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Substandard anodes can add as much as $100/t to the cost of metal produced in the pot line and increase the quantity of GHG emissions. Thus careful attention to the quality of raw materials and furnace design and operation are vital to produce anodes which give optimum performance in the pot line.
Why should smelter management care about anode quality? From considering all the input materials required to produce primary aluminium, those for anode production have the greatest variation of properties relevant to quality. Substandard anodes have a significant impact on the cost of metal production and greenhouse gas (GHG) emissions.
Modern smelters typically have annual capacities in the range of 75okt/y - 8ookt/y and are designed to double capacity in expansion phases. Such smelters require anode plants with an initial annual output of 5ookt/y which has to be doubled if the smelter is expanded to twice its size subsequently.
Many years of steady development and design work have enabled smelters to increase the amperage and number of cells and adapt rectifiers with higher voltages to boost output. Unfortunately similar developments and design of anode plants is practically non existent resulting in even the latest anode plants having low throughputs (35t/h) and limited availabilities. Therefore, a technology is urgently needed for the efficient production of high quality anodes, at the lowest possible production cost, and capable of using inferior raw material as premium grades become increasingly unavailable. These anode plants must also have the lowest possible environmental emissions and operate with a high standard of workforce safety and hygiene. Such a technology must be able to handle large volumes of raw materials each day and to produce, move and store large quantities of green and baked anodes. The supplier of anode plant technology must also take into account that smelters will always try to increase output by further increasing cell amperage and are often asking for larger anodes (Fig i).
This paper describes a technology approach for designing and operating large anode plants adapted to the needs of large smelters. This technology has been developed by R&D Carbon Ltd in Sierre, Switzerland (RDC) in cooperation with major suppliers of green paste plants, anode bake furnaces and specific equipment suppliers. It takes into consideration operational...