US 2871180 A
Description (Le texte OCR peut contenir des erreurs.)
Jan. 27, 1959 M. c. LOWMAN, JR., ET AL 2,871,180
RECOVERY OF OIL FROM TAR SANDS Filed May 24. 1957 INVENTORSI EDWIN J. FISCH MALDEN C. LOWMAN JR.
United States Patent-" 2,371,180 I RECOVERY or on .FnoM sauna Maiden 'C. Lowman, Jr., San Rafael, and Edwin J. Fisch, Castro Valley, Galifl, assignors 1,0 :Shell Development Company, New York, Y., a corporation of Delaware h i e a 19s1,. e i ugeuro:
5 Claims. (Cl. 203-11) This n n n re a es n improv d proces to extracting crude oi rom bitumih he. sand. w th .th crude oil b n pa d i a deespha ted componen and an asphaltene component.
Th e a v a lar o eurre es o bituminous a n th w r n muc ef o t has been, exe ted t th el pm n .0! m thod y wh ch the bitum n o crude i may e s p rated from h mods available tor use. T-he term bituminous sand s A herein to include these ma e ia s womanl re e red t as o san s tar s d and othe li e i heari g m t sa ue e me have heen pro o ed and trie with v rying deg s of su ee :It is ea nm nraetie 10 epa the tude o or b t me tram-th sand .as-a n e mpon t whieh aep a ed men m y then b o to reed a eeke 4 t whieh eanh un-her r fin in o d n w th conventional .refin t nes. an a ter a i r e raweaad may be. reetly reterted in ei he a mo in or a f ui hed sy temic P o uc a eoker dis lla e wi h he o :hi h deposi on he S beingh ned to P o ide th memes-h at.
d o l from th m nera ma er. We hav ioundthat itis p ssib e t per t t e ndvenud oil separation Procedure in a manne to p ovid si n tan ously .a .deas-nhalte mp n n nd an asnhaln ina ion. imo t e n ess t f pl i a econd s eni part I JI'Qm the separation procedure itself, and without resorting v1 a. h ma r a n operat on,
J. Qhieet-otthis invent on to p evidezanimproved pro duretorthe separation oferudeoil rem bitum nous sand It is a further o ie et this eh a PIQCFSS in w e t e. crud .o -l. is separated-from h s n a de sp e c mponen and an a ph ltene compo en These and other objects will become more apparent with .a study of :the =dese-ription ,ot-theinvention taken in conjunction with the accompanying drawing which is a diagrammatic representation of .a preferred system tor performing the improved process.
It has now been discovered-that the cnidaoilnassociated 'with a bituminous sand may be. advantageously andv efliciently separated from the sand inria process'mhich .Wlll simultaneously fractionate :tlie .crude oil, making immediately available a deasphalted 'oilwhieh' can then be further refined by more or less-typical" refinery procedures. -The sand from the process is substantially '2 .oil free. Generally speaking. it is contemplated to supply aqueous pulp of the bituminous sand to a vertical extraction zone and to flow a liquid low molecular weight paraflinic solvent in an upward direction of the yert cal extraction zone in -ountercurrent direction to the downwardly descending sand. During tne counter- .current movement of the aqueous .pulp and solvent, there is formed a deasphalted oil and solvent phase, an asphaltene phase diluted with a lesser portion'ot the solvent, a water phase and a substantially oil-free sand. The seyer-al phases and sand are then separated into distinct layers with the asphaltene-enriched layer. being disposed below the point of introduction of the hydrocarbon solvent and the water layer immediately below the asphaltene layer. The sand settles to tne bottom of the Water layer. v. deasphalted-oil enriched solvent layer forms above the point of introduction of the aqueous pulp.
.ing the s olvent ex raction.
the alkaline side is trequently desirable to obtain .a clear .sepapation. 'Ihe water layer which forms at the bottom .of the extraction zone serves .a very useful purpose in that it assures deentraining of any hydrocarbon material that -,I,na -y possibly be associated with the falling sand.
vAs will be subsequently-described, regulation of the depth of the water layer facilitates the removal of the ,oyerl' giasphaltene-enriched layer.
Wl 0u l w molecular weight paraifinic hydrocarbons may be used as a solvent. It is best that the solvent contain no appreciable amount .of hydrocarbons having more phan si r carbon atoms per molecule. Among the desirable solvents are propane, butane, mixtures of propane cand'blltane and light ends collected in the furrher processing of the separated crude oil. Where the site of the bituminous deposit is geographically isolated, the light ends may be conveniently and advantageously used. The solvent is continually recovered and recirculated to the extraction zone. The extraction zone is closed and willfhave a pressure dependent upon the vapor .in r asfii jl o th hydrocarbon solvent at the temperature iofs he operation. For instance, where propane 'is being employed and the process is conductedat a temperature in the vicinity .of F., the pressure will be approximately p. is. ,i. g. This high pressure points up an advantage in using light hydrocarbon .ends which will usually have a vapor pressure of perhaps .25 pounds .p. s. i. g. at the same temperature.
fifhe pulper employed may be any of the type conventionally used in the preparation of crude bituminous sands for extraction. Preferably the water which is added to :the bituminous sand contained in the pulp'er is heated to a temperature in the range of 100-200 F. as an elevated temperature lowers the viscosity of .the crude oil making it more easily separated from the sand. The water may be introduced warm to the pulper or alternatively steam may be introduced with the water or directly into the pnlper. The primary purpose of the pnlpingoperation is to disrupt the oil structure .or film andntliereby disperse the crude oil throughout the pulp as detached flecks among water wet sand g ains. This places the crude-oil in a form which makes it possible to solvent. extract it readily in the subsequent extraction .step. The amount of water added to the bituminous V sand will yaryconsiderably depending among other-things :uponqtheiniti-alwater content of the sand and-the amount of elay present. Clay tends to create an emulsion and in some instances, it may be necessary to use largercrude oil in the bituminous sand will provide satisfactory extraction.
solvent in solution with the deasphalted oil will depend on its inlet temperature and the temperature of the aqueous pulp entering the extraction zone. But in any event, since relatively large quantities of solvent are employed, the exit temperature will not be greatly in excess of the temperature ofthe incoming stream of solvent. It is believed that the solvent functions to separate and coalesce the crude oil flecks into two phases, viz. the asphaltene enriched phase and the deasphalted-oil enriched extract. It can be generally expected that the asphaltene-enriched phase will have a specific gravity in the vicinity of .9 and the deasphalted oil enriched phase a specific gravity of approximately from .6 to .8. The amount of solvent in the overhead deasphalted oil layer is much greater than that diluting the asphaltenes.
It has been occasionally experienced in the deasphaltizing of hydrocrabon oils that the precipitated asphaltenes plug the fractionating tower. This plugging has normally occurred in the region adjacent and below the feed entry. Various schemes have been suggested for preventing the plugging and among these is the use of very finely divided solid particles. It may be that the fortuitous presence of the fine pulp sand forestalls the occurrence of this phenomenon in our process. In any event, it is believed that the cascading sand passing over the baffies of the extraction zone afford an erosion effect which keeps these bafiles clean.
The retention time in the pulper need be only long enough to erupt the oil film and to disperse the oil as flecks among the sand grains. The time should be sufficiently long to assure that the sand grains are thoroughly water wet. Normally, a pulping operation of several minutes, say 5 to minutes is suflicient. It has been generally experienced in other oil extraction processes that long periods of pulping of several hours duration do not affect the yield one Way or another.
With the system shown in the accompanying drawing, it is possible simultaneously to recover a bitumen or crude oil from a bituminous sand and to separate it into an asphaltene-free and an asphaltene-rich fraction. A typical crude oil that may be separated with the process has a composition comprising 24.5% by weight of saturated hydrocarbons, 24.4% (wt) aromatic hydrocarbons, 32.2% (wt.) resins, and 18.9% (wt.) asphaltene in the use of an iso-pentane extraction. The oil has a pour point of 75 R, an A. P. I. gravity of 6.1 and may constitute up to by weight of the tar sand. The foregoing compositions are only representative and tar .oils
of widely varying compositions may be processed.
Raw tar sand is placed in a feed hoper 10 which is disposed above and empties through a line 12 into a ro tary type pulper 14. The pulper is a cylindrical drum having internal lifts and is provided with means vfor in-' jecting steam and water to its interior. Itis sometimes advantageous to inject steam along with the hot water entering through a line 15' to lower the viscosity of the oil. It is possible to use unheated water in the pulper but this is not generally done as it becomes more difiicult to disrupt the oil structure of the bituminous sand. It 'is preferred to introduce only that heat required to erupt elfectively the oil film as additional heat raises the temperature of operation of the extraction zone. which is undesirable when a very volatile solvent, such as'propane, is used. However, if the light ends of the crude oil are used as solvent, high pressure is not a problem because The outlet temperature of the hydrocarbon i of their low vapor pressures. The aqueous pulp leaves the pulper from its far end through a line 16 which opens into the upper end of an inclined and enclosed screw conveyor 18. The conveyor slants downwardly from the line 16 to the place where it opens into a cylindrical, vertical extraction vessel 20. It may be desirable to provide a fan 21 at the lower end of the screw conveyor for breaking up the extruded aqueous pulp and dispersing it over the cross section of the extraction zone.
The tower is supplied with a plurality of spaced conventional baifies 23 below the place of entry of the screw conveyor. Hydrocarbon solvent enters the extraction zone of the tower 20 through a line 24 which opens into the bottom of the zone. At the lower end of the extraction zone proper of the tower 20 there is a downwardly slanting baffle 25 which covers approximately two-thirds of the towers cross section. This baffle serves to direct the cascading sand to one side of the tower. A weir 26 is disposed inthe tower adjacent a portion of the tower wall and underneath the protecting bafile 25. The solvent flows upwardly through the extraction zone, contacting the downwardly descending aqueous pulp and during this countercurrent passage, the crude oil is solvent extracted to form a deasphalted oil and solvent phase and an asphaltene phase diluted with a much lesser portion of the solvent. The gravitating water wet sand particles tend to maintain the contacting mass in a somewhat turbulent state and it is believed that this serves to avoid possible pluggingof the contacting zone with asphalt. As mentioned before, since the sand particles are water-wet they tend to entrain aminimum of the solvent and oil with the result the separation is more complete. Furthermore, if there should by chance be any entrained hydrocarbon on the sand, it will generally be dislodged as it passes through a water layer 28 which forms in the conical bottom-of the tower. The sand collects in the bottom portion ofthis layer. The sand and water are removed througha'suitable rotary star valve 29 in a line 30 to a flume 32. The flume is provided with a flushing water from a line 33 which moves the sand to a disposal pond.
A deasphalted oil solvent layer 35 forms in the tower above the extraction zone proper. This deasphalted oil enriched layer is removed from the tower through a line 37 to a conventional stripper where the solvent is separated from the oil and returned after cooling through the previously mentioned line 24 to the bottom of the extraction zone. An asphaltene enriched layer 39 forms in the tower immediately above the water layer 23 and below the place of introduction of the hydrocarbon solvent. The asphaltene layer is withdrawn from the tower through a line 41 opening into the bottom of a compartment 42 which is formed in the lower part of the tower between a portion of the tower wall and the previously mentioned weir 26.
The asphaltene layer spills over the top edge of the weir into the compartment 42 and collects in the bottom of that compartment, displacing any of the hydrocarbon solvent that may be there. An asphaltene-water interface level controller arrangement 44 assures that the asphaltene layer is so positioned as to spill over the weir. If the interface between the two phases should-drop unduly low in ,the tower, a float 45 following the interface actuates the controller proper which sends a signal through a line 45 to a motor 49 mechanically linked to a valve 46. The line 45 may be either an electrical circuit or a pneumatic line. The valve 46 opens and permits water to flow under pressure through a line 47 into the tower. The water continues to flow until the interface between the asphaltene phase and water has risen to the proper level at which time a second signal is' relayed Y to the power-driven valve shutting it off. Through the foregoing arrangement, the proper level of the asphaltene layer is maintained to enable its withdrawal from the tower as an intermediate layer. The maintenance of the water-asphaltene interface at the proper level also ensures that there will always be present sufficient Water to form a pumpable sand water slurry out of the bottom of the tower and in addition, the maintenance of the water layer at an adequate depth provides for the deen-' trainment of any hydrocarbon material that may come down with the fine sand. Normally, however, entrainment will not occur as the surfaces of the sand grains will be water-wet which will forestall their wetting by the hydrocarbon solvent.
The extraction tower is provided with a second interface level controller arrangement 48 whose purpose is to maintain a reservoir of the asphaltene in the compantment 42. It will be appreciated that if all of the asphaltene-rich layer should be removed and there was no means for regulating the flow through the line 41, that in this instance the hydrocarbon solvent would also be withdrawn through this latter line. This possibility is prevented by the controller 48 which is provided with v a float 50 adapted to follow the interface existing between the hydrocarbon solvent and the asphaltene. Here, as in the case of the other controller, if the float drops below its normal setting a signal is sent from the controller proper through a line 52 to a motor 53. The motor is mechanically linked to a valve 55 disposed in the removal line 41. The motor, where the float has dropped unduly low, moves the valve towards or to its closed position, thus, slowing up or entirely preventing the removal of the asphaltene-enriched stream. This will have the effect of raising the solvent-asphaltene interface to its proper level.
The withdrawn asphaltene-rich stream may be passed to a conventional stripper where the small amount of solvent appearing in the stream is removed and recirculated after cooling with the solvent recovered from the deasphalted oil. It may be advantageous to use the asphaltene-rich stream, without stripping, as a charge to a fluid bed coking unit. It so happens that the asphalteneenriched stream is a fortuitously ideal charge since the light hydrocarbon solvent present acts as a dispersant for the heavier asphaltenes as they vaporize in the coker inlet nozzles. Steam is generally used for this purpose. In some operations, it may be advantageous to use the asphaltene simply as fuel. Where the asphaltene-rich layer is processed in a fluid bed coking unit, the light ends recovered therefrom may be combined with the deasphalted oils from the solvent-deasphalted oil stripper and the combined materials subjected to a desulfurization by hydrogenation. A portion of the light ends from this latter operation may be separated and used as the hydrocarbon solvent for the extraction tower. Actually, when the process is once in operation, only a small amount of the light ends need be added as make-up solvent.
We claim as our invention:
1. A process for separating crude oil from a bituminous sand in a deasphalted oil enriched layer and an asphaltene enriched layer which comprises providing an aqueous pulp of the bituminous sand in a vertical extraction zone, introducing a liquid low molecular weight parafiinic hydrocarbon solvent into the zone at a level below the point of introduction of the aqueous bituminous sand pulp, fiowing the solvent upwardly of the vertical extraction Zone in countercurrent direction to the descending sand and during said countercurrent movement forming 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, said phases and sand having increasing specific gravities in the order presented, separating the several phases and sand into layers with the asphaltene enriched layer being disposed below the place of introduction of the hydrocarbon solvent and above the water layer and sand, and with the deasphalted oil enriched layer being formed above the point of introduction of the aqueous pulp.
2. A process as described in claim 1 wherein the paraffinic hydrocarbon solvent is propane.
3. A- process as described in claim 1 wherein the paraffinic solvent is made up of light ends collected from further processing of the separated crude oil.
4. A process, for separating crude oil from a bituminous sand and simultaneously fractionating the crude oil into a deasphalted oil enriched portion and an asphaltene enriched portion, the improvement which comprises agitating the bituminous sand in the presence of warm water to form an aqueous pulp and during said agitation rupturing the oil structure, thereby substantially dispersing the crude oil as detached flecks among water wet sand grains, introducing the aqueous pulp to a vertical extraction zone, introducing a liquid low molecular weight hydrocarbon solvent into said zone at a point below the point of introduction of the aqueous pulp, flowing the solvent in an upwardly direction countercurrent to the descending aqueous pulp to obtain a deasphalted oil and solvent phase, an asphaltene enriched phase diluted with much'less solvent than present in saidother phase, water, and substantially oil free sand, separating the several phases and sand into layers, with the uppermost layer being an enriched deasphalted oil layer formed above the place of introduction of the aqueous pulp, an asphaltene enriched layer below the place of introduction of the solvent and immediately above a water layer which contains in its bottom portion the oil free sand, andremoving the several phases and sand from the zone.
5. A process as described in claim 4 wherein the pH of the aqueous pulp is adjusted to the alkaline side.
7 References Cited in the file of this patent UNITED STATES PATENTS Canada Dec. 16, 1952
Citations de brevets