Pyrometallurgical recovery of iron from iron silicate slags

Abstract

A process for recovering iron from preliminarily decopperized molten copper smelter slags having an initial composition which includes iron oxide, silica, and aluminum oxide as the major constituents. These constituents are initially present in the range of 40-70 percent FeO, 25-40 percent SiO.sub.2 and 5-10 percent Al.sub.2 O.sub.3. The slag is maintained in a molten state and a solid reductant is mixed into the slag using an internally cooled, metal bladed, rotating stirrer, which rotates at a rate sufficient to pump the reductant into the slag to enhance the reduction of the iron oxide. An important aspect of this invention is to reduce slag to recover iron when the slag contains the following constituents, 40-60 percent SiO.sub.2, 15-35 percent CaO, less than 20 percent FeO and 5-10 percent Al.sub.2 O.sub.3. Although the above constituents can vary within the range set forth, it is important to maintain the SiO.sub.2 to CaO ratio in the range of about 2.0 - 3.3. Thus, along with the reducing agent, other constituents are added to the molten slag to maintain the slag with the desired composition set forth above. After reduction of the slag in accordance with the foregoing procedure, the iron bearing phase is separated from the slag in the form of a metal-rich matte containing 85-90 percent iron.