Electrolytic Zinc Production from Crude Zinc Oxides with the Ezinex® Process

The state of the art for the recovery of metals from steel industry by-products using hydrometallurgical processes is reviewed. The steel by-products are different slags, dusts, and sludges from a blast furnace (BF), basic oxygen furnace (BOF), electric arc furnace (EAF), and sinter plant, as well as oily mill scale and pickling sludge. The review highlights that dusts and sludges are harder to valorize than slags, while the internal recycling of dusts and sludges in steelmaking is inhibited by their high zinc content. Although the objectives of treating BF sludges, BOF sludges, and EAF dust are similar, i.e., the removal of zinc and the generation of an Fe-rich residue to be returned to the steel plant, these three classes of by-products have specific mineralogical compositions and zinc contents. Because wide variations in the mineralogical composition and zinc content occur, it is impossible to develop a one-size-fits-all flow sheet with a fixed set of process conditions. The reason for the interest in EAF dust is its high zinc content, by far the highest of all steel by-products. However, EAF dust is usually studied from the perspective of the zinc industry. There are not only different concentrations of zinc, but also variations in the all-important ZnO/ZnFe2O4 (zincite-to-franklinite) ratio. In many chemical processes, only the ZnO dissolves, while the ZnFe2O4 is too refractory and reports to the residue. It only dissolves in concentrated acids, or if the dust is pre-treated, e.g., with a reductive roasting step. The dissolution of ZnFe2O4 in acidic solutions also brings significant amounts of iron in solution. Finally, due to its high potassium chloride content, sinter-plant dust could be a source of potassium for the fertilizer industry. Graphical Abstract

Section: Ammonium Chloride Leachingmentioning

confidence: 99%

Hydrometallurgical Processes for the Recovery of Metals from Steel Industry By-Products: A Critical Review

Binnemans

Jones

Fernández

et al. 2020

“…The hydrometallurgical methods for recycling EAFD include various leaching and extraction steps [1]. The Ezinex and the modified Zincex processes are implemented in industrial scale for treatment of dusts with low zinc ferrite contents [5,6]. Despite low energy consumption, high efficiency, and low content of impurities in the products, application of the hydrometallurgical procedures is limited by the complications involved in leaching of zinc ferrite.…”

Section: Introductionmentioning

confidence: 99%

“…Despite low energy consumption, high efficiency, and low content of impurities in the products, application of the hydrometallurgical procedures is limited by the complications involved in leaching of zinc ferrite. Thus, several works have focused on optimization of leaching conditions for ZnFe 2 O 4 and using methods such as pressure leaching and high-temperature leaching [5][6][7][8].…”

Section: Introductionmentioning

confidence: 99%

Investigation of Selective Reduction of Iron Oxide in Zinc Ferrite by Carbon and Hydrogen

Kazemi

Sichen

2015

The feasibility of selective reduction of iron oxide in zinc ferrite, which is one of the main components of electric arc furnace dust (EAFD), was examined. Experiments were carried out by using graphite powder or pure hydrogen gas as reducing agents. The carbothermal reduction experiments performed at temperatures between 973 and 1073 K in inert atmosphere indicated that the method was difficult to apply in practice due to slow rates of reaction and vaporization of zinc. Selective reduction of iron oxide in zinc ferrite was achieved by using pure hydrogen gas as the reductant. The iron oxide was reduced to metallic iron, while ZnO remained unreacted in the solid phase. As reaction times were increased at 873 K, ZnO was also reduced and zinc evaporated. The main advantages of H 2 reduction are high reaction rates, low energy requirements, and no CO 2 emissions. The addition of this process prior to the hydrometallurgical techniques for treatment of EAFD could overcome the difficulties for dissolution of zinc ferrite.

“…produced in any kind of fuming process, a very powerful system to deal with a variety of wastes and/or secondaries in a very simple process is created. A conceptual plant flowsheet, based on Engitec's INDUTEC Ò thermal process [14,15], is shown in Fig. 7 where diverse materials coming from different industries can be processed.…”

Section: /Ezinex\processmentioning

confidence: 99%

“…At the beginning of nineties, Engitec developed the EZINEX Ò Processes [10] to treat zinc-bearing materials such as EAF dust. In 1993, a pilot plant producing 500 t/y zinc from EAF dust was erected and operated.…”

Section: Introductionmentioning

confidence: 99%

INDUTEC®/EZINEX® Integrate Process on Secondary Zinc-Bearing Materials

Maccagni¹

2016

Steel used for many different applications is more and more often coated with zinc for corrosion protection purposes. The growing amount of Electric Arc Furnace Dust (EAFD) generated during the production of steel requires treatment that is able to convert this dust into usable materials. The current state of the art for the treatment of these wastes is based on the use of a Waelz Kiln, or any other zinc fuming system, where the zinc contained in the EAFD is concentrated in Crude Zinc Oxide (C.Z.O.), which is then fed to sulfate electrowinning or to the Imperial Smelting Process to produce zinc metal. These two processes require that the C.Z.O. be pre-treated, or at least washed, to meet the requirements of the processes. Engitec developed the EZINEX Ò Process that is able to convert C.Z.O. and other zinc oxides directly to metallic zinc cathodes. Engitec also studied the INDUTEC Ò Process, a pyrotechnology competitive to the Waelz Kiln. The INDUTEC Ò /EZINEX Ò Integrate Process will be described.