Electric arc furnace (EAF) dust: Application of air classification for improved zinc enrichment in in-plant recycling C. Lanzerstorfer University of Applied Sciences Upper Austria, School of Engineering, Stelzhamerstraße 23, A-4600, Wels, Austria article info Article history: Received 16 June 2017 Received in revised form 24 October 2017 Accepted 29 October 2017 Keywords: EAF dust In-plant recycling Zinc abstract Currently, more than half of the electric arc furnace (EAF) dust produced worldwide is still sent to landfill. This dust contains approximately 7.0% of the world Zn production. The other half of the EAF dust is processed pyrometallurgically or hydrometallurgically to recover Zn. The processing costs for EAF dust strongly depend on the Zn concentration. Therefore, several steel mills apply in-plant enrichment of Zn by recycling part of the dust back into the furnace to reduce the specific processing cost for the EAF dust and at the same time decrease the amount of dust that has to be discharged. Separation of EAF dust into size fractions by air classification showed a distinct dependence of the Zn concentration on the particle size with an enrichment of Zn in the fine size fractions and depletion in the coarse fractions. Therefore, in in-plant dust recycling, air classification of the dust could be used to reduce the amount of recycled Zn and dust but still reaching the same Zn concentration in the discharged dust. This would reduce the energy demand for Zn volatilization in the furnace and the required capacity of the dust recycling system. © 2017 Elsevier Ltd. All rights reserved. 1. Introduction In the production of steel a significant amount of dust is pro- duced. A range of 10e30 kg of dust per ton of liquid steel (kg/t LS) has been reported for smelting of scrap and direct reduced iron in an electric arc furnace (EAF) by Remus et al. (2013) in the comprehensive work “Best Available Techniques (BAT) Reference Document for Iron and Steel Production”. The main component in EAF dust is usually Fe, but Zn and other metals volatile at steel- making conditions can also be found in the dust at elevated con- centrations. Zn is found in EAF dusts at higher concentrations because of its wide-spread use for corrosion protection of steel. The Zn enters the furnace with the scrap and it is subsequently volat- ized there because of the high temperature and the reducing con- ditions. The Zn leaves the furnace with the off-gas and is deposited on the dust particles during cooling of the off-gas. Reported values of the Zn concentration of EAF dust are in the range of 2e43% (Remus et al., 2013). The concentration of Zn in the EAF dust is not constant during the time of a heat as shown by Sasamoto and Fujisawa (1997) in their experiments with a 20 t EAF. In the EAF dust Zn is mainly present as Zn oxide (ZnO, zincite) and as Zn ferrite (ZnFe 2 O 4 , franklinite) as demonstrated by Pickles (2003) in his study about EAF dust recycling. Annual production of EAF dust in 2013 was estimated at 8.5 million tons of which 4.0 million tons were recycled and 4.5 million tons were landfilled (Antrekowitsch et al., 2015). In their review of the recycling of steel mill dust they concluded that also new de- velopments in the area of treatment of these dusts still suffer from lack of efficiency. Prior to landfilling the EAF dust usually has to be chemically treated. For stabilization and safe disposal, mixing of EAF dust with Portland cement and lime (Salihoglu and Pinarli, 2008) or low grade magnesium oxide (Cubukcuoglu and Ouki, 2012) has been investigated. In both studies it was concluded that stabilization of EAF in compliance with the regulatory land- filling criteria is possible though increase in the amount of the waste as a natural result of the stabilization process has to be considered. However, landfill is not a sustainable solution because the EAF dust sent to landfill contains approximately 7.0% of the world Zn production (Antrekowitsch et al., 2015). EAF dust can be used as a filler in concrete or asphalt as investigated by Sayadi and Hesami (2017) or in the production of ceramics as suggested by Mymrin et al. (2016). The authors of both studies concluded that in these applications natural materials can be replaced and no haz- ardous impact on the environment results from such utilization. However, in these applications the Zn contained in the EAF dust is spread in the environment and, therefore, lost for recycling. From an environmental point of view, the most sensible solution is to E-mail address: christof.lanzerstorfer@fh-wels.at. Contents lists available at ScienceDirect Journal of Cleaner Production journal homepage: www.elsevier.com/locate/jclepro https://doi.org/10.1016/j.jclepro.2017.10.312 0959-6526/© 2017 Elsevier Ltd. All rights reserved. Journal of Cleaner Production 174 (2018) 1e6