An Investigation into the Alkali Metals Removal from Zn-Bearing Dust Pellets in Direct Reduction

Zinc-bearing dusts are typical hazardous solid wastes generated in iron and steel production. In general, the iron-rich dusts can be recycled as burden for blast furnace after harmful elements removal and agglomeration. In this article, direct reduction of carbon-containing Zn-bearing dust pellets was conducted, and the removal behavior of alkali metals was revealed. The reduced pellets with compressive strength of 1171 Newton center dot pellet(-1) and low contents of harmful metals (0.05% K, 0.08% Na and 0.03% Zn) could be directly used as burden for blast furnaces. The harmful metals removal and the agglomeration of reduced dusts were achieved in one step. The removal kinetics and mechanism of potassium and sodium in direct reduction were investigated, and the results showed that the removal rates of potassium and sodium were controlled by reduction reactions of potassium and sodium-bearing phases. The metallic iron bridge generated in high temperature dominated the consolidation of reduced pellets.

Automated summary

This study investigated the direct reduction of carbon-containing Zn-bearing dust pellets and revealed that the reduced pellets can be used as burden for blast furnaces with high compressive strength and low contents of harmful metals. The removal mechanism of potassium and sodium as well as the role of metallic iron bridge in pellet consolidation were also elucidated.