New Discoveries in the Relationship Between Macro and Micro Grindability

CIM Toronto 2009
John Starkey, Mike Samuels,
Abstract This paper examines grinding test results from two recent projects, Fortune Minerals NICO, and Aurora Resources Michelin deposits located in the NT and NL respectively. The ratio of required SAG mill to ball mill pinion energy for these two ores showed vast differences, even though both ores had similar average Bond ball mill work index values - about 13 and 10 kWh/t for the two deposits respectively. SAG pinion energy to grind the NICO cobalt-gold-bismuth-copper ore from F80 152 mm to T80 1.7 mm varies from 16 to 35 kWh/t in the first case, and for the Michelin uranium ore, it varies from 2 to 9 kWh/t.

Should the mill design for these projects be done by direct measurement or by simulation? For NICO, the ore is off the charts for simulation design techniques because there is no comparable operating SAG mill in the data base for ore that is this macro-competent. SAG pinion energy is more than double the ball mill pinion energy using a transfer size T80 of 1.7 mm and a final grind P80 of 74 microns. NICO ore is also harder than can be correctly measured by any other known method. For Aurora, the relationship between SAG and ball mill pinion energy is reversed in that the SAG mill requires less than half of the pinion energy to grind to T80 1.7 mm, than the ball mill requires to grind to a P80 of 90 microns (starting from 1.7 mm).
Keywords: SAGDesign test, Simulation, Micro, Grindability, Aurora Resources, SAG mill, Fortune Minerals, Ball mill, Direct measurement of pinion energy, Macro
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