XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 125
BEYOND THE CURRENT STATUS
For future circuits, it is the orebody specific and custom-
ized combination of comminution, separation and, benefi-
ciation (inc. preconcentration) equipment, that will deliver
the required metal recovery, whilst being the most effective
in terms of energy and water.
In order to optimize beneficiation, the role of com-
minution has always been to deliver streams suited to the
characteristics of the beneficiation equipment and this does
not change. What can and will change further is that pro-
cess equipment/methods such as Coarse Particle Flotation
(via new or modified equipment), CiDRA P29 and other
methods can target the coarser size fractions, whilst exist-
ing or variants thereof, can be deployed to more efficiently
treat the finer fractions. What needs to be understood for
any orebody on a size fraction basis are what proportions
are considered coarse and fine and across the size fractions
what percentage of particles are locked or accessible, and
importantly how can comminution effect changes that can
be exploited by new and improved beneficiation methods.
Beyond modifying the size distribution, the future
options must consider the potential to enhance liberation
behavior. Microwave and EPD techniques have been men-
tioned earlier in this paper on the basis of offering enhanced
comminution. In the case of the S.H.O.T. microwave sys-
tem, it stands on the verge of continuous field scale deploy-
ment and it should be hoped that others including EPD
will do the same in the medium term. The key consider-
ation within future flowsheets is how these can be deployed
to allow short-cuts to liberation and recovery that would
otherwise require much greater energy input. As with any
of the equipment discussed above, blanket application of
targeted recovery methods should not be the aim. In a typi-
cal base metals ore feed, the percentage of particles where
the target mineral is locked, or otherwise inaccessible, at a
traditional primary grind size, may only be 15–25%. If this
locked value can be accessed either at existing grind sizes, or
preferably at coarser grind sizes, then there is potential for
significant reductions in comminution energy.
Engineering customized circuits requires a very strong
understanding of content and composition of particles
in individual streams. Any evaluation approach must use
evidence-based decisions on the equipment to be deployed
and the positions in the circuit, on the basis of size, grade,
mass yield and recovery. As part of the full understanding
and economics, the evaluation must also be cognizant of
the impact of feed variability and heterogeneity on overall
process performance and project economics.
As previously mentioned, testwork and modelling play
a major role in this assessment, but equally a deeper, higher
resolution view of the ore heterogeneity is also required.
In terms of comminution, the ability to test far greater
numbers of samples using automated methods is a recent
development that would appear critical to the improved
definition of strength variation and therefore what flexibility
customized comminution circuits will need to incorporate.
CONCLUSIONS
The relationship between comminution and energy con-
sumption have traditionally been the basis for much of
the negative press related to comminution. The projected
increase in minerals extraction and therefore energy con-
sumption, further animates the discussions.
As noted by Morrell (2023), the more rational discus-
sion needs to be focused on emissions and the improved
definition of the contribution of comminution. Through
this lens, the move to low emission power generation is
likely to heavily compensate for the expected increase in
comminution energy consumption, related to the extra
demand for minerals. The overall CO2 emissions from
comminution may therefore, only rise slightly from exist-
ing levels, or even decrease, if projections of low carbon
energy generation are met.
Table 1. Comparison of SABC circuit with alternatives, SLR, (2023)
Metric
Conventional
SABC circuit Circuit 1 Circuit 2 Circuit 3
Power drawn (kW) 44,012 31,461 27,640 25,730
Energy consumption (MWh/y) 345,480 243,354 213,229 198,171
Grinding media consumption (t/y) 13,170 6,780 1,062 911
Operating emissions (tCO
2 e/y) 145,032 102,160 89,514 83,192
Grinding media emissions (tCO2e/y) 30,028 15,458 2,421 2,077
Total emissions (tCO2e/y) 175,060 117,618 91,934 85,269
%gain relative to SABC SABC HPGR +BM HPGR +VSM HPGR +VSM +CPF
%Energy avoided 0% 30% 38% 43%
%CO2e avoided 0% 33% 47% 51%
BEYOND THE CURRENT STATUS
For future circuits, it is the orebody specific and custom-
ized combination of comminution, separation and, benefi-
ciation (inc. preconcentration) equipment, that will deliver
the required metal recovery, whilst being the most effective
in terms of energy and water.
In order to optimize beneficiation, the role of com-
minution has always been to deliver streams suited to the
characteristics of the beneficiation equipment and this does
not change. What can and will change further is that pro-
cess equipment/methods such as Coarse Particle Flotation
(via new or modified equipment), CiDRA P29 and other
methods can target the coarser size fractions, whilst exist-
ing or variants thereof, can be deployed to more efficiently
treat the finer fractions. What needs to be understood for
any orebody on a size fraction basis are what proportions
are considered coarse and fine and across the size fractions
what percentage of particles are locked or accessible, and
importantly how can comminution effect changes that can
be exploited by new and improved beneficiation methods.
Beyond modifying the size distribution, the future
options must consider the potential to enhance liberation
behavior. Microwave and EPD techniques have been men-
tioned earlier in this paper on the basis of offering enhanced
comminution. In the case of the S.H.O.T. microwave sys-
tem, it stands on the verge of continuous field scale deploy-
ment and it should be hoped that others including EPD
will do the same in the medium term. The key consider-
ation within future flowsheets is how these can be deployed
to allow short-cuts to liberation and recovery that would
otherwise require much greater energy input. As with any
of the equipment discussed above, blanket application of
targeted recovery methods should not be the aim. In a typi-
cal base metals ore feed, the percentage of particles where
the target mineral is locked, or otherwise inaccessible, at a
traditional primary grind size, may only be 15–25%. If this
locked value can be accessed either at existing grind sizes, or
preferably at coarser grind sizes, then there is potential for
significant reductions in comminution energy.
Engineering customized circuits requires a very strong
understanding of content and composition of particles
in individual streams. Any evaluation approach must use
evidence-based decisions on the equipment to be deployed
and the positions in the circuit, on the basis of size, grade,
mass yield and recovery. As part of the full understanding
and economics, the evaluation must also be cognizant of
the impact of feed variability and heterogeneity on overall
process performance and project economics.
As previously mentioned, testwork and modelling play
a major role in this assessment, but equally a deeper, higher
resolution view of the ore heterogeneity is also required.
In terms of comminution, the ability to test far greater
numbers of samples using automated methods is a recent
development that would appear critical to the improved
definition of strength variation and therefore what flexibility
customized comminution circuits will need to incorporate.
CONCLUSIONS
The relationship between comminution and energy con-
sumption have traditionally been the basis for much of
the negative press related to comminution. The projected
increase in minerals extraction and therefore energy con-
sumption, further animates the discussions.
As noted by Morrell (2023), the more rational discus-
sion needs to be focused on emissions and the improved
definition of the contribution of comminution. Through
this lens, the move to low emission power generation is
likely to heavily compensate for the expected increase in
comminution energy consumption, related to the extra
demand for minerals. The overall CO2 emissions from
comminution may therefore, only rise slightly from exist-
ing levels, or even decrease, if projections of low carbon
energy generation are met.
Table 1. Comparison of SABC circuit with alternatives, SLR, (2023)
Metric
Conventional
SABC circuit Circuit 1 Circuit 2 Circuit 3
Power drawn (kW) 44,012 31,461 27,640 25,730
Energy consumption (MWh/y) 345,480 243,354 213,229 198,171
Grinding media consumption (t/y) 13,170 6,780 1,062 911
Operating emissions (tCO
2 e/y) 145,032 102,160 89,514 83,192
Grinding media emissions (tCO2e/y) 30,028 15,458 2,421 2,077
Total emissions (tCO2e/y) 175,060 117,618 91,934 85,269
%gain relative to SABC SABC HPGR +BM HPGR +VSM HPGR +VSM +CPF
%Energy avoided 0% 30% 38% 43%
%CO2e avoided 0% 33% 47% 51%