Coal Preparation » Gravity Separation
Washability data has traditionally been generated for the coal industry using the float-sink method AS4156.1-1994. This technique relies on heavy organic liquids to fractionate coal and mineral particles based on particle density. These organic liquids are considered problematic for both health and safety and environmental reasons and hence several alternative methods for attaining washability information have been investigated. This study examines the potential of water based methods for providing a rapid, accurate and safe alternative to using heavy liquids in float-sink testing.
The Australian Coal Association Research Program (ACARP) commissioned this study to assess water based test methods for generating coal washability data. This project was an extension of a previous ACARP study, Small Coal Washability by Water Fluidisation (Project C10050), with the inclusion of jigging to help extend the particle size range. The objective of the new study was to provide an alternative to the current industry standard ‘float-sink’ test, in order to provide a rapid and safe method for determining coal washability data for the -50 +0.045 mm particle size range.
The study evaluated a number of water based test methods, namely, a water fluidisation column, a mechanical Boner jig in which the entire sample oscillates within a water tank, and a more conventional hydraulic Mintek Mineral Density Separator (MDS) jig. The water fluidisation column was designed by the University of Newcastle (Australia), the Boner jig apparatus was developed and supplied for the project by Lindsey Bone (Anglo Coal, Australia) and the Mintek jig is a commercially available laboratory-scale separation device (Mintek Pty Ltd, South Africa). This report describes the commissioning, evaluation and optimisation of each water based technique.