Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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APPARATUS AND PROCESS FOR WET CRUSHING OIL SAND
The present invention relates to an apparatus and process for wet crushing oil
sand to form a pumpable and pipelinable oil sand slurry without screening.
BACKGROUND OF THE INVENTION
Oil sand containing bitumen mined from the ground is generally slurried with a
solvent such as water as part of an initial process for eventually removing
the bitumen
from the oil sand. Oil sand is a type of bitumen deposit typically containing
sand, water
and very viscous oil (the bitumen). When the oil sand deposit is located
relatively close
below the ground surface, the oil sand is often extracted from the deposit by
mining. The
oil sand is mined by excavating down through the ground surface to where the
oil sand
deposit occurs and removing oil sand from the deposit with heavy machinery.
Typically, this removal of the oil sand from the deposit is done with some of
the
largest power shovels and dump trucks in the world, with the power shovels
removing
shovel-loads of oil sand from the deposit and loading the collected oil sand
onto
conveyors to be carried away for further processing.
The viscous bitumen tends to hold the sand and water together causing the
mined
oil sand to contain lumps and chunks, some of which can be quite large.
Because of the
size of some of these pieces of mined oil sand, the mined oil sand is
typically "pre-
crushed" by running it through a preliminary crusher to crush the pieces of
oil sand to a
suitable size for transport on a conveyor (i.e. conveyable size).
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The pre-crushed oil sand is then transported by conveyor to a slurry
preparation
unit as known in the art where the pre-crushed oil sand is further processed
to form an oil
sand and water slurry.
The slurry preparation unit has to ensure that the pieces of oil sand in the
oil sand
and water slurry are of pumpable size before the slurry is directed to a pump
box and
pump to be pumped to the next step in its processing, for example,
hydrotransporting the
slurry in a pipeline for further conditioning. Therefore, oversize pieces of
oil sand or
other materials have to be prevented from being directed to the pump in order
to obtain a
pumpable, pipelinable oil sand slurry. There are at least two forms of slurry
preparation
units that have been used to form the oil sand and water slurry; slurry
preparation units
that use screening and more recent screen-less slurry preparation units.
Slurry preparation units that use screening typically comprise a vertically
stacked
series of components. The pre-crushed oil sand is initially fed into a mixing
box where
water is mixed with the oil sand to form the slurry. From the mixing box, the
oil sand
and water slurry is passed through some sort of screening device to remove
oversize from
the oil sand and water slurry. The slurry that passes through the screening
device passes
into a pump box where it is pumped to the next stage of the process. The
rejected
oversize that does not pass through the screening device is rerouted to a
crusher to be
comminuted and then added to a secondary mix box and again mixed with water to
form
a slurry before this slurry is passed through another screening device. The
portion of the
slurry that passes through this other screening device is then returned to the
main slurry
components. The oversize rejects that do not pass through the second screening
device
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are treated as rejects and removed from the system. The removed rejects are
typically
eventually hauled away by trucks and dumped in a discard area.
Screening devices commonly used in the industry include fixed screen devices;
vibrating screen devices; and rotating screen devices. Fixed screen devices
are simply
one or more fixed screens that the slurry is pored through. They have the
advantage of
having a relatively high reliability because they do not have as many moving
components
as other screening device; however, they have lower efficiencies and tend to
have higher
rejects rates. Vibrating screens typically have a lower reject rate because
the movement
of the screens allows more material to pass through, however, because of their
motion
they tend to have lower reliability. Rotating screens can potentially have
higher
reliability and efficiency than vibrating screens, however, they are very
complex
requiring an extensive structure and typically have a lower throughput than
vibrating
screens.
Slurry preparation units that use screens have a disadvantage in that a
portion of
the oil sand passing through the slurry preparation units is rejected by the
system. This
rejection of a portion of the oil sand means that the bitumen in this rejected
oil sand is
lost, as it is not extracted at later process stages like the rest of the
system. In some
screening processes, the rejection rate can be as high as 8%. This rejection
rate can add
up to a significant amount of bitumen that is simply being thrown away. More
recently,
screen-less slurry preparation towers have been used such as the screen-less
system
described in United State Patent No. 7,431,830.
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Screen-less slurry preparation towers form all of the oil sand and other
materials
entering the slurry preparation tower into a slurry and as such avoid rejects.
In particular,
essentially all of the oil sand that enters the tower is typically comminuted
in one or more
stages to a pumpable size while water is being added to it to form a slurry.
This allows
bitumen to be extracted from essentially all of the oil sand delivered to the
slurry
preparation tower, thereby essentially eliminating rejects.
Occasionally, however, there may be instances where tramp metal inclusions in
mined oil sand may pose a problem for these screen-less slurry preparation
towers.
Tramp metal is often a piece of metal from machinery used earlier in the
process, such as
a piece of shovel tooth from the power shovel or a piece of crusher tooth from
the
primary crusher. If this piece of tramp metal is large enough, when it is fed
into the
slurry preparation tower along with a portion of oil sand, the tramp metal may
damage or
even jam one of the roll crushers used in the slurry preparation tower. This
may result in
the entire process being stopped while the crusher rolls are either repaired
or the jam is
located and the tramp metal removed. This may lead to lengthy outages to
remove the
object from the crusher rolls and affect repairs if any damage has occurred.
The prior art screening processes will typically remove the tramp metal
through
the screening apparatus, However, with screen-less slurry preparation
processes, it may
be desirable to remove the tramp metal prior to crushing in the slurry
preparation tower to
avoid such outages.
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SUMMARY OF THE INVENTION
In an aspect, a system for forming an oil sand slurry from mined oil sand is
provided, comprising a slurry preparation tower comprising in series an intake
opening
through which oil sand enters the slurry preparation tower; a first sizer
device operative
to comminute oil sand passing through the first sizer to a first upper size
threshold; a
second sizer device operative to comminute oil sand passing through the second
sizer to a
second upper size threshold, wherein the second upper size threshold is less
than the first
upper size threshold; and a pump box for receiving oil sand that has passed
through the
second sizer and feeding it to a pump; at least one conveyor, having a
discharge end, for
transporting mined oil sand to the slurry preparation tower; a metal detector
for detecting
a piece of metal in the mined oil sand and transmitting a signal; and a metal
rejection
device operative to, in response to the signal from the metal detector, reject
a portion of
oil sand containing the piece of metal before the portion of oil sand enters
the slurry
preparation tower.
In another aspect, a method of forming a pumpable oil sand slurry is provided
comprising the steps of providing at least one conveyor for delivering the
mined oil sand
to a slurry preparation tower, the slurry preparation tower having a first
sizer and a
second sizer; monitoring the mined oil sand being delivered by the at least
one conveyor
for a piece of metal and in response to locating the piece of metal,
automatically
removing a part of the oil sand containing the piece of metal prior to
delivery to the slurry
preparation tower; comminuting the oil sand in the first sizer to a first
upper size
threshold; comminuting the oil sand that has passed through the first sizer in
the second
sizer to a second upper size threshold that is less than the first upper size
threshold;
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adding a solvent to the oil sand as it passes through the slurry processing
tower; and
pumping formed oil sand slurry out of the slurry preparation tower; whereby
substantially
all of the oil sand entering the slurry preparation tower exists the slurry
preparation tower
as oil sand slurry.
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 figures,
wherein:
Fig. 1 is a schematic illustration of a process for forming a pumpable oils
and
water slurry;
Fig. 2 is a schematic illustration of the internal stages is a slurry
preparation tower
to form an oil sand and water slurry;
Fig. 3 is a schematic illustration of a variation of a slurry preparation
tower using
a mixing box;
Fig. 4 is a schematic illustration of a system, in a first aspect, for
detecting a
piece of metal in particulate oil sand being carried along a conveyor and
rejecting a
portion of the particulate oil sand containing the piece of metal;
Fig. 5 is a schematic illustration of a data processing system for use as a
controller
in one aspect;
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Fig. 6 is a flowchart illustrating a method followed by the controller of Fig.
5 to
activate a metal rejection device in response to a signal that metal has been
detected;
Fig. 7 is a schematic illustration of a process for forming a pumpable oil
sand and
water slurry wherein a surge bin is not used;
Fig. 8 is a schematic illustration of a system, in a further aspect, for
detecting a
piece of metal in particulate oil sand carried along a conveyor and rejecting
a portion of
the particulate oil sand containing the piece of metal, using a baffle wall;
and
Fig. 9 is a schematic illustration of a data processing system for use as a
controller
in one aspect.
DESCRIPTION OF VARIOUS 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
inventors.
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.
Fig. 1 illustrates a process wherein oil sand is mined then processed to form
an oil
sand slurry ready for hydrotransport (pumpable oil sand slurry). Oil sand
mined from an
oil sand deposit 2 by a power shovel 4 is fed into a hopper 6 of a preliminary
conveyor 8.
The preliminary conveyor 8 deposits a flow of the mined oil sand into a
preliminary (or
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primary) crusher 10 that reduces the size of the mined oil sand to pieces of
conveyable
size (pre-crushed oil sand). From the preliminary crusher 10 the pre-crushed
oil sand is
fed to a transport conveyor 310, using a loading conveyor 12, where the
particulate oil
sand is transported along the transport conveyor 310 to a discharge end 312 of
the
transport conveyor 310. At the discharge end 312 of the transport conveyor
310, the pre-
crushed oil sand is discharged through an intake opening 25 of a surge bin 20,
where it is
eventually carried up a conveyor 110 and discharged into an intake opening 55
of the
slurry preparation tower 50. The slurry preparation tower 50 takes the flow of
particulate
oil sand discharging from a discharge end 112 of the conveyor 110 and
processes the
flow of particulate oil sand to form a pumpable oil sand slurry.
Fig. 2 is a schematic illustration of the internal components of the slurry
preparation tower 50 used to form the oil sand into an oil sand and water
slurry where the
oil sand in the oil sand and water slurry is of pumpable size.
An apron feeder 40 is positioned below the discharge end 112 of the conveyor
110 with a first end 42 of the apron feeder 40 positioned over an intake
opening 55 in the
slurry preparation tower 50.
The slurry preparation tower 50 has two comminuting stages implement with a
first sizer 52 and a second sizer 54.
The first sizer 52 is positioned below the first end 42 of the apron feeder 40
so
that oil sand discharging off the first end 42 of the apron feeder 40 can drop
directly
downwards onto the first sizer 52. The first sizer 52 comminutes the oil sand
passing
through the first sizer 52 to a first upper threshold size so that
substantially all the pieces
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of oil sand that have passed through the first sizer 52 are no greater in size
than the first
upper threshold size. In one aspect, this first upper threshold size is
approximately eight
(8) inches so that substantially all of the pieces of oil sand that have
passed through the
secondary sizer 52 are eight (8) inches in size or less.
In one aspect, the first sizer 52 can include four (4) rotatable elements in
the form
of crusher rolls 81 having a generally cylindrical shape and positioned side-
by-side,
however, it is understood that any type of mineral sizer that is known in the
art could be
used for the first sizer 52. Each of the crusher rolls 81 have a plurality of
crusher teeth 82
to aid in comminuting large pieces of oil sand. The crusher rolls 81 are
spaced a set
horizontal distance apart to form gaps between adjacent crusher rolls 81. The
size of the
gaps determines the first upper size threshold the secondary sizer 52 will
size oil sand
passing through the first sizer 52 to.
The second sizer 54 comminutes the oil sand passing through the second sizer
54
to a second upper threshold size. The second upper threshold size is smaller
than the first
upper threshold size. In this manner, the second sizer 54 reduces the size of
the larger
pieces of oil sand even more than the first sizer 52. In one aspect, this
second upper
threshold size is approximately four (4) inches so that substantially all of
the pieces of oil
sand that have passed through the second sizer 52 are four (4) inches in size
or less.
In one aspect, the second sizer 54 can include four (4) rotatable elements in
the
form of crusher rolls 91 positioned side-by-side, however, as previously
mentioned, any
type of mineral sizer known in the art could be used for the second sizer 54.
Each of the
crusher rolls 91 have a plurality of crusher teeth 92 to aid in comminuting
large pieces of
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oil sand. However, the gaps between adjacent crusher rolls 91 are smaller than
the gaps
between adjacent crusher rolls 81 of the first sizer 52, so that the second
sizer 54
comminutes material to a smaller size than the first sizer 54. Additionally,
the crusher
teeth 92 on the crusher rolls 91 may be smaller and there may be more crusher
teeth 92
on a crusher roll 91 than the number of crusher teeth 82 on the crusher rolls
81 of the first
sizer 52.
The second sizer 54 can be positioned directly below the first sizer 52 so
that
substantially all of the oil sand passing through the first sizer 52 drops
unimpeded onto
the second sizer 54.
A first liquid outlet 62 is provided above the first sizer 52 so that a
solvent, such
as water, can be added to the oil sand as it falls onto the first sizer 52. A
second liquid
outlet 64 is provided above the second sizer 54 but below the first sizer 52
so that a
solvent, such as water, can be added to the oil sand passing out of the first
sizer 52 as it
drops to the second sizer 54. In one aspect, each outlet can comprise one or
more
nozzles.
A pump box 70 is provided below the second sizer 54 so that oil sand that has
passed through the second sizer 54 drops into the pump box 70, where it can be
pumped
by one or more pumps 72 to the next stage in the process.
In operation, oil sand is discharged from the discharge end 112 of the
conveyor
110 and onto the apron feeder 40. In normal operation, the apron feeder 40
discharges
the oil sand from the first end 42 of the apron feeder 40 through the intake
opening 55
and drops it downwards towards the first sizer 52. As the oil sand falls
towards the first
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sizer 52, a solvent, such as water, can be sprayed onto the falling oils sand
using the first
liquid outlet 62, wetting the falling oil sand that contacts the first sizer
52.
When the oil sand reaches the first sizer 52, the oil sand is comminuted as it
passes through the first sizer 52 to a size equal to or smaller than the first
upper size
threshold before the oil sand exits the first sizer 52 and drops towards the
second sizer 54.
Oil sand that has passed through the first sizer 52 falls downwards towards
the
second sizer 54. As the oil sand falls towards the second sizer 54, a solvent,
such as
water, can be sprayed onto the falling oils sand using the second liquid
outlet 62, wetting
the falling oil sand that contacts the second sizer 54.
The second sizer 54 comminutes the oil sand to a size equal to or smaller than
the second upper size threshold before allowing the oil sand to pass through
the second
sizer 54.
Oils sand that has passed through the second sizer 54 drops into the pump box
70
positioned below the second sizer 54 where the oil sand and water slurry will
be pumped
by the one or more pumps 72 to the next stage of the bitumen extraction
process for
further processing.
In this manner, substantially all of the oil sand that is introduced into the
slurry
preparation tower 50 through the intake opening 55, exits the slurry
preparation tower in
an oil sand and water slurry to be transported to the next stage in its
processing. All of
the oil sand in the slurry has been reduced to a pumpable size and none of the
oil sand is
rejected from the slurry preparation tower to be hauled away and discarded.
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Fig. 3 is a schematic illustration of a further aspect of the internal
components of
the slurry preparation tower 50 where a mixing box 75 is provided. A number of
overlapping, downwardly inclined, descending shelves 76 are provided in the
mixing box
76 to mix the oil sand and water slurry as it passes through the mixing box 75
before
entering the pump box 70.
In the slurry preparation tower 50 shown in Fig. 2 and Fig. 3, substantially
all of
the oil sand that is introduced into the slurry preparation tower 50 through
the intake
opening 55, is formed into a slurry and exits the slurry preparation tower as
this slurry to
be pumped to the next stage in its processing. All of the oil sand in the
slurry has been
reduced to a pumpable size and none of the oil sand is rejected from the
slurry
preparation tower to be hauled away and discarded.
Because all of the oil sand and any other materials that enter the slurry
preparation
tower pass through the first sizer device 52 and second sizer device 54, it
may at times be
beneficial to detect pieces of metal in the oil sand that is being transported
to the slurry
preparation tower 50 and remove the detected pieces of metal before the pieces
or metal
are delivered to the slurry preparation tower 50.
Fig. 4 is a schematic illustration of a system 100 in a first aspect. The
system 100
supplies a flow of particulate oil sand to the slurry preparation tower 50,
where the oil
sand will be further crushed and slurried with water to form a pumpable oil
sand slurry
for further processing. The system 100 comprises: a first conveyor 110; a
redirecting
device 105 including the apron feeder 40; a metal detector 140; and a control
device 150.
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g
The first conveyor 110 transports a flow of particulate oil sand along a
length of
the first conveyor 110 towards a discharge end 112 of the first conveyor 110.
The
discharge end 112 is provided generally above an intake opening 55 of the
slurry
preparation tower 50.
The redirection device 105 includes the apron feeder 40. The apron feeder 40
is
provided below the discharge end 112 so that a flow of particulate oil sand
being
discharged from the discharge end 112 of the first conveyor 110 lands on the
apron
feeder 40. The apron feeder 40 is bi-directional so that the second conveyor
120 can be
driven to carry material along the apron feeder 40 either in a first
direction, A, or a
second direction, B. The apron feeder 40 is positioned so that particulate oil
sand moved
by the apron feeder 40 in the first direction, A, and discharged from a first
end 42 of the
apron feeder 40 will drop into the intake opening 55 of the slurry preparation
tower 50.
A second end 44 of the apron feeder 40 is positioned so that particulate oil
sand moved
by the apron feeder 40 in the second direction, B, and discharged from the
second end 44
of the second conveyor 120 will not fall into the intake opening 55 of the
slurry
preparation tower 50. In an aspect, the second end 44 of the apron feeder 40
is positioned
so that oil sand discharged off of the second end 44 of the apron feeder 40
falls to a
ground surface, 41, beside the slurry preparation tower 50.
The metal detector 140 is positioned along the first conveyor 110 a travel
distance, TD, from the discharge end 112 of the first conveyor 110. The metal
detector
140 can detect a piece of metal in the flow of particulate oil sand traveling
along the first
conveyor 110 past the metal detector 140.
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The controller 150 is operatively connected to the metal detector 140 and the
apron feeder 40. The controller 150 could be a computer, a programmable logic
controller (PLC), etc. operative to receive and transmit signals to control
the operation of
the system 100, such as the data processing device 800 shown in Fig. 5. The
data
processing device 800 includes a processor 810, system buses 820, memory 830
containing program instructions 840 and an I/O interface 850. The processor
810 is a
central processing unit that is typically microprocessor based to implement
the program
instructions 840 and control the operation of the data processing device 800.
The system
buses 820 allow the transmissions of digital signals between the various
components of
the data processing device 800. The memory 830 stores the operating system,
data
needed for the operation of the data processing device and the program
instructions 840.
Typically, the memory 830 will contain RAM for data and an EPROM or Rom for
storing the operating system and program instructions 840. The I/0 interface
850 allows
for the connection to remote components to receive signals from remote
components and
transmit signals to the remote components. A person skilled in the art will
appreciate that
the data processing system 800 will also include components, such as a power
supply, in
addition to those illustrated in Fig. 5.
Referring again to Fig. 4, the controller 150 is operatively connected to the
metal
detector 140 so that the controller 150 can receive a metal detected signal
from the metal
detector 140 when the metal detector 140 detects a piece of metal in the flow
of
particulate oil sand traveling along the first conveyor 110. The controller
150 is
operatively connected to the apron feeder 40 so that the controller 150 can
control the
direction of the apron feeder 40. In an aspect, the controller 150 is
operatively connected
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to a speed sensing device 160, such as a pulley mounted speed encoder, to
obtain a speed
of the first conveyor 110.
Fig. 6 is a flowchart illustrating a method 200 used by the controller 150, in
Fig.
2, to control the system 100. The method 200 comprises the steps of:
determining a
travel time 220; running a first timer 230; generating a reject signal 240;
running a
second timer 250; and triggering a resume signal 260.
Referring to Figs. 4 and 6, method 200 is started at step 210 when the
controller
150 receives a metal detected signal from the metal detector 140, indicating
that a piece
of metal has been detected in the flow of particulate oil sand traveling along
the first
conveyor 110.
At step 220, a travel time for the piece of metal detected by the metal
detector 140
to reach the discharge end 112 is determined. The travel time is determined
based on the
travel distance, TD, of the metal detector 140 from the discharge end 112 of
the first
conveyor 110 and the operating speed of the first conveyor 110. The travel
distance, TD,
provides the distance the piece of metal will have to travel after it has
passed the metal
detector 140 before it reaches the discharge end 112 of the first conveyor
110. The
operating speed of the first conveyor 110 indicates the speed at which the
metal object
and the oil sand are being carried along the first conveyor 110. The operating
speed of
the first conveyor 110 could be obtained by the controller 150 by having the
first
conveyor 110 maintain a constant operating speed, however, because the travel
distance,
TD, can be quite long and the travel time relatively long (more than a minute)
it might be
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desirable to obtain the operating speed of the conveyor belt 110 directly from
the speed
sensing device, 160, or from a device controlling the speed of the first
conveyor belt 110.
At step 230, the method 200 runs a first timer for a period of time equal to
the
travel time minus a buffer time.
At step 240, after the first timer has been run, a reject signal is generated
from the
controller 150 to the apron feeder 40. Step 240 is performed by the controller
150 after
the first timer is run. The first timer runs for a period of time equal to the
travel time
determined at step 220, for the piece of metal to reach the discharge end 112
of the first
conveyor 110 less a buffer time. The buffer time is a short period of time
used so that a
reject signal is generated by the controller 150, at step 240, before the
piece of metal is
discharged from the discharge end 112 of the first conveyor 110. The buffer
time can
allow enough time for the direction of operation of the apron feeder 40 to be
reversed
before the particulate oil sand containing the piece of metal falls onto the
apron feeder 40,
so that the apron feeder 40 is already operating in the second direction, B,
by the time the
piece of metal lands on the apron feeder 40. The buffer time can also be used
to account
for inaccuracies in the travel time determined at step 220 and delays in the
transmission
of the reject signal by increasing the buffer timer to have the reject signal
transmitted
earlier.
The travel time is use to determine when the piece of metal detected by the
metal
detector 140 has traveled along the first conveyor 110 to the discharge end
112 of the first
conveyor 110. Before the piece of metal is discharged off the discharge end
112 of the
first conveyor 110, the controller 130 transmits the reject signal to the
apron feeder 40.
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When the apron feeder 40 receives the reject signal from the controller 150,
the
apron feeder 40 reverses its direction of travel, moving material on the apron
feeder 40
in the direction, B, carrying particulate oil sand discharged onto the apron
feeder 40, from
the first conveyor 110, off the second end 44 of the apron feeder 40 so that
the oil sand
does not fall into the intake opening 55 of the slurry preparation tower 50
and into the
number of crusher rolls (not shown) contained in the slurry preparation tower
50.
At step 250, a second timer is run for a discharge time. The discharge time
will
be based on the length of the apron feeder 40 and the time required for
particulate
material landing on the apron feeder 40 from the first conveyor 110 to be
carried off the
second end 44 of the apron feeder 40 and how quickly the direction of
operation of the
apron feeder 40 can be reversed. Typically, this time is less than one (1)
minute with
times of ten (10) seconds or less being possible to reduce the time the flow
of particulate
oil sand is stopped.
After the second timer has run for the discharge time, the method 200 proceeds
to
step 260 and a resume signal is transmitted. The controller 150 generates a
resume signal
and transmits it to the apron feeder 40 causing the apron feeder 40 to once
again change
the direction and resume normal operation. The apron feeder 40 reverses the
direction of
travel from the second direction, B, back to the first direction, A, causing
particulate oil
sand discharged from the first conveyor 110 onto apron feeder 40 to once again
be
discharged off the first end 42 of the apron feeder 40 and into the intake
opening 55 of
the slurry preparation tower 50.
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With step 260 completed, the system 100 is once again operating under normal
conditions delivering a flow of particulate oil sand to the slurry preparation
tower 50 and
the method 200 ends.
The method 200 will be invoked again if the metal detector 140 determines that
there is another piece of metal in the particulate oil sand traveling along
the first
conveyor 110.
In this manner, when the system 100 detects a piece of metal in the oil sand
traveling along the first conveyor 110, the system 100 approximates when the
piece of
metal will reach the discharge end 112 of the first conveyor 110 and be
discharged from
the first conveyor 110. Shortly before the piece of metal is discharged off
the first
conveyor 110, the direction of travel of the apron feeder 40 is reversed so
that particulate
oil sand on the apron feeder 40 is rejected from the system 100 by the apron
feeder 40.
The reversal of direction of the apron feeder 40 discharges a portion of
particulate oil
sand off the second end 44 of the apron feeder 40, preventing the portion of
particulate
oil sand from entering the slurry preparation tower 50. During this time, the
piece of
metal is discharged off the discharge end 112 of the first conveyor 110, onto
the second
conveyor 120, where it is rejected from the system. After a relatively short
period of
time, sufficient for the portion of particulate oil sand containing the piece
of metal to be
discharged off the apron feeder 40, the direction of the apron feeder 40 is
once again
reversed and oil sand discharged from the first conveyor 110 to the apron
feeder 40 is
once again fed into the intake opening 55 of the slurry preparation tower 50.
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Although a portion of the oil sand is rejected along with the piece of metal,
the
amount of time the flow of oil sand entering the slurry preparation tower 50
is halted is
relatively short, only the short period of time for the piece of metal to be
discharged off
the end of the first conveyor 110 onto the apron feeder 40, and then
discharged off the
second end 44 of the apron feeder 40. This short period of time is based on
the length of
the apron feeder 40. The shorter the apron feeder 40 and the faster the apron
feeder 40
can change its direction of operation, the shorter the short period of time
can be.
Because only the operation of the apron feeder 40 is affected, the first
conveyor
110 can be operated at a constant speed of operation throughout the operation
of the
method 200. Stopping the first conveyor 110 or even altering the speed of
first conveyor
110 requires significantly more force and time than stopping or altering the
direction of
motion of the apron feeder 40 because of the greater inertia of the moving
much larger
conveyor belt of the first conveyor 110. Once the first conveyor 110 is
stopped,
significant force is also required to get the first conveyor 110 back up to
operating speed.
This can significantly impact the slurrying of the oil sand, because the
slurry preparation
is a continuous process. This continuous process is affected by the slowing
down of the
first conveyor 110 because this alters the flow rate of particulate oil sand
entering the
slurry preparation tower 50, which can result in variations in density of the
resulting oil
sand slurry. The process is also interrupted for the duration of the time the
first conveyor
110 is stopped because there is no particulate oil sand entering the slurry
preparation
tower 50 while the first conveyor 110 has stopped operating. Finally, starting
the first
conveyor 110 up again, after the interruption, requires the first conveyor 110
to be
accelerated back up to operating speed, which again requires some time,
resulting in an
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uneven flow rate of particulate oil sand entering the slurry preparation tower
50 during
this period, until the first conveyor 110 once again achieves operating speed.
Because the apron feeder 40 is significantly shorter than the first conveyor
110,
altering the speed of the apron feeder 40 is much easier, requiring much less
force and
time than the first conveyor 110 to bring the apron feeder 40 up to operating
speed.
Because the first conveyor 110 can be operated at a constant operating speed
while the
direction of the apron feeder 40 is reversed, the flow rate of particulate oil
sand being
discharged from the first conveyor 110 onto the apron feeder 40 remains
constant,
resulting in a more constant flow rate of particulate oil sand being delivered
to the slurry
preparation tower 50.
In some aspects, the surge bin 20 may not be used. Fig. 7 is a schematic
illustration of a variation of a process for taking mined oil sand and forming
an oil sand
slurry from the mined oil sand. This process is similar to the process shown
in Fig. 1,
with the exception that the surge bin 20 and the conveyor 110 are not used.
Instead, the
transport conveyor 310 discharges directly into the intake opening 55 of the
slurry
preparation tower 50. The system 100 shown in Fig. 7 can be used with the
transport
conveyor 310, when the transport conveyor 310 is discharging directly into the
slurry
preparation tower 50. The metal detector 140 can be placed at a point along
the length of
the transport conveyor 310.
With the transport conveyor 310 discharging directly into the slurry
preparation
tower 50, the difference in size between the transport conveyor 310 and the
second
conveyor 120 is even greater. The transport conveyor 310 may be quite long in
aspects
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where it has to carry particulate oil sand from a preliminary crushing stage
to the slurry
preparation tower 50, while the second conveyor 120 is much shorter than the
transport
conveyor 310. In some instances, the transport conveyor 310 can be five
hundred (500)
meters long or more, requiring more than a kilometer of conveyor belt. Because
of this,
the forces required to slow down and stop the transport conveyor 310 are much
greater
than those required to alter the direction of motion of the second conveyor
120.
Additionally, to once again get the transport conveyor 310 up to a desired
operating
speed after the transport conveyor 310 is stopped, significant force and time
is required to
accelerate the transport conveyor 310 back to the desired operating speed.
These
variations in speed and stopping time can significantly affect the slurrying
process.
Referring again to Fig. 1, even when the surge bin 20 and the conveyor 110 are
used, in some cases it may be desirable to reject a piece of metal from the
transport
conveyor 310, rather than the conveyor 110. Figs. 8 and 9 are schematic
illustrations of a
system 300 in a further aspect. Because the conveyor 310 does not discharge
directly
into the slurry preparation tower 50, but rather into the surge bin 20, system
300 has to be
modified from system 100, shown in Fig. 4 to take into account this
difference. The
system 300 comprises: a first conveyor 310; a redirection device 305,
including a second
conveyor 320 and a baffle wall 370; a chute 375; a metal detector 340; and a
controller
150.
The first conveyor 310 has a discharge end 312. Particulate oil sand traveling
along the first conveyor 310 is discharged from the first conveyor 310 at the
discharge
end 312 of the first conveyor 310.
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The redirection device 305 is provided at the discharge end 312 of the
conveyor
310. The second conveyor 320 is positioned below the discharge end 312 of the
first
conveyor 310. The second conveyor 320 is bi-directional so that it can be
operated in a
first direction, A, or a second direction, B. A first end 322 of the second
conveyor 320 is
positioned so that material discharged from the first end 322 of the second
conveyor 320,
when the second conveyor 320 is operating in the first direction, A, falls
into the intake
opening 25 of the surge bin 20. The second end 324 of the second conveyor 320
is
positioned so that material discharged from the second end 324 of the second
conveyor
320 is discharged to the chute 375 and the chute 375 directs the material away
from the
intake opening 25 of the surge bin 20.
The baffle wall 370 is positioned relative to the discharge end 312 and can be
moved between a first position and a second position. In the first position,
as shown in
Fig. 8, the baffle wall 370 allows particulate oil sand being discharged from
the discharge
end 312 of the first conveyor 310 to fall into the intake opening 25 of the
surge bin 20,
with any of the particulate oil sand falling on the second conveyor 320 being
carried in
the first direction, A, by the second conveyor 320, until the particulate oil
sand is
discharged off the first end 322 of the second conveyor 320 into the intake
opening 25 of
the surge bin 20. With the baffle wall 370 placed in the second position, as
shown in Fig.
9, the baffle wall 370 deflects all of the particulate oil sand discharging
from the
discharge end 312 of the first conveyor 310 towards the second conveyor 320.
Typically, a hydraulic cylinder 372 is used to move the baffle wall 370
between
the first position and the second position.
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The metal detector 340 is positioned a travel distance, TD, upstream from the
discharge end 312 of the first conveyor 310. The metal detector 340 can detect
a piece of
metal passing by the metal detector on the first conveyor 310.
The controller 150 is operatively connected to the metal detector 340, the
baffle
wall 370 (specifically the hydraulic cylinder 372), the second conveyor 320
and
optionally a speed determining device 360.
The controller 150 could be a computer, programmable logic controller, etc.
operative to control the operation of the system 300. The controller 150 is
operatively
connected to the metal detector 340 to receive metal detected signals from the
metal
detector 340 when the metal detector 340 detects a piece of metal passing the
metal
detector 340 on the first conveyor 310. The controller 150 is operatively
connected to the
hydraulic cylinder 372 and the second conveyor 320 so that the controller 150
can
transmit reject signals and resume signals to the hydraulic cylinder 372 and
the second
conveyor 320.
In response to receiving a reject signal from the controller 150, the second
conveyor 320 reverses its direction of operation from the first direction, A,
with the
second conveyor 320 discharging into the intake opening 25 of the surge bin
20, to the
second direction, B and the hydraulic cylinder 372 moves the baffle wall 370
from the
first position (shown in Fig. 8) to the second position (shown in Fig. 9). In
this manner,
particulate oil sand discharging from the first conveyor 310 is directed away
from the
intake opening 25 of the surge bin 20, so that a portion of the particulate
oil sand is
prevented from entering the surge bin 20 and continuing through the process.
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In response to receive a resume signal, the second conveyor 320 reverses its
direction of operation back to the first direction, A, and the hydraulic
cylinder 372 moves
the baffle wall 370 back to the first position (shown in Fig. 8) and the
system 300
resumes normal operation, continuing to transport a flow of particulate oil
sand to the
slurry preparation tower 50.
Referring to Figs. 6, 8 and 9, the controller 150 uses the method 200
illustrated in
Fig. 3 to control the operation of the system 300 when a piece of metal is
detected by the
metal detector 340.
Method 200 begins at step 210 when controller 150 receives a metal detected
signal from the metal detector 340. At step 220, the controller 150 determines
a travel
time for the piece of metal to travel the travel distance, TD, along the first
conveyor 310
from the metal detector 340 to the discharge end 312.
Using the travel time determined at step 220, the controller 150 runs a first
timer
for a timer period equal to the travel time minus a buffer time. When the
first timer ends,
a reject signal is generated and transmitted to the hydraulic cylinder 372 and
the second
conveyor 320 at step 240.
Upon receiving the reject signal from the controller 150, the hydraulic
cylinder
372 is activated, moving the baffle wall 370 from the first position (as shown
in Fig. 8) to
the second position (as shown in Fig. 9). With the baffle wall 370 moved to
the second
. position, particulate oil sand discharging from the discharge end 312 of the
first conveyor
310 is deflected to the second conveyor 320. When the second conveyor 320
receives the
reject signal transmitted by the controller 150, the direction of operation of
the second
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conveyor 320 is reversed from the first direction, A, to the second direction,
B, causing
particulate matter landing on the second conveyor 320 to be moved in the
second
direction, B, and off the second end 324 of the second conveyor 320 into the
chute 375.
After step 240, any particulate oil sand discharged from the discharge end 312
of
the first conveyor 310 is deflected by the baffle wall 370 to the second
conveyor 320.
Once on the second conveyor 320, the oil sand is carried to the second end 324
of the
second conveyor 320 where the chute 375 directs the particulate oil sand away
from the
intake opening 25 of the surge bin 20. In this manner, the system 300
temporarily directs
a portion of the particulate oil sand flow being discharged from the discharge
end 312 of
the first conveyor 310 away from the intake opening 25 of the surge bin 20,
removing
this portion of oil sand containing a piece of metal from the process of
creating an oil
sand slurry and preventing the piece of metal contained within the portion of
particulate
oil sand flow from carrying on through later steps in the process.
At step 240, the controller 150 runs a second timer for a discharge time and
after
the second timer has run for the discharge time, step 250 is performed and a
resume
signal transmitted by the controller 150 to the hydraulic cylinder 372 and the
second
conveyor 320. Upon receiving the resume signal, the hydraulic cylinder 372
moves the
baffle wall 370 from the second position (as show in Fig. 9), where the baffle
wall 370 is
deflecting the particulate matter discharging from the discharge end 312 of
the first
conveyor 310 towards the second conveyor 320, back to the first position (as
shown in
Fig. 8. The resume signal also causes the direction of operation of the second
conveyor
320 to be once again reversed so that the direction of operation of the second
conveyor
320 is once again in the first direction, A. With the baffle wall 370 back in
the first
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position and the second conveyor 320 moving in the first direction, A, the
system 300 is
back operating in a normal fashion and oil sand discharged from the first
conveyor 310 is
= eventually moved through the process to be contained in an oil sand
slurry. After step
260, method 200 ends.
In this manner, system 300 allows a portion of oil sand containing a piece of
metal to be rejected from the system 300 preventing the metal from damaging
components in the slurry processing tower 50.
The previous description of the disclosed embodiments is provided to enable
any
person skilled in the art to make or use the present invention. Various
modifications to
those embodiments will be readily apparent to those skilled in the art, and
the generic
principles defined herein may be applied to other embodiments without
departing from
the scope of the invention. Thus, the present invention is not intended to be
limited to the
embodiments shown herein, but is to be accorded the full scope consistent with
the
claims, wherein reference to an element in the singular, such as by use of the
article "a"
or "an" is not intended to mean "one and only one" unless specifically so
stated, but
rather "one or more". All structural and functional equivalents to the
elements of the
various embodiments described throughout the disclosure that are known or
later come to
be known to those of ordinary skill in the art are intended to be encompassed
by the
elements of the claims, Moreover, nothing disclosed herein is intended to be
dedicated to
the public regardless of whether such disclosure is explicitly recited in the
claims.
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