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Reducing zinc contamination in basic oxygen steelmaking dust

Heinrich, Tobias 2016. Reducing zinc contamination in basic oxygen steelmaking dust. PhD Thesis, Cardiff University.
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Abstract

Basic oxygen steelmaking (BOS) produces significant quantities of dust which are both rich in iron, and varied in composition, presenting either a potential recycling resource or disposal liability. In particular, the increasing use of galvanised steel in the automotive industry has resulted in larger quantities of galvanised scrap recycling during BOS manufacturing. The zinc from this scrap finds its way into the process dusts, contaminating them and causing difficulties in their recycling. The treatment of BOS dust via pyrometallurgical and hydrometallurgical processes has been researched extensively and proven to be difficult to be commercially successful. The objectives of this study were to characterise the zinc contamination of BOS dust; assess the impact of charging different amounts of galvanised scrap and waste oxide briquettes (WOBs); and to analyse if zinc contamination can be reduced by holding galvanised scrap in a hot converter in an inert nitrogen atmosphere, prior to the hot metal addition, to volatilise the zinc. The impact of the different scrap charges and the success of holding the galvanised scrap were evaluated by measuring the mass and concentration of the zinc in the BOS dust extraction systems. The finding of this work includes: 25% of the BOS dust has a coarse particle size and is predominantly made up of iron spheres with little zinc contamination suitable for recycling via the sinter plant. T. Heinrich 2015 Reducing zinc contamination in BOS dust ii Further physical separation of the fines section of the dust is not possible since the zinc oxide either attaches to the other particles or reacts with their surface. Adding WOBs during the blow causes an increase of zinc contamination, especially at the later stages of the blow. By holding the scrap for more than ten minutes in the nitrogen purged converter, approximately 50% of the zinc contained in the scrap is volatilised and can be diverted away using the secondary dust collection system. This resulted in halving the zinc contamination in the primary dust extraction system. Charging the converter with a reduced amount of galvanised scrap makes it is possible to produce a dust with low zinc contamination which can be recovered through the sinter plant and blast furnace.

Item Type: Thesis (PhD)
Date Type: Publication
Status: Unpublished
Schools: Engineering
Uncontrolled Keywords: Steelmaking; BOS; Dust; Zinc; Scrap; Volatilisation.
Date of First Compliant Deposit: 17 November 2016
Last Modified: 04 Jun 2017 09:30
URI: http://orca.cf.ac.uk/id/eprint/96232

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