*

Types of Separation Processes and Methods

Equilibrium Relations between Phases

Mass Transfer between Phases

Continuous Humidification Processes

Single and Multiple Equilibrium Contact Stages

Absorption in Plate and Packed Towers

Absorption of Concentrated Mixtures in Packed Tower

CHAPTER 10: GAS - LIQUID SEPARATION PROCESSES OVERVIEW

MASS TRANSFER BETWEEN PHASES*

*The solute A transferred from the fluid phase by convection mass transfer and through the solid by diffusion Concentration profiles in interface mass transferMass Transfer Between Phases

*Equimolar counterdiffusion

Mass Transfer Between Phases using film mass transfer coefficients and interface concentration

*Diffusion of A through stagnant or nondiffusing B Mass Transfer Between Phases using film mass transfer coefficients and interface concentration

*Mass Transfer Between Phases using film mass transfer coefficients and interface concentration

*EXAMPLE 10.4-1System boundaryQinThe solute A is being absorbed from a gas mixture of A and B in a wetted wall tower with the liquid flowing as a film downward along the wall. At a certain point in the tower the bulk gas concentration yAG=0.380 mol fraction and the bulk liquid concentration is xAL=0.100. The tower is operating at 298K and 1.013x105 Pa and the equilibrium data are tabulated in the table.The solute A diffuses through stagnant B in the gas phase and then through a nondiffusing liquid.Using correlations for dilute solutions in wetted wall towers, the film mass transfer coefficient for A in the gas phase is predicted as ky=1.465x10-3 kgmol A/s.m2.mol fraction liquid phase as kx=1.967x10-3 kgmol A/s.m2.mol fractionCalculate the interface concentrations yAi and xAi and flux NA.

*Since dilute solutions, (1-yA)iM 1.0 and (1-xA)iM 1.0Therefore,k`y=ky and k`x=kxEquilibrium data are plotted in figure 10.4-4.Point P:yAG = 0.380xAL = 0.100First trial,(1-yA)iM = 1.0(1-xA)iM = 1.0Slope PM (from Equation 10.4-9)

EXAMPLE 10.4-1 : solutionA line through point P with a slope of 1.342 is plotted intersecting the equilibrium line at M1. Point M1yAi=0.183xAi=0.247

*Second trial, use yAi and xAi from first trial to calculate the new slope.

Substituting into Eqs. (10.4-6) and (10.4-7),

Substituting into Eq.(10.4-9) to obtain the new slope,

A line through point P with a slope of 1.163 is plotted intersecting the equilibrium line at M. Point MyAi = 0.197xAi = 0.257

*Third trial, use yAi and xAi from second trial to calculate the new slope.

Substituting into Eqs. (10.4-6) and (10.4-7),

Substituting into Eq.(10.4-9) to obtain the new slope,

This slope is the same as the slope for 2nd trial.Final values:At point MyAi = 0.197xAi = 0.257

*To calculate the flux (Equation 10.4-8) is used.

*yAGxALPyAixAiM1M

Chart4

00.11160.1830.1830.0632110.380.380.1970.197

0.0220.18300.1830.19700.197

0.052

0.087

0.131

0.187

0.265

0.385

Equilibrium Line

Line PM1

Line PM

10.4-1

Equilibrium Line

xAyA

0.000

0.050.022

0.100.052

0.150.087

0.200.131

0.250.187

0.300.265

0.350.385

Point PPoint M1

yAGslope(m)csetting xsetting yxAiyAi

0.1000.380-1.3420.51420.30.11160.2470.1830.2470.183

0.2470

Line PM1

0.1000.3800.2470.183

0.2470.18300.183

Point M1Point M

xAiyAislope(m)csetting xsetting yxAiyAi

0.2470.183-1.1630.4702610.350.0632110.2570.1970.2570.197

0.2570

Line PM

0.1000.3800.2570.197

0.2570.19700.197

10.4-1

Equilibrium Line

Line PM1

Line PM

10.4-1PowerPT

Equilibrium Line

xAyA

0.000

0.050.022

0.100.052

0.150.087

0.200.131

0.250.187

0.300.265

0.350.385

Point PPoint M1

yAGslope(m)csetting xsetting yxAiyAi

0.1000.380-1.3420.51420.30.11160.2470.1830.2470.183

0.2470

Line PM1

0.1000.3800.2470.183

0.2470.18300.183

Point M1Point M

xAiyAislope(m)csetting xsetting yxAiyAi

0.2470.183-1.1630.4702610.350.0632110.2570.1970.2570.197

0.2570

Line PM

0.1000.3800.2570.197

0.2570.19700.197

P

M1

M

10.4-1PowerPT

Equilibrium Line

Line PM1

Line PM

10.4-2

Equilibrium Line

xAyA

0.000

0.050.022

0.100.052

0.150.087

0.200.131

0.250.187

0.300.265

0.350.385

Point PPoint M1

yAGslope(m)csetting xsetting yxAiyAi

0.1000.380-1.3420.51420.30.11160.2470.1830.2470.183

0.2470

Line PM1

0.1000.3800.2470.183

0.2470.18300.183

Point M1Point M

xAiyAislope(m)csetting xsetting yxAiyAi

0.2470.183-1.1630.4702610.350.0632110.2570.1970.2570.197

0.2570

Line PM

0.1000.3800.2570.197

0.2570.19700.197

Overall Driving VorcexLy*

0.1000.3800.1000.052

0.10000.0000.052

10.4-2

Equilibrium Line

Line PM1

Line PM

10.5-EX

Equilibrium Line(Hyi1-Hy1)-(Hyi2-Hy2)Hy2-Hy1

TLHy(Hyi)10-3(Hy)10-3(Hyi-Hy)10-3ln[(Hyi1-Hy1)/Hyi2-Hy2)](Hyi-Hy)M

26.78494.471.722.723.78304355690.4961518055

29.497.2108.483.524.927.13504749390.4201208788

32.3112.1124.494.929.532.31329174290.3589854012

35128.9141.8106.535.339.35068776250.3024089457

37.8148.2162.1118.443.749.04081211390.2344985636

40.6172.1184.7129.954.8

43.3197.21.8121655948

46.1224.5

Operating Line

TLHy

29.471.7

43.3129.9

yxslopeintersectsettingsetting

HyTLmcxy

71.729.3995844379-41.871302.66060041562988.4306004156

83.532.2177640849-41.871432.457782235931134.4877822359

94.934.9404122185-41.871557.855059587834134.2750595878

106.537.7108261088-41.871685.452289173936178.1322891739

118.440.5528886341-41.871816.349447111439183.4194471114

129.943.2994196461-41.871942.846700580442184.3067005804

P

M1

M

E

10.5-EX

0

0

0

0

0

0

0

0

Equilibrium Line

Liquid Temperature (oC)

Enthalpy Hy [(J/kg)10-3]

10.5-1

Equilibrium Line(Hyi1-Hy1)-(Hyi2-Hy2)Hy2-Hy1

TLHy(Hyi)10-3(Hy)10-3(Hyi-Hy)10-3ln[(Hyi1-Hy1)/Hyi2-Hy2)](Hyi-Hy)M

26.78494.471.722.723.78304355690.4961518055

29.497.2108.483.524.927.13504749390.4201208788

32.3112.1124.494.929.532.31329174290.3589854012

35128.9141.8106.535.339.35068776250.3024089457

37.8148.2162.1118.443.749.04081211390.2344985636

40.6172.1184.7129.954.8

43.3197.21.8121655948

46.1224.5

Operating Line

TLHy

29.471.7

43.3129.9

yxslopeintersectsettingsetting

HyTLmcxy

71.729.3995844379-41.871302.66060041562988.4306004156

83.532.2177640849-41.871432.457782235931134.4877822359

94.934.9404122185-41.871557.855059587834134.2750595878

106.537.7108261088-41.871685.452289173936178.1322891739

118.440.5528886341-41.871816.349447111439183.4194471114

129.943.2994196461-41.871942.846700580442184.3067005804

10.5-1

0000

0000

000

000

000

000

0

0

Equilibrium Line

Operating line

Liquid Temperature (oC)

Enthalpy Hy [(J/kg)10-3]

10.7-1

Operating Line

xy

00.02

0.0003320.04

0.0008550.07

0.002010.13

0.003550.2

Equilibrium Line

xy

00

0.00014030.00158

0.0004220.00763

0.0008420.01855

0.0019650.0513

0.00420.121

0.006980.212

0.000460.009

00.02

0.001030.0235

0.0003320.04

0.001850.0476

0.0008550.07

0.003550.1015

0.002010.13

0.005650.1685

0.003550.2

10.7-1

000000

000000

00

00

00

0

0

Equilibrium Line

Operating Line

mole fraction, x

mole fraction, y

Sheet1

f(y)y

19.250.020.0219.25

12.770.040.020

9.290.07

7.160.130.0412.77

6.330.200.040

0.079.29

0.070

0.137.16

0.130

0.26.33

0.20

Sheet1

000000

000000

0

0

0

y

f(y)

examplePP

Equilibrium Line(Hyi1-Hy1)-(Hyi2-Hy2)Hy2-Hy1

TLHy(Hyi)10-3(Hy)10-3(Hyi-Hy)10-3ln[(Hyi1-Hy1)/Hyi2-Hy2)](Hyi-Hy)M

26.78494.471.722.723.78304355690.4961518055

29.497.2108.483.524.927.13504749390.4201208788

32.3112.1124.494.929.532.31329174290.3589854012

35128.9141.8106.535.339.35068776250.3024089457

37.8148.2162.1118.443.749.04081211390.2344985636

40.6172.1184.7129.954.8

43.3197.21.8121655948

46.1224.5

Operating Line

TLHy

29.471.7

43.3129.9

yxslopeintersectsettingsetting

HyTLmcxy

71.729.3995844379-41.871302.66060041562988.4306004156

83.532.2177640849-41.871432.457782235931134.4877822359

94.934.9404122185-41.871557.855059587834134.2750595878

106.537.7108261088-41.871685.452289173936178.1322891739

118.440.5528886341-41.871816.349447111439183.4194471114

129.943.2994196461-41.871942.846700580442184.3067005804

examplePP

Equilibrium Line

Operating line

Liquid Temperature (oC)

Enthalpy Hy [(J/kg)10-3]

*Equimolar counterdiffusion and/or diffusion in dilute solutions

GAS CONTROLLING LIQUID CONTROLLINGMass Transfer Between Phases Overall mass transfer coefficients and driving forces

*

*Diffusion of A through stagnant or nondiffusing B

Mass Transfer Between Phases Overall mass transfer coefficients and driving forces

Chapter 2 : Work and HeatChapter 2 : Work and Heat*Chapter 2 : Work and HeatChapter 2 : Work and Heat*Chapter 2 : Work and HeatChapter 2 : Work and Heat*Chapter 2 : Work and HeatChapter 2 : Work and Heat*Chapter 2 : Work and HeatChapter 2 : Work and Heat*Chapter 2 : Work and HeatChapter 2 : Work and Heat*Chapter 2 : Work and HeatChapter 2 : Work and Heat*Chapter 2 : Work and HeatChapter 2 : Work and Heat*