A detoxification and value-added process for chromium ore processing residue (COPR) and Fe-C-bearing dust: Direct reduction-magnetic separation

Abstract

Chromium ore processing residue (COPR), containing much virulent hexavalent chromium [Cr(VI)], is a by-product derived from chromate production. Fe-C-bearing dust from steel industry is very difficult to be utilized effectively because of its complex composition and unstable properties. The dust was co-processed with COPR by a direct reduction-magnetic separation process in this study. Through the strong reducing ability of solid carbon in Fe-C-bearing dust, the compounds of Cr and Fe were reduced to (Cr, Fe)7C3 alloy during the reduction roasting process and then selectively recovered by magnetic separation. In addition, the Pb and Zn compounds were reduced and volatilized into flue gas at high temperature. Under the optimal conditions, the results indicated that Cr-containing iron powder with 72.59 % Fe and 6.34 % Cr was obtained, and the recoveries of Fe and Cr were respectively 79.1 % and 76.9 %. The volatilization rates of Pb and Zn met 97.47 % and 99.95 %, respectively. The non-magnetic tailings were determined to be nontoxic and could be used as high-quality raw materials for building.