(1) Disseminated copper ore flotation: The process for disseminated copper ore flotation is relatively simple, typically involving grinding the ore to a fineness of -200 mesh, selecting it 2 or 3 times, and sweeping it once or twice. For small copper minerals, adjustments may be made to the grinding and separation processes. Treatment at a copper concentrator usually involves coarse concentrate regrinding, followed by stage grinding and separation through a mixed-flotation process. The coarse concentrate is first subjected to roughing and scavenging through a jaw crusher, followed by regrinding to obtain a high-grade copper concentrate. The coarse ground degree should be about 45% to 50% at -200 mesh, and then the degree of pulverization should be increased to about 90% to 95% at -200 mesh.
(2) Dense compact copper ore flotation: Dense compact copper ore typically involves chalcopyrite and pyrite that are tightly symbiotic. The high content of activated pyrite often makes the separation process difficult. The sorting process requires obtaining copper concentrate and concentrate simultaneously, with the copper tailings often becoming pyrite concentrate. If the ore gangue content is higher than 20% to 25%, sorting through a ball mill is necessary to obtain sulfur concentrate. Dense copper ore processing often involves two stages of grinding, requiring smaller grinding fineness. A larger amount of reagent is typically used, with xanthate dosage being above 100g/(t ore), and lime usage at 8~10kg/(t ore) or above. Most copper ores contain only a small percentage of copper metal, with the remainder being unwanted rock or gangue minerals. Typically, silicate or oxide minerals are present that hold no value. The average grade of copper ores in the 21st century is below 0.6% Cu, with a proportion of ore minerals being less than 2% of the total volume of the ore rock. A key objective in the metallurgical treatment of any ore is the separation of ore minerals from gangue minerals within the rock. The first stage of any process within a metallurgical treatment circuit is comminution, where the rock particles are reduced in size such that ore particles can be efficiently separated from gangue particles, followed by a process of physically liberating the ore minerals from the rock. The process of liberation of copper ores depends upon whether they are oxide or sulfide ores. For oxide ores, a hydrometallurgical liberation process is normally undertaken, which uses the soluble nature of the ore minerals to the advantage of the metallurgical treatment plant. For sulfide ores, both secondary (supergene) and primary (unweathered), froth flotation is utilized to physically separate the ore from the gangue. In special cases, native copper can be recovered by a simple gravity circuit.
The above flowsheet shows a basic copper mining process, from the mine to the metal. There are two distinct types of copper ores: sulfide ore and oxide ore. Sulfide ores are beneficiated in flotation cells, while oxide ores are generally leached. First, the copper ore is blasted, loaded, and transported from an open pit mine to the primary crushers. Then, the ore is crushed and screened, with the fine sulfide ore (~-0.5 mm) going to froth flotation cells for recovery of copper, while the coarser ore goes to the heap leach, where the copper is subjected to a dilute sulfuric acid solution to dissolve the copper. The leach solution containing the dissolved copper is then subjected to a process called solvent extraction (SX).
The SX process concentrates and purifies the copper leach solution so that the copper can be recovered at a high electrical current efficiency by the electrowinning cells. This is done by adding a chemical reagent to the SX tanks that selectively binds with and extracts the copper. The reagent is easily separated from the copper (stripped), and as much of it as possible is recovered for reuse. The concentrated copper solution is dissolved in sulfuric acid and sent to the electrolytic cells for recovery as copper plates (cathodes). The copper cathodes can then be manufactured into wire, appliances, and other everyday items.