US3117072A - Recovery of oil from oil shale - Google Patents

Description

Jan. 7, 1964 nu Bols EAsTMAN ETAL 3,117,072

RECOVERY OF OIL FROM OIL SHLE Filed July 5, 1958 Adi www@

3,ll7,tl72 RECOVERY 01? @lli FROM @lL SHALE du Bois Eastman, Whittier, and Warren G. Schlinger, Pasadena, Celli., assignors to Texaco lne., a corporation of Delaware Filed .luly 3, 1953, Ser. No. 746,533 3 Claims. (Qi. Edd-ll) This invention relates to the recovery of oil from oil shale. In one oi its more specific aspects, this invention relates to simultaneous retorting of oil shale to recover shale oil therefrom and hydrogenation of said recovered shale oil. The process results in the production of a recovered oil or reduced viscosity, lower sulfur and nitrogen content, and improved reflnability as compared with oil recovered from shale by conventional retorting in the presence of relatively inert gases.

We have discovered that retorting shale suspended in shale oil und-er high temperature and pressure in the presence of hydrogen and with a high le\ el of turbulence gives superior results. Not only is the kerogen resolved and converted into oil at near theoretical yields, based on the Fischer assay analysis, but also that the shale oil So recovered has improved properties.

As is wel known in art, a disadvantage of shale oil is its poor quality as compared with crude petroleum oils. ln particular, crude shale oil generally is extremely viscous and contains large quantities of organic sulfur and nitrogen compounds. Yields of motor fuels from shale oil by conventional petroleum refining processes are comparatively poor. Expensive treating and relining operations are necessary to remove nitrogen and sulfur and to obtain maximum yields of usable products from the crude shale oil. The process of this invention provides a method for recovery of shale oil of improved product quality directly from the oil shale by a combination retorting and hydrogenation operation.

We are aware of the fact that it has been proposed heretofore to retort oil shale in the presence of hydrogen for the express purpose of improving product quality. insofar as we are aware, such operations involve only the addition oi a hydrogen atmosphere to a heated retort in which oil shale in lump form or in the form of lne particles in a duid bed is heated to eiect conversion of kerogen in the shale to shale oil.

The use of hydrogen for the simultaneous retorting of the oil nale and upgrading the recovered shale oil to more valuable products is attractive because the yields and quality of the products obtained are superior to those which can be obtained by other processing methods. The application of hydrogeuation separately to the retorting of oil shale and to upgrading shale oil have been previously proposed. A serious drawback to previously proposed processes for retorting oil shale in the presence of hydrogen has been the high cost of large pressure vessels required for such processes. This drawback alone has been sufficient to make the rotor-ting of oil shale with hydrogen commercially unattractive. The present process provides for retorting of the raw shale and simultaneous hydrogenation ol` shale oil in a compact apparatus of relatively low cost.

The process of this invention is not to be confused with treatment with hydrogen at relatively low velocities in large diameter pr ssure vessels, or with conventional viscosity breaking. The provision of a high hydrogen concentration by the method of this invention effectively prevents the formation of heavy polymers or carbonaceous residues which characterize known processes. Hydrogen suppresses the formation of degradation products and results in correspondingly increased production of valuable liquid hydrocarbons.

@ne disadvantage of prior processes for treating heavy yPatented dan. 7, 1964 oils, such as shale oil, with hydrogen results from the large volume-time relationship required to maintain sur"- licient hydrogen concentration at the reaction centers so that the active hydrocarbon fragments resulting from cracking are saturated as rapidly as they are formed. It the rate of thermal decomposition is allowed to exceed the rate of solution of hydrogen in the liquid, the available supply of hydrogen is depleted and the undesirable thermal end-products, gas and coke, are produced.

In the conventional hydrogenation of heavy petroleum Oils, for example, as practiced in Germany, the main or splitting reaction is carried out in large unpacked reactors which contain a heavy viscous liquid phase through which the hydrogen slowly bubbles. The poor agitation in such a system limits the rate at which the reaction can proceed because of the local depletion oi dissolved hydrogen. This limitation has been appreciated but efforts to provide a practical means to achieve agitation in the high pressure equipment required have not been successful.

A similar situation exists in packed beds, for example, where hydrogen-rich gas is used for the retorting of shale. The hydrogen must move through the oil rilrn surrounding the shale lump by diiusion. The reaction is slow at best and large vessels are required to provide ample reaction time. Furthermore, the addition and removal of shale to and from the high pressure reaction zone requires extensive auxiliary equipment. These disadvantages are largely eliminated by the process of this invention as brought out below.

ln the process of this invention, a fluid mixture or slurry, of hydrogen, shale oil, and particles of oil shale is passed through an elongated tubular reactor of relatively great length in comparison with its cross-sectional area. The volume ot flow of feed material in the reaction zone is maintained at a rate such that velocities sufllcient to completely disperse the shale particles in the oil-hydrogen composite huid and obtain highly turbulent flow conditions is ensured. Such velocities may be readily obtained by passing the slurry feed mixture through a tube 01E relatively small internal diameter, for example, one half to one inch tubular reactor. Under these conditions, the hydrogen ditlusion distance is greatly reduced and the allowable rate of reaction correspondingly increased. By the use of highly turbulent flow conditions, the hydrogenation reaction may be accelerated so that conversion of heavy shale oil to lig ter products is accelerated and the shale oil product is considerably upgraded by increasing the yield of lower boiling products without the concomitant formation of high boiling polymers or colte.

ln the process of this invention, oil feed rate, hydrogen recycle rate, reaction tube diameter, and operating conditions of temperature and pressure all tend to ailect velocity of low and turbulence. It has been found convenient to express turbulence in terms of the ratio of the average apparent viscosity of the flowing stream.

to the molecular or kinematic viscosity u, viz

Hereinafter, we shall referto this ratio,

as turbulence level. The apparent viscosity of the llowing stream,

equals the sum of the eddy viscosity, em, and the kinematic viscosity v which may be shown in the expression Under conditions of turbulence, em has a nite value and it is apparent that if the magnitude of the apparent viscosity exceeds the kinematic viscosity at the point in question, that the ratio of exceeds unity. For a given system, it follows that the average value of the ratio, as expressed by exceeds unity. The average apparent Viscosity,

as employed herein is deiined by the equation where ro is the radius of the conduit. By substitution and integration, employing the parameters described by Corcoran et al., Industrial and Engineering Chemistry, 44, 410 (1952), this expression g :n ma@ -m I 2a' dll The latter equation is in terms which may be readily determined for a given system; ro eing the conduit radius, a the specific Weight of the flowing fluid, g the acceleration of gravity and al1-differential :acceleration of gravity, feet per second 2 p=pressure, pounds per square foot r=radial distance from center of conduit, feet r0=radius of conduit, feet x=distance, feet em=eddy viscosity, square feet per second may be rewritten m=apparent viscosity, square feet per second em=average apparent viscosity, square feet per second v=kinernatic viscosity, square feet per second azspecic weight, pounds per cubic foot Temperatures of 700 to 1500" F. may be employed. A preferred range of temperatures is from 800 to 1,000 F. Pressures of 1,000 to 20,000 p.s.i.g. may be employed, although pressures of 1,500 to 10,000 p sig. are preferred. Hydrogen feed rates of 1,000 to 100,000 standard cubic feet per barrel of slurry feed may be employed, but hydrogen feed rates of 2,000 to 50,000 standard cubic feet per barrel of feed slurry are preferred. Hydrogen may be supplied in relatively pure form or in concentrations as low as 25 volume percent. Synthesis gas, i.e. a mixture of carbon monoxide and hydrogen may be used. Although reaction times from one second to two hours may be employed, reaction times of twenty to three hundred seconds are preferred.

With reference to the figures, a specific embodiment of apparatus suitable for carrying out the invention is illustrated. In this embodiment, moderately pulverized shale, eg. shale having a particle size smaller than onequarter inch in average diameter, is charged to a mixer 5 in which it is mixed with oil derived from the shale, as hereinafter described, optionally together' with water to form a pumpable slurry. The addition of Water to the slurry, as illustrated, and the addition of catalyst, eg. iodine, a hydrogen halide, especially hydrogen iodide, organic iodine compounds, eg. methyl iodide, and volatile halides of aluminum, zinc, boron or phosphorus, are optional.

The resulting slurry is raised to an elevated pressure by pump 6, mixed with hydrogen under pressure from line 7 and passed through converter at a velocity such that a turbulence level (as defined hereinabove) above l0, preferably above 25, is maintained in the converter. As illustrated, converter S comprises a helical -coil of pipe, a preferred form of the converter. Alternatively, the converter may comprise a pipe still type furnace with straight tubes and 180 return bends of the general type employed in petroleum refining operations,

In coil d, which serves the dual function of a retort for the oil shale and a hydrogenation reaction zone for shale oil, the kerogen in the shale is converted to shale oil and, at the same time, hydrogenation of the oil takes place. Heat from a suitable source, for example, furnace 9, is supplied to the heating coil to maintain the reaction temperature within the desired range of 700 to 1,500 F. Average pressure in the reaction coil 8 is of the order of several thousand pounds per square inch gauge, i.e. within the range of 1,000 to 10,000 p.s.i.g. and suitably 3,000 to 5,000 p.s.i.g.

In addition to the retorting and hydrogenation which take place in coil 8, a considerable amount of disintegration of the shale oil particles takes place within the coil due to the combined action of heat and highly turbulent flow. With some oil shales, disintegration takes place as a result of heating under pressure in the presence of oil, as disclosed in U.S. Patent 2,793,194 to H. V. Rees. Additional pulverization of the oil shale particles results from the highly turbulent flow and resulting collisions of particles with one another and with the wall of the reactor. The resulting mixture of treated pulverized shale, shale oil, and residual hydrogen is discharged from conversion coil 8 through line 11 into separator 12 without reduction in pressure.

The primary purpose of separator 12 is to effect separation between residual solid and oil product. At the base of separator 12, hydrogen from a suitable source is introduced through line 14 effecting stripping of oil and oil vapors from the residual shale solids. All of the hydrogen required for the process is preferably introduced at this point.

Hydrogen, shale oil, and shale oil vapors are discharged from separator 12 through line 16 to a gas-liquid separator 17. In separator 17, which preferably is operated at the same pressure as separator 12, unreacted hydrogen is separated from liquid products and any entrained solids carried over from separator 12. Hydrogen from separator 17 is recycled by compressor 13 to line 7 from which it flows into conversion coil S. Additional fresh feed hydrogen may be, if desired, supplied to the system through line 19.

Residual solid from separator 12, together with part of the oil, is Withdrawn through line 21 to separator 22, preferably operated at the same pressure as separator 12, wherein hydrogen and oil are displaced from the residual solid by means of Water. Water entering through line 23 preferentially wets the solid mineral residue from the shale, displacing oil and hydrogen through line 24 and pressure reducing valve 25 to separator 29. Spent shale and water are discharged through line 26 and discarded.

Separators 12 and 22 may be combined into a single vessel with hydrogen and Water entering at intermediate points in the vessel t d with the hydrogen, vapors, and oil going overhead to separator 17 as illustrated in connection with separator 12 and with Water and spent shale particles being Withdrawn from the bottom of the vessel as illustrated in connection with separator 22.

The separa-tions which are eifected in separators 12, 17, and 22 preferably are carried out at elevated pressure, for example, substantially at the reactor discharge pressure.

Liquid separated `in separator 17, together with any entrained solid which may be present therein (usually a part of lthe oil shale fines), passes through reducing valve 28 into a fractionation system 29 IWhere a final separation is made into various shale oil products. The shale oil recovered in the process is separated into various fractions according to product requirements. A gaseous fraction is taken from the fractionation system through line 31. This gas may be processed 'for recovery of hydrogen in known manner, or used directly for fuel. Liquid products of intermediate boiling ran-ge are drawn from the fractionation system through line 32. Heavy oil, which may contain ne particles of oil shale residue which find their way through the various separators into the fractionation system, is withdrawn through line 33 for disposal in a suitable manner. This oil may be used directly as fuel, e.g. -to supply heat for the process; it is also useful as fuel for the generation of hydrogen for the process by partial combustion with oxygen.

Recycle oil is drawn from the fractionation system through line 34 and supplied to mixer 5 for the preparation of the oil shale feed slurry for the process. Preferably the recycle y.oil is a fraction boiling below the heavy resid-num, eg. having a boiling range of 500 to 700 F.

The process disclosed in U.S. Patent 2,809,104 to Strasser et al. is particularly useful for the conversion of the heavy oil to carbon monoxide and hydrogen. Carbon monoxide so produced may be subjected to a shift conversion operation in the presence of an iron catalyst eecting reaction with steam to produce carbon dioxide and hydrogen. Following removal of carbon dioxide, hydrogen is obtained which is suitable for use in the process of this invention.

Oil from separator 12, containing spent shale, may be withdrawn through line 37, and is suitable for use as fuel in the process or for the production of hydrogen. This oil may be treated for removal of solids or utilized directly as iuel. if oil is Withdrawn from separator V12 through line 37 for use as fuel, it is preferable to separate hydro-gen in known manner therefrom, as by pressure reduction and heating, prior to its use as fuel.

Oil shale compositions from various sources vary considerable in recoverable shale oil content. The recoverable shale oil content may vary from 20 to 120 gallons per ton of shale. ln general, the shale oil contents of commercial sliales fall Within the range of from about 30 to 60 'gallons per ton. Oil shales having a shale oil content of at least 30 gallons of recoverable oil per ton, as determined by the Fischer assay method, are preferred for the present process. The Fischer assay method is described by F. Fischer and H. Schrader, Z. angelw. Chem., 33, I, 172-5 (1920), abstract: C.A., 14, 3149-50 (1920), and in U.S. Bureau Mines, RI. 3977 (October 1946).

The amount of oil mixed with the shale to form a flowable slurry may vary from about 50 to 200 percent by weight, based on the weight of the shale. ln general, about equal weights of shale and oil are desirable in the slurry. Stated another way, the shale content of the slurry may vary from about 35 to about 65 weight percent. About 35 weight percent oil (65 weight percent shale) is generally the minimum oil required to form a owable slurry. Larger amounts of oil than the above indicated 65 weight percent may be employed but generally are not required no-r desirable.

6 Examples Oil shale having a Fischer assay of 27.7 gallons per ton is treated by the process of this invention. The shale oil recovered from this shale by a conventional retorting procedure has the following characteristics:

API gravity 20 Viscosity:

SUS at 130 F 145 SUS at 210 F 48 Pour point, VF +90 Sulfur in oil, Wt. percent 0.7 Nitrogen in oil, Wt. percent 2.6 Carbon residue, Wt. percent 4.4 ASTM distillation: F.

The oil shale is crushed to minus 20 mesh (US. Bureau of Standards Standard Screen Series, 1919), mixed with an equal 'weight of treated oil from the process, and treated without a catalyst under the conditions and with the :results indicated in the following table. ln each instance, the Ihydrogen stream and the slurry o-f shale in shale oil are separately preheated to approximately reaction temperature. After combining the hydrogen with the slurry, the composite mixture is passed through a one thousand foot tubular reactor havin-g an internal diameter of 0.312 inch.

Examples Average temperature, F 700 700 740 800 Average pressure, p.s.i.g 3,000 5,000 5,000 5,000 Turbulence level, ave 150 140 130 Total hydrogen feed rate std. cu.

bl. oil 27, 400 21,000 26, 000 29, 000 Hydrogen feed purity, vol. pereent 89 82 7G 74 H2 consumed, cu. ftjbbl. oil 430 580 665 1, 630 Liquid yield, vol. percent 1 99. 7 100. 7 96. 9 81.6 API Gravity 27. 7 20. 5 28. 7 86. 7 Viscosity- SUS at 100 F 74.0 77.0 42.0 32 0 SUS at 210 F 32.5 ASTM Distillation:

. .P., 165 200 158 110 1.13.9.-400 F., vol. pereent 15 12 25 G0 400-760 F., vol. perccnt 61 60 65 28 Above 760 F., vol. percent. 24 28 10 1?. Sulfur, Wt. percent 0. 34 0. 68 0.27 0. 13 Nitrogen, Wt. percent." 1. S9 1. 74 2.1/1 2. 47 Carbon residue, Wt. percent 2. 83 2. 99 2. 77 2. 70

l Basis Fischer assay yield.

Obviously many modifications and variations of the invention, as hereinbefore set forth, may be made without eparting from the spirit and scope thereof, :and thereif re only such limitations should be imposed as are indicated in the appended claims.

We claim:

l. The method of recovering oil of improved physical properties from oil shale which comprises forming a pumpa le mixture of oil shale particles in a carrier liquid selected from the group consisting of Water and treated shale oil as defined hereinafter, passing said mixture together with hydrogen in the range of 1,000 to 100,000 standard cubic feet of hydrogen per barrel of said mixture through a tubular retorting Zone of relatively small diameter at a velocity sufficient to maintain highly turbulent ilow with a turbulence level 4above 25 as expressed by the ratio wherein em is the average eddy viscosity and 1/ is the kinematic viscosity, subjecting sai-d mixture to reaction with hydrogen in said rcterting zone at a temperature in the range of 71K)I to 1500 F. and a pressure in the range of 1,560 to: 10,00) psig. for a period of time within the range of 1 to 390 .seconds simultaneously retoning oil from said oil shale and llydrogenatinrg Isaid retorted shale Oil, said mixture being maintained in Said tubular reaction Zone under said pressure :and turbulence conditions until said rctortirrg is -tsubstanially complete, and thereafter recovering resuiting treated shale :oil from residual solid material from said oil shale.

2. The method according to claim 1 in which water is included in said pumpable mixture as charge to said tubular retori-ng zone.

3. The method according to elan 1 wherein the mix- 8 tureirl tlie retoring zone is subjected .to an average turbulence level in the range of 101') to 150 and a tempel-attire or" the order of 7G() to 9C-0 i?. under a pressure of the order of 3,300 to 5,006 pounds per square inch.

Referenees Cited in the lle of this patent UNITED STATES PATENTS 1,458,983 Kirby June 19, 1923 2,207,494 Viktera. July 9, 194() 2,639,982 Kalbach May 26, 1953 2,658,861 Pevere etal Nov. 10, 1953 2,793,104 Rees May 11, 1957 2,847,306 Stewart et al Aug. 12, 1958

Claims (1)

1. THE METHOD OF RECOVERING OIL OF IMPROVED PHYSICAL PROPERTIES FROM OIL SHALE WHICH COMPRISES FORMING A PUMPABLE MIXTURE OF OIL SHALE PARTICLES IN A CARRIER LIQUID SELECTED FROM THE GROUP CONSISTING OF WATER AND TREATED SHALE OIL AS DEFINED HEREINAFTER, PASSING SAID MIXTURE TOGETHER WITH HYDROGEN IN THE RANGE OF 1,000 TO 100,000 STANDARD CUBIC FEET OF HYDROGEN PER BARREL OF SAID MIXTURE THROUGH A TUBULAR RETORTING ZONE OF RELATIVELY SMALL DIAMETER AT A VELOCITY SUFFICIENT TO MAINTAIN HIGHLY TURBULENT FLOW WITH A TURBULENCE LEVEL ABOVE 25 AS EXPRESSED BY THE RATIO $M/V WHEREIN $M IS THE AVERAGE EDDY VISCOSITY AND V IS THE KINEMATIC VISCOSITY, SUBJECTING SAID MIXTURE TO REACTION WITH HYDROGEN IN SAID RETORTING ZONE AT A TEMPERATURE IN THE RANGE OF 700 TO 1500*F. AND A PRESSURE IN THE RANGE OF 1,500 TO 10,000 P.S.I.G. FOR A PERIOD OF TIME WITHIN THE RANGE OF 1 TO 300 SECONDS SIMULTANEOUSLY RETORTING OIL FROM SAID OIL SHALE AND HYDROGENATING SAID RETORTED SHALE OIL, SAID MIXTURE BEING MAINTAINED IN SAID TUBULAR REACTION ZONE UNDER SAID PRESSURE AND TURBULENCE CONDITIONS UNTIL SAID RETORTING IS SUBSTANTIALLY COMPLETE, AND THEREAFTER RECOVERING RESULTING TRATED SHALE OIL FROM RESIDUAL SOLID MATERIAL FROM SAID OIL SHALE.

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