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.