presentation clarkson-kooijman 070504
TRANSCRIPT
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 vs. Packed Bed Height
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 vs. Packed Bed Height
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
HETP vs. Packed Bed Height
HETP varies due to:– T & p changes– Concentration changes– Consequent changes in
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
HETP vs. Packed Bed Height
HETP varies due to:– T & p changes– Concentration changes– Consequent changes in
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
HETP vs. Packed Bed Height
HETP varies due to:– T & p changes– Concentration changes– Consequent changes in
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)
HETP vs. Packed Bed Height
HETP varies due to:– T & p changes– Concentration changes– Consequent changes in
densities, viscosities, surface tension, and diffusivities
– 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
HETP vs. Packed Bed Height
HETP varies due to:– T & p changes– Concentration changes– Consequent changes in
densities, viscosities, surface tension, and diffusivities
– And changes in relative volatility
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
HETP vs. Packed Bed Height
HETP varies due to:– T & p changes– Concentration changes– Consequent changes in
densities, viscosities, surface tension, and diffusivities
– And changes in relative volatility
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?