Final Report Summary - REDILP (Recycling of EAF dust by an integrated leach-grinding process)
Steel producers in Europe maintain their global competitiveness by using small mills supplied with electric arc furnaces (EAFs) and utilising the waste metallic scrap as raw material. During the steel making process, zinc and other ferrous and non-ferrous relatively volatile metals from the metallic scrap melt, evaporate and condensate at a later stage as airborne particles. The existing processes for the recycling of EAFs dust are characterised by high energy consumption, contribute to the greenhouse effect and global warming, and produce residues which have to be landfilled as hazardous waste.
In this context, the aim of the REDILP project was to develop a hydrometallurgical 'cold' process to recycle EAF dust and produce valuable zinc (Zn), iron (Fe) and lead (Pb) products in close circuit, without residues. Secondary project objectives were therefore the reduce in consumption of natural resources and energy, the decrease of the associated environmental burden and the decrease of the EAFs impact on the greenhouse effect and global warming.
The proposal consisted of the combination of mass transfer in an aqueous medium with a mechanical impact to enhance the solubilisation of phases that were either easy or difficult to leach, such as zincite and ferrites respectively. Firstly, samples from numerous steel mills were collected and examined in detail. A series of laboratory experiments was subsequently performed based on the results of this analysis in order to optimise the leaching and precipitation steps. In addition, a prototype plant was constructed and operated, resulting in successful Zn recovery. A time extension of six months was necessary for the completion of the abovementioned tasks.
The novelty of the process relied in the integration of leaching and grinding of EAFs' dust in a single step, which resulted in lower costs than those required for processing and disposal of the conventional steel mills' residues. Furthermore, the recycling process reduced the burden of landfill waste while preserving valuable natural resources. The project represented a considerable progress in comparison to the state of the art, and it was anticipated that the compilation and capabilities of the partner consortium would minimise the technical risk and strongly reduce the time that would normally be required to fully develop the proposed activating leach grinding technology.
In this context, the aim of the REDILP project was to develop a hydrometallurgical 'cold' process to recycle EAF dust and produce valuable zinc (Zn), iron (Fe) and lead (Pb) products in close circuit, without residues. Secondary project objectives were therefore the reduce in consumption of natural resources and energy, the decrease of the associated environmental burden and the decrease of the EAFs impact on the greenhouse effect and global warming.
The proposal consisted of the combination of mass transfer in an aqueous medium with a mechanical impact to enhance the solubilisation of phases that were either easy or difficult to leach, such as zincite and ferrites respectively. Firstly, samples from numerous steel mills were collected and examined in detail. A series of laboratory experiments was subsequently performed based on the results of this analysis in order to optimise the leaching and precipitation steps. In addition, a prototype plant was constructed and operated, resulting in successful Zn recovery. A time extension of six months was necessary for the completion of the abovementioned tasks.
The novelty of the process relied in the integration of leaching and grinding of EAFs' dust in a single step, which resulted in lower costs than those required for processing and disposal of the conventional steel mills' residues. Furthermore, the recycling process reduced the burden of landfill waste while preserving valuable natural resources. The project represented a considerable progress in comparison to the state of the art, and it was anticipated that the compilation and capabilities of the partner consortium would minimise the technical risk and strongly reduce the time that would normally be required to fully develop the proposed activating leach grinding technology.