scholarly journals Non-spherical particle mixing behaviors by spherical inert particles assisted in a fluidized bed

2019 ◽  
Vol 17 (2) ◽  
pp. 509-524 ◽  
Author(s):  
An-Xing Ren ◽  
Tian-Yu Wang ◽  
Tian-Qi Tang ◽  
Yu-Rong He
Keyword(s):  
Fluidized Bed ◽  
Binary Mixtures ◽  
Volume Fraction ◽  
Fluid Dynamic ◽  
Rolling Friction ◽  
Spherical Particles ◽  
Industrial Processes ◽  
Vertical Orientation ◽  
Inert Particles ◽  
Particle Velocities

AbstractFluidized beds are widely used in many industrial fields such as petroleum, chemical and energy. In actual industrial processes, spherical inert particles are typically added to the fluidized bed to promote fluidization of non-spherical particles. Understanding mixing behaviors of binary mixtures in a fluidized bed has specific significance for the design and optimization of related industrial processes. In this study, the computational fluid dynamic–discrete element method with the consideration of rolling friction was applied to evaluate the mixing behaviors of binary mixtures comprising spherocylindrical particles and spherical particles in a fluidized bed. The simulation results indicate that the differences between rotational particle velocities were higher than those of translational particle velocities for spherical and non-spherical particles when well mixed. Moreover, as the volume fraction of the spherocylindrical particles increases, translational and rotational granular temperatures gradually increase. In addition, the addition of the spherical particles makes the spherocylindrical particles preferably distributed in a vertical orientation.

Kinetic Simulations for Analysing the Wall Collision Process of Non-Spherical Particles

2002 ◽  
Author(s):  
M. Sommerfeld
Keyword(s):  
Particle Shape ◽  
Fluid Dynamic ◽  
Impact Angle ◽  
Distribution Functions ◽  
Spherical Particles ◽  
Collision Process ◽  
Wall Collision ◽  
Particle Velocities ◽  
The Impact ◽  
Particle Shapes

In wall-bounded gas-solid flows the wall collision process plays an important role and may be strongly affected by wall roughness and particle shape. The modelling of the particle-wall collision mostly relies on the assumption of spherical particles. To extend such models appropriately for non-spherical particles, two-dimensional kinetic simulations were performed for different particle shapes. This implies, that the particle translational and angular motion is calculated by considering the particle shape, however neglecting fluid dynamic effects. The change of the particle velocities during the impact and rebound process was calculated by solving the impulse equations together with Coulombs law of friction. The simulations were performed for a given initial particle velocity by varying impact angle and initial angular velocity. The results for 2000 particle wall collisions allowed us to derive the distribution functions of the impact parameters required to describe the wall collision process for non-spherical particles correctly. Moreover, other wall collision properties, such as rebound angle and velocity ratios could be determined. Finally also a comparison with measurements was possible.

The effect of ring baffles on the hydrodynamics of a gas—solid bubbling fluidized bed using computational fluid dynamics

2009 ◽  
Vol 223 (10) ◽  
pp. 2281-2289 ◽  
Author(s):  
S H Hosseini ◽  
R Rahimi ◽  
M Zivdar ◽  
A Samimi
Keyword(s):  
Fluidized Bed ◽  
Volume Fraction ◽  
Fluid Model ◽  
Expansion Ratio ◽  
Bubbling Fluidized Bed ◽  
Gas Volume Fraction ◽  
Two Fluid Model ◽  
Particle Velocities ◽  
Bed Expansion ◽  
Gas Volume

An Eulerian—Eulerian two-fluid model (TFM) integrating the kinetic theory for emulsion phase was used to simulate gas—solid fluidized beds. Validation of the model was investigated based on hydrodynamic parameters such as bed expansion ratio, H/ H0, gas volume fraction profile, bubble behaviour, and motion of the particles. A good agreement was found between numerical results and experimental values. The model was used to study a bubbling fluidized bed (BFB) including the ring baffles. Predicted results show that the ring baffles have an important role in the flow pattern of the bed. Baffles increase the bed expansion height and particle velocities at axial locations on the top of the highest baffle as well as uniform distribution of gas volume fraction between the baffles area. In spite of increasing the dead zones in the bed, ring baffles cause the improvement of mixing and heat transfer in the bed. The present study provides a useful basis for further works on the effect of baffles in BFBs.

Experimental and computational investigation of the electrocatalytic hydrogenation of phenol in an electrochemical cell

2004 ◽  
Vol 82 (5) ◽  
pp. 641-648 ◽  
Author(s):  
A Chagnes ◽  
F Laplante ◽  
F Kerdouss ◽  
P Proulx ◽  
H Ménard
Keyword(s):  
Fluidized Bed ◽  
Cathodic Polarization ◽  
Volume Fraction ◽  
Fluid Dynamic ◽  
Aqueous Media ◽  
Vitreous Carbon ◽  
High Porosity ◽  
Electrocatalytic Hydrogenation ◽  
Reticulated Vitreous Carbon ◽  
Fluidized Bed Electrode

The electrocatalytic hydrogenation (ECH) of phenol was carried out in aqueous media with a commercial Pd/Al2O3 (5% w/w) catalyst. A porous matrix of reticulated vitreous carbon (RVC) was used to study the porosity – stirring speed coupling (PSSC) effect on the phenol hydrogenation to form cyclohexanone and cyclohexanol. In accordance with the PSSC, the electrode can act as a fluidized bed electrode or as an agglomerated electrode. Fluidized bed electrodes develop for low porosity matrices (10–30 ppi, ppi = pores per inch) at high stirring speeds (>600 rpm), while agglomerated electrodes are obtained for high porosity matrices (60–100 ppi) with moderate stirring speeds under cathodic polarization. The distribution of the volume fraction of the particles and the agglomeration of the particles have been simulated by computational fluid dynamic (CFD) methods with FLUENT software. For the agglomerated electrode, the numerical simulations demonstrate the beneficial contribution of the cathodic polarization to the agglomeration process. However, at 650 rpm, for the fluidized bed electrode, the volume fraction of the particles in the RVC does not account for the distinction in the ECH efficiency between the 30 ppi matrix and the 100 ppi matrix. For a given amount of Pd/Al2O3 catalyst, it is observed that the ECH rates depend on the PSSC and increase in the following order: 100/650 < 30/650 < 100/200. Key words: electrocatalytic hydrogenation (ECH), CFD, fluid mechanics, porous media, powder, porosity – stirring speed coupling (PSSC), reticulated vitreous carbon (RVC).

Three-dimensional computational fluid dynamics investigation of hydrodynamics behaviour of gas–solid flow in fluidized bed of Geldart D particles

2021 ◽  
pp. 095440892098769
Author(s):  
Fazia Aiche ◽  
Salah Belaadi ◽  
Adel Lalaoua ◽  
Abdallah Sofiane Berrouk ◽  
Abdelwahid Azzi
Keyword(s):  
Fluidized Bed ◽  
Gas Flow ◽  
Turbulence Modeling ◽  
Volume Fraction ◽  
Solid Phase ◽  
Fluid Model ◽  
Flow Behavior ◽  
Three Dimensional ◽  
Industrial Processes ◽  
Cyclic Process

Fluidized beds are widely used in many industrial processes as they ensure the desirable high-intensity heat and mass transfers between gas and particles and offer the possibility to perform operations in a continuous mode and powders recycling. Some of these industrial processes use Geldart D type of powders and operate in the slugging mode. This paper presents a 3 D numerical model of gas-solid flows in a fluidized bed based on the Two-Fluid Model (TFM). Turbulence modeling (k- ε) was used to predict flow behavior in fluidized bed of Geldart D particles. The solid phase consists of Geldart D powders and the gas flow is in a slug regime. The numerical results are validated against the experimental work of Azzi et al. Model predictions on flow patterns, bed expansion, volume fraction time series and pressure drop fluctuations are presented and discussed in details in order to demonstrate the cyclic process of slug formation (onset, growth, rising and bursting of slugs) and its effects on the overall performance of beds fluidizing Geldart D type of powders.

Effect of Fluidized Bed on Permeate Flux in Ceramic Membrane Cross-Flow Microfiltration

1995 ◽  
Vol 60 (12) ◽  
pp. 2074-2084
Author(s):  
Petr Mikulášek
Keyword(s):  
Fluidized Bed ◽  
Ceramic Membrane ◽  
Cross Flow ◽  
Experimental System ◽  
Experimental Results ◽  
Spherical Particles ◽  
Permeate Flux ◽  
Model Fluid ◽  
Optimum Porosity ◽  
Tubular Membranes

The microfiltration of a model fluid on an α-alumina microfiltration tubular membrane in the presence of a fluidized bed has been examined. Following the description of the basic characteristic of alumina tubular membranes, model dispersion and spherical particles used, some comments on the experimental system and experimental results for different microfiltration systems are presented. From the analysis of experimental results it may be concluded that the use of turbulence-promoting agents resulted in a significant increase of permeate flux through the membrane. It was found out that the optimum porosity of fluidized bed for which the maximum values of permeate flux were reached is approximately 0.8.

CFD‐DEM analysis of the spouted fluidized bed with non‐spherical particles

2021 ◽  
Author(s):  
Behrad Esgandari ◽  
Shahab Golshan ◽  
Reza Zarghami ◽  
Rahmat Sotudeh‐Gharebagh ◽  
Jamal Chaouki
Keyword(s):  
Fluidized Bed ◽  
Spherical Particles ◽  
Dem Analysis
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