Beneficiation of fine ores using the Longi wet high magnetic separator
Date
2014
Authors
Makhula, Mpho Johanna
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Abstract
Magnetic separation has been used since 1955 for processing a variety of minerals from iron
ore in steel production to the desulphurisation of coal. The accumulation of such fines and
slimes during mining operations and the increasing global demand for quality products
motivated the use of the semi-continuous pilot wet high intensity magnetic separator
(WHIMS) introduced in 2008. Its unique features were considered to be favourable for
beneficiating a Sishen low grade hematite-rich ore and an ash-rich Witbank coal.
An automated Mineral Liberation Analyser (MLA) was used to characterise the size
distribution of the hematite-rich material thereby providing an estimated grade at the same
time. This type of analysis characterises mineral types in terms of particle size and elemental
composition, specific density, weight percent, area of particle, particle shape, circularity and
equivalent circle diameter. However, for this research study only size and elemental
composition were considered.
The application of the Longi LGS 500 WHIMS for beneficiating a low grade South African
iron ore material was investigated by determining the effects of changing the operating
parameters of pulp solids, magnetic field intensity and the pulsation frequency. This was
followed by a 33 full factorial design which consisted of twenty seven (27) test matrix, with
mass yield of concentrate and Fe grade selected as the main responses to the changing of the
parameters. The results obtained were validated using the analysis of variance (ANOY A) and
the mathematical model, which showed the variables as being significant to the investigation
process, thus rejecting the null hypothesis. The significance of the variables was in the order
of magnetic field intensity followed by pulsation frequency and lastly the percentage pulp
solids. The model predictions and actual data were in good agreement, reporting regression
coefficients ranging between 0.83 and 0.94. It was shown that a single stage magnetic
separation has the potential to produce a 55% Fe product.
Description
Keywords
Ore-dressing