Note: Descriptions are shown in the official language in which they were submitted.
CA 02499840 2007-06-11
Self Clearing Crusher Flowsheet
1 INTRODUCTION AND PRIOR ART
2
3 Oil-sand mining and processing equipment technology is unique to the
deposits
4 found in Northem Alberta, Canada, in terms of the evolution of process
equipment
suitable for mining and processing the oil-sand ore. In the oil-sand mine,
equipment
6 used to excavate and transport the run-of-mine (ROM) oil-sand ore is as
large in scale
7 as at any world-wide mining operations, typically using electric-hydraulic
shovels of up to
8 62 cubic metre capacity buckets loading into haulage trucks of up to 400
tons capacity to
9 transport the ROM oil-sand ore to a centralized oil-sand slurry preparation
facility.
Due to the massive scale of the mining equipment and the characteristics of
the
11 oil-sand itself, the ore mined typically contains a very large range of
lump sizes spanning
12 from 3,500 mm weighing up to 30 tonnes, down to clay particles of a less
than one
13 millimeter diameter. The ROM oil-sand ore typically contains up to 15% free
water, 6%
14 to 18% bitumen and 75% to 85% solids of which 95% is sand content by weight
and also
contains amounts of siltstone rock having an unconfined compressive strength
of 165 to
16 221 MPa as a waste component.
17 The harsh environmental conditions at oil-sand operations encompass an
18 ambient temperature range from +35 degrees Celsius down to -51 degrees
Celsius.
19 Materials handling properties of the ROM ore are highly variable over this
temperature
range. The oil-sand ore comprises frozen, highly abrasive lumps in winter but
exhibits
21 sticky, cohesive behaviour in summer, largely due to the influence of the
contained
22 moisture and bitumen components.
23 A slurry preparation process step is typically required to prepare all ROM
ore to
24 be suitable for long-distance transport as a water slurry to be pumped to a
remote
upgrading facility, at single-stream production rates which may exceed 10,000
tonnes
26 per hour of ROM oil-sand ore. Typical prerequisites for efficient slurry
pumping are
27 crushing the oil-sand ore to minus 100 mm followed by the preparation of a
28 homogeneous water slurry, typically with a consistency of about 64% solids
by weight at
29 a slurry specific gravity of 1.5.
All mining and slurry preparation equipment is required to function with
31 unhindered effectiveness and productivity under these extreme ambient
conditions.
32 Current practice for oil-sand slurry preparation in the industry requires
the use of
33 multiple series-wise equipment processing steps to accomplish controlled
ore feeding,
34 screening and crushing prior to slurry pipelining. Designers and equipment
vendors are
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Self Clearing Crusher Flowsheet
1 challenged to create a processing facility containing multipie items of
equipment,
2 typically having intermediary gravity feed and conveying transfer stages.
The oil-sand
3 slurry preparation equipment, for example, is typically housed within large,
structural
4 steel modules located within the active oil-sand mining area. These modules
must be
constructed suitably for re-location on a typical frequency of 1 to 3 years
per operating
6 location.
7 Disadvantages of the prior art for oil-sand slurry preparation arise largely
from
8 adapting conventional process equipment and conventional process flowsheet
logic to
9 the Canadian oil-sand context, including the primary constraint of requiring
a screening
process step to ensure control of the maximum size of lumps, with the
corollary
11 requirement of adding one or more oil-sand re-handling process steps and
the creation
12 and accumulation of a "rejects" waste pile adjacent to the slurry
preparation facility.
13 Maintenance effort is also high due to the large quantity of equipment used
to implement
14 the required flowsheet. The prior art can therefore be characterized as
"process
flowsheet deficient" with respect to inherent limitations in meeting modern
oil-sand
16 mining plant requirements in a practical and efficient manner.
17 A preferred embodiment of this invention comprises an improved oil-sand
process
18 flowsheet logic utilizing unique, enabling, materials handling and
processing equipment
19 innovations. These improvements include minimizing all crushing and
screening steps
and eliminating oil sand re-handling process steps, primariiy by introducing
unique a
21 single-pass crushing process step. This process flowsheet improvement
beneficially
22 impacts the design of the slurry preparation plant and also facilitates
design for
23 portability or mobility of the slurry preparation plant facility.
24 The need for controlling oil-sand lump size lies in the requirements of the
slurry
transportation step, in which the minimum slurry pumping velocity is strongly
dictated by
26 maximum lump size and density of contained lumps. For example, if foreign
material
27 such as pieces of steel, often found in oil-sand mining ore delivered for
slurry
28 preparation, is allowed by the process flowsheet to enter the sluny
preparation tank
29 along with typical cnished oil-sand, the resulting mixture is difficult to
pump successfully
due to a density range of at least 3 to 1 between steel, rocks and oil-sand
ore. Besides
31 the risks of plugging the slurry tank, pipeline valves, the pump itself or
the pipeline,
32 damage to pumping and other downstream equipment may result. For this
reason the
33 process flowsheet for an oil-sand slurry preparation plant must incorporate
positive
34 rejection of pieces of steel and any other uncrushable material so as to
protect the
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Self Clearing Crusher Flowsheet
1 integrity of the downstream processes. Prior art flowsheets thus
incorporating these
2 protections suffer many compromises and complications in comparison to the
improved
3 flowsheet described in this patent application.
4
With reference to the Figures:
6 Figure 1 is a conventional oii-sand slurry preparation plant process
flowsheet
7 illustrating best practices of the prior art.
8 Figure 2 is an improved oil-sand slurry preparation plant process flowsheet
9 incorporating preferred embodiments of the invention.
Figure 3 is an improved, self clearing crusher featuring a single crushing
roll
11 working in combination with a reversible endless chain of flat connected
crushing plates,
12 this crusher having unique design features so as to positively reject
uncrushable objects
13 and to positively eliminate the passage of oversize objects into the
downstream process.
14 Figure 4 is an improved, self clearing crusher featuring a single jaw
crushing
assembly working in combination with a reversible chain of flat connected
crushing
16 plates, this crusher being designed to positively reject uncrushable
objects and to
17 eliminate the passage of oversize objects into the downstream process.
18
19 In prior-art Figure 1 oil-sand ore is delivered from a prior process step
by
conveyor 1 to ore-preparation gravity mix box 2, which may comprise any
suitable
21 intemal configuration for mixing oil-sand ore 3 with recirculated slurry
stream 4 and
22 make-up water stream 5 using intemai baffles or the like known in the art,
the details of
23 which are not shown. Mixture stream 6 discharges to primary screen 7
through which
24 the undersize fraction 8 falls into primary pump box 9 and the oversize
fraction 10
discharges to the secondary crusher 11, shown in this figure as a single
crushing roll 12
26 operating in conjunction with a pressure-relievable concave surface 13.
Crusher
27 discharge stream 14 passes onto secondary screen 15 through which the
undersize
28 fraction 16 falls into the secondary pump box 17 and the oversize fraction
18 passes to
29 rejects pile 19. From the secondary pump box 17, secondary slurry pump 20
pumps
recircuiation stream 4 to mix box 2 from which mixture 6 passes through
primary screen
31 7 to report to primary pump box 9 or be again rejected as oversize stream
10 returning
32 to secondary crusher 11, thus illustrating the possibility in the known art
of continuously
33 recirculating uncrushable and over-size lumps.
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Self Clearing Crusher Flowsheet
I Oil-sand material stream 8 accepted at primary screen 7 enters primary pump
2 box 9 which is equipped with suitable slurry mixing means known in the art
(not shown)
3 in preparation for pumping by hydro-transport pump 21 as stream 22 to a
subsequent
4 process step (not shown).
In Figure 1 at least some of the undersize materials 14 passing onto secondary
6 screen 15 may be larger than desired due to the pressure-relievable action
of concave
7 surface 13, which is an essential protection feature for crusher 11 against
encountering
8 uncrushable objects. Crusher designers are limited, however, in the maximum
9 achievable relieving stroke distance of concave surface 13, allowing the
possibility that
some uncrushable objects may simply be too large to pass through either the
normal or
11 the pressure-relieved crushing gap and may damage, stall or block crusher
11. In this
12 case the operation of the slurry preparation facility must be shut-down
until crusher 11
13 can be repaired or the blockage removed. Other crusher designs such as the
dual-roll
14 crusher are similarly provided with pressure-relieving design features, in
which the
concave surface 13 could be replaced by a movable crushing roll similar to and
working
16 in conjunction with crusher roll 12.
17 A further prior art flowsheet compromise in Figure 1 is choosing primary
screen 7
18 and secondary screen 15 to have smaller than optimum sized mesh openings so
as to
19 maximize the probability of rejecting uncrushable, over-size objects to
rejects pile 19.
The practical result of this compromise selection may be to reject significant
amounts of
21 valuable oil-sand lump material to rejects pile 19 which could otherwise
have been
22 suitably accepted at primary screen 7 or prepared to pumpable
specifications by once
23 more passing through the recycle loop 4 and secondary crusher 11.
24 In the improved flowsheet of Figure 2 typical oii-sand ore 23 is delivered
from a
prior process step by conveyor 24 to ore-preparation gravity mix box 25, which
may
26 comprise any suitable intemal configuration for mixing oil-sand ore 23 with
make-up
27 water stream 26 using internal baffles or the like known in the art, the
details of which
28 are not shown. Mixture stream 27 discharges to screen 28 through which the
undersize
29 fraction 29 falls into pump box 30 and oversize fraction 31 discharges to
the self-clearing
crusher 32, shown in this figure as a single fixed crushing roll 33 operating
in conjunction
31 with a horizontal, flat crushing surface 34 which is configured as an
endless conveyor
32 chain having head pulley 35 and tail pulley 36. Crusher discharge stream 37
passes into
33 primary pump box 30 to be mixed with screen undersize fraction 29 and
prepared for
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Self Clearing Crusher Flowsheet
1 pumping by hydro-transport pump 37 as stream 38 to a subsequent process step
(not
2 shown).
3 Self-clearing crusher 32 is equipped with a reversible drive for endless
conveyor
4 34 for the purpose of handling uncrushable objects. Unlike prior art
crushers, neither
crushing roll 33 nor flat crushing surface 34 has a pressure-relieving design
feature such
6 as the design feature of crusher 11 in Figure 1. Rather, self-clearing
crusher 32 is
7 controlled to reverse the direction of conveyor 34 when an uncrushable
object is
8 encountered, causing the uncrushable object and some accompanying portion of
normal
9 oil-sand ore to be discharged as rejects stream 39 to rejects pile 40.
Normal oversize
fraction crushing operation can be resumed immediately after the crusher
clears itself by
11 this means.
12 Figure 3 illustrates features of the self-clearing crusher 32 of Figure 2
in greater
13 detail including the single crushing roll 33, the reversible endless chain
of flat connected
14 crushing plates 34 forming an endless conveyor with longitudinal extent
defined by head
pulley 41 and tail pulley 42 and arranged with gap 43 defining a crushing zone
set
16 between crushing roll 33 and flat crushing plates 34. In operation the
crushing plates 34
17 forming a conveyor can be motivated to draw lumpy material 44 into gap 43
producing
18 crushed ore stream 45 which falls into slurry preparation vessel 46. If an
uncrushable
19 object is encountered, the motivation of the crushing plates 34 forming a
conveyor can
be reversed so as to convey the uncrushable object away from the crushing zone
21 defined by gap 43 to be discharged as stream 47 to rejects pile 48. By this
means the
22 uncrushable object, which may be a piece of steel, is prevented from
entering the slurry
23 preparation process step and the crushing operation need only be delayed
for several
24 seconds to ailow the clearing action to take place.
Figure 4 illustrates an aitemate arrangement of the self-clearing crusher 32
of
26 Figure 2 in which a single jaw 49 is substituted for crusher roll 33, all
other elements of
27 the crusher and its operation remaining the same between Figures 3 and 4.
28 The primary enabling technology of the improved process flowsheet of Figure
2
29 being the beneficial use of self-clearing crushing means as described
herein.
31
32
33
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Self Clearing Crusher Flowsheet
1 The prior art oil-sand slurry preparation plant process flowsheet of Figure
1 is
2 clearly more complex containing additional process steps and processing
equipment
3 than the improved oil-sand slurry preparation plant process flowsheet of
Figure 2 using
4 the self-clearing crusher designs of Figures 3 or 4. In particular the
secondary screen 7,
the secondary pump box 17 and the oil-sand re-circulation pump 20 of the prior
art
6 flowsheet of Figure 1 are not required in the improved flowsheet of Figure
2..
7 In this patent disclosure the oil-sand slurry preparation circuits beginning
at tank
8 30 of Figure 2 could also represent any "subsequent process step" of any ore
9 preparation plant whether or not it involves the preparation of a slurry. An
alternate
subsequent process step, for example, may be a milling and grinding process
step in
11 which lump size received from the ore preparation plant will undergo
further size
12 reduction.
13 It will be clear to one practiced in the art that the elimination of a
screening step,
14 secondary slurry preparation tank and re-circulation pump equipment in the
improved
process flowsheet makes the design and construction of plant equipment modules
to be
16 more suitable for portability or mobility, enabling more efficient
relocation of the oil-sand
17 slurry preparation plant within the mining areas.
18 It will be readily appreciated by one practiced in the art that although
the
19 flowsheet illustrates water being introduced prior to screening, water
could be introduced
later in the process after the screening step. Also, the quoting of specific
capacity or
21 dimensional data for equipment or process steps of the oil-sands operations
is not
22 intended to limit the use of other capacities and dimensions when such use
falls within
23 the spirit of the invention.
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