An important parameter in pneumatic conveying, which is an integral operation in a range of chemical industries from oil and gas to pharmaceutical, is the minimum pickup velocity (Upu). Upu is defined as the gas velocity needed to initiate rolling or suspend a particle initially at rest. Knowledge of Upu is essential to ensure efficient operation of pneumatic transport systems. Previous studies on Upu have focused on micron-sized particles of a wide size range (40-3000 μm) [1-3]. However, no understanding on the Upu of nanoparticles is available to date, even though the processing of nanoparticles is becoming increasingly important .
Therefore this effort attempts to bridge the gap by quantifying the Upu of nanoparticles via the mass loss method . The nanoparticles investigated were polar and apolar forms of SiO2, Al2O3 and TiO2 having a particle diameter range of 13-21 nm. An observation worth highlighting is that, unlike their micron-sized counterparts, nanoparticles are picked up as lumps or agglomerates instead of individual particles. Results show that polar and apolar nanoparticles exhibit distinctly different mass loss curves (i.e., mass loss vs superficial air velocity) having clearly different shapes, with the former being linear and the latter being S-shaped. Also, the Upu of polar nanoparticles is greater than that of apolar ones, which agrees with the analogous Umf values for the same nanoparticles reported earlier . This increased insight in nanoparticle transport will facilitate the development of novel schemes involving nanoparticle processing for materials with applications in spanning pharmaceutical, catalysis and energy storage.
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