12. Property Function to Compute the Dustiness of Powders

The dustiness of a disperse solid can be understood as a property, which when handled in a gaseous environment, behaves similar to an aerosol, releasing the respective particle fraction of given quantity and size distribution. In general, this release of dust is undesirable because it might result in material loss and often is associated with an exposure of personnel involved or represents a risk of environmental pollution. The dustiness is therefore a product property, which might change along the process path, for example through comminution, agglomeration, classification or mixing of solids involved. Property functions which describe time variable dustiness integrated in dynamic processes as a function of the distribution of particle size, particle shape, and particle interaction during a certain handling, were determined as part of this project. For this purpose, experiments with laboratory equipment such as “free fall in still air”, “moving in a rotating drum”, “dispersion, pressure surges method”, or “airflow dispersion” were performed at very well defined boundary conditions and physically based models were established. The prediction functions were successfully implemented in the flow sheet simulation DYSSOL. These models will be further used through the introduction of the so called “Fractionated grade of release”. Together with the description of time-dependent changes of the related strain-functions (apparatus properties) and rigidity-functions (material properties) this approach will help to better predict transient processes of dustiness in future.