http://nova.newcastle.edu.au/vital/access/services/Feed ${session.getAttribute("locale")} 5 http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:11420 This paper is concerned with the gravity separation of fine particles in a Reflux Classifier, a fluidized bed device with a system of parallel inclined channels located above. A significant advance is reported here over what was previously possible, through the application of a recent discovery described by Galvin et al. (2009). By using closely spaced inclined channels it is possible to achieve significant suppression of the effects of particle size, and hence produce a powerful separation on the basis of density. Experimental work was undertaken on the continuous steady state separation of coal and mineral matter, with a very narrow channel spacing of 1.77 mm used to process a feed finer than 0.5 mm in diameter, and a channel spacing of 4.2 mm used to process coarser feeds finer than 2.0 mm. These results are compared with previous findings reported in the literature for wider channels. The gravity separation performance is shown to be remarkably high, with a significant reduction in the variation of the separation density with particle size, and a significant reduction in the Ecart probable error, E_p. For example, over the particle size range 0.25–2.0 mm the composite E_p for the size range decreased from 0.14 for the wide channels used in previous studies to a typical level of 0.06 for the closely spaced inclined channels used in the present study. The separation performance was also shown to be insensitive to feed pulp density and feed solids throughput over a very broad range. 2012-08-30T01:10:48.235Z ]]> http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:9057 A Reflux Classifier consists of a set of parallel inclined channels above a conventional fluidized bed. Recently we (Galvin et al, Chemical Engineering Science, 2009) discovered a new and powerful separation mechanism for elutriating particles on the basis of density, utilizing closely spaced channels. This arrangement suppresses the effects of particle size, thus promoting the effect of particle density. Interestingly, as the channel spacing increases, we observe a transition from laminar flow to particle-induced turbulent re-suspension, with the separations in the wider channels governed according to our previous model described by Laskovski et al (2006). A series of particle fractionation experiments was conducted in this study to examine the effects of the channel spacing, and the transition from laminar to turbuelent re-suspension. Inclined channel spacings of 4, 7, 9, and 18 mm were used in the work. A continuous distribution of coal and mineral matter, consisting of particles in the size range from 0.25 to 2.0 mm was used, with the particle density ranging from 1275 to 2600 kg/m³. The results demonstrate the benefits of the new separation mechanism, with greatly improved fractionation achieved using the more closely spaced channels. 2011-09-27T00:40:15.265Z ]]> http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:6236 The influence of a magnetic field on the motion of iron particles located in a viscous fluid was investigated in this study. A magnetic field gradient was formed by orienting the poles of the magnet to produce a variable gap between the poles. The non-uniform magnetic field caused magnetisable particles to travel along the direction of the field gradient. The particles were found to undergo a process of aggregation, which in turn produced larger particles. The particles were also found to align in the direction of the field and hence in a direction perpendicular to the field gradient. Upon aggregation the new entity continued to move along the direction of the field gradient, but at a velocity distinctly higher than that of the aggregating units. When further aggregation occurred the entity increased to an even higher velocity, though the rate of increase in the velocity decreased, leading to an asymptotic velocity for very large aggregates. This behaviour was examined for spherical particles of different diameter and for rod shaped particles. This work shows the effective magnetisation of the iron particles is governed by the aspect ratio of the particles, indeed the mass distribution of the particles within the magnetic field. 2010-05-11T04:30:03.103Z ]]>