Dewatering of Ultrafine Coals and Tailings by CentribaricTM Technology - Laboratory Scale Tests

This report describes the responses of Australian coals and tailings to the commercialised Centribaric^TM dewatering technology at laboratory scale and in batch mode. It provides detailed information on the impact of operating variables and particle size and type on the efficiency of Centribaric^TM dewatering, including product moisture and solid recovery.

The results for the samples received from Queensland and New South Wales showed that increasing air pressure from 0 to 3 bar could cut coal moisture by 21% to 65%, and the solid recovery exceeded 99%. These results confirmed the concept of the hyperbaric centrifugation, that is, combining increased spinning and compressed air brings about a synergistic effect on dewatering. Further reduction in product moisture was achievable for ultrafine coal samples with using the split dewatering concept (dewatering at different particle size fractions), at the cost of a small decrease in solid recovery.

There was a strong correlation between the Centribaric^TM dewatering performance and the mass fraction of ultrafines (-45 µm materials). The more ultrafine particles in the feed, the higher the total moisture of the dewatered product would be.

Surface moistures were lower than the corresponding total moisture by 0.3 to 4.8 percentage points, depending on sample type. The 50% passing size (by volume) of the particles lost to effluent varied from 30 µm to 238 µm, which appeared to be related to the percentage of ultrafines present in the feed to the Centribaric^TM test unit.