Benchmarking Mass Transfer Correlations with a Nonequilibrium Model Harry Kooijman & Ross Taylor Clarkson University
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
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 1 0 2 0 C h e m S e p 3 0 Stage c-c6/n-c7 1atm, 3m bed 4 0 5 0 6 0 8 0 8 5 9 0 9 5 T e m p e ra tu re (o C )
HETP vs. Packed Bed Height HETP varies due to: T & p changes Concentration changes 1 0 2 0 3 0 C h e m S e p Stage 4 0 5 0 6 0 0 0.2 0.4 0.6 0.8 1 Liquid mole fraction C 6 H 1 2 C 7 H 1 6
HETP vs. Packed Bed Height HETP varies due to: T & p changes Concentration changes Consequent changes in densities Stage 1 0 2 0 3 0 4 0 L iq u id D e n s ity (k g /m 3 ) 6 2 0 6 4 0 6 6 0 6 8 0 7 0 0 7 2 0 C h e m S e p 5 0 6 0 3 3.1 3.2 3.3 3.4 Va p o u r D e n s ity (kg /m 3 )
HETP vs. Packed Bed Height HETP varies due to: T & p changes Concentration changes Consequent changes in densities, viscosities Stage 1 0 2 0 3 0 4 0 L iq u id Visc o s ity (N /m 2.s ) 0 5 e -0 0 5 0.0 0 0 1 0.0 0 0 1 5 C h e m S e p 5 0 6 0 7.6 e -0 0 6 7.8 e -0 0 6 8 e -0 0 6 8.2 e -0 0 6 8.4 e -0 0 6 Va p o u r Vis co s ity (N /m 2.s )
HETP vs. Packed Bed Height HETP varies due to: T & p changes Concentration changes Consequent changes in densities, viscosities, surface tension Stage 1 0 2 0 3 0 4 0 5 0 C h e m S e p 6 0 0.0 1 3 0.0 1 4 0.0 1 5 0.0 1 6 0.0 1 7 0.0 1 8 S u rfa c e te n s io n (N /m )
HETP vs. Packed Bed Height HETP varies due to: T & p changes Concentration changes Consequent changes in densities, viscosities, surface tension, and diffusivities Stage 10 20 30 40 50 60 0 2 4 6 8 10 12 14 Liquid D iffusivity (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 Stage 1 0 2 0 3 0 4 0 5 0 6 0 p=1.03bar p=0.33bar 1.6 1.6 5 1.7 1.7 5 1.8 1.8 5 1.9 1.9 5 2 a lp h a
HETP vs. Packed Bed Height HETP varies due to: T & p changes 1 0 1.03bar C h e m S e p Concentration changes 2 0 0.33bar Consequent changes in densities, viscosities, surface tension, and diffusivities Stage 3 0 4 0 5 0 4.13bar And changes in relative volatility 6 0 0.2 5 0.3 0.3 5 H E T P
HETP vs. Packed Bed Height HETP varies due to: T & p changes 1 0 1.03bar C h e m S e p Concentration changes 2 0 0.33bar Consequent changes in densities, viscosities, surface tension, and diffusivities And changes in relative volatility We must average HETP over the bed height! Stage 3 0 4 0 5 0 6 0 0.2 5 0.3 0.3 5 H E T P 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 bed Problem: 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 0.3 B X o /p -Xyle n e 1 6 T o rr @ F R I (1.2 2 m ID ) 0.2 5 0.2 Average HETP (m) 0.1 5 0.1 0.0 5 0 0 1 2 3 4 F -fa cto r B R F 8 5 e xp.
Model Fitness B X o/p -Xylene 16 T orr @ F R I (1.22m ID ) 0.3 0.25 Average HETP (m) 0.2 0.15 0.1 0.05 0 average error = 35mm 0 1 2 3 4 F -fa cto r B Z 95 exp. E rrors
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 B X o/p -Xylene 16 T orr @ F R I (1.22m ID ) 0.3 0.25 Average HETP (m) 0.2 0.15 0.1 0.05 0 0 1 2 3 4 F -fa cto r B Z 95 exp. Z T M 83 B R F 96 B R F 85
Sulzer-BX B X o /p-xyle ne 730 T orr @ F R I (1.22m ID ) 0.3 0.25 Average HETP (m) 0.2 0.15 0.1 0.05 0 0 1 2 3 F -fa cto r B R F 85 exp. B Z 9 5
Sulzer Mellapak 250Y 0.6 M 250Y C B /E B 100mb ar @ S u lze r (1 ID ) 0.5 Average HETP (m) 0.4 0.3 0.2 0.1 0 0 0.0 2 0.04 0.06 0.08 0.1 0.12 C -factor B R F 92 E xp. S ulzer
Montz B1-250M B 1-2 5 0 M c C 6 /n C 7 1.0 3 b a r 0.6 0.5 Average HETP (m) 0.4 0.3 0.2 0.1 0 0 0.5 1 1.5 2 2.5 3 3.5 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
Billet-Schultes MTC: Effect C V 0.6 B 1-250M cc 6/nC 7 1.0 3bar 0.5 Average HETP (m) 0.4 0.3 0.2 0.2 0.3 0.4 0.1 0 0 0.5 1 1.5 2 2.5 3 3.5 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
Billet-Schultes MTC: Effect C L 0.6 B 1-2 5 0 M cc 6 /n C 7 1.0 3 b a r 0.5 Average HETP (m) 0.4 0.3 0.2 0.3 0.5 10 0.9 0.1 0 0 0.5 1 1.5 2 2.5 3 3.5 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
Koch-Glitsch Flexipac 2 0.6 F lexip ac 2 cc 6 /nc 7 0.3 3bar 0.5 Average HETP (m) 0.4 0.3 0.2 0.1 0 0 0.5 1 1.5 2 2.5 3 3.5 F -facto r R 95 E xp. H E T P
Raschig SuperPak 300 0.6 S u perp ak 3 00 cc 6/n C 7 1.65bar 0.5 Average HETP (m) 0.4 0.3 0.2 0.1 0 0 0.5 1 1.5 2 2.5 3 3.5 F -facto r B R F 92 E xp. H E T P Lack of geometry data (other than Ap): Estimated d eq 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?