Minimisation of the Production of Baghouse Dust in Electric Arc Furnaces by Introducing Self-Reducing Briquettes together with the Scrap

摘要

The electric arc furnace dust is a residue produced during the melting of scraps in electric arc furnaces. It consists mainly of metallic oxides (Fe, Zn, Pb) and volatile salts. It is catalogued as a hazardous waste and has to be treated. The amount of electric arc furnace dust produced depends on the oxidation state of the scrap, its surface treatments and other residues that can come with it (plastics, woods, soil, etc). The process described in this document consists of the reintroduction of this dust, produced in the melting of scraps, as self-reducing briquettes. The composition of the briquettes and the working procedures establish the suitable conditions to have all the oxides inside the briquettes reduced. The iron goes to the molten metal, the non-metallic oxides to the slag and the volatile oxides and chlorides to the dust collected in the baghouse. The materials with a high enough content in zinc and lead oxides can be catalogued as secondary raw materials and be recovered in the non-ferrous metallurgical industry. So, a hazardous waste has been separated into three valuable fractions using a simple technique. This process was tested at lab scale level, pilot plant level and semi industrial plant level. Currently an industrial unit is working inside a steel mill in the north of Spain with good results. Since the economic feasibility of this process is based mainly on the value of the non-ferrous metallic oxides concentrate (zinc content), a specific furnace that would work only with briquettes is being designed to apply this technology with the dust coming from steel mills that do not fulfill the previous requirements (initial zinc oxides content in the dust, baghouse capacity, etc). This option does not look for the minimization of the dust production but reach high enough zinc concentration levels in the collected dust that let the material enter the zinc raw materials market, to produce pig iron ingot and slag useful in civil works. This process would produce no residue.