250 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
• Control of ore residence time (unimpeded and stable
flow, etc)
• Control of ore presentation (voidage, segregation,
blockage, etc)
• Isolation of ore load from the applicator space (to
prevent dust build up and potential damage to the
applicator during periods of unstable operation)
The selected method was a mechanically simple, grav-
ity-fed, packed bed, mass flow of ore through a robust,
hard-wearing, microwave transparent (i.e., non-heating)
applicator tube. Proper design of the feed hopper and dis-
charge feeder would enable close control of ore presenta-
tion, residence time, flow stability and force distribution in
the applicator tube.
Buttress et al. (2017) described the as-built large-scale
microwave treatment system capable of operating up to
150 t/h for semi-continuous processing over an order of
several minutes time (6 tonne batch capacity) and utilized
two 100 kW microwave generators, illustrated in Figure 1.
Different feed materials were loaded from bulk bags into
feed bins A01-A04 by jib crane J01. The materials were
then charged or blended onto conveyor C05 by feeding at
different rates from feed bin discharge conveyors C01-C04.
The material was carried to bin A05 by bucket elevator E01
and transfer conveyor C06. Bin A05 was the mass flow
hopper used to feed the microwave applicator tube AT01.
Apron feeder FD01 controlled the throughput and micro-
wave generators M01 and M02 provided microwave power,
the combination of which controlled the specific micro-
wave energy input. FD01 discharged material to slewing
conveyor C08 which swung between four discharge bulk
bags DB01-DB04 over the course of the run.
The system was limited by ore storage capacity at site
(a warehouse in an urban environment), necessitating semi-
continuous operation. However, the system could be made
fully continuous at a larger industrial site or mine site by
changing the materials handling systems. The team had also
designed and provided operational support to another fully
continuous large-scale microwave-assisted ore sorting sys-
tem operating at up to 100 t/h at a mine in the USA around
the same time (Batchelor et al. 2016b, 2016c).
Batchelor et al. (2017) described metallurgical testing
results from the large-scale fracture system, demonstrat-
ing reduced ore competency, improved liberation and the
potential for coarser grinding and values recovery. This
work also validated the small laboratory scale work reported
earlier by Batchelor et al. (2015 2016) at industrial micro-
wave frequency and scale.
Routes to Scale-Up for Microwave Treatment Systems
There are two methods to scale-up microwave treatment
systems, namely using lower microwave frequencies with
single-mode applicators and/or by utilizing multimode
applicators. There are three Industrial, Scientific and
Medical (ISM) frequencies allocated for microwave heat-
ing, namely 2.45 GHz, 896 MHz (in the UK, 922 MHz
INFEED
OUTFEED
J01
C01-C04
A01-A04
DB01-DB04
C08
M01-M02
AT01
FD01
A05
C06
E01
Source: Buttress et al. 2017
Figure 1. Large-scale microwave treatment system
• Control of ore residence time (unimpeded and stable
flow, etc)
• Control of ore presentation (voidage, segregation,
blockage, etc)
• Isolation of ore load from the applicator space (to
prevent dust build up and potential damage to the
applicator during periods of unstable operation)
The selected method was a mechanically simple, grav-
ity-fed, packed bed, mass flow of ore through a robust,
hard-wearing, microwave transparent (i.e., non-heating)
applicator tube. Proper design of the feed hopper and dis-
charge feeder would enable close control of ore presenta-
tion, residence time, flow stability and force distribution in
the applicator tube.
Buttress et al. (2017) described the as-built large-scale
microwave treatment system capable of operating up to
150 t/h for semi-continuous processing over an order of
several minutes time (6 tonne batch capacity) and utilized
two 100 kW microwave generators, illustrated in Figure 1.
Different feed materials were loaded from bulk bags into
feed bins A01-A04 by jib crane J01. The materials were
then charged or blended onto conveyor C05 by feeding at
different rates from feed bin discharge conveyors C01-C04.
The material was carried to bin A05 by bucket elevator E01
and transfer conveyor C06. Bin A05 was the mass flow
hopper used to feed the microwave applicator tube AT01.
Apron feeder FD01 controlled the throughput and micro-
wave generators M01 and M02 provided microwave power,
the combination of which controlled the specific micro-
wave energy input. FD01 discharged material to slewing
conveyor C08 which swung between four discharge bulk
bags DB01-DB04 over the course of the run.
The system was limited by ore storage capacity at site
(a warehouse in an urban environment), necessitating semi-
continuous operation. However, the system could be made
fully continuous at a larger industrial site or mine site by
changing the materials handling systems. The team had also
designed and provided operational support to another fully
continuous large-scale microwave-assisted ore sorting sys-
tem operating at up to 100 t/h at a mine in the USA around
the same time (Batchelor et al. 2016b, 2016c).
Batchelor et al. (2017) described metallurgical testing
results from the large-scale fracture system, demonstrat-
ing reduced ore competency, improved liberation and the
potential for coarser grinding and values recovery. This
work also validated the small laboratory scale work reported
earlier by Batchelor et al. (2015 2016) at industrial micro-
wave frequency and scale.
Routes to Scale-Up for Microwave Treatment Systems
There are two methods to scale-up microwave treatment
systems, namely using lower microwave frequencies with
single-mode applicators and/or by utilizing multimode
applicators. There are three Industrial, Scientific and
Medical (ISM) frequencies allocated for microwave heat-
ing, namely 2.45 GHz, 896 MHz (in the UK, 922 MHz
INFEED
OUTFEED
J01
C01-C04
A01-A04
DB01-DB04
C08
M01-M02
AT01
FD01
A05
C06
E01
Source: Buttress et al. 2017
Figure 1. Large-scale microwave treatment system