Lead extraction in low-temperature dust roasting during metal scrap melting in electric arc furnace together with ammonium chloride

Processing of zinc-containing dust from conventional steel making processes is rather actual problem and causesnecessity to research and develop the new technologies. Possibility of selective lead extraction via low-temperature roasting of preliminary separated non-magnetic fraction of zinc-containing dust together with ammonium chloride is shown in this work. Based on the results of thermodynamic calculations of Gibbs free energy for interaction reactions between oxides of lead, zinc and iron with NH4Cl, possibility of selective lead extraction from dust in the form of its chloride is displayed. The results of thermodynamic analysis are confirmed by the data of laboratorial experiments, when influence of temperature and chloride ammonium consumption on degree of lead sublimation was examined. Dramatic lowering of lead content in a cinder was revealed within the temperature range from 300 °С to 500 °С. The minimal lead content in a cinder was 0.18 %, it was reached at 600 °С. Further temperature rise has slight effect on decrease of lead content in a cinder. Optimal technological parameters were established: temperature – 500 °С, NH4Cl consumption – the value exceeding its stoichiometric required amount (SRA) for lead chlorination by 1.5 times, roasting duration – 60 min. A cinder with minimal lead content with the following composition, % (mass.): ~49 Zn; 0.2 Pb; 19 Fe; 8 SiO2 and other, was obtained for the optimal technological parameters. Lead extraction in fumes was high, more than ~97 %. The obtained results will be used in building of the complex technology for processing of zinc-containing dust and other products with similar composition from iron and steel enterprises. The research was carried out within the range of grant financing by the Science committee of the Ministry of science and higher education of Kazakhstan Republic for 2023–2025, according to the priority direction “Rational use of water resources, fauna and flora, ecology”, the project АР19679572 “Development of the new technology for zinc dust utilization after steelmaking production with obtain of commercial products”.