scholarly journals Sedimentation Velocity and Expansion Ratio of Emulsion Phase in Gas-Solid Fluidized Bed

1973 ◽  
Vol 37 (5) ◽  
pp. 485-490,a1 ◽  
Author(s):  
Shigeharu Morooka ◽  
Masayuki Nshinaka ◽  
Yasuo Kato
Keyword(s):  
Fluidized Bed ◽  
Expansion Ratio ◽  
Sedimentation Velocity ◽  
Emulsion Phase

Contribution of hydrodynamic characteristics on the performance of an aerobic biofilm conical fluidized bed

2011 ◽  
Vol 63 (6) ◽  
pp. 1160-1167 ◽  
Author(s):  
D. Zhou ◽  
X. T. Bi ◽  
S. Dong
Keyword(s):  
Fluidized Bed ◽  
Microbial Population ◽  
Expansion Ratio ◽  
Hydrodynamic Characteristics ◽  
Internal Circulation ◽  
Axial Distribution ◽  
Biofilm Thickness ◽  
Cell Matrix ◽  
Bed Expansion ◽  
Conical Fluidized Bed

The performance of a conical fluidized bed (TFB) bioreactor, including the biofilm thickness, microbial space density, microbial cell matrix and its efficiency for COD degradation at a bed expansion ratio of 14 to 90%, was studied and compared with a cylindrical fluidized bed (CFB) bioreactor. The hydrodynamic characteristics of the TFB, especially the internal-circulation of bioparticles associated with its unique tapered geometry of the bed, created a much more uniform axial distribution of the bioparticles, leading to the formation of thinner and more compacted biofilms in the TFB compared to that in the CFB. The thinner biofilm in the TFB tended to be stable and possessed more than 6 times of microbial population density compared to the CFB. As a result, thinner biofilms in the TFB contributed to a higher COD removal efficiency, which remained at over 95% at operated expansion ratios, about 15 to 25% higher than that in the CFB.

Effect of the Shape of the Baffles on the Hydrodynamics of a Fluidized Bed

2008 ◽  
Vol 6 (1) ◽  
Author(s):  
Srinivasa Rao Venkata Naga Kaza
Keyword(s):  
Fluidized Bed ◽  
Fluidized Beds ◽  
Gas Flow ◽  
Experimental Studies ◽  
Expansion Ratio ◽  
Blockage Ratio ◽  
Minimum Fluidization Velocity ◽  
Fluidization Velocity ◽  
Minimum Fluidization ◽  
Bubbling Fluidized Bed

Gas flow in a gas–solid fluidized bed is characterized by the predominance of bubbles. When gas flow is more than the minimum fluidization velocity, the top of the fluidized bed may fluctuate vigorously leading to unstable operation. Bed fluctuation and fluidization quality are interrelated. The quality of fluidization can largely be improved by introducing baffles in bubbling and turbulent fluidized beds. In the present work three baffle geometries, i.e., circular, triangular and square are used to determine different hydrodynamic parameters such as minimum fluidization velocity, bed expansion, pressure drop across the bed, fluctuation ratio, expansion ratio, etc. in a bubbling fluidized bed. A new parameter blockage ratio is introduced to analyze the behaviour of baffled fluidized beds. It is found from the current experimental studies that the blockage ratio mainly influences the hydrodynamics of the bed rather than the shape of the baffle.

The motion of particles near a bubble in a gas-fluidized bed

1996 ◽  
Vol 323 ◽  
pp. 377-385 ◽  
Author(s):  
M. A. Gilbertson ◽  
J. G. Yates
Keyword(s):  
Particle Size ◽  
Fluidized Bed ◽  
Central Region ◽  
Fluidized Beds ◽  
Gas Bubbles ◽  
Toroidal Vortex ◽  
Emulsion Phase ◽  
Light Particles

Most models of gas bubbles in fluidized beds are based on the assumption of an empty central region, the void, surrounded by a ‘cloud’ or ‘shell’ of particles whose voidage is larger than that of the remote emulsion phase. Batchelor & Nitsche (1994) investigated the formation of a void by tracking the paths of particles initially within a buoyant ‘blob’ of gas that has the form of a toroidal vortex. They showed that the particles dropped through the floor of the blob under the influence of gravity, leaving it empty. This paper extends their method to particles initially outside the blob. It is shown that inertia allows these particles to penetrate the blob and it is the extent of this penetration that determines the size of the void. The void is nearly as large as the blob for small, light particles, but becomes smaller relative to the blob with increasing particle size and weight until it disappears altogether. This provides an explanation for experimental observations of voids smaller than the blob (or ‘cloud’ as it is sometimes known), and suggests that when examining bubbles in a gas-fluidized bed the most significant dimension is the diameter of the blob and not that of the void.

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