Effect of Frequency on Pulsed Fluidized Beds of Ultrafine Powders

Abstract

Deagglomeration of ultrafine powders poses an important challenge towards their efficient and effective utilization. In the present study, we investigate the effect of frequency on the hydrodynamics of pulsed fluidized beds of ultrafine powders that show strong agglomeration behavior. We have carefully selected square waves of three different frequencies: 0.05 Hz, 0.10 Hz, and 0.25 Hz. The lowest frequency used here allowed the fluidized bed to settle completely before another pulse was introduced whilst the highest frequency ensured that the bed remained in a state of continuous turbulence between occurrences of consecutive pulses. On the other hand, the intermediate frequency pulse was just sufficient to complete the process of bed collapse before the start of the next pulse. Both local and global bed dynamics in all the three cases were rigorously monitored using fast response pressure transducers. The pressure transient data during the bed collapse were processed using the bed collapse model reported in the literature to compute the effective hydrodynamic diameter of agglomerates. Though there was substantial decrease in the agglomerate size, the effect of the frequency appeared to be rather insignificant as the global pressure transients remained rather insensitive to the change of the fluidization velocity.

Mechanical Properties of Ultraviolet-Assisted Paste Extrusion and Postextrusion Ultraviolet-Curing of Three-Dimensional Printed Biocomposites

“…The primary particle size of fumed silica is in the range of nanometers, but the majority among them usually appear in larger aggregates in the range of 4-200 lm 34 (Aerosil 200 dry size 20 lm, distribution 2-100 lm). 35 All mentioned pastes were applied for printing and the combination of AA/CA/ a-cellulose/fumed silica (Resin C) was selected for experiments, because of high-dimensional printing accuracy, the ability to extrude with suitable pressure levels between 2 and 5 bars, and the reduction of clogging. This material contains a cellulose ratio of 27.9 vol-%, composed of the cellulose share in the CA and the a-cellulose fibers.…”

Spherical nanoparticle effects on the lower critical solution temperature phase behavior of poly(ε‐caprolactone)/poly(styrene‐co‐acrylonitrile) blends: Separation of thermodynamic aspects from kinetics

“…SAN (182850) with acrylonitrile co‐monomer content of 25 wt % and M w of 165 kg mol −1 was also provided by Sigma‐Aldrich Co (St. Louis, Missouri, United States). Hydrophilic fumed silica (Si, Aerosil 200) with a specific surface area of 200 m 2 g −1 and average primary particle size of 12 nm was purchased from Evonik Co (Essen, Germany) …”

Deagglomeration of Ultrafine Hydrophilic Nanopowder Using Low-Frequency Pulsed Fluidization

“…Strategies for improving fluidization hydrodynamics of powders are often known as assisted fluidization techniques. Examples are acoustics [9][10][11][12][13][14], particle-mixing [15][16][17][18][19][20], flow pulsations [21][22][23][24][25][26][27][28][29], and mechanical vibrations [30][31][32][33][34]. In some cases, a combination of two assisted fluidization technique has been suggested [20,35].…”