US 2752292 A
Description (OCR text may contain errors)
June 26, 1956 J. w. SCOTT, JR 2,752,292
SHALE RETORTING PROCESS Filed Aug. 31, 1951 INVENTOR JOHN w. SCOTT JR.
ATTORNEYS United States Patent 2,752,292 SHALE RETORTING PROCESS John W. Scott, Jr., Berkeley, Calif., assignor to California Research Corporation, ration of Delaware Application August 31, 1951, Serial No. 244,620 2 Claims. (Cl. 202-19) San Francisco, Calif., 21 corpo- This invention relates to an improved process for retorting oil shale and bituminous solids of similar charac- .'ter in order to recover valuable liquid and gaseous hydrocarbon products.
In the process of this invention, shale is retorted by contacting it countercurrently with hot fixed gases produced from shale. All of the heat required to effect the conversion of the kerogenic constituents of the shale to liquid and gaseous hydrocarbons is supplied as sensibleheat of the fixed gases. The gases are heated by contacting the gases countercurrently with spent shale as it comes from the retort and then burning a portion of them in a combustion zone prior to their introduction into the retort.
The process of this invention will be described in detail with reference to the appended drawing, in which fixed gases recovered from the shale are contacted with spent its kerogenic con- Shale particles having a size in the range M1 inch to 2 inches in diameter are passed through line and gastight valve 11 into conveyor-condenser 12. The shale is carried by the conveyor chain 13 into line 14, through which it passes into retort 15. Retorted shale is passed from retort 15 through line 16 and gas-tight valve 17 into cooler 18. Cooled retorted shale is withdrawn from cooler 18 through line 19 and gas-tight valve 20. Gas and vaporous products from retort 15 pass through line 14 and conveyor-condenser 12 in countercurrent contact with fresh shale en route to retort 15. Liquid shale oil is withdrawn from conveyor-condenser 12 through line 21. Shale gas and uncondensed shale vapor is withdrawn from conveyor-condenser 12 at a point intermediate the junction of the conveyor-condenser with lines 21 and 14 through line 22. These gases and vapors pass through heat exchanger 23 into liquid gas separator 24. Shale oil is withdrawn from liquid gas separator 24 through line 25, and fixed shale gases are withdrawn from the separator through line 26 and pass through pump 27. A portion of the fixed shale gases is withdrawn through line 28 as a net gas product, and the remainder is recycled back to the retorting system through line 29 into cooler 18, Where it countercurrently contacts hot shale from retort 15. These gases, preheated in cooler 18 by contact with the spent shale, pass through line 30 into combustion chamber 31. Air is introduced into combustion chamber 31 through line 32 in amount sufiicient to raise the temperature of the total gas stream entering the retort 15 to the temperature required for retorting. This may require the combustion of about 10% of the true make gas of the process. The unburned recycle gas and the combustion product are passed from combustion chamber 31 through line 33 into retort 15, where they countercurrently contact the fresh shale in the retort to effect the conversion of its kerogenic components.
2,752,292 l atht'ed June 26, i 1956 The following table is illustrative of the amounts and temperatures of the process materials involved in typical operation of the process described.
Material Amount S P" Fresh Shale to 2") 500 lb./hr 60 Retortcd Shale (line 16) 414 lb./hr 1, 000 Cooled Shale (line 19)--.. 250 Shale Oil (lines 21 and 25) Shale Gas (line 28) 175 Recycle Gas (line 29) 175 Air (line 32) Recycle Gas (line 33) 249 lb./h 1,050 True Make Gas burned in Combustion 9 percent Chamber 3]. Flue Gas in Make Gas (line 28) 32 percent In the invention described above the combustion of a relatively small proportion of the recycle gas is found to supply suflicient heat to retort the fresh shale. This proportion is ordinarily so small that the net product gas withdrawn from the process through line 28 has a high heat content.
An advantage inherent to the use of a retorting process employing a gas combustion zone separate from the retorting zone is that close control is possible over the temperature of the gas retorting medium, and carbonate decomposition within the retorting zone can thereby be minimized. A further advantage associated with separation of the gas combustion process from the retorting process is the fact that close control over the amount of residual oxygen entering the retort with the hot gas stream may be maintained for the purpose of avoiding an oxidizing atmosphere within the retort which would result in lower yields of liquid products.
In the foregoing specific embodiment of the invention as represented by the appended drawing, it is to be understood that certain modifications in processing techniques and apparatus may be indulged without departing from the basic features of the invention. Thus, the illustrated conveyor condenser 12 may be simplified into a conven tional hopper arrangement located directly above line 14, and shale particles of varying size may be directly fed into the hopper for gravitational loading into the retorting zone. The normally liquid and gaseous products may also be taken from the retorting zone 15 in a conventional manner without affecting the retorting process of the invention. As a conventional modification of the illustrated recovery system, the vaporized products from the retorting zone may be withdrawn from the upper section of the retorting zone and passed into a condensing or mist agglomeration system. The liquid products may be withdrawn from one or more condensers and the product gas accumulated with a distribution into net product gas and recycle gas.
The basic features of the invention involve a recycle of a portion of the product gas which is introduced into countercurrent contact with the spent shale. After preheating by passage through the spent shale, the preheated recycle gas is withdrawn from contact with the shale and passed through a combustion chamber wherein a suflicient portion thereof is burned in contact with controlled introduction of air or oxygen-containing gas to raise the temperature of the recycle gas to the desired retorting temperature and provide the balance of necessary retorting heat, after which it is brought into contact with fresh shale as the retorting heat carrier medium.
This application is a continuation-in-part of application by John W. Scott, Jr., Serial No. 116,260, filed September 17, 1949, now abandoned Obviously many modifications and variations of the invention as hereinabove set forth may be made without departing from the spirit and scope thereof, and only such limitations should be imposed as are indicated in the appended claims.
I claim: I
1. In a process for retorting shale by countercurrently contacting downwardly moving shale particles with hot gas in a retorting zone to decompose the organic constituents of the shale forming shale oil and shale gas, the improved method which comprises Withdrawing vapors comprising normally liquid and normally gaseous products from the upper portion of the retorting zone, cooling the vapors to condense shale oil, withdrawing a minor proportion of the uncondensed gas as a product, reheating the major proportion of the uncondensed gas by contacting it with hot spent shale in a reheating zone, withdrawing reheated gas from the reheating zone and passing it into a combustion zone, introducing into the combustion zone a quantity of a free oxygen-containing gas having an oxygen content stoichiometrically suflicient to cause combustion of only a minor proportion of the reheated gas and burning a minor proportion of the reheated gas sufiicient to raise the temperature of the mixture of combustion products and unburned gas to retorting temperature in the combustion zone, and passing the mixture of combustion products and unburned gas from the combustion zone into the retorting zone.
2. Method substantially as described in claim 1, wherein about 10% of the reheated gas is burned in the combustion zone;
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