46 DÄGER REVIEW 120 | 2 / 2019

INDUSTRIEPRECIOUS METALS

RED GOLDCopper wires are the nerve pathways of industrial society.

Aurubis in Hamburg produces the preliminary products in pure form.

TEXT CONSTANZE SANDERS   PHOTOS PATRICK OHLIGSCHLÄGER

47DÄGER REVIEW 120 | 2 / 2019

Copper is everywhere. It is in refrigerators, cell phones, and e-bikes. Nothing works without cables, wires, and coils. Modern technology depends on cop-per wire. Without the red metal, nights would be dark, roads would be empty, and the world would suddenly be analog. Cop-per is coveted. “The copper price is an indicator for the state of the global econ-omy,” says Caspar Burgering, metal ana-lyst at ABM Amro. The fever chart tracing price and demand is seen as an early sign of the economic health of the world. If it fluctuates, attention turns to many other parameters, such as the price of oil and gold or the Dow Jones Index.

“Doctor Copper,” as it is known, takes the pulse. The plethora of technical pos-sibilities makes the raw material a com-modity metal – it is the world’s most used metal after iron and aluminum. “Chi-na’s rapid rise to become the world’s most important production location is also reflected in the use of copper,” say researchers at the Fraunhofer Institute

for Systems and Innovation Research. In 1990, Chinese consumption per cap-ita was running at seven kilograms, but by 2015 that figure had risen to 60 kilo-grams. At the same time, China’s share of global economic output rose more than fivefold.

A MATERIAL WITHOUT LIMITSCopper is virtually an all-rounder. It can be shaped, forged, sawed, and hammered. It connects and separates, cools and con-ducts heat. It doesn’t crack or rust. Cop-per can be alloyed, coated, or refined with countless other metals. It is also a germ killer. “The antibacterial effect of copper remains on the surface for a long peri-od of time,” says Frank Mücklich, presi-dent of the German Materials Society and professor at Saarland University. Hospi-tals benefit from copper alloys to prevent germs on door handles and light switch-es. The research group is currently devel-oping contact materials with an active germicidal effect. It has been known

HOT AND FLOWINGBlister copper comes from the

converter furnace at 1,200 degrees Celsius. The heart of

Aurubis’ copper smelting works in Hamburg beats 24 hours a

day, seven days a week

48 DRÄGER REVIEW 120 | 2 / 2019

since the end of the 19th century that cop-per conducts electricity. Only silver can do it better, but it is much more expen-sive. “The transformation of the ener-gy system would not be possible without copper,” says Michael Sander from the German Copper Institute in Düsseldorf. Coils in the generators of large wind tur-bines need kilometers of flat and round copper wire.

A RAW MATERIAL WITH A FUTUREAn offshore wind turbine contains up to 30 metric tons of copper, which also pro-tects the turbines from the sea climate in the form of a rust-resistant copper-nickel alloy. Almost 24 million metric tons were produced worldwide in 2018 (see also Dräger Review 119, p. 6 ff.). Production is growing at a rate of over three percent annually. Copper is an almost inexhaust-ible resource. In terms of figures, the sup-ply is secure for the next three centuries, with reserves estimated at 5.6 billion met-ric tons. At 1.2 million metric tons annual-ly, Germany is the third-biggest consum-er after the USA. China consumes the most. Electric mobility and rapid urban growth are fueling the demand. A fully electric car needs 80 kilograms of copper,

HELMET, BREATHING PROTECTION: Project manager Torben Edens during a safety training session at Aurubis in Hamburg

LAST STOP in the smelting works: the

casting carousel forms anodes from raw

molten copper – each weighing 400 kilograms

COPPER IS ANALL-ROUNDER

49DRÄGER REVIEW 120 | 2 / 2019

INDUSTRYPRECIOUS METALS

49

plus 20 kilograms per charging station. In the short term, China is planning to build almost five million electric charging sta-tions. As more research is conducted into the raw material, a growing number of usage options emerge. The German Min-eral Resources Agency (DERA) has identi-fied a need for five million metric tons by the year 2035. It won’t be long before cop-per will permit everyday things to commu-nicate with us independently. On a water bottle, for example, an ultrathin film of copper will monitor the current fill level. The user can access the data via Wi-Fi and check their daily water consumption. The label comes from the printer and requires no chip, battery, or mains supply. That’s how the researchers at the University of California in San Diego see things. A clear case for Doctor Copper.

NUMBER ONE IN EUROPEThe base product is produced from cop-per concentrate in huge smelting works. At the Aurubis plant in Hamburg, Torben Edens opens the door to the works. The air is vibrating and the generators and platforms are covered in the gray and brown dust of the copper concentrate. There is also a smell of sulfur in the air. “We use large filters to extract everything

from the hall,” says Edens, project man-ager at Aurubis.

The heart of the copper works in Hamburg’s port beats 24 hours a day, seven days a week. There is molten rock and no daylight. The constant pounding of the heavy machinery can be heard. It may not be an easy job, but it is certain-ly an extraordinary one. Thirty process mechanics per shift work in the eastern plant of the smelting works, which is the third-largest of its kind in the world by capacity, processing more than one mil-lion metric tons of copper concentrate per year. It is number one in Europe. The previously dried and roasted ore mixture

sweeps down the tall reaction shaft with sand and hot air and melts at a tempera-ture of 1,100 degrees Celsius.

In the process, copper matte with a copper content of 64 percent is extract-ed. Iron silicate slag floats to the sur-face and is skimmed off; gasiform sul-fur dioxide goes to the contact process plant. Both are intermediate products that are further processed to produce base materials for the building sector and chemical industry. “The plant produces about one million metric tons of sulfu-ric acid and 700,000 tons of iron silicate each year,” says Edens. “Copper comes in at third place at almost 400,000 tons.”

PURE SCRAP COPPER is recycled as a crushed package without the need for additional energy

VALUABLE COMPANIONSCopper ore contains other valuable by-products: A precious metal content of between six and 15 percent, primarily silver and gold, is found in the anode sludge at the end of the electrolysis process. Aurubis produces around 900 metric tons of silver and 48 tons of gold every year. The gold is sold exclusively to commercial users (jewelry manufacturers, dental technicians, or the electrical industry). The number of diffi cult-to-process by-products in complex concentrates is rising. Urubis develops techniques that optimally process all contents, including nickel, selenium, tellurium, and metals in the platinum group. New technologies for extracting lead are planned. This is used for air-conditioning systems or batteries that power the automatic start-stop system in cars. The copper smelting works is turning into a multi-metal operation.

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INDUSTRYPRECIOUS METALS

FROM ORE TO COPPERSmelting and refi ning are processes used to concentrate ores and clean raw metals. Copper (Cu) with a purity of 99.99 percent is ultimately produced from copper concentrate. The by-products are sulfuric acid and iron silicate. The concentration increases after each step of the process. Follow-up processes isolate elements such as gold, silver, lead, and others.

A spark-emitting steel bucket, suspend-ed from the crane’s heavy hinges, trans-ports 85 tons of molten copper matte to one of the three converters. Injected air combines here with the residual sulfur, leaving 98 percent crude copper. The oxi-dation produces so much heat that the converter has to be cooled with scrap. Old copper material goes to be recycled here without the need for additional energy. “Recycling is one of our strengths,” says Aurubis spokesman Malte Blombach. In the works yard stand mountains of neatly separated stamped parts, printed circuit boards, and wires. Copper can be recy-cled an infinite number of times with no

Copper oreMined

Copper concentrateMine: fl otation,

arrives in Hamburg

Copper matteFlash smelting

furnace

Blister copperConverter: oxidation

Crude copperAnode furnace:

Fire refi ning

AnodeCasting wheel

CathodeElectrolysis

Max.

2 %Cu

Up to

30 %Cu

Up to

64 %Cu

Up to

98 %Cu

Up to

99.5 %Cu

99.99%Cu

loss of quality. At Aurubis, 400,000 met-ric tons of old copper and 300,000 tons of electrical waste are recycled annu-ally across four different sites in Ham-burg, Lünen, Olen (Belgium), and Pirdop (Bulgaria). The company is the world’s biggest recycler.

SLABS WEIGHING 400 KILOSOre contains barely more than two per-cent copper nowadays. This is too expen-sive to transport, which is why the mines in Chile, Peru, and China grind it down to a fine dust and enrich it to a concen-trate using the flotation method until its copper content is 30 percent. The mixture

travels by ship to Hamburg via Brunsbüt-tel, where it is presorted. “The anode is a product of the smelting works,” says Edens. The thick, 400-kilo slabs consist of 99.5 percent copper when they leave the smelting works. Beforehand, the fire refining process in the anode furnace removes oxygen and residual sulfur. Mol-ten copper pours out of the rotary furnace into a swinging trough, which transfers it to the casting wheel’s molds with a copper green flame. Empty rotating molds make their way to technicians wearing reflec-tive heat protection. They chip crusts off the grooves, because the anodes have to be perfect. Finally, the cold immersion

EUROPE’S BIGGEST COPPER ELECTROLYSIS PLANT in Hamburg produces almost 400,000 tons of cathode per year

ALL OK? Process mechanics check the values at the anode furnace

INFO

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bath. The most important job of the pro-cess mechanics is quality control and tak-ing samples. Using a steel lance, depos-its are broken off at the run-off about twice an hour. Dräger breathing protec-tion (especially full-face and half masks with filters to protect against dust par-ticles, SO2, and CO2) is routinely worn here. And Dräger gas detection technol-ogy monitors carbon monoxide escaping from the electric furnace. “This can form when the slag is reduced,” says Edens. “We also measure the oxygen content by the drum dryer, because we use nitrogen for drying the concentrate.”

ELECTRIFYING FINALEOne of the most important properties of copper is its electrical conductivity. Even a slight impurity can impair this. Electrol-ysis makes the material a real all-rounder, a multi-talent in industrial production. It extracts the remaining by-products from the anode in a copper sulfate solution at a temperature of 60 degrees Celsius. The electricity that flows prompts the copper ions to adhere to two stainless-steel cath-odes. Emil Wohlwill, former head chem-ist at the plant, invented this process back in 1876. He calculated the voltage in the electrolyte so that ions of arsenic, nickel, and zinc remained in the alkaline solu-tion. Gold, silver, selenium, and lead do not dissolve and sink to the bottom of the trough as anode sludge – a brown, highly valuable slush. After one week, millimeter-thin, salmon-red copper cathodes measur-ing two square meters are produced, made of 99.99 percent pure copper. The plant uses this to produce heavy preliminary products for industry, continuous casting formats, special wire, but also alloys. “The main preliminary products are coils,” says Edens. “Rolls of wire weighing five tons and as tall as a human being.” Everybody pulls their weight at Aurubis.

READY FOR DISPATCH: Employees cut the endless roll of copper wire. A new fi ve-ton coil is produced every ten minutes

PROVISIONAL END PRODUCT: Copper cathodes as a raw material for a wide range of uses in industry and the energy and IT sectors

A HIGH-QUALITY METAL