Characterization and technology of fast reducing roasting for fine iron materials

Abstract

The features of the techniques of fast reducing roasting (FRR) and conventional magnetic roasting, as well as tremendous demands of iron ores in iron and steel industry of China, were briefly described. The test equipment suitable for FRR of fine-grained materials was introduced. Weakly magnetic materials with grain size of <0.30 mm were converted into strongly magnetic materials by FRR for several to dozens of seconds. In a weakly reducing atmosphere and at 740–800 °C, refractory powder iron material (<0.30 mm) which is rich in specularite, limonite and Mg-Mn siderite was subjected to FRR for a few seconds to 60 s. Concentrate with iron grade of 55.67%–55.21%, high contents of Mg and Mn in the ore is obtained and the yield of magnetic separation reaches 81.66%–86.57%. The results of X-ray diffraction (XRD) analysis and magnetism detection of the material before and after FRR indicate that weakly magnetic material is mainly converted into strongly magnetic material Fe3O4 with specific saturation magnetic moment. The efficiency of FRR is consistent with TFe recovery of magnetic separation; meantime, the specific saturation magnetic moment increases from 33 to 42 times after FRR. Calculations show that speeds of flash magnetic roasting are obtained from several dozen to two or three hundred times, compared with rotary kiln or shaft furnace. This indicates that it is practicable to use the fast reducing roasting technique to improve the comprehensive utilization of iron ore resources.