A short-lived radioactive tracer method for the measurement of closed circuit ball mill residence time distributions

This paper describes an extension of the short-lived radioactive tracer method to the on-stream measurement of residence time distributions of ball mills in closed circuit with a classifier. In essence, the method calls for tracing a size of irradiated circuit feed particles for which the classifier behaves as a simple splitter. By assuming that the mill RTD is particle size independent and that there is negligible tracer dispersion in the classifier, tracer data obtained in the mill product are mathematically treated to give the mill RTD. The extended method is derived, developed and demonstrated on a closed circuit test loop and on a pilot-plant scale ball mill in closed circuit with a hydrocyclone.