The Role of Fines in Controlling the Flow of Bulk Solids

It is widely assumed that fines control the flow of bulk solids but this has not been quantified in prior work. This study examines the effect of fines on the flow of bulk solids as function of fines loading in a bulk solid system. Using a Schulze ring shear tester, various systems of different types of bulk solids were studied including organic powders like sugar and inorganic systems such as sodium bicarbonate and sodium chloride across a wide variety of particle sizes. Key parameters such as unconfined yield stress, angle of internal friction and effective angle of internal friction as function of consolidation stress were determined for each system. Of particular interest are situations where the fines completely fill the interstices of the continuous coarse fraction. This work has application for bin design as well as design of materials for “tailored” flowability.