The milling circuit consists of a primary and secondary mill, cone crusher and a cyclone cluster. The objective is to run at:
• the highest possible throughput and
• on target quality while
• not exceeding up or downstream process constraints and
• to minimize maintenance cost.
Process data is interpreted in real-time and visualization takes place via a web-based application. Intuitive and actionable information is presented.
The client team actively participated in activities that captured client knowledge, defined systems and interpreted analytic results. These activities serve to facilitated change management, alignment and deliver insight to the client team. Time-in-State facilitated the analysis and derivation of the Optimum Operating Envelope (OOE) for the respective systems within the milling circuit.
Milling circuit energy efficiency numbers are shown in the table below. An optimum envelope was defined at the start of the project (before column). Energy efficiency was 22.1 kWh/t under optimum conditions (inside OOE). Outside OOE the energy efficiency was 25.7 kWh/t. Optimum conditions, therefore, delivered 14% better energy efficiency compared to conditions outside OEE. This assessment facilitated the definition of set points that were implemented in the control system.
Time-in-State methodology drives continuous improvement. The outcome of this improvement is illustrated in the “After” column. The “After” assessment was executed 6 months later. This column shows that the average energy efficiency improved by 7.4%.
The OOE definition was subsequently refined – the smaller difference between “inside” and “outside” OOE) refer to the “After” column) confirms that the process variance is less. This project, therefore, contributed to improved process stability as well.The OOE definition was subsequent refined – the smaller difference between “inside” and “outside” OOE) refer to the “After” column) confirms that the process variance is less. This project therefore contributed toward improved process stability as well.