Platinum is the rarest of the world’s metals. Annually, only about 133 tons of the metal are extracted from the earth, compared to around 1,800 tons of gold. It is resistant to fading, and its malleability helps hold diamonds and other jewels in place.
Anglo Platinum in South Africa is the world’s largest platinum producer. A subsidiary of Anglo American, the company processes nearly 40 percent of all newly mined platinum annually. Uses for platinum extend well beyond jewelry, too. The precious metal helps catalytic converters strip pollutants from car exhaust gases, and platinum fuel cells are increasingly considered an alternative energy source.
Its precious metal refinery (PMR) is located near two of the largest platinum mines in the world. In addition to platinum, the ore processed by the refinery contains precious group metals (PGM) including ruthenium, rhodium, palladium, osmium and iridium. The refinery also extracts base metals, such as nickel, copper and zinc.
The refining process is complex because of the variety of metals extracted. In particular, Anglo Platinum found its process automation system increasingly difficult to support and too fragmented to handle the refinery’s intricate process, so it began searching for a solution.
Processing PGMs begins by removing ore from either an underground or open pit mine. The company then transfers the ore to one of its concentrated plants, where the ore is crushed and floated. From there, it enters the smelting process, which removes unwanted elements from the ore. A converter then transfers the product to the company’s magnetic concentrator plant, where base and precious group metals are separated.
Operations were complicated by the 1980s-era legacy control system, which had been compiled by various vendors. The result was a legacy system that required specialized skills to maintain and was also hard to upgrade.
"We have both batch and continuous processes occurring in our refinery, so variation was a key consideration when searching for a new solution," said Hermanus du Preez, control technology specialist for Anglo Platinum. "Our system needs to be able to maintain continuous processes and monitor batches. In other words, it needs to cater to our complexity."
The PMR faced issues with efficiently routing and sharing equipment used for multiple recipes. Operators needed to decide which equipment should be used when and by what process to cater to various recipes, but they were unable to schedule equipment sharing in advance, often causing delays.
To gain a scalable and flexible system, the company decided to move forward with a single vendor. "We needed to standardize, align with international best practices and upgrade our system to prepare for the next 10 to 15 years of operation," said du Preez.
The PMR already had a network infrastructure in place using a Rockwell Automation control system, so the company selected the PlantPAx system also from Rockwell to standardize its control systems with one vendor.
The PlantPAx system is a modern distributed control system (DCS) designed to manage plant-wide automation systems. As a result, Anglo Platinum can use the same automation technology throughout the refinery. This enables seamless integration, easy access to information, and easy modifications as demand or
"We were able to put the full, robust system on top of our existing control base, which helped us create standard control modules needed for our processes," du Preez said.
Customization was a critical element of the solution. Working closely with the vendor, the platinum processor implemented a hybrid process system that caters to batch and continuous processes and is compliant with ISA-88 standards. For example, a "routing block" to the refinery’s operation allows operators to effectively schedule and control equipment for equipment sharing. Operators are also able to re-prioritize changes in the queue if needed and can do so online – a new, time-saving option with the modern DCS system.
The PMR now has batch reporting capabilities because the procedural and regulatory control are embedded inside, and the flexibility of the system allows customized add-on instructions. These capabilities are delivered using their custom-build batch report automated operator interface. This improves the operator’s ability to better control the plant by displaying which key performance indicators (KPI) — such as operation and critical phase times, throughput capacity and batch variability — at each stage on an operator screen.
Reports displaying recipe parameters that are met and deviated from provide operators with access to real-time data that allow for enhanced reliability for
For example, historian software taps into information that has been automatically identified, gathered and stored to help operators analyze process-related data. Refinery operators now can see the time it took to validate a sample or for a piece of equipment to become available.
"Our operators have gained valuable information to help them understand why a certain batch took 20 hours to produce when it was supposed to take 16 hours," du Preez said. "This improved visibility enables us to identify constraints in the refinery’s processes that we weren’t always aware of before."
Stricter control is another benefit of the new modern DCS system. Each start and stop during production is reported through the historian software, so operators receive a more realistic picture of each process and batch.
For example, if a batch abnormally deviates from its recipe parameters, the process will go into a safe state. When corrected and re-started, the batch will pick up where it paused by referencing specific KPIs. Previously, any disruptions in the process were dependent on human intervention and were not always reported. Even though it is automated, operators still have the flexibility to intervene if needed.
With this solution, Anglo Platinum managers can develop standard recipe templates and libraries. From a maintenance perspective, this makes it easier to identify areas within the operation that might be experiencing unnecessary trips, faults or other issues.
With the new DCS, operators at the platinum facility have access to reporting across every stage and level of the process, enabling them to keep track of recipes in real time and maintain stricter control during production.
"We have a more realistic view of operations now," du Preez said. "With additional information and increased visibility, our operators can better understand the process."
Operators can quickly compare batches and KPIs, and identify if and when a batch is deviating. As they get used to the system and monitor consecutive
batches, they will know how long a certain batch should take and when there is an issue.
The ISA-88-structured solution has also improved maintenance and troubleshooting, which helps the platinum company comply with strict international process control standards.
"What the PlantPAx modern DCS system is bringing to the table is flexibility and scalability," du Preez said. "We will always have unique requirements that we need to cater to, and this system gives us the option to meet those and remain compliant."
Editor’s note: The results in this article are specific to Anglo Platinum’s use of Rockwell Automation products and services in conjunction with other products. Specific results may vary for other customers. PlantPAx is a trademark of Rockwell Automation Inc.
Tim Schmidt is the global marketing lead for process at Rockwell Automation Inc. For 15 years he has been focused on helping process customers solve problems with engineering and business development roles. He has a bachelor’s degree from the Milwaukee School of Engineering and a master’s in engineering from the University of Wisconsin.