Predicting the specific energy of autogenous and semi-autogenous mills from small diameter drill core samples

Abstract A rock breakage test has been developed that can help predict autogenous (AG) and semi-autogenous (SAG) mill performance in situations where only limited quantities of rock samples are available. The test was originally developed to make use of quartered (slivered) core but whole core, half core and lump material can also be used. Original core diameters in the range 27–85 mm are suitable. The samples, once broken, can be used subsequently for Bond ball mill work index or batch grinding tests, therefore limiting overall sample requirements. The test generates an index (DW i ) that can be used to estimate the throughput of AG and SAG circuits through a combination of power-based and model-based approaches. The model-based approach makes use of the direct relationship between the DW i and the JK rock breakage parameters A and b . The power-based route uses correlations which have been developed between the DW i and the specific energies of a very wide range of operating AG and SAG circuits. Its usefulness also extends to rock mass characterisation in mining applications, as it is also correlated with the point load index/UCS. It is therefore ideally suited for mine-to-mill studies where it can be simultaneously used to predict comminution circuit performance and to augment input to blast fragmentation models. This makes it a useful tool for orebody profiling in greenfield, brownfield and established operations as, in conjunction with a mine’s block model, a detailed picture can built of the blast fragmentation and comminution circuit response.