Application of fluidization to obtain washability data

There is considerable interest in developing new approaches to obtaining wa shability data, especially in coal preparation. Here, the traditional "sink -float" method has been used for decades. Obtaining the data, however, is c ostly, and often the analysis time required is too long for the data to be useful as part of a feed-back control strategy. Further, the dense liquids used to conduct the analysis can be problematic, on health and environmenta l grounds. The purpose of this paper is to describe a new method for conducting washab ility analysis, using fluidization. Although we have used this method on co al particles smaller than 2 mm, the method may be applied to particles of a ny size or density. Although the process of fluidization is well establishe d, its application to obtaining washability data appears to be novel. Narro w size fractions of the sample are obtained using conventional sieving. One of the narrow size fractions is placed into the fluidized column, where it segregates readily producing a pressure profile, with the less dense parti cles at the top and the progressively denser particles below. The pressure profile of the suspension is measured using differential pressure transduce rs. Samples of the suspension are removed from the vessel the change in the suspension pressure profile measured, and the dry weight of the discharged sample determined. These data are then used to obtain the particle density . (C) 1999 Elsevier Science Ltd. All rights reserved.