Studies on the regularities of the steelmaking zinc-bearing dusts leaching in ammonium chloride solutions

摘要

Dust from steelmaking production, in particular electric arc furnace dust (EAFD), is a rich secondary source of zinc. Different approaches to the EAFDs processing with the production of zinc oxide and metal phases as a final product have been studied. Ammonium chloride leaching is selective for zinc, does not require special acid-resistant equipment, and is relatively cheap. The advantages of this method are the possibility of obtaining metallic zinc as a commercial product and the absence of the need for additional solution purification from iron and chlorine ions. Chemical and mineral characterization of Waelz-oxide after the first stage of calcination are presented, the main identified phase is zinc oxide (ZnO), a small amount of Zn associated with iron (Zn_2Fe_2O_4) in the ferrites form and lead in the oxide phase (PbO) are also determined. The thermodynamic analysis of the Zn(II) - NH_4CI - NH_3 - H_2O system in the HYDRA software medium was carried out, the main zinc compounds were determined under leaching conditions. A matrix of changing conditions is compiled with using the full three-factor experiment method. Based on the obtained results, in the Statistica-10 program, three-dimensional dependences of zinc extraction on varied parameters were constructed and equations describing these dependencies were obtained. The optimal leaching parameters were determined: the concentration of ammonium chloride 4 mol/dm~3, the concentration of ammonia 4 mol/dm~3, the ratio L:S = 15.