XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 2669
comminution, it affects the subsequent processes. When
the ore is dispersed and selectively flocculated in desliming,
it affects the subsequent processes. It is easy to make optimi-
zations which improve the performance of one unit, but it is
important to ensure that the subsequent processes also ben-
efit – from additional feed, or better performance, or lower
costs, or at the very least nothing is negatively impacted.
We will share a few cases where optimizations in one part
of the process were limited by, inspired by, or turned out to
be mostly critical for the downstream processes.
CASE 1: GRINDING AIDS
The goal of grinding the raw iron ore is to liberate the iron
bearing minerals from the gangue materials, so that they
can be separated by the flotation process. For most iron
ore deposits exploited in the Americas, the liberation size
which must be achieved during grinding is on the lower
end of a range of 25 to 70 microns. Achieving this grind is
a tremendous energy cost, which can be mitigated with a
variety of techniques.
It has long been known that the addition of grind-
ing aids can significantly improve grinding efficiency
(Klimpel and Austin, 1982 Chipakwe et al., 2020). These
reagents reduce grinding energy costs and improve grinding
performance. Since between crushing, grinding, and any
induration processes which may be performed for agglom-
eration account for most of the energy usage in a concen-
trator, any reduction in grinding energy costs can have a
significant impact on the efficiency of the plant. Grinding
aids can also help reduce overgrinding and lead to narrower
grind size distributions, which in turn can help improve
separation performance.
However, most grinding aids are potent surface-active
reagents which can have strong implications for flotation
performance. While the exact mechanisms by which grind-
ing aids operate are still debated (Chipakwe et al., 2020),
many of the more effective grinding aids are potent disper-
sants, which help separate the materials from each other as
they are comminuted. There are many different grinding
aid chemistries available, including various organic poly-
mers and inorganic additives.
The introduction of grinding aids can also impact the
slurry’s rheology, such as by decreasing slurry viscosity by
dispersing slimes. While the intention of dispersing slimes
is to allow for better transport of energy from the grind-
ing media to the solids, this also has implications on the
slurry’s flow characteristics. In iron ore circuits it has pre-
viously been shown that changing slurry viscosity, in the
Figure 1. An example iron ore concentration process from crushing to filtering
comminution, it affects the subsequent processes. When
the ore is dispersed and selectively flocculated in desliming,
it affects the subsequent processes. It is easy to make optimi-
zations which improve the performance of one unit, but it is
important to ensure that the subsequent processes also ben-
efit – from additional feed, or better performance, or lower
costs, or at the very least nothing is negatively impacted.
We will share a few cases where optimizations in one part
of the process were limited by, inspired by, or turned out to
be mostly critical for the downstream processes.
CASE 1: GRINDING AIDS
The goal of grinding the raw iron ore is to liberate the iron
bearing minerals from the gangue materials, so that they
can be separated by the flotation process. For most iron
ore deposits exploited in the Americas, the liberation size
which must be achieved during grinding is on the lower
end of a range of 25 to 70 microns. Achieving this grind is
a tremendous energy cost, which can be mitigated with a
variety of techniques.
It has long been known that the addition of grind-
ing aids can significantly improve grinding efficiency
(Klimpel and Austin, 1982 Chipakwe et al., 2020). These
reagents reduce grinding energy costs and improve grinding
performance. Since between crushing, grinding, and any
induration processes which may be performed for agglom-
eration account for most of the energy usage in a concen-
trator, any reduction in grinding energy costs can have a
significant impact on the efficiency of the plant. Grinding
aids can also help reduce overgrinding and lead to narrower
grind size distributions, which in turn can help improve
separation performance.
However, most grinding aids are potent surface-active
reagents which can have strong implications for flotation
performance. While the exact mechanisms by which grind-
ing aids operate are still debated (Chipakwe et al., 2020),
many of the more effective grinding aids are potent disper-
sants, which help separate the materials from each other as
they are comminuted. There are many different grinding
aid chemistries available, including various organic poly-
mers and inorganic additives.
The introduction of grinding aids can also impact the
slurry’s rheology, such as by decreasing slurry viscosity by
dispersing slimes. While the intention of dispersing slimes
is to allow for better transport of energy from the grind-
ing media to the solids, this also has implications on the
slurry’s flow characteristics. In iron ore circuits it has pre-
viously been shown that changing slurry viscosity, in the
Figure 1. An example iron ore concentration process from crushing to filtering