The Influence of Varying Thermal Treatment Conditions on Reducing Zinc Content from a Steelmaking and Blast Furnace Sludge

Abstract

The prospects of processing blast furnace and steelmaking sludge using Waelz process in a laboratory rotary kiln is shown. The influence of varying thermal treatment modes, furnace atmosphere and type of reducing agents on the level of zinc reduction from sludges was analyzed. In general, the blast furnace sludge contains a high portion of iron (approx.48 wt. %) and can be reused as a charge after satisfactory zinc reduction. It was found that N- atmosphere and high content of the graphite or coke oven reducing agent in combination with high temperature can reduce the content of Zn in the sludge to 0.08 wt. % at 1200 °C for mixture of steelmaking and blast furnace sludge. A significant reduction in the Zn content to 0.66 wt. % occurs at 1100 °C. The content and type of reducing agent play an important role; graphite has shown a better reducing ability compared to coke oven dust. When nitrogen is used, zinc is reduced even without an additional reducing agent, since the carbon contained in the sludge is made use of for the reduction. In an air atmosphere, without the use of a reducing agent, there was no reduction in the Zn content.