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Comminution Circuits – Featured Projects


Southern Peru, 2009-2013 (108,000 tpd – 80,000 tpd)

Predictions of mill throughput from a porphyry copper open pit based on comminution test results of 22 composites and the available motor power of a “Standard” SAG Mill/Ball Mill circuit consisting of one 40 ft dia. x 22 ft EGL SAG Mill rated at 24 MW GMD and two Ball Mills, each 26 ft dia. x 40 ft EGL and rated at 16.4 MW GMD. DJB’s in-house Bond Work Index-based “Millpower2000” simulation software was used to create these predictions for comparison with those of other comminution protocols, e.g., SMC/DWI and SPI/CI, and to assist Xstrata Copper in setting design criteria for the plant. This grinding circuit was successfully commissioned and operated within the predicted range of daily mill throughput during its first year of production.


Northern Chile, 2009-2011 (135,000 tpd)

Two phases of access to and sampling of drill core at site were completed to yield 54 half-HQ samples (Phase 1 in 2009) and 335 half-HQ plus 94 whole dia. PQ samples (Phase 2 in 2010) for comminution testing of a large copper-molybdenum porphyry at high altitude. Phase 1 was for a Pre-Feasibility Study and Phase 2 was for a Bankable Feasibility Study. Bond Work Indices for low energy impact crushing (predicted for half-HQ and tested for PQ samples), rod milling, and ball milling were completed for input of results into “Millpower2000” and assessment of different combinations of SAG Mill and Ball Mill sizes and motor powers to assist preliminary engineering, equipment purchase, and mine production optimization studies. Test results from SMC/DWI and SPI/CI protocols were also completed on a “same sample interval basis” as the Bond samples so that true comparisons of predictions of mill throughput by other consultants could be made.


Sudbury, Canada, 1988-1991 (20,000 tpd)

Following a review of pilot plant test work, sizing and specification of equipment, and establishment of production targets for a 32 ft dia. x 13 ft EGL SAG Mill rated at 8.2 MW with a twin pinion DC motor drive commissioned in 1991 with conversion of rod mills to ball mills as part of detailed engineering (with Fluor Daniel Wright) for INCO’s (now VALE) Mill Rationalization Program, the conventional plant was expanded to process 40,000 tpd of copper, nickel, and platinum metals ore.


Central Chile, 1985-1987 (20,000 tpd)

This project (with Wright Engineers Limited) began with specification, supervision, and evaluation of pilot plant test work followed by sizing and specification of equipment, establishment of production targets, and continued with basic engineering for a 36 ft dia. x 15 ft EGL SAG Mill rated at 11.2 MW GMD and two 18 ft dia. x 27.5 ft EGL Ball Mills, each rated at 4.85 MW with a single pinion drive and a synchronous motor as part of the Expansion of the Colon Concentrator to process 110,000 tpd of harder primary sulphide ore from underground.


Sumbawa, Indonesia, 1995-2000 (120,000 tpd)

Due to environmental constraints on surface which precluded extraction of bulk samples for pilot plant test work, this plant is believed to be the first grinding circuit to be designed (with Fluor) for a large tonnage copper-gold porphyry ore from bench-scale Bond Work Index tests on drill core. Initially, 105 contiguous PQ drill core sample intervals were selected by bench height and tested within preliminary mine production plan limits for the payback period and up to 10 years of mill feed. Two grinding lines, each consisting of one 36 ft dia. x 19 ft EGL SAG Mill rated at 13.4 MW GMD and two 20 ft dia. x 33.5 ft EGL Ball mills, each rated at 7.09 MW with a single pinion drive and a synchronous motor, were commissioned. Each line had one MP1000 pebble crusher. The operation was ramped up ahead of schedule with minor modifications and exceeded the 120,000 tpd design capacity during the second year of production.

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