XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 3931
indicators are used to detect changes within the slag parti-
cle’s brittle breakage behavior. These indicators include the
audible cracking of the specimen as it yields under com-
pressive force and the real-time tracking of force-distance
curves (Figure 1). Force-distance curves may not consis-
tently exhibit the idealized pattern (state I), showing a steep
increase in force until the breakage event and followed by a
sudden drop in force. Curve patterns may include multiple
breakage events. After the initial peak, there may not be a
pronounced force decrease. Instead, the curve may briefly
increase again, potentially repeating this pattern until a
substantial force drop occurs (state II). Another curve pat-
tern (state III) may present a gradual rise, followed by sev-
eral smaller maxima, each with significantly lower forces.
This curve is generally smoother and flatter, lacking the
pronounced jaggedness commonly associated with brittle
materials.
The breakage force is determined by identifying the
maxima of the force-displacement curves (Tavares 2007).
The first local maximum indicates the first breakage event.
If there are multiple peaks, the breakage force is also deter-
mined at the maximum that is followed by a high force
drop and this point is described as the maximum break-
age event. Estimating the breakage force is useful for in-situ
compression because it allows for the timely termination
of the experiment when a breakage event occurs, prevent-
ing unnecessary loading of the sample. The aim is to mea-
sure the breakage event as accurately as possible, capturing
any cracks or deformations that may have occurred in the
sample. Measurements are also taken prior to the breakage
event for comparison.
In-Situ Compression – XCT Data Acquisition
The measurement series is conducted in-situ at various
force levels and is therefore controlled by force. The first
measurement is taken of the intact particle at F =0 N. The
subsequent measurement is taken at F =5 N, where force
is applied to the particle, but no deformations or altera-
tions are to be expected. In this measurement, the particle
remains without any motion and stable between the ceramic
pistons. Another measurement is performed at 80% of the
estimated breakage force. Following this, the sample is sub-
jected to stress until a change in transmission occurs and
can be observed in the projection image. The measurement
and reconstruction settings are listed in Table 1.
RESULTS AND DISCUSSION
Ex-Situ Single Particle Breakage Experiments
Of all the slag particles examined, 50% exhibited a force-
displacement curve pattern categorized as ‘state I,’ followed
by 36.7% in ‘state II.’ It is important to note that this out-
come cannot be universally applied to all regions within a
slag block since microstructural properties can vary due to
the thermodynamics of crystal growth and the unpredict-
able orientation of individual crystals can influence their
mechanical properties (Buchmann et al. 2020). Anisotropy
in hardness cannot be ruled out, and the crystal structure
and glide system may lead to varying hardness values based
on particle shape. Still, this information was sufficient for
developing the in-situ measurement methodology in XCT,
particularly for a quick estimate of the breakage force range
of slag particles within this size fraction.
The study also examined the difference in breakage
forces between the first breakage event and the maximal
breakage event (Figure 2). The initial measurable peak in
the force-distance curve is marked by the first breakage
event, which represents the point where primary particle
breakage should occur. The maximum breakage event is
determined by the peak of the force-distance curve, where a
force drop of over 20% is observed. The first and maximum
breakage forces of each force-distance curve are determined
and then plotted as a sum distribution.
The difference between the first and the maximum
breakage event is important to identify changes in the
Figure 1. Force-distance curve progressions of single particle breakages distinguished by three states: state I: ideal force-
distance curve, state II: multiple maxima with one distinct force drop, state III: poor force increase and multiple maxima with
lower force drops
indicators are used to detect changes within the slag parti-
cle’s brittle breakage behavior. These indicators include the
audible cracking of the specimen as it yields under com-
pressive force and the real-time tracking of force-distance
curves (Figure 1). Force-distance curves may not consis-
tently exhibit the idealized pattern (state I), showing a steep
increase in force until the breakage event and followed by a
sudden drop in force. Curve patterns may include multiple
breakage events. After the initial peak, there may not be a
pronounced force decrease. Instead, the curve may briefly
increase again, potentially repeating this pattern until a
substantial force drop occurs (state II). Another curve pat-
tern (state III) may present a gradual rise, followed by sev-
eral smaller maxima, each with significantly lower forces.
This curve is generally smoother and flatter, lacking the
pronounced jaggedness commonly associated with brittle
materials.
The breakage force is determined by identifying the
maxima of the force-displacement curves (Tavares 2007).
The first local maximum indicates the first breakage event.
If there are multiple peaks, the breakage force is also deter-
mined at the maximum that is followed by a high force
drop and this point is described as the maximum break-
age event. Estimating the breakage force is useful for in-situ
compression because it allows for the timely termination
of the experiment when a breakage event occurs, prevent-
ing unnecessary loading of the sample. The aim is to mea-
sure the breakage event as accurately as possible, capturing
any cracks or deformations that may have occurred in the
sample. Measurements are also taken prior to the breakage
event for comparison.
In-Situ Compression – XCT Data Acquisition
The measurement series is conducted in-situ at various
force levels and is therefore controlled by force. The first
measurement is taken of the intact particle at F =0 N. The
subsequent measurement is taken at F =5 N, where force
is applied to the particle, but no deformations or altera-
tions are to be expected. In this measurement, the particle
remains without any motion and stable between the ceramic
pistons. Another measurement is performed at 80% of the
estimated breakage force. Following this, the sample is sub-
jected to stress until a change in transmission occurs and
can be observed in the projection image. The measurement
and reconstruction settings are listed in Table 1.
RESULTS AND DISCUSSION
Ex-Situ Single Particle Breakage Experiments
Of all the slag particles examined, 50% exhibited a force-
displacement curve pattern categorized as ‘state I,’ followed
by 36.7% in ‘state II.’ It is important to note that this out-
come cannot be universally applied to all regions within a
slag block since microstructural properties can vary due to
the thermodynamics of crystal growth and the unpredict-
able orientation of individual crystals can influence their
mechanical properties (Buchmann et al. 2020). Anisotropy
in hardness cannot be ruled out, and the crystal structure
and glide system may lead to varying hardness values based
on particle shape. Still, this information was sufficient for
developing the in-situ measurement methodology in XCT,
particularly for a quick estimate of the breakage force range
of slag particles within this size fraction.
The study also examined the difference in breakage
forces between the first breakage event and the maximal
breakage event (Figure 2). The initial measurable peak in
the force-distance curve is marked by the first breakage
event, which represents the point where primary particle
breakage should occur. The maximum breakage event is
determined by the peak of the force-distance curve, where a
force drop of over 20% is observed. The first and maximum
breakage forces of each force-distance curve are determined
and then plotted as a sum distribution.
The difference between the first and the maximum
breakage event is important to identify changes in the
Figure 1. Force-distance curve progressions of single particle breakages distinguished by three states: state I: ideal force-
distance curve, state II: multiple maxima with one distinct force drop, state III: poor force increase and multiple maxima with
lower force drops