Experimental and Numerical. on Distillation Trays. Authors: Henry França Meier Dirceu Noriler

Transcription

1 Experimental and Numerical Analysis of Gas-Liquid Flow on Distillation Trays Authors: Henry França Meier Dirceu Noriler

2 Summary State of Art Objectives this wor Experimental Setup Numerical analysis Model Validation Conclusions

3 State of Art Oil Industries Hydrocarbon fractionating process Equilibrium and Nonequilibrium stage model Macroscopic Models (90 century) Now - CFD Models

4 State of Art (CFD Models) Bubble Columns: Boisson and Malin (1996) Euler-Euler Model (Non-Drag Forces) Delnoij et al. (1997) - Euler-Lagrange Model; Solichin and Eigenberger (1999) 2D and 3D Models; Pfleger and Becer (2001) Experimental versus CFD Model; Michele and Hempel (2002) - Three-Phase Model; Krishna, van Baten, Urseanu e Ellenberger (1999, 2001) Two Regime of Bubble Flow Three Phase Model;

5 State of Art (CFD Models) Distillation Columns Liu et al. (2000, 2004, 2005) 2D Monophase model; van Baten and Krishna (2000) 3D Two-Phase Model; Gesit et al. (2003) - 3D Two-Phase Model Commercial Scale; Soares et al. (2002) and Noriler (2004) Homogeneous Model versus Heterogeneous Model; Noriler (2008) Thermal Fluid Dynamics Model Noriler (2007) Mass, Energy and Momentum Coupled Model

6 State of Art (Experimental) Based on Bennett et al. (1983) e Cowell (1979) wors, the pressure drop in sieve tray is compound by 3 components: Liquid Height: Dry tray: Superficial tension:

7 Our contributions By CFDOIL 1st CFD Worshop to thr Oil Industry: 2D Monophase model and 3D Homogeneous Two-Phase Model CFD OIL 2005: 3D Homogeneous Two-Phase Model with energy balance CFD OIL 2006: 3D Homogeneous Two-Phase Model with mass and energy balance Now CFD OIL 2006: Experimental analysis

8 Objective The mains objectives of this wor are: To develop a experimental wor to provide data for validation the models; To execute a numerical analysis and to compare the results with experimental results; To predict the efficiency of the distillation sieve tray.

9 Experimental Setup

10 66 holes with 6 mm in diameter. The perforated area is 2.26% based on bubble area. Hi=0.040 m H=0.750 m W=0.234 m D=0.350 m hw= m Lp=0.260 m

11 Image of apparatus

12 Data acquisition scheme

13 Image of Image of sensors

14 Signal integration

15 Software acquisition

16 Experimental movie

17 Statistics treatments V S =0.193 m/s; Q L /W=2.4 x 10-3 m 3 s -1 m -1

18 a and cv Constants Dry tray contribution

19 Pressure Drop Components. Q L /W=2.4 x 10-3 m 3 s -1 m -1

20 Clear Liquid Height and Center Point Clear Liquid Height Liquid Rate Dependence. V s =0.348 m/s Superficial Gás Velocity Dependence. Q L /W=2.4 x 10-3 m 3 s -1 m -1

21 Comparison with Bennett et al. (1983) correlation

22 Numerical Analysis The model consider the Inter-phase transfer term for momentum equation ( this is used approach that was developed by rishna et al.(2000)): ( ) β β β β ρ = v v v v M D D C d f 4 3 With and Bennett et al. (1983) correlation for average volume fraction of liquid 2 p D 1 gd 3 4 C β β ρ ρ ρ = v v average S f V β β = v v B S A Q V β = ρ ρ ρ = β β β 0.91 S average V exp 1 f

23 Numerical Methods Grid Top viewer Grid Side viewer

24 Clear liquid height as a function of superficial velocity Q L /W=2.4 x 10-3 m 3 s -1 m -1

25 Qualitative model Validation

26 Qualitative Validation Q L /W 2.14 x 10-3 m 3 s -1 m -1

27 Quantitative Validation Clear Liquid Height. Q L /W=2,14 x 10-3 m 3 s -1 m -1

28 Quantitative Validation Numerical and Experimental Data Relation. Q L /W=2,14 x 10-3 m 3 s -1 m -1

29 Efficiency Prediction

30 Mathematical Modeling Continuity equation: t ( f ρ ) + ( f ρ v ) 0 = Momentum equation: t With, ( ) ( ) [ ( )] ' eff T f ρ v + f ρ v v = f p + f µ v + v µ eff t =µ + µ + f ρ g+ F j

31 Mathematical Modeling Energy equation: t λ eff Mass equation: t D eff ( fρh ) + ( fρvh ) = ( fλ T) Qj =λ µ + Pr t t e eff ( f ρ y ) + ( f v y ) + ( f ρ D ( y )) eff A = D A A µ + Pr eff t m A A A Y Aj

32 Mathematical Modeling Where, F j inter - phase transfer term of momentum equation, and Q Y j Aj inter - phase transfer term of energy equation inter - phase transfer term of mass equation.

33 Turbulence- standard -ε: Constitutive Equation ( ) ( ) ε ρ = σ µ + µ ρ + ρ P f f f t t v Where, and ( ) ( ) ε ε ρ ε = ε σ µ + µ ε ρ + ε ρ 2 1 t C C P f f f t v µ ε = µ t t C ( ) ( ) T t P + µ = v v v

34 Inter-phase transfer term for momentum equation: With ( ) j j D j D j C d f 4 3 v v v v F ρ = Constitutive Equation and Bennett et al. (1983) correlation for average volume fraction of liquid 2 j p j D 1 gd 3 4 C v v ρ ρ ρ = average j S j f V = v v B j S A Q V = ρ ρ ρ = 0,91 j j S average j V exp 1 f

35 Constitutive Equation Inter-phase transfer term for energy equation Q j = h j A j ( T T ) j with A = j 6f d P Modelo γ-φ UNIQUAC -γ IDEAL -φ Inter-phase transfer term for energy equation Antoine - P Sat and Y Aj A j ( ) c e c = jajρ yaj ya with j = µ 43 = A 0,3 h B ( V ρ ) S j 20 H σ L ρ j ρ H F 5 (Zuiderweg (1982))

36 Simulation Results Momentum Balances Distribution of average liquid holdup in x-y plane along height of dispersion. Source: Zuiderweg, Height Along Dispersion (m) Source: Bennett et al., Liquid Holdup

37 Simulation Results Energy Balances b) Temperature 82,11 ºC 82.3 liquid temperature (ºC) b) Temperature 82,32 ºC Liquid Inlet Distance (m) Weir

38 0.766 Liquid Phase Chemical Species Balances Ethanol Mass Fraction Ethanol Mass Fraction Average Ethanol Mass Fraction in the Liquid Phase = Quasi-Steady State Ethanol Mass Fraction Average Ethanol Mass Fraction = Time (s) Vapour Phase Average Ethanol Mass Fraction = Time (s) Time (s)

39 Snapshots of the properties

40 Tray Efficiency Tray Efficiency = % Murphree Efficiency (%) Murphree (1925) Effi = y y out eq West et al. (1952) y y in in Point Efficiency based on Murphree Efficiency Point

41 Conclusions A experimental setup was built to provide data to validate the CFD models; the proposed model was validated qualitatively and quantitatively; It is possible to predict the Tray Efficiency by CFD Techniques. The Tray efficiency for ethanol/water mixture is about 64 % for distillation tray studied; The CFD tools presented and discussed in this wor mae possible to now better the turbulent gas-liquid flow on a sieve plate of distillation columns and they can be used to optimize design and operating condition of such processes.