Flowability of dusts from dry off-gas cleaning: the influence of particle size and the spread of the particle size distribution

Considerable amounts of fine granular dusts result from dry off-gas cleaning systems. The flowability of these dusts is an important characteristic for the design of dust-conveying and storage equipment. In this study the relation between the flow-relevant properties unconfined yield strength and flowability and important properties of the dust (Sauter mean diameter, spread of the particle size distribution) were investigated based on the data of seventy dusts from dry off-gas cleaning systems. The results showed that the Sauter mean diameter of a dust from dry off-gas cleaning can be used as the basis for a rough estimate of the unconfined yield strength and the flowability. As is well-known, for coarser dust the unconfined yield strength is typically lower and the flowability is higher. The influence of the spread of the particle size distribution is comparatively low. However, to obtain reliable flowability data shear tests are obligatory.