Note: Descriptions are shown in the official language in which they were submitted.
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FROTH FLOTATION METHOD FOX Recovery OF BITUMEN
FROM AUDI SUSPENSION OF TAR WANDS
This invention relate to a froth flotation method
or the recovery of bitumen prom aqueous suspensions of
tar sand.
The invention it particularly useful in
conjunction with the Hot Water Process for the extraction
of bitumen prom tar sands, because in this process a
number of flotation operations are or can be performed.
Tar sands deposits, also known as oil sands and
bituminous sands, have been identified in many areas ox
the world including four major deposits in Alberta,
Canada.
The Alberta tar sands typically contain between 70
and 90 percent by weight ox mineral solids, 5 and 20 per
cent of viscous petroleum having a 6 to 10 APT gravity
and specific gravity ox about 1~0 commonly referred to as
Bohemian and Prom aye 1 Jo 10 percent of water. The
mineral solids usually referred to a "coarse" are mostly
quartz sand over 45 micron in particle size, whereas
those referred to as phonies" are mostly clay, silts and
wine sand having particle size lest than 45 microns. The
content ox fines has been generally wound to increase with
the decrease in bitumen content in the tar sands. The
usually accepted physical arrangement ox the sand-bitumen-
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water mixture that constitute the tar sands depicts an
aqueous phase which anvelop3 the hydrophilic sand grains
and separates them prom the bitumen phase. queue key
requirement for the production of bitumen is a fast and
complete separation of the bitumen from the mineral
solids. Various techniques or separating the bitumen
prom mined tar sand have been developed to die rent
degrees in thy last several decades. These include: direct
coking, vent extraction, cold water separation,
lo spherical agglomeration and a sand reduction process just
to mention a few. These method are not being used on
commercial scale due to a variety of reasons, such as
material handling problems, low bitumen recoveries, high
energy retirement solvent losses, etc.
The present commercial plant, Succor and Sync rude, are
based on the Hot Water Process which war initiated in the
1920'~ by the Research Council of Alberta led by K. A.
Clark.
An excellent write-up on tar sands and on bitumen
recovery technology is presented by Donald Tyson in Kirk-
Other Encyclopedia of Chemical Technology, Third Edition,
pages 602-6Q7.
It the Hot Water Process, the mined tar sands are
treated in a tumbler with hot water, steam and additives,
usually caustic, to break down the lumps and produce a
slurry at approximately 80C-90C. The slurry is diluted
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with hot water to approximately 50% old, then pumped
into a gravity separation cell where entrained air causes
the bitumen to float. The flotation process produces the
primary froth, middlings and an under flow, which
constitutes the primary tailings.
The secondary froth, which is produced from the
middlings by air flotation, contains approximately twice
the amount ox solids and water as compared to the primary
Roth. Tailings from the secondary circuit join the
primary tailings to form the extraction plant tailings.
Following duration and heating, the combined Roth
stream is further treated by dilution and centrifuging to
remove the solids and water prom the bitumen in
preparation for the upgrading or coking process. The
solids and water removed together with residual
hydrocarbons constitute the froth treatment plant
tailings.
Since the early stages of development of the Hot Neater
Process, it has been recognized that lower grad ore, with
its higher percentage of fines and lower bitumen content,
results in lower bitumen recovery in the primary
separation stage and increased load total middlings flow
and solids content) in the secondary air flotation
circuit. Since the secondary separation produces Roth
with high, mainly fine solids content, the total solids
and water content may surpass the handling capability of
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the Roth treatment plant. Con equently, large amounts of
bitumen are lost in the traction plant tailings. A more
efficient separation of bitumen from the middlings stream
it highly desirable it a high level of bitumen recovery it
to by achieved This may also allow for reduced cutoff
grade of tar sands ore at the mine and increase the total
tar sand resource available for processing.
Many improvements of the Hot Water Process have been
proposed which could be classified under two headings:
lo l. Improved control to increase bitumen recovery and
separation efficiency of the existing plants;
2. Development of methods for the recovery of the
residual hydrocarbons prom the tailings and for
improving the settling characteristics ox the
sludge.
Some of these proposals seem to be more effective than
other; however, most are not C08t effective because they
require major modifications to the existing plants.
It is, therefore, the object ox the present invention
to provide a novel flotation method whereby a high quality
froth with high bitumen recoveries is obtained, and this
without requiring major modifications to the existing
installations. This object is achieved by carrying out
flotation with COY in the presence of a
dispersing/sequestering agent.
C2 gas flotation is already known and is disclosed in
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Canadian Patent Nos. 949,910 and l,023,677. Carbon dioxide
flotation reduces the pulp pi and enhances destruction of
the mineral hydrocarbon bond thus increasing froth grade
t~Bitumen/(Bitumen solids water) over that with air
flotation. However, bitumen recovery to the concentrate
remains about the same or lower compare to air flotation.
It it also known to perform C02 flotation with acid
addition to the pulp to initially reduce the pi to about
phi a it disclosed in Canadian Patent No. 1,022,098. This
way wound to increase bitumen recovery over C02 flotation
but the froth grade is drastically reduced.
On the other hand, it is also known to perform air
flotation with addition of dispersing agents such as
sodium phosphate compounds or soda ash to the pulp as
disclosed in Canadian Patents 775,088 and 914,093 and US.
Patent 3l846,276 and 4,425,227. Although the addition of
a do pursing agent generally increases froth grade, it has
been found to have a devastating eject on thy overall
Bitumen recovery.
Applicant has surprisingly found in accordance with thy
present invention, that the addition of a disappearing
sequestering agent in the tar sand pulp during C02 gas
flotation not only results in a significant improvement in
froth quality (i.e. lower solids content) but also
increases bitumen recovery. It is believed that the prime
function ox the dispersing/sequestering agent during C02
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flotation it to sequester or syllable complexes) or
precipitate undesirable cations, such a calcium, which
contribute to the mineral-bitumen bond and enhance mineral
flotation. Once this bond it destructed the mineral
flotation is depressed while the bitumen and the
surfactants present in the pulp are readily attached to
the C02 gay bubble and form the froth. The
dispersing/sequestering or precipitating agent may, o'er
example, be a phosphate compound, such a sodium
tripolyphosphate or soda ash. The amount of
dispersiny/sequestering agent to be added may vary
depending on the agent used and on the actual process or
treatment in which it is employed. When using sodium
tripolyphosphate and soda ash, it ha been found that
disper~ant additions of up to 0.7 kg/t ox pulp are
sufficient to improve recovery to the point that no
further addition is beneficial. The dispersing/
sequestering gent may be added prior to or during
flotation or in stages during flotation,
The invention will now be further described with
reverence to a non-limltative example, and with reference
to the appended drawing in which Figure 1 shows
comparative value ox bitumen recovery versus froth grade
using various flotation methods.
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ampule: E
Tests were conducted on primary separation vessel
middlings containing 1.1% bitumen and 33~ solids. The
flotation tests were conducted with air, with Coy, with
C2 and HO with air and a dispersing/sequestering
agent and finally with COY and a dispersing/sequestering
agent. The dispersing/sequestering agent dosages were
varied. The froth was collected after 6 and 12 minutes of
flotation. The results of the tests are presented in
Figure 1 and in the following Table.
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TABLE
6 MINUTE O~NeE~TR~lE 12 MINUTE oCNCE~lRArE
METHOD Grow ~XIUMEN Recovery GRACE gENCVTRY
Betty web Betty web
(wit basis) (jet basis)
I 1~.7 73.3 11.3 81.0
CX~2 ~2S44~ 71.8 4.5 84.0
AIR 12.5 76.8 9.1 81.
AIR ARTS*
STOP 0.08424.~ 72.8 16.1 78,1
STOP 0.1~830.7 ~6.9 21.4 73.8
STOP ~.67240.9 57.5 31.~ 65.9
soda ash 0.16R 15.4 72.9 15.4 78.6
Soda ash 0.336 21.0 70.9 13.8 78.2
soda ash 0.705 18.9 69.g 18.9 76.1
2 Hyannis*
SIP 0.16~19.4 8~,2 15.6 84.3
Soda Ash 0.336 16.4 77.5 12.7 84.2
STOP 0~504 - - 19.5 ~2.3
osseous are in Xg/ton meddlings Eye
9--
Thy above Table and Figure 1 depict the bitumen
recovery and concentrate grad after 6 and 12 minutes of
flotation lima at 80C using COY, COY + H2SO4,
Air, Air + dispersing/sequestering event and finally C02 +
disper~ing/se~uestering agent. From the above results, the
following operations can be mad:
a) the application of sodium tripol~phosphate or soda
ash with air or carbon dioxide as flotation gas
substantially improves thy concentrate bitumen grade over
lo the standard air flotation.
by all levels of sodium tripolyphosphate and soda ash
when used with air had the effect of reducing the rate of
bitumen recovery. This phenomenon was not observed with
carbon dioxide where the rate of bitumen recovery was
increased by about 3% over the standard air flotation.
Applicant ha alto found that the addition of a
dispel ing/~e~uestering agent during C02 flotation raises
the initial pulp pi from 8.3 to 8.5 while flotation with
C2 alone as disclosed in Canadian Patents 949,910 and
1,023,677, or with COY H2SO4 as disclosed in Canadian
Patent l,022,098 reduces the initial phi
The invention is not limited to the specific
embodiments described above and any modifications obvious
to those skilled in the art are also included therein. The
novel method can be used in any system that utilizes
induced or forced COY gas flotation but it is particularly
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useful in con; unctioll with the Hot Water Process where it
can be employed, with advantage, at various stages such
as, middlings streams, tailings streams tailings ponds
and any combine lions of the above .
