XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 239
The resulting mineral size distribution for biotite was
also evaluated and is shown in Figure 16. The coarsest size
distribution of biotite is measured for the material with the
lowest EEIT (0.44 kWh/t), while the finest size distribution
of biotite is reported for the material with the largest energy
input. The sample with the second lowest energy input,
only 1.18 kWh/t, lies between both distributions.
TESTS AND RESULTS ON SCHEELITE ORE
Scheelite Ore
The tests on scheelite ore were conducted within a joint
project financed by the German Federal Environmental
Foundation (DBU AZ: 35693). In the case of scheelite ore,
the fraction of material up to 5.6 mm was tested.
Table 6 summarizes the properties of the scheelite ore
used. Further analysis of the microstructure determined
that the scheelite is found preferentially in the amphibolite
and gneiss phases, see Figure 17. The scheelite content for
this fraction was determined to be 0.36 wt%.
The testing program was reduced to consider only two
energy levels (140 J and 280 J) and two frequency levels (3
and 10 Hz), the water flow rate was kept constant at 0.7 l/s
and the material feed rate was varied to cover only the
range of energy input intended for the high-voltage elec-
trical impulse pre-treatment, namely between 0.43 kWh/t
Table 4. Test Results for granodiorite regarding specific milling energy reduction after treatment with high-voltage electrical
impulses (average of three measurements)
Sample Energy, J Frequency, Hz
Flow Rate,
l/s
Feed Rate,
%
Electrical Impulse
Treatment EEIT
Total Energy,
kWh/t
%Reduction Specific
Milling Energy
1 70 15 1.2 60 1.31 16%
2 70 15 0.7 60 1.31 16%
3 70 15 0.95 80 1.20 15%
4 70 15 0.95 40 1.42 18%
5 70 5 0.95 60 0.44 18%
6 70 25 0.95 60 2.19 16%
7 280 5 0.95 60 1.75 14%
8 280 15 0.95 40 5.69 13%
9 280 15 0.95 80 4.81 20%
10 280 15 1.2 60 5.25 16%
11 280 15 0.7 60 5.25 16%
12 280 25 0.95 60 8.75 13%
13 175 15 0.95 60 3.28 16%
14 175 15 0.7 40 3.55 17%
15 175 25 0.95 80 5.01 21%
16 175 15 0.7 80 3.01 16%
17 175 15 1.2 40 3.55 14%
18 175 15 1.2 80 3.01 15%
19 175 5 0.7 60 1.09 15%
20 175 15 0.95 60 3.28 14%
21 175 25 0.7 60 5.47 13%
22 175 25 1.2 60 5.47 20%
23 175 5 0.95 40 1.18 18%
24 175 25 0.95 40 5.92 13%
25 175 5 0.95 80 1.00 16%
26 175 5 1.2 60 1.09 16%
27 175 15 0.95 60 3.28 20%
Table 5. Selected Samples for MLA Analysis after testing
with HV Electrical Impulses
Sample ID Testing Conditions
5 70 J, 5 Hz, 0.95 l/s, 60%
10 280 J, 15 Hz, 1.2 l/s, 60%
12 280 J, 25 Hz, 0.95 l/s, 60%
22 175 J, 25 Hz, 1.2 l/s, 60%
23 175 J, 5 Hz, 0.95 l/s, 40%
The resulting mineral size distribution for biotite was
also evaluated and is shown in Figure 16. The coarsest size
distribution of biotite is measured for the material with the
lowest EEIT (0.44 kWh/t), while the finest size distribution
of biotite is reported for the material with the largest energy
input. The sample with the second lowest energy input,
only 1.18 kWh/t, lies between both distributions.
TESTS AND RESULTS ON SCHEELITE ORE
Scheelite Ore
The tests on scheelite ore were conducted within a joint
project financed by the German Federal Environmental
Foundation (DBU AZ: 35693). In the case of scheelite ore,
the fraction of material up to 5.6 mm was tested.
Table 6 summarizes the properties of the scheelite ore
used. Further analysis of the microstructure determined
that the scheelite is found preferentially in the amphibolite
and gneiss phases, see Figure 17. The scheelite content for
this fraction was determined to be 0.36 wt%.
The testing program was reduced to consider only two
energy levels (140 J and 280 J) and two frequency levels (3
and 10 Hz), the water flow rate was kept constant at 0.7 l/s
and the material feed rate was varied to cover only the
range of energy input intended for the high-voltage elec-
trical impulse pre-treatment, namely between 0.43 kWh/t
Table 4. Test Results for granodiorite regarding specific milling energy reduction after treatment with high-voltage electrical
impulses (average of three measurements)
Sample Energy, J Frequency, Hz
Flow Rate,
l/s
Feed Rate,
%
Electrical Impulse
Treatment EEIT
Total Energy,
kWh/t
%Reduction Specific
Milling Energy
1 70 15 1.2 60 1.31 16%
2 70 15 0.7 60 1.31 16%
3 70 15 0.95 80 1.20 15%
4 70 15 0.95 40 1.42 18%
5 70 5 0.95 60 0.44 18%
6 70 25 0.95 60 2.19 16%
7 280 5 0.95 60 1.75 14%
8 280 15 0.95 40 5.69 13%
9 280 15 0.95 80 4.81 20%
10 280 15 1.2 60 5.25 16%
11 280 15 0.7 60 5.25 16%
12 280 25 0.95 60 8.75 13%
13 175 15 0.95 60 3.28 16%
14 175 15 0.7 40 3.55 17%
15 175 25 0.95 80 5.01 21%
16 175 15 0.7 80 3.01 16%
17 175 15 1.2 40 3.55 14%
18 175 15 1.2 80 3.01 15%
19 175 5 0.7 60 1.09 15%
20 175 15 0.95 60 3.28 14%
21 175 25 0.7 60 5.47 13%
22 175 25 1.2 60 5.47 20%
23 175 5 0.95 40 1.18 18%
24 175 25 0.95 40 5.92 13%
25 175 5 0.95 80 1.00 16%
26 175 5 1.2 60 1.09 16%
27 175 15 0.95 60 3.28 20%
Table 5. Selected Samples for MLA Analysis after testing
with HV Electrical Impulses
Sample ID Testing Conditions
5 70 J, 5 Hz, 0.95 l/s, 60%
10 280 J, 15 Hz, 1.2 l/s, 60%
12 280 J, 25 Hz, 0.95 l/s, 60%
22 175 J, 25 Hz, 1.2 l/s, 60%
23 175 J, 5 Hz, 0.95 l/s, 40%