Magnetic Roasting of Hematite-Limonite by Microwave Heating

Hematite-limonite (HL) is one of typical low-grade iron ores, which has characteristics of low-grade, complex components and difficult for beneficiation. Traditional magnetic roasting (MR) for HL pellets can easily lead to cold center and over reduction of the surface, even fayalite or other compounds will appear in the process of MR, which adds great difficult for the separation of iron minerals and gangues. A novel method of MR by microwave radiation can heat the center and surface of pellets simultaneously and give priority to heat coal particles and iron minerals which will accelerate the transformation of HL to magnetite while gangues remain lower temperature due to their weak absorbing microwave capacity, thus the formation of fayalite or other compounds is greatly restrained. The result indicated that, under the conditions of coal-containing HL pellets of 350g, microwave energy-of 1.5KW, the temperature of the sample could reach to800 degrees C at 35min, followed the size of grinding <0.074mm 81.68%, and magnetic field intensity of 1.52x10(5)A/m, the iron grade and recovery up to 61.15% and 88.35% respectively.