MID-SIZED SILICA PARTICLES: THE MAJOR CONTAMINANTS OF IRON CONCENTRATE IN SPIRAL SEPARATORS
*M. Sadeghi¹, C. Bazin¹, and M. Renaud²
¹Department of mining, metallurgy and materials engineering, Université Laval
1065, avenue de la Médecine,
Québec, QC, Canada G1V 0A6
(*Corresponding author: )
²COREM
1180, rue de la Minéralogie
Québec, QC, Canada G1N 1X7
ABSTRACT
Spiral concentrators are used in the iron ore industry to separate heavy iron oxide carrier particles from light silica carrier particles. Losses of iron occur mainly in the fine (–75µm) and coarse (+600 µm) size fractions. The radial distribution of iron oxide and silica particles in the reject flow of a spiral is analyzed in this presentation. Thesplitter shown in Figure 1 divides the reject flow into six streams that can be sampled individually. Four replicate tests were conducted at the COREM research center in Québec, Canada, on a 7 turn WW6E spiral (Mineral Technologies).Tests were conducted at the recommended operating conditions of the spiral (i.e., solids flow rate: 1.7t/h, slurry solids concentration33%w/w,a slurry volumetric flow rate of 67 L/min, and a total wash water additionrate of 29 L/min. The iron ore used for the tests was provided by theMount Wright concentrator of ArcelorMittal Exploitation Minière Canada. The ore consists mainly of hematite (47% Fe2O3, SG=5.0) and quartz (49% SiO2, SG=2.7).Results show that coarse iron carrier particles settle mainly in the inner part of the spiral trough. Although fine iron carriers particles are mostly concentrated in the outer part of the spiral trough, a significant proportion of these particles remain captive close to the concentrate ports. Counterintuitively, coarse silica particles (+600 µm) are not concentrated in the innermost part of the spiral trough, while a significant concentration of silica particles in the size range of 75–212 µm is found in the vicinity of the concentrate ports.This observation is coherent with the size of the silica particles that contaminate the spiral concentrate. These results are summarized in Figure 2.
Figure 1 – Spiral discharge division and streams numbering
Figure 2 – Silica split from the spiral feed to the reject stream bands as a function of particle size
KEYWORDS
Iron ore processing, spiral concentrators, particles size recovery curves, gravity concentration
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