Scaling-up down flow reactors. CPFD simulations and model validation

Lanza, A.; Lasa, Hugo de

doi:10.1016/j.compchemeng.2017.02.034

Cited by 10 publications

(16 citation statements)

References 28 publications

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“…For the catalyst, a mean diameter of 8.46 × 10 −5 m, a catalyst density of 1525 kg/m 3 , and a particle specific heat capacity of 1090 J/kg • K [38] were considered. The particle density (ρp) and diameter are similar to those in other studies [39], [40]. The dimensions of the reaction zone are described below.…”

Section: Cfd Simulationsupporting

confidence: 67%

In-Situ Characterization of 1-Hexene Concentration with a Helium-Neon Laser in the presence of a Solid Catalyst

Lacayo

López

Soto

et al. 2020

TecnoL.

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This study provides evidence that a helium-neon (He-Ne) laser operating in the Mid-infrared (MIR) at a wavelength of 3.39 μm can detect variations in 1-hexene concentration in the presence of a solid catalyst. The in-situ and online characterization of the concentration of 1-hexene, as an example of a hydrocarbon, is relevant to enhance the current understanding of the interaction between hydrodynamics and chemistry in different heterogeneous catalytic processes. We designed and built a laboratory-scale downer unit that enabled us to analyze heterogeneous catalytic reactions and provided optical access. The lab-scale reactor was 180-cm long, had an internal diameter of 1.3 cm, and was made of fused quartz to allow the passage of the laser beam. 1-hexene was carefully measured, vaporized, and fed into the reactor through two inlets located at an angle of 45 degrees from the vertical descendent flow and 70 cm below the input of a solid catalyst and a purge flow entraining N2. A system of five heaters, which can be moved in the vertical direction to allow the passage of the laser beam, guaranteed temperatures up to 823 K. Computational Fluid Dynamics (CFD) simulations of the hydrodynamics of the system indicated that a uniform temperature profile in the reaction section was reached after the catalyst and the feed mixed. The estimated catalyst to oil ratio and time on stream in the experiments were, respectively, 0.4 to 1.3 and 2 s. After a correction for laser power drift, the experimental results showed a linear response of the fractional transmission to the 1-hexene concentration that was independent of temperature in the 373 K–673 K range. Even in the presence of a catalyst, the absorption of 1-hexene at the MIR frequency of the laser was high enough to enable the detection of 1-hexene since the fractional absorption of the absorbing path length in these experiments was close to zero (0.013 m) and the 1-hexene concentrations were higher than 1.254 × 10-5 mol/cm3. This result demonstrated the ability of the laser system to measure the concentration of 1-hexene in the presence of a catalyst and indicates that it can be used to better decouple hydrodynamics from kinetics in heterogeneous catalytic processes.

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Section: Cfd Simulationsupporting

confidence: 67%

In-Situ Characterization of 1-Hexene Concentration with a Helium-Neon Laser in the presence of a Solid Catalyst

Lacayo

López

Soto

et al. 2020

TecnoL.

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“…In these studies, the Ganser correlation for nonspherical particles yielded the lowest error percentages for the expected configurations of the clusters in this system. Based on these findings, Lanza and de Lasa 20 selected the Ganser drag model for the calculations reported in their work. The Ganser drag coefficient is calculated with eqs 15 and 16 as follows…”

Section: Modelingmentioning

confidence: 99%

“…Based on these findings, Lanza and de Lasa selected the Ganser drag model for the calculations reported in their work. The Ganser drag coefficient is calculated with eqs and as follows …”

Section: Modelingmentioning

confidence: 99%

“…Lanza et al , implemented a hybrid numerical model in CPFD Barracuda VR by using the data from experimental cluster size distributions in two downers of different cross-sectional areas. This model designated as the “hybrid experimental–numerical cluster” model permitted an accurate prediction of solid-phase properties in the developed flow sections of both downers.…”

Section: Introductionmentioning

confidence: 99%

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Hybrid Particle Cluster CPFD Simulation in the Acceleration and Stabilized Sections of a Downflow Circulating Fluidized Bed

Medina‐Pedraza

Lasa

2020

Ind. Eng. Chem. Res.

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This study reports a numerical hybrid cluster simulation of a downer reactor unit using CPFD Barracuda VR software. This model includes an experimentally determined particle cluster size distribution to describe the particle cluster morphological changes as well as the cluster acceleration. Gas–solid flows are considered for a fluid catalytic cracking catalyst with an apparent particle density of 1722 kg/m3, flowing in a 5.08 cm-ID column with air at 300 K and with a pressure close to atmospheric. Conditions for the simulations consist of 1.0–1.6 m/s superficial gas velocity and 30–50 kg/m2 s solid mass flux ranges. Calculations developed involve the Hölzer–Sommerfeld and Ganser drag correlations. The proposed numerical model is validated by comparing experimental and simulated radial cluster particle velocities and particle volume fractions. Simulations developed show that the Hölzer–Sommerfeld drag function in conjunction with a proper selection of cluster geometry provides good cluster velocities and particle volume fraction values both in the cluster acceleration and cluster-stabilized flow unit sections.

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“…Currently, considerable efforts have been devoted to simulate the CFB downer and riser by using CPFD approach. Lanza et al [26,27] presented studies to predict the flow behaviors in the developed flow region of a downer using CPFD approach. Wu et al [28] established a CPFD model coupled with EMMS-based drag model and predicted the flow behavior of a pilot-scale CFB riser handling Geldart A particles and of an industrial-scale FCC riser with a 14-lump kinetic model.…”

Section: Introductionmentioning

confidence: 99%

3D CPFD Simulation of Circulating Fluidized Bed Downer and Riser: Comparisons of Flow Structure and Solids Back-Mixing Behavior

Liu

Shi

et al. 2020

Processes

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The difference of gas-solids flow between a circulating fluidized bed (CFB) downer and riser was compared by computational particle fluid dynamics (CPFD) approach. The comparison was conducted under the same operating conditions. Simulation results demonstrated that the downer showed much more uniform solids holdup and solids velocity distribution compared with the riser. The radial non-uniformity index of the solids holdup in the riser was over 10 times than that in the downer. In addition, small clusters tended to be present in the whole downer, large clusters tended to be present near the wall in riser. It was found that the different cluster behavior is important in determining the different flow behaviors of solids in the downer and riser. While the particle residence time increased evenly along the downward direction in the downer, particles with both shorter and longer residence time were predicted in the whole riser. The nearly vertical cumulative residence time distribution (RTD) curve in the downer further demonstrated that the solids back-mixing in the downer is limited while that in the riser is severe. Solids turbulence in the downer was much weaker compared with the riser, while the large clusters formation near the wall in the riser would hinder solids transportation ability.

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Scaling-up down flow reactors. CPFD simulations and model validation

Cited by 10 publications

References 28 publications

In-Situ Characterization of 1-Hexene Concentration with a Helium-Neon Laser in the presence of a Solid Catalyst

In-Situ Characterization of 1-Hexene Concentration with a Helium-Neon Laser in the presence of a Solid Catalyst

Hybrid Particle Cluster CPFD Simulation in the Acceleration and Stabilized Sections of a Downflow Circulating Fluidized Bed

3D CPFD Simulation of Circulating Fluidized Bed Downer and Riser: Comparisons of Flow Structure and Solids Back-Mixing Behavior

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