Coal Preparation

Improved Classification Accuracy at 100 - 350 Microns

Coal Preparation » Fine Coal

Published: May 07Project Number: C15051

Get ReportAuthor: Andrew Vince | Elsa Consulting Group

The pilot scale performance of the following different screen types has been assessed:

  • A Derrick Stack Sizer™ ; Tested by Derrick Corporation in Buffalo, New York State
  • A Kroosh high frequency screen; Tested by ACIRL Maitland, New South Wales
  • A Multotec Pty Ltd static sieve bend; Tested by Roche Mining (MT), Queensland.
  • A Conn-Weld Industries Inc static sieve bend; Tested by Roche Mining (MT), Queensland.


In addition, Minco Tech Australia Pty Ltd used their proprietary classifying cyclone simulation capability to estimate classifying cyclones separations.

Based on the results of this investigation, the following conclusions have been derived:

  • The Derrick Stack Sizer™ was demonstrated to process high rates of fine coal feed effectively and efficiently at the low cut (S50) points targeted.
  • The Kroosh Vibratory screen also processed fine coal feed efficiently at low cut points, but at a much lower unit feed rate.  Further optimisation of the stroke and angle has the possibility of increasing unit capacity, but it is considered unlikely to reach the capacity of the Derrick Stack Sizer™.
  • The Multotec Static Sieve Bend units tested made efficient separations, but were unable to achieve the low cut points targeted.  This is an unexpected outcome, and further investigation is recommended.
  • The Conn-Weld static sieve bend gave effective separations with cut points at around 0.250mm as a single unit, but was shown to make better separations when simulated in a re-pulp configuration.  However, cut points were higher than the expected 50% of aperture size

Based on the results of this investigation, the following recommendations are made:

  • The Derrick Stack Sizer™ unit should be included in the design considerations for any new or existing coal preparation plant that requires effective separation at or around a cut point (S50) of 0.10 – 0.35mm.
  • The Conn-Weld Static Sieve Bend, used either singularly or in the re-pulp configuration, should be included in the design considerations for any new or existing coal preparation plant that requires effective separation at or around a cut point (S50) of 0.25 – 0.35mm.
  • Investigate why the unexpectedly high Multotec and Conn-Weld Static Sieve Bend cut points were achieved.

The results and findings of this investigation could be used by coal preparation design engineers, process engineers and the like in a number of functions, including:

  • Equipment selection and process design
  • Troubleshooting and process optimisation
  • Process simulations.
Around 2-3 industrial Stack Sizer™ units would be expected to have an equivalent throughput capability to a single 900mm classifying cyclone.


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