This flowchart made of machinery icons explains or expresses in simple but clear terms the step of theCopper Mining and Copper Extraction Process. Starting from either open-pit or underground mining and using a different relevant treatment method for oxide or sulphide copper mineral (ore).
Havinga quick look now at how porphyry ores are treated and the metals extracted. There are two main process streams; one for sulfide ores and the other for ore that is being weathered to oxidize sulfides the so-called oxide ores. All ore in the pit is drilled and blasted and loaded into trucks and hauled for treatment if the ore is un-oxidized sulfidic ore then it needs to be crushed and milled to a fine slurry then it gets past through flotation cells in a concentrator to separate and concentrate the sulfides. The top picture shows the interior of a large concentrator with rows of individual flotation cells the floatation agent is added to the slurry and stirred. The floatation agent preferably sticks to the sulfide minerals rather than the waste minerals and then air is bubbled through the mixture and the floatation agent traps the fine bubbles which carry the sulfides to the surface of the cell where they are carried over aware and separated. From there they are dried to provide a concentrate which then goes on to a smelter. This is the same process for both copper and molybdenum porphyries. The smelter is basically a large furnace which melts the concentrate and drives off the sulfide to leave molten copper metal this is still contains impurities and it needs to be refined further to make it a salable product.
Returning to the overall process; that is the process for the sulfide ores and the oxide ore as I said are treated differently. Direct from the pit the oxide ore is piled onto large lined leach pads and the sulfuric acid. The top photo shows one of these leach pads with the new thick black plastic liner visible on the right of the pad. The copper oxide minimum minerals are dissolved by the acid to give a blue copper rich solution mainly of copper sulfate. This solution is tapped off from the bottom of the pad and placed into big tanks with steel plates an electrical current is passed from the tank to the steel which is then electroplated with pure copper. This process as the advantage of avoiding the smelting and refining stages required for sulfide ores.
The four major steps in the production of marketable copper are mining, concentrating, smelting, and refining. In a few instances, however, leaching takes the place of concentrating, smelting, and refining. At present, although considerable leaching and direct-smelting ores are produced, the bulk of the copper ore mined is concentrated.
The milling of copper ores as practiced in the larger concentrators has changed to such an extent that comparatively few of the machines in use at the beginning of the period remain in service today. Primary and secondary crushing by machines of the Blake and gyratory types and intermediate and fine crushing by rolls has survived, but in the grinding field the development of pebble-mill grinding, the substitution of balls for pebbles, and the parallel development of drag-type classifiers have all but eliminated Chilean and Huntington mills. In the concentrating field, machines which effected separations on the basis of difference in specific gravity between copper and gangue minerals have been almost completely replaced by flotation equipment. In the Lake Superior district jigs and tables have, of course, been retained, and in a few concentrators which treat sulphide copper ores tables have been retained owing to unusual conditions at the plants or the smelters that treat the mill concentrates.
The flotation process, which was responsible for the almost complete change in equipment, has also undergone marked changes since its introduction in large-capacity concentrators. Flotation, when first introduced between 1913 and 1916, was used primarily to reduce losses of copper in the fine tailings of gravity plants. From an accessory to gravity methods, flotation very rapidly became a major process and finally, from 1923 to 1927, all but eliminated the gravity method in the treatment of low-grade sulfide copper ores.
The rapid development of ball-mill grinding must also be attributed to the adoption of the flotation process, since it was the incentive for developing grinding methods which produced considerable copper minerals too finely divided for successful recovery by existing gravity methods.
As with gold and other ores, details of practice vary because of differences in the ores or on account of economic considerations. Five figures are presented to illustrate in a general way the concentrating methods employed for treating the different types of ores.
Figure 150 is the flow sheet of one unit of the gravity concentration section of the Calumet & Hecla Conglomerate mill. The sand tailing from the mill is treated by ammonia leaching and the slime tailing by flotation. Since metallic copper is malleable, it cannot be broken and pulverized as can the more friable minerals, and after first picking out the larger lumps or nuggets of copper by hand, crushing is done by steam stamps; pebble mills instead of ball mills are employed for grinding because of the abrasive qualities of the gangue.
Figure 151 is the flow sheet of one section of the Cananea Consolidated Copper Co. mill as it was in 1929. This is a simple straight-flotation process that replaced an earlier combined gravity and bulk-
Figure 152 is the flow sheet of the Miami Copper Co. concentrator as it was in 1932; A shows the crushing plant and B the grinding and flotation units. Figure 153 is the flow sheet of the Miami concentrate re-treatment and filter plants. The ores are composed of chalcocite and pyrite with subordinate amounts of oxidized copper minerals disseminated mainly in a quartz-sericite schist.
pyrite with minor amounts of gold and silver. The bulk concentrates are dewatered and, after additional grinding, are again subjected to flotation. The latter operation produces finished copper concentrate, finished pyrite concentrate, and middlings which are re-treated.
Taseko Mines (TSE: TKO) wants to produce copper in Arizona using a process that evokes oilfield fracking, but first the company has to convince the U.S. Environmental Protection Agency (EPA) that it will not harm the states water supply.
The Canadian firm, which said it expects an EPA decision imminently, wants to use a process that involves injecting sulfuric acid and water deep underground to break up a mineral deposit. Uranium miners in rural parts of Australia and the United States have used the process, known as in situ leaching, for decades, but it has rarely been used to extract copper.
A U.S. appeals court this past spring put an end to the towns legal roadblocks, which included an attempt to take the companys land via eminent domain. The EPA is now deciding whether to approve Tasekos plan.
Its a very green way of producing copper, said Stuart McDonald, Tasekos president, adding the proven technology can safely boost U.S. production of a metal key to President Joe Bidens electrification plans.
Theres no way you can put sulfuric acid in the aquifer and not pollute it, John Anderson, a council member in Florence, about 63 miles (101 km) southwest of Phoenix, told state officials at a public hearing last year.
Vancouver-based Taseko has told investors it expects a decision very soon. Investors see the mines opening as key to boosting Tasekos stock price, which an average of analysts believe is undervalued by about 22%, according to Refinitiv data.
After the mixture of water and acid is injected and dissolves the copper at a pressure less than oilfield fracking the solution is drawn back to the surface where a process similar to electrolysis separates out the metal. Taseko said it aims to produce 85 million pounds of copper annually, enough to make nearly 500,000 electric vehicles.
In situ leaching does not require an open-pit mine or a smelter. It also emits less carbon than most copper mines, according to ESG consultancy Skarn Associates. A two-year study by Taseko did not detect any leaks from test wells.
The EPA is studying whether the project complies with regulations designed to ensure that underground sources of drinking water are protected from contamination by any authorized subsurface injection activities, said spokesperson Joshua Alexander.
The EPA is also worried construction of tanks and other equipment could damage Native American historical sites. The agency is talking with tribes to determine whether the project complies with the National Historical Preservation Act.
Theres no better way to recover copper if you want to minimize the impact on the environment, said Enders, who added the process could potentially be used at a few other Arizona copper deposits that are naturally fractured, like Tasekos.