Benchmarking Mass Transfer Correlations with a Nonequilibrium Model

Transcription

1 Benchmarking Mass Transfer Correlations with a Nonequilibrium Model Harry Kooijman & Ross Taylor Clarkson University

2 Packed Column Design Column Diameter: Capacity: F-factor or C-factor Pressure Drop: HETP/ p Column Height H Mass Transfer: HETP Which models to use for a particular packing? D

3 Recent new MTC Models Olujic-Delft [Various] Erasmus-Nieuwoudt [IECR, 40, pp ] Del Carlo-Olujic-Paglianti 2006 [IECR, 45, pp ] How good are these models?

4 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

5 Distillation Test Data Typical Systems, Pressures, Thermodynamics: c-c6/n-c7, bar, UNIFAC+Antoine o/p-xylene, 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?

6 HETP vs. Packed Bed Height HETP varies due to: T & p changes C h e m S e p 3 0 Stage c-c6/n-c7 1atm, 3m bed T e m p e ra tu re (o C )

7 HETP vs. Packed Bed Height HETP varies due to: T & p changes Concentration changes C h e m S e p Stage Liquid mole fraction C 6 H 1 2 C 7 H 1 6

8 HETP vs. Packed Bed Height HETP varies due to: T & p changes Concentration changes Consequent changes in densities Stage L iq u id D e n s ity (k g /m 3 ) C h e m S e p Va p o u r D e n s ity (kg /m 3 )

9 HETP vs. Packed Bed Height HETP varies due to: T & p changes Concentration changes Consequent changes in densities, viscosities Stage L iq u id Visc o s ity (N /m 2.s ) 0 5 e C h e m S e p e e e e e Va p o u r Vis co s ity (N /m 2.s )

10 HETP vs. Packed Bed Height HETP varies due to: T & p changes Concentration changes Consequent changes in densities, viscosities, surface tension Stage C h e m S e p S u rfa c e te n s io n (N /m )

11 HETP vs. Packed Bed Height HETP varies due to: T & p changes Concentration changes Consequent changes in densities, viscosities, surface tension, and diffusivities Stage Liquid D iffusivity (1e-8m2/s)

12 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 Stage p=1.03bar p=0.33bar a lp h a

13 HETP vs. Packed Bed Height HETP varies due to: T & p changes bar C h e m S e p Concentration changes bar Consequent changes in densities, viscosities, surface tension, and diffusivities Stage bar And changes in relative volatility H E T P

14 HETP vs. Packed Bed Height HETP varies due to: T & p changes bar C h e m S e p Concentration changes bar Consequent changes in densities, viscosities, surface tension, and diffusivities And changes in relative volatility We must average HETP over the bed height! Stage H E T P 4.13bar

15 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 bed Problem: Often no concentration gradient published. Use educated guess from T & p

16 Collecting Data ScanIt

17 Collecting Data ScanIt Simulate it: ChemSep Total Reflux

18 Collecting Data ScanIt Simulate it: ChemSep Total Reflux Parametric Study to plot average HETP vs F-factor

19 Collecting Data 0.3 B X o /p -Xyle n e 1 6 T o F R I (1.2 2 m ID ) Average HETP (m) F -fa cto r B R F 8 5 e xp.

20 Model Fitness B X o/p -Xylene 16 T F R I (1.22m ID ) Average HETP (m) average error = 35mm F -fa cto r B Z 95 exp. E rrors

21 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

22 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]

23 MTC Models Sheet Metal Structured Packings: Bravo-Rocha-Fair 1992/1996 [DA1992, IECR] Billet-Schultes 1992 [Chem.Eng.Technol., 16, pp ] Ronge 1995 [PhD] Olujic-Delft [various] Erasmus-Nieuwoudt [IECR, 40, pp ] Del Carlo-Olujic-Paglianti 2006 [IECR, 45, pp ]

24 Sulzer-BX B X o/p -Xylene 16 T F R I (1.22m ID ) Average HETP (m) F -fa cto r B Z 95 exp. Z T M 83 B R F 96 B R F 85

25 Sulzer-BX B X o /p-xyle ne 730 T F R I (1.22m ID ) Average HETP (m) F -fa cto r B R F 85 exp. B Z 9 5

26 Sulzer Mellapak 250Y 0.6 M 250Y C B /E B 100mb S u lze r (1 ID ) 0.5 Average HETP (m) C -factor B R F 92 E xp. S ulzer

27 Montz B1-250M B M c C 6 /n C b a r Average HETP (m) B S 9 2 E xp. H E T P F -fa c to r B R F 8 5 B R F 9 2 B R F 9 6 R 9 5

28 Billet-Schultes MTC: Effect C V 0.6 B 1-250M cc 6/nC bar 0.5 Average HETP (m) F -facto r B S '92 C v= 0.3 C l= 0.9 E xp. H E T P B S '92 C v= 0.2 B S '92 C v= 0.4

29 Billet-Schultes MTC: Effect C L 0.6 B M cc 6 /n C b a r 0.5 Average HETP (m) F -fa cto r B S '9 2 C v= 0.3 C l= 0.9 E xp. H E T P B S '9 2 C v= 0.3 C l= 0.3 B S '9 2 C v= 0.3 C l= 0.5 B S '9 2 C v= 0.3 C l= 1 0.0

30 Koch-Glitsch Flexipac F lexip ac 2 cc 6 /nc bar 0.5 Average HETP (m) F -facto r R 95 E xp. H E T P

31 Raschig SuperPak S u perp ak 3 00 cc 6/n C bar 0.5 Average HETP (m) F -facto r B R F 92 E xp. H E T P Lack of geometry data (other than Ap): Estimated d eq 30mm

32 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

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