Coal Preparation » Gravity Separation
The novel dense medium cyclone (DMC) developed at the JKMRC was scaled up to 200mm in diameter and tested in the JKMRC pilot plant while its geometry was optimised. A 200mm DSM type cyclone was also tested for comparison.
Colour-coded narrow increment density tracers, 8-0.3mm in size, were used as the feed material. The Irregularly shaped tracers were specially prepared, in that particles which were more than 0.01 RD units from their nominal density were eliminated through float-sink procedures. Statistical considerations were made to ensure that the tracer number for every density and size fraction is sufficient to achieve certain accuracy and confidence level for the partition number.
The DMCs were pump fed at a nominal feed pressure of 22 kPa that is 11 times the DMC diameter. To significantly reduce the test number while achieving good test results, an orthogonal design (or Taguchi array) was applied.
The separation sharpness (or Ep values) of the novel DMC is always better than the DSM cyclone in all size fractions, in particular for the finest particles (0.5-0.3mm size fraction), despite the changes of all the component dimensions from test to test for the novel DMC. The average Ep values at the feed pressure of 22 kPa are 0.015, 0.016, 0.021 and 0.030 for the 8-2, 2-1, 1-0.5 and 0.5-0.3mm respectively for the novel DMC, and 0.020, 0.023, 0.029 and 0.048 for the DSM cyclone.
Both the DMCs were also tested at lower feed pressures, 20Kpa and/or 16 kPa, and found that the novel DMC can be well operated at the feed pressures of around 18 kPa while retaining good separation performance.
Based on the investigation, the optimal dimension of every cyclone component for the novel DMC has been selected within the component designs investigated, that will be used as a basis for further scaling up the novel DMC to an industry-sized DMC.
An analysis of variance was implemented from which the cyclone components giving significant effects on the novel DMC performance are identified.