Selective extraction of heavy metals Cr,Ni and Zn from stainless steel-making dust

Heavy metal elements such as Cr, Ni and Zn were extracted from stainless steel-making dust through the direct reduction and melting process on the basis of thermodynamic analysis. Carbon deoxidization experiment results show that the optimal carbon addition percentage in the dust is 20%, and the lowest reduction temperature is 1 050℃ for Fe, Ni and Zn and 1 400℃ for Cr, which are in agreement with the thermodynamic calculation results. These metals can be selectively reduced through controlling the temperature. According to direct reduction and melting experiment results, the optimal melting temperature of the Fe-Cr alloy is 1 550℃, metals in the dust are extracted as the Fe-Ni-Cr alloy, and the slag is separated from the metals quite well. The metal extraction rate is about 75% after 5 min reaction; but after 15 min reaction the Fe and Cr extraction rates surpass 85%, while the Ni extraction rate is over 90%. These experimental results indicate that it is completely feasible to return the stainless steel-making dust to the steel-making main flow and recycle its heavy metals by controlling the carbon content, reduction time and temperature without modifying the present process.