XXXI International Mineral Processing Congress 2024 Proceedings Page 224 (248 of 3836)

234 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
0,5 m³
Water pump
Processed
Material with
Electrical
Impulses
Marx-Generator
Overflow (water, fine
particles)
200 μm
1 mm 0.5 mm
3
Figure 3. Flow Chart for continuous electrical comminution machine (Source: Mezzetti/TUBAF-IART)
Figure 4. Pilot system for continuously processing with high-voltage electrical impulses
(Source: Mezzetti/TUBAF-IART)

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234 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
0,5 m³
Water pump
Processed
Material with
Electrical
Impulses
Marx-Generator
Overflow (water, fine
particles)
200 μm
1 mm 0.5 mm
3
Figure 3. Flow Chart for continuous electrical comminution machine (Source: Mezzetti/TUBAF-IART)
Figure 4. Pilot system for continuously processing with high-voltage electrical impulses
(Source: Mezzetti/TUBAF-IART)

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XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 233
later modified and expanded into a continuously operating
one with a design throughput capacity of 500 kg/h.
The generation of the high-voltage electrical impulses
occurs through a state-of-the-art Marx generator built spe-
cifically for this purpose. The Marx generator consists of
15-stages and allows the high voltage electrical impulses
to be created by parallel charging of the capacitors in each
stage and discharging in series. The machine also has an
integrated water processing module (closed loop) as well
as an external control panel, which allows monitoring and
controlling of the process parameters.
The ELIZE pilot plant relies on the flow of the material
between the electrodes without necessarily having a con-
tact with them. The material is brought into the processing
chamber and the water is pumped in the opposite direc-
tion, counteracting the sink velocity of the particles, hence
allowing a regulation of the residence time and the particle
location at any given moment. The concept underlying the
pilot plant has been patented (Lieberwirth, 2018).
The design of the process chamber includes the geo-
metric design of the electrodes and their arrangement, the
distance between the electrodes, the resulting electrical
field, and the relative position of the material. For this pur-
pose, the electrical field conditions in the process chamber
were modelled, see Figure 2.
The simulation included the evaluation of an electrode
distance up to 100 mm, which represents a significant
increase from the 60 mm originally used for the laboratory
unit. The results showed that the use of a compact group of
particles resulted in a continuous electrical field, thus a con-
tinuous path for the discharge of the high-voltage electrical
impulse. From these results, it was possible to conclude that
the approach proposed allowed the treatment of several
particles at once with a single electrical discharge (impulse).
Furthermore, the presence of a compact group of par-
ticles, e.g., small particle size, increases the efficiency of the
process and allows an increase of the material throughput,
which is one of the upmost requirements for an industrial
application. The main objective of this system development
is a weakening of the particles microstructure by introduc-
ing cracks into the material. It is expected that the pres-
ence of these cracks reduces the energy needed in further
mechanical processing.
The flow chart depicting the integration of the contin-
uous high-voltage electrical impulse comminution system
can be seen in Figure 3. In Figure 4, a picture of the actual
machine is presented. In Table 1, the technical capacities of
the system are given.
The material to be tested is first placed in the hopper,
which has a maximum capacity of 0.5 m3. The material is
then discharged by a vibrating feeder and falls into a receiv-
ing hopper. The material passes then to the process cham-
ber by gravity forces only. The material in the processing
chamber is treated with single electrical impulses when an
impulse is ignited. The material is then transported with
a dewatering screw conveyor and falls onto a dewatering
screen. From here the material is conducted into a container
waiting to be analysed or for further processing. During the
entire process, a continuous water counterflow circulates
through the system. Particles finer than 0.5 mm are carried
away and transported through the overflow gate located in
the upper part of the processing chamber.
The given capacities for the output voltage, frequency
and impulse energy are adjustable and allow a selection of
the processing parameters depending on the material.
Figure 2. Electrical field distribution in a group of particles in a system with 100 mm
electrode distance (Anders et al., 2020)

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XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 235
EXPERIMENTAL PROCEDURE
This pilot system has the objective of performing pre-
treatment of mineral material such as ores and slags. While
the system offers the possibility of adjusting the processing
parameters, initially it was necessary to determine which
factors are decisive within the area of specific energy that is
considered reasonable for a pre-treatment, namely between
1 and 3 kWh/t.
The processing with high-voltage electrical impulses is
expected to introduce cracks in the microstructure of the
material, which consequently reduce the strength of the
material and the energy needed for further mechanical pro-
cessing. As a pre-treatment, this system should be used in
combination with a further comminution step. It is also
expected that different materials will require different pro-
cessing parameters depending on the microstructure and
mechanical properties.
The general procedure followed for the characterization
of the materials included the microstructural evaluation
through the quantitative microstructural analysis (QMA),
the determination of the mechanical properties by means
of Point Load Testing (PLT) and the determination of the
particle size distribution of the starting material. The QMA
technique was developed by Popov and allows a mathe-
matical description of the relevant microstructural features
(Popov, 13.07.07). The description includes the identifica-
tion of the existing phases and their volume percentages,
size, shape, roughness, as well as the structure (orientation,
distribution, space filling).
For using the QMA- technique, three orthogonally
arranged thin sections from selected material samples need
to be prepared, seeFigure 5. These samples are then evalu-
ated by using the mathematical- petrographic method.
After the initial characterisation of the raw material, the
material was then tested according to a previously defined
trial program with varying processing conditions. The min-
imum sample size was determined according to Gy’s equa-
tion. Samples of material after continuous high-voltage
electrical impulse treatment were obtained and character-
ized for the resulting particle size distribution. Given the
low level of energy and taking into consideration that this
is only a pre-treatment without the objective or expectation
of a size reduction, no large difference is expected when
compared to the raw material without treatment.
However, it is desirable to measure the effect of the
continuous treatment with high-voltage electrical impulses.
For this purpose, samples of material after the continuous
high-voltage electrical impulse treatment were subjected
to milling tests with a universal mill by using the impact
blow nose rotor tool, which allowed the determination of
the specific milling energy. The PSD for these samples was
also measured.
The main objective of the milling tests was to open the
cracks introduced by the treatment with electrical impulses.
Through the milling tests is possible to measure the power
draw requirement to mill a certain amount of material. The
integration of the area under the milling power curve allows
the calculation of the specific energy after milling.
Table 1. Technical capacities for the continuous electrical
impulses processing pilot system
Maximal Output Voltage 600 kV
Frequency Up to 25 Hz
Single Impulse Energy Up to 500 J
Throughput About 500 kg/h
Particle Size (d
A )1 to 22 mm
Figure 5. Process flow for preparation of thin sections (Popov, 13.07.07)

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