Note: Descriptions are shown in the official language in which they were submitted.
~2~34~
FIELD OF THE INVENTION
2 This invention relates to a method and apparatus for
3 recovering bitumen from a feed stream comprising solids, water and bitumen,
4 preferably one or both of the tailings and middlings streams from the
primary separation vessel used in the extraction of bitumen from tar
6 sand by the hot water process.
7 BACKGROUND OF THE INVENTION
8 Tar sand is currently being exploited for the recovery of
9 bitumen therefrom by two large commercial plants in the Athabasca region
of Alberta. In general, the tar sand is mined, the bitumen is extracted
1l from it by means of the hot water process, and the bitumen is upgraded
12 in a refinery-like operation to produce synthetic crude.
13 The mined tar sand comprises coarse sand particles,
4 individually sheathed in a thin film of connate water, with bitumen
trapped in the interstices and clay-size mineral particles ttermed
16 'fines') distributed in the sheaths.
7 The tar sand is not constant in composition. There is a
1~ significant variation in its nature and processibility. In general, the19 bitumen content diminishes and the fines content increases as the gradeof the tar sand deteriorates. A "rich" tar sand typically might comprise:
21 Total solids - 85.0%
22 bitumen - > 12%
23 fines - 5% of total solids
24 A "poor" tar sand typically might comprise:
Total solids - > 85%
26 bitumen - 8.0%
27 fines - up to 25% of total solids
3~2~8476
Typically, one might expect to recover greater than 90% of the contained
2 bitumen from a "rich" tar sand and only about 60% from a "poor" tar sand,
3 in the primary separation step of the hot water extraction process.
4 The variation in the nature and quality of the tar sand
5 feed depends on factors such as location, depth in the deposit, and
6 the like. As a general statement, it is true that the ever-varying
7 quality of the tar sand feed generates significant operating and
8 recovery problems for the extraction plant.
9 At this point, it is appropriate to describe the hot
water process in a general sense. The details of the process are
1l well documented in the literature.
12 In the first step of the process, the as-mined tar sand
3 is fed into a horizontal, rotating drum. Hot water, having a temperature
4 of about 180F, is also fed into the drum and steam is sparged into the
mixture, to maintain a slurry temperature of about 180F. The rotating
16 drum cascades the porridge-like mixture, with the result that air
17 bubbles become entrained therein. After a residence time of perhaps
18 10 minutes, the slurry is discharged onto a screen, to separate
19 oversize material.
This initial step is referred to as "conditioning".
21 Pursuant to it, the bitumen is heated, the tar sand components are
22 diluted with water and dispersed in a preliminary fashion; and air
23 bubbles are entrained in the mixture.
24 The screened, conditioned slurry is then diluted with
25 additional hot water and introduced into a thickener-like flotation
26 vessel. This vessel is referred to as the primary separation vessel
27 ("PSV"). It is shown schematically in Figure la. As illustrated,
28 it is an open-topped vessel, having a cylindrical upper end and a
29 shallow cone lower end. The angularity of the cone end is in the
30 order of 23. The vessel has a launder at its upper end, so that
~4~
1 froth formed at the surface of the vessel contents may overflow and be
2 recovered. It further has an internal rake assembly in the cone, for
3 moving sand collected and concentrated therein to a bottom outlet.
4 The slurry feed is added to the vessel contents via a conduit and central
well. An outlet is provided in the mid-section of the vessel, for the
6 withdrawal of middlings.
7 In the PSV, the bulk of the sand settles into the conical
8 end, where it is concentrated, with a concomitant expulsion of liquid
9 phase. The resultant sand layer typically has a liquid content of 65%
by weight. This product, termed "primary tailings", is withdrawn
11 through the bottom outlet. Most of the bitumen particles entering
12 the PSV with the feed slurry are attached to or become attached to air
3 bubbles and rise to form a froth layer at the surface of the vessel
4 contents. This froth is recovered via the launder, as aforesaid, and is
referred to as "primary froth". The bulk of the water in the feed,
16 together with some bitumen and solids, collects in the mid-section of the
17 vessel and is referred to as PSV "middlings" . A dragstream of middlings
18 is continuously withdrawn at a controlled rate through outlets in the
19 vessel side wall. The desired level of the froth-middlings interface is
maintained by control of the rate of PSV middlings withdrawal. The level
21 of the middlings-sand interface is controlled by varying the rate of
22 tailings withdrawal.
23 As stated, the PSV middlings is largely water, but it
24 includes some bitumen and solids. The bitumen was insufficiently
buoyant to reach the froth layer in the PSV. The solids is mostly
26 fines.
347~
The middlings dragstream is processed in one or more induced
2 air flotation cells. Each of these cells, termed "secondary recovery
3 cells", is equipped with an up-throwing impellor positioned in its bottom
4 end. Air is induced to flow downwardly through the hollow shaft of the
impellor and is released at the impellor blade. So the cells incorporate
6 turbulent agitation and copious aeration. As a result, some of the
7 middlings bitumen forms a froth layer on the surface of the cell contents.
8 This froth, called "secondary froth", is recovered. A bitumen-depleted,
9 watery underflow, termed "secondary tailings" is withdrawn through an
outlet in the base of the cell.
1l The secondary froth is settled in a tank, to remove some
12 water and solids from it, and then is combined with the primary froth.
13 This latter stream is subjected to downstream cleaning and upgrading, to
4 yield a saleable product. The primary and secondary tailings are combined
and impounded in waste ponds.
16 Now, two main objectives in managing the hot water process
17 are to maximize the proportion of feed bitumen which reports as primary
18 froth and to minimize the proportion lost with the two tailings streams.
19 The losses with the tailings are substantial. In applicant's plant, which
produces in the order of 130,000 barrels of synthetic crude per day, the
21 combined tailings are produced at a typical rate of 7600 kg./sec. and
22 the present bitumen losses with said tailings is in the order of 6
23 million barrels per year.
24 In managing the process, the withdrawal of middlings and
tailings from the PSV is adjusted as required:
26 - to try to maintain the froth-middlings interface at a
27 generally constant elevation;
28 - and to try to maintain the solids content of the with-
29 drawn tailings as close to about 65% by weight as
possible, by controlling the depth of the sand bed in the
31 cone.
12484~76
1 If the level of the froth-middlings interface rises, the
2 PSV will overflowj if the level drops, then bitumen losses will rise.
3 If too much liquid leaves with the tailings, then bitumen losses again
4 rise, as the bitumen accompanies the water.
Another complicating factor affecting the performance of
6 the PSV is the nature or grade of the tar sand being processed. If the
7 feed is "rich" tar sand, then the fines content in the slurry is
8 relatively low and thus the slurry viscosity is relatively low. The
9 bitumen particles in rich tar sand are relatively large in size and
10 are more likely to have become aerated. Thus they can relatively
11 easily rise through the middlings and primary froth recovery is relatively
12 high. And all this can be realized with relatively modest water addition.
13 But if the feed is "poor" tar sand, then fines content is high and the
14 viscosity of the middlings rises. In addition, the bitumen particles
are smaller with this type of feed and they do not aerate well. As a
16 result, they do not rise well and the primary froth yield diminishes.
17 So the operator must make process adjustments, to try to minimize the
18 undesirable effects taking place.
19 If the operator is varying water addition, then it follows
that the middlings withdrawal rates have to be varied, to maintain the
21 froth-middlings interface level constant and to maintain the primary
22 tailings dense. Varying the feed rate to the secondary recovery circuit
23 can lead to overloading of that circuit. As a result, bitumen losses with
24 the secondary tailings increase, in conjunction with an increase in
other operating difficulties.
26 With this background in mind, it will be appreciated
27 that there is a need to improve the hot water process to achieve the
28 following:
12~8~76
1 - reduction in bitumen losses with the tailings; and
2 - relief of the need to widely vary primary middlings
3 withdrawal rates, by loosening the required density
4 control on the primary tailings. This would smooth
out fluctuations in the feed rate to the secondary
6 circuit and permit of better management of that circuit.
7 In a general sense, this would involve treating the primary
8 tailings. In considering how to obtain such an improvement, one is
9 faced with certain problematical facts, namely:
- that the potential feedstock, PSV tailings, has a
1l very large proportion of solids and a small proportion
12 of bitumen (see Table I following below);
3 - that the volume of such a feedstock is very large and
4 there is relatively little valuable product to be
obtained from it, so the process used must be simple
16 and inexpensive;
7 - and that the bitumen in the tailings is bitumen which
18 was insufficiently buoyant to be recoverable from the
19 medium of the dilute middlings in the PSV.
TABLE I
21 Composition of a Typical Primary Tailings
22 Bitumen 0.4 weight %
23 Water 34.6 weight %
24 Solids 65.0 weight %
~2~347~
1 SUMMARy OF THE INVENTION
2 In accordance with the invention, a feed stream, comprising
3 water, sand, bitumen and fines, preferably consisting of combined PSV
4 tailings and PSV middlings, is fed to a tailings oil recovery vessel
(TORV). This vessel preferably has the form of a deep cone thickener- that
6 is, it has a cylindrical upper section and a sharp angled, conical lower
7 section. No rake assembly is provided in the conical section.
8 The fresh feed is delivered to the surface of the middlings
9 in the TORV and is spread or deflected outwardly, preferably with
a transversely extending baffle or the like, so that said newly added
11 feed tends to assume a generally horizontal, outwardly radiating form
12 as it joins the feed already in the TORV. At the same time, the newly
3 added feed is contacted from below by an upwelling aerated middlings
4 current. This current is generated in the middlings already in the
TORV. Preferably, the current is generated by withdrawing middlings
16 from the TORV and pumping them through a conduit loop to discharge
17 upwardly through a nozzle into an eductor positioned centrally in the
18 TORV middlings. The middlings so pumped induce additional middlings
19 to circulate upwardly through the eductor and an upwelling, central
current is thus generated . This current is aerated, for example by a
21 sparger associated with the nozzle, with a multitude of small air bubbles.
22 By means of this preferred combination of mechanical and
23 hydraulic deflection, the bitumen particles in the feed are to a considerable
24 extent initially kept from plunging into the depths of the TORV
middlings and are mixed with copious quantities of air bubbles. It is
26 found that much of the bitumen in the newly added feed forms froth as
27 a result and may be recovered. By using TORV middlings to provide the
28 upwelling current, many of the bitumen particles which have settled into
29 the middlings zone are recycled to the aerated zone and may be recovered.
~2~8~'7~i
1 The water in the feed, and some associated bitumen and
2 solids, accumulates as middlings in the mid-section of the TORV. Such
3 middlings are withdrawn from the TORV mid-section and are preferably fed
4 to the secondary recovery circuit.
The sand in the feed is distributed across the cross-
6 section of the TORV contents when first delivered. Most of it settles
7 through the middlings and enters the deep cone section. Here the liquid
8 associated with the sand is largely squeezed or displaced out, to rejoin
9 the middlings. There is produced at the base of the conical section a
high solids (in the order of > 65% by wt. solids) sand béd which is very low
11 in bitumen content. In most circumstances, it is necessary to dilute this12 stream with some water brought into the cone from an external source, to
13 fluidize the sand-laden tailings so that it will flow out of the
14 TORV through a bottom outlet.
From the foregoing, it will bé noted that the invention in-
16 volves two features in combination, namely:
17 - maximizing quick and extensive conversion of bitumen
18 to froth, so that there is a low concentration of
19 bitumen in any water lost with the TORV underflow;
- and minimizing the loss of liquid with the TORV
21 underflow tailings, by creating a dense sand bed in
22 the deep cone section, to squeeze out a relatively
23 high proportion of the liquid associated with the
24 sand.
The invention is characterized by a number of advantages,
26 including:
27 1. All of the feed passes through the aeration zone
28 and a significant recovery of bitumen is realized;
~24~3~7~
1 2. Aeration of the bitumen occurs at the surface of
2 the TORV contents, thus minimizing the length of
3 the travel that an aerated bubble of bitumen must
4 traverse (in contradistinction to the situation
in a secondary flotation cell, wherein the air is
6 introduced at the base of the cell);
7 3. A TORV tailings underflow is obtained which is quite
8 clean, with the result that the environmental
g impact of the pond into which the stream is dis-
lo charged is improved;
11 4. The fluctuations in feed rate to the secondary
12 recovery circuit are to a significant extent
smoothed out;
14
16 5. The need for close control of the bitumen content
17 in the PSV underflow is diminished, as this bitumen
18 can be recaptured in the TORV - this simplifies
lY operating problems heretofore associated with the
PSV;
21 6. The process mechanisms of aeration, flotation,
22 mixing, settling, separation, and removal are all
23 practised together in one vessel without internal
24 moving parts;
-- 10 --
~24l347~
1 7. The combination of the.. deep cone and fluidization
2 permits of gravity:or:suction transport~of the sand
3 to the bottom outlet~ without need for a rake system
4 and the problems attendant therewith; and
8. The sensitivity of the hot water extraction process
6 plant to variations in tar sand feed grade is
7 diminished.
8 Broadly stated, the invention is a method for continuously
9 recovering bitumen from a feed stream comprising water, sand, bitumen
and fines in a vessel having a conical lower end and which defines a
1l processing chamber, comprising: delivering said feed stream to be pro-
12 cessed at the surface of the body of middlings already in the chamber;
13 substantially simultaneously contacting the newly added feed with a
14 current of outwardly and generally horizontally moving.aerated middlings;
whereby said newly added feed moves generally radially of the chamber in
16 contact with the aerated middlings current, part of the.bitumen con-
17 tained in said newly added feed forms a froth layer at the surface of18 the body, bitumen-depleted feed forms a body of middlings in the chamber
19 below the froth layer, and sand particles contained in said newly added
feed settle downwardly;concentrating the.settling sand particles in the
21 conical lower end of the vessel into the form of a dense solids bed,
22 thereby separating the greatest part of the liquid phase from the
23 solids phase; recovering the greatest part of the froth from the vessel;
24 withdrawing an underflow tailings stream from the base of the vessel; and
withdrawing a middlings stream from the vessel mid-section.
-- 1 1 --
12~47~j,
1 DESCRIPTION:OF THE DRAWINGS
2 Figure l(a) is a schematic side section view showing a
3 prior art PSV;
4 Figure l(b) is a schematic side section view showing the
TORV of the present invention;
6 Figure 2 is a schematic, partly sectional, side view of
7 the TORV, with arrows indicating the current upwelling centrally and
8 circulating downwardly in the outer reaches of the vessel chamber;
9 Figure 3 is a schematic, partly sectional, side view of theeductor/aerator assembly and plenum chamber positioned in the TORV,
1l with the air bubbles, sand grains, froth and current suitably identified;
12 Figure 4 is a schematic showing the TORV incorporated into
3 a hot water process plant; and
14 Figure 5 is a sectional side view of a single eductor/aerator
assembly.
- 12 -
- ~Z~ 76
DESCRIPTION OF THE~PREFERRED EMBO~IMENT
2 The tailings oil recovery-vessel (TORV) 1 has the general
3 configuration of a deep cone thickener. It comprises a generally
4 cylindrical upper section 2, a shallow angle (60) intermediate cone
section 3, a steeper angle (68~) lower cone section 4, and a cylindrical
6 base section 5.
7 A feed assembly 6 is centrally mounted on the TORV 1 at
8 its upper end. The feed stream to be processed is delivered to the TORV
9 via this assembly. More particularly, the assembly 6 comprises a vertically
10 positioned, tubular feed well 7 supported by a cross-member 8 attached
1l to the TORV sidewall. A vertical, tubular feed pipe 9 is mounted in the
12 feed well 7 and extends downwardly through the floor of the latter. A
3 feed conduit 10 connects tangentially with the side wall of the feed
4 well 7 and communicates with the feed well chamber 11.
The feed to be processed, preferably comprising a slurry
16 of sand, bitumen, water, and fines, most preferably being a mixture of
17 PSV tailings and middlings, is introduced to the feed well 7 through the18 conduit 10. The slurry rises in the well chamber 11 and overflows into
19 the pipe 9, from whence it discharges downwardly into the TORV.
A conical distributor baffle 12 is positioned directly
21 below the outlet of the feed pipe 9 and extends transversely thereacross.
22 The baffle 12 is suspended in spaced relation to the feed pipe outlet by
23 members 13 secured to the cross-member 8.
24 The distributor baffle 12 functions to deflect the slurry,
25 discharging fromthe feed pipe 9, outwardly into a generally horizontal
26 plane, so that it spreads radially along the surface 13a of the body 14
27 of middlings already present in the vessel chamber 15.
` 31Z48~7~
1 A plenum assembly 16, forming a plenum chamber 17, is
2 attached to the underside of the distribution baffle 12. The plenum
3 assembly 16 is centrally positioned in the body 14 of middlings and is
4 submerged therein. The upper and lower walls 18, 19 of the plenum assembly
16 combine to form a peripheral, slot-like outlet 20 extending around the
6 upper edge of the plenum chamber 17.
7 A plurality of open-ended eductor tubes 21 extend out-
8 wardly from the plenum assembly lower wall 19 and interconnect the plenum
9 chamber 16 with the body 14 of the middlings.
As shown in Figure 5, a tubular nozzle member 22 is
1l mounted in coaxial, outwardly spaced alignment on each such eductor tube
12 21 by a bracket 23.
3 Each nozzle member 22 is circumscribed by a tubular sparger
4 23a mounted thereon. This sparger 23a is connected by a line 24 with a
source (not shown) of pressurized air. At its end remote from the plenum
16 assembly, the nozzle member 22 is connected by a line 25 with a pump 26,
17 which supplies recirculated middlings under pressure from a storage tank
18 27. At its end adjacent the eductor tube 21, the nozzle member 22
19 forms an orifice 28 for the discharge of a jet of aerated middlings.
The eductor tube 21, nozzle member 22, and sparger 23a
21 together combine to form an eductor/aerator assembly 61.
22 Each of these eductor/aerator assemblies 61 is operative to
23 direct or inject a jet of copiously aerated, recirculated middlings into the
24 inlet 29 of the eductor tube 21. These injected streams or jets function
to induce additional middlings, from the main body 14, to flow into the
26 plenum chamber 17 through the tubes 21. The aerated middlings are dis-
27 charged outwardly, slightly upwardly, and generally radially from the
28 plenum chamber 17 through the slot-like outlet 20.
- 14 -
~2~847~
1 As a result of such middlings injection, a generally circular
2 pattern is established in the TORV, as indicated by the arrows in the drawing.
3 This current pattern includes an upwelling leg through the plenum chamber,
4 an outwardly, radially moving leg contiguous to the outwardly radiating,
newly introduced slurry, and a downwardly descending leg in the outer
6 reaches of the body 14 of middlings. The incoming slurry is spread as a
7 thin layer on top of the fast-moving layer of aerated middlings dis-
8 charged from the plenum assembly. As the two layers contact and mix, the
9 fine air bubbles have an opportunity to contact the bitumen in the newly arrived slurry and recirculated middlings and form froth.
1l The formed froth accumulates as a layer 29a at the periphery
12 of the middlings surface 13a.
3 A vertical, circular weir 30 is suspended in the vessel
4 chamber 15 in spaced relation to the side wall 37 of the cylindrical
upper section 2. The weir 30 is positioned so that its upper edge is
16 just below the anticipated upper surface of the froth layer 29a. The
17 weir 30 is submerged, but functions to retain most of the layer 29a of
18 froth. A second vertical, circular weir 31 is positioned outwardly
19 from the weir 30 in spaced relation. This second weir 31 extends
downwardly a short distance below the top edge of the first weir 30.
21 Between them, the weirs 30, 31 form a zone 32 referred to as the froth
22 wash zone. A circular pipe 33 is mounted on the TORV immediately above
23 the froth wash zone 32. The pipe 33 has spaced spray nozzles 34 ex-
24 tending downwardly from it and is connected to a source (not shown) of
pressurized, clean water. The pipe 33 is thus operative to deliver a
26 spray of water down onto the froth which has overflowed the inner weir 30.
27 This water partly deaerates the froth and washes away some of the solids
28 attached to it.
29 The TORV froth thus accumulates as a layer 29a, overflows into the zone 32, and is washed by the water spray.
~24~7~
1 The cleaned, partly deaerated froth can leave the wash
2 zone 32 by moving beneath the outer weir 31.
3 A froth launder 35, having a discharge pipe 36, is attached
4 to the TORV sidewall on the outer side of the outer weir 31. The cleaned,
partly deaerated froth overflows into this launder 35 and is recovered.
6 The side wall 37 of the vessel's cylindrical upper section
7 2 has a vertically movable weir 38 attached thereto at its upper end.
8 This weir 38 can be adjusted up or down to control the level of the upper
9 surface 13a of the body 14 of middlings. A middlings launder 39 is
secured to the side wall 37, whereby excess middlings may overflow the
1l weir 38 and drop thereinto. The middlings launder 39 is connected by a
12 line 40 with the storage tank 27.
13 Means are provided in the lower end of the TORV 1 for
14 withdrawing sand collected there. Such means comprise a suction spider
41, having a plurality of inlets 42, and a suction conduit 43 connected
16 with the spider and extending out of the vessel. The conduit 43 is
17 connected with a pump for applying suction. Flush nozzles 44,
18 connected with a source of pressurized water, are provided
19 at the spider inlets 42, to direct jets of water at the inlets to unplug them on start-up.
21 The sand grains contained in the newly delivered slurry
22 settle downwardly in the chamber 15 and collect in the form of a
23 relatively high density (> 65% by weight) sand bed 45. The density and
24 height of this sand bed 45 are adjusted to desired levels by varying the
rate of tailings withdrawal.
26 The TORV is shown in Figure 4 in the context of a flow
27 circuit. The general operation of this circuit will now be described,
28 with particular detail given as to the process mechanisms which take
29 place within the TORV.
- 16 -
8~
1 Conditioned tar sand slurry ~rom a drum or tumbler 50
2 is discharged into a flood box 51, wherein it is diluted with flood
3 water. The dilute slurry is pumped through line 52 into a PSV 53.
4 Primary froth from the PSV is produced through line 54. The PSV under-
flow tailings are pumped through feed conduit 10 to the TORV 1. The
6 PSV middlings are pumped through line 55 to connect with feed conduit 10,
7 wherein they combine with the PSV primary tailings to form the TORV
8 feed.
9 The froth produced by the TORV is removed through line
36. Overflow middlings are produced through line 40 into storage tank
1l 27. Middlings are withdrawn from the tank 27 and pumped through line 25
12 to nozzle members 22. The tailings stream produced by the TORV is
~3 removed through line 43 for disposal in a pond or the like.
4 All of the excess middlings in the storage tank 27 are
pumped through line 56 to the secondary recovery flotation cells 57.
16 Secondary froth from the flotation cells 57 is produced through line 58
17 and secondary tailings is produced through line 59. Some of the
18 secondary tailings is diverted from line 59 through feed line 60, to
19 supply fluidizing fluid to the spider nozzles 44.
In the TORV, the incoming feed is delivered downwardly
21 onto the distributor baffle 12, which deflects and distributes the
22 slurry outwardly and generally horizontally as a relatively thin sheet,
23 on top of the fast moving, underlying~ upwelling layer of aerated mid-
24 dlings. At the same time, aerated middlings are being discharged from
the circular slot-like outlet 20 of the plenum assembly 16 in a radial,
26 outward, and gradually upwelling flow. As the outwardly-moving and slightly
27 upwelling flow of aerated middlings comes into contact with the
28 superimposed layer of bitumen-laden feed, the bubbles of air released
29 from the middlings must pass upwardly through the layer of feed before
- 17 -
~4~
1 escaping to atmosphere and all feed must pass downwardly through the
2 layer of aerated middlings before entering the main body 14 of middlings.
3 As the two streams contact and mix, both move outwardly towards the
4 periphery of the TORV. As the outward flow velocity slackens, the aerated
S globules of bitumen remain on the surface in the form of light, loose
6 froth, whereas the sand particles settle downwardly. The water and
7 suspended fine solids, as well as suspended fine bitumen globules which
8 did not form froth, join the body 14 of middlings. A portion of those
9 middlings is induced to move through the plenum assembly 16 and the
excess overflows the rim of the vessel over the adjustable weir 38
1l into the middlings launder 39 and is collected in the middlings storage
12 tank 27. The sand particles settle downwardly in the cone sections 3,4
3 and concentrate into a dense bed 45 of sand , having a solids content
4 typically in the order of at least 65~ by weight. The bottom portion of
this bed 45 is continually removed by the suction means. If necessary
16 the density of the withdrawn underflow stream can be reduced by injection
7 of water through the flush nozzles 44.
18 Example I
19 This example gives the results obtained from the operation
of a 3m diameter field pilot vessel.
21 3m TORV
22 Run 1 2 3 4
23 TORV FEED
24 PSV tails
rate (kg/s) 50.21 46.5 46.1 48.2
26 % bitumen 0.44 0.37 0.41 0.38
27 % solids 65.47 50.1 58.2 62.6
- 18 -
~Z4t~
1 Run 1 2 3 4
2 PSV middlin95
3 rate (kg/s) 6.72 6.1 -__ ___
4 % bitumen 1.11 1.72 --- ---
% solids 19.85 24 0 --- ___
6 CONDITION
7 Middlings
8 recycle
9 Rate (L/s) 7.~07 7.9 8.1 10.0
Air addition
11 Rate (L/s) 54.30 70.8 70.8 37.8
12 TORV PRODUCTS
3 TORV Froth
4 before cleaning
Rate (kg/s) 0.23 0.71 0.4 0.37
16 % bitumen 27.02 11.9 11.6 24.0
17 % solids 20.4 19.9 20.3 18.9
18 TORV Middlings
19 to further flot~
Rate (kg/s) 11.87 11.98 9.06 8.87
21 % bitumen 1.05 1.00 1.12 0.27
22 % solids 40.03 20.41 30.6 49.28
23 TORV Tails
24 Rate (kg/s) 44.83 40.77 36.62 38.95
% bitumen 0.24 0.21 0.11 0.18
26 % solids 65.6 68.26 65.49 66.1
_ 19 _
12 ~1 8 L?~
1 When converted into commercial process ratesj these results
2 could represent a saving of 2 million barrels of bitumen per year.
3 Example II
4 lm Diameter TORV
The lm diameter TORV was an investigatory research-scale
6 pilot vessel having a vertical draft tube and eductor, instead of the
7 eductor and plenum assembly of the 3m vessel. The distribution of bitumen
8 in four separate runs is presented. Both the hot water extraction process
9 and the tailings oil recovery were performed in continuous units. For
this reason, there is some variation in the streams which were fed to
11 the TORV.
12 The data shows the different results obtained with the
3 TORV, as one alters middlings recycle rate and air addition.
4 Also shown is the improvement obtained in TORV froth
quality, which results from washing the froth. The table presents these
16 results for a low bitumen and a higher bitumen TORV froth.
17 Middlings recycle rate Air addition
18 (kg/h) (scfm)
19 Run a 0 0
Run b 400
21 Run c
22 Run d 400 40
- 20 -
~24~
1 Run a b c d
2 Feed (i.e., ~SV tails
3 + PSV middlings)
4 Rate (kg/h) 42204243 4242 4229
Bitumen (wt.%) 1.451.07 2.14 1.16
6 Froth (before settling
7 in cleaner)
8 Rate (kg/h) 117 330 427 230
g Bitumen (wt. %) 25.755.45 10.32 14.02
lo Recovery (expressed
11 as % of TORV feed
12 bitumen) 49.2439.61 48.54 65.73
13 Sand bed density (kg/L) 1.691.65 1.71 1.75
14 Froth (after settling)
Rate (kg/h) --- 30 72 80
16 Bitumen (wt.%) 49.9952.51 54.39 39.53
17 Middlings
18 Rate (kg/h) 1151 794 1086 1129
19 Bitumen (wt.%) ` 3.971.37 2.45 0.68
Tailings (after dilution)
21 Rate (kg/h) 36903456 3052 3750
22 Bitumen (wt.%) 0.410.32 0.58 0.27
23 Density (kg/L) 1.521.60 1.63 1.52
24 % Bitumen lost based on total
bitumen entering TORV as feed21.422.1 17.5 14.2
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Examples of improved froth.quality.as.a result of.froth washing
2 % Bitumen % Solids Ratio of
3 solids/bitumen
4 1 2 1 2 1 2
Raw froth from TORV 25.3 32.16 31.58 19.36 1.25 0.60
6 Froth after washing 42.93 52.24 21.77 12.93 0.51 0.25
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