Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
13~16~Z 87-003
PRO~ESS FOR FLO~CULATING RECYCLE WATER FROM OIL
SANDS PROCESSING TO EFFECT PROCESS EFFICIENCIES
BACKGROUND OF THE I~VENTION
ThlE lnventlon relateE to an lmprovement ln the
proce661ng of recycle water ~rom oll Eand6 operatlon6 whereln
bltumen 16 recovered ~rom tar Eand6 whlch are EubEequently
converted to petroleum product6.
In the hot water extractlon procesB of oll ~and6 (al~o
known a6 tar Eand6) ln the northeaEt provlnce o~ Alberta,
Canada, the extractlon method comprl6e6 three maJor proce6s
6tep6 plus a flnal extractlon u6ed to clean up the recovered
bltumen ~or ~urther proce661ng. In the ~lr6t 6tep, called
condltloning, oil 6and 16 mlxed with water snd heated with
open steam to i'orm a pulp o~ 70-85 wt.~ 6011d6. Sodlum
hydroxlde or other reagent6 are added a6 requlred to malntaln
the pH ln the range o~ about 8.0-8.5. In the 6econd 6tep,
called 6eparatlon, the condltloned pulp 16 dlluted ~urther
with hot water 60 that separation can take place. The bulk
o~ the sand-612ed particle6 ~greater than 325 me6h Ecreen)
rapidly 6ettle6 and 16 wlthdrawn a6 6and talllng6. Mo6t o~
the bitumen rapldly float~ (6ettle6 upward) to i'orm a
coherent ma66 known a~ bitumen froth whlch i6 recovered by
6klmmlng the 6eparation ve66el. An aqueou~ middllng6 layer
containlng 60me mineral and bitumen i6 formed between the6e
layerE. A ECavenger 6tep may be conducted ln the mlddllng6
~$
13~16~2
layer ~rom the prlmary Eeparation Etep to recover addltlonal
amountE o~ bltumen thereSrom and thls Etep usually comprl~eE
aeratlng the mlddllngs. The frothE recovered from the
prlmary and the Ecavenger 6tep can be combined, dlluted wlth
naphtha and centrl~uged to remove water and mlnerals. The
naphtha 1E then dlstllled ~or further proceEElng. Hot water
proceEEeE are deEcrlbed ln Canadian Patent NumberE B82,668;
866,226; 891,472; 892,548; and g73,500. TalllngE can be
collected Srom the a~orementloned proceEslng Eteps and
generally wlll contaln Eolld6 aE well a~ dlEEolved chemlcal6.
l'he talllngE are collected ln a retentlon pond ln whlch
addltlonal 6eparatlon occurE. The talllng6 can alEo be
consldered aE proceEElng water contalnlng EolldE whlch are
dlEcharged ~rom the extractlon proceEE. The talllngE
comprlEe water, both the natural occurrlng water and added
water, bltumen and mlneral.
Condltlonlng tar EandE Sor the recovery oS bltumen
conElEtE oS heatlng the oll Eand/water mlxture to proceEE
temperature (180-200F.), phy61cally mlxlng the pulp to
unlform compoEltlon and conEiEtency, and the conEumptlon ~by
chemlcal reactlon~ oS the cauEtic or other added reagentE.
Under theEe condltlonE, bltumen 1E Etrlpped Srom the
lndlvldual Eand gralns and mixed lnto the pulp ln the Sorm oS
dlEcrete dropletE o~ a partlcle Elze on the 6ame order aE
that oS the Eand graln6. ~urlng condltlonlng, a large
fractlon of the clay partlcle6 become6 well dlEperEed and
mlxed throughout the pulp. The condltlonlng procesE whlch
13~6~
prlepares bltumen for efflclent recovery durlng the following
proceEE stepE alEo caUEeE the clayE to be the moEt dlfflcult
to deal wlth ln the talllngE dl6poEal operatlon.
The other proceEE Etep, called ~eparatlon, 1 actually
the bltumen recovery Etep, the Eeparatlon havlng already
occurred durlng condltlonlng. The condltloned oll sand pulp
16 Ecreened to remove rock~ and uncondltlonable lumps of tar
EandE and clay. The re~ect materlal, ~Ecreen overEize,~ is
dlEcarded. The Ecreened pulp 1E further dlluted wlth water
to promote two Eeparatlon proceEEes. Globules of bltumen,
eE6entlally mlneral-free, float upward to form a coherent
maEE of froth on the Eurface of the Eeparatlon unlt6; and, at
the eame tlme, mlneral partlcleE, partlcularly the Eand Elze
materlal, Eettle down and are removed ~rom the bottom of the
Eeparatlon unlt aE OEand talllngE. TheEe two Eettllng
procesEeE ta~e place through a medlum called the mlddllngE.
The mlddllngE conElEt prlmarlly of water, bltumen partlcle6,
and Euepended flneE.
The partlcle ElzeE and denEltles of the Eand and of the
bltumen partlcleE are relatlvely flxed. The parameter whlch
ln~luenceOE the 6eparatlon proceEEeE moEt 1E the apparent
vlEcoElty of the mlddllngE. CharacterlEtlcally, aE the
EuEpended materlal content rlEeE above a certaln thre6hold,
whlch varle~ accordlng to the compoEltlon of the EuEpended
flneE, apparent vlEcoElty rapldly achleveE hlgh valueE wlth
the ef~ect that the Eeparatlon proceE6eE eEEentlally Etop.
Llttle or no bltumen 1E recovered and all EtreamE exltlng the
13~16~Z
unit have about the 6ame compoeltlon 9E the ~eed. Ae the
feed Eu6pended flneE content lncreaeee, more water muet be
uEed ln the proceEE to malntaln mlddllng~ vlEcoElty wlthln
the operable range.
The thlrd Etep of the hot water proceEE 1E ECaVen91n9
The feed of 6u~pended flneE content determlne~ the proce~
water requlrement through the need to control mlddllng6
vlEcoElty whlch, as noted before, 1E governed by the
clay~water ratlo and the type o~ clay mineralE. It 16
uEually neceEEary to wlthdraw a drag Etream of mlddllngE to
malntaln the Eeparatlon unlt materlal balance, and thlE
Etream o~ mlddllng& can be Ecavenged for recovery of
lncremental amount6 o~ bltumen. Alr ~lotatlon 1~ an
e~fectlve Ecavenglng method ~or thlE mlddllngE Etream.
Flnal extractlon or froth clean-up 1E UEUa11Y
accompllEhed by centrlfugatlon. Froth from prlmary
extractlon le dlluted wlth naphtha, and the dlluted froth 1E
then 6ub~ected to a two Etage centrlfugatlon. Thl6 process
yleldE an oll product of eEsentlally pure, but dlluted,
bltumen. Water and mlneral and any unrecovered bltumen
removed from the froth conEtltuteE an addltlonal talllng
Etream whlch muEt be dlEpoEed.
In the termlnology o~ extractlve proceEElng, talllngE
are a throwaway materlal generated ln the cour6e of
extractlng the valuable materlal from the non-valuable
materlal. In oll ~andE proceEElng, talllngE con~lst of the
whole oll Eand~ plu6 net addltlonE of proceEE water leEE only
13~316~Z
the recovered bltumen product. 011 ~and tall lngE can be
6ubdlvlded lnto three categorle6~ creen overElze;
~2) Eand talllngs--the fraction that EettleE rapldly, and
(3) mlddllng~--the fractlon that settles slowly. Screen
overElze 1~ typlcally collected and handled aE a ~eparate
stream .
Talllngs dlsposal 1~ the operatlon regulred to place the
talllngE ln a flnal reEtlng place. ~ecauce the tailings
contaln bltumen emulElon6, flnely dlEperEed clay wlth poor
Eettllng characterlEtlcE and other contamlnantE, water
pollutlon conElderatlons prohlblt dlEcardlng the talllngs
into rlvers, lakeE, or other natural bodieE. Currently, the
talllngE are ~tored in retentlon pondc whlch lnvolve large
6pace requlrementE and the conEtructlon of expenslve
encloEure dlkeE. A portlon o~ the clear water layer at the
top o~ the talllnq6 pond may be recycled back lnto the water
extractlon proceEE a6 an economlc mea6ure to con6erve water.
Currently, two maln operatlng mode6 ~or talllng6 dl6posal
are: ~1) dlke bulldlng--hydraullc conveylng of taillng6
followed by mechanlcal compactlon of the 6and talllngs
fractlon; and (2) overboardlng--hydraullc tran6port wlth no
mechanlcal compactlon.
The pre6ent lnventlon 16 dlrected to the water ln the
talllngE from the 6eparatlon cellE and/or the 6cavenglng
clrcultE whlch, ln accord wlth the lnventlon, 16 recycled
back lnto the water extractlon proceEs and provldeE for
i~proved proceEE e~flclencleE and lmproved proces6 economlc6.
13~169Z
~UMMARY OF THE INVENTION
The proceE6 of the lnventlon lnvolveE flocculating the
dl6charge from the 6eparatlon cellE and/or the scavenger
clrcults employed ln the oll Eands proce~sing and returning
to the condltloning drumE and Eeparatlon cells water
recovered from the flocculated talllngE. As a result of the
proce6~ of the lnventlon, water conEervatlon, energy 6avlngs,
lncrea6ed bltumen recovery, and other beneflt6, a6 wlll be
detalled later, are obtalned.
DESCRIPTION OF THE DRAWINGS
Flg. 1 16 a 6chematlc flow dlagram of water uEe ln the
ol1 sand6 extractlon proce6s as presently practlced.
Flg. 2 16 a echematlc flow dlagram 6howlng the
flocculatlng 6tep of the lnventlon and recycle of the
water from the flocculated talllng~ to the extractlon
proce~6.
Flg. ~ 16 a 6chematlc flow dlagram showlng a further
embodlment of the lnvention.
DETAILED DESCRIPTION OF THE INVENTION
Reference 16 made to Flgure 1 whlch lndlcate6 the manner
ln whi~h pro~eEe w3ter le preeently ueed ln the extractlon
~3~?1692
proces6. AE can be 6een from the diagram, proceEE water
enter6 the Eteam exchangerE through llne 11 ~or heat exchange
purpoEeE and then pas6eE lnto the condltionlng drumE and then
to the Eeparatlon cellE and the Ecavenger clrcult~. The
waEte water talllngE from the Eeparatlon cellE (llne 13) and
6cavenger clrcultE (llne 15) 1E ~ed to a talllng~ EUmp ~rom
whlch lt pa6EeE to a dlEtrlbutor whlch directE the water to
the retentlon pond. The upper layer of water ln the talllng
pond or rlver water 1E the Eource o~ proceEE water (llne 11)
and Elnce thlE water 1E cold, usually from about 40 to about
65F., lt muEt be heated be~ore enterlng the condltlonlng
drumE .
In the prOce6E o~ the lnventlon, however, aE 6hown ln
Flgure 2, the waEte water i'rom the Ecavenger circuitE is fed
through line 1~ to one or more ~locculating tank6. These
tankE, usually cyllndrical, hold the waEte water while
~locculating agentE are added. U6e~ul agentE are any of the
numerouE and well known i~locculating agentE, but a
partlcularly preferred agent iE high molecular weight (4 to 6
mllllon) water soluble, anionic polyacrylamide whlch has
about 26~ to about 36~ of ltE amlde grOupE hydrolyzed to
carboxy groupE and, prei~erably, converted to the Eodlum Ealt.
ThlE polyacrylamlde ha~ been characteri2ed by Chemical
AbEtractE under RegiEtry No. 37224-28-5 and iE commercially
avallable ~rom Dow Chemlcal Company aE SEPARAN~ AP273
polymer ~Eee alEo U.S. 3,965,708 and BalakriEhnan et al.,
AICHE J. 21~6), 1225-7). Another pre~erred ~locculant iE
~3~?~6~12
PERCOLTM 1017 whlch ls a medlum hlgh molecular welght anlonlc
flocculant available from Al11ed Colloids Company. Of
co~rse, lt will be understood that injection of the
flocculant in talllngs lines as well a~ other techniques may
be used instead of direct addltlon to the flocculating tank.
The effect of the flocculant ls, of course, to effect a
flocculatlon of the inorganlc sollds ln the waste w~ter. The
flocculated inorganlc material settles to the bottom of the
tank and ls taken to a talllngs sump, as shown, and then
dlsposed to the dlstrlbutor for dlrectlon to the retentlon
pond. The bitumen rlses to the top of the tank and ls taken
through line 25 and combined with the bitumen froth from the
Eeparatlon cells and Ecavenger circuits. The released water
which rises to the top section of the tank is essentlally
free o~ the sollds and ls recycled through llne 19, as shown,
to the steam exchangers and then to the condltioning drums.
The taillngs water from the flocculating tank (llne 21) is
taken to a tailings sump where it is comblned with the
taillngs from the separatlon cells (llne 23).
Another embodlment o~ the lnventlon ls shown ln
Flgure 3. As can be seen, ln thls procedure, the talllngs
from the separatlon cells and the scavenger circuits (whole
taillngs) are comblned and the combined tailings ln llne 29
are injected with flocculant and fed to the flocculating
tank. Thls procdure provldes excellent mixing o~ the
flocculant and better mixing of the sand from the separatlon
cells and mlddllngs from the scavenger circults. Thls
.. . , ,, ~, ~
13~ Z
technlque 1~ very CoEt efflclent ln that lt reduceE the
capltal expenEe for plplng. It 1E de61rable to conEtruct
the flocculatlng tank with two concentrlc welrE, the upper
welr enabllng the bltumen froth to splll over for transport
through llne 25, and the Eecond, lower welr belng uEed to
collect the releaEed water for tran6port through llne lg.
A deElrable embodlment of the lnventlon 1~ to employ a
plastlc or other Euitable veEEel a~ the flocculatlng tank
whlch 1E floated ln the retentlon pond. The bltumen and
releaEed water are Elmply pumped from the welrE at the top of
the plaEtlc contalner and the Eettled 6011dE allowed to drop
lnto the pond through the bottom of the veEEel.
The amount o~ flocculant whlch 16 added to the waEte
talllngE need only be Eu~flclent to effect flocculatlon of
the EolldE and, ln general, thlc wlll be doEageE from about
2.5 to about lOO ppm. It wlll be underEtood, o~ cour6e, that
the actual doEage to be uEed wlll vary wlth the partlcular
flocculant employed and wlth the partlcular characterlEtlcE
o~ the tallE, but Euch parameterE are readlly determined by
the skllled art worker.
Preference for uEe o~ the SEPARANSM AD273 flocculant 1E
based on the fact that lt 1E extremely e~fectlve ln maklng a
6eparatlon o~ 6011dE ~rom the bltumen and water and, ln fact,
thlE ~locculant can cauEe about 70~ or more o~ the bltumen ln
the waEte water to float on the recovered water'6 Eur~ace.
The proceEE of the lnventlon provldeE numerouE benefltE whlch
in~l~de a very hlgh recovery of the bltumen heretofore loEt
13(~16~Z
tD tail~. In addition, there iE reduced CoEt of pumping
taillngE and recycle water and reduced Eludge accumulatlon
and aEEoclated reclamatlon CoEtE. ThlE reEult~ from the
flneE ln the bottom of the ~locculatlng tank entrapplng the
Eand preEent and thlE effectlvely ellmlnate~ the formatlon of
Eludge, thu~ maklng the waEte water more ea~lly tranEported
and more envlronmentally acceptable. Stlll another ma~or
advantage of the proceE6 1E the heat EavlngE obtalned from
the UEe of the hot recycle water ~llne 19) fed to the
extractlon EyEtem. Slnce thlE recycle water iE at a
temperature between about 120 to about 140F., lt
slgni~lcantly reduces the amount of Eteam needed to heat the
addltional cold make-up water ~or the proceEE whlch comeE
~rom the talllngE pond or rlver.
The followlng Table llluEtrateE the bene~ltE obtalned
~rom the proceEE o~ the lnventlon. The Table 1E baEed on
calculatlonE whlch 6how the ~avlngE obtalned over a ten-year
perlod uEing preEent productlon level~ a6 a ba~e llne at a
prlce of $20.00 (Cdn.) per barrel ~or bltumen.
~3C~16~Z
TABLE
ESTIMATED DOLLAR SAVINGS USING A FLOCCULATING TREATMENT
-
FOR SCAVENGER TAILINGS IN AN OIL SANDS PROCESSING PLANT
X lo~
IncreaEed Bltumen Recovered: 252
Reduced C06t o~ Natural Gac ~or Steam and Boller~: 7
Reduced pumplng c06t6: 1
Total 260
Lec6 Flocculant C06t6: 2
Net Savlng~: 228
