PROJECT DESCRIPTION
BACKGROUND
The research studies carried out by Wheelabrator Allevard in collaboration with the french company Recupyl led to the development of the RECUPAC process whose aim is to valorize both non ferrous metals and iron oxides from EAF steel dust. Existing processes for EAF dust treatment are either direct thermal processes which are energy consuming and transfer pollution to atmosphere through gas exhaust, or partial chemical treatments leading to a valorization rate of less than 30%. Thanks to the combination of physico-chemical, mechanical and thermal technologies well-known in other industries, the RECUPAC process can reach a valorization rate of 95% as follows : - 20% of purified non ferrous metals, - 60% of purified iron oxides, - 15% going back to the furnace. The process, based on the know-how in hydrometallurgical treatment of batteries, goes through several steps among those hydromechanical classification, chemical extraction of salts, selective chemical and electrochemical extraction of non ferrous metals, thermochemical conversion of mineral phases at less than 800°C. Each step will be optimized at the pilot scale and will lead to established industrial procedures. The final task consists in having all the output materials approved by the already identified industrial channels through the supply of test batches produced from several kinds of EAF steel dust. The project will have reached its objectives by demonstrating at the end of the 30 months action on an industrial scale pilot that the RECUPAC process allows to avoid the waste disposal and to protect natural resources meanwhile avoiding any pollution transfer. EAF steel dust will then not be regarded anymore as a waste but as a secondary raw materials. Steel production by the electric arc furnace (EAF) technology has been facing for 20 years a steady increase compared to the blast furnace technology. The share for EAF technology was of 33% in 1997 for Europe and 41% in 1998 for France. One EAF specificity is to use steel scraps recovered from automotive or metallurgy industries, which have a high heavy metals -like zinc and lead- content. These metals, which are volatil, end up in the EAF dust. In 1993, a 400.000 tons per year dust production was already estimated in Europe from EAF steel mills, among which 80.000 tons for France. Due to heavy metals possible release through leaching, EAF dust have to be stored in type 1 landfills after being inerted. Beside doubling the amount of waste to be disposed, the inerting step does not lead to any valorisation and will face in 2002 the new french regulation which will limit the acceptance in type 1 landfills to the only waste which are definitely recognized to be ultimate, i.e. non valorisable. The project proposed by Wheelabrator Allevard and developped in collaboration with the french company Recupyl SA is aimed at demonstrating that it is possible to valorize more than 95% of the EAF steel dust thanks to a patented process which combines non-polluting techniques like hydrometallurgy, mechanical treatments and thermal treatments at moderate temperatures. The objectives of the project is to qualify the materials derived from the dust in already identified industrial channels, these materials being mostly non ferrous metals and iron oxides. Achieving the objectives by february 2002 will go through the building of a pilot plant and the set up and optimization of the process.