8 | 21ST CENTURY SMELTING
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Innovating for future generations Phillip Mackey provides a detailed review into the history and operation of the outstanding Aurubis Hamburg copper plant To the question “How do you become one of the best-run plants in the world?” the answer given by any Smelter Site Manager today is invariably “Good design in all plant areas, excellent operations and maintenance with very skilled supervisory and operating personnel.” The Aurubis Hamburg Primary Smelter, admirably fits this description. Reference has been made in these pages on the factors described by Arie de Geus in his book “The Living Company” as influencing the overall strength of an enterprise and the characteristics of a truly successful company. Aurubis, formerly Norddeutsche Affinerie, also fits well into this category and has done so for over 150 years. In the beginning The company’s history dates back to 1866 with the founding of Norddeutsche Affinerie AG and consolidation of the early smelting and refining facilities originally located at Elbstrasse in Hamburg. The plant was moved to the more spacious areas on Peute Island in the Elbe River in 1908 - the present location - accompanied by a number of plant expansions. The history of the Hamburg plant features a number of very significant metallurgical innovations and milestones - too numerous to cover them all here except to note a few key ones - and a winning culture that strives to be the best, starting in the late 1800s. For example, in 1876 Norddeutsche Affinerie was the first company outside of the United Kingdom to install the then new electrolytic copper refining process that had been pioneered at Pembrey in the UK in 1869. The Hamburg plant was similar but somewhat larger compared to that at the Pembrey facility. Hamburg later expanded the tankhouse considerably and today it is one of the largest in the world. Copper electrorefining was perfected at Norddeutsche by Dr. Emil Wohlwill. He also invented a new process for gold and silver, an approach still used to this day. Dr. Wohlwill also experimented with reagent additions to the copper electrolyte and was the first to use chloride additions to help smooth out the copper deposit. All refineries today worldwide continue to use chloride additions, and still follow the main principles originally developed at these two plants. Early plant Facilities were soon in place to also treat copper scrap in addition to copper concentrate feed, and a lead smelting plant was also built. In the late 1930s, the annual capacity of the plant was about 95,000 of electrolytic copper and 36,000 tonnes of lead. By-products included gold, silver, nickel, tin, bismuth, cobalt and a number of metal salts. An acid plant was installed in the 1930s and was one of the first acid plants installed in a smelter anywhere in the world. Following rebuilding after World War 2 - bombing had destroyed parts of the plant in 1944 - Germany experienced huge economic growth and the Hamburg plant undertook a number of expansions.
The double contact (double absorption) acid plant at dusk. Photo: Aurubis
By this time, copper concentrates sourced from all over the world were roasted in a number of multiple hearth roasters and smelted in a reverberatory furnace, producing a copper matte containing about 45% Cu. This matte was converted in one of two Peirce-Smith converters. Blister copper was processed to anodes for the copper refinery. This facility had also been expanded, and due to space limitations, a number of cells were built on the second floor of the tankhouse - likely the only plant with such an arrangement. The flash era In the late 1960s, with the plant eying a further expansion to meet the growing copper demand, alternative smelting technologies were evaluated - including electric furnace smelting of roasted concentrate and Outokumpu (now Outotec) flash smelting. At this point there were over eight new flash furnaces operating worldwide and this technology was wisely chosen for Hamburg. The flash furnace was built in a new area of the site. The plant, commissioned in March 1972, had a design capacity of 400,000 tonnes of 27% Cu conc. /yr, or a smelting rate of 50 t conc. /hr, producing 60% Cu matte. The facility included a 2 MW (nominal), 10 m dia. electric furnace for cleaning the flash furnace slag; converter slag was returned to the flash furnace. A new double contact (double absorption) acid plant was also built - likely the first or one of the first double absorption acid plants at a copper smelter. Concentrate receipts were handled at the nearby port and brought to the plant by barge. Blending facilities were also improved. In operation, copper concentrates were dried in a new, 30 m long kiln dryer fired with natural gas, with dry concentrate conveyed to storage bins located above the flash furnace. Initially the flash furnace operated with 540 oC preheated air and the reaction shaft was cooled - as at many flash furnaces of the era - with a falling water Copper Worldwide Vol 11 No 2
Aerial view of Aurubis Hamburg. Photo: Aurubis
film. Later oxygen enrichment was introduced and shell cooling elements replaced the water film cooling. Off-gases were cooled in a waste heat boiler rated at 49 t steam (60 bar)/hr. It was reported that cleaned slag at the electric furnace contained about 0.65% Cu. Tapped slag was cast in small ladles and after crushing was used for construction and for river dikes. At the time, there were still two 4.25 m by 11 m Peirce-Smith converters installed, with one blowing, and one on standby. Oxygen enrichment to about 25% O2 was used to assist in skull and scrap smelting. Blister copper was handled in two rotary anode furnaces with natural gas used for poling. It is understood that the reverberatory furnace remained in use for some time. By the mid-1990s, concentrate throughput at the flash furnace had been increased to 70 tonnes of conc./hr, or about 600,000 t conc./ yr, primarily by the use of oxygen enrichment supplied by a 240 t/d oxygen plant, along with a number of other plant improvements. Environmental enhancements introduced included secondary hooding on the converters and side charging at the hood for scrap, a new concentrate storage building (100,000 t capacity), improved performance of the waste heat boiler, gas cleaning
