The Assessment of Fine Coal Cleanability

Abstract

ABSTRACT The ultimate cleanability of a coal by a physical separation process is dictated by its washability. In general, coal washability improves as particle size is reduced. Unfortunately, standard methods of accurately determining fine coal washability have not yet been established. In the present work, washability data for 28 mesh × 0, 200 mesh × 0, and 20 µm × 0 Pittsburgh No. 8 coal are obtained and compared using three different experimental characterization techniques. These techniques include image analysis, centrifugal float-sink analysis, and flotation release analysis. The image analysis and centrifugal float-sink techniques are found to produce similar washability results since these techniques are governed by the bulk properties of the coal. Release analysis, on the other hand, is governed by the surface properties of the coal and always produces an inferior separation. The results of the present work strongly suggest a need for developing improved gravity separation techniques for processing fine coal.