Mark E. Schlesinger’s research while affiliated with Missouri University of Science and Technology and other places

Flash smelting accounts for around half of all Cu matte smelting. It entails blowing oxygen, air, concentrate, flux, and recycle materials into a hearth furnace. The process is continuous. When extensive oxygen enrichment of the blast is practiced, it is nearly autothermal. It is perfectly matched to smelting fine particulate concentrates produced by froth flotation. The products of flash smelting are molten matte, slag, and hot dust–laden offgas.

The pyrometallurgical production of copper from sulfide concentrates is a journey involving the gradual oxidation of copper concentrates in sequential steps. These steps are smelting, converting, and refining. The overall copper making process can be explained by using the copper–oxygen–sulfur predominance diagrams. This tool is a navigation chart to understand the overall copper making process. A proper understanding of the influence of the sulfur and oxygen potential is needed to define proper operating points by selecting appropriate matte grade for the smelting process, adequate slag compositions to ensure suitable slag quality, and controlled copper losses.

This chapter (a) describes the investment and production costs of producing copper metal from ore, (b) discusses how these costs are affected by such factors as ore grade, process route, and inflation and, (c) indicates where cost savings might be made in the future. The discussion centers on mine, concentrator, smelter, and refinery costs. Costs of producing copper by leach/solvent extraction/electrowinning and from scrap are also discussed.

About 95% of the copper currently produced in the United States has existed as cathode copper at some time during its processing. To make it useful, this copper must be melted, alloyed as needed, cast, and fabricated. Much of the fabrication process for copper and its alloys is beyond the scope of this book. However, melting and casting are often the last steps in a copper smelter or refinery. A discussion of these processes is therefore in order.

This chapter explains how Cu²⁺ ions generated by leaching are reduced and electrowon as pure metallic copper in the form of cathodes. The electrowinning process entails (a) immersing metal cathodes and inert (but conductive) anodes into a purified electrolyte containing CuSO4 and H2SO4; (b) applying an electrical current from an external source, such as a rectifier, which causes current to flow through the electrolyte between the cathodes and anodes; and (c) plating pure metallic copper from the electrolyte onto the cathodes using the energy provided by the electrical current to drive the reduction of the Cu²⁺ ions to copper metal.

Continuous copper making processes can be achieved in a single, double, or three stages. The selection of the process depends on the type of material to be processed and the aimed final product.

Hydrometallurgical extraction accounts for about 20% of total primary copper production. Most of this is produced by heap leaching. Heap leaching consists of trickling H2SO4-containing lixiviant uniformly through flat-surfaced heaps of crushed ore, agglomerated, or run-of-mine ore. Heap leaching generates a pregnant leach solution (PLS) containing 1–6 g/L Cu²⁺, which is sent to solvent extraction and electrowinning for copper production. The Cu²⁺-depleted raffinate from SX is recycled to leaching, with the acid strength usually increased by the addition of concentrated H2SO4. Low-grade ores are treated by dump leaching, while vat leaching can be used to treat higher grade oxide ore. Agitation leaching in stirred tanks is applied to both oxide and sulfide materials: the PLS concentrations can be up to 25 g/L Cu. Most copper minerals are amenable to leaching under atmospheric conditions. A critical exception is chalcopyrite (CuFeS2), which does not dissolve under percolation leach conditions. Several process routes for the hydrometallurgical treatment of chalcopyrite have been proposed and are the topics of ongoing research, but few have yet been successfully commercialized.

Sulfur is evolved by most copper extraction processes. The most common form of evolved sulfur is sulfur dioxide (SO2) gas from smelting and converting. It must be prevented from reaching the environment. Most smelters capture a large fraction of their SO2. It is almost always made into sulfuric acid, occasionally liquid SO2 or gypsum. This chapter describes off-gases from smelting and converting, manufacture of sulfuric acid from smelter gases, and recent and future developments in sulfur capture.

Impure leach solutions containing relatively low concentrations of copper are processed to high copper concentration, pure electrowinning (EW) electrolytes by Solvent extraction (SX). It is a crucial step in producing high-purity electrowon copper from leached ores. The SX process consists of extracting Cu²⁺ from aqueous PLS into a copper-specific organic extractant, separating the aqueous and organic phases by gravity, and then stripping Cu²⁺ from the organic extractant into high-H2SO4 electrolyte returned from the EW circuit. The process is continuous and is carried out in large mixer-settlers. About 4.64 million tonnes of Cu per year are treated by SX followed by EW. Copper production by SXEW continues to grow as increasing volumes of ore and concentrates are processed by leaching technologies.

Metallic copper has been known to man since about 10,000 B.C. Although its use gradually increased over the years, it was only in the 20th century, with the global adoption of electricity, that copper usage really expanded. Copper is essential to economic and technological development, so substantial growth in its applications has continued in the 21st century, driven by the rapid industrialization of China and other emerging market economies. This chapter discusses production and use of copper around the world. It gives production, use, and price statistics, and identifies and locates the world's largest copper-producing plants.