Note: Descriptions are shown in the official language in which they were submitted.
CA 02811519 2013-03-18
W02012/034180
PCT/AU2011/001187
1
BLENDING MINED MATERIAL
The present invention relates to a method of
blending mined material to produce a blended product of a
required customer specification.
The mined material may be a metalliferous or a
non-metalliferous material. Iron-containing and copper-
containing ores are examples of metalliferous materials.
Coal is an example of a non-metalliferous material.
The present invention relates particularly
although by no means exclusively to a mined material in
the form of iron ore (and stockpiled iron ore) and is
described hereinafter in this context. However, the
present invention also extends to other mined and
stockpiled materials.
It is known to mine iron ore in large blocks of
the ore from benches. In this conventional mining
operation, typically, the blocks of ore are substantial,
for example 40 m long by 20 m deep by 10 m high and
contain 8000 tonnes of ore. Typically, a section of a
bench is assayed by chemically analysing samples of ore
taken from a series of drilled holes in the section to
determine whether the ore is (a) high grade, (b) low grade
or (c) waste material on a mass average basis. The cut-
offs between high and low grades and between low grade and
waste material are dependent on a range of factors and may
vary from mine to mine and in different sections of mines.
When the analysis is completed, a blockout plan of the
section is prepared. The plan locates the drilled samples
on a plan map of the section. Regions of (a) high grade,
(b) low grade or (c) waste material are determined by
sample analysis (such as chemical assay and/or
mineral/material type abundances) and are marked on the
plan, with marked boundaries separating different regions.
CA 02811519 2013-03-18
W02012/034180
PCT/AU2011/001187
2
The boundaries are also selected having regard to other
factors, such as geological factors. The regions define
blocks to be subsequently mined. The blocks of ore are
blasted using explosives and are picked up from a mine pit
and transported from the mine pit. The ore is processed
inside and outside the mine pit depending on the grade
determination for each block. For example, waste ore is
used as mine fill, low grade ore is stockpiled or used to
blend with high grade ore, and high grade ore is processed
further as required to form a marketable product. The
further processing of high grade ore ranges from simple
crushing and screening to a standard size range through to
processes that beneficiate or upgrade the iron ore to
produce a product of a required customer specification.
The processing may be wet or dry.
A significant proportion of low grade ore is not
blended and remains as stockpiled ore. As a consequence,
there are large stockpiles of mined ore that have been
classified as low grade ore that have potentially
significant economic value notwithstanding the low grade
of the ore.
International application PCT/AU2009/001364
(International publication WO 2010/042994) in the name of
the applicant describes a method of sorting mined
material, such iron ore, including low grade iron ore,
comprising:
(a) determining whether a volume of a material
to be mined is upgradable and mining the volume of
material or determining whether a volume of a material in
a stockpile of mined material is upgradable; and
(b) after suitable size reduction (for example
by crushing and screening) dry sorting the mined or
CA 02811519 2013-03-18
W02012/034180
PCT/AU2011/001187
3
stockpiled material that is determined to be upgradable
and producing an upgraded mined material.
The upgraded mined material may be a product that
meets a required customer specification or may be suitable
to be processed further, for example by blending with
other material, to produce a product of a required
customer specification.
The International application also describes a
dry sorting apparatus for sorting the mined or stockpiled
material that is determined to be upgradable.
The disclosure in the specification of the
International application is incorporated herein by cross-
reference.
The approach of the method of the International
application of determining whether material is upgradeable
is a quite different approach to conventional mining, as
discussed above, which is based on making a mass average
assessment of blocks of ore and categorising the ore as
high grade, low grade, or waste material.
In the International application (and herein) the
term "upgradable" is understood to mean that the mined or
stockpiled material is a material that is capable of being
dry sorted to improve the actual or potential economic
value of the material. The International application
describes what is meant by the term "upgradable" in the
following terms.
"The criteria for deciding whether, a material
(including material to be mined and stockpiled material)
is upgradable is not limited to the grade and may include
factors relevant to a particular mine, such as the
characteristics of the material, and may include other
CA 02811519 2013-03-18
W02012/034180
PCT/AU2011/001187
4
factors such as market requirements for the material. The
material characteristics may include the extent to which
valuable constituents of a material can be liberated, for
example by particle size reduction, the mineral
abundances, and material types.
In some situations the term "upgradable" may be
understood herein to mean that there is a range of grades
in the individual particles making up the material in a
volume of material to be mined, such as a block of the
type described above, whereby some particles are higher
grades than other particles, and there would be a benefit
in separating the volume of material into higher and lower
grade components.
In other situations the term "upgradable" may
also be understood herein to mean that there is a range of
grades of materials in the particles of material in a
stockpile of mined material that has been classified as
low grade material, whereby some particles are higher
grades than other particles, and there would be a benefit
in separating the stockpiled material into higher and
lower grade components.
In other situations the term "upgradable" may
also be understood herein to mean that the material
contains particles of "impurities" within a volume of
material to be mined or in a stockpile. For example, in
the context of coal, the impurities may comprise any one
or more of shale and silica and other ash components.
The term "grade" as used herein is understood to
mean an average of the amount of a selected constituent in
a given volume of particles of a mined material, such as
ore, expressed as a percentage, with the grade calculation
being based on amounts by weight. In the context of iron
ore, grade relates to the percentage by weight of iron and
CA 02811519 2013-03-18
W02012/034180
PCT/AU2011/001187
other constituents of the ore that are considered to be
important by customers. The other constituents include,
by way of example, silica, aluminium, and phosphorous."
5 The
International application describes that the
term "dry sorting" is understood to mean any sorting
process that does not required added moisture for the
purpose of effecting separation.
The term "dry sorting" is understood to have the
same meaning in this specification.
The method and the apparatus described in the
International application makes it possible to recover
value from mined and stockpiled material such as iron ore
that would otherwise be classified as low grade material
or waste material as described above on a mass average
basis. This is particularly the case where the particles
in low grade material or waste material comprise one group
of discrete particles that are above a threshold grade and
another group of discrete particles that are below the
threshold grade. The method and the apparatus also makes
it possible to recover value from mined and stockpiled
material such as coal that contains particles of shale and
silica or other "impurities" by separating coal particles
and these "impurity" particles. The end result is the
production of products to required customer
specifications.
The International application describes that dual
energy x-ray analysis is one option for use in determining
whether a mined material is upgradable. The International
application also describes that dual energy x-ray analysis
is one option for use in dry sorting particles of material
that has been determined to be upgradeable material.
CA 02811519 2013-03-18
W02012/034180
PCT/AU2011/001187
6
International application PCT/AU2009/001179
(International publication WO 2010/025528) in the name of
the applicant describes a method and an apparatus for dual
energy x-ray analysis of a mined material. The term "dual
energy x-ray analysis" is understood herein to mean
analysis that is based on processing data of detected
transmitted x-rays through the full thickness of each
particle obtained at different photon energies. Such
processing makes it possible to minimise the effects of
non-compositional factors on the detected data so that the
data provides clearer information on the composition,
type, or form of the material. The disclosure in the
specification of the International application is
incorporated herein by cross-reference.
The applicant has carried out further research
and development work on the method and the apparatus for
sorting mined or stockpiled material and the method and
the apparatus for dual energy x-ray analysis of a mined or
stockpiled material described in the above International
applications. In particular, the applicant has carried
out further research and development work on a dry sorter
for mined or stockpiled material that uses dual energy x-
ray analysis to assist in determining whether particles of
a mined or stockpiled material are above or below a
threshold grade and then dry sorting the particles of the
material on the basis of the grade determination.
The above description is not to be taken as a
description of the common general knowledge in Australia
or elsewhere.
The applicant has realised that the dry sorting
method and apparatus described in the above International
applications can be used in a wide range of situations in
a mining operation to facilitate the production of a range
of products to required customer specifications. In
CA 02811519 2013-03-18
W02012/034180
PCT/AU2011/001187
7
particular, the applicant has realised that the use of the
dry sorting method and apparatus is not limited to sorting
mined and stockpiled material that has been determined to
be upgradable and extends to any mined material and
stockpiled material. In particular, the applicant has
realised that there are considerable benefits in terms of
production of products to required specifications that can
be achieved in selectively using the dry sorting method
and apparatus in a mining operation for processing some
but not necessarily all of the mined material at a mine
and/or at a shipping facility of the mining operation. In
particular, the applicant has realised that the selective
use of the dry sorting method and apparatus can provide
considerable flexibility to mine operators in scheduling
production to meet customer requirements and to maximise
recovery of value from mines, including stockpiled
material that has been classified as being low grade or
waste material. In particular, the applicant has realised
that the selective use of the dry sorting method and
apparatus can provide considerable flexibility to a mining
operation and make it possible to maintain shipped
tonnages of material to customers in situations where
there are unscheduled disruptions to mining operations at
one or more mines.
In addition to the above, in the context of the
present invention, the applicant has realised that the dry
sorting method and apparatus provides an opportunity for
considerable flexibility for blending mined and/or
stockpiled material from different sections of one mine
and/or from multiple mines to produce a range of different
blended products that meet customer requirements.
Moreover, the applicant has realised that this opportunity
for flexibility extends to dry sorting and blending mined
and/or stockpiled material at locations ranging from the
mines through to customer operations and any locations
between these locations.
CA 02811519 2013-03-18
W02012/034180
PCT/AU2011/001187
8
According to the present invention there is
provided a method of blending mined and/or stockpiled
material from different sections of one mine and/or from
more than one mine that includes dry sorting mined and/or
stockpiled material and producing an upgraded material,
and blending the upgraded material with other material
from the mine and/or with material from one or more than
one other mine and producing the product of the required
customer specification.
According to the present invention there is
provided a method of blending mined and/or stockpiled
material from different sections of one mine and/or from
more than one mine to produce a blended product of a
required customer specification, the method comprising the
steps of:
(a) dry sorting mined and/or stockpiled
material from at least one section of at least one mine in
at least one dry sorter and producing an upgraded
material, and
(b) blending the upgraded material with other
material from the mine and/or with material from one or
more than one other mine and producing the product of the
required customer specification.
The dry sorting step and the blending step may
be carried out at any suitable location or locations.
For example, the dry sorting step and the
blending step may be carried out at a mine or mines, a
shipping facility such as a sea port, or a customer
operation.
CA 02811519 2013-03-18
W02012/034180
PCT/AU2011/001187
9
By way of particular example, in a situation
where the mined and/or stockpiled material is iron ore and
the customer operation is a steel works, the dry sorting
step and the blending step may be carried out at the steel
works. In that situation, the upgraded material may be
blended with other material from the mine or one or more
than one other mine, including mines of other suppliers to
the steelmaker. Dry sorting and blending the iron ore at
the steel works makes it possible to take into account the
parameters of the other material at the steel works and to
operate the dry sorting step to ensure that the blended
product meets the required customer specification.
The blending step may comprise blending (a)
upgraded material from the dry sorter or sorters and (b)
mined and/or stockpiled material that is not dry sorted
material.
The blending step may comprise blending upgraded
material from a plurality of dry sorters only.
The term "upgraded" material as used herein is
understood to mean that the material from the dry sorter
has a higher measure of a selected parameter that is
relevant to the required customer specification than the
average measure of that parameter in the feed material to
the sorter.
In any given situation, the required customer
product specification may be based on any one or more than
one suitable parameter for the product.
For example, the required customer product
specification may be based on any one of more than one of
grade, particle size, particle size distribution, density,
and particle shape.
CA 02811519 2013-03-18
W02012/034180
PCT/AU2011/001187
Grade may be based on one element in the material
or on other elements and/or compounds in the material.
For example, in the case of iron ore, one element may be
iron, another element may be phosphorus, one compound may
5 be alumina, and another compound may be silica.
Typically, the required customer product
specification is a combination of at least two parameters.
10 The blending step may be based on grade to
achieve a required customer specification for product
grade.
The blending step may be based on particle size
to achieve a required customer specification for particle
size.
The blending step may be based on particle size
distribution to achieve a required customer specification
for particle size distribution.
The blending step may be based on density to
achieve a required customer specification for density.
The blending step may be based on particle shape
to achieve a required customer specification for particle
shape.
The blending step may be based on two or more
than two of the above parameters to achieve required
customer specifications for these parameters.
The method may comprise monitoring the operation
the dry sorter or sorters for grade and/or another
parameter that is relevant to the required customer
product specification.
CA 02811519 2013-03-18
W02012/034180
PCT/AU2011/001187
11
The method may comprise controlling the operation
of the dry sorter or sorters to produce upgraded material
having parameters as required for use in the blending step
to produce the blended product of the required customer
product specification.
The method may include controlling the operation
of the dry sorter or sorters using a control system that
monitors all of the material being processed at the mine
or mines that is used in the blending step, including
material that is not being processed in the dry sorter or
sorters, whereby production operators are able to take
into account the parameters of any non-dry sorter feed to
the blending step that are relevant to the blended product
when determining operational settings for the dry sorter
or sorters so that the upgraded material from the dry
sorter or sorters has the required parameters to
facilitate producing the blended product of the required
customer specification when blended with non-dry sorter
material.
The mine or mines may be part of a mining
operation that further comprises a shipping facility for
shipping the product of the required customer
specification to a customer, a transportation link for
transporting material from the mine to the shipping
facility, and a blending facility.
The transportation link may transport to the
shipping facility any one or more of mined material,
stockpiled material, upgraded material produced in the dry
sorter or sorters, and the product of the required
customer specification.
The shipping facility may be a sea port facility,
with capacity for loading one or more than one product
carrier ships.
CA 02811519 2013-03-18
W02012/034180
PCT/AU2011/001187
12
The shipping facility may be a rail facility,
with capacity for loading one or more than one product
rail trains.
The transportation link may be a railway line
and/or a roadway system.
The blending facility may be at any suitable
location.
The upgraded material from the dry sorter or
sorters may be any appropriate percentage by weight of the
total production from the mine or mines having regard to
relevant factors including capital and operating costs of
equipment and the required customer specifications and the
properties of the mined material at the mine or mines.
The upgraded material from the dry sorter or
sorters may be less than 25% by weight of the total
production from the mine or mines.
The upgraded material from the dry sorter or
sorters may be less than 20% by weight of the total
production from the mine or mines.
The upgraded material from the dry sorter or
sorters may be less than 15% by weight of the total
production from the mine or mines.
The basis of operation of a dry sorter may be
changed as required from time to time.
For example, the dry sorter may be operated for a
period of time having regard to a particular element in
the material that is relevant for one customer
specification and may be operated for another period of
CA 02811519 2013-03-18
W02012/034180
PCT/AU2011/001187
13
time having regard to another element in the material that
is relevant for another customer specification.
By way of further example, a threshold grade for
a given element may be increased or decreased over time
depending on the grade of that element in other mined or
stockpiled material from the same mine and/or from other
mines that is used in the blending step.
The upgraded material from the dry sorter or
sorters may be processed further to facilitate production
of the blended product to the required customer
specification. For example, the upgraded material may be
subjected to size reduction, for example in a crusher, to
a required particle size range. By way of further
example, the upgraded material may be subjected to further
sorting operations. The further sorting operations may be
wet or dry sorting operations.
The material supplied to the dry sorter or
sorters may be mined or stockpiled material that has been
assessed as being upgradable material, as described
herein.
In the event that the dry sorter or sorters are
operated to sort upgradable material, the mining operation
may include analysis of material to be mined or of
material in existing stockpiles of mined material to
determine whether the material is upgradable material.
The analysis may comprise taking a plurality of
samples, such as drilled samples, from a volume of
material to be mined, such as a block of ore of the type
described above, prior to mining the material and
analysing the samples, for example by determining the
grade of each of the samples, and making an assessment of
whether the ore in the volume of ore is upgradable.
CA 02811519 2013-03-18
W02012/034180
PCT/AU2011/001187
14
The analysis may also comprise taking a plurality
of samples from a stockpiled material and analysing the
samples, for example by determining the grade of each of
the samples, and making an assessment of whether the
material in the stockpiled material is upgradable.
The number of samples required in any given
situation will depend on factors relating to a particular
mine or a section of the mine to be mined.
Any suitable technique may be used to analyse the
samples in the analysis step.
The dry sorter or sorters may use any suitable
analytical technique to determine the basis for sorting
particles of material being processed in the sorter.
There may be a correlation between the analysis
technique used in the analysis step and the dry sorter or
sorters.
One suitable analytical technique for the
analysis step and the dry sorter or sorters is dual energy
x-ray analysis. Other analytical techniques include, by
way of example, x-ray fluorescence, radiometric,
electromagnetic, optical, and photometric techniques. The
applicability of any one or more of these (and other)
techniques will depend on factors relating to a particular
mine ore or a section of the mine to be mined.
The dry sorter may be adapted to dry sort on the
basis of analysis of a parameter, such as grade, of
individual particles of the material.
The material may be mined by any suitable mining
method and equipment. For example, the material may be
CA 02811519 2013-03-18
W02012/034180
PCT/AU2011/001187
mined by drilling and blasting blocks of ore from a pit
and transporting the mined ore from the pit by trucks
and/or conveyors. By way of further example, the material
may be mined by surface miners moving over a pit floor and
5 transported from the pit by trucks and/or conveyors.
The present invention also provides a method of
producing a product of a required customer specification
in the above-described mining operation, which method
10 includes mining material from at least one mine,
transporting material from the mine or the mines to a
shipping facility, and shipping a product of the required
customer specification, to a customer, and which method
also includes processing at least some of the material at
15 the mine or mines or at the shipping facility in at least
one dry sorter and producing an upgraded mined material,
and producing at least some of the product of the required
customer specification by blending upgraded material and
other material from the mine of the mines.
The present invention is described further with
reference to the accompanying drawings, of which:
Figure 1 is an example of a blockout plan for a
section of a mine bench in a conventional mining
operation, with the Figure being Figure 1 of the
specification of International application
PCT/AU2009/001364;
Figure 2 is one embodiment of a mining operation
in accordance with the present invention; and
Figure 3 is a flowsheet illustrating one,
although not the only, embodiment of the method and an
apparatus for sorting ore in accordance with the present
invention, with the Figure being Figure 2 of the
CA 02811519 2013-03-18
WO 2012/034180
PCT/AU2011/001187
16
specification of International application
PCT/AU2009/001364.
The description of the invention is in the
context of a mined material in the form of iron ore. It
is noted that the invention is not confined to iron ore
and extends to other mined materials containing valuable
components. The invention relates generally to mined
metalliferous and non-metalliferous materials. In
addition to iron ore, copper is an example of a
metalliferous material. Coal is an example of a non-
metalliferous material.
Figure 1 is a blockout plan for a section 51 of a
bench in an open pit iron ore mine operating as a
conventional mine. The plan shows the locations of a
series of drilled holes 53 (indicated by crosses) that
have been drilled to obtain samples. The samples are
analysed to determine the grade of ore in the samples.
The plan also shows assayed and is marked with a series of
boundaries 55 that divide the section into a series of
blocks 57 on the basis of whether the ore in the blocks is
determined by the sample analysis to be (a) high grade,
(b) low grade or (c) waste material based on ore grade.
There are six blocks 57 shown in the Figure. High grade
blocks 57 are referred to as "HG", low grade blocks are
referred to as "LG", and waste blocks are referred to as
"W" in the Figure. The cut-offs between high and low
grades and between low grade and waste material are
dependent on a range of factors and may vary from mine to
mine and in different sections of mines. Each block 57 of
ore is blasted using explosives and is picked up from a
mine pit and transported from the mine pit. The ore is
processed inside and outside the mine pit depending on the
grade determination for each block. For example, waste
ore is used as mine fill, low grade ore is stockpiled or
used to blend with high grade ore, and high grade ore is
CA 02811519 2013-03-18
W02012/034180
PCT/AU2011/001187
17
processed further as required to form a marketable
product. The processing may be wet or dry.
In a conventional iron ore mining operation, the
low grade ore blocks are not usually blended with other
ore and are stockpiled and not sold and hence represent
significant lost economic value. However, some or all of
these blocks and existing stockpiles of previously mined
ore that has been classified as low grade material, may be
suitable for upgrading in accordance with the present
invention and are processed, including dry sorted, by way
of example with reference to the flowsheet of Figure 3.
As is described above, International application
PCT/AU2009/001364 describes an alternative approach to
mining material which, in the context of iron ore, is
based on assessing whether an ore to be mined or a
stockpiled ore is "upgradable", with an assessment of
whether an ore is upgradable being based on a number of
factors. The factors include whether the ore particles
can be sorted into particle streams that are above or
below a threshold grade. Upgradable ore includes ore that
has discrete particles that are above the threshold grade
and discrete particles that are below the threshold grade.
The assessment may include assessing the extent to which
size reduction of ore can separate ore into such discrete
particles. Ore that has finely disseminated iron through
all the particles is generally not upgradeable.
The present invention is based on a realisation
of the applicant that dry sorters, particularly dry
sorters that process ore to be mined or stockpiled ore
that is upgradable and would otherwise be classified as
low grade ore on the basis of conventional mining
methodology, can provide a mining operation with
considerable flexibility to blend mined and/or stockpiled
ore to produce a range of blended products having required
CA 02811519 2013-03-18
W02012/034180
PCT/AU2011/001187
18
customer specifications and to maintain maximum shipped
ore tonnages in situations where there are interruptions
to scheduled operation at one or more mines. In
particular, the present invention is based on a
realisation of the applicant that this opportunity for
flexibility extends to dry sorting and blending mined
and/or stockpiled material at locations ranging from the
mines through to customer operations and any locations
between these locations.
With reference to Figure 2, the embodiment of the
mining operation in accordance with the invention
illustrated in the Figure comprises three iron ore mines
identified by the numerals "1", "2" and "3". Each of the
mines produces crushed iron ore of a required particle
size range for customer product requirements that is
transported by trains to a shipping facility in the form
of a sea port. The ore is unloaded from the trains into
stockpiles. The stockpiled material is subsequently
loaded onto ships and transported to customers in
Australia and overseas. Each of the mines is operated to
load trains with iron ore of a selected grade, which may
be different for different mines. The basis of the
selection is that the ore on the trains can be blended to
produce blended ore of the required customer
specification. As is illustrated in the Figure, at the
particular point in time of the mining operation captured
by the Figure, mine 1 produces trains of ore of grade "A",
mine 2 produces trains of ore of grade "B", and mine 3
produces trains of ore of grade "C". The unloading
sequence of the trains is controlled to blend the ore so
that the stockpiles comprise ore of the required customer
specification in terms of ore grade. The operation of the
mines is monitored and controlled to produce ore of
selected grades that can be blended at the port to produce
a product of the required customer specification. Each of
the mines includes one or more than one dry sorter, such
CA 02811519 2013-03-18
W02012/034180
PCT/AU2011/001187
19
as a dry sorter operating on the basis of dual energy x-
ray analysis, such as described in International
application PCT/AU2009/001179, for sorting mined or
stockpiled ore that has been assessed as "upgradable" as
described above. Each of the mines also mines and
processes mined and stockpiled ore in accordance with
conventional mining practice of categorising blocks of
ores as high grade, low grade, and waste material based on
mass average assessment of the blocks. In the case of mine
1 the dry sorter(s) at the mine processes 10% of the mined
material in the sorter. In the case of mine 2 the dry
sorter(s) at the mine processes 15% of the stockpiled ore
in the sorter. In the case of mine 3 the dry sorter(s) at
the mine processes 10% of the total mined production from
mined and stockpiled ore in the sorter. The mining
operation also includes a control system that monitors the
production from the mines in terms of the parameters for a
given required customer product specification. These
parameters may include grade, particle size, particle size
distribution, density, and particle shape. In the
present embodiment, grade is the key parameter. The grade
may be the iron content. The grade may be the content of
other elements and compounds in iron ore. One such
element is phosphorous. One such compound is silica.
Another compound is alumina. The parameters also include
the required tonnage of the product for the customer. The
control system assesses the output in terms of grade from
the dry sorters that is required to produce upgraded ore
from the sorters that, when blended with other ore
produced from the mines, produces the blended product of
the required customer specification. The control system
adjusts the operation of the dry sorters as required to
produce the upgraded material of the required grade (or
other selected parameter or parameters). For example, the
control system may adjust a threshold grade for ore, with
ore above the threshold grade being upgraded material and
ore below the threshold grade being waste material. It
CA 02811519 2013-03-18
W02012/034180
PCT/AU2011/001187
can be appreciated that the dry sorters operate to tune
the mine production to smooth out perturbations in the
grade of the other material supplied to the blending
facility to make it possible to produce on-specification
5 product. By way of particular example, in a situation
where the bulk of the ore from mine 1 is below a required
customer specification for the ore grade, the dry
sorter(s) at mine 1 and/or the other mines may be operated
to provide upgraded ore that is above the required
10 customer grade to blend with the ore that is below the
required customer grade and produce on-specification
product. This is a particularly useful outcome where the
upgraded ore comes from stockpiles that are categorised as
low grade. Such use of low grade ore optimises recovery
15 of value from the mining operation.
The flowsheet shown in Figure 3 is one
embodiment of a dry sorting operation that includes the
use of a dry sorter as described above.
The flowsheet shown in Figure 3 is described in
the context of ore that has been transported from a mine
pit to a primary crusher 3 and is crushed in the crusher.
It is noted that the invention also extends to situations
in which the ore is crushed and sorted in the mine pit.
With reference to Figure 3, the crushed ore from
the primary crusher 3 is supplied to a scalping screen 5,
for example in the form of a vibrating screen, that
separates the ore on the basis of particle size into an
oversize fraction of +75 mm and an undersize fraction of -
75 mm.
The oversize fraction from the scalping screen 5
is transferred to a secondary crusher 7 and, after size
reduction in the crusher, is transferred back to the
stream from the primary crusher 3.
CA 02811519 2013-03-18
W02012/034180
PCT/AU2011/001187
21
The undersize fraction from the scalping screen 5
3 is transferred to a downstream scalping screen 9, for
example in the form of a vibrating screen, that separates
the ore on the basis of particle size into an oversize
fraction of 8-75 mm and an undersize fraction of -8mm.
The undersize fraction from the scalping screen 9
is a fines stream that is transferred for further wet or
dry processing.
The oversize fraction from the scalping screen 9
is transferred to a product screen 11, for example in the
form of a vibrating screen. The product screen 11
separates the ore on the basis of particle size into an
oversize fraction of 32-75 mm and an undersize fraction of
-32 mm.
The oversize fraction from the product screen 11
is transferred to the secondary crusher 7 and, after size
reduction in the crusher, is transferred back to the
stream from the primary crusher 3.
The undersize fraction from the product screen 11
is transferred to downstream product screen 13 that
separates the ore on the basis of particle size into an
oversize fraction of 8-32 mm and an undersize fraction of
-8 mm.
The undersize fraction from the product screen 13
is a fines stream that is transferred for further
processing with the undersize fraction from the scalping
screen 9.
The oversize fraction from the product screen 13
is a product stream, at least in terms of particle size
distribution.
CA 02811519 2013-03-18
W02012/034180
PCT/AU2011/001187
22
The oversize fraction from the product screen 13
is transferred to an ore sorter 15 and the particles are
sorted on the basis of ore grade, i.e. average
composition, of the particles into two streams. The
sorter 15 may be a sorter that uses dual x-ray analysis or
any other suitable analytical technique to determine ore
grade of particles processed in the sorter. One stream,
referred to as "lump" in the Figure, from the ore sorter
15 comprises ore that has an iron concentration above a
threshold ore grade, for example 63 wt. % Fe. This stream
is a required product stream, in terms of particle size
distribution and composition, and forms a marketable
product or a product that can be blended with other ore
streams to produce a marketable product. The other
stream, referred to as "rejects" in the Figure, from the
ore sorter 15 comprises ore that has an iron concentration
below a threshold ore grade, for example 63 wt.% Fe. This
stream is transferred to a stockpile to be used, for
example, as land fill.
A key feature of the above-described flowsheet is
of Figure 3 that the grade sorting step is carried out
only on the ore that is in the required product particle
size distribution, i.e. the 8-32 mm size fraction. This
fraction is an oversize fraction from the product screen
and there is no ore sorting of fines.
The above-described embodiment is an example of
a number of possible embodiments for sorting ore in a dry
sorter. There is a large number of other possible
embodiments, each of which has particular features that
may be appropriate depending on the requirements of a
particular mining operation.
Many modifications may be made to the embodiment
of the present invention described above in relation to
CA 02811519 2013-03-18
W02012/034180
PCT/AU2011/001187
23
Figures 2 and 3 without departing from the spirit and
scope of the invention.
By way of example, whilst the embodiment of the
sorter shown in Figure 3 describes particular size
fractions, the present invention is not so limited and
extends to separating ore into any suitable size fractions
for a particular mine and mining operation and downstream
market requirements. Specifically, it is noted that the
present invention is not confined to the specific product
size fractions described in relation to the embodiment.
In addition, whilst the embodiment of the sorter
shown in Figure 3 describes a particular product grade,
the present invention is not so limited and extends to any
suitable grades for a given market.
