May 22-27, 2016
This paper represents the first systematic study of the pneumatic conveying of nanoparticles. The minimum pickup velocity, Upu, of six nanoparticle species of different materials (i.e., silicon dioxide (SiO2), aluminum oxide (Al2O3) and titanium dioxide (TiO2)) and surfaces (i.e., apolar and polar) were determined by the weight loss method. Specifically, the weight loss method involves measuring the mass loss from the particle sample at various superficial gas velocities (U), and the Upu is the U value at which mass loss is zero. Nanoparticles were picked up as agglomerates rather than individually. Results show that (a) due to relative lack of hydrogen bonding, apolar nanoparticles have higher mass loss values at the same velocities, mass loss curves with accentuated S-shaped profiles, and lower Upu values; (b) among the three species, SiO2, which has the lowest Hamaker coefficient, exhibited the greatest discrepancy between apolar and polar surfaces with respect to both mass loss curves and Upu values; (c) Umf,polar/Umf,apolar was between 1 – 3.5 times that of Upu,polar/Upu,apolar due to greater extents of hydrogen bonding associated with Umf ; (d) Upu values are at least an order-of-magnitude lower than that expected from the well-acknowledged Upu correlation (1) due to agglomeration; (e) although nanoparticles should be categorized as Zone III (1) (or Geldart Group C (2)), the nanoparticles, and primary and complex agglomerates agree more with the Zone I (or Geldart Group B) correlation (Figure 1, whereby Rep* and Ar are the particle Reynolds number and Archimedes number, respectively (1)). In view of the importance of surface polarity on the pneumatic conveying of nanoparticles, more studies are on-going to further understand such surface effects.
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Jia Wei Chew, J. Ruud van Ommen, and Aditya Anantharaman, "Pickup velocity of nanoparticles" in "Fluidization XV", Jamal Chaouki, Ecole Polytechnique de Montreal, Canada Franco Berruti, Wewstern University, Canada Xiaotao Bi, UBC, Canada Ray Cocco, PSRI Inc. USA Eds, ECI Symposium Series, (2016). http://dc.engconfintl.org/fluidization_xv/23