1027
Liberation Curves: A New Approach to Interpreting Mineral
Liberation Data
Luis Salinas-Farran, Jan Cilliers
Department of Earth Science and Engineering, Imperial College London
Kathryn Hadler
European Space Resources Innovation Centre
ABSTRACT: Mineral liberation analysis plays a crucial role in optimising and troubleshooting mineral
separations. However, comparing products from different comminution techniques is extremely challenging.
Currently, reported data mainly focus on the mass of a mineral in a given liberation class, lacking information on
breakage nature. To address this, we propose an evaluation approach considering both mass and the number of
grains to compare different microwaving and comminution devices. We introduce a rapid evaluation technique
of grind sizes, reporting the results for thousands of mineral grains. This approach represents a critical step
toward liberation-based assessment and comparison of grinding circuits.
INTRODUCTION
Mineral liberation is a critical parameter for minerals pro-
cessing operations. Understanding the interplay between
comminution and liberation is key to achieve an optimum
operation (Wang et al., 2019). Consequently, the commi-
nution circuit should be tailored considering the specific ore
characteristics in order to find a perfect balance of grinding
media, mill speed, particle size (Garcia and Smith, 2017).
Fracture of mineral particles during comminution
can be described as random or non-random, where non-
random breakage can be classified as preferential breakage
(including selective breakage) or phase boundary breakage.
Phase boundary breakage is desirable, as it has the potential
to generate liberation of mineral grains at larger sizes than
with preferential breakage.
High-pressure grinding rolls (HPGR) have been pre-
sented as an alternative to conventional grinding methods
for its influence on liberation mechanisms and enhanced
energy efficiency (Wang et al., 2019). Another technique
that shows promising results is microwave-assisted commi-
nution. It relies on the ability of microwave to heat indi-
vidual phases within the ore matrix, being especially strong
for sulphides, arsenides, sulphonates and sulphoarsenides,
as they are absorbers to the microwave radiation (Kumar
et al., 2006, Garcia and Smith, 2017). The integration
of innovative approaches, such as HPGR or microwave-
assisted comminution further expands the toolkit for opti-
mising mineral liberation. Still, the approach that different
researchers use to assess the impact that different comminu-
tion methods have on liberation remains an open matter of
discussion.
Conventional liberation analysis is considered by
assessing the total mass of mineral in a certain liberation
class. This liberation class is determined by the area libera-
tion across particle surface. More targeted methods of eval-
uating the nature of breakage include use of conservation of
shape, conservation of phase specific interface area (PSIA)
and comparison with random fracture (Little et al., 2016).
Liberation Curves: A New Approach to Interpreting Mineral
Liberation Data
Luis Salinas-Farran, Jan Cilliers
Department of Earth Science and Engineering, Imperial College London
Kathryn Hadler
European Space Resources Innovation Centre
ABSTRACT: Mineral liberation analysis plays a crucial role in optimising and troubleshooting mineral
separations. However, comparing products from different comminution techniques is extremely challenging.
Currently, reported data mainly focus on the mass of a mineral in a given liberation class, lacking information on
breakage nature. To address this, we propose an evaluation approach considering both mass and the number of
grains to compare different microwaving and comminution devices. We introduce a rapid evaluation technique
of grind sizes, reporting the results for thousands of mineral grains. This approach represents a critical step
toward liberation-based assessment and comparison of grinding circuits.
INTRODUCTION
Mineral liberation is a critical parameter for minerals pro-
cessing operations. Understanding the interplay between
comminution and liberation is key to achieve an optimum
operation (Wang et al., 2019). Consequently, the commi-
nution circuit should be tailored considering the specific ore
characteristics in order to find a perfect balance of grinding
media, mill speed, particle size (Garcia and Smith, 2017).
Fracture of mineral particles during comminution
can be described as random or non-random, where non-
random breakage can be classified as preferential breakage
(including selective breakage) or phase boundary breakage.
Phase boundary breakage is desirable, as it has the potential
to generate liberation of mineral grains at larger sizes than
with preferential breakage.
High-pressure grinding rolls (HPGR) have been pre-
sented as an alternative to conventional grinding methods
for its influence on liberation mechanisms and enhanced
energy efficiency (Wang et al., 2019). Another technique
that shows promising results is microwave-assisted commi-
nution. It relies on the ability of microwave to heat indi-
vidual phases within the ore matrix, being especially strong
for sulphides, arsenides, sulphonates and sulphoarsenides,
as they are absorbers to the microwave radiation (Kumar
et al., 2006, Garcia and Smith, 2017). The integration
of innovative approaches, such as HPGR or microwave-
assisted comminution further expands the toolkit for opti-
mising mineral liberation. Still, the approach that different
researchers use to assess the impact that different comminu-
tion methods have on liberation remains an open matter of
discussion.
Conventional liberation analysis is considered by
assessing the total mass of mineral in a certain liberation
class. This liberation class is determined by the area libera-
tion across particle surface. More targeted methods of eval-
uating the nature of breakage include use of conservation of
shape, conservation of phase specific interface area (PSIA)
and comparison with random fracture (Little et al., 2016).
