Flow of dry particulates in the Szego mill

Abstract

The Szego mill is a planetary, ring-roller mill used for continuous, wet and dry grinding of materials. The transport of dry particulates in the mill has been determined with coal, wheat and limestone as feed materials. The influence of operating variables on the mean residence time and variance of the residence time distributions in a laboratory mill, obtained by a stimulus—response technique, is discussed. The operating variables considered are feed rate and size distribution, mill rotational speed, and the number of rollers and their length. Bulk mean residence times in a pilot-scale mill obtained from holdup and feed rate measurements suggest flow behaviour similar to that in the laboratory mill. The tanks-in-series model gives a good fit to the residence time distributions at most operating conditions, the number of tanks in series being greater than eight. The flow behaviour in the mill is very sensitive to the operating variables.