Use of Virtual Fractions for MLA of Y- Bearing REE Ores
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R. Gerhard Merker - mineral processing engineer (MMP) Use of virtual fractions for MLA of Y- bearing REE ores
Authors:
R. Gerhard Merker (MMP Elpenrod), Prof. Dr. Bernhard Schulz (TU-BAF Freiberg), Thomas Leißner (TU-BAF Freiberg),
Abstract:
Rare earth ores enriched in critical rare earth elements (CREE) are currently of particular interest. The CREE are Nd, Eu, Tb, Dy, including Y.
In conjunction with beneficiation tests on Y-mineral bearing flotation tailings with complicated mineralogy, the authors applied the Mineral Liberation Analyses (MLA) to processing characteristics in terms of modal mineralogy, mineral recovery, locking/liberation and particle size.
“Actual” as well as “virtual” fractions of milling products were investigated comparatively.
Actual fractions were produced by mechanical screening whereas the virtual sizing was done by the MLA software.
The "virtual-sizing-approach" features a much simpler sample preparation procedure and considerably lower cost. It can be conveniently applied to intimately locked ores needing a fine grinding to a particle size distribution (PSD) below a "99%-passing-value" (P99) of 25 microns. However, its practical use is in dispute in terms of the reliability of the results.
Selected results are shown for a main gangue mineral (zircon) and the minor Y-mineral xenotime.
The influence of sample representativeness and particle counting statistics turned out to be of crucial importance.
From the results, it can be concluded that the virtual-sizing-approach can be used if grain counting numbers are high enough to ensure a variation coefficient below 20 %. This precondition is of particular importance in case of low-grade ores.
Given that all preconditions are met, grade-recovery curves, modal mineralogy, locking figures and even PSD trends can be read from virtual fractions. Prudence is recommended if the mineral recovery needs to be calculated for fractions.
The authors encourage processing engineers to use the virtual approach and offer further practical recommendations to verify and improve the reliability of the MLA results.
R. Gerhard Merker, Elpenrod, Sept 28th, 2015 R. Gerhard Merker - mineral processing engineer (MMP)
Fractions and head sample I minus 500, Cumulative mineral recovery of xenotime (with 95% mineral grade)
100
90
) Minus % (
500, real
.
c screen e
R 80
e m i t o n
e 70 X
e
v Minus i t
a 500, l
u virtual
m 60
u screen c
50
40
Fractions of head samples minus 500 microns,
Figure 1: Cumulative mineral recovery of Xenotime at a 95 % mineral grade after real and virtual screening