scholarly journals Modeling of the Minimum Fluidization Velocity and the Incipient Fluidization Pressure Drop in a Conical Fluidized Bed with Negative Pressure

2020 ◽  
Vol 10 (24) ◽  
pp. 8764
Author(s):  
Sheng Fang ◽  
Yanding Wei ◽  
Lei Fu ◽  
Geng Tian ◽  
Haibin Qu
Keyword(s):  
Particle Size ◽  
Pressure Drop ◽  
Minimum Fluidization Velocity ◽  
Ergun Equation ◽  
Advantages And Disadvantages ◽  
Fluidization Velocity ◽  
Minimum Fluidization ◽  
Series Of Experiments ◽  
Superficial Gas Velocity ◽  
Dimensional Analysis Method

The modeling of the minimum fluidization velocity (U0mf) and the incipient fluidization pressure drop (ΔPmf) is a valuable research topic in the fluidization field. In this paper, first, a series of experiments are carried out by changing the particle size and material mass to explore their effects on U0mf and ΔPmf. Then, an Ergun equation modifying method and the dimensional analysis method are used to obtain the modeling correlations of U0mf and ΔPmf by fitting the experimental data, and the advantages and disadvantages of the two methods are discussed. The experimental results show that U0mf increases significantly with increasing particle size but has little relationship with the material mass; ΔPmf increases significantly with increasing material mass but has little relationship with the particle size. Experiments with small particles show a significant increase at large superficial gas velocity; we propose a conjecture that the particles’ collision with the fluidization chamber’s top surface causes this phenomenon. The fitting accuracy of the modified Ergun equation is lower than that of the dimensionless model. When using the Ergun equation modifying method, it is deduced that the gas drag force is approximately 0.8995 times the material total weight at the incipient fluidized state.

Fluidization of Geldart Type-D Particles in a Swirling Fluidized Bed

2011 ◽  
Vol 110-116 ◽  
pp. 3720-3727 ◽  
Author(s):  
Mohd Faizal Mohideen ◽  
Suzairin Md Seri ◽  
Vijay Raj Raghavan
Keyword(s):  
Particle Size ◽  
Pressure Drop ◽  
Fluidized Bed ◽  
Fluidized Beds ◽  
Superficial Velocity ◽  
Minimum Fluidization Velocity ◽  
Fluidization Velocity ◽  
Type D ◽  
Minimum Fluidization ◽  
Bed Material

Geldart Type-D particles are often associated with poor fluidization characteristics due to their large sizes and higher densities. This paper reports the hydrodynamics of various Geldart Type-D particles when fluidized in a swirling fluidized bed (SFB). Four different sizes of particles ranging from 3.85 mm to 9.84 mm with respective densities ranging from 840 kg/m3 to 1200 kg/m3 were used as bed material to study the effect of various bed weights (500 gram to 2000 gram) and centre bodies (cone and cylinder) for superficial velocities up to 6 m/s. The performance of the SFB was assessed in terms of pressure drop values, minimum fluidization velocity, Umf and fluidization quality by physical observation on regimes of operation. The swirling fluidized bed showed excellent capability in fluidizing Geldart Type-D particles in contrast to the conventional fluidized beds. The bed pressure drop of increased with superficial velocity after minimum fluidization as a result of increasing centrifugal bed weight. It was also found that the particle size and centre body strongly influence the bed hydrodynamics.

Minimum Fluidization Velocity of Fine Particles

2008 ◽  
Vol 591-593 ◽  
pp. 335-340 ◽  
Author(s):  
Cássia Regina Cardoso ◽  
Carlos Henrique Ataíde ◽  
J.M. Abreu
Keyword(s):  
Pressure Drop ◽  
Fine Particles ◽  
Zinc Powder ◽  
Gas Velocity ◽  
Minimum Fluidization Velocity ◽  
Fluidization Velocity ◽  
Glass Spheres ◽  
Minimum Fluidization ◽  
Industrial Unit ◽  
Superficial Gas Velocity

The minimum fluidization velocity is an important parameter in the design and operation of an industrial unit of fluidization. In the present work the minimum fluidization velocities of fine particles were obtained through two experimental methodologies. The first one is the classic procedure to determine that parameter analyzing the diagram of medium pressure drop in the bed in function of the superficial gas velocity, during the defluidization of the bed. And the second is the technique of identifying the minimum fluidization velocity interpreting the behavior of the normalized standard deviation of the pressure drop in the bed. A cylindrical bed of transparent acrylic was used in the process and the used particles were glass spheres, FCC and zinc powder. To compare the precision of the two methodologies some equations that predict the minimum fluidization velocity were used.

scholarly journals SIMULASI PENGARUH KECEPATAN GAS TERHADAP KARAKTERISTIK FLUIDISASI PADA FLUIDIZED BED MENGGUNAKAN METODE CFD

POROS ◽  
2018 ◽  
Vol 16 (1) ◽  
Author(s):  
Asyari Daryus Daryus
Keyword(s):  
Pressure Drop ◽  
Fluidized Bed ◽  
Particle Density ◽  
Gas Velocity ◽  
Experiment Data ◽  
Minimum Fluidization Velocity ◽  
Fluidization Velocity ◽  
Minimum Fluidization ◽  
Gas Fluidization ◽  
Simulation Results

The gas fluidization velocity or superficial gas velocity entering the fluidized bed will affect the fluidization in fluidized bed. If the superficial velocity is below the minimum fluidization velocity then there is no fluidization, and if it is more than it should be then the fluidization characteristic will be different. To obtain the effect of gas fluidization velocity to fluidization characteristics, it had been conducted the research on lab scale fluidized bed using CFD simulation method validated with the experiment data. The simulations used Gidaspow model for drag force and k-ε model for turbulent flow. From the experiments obtained that the minimum fluidization velocity was 0.4 m/s and the pressure drop was around 700 Pa. The simulation results for pressure drop across the bed were close to the experiment data for the gas fluidization velocity equal and bigger than the minimum fluidization velocity. For the velocity below the minimum fluidization velocity, there was the big differences between the simulation results and the experiment, so the simulation results cannot be used. For the fluidization velocity of 0.4 m/s and 0.45 m/s, fluidized bed showed the bubbling phenomena, and the higher velocity showed the bigger bubble. For the fluidization velocity of 0.50 m/s to 0.70 m/s, the fluidized bed showed the turbulent regime. In this regime, the bubble was breaking instead of growing and there was no clear bed surface observed. The simulation result for particle density showed that if the gas velocity was higher, the density of particles at the base of bed was decreasing since many of the particles was moving upwards. The particle density was lower in this regime than that of bubbling regime.

Hydrodynamic Studies on Three-Phase Combined (Internal & External) Loop Airlift Fluidized Bed Reactor Using Newtonian and non-Newtonian Liquids: Minimum Fluidization Velocity and Liquid Holdup

2011 ◽  
Vol 9 (1) ◽  
Author(s):  
Sivakumar Venkatachalam ◽  
Akilamudhan Palaniappan ◽  
Kannan Kandasamy
Keyword(s):  
Fluidized Bed Reactor ◽  
Newtonian Fluids ◽  
Experimental Results ◽  
Gas Velocity ◽  
Liquid Holdup ◽  
Minimum Fluidization Velocity ◽  
Fluidization Velocity ◽  
Minimum Fluidization ◽  
Newtonian Liquids ◽  
Superficial Gas Velocity

A novel combined airlift loop fluidized bed reactor was proposed in this work. The internal and external loops were combined and the hydrodynamic parameters like minimum fluidization velocity and liquid holdup were studied for Newtonian and non-Newtonian fluids. Studies were conducted using Newtonian fluids of water, n-butanol, 60% and 80% glycerol and non - Newtonian fluids such as 0.25%, 0.6% and 1.0% Carboxy Methyl Cellulose (CMC) aqueous solutions were employed in the liquid phases. Spheres, Bearl saddle and Raschig ring with different sizes were used as solid phase. The experimental results indicated that the increase in particle size and sphericity increased minimum fluidization velocity whereas increase in superficial gas velocity decreased minimum fluidization velocity. In addition, the liquid holdup increased with increase in particle size and superficial liquid velocity. Furthermore, an increase in superficial gas velocity decreased the liquid holdup for Newtonian and non-Newtonian systems. Two separate correlations were developed to predict the minimum fluidization velocity and liquid holdup based on the experimental results for both Newtonian and non-Newtonian liquids for a wide range of operating conditions. The capability of the proposed correlation for minimum fluidization velocity and liquid holdup was examined and reasonable agreement between predicted and experimental results of Newtonian and non-Newtonian liquids suggested the applicability of the proposed correlations.

On the Modeling of Gas-Solid Fluidization: Which Physics Are Most Important to Capture?

2010 ◽  
Author(s):  
Francine Battaglia ◽  
Jonas A. England ◽  
Santhip Kanholy ◽  
Mirka Deza
Keyword(s):  
Experimental Data ◽  
Pressure Drop ◽  
Packing Fraction ◽  
Walnut Shell ◽  
Minimum Fluidization Velocity ◽  
Fluidization Velocity ◽  
Bed Height ◽  
Minimum Fluidization ◽  
Two Parameters ◽  
Bed Material

Recent studies to predict biomass fluidization hydrodynamics motivated a new study to reassess how to model gas-solid characteristics that capture the same physics as that measured in experiments. An Eulerian-Eulerian multifluid model was used to simulate and analyze gas-solid hydrodynamic behavior of the fluidized beds. The relations for the pressure drop measured at fluidization were used to correct for the bed mass by either adjusting the initial solids packing fraction or initial bed height, two parameters that must be specified in a CFD model. Simulations using sand as the bed medium were compared with experiments and it was found that adjusting the bulk density, or in other words, the initial solids volume packing, correctly predicted the pressure drop measured experimentally, but significantly under-predicted the minimum fluidization velocity. By adjusting the initial bed height to correct for the mass, both the pressure drop and minimum fluidization velocity were successfully predicted. Ground walnut shell and ground corncob were used as biomass media and simulations were performed for two reactor bed diameters by simply adjusting the initial bed height to match the measured pressure drop. All of the simulations correctly predicted the pressure drop curves of the experimental data. Further examination of the simulations and experimental data for walnut shell confirmed that adjusting the bed height was the best approach to model fluidization without artificially altering the physics and retaining the known characteristics of the bed material.

Determination of Minimum Fluidization Velocity for Gas-Solid Beds by Experimental Data and Numerical Simulations

2011 ◽  
Author(s):  
Meire Pereira de Souza Braun ◽  
Geraldo Luiz Palma ◽  
Helio Aparecido Navarro ◽  
Paulo Sergio Varoto
Keyword(s):  
Experimental Data ◽  
Numerical Simulations ◽  
Particle Diameter ◽  
Minimum Fluidization Velocity ◽  
Ergun Equation ◽  
Fluidization Velocity ◽  
Minimum Fluidization ◽  
Experimental Apparatus ◽  
Good Agreement

The purpose of this work is to predict the minimum fluidization velocity Umf in a gas-solid fluidized bed. The study was carried out with an experimental apparatus for sand particles with diameters between 310μm and 590μm, and density of 2,590kg/m3. The experimental results were compared with numerical simulations developed in MFIX (Multiphase Flow with Interphase eXchange) open source code [1], for three different sizes of particles: 310mum, 450μm and 590μm. A homogeneous mixture with the three kinds of particles was also studied. The influence of the particle diameter was presented and discussed. The Ergun equation was also used to describe the minimum fluidization velocity. The experimental data presented a good agreement with Ergun equation and numerical simulations.

An Inlet Area for Particle Mixing in a Two-Dimensional Fluidized Bed Using a CFD-DEM Model

2013 ◽  
Vol 467 ◽  
pp. 367-373
Author(s):  
Sumol Sae Heng Pisitsungkakarn
Keyword(s):  
Fluidized Bed ◽  
Distinct Element ◽  
Two Dimensional ◽  
Mixing Index ◽  
Minimum Fluidization Velocity ◽  
Fluidization Velocity ◽  
Particle Mixing ◽  
Minimum Fluidization ◽  
Superficial Gas Velocity ◽  
Dem Model

Fluidized beds are widely used in many industries since they are effective in mixing process. The distinct element method (DEM) has recently received more attention for investigating the phenomena of multiphase flow because the technique is effective in gathering detailed information on the complex phenomena without physically disturbing the flows. A CFD-DEM model has been developed for calculating the minimum fluidization velocity and particle mixing in a two-dimensional fluidized bed. In this research, the inlet area on the particle mixing was investigated. From the result, it was indicated that the developed CFD-DEM model was performed adequately in predicting the phenomena in a two dimensional fluidized bed. The minimum fluidization velocity predicted by the developed model agreed well with the theory and correlation of Grace. Based on Lacey mixing index, it was found that the mixing index increased with an increase in time and superficial gas velocity. In addition, the inlet area of 20% gave a good mixing.

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