CA1036524A - Treatment of tailings from tar sands - Google Patents
Treatment of tailings from tar sandsInfo
- Publication number
- CA1036524A CA1036524A CA289,225A CA289225A CA1036524A CA 1036524 A CA1036524 A CA 1036524A CA 289225 A CA289225 A CA 289225A CA 1036524 A CA1036524 A CA 1036524A
- Authority
- CA
- Canada
- Prior art keywords
- bitumen
- sludge
- water
- tailings
- pond
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
- C10G1/00—Production of liquid hydrocarbon mixtures from oil-shale, oil-sand, or non-melting solid carbonaceous or similar materials, e.g. wood, coal
- C10G1/04—Production of liquid hydrocarbon mixtures from oil-shale, oil-sand, or non-melting solid carbonaceous or similar materials, e.g. wood, coal by extraction
- C10G1/047—Hot water or cold water extraction processes
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Life Sciences & Earth Sciences (AREA)
- Wood Science & Technology (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Production Of Liquid Hydrocarbon Mixture For Refining Petroleum (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A process for the recovery of bitumen from the tailings ponds resultant from tar sands oil extraction, the process comprising rapidly dispersing throughout the aqueous sludge at least one additive compound in an amount sufficient to coagulate sludge solids into an inert solid material, bitumen in the aqueous sludge separating out as a froth on the surface of the aqueous sludge. Valuable oil is thus recovered from tail-ings ponds in a manner which is now economically viable on a large scale, the large space requirements and consequent pollution problems associated with the tailings ponds now being reduced.
A process for the recovery of bitumen from the tailings ponds resultant from tar sands oil extraction, the process comprising rapidly dispersing throughout the aqueous sludge at least one additive compound in an amount sufficient to coagulate sludge solids into an inert solid material, bitumen in the aqueous sludge separating out as a froth on the surface of the aqueous sludge. Valuable oil is thus recovered from tail-ings ponds in a manner which is now economically viable on a large scale, the large space requirements and consequent pollution problems associated with the tailings ponds now being reduced.
Description
' 11~3652~ ~
This invention relates ~o a me~hod for separating and solidify-ing fluid sludge or middlings, as produced in the process for recovering .. . -: .
tar and oil from the tar sands in Northern Alberta. More particularly, this invention relates to a method for treating the sludge layer which is approximately one hundred and fifty feet down in a retention pond to recover bitumen and water.
Tar sands, which are also known as oil sands and bituminous sands, are silicious materials which are impregnated with a heavy petroleum. The largest and most important deposits of the tar sands are the Athabasca sands, found in Northern Alberta, Canada. These sands underlay more than 13,000 square miles at a depth of 0 to 2,000 fee~ or more. Total recoverable reserves ater extraction and processing are estimat~d at more than 300 billion barrels- just equal to the world-wide reserves of conventlonal oil -sixty percent of which is in the Middlc East. By way of contrast, the America Institute estimated total United States oil reserves at the end of 1965 at 39.4 billion barrels.
Tar sands are 'primarily silica' having closely associated there-with an oil film which varies from about 5 percent to 21 percent by weight, with a typical content of 13 weight percent of the sand. The oil is quite viscous - 6 to 8 A.P.I. gravity - and contains typically 4.5 percent sulfur and 38 percent aromatics.
The sands contain, in addition to the oil and sand components, clay and silt in quantities from 1 to 50 percent weight, more usually 10 to 30 percent. The sands also contain a small amount of water~ in quantities o 1 to 10 percent by weight, in the form of a film around the sand grains.
Several basic extraction methods have been known for years for the separa~ion of oil from the tar sands. In the so called "Cold Water"
method, the separation is accomplished by mixing the sands with a solvent capable of dissolving the bitumen cons~ituent. The mixture is then intro-:" ., ` '.
_ ~ _ )36SZ4 duced in~o a large volume of wa~er, water with a surface agent added, or a ~ -solution of a neutral salt in water, which salt is capable of acting as an electrolyte. The combined mass is then subjected to a pressure or gravity separation.
In the "Hot Water" method, as disclosed in the Canadian Patent `
841,581 issued May 13, 1970, the bituminous sands are jetted with steam and mulled with a minor amount o ho~ water at temperatures of 170 to 190F.
The resulting pulp is ~hen dropped into a turbulent s~ream of circulat-ing hot water and carried to a separation cell maintained at a temperature of about 185~. In the separation cell, sand settles ~o the bottom as tailings and oil rises to the top in ~he form of a roth. An aqueous middlings layer comprising clay and silt and some oil is formed between these layers. This basic process may be comblned with a scavcngcr stop Eor further treatment of the middlings layer obtained from the primary separat-ion step to recover additional amounts of oil therefrom.
The middlings layer, either as it is recovered from the primary process or as it is recovered after the scavenger step, comprises of water, clay, and oil. The oil content is, of course, higher in middlings which have not undergone secondary scavenger steps. `
Effluent discharge is middling material of depleted oil content whlch has undergone final treatment and which comprises clay dispersed in water. The tailings layer also contains some clay and bitumen and other discharged water-containing fractions such as the sand tailings of the extraction cell which are not the primary products of the hot water pro-cess but are recovered as waste products. The effluent discharge is removed from the process plant as a slurry of about 35 to SS percent, typically 45 percent, solids by weight. Included in the slurry is sand, silts, clay, and small quantities of bitumen ranging from about 0.5 to 20 weight percent of total discharge. In this invention, sand refers to ~;
silicious material which will pass a 325 mesh screen, silt will pass 325 . ~':,' ~'', .
This invention relates ~o a me~hod for separating and solidify-ing fluid sludge or middlings, as produced in the process for recovering .. . -: .
tar and oil from the tar sands in Northern Alberta. More particularly, this invention relates to a method for treating the sludge layer which is approximately one hundred and fifty feet down in a retention pond to recover bitumen and water.
Tar sands, which are also known as oil sands and bituminous sands, are silicious materials which are impregnated with a heavy petroleum. The largest and most important deposits of the tar sands are the Athabasca sands, found in Northern Alberta, Canada. These sands underlay more than 13,000 square miles at a depth of 0 to 2,000 fee~ or more. Total recoverable reserves ater extraction and processing are estimat~d at more than 300 billion barrels- just equal to the world-wide reserves of conventlonal oil -sixty percent of which is in the Middlc East. By way of contrast, the America Institute estimated total United States oil reserves at the end of 1965 at 39.4 billion barrels.
Tar sands are 'primarily silica' having closely associated there-with an oil film which varies from about 5 percent to 21 percent by weight, with a typical content of 13 weight percent of the sand. The oil is quite viscous - 6 to 8 A.P.I. gravity - and contains typically 4.5 percent sulfur and 38 percent aromatics.
The sands contain, in addition to the oil and sand components, clay and silt in quantities from 1 to 50 percent weight, more usually 10 to 30 percent. The sands also contain a small amount of water~ in quantities o 1 to 10 percent by weight, in the form of a film around the sand grains.
Several basic extraction methods have been known for years for the separa~ion of oil from the tar sands. In the so called "Cold Water"
method, the separation is accomplished by mixing the sands with a solvent capable of dissolving the bitumen cons~ituent. The mixture is then intro-:" ., ` '.
_ ~ _ )36SZ4 duced in~o a large volume of wa~er, water with a surface agent added, or a ~ -solution of a neutral salt in water, which salt is capable of acting as an electrolyte. The combined mass is then subjected to a pressure or gravity separation.
In the "Hot Water" method, as disclosed in the Canadian Patent `
841,581 issued May 13, 1970, the bituminous sands are jetted with steam and mulled with a minor amount o ho~ water at temperatures of 170 to 190F.
The resulting pulp is ~hen dropped into a turbulent s~ream of circulat-ing hot water and carried to a separation cell maintained at a temperature of about 185~. In the separation cell, sand settles ~o the bottom as tailings and oil rises to the top in ~he form of a roth. An aqueous middlings layer comprising clay and silt and some oil is formed between these layers. This basic process may be comblned with a scavcngcr stop Eor further treatment of the middlings layer obtained from the primary separat-ion step to recover additional amounts of oil therefrom.
The middlings layer, either as it is recovered from the primary process or as it is recovered after the scavenger step, comprises of water, clay, and oil. The oil content is, of course, higher in middlings which have not undergone secondary scavenger steps. `
Effluent discharge is middling material of depleted oil content whlch has undergone final treatment and which comprises clay dispersed in water. The tailings layer also contains some clay and bitumen and other discharged water-containing fractions such as the sand tailings of the extraction cell which are not the primary products of the hot water pro-cess but are recovered as waste products. The effluent discharge is removed from the process plant as a slurry of about 35 to SS percent, typically 45 percent, solids by weight. Included in the slurry is sand, silts, clay, and small quantities of bitumen ranging from about 0.5 to 20 weight percent of total discharge. In this invention, sand refers to ~;
silicious material which will pass a 325 mesh screen, silt will pass 325 . ~':,' ~'', .
-2-~0365~ ~
mesh but is larger than 2 microns. Clay is material smaller ~han 2 microns ;
including some silicious ma~erial of that size.
Since the effluent contains oil emulsions, finely dispersed clay with poor settling characteristics and other contaminants, water pollution considerations prohibit discarding the effluent into rivers, lakes, or other natural bodies of water. The disposal of the effluent discharge has therefore presented a serious problem. ;
CurrentlyJ effluent discharge is stored in evaporation or retent- :
ion ponds which involve large space requirements and the construction of expensive enclosure dikes which may be 120 feet high. A portion of the water in the e~1uent discharge is recycled back into the hot water extraction process as an economic measure to conserve both heat and water. ;;
~loweverJ experience has shown that the dispersed silt and clay content of the recycled water can reduce pr~mary froth yield by lncr~asLng the viscosity of the middlings layer and retarding the upward settling of oil flecks. When this occurs, the smaller oil flecks and those that are more heavily laden with mineral matter stay suspended in the water of the pond.
The effluent discharge from the hot water process contains a substantial amount of mineral matter much of which is colloidally dispersed ;
and therefore does not settle very readily when stored in the retention pond. The lower layer of the retention pond can contain up to 50 percent dispersed mineral matterJ substan~ially of clay and silt as well as up to 5 percent bitumen. This part of the pond water is normally referred to as sludge. Sludge is not suitable for recycling to the hot water extraction process for the reason that i~s addition into the separation cell or the scavenger cell at the normal inlet means it would raise the mineral content of the middlings of the cell to the extent that recovery of bitumen would be substantially reduced. GenerallyJ the settling which does take place in the pond provides a body of water in which the concentration of mineral matter increases substantially from the surface of the pond to the . . .
mesh but is larger than 2 microns. Clay is material smaller ~han 2 microns ;
including some silicious ma~erial of that size.
Since the effluent contains oil emulsions, finely dispersed clay with poor settling characteristics and other contaminants, water pollution considerations prohibit discarding the effluent into rivers, lakes, or other natural bodies of water. The disposal of the effluent discharge has therefore presented a serious problem. ;
CurrentlyJ effluent discharge is stored in evaporation or retent- :
ion ponds which involve large space requirements and the construction of expensive enclosure dikes which may be 120 feet high. A portion of the water in the e~1uent discharge is recycled back into the hot water extraction process as an economic measure to conserve both heat and water. ;;
~loweverJ experience has shown that the dispersed silt and clay content of the recycled water can reduce pr~mary froth yield by lncr~asLng the viscosity of the middlings layer and retarding the upward settling of oil flecks. When this occurs, the smaller oil flecks and those that are more heavily laden with mineral matter stay suspended in the water of the pond.
The effluent discharge from the hot water process contains a substantial amount of mineral matter much of which is colloidally dispersed ;
and therefore does not settle very readily when stored in the retention pond. The lower layer of the retention pond can contain up to 50 percent dispersed mineral matterJ substan~ially of clay and silt as well as up to 5 percent bitumen. This part of the pond water is normally referred to as sludge. Sludge is not suitable for recycling to the hot water extraction process for the reason that i~s addition into the separation cell or the scavenger cell at the normal inlet means it would raise the mineral content of the middlings of the cell to the extent that recovery of bitumen would be substantially reduced. GenerallyJ the settling which does take place in the pond provides a body of water in which the concentration of mineral matter increases substantially from the surface of the pond to the . . .
-3- ~
~31~;SZ~
bottom thereof. For example, A pond of effluent discharge having a surface area of a~out lO00 acres and an average depth of 40 feet can be character-ized as follows:
From the surface of the pond to a depth of 15 feet the mineral concentration, which is primarily clay, is found to be about 0.5 to 5.0 weight percent. This pond water can normally be recycled to a hot water extraction plant without interfering with the extraction of bitumen from the tar sands.
The layer of water in the pond between 15 and 25 feet from the surface contains between 6 and 15 percent mineral matter. If this water were recycled to the separation cell feed with fresh tar sands, the mineral content of the middlings portion of the cell would increase to the point that little bitumen would be recovered.
~inally, the scction o~ thc poncl between 25 ~ect aTld thc l~ottom of the pond contains 16 to 50 pcrcont mineral m.atter and is nornlally re-~erred to as sludge which, for purposes of the descriptlon of the present invention, includes the composition of water, mineral matter, and bitumen.
Many solutions to the problem of bitumen recovery and water recycling from the retention ponds have been proposed among wh;ch are flocculation, filtration, use of hydrocyclones and centrifuges, distillation and freeze-thaw methods All of these approaches have either failed for technical reasons or have been totally uneconomic.
Ideally, if these sludges could be converted to solid material in the tailing pond, an ecological balance and recovery would result. ;
This invention attempts to provide an effective and economic pro-cess for converting these fluid sludges to a solid form in the retention pond, so that the oil and water may be recovered and the water utilized in the primary extraction process back in the plant.
According to the present invention, there is provided a process for recovering bitumen from an aqueous bitumen-containing sludge produced as tailings during the recovery of bitumen from tar sands, which process G
- ~o365Z4 : ~
comprises rapidly dispersing throughout the aqueous sludge at least one additive compound selected from the group consisting of sodium aluminate and methanamide under pressure in an amount sufficient to coagulate sludge solids into an inert solid material, bitumen in the aqueous sludge separating out as a froth on the surface of the aqueous sludge in a tailings pond and then collecting said bitumen from said surface.
The sludge solidification process o the present invention provides solidification at an extremely low cost as compared to any other treatment process ~e.g. a cost of 0.1¢ or less per gallon of sludge based on 1977 costs).
Thus, the process of the invention provides a tar sands tailings solidification process whereby the tailings are soLi.dified in the retention pond and the oil and water are recyclecl to the plant.
Pre~erred additive compounds wh:icll are su:itablo ~or tlle proeos~ of the invention include, Sod:ium Aluminate, NaA102, ancl Methanalni~le or formamide, HCON~l2. These compounds are preferred additives because they are highly effective even in very small amounts. ~urthermore, these compounds are normally available at low cost at the site of most commercial oil sands treat-ment plants.
The quantity of additive compound used depends on the particular additive compound~ the desired rate of solidification, and economic factors.
The minimum amount of additive compound is that which will be èffective to cause the break down of the sludge, and the separation of the oil and water therefrom. In general, as little as 0.006% Sodium Aluminate by weight additive compound is sufficient to initiate the action which results in the separation of the oil and water from the sludge although quantities several times larger than this may be employed if circumstances warrant it.
If the additive compound is dispersed throughout the entire mass of sludge under treatment before initial reaction between the additive compound and the sludge is complete, then the entlre mass of the sludge will be solicli-fied as the reaction proceeds to completion.
f~ , .~ .
36SZq~
In a commercial scale operation where very large volumes of sludge must be handled, it is not generally economical or feasable to inject the chemical into the discharge or tailings pipes although this can be done if desired in a particular instance.
Because of the very complex chemical and physical nature of the oil sands tailings sludges, it is not possible to explain the precise mechanism of the reactions which occur as a result of the rapid dispersal of the additive compounds in the sludge in accordance with the invention.
However, it is believed that the present invention will be more readily understood by an app~eciation of the following preferred embodiment, which is given by way of example only, with reference to the accompanying drawings in which:
~igure 1 is a diagranlmatic illustrati.on oE capparatus eor carry:ing out the present invention.
~igure 2jis a diagrammatic illustration of a pumping system used in the apparatus of ~igure 1.
A barge 1 with two tanks, one tank 2 containing 25,000 gallons of NaA102 and the other tank 3 containing 25,000 gallons of HCONH2, is pulled by a tug or is self-propelled on a tailings pond 4. A seismic rig 5 is placed on the barge 1 having a capacity depth of two hundred feet, option-ally with a T-bar (not shown) revolving at the desired speed to agitate the bottom of the pond. At least one of the chemical additives is pumped, together with water taken from an upper zone A of the pond 4, through drill ';
stem 6 and into, primarily, the sludge zone C where the sludge is agitated `
and the chemical additive rapidly dispersed through the sludge. The depth of the drill stem 6 can be varied and, since there is no clear boundary between zone C and zone B twhich is approximately between 15 and 25 feet from the pond surEace and contains less bitumen), the drill stem may be introduced into zone B depending upon the demands for bitumen recovery. Bitumen Eroth rises to the surface of the pond 4 while mineral and water sink and form a lower layer in the pond 4. The ~ ' .
` ~0365~
froth product is ~hen recovered from the pond 4 by suction and recycled :~
to the plant for further processing. The layer of water below the bitumen froth is also recycled back into the plant for reuse.
In the tar sands hot water extraction process, steam and water are ~
introduced into a hot water extraction zone. The present invention provides `
for recycled pond water from the surface of the pond to be transferred into the hot water extraction zone. The efluent discharge from the hot water extraction process is then, in turn, transferred into the tailings or retent-ion pond. As mentioned above, the pond can be thought of as having three zones A, B and C having separate concentrations of mineral matter and bitumen dispersed in water. The upper zone A oE the pond normally contains about 5 to 80 percent of the pond volume and extends to a dopth oE approx~-mately 15 feet. This layer of the pond generally contains between 0.5 and 5.0 weight percent mineral matter generally in the form of fine clay less than two microns in size. The intermediate zone B of the pond 4 contains somewhere "
in the range of 5 to 20 percent mineral matter including clay and silt colloidally dispersed. The lower layer or slud~e zone C of the pond can com-prise 10 to ~0 percent of the volume of the pond. This layer normally con-tains the highest quantity of mineral matter which can be up to 50 percent by weigh~ of mineral dispersed in the water. This layer of the pond is commonly referred to as sludge and is normally not suitable for use in any part of the primary hot water extraction process as diclosed above. However, this is the layer of the pond which is particularly suited for treatment by the pro-cess of the present invention for recovering additional bitumen.
Recycled tailings water in the pond which is pumped down into the treating zone of the pond is admixed with the sludge. ~his water from the pond is transferred together with the above-mentioned chemical additive down into the treating zone. The sludge material is also agitated in the treating zone by drill steam under approximately 1,500 psi and the trapped bitumen and water is permitted to rise to the top of the retention pond.
~0;1652~L ~
Referring now to Figure 2, tanks 2 and 3 hold the preferred chemical additives, sodium aluminate and methanamide. Pumps 7 and 8 pump the chemical additive from tanks 2 and 3 respectively through feed lines to the drill stem 6. Sight gauges 9 and 10, pressure gauges 11 and 12, quick opening valves 13 and 1~ and variable speed drives 15 and 16 from motor 17 control the flow of chemical additive to the drill stem 6. An oriice arrangement 18 prevents pressure back-up of the chemical additive from tank 3.
Water is drawn from zone A of the pond 4 by high pressure pumps 19 and 20 and mixed with the chemical additive in the feed line before entering drill stem 6.
Thus by the method of the present invention, bitumen, and water pre-viously not recovered Erom retention ponds and which is ~ound ln the bo~tom zone of the retention pond is now rocoverable.
Thus, in summary, retention pond water is fed, together with a `
chemical additive down a drill stem or pipe under a pressure of between ,~
1,000-2,500 psi, and preferably about 1,500 psi, into the treating zone -wherein material near the bottom of the retention pond is mixed with the above mentioned chemical additive allowing the bitumen and water to rise as a froth to the top of the retention pond so that it can be recycled back into the primary extraction plant.
The present invention is preferably operable with feed material at ~^
any temperature in the range of approximately 50 below to 200F.
Although water used in the feed material is generally the effluent stored in zone A of the retention pond, water from any source may be used.
As a practical matter, the bitumen content of the water stored in the retention pond is higher in the sludge layer of the pond. Thus the sludge layer at the bottom of the retention pond is most attractive for processing in accordance with the method of the present invention. This sludge layer can contain 5 to 50 percent mineral and 0.5 to 25 percent by weight bitumen.
Furthermore, in some instances, this sludge layer can also contain ~`
' ''.
1~6524 0.2 to 5.0 weight percent light hydrocarbons which result from a particular method of hot water extraction. In the instance where the sludge layer contains heavy hydrocarbons, a slightly longer agitation period or increased pressure in the feed line provides a more efficient recovery of bitumen and water from the sludge layer. In general, the water recovered from the top ~
of the retention pond and recycled down through the drill stem to the sludge ~ -layer can be adjusted to get complete recovery of bitumen and water from the sludge layer. Bitumen froth and water recovered from the top of the retention pond is normally transferred into a froth recovery line wherein it is combined with a froth recovered during the primary hot water extraction. The froth is thereafter processed further to provide a synthetic oil suitable Eor use in a general commercial trade.
By the method of this invcntion, additional bi-tuln~ll and water arc recovered from the bottom of the retention pond, therefore providing an addi-tional bitumen product as well as more efficient use of fresh water since water from the pond is now made suitable for recycling to the primary hot water extraction process.
As a typical example of the operation of the method of the present invention and again referring to the drawing, the feed material from the pond 2~ which is transferred directly to the sludge zone C can be characterized as having 74.2 percent water, 22.5 percent mineral matter, and 3.3 percent bitumen. After treatment in the sludge zone the bitumen and water rise to the top of the retention pond. The bitumen and water froth at the top of the retention pond is characterized as containing 36.7 percent water, 1~.8 percent mineral matter, and 52.5 percent bitumen.
~.
. ~ .. . : . .
~31~;SZ~
bottom thereof. For example, A pond of effluent discharge having a surface area of a~out lO00 acres and an average depth of 40 feet can be character-ized as follows:
From the surface of the pond to a depth of 15 feet the mineral concentration, which is primarily clay, is found to be about 0.5 to 5.0 weight percent. This pond water can normally be recycled to a hot water extraction plant without interfering with the extraction of bitumen from the tar sands.
The layer of water in the pond between 15 and 25 feet from the surface contains between 6 and 15 percent mineral matter. If this water were recycled to the separation cell feed with fresh tar sands, the mineral content of the middlings portion of the cell would increase to the point that little bitumen would be recovered.
~inally, the scction o~ thc poncl between 25 ~ect aTld thc l~ottom of the pond contains 16 to 50 pcrcont mineral m.atter and is nornlally re-~erred to as sludge which, for purposes of the descriptlon of the present invention, includes the composition of water, mineral matter, and bitumen.
Many solutions to the problem of bitumen recovery and water recycling from the retention ponds have been proposed among wh;ch are flocculation, filtration, use of hydrocyclones and centrifuges, distillation and freeze-thaw methods All of these approaches have either failed for technical reasons or have been totally uneconomic.
Ideally, if these sludges could be converted to solid material in the tailing pond, an ecological balance and recovery would result. ;
This invention attempts to provide an effective and economic pro-cess for converting these fluid sludges to a solid form in the retention pond, so that the oil and water may be recovered and the water utilized in the primary extraction process back in the plant.
According to the present invention, there is provided a process for recovering bitumen from an aqueous bitumen-containing sludge produced as tailings during the recovery of bitumen from tar sands, which process G
- ~o365Z4 : ~
comprises rapidly dispersing throughout the aqueous sludge at least one additive compound selected from the group consisting of sodium aluminate and methanamide under pressure in an amount sufficient to coagulate sludge solids into an inert solid material, bitumen in the aqueous sludge separating out as a froth on the surface of the aqueous sludge in a tailings pond and then collecting said bitumen from said surface.
The sludge solidification process o the present invention provides solidification at an extremely low cost as compared to any other treatment process ~e.g. a cost of 0.1¢ or less per gallon of sludge based on 1977 costs).
Thus, the process of the invention provides a tar sands tailings solidification process whereby the tailings are soLi.dified in the retention pond and the oil and water are recyclecl to the plant.
Pre~erred additive compounds wh:icll are su:itablo ~or tlle proeos~ of the invention include, Sod:ium Aluminate, NaA102, ancl Methanalni~le or formamide, HCON~l2. These compounds are preferred additives because they are highly effective even in very small amounts. ~urthermore, these compounds are normally available at low cost at the site of most commercial oil sands treat-ment plants.
The quantity of additive compound used depends on the particular additive compound~ the desired rate of solidification, and economic factors.
The minimum amount of additive compound is that which will be èffective to cause the break down of the sludge, and the separation of the oil and water therefrom. In general, as little as 0.006% Sodium Aluminate by weight additive compound is sufficient to initiate the action which results in the separation of the oil and water from the sludge although quantities several times larger than this may be employed if circumstances warrant it.
If the additive compound is dispersed throughout the entire mass of sludge under treatment before initial reaction between the additive compound and the sludge is complete, then the entlre mass of the sludge will be solicli-fied as the reaction proceeds to completion.
f~ , .~ .
36SZq~
In a commercial scale operation where very large volumes of sludge must be handled, it is not generally economical or feasable to inject the chemical into the discharge or tailings pipes although this can be done if desired in a particular instance.
Because of the very complex chemical and physical nature of the oil sands tailings sludges, it is not possible to explain the precise mechanism of the reactions which occur as a result of the rapid dispersal of the additive compounds in the sludge in accordance with the invention.
However, it is believed that the present invention will be more readily understood by an app~eciation of the following preferred embodiment, which is given by way of example only, with reference to the accompanying drawings in which:
~igure 1 is a diagranlmatic illustrati.on oE capparatus eor carry:ing out the present invention.
~igure 2jis a diagrammatic illustration of a pumping system used in the apparatus of ~igure 1.
A barge 1 with two tanks, one tank 2 containing 25,000 gallons of NaA102 and the other tank 3 containing 25,000 gallons of HCONH2, is pulled by a tug or is self-propelled on a tailings pond 4. A seismic rig 5 is placed on the barge 1 having a capacity depth of two hundred feet, option-ally with a T-bar (not shown) revolving at the desired speed to agitate the bottom of the pond. At least one of the chemical additives is pumped, together with water taken from an upper zone A of the pond 4, through drill ';
stem 6 and into, primarily, the sludge zone C where the sludge is agitated `
and the chemical additive rapidly dispersed through the sludge. The depth of the drill stem 6 can be varied and, since there is no clear boundary between zone C and zone B twhich is approximately between 15 and 25 feet from the pond surEace and contains less bitumen), the drill stem may be introduced into zone B depending upon the demands for bitumen recovery. Bitumen Eroth rises to the surface of the pond 4 while mineral and water sink and form a lower layer in the pond 4. The ~ ' .
` ~0365~
froth product is ~hen recovered from the pond 4 by suction and recycled :~
to the plant for further processing. The layer of water below the bitumen froth is also recycled back into the plant for reuse.
In the tar sands hot water extraction process, steam and water are ~
introduced into a hot water extraction zone. The present invention provides `
for recycled pond water from the surface of the pond to be transferred into the hot water extraction zone. The efluent discharge from the hot water extraction process is then, in turn, transferred into the tailings or retent-ion pond. As mentioned above, the pond can be thought of as having three zones A, B and C having separate concentrations of mineral matter and bitumen dispersed in water. The upper zone A oE the pond normally contains about 5 to 80 percent of the pond volume and extends to a dopth oE approx~-mately 15 feet. This layer of the pond generally contains between 0.5 and 5.0 weight percent mineral matter generally in the form of fine clay less than two microns in size. The intermediate zone B of the pond 4 contains somewhere "
in the range of 5 to 20 percent mineral matter including clay and silt colloidally dispersed. The lower layer or slud~e zone C of the pond can com-prise 10 to ~0 percent of the volume of the pond. This layer normally con-tains the highest quantity of mineral matter which can be up to 50 percent by weigh~ of mineral dispersed in the water. This layer of the pond is commonly referred to as sludge and is normally not suitable for use in any part of the primary hot water extraction process as diclosed above. However, this is the layer of the pond which is particularly suited for treatment by the pro-cess of the present invention for recovering additional bitumen.
Recycled tailings water in the pond which is pumped down into the treating zone of the pond is admixed with the sludge. ~his water from the pond is transferred together with the above-mentioned chemical additive down into the treating zone. The sludge material is also agitated in the treating zone by drill steam under approximately 1,500 psi and the trapped bitumen and water is permitted to rise to the top of the retention pond.
~0;1652~L ~
Referring now to Figure 2, tanks 2 and 3 hold the preferred chemical additives, sodium aluminate and methanamide. Pumps 7 and 8 pump the chemical additive from tanks 2 and 3 respectively through feed lines to the drill stem 6. Sight gauges 9 and 10, pressure gauges 11 and 12, quick opening valves 13 and 1~ and variable speed drives 15 and 16 from motor 17 control the flow of chemical additive to the drill stem 6. An oriice arrangement 18 prevents pressure back-up of the chemical additive from tank 3.
Water is drawn from zone A of the pond 4 by high pressure pumps 19 and 20 and mixed with the chemical additive in the feed line before entering drill stem 6.
Thus by the method of the present invention, bitumen, and water pre-viously not recovered Erom retention ponds and which is ~ound ln the bo~tom zone of the retention pond is now rocoverable.
Thus, in summary, retention pond water is fed, together with a `
chemical additive down a drill stem or pipe under a pressure of between ,~
1,000-2,500 psi, and preferably about 1,500 psi, into the treating zone -wherein material near the bottom of the retention pond is mixed with the above mentioned chemical additive allowing the bitumen and water to rise as a froth to the top of the retention pond so that it can be recycled back into the primary extraction plant.
The present invention is preferably operable with feed material at ~^
any temperature in the range of approximately 50 below to 200F.
Although water used in the feed material is generally the effluent stored in zone A of the retention pond, water from any source may be used.
As a practical matter, the bitumen content of the water stored in the retention pond is higher in the sludge layer of the pond. Thus the sludge layer at the bottom of the retention pond is most attractive for processing in accordance with the method of the present invention. This sludge layer can contain 5 to 50 percent mineral and 0.5 to 25 percent by weight bitumen.
Furthermore, in some instances, this sludge layer can also contain ~`
' ''.
1~6524 0.2 to 5.0 weight percent light hydrocarbons which result from a particular method of hot water extraction. In the instance where the sludge layer contains heavy hydrocarbons, a slightly longer agitation period or increased pressure in the feed line provides a more efficient recovery of bitumen and water from the sludge layer. In general, the water recovered from the top ~
of the retention pond and recycled down through the drill stem to the sludge ~ -layer can be adjusted to get complete recovery of bitumen and water from the sludge layer. Bitumen froth and water recovered from the top of the retention pond is normally transferred into a froth recovery line wherein it is combined with a froth recovered during the primary hot water extraction. The froth is thereafter processed further to provide a synthetic oil suitable Eor use in a general commercial trade.
By the method of this invcntion, additional bi-tuln~ll and water arc recovered from the bottom of the retention pond, therefore providing an addi-tional bitumen product as well as more efficient use of fresh water since water from the pond is now made suitable for recycling to the primary hot water extraction process.
As a typical example of the operation of the method of the present invention and again referring to the drawing, the feed material from the pond 2~ which is transferred directly to the sludge zone C can be characterized as having 74.2 percent water, 22.5 percent mineral matter, and 3.3 percent bitumen. After treatment in the sludge zone the bitumen and water rise to the top of the retention pond. The bitumen and water froth at the top of the retention pond is characterized as containing 36.7 percent water, 1~.8 percent mineral matter, and 52.5 percent bitumen.
~.
. ~ .. . : . .
Claims (8)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A process for recovering bitumen from an aqueous bitumen-contain-ing sludge produced as tailings during the recovery of bitumen from tar sands, which process comprises rapidly dispersing throughout the aqueous sludge at least one additive compound selected from the group consisting of sodium aluminate and methanamide under pressure in an amount sufficient to coagulate sludge solids into an inert solid material, bitumen in the aqueous sludge separating out as a froth on the surface of the aqueous sludge in a tailings pond and then collecting said bitumen from said surface.
2. A process according to claim 1 wherein the additive compound together with water, is fed into the sludge.
3. A process according to claim 1 or 2 wherein the water is pumped from an upper zone of said aqueous sludge in a tailings pond and mixed with the additive compound before contact with the aqueous sludge under treatment.
4. A process according to claim 2 wherein said pressure is between 1,000 and 2,500 psi.
5. In the hot water process for extracting bitumen from tar sands, the improvement comprising rapid dispersal of at least one additive compound selected from the group consisting of sodium aluminate and methanamide in tailings produced as an aqueous sludge during the hot water bitumen extraction process, said additive compound being added in an amount sufficient to coagulate sludge solids in the tailings, bitumen in the tailings separat-ing out as a froth at the surface of the tailings mass where it is collected and recycled back to a separation cell for recovery in a hot water extraction plant.
6. The process according to claim 5 wherein said additive compound is added to the tailings together with water which has been removed from an upper layer of said tailings mass, some of the water from said upper layer being recycled back to the hot water extraction plant.
7. A process according to claim 1 or 5 wherein said additive compound together with water is introduced to the aqueous sludge at a pressure of about 1500 psi.
8. A process according to claim 1 or 5 wherein said additive compound together with water is introduced to the aqueous sludge at a temperature of between about 50 to about 200°F.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA289,225A CA1036524A (en) | 1977-10-21 | 1977-10-21 | Treatment of tailings from tar sands |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA289,225A CA1036524A (en) | 1977-10-21 | 1977-10-21 | Treatment of tailings from tar sands |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1036524A true CA1036524A (en) | 1978-08-15 |
Family
ID=4109820
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA289,225A Expired CA1036524A (en) | 1977-10-21 | 1977-10-21 | Treatment of tailings from tar sands |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1036524A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4357230A (en) * | 1980-09-25 | 1982-11-02 | Carrier Corporation | Extraction of oil using amides |
-
1977
- 1977-10-21 CA CA289,225A patent/CA1036524A/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4357230A (en) * | 1980-09-25 | 1982-11-02 | Carrier Corporation | Extraction of oil using amides |
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