XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 1217
circuit development. In addition, barren oversize with size
2 mm was removed.
Due to the very fine sizing of the valuable minerals,
processing was completed using a 2-stage de-sliming circuit
to maximize the recovery of ultra fine valuable minerals,
notably those in the range –45+20 µm. FPP recovery of in-
size rare earth mineral to the PCP feed was 97% relative
to the run-of-mine ore and consistent with performance
achieved by ore-1.
Initial PCP Results
Initial spiral concentration showed relatively poor separa-
tion efficiency while utilizing conventional gravity spiral
models operating at typical loadings. The separation per-
formance was consistent with the fineness of the minerals as
well as the elevated proportion of near-SG minerals.
Discussion
While the use alternative beneficiation techniques are avail-
able and were considered (flotation, enhanced gravity sepa-
ration), the use of gravity spirals was pursued because they
are recognized as a low-cost and environmentally friendly
process (Burt 1999). In recent years several new process
technologies have emerged, allowing ever-finer materials to
be successfully beneficiated. Fine mineral spiral separators
are just one of these technologies that have the potential to
efficiently separate mineral species down to 30 μm. Spirals
are simple, low energy beneficiation equipment that have
proven to be metallurgically efficient and cost-effective
since their widespread commercial introduction.
Conventional Spiral Separator
A broad range of spiral separator designs is available for
various applications including different density minerals,
varying particle sizes and range of feed grades. Depending
on the application, each spiral separator model has a unique
profile and features to ensure it performs efficiently.
Very fine heavy particles below approximately 53 μm
are typically carried in the highly turbulent outer regions
of the trough and are lost to tailings due to their failure to
migrate inwards to the concentrate collection area. In addi-
tion, coarse particles are also swept along in the middle and
outer region of the spiral due to rolling outwards owing to
low friction (Holland-Batt 1995).
For spirals to perform efficient separations outside the
traditional operating window, unique conditions need to
prevail in the flowing medium. Such conditions can only
be provided by the trough geometry, trough features and/or
feed characteristics e.g., flow rate or slurry density.
Fine Mineral Spiral Separator
Considerable effort has been expended on the development
of new gravity separators to achieve separation at finer sizes
and more discrete processing capabilities to accommodate
difficulties such as smaller particle density differences. The
FM1 spiral was specifically developed to operate down
to 30 μm whilst achieving acceptable recoveries. More
recently, the MG12 model was demonstrated to achieve
better selectivity than the FM1, when operating under par-
ticular conditions.
The key factor in the design of a fine mineral spiral
separator is the overall control of turbulence (Reynolds
numbers) across the entire trough to ensure conditions
throughout the flowing medium are conducive to con-
trolled settling (Holland-Batt 1991). Also, due to the low
settling velocities encountered by very fine mineral parti-
cles, the separation processes take longer to fully develop.
Accordingly, a fine mineral spiral separator is typically lon-
ger than traditional units to allow these very delicate pro-
cesses to produce an adequate separation. In addition, due
to the laminar flows and the relatively small bed depths
on a spiral trough of such design, longer residence time is
required for useful separation to occur.
Holland-Batt (1995) indicated that on conventional
spiral separators, the greatest recovery and grade are
obtained from the first two to four turns of the spiral sepa-
rator, with further, but reduced performance gained from
additional turns. For the FM1 and MG12 spiral separators
a contrary effect has been observed, with improved selectiv-
ity being obtained progressively down the spiral separator.
It is for this reason that the FM1 and MG12 spiral separa-
tors have multiple off-takes that need to be operated such
that small increments of high-grade high density mineral
concentrate cuts are taken progressively down the spiral
trough.
Table 4. Ore-1 REE-concentrate chemical composition
Description TiO
2 Fe
2 O
3 SiO
2 Al
2 O
3 ZrO
2 P
2 O
5 U Th CeO
2 Y
2 O
3
Unit %%%%%%%%,%%
Detection Limit 0.01 0.01 0.01 0.01 0.01 0.01 0.001 0.001 0.01 0.01
Conventional MSP 3.31 2.77 1.45 0.34 1.72 26.9 0.36 4.24 23.0 2.50
Hybrid MSP 0.96 0.57 1.88 0.72 0.92 28.5 0.30 3.54 21.3 3.50
circuit development. In addition, barren oversize with size
2 mm was removed.
Due to the very fine sizing of the valuable minerals,
processing was completed using a 2-stage de-sliming circuit
to maximize the recovery of ultra fine valuable minerals,
notably those in the range –45+20 µm. FPP recovery of in-
size rare earth mineral to the PCP feed was 97% relative
to the run-of-mine ore and consistent with performance
achieved by ore-1.
Initial PCP Results
Initial spiral concentration showed relatively poor separa-
tion efficiency while utilizing conventional gravity spiral
models operating at typical loadings. The separation per-
formance was consistent with the fineness of the minerals as
well as the elevated proportion of near-SG minerals.
Discussion
While the use alternative beneficiation techniques are avail-
able and were considered (flotation, enhanced gravity sepa-
ration), the use of gravity spirals was pursued because they
are recognized as a low-cost and environmentally friendly
process (Burt 1999). In recent years several new process
technologies have emerged, allowing ever-finer materials to
be successfully beneficiated. Fine mineral spiral separators
are just one of these technologies that have the potential to
efficiently separate mineral species down to 30 μm. Spirals
are simple, low energy beneficiation equipment that have
proven to be metallurgically efficient and cost-effective
since their widespread commercial introduction.
Conventional Spiral Separator
A broad range of spiral separator designs is available for
various applications including different density minerals,
varying particle sizes and range of feed grades. Depending
on the application, each spiral separator model has a unique
profile and features to ensure it performs efficiently.
Very fine heavy particles below approximately 53 μm
are typically carried in the highly turbulent outer regions
of the trough and are lost to tailings due to their failure to
migrate inwards to the concentrate collection area. In addi-
tion, coarse particles are also swept along in the middle and
outer region of the spiral due to rolling outwards owing to
low friction (Holland-Batt 1995).
For spirals to perform efficient separations outside the
traditional operating window, unique conditions need to
prevail in the flowing medium. Such conditions can only
be provided by the trough geometry, trough features and/or
feed characteristics e.g., flow rate or slurry density.
Fine Mineral Spiral Separator
Considerable effort has been expended on the development
of new gravity separators to achieve separation at finer sizes
and more discrete processing capabilities to accommodate
difficulties such as smaller particle density differences. The
FM1 spiral was specifically developed to operate down
to 30 μm whilst achieving acceptable recoveries. More
recently, the MG12 model was demonstrated to achieve
better selectivity than the FM1, when operating under par-
ticular conditions.
The key factor in the design of a fine mineral spiral
separator is the overall control of turbulence (Reynolds
numbers) across the entire trough to ensure conditions
throughout the flowing medium are conducive to con-
trolled settling (Holland-Batt 1991). Also, due to the low
settling velocities encountered by very fine mineral parti-
cles, the separation processes take longer to fully develop.
Accordingly, a fine mineral spiral separator is typically lon-
ger than traditional units to allow these very delicate pro-
cesses to produce an adequate separation. In addition, due
to the laminar flows and the relatively small bed depths
on a spiral trough of such design, longer residence time is
required for useful separation to occur.
Holland-Batt (1995) indicated that on conventional
spiral separators, the greatest recovery and grade are
obtained from the first two to four turns of the spiral sepa-
rator, with further, but reduced performance gained from
additional turns. For the FM1 and MG12 spiral separators
a contrary effect has been observed, with improved selectiv-
ity being obtained progressively down the spiral separator.
It is for this reason that the FM1 and MG12 spiral separa-
tors have multiple off-takes that need to be operated such
that small increments of high-grade high density mineral
concentrate cuts are taken progressively down the spiral
trough.
Table 4. Ore-1 REE-concentrate chemical composition
Description TiO
2 Fe
2 O
3 SiO
2 Al
2 O
3 ZrO
2 P
2 O
5 U Th CeO
2 Y
2 O
3
Unit %%%%%%%%,%%
Detection Limit 0.01 0.01 0.01 0.01 0.01 0.01 0.001 0.001 0.01 0.01
Conventional MSP 3.31 2.77 1.45 0.34 1.72 26.9 0.36 4.24 23.0 2.50
Hybrid MSP 0.96 0.57 1.88 0.72 0.92 28.5 0.30 3.54 21.3 3.50