US3484364A

US3484364A - Fluidized retorting of oil shale

Info

Publication number: US3484364A
Application number: US620124A
Authority: US
Inventors: Charles E Hemminger
Original assignee: Exxon Research and Engineering Co
Current assignee: ExxonMobil Technology and Engineering Co
Priority date: 1967-03-02
Filing date: 1967-03-02
Publication date: 1969-12-16
Anticipated expiration: 1986-12-16

Description

United States Patent O US. Cl. 20811 7 Claims ABSTRACT OF THE DISCLOSURE Oil shale is contacted with hot hydrogen in a fluidized system under conditions to conserve heat, to give increased yields and to produce products which are susceptible to removal of nitrogen. The hot hydrogen con-.

taining gas is produced from the cracking of a heavy residue recycle in the presence of the hydrogen containing gas. The cracking takes place in a separate zone and supplies at least a portion of the heat necessary for the retorting of the shale.

FIELD OF THE INVENTION The present invention is direced to retorting of oil shale. More particularly, the invention is concerned with the fluidized retorting of oil shale. In its more specific as pects, the invention is concerned with the fluidized retorting of oil shale by contact of the fluidized oil shale with a hot free hydrogen-containing gas.

DESCRIPTION OF THE PRIOR ART It is known to retort oil shale under fluidized conditions. It is also known to retort oil shale by contact of oil shale in a bed with hot hydrogen. The U.S. patents listed below constitute the prior art considered with respect to the present invention:

None of the aforementioned prior art teaches the retorting of oil shale with hot hydrogen in a fluidized system. Neither does the prior art teach the production of a product from retorting in the presence of hydrogen in a fluidized system from which nitrogen is readily removed. The prior art also does not teach that oil shale particles having small diameters such as oil shale fines may be retorted in a fluidized system.

SUMMARY The present invention may be briefly described and summarized as involving the retorting of crushed oil shale in which a hot free hydrogen-containing gas is employed to retort the crushed oil shale and in which the crushed oil shale is introduced into and flows serially through a preheating zone, retorting zone, and a cooling zone. In the present invention, crushed oil shale including particles having diameters less than about 4 to about inch, preferably less than A inch, is flowed counter-currently to free hydrogen-containing gas under fluidized conditions to form the crushed oil shale into fluidized beds in each of said zones and to decompose kerogen in the crushed oil shale to vaporized shale oil in said retorting zone. A product is recovered from the preheating zone comprising shale oil and free hydrogen-containing gas. The product is separated into shale oil which is recovered and is distilled to recover a heavy residue from the shale oil boiling above about 800 F. which is admixed with free hydrogen-containing gas and subjected to cracking conditions to crack the heavy residue and to form the free hydrogen-containing gas used in retorting the crushed oil shale. By operating in this manner, heat is conserved and cracking of the heavy residue provides a shale oil from which nitrogen is readily removed. Heat from consumption of hydrogen in the retorting zone provides at least a portion of the heat of reaction for retorting the crushed oil shale and finally increased yields are obtained.

BRIEF DESCRIPTION OF THE DRAWING DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawing, numeral 11 designates a preheating zone, numeral 12 designates a retorting zone, and numeral 13 designates a cooling zone. Crushed or ground oil shale containing fine particles having diameters ranging from about 0.1 to about 0.01 inch and having diameters less than about to about 3/ inch are introduced into the system by Way of conduit 14 which may suitably include a lock hopper mechanism for introducing the crushed or ground oil shale. The small diameter particles or fines may comprise from about 1% to about 20% by weight of the shale introduced by conduit 14, but ordinarily will comprise from about 5% to about 15% by weight. In preheating zone 11 the crushed oil shale is heated to a temperature within the range from about 200 to about 500 F., preferably about 300 F., by contact with free hydrogen-containing gas and vapors introduced into zone 11 by line 15 from retorting zone 12. The preheated oil shale from zone 11 is discharged into retorting zone 12 by way of line 16, it being noted that the crushed or ground oil shale and the free hydrogencontaining gas and vapors flow counter-current to each other.

In retorting zone 12 the preheating crushed oil shale is retorted at a temperature within the range from about 700 to about 1000 F. by contact with hot free hydrogencontaining gas, the source of which will be described further. The amount of hot free hydrogen-containing gas may range from about 10,000 to about 18,000 cubic feet/ton of crushed oil shale introduced into preheating zone 11. The retorted oil shale is discharged from zone 12 by way of line 17 into cooling zone 13 wherein it is contacted with cooling free hydrogen-containing gas at ambient temperatures which is introduced into zone 13 by line 18 from a source which will be described further while the spent oil shale, containing about l3% of carbonaceous material, is discharged from zone 13 by conduit 19 on to conveying means such as a conveyor belt for conveying the spent oil shale to a waste pile.

In cooling zone 13, the retorted oil shale is cooled to a temperature within the range from about 200 to about 400 F. Preferably the retorted shale is cooled to a temperature of about 225 F.

The free hydrogen-containing gas introduced by line 18 into zone 13 is preheated to a temperature Within the range from about 650 to about 950 F. by contact in zone 13 with the retorted oil shale introduced from zone 12 by line 17. The preheated free hydrogen-containing gas is then introduced by line 20 containing a compressor 20a into a heating means such as a furnace 21 where it is heated in admixture with a suitable amount of heavy residue introduced into line 20 by line 22 from a source which will be described further. Compressor 20a offsets any pressure drop in furnace 20. This heavy residue 18 preferably a heavy residue from shale oil and is employed in an amount of about 8 to about 15 gallons/ton of raw oil shale introduced by conduit 14. A suitable amount may be about 12 gallons/ton of raw oil shale. The mole ratio of free hydrogen to heavy residue is within the range of to about 50. In furnace 21, the hydrogen and heavy residue mixture is subjected to elevated temperatures within the range from about 800 to about 1200 P. which cause hydro-cracking of the heavy residue and heating of the free hydrogen-containing gas. Small amounts of fine shale carried in the gas from vessel 13 in line 20 scour and keep clean the tubes in furnace 21. A mixture of hot vapors and hot free hydrogen-containing gas is discharged from furnace 21 by line 23 into retorting zone 12 at a temperature of about 800 to about 1300 F. for retorting the preheated oil shale introduced into zone 12 by line 16 and to cause decomposition of kerogen to vaporize shale oil. If desired, a portion of the preheated hydrogen in line 20 may be introduced by line 20b controlled by valve 20c into line 23 by passing furnace 21 to provide flexibility of flow through furnace 21. It also may be desirable to flow hot preheated hydrogen and recycle gas directly from zone 13 to zone 12. To this end line 23a controlled by valve 23b allows all or part or none of the gasses from zone 13 to be introduced directly into zone 12. With this mode of operation compressor 20a would be utilized to introduce makeup hydrogen into furnace 21 allowing compressor 20a to operate with a low rather than a high temperature inlet as is the case when it is used to offset pressure drop when moving gas from zone 13 into furnace 21.

When gas is fed directly from zone 13 to zone 12, furnace 21 will have a higher exit temperature Within the range of about l400 to 1600 F. because of decreased gas flow through it.

Product comprising hydrogen and hydrocarbon vapors including vaporized shale oil is withdrawn from zone 11 by line 24 containing a condenser-cooler 25 which serves to cool the gases and vapors and to allow a separation between gases and liquids in separation zone 26. In separation zone 26, water produced in the operation separates and is withdrawn from water leg 26a by line 27 controlled by valve 28. Free hydrogen and other gases are separated in zone 26 and withdrawn by line 29 for use as will be described further. Hydrocarbons including shale oil and the products of cracking in furnace 21 are withdrawn by line 30 and introduced thereby into a distribution zone 31 which suitably may be a fractional distillation tower provided with all auxiliary means for effective fractional distillation including vapor-liquid contacting means, condensing and cooling means, and the like. By way of illustration, distribution tower 31 is provided with a heating means such as a steam heating coil 32 to allow fractional distillation of the hydrocarbons into various fractions as may be desired. For example, an overhead fraction comprising light components is withdrawn by line 33, a side stream of heavier hydrocarbon materials is withdrawn by line 34, and a still heavier fraction which may include gas oil components is recovered by line 35. Heavy residue having a true boiling point of 800 or above may be discharged by line 36 and introduced by branch line 37 and line 22 into line 20 for admixture of free hydrogen-containing gas introduced into furnace 21. If desired, a portion of the heavy residue in line 36 may be discharged from the system by opening valve 38. Likewise, heavy material from another source may be introduced into line 20 by opening valve 39 in line 22. If desired, such heavy material may be introduced into zone 12 by line 39a controlled by valve 3%.

To avoid build up of undesirable gases in the system, from time to time it may be desirable to discharge a portibn of the recycle gas from line 29 by opening valve 40. Make-up hydrogen may be introduced into line 18 by opening valve 41 connecting to a source of free hydrogen containing gas.

The free hydrogen-containing gas employed in the present invention may be pure hydrogen, but preferably .4 is a free hydrogen-containing gas containing from about to about mole percent of free hydrogen with other components including gaseous or vaporous hydrocarbons and the like such as 0.5 to 10% of CH C H CO N and CO.

In the practice of the present invention the free-hydrogen-containing gas is flowed through the several zones at a suflicient velocity to provide fluidized beds. For example, the hydrogen velocity may range from about 1 to about 7 feet/second and preferably about 4 feet/ second. Likewise, the employment of pressure is desirable in the practice of the present invention and suitable provision is made to employ a pressurized system which may include a suitable lock hopper device in conduit 14 and a suitable pressure discharge mechanism in conduit 19 to maintain a pressure on the system within the range from about 300 to about 800 p.s.i.

In the practice of the present invention by employing fluidized hydroretorting with the hydrogen and the oil shale flowing countercurrent to each other at pressures from 300 to 800 p.s.i. Fischer Assay yields within the range from about to about are obtainable. Yield and quality data obtainable in the present invention are compared to the conventional Bureau of Mines Also, a light prodct from which nitrogen is readily removed is obtained. For example, in the present invention the product from line 36, after the process has been lined out, may comprise products having a true boiling point below about 800 F. from which nitrogen may be readily removed, or the product obtained from line 35 may be subjected to treatment for removal of nitrogen. For example, nitrogen may be removed from any of the product produced in the present invention by contact in the vapor phase in the presence of hydrogen with a cobalt molybdate alumina-supported catalyst. The relative ease of denitrogenation of shale oil in the standard hydro denitrogenation test is indicated below:

Nitrogen, weight The present invention is also quite advantageous in that the heat from consumption of hydrogen in the retorting zone 12 provides a portion of the heat for reaction in retorting oil shale in retorting zone 12. If the same hydro gen were added to a retorted shale oil as produced conventionally to improve its quality and decrease its molecular weight, the heat of reaction would be removed from the retorting system only at considerable expense which the present invention avoids.

Fluidized retoiting employing hydrogen is also quite advantageous because fine shale particles from the mining process may be processed which heretofore was not possible economically. When employing hot hydrogen, sufficient carbon remains on the shale so that the dust nuisance from the spent shale is markedly decreased. Also, in the present invention, the hydrogen introduced into cooling zone 13 strips the spent or retorted oil shale such that there is little or no oil remaining on the shale.

In the practice of the present invention, it is contemplated that the furnace 21 may be fired with gases produced in the process as a source of fuel, or the spent shale containing carbonaceous material may be the source of fuel, or other fossil fuels may be used.

The nature and objects of the present invention having been completely described and illstrated and the best mode contemplated set forth, what I wish to claim as new and useful and secure by Letters Patent is:

1. In a method for restorting crushed oil shale in which a hot free hydrogen-containing gas is employed to retort said crushed oil shale and in which said crushed oil shale is introduced into and flows serially through a preheating zone, a retorting zone, and a cooling zone, the steps which comprise:

flowing crushed oil shale including particles having diameters less than about 0.2. to about 0.3 inch countercurrently through said zones to free hydrogen-containing gas under flow conditions to form said crushed oil shale into fluidized beds in each of said zones and to decompose kerogen in said crushed oil shale to vaporized shale oil in said retorting zone;

recovering a product comprising shale oil and free hydrogen-containing gas from said preheating zone;

separating shale oil from said product and distilling the separated shale oil to recover a heavy residue from said shale oil boiling above about 800 F.;

admixing free. hydrogen-containing gas with said heavy residue; and

subjecting said admixture to cracking conditions in a separate cracking zone to crack said heavy residue and to form said hot free hydrogen-containing gas for retorting said crushed oil shale.

2. A methodin accordance with claim 1 in which said crushed oil shale is retorted at a temperature within the range from about 700 to 1000 F.

3. A method in accordance with claim 1 in which the flow conditions in said preheating, reto-rting, and cooling zones includes a velocity of hydrogen within the range from about 1 to about 7 feet per second.

4. A method in accordance with claim 1 in which the crushed oil shale is preheated and cooled in said preheating and cooling zones, respectively, to a temperature within the range from about 200 to about 400 F.

5. A method in accordance with claim 1 in which the crushed oil shale introduced into said preheating zone contains from about 1% to about 20% of particles having diameters less than about 0.2 to about 0.3 inch.

6. A method in accordance with claim 1 in which said crushed oil shale is retorted at a pressure within the range from about 300 to about 800 p.s.i.

7. A method in accordance with claim 1 in which said hot free hydrogen-containing gas is introduced into said retorting zone at a temperature within the range from about 800 to about 1300" F.

References Cited UNITED STATES PATENTS 3,044,948 7/1962 Eastman et al. 208-11 DELBERT E. GANTZ, Primary Examiner T. H. YOUNG, Assistant Examiner US. Cl. X.R. 201-29, 31