Last week MZS’s fourth-grade and fifth-grade students left the familiar confines of their classrooms and journeyed into the mysterious territory of their fathers’ workplace. They traveled beyond the roads they knew, passed by buildings they had never seen, and went through security check points they have never crossed to experience the mammoth undertakings of PTFI’s mining and milling operations. Equipped with hard hats, safety glasses, earplugs, and steel-toed boots, the group of students saw, for the first time, the specialized mechanics of metal processing.
Kylee (leaning against the wooden pillar) with her peers and teachers taking a group photo before leaving on their field trip.
PTFI’s open pit and underground mines extract about 200,000 tons of ore every day. Like a colony of ants, a constant flow of haul trucks transport extracted ore to massive crushers, which break the boulders into smaller rocks and drop them onto a system of gigantic conveyors, which carry them to the mill where they are ground into fine mud. The mud is blended with chemicals to separate the copper, gold, and silver from the worthless rock (tailing). The concentrated ore, containing the metals, is piped as a slurry from the mill to a dewatering plant in the lowlands using a 110km long pipeline. After it is dewatered, the final product is shipped to smelters in Indonesia and around the world where it is then purified and poured into copper plates.
The students watching John Wilmot, Milling Guru, explain a Semi-Autogenous Grinding Mill (“SAG Mill”), which uses large steel balls in a machine like a humongous tumble dryer to grind the crushed ore into small pebbles and mud. Photo courtesy of Kylee Rose.
Ball Mills, similar to the SAG Mill, process crushed ore into mud. Photo courtesy of Kylee Rose.
Wet screens that wash the ore mud from the ore pebbles. The mud passes through the screen and moves to the metal extraction stage; the pebbles get conveyed back to the ball mills for another cycle. Photo courtesy of Kylee Rose.
The ore mud is mixed with chemicals that stick to metal-sulfur minerals, and detergent chemicals that make a froth. The valuable metals bubble up like shiny copper-colored root beer foam, which gets skimmed off. The other 99% sinks to the bottom and gets flushed away as tailing. In this photo, Kylee grabs a handful of the good stuff. Photo courtesy of Kylee Rose.
The first guys to pull the ore out of the mountain in PTFI’s underground mines have always had one of the most hazardous jobs. As a result, PTFI now extracts most of its ore through semi-automated mining machines that are run from several kilometers away on the surface. When the system is running smoothly, one operator can run several loaders at once from a clean, comfortable, and safe office building (the same building as Chris’s office). Kylee tried her hand at it during the tour. Photo courtesy of Kylee’s friend, Tara.
Maybe her time playing “Mario Kart” on the Wii will prepare her for a future job! Modern mines are becoming more like a video game than manual labor. Photo courtesy of Kylee’s friend, Tara.