Influence of Particle Size on Magnetizing Roasting of the Hematite Quartzite in an Atmosphere of Carbon Monoxide

UDC 549.5 + 549.731.13 + 549.057 + 549.08
https://doi.org/10.15407/mineraljournal.39.02.019

V.P. Ponomar, A.B. Brik, Yu.I. Cherevko, V.V. Ovsienko
M.P. Semenenko Institute of Geochemistry, Mineralogy and Ore Formation of the NAS of Ukraine
34, Acad. Palladin Av., Kyiv-142, Ukraine, 03680
E-mail: vitaliyponomar.vp@gmail.com
Language: Ukrainian
Mineralogical journal 2017, 39 (2): 19-28
Abstract: Influence of particle size on hematite transformation to magnetite was determined in this work in order to optimize the production of iron ore concentrates from oxidized iron ores by magnetic separation. The initial sample of hematite quartzite consists of quartz and hematite, in approximately equal proportions, by mass. It was divided into fractions of <0.05; 0.05—0.1; 0.1—0.16; 0.16—0.25; 0.25—0.4; 0.4—0.63; 0.63—1.0; 1.0—1.6; 1.6—2.5, and >2.5 mm. After heat treatment at 500 °c in the atmosphere of carbon monoxide during 40 min, the magnetization of the samples increases significantly up to 35—60 a · m2/kg due to the formation of magnetite with a bulk saturation magnetization of 92 a · m2/kg. The variability of obtained magnetic characteristic depends mainly on the concentration of iron in the initial fractions. Moreover, the conversion of hematite to magnetite is not complete for the samples that have a grain size from 0.4 to 2.5 mm due to the incomplete disclosure of minerals and formation of the magnetite layer on the surface of the hematite, which further decelerates the reaction. For these coarse fractions, the amount of newly formed magnetite decreases from 80 to 60 % by increasing the size of the initial ores. When heated in a time interval of 10—60 minutes, the magnetization of the samples with the different grain size increases significantly in 30 minutes for the fine particles and 40 minutes for the coarse ones. The increasing time of thermal treatment does not change the magnetization of the transformed samples. The rate constant for conversion of fine particles depends more on specific surface area of the reagent and for the coarse samples depends on disclosure of minerals and the possible inhibitory effect of the reaction product formed at the surface of hematite grains. The results of this work are important for determining the optimal conditions of magnetizing roasting of oxidized iron ores.
Keywords: ontogenesis, latticelike aggregate, goethite, Kryvyi Rih basin.
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