US 3560369 A
Description (OCR text may contain errors)
RETORTING OIL SHALE INCLUDING AGGLOMERATED FINES Filed June s. 196e Feb. 2,1971 C, A, ROWLAND ETAL 2 sheets-sheet 1 RETORTING OIL SHALE INCLUDING AGGLOMERATED FINES Filed June 5. 1968 C. A. ROWLAND ETAI- Feb. 2, 1971 2 Sheets-Sheet 2 Ill s/v A .Wm @7 ,w
United States Patent O 3,560,369 RETORTING OIL SHALE INCLUDING AGGLOMERATED FINES Chester A. Rowland, Shorewood, and Robert D. Frans,
3,560,369 Patented Feb. 2, 1971 lCe and Apparatus for the Recovery of Oil From Shale by Indirect Heating; and Robert D. Frans, Ser. No. 705,989, led Feb. 16, 1968, and entitled Method and Apparatus for the Recovery of Oil From Shale by Gases of Fuel Burned External Thereof; and is related to further irnllgflllegloynvgnyasslgnors to Ams'chalmers Manu' 5 provements tothe method-process concepts disclosed and Filed June 5 1968 SELNL 734,667 cialmed thereln, and 1n copending U.S. patent apphca- Int, CL Clog 7/02 t1on of Chester A. Rowland and `Robert D, Frans, Ser. US, Cl. 208-11 3 Claims No. 734,666, liled June 5, 1968, and entitled Traveling l0 Grate Method for the Recovery of Oil From Shale. ABSTRACT oF THE DISCLOSURE BACKGRO'UND 0F I NVENTION A `system is disclosed for recovering oil from oil bear- Fleld of the Inventum ing shale rock in which the rock is screened to separate This invention relates to cross-flow transfer of heat rines from larger particles having a dimension of at least 15 and nllSS betWeen Particulate materiel and heated gases about 1A inch. The system includes a retorting zone in Such as may be applied, fOr example, t0 processes and which heated gases, reducing or neutral, are passed apparatus for the recovery of oil from carbonaceous mathrough the larger particles and agglomerates of the fines terials including oil shale of the character found in the to heat these particles and agglomerates t0 Oil educting State 0f COlOIadO. In particular, this iIlVeDtiOn iS directed temperature and after which the gases, then containing to a method utilizing certain heavy fractions of oil educted educted oil, are passed through a zone in which particles from Shale, 3S a hinder in an agglomerate of Shale fines; and agglomerates are preheated and the gases cooled to arranging SnCh agglomeretes and other Particles of Shale condense the oil to small droplets and vapor in the gases. in a multilayer hed on an aPPerituS of the horizontal The oil is separated from the gases and into various traveling grate type; and passing gases therethrough in fractions. The heaviest fractions of the oil, representing 20 a path transverse to the path of material movement. an amount in a range of from about 5% to 50% of the total oil educted, are recirculated through the system by Description of the pnor art using such oil as binder to agglomerate the nes into United States Bureau of Mines Bulletin 635 published agglomerares of at least iz, rrreh. These agglomerares in 1966 states that 53 companies were producing oil from may be advantageously utilized by charging them to a Coal and shale in 1860 but the discovery of liquid oil in traveling grate apparatus with the larger particles to form the United States in i859 Soon ended that industry in the a bed, with the agglomerares forming arr intermediate United States. This bulletin tells about the rapid rise in layer between upper and lower layers of the larger par- Consumption of Petroleum Products that eventuellll retieles. The larger particles will, rrr a prehearrrrg e0rrderrs sulted in a revived interest in searching for an oil shale irrg zene, trap and prevent escape from the bed, dust and retorting system that would be satisfactory from a standdrops of heavy binder oil (which may escape from agpoint of economics, operability and the character of oil. glomates). With either an upilow or downilow of gas Produced` in this preheating-condensing zone, heavy binder oil at- The Bureau of Mines bulletin states that oil shale tempting to escape the bed will adhere to and coat parretorts may be divided into four general classes based on ticles in the upper or lower layers and dust attempting the method of heat application:
Class Method 0i heat application Examples I Heat is transferred to the shale through a Wall Pumpherst'on Hayes, Berg. Il Heat is transferred to the shale from the combustion occurringinthe N-T-U, Union Oil Co., Pintsch, Bureau of Mines gas-combustion.
retort by burning product gases and the residual carbon in the III iiasnhsiiired to the shale by passing previously heated gases Swedish Industrial, Bureau of Mines gas-now, Royster.
or liquids through the shale bed. 1V Heat is transferred to the shale by introduction of hot solids into the Standard Oil Co. iluidized bed, Bureau of Mines hot-solids-contaet,
to escape the bed will adhere to the larger particles coated by the heavy binder oil. Thus, both the heavy binder oil and dust attempting to escape in this preheating-condensing zone will be trapped in the bed. In the retorting zone such heavy fraction binder oil retained in the bed will pyrolyze to produce further useful lighter oil, which will leave the bed as vapor, and residual coke which will remain in the bed.
CROSS-REFERENCE TO RELATED PATENT APPLICATION Further information relating to these prior art systems may be found in the Bulletin and references cited therein. An index of patents, issued by the United States and other nations, relating to the mining and retorting of oil shale and the recovery of its products, has been published by the United States Bureau of Mines as Bulletin 468, in 1948 (650 pages). A three part supplement identified as Bulletin 574 was published in 1958 (Part I, 134 pages; Part Il, pages; and, Part III, 62 pages).
As will be explained later, the methods and apparatus disclosed hereafter with reference to the present invention may be applied to Class II and Class III systems for ing grate. Certain of prior art patents including some ing grate. Certain of prior art patients including some related to fields other than oil shale, provide disclosures useful in describing the evolution of the present invention and these will now be specifically discussed.
The evolution of horizontal traveling grates in the held of retorting oil shale may be illustrated by reference to a few patents, such as U.S. 1,317,514 of 1919; British Pats. 278,694 and 278,740 of 1928; U.S. 2,269,025 of 1942; and,
3 U.S. 3,325,395 of 1967. Of these patents only U.S. 3,325,- 395 suggests forming a bed of shale particles segregated to form three layers.
It was recognized, in U.S. 3,228,869 of 1966, that certain heavy fractions of the oil educted from shale rock, were undesirable as components of a fiuid oil product requiring transport and further fractionating into useful commercial oil products. This patent suggested not only that such heavy fractions be removed from the oil, but also that such unwanted oil fractions be utilized in processing shale rock so that the values of such oil fractions are not lost.
In fields other than shale retorting, many processes have been developed that involve agglomerating fines into briquettes, balls, flakes or cakes before processing at high temperatures. Many different materials have been suggested as an additive to provide a binder when making agglomerates of lines. U.S. 2,325,840 of 1943 recognizes that it was previously known that certain heavy oil products, such as tar and asphalt, were useful as binders for fuel briquettes. It was also recognized, for example in U.S. 1,926,032 of 1933, that agglomerates of fines could be utilized in a multilayer bed of material to be processed in a horizontal traveling grate type furnace.
All of the aforementioned prior art patents, while helpful to understand the evolution of the technology, suggest agglomerate compositions, bed formations on traveling grates with particle size arrangements, and systems, different than are involved in the present invention and that will hereinafter ybe described.
SUMMARY OF THE INVENTION The objects of the present invention are directed to a search for a method and apparatus for the recovery of oil from oil bearing material, which is satisfactory from the standpoints of economics, operability, and character of the oil recovered; and to achieve to the greatest extent possible nine requirements that have been dened by the United States Bureau of Mines and set forth in Bulletin 635 (page 6). The nine requirements for a desirable system there set forth are the following:
(1) It should be continuous.
(2) It should have a high feed rate per unit cross sectional area.
(3) It should have high oil recovery efficiency.
(4) It should require a low capital investment, and possess a high operating time factor with low operating costs.
(5) It should be thermally self-sufficient; that is, all heat and energy requirements should be supplied wlthout burning any of the product oil.
(6) It should be ameanable to enlargement into hlghtonnage retorts rather than to a multiplicity of small units.
(7) It should require little or nol water because the Green River oil shale deposits are located in an arid region of the State of Colorado.
(8) It should be capable of efficiently processing oil shale of a reasonable wide range of particle sizes to minimize crushing and screening.
(9) It should be mechanically simple, easily operable.
Another object of the present invention is to provide an improved system for educting oil from oil bearing material, utilizing fines of the materal and less desirable heavy fractions of oil educted from agglomerates of the ines of the material, with the heavy oil fractions used as a binder additive in the agglomerates of the fines to recycle the less desirable heavy fractions of oil through the system in the agglomerates while educting oil from the agglomerated material.
Another object of the present invention is to provide an improved system for educting oil from oil bearing material, utilizing fines of the material, larger particles of the material and less desirable heavy fractions of oil educted from agglomerates of the fines and larger particles, with the heavy oil fractions used as a `binder additive in the agglomerates of the iines to recycle the less desirable heavy fractions of oil through the system in the agglomerates while educting oil from the agglomerated iines and larger particles of the material.
Still another object of the invention is to provide an improved system for educting oil from a multilayer bed of oil bearing rock on a horizontal traveling grate furnace with improved retention of nes within the bed, t0 eHiciently utilize fines, larger particles of the rock, and less desirable heavy fractions of oil educted from agglomerates of the fines and larger particles; and with the heavy oil fractions used as a binder in the agglomerates of the iines to recycle the less desirable heavy fractions of oil through the system in the agglomerate while educting oil from the rock and pyrolyzing the heavy binder oil to produce additional quantities of useful lighter oil and residual coke.
In the following description of how these objects are attained, and claims related thereto, a stream of gases will be referred to as a noncondensable combustible gas stream, either oxygen free or mixed with combustion air. By this terminology it is meant gases such as are driven from shale rock heated in an oxygen free atmosphere and these gases are a mixture of carbonaceous gases including light hydrocarbon fractions, hydrogen, nitrogen and other gases in trace amounts. By referring to such a gas stream as being noncondensable, it is meant that the gas stream cannot be condensed, as a practical matter, with equipment and in enviroments such as are herein disclosed or found in oil refineries; and that these gases are therefore of a character similar to those produced by oil refining operations which are burned at the refinery to dispose of them safely.
According to one practice of the present invention as applied to the retorting of oil bearing shale rock on a horizontal grate, the shale is crushed and screened to provide particles larger than about 1A: inch and separate therefrom smaller particles which will be referred to as nes. The fines may be mixed with a binder additive, tne source of -which will be explained as this description proceeds, and formed into agglomerates larger than about 1A inch. The agglomerates may be formed in conventional agglomerating equipment, as `for example a balling drum such as is disclosed in U.S. 2,411,873 of 1946. The agglomerates and larger pieces may then be formed into a multilayer bed on a horizontal traveling grate, with the agglomerated fines occupying a middle layer between an upper and lower layer of the larger size particles. This bed of material may then be transported tnrough at least a material preheating and oil condensing zone; a retorting zone where oil is educted from the shale; and a cooling zone. A stream of oxygen free combustible gas, the source of which will be explained later, is preheated by passing through shale in the cooling zone. The preheated gas is delivered to a combustion chamber where a controlled amount of combustion air is mixed with the preheated gas (and if desired an additional nonpreheated quantity of the gas stream for added temperature control purposes) in such quantities as are necessary to provide for combustion that provides an oxygen free gas stream at about 1200 to 1600 F. The oxygen free combustion gases at about 1200" to 1600 F. then pass through the shale in the retorting zone to educt oil and quantities of the noncondensable oxygen free cornbustible stream of gases from the shale, and then througn the shale in the material preheating and oil condensing zone where the educted oil is condensed and becomes suspended as a stable mist in the oxygen free noncondensable combustible gas stream from which the oil may be mechanically separated. This gas stream, after the oil is separated therefrom provides the gas stream, previously referred to, that cools spent shale and is thereafter partially burned to efficiently utilize this fuel heat source to the extent necessary to provide the desired oxygen free gas stream at 1200 to 160 F. The oil separated from the gases is itself separated into at least two portions with one portion being the heaviest fractions of the oil and representing an amount of from 5% to 50% of the total (and heaviest) oil educted from the material. This portion of the oil containing the heaviest fractions is the binder additive previously referred to as being mixed with the fines to form agglomerates. With these agglomerates of fines occupying a middle layer in the bed, between layers of the larger particles of rock, the bed is carried through the preheatingcondensing zone. As the gas stream passes through the layers of material in this zone the larger particles will trap and prevent the escape from the bed, dust and drops of heavy binder oil (which may escape from the agglomerates forming the middle layer of the bed). With either an upflow or downflow of gas in this treating zone, heavy binder oil attempting to escape the bed will adhere to and coat particles in the upper or lower layers (depending upon whether gas flow is up or down) and dust attempting to escape the bed will adhere to the larger particles coated by the heavy binder oil. Thus, both the heavy binder oil and dust attempting to escape in this zone will become trapped in the bed. In the retorting zone the heavy fraction binder oil retained in the bed, Whether in agglomerates or coating particles of rock, will pyrolyze to produce additional quantities of useful lighter oil, which wlll leave the bed as vapor, and residual coke which will remain in the bed.
Other features and objects of the invention and how such have been attained by this invention will appear from the more detailed description to follow with reference to an embodiment of the present invention shown in the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. l shows diagrammatically an apparatus to which the present invention has been applied and including a horizontal traveling grate shown in side elevation and in section; and
FIG. 2 is a flow diagram showing the manner in which materials flow from one operation and apparatus to another in a system according to the present invention.
DESCRIPTION OF THE PREFERRED EMBODI- MENT Referring to fFIG. 1 of the drawing, a gas permeable traveling grate assembly 1 defines a loop with an upper strand 2 supported between head and tail shafts 3 and 4 for movement in a generally horizontal path in the direction indicated by arrows. A housing assembly 5 is arranged below and over the upper strand 2 and baffles t6, 7 above strand 2 and bafes 8, 9 below strand 2 divide the interior of the housing assembly 5 into at least three chambers 15, 16 and 17 above strand 2 and -windboxes 19, 20 and 21 beneath strand 2 and in vertical alignment with the chambers 15, v16 and 17, respectively. A feed hopper assembly 22 having three feed chambers 22a, 22b and 22C is provided for feeding, through chamber 22b, agglomerated nes on top of and beneath particles of rock feed through chambers 22a and 22e, to provide a three layer bed of material on strand 2. A combustion chamber 25 is provided remote from strand 2 and housing assembly 5. An oil separator station is indicated at 30, which may be one or more mechanical oil-gas separators, with or without gas coolers as desired. The oil-gas separating operation is also located apart from the strand 2 and housing S. Separators suitable for the use that will be described are known to this art and an example of a patent disclosing such a device is U.S. 2,386,196 of 1945.
A gas stream conveying system connects the grate assembly 1, the combustion chamber 25 and the separator 30, in a manner that will now be described. The gas stream conveying system includes a blower 40 and a first conduit 41 for delivering gas to windbox 21. A second conduit 42 with a blower 43 is provided for delivering preheated gas to combustion chamber 25. Gas ow communication from the first conduit 41 to the second conduit 42 is by a path established through windbox 21 and material on strand 2 in chamber 17. A gas stream passing from conduit 41 6 through material on strand 2 to conduit 42 thereby cools the material and is itself preheated before entering combustion chamber 25.
A third conduit 44 is connected to combustion chamber 25 for delivery thereto combustion air. Means for controlling the combustion air admitted to chamber 25 is indicated by the valve 45. A- fourth conduit 46 is connected to combustion chamber 25 to exit an oxygen free mixture of combustion products and noncondensable combustible gases and deliver such gases to the retorting chamber 16. The gas discharged by conduit 46 to chamber 16 passes downward through material on strand 2 in chamber 16. A .fth conduit 47 is connected to windbox 20 to provide an exit therefrom and establish gas ow communication from the fourth conduit 46 through the upper strand 2 of the grate assembly 1 to the fth conduit 47. A blower 48 is provided in conduit 47 to blow gases from windbox 20 into windbox 19 and up through strand 2 and into chamber 15. A sixth conduit 49 is connected to chamber 15 and to the oil separator 30. A blower 50 is provided in conduit 49 to deliver to the separator 30 liquid oil (mist) and a stream of noncondensable combustible oxygen free gases educted from the shale. The stream of gases passing out of chamber 16 through windbox 20 and conduit 47 is of greater quantity than the quantity of the gas stream passing into chamber 16 from conduit 46. This is true of course because as the heated gas stream passes through the shale, vaporized oil and noncondensable gases are educted from the shale and added to the gas stream.
Liquid oil from the shale separated from noncondensable gases at 30 may be discharged through an exit at 51 and led off to oil refining apparatus (not shown). The stream of noncondensable combustible gases from the separator at 30 may be discharged through an exit at 52 to a seventh conduit 54 which is connected to the rst described conduit 41. Thus the stream of noncondensable combustible gases educted from the shale supplies the need for an oxygen free nonburning gas stream to cool the shale material in chamber 17 and the need (after being preheated and mixed with combustion air from conduit 44) for a burning stream of gases for heating the shale material in the retorting zone 16. An eighth conduit 55 is connected on one end to separator gas exit 52 to deliver some of the gas from separator 30 to combustion chamber 25 without passing through material on strand 2. Means for controlling this ow is indicated by the valve 56.
Because burning fuel in combustion chamber 25 and heating the shale in retorting chamber 16 generates additional volumes of gases which are continuously added to the system, a bleed off will be necessary and may be provided as at l57.
An agglomerating device, such as the balling drum `60 shown in FIG. 1, is feed fines by a conveyor 61 and heavy binder oil through conduit 62. Drum 60 mixes and agglomerates the material fed thereto and discharges agglomerates to a conveyer 63 for delivery to chamber 22h. The balling drum -60 may be of the type disclosed in U.S. 2,411,873. The heavy binder oil delivered to drum 60 by conduit 62 comprises heavy fractions of the oil discharged from the oil-gas separating apparatus 30 to a fractionator at 51. The fractionator (not shown, except for its location in the system being indicated) may be a vacuum fractional distillation column operated to divide the oil into two portions, one of light fractions and the other of heavy, i.e., high boiling point, fractions (with the heavy fraction portion being between 5% and 50% of the total volume of oil) as is described in the previously mentioned patent U.S. 3,228,869. In the best interests of an overall process, such as will be described later with reference to FIG. 2, the amount of oil recycled through the system as binder oil would be advantageously adjusted within the 5% to 50% range referred to, according to changes in weather. That is, in cold weather more heavy fractions would be desirably removed and recycled to maintain the desired flowability of the lighter oils shipped or pumped to a refinery.
To operate an apparatus such as shown in FIG. 1 and apply thereto the method of operation of the present invention, shale rock that has been crushed and screened to provide pieces at least about Mi inch (the upper size limit is not important to this invention and may be as desired, perhaps for example about 2 inches). These pieces are charged to feed hopper chambers 22a and 22C. The feed hopper 22 discharges such particles of crushed shale on the upper strand 2 of the grate assembly 1 which is driven by means (not shown) to move the grate in the direction shown by arrows. Agglomerates of nes formed in drum 60 are screened, as indicated in FIG. 2, to recycle pieces smaller than about 1A inch and the agglomerates that are larger than about 1A inch are charged to feed hopper chamber 22b which discharges this size fraction as a middle layer upon strand 2 thus forming a three layer bed on strand 2. The grate 1 carries the bed of shale through the chambers 15, 16 and 17, which in the practice of this embodiment of the invention define a downstream material ow sequence comprising a shale preheating and oil condensing zone (in chamber a retorting and oil educting zone (in chamber 16); and, a cooling zone (in chamber 17).
After the shale material has given up oil as a vapor and noncondensable gases while in chamber 16 the residue is moved through the cooling zone in chamber 17 where gas from separator at perhaps 100 F. is blown by blower through the first conduit 41 upwardly through windbox 21, strand 2, and into cooling chamber 17, to cool the material thereon to a temperature for handling by rubber conveyer belts or the like, and preheat the gas to perhaps about 860 F. The preheated gas passes from chamber 17 into conduit 42. This preheated air is then drawn in by blower 43 and delivered to combustion chamber 25 where controlled amounts of combustion air from conduit 44 and gases from conduit 55 mix therewith to burn a portion of the combustibles therein. Valve 45 controls the air flow through conduit 44 and provides a primary control to cause sufiicient combustion 0f gases from conduit 42 to occur to provide a mixture of unburned noncondensable gases and combustion products, free of oxygen, to exit from combustion chamber 25 through conduit 46 at about 1200" to 1600" F. Conduit 46 delivers these gases to the retorting chamber 16. Valve 56 provides additional control of the combustion taking place in chamber 25. These gases from conduit 46 pass downwardly through the shale on strand 2 in chamber 16 and heat the shale to at least slightly above oil educting temperature which may be expected to be about 800 F. The gases drawn from windbox 20 at slightly above educting, condensing temperature are blown through conduit 47, windbox 19, and through the shale on strand 2 in chamber 15. The condensable vaporized oil and noncondensable gases educted from the shale in the retorting chamber 16, along with the hot gases from conduit 46, are passed through the bed of shale in chamber 15 which condenses the oil vapors to a stable mist while preheating raw shale from hopper 22. Oil mist and a stream of noncondensable combustible gases exit lfrom chamber 15 through conduit 49 at about 250 F. and are delivered to the mechanical oil-gas separating station 30. Multistage separating, perhaps including or resulting in further cooling, may provide gases in conduits 54, 41 and 55, 44 at about 100 F.
A complete process, including the method of operation that has been described with reference to the apparatus of FIG. l, will now be described with reference to the fiow diagram of FIG. 2.
As indicated by the legend labels in FIG. .2, oil bearing shale is delivered to a crushing and/or grinding operation and then to a screening operation that separates pieces which may, for example, be larger than Mi inch,
from smaller pieces which are referred to as fines. The plus 1/4 inch particles are delivered to a retorting stage indicated by a box so labeled and additionally labeled with the reference numeral 1 to indicate that this stage may include the entire assembly identified with the numeral 1 in FIG. l. The particles delivered to this stage are discharged into the feed hopper assembly 22, which is also indicated at the box 1. Fines from the screening operation are indicated in FIG. 2 t0 be carried by the conveyor 62 to an agglomerating stage, which may be the balling drum `60 of FIG. l. As shown in FIG. 2, agglomerates from drum 60 may be screened with fines being recirculated through the agglomerating stage and the agglomerates at least about 1A: inch in size are delivered by the conveyor 63 to the feed hopper assembly 22. Oil (as mist) and gas from the retorting and condensing stage 1, are delivered by the conduit 49' to a gas-oil and light oil-heavy oil separation stage. The gas from this stage passes into conduit 52 for uses indicated in FIG. l. The light oil fractions may be delivered or conveyed as indicated in FIG. 2 to a refinery, and this may be accomplished by such as pipe lines or tank cars as desired. The heavy oil fractions are conveyed by conduit 61 to agglomerating drum 60 for use therein as a binder additive.
With the apparatus and method of its operation described with reference to FIG. l, and the overall process incorporating the aforesaid and described with reference to FIG. 2, it has been shown how to efficiently utilize nes and larger particles of an oil bearing rock, and less desirable heavy fractions of oil educted from both particles of the rock and agglomerated fines of the rock. This has been accomplished by novel concepts including such as utilizing the heavy oil fractions as a binder additive in the making of agglomerates of the fines. With such agglomerates and pieces arranged in a multilayer bed for treatment in preheating-condensing and retorting educting zones according to the present invention, nes and droplets of heavy binder oil are trapped within the bed and the heavy binder oil is pyrolyzed to produce additional quantities of lighter more commercially valuable oil and residual coke.
The manner in which and the fractions into which the educted oil is divided, for recycling versus commercial refining, is subject to some variation. For example, in moderate climates or during warm summer months, it may be possible to reduce the percentage of educted oil that is recycled because warm weather will make it easier to pump an oil mixture including more of the heavier fractions Likewise during cold weather more of the heavier fractions may have to be removed from the oil in order to efficiently pump the oil, thus resulting in a need to recycle more of these heavy oils as a binder additive in agglomerated fines.
From the foregoing detailed description it has been shown how the objects of the invention have been attained in a preferred manner. However, modification to (for example, described temperature ranges, particle sizes, percentage of oil recycled, etc.) and equivalents of the disclosed concepts such as readily occur to those skilled in the art are intended to be included within the scope of this invention. Thus, the scope of this invention is intended to be limited solely by the scope of the claims such as are or may hereafter be appended hereto.
The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:
1. A method of recovering oil from oil bearing shale comprising the steps of:
(A) separating said shale into particles larger than about 1A inch and smaller particle fines;
(B) agglomerating said fines with a subsequently derived heavy product liquid oil to form agglomerates larger than approximately 1A inch;
(C) forming said agglomerated fines and said larger particles of shale into a multilayer bed on a horizontal traveling grate, with the agglomerated layer occupying a middle layer between an upper and a lower layer of the larger size particles;
(D) retorting said multilayer bed by passing into contact therewith a stream of noncondensable oxygen free gases heated to at least the temperature required to vaporize and educe the oil as a vapor into the gas stream;
(E) cooling said gas stream containing entrained vaporized oil to condense the oil vapor to a mist;
(F) separating the oil mist from the gas stream;
(G) dividing the oil into at least two portions with one portion containing heavy liquid fractions in an amount of between and 50 percent of the total quantity of oil; and
(H) recycling said heavy fractions portion of the oil by mixing said heavy fractions portion as a binder additive with said nes to produce said agglomerates as oil bound agglomerates of said nes for retorting as hereinbefore set forth in this claim.
2. In a method according to claim 1, wherein said bed on said horizontal traveling grate passes through a first zone in which said material is preheated by passing through said bed a gas stream containing entrained vaporized oil to cool said gas stream while said oil vapor in said preheating gas stream is condensed and a second zone in which said material is retorted.
3. In a method according to claim 2, wherein said bed on said grate passes from said second zone through a third zone in which said bed of agglomerates and discrete particles are cooled by the gas stream from which the oil mist has been separated and after said bed is cooled and the gas stream is thereby again heated the gas stream is delivered to a combustion chamber for further heating to said temperature required to educe oil from said material, after which said gas stream re-enters said second zone to retort said material.
References Cited PATRICK P. GARVIN, Primary Examiner P. E. KONOPKA, Assistant Examiner U.S. Cl. X.R.