Claims
- 1. A method of recovery of bitumen from tar sands comprising the steps of:
- mixing tar sands, an organic solvent effective in solubilizing bitumen including asphaltenes from the mineral of said tar sand and a displacing amount of no more than about one void volume of an aqueous medium effective in displacing bitumen-rich solvent from said ground tar sands and in avoiding substantially spontaneous emulsion formation to form a first mixture, said mixing being at tar sands mixing conditions including mixing intensity and duration to suspend said tar sand and provide sufficient mass transfer between phases of said first mixture without significant emulsion formation, said first mixture being readily separable to a bitumen solution and a sand-water mixture upon cessation of said mixing;
- separating a bitumen-rich solvent phase from said first mixture leaving an aqueous mineral phase containing a residual amount of said solvent; and
- recovering bitumen from the bitumen-rich solvent phase.
- 2. The method of claim 1 wherein said tar sands are at least partially consolidated and wherein prior to said mixing step said tar sands are ground to a particle size of no larger than about 1/2 inch.
- 3. The method of claim 2 wherein said at least partially consolidated tar sand is ground using a wet grinding technique.
- 4. The method of claim 3 wherein said wet grinding technique is selected from the group consisting of solvent wet grinding, water wet grinding and solvent/water wet grinding.
- 5. The method of claim 3 wherein said wet grinding is done in an autogeneous or semi-autogeneous mill.
- 6. The method of claim 1 additionally comprising the step of stripping residual solvent from said aqueous mineral phase.
- 7. The method of claim 6 additionally comprising the step of recovering water from the solvent stripped aqueous mineral phase.
- 8. The method of claim 1 additionally comprising the step of reducing the fines content of the bitumen-rich solvent phase.
- 9. The method of claim 8 wherein said step of reducing the fines content comprises the step of deasphaltening said bitumen-rich solvent phase prior to the recovery of the bitumen from said bitumen-rich solvent phase.
- 10. The method of claim 1 wherein said tar sands comprise oil wet tar sands.
- 11. The method of claim 1 wherein said mixing and separating steps are conducted at an operating temperature of about 110.degree.-130.degree. F.
- 12. The method of claim 11 wherein said operating temperature is about 120.degree. F.
- 13. The method of claim 1 wherein said first mixture comprises an aqueous phase having a pH of no greater than about 9.
- 14. The method of claim 1 wherein said aqueous medium consists essentially of water.
- 15. The method of claim 1 wherein said displacing amount of said aqueous medium comprises about 0.22-0.27 pounds of water per pound of mineral.
- 16. The method of claim 1 wherein said organic solvent is added in an amount of about 2-5 parts solvent per part bitumen.
- 17. The method of claim 1 wherein said mixing conditions comprises a mixing power input of at least one horsepower per thousand gallons of said first mixture.
- 18. The method of claim 17 wherein said mixing conditions comprises a mixing power input of about 1-50 horsepower per thousand gallons of said first mixture.
- 19. A method of recovery of bitumen from tar sand, said tar sand being at least partially consolidated, said method comprising the steps of:
- solvent/water wet grinding said tar sands;
- mixing the ground tar sands, an organic solvent effective in solubilizing bitumen including asphaltenes from the mineral of said tar sands and a displacing amount of no more than about one void volume of an aqueous medium effective in displacing bitumen-rich solvent from said ground tar sands and in avoiding substantially spontaneous emulsion formation to form a first mixture, said mixing being at tar sands mixing conditions including mixing intensity and duration to suspend said tar sands and provide sufficient mass transfer between phases of said first mixture without significant emulsion formation, said first mixture being readily separable to a bitumen solution and a sand-water mixture upon cessation of said mixing;
- separating a bitumen-rich solvent phase from said first mixture leaving an aqueous mineral phase containing a residual amount of said solvent;
- stripping residual solvent from said aqueous mineral phase;
- recovering water from said solvent stripped aqueous mineral phase;
- removing fines from said bitumen-rich solvent phase; and
- recovering bitumen from said bitumen-rich solvent phase.
- 20. The method of claim 19 wherein said ground tar sands comprise tar sands ground to a particle size of no larger than about one-half inch.
- 21. The method of claim 19 wherein said tar sands comprise oil wet tar sands.
- 22. The method of claim 19 wherein said mixing and separating steps are conducted at an operating temperature of about 110.degree.-130.degree. F.
- 23. The method of claim 22 wherein said operating temperature is about 120.degree. F.
- 24. The method of claim 19 wherein said aqueous medium consists essentially of water.
- 25. The method of claim 19 wherein said displacing amount of said aqueous medium comprises about 0.22-0.27 pounds of water per pound of mineral.
- 26. The method of claim 19 wherein said organic solvent is added in an amount of about 2-5 parts solvent per part bitumen.
- 27. The method of claim 19 wherein said mixing conditions comprises a mixing power input of at least one horsepower per thousand gallons of said first mixture.
- 28. The method of claim 27 wherein said mixing conditions comprises a mixing power input of about 1-50 horsepower per thousand gallons of said first mixture.
- 29. A method of recovery of bitumen from tar sand, said tar sand being at least partially consolidated oil wet tar sand from the Sunnyside deposit in Carbon County, Utah, said method comprising the steps of:
- wet grinding said tar sands to a particle size of no larger than about one-half inch;
- mixing said ground tar sands, an organic solvent effective in solubilizing bitumen including asphaltenes from the mineral of said tar sands and a displacing amount of no more than about one void volume of an aqueous medium effective in displacing bitumen-rich solvent from said ground tar sands and in avoiding substantially spontaneous emulsion formation to form a first mixture, said displacing amount of said aqueous medium comprising about 0.22-0.27 pounds of water per pound of mineral, said mixing being at tar sand mixing conditions including a mixing intensity of at least about one horsepower per thousand gallons of said mixture and a mixing duration of at least one minute to suspend said tar sands and provide sufficient mass transfer between phases of the mixture without significant emulsion formation, said first mixture being readily separable to a bitumen solution and a sand-water mixture upon cessation of said mixing;
- separating a bitumen-rich solvent phase from said first mixture leaving an aqueous mineral phase containing a residual amount of said solvent;
- stripping residual solvent from said aqueous mineral phase;
- recovering water from said solvent stripped aqueous mineral phase;
- reducing the fines contents of the bitumen-rich solvent phase; and
- recovering bitumen from said bitumen-rich solvent phase.
- 30. The method of claim 29 wherein said tar sand is ground using a grinding technique selected from the group consisting of solvent wet grinding, water wet grinding and solvent/water wet grinding.
- 31. The method of claim 30 wherein said grinding is conducted in an autogeneous or semi-autogeneous mill.
- 32. The method of claim 29 wherein said step of reducing the fines content comprises the step of deasphaltening said bitumen-rich solvent phase prior to the recovery of the bitumen from said bitumen-rich solvent phase.
- 33. The method of claim 29 wherein said first mixture comprises an aqueous phase having a pH of no greater than about 9.
- 34. The method of claim 29 wherein said aqueous medium consists essentially of water.
- 35. The method of claim 29 wherein said organic solvent is added in an amount of about 2-5 parts solvent per part bitumen.
CROSS-REFERENCE TO RELATED APPLICATION
This application is a continuation-in-part of Ser. No. 546,828, filed on Oct. 31, 1983, now U.S. Pat. No. 4,722,782.
This invention relates generally to the recovery of bitumen from tar sands and, more specifically, this invention relates to a water displacement extraction process for tar sand bitumen recovery.
Tar sands, also commonly referred to as oil sands or bitumen sands, are generally characterized as comprising a porous mineral structure, e.g., sandstone, which contains a high proportion of bitumen, i.e., a three component system of oils, resins and asphaltenes. While tar sand deposits are known to exist in various parts of the world, these deposits vary considerably in composition and property. Some tar sand deposits are relatively soft and free flowing while others are very hard or rock-like. Also, the tar or bitumen content of tar sand deposits may vary over a wide range.
Tar sands are frequently characterized by their mineralogy, such as by the liquid medium which is in contact with the mineral particles of the tar sand. For example, "water wet tar sands", such as the tar sand deposits generally found in the Athabasca deposit of Canada, comprise mineral particles surrounded by an envelope of water, sometimes referred to as connate water. Generally, the bitumen of such water wet tar sands is not in direct physical contact with the mineral particles but rather forms a relatively thin film which surrounds the water envelope around the mineral particles.
Alternatively, some tar sand deposits are characterized as "oil wet tar sands." While oil wet tar sands may, and generally do, include some minor amounts of water, such tar sand deposits generally do not include a water envelope barrier between the bitumen and the mineral particles thereof but rather comprise bitumen in direct physical contact with the mineral component of tar sand.
In addition, tar sands are frequently characterized by their richness or the amount of bitumen they contain and the quality thereof. For example, common parameters used to characterized bitumen quality include the boiling range of the bitumen; sulfur, nitrogen, oxygen and trace metal content; aromaticity and ease of hydrotreatment. In addition, tar sand deposits can be characterized by the presence or absence of naturally occurring surfactants.
The largest known tar sand deposit in North America is in the Athabasca region of Alberta, Canada and, as discussed above, primarily comprises unconsolidated, water wet tar sand. Smaller tar sand deposits are known to exist in the United States and in particular in the western United States. One of the largest minable tar sand deposits in the United States is referred to as the Sunnyside deposit and is located about 120 miles southeast of Salt Lake City in the mountains of Carbon County, Utah. The Sunnyside deposit comprises primarily partially consolidated, oil wet tar sand with minable reserves estimated at 1 to 2 billion barrels of bitumen, enough to provide up to about 100,000 barrels/day of syncrude for about 40 years. Consequently, such tar sand deposits could in the future serve as a secure domestic supply of hydrocarbons.
With respect to the Sunnyside deposit, it is believed that an ancient lake river delta system deposited porous beds of sand interlaced with non-porous beds of shale, called interburden. A heavy oil, known as bitumen, flowed into the porous sand beds at a later time from an unknown source to produce tar zones. Generally, bitumen is present at a level of about 4 to 13 weight percent of the tar sands in these porous sand beds. The Sunnyside deposit is further characterized in that the bitumen thereof is a low gravity, tar-like hydrocarbon having low sulfur and nitrogen concentrations with only about 25 wt. % of the bitumen having a boiling point of less than 1000.degree. F.
In addition, the sandstone/mineral of the Sunnyside deposit is partially consolidated with carbonate minerals, e.g., mineral grains are held together by carbonate minerals. Thus, conventional oil recovery techniques such as steam flooding have generally proven unsuccessful when applied to such resources. Consequently, the common techniques for the recovery of hydrocarbons from such tar sands require that the tar sands be mined and processed. However, the small mineral particle size and the high viscosity of the tar-like bitumen makes recovery of bitumen from Sunnyside-like tar sands difficult as the bitumen is generally not readily separable from the mineral.
In the past, various methods have been proposed for the recovery of bitumen from tar sands but none of these methods have been entirely successful, particularly for the recovery of bitumen from oil wet tar sand deposits.
For example, a hot water process, also generally referred to as water flotation, has to a limited degree been successfully practiced as a processing technique for the water wet tar sands of the Athabasca deposit. Typically, such hot water processes utilize the film of water, e.g. connate water, which is found between the mineral and the bitumen to facilitate separation. For example, in one such hot water process, steam and hot water are commonly jetted through ground tar sand to form a slurry, with the mineral particles separating from the bitumen and water. When this slurry is allowed to stand, the mineral particles will tend to settle to the bottom of the vessel, and a large portion of the bitumen will float on the water. A significant portion of the bitumen will, however, remain in a middling layer composed of a froth of bitumen, water, air and light mineral particles from which separation of the bitumen is difficult. This method also suffers as it requires relatively large volumes of water to effect the separation of bitumen from the mineral matter. Further, the process has not proven to be practical for the recovery of bitumen from tar sands which lack the thin film of water surrounding the mineral particles, such as tar sand deposits found in the Western United States.
Other methods for the recovery of bitumen from tar sands have been developed which utilize solvent extraction. These methods generally suffer from the disadvantage of necessitating the difficult separation of mineral particles from the solvent extract phase. Still other methods use multisolvent systems wherein the tar sand is subjected to a series of solvents before it is finally recovered, which also exhibit a mineral separation problem.
Some methods have combined solvent and water processing of tar sands. For example, Alquist et al., U.S. Pat. No. 4,229,281 (Oct. 21, 1980) "Process for Extracting Bitumen from Tar Sands," discloses a method for the removal of sand fines generated during the solvent extraction of bitumen from tar sands. In this method a solvent solution of bitumen which has been separated from the mineral is contacted with an aqueous solution of cationic surfactant to effect the removal of sand fines from the solution.
Lowman, Jr. et al., U.S. Pat. No. 2,871,180 (Jan. 27, 1959) "Recovery of Oil from Tar Sands," discloses introducing an aqueous pulp of bituminous sand and a low molecular weight paraffinic solvent in a countercurrent fashion in a vertical extraction zone. During the countercurrent movement of the aqueous pulp and the solvent, a deasphalted oil and solvent phase, an asphaltene phase diluted with a lesser portion of the solvent, a water phase and a substantially oil-free sand are formed. The several phases and sand are then separated and further processed. It is disclosed that it is essential that the sand be initially thoroughly water wet to forestall subsequent oil wetting of the sand particles during solvent extraction. Further, the addition of larger quantities of water is disclosed as useful to break emulsions.
Rosenbloom, U.S. Pat. No. 3,875,046 (Apr. 1, 1975) "Recovery of Oil from Tar Sand by an Improved Extraction Process," discloses a process wherein tar sand and a liquid extraction stream are introduced to a single-stage extraction vessel in a countercurrent fashion. An oil phase and a water phase are separated in the extraction vessel with a water stream from the water phase being recycled to the extraction vessel. The initial mixing of the tar sands must be sufficiently gentle to avoid displacement of the tar sand fines.
Peterson et al, U.S. Pat. No. 4,110,194 (Aug. 29, 1978) "Process and Apparatus for Extracting Bituminous Oil from Tar Sands," discloses a method for recovering bituminous oil from tar sands comprising intimately mixing tar sands with a hydrocarbon solvent and continuing the mixing to produce a slurry of solid particles suspended in a solution of bituminous oil dissolved in the solvent. The slurry is then fed into a body of water, beneath the surface thereof, and the slurry is allowed to settle. Water-wet solid particles are removed from the bottom of the body of the water and a solution of hydrocarbon solvent and dissolved bituminous oil is removed from the surface of the body of the water. The dissolved bituminous oil is then recovered from the hydrocarbon solvent.
Gagon, U.S. Pat. No. 4,342,639 (Aug. 3, 1982) "Process to Separate Bituminous Material from Sand (Tar Sands)," discloses a method of extracting bitumen from tar sand utilizing a halogenated organic solvent having a density greater than water wherein the specified solvent containing mineral and dissolved bitumen is continuously transferred via a conveyor system partially submerged in water. As the material moves through the water on the conveyor, the organic solvent containing the bitumen separates from the mineral and forms a separate phase beneath the water. The mineral is ultimately moved upward on the conveyor for removal from the water.
European Patent Application 81305751.0, "Process and Apparatus for Extracting Bitumen Oil from Bitumen Containing Material," Rendall, published Jun. 15, 1983, discloses forming a slurry of solvent, tar sand and hot water while excluding substantially all air therefrom. The exclusion of air is disclosed as serving to greatly reduce the formation of emulsions of fine particles, water, bitumen and air. The treatment of oil wet tar sands is disclosed as necessitating the soaking of the ore in solvent prior to slurry formation with hot water. For the treatment of water wet tar sands, the need for solvent addition is disclosed as limited to the establishment of the preferred specific gravity desired for bitumen extract separation. By sparging the formed slurry with steam, the slurry is then separated into an upper bitumen extract phase, a middle water and sand phase and a lower damp sand phase. Each of these phases is thereafter processed to produce bitumen, recovered solvent, water, and spent sand.
Benson, U.S. Pat. No. 3,459,653 (Aug. 5, 1969) "Filtration of Solvent-Water Extracted Tar Sand," discloses a method for removing tar from tar sands comprising slurring tar sands and solvent in the presence of about 1 to 7 wt. % water (based on weight of tar sand), and then filtering the slurry through a bed of tar sands to produce a tar rich solvent filtrate. The water maintains an easily filtered slurry through control of sand fines.
Rendall, Great Britain Patent Document 1527269 "Solvent Extraction Process," discloses a solvent extraction process for the extraction of bitumen oils from tar sands, defined therein as the above-described water wet tar sands. In this process a tar sand and water slurry is formed and introduced through a specially designed contactor wherein solvent extraction occurs. The amount of water in the feed stream is determined by 1) the possible need to pump the tar sand/water slurry to the contactor, 2) the need for the tar sand/water stream to flow reasonably easily through the contactor and 3) the need to have the sand in the contactor adequately surrounded by water to prevent solvent from coming in contact with the sand except during the time interval when the sand is showered through the solvent. Accordingly, the amount of water should constitute at least 20 wt. %, advantageously over 40 wt. % and, preferably 50 wt. % of the tar sand/water stream on entry. Further, the presence of an enveloping volume of water with the sand is noted as serving the important function of forming a barrier separating the solvent from the sand and causing rapid displacement of any solvent retained on the sand.
Kelley, U.S. Pat. No. 2,980,600 (Apr. 18, 1961) "Process And Apparatus For Bituminous Sand Treatment," discloses a process and apparatus for treating tar sand with a warm basic aqueous solution of a special alkali metal silicate and a moderately heavy hydrocarbon diluent to separate the heavy oil from the bituminous sands. Freshly mined tar sand is mixed with diluent oil and the specified aqueous silicate solution at a temperature higher than about 160.degree. F. and preferably maintained above 180.degree. F. The effluent slurry from the mixture is discharged to a primary separation zone in which the treated solids are separated from the fluid. In the primary separation zone it is necessary to liberate oil drops from the sand stream. Such separation is effected via the agitation provided by means of a plurality of baffles contained in the zone. Further, to enhance the agitation and to ensure that the downwardly moving sand is sufficiently agitated to liberate trapped oil particles, a fluid stream, such as recirculated dilute aqueous silicate solution, is introduced to effect a net upward flow of the aqueous phase through the separator and to agitate the sand particles. The wet oil effluent and aqueous phases are discharged from the primary separator to the separation thickener wherein an interface between the oil emulsion and aqueous phases is formed. Wet oil is then discharged from the thickener to a settling zone wherein the wet oil phase is allowed to stand for a sufficient period of time, preferably a residence time of about twelve hours, to permit it to separate into dry oil and aqueous phases. In addition, water and diluent oil recovery and recirculation are disclosed.
Irani, et al., U.S. Pat. No. 4,036,732 (Jul. 19, 1977) "Tar Sands Extraction Process," discloses a tar sands extraction process for water wet tar sands wherein dry ground tar sand is contacted with water to form a slurry. The tar sand water slurry is then contacted countercurrently or in a single stage with a solvent forming three phases; a) a phase wherein a major amount of the bitumen present in the tar sand will be dissolved in a major portion of the solvent, b) a phase comprising the asphaltenes which are substantially insoluble in the solvent, and c) a phase comprising the sand along with a major portion of the added water and the water originally present in the tar sands, as well as minor amounts of bitumen and solvent. After separation from the other phases, the third phase comprising the sand along with the major portion of the water, as well as minor amounts of bitumen and solvent, may be further treated such as by contacting the sand with water.
Generally, the extent of bitumen recovery that is practically and economically obtainable by such methods which combine solvent and water treatment or conditioning of tar sand is limited due to the formation of difficult to break emulsions of water and bitumen-rich solution. Bitumen tied up in the form of an emulsion generally is not easily or economically recoverable, resulting in reduced bitumen recoveries and/or increased operating and capital cost.
It is an object of the invention to overcome one or more of the problems described above.
According to the invention, a method of recovery of bitumen from tar sands includes the step of mixing tar sands, an organic solvent and an aqueous medium at tar sands mixing conditions to suspend the tar sands in the mixture and to provide sufficient mass transfer between phases of the mixture without significant emulsion formation. Upon cessation of the mixing, the mixture is readily separable to a bitumen solution and a sand-water mixture. The organic solvent is effective in solubilizing bitumen including asphaltenes from the mineral of the tar sand. A displacing amount of no more than about one void volume of the aqueous medium is used. Further, the aqueous medium is effective in displacing bitumen-rich solvent from the tar sands and avoiding substantially spontaneous emulsion formation. A bitumen-rich solvent phase is separated from the mixture leaving an aqueous mineral phase containing a residual amount of the solvent. Subsequently, bitumen is recovered from the bitumen-rich solvent phase.
Other objects and advantages of the invention will be apparent to those skilled in the art from the following detailed description taken in conjunction with the drawings and the appended claims.
US Referenced Citations (6)
Continuation in Parts (1)
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546828 |
Oct 1985 |
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Patent Grant
5143598
