US3476650A - Oil shale process - Google Patents

Description

Nov. 4, 1969 D. w. EEAcocK 3,476,650

` OIL SHALE PROCESS Filed sept. 26. 196e /NVENTOR D, W. PEACOCK er q* G A T TORNEYS United States Patent O U.S. Cl. 201-32 5 Claims ABSTRACT F THE DISCLOSURE Oil shale is combusted under a partial pressure of oxygen of to 105 p.s.i.a. at 500 to 700 F. thereby producing a valuable metallurgical coke suitable for smelting iron, a heavy hydrocarbon fraction and a gaseous fraction.

This invention relates to a method for the recovery of oil from oil bearing solids, such as shales, diatomite, and tar sands.

The recovery of petroleum products from oil bearing solids has been accomplished in prior art, generally utilizing a heating or roasting process. These processes have proven to be unsatisfactory due to the energy requirements. There are other processes which remove hydrocarbon products from rather large particles of oil bearing solids by the process of eduction. There are still other processes which remove the hydrocarbon by a combination of eduction and steam treatment. All of the above processes have proven to be relatively unsatisfactory due to the production of low specic gravity products containing a high percentage of waxes and aromatic and naphthalenic components, and the production of a residual material that requires costly disposal facilities.

My invention is superior over the prior art in that lower energy input requirements are necessary, the liquid hydrocarbon product is of high molecular weight, is primarily paraffinic, and is free of waxes and aromatic and naphthalenic components, and the residual material comprises a valuable metallurgical coke as opposed to a waste product requiring costly removal and disposal facilities. In summary, my invention comprises a method whereby oil bearing solids are introduced in the lower portion of a combustion chamber containing air at 75 to 525 p.s.i.a. at 500 to 700 F. wherein the solids are combusted and liquid, gaseous, and coke products are removed.

Accordingly, an object of my invention is to provide a method for removing hydrocarbon components from oil bearing solids. v

Another object of my invention is a process for manufacturing a valuable metallurgical coke.

Other objects, advantages, and features of my invention will be readily apparent to those skilled inthe art from the following description, drawing, and appended claims.

With reference to the attached figure, there is indicated an elevation view in cross-section of one embodiment of the inventive method and apparatus.

With particular reference to the attached figure, there is indicated combustion chamber means 10. Oil bearing solids, such as oil shale, are introduced into said combustion chamber means 10 and therein combusted. To accomplish this the oil bearing solids are introduced into feed hopper means 11, whereupon solids injection means 12 continually introduces oil bearing solids into combustion chamber means 10. The oil bearing solids are combusted within combustion chamber means 10 by means of oxygen being contained in ordinary atmospheric air introduced through air inlet conduit means 13 and 14. The combustion process is in an environment that provides for minimum cracking of the shale oil, minimum Mice production of non-condensable products, and conversion of carbon components into a valuable coke. The environment of temperature and pressure employed in accordance with this invention is such that it inhibits the decomposition of the alkaline earth and magnesium carbonate components so that the coke particles now contain a natural flux. As a result, the solid formed from the low temperature hydrolysis will be a valuable product of the oil bearing solids production, instead of a Waste material which adds to the materials handling cost. The environment necessary to achieve these desirable results is 15 to p.s.i.a. oxygen partial pressure at 500 to 700 F.

Departure from the above combustion chamber environmental conditions produces undesirable liquid and gaseous components, and valueless carbon products which create a disposal problem. Specifically, temperatures above 700 F. result in the decomposition of the components of the oil bearing solids; while temperatures below 500 F. fail to produce a good coke because the reduced temperature fails to remove light components that would result in poor quality coke. It is only within the critical range, bounded on one side by decomposition of the components and on the other by a failure to remove light components, that a useful coke together with useful gaseous fractions can be produced.

The flow rate of air entering combustion chamber means 10 via air inlet conduit means 13 and 14 can be any quantity necessary to achieve the desired partial pressure of oxygen. The process is designed to operate continually with any ow rate that is desirable for the application.

After the oil bearing solids, now combusted into coke, rise through combustion chamber means 10, as a result of the action of solids injection means 12, they are contacted with steam or water entering combustion chamber means 10 through conduit means 15. As a result of the contact of steam or water with the coke, the coke is broken into much smaller particles by the thermally induced tensile and compressive forces. The coke further rises through combustion chamber means 10, whereupon the coke falls by gravity from around the upper perimeter of combustion chamber means 10, and is removed from the process by exiting coke removal means 16, equipped with back pressure maintenance means 17. Exiting coke removal means 16 comprises an auger suitable for the transportation of solid particles. Back pressure maintenance means 17 comprises a star valve.

The combustion process occurring in combustion chamber means 10 and under the aforementioned environment produces a liquid hydrocarbon product, which exits from combustion chamber means 10 via hydrocarbon conduit means 18. The combustion process occurring in combustion chamber means 10 also produces a gaseous product, which exits from combustion chamber means 10 via gaseous conduit means 19. The quantity and components of the liquid and gaseous streams are determined by the precise environmental combustion chamber conditions, as well as the characteristics of the oil bearing solids being processed.

In summary, the operation of my invention can be described as introducing a bottom feed of raw crushed oil shale into the combustion chamber along with process air which is pressurized to the desired pressure, the oil shale combusted and quenched with water or steam, and the extraction of a liquid, a gaseous, and a coke product from the combustion chamber.

This invention is thus broadly applicable to the removal of hydrocarbons from oil bearing solids and production of valuable metallurgical coke.

Various modifications of this invention can be made in view of the foregoing disclosure and the appended claims without departing from the spirit or scope thereof.

The effect of varying the partial pressure of oxygen in the oxidative pyrolysis zone is illustrated by Table I in which oxidation peaks were measured through differential thermal analysis by varying the partial pressure f oxygen passing into the zone. It is readily apparent that to coke with minimium cracking the pressure should exceed 3 atmospheres. Oxygen partial pressure higher than 7 atmospheres does not materially lower the oxidation peaks.

The oxidative pyrolysis of oil bearing solids results in the evolution of three distinctive gaseous fractions. First, the very light hydrocarbon components and inorganic gases are evolved. Second, the rather heavy hydrocarbon fractions are expelled. And third, the residual hydrocarbons not previously expelled are cracked and expelled. The production of good coke demands some hydrocarbon residue; hence, no cracking must occur. Equally as important in the production of good coke is the removal of the light hydrocarbon fractions. Since cracking occurs for heavy hydrocarbons at approximately 690 F., the third step of cracking can be avoided if the operating temperature is controlled below that figure. Since the temperature must be at least 500 F. to remove the light fractions, the temperature must be held above this level. Table 1 represents data indicating temperatures at which the three stages occur. Upon reference to the Table I, it can be seen that the third step of cracking can be eliminated and the first step fully effected only by maintaining the temperature from 500 to 700 F. In order to maintain the temperature above 500 F. but below 700 F. it is necessary to maintain the pressure between 105 p.s.i.a. and 15 p.s.i.a. Stated another way, the pressure must be at least p.s.i.a. for the initial oxidation step to occur.

TABLE I.-EFEECT 0F PARTIAL PRESSURE 0F OXYGEN ON THE TEMPERATURE AT WHICH OXIDATION PEAKS OCCUR IN GREEN RIVER OIL SHALE l Temperature at which Oxidation Peaks Occur, F.

Partial Pressure of Oxygen 1 Samples used-50 gal/ton Green River Oil Shale, 5 percent by weight on Mill Creek Sand.

2 No peak.

In a specific embodiment of my invention oil shale was combusted to produce a valuable metallurgical coke, a liquid hydrocarbon product, and a gaseous hydrocarbon product. This was accomplished by introducing a feed of raw crushed oil shale into the bottom of the combustion chamber simultaneously with the introduction of suflcient process air, preheated to 1000 F., to achieve an oxygen partial pressure of `80 p.s.i.a. and 536 F. The partial pressure of oxygen to be maintained in the combustion chamber depending primarily upon the characteristics of the oil shale and was determined by the use of differential thermal analysis. In the instant experiment the optimum oxygen partial pressure for a Green River oil shale was determined by the use of the differential thermal analysis method to be 100 p.s.i.a. at 600 F. by utilization of the above method.

The combustion environment was controlled in such a manner that there occurred only minor cracking of the shale oil, minor production of non-condensable products, and transformation of the carbon into a valuable metallurgical coke. The low temperature component of the environment was particularly conducive to inhibiting the decomposition of the alkaline earth and magnesium carbonates, thereby producing the coke ux.

After combustion to coke, the coke moved upward and was contacted with steam. This contact with steam broke the coke up into small particles through the thermally induced tensile and compressive forces. The coke continued to rise through the combustion chamber and subsequently fell from the upper perimeter of the combustion chamber and was removed from the process by a rotating auger equipped with a device to maintain back pressure in the combustion chamber.

The liquid hydrocarbon product passed from the process as bottoms product and was available for further processing. The gaseous overhead product was withdrawn from the process and was available for further processing.

I claim:

l. A process for treatment of oil shale and production of metallurgical coke comprising the steps of combusting said oil shale in a combustion zone with a partial pressure of oxygen from a free oxygen containing gas of 15 to 105 p.s.i.a. at 500 to 700 F. and thereby producing a valuable metallurgical coke suitable for smelting iron; removing a heavy hydrocarbon fraction from the combustion zone; removing a gaseous fraction from the combustion zone; and removing the metallurgical coke without further treating above 700 F.

2. The process of claim 1 wherein the free oxygen containing gas is atmospheric air and the pressure of the atmospheric air in the combustion zone is from to 525 p.s.i.a.

3. The process of claim 1 including the step of breaking the combusted shale particles into still smaller particles by quenching with a fluid selected from the group consisting of water and stem.

4. The process of claim 1 including the steps of pumping the oil shale solids upward into the combustion zone wherein combustion occurs; then upward into a coke removal zone wherein the coke moves by gravitational forces into a coke conveyance means and thereby is removed from the coke removal zone.

5. The process of claim 1 wherein the combustion is conducted at a temperature of approximately 600 F. and at an oxygen partial pressure of approximately p.s.i.a.

References Cited UNITED STATES PATENTS 2,640,014 5/1953 Berg 201-36 XR 2,875,137 2/1959 Lieifers et al. 201--32 XR 3,133,010 5/1964 Irish et al. 201-32 XR 3,361,644 1/1968 Deering 201-32 XR NORMAN YUDKOFF, Primary Examiner D. EDWARDS, Assistant Examiner U.S. Cl. X.R. 201-39; 208-11

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