Note: Descriptions are shown in the official language in which they were submitted.
~` 2088320
-1-
Method for Oil Extraction From Oil Sands
And/3r Tailings
BACKGROUND OF THE INVENTION
S ~ ~
Field of the Invention
This invention relates to a method for linking -
methods of mining and economic transportation of oil
sands into oil extraction plants for the efficient
removal of bitumen, producing tailings for economic
recovery of minerals/metals and provides an immediate ~-
backfill for reclamation before and/or after
mineral/metal extraction. The method also provides
for cleaning up pre-existing tailings from ore
extractlon from oil sands. Such tailings may include
extractions from hot water processes; and be
implemented to recover tailings from tailings ponds.
The proces~ bleeds or pumps sludge, water and sand
from such ponds back into the process to empty and -
clean such ponds, while producing minerals/metals/oil ~ ;~ "~
ar.d clean tailings for immediate backfill and
reclamation.
Description of the Prior Art
Cuerently, synthetic crude oil is widely produced
from oil sands ore bodies. For example, hundreds of
thousands of bar~ells pe'r day of synthetic crude oil
are being produced. The known reserves in the United
StateS~ Canada and elsewhere, are capable of
sustaining this and higher production levels -
throughout the twenty-first century.
'" ~ .
.
,,
-2- 2 0 8 8 3 2 0
~- ~ " ~ ~
Solid waste tailings generated from the recovery ` ~ -
of oil from such oil s~nds ore bodies are vast and in
the order of millions of tons per year. Approximately
two tons of ore to oil sands extraction processes are
required per barrel of synthetic crude oil. The waste
produced is over 2.5 tons with the extra water locked
up in the sludge component. These tailings are
commonly retained in tailing ponds! Such tailings
pond~ create a large environmental problem. They
constitute toxic waste. Such ponds are frequently
confined within sand dikes which are subject to damage
by heavy rains, seismic activity and/or wind erosion.
Should a dike break, adjoining areas are subject to
attack by the toxic water, sludge and bitumen. Also, ~-
such tailings ponds are acutely toxic to aquatic
organisms. For example, wild life, such as migrating
ducks frequently die as a result of being coated with
tar from such ponds. Obviously, such water is highly
toxic to fish.
A wide range of processes have been proposed for
the extraction of bitumen from the surface-mined
tar-sands ore. Ma~or important considerations in
developing and implementing such processes is the
commercial v~ability and ecological compatibility of
each process. Bitumen extraction techniques may be
broken down into two major categories: (1) those
which employ water, either hot or cold, to float the
bitumen oils away Prom'thie tar-sands~ and ~2) those
which employ an organic solvent to dissolve the
bitumen oils. Hot water processes are technology
practiced commercially for extraction of oil from oil
sands. The tailings from two commercial plants in
Athabasca, Alberta, Canada contain the solids from the
ore feed together with large volumes of hot water
.: - ,,, ~ :
': . ,.: :,. :: .:
:, ~,,i., ,.: ;,,
2088320
-3-
':
containing many contaminants and sludge composed in ~ -
the main of eines/clay~, solvents, oil and water. The
sand component containing toxic sludge goe~ to build
the containment dykes. Large volumes of toxic water
and sludge are then contained in large tailings pondS
from which the water is recycled and in which the ~ --
sludge continues to build up. AS much as slx barrelS ~ ~
of ~ludge are produced per barrel of synthetic crude ~ ;
oil. '~
1 0 ~ ;. ,"
Solvent processes without water are under '~
development and typically follow the practices of the -;~
Oil seed extraction technologies. Percolation and
immersion-type extractors have been used, but the ~' ''''
special designs and scale-up for abraslve tar-sands ' '' -''
processing may be dlfficult. Other solvent, hot water '- ; ' ' -'~
extraction processes or combinations are disclosed in
,,
U.S. Patents 4,347,118, issued to Funk, et al. and ' ;'-~-
3,925,189, issued to Wicks, III. All of these '
method~, however, suffer commercial or ecological '
drawbacks~ rendering them undersirable. A method for
solvent and hot water extraction of bitumen from
tar-~ands is the sub~ect of U.S. Patent 4,424,112,
issued to Rendall. This process however, requires
numerous pieces of equipment.
U.S. Patent 4,875,99B, issued to Rendall
describes a process where air is not used as a
flotation agent, bu't insteàd, solvents are~added'to
cleanly separate the oil from the mineral matter of
the oil sands ore. The resultant tailings of this
process are amenable to rnineral/metal removal if
~1 needed as per U.S. Patent Application Serial No.
~ 07/542,723, assigned to Solv-Ex Corporation. This
35 1 process, however, still has many process steps for ~ '
,.~.
- . .:
. ~
.. , " - .. - ,.. ~
.- ., . ,.: .,. ":,:: .
~ ., . ,i, ", . ~ .
;:: ' ~;.'' -.
- ~ : , : ' : ; , ,
,, :`
2088320 ~:
-4- ~ ~
.
"oil wet" oil sands. However, there is need for a
simplified system to w~sh the oil from the sand and
the oversize.
Although tailings ponds may be eventually
reclaimed, the manner and cost of such reclamation has ~ -
not been satisfactorily deteemined. It is estimated
that one billion tons of toxic sludge have accumulated
to date. In addition, there are environmental and ~ ; -
regulatory pressures to eliminate the use of tailing9
Ponds with processing effluent such as those
described.
The solid waste tailings, including those from
the Canadian production of synthetic crude oil,
Commonly contain a significant amount of valuable
minerals including precious metals. Past efforts to
recover the valuable minerals and precious metals were
directed to processing the waste tailings from the
existing production of oil by hot water process or
modific~tions thereof. These efforts have produced
limited results and have not eliminated the environ-
mental problem of large tailings ponds. There are
various methods for recovering minerals from the waste
tailings produced by the hot water process as
disclosed in U.S. Patent 4,225,422, by Trevoy, et al;
U.S. Patent 4,138,467, by Kamisky, et al; U.S. Patent
3,990,885, by Baillie, et als and Canadian Patent
1,200,778, by Ma~id, et al. The economics of these
efforts have floundered because of the emulsified
nature of the waste tailings which include oil, clay, -~
solvent, water and caustic discharged into such ~ -
tailings pond. ; ;
..... , . ~
.:,.;, ' ',, '.,'' - ."':
. ~, . ,. ~ .
20~320
-5-
,~
A eequirement exists for a tailings clean-up
technology. Many have been proposed, such as Jan
~euyer, CH-Synfuels, et al. Also, there is a ~ ;~
requirement for economic recovery of the valuable
components of the tailings such as residual oil,
sOlvents, hot water and the mineral/metals (alumina,
titanium, iron, gold, silver, etc.) contained therein. ~ ~
There is further requirement that the resultant ~;
tailings be capable of providing an immediate backfill
for reclamàtlon before or after mineral/metal
extraction and without having to be processed through
tailingS ponds. ~-
~ .
SUMMARY OF THE PRESENT INVENTION
An object of the present invention is to provide
a means of simplifying the mining and extraction of
oil from oil sands using a slurry pipeline to
condition the oil sands with hot water and, if
necessary solvent; and then washing the oil/clay fines
fraction from the sand to provide a clean sand
fraction for safe disposal/backfill before or after
mineral/metal extraction, if necessary. The
oil/clay fines fraction is then solvent extracted for
oil removal while the clay/fines fraction with the
water is dewatered, centrifuged and dried to remove
residual oil/solvent and water and thereby make it
available for mineral/metals extraction.
Another object of the present invention is to ~ -
minimize the transportation and handling of waste sand
~the bulk of the ore), by removal of waste sand
fraction at the mine itself. ;- ;~
`
. . ~
, , :, ~ .
.~ ,: : . : . "
2088320
6 69368-66
Another object of the present inventlon is to provide
a method for recovery of residual oil, solvent and hot water
from tailings and leaving damp solids ready for backfill and
reclamation of a mlne. ,~
,~ :
Another ob~ect of the present invention is to provide
a method for generating clean tailings for environmentally
acceptable extractlon of valuable minerals, e.g. alumina, iron,
titanium and compounds thereof and precious metals such as
gold, silver and/or platlnum.
Another ob~ect of the present lnvention i5 to provlde
a method for recovery of bitumen and avoid the need for
taillngs ponds which contain caustic sllme of oil, clay and
water.
Other ob~ects of the present inventlon are to provide
a method for processing toxic sludge and emptying existing
tailings ponds by feeding a bleed stream from the pond into a
main tailings treatment to enable clean-up of the tailings
ponds ln an economical and envlronmentally acceptable manner.
Briefly, a preferred embodlment of the present
, . :.,
invention starts with mlned oils sands and/or tallings. These ~ -
tallings, which may be from existing commercial facillties -;
,-,: ., ::: .: .,.
processing oil sands and/or from tailing ponds comprising ~ - ~
' . ' ! ! I . ~ ' ' ' ' -
tailings of processed oil sands, are hydro-transported to a ~
. . .~ :. .,: .
sands/fine separation stage for separation of sands from fines, - ~- ~
: - . .:, , :~ .::
if necessary. The separation may provide fines of particle
size less than a preferred maximum, e.g. -325 mesh, for
.: . .:,: :-
settling and sands exceeding such size. If such separation of
the tailings is not necessary, the
~ ::, , ,'.'': ' :: ' ','
.. .' ' ~ ,.:''
, ` : ' ' :.
. ,; ., .
:
208~'320 - - ~
-7- -~ ;
tailings may be bydro-transported to a mixer stage for
mixing with solvent.
:
The mined oil sands will be diffeeent for noil
wet" rocks of Utah, USA, compared with the Hwater wet~
Oil sands of Athabasca, Canada. In the case of the
former, though truck and shovels can be used,
Peeferably miners remove the ore for crushing and
continuously move the ore by hydro transporting mixed
with recycled hot water and solvent to sand washers.
In the case of Athabasca oil sands, the preferred
method is by a dredge (although truck/shovels or
continuous minees could be used) with the oil sands
conditioned in a slurry pipeline with recycled water
with or without solvents. The oil sand slurry and/or ~ -
the plant tailings (with or without the froth
treatment tailings) are fed to a separation station
including a series of sand washers (spiral
clas~ifiers), preferably two. There, the sand
fraction of particle size greater than the desired
size, e.g. 325 mesh, are washed to remove most of the
liguids and solids of particle size less than 325 mesh
(44jmicrons)~
The particles of +325 mesh sand fraction, after
wa~hing with clean water, contain about twenty percent
moisture, and are fed to a gold flotation cell with a
recycle water stream and a small dosage of MIBC or ~ ld~
similar `gold fldtation'agent. A small amount of
residual oil and the gold with some minerals, floats.
These floating items may be removed, and then -
processed pursuant to the processes described in U.S.
¦ Patent Application No. 07/542,723 for recovery of
minerals and precious metals.
. :. . ~ . ,,:
:" ~ ' '~': ..
- . :: :.,:
` ~, ' '
:~
2088320 , : ~:
8 69368~66 -
The +325 mesh sand fractlon minus the gold is fed ;
through a series of heavy mineral separators to remove the
heavy mineral concentration~ which are mainly titanium,
zirconium, iron and alumina minerals. These separators may be,
and preferably are, Relchert Cones. The heavy metal
concentrates are then beneflclated by standard methods for
commerclal products. This step may not be essential and is
preferably used only lf the quantities of heavy metals ln this
size fraction requlre removal.
The +325 mesh sand fraction particles minus the gold
and heavy minerals (if necessary) are then dewatered,
preferably by large bucket wheel dewaterers, and then removed - -
with about ten percent moisture by weight for a backfill ~
: ' ~ . .: : .
reclamatlon operation. The process water may be recycled.
When a bleed stream of sludge of -325 mesh fines/clay ~ ~-
fraction particles is added for co-processing or when the
sludge is derived from processing sand tailings from the hot
water process, a preliminary treatment with sulphuric acid may - ` -
be necessary for acidification and neutralization. -
"
The -325 mesh fines/clay fraction particles are
processed by a mixer and diluted with recycled water to between ~ -
ten - fifteen percent by weight solids. Simultaneously with,
or prior to the water addition, solvent is added to provide a` ~ ;
minimum of 40t60 bitumen-to-solvent ratio within the mixture.
This mixture is fed to a suitable oil, water, clay separator
from which the oil (bitumen~solvent) is floated away for -
further treatment involving water-solids removal by static
settling and/or centrifuges. There may be multlple stages for ~ ;
repeating this step. It is repeated once in the preferred ;
embodlment.
:: ~ -. ' ' ': ~ '
~ ' ~., ~' , '
2 0 ~ ~ 3 2 0
8a 69368-66 :.
The clay/fines slurry is then passed to a thickener
wherein a suitable flocculent is added to form a clay/fines
sludge of a solids content~of better
~ :....:. ~ ::;
. ,-.... . - . '-' . .
~ `' :'''"-,'`
'' '.' :~..'. ''.:
,' ' ~ : '`',~'',, :`"
~ ' .. '' " ~ "' ,'"
': ; ~' " .'" ~
2088320 -
: .
than fifty percent, in the preferred embodiment. The
sludge is then centrifbged to a cake of about seventy
percent solids.
The clay/fines cake containing about seventy
percent solids and about twenty-five percent water
with the eemaining small amounts of bitumen and ' '' '
solvent are mixed with dried clay/fines to produce a
mixture suitable for drying in a heated rotary screw.
In the preferred embodiment, the water content of the ' '
mixture is kept at about ten percent. There are ' ' ''
various methods for drying the cake - but the cake ' '-' ' ' '
needs drying to remove the solvent before the mineral
processing steps commence. The solvent vapor and - ~ ~:
moisture from the drier may be used to heat and ' '~
desolventize the process recycle water. It may also '~ '';
be cooled to recover the solvent. Also, all process -'' '~
water may be recycled. ~ '-; ' ;
~he dried clay/fines fraction cakes may then be ;~
processed for mineral extraction pursuant to the ~ '~
process described in U.S. Patent Application Serial '-'' ' ;'-'
~ No. 07/S42,723.
; ~ 25 Tailings resulting from froth treatment, e.g.
centrifuge tailings of the hot water process, may be
Processed separately in order to increase the yield
from the rutile fraction of the titanium minerals. In
~doing' so, the ta'ilings'ar`e'neutràIized (pH 5-6) and
diluted to a solids content of about six percent using ' ~ -
recycled water with additional solvent added at the
same time in order that the remaining bitumen/solvent ~ -
floats in a separation cell as is practiced by those
familiar with the art. This step can be repeated '-
several times and is repeated once in the preferred ' '
,~ ., ~ ` ,. ~i,,
2~88320
--10--
embodiment with solvent flowing counter currently to
the clay/fines slurry. The eesulting clay/fine~
slurry is passed with flocculent to a thickener where
the thickened clay fraction of about thirty to forty
S percent solids i9 removed, centrifuged and dried.
The solvent-washed and dried clay/fines from the
froth treatment tailings are then pressure leached
with sulphuric acid to form a cake and then made into
a slurry which is fed to the pugmill of the dried
clay/fines from the maln tailings as described in U.S. ~ ~
/ Patent Application No. 07/542,723. Alternatively, the ~ ; ;;- -
slurry containing the soluble salts of aluminum,
¦ ` titanium and iron, and/or other metal salts, is -
15 I filteeed and washed with the leach liquor treated as
in U.S. Patent Application No. 07/542,723, for ~ ~ -
removal and upgrading of the aluminum, titanium and
iron salt~ into marketable commodities.
. :.;
An advantage of the method of the present
invention i~ that it reduces the process steps
nece~sary to extract oil from oil sands, while
producing clean damp sand and dry clay/fines
tailing~
Another advantage of the method i5 that it allows
for early re~ection of the sand fraction (the bulk of
the ore) at the mine site.
Another advantage of the method is that roc~s
and clay lumps normally rejected ~with bitumen) as - ~-
oversized, can be treated in the pipeline transport
system.
:: -
~ ~ -
;:
;' ~ "' ;' '; '-~ ~:
.: , .. .
2088320
"
Another advantage of the method of the present
invention is that it produces clean damp sand and dry
clay/fines tailings from the sand/sludge tailings.
Another advantage of the present invention is
that the clean damp sand and dry clay/fines tailings
.. . .
produced can be processed to economically recover -
mineral/metal values contalned therein. - ;
~~
Another advantage of the present invention is ~ ~ ~
... .
that in produc~ng clean damp sand tailings, the dry
clay/fines tailings, residual bitumen, solvent
recovery and hot water recovery it provides for
enhanced economics. ; -
.. ... .. ..
Another advantage of the present invention is - ~ ; -
that large tailings ponds are avoided and the clean ~ `
damp sand tailings and the dry clay/fines tailings are ; ~ ;
available for immediate backfill and reclama~ion of
. , .
mined out areas. ~ :
: ,.. ,::
Another advantage of the present invention is
that it can be used synergistically with other
processes to produce and upgrade mineral/metals ;- ~
contained therein. ~ --
:: ,.:
Another advantage is that the process does not
result in any tailings ponds, and does not require the
use of any causticlchemicals or air.
These and other objects and advantages of the ~-
present invention will no doubt become obvious to
those of ordinary skill in the art after having read
the followlng detailed description of the preferred
: :
- 2~$`~20
-12-
embodiment which is illustrated in the drawing
figure.
IN THE DRAWINGS
S - `
Fig. 1 is a block diagram of the overall process
o the present invention. ~ ~
: '' ' ''~ ,"'"' '
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT -:- :~
:.~ . . .: ::
1 0 ~ "; ' , . " ', ' "
Fig. 1 illustrates the overall process of the - ~
present invention and referred to by the general ~ ~ ;
reference character 10. The process beglns with a
step 20 of producing the ores or tailings for
processing. Such step 20 may include, in the ca~e of
oil sand ores, mining the ore body, e.g. by ;
truck/shovels or other conventional means as is being
used currently~ continuous mining, or dredge mining.
The ore i~ eeduced by feeder breaker and hot water ;
wlth/or without solvent added. The resultant slurry
ig about forty percent solids and hydro transported
through a pipe (gentle conditioning in the absence of
air) to a ~ands/fines separation and washing means 30
which may be suitably situated near the mine site for
discharge of the clean sand. The oversized ore`
p~rticles may be separated by screening from the clean
sands, and then crushed to about -1/4 inch and
reproce~qed for oil recovery.
Alternatively, when pre-existing tailings, such
as exist in tailing ponds, the process begins with -~ ;
; step 20 wherein the tailings previously discharged, ;~
for example from a facility using the Clarke Hot Water ~ ; .;
Process, are hydro-transported to the sands/fines
separation and washing means 30, if necessary. ThiS
~':
2~88320 ~
~ -
-13- ''
.; , .. ... . ..
may also be conveniently situated neae the site of the
plant, mine, or existi~g tailings pond. If the ;'
tailinys size are sufficient, they maybe transported ' -~
directly to a mixer. Alternatively, a~ hereinafter '~
explained, froth flotation tailings may be separately ~ ;
fed to a solvent extraction and drying means.
., ": ,;
The sand/fines separation means 30 includes a
series of spiral classifiers as used in the sand '~' '
washing industry wherein the ines/clay, as classified -~ - ~
of a size less than a predetermined maximum ~ ~ -
diametrical size, e.g. 325 mesh, are separated from ; '';~
particles exceeding such size. Preferably, a series '
of two spiral classifiers are used with one feeding
the other. The fines/clay of -325 mesh fraction are
then mixed at a mixer 31 ~which preferably is the
transportation pipe from the mine ~reclaim site where ';
the sand i8 re~ected) to the plant site] with process ' ~:;''''
water and solvent to form a slurry mixture of ' ' ''
water/solvent/bitumen. Thus, the fines/clay slurry is ~ ' '
..
` washed clear of the ~325 mesh sand raction particles. '-' ''';;''~
The -325 mesh clay/fines fraction with the ' ';~
oil/solvent/hot water is sent to a separator 45 for '~
oil/solvent and clay/fines extraction and drying. ~' ' '~''
~''''
'~ The washed ~325 mesh sand is fed to a flotation ~ '-~ -'
means 40, e.g. gold flotation means, with a suitable ;~ ;' '~;
flocculation agent such as MIBC added. The flotation
means 40' comprises'flo~ation cells'when gold, silver ! ' ~'
and/or other precious metals are present in the sand
-~ fraction. Residual oil is floated off. Also, a '
concentration of the precious metals are floated off
and sent to a precious metal recovery means as is
commercially practiced. The sand slurry from the
flotation means 40 may be sent to a heavy mineral ~'
~ , ~
... ~ .. ...
. . .. . . ..
., ~,. .
14 2088320 69368-66 ~
separation means 50, lf desired, or it may be directly ; -~
dewatered by a sand dewaterer means 60 to produce damp sand for -
. . , -, . -
a backfill. The dewaterer means 60 may be conventional ~ - -
:. ::
equipment such as bucket wheel dewaterers. The water, l.e.
processed water, from dewaterer means 60 may be recycled to the
flotation means 40 and the mlneral separatlon means 50, and a ~ -
bleed off to separator 45.
Should removal of the heavy minerals from the sand
fraction be desired, the heavy mlneral separation means 50 may ~ ;~
include heavy mlneral separators such as those commerclally -
avallable and referred to as Relchart Cones. The heavy ;
minerals concentrate ls further processed by purification and
upgradlng and the sand/water slurry ls processed to sand
dewaterer means 60 for water removal. The separated heavy
minerals may then be processed as disclosed in United States
Patent Application No. 07/542,723.
The clay/fines -325 mesh fraction with the
oll/solvent/water from mlxer 31 18 fed (after acldlflcatlon
with sulphuric acid and neutralization, if necessary, for CHWE
tallings or talllngs from exlsting sludge ponds) to the
separator 45. The bitumen is dlluted at the mlxer 31 by the ;-~ ;
additlon of recycle solvent. This forms a dllute slurry of oll
in solvent of thlrty to forty percent oll. The clay/fine
solids in water are separated from the bltumen and solvent.
The clay~flnes are malntalned ln slurry form at a concentration
A f about~percent sollds. Thls ls done by dllutlon wlth other - ;
~ process hot water recycle streams. Within the separator 45,
the entlre mixture of slurry ls fed to a separatlon cell as
commercially practlced. The cell may lnclude a rake about the ~ ,
bottom of the cell such
.~ ': ' ~ ' ',: '
208~20 -
,.
.,
-15-
~ '" ,"' ,:' ' '' ~
that the oil/solvent layer floats to the top.
Alternatively, static inclined plate separators may be
used. The oil/solvent layer may then be separated and ~ -;
transported to a bitumen/solvent/hot water separation
means 70. The remaining slurry of clay/fines may
again be treated with fresh solvent at the means 45
for processing to form another top oil/solvent layer
for floating to the means 70. This solvent extraction
step can be repeated several times depending on the
efflciency of the system which may be dependent on the
content of the ores and/or tailings to be processed
with the solvent flowing countercurrent to the clay
water slurry. In the preferred embodiment the solvent
extraction is carried out twice. -
1 5 :, .:.,:, ., ,:,
At the means 70, the bitumen, solvent and hot ; ~ ;
water are separated by static inclined plate ~-~
9eparators and/oe centrifuges and a portion of the hot
water from the top, may be recycled, if desired to
maintain slurry density of the incoming feed at stage
30. The solvent is stripped from the bitumen by - i
distillation using flash evaporation and/or in a
column using steam and/or vapor and the resultant
solvent may be recycled for reuse. This separation of
bitumen (oil) from the solvent may also be carried out
in an upgrading facility for the bitumen.
The clay/fines mixture is fed to a thickener
stage 71 wherein~flocculant may be added a~d the
sludge from the bottom of the thickener 71, with a
solids density of about fifty percent, is sent to a
solid bowl centrifuge of the stage 71, where most of
the oil/solvent and water is removed or recycled. ~ ;
Then, a sludge cake, composed of about seventy percent
solids, twenty-five percent water and five percent
:'-. ,.~ ' '. ,:
: ' :' . .',,-
~ "'
: ;''''.''-".
2088320 ;
... . .
-16-
~:
oil/solvents is mixed at a mixer dryer 72 with a dry
recycle of clay fines (from the dryer) to maintain
about ten percent moisture in the cake as it i9 fed to
a hot oil heated scroll conveyer/dryer (within the
dryer in the preferred embodiment). Resultant oil and
Solvent are then passed through the separation stage
70. The hot water may also be recycled. In the
preferred embodiment, clay/fines fraction contain
about 100 ppm solvent, drying can be carried out to
less than 1 ppm solvent. The resultant dry cake i8
then sent for minerals/metal removal at a step 80 for
separation of minerals and precious metals.
At step 80, in case of minerals/metals extraction
including gold and silver, a pug mill forms
agglomerates with sulphuric acid, and for gold and
silver only, 1~ carried out with lime with or without
sodium cyanide, as disclosed in U.S. Patent
~ Application Serial No. 07/542,723. The agglomerates
20 ~ may be leached with recycle leach liquor and washed ;;
with clean water and neutralized aa necessary for safe ~;;
backfill. The sulfuric acid may be recovered from
roaater~ and recycled and the metal~ and minerals / ~-
extracted. ~-
~ In the event of froth floatation tailings, they
- may be processed through a neutralizer 90 and ;~
neutralized (pH 5-6) and diluted to a solids content
of about six percent usIng processed water and
recycled solvent, and additional solvent, if
necessary, such that oil solvent floats and may be
separated and processed by step 70. The clay/fines,
with flocculant, is processed by a thickener 92 where ;~
the thickened clay fraction of about thirty to foety ;
percent solids is removed, centrifuged and dried. It `~
: ~ ~ ,- :
. . i . : . .
".,,:,
~, ;: ',,
' ~
:, . . .
:' '.
-17- 2 0 8 g 3 2 0
,,'
i9 then pressure leached with sulphuric acid at step
93 to form a cake and ~then a slurry which is fed to
step 80.
S In the event tailings sludge from the existing
tailings ponds are co-processed with the oil sands,
they are neutralized to a suitable pH, preferably
around 6, and fed to mixer means 31 (a pipe line in
the preferred embodiment). The sludge component in ~ -
the tailings ponds is mostly a -325 mesh fraction. ~ -
., , ,. ~; ":
Although the present invention has been described
in terms of the presently preeerred embodiment, it is ;~
to be understood that such disclosure is not to be ;~
interpreted as limiting. Various alterations and
mOdifications will no doubt become apparent to those
skilled in the art after having read the above
disclo6ure. Accordingly, it is intended that the
appended claims be interpreted as covering all
alterations and modifications as fall within the true
spirit and scope of the invention.
- :,, -
~ 25
.. . . . ..
::-,. - ,., ,,.~. .
-, ~
, . 1 - ,~,.. .....
~
'. "'', ~'' '~
,,,:: ': ' ::.', ' ~,'.
., '' . .,.', : ..
-": , ' .,' '; :''
': ' :,': ' :'~:
