Vapor liquid equilibrium( ethanol+water)

Vapor-Liquid Equilibrium

Course Number: ChE-302 Course Title: Chemical Engineering Laboratory-II

Experiment Number: 03 Name of the Experiment: apor-Li!ui" apor-Li!ui" E!uilibrium

#ubmitte" by:

#ubmitte" to:

$ahe %u&h

+r #ye"a #ultana %aia

#tu"ent Number: '20203(

,rofessor

#ection: )2

+epartment of chemical engineering

*roup Number: 02

+epartment of Chemical Engineering

,artners #tu"ent Numbers: '20203.

+ate of

'20203/ ,erformance:

'20203 036'06'7

'202010

+ate of #ubmission: '06'06'7 1|Page


'0 #ummary The aim of this experiment is to produce vapor-liquid equilibrium at atmospheric pressure and to determine equilibrium composition and temperature. This experiment helps one to inspect the rela relati tion onsh ship ip betw betwee een n vapo vaporr and and liqu liquid id phas phases es and and to unde unders rsta tand nd the the conc concep eptt of VLE comprehensi comprehensively vely.. A binary system system e.g. ethanol-wat ethanol-water er system was used in this experiment. experiment. The mixture was fed into an evaporator and the evaporated vapor was cooled down using condenser. The The conde condens nsed ed liqui liquid d fall fallss bac bac into into roun round d bott bottom om flas flas. . This This cycl cyclee cont contin inue uess unti untill the the temperature becomes constant. !amples from both round bottle flas and distillate collector were collected to measure refractive indices. At equilibrium point refractive indices of vapor and liquid liquid achieve constant values. "sing "sing refractive refractive index vs. compositio composition n diagram diagram equilibrium equilibrium composition was measured. The experimental values of equilibrium compositions with #Txy$ diagram and #%-&$ diagram are then compared with the theoretical values. The equilibrium temperature of the vapor liquid equilibrium system was found to be '( )*. The mole fraction of ethanol in liquid phase was .+) and that in vapor phase was ., while the corresponding theoretical values are ).(/ and ).,0 correspondingly.

20 Intro"uction Equilibrium can be referred to as a static condition in which there is no change in macroscopic properties of a system with time. According to Vapor-liquid apor-liquid equilibrium1VLE2 the rate of condensation of vapor is equal to the rate of vapori3ation without any net interconversion between liquid and vapor phase. 4n this experiment our goal was to create vapor liquid equilibrium at atmospheric pressure and to determine equilibrium temperature and composition for a binary system. "ndoubtedly the concept of vapor liquid equilibrium is the heart of many chemical processes and has immense importance in chemical and environmental engineering as various processes lie drying distillation and evaporation depend greatly on VLE. According to theory it needs forever to reach equilibrium but in real practice it can be reached in a closed space if vapor and liquid phases are in contact with each other for long period without any

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Vapor-Liquid Equilibrium interference. 5or multicomponent system equilibrium condition can be defined by following equations 6 6 and 7here 8 and T are pressure and temperature of different phases and 9 is 9ibb$s free energy also called as chemical potential. Temperature-composition Temperature-composition curve 1T-xy diagram2 composition of liquid phase vs. composition of vapour phase 1y-x diagram2 are the most common graphical representation of binary vapor liquid equilibrium system. And And these diagrams were used to obtain obta in result. This experiment also gives us insight on distillation process.

30 Experimental 8or& 3' )pparatus     

:efractometer Thermometer :ound bottom flas !ample collector !;LTE<= Vapor Liquid Equilibrium "nit

3' Experimental setup 3|Page


5igure-)+> Experimental setup for vapor-liquid equilibrium

32 Procedure  

At first the refractive index of the feed solution was determined at room temperature. Then ()) ml of ethanol water feed solution of composition (? ethanol 1by weight2 was poured to the equilibrium still through thermometer point and no gas leaage must be



ensured As Temperatu Temperature re should not exceed ')-degree ')-degree *elsius cooling water flow was started to



condenser. Then the mixture was heated by electric heater. The heater needed to be ad@usted in such a way that the mixture of vapor and liquid was raised through the narrow nec above the



flas. After ) minutes when temperature reached a constant value samples were collected from both round bottom flux and distillate collector in small sample bottles. And their corresponding refractive indices were recorded after they coo l down.

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

!tep , was repeated until a constant refractive index was obtained and the system was

 

assumed to reach equilibrium. The temperature was recorded with thermometer which was the equilibrium temperature. !ampl !amples es from from both both round round botto bottom m flux flux and and dist distil illa late te colle collect ctor or ware ware colle collect cted ed and and



refractive indices were measured with refractometer. At last refractive index-composition curve was used to obtain the equilibrium conditions.

10 9bsere" "ata :efractive index of feed solutionB +.,0 4nitial composition of feed solutionB ( mole? ethanol Table )+> Cata for refractive index of ethanol water system in liquid and vapor phase

:efractive index Do. of observation

liquid phase

:efractive index vapor phase

1average values2

1average values2

Temperature o

1 *2

+

'(

+.,,

+.+

(

'(

+.'

+.((



'(

+.,(

+.(,



'(

+.',

+.(

,

'(

+.'0,

+.(



'(

+.'

+.(

70 Calculate" "ata Table Table 02: Data for compoitio! compoitio! of et"a!ol et"a!ol #ater $tem $tem i! liquid liquid a!d %apor p"ae

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'o( of ober%ati o!

Temperatur Temperatur e )o*+

,efracti%e i!de liquid p"ae )a%erage %alue+

.ole fractio!/  )mole +

,efracti% e i!de %apor p"ae

.ole fractio!/ $ )mole +

)a%erage %alue+

1

82

1(3&&

20

1(31

41

2

82

1(34

12

1(322&

0

3

82

1(3&2

10

1(32&

0

4

82

1(34&

11

1(32

&4

&

82

1(34&

11

1(32

&4



82

1(34

10

1(32

&4

(0 #ample Calculation Equilibrium temperatureB '(o* 5rom experiment *omposition of ethanol in mole percent 4n vapor phaseB ,? 4n liquid phaseB +)? Literature values of composition of ethanol in mole percent from Txy diagram Liquid phase B (/? Vapor phase B ,0 ? 5rom the x-y diagram Vapor Vapor phase B  1mole ?2 ethanol for the composition of liquid phase B + ) 1mole ?2 ethanol. Liquid phase B ( 1mole ?2 ethanol ethano l for the composition of vapor phase B , 1mole ?2 ethanol.

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.0 *raphical representation 10& 10&

100 100

&

0

Temp emparat aratu ure ( C) liquid &

%apor

0(2 0(& 0(1

0

&

0 0

0(1

0(2

0(3

0(4

0(&

0(

0(

0(

0(

1

Mole fraction of liquid (x) and vapor (y) of Ethanol

5igure )(> )(> Temperature Temperature vs. molar molar composition composition of liquid1x2 and vapor1y2 phase phase

|Page


1

0(

0(

0(

0(

Molar composition of Ethanol in vapor (y)

0(&

0(4

0(3

0(2

0(1

0 0 0(1 0(2 0(3 0(4 0(& 0( 0( 0( 0( 1

Molar composition of Ethanol in Liquid (x)

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5igure 5igure )> Folar Folar compos compositi ition on of Ethano Ethanoll in liquid liquid vs. molar molar compos compositi ition on of Ethanol in vapor

/0 %esults Equilibrium temperatureB '(o* Equilibrium composition of ethanol in liquid phaseB +)?1mole2 Equilibrium composition of ethanol in vapor phaseB ,?1mole2

0 +iscussions The experi experimen mentt was carri carried ed out succes successfu sfully lly by follow following ing the procedu procedures res.. The values values we obtained experimentally showed deviations from literature values due to errors introduced in the experiment. At '(-degree *elsius the equilibrium composition of Ethanol in liquid and vapor phase should be (/? and ,0? respectively. 7hereas we achieved +) mole? ethanol composition in liquid phase and ,mole? in vapor phase. 5rom the data it is evident that deviation is significant. Foreover from %-& diagram we can observe experimentally obtained equilibrium composition lay below the theoretically obtained equilibrium values. Gowever the compo composi siti tions ons obtai obtaine ned d expe experi rime menta ntall lly y shou should ld have have lied lied on equil equilib ibri rium um curv curves es as the compos compositi itions ons are equilib equilibriu rium m compos compositi itions ons.. The probabl probablee causes causes for such such deviat deviation ionss are explained below

The provided graph of refractive index vs. composition graph was for )o *. but the temperature of the day of performance was above )o* which may have influenced the result.

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

ethanol is highly volatile and transfer of ethanol from one vessel to another vessel provided room for ethanol loss. As a result measurement of refractive index was not



accurate. ;ur system was not properly insulated and there was temperature difference between top and bottom part of the equilibrium still. Gence the temperature values that were recorded were were not not the the actual actual temp temper erat atur uree value valuess of the the mixt mixtur ure. e. Ther Theref efor ore e lac lac of prop proper er



insulation is responsible for deviation in results. Darrow pipes were used in the apparatus which increased pressure above the liquid. As a result vapor could not pass freely and pressure was not constant everywhere. Hut this process should be isobaric and constancy of pressure is a prime requirement of this



experiment. After After measur measuring ing refracti refractive ve index index of a sample sample the sampling sampling bottle bottle was not cleane cleaned d properly. Any drop of liquid from previous sample can change concentration of new sample and manipulate results.

'00 %eferences 

7anat 8hillip.*. 1()+(2. !eparations process engineeringrd edition "pper !addle

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:iver Dew Iersey> 8rentice Gall. 4ntroductio 4ntroduction n to *hemical *hemical Engineering Engineering 8rocessesJV 8rocessesJVaapor-Liqui por-Liquid d equilibrium equilibrium Wikibooks, retrieved from https>JJen.wiiboos.orgJwiiJ4ntroductionKtoK*hemicalKEngineeringK8rocessesJV https>JJen.wiiboos.orgJwi iJ4ntroductionKtoK*hemicalKEngineeringK8rocessesJVapor apor--





LiquidKequilibrium Vaporliquid Vaporliquid equilibrium Wikipedia, retrieved from https>JJen.wiipedia.orgJwiiJVa https>JJen.wiipedia.orgJwiiJ Vapor?E(?')?/liquidKequilibrium por?E(?')?/liquidKequilibrium VLE Academia, VLE Academia, retrieved from https>JJwww.academia.eduJ++'+)+JVLEKLabK:eportK()+,K

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$ar&ing #cheme: Normal %eport Name: $ahe %u&h #tu"ent number: '20203( Section and marks allocated !ummary1+2 4ntroduction 1+2 Experimental 7or 1+.,2 ;bserved Cata 1+2 *alculated Cata 1+2 !ample *alculation 1+2 9raphs 1+2 :esults and Ciscussion 1+2 :eferences and Domenclature 1).,2 7riting 7riting
Marks

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Vapor liquid equilibrium( ethanol+water)

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