(54h) Modelling Deposition of Powders into a Confined Space

Many industrial processes involve deposition of powders into confided spaces, such as filling bins, silos and bags in bulk solids handling, depositing powders into dies in particulate product manufacturing. In these processes, powders are normally discharged from hopper-like equipment into specifically designed receiving-devices, which generally operate in air, so that the air presence can have a significant impact on the deposition behavior. It is important to predict the mass flow rate of powder during deposition and content uniformity of the discharged powder mass. In this study, analytical models are developed to predict the overall mass flow rate during the flow of powder into confined spaces, based upon air sensitivity classifications. Furthermore, a critical deposition rate can also be obtained from the model. Comparison with experimental data obtained for fine powders reveals that the models can accurately predict not only the overall mass flow rate, but also the critical deposition rate. Therefore, the models can be useful predictive tools for process development and formulation design in a number of industries.