US2627499A - Catalytic distillation of shale - Google Patents

Description

Feb. 3, 1953 R. w. KREBs 2,527,499

CATALYTIC DlsTILLATIoN 0F SHALE Filed June 11. 1947 A12. AMD matr @N5 IN1-U' Robert CDKreBS BfJ-Ve-flbof @DS Z- NW Clbbovaec-QS Patented Feb. 3, 1953 CATALYTIC DISTILLATIN OF SHALE Robert W. Krebs, Baton Rouge, La., assigner to Standard Oil Development Company, a corporation of Delaware Application 'June 11, 1947, serial No. 754,028

(ci. 2oz-6) 12 Claims.

The present invention relates to the art of distilling 4carbonizab'le solids. Mere particularly, the present invention relates to a novel process for the recovery of valuable volatile fuels such as combustible gases, motor fuels, heating and fuel oils from oil-bearing minerals such oil shalc, oil sands, 'tar sands, and the like.

It Iis known that certain types of naturally occurring oil-bearing minerals, such as oil shale, contain materials which may be converted by a pyrol'ytic treatment into hydrocarbon oils, including oils boiling in the gasoline and gas oil ranges, in commercially feasible yields.

Prior to the present invention, others proposed Acarrying out the pyrolytic treatment of the shale in the form of a powder or rather large aggregates of up to about 1/4 in. diameter, in a highly turbulent state, fluidized by an upwardly flowing gas, in a distillation or pyrolytic zone, while supplying the heat necessary for the reaction by combastion, that is, either by burning a portion of the combustibles in the distillation or pyrolitic zone, or by burning the spent shale in a` separate combustion zone and returning the burnt substantially uncooled shale to the distillation or pyrolytic zone. The former method has the advantage of a simple design whilethe latter method permits the production of oil free of gaseous combustion products. However, all these processes have marked disadvantages. t

It is a matter of record that oil shale disintegrates rapidly in the process of distillation to form powders of extremely small particle size, substantially independent of the particle size at which the shale is supplied to the distillation zone initially. The disintegrated shale powder is so fine that it seriously interferes with the maintenance of proper iiuidization conditions which normally require a relatively low percentage of say, less than 20%, of particle sizes below 20 microns. However, the oil shale powder formed during distillation has a particle size generally below 40 and mostly below 20 microns which results in channelling and slugging thus vitiating most of the advantages of fluid operation such as perfect heat distribution and transfer, etc.

The product recovered from conventional shale distillation processes consists predominantly of gas oils Straight-run gasoline is produced in poor yields and relatively poor quality. Particularly the octane rating and volatility distribution are unsatisfactory, in comparison with the corresponding characteristics of cracked gasolinas.

The present invention has for its principal ob ject the improvement of iluid oil shale or oil sand distillation processes with respect to both fluidity characteristics and gasoline yields and quality.

and higher boiling hydrocarbons.;

In accordance with the present invention, finely divided olif-bearing minerals of the type specified are subjected to distillation in the form `of a dense, turbulent, fluidizled mass of solids in the presence of a nelydivided conventional cracking catalyst having a particle size substantially larger than the particle size of` the oil-bearing mineral after disintegration during the dist' tion process. The amounts of relatively lca cracking catalyst are so `chosen that the particle size distributionl vof the fluidized solids phase is `maintained within ell-iluidizable ranges 'and that substantial cracking of gas oil range and heavier hydrocarbons into gasoline range products takes place. y, t

Well fluidizable particle size ranges may fall within the approximate limits given below:

. Per cent 0-20'1nicrons I --.i less than 2O 20-i0 microns 10-25 Llil-80 microns `20-30 80+ microns 2B-35 While the above size distribution is preferred` and affords excellent fluidization, it should beunderstood that good iluidization may be obtained at different distributions provided` that neV and coarse sizes are properly adjusted. (For example, the particles of less than 20 micronsniay amount to as much as about V50% if sui'cient, amounts ,of particles of intermediate ranges, say of 2074-80y microns size, are present. ,A substantial propor tion of the particles above 2() micron size 'required for proper fluidization will normally be present in the form of fresh process solids which may be charged in desirable sizes and which maintain their original size for a limited length of time.

The cracking catalyst becomes rapidly deactivated mainly clue to the formation of carbon which deposits on the catalyst. As aresult'of the larger particle Vsize of the catalyst, deactivated carbonized catalyst may be readil'yseparated from the ner particles of the treated mineral, by taking advantage of the difference rin gas buoyancy of the `particles to be` separated. The carbonized and Aselnarated catalyst may be regenerated in aV conventional fluid regeneration zone by a combustion reaction with 'anoxi'di'zing gas and returned to the distillation zone. "In this manner, heat generated by th'e cliibrstiorir'eaction may be supplied to the cracking-distillation zone as sensible heat of the catalyst, arprocedure which is known per se in the a'rt if catalytic cracking. Y

The amount of catalyst required in the distillation zone and in circulation` between the distillation and regeneration znes` will therefore depend on the particle size distribution Within the iiuid distillation ,zorie, the parti-cle size', specific gravity and cracking activity of the catalyst, and the amount of heat which it is desired to supply to the distillation zone as sensible heat ofregenerated catalyst. It will be appreciated that this amount of catalyst may vary Within fairly wide ranges. Quite generally, it may be stated, however, that when using such conventional cracking catalysts as Super Filtrol (which is a bentonite clay, containing largely hydrated aluminum silicates, which have been acid treated), silica-magnesia catalyst containing 30-35% magnesia, or silica-alumina catalysts containing -20% alumina, preferably in the form of microspheres, in particle sizes of about 50-500 microns and assuming a disintegrated particle size of the process solids of less than 40 microns and a crackable oil content of the process solids of about 0.3-1.0 bbl. per ton, an amount of about 10% to 400% of circulating catalyst based on process solids, is usually adequate depending on the proportion of heat supply desired in the form of sensible heat of catalyst. For example, the amount of circulating catalyst may be about -100% "by weight of a shale containing about 0.5 bbl. of cracka'ble oil per ton. 'Ihe proportion of catalyst in the distillation zone itself may fall within similar ranges. Any additional heat required may be supplied as preheat of solid and/or gaseous process materials and/or by conducting a limited combustion Within the distillation zone itself.

Separation of coarse catalyst from process solids fines may be readily accomplished by so controlling the superficial velocity of the iiuidizing gas within the distillation zone that process solids nes are fully entrained and carried overhead by the fluidizing gas while the distintegration of coarse catalyst is insignificant and it remainsin the distillation zone as Ia dense uidized solids phase from which it may be Withdrawn downwardly and separately from the rines as a stream of uidized solids. Superficial gas velocities of about 0.5-3 ft. per second, preferably about 1 ft. per second are normally adequate at the particle size distribution indicated above.

The temperatures in the distillation zone may be those usually employed in the distillation yof oil shades, that is about 8001100 F. These temperatures are simultaneously conducive to appreciable catalytic cracking of gas oil and heavier hydrocarbons at relatively low presssures of atmospheric to about 10 atmospheres. Catalyst regeneration is preferably carried out at slightly higher temperatures, say about 100200 F. higher, and at substantially atmospheric pressure.

It will be appreciated from thev foregoing that the present invention affords substantial improvements with respect to both uidization control and gasoline yield. Simultaneously, the gasoline quality is considerably improved as a result of the beneficial influence of the catalytic .cracking reaction on octane rating and volatility distribution.

Having set forth its general nature and objects the invention will be best understood from the more specific description hereinafter where- `in reference will be made to the accompanying ydrawing the single figure of which is a partly schematical, partly diagrammatlcal illustration of a system suitable for carrying out a preferred embodiment of the invention.

Referring now in detail to the drawing the system illustrated therein essentially comprises a cracking-distillation chamber I5 and a regenerator-combustion chamber the functions and cooperation of which will be forthwith described using as an example the treatment of an oil shale containing about 0.5 bbl. of oil constituents per ton. It should be understood, however, that other oil-bearing minerals may -be treated in a substantially analogous manner.

In operation, feed hopper I contains fresh oil shale crushed to a particle size of about -100 microns, which may be dried and preheated, preferably in heat exchange with hot product or iiue gases, to a temperature of about 10W-'700 F. The preheating gases may be supplied through lines 3 to serve simultaneously as aeration gases maintaining the shale feed in a readily flowing, quasi-fluid state. Fresh preheated finely divided shale flows from hopper l downwardly through a conventional standpipe 5 aerated through one or more taps 0 with small amounts of steam or fiue gas to facilitate the solids flow which may be controlled by slide valve 8.

Fresh shale discharges under the pseudohydrostatic pressure of standpipe 5 into line I0. Simultaneously, a gas is supplied to line Iii which may be `an inert or a free oxygen-containing gas such as air or air diluted with steam or iiue gas, preheated preferably by heat exchange with 'hot product or waste gases or solids, to a temperature of about 8001200 F. The fresh shale is suspended in this gas to form a relatively dilute suspension which is forced under the pressure of standpipe 5 upwardly through pipe I2. The suspension enters chamber I5 through a conical distributing device IS provided with a perforated cover plate such as a grid I4.

Chamber I5 contains a mass of nely divided cracking catalyst such as Super Filtrol clay hav- -ing a particle size larger than 50 microns, say about 1D0-500 microns. The bulk of this catalyst may be supplied to chamber I 5 from feed hopper I in the initial stages of the process substantially as described above in connection with .the fresh shale feed. Make-up catalyst may be continuously or periodically supplied together with the fresh shale as required. The dimensions vvof chamber I5, the superficial velocity of the gas supplied through line I2 and the amount of catalyst are so correlated that the combined catalyst and fresh shale particles form a dense, highly turbulent mass I1 of fluidized solids having la well defined upper level L15 and providing for an average shale residence time within said dense mass of about 0.5-5 minutes, preferably -about 1-3 minutes. Superficial gas velocities within the range of about 0.5-3 ft. per second and a catalyst to fresh shale weight ratio of about 0.5 to 1, are generally suitable for this purpose.

The temperature within chamber E5 is maintained preferably at about 800-1000 F. This may be accomplished either by sufciently preheating the process solids and gases as indicated above or by conducting a limited combustion of combustible shale constituents within mass Il' or by supplying suitable proportions of hot regenerated catalyst from regeneratcr t5 as will appear more clearly hereinafter, or by any suitable combination of these heating means. For example, temperatures of the range specified may be maintained by preheating the shale to about 600 F., preheating the gas in line I@ to about 1000 F., supplying about 0.1 to 0.2 molsrof oxygen noemen andabout 1000 to 2000 normal cu. ft. of total gas through line l2 and recycling about 1 ton of regenerated catalyst having a temperature of about l100*1200 F. from regenerator t5, per ton of shale to be treated. The pressure within chamber I5 is preferably maintained. at about 3 to 30 lbs. per sq. in. gauge.

At the conditions specined the shale undergoes rapid distillation and disintegration. After, say, about half of its total residence time in mass il' the shale particles may have disintegrated to an average particle size smaller than that of the catalyst, to be reduced to sizes below microns during the remainder of the residence time. The oil evolved during this transformation is cracked into predominating proportions of gasoline. At the prevailing gas velocities a substantially com plete separation of catalyst and substantially spent shale fines having particle sizes below 20 microns is accomplished, the shale fines being carried as gas entrainment upwardly beyond level L15 and the larger catalyst particles which are not subject to disintegration remaining within mass il.

Volatile cracking and distillation products and entrained spent shale fines are Withdrawn overhead from level L15 and passed through line i@ to a gas-solids separation system 2|, 23 which may comprise conventional centrifugal and/ or electric precipitators. Volatile products are withdrawn through line 2d and passed to a conventional product recovery (system not shown). Separated spent shale fines are collected in vessel 2l'. Their sensible heat may be used substantially at the temperature of chamber i5 to preheat process gases, using any suitable conventional means of heat exchange. Spent shale may be finally removed through line 2t. Its residual carbon content is available for fuel purposes, for example to generate .steam used in the process.

As a result of the extensive cracking taking place in chamber i5 the cracking catalyst becomes deactivated by carbon deposition and must be regenerated. For this purpose catalyst is withdrawn. from the lower portion of `chamber l5, preferably from a point below distributing device i3 through a conventional standpipe t5 aerated through one or more taps 3l and provided with slide valve Eil. In order to prevent spent shale particles of smaller than catalyst size from entering pipe additional amounts of fluidizing gas may be supplied through lines El to the annular space 33 formed by cone I3 and chamber l5, so as to exert an elutriating eifect on the solids in annular space t3. The fluidizing gas supplied through lines Si may simultaneously act as a stripping gas to remove adhering valuable volatiles from the catalyst prior to its removal from chamber I5.

Deactivated catalyst which normally includes only insignificant amounts of shale particles of similar size flows under the pseudo-hydrostatic pressure of standpipe S5 through control valve Si! into pipe lli. An oxidizing gas such as air and/or oxygen, preferably preheated in heat exchange with process flue gases to about 800- lc" is supplied to line il and carries the spent catalyst as a dilute suspension upwardly into regenerator l5 through a distributing device it similar to device i3, under the pressure of standpipe 35. The amount of oxygen supplied through line si should be sufficient to remove about fio-100% of the carbon on the catalyst by combustion. About 0.5 to 5 mols of oxygen per ton of Ashale treated is usually suiicient for this '..purpose.

The catalyst-in-gas suspension enters regen erator lib at a superficial `gas velocity of about 0.5-3 ft. per second to form a dense iiuidized solidsmass '4l therein, similar to mass Il. The temperature within mass lll is preferably maintained at about 10001200 F. by any conventional cooling means (not shown). Higher temperatures may be employed if they have no adverse effect on the catalyst. Hot flue gases which contain some `entra-ined catalyst are Withdrawn overhead from level L45 and passed to a gas solids separatorsuch as a cyclone Gil. Flue gases free of solids are Withdrawn through line 5i to be used for heat'exchange With process gases and solids as described above. Separated catalyst may be returned to mass lil through line E2 and catalyst particles of undesired small sise may be discarded through line 53.

Regenerated catalyst is withdrawn downwardly from regenerator [l5 through a conventional standpipe 55 aerated through taps 56 and'provided with control valve 5l. The `solids flow from regenerator ll'e may be facilitated by injecting small amounts of fluidizing gas such as air into annular space E12 through taps 5ft. `Catalyst. from standpipe 5t discharges under the pressure of this standpipe into line 59 wherein it is taken up by a carrier gas which maybe an inert or combustion supporting gas similar to that supplied to line i@ and preheated to about the same temperature. The catalyst suspension in line 59 is passed substantially at the temperature of regenerator 45 to line l2 and from there to chamber i5, to complete the cycle. As previously stated the amount of catalyst circulating through lines d5, fil, 55 and 59 should be about 0.2 to l ton per ton of fresh shale treated at the conditions indicated.

The system illustrated by the drawing permits of various modifications. Instead of supplying fresh shale through standpipe 5 and gas-suspen sion line i2 to the bottom portion of chamber l5 it may be desirable in many cases to charge the fresh shale to the top of chamber l, for instance by gravity from a hopper 50 through line il i This arrangement is of particular advantage when substantial amounts of heat are to be generated by combustion Within chamber i5. W hen feeding the combustion supporting gas to the bottom and the fresh shale to the top of chamber it a slight degree of countencurrent flow of solids and gases is accomplished resulting in the contact of the combustiomsupporting gas predominantly with carbonized rather than with fresh shale whereby excessive losses of valuable volatiles by combustion are avoided. If the amount of carbon deposited on the catalyst is insufficient to generato the desired amount of heat by combustion in regenerator t5 additional fuel in the form of a fuel gas or, preferably, in the form of shale circulated from still iii may be supplied to regenerator t5. Instead of using standpipes 5, 35 and lib other conventional means for conveying finely divided solids such as lock hoppers, mechanical conveyors, etc. may be employed. The process of the invention may be conducted in a fully continuous manner by continuously charging process solids and gases, continuously withdrawing product vapors and solids and continuously circulating the. cati alyst as indicated. @ther vmodifications, may ocour to those skilled in the art.

1t will be undersood that the gasoline yields obtainable by the process of the invention depend largely on the starting material used and the specic conditions applied. Quite generally the invention may permit an increase of about -100% in the straight-run gasoline yield as compared with conventional operation. The octane number of this gasoline may reach 60-75 by the research method as compared with about Llllin conventional operation.

While the foregoing description and exemplary operations have served to illustrate specic applications and results of the invention, other modifications obvious to those skilled in the art are within the scope of the invention. Only such limitations should be imposed on the invention as are indicated in the appended claims.

I claim:

l. In the method of distilling oil-bearing minerals which tend to disintegrate upon distillation, to produce therefrom volatile products rich in gasoline-range constituents by subjecting the finely divided starting material to distillation temperatures in a dense turbulent mass of iinely divided solids fluidized by an upwardly flowing gas in a distillation zone, the improvement which comprises admixing with said material undergoing distillation a relatively disintegration resistant cracking catalyst having a particle size substantially larger than 50 microns, the particle size of said material after distillation being substantially smaller than 50 microns and amounting to less than about by weight of said mass so as to maintain a well fiuidizable particle size distribution in said mass, recovering a gas-distillate mixture containing cracked gasoline from said distillation zone, and controlling the superoial velocity of said gas so that particles of said material disintegrated to said size reached after distillation are preferentially entrained and carried out of said mass by said mixture and catalyst particles are preferentially retained.

2. The process of claim 1 in which particles of less than 20 microns size within said mass amount to less than 50% by weight of said mass.

3. The process of claim 2 in which the supercial velocity of said gas is about 0.5-3 ft. per second.

4. The process of claim 1 in which said temperature is about 8001000 F.

5. The process of claim 1 in which said gas contains oxygen supporting a limited combustion within said distillation zone yand said material is charged to said distillation zone counter-currently to said gas.

6. The process of claim 1 in Vwhich said material is oil shale.

7. The process of claim 1 in which the particle size of said catalyst is about 10G-500 microns.

8. In the method of distilling oil-bearing minerals which tend to disintegrate upon distillation, to produce therefrom volatile products rich in gasoline-range constituents by subjecting the finely divided starting material to distillation temperatures in a dense turbulent mass of finely divided solids fluidized by an upwardly flowing gas in a distillation zone, the improvement which comprises admixing with said material undergoing distillation a relatively disintegration resistant cracking catalyst having a particle size substantially larger than 50 microns, the particle size of said material after distillation being substantially smaller than 50 microns and amounting to less than about 60% by weight of said mass so as to maintain a well uidizable particle size distribution in said mass, recovering a gas-distillate mixture containing cracked gasoline from said distillation zone, controlling the superficial velocity of said gas so that particles of said material disintegrated to said size reached after distillation are preferentially entrained and carried out of said mass by said mixture and catalyst particles are preferentially retained, withdrawing solids consisting predominantly of catalyst from said mass separately from said material and said mixture, passing said withdrawn solids to a regeneration zone, contacting said withdrawn solids in said regeneration zone with a combustion-Supporting gas to burn olf carbon from said catalyst and to regenerate said catalyst, and returning said regenerated catalyst to said distillation zone.

9. The process of claim 8 in which said regeneration zone is maintained at a temperature substantially higher than said distillation temperature and said catalyst is returned substantially at said higher temperature.

10. The process of claim 9 in which said catalyst circulating from said regeneration zone to said distillation zone amounts to about lil-400% by Weight of said material subjected to distillation Within the same time.

1l. The process of claim 8 in which heat of the gaseous combustion products from said regeneration zone is transferred to said distillation zone.

12. A method of distilling oil-bearing minerals which tend to disintegrate upon distillation, to produce therefrom volatile products rich in gasoline-range constituents by subjecting the nely divided starting material to distillation temperatures in a dense turbulent mass of nely divided solids fluidized by an upwardly flowing gas in a distillation zone, which comprises adinixing with said material undergoing distillation a relatively disintegrationV resistant cracking catalyst having a particle size of about 10S-560 microns, said material after distillation having a particle size substantially smaller' than 56 microns and amounting to less than about 6Gl% by weight of said mass, so as to maintain a well fiuidizable particle size distribution in said mass, preferentially entraining disintegrated particles of said materialA in said gas and preferentially retaining catalyst in said mass by maintaining the superficial gas velocity within said mass at about 0.53 it. per second, removing a distillate containing cracked gasolinavuidizing gas, and disintegrated particles overhead from said zone and separately removing solids consisting predominantly oi" catalyst from said mass. ROBERT W. KREBS.

CES CITED The following references are of record in the ille of this patent:

UNITED STATES PATENTS Number Name Date 1,276,879 Crane Aug. 27, 1916 1,941,809 McKee f Jan. 2, 1934 1,983,943 Odell Dec. 11, w34 1,984,380 Odell Dec. 18, 1934 2,327,175 Conn Aug. 17, 1943 2,480,670 Peck Aug. 30, 1949 2,573,986 Hui Nov. 6, i

FOREIGN PATENTS Number Country Date 189,542 Great Britain Dec. l, 1922

Claims (1)

1. 8. IN THE METHOD OF DISINTEGRATE UPON DISTILLATION, ERALS WHICH TEND TO DISTINEGRATE UPON DISTILLATION, TO PRODUCE THEREFROM VOLATILE PRODUCTS RICH IN GASOLINE-RANGE CONSTITUENTS BY SUBJECTING THE FINELY DIVIDED STARTING MATERIAL TO DISTILLATION TEMPERATURES IN A DENSE TURBULENT MASS OF FINELY DIVIDED SOLIDS FLUIDIZED BY AN UPWARDLY FLOWING GAS IN A DISTILLATION ZONE, THE IMPROVEMENT WHICH COMPRISES ADMIXING WITH SAID MATERIAL UNDERGOING DISTILLATION A RELATIVELY DISINTEGRATION RESISTANT CRACKING CATALYST HAVING A PARTICLE SIZE SUBSTANTIALLY LARGER THAN 50 MICRONS, THE PARTICLE SIZE OF SAID MATERIAL AFTER DISTILLATION BEING SUBSTANTIALLY SMALLER THAN 50 MICRONS AND AMOUNTING TO LESS THAN ABOUT 60% BY WEIGTH OF SAID MASS SO AS TO MAINTAIN A WELL FLUIDIZABLE PARTICLE SIZE DISTRIBUTION IN SAID MASS, RECOVERING A GAS-DISTILLATE MIXTURE CONTAINING CRACKED GASOLINE FROM SAID DISTILLATION ZONE, CONTROLLING THE SUPERFICIAL VELOCITY OF SAID GAS SO THAT PARTICLES OF SAID MATERIAL DISINTEGRATED TO SAID SIZE REACHED AFTER DISTILLATION ARE PREFERENTIALLY ENTRAINED AND CARRIED OUT OF SAID MASS BY SAID MIXTURE AND CATALYST PARTICLES ARE PREFERENTIALLY RETAINED, WITHDRAWING SOLIDS CONSISTING PREDOMINANTLY OF CATALYST FROM SAID MASS SEPARATELY FROM SAID MATERIAL AND SAID MIXTURE, PASSING SAID WITHDRAWN SOLIDS TO A RE-

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