Strategy To Recover Valuable Elements From Steel Scrap And Steelmaking Slag

Abstract:

From the material flow of various elements, many of them are consumed as alloying elements for steel. It is well known that the excellent characteristics of steel are generated by the precise addition of alloying elements. Although steel is recycled as steel scrap, in the steel scrap, the values of the added alloying elements are not considered and the scraps are reused in low grade steel. In these sense, steel is a place where the elements play active parts but also the place for the elements as graveyard. On the other hand, steelmaking slag contains many valuable elements. To extract these elements, separation of harmful element, i.e. P and S is imperative. In this paper, the relation of element circulation and steel scrap recycling was discussed and it was clarified that the contribution of the steel scrap recycling on the element circulation is not effective except the austenitic stainless steel. In addition, the possibility to extract the valuable elements from scrap and steelmaking slag was discussed by the thermodynamic consideration. The result indicates that the formation of slag by oxidation is an effective method to enrich these elements, although the oxidation of P also occurs. As most of the phosphorous in slag forms the solid solution and the P content in the other phase is low, some technologies have been proposed to remove P from other oxide, using the difference of density, magnetic property and water solubility between these phases. On the contrary, by the sulfurization, Mn would be enriched in sulfide phase without containing P. For the recovery of valuable elements from steel scrap and slag, the sulfurization process combined with oxidation is undergoing.

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