in mole frctions. The results re thermodynmiclly consistent ccording to point-to-point consistency test. The dt were correlted with five liquid phse ctivity coefficients models (Mrgules, Vn Lr, Wilson, NRTL, UNIQUAC. Vicente Mrtinez-Sori et l., 1999 [6] hve conducted experiments for vpor-liquid equilibri, which were conducted for binry systems of iso-butyl lcohol with toluene, isooctne nd methylcyclohexne t Kp using recirculting still. Experimentl vlues of the vpor pressure of non-oxygented pure components hve been obtined. The ccurcy of experimentl mesurements ws ±0.01 K in temperture, Tele: E-mil ddresses: d_krishn76@rediffmil.com 011 Elixir All rights reserved

2 5550 D.Krishn/ Elixir Chem. Engg. 40 ( ±0.001 Kp in pressure, nd ±0.001 in mole frctions. The results re thermodynmiclly consistent ccording to point-topoint consistency test. The dt were correlted with five liquid phse ctivity coefficients models (Mrgules, Vn Lr, Wilson, NRTL, UNIQUAC. Miguel Iglesis et l., 1999 [7] hve conducted experiments for vpor-liquid equilibri t Kp which were conducted for the ternry system, cetone+methnol+wter in n equilibrium still with circultion phses. Stisfctory results were obtined for the prediction of ctivity coefficients nd the equilibrium compositions with group contribution models(asog, UNIFAC, UNIFAC-Dortmund nd UNIFAC- Lyngby. Smll stndrd devitions of vpor molr frction nd temperture were clculted. Azeotropic behvior ws observed only in the cetone+methnol mixture. The correltion prmeters for the Tmir-Wisnik nd UNIQUAC equtions were presented. Bossen B.S. et l., 1993 [8] hve described the computtionl tools needed for simultion, design, nd nlysis of zeotropic distilltion opertions. These tools include simple methods to identify the existence of binry nd ternry zeotropes nd to clssify ternry mixtures s homogeneous or heterogeneous. The tools lso include more complex methods to compute the phse digrm (or heterogeneous liquid boiling surfce, predict liquid-vpor phse equilibrium, nd/or predict liquid-liquid-vpor phse equilibrium for simultions of btch nd continuous distilltion column opertions. Importnt new fetures of these tools re the incorportion of fst nd efficient method for test of phse stbility in simultion of distilltion opertions, the bility to hndle lrge rnge of mixtures (including mixtures with supercriticl compounds, nd the bility for computtions covering wide rnges of temperture nd pressure. On the bsis of these tools, simple nd consistent design lgorithms re developed. The pplicbility of the design lgorithms is verified through process simultion nd nlysis of the predicted behvior nd dt from the open literture. Conditions re given for exmples illustrting (when nd how possible distilltion boundries cn be crossed how multiple stedy sttes cn be obtined. Finlly, the effect of chnges in operting conditions on the dynmic behvior of the zeotropic distilltion columns nd the sensitivity of design to the prediction of phse equilibri re presented. The computtion of homogeneous zeotropes is problem tht hs been explored by severl reserchers nd tht hs been reviewed by Widgdo et l., 1996 [9]. Most of these solution techniques re bsed on itertive processes tht require some initil guess to begin the serch. Although these techniques re very efficient for locting some solutions, they do not provide gurntee tht ll solutions will be found. Moreover if no solution re found using these techniques, this does not provide gurntee tht no solutions exist. Fidkowski et l., 1993 [10] hve worked on zeotropic mixtures nd pplied on continution techniques. While these techniques re reported to be very relible, they still provide no theoreticl gurntee tht ll existing zeotropes hve been found. Hrding et l., 1997 [11] hve pplied globl oimiztion procedure, bsed on brnch nd bound techniques to solve the problem. While this techniques does provide mthemticl gurntee tht ll solutions will be found, in prctice it is possible tht computtionl problems due to rounding error my result in the loss of one or more solutions. The determintion of zeotropes strictly from the experiment cn be expensive. Predicting zeotropes computtionlly is one method of reducing the cost, s the computtionl results cn be used to nrrow the experimentl serch spce. It is obviously importnt tht the computtionl used be cpble of finding ll zeotropes or determing with certinty tht there re none, nd doing this t resonble cost in terms computer time. In the present work, simple method for finding, breking of zeotropic mixture by ddition of solvent is proposed. Roult s lw is pplied to vrious cse studies. Simultion results for vrious cse studies re given to show the efficiency of the proposed method. Mthemticl modelling: For n idel solution Roult s lw is given by p P x (1 p b Pb (1 x ( If the vpor is lso idel, Dlton s lw is pplicble p + p b P x + Pb (1 x (3 p y p (4 t p b Pb (1 x 1 y (5 Where P nd P b re the vpor pressures, which re clculted by Antoine eqution. It is given by B ln P A ( T + C (6 Where A, B nd C re the Antoine constnts. T is in degree Kelvin. To llow for devition from Roult s lw the ctivity coefficient γ must be tken into considertion. With this fctor equtions for non idel solutions my be written s follows p γ P x (7 pb γ bpb xb (8 The coefficient γ is not constnt. It s numericl vlue is function of ll components in the solution nd of their concentrtions. The ctivity coefficient of ech component increses s the solvent concentrtion increses from 0 to 100%. The ctivity coefficients re clculted from Vn Lr eqution or Mrgules equtions. Among the most useful reltionships re the Vn Lr equtions A lnγ 1 (9 Ax1 (1 + Bx B lnγ (10 Bx (1 + Ax1 Where A nd B re empiricl constnts. Another set of equtions developed by Mrgules cn be written s ln γ 1 x ( A + x1( B A (11 ln γ x1 ( B + x ( A B (1

3 5551 D.Krishn/ Elixir Chem. Engg. 40 ( Simultion results In this section, Roult s lw is pplied to vrious cse studies of zeotropic mixtures by writing progrmming in Mtlb. Seprtion of zeotropic mixture by dding third component is nlyzed in the following cse studies. Cse studies Consider the following binry systems 1. IBA(1+Toluene( t Kp. IBA(1+Isooctne( t Kp 3. IBA(1+Methylcyclohexne t Kp Norml boiling points T b nd densities ρ re reported in tble 1. Antoine constnts of the bove binry systems re reported in tble. Azeotropic dt for the two binry systems t Kp re reported in tble 3. Experimentl isobric vpor liquid equilibrium dt re reported in tble 4. Computed results for Chlooform(1+Methnol( t Kp by ddition of solvent i.e Acetone re reported in tble 5. Results nd discussions It is used for finding the zeotropic mixture composition from vpor-liquid equilibrium which is obtined from literture. There is looped re exist in fig 1, fig nd fig 4 i.e equlibrium curve is somewht fr wy from 45 degree line. Hence there is seprtion of vrious zeotropic mixture by ddition of vrious third component, solvent. From fig 3, there is gin zeotropic composition (x1y10.08 from Tble 4. hence there is no seprtion t x1y In this rticle, selection of third component is key role to seprte zeotropic mixture. The determintion of zeotropes strictly from the experiment cn be expensive. Predicting zeotropes computtionlly is one method of reducing the cost, s the computtionl results cn be used to nrrow the experimentl serch spce. It is obviously importnt tht the computtionl used be cpble of finding ll zeotropes or determing with certinty tht there re none, nd doing this t resonble cost in terms computer time. References [1] Ewell RH, Hrrison LM, Berg L, zeotropic distilltion, Ind.Eng.Chem,1944, 36(10, [] Toshihiko Hiki, Kiyofumi Kurihr & Kruo Kojim, vpor-liquid equilibri for cetone+chloroform+methnol nd constituent binry systems t Kp, J.Chem.Engg.Dt, 1994,39, [3] Orge B, Iglesis M, Dominguez A, nd Tojo J, vpor- Liquid Equilibri for the ternry system Acetone+Methnol+Chlorobenzene t KP, J.Chem.Eng.Dt 1995,40, [4] Robert By Mier W, Brennecke Jon F, nd Stdtherr A, computing homogeneous zetropes using intervl nlysis, chemicl Eng Technology (1999 1, [5] Vicente Mrtinez-Sori, Pilr Pen M nd Monton Jun B, Vpor-Liquid Equilibri for the binry systems tert-butyl Alcohol+Toluene,+Isooctne, nd +Methylcyclohexne t 101.3KP, J.Chem.Eng.Dt, 1999,44, [6] Vicente Mrtinez-Sori, Pilr Pen M nd Monton Jun B, Vpor-Liquid Equilibri for the binry systems tert-butyl Alcohol+Toluene,+Isooctne, nd +Methylcyclohexne t 101.3KP, J.Chem.Eng.Dt, 1999,44, [7] Miguel Iglesls, Betriz orge, Gonzlo Mrine & Tojo, vpor-liquid equlibri for the ternry system cetone+methnol+wter t Kp, J.Chem.Engg.Dt, 1999, 44, [8] Bosen BS, Jorgensen SB, nd Gni R, simultion, design nd nlysis of zeotropic distilltion, Industril & Engineering chemistry reserch, 1993,3 (4, [9] Widgdo S nd Seider WD, zeotropic distilltion, AIche, 1996,4(1, [10] Fidkowski ZT, Doherty MF, nd Mlone MF, Fesibility of seprtions for ditilltion of nonidel ternry mixtures,aichej,39(8, [11] Hrding ST, Mrns CD, McDonld CM nd Flouds CA, Locting ll homogeneous zeotropes in multicomponent mixtures,ind.eng.chem.res,1997,36(1, Tble 1: Antoine constnts for chemicls used Nme of chemicl A B C IBA Isooctne MCH Toluene

4 555 D.Krishn/ Elixir Chem. Engg. 40 ( Tble. Computed results for IBA(1+Toluent(, binry systems t Kp by ddition of solvent i.e. MCH x 1 x x 3 y 1 y y 3 T(K Tble 3: computed results for IBA(1+Toluene( binry mixture t Kp by ddition of solvent i.e. Isooctne x 1 x x 3 y 1 y y 3 T(K Tble 4: computed results for IBA(1+Isooctne( binry mixture t Kp by ddition of solvent i.e. Toluene x 1 x x 3 y 1 y y 3 T(K

5 5553 D.Krishn/ Elixir Chem. Engg. 40 ( Tble 5: computed results for IBA(1+MCH( binry mixture t Kp by ddition of solvent i.e. Isooctne x 1 x x 3 y 1 y y 3 T(K

The Predom module. Predom calculates and plots isothermal 1-, 2- and 3-metal predominance area diagrams. Predom accesses only compound databases.

The Predom module. Predom calculates and plots isothermal 1-, 2- and 3-metal predominance area diagrams. Predom accesses only compound databases. Section 1 Section 2 The module clcultes nd plots isotherml 1-, 2- nd 3-metl predominnce re digrms. ccesses only compound dtbses. Tble of Contents Tble of Contents Opening the module Section 3 Stoichiometric