Effects of Particle Rotation on the Hydrodynamic Modeling of Segregation in Gas-Fluidized Beds

2004 ◽  
Author(s):  
Jin Sun ◽  
Francine Battaglia

A multi-fluid Eulerian model has been improved by incorporating particle rotation using a simple kinetic theory for rapid granular flow of slightly frictional spheres. The model was implemented without changing the current kinetic theory framework by introducing an effective coefficient of restitution to account for additional energy dissipation due to frictional collisions. Simulations with and without particle rotation were performed to study the bubble dynamics in a monodispersed gas-solid fluidized bed and the segregation phenomena in a bidispersed gas-solid fluidized bed. Results were compared between simulations with and without particle rotation and with corresponding experimental results. It was found that the multi-fluid model with particle rotation better captures the bubble dynamics and time-averaged bed behavior. The model predicted lower segregation percentages and a lower segregation rate due to increased bubble intensity.

AIChE Journal ◽  
2014 ◽  
Vol 60 (5) ◽  
pp. 1632-1644 ◽  
Author(s):  
Vikrant Verma ◽  
Johan T. Padding ◽  
Niels G. Deen ◽  
J. A. M. Hans Kuipers ◽  
Frank Barthel ◽  
...  

2021 ◽  
Vol 2021 (5) ◽  
Author(s):  
Artem Alexandrov ◽  
Pavel Mitkin

Abstract We consider the notion of zilch current that was recently discussed in the literature as an alternative helicity measure for photons. Developing this idea, we suggest the generalization of the zilch for the systems of fermions. We start with the definition of the photonic zilch current in chiral kinetic theory framework and work out field-theoretical definition of the fermionic zilch using the Wigner function formalism. This object has similar properties to the photonic zilch and is conserved in the non-interacting theory. We also show that, in full analogy with a case of photons, the fermionic zilch acquires a non-trivial contribution due to the medium rotation - zilch vortical effect (ZVE) for fermions. Combined with a previously studied ZVE for photons, these results form a wider set of chiral effects parameterized by the spin of the particles and the spin of the current. We briefly discuss the origin of the ZVE, its possible relation to the anomalies in the underlying microscopic theory and possible application for studying the spin polarization in chiral media.


2019 ◽  
Vol 141 (7) ◽  
Author(s):  
Peter Ostermeier ◽  
Annelies Vandersickel ◽  
Stephan Gleis ◽  
Hartmut Spliethoff

Gas–solid fluidized bed reactors play an important role in many industrial applications. Nevertheless, there is a lack of knowledge of the processes occurring inside the bed, which impedes proper design and upscaling. In this work, numerical approaches in the Eulerian and the Lagrangian framework are compared and applied in order to investigate internal fluidized bed phenomena. The considered system uses steam/air/nitrogen as fluidization gas, entering the three-dimensional geometry through a Tuyere nozzle distributor, and calcium oxide/corundum/calcium carbonate as solid bed material. In the two-fluid model (TFM) and the multifluid model (MFM), both gas and powder are modeled as Eulerian phases. The size distribution of the particles is approximated by one or more granular phases with corresponding mean diameters and a sphericity factor accounting for their nonspherical shape. The solid–solid and fluid–solid interactions are considered by incorporating the kinetic theory of granular flow (KTGF) and a drag model, which is modified by the aforementioned sphericity factor. The dense discrete phase model (DDPM) can be interpreted as a hybrid model, where the interactions are also modeled using the KTGF; however, the particles are clustered to parcels and tracked in a Lagrangian way, resulting in a more accurate and computational affordable resolution of the size distribution. In the computational fluid dynamics–discrete element method (CFD–DEM) approach, particle collisions are calculated using the DEM. Thereby, more detailed interparticulate phenomena (e.g., cohesion) can be assessed. The three approaches (TFM, DDPM, CFD–DEM) are evaluated in terms of grid- and time-independency as well as computational demand. The TFM and CFD–DEM models show qualitative accordance and are therefore applied for further investigations. The MFM (as a variation of the TFM) is applied in order to simulate hydrodynamics and heat transfer to immersed objects in a small-scale experimental test rig because the MFM can handle the required small computational cells. Corundum is used as a nearly monodisperse powder, being more suitable for Eulerian models, and air is used as fluidization gas. Simulation results are compared to experimental data in order to validate the approach. The CFD–DEM model is applied in order to predict mixing behavior and cohesion effects of a polydisperse calcium carbonate powder in a larger scale energy storage reactor.


1994 ◽  
Vol 278 ◽  
pp. 63-81 ◽  
Author(s):  
G. K. Batchelor ◽  
J. M. Nitsche

It is a significant feature of most gas-fluidized beds that they contain rising ‘bubbles’ of almost clear gas. The purpose of this paper is to account plausibly for this remarkable property first by supposing that primary and secondary instabilities of the fluidized bed generate compact regions of above-average or below-average particle concentration, and second by invoking a mechanism for the expulsion of particles from a buoyant compact blob of smaller particle concentration. We postulate that the rising of such an incipient bubble generates a toroidal circulation of the gas in the bubble, roughly like that in a drop of liquid rising through a second liquid of larger density, and that particles in the blob carried round by the fluid move on trajectories which ultimately cross the bubble boundary. Numerical calculations of particle trajectories for practical values of the relevant parameters show that a large percentage of particles, of such small concentration that they move independently, are expelled from a bubble in the time taken by it to rise through a distance of several bubble diameters.Similar calculations for a liquid-fluidized bed show that the expulsion mechanism is much weaker, as a consequence of the larger density and viscosity of a liquid, which is consistent with the absence of observations of relatively empty bubbles in liquid-fluidized beds.It is found to be possible, with the help of the Richardson-Zaki correlation, to adjust the results of these calculations so as to allow approximately for the effect of interaction of particles in a bubble in either a gas- or a liquid-fluidized bed. The interaction of particles at volume fractions of 20 or 30 % lengthens the expulsion times, although without changing the qualitative conclusions.


2018 ◽  
Vol 1125 ◽  
pp. 012021 ◽  
Author(s):  
Q. Wargnier ◽  
A. Alvarez Laguna ◽  
P. Kestener ◽  
B. Graille ◽  
N. N. Mansour ◽  
...  

Particuology ◽  
2017 ◽  
Vol 31 ◽  
pp. 95-104 ◽  
Author(s):  
Shuyan Wang ◽  
Baoli Shao ◽  
Xiangyu Li ◽  
Jian Zhao ◽  
Lili Liu ◽  
...  

2018 ◽  
Vol 344 ◽  
pp. 71-85 ◽  
Author(s):  
Abdelghafour Zaabout ◽  
Anthony Bernus ◽  
Schalk Cloete ◽  
Shahriar Amini

2020 ◽  
Vol 141 ◽  
pp. 01012
Author(s):  
Parinya Khongprom ◽  
Thanapat Whansungnoen ◽  
Permsak Pienduangsri ◽  
Waritnan Wanchan ◽  
Sunun Limtrakul

Because of the continuous increase in the amount of plastic waste, catalytic cracking is an interesting method that could be used to convert heavy oil from thermal cracking of plastic waste into fuel. The objective of this study was to investigate the hydrodynamic behavior and the performance of catalytic cracking of heavy oil in a circulating fluidized bed reactor using computational fluid dynamics. The two– fluid model incorporated with the kinetic theory of granular flow was applied to predict the hydrodynamic behavior with a reactive flow. Three reactor geometries were studied, which included a conventional riser, tapered–out riser, and tapered–in riser. The four–lump kinetic model was used to describe the catalytic cracking of heavy oil from waste plastic. A core–annulus flow pattern was found in the three reactor geometries. The solid fraction distribution of the tapered reactor was found to be more uniform than that of the conventional riser. The tapered–in riser showed the highest heavy oil conversion with the lowest gasoline selectivity. However, the heavy oil conversion and gasoline selectivity of the conventional and tapered–out reactors were not significantly different.


Fuel ◽  
2014 ◽  
Vol 130 ◽  
pp. 197-202 ◽  
Author(s):  
Wang Shuai ◽  
Lu Huang ◽  
Hao Zhenhua ◽  
Lu Huilin ◽  
Liu Guodong ◽  
...  

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