Behavior of Zn and Fe Content in Electric Arc Furnace Dust as Submitted to Chlorination Methods

Abstract

This work covers initially a general thermodynamics assessment regarding the zinc ferrite (ZnFe 2 O 4 ) behavior toward direct and reducing chlorination. Then, the use of alternative chlorination agents were also theoretically appreciated, before a set of experiments has been carried out with industrial residue (electric arc furnace dust). Besides identifying zinc ferrite (95.4 pct), the XRD analysis indicated the presence of ZnO (4.6 pct). Therefore, the main objective of the present work is related to a theoretical (thermodynamics) and experimental (kinetics) evaluation of the mentioned residue chemical behavior as submitted to chlorination methods. Several characterization methods were used, such as X-ray diffraction, scanning electron microscopy, X-ray fluorescence, mass spectroscopy (ICP-MS), and energy-dispersive X-ray spectroscopy (EDS). It was observed that zinc was present, mostly, in the form of zinc ferrite (franklinite). The thermodynamics study revealed that Zn has a more susceptible behavior regarding the oxides conversion into chlorides. However, this tendency is not necessarily associated with a selective reaction, as showed for the chlorination in the presence of carbon, as both iron and zinc chlorides formation is feasible. The experimental results have indicated that some reaction systems can be further studied in order to identify operational conditions that enable selective formations. So, it was observed that for the calcium chloride reaction conducted at 1273 K (1000°C) for 30 minutes, the iron content in the residue slightly increases (with 15 pct removal), whereas the zinc content decreases from 20 to 12 pct (53 pct removal), suggesting complementary studies where this possible selectivity could be even more determinant. Such results have also indicated that the direct action of chlorine at 1073 K (800°C) allowed complete removal of zinc, followed by conversion in the order of 40 pct in iron. Therefore, a complementary investigation over these alternatives is identified as a promising option in the field of electric arc furnace dust treatment, particularly when the Zn content is very low.

Influence of Temperature on the Selective Chlorination and Evaporation Reactions of Zn and Pb in EAF Dust

“…13) However, if no oxygen is supplied and P Cl 2 / P O 2 value is too high, the chlorination reaction of iron oxide proceeds forward, which leads to the result of iron loss as reported by some researches 11,13,14) . In order to chlorinate zinc and lead while preventing chlorination of iron, high partial pressure of oxygen is essential.…”

“…[6][7][8][9][10][11] Chlorides of Zn and Pb have relatively low boiling points (ZnCl 2 : 1004 K, PbCl 2 : 1223 K), 12) which can be employed to extract noble metals from EAF dust. Many chlorine bearing materials such as hydrochloric acid, chlorine gas and calcium chloride were used as chlorinating agents for the reaction.…”

Nonisothermal Investigation of Reaction Kinetics between Electric Arc Furnace Dust and Calcium Chloride under Carbon-Containing Conditions

“…metallic zinc by electrolysis, and the residue is expected to be reused in steelmaking because of its high iron concentration. Although prior researchers have investigated this method using chlorine gas [4][5][6][7][8][9] and PVC, [10][11][12] this study aims to recover zinc from dust using calcium chloride, which is easier and safer to handle. Sato and Okumura 13) reported zinc oxide can be reduced by carbon in EAF dust and proposed a zinc recovery method combining carbothermic reduction by carbon and chloride volatilization by calcium chloride; however, no reaction rate analyses have been performed.…”

Microwave assisted alkaline roasting-water leaching for the valorisation of goethite sludge from zinc refining process

“…Franklinite is a very stable spinel structure that requires other routes than those above mentioned to liberate Zn for dissolution. Those may include several methods to decompose the franklinite structure or to reduce the iron and the zinc present in the spinel, as illustrated in Table 1 (Güler et al, 2011;Havlik et al, 2004;Kazemi and Sichen, 2016;Kukurugya et al, 2015;Omran et al, 2017;Santos et al, 2015;Turan et al, 2004;Stanforth, 2000a, 2000b;Zang et al, 2016). Amongst these techniques, an effective and selective combination of thermal and hydrometallurgical treatments, composed of preliminary hydrolysis-NaOH roasting-NaOH leaching, was explored by Youcai et al to quantitatively extract zinc from franklinite-bearing EAF dusts (Zhao Stanforth, 2000b, 2000a).…”