06 August 2008

SCIENCE: Characterization of steel mill electric-arc furnace dust

Article in Journal of Hazardous Materials B109 (2004) 59–70 by Tahir Sofilic, Alenka Rastovcan-Mioc, Stefica Cerjan-Stefanovic, Vjera Novosel-Radovic , Monika Jenko of Željezara Sisak Ltd., Sisak, Croatia & Faculty of Metallurgy, University of Zagreb, Croatia & Faculty of Chemical Engineering and Technology, University of Zagreb, Zagreb, Croatia & Institute of Metals and Technology, Ljubljana, Slovenia.

Abstract

In order to make a complete characterization of electric-arc furnace (EAF) dust, as hazardous industrial waste, and to solve its permanent disposal and/or recovery, bearing in mind both the volumes formed in the Croatian steel industry and experiences of developed industrial countries, a study of its properties was undertaken. For this purpose, samples of EAF dust, taken from the regular production process in the Željezara Sisak Steel Mill between December 2000 and December 2001, were subjected to a series of tests. The chemical composition of EAF dust samples was investigated by means of a several different analytical methods. The results from the chemical analysis show that the approximate order of abundance of major elements in EAF dusts is as follows: Fe, Zn, Mn, Ca, Mg, Si, Pb, S, Cr, Cu, Al, C, Ni, Cd, As and Hg. Granular-metric composition of single samples was determined by applying sieve separation. Scanning electron micro-structural examination of EAF dust microstructure was performed and results indicated that all twelve EAF dusts were composed of solid spherical agglomerates with Fe, Zn, Pb, O, Si and Ca as the principal element. The investigation of grain morphology and the mineralogical composition of EAF dust were taken by combination of high resolution Auger electron spectroscopy (HR AES), X-ray photoelectron spectroscopy (XPS) and X-ray powder diffraction analysis. The analysis of XPS-spectra determined the presence of zinc in the form of ZnO phase and the presence of lead in the form of PbO phase, i.e. PbSO3/PbSO4 forms. The results of the X-ray diffraction phase analysis show that the basis of the examined EAF dust samples is made of a mixture of metal oxides, silicates and sulphates. The metal concentration, anions, pH value and conductivity in water eluates was determined in order to define the influence of EAF dust on the environment.

Extracts

Major pollution that is released into the atmosphere during the steel making process includes solid particles (dust), carbon (II) oxide, nitrogen oxides, and volatile organic compounds. …

Due to its chemical and physical properties, the electric-arc furnace dust was categorized as hazardous waste according to the US EPA classification of 1980 [2]. Being treated as hazardous waste, it is partly disposed of permanently at appropriate, regulation-prescribed waste dumps, or it can be used as secondary raw material in the production of zinc, iron, lead, etc. ...

3. Results and discussion
3.1. Characterization of samples
3.1.1. Chemical analysis

The chemical composition of electric-arc furnace dust depends on the quality of steel scrap processed, the type of steel being produced, technological and operating conditions and the degree of return of the dust into the process. Reference data [11–24] imply that the prevailing elements in EAF dust vary in concentration: Fe 10–45%, Zn 2–46%, Pb 0.40–15.14%, Cr 0.2–11%, Cd 0.01–0.30%, Mn 1–5%, Cu <>

The results of the chemical analysis of the EAF dust samples are shown in Table 1. ...

The results of granular-metric analysis have shown that a sample of electric furnace dust basically consists of 100–125µm particles, while 90–100 µm particles are least represented. Although the results of granular-metric analysis show that the smallest measured fraction has the grain size <50µm,>particles with grain diameter = 1µm which mostly form agglomerates, the size of which can exceed 200 µm, Fig. 3. ...

Conclusion

The obtained research results show that the volume of EAF dust formed per tonne of crude steel in Croatia does not differ from the volumes of EAF dust formed in other steel mills in the world using the electric-arc furnace procedure.

The chemical composition of the domestic EAF dust is mostly identical to the chemical composition of EAF dust of other steel producers. Major differences refer to the zinc content, which has a mass share not greater than 10% in EAF dust samples from domestic steel mills. This is a direct consequence of applying high-quality steel scrap (containing very little galvanized steel). …



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