Mr. Thomas Wolfgang Howard, Dipl.-Ing.

Abstract:

In the aspect of growing production rates in most metallurgical industries in the recent past, the accumulation of the associated by-products like sludges, slags and dust also followed this trend  [1]. One such residue is the dust generated by stainless steel production, which contains both Cr and Ni in significant amounts [2]. If not recovered, this would conclude with a double loss for producers, as they lose these metals in residues, for which in most western countries landfilling costs arise. Furthermore, this also constitutes an enormous burden for the environment and eventually humanity itself, which suffer under the consequences of potentially hazardous compounds, like hexavalent Cr, accompanied in the respective residues [3]. Most of the today's applied processes to recover these metals are of pyrometallurgical nature, which aside from being energy intensive and carbon based, are only capable of producing a mixed Fe-Ni-Cr alloy and are few and far between [4]. For those reasons, the authors have studied potential hydrometallurgical treatment for such Cr-Ni-rich dusts as for their recovery. In the first steps, the dust was characterized thoroughly, leached with hydrochloric acid, and investigated for the optimal leaching parameters. The aim of the follow-up recovery was the separation into a Cr-rich and Ni-rich fraction, by the means of neutralization precipitation with NaOH. These experiments were both conducted with synthetic solutions. The experiments conducted have shown that a selective recovery of Cr and Ni is plausible under specific conditions to gain these metal specific rich fractions. These products were characterized by SEM-EDX among others to determine the potential usage for ferro-alloys or other industries.