A CFD‐DEM study of the solid‐like and fluid‐like states in the homogeneous fluidization regime of Geldart A particles

AIChE Journal ◽  
2021 ◽  
Author(s):  
Qiang Guo ◽  
Alireza Bordbar ◽  
Likun Ma ◽  
Yaxiong Yu ◽  
Shuliang Xu ◽  
...  
Keyword(s):  
Fluidization Regime

Measurement and Computation of Turbulence in Risers Using Kinetic Theory

2003 ◽  
Author(s):  
Mehmet Tartan ◽  
Dimitri Gidaspow ◽  
Jonghwun Jung
Keyword(s):  
Particle Velocity ◽  
Circulating Fluidized Bed ◽  
Flow Region ◽  
Granular Temperature ◽  
Reynolds Stresses ◽  
Mean Velocity ◽  
Cfd Models ◽  
Viscous Heat ◽  
Fluidization Regime ◽  
Bubbling Beds

Detailed experimental velocity, particle concentration and stresses for flow of particles in a vertical pipe, riser are needed for verification of various CFD models for multiphase flow in the industrially important circulating fluidized bed (fast fluidization) regime. This study provides such information for flow of 530 μm glass beads in the fully developed flow region of a 7 m symmetric riser with a splash plate. Instantaneous particle velocity distributions were obtained using a particle velocity imaging technique and a probe inserted into the riser, while the particle concentrations were measured with a gammaray densitometer. Time averaged particle velocity distributions can be well represented by a parabolic velocity distribution, with the mean velocity obtained from flux divided by the measured bulk density. The radial granular temperature profiles agree with an analytical expression similar to the thermal temperature distribution in Poiseuille flow with viscous heat generation. A solution to the complete CFD model shows that the assumptions made in the analytical solution are valid. Our measurements of stresses in the risers and bubbling beds show the existence of two types of random kinetic energies or granular temperatures. The true granular temperature is due to oscillations of particles, while the second is the average of the normal Reynolds stresses. In the core of the riser, the true granular temperature is much larger than the Reynolds type granular temperature. The reverse is true in the bubbling bed.

scholarly journals Design of a Fast Internal Circulating Fluidized-Bed Gasifier with a conical bed angle

2019 ◽  
Vol 23 (1) ◽  
pp. 33-45 ◽  
Author(s):  
Jernej Mele ◽  
Andrej Senegacnik
Keyword(s):  
Fluidized Bed ◽  
Circulating Fluidized Bed ◽  
Industrial Process ◽  
Calorific Value ◽  
Fluidization Regime ◽  
Entire Height ◽  
Proper Design ◽  
Industrial Unit ◽  
Fluidized Bed Gasifier ◽  
Set Up

The main purpose of a fast internal circulating fluidized bed gasifier is the steam reforming of solid organic matter, like biomass, to a nearly nitrogen-free syngas. The calorific value of this syngas is approximately three times higher than the gas from common air-driven gasifiers. This article deals with a study of the particle dynamics in a 1 MWt fast internal circulating fluidized bed plant and focuses on the design of the gasification reactor?s geometry. Superheated steam is used for the fluidization and gasification in the reactor. The gasification of solid fuels causes an increase in the volume flow of the fluidizing gas and at the same time also a change in the fluidization regime. Approaching a turbulent fluidization regime or even fast fluidization is not desirable. However, with the proper design of reactor, i. e., an appropriately conical bed angle, suitable gasification conditions in the form of a fluidizing regime can be achieved across the entire height of the bed. For the purposes of the experimental research, a semi-industrial unit was set-up. The process was designed and experimentally tested on a lab-scale, cold-flow model and scaled-up to a semi-industrial process. The guidelines for designing the geometry of the gasification reactor were set.

scholarly journals Granular Stack Density’s Influence on Homogeneous Fluidization Regime: Numerical Study Based on EDEM-CFD Coupling

2021 ◽  
Vol 11 (18) ◽  
pp. 8696
Author(s):  
Aboubacar Sidiki Drame ◽  
Li Wang ◽  
Yanping Zhang
Keyword(s):  
Volume Fraction ◽  
Numerical Study ◽  
Initial Density ◽  
Strong Impact ◽  
Fast Kinetics ◽  
Bed Height ◽  
Initial Volume Fraction ◽  
Fluidization Regime ◽  
Original Observation ◽  
Initial Packing

FLUENT and EDEM were applied to simulate liquid–solid coupling in a 3D homogenous fluidization. The dynamics of destabilization of the granular material immersed by homogeneous fluidization were observed. The effect of initial packing density of granular stack and fluidization rate on the fluidization’s transient regime, the configuration of particles in the fluidized bed and the variation of bed height were analyzed and discussed. According to the results, there was an original observation of a strong impact of the initial density of an initially static granular stack on the transient fluidization regime. Depending on the material initial volume fraction, there was a difference in grain dynamics. For an initially loose stack, a homogeneous turbulent fluidization was observed, whereas for an initially dense stack, there was a mass takeoff of the stack. The propagation of wave porosity instability, from the bottom to the top of the stack with fast kinetics that decompacted the medium, followed this mass takeoff.

scholarly journals Systematic Study of Pressure Fluctuation in the Riser of a Dual Inter-Connected Circulating Fluidized Bed: Using Single and Binary Particle Species

Processes ◽  
2019 ◽  
Vol 7 (12) ◽  
pp. 890 ◽  
Author(s):  
Yusif A. Alghamdi ◽  
Zhengbiao Peng ◽  
Caimao Luo ◽  
Zeyad Almutairi ◽  
Behdad Moghtaderi ◽  
...  
Keyword(s):  
Fluidized Bed ◽  
Pressure Fluctuation ◽  
Circulating Fluidized Bed ◽  
Pressure Fluctuations ◽  
Single Species ◽  
Terminal Velocity ◽  
Operating Conditions ◽  
Cold Flow ◽  
Fluidization Regime ◽  
Spectrum Density

This study systematically investigates the pressure fluctuation in the riser of a dual interconnected circulating fluidized bed (CFB) representing a 10 kWth cold-flow model (CFM) of a chemical-looping combustion (CLC) system. Specifically, a single-species system (SSS) and a binary-mixtures system (BMS) of particles with different sizes and densities were utilized. The pressure fluctuation was analyzed using the fast Fourier transform (FFT) method. The effect of introducing a second particle, changing the inventory, composition (i.e., 5, 10 to 20 wt.%), particle size ratio, and fluidization velocity were investigated. For typical SSS experiments, the results were similar to those scarcely reported in the literature, where the pressure fluctuation intensity was influenced by varying the initial operating conditions. The pressure fluctuations of BMS were investigated in detail and compared with those obtained from SSS experiments. BMS exhibited different behaviour; it had intense pressure fluctuation in the air reactor and in the riser when compared to SSS experiments. The standard deviation (SD) of the pressure fluctuation was found to be influenced by the fluidization regime and initial operating conditions, while the power spectrum density (PSD) values were more sensitive to the presence of the particles with the higher terminal velocity in the binary mixture.

Using particle trajectory for determining the fluidization regime in gas–solid fluidized beds

2012 ◽  
Vol 23 (3) ◽  
pp. 349-351 ◽  
Author(s):  
M.R. Tamadondar ◽  
H. Azizpour ◽  
R. Zarghami ◽  
N. Mostoufi ◽  
J. Chaouki
Keyword(s):  
Fluidized Beds ◽  
Particle Trajectory ◽  
Fluidization Regime

Development and industrial adoption of a drying process of crystalline vitamin D2 under a pulse fluidization regime

1981 ◽  
Vol 15 (7) ◽  
pp. 528-529
Author(s):  
F. I. Luknitskai ◽  
Yu. Kh. Lokshin ◽  
M. S. Yufa ◽  
L. N. Vysotskii ◽  
N. P. Selyugin ◽  
...  
Keyword(s):  
Vitamin D2 ◽  
Drying Process ◽  
Fluidization Regime ◽  
Industrial Adoption

scholarly journals A NEW SCALING STRATEGY OF BUBBLING FLUIDIZED BED REACTORS BASED ON POPULATION-BALANCE MODEL

2021 ◽  
Author(s):  
Robert Macias ◽  
Juan Maya ◽  
Farid Chejne ◽  
Carlos Londoño ◽  
Javier De La Cruz
Keyword(s):  
Fluidized Bed ◽  
Chemical Reactivity ◽  
Operating Conditions ◽  
Balance Model ◽  
Fluidized Bed Reactors ◽  
Dimensionless Number ◽  
Computational Simulations ◽  
Fluidization Regime ◽  
New Strategy ◽  
Bubbling Fluidized Bed

This work proposes a new strategy for the scaling of bubbling fluidized bed reactors. This strategy is based on the bubble size distribution, bubble coalescence phenomenon, and the chemical reactivity, allowing to deduct the dimensionless number Chejne-Macias-Maya that must remain constant at different scales to guarantee the fluidization regime. The proposed strategy is validated from computational simulations carried out at different operating conditions. Additionally, limits for the validity of this scaling strategy were determined, which agrees with those reported in the literature.

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