presentation clarkson-kooijman 070504

Benchmarking Mass Transfer Correlations with a

Nonequilibrium Model

Harry Kooijman & Ross TaylorClarkson University

Packed Column Design● Column Diameter:

– Capacity: F-factor or C-factor– Pressure Drop: HETP/∆p

● Column Height– Mass Transfer: HETP

Which models to use for a particular packing?

H

D

Recent new MTC Models● Olujic-Delft 1997-2003 [Various]

● Erasmus-Nieuwoudt [IECR, 40, pp.2310-2321]

● Del Carlo-Olujic-Paglianti 2006 [IECR, 45, pp.7967-7976]

How good are these models?

Traditional MTC Model Development● Total Reflux data (FRI, SRP, TU Delft, Koch-

Glitsch, Sulzer ChemTech, ...)● Simulation with equilibrium model:

– Determine number of stages– Plot average HETP versus F or C-factor– Plot pressure drop versus F or C-factor

● Correlate HETP using:– One or two-film approach– Fixed physical properties

Distillation Test Data● Typical Systems, Pressures, Thermodynamics:

– c-C6/n-C7, 0.3-4.1 bar, UNIFAC+Antoine– o/p-Xylene, 0.1-0.3 bar, Ideal+Antoine– iC4/nC4, 7-11 bar, SRK or PR– EB/CB, 0.1 bar, Ideal+Antoine– EB/ST, 0.1 bar, Ideal+Antoine– MeOH/H2O, 1 bar, NRTL+Antoine

How constant is the HETP?

HETP vs. Packed Bed Height

HETP varies due to:– T & p changes

c-C6/n-C7 1atm, 3m bed

10

20

30

40

50

60

80 85 90 95

Stage

T empe ra tu re (oC )

C hemS e p


HETP varies due to:– T & p changes– Concentration changes

10

20

30

40

50

60

0 0 .2 0 .4 0 .6 0 .8 1

Stage

L iqu id mo le frac tion

C hemS ep

C 6H 12 C 7 H 1 6


HETP varies due to:– T & p changes– Concentration changes– Consequent changes in

densities

1 0

2 0

3 0

4 0

5 0

6 0

3 3 .1 3 .2 3 .3 3 .4

6 2 0 6 4 0 6 60 6 8 0 70 0 7 2 0

Stag

e

Va p o u r D e n s ity (kg /m 3 )

L iq u id D e n s ity (kg /m 3 )

C h e mS e p



densities, viscosities

1 0

2 0

3 0

4 0

5 0

6 0

7 .6 e -0 0 6 7 .8 e -0 0 6 8 e -0 06 8 .2 e -0 0 6 8 .4 e -0 0 6

0 5 e -0 0 5 0 .0 0 0 1 0 .0 0 0 1 5

Stag

e

Va p o u r Visco s ity (N /m 2 .s )

L iq u id Visco s ity (N /m 2 .s )

C h e mS e p



densities, viscosities, surface tension

10

20

30

40

50

60

0 .013 0 .014 0 .01 5 0 .0 16 0 .01 7 0 .018St

age

S u rfa ce ten s ion (N /m )

C he m S e p



densities, viscosities, surface tension, and diffusivities

10

20

30

40

50

60

0 2 4 6 8 10 12 14St

age

L iqu id D iffus iv ity (1e-8m2/s)




– And changes in relative volatility

p=1.03bar

p=0.33bar

1 0

2 0

3 0

4 0

5 0

6 0

1 .6 1 .6 5 1 .7 1 .7 5 1 .8 1 .8 5 1 .9 1 .9 5 2

Stag

e

a lp h a





1.03bar 10

20

30

40

50

60

0 .2 5 0 .3 0 .3 5

Stag

e

H E T P

C h e mS e p

0.33bar

4.13bar





We must average HETP over the bed height!

1.03bar 10

20

30

40

50

60

0 .2 5 0 .3 0 .3 5

Stag

e

H E T P

C h e mS e p

0.33bar

4.13bar

A Different Approach● Data for multiple systems/pressures● Simulate in nonequilibrium model (ChemSep)● Compute HETP from back-calculated efficiency● Average HETP over the whole packed bedProblem: Often no concentration gradient

published. Use educated guess from T & p

Collecting Data● “ScanIt”

Collecting Data● “ScanIt”● Simulate it:

ChemSep Total Reflux

Collecting Data● “ScanIt”● Simulate it:

ChemSep Total Reflux

● Parametric Study to plot average HETP vs F-factor

Collecting Data

0

0 .0 5

0 .1

0 .1 5

0 .2

0 .2 5

0 .3

0 1 2 3 4

Aver

age H

ETP

(m)

F -fac to r

B X o /p -Xy le ne 1 6 T orr @ F R I (1 .2 2m ID )

B R F 8 5 exp .

Model Fitness

0

0 .05

0 .1

0 .15

0 .2

0 .25

0 .3

0 1 2 3 4

Aver

age

HETP

(m)

F -fac to r

B X o /p -Xy lene 16 T orr @ FR I (1 .22m ID )

B Z 95 exp. E rro rs

average error = 35mm

Structured Packing Test Data● Sulzer Mellapak 250Y, Mellapak Plus 252Y● Montz B1-250, B1-250M● Koch-Glitsch Flexipac 2Y, Flexipac HC● Raschig SuperPak 300● Sulzer BX, BX-Plus

MTC Models

Gauze Metal Structured Packing:● Zogg(+Toor-Marchello) 1983 [Chem.Ing.Tech., 45, p.67]

● Bravo-Fair 1985 [Hydrocarbon Processing, January]

● Brunazzi 1995 [Chem.Eng.Technol., 19, pp.20-27]

● Bravo-Rocha-Fair 1996 [IECR]

MTC Models

Sheet Metal Structured Packings:● Bravo-Rocha-Fair 1992/1996 [DA1992, IECR]

● Billet-Schultes 1992 [Chem.Eng.Technol., 16, pp.370-375] ● Ronge 1995 [PhD]

● Olujic-Delft 1997-2003 [various]

● Erasmus-Nieuwoudt [IECR, 40, pp.2310-2321]

● Del Carlo-Olujic-Paglianti 2006 [IECR, 45, pp.7967-7976]

Sulzer-BX

0

0 .05

0 .1

0 .15

0 .2

0 .25

0 .3

0 1 2 3 4

Aver

age

HETP

(m)

F -fac to r

B X o /p -Xy lene 16 T orr @ FR I (1 .22m ID )

B Z 95 exp . Z T M 83 B R F 96 B R F 85

Sulzer-BX

0

0 .05

0 .1

0 .15

0 .2

0 .25

0 .3

0 1 2 3

Aver

age

HETP

(m)

F -fac to r

B X o /p -Xy lene 730 T orr @ F R I (1 .22m ID )

B R F 85 exp . B Z95

Sulzer Mellapak 250Y

0

0 .1

0 .2

0 .3

0 .4

0 .5

0 .6

0 0 .02 0 .04 0 .06 0 .08 0 .1 0 .12

Aver

age

HETP

(m)

C -fac to r

M 250Y C B /E B 100mbar @ S u lze r (1 ID )

B R F 92 E xp . S u lzer

Montz B1-250M

0

0 .1

0 .2

0 .3

0 .4

0 .5

0 .6

0 0 .5 1 1 .5 2 2 .5 3 3 .5

Aver

age H

ETP

(m)

F -fac to r

B 1 -25 0M cC 6 /nC 7 1 .0 3ba r

B S 9 2E xp . H E T P

B R F 85 B R F 92

B R F 9 6 R 9 5

Billet-Schultes MTC: Effect CV

0.3

0.2

0.4

0

0 .1

0 .2

0 .3

0 .4

0 .5

0 .6

0 0 .5 1 1 .5 2 2 .5 3 3 .5

Aver

age

HETP

(m)

F -fac to r

B 1 -250M cC 6/nC 7 1 .03ba r

B S '92 C v= 0.3 C l= 0 .9E xp . H E T P

B S '92 C v= 0.2 B S '92 C v= 0.4

Billet-Schultes MTC: Effect CL

10 0.90.50.3

0

0 .1

0 .2

0 .3

0 .4

0 .5

0 .6

0 0 .5 1 1 .5 2 2 .5 3 3 .5

Aver

age H

ETP

(m)

F -fac to r

B 1 -25 0M cC 6 /nC 7 1 .0 3ba r

B S '92 C v= 0 .3 C l= 0 .9E xp . H E T P

B S '92 C v= 0 .3 C l= 0 .3

B S '92 C v= 0 .3 C l= 0 .5 B S '9 2 C v= 0 .3 C l= 1 0 .0

Koch-Glitsch Flexipac 2

0

0 .1

0 .2

0 .3

0 .4

0 .5

0 .6

0 0 .5 1 1 .5 2 2 .5 3 3 .5

Aver

age

HETP

(m)

F -fac to r

F lexipac 2 cC 6 /nC 7 0 .33ba r

R 95 E xp. H E T P

Raschig SuperPak 300

0

0 .1

0 .2

0 .3

0 .4

0 .5

0 .6

0 0 .5 1 1 .5 2 2 .5 3 3 .5

Aver

age

HETP

(m)

F -fac to r

S uperP ak 300 cC 6/nC 7 1 .65bar

B R F 92 E xp. H E T P

Lack of geometry data (other than Ap): Estimated deq

30mm

Conclusions● Consistent HETP comparisons for c-C6/n-C7● Public distillation test data collection

(work in progress) ● Overall best MTC correlations (so far):

– Gauze packings: Brunazzi '95– Sheet metal packings: Bravo-Rocha-Fair '92– New models do not provide better predictions

Future Work● Compare pressure drop & capacity models● Benchmark random packing models● Model liquid entrainment @ flood in MTC?

Questions?

presentation clarkson-kooijman 070504

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