SLURRYING OIL SAND FOR HYDROTRANSPORT IN A PIPELINE

MISE EN SUSPENSION EPAISSE DE SABLE BITUMINEUX POUR HYDROTRANSPORT EN PIPELINE

English Abstract

A mixer circuit, in the form of a vertically oriented stack of components,
functions to slurry oil sand with water in preparation for pumping through a pipeline.
The oil sand is initially dropped from the end of a conveyor. It is contacted in mid-air
with a stream of water to distribute the water through the oil sand and to wet the latter.
The mixture drops into a downwardly slanted trough. The water and oil sand mix as
they move turbulently through the open-ended trough. The slurry is deflected as it
leaves the trough and is spread in the form of a thin sheet on an apron. It is then fed
over screens to reject oversize lumps. The screened slurry drops into a pump box.
The rejected lumps are comminuted in an impactor positioned at the end of the
screens. The comminuted oil sand is screened to remove remaining oversize lumps
and the screened comminuted oil sands are delivered into the pump box. The
structure is compact and the oversize reject loss is relatively low.

French Abstract

Un circuit de mélange, sous forme de composantes superposées, fonctionne en vue de mettre en suspension épaisse du sable bitumineux avec de l'eau en vue de son pompage dans un pipeline. Le sable bitumineux tombe initialement du bout d'un convoyeur. Il est mis en contact à mi-hauteur avec un jet d'eau pour que l'eau se distribue dans la masse du sable bitumineux et le mouille. Le mélange est déversé dans une auge inclinée vers le bas. L'eau et le sable bitumineux se mélangent pendant qu'ils se déplacent avec turbulence dans l'auge à bout ouvert. La suspension épaisse est dispersée à sa sortie de l'auge et étalée en une mince couche sur un tablier. Elle est ensuite acheminée sur des tamis pour rejet des fragments trop gros. La suspension tamisée tombe dans une boîte de pompage. Les fragments rejetés sont affinés dans un impacteur placé au bout des tamis. Le sable bitumineux affiné est tamisé pour enlèvement des fragments trop gros qui restent et les sables bitumineux affinés et tamisés sont déversés dans la boîte de pompage. L'installation est compacte et la perte par rejet de fragments trop gros est relativement faible.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A process for slurrying oil sand, containing oversize lumps, with
water to produce a slurry and removing oversize lumps from eth slurry to produce
slurry suitable for pumping through a pipeline, comprising:
dropping the oil sand through air from the discharge end of a conveyor
onto a downwardly slanted surface spaced below the conveyor discharge end;
contacting the oil sand with a stream of water as the oil sand moves
through the air between the conveyor discharge end and the surface, to wet the oil
sand;
mixing the oil sand and water as they move together along the surface,
to form a slurry stream;
discharging the slurry stream onto first screen means and screening it
to reject oversize lumps; and
directing the screened slurry into a pump box prior to pumping it into a
pipeline.
2. The process as set forth in claim 1 wherein:
the initial portion of the downwardly slanted surface is provided by an
open-topped trough having a discharge outlet at its lower end.

3. The process as set forth in claim 2 comprising:
discharging the slurry stream from the trough and deflecting the stream
with upstanding wall means to change its direction of flow and induce further mixing
of the slurry; and
spreading the deflected slurry stream over a downwardly slanted apron
extending from the wall means, to establish a sheet of slurry which is discharged onto
the first screen means.
4. The process as set forth in claims 1, 2 or 3 comprising
comminuting rejected oversize lumps discharged from the first screen
means, to produce comminuted product;
and discharging the comminuted product into the pump box.
5. The process as set forth in claims 1, 2 or 3 comprising:
comminuting rejected oversize lumps discharged from the first screen
means, to produce comminuted product associated with residual oversize lumps;
screening the comminuted product to reject residual oversize lumps; and
discharging the comminuted product into the pump box.

6. An assembly of vertically oriented components for slurrying oil sand,
containing oversize lumps, with water to produce a slurry and removing oversize lumps
from the slurry to produce slurry suitable for pumping through a pipeline, comprising:
conveyor means, having a discharge end, for delivering and dropping a
stream of oil sand;
a downwardly slanted surface positioned in spaced relation below the
conveyor means discharge end, so that the oil sand drops thereon;
means for delivering a stream of water so that it contacts and wets the
oil sand as it drops between the conveyor means discharge end and the support
surface;
whereby the oil sand and water may mix as they move along the surface
and form a slurry stream;
first screen means for screening the slurry stream to reject oversize
lumps and produce screened slurry; and
pump box means for receiving the screened slurry.
7. The assembly as set forth in claim 6 comprising:
means for comminuting the rejected oversize lumps as they leave the
first screen means to produce comminuted product; and
means for transferring the comminuted product into the pump box means.
8. The assembly as set forth in claim 7 comprising:
second screen means for screening the comminuted product to reject
residual oversize lumps before the comminuted product is transferred into the pump
box means.
12

9. An assembly of vertically oriented components for slurrying oil sand,
containing oversize lumps, with water to produce a slurry and removing oversize lumps
from the slurry to produce slurry suitable for pumping through a pipeline, comprising:
conveyor means, having a discharge end, for delivering and dropping a
stream of oil sand;
a downwardly slanted, open-topped trough having a discharge opening
at its lower end, said trough being positioned in spaced relation below the conveyor
means discharge end, so that the oil sand drops therein;
means for delivering a stream of water so that it contacts and wets the
oil sand as it drops between the conveyor means discharge end and the trough;
whereby the oil sand and water may mix as they move through the
trough and form a slurry stream discharging from its lower end;
wall means, spaced from the trough's lower end, for deflecting the slurry
stream and changing its direction of flow and spreading the stream to form a sheet of
slurry;
first screen means for screening the slurry stream to reject oversize
lumps and produce screened slurry;
pump box means for receiving the screened slurry;
means for comminuting the rejected oversize lumps as they leave the
first screen means to produce comminuted product;
second screen means for screening the comminuted product to reject
uncomminuted oversize lumps and produce screened comminuted product; and
means for transferring the screened comminuted product into the pump
box means.
13

Description

~ 2195604
FIELD OF THE INVENTION
2 This invention relates to a process and mixer circuit for mixing oil sand
3 with water to produce a slurry which can be pumped through a pipeline.
BACKGROUND OF THE INVENTION
6 The McMurray oil sands of Alberta constitute one of the largest deposits
7 of hydrocarbons in the world.
8 At the presenl time, there are two very large scale plants extracting
9 bitumen (a heavy and viscous oil) from these oil sands. Each of these plants
incorporates a sequence of mining, bitumen extraction and bitumen upgrading
1 1 operations.
12 For many years, the as-mined oil sand was moved by conveyor belt13 assemblies from the mine site to the extraction plant.
14 In recent years, slurry pipelines have begun to replace the conveyor belt
1 5 systems.
16 In connection therewith, one needs to provide suitable means for17 slurrying the oil sand with water and entrained air, to produce a slurry that is suitable
18 for pumping down the pipeline.
19 The mixer circuit so provided is required to cope with very large volumes
of throughput - typically 10,000 tons of oil sand per hour. The oil sand is highly
21 erosive, so the mixer circuit should have minimal moving parts and be very durable.
22 In addition, the as-mined oil sand contains a variety of lumps including rocks, clay
23 lumps, and oil sand lumps. The concentration of lumps is greater in winter, when
24 some of the oil sand reports in the form of frozen chunks. Usually the as-mined oil
sand will have passed through a double roll crusher prior to slurrying, to reduce lump

~_ 21 95604
size below 24 inches. However, the crushed oil sand still contains oversize lumps
2 which are unsuitable for pumping and feeding into the pipeline. Therefore the mixer
3 circuit requires some means for rejecting the oversize lumps (otherwise referred to
4 herein as "oversize").
In United States patent No. 5039227, issued to Leung et al and
6 assigned to the owners of the present application, one mixer circuit for this purpose
7 has been rlisclosed.
8 In the Leung et al mixer circuit, an oil sand stream is dropped from the
9 end of a conveyor into a mixer tank. The mixer tank is open-topped, has a cylindrical
10 body and conical bottom and forms a central bottom outlet. A swirling vortex of slurry
11 is maintained in the tank and the incoming oil sand is fed into it. Slurry leaves the tank
12 through the bottom outlet, is screened using vibrating screens to reject oversize, and
13 is temporarily collected in an underlying pump box. Some of the slurry in the pump
14 box is withdrawn and pumped back through a return line to be introduced tangentially
into the mixer tank to form the swirling vortex. The balance of slurry in the pump box
16 is withdrawn and pumped into the pipeline.
17 The Leung et al mixer circuit has been successfully applied on a
18 commercial scale. However, it is characterized by certain shortcomings.
19 One problem has to do with the fact that a large proportion of the
20 produced slurry has to be pumped back into the mixer tank to maintain the vortex. As
21 a result, the slurry volume that undergoes screening is about twice the volume
22 pumped into the pipeline. This requires provision of a very large screen area. The
23 screens are necessarily located in confined quarters. As a result, one cannot increase
24 the throughput of the circuit because the screens constitute a bottleneck that is not
easily resolved.

2 1 95604
Another problem lies in the oversize reject rate. At present the screens
2 reject lumps having a diameter greater than 2 inches. About 10% of the oil sand feed
3 is so rejected. These rejects represent a significant oil loss. To reduce this loss, the
4 rejects are conveyed to a second mixer circuit and are re-processed. This is expensive
5 to implement.
6 From the foregoing, it is apparent that there is a need for a mixer circuit
7 which operales without slurry recycle and which has improved reject rates.
8 It is the purpose of the present invention to provide such a mixer circuit.
SUMMARY OF THE INVENTION
11 In a preferred form of the invention, we have provided a stack of
12 vertically oriented components which convey the oil sand and water downwardly along
13 a generally zig-zag path, comprising:
14 ~ A conveyor having a discharge end for delivering a continuous
stream of oil sand that falls through air into a trough;
16 ~ A pipe for delivering a stream of water which contacts and wets
17 the falling oil sand in mid-air;
18 ~ The trough being downwardly slanted, open-topped and
19 positioned in spaced relation below the conveyor discharge end
and the water pipe. The trough is operative to receive the
21 mixture of oil sand and water and confine it temporarily to allow
22 the oil sand and water to turbulently mix and form a slurry stream
23 as they flow along its length and discharge from its open lower
24 end;

21 95604
~ An upstanding wall positioned adjacent the trough's lower end
2 and spaced therefrom so that the slurry stream hits it and is
3 deflected, with the result that its direction of flow is changed and
4 further mixing is induced;
~ An apron providing a broad surface for receiving the deflected
6 stream, whereby the stream is spread out and thinned to form a
7 slurry sheet adapted to efficiently utilize the screen area;
8 ~ A first screen assembly for receiving and screening the slurry
9 sheet to reject oversize and produce a screened slurry stream;
and
11 ~ A pump box for collecting the screened slurry stream and feeding
12 a pump to deliver the slurry into the pipeline.
13 This assembly has successfully been tested to demonstrate:
14 ~ that a slurry suitable for pipeline conveyance can be formed using
only the amount of water required for hydrotransport in the
16 pipeline; and
17 ~ that the screen area required for each unit volume of oil sand
18 treated is reduced in comparison to our prior art system.
19 It has been found that the water needs to contact the curtain of falling
20 oil sand in mid-air. If the water is added at the trough, it has a tendency to channel
21 through the oil sand and mixing is inadequate. The oil sand then does not flow easily
22 along the trough. It has been found that contacting the oil sand in mid-air with water
23 yields good distribution of the water in the oil sand and produces a slurry that flows
24 easily on contacting the trough surface.

2 1 95604
-
In a prefer,ed extension of the invention, the rejected oversize lumps
2 from the first screen assembly are fed directly into an impactor and co",r,linuted. The
3 comminuted product is screened by a second screen assembly to reject any remaining
4 oversize. The comminuted, screened product is then delivered into the same pump
5 box which receives the screened slurry from the first screen assembly.
6 As a result of combining components in this way, the following
7 improvements have been achieved:
8 ~ the vertical stacking of the components yields a structure that is
9 compact relative to the prior assembly amd relies on gravity to
",obili~e the oil sand and water;
11 ~ the need for recycling slurry has been eliminated, with the result
12 that screen loading is decreased; and
13 ~ reject rates have been reduced below 3%.
14 Broadly stated, in one aspect the invention comprises a process for
15 slurrying oil sand, containing oversize lumps, with water to produce a slurry and
16 removing oversize lumps from the slurry to produce slurry suitable for pumping through
17 a pipeline, comprising: dloppi.1g the oil sand through air from the discharge end of a
18 conveyor onto a downwardly slanted surface spaced below the conveyor discharge
19 end; contacting the oil sand with a stream of water as the oil sand moves through the
20 air between the conveyor discharge end and the surface, to wet the oil sand; mixing
21 the oil sand and water as they move together along the surface, to form a slurry
22 stream; discharging the slurry stream onto first screen means and screening it to reject
23 oversize lumps; and directing the screened slurry into a pump box prior to pumping it
24 into a pipeline.

21 95604
Broadly stated, in another aspect the invention comprises an assembly
2 of vertically oriented components for slurrying oil sand, containing oversize lumps, with
3 water to produce a slurry and removing oversize lumps from the slurry to produce
4 slurry suitable for pumping through a pipeline, comprising: conveyor means, having
a discharge end, for delivering and dropping a stream of oil sand; a downwardly
6 slanted surface positioned in spaced relation below the conveyor means discharge end,
7 so that the oil sand drops thereon; means for delivering a stream of water so that it
8 contacts and wets the oil sand as it drops bel-veen the conveyor means discharge end
9 and the support surface; whereby the oil sand and water may mix as they move along
the surface and form a slurry stream; first screen means for screening the slurry stream
11 to reject oversize lumps and produce screened slurry; and pump box means for
12 receiving the screened slurry.
13
14 DESCRIPTION OF THE DRAWINGS
Figure 1 is a schematic side view showing the preferred embodiment of
16 the invention.
17
18 DESCRIPTION OF THE PREFERRED EMBODIMENT
19 As-mined oil sand to be pipelined is first crushed before conveying it to
a mixer circuit 1. This is commonly done by passing it through a set of double rolls,
21 producing 24 inch product. This pre-treatment (which forms no part of the invention)
22 is done to break down the very large contained lumps.
23 The crushed oil sand contains lumps of varying size and con,posilion.
24 The mixer circuit 1 comprises a series of downwardly arranged
components.

21 95604
The uppermost component is a conveyor 2 for continuously delivering a
2 stream of crushed oil sand 3. The oil sand c~cc~des or falls from the discharge end
3 4 of the conveyor 2- it drops downwardly through an air space 5.
4 A horizontal pipe 6 is positioned opposite to the conveyor discharge end
4. The pipe discharges a stream 7 of water into the falling oil sand in mid-air at a
6 sufficient rate so that the water/oil sand ratio is equivalent to that of the pipeline slurry.
7 Typically this ratio is about 1:3 by weight. The stream 7 contacts the downwardly
8 descending oil sand is distributed through it and wets it.
9 The oil sand and water drop into a downwardly slanted, open-topped,
open-ended trough 8. The trough is formed of plate steel.
11 AS the oil sand and water move through the trough, they mix turbulently
12 and form a slurry.
13 A solid, vertical wall 10 formed of steel is positioned adjacent the lower
14 end 11 of the trough 8. The wall 10 is spaced from the trough's lower end 11 and
extends across the trajectory path of the slurry stream 13 discharging from the trough.
16 A downwardly slanted apron 14 extends downwardly from the wall 10 in
17 a direction opposile to that of the trough 8.
18 The slurry stream 13 hits the wall 10, is deflected and changes its
19 direction of movement, being discharged onto an apron 14 having solid and then
apertured portions. In the course of these movements, further turbulent mixing of the
21 oil sand and water occurs. On reaching the apron, the slurry spreads out laterally and
22 is thinned, to form a slurry sheet 15. Some slurry drops through the apertures into the
23 pump box 18.
24 The slurry sheet 15 flows from the apron 14 onto a contiguous first
vibrating screen 16. It is sized to retain +4 inch material.

~ 1 9~604
The slurry 17 passing through the screen drops into a pump box 18.
2 Here the slurry is collected and temporarily retained before being pumped from an
3 outlet into a pipeline (not shown).
4 The oversize lumps 20 retained by the vibrating screen 16 are delivered
into an impactor 24. The lumps 20 are largely oil sand in composition and many
6 disinlegrale when impacted by the rotating arms of the impactor, producing
7 comminuted product 27. This product discharges from the outlet of the impactor onto
8 a second vibrating screen 30. The screened comminuted product is discharged
9 through hopper 31 into pump box 18. The oversize lumps retained by the screen 30
are discarded.
11

Representative Drawing