U.S. patent application number 14/511474 was filed with the patent office on 2015-04-16 for feed delivery system for a froth settling unit.
The applicant listed for this patent is TOTAL E&P CANADA LTD.. Invention is credited to William Nicholas GARNER, Trevor Lloyd HILDERMAN, Darwin Edward KIEL, Saba MOETAMED-SHARIATI.
Application Number | 20150101962 14/511474 |
Document ID | / |
Family ID | 52808739 |
Filed Date | 2015-04-16 |
United States Patent
Application |
20150101962 |
Kind Code |
A1 |
GARNER; William Nicholas ;
et al. |
April 16, 2015 |
FEED DELIVERY SYSTEM FOR A FROTH SETTLING UNIT
Abstract
Embodiments of a feedwell discharge a solvent treated
bitumen-containing froth feed to a froth settling vessel at a
Richardson number less than 1.0. Feed is discharged from feedwell
inlets to the vessel, either located at a center of the vessel or
at a perimeter wall of the vessel along a substantially horizontal
path across the vessel. The high velocity maximizes the horizontal
path. As the velocity is reduced along the path and as a result of
collision in the vessel with the perimeter wall or with feed
entering the vessel from an opposing inlet, the feed separates into
diluted bitumen and solvent which rises in the vessel for discharge
as an overflow product and a waste stream, comprising water, solids
and asphaltenes, which settles to the bottom of the vessel to be
discharged as an underflow. A relatively uniform clarification zone
forms above the inlets submerged in the vessel.
Inventors: |
GARNER; William Nicholas;
(Calgary, CA) ; MOETAMED-SHARIATI; Saba; (Calgary,
CA) ; HILDERMAN; Trevor Lloyd; (Port Coquitlam,
CA) ; KIEL; Darwin Edward; (New Westminster,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
TOTAL E&P CANADA LTD. |
Calgary |
|
CA |
|
|
Family ID: |
52808739 |
Appl. No.: |
14/511474 |
Filed: |
October 10, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61889692 |
Oct 11, 2013 |
|
|
|
Current U.S.
Class: |
208/390 ;
196/14.52 |
Current CPC
Class: |
C10G 1/045 20130101 |
Class at
Publication: |
208/390 ;
196/14.52 |
International
Class: |
C10G 1/04 20060101
C10G001/04 |
Claims
1. A method for treating a bitumen-containing, paraffinic froth
feed containing a solvent-diluted bitumen, water, solids and
asphaltenes in a froth settling vessel comprising: delivering the
feed to a separation zone within the vessel; discharging the feed
into the separation zone, through one or more inlets, each inlet
discharging the feed at a high velocity for forming a coherent
stream along a flow path generally horizontally toward a boundary
and having a Richardson number less than about unity for maximizing
the flow path in the separation zone, the flow velocity of the flow
path dissipating adjacent the boundary for separating the feed into
a diluted bitumen and solvent product which rises to a top of the
vessel and a waste stream comprising water, solids and asphaltenes
which settles by gravity to a bottom of the vessel.
2. The method of claim 1 wherein un-coalesced water droplets are
carried above the separation zone, the method further comprising:
coalescing of the un-coalesced water droplets in a coalescing zone
above the separation zone, wherein the coalesced water droplets
fall by gravity through the separation zone, to settle at the
bottom of the vessel, carrying suspended solids associated
therewith.
3. The method of claim 1 wherein the discharging the feed into the
separation zone further comprises discharging the feed at a
Richardson number between about 0.001 to about 0.8.
4. The method of claim 1 wherein the discharging the feed into the
separation zone further comprises discharging the feed at a
Richardson number between about 0.001 to about 0.5.
5. The method of claim 1 wherein the discharging the feed into the
separation zone further comprises discharging the feed at a
Richardson number between about 0.001 to about 0.125.
6. The method of claim 1 wherein the discharging the feed into the
separation zone further comprises: discharging the feed through one
or more inlets in, at or adjacent a perimeter wall of the vessel
and normal thereto for directing the coherent stream of feed on the
horizontal path toward the boundary adjacent a center of the
vessel.
7. The method of claim 1 wherein the discharging the feed into the
separation zone further comprises: discharging the feed through one
or more inlets in, at or adjacent a perimeter wall of the vessel
and angled relative thereto for directing the coherent stream of
feed on the horizontal path and in a circular flow pattern within
the vessel toward the boundary.
8. The method of claim 1 wherein the discharging the feed into the
separation zone further comprises: discharging the feed through one
or more inlets fluidly connected to an inlet pipe extending into
the vessel along an axis of the vessel for directing the coherent
stream of feed horizontally outwardly therefrom on the horizontal
path, wherein the boundary is a perimeter wall of the vessel.
9. The method of claim 1 wherein the discharging the feed into the
separation zone further comprises: discharging the feed through one
or more inlets fluidly connected to an inlet pipe extending into
the vessel along an axis of the vessel, the one or more inlets
being angled relative to the inlet pipe for directing the feed on
the horizontal path and in a circular flow pattern within the
vessel toward the boundary.
10. The method of claim 1 further comprising: positioning the one
or more inlets at a height in the vessel wherein a height of a
cylindrical portion thereabove is about equivalent to a diameter of
the vessel.
11. The method of claim 1 further comprising: positioning the one
or more inlets in the vessel wherein the inlets are immersed in
fluid contained within the vessel wherein the fluid contains about
60% of an aqueous phase and about 40% of a hydrocarbon phase.
12. A system for separating a feed into a diluted bitumen and
solvent product stream and a waste stream comprising: a settling
vessel having an upper cylindrical portion and a conical bottom
portion, the product stream being discharged as an overflow
therefrom and the waste steam being discharged as an underflow
therefrom; and a feedwell, having one or more inlets to the vessel,
delivering the feed to a separation zone within the vessel for
discharging the feed into the separation zone through one or more
inlets, each inlet discharging the feed at a high velocity, having
a Richardson number less than about unity, for forming a coherent
stream along a flow path generally horizontally toward a boundary
for maximizing the flow path in the separation zone, the velocity
dissipating at about the boundary for separating the feed into the
product stream which rises to a top of the vessel and the waste
stream comprising water, solids and asphaltenes which settles by
gravity to a bottom of the vessel.
13. The system of claim 12 wherein the coherent stream further
comprises un-coalesced water droplets which are carried above the
separation zone; the system further comprising: a coalescing zone
formed above the separation zone wherein the un-coalesced water
droplet coalesce, the coalesced water droplets thereafter falling
by gravity through the separation zone as a result of increased
diameter and terminal downward velocity, to settle at the bottom of
the vessel, carrying suspended solids associated therewith.
14. The system of claim 12 wherein the feed is discharged into the
separation zone at a Richardson number between about 0.001 to about
0.8.
15. The system of claim 12 further wherein the feed is discharged
into the separation zone at a Richardson number between about 0.001
to about 0.5.
16. The system of claim 12 wherein the feed is discharged into the
separation zone a Richardson number between about 0.001 to about
0.125.
17. The system of claim 12 wherein the one or more inlets are
submerged within the separation zone, a height of the cylindrical
portion thereabove being about equivalent to a diameter of the
vessel.
18. The system of claim 12 wherein the one or more inlets are
immersed in fluid contained within the vessel wherein the fluid
contains about 60% of an aqueous phase and about 40% of a
hydrocarbon phase.
19. The system of claim 12 wherein the feedwell further comprises:
an inlet pipe extending within the vessel along an axis of the
vessel, the inlet pipe being fluidly connected to the one or more
inlets to the vessel.
20. The system of claim 19 wherein the one or more inlets are
fluidly connected to a distal end of the inlet pipe and extend
radially outwardly therefrom for discharging the feed along the
generally horizontal path toward a perimeter wall of the
vessel.
21. The system of claim 19 wherein the one or more inlets extend
normal to the inlet pipe.
22. The system of claim 19 wherein the one or more inlets are
angled or tangential to the inlet pipe for discharging the feed
along the generally horizontal path in a circular flow pattern.
23. The system of claim 19 wherein the one or more inlets are in,
at or spaced from a perimeter wall of the vessel and extend
radially inwardly therefrom for discharging the feed toward a
center of the vessel.
24. The system of claim 23 wherein the one or more inlets extend
normal to the perimeter wall.
25. The system of claim 23 wherein the one or more inlets are
angled or tangential to the perimeter wall for discharging the feed
along the generally horizontal path in a circular flow pattern.
26. The system of claim 23 further comprising: an inlet pipe
extending into the vessel along an axis of the vessel; one or more
radially outwardly extending pipes connected to a distal end of the
inlet pipe; one or more downwardly extending pipes fluidly
connected to the one or more radially outwardly extending pipes and
extending at or adjacent the perimeter wall of the vessel, wherein
the one or more downwardly extending pipes are fluidly connected at
a distal end to the one or more inlets and the one or more inlets
extend radially inwardly therefrom for discharging the feed
therefrom toward a center of the vessel.
27. The system of claim 26 wherein the one or more inlets extend
normal to the inlet pipe.
28. The system of claim 26 wherein the one or more inlets are
angled or tangential to the inlet pipe for discharging the feed
along the generally horizontal path in a circular flow pattern.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Patent application Ser. No. 61/889,692, filed, Oct. 11, 2013, the
entirety of which is incorporated herein by reference.
FIELD
[0002] Embodiments disclosed herein relate to feed delivery systems
for separation vessels and, more particularly, to a high velocity
feedwell for a froth separation vessel.
BACKGROUND
[0003] Separation vessels are well known in a variety of
industries, such as for separation of solid particles from a liquid
phase. Gravity separators typically separate solids by gravity
settling, creating a generally quiescent environment in the vessel
so as to minimize bulk fluid flux for minimizing the effect of
terminal velocities of the components therein. The solids are
generally discharged from a bottom of the vessel and the clarified
fluid is discharged from a top of the vessel.
[0004] In the case of extraction of bitumen from mined oil sands,
the oil sand is typically mixed with water, which may be hot, for
forming a slurry. The slurry is conditioned and delivered to a
primary settling cell (PSC). Droplets of bitumen separate from the
majority of the solids therein which settle by gravity and rise to
the top of the PSC as a froth. Typically about 10% of the slurry
feed stream becomes froth. The froth typically comprises about 55
wt % bitumen, 35 wt % water and 10 wt % fine solids. The froth is
thereafter removed from the PSC for further treatment to remove the
water and the fine solids. As is well understood in the industry,
the froth is diluted with a solvent, naphthenic or paraffinic, and
is separated in a froth settling unit (FSU) to produce diluted
bitumen as the product stream. Typically, about 80% of the feed
stream to the FSU becomes diluted bitumen.
[0005] It is known by those skilled in the art that, in paraffinic
froth treatment, asphaltenes are precipitated and form aggregates,
prior to reaching the FSU, which may trap some of the fine solids
therein. The negatively buoyant aggregates, as well as the coarser
solids and water settle within the FSU and the cleaned,
solvent-diluted bitumen product (dilbit) is removed from the top of
the FSU.
[0006] It is also well known to deliver a feedstream to separation
vessels using a feedwell. Conventional feedwells for delivering
feed to the separation vessel are often a single, vertical pipe
design with a deflector plate spaced from the discharge end for
distributing the slurry feed radially to the vessel.
[0007] In the case of PSCs, feedwells are known for delivering the
conditioned slurry feedstream, which typically comprises bitumen,
water and both coarse solids (.gtoreq.44 um) and fine solids,
(.ltoreq.44 um). As one of skill in the art will appreciate, the
feed stream, being the conditioned slurry, has significantly
different settling properties than the solvent-diluted froth.
Generally the slurry, which comprises the about 55% bitumen, 10%
solids and 35% water, does not contain solvent or asphaltenes and
is primarily the result of an effort to separate bitumen from
tailings and is not directed, at this stage, to product
quality.
[0008] In the case of Canadian Patent 2,734,811, to Imperial Oil
Resources, a PSC feedwell comprises a centrally located feedwell,
typically positioned near a top of the vessel. The PSC feedwell has
a bottom deflector plate and a protector plate to improve the
underwash layer stability. The protector plate has ventilation
openings which reduce the discharge velocity, limit the formation
of an adverse pressure gradient and encourage circumferential
distribution. Thus, energy in the feed is dissipated within the
feedwell and the feed is delivered radially outwardly therefrom
rather than being directed downward toward the vessel underflow
before separation of the froth from the tailings can occur.
[0009] In Canadian patent application 2,809,959 to Syncrude, a
central PSC feedwell is designed to deliver slurry toward the
center of a plurality of inclined plate assemblies.
[0010] In the case of delivery of solvent-diluted froth to an FSU,
Canadian patent 2,672,004 to Imperial Oil Resources Limited (IOL)
teaches delivering the feed to the FSU through one or more side
wall ports in the FSU, preferably situated about half the height of
the vessel and entering normal thereto, which deliver the feed such
that it flows down the inside wall of the vessel. The feed delivery
is at low velocity and is characterized by a Richardson number of
greater than 1.0. The gentle flow of the feed to the FSU vessel is
purported to mitigate upward flux of the smaller particles, such as
mineral solids, by trapping the smaller particles below the larger
particles, such as the asphaltene aggregates which formed as a
result of dilution with a paraffinic solvent in the feed line prior
to the FSU. The minerals solids are thus carried to the discharge
of the vessel by the larger particles. Further, efforts were made
by IOL to design the side-inlets in such a way as to have a reduced
Reynolds number, about 2500 to 35000, at the vessel.
[0011] Conventionally, large scale settler, typically clarifiers or
thickeners, have a low height to diameter aspect ratio, such as
about 1:10, wherein energy dispersion and creation of a zero
vertical flux zone are key to effective settling therein. As such,
turbulence, if formed in the vessel, may result in ejecting bulk
fluid from the vessel without separation. FSU height to diameter
ratio is typically between about 1:0.5 to 1:2.
[0012] Clearly there is interest in apparatus for feeding a
bitumen-rich feed to a separation vessel so as to support the
separation of solids and liquids in the vessel for producing a
product overflow stream which is substantially free of fine solids
and water, while at least minimizing the cross-sectional area of
the vessel required to do so.
SUMMARY
[0013] Embodiments of FSU taught herein deliver feed to a
separation zone within the FSU vessel at a Richardson number less
than about unity for maximizing the flow path in the separation
zone. In embodiments, the feed is discharged into the separation
zone at a Richardson number between about 0.001 to about 0.8.
[0014] In one broad aspect, a method for treating a
bitumen-containing, paraffinic froth feed containing a
solvent-diluted bitumen, water, solids and asphaltenes in a froth
settling vessel comprises delivering the feed to a separation zone
within the vessel. The feed is discharged into the separation zone,
through one or more inlets, each inlet discharging the feed at a
high velocity for forming a coherent stream along a flow path
generally horizontally toward a boundary and having a Richardson
number less than about unity for maximizing the flow path in the
separation zone. The flow velocity of the flow path dissipates
adjacent the boundary for separating the feed into a diluted
bitumen and solvent product which rises to a top of the vessel and
a waste stream comprising water, solids and asphaltenes which
settles by gravity to a bottom of the vessel.
[0015] In another broad aspect, a system for separating a feed into
a diluted bitumen and solvent product stream and a waste stream
comprises a settling vessel having an upper cylindrical portion and
a conical bottom portion, the product stream being discharged as an
overflow therefrom and the waste steam being discharged as an
underflow therefrom. A feedwell, having one or more inlets to the
vessel, delivers the feed to a separation zone within the vessel
for discharging the feed into the separation zone through one or
more inlets, each inlet discharging the feed at a high velocity,
having a Richardson number less than about unity. A coherent stream
is formed along a flow path generally horizontally toward a
boundary for maximizing the flow path in the separation zone. The
velocity dissipates at about the boundary for separating the feed
into the product stream which rises to a top of the vessel and the
waste stream comprising water, solids and asphaltenes which settles
by gravity to a bottom of the vessel.
[0016] Un-coalesced water droplets are carried above the separation
zone and are coalesced in a coalescing zone above the separation
zone. The coalesced water droplets fall by gravity through the
separation zone, to settle at the bottom of the vessel, carrying
suspended solids associated therewith.
[0017] The inlets which discharge feed into the vessel are arranged
about the center or axis of the vessel for directing the feed
outwardly toward the perimeter of the vessel. Alternatively, the
inlets are arranged at the perimeter of the vessel for directing
the feed inwardly toward the axis. The inlets can be normal to an
inlet pipe or angled or tangential relative to the inlet pipe.
[0018] FSU according to embodiments taught herein have a reduced
footprint as well as reduced costs associated therewith. Costs are
reduced including one or more of reducing the foundation structure
required to support the vessel weight, including the weight of the
contents, lowering the amount of solvent inventory required,
reducing the de-inventory storage facility size and better
controlling of the system having a smaller size vessel and reduced
residence time.
BRIEF DESCRIPTION OF DRAWINGS
[0019] The patent or application file contains at least one drawing
executed in color. Copies of this patent or patent application with
color drawing(s) will be provided by the Office upon request and
payment of the necessary fee.
[0020] FIG. 1 is a schematic representation of a froth separation
vessel having a feedwell for delivering a diluted froth stream
therein according to an embodiment taught herein;
[0021] FIGS. 2A-2D are plan views of a plurality of alternate
embodiments of the feedwell of FIG. 1;
[0022] FIG. 3 is a perspective view of a feedwell according to an
embodiment taught herein, inlets for delivering the diluted froth
being directed toward a center of the vessel;
[0023] FIG. 4 is a perspective plan view of the feedwell of FIG. 3,
the inlets for delivering the diluted froth being directed
generally tangential to the vessel for delivering the diluted froth
circumferentially therein;
[0024] FIGS. 5A and 5B are side and front views, respectively, of
an inlet having dye discharged therefrom;
[0025] FIGS. 5C and 5D are side views of the vessel of FIG. 1, dye
being discharged from the inlets for illustrating the flow of fluid
delivered therefrom;
[0026] FIG. 6A1 is a vertical slice of a CFD (Computational Fluid
Dynamics--ANSYS.RTM. fluent) simulation, illustrating a vertical
velocity component in mm/min, ranging from -3000 to +3000, feed
being introduced to the vessel from inlets at about a center of the
vessel and directed toward a perimeter wall of the vessel;
[0027] FIG. 6A2 is a line drawing representative of FIG. 6A1;
[0028] FIG. 6B is a plan view according to FIG. 6A2, sectioned
above the inlets;
[0029] FIG. 6C1 is a vertical slice of a CFD simulation
illustrating a vertical velocity component in mm/min, ranging from
-3000 to +3000, feed being introduced to the vessel from inlets at
about the perimeter wall of the vessel and directed toward the
center of the vessel;
[0030] FIG. 6C2 is a line drawing representative of FIG. 6C1;
[0031] FIG. 6D is a plan view according to FIG. 6C2, sectioned
above the inlets;
[0032] FIG. 7 is a plot illustrating the relationship between
Richardson number and the ratio of the superficial flux rate to the
settling rate in a vessel including extrapolation to a Richardson
number of about 0.9, utilizing an embodiment of a feedwell which
discharges froth from a center of an FSU vessel horizontally
outwardly toward a perimeter wall thereof;
[0033] FIG. 8 is a plot illustrating the relationship between
Richardson number and the ratio of the superficial flux rate to the
settling rate in a vessel, and extrapolation therefrom to a
Richardson number of about 0.9, utilizing an embodiment of a
feedwell which discharges froth from the perimeter wall of the FSU
vessel horizontally inwardly toward the center of the vessel;
[0034] FIG. 9 is a plot according to FIGS. 7 and 8, illustrating
the comparison of modelled data and extrapolated data between
feedwells which discharge from the center of the vessel toward the
perimeter wall and from the perimeter wall toward the center of the
vessel;
[0035] FIG. 10 is a comparison plot illustrating the relationship
between Richardson number and the ratio of the superficial flux
rate to the settling rate in a vessel at 100% capacity compared to
a vessel turned down to 30% capacity, utilizing a feedwell
according to the embodiment of FIG. 8.
DETAILED DESCRIPTION
[0036] Generally, the term "feedwell" implies a structure, such as
a chamber which is positioned within a vessel, such as a settling
vessel, the chamber having inlets therefrom to the vessel. In
embodiments described herein, the term "feedwell" is used
interchangeably to refer to a structure which provides the inlets
to the vessel and to the inlets themselves.
[0037] Embodiments of a feedwell 10 for a froth settling unit (FSU)
or vessel 12 are described herein and, in contradistinction to the
prior art, a diluted bitumen froth F is delivered to the FSU in a
vigorous manner and along a flow path characterized by a low
Richardson number Ri, being less than about unity. The froth F may
carry at least some insoluble asphaltenes therewith. The Richardson
number Ri in a vessel is related to the fluid properties, spatial
arrangement and the feed inlet velocity.
[0038] A low Richardson number is generally understood to represent
a flow having sufficient kinetic energy that the feed stream
exiting the inlet to the vessel is coherent and generally
unaffected by buoyancy. Therefore, one can determine the discharge
parameters for the feed F to achieve the Richardson number Ri given
characteristics of the feed F, the velocity of discharge and the
areal influence on the feed F once delivered to the FSU vessel.
[0039] More particularly, as discussed herein, the Richardson
number for the incoming feed or feed jet is based on a feedwell
outlet diameter (d), a feed density (.rho.-feed), a fluid density
surrounding the feed zone (.rho._fluid), a velocity of the feed jet
(u) and gravitational acceleration (g) as represented in the
following equation:
Ri=d*g*(.rho._feed-.rho._fluid)/.rho._fluid/u.sup.2
[0040] In embodiments, the Richardson number is in the range of
0.001 to 0.8. In embodiments, the Richardson number may be from
about 0.001 to about 0.5, and more particularly from about 0.001 to
about 0.125.
[0041] The feed F is discharged from the feedwell 10 generally
horizontally and across the FSU vessel 12 for utilizing a
substantial portion of the vessel's cross-section and achieving
effective separation. Substantially maximum utilization of the
vessel occurs at low Richardson numbers. The substantially 100%
utilization results from local upward velocities which approach
average upward velocities in the clarification zone. The feedwell
discharges the bitumen-containing feed through one or more feed
inlets 14 at a relatively high velocity resulting in the low
Richardson number and the coherent, generally horizontal feed
stream until such time as the kinetic energy is dissipated and bulk
separation can occur. Use of a large portion of the FSU vessel 12
enables use of smaller vessels for the same feed stream, or more
effective separation and higher capacity than in conventionally
sized FSU vessels. Applicant believes that the lower the Richardson
number, at the feed inlet, particularly within the range of about
0.001 to about 0.8, the more the hydraulics of the fluid flow in
the vessel 12 approach average for the whole clarification zone and
thus, the smaller the resulting FSU vessel 12 cross sectional area.
Thus, FSU vessels 12 utilizing feedwells 10, according to
embodiments taught herein, are capable of efficiently separating
diluted bitumen and solvent from water, solids and asphaltenes in
the feed F and have a reduced footprint as well as reduced costs
associated therewith.
[0042] In embodiments, for example, where the froth F is diluted
with pentane (C.sub.5), the hydrocarbon phase may comprise from
about 30% to about 95% of the froth feed F. In embodiments where
the froth F is diluted with butane (C.sub.4) the hydrocarbon phase
may comprise about 20% to about 95% of the feed F. Fine particles
are typically distributed in both the hydrocarbon rich phase and
the aqueous phase. In the FSU 12, as the aqueous phase has a higher
density (920-1400 g/L) than the hydrocarbon phase (550-750 g/L),
the aqueous phase settles to a bottom 16 of the vessel 12 with the
coarse particles and carries the suspended fine particles therewith
toward a vessel underflow 18. The FSU 12 is typically operated at
between about 65.degree. C. and about 150.degree. C.
[0043] Any coarse solids in the feed F are caused to separate under
gravity as the energy in the feed F, discharged from the feed
inlets 14 and resulting from the relatively high velocity, is
dissipated along the flow path across an extent of the FSU vessel
12. Separated coarse and fine solids are recovered at the underflow
18 and may comprise between about 0% to about 75% hydrocarbon, 0%
to about 75% trapped water or a combination thereof. The
hydrocarbon, when diluted with a paraffinic solvent, contains
asphaltenes. The hydrocarbon in the solid phase contains about 20%
to about 99% asphaltenes.
[0044] As one of skill in the art will appreciate, in embodiments
taught herein, the term "inlet" refers to any type of inlet 14
which is capable of delivering feed F to the vessel 12 in a stream
at a velocity to result in the specified range of Richardson
number. In embodiments, the inlet 14 can be an open pipe, a nozzle
or other such fluid feed delivery apparatus, as is well understood
in the art.
[0045] In an embodiment, as shown in FIG. 1, the feed F is
delivered to a separation horizon or zone Z of the froth settling
unit or vessel (FSU) 12 through the feedwell 10 which comprises a
single, substantially vertical inlet pipe 20 which extends into the
FSU 12. The feedwell 10 extends along an axis of the vessel 12 to
access the separation zone Z for delivery of feed F through one or
more inlets 14 extending radially outwardly from the inlet pipe 20.
The feed F is delivered from the inlet or inlets 14 in a stream
that is initially generally horizontally radially outwardly toward
a perimeter wall 22 of the FSU 12. A resulting generally horizontal
flow path of feed F, exiting the one or more inlets 14, has a
Richardson number less than about unity. As a result of the
relatively high velocity, the feed F exits in a coherent stream,
which generally resists separation and dispersion of the components
of the stream as it enters the vessel 12. The stream remains
coherent until such time as the energy in the stream has
dissipated, referred to herein as a boundary P. In embodiments
where the one or more inlets 14 are at or adjacent the perimeter
wall 22 of the vessel 12, the boundary P is at a point approaching
a center C of the FSU vessel 12, the energy generally dissipating
before opposing streams collide. In embodiments wherein the one or
more inlets 14 are at about the center C of the vessel 12, the
boundary P is adjacent the perimeter wall 22 of the vessel 12. The
flow path is therefore maximized within the FSU vessel 12 for
effective separation of hydrocarbon and aqueous phases.
[0046] The separation horizon or zone is at or about a discharge of
the feedwell 10 which is positioned in the vessel 12 such that the
one or more inlets 14 are immersed in fluid contained within the
vessel wherein the fluid contains about 60% of the aqueous phase
and about 40% of the hydrocarbon phase, regardless the height of
the vessel 12. The FSU vessel 12 has a conical bottom 16 and a
cylindrical upper portion 24 extending upwardly therefrom. The
conical bottom 16 of the vessel 12 typically has an angle of
between about 45.degree. to about 75.degree.. In embodiments, a
height of the cylindrical portion 24 of the vessel 12, above the
one or more inlets 14 in the separation zone Z, is about a height
equivalent to a diameter of the vessel 12.
[0047] In the embodiment shown in FIGS. 1 and 2A, the one or more
inlets 14 are four, radially outwardly extending inlets 14 which
are spaced circumferentially about a bottom 26 of the feedwell's
inlet pipe 20 and extend normal thereto. The inlets 14 are fluidly
connected to the inlet pipe 20. Feed F discharged from the inlets
14 is directed in the coherent stream substantially horizontally
outwardly toward the boundary P at or adjacent the perimeter wall
22 of the FSU 12.
[0048] Having reference to FIGS. 2A to 2D, various embodiments are
contemplated in which the one or more inlets 14 direct the feed F
along various alternate flow paths across an extent of the vessel.
In FIGS. 2A, 2B and 3, the inlets 14 extend radially from the inlet
pipe 20. In FIGS. 2C-2D and 4 the inlets 14 pinwheel or extend
angled, and generally tangential to the inlet pipe 20. In the case
where the one or more inlets 14 extend tangentially from the inlet
pipe 20, the feed F is discharged in the coherent stream
substantially horizontally and can flow somewhat circumferentially
within the vessel forming a generally circular flow pattern
therein. The boundary P is generally at or near the perimeter wall
22 of the vessel 12 generally opposing the inlet 14 to the vessel
12. In embodiments, there may be as many as eight inlets 14, evenly
spaced about the distal end 26 of the inlet pipe 20.
[0049] As shown in FIG. 3, and in another embodiment, the feedwell
comprises the single inlet pipe 20 fluidly connected at its distal
end 26, by a plurality of radially outwardly extending pipes 28
each of which is connected to a downwardly extending pipe 30. The
downwardly extending pipes 30 extend along the perimeter wall 22 of
the vessel 12 or spaced inwardly and substantially parallel
thereto. Each of the downwardly extending pipes 30 has one or more
of the one or more inlets 14 located at a distal end 32 for
delivering the feed F into the FSU vessel 12. The inlets 14 to the
vessel 12 extend radially inwardly toward the center of the FSU 12.
As the coherent stream of feed F exits generally horizontally from
the plurality of radially inwardly extending inlets 14, at a
Richardson number less than about unity, and more particularly in
the range of about 0.001 to about 0.8, the path of the feed F is
maximized across the extent of the vessel to a point at or adjacent
the center of the vessel. The centrally directed coherent stream of
F from opposing inlets 14 can collide, further acting to reduce the
velocity of the feed F within the vessel 12. In the embodiment, as
shown, four downwardly extending pipes 30 are used to deliver the
feed to the inlets 14 to the vessel 12, dividing the feed F
therebetween.
[0050] As shown in FIG. 4, in a feedwell 10 configured as for FIG.
3, the one or more inlets 14 can be rotated towards a more
tangential alignment for delivering the coherent stream of feed F
therefrom in a generally circular flow pattern.
[0051] Applicant further contemplates embodiments wherein the feed
F enters the vessel 12 through one or more inlets 14 which extend
through the perimeter wall 22 of the FSU vessel 12, spaced about a
circumference thereof. The feed F enters the vessel 12 at the high
velocity, having the Richardson number of less than unity and more
particularly between 0.001 and 0.8. As in the case of FIG. 3, the
feed F can flows generally horizontally across a diameter of the
vessel 12. Further, collision of the feed F with feed F entering
the vessel 12 from opposing inlets 14 or against the perimeter wall
22 of the vessel 12 results in a reduction of velocity within the
vessel 12. The one or more inlets 14 can be normal to the perimeter
wall 22, enter angled from normal, or substantially tangential
thereto.
[0052] Having reference to FIGS. 5A to 5D, dye tests were conducted
in a model of an FSU 12 having the conical bottom portion 16 and
the cylindrical upper portion 24, as shown in FIG. 1. The dye tests
illustrate the initially coherent and generally horizontal flow
path of feed F outwardly from the one or more inlets 14 within the
vessel 12. The flow path extends substantially horizontally toward
the boundary P, being at or adjacent the opposing perimeter wall 22
for maximizing horizontal displacement of feed F therein.
Generally, as the energy which maintains the feed F in a coherent
stream dissipates at the boundary P, separation can occur. The less
dense solvent-diluted bitumen, separated from the feed F in the
vessel 12, rises to a top 34 of the vessel 12 for discharge as an
overflow therefrom as the product. The more dense water, solids and
asphaltenes settle to the bottom 16 of the vessel 12 and are
discharged therefrom as the underflow stream 18.
[0053] As shown in FIGS. 6A1 to 6D, Computational Flow Dynamics
(CFD) simulations illustrate the separation and the formation of a
relatively uniform clarification zone 40 above the one or more
inlets 14. In embodiments, the vessel 12 has a height to diameter
aspect ratio of greater than about 0.5. In embodiments, a height of
the cylindrical portion 24 of the vessel 12 above the one or more
inlets 14 is about the diameter of the vessel 12.
[0054] Having reference to FIGS. 6A1, 6A2 and 6B, in embodiments
wherein the one or more inlets 14 are positioned at or near the
center of the vessel 12, feed F exits the one or more inlets 14 to
the vessel 12 at the separation horizon or zone Z in the vessel 12
as a coherent stream which is directed to the boundary P, being at
or adjacent the perimeter wall 22. As can be seen, the lightest
components and most dense components of the feed F, may begin to
rise or fall, respectively, before the majority of the coherent
stream of feed F reaches the boundary P. Thereafter, at the
boundary P of the separation zone Z, when the energy is dissipated
therefrom, dense components, such as water W, solids S and
asphaltenes A, plunge generally downward in the vessel 12, under
the effect of gravity, for settling to the bottom 16 of the vessel
12. The less dense components, such as solvent V and bitumen B,
rise in the vessel 12.
[0055] The upward and downward flows are generally segregated from
the incoming coherent stream of feed F, such as in areas within the
vessel 12, between the coherent feed streams F. As one of skill
will appreciate, as constituents of the feed F begin to separate
within the vessel 12, the constituents largely avoid the more
violently mixed areas of the vessel, such as near the incoming
coherent streams of feed F, by rising and falling in the areas of
the vessel between the incoming feeds.
[0056] In embodiments taught herein, the segregation of the upward
and downward flows occurs without the need for baffles or other
mechanical internals which are prone to mechanical failure,
plugging and which may not be robust with respect to variances in
operating parameters affecting the sizes of the upward and downward
flows.
[0057] As will be understood by those of skill in the art, light
components may be carried downward with heavier components as they
separate and further, some heavier components may be carried upward
with the solvent and diluted bitumen rising in the vessel 12. More
particularly, as the upward flow of lighter components passes the
incoming coherent stream of feed F, an upward impetus or flux is
created which is sufficient to carry some un-coalesced water
droplets W therewith above the separation zone Z and into the
clarification zone 40 thereabove. As the water droplets W in the
clarification zone 40 coalesce, such as in a water coalescing zone
WC above the incoming coherent feed streams, the coalesced water
droplets W therein achieve a terminal velocity sufficient to
counteract the upward flux. Thereafter, the coalesced water
droplets W fall through the separation zone Z, between the incoming
coherent feed streams F to a water-rich zone 42 below the inlets
14, carrying solids S suspended in the water W therewith.
Similarly, any solvent V and diluted bitumen B which is carried
downward with the denser components, such as the bulk of the water
W, solids S and asphaltenes A, as they plunge in the vessel 12
separates from the denser components below the separation zone Z
and rises through the separation zone Z between the incoming
coherent feed streams F.
[0058] FIGS. 6C1, 6C2 and 6D illustrate an embodiment wherein the
one or more inlets 14 are positioned in, at or adjacent the
perimeter wall 22 of the, feed F exiting the one or more inlets 14
to the vessel 12 at the separation zone Z in the vessel 12 as a
coherent stream of feed F which is directed to the boundary P,
being at or adjacent the center C of the vessel 12. Separation
occurs generally as described for FIGS. 6A1, 6A2 and 6B.
EXAMPLES
[0059] By way of example, an ideal FSU vessel 12 has a superficial
flux rate approaching the settling rate. The superficial flux rate
is defined herein as the average upward velocity of the diluted
bitumen and solvent toward the top 34 of the vessel 12. The
superficial flux rate is generally calculated as flowrate divided
by cross-sectional area of the FSU 12. The settling rate is defined
herein as a terminal settling velocity to achieve a product being
99.5% pure within the vessel.
[0060] Having reference to FIGS. 7 to 9, based upon modelling using
feedwells 10, according to embodiments disclosed herein, the
relationship between the Richardson number and the ratio of the
superficial flux rate and the settling rate was determined at
Richardson numbers less than 1.0.
[0061] More particularly, FIG. 7 represents modeled and
extrapolated data using a feedwell 10 having one or more inlets 14
to the vessel 12 which symmetrically and horizontally distribute
the feed F from the inlets 14, at a center of the vessel 12,
directing the feed F toward the perimeter wall 22 of the vessel
12.
[0062] FIG. 8 represents modeled and extrapolated data using a
feedwell 10 having one or more inlets 14 to the vessel 12 which
symmetrically and horizontally distribute the feed F from inlets
14, in, at or adjacent the perimeter wall 22, for directing the
feed F toward the center of the vessel 12.
[0063] The results of FIGS. 7 and 8 are summarized in FIG. 9 which
illustrates the comparison between the data, both modelled and
extrapolated, for each feedwell configuration. It is clear to one
of skill in the art that the lower the Richardson number,
regardless the configuration of the feedwell's inlets 14 to the
vessel 12, the closer the superficial flux rate is to the settling
rate, which approaches the ideal.
[0064] In designing an FSU vessel 12, the flowrate is fixed, thus
the higher the superficial flux rate, the smaller the vessel 12. By
way of example, if the settling rate for solids in the ideal FSU
vessel 12 is determined to be 260 mm/min and the output is designed
to be 3000 m.sup.3/hr of product, being 99.5% pure solvent-diluted
bitumen, the cross-sectional area of the ideal FSU vessel 12 would
be 192.3 m.sup.2.
[0065] The size of the vessel 12 required to achieve the desired
characteristics is then calculated for various Richardson numbers,
as shown in Table A, based upon the relationships shown in FIGS. 7
and 8.
TABLE-US-00001 TABLE A Richardson Avg. Superficial Flux Ideal FSU
area Calculated Number rate/settling rate m.sup.2 (100%) FSU area
m.sup.2 0.001 94% 192 205 0.002 84% 192 229 0.005 70% 192 275 0.1
40% 192 480 1.0 30% 192 640
[0066] Having reference to FIG. 10, a vessel 12 having one or more
inlets 14 thereto from a feedwell 10 directing feed F from in, at
or adjacent the perimeter wall 22 of the vessel 12 toward the
center of the vessel 12 was used to model the relationship between
Richardson number and the superficial flux rate in mm/min at 100%
capacity in the vessel and at 30% capacity.
[0067] When the capacity is turned down to 30%, the operating line
is below the design line which indicates the vessel 12 can still
perform for turn down rates.
[0068] It is clear to one of skill in the art that as the feed flow
rate of the FSU vessel decreases, the Richardson number increases
and the tolerable vertical flux decreases, however even at 30%
capacity the resulting flux is below the Richardson's adjusted
tolerable flux and therefore, Applicant believes that embodiments
described herein are effective even when the operating rate of the
vessel is less than 100% of the design capacity.
* * * * *