Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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IMPROVED PROCESS FOR OIL SANDS PROCESSING
Thls ln~ention ls dlrected to an lmprovement ln a
processlng step ln the recovery of bltumen from oll ~ands,
partlcularly, whereln centrlfugatlon of a hydrocarbon-dlluted
bltumen froth or other dllutlon technlque ls replaced by an
aqueous ba6ed gravlty separatlon of the bltumen from the
lnorganlc mlnerals and water ln the syEtem.
BACKGROUND OE THE INVENTION
Tar 6and~ ~whlch are alco known a~ oll cand6 and
bl~umlnous Eands) are 6and depo61ts whlch are lmpregnated
wlth den~e, v16cou~, petroleum. Tar 6ands are ~ound
throughout the world, often ln the same geographlcal area~ a6
conventlonal petroleum. The large6t depo61t, and the only
one o~ pre6ent commerclal lmportance, ls ln the Athabasca
reglon ln the northea~t of the provlnce o~ Alberta, Canada.
Whlle much o~ the Athaba6ca depo61t 16 not economlcally
recoverable on a commerclal 6cale wlth current technology,
nonetheleE~, a ~ubstantlal portlon 1E ~ltuated at, or very
near, the 6urface where lt may ~alrly readlly be mlned and
processed lnto ~ynthetlc crude oll, and thl6 procedure ls
belng carrled out commerclally on a very large Ecale by
Suncor, Inc., 011 Sandc Dlvl610n and Syncrude near Fort
NcMurray, Alberta.
Athaba6ca tar sands 1 E a three-component mlxture o~
bltumen, mlneral and water. Bltumen 1E the valuable
component for the extractlon o$ whlch tar Eand6 are mlned and
proceE6ed. The bltumen content 1~ varlable, averaglng 12 wt~
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of the dep~lt, but ranglng from zero to lB wt~. Water
typically runE 3 to 6 wt~ of the mlxture, and generally
lncrease6 a~ the bltumen content decreaEeE. The mlneral
content 1~ relatlvely con~tant, ranglng from 84 to 86 wt~.
Whlle several ba61c extractlon method~ to 6eparate the
bltumen from the Eand have been known ~or many year~, the
"hot water~ proceEE 1E the only one o~ preEent commerclal
Elgnlflcance and 16 employed by both Suncor and Syncrude.
The hot water proce66 ~or achlevlng prlmary extractlon o~
bltumen from oll 6andE lnvolveE (a) Mlnlng the oll sandE for
dellvery to the extractlon plant; (b) Hot Water Extractlon
whereln the tar Eand6 are heated wlth ~team, ~looded wlth
water and charged to a Eeparatlon veOEEel where the maJorlty
of the water and mlneral are removed from the veEEel bottom
a6 a tallE product and Eent to dlEpo6al, and the bltumen
~loatE to the top and 1E recovered a6 a ~froth." The ~roth
compo61tlon may vary wlth the quallty o~ the tar Eand6 belng
mlned and the extractlon condltlonE, however, typlcally, -
froth i~ about 55% bltumen, 35~ water, and 10~ mlneral;
~c) Dllutlon Centrlfuqlng - u6ed becau6e bltumen and water
have eEsentlally the same Epeclflc gravltleE and for that
rea60n dlluent (naphtha) 1E added to the froth to reduce the
vlEcoslty o~ the bltumen and reduce the Epecl~lc gravlty of
the bltumen-naphtha mlxture to about 0.9. The froth-naphtha
mlxture 1~ charged to centri~uglng Etages whlch remove mo~t
o~ the water and mlneral and produceE a naphtha-bltumen
product typlcally contalnlng 0.4 to 0.8 wt% mlneral and 4.0
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to 6.0 wt~ water; and ~d) Diluent Recovery wherein the
dlluted bltumen is heated and the water and naphtha are
removed by vaporlzatlon to produce a hot dry bltumen
containlng about 1.0~ mlneral and up to about 2~ naphtha.
The bltumen product 1~ charged to the up-grading unlt~ for
further proces~lng lnto synthetic crude. The naphtha and
water are conden~ed and allowed to ~eparate. The water ls
6ent to dl6po6al and the naphtha re-u6ed a~ dlluent ln 6tep
~c) above. Some make up naphtha 1~ added to the recycle to
account ~or the amount 106t wlth the water and bitumen.
Thi~ lnvention 16 directed to replaclng 6teps (c) li.e.
dllutlon centrlfuging or other dllutlon technlgue) and td)
wlth a llguld-llquld gravlty separatlon of the bltumen from ';
the water-mlneral pha6e and by dolng EO obtaln~ ceveral
advantage6 over the pre6ent practlce.
A maJor advantage of the proceE6 o~ the lnventlon 16 ln
61gnl~1cantly lncrea6ed safety ~lnce the low bolllng
hydrocarbon dlluent (naphtha) 16 ellmlnated a6 1E the hlgh
6peed rotating mechanlcal egulpment (centrlfuge6), Secondly,
operatlng c06t6 are reduced ae no make up dlluent 16 needed
to replace the lo&se6 whlch occur ln the preEent practlce.
Egulpment malntenance 18 aleo reduced by the proce66 of the
lnventlon and the energy requlrement 18 slgnlflcantly reduced
61nce the energy needed to operate the centrl~ugeE and
vaporlze the naphtha dlluent for separating naphtha and water
~rom bltumen 16 replaced by a slmple gravlty 6ettler. A
Etlll ~urther advantage 1E an envlronmental bene~lt 61nce no
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dlluent ~oeE ta the t~ilingE pand whi~h dilu~nt w~uld th~n
evaporate to the atmosphere.
DISCUSSION OF THE PRIOR ART
It 1B known ln the art of petroleum processlng, a~ :
dl6cloEed ln U.S. 1,028,G39, to separate water ~rom oll by
heatlng the oil under pre6~ure somewhat above the bolllng
polnt o~ water, allowlng the oll to rl~e ln a body or mase of
oll at the elevated temperature and, whlle gradually reduclng
the pres6ure, allow the water to evaporate. A1BO~ U.S.
2,231,544 dl~closes an emul~lon breaklng proce6s by heatlng
an agueou~ emulslon o~ oll to above the bolllng polnt of
water and under su~lclent pres6ure to prevent vaporlzatlon
o~ the water and then expandlng the emulslon through an
or~lce whereby a foam 1~ ~ormed whlch on standlng ~eparates
lnto oll and 6team.
Nelther of theee dlsclosure~, however, relateE to a
llguld-llquld gravlty separatlon of water from heavy, vl~cou~
bltumen whlch ha~ ~pecl~lc gravltles 80 close to water that
gravlty separatlons have hereto~ore been consldered
lmpractlcal wlthout the addltlon of a dlluent to reduce the ;~
bltumen gravlty and vlscoslty.
BRIEF DESCRIPTION OF THE INVENTION
The proce~ o~ ~hls lnventlon comprlses the Eteps of
~1) heatlng the bitumen ~roth ~rom the hot water extractlon
step o~ an oll sand~ process ~or bltumen recovery ln a
gravlty settler to a temperature o~ from about 250F. to
about ~50F. to reduce the vlsco~lty o~ the bltumen and
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malntalnlng the froth under sufi'lclent pre~sure to prevent
vaporization of water and bltumen; t2) whlle malntalnlng the
elevated temperature and pres6ure, removing the bltumen from
the settler a6 a llght phase from a heavler water-mlneral
pha~e; and, optlonally, ~3) rapldly reduclng pre66ure on the
6eparated bltumen product to remove any residual water and
llght hydrocarbon~ by i'laEh drying.
DESCRIPTION OF THE DRAWINGS
Flgure 1 16 a ~low dlagram of the proceE6 of the
lnventlon.
Flgure 2 16 a ~low dlagram oi' the inventlon 6howlng
aIternate detall~ useful under certain speclal condltion&.
DETAILED DESCRIPTION OF THE INVENTION
In the recovery oi' bltumen from oll Eand6, the bltumen
i'roth obtalned ~rom the hot water extractlon 6tep conslsts of
a mlxture of water, sand, sllt, flnes, and other component~
whl~h form a complex havlng a 6pecl~1c gravlty hlgher than
elther water alone or bltumen. Thl6 complex 16 6tsble ln
that the 6teps oP pumplng, heatlng, or other proce6~1ng
condltlon6 encountered ln the hot water extraction proce6s do
not break down thie den~e water-mlneral phase. Thu6, ln
accord wlth thls lnventlon, a~ter heatlng the froth to
between about 250~F. and about 450F. to reduce the bltumen
v16c061ty, the bltumen and the water-mlneral pha6e can be
6eparated by gravlty 6ettllng, becau6e, aOE haOE been ~ound,
the water and mlneral6 act aE a 61ngle pha6e and the bitumen
act6 a6 a 6econd pha6e whlch, becau6e o~ lt~ lower denslty
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than the water-mlneral phase, rlEe~ to the top.
In srder to deEcrlbe the proce~s ln more detall,
re~erence 16 now made to Flgure 1 whlch 1E a 61mpll~1ed flow
dlagram ~or the proceE~ o~ the lnventlon. A6 Ehown ln Fl~ure
1, ~roth from the hot water extractlon plant iE taken by llne
11 to one or mor~ ~entrli~e~ o ~ep~ e f~ee
Eand or other partl~leE and then taken thraugh llne 15 to one
or more optlonal ~llter6 17 to remove any tra~h, 6uch as
leave6, root6, and the llke whlch may be pre6ent ln the ~roth
stream. The i~roth emul610n 1E then taken by llne 19 to an
optlonal Etorage tank 21 ~rom whlch lt 1E pumped through llne
23 to a heat exchanger 25 where lt 1E heated wlth 6team or
other mean6 to reduce the v16coElty of the bltumen. The
heated ~roth 1E taken through llne 27 to one or more gravity
6ettlerE 2g where the ~roth 1E held at a temperature between
about 250F. and about ~50F. (preferably about 300F. to
about 350F.) and 1E malntalned under a preEEure Euf~lclent
to prevent vaporlzatlon of the water and bltumen (uEually
between about 110 and 170 lbe./Eq. in.). AE the bltumen ln
the Eettler rl6eE to the top lt may be taken by da6hed llne
31a at the elevated preEEure and temperature ~or further
proce~Elng or, optlonally, and pre~erably, the bitumen 1E
taken by llne 31b to a ~la6h drum 33 where the preeEure 1
releaEed to ~laEh o~i' any llght hydrocarbonE and any resldual
water ln the bltumen. The dry bltumen 1E then removed from
the ~laEh drum through llne 35 and taken to storage or
dlrectly to ~urther proce~slng. The aqueouE phaEe contalning
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the m~neralE i~ taken from the bottom of the settler 29
through line ~7 and, after coollng and reduclng the pres~ure,
1E sent to dlEposal.
The gravlty Eettler~ uEed ln the proCeEOE o~ the
lnventlon may be and, preforably are, augmented ln thelr
operatlon by use o~ a hlgh voltage electroEtatlc ~leld ln~lde
the settllng veE6el. TheEe electroEtatlc unit~ are well
known and are used ln crude oll electroEtatic deEalting
proces6eE whereby water dropletE are cau6ed to agglomerate
and 6ettle ln the bottom oi' the ve6OEel. The use o~ 6uch
electro6tatlc deviceE, while not es~entlal to the process,
may 6ignli'1cantly increaEe the efflclency of the proce~6 o~
the inventlon.
AE indicated above, the bitumen ~roth compoEition may
vary with the quallty of oll EandE mlned and, in æome ca~es,
the agueouE ~roth ~ay have in6u~iclent Eolld6 to make the
proce66 rui'i~lclently ei'ficlent. That is, there may be
lnEui'ficient ~ollds to provide a 6011dE-water mlxture whlch
haE a 6pecl~1c gravity above that of water alone. Such
situation6 may be remedled by uslng a mineral~-contalning
~ake-up slurry which 16 i'ed lnto the low solids bltumen froth
input. Figure 2 illu6trateE how OEuch a procedure may he u6ed !`
employlng the aqueouE pha6e removed from the Eettllng veE6el
~or recycle. AE can be seen, Flgure 2 1E Elmllar to Flgure
1, but the aqueou6 phaEe removed from the Eettler through
llne 41 1E pa6Eed through one or more cycloneE ~3 to obtain
an agueouE dlsperEion oi~ mineral ~ine6 a6 the e$fluent ~rom
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the cyclone6 ~llne 45~ which ie fed di~ectly ta the inp~
etream of low EolldE froth aE a Eolld6 make-up. Al60
employed ln thlE technlgue 1E a make-up slurry ~llne 47)
whlch 1~ a ~lne mlneral dlsper610n ~clay and sllt) whlch may
be uEed wlth the cyclone e~fluent or uEed alone lf the
cyclone e~fluent ls lnadequate or not used for any reason.
It wlll be understood that various technlques can be
uEed ln the process. For example, lamlnar flow on an
lncllned plane to coaleEce the water withln the Eeparator may
be used wlth or wlthout the electroEtatlc coaleEcer. Other
syetem& to produce lamlnar ~low wlthln the eeparator may also
be uEed.
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