Copper processing is a complicated process that begins with mining of the ore (less than 1% copper) and ends with sheets of 99.99% pure copper called cathodes, which will ultimately be made into products for everyday use.Sentinel Copper Mine is one of the World 's leading Copper Producers with the the ability to produce around 1.2 million tonnes of finished copper a year – comfortably above current production levels of around 750 000 tonnes a year from its Four Smelters.

Mining is a long-term business
Sentinel Copper Mine’s smelter was designed to be expanded; tie-ins have been installed and areas for future equipment already allocated. A further big investment would enable its production capacity to rise from the current 300 000 tonnes of finished anode copper a year to 500 000 tonnes or more.

Mining at Sentinel
Mining at Sentinel is carried out using conventional open pit methods, with electric shovels, hydraulic excavators and a fleet of ultra class trucks enhanced by trolley-assisted haulage technology. Initial mine development commenced in mid 2013 to establish two starter pits within which in-pit crushing and conveying (IPCC) infrastructure was installed. These starter pits are located in the first of a number of along-strike mining phases, extending east to west over an ultimate length of 5.4 km. Since 2013, the initial Phase 1 pit has been mined along its full length of 1.8 km, to a width of 1.5 km, and to a current depth of approximately 200 m. Sentinel – production rampup is as follows below -

Consistency improvements and production rampup

Potential 38,000 – 60,000t Ni production per annum

Oxide ores are generally processed using hydrometallurgy. This process uses aqueous (water-based) solutions to extract and purify copper from copper oxide ores at ordinary temperatures, usually in three steps: heap leaching, solvent extraction, and electrowinning.

Sulfide ores are generally processed using pyrometallurgy, the extraction and purification of metals by processes involving the application of heat. This process uses a series of physical steps and high temperatures to extract and purify copper from copper sulfide ores, in four basic steps: 1) froth flotation, 2) thickening, 3) smelting, and 4) electrolysis.

is used to separate the copper minerals from the gangue. Chemical reagents called “collectors” are added to the slurry and bind to the copper particles, making them hydrophobic, or waterproof. Pipes are used to blow air into the bottom of the tank to create bubbles, which rise to the surface, taking the waterproof copper sulfide particles along. The froth of copper-rich bubbles at the top of the tank is then skimmed off for further processing. The gangue sinks to the bottom of the tank to be removed or disposed of as mine tailings.

The heated liquid
The heated liquid is poured into a slag-settling furnace. This step produces a combination of matte, a mixture of copper, sulfur and iron, and slag, a dense, glassy material made of iron, silica, and other impurities. The copper matte created by the smelting furnace contains 58-60% copper.

The molten matte
The molten matte is then taken to another furnace called a converter to have the remaining iron and sulfur burned off; the product is referred to as blister copper, which contains 98% copper, and taken to the anode smelter. The blister copper is yellow; when the oxygen in the copper is burned off in the anode smelter, it turns a blue-green color.

The resulting product, molten anode copper
The resulting product, molten anode copper, is poured into molds called anode-casting wheels. The cooled anode slabs are 99% pure copper, are now copper-colored, have two handles molded on top, and are two inches thick, three feet wide, three-and-a-half feet high, and weigh 750 pounds.

Electrolysis
The copper anode slabs are then refined in a final step called electrolysis. The anode slabs are hung in a large tank full of an electrolyte solution made of copper sulfate and sulfuric acid. Thin sheets of pure copper, which are called cathodes and weigh about 15 pounds each, are hung in between the anodes. An electric current is applied, and positively-charged copper ions (called cations) leave the anode (positive electrode) and move in solution through the electrolyte solution to be plated on the cathode (negative electrode). Other metals and impurities also leave the anode to drop to the bottom of the tank or stay in the electrolytic solution. These impurities are collected and may be refined to recover other metals such as silver and gold. After 14 days of electrolysis, the anodes have gradually disappeared, and the copper cathodes now weigh 375 pounds each and contain 99.99% pure copper. The cathodes are taken out of the tank and rinsed with water to prevent further reaction.