Dressing Weakly Magnetic Iron Ores by Dry Magnetic Separation Process

Abstract

Iron ore samples were obtained from El Bajrawiya iron ore deposits in order to beneficiate these ores. Chemical analyses and microscopic examination have shown that these ores mainly contain valuable mixtures of weakly magnetic iron oxides; (goethite, limonite and hematite), and non magnetic gangue materials; (silica), and clay minerals as major impurities. These materials were prepared to be beneficiated by dry high intensity magnetic separation process, by crushing and grinding to liberate the iron oxide grains from the cement of the ore matrix. Crushing and grinding processes produced significant amounts of fine materials (-53μm), which could not be treated by the available machine within the Central Petroleum Laboratories (dry high intensity magnetic separator). Hence, all ground samples materials were washed to remove the fines by wet screening on the 53 micron sieve. The portions of each sample coarser than 53 μm were dried and screened on a nest of sieves to yield four size fractions each having closer ranges for the magnetic separation in order to avoid the gravity effect on the process. The Frantz Magnetic Barrier Laboratory Separator Model (LB-1) was used to conduct the separation tests on each size fractions of the washed various ores. Recovery of iron values and the separation efficiency were assessed by determining the percentages of Fe in the concentrates and tailings by Atomic Absorption Spectrometry (AAS) techniques.. The separation process was applied on four mixtures of iron oxides as feed for the process. They were having average grades 32.94, 41.43, 17.00 and 48.00% Fe. The process of treatment gave concentrates having average grades from the feed 39.79, 49.82, 47.67and 52.76 % Fe and average iron recoveries were 86.83, 87.63, 76.32 and 83.51 %, respectively. The flow rates of the feed into the separator were: 19.63, 20.32, 25.66 and 12.37 g / minute, respectively. These results were achieved when the Frantiz separator was operated at 0.8 ampere. However, when the ampere of the separator was increased to 1.0 ampere, the recoveries were increased on the account of the grades which were decreased remarkably