As one of the largest copper producers in the United States, Rio Tinto Kennecott comprises nearly 8 percent of U.S. annual copper production. The Bingham Canyon Mine is one of the top producing copper mines in the world with production at more than 20 million tons.
The Bingham Canyon Mine is the largest man-made excavation on Earth. It measures two and three-quarter miles across at the top and three-quarters of a mile deep. If you stacked two Willis Towers (formerly the Sears Tower) on top of each other, they still would not reach the top of the mine. You could lay the soccer field at Rio Tinto Stadium in Sandy, Utah, end-to-end more than 38 times across the top of the Bingham Canyon Mine before it would reach both sides.
Explore Kennecott's operations at the Bingham Canyon Mine
Copper production begins at the Bingham Canyon Mine. We carry out a sequence of drilling, blasting, loading, hauling, crushing and conveying 24 hours a day, seven days a week, 52 weeks a year.
Drilling and blasting
We detonate 1,200 pounds of explosives twice daily in holes 55 feet deep to break up the rock and remove the ore out of the ground.
Loading and hauling
After the blasts, our electric shovels and haulage trucks move in. After the shovels load the ore and waste, the fleet of 70 haulage trucks transports ore to the in-pit crusher and non-economic material to rock repositories.
Crushing and conveying
At the gyratory crusher, we reduce approximately 150,000 tons of ore per day to pieces about 10 inches in diameter. We then transport the crushed ore by a five-mile conveyer system at the speed of about 900 feet per minute: three miles through a tunnel in the mountain and two miles above ground to the Copperton Concentrator. Ore arrives from the mine at the Copperton Concentrator in about 28 minutes, where it is temporarily stored in a 500,000-ton coarse ore stockpile.
In the second step of the production process, we concentrate the ore, which separates valuable minerals from the ore into a concentrated liquid.
We turn the crushed ore into a slurry and transport it to flotation cells. We then mix the slurry with reagents to produce a bubbly froth. As a result, ore particles containing most of the valuable minerals adhere to the bubbles, which float over the sides of the flotation cells. We then collect and filter this material, called concentrate.
The concentrate, which contains about 26 percent copper and by-products such as gold and silver, moves through a pipeline to Kennecott’s smelter, located about 17 miles to the north, for further processing.
The next stage, smelting, is a process of heating and melting the copper concentrates to cause a chemical reaction, which removes the copper from other elements in the ore. At the smelter, we produce large 750-pound anodes and transport them by rail to the Refinery. The copper is 99 percent pure at this stage.
The smelter at Kennecott captures 99.9 percent of the sulfur in the feed, making it one of the cleanest in the world. The smelter also recovers heat from the furnaces, which generates 60 percent of the facility’s total electricity.
Refining is the final step in the copper production cycle and is where precious metals are separated from the copper and recovered.
At the refining stage, the copper is in anode form. We subject the 750-pound copper anode plates to an electric current for 10 days and turn them into two 300-pound copper cathodes. This further separates the copper from other metals, resulting in 99.999 percent pure copper.
At the refinery, all the other impurities — including silver and gold particles — drop off into the solution and settle to the bottom. The residue from that solution goes to the precious metals plant, where we put it through a series of chemical processes to separate out the gold and silver.
The last step in the production process is to stamp each gold and silver bar with Kennecott’s brand, the lot number, the weight and the fineness, or percentage of gold or silver in the bar.