Gas Flow in a Multiliquid-Inlet Rotating Packed Bed: Three

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Gas flow in a multiliquid-inlet rotating packed bed: 3D numerical simulation and internal optimization Wei Wu, Yong Luo, Guang-Wen Chu, Yi Liu, Haikui Zou, and Jian-Feng Chen Ind. Eng. Chem. Res., Just Accepted Manuscript • DOI: 10.1021/acs.iecr.7b04901 • Publication Date (Web): 15 Jan 2018 Downloaded from http://pubs.acs.org on January 15, 2018

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Industrial & Engineering Chemistry Research

Gas Flow in a Multiliquid-Inlet Rotating Packed Bed: 3D Numerical Simulation and Internal Optimization

Wei Wu a,b, Yong Luo a,b, Guang-Wen Chu a,b*, Yi Liu a,b, Hai-Kui Zou a,b, Jian-Feng Chen a,b

a

State Key Laboratory of Organic-Inorganic Composites and bResearch Center of the

Ministry of Education for High Gravity Engineering and Technology, Beijing University of Chemical Technology, Beijing 100029, PR China

* Corresponding author. Tel: +86 10 64446466; Fax: +86 10 64434784. E-mail address: [email protected].

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ABSTRACT A novel multiliquid-inlet rotating packed bed (MLI-RPB) has been demonstrated to be a higher gas-liquid mass transfer reactor in our previous studies (Ind. Eng. Chem. Res. 2014, 53, 18580-18584), compared to the conventional RPB. Comprehensive understanding the fluid flow inside the MLI-RPB is significant for the internal optimization. In this work, the gas flow in a MLI-RPB was investigated by the three-dimensional computational fluid dynamics simulation. The simulated gas pressure drop was validated by the experimental data, within a deviation of ±15%. Simulation results reveal that the MLI-RPB has special features in the hollow annular zones among packing rings. Five types of internal combinations were designed to improve the turbulence of the gas flow in the hollow annular zones. The tangential slip velocity, turbulence kinetic energy, ratio of turbulence kinetic energy and overall gas pressure drop of the MLI-RPB with these internal combinations were 1~2, 1~4, and 1~4 times the original MLI-RPB, respectively. Keywords: Multiliquid-inlet rotating packed bed, computational fluid dynamics, three-dimensional simulation, internals, optimization

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1. Introduction As a high-efficient and energy-saving chemical reactor, the rotating packed bed (RPB) has been widely exploited in chemical industry, such as absorption and desorption,1-3 nanoparticle syntheses,4-6 sulfnation,7 Fischer-Tropsch synthesis, 8 etc. The mass transfer coefficient of a RPB can be up to 1-3 orders of magnitude larger than that of a conventional packed column, exhibiting prominent process intensification characteristics.9 In recent years, more and more researchers have focused on the novel design and optimization of RPBs’ structures for the purpose of further mass transfer enhancement.10-12 Our group has developed a novel Multiliquid-inlet rotating packed bed (MLI-RPB) that has multiple end effect zones and less packing. 13 As shown in Figure 1(a), the MLI-RPB has three rotational circular rings packed with stainless steel wire mesh packing, two hollow annular zones among packing rings, and multiple static liquid distributors. Compared with the traditional RPB shown in Figure 1(b), the MLI-RPB has a higher mass transfer efficiency and smaller gas pressure drop, so that the energy consumption is lower. 14 So far, the characteristics of fluid dynamics in the MLI-RPB with this novel structure have not been analyzed, which is essential for the structure optimization. As an efficient and economical tool, computational fluid dynamics (CFD) simulation can easily visualize and analyze the detailed fluid flow information,

15, 16

and furthermore design and optimize the inner structure of various chemical devices.17 The CFD simulation can be preferable to explain the fluid flow behavior inside the

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RPBs, even though the RPB is a rotating device with complex inner structure. 18 According to the types of physical models, there are two-dimensional (2D) and three-dimensional (3D) simulations for RPBs. Compared with 2D simulation model, the 3D simulation model can display more detailed fluid flow inside the RPB but also increases the difficulty of simulation as well. There are a few reports about the 3D CFD simulation of fluid flow in RPBs. Llerena-Cavez et al.19 have simulated the gas flow patterns in the RPB based on a 3D model and the simulation results were validated by the literature’s experimental data. Sun et al.

20

developed a 3D model to

predict the gas flow behavior in a rotating zigzag bed (RZB) and found that the effect of the thickness of the rotating bed on the flow-filed distribution can be ignored. Yang et al.21 suggested an optimum structure in the outer cavity zone of the RPB to improve the gas distribution at the gas inlet. Larsson et al. 22 studied a rotating bed reactor of the liquid flow patterns by the CFD simulations. Guo et al.

23

used a simplified 3D

RPB model with wire mesh packing for the gas and liquid flow simulations. Liu et al.24 proposed some structures to weaken vortex flow in the inner cavity zone of the RPB. Up to now, about the optimization of rotational zone which is the most important part of a RPB, there are few investigations based on the 3D CFD simulation. In this work, the 3D CFD simulation of gas flow in the MLI-RPB was studied. Based on the simulation data of gas flow behavior in various zones, we designed some internals inserted into the hollow annular zones among packing rings to optimize the gas flow in the rotational zone of the MLI-RPB. The comparison of the tangential slip

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velocity, turbulence kinetic energy, and ratio of turbulence kinetic energy and overall gas pressure drop of the MLI-RPB with different internal combinations was then conducted.

2. CFD simulation 2.1 Physical model The detailed parameters of the MLI-RPB are listed in Table 1. The 2D physical model and 3D physical model of the MLI-RPB are respectively displayed in Figure 2(a) and 2(b). The schematic gas flow path is shown in Figure 2(b). Gas is tangentially introduced into the outer cavity zone at the gas inlet and then flows through the outer packing ring. Later on, gas flows through the middle packing ring after passing the outer hollow annular zone. Similarly, gas flows through the inner hollow annular zone and the inner packing ring in sequence. Finally, gas flows into the inner cavity zone and vents out through the gas outlet. The 2D physical model can be regarded as a cutting plane (z = 30 mm) of the 3D physical model. On the one hand, it is evident that the 3D physical model is better congruent with the real structure of the MLI-RPB and able to reveal the gas flow vividly. On the other hand, the numerical simulation based on 3D physical model was calculated at the expense of abundant computing resource. The 2D and 3D models were both meshed into mixture grids of hexahedron and tetrahedron. Local grid refinement was implemented near walls and packing supports. In order to obtain the detailed fluid information, local grids were also refined in the hollow annular zones. The MLI-RPB is a pilot scale

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device and several grids with different number of cells were tested in order to find grid-independent. Finally, the numbers of cells of the 2D and 3D model are 102, 473 and 30, 623, 090, respectively. 2.2 Mathematical model 2.2.1 Continuity equations and momentum equations In this study, all processes were assumed to be nonreactive and isothermal. Only continuity equations and momentum equations were utilized. The fluid zone model of MLI-RPB can be divided into two parts: stationary zone and rotational zone. In the stationary zone, the medium air as the single phase was regarded as incompressible phase and the continuity equation could be expressed as follows:

∂ ρ ∂ ( ρ vi ) + =0 ∂t ∂ xi

(1)

where i = 1, 2 for 2D simulation, and i = 1, 2, 3 for 3D simulation. The equation of momentum conservation in non-accelerating reference frame was described by

∂ ( ρvi ) ∂ ( ρvi v j ) ∂ 2 vi ∂p + =− +µ + ρSi ∂xi ∂x j ∂xi ∂xi ∂x j

(2)

where i, j = 1, 2 for 2D simulation, and i, j = 1, 2, 3 for 3D simulation. Si is the source term which contains the gravitational and external body force. In the rotational zone, the multiple reference frame (MRF) model is employed and the fluid velocities were transformed from stationary frame to moving frame by using the following relation:

r r r vr = v − u r

(3)

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and

r r r r u r = vt + ω × r

(4)

r In these two equations above, v r is the relative velocity (the velocity viewed

r from a moving frame), v is the absolute velocity (the velocity viewed from the r stationary frame), ur is the velocity of moving frame relative to the inertial reference r r frame, vt is the translational frame velocity, and ω is the angular velocity. When r the fluid velocity is solved in a moving reference frame, the dependent variable v is

r replaced by v r in all governing equations. 2.2.2 Porous media model In the packing zone, packing was simulated as porous media model by adding another source term (Sp) into the momentum conservation equation in moving reference.25 Sp contains two parts: a viscous loss term (Kperm) and an inertial loss term (Kloss).

r r  µ r 1 Sp = − v + K loss ρ v v  K  2  perm 

(5)

r where v is the velocity of fluid in rotational packing zone, Kperm is the permeability, and Kloss is the loss coefficient. The momentum sinking in the packing zone contributes to a pressure gradient in the porous zone, creating a pressure drop that is proportional to the fluid velocity. The porous media parameters (Kperm and Kloss) could be calculated with Ergun equation: 26

K perm =

ε P3 150 (1 − ε P )2 Dp2

(6)

and

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Kloss =

3.5 (1 − ε P ) DP ε P 3

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(7)

where Dp is an equivalent diameter of packing and εp is the porosity of packing. Dp could be obtained by the following equation: 27

DP =

6 (1-ε P ) SV ⋅ψ

(8)

where SV is the surface area of packing, and ψ is the sphericity. 2.2.3 Turbulence model This study employed the k-ε model to close the above governing equations. In the equation of momentum conservation, µt which is turbulent (or eddy) viscosity, can be computed by combining turbulence kinetic energy (k) and rate of energy dissipation (ε) as follows:

µt = Cµ ρ

k2

ε

(9)

The k-ε model allows for the determination of turbulence and time by solving two separate transport equations, as a viscous model. The turbulence kinetic energy and its rate of dissipation were obtained from the following transport equations:

∂v ∂ (ρk ) ∂ (ρk ) µ t  ∂k ∂v ∂v  ∂  + vi = + µt ( j + i ) i  − ρε  µ +  ∂t ∂xi ∂xi   ∂xi ∂x j ∂x j  σ k  ∂xi

(10)

and

∂ ∂ ∂ ( ρε) + ( ρvi ε) = ∂t ∂xi ∂xi

 µt  ∂ε  ε2 ε ∂v j ∂vi ∂vi + ) - C2ε ρ  µ +   +C1ε µt ( k ∂xi ∂x j ∂x j k σ ε  ∂xi  

(11)

where i, j = 1, 2 for 2D simulation, and i, j = 1, 2, 3 for 3D simulation. The values of constants, such as Cµ C1ε, C2ε, σk and σε, all depend on the type of k-ε model.28 Previous work showed that the realizable k-ε model was better than the standard k-ε 8


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model for the gas flow simulation in a RPB.29 Thus, the realizable k-ε model was employed in this work. 2.3 Boundary conditions and solution procedure The gas inlet and gas outlet of the MLI-RPB were set as the velocity inlet boundary condition and pressure outlet boundary condition, respectively. The operation conditions for the simulation were set as follows: gas flow rate in the range of 10-50 m3/h and rotational speed of RPB in the range of 600-1400 r/min. The enhanced wall function was used to model the near-wall region. The surfaces of the rotational zone were defined as moving walls relative to the adjacent cell zone, while the rest were all set as stable walls. All simulations were carried out under steady state conditions. The pressure-velocity coupling was obtained by the SIMPLE algorithm, and a standard scheme was employed for pressure discretization. Meanwhile, second-order upwind was used for momentum equations and first-order upwind was used for other equations. The convergence criterion of the simulation was assumed when the values of all governing equations residuals were less than 10-3. Calculations were run on a HP Z840 workstation equipped with 2 CPUs with 36 cores, which has 2×Intel(R) Xeon(R) E5 [email protected] and 512GB random access memory.

3. Experimental In order to validate the results of CFD simulations, experimental values of gas pressure drop were measured in the MLI-RPB. According to the single factor method,

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effects of rotational speed and gas flow rate on the gas pressure drop were examined. Figure 3 shows a schematic diagram of the experimental setup. The gas was introduced into the MLI-RPB through the gas inlet by a blower, flowed inward into the rotational zone, and exited the MLI-RPB at the gas outlet. At the same time, the liquid inlet and outlet were both closed. The rotational speed and gas flow rate were controlled by frequency converters. The gas flow rate is ranging from 10 to 50 m3/h, and the rotational speed is ranging from 600 to 1400 r/min. There are two gas pressure measurement points (A and B) at the gas inlet and the gas outlet, respectively. The overall gas pressure drop (∆P) is defined as: ∆P = P1 – P2

(12)

The pressure data were obtained by a digital pressure sensor XYFS-01 (Beijing Xieya Electronic Co., LTD).

4. Results and discussion 4.1 Validation of simulation Figures 4(a) and 5(b) show the effects of rotational speed and gas flow rate on the overall gas pressure drop in the MLI-RPB, respectively. The two lines show simulated gas pressure drop and the scatter points indicate experimental gas pressure drop. Both figures reveal that the overall gas pressure drop in the MLI-RPB rises with an increasing rotational speed and gas flow rate. A higher gas flow rate leads to a larger flow flux in per unit volume in the rotational zone, thereby causing a stronger frictional force and consequently leading to the increase of the frictional pressure

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drop.30 Also, a higher rotational speed causes a stronger centrifugal force and subsequently an increase of gas pressure drop.31 The pressure values of 3D and 2D simulations are mostly higher than the experimental values. The possible reason is that the porous media model is just an equivalent model, which is limited by porous medium’s parameters and ignores the real packing structure. Besides, simulated values based on the 3D model are closer to the experimental values than that on the 2D model. The gas outlet of 2D model is not the real gas outlet boundary, in which the actual pressure should be negative but not zero, resulted in a higher pressure drop than 3D simulation. Subsequently, the gas flow was simulated on the 3D model in a variety of operation conditions (G = 10-50 m3/h, N = 600-1400 r/min). Figure 5 displays the comparisons of gas pressure drop values between simulations and experiments in the MLI-RPB. The relative errors between 3D simulated and experimental values are within ±15%. The gas pressure drop in the MLI-RPB can be predicted well in most operating conditions, showing that this 3D simulation method is reasonable for the MLI-RPB. In the following studies, only the 3D CFD simulations are conducted. 4.2 Analysis of gas flow characteristics in the MLI-RPB As two important gas flow characteristics, pressure field and velocity field are analyzed in Figures 6 and 7. Figure 6(a) shows the contour of pressure in the MLI-RPB at the cutting plane z = 30 mm (an elevation about half axial thickness of the rotor). Judging from the pressure contour, pressure distributes along the circumference uniformly and symmetrically. The pressure increases along the radial

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position and the rotational zone contributes a lot for the gas pressure drop. As a contrast, a traditional RPB was also simulated, which has the same size with the MLI-RPB as shown in Figure 1(b). For more accurate quantitative comparison, simulated data were contrasted instead of the contours. The pressure values were obtained along the radial position at the same cutting plane z = 30 mm. In the area close to the gas outlet, gas flow direction changes from radial and tangential directions to axial direction sharply and the pressure distribution even displays the negative pressure. In the area near the shell wall, gas flow pattern is affected by the boundary layer and different from the main flow. Therefore, the values in the area close to the gas outlet and shell wall were omitted in Figure 6(b). Due to the different inner structure, the pressure distributions in the MLI-RPB are different from the traditional RPB. Figure 6(b) shows that the pressure increases along the radial position in the rotational zone, no matter of the traditional RPB or MLI-RPB. The pressure trend of the MLI-RPB has no obvious differences with the traditional RPB. In the inner cavity zone (r < 69.5 mm), the pressure value of the MLI-RPB is about 50 Pa lower than the traditional RPB. In the outer cavity zone (165.5 mm < r < 250 mm), the pressure value of the MLI-RPB is about 80 Pa lower than the traditional RPB. A probable reason is that the MLI-RPB has less packing but more hollow zones than the traditional RPB. The slight fluctuation of the slope change of the pressure values is ascribed to the alternative structure of packing rings and hollow annular zones in the MLI-RPB. The distribution of velocity magnitude is shown in Figure 7(a). Similarly, the

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velocity magnitude distributes along the circumference uniformly and symmetrically. Along the radial position, the velocity magnitude changes a lot in the MLI-RPB. Lacking of packing dragging, the gas velocity is low in the two hollow annular zones. Figure 7(b) displays the variations of velocity magnitude along the radial position in the MLI-RPB and traditional RPB, respectively. The curve tendency of the MLI-RPB is similar to that of the traditional RPB, but there are still some differences in the rotational zone. For the MLI-RPB, the turning points of curve appear obviously at the inner and outer edges of each packing ring (r = 69.5, 93.5, 105.5, 129.5, 191.5 and 150.5 mm). At the same rotational speed, the velocity direction of gas changes drastically from hollow annular zone into packing ring as well as from packing ring into next hollow annular zone. The gas velocity magnitude at the edges of packing rings is bigger than that at the adjacent hollow zone. In the traditional RPB, there are only two turning points along the radial position because of only one packing ring. In the partial enlarged view of the rotational zone in the MLI-RPB, the gas flow direction changes only near the liquid distributors that can be regarded as cylindrical internals, as displayed in Figure 8(a). Figure 8(b) shows that the turbulent kinetic energy near liquid distributors is higher than the adjacent area. Previous literature indicates that turbulence is of great significance to enhance mass transfer performance by the violent vortex.32 Thus, the hollow annular zones among packing rings of the MLI-RPB has the potential to be inserted into internals to enhance the gas turbulence in the rotational zone. 4.3 Optimization for internals

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The turbulence causes flow convection movement and renews the phase interface, so that the mass transfer resistance can be greatly reduced to increase the mass transfer coefficient.33 Promoting the tangential slip velocity between the gas and the packing can also increase the gas-side mass transfer coefficient.34 The aim of the internal optimization is to promote the disturbance of gas flow in the hollow annular zones among packing rings. In the MLI-RPB, the gas attains a circumferential velocity as it enters the rotational zone. As shown in Figure 8(a) of the velocity vector, gas flows circumferentially and synchronously in the hollow annular zones. For the sake of gas turbulence enhancement, inserting internals seems a good way to disturb the gas flow in the hollow annular zones. As illustrated in Figure 9, the internals are stainless steel laths (3 mm × 8 mm × 60 mm) with different radial angles (0°, ±30°, ±60°), which are fixed statically on the upper cover of the MLI-RPB. Because of two hollow annular zones, the internals are combined as five different combinations according to the radial angle, named as combination A (0°, 0°), B (+30°, -30°), C (+60°, -60°), D (+30°, -60°) and E (+60°, -30°). In the brackets above, the former angle represents the radial angle of laths in the inner hollow annular zone, and the latter angle represents the outer one. No internals in the MLI-RPB is considered as F. For combinations A-E, there are 16 and 20 laths in the inner hollow annular zone and the outer one, respectively. Based on the 3D simulation method, the gas flow in the MLI-RPB with five different combinations was also simulated. The influence of internals on the gas flow

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is mainly concentrated in the hollow annular zones among packing rings. Since the gas phase contours distribute circumferentially and symmetrically in the rotational zone, only a quarter of the rotational zone is shown in Figure 10. Near the laths, the gas flow changes quickly in horizontal direction and has many vortexes in the hollow annular zones. As shown in Figure 11, in the hollow annular zones, the turbulent kinetic energy is obviously higher nearby the laths. It can be seen that the laths definitely disturb the gas flow in the hollow annular zones, no matter of which combination types. As for individual combination, it is obviously that the bigger radial angle is, the more violent turbulence of the gas flow is. Only with the analysis above, it is hard to distinguish the internals accurately and select the best combination. It is necessary to introduce quantitative parameters to select the internals. In the MLI-RPB, if the tangential slip velocity between gas flow and packing is nonzero, gas flow would take a curved path and develop vortexes. Therefore, the tangential slip velocity and turbulent kinetic energy can both reveal the influence of internals on the disturbance of gas flow in the hollow annular zones. Since the internals obstacle the gas flowing from a packing ring to the next one, the power to blow the gas into the MLI-RPB will be higher. At comprehensive view, three reasonable parameters were employed to quantify the internals performance: the overall gas pressure drop, turbulent kinetic energy, and the ratio of k and ∆P (k/∆P). The ∆P represents the influence of internals on the power consumption. The k, obtained from the two hollow annular zones and calculated based on area-weighted average, represents the influence of internals on disturbing the gas flow in the hollow

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annular zones. The k/∆P, considering both effects of turbulent kinetic energy and overall gas pressure drop, represents the synthetic effect of internals. As shown in Figure 12, in the hollow annular zones, the tangential slip velocity (vs) of the combination types of A-E is 1-2 times the combination F without internals. Combination C with a large radial angle of ±60° disrupts synchronous rotation of gas flow in the hollow annular zones, having a biggest tangentially slip velocity. In the inner hollow annular zone and outer one, the maximum tangential slip velocity rises up to 12.02 m/s and 17.14 m/s, respectively. Figure 13 illustrates that turbulence kinetic energy of gas flow is 1-4 times the combination F. Combination C has the biggest turbulence kinetic energy. In the inner hollow annular zone and outer one, the maximum turbulent kinetic energy rises up to 6.12 m2/s2 and 5.02 m2/s2, respectively. Because the internals are small in size, the effect on the overall gas pressure drop is little and the comparison of ∆P is ignored in this work. On economical evaluation, k/∆P increases by 1-4 times as displayed in Figure 14. Combination C is the best option as internals in the rotational zone of the MLI-RPB.

5. Conclusions The gas flow in the MLI-RPB has been investigated by the 3D CFD simulation, and internals were optimized to improve the disturbance of gas flow in rotational zone. The CFD simulation values of gas pressure drop agreed well with the experimental results with a deviation of ±15%. CFD simulation results of gas pressure and velocity magnitude reveal that, the gas flow in the MLI-RPB has special features in the hollow

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annular zones such as velocity magnitude turning points near each edge of packing rings. Five types of internal combinations aiming to enhance the turbulence of the gas flow have been designed and discussed. Nearby internals, the gas flow direction changes quickly and there are many vortexes. In the hollow annular zones, the tangential slip velocity, turbulence kinetic energy and k/∆P of the combinations A-E were 1-2, 1-4, and 1-4 times the combination F, respectively. The combination C (+60°, -60°) is superior among all internals combinations. The 3D CFD simulation method in this work not only reveals the gas flow characteristics in the MLI-RPB, but also provides fundamental and technical support for the structure optimization of RPB, especially in the rotational zone.

Acknowledgment This work was supported by the National Natural Science Foundation of China (Nos. 21725601, 21406009, and 21436001).

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Nomenclatures

Cµ

=

constant

C1ε

=

constant

C2ε

=

constant

Dp

=

equivalent diameter of packing, mm

G

=

gas flow rate, m3/h

k

=

turbulent kinetic energy, m2/s2

Kperm =

permeability

Kloss

=

loss coefficient

N

=

rotational speed, r/min

P

=

pressure, Pa

P1

=

pressure in the gas inlet, Pa

P2

=

pressure in the gas outlet, Pa

∆P

=

pressure drop, Pa

r

=

radius, mm

Si

=

generalized source term of momentum conservation equation in i (x, y or z) directions

Sp

=

source term of momentum conservation equation based on porous media model

SV

=

specific surface area of packing

=

relative velocity (the velocity viewed from a moving frame), m/s

=

translational frame velocity, m/s

vs

=

slip velocity, m/s

|v|

=

velocity magnitude, m/s

r ur

=

velocity of moving frame relative to inertial reference frame, m/s

r v r vt

18


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Greek letters

σk =

constant

σε

=

constant

β

=

radial angle of internals, °

ρ

=

fluid density, kg/m3

µ

=

viscosity, m·Pa·s

µt

=

turbulent (or eddy) viscosity, m·Pa·s

ψ

=

sphericity

ε

=

turbulent energy dissipation rate, m2/s3

εP

=

porosity of packing

=

angular velocity, rad/s

r

ω

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References (1) Zhang, L. L.; Wang, J. X.; Xiang, Y.; Zeng, X. F.; Chen, J. F. Absorption of carbon dioxide with ionic liquid in a rotating packed bed contactor: mass transfer study. Ind. Eng. Chem. Res. 2011, 50, 6957-6964. (2) Yi, F.; Zou, H. K.; Chu, G. W.; Shao, L.; Chen, J. F. Modeling and experimental studies on absorption of CO2 by Benfield solution in rotating packed bed. Chem. Eng. J. 2009, 145, 377-384. (3) Jassim, M. S.; Rochelle, G.; Eimer, D.; Ramshaw, C. Carbon dioxide absorption and desorption in aqueous monoethanolamine solutions in a rotating packed bed. Ind. Eng. Chem. Res. 2007, 46, 2823-2833. (4) Chen, J. F.; Wang, Y. H.; Guo, F.; Wang, X. M.; Zheng, C. Synthesis of nanoparticles with novel technology: High-gravity reactive precipitation. Ind. Eng. Chem. Res. 2000, 39, 948-954. (5) Sun, B. C.; Wang, X. M.; Chen, J. M.; Chu, G. W.; Chen, J. F.; Shao, L. Synthesis of nano-CaCO3 by simultaneous absorption of CO2 and NH3 into CaCl2 solution in a rotating packed bed. Chem. Eng. J. 2011, 168, 731-736. (6) Zhao, H.; Shao, L.; Chen, J. F. High-gravity process intensification technology and application. Chem. Eng. J. 2010, 156, 588-593. (7) Zhang, D.; Zhang, P. Y.; Zou, H. K.; Chu, G. W.; Wu, W.; Shao, L.; Chen, J. F. Application of HIGEE process intensification technology in synthesis of petroleum sulfonate surfactant. Chem. Eng. Process. 2010, 49, 508-513. (8) Chen, J. F.; Liu, Y.; Zhang, Y. Control of product distribution of Fischer-Tropsch

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synthesis with a novel rotating packed-bed reactor: From diesel to light olefin. Ind. Eng. Chem. Res. 2012, 51, 8700-8703. (9) Rao, D. P.; Bansal, A.; Goswami, P. S. Process intensification in rotating packed beds (HIGEE): An appraisal. Ind. Eng. Chem. Res. 2004, 43, 1150-1162. (10) Jiao, W. Z.; Liu, Y. Z.; Qi, G. S. Gas pressure drop and mass transfer characteristics in a cross-flow rotating packed bed with porous plate packing. Ind. Eng. Chem. Res. 2010, 49, 3732-3740. (11) Sung, W. D.; Chen, Y. S. Characteristics of a rotating packed bed equipped with blade packings and baffles. Sep. Purif. Technol. 2012, 93, 52-58. (12) Luo, Y.; Chu, G. W.; Zou, H. K.; Wang, F., Shao, L.; Chen, J. F. Mass transfer studies in a rotating packed bed with novel rotors: chemisorption of CO2. Ind. Eng. Chem. Res. 2012, 51, 9164-9172. (13) Chen, J. F.; Luo, Y.; Chu, G. W.; Zou, H. K.; Xiang, Y. Segmented liquid feed for enhancing the end effect in a rotating packed bed, Chin. Patent No. 201110153297.1, 2011. (14) Chu, G. W.; Luo, Y.; Xing, Z. Y.; Sang, L.; Zou, H. K.; Shao, L.; Chen, J. F. Mass-transfer studies in a novel Multiliquid-inlet rotating packed bed. Ind. Eng. Chem. Res. 2014, 53, 18580-18584. (15) Ouyang, Y.; Xiang, Y.; Zou, H. K.; Chu, G. W.; Chen, J. F. Flow characteristics and micromixing modeling in a microporous tube-in-tube microchannel reactor by CFD. Chem. Eng. J. 2017, 321, 533-545. (16) Shi, X.; Xiang, Y.; Wen, L. X.; Chen, J. F. CFD analysis of flow patterns and

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micromixing efficiency in a Y-type microchannel reactor. Ind. Eng. Chem. Res. 2012, 51, 13944-13952. (17) Robbins, D. J.; Bachir, M. S.; Gladden, L. F.; Cant, R. S.; Harbou, E. CFD modeling of single-phase flow in a packed bed with MRI validation. AIChE J. 2012, 58, 3904-3915. (18) Shi, X.; Xiang, Y.; Wen, L. X.; Chen, J. F. CFD analysis of liquid phase flow in a rotating packed bed reactor. Chem. Eng. J. 2013, 228, 1040-1049. (19) Llerena-Chavez, H.; Larachi, F. Analysis of flow in rotating packed beds via CFD simulations-dry pressure drop and gas flow maldistribution. Chem. Eng. Sci. 2009, 64, 2113-2126. (20) Sun, Y. L; Zhang, Y.; Zhang, L. H,; Jiang, B.; Zhao, Z. X. Structure optimization of a rotating zigzag bed via computational fluid dynamics simulation. Ind. Eng. Chem. Res. 2014, 53, 13764-13772. (21) Yang, Y. C.; Xiang, Y.; Li, Y. G.; Chu, G. W.; Zou, H. K.; Arowo, M.; Chen, J. F. 3D CFD modeling and optimization of single-phase flow in rotating packed beds. Can. J. Chem. Eng. 2015, 93, 1138-1148. (22) Larsson, H.; Andersen, P. A. S.; Byström, E.; Gernaey, K. V.; Krühne, U. CFD modeling of flow and ion exchange kinetics in a rotating bed reactor system. Ind. Eng. Chem. Res. 2017, 56, 3853-3865. (23) Guo, T. Y.; Cheng, K. P.; Wen, L. X.; Andersson, R.; Chen, J. F. 3D simulation on liquid flow in a rotating packed bed reactor. Ind. Eng. Chem. Res. 2017, 56, 8169-8179.

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(24) Liu, Y.; Luo, Y.; Chu, G. W.; Luo, J. Z.; Arowo, M.; Chen, J. F. 3D numerical simulation of a rotating packed bed with structured stainless steel wire mesh packing. Chem. Eng. Sci. 2017, 170, 365-377. (25) Martínez, E. L.; Jaimes, R.; Gomez, J. L.; Filho, R. M. CFD Simulation of three-dimensional multiphase flow in a rotating packed bed. Proceedings of ESCAPE22. 2012, 30, 1158-1162. (26) Ergun, S. Fluid flow through packed columns. Chem. Eng. Prog. 1952, 48, 89-94. (27) Chen, Y. S.; Lin, F. Y.; Lin, C. C.; Tai, Y. D.; Liu, H. S. Packing characteristics for mass transfer in a rotating packed bed. Ind. Eng. Chem. Res. 2006, 45, 6846-6853. (28) User’s Guide to FLUENT 14; Fluent Inc.: Lebanon, NH, 2011. (29) Yang, W. J.; Wang, Y. D.; Chen, J. F.; Fei, W. Y. Computational fluid dynamic simulation of fluid flow in a rotating packed bed. Chem. Eng. J. 2010, 156, 582-587. (30) Kumar, M. P.; Rao, D. P. Studies on a high-gravity gas-liquid contactor. Ind. Eng. Chem. Res. 1990, 29, 917-920. (31) Kelleher, T.; Fair, J. R. Distillation studies in a high-gravity contactor. Ind. Eng. Chem. Res. 1996, 35, 4646-4655. (32) Eeten, K.; Verzicco, R.; Schaaf, J.; Heijst, G.; Schouten, J. A numerical study on gas-liquid mass transfer in the rotor-stator spinning disc reactor. Chem. Eng. Sci. 2015, 129, 14-24. (33) Ma, Y. G.; Yang, X. W.; Feng, H. S.; Yu, G. C. Influence of interfacial turbulence on gas-liquid mass transfer. Chem. Eng. 2004, 32, 1-4.

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(34) Chandra, A.; Goswami, P. S.; Rao, D. P. Characteristics of flow in a rotating packed bed (HIGEE) with split packing. Ind. Eng. Chem. Res. 2005, 44, 4051-4060.

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(a)

(b) Figure 1. Main structure diagrams of (a) MLI-RPB and (b) traditional RPB (1) liquid outlet, (2) gas inlet, (3) packing support, (4) liquid distributors, (5) liquid droplets capture device, (6) gas outlet, (7) liquid inlets, (8) cover, (9) packing rings: (9-1) outer packing ring, (9-2) middle packing ring, and (9-3) inner packing ring, (10) hollow annular zones: (10-1) inner hollow annular zone and (10-2) outer hollow annular zone. 25



Page 26 of 40

(a)

(b) Figure 2. (a) 2D and (b) 3D physical model of fluid zone in the MLI-RPB.

26


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Figure 3. Schematic diagram of experimental setup for overall gas pressure drop measurement. (A, B: gas pressure measurement points)

27



800

∆P (Pa)

600

Experiment 3D simulation 2D simulation 3

G = 30 m /h

400

200

0

600

800

1000

1200

1400

40

50

N (r/min)

(a) 500 Experiment 3D simulation 2D simulation

400

N = 800 r/min ∆P (Pa)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

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300

200

100

0

10

20

30 3

G (m /h)

(b) Figure 4. Effects of (a) rotational speed and (b) gas flow rate on the gas pressure drop in the MLI-RPB. 28


Page 29 of 40

500

400

Simulated ∆P (Pa)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


+15% 300

200

-15% 100

0

0

100

200

300

400

500

Experimental ∆P (Pa) Figure 5. Comparison of overall gas pressure drop between simulated and experimental values. (G = 10-50 m3/h, N = 600-1400 r/min)

29



(a)

300 Traditional RPB MLI-RPB

250

N = 800 r/min 3 G = 30 m /h

200

P (Pa)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 30 of 40

150 Inner cavity zone

100

Rotational zone

50 0

Outer cavity zone

0

50

100

150

200

250

r (mm) (b)

Figure 6. Distribution of pressure in the MLI-RPB (a) at cutting plane of z = 30 mm and (b) along the radial position.

30


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(a)

15 Traditional RPB MLI-RPB

12

|v| (m/s)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


N = 800 r/min 3 G = 30 m /h

9

6

3

0

Inner cavity zone

0

50

Outer cavity zone

Rotational zone

100

150

200

250

r (mm) (b)

Figure 7. Distribution of velocity magnitude in the MLI-RPB (a) at cutting plane of z = 30 mm and (b) along the radial position.

31



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(a)

(b)

Figure 8. Partial views of (a) vector of velocity and (b) turbulent kinetic energy contour nearby the liquid distributors. (G = 30 m3/h, N = 800 r/min; cutting plane of z = 30 mm)

32


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Figure 9. Schematic diagrams of internals design in the MLI-RPB.

33



(a)

(b)

(c)

(d)

(e)

(f)

Page 34 of 40

Figure 10. Partial views of gas streamlines in the MLI-RPB with different internals combinations (G = 30 m3/h, N = 800 r/min).

34


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(a)

(b)

(c)

(d)

(e)

(f)

Figure 11. Partial views of gas turbulent kinetic energy contours in the MLI-RPB with different internals combinations (G = 30 m3/h, N = 800 r/min).

35



25 Outer hollow annular zone Inner hollow annular zone

20

vs (m/s)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 36 of 40

N = 800 r/min 3 G = 30 m /h

15

10

5

0 A

B

C

D

E

F

Combination type of inner components Figure 12. Effect of the combination type of internals on gas tangential slip velocity.

36


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10 Outer hollow annular zone Inner hollow annular zone

8

N = 800 r/min 3 G = 30 m /h

6

2

2

k (m /s )

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


4

2

0 A

B

C

D

E

F

Combination type of inner components Figure 13. Effect of the combination type of internals on turbulent kinetic energy.

37



0.05 Outer hollow annular zone Inner hollow annular zone

0.04

N = 800 r/min 3 G = 30 m /h

0.03

2

2

k/∆P (m /(s ·Pa))

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 38 of 40

0.02

0.01

0.00 A

B C D F E Combination type of inner components

Figure 14. Effect of the combination type of internals on k/∆P.

38


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Table 1. Specifications of MLI-RPB adopted in this study. Items

Values

Outer cavity zone Inner diameter

331 mm

Outer diameter

500 mm

Axial thickness

268 mm

Pipe diameter of gas inlet

51 mm

Packing zone Inner packing ring: inner diameter / outer diameter

139 / 187 mm

Middle packing ring: inner diameter / outer diameter

211 / 259 mm

Outer packing ring: inner diameter / outer diameter

283 / 331 mm

Height of packing rings

50 mm

Porosity of packing

0.96

Specific surface area of packing

~500 m2/m3

Inner cavity zone Outer diameter

139 mm

Pipe diameter of gas outlet

70 mm

39



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TOC graphic

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Gas Flow in a Multiliquid-Inlet Rotating Packed Bed: Three

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