Note: Descriptions are shown in the official language in which they were submitted.
NS-521
MINING AND PROCESSING SYSTEM FOR OIL SAND ORE BODIES
FIELD OF THE INVENTION
The present invention relates to mining technology and a process line for
increasing the
efficiency of an ore mining operation.
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 wi.%
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 lam.
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
mixed with hot water, caustic (e.g., sodium hydroxide) and naturally entrained
air to yield an oil
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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, all of the applicant's primary crushing plants are located at
grade, adjacent to
the mine pits, so that all ore must be trucked out of the pit and up an
additional ¨20 in ramp in
order to dump the ore into the primary crusher hopper. This average haul
distance is currently 4-
5 km and future ore bodies would require truck hauls of 10-20 km to existing
primary crusher
locations. Once the ore is crushed, the crushed ore is conveyed from the
discharge of the
primary crusher to a surge pile, which is in turn fed to the slurry
preparation plant. At present,
the applicant operates both semi-mobile and fixed location slurry preparation
plants, Even
though the applicant's primary crushers are semi-mobile, in order to relocate
the semi-mobile
.. crushers, a ¨20 m tall Mechanically Stabilized Earth (MSE) wall needs to be
constructed, which
takes 12-18 months and costs a great deal of money. Thus, due to the time and
expense, it is
impractical to relocate the primary crushers to keep them close to the mining
face.
The applicant currently operates its hydrotransport systems (pipelines) at 45-
50 C and
100-125 mm nominal ore top size, For these systems, around 10 minutes is the
minimum
.. residence time in the pipeline to achieve sufficient oil sand conditioning
in order to get
acceptable primary bitumen recovery in the PSV. Thus, the equivalent minimum
hydrotransport
pipeline length is about 3 km, however, can be longer, for example, 4.5 km,
which is equivalent
to 18-20 minutes residence time. Optionally, oversize material (>50 mm) may be
screened prior
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to the extraction plant, but other than this, all coarse solids are sent
through the PSV and then
must travel through coarse tailings systems to the tailings deposition areas.
Oil sand is about
85% solids, which can be considered waste, and about 70% of the solids could
be considered
'coarse' (i.e., >44 !_tm). The average total travel distance for this coarse
waste material is
currently 15-20 km. Hence, both front-end truck haul and back-end tailings
pumping distances
will increase as operations move to more remote ore bodies throughout the next
8-50 years.
Operating costs for these semi-remote mineable oil sand ore bodies will
increase
significantly from today's costs, due to long truck hauls and long-distance
waste hydrotransport.
"Semi-remote" is defined herein as an ore body having a centroid more than 6-8
km from an
existing extraction plant. Thus, there is a need for improved equipment
layouts in order to deal
with these semi-remote sites and minimize truck haul distances and minimize
waste handling.
Although the equipment layouts described herein are described in relation to
oil sand ore bodies,
it is understood that these equipment layouts could offer benefits in almost
any scenario.
SUMMARY OF THE INVENTION
In one aspect, a process line is provided comprising a combination of three
semi-mobile
technologies that will minimize truck haul distances and minimize waste
handling (e.g., coarse
tailings disposal). In one embodiment, the process line comprises: a semi-
mobile crushing
station for receiving as-mined oil sand ore and comminuting the oil sand ore
to a first size; a
semi-mobile compact slurry preparation unit for receiving the comminuted oil
sand ore and
mixing the oil sand ore with water to form an oil sand slurry; and a semi-
mobile solids removal
assembly for removing a portion of the coarse solids from the oil sand slurry
prior to extracting
from the slurry an enriched bitumen froth.
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In one embodiment, the semi-mobile solids removal assembly comprises a semi-
mobile
desanding assembly. In one embodiment, the semi-mobile solids removal assembly
comprises a
semi-mobile screening assembly. In one embodiment, the semi-mobile solids
removal assembly
comprises a semi-mobile screening assembly and a semi-mobile desanding
assembly.
BRIEF DESCRIPTION OF THE DRAWINGS
Referring to the drawings wherein like reference numerals indicate similar
parts 1
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.
Fig. 2 is a schematic depiction of another embodiment of the process line 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.
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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, the
.. mine face 2 is a mine face in a mineable oil sand mine or 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 semi-mobile crushing station 5. In the embodiment
shown in Fig, 1,
semi-mobile crushing station 5 for receiving as-mined oil sand ore and
comminuting the oil sand
ore to a first size is a dual truck mobile sizer (DTMS) such as described in
Canadian Patent No,
2,737,492. As used in the present invention, the DTMS is considered to be semi-
mobile, as it is
anticipated that the DTMS will only have to be relocated every year or so. It
is understood,
however, that other moveable crushing units known in the art can also be used
in the present
invention.
In the embodiment shown in Fig. 1, the DTMS generally comprises 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 two earth moving vehicles, in
particular dump
trucks, at the same time. In one embodiment, the DTMS comprises two spaced
apart pivoting
truck skips having hinged floors for receiving/feeding the mined ore to a
sizer having two
.. parallel oppositely rotatable rock crushing drums. The comminuted ore is
then discharged onto a
discharge conveyor. Because the DTMS is relocatable by using crawlers and the
like, it can
follow the ore body that is being mined so that there will only need to be
short truck hauls (e.g.,
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1-3 km). The DTMS serves as a Mobile Truck Conveyor Interface or MTCI. Thus,
DTMS is
deployed to enable perpetual short-haul,
A short conveyor 8 receives the comminuted oil sand ore from the discharge
conveyor of
the DTMS and delivers the comminuted oil sand ore to a semi-mobile compact
slurry preparation
(CSP) unit 6. In this embodiment, the semi-mobile compact slurry preparation
unit 6 is a wet
crushing unit as described in Canadian Patent No. 2,480,122, Semi-mobile
compact slurry
preparation unit 6 generally comprises a surge pile 10, apron feeders 12/13,
ore sizing equipment
14 and slurry pumps 25, and can be moved by means of tracks 27, 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 feed
wetting point step, or
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 6
can then be
transported and conditioned in hydrotransport pipeline 28. Hydrotransport
pipeline 28 is
.. generally around 3-4,5 km in length, its length being sufficient to ensure
proper conditioning of
the oil sand slurry. Thus, hydrotranspod pipeline 28 receives oil sand slurry
from semi-mobile
compact slurry preparation unit 6, transports the slurry while simultaneously
conditioning it, and
delivers the conditioned slurry to a semi-mobile solids removal assembly. In
this embodiment,
the semi-mobile solids removal assembly is a semi-mobile desanding assembly 29
for removing
.. a portion of the coarse solids and 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 27. It is
understood, however, that other moveable desanders or desanding circuits can
be used.
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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.
The inherent operating cost of haul trucks is over three times that of
conveying or
hydrotransport, due to differences in many factors such as energy efficiency,
maintenance
requirements and workforce. However, trucks provide a mobile, flexible front
end to the mining
process, so it is not likely optimal to eliminate them entirely. One key
advantage provided by
trucks is the ability to seamlessly deal with interburden in the ore body and
ore blending for
recovery, simply by dispatching the trucks appropriately. Second, a short
front-end haul serves
to minimize the number of relocations required for the crushing and slurry
preparation plants,
which may weigh several thousand tonnes ¨ without trucks, this weight would
need to be moved
continuously, to follow the shovels.
The DTMS system, which was developed by FLSmidthTM, is well-suited to
minimizing =
oil sand hauling distances. The average haul distance could be reduced, for
example, to about 2
km or less and multiple DTMS systems may be deployed in an oil sand mine, The
DTMS is a
semi-mobile truck/conveyor interface, which includes primary crushing to allow
for reliable
conveyor operation. One of the advantages of DTMS is that it eliminates the
need for an MSE
wall because it uses hydraulics to lift the ore into the crusher hopper,
rather than an earthworks
ramp and the truck engines.
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To remain close to the active mine faces, it is contemplated that one would be
able to
relocate the DTMS system and extend the take-away conveyor network within a
two-week
window, and this could be conducted on an annual basis, On the other hand, it
is contemplated
that the semi-mobile compact slurry preparation unit and the semi-mobile
desanding assembly
would be more costly and complex moves and may stay in one location for a
longer period.
The lowest operating cost for the present process line is achieved when the
hydrotransport process is started as soon as possible. Once the optimal
hydrotransport
distance/residence time is reached, there is negative value in moving the
coarse solids any
further. Thus, a desander may be implemented to reduce the solid content of
the oil sand slurry
prior to bitumen extraction. In one embodiment, a desander similar to a
Primary Separation
Vessel (PSV) can be used. In one embodiment, using an 8000 m3 vessel, up to
90% of the feed
solids in the conditioned oil sand slurry from the hydrotransport system can
be separated from
the bitumen and fines, with about a 3,5% bitumen loss to tailings.
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.
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Fig. 2 illustrates another embodiment of the present process line. In this
embodiment, the
mine face 102 is a mine face in a mineable oil sand mine or pit. A mining
shovel 103 is used to
excavate the oil sand ore at the mine face 102 and it is operative to advance
along the mine face
102 and deposit the as-mined oil sand ore into mobile trucks 104. The mobile
trucks 104 deliver
the as-mined oil sand ore to a semi-mobile crushing station 105. In the
embodiment shown in
Fig. 2, semi-mobile crushing station 105 for receiving as-mined oil sand ore
and comminuting
the oil sand ore to a first size is a dual truck mobile sizer (DTMS) such as
described in Canadian
Patent No, 2,737,492.
A short conveyor 108 receives the comminuted oil sand ore from the discharge
conveyor
of the semi-mobile crushing station 105 and delivers the comminuted oil sand
ore to a semi-
mobile compact slurry preparation (CSP) unit 106. In this embodiment, the semi-
mobile
compact slurry preparation unit 106 is a wet crushing unit as described in
Canadian Patent No.
2,480,122. Oil sand slurry prepared in the semi-mobile compact slurry
preparation unit 106 can
then be transported and conditioned in hydrotransport pipeline 128.
Hydrotransport pipeline 128
is generally around 3-4.5 km in length, its length being sufficient to ensure
proper conditioning
of the oil sand slurry.
In this embodiment, the hydrotransport pipeline 128 receives oil sand slurry
from semi-
mobile compact slurry preparation unit 106, transports the slurry while
simultaneously
conditioning it, and delivers the conditioned slurry to a semi-mobile solids
removal assembly
which comprises a screening assembly 140 for removing a portion of the coarse
solids, in
particular, lumps and rocks, therefrom. Screening assembly 140 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 140 may be
relocatable by means
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of tracks 127. In one embodiment, the screening assembly 140 may be positioned
further
upstream, i.e., along the hydrotransport pipeline 128, 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 128.
In one embodiment, about 10% of solids in the conditioned slurry are removed
by use of
the screening assembly. Removal of larger rocks and clay lumps may provide one
or more of the
following benefits: lower wear on downstream equipment; improved (unhindered)
settling at
sand separation stage; reduce solids (including clay clumps) directed to
tailings ponds; and
residual value of screenings (lumpy waste) in context of viable construction
materials for
temporary haul routes. Generally, rocks/lumps above 12mm cause the majority of
pump,
pipeline and vessel wear. By removing these lumps, it will allow for cost-
effective long-distance
pipeline transport to extraction, which is especially important if bitumen
extraction equipment
such as a primary separation vessel (PSV) is far from the mine. Also, removal
of the clay lumps
at this stage means less fluid fine tailings (which are primarily clay) are
formed in tailings ponds.
The lumps 142 (rejects) removed from the conditioned slurry can be transported
a short distance
to a lump storage facility.
In one embodiment, the screened slurry 144, which still includes sand, may be
directly
transported to bitumen extraction facilities. In another embodiment, the semi-
mobile solids
removal assembly further comprises a semi-mobile desanding assembly 129 for
removing a
portion of the sand still present in screened slurry 144. The semi-mobile
desanding assembly
129 may comprise a near pit desander (NPD), or separator, as described in
Canadian Patent
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Application No. 2,809,959, which is moveable by means of tracks 127. It is
understood,
however, that other moveable desanders or desanding circuits can be used. In
this embodiment,
a relatively clean (i.e., relatively free from bitumen) sand underflow 148 is
produced which only
needs to be transported a short distance to sand storage. The reduced solids
upper zone or
overflow 146 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.
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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