Note: Descriptions are shown in the official language in which they were submitted.
NS-573
BLENDING MINED OIL SAND ORES FOR BITUMEN EXTRACTION OPERATIONS
FIELD OF THE INVENTION
The present invention relates to mining technology and, in particular,
decoupling real-
time mining of oil sand ore from bitumen extraction operations to enable
favorable oil sand ore
blending by using a stockyard where blending and storing of oil sand ores can
occur.
BACKGROUND OF THE INVENTION
Oil sand ore, such as is mined in the Fort McMurray region of Alberta,
generally
comprises water-wet sand grains held together by a matrix of viscous bitumen.
Typically, a "low
grade" oil sand ore will contain between about 6 to 10 wt.% bitumen with about
25 to 35 wt.%
fines. An "average grade" oil sand ore will typically contain at least 10 wt.%
bitumen to about
12.5 wt.% bitumen with about 15 to 25 wt.% fines and a "high grade" oil sand
ore will typically
contain greater than 12.5 wt.% bitumen with less than 15 wt.% fines. "Fines"
are generally
defined as those solids having a size less about 44 m.
Oil sand lends itself to liberation of the sand grains from the bitumen,
preferably by
slurrying the oil sand with heated water, allowing the bitumen to move to the
aqueous phase.
For many years, the bitumen in the McMurray sand has been commercially removed
from oil
sand using what is commonly referred to in the industry as the "hot water
process". In general
terms, the hot water process involves dry mining the oil sand at a mine site
that can be kilometers
from an extraction plant; transporting the as-mined oil sand in large ore
trucks to a primary
crushing plant; conveying the crushed ore to a slurry preparation plant where
the oil sand is
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mixed with hot water, caustic (e.g., sodium hydroxide) and naturally entrained
air to yield an oil
sand slurry; "conditioning" the oil sand slurry (for example, in a
hydrotransport pipeline) so that
lumps of oil sand are ablated or disintegrated, the released sand grains and
separated bitumen
flecks are dispersed in the water where the bitumen flecks coalesce and grow
in size, and the
bitumen flecks may contact air bubbles and coat them to become aerated
bitumen; and removing
the bitumen froth from the slurry in an extraction plant comprising one or
more separators (for
example, a primary separation vessel or PSV).
Currently, most oil sand mining operations use trucks and shovels to mine the
oil sand
ore from the mine face and transport the mined ore to a primary crusher/slurry
preparation plant.
To date, most primary crushers and slurry preparation plants are fixed, i.e.,
not readily
relocatable. In the applicant's mining operation, the average haul distance is
currently 4-5 km.
However, future ore bodies would require truck hauls of 10-20km to existing
primary crusher
locations. Thus, the costs of mining will be increasing due to the long
distances and outward
migration of mining faces away from fixed plants. The reliance on "on-time
delivery" of ore
from haul trucks and the need to apply appropriate ore blending prior to
slurry preparation makes
it ever more difficult to manage costs. Hence, the truck and shovel mining
operation may suffer
from lower productivity due to these two constraints.
Under present operations, oil sand ore blending occurs in "real time", i.e.,
when the haul
trucks unload the ore into the primary crusher. This is done to ensure a
continuous supply of ore
to the slurry preparation plant. Since most crushers can only accommodate two
truckloads
(payloads) of ore at a time, one can only achieve a 50-50 blend of two ores.
However, there are
instances when further blending would be optimal to achieve the desired
processability of the
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ore. Thus, the extraction operation suffers from lower recovery due to less
than optimum ore
blending.
In the face of ever-increasing presence of poorer ore grades, ore blending has
become
even more important to maintain acceptable bitumen recovery rates. However, as
currently
practiced, mining productivity suffers because of the increased demand for
improved ore
blending. Thus, there is a need in the industry for improved ore blending
without sacrificing
mining productivity.
In addition, under present operations, trucks are often queued up to make sure
the right
blend of ore is obtained. However, this can result in wait times of up to
three minutes or more
which may result in a loss of up to 200,000 payloads of opportunity. Thus,
there is a further
need in the industry to decouple the mining operation from the extraction
operation to avoid wait
times for haulers to dump their load.
Finally, the present invention allows for the placement of haul destinations
closer to the
active mine area.
SUMMARY OF THE INVENTION
The present invention is directed to a process and process line that
effectively decouples
'real-time' oil sand ore mining from bitumen extraction operations to enable
quality oil sand ore
blending. Thus, the present invention may result in one or more of the
additional benefits: lower
capital costs; lower operating costs; lower relocation costs; compact and
readily placed 'in-pit';
and minimal construction area lead time (i.e. no civil mega-projects).
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In one aspect, a process line is provided for mining and blending oil sand
ore,
comprising:
= a plurality of shovels for mining oil sand ore at at least two separate
mine faces,
wherein at least one shovel is mining oil sand at a first mine face and at
least one
shovel is mining oil sand at a second mine face;
= a plurality of haul trucks for receiving oil sand ore, whereby at least
one haul truck is
receiving oil sand ore from a shovel mining at the first mine face and at
least one
haul truck is receiving oil sand ore from a shovel mining at the second mine
site;
= an open stockyard for blending and stockpiling the oil sand ore, where
blending of
oil sand ore is managed by each haul truck dumping at a dispatched coordinate
on the
perimeter of the stockyard; and
= a device which moves the oil sand ore from the perimeter of the stockyard
into the
stockyard to form at least one stockpile of blended ore.
Hence, once the at least one stockpile is formed, the blended ore from the
stockpile can be
continuously fed to a primary crusher for crushing prior to oil sand slurry
preparation at a slurry
preparation plant. The at least one stockpile is then continuously replenished
with new ore being
delivered by the haul trucks.
In one embodiment, it may be desirable to have the stockyard located at or
near the mine
face. In this embodiment, it is preferable that the primary crusher is a semi-
mobile crusher. In
one embodiment, the slurry preparation plant is also relocatable.
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In another aspect, a method for blending at least two different oil sand ores,
each oil sand
ore having a different grade, is provided, comprising:
= providing at least one haul truck for each oil sand ore for delivering
the oil sand ore
to a designated area;
= mapping out a grid on the designated area indicating locations where each
ore sand
ore is to be deposited;
= mixing the oil sand ore in the designated area to form a stockpile
comprising a
substantially uniform grade of blended oil sand ore.
BRIEF DESCRIPTION OF THE DRAWINGS
Referring to the drawings wherein like reference numerals indicate similar
parts
throughout the several views, several aspects of the present invention are
illustrated by way of
example, and not by way of limitation, in detail in the following figures. It
is understood that the
drawings provided herein are for illustration purposes only and are not
necessarily drawn to
scale.
Fig. 1 is a schematic depiction of one embodiment of the process line of the
present
invention.
Figs. 2A and 2B are schematic depictions of oil sand ore blending according to
the
present invention.
Figs. 3A and 3B are aerial and side views, respectively, of a stockyard
according to an
embodiment of the present invention.
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Figs. 4A and 4B are an aerial view of a stockyard according to another
embodiment of
the present invention and a map illustrating where four different oil sand
ores are to be placed on
the perimeter of a stockyard according to the present invention, respectively.
Fig. 5 is an aerial view of a low complexity stockyard of the present
invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
The detailed description set forth below in connection with the appended
drawings is
intended as a description of various embodiments of the present invention and
is not intended to
represent the only embodiments contemplated by the inventor. The detailed
description includes
specific details for the purpose of providing a comprehensive understanding of
the present
invention. However, it will be apparent to those skilled in the art that the
present invention may
be practiced without these specific details.
As used herein, "semi-mobile" equipment refers to equipment that is designed
to be
relatively easy to relocate (i.e., relocateable) but which generally does not
move on a regular
hourly or daily basis as mobile shovels and trucks do.
Fig. 1 illustrates one embodiment of the present process line. In this
embodiment, mine
face 2 is a mine face in a mineable oil sand mine or pit. However, it is
understood that in the
present invention there are at least two mine faces that are being excavated
at the same time,
each mine face being located in different locations within a mine pit. A
mining shovel 3 is used
to excavate the oil sand ore at the mine face 2 and it is operative to advance
along the mine face
2 and deposit the as-mined oil sand ore into mobile trucks 4. The mobile
trucks 4 deliver the as-
mined oil sand ore to a common stockyard 5 where the oil sand ore is blended
to provide a
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substantially homogenous mixture of the oil sand ores from the at least two
mine faces
(stockpile). Blended oil sand ore is then excavated from the stockpile using
shovel 6 and
delivered to a mobile crushing station 7.
In the embodiment shown in Fig. 1, the mobile crushing station 7 generally
comprises a
receiving hopper, an integral rock crusher and discharge conveyor that is
movable under its own
power and may receive and comminute excavated/mined oil sand ore from a
shovel. A metal
detection system may be installed on the discharge conveyor of the mobile
crushing station, and
a kick-out mechanism may be used to dump the portion of crushed ore containing
metal on the
ground, rather than transferring it to conveyor 8. Conveyor 8 receives the
comminuted oil sand
ore from the discharge conveyor of the mobile crushing station and delivers
the comminuted oil
sand ore to compact slurry plant 10 which comprises a semi-mobile slurry
preparation unit 9. In
this embodiment, the semi-mobile compact slurry preparation unit 9 is a wet
crushing unit as
described in Canadian Patent No. 2,480,122. Semi-mobile compact slurry
preparation unit can
be moved by means of tracks 11, so that the entire unit may periodically be
advanced to a new
location. It is understood, however, that any semi-mobile, relocatable slurry
preparation unit or
assembly can be used. Thus, the oil sand slurry preparation step can be moved
as close as
possible to mine face 2, i.e., in-pit or near-pit crest.
Oil sand slurry prepared in the semi-mobile compact slurry preparation unit 9
can then be
transported and conditioned in hydrotransport pipeline 28. Hydrotransport
pipeline 28 is
.. generally around 3 km in length, its length being sufficient to ensure
proper conditioning of the
oil sand slurry. Thus, hydrotransport pipeline 28 receives oil sand slurry
from semi-mobile
compact slurry preparation unit 9, transports the slurry while simultaneously
conditioning it, and,
optionally, delivers the conditioned slurry to a screening assembly 40 for
removing a portion of
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the coarse solids, in particular, clay lumps and rocks, therefrom. Screening
assembly 40
comprises a slurry screen for scalping/removal of wear-inducing lumps in the
conditioned slurry
down to a nominal size (e.g. about 12 to 15mm and larger is removed).
Screening assembly 40
may be relocatable by means of tracks 27. In one embodiment, the screening
assembly 40 may
be positioned further upstream, i.e., along the hydrotransport pipeline 28,
before the oil sand
slurry is fully conditioned. There may be instances where it is more desirable
to remove the clay
lumps and rocks as soon as possible, so there will be an optimal screening
assembly location,
where oil sand lumps have been ablated just below the screen cut size, for
example, 1.5-2.5 km
from the start of the hydrotransport pipeline 28.
The screened slurry 28 can optionally be further desanded using a semi-mobile
solids
removal assembly 29 for removing coarse sand therefrom. In one embodiment,
semi-mobile
desanding assembly 29 comprises a near pit desander (NPD), or separator, as
described in
Canadian Patent Application No. 2,809,959. In this embodiment, NPD is moveable
by means of
tracks 37. It is understood, however, that other moveable desanders or
desanding circuits can be
used.
The semi-mobile desanding assembly 29 produces a relatively clean (i.e.,
relatively free
from bitumen) coarse solids underflow 31, which only needs to be transported a
short distance to
sand storage 32. The reduced solids upper zone or overflow 30 comprises
bitumen, fines and
water and is amenable to long distance transport through a pipeline to a
bitumen extraction plant
for polishing/water reheat and return. It was discovered that desanded oil
sand slurry could be
pumped long distances, has a lower power constraint and produces low wear on
downstream
equipment.
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Operating cost for a slurry pumping system is relative to the mass
transported. Thus, by
removing 70% to 90% of the solids, the required energy, wear and capital costs
all decline
significantly. The resulting de-sanded slurry is also much easier to transport
over long distances.
The desanding vessel would be optimally located near the tailings deposition
area, which may be
an exhausted mine pit, to minimize the total transport distance of the coarse
solids. In addition,
by removing much of the sand prior to bitumen extraction, a higher quality and
lower solids
product would be delivered to extraction facilities. This would result in a
higher residence time
in separation vessels (such as existing PSVs) due to a reduction of flow rate,
as a large fraction
of flow has been diverted at the desander. In turn, this would result in
bitumen yield uplift, as
product quality is improved down the entire process stream.
One embodiment of oil sand ore blending is described in more detail with
reference now
to Figs. 2A and 2B. In this particular embodiment, four different oil sand
ores, each being of a
different grade, have been excavated from four distinct mine faces within a
mine pit and
delivered to stockyard 205. Stockyard 205 comprises a dug out pit 244 and a
bench 246. As
.. shown in Fig. 2A, haul truck 204 is hauling oil sand ore 240, which has
been excavated from a
first mine site, and dumping its payload to form ore pile 242 on bench 246. As
shown in Fig.
2A, there are three additional ore piles comprising three different ore types,
namely, ore pile
242', ore pile 242", and ore pile 242"1. Once piles are formed, each pile
comprising the
appropriate amount of particular oil sand ores for optimal blending to occur,
the piles are then
moved from bench 246 by bulldozer 248 into pit 244 to form blended oil sand
ore 250. Blended
ore is continuously stockpiled in pit 244 to form a stockpile 252 of properly
blended ore.
With reference now to Figs. 3A and 3B, Fig. 3A is an aerial view of a
stockyard 305 of
the present invention and Fig. 3B a side view of a stockyard 305 of the
present invention. In this
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embodiment, oil sand ore is blended by free dumping the various oil sand ores
directly into a
stockyard pit. Stockyard 305 comprises an elevated bench 346, which is
designed to support
haul trucks 304 so that the haul trucks can dump oil sand ore directly into
pit 344 for blending
and retaining ore received from the haul trucks 304 as stockpile 352. In this
embodiment,
elevated bench 346 is about eight (8) meters high. Haul trucks 304 are
responsible for delivering
a particular ore from a particular oil sand face anddumping the particulars
ores in a defined
sequence. in this fashion, the ores are blended together to form a
substantially uniform stockpile
352 in pit 344. By way of example, the haul trucks can deliver 60 payloads of
four different oil
sand ores and dump the ores in a 20-15-15-10 split to obtain the desired oil
sand ore blend.
Also present within the stockyard 305 is shovel 306 for excavating stockpile
352 and
delivering the blended ore to a primary crusher 307, which is shown in Fig. 3A
to be a two track
mobile sizer. The crushed blended ore is then conveyed on conveyor 308 to a
compact slurry
preparation plant 310 where oil sand slurry is formed. In another embodiment
the stocked ore is
reclaimed using a bucketwheel or similar near-continuous stockpile reclaim
system which
discharges to a feed rate stabilizing hopper prior to conveyance into the
slurry preparation
facility.
It is understood that more than one stockpile can be present in a given
stockyard. For
example, Fig. 4A shows stockyard 405 which comprises two elevated benches,
446, 446, for
receiving various ores from haul trucks 404, for forming two stockpiles, 450,
450'. In this
embodiment, a single conveyor 408 could be used for feeding blended ore to the
slurry
preparation plant 410 from both stockpiles 452, 452'. For example, stockpile
452 could be
reclaimed by extraction, while the mining operation rebuilds stocked ore
volumes in stockpile
452' unfettered and to a set blending proportion. While in this embodiment the
conveyor bisects
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the pair of stockpiles to offer a simple partitioning effect, nevertheless,
numerous pile shapes, ore
partitioning, and conveyance linkage schemes can be rationalized.
Fig. 4B is a close-up view of an example "cluster" of sixteen truckloads of
four different
oil sand ores which may be placed on the perimeter of the stockyard, e.g., on
a raised bench and
the like, for optimal ore blending. In the alternative, the four different oil
sand ores may be
dumped directly into the stockyard pit 444. The particular pattern as shown in
Fig. 4B assures
proper blending of the four particular ores, however, it is understood that
other patterns may be
preferred, depending on the grades of the four different oil sand ores. Thus,
where a haul truck
destination of as mined oil sand ore is specified to an open stockyard, the
haul truck is then
slated to dump the ore at a dispatched coordinate on the perimeter of the
stockyard, where the
blending of oil sand ore is then managed by forming a stockpile in the
stockyard by bulldozing
the dumped ore into the stockyard pit. By implementing a large enough
stockyard, the 'real
time' interaction of mining and ore processing is measured in days rather than
minutes typical of
oil sands mining operations.
In particular, Fig. 4B shows multiple ovals, each oval representing where a
particular oil
sand ore should be initially deposited. In Fig. 4B, there are four different
types of ovals
representing four different grades of oil sand ore mined from four different
oil sand faces,
namely, 442, 442', 442" and 4421". When all of the ore positions have been
filled with the
appropriate ore, the multiple ores are blended together to form a single
stockpile of a
substantially uniform grade of ore. While Fig. 4B shows an even blending
pattern, with 25% of
each ore grade, it is understood that where different proportions of each ore
are optimal for
blending, this can easily be achieved through properly dispatched dumping of
haul trucks in the
appropriate locations on the bench.
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Fig. 5 illustrates a low complexity stockyard of the present invention that
employs both
types of oil sand ore blending described above. For ease of illustration, the
stockyard has been
broken into individual zones 1 to 6. Zone 1 is shown to be empty and ready for
delivery of oil
sand ore. Zone 2 shows oil sand ores, ore 542' and ore 542", being dumped from
haul trucks
504 on elevated bench 546 directly into pit 544, where blending occurs. Zone 3
shows ore
blending occurring by dumping loads of different oil sand ores, i.e., two
loads or ore 542a, one
load of ore 542b and one load of ore 542c, on the perimeter of bench 546 where
the loads will
then be bulldozed into the pit 544, resulting in blended ore. Zone 4 shows
completed stockpile
of blended ore that is now ready to be shoveled using shovel 506, crushed
using crusher 507 and
conveyed on conveyor 508 to slurry preparation unit 510. Zone 5 is now
excavated and ready
for additional oil sand ores to be delivered. Zone 6 shows oil sand ores being
dumped from haul
trucks 504 on elevated bench 546 directly into pit 544, where blending occurs,
thereby replacing
the ore that has already been removed for slurry preparation.
Thus, in the stockyard as shown in Fig. 5, about 40% of the stockpile is free-
dumped and
the remaining 60% is readily dozed with a short, mostly horizontal push. In
one embodiment,
there will be fifteen or more aisles open for dumping and up to 500 payloads
storage capacity.
In summary, potential benefits of the present invention may include:
= Multiple dump locations enable fully optimized, well averaged blending of
ore from
mining;
= Standard equipment can be used;
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= Unleashes shovel and ore haul productivity; Shovel & trucks not
constrained to the real
time production rate of hydro transport; eliminates 'just on time' constraints
on mining
operation;
= Reserve ore (reclaimable when haul trucks are hindered due to inclement
weather);
= Simplification of civil works allows system to be positioned, and re-
positioned, much
closer to the mining face, thereby providing shorter haul distance.
From the foregoing description, one skilled in the art can easily ascertain
the essential
characteristics of this invention. However, the scope of the claims should not
be limited by the
preferred embodiments set forth in the examples, but should be given the
broadest interpretation
consistent with the description as a whole.
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