ITK-234 Termodinamika Teknik Kimia II

ITK-234Termodinamika Teknik Kimia II

(2 SKS)

Dicky Dermawanwww.dickydermawan.net78.net

[email protected]

Sylabus:Multicomponent Thermodynamics

• Phase Equilibria (80%)• Chemical Equilibria (20%)

Textbooks & References

• Smith, Introduction 2 Chemical Engineering Thermodynamics

• Daubert, Chemical Engineering Thermodynamics

Score & Grade• 20 4 all homework & quiz• 25 4 1st midterm exam• 25 4 2nd midterm exam• 30 4 final term examination

A 4 74.5 ++B 4 59.5 ++C 4 49.5 ++D 4 39.5 ++

Phase Equilbria:Raoult’s Law

Nomenclature• Closed System• xi : mol fraction in liquid

phase• yi : mol fraction in gas phase

• i = 1,2,3,…• Sorted by

vapor pressure from the higher one

• Vapor pressure: tendency of certain liquid to vaporize

• The higher the temperature, the higher the vapor pressure

Vapor Pressure Model

Antoine

P [=] torrt [=] oC

Antoine Vapor Pressure Model

P [=] torrt [=] oC

Antoine Vapor Pressure Model

P [=] torrt [=] oC

What will be needed in the near future:

Hand Calculator

Computer Programs• Microsoft

Excel• MathCAD

Phase Equilibria Problem Relation

among T, P, xi & yi at equilibrium condition

Experimental ApproachMixture:

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

50oCP, 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 Diagram

t-x-y diagramP-x-y diagram

Experimental Approach - Drawback

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 - Drawback

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 - Drawback

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 QuestionDo 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:Criteria 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 Equilibria

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

)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 DiagramUsing Raoult’s Law: Binary Mixture sat

iii PxPy

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

Acetonitril(1)/Nitromethane(2)

65

70

75

80

85

90

0 0.2 0.4 0.6 0.8 1x1, y1

t, o C

@ P = 70 kPa

Berdasarkan Diagram,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 Mixture

Raoult’s Law: Binary Mixture

Type of Phase Equilibria CalculationsGiven T & P, find the equilibrium composition

xi, yi

BUBL P calculation:Given T & liquid composition xi,Find the bubble point Pb & vapor composition

DEW P calculation:Given T & vapor composition yi,Find the dew point Pd & vapor composition

Type of Phase Equilibria CalculationsBUBL t calculation:

Given P & liquid composition xi,Find the bubble point tb & vapor composition

DEW t calculation:Given P & vapor composition yi,Find the dew point Pd & vapor composition

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

Raoult’s Law; Binary Mixture

Type of Phase Equilibria Calculationsa. 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 Calculationsd. 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 phase diagram to make calculation?

No, we don’t have to

We can just perform the calculations

Raoult’s Law: Binary mixture

Raoult’s Law: Binary mixture

Extension to Ternary and Multi Component Mixtures

We can’t even prepare the diagram!

But we still able to make the calculations

Raoult’s Law: Ternary Mixture

Raoult’s Law: Ternary Mixture

Raoult’s Law: Ternary Mixture

Raoult’s Law: Ternary Mixture

Raoult’s Law: Ternary Mixture

KUIS 1 HUKUM RAOULTKamis, 15 Maret 2007

1. Dengan asumsi keberlakuan Hukum Raoult, sketsalah diagram txy untuk campuran biner benzena(1)/etilbenzena(2) pada tekanan 101,33 kPa.Berdasarkan diagram yang saudara konstruksi, tentukan dan tunjukkan dalam diagram:a. Titik didih normal etilbenzenab. Fasa campuran dengan fraksi mol etilbenzena = 0,22 pada tekanan atmosferik dan suhu 110oCc. Bila campuran ekimolar bersuhu kamar 25oC dipanaskan perlahan-lahan hingga mendidih, tentukan komposisi uap yang mula-mula terbentukd. Pada temperatur berapa seluruh cairan pada (c) teruapkan ?e. Uap yang diperoleh pada (c) dikondensasikan sehingga mencair. Cairan ini kemudian dibiarkan setimbang dengan uapnya pada tekanan atmosferik. Gambarkan proses ini dalam diagram dan tentukan komposisi uap baru yang terbentuk.

Tekanan uap masing-masing komponen murni mengikuti persamaan: 20,213C/t

47,32790045,14kPa/P ln osat2

79,220C/t51,27888858,13kPa/P ln o

sat1

KUIS 1 HUKUM RAOULTKamis, 15 Maret 2007

2. Kesetimbangan uap - cair campuran biner n-pentana(1)/n-heptana(2), karena kemiripan struktur molekulnya, dapat diasumsikan memenuhi hukum Raoult. Pada tekanan konstan 115 kPa: a. Tunjukkan bahwa campuran dengan komposisi60% mol n-pentana pada suhu 100oC berfasa uapb. Campuran pada (a) didinginkan perlahan-lahan

hingga uap mengembun sedikit demi sedikit.Perkirakan suhu yang diperlukan untuk

mengembunkan 50% dari uap pada (a)

21,233C/t07,24778183,13kPa/P ln o

sat1

64,216C/t32,29118587,13kPa/P ln o

sat2