STUDY OF LIQUIDDISTRIBUTION IN A

TRICKLE BED REACTOR

Manuel Martınez

Supervisors:

Dr. Jordi PallaresDr. Francesc Xavier Grau

June 2007Master in Chemical and Process Engineering

Contents

1 Introduction and background 1

2 Formulation of the problem to investigate 32.1 Model validation . . . . . . . . . . . . . . . . . . . . . . . . . 32.2 Numerical simulation of the trickle-bed reactor . . . . . . . . . 4

3 Objectives 6

4 Methodology 74.1 Mathematical model . . . . . . . . . . . . . . . . . . . . . . . 7

4.1.1 Porous media model . . . . . . . . . . . . . . . . . . . 84.1.2 Granular phase model . . . . . . . . . . . . . . . . . . 84.1.3 Model validation . . . . . . . . . . . . . . . . . . . . . 94.1.4 Numerical simulation of the trickle bed reactor . . . . . 9

4.2 Numerical model . . . . . . . . . . . . . . . . . . . . . . . . . 12

5 Results and discussion 135.1 Model validation . . . . . . . . . . . . . . . . . . . . . . . . . 13

5.1.1 Porous media model . . . . . . . . . . . . . . . . . . . 135.1.2 Granular phase model . . . . . . . . . . . . . . . . . . 15

5.2 Numerical simulation of the trickle bed reactor . . . . . . . . . 165.2.1 Central region . . . . . . . . . . . . . . . . . . . . . . . 165.2.2 Near-wall region . . . . . . . . . . . . . . . . . . . . . . 19

6 Conclusions 21

7 Future work 22

List of Figures

2.1 Sketch of the reactor . . . . . . . . . . . . . . . . . . . . . . . 5

4.1 Liquid volume fraction contours at the inlet of the first bed . . 104.2 Isosurface of liquid volume fraction of 0.3 . . . . . . . . . . . . 104.3 Computational domain for the central region simulation . . . . 114.4 Computational domain for the near-wall region simulation . . 12

5.1 Contours of liquid volume fraction of 0.12 in a r-z plane of thecylindrical bed. Porous media model validation . . . . . . . . 14

5.2 Contours of liquid volume fraction of 0.12 in a r-z plane of thecylindrical bed. Effect of capillary term . . . . . . . . . . . . . 15

5.3 Contours of liquid volume fraction of 0.12 in a r-z plane of thecylindrical bed. Granular phase model validation . . . . . . . 16

5.4 Liquid distribution in the zone surrounding one chimney inthe central region of the reactor. Isosurface of volume fractionof 0.10 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

5.5 Contours of liquid volume fraction on horizontal slices of thefour different beds. The position of the slices is indicated inFigure 5.4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

5.6 Liquid distribution in the zone surrounding one chimney in thenear-wall region of the reactor. Isosurface of volume fractionof 0.10 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

5.7 Contours of liquid volume fraction on horizontal slices of thefour different beds. The position of the slices is indicated inFigure 5.6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

List of Tables

2.1 Bed porosities and lengths . . . . . . . . . . . . . . . . . . . . 42.2 Physical properties . . . . . . . . . . . . . . . . . . . . . . . . 4

7.1 Stages in the development of the code . . . . . . . . . . . . . . 22

Nomenclature

A, coefficient for fluid-particle interaction, m−2

B, coefficient for fluid-particle interaction, m−1

C2, inertial resistance coefficient, m−1

de, equivalent diameter, mdmin, minimum equivalent diameter of the area between three spheres in con-

tact, m, where dmin =√√

3π− 0.5 dp

dp, particle diameter, mf, wetting efficiency, dimensionlessF, force per unit volume, N m−3

FD, drag force per unit volume, N m−3

F ρg

ρl, pressure factor, dimensionless

g, gravity acceleration, m s−2

p, capillary pressure, PaSm, source term, kg s−1 m−3

u, interstitial velocity, m s−1

U, superficial velocity, m s−1

v, velocity, m/st, time, sX, exchange coefficient, kg m−3 s−1

Greek letters

α, permeability, m2

ε, porosity, dimensionlessµ, viscosity, Pa sθ, volume fraction, dimensionlessρ, density, kg m−3

σs, surface tension, N m−1

τ , stress, N m−2

Subscripts

l, liquid phaseg, gas phases, solid phasek, fluid

Acknowledgements

I would like to thank

My supervisors, Dr. Pallares and Dr. Grau, for their help and support.Everyone at ECoMMFiT.Repsol-YPF for the financial support.

Abstract

Numerical simulations of isothermal non-reactive two-phase flow distri-bution in the packed beds of a reactor used for fuel hydrodesulfuration arereported. The reactor considered has, above the beds, a distribution trayequipped with chimneys. The boundary conditions at the inlet of the reactorbeds were obtained from simulations of the flow at the exit of a chimney[Martınez et al. [1]]. An Eulerian three-phase model that considers the parti-cles of catalyst as a granular static phase has been used following the Holubsingle slit model for particle fluid interaction to compute the liquid-solid andgas-solid drag coefficients. A numerical simulation of the dispersion of water-air flow in a column of glass beads using this model was initially carried outand results were found to be in reasonable agreement with numerical andexperimental data available in the literature. The simulations consider theflow dispersion in the central region of the reactor beds as well as in theregion close to the cylindrical lateral wall of the reactor. In both cases thedistributions of the liquid concentration do not change significatively as thedepth of the bed is increased except at the top part of the first bed, in thethird bed and at the interface of two beds with different porosity. The liquidin the near-wall region tends to attach the wall of the reactor as the depthof the bed is increased.

Chapter 1

Introduction and background

In the trickle bed reactors used in the petrochemical industry for fuel hy-drodesulfuration processes the gas and the liquid flow co-currently downwardthrough a packed bed of catalytic solid particles. The uniformity of the two-phase flow in the bed is an important parameter for the correct operationof the catalyst. For example, a poor distribution of the liquid-gas mixturereduces the effective volume of the reactor in which the hydrodesulfurationtakes place and this can produce hot spots that may decrease the life of thecatalyst.The interest to obtain a uniform well mixed two-phase flow in catalytic bedshas motivated most of the studies carried out to determine the liquid spread-ing in packed beds. Cihla and Schmidt [2] proposed a series of analyticalsolutions to an advection-diffusion equation to predict the liquid spreadingin a column, for different types of inlet distributors. The mathematical modelassumes a radial diffusion term with an adjustable diffusion coefficient andan advection term along the axial direction. Baker et al. [3] carried out ex-perimental studies in columns of different sizes and filled with particles ofdifferent shapes and sizes to evaluate the radial liquid spreading. These au-thors found that initial uniform distribution is essential, since the flow froma single stream needs a length equivalent to four or five column diametersto become uniform. Jiang et al. [4, 5] simulated the macroscale multiphaseflow in packed beds and compared the results with available experimentaldata. The CFDLIB package, based in the Eulerian k-fluid model, was usedin their simulations. The Holub (Holub et al. [6]) model for particle-fluidinteractions and the Attou (Attou and Ferschneider [7]) model for gas-liquidinteraction were implemented in the model. The comparison showed that thek-fluid model predicted reasonably well the pressure gradient and the globalliquid saturation in the trickle flow regime for liquid upflow in a cylindricalpacked bed. Boyer et al. [8] studied liquid spreading from a point source in a

1

column through gamma-ray tomography and CFD simulation. CFDLIB wasalso used in their simulations. The comparison showed that the predictionof the radial liquid spreading was strongly affected by the capillary pressureterm. Several models for this term were tested and a modification of thiscapillary pressure term was proposed to fit experimental data better.

2

Chapter 2

Formulation of the problem toinvestigate

The prediction of the liquid and gas distributions in a porous bed of a cat-alytic reactor by means of numerical simulations is the main objective ofthis study. In order to achieve this, it is convenient to validate the differentmodels available in the commercial CFD code Fluent,which has been usedin this study, before carrying out the simulation of the flow in the reactor.Thus, two problems have been investigated: the model validation using dataavailable in the literature and the numerical simulation of the isothermalnon-reactive two-phase flow dispersion in the beds of the reactor.

2.1 Model validation

Boyer et al. [8] studied numerically and experimentally the two phase flow dis-persion in a vertical cylindrical column of spherical glass particles of 1.99 mmof diameter. The column had an inner diameter of 0.4 m and a bed heightof 1.80 m. Although the axial porosity distribution is reported, an averageporosity of 0.365 has been considered for the present simulation. The fluidsused were water and air at ambient temperature. The liquid was introducedthrough a tube of 8 mm of inner diameter located in the center of the top ofthe bed while the air was injected all around the liquid tube over the wholecross-section of the bed. The liquid and gas flow rates were 0.128 m3/h and45 m3/h, respectively.

3

2.2 Numerical simulation of the trickle-bed

reactor

The reactor considered has a distribution tray with chimneys above the cat-alyst bed to produce a uniform two-phase flow distribution at the inlet ofthe bed. The bed is divided in four sections with different particle sizes andporosity. A sketch of the reactor is shown in Figure 2.1. The beds porositiesand lengths are shown in Table 2.1. The liquid has an initial distributionbefore entering the beds, due to the effect of the distribution tray. The rele-vant physical properties of the liquid and the gas, which are assumed to beconstant, are shown in Table 2.2. It is desired to know the liquid distributionalong the reactor. Once the most adequate model has been chosen in the firstpart of the study (model validation), numerical simulations of the reactor areperformed. As a first step, this model has been used to simulate the isother-mal three-dimensional two-phase flow dispersion in the reactor bed withoutconsidering the chemical reactions and the heat transfer processes that occurin a real reactor. The implementation of the chemical reactions and the heattransfer is left for future studies.

Table 2.1: Bed porosities and lengthsBed Porosity Bed length (mm)1 0.33 1502 0.53 1503 0.45 1504 0.40 15560

Table 2.2: Physical propertiesDensity (kg m−3) Viscosity (kg m−1 s−1)

Liquid 611 1.7 10−4

Gas 20.8 2.52 10−2

Two different cases have been studied: the first one considers the flowdispersion in the bed underneath a group of chimneys installed in a centralregion of the reactor, far from the cylindrical lateral wall of the reactor. Thesecond case considers the dispersion near the walls of the reactor.

4

Figure 2.1: Sketch of the reactor

5

Chapter 3

Objectives

The specific objectives are:

1. To validate the different models available in the commercial CFD codeFluent to predict the two-phase flow dispersion in porous media.

2. To obtain the liquid distribution along the reactor simulating the packedbeds with the most adequate model according to Objective 1.

6

Chapter 4

Methodology

The procedure to carry out the simulations has been the following:

1. Grid generation using the commercial software Gambit.

2. Numerical simulation using the commercial software Fluent.

(a) Choice of discretization schemes for the equations to be solved.

(b) Set the boundary conditions.

3. In the case of Objective 1, comparison with experimental data availablein the literature.

4.1 Mathematical model

Two models for the simulation of two-phase flow in porous media havebeen tested to predict the experimental and numerical results of Boyer etal. [8]. The models considered are the porous media model and the granularphase model. Both models consider the continuity (Eq. 4.1) and momentum(Eq. 4.2) equations for each phase as starting point.

∂

∂t(θρ) +∇ (θρ~v) = Sm (4.1)

∂

∂t(θρ~v) +∇ (θρ~v~v) = −θ∇P +∇ (τ) + θρ~g + ~F (4.2)

7

4.1.1 Porous media model

In this model a two-phase flow (gas and liquid) is solved, and the solidparticles are modeled as a porous media. The mathematical treatment of thismedia is carried out through the addition of a pressure drop term (Eq. 4.3)based on the Ergun equation to the momentum equations. This term consistsof a viscous term, proportional to the viscosity (µ) of the fluid phase, and aninertial term, proportional to the square of the velocity (U).

∆P =µ

αUi + C2

ρ

2|Ui|Ui (4.3)

In Eq. 4.3 the viscous and inertial resistance coefficients, α and C2, canbe computed using Eqs. 4.4 and 4.5, respectively:

1

α→ α =

d2p

150

ε3

(1− ε)2 (4.4)

C2 =3.5

dp

(1− ε)

ε3(4.5)

4.1.2 Granular phase model

In this model particles are defined as a static granular phase with the cor-responding volume fraction. The phase interaction is modeled through dragcoefficients, and in this study, they have been modeled according to thesingle-slit model proposed by Holub et al. [6]. In this model the drag force,that has to be included in the corresponding momentum equations for eachphase, can be expressed as,

FDks = θkθsXks (uk − us) (4.6)

where the exchange or drag coefficient Xks is defined as

Xks =(AksµkUk + BksρkU

2k

) 1

(1− ε) |uk| (4.7)

and

Aks = 180(1− ε)2

θ3d2p

(4.8)

Bks = 1.8(1− ε)

θ3dp

(4.9)

8

The particular forms of the drag forces used for the simulation are givenin Eqs. 4.6-4.9 and have been included in the simulation code through user-defined functions.

4.1.3 Model validation

The two-dimensional axisymmetric computational domain was divided intorectangular finite volumes using a uniform grid distribution similar to thatused by Boyer et al. [8], with 1 cm spacing in axial direction and 0.4 cmin radial direction. As reported by Jiang et al. [9] and also according topreliminary simulations using the k-ε turbulence model, the Reynolds stressterm does not influence the behavior of the two phase flow in the bed for theflow conditions considered. Consequently, the simulations were carried outwithout any turbulence model.

4.1.4 Numerical simulation of the trickle bed reactor

Central region

The computational domain for this case consists in a prism of rhombic crosssection. The dimensions of this cross section, which is centered in the pro-jection of one chimney, were selected according to the symmetry elements ofthe distribution of chimneys in the tray. The velocity and volume fractiondistributions imposed on the inlet top surface of the computational domainwere taken from a previous simulation of the flow in a chimney reported inMartınez et al. [1] and shown in Figure 4.1. Figure 4.2 shows an isosurface ofvolume fraction 0.3 of the flow inside a chimney. The liquid, as can be seen,enters the chimney through the lateral holes, while the gas enters throughthe top opening.As can be seen in both figures, two main regions are formed.Figure 4.3 shows the computational domain for this case. The projectionof the chimney is indicated in Figure 4.3 on the top of the bed. The fourdifferent beds are also indicated in this figure. Periodic boundary conditionsare imposed on the lateral faces of the domain to model the effect of the sur-rounding chimneys. The height of the fourth bed has been considered to be450 mm, because preliminary simulations carried out predict fully developedflow conditions for bed depths larger than 70 mm. A hexahedral regular meshof 1346700 cells has been used in the numerical simulation corresponding tothis case.

9

Figure 4.1: Liquid volume fraction contours at the inlet of the first bed

Figure 4.2: Isosurface of liquid volume fraction of 0.3

Near-wall region

The computational domain for the near-wall region, shown in Figure 4.4,consists in a prism of rectangular cross section. The projections of the chim-

10

neys contained in the rectangle representing the top of the bed are indicatedin Figure 4.4. As shown in Figure 4.4, the top surface of the computationaldomain contains the circular projection of one chimney located near thewall and three halves of the projection of one chimney distributed along theperimeter of the top surface. Specific distributions of volume fraction andinlet velocity are imposed on the top of the bed as inlet conditions, accordingto numerical simulations of the flow at the exit of one chimney, reported inMartınez et al. [1] and previously shown in Figure 4.1. The no slip conditionis imposed at the wall and symmetry boundary conditions are imposed at thelateral faces of the domain, which are perpendicular to the y-direction. Atthe boundaries opposed to the wall, the distributions of velocity and volumefraction imposed were taken from a simulation of the flow in a central regionof the bed. A hexahedral regular mesh of 1228500 cells has been used in thissimulation.

Figure 4.3: Computational domain for the central region simulation

11

Figure 4.4: Computational domain for the near-wall region simulation

4.2 Numerical model

In all cases, pressure-velocity coupling has been solved through Phase-coupledSIMPLE algorithm ([10]), while momentum and volume fraction equationshave been discretized with a first order Upwind scheme ([10]).

12

Chapter 5

Results and discussion

The results have been divided in two parts according to the previously definedobjectives:

5.1 Model validation

5.1.1 Porous media model

Figure 5.1 shows the comparison of the experimental and numerical resultsof Boyer et al [8] and the present numerical results obtained with the porousmedia model. The lines plotted in this figure correspond to a value of liquidvolume fraction of 0.12. It should be noted that the liquid is introducedat the center (r<4 mm) of the top of the bed (z=1.8 m). As can be seenin Figure 5.1, the liquid spreading for the conditions considered is clearlyunderpredicted by the porous media model. A simulation carried out witha porosity of 0.339, corresponding to the minimum value of the distributionreported by Boyer et al. [8], shows no significant differences with that pre-sented in Figure 5.1 using a porosity value of 0.365.

As shown in Figure 5.1, the porous media model is not capable to repro-duce the data reported by Boyer et al. [8]. As suggested by Jiang et al. [4, 5]the inclusion of a capillary pressure term Eq. 5.1 in the momentum equationsincreases the flow dispersion.

−∇θl (pl − pg) (5.1)

Two cases with different capillary pressure correlations have been simu-lated, one with the correlation given by Attou and Ferschneider [7] (Eq. 5.2)and another with the correlation proposed by Grosser et al. [11] (Eq. 5.3).

13

Figure 5.1: Contours of liquid volume fraction of 0.12 in a r-z plane of thecylindrical bed. Porous media model validation

pl = pg − 2σs (1− f)

[θs

1− θg

] 13

[1

dp

+1

dmin

]F

(ρg

ρl

)(5.2)

pl = pg − (1− f) σs

√180θs

(1− θs) de

[0.48 + 0.036 ln

(1− θs − θl

θl

)](5.3)

In Eq. 5.2 the pressure factor, F, can be computed as:

F

(ρg

ρl

)= 1 + 88.1

ρg

ρl

(5.4)

and the wetting efficiency, f, is given in Eq. 5.5 according to [12]:

f = 1.021

(θl

1− θs

)0.224

(5.5)

14

It should be noted that the computation of capillary pressure term hasbeen added to the simulation code using a user-defined function. The effectof the addition of the capillary pressure term using Eq. 5.2 on the liquiddistribution is shown in Figure 5.2. The results obtained using Eq. 5.3 arenot significantly different in comparison with those shown in Figure 5.2 andconsequently have been omitted. As can be seen, the model with the cap-illary term predicts approximately the same liquid spreading in comparisonwith the default porous media model and it does not provide a noticeableimprovement of the radial spreading.

Figure 5.2: Contours of liquid volume fraction of 0.12 in a r-z plane of thecylindrical bed. Effect of capillary term

5.1.2 Granular phase model

Figure 5.3 shows contours of liquid volume fraction for the granular phasemodel and their comparison with the experimental and numerical simulationresults of Boyer et al. [8]. As it can be seen in Figure 5.3.d, the granular

15

phase model fits reasonably well the experimental data near the exit of thebed, although in the initial section of the domain, the model over predictsthe liquid spreading that reaches a developed condition flow for z<1.7 m.

Figure 5.3: Contours of liquid volume fraction of 0.12 in a r-z plane of thecylindrical bed. Granular phase model validation

5.2 Numerical simulation of the trickle bed

reactor

The granular phase model, with the fluid-particle interaction model of Holubet al. [6] implemented in the code through user defined functions, has beenchosen for the simulation of the trickle-bed reactor.

5.2.1 Central region

The liquid distribution in a central region of the trickle-bed reactor can beseen in Figure 5.4, in terms of an isosurface of the liquid volume fraction

16

corresponding to the value 0.10. The circular region on the top of the bedrepresents the projection of one chimney and the arrow indicates the inletdirection of gas into the chimney. It can be seen in Figure 5.4 that theliquid in the first bed spreads slightly to the outer part of the computationaldomain, while the gas occupies the center. In the second bed, the liquidconcentrates again while in the third bed it spreads continuously until theinterface with the fourth bed. In the fourth bed the distribution of theconcentration of liquid does not change significatively as the depth of thebed is increased. The change of the liquid distribution at the interface of thebeds agrees with the different porosity of the beds. For example, it can beseen in Figure 5.5 that the liquid is more dispersed in the first bed, with lowerporosity (ε=0.33, Fig. 5.5.a), while it is more concentrated in the second bed,in which the porosity is 0.53 (Fig. 5.5.b). The same reasoning can be appliedto Figures 5.5.c and 5.5.d. which show the liquid distribution on slices ofthe third (ε=0.45) and fourth (ε=0.40) beds. However, it should be notedthat the re-concentration of liquid in the second bed seems to lack physicalmeaning, since it was expected, at least, to maintain the same distributionthat the first bed. Due to that fact, another simulation is currently beingcarried out including the capillary term. In principle, this term was discardedsince in the model validation it seemed not to affect significatively the liquidspreading. However, since the model validation and the reactor simulationdeal with two different systems, for this particular case it could have someeffect. The results obtained at the moment seem to point in that direction.

17

Figure 5.4: Liquid distribution in the zone surrounding one chimney in thecentral region of the reactor. Isosurface of volume fraction of 0.10

Figure 5.5: Contours of liquid volume fraction on horizontal slices of the fourdifferent beds. The position of the slices is indicated in Figure 5.4

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5.2.2 Near-wall region

The liquid distribution in the near-wall region is shown in Figure 5.6, interms of an isosurface of liquid volume fraction (θl=0.10). The circular re-gions indicated on the top of the bed represent the projections of the abovechimneys, while the arrows indicate the inlet direction of gas into the chim-ney. As previously seen in the case of the flow underneath a chimney locatedin the central region of the reactor, the liquid spreads slightly in the first bedto the outer part of the computational domain, while the gas occupies thecenter, it concentrates again in the second bed and in the third bed it spreadscontinuously until the interface with the fourth bed. As in the central regioncase, there is no significantly liquid spreading in the fourth bed except forthe chimney projection that is closest to the wall. Figure 5.6 shows thatthe liquid tends to attach the wall of the reactor as the depth of the bed isincreased. This can be observed noting the inclination towards the wall ofthe surface depicted in Figure 5.6. As in Figure 5.4, corresponding to thedispersion of the flow underneath a central chimney, the liquid distributionin the bed does not change significatively except at the top of the first bed,in the third bed and at the interfaces of the different beds. The effect ofthe different porosity of the beds can be seen in Figure 5.7 that shows con-tours of liquid volume fraction in four horizontal slices of the beds indicatedin Figure 5.6. It can be seen in Figure 5.7 that the beds of lower porosityshow a more dispersed liquid than the beds of higher porosity. For example,the liquid is more dispersed in the first bed (Fig. 5.7.a, ε=0.33) than in thesecond bed (Fig. 5.7.b, ε=0.53). Figures 5.7.c and 5.7.d show liquid moredispersed due to the lower porosity of these beds, 0.45 and 0.40 respectively,in comparison with the second bed. As it has been previously exposed for thecentral region, the results obtained for the second bed are currently underinvestigation for the same reason that has been previously explained.

19

Figure 5.6: Liquid distribution in the zone surrounding one chimney in thenear-wall region of the reactor. Isosurface of volume fraction of 0.10

Figure 5.7: Contours of liquid volume fraction on horizontal slices of the fourdifferent beds. The position of the slices is indicated in Figure 5.6

20

Chapter 6

Conclusions

Numerical simulations of the isothermal two-phase flow dispersion in the bedof a hydrodesulfuration reactor have been reported. For the flow conditionsconsidered, the porous media model is not adequate to simulate the flowdispersion in a catalytic bed, even the inclusion in the model of the capillarypressure effect. A granular phase model has been used for the two simulationscarried out to predict the flow dispersion in the trickle bed. One simulationconsiders the flow underneath the central region of the reactor, far from thewalls, and the other considers the flow in the bed near the cylindrical lateralwall of the reactor. In both cases, most of the liquid spreading takes place inthe first and third beds. The distributions of the liquid concentration do notchange significatively as the depth of the bed is increased except in the thirdbed and at the interface of two beds with different porosity. The simulationsindicate that, for the flow conditions considered, a completely uniform liquiddistribution is not achieved. The values of local liquid volume fractions atthe bottom of the trickle-bed range between 0.05 and 0.45. However, theseresults are not definitive and they should be taken with caution, since thisstudy is being further carried out due to the apparent lack of meaning of theflow behaviour in the second bed of the reactor.

21

Chapter 7

Future work

The work that has been presented in this report will serve as the basis for thedevelopment of a Doctoral Thesis to be carried out in the next three years.The same reactor will be the object of study in the thesis, but instead ofusing a commercial CFD code, the Thesis will consist in the development ofa domestic three-dimensional code able to predict the flow, chemical speciesand temperature distributions in the reactor. Thus, not only continuityand momentum equations will need to be solved, but also chemical speciestransport and energy equations. The development of the code will take placein six different stages, as described in Table 7.1.

Table 7.1: Stages in the development of the codeStage Dimension Chemical reactions Heat transfer

1 2D No No2 2D Yes No3 2D Yes Yes4 3D No No5 3D Yes No6 3D Yes Yes

This code will be a useful tool for the performance and design optimiza-tion of this type of reactors. If the goal is achieved, it will be an importantcontribution to the field of computational studies of trickle bed reactors, sincethe results published at the moment in the literature do not combine phasesdistribution, chemical reactions and heat transfer.

22

Bibliography

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[2] Cihla, Z., Schmidt, O. A study of the flow of liquid when freely tricklingover the packing in a cylindrical tower. Collection Czechoslov. Chem.Commun. (1957) 22, pp. 896.

[3] Baker, T., Chilton, T.H., Vernon, H.C. The course of liquor flow inpacked towers. Presented at the Wilmington, Delaware, Meeting (1935).

[4] Jiang, Y., Khadilkar, M.R., Al-Dahhan, M.H., Dudukovic, M.P. CFDof multiphase flow in packed-bed reactors: I. k-fluid modeling issues.AIChE Journal (2002) 48, pp. 701.

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[6] Holub, R.A., Dudukovic, M.P., Ramachadran, P.A. A phenomenologicalmodel for pressure drop, liquid holdup, and flow regime transition in gas-liquid trickle flow. Chemical Engineering Science (1992) 47, pp. 2343.

[7] Attou, A., Ferschneider, G. A two-fluid hydrodynamic model for the tran-sition between trickle and pulse flow in a cocurrent gas-liquid packed bedreactor. Chemical Engineering Science (2000) 55, pp. 491.

[8] Boyer, C., Koudil, A., Chen, P., Dudukovic, M.P. Study of liquid spread-ing from a point source in a trickle bed via gamma-ray tomography andCFD simulation. Chemical Engineering Science (2005) 60, pp. 6279.

[9] Jiang, Y., Khadilkar, M.R., Al-Dahhan, M.H., Dudukovic, M.P. Sin-gle phase flow modeling in packed beds: discrete cell approach revisited.Chemical Engineering Science (2000) 55, pp. 1829.

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[10] Versteeg, H.K., Malalasekera, W. An introduction to computational fluiddynamics. The finite volume method. Pearson Education Limited, 1995.

[11] Grosser, K.A., Carbonell, R.G., Sundaresan, S. Onset of pulsing in two-phase cocurrent downflow through a packed bed. AIChE Journal (1988)34, pp. 1850.

[12] El-Hisnawi, A.A. Tracer and reaction studies in trickle-bed reactors.D.Sc. Thesis, Washington University, St. Louis, USA (1981).

[13] Fluent 6.1 Documentation, Fluent Inc., Lebanon, NH, USA

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