What can go wrong in comminution circuit design?

Tenth Mill Operators’ Conference, Adelaide, SA, 12 - 14 October 2009


The design of semi-autogenous grinding (SAG) mill based comminution circuits for the treatment of competent ores, similar to those at Geita and Boddington, involves the same process of sample selection, test work, data analysis and data modelling/interpretation as that used for 'average' competency ores. However, over the past couple of years a number of issues have arisen that are common to the design of circuits for the comminution of 'highly' competent ores. The impact of these issues on project viability is generally more pronounced when treating hard ores than average to soft ores due to the greater impact on capital and operating costs.

The issues encountered have included:

  • standard test procedures have been modified;
  • test equipment has worn or been damaged;
  • different procedures yield different data and varying interpretation; and
  • modelling and empirical calculations have been based on poor benchmarks, or used incorrectly in the case of JKSimMet, yielding misleading outcomes.

The purpose of this paper is to present, discuss and clarify some of the issues associated with conducting test work and designing comminution circuits for the treatment of 'highly' competent ores in order to reduce the level of conflict arising from interpretation and application of test work data.

Specifically, the issues associated with the bond crushing (impact) and rod work indices measurement, the various SAG mill specific energy tests, and the interpretation of the resulting data will be discussed in the context of case studies.

CEEC Technical Review Committee Comments:

This paper provides extremely useful “food for thought” in the area of grinding circuit design. Comminution specialists offer advice as to the best approach in applying comminution design, tools and data – to ensure the comminution equipment is sized correctly and optimally configured. The paper also highlights tricks for young players such as best method for circuit design given competent and soft ores, and provides insight to the world of interpreting test work parameters.

It is essential reading for anyone attempting to understand and apply comminution design information, offering advice to help avoid common pitfalls.

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