Hydrometallurgical processes for Waelz oxide valorisation – An overview

Abstract

The steelmaking industry that uses electric arc furnaces to recycle steel scrap generates dust (EAFD) as its main residue. This waste must be treated to recycle some heavy metals for economic reasons and to prevent negative environmental impacts. It is formed basically by different metallic oxides with heterogeneous composition and size. The Waelz Kiln Technology is the most commonly used technology for this purpose, generating concentrates of Zn and Pb oxides (called Waelz oxides). The main component of Waelz oxides is zinc and nowadays the production of metallic zinc and high purity zinc oxide covers approximately 97 % of the zinc market. The impurities content in the Waelz oxides (different heavy metals, halogens, …) makes impossible to use it as raw material to produce industrial high purity zinc oxide or in the electrolytic production of metallic zinc. At present, the Waelz oxides are blended with other purer raw materials. That supposes the unfeasibility of obtaining these products only through direct recycling EAFD. Therefore, the goal of this work is an in-depth study of the newest hydrometallurgical processes in order to achieve the production of these zinc products from Waelz oxides, showing their possibilities and limitations.