Minimum spouting velocity of binary mixture with non-spherical particles

Abstract

The minimum spouting velocity, Ums, defined for stable external spouting, is found also crucial to ensure good mixing when multi-component particles are involved in spouted beds. In this study, experiments were performed in a cylindrical-conical spouted bed to study the influences of diverse factors on the Ums of a binary system with the cylindrical particles and the spherical bed material. The results showed that the changes in Ums with the particle properties (particle shape, size, and density) and operating conditions were closely related to the blending ratio of the mixture. When the volume fraction of the non-spherical particles was relatively small (less than 40% to 50%), Ums mainly depended on the properties of the bed material. It was considered acceptable to estimate Ums by assuming that the system only consisted of the spherical bed material. Otherwise, the cylindrical particle shape has a significant influence on the flow dynamics and Ums. For such spouting systems, an equivalent diameter of the bed material was proposed to reflect the shape effects of non-spherical particles, whereby Ums would be independent of the blending ratio. Consequently, a novel empirical correlation is proposed to quantitatively predict the Ums of binary mixtures.