Gas Fluidisation of Nano-particle Assemblies: Modified Geldart classification to account for multiple-scale fluidisation of agglomerates and clusters

Abstract

Recent literature of the past several years has borne out gas fluidisation phenomena of nano-particle beds and assemblies quite unlike the conventional behaviour observed in fluidisation of micron size or larger particles. A review is presented of the recent publications in the field in comparison with more recent studies of nano-particle assembly fluidisation at Surrey University with the use of high resolution and high speed microtomography techniques. These studies support well the previously published observations in incipiently fluidised 2-D and 3-D beds as well as providing further insight into the highly expanding behaviour of dynamic nano-particle clusters observed at fluidisation velocities much in excess of the incipient fluidisation velocity of a packed bed. It has proved possible to explain the observed behaviour of nano-particle agglomerates in incipiently fluidised beds and those expanding dynamic clusters observed in high gas velocities by extending the established framework of the Geldart Classification to sub-micron particle sizes and to immersed bulk densities as low as 100th of the solid density. Further quantification studies are underway to establish the various long and short range force contributions to the observed dynamic force fields of nano-particle assemblies over a wide range of percolating gas velocities.

Keywords

• nano-particles
• gas fluidisation
• multiple-scale agglomerates
• dynamic clusters
• geldart classification