Process for reducing the amounts of zinc (ZN) and lead (PB) in materials containing iron (FE)

Abstract

The present invention relates to a process for reducing the amounts of zinc and lead in starting materials comprising iron which comprises the steps of: —selectively leaching Zn and Pb comprised in the starting materials by mixing the starting materials with hydrochloric acid and an oxidizing agent comprising at least 5 wt-% of manganese dioxide in one or several reactor(s) at a temperature superior or equal to 35° C. and at a p H comprised between 0.5 and 3.5, —filtrating the mixture obtained in order to separate the solid and the filtrate, —washing the solid with water, the resulting solid comprising mainly Fe, a reduced amount of Zn and Pb compared to the original starting materials, —recovering the filtrate of step b) and the washing water of step c) which comprise chloride, solubilized Zn and Pb in one or several reactor(s), —precipitating solubilized Zn, Pb in the recovered filtrate and the washing water by mixing with a neutralizing agent, —filtrating and washing the solid residues obtained in step e) in order to remove the chloride from the solid residues which comprise at least Pb and Zn. The present invention also refers to the use of the materials obtained after treatment in a in a sinter plant and blast furnace or in all pyrometallurgical furnace which value iron such as electrical arc furnace (EAF), cupola furnace, oxycup furnace, submerged arc furnace (SAF), a plasma furnace, rotary hearth furnace.

Description

TECHNICAL FIELD[0001]The present invention generally relates to the treatment of starting materials comprising iron (Fe), zinc (Zn), lead (Pb) and possibly carbon (C) by hydrometallurgy process and in particular to the removal of Zn and Pb from these starting materials.BACKGROUND ART[0002]The chemical and metallurgical industries generate various forms of wastes containing pollutant elements. For example, the steel making industry involves the use of blast furnace for smelting in order to produce industrial metals such as pig iron and the use of basic oxygen furnace (BOF) in order to produce steel from pig iron. Blast furnace and BOF in operation produces a lot of dusts and sludge at the outlet of the gas cleaning plant. These sludge or dusts are composed of different metals. In particular, these sludge or dusts comprise iron, carbon, zinc and lead. In order to reduce the operating cost linked to the operations of such industries, it is desirable to recycle these materials in order ...

AI Technical Summary

Benefits of technology

[0014]An efficient and easy to implement process is provided which allows selectively separating and reducing the z

Problems solved by technology

Although these sludges (or dusts) comprise iron and carbon, which could be recycled to recover contained metals, the presence of zinc and lead prevents the reuse of these sludge or dusts.

It is thus impossible to recycle directly these materials without affecting the blast furnace operation.

Thus, the sludges (or dusts) comprising zinc and lead cannot be recycled to the sinter plant in order to be retreated by the blast furnace.

However, this constitutes a major environmental and economic problem.

Indeed, the storage of this kind of materials can be detrimental for the environment since the contaminants can affect the surrounding soils or ground waters.

This may be a real threat for the health and more specifically for the fauna and flora.

Furthermore, even from an economic point of view, the dumping of these materials cannot be regarded as an advantageous solution.

Indeed, the available place for internal dumping in plant area decreases whereas the costs linked to the external dumping increase.

However, this type of process shows several drawbacks.

One of the main drawb

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