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The steel industry is a major contributor to the global economy, but at the same time generates significant amounts of emissions and residues. Most are valorised by internal recycling or external use, but there are still significant values in terms of carbon and iron units that cannot be recycled because the zinc content in the dust and sludge is too high, but too low and full of impurities to be sent to zinc producers. For the recycling of these residues in steelmaking processes, the removal of zinc is important since this element creates various problems in steel plants. Dust and sludge that are not recycled, cause both raw materials losses and additional costs for preparing safe deposits and conducting landfilling.
Among steel producers in EU, about 900 kt of blast furnace (BF) dust and sludge along with 1,300 kt of basic oxygen furnace (BOF) dust and sludge are generated each year, of which approximately 50% are recycled. In EAF steelmaking, about 30% of the dust cannot be recycled due to the low zinc content. It is anticipated that the zinc content of EAF dust will be lower in the future as DRI/HBI partly or fully will replace steel scrap when the transition towards green steel production is realized.
Although the objectives of residue treatment are common to all steel plants, an efficient and economically feasible method for the removal of zinc and the generation of an iron-rich residue for recycling within the production cycle is not yet available.