JOURNAL PAPER

pH advanced process control solution for Impala BMR first stage high pressure acid-oxygen leach

A.F. Khan^I; T. Spandiel^I; T. van Schalkwyk^II; J.A.M. Rademan^III

^IImpala Platinum Ltd
^IIBlue Nickel Solutions CC
^IIICSence Systems (Pty) Ltd

SYNOPSIS

The CSense advanced process control (APC) solution's main objective was to improve the stability of the pH in the first stage leach process thereby improving nickel and iron extraction efficiencies and reducing the base metal (BM) content in the platinum group metals (PGM) concentrate. By improving the stability of the control of the pH on the first stage leach it had the corresponding effect of improving the Ni extraction efficiency by 0.5% and the Fe extraction efficiency by 3.3%. The system relieved the operators of many decisions that were virtually impossible to make given the complex, variable and real-time nature of the processes in their charge. On the operational side, the operators understand the APC system and they trust it. Another benefit is the reduction in pH peaks in the autoclave, which can oxidize certain elements whereby they become difficult, if not impossible, to leach. These elements go right through the process and end up contaminating the PGM solids, with the result that the entire batch has to be recycled through a lengthy and costly processing pipeline.

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