U.S. patent application number 14/227064 was filed with the patent office on 2015-10-01 for apparatus and method for bitumen froth storage.
This patent application is currently assigned to TOTAL E&P CANADA LTD.. The applicant listed for this patent is TOTAL E&P CANADA LTD.. Invention is credited to William Nicholas GARNER, Mohammad Afzal KHAN, Saba MOETAMED-SHARIATI, Wei Y. ZHANG.
Application Number | 20150275095 14/227064 |
Document ID | / |
Family ID | 54189451 |
Filed Date | 2015-10-01 |
United States Patent
Application |
20150275095 |
Kind Code |
A1 |
GARNER; William Nicholas ;
et al. |
October 1, 2015 |
APPARATUS AND METHOD FOR BITUMEN FROTH STORAGE
Abstract
An apparatus and methodology for storing bitumen froth
comprising a fluidized bottom, froth first feed holding tank for
maintaining effective tank capacity while reducing overall solid
bed build up at side walls and minimizing sloughing of solids to
the froth discharge outlet. Froth is fed to the tank through one or
more feed inlets located between the froth outlet and side walls
for fluidizing settling solids. The feed inlets urge solids to
settle in sub-beds about the feed inlets, the height of which that
manifests adjacent the side walls being less that some design
threshold height; if not, then successive feed inlets are located
between the side walls and the precious feed inlets to build
further sub-beds that have a height at the wall that is less than
the threshold height.
Inventors: |
GARNER; William Nicholas;
(Calgary, CA) ; MOETAMED-SHARIATI; Saba; (Calgary,
CA) ; KHAN; Mohammad Afzal; (Calgary, CA) ;
ZHANG; Wei Y.; (Calgary, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
TOTAL E&P CANADA LTD. |
Calgary |
|
CA |
|
|
Assignee: |
TOTAL E&P CANADA LTD.
Calgary
CA
|
Family ID: |
54189451 |
Appl. No.: |
14/227064 |
Filed: |
March 27, 2014 |
Current U.S.
Class: |
208/177 ;
196/46 |
Current CPC
Class: |
C10G 1/045 20130101 |
International
Class: |
C10G 1/04 20060101
C10G001/04 |
Claims
1. A tank for holding froth from extracted oil sands, the froth
containing at least bitumen and solids, the tank comprising: a side
wall and a bottom wall forming an inner storage chamber having side
walls, one or more feed inlets located adjacent the bottom wall for
introducing the froth upwardly into to the chamber, an outlet
located adjacent the bottom wall for removing froth from the
chamber, wherein the one or more feed inlets are located
intermediate the outlet and the side walls, each feed inlet for
fluidizing solids settling thereabout and forming a bed of solids
about the feed inlet, each bed that reaches the side walls having a
maximum height of less than a threshold height.
2. The tank of claim 1, wherein the threshold height is that less
than that capable of imposing a threshold loading on the side
walls.
3. The tank of claim 1 wherein, when a height of a bed about a
first feed inlet of the one or more feed inlets would reach the
side wall at a height that exceeds the threshold height, one or
more successive feed inlets are located intermediate the first feed
inlet and the side walls.
4. The tank of claim 1, wherein the bottom wall is generally
horizontal.
5. The tank of claim 1, wherein some of the one or more inlets may
be positioned substantially at or near the bottom wall.
6. The tank of claim 5, wherein some of the one or more inlets may
be positioned through the bottom wall, through the side wall, or
through an elevated inlet.
7. The tank of claim 1, wherein the one or more feed inlets may
comprise a plurality of inlets arranged in an array for fluidizing
solids settling thereat and forming a plurality of sub-beds
thereabout each one or more feed inlet.
8. The tank of claim 7, wherein each sub-bed formed thereabout has
a maximum height of less than a threshold height.
9. The tank of claim 7, wherein the one or more inlets may be
positioned to form one or more arrays of feed inlets spaced about
and circumferentially about the outlet.
10. The tank of claim 9, wherein the spacing of the one or more
inlets minimizes sloughing of solids and prevents outlet
blockage.
11. The tank of claim 1, wherein the tank further comprises sloped
directing elements for guiding settling solids in the chamber
towards one or more of the feed inlets.
12. The tank of claim 11, wherein one or more directing elements
comprises at least one internal annular element projecting from the
side walls for directing the solids away from the side walls.
13. The tank of claim 12, wherein the at least one internal annular
elements are vertically stacked within the chamber.
14. The tank of claim 11, wherein the one or more directing
elements comprise at least one transverse member extending across
the chamber.
15. The tank of claim 14, wherein the at least one transverse
members are offset.
16. The tank of claim 11, wherein the directing elements comprise
at least one conical skirt encircling at least one of the one or
more feed inlets for directing settling solids to the encircled
feed inlet.
17. The tank of claim 11, wherein the directing elements may
comprise at least one internal annular element, at least one
transverse member, at least one conical skirt or a combination
thereof.
18. A method for holding froth from extracted oil sands between
froth processing stages is provided, the froth containing at least
bitumen and solids, the method comprising: introducing the froth
into a holding tank having side walls; fluidizing the settling
solids in the froth about one or more froth feed inlets located
intermediate a discharge and the side walls such that the solids
remain suspended in the froth about each feed inlet; and settling
solids about each of the one or more feed inlets to form one or
more bed of solids, each bed reaching the side walls having a
maximum height less than a threshold height.
19. The method of claim 18 wherein the one or more feed inlets are
first feed inlets, and where beds about the first feed inlets reach
the side walls having a maximum height greater than the threshold
height, further comprising: locating one or more successive feed
inlets between the first feed inlets and the side walls for
fluidizing the settling solids in the froth about one or more
successive feed inlets such that settling solids about each of the
one or more successive feed inlets form one or more successive beds
of solids, each successive bed reaching the side walls having a
maximum height less than the threshold height.
Description
FIELD
[0001] Embodiments disclosed herein relate to the field of
processes for recovering bitumen from oil sand and, more
particularly, to a fluidized froth holding tank for improved froth
handling.
BACKGROUND
[0002] Oil sands extracted from deposits, such as those found in
Alberta, Canada, comprise water-wet sands that are held together by
a matrix of viscous heavy oil or "bitumen". Bitumen recovery
processes can involve extracting the oil sands from mines, slurry
conditioning the oil sands, such as with hot water, for transport
to extraction and froth treatment. The bitumen, water, sand, silt
and clay matrix is transported for further processing via a primary
separation process and downstream froth treatment processes such as
froth separation units (FSUs). FSU's, are commonly used in which
bitumen-rich froth and solvent are fed to the FSU, whereby mineral
and non-mineral solids separate (via gravity) from the solvent
diluted bitumen. Solvent is later recovered in various solvent
recovery processes.
[0003] Such processes are subject to the vagaries of large scale
materials processing resulting in the occasional need for surge
between the various stages. In one instance, it is known to provide
surge capacity between the primary separation and froth treatment
stages using an intermediate froth storage or holding tank. The
tank receives bitumen froth and ultimately discharges the entire
contents for transport to the FSU or other downstream processing,
however, during continuous or surge operation, free solids can
settle to the bottom. The tank has a discharge located at the
bottom and solids tend build up as a sloped bed on the bottom
forming a semi-stable bed surface at an angle of repose angled from
a low point, at the tank discharge, to one or more high points
spaced from the tank discharge.
[0004] Main issues arising with solids build up include:
accumulation reduces tank holding capacity with dead volume lost to
solids and commensurate loss of operating capacity, accumulation at
a high side of the bed places inordinate loading on the tank side
walls, and periodic sloughing of solids from the bed surface can
overwhelm and block the discharge (e.g. outflow/pump suction line),
which is typically mitigated by maintaining a liquid level above
the solids build up and this itself contributes to additional
operating capacity loss.
[0005] Prior solutions include an acceptance of lost storage volume
by designing larger tanks and with the use of reinforced
construction to resist the increased pressure on tank walls from
the dead load including reinforced floor and foundation.
[0006] Build up and sloughing issues have been addressed using
tanks having conical-shaped bottoms to both urge solids to the
discharge with minimal to no accumulation and to keep the solids
flowing to avoid periodic sloughing. The lower conical walls of
such tanks are typically angled to avoid solids build up. Further,
mechanical aids such as rotating rakes can be used to guide solids
towards the discharge, however the costs of operating and
maintaining rakes capable of guiding highly viscous media is
extremely high. Conical vessels significantly add to the height,
supporting structure and capital cost.
[0007] There is interest in providing an improved, generally flat
bottomed froth holding tank for storing bitumen froth that is
reliable, low cost and maintains the capacity to effectively store
froth over extended periods of time.
BRIEF DESCRIPTION OF DRAWINGS
[0008] FIG. 1 is a schematic cross-sectional illustration of the
buildup of a bed of solid materials in prior art flat-bottomed
froth holding tanks showing the minimum surface level of fluid
allowable (to prevent sloughing of solids) in the tank;
[0009] FIG. 2 is a schematic representation of a froth holding tank
according to one embodiment described herein illustrating an array
of fluidization feed nozzles and a side discharge;
[0010] FIG. 3A depicts a top view of the froth holding tank
according to another embodiment illustrating an array of
fluidization feed nozzles, a side discharge and a recirculation
line from discharge to froth inlet;
[0011] FIG. 3B illustrates a detailed cross-section of the general
bed formation about a typical feed nozzle,
[0012] FIGS. 4A and 4B are plan view and cross-sectional side views
respectively of a tank utilizing embodiments of the fluidized
bottom for overall bed height reduction, the tank of FIG. 4A having
one example configuration of a first circular array of feed
nozzles;
[0013] FIGS. 5A and 5B are plan view and cross-sectional side views
respectively of a tank utilizing embodiments of the fluidized
bottom for overall bed height reduction, the tank having one
example configuration of first and second circular and generally
concentric arrays of feed nozzles;
[0014] FIGS. 6A and 6B are plan view and cross-sectional side views
respectively of an alternate embodiment of a froth holding tank
having an internal annular element for aiding in side wall relief
in combination with the example first circular array of feed
nozzles shown in FIGS. 4A and 4B;
[0015] FIGS. 7A and 7B are plan view and cross-sectional side views
respectively of an alternate embodiment of a froth holding tank
having an internal annular element for aiding in side wall relief
in combination with the example first and second circular and
generally concentric arrays of feed nozzles;
[0016] FIGS. 8A and 8B are cross-sectional side view and plan views
respectively of an alternate embodiment of the tank of FIGS. 6A and
6B having a pair of vertically stacked internal annular elements,
FIG. 8A having feed nozzles also illustrated therein;
[0017] FIGS. 9A and 9B are cross-sectional side view and plan views
respectively of an alternate embodiment of a tank having internal
annular elements and transverse shed elements for aiding in reduced
bed formation, fluidization feed nozzles being omitted from the
illustration;
[0018] FIGS. 10A and 10B are cross-sectional side view and plan
views respectively of an alternate embodiment of a froth holding
tank having a plurality of conical skirts about each feed nozzle
for minimizing bed formation, and
[0019] FIG. 11 shows a cross-sectional side view of one example
enhancement to each nozzle described herein.
SUMMARY
[0020] In accordance with the present description, apparatus and
methodology for settling solids management in a froth surge or
holding tank is provided. Generally, a flat bottomed tank is
provided with arrays of fluidization nozzles for maintaining one of
or a combination of characteristics including maintaining any
solids in a stable, generally fluidized state for eventual
discharge. Where solids do settle, if any, a series of low
elevation, conical-sloped beds or sub-beds are formed, thereby
minimizing the height of solids accumulation against the tank side
walls. Settled solids are discouraged from settling adjacent side
walls, or in some embodiments even to substantially eliminate the
settling of solids at all, thereby resulting in the ability to
store froth for longer periods of time (e.g. for a minimum of four
hours, and upwards of approximately fifteen to twenty hours).
[0021] It is understood herein that the term solids includes that
which settles in a typical tank environment, including mineral, or
combinations of mineral, bitumen and trapped water as is known in
the oilsands of northern Alberta, Canada. Oilsands are also
referred to in the art as oil-sands, oil sands and tar sands and
tarsands.
[0022] In embodiments described herein, froth holding tanks have a
chamber formed within a vessel having a substantially flat bottom
wall and cylindrical side walls. The bottom wall can be slightly
sloped to a discharge outlet that can aid in maintenance, including
cleaning, but does not significantly impact structural height and
related considerations. Slight sloping of the bottom wall can
include a minimal slope below a normal angle of repose of settled
solids without embodiments described herein would suffer the same
accumulation disadvantages as flat bottom tanks.
[0023] Froth is delivered to the tank through at least one froth
feed inlet or nozzle located at or near the bottom wall and
directed generally upwardly into the chamber for suspending solids
thereabove in a fluidized state within the chamber. Froth is
removed from the tank through at least one outlet located at or
near the bottom wall. In embodiments, around each feed inlet is
formed a sub-bed in the form of an inverted cone or a funnel. A
plurality of feed inlets produces a plurality of sub-beds, each of
which has a low height and when arranged as set forth herein,
obviates side wall loading and sloughing risk. Simplistically, a
bed of settled solids that would normally build up at side walls to
a maximum bed height that exceeds design criteria is interrupted by
a feed nozzle for fluidizing the solids settling thereat and
forming a sub-bed. The sub-bed resets the build-up of settled
solids to a new bed height about the periphery of the funnel. A
sub-bed that is sufficiently spaced from a side wall could also
build up to a maximum bed height that exceeds design criteria.
Accordingly, froth is introduced at spaced locations between the
outlet and the side walls as necessary to form a series of sub-beds
as necessary to maintain the maximum bed height at an elevation
equal to or below a design threshold height. The threshold height
can be equal to or less than the height that imposes a maximum
loading on the side walls; the maximum loading typically including
a factor of safety. The desired bed height may range from
approximately 0 (substantially no settling of solids) to a
pre-determined maximum threshold height of the bed contacting the
side walls.
[0024] In further embodiments, internal annular elements within
chamber provide additional side wall relief by directing solids
radially inwardly away from the walls.
[0025] Further, conical skirts about one or more of the feed inlet
(and possibly the outlet), having conical slopes at or about the
angle of repose, can minimize or eliminate bed formation, all of
the active settling solids being engaged by the feed inlets (and
outlets, where applicable) for fluidization.
[0026] A methodology for holding froth produced from extracted oil
sands between froth processing stages is provided, wherein the
froth contains at least bitumen and solids, the method comprising:
introducing the froth into a tank, fluidizing the settling solids
in the froth such that the solids remain suspended in the froth or
distribute to form a bed of solids having a maximum height of less
than a maximum threshold height.
[0027] The above-mentioned and other features of the present
apparatus and methodology will be best understood by reference to
the following description of the embodiments.
DESCRIPTION OF THE EMBODIMENTS
[0028] As will be appreciated by those of skill in the art,
embodiments of holding tanks taught herein are suitable for
extended storage of froth streams produced as a result of an oil
sands extraction process. The froth typically comprises a
bitumen-to-solids ratio of about 4:1. Solids in the froth are
largely fine solids, typically having a size less than about 44
microns. Froth is therefore significantly different than initial
oil sands slurries in the extraction process which have a
bitumen-to-solids ratio of about 1:8 in which the solids include
both coarse and fine solids. Holding tanks according to embodiments
taught herein are generally unsuitable for use for storage of oil
sand slurries and particularly for extended periods of time.
[0029] An improved fluidized froth holding tank is provided having
regard to FIGS. 1-11. The holding tank is configured to receive,
store and inventory bitumen-rich feed for froth intermediate
treatment stages of oil sands operations, namely receiving
highly-viscous produced froth from extracted oil sands and
discharging same to downstream treatment vessels. Using embodiments
described herein, it is desired that such a tank firstly promote
and maintain the suspension of solids therein during typical
operations. It is further desired that such a tank distribute
settling solids, forming a series of low-elevation, conical-sloped
beds, thereby minimizing the height of any accumulations of solids
that do settle.
[0030] With reference to FIG. 1, a cross-sectional illustration of
the typical accumulation of settled solids in known, prior art
flat-bottomed froth holding tanks. In the case of a central outlet,
over time, solids accumulate radially about the outlet, forming a
large sloped bed having an inverted conical fluid section, or
funnel, with the outlet at the bottom of the funnel. At the base of
the funnel, presenting at the side walls, the height of the
accumulation of solids, in larger tanks in the order of 38 meters
in diameter, can reach bed heights as high as 11 meters. As the
solids build up, a semi-stable bed surface forms at an angle of
repose angled upwardly from the tank outlet. A steady state
operation of sorts is reached as solids continue to settle,
accumulation on the bed surface and periodically slough down the
bed surface to the outlet. Such sloughing results in slugging at
the outlet and can even occasionally block the outlet. The
accumulated solids significantly reduce overall tank holding
capacity, reducing inventory and surge capacity, or requiring the
design of larger tanks to compensate for lost volume. Further, the
high side wall accumulation of solids requires corresponding
structural designs to resist the loading.
[0031] With reference to FIGS. 2 through 11, embodiments taught
herein are designed to introduce froth to the tank in such a manner
so as to locally fluidize settling solids pending withdrawal or
removal from the tank, interrupting or distributing bed formation
for minimizing the maximum bed height of accumulated solids.
Formation of an array of smaller, low-elevation sloped sub-beds
within the tank can reduce the dead volume lost to accumulation and
minimizes or substantially eliminates the effect of sloughing. One
can improve or maintain high tank inventory capacity, can allow for
economy of tank material and other structure construction
considerations, and can even allow for larger diameter,
flat-bottomed tanks to be used without having to construct stronger
reinforced foundations compared to conical-bottomed tanks of
equivalent size and capacity.
[0032] As shown in FIG. 2, one embodiment of the present froth tank
10 comprises a vessel having an inner cylindrical chamber 12 having
side walls 14 and a bottom wall 16. In one embodiment, the bottom
wall 16 of the tank is generally horizontal. In an alternative
embodiment, the bottom wall 16 may nearly-flat or slightly sloped
from horizontal, the angle being somewhat less that a normal angle
of repose of the typical settled solids, in contradistinction from
conical bottom tanks. In embodiments, a slightly sloped bottom wall
might be in the order of up to about an angle less than 10.degree.
from horizontal. The top of the tank 10 may be open or closed to
the external environment. Where closed, the tank 10 may comprise a
top wall as known to those in the art.
[0033] Tank 10 can include at least one entry inlet 18 for
introducing froth into the chamber 12. The froth may be introduced
via entry 18 positioned substantially at or near the bottom of tank
10, through the bottom wall 16, through side wall 14 or through an
elevated entry inlet 18a, with or without an anti-syphon system in
order to avoid backflow.
[0034] Froth is discharged or removed from the tank 10 via outlet
22. Outlet 22 is positioned substantially at or near bottom wall
16, and may be located adjacent a side wall 14 per FIGS. 2 and 3A,
or along the bottom wall 16 such per FIGS. 4A-10B. Outlet 22 can be
positioned at a minimum elevation equal to the elevation of entry
18 within chamber 12.
[0035] In one embodiment, the froth is pumped into chamber 12
through one or more feed inlets or nozzles 20 positioned low in the
chamber 12 such as adjacent the bottom wall 16. Each feed inlet 20
can direct a flow of froth upwardly into the chamber 12 to engage
solids settling therein. For example, froth flow rate via inlets 20
may be sufficient to maintain an approximate feed vertical
component velocity of at least 0.5 m/s at the inlets 20. In one
embodiment, secondary feed inlet nozzles 20a may be oriented
horizontally, or substantially parallel with the bottom wall 16,
such as to direct settling or settled solids towards
vertically-oriented inlets 20. As shown in FIG. 3A, froth may be
recirculated from outlet 22 back to into chamber 12 via entry 18
when froth processing rates fall below that optimal for management
of settled solids within chamber 12.
[0036] The size, location and capacity of the feed inlets 20 is
configured to maintain and distribute suspended solids in a stable,
generally fluidized state pending recovery from outlet 22. FIGS. 2
and 3A show example arrangements of feed inlet arrays 21 capable of
fluidizing a large portion of the solids settling over the bottom
wall 16. For example, FIG. 2 shows a tree-like array 21 distributed
about a substantial portion of the bottom wall 16.
[0037] The one or more feed inlets 20 are located intermediate the
outlet 22 and the side walls 14, each feed inlet 20 fluidizing
solids settling thereabout and forming a bed 23 of solids about its
respective feed inlet 20, each bed 23 that reaches the side walls
14 having a maximum height of less than a threshold height. If a
bed reaches a height greater than the threshold height at or before
reaching the side walls, then a successive feed inlet is located
between the previous or first feed inlet and the side walls 14.
[0038] As shown in FIG. 3B, each feed inlet 20 produces its own
small, inverse-conical sub-bed of solids thereabout, the inverse
base height having a low elevation and at about a threshold
elevation per the tank wall loading design criteria. In an
embodiment, feed inlets 20 may be designed to fluidize an inverse
cone having an inverse base height of about three meters, at a base
diameter of about 10.4 meters, assuming an angle of repose of
settled solids of about 30 degrees. With feed inlet 20 effective
inlet offset from the bottom wall 16 of one meter, the maximum
inverse base height is four meters, being significantly less than
the 11 meters of the prior art. At the side wall 14 the threshold
height could be about four meters. As the inverse base has a
diameter smaller than the side wall 14 diameter, there is variation
of the bed height along the side wall 14, the threshold height
being an approximate value and subject to variation. A safety
factor could be applied to ensure that greater heights, such as
between two sub-beds, are within the design height and the maximum
inverse base heights are lower than the threshold heights.
[0039] Feed inlets 20 or array 21 of feed inlets 20 can be spaced
areally so that at least the sub-beds of settling solids formed
adjacent the side walls 14 have an elevation below a design loading
threshold. The spacing of the feed inlets 20 and resulting sub-beds
in the array 21 is such that many adjacent sub-beds about may
intersect at the threshold elevation.
[0040] The size, location and position of the feed inlets 20 and
arrangement thereof can vary depending upon the size and capacity
of tank 10 and upon the characteristics of the froth. It is desired
that the size, location and position of the feed inlets 20 are
configured to fluidize relatively large solids (e.g. maximum
approximate size of 250 microns and average diameter of 20-22
microns), in fluid having relatively low viscosity (e.g. >100
cP), by providing sufficient spacing and discharge velocity of the
inlets 20.
[0041] With reference to FIGS. 4A and 4B, in one embodiment, the
feed inlets 20 can be arranged in a circular array 21 about a
centrally-located outlet 22. The array 21 of feed inlets 20 direct
settling solids to form a series of smaller sub-beds 23. For
example, in smaller tanks, typically about 18 meters in diameter,
an array 21 of at least four inlets 20 can be positioned at
pre-determined locations about outlet 22, wherein four smaller
sub-beds 23 of solids are formed, each having a low inverse base
design height shown in dashed circles. Radially outside the design
height, the height of the sub-bed 23 increases. Thus, the lateral
extent of design height of peripheral sub-beds 23 and the maximum
elevation thereof, is arranged to coincide at about the side wall
14. As shown in FIG. 4B, the radial proximity of the feed inlets 20
to the outlet 22 results in a localized and low sub-bed 23 height
and substantially insignificant sloughing issues.
[0042] Having regard to FIGS. 5A and 5B, such as is the case for
larger tanks typically about 38 meters in diameter, the feed inlets
20 may be configured to form two or more circular arrays 21a,21b
within the chamber 12 and around outlet 22. The number of feed
inlets 20 and arrangement thereof, result in a low inverse base
design height, shown in dashed circles, that covers a substantial
portion of the bottom wall 16.
[0043] As shown in FIG. 5B, the desired threshold inverse base
height of settled solids H1 can be achieved with the progressive
addition of feed inlets 20 spaced between the outlet 22 and the
side walls 14. The inverse base height of solids in prior art tanks
lacking feed inlets can be significantly higher (H3) than the
threshold base design height in smaller tanks of the present design
having one feed inlet 20 (H2), or in larger tanks of the present
design wherein successive feed inlets 20 (H1) are provided, each of
which interrupts the growth of the height of the sub-beds 23 about
each feed inlet 20.
[0044] Simply, where the one or more feed inlets 20 are arranged as
first array 21a, and where beds 23 about the array 21a would reach
the side wall 14 having a maximum height greater than the threshold
height, then the beds 23 need to be interrupted with additional and
successive feed inlets (e.g. arranged as feed array 21b). This, one
or more successive feed inlets 20 can be located between the first
array 21a and the side wall 14 for fluidizing the settling solids
in the froth about one or more successive feed inlets 20 such that
settling solids about each of the one or more successive feed
inlets 20 form one or more successive beds 23 of solids, each
successive bed 23 reaching the side wall 14 having a maximum height
less than the threshold height.
[0045] As further shown in FIG. 5B, where tanks 10 comprise only
one or a first feed inlet 20 or array 21 of feed inlets 20, the
height of the resulting sub-beds 23 increases beyond the design
threshold height at the extent of the dashed circles, the maximum
bed height between the first feed outlets 21a and side wall 14 may
be greater than the threshold or design height H1. The spacing
between a first circular array 21a and a successive circular array
21b is such that the maximum height H2 (e.g. 5 meters) of first
sub-beds 23 can be greater than the side wall threshold height H1
(e.g. 4 meters). However, being spaced from the side wall 14,
higher bed heights H2 do not impose extra force on side wall 14 and
are not of significant import.
[0046] The sub-bed 23 height, from the second or successive feed
inlets array 21b, results in bed heights less than or about the
threshold or design height H1.
[0047] Tank 10 may further be configured to comprise one or more
directing elements for urging or guiding of settling solids in a
manner to optimize fluidization thereof.
[0048] In one embodiment, having regard to FIGS. 6A, 6B, 7A and 7B,
tank 10 may be configured to have directing means comprising at
least one internal annular element 24 for urging settling solids
away from side wall 14 or towards one or more inlets 20. At least
one, side wall 14 located, internal annular element 24 may extend
inwardly from side wall 14 at an incline at or steeper than the
angle of repose to avoid hold-up of solids thereon and directing
settled solids radially inwards, thereby aiding in side wall 14
relief. Tank 10 may be configured to minimize or negate any
pressure gradient above or below at least one annular element 24,
thereby allowing for the use of lighter-gauge steel in the
manufacture thereof.
[0049] Having regard to FIGS. 8A and 8B, tank 10 may be configured
to comprise a plurality of vertically-stacked internal annular
elements 24. For example, it may be desirable to provide
vertically-stacked annular elements 24 as backup should failure of
one element occur, or to distribute high weight loads off of each
individual element. It should be understood that one or more
internal annular elements 24 may be used alone or in combination
with any configuration of inlets 20, thereby optimizing the
capacity of tank 10.
[0050] In another embodiment, having regard to FIGS. 9A and 9B,
tank 10 may be configured to have directing means comprising at
least one transverse shed element 26 for minimizing or distributing
solid bed 23 formation. Shed elements 26 may be inclined at or
steeper than the angle of repose, and may extend across or
substantially across the diameter of tank 10. Tank 10 may comprise
a plurality of vertically stacked transverse shed elements 26. Tank
10 may be configured to minimize or negate any pressure gradient
above or below shed elements 26, thereby allowing for the use of
lighter-gauge steel in the manufacture thereof. It should be
understood shed elements 26 may be used alone or in combination
with annular elements 24 and with any configuration of feed inlets
20, thereby optimizing the capacity of tank 10.
[0051] In yet another embodiment, having regard to FIGS. 10A and
10B, tank 10 may be configured to have directing means comprising
at least one inverse conical skirt 28 having an apex towards the
bottom wall 16 for minimizing or distributing the solid bed 23
formation. At the each apex, a feed inlet 20 is located for
fluidizing solids and minimizing or distributing sub-bed 23
formation. One or more of the conical skirts 28 may be angled at,
or slightly less than, the angle of repose, for urging most solids
settling thereon to flow or slough towards the feed inlet 20 and be
re-fluidized. Thus tank 10 may be configured to minimize or negate
any bed loading above or below at least one conical skirt 28,
thereby allowing for the use of lighter-gauge steel in the
manufacture thereof. It should be understood that one or more
conical skirts 28 and feed inlets 20 may be used alone or in
combination with annular elements 24, shed members 26, thereby
optimizing the capacity of tank 10.
[0052] Having regard to FIG. 11, the capacity of tank 10 may be
optimized through the use of one or more velocity enhancement means
30 for increasing fluidization. Velocity flow through feed inlets
20 may be enhanced by creating suction or lower pressure at the
feed inlets 20, causing solids and surrounding media to be drawn
into and pushed out of inlets 20 at high velocities (arrows). Such
enhancement means 30 may comprise, for example, the use of a
diffuser, an eductor, or the like.
[0053] A methodology for storing or handling bitumen froth produced
from extracted oil sands between bitumen processing stages is
provided, the method comprising introducing the bitumen froth into
the tank 10, and suspending or distributing settling solids in the
bitumen froth in a fluidized bed within the tank 10 until such time
as the bitumen froth is removed from the tank 10.
[0054] The present disclosure provides a detailed description of
various elements required to operate a fluidized froth holding
tank, but many other known elements such as valves, pumps and other
tanks interconnected to tank 10, and required to operate the
present apparatus and method, have not been described herein.
[0055] Example embodiments of the present invention are described
in the following Examples, which are set forth to aid in the
understanding of the present tank 10, and should not be construed
to limit in any way the scope of the invention as defined in the
claims which follow thereafter.
Example 1
Testing of a Small Fluidized Froth Tank
[0056] With reference to FIG. 4A, simulation analyses were
performed to assess the capacity of a fluidized froth holding tank
having a diameter of 18 meters to function as a froth storage tank
for extended periods of time. The flow rate of bitumen froth feed
into and out of the tank was 1100 m.sup.3/hr. The froth feed had an
approximate temperature of 60.degree. C., an approximate viscosity
of 0.5 Pas, an approximate feed density of 1050 kg/m.sup.3 and
density of the solids of 2650 kg/m.sup.3. The flow rate of the
bitumen froth feed out of the tank was 1100 m.sup.3/hr. It was
estimated that the froth feed into the tank had the following
approximate mineral distribution: fine particles smaller than 44
microns 60.60 wt % and sand of 39.40 wt %. The largest size of the
sand was estimated to have a diameter of approximately 250
microns.
[0057] As such, using Stock's law, the settling velocity of the
particles is shown in Table 1:
TABLE-US-00001 TABLE 1 Particle Size Settling Rate: Micron m/h m/s
45 0.0094 2.60E-06 75 0.0313 8.68E-06 150 0.1875 5.21E-05 250
0.3750 1.04E-04
[0058] A total of four inlets, each inlet having an internal
diameter (ID) of 6 or 8 inches, were used, the size of which being
selected to achieve the desired velocity. As shown in Table 2, the
desired discharge velocity of each inlet was significantly higher
than the settling velocity for the largest mineral particles,
thereby optimizing mixing and fluidization of the fluids in the
tank.
TABLE-US-00002 TABLE 2 Velocity Number ID Radius Area Total A Flow
each of Nozzle Nozzle Nozzle 4 nozzles 4 nozzles Nozzle nozzles
Inch m m2 m2 m3/hr m/s 4 6 0.0762 0.01824 0.073 1100 4.2 4 8 0.1016
0.03243 0.130 1100 2.4
Example 2
Testing of Large diameter Fluidized Froth Tank
[0059] With reference to FIG. 5A, simulation analyses were
performed to assess the capacity of a fluidized froth tank having a
diameter of 38 meters to function as a froth storage tank. The flow
rate of bitumen froth feed into and out of the tank was 1100
m.sup.3/hr.
[0060] A total of 13 inlets were used, having an ID of 3 or 4
inches, the size of which being selected to achieve the desired
velocity. As shown in Table 3, the desired discharge velocity of
each inlet was significantly higher than the settling velocity for
the largest mineral particles, thereby optimizing mixing and
fluidization of the fluids in the tank.
TABLE-US-00003 TABLE 3 Velocity Number ID Radius Area Total A Flow
each of Nozzle Nozzle Nozzle 4 nozzles 4 nozzles Nozzle nozzles
inches M m2 m2 m3/hr m/s 13 4 0.0508 0.00811 0.105 1100 2.9 13 3
0.0381 0.00456 0.059 1100 5.2
[0061] Although a few embodiments have been shown and described, it
will be appreciated by those skilled in the art that various
changes and modifications might be made without departing from the
scope of the invention. The terms and expressions used have been
used as terms of description and not of limitation, and there is no
intention in the use of such terms and expressions of excluding
equivalents of the features shown and described or portions
thereof, it being recognized that the invention is defined and
limited only by the claims that follow.
* * * * *