A Reflux Classifier consists of a set of parallel inclined channels above a conventional fluidised bed. Recently Galvin et al. (2009, 2010)[3,2] discovered a new and powerful separation mechanism for elu-triating particles on the basis of density, utilising closely spaced channels. This arrangement suppresses the effects of particle size, thus promoting the effect of particle density. A series of particle fractionation experiments was conducted in this study to examine the effects of the channel spacing. Inclined channel spacings of 1.77, 4.2, 7, 9, and 18 mm were used in the work. A continuous distribution of coal and mineral matter, consisting of particles in the size ranges from 0.25 to 2.0 mm and 0.038 to 0.25 mm were used, with the particle density ranging from 1275 to 2600 kg/m(3). The results demonstrate the benefits of the new separation mechanism, with greatly improved fractionation achieved using the more closely spaced channels. (C) 2010 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.