OBJECTIVES
The main objective of this project estabilish an effective self-sustaining network of EAF/CF dust value chain stakeholders interested in processing metallurgical dusts with near-zero waste vision. To reach this overall goal, the main innovation and research objectives are:
Perform sampling and characterisation of different EAF/CF dusts
a) screening of the selected EAF and CF dust sources
The main objective of this task is to collect and evaluate samples from selected producers of EAF and CF dusts in the region to determine the homogeneity and characteristics of these sources. First, a sampling plan will be established, followed by the determination of the most economically interesting Zn content, as well as Si, Al, Mg, Ca, Fe, Mn, Ni, Cr
b) testing the best avaliable technolgy for gravity and magnetic separation of metals in EAF and CF dusts
Larger quantities of selected samples will be collected followed by magnetic separation. Optimal separation conditions will be tuned for the best quality product and magnetic minerals mass pull to be achieved and concentrate for further tests will be prepared. Non-magnetic fraction will be separated by gravity separation prospecting both hydrocyclones and enhanced gravity separators.
Recover valuable metals from EAF and CF dust
a) removal of soluble halides and hydrometallurgical separation of the metals
Removal of halides will be done using facile and inexpensive methods. Washing with hot water will be examined at first as the easiest way for depletion of undesirable ions. Leaching of the zinc-rich fraction will be studied with sulfuric acid to selectively dissolve zinc. Since small amounts of iron affect the further purification step, we want to test different bases to precipitate dissolved iron. EAF dusts may contain up to several percent lead that is present in form of insoluble lead sulphate after the leaching. The selective lixiviant for lead sulphate will be triethylenetetramine solution in water, which is highly selective towards lead sulphate and is capable of extracting entire lead into solution.
b) reduction and utilization of Fe-, Mn-, Ni-, Cr-rich magnetic fraction
Carbon-thermal reduction of the Fe-, Mn-, Ni-, Cr-rich magnetic fraction into an iron-based alloy to recover Fe, Mn, Cr, Ni and separate the resulting slag for civil engineering application purposes. Two different reducing agents will be used: pure graphite (as a control batch) and
biochar.
Evaluate final residues for the construction products
Establishing a near zero-waste approach of the whole process by recycling non-metallic residues
obtained from the magnetic and gravimetric separation is the goal of this task. A detailed
characterization of the residues for the geotechnical works, aggregate and cementitious composites
will be carried out in order to determine its mineralogical, chemical, physical and environmental
parameters. This information is essential for the evaluation of the further use of this material in construction products. A set of composites for geotechnical works and cementitious products will be designed, produced and tested on the laboratory level and in small test-beds.