Towards a Theoretical Understanding of Dustiness

While there are plenty of experimental studies pertaining to the dust generation from and dustiness of powders, few of them aim at reaching a theoretical understanding of the phenomena. In the present article, the literature on dustiness has been systematically reviewed with respect to its contribution to a better comprehension of the processes involved. The majority of industrial raw materials exist in the form of dry powders. Due to the complex interplay of multiple parameters, a theoretical understanding of dust generation processes is not trivial and presently relies on experimental studies using bench top testers called dustiness testers. Given the existence of several reviews about dustiness testers, the present review is limited to the presentation of the drop test and the rotating drum and a relatively new tester, the vortex shaker. The vortex shaker uses mechanical agitation (‘shaking’) of a small bulk solid sample to generate dust particles. Parametric studies related to sample mass, particle size and particle size distribution, moisture content, bulk density, particle shape, temporal evolution, angle of repose, and cohesion were reviewed. Approaches to modelling dustiness have been systematically reviewed. The simplest and most straightforward one consists of defining the dust emission as a result of empirical terms describing the ratio between the cohesion and separation forces. Good results could be reached through that approach but its simplistic assumptions may limit its validity to narrow ranges of conditions the parameters must be adapted to. To reach a more systematic understanding, numerical modelling methods such as computational fluid dynamics and discrete element method must be considered. Their combined use along with population balance modelling is currently the most complete approach but it is computationally very demanding. In order to make progress in theoretical dustiness studies, both the simplified and the numerical modelling approaches should be followed.