scholarly journals Effect of Particle Size Distributions on Minimum Fluidization Velocity with Varying Gas Temperature

2020 ◽  
Vol 11 (11) ◽  
pp. 524-529
Author(s):  
Krittin Korkerd ◽  
◽  
Chaiwat Soanuch ◽  
Pornpote Piumsomboon ◽  
Benjapon Chalermsinsuwan
Keyword(s):  
Particle Size ◽  
Standard Deviation ◽  
Particle Diameter ◽  
Skewed Distribution ◽  
Average Particle ◽  
Average Particle Diameter ◽  
Gas Temperature ◽  
Minimum Fluidization Velocity ◽  
Fluidization Velocity ◽  
Minimum Fluidization

The particle size distribution (PSD) is an important property that can influence the hydrodynamics and chemical conversion in fluidized bed system. The objective of this study is to investigate the effect of PSDs of particle and gas temperature on minimum fluidization velocity (Umf). Here, the silica sand with three average diameters and five PSDs including narrow cut, Gaussian, Gaussian with high standard deviation, negative skewed distribution and positive skewed distribution were used. The considered gas temperature ranged from 30 to 120 °C. The results showed that the Umf values with wide PSDs were lower than the Umf values for narrow cut particle with the same average diameter. The reason can be explained by the addition of smaller particle will improve the fluidization characteristics. The standard deviation and skewness of PSD also influenced on the Umf. The Umf was observed to decrease with increasing gas temperature. In addition, the effect of average particle diameter could also be seen. The Umf increased with the increasing of average particle diameter.

Use of Calixarene Host Molecules to Stabilize Quantum-confined Cadmium Sulfide Formation

1992 ◽  
Vol 272 ◽  
Author(s):  
Robin R. Chandler ◽  
Jeffery L. Coffer ◽  
C. David Gutsche ◽  
Iftikhar Alam ◽  
Hong Yang ◽  
...  
Keyword(s):  
Particle Size ◽  
Particle Diameter ◽  
Spectroscopic Studies ◽  
Average Particle ◽  
Average Particle Diameter ◽  
Absorption And Emission ◽  
Zinc Blende ◽  
High Resolution Tem ◽  
Quantum Confined ◽  
Macrocyclic Molecules

ABSTRACTWe describe here the use of calixarenes, methylene (-CH2-) linked phenolic macrocyclic molecules, to stabilize the formation of quantum-confined (Q-) CdS clusters. Specifically, we focus on the use of an amino-derivatized calixarene, para-[(dimethylamino)- methyl]calix[6]arene, to stabilize Q-CdS clusters which have been characterized by High Resolution TEM (HREM), as well as absorption and emission spectroscopies. Under typical preparative conditions, an average particle diameter of 36 Å is obtained. HREM, in combination with Selected Area Diffraction (SAD), confirms the structure of the clusters as zinc blende CdS. Spectroscopic studies using absorption and emission methods indicate that both particle size and cluster photophysics are sensitive to the ratio of CdS to calixarene.

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.

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.

Fluidization characteristics of wide-size-distribution particles in a gas-solid fluidized bed reactor

2020 ◽  
Vol 18 (12) ◽  
Author(s):  
Chaojie Li ◽  
Weiwen Wang ◽  
Xiuling Guo ◽  
Jihai Duan
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Fluidized Bed ◽  
Particle System ◽  
Fluidized Bed Reactor ◽  
Minimum Fluidization Velocity ◽  
Fluidization Velocity ◽  
Minimum Fluidization ◽  
Wide Size Distribution

AbstractFluidization characteristics of wide-size-distribution particles in the gas-solid fluidized bed reactor are investigated by applying experiment and computational fluid dynamics (CFD) methods. In this study, three types of narrow-cut particles and two sets of wide-size-distribution particles are used. A model considering particle size distribution is developed in the Eulerian frame, and good agreement between numerical results and experimental data is observed. The particle size distribution has an important effect on the average bed voidage. The axial particle diameter profiles along bed height have a “S” type feature. Minimum fluidization velocity is determined from the standard deviation of pressure fluctuations and bubble dynamics are analyzed based on power spectra. Results indicate that fine particle composition can reduce the minimum fluidization velocity of wide-size-distribution particle system and the bubble diameter in the fluidized bed.

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.

“Colloidal” Zinc Oxide

1937 ◽  
Vol 10 (2) ◽  
pp. 309-311
Author(s):  
H. A. Curran ◽  
T. R. Dawson
Keyword(s):  
Particle Size ◽  
Zinc Oxide ◽  
Manufacturing Industry ◽  
Average Particle Size ◽  
Particle Diameter ◽  
Average Particle ◽  
Average Particle Diameter ◽  
Zinc Oxides ◽  
Two Samples ◽  
Good Grade

Abstract Some ten years ago, when so-called “colloidal” zinc oxides were being introduced to the rubber manufacturing industry, two samples were investigated to determine their behavior in rubber compared with ordinary good quality zinc oxide used in rubber. According to accounts published at the time, “colloidal” zinc oxide possesses an average particle size just within the limit of resolution of high-power microscopes, and an average particle diameter of 0.15 micron. In rubber it has been claimed to impart superior reinforcement, higher tensile strength, greater resistance to abrasion, and enhanced activation of organic accelerators. In the following report, samples A and B represent two samples of the same grade of “colloidal” zinc oxide, and C a good grade of regular zinc oxide.

Preparation of Mesocarbon Microbeads (MCMB) from Suspensions of a Synthetic Naphthalene Isotropic Pitch

2017 ◽  
Vol 753 ◽  
pp. 231-236
Author(s):  
Sheng Juan Ji ◽  
Xiang Lin Cheng ◽  
Jian Hong Zhao ◽  
Qing Ling Bi ◽  
Liu Cheng Wang ◽  
...  
Keyword(s):  
Particle Size ◽  
Particle Diameter ◽  
Average Particle ◽  
Average Particle Diameter ◽  
X Ray ◽  
Mesocarbon Microbeads ◽  
Dispersion Degree ◽  
Isotropic Pitch ◽  
Particle Size Analyzer ◽  
Size Dispersion

A synthetic naphthalene isotropic pitch, which was manufactured with HF/BF3 acting as catalyst, was used as material to prepare mesocarbon microbeads (MCMB) through suspension method. The material pitch was dissolved in tetrahydrofuran (THF) and the pitch-THF solution is dispersed in a 2% polyvinyl alcohol aqueous solution. After THF was volatilized, the solution was cooled and then filtered to attain little pitch sphere. The pitch spheres were oxidized in 65% HNO3 solution, and the oxidized pitch spheres were carbonized up to 1000°C to get MCMB. MCMB was analyzed by scanning electron microscope (SEM), laser particle size analyzer and X ray diffractometer. The result showed that the particle size of MCMB was 2-30 μm and the average particle diameter size of D50 was 15.83 μm. The particle size distribution accords to the normal distribution, and the particle size dispersion degree was 0.7574. The effect of 65% HNO3 oxidation of the pitch sphere showed a satisfactory result. After carbonization at 1000°C, the oxidized pitch sphere exhibited a better orientation arrangement, the distance between the aromatic plane (d002) was decreased, and the thickness of the piled plane is increased.

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