The performance of the mixer-type disperser has been studied experimentally with particular attention to the effect of the impeller position and the blade angle. The experimental results showed the relatively higher position and narrow impeller were better for attaining good performance. The variation of the dispersion efficiency was well correlated by a newly introduced parameter, a non-dimensional residence time. The non-dimensional parameter represents the amount of recirculating flow in the vessel, because it was inversely proportional to a non-dimensional air flow rate, which is defined by the ratio of the discharged air flow rate to the flow rate exhausted from the impeller. It was concluded that the best disperser has no recirculating flow. As for the effect of the angle, the blade perpendicular to the bottom attained the best performance as a result of no short cut particles and no recirculating particles.