Volcan Mining Co. operates in one of the world’s most remote regions: the mineral-rich Andes Mountains of central Peru. More than 2.5 miles above sea level — and a 7-hour drive from the capital, Lima — Volcan workers extract silver, zinc, lead and copper ore from eight mines and partly process the metals for eventual sale in world markets.

Silver is the rarest metal that Volcan mines. To capitalize on the international demand for silver bullion, the 70-year-old company recently built its first silver leaching and smelting plant. The plant contains a complex process involving multiple stages.

First, the raw ore is crushed and ground. Resulting particulates are conveyed into the milling section, then moved to agitating tanks containing a cyanide solution to dissolve the mineral. Zinc dust is then applied as a thickening agent to help gravity separate the silver from the solution. Finally, the silver is filtered, melted and molded into bullion bars.

Cyanide challenges

“Working with cyanide is a challenge because it can be toxic,” explained Jorge Luis Oviedo, corporate automation project manager for Volcan Mining Company. “We must maintain a precise pH value in the agitation tanks to avoid the generation of cyanide gas.”

That is just one of many variables that demand the synchronization of the leaching and smelting operation. The greenfield plant processes 2,500 metric tons of ore every day. A problem at any stage in the sequence could trigger an unwanted stoppage.

“For example, the conveyor that carries the ore into the crusher will halt if the crusher becomes overloaded,” Oviedo explained. “This means we lose production time until we can restart operations properly.”

Volcan executives recognized that they needed a highly reliable and available process automation system to tightly integrate and coordinate multiple control systems throughout the plant. Many of those controls came from specialized vendors in the mineral mining industry that Volcan purchased before launching the search for a modern distributed control system (DCS).

“We needed a master automation system that could integrate all the vendor products, the various instrumentations and the large number of sensors,” Oviedo said. “The ability to communicate across so many protocols and brands was essential.”

Equally essential was a system that was easy to learn and intuitive to operate for the Volcan plant’s 120 workers. In case any problems arose that employees could not handle, the company wanted support from local experts to prevent a serious loss of production time.

“We interviewed representatives from the world’s top automation companies to see who had the best solution to meet our needs,” Oviedo said. “At the same time, we wanted proven experience in silver mining to reduce startup time and life-cycle costs.”

Beneficial solution

Volcan chose the PlantPAx modern DCS from Rockwell Automation, which provides integrated control across the new facility, from crushing the raw ore to molding the silver bullion.

Control System Integration, a Rockwell Automation Recognized System Integrator based in Peru, provided engineering services and technical support to design and
commission the platform.

The team used the system’s “estimator” for guidance in sizing the platform for optimal performance in the Volcan plant.

The system includes three redundant pairs of processors and redundant servers for 250 active devices, such as human machine interfaces (HMIs), vendor controllers and a historian, connected via an EtherNet/IP network. FactoryTalk VantagePoint software from Rockwell Automation provides access to production data reports, allowing plant managers to make informed business decisions in real time.

“The system is highly intuitive,” Oviedo said. “With the training our employees received, they can easily understand and operate the system, and we have local support when we need it from Control System Integration.”

Refined results

User-defined tags, add-on instructions and faceplates available through a library of
process objects helped Control System Integration develop and deploy a device-level library of pretested and fully functional code, which was customized for Volcan’s operations. This helped simplify the integration and shaved five weeks off the pre-commissioning and startup time for the system.

“Now, we have communication with all our instrumentation, vendor equipment and motor control centers,” Oviedo said. “And our network response time is 0.1 second — very high, considering the many intervals in our process.”

Oviedo and other plant managers look forward to expanding the plant’s capacity in the next two to three years, from 2,500 to 4,000 metric tons of ore daily.