SAG Mill Operation Optimization for Different Types of Ores Based on a "Virtual Geologist"

The main disturbance for stability in primary grinding using SAG mills is related to continuous changes in the ore being fed to the plant, such as size and hardness. Searching for stability is the first step to accomplish, before trying to maximize the mill throughput. The time variability in the characteristics of the ore being fed from the mine to the plant must be known or inferred to perform adaptive changes in the grinding process control. In day to day operation, such information is not available in real time. Transport times and inventories between the mine and the plant complicate the situation. Under this scenario, Minera Los Pelambres implemented a grinding optimization strategy, based on the real time analysis of certain process variables, such as ore size, mill current consumption, pebble generation and throughput. As a result, both grindability and stability indexes are inferred. This is equivalent to inferring the ore characteristics by knowing its effect on the grinding behavior. These two indexes permit control of the SAG mill total charge level and hence, allow optimization of throughput by means of an expert control system.