Optimization and Microstructure Study of the Reduction of Nickel Smelting Slag Mixed with Calcium Carbide Slag and Coke Dust for Recovering Iron

Abstract

How to treat more industrial solid waste friendly and environmental have become the global issues. In this study, direct reduction-magnetic separation (DRMS) process was employed to recovery iron from the nickel smelting slag (NSS) with calcium carbide slag (CCS) as the additive and coke dust (CD) as the reductant. Response surface methodology (RSM) approach using central composite design (CCD) was adopted for optimizing the effects of reduction temperature, reduction time and CCS dosage on the iron content of iron concentrate powder (ICP) and iron recovery. The results were modeled and the impact factors were evaluated. All the plots show that there were positive correlations between investigated impact factors and responses in a certain range but if exceeded, the positive correlations would be broken down. The overall optimization reaction conditions were converged as around 1287 ºC, 2.8 h and CCS dosage of 57.19 %. Under these proven optimization reaction conditions, the iron content of ICP and iron recovery were reached up to 91.30 % and 95.44 % respectively. The micro phase of reduced samples were investigated by X-ray diffraction analysis (XRD), in reduction process, and the microstructure of reduced samples under the optimal condition were investigated by SEM for further discussion and analyzation. The experimental results and microstructure analysis suggests that utilizing CCS and CD in DRMS process were viable.