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.

1 . A method for fluidizing nanoparticles comprising the steps of: 
 (a) providing a nanoparticle feedstock having an initial agglomerate size distribution;    (b) exposing said nanoparticle feedstock to a flow of fluidizing gas and at least one additional force or a pre-treatment selected from the group consisting of (i) sieving, (ii) a vibration force; (iii) a magnetic force, (iv) an acoustic force, (v) a rotational force, and (vi) a combination of two or more of said forces;    wherein exposure of said nanoparticle feedstock to said flow of fluidizing gas and said at least one additional force is effective to modify said initial agglomerate size distribution from said initial agglomerate size distribution to a second, reduced agglomerate size distribution; and    (c) establishing an expanded fluidized bed with said nanoparticle feedstock in a substantially fluidized state, wherein the agglomerate size distribution of said nanoparticle feedstock in said fluidized state is in dynamic equilibrium and is substantially equivalent to said second, reduced agglomerate size distribution.    
     
     
         2 . The method of  claim 1 , wherein said fluidizing gas is selected from the group consisting of: air, nitrogen, helium, argon, oxygen and mixtures thereof.  
     
     
         3 . The method of  claim 1 , wherein said nanoparticle feedstock in said fluidized state forms highly porous agglomerates in a size range of about 50 microns to about 1000 microns.  
     
     
         4 . The method of  claim 1 , further comprising a pre-screening step wherein said nanoparticle feedstock is sieved to remove nanoparticle agglomerates that exceed a predetermined threshold size.  
     
     
         5 . The method of  claim 4 , wherein said predetermined threshold size is about 500 μm.  
     
     
         6 . The method of  claim 1 , wherein said at least one additional force is sufficient to disrupt interparticle forces between nanoparticle agglomerates, thereby reducing the initial particle size distribution of said nanoparticle feedstock.  
     
     
         7 . The method of  claim 6 , wherein said at least one force is a magnetic force and said magnetic force is imparted by magnetic particles that are independent of said nanoparticle feedstock.  
     
     
         8 . The method of  claim 7 , wherein said magnetic particles are not fluidized by said flow of fluidizing gas.  
     
     
         9 . The method of  claim 7 , wherein said magnetic particles are energized by a force of at least 100 Gauss.  
     
     
         10 . The method of  claim 6 , wherein said at least one force is a vibratory force.  
     
     
         11 . The method of  claim 10 , wherein said vibratory force is generated by vibrational energy of at least 1.5 g.  
     
     
         12 . The method of  claim 6 , wherein said at least one force is an acoustic force.  
     
     
         13 . The method of  claim 12 , wherein said acoustic force is generated by acoustic energy of at least 90 dB.  
     
     
         14 . The method of  claim 6 , wherein said at least one force is a rotational force.  
     
     
         15 . The method of  claim 14 , wherein said rotational force is generated by centrifugal forces of at least 5 g.  
     
     
         16 . The method of  claim 1 , further comprising introducing a coating material such that said coating material coats said nanoparticle feedstock in said substantially fluidized state.  
     
     
         17 . The method of  claim 1 , wherein said nanoparticle feedstock includes a first reactant, and further comprising introducing at least one additional reactant, such that a reaction occurs between said first reactant and said at least one additional reactant when said nanoparticle feedstock is in said substantially fluidized state.  
     
     
         18 . The method of  claim 1 , wherein said exposure of said nanoparticle feedstock to said flow of fluidizing gas and said at least one additional force or pre-treatment is effective to achieve at least one of the following performance attributes: a reduction in bubble level within the fluidized system, a reduction in gas bypass relative to the fluidized bed, smooth fluidization behavior, a reduction in elutriation, a high level of bed expansion, a reduction in gas velocity levels to achieve a desired fluidization performance, enhanced control of agglomerate size or agglomerate distribution, and a combination of the foregoing performance attributes.  
     
     
         19 . An apparatus for use in fluidizing a nanoparticle feedstock, comprising: 
 at least one gas inlet, at least one distributor, a fluidization chamber, and at least one vent;    at least one ancillary energy source communicating with said fluidization chamber, said at least one ancillary energy source effective to provide sufficient energy to a nanoparticle feedstock within said fluidization chamber to reduce the agglomerate size distribution of said nanoparticle feedstock by an amount effective to facilitate fluidization thereof, said at least one ancillary energy source being selected from the group consisting of: (i) a source of vibration force; (ii) a source of magnetic force, (iii) a source of acoustic force, and (iv) a source of rotational force.    
     
     
         20 . The apparatus of  claim 19 , wherein said source of magnetic force is an electric field generator coil operatively connected to one or more electric power supplies surrounding a portion of said fluidization chamber.  
     
     
         21 . The apparatus of  claim 19 , wherein said fluidization chamber has a substantially cylindrical geometry.  
     
     
         22 . The apparatus of  claim 19 , wherein said at least one ancillary energy source is a source of vibrational force.  
     
     
         23 . The apparatus of  claim 22 , wherein said source of vibrational force includes a mechanical, electromagnetic or piezoelectric component that is caused to oscillate by an input current, voltage or drive signal from a power amplifier to impart said vibrational force.  
     
     
         24 . The apparatus of  claim 19 , wherein said at least one ancillary energy source is a source of magnetic force, and wherein said source of magnetic force includes at least one magnetic coil operatively connected to one or more magnetic field generators.  
     
     
         25 . The apparatus of  claim 24 , wherein said one or more magnetic field generators are positioned around at least a portion of said fluidization chamber.  
     
     
         26 . The apparatus of  claim 24 , further comprising magnetic particles positioned within said fluidization chamber and wherein a magnetic field generated by said one or more magnetic field generators causes said magnetic particles to impart exciting force within said fluidization chamber.  
     
     
         27 . The apparatus of  claim 26 , wherein said magnetic particles are substantially spherical and include a rough exterior surface.  
     
     
         28 . The apparatus of  claim 24 , wherein said fluidization chamber defines a plurality of spaced stages, and wherein magnetic particles are positioned within each of said plurality of spaced stages.  
     
     
         29 . The apparatus of  claim 28 , wherein a first set of magnetic particles are confined to a first spaced stage and wherein a second set of magnetic particles are confined to a second spaced stage.  
     
     
         30 . The apparatus of  claim 19 , wherein said at least one ancillary energy source is a source of acoustic force, and wherein said source of acoustic force includes a function generator, an amplifier and at least one loudspeaker.  
     
     
         31 . The apparatus of  claim 19 , wherein said at least one ancillary energy source is a source of rotational force, and wherein said source of rotational force includes a motor for causing said fluidization chamber to rotate around its axis or an angle offset from said axis.  
     
     
         32 . The apparatus of  claim 31 , wherein said motor is adapted to impart variable rotational speed to said fluidization chamber.  
     
     
         33 . The apparatus of  claim 19 , wherein said at least one ancillary energy source is a source of vibrational force, and wherein said source of vibrational force is positioned substantially below said fluidization chamber and is adapted to impart axially oriented vibrations to said fluidization chamber.  
     
     
         34 . The apparatus of  claim 33 , wherein said source of vibrational force is adapted to generate a vibrational force of at least 1.5 g at a frequency of between about 20 Hz and about 200 Hz.  
     
     
         35 . A method for mixing nanoparticles that comprises the steps of: 
 (a) introducing a first nanoparticle species into a fluidization chamber;    (b) introducing a second nanoparticle species into said fluidization chamber;    said first and second nanoparticle species to a flow of fluidizing gas and at least one additional force or pre-treatment selected from the group consisting of (i) sieving; (ii) a vibration force; (iii) a magnetic force, (iv) an acoustic force, (v) a rotational force; and (vi) a combination of two or more of said forces,    (c) establishing an expanded fluidized bed with said first and second nanoparticle species in a substantially fluidized state, wherein the agglomerate size distribution of said first and second nanoparticle species in said fluidized state is in dynamic equilibrium and is substantially equivalent to a reduced agglomerate size distribution;    (d) effecting mixing of said first and second nanoparticle species within said substantially fluidized state.    
     
     
         36 . A method for treating nanoparticles comprising the steps of: 
 (a) providing a volume of nanoparticles having an initial agglomerate size distribution;    (b) introducing said volume of nanoparticles to a fluidization chamber    (c) exposing said volume of nanoparticles to a flow of fluidizing gas and at least one additional force or pre-treatment selected from the group consisting of (i) sieving, (ii) a vibration force; (iii) a magnetic force, (iv) an acoustic force, (v) a rotational force, and (vi) a combination of two or more of said forces;    wherein exposure of said volume of nanop articles to said flow of fluidizing gas and said at least one additional force or pre-treatment is effective to modify said initial agglomerate size distribution from said initial agglomerate size distribution to a second, reduced agglomerate size distribution;    (d) establishing an expanded fluidized bed with said volume of nanoparticles in a substantially fluidized state, wherein the agglomerate size distribution of said nanoparticles in said fluidized state is in dynamic equilibrium and is substantially equivalent to said second, reduced agglomerate size distribution; and    (e) effecting a treatment of said volume of nanoparticles in said substantially fluidized state.    
     
     
         37 . The method of  claim 36 , wherein said treatment includes coating said volume of nanoparticles with a coating material introduced to said fluidization chamber.  
     
     
         38 . The method of  claim 36 , wherein said treatment includes effecting a surface modification to said volume of nanoparticles in said substantially fluidized state.  
     
     
         39 . The method of  claim 36 , wherein said treatment includes effecting a reaction between said volume of nanoparticles and an additional reactant introduced to said fluidization chamber.  
     
     
         40 . The method of  claim 36 , wherein said treatment includes a chemical reaction, and wherein said volume of nanoparticles functions as a catalyst for said chemical reaction.