US2764531A - Process and apparatus for retorting oil shale - Google Patents

Description

C. E. ADAMS 'Sept. 25, 1956 PROCESS AND APPARATUS FOR RETORTING OIL SHALE Filed Aug. l,- 1952 Y 2 Sheets-Sheet 1 Sept. 25, 1956 c. E; ADAMS 2,764,531

PROCESS AND APPARATUS FOR RETORTING OIL SHALE Filed Aug. 1, 1952 2 Sheets-Sheet 2 Q1 dr'h Adams Srzvenbor PROCESS AND APPARATUS FOR REPORTING OIL SHALE Clark E. Adams, Baton Rouge, La., assignor to Esso Research and Engineering Company, a corporation of Delaware Application August 1, 1952, Serial No. 302,081.

1 Claim. (Cl. 20214) The present invention relates to improvements in a process and apparatus for retorting oil shale and the like. The invention is applicable also to the treatment of analogous finely divided solid materials such as coal as well as to shale and other oil bearing solids.

In the prior art numerous processes have been proposed for retorting oil shale to recover hydrocarbon oils and other volatile or volatilizable organic materials from rocks. In general, oil shale is processed by crushing it to a predetermined size, heating the crushed shale to a temperature and for a sufficient time under conditions suitable for driving off all oils and other organic matter. In this process some of the organic matter is carbonized leaving deposits of coke and other materials which cannot be volatilized and these materials are usually burned, the heat of combustion thereof supplying most or all of the heating for the retorting process.

It has also been proposed in the prior art to fluidize the finely divided shale which is being treated in order to obtain more eflicient extraction or volatilization of the oil and other vaporizable organic constituents. The present invention relates to certain improvements in the general process just described and relates also to specific means for carrying out such process.

According to one aspect of the present invention raw shale which is suitably ground or crushed to a particle size which can conveniently be fluidized or suspended in a dense turbulent bed by means of a gas stream is subjected to heating under retorting conditions in the presence of a mass of relatively much larger, denser, non-adsorbent and relatively smooth and inert solid particles. These particles should have an average diameter of at least 70 microns, preferably more. The shale which is rather finely divided is introduced into a fluidized bed of inert abrasion resistant and non-adsorbent solid particles such as sea sand, small pebbles, or metal shot, preferably of steel or other highly resistant metal, with the result that the turbulent action of the composite fluidized bed rapidly pulverizes and disintegrates the shale as it is being retorted. The recovery of organic matter from the shale is enhanced due to both the disintegration of the shale particles and the non-adsorbent and inert nature of the bulk of the bed. The cracking activity and oil adsorptivity of the shale residue result in reduced oil yields when spent or burnt shale makes up the bulk of the retorting bed. In this invention the shale residue forms only a small proportion, less than 25%, of the bed as it is readily removed in a continuous manner from the larger and denser particles in the retorting bed.

According to another aspect of the invention pulverization of the shale which is being retorted is enhanced and accelerated by first subjecting the raw shale to relatively high pressure with gasiform fluids such as hydrocarbon gases, steam, etc. and then suddenly releasing the preheated and pressured shale into a zone of relatively lower pressure or a zone where it is quickly heated, or both. The temperature in the zone of pressure release States Patent ice may be considerably higher than that of the preheated shale. In any case the conditions preferably are so adjusted that there is a very sudden reduction in ambient pressure and/or a relatively sudden and substantial rise in temperature with a consequent sudden release of the occluded and dissolved gases or gasiform fluids in the preheated shale. The shale is rapidly disintegrated and its oil or other vaporizable constituents are quickly released by the procedure just described. Gaseous hydrocarbons or steam may be used as the saturating material for the preheated shale. Alternatively, any liquid may be used to saturate the shale which will vaporize at the lower pressure and/ or higher tempertaure, such as Water, extraneous hydrocarbons, or some of the product from the retorting step. The latter may be formed in situ by heating the shale under pressure to a temperature at which incipient retorting will take place. Thus the raw shale may be injected into a hot bed of inert and non-adsorbent particles previously utilized, to preheat the raw shale by direct heat exchange. The latter forms a feature of the invention.

The invention will be better understood by referring to the accompanying drawings in which Figure 1 shows diagrammatically a system or apparatus for the retorting of a shale, using the heat of the burning spent shale to indirectly heat the raw shale as it is introduced for processing.

Figure 2 shows a system and apparatus generally similar to that of Figure l incorporating the additional feature of pressurizing and preheating the raw shale and releasing it to a relatively lower pressure for more complete disintegration.

Referring first to Figure 1, there is shown a reactor vessel 11 having an upper zone 13 and a lower zone 15 separated by a transfer partition element 17. Fluidized solid materials are introduced into the upper zone 13 and aerated with a suitable gasiform fluid such as steam or hydrocarbon gases so as to produce a dense turbulent mass having an upper interface 19 which tends to maintain a more or less regular level under stable operating conditions. After the retorting operation is under way the retorting itself may supply substantially all of the aeration fluid required, except necessary bleeds or special jets which may be required for circulation, etc. Gas required for circulation in loops or dip legs may supply all aeration required, above that obtained from retorting.

Coils or manifolds 21 preferably extend from the zone 13 into the lower zone 15 so that solids can be circulated through them and be heated indirectly by a mass in zone 15.to be described.

Fresh shale, suitably ground or pulverized, preferably to a size below 4 inch, is introduced into zone 13, with suitable aeration or other conveying means through a tube 25. Any suitable means for feeding the ground or crushed shale may be used, such as a screw feeder, e. g. that shown at'81 in Fig. 2. The bed 13 may be aerated by conventional means, indicated diagrammatically at 27, if required.

Bed 13 is composed of a substantial proportion of relatively large inert particles having a minimum size of about 70 microns and preferably a minimum of about microns average diameter. A considerable mass of this relatively large particle inert and smooth surfaced material is used and fluidization should be suificiently active that there is substantial movement within the bed so as to enhance the grinding or attrition of the shale particles introduced through line 25. The relatively large, smooth, inert particles should have a packed density of at least one and preferably greater than one (density of Water: 1 Such density, measured when the solids are unfluidized, also called the apparent density, enhances separation of the less dense spent shale particles and such a bed is quite different from a conventional bed of spent shale residues.

The fluidizing velocity of the gases passing upwardly through bed 13 must be great enough to obtain complete fluidization of the coarse inert particles and preferably is as high as can be tolerated without excessive elutriation of the raw shale before it is stripped of its oil. In general, the gas velocity should be at least two feet per second and in many cases it may be considerably higher up to feet per second or more, depending on the density and granular size of the inert solids.

The hydrocarbon and other volatile gases or vapors carrying the spent shale residues are passed into a cyclone separator 31 of conventional type where entrained spent shale is separated and passed downward through the tube 33. The hydrocarbons and other recovered organic products are taken through tube 35 upwardly for recovery and/ or further processing.

The spent shale residue passes down through tube 33. Part of it may be withdrawn from the system, if desired, through a valve 37. Ordinarily, however, a larger part of it is diverted into a connecting tube 39 controlled by valve 41. Tube 39 leads into the bottom zone where the spent shale is burned. Air or other oxidizing gas is introduced into the bottom of zone 15 through a tube 45 and preferably through a suitable grid of conventional type 47. The air velocity should be such that the spent shale is fluidized, the upper level of the dense fluid bed thus formed substantially surrounding the manifold or coils 21 through which the particles in the retorting bed 13 are being circulated for heat transfer to the retorting zone 13. Spent shale, after burning, may be withdrawn through a tube 49 controlled by valve 51 and/ or recovered from the cyclone dip leg 59.

Other methods of heating the bed 15 may be used, such as burning waste gases from the process or other extraneous sources. Also, other indirect methods of heating bed 13 may be used such as coils in bed 13 through which retorted shale fines, etc., are circulated and burned with air or oxygen.

The uper level of the dense phase indicated at 53 is preferably well up around the coils or loops 21 so that the heating coils and the solids therein may be heated as eflicien-tly as possible. Suitable means such as steam jets 54 are provided for causing a rapid circulation of retorting bed solids, through the indirect heat exchanger means provided by coils or manifolds 21. The rapid circulation through coils 21 is required to provide heat of retorting for the retorting zone.

The flue gases from the spent shale are passed upwardly through a tube 55 and through a conventional cyclone 57 from which solids are taken downwardly through pipe 59 for discharge or re-addition to heating zone 15. The solids-free flue gases are taken out through stack 61 to the atmosphere or to other disposal means.

By utilizing the indirect heat exchangers 21 the retort may be maintained at high temperature without contaminating the gases released therefrom with the combustion gases in zone 15. The preheated shale is rapidly pulverized in the turbulent bed 13 by the impact of the large inert solid particles, steel shot, sea sand, small pebbles or the like, which pounds the shale rapidly into a very fine powder. As noted above, this fine powder separates readily from the smooth inert solids which are relatively much larger and quite non-adsorbent. From this fine powder the recoverable oil and other organic gases and vapors may rapidly be recovered to a maximum extent.

Referring now to Figure 2 there is disclosed a reaction vessel 71 which, in general, is quite similar to vessel 11 of Figure 1. It has an upper zone 73, with dense phase interface 74, a lower zone 75, with a dense phase interface 76, a cyclone 77 and a transverse partition 78 which are similar, in general, to the corresponding elements of Figure 1. A dip leg or loop 79, or a plurality of such, is.

provided to convey mixed solids from bed 73 through lower bed 75 for heat transfer. Aerating gas to effect circulation through 79 is supplied through an inlet 80.

Raw shale to be introduced into the system of Figure 2 is fed through a pressurizing device 81, e. g. a screw type feeder, and suitably pressured with a hydrocarbon gas or with steam supplied through a line 83. The raw shale then enters a manifold which has substantially immersed in the fluidized spent shale bed 75 coils or other branches 87, provided to pass through the bed and extract heat therefrom. Steam or other aerating gas is supplied to the coils 87 through a suitable line or manifold 88.

The fresh shale subjected to the preheating treatment and pressurizing just described is permitted to expand rapidly through one or preferably several expansion nozzles 89. Means such as nozzles or manifold 93 may be provided for introducing additional aerating gas, if re quired. Such aerating gas may be a hydrocarbon gas or steam, or it may be an inert gas if desired.

As in the case of Figure l the upper zone 73 contains a mass of relatively large, smooth, non-adsorbent and inert particles such as steel shot, small pebbles or sea sand which are actively fluidized under operating conditions. The preheated shale, largely disintegrated upon expansion or pressure release from nozzles 89, is further disintegrated by both the heat received from and the impact between the larger solid particles in bed 73.

The hydrocarbon and other volatile gases pass upwardly into cyclone separator 77 and to a recovery system (not shown) through tube 95. The spent shale is separated in the cyclone and is conducted downwardly and out of the reactor through tube 97 to a discharge valve 99. Preferably a major part, and in some cases all, of the shale is diverted into tube 1&1 controlled by valve 103 from which it passes to the shale burning bed 75. As in the case of Figure l the shale is burned in bed 75 by introducing air or other oxidizing gas through tube 105 and grid 107, the gas velocity being suflicient to keep the bed fluidized to a height Well up around the preheating coils 87. The combustion gases with some entrained spent shale fines pass upwardly through tube 109 to cyclone separator 111. From the latter the gases pass out through tube 113 to a stack or other disposal device. The spent shale fines may be discharged from the bottom of the cyclone through tube 115 and other spent shale may be withdrawn from the reactor through tube 1117 controlled by valve 119.

The particular combination of means for disintegrating the shale by means of successive pressurizing with gases and releasing, followed by attrition between large inert particles expedites the recovery of oil from shale and constitutes a major advantage of the invention. It will be understood, of course, that the system can be varied somewhat and may be applied to finely divided coal which is to be converted by expansion or otherwise. The system may also be applied to other materials undergoing similar processing.

What is claimed is:

A process for distilling oil shale to recover oil vapors therefrom which comprises the steps of: passing subdivided raw shale through a preheating zone, introducing a gas under pressure into said preheating zone, suddenly releasing preheated and pressurized shale into the upper portion of a retorting zone maintained at a reduced pressure and containing a fluidized mass of particulate inert solids above 70 microns in size maintained at a distillation temperature, said inert solids being relatively smooth, non-absorbent, and attrition resistant and having a packed density greater than 1, the proportion of shale in said mass being less than 25%, said mass being fluidized at a gas velocity above 2 ft./sec. sufiiciently high to entrain shale residue but at a gas velocity below the entrainment velocity of said inert solids, whereby volatile constituents are distilled from said shale and said shale is reduced to a more finely divided shale residue, removing overhead said volatile constituents and said finely divided shale residue, separating in a cyclone separating zone said shale residue from said volatile constituents, transferring the shale residue so separated to a burning zone below said retorting zone, fluidizing and burning said shale residue in said burning zone with an oxidizing gas at a temperature substantially higher than said distillation temperature, circulating portions of said mass through indirect heat exchange with the burning spent residue whereby said mass is maintained at said distillation temperature, and removing flue gases and burned shale residue from said burning zone.

References Cited in the file of this patent UNITED STATES PATENTS Johnson May 2, 1944 Krebs Nov. 28, 1944 Yellott July 18, 1950 Kearby Sept. 18, 1951 Ogorzaly Nov. 25, 1952 Krebs Feb. 3, 1953 Carr June 23, 1953 Nicolai Dec. 21, 1954 FOREIGN PATENTS Great Britain Dec. 1, 1922

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