Figures 9(a) and (b) show that both weight and toe angle control strategies achieved a comparable distribution of each controlled variable to its respective set point. Notable is that a narrow weight distribution did not result in a narrow toe angle distribution (and vice versa), highlighting the drifting nature of the weight signal. Further, the power histogram, Figure 9(d), developed during the toe angle control trial presented a more defined, narrower peak than that developed during the weight control period. Given that a reasonably consistent speed distribution (Figure 9(c)) exists between the two compared data sets, it was assessed that a narrower distribution of SAG mill volumetric filling was achieved when the SAG mill was operated toe angle control in comparison to the incumbent weight control.
Initial results indicate that toe angle control has delivered a benefit to Lihir process control by being repeatable measurement, consistent through process interruptions and independent of mill liner wear. Quantifiable production improvements were not available at the time of writing, but improved control of volumetric filling was achieved and reduced the risk of further mill overload events was realized by the implementation of toe angle control on the HGO1 SAG mill.
This article is based on the ‘Toe angle measurement for SAG mill control at Lihir gold mine’ paper presented at the AusIMM Mill Operators’ Conference, August 29-31, 2018. The authors of the conference paper are listed below. The contributions of the Lihir metallurgy, operations, instrumentation and process control teams provided valuable feedback and assistance throughout the development and implementation of MillSense. Without their collective contributions the success of this installation would not have been achieved.
F Burns1, C Aisthorpe2, P Blanz3, M Randall4, P Ebzery5
1. Senior Metallurgist – Plant Optimisation, Lihir Gold Mine, Newcrest Mining Limited.
2. MAusIMM, Senior Metallurgist – Plant Optimisation, Lihir Gold Mine, Newcrest Mining Limited
3. Product Manager – Advanced Process Control, Outotec.
4. Senior Metallurgist – Process Control, Lihir Gold Mine, Newcrest Mining Limited
5. Specialist – Process Control, Lihir Gold Mine, Newcrest Mining Limited
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