94 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
2003) described the two major impediments, which are “a
poor equal setting ratio and the difficulty and expense of
dust containment.” (Fuerstenau and Han, p. 212)
Electrostatic
Electrostatic separation is applicable when the minerals
being separated have sufficiently different electrical con-
ductivity. Electrostatic separators were described by Taggart
(1945) and the schematic representation of a Sutton separa-
tor, shown in Figure 5 remains valid today.
Screening
Screening is a method to separate particles into different size
fractions by using equipment such as plates, wire mesh, or
polyurethane panels with aperture openings to allow finer
material to pass through. Dry sieving is employed when the
material requires dry grinding and reacts with water either
chemically (e.g., Portland cement) or physically (e.g., ben-
tonite clay). Dry classification can also be conducted pneu-
matically within an air-swept mill or air cyclones.
Sensor-based
Sensors can be used to detect differences in dry mineral
particles exposed to electromagnetic radiation such as
X-ray fluorescence (XRF), X-ray Luminescence (XRL) and
Optical Fluorescence, X-ray Transmission (XRT), Prompt
Gamma Neutron Activation Analysis (PGNAA), or Optical
and Hyperspectral Imaging (Peukert, et al. 2022). An excel-
lent comprehensive chapter on mineral sorting is available
in Klein and Bamber (2019) describing the hurdles to
adoption, sensor types, applications, commercial opera-
tions, and recovery results for various ore types including
lead-zinc, uranium, nickel, nickel-copper and gold at 41
installations.
Drying
Drying is the process of removing water from a material by
evaporation, as opposed to mechanical dewatering. Drying
is employed in mill operations for various reasons includ-
ing to increase efficiency of dry processing such as screen-
ing, air separation, and electrostatic separation (Taggart,
1945). Drying may be required upstream prior to dry
beneficiation.
TWO OPERATIONAL EXAMPLES OF DRY
BENEFICIAITON
Electrostatic Separation—Operational Example No. 1
of 2
Electrostatic separation is used to remove silica gangue and
upgrade the hematite concentrate at an iron ore operation
in Canada. The flowsheet is shown in Figure 3. Until the
upstream wet unit operations were optimized to consider
the impacts on dry processing, the concentrate could actu-
ally downgrade. The key takeaway from this evaluation
was that the standard method of optimizing individual
unit operation in isolation can sometimes reduce overall
plant performance and that each unit operation must be
considered as individual components working together
in a system. It was important optimize the concentrator
as a system and not simply optimize each unit operation.
Optimizing the grade and recovery from the hydrosizer
(Figure 4) negatively impacted the overall recovery after the
hydrosizer’s concentrate fed the dry electrostatic separation.
Understanding and optimization of dry unit processing
techniques was fundamental to this evaluation.
Between 2002 and 2004, the performance of a six mil-
lion ton per year iron ore beneficiation plant dropped sig-
nificantly. The average annual final product grade decreased
8% (indicated by an increase in silicate gangue from 2.8%
to 3.0%) while the mass recovery also decreased by 8%
(from 37.9% to 34.8%). This represented a loss of 832,000
tons of iron ore worth about $16 million for the two-year
period. The concentrator had been optimized to produce
a high-grade wet concentrate as feed to the dry side of the
plant.
Research conducted at the plant decades ago shows that
electrostatic separation performs best between a specific
size range. Figure 7 shows that momentum overcomes the
electrostatic pinning force for particles coarser than about
35 mesh and they report to concentrate whether they are
hematite or silica electrostatic separation became unselec-
tive at coarse sizes. High tension performs well at 65 mesh,
for example, because a 1% silica concentrate was produced
Table 1. Results from PeT pilot campaigns
Pilot Plant
Phase No.
Tons of Raw Sand
Processed
Tons of Magnetite
Concentrate Produced
Magnetic Concentrate
Weight Recovery, %
Concentrate Grade, %
Fe (±1 std)
I 83 4.8 5.8 47.9 ± 2.4
II 613 46.0 7.5 55.5 ± 2.8
III 82 19.0 10.6 57.1
Total 778 56.8 7.3
2003) described the two major impediments, which are “a
poor equal setting ratio and the difficulty and expense of
dust containment.” (Fuerstenau and Han, p. 212)
Electrostatic
Electrostatic separation is applicable when the minerals
being separated have sufficiently different electrical con-
ductivity. Electrostatic separators were described by Taggart
(1945) and the schematic representation of a Sutton separa-
tor, shown in Figure 5 remains valid today.
Screening
Screening is a method to separate particles into different size
fractions by using equipment such as plates, wire mesh, or
polyurethane panels with aperture openings to allow finer
material to pass through. Dry sieving is employed when the
material requires dry grinding and reacts with water either
chemically (e.g., Portland cement) or physically (e.g., ben-
tonite clay). Dry classification can also be conducted pneu-
matically within an air-swept mill or air cyclones.
Sensor-based
Sensors can be used to detect differences in dry mineral
particles exposed to electromagnetic radiation such as
X-ray fluorescence (XRF), X-ray Luminescence (XRL) and
Optical Fluorescence, X-ray Transmission (XRT), Prompt
Gamma Neutron Activation Analysis (PGNAA), or Optical
and Hyperspectral Imaging (Peukert, et al. 2022). An excel-
lent comprehensive chapter on mineral sorting is available
in Klein and Bamber (2019) describing the hurdles to
adoption, sensor types, applications, commercial opera-
tions, and recovery results for various ore types including
lead-zinc, uranium, nickel, nickel-copper and gold at 41
installations.
Drying
Drying is the process of removing water from a material by
evaporation, as opposed to mechanical dewatering. Drying
is employed in mill operations for various reasons includ-
ing to increase efficiency of dry processing such as screen-
ing, air separation, and electrostatic separation (Taggart,
1945). Drying may be required upstream prior to dry
beneficiation.
TWO OPERATIONAL EXAMPLES OF DRY
BENEFICIAITON
Electrostatic Separation—Operational Example No. 1
of 2
Electrostatic separation is used to remove silica gangue and
upgrade the hematite concentrate at an iron ore operation
in Canada. The flowsheet is shown in Figure 3. Until the
upstream wet unit operations were optimized to consider
the impacts on dry processing, the concentrate could actu-
ally downgrade. The key takeaway from this evaluation
was that the standard method of optimizing individual
unit operation in isolation can sometimes reduce overall
plant performance and that each unit operation must be
considered as individual components working together
in a system. It was important optimize the concentrator
as a system and not simply optimize each unit operation.
Optimizing the grade and recovery from the hydrosizer
(Figure 4) negatively impacted the overall recovery after the
hydrosizer’s concentrate fed the dry electrostatic separation.
Understanding and optimization of dry unit processing
techniques was fundamental to this evaluation.
Between 2002 and 2004, the performance of a six mil-
lion ton per year iron ore beneficiation plant dropped sig-
nificantly. The average annual final product grade decreased
8% (indicated by an increase in silicate gangue from 2.8%
to 3.0%) while the mass recovery also decreased by 8%
(from 37.9% to 34.8%). This represented a loss of 832,000
tons of iron ore worth about $16 million for the two-year
period. The concentrator had been optimized to produce
a high-grade wet concentrate as feed to the dry side of the
plant.
Research conducted at the plant decades ago shows that
electrostatic separation performs best between a specific
size range. Figure 7 shows that momentum overcomes the
electrostatic pinning force for particles coarser than about
35 mesh and they report to concentrate whether they are
hematite or silica electrostatic separation became unselec-
tive at coarse sizes. High tension performs well at 65 mesh,
for example, because a 1% silica concentrate was produced
Table 1. Results from PeT pilot campaigns
Pilot Plant
Phase No.
Tons of Raw Sand
Processed
Tons of Magnetite
Concentrate Produced
Magnetic Concentrate
Weight Recovery, %
Concentrate Grade, %
Fe (±1 std)
I 83 4.8 5.8 47.9 ± 2.4
II 613 46.0 7.5 55.5 ± 2.8
III 82 19.0 10.6 57.1
Total 778 56.8 7.3