Thermodynamics calculation on the oxidation and sulfur removal abilities of slag in EAF dust pellet reduction process

Abstract

The valuable metals in the dust can be recycled by mixing it with reducing agent carbon and lignosulfonate as the binder to make pellets, then returning the pellets to electric arc furnace (EAF) and adding ferro-silicon. Part of valuable metals in the dust is reduced by carbon and part of them reduced by ferro-silicon for the economical consideration. The reduced metals get into the steel in the stainless steel or special steel production. But the sulfur in the lignosulfonate may affect the quality of produced steel, which is dependent on the status of the smelting slag. The experiments were conducted in the way of changing the ratio of start iron, pellets, ferro-silicon and lime. The content of the slag was checked by XRF for the calculation thermodynamics study. The active concentrations of materials in the slag, the slag abilities of oxidation and sulfur removal in EAF dust reduction process were determined by thermodynamics calculation study on CaO-MgO-FeO-Fe₂O₃-SiO₂-S slag at 1 550 °C. The oxidation ability of slag can be expressed as N(FeO)=N(FetO)+6N(Fe₂O₃)+8N(Fe₃O₄). The sulfur removal ability is dependent on the amount of added ferro-silicon and the basicity of the slag. The calculation thermodynamics model was set up and it could be applied to the practical production.

Keywords

thermodynamics calculation / slag / electric arc furnace / dust

References

[1] US EPA. Land disposal restriction for electric arc furnace dust (K061)[P]. Federal Register, 1991, 56: 41164-41164

[2] ZhengG, KozinskiJ A. Solid waste remediation in the metallurgical industry: Application and environmental impact[J]. Environmental Progress, 1996, 15(4): 283-291

[3] LiDing-yi. Application of plasma technology to treat EAF dust[J]. Iron and Steel, 1995, 30(3): 72-74

[4] John Floyd. EAF dust treatment in an ausmelt furnace system[J]. SEAISI Quarterly, 1993, (2): 60–65.

[5] Mastsuoka S. New technology for treating electric arc furnace dust[J]. Iron & Steel Engineer, 1991, (2): 37–40.

[6] Charles J Labee. Update on electric arc furnace dust treatment[J]. Iron and Steel Engineer, 1992, (5): 48–49.

[7] Jan T Jensen. Reduction of EAF dust emissions by injecting it into the furnace[J]. MPT International, 1997, (3): 58–62.

[8] Honjo. Results of AOD dust melting in an arc furnace[J]. ISIJ, 1997, (10): 50–53.

[9] Dancy T E. The development of direct reduction processes[J]. Scandinavian Journal of Metallurgy, 1993, (22): 100–108.

[10] LobelJ, PengB, BourassaM, et al.. Pilot-scale direct recycling of flue dust generated in electric stainless steelmaking[J]. Iron and Steelmaker, 2000, 27(1): 41-45

[11] RoineAHSC chemistry (ver. 1. 10)[CP], 1993, Pori, Outokumpu Research Oy

[12] Sims ClarenceEElectric furnace steelmaking(version 2)[M], 1962, New York, Interscience: 54-67