Optimization of dust recycling with respect to zinc by use of air classification

Beschreibung

In integrated steel mills the separation of dust from process off-gases generates large amounts of waste fines, which consist mainly of iron oxides, lime and carbon. Due to the high temperatures in processes, volatile compounds, especially zinc, are enriched in these fines. On the one hand, this enrichment limits recycling of the dusts because of the zinc limit for the BF charge. On the other hand, the zinc content is usually too low for zinc recovery to be feasible by external providers. For zero waste steelmaking in integrated steel mills, up-cycling of the zinc concentration in a small dust stream which is shipped to secondary zinc production is a feasible solution. Thereby, the number of cycles in which a zinc atom is reduced to metallic zinc and volatilized in a process and subsequently redeposited during process off-gas cooling should be minimized because each cycle transfers energy from the processes into the off-gas. In several studies it has been shown that in dusts from dry off-gas cleaning in BFs and BOFs the zinc concentration is higher in the fine size fractions of the dusts and lower in the coarser size fractions. Consequently, size fractionation can be applied to produce zinc-enriched and zinc-depleted fractions of the dusts. Because of the fine grain size of the dusts, only air classification can achieve for such separation. Therefore, optimized dust recycling in an integrated steel mill could be achieved by air classification of BF and BOF dusts, which allows establishing a low zinc concentration dust cycle in the ironmaking section, a medium zinc concentration dust cycle in the BOF shop and a high zinc concentration dust discharge to an external secondary zinc producer.

Zeitraum	18 Okt. 2022
Ereignistitel	6th European Conference on Clean Technologies in the Steel Industry
Veranstaltungstyp	Konferenz
Ort	Aachen, DeutschlandAuf Karte anzeigen
Bekanntheitsgrad	International