Bed height and material density effects on fluidized bed hydrodynamics

The aim of this study is to use the dry fibers of date palm as low-cost biosorbent for the removal of Cd(II), and Ni(II) ions from aqueous solution by fluidized bed column. The effects of many operating conditions such as superficial velocity, static bed height, and initial concentration on the removal efficiency of metal ions were investigated. FTIR analyses clarified that hydroxyl, amine and carboxyl groups could be very effective for bio-sorption of these heavy metal ions. SEM images showed that dry fibers of date palm have a high porosity and that metal ions can be trapped and sorbed into pores. The results show that a bed height of 6 cm, velocity of 1.1Umf and initial concentration for each heavy metal ions of 50 mg/L are most feasible and give high removal efficiency. The fluidized bed reactor was modeled using ideal plug flow and this model was solved numerically by utilizing the MATLAB software for fitting the measured breakthrough results. The breakthrough curves for metal ions gave the order of bio-sorption capacity as follow: Cd(II)]Ni(II).

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Experimental constraints on volcanic ash generation and clast morphometrics in pyroclastic density currents and granular flows

10.5194/egusphere-egu21-8568 ◽

2021 ◽

Author(s):

Adrian Hornby ◽

Ulrich Kueppers ◽

Benedikt Maurer ◽

Carina Poetsch ◽

Donald Dingwell

Keyword(s):

Experimental Approach ◽

Direct Evidence ◽

General Description ◽

Pyroclastic Density Currents ◽

Density Currents ◽

Shape Factors ◽

Material Density ◽

Bed Height ◽

Rotary Drum ◽

Basal Flow

<p>Pyroclastic density currents (PDCs) present perhaps the greatest proximal primary hazard of volcanic activity and produce abundant fine ash that can present a range of health, environment and infrastructure hazards. However, direct, fully quantitative observation of ash production in PDCs is lacking, and little direct evidence exists to constrain the parameters controlling ash generation in PDCs. Here, we use an experimental approach to investigate the effects of starting mass, material density and ash removal on the efficiency of ash generation and concurrent clast rounding in the dense basal flow of PDCs. We employ a rotary drum to tumble pumice and scoria lapilli clasts over multiple transport &#8220;distance&#8221; steps (from 0.2 to 6&#160;km). We observe increased ash generation rates with the periodic removal of ash during the experiments and with increasing starting mass. By scaling to the bed height and clast diameter we obtain a general description for ash production in all experiments as a function of flow distance, bed height and average clast diameter. We confirm that changes in lapilli shape factors correlate with the ash fraction generated and that the grain size of ash produced decreases with distance. Finally, we estimate shear rate in our experiments and calculate the inertial number, which describes the ratio between clast-scale and flow-scale rearrangement during flow. We show that, under certain conditions, fractional ash production can be calculated accurately for any starting mass solely as a function of the inertial number and the flow distance. This work sheds light on some of the first systematic and generalizable experimental parameterizations of ash production and associated clast evolution in PDCs and should advance our ability to understand flow mobility and associated hazards.</p>

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Transient Computational Fluid Dynamics/Discrete Element Method Simulation of Gas–Solid Flow in a Spouted Bed and Its Validation by High-Speed Imaging Experiment

Journal of Energy Resources Technology ◽

10.1115/1.4037685 ◽

2017 ◽

Vol 140 (1) ◽

Cited By ~ 6

Author(s):

Ling Zhou ◽

Lingjie Zhang ◽

Weidong Shi ◽

Ramesh Agarwal ◽

Wei Li

Keyword(s):

Fluid Dynamics ◽

Computational Fluid Dynamics ◽

Discrete Element Method ◽

Fluidized Bed ◽

High Speed ◽

Discrete Element ◽

Bubble Shape ◽

High Speed Imaging ◽

Bed Height ◽

Simulation Results

A coupled computational fluid dynamics (CFD)/discrete element method (DEM) is used to simulate the gas–solid two-phase flow in a laboratory-scale spouted fluidized bed. Transient experimental results in the spouted fluidized bed are obtained in a special test rig using the high-speed imaging technique. The computational domain of the quasi-three-dimensional (3D) spouted fluidized bed is simulated using the commercial CFD flow solver ANSYS-fluent. Hydrodynamic flow field is computed by solving the incompressible continuity and Navier–Stokes equations, while the motion of the solid particles is modeled by the Newtonian equations of motion. Thus, an Eulerian–Lagrangian approach is used to couple the hydrodynamics with the particle dynamics. The bed height, bubble shape, and static pressure are compared between the simulation and the experiment. At the initial stage of fluidization, the simulation results are in a very good agreement with the experimental results; the bed height and the bubble shape are almost identical. However, the bubble diameter and the height of the bed are slightly smaller than in the experimental measurements near the stage of bubble breakup. The simulation results with their experimental validation demonstrate that the CFD/DEM coupled method can be successfully used to simulate the transient gas–solid flow behavior in a fluidized bed which is not possible to simulate accurately using the granular approach of purely Euler simulation. This work should help in gaining deeper insight into the spouted fluidized bed behavior to determine best practices for further modeling and design of the industrial scale fluidized beds.

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The Pressure Drop at Critical Fluidization of Large Particles in Vibrated Fluidization Bed

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.550-553.2763 ◽

2012 ◽

Vol 550-553 ◽

pp. 2763-2766

Author(s):

Xue Jun Zhu ◽

Jun Deng

Keyword(s):

Pressure Drop ◽

Fluidized Bed ◽

Large Particle ◽

Particle Diameter ◽

Future Design ◽

Vibration Strength ◽

Bed Height ◽

Large Particles ◽

Vibrated Fluidized Bed ◽

Critical Fluidization

The pressure drop at critical fluidization for two-dimensional vibrated fluidized bed(240 mm×80 mm) was studied, with large particle glass beads of average diameters dp of 1.8mm, 2.5mm and 3.2mm.The effect of the vibration strength, the static bed height and the particle diameter on the pressure drop was analyzed. The results of the study show that the pressure drop decreases with the increase of the vibration strength. It plays an even more prominent part with decreases of the static bed height and the particle diameter. The empirical correlation equations to predict the pressure drop was established, and the results of the prediction was compared with the experimental data, the error is in range of ±10%. The results can provide references for future design and research on the vibrated fluidized bed.

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CFD-DEM Numerical Simulation and Experimental Validation of Heat Transfer and Two-Component Flow in Fluidized Bed

International Journal of Chemical Reactor Engineering ◽

10.1515/ijcre-2016-0207 ◽

2017 ◽

Vol 16 (1) ◽

Cited By ~ 1

Author(s):

Feihong Guo ◽

Zhaoping Zhong

Keyword(s):

Heat Transfer ◽

Numerical Simulation ◽

Fluidized Bed ◽

Quartz Sand ◽

Thermal Imager ◽

Gas Velocity ◽

Bed Height ◽

Two Component ◽

Superficial Gas Velocity ◽

Infrared Thermal Imager

AbstractBased on the improved computational fluid dynamics and discrete element method (CFD-DEM), heat transfer and two-component flow of biomass and quartz sand have been studied from experiments and numerical simulation in this paper. During experiments, the particle temperature and moving images are respectively recorded by infrared thermal imager and high speed camera. With the increase of the velocity, the mixing index (MI) and the cooling rate of the particles are rising. Due to larger heat capacity and mass, the temperature of biomass drops slower than that of quartz sand. Fictitious element method is employed to solve the incompatibility of the traditional CFD-DEM where the cylindrical biomass are considered as an aggregation of numerous fictitious sphere particles arranged in certain sequence. By the comparison of data collected by infrared thermal imager and the simulated results, it can be concluded that experimental data is basically agreement with numerical simulation results. Directly affected by inflow air (25℃), the average temperature of particles in the bed height area (h>30 mm) is about 3 degrees lower than that of the other heights. When the superficial gas velocity is larger, the fluidization is good, and the gas temperature distribution is more uniform in the whole area. On the contrary, bubbles are not easy to produce and the fluidization is restricted at lower superficial gas velocity. Gas-solid heat transfer mainly exists under the bed height of 10 mm, and decreases rapidly on fluidized bed height. The mixing index (MI) is employed to quantitatively discuss the mixing effectiveness, which first rises accelerate, then rising speed decreases, finally tends to a upper limit.

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Electrolytic Treatment of Cyanide Wastes VI. Effect of the Bed Height of a Fluidized Bed Electrode Cell on the Electrolytic Oxidation of Cyanide Ion

Denki Kagaku oyobi Kogyo Butsuri Kagaku ◽

10.5796/kogyobutsurikagaku.57.682 ◽

1989 ◽

Vol 57 (7) ◽

pp. 682-686 ◽

Cited By ~ 4

Author(s):

Morihiro YASUDA ◽

Akira OHKAWA ◽

Masaru TONSHO ◽

Saburo YASUKAWA

Keyword(s):

Fluidized Bed ◽

Cyanide Ion ◽

Bed Height ◽

Electrode Cell ◽

Electrolytic Oxidation ◽

Fluidized Bed Electrode ◽

Electrolytic Treatment

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Study on Fluidization Characteristics of Magnetically Fluidized Beds for Microfine Particles

Minerals ◽

10.3390/min12010061 ◽

2022 ◽

Vol 12 (1) ◽

pp. 61

Author(s):

Yakun Tian ◽

Shulei Song ◽

Xuan Xu ◽

Xinyu Wei ◽

Shanwen Yan ◽

...

Keyword(s):

Magnetic Field ◽

Field Strength ◽

Fluidized Bed ◽

Magnetic Field Strength ◽

Fluidized Beds ◽

Expansion Rate ◽

Gas Velocity ◽

Bed Height ◽

Bed Expansion ◽

The Magnetic Field

The bed pressure drop, minimum fluidized gas velocity, bed density, and bed expansion rate are important parameters characterizing the fluidization characteristics of gas-solid fluidized beds. By analyzing these parameters, the advantages and disadvantages of the fluidization state can be known. In this study, experiments were conducted to study the fluidization characteristics of a gas-solid magnetically fluidized bed for microfine particles by changing the magnetic field strength, magnetic field addition sequence, and static bed height. The experimental results show that when the magnetic field strength increased from 0 KA/m to 5 KA/m, the minimum fluidized gas velocity of particles increased from 4.42 cm/s to 10.32 cm/s, while the bed pressure drop first increased and then decreased. When the magnetic field strength is less than 3.4 KA/m, the microfine particles in the bed are mainly acted on by the airflow; while when the magnetic field strength is greater than 3.4 KA/m, the microfine particles are mainly dominated by the magnetic field. The magnetic field addition sequence affects the fluidization quality of microfine particles. The fluidized bed with ‘adding magnetic field first’ shows a more stable fluidization state than ‘adding magnetic field later’. Increasing of the static bed height reduces the bed expansion rate. The bed expansion rate is up to 112.5% at a static bed height of h0 = 40 mm and H = 5 KA/m. This will broaden the range of density regulation of a single magnetic particle and lay the advantage of gas-solid magnetically fluidized bed for microfine particles in the field of separation of fine coal.

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