P-A ELV Sep_bb3 VLE -Bin Dist_2012

7/29/2019 P-A ELV Sep_bb3 VLE -Bin Dist_2012

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SEPARATION PROCESSES

Vapor-Liquid Equilibrium Separation Processes

Unit operat ions in chemical engineeringby Mccabe, Smith and

Harriot

Transport Processes and Separation Process PrinciplesCHRISTIE

J. GEANKOPLIS

Separation process principles by Seader and Henley

Separation processes by King

Chemical Engineeringby Coulson and Richardson

The single separation process is the simplest process in which two

phases in contact are brought to physical equilibrium, followed by phase

separation.

ifi

ii

y

K x very large a single contacting stage may be sufficient

to achieve a desired separation between them

if not multiple stages are required

Vapor-Liquid Equilibrium Separation Processes


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BINARY VAPOR-LIQUID SYSTEMS

four intensive variables: T, P, yA, andxA

vapor-liquid equilibrium data for systems containing two components, A and B

A is the more volatile component

C= 2; P=2

F= 2

F= C-P+2

T, yA, and xA are tabulated for a fixed P for ranges of yAand xA from 0 to 1

T-x,y diagram


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TiC

iBiAPIn

o

i

)(

)()()(

Relative volatility


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EXAMPLE: Calculate the vapor and liquid compositions in equilibrium at 95C(368.2 K) for benzene-toluene using the vapor pressure from Table given below

at 101.32 kPa.

Transport Processes and Separation Process Principles, GEANKOPLIS


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SINGLE-STAGE EQUILIBRIUM CONTACT FOR VAPOR-LIQUID SYSTEM

EXAMPLE: A vapor at the dew point and 101.32 kPa containing a mole fraction of0.40 benzene (A) and 0.60 toluene (B) and 100 kg mol total is contacted with 110

kg mol of a liquid at the boiling point containing a mole fraction of 0.30 benzene

and 0.70 toluene. The two streams are contacted in a single stage, and the outlet

streams leave in equilibrium with each other. Assume constant molal overflow.

Calculate the amounts and compositions of the exit streams.

For constant molal overflow

V2= 100 kg mol

yA2= 0.40

L0= 110 kg mol

xA0= 0.30

x1 and y1 @ equilibrium


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trial and error

Flash distillation

x and y @ equilibrium


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CONTINUOUS DISTILLATION WITH REFLUX

11

1

1

11

1

ionRectificat

n

Dn

n

nn

nn

aaaaD

n

aaaan

n

nn

V

Dxx

V

Ly

LDV

xLyvDx

V

xLyVx

V

Ly

11

1

n

Dn

n

nn

V

Dxx

V

Ly

nnLDV

1

VV

LL

n

n

1

n

Dn

n

nn

LD

Dxx

LD

Ly

1

DLD

DDxx

DLD

DLy D

nn/)(

/

/)(

/1

111

D

Dn

D

Dn

R

xx

R

Ry

D

DV

D

LRD

MASS BALANCES


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1

BL

Bxx

BL

Ly

m

Bm

m

mm

1

BLBxx

BLLy Bmm

1

VVLLmm

1

BL

Bxx

BL

Ly

BLVV

Bxx

V

Ly

BxxLyV

Stripping

m

Bm

m

m1m

m1m

1m

Bm

1m

m1m

Bmm1m1m

baxy

R

xx

R

Ry

D

Dn

D

Dn

111

1R

Rslope

D

D

1R

x:intercept

D

D

Operating line for rectification

11

1

n

Dn

n

nn

V

Dxx

V

Ly

1D

D

R

x

1

2

),(DDxx

y

x

xDx1x2

y2

y1

y3y2

y1

y3

McCAbe-Thile Method- Number of ideal plate


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1yxx Do

1st tray

Total condenser Partial condenser

Operation line for Stripping

BL

Bxx

BL

Ly Bmm

1

Operating line for stripping


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1

FEED PLATE

Cold liquid Saturated liquid

(at bubble point)Partially vaporized

LFL

VV

qf

10

1

0

q

f

qFLFfLL

FqVfFVV

qf

)1(

)1(

1010

)(

)(1

FbPL

FbPL

TTCf

TTCq

q+f=1

Besleme dorusunun denklemi

Saturated vapor Superheated vapor

FVV

LL

q

f

0

1

0

1

q

f

)(1

)(

DFPV

dFPV

TTCf

TTCq


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1

(xF, xF)

q

xx

q

qy F

11

f

xx

f

fy F

)1(

1 qf

f=1

q=0

f=0

q=1

0


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1

HEATING AND COOLING REQUIREMENTS

111

D

Dn

D

Dn

R

xx

R

Ry

0

1

11

1

D

D

D

DD

D

D

R

x

R

RR

R

Rslope

AB

DBBDxxxx

Nln

)]1(/)1([Inmin

ANALYTICAL EQUATION

MINIMUM NUMBER OF PLATES

Fenske quation


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RD

D

L

D

LR

D

min

min

'

'

1min

min

xx

yx

R

R

D

D

D

D

''

'

minxy

yx

RD

D

MINIMUM REFLUX

min

1min

D

D

R

x

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P-A ELV Sep_bb3 VLE -Bin Dist_2012