A combined hydro-pyrometallurgical process for zinc oxide and iron oxide extraction from electric arc furnace dust waste

Electric arc furnace (EAF) dust waste is generated during EAF steelmaking process. Zinc and iron which comprise the highest composition in EAF dust are secondary resources for making steel products. They mainly present in the form of stable zinc ferrite (ZnFe2O4), leading to the extraction process difficult. In this study, a combined hydro-pyrometallurgical process was developed to extract both zinc oxide and iron oxide from EAF dust. Initially, hydrometallurgical leaching was used to leach zinc and iron from EAF dust. Results show that 10 M of hydrochloric acid (HCl) at 25°C can achieve zinc and iron leaching of 92% and 91%, respectively. The liquid solution post leaching was subjected to pyrometallurgical process to form Fe2O3 mixture at 250°C while retaining zinc chloride (ZnCl2) as solid residue. Then, the obtained ZnCl2 was treated with sodium hydroxide (NaOH) and nitric acid (HNO3) to form ZnO. The Fe2O3 and ZnO extraction were 2.5 g and 1.5 g, respectively out of 10 g of EAF dust with their respective purity of 87% and 98%. The developed process can provide new insight into recovering zinc oxide and iron oxide simultaneously from EAF dust, thereby paving the way to circular economy development and sustainable steel dust waste management for steel industries.

Investigation of dielectric heating method of zinc-containing materials for chlorides removal

The technological development of the world community makes it necessary to resolve the issues of the produced industrial residues utilization. Worn-out galvanized metal cars, ceilings and other metal structures require orderly utilization. Utilization of galvanized scrap may be carried out in Electric Arc Furnaces (EAF) to obtain intermediate steel and EAF dust. Electric Arc Furnaces dus contains zinc, so it is used as a secondary raw material for the production of metallic zinc. Waelz oxides are formed in Waelz kilns, after the primary processing of EAF dust. Waelz oxide contains halides that must be removed first. Halides may be removed by heating to temperatures of about 1000°C. Dielectric (microwave) heating is a promising and environmentally friendly method for material processing. Microwave heating is carried out without burning natural gas, which leads to decrease of waste gases volume. The work experimentally confirmed the possibility of zinc-containing materials heating at electromagnetic emission exposure. The duration of products heating up to the temperature of 1000°C was 128 - 188 s. The residual content of chloride ions in the calcined products is less than 0.05 wt%.

Optimization of the Microwave-Assisted Carbothermical Reduction Process for Metals from Electric Arc Furnace Dust with Biochar

The main purpose of this work was to extract valuable metals from EAF dust with the addition of biochar, using microwaves to control and optimize the carbothermical reduction process. To achieve better microwave penetration and the most homogeneous electromagnetic heat source distribution possible in a sample, the content of EAF dust and biochar in centimeter-size spherical particles prepared by the pelletization process was considered to be radially heterogeneous. The content of EAF dust was determined experimentally and the effective permittivity, permeability, and thermal conductivity of the EAF dust as well as biochar–EAF powder mixture were determined using effective medium approximation. The microwave heating of a multilayered pellet of biochar-containing EAF dust was simulated and investigated. The influence of the distribution of the components within the pellet on the effectiveness of the microwave heating was investigated, as was the influence of the biochar conductivity. The interaction of the pellet with both plane waves in free space and with H10 mode waves in a single-mode waveguide was considered. The most optimal distribution of EAF dust and biochar within the pellet for the reduction process was determined.

Effective electrodynamical parameters and microwave heating of radially heterogeneous pellets containing EAF dust and biochar

In this work, we investigated the effect of microwave radiation with radially heterogeneous pellets consisting of electric arc furnace (EAF) dust and biochar. We reviewed the possible content of EAF dust in terms of permittivity and permeability of its components and calculated effective permittivity and permeability of EAF dust by an effective medium approach. Using obtained values we calculated dependencies of effective permittivity and permeability of EAF dust - biochar composite mixture on the volume fraction of EAF dust and conductivity of biochar. Taking into account these dependencies we simulated electromagnetic field and temperature distribution within pellet with a radial dependency of volume fraction of EAF dust and effective permittivity correspondingly.

High-Performance Method of Recovery of Metals from EAF Dust—Processing without Solid Waste

A highly effective method of the processing of steelmaking dust in an arc-resistant furnace has been presented. The aim of the research was to investigate the possibility of processing steelmaking dust in terms of waste minimization and selective recovery of valuable components. For this purpose, an electric arc resistance furnace was used. Granulated steelmaking dust with reducer (coal dust) was the input material. The products of the process are zinc oxide, iron alloy and slag, with properties meeting high ecological requirements. The technology does not generate solid waste. Zinc recovery is over 99% and iron recovery over 98%. The content of heavy metals (Zn + Pb + Cu) in glassy slag is below 0.2%, which ensures very low leachability.

Purification of Zinc Oxide from Chlorides Using Microwave Radiation

Waelz oxide is a secondary zinc raw material and a product of Electric Arc Furnaces (EAF) dust, copper smelters dust and zinc production residues. The use of Waelz oxide in the traditional RLE (Roasting-Leaching-Electrowinning) zinc production scheme requires the removal of halogens (fluorides and chlorides). Waelz oxide is mainly composed of zinc oxide, also contains zinc chloride. Zinc chloride is removed into the gas phase at heating. Microwave heating is one of the promising methods. Test experiments of microwave heating of a ZnO-ZnCl2 mixture were carried out. It was shown that zinc chloride absorbs microwave radiation; zinc oxide does not absorb microwave radiation. The degree of zinc chloride removal from ZnO-ZnCl2 mixture was 100%.