188 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
HAM18, PB-016. Most chemical elements are evenly dis-
tributed in the various size fractions. For Al2O3 for exam-
ple, the average content is 7.251% with a small standard
deviation of 0.278%, resulting in a variation coefficient
of 3.837% only. For SiO2 or MgO, those values are even
smaller. Even the values for tin fall below (reddish column).
The picture is completely different, however, for
the zinc (greenish column). Here the content grows rap-
idly from 1.02 %in the coarse fraction 22.4/31.5 mm
to 9.36 %with the fine fraction 0/1 mm, an increase by
800 %.Obviously, there is a massive deportment of zinc
in the form of the zinc containing mineral sphalerite into
the fine fractions just by rather gentle impact comminu-
tion, despite the overall size reduction of this test was little.
The d50 of the test hardly deviated from the one of the feed
material. The d10 reflected that some material, belonging
already to the finer sizes of the feed was further crushed
(d10,feed =11 mm d10,product =5.3 mm). Also, the cad-
mium content increases rapidly, yet at much smaller abso-
lute values. Its content is already at the accuracy limits of
the used measuring device and will not be discussed further.
That situation becomes more evident when looking at
a graph indicating the development of the mineral mass
content from coarser to finer fractions (Figure 8). While
most of the elements/ oxides do not show any significant
changes only zinc and SO3 do. This change is remarkable.
The tendency even increases and the curve becomes ever
steeper the finer the particles are.
In order to evaluate the commercial potential of the
Selective Comminution, in addition to the concentration
also the relative mass content of the valuable component in
a certain fraction has to be considered. The distribution of
the overall amount of zinc onto the various size fractions is
shown at the graph of Figure 9 for test HAM18, PB-016.
Despite of the very little size reduction in the coarser frac-
tion, it is obvious that a severe amount of zinc is deported
from the coarse fractions d 11.2 mm to the very fine frac-
tion d 1 mm. While the fine fraction contains only 2.9
mass-% of the overall material sample, it contains 16.9%
of the overall zinc.
The picture becomes more interesting with the impact
comminution is more in-tensive due to a smaller crushing
gap in the impact crusher. Figure 10 shows the zinc and
gangue contents per fraction relative to the overall zinc and
gangue content in the sample tested in HAM18, PB-006
(gap width w =15 mm). Quite obvious, the material mass
of the coarser fractions is reduced (see also Figure 7). Only
about 2.0 mass-percent of gangue material is contained in
the fraction 22.4 mm. This compares to 24.5% with test
HAM18, PB-016. While there the zinc content was still
15.7%, with the narrower gap only 0.2% of the overall zinc
is contained in the coarsest fraction. That fraction can be
discarded practically without loss. On the other end, how-
ever, the finest fraction (1mm) with 13.5% of the gangue
material contains 58.61% of the overall zinc in the sample.
The drop in zinc content towards the next larger fraction is
severe. The fraction 1/1.5 mm contains only about 5.1% of
the zinc and about 3.5% of the gangue material.
For analyzing the reasons of the rapid shift of the
sphalerite ore into the smaller fractions, while most of the
material is still rather coarse, it is necessary to look at the
vein structure of the orebody. Obviously, the bridle sphal-
erite minerals were mainly concentrated as aggregates in
veins. Already in primary comminution, cracks preferably
propagated along these veins as weakest zones. This process
already exposed the sphalerite minerals to the rock surface.
A cautious stressing in the HIS caused the exposed layers of
Table 4. Concentration of chemical elements/oxides in the various fraction of sample HAM18, PB-016, acc. to (Villarroel und
Jenkner 2019)
Size fraction
[mm] Al2O3 Cu CaO Cd Fe2O3 K2O MgO SiO2 Sn SO3 Zn
0/1 5,83 0,09 7,10 0,04 33,69 0,91 2,46 25,08 0,69 12,10 9,36
1/1.5 6,81 0,08 6,60 0,03 35,85 1,13 2,92 30,45 0,69 7,54 5,45
1.5/2 7,33 0,08 7,00 0,02 34,27 1,26 3,12 33,05 0,72 6,36 4,28
2/2.5 7,47 0,06 7,09 0,02 35,11 1,30 3,15 33,92 0,72 5,25 3,44
2.5/4 7,85 0,06 7,39 0,01 34,18 1,33 3,26 35,38 0,72 4,49 2,79
4/5.6 7,71 0,08 7,05 0,01 35,63 1,31 3,20 34,76 0,72 3,51 2,16
5.6/8 7,98 0,08 7,02 0,01 37,02 1,38 3,31 35,60 0,74 2,84 1,71
8/11.2 7,73 0,07 7,18 0,01 36,94 1,34 3,34 36,08 0,75 2,50 1,55
11.2/16 7,92 0,06 7,55 0,01 36,32 1,35 3,57 36,42 0,74 2,29 1,33
16/22.4 7,66 0,07 7,47 0,01 38,10 1,29 3,59 35,56 0,78 1,96 1,08
22.4/31.5 7,25 0,06 7,37 0,01 39,92 1,19 3,47 34,74 0,80 1,85 1,02
Mass content of chemical elements /oxides [%]
HAM18, PB-016. Most chemical elements are evenly dis-
tributed in the various size fractions. For Al2O3 for exam-
ple, the average content is 7.251% with a small standard
deviation of 0.278%, resulting in a variation coefficient
of 3.837% only. For SiO2 or MgO, those values are even
smaller. Even the values for tin fall below (reddish column).
The picture is completely different, however, for
the zinc (greenish column). Here the content grows rap-
idly from 1.02 %in the coarse fraction 22.4/31.5 mm
to 9.36 %with the fine fraction 0/1 mm, an increase by
800 %.Obviously, there is a massive deportment of zinc
in the form of the zinc containing mineral sphalerite into
the fine fractions just by rather gentle impact comminu-
tion, despite the overall size reduction of this test was little.
The d50 of the test hardly deviated from the one of the feed
material. The d10 reflected that some material, belonging
already to the finer sizes of the feed was further crushed
(d10,feed =11 mm d10,product =5.3 mm). Also, the cad-
mium content increases rapidly, yet at much smaller abso-
lute values. Its content is already at the accuracy limits of
the used measuring device and will not be discussed further.
That situation becomes more evident when looking at
a graph indicating the development of the mineral mass
content from coarser to finer fractions (Figure 8). While
most of the elements/ oxides do not show any significant
changes only zinc and SO3 do. This change is remarkable.
The tendency even increases and the curve becomes ever
steeper the finer the particles are.
In order to evaluate the commercial potential of the
Selective Comminution, in addition to the concentration
also the relative mass content of the valuable component in
a certain fraction has to be considered. The distribution of
the overall amount of zinc onto the various size fractions is
shown at the graph of Figure 9 for test HAM18, PB-016.
Despite of the very little size reduction in the coarser frac-
tion, it is obvious that a severe amount of zinc is deported
from the coarse fractions d 11.2 mm to the very fine frac-
tion d 1 mm. While the fine fraction contains only 2.9
mass-% of the overall material sample, it contains 16.9%
of the overall zinc.
The picture becomes more interesting with the impact
comminution is more in-tensive due to a smaller crushing
gap in the impact crusher. Figure 10 shows the zinc and
gangue contents per fraction relative to the overall zinc and
gangue content in the sample tested in HAM18, PB-006
(gap width w =15 mm). Quite obvious, the material mass
of the coarser fractions is reduced (see also Figure 7). Only
about 2.0 mass-percent of gangue material is contained in
the fraction 22.4 mm. This compares to 24.5% with test
HAM18, PB-016. While there the zinc content was still
15.7%, with the narrower gap only 0.2% of the overall zinc
is contained in the coarsest fraction. That fraction can be
discarded practically without loss. On the other end, how-
ever, the finest fraction (1mm) with 13.5% of the gangue
material contains 58.61% of the overall zinc in the sample.
The drop in zinc content towards the next larger fraction is
severe. The fraction 1/1.5 mm contains only about 5.1% of
the zinc and about 3.5% of the gangue material.
For analyzing the reasons of the rapid shift of the
sphalerite ore into the smaller fractions, while most of the
material is still rather coarse, it is necessary to look at the
vein structure of the orebody. Obviously, the bridle sphal-
erite minerals were mainly concentrated as aggregates in
veins. Already in primary comminution, cracks preferably
propagated along these veins as weakest zones. This process
already exposed the sphalerite minerals to the rock surface.
A cautious stressing in the HIS caused the exposed layers of
Table 4. Concentration of chemical elements/oxides in the various fraction of sample HAM18, PB-016, acc. to (Villarroel und
Jenkner 2019)
Size fraction
[mm] Al2O3 Cu CaO Cd Fe2O3 K2O MgO SiO2 Sn SO3 Zn
0/1 5,83 0,09 7,10 0,04 33,69 0,91 2,46 25,08 0,69 12,10 9,36
1/1.5 6,81 0,08 6,60 0,03 35,85 1,13 2,92 30,45 0,69 7,54 5,45
1.5/2 7,33 0,08 7,00 0,02 34,27 1,26 3,12 33,05 0,72 6,36 4,28
2/2.5 7,47 0,06 7,09 0,02 35,11 1,30 3,15 33,92 0,72 5,25 3,44
2.5/4 7,85 0,06 7,39 0,01 34,18 1,33 3,26 35,38 0,72 4,49 2,79
4/5.6 7,71 0,08 7,05 0,01 35,63 1,31 3,20 34,76 0,72 3,51 2,16
5.6/8 7,98 0,08 7,02 0,01 37,02 1,38 3,31 35,60 0,74 2,84 1,71
8/11.2 7,73 0,07 7,18 0,01 36,94 1,34 3,34 36,08 0,75 2,50 1,55
11.2/16 7,92 0,06 7,55 0,01 36,32 1,35 3,57 36,42 0,74 2,29 1,33
16/22.4 7,66 0,07 7,47 0,01 38,10 1,29 3,59 35,56 0,78 1,96 1,08
22.4/31.5 7,25 0,06 7,37 0,01 39,92 1,19 3,47 34,74 0,80 1,85 1,02
Mass content of chemical elements /oxides [%]