US 3442789 A
Description (OCR text may contain errors)
May 6, 1969 M. U. ZIMMERMAN,
SHALE OIL RECOVERY PROCESS Original Filed Oct. 31.
INVENTOR. MARLIN U. ZIM MERMA N, JR.
l IIBY United States Patent 3,442,789 SHALE OIL RECOVERY PROCESS Marlin U. Zimmerman, Jr., Shaker Heights, Ohio, as-
signor, by mesne assignments, to Technikoil, Inc., Cleveland, Ohio, a corporation of Ohio Continuation of application Ser. No. 320,451, Oct. 31, 1963. This application Oct. 26, 1966, Ser. No. 589,756 Int. Cl. Cb 53/06; C10g 9/28 US. Cl. 208-8 9 Claims ABSTRACT OF THE DISCLOSURE This application is a continuation of Ser. No. 320,451, filed Oct. 31, 1963, now abandoned.
The present invention relates to the distillation of oilbearing minerals such as oil shale, oil sands, tar sands, coal, lignite, peat and the like. More particularly, the present invention pertains to an improved process for distilling oil shale or the like wherein at least a portion of the heat required for distillation is supplied by direct heat exchange of the fresh shale with an extraneous gaseous heat carrier.
It is known that certain types of naturally occurring oil-bearing minerals such as oil shale and bitumen, contain materials which may be converted by a pyrolytic treatment into hydrocarbon oils in commercially feasible yields.
In general, oil shale retorting plants must have facilities for handling crushed raw shale, heating it to retorting temperatures, discharging the spent shale and collecting the retort products.
Oil shale has been defined by the'American Society for Testing Materials (D288-47) as a compact rock of sedimentary origin, with ash content of more than 33% and containing organic matter that yields oil when destructively distilled but not appreciably when extracted with the ordinary solvents for petroleum.
An object of this invention is to effect the distillation of oil shale and the like at relatively low temperatures; with a rapid transfer of the distilling heat to the material being distilled, and without any necessity for employing the expensive heating surfaces heretofore required because of the slow and inefficient heat transfer of prior low temperature distillation practice.
The present invention, in some of its aspects represents an improvement over the Swedish Aspeco shale oil distillation process in that the preferred embodiment of it employs the so-called ball-furnace type of heat exchanger although it differs from the Aspeco process, for instance, in that it eliminates the necessity for the circulation of hot balls and attendant equipment. The heat transfer medium in the present process is a gas, and preferably a light hydrocarbon gaseous product of the distillation step. The recycle hydrocarbon stream is used to transfer heat required for the release of oil from the oil shale.
The present invention makes effective use of the highly efficient heat transfer from hot gases to cooler solids. At the same time it avoids the disadvantage of mixing combustion products with the recovered oil and gases.
The invention mainly resides in a method of heating granular or pulverulent materials by admixing into said ICC material loose solid bodies and a hot gas, said solid bodies being preferably attrition resistant and generally of larger piece-size than that of said material, and separating said material from said solid bodies after the solid material has been heat treated in a rotary furnace in cofiow or counterfiow.
Broadly, the invention involves feeding crushed shale through a system comprising several superimposed sections. The cold raw shale in lump form is preferably preheated. The preheated raw shale then passes into a retorting or pyrolysis section where it is contacted with hot gases. Finally, if it is so desired, the spent shale with most of the hydrocarbons removed, but containing carbonaceous deposits, is passed to the combustion section where a combustion supporting gas, such as air or oxygen, is contacted with the carbonaceous spent shale to supply heat for carrying out the process.
The pyrolysis vessel or kiln in the instant process is preferably a ball mill equipped with a set of loose solid bodies, such as steel balls, an inlet for fresh shale, an inlet for the hot recycle gas heat-transfer medium and outlets for the spent shale and the cooled recycle gas and some means for retaining the balls in the ball mill .apparatus. It is not necessary that the pyrolysis vessel contain the permanent solid bodies, but it is preferred that the solid bodies be present because they reduce the tendency of the shale to bridge or agglomerate during the pyrolysis and they aid in the transfer of heat from the hot gases to the oil shale.
The term pyrolysis as referred to herein, denotes the actual conversion of kerogen or organic matter in the oil shale to oil or oil vapors and gases. Included within this term pyrolysis is the process of separation of oil from other oil-bearing materials, such as bituminous sand (e.g., tar sands, oil sands). The pyrolyzed carbon-containing residue is referred to hereinafter as shale coke and the combusted shale coke is referred to hereinafter as shale ash.
The accompanying drawing forms a part of this specification, and shows for purposes of exemplification, one form of apparatus for carrying'out the improved low temperature distillation of the present invention without limiting the invention specifically to such illustrative instance.
In the drawing the cold oil-bearing shale 1 enters the preheater 2 wherein the shale is preheated either by exchanger or by direct contact. The preheated shale 3 from the preheater next enters the pyrolysis drum 4 wherein pyrolysis takes place. The pyrolysis drum is rotatably mounted and rotatably supported, for example, on rollers and a base and preferably is somewhat tilted on its axis of rotation to allow the gravity flow of the shale from one end of the pyrolysis drum to the other and may contain solid bodies such as steel balls. The pyrolysis drum may also be fixed and equipped with a rotatable screw and external means for recycling the balls from the top to the bottom of the drum as described and claimed in the copending US. patent application of Howard P. West, Ser. No. 320,450, filed Oct. 31,1963. The spent shale or shale coke which still contains carbonaceous materials leaves the pyrolysis drum and enters a hopper 5 equipped with a cyclone 6 for removal of finely entrained solids. The hot shale coke enters the coke burner 7 where the mixture of shale coke and air (or any oxygen-containing gas capable of supporting combustion) from the air blower 8 is combusted to form hot gases which are used in heating the recycle gas in the heater 9. The shale ash is removed from the bottom of the coke burner as it forms. The pyrolysis vapors 10 from the pyrolysis drum 4 pass overhead from the hopper 5 and cyclone 6 which removes entrained solid fines to an efiicient fractionater 11 from which the shale gas oil is taken off at 12 and the residual oil which goes to fuel or further processing is taken off at the bottom of the fractionater 13. The overhead gases from the fractionater 14 are cooled with air 15 by indirect heat exchange, water, etc., partially condensed 16 and compressed 17 and passed to an absorber-stripper 18 where the condensed hydrocarbon is removed at the bottom 19 and the gas is removed overhead 20 and may be recirculated. The condensed hydrocarbon is then passed to a debutanizer 21 from which butane and similar hydrocarbons are removed and circulated 22 to the heater 9 where they are heated and converted to vapor having a temperature of from about 800 to 1200 F. and the heated vapors 23 are then passed into the pyrolysis drum 4 to supply the heat for the pyrolysis. If the gas is recirculated from 20 it is brought into the system at 24.
The solid bodies useful in the pyrolysis drum in the preferred form of the present invention are preferably in the form of balls, pebbles or shot of suitable size and specific gravity. These solid bodies can be composed of cemented shale ash or inexpensive metals such as iron, steel, aluminum, high melting lead alloys and the like as well as refractory materials and particularly ceramic materials which have relatively high heat capacities and are not subject to oxidation or reduction. The particle sizes of these solid bodies or balls can vary from about 50 mesh to about 1 inch in diameter. It is usually necessary that the balls be larger than the crushed shale coke so that the shale coke can be separated from the balls as it leaves the pyrolysis drum.
Most oil shales are preferably preheated to a temperature of between approximately 400 and 600 F. in the preheater. At temperatures above 600 F., pyrolysis of the oil shale commences with consequent loss of oil vapors and gases. Also at temperatures higher than about 600 F., the oil shale commences to become sticky or gummy and it is undesirable for this condition to exist in the preheating zone.
The hydrocarbon oil recovered from the shale is converted to a volatile product which can be treated according to the customary oil refining practice and be separated into various fractions such as normally gaseous hydrocarbons, gasoline constituents, gas oil, tar, coke and the like as desired.
A temperature from about 750 F. to about 1800 F. and more preferably 800 F. to 1300 F. is maintained within the reaction zone. The pressure is not critical and may be atmospheric or a few pounds above atmospheric, in other words, sufficient to overcome pressure drops in the system. The shale remains resident in the reaction zone for a sufficient period of time to effect the desired conversion.
Accurate control of temperature is possible by use of heat-carrying gas, and the temperature in the pyrolysis zone is readily raised or lowered, depending upon the nature of the product desired, by merely increasing or decreasing the rate of flow of the heat-carrying gas or alternatively by varying the temperature of the heatcarrying gas.
In all retorting operations, the time-controlling factor is the rate of heat transmission to the shale particles. In the instant process residence times as low as eight minutes may be used. Little is gained by increasing the contact time past eight to ten minutes. This compares with holdup times of 60 to 160 minutes in more conventional retorts. Charge rates as high as 500 to 1250 pounds of shale per hour per square foot of reactor cross-section are possible in the instant process.
It has been found that high oil yield is favored by decreasing temperature and shale particle size; the space velocity function passes through a maximum oil yield value. Retorting rate is favorably affected by increased space velocity and gas temperature, both of which tend to improve heat transfer characteristics.
The use of vacuum retorting is within the scope of the present process.
While the preferred embodiment of my invention has been shown and described, it will be understood that changes and modifications may be made that lie within the skill of the art. Hence, I intend to be limited only by the appended claims.
1. A process for producing oil and gas from a solid oil-bearing particulate material which comprises delivering said material as fresh feed to a pyrolysis zone and pyrolyzing said material in the pyrolysis zone while rotating and milling said material with extraneous heatcarrying bodies having a particle size greater than the particle size of said material, recovering a hydrocarbon overhead portion and a residue portion separately from said zone while retaining said bodies in said zone, introducing hot non-combustion supporting gas into the pyrolysis zone at a rate insufficient to suspend said bodies in the gas, contacting the gas with said bodies to heat said bodies by non-combustion contact in situ in said zone, and maintaining the amount of heat introduced into said pyrolysis zone by said hot gas at a level providing the desired pyrolyzing temperature in said pyrolyzing zone.
2. The process of claim 1 wherein said maintaining step comprises adjsuting the rate of flow of gas into the pyrolysis zone.
3. The process of claim 1 including the step of controlling the pyrolysis temperature by adjusting the temperature of the gas introduced into the pyrolysis zone.
4. The process of claim 1 including the steps of fractionating said overhead portion to provide a hot light fraction, recycling at least a portion of said hot light fraction as said gas to said pyrolysis zone, and maintaining the rate of recycle suflicient to provide the proper pyrolyzing temperature in said pyrolysis zone.
5. The process of claim 4 including the steps of burning at least part of said residue portion and passing said gas in indirect heat exchange with the combustion gases from the burning step during the recycling step.
6. A process for producing oil and gas from a solid oil-bearing particulate material which comprises delivering said material as fresh feed to a pyrolysis zone and flowing said material through said zone by gravity flow, pyrolyzing said material during its gravity flow through the pyrolysis zone while rotating said material with extraneous heat-carrying bodies having a particle size greater than the particle size of said material, recovering a hydrocarbon overhead portion and a residue portion separately from said zone while retaining said bodies in said zone, debutanizing the hydrocarbon overhead to separate a hot light butanes fraction, recycling the hot butanes fraction as recycle gas to the pyrolysis zone and introducing the recycled gas generally horizontally into the pyrolysis zone for contacting the recycle gas with said bodies and particulate material to heat said bodies and particulate material by non-combustion contact in situ in said zone, combusting the recovered residue to produce heat, transferring heat of combustion from the residue to the pyrolysis zone by flowing the recycle gas as a heat transfer medium in heat exchange with the combustion gases during said recycling step, controlling the amount of heat transferred by the recycle to said pyrolysis zone to maintain said zone at pyrolyzing temperature, and passing the combustion gases from heat exchange with the recycle gas into heat exchange with said fresh feed to preheat said feed.
7. A process for producing oil and gas from a solid oil-bearing particulate material which comprises delivering said material as fresh feed to a preheater, delivering flue gas through said preheater for preheating said material to a temperature below the pyrolysis temperature of said material, delivering the resulting preheated material from said preheater to a separate rotating pyrolysis zone, pyrolyzing said material in the pyrolysis zone while rotating and milling said material with another heat-carrying material which supplies heat for pyrolysis to said first material by intimate milling contact therewith, recovering the results of said pyrolysis from said zone as product, providing a source of hot flue gas and transferring the heat therefrom to a portion of said product to provide a heat transfer medium, introducing the heat transfer medium into said pyrolysis zone in direct heat transfer contact with the materials therein to transfer heat to said materials while said first material is rotating and milling substantially in the absence of combustion-supporting gas and substantially in the absence of gaseous suspension of the heat-carrying material in said zone to thereby supply the heat of pyrolysis by direct non-combustion contact in situ with the materials in said zone, and maintaining the amount of heat introduced into said zone by said heat-transfer medium at a level providing the desired pyrolyzing temperature in said zone.
8. The process of claim 7 wherein said portion of said product is a butanes fraction of the pyrolysis vapors.
9. The process of claim 7 wherein the heat transferring step is by indirect heat exchange in the absence of combustion of the heated portion.
References Cited UNITED STATES PATENTS 4/1931 Anderson 202218 11/1934 Reed et a1. 201-12 8/1948 Lantz 201-37 11/1957 Lankford et al. 201-43 2/1962 Nevgns et al. 208-11 5/1962 Nea'ens 20811 10/1962 tis 20811 11/1963 Natland 208-11 REIGN PATENTS 9/ 1954 Great Britain.
15 DANIEL E. WYMAN, Primary Examiner. PAUL E. KONOPKA, Assistant Examiner.
US. Cl. X.R.