Bubble size prediction in gas–solid fluidized beds using genetic programming

The hydrodynamics of a gas–solid fluidized bed (FB) is affected by the bubble diameter, which in turn strongly influences the performance of a fluidized bed reactor (FBR). Thus, determining the bubble diameter accurately is of crucial importance in the design and operation of an FBR. Various equations are available for calculating the bubble diameter in an FBR. It has been found in this study that these models show a large variation while predicting the experimentally measured bubble diameters. Accordingly, the present study proposes a new equation for computing the bubble diameter in a fluidized bed. This equation has been developed using an efficient, yet infrequently employed computational intelligence (CI)-based datadriven modelling method termed genetic programming (GP). The prediction and generalization performance of the GP-based equation has been compared with that of a number of currently available equations for computing the bubble diameter in a fluidized bed and the results obtained show a good performance by the newly developed equation

Experimental analysis and computational fluid dynamics simulations for heat transfer in sound assisted fluidized bed of fine powders

Fine powders in the size range of 20-200 μm are widely used in industries for fluid bed operations and are ideal for gas-solid reactions because of their large external surface areas and favorable heat transfer rates. The fine powders have very poor flow characteristics. Most of the earlier research work in heat transfer in bubbling fluidized beds is focused on coarse grained Geldart B and D particles. Acoustic energy of sufficient intensity and sound pressure level improved the quality of fluidization of fine powders. The objective of this investigation is experimental analysis and CFD simulations for heat transfer in a fluidized bed of fine powders at different acoustic conditions. The Eulerian approach has been identified as an efficient method for the numerical simulation of fluidized beds. The experimental and CFD results are in good agreement with each other

The influence of acoustic field and frequency on Hydrodynamics of Group B particles

Sound Assisted Fluidized Bed (SAFB) of group B particles (180μm glass bead) has been studied in a 46mm I.D. column with aspect ratios of 1.4 and 2.9. A loudspeaker mounted on the top of the bed was supplied by a function generator with square wave to generate the sound as the source of vibration of the fluidized bed. The sound pressure level (referred to 20μpa) was varied from 102 to 140dB and frequencies from 70Hz to 170Hz were applied. The effects of sound pressure level, sound frequency and particle loading on the properties of SAFB were investigated. The experimental result showed that the minimum fluidization velocity decreased with the increase in sound pressure level, also minimum fluidization velocity was varied with variation of frequencies. At resonance frequency minimum fluidization velocity was found to be minimum. The bed height did not show an appreciable increase in presence of high acoustic field and at resonant frequency. Minimum fluidization velocity verses frequency curve in presence of sound intensity varied with variation of bed weight

Bubble dynamics investigation in a slurry bubble column

The Application of Four-Point Optical Probe Has Been for the First Time Extended to a Slurry System in a 10.2-Cm ID Column. Bubble Dynamics (Local Gas Holdup, Bubble Chord Length, Bubble Velocity, Bubble Frequency, and Specific Interfacial Area) Were Investigated using an Air-Water-Catalyst System under Atmospheric Pressure. with an Increase in Solids Loading, the Local Gas Holdup, Specific Interfacial Area, and Bubble Frequency Decreased, While the Bubble Velocity Changed Slightly. Bubble Chord Length Increased Noticeably, and the Bubble Chord Length Distribution Spread More Widely at High Solids Loading. It Has Also Been Found that the Probe Orientation is Important for an Investigation using Probes, especially in the Wall Region of the Column. © 2008 American Institute of Chemical Engineers