APC Case Studies

Advanced pH Controller helps Impala BMR improve efficiency and quality

Impala’s BMR identified difficulties in controlling the pH in the first stage autoclaves. Poor pH control has a serious and negative impact on the Precious Metals Refinery (PMR) processes. This meant that they had to decrease the base metals content (thereby increasing the precious metal content in the concentrate) and this could be done by controlling the pH and consequently improving the nickel and iron extraction efficiencies of the process. But this was a difficult process involving simultaneous control of a multitude of interdependent variables – in other words, an ideal candidate for APC.

In accordance with the above APC implementation recommendations, one of CSense’s control engineers created a model of the whole solution, which was then transferred as a blueprint onto CSense in a simulated environment. This demonstrated that the refinery had 80-90% of the logic correct and this later greatly decreased the commissioning period.



Process overview of Impala’s Base Metals Refinery


Realised benefits

• Through less iron and nickel content, the PGM concentrate grade is much improved
• From a performance analysis conducted in March 2007:
• The pH variation has been reduced from 1,2 to 0,7 (an improvement of 40% in pH stability)
• The nickel extraction efficiency has increased by 0,5%
• The iron extraction efficiency has increased by 3,3%
• The PGM grade has increased by 1,4%
• A reduction in pH peaks in the autoclave, which can oxidise 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.
• Acceptance of the system by operating staff who now also trust it to do the right thing
• Stable process control in spite of variations (one specific batch of matte had an iron content of 11% instead of the usual 0,7% or less yet the system ensured that the PGM solids were within specifications).
• Indirectly limiting environmental emissions
• Real savings affecting Impala’s business bottom line

CSense intelligence helps Lonmin improve smelter efficiency

Part of the smelting operation at Lonmin's facility involves drying platinum group metals concentrate through filtering and flash-drying processes – which were identified as a production bottleneck. The solution proved to be more difficult than anyone had thought and required the help of an expert system that could help operators effectively manage a complex, multivariate environment.

Having identified the need for a system that detects problems and predict the outcome, engineers examined the existing data sets and started to build the control model as was described in the six-sigma project that they had done. This served them in good stead when implementing CSense.



Process overview the smelter: blue indicates those plant facilities now under CSense control and yellow indicates the control network


Realised benefits

• 16 000 tons/month is now over 20 000 tons (although other factors are also contributing to this.)
• The initial claim was that CSense could improve production by 10% but the real number is well above that yet difficult to isolate precisely because of the interdependencies of the processes involved.
• Operators no longer have to worry about changing set points and can focus on other issues.
• Incorrect temperatures due to bad control are now a thing of the past.
• CSense was easy to integrate with the current control system and its rules can be changed just as easily by authorised end-users
• By eliminating uncertainties, CSense has helped the client “see the wood for the trees” and to focus on the next level of productivity challenges.

CSense lifts Hillside Aluminium's paste plants to new heights

At the paste plants of primary aluminium smelters, green-anodes are produced and processed further downstream into pre-bake anodes. These anodes are consumed in the reduction pot lines to produce aluminium from the reduction of alumina. High throughput of good, consistent quality anodes is important for an efficient alumina reduction process to produce aluminium.

Advanced anode height controller on CSense
A CSense advanced control system with exceptional performance has been implemented culminating in:

• a significant reduction in waste production rates from about 3% to just over 1%;
• an automated production process with 'the best operator 24 hours every day, consistently producing anodes of high quality' and;
• rich, focused and continuous information for management, operators and process specialists.

The deployment of CSense at the paste plants of Hillside Aluminium resulted in significant business improvements. This acts as a showcase of the ability of CSense to assist manufacturing plants in their drive to continuously improve, gain process knowledge, and optimize.