Using several types of mixers, Horizontal cylindertype (HC), V-type (V), Horizontal ribbon type (HR) and Vertical ribbon type (VR), experimental investigation was made for the effect of the density, Particle size of powder and the rotational speed on the mixing performances i.e., mixing process, mixing rate and final degree of mixedness etc.
1) The Segregatinon in HC and V mixers was strikingly observed on mixing curves, while the segregation in HR and VR mixers were little found.
2) The effect of powder density ratio of two components on mixing rate of HR and VR mixers was less than on that of HC and V mixers.
3) Both at high rotational speed and at low rotational speed, the good final degree of mixedness was not obtained because of segregation due to differences in density, At proper rotational speed, good final degree of mixedness was observed. This proper rotational speed was experimentally determined for various types of mixers.
4) Especially, the effect of powder properties (particle density and size ratio) on the performances of VR mixers was less that on those of HC and V mixers.

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Several studies on the flow pattern of particles in a horizontal rotary cylinder have been published. However, most of them dealt with the experimental explanation only. In this report, behavior of particles was investigated from viewpoint of dynamical and geometrical correlation, and a model concerning to the particles flow was provided for estimating the breadth of upward and downward flow, and the average circulation time at a cross section by giving such data as the internal friction coefficient μ of particles, the dynamic repose angle β at cascading, and the operating condition of cylinder.
Moreover, the variation of bed depth along the drum axis and the hold up in it were also correlated on the basis of the theoretically derived circulation time of particles flow at a section of the drum.

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