Analysis of the melting process of carbon-bearing pellets in iron bath, slag bath and graphite crucible

Background With the increase in the amount of scrap steel in society, the proportion of electric furnace steelmaking is increasing year by year, especially in China. Due to the high Zn content, the electric furnace arc dust (EAFD) needs to be recovered by non-blast furnace process. Due to EAFD containing a large amount of zinc ferrite, it needs to be recovered by fire process. It is a promising process to melt the EAFD pellets to get the discount and zinc-rich secondary ash. Methods To clarify the melting behavior of pellets in the metallurgical process, the slag phase diagram and the effect of temperature and FeO on slag viscosity were calculated using FactSage, and the melting process of electric furnace arc dust (EAFD) pellets in a graphite crucible, iron bath, and slag bath were experimentally investigated. Results The experimental results show that the viscosity of the slag system decreases with increasing temperature and FeO content, and the effect of FeO on viscosity is greater. The viscosity decreased from 0.305 to 0.276 Pa·s when the FeO content in the slag was increased from 0 wt. % to 2 wt.% at 1773 K. The melting process of the EAFD pellets in an iron bath and graphite crucible was consistent, and after the formation of liquid-phase slag in the pellets, the liquid-phase slag was diffused to melt the pellets. Conclusions The iron bath improved the heat transfer conditions of the pellets, reducing the smelting time from 600 to 360 s. The slag bath promoted the slagging reaction of the contact part to change the pellet melting process and increase the pellet melting speed, and the EAFD pellets melted within 240 s in a slag bath.