Behavior of residual Zn oxides in metallized pellets applied in the converter steelmaking process

Abstract

Metallized pellets serve as a significant recycling product derived from the iron and steel production, comprising dust and sludge. However, the substantial presence of residual zinc within these pellets poses challenges such as vaporization, condensation, and accumulation, ultimately leading to severe clogging in off-gas pipes and potential erosion of refractory materials. To address this, a novel approach is proposed to efficiently harness the potential of metallized pellets within the converter process, focusing on investigating the behavior and mechanism of zinc oxides. Results reveal that metallized pellets introduce Zn elements with a distribution ratio of approximately 1:1 in the steel-gas phase and only around 3% in the slag. The Zn element can remain stable in the over-oxidized molten steel, and an inverse proportional relationship between [C] and [Zn] contents in the molten steel has been derived from industrial and laboratory experiments as follows.[%C]0.84·[%Zn]=0.0055Furthermore, the end-point Zn content in the molten steel is closely related to the C content in the molten steel before the addition of the metallized pellets. The ZnO contained within the metallized pellets must undergo reduction by the [C] present in the molten steel, as well as by the [C] to facilitate vaporization and escape. Consequently, a critical carbon content (approximately 0.3%) emerges, wherein the addition of metallized pellets enables the maximum and enduring presence of Zn elements within the molten steel while minimizing vaporization and escape of Zn into the off-gas pipeline.