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Insights into Slag Particle Breakage: Integrating Ex‑Situ
Experiments with In-Situ Compression via X-Ray
Computed Tomography
Thu Trang Võ, Urs A. Peuker
TU Bergakademie Freiberg, Institute of Mechanical Process Engineering and Mineral Processing
ABSTRACT: The breakage behavior of slag particles is investigated through ex-situ and in-situ single particle
experiments, coupled with X-ray tomography (XCT). Four distinct fragmentation types are identified,
revealing diverse breakage outcomes. By conducting XCT measurements at various force levels that is exerted
onto slag particles, insight into the complex, dendritic microstructure can be gained and considered in the
interpretation of the resulting breakage behavior. The correlation between force-distance curves and optical
results enhances the understanding during breakage. The brittle nature of slag is highlighted by the overlapping
pore distributions post-breakage, indicating a random breakage mechanism with no preferential crack paths.
The developed methodologies provide valuable tools for characterizing and predicting breakage events in slag
and similar materials, with broader implications for industrial applications.
Keywords: X-ray tomography, microstructure, breakage, fracture
INTRODUCTION
The comminution of minerals and secondary raw materials
is a key process for resource conservation and sustainable
recovery. In particular, essential elements such as lithium,
tantalum, and copper are intricately embedded in indus-
trial and electronic wastes, arising either as byproducts
during production or accumulating at the conclusion of a
product’s life cycle (Kaya 2016). These elements are called
critical due to their significance in the economic compe-
tition and development of advanced high-tech products
for the European market (European Commission 2023).
Aligned with the zero-waste concept, which stands for the
complete recovery of all invested materials (Binnemans et
al. 2015, Curran and Williams 2012), low-concentration
elements are transferred into slags pyrometallurgically. This
strategy prevents their loss in the recycling stream of main
components, with the slag serving as a carrier for critical
elements. The controlled cooling of the slag facilitates the
transformation of these elements into minerals, i.e., engi-
neered artificial minerals (EnAM), whether in the form of
crystals or amorphous phases (Rachmawati et al. 2024, Võ
et al. 2024). The former allows for a more concentrated
enrichment of elements, and requires liberation from the
residue or matrix.
The efficiency of liberation is directly related to the
breakage mechanism. Gaudin (1940) gave the first classi-
fication, distinguishing between liberation by comminu-
tion and liberation by detachment. The former describes
a breakage that occurs independently of particle properties
such as chemical composition, mineralogy, morphology,
Insights into Slag Particle Breakage: Integrating Ex‑Situ
Experiments with In-Situ Compression via X-Ray
Computed Tomography
Thu Trang Võ, Urs A. Peuker
TU Bergakademie Freiberg, Institute of Mechanical Process Engineering and Mineral Processing
ABSTRACT: The breakage behavior of slag particles is investigated through ex-situ and in-situ single particle
experiments, coupled with X-ray tomography (XCT). Four distinct fragmentation types are identified,
revealing diverse breakage outcomes. By conducting XCT measurements at various force levels that is exerted
onto slag particles, insight into the complex, dendritic microstructure can be gained and considered in the
interpretation of the resulting breakage behavior. The correlation between force-distance curves and optical
results enhances the understanding during breakage. The brittle nature of slag is highlighted by the overlapping
pore distributions post-breakage, indicating a random breakage mechanism with no preferential crack paths.
The developed methodologies provide valuable tools for characterizing and predicting breakage events in slag
and similar materials, with broader implications for industrial applications.
Keywords: X-ray tomography, microstructure, breakage, fracture
INTRODUCTION
The comminution of minerals and secondary raw materials
is a key process for resource conservation and sustainable
recovery. In particular, essential elements such as lithium,
tantalum, and copper are intricately embedded in indus-
trial and electronic wastes, arising either as byproducts
during production or accumulating at the conclusion of a
product’s life cycle (Kaya 2016). These elements are called
critical due to their significance in the economic compe-
tition and development of advanced high-tech products
for the European market (European Commission 2023).
Aligned with the zero-waste concept, which stands for the
complete recovery of all invested materials (Binnemans et
al. 2015, Curran and Williams 2012), low-concentration
elements are transferred into slags pyrometallurgically. This
strategy prevents their loss in the recycling stream of main
components, with the slag serving as a carrier for critical
elements. The controlled cooling of the slag facilitates the
transformation of these elements into minerals, i.e., engi-
neered artificial minerals (EnAM), whether in the form of
crystals or amorphous phases (Rachmawati et al. 2024, Võ
et al. 2024). The former allows for a more concentrated
enrichment of elements, and requires liberation from the
residue or matrix.
The efficiency of liberation is directly related to the
breakage mechanism. Gaudin (1940) gave the first classi-
fication, distinguishing between liberation by comminu-
tion and liberation by detachment. The former describes
a breakage that occurs independently of particle properties
such as chemical composition, mineralogy, morphology,