Development of a new apparatus for evaluating flowability of particle with poor flow behavior

A new apparatus was developed to evaluate the flowability of particles with poor flow behavior. This apparatus uses the phenomenon that particles drain from a particle-bed as stress on the bed is gradually increased. Samples employed were coarse particles with good flow behavior (133, 158, 306 μm) and fine particles with poor flow behavior (1.6, 4.5, 32.9 μm). The drained angles of coarse particles obtained with the new apparatus agree with those obtained with a conventional apparatus. Hence, the new apparatus is applicable for coarse particles. On the other hand, the drained angles of the fine particles could not be measured by the conventional method, as particles did not drain from the container. However, with the new apparatus, a particle-bed of fine particles (≤4.5 μm) suddenly collapsed drained at a certain level of applied stress. From this stress value, the forces acting between particles in the bed were calculated, and these forces agreed with those obtained with a direct shear tester. Thus, the new apparatus can also be used to estimate shear stress. Furthermore, the apparent drained angle is proposed as a new flow property for particles with poor flow behavior, and this allows the flowability of these particles to be evaluated.