Molybdenum and rhenium are not exactly names that roll off the tongue or carry the familiarity of the copper produced by Rio Tinto's Bingham Canyon mine in Utah's Oquirrh Mountains. While not familiar elements to most people, molybdenum and rhenium are nonetheless valuable to steel and petroleum producers, which is why Rio Tinto, the parent company of Kennecott Utah Copper (KUC), is investing approximately $340 million into building a one-of-a-kind facility to extract, process and package the minerals, using a process developed and patented by Rio Tinto.
Kennecott's new molybdenum autoclave process (MAP) facility is rising on what was a brownfield site at the south end of the Great Salt Lake, where the pioneer town of Garfield once stood on the western side of the Salt Lake Valley. The 25-acre site will contain eight separate buildings, including its own power generation and heat recovery system.
While Kennecott has been producing molybdenum since 1930 and shipping it to out to Mexico and Belgium for processing, there are several reasons for building the new plant now, says Douglas Stauffer, project director for Kennecott Utah Copper. "This plant will improve our recovery of the material. It will produce higher-quality material, and we'll be able to recover the rhenium we were not getting before," Stauffer says.
The higher-grade molybdenum is in demand as an additive to strengthen steel and as a catalyst in removing sulfur from diesel fuel. Rhenium is also used to harden steel and is sought by the aerospace industry to upgrade blades in jet turbines so that they can run more efficiently at higher speeds.
Extending Mine Life
Constructing the autoclave plant is part of KUC's plans to extend the life of the Bingham Canyon mine past 2020 and into the mid-2030s. Rio Tinto is currently reviewing plans to excavate the Bingham pit 1,000 ft farther south and several hundred feet down to recover more copper and molybdenum.
When complete, the MAP facility will produce chemical-grade molybdenum oxide, ammonium dimolybdate, autoclaved molybdenum concentrate and catalyst-grade ammonium perrhenate. Rhenium will be recovered through the MAP facility and Kennecott's smelter as catalytic-grade ammonium perrhenate and packaged in powder or pellet form. According to information from the owner, the MAP facility will position Kennecott as one of the world's largest suppliers of rhenium.
Sitework at the MAP facility began in the last quarter of 2010 with excavation and soil stabilization. Stauffer says crews placed 300 piles and 28,000 micropiles at the site. "We installed the piles because of the large loads imposed by some of the process equipment tanks," Stauffer says. "We spent the first 18 months moving ground and setting utility lines. We are at the point now where we are starting to get the vertical structures built."
Jacobs Engineering, based in Pasadena, Calif., is managing the project as the construction engineer, working under an engineering, procurement and construction management contract. According to Stauffer, the EPCM delivery method allows for better coordination among Kennecott, the engineering team and local contractors at the site. Local firms include Salt Lake City-based Big-D Construction, which was contracted for the concrete work; Ames Construction for piling, earthwork and finish grading; and Sunrise Engineering for surveying.