US2940919A - Water washing of tar sands - Google Patents

Description

June 14, 1960 OIL-WATER 22 WASHERISEPARATOR C. E. HEMMINGER WATER WASHING OF TAR SANDS Filed May 9, 1958 FRESH SAND DRYING 20m: l3

VESSEL WATER 25 'SETTLIEIR UNIT Charles E. Hemminger y Attorney FRESH WATER F HEAT EXCHANGER RECYCLE WATER IL 44 BURNIN4G ZONE I Unite Patented June 14, 1960 2' ice 2,940,919 WATER WASHING F TAR SANDS Charles E. Hemminger, Westfield, N.J., assignor to'Esso Research and Engineering Company, a corporation of Delaware Filed May 9, 1958, Ser. No. 734,244

11 Claims. (Cl. 208-11) The present invention deals with an improved method ofrecovering oil from oil-bearing solids by washing techniques. More particularly, it is concerned with providing necessary heat for hot water washing as well as effectively-recovering and/ or utilizing the hydrocarbon matter contained in such solids.

For many years, the prior art has been aware of the fact that in addition to crude petroleum oil sources, vast quantities of hydrocarbon materials are present in various oil-bearing solids, such as oil or tar sands, peat, lignite, shale etc. Among the numerous schemes advanced for recovering hydrocarbons from these solids have been subjecting them to pyrolytic treatment to free the oil, i.e., conventional retorting'operations, and underground recovery. In addition, a fairly large amount of work has been done in the general field of extracting the oils from the 'solids by means of extractive procedures, e.g., water washing.

The present invention is directed to the latter method of recovering oil from oil-bearing solids, particularly tar sands, by the use of 'hot liquid extraction procedures. Experimental work has indicated that when the tar sands are subjected to a hot aqueous wash, e.g., ISO-200 F., oil is liberated from the oil sands and passes into the aqueous phase whencefrom it is ultimately separated and recovered as product.

However, heretofore such water washing steps were rather inefi'icient as measured-by the quantity of oil produced per unit of external energy which had to be supplied to the system. When treating average tar sand material having an initial oil content of about 10 weight percent, approximately a fifth or more or" the oil remained as residual bitumen on the washed, spent solid. Since the residual bitumen in the sand is only of the order of 2 weight percent or less, it was normally discarded since conventional furnaces and burners cannot be utilized to burn materials of such a low carbon content. Partially because of the necessity for discarding the spent tar sands, increased effort has been made to further reduce the residual bitumen content of the tar sands but the physical nature of the tar sands makes recovery of this residual diflicult and quite costly. The economics of expenditures per unit quantity of oil recovered have dictated that at least 15 weight percent of the oil initially in the fresh tar sands be discarded as residual bitumen remaining on the tar sands.

In accordance with the present invention, additional oil recovery in the water washing stage may be obtained by increased energy-consuming efforts therein without necessitating increased use of externally provided energy, and/or less effort need be directed to recovery of the residual bitumen as oil product since it can be efiectively utilized to supply all or the major part of the energy requirements of the washing system as well as other refinery operations to process the separated oil and energy to transport it in pipelines. Thus, the value of high clay sands is markedly increased. The economy of prior 0 trained fine sand particles.

cyclones may be used to remove fine solids from the;

art extractive procedures wherein 1'5 weight percent or -less of the bitumen was discarded as unrecovered material is greatly improved.

More particularly, spent washed tar sands are passed from the washing zone preferably after a drying step, to -a fluidized solids combustion zone, e.g., a fiuid bed burner. The tar sands as mined generally range from 10-200 mesh in size and thus are naturally suited to fluidization by passing a gas upwardly -therethrough. By utilizing afluidized combustion zone as opposed to other types of furnaces or burners, it is possible to eifectively burn the less than 2 weight percent residual bitumen in the sand, thus liberating thermal energy. Such fluidized combustion zones have been found to burn materials having carbonaceous contents of as low as 0.1-0.7 weight percent. The heat liberated from the fluidized combustion zone is then utilized to supply the thermal requirements of the over-all system, e.g., heating the wash medium, effecting drying of spent sands, preheating fresh sand feed, etc. Additionally, it can be converted into mechanical or electrical energy for the mining and transportation of the sand as well as providing power for the washing system itself.

By way of indicating the distinct advantages of the present invention over other methods of oil recovery, pyrolytic (retorting) and underground systems are characterized by a low degree of recovery under largely uncontrolled conditions usually resulting in cracking of the oilliberated into less desirable fractions. In accordance with the present invention, oils are removed from oil,- bearing solids under well controlled conditions, substantia lyall the hydrocarbons conta'inedin the fresh solids serving a useful function.

The various aspects and possible modifications of the present invention will be made more clearly apparent by reference to the following description, drawing and accompanying example.

Referring to the drawing there is depicted a system for treating oil-bearing solids, e.g., Athabasca tar sands, by the application of the present invention. Basically, there is shown a washer-separator zone 10, settler 1-1, and a burning and drying vessel 12. While a distinct settling unit and drying zone are not absolutely necessary, it is normally desired to utilize settling and dryingcf spent solids in orderto minimize their water content before being introduced into the burning zone.

Fresh tar sand, which may be heated to 50-100 in external equipment, is introduced into washer vessel -10 by line 15. By way of example, the fresh tar sand contains about 3 weight percent water, 10 weight percent oil, the balance being mineral matter, e.g., clay, quartz, etc. Generally, tar sands of this type contain from 10l7 weight percent oil. As mined from the ground, the sands are less than 1.000 microns in size, predominantly ranging from to 400 microns in diameter.

Washing vessel 10 is provided with a series of distributing grids 16 and downcomers 17 in order to promote countercurrent contact between the tar sands and the hot water wash introduced at the bottom of the vessel by multiple injector 21. The tar sands are thus contacted in several stages with hot water passing up through the distributing grids, partially depleted sands passing through the downcomer into the next stage.

Though washing by relatively high water velocity, e.g. ODS-0.5 feet/second, countercurrent flow is preferred, co-current flow or merely batch mixing may be employed. Means, not shown, may be provided in the vicinity of outlet 22 of the contactor for removing en- For example, one or more withdrawn water-oil mixture.

, perforated plate or distributing grid 33.

I The water temperature in the contactor may range from 150 .to 180 F. at atmospheric pressure. It 15 desired to utilize pressures of up to 200 p.s.i., in order to allow water washing at' temperatures of 300m 3, 50 F. .By using the'higher temperature, better separatlon of elayjand oily particles is obtained-because viscosity of tar is reduced at hundredfold as compared to only a fourfold decrease in viscosity of water in going fromlSO to r 350 F Undesirable froth formation is also avoided. During-thewashing step, oil material passes into the washing fluid forming an'oil-rich, aqueous phase which is withdrawn through outlet 22 and passed into an oil recovery unit 23. The oil recovering unit may be a conventional distillation zone, decanter or the like, oil prodnot .being withdrawn by line 24. Wash water is removed by line 25 and may be discarded, directly recycled to washerlO by line 20, or heated as will be later described.

In the specific embodiment shown, the residence time Fresh water at ambienttemperatureis introduced into the system through line 38, .the water being preheated in heat exchanger 39 toa temperature of about 125 F. by contact with the burner-drying zone gaseous eflluent (at a temperature of about 200 F.) taken overhead from unit 12 by line 37. The cooled, gases, e.g., at a temperature of 150 F., may be discarded or further circulated by line 40' to additional heat exchange with, for example, f reshtar sand. 7 h

The freshfmakeup water-then passes through lines 41 and 43 into a heat exchanging coil immersed in thefluidized combustion bed in section 45. In addition to the fresh water, recycle water, emanating from the settler unit 11 and/or oil-water separator 23, is added by line 42 and is heated in coil 44. .The'passage of the relatively cool water streams maintains the fluidized solids mass in section 45 at a temperature of about 400-600 F. while the water is heated under pressure to about 350 F. Partial .vaporization of the water is practiced to increase the heat is withdrawn through conduit 29 and may be discarded 1 orffurther recycled to the washing zone as will be later discussed. Partially dried. spent tar sand is removed transfer from theburner vessel 12 to the separator 10 for the same mass of water. Additional combustion takes place abovesection 45 so that the temperature of the flue gases passing to the drying zone is about 900 so that substantially complete combustion of the bitumen is attained.

The hot water, partially in the form of steam, is withdrawn from unit 12 and is passed to the washer by line 19, whencefrom it is injected into the washer by nozzle 21. Part of the hot water-steam mixture can be removed by line 30 and passed to vessel 12. Valve '31 is anexpansion valve through which the liquid suspension of.

sand is flashed .to essentially atmospheric pressure and .a vapor solid mixture.

Vessel 12 consists essentially of drying zone 13 and burner zone 14, zone 13 being, superimposed directly upon the fluidized combustion zone. Of course, if desired, drying may be efiectedin a zone entirely distinct from the area of residual bitumen combustion. As shown, spent sands are introduced into zone 13 onto As they pass along grid 33, they contact upfiowing hot flue gases from the burner zone, residual adhering liquid flashing off overhead with the combustion gases. The sands then pass through downco-mer 32 onto the next grid plate within'additional solids-hot gas contact is obtained.

The dry solids thereafter pass into burner zone 14, normally similarly fitted with a series of 'grid-downcomer configurations for promoting stagewise contact with good gas distribution. 'Of course, a one-stage fluidized bed combustion zone. can be used whenever countercurrent heat exchange is notparticularly desired. i Air or other oxygen-containing gas is introduced in vessel 12 by inlet 34, the air being preheated to a tempe rature of 160 F. by contact with hot combusted spent solids as they pass along grid 36 into withdrawal conduit '35. The air is introduced at a superficial velocity of 0.5 to 3 feet per second andservesto maintain thepburn-' ing solids in theform of relatively dense turbulent beds having the appearance of a pseudo-liquid. The fluidized bed or beds of the burner zone have an apparent density of 40 to 100 pounds per cubic foot.

In the embodiment described, the spent tar sands contain 1 weight percent residual bitumen as they enter the burning zone and approximately 90% of this bitumen fraction is consumed in the combustion step and converted to thermal energy. Thus, the solid residue re-' cmoved through .line 35- contains only about 0.1 weight percent bitumen. 7

While the heat liberated 'in the burning zone can be utilized in many ways to supply requisite energy for the hot waterv Washing, e.g.,' as by passing hot flue gas into the washing zone, preheating fresh tar sands, etc., a

over-all process will now be detailed.

particularly desirable method of supplying heat for the to a steam turbine. The steam is separated from the water in a separator, and the steam expanded through ,a turbine forrpower and the condensate pumped back to line 42. V V V I The following table is'a compilation of pertinentconditions with respect to the system described.

Table 1 Bread Preferred Range Washing Zone: Temperature, F 150-375 190-225 Pressure, p.s.i.g- 0300 0-50 Wt. Ratio of Water to Fresh Solids O 1 to 3 0, 3 to 1. 0 Burner Zone: 7 e V Bitumen on Solids Sent to Burner, Wt. Percent 0. 5 to 3 1 to 1. 5 Bitumen on Solids Discharged, Wt.

Percent 0 1 to 0. 6 0. 2 to 0. 4 Apparent Density of Fluidized Solids,

lbs/it; 40-100 60-80 Superficial Fluidizing Velocity, it./sec- O. 5 to 3. 0 1. 2 to 1. 8 Temperature, F., in Areas without 700-1, 500 850950 Cooling Coils heat produced by burning the low content bitumenrof a useful function of either being recovered as product or spent, washed tar sands solids has been described, numerous other heat exchange schemes 'can'be devisedto effectively utilize the energy released by the combustion of the spent solids. ,'For example, other fuels as natural gas, refinery'gases, coke or tar, which are naturally occurring or produced in refining the bitumen recovered from sand, may be added to vessel 12. The present invention deals with water washing of oil-bearing solids and burning the small residual hydrocarbon fraction on 'the spent solids under fluidized combustion techniques so as .to supply energy for the water washing step, and is not -necessarily'limited to the particular water washing technique or apparatus which has previously been described.

In accordance with the present invention, the value of low oil content solids is'enhanced since'oil not recovered by washing nevertheless serves a valuable function. Less costly water washing proceduresmay be resorted to since substantiallyv all the oil present in th'e fresh solids serves consumed to provide requisite energy.

Having described the invention, the following claims succinctly define the invention claimed.

What is claimed is:

1. An improved method for recovery of oil from oilbearing solids which comprises subjecting the oil-bearing solids to contact with a hot, aqueous mass in a washing zone for a time sufiicient to cause a substantial portion of the oil contained in said solids to be freed therefrom and to pass into aqueous phase, separating an aqueous phase rich in oil from the spent oil-bearing solids and recovering an oil fraction from said aqueous fraction, passing spent oil-bearing solids to a fluidized solids combustion zone, adding oxygen-containing gas to said fluidized combustion zone so as to oxidize residual bitumen remaining on said spent solids, and utilizing the heat of combustion to supply requisite thermal energy to said aqueous mass.

2. The method of claim 1 wherein a drying zone is positioned between said Washing zone and said fluidized combustion zone, spent solids being passed from said washing zone to said drying zone and thence to said combustion zone.

3. The method of claim 1 wherein said oil-bearing solid is tar sand, and the residual bitumen present in the sand as it is passed to said combustion zone is less than about 2 weight percent.

4. The method of claim 1 wherein an aqueous mass is first heated by contact with the combustion gases produced in said combustion zone, thereafter is further heated by indirect heat exchange with the fluidized spent solids mass in said combustion zone, and is then introduced into said washing zone.

5. The method of claim 2 wherein said oil-bearing solids and said aqueous mass are countercurrently contacted, and said drying zone is superimposed upon said fluidized combustion zone, combustion gases serving to vaporize aqueous matter from said spent solids in said drying zone.

6. A process for utilizing the bitumen of oil-bearing solids which comprises, the steps of, countercurrently contacting fresh oil-bearing solids With a stream of hot water in a washing zone so as to separate a substantial portion of the oil from said solids, said oil passing into an aqueous phase, separating said aqueous phase from spent solids, withdrawing it and recovering oil therefrom, passing said spent solids to a drying zone, passing relatively dry spent solids containing less than about 2 weight percent residual bitumen from said drying zone to a fluidized bed combustion zone, introducing oxygen-containing gas into said combustion zone in amounts suflicient to oridize the residual bitumen on said solids under turbulent, fluidized dense bed conditions, withdrawing oxidized solids from said combustion zone, and utilizing the products of combustion from said fluidized bed combustion zone to heat the water utilized in said washing zone.

7. The process of claim 6 wherein said drying zone and said combustion zone are in open contiguous relationship, combustion gases from said fluidized bed combustion zone first serving to dry spent solids and thereafter being subjected to indirect heat exchange with at least a portion of the Water employed in said Washing zone so as to supply heat thereto.

8. A process for utilizing the bitumen of oil-bearing solids which comprises countercurrently contacting fresh oil-bearing solids with an upflowing stream of hot water in a washing zone so as to separate a substantial portion of the oil from said solids, said oil passing into an oil rich aqueous phase, separating said oil rich aqueous phase from spent solids, withdrawing it and recovering oil therefrom, passing said spent solids to a drying zone, passing relatively dry spent solids containing less than about 2 weight percent residual bitumen from said drying zone to a fluidized bed combustion zone, introducing air into the bottom portion of said combustion zone in amounts sufficient to burn the residual bitumen on said solids under turbulent, fluidized dense bed conditions, withdrawing burned solids from said combustion zone, utilizing the products of combustion leaving said fluidized bed combustion zone to heat the water utilized in said Washing zone by indirect heat exchange and adding further heat to the water by passing it through a portion of said dense fluidized bed of solids in said combustion zone as a confined stream in indirect heat exchange with said solids in said dense fluidized bed.

9. The process of claim 8 wherein said drying zone and said combustion zone are in superimposed relation and combustion gases leaving the upper portion of said fluidized bed combustion zone are first used to dry spent solids in said drying zone and thereafter are passed in indirect heat exchange with at least a portion of the water employed in said Washing zone so as to supply heat to said water.

10. A process for utilizing the bitumen of oil-bearing solids which comprises countercurrently contacting fresh oil-bearing solids with a stream of upfiowing hot water in a washing zone so as to separate a substantial portion of the oil from said solids, said oil passing upwardly and forming an oil rich aqueous phase, separating said oil rich aqueous phase from spent solids, withdrawing said oil rich aqueous phase from the upper portion of said washing zone and recovering oil therefrom, passing said spent solids to a drying zone, then passing relatively dry spent solids from said drying zone to a fluidized bed combustion zone, introducing air into the bottom portion of said combustion zone in amounts sufiicient to burn the residual bitumen on said solids under turbulent, fluidized dense bed conditions, withdrawing burned solids from said combustion zone, and utilizing said fluidized bed in said combustion zone to heat the water utilized in said Washing zone by passing a confined stream of water submerged in said fluidized bed by indirect heat exchange with the solids in said fluidized bed in said combustion zone.

11. The process of claim 10 wherein said drying zone and said combustion zone are arranged one above the other so that combustion gases leaving the upper portion of said fluidized bed in said combustion zone are first used to dry spent solids and thereafter are passed in indirect heat exchange with at least a portion of the Water employed in said washing zone so as to supply heat to said Water.

References Cited in the file of this patent UNITED STATES PATENTS 1,497,607 Streppel an 10, 1924 2,480,670 Peck Aug. 30, 1949 2,557,680 Odell June 19, 1951

Claims (1)

1. AN IMPROVED METHOD FOR RECOVERY OF OIL FROM OILBEARING SOLIDS WHICH COMPRISES SUBJECTING THE OIL-BEARING SOLIDS TO CONTACT WITH A HOT, AQUEOUS MASS IN A WASHING ZONE FOR A TIME SUFFICIENT TO CAUSE A SUBSTANTIAL PORTION OF THE OIL CONTAINED IN SAID SOLIDS TO BE FREED THEREFROM AND TO PASS INTO AQUEOUS PHASE, SEPARATING IN AQUEOUS PHASE RICH IN OIL FROM THE SPENT OIL-BEARING SOLIDS AND RECOVERING AN OIL FRACTION FROM SAID AQUEOUS FRACTION PASSING SPENT OIL-BEARING SOLIDS TO A FLUIDIZED SOLIDS COMBUSTION ZONE, ADDING OXYGEN-CONTAINING GAS TO SAID FLUIDIZED COMBUSTION ZONE SO AS TO OXIDIZE RESIDUAL BITUMEN REMAINING AND SAID SPENT SOLIDS, AND UTILIZING THE HEAT OF COMBUSTION TO SUPPLY REQUISITE THERMAL ENERGY TO SAID AQUEOUS MASS.

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