Heating and melting mechanism of stainless steelmaking dust pellet in liquid slag

Abstract

The heating and melting mechanisms of the pellets immersed in liquid slag were investigated, and the effect of the pellet heating and the melting conditions were studied. The results show that the dust component in the pellet is melted from the surface and no metallic elements are melted before the dust component, the time for the pellet completely melted is reduced as the iron powder content increases since the metallic iron has high thermal conductivity. These are four stages of heating and melting of pellet in liquid slag, they are the growth and melt of solid slag shell, penetration of liquid slag, dissolving of dust component and melting of reduced metals. The lifetime of the solid slag shell is in the range of 7–16 s and increasing the pre-heating temperature of the pellet and the slag temperature can shorten the slag shell lifetime. The time for the dust component in the pellet to be melted completely is in the range of 20–45 s and increasing the pre-heating temperature, especially in the range of 600–800 °C, can obviously reduce the melting time. A higher slag temperature can also improve the pellet melting and the melting time is reduced by 10–15 s when the slag temperature is increased from 1 450 to 1 550 °C. The pellet with higher content of iron powder is beneficial to the melting by improving the heat conductivity.