ITK-234ITK-234Termodinamika Teknik Kimia IITermodinamika Teknik Kimia II

(2 SKS)(2 SKS)

Dicky DermawanDicky Dermawan

2d@itenas.ac.id2d@itenas.ac.id

Sylabus:Sylabus:Multicomponent ThermodynamicsMulticomponent Thermodynamics

• Phase EquilibriaPhase Equilibria (80%)(80%)

• Chemical EquilibriaChemical Equilibria (20%)(20%)

Textbooks & Textbooks & ReferencesReferences

• Smith, Introduction 2 Chemical Smith, Introduction 2 Chemical Engineering ThermodynamicsEngineering Thermodynamics

• Daubert, Chemical Engineering Daubert, Chemical Engineering Thermodynamics Thermodynamics

Score & GradeScore & Grade

• 20 4 all homework & quiz

• 25 4 1st midterm exam

• 25 4 2nd midterm exam

• 30 4 final term examinationA 4 74.5 ++B 4 59.5 ++C 4 49.5 ++D 4 39.5 ++

Phase Equilbria:Phase Equilbria:

Raoult’s LawRaoult’s Law

NomenclatureNomenclature

• Closed System

• xi : mol fraction in liquid phase

• yi : mol fraction in gas phase

• i = 1,2,3,…

• Sorted byvapor pressure

from the higher one

• Vapor pressure: tendency of certain liquid to vaporize

• The higher the temperature, the higher the vapor pressure

Vapor Vapor Pressure Pressure ModelModel

AntoineAntoine

P [=] torrP [=] torr

t [=] t [=] ooCC

AntoineAntoine Vapor Pressure Vapor Pressure ModelModel

P [=] torrP [=] torr

t [=] t [=] ooCC

AntoineAntoine Vapor Pressure Vapor Pressure ModelModel

P [=] torrP [=] torr

t [=] t [=] ooCC

What will be needed in the near What will be needed in the near future:future:

Hand CalculatorHand Calculator

Computer ProgramsComputer Programs• Microsoft Microsoft

ExcelExcel

• MathCADMathCAD

Phase Equilibria ProblemPhase Equilibria Problem

Relation Relation among among T, P, xT, P, xii & y& yii at at equilibrium equilibrium conditioncondition

Experimental ApproachExperimental ApproachMixture:

Methyl-ethyl-ketone (1) / Toluene (2)Temperature:

50oC

P, kPa x1 y1

15.51 0.0895 0.271618.61 0.1981 0.456521.63 0.3193 0.5934

Plot the P-x-y diagram

24.01 0.4232 0.681525.92 0.5119 0.744029.96 0.6096 0.805030.12 0.7135 0.863931.75 0.7934 0.904834.15 0.9102 0.9590

27.96

Typical DiagramTypical Diagram

t-x-y diagramP-x-y diagram

Experimental Approach - Experimental Approach - DrawbackDrawback

For the same binary mixture:Methyl-ethyl-ketone (1) / Toluene(2)

What if we need the equilibrium data at 40oC?You’ve got to make experiment at that temperature!

What if we need the equilibrium data at 50oC?

You already have one!

What if we need the equilibrium data at 60oC?You’ve got to make experiment at that temperature!

Even for a simple binary mixture we must carry out many experiment in order to gather data

Experimental Approach - Experimental Approach - DrawbackDrawback

What about other binary mixture:

Chloroform (1) / Dioxane (2)

You’ve got to perform other experiments!

You’ve got to perform other experiments!

How many experiment should be carried out to obtain binary mixture vapor – liquid equilibria

from a combination of 8 components?

Diethyl ketone (1) / n-hexane (2)

Acetonitrile (1) / Nitromethane (2)

You’ve got to perform other experiments!

Waw!

Experimental Approach - Experimental Approach - DrawbackDrawback

What about ternary mixture such as:Benzene (1) / Toluene (2) / Ethylbenzene (3) ?

You’ve certainly got to perform other experiments!

You know the answer!

How many experiment should be carried out to obtain mixtures vapor – liquid equilibria

from a combination of 100 components?Waw!

What about multicomponents mixture such as:Ethane (1) / Propane (2) / Isobutane (3) / Isopentane (4) ?

Fundamental QuestionFundamental Question

Do we really have to do these experiments?

100 years ago the answer is Yes!

Not now!

That’s why we take this course, folks!

Thermodynamics Approach:Thermodynamics Approach:Criteria for System in EquilibriaCriteria for System in Equilibria

i ....

P ....P P

T ....T T

iii

jn,P,Tii n

)nG(

The chemical potential of i-th component is defined as:

Criteria for Vapor - Liquid Criteria for Vapor - Liquid EquilibriaEquilibria

i

PP

TT

ig

i

g

g

jn,P,Tii n

)nG(

The chemical potential of i-th component is defined as:

Raoult’s Law Raoult’s Law

)yln(TRG iig

iig

i

jn,P,Tii n

)nG(

For ideal gases:

For ideal solution: )xln(TRG iiid

i

Neglecting effect of pressure on , we obtain:iG

satiii PxPy Raoult’s law

The chemical potential of i:

Construction of Phase DiagramConstruction of Phase DiagramUsing Raoult’s Law: Binary MixtureUsing Raoult’s Law: Binary Mixture sat

iii PxPy

Physical Interpretation of Phase Physical Interpretation of Phase Diagram: Diagram: PxyPxy

P-xy Diagram Acetonitril(1)/Nitrometana(2) @

75oC

40

45

50

55

60

65

70

75

80

85

0 0.2 0.4 0.6 0.8 1

x1, y1

P

Physical Interpretation of Phase Physical Interpretation of Phase Diagram: Diagram: txytxy txy diagram

Acetonitril(1)/Nitromethane(2)

65

70

75

80

85

90

0 0.2 0.4 0.6 0.8 1x1, y1

t, oC

@ P = 70 kPa

Berdasarkan Diagram,Berdasarkan Diagram,Tentukan dan Tunjukkan:Tentukan dan Tunjukkan:

a. Titik didih normal asetonitrilb. Fasa campuran dengan fraksi mol asetonitril =

0,22 pada tekanan 70 kPa dan suhu 95oCc. Bila campuran ekimolar bersuhu kamar 25oC

dipanaskan perlahan-lahan hingga mendidih, tentukan komposisi uap yang mula-mula terbentuk

d. Pada temperatur berapa seluruh cairan pada (c) teruapkan ?

e. Uap yang diperoleh pada (c) dikondensasikan. Cairan ini kemudian dibiarkan setimbang dengan uapnya pada tekanan 70 kPa. Gambarkan proses ini dalam diagram dan tentukan komposisi uap baru yang terbentuk.

Raoult’s Law: Binary MixtureRaoult’s Law: Binary Mixture

Raoult’s Law: Binary MixtureRaoult’s Law: Binary Mixture

Type of Phase Equilibria Type of Phase Equilibria CalculationsCalculations

Given T & P, find the equilibrium composition Given T & P, find the equilibrium composition xxii, y, yii

BUBL P calculation:BUBL P calculation:Given T & liquid composition xGiven T & liquid composition xii,,Find the bubble point PFind the bubble point Pbb & vapor composition & vapor composition

DEW P calculation:DEW P calculation:Given T & vapor composition yGiven T & vapor composition yii,,Find the dew point PFind the dew point Pdd & vapor composition & vapor composition

Type of Phase Equilibria Type of Phase Equilibria CalculationsCalculationsBUBL t calculation:BUBL t calculation:

Given P & liquid composition xGiven P & liquid composition xii,,Find the bubble point tFind the bubble point tbb & vapor composition & vapor composition

DEW t calculation:DEW t calculation:Given P & vapor composition yGiven P & vapor composition yii,,Find the dew point PFind the dew point Pdd & vapor composition & vapor composition

FLASH calculation:FLASH calculation:Given P, T & overall composition,Given P, T & overall composition,Find the fraction of system which is liquid (L) & Find the fraction of system which is liquid (L) & vapor (V) and their respective compositions xvapor (V) and their respective compositions xii & y & yii

Raoult’s Law; Binary MixtureRaoult’s Law; Binary Mixture

Type of Phase Equilibria Type of Phase Equilibria CalculationsCalculations

a. Given T= 100oC & P = 1 atm, find the equilibrium composition xi, yi

b. BUBL P calculation:Given T = 100oC & liquid composition x1 = 25%Find the bubble point Pb & vapor composition

c. DEW P calculation:Given T = 100oC & vapor composition y1 = 25%,Find the dew point Pd & dew composition

Type of Phase Equilibria Type of Phase Equilibria CalculationsCalculationsd. BUBL t calculation:

Given P = 1 atm & liquid composition x1= 25%Find the bubble point tb & vapor composition

e. DEW t calculation:Given P = 1 atm & vapor composition y1,= 25%Find the dew point td & dew composition

f. FLASH calculation:Given P = 1 atm, T = 115oC & overall composition, z1=25%Find the fraction of system which is liquid (L) & vapor (V) and their respective compositions xi & yi

Do we always have to prepare Do we always have to prepare phase diagram to make phase diagram to make calculation?calculation?

No, we don’t have toNo, we don’t have to

We can just perform the We can just perform the calculationscalculations

Raoult’s Law: Binary Raoult’s Law: Binary mixturemixture

Raoult’s Law: Binary Raoult’s Law: Binary mixturemixture

Extention to ternary mixtureExtention to ternary mixture

We can’t even prepare the diagram!We can’t even prepare the diagram!

But we still able to make the But we still able to make the calculationscalculations

Raoult’s Law: Ternary Raoult’s Law: Ternary MixtureMixture

Raoult’s Law: Ternary Raoult’s Law: Ternary MixtureMixture

Raoult’s Law: Ternary Raoult’s Law: Ternary MixtureMixture

Raoult’s Law: Ternary Raoult’s Law: Ternary MixtureMixture