Abstract
In the present study, we report the fluidization behavior of ultrafine nanopowder using the assisted fluidization technique of particle mixing, which was further superimposed with the pulsation of the inlet gas flow to the fluidized bed. The powder selected in the present study was hydrophilic nanosilica, which shows strong agglomeration behavior leading to poor fluidization hydrodynamics. For particle mixing, small proportions of inert particles of Geldart group A classification were used. The inlet gas flow to the fluidized bed was pulsed with a square wave of frequency 0.1 Hz with the help of a solenoid valve controlled using the data acquisition system (DAQ). In addition to the gas flow rate to the fluidized bed, pressure transients were carefully monitored using sensitive pressure transducers connected to the DAQ. Our results indicate a substantial reduction in the effective agglomerate size as a result of the simultaneous implementation of the assisted fluidization techniques of particle mixing and flow pulsation.
Highlights
Process industries often employ fine and ultrafine powders to enhance surface-based rate processes such as gas–solid-catalyzed reactions and various separation processes [1,2]
We have investigated the fluidization hydrodynamics of a fluidized bed of hydrophilic nanopowder that was subjected to unassisted fluidization, assisted fluidization of particle mixing, and a combination of both assisted fluidization techniques of particle mixing and flow pulsation
The hysteresis effect is reduced by the assisted fluidization technique of particle mixing and almost completely eliminated by the combined application of particle mixing and flow pulsation
Summary
Process industries often employ fine and ultrafine powders to enhance surface-based rate processes such as gas–solid-catalyzed reactions and various separation processes [1,2]. Fluidized beds enhance the interphase mixing, and impart high mass and heat transfer rates while limiting the pressure drop to effective bed weight, even at high fluid velocities Their hydrodynamics, strongly depend on the physical characteristics of the solid particles such as particle diameter and density [1,8,9]. Levy and Celeste [6] studied the hydrodynamics of fine powders with sizes ranging from 12 nm to 15 μm in bubbling fluidized beds They used the combined assisted techniques of horizontal mechanical vibrations and acoustic vibrations to enhance the fluidization behavior. A combination of two assisted fluidization techniques, namely, particle mixing and flow pulsation, is used to improve the fluidization behavior of a bed of nanopowder. The experimental data were used to compute the minimum fluidization velocity and the agglomerate diameter
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