Development of impurities removal process for low-grade Sanje iron ore using mineral processing technologies

Abstract

In this study, the impurities removal process for low-grade Sanje iron ore was developed using Wet High-intensity magnetic separation (WHIMS) and Reverse flotation (RF). Sanje Iron Ore is the low-grade hematite ores found in Nampundwe area of Zambia from which Iron is to be extracted and used as the feed in the steelmaking process. The ore contains 34.18 mass per cent Iron grade, 31.10 mass% of Silica (SiO2) and 7.65 mass per cent Alumina (Al2O3). Magnetic Separation experiments were done using Series L Model 4 laboratory magnetic Separator (L-4 Machine) as the first stage impurity removal process and the effect of various magnetic separation parameters such as magnetic flux density, particle size density and pulp density of the feed were studied. The results showed that 10 T was optimal magnetic flux density which enhanced the recovery of 93 per cent of iron with 53.22 mass per cent grade. The iron concentrate produced from magnetic separation contained 12.04 massper cent Silica and 3.94 massper cent Alumna and therefore, it was further treated using Reverse flotation. In reverse flotation, various parameters such as pH, collector dosage, Iron depressant dosage and quartz activator dosage were investigated. The results showed that 81.94 per cent was recovered at the concentrate’s pH of 6.8 using 200 g/T of 0.1 per cent calcium oxide (CaO) as silica activator and one kg/T of 0.1 per cent causticised starch as Iron depressant. Sodium Oleate (NaOL) and Dodceylamine Acetate (DAA) each with discrete dosage, were used as Anionic and Cationic collectors respectively. Alumina was consequently reduced to 1.04 mass per cent and Silica to 2.04 mass per cent at optimum respective collector’s dosage of 0.250 kg/T using 0.02 kg/T of Methyl Isobutyl Carbinol (MIBC) frother. Additionally, phosphorous was also observed to be reduced from 0.05 mass per cent to 0.01 mass per cent. The designed multi-stage process involving feeding the concentrate from WHIMS into RF process therefore produced a high-grade iron concentrate iron with 67.27 mass per cent grade, 2.04 mass per cent silica, 1.04 mass per cent alumina.