236 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
The milling tests were performed on a universal mill,
Jehmlich mill. In this mill it is possible to perform a series
of impact milling tests with variable tools, for example, pin
rotor tool or impact blow nose blow tool. The impact-blow
nose mill works with velocities between 20 m/s and 80 m/s.
Since one of the objectives is to open the cracks introduced
by treatment with high-voltage electrical impulses without
overmilling, the lowest velocity of 20 m/s was selected to
achieve this objective.
In Figure 6 the universal mill, the impact nose rotor
tool as well as the resulting mill curves are depicted.
The power draw curves were recorded with a Kistler
torque measuring device, CoMo Torque Type 4700B. The
milling tests resulted in curves that allowed the plotting of
the power draw needed for milling against the time.
The milling power draw curve provides the informa-
tion about how much energy is required to mill the sample.
The milling energy for the specific sub-sample is calculated
considering the mass for the specific test and the result of
the integrated area from the milling curve. A graphical
example of the difference in the milling power draw curves
is provided in Figure 6 by overlapping the milling draw
curve of the raw material sample against one of material
treated with high-voltage electrical impulses. The impor-
tant result obtained from the milling curves is the value
of the integrated surface. The mass of the sample and the
integrated surface allow for the calculation of the specific
milling energy.
A comparison to material without impulses, “raw”
material, is performed and the parameter %Ered, e.g., the
difference in the average specific milling energy between
the raw material (EMillRAW) and the test material treated
with high-voltage electrical impulses (EEIT), the average of
the three samples, is calculated.
%E EMillRAW
E E
100
red
MillRAW MillEIT =
-
This result was then compared against the results of
milling tests performed on raw material without high-volt-
age electrical impulses.
Continuous testing was conducted on granodiorite and
on scheelite ore, each material will be presented separately
for a better understanding of the investigations conducted
in each material and the corresponding results. In the case
of the granodiorite material, additional tests regarding the
mineral liberation of mica were conducted. The general
experimental procedure is visualized in Figure 7.
TESTS AND RESULTS ON
GRANODIORITE
Granodiorite was selected as a suitable material for per-
forming the initial tests in the pilot system, given its nearly
isotropic microstructure with clearly identifiable phases, its
relative coarse size, and the strength of the material. The
results of the initial characterization of granodiorite are pre-
sented in Table 2. In Figure 8, representative micrographs
obtained from the thin sections used for the QMA are
presented.
For the tests in the pilot system, only material from
the fraction 5–8 mm was used. The tests were conducted
by following a statistical design of experiments (DoE),
specifically a Box-Behnken plan. The statistical design of
experiments was used to determine which parameters are
decisive within the range of operation defined for the ini-
tial tests and the material in question. The objective of the
0 10 20 30 40 50 60 70 80 90 100
0.6
0.5
0.4
0.3
0.2
0.1
0.0
Power -Raw Material
Time, s
Power -Test Material After EI-Treatment
Figure 6. Diagram depicting the Universal mill and the blow-nose element (Gebr. Jehmlich GmbH, 2015) and comparison
between the power draw curves for raw material and a sample of material treated with high-voltage electrical impulses
Pow
erkW
,
The milling tests were performed on a universal mill,
Jehmlich mill. In this mill it is possible to perform a series
of impact milling tests with variable tools, for example, pin
rotor tool or impact blow nose blow tool. The impact-blow
nose mill works with velocities between 20 m/s and 80 m/s.
Since one of the objectives is to open the cracks introduced
by treatment with high-voltage electrical impulses without
overmilling, the lowest velocity of 20 m/s was selected to
achieve this objective.
In Figure 6 the universal mill, the impact nose rotor
tool as well as the resulting mill curves are depicted.
The power draw curves were recorded with a Kistler
torque measuring device, CoMo Torque Type 4700B. The
milling tests resulted in curves that allowed the plotting of
the power draw needed for milling against the time.
The milling power draw curve provides the informa-
tion about how much energy is required to mill the sample.
The milling energy for the specific sub-sample is calculated
considering the mass for the specific test and the result of
the integrated area from the milling curve. A graphical
example of the difference in the milling power draw curves
is provided in Figure 6 by overlapping the milling draw
curve of the raw material sample against one of material
treated with high-voltage electrical impulses. The impor-
tant result obtained from the milling curves is the value
of the integrated surface. The mass of the sample and the
integrated surface allow for the calculation of the specific
milling energy.
A comparison to material without impulses, “raw”
material, is performed and the parameter %Ered, e.g., the
difference in the average specific milling energy between
the raw material (EMillRAW) and the test material treated
with high-voltage electrical impulses (EEIT), the average of
the three samples, is calculated.
%E EMillRAW
E E
100
red
MillRAW MillEIT =
-
This result was then compared against the results of
milling tests performed on raw material without high-volt-
age electrical impulses.
Continuous testing was conducted on granodiorite and
on scheelite ore, each material will be presented separately
for a better understanding of the investigations conducted
in each material and the corresponding results. In the case
of the granodiorite material, additional tests regarding the
mineral liberation of mica were conducted. The general
experimental procedure is visualized in Figure 7.
TESTS AND RESULTS ON
GRANODIORITE
Granodiorite was selected as a suitable material for per-
forming the initial tests in the pilot system, given its nearly
isotropic microstructure with clearly identifiable phases, its
relative coarse size, and the strength of the material. The
results of the initial characterization of granodiorite are pre-
sented in Table 2. In Figure 8, representative micrographs
obtained from the thin sections used for the QMA are
presented.
For the tests in the pilot system, only material from
the fraction 5–8 mm was used. The tests were conducted
by following a statistical design of experiments (DoE),
specifically a Box-Behnken plan. The statistical design of
experiments was used to determine which parameters are
decisive within the range of operation defined for the ini-
tial tests and the material in question. The objective of the
0 10 20 30 40 50 60 70 80 90 100
0.6
0.5
0.4
0.3
0.2
0.1
0.0
Power -Raw Material
Time, s
Power -Test Material After EI-Treatment
Figure 6. Diagram depicting the Universal mill and the blow-nose element (Gebr. Jehmlich GmbH, 2015) and comparison
between the power draw curves for raw material and a sample of material treated with high-voltage electrical impulses
Pow
erkW
,