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59-529: The Corocoro United Copper Mines, Ltd. was the largest copper mine in Bolivia , an honor previously held by Compania Corocoro de Bolivia. The corporate office was at 151 Finsbury Pavement House, London , England, while the mine office was at Coro Coro, Bolivia . It was organized August 6, 1909 under the laws of Great Britain. The lands included 515 claims in the Coro Coro district . The principal mines were

118-413: A heap leaching or dump leaching . The resulting pregnant leach solution is purified by solvent extraction (SX). It is treated with an organic solvent and an organic chelators. The chelators bind the copper ions (and no other ions, ideally), the resulting complexes dissolve in the organic phase. This organic solvent is evaporated, leaving a residue of the copper complexes. The copper ions are liberated from

177-407: A charge, enters the ignition furnace into rows of multi-slit burners. In the case of one plant, the first (ignition) zone has eleven burners. The next (soaking/ annealing ) zone typically offers 12 burners. Air is sucked from the bottom of the bed of mixed material throughout the sintering machine. Fire penetrates the mixed material gradually, until it reaches the hearth layer. This end point of burning

236-442: A concentrates with 27–29% and 37–40% copper contents from chalcopyrite and chalcocite , respectively. Oxidised copper ores include carbonates such as azurite and malachite , the silicate chrysocolla , and sulfates such as atacamite . In some cases, sulfide ores are allowed to degrade to oxides. Such ores are amenable to hydrometallurgy. Specifically, such oxide ores are usually extracted into aqueous sulfuric acid , usually in

295-519: A few years before selling their copper assets. Reportedly gains were not as high as anticipated. Investments in copper mining concentrated in Chile in the 1980s and 1990s given that copper mining in other countries faced problems like political instability ( Peru ), increased environmental requirements (developed countries) or overall disinterest in foreign investment in a nationalized mining industry ( Zaire , Zambia ). The average grade of copper ores in

354-406: A high grade copper concentrate. The roasting process is generally undertaken in combination with reverberatory furnaces . In the roaster, the copper concentrate is partially oxidised to produce " calcine ". Sulfur dioxide is liberated. The stoichiometry of the reaction is: Roasting generally leaves more sulfur in the calcined product (15% in the case of the roaster at Mount Isa Mines ) than

413-488: A higher profit. This extraction process can be applied to large quantities of low-grade ores, at a lower capital cost with minimal environmental impact. Generally, direct froth flotation is not used to concentrate copper oxide ores, as a result of the largely ionic and hydrophilic structure of the copper oxide mineral surface. Copper oxide ores are typically treated via chelating-reagent flotation and fatty-acid flotation, which use organic reagents to ensure adsorption onto

472-583: A parallel reaction the iron sulfide is converted to slag: The purity of this product is 98%, it is known as blister because of the broken surface created by the escape of sulfur dioxide gas as blister copper pigs or ingots are cooled. By-products generated in the process are sulfur dioxide and slag . The sulfur dioxide is captured and converted to sulfuric acid and either sold on the open market or used in copper leaching processes. Sinter plant Sinter plants agglomerate iron ore fines (dust) with other fine materials at high temperature, to create

531-505: A product that can be used in a blast furnace . The final product, a sinter , is a small, irregular nodule of iron mixed with small amounts of other minerals. The process, called sintering , causes the constituent materials to fuse to make a single porous mass with little change in the chemical properties of the ingredients. The purpose of sinter are to be used converting iron into steel . Sinter plants, in combination with blast furnaces, are also used in non-ferrous smelting . About 70% of

590-424: A significant portion of the sulfur has been eliminated during the roasting stage, and the calcine consists of a mixture of copper and iron oxides and sulfides. The reverberatory furnace acts to allow these species to approach chemical equilibrium at the furnace operating temperature (approximately 1600 °C at the burner end of the furnace and about 1200 °C at the flue end; the matte is about 1100 °C and

649-527: A sinter plant leaves in the sintered product (about 7% in the case of the Electrolytic Refining and Smelting smelter ). As of 2005, roasting is no longer common in copper concentrate treatment because its combination with reverberatory furnaces is not energy efficient and the SO 2 concentration in the roaster offgas is too dilute for cost-effective capture. Direct smelting is now favored, and uses

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708-474: Is a minor part of a supergene profile it will not be recovered and will report to the tailings . When rich enough, native copper ore bodies may be treated to recover the contained copper by gravity separation . Often, the nature of the gangue is important, as clay-rich native copper ores prove difficult to liberate. This is because clay minerals interact with flotation reagents used in extraction processes, that are then consumed, which results in minimal recovery of

767-422: Is a mixture of copper, iron and sulfur that is enriched in copper, which is called matte or copper matte . The term matte grade is normally used to refer to the copper content of the matte. The purpose of the matte smelting stage is to eliminate as much of the unwanted iron, sulfur and gangue minerals (such as silica, magnesia, alumina and limestone) as possible, while minimizing the loss of copper. This

826-421: Is achieved by reacting iron sulfides with oxygen (in air or oxygen enriched air) to produce iron oxides (mainly as FeO , but with some magnetite (Fe 3 O 4 )) and sulfur dioxide . Copper sulfide and iron oxide can mix, but when sufficient silica is added, a separate slag layer is formed. Adding silica also reduces the melting point (or, more properly, the liquidus temperature) of the slag, meaning that

885-614: Is an energy-efficient smelting process that was jointly developed from the 1970s to the 1990s by Mount Isa Mines (a subsidiary of MIM Holdings and now part of Glencore ) and the Government of Australia 's CSIRO . It has relatively low capital and operating costs for a smelting process. ISASMELT technology has been applied to lead, copper, and nickel smelting. As of 2021, 22 plants were in operation in eleven countries, along with three demonstration plants located at Mt Isa. The installed capacity of copper/nickel operating plants in 2020

944-583: Is called burn through point (BTP). The hearth layer, which is nothing but sinter in smaller size, restricts sticking of hot sinter with pallets. BTP is achieved in a certain zone of sinter machine, to optimize the process, by means of several temperature measuring instrument placed throughout the sinter machine. After completion of burning, the mix converts into sinter, which then breaks into smaller size by sinter breaker. After breaking into small sizes, it cools down in cooler (linear or circular) by means of forced air. At discharge of sinter cooler, temperature of sinter

1003-465: Is constantly forced through the slurry. The air bubbles attach to the hydrophobic copper sulfide particles, which are conveyed to the surface where the froth is skimmed off. These skimmings are generally subjected to a cleaner-scavenger cell to remove excess silicates and to remove other sulfide minerals that can deleteriously impact the concentrate quality (typically, galena ), and the final concentrate sent for smelting. The rock that has not floated off in

1062-411: Is eliminated from the concentrate). It is essentially a melting process. Consequently, wet-charged reverberatory furnaces have less copper in their matte product than calcine-charged furnaces, and they also have lower copper losses to slag. Gill quotes a copper in slag value of 0.23% for a wet-charged reverberatory furnace vs 0.37% for a calcine-charged furnace. In the case of calcine-charged furnaces,

1121-501: Is located in Chennai, India, and employs 10,000 people. Main feed into a sinter plant is base mix, which consists of iron ore fines, coke fines and flux (limestone) fines. In addition to base mix, coke fines, flux fines, sinter fines, iron dust (collected from plant de-dusting system and electrostatic precipitator ) and plant waste are mixed in proportion (by weight) in a rotary drum, often called mixing and nodulizing drum. Calcined lime

1180-620: Is maintained as low, so that the hot sinter can be transported by a conveyor belt made of rubber. Necessary precautions are taken to trace any existence of fire in the belt and necessary extinguishing is done by spraying water. Then this product is being passed through a jaw-crusher, where the size of sinter is further reduced (~ 50 mm) into smaller size. Then the complete mixture is being passed through two screens. Smallest sinter fines (< 5 mm) are stored in proportioning bins and reused for preparing sinter again through mixing and nodulizing drum and fed to sinter machine for burning. A part of

1239-427: Is normally added to help form the slag. The furnace is fired with burners using pulverized coal, fuel oil or natural gas. Reverberatory furnaces can additionally be fed with molten slag from the later converting stage to recover the contained copper and other materials with a high copper content. Because the reverberatory furnace bath is quiescent, very little oxidation of the feed occurs (and thus very little sulfur

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1298-431: Is used as binder of the mixed material along with water (all in particular proportion by weight) to form feed-sinter of about 5 to 7 mm in size. This sinter globules are fed to sintering machine and burnt therein to produce blast furnace feed sinter. Material is put on a sinter machine in two layers. The bottom layer may vary in thickness from 30 to 75 millimetres (1.2 to 3.0 in). A 12 to 20 mm sinter fraction

1357-400: Is used, also referred to as the hearth layer. The second, covering layer consists of mixed materials, making for a total bed height of 350 to 660 millimetres (14 to 26 in). The mixed materials are applied with drum feeders and roll feeders, which distributes the nodules in certain depth throughout the sintering machine. The upper layer is smoothed using a leveler. The material, also known as

1416-469: The refractory bricks lining the furnace. When the removal of the matte or slag is complete, the hole is normally plugged with clay, which is removed when the furnace is ready to be tapped again. Reverberatory furnaces were often used to treat molten converter slag to recover contained copper. This would be poured into the furnaces from ladles carried by cranes. However, the converter slag is high in magnetite and some of this magnetite would precipitate from

1475-450: The 1960s. In the 1960s and 1970s large copper mining operations by U.S. companies were nationalized in many of the main copper producing countries. Thus by the 1980s state owned enterpises overtook the dominant role U.S. companies like Anaconda Copper and Kennecott had had until then. In the late 1970s and early 1980s various oil companies like ARCO , Exxon ( Exxon Minerals ) and Standard Oil Company expanded into copper mining for

1534-517: The 21st century is below 0.6% copper, with a proportion of economic ore minerals being less than 2% of the total volume of the ore rock. Thus, all mining operations, the ore must usually be beneficiated (concentrated). The concentrate is typically sold to distant smelters , although some large mines have smelters located nearby. Such colocation of mines and smelters was more typical in the 19th and early 20th centuries, when smaller smelters could be economic. The subsequent processing techniques depend on

1593-718: The Wisk'achani, formerly owned by J. K. Child & Co., Ltd.; the Santa Rosa, formerly owned by Carreras Hermanos; and the Guallatiri, formerly owned by the Succession Noel Berthin. The mines were opened on two successive conglomerate strata of different geological horizons, and similar only in their origin and cupriferous nature. The mines are believed to have been worked by the Incas . The nearest water supply

1652-412: The concentrate is dispersed in an air or oxygen stream and the smelting reactions are largely completed while the mineral particles are still in flight. The reacted particles then settle in a bath at the bottom of the furnace, where they behave like calcine in a reverberatory furnace. A slag layer forms on top of the matte layer, and they can separately be tapped from the furnace. The ISASMELT process

1711-452: The concentration of copper in the ore bodies decreased, the energy costs of smelting the whole ore also became prohibitive, and it became necessary to concentrate the ores first. Initial concentration techniques included hand-sorting and gravity concentration. These resulted in high losses of copper. Consequently, the development of the froth flotation process was a major step forward in mineral processing. The modern froth flotation process

1770-406: The converter slag (due to its higher melting point), forming an accretion on the hearth of the reverberatory furnace and necessitating shut downs of the furnace to remove the accretion. This accretion formation limits the quantity of converter slag that can be treated in a reverberatory furnace. While reverberatory furnaces have very low copper losses to slag, they are not very energy-efficient and

1829-519: The conveyor carrying the sinter for the blast furnace and, along with blast furnace grade sinter, either goes to sinter storage bunkers or to blast furnace bunkers. Blast furnace-grade sinter consists of particles sized 5 to 12 mm as well as 20 mm and above. There are certain advantages of using sinters as opposed to using other materials which include recycling the fines and other waste products, to include flue dust, mill scale, lime dust and sludge. Processing sinter helps eliminate raw flux, which

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1888-421: The copper dissolved in slags from mattes containing less than 50% copper is sulfidic copper. Above this figure, oxidic copper begins to dominate. The loss of copper as prills suspended in the slag depends on the size of the prills, the viscosity of the slag and the settling time available. Rosenqvist suggested that about half the copper losses to slag were due to suspended prills. The mass of slag generated in

1947-467: The copper from the pregnant leach solution . To ensure the best recovery of copper, it is important to acknowledge the effect copper dissolution, acid consumption, and gangue mineral composition has on the efficacy of extraction. Supergene sulfide ores rich in native copper are refractory to treatment with sulfuric acid leaching on all practicable time scales, and the dense metal particles do not react with froth flotation media. Typically, if native copper

2006-404: The crushed ore is wetted, suspended in a slurry, and mixed with reagents that render the sulfide particles hydrophobic . Typical reagents ("collectors") include potassium ethylxanthate and sodium ethylxanthate , but dithiophosphates and dithiocarbamates are also used. The slurry is introduced to a water-filled aeration tank containing a surfactant such as methylisobutyl carbinol (MIBC). Air

2065-409: The depletion of copper resources. Processes including in situ, dump, and heap leaching are cost-effective methods that are suitable for extracting copper from low-grade ores. Extraction processes for secondary copper sulfides and low-grade ores includes the process of heap bioleaching. Heap bioleaching presents a cost efficient extraction method that requires a less intensive energy input resulting in

2124-606: The earlier record of copper smelting from Rudna Glava ( Serbia ). Copper smelting technology gave rise to the Copper Age , aka Chalcolithic Age, and then the Bronze Age . The Bronze Age would not have been possible without the development of smelting technology. Until the latter half of the 20th century, smelting sulfide ores was almost the sole means of producing copper metal from mined ores ( primary copper production). As of 2002, 80% of global primary copper production

2183-435: The early 20th century, sinter technology was developed for converting ore fines into lumpy material chargeable in blast furnaces. Sinter technology took 30 years to gain acceptance in the iron-making domain, but now plays an important role. Initially developed to generate steel, it is now a means of using metallurgical waste generated in steel plants to enhance blast furnace operation and reducing waste. The largest sinter plant

2242-402: The flotation cell is either discarded as tailings or further processed to extract other metals such as lead (from galena) and zinc (from sphalerite ), should they exist. A variety of measures are taken to improve the efficiency of the froth flotation. Lime is used to raise the pH of the water bath, causing the collector to bond more efficiently to the copper sulfides. The process can produce

2301-449: The following smelting technologies: flash smelting , Isasmelt , Noranda, Mitsubishi or El Teniente furnaces. The initial melting of the material to be smelted is usually referred to as the smelting or matte smelting stage. It can be undertaken in a variety of furnaces, including the largely obsolete blast furnaces and reverberatory furnaces , as well as flash furnaces , Isasmelt furnaces, etc. The product of this smelting stage

2360-427: The furnace as separate streams. The slag layer is periodically allowed to flow through a hole in the wall of the furnace above the height of the matte layer. The matte is removed by draining it through a hole into ladles for it to be carried by crane to the converters. This draining process is known as tapping the furnace. The matte taphole is normally a hole through a water-cooled copper block that prevents erosion of

2419-459: The loss of copper to slag in the smelting stage are: This means that there is a practical limit on how high the matte grade can be if the loss of copper to slag is to be minimized. Therefore, further stages of processing (converting and fire refining) are required. The following subsections briefly describe some of the processes used in matte smelting. Reverberatory furnaces are long furnaces that can treat wet, dry, or roasted concentrate. Most of

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2478-463: The low concentrations of sulfur dioxide in their off-gases make its capture uneconomic. Consequently, smelter operators devoted a lot of money in the 1970s and 1980s to developing new, more efficient copper smelting processes. In addition, flash smelting technologies had been developed in earlier years and began to replace reverberatory furnaces. By 2002, 20 of the 30 reverberatory furnaces still operating in 1994 had been shut down. In flash smelting ,

2537-437: The mineral chalcocite; a mineral formed from primary sulfides, like chalcopyrite , that undergo chemical processes such as oxidation or reduction. Typically, secondary sulfide ores are concentrated using froth flotation. Other extraction processes like leaching are effectively used for the extraction of secondary copper sulfides, but as demand for copper rises, extraction processes tailored for low-grade ores are required, due to

2596-426: The mineral surface through the formation of hydrophobic compounds on the mineral surface. Some supergene sulfide deposits can be leached using a bacterial oxidation heap leach process to oxidize the sulfides to sulfuric acid, which also allows for simultaneous leaching with sulfuric acid to produce a copper sulfate solution. For oxide ores, solvent extraction and electrowinning technologies are used to recover

2655-409: The nature of the ore. In the usual case when it is primarily sulfide copper minerals (such as chalcopyrite , FeCuS 2 ), the ore is treated by comminution , where the rock is crushed to produce small particles (<100 μm) consisting of individual mineral phases. These particles are then ready to be separated to remove gangue (silicate rocks residues) using froth flotation. In froth flotation,

2714-403: The oxygen potential of the slag increases. The oxygen potential generally increases as the copper content of the matte is increased. Thus, the loss of copper as oxide increases as the copper content of the matte increases. On the other hand, the solubility of sulfidic copper in slag decreases as the copper content of the matte increases beyond about 40%. Nagamori calculated that more than half

2773-517: The residue with sulfuric acid. The barred (denuded) sulfuric acid recycled back on to the heaps. The organic ligands are recovered and recycled as well. Alternatively, the copper can be precipitated out of the pregnant solution by contacting it with scrap iron; a process called cementation . Cement copper is normally less pure than SX-EW copper. Secondary sulfides—those formed by supergene secondary enrichment—are resistant ( refractory ) to sulfuric leaching. Secondary copper sulfides are dominated by

2832-428: The reverberatory furnaces used in the latter years treated roasted concentrate because putting dry feed materials into the reverberatory furnace is more energy efficient, and because the elimination of some of the sulfur in the roaster results in higher matte grades. The reverberatory furnace feed is added to the furnace through feed holes along the sides of the furnace, and the solid charge is melted. Additional silica

2891-403: The slag is about 1195 °C ). In this equilibration process, oxygen associated with copper compounds exchanges with sulfur associated with iron compounds, increasing the iron oxide content of the furnace, and the iron oxides interact with silica and other oxide materials to form the slag. The main equilibration reaction is: The slag and the matte form distinct layers that can be removed from

2950-421: The smaller one ( 5 – 20 mm) is used for hearth layer in sinter machine and the rest is taken to the blast furnace along with the biggest sized sinters. The temperature is typically maintained between 1,150 and 1,250 °C (2,100 and 2,280 °F) in the ignition zone and between 900 and 1000 °C in the soaking zone to prevent sudden quenching of the sintered layer. The top 5 mm from screens goes to

3009-453: The smelting process can be operated at a lower temperature. The slag forming reaction is: Slag is less dense than matte, so it forms a layer that floats on top of the matte. Copper can be lost from the matte in three ways: as cuprous oxide (Cu 2 O) dissolved in the slag, as sulfide copper dissolved in the slag or as tiny droplets (or prills ) of matte suspended in the slag. The amount of copper lost as oxide copper increases as

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3068-401: The smelting stage depends on the iron content of the material fed into the smelting furnace and the target matte grade. The greater the iron content of the feed, the more iron that will need to be rejected to the slag for a given matte grade. Similarly, increasing the target matte grade requires the rejection of more iron and an increase in the slag volume. Thus, the two factors that most affect

3127-554: The world's oldest known copper mines, as opposed to usage of surface deposits, is at Timna Valley , Israel, and has been used since the fourth millennium BC, with surface deposit usage occurring in the fifth and sixth millennium. The Pločnik archaeological site in southeastern Europe ( Serbia ) contains the oldest securely dated evidence of copper making at high temperature, from 5,000 BCE. The find in June 2010 extends for an additional 500 years, dated to 5th millennium BCE, representing

3186-529: The world's primary lead production is still produced this way. The combination was once used in copper smelting, as at the Electrolytic Refining and Smelting smelter in Wollongong , New South Wales . Many countries, including India , France and Germany , have underground deposits of iron ore in dust form (blue dust). Such iron ore cannot be directly charged in a blast furnace . In

3245-473: The world. The earliest evidence of the cold-hammering of native copper comes from the excavation at Çayönü Tepesi in eastern Anatolia , which dates between 7200 to 6600 BCE. Among the various items considered to be votive or amulets, there was one that looked like a fishhook and one like an awl. Another find, at Shanidar Cave in Mergasur, Iraq, contained copper beads, and dates back to 8,700 BCE. One of

3304-419: Was 9.76 million tonnes per year of feed materials and 750 thousand tonnes per year across lead operating plants. The matte, which is produced in the smelter, contains 30–70% copper (depending on the process used and the operating philosophy of the smelter), primarily as copper sulfide, as well as iron sulfide. The sulfur is removed at a high temperature as sulfur dioxide by blowing air through molten matte: In

3363-425: Was from copper–iron–sulfur minerals, and the vast majority of these were treated by smelting. Copper was initially recovered from sulfide ores by directly smelting the ore in a furnace. The smelters were initially located near the mines to minimize the cost of transport. This avoided the prohibitive costs of transporting the waste minerals and the sulfur and iron present in the copper-containing minerals. However, as

3422-590: Was independently invented in the early 1900s in Australia by C.V Potter and around the same time by G. D. Delprat . It made the development of the giant Bingham Canyon mine in Utah possible. In the twentieth century, most ores were concentrated before smelting. Smelting was initially undertaken using sinter plants and blast furnaces , or with roasters and reverberatory furnaces . Roasting and reverberatory furnace smelting dominated primary copper production until

3481-527: Was the Rio Desaguadero , 14 miles (23 km) away, down which the copper was shipped by way of Puerto de Desaguadero , and from there to Mollendo , Chile , for export to Europe. Copper extraction techniques The Old Copper Complex in North America has been radiometrically dated to 9500 BP—i.e., about 7480 BCE—making it one of the oldest known examples of copper extraction in

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