Copper recovery process

Winterhager, H and Kammel, R, 1961. Viscosity measurements in process slags from lead and copper recovery processes, Erzmetall, 14 319-328. 

Asahi Chemical Industries (ACl, Japan) are now the leading producers of cuprammonium rayon. In 1990 they made 28,000 t/yr of filament and spunbond nonwoven from cotton ceUulose (65). Their continuing success with a process which has suffered intense competition from the cheaper viscose and synthetic fibers owes much to their developments of high speed spinning technology and of efficient copper recovery systems. Bemberg SpA in Italy, the only other producer of cuprammonium textile fibers, was making about 2000 t of filament yam in 1990. 

Secondary Recovery. Metal returning from the store of metal in use is referred to as old scrap, in contrast with scrap generated within the copper fabrication process, which is called new scrap (see Recycling). In 1990 the amount of the U.S. copper supply derived from old scrap was 24% of the total copper consumed. About 40% of old scrap is used for producing refined copper most of the remainder is used in the production of brass and bronze ingots (see Copper alloys). About 75% of new scrap is consumed by brass mills, with most of the remainder used in the production of refined copper. Some estimates suggest that as much as 60% of the copper produced is ultimately recycled for reuse. Old scrap combined with new scrap from fabricating plants accounts for about 40% of the metallic input to domestic copper furnaces. 

The conversion process for the copper matte removes iron, sulfur and other impurities from matte, thereby yielding liquid metallic copper of about 99% purity (blister copper). The slags which come out of converters contain from 2 to 15% copper and must go through treatment for copper recovery, usually by froth flotation of the copper from solidified and slowly cooled slag. 

Copper production is quite a complex process to plan and to schedule due to the many process interdependencies (shared continuous casters and cranes, emission level restrictions, limited material availability, to name a few). This makes it very difficult to foresee the overall consequences of a local decision. The variability of the raw material has alone a significant impact on the process, various disturbances and equipment breakdowns are common, daily maintenance operations are needed and material bottlenecks occur from time to time. The solution that is presented here considers simultaneously, and in a rigorous and optimal way, the above mentioned aspects that affect the copper production process. As a consequence, this scheduling solution supports reducing the impact of various disturbance factors. It enables a more efficient production, better overall coordination and visualization of the process, faster recovery from disturbances and supports optimal... 

Cadmium is obtained as a byproduct in zinc recovery processes. The metal volatdizes during roasting of zinc concentrates and collected as dust or fume in bag houses or electrostatic precipitators. The dusts are mixed with coal (or coke) and zinc chloride and calcined. The cadmium chloride formed volatihzes upon calcination and thus separates out from zinc. The chloride then is treated with sulfuric acid in the presence of an oxidizing agent. This converts lead, present as impurity in cadmium ore, to lead sulfate which precipitates out. Cadmium is finally separated from copper by the addition of zinc dust and... 

Because of cost factors, solvent extraction applied to large scale hydrometallurgical processes, such as the recovery of copper from acidic ore leach solutions, is carried out with the most selective reagent for e.g., copper versus iron, which is not itself a liquid solvent, in a petroleum diluent that confers on the mixture the desired physical properties. For the particular case of copper recovery, commercial hydroxyoxime reagents have been used on a very large scale, but their discussion is outside the scope of this book. 

Urtiaga, A., Abelian, M.J., Irabien, J.A. and Ortiz, I. (2005) Membrane contactors for the recovery of metallic compounds Modelling of copper recovery from WPO processes. Journal of Membrane Science, 257, 161. 

Bergmann et al. developed a vertically moving particle bed (VMPB) electrochemical reactor for copper recovery from dilute solutions (0.1-10000 ppm) [17]. Although higher rotation rates increased the current efficiency for copper removal at lower cell currents, rotation rates of below 5min were chosen to minimize mechanical wear. Impurities such as chloride ions, citric acid, and surfactants did not seem to interfere with the current efficiency of the process. This reactor was able to bring metal ion concentrations down to 0.5 ppm. A schematic of the VMPB reactor is shown in Fig. 3. 

The most important copper electrowinning production method is heap leaching of oxide copper ores with recovery by solvent extraction and electrowinning (SX-EW process). The general flowsheet of an SX-EW process is shown in Fig. 18. It is a low-cost method of copper recovery. This technology has recently been applied successfully to mixed oxide and chalcocite ores, notably in Chile. Currently, there are significant development efforts underway to try to extend heap leaching to chalcopy-rite ores. 

Ammonia complexation has also been employed, primarily for nickel-copper separations but also for copper recovery, when this is from native copper or copper oxide ores [15]. The dissolving process is thought to involve formation of soluble cuprous ammonium carbonate [53] (Eqs. 13.51 and 13.52). 

This is only a complexation reaction, as the copper is already in its desired oxidation state. The gold recovery process described above involves both oxidation and complexation. Another example of such a reaction is nickel sulfide pressure leaching, where it is the sulfur anion that is oxidized, the nickel remaining in its Ni(II) form throughout (9.3). 

Copper recovery from etchant baths is a particularly promising application of coupled transport because the high copper concentrations in the etchant solutions result in high fluxes. A relatively small unit is, therefore, able to process a large volume of solution. 

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