System and method for nanoparticle and nanoagglomerate fluidization

Abstract

With the coupling of an external field and aeration (or a flow of another gas), nanoparticles can be smoothly and vigorously fluidized. Multiple external fields and / or pre-treatment may be employed with the fluidizing gas: sieving, magnetic assistance, vibration, acoustic / sound or rotational / centrifugal forces. Any of these forces, either alone or in combination, when coupled with a fluidizing medium, provide excellent means for achieving homogenous nanofluidization. The additional force(s) help to break channels as well as provide enough energy to disrupt the strong interparticle forces, thereby establishing an advantageous agglomerate size distribution. Enhanced fluidization is reflected by at least one of the following performance-related attributes: reduced levels of bubbles within the fluidized system, reduced gas bypass relative to the fluidized bed, smooth fluidization behavior, reduced elutriation, a high level of bed expansion, reduced gas velocity levels to achieve desired fluidization performance, and / or enhanced control of agglomerate size / distribution. The fluidized nanoparticles may be coated, surface-treated and / or surface-modified in the fluidized state. In addition, the fluidized nanoparticles may participate in a reaction, either as a reactant or a catalyst, while in the fluidized state.

Description

CROSS-REFERENCE TO RELATED APPLICATION [0001] The present application claims the benefit of the following co-pending, commonly assigned provisional patent applications: (i) “Vibrofluidization and Magnetically Assisted Fluidization of Nanoparticles,” filed on Jul. 29, 2003 and assigned Ser. No. 60 / 490,912, and (ii) “Nanoparticle and Nanoagglomerate Fluidization System and Method,” filed on May 4, 2004 and assigned Ser. No. 60 / 568,131. The contents of each of the foregoing provisional patent applications are incorporated herein by reference.BACKGROUND OF THE DISCLOSURE [0002] 1. Technical Field [0003] The present disclosure relates to system(s) and method(s) / process(es) for fluidizing nanoparticles and nanoagglomerates. More particularly, the present disclosure is directed to systems and methods / processes for fluidizing nanoparticles and nanoagglomerates utilizing a fluidizing gas with one or more external forces, e.g., a vibration force, a magnetic force, an acoustic force, a rotatio...

AI Technical Summary

Benefits of technology

[0022] As used herein, “enhanced fluidization” is reflected by at least one of the following performance-related attributes: reduced levels of bubbles within the fluidized system, reduced gas bypass relative to the fluidized bed, smooth fluidization behavior, reduced elutriation, a high level of bed expansion, reduced gas velocity levels to achieve desired fluidization performance, and / or enhanced control of agglomerate size / distribution.

[0028] According to further aspects of the present disclosure, fluidization characteristics of a variety of different nanoparticles are provided and such fluidization characteristics are advantageously correlated with macroscopic fluidization behavior (APF or ABF) of the nanoagglomerates. To establish such correlation, the properties of primary nanoparticles were established in a conventional gravity-driven fluidized bed without any additional external forces present. In addition, a simple and effective method for estimating the average size of agglomerates and bed voidage around the agglomerates is provided. The estimation methodology can then be used in models to determine the minimum fluidization velocity, pressure drop and other pertinent variables of the fluidization process, and to determine the external force(s) required to establish a desired particle size distribution to achieve and support efficacious nanoparticle / nanoagglomerate fluidization, as described herein.

Problems solved by technology

However, the fluidization behavior of ultrafine particles, including nanoparticles which are in the extreme low end of Group C particles (<20 microns) in Geldart's Classification of Powders, is much more complex and has received relatively little attention in the literature.

Nanoparticles are difficult to fluidize due to their strong interparticle forces.

As far as is known, fluidization of nanoparticles (which are three orders of magnitude smaller than traditional group C powders) has heretofore been extremely difficult, if not impossible, to effectively achieve.

However, there tends to be significant powder loss and non-uniform fluidization behavior.

In addition, large agglomerates can form near the distributor.

For other nanoparticles, fluidization results in a very limited bed expansion, and large bubbles rise up very quickly through the bed.

However, even for the homogeneously fluidized nanoparticles, relatively large powder elutriation occurs at the high gas velocities required to fluidize the nanoagglomerates.

This loss of particles may hinder the applicability of fluidization of nanoparticle agglomerates in industrial processes.

However, very little experimental data on the fluidization characteristics and differences between APF and ABF nanoparticles, such as minimum fluidization velocity, agglomerate size, hysteresis effects, and the effect of nanoparticle material properties, are available.

However, notwithstanding the benefits associated with these known fluidizing techniques, often a dense immobile phase forms at a bottom of a fluidizing bed.

However, the disclosed technique does not include loosening up cohesive materials for application in a fluidized bed.

Similarly, U.S. Pat. No. 6,471,096 to Dave discloses the use of alternating magnetic field along with permanent magnets to produce controllable discharge of cohesive powders from a container, but does not provide for fluidization of nano-powders.

U.S. Pat. No. 3,848,363 to Lovness et al. discloses the use of magnetic force to move particles in a predetermined area, but again does not provide for any application to fluidization.

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