The Ludowici LMPE Reflux Classifier is a new device designed for classifying and separating particles on the basis of size or density. This work presents a series of experimental results obtained from the first pilot scale study of the reflux classifier (RC). The main focus of the investigation was to assess the particle gravity separation and throughput performance of the device. In this study, the classifier was used to separate coal and mineral matter less than 2 mm in size. The experimental results were then compared with the performance data on a teetered bed separator (TBS). It was concluded that the classifier could offer an excellent gravity separation at a remarkably high solids throughput of 47 t/m(2) h more than 3 times higher than for a TBS. The separation performance of the RC was also better, with significantly less variation in the D-50 with particle size. A simple theoretical model providing an explanation of the separation performance is also presented. (C) 2002 Elsevier Science Ltd. All rights reserved.