US2589109A - Fluidized distillation of shale - Google Patents

Description

March 1952 H. z. MARTIN EIAL FLUIDIZED DISTILLATION OF SHALE 2 SHEETS-SHEET 1 Filed Dec. 29, 1945 @w J 41 Q 0? n w w w l 0 H h ,7 I Q E T a 8 \M i s Q .u

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q Clbbrneq Patented Mar. 11, 1952 UNITED STATES ATENT OFFICE FLUIDIZED DISTILLATION OF SHALE Application December 29, 1945, Serial No. 638,422 glaims. (01. 2026) The present invention relates to the novel features hereinafter fully disclosed in the following specification and claims considered in connection with the accompanying drawing.

It is known that certain types of naturally occurring oil-bearing minerals, such as shale or oil sands, contain materials which may be converted by pyrolytic treatment into commercially feasible quantities of hydrocarbon oils, including 'oils boiling in the gasoline and gas oil range.

Prior to our invention, others proposed carrying out the pyrolytic treatment of the shale while the same was in the form of a powder or rather large aggregates, which may be as large as four mesh, in a fluidized state in a distillation or pyrolytic zone, while supplying the heat necessary for the reaction by combustion, that is, either by burning a portion of the combustibles in the distillation or pyrolytic zone or by burning the spent shale in a separate combustion zone and returning the burnt substan tially uncooled shale to the distillation or pyrolytic zone. The former method has the advantage of a simple design, while the latter method permits the production of oil free of gaseous combustion products. However, both methods have marked disadvantages. .The heat supplied by burning residual spent or partially spent shale consumes combustible material equivalent to as high as 0.1 to 0.4 barrel of oil perton of shale, and will actually reduce the oil yield by the amount that truly non-distillable carbonaceous residue cannot supply. Heat supply by combustion within the distillation zone, if not controlled with extreme care, may lead to loss of valuable distillation products which are burned instead of non-distillable residue as a result of the low concentration of the residual carbon available for this purpose. When spent shale is burnt in a separate combustion zone, the combustibles content of this shale is present in high dilution in ash which results in a low rate of combustion. To supply in this manner the heat required for distillation, excessive volumes of spent shale and correspondingly large heater dimensions are required.

The present invention overcomes the aforementioned difiiculties and affords various additional advantages. These advantages, the nature of the invention and the manner in which it is performed will be fully understood from the following description thereof read with reference to the drawing which shows semi-diagrammatic views of apparatus particularly adapted to carry out the invention.

The main object of our present invention relates to improvements in the continuous distillation and/or pyrolytic treatment of shale or oil sands wherein the operation is performed in a manner which induces a greater production of valuable hydrocarbon oil per ton of shale.

A second object of our present invention has to do with supplying the heat necessary for supporting the distillation of naturally occurring shale or oil sands under conditions such that burning of the desired oil in the shale is substantially avoided.

A still further object of our invention concerns the supply of the heat necessary for supporting the distillation of naturally occurring shale or oil sands in the form of a dense turbulent bed of fluidized finely-divided solids under conditions such that burning of the desired oil in the shale is substantially avoided.

Other and further objects and advantages of the present invention will appear from the following more detailed description and claims.

We have found that these objects and advantages may be accomplished by supplying the heat-generating combustion stage of the distillation process with extraneous fuel, that is, fuel other than carbonaceous constituents of the shale or oil sands undergoing distillation. For example, we may add extraneous solid fuel, preferably of a relatively low ignition temperature, such as coal, particularly lignites or bituminous coals, or wood, e. g., sawdust, to the material to be distilled, and supply an oxidizing gas to the distillation zone to generate the heat required for the distillation by a preferred combustion of the added extraneous material. The combustion of the extraneous material may be further favored over that of the shale by charging the former in a particle size different from that of the latter. If the particle size of the extraneous fuel is larger, the combustion takes place in a partially differentiated layer of the total process solids which consists mainly of extraneous fuel. If this particle size is smaller, the larger surface presented favors combustion of the fuel over that of the shale. If desired, spent shale may be circulated to a separate combustion zone or heater, highly heated therein by combustion of residual carbon and returned to the distillation zone to supply additional heat. Depending on the amount of oil to be distilled, the coke content of the spent shale or sand and the type of extraneous fuel employed, the latter may be added in proportions of about 50 to 200 lbs. per ton of oil-bearing solids. One ton of an oil shale containing about 0A bbl. of oil, for example, may require about lbs. of a bituminous coal. In this manner, the

loss of otherwise recoverable oil by combustion is substantially completely eliminated.

When applied to a distillation system involving a separate heater, our invention may be practiced to greatest advantage by burning extraneous solid fuel in the heater and feeding hot solid combustion residue to the distillation zone containing the oil-bearing solids to be distilled. If no other inexpensive solid fuels are readily available, fresh shale may be used for this purpose. Other solid fuels such as coal, coke, wood or the like, may be burnt in the heater in the presence of inerts such as ash, spent shale, etc., which are circulated to the distillation zone to supply the heat required therein. In both cases. solid distillation residue, such as spent shale, may be circulated to the heater to serve as-heat carrier and/or to contribute combustibles. If this is the case, a combustible gas may be used as an extraneous fuel for the heater. The amount of extraneousfuelsupplied tothe heater depends on. numerous variables, such asthe heat requirement in the distillation zone, heatcarrier circulation rate,.type ,of ,extraneousrfuel, etc.

Broadly, operative amounts may vary from 1000 to 1500 lbs. of shale to be burnt, from 40 to 180 lbs. of coal, and 100 to 800 lbs. of wood per ton of shale containingOA bbl. of oilv to be distilled. The use of a separate heater operated. by-the process of our invention affords a high concentration of combustibles in the heater, thus p rmitting a considerable reduction in heater size, and allows. independentcontrol of heater operation.-

Havingsetforthathe general nature and objects, our invention will be best understood from the more detailed description hereinafter, in which reference will bemade totheaccompanying drawing wherein Fig. 1 isapartlyv schematic, partly diagrammatic illustration of-a system suitable for carrying out the process-ofour inventionby combustion of extraneous "fuel in the distillation zone; and

Fig. 2 is a similarillustration of apparatus for, carrying out the process of our invention by g8nerating'heat ina separate heater.

Referring now-in-detail to Fig; 1, I represents a cylindrical-case orreactor having a'conical crown-piece and base; I is also provided with a distributor G which may be in the form of an ordinary grid, the purpose of this being to-causeuniform distribution of a fluidized mass which is a size up to one-quarter inch for it has been found that particles of shale of thissize may be-conveniently-fiuidized, i. e., maintained, in a turbulent and highly mobile condition-by causing a gasiform material, for example fixed hydrocarbongases fromthe process; to flow upwardly therethrough at a controlled'rate of speed. The raw shale discharges through a, star feeder 4-anda pipe 5 into the reaction zone Meanwhile, an oxygen-containing gas,. such as air for example, is introduced, into, the bottom of the reaction vessel 1 through line I0 and passesupwardly through the grid- G; By controlling the linear.

velocity of the gas passing upwardly in reactor l, we may eifect the state of fluidization as follows:

Depending on thesize of the aggregates present The shale in the feed hopper 3.

in the reactor, the velocity should vary from onehalf to 10 to 12 ft. per second, the larger particles of course requiring the higher velocities in order to maintain the shale in a highly fluidized suspension of solid in gasiform material. If the shale has a particle size of, say, 200 mesh the net velocity of the gas in reactor I will be of the order of 1 to 2 ft. per second. On the other hand, if the average size of the particles in the reactor is about A inch, then the velocity of the gasiform material should be of the order of 4 to 10 ft. per second.

When the-shaleenters the reaction zone, whichis 1maintained at a temperature of about 850- 1100? F., certain agglutinants present in the shale become decomposed, thus causing usually physical distintegration of the shale in the case where the particles or aggregates are of appreciable size, say inch. Thereafter, the distillation of the volatilizable constituents of the shale takes place at an accelerated rate. Simultaneously, the solids in the-reaction zone are classified to acertain degree by size and/or specific gravity, heavy particles tending to concentrate in the lower layers ofgthe fluidized'b'ed- The air entering through line It] contacts the spentshale and consumes thefixedcarbon or a substantial portion thereof, thus evolving heat which supports. the pyrolytic treatment takingplaceabove the combustion portion ,of the mass. The pressure in the reaction zone is preferably. atmospheric, though slightly reduced j'pressures or elevated pressures ranging uptoabout175 lbs/sq. in. may be used.

Our present invention relates to adding to the shalerpreferably ,ingthe lower portion thereof or inlthegvicinity of the grid G, a quantity of extraneousfuel, such as finely-divided coal. To this end, therefore, coal rather than feed may be passed from, hopper20 through star feeder 22 and a pipe 23into the lower portion of vessel 1. The amount of ,coal thusadded depends on the kind andamount of ,distillable substances and residual combustibles-mthe shale, and the temperature andjrate of distillation employed, and may vary withinbroad ranges. For example, many shales containingiin the neighborhood of 5% of water and, about 0.4 bbl. of .oil per ton will require between about 40and v180 lbs. of coal, say about 80.to.-120;lbs..of.a.13,000 B. t. 11. coal. The shale feed is preferably maintained at about -500 lbs. ofshale perhour-per cubic foot of dense solidsphasa Ata fresh shale particle size of about- A, inch, good. results are obtained at gas velocitiesof. about 3-5 ft. per second. If desired, the particle size-of the coal may be larger than thatof the shale so as to favor concentration and combustion of the coal in the lower layers of the dense solids phase before that of any significant quantity of the shale, thereby consuming the oxygen'supplied', and-conserving the shale oil for recovery,

It-is;-advisable-to control the amount of air supplied so 'as'to approximate the oxygen supply theoretically required'for the combustion of the coal and any carbonaceous shale residue. Proportions of about -200 cu. ft. of air at 60 F. per lb of coal or about 5,000-40,000 cu. ft. of air per ton :ofishale aregenerally operative for that purpose. This amount of air may under certain circumstances not be sufiicient to provide proper fluidizationof :the dense solids phase. If this is the -case,-,itin advisable, to feed an additional fluidizinggas; suchas stean, or gaseous products of the distillation to the dense phase preferably; above the zone in which the main portion of the combustion takes place, for instance by line 8. advantage of establishing an aeration differential between top and bottom layers of the dense phase which favors gravitation through the dense phase in a downward direction.

Under the conditions stated, the shale undergoing distillation together with volatile products may be withdrawn through line 30 and passed through a purification and product recovery system 32 for recovery of gasoline, gas oil, heating oil, and other valuable products in a system which need not be illustrated in detail herein, for the skilled petroleum engineer need not have this recovery and purification system explained to him or illustrated in the drawing.

It is pointed out in connection with the grid G that the same may be in the form of a revolving grid driven by a suitable driving means which will cause further agitation of the shale in the region of the grates, thus tending to prevent the formation of relatively large aggregates of slag and/or ash. Also, it may be desirable to continuously withdraw ash by any suitable means from G via a draw-off pipe 40.

Another modification of this embodiment of our invention includes an operation wherein the spent shale is withdrawn from reactor 1 via a draw-off pipe 42. Pipes 23 and 42 are provided with taps t, into which a slow current of gas may be continuously injected in order to fiuidize the solids flowing therein, thus preventing bridging and plugging of the said pipes and causing the solids to flow freely.

The embodiment of our invention illustrated in Fig. 2, which relies substantially on heat generated outside the distillation zone, essentially comprises a distillation reactor 201 and a combustion zone or heater 250 cooperating, as will be presently described.

Fresh shale or oil sands having a fluidizable particle size, preferably of about 4 inch on the average, is fed from fresh shale hopper 203 to the distillation reactor 20l to form therein, above distribution plate or grid G, a dense turbulent mass of solids fluidized by a fluidizing gas, such as steam, product gas or flue gas from the process, etc., supplied to reactor 20! through line 2H! below grid G. The feed shale may be conveyed from hopper 203 to reactor 20| in any conventional manner, for example by gravity through line 205 or by means of a standpipe 201 feeding the shale to the fluidizing gas line 2H3 wherein it is picked up by the fluidizing gas, e. g., steam, and passed to the bottom of reactor 2M under the pressure of standpipe 201. The flow of solids through lines 205 and/or 201 is facilitated by the addition of small amounts of fluidizing gas through lines 265a and/or 2011:, respectively. The shale in reactor 20! is maintained at the desired distillation temperature of about 8501100 F. by means of hot solid circulated to reactor 21H from heater 250, as will appear more clearly hereinafter.

Volatile distillation products are taken overhead from the dense solids phase in reactor 20!, passed, if desired, through a conventional gassolids separator 225 from which solids may be returned through pipe 226, and thence withdrawn through line 230 to be processed in any conventional manner. Spent shale is withdrawn downwardly through overflow pipe 240 and may be discharged from the system through line 2 having a valve IA.

The heat required in reactor 2M is generated Such a procedure has the additional.

in heater 250. For this purpose, a finely-divided solid fuel of fiuidizable particle size is fed from fuel hopper 245 through a standpipe 24'! to line 248 wherein it is suspended in an oxidizing gas, such as air and/or oxygen, and passed to the bottom of heater 250 which has a design similar to that of reactor 20L The fuel suspension enters the combustion zone 252 through grid G50 to form thereabove a dense turbulent mass of solids fluidized by the oxidizing gas and the combustion gases produced. While We may burn in heater 250 any type of solid fuel, such as coal, lignite, wood, etc., fresh shale or tar sands which leave a larger amount of non-combustible residue suitable as a heat carrier may also be used if desired. An additional advantage of the use of high-ash solid fuels resides in the fact that the presence of inerts in high concentrations favors the complete combustion of carbon to CO2 by limiting the heat-consuming reaction between carbon and CO2 to form CO. The net result is the generation of more heat from the total amount of carbon available by means of smaller amounts of oxygen. The temperature in heater 25!) may be controlled by a proper oxygen supply at any desired level within the approximate limits of 1100 and 1800 F.

Flue gases are withdrawn overhead through conventional gas-solids separator 254 provided with solids return line 256, and discharged through line 258 for any desired use, including fiuidization of the reactor and standpipes of the process. Solid fluidized combustion residue is withdrawn downwardly from heater 250 substantially at the temperature of zone 252, through overflow-standpipe 260 and fed to reactor 20! in amounts suflicient to supply the heat required therein. The flow of solids through standpipe 260 is facilitated by fluidizing gas admitted through line 260a. It will be understood that, instead of suspending the solid fuel in the gases carried by line 248, these solids may be fed directly by gravity or mechanical conveyors to heater 250 at any suitable point, for example in a manner similar to the feed of fresh shale through line 205 to reactor 2M; On the other hand, standpipe 260 may lead into fiuidizing gas line 2| 0 to supply hot solid combustion residue in the form of a low density suspension through line 210- to the bottom of reactor 20!.

In case low-ash solid fuels, such as coal or wood, are employed in heater 250, it might be necessary to add inert solids to heater 250 in order to provide the amount of heat carrier required for the supply of heat to reactor 20 I. For this purpose, we prefer to use spent shale Withdrawn from reactor 2M through overflow pipe 240 and passed through line 262 to feed line 248 of heater 250. If desired, this spent shale may be suspended in air or other oxidizing gas supplied to line 262 through line 264. A substantial portion of the residual carbon on the spent shale will burn in heater 250 and thus contribute to the generation of heat.

The amounts of solid fuel and oxygen supplied to the heater and the rate of heat carrier circulation from heater 250 to reactor 20| may vary within fairly wide ranges, depending on the type Of fuel used and the heat requirements in heater 20L For example, when fresh shale containing about 0.4 bbl. of combustibles per ton of shale is usedfor heat generation and distillation, we may feed per lb. of distillation shale supplied to reactor 20] about 0.8110. to 1.0 lb. of fuel shale and about 0.15119. to 0.16 lb. of oxygen to heater about 1000 F. These .figures'change when other fuels are usedroughly-asitheiB; t. u. contentjof' the fuel changes. Thesuperficial velocities of the feed gases: may vary within-the:wideranges of 0.5j-lft. persecond, depending; on thepar? ticle size. and specific: gravity of:the respective solids. Velocities of l to ft; per secondare generally preferred.

It'will .be, understood that even if fresh shale isv used; as. thefuel, .a; certain amountofr spent shale may be; circulated fromreactor: 2! to heater 250 whereby. the consumption of fresh shaleper unit .of product recovered t is; reduced. Also, some extraneous: fuel may 'bechargedto reactor 2| in themanner outlined in connection with Fig. l; in order toyassist in the heat supply, Other. modifications, which may' occur to those skilled in 1. the artare within the .scope of our invention.

The process of .our invention may bemade'fully continuous bycontinuously chargin process.ma-, terials and-continuously withdrawing solid; and volatile products in the, manner, outlinedabove with reference to Figs. 1 and 2. Any oriall of' the process materials may be; preheated to;;any desired temperatures, particularly for-purposes of starting upthe process: Suitable modification Z of flow quantities .will, ofcourse, benecessary to adjustithe systemzfor; the. effect of preheat. The system, particularly the distillation: zone. may be operated at :elevatedlpressures; say about 75 lbs..per sq. in. or more, if:desired; The gassolids separators may be located:outside the high-, temperature chambers, for instancesubsequent to waste heat boilers arrangedv on the: gas and.

vapor withdrawal lines'from thevhigh-temperature chambers.

It is noted that.there..are..certain naturallyoccurring shales which are:convertible intosub'e stantial quantities of hydrocarbonoils where the heat required for distill'ation1may. be'supplied' "45' zone and, even if the:equivalent.of;0.l to.:0.4'1

by burning thespent'shale within theidistillation barrel iof oil is consumediper ton ofLshale; these processes .may. be. commercially; feasible if L the amount of oil burnt, represents: only 'a..small fraction of theoil'in' the shale.. However,- for shales of lower oil content;.say lessthan. one

barrel per ton, which: probably, constitute .the'

greater proportion offall shales available:(par.- ticularyv inthe U. S. A.) this ;internal fuel .18-

quirement represents considerable :loss of value able product; Indeed, many shaleswhich might otherwise be economically processed wouldgive practically no oil yield after fuel requirements were taken care of. Consequently, our :improvements are particularly suitable for the. processing of shales .containingarelatlvely small quan- 'ty of oil;

We have'found that low oil contentshales can be economically treated by chargingeith'er with the shale to be distilled or tart-separate heater an amountiof extraneous. properly. sized fuel sufficient to supply fuelrequirements for the. process. As mentioned before,it is desirablesthat.

the fuel charged to the distillation zone have a.

relatively low ignition temperature, although all coals have ignition temperatures considerably lower than the processing temperature for oil recovery from the shale. nouscoal are particularly-suitable on this .account, having ignition temperaturesin hot'air Lignites and bitimi- 8 inthe .neighborhood of-300"-450"v F. In addition, these, coals yield in many cases appreciable amountspf' valuable low-temperature tar which example, in the reactor l the fluidized solid will attain' an upper dense phase level at L which may be, say, 20 ft. from G and above L the density or concentration of the solid in gas will be greatly reduced so that the gases and vapors issuing through line will. contain only a minimum amount of solids whichmay be removed by passing through solid-contacting devices, such as centrifugal separators, electrical precipitators, and the like, as shown at 225 and 254 of Fig. 2. The level L may be fixed by controlling the quantity of shale and coal fed to the reactor l and the rate of purging of spent shale. Also, the density. of the fluidized mass between L and G is fixed'by the gas or vapor velocity; ordinarily the density of the fluidized mass is greater than 3 lbs. per cu. ft., usually from 10-25 lbs. per cu. ft. Similar considerations applyto corresponding features of Fig. 2.

Our invention will be further illustrated by the following specific example.

Example is supplied with'about 159 tons of coal having a.

heating value of. about 13,000 B. t. u. per lb. Operation of the heater requires about 25,800 standard cu. ft. of air per minute while the temperaturevin the distillation zone is maintained at about 1000 F. by circulating about 23 tons of solids per minute, having a temperature of about 1100 F., from the heater to the distillation zone.

If no extraneous coal were used in this procedure and the heat required for distillation were generated by the .combustion of carbonaceous constituents of the distilled shale, about 4600 tons :of shale would be required to produce 1000 bbls. of distillate per day.

Numerous modifications of our invention will appear to those familiar with the art without departingfrom the spirit thereof.

We claim:

1. A continuous method of distilling oil shale to produce therefrom volatile constituents containing normally liquid hydrocarbon oils by subjecting the subdivided oil shale to elevated temperatures in the fluidized state, which comprises continuously charging subdivided fresh oil shale to a distillation zone, maintaining said shale in said zone at distillation temperatures in the form of a dense fluidized bed of subdivided solids, adding to said zone subdivided solid carbonaceous materials selected from the group consisting of lignites and bituminous coals and having a particle size substantially different from that of said freshoil shale, supplying a free oxygenburning said materials in said zone, continuously supplying throughout the course of the distillation heat so generated to said distillation zone by direct heat exchange between said oil shale and materials directly heated by said burning, said heat being suflicient in amount to support the distillation in said distillation zone, continuously withdrawing from said distillation zone a vapor stream containing normally liquid hydrocarbons and continuously withdrawing a downward stream of said solids from said reaction zone.

2. The method of claim 1 in which said carbonaceous materials have a particle size substantially larger than that of said fresh shale and said carbonaceous materials are concentrated and burned in a fluidized bed of solids concentrated below the fluidized fresh shale in said distillation zone.

3. The method of claim 2 in which said fresh oil shale is supplied directly to said distillation zone and said carbonaceous materials are supplied directly to said lower bed.

4. The method of claim 1 in which an additional fiuidizing gas is introduced directly above said lower bed.

5. The method of claim 2 in which said carbonaceous materials have a particle size substan- 10 tially smaller than that of said fresh shale whereby said carbonaceous materials are burned in contact with, but in preference to, said fresh shale.

HOMER Z. MARTIN. FRANK T. BARR REFERENCES CITED The following. references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,334,404 Rodman Mar. 23, 1920 1,432,101 Danclswardt Oct. 17, 1922 1,781,934 Snyder Nov. 18, 1930 1,899,887 Thiele Feb. 28, 1933 1,917,196 Perry July 4, 1933 1,918,162 Willson July 11, 1933 1,941,809 McKee Jan. 2, 1934 1,950,558 Karrick Mar. 13, 1934 1,983,943 Odell Dec. 11, 1934 2,327,175 Conn Aug. 17, 1943 2,396,036 Blanding Mar. 5, 1946 2,406,810 Day Sept. 3, 1946 FOREIGN PATENTS Number Country Date 189,542 Great Britain Dec. 1, 1922

Claims (1)

1. A CONTINUOUS METHOD OF DISTILLING OIL SALE TO PRODUCE THEREFROM VOLATILE CONSTITUENTS CONTAINING NORMALLY LIQUID HYDROCARBON OILS BY SUBJECTING THE SUBDIVIDED OIL SHALE TO ELEVATED TEMPERATURES IN THE FLUIDIZED STATE, WHICH COMPRISES CONTINUOUSLY CHARGING SUBDIVIDED FRESH OIL SHALE TO A DISTILLATION ZONE, MAINTAINING SAID SHALE IN SAID ZONE AT DISTILLATION TEMPERATURE IN THE FORM OF A DENSE FLUIDIZED BED OF SUBDIVIDED SOLIDS, ADDING TO SAID ZONE SUBDIVIDED SOLID CARBONACEOUS MATERIALS SELECTED FROM THE GROUP CONSISTING OF LIGNITES AND BITUMINOUS COALS AND HAVING A PARTICLE SIZE SUBSTANTIALLY DIFFERENT FROM THAT OF SAID FRESH OIL SHALE, SUPPLYING A FREE OXYGENCONTAINING GAS TO SAID ZONE TO GENERATE HEAT BY BURNING SAID MATERIALS IN SAID ZONE, CONTINUOUSLY SUPPLYING THROUGHOUT THE COURSE OF THE DISTILLATION HEAT SO GENERATED TO SAID DISTIALLATION ZONE BY DIRECT HEAT EXCHANGE BETWEEN SAID OIL SHALE AND MATERIALS DIRECTLY HEATED BY SAID OIL SHALE SAID HEAT BEING SUFFICIENT IN AMOUNT TO SUPPORT THE DISTILLATION IN SAID DISTIALLATION ZONE, CONTINUOUSLY WITHDRAWING FROM SAID DISTILLATION ZONE A VAPOR STREAM CONTAINING NORMALLY LIQUID HYDROCARBONS AND CONTINUOUSLY WITHDRAWING A DOWNWARD STREAM OF SAID SOLIDS FROM SAID REACTION ZONE.

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