UTILISATION OF THE SMARTDIVER PROBE TO IMPROVE CONTROL OF SETTLERS AND WASHERS IN THE BAYER PROCESS

The two key parameters for the effective control of settlers and washers are the interface and mud level. In the past the interface and mud level have been obtained manually. The process of obtaining a reading was a risky, difficult and labour-intensive process which was open to error due to the visual nature of the test. With the introduction of the SmartDiver it is now possible to gather suspended solids and density data of a settler or washer throughout the entire profile of the vessel, automatically and semi-continuously, through the use of an automated dive mechanism. This provides a more accurate measurement for the control of the interface and mud levels that is easy to incorporate into a control system such as a Programmable Logic Controller (PLC) or Distributed Control System (DCS).

Once an interface and mud level measurement is obtained a number of different control methods can be utilised, in which the interface level is utilised in the control of flocculant dosing and the mud level is utilised in the control of the underflow pumping. The control strategies utilised range in complexity from standard feedback control through to feed-forward and model predictive control. The end result of this improved control is the reduction in overflow suspended solids, while using the minimum quantity of expensive flocculant. The enhanced control of the mud level allows for increased underflow density. This results in less liquor (due to the higher percentage of solids being pumped) passing through to the washers in the case of a settler and improves the washing efficiency of any washers within a Counter Current Decantation (CCD) circuit.

Improving the performance of the settlers, washers and tailings thickener in this way provides significant cost and environmental benefits.