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APC in secondary mining applications can improve throughput and yield

Rockwell Automation’s Andrew Sia talks to PACE Editor Kevin Gomez about advanced process control which can help improve plant throughput and yield. In a typical application, it is possible to increase throughput from about five to 10 per cent.

How do you define secondary mining and what are some of the key processes that are employed?

Secondary mining is defined as the processing of material within a mining operation. Mineral processing or smelting would be regarded as secondary mining. We’re assuming here that the regulatory control, which is the minimal standard for these plants, is in place. So you would typically have a DCS or a loop controller executing PID control, providing the regulatory control. In addition, to satisfy advanced regulatory and supervisory control, you would adopt advanced process control (APC).

Processing plants are typically high yield and there’s a certain efficiency rate in terms of converting ore or raw product into a useable product. For advanced process control you mix and match dead time compensation, constraint control, multi-variable cascading, gain scheduling, fuzzy and feed forward and several other techniques to improve plant throughput and yield.

What are the benefits of APC?

APC can improve throughput and yield. In a typical application, you would be able to increase throughput from about five to 10 per cent. Obviously it could be a lot higher if the plant is in a very poor state as far as its throughput is considered. From our experience with mining companies in Australia, yield increases in the five to 10 per cent range are realistic. As far as dollars are concerned, it varies, but gains of $10 million to $20 million are feasible. In most cases, the typical payback time could be six months to a year. This is a key consid eration for companies seeking to invest in this area.

Does the solution vary across sites?

No two applications or processes are identical. If you check out several process control loops for example, one may use fuzzy logic control, another may use cascade control only and the third could use feed-back control. It depends on the base — the state of the regulatory control. To ensure a successful implementation, all the control elements such as instrumentation and valves have to work well and be in a good condition. It is only after that that you can implement advanced process control well and derive the full benefit.

What’s preventing more companies from imple menting APC?

It really comes down to skill set availability. The chal lenge for us, in Australia, is to have people who are very familiar with their industry, their application and who also know process control theory. Within Australia, there would only be a small community with the extremely advanced level of knowledge and competency required to design, build and run the systems with the tools available.

However, with the tools becoming more generic and intuitive, the situation is getting better. You no longer have to be a PhD or a metallurgist or an expert in control to be able to use them, as the tools are often standard “out-of-the-box”. But if you ask me why there aren’t more of these, I’d say end users may be restricted by their level of knowledge and business risk to actually operate these systems onsite. There are plenty of people implementing process control and able to design systems, but there are few that combine control princi ples with process application and tie that into APC technology to produce tangible business results.

Who caters for APC in Australia?

There are a few specialists, such as Manta Controls who is also a systems integrator and implements advanced process control solutions. But very few other companies specialise in this area. Rockwell Automation has the ability to provide advanced process control through systems integrators or internal specialist resources, which highlights the flexibility of our business. One such example was a solution provided via Manta on the St Ives gold mine. I would say Australia is at the fore front of APC technology. While it’s good we have in- country knowledge and expertise, my lament is that we have so few experts. Fortunately, Adelaide-based Manta Controls does provide training in this particular area and is one of the very few in the region to do so.

Can APC be used in other industries?

APC is applicable across a variety of industries, not just in mining. Personally, I’ve worked on chemical and oil & gas APC applications, and they have been successful. Other industries could definitely benefit from the tech nology. Till recently, advanced process control was treated as a black box which could only be understood and manipulated by so called propeller heads or PhDs who implemented very complex algorithms. People tended to shy away because of the expertise required.

But the situation is changing. For example, the Rockwell Automation PlantPAx system does have out- of-the-box functionality that is rather straightforward to implement. The configuration software allows you to easily drag and drop boxes to create fuzzy control blocks, a cascade loop or dead time compensation.

System simulation and analysis is also made easy by the advances in processing power of modern day computing. Moreover, it’s becoming quite inexpensive. We used to see price tags of $100,000 and even going up to $300,000, to implement such solutions. With these tools, we’re talking only several thousand dollars and this could see the number of implementations grow, given of course there are people willing to learn and deliver quantifiable business results.

[Andrew Sia is Rockwell Automation Business Development Manager, Process Solutions, South Pacific.]

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