Measuring and modelling the impact of primary crusher stockpiles on autogenous/semi-autogenous mill feed size

Abstract

Comminution circuits generally have a coarse ore stockpile after the primary crusher to decouple the relatively uneven mined ore supply from the downstream comminution and concentrator circuits which require a stable feed. Whilst this assists with evening-out throughput disturbances, it can influence the size distribution presented to the downstream comminution circuits through size-segregation effects. This is particularly important in Autogenous (AG) and Semi-autogenous (SAG) circuits. What is not often considered, however, is that the stockpile may also cause size reduction.

Size distribution data from stockpile feeds and stockpile products were collected from 13 different plants around the world. Analysis of these data supports the assertion that size reduction occurs in the stockpile. A simple power-based model is described which accurately predicts the degree of size reduction measured. Worked examples are provided which show how the model can be used to predict the stockpile product size given data on stockpile geometry and ore hardness.