Microjet- and Vibration-Assisted (MVA) Fluidization of Nanoparticles
Fluidization is used in many industries to disperse nanosized particles in a gas phase, which increases availability of surface area per unit mass of nanoparticles. However, due to large interparticle forces, agglomeration of nanosized particles may greatly restrict bed expansion and lead to large bubble formation. Methods to combat these effects include: (1) microjet-assisted fluidization, which employs a high-velocity jet of gas from a downward-pointed nozzle in the reactor, and (2) vibration-assisted fluidization, wherein the reactor is mechanically vibrated. These two methods, though effective, typically require the addition of alcohol to minimize electrostatic forces in the system to improve fluidization. For some applications such as those involving titanium dioxide (TiO2) for environmental remediation, alcohol introduces unwanted chemical reactions. Therefore, a need exists for an effective fluidization technique that minimizes agglomeration without the use of chemical additives.
Researchers at Arizona State University have developed a novel particle fluidization system that combines the dual effect of vibration and a downward-facing micronozzle. This system is designed to operate across a wide range of pressures and without the aid of chemicals such as alcohol. This microjet- and vibration-assisted (MVA) fluidization method results in enhanced dispersion of nanoparticles in a matrix for development of well-mixed composite structures, including civil infrastructure materials. MVA experiments have been conducted with nanosized P25 TiO2, a photocatalyst with air pollution control applications. Compared to vibration-assisted operation and microjet-assisted operation, the MVA system delivers superior bed expansion, achieving an expansion height similar to a previously published microjet-assisted method that employed an alcohol solution. Thus, the MVA system presents a viable solution for nanosized particle fluidization especially when use of additional chemicals would be detrimental to desired processes.
• Advanced mixing operations including for infrastructure materials
• Environmental remediation activities using photocatalysts
• Gas-solid reaction engineering
Benefits and Advantages
• Improved particle mixing and surface area interactions without use of chemical aids
• Improved light penetration if system is used with photocatalytic particles
• Operates under a variety of pressure conditions without the requirement of choked flow
• Fluidization experiments demonstrate similar bed expansion to alcohol-facilitated microjet method