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Building and setup of prototype for "Dusts of E A F" treatment and metal recovery (Dusts of E A F)
Date du début: 1 janv. 2001, Date de fin: 31 déc. 2002 PROJET  TERMINÉ 

Background Companies in the iron and steel industry who focus their activities on obtaining steel from the electric furnace smelting of scrap metal have a significant environmental problem associated with steelwork smoke dust. The process of electric furnace smelting generates smoke or gases which, once collected and treated in a sleeve filter, produce a filtrate powder with a high content of oxidised materials such as zinc oxide and lead oxide. This filtrate powder is made up of a residue classified as toxic and hazardous, therefore, once split up it needs to be sent to an outside treatment plant. In Spain, there is only one plant for the treatment of electric arc furnace dust (E.A.F. dust) located in Bilbao. The technology currently being used (Waelz process) allows the recovery of the zinc in form of a Waelz oxide which can be subsequently re-used in the galvanising sector among others, while the remaining fraction is made inert. The cost of these systems entails approximately 60 euros/metric tonne. Given that the volume of waste generated in an electric furnace is significant (15kg of dust per metric tonne of liquid steel), the iron and steel industries are obliged to study other alternatives to the Waelz process which generate fewer environmental and economic repercussions. Objectives The aim of this demonstration project was to design, construct and optimise a prototype for the treatment of the dust and the recovery of zinc and lead. The objective of this project is to prove the feasibility of an innovative process for treating the Electric Arc Furnace (EAF) dust of steelworks and to optimise it. The project intended to recover zinc and lead in their metal forms and, at the same time, produce a small amount of energy from the reacted gases produced after exposing the waste to the primary gas mixture. The objectives were the following:  To prove that there is a viable alternative process for the treatment of the dangerous polluting dust from Electric Arc Furnace fumes,  To recover metals (Zn and Pb) contained in the dust. These could be used as primary materials in other industrial processes  To use the gas obtained in the redox reaction to produce energy. Results The first objective of the project was to prove the viability of the alternative process for the treatment of E.A.F. dusts. Although the beneficiary hoped to reach this alternative, the results of the first prototype were unsuccessful. The reason for this was that it was impossible to obtain the necessary high temperatures to volatilise the metals. The second objective was to recover metals contained in the dust /Zn and Pb). The results have been successful at a laboratory scale, but not in the prototype. However, the beneficiary has obtained a reusable by-product: pre-reduced and ZnO materials. The last objective was to use the gas produced in the redox reaction to produce energy. This energy had to be used in other stages of the process. Again this last objective has been partially successful. The gas produced has proved to be combustible, but the beneficiary was not able to use it in the prototype.


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