Segregation of binary size materials in a ordinary and a quadrated rotary drums was observed through the glass plate, and it was found that the small particles segregated at the upper portion of the bed when the ratio of particle size was in the range between 0.15 and 0.40, and at the inside of the bed when the ratio was less than 0.15. Besides, the segregation became indistinct when the fraction of small particles exceeds 0.4.
The movement of particles in the quadrated drum is so complicated as to be described in detail, but it could be said as a whole that the large particles cascaded longer path at the surface.
In such a condition that the segregation occurs, the retention times of each material are separated. Experimental data about this phenomenon were in reasonable accordance with the calculated results based on the trajectory models of the concentric circulation and the mean cascade path.
Standard deviation of the retention time in the quadrated drum was twice as much as in the ordinary drum. In both drums, the retention time of the large particles showed large deviation, which was explained by the longer cascading path.
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