Solid Fluidized Beds

Property Trickle bed Flooded Stirred tank Entrained solids Fluidized bed... 

Solid-gas Mixing of immiscible liquids Pneumatic conveying of solids Fluidized beds... 

Marmo, L., Rovero, G., and Baldi, G., Modeling of catalytic gas-solid fluidized bed reactors, Catal. Today, 52, 235-247 (1999). 

Recent research development of hydrodynamics and heat and mass transfer in inverse and circulating three-phase fluidized beds for waste water treatment is summarized. The three-phase (gas-liquid-solid) fluidized bed can be utilized for catalytic and photo-catalytic gas-liquid reactions such as chemical, biochemical, biofilm and electrode reactions. For the more effective treatment of wastewater, recently, new processing modes such as the inverse and circulation fluidization have been developed and adopted to circumvent the conventional three-phase fluidized bed reactors [1-6]. 

Bavarian and Fan [3, 4] reported a similar phenomenon occurring in a three-phase fluidized bed. In their case, the hydraulic transport of a packed bed occurred at the start-up of a gas-liquid-solid fluidized bed. Although the cause was different from the case reported in the present study, similar phenomena were observed in both cases. 

Two fixed-bed reactors can be used in parallel, one reacting and the other regenerating. However, there are many disadvantages in carrying out this type of reaction in a packed bed. The operation is not under steady state conditions, and this can present control problems. Eventually, the bed must be taken off line to replace the solid. Fluidized beds (to be discussed later) are usually preferred for gas-solid noncatalytic reactions. 

Bi, H. T., Grace, J. R., and Zhu. J., Propagation of Pressure Waves and Forced Oscillations in Gas-solid Fluidized Beds and their Influence on Diagnostics of Local Hydrodynamics, Powder Technol., 82 239 (1995)... 

Van Swaaij, W. P. M., and Zuiderweg, F. J., The Design of Gas-Solids Fluidized Beds - Prediction of Chemical Conversion, Proc. Int. Symp. on Fluidization and itsAppl., Ste Chimie Industrielle, Toulouse (1973)... 

Bock, H. J., and Schweinzer, J., Heat Transfer to Horizontal Tube Banks in a Pressurized Gas Solid Fluidized Bed, German Chem. Eng., 9(1) 16-23 (1986)... 

Fan, L. S., Hwang, S. J., and Matsuura, A., Some Remarks on Hydrodynamic Behavior of a Draft Tube Gas-Liquid-Solid Fluidized Bed, AIChE Symp. Ser., 80(234) 91 (1984)... 

Morooka, S., Kawazuishi, K., and Kato, Y., Holdup and Flow Pattern of Solid Particles in Freeboard of Gas-Solid Fluidized Bed with Fine Particles, Powder Technol., 26 75 (1980)... 

Fan, L. S., Fujie, K., Long, T. R., and Tang, W. T., Characteristics of Draft Tube Gas-Liquid-Solid Fluidized-Bed Bioreactor with Immobilized Living Cells for Phenol Degradation, Biotechnol. Bioeng., 30 498 (1987b)... 

III. System 1 Flow Dynamics of Gas-Liquid-Solid Fluidized Beds... 

Subsequently, simulations are performed for the air Paratherm solid fluidized bed system with solid particles of 0.08 cm in diameter and 0.896 g/cm3 in density. The solid particle density is very close to the liquid density (0.868 g/ cm3). The boundary condition for the gas phase is inflow and outflow for the bottom and the top walls, respectively. Particles are initially distributed in the liquid medium in which no flows for the liquid and particles are allowed through the bottom and top walls. Free slip boundary conditions are imposed on the four side walls. Specific simulation conditions for the particles are given as follows Case (b) 2,000 particles randomly placed in a 4 x 4 x 8 cm3 column Case (c) 8,000 particles randomly placed in a 4 x 4 x 8 cm3 column and Case (d) 8,000 particles randomly placed in the lower half of the 4x4x8 cm3 column. The solids volume fractions are 0.42, 1.68, and 3.35%, respectively for Cases (b), (c), and (d). 

In system 1, the 3-D dynamic bubbling phenomena in a gas liquid bubble column and a gas liquid solid fluidized bed are simulated using the level-set method coupled with an SGS model for liquid turbulence. The computational scheme in this study captures the complex topological changes related to the bubble deformation, coalescence, and breakup in bubbling flows. In system 2, the hydrodynamics and heat-transfer phenomena of liquid droplets impacting upon a hot flat surface and particle are analyzed based on 3-D level-set method and IBM with consideration of the film-boiling behavior. The heat transfers in... 

Reactors, 14 89. See also Autoclaves airlift, 15 708-709, 713-714 boiling water, 17 578-582 bubble column, 15 708-709 deep shaft, 15 713, 714 draft-tube sparged concentric draft-tube airlift, 15 712-713 fast-breeder, 17 585-588 gas-liquid-solid fluidized bed,... 

In a similar way, a high liquid velocity will cause hydraulic conveying in a liquid-solid fluidized bed. 

Particulate fluidization, where the fluidizing medium is usually a liquid, is characterised by a smooth expansion of fhe bed. Liquid-solid fluidized beds are used in continuous crystallisers, as bioreactors in which immobilised enzyme beads are fluidized by the reactant solution and in physical operations such as the washing and preparation of vegetables. The empirical Richardson-Zaki equation (Richardson... 

For ethanol production a substantial improvement over the packed bed reactor is offered by the gas-solid fluidized bed fermenter which uses a liquid instead of a solid substrate and replaces the packed bed of substrate or micro-organisms with a fluidized bed of yeast pellets (Smith et al, 1997). This system can be viewed as a standard fermentation against which the performance of different bioreactors may be assessed. 

A theoretical model (Beck and Bauer, 1989), based on ethanol inhibition alone as the limiting factor in gas-solid fluidized bed fermenters run with recirculating inert gas, suggested that the potential of this technique has not been fully explored. Hayes (1998) suggested significant improvements to the model and provided experimental confirmation of its validity. 

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