Chapter 6 Copper Production Technology CONTENTS Page Figure Page History . ............................103 6-14. Types of in Situ Leaching Systems ..124 Exploration . .........................113 6-15. Jaw Crusher . ...............127 Mining . ..............116 6-16. Hydrocyclone, . ...............129 Comminution and Separation . .. ...127 6-17. Flotation Cells.. ................130 Beneficiation. ...; ...130 6-18. Flowsheets for Copper Flotation ....132 Pyrometallurgy. .$ ...................133 6-19. Column Ceil . ...................133 Hydrometallurgy . ....................140 6-20. Development of Smelting Electrometallurgy. ..................142 Technology Compared with World Melting and Casting. .................145 Copper Production . ..............135 6-21. Reverberatory Furnace . ....136 Boxes 6-22. Electric Furnace . ................137 Furnace . Box Page 6-23, INCO Flash .. ....138 6-A.The Lakeshore Mine in Situ Project ..126 6-24. Outokumpu Flash Furnace . .......138 6-B. Smelting Furnaces . 136 6-25. Pierce-Smith Converter ... ... ... ..139 6-26. Noranda Reactor . ...............139 6-27. Mitsubishi Continuous Smelting Figures System . ................140 Figure Page 6-28. Kennecott Cone Precipitator . ......142 6-1. Flow Sheets for Copper 6-29. Flowsheet for Solvent Extraction ....143 Production . 104 6-30. Continuous Casting Wheel . .......146 6-2. Early Smelting Technology. .......107 6-31. Continuous Rod Rolling Mill ., ....,147 6-3. Early Copper-Producing Areasof Europe and the Middle East . ......108 Tables 6-4. Copper Deposits of Northern Michigan . ......................109 Table Page 6-5. Copper Production Areas of the 6-1. Summary of Pyrometallurgical Northern and Central Rocky Processes . .................105 Mountains . ................112 6-2. Summary of Hydrometallurgical 6-6. Copper Production Areas of the Processes . .................106 Southwest . .....................112 6-3. Major U.S. Copper Mines . .........110 6-7. Sample Geologic Map . ...........114 6-4. Remote Sensing Systems and Image 6-8. Model of Hydrothermal Alteration Types for Mineral Exploration . ......117 Zones Associated With Porphyry 6-5. Considerations in Choice of Mining Copper Deposits . .......115 Method . ........................118 6-9. Stages of Mineral Exploration .. ....116 6-6. Characteristics of Solution Mining 6-10. Underground Mining Terms . ......119 Techniques . .....................122 6-11. Two Underground Mining 6-7, Summary of in Situ Copper Mining Methods . ... ...12O Activities . .......................125 6-12. Open Pit Mining Terms . ..........121 6-8. Smelter Technology in the 6-13. Heap and Dump Leaching . .......123 United States . ..........138 Chapter 6 Copper Production Technology The last boom in technological innovation for This chapter briefly describes the technology the copper industry occurred in the first two dec- for producing copper, from exploration, through ades of this century, when open pit mining, flo- mining and milling, to smelting and refining or tation concentration, and the reverberatory solvent extraction and electrowinning. The chap- smelter were adapted to porphyry copper ores. ter begins with an overview of the history of cop- With the exception of leaching-solvent extrac- per technology development. Then, for each tion-electrowinning, the basic methods of cop- stage i n copper production, it reviews the cur- per production have remained unchanged for 65 rent state-of-the-art, identifies recent technologi- years. Moreover, six of the mines opened be- cal advances, reviews probable future advances tween 1900 and 1920 are still among the major and research and development needs, and dis- copper producers in the United States today. cusses the importance of further advances to the competitiveness of the U.S. industry. Figure 6-1 Instead of great leaps forward, technological shows flow-sheets for pyrometallurgical’ and innovation in the copper industry in the last 65 hydrometallurgical 2 copper production. Tables years has consisted largely of incremental 6-1 and 6-2 provide capsule summaries of these changes that allowed companies to exploit lower processes. grade ores and continually reduce the costs of production. Economies of scale have been real- 1 ized in all phases of copper production. Both ma- PyrometaIIurgy IS the extractIon of metaI from ores anD concen- trates using chemical reactions at high temperatures. chine and human productivity have increased 2 Hydrometallurgy is the recovery of metaIs from ores using water- dramatically. based solutions. As early as 6000 B. C., native copper–the pure have found only a few additional deposits, and metal—was found as reddish stones in the Med- almost all of Rio Tinto’s modern production has iterranean area and hammered into utensils, been from ore first discovered by the Remans.3 weapons, and tools. Around 5000 B. C., artisans At Rio Tinto, the Remans mined the upper, ox- discovered that heat made copper more malle- idized, part of the ore and collected the copper- able. Casting and smelting of copper began Iaden solutions produced by water slowly seep- around 4000-3500 B.C. (see figure 6-2). About ing down through the suIfide ore bodies. When 2500 B. C., copper was combined with tin to the Moors conquered this part of Spain during make bronze—an alloy that allowed stronger the Middle Ages, the oxide ores had largely been weapons and tools. Brass, an alloy of copper and exhausted. Learning from the Roman experience zinc, probably was not developed until 300 A.D. with seepage, the Moors developed open pit min- Copper was first mined (as opposed to found ing, heap leaching, and iron precipitation tech- on the ground) in the Timna Valley in Israel—a niques that continued to be used at Rio Tinto into desolate area believed to be the site of King Solo- the 20th century. mon’s Mines (see figure 6-3). The Phoenicians In Britain, copper and tin were worked in Corn- and Remans, who worked the great mines on wall and traded with the Phoenicians as early as Cyprus and in the Rio Tinto area of southern 1500 B.C. The Remans brought improved metal- Spain, made the early advances in copper explo- lurgical techniques to Britain, and spurred devel- ration and mining methods. For example, the Ro- mans found nearly 100 lens-shaped ore bodies in 3ira B. joralemon, Copper; The Encompassing Story of MankInd’s the Rio Tinto copper district. Modern geologists First MetaL (Berkeley, CA: Howell-North Books, 1973). 103 104 Figure 6-1.-FIow Sheets for Copper Production Pyrometallurgical Hydrometalluigical Sulfide ores Oxide and sulfide ores (0.5-2% Cu) (0.3-2.0% Cu) Comminution Leaching I 1 Pregnant Ieachate I I (20-50% Cu) I FIotation I Concent rates Precipitation Solvent (20-30% Cu) extract ion 1 I Smelting I I Cement copper 1 (85-90% Cu) Matte (50-75% Cu) I I I Converting i Cathodes (99.99+% Cu) Anode refining and casting I I I Anodes (99.5% Cu) I Cathodes (99.99+% Cu) SOURCE: Office of Technology Assessment. opment of the mines of Cumberland and North King Henry Vlll reopened the mines in Cum- Wales. When the Remans left Britain early in the berland and elsewhere, and Britain became 5th century, however, economic development famed for bronze casting and the manufacture stagnated and it was a thousand years or more of armaments. By the end of the 16th century, before Britain’s metal industry was reestablished.4 Britain was producing 75 percent of the world’s In the interim, Germany became the center of copper. British advances in metallurgy helped to the European copper industry, bringing a num- establish a world monopoly in smelting that con- ber of improvements in copper mining, metal- tinued until around 1900, when foreign producers lurgy, and fabricating.5 built large mills and smelters that took advantage of such British inventions as the reverberatory fur- 4Sir Ronald L. Prain, Copper: The Anatomy of an Industry (Lon- nace and froth flotation. b Moreover, the miners don: Mining journal Books Ltd., 1975). ‘Raymond F. Mikesell, The World Copper Industry: Structure and Economic Analysis (Baltimore, MD: The Johns Hopkins Press, 1979). 6Prain, supra note 4. Table 6-1. —Summary of Pyrometallurgical Processes Activity Product Constituents Percent copper Purpose or result Big Bang . Universe 0.0058 Formation of the earth Hydrothermal alteration . Porphyry rocks Pyrite, chalcopyrite, etc. 0.2-6.0 Concentration of copper in earth’s crust Exploration and development . Deposit Copper ore, other minerals, waste rock 0.2-6.0 Location of economic resource (gangue) Mining . .Ore Copper minerals, iron and other metallic 0.5-6.0 Remove ore from ground and surrounding pyrites, byproducts, and gangue rock or overburden Comminution. Pulverized ore Same as mining but in the form of fine 0.5-6.0 Creation of large surface area as preparation particles for flotation Beneficiation (flotation) . .Concentrate Copper minerals, iron pyrites, miscellaneous 20-300/o dry Removal of most gangue and collection of minerals (including valuable byproducts), some byproduct minerals (e.g., Mo, Ni, Pb, and water (8-10%) Zn) to avoid further expense in materials handling, transportation, and smelting Smelting. Matte Copper sulfide (CU2S), iron sulfide (FeS), 30-40°/0 reverb, Heat-induced separation of complex sulfides byproducts, tramp elements, and up to 50-75°/0 flash into copper sulfides, iron sulfides, and 3°/0 dissolved oxygen sulfur; removal of sulfur as off gas (SO2) and removal of gangue via slag; in oxygen- charged systems, partial (50-90°/0) oxidation of iron to produce iron