Date of Award

Fall 2006

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Chemical Engineering - (Ph.D.)

Department

Chemical Engineering

First Advisor

Robert Pfeffer

Second Advisor

Rajesh N. Dave

Third Advisor

Piero M. Armenante

Fourth Advisor

Michael Chien-Yueh Huang

Fifth Advisor

Chao Zhu

Abstract

Previous works have classified the fluidization behavior of nanoparticles as Agglomerate Particulate Fluidization (APF) and Agglomerate Bubbling Fluidization (ABE). These fluidization behaviors are quite different in regard to the fluidized bed expansion, the presence of bubbles and the smoothness of the bed surface, with APF nanopowders showing a much more homogeneous fluidization and a much better dispersion than ABE nanopowders which are generally very difficult to fluidize and show vigorous bubbling. In the present work, the fluidization of APF as well as ABF nanopowders is studied in depth, both conventionally, and in the presence of extemal assistance; several related topics are discussed such as the presence of pressure fluctuations, electrostatic charge effects, magnetic, vibration and centrifugal (in a rotating fluidized bed) assisted fluidization, jet assisted fluidization and mass transport rates during humidification and drying of hydrophilic fluidized nanopowders. The research on jet assisted fluidization of nanopowders coupled with the reduction of electrostatic charges is one of the most important contributions of the present work. For APE nanopowders, fluidized bed heights of about an order of magnitude larger than the initial bed height are obtained, and for ABF nanopowders, the fluidization behavior is transformed into APF.

In a different but related topic, liquid-solid inverse fluidization of silica aerogel granules-Nanogel®-has been studied for the removal of oil from wastewater. The granules are several hundred microns or larger in size, but they have a nano-porous structure that provides large surface area and low density. The hydrodynamic characteristics of the granules during inverse fluidization and their oil removal efficiency and capacity are described.

The third topic of study was the filtration of submicron particles by customized granular media made of either agglomerates of nanoparticles, aerogel granules or carbon black granules challenged against submicron aerosol particles and oil droplets. Both packed and fluidized customized filters were studied. It is shown that a granular bed filter of porous granules can have a collection efficiency equivalent to HEPA filters but with a larger capacity. Also, the customized filters show larger collection efficiency for the removal of oil droplets when compared against HEPA filters.

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