Danish engineering company FLSmidth has launched a process optimisation solution for semi-autogenous grinding (SAG) milling, SAGwiseTM.

The system is designed to optimise the use of the three main consumables in SAG milling: power, media and liners.

The SAGwiseTM is a total process control system and can reduce energy consumption at SAG mills by up to 6%. As SAG mills are typically one of the single largest power consumers within a processing plant, this is a significant reduction.

To reduce power consumption, the SAGwiseTM makes use of specially designed acoustic sensors and process control software that monitors the induced impacts, caused by steel balls striking the mill liners, in the SAG mill. The system registers undesirable high-energy impacts that are categorised as critical impacts and makes small, frequent adjustments to the mill operational conditions. These changes reduce the critical impacts and improve ore reduction and energy efficiency.

“This solution employs high-quality process control technologies to reduce critical impacts to the desired targets, stabilising and then optimising the operation of the SAG mill. Multiple process control technologies, such as model predictive control and fuzzy logic, are embedded into the solution, modelling both the process and the human operators,” FLSmidth global product line manager for automation process control King Becerra highlighted in a press release.

In addition, the system can reduce up to 45% of ball-on-liner impacts, prolong liner life, minimise media degradation and reduce costs associated with replacing worn mill liners. As each liner weights up to 4 t and can cost over $1-million, there is a significant amount of time and effort needed to replace them. This affects productivity and therefore profits.

“High mill availability is crucial. A gold processing plant I visited recently valued their SAG mill downtime at $130 000 an hour,” FLSmidth liners global product manager Jack Meegan said in a press release. He went on to explain that return investment on the SAGwiseTM is about six months, but if reduced unscheduled maintenance is factored in, the return is a lot sooner.

Lastly, the SAGwiseTM can improve the safety performance of a SAG mill. This can be attributed to the reduced amount of times employees are required to move heavy equipment inside the mill, improved inventory management and improved predictive maintenance planning.