CA2088320A1 - Method for oil extraction from oil sands and/or tailings - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A method of oil extraction from oil sands or from tailings of a treatment plant resulting from the extraction of oil from the oil sands using hot water or similar processes recovering solvents and hot water for recycle; and producing solid tailings in a form suitable for immediate backfill. Clean-up of existing tailings ponds can be achieved by bleeding back sludge from such ponds into said process.

Description

~` 2088320 Method for Oil Extraction From Oil Sands And/3r Tailings BACKGROUND OF THE INVENTION
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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.

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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 .: - ,,, ~ :

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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. '~
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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 ~ ' ,.~.

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"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. ; ;
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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. ;- ;~

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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. ,~
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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 -;
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processing oil sands and/or from tailing ponds comprising ~ - ~
' . ' ! ! I . ~ ' ' ' ' -tailings of processed oil sands, are hydro-transported to a ~
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sands/fine separation stage for separation of sands from fines, - ~- ~
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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 ~ ::, , ,'.'': ' :: ' ',' .. .' ' ~ ,.:'' , ` : ' ' :.
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tailings may be bydro-transported to a mixer stage for mixing with solvent.
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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.

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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 ~
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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.
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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 ~ :....:. ~ ::;

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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 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.
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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.
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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. - ;
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Another advantage of the present invention is ~ ~ ~
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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. ~ :
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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 embodiment which is illustrated in the drawing figure.

IN THE DRAWINGS
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Fig. 1 is a block diagram of the overall process o the present invention. ~ ~
: '' ' ''~ ,"'"' ' DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT -:- :~
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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

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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.
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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 ~' ~ , ~

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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 -,.
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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 :'-. ,.~ ' '. ,:

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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 `~
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-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.

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Claims (11)

1. A method for extracting oil from oil sands using:
a. conditioning oil sands with hot water or hot water and solvent to form a slurry;

b. separating from said slurry washed sand over a predetermined size from clay/fines of less than said predetermined size;

c. recovering by solvent extraction, bitumen from the remaining slurry of clay/fines to form a clay/fines fraction; and d. drying the clay/fines fraction by dewatering and desolventising; whereby said dried clay/fines fraction may be used for mineral extraction and/or backfill.

2. The method of claim 1 wherein, said predetermined size is 325 mesh.

3. The method of claim 1 wherein, said separating and washing is performed by spiral screw classifiers.

4. The method of claim 1 wherein, said sand over said predetermined size is screened from washed sand and crushed for reprocessing to recover bitumen, minerals and metals.

5. The method of claim 4 wherein, said predetermined size is one-quarter inch in diameter.

6. A method for cleaning tailings from processed oil sands and recovering residual oil, solvent and hot water, and producing a clean backfill, comprising the steps of:

a. separating a first group of tailings exceeding a first dimensional size from a second group of tailings of a size less than said first dimensional size;

b. washing said first group of tailings to be substantially free of clay, fines, bitumen and solvents ready for backfill or mineral/metal extraction;

c. removing residual oil and solvent from said second group of tailings by solvent extraction means, and forming a clay/fines slurry;

d. producing a thickening sludge from said clay/fines slurry using a flocculent and thickeners;

e. then centrifuging said sludge to produce a cake; and f. drying said cake for backfill or mineral/metal extraction.

7. The method of claim 1 wherein, said first dimensional size is 325 mesh.

8. The method of claim 6 wherein, said separating and washing is performed by spiral screw classifiers.

9. The method of claim 6 wherein, the oversize is screened from the washed Sand and crushed for reprocessing to recover oil/minerals/metals.

10. The method of claim 9 wherein, said predetermined size is one-quarter inch in diameter.

11. The method of claim 1 further including the step of, adding neutralized sludge from existing tailings ponds to said remaining slurry of clay/fines.