US2480670A - Two-zone fluidized destructive distillation process - Google Patents

Description

- 2,480,670 TWO-ZONE FLUIDIZED DESTRUCTIVE DISTILLATION PROCESS Filed May 2, 1942 E. 'B. PECK Aug. 30, 1949.

2 Sheets$heet 1 ,4 IR INLET zusi-ILAA r: on) VESSEL INA'RT GAS r0417- INERT 0A 8 INl-l T E. B. PECK Aug. 30, 1949.

TWO-ZONE FLUIDIZED DESTRUCTIVE DISTILLA TION PROCESS 2 Sheets-Sheet 2 Filed May 2, 1942 PEGENERATOR JPINT .SHALE SUSPENSION [NI-8T Patented Aug. 30, 1949 TWO-ZONE FLUIDIZED DESTRUCTIVE DISTILLATION PROCESS Edward B. Peck, Elizabeth, N. 3., assignor to Standard Oil Development Company, a corporation of Delaware Application May 2, 1942, Serial No. 441,435 4 Claims. (01. 202-12) The present invention relates to improvements in the art of treating oil shale and other oilbearing sands and/or minerals for the purpose of recovering therefrom hydrocarbon oil, in particular, hydrocarbon oils boiling within the gasoline range. More specifically, my present invention relates to a continuous method for distilling shale or other oil-bearing material in a continuous operation under conditions wherein the shale is charged to the distilling zone in lump orm.

According to my present invention, I first coarse grind mineral shale and then discharge it from a receiving hopper into a distillation zone at the bottom of which is located a revolvable grate or other agitating apparatus. The shale as it enters the distillation zone, being roughly ground, does not have a uniform particle size, such as it inch orthe like, but has a large percentage of fine material and perhaps 20-30% of particle size as large as a A inch in diameter. I cause gases to be forced upwardly through the grate at such a velocity that the shale in finely divided condition and above the grate isfluidized, that is to say, it is in the form of a dense suspension wherein, supported bygthe gas, the mass of shale is in a turbulent condition resembling a boiling liquid. This condition is not to be confused with the ordinary suspension of a solid in a gas where there is no free motion of the particles with respect to the gaseous medium due to the speed of the carrier gas. By regulating the velocities of the gas in my process, the finer particles of shale are in such a state that there is aslippage or motion which may be in a direction diiferent from the general upward motion of the gas stream. Since the particles or aggregates of the charged shale will classify or settle within the reactor normally according to the size of the particles or aggregates, the largest particles tending to concentrate in close proximity to the grate, I vary the internal dimensions of the distillation zone, constructing it so that the said diameter increases upwardly thus causing a decrease in gas velocities as-the gas proceeds upwardly. z

One obiect of my present invention therefore is to distill rough ground shale in a continuous manner and under such control of time and temperature that the shale is intermixed with a flowing stream of gas which causes at least the finer particles to be in a turbulent state resembling a boiling liquid, to produce good yields of hydrocarbons, including hydrocarbon oils boiling Si hstantially within the gasoline range,,

Another object of my invention is to roughly grind shale and then to feed it into a. distillation zone where it encounters a flowing stream of gas and superheated spent shale, whose linear velocity is so regulated as to cause the finer particles of shale to have a mobility resembling that of a liquid and to provide mechanical means tending to cause disintengration of the larger lumps within the distillation zone thus tending towards at least rough equalization of the particle sizes within the said zone.

As a corollary to the next preceding object, it is a further object of my invention to eifect disintegration of the particles of raw shale within the distillation zone by removing from the particles the agglutinants consisting in part of the distillation products.

A further object of my invention is to withdraw a spent shale from the distillation zone and to convey it in the form of a suspension to a combustion zone where combustibles thereon are burnt, whereupon the shale is heated and thereafter to convey the thus heated shale to the distillation zone where a part of its sensible heat is made available for carrying out the distillation.

A still further object of my invention is to distill roughly ground shale of non-uniform particle size, including relatively large lumps, in a distillation zone having a. greater diameter at the top thereof than at the bottom, in which zone the powdered shale is in the form of a fluidized mass heretofore referred to, and in which zone the coarser particles tending to collect at the bottom of said zone are disintegrated by the combined effect of heat treament which releases bydrocarbons and agitation as by a rotating grate.

Other and further objects of my invention will appear from the following more detailed description.

In order to afford a better understanding of my invention reference is had to the accompanying drawings in which I have shown diagrammatically in Fig. I, a form and arrangement of apparatus elements in which my invention may be carried into effect, and in Fig. II, I have shown a modification in which the construction of the distillation zone is somewhat different.

I shall now set forth a. preferred method of operating my improved process and in so doing I shall refer to the drawings.

Referring in detail to Fig. I, the apparatus therein shown consists essentially of a distillation vessel I in communication with a feed hopper 2 from which raw shale 3 having a size produced by rough crushing and/or grinding and shale contained therein,

not exceeding a particle size of say 54 inch to A inch diameter is fed by gravity through pipe into the distillation zone I where it is heated sufliciently high to remove distillable hydrocarbons. A flow control valve 4 is disposed in line 5. Subsequently, it will be more fully explained that in vessel IS the spent shale containing fixed carbon not removed by the distillation operation is burnt. The oil! gases from this vessel are taken overhead through line "I and a portion of these gases is discharged through line 42 into hopper 2 where they serve to dry and preheat the as well as to more or less fluidize" the same. Also in apparatus not shown, the shale in hopper 2 is subjected to a preliminary crushing or grinding in order to reduce it to the size indicated, before discharging it into said hopper.

Located at near the bottom oi the distillation vessel l is a rotating grate which is driven by a motor or other driving means I2 for a purpose which will presently be apparent.

Vessel I5 is, as indicated, a combustion zone and into it a suspension of the spent shale is discharged through line IS, in communication, as shown, with the interior of distillation zone I. The spent shale which has undergone distillation in vessel I is withdrawn through said line I6 and mixed with air or other oxygen-containing gas introduced into pipe l8 through line 20. The shale in i5 forms a dense mass of solid and gas and may weigh from -40 lbs./cu. it. The linear velocity of the gas in I! is so adjusted, say at a rate of from 1-5 ftJsec. to give this density.

The mass discharges into a spillway 2I where it is conveyed by gravity through pipe 22 into a pipe 23 carrying into the bottom of distillation vessel I at a point below the rotatable grate in through an entrance throat II. A carrier gas, preferably hydrocarbon gases recovered from the distillation of the shale (although it may be some other gasiform material such as steam) is used to form a suspension of the spent shale in pipe 23. This gas is discharged from line 25 into line 23 where it forms with the hot shale the suspension of spent shale which is discharged into vessel I in the manner indicated. Meanwhile the fresh shale is discharged, as previously indicated, in rough ground form into the distillation zone where it contacts the hot shale from, I5. The first eiiect of the contact between the shale from 2 with the hot shale from I5 is to tend to cause the former to disintegrate physically by release of hydrocarbons which act as agglutinants. The vapors are eventually withdrawn through line 30. The vapors in line 30 are discharged into a cyclone separator t5 where the fines are removed and conducted through line 46 into the distillation vessel, or into pipe IS. The vapors, on the other hand, are conveyed to condensing and fractionating equipment (not shown) to recover desired products.

Gas velocity is regulated so that the following conditions exist in vessel I: At the bottom in close proximity to the revolving grate are the larger aggregates or lumps. Above this region, the shale which is of smaller size, say below 30 mesh average size is in a fluidized state, i. e., a dense phase .ebullient mass of hot spent shale and shale undergoing distillation. At L in Fig. I, the dense phase has its upper level and above L, the gases or vapors contain sharply decreasing amounts of powdered shale so that where there is say a 10 ft. disengaging space from L to the flow control valve 24 leading top of the reactor, the outlet gas may contain only very fine material and have a density of the order of say 0.003 to 0.030 lb./cu. it.

It is pointed out that rotating grate It serves the dual purpose of distributing uniformly the gas discharged into distillation vessel I and also serves to agitate the lumps of shale discharged into vessel I through line 5 from hopper 2.

It has been pointed out that the shale in 2| is in communication through line 33 with feed hopper 2, so that some of the burnt shale may be discharged into hopper 2. Spent shale may be withdrawn from the system through line 48 in communication with line [6, or it may be withdrawn through line 5| in communication with pipe 22.

Attention is directed to the fact that in order to fluidize the solid in lines 5 and 22, it is desirable to discharge into said pipes through line 50 a. fluidizing gas such as steam, flue gas and hydrocarbon gases.

Another matter of importance is that since shale is a mineral, it will contain foreign matter, and this may collect (together with clinkered shale) on grate ID. This can be drawn oil through an outlet valved pipe I4 periodically or continuously, as desired, without shutting down the unit by operation of the valve in line It, or in any other known manner.

I also wish to direct attention to the fact that vessel I is conical in shape which means that gas velocities are greater at the bottom where due to its size, higher gas velocities are required to fluidize the shale. I

The operating conditions in vessel I which produced best results are the following:

Temperature 850 F.-1000 F, Pressure 0 -20 lbs/sq. in. gauge Ratio of burnt shale to fresh shale 2 -10 parts by weight Below is a table indicating the gas velocities required to fluidize shale of the specified size particles:

If the diameter in the bottom of the vessel is restricted to give a velocity of 8 ftJsecond, everything up to A inch will be fluidized, and if the top of the reactor is large enough to slow the gases to 1 ft./second, most of the very fine material will be in dense phase fluidized condition without excessive blowing over into the cyclone 45. These details of operation can be readi y satisfied by test.

In Fig. II, I have shown a modification of my invention. In this modification, the roughly ground raw shale is withdrawn from a hopper Hi2 and discharged into a compression screw pump driven by a suitable driving means such as a motor I05. This conveyor forms a seal to prevent escape or vapors from the distillation which may operate under superatmospheric pressure. The shale is discharged into a distillation vessel H0 where the lumps of shale descend by gravity onto a grate Il2. superheated burnt shale is discharged into vessel H0 in the form of a suspension through line H4 and passes up through grate II2 where it mixes with the fresh shale and supplies heat thereto, which heat serves to disintegrate the fresh shale, and in this latter -and discharge outlet 8.

form it forms a dense mass as previously described, having an upper level at L. As before, the spent shale is discharged into distillation vessel 0 with the aid of a carrier gas and by controlling the linear velocity of this gas in vessel 0. a fluidized mass will be formed. The grate H2 may be rotated by suitable driving means in order to cause the coarse shale to be agitated and thus to prevent channeling of gases through the said shale. The spent shale may be withdrawn from vessel I I0 through spillway IIB Slag is withdrawn through line 9. The vapors released'during the distillation may be withdrawn through line I and delivered to equipment (not shown) to recover desired products.

It will be understood that if the gasoline obtained by the foregoing described process is of low octane number, as, say, in the neighborhood of 70 C. F. R... I propose to improve the octane number in known manner as by recracking in .the

presence of an active catalyst, such as silica gel admixed with magnesia geLor any other known synthetic active catalyst. The recracking is accomplished by heating the "wild gasoline, that is to say, a fraction boiling up to 400-F.. and including the normally gaseous components, such as excess butane, and the Ca and C2 hydrocarbons, and subiecting this fraction in vapor phase at tem eratures around 800 F.-900 F. to cracking in the presence of the aforementioned catalyst. This method of recracking yields a base stock which may be blended with an alkylate in the proportion of 40-65% by volume of gasoline and 35 60% by volume of alkylate to give 100 octane number gasoline.

To recapitulate, my present invention relates to a method for processing shale, and in its essence. it involves a continuous operation wherein coarselv ground shale containing fines is discharged into a distillation zone where it is heated by hot s ent shale, and the larger particles thereof are disintegrated by heatin and a itation. A fluidizing gas causes fluidity or mobility to the finer shale particles so that the latter have a flowability resembling a liouid. The gas used to fl idize the shale may be hydrocarbon vapors (say from the shale distillation) or it may be some other gasii'orm material such as 002, superheated steam, and the like. Instead of using a screen or grid throu h which the gas is forced to cause uniform distribution within the distillation zone, I preferably use a revolving grate mechanism, since the grate by mechanical action tends to disintegrate within the reaction zone the larger lumps of shale which tend to accumulate in the re ion of the grate. I have found that the distillation itself aids in the physical disintegration of the lar er lumps of shale since, as the hydrocarbons which apparently possess adhesive oualities, are released. the shale falls apart or disintegrates. Hence. one of the main features of my invention is the discovery that instead of discharging a true 100% powdered material into a distillation zone where it is fluidized under the conditions herein described, I may save the cost of pulverizing a raw shale to a particle size of 100 mesh or smaller, since I may feed into the distillation zone relatively large size lumps of shale. I consider this a very important advantage of my invention, since ordinarily the cost per ton to grind bituminous materials like shale from rough sizes down to a state where 90% will pass through a 200 mesh, is from about 35 to 50 per ton.

Another advantage of my invention resides inv the concept of transferring heat from the burning of the spent shale in a combustion zone through the medium of the shale itself to the distillation zone. The burnt shale leaving the combustion zone may have a temperature of from 1200-1500 F. I may, however, use extraneous heat such as superheated steam to aid in the distillation.

As used herein, by the word "lump I mean to imply a particle size greater than from 30-400 mesh which size is normally considered to be a powder, and therefore by the term "lump I mean to imply aggregates of shale havin a size up to V inch in diameter.

By the term fluidized mass. I mean a dense mixture of a gas and solid which has a flowability approaching that of a liquid, but I do not mean to include asuspension of solid in a gas traveling at such a velocity that there is practically no "slippage" or directional motion by the solid independent of, or different from that of the gas.

It is to be distinctly understood that the foregoing description and the accompanying drawings are purely illustrative of my invention and do not impose any limitations thereon, and I wish to claim as my invention all of the subject matter specifically disclosed herein, as well as that readily deducible and within the spirit of my invention.

1. The process of distillation, which comprises introducing finely divided carbonaceous solids into a confined distillation zone, retaining a quantity of said finely divided solids as a bed in said zone, introducing a stream of heated non-oxidizing fluid into the lowest portion of said zone, said fluid being introduced at a rate to maintain said bed in a fluidized condition, removing said nonoxidizing fluid and the volatiles evolved from the solids from the top of said bed, removing a portion of the solids from said bed, introducing the solids thus removed into a combustion zone, retaining the solids as a bed in said combustion zone, introducing an oxidizing gas into the lower portion of said zone at a rate to maintain said solids in a turbulent fluidized state, burning said solids in said combustion zone, removing a portion of the highly heated solids from said combustion zone, mixing said heated solids from the combustion zone with the non-oxidizing fluid and introducing the mixture into the distillation zone at the lowest portion of the distillation zone.

2. The process of claim 1 in which the solids removed from the distillation zone are mixed with the oxidizing gas before introduction into the combustion zone.

-3. A continuous method for distilling shale to recover hydrocarbons therefrom which comprises continuously discharging the roughly ground shale containing lumps of sizes up to A" in diam-v eter and finely divided material into a vertically expanding distillation zone, subjecting the said shale to the influence of heat in said distillation zone whereupon it is reduced in size, discharging a gas into said distillation zone at near the bottom thereof and causing said gas to flow upwardly in order to form a dense phase ebullient, fluidized mass of shale in said distillation zone, permitting the shale to remain resident in the distillation zone under distillation conditions for a suflicient period of time to eifect the release of valuable hydrocarbons therefrom, continuously withdrawing spent shale from said distillation zone, suspending the withdrawn spent shale in an oxygencontaining gas, discharging the resultant suspension into a combustion zone wherein it is sub- Jected to oxidizing conditions to cause a combustion 01' combustibles on said spent shale thereby increasing the heat content of the shale particles, returning at least a portion of the burnt shale to the distillation zone in order to supply heat to the distillation, and continuously recovering valuable hydrocarbons from said distillation zone.

4. A continuous method for distilling shale to recover hydrocarbons therefrom which comprises continuously discharging the roughly ground shale containing lumps up to sizes of /2 in diameter and finely divided material into the top of a vertically expanding distillation zone, subjecting the said shale to the influence of heat in said distillation zone whereupon valuable hydrocarbons are released, discharging a gas into said distillation zone during the distillation operation at near the bottom thereof, and causing said gas to flow upwardly in order to form a dense phase, ebullient, fluidized mass of shale in said distillation zone, recovering valuable hydrocarbons from said distillation zone, recovering spent shale from said distillation zone, suspending said shale in an oxygen-containing gas, conducting the suspension to a combustion zone causing the combustion of the fixed carbon and other combustibles contained in the spent shale whereupon its tempera- 8 ture is increased, and returning at least a portion of the burnt spent shale to the distillation zone to supply heat thereto.

EDWARD B. PECK.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,432,101 Dankwardt Oct. 17, 1922 1,899,887 Thiele Feb. 28, 1933 1,913,968 Winkler June 13, 1933 1,937,552 Davis Dec. 9, 1933 1,983,943 Odell Dec. 11, 1934 1,984,380 Odell Dec. 18, 1934 2,111,579 Winkler Mar. 22, 1938 2,341,193 Scheineman Feb. 8, 1944 2,360,787 Murphee Oct. 17, 1944 2,367,281 Johnson Jan. 16, 1945 FOREIGN PATENTS Number Country Date 331,322 Great Britain July 3, 1930

Images