Mining for modern life
The metals and minerals Rio Tinto Kennecott produces are essential for modern life. Whether it’s the cars we drive or the mobile devices we use daily, most of the items that we rely on for modern living are made from the products we mine. The next time you use a smart phone to text or talk to your family and friends, remember that copper is a vital component that makes your communication possible.
Copper plays a vital role in many branches of modern society and technology. Copper’s ability to be turned into wire and pipe led to its use in contemporary plumbing and heating systems. Its corrosion resistance makes it an excellent roofing material for buildings. Its electrical conductivity remains the key to modern power generation and distribution.
Copper is 100 percent recyclable and retains its quality (its chemical or physical properties) when recycled. To date, it is one of the most recycled metals. In the United States, nearly as much copper is recovered from recycled material as is derived from newly mined ore.
At Rio Tinto Kennecott, we extract ore from the Bingham Canyon Mine by blasting with explosives. Massive trucks carry the ore to a crusher that breaks the rock into pieces less than 10 inches in diameter.
The crushed ore then travels five miles by conveyer belt to the concentrator. There, we mix the ore with an aqueous solution and grind it into a fine powder. We then mix the ore powder with water, chemicals and air in flotation cells. This process causes the copper-bearing minerals to stick to air bubbles in the cells. When the bubbles float off the top, we collect them as a liquid concentrate that is 28 percent copper.
The concentrate travels 17 miles to Kennecott’s smelter. We dry it and send it into a flash-smelting furnace, which separates it into several products, including a copper matte that is 70 percent copper.
After the copper matte cools, we feed it into several furnaces that remove most of the remaining impurities, achieving 99.6 percent purity. We then cast the copper into 750-pound anodes.
We place the anodes in an acid solution, interleaved with stainless steel cathodes. For 10 days, an electric current passes between the anode and the cathode, causing the copper ions to migrate from the anode to the cathode. Other impurities, including gold and silver, drop off into the bottom of the tank where they are collected for further processing.
The electrolytic process forms a plate of 99.99 percent pure copper. One anode will produce two cathodes, each weighing about 300 pounds. These copper cathodes are Kennecott’s finished products. We strap them together in 5,500-pound bundles, load them onto railcars, and ship them to our customers.
Molybdenum is highly versatile as an alloy in steel, improving strength, hardness, toughness, weldability, elevated temperature strength and corrosion resistance.
Molybdenum’s unique properties also make it ideal for other applications beyond alloys. Many chemical applications such as catalysts, pigments, corrosion inhibitors, smoke suppressants and lubricants use molybdenum.
Many copper mines contain molybdenum, and the Kennecott Bingham Canyon Mine is no exception. We send extracted ore from Bingham Canyon to the concentrator, then mix it with an aqueous solution and ground it to a powdery consistency.
Then we use a process called froth flotation to separate molybdenum, copper, gold and silver minerals. We filter, dry and package the molybdenum concentrate, then ship it to roasting facilities that further process the concentrate into the base finished product — molybdenum oxide.
Gold, along with copper, was one of the first metals discovered by human beings. Throughout history, gold has been the most highly sought after precious metal. A wide range of electronic, space aeronautics and medical applications contain gold due to its high conductivity, complete reflectivity and absolute resistance to corrosion and oxidation.
In addition, space vehicles integrate gold-coated film to reflect infrared radiation and stabilize the temperature of the spacecraft. Gold is 100 percent recyclable. Today, about 15 percent of gold consumption is recycled annually.
Silver’s superior and unique properties make it an indispensable and highly desirable metal. Of all metals, silver is the best electrical conductor. It is beautiful and strong, sensitive to light, malleable and ductile, reflective and 100 percent recyclable.
Silver has superior conductivity even when tarnished and can endure extreme temperature changes. Because silver can achieve the highest brilliance of any metal when polished and because of its durability, silver has been used to make coins, jewelry, dinnerware, ornaments and medals since ancient times.
Gold and silver are products of the copper mining and smelting process. They follow the same production pathway as our copper ore from the mine to the smelter.
At the refinery, we lower copper anodes (which contain gold and silver) into an acid solution. Gold and silver drop off into the bottom of the tank as electrolytic slimes. We send these slimes to the Precious Metals plant where we separate the gold from the silver. After the separation, we refine the gold and silver into a dry sand, which we melt and cast into bars.
Sulfuric acid is a corrosive, colorless, odorless, oily liquid that is the largest-volume industrial chemical produced in the world. Sulfuric acid plays some part in the production of nearly all manufactured goods. We produce about 1 million tons of sulfuric acid each year as a product of the smelting process.
We deliver sulfuric acid to gold, copper, uranium, and beryllium metal producers, fertilizer producers, chemical manufacturers, power plants, steel companies, farmers, and companies involved in water treatment across the United States.
Many of the world’s most important metal ore bodies are sulfides — that is, mineral compounds that contain sulfur. The Bingham Canyon Mine contains veins of copper sulfide, so the ore extracted contains sulfur, which needs to be separated from the copper.
We upgrade ore from the mine to produce copper concentrate using a flotation process. The copper concentrate entering the smelter is about one-third copper, one-third iron, and one-third sulfur, with other trace minerals. The smelting process breaks the elements apart and the sulfur is driven off as sulfur dioxide gas.
Kennecott’s smelter is one of the most modern and cleanest in the world. It captures 99.9 percent of the sulfur dioxide emissions produced. We clean the sulfur dioxide gas and pipe it to a double-contact acid plant. There, we convert the sulfur dioxide to sulfuric acid.