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.

The effect of ring baffles on the hydrodynamics of a gas—solid bubbling fluidized bed using computational fluid dynamics

2009 ◽  
Vol 223 (10) ◽  
pp. 2281-2289 ◽  
Author(s):  
S H Hosseini ◽  
R Rahimi ◽  
M Zivdar ◽  
A Samimi
Keyword(s):  
Fluidized Bed ◽  
Volume Fraction ◽  
Fluid Model ◽  
Expansion Ratio ◽  
Bubbling Fluidized Bed ◽  
Gas Volume Fraction ◽  
Two Fluid Model ◽  
Particle Velocities ◽  
Bed Expansion ◽  
Gas Volume

An Eulerian—Eulerian two-fluid model (TFM) integrating the kinetic theory for emulsion phase was used to simulate gas—solid fluidized beds. Validation of the model was investigated based on hydrodynamic parameters such as bed expansion ratio, H/ H0, gas volume fraction profile, bubble behaviour, and motion of the particles. A good agreement was found between numerical results and experimental values. The model was used to study a bubbling fluidized bed (BFB) including the ring baffles. Predicted results show that the ring baffles have an important role in the flow pattern of the bed. Baffles increase the bed expansion height and particle velocities at axial locations on the top of the highest baffle as well as uniform distribution of gas volume fraction between the baffles area. In spite of increasing the dead zones in the bed, ring baffles cause the improvement of mixing and heat transfer in the bed. The present study provides a useful basis for further works on the effect of baffles in BFBs.

Experiment and Numerical Simulation on Slugging Fluidization of Large Particles in Gas-Solid Fluidized Bed

2014 ◽  
Vol 881-883 ◽  
pp. 689-697
Author(s):  
Hui Yang ◽  
Dong Yu Wan ◽  
Chang Qing Cao
Keyword(s):  
Fluidized Bed ◽  
Expansion Ratio ◽  
Solid Particles ◽  
Momentum Exchange ◽  
Cold Model ◽  
State Behavior ◽  
Large Particles ◽  
Computational Fluid Dynamics Cfd ◽  
Bed Expansion

The hydrodynamics of a two-dimensional gas-solid fluidized bed with 0.03 m diameter and 0.3 m height were studied experimentally and computationally. The slugging fluidization of large particles was experimentally investigated and simulated using the Fluent 6.3 computational fluid dynamics (CFD) package. By a series of cold-model test, characterization of gas-solid fluidization with large particles was studied. These results can be used to research slugging characteristics. A multifluid Eulerian model incorporating the kinetic theory for solid particles was applied to simulate the unsteady-state behavior and momentum exchange coefficients were calculated by using the Syamlal-OBrien drag functions. These results of the transfer of fluidization state, maximum bed expansion ratio and pressure fluctuation were systemically simulated in a gas-solid fluidized bed. The modeling predictions compared reasonably well with experimental data and qualitative slugging regime. The simulation results can better predict the slugging fluidization characterization of large particles.

scholarly journals CFD investigation of slugging behavior in a gas-solids fluidized bed

2017 ◽  
Vol 23 (4) ◽  
pp. 529-536 ◽  
Author(s):  
Yanjun Guan ◽  
Xiuying Yao ◽  
Guiying Wu ◽  
Kai Zhang
Keyword(s):  
Fluidized Bed ◽  
Volume Fraction ◽  
Fluid Model ◽  
Predictive Ability ◽  
Momentum Equation ◽  
Expansion Ratio ◽  
Viscous Force ◽  
Spectrum Density ◽  
Two Fluid Model ◽  
Bed Expansion

The hydrodynamics of a slugging fluidized bed is investigated numerically by using a two-fluid model suggested by Brandani and Zhang [22]. Numerical simulations are carried out in the platform of a commercial software package, CFX 4.4, by adding user-defined subroutines. The bed expansion ratio, the pressure drop fluctuation and its power spectrum density at the equipment scale and the solids volume fraction distributions at the grid scale are predicted to explore the slugging fluidization characteristics for Geldart group D particles. By comparing with the experimental data in the literature, the numerical model is found to have better predictive ability when the viscous force term is considered in the gas phase momentum equation.

Biofilm Performance of a Fluidized Bed Biofilm Reactor for Drinking Water Denitrification

1992 ◽  
Vol 26 (3-4) ◽  
pp. 555-566 ◽  
Author(s):  
V. Z. Lazarova ◽  
B. Capdeville ◽  
L. Nikolov
Keyword(s):  
Drinking Water ◽  
Fluidized Bed ◽  
Nitrate Reduction ◽  
Protein Concentration ◽  
Biofilm Reactor ◽  
Physiological Characteristics ◽  
Fluidized Bed Bioreactor ◽  
Biofilm Thickness ◽  
Residual Nitrite ◽  
Bed Expansion

The properties of two biofilms generated with different predominant organisms were studied in a laboratory-scale fluidized bed bioreactor. Bed expansion, biofilm thickness, biofilm density, protein and polysaccharide concentrations were measured and compared. A high polysaccharide concentration was observed in the less dense and more fragile biofilm of Ps. aeruginosa. The more active biofilm of Ps. stutzeri was characterized by higher protein concentration and density. The results demonstrated that the biofilm performance mostly depended on the physiological characteristics of the preponderant organism. Complete nitrate reduction was reached in both biofilms at very low biofilm thickness. Elevated residual nitrite was observed only in the biofilm of Ps. aeruginosa.

Hydrodynamic characteristics of the dense medium gas–solid fluidized bed for coal beneficiation and cleaning

2015 ◽  
Vol 34 (2) ◽  
pp. 173-183 ◽  
Author(s):  
Jingfeng He ◽  
Yuemin Zhao ◽  
Yaqun He ◽  
Zhenfu Luo ◽  
Hong Li ◽  
...  
Keyword(s):  
Fluidized Bed ◽  
Dense Medium ◽  
Hydrodynamic Characteristics ◽  
Coal Beneficiation

Segregation by size difference in a conical fluidized bed of pharmaceutical granulate

2005 ◽  
Vol 153 (1) ◽  
pp. 72-80 ◽  
Author(s):  
Michael Wormsbecker ◽  
Amber Adams ◽  
Todd Pugsley ◽  
Conrad Winters
Keyword(s):  
Fluidized Bed ◽  
Size Difference ◽  
Conical Fluidized Bed

scholarly journals Improved models for predicting bubble velocity, bubble frequency and bed expansion in a bubbling fluidized bed

2019 ◽  
Vol 141 ◽  
pp. 361-371 ◽  
Author(s):  
Cornelius Emeka Agu ◽  
Lars-Andre Tokheim ◽  
Marianne Eikeland ◽  
Britt M.E. Moldestad
Keyword(s):  
Fluidized Bed ◽  
Bubble Velocity ◽  
Bubble Frequency ◽  
Bubbling Fluidized Bed ◽  
Bed Expansion
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