Upgrading the iron from low-grade and high-silicate iron ores by magnetic separation

摘要

The degradation of iron grade and an increase of impurities such as quartz, aluminium oxide, and phosphorus in iron ores, cause problems in various processes on the iron making process through blast furnaces. The main aim of this study was to produce a better grade of iron concentrates (greater than 60 mass-% of iron) containing lower content of impurities, especially SiO2, Al2O3 (totally <5 mass-%) and P (<0.1 mass-%) from low grade iron ores, which mainly compose of magnetite (iron ore A - 32.1 mass-% Fe) and hematite (iron ore B - 34.1 mass-% Fe) respectively. Low-grade magnetite-based iron ore (iron ore A) was conducted to wet alternating magnetic separation (WAN/IS) with rinsing and re-grinding to upgrade iron grade and recovery. In contrast, low-grade hematite-based iron ore (iron ore B) was processed via wet high-intensity magnetic separation (WHIMS). Experimental results showed higher than 75 % of iron recovery by WAMS with rinsing and re-grinding processing. Iron and SiO2+Al2O3 grades in a concentrate obtained from the low-grade magnetite-based iron ore (iron ore A) were 67.8 mass-% and 5.5 mass-%, respectively. On the other hand, about 41.3 % of iron recovery by WHIMS from hematite-based ore (iron ore B) under the conditions, which were particle size of <45 urn, magnetic density of 1000 mT (without matrix), pulp density of 2.5 % and flow rate of 7 L/min using compacted iron matrix in recovery box. Fe and total SiO2+Al2O3 grades in a concentrate resulted from the low-grade hematite-based ore (B) were modified to 63.5 mass-% and 7.1 mass-%, respectively.