Note: Descriptions are shown in the official language in which they were submitted.
2 ~
BACKGROUND OF THE lNV~;NllON
This invention relates to a process for separating
bitumen from bitumen froth. More particularly, it
relates to a process for separating bitumen by heating
the bitumen froth at an elevated temperature and pressure
and gravity separating the water and solid components
from the bitumen froth. ~ -~
The reserves of liquid hydrocarbons in bitumen
deposits are very substantial and form a large portion of
the world's known energy reserves. These deposits are
relatively expensive to develop compared with -;-
conventional petroleum crude oils. The heavy oils are
extracted from the deposits either by mining methods or
in-situ steam injection. The mined ore is s-lhsequently
lS treated with steam, hot water and caustic in a hot water
extraction process carried out at approximately 80~C to
liberate the bitumen from the sand to form a froth. This
froth contains a significant portion of water and solids
which must be substantially re~lce~ prior to an upgrading ; -
step. Heavy oil pro~uce~ by in-situ methods also contain
significant quantities of water and solids which must be
treated prior to upgrading. The upgrading processes
convert the heavy oil to lighter fractions which can be -
further procPsse~ into naphtha, gasoline, jet fuel and -~
numerous other petroleum products.
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These heavy oils and bitumen froths are deaerated --
to remove entrained air and treated to remove significant
water and solids. The most common method of purification -~ -
is to dilute the produced froth or heavy oil with naphtha
to reduce the viscosity. With bitumen froth, the
naphtha is added in approximately a 1:1 ratio on a volume
basis. The diluted bitumen may then be subjected to ~-~
centrifugation in two stages. In the first stage, coarse
solids are removed using scroll type maçhin~. The
product from this step is then processed in disc
centrifuges which remove a significant portion of the
water and solids. The naphtha diluent is recovered from -~
this bitumen by flash distillation and recycled to the ~ -
froth treatment step to be reused. In the case of in~
situ produced heavy oils, a similar diluent is added to ~
reduce the heavy oil viscosity for the purposes of ~ ;' ;
separation of solids and water and snh6e~l~nt pipeline
transport. The removed solids and water are ~ispose~ of '~
..:.. ;,...
in a tailings pond or other containment area. The
diluent may either be recovered for reuse, or it may be -~
left in the Lecovered heavy oil to be used in pipeline -~
trAncport of the product.
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The bitumen or heavy oils are upgraded or refined
in processes such as fluid coking, LC-FiningTM, residuum
hydrotreating or solvent deasphalting. It is desirable
to eliminate essentially all the water and to reduce the
solids to less than 1 per cent by weight before
proceP~ i ng with any of these processes. The
conventional specification for pipeline feed of oil is a
-~; of 0.5 per cent bottom sedi -nt and water
, (BS&W). With bitumen produced from froths by
centrifugation following conventional mining and
extraction processing, the solids content of the bitumen ,
is seldom less than 1 per cent. From in-situ production,
the specification of 0.5 per cent BS&W may be achieved.
Various methods have been used to remove water and
solids from such froths. Given et al (U.S. Patent
3,338,814) describe a process whereby froths pro~uced by ~-
hot water extraction of bitumen are dehydrated by heating -
to temperatures from 225-F to 550-F (preferably 350-F to
450-F). The dehydrated bitumen, contAining 5% to 25%
solids is then subjected to cycloning or filtration to
~c ve solids. In a variation to the basic process, a
light hydLoc~rho~ can be added to the dry bitumen to
improve the filtration step. The hydrocarbon can be -'
recovered by distillation and recycled. This is
essentially a two-stage process that requires a ~ ~
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considerable amount of energy in order to obtain a
satisfactory degree of extraction.
Another attempt to remove water and solids from ~ ~;bitumen froths was disclosed by Leto et al (U.S. Patent
4,648,964). In this process, bitumen froths are heated
to temperatures above 300~C at pressures above 1000 psig
to heat/pressure treat the froth prior to separation of a
hydrocarbon layer from water and solids at atmospheric ; ~-
pressure in a second stage. The S~GOn~ stage of the ~ ~r~
process requires pressure reduction and cooling of the
material to a temperature about 80~C. Naphtha, in a
weight ratio of naptha to treated stream in the range of ~
0.5 - 1.0:1.0, is then added to the bitumen and the ~ - '
mixture is intro~uGe~ into a gravity separation vessel at
atmospheric pressure. The hyd.ocarbon is withdrawn from
.,,, . :,.. ..
the top of the vessel and a solids and water fraction is '~
removed from the bottom. The bottoms are transferred to '
a second settling vessel where clarified water is
withdrawn from the overflow and solids are removed from -~
the underflow for ~;SPOSA1. Since this process requires
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extremely high temperatures and pressures and a ~;
relatively intricate apparatus for conL.olling the
changing temperatures and pressures from a high pressure ;;~;
separation in a first stage to at ~'eric pressure
separation in a secon~ stage of the two-stage process, ~ ~
the extraction costs are relatively high. ~ -
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Baillie (Canadian patents 952,837, 952,838, 952,839
and 952,840~ discloses embo~i -nts of a method for
upgrading bitumen froth in which diluted bitumen froth
recovered from a scroll centrifuge is heated to a
temperature in the range of 300-1000~F and transferred to -
an autoclave settling zone for settling at a pressure in
the range of 0-1000 psi. The tailings are cooled and
passed to a disc centrifuge for secondary recovery at
ambient pressure. This process requires the use of -~
exr~ncive centrifuges which are costly to operate and
maintain and which are prone to shut-down due to wear
because of the erosive nature of the material treated. ~ -~
In addition, the method requires the use of higher ~ ~ -
boiling liquid hydrocarbon diluents boiling in the range -
of 350-750~F and necessitates the steps of pressure
reduction and cooling for the secon~ry stage disc
centrifugation at atmospheric pressure. ~ '
A process developed by Shelfantook et al (U.S. ;
Patent 4,859,317) as an alternative to conventional
dilution centrifuging circuits for purifying bitumen '
froths proposes three stages of inclined plate settlers ;--~-
to remove water and solids from bitumen froths. This ;
process is carried out at approximately 80-C using ; '
naphtha as diluent in a 1:1 volume ratio based on the oil
content in the froth. The lower temperature operation
however results in a diluted bitumen product which
contains a significant quantity of solids. The residual ,~
~ ~ 2 ~
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solids are at substantially higher levels than the ~; -~:
specification required for pipelining and for some
refining proce ses.
It is a principal object of the present invention
to provide an improved process for effectively
separating the bitumen component from the water and
solids components of a bitumen froth by treating the :
froth at a relatively moderately elevated temperature and .
pressure, and gravity separating the said components ~ .
while maintaining said temperature and pressure.
It is another object of the present inventian to
provide an improved process for separating the bitumen
component from the water and solids of an bitumen froth ... -. :
using a substantially constant elevated temperature and :~
pressure during the separation stages for ~nhAnce~
recovery of bitumen with the use of simple and relatively :
;n~Ypencive gravity separation equipment.
summarv of the Invention :. .
These and other objects of the invention are
obtA;ne~ by means of a process for treating bitumen froth
contA;n;ng mixtures of a hyd~ocarbon component, water and ~: -
solids comprising heating said bitumen froth to a :: :
' I , . ':
temperature in the range of about 80~C to about 300~C ~:
under pressure of about 150 to about 5000 kPa sufficient
to maintain said hydrocArbon component in a liquid phase,
passing said heated froth into a plurality of separation
~2~ ~5
stages in series and gravity settling the solids and
water from the hydrocarbon layer while maint~;ning said
pressure within the liquid phase range of the
hydrocarbons. Although the process of the invention has
been found operative with diluent mixed with the bitumen
in amounts of o to about 60 per cent by weight of the -;
bitumen, depending on the characteristices of the bitumen
froth and separating temperature, at temperatures of ~ ;
about 80~C to about 300~C the addition of a diluent
hydlocarbon in the range of about 15 to 50 per cent by
weight of the bitumen is preferred. The diluent provides ~
a greater viscosity reduction and density difference for - -
the hydrocarbon relative to solids and water.
.; .~.. ..
The pressure in the separation preferably is in the ;
range of about 100 to about 250 psig and the temperature
preferably is in the range of about 100~C to about 180~C. -~
It has been found that the precon~itioning of a ;-~:
mixture of bitumen froth cont~;ning an oil component such
as bitumen together with water and solids, followed by ~ ~
gravity settling, is highly effective for rejecting the ' ;
water and solids cont~ in~ntS. This preconAitioning step
comprises efficient mixing, possible addition of a -
diluent miscible with the oil component, and heating to a
temperature in the range 80-C to 300~C. Although
temperatures above 300~C may also promote separation,
these high te~peratures produce highly undesirable
~ ~ 2 ~ ~ 8 ~ ~
g . -
chemical cracking and oxidation reactions which can
degrade the oil component, produce noxious gases such as
hydrogen sulphide, and result in coke formation and
fouling of heat exchange surPaces. Below 80~C, chemical
reaction is insignificant but the separation process is
much less effective. The range described in this i~
application therefore represents an optimum for achieving
effective separation without deleterious chemical
reactions.
The mixture used as feedstock, and to which the ~
main application of this process has been directed, is -
bitumen froth derived from oil sands extraction. ~ -
Ilowever, other mixtures containing essentially the same
components, namely mixtures of oil, water and solids,
could also be advantageously treated by this process. ;
Examples would include sludges from refining and ~ ;
petroleum-producing operations, tank cle~ni~g and filter
backwash residues, and in-situ pro~uce~ heavy oils. It
will accordingly be understood that the term "bitumen
froth" used herein ~nc ~c~~s emulsions of oil such as
sludges, heavy oils and the like. -'
Final products from this process are a hydrocarbon
phase essentially free of contaminants and a water/solids ~ -
stream essentially free of oil.
The process of the invention will be described with
reference to bitumen froth recovered from bitumen. Since
2~
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bitumen froth, as produced, contains a significant amount
of air which would be deleterious to the froth treatment
process, this air must first be removed in a deaeration
step. Deaeration is normally accomplished by heating the
froth up to a temperature in the range of about 80~C
100~C and allowing air to separate and be withdrawn. ;~ -
For conventional biL, inous froth feedstock, two
stages of mixing and settling to be described herein
allow for meeting both a hydrocarbon phase specification ~ -
and a tailings product specification. However, it is ;~
within the scope of this invention to add mixing and --:~
settling stages to effect further quality improvement on
either the h~Locarbon phase or tailings phase if
circumstAnc~s require.
The separation step itself is carried out in a - -
vessel maint~i~ed at the required temperature and -
sufficient pressure to prevent vaporization of fluid ~; -
components. Under these conditions the water droplets
and solids particles, being ~n~er than the contin~lQ~lC
hydLocarbon phase, separate under the influence of
gravity. It is well established in the scientific
.,:~ , .
literature that the downward velocity of these particles
increases as their diameter increases. One p~L~ose of ~,~
the preconditioning step referred to above is therefore
to promote coal~scence of small droplets into larger
particles which settle faster: effec~ive mixing prior to
settling is designed to achi-ve thia. '.~.
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If a diluent is used in the process, both teL ;n~l
streams from the separation step, namely hydrocarbon
product and aqueous tailings, will contain some
concentration of the diluent. Normally, this diluent
must be recovered for recycle within the process and
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methods suitable for accomplishing this are distillation ~
and membrane separation, which can be applied to both of ~ ~-
the above streams. In the event that the product stream
is to be pipelined, then some diluent may be necessAry to ~;
reduce viscosity and density of the bitumen down to
levels acceptable for pipelining. It would be
advantageous in this instance to permit all or part of
the diluent in the hydrocarbon product stream to remain ~-
with the bitumen; this could be ~AC~ lished either by a
partial diluent recovery step, or by elimination of
diluent recovery completely at the froth treatment
plant.
Ultimate ~;~POSA1 of the tailings requires a
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facility for allowing the fine solids to be removed from
water. Conventionally, a settling pond is used for this
~uL~ose; after sufficient time has elapsed to settle most
of the fine solids present, water can be withdrawn and -
the solids allowed to compact.
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12
Brief Descri~tion of the Drawinqs
The process of the invention will now be described
with reference to the accompanying drawings, in which~
Figure 1 is a schematic flow diagram of a preferred
embodiment of the present invention; ~' -
Figure 2 is a graph showing the separation rate of
solids and water from bitumen at various temperatures~
Figures 3(a) and 3(b) are graphs comparing the
settling behaviour of froth constituents at different
temperatures; and
Figure 4 is a Sçh- -tic flow diagram of a
continuous pilot process of the present invention. ~'~
Detailed Description of the Invention ~ ;
A flow diagram of the bitumen froth treating ~''''b~
process of the invention is shown in Figure 1. A stream
of bitumen froth is heated to a temperature in the range "~
of about 80-C to 100~C prior tc feed to deaeration stage
10 where sufficient resi~nce time is provided in a ', ~ '~'~
deaeration tank to allow air to separate from the froth.
The deaerated froth is heated to a temperature in the
range of about 100~C to 300~C while a pressure is ;;~
provided sufficient to maintain light hydLocarbon
c- p~ ~nts in the liquid phase and to prevent
vaporization. A pressure in the range of about 800 kPa
up to about 5000 kPa was found to be suitable. ;~ -'
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It was observed that the temperature range of about
100~C to about 3000C is sufficiently high to give a large
viscosity reduction in the bitumen component to ~nh~nce
separation of solids and water therefrom, to be
described while maintaining the temperature below the
point of thermal degradation. While some temperature and
pressure changes are permitted for purposes of ~
operability, the said temperature and pressure ranges ~ ;
are essentially maintained. Heat can be provided in a ~ ~ ;
heat exchanger using steam or hot oil. --
A low molecular weight hydrocarbon diluent, such as
typified by naphtha, kerosene, varsol, toluene or
natural gas con~nR~te, may be added to the deaerated ~ ;
froth and the mixture heated or the diluent may be heated - -
separately prior to feed to mixing stage 12. A naphtha -
diluent having 90% volume of the naphtha boiling between
about 50~C and 170~C, for example, was found to be ~
effective. The bitumen-diluent mixture preferably is - - '
mixed in a mixer for precon~itioning to yield a
h~ neollc hydrocarbon liquid phase and to provide a
greater viscosity reduction and density difference ~'
relative to solids and water prior to feed to settling
stage 14 for gravity separation.
If the water content of the froth is low, ~;
additional water can be added before or after mixing
stage 12 to provide a carrier phase for transport of
solids to be settled in settling stage 14.
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14
The preconditioned bitumen froth is fed to settling
~, . . :, .
stage 14 and component layers of bitumen and settled ~' - ;
solids and water are formed and maintained for a period -
of time sufficient for the bitumen to collect on the ~ -
surface and the water and solids to collect as sediment
in the bottom of a settling vessel in settling stage 14.
The water-solids are separated out to a desired
degree and discharged as underflow for a secondary
separation with addition of diluent, if necessAry, and
i~;ng in second i~i ng stage 16 for preconditioning
prior to feed to a second settling stage 18 for gravity
separation at essentially the same pressure within the
range of from about 10 to about 750 psig and within the
temperature range of up to 300-C. A further repeat of
this operation may be desired if sufficient quantities of
. : :; . .~, .
bitumen remain mixed with the solids.
Underflow passing from settling stage 14 through
mixing stage 16 to settling stage 18, and the several ' '-
ancillary recycle flow and product lines, are
continuously maintained at an elevated pressure
sufficient to mantain light hydrocarbons in the liquid . ~
phase and to prevent vapourization of water, and to drive ;-
the components through the system by pressure. The
initial pressurizing of preconditioned bitumen froth fed
to settling stage 14 is adequate to maintain the desired
elevated pressure throughout the system thereby avoiding
the need for several stages of pumps and precluding the -
need to cool the streams below the boiling temperatures
of the liquid components while retaining the advantage of ;-~
separating the components at higher temperatures with
attendAnt low viscosities. ; ~
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The diluted bitumen component layer is passed from
the settling stage 14 to diluent recovery stage 20 such
as a conventional distillation vessel in which the
diluent is distilled off and recycled, if desired, and -
the bitumen recovered for further processing in a manner
well-known in the art. It may be preferred to leave a ;~
portion of all of the diluent in the bitumen product to
facilitate pipelining of the product by meeting
pipelining specifications. The bitumen thus is clarified
to a crude oil grade suitable for pipeline
transportation, i.e. oil contain_ng less than 0.5% BS~W.
The diluted bitumen separated from secon~ settling
stage 18 can be combined with diluent in first mixing
stage 12, and recycled to first settling stage 14. The -
water-solids from settling stage 18 are dischArged as
underflow substantially free of bitumen and residual
diluent can be recovered in a diluent recovery stage 22 ; ,~.
such as a conventional disti~lation vessel. Recovered -
diluent can be recycled to second iYing stage 16 or to ~-
first mixing stage 12.
The advantage of operating at uniform pressure
throughout the treating and separation stages is
particularly demonstrated by the simplicity of th-
continuous extraction process and surprisingly high yield
of clean bitumen product. Unlike prior art process~s for
hydrocarbon recovery, the present multi-stage extraction -
process does not require raising and lowering pressure at
various stages and thus by maintA i n i ng a substantially
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uniform pressure throughout the system, even when a
diluent is added, continuous maintsnance of a desired ; -~
high temperature is permitted for optimum separation of
bitumen from water and solids.
The process of the invention will now be described
with reference to the following non;-limitative examples.
Example 1 ~-
The rate at which the froth co _nents are gravity
separated under pressure is Lron~ly infll~Pnce~ by the ~ '
temperature within the separation vessel. A sample of
bitumen froth was mixed with diluent in the ratio~60:40 ~ -
by volume of froth:diluent and separated into two equal
samples. One sample was settled at ambient temperature ;~-
(25~C) and the other at elevated temperature (180-C). :
The latter sample was pressured to 250 psig in an
autoclave in order to prevent vaporization of any lighter
, ., .~ ~, . ...
components. After a settling time of 30 minutes, the top
pha~e in each test was sampled and analyzed to give the
results shown in Table 1. Quality of the hydrocarbon
phase, in terms of solids and water content, is markedly
superior for settling at higher temperature and pressure.
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T~LE1 '~
LABORATORY SEPARATION AT HIGH AND LOW TEMPERATURE
Froth /diluent ratio = 60/40 volume ~ -
Co",posit;on wt% (ex diluent)
Oil Solids Water ~ j
Feed froth 63.7 17.5 18.8 ..
Bitumen phase settled at 25 ~C 86.4 2.2 11.4
Bitumen phase settled at 180 ~C 94.4 0.4 5.2
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17 ~-:
Exam~le 2
The aqueous tailings stream (bottom phase #1) from
a single stage separation of bitumen froth contained some
bitumen, as shown in Table 2. This stream was ~
recontacted in a second stage with more diluent and ..
settled again. Bitumen recovery wa~ increased from 91
wt% for a single stage to 98.5 wt% for the two stages. -~ ;
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TABLE2
EFFECT OF MULTIPLE STAGES ON HIGH TEMPERATURE SEPARATION ~ .
~ Material balance derived frorn batch ex~,eri",ental data
~ All data on weight basis, relative to 100 wt units of froth ::
,~
Stage #l
~ Stage #2
Coi"ponentFeed to Top Phase Bottom phase Top Phase Bottom Phase
Stage#1 #1 #1 #2 #2
Bitumen 65 59 6 5
Solids 9 0.5 8.5 0.1 8.4 : .
Water ~ 1 25 1 24 -.
Froth 1 00
Diluent 41 40 1 20 ~1 . .
+20 added for stage #2
~ Bitumen recovery from first stage = 91%
~ Bitumen recovery from two stages = 98.5%
,.' ~3 2 ~ 1 ~ 5
18
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ExamPle 3
Two different types of bitumen froth were obtained,
one from a conventional hot water extraction utilizing
caustic additiQn, as employed at commercial plants in
Alberta, Canada, and one experimental froth generated
without the use of caustic. Composition of these froths
is shown in Table 3; although the bitumen content is
similar, the ratio of solids to water i5 quite different
owing to the different extraction processing. ~;
lo Each feed froth was separated at 80-c and 180-C,
and at one int~ te temperature of 115 C or 166-C, in
batch autoclave runs. This autoclave, of one litre
-: , "
capacity, was charged with the feed mixture, sealed, then '~
stirred while being heated to the target temperature. ; ~-
..
After reaching this temperature, mixing was stopped and
samples taken into small sample bombs at various time ; -
intervals. The data shown in Table 3 refer to 20 minutes ;
settling time, and clearly illustrate that the product
quality, in terms of residual solids and water content,
. ~
improves with separation at higher temperature. Similar
~ LOV~ -nts observed with the two different froth types ~' .;
indicate that this rh~r~ n is of wide applicability.
TA8LE 3 .- ;.
FROTH SEPARATION IN i3ATCIl AUTOCLAVE ' ~ ;;.
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Temperature Diluent Product Composition, wt%
~C wt% on bit. Oll Solids Water
(a) Feed - derived from Hot Water EAtldction 56 8 36 : : .'':
pracess with caustic addition
80 41 91.4 1.6 7.0 . ~ - -
115 41 96.7 0.5 2.8 ~ ~ .
180 41 98.5 0.1 1.5 -
(b) Feed-defivedfrom non-caustic55 . 17 28 ~ ~:
proc~ss '- " '~' :'
44 91.7 1.6 6.7 ~ .
166 38 96.5 2.1 1.4 : ~ .
180 44 99.0 0.4 0.6 .
(1) S~ttling time = 20 minutes
2 ~ 2 ~
Exam~le 4
Separation at higher temperatures gives not only
benefits in terms of ultimate product quality but also in
the increase in the rate of separation. The data plotted
in Figure 2 were obtained by charging an autoclave with
froth and diluent, mixing, and heating up to desired
temperature. At this temperatllre, mixing was stopped and
small samples were taken at regular time intervals and
analyzed for oil, water and solids : ~ -nts. The data
clearly illustrate that higher temperatures provide both
faster settling, in that contaminants are rejected more
quickly, and in addition, provide an ultimately superior
product quality at completion of settling. -~
This advantage in faster settling means that
eq~ nt size can be re~-ce~, or that th~yhpu~ for
given equipment size can be increased over what would be ;-
possible at lower temperature.
Example 5
It is common, in settling experiments, to cover a
range of variables such as temperature, diluent/feed
ratio and settling time. This number of variables makes ;~ ;
correlation of results difficult. It is well known in
the art that Stokes' Law represents gravity settling of
particles from a continuous fluid phase. For a given ~-
system, Stokes' Law states that settling velocity of
particles is inversely proportional to viscosity. The
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degree of settling will, in addition, depend on the ~;
settling time available. Hence a "Settling Parameter"
can be devised which combines several variables and is
. ,-., .
defined as follows: ~
Settling Parameter = settling time/viscosity
Viscosity in turn will be a function of temperature
and diluent/feed ratio. ~--
, . . ~ .
It follows from the above relationship that product
quality should correlate with the Settling Parameter, as ~ 5'-~
.~ ' '. ~ ':, , I
a means of normalizing the data. Results from autoclave
runs are plotted in Figures 3(a) and 3(b). The high
temperature results show a definite and unexpected
benefit over that related simply to predictable viscosity -~
effects. For example, a given viscosity can be achieved ~ n'
either at 180~C or at 80-C by A~Aing more diluent. ~;
Stokes' Law would then predict equivalent settling rates. ~
However, as Figures 3(a) and 3(b) show, this is not the -
case; higher temperature settling shows an l~neYpected and
unique benefit, on both froth types studied. As evident
from Figures 3(a) and 3(b), for a given value of settling
parameter, separation at higher temperature as shown in
Curve B provides l~neypectly lower solids and water in the
product compared to the lower temperature separation as -
shown in Curve A.
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21
Example 6
Very slow settling of solids and water from bitumen
froth will occur without diluent addition over a period
of weeks or months at ambient temperature, but this is
not a practical basis for a process. However, at
elevated temperature, this separation does become
feasible. The data in Table 4, generated from an
autoclave experiment using froth only, with no added
diluent, show effective separation of solids and water
from the bitumen at a temperature o~ 180~C. At 80~C
under the same conditions, no significant separation
occurs. . .
TABLE4
HIGH TEMPERATURE FROTH SEPARATION WITHOUT DILUENT
Conditions: Froth from Hot Water Extraction
Mixing/Settling Temperature: 180~C .. ~'
- :. ... ~ .. -
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Settling Time Co",position, wt%
mins OilSolids Water
Product Phase 0 65.3 6.5 28.2
3 73.8 4.8 21.4 'i~ '. -i''-'' :~.'
93.5 0.8 5.7
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Bitumen Recovery: 90 wt% .~ ~ '
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Example 7
Efficient mixing, prior to gravity settling, is an
important aspect of the present invention, particularly
with respect to the second stage, which determines the
ultimate bitumen recovery. Batch runs were performed in -~ -
an autoclave at different temperatures and mixing
intensity, as shown in Table 5. Feed for these runs ~ -
comprised the tailings stream from a prior separation of
bitumen froth, with the composition as shown. Naphtha ~;
diluent was added and the mixture stirred in an autoclave
as it was heated up to temperature. Any oil recovered
from this feed floated to form a light phase and the
remaining heavy phase was analyzed. At 180~C with a low -
level of iYi n~, the oil content and solids/oil ratio
L~ ine~ at about the feed level. However, at higher
iYin~ severity, a major reduction in oil remaining in
the bottom phase was achieved, corres~o~i n~ to an
increase in overall bitumen recovery from about 90 to 97
wt%
TABLE 5
THE IMPORTANCE OF MIXING INTENSITY FOR OIL RECOVERY
Feed: Tailings from first stage separation (froth +diluent)
Tailings/~,aphtl,a = 2/1 wt
, .,, ~, -
Second Stage Tailings Est.Overall
Com~sition. wt% Solids/OilBit. recovery
Temp. ~CMixer OilWaterSolids ratio wt% :
rpm
Feed - 13 61 26 2.0 90
180 150 15 54 31 2.1 90.5
1 80 400 5 63 32 6.4 97 -
202~18~
23
Exam~le 8
The purpose of added diluent is primarily to reduce
viscosity of the continuous fluid phase, hence promote
coalescence and settling of water droplats and solid
particles. Any low viscogity hydrocarbon may therefore
be utilized. Some examples of diluents are naphtha, ~
kerosene and natural gas condensate. These comprise a ~ -
boiling range from light hydrocarbons such as pentane to
heavier hydrocarbons in the range of for example, 50~C to
170~C for 90% of naptha. Natural gas condensate -~
comprises light paraffins such as hexane and heptane
which are miscible with bitumen and represents the
condensible liquids coproduced from certain natùral gas
fields. ;~:
In order to demonstrate that the present invention -~
is applicable to a wide range of diluents, autoclave -
experiments were performed using froth derived from a
commerical hot water extraction proce~s together with one i -
of the three diluents tested. After charging the mixture -;
to the autoclave, it was sealed and stirred during i~
heating up to temperature. The stirrer was then switched ~-
off and samples taken after lS minutes. As the data in ,
Table 6 illustrate, the amount of solids and water ~.''','~J~
~ n~ n~ in the bitumen phase were significantly reduced
I at 180-C versus 80-C for each of the three diluent types.
rABLL6 ''!~';~' j~
RANGE OF DILUENT TYPES I tS I tu ~ ~-
Fro1h: Derived fron Hot Water Extraction Process
Froth/Diluent ratio = 1/0.6 wt
Settling Time = 15 minutes
Oil Phase Co",pas !ion,wt%
DiluentTemp. ~C OilSolids Water Solids+Water .
- Feed 78 5 .17 22
Naphtha 80 95 1 4 5 ,,~ ;x,
1 80 98 0.5 1 .5 2
Varsol 80 96 1 3 4 ';-;'~
180 98.8- 0.2 1 1.2
Nat. GasCond.~ 80 94 1 5 6 ~ ' ' ~' i
~ao 97 05 25 3
~, 3 ,~ 1 1 ~ ~ ~
24
Example g -~
A continuous pilot plant test based on the
underlying principles of this invention was carried out
in a two-stage configuration. The invention will now be
described with respect to the two-stage configuration,
although it could be carried out in three or more stages ~ i
if this was advantageous for any given application. The
flow scheme as tested is represented in Figure 4.
.
Feed to the unit was a bituminous froth prepared by -
a commercial bitumen plan~. The froth was heated and ~ i
deaerated in a feed tank at atmospheric pressure and ;
introduced under pressure to the i~i n~ and separating
stages of the process on a continuous basis. Details of
stream c_ ,-sitions and process conditions are shown in
Table 7. ;~
'~,, ~;,
,.: ' ~.' ' ' ~ ',
Table ~ -
Pilot plPrlt De"~Gnst,~t~ of Froth Tr~."enl P,ocess
Wl% of CG",ponent Naphll,a Temp Pressure Flow
StreamBitumen Water Solids Wt% on Bit. ~C kPa kg/min
Froth feed 51 40.0 9.0 N/A 137 1400 0.72
1 st stage feed 39.3 30.7 6.0 24.6 137 1400 1.00
1st stage prod. 58.1 2.0 0.4 39.6 137 1400 0.61
1st stage under- 9.6 76.0 14.7 0.9 137 1400 0.39
2nd stage feed 3.9 61.4 6.0 29.2 117 1100 0.95
2nd stage recycle11.6 6.7 0.2 87.8 30 100 0.28
2ndstagetaillngs 0.8 86.2 8.4 4.7 tto t100 0.67 ~ ~
' '" -::
'' ~',;',~'
,, .
~2~ ~ ~'5
-
With reference now to Figure 4, froth from an
extraction process was pumped through strainers 100, to
remove large solid particles, to a feed tank 102 which
was maintained at a temperature of about 90~C to effect
deaeration. Deaerated froth was pumped through a heat
exchanger 104 to a mixer 106 where diluent (naphtha),
heated and ~ in separately through line 108, was
mixed with the froth in vessel 106 equipped with motor~
driven stirrer 110. The mixture was then further heated ;
and fed under pressure to the first stage settling vessel
112. The hydrocarbon phase was removed as a light '~ ;~
overhead stream 114, under pressure by control valve 116. --
The aqueous solids-containing underflow stream 118 with ' ,;~-
residual bitumen was withdrawn under liquid level
control, then combined with further heated diluent
through line 120 and mixed in ~econ~ mixing vessel 122.
This latter stream flowed through another heat ~Y~h~nger
124 to the seCon~ stage settling vessel 125. Overhead
pro~uct 126 from the secon~ stage settler 125 could be
recycled, via a recycle tank 128, to the first stage
mixer 106, to obtain -Yi utilization of diluent.
Diluent can be added by line 120, line 108 or by a
combination of both lines.
This pilot unit was fully instrumented with
temperature and pressure sensors, and flowmeters, to .
permit extensive data-gathering and analysis.
"~ ,,,,~ " -,
,.:, . :. ~ .,:,
", "
:':
~ 3 2 ~ ~
. ~
26 :~
With reference to Table 6, the first stage :
separation was carried out at a temperature of 137~C ~
under a pressure of 1400 kPa and the second stage ~ .
separation was carried out at a temperature of 117~C at a
pressure of 1100 kPa. Bitumen recovery relative to .
bitumen feed was about 93 wt% in the first separation
stage with 5 wt% in the second separation stage for a ~
total of 98.6 wt% recovery. ~ :'
It will be understood, of course, that
modifications can be made in the ~ nt of the
invention illustrated and described herein without ;
departing from the scope and purview of the invention as
defined by the ~pp~n~eA claims.
~; ~
