Note: Descriptions are shown in the official language in which they were submitted.
TC~E~NYAK
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DEAERATION APPARATUS INT~GRAL WITH A
SEPARATION CELL EMPLOY~D IN A HOT WATE~ PROCESS
FOR E~TRACTING OIL FROM OIL SANDS
BACKGROUND OF T~E INVENTION
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This invention relates to the separation of oil from
bitumlnous sands such as Athabasca oil sands. More particu-
larly,~ the invention relates to a modification to the hot water
process for extracting bitumen from oil sands, by which modi-
fication deaerated bitumen is produced in a deaeration zone
directly adjacent the separation cell to obtain froth which
is readily pumpabIe.
In the hot water process employed for recovering oil
from oil sands (also known as tar and bituminous sands), such
as presently practiced at the Suncor (formerly GCOS) and Syncrude
plants in northern Alberta, the oil sands are mulled and jetted
with steam together with a minor amount of hot water at temper-
atures typically in the range 170F to 190F, and the resulting
pulp is mixed with hot water and transferred -to a separation
cell maintained at temperatures from 140F to 185F. In the
separation cell, sand settles to the bottom as tailings, and oil
rises to the top in the form of a froth. An aqueous middlings
layer comprising clay, silt and some oil is formed between the
sand and froth layers. This basic process may be combined with
a scavenger step for further treatment of the middlings layer
obtained from the primary separation step to recover additional
amounts of oil therefrom.
In recovering bituminous froth utilizing the process
disclosed in Canadian Patent No, 841,581 and the hot water sep-
aration cell disclosed in Canadian Patent No. 882,667, the froth
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is recovered in overflow launders disposed on the upper edge of
the extraction cel'l-. There~after, the froth flows by gravity
into a collection vessel located near the separation cell be-
low the level of the~froth collection launders. Often, one
collection vessel serves four or more separation cells to pro-
vide a central collection' means for recovered froth. Froth from
secondary scavenger steps can also be` coll'ected in this same
vessel. Thereafter1 the fro-th is heated and transferred to a
centrifuge zone or to other means for effecting demineralization
and dehydration. Normally, the froth is diluted with a liquid
hydrocarbon before the demineralization and dehydration steps.
Methods for accomplishing water and mineral removal from the
froth are disclosed in Canadian Patent No. 910,271 and Canadian
Patent No~ 918,091.
The bituminous froth, as recovered from the hot water
separation cell, resembles a liquid foam with poor flow charac-
teristics. The froth'is difficult to pump and therefore must be
treated to improve its liquid flow characteristics if it is to
be handled by centrifugal pumps. The characteristics of the
froth particularly detrimental to handling with centrifugal
pumps ar'e: (i) high air content and (ii) high viscosity on the
order of 7500 centipoise at 150F.
Canadian Patent No. 630,710 discloses that bituminous
froth can be collected and transferred to a deaeration zone
where it is heated with steam at subatmospheric pressures to
remove'air bubbles from the froth. This end can be accomplished
by adding the froth to a steam heated oil bath maintained at
subatmospheric pressure. The froth is therein diluted with oil
and a~itated to remove air bubbIes from the froth. Although
this method'improves the'froth, transferring the froth to the
treatment apparatus disclosed nevertheless renders the process
cumbersome and expensive.
Canadian Patent Application Serial Number 338,510,
filed October 26, 1979, and entitled "Bitumen Deaeration
Process Carried Out in the Separation Cell", by Roy Wood,
discloses means for obtaining deaerated froth directly
f~om the separation cell by adding a defoaming agent
(such as Dow Corning Silicone 200) to the oil sands feed
; on a conveyor belt as it flows into the conditioning drum or,
alternatively, after the conditioning step in the feed to
the separation cell or to the froth launder itself. This
process achieves a readily pumpable froth directly from the
separation cell, but is somewhat expensive to implement
and operate. Additio~ally, and more importantly, the
cumulative effects of long term use of defoaming agents
in the hot water process may have adverse effects on the
subsequent recovery of bitumen from the sludge layer of
the tailings pond or ponds associated with the hot water
process as well as the treatment of the sludge layer to
meet certain ecological reguirements.
Thus, it will be appreciated by those skilled in the
art that it would be highly desirable to provide means for
deaerating bituminous froth which is simple and inexpensive
and which does not bring about long term, possibly
detrimental, side effects to the system.
OBJECTS OF THE IN~IENTION
It is therefore a broad object of this invention to
provide an improved hot water process for extracting bitumen
from oil sands.
It is a more particular object of this invention to
provide imprsved means for deaerating bitumen froth obtained
in a hot water process for extracting bitumen from oil sands
such that the froth is readily pumpable and may be more easily
subsequently processed into synthetic crude oil.
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Still more specifically~ it is an object of this inven-
tion to provide, in a hot water process for extracting bitumen
from oil sands, a froth deaeration system including at least one
deaerator box directly adjunct the periphery of each separation
cell for receiving bitumen froth from the separation cell over-
flow launders by gravity feed and pump means proximately situated
below the deaeration box for transferring the deaerated froth
downstream for further processing.
Thus, in accordance with the present teachings, an improve-
ment is provided in a system for effecting a hot water process forextracting bitumen from oil sands wherein the process includes
the steps of forming a mixture of oil sands and water, passing
the mixture to a separation cell to form an upper bitumen froth
layer, a middlings layer, and a sand tailings layer and recovering
the bitumen froth layer by means of an overflow froth launder
disposed circumferentially around the separation cell proximate
the top thereof. The improvement which is provided comprises
providing at least one deaerator box disposed adjacent the separa- -
tion cell and generally below the launder and conduit means for
conducting froth downwardly by gravity flow from the launder to
the deaerator box whereby deaerated and more easily pumped froth
is obtained from the deaerator box.
DESCRIPTION OF THE DRAWING
The subject matter of the invention is particularly
pointed out and distinctly claimed in the concluding portion of
the specification. The invention, however, both as to organization
and method,of operation, may best be understood by reference to
the following description in conjunction with the accompanying
drawing of which:
Figure 1 is a simplified schematic representation of a
hot water process, employing the present invention, for extract-
ing bitumen from oil sands;
Figure 2 is a top plan view of a practical installation
for the present invention, which plan view omits, for clarity,
certain steam lines and related structures shown in other Figures;
Figure 3 is an elevational view taken generally along and
between the lines 3-3 of Figure 2, but showing additional structure;
Figure 4 is an elevational view, partially cutaway, taken
generally along and between the lines 4-4 of Figure 2, but show-
ing additional detail;
Figure 5 is a top plan view similar to Figure 1, but `-
omitting, for clarity, certain structure included in Figure 1 and
showing other structure not included in Figure l;
Figure 6 is a partially cutaway sectional view along the
lines 6-6 of Figure 2; and
Figure 7 is a partially cutaway fragmentary view taken
along the lines 7-7 of Figure 2.
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DETA-ILED DESCRIPTION OF THE I:NVENTION
Referring now to Figure 1, mined oil sands are fed into
the system through a line 10 and are carried by a conveyor 9 to
a conditioning drum or muller 11. Water is fed to the muller by
a line 12, and steam is introduced thereto through line 13. The
total water so introduced in liquid and vapor form is a minor
amount based on the weight of the oil sands processed. The con-
ditioning drum lI is provided with suitable kneading or mixing
means (not shown) to give the:`desired mulling action. Enough
steam is introduced through line 13 to raise the temperature
in the conditioning drum to within the range of 130-210F and
preferably to above 170F. Mulling of the oil sands produces
a pulp which then passes from the conditioning drum as indicated
by line 14 to a screen indicated at 15. The purpose of the
screen 15 is to remove from the oil sands pulp any debris, rocks,
or oversize lumps as indicated generally at 16. The conditioned
oil sands pass from the screen 15 to a pulp box 17 which serves
; as a zone for diluting the pulp with additional water before
passage to a primary separation zone 15. Hot water ~rom a heater
27 is passed through a line 19 to pulp box 17, and additional
steam is fed thereto through a line 20, if necessary, to main-
tain the range of 130-210F and preferably above 170F. Also,
a middlings stream, which is withdrawn from the primary separator
18, may be recycled through lines 21 and 19 to the pulp box.
; This recycle stream serves to provide sufficient liquid to flood
the oil sands pulp from the pulp box and effect transfer of the
pulp to the separator. Another function of the recycle stream
is to cause dispersion of the pulped material as it is fed into
the separation:zone 18.~ However, such recycling of middlings is
not essential in all cases, partieularly when the clay content
of the tar sands is high. In this event, a reIatively high rate
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of fresh water introduction through heater 27 can be employed
to compensate for the high'clay content while the corresponding-
ly high rate of transfer of middlings layer through line 26 as
hereinafter described can be maintained. Under these circum-
stances, recycling of the other stream of middlings through
lines 21 and 19 to pulp box 17 is not required.
Modifications that may be made in -the process as a'bove
described include sending a minor portion of the middlings re-
cycle stream from line 21'through a suitable line (not shown)
to muller lI to supply all or a part of the water therein other
than that supplled through condensation of the steam which is
consumed. Also, if desired, a stream of the middlings recycle
can be introduced onto the'screen 15 to flush the pulp there-
through and into pulp box 17.
Separation zone 18 may comprise a large cylindrical or
rectangular -tank, or battery of tanks, which may, if desired,
be provided with heating coils 22 for maintaining a temperature
in the range of 130-2I0F, and preferabl'y above 170F. A launder
4 about the upper periphery of a separator collects froth as it
floats to the top of the separator and flows over the upper lip
thereof. A sand tailings removal line having a star valve 24
or any other suitable control discharge means is provided at the
bottom of the separator 18. Separator 18 also has an intermedi-
ate withdrawal line 26 through which astream of middlings layer
is removed in addition to that recycled through line 21.
Because of the high air content in the froth which flows
into the lauders 4, the froth is difficult to pump. Thus, accor-
ding to the present invention, a deaerator box 1 affixed to the
separator 18 receives froth from the launders by gravi-ty flow
th.rough lines 2. Steam is injected into the deaerator through
a line 3 to promote deaeration of the froth as more fully described
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below. The deaerated froth then flows through a line 5 by
gravity into a suction tank 6 from wh`i'ch'i-t is withdrawn through
a line 7 by a pump 8. The deaerated froth'is conveyed downstream
through a line 23 for further proces'sing.
The middlings layer obtained in separation zone 18 will
contain most of the silt and clay which was pres'ent in the oil
sands in the'ir natural state. In order to prevent the build up
of clay in the'system, it is necessary to continually discard
some of the middlings layer and supply en'ough water in the con-
ditioning operations to c'ompensate for that so discarded. Therate at which the` middlings needs to be'removed from the system
depends upon the content of clay and silt present in the oil
sands feed, and this will vary from time to ~ime as the content ''
of these fines varies~ If the clay and silt content is allowed
to build up in the syst'em, both the density and the viscosity of
the middlings layer will increase. Concurrently, with such in- -
crease, an increase in the'proportions of both the oil and the
sand retained by the middlings will occur. I~ the clay and silt
content is allowed to build up too high in the system, effective
separation will no longer occur, and the-process will become
inoper~ative. Hence, it is important to regulate the withdrawal
of middlings through line 26, and the addition of fresh water
to the system to compensate for water thus removed, in a way
that wi-ll keep the separation step operating properly. However,
when this separation step is oeprating in an optimum manner, the
middlings layer withdrawn through line 26 will contain a sub-
stantial amount of oil which did not separate. Hence, the
middlings layer withdrawn through line 26 is, for purpose of
' description, herein referred to as "oil-rich middlings."
The rate'of addition of fresh'water to the system and
the rate'of removal of middlings layer -~rom separation zone 18
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through line 26 are regulated in accordance with either *he
density or the viscosity of the` middlings layer or both. When
densi-ty is used for the control, such addition and removal are
carried out so that the middlings density is main-tained in the
range of 1.03-1.50 gm/cc, more preferably 1.10-1.20 gm/cc. It
is preferred, however, to utilize viscosity to effect the con-
trol in which case the water addition and removal are carried
out to maintain the middlings viscosity in the range of 0.5 to
10 centipoise, more preferably 0.6 to 3.0 centipoise. Periodic
or continuous measurements of either viscosity or density for
the middlings phase can be made, and the removal of middlings
through line 26 and corresponding addition of fresh water to
the system can be regulated in accordance with the measured
values to maintain the value within the range desired. Whenever
either density or viscosity tends to become higher than is de-
sired; an increase is made in the rate of middlings removal and
corresponding rate of fresh water addition; and if density or
viscosity values tend to become too low, decreases in these
removal rates are effected.
As previously men-tioned, the middlings layer withdrawn
through line 26 will still contain a substantial amount of oil
even though the separation step is operated under optimum con-
ditions. The amount of oil remaining in the middlings layer
appears to be more or less related to the percentage of clay
and/or silt present in the oil sands being processed, varying
directly with the amount of clay and/or silt present. For ex-
ample, typical oil recovery values for the froth from oil sands
in which 15% of the mineral matter is less than 44 microns and
from sands in which 25-%0% is less than this slze are, respec-
tively, 85% and 60%. ~or commercial operation, it is highly
desirable -to obtain increased recoveries over such values, and
-this is particularly true when the tar sands mined contain a
relatively high proportion of clay and silt components. In a
large sizé commercial operation~ an increase of oil recovery of
even a few percentages values can amount to a large volume of
additional oil per day.
To carry out such secondary recovery, the oil-rich
middlings stream withdrawn from separator 18 through line 26 is
sent to a scavenger zone 2g wherein an air flotation operation
is conducted. The processing conducted in scavenger zone 29
provides a controlled zone of aeration in the flotation cell at
a locus where agitation of the middlings is being effected so
that air becomes dispersed in the middlings in the form of small
bubbles. Figure 1 illustrates a flotation cell of the subaera-
tion type wherein a motorized rotary agitator 30 is provided
and air is fed thereto in controlled amount as by means of line
31. Alternatively, the air can be sucked in through the shaft
of the rotor. The rotor effects dispersion of the air in the
middlings. This air causes the formation of additional oil
froth which passes from the scavenger zone 29 through line 32
and thence to line 23 for further processing in admi~ture with
the froth derived from the primary separation in zone 18. An
oil-lean middlings stream is removed from the bottom of scavenger
zone 29 via line 33 and is discarded from the process. The
oil-lean middlings contains a substantial proportion of the clay
and silt components that were present in the original tar sands,
and discarding thereof from the process prevents the build up
of this fines material in the separation zone 18. The amount
so discarded is such as to maintain the viscosity and density
of the oil-rich middlings in zone 18 within the ranges as speci-
fied hereinbefore.
The mixed froths from lines 23 and 32 will contain some
water and an appreciable amount of the finer mineral matter that
was present in the tar sands. Generally this material will be
sent to a processing zone (not shown) wherein the water and
mineral matter are removed. This can be achieved by diluting
the froth with naphtha and -treating the mixture in an electro-
static precipitator or in centrifuges to effect dehyclration and
demineralization.
A practical installation employing the froth deaerating
system of the present invention is shown in Figures 2-7. ~ach
of an array of four separation cells 18a, 18b, 18c, 18d, carries,
about its periphery, three deaeration boxes: lal, la2, la3;
lbl, lb2, lb3; lcl, lc2, lc3; and ldl, ld2, ld3; respectively-
Downwardly inclines pipes 50 and 51 lead, respectively, from
deaerator boxes lal and la2 to deaerator box la3 from which line
52 tees (with a corresponding line 55) into a line 56 through
which deaerated bitumen is conveyed to a suction tank 57. Down-
wardly inclined lines 53 and 54 lead, respectively, from deaer-
ator boxes lbl and lb2 to deaerator box lb3 from which line 55
extends.
Similarly, downwardly inclined lines 58 and 59 from de-
aerator boxes lcl and lc2 feed deaerated froth to deaerator box
lc3, and downwardly inclined lines 61 and 62 feed deaerated froth
from deaerator boxes ldl and ld2 to deaerator box ld3. ~he de-
aera-ted froth from the deaerator boxes lc3 and ld3 flow, respec-
tively, through pipes 60 and 63 to pipe 64 which feeds suction
tank 65.
Deaerated froth is withdrawn from the suction tank 57 by
parallel pumps 66 and 67 which feed ou-tput lin~ 68. Similarly,
deaerated froth is withdrawn from suction tan~ 65 by parallel
pumps 69 and 70 which feed output line 71. The output lines 68
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and 71 merge into the primary output line 72 which is the counter-
part of the line 23 shown in the simplified schematic represen-
tation of ~igure 1.
As best shown in Figure 4, sparge steam for carrying out
the deaerating process within the cleaerator boxes (deaerator box
ldl in Figure ~) is introduced near the deaerator box bottom at
inlet 73 which is coupled to a supply steam header (not shown
in Figure 4) as will be described in more detail below. The
sparge steam moves upwardly in the deaerator boxes and is col-
lected in a steam vent header system as illustrated in Figure 5in which the various steam vent pipe branches 7~- feed steam
vented from the deaerator boxes to a common steam vent output
line 75.
The flow paths of the fluid within a typical deaeration
box (ld ) may best be understood by reference to Figures 6 and 7.
Bituminous froth which has overflowed from the separation cell
18d into the launder 81 (illustrated in the simplified schematic
of Figure 1 as launder ~) passes through conduit 82 to distribu-
tion pipe 83 situated within the deaerator box ldl near the top.
The distribution pipe 83 has a series of openings 84 distributed
along its length in order to spread the bitumen stream laterally
and permit it to extend as a more or less uniform sheet across
the full width of the deaerator box ldl. As the bitumen stream
descends, it cascades from tier to tier of a shed deck 85. Steam
from a header 86 is distributed across the width of the deaerator
box ldl near the bottom by a perforated pipe 87. As the steam
upwardly through the distribution box ldl it encounters the
sheet of bitumen froth cascading downwardly over the individual
elements of the shed deck and shears away the air from the bitu-
men stream. Thus, the froth reaching the bottom of the deaerator
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box ld is substantially purged of air and is withdrawn through
line 61 as a pumpable liquid ready for downstream processing.
One presently preferred configuration for the shed deck
85 is illus-trated in Figure 6. The shed declc 85 comprises al-
ternate downwardly slanted elements 88 and 89. The elements 89
extend from each side of the deaerator box interior wall and
slope downwardly toward the center. The elements 89 are cen-
trally disposed and have a roof-like configuration sloping down-
wardly toward the inner walls of the deaerator box ldl from a
central peak. Thus, it will be understood that the ~roth in-
troduced into the top of the deaerator box ldl cascades back and
forth between the alternate elements 88 and 89 to provide maxi-
mum expose of the froth to the stripping action of the steam
moving upwardly through the deaerator box.
While the principles of the invention have now been made
clear in an illustrative embodiment, there will be immediately
obvious to those skilled in -the art many modifications of struc-
ture, arrangements, proportions, the elements, materials, and
components, used in the practice of the invention which are par-
ticularly adapted for specific environments and operating require-
ments without departing from those principles. i -
