Modelling and experiments on the effect of air humidity on the flow properties of glass powders

Linking micro‐scale predictions of capillary forces to macro‐scale fluidization experiments in humid environments

“…Analogous to the micro‐scale, the impact of roughness on capillary forces has also been considered when analyzing macro‐scale experiments. For instance, Landi et al calculated capillary forces between asperities and found qualitative agreement with their measured shear cell results when they used assumed, rather than measured, roughness values (i.e., asperity heights and minimum separation distance). An objective method to quantify surface roughness was recently developed by LaMarche et al, and was found critical to the accurate prediction of cohesion arising from van der Waals forces.…”

“…Consequently, proper prediction of F cap requires a theory that considers surface roughness. Such a theory is instituted here, which is a combination of several existing theories, and is similar to the model used by Landi et al The novelty of this theory, as applied to capillary forces, is that it (1) includes two scales of roughness, and (2) incorporates asperity geometries measured directly from AFM surface roughness maps using an objective method to quantify surface roughness developed by LaMarche et al Figure is a schematic of a capillary bridge formed between two rough particles with radii R . The method of Rabinovich et al is used to describe the surface, in which roughness is separated into two scales (large and small) of asperities represented as submerged spheres.…”

“…Additionally, Tsinontides and Jackson found fluidization, defluidization, and bed expansion of catalyst particles sensitive to fluidizing with dry ( RH ∼0%) or humid ( RH not reported) air. It is worth noting that in other (non‐fluidized‐bed) systems, gradual increases in RH reveal a corresponding increase in cohesion . For fluidized systems, however, the nature of flow behavior across a well‐controlled range of RH values is missing from the literature.…”

“…An objective method to quantify surface roughness was recently developed by LaMarche et al, and was found critical to the accurate prediction of cohesion arising from van der Waals forces. However, using similar measurements of surface roughness, rather than assumed or fitted values, to predict the capillary forces has yet to be performed.…”

Experimental and theoretical analysis of TiO2 powders flow properties at ambient and high temperatures

“…Furthermore, the flow properties at realistic process conditions need to be evaluated in order to analyse to what extent physical and mechanical particle properties (Pilpel and Britten, 1979;Fu et al, 2012;Liang et al, 2012), temperature (Kanaoka et al, 2001;Tomasetta et al, 2011;Chirone et al, 2016), humidity (Pierrat and Caram, 1997;Pierrat et al, 1998;Teunou and Fitzpatrick, 1999;Gröger et al, 2003;Landi et al, 2011) and loosely compacted conditions (Kono et al, 1994;Bruni et al, 2007b;Barletta and Poletto, 2012) affect the flow behaviour.…”