Study of residence time distribution and mill hold-up for a continuous centrifugal mill with various G/D ratios in a dry-grinding environment

It is important to determine the residence time distribution (RTD) of a mill in order to predict the performance of the mill. In this study, the residence time distribution of a continuous centrifugal mill was measured experimentally by using aluminum powder as a tracer in a dry-grinding environment. Aluminum powder was placed into the continuous centrifugal mill chamber as a pulse under a steady-state condition, and then, the discharge time and proportional concentration of the tracer was measured using a metal detector at various G/D ratios and feed rates. During the measurement procedure, the mill product was collected and analyzed with regard to the size distribution to investigate the relationship between the mill product and the characteristics of RTD. In addition, the mill hold-up data was also analyzed after measurement. These test results can be used to predict the mill product size distribution in combination with a kinetic grinding model.

When the mill revolution speed is low, the RTD is closely approximating full-mixed flow. With increasing the mill speed, the peak of the RTD curve shifts towards the right, resembling multiple in series mixer model. The one large/two small fully mixed reactor-in-series model was found to fit all the data reasonably well.Figure optionsDownload as PowerPoint slideResearch highlights
► Increasing the centrifugal mill revolution speed and the G/D ratio promoted mass transport along the mill axis.
► The RTD was found to be normalizable with respect to the feed rate.
► A one large/two small fully mixed model fits all the data reasonably well.