Dynamics of intraparticle desorption and chemical reaction in fixed-beds using inert core spherical particles

2011 ◽  
Vol 172 (1) ◽  
pp. 500-506 ◽  
Author(s):  
K. Shams ◽  
S. Najari
Keyword(s):  
Chemical Reaction ◽  
Spherical Particles ◽  
Inert Core ◽  
Fixed Beds

Volatilization of Packed Beds of Oil Sand Particles

1987 ◽  
Vol 109 (2) ◽  
pp. 71-74
Author(s):  
M. A. Abdrabboh ◽  
G. A. Karim
Keyword(s):  
Experimental Data ◽  
Mass Transfer ◽  
Reynolds Numbers ◽  
Spherical Particles ◽  
Packed Beds ◽  
Oil Sand ◽  
Transfer Coefficients ◽  
Simple Analytical Expression ◽  
Low Reynolds Numbers ◽  
Fixed Beds

Based on a quasi-steady system, published experimental data on mass transfer in packed beds of spherical particles at relatively low Reynolds numbers, were employed to estimate the convective mass-transfer coefficients in the bed in terms of the corresponding values for single particles. The average transient fluid concentrations within the bed of particles were also obtained in terms of the corresponding single-particle concentrations using the lumped-heat-capacity system. Thus, experimental data published on volatilization of single oil sand spheres could then be extended to estimate the rates of volatilization of packed beds of oil sand spheres. A simple analytical expression could, therefore, be derived for estimating the transient mass loss from fixed beds of oil sand spheres in terms of the parameters involved.

Sorption dynamics in fixed-beds of inert core spherical adsorbents including axial dispersion and Langmuir isotherm

AIChE Journal ◽  
2009 ◽  
Vol 55 (7) ◽  
pp. 1784-1792 ◽  
Author(s):  
M. Khosravi Koocheksarayi ◽  
K. Shams ◽  
Y. Z. Liu
Keyword(s):  
Langmuir Isotherm ◽  
Axial Dispersion ◽  
Sorption Dynamics ◽  
Inert Core ◽  
Fixed Beds

scholarly journals DEM--CFD modeling and simulations of hydrodynamic characteristics and flow resistance coefficient in fixed-bed reactors

2021 ◽  
Author(s):  
Yaping Li ◽  
Le Xie ◽  
Yonghua Zhou ◽  
Chongwen Jiang ◽  
Hong Zhong
Keyword(s):  
Pressure Drop ◽  
Flow Resistance ◽  
Fixed Bed ◽  
Resistance Coefficient ◽  
Spherical Particles ◽  
Hydrodynamic Characteristics ◽  
Model Parameters ◽  
Large Set ◽  
Fixed Bed Reactors ◽  
Fixed Beds

The ability to predict void fraction, pressure drop, and flow resistance coefficient in fixed-bed reactors is significant to their optimal design. In this study, the discrete element method (DEM) is combined with computational fluid dynamics (CFD) to simulate the hydrodynamic characteristics of fixed-beds. A realistic random packing structure for fixed-beds with spherical particles was generated via the DEM method and then meshed using Ansys ICEM software for the CFD simulation. A grid independency study was performed to select appropriate grid model parameters. A large set of numerical experiments was conducted to investigate the hydrodynamic characteristics with respect to different inlet velocities and particle sizes, and the simulated pressure drop data were used to calculate the flow resistance coefficient. The output flow resistance coefficients agreed well with those calculated by the classical models in laminar and turbulent flow regimes, thereby indicating the accuracy and advantage of the proposed DEM–CFD approach.

STEM Study of Surface Plasmon Excitation in Small Spherical Particles

1990 ◽  
Vol 48 (2) ◽  
pp. 42-43
Author(s):  
Daniel UGARTE
Keyword(s):  
Energy Loss ◽  
Spherical Particles ◽  
Small Particles ◽  
Bulk Materials ◽  
Low Loss ◽  
Plasmon Excitation ◽  
Surface Modes ◽  
Surface Plasmon Excitation ◽  
Analytical Electron ◽  
Analytical Electron Microscope

Small particles exhibit chemical and physical behaviors substantially different from bulk materials. This is due to the fact that boundary conditions can induce specific constraints on the observed properties. As an example, energy loss experiments carried out in an analytical electron microscope, constitute a powerful technique to investigate the excitation of collective surface modes (plasmons), which are modified in a limited size medium. In this work a STEM VG HB501 has been used to study the low energy loss spectrum (1-40 eV) of silicon spherical particles [1], and the spatial localization of the different modes has been analyzed through digitally acquired energy filtered images. This material and its oxides have been extensively studied and are very well characterized, because of their applications in microelectronics. These particles are thus ideal objects to test the validity of theories developed up to now.Typical EELS spectra in the low loss region are shown in fig. 2 and energy filtered images for the main spectral features in fig. 3.

Directional observation on lipid of male nectary of Lindera megaphylla hemsl. by the rapid embedding method with polyethylene glycol (PEG)

1990 ◽  
Vol 48 (3) ◽  
pp. 718-719
Author(s):  
Dai Dalin ◽  
Guo Jianmin
Keyword(s):  
Electron Microscope ◽  
Polyethylene Glycol ◽  
Chemical Reaction ◽  
Traditional Method ◽  
Osmium Tetroxide ◽  
Unsaturated Lipid ◽  
Embedding Method ◽  
Long Period ◽  
New Methods

Lipid cytochemistry has not yet advanced far at the EM level. A major problem has been the loss of lipid during dehydration and embedding. Although the adoption of glutaraldehyde and osmium tetroxide accelerate the chemical reaction of lipid and osmium tetroxide can react on the double bouds of unsaturated lipid to from the osmium black, osmium tetroxide can be reduced in saturated lipid and subsequently some of unsaturated lipid are lost during dehydration. In order to reduce the loss of lipid by traditional method, some researchers adopted a few new methods, such as the change of embedding procedure and the adoption of new embedding media, to solve the problem. In a sense, these new methods are effective. They, however, usually require a long period of preparation. In this paper, we do research on the fiora nectary strucure of lauraceae by the rapid-embedding method wwith PEG under electron microscope and attempt to find a better method to solve the problem mentioned above.

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