US2847306A - Process for recovery of oil from shale - Google Patents

Description

Aug. 12, 1958 J.. STEWART ET AL FROOEss FOR RECOVERY OF OIL FROM sHALE A Filed July 1, v1955 mefm #Zwam a m .d n n w m H n d@ nr f e mmmm w.u.a` 6.1- HW h r 0U @why SeTB otr JSA nited States *i aterit Zdbd Patented Aug. l2, i958 2,847,306 rnocnss Fon nacovnur or on. FROM SHALE .loseph Stewart, Cranford, Stewart C. Fulton, Elizabeth, and Arthur W. Langer, Jr., Nixon, N. J., assignors to Esso Research and Engineering Company, a corporation of Delaware Application .luly 1, 1953, Serial No. 365,343

v 1 Claim. (Cl. 196'14) The present invention relates to an improved process for the recovery of oil from shale and from analogous minerals. lt pertains more particularly to a process by which oil may be recovered or extracted from shale and other minerals by a hydrogen donor action.

As particularly described in a concurrently tiled application by Langer, one of thepresent inventors, Serial No. 365,335, now abandoned, it has been found that various oil residua which are relatively low in hydrogen content may be upgraded by treating them with certain types of partially hydrogenated condensed ring aromatic fractions. The present invention is related to that just mentioned but is distinguished therefrom in its application to oil shale. Gil shale, so-called, ordinarily does not contain oil as such but contains rather a solid organic predominantly hydrocarbon material known as kerogen. in conventional processes, a crude oil is obtained from shale by retorting. This crude oil is then further refined by distillation, cracking, etc., to obtain the desired oil products. The shale is usually subdivided into small particles and heated for a prolonged period so as to crack the kerogen into liquid oil. The temperature for retorting is usually around 800 to 1000 F. At this temperature, in conventional retorting, a substantial part of the kerogen is converted to coke which remains in situ in the shale residue. Hence, a substantial part of the potential oil yield is lost. For this reason, among others, the recovery of oil from shale by retorting has not been economically attractive.

The prior art has also proposed to recover oil from shale by high pressure hydrogenation. The cost of large scale high pressure equipment alone is such as to make this process unattractive, aside from the cost of hydrogen, problems of hydrogenation catalyst contamination, etc.

According to the present invention practically all of the organic material in oil shale is recovered in a useful form. A liquid diluent, which is also a hydrogen donor, is heated with subdivided shale to convert most of the kerogen to liquid oil, in situ. The diluent-donor extracts the liquid oil as it is formed and substantially total conversion of the kerogen to oil takes place with comparatively little coke formation. Such carbonaceous material as remains in the shale is recovered as CO and utilized as described below.

A particular feature of the invention is the choice of a very inexpensive yet highly effective donor material. While the prior art has suggested the use of certain chemicals of comparatively very high cost for use as hydrogen donor materials in some types of hydrocarbon conversions, these have not gone into commercial use. According to the present invention, a partially hydrogenated highly aromatic oil fraction, such as thermal tar from petroleum catalytic cracker bottoms, is a preferred donor diluent. It may have a boiling range between about 500 and 950 F., or two fractions, one of boiling range of about 600 to 950 F. and the other of a somewhat lower range, e. g. 500 to 750 F., may be used sequentially. The rst is mixed with the shale in a slurry tank or drum, under pressure of 200 to 500 p. s. i. g. or more. The slurry is passed into a soaker drum or series of drums where heating is continued for about 0.5 to l0 hours at a temperature within the range of about 700 to 950 F., preferably 750 to 900 F. lt is preferred usually that not all of the diluent be added in the slurry tank, a portion, preferably of lower boiling range, being added to the soaker at reaction temperature. This portion preferably is of lower boiling range so as to diffuse more rapidly into the shale and thereby remove the oil more effectively. The total amount of donordiluent should be about 5 to l5 times the weight of the kerogen in the shale.

The extracted shale, which settles to the bottom of the soaker tank or tanks, is removed therefrom after the desired soaking period and passed into a reactor vessel. Here it is lluidized by passing steam upwardly through it. The steam strips out essentially all of the diluent and most of the kerogen, now converted to a liquid oil. The oil phase from the stripper is taken to a fractionator. The hot dried shale residue, which still contains a small amount of carbonaceous matter, is taken to a second reactor, preferably of the iluid bed type, where it is contacted with an oxidizing gas to form carbon monoxide. Here it is further heated, by the combustion process, to a temperature of about 1000 to 1200 F. The carbon monoxide is reformed by the well known water gas reaction to produce hydrogen and CO2. The C02 is scrubbed out by conventional alkaline reactants such as ethanolamine or the like and the product hydrogen is used to hydrogenate the donor diluent.

The donor-diluent, introduced originally from an extraneous source, is largely recycled and rehydrogenated so that requirements for continuous or periodic addition of extraneous material are minimized. Hydrogenation of the donor diluent is accomplished in a conventional manner, using moderate pressures and a suitable hydrogenation catalyst. Although any residual CO in the hydrogen may be removed, e. g. by scrubbing with ammoniacal cuprous sulfate, so as to avoid contamination of the hydrogenation catalyst, it is usually preferred to use an insensitive catalyst such as molybdenum sulfide which is not subject to poisoning either by CO or by the sulfur content of the donor-diluent to be hydrogenated. In this Way, removal of the CO becomes unnecessary.

The hot spent shale, now substantially free of all organic matter, is discharged through a heat exchanger to recover its sensible heat, preferably for generation of required steam for the process, although the heat may be used for other purposes.

The invention will be more fully understood oy reference to a specific embodiment illustrated diagrammati cally in the attached drawing which forms a part of this specification.

In the drawing, shale which is crushed to small particles, e. g. less than one inch and preferably less than onequarter inch in average diameter, is fed to a hopper or slurry tank 11. The crushing operation is conventional and need not be illustrated. A liquid oil fraction, referred to hereafter as a diluent, hydrogen donor, or donor-diluent, is fed into tank 11 from a line 13 to form a slurry.

The slurry is passed through a line 15 and through a preheating coil i7, heated in any appropriate manner, into the soaking or extractor drum 19. Here the slurry is kept at a temperature within the range of 700 to 950 F., preferably between 750 and 900 F., for a period of time sucient to convert substantially all of the kerogen to liquid oil and to extract it from the shale. The time required is ordinarily between 0.5 and l0 hours. During this period of time, the hydrogen donor diluent not only adds hydrogen to the cracked kerogen to form liquid oil in situ in the shale but it also acts as a solvent to extract the oil as it is formed. The slurry is kept agitated in vessel 19 but the shale is gradually settled out and conveyed through a line 21, preferably by gravity, to a stripping zone The oil phase is taken out above the settling shale through a line 23. The oil and shale are preferably under pressure of 100 to 1000 p. s. i. g. in this vessel, a pressure above 250 p. s. i. g. being preferred.

The amount of donor-diluent employed may vary somewhat with types of shale, ineness of subdivision, and heating temperatures. in general, the total weight of diluent will be from to 15 times the weight of the kerogen content of the shale. Thus with a shale running 1 barrel of oil per ton, 5 to 15 barrels of donor-diluent will be used to slurry each ton of shale. The hydrogen donor requirements in such large quantities of diluent are relatively very low, about 20 to 500 s. c. f. per barrel of diluent, as compared with 200 to 2000 in hydrogen donor diluent cracking (HDDC) of petroleum residua, as described in the copending application mentioned at the beginning of this specification. Hence overall hydrogen requirements are moderate.

The shale is taken into a stripper where it is fluidized and stripped with steam fed in at 27. Fluidization of the shale is not always necessary but is preferred. The steam, at a temperature comparable with that of the shale or a little higher, 750 to l000 F., removes substantially all of the diluent and nearly all of the other organic matter. A small amount, however, remains with the shale. The shale is then passed to a burner 29 through line 31.

The stripped vapors from the fluidized shale in vessel 25 are taken out through a line 33 through suitable solids separating means such as a conventional cyclone (not shown) to a heat exchanger 35 and a condenser 37 where the condensed steam is withdrawn. The oil layer passes through a line 39 to join the oil phase in line 23 to a fractionator 41.

ln fraetionator 41 the oil plus spent diluentis fractionated, appropriate side streams being provided for gas, gasoline, light gas oil, diluent and heavy gas oil, as in dicated at 43, 45, 47, 49 and :71. The diluent fraction, boiling preferably between about 600 and 900 F., though other fractions may be used as previously mentioned, is taken through line S3 to a hydrogenator 55. To maintain the aromaticity of the fraction and retain ease of hydrogenation, a small portion is preferably purged through a line 57, and a similar quantity of thermal tar is added through line 9S.

The bottoms from fractionator 41 is recycled through aline 59 to join with recycled hydrogen donor diluent to the slurry tank 11. A portion of this fraction may be purged to prevent undue build-up of objectionable constituents through a line 61.

in burner 29 air or oxygen, preferably air, is admitted through a line 65 at such a rate as to convert the carbon in the shale residue to carbon monoxide and to heat the residue to a temperature within the range of about 1000 to 1200 F. This air may also be used to uidize the shale in burner 29, auxiliary lluidizing gas being introduced at appropriate points (not shown) if needed, as will be obvious. The spent shale is then withdrawn through a line 67 after recovery of its heat for the generation of steam for stripping in line 27, steam for reacting with the carbon monoxide, etc.

The carbon monoxide gas from the spent shale passes overhead through a line 69 into a hydrogen producer vessel 71. Steam is supplied to this vessel through a line 73. The reaction produces a mixture of carbon dioxide and hydrogen which passes through line 75 into a scrubber 77 where the carbon dioxide is removed.

The scrubbed hydrogen gas which is now fairly pure, containing usually around 1 to 2% of CO, passes through a line 81 into the hydrogenator 55. Here, under appro- '4 priate hydrogenation conditions, e. g. a `pressure of 250 to 2000 p. s. i. g. and in the presence of a suitable catalyst such as molybdenum sulde, the diluent fraction is mildly hydrogenated.

The gases which pass overhead from the hydrogenator S5 may be purged at 83, a substantial portion, however, being recycled through a line 85. The now partially hydrogenated donor diluent passes through a line 87, 89 to recycle into line 13 and to slurry tank 11. A portion of this donor diluent is fed into the soaker or extractor 19 through a line 91. Usually one-third to two-thirds of the donor diluent is used in the slurry tank and the remainder in the soaker extractor 19.

As mentioned above, a lower boiling portion of donor diluent may be used in the extractor and this may be derived from an extraneous source or from a separate fraction if desired. A line 93 is provided for this purpose, appropriate control valves (not shown) being provided also as will be obvious.

It will readily be apparent to those skilled in the art that various other modifications may be made without departing from the spirit of the invention.

What is claimed is:

A process for recovering and converting oils from oil shale which comprises subdividing the oil shale into small particles, forming a slurry of the subdivided oil shale particles with a partially hydrogenated thermal tar, said thermal tar having been obtained as bottoms from a catalytic cracking operation, said partially hydrogenated thermal tar having a boiling point in the range between about 600 and 950 F., heating the slurry to a temperature between about 750 and 950 F. and passing the heated slurry to a soaking Zone wherein it is maintained at a temperature between about 750 and 950 F. for a time between about 0.5 and 10 hours and under a pressure of at least 200 p. s. i. g., adding partially hydrogenated thermal tar lower boiling than said first-mentioned partially hydrogenated thermal tar to the slurry in said soaking zone, said second-mentioned partially hydrogenated thermal tar having a boiling range between about 500 and 750 F., whereby oil is extracted from the subdivided oil shale particles by the solvent action of said partially hydrogenated thermal tar fractions and hydrogen is transferred from the partially hydrogenated thermal tar fractions to said oil, the total amount of partially hydrogenated thermal tar used being in the range of about 5 to 15 parts by weight based on the weight of kerogen in the oil shale, separating an oil phase from spent shale particles by settling, 'treating the oil phase to recover oil products and a spent thermal tar fraction for reuse in the process, passing the spent shale particles to a stripping zone," stripping the spent shale particles in said stripping Zone to recover oil from the spent shale particles and burning the stripped shale particles to provide heat for at least part of the process.

References Cited in the le of this patent UNITED STATES PATENTS 1,711,499 Hofsass May 7, 1929 1,794,865 Pier et al. Mar. 3, 1931 2,147,753 Pott et al. Feb. 2l, 1939 2,322,863 Marschner et al. June 29, 1943 2,426,929 Greensfelder Sept. 2, 1947 2,467,920 Voge et al Apr. 19, 1949 2,502,958 Johnson Apr. 4, 1950 2,587,729 Huff Mar. 4, 1952 2,601,257 Buchan June 24, 1952 2,614,067 Reed et al. Oct. 14, 1952 2,658,861 Pevere et al. Nov. 10, 1953 OTHER REFERENCES Hodgman et al.: Handbook of Chemistry and Physics, 35th ed., pages 732 and 733, publ. by Chemical Rubber Publishing Co., Cleveland, Ohio (1953).

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