Powder mixing — a literature survey

Mixing behavior of binary and multi-component mixtures of particles in waste fluidized beds

A high-shear mixer was used to mix a two-component system different only in the density, which was subjected to DEM (Discrete Element Method) simulation. In the first place, the kinetic motion of particles in an agitating vessel was visualized to obtain the information on how particles different in granular density were mixed and segregated. Then, segregation index was defined to clarify the relationship of segregation index and density ratio with operational conditions. The conditions were also clarified for obtaining favorable mixing conditions while segregation was prevented. In other words, it has been pointed out that DEM simulation could be not only employed to readily understand the mixing and segregation conditions of particles in a mixer but also effective in determining optimal operational conditions for obtaining favorable mixing conditions even when the density ratio is different.

DEM Simulation of Mixing and Segregation in High-Shear Mixer

DEM Simulation of Mixing and Segregation in High-Shear Mixer (特集 材料設計のための粉体評価)

In our previous paper we reported the influence of physical properties of powder on the mixingdegree and mixing speed in several types of mixers.The present paper deals with our continued studies on the influence of particle size of powder on the above-mentioned factors observed in several types of mixers.The experiments were made by mixing three kinds of dry powder system: Na2CO3-sand system, having the particle-size distributions shown in Table 1, such as (1) the kind in which both the sample powders have the same size range and comparatively narrow size distributions, (2) another kind in which both the powders have the same size range and wide size distributions, and (3) the other kind in which both the powders have different size range and comparatively narrow distributions.What we made clear by our researches were:1) The optimum rotational speed of each mixer Nop was increased as the particle diameter (mean) increased, as shown in Fig. 3 and Eq. (4). The optimum volumes of powder to be charged were almost independent of the particle size in all experiments as shown in Fig. 2-a.2) The influence of particle size might be divided into two kinds:a) The influence observed when both the components had the same size.b) The influence observed when both the components had different size.In a), when the particle size of the powder was comparatively larger, the values of σs became larger, due to the median diameter of the distribution size as shown in Fig. 4.But, in b), as the particle size-ratio of the two components was increased, it became more and more difficult to obtain an intimate mixture, as shown in Figs. 6 and 7.

I. Kanise

Papers

Influence of Particle Size of Powder on Mixing Degree and Mixing Speed in Several Types of Mixers