Note: Descriptions are shown in the official language in which they were submitted.
92/09672 - 1 - f~ 3 PCT/CA91/0041
METHOD AND APPARATUS FOR R~T.~.A.~ING AND SEPARATING
OIL FROM OIL SANDS
FIELD OF THE INVENTION
This invention relates to an oil sands separator
and a method of separating oil from oil sands.
BACKGROUND OF THE I~V~N'1'1ON
By "oil sands" are meant mineable oil sands of the
morphology found in the Athabasca deposits in Northern
Alberta, and deposits elsewhere in the world having similar
characteristics. To the extent that it may be possible to
condition oil and sand combinations found elsewhere,
naturally or as a result of oil spills, to have generally
similar morphology, the invention is also applicable to
such combinations. This morphology and some of its
implications from the point of view of separating the
bitumen content of the sand are discussed in a paper
"Athabasca Mineable Oil Sands: The RTR/Gulf Extraction
Process - Theoretical Model of Detachment", A. Corti and M.
Dente, Paper No. 81, Fourth UNITAR/UNDP Conference on Heavy
crude and Tar Sands. A process and apparatus for
practically implementing the theory set forth in this paper
are described in Canadian Patents NOS. 1,165,712 of RTR
Riotinto Til Holding S.A. and 1,167,238 of Ingeco
International S.A., discussed further below. For the
purposes of the present specification, the entities
referred to variously as lumps, particles and matrices in
the published art are referred to as granules, to
distinguish them on the one hand from sand grains or
=
W092/09672 ~ 3 PCT/CA91/00
-- 2
particles which they contain, and on the other hand from
large lumps of oil sand as mined. Such granules consist of
a nucleus of sand grains covered with a film of connate
water, which may itself contain fine particles,
encapsulated, often with gas inclusions, within a layer of
the heavy oil known as bitumen, which is essentially solid
at ground temperatures. The terms oil and bitumen are used
interchangeably in this specification.
The originally developed process for releasing
bitumen from tar sands was the Clark hot water process,
based on the work of Dr. K.A. Clark, and discussed in the
above paper. The Clark process has disadvantages, some of
which are discussed in the introductory passage of United
States Patent No. 4,946,597, notably a requirement for a
large net input of thermal and mechanical energy, complex
procedures for separating the released oil, and the
generation of large quantities of sludge requiring
indefinite storage.
Both the presently used commercial method and
apparatus for the separation of oil or bitumen from oil
sands based on the Clark process, and the similar process
and apparatus described in United States Patent No.
4,946,597, use vigorous mechanical agitation of the oil
sands with water and caustic alkali to disrupt the granules
and form a slurry, after which the slurry is passed to a
separation tank for the flotation of the bitumen from which
the bitumen is skimmed. As proposed in the U.S. patent,
the process may be operated at ambient temperatures, with
a conditioning agent being added to the slurry. Earlier
methods, such as the Clark process, used temperatures of
85~C and above together with vigorous mechanical agitation,
and are highly energy inefficient.
It is characteristic of both of the above processes
that a great deal of mechanical energy is expended on
92/09672 f~ PCT/CA9l/00415
-- 3
physically disintegrating the oil sands structure and
placing the resulting material in fluid suspension, this
disintegration being followed by physical separation of the
constituents of the suspension. Chemical adjuvants,
particularly alkalis, are utilized to assist these
processes. The separation process particularly is quite
complex, as will be readily apparent from a study of U.S.
Patent No. 4,946,597, and certain phases have presented
particularly intractable problems. Oil sands typically
contain substantial but variable quantities of clay, and
the very fine particles constituting this clay are
dispersed during the process, limiting the degree to which
the water utilized in the process can be recovered by
flocculation of the clay particles. No economical means
has been discovered of disposing of the flocculated and
thickened clay particles, which form a sludge which must be
stored in sludge ponds where it remains in a gel-like state
indefinitely.
The Corti and Dente paper mentioned above suggests
that better results should be obtained with a proper
balance of mechanical action and heat application, and
Canadian Patent No. 1,165,712 (the '712 patent) points out
that more moderate mechanical action will reduce
disaggregation of the clay content of t:he sands.
Nevertheless, it continues to regard external mechanical
action as playing an essential role in the disintegration
of the oil and granules, which will inevitably result in
partial dispersion of the clay.
Thus it proposes to use relatively more gentle
agitation of the sand in a slowly rotating digester
described in Canadian Patent No. 1,167,238 (the '238
patent). The digester in the '238 patent comprises in its
broadest embodiment a shell, means for entry of liquids and
solids into the shell at one end of the shell, a tubular
outlet at the other end of the shell for discharge of
W092/09672 ~ PCT/CA91/004
liquids, a solids outlet at the same end as said liquids
outlet, surrounding but separated from the liquids outlet,
and a screw which surrounds the tubular liquids outlet to
urge solids to and through the solids outlet, which screw
is secured at its outer periphery to the shell. As seen in
Figures 1, 2, 3 and 4 of the '238 patent, the operating
embodiment of the digester includes numerous plates and
bars secured to the shell for moving the solids along the
shell, and a set of bars for separating the clay from the
oil sands. Slurry is introduced at one end of the shell.
This slurry is a mixture of oil sands and hot water. The
slurry is moved by the plates, bars and screw down the
shell during which it is agitated and the oil and water
gradually separate from the solids. At the other end of
the shell, such oil and water, together with some fine
material that has separated from the solids, is removed
from one central, axial outlet, while the solids exit the
digester at its base.
This process, which is a cocurrent process, still
requires considerable post digestion treatment, as
described in the '712 patent. The post digestion steps
include further separation of the liquids into an oil rich
component and a middlings component consisting primarily
of water and fines, removing the fines from the middlings
component by flocculation and centrifuging, and further
treating the oil rich component for the removal of
contained water, fines and solids. A detailed outline of
the process is described with reference to Figure 1 of the
'712 patent.
SUMMARY OF THE INVENTION
The present inventor has appreciated, and
experimentally verified, that oil sand granules exposed to
hot water at a temperature, typically above 50~, sufficient
to soften the bitumen will essentially spontaneously
undergo liberation of the sand grains from within the
~ ~ 2 ~
- 5 -
granules as its bitumen coating ruptures and agglomerates
into droplets. The water then permits separation of the
sand grains from the bitumen droplets. Whilst bitumen has
a specific gravity which is very slightly great:er than that
of water, the gas inclusions that occur in the bitumen and
any air bubbles in the water tend to adhere to the bitumen
droplets, which in turn tend to adhere to one another,
reducing the effective specific gravity of the bitumen to
a degree which permits it to float as a "froth". He
therefore seeks to permit sufficient contact time between
the granules and the hot water to occur to permit the akove
two stages of sand grain liberation or release, and
separation-of the bitumen, to occur, whilst applying only
such mechanical agitation to the material being treated as
is necessary to ensure ade~uate exposure of the granules to
hot water to provide thermal transfer and opportunity for
the liberated sand and bitumen to separate.
Rather than seeking to find a balance of thermal
and ~h~n; cal action to release the oil from the sand, the
present invention seeks to rely essentially on thermal
action alone to provide release or liberation of the oil,
and the presence of hot water as a=medium both for heat
transfer and for separation to occur, mechanical action
being used merely to ensure adequate contact between the
water and the oil sand and its separated constituents so as
to permit it to act effectively as both a heat transfer
medium and a separation medium.
Accordingly the invention provides a method of
liberating and separating oil from oil sandr comprising
submerging sand to be treated into a bath of hot water,
gently rolling the sand within the bath, resultant
agitation of the water being~sufficient to ~n~ liberated
oil droplets from migrating to the surface of the bath, and
the rolling of the sand being insufficiently aggressive to
cause substantial dispersion of any clay present, but
W092/09672 PCT/CA91/004 ~
-- 6
sufficiently prolonged to permit substantial release and
separation of oil coating from granules of the sand,
removing sand from one end of the bath, and removing water
and oil from the other end of the bath, sand and hot water
being supplied at opposite ends of the bath to those at
which they are removed.
By passing the oil sand to be treated and the hot
water in opposite directions through the bath, various
advantages accrue. Firstly, separated oil froth passes
with the water towards the opposite end of the bath from
that at which the separated sand is removed, thus
minimizing the risk of reentrainment of oil on the sand as
the latter is removed. The sand is exposed to the hottest
water in the later stages of its treatment, thus favouring
completion of liberation of the oil and the separation
process. A settling zone may be provided at the end of the
bath from which the oil is removed, thus again favouring
separation of the suspended solid particles from the water
and oil before the latter leaves the bath.
It is an important objective of the invention to
mi n; ; ~e the attrition of clay lumps in the oil sands with
resultant suspension of clay solids in the treatment water.
This is achieved by ; n; ; zing mechanical working of the
oil sands during the release and separation process. The
less clay is suspended, the easier is the treatment and
recycling of the water used in the process, and the less
clay sludge is produced requiring indefinite storage. An
objective is to leave most of the clay essentially in its
original state so that it may be returned, together with
the separated sand, to the site from which the raw oil
sands were extracted.
While countercurrent methods have been proposed
for mineral extraction with solvents such as in the United
States Patent No. 4,098,648 to Kraemer et al and United
092/09672 ~ PCT/CA91/00415
-- 7 --
States Patent No. 889,159 to Trump, the t~chn;que has not
previously been proposed for the release and separation of
oil from oil sands. The mineral or oil extraction process
using solvents, while using a countercurrent flow of
solvent, works in a different way to the present invention
because there the solvent is percolated throu~h the feed.
Hence the shells used in those devices, wllile having
apparent similarity to the present invention, are typically
perforated or have perforated spiral ribbons to allow the
percolation of the solvent. In the present invention, the
water is deeper than the feed solids and thus released
bitumen floats to the top of the water and is moved towards
the discharge end of the drum. The solvent extraction
process has not to the knowledge of the inventor previously
been considered applicable to oil sands treatment with
water.
Apparatus is also known for the heavy medium
separation of minerals, in which a finely crushed ore to be
separated is blended with a medium intermediate in specific
gravity between fractions to be separated, so that one
fraction floats and the other sinks. The medium is usually
a pseudo-fluid in the form of a suspension of finely ground
and easily separated mineral of suitable specific gravity
such as magnetite. Such a process is purely a separation
process. The fractions to be separated have already been
released from one another by crushing or grinding.
The invention also extends to apparatus for
releasing and separating oil and solids from oil sand
comprising: a drum having a solids discharge end and a
liquid discharge end; means for advancing solids towards
said solids discharge end with a rolling action including
a spiral ribbon having a plurality of flights wound inside
the interior of the drum, the spiral ribbon extending from
the solids discharge end to adjacent the liquid discharge
end; a first plate partially closing the solids discharge
W092/09672 PCT/CA91/0041 ~
~2~
-- 8
end and having a first opening disposed within it; a second
plate partially closing the liquid discharge end and having
a second opening disposed within it; means at the liquid
discharge end for conveying oil sand into the drum through
the second opening and into at least one flight of the
spiral ribbon; means at the solids discharge end for
conveying hot water into the drum through the first
opening; means at the solids discharge end for removing
solids from the drum; means at the liquid discharge end for
discharging water and oil floating on the water; and drive
means for rotating the spiral ribbon.
In a preferred embodiment, the spiral ribbon is
attached to the inside of the drum and the spiral ribbon
rotates with the drum.
Also in a preferred embodiment, the apparatus
includes a settling zone at the liquids discharge end of
the drum to promote setting of solids and floating of oil
froth.
Preferably the counter current flow is established
by having the second opening lower than the first opening.
The means at the solids discharge end for removing
solids from the drum preferably includes a plurality of
pockets circumferentially disposed about the drum and a
receiver for receiving solids from the pockets.
BRIEF DESCRIPTION OF THE DRAWINGS
There will now be described a preferred embodiment
of the invention with reference to the accompanying
drawings by way of example in which like elements are
identified by like numerals and in which: '
Figure 1 is a side elevation of a separator
according to the invention;
-
~ 92/09672~ r~ CT/CA91/0041~
g
Figure 2 is a longitudinal section of the separatorof Figure 1;
Figure 3 is an end elevation of the separator of
Figure 1; and
5Figure 4 is a centre cross-section of the separator
of Figure 1.
DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION
The apparatus of the invention for releasing and
separating oil from oil sands is constituted in the
preferred embodiment by a rotary drum 10 having a shell 11,
mounted on rollers 12 for rotation about a horizontal axis
13 and driven by rotation of the rollers 12 or of a girth
gear (not shown) by any of various drive means, not shown
but well known in the art.
15Secured to the internal wall of the shell 11, in
the central portion of the drum 10, there is a spiral
ribbon 14. This is a preferred arrangement of the spiral
ribbon 14 within the drum 10. The separator could use a
rotating ribbon 14 within a curved trough in which the
spiral ribbon rotates but not the trough, but such an
arrangement would require the spiral ribbon to be mounted
on bearings, and the bearings would need to be sealed. In
such a case, the drive means would be independent of the
drum, but in the preferred embodiment the drive means for
the spiral ribbon includes the drum.
The spiral ribbon 14 has several flights forming
compartments 16. Pulp mixers 20, which consist of flat
blades, are attached to the shell 11 and the spiral ribbon
14 in sufficient numbers to ensure such engagement between
3~ the drum and flights and the sand as will produce a rolling
action of sand in the water as the drum rotates. By a
rolling action is meant a gentle circulating movement of
the sand within the rotating drum relative to the water
therein.
me e~ds :~;~ ~L 24 o~ ~e c~ $0 ~ p~t y
clsser~ by c:~r~r p~a~e~ 26 ~nd Z~3 r~L~ ~Qly ~ ~cr
~h~ c~r~r e~goe c~ ~ cyl~ s2~ L 1 Th~ f~d
en~l Z2 i~; p;~t~al~y clo~i~l .by ~ p:}.~te 2~ ch ha~
S la~ge op~i~ 3~ c~nCral}y an~ ~X~
1~2 ~lid C~i5~ 4 ~ ClC~ ~ p~lt~ ;~g
~ller openin~F 3 ~ l~ ~ a~i ~ y
disp~s~d ~ e ax~s o~ ~ ~r~ c
til~:ed ~C? ~ ~ 2~ ef f ect s:~l~r ~o ~'c c~f
1<~ di~fer~e: si:cec~ , ~n~ ~;~c~ 2 ~ t c~ould ~e ~i~z~
~n~ tc ~esc~ ~e san~ cn~ o~ ~ f ~ ~ ~ r
hori~on'cal c~ 11 pro~ e ~e ~ uL o:E
oil sar~d ~c~r l-L~ or q~ i~ior~ of ~e d~m a~
ref~err~d~
~s ~e l~ e~ :~n ~e dn~ ~0 ~s~o~n a~ a
l~ne ~ n Fi~ur~ 21 :~s esi~ab~ ~ ~r the ~;~ of ~e f~
f li~5 'mè ~on ~ , wni
ZQ cc~ C~rL ~!IIt r i~ det~~h~d b~ ~e 3~ ~;L:Lve A~els c~'
opc3~1~; 3~ ~ :t2~ ~n ~5
~l~e5, Z~ ~nd ;~S r~a~e wi~ ~ , a~ e opP~
~C~ an~ 32 are ~lly ~pos~d wi~ ~ir res~r~ r
plat~s ~ ~ opesli~ 3 ~ ~ ~an ~e oi~s ~ ~
25 ~o es~ ~e f~ ~cm ~e sand or 50~:L~5 d~s~rge en~l
i!4 e:o ~e llc~id ~ e ~rx~ 22
A :5~ling zs:~e ~4 ~ pr~decE ~w~- U~e ~3i~l1 -
4 ;~d t~e feefl end pl~ :2G ~s zone al3 a~rs f~e
30 ~erials ~at ~x ~>ende~ ~e l~c~ d~ ~:o ~s,~e o~
of ~e li~ r ~ s s~rf~e in tbe re~ a~
~:~ envi. o~ c~ ~l ~ ~e a~sen~e c~ xer~ an~d
spi:r~l ~~ ~t\on ~ 5~.KL~ 2:one is ~f~er:re~ ~ a
d~ens i ~n of o 1 -- ~ . 2 ~ F~r ~ ho~r T~e
Tl-lThL P.13_
~ 92/09672 ~ PCT/CA91/00415
~ . -- 11 --
dimension is defined by the area of the surface of the
water in the settling zone.
At the solid discharge end 24 there is a series of
sand lifting and draining pockets 40 circumferentially
attached to the inside of the shell 11. The pockets 40
rotate with the shell 11, lifting solids at the solids
discharge end 24, and dump the solids into the solids
receiver 42. The solids receiver 42 is attached to the
discharge chute 44. The chute 44 and receiver 42 are
externally supported by a structure (not shown). The
pockets 40, receiver 42 and discharge chute 44 together
form one means for removing solids from the drum lO.
Oil sand is fed to the drum lO by feeder 46 which
can be a belt conveyer, screw conveyor, or other suitable
means for conveying feed into the drum 10. The feeder 46
extends into the drum 10 at least far enough that the oil
sand can be guided within the first flight of the spiral
ribbon 14. Hot water is admitted from a hot water source
(not shown) through means for conveying hot water to the
drum lO such as pipe 50 to the solid discharge end 24 of
the drum 10 and flows from there to the feed end 22, where
it exits the drum 10 at the lower level of opening 30.
This direction of flow is counter to the direction of
movement of material held in the spiral ribbon 14. It may
be helpful to discharge the water from the pipe 50 as a
spray or some other directed manner such as to repel any
floating bitumen tending to approach the solids discharge
end of the drum.
OPERATION OF THE INVENTION
Operation of the invention may be described in its
" preferred embodiment as follows. Oil sand is continuously
fed into the drum 10 by feeder 46 and directed into the
space between the flights of the spiral ribbon 14 at the
feed end of the drum. The oil sand may be in as-mined
W092/09672 PCT/CA9l/0041 ~
2 ~
- 12 -
condition, subject only to such crushing as will avoid the
presence of lumps large enough to jam between flights of
the ribbon 14 or other structures associated with the drum.
The oil sand forms a pulp in the compartments 16 by mixing
with the hot water flowing counter currently from the water
inlet 50 at the other end of the drum 10. The rotation of
the drum 10 is such that the spiral ribbon 14 slowly
propels the pulp from the feed end forward to the solids
discharge end of the drum 10. Hot water is fed into the
solids discharge end through the pipe 50 in an amount and
to a depth sufficient to cover both the solid materiàl
being moved by the spiral ribbon and the spiral ribbon
itself. The hot water flows over the solids in the spiral
ribbon and part of it mixes with the solids as the latter
are rolled by the mixers. As the drum 10 rotates the pulp
mixers 20 roll the pulp in the compartments 16 and cause
mixing of the pulp with the counter flowing hot water. The
mixing with hot water causes softening of the bitumen,
followed by rupture of the bitumen coating of the oil sand
granules, expulsion of the sand particles, and formation of
oil droplets. The released sand sinks, whilst the oil
droplets and any gas within the granules tend to
agglomerate and float as a bitumen froth. The released
bitumen froth floats with the counter flowing water to the
settling zone 34. In the settling zone 34 fine minerals
which may have entered the water have an opportunity to
settle to the bottom of the drum 10 and flow to the spiral
ribbon 14 whence they are transported to the solids
discharge end of the drum 10.
Water carrying the bitumen froth flows from the
feed end circular opening 30 into a collecting launder 52
(not shown) for further separation and processing. Initial
tests have indicated that the use of caustic soda to assist
release of the bitumen should not normally be necessary,
and the absence of this chemical assists subsequent
processing and reduces dispersion of clays.
092/09672 ~ ~ 4 ~ ~ 9 ~CT/CA91/00415
The rotation of drum 10 is very slow, typically to
achieve a drum peripheral velocity of about 5 feet per
minute. The peripheral velocity required depends upon the
oil sand being treated and the mechanical action required
to release sand particles from the bitumen while limiting
disaggregation of the clay lumps. Thus the m~ch~n;cal
action on clay lumps contained in the oil sand is very
gentle and the clay lumps will pass through the drum 10
with limited disaggregation. The speed of rotation, and
the configuration of the mixers, should be designed to
; n; ; ze suspension o~ clay solids, whilst achieving a
sufficient residence time for the oil sand in the drum for
a high degree of release and separation of the oil or
bitumen ~rom the sand to take place.
By the time the sand reaches the solid discharge
end of the drum 10 most of the bitumen will have been
released and have floated away towards the liquid discharge
end.
The r~ ~; n i ng sand, clay lumps, and tramp rocks
then reach the lifting pockets 40. The rotation of the
drum 10 lifts and drains water from the sand, lumps, and
rocks contained in the lifting pockets 40. When the
lifting pockets 40 reach a sufficient elevation the
remaining damp material falls into the receiver 42 and
slides out the solid discharge chute 44.
The ratio of length to diameter of the drum 10 may
be between about 1.5 to 1.0 and 10.0 to 1.0 but preferred
is about 2.0 to 1.0 and 3.0 to 1Ø
The diameter of the feed end opening 30 is
preferably about 90% of the inner diameter of the spiral
ribbon 14. As noted above, where a circular opening 30 is
used (as is required in the case of a rotating drum),
having the diameter of the opening 30 smaller than the
KC~ 13A~ .L~ '.) ' : 17 ~3'J _ l lG :~G ~ (38 ':3-- + 1'~1 ~''3 ~?94.1.~;5 ~ ~;
-- 14 --
dia3~ete~ o~ t~e sp~al rib~on 14 er~sure5 t~e co~lnteYc~.
f lo~ o~ ~ water i~ t~e dru~ axis ~.s hori~on~Ll
The di~eter o~ ~he solid ~ ~3~h~ ~ o~r~; n~7 32 is
~s smat 1 a~ pra~ e wh~ le allowing ro~ ~or t~e
~ 5 disc~arye c~ute 44 and the ~ate~ pipe SO~
'rh~ sp~ral rib}~on wi~ pically h~e ~et~n a~out
3 an~ ~ O ~1~ ght~ ~ ~nc 3 . A~o~t ~ ~ f li~h~: is. bsl ~ 8
~e pre~ra~ e~
T~e rat~ o~ ro~tion can 1~ t the
10 per:Lphe~al tr~ ty o~ t~e drum is ~L.~ and ,~ ~~s
pex n~ ute . T~ relat c onsh c p ~ ~e~n t~e d~ ripheral
l~eloc y a~ sp~-al con~4~ tion will }x sut~ s to
pro~ride a residence t~e ~or the pul~? ~n t~e s~ 1 zone of
a~out 10 m~nut es, whic~ ini~ia~ tests ha~re in~icated ~~ a
1~; suff ic ent: ti~l3 fo~ sat~sfacto~y releas~ and s~p~a~on of
~he 3:~itt~len us~ng wat~r t~mperab~es as C~ s~ belo~.
Sc~ nc~ase cr d~ ease s:~ ~is ~me ~ay ~e de ~ e t~
suit par~icu}~r ~ allat~ons or ~r~d~_~ of oi~ cand. ~
nw~e~ of puip m~xers ~o c~n ~e ~e~ en one and eight per
20 ~light.
Ihe size znd nuD~er ~f the lifti~sF pocket~ 4CI
shou7 d. ~~ select;es~ to ~Lc~pe~ly ~ispose of the ex~ed
a~ount of ~:~nd pr~duc~d at t:h~ so~ i h~rge er2d.
r~e m~xi~ l~p s~ze of ~he oil ~a~d should no~
25 excee~ the space ~etween ~he spiral fligh~s 14t ~e size of
the li~ting pockets 40, or 1:he ~ize o~ the ~ ~e c~e
44 .
~ e ~ eed rate canno~ e ~rol~etric
cap~city of ~che s~ral f}ishts 14 and ~e pulp c~par~en~s
3~ 16 to comrey p~lp to ~he soLids disc~arge end 3Z of ~he
d~m 10.
4 92/09672 ~ PCT/CA91/0041
- 15 -
The amount and temperature of the hot water should
be such that the water discharge at the feed end will be
between 40~C and 70OC. The preferred discharge temperature
is about 50~C and is required to ensure that bitumen has
softened and separated from the oil sand in the preferred
l0 minutes residence time. To achieve this preferred
temperature the hot water temperature feed at the pipe 50
that is required will be about 80~-90~C and the amount of
water about 40%-50% of the weight of oil sand feed. If
cold or frozen oil sand is being processed more water or
higher temperature water may be required.
It should be noted that the amount of hot water
required is a function of the process heat requirement, and
the requirement to provide adequate free water to allow the
bitumen to separate from the sand, rather than a
requirement to provide dilution of clay slurry as in the
Clark process. Because of the gentle action of the drum
l0 the clays contained in the oil sands feed are dispersed
only to a very limited degree and the quantity of clay
dispersion formed is greatly reduced. Because of the
limited dispersion of clay, it will normally be possible to
recycle a substantial portion of the water utilized, thus
substantially reducing the water and thermal requirements
of the process, possibly by as much as 50% compared to
conventional techniques based on the Clark process.
Test results from a small pilot plant operating at
the preferred conditions suggest that the weight percentage
of the bitumen in the oil sand feed which is recovered is
expected to be greater than 80%. Over 85% of the mineral
solids in the feed are expected to be recovered at the
solids discharge, and the material recovered is expected to
be more than 75% solids. Considerable variations may occur
according to the characteristics of the feed and conditions
W092/09672 ~ PCT/CA91/0041
- 16 -
of operation, but an oil recovery in the 65 - 90% range may
be realistically expected.
The bitumen 'froth' can flow or be pumped to
conventional separation vessels or flotation machinery.
The small amount of clay fines in the water can be
separated by flocculation and thickening for disposal, and
should be more amenable to treatment as alkali has not been
used in the processing.
The damp sand, clay lumps, and rocks discharged at
the solids discharge can be conveyed on belt conveyors or
trucked immediately back into the mine or for permanent
disposal. Some pile draining may be required for final
water removal from the solids discharge.
Variations to the apparatus or process of the
invention may be made within the scope of the appended
claims.
