Orebreak Controls

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During maintenance periods of an ore scrubbing circuit, ore needs to not be added to that circuit’s feed bin. To facilitate this, ore gaps need to be planned in for when the shuttle will move over this unused bin.

The orebreak needs to be planned ahead of time as the feed sources are up to a few minutes upstream of the bins. This requires calculations to be done to predict when a bin will be filled to the required level.

There is a production cost in getting the prediction wrong as under-filling the bin will mean a scrubber runs out of feed before the bin can be filled again. Overfilling a bin is even worse as it will trigger the high level protections and trip all the feed to the plant.

Algorithms were developed to improve the prediction capability of orebreak planning. Online adaptive algorithms were incorporated to react to changes in ore to avoid regular process control tuning and support requirements.

Benefit

By improving the prediction calculations, the variation of bin level was reduced (see Table 1: Rocket Orebreak Optimisation).

This allowed a dramatic reduction in both under-filling and overfilling of the bin and thereby supported increased production.

This also stabilised the production rates of the plant which improved plant reliability and supported the ore beneficiation process to improve product yield and upgrades.

Further, due to the online adaptive components of the new control, the process control team were not required to regularly re-tune orebreak operation.

Another mode of orebreak which was less frequently used was hybrid orebreak. This mode creates the ore gaps for shuttle movements by redirecting feed away from the scrubbing circuit to the dry screening plant. The previous control for this used similar prediction calculations as the standard rocket orebreak (see Table 2: Hybrid Orebreak Optimisation).

This mode of orebreak was significantly improved by removing the prediction components and instead using small changes in belt speed to achieve the same operational requirements. This resulted in a much tighter control with the same types of benefits as achieved in rocket orebreak mode.

Orebreak Controls

Benefit

Optimisation and automation for safety, production output and efficiency