US3617468A

US3617468A - Process for removing the hydrocarbon content of carbonaceous materials

Info

Publication number: US3617468A
Application number: US781754A
Authority: US
Inventors: Alan K Reyburn; Rex T Ellington
Original assignee: Atlantic Richfield Co
Current assignee: Atlantic Richfield Co
Priority date: 1968-12-06
Filing date: 1968-12-06
Publication date: 1971-11-02
Anticipated expiration: 1988-11-02

Abstract

A process for the recovery of volatile material from solid carbonaceous material, such as oil shale, tar sands, coal, lignite and the like, which comprises introducing the solid carbonaceous material into a retorting zone and fluidizing the solid carbonaceous material within the retorting zone. The fluidized solid carbonaceous material in the retorting zone is heated and volatile material is retorted therefrom and withdrawn from the retorting zone. The spent solid carbonaceous material is withdrawn from the retorting zone and transferred to a burnoff zone. The spent solid carbonaceous material is fluidized in the burnoff zone and carbon is burned off the fluidized spent solid carbonaceous material therein. The burned-off spent solid carbonaceous material and combustion products are then withdrawn from the burnoff zone.

Description

United States Patent 1111 3,617,468

[72] Inv n r A y 3,346,481 10/1967 .lohnsen 208/1 1 Rex T. Ellington, both of Tulsa, Okla. 3,349,022 10/1967 Mitchell 208/1 1 [21] Appl. No. 781,754 3,440,162 4/1969 Lawson 201/36 [22] Filed Dec. 6, 1968 3,480,082 11/1969 Gilliland 208/1 1 [4S] Patented Nov. 2, 1971 [73] Assignee Atlantic Richfield Company Primary Examiner-Curtis Davls New York, NY. Att0rneyMcLean, Morton & Boustead ABSTRACT: A process for the recovery of volatile material [54] PROCESS FOR REMOVING THE HYDROCARBON from solid carbonaceous material, such as oil shale, tar sands, CONTENT OF CARBONACEOUS MATERIALS coal, lignite and the like, which comprises introducing the 20 Chin's, 5 Drawing Figs. solid carbonaceous material into a retorting zone and fluidizing the solid carbonaceous material within the relorting zone.

[52] US. Cl 208/11, The fl idi d solid carbonaceous material in [he fawning 208/16 zone is heated and volatile material is retorted therefrom and Int. withdrawn from he rationing one The pent car.

[50] Field of Search 201/29, 31, bonaceous material is withdrawn f he fawning Zone and 36; 208/ transferred to a burnoff zone. The spent solid carbonaceous material is fluidized in the burnoff zone and carbon is burned [56] References Cited ofi' the fluidized spent solid carbonaceous material therein.

UNlTED STATES PATENTS The burned-off spent solid carbonaceous material and com- 3,074,877 1/1963 Friedman 201/32 bustion products are then withdrawn from the burnoff zone.

llOT GASEOUS I34 COMBUSTTON PRODUCTS RAVI SHALE AMBIENT TEMP lOO GAS,OIL,WATERDTAJST (940T H6 CONVENTTONAL RAY, FLUID BED PRODUCT RETXNETY SHALE RETORT mm PREHEATER 940 M m AND WATER rum) BED on COMBUSTION 128 GAS OUALITY PROCESS FLOW IEASURETENT I06 I I24 PREHEATED RAW SHALE 600 PRODUCT 40 I08 I26 MAKE GB COllBUSTlGl AIR l5 BB 3 WITHDRM GAS QUALITY CONTROL AND I42 FLOW IEASlIlElAEllT 6 I36 I02 NATURAL GAESED BURNETT-OFF ggug g g MAKE UP BL SPENT SHALE COOLER MED LOOP DIRECT CONTACT GASEOUS HEAT EXCHANGE lEDlUll OOOL BURNETT-OFF 102 SPENT SHALE m DISPOSAL PATENTEU nave IBYI SHEET 2 BF 3 2:52; 2E E 25528 :22 2o L T was; g g as; a

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PATENTEDNUVZ Em 351E468 SHEET 3 BF 3 FEE. 4

01L YIELD (WT. EAT- AVERAGE RESIDENCE TIME (MlN.) (70F T0 RETORT TEMPERATURE) U I 960F OIL YIELD (VIT EA.)

2468IOT2|4|6 I820 RESIDENCE TIME (MINT PROCESS FOR REMOVING THE HYDROCARBON CONTENT OF CARBONACEOUS MATERIALS This invention relates to the removal of volatile material from solid carbonaceous material. More particularly, this invention relates to an improved process for the recovery of volatile material, such as combustible gases, liquid motor fuels, and various grades of oil, from solid carbonaceous material, such as oil shale, tar sand, coal, lignite and the like.

Many techniques have been employed for the beneficiation of solid carbonaceous material. For example, oil shale has been retorted in batch-type fixed-bed operations, rotating drums, chain grate kilns, moving-bed retorts, and fluidized beds.

Previously proposed fluidized-bed solid carbonaceous material retorts have several disadvantages. Some of these disadvantages are found in the heating methods, control of retorting atmosphere and location of the solids inlet and outlet.

Some retorts utilize the sensible heat of the fluidizing gas to supply the heat of retorting, necessitating the use of large volumes of gas to carry out the retorting of the volatile material from the carbonaceous material because the solid particles and the gas used in these processes have a similar heat capacity per unit mass. The high gas flow rates may be reduced by introducing into the retorting bed a combustion-supporting gas and allowing limited combustion to occur in the bed, thus supplying the heat of retorting. But in this case, some of the volatile material products are lost through combustion and the gaseous material from the retort is seriously diluted with combustion products. In still another method, it is proposed that hot solids, either spent solid carbonaceous material from a combustion unit or other hot inert solids, be added to the retort to supply heat. This method involves additional solidshandling costs and, when bumed-off spent solid carbonaceous material is added, considerable fly ash will be generated and will be difficult to remove from the liquid and gaseous products. In addition, there is evidence that the burned-off spent solid carbonaceous material absorbs some of the volatile material products and thus contributes to a loss of yield.

In cases in which inert gas is used as the fluidizing medium, it may be heated indirectly by burning product, which is highly disadvantageous. Although most of the previous fluidized-bed retorting methods used either air or a combination of air and recycled combustion products as the fluidizing medium, as mentioned above, such fluidizing media cause loss of product through combustion and the off-gas from the retort is of little or no value. In the prior art it was not feasible to "control the chemical composition of the fluidizing gas in order to enhance the quantity and/or quality of the liquid product or to facilitate the processing of the product stream (oil, gas, water and dust) outside of the retort.

Also, in previous fluidized-bed retorts, the solids inlet has usually been at the top of the bed. In such a process, the produced oil vapors must pass through a zone of relatively cold, incoming solid carbonaceous material. While this has the advantage of effecting some of the cooling necessary to condense the oil vapors and preheat the cold incoming raw solid carbonaceous material by direct contact, there are overriding disadvantages. Some of the mist droplets formed when the vaporous material condenses impinge on the raw solid carbonaceous material and are carried back into the retort bed where product loss can occur. An even more serious disadvantage is the fact that the mist droplets in the off-gas stream will be removed in large part by the equipment that removes the dust particles from the off-gas. The problem of removing the dust from the oil can be difficult and costly.

Fluid bed operation has a number of inherent advantages, including uniformity of temperature in both the horizontal and vertical directions, excellent heat transfer, uniform solid and gas distributions, intimate solid-gas contacting, convenient solids handling, large surface area per unit weight of solid for heat and mass transfer, and rapid transport of the evolved hydrocarbon from the retorting zone. In view of foregoing prior art, it is a major advantage of the present invention to retort solid carbonaceous material and the like in a fluidized bed in a process which eliminates many of the disadvantages of former processes discussed above. Another advantage of the process of he present invention is the control of the composition of the fluidizing gaseous material in order to increase the amount of product, and the control of gas velocities so that product is withdrawn from the retorting zone before cracking can occur through prolonged residence at high temperatures thereby maximizing product yield. Another benefit of rapid withdrawal of product from the retorting zone is the fact that raw shale oil has a marked instability at temperatures up to cracking temperatures and has a tendency to form polymerization or condensation products with high boiling points. Another advantage of the process of the present invention is the transfer of heat generated by burning off carbon on the spent solid carbonaceous material to the retorting zone and its use to heat the retorting zone without contaminating the fluidizing atmosphere of the retorting zone. Still another advantage of the process of the present invention is the ability to control the residence time of the shale in the retorting zone to maximize yield while minimizing equipment size. In a preferred embodiment, the fluidized solid carbonaceous material in the retorting zone is heated by means of a single heat transfer barrier separating the fluidized spent solid carbonaceous material in the burn-off zone and the fluidized solid carbonaceous material in the retorting zone thereby benefiting from the high heat transfer coefficients obtainable. The process of the invention is further advantageous in that heat from the bumed-off spent solid carbonaceous material and its combustion products can be used to preheat cold gaseous fluidizing medium and cold raw solid carbonaceous material and other process streams to increase the thermal efficiency of the process and the bumoff process can be controlled so that maximum cementing properties are developed in the bumedoff spent solid carbonaceous material to facilitate disposal. Finally, the raw solid carbonaceous material feed inlet can be positioned so that product comes into minimum contact with cold solid carbonaceous material thereby reducing loss of volatile material product. Relatively wide particle size ranges of solid carbonaceous material may be employed in this process, e.g. inch to 10 microns, as contrasted to the narrow size ranges of solid particles employed in fluidized-bed catalytic cracking units, eg about 10 to microns. Each retort can be designed to process a certain particle size range of interest, the main difference among the various retort designs being the flow rate of fluidizing gas used. It also is possible that there would be only one particle size range of interest, said one-half inch minus, or one-fourth inch minus, and that all the raw solid carbonaceous material would be crushed to this size range and processed in retorts of one design.

In general, the process for the recovery of volatile material from solid carbonaceous material, such as oil shale, tar sands, coal, lignite and the like of this invention comprises introducing the solid carbonaceous material into a retorting zone and fluidizing the solid carbonaceous material within the retorting zone by introducing a gaseous material. The fluidized solid carbonaceous material in the retorting zone is heated and volatile material is retorted and withdrawn from the retorting zone. The spent solid carbonaceous material is withdrawn from the retorting zone and transferred to a burnoff zone. The spent solid carbonaceous material is fluidized in the burnoff zone by introducing oxygen-containing gas into the burnoff zone and carbon is burned off the fluidized spent solid carbonaceous material therein. The bumed-off spent solid car bonaceous material and combustion products are then withdrawn from the burnofl zone. A part of the stream of gaseous combustion products from the burnoff zone can be recycled and mixed with air to provide the oxygen-containing gas which is introduced into the burnofl zone. in this manner, the partial pressure of oxygen in the oxygen-containing gas can be controlled in such a way as to limit the peak temperature in the burnoff zone to a desired value.

A portion of thegaseous material introduced into the retorting zone can be a portion of the gaseous material withdrawn from the retorting zone. In such an embodiment, the gaseous material is noncombustion supporting and the chemical composition and gas velocity of the fluidizing gaseous material can be controlled to maximize product yield as is taught in our copending US. Pat. application Ser. No. 781,901, filed of even date herewith. The product yield would be maximized by these methods because the gas composition to be used, as has been proven in the laboratory and shown in the aforesaid copending application, gives greater oil yields than gases used heretofore in such a process. When the fluidizing gaseous material is a noncombustion-supporting material, there is no loss of product through combustion in the retorting zone. The fluidizing gaseous material can be preheated prior to introduction to the retorting zone, preferably by indirect heat exchange with the gaseous products from the combustion in the burnoff zone. Some heat will also be supplied to the fluidizing gaseous material from that portion of the gaseous material withdrawn from the retorting zone which is mixed with it.

The solid carbonaceous material can be preheated with a hot gaseous medium prior to introduction of the solid carbonaceous material into the retorting zone. The fluidized solid carbonaceous material in the retorting zone can be heated by indirect heat exchange with the fluidized spent solid carbonaceous material in the bumofi zone either by circulating a liquid or gaseous heat transfer medium in indirect heat exchange with the fluidized spent solid carbonaceous material in the bumoff zone and the fluidized solid retorting zone or by means of a single heat transfer barrier separating the fluidized spent solid carbonaceous material in the burnoff zone and the fluidized solid carbonaceous material in the retorting zone thereby benefiting from the high heat transfer coefficients obtainable.

The temperature of the fluidized solid carbonaceous material in the retorting zone is maintained at retorting temperature, e.g. within the range of about 800 to l,000 F., preferably about 900 to 950 F. The solid carbonaceous material is retained in the retorting zone for a time sufficient to retort the kerogens, e.g. shale oil, from the material. Average residence times within the range of about 3 to 20 minutes, preferably about 5 to minutes, are generally sufficient, at the desired retorting temperatures, for all of the volatile and gaseous products to be evolved. The burning in the bumoff zone is frequently carried out at a maximum temperature within the range of about l,000 to- 1,500 E, generally within the range of l,200 to L400" F., to develop maximum cementing properties in the burned-off spent solid carbonaceous material to facilitate disposal.

The solid carbonaceous material can be introduced adjacent the bottom of the retorting zone providing minimum contact with the volatile material withdrawn adjacent the top of the retorting zone thereby reducing loss of volatile material product. Relatively wide particle size ranges of solid carbonaceous material may be employed in this process, e.g. onehalf inch to ID microns, preferably one-eighth inch to 4OO mesh, as contrasted to the narrow size ranges of solid particles employed in fluidized-bed catalytic cracking units, e.g., ID to I00 microns. Each retort can be designed to process a certain particle size range of interest, the main difference among the various retort designs being the flow rate of fluidizing gas used. It also is possible that there would be only one particle size range of interest, say one-half inch minus, or one-fourth inch minus, and that all the raw solid carbonaceous material would be crushed to this size range and processed in retorts of one design. I

The invention will be describe in more detail with reference to the appended drawings in which:

FIG. I schematically illustrates a retort designed for carrying out the preferred process of the invention wherein the retorting chamber and burnoff chamber are contained in one process vessel and the retorting chamber is heated by means of a single heat transfer barrier separating the fluidized spent solid carbonaceous material in the retorting chamber;

FIG. 2 schematically illustrates a retort for carrying out the preferred process of the invention wherein the fluidized solid carbonaceous material in the retort is heated by circulating a liquid or gaseous heat transfer medium in indirect heat exchange therewith and with the fluidized spent solid carbonaceous material in the burner;

FIG. 3 is a flow diagram illustrating the process of the instant invention using the retort and combustion chambers of either FIG. I or FIG. 2;

FIG. 4 is a graph of the effect of average residence time on oil yield for unpreheated oil shale at various temperatures for the continuous feed unit, using natural gas as the fluidizing gas; and

FIG. 5 is a graph of the effect of average residence time on oil yield for unpreheated oil shale at various temperatures for the continuing feed unit, using either natural gas or 90 percent natural gas-10 percent CO as the fluidizing gas.

Referring to FIG. 1, solid carbonaceous material, crushed to a suitable size range and preheated to a desirable temperature, is introduced into process vessel 11 through conduits I0, of which there may be several, by screw feeders 15 into retorting chamber 12. Introduction of solid carbonaceous material can also be accomplished using a gas drive similar to that used in supplying solids to fluid bed catalytic cracking units, or it can be accomplished by using gravity feed through vertical tubes discharging somewhere in the retorting bed, as in FIG. 2. The fluidizing gaseous material, preheated to a suitable temperature and of a suitable flow rate and composition, is introduced into vessel 34 through conduits 13 into chamber 14. The composition of the fluidizing gas can be controlled by an online chromatograph to hold its carbon dioxide content to particular values in the range of 0.5 to 20 volume percent, preferably 10 to [5 volume percent, with the bulk of the remaining gaseous material being light hydrocarbons and hydrogen, as is taught in our copending application Ser. No. 78 I ,90l, filed of even date herewith. This mixture can be obtained by mixing natural gas or another light hydrocarbon gas with the gaseous product from the retort, which contains carbon dioxide, to obtain the desired concentration of carbon dioxide in the retort fluidizing gas. In some cases, the concentration of carbon dioxide in the gaseous product from the retort will be the concentration desired in the retort fluidizing gas. In such cases, natural gasor another light hydrocarbon gas is used only to start the unit, and for occasional makeup necessitated by upsets or leaks. The noncombustion-supporting fluidizing gaseous material of the process of the invention is advantageous because there is no need for combustion within the retorting chamber for heat generation. Such combustion tends to consume volatile material product in preference to carbon on the spent carbonaceous material. For example, oil shale was retorted in the laboratory in a 4-inch-diameter batch fluidized bed at temperature of 915 F. A fluidizing gas was used containing about 5-percent oxygen, as might beused in a gascombustion retort, and the oil yield was about to 88 weight percent of Fischer Assay. oil as is frequently obtained in a gascombustion retort. When heat of retorting was supplied by other means and a mixture of lO-volume-percent carbon dioxide and 90-volume-percent natural gas was used as the fluidizing gaseous material, the oil yield was about 107 weight percent Fischer Assay oil. Similarly, natural gas yielded about I02 weight percent Fischer Assay oil. In these batch tests, a total residence time in the retort bed of about 7 to 9 minutes was necessary for the unpreheated oil shale to completely evolve the volatile and gaseous material products to give the stated yields. When this 4-inch-diameter fluidized bed was operated as a continuous feed unit, the effect of average residence time in the retort bed on oil yields could be studied at different temperatures. The average residence time in the continuous unit is a composite of a wide range of actual particle residence times, whereas all the oil shale was in the retort bed for the stated residence time in the batch tests. FIG. 4 shows the effect of average residence time on oil yield for unpreheated oil shale at various temperatures for the continuous feed unit, using natural gas as the fluidizing gas. There are no numbers on the yield axis in FIG. 4 because the data obtained for the runs depicted in HO. 4 were weight percent Fischer Assay oil yield loss to the spent shale, as shown in table I, rather than actual oil recovered. in other words, the success of a particular run was gauged by how much oil did not get produced. Such results give relative comparisons among various combinations of temperature and residence time. Once this screening procedure narrowed the ranges of interest in temperature and residence time, runs were made in which the oil was actually recovered. in this series of runs the variable of fluidizing gas composition was added. The results of these runs may be seen in table ll, and FIG. 5.

TABLE I Approx. Oil Yield Average Loss in Spent Shale Retort Temp. Rcsid. Time (Wt.

( F.) (min.) F.A.)

940 9.12 15.77 we run; 7.49 940 15.44 3.65 960 9.12 6.90

TABLE II Retort Average Oil yield Fluldizing gas temp. residence (wt. percent Run Compositions F.) time (min.) F. A.)

940 15. 44 96. 09 940 9. 12 88. 67 960 15. 44 99. 28 960 9. 12 91. 42 vol. percent 940 15. 44 97. 87 N.G. plus 10 vol. percent C02. F-l do 940 9. 12 90. 52 960 15. 44 106. 32 960 9. 12 100. 38

The fluidizing gaseous material passes from chamber 14 through gas distributor 16 into retorting chamber 12, thereby fluidizing the carbonaceous material in retorting chamber 12. The gas distributor can be any of several types now in use on commercial fluidized beds or it can be made up of sections of sintered metal such as lnconel thereby giving an excellent distribution of gaseous material entering retorting chamber 12. Volatile and gaseous product material containing dust and water are withdrawn from retorting chamber 12 through conduits 26.

The retorting fluidized carbonaceous material passes upward through retorting chamber 12 until it reaches the tops of standpipes 17. The height of standpipes 17 is determined by the residence time required and the raw carbonaceous material feed rate through feeders 15. The spent carbonaceous material falls over standpipes l7 and passes down into catch basin 18. As an alternative to standpipes 17, a shroud could be placed around and openly connected with retort shell 34, into which the spent solid carbonaceous material would spill from retorting chamber 12. This spent solid carbonaceous material would then be conveyed via appropriate piping to catch basin 18. As another alternative to standpipes 17, the above setup can be used with a concentric cylinder replacing the shroud mentioned above. Oxygen-containing gas is introduced through conduits 19 into catch basin 18 at a sufficient rate that spent carbonaceous material is fluidized, passed upward into and through tubes 20, and the carbon on the fluidized spent carbonaceous material is burned off at a temperature level between l,000 and l,500 F., preferably l,200 and 1,400 F., to supply heat to retorting chamber 12. If the heat derived from burning the carbon off the spent carbonaceous material is insufficient to supply the heat of retorting, then enough other fuel, such as fuel oil, natural gas, coke, etc., to supply the retorting heat requirements can be added to the oxygen-containing gas in conduit 19. The burned-off spent carbonaceous material overflows from tubes 20 into chamber 21 and passes down through the chamber 21, helping to maintain retorting chamber 12 temperature at the desired value, and exits chamber 21 and vessel 11 through conduits 22. The combustion products given off by burning the carbon on the spent carbonaceous material pass through cyclones 23 or other devices which remove most of the entrained dust and then pass out through manifold 24 and conduit 25.

Referring to FIG. 2, solid carbonaceous material 40, crushed to a suitable size range and preheated to a desirable temperature, is introduced into fluid bed retort 46 through conduits 42, of which there may be several, at some point below the bed level 48. The feed rate of the solid carbonaceous material 40 into the fluid bed retort 46 can be controlled by cone valves 44 or some other suitable device. Introduction of solid carbonaceous material can also be accomplished using a gas drive similar to that used in supplying solids to fluid bed catalytic cracking units, or it can be accomplished by using screw feeders, as in FIG. 1.

The fluidizing gaseous material 50, preheated to a suitable temperature and of a suitable flow rate and composition, is introduced into chamber 54 through conduits 52. The composition of the fluidizing gas can be controlled by an online chromatograph to hold its carbon dioxide content to particular values in the range of 0.5 to 20 volume percent, preferably l() to l5 volume percent, with the bulk of the remaining gaseous material being light hydrocarbons and hydrogen similar to that done with the apparatus of FIG. 1. This mixture can be obtained by mixing natural gas or another light hydrocarbon gas with the gaseous product from the retort, which contains carbon dioxide, to obtain the desired concentration of carbon dioxide in the retort fluidizing gas. ln some cases, the concentration of carbon dioxide in the gaseous product from the retort may be the concentration desired in the retort fluidizing gas. In such cases, natural gas or another light hydrocarbon gas is used only to start the unit, and for occasional makeup necessitated by upsets or leaks.

The fluidizing gaseous material passes from chamber 54 through gas distributor 56 into the retorting bed, thereby fluidizing the carbonaceous material in the retorting bed. The gas distributor can be any of several types now in use on commercial fluidized beds or it can be made up of sections of sintered metal such as lnconel thereby giving an excellent dis tribution of gaseous material entering the retorting bed. Volatile and gaseous material containing dust and water are withdrawn from retorting chamber 46 through conduits 60 as streams 58.

The retorting fluidized carbonaceous material is entrained in the various solids flow patterns in the retorting bed until it reaches the inlets 61 to spent carbonaceous material downcomers 62. These inlets 61 can be located at the level of the gas distributor 56, as shown in H6. 2, or anywhere within the retorting bed up the bed level 48. The spent carbonaceous material passes through downcomers 62 into fluid bed combustion chamber 66. The feed rate of the spent solid carbonaceous material into the fluid bed combustion chamber 66 can be controlled by cone valves 64 or some other suitable device. Oxygen-containing gas 70 is introduced through conduits 72 into chamber 74, and passes through gas distributor 76 at a sufficient rate that the spent carbonaceous material in the combustion chamber is fluidized, and most if not all of the combustible carbon left on the spent carbonaceous material is combusted at a temperature level between I,000 and l,500 F., preferably 1,200 and I,400 F., to provide the heat necessary to carry out the retorting in retorting chamber 46. The heat of combustion so generated is transferred to a plurality of horizontal tubes 96, containing a flowing liquid or gaseous heat transfer medium, preferably a liquid such as molten sodium. This hot heat transfer medium is circulated by pump 92 through pipe 91 to a plurality of horizontal tubes 94 in retorting chamber 46, where enough heat is transferred from it to the bed of solid carbonaceous material to effect complete retorting at the desired temperature level. The heat transfer medium, now cooled, exits retorting chamber 46 and is circulated to cleanup system 98 in which contaminants 97 are removed, and then makeup heat transfer medium 99 is supplied as necessary and the resulting stream passes through pump 92 and line 90 as it is circulated back to the combustion bed to be reheated. The burning spent carbonaceous material is entrained in the various solids flow patterns in the fluid bed combustion chamber until it reaches the inlets 77 of the burned-off spent carbonaceous material downcomers 82, from which it exits as stream 84 and goes to further cooling and disposal. These inlets 77 can be located at the level of the gas distributor 76, as shown in FIG. 2, or anywhere within the retorting bed up to the bed level 68. The combustion products given off by burning the carbon onthe spent carbonaceous material pass out of combustion chamber 66 through conduits 80 as streams 78 and are circulated to conventional heat recovery devices. If the heat derived from burning the carbon off the spent carbonaceous material is insufficient to supply the heat of retorting, then enough other fuel 86, such as fuel oil, natural gas, coke, etc., to supply the retorting heat requirements can be added to combustion chamber 66 through conduits 88.

In FIG. 2 retorting chamber 46 and combustion chamber 66 are shown as being stacked vertically, as preferred, but they can also be built side by side. In addition, retorting chamber 46 and combustion chamber 66 are shown as being the same size, although they can be of different heights and diameters. The heat transfer loop shown in FIG. 2 is the preferred method of transferring heat from combustion chamber 66 to retorting chamber 46. However, if desired, this heat transfer can be accomplished by a different method; for example, steam can be generated in tubes 96, which would then be used to generate electricity, which in turn would be used to heat the retorting bed by operating in-bed electrical heaters in place of tubes 94.

FIG. 3 is an example of what a process flow chart built around the retort and combustion chamber of either FIG. 1 or 2 might look likeKThe temperature levels cited constitute one example of the process but the process is not limited to this example and can be used within the levels discussed above.

Referring to FIG. 3, crushed solid carbonaceous material, oil shale in this example, of a suitable particle size range 100 is preheated to about 600 F. in the raw shale preheater 104 by the hot gaseous closed-loop heat exchange medium 102. The preheated raw shale 108 is introduced into the fluid bed retort I10, where it is fluidized by preheated fluidizing gas 114 and retorted, and the carbon is burned off the spent shale in the separated combustion zone 106 by oxygen-containing gas stream 150. A bypass line 152 to carry flue gas from the flue gas exhaust line 156 to the air inlet through control valve 154 is provided so that the temperature in the combustion chamber can be controlled as desired by varying the partial pressure of the oxygen in the combustion supporting air plus flue gas stream into the combustion chamber.

The product stream 116, consisting of gas, oil vapors, dust, and water exits the fluid bed retort I and is introduced into the conventional product recovery train 118. The first unit or units in the conventional product recovery train would be the dust removal equipment. This dust removal equipment is operated at the retorting temperature so that the dust can be removed from the product stream while the oil is still in the vapor state, and consists of mechanical separators such as cyclones, or electrostatic precipitators, or a combination of the two. The dust so removed is transferred to the combustion chamber 106 or to the burnedoff spent shale cooler 148. The remainder of the product stream, consisting of oil, gas, and water, is transferred to a system of recovery equipment such as heat exchangers, fractionation towers, etc., resulting in the effluent streams of oil 128, water 132, and gas 134. The gas stream l34 is sent through the gas quality control and flow measurement section 138, which is an online chromatograph and a standard flow measurement device, and which regulates the flow rates of the make gas withdrawal stream and the light hydrocarbon gas makeup bleed stream 142, as necessary, and therefore also regulates the flow rate and composition of the fluidizing gas stream 114. The fluidizing gas stream 114 is heated to retorting temperature in heat exchanger 130 by indirect heat exchange with the hot gaseous combustion products 122 from the combustion zone 106, and is then introduced into the fluid bed retort 110. The hot burned-off spent shale 112 exits combustion chamber 106 and is fed to the burned-off spent shale cooler 148, from which the cooled burned-off spent shale 146 exits and is sent to disposal. The burned-off spent shale is cooled by the closed loop direct contact gaseous heat exchange medium 102. This can be any gaseous medium as long as oxygen content is minimized or preferably eliminated. The heat transferred to the closed-loop gas stream 102 in the burned-off spent shale cooler 148 is then transferred to the raw shale in the raw shale preheater 104. The cool closed-loop gas stream exiting from the raw shale preheater 104 is passed through a gas quality control andflow measurement section 124, which could consist of an online chromatograph, H S removal equipment, and a standard flow measurement device, and which regulates the flow rates of the make gas withdrawal stream 126 and the makeup gas bleed stream 158, as necessary, and therefore also regulates the flow rates and composition of the closed-loop gaseous heat exchange medium I02 to be fed to the burned-off spent shale cooler 148.

As a more specific illustration of the process described above, the following examples are presented.

EXAMPLE I In the modification shown in FIG. 1, oil shale, crushed to a suitable size range, say I2+60 mesh, is introduced into process vessel 11 at a suitable rate to give an average particle residence time in the bed of about 10 minutes and is fluidized with a gaseous material. The composition of the fluidizing gaseous material is controlled to an online chromatograph and is held constant at l0-volume-percent carbon dioxide and 90- volume-percent light hydrocarbons and hydrogen. The fluidizing gaseous material is introduced into process vessel II at a rate of 3,370 s.c.f./ton of raw shale. The fluidized oil shale is rctorted in retorting chamber 12 at a temperature of 925 F., yielding 107 weight percent of the Fischer Assay oil. Air is introduced into vessel 11 at a rate sufficient to fluidize the spent shale in catch basin 18. The spent shale is burned at a temperature of l,300 F. in tubes 20 to supply the heat required to maintain the 925 F. temperature in retorting chamber 12.

EXAMPLE II In the modification shown in FIG. 2, crushed oil shale with relatively wide particle size range (e.g., one-eighth inch minus) is introduced into retort 46 at a suitable rate to give an average particle residence time in the bed of about 10 minutes. Preheated fluidizing gaseous material is introduced into the bottom of retort 46 at a rate of 3,370 s.c.f./ton of raw shale, and its composition is controlled by an online chromatograph and is held constant at lO-VoIume-percent carbon dioxide and 90-volume-percentlight hydrocarbons and hydrogen. Molten sodium is circulated through pipe 90 at a suitable rate and transfers from burner 66 to retorting bed 46 the heat required to bring the inlet oil shale to retorting temperature and retorting heat. The fluidized oil shale is retorted in retorting bed 46 ata temperature of 925 F., yielding 107 weight percent of the Fischer Assay oil. Air is introduced into burner 66 at a rate sufficient to fluidize the spent shale transferred from retort 46. The spent shale is burned at a maximum temperature of l,400 to l,500 F. in burner 66 to supply the heat required to maintain the 925 F. temperature in retorting bed 46.

It is claimed:

1. A process for the recovery of volatile material from solid carbonaceous material, which comprises the steps of:

introducing the solid carbonaceous materialinto a retorting zone;

fluidizing the solid carbonaceous material within the retorting zone;

heating the fluidized solid carbonaceous material in the retorting zone thereby retorting volatile material therefrom; withdrawing volatile material from the retorting zone; withdrawing and transferring spent solid carbonaceous material from the retorting zone to a bumoff zone; fluidizing the spent solid carbonaceous material in the burnoff zone by introducing oxygen-containing gas into the bumoff zone and burning carbon off the fluidized spent solid carbonaceous material therein; and

withdrawing burned-off spent carbonaceous material and gaseous combustion products from the bumoff zone.

2. The process of claim I wherein the solid carbonaceous material is oil shale and the volatile material contains oil.

3. The process of claim 2 wherein the oil shale is fluidized within the retorting zone by a noncombustion-supporting gaseous fluidizing material taken from the group consisting of natural gas or a gas of similar composition to natural gas and natural gas containing up to -volume-percent carbon dioxide.

4. The process of claim 3 wherein the volatile material is treated to remove any dust, oil and water contained therein and part of the remaining volatile material is reintroduced into the retort zone as a portion of the noncombustion-supporting gaseous material.

5. The process of claim 3 wherein a portion of the noncombustion-supporting gaseous material introduced into the retorting zone is a portion of the volatile material withdrawn from the retorting zone.

6. The process of claim I wherein the fluidized solid carbonaceous material in the retorting zone is heated by indirect heat exchange with the fluidized spent solid carbonaceous material in the bumoff zone.

7. The process of claim 3 wherein the noncombustion-supporting gaseous material is preheated prior to introduction to the retorting zone.

8. The process of claim 7 wherein the said gaseous material is preheated by indirect heat exchange with the gaseous combustion products withdrawn from the burnoff zone.

9. The process of claim 2 wherein the burning in the burnoff zone is at a temperature of about 1,000 to about L500 F. to develop maximum cementing properties in the burned-off spent solid carbonaceous material to facilitate disposal.

10. The process of claim 6 wherein the fluidized solid carbonaceous material in the retorting zone is heated by means of a single heat transfer barrier separating the fluidized spent solid carbonaceous material in the burnoff zone and the fluidized solid carbonaceous material in the retorting zone.

11. The process of claim 6 wherein the fluidizing solid carbonaceous material in the retorting zone is heated by circulating a heat transfer medium in indirect heat exchange therewith and with the fluidized spent solid carbonaceous material in the bumoff zone.

12. The process of claim 1 1 wherein heat transfer medium is liquid sodium.

13. The process of claim 1 wherein the solid carbonaceous material is introduced adjacent the bottom of the retorting zone and the volatile material is withdrawn adjacent the top of the retorting zone to provide minimum contact between the two materials thereby reducing loss of volatile material product.

14. The process of claim 1 wherein the bumed-off spent carbonaceous material is withdrawn to a cooling zone and the solid carbonaceous material is preheated by direct contact with a closed-loop gaseous heat exchange medium which is in direct contact with said spent carbonaceous material in its cooling zone.

15. The process of claim 3 wherein the noncombustion-supporting gaseous material contains 0.5 to 20-volume-percent carbon dioxide and the bulk of the remainder consists essentially of light hydrocarbons and hydrogen.

16. The process of claim 15 wherein the carbon dioxide content of the noncombustion-supporting gaseous material is l0 to 15 volume percent.

17. The process of claim 2 wherein the'solid carbonaceous material in the retorting zone is maintained at a temperature level within the range of about 850 to about l,000 F. and is retained in the retorting zone for an average residence time within the range of about 3 to about 20 minutes.

18. The process of claim 17 wherein the temperature level is within the range of about 900 to about 950 F. and the average residence time is within the range of about 5 to about 10 minutes.

19. The process of claim 3 wherein the noncombustion-supporting gaseous fluidizing material is natural gas.

20. The process of claim 15 wherein the light hydrocarbons and hydrogen are produced by the retorting of the oil shale.

t i I i= i

Claims

2. The process of claim 1 wherein the solid carbonaceous material is oil shale and the volatile material contains oil.
3. The process of claim 2 wherein the oil shale is fluidized within the retorting zone by a noncombustion-supporting gaseous fluidizing material taken from the group consisting of natural gas or a gas of similar composition to natural gas and natural gas containing up to 20-volume-percent carbon dioxide.
4. The process of claim 3 wherein the volatile material is treated to remove any dust, oil and water contained therein and part of the remaining volatile material is reintroduced into the retort zone as a portion of the noncombustion-supporting gaseous material.
5. The process of claim 3 wherein a portion of the noncombustion-supporting gaseous material introduced into the retorting zone is a portion of the volatile material withdrawn from the retorting zone.
6. The process of claim 1 wherein the fluidized solid carbonaceous material in the retorting zone is heated by indirect heat exchange with the fluidized spent solid carbonaceous material in the burnoff zone.
7. The process of claim 3 wherein the noncombustion-supporting gaseous material is preheated prior to introduction to the retorting zone.
8. The process of claim 7 wherein the said gaseous material is preheated by indirect heat exchange with the gaseous combustion products withdrawn from the burnoff zone.
9. The process of claim 2 wherein the burning in the burnoff zone is at a temperature of about 1,000* to about 1,500* F. to develop maximum cementing properties in the burned-off spent solid carbonaceous material to facilitate disposal.
10. The process of claim 6 wherein the fluidized solid carbonaceous material in the retorting zone is heated by means of a single heat transfer barrier separating the fluidized spent solid carbonaceous material in the burnoff zone and the fluidized solid carbonaceous material in the retorting zone.
11. The process of claim 6 wherein the fluidizing solid carbonaceous material in the retorting zone is heated by circulating a heat transfer medium in indirect heat exchange therewith and with the fluidized spent solid carbonaceous material in the burnoff zone.
12. The process of claim 11 wherein heat transfer medium is liquid sodium.
13. The process of claim 1 wherein the solid carbonaceous material is introduced adjacent the bottom of the retorting zone and the volatile material is withdrawn adjacent the top of the retorting zone to provide minimum contact between the two materials thereby reducing loss of volatile material product.
14. The process of claim 1 wherein the burned-off spent carbonaceous material is withdrawn to a cooling zone and the solid carbonaceous material is preheated by direct contact with a closed-loop gaseous heat exchange medium which is in direct contact with said spent carbonaceous material in its cooling zone.
15. The process of claim 3 wherein the noncombustion-supporting gaseous material contains 0.5 to 20-volume-percent carbon dioxide and the bulk of the remainder consists essentially of light hydrocarbons and hydrogen.
16. The process of claim 15 wherein the carbon dioxide content of the noncombustion-supporting gaseous material is 10 to 15 volume percent.
17. The process of claim 2 wherein the solid carbonaceous material in the retorting zone is maintained at a temperAture level within the range of about 850* to about 1,000* F. and is retained in the retorting zone for an average residence time within the range of about 3 to about 20 minutes.
18. The process of claim 17 wherein the temperature level is within the range of about 900* to about 950* F. and the average residence time is within the range of about 5 to about 10 minutes.
19. The process of claim 3 wherein the noncombustion-supporting gaseous fluidizing material is natural gas.
20. The process of claim 15 wherein the light hydrocarbons and hydrogen are produced by the retorting of the oil shale.