The dispersion of bulk powders, from a dense aggregated phase to a lean phase, is important for many applications including particle characterisation and delivery of therapeutic drugs to the lungs via Dry Powder Inhalers (DPIs). It can be challenging to fully disperse fine powders due to relatively large interparticle attraction forces compared to separating forces.
Dispersion of powders can be achieved in a gas or a liquid depending on the material and application of interest. Within our research group we have access to a number of devices for dispersing powdered systems including:
The Mastersizer and Spraytec instruments determine the particle size distributions of powders using laser diffraction technology, whereas, the Morphologi G3 measures particle size distributions and morphology using an optical microscopy system.
In a recent research programme we related the aerodynamic dispersion efficiency of a powder to a relevant measurement of cohesion. A good correlation has been found between dispersion efficiency (comparison between a reference size distribution and that measured following aerodynamic dispersion) and flow function (measured using the Schulze ring shear tester), which simply states that as flow function decreases it becomes more difficult to aerodynamically disperse a powder.
Our research also adopts computational methods to further probe powder systems and develop mechanistic relationships. The Distinct Element Method (DEM) and Computational Fluid Dynamics (CFD) have been used to investigate powder dispersion.
- G. Calvert, M. Ghadiri, R. Tweedie, Aerodynamic dispersion of cohesive powders: A review of understanding and technology, Advanced Powder Technology, Volume 20, Issue 1, January 2009, Pages 4-16, ISSN 0921-8831, 10.1016/j.apt.2008.09.001.
- G.Calvert, A. Hassanpour, M. Ghadiri, Mechanistic analysis and computer simulation of the aerodynamic dispersion of loose aggregates, Chemical Engineering Research and Design, Volume 89, Issue 5, May 2011, Pages 519-525, ISSN 0263-8762, 10.1016/j.cherd.2010.08.013.
- G. Calvert, A. Hassanpour, M. Ghadiri, Analysis of aerodynamic dispersion of cohesive clusters, Chemical Engineering Science, Volume 86, 4 February 2013, Pages 146-150, ISSN 0009-2509, 10.1016/j.ces.2012.06.035.
- G. Calvert, M. Ghadiri, M. Dyson, P. Kippax, F. McNeil-Watson, The flowability and aerodynamic dispersion of cohesive powders, Powder Technology, Volume 240, May 2013, Pages 88-94, ISSN 0032-5910, 10.1016/j.powtec.2012.07.003.