US3372734A - Fluid process useful in the recovery of hydrocarbons from tar sands - Google Patents

Description

March 12, 1968 G. c. GRUBB ETAL FLUID PROCESS USEFUL IN THE REC OVERY OF HYDROCARBONS FROM TAR SANDS Original Filed June l, 1965 2 Sheets-Sheet l March 12,1968 G, C. GRUBB ETAL 3,372,734

FLUID PROCESS USEFUL IN THE RECOVERY O HYDROCARBONS FROM TAR SANDS IN VEN TOR5 Geary@ 62 Grt/ BY Mrz/M i. /l/afa/l United States Patent Olihce 3,372,734 Patented Mar. 12, 1968 2 Claims. (Cl. 16S- 1) This invention is a division of application Ser. No. 460,367, tiled June 1, 1965, now abandoned.

The present invention relates to a uid process useful in the recovery of hydrocarbons from tar sands. More particularly, the invention relates to improvements in the recovery of hydrocarbons from tar sands by direct thermal processing of the tar sands. Still more particularly, this invention relates to a novel and efficient fluid process for the recovery of hydrocarbons from tar sands such as the Athabaska tar sands which are not readily susceptible to processing by conventional solvent extraction and hot Water processing techniques. In accordance with one aspect, the present invention relates to a method for introducing tar sands into a uid bed conversion Zone. In another aspect, the invention relates to a novel fluid process for recovering hydrocarbon values from tar sands in highly efcient manner with respect to product yields and heat recovery.

Tar sands exist in various areas of the world and contain appreciable quantites of hydrocarbons. The Athabaska tar sands of Canada is one example of a deposit of such sands which comprise a vast reserve of hydrocarbon constituents. It is known that the oil content of such sands may vary from about 5 percent to about 21 percent by volume, the gravity of the oil ranging from about 6 to about 10 API. These sands may lie from about 200 to about 300 feet below an overburden and the beds may range from about 100 to about 400 feet in depth. As mined and received for processing, the tar sands are generally present as agglomerates or lumps consisting essentially of line grain sand and clay, water, and viscous hydrocarbonaceous material called bitumin. These agglomeraties may range in size from about 1/2 to 4 inches in diameter depending upon the mining method and equipment employed. A typical oil recovered from the sands has an initial boiling point of about 30 F., 1 percent distilled to 430 F., 20 percent distilled to 650 F., and 50 percent distilled to 980 F.

Unfortunately, the tar sands received from the mine in an agglomerated condition are unsuited for direct introduction to a fluid bed conversion zone to recover the hydrocarbon values. Moreover, Athabaska sands, for example, cannot be readily recovered by conventional water techniques, since clay exists in the sands which greatly retards recovery of the oil. Prior art methods have proceeded by treating tar sands in accordance with solvent extraction techniques to prepare hydrocarbons for introduction to a suitable conversion zone. In accordance with one such solvent extraction technique, the tar sands agglomerates are contacted with a suitable solvent such as a gas-oil boiling range fraction to produce a solution of bitumin and gas-oil. Such solution is separated from the sand and is passed to a conventional hydrocarbon conversion unit, such as a fluid coking or cracking unit. An-

other extraction technique requires the addition of water to the tar sands and passage through a shearing-mixing zone in order to separate an oil phase from a water phase, the oil phase then being passed to a conventional hydrocarbon conversion unit. Unfortunately, the pretreatment of the tar sands by such techniques in order to separate an enriched hydrocarbon stream from the sand material substantially increases the recovery c-osts. It is desirable to treat tar sands directly in a fluid hydrocarbon conversion process Without resorting to hot water or solvent extraction techniques for preparing the feed material. lt is, therefore, an object of the present invention to overcome the inherent disadvantages of the prior art and to provide efcient method and means for the recovery of hydrocarbons from tar sands.

Another object of this invention is to provide an elficient method for the introduction of tar sands to a hydrocarbon conversion zone wherein a fluidized bed of solid material is maintained at an elevated temperature.

Another object of the present invention is to provide a method for recovering hydrocarbons from tar sands employing direct thermal treatment thereof whereby the recovery of hydrocarbon oils is maximized.

A further object is to provide a tar sands recovery method employing uid bed techniques in which the large quantity of heat imparted to the inert material in the feed is eeiently recovered therefrom.

A further object is to provide a method for withdrawing the hydrocarbon vaporous eilluent from a hydrocarbon conversion zone and passing same into a hydrocarbon recovery zone in a manner such that the excessive coking and fouling experienced in the past with respect to transport lines and equipment is substantially reduced and eliminated.

Further objects and advantages of the present invention will become apparent to those skilled in the art from the following description and disclosure.

The objects are generally accomplished in accordance with the present invention by the introduction of tar sands agglomerates consisting essentially of sand particles and inert material, hydrocarbon material, and water, essentially as mined into a feed preparation zone, admixing relatively hot contact material with the agglomerates in the rst zone in order to reduct the viscosity of hydrocarbon material and drive olf Water thereby providing a l'luidizable mixture of sand particles and hydrocarbon material. A portion of the iluidizable mixture is then passed through a pressure developing zone, e.g., such as a pressure developing column of the lluidizable mixture maintained in a standpipe, and introduced into a second zone, which is a reaction zone containing a liuidized bed of solid particulate material, eg., such as a hydrocarbon conversion zone maintained under conditions suitable for carrying out thermal coking of the hydrocarbon material introduced thereto.

The term relatively hot contact material in the specification includes solid contact material such as sand particles, for example, as Well as gaseous material such as hydrocarbon vapors, llue gas, stream, or mixtures thereof, such contact material being at a Substantially elevated temperature relative to the tempera-ture of the tar sands agglomerates. The term tar sands agglomerates refers to the tar sands feed material essentially as it is received from the mining operation. The agglomerates consist essentially of said particles and other inert maas employed terial, e.g., clay, held together in lumps of irregular size and shape by the viscous hydrocarbon material and water. The agglomerates are unsuited for handling by conventional fluidization techniques by reason of their large and irregular sizes and shapes ranging, for example, between 1/2 and 4 inches in diameter. The agglomerates are preferably reduced in size prior to introduction to the feed preparation zone in which they are admixed with relatively hot contact material in order to provide a uniform top size which is preferably about l inch in diameter. The temperature of the agglomerates fed into the first zone is usually the ambient temperature, although it is apparent that the feed can be preheated prior to introduction to the first zone.

The term fluidizable mixture employed in this specification to denote the product of the feed preparation zone encompasses mixtures of hot contact material with sand and hydrocarbons derived from the feed agglomerates which have lost the characteristics of separate agglomerates having been flowed together by the action of the elevated temperature contact material. Such fluidizable mixtures can be flowed downwardly as a pressure developing column of solid material employing mechanical agitation as needed to prevent solids bridging `of the column. It is thus pointed out that the term tiuidizable mixture as employed herein is not limited to those mixtures which may be fluidized by means of gaseous material, alone, but includes flowable mixtures of sand and hydrocarbons which are tiuidizable by means of gaseous material in conjunction with mechanical fluidization aids, eg., such as hereinafter described, or by mechanical means, alone.

In accordance with a preferred embodiment of the method of the present invention, tar sands agglomeraties are introduced into a feed preparation zone and admixed therein with relatively hot particulate material obtained from a reaction zone. The feed preparation zone is maintained under temperature conditions to convert the agglomerates and particulate material into a iiuidizable mixture suitable for introduction as feed material into a fluidized bed reaction zone and at a pressure suitable for feeding agglomerates into the feed preparation zone. Mixing in the feed preparation zone is preferably carried out in a fixed bed agitated by suitable method and means to insure adequate intermixing of the agglomerates and hot particulate material, although it is within the scope of the present invention Ito employ a liuid bed feed preparation zone. The relatively hot particulate material can be btained at a suitable elevated temperature, which is preferably between about 400 and about 1400 F., from a hydrocarbon conversion zone or from a heat generation zone employed in the process as hereinafter described. The ratio of relatively hot particulate material to agglomerates feed is preferably maintained between about 0.5 :1 and about 2.5 :l in order to regulate the temperature of the bed in the feed preparation zone at the desired level. Hot particulate material, such as sand, is a preferred hot contact material, since it serves as a fluidization promoting diluent for the sand-oil mixtures contained in the agglomeraties feed as well as a heating medium to reduce the viscosity of the heavy hydrocarbons in the feed.

The temperature in the feed prepartion zone is generally maintained at a level which is sufficiently high to cause reduction in viscosity and expel water from the agglomerates so that the agglomerates are triturated, and yet, preferably, below the level at which any substantial percentage of the entering hydrocarbon material is converted to gaseous material which is not condensable under atmospheric pressure conditions, eg., dry gas. It is important tominimize dry gas production at this point in order to minimize the cost of separating expelled water from distilled hydrocarbon materials which must be returned for further utilization or recovery. For these purposes, the preferred temperature range in the feed preparation zone is maintained between about 250 and about 600 F., and most preferably between about 275 and about 450 F. the first zone is preferably maintained under essentially atmospheric pressure, and most preferably under a subatmospheric pressure to prevent loss of gaseous material at the agglomerates feed point. It has been found that agglomerates feed can be converted into a iiuidizable mixture employing relatively hot particulate material as the contacting agent and employing an agglomerates residence time in the feed preparation zone preferably between about l and about l0 minutes, it be ing understood, however, that substantially longer or shorter residence time may be employed in such zone, depending upon the nature of the feed and conditions of operation of such zone.

The fluidizable mixture produced in the first zone by the action of the relatively hot contact material admixed with the agglomerates feed is withdrawn from the feed preparation zone into a pressure developing zone for passage as at least a portion of the feed material into a hydrocarbcn conversion zone which is preferably a coking zone containing a dense bed of fluidized solids material Operating at an elevated temperature and pressure substantially above the conditions in the feed preparation zone. Preferably, the feed preparation zone is situated at an elevation above that of the thermal colting zone such that the fluidizable mixture can be passed to the upper portion of a standpipe communicating between such zones for passage by gravity into ythe iuidized bed of the thermal colting zone. Suitable agitation means is provided preferably within the standpipe in order to prevent bridging of the standpipe. it is to be understood that when it is desirable to locate the feed preparation zone and thermal coking zone in a side-by-side relation, that the iiuidizable mixture produced in the feed prepartion zone can be flowed therefrom into the hydrocarbon conversion zone by means of a transport line iiuidized, for example, by means of steam, air or other inert gaseous material.

The hyrocarbon conversion zone employed to convert the hydrocarbon material contained in the fluidizable mixture of tar sands and particulate material produced in the first zone comprises a luidized bed of particulate material maintained, for example, under thermal coking conditions which are well-known in the art. In the coking zone heavy oil adhering to the solid particles undergoes pyrolysis evolving hydrocarbon vapors and leaving carbonaceous residue denoted as coke deposited on the solids. Temperatures between about 800 F. and about l F. and pressure between about atmospheric and about 40 p.s.i.g. are preferable. Particulate material bearing colte at the surface thereof is passed from the hydrocarbonaceous conversion zone into a heat generation zone in which coke is burned olf the surface of the particulate material thereby raising the temperature of the material to an elevated level. Heated particulate material at a temperature preferably about 200 to 300 F. above the temperature in the conversion zone and in the range from about 1050 and about 1400" F. is passed from the heat generation zone into the conversion zone to supply heat required for the hydrocarbon conversion.

ln another aspect, the present invention relates to a combination of process steps which comprises preparing a iiuidizable mixture of solid material, eg., sand, and relatively heavy hydrocarbon material, for example, from tar sand agglomerates, and introducing the mixture into a coking zone containing a iuidized bed of finely divided solids, The hydrocarbon material undergoes pyrolysis evolving lighter hydrocarbon vapors leaving carbonaceous residue denoted as colte deposited on the solids. Vapors are separated from entrained particulate material above the liuidized bed and passed to the hydrocarbon recovery section of the process. Particulate material bearing the carbonaceous residue, i.e., sand having a layer of coke deposited thereon, is passed to a heat generator or combustion zone wherein the carbonaceous material is removed by burning in an oxygen-containing gas, eg., air, thereby producing solid material and iiue gas at an elevated temperature. A portion of the heated solid material is returned to the Coking zone to maintain the desired Coking temperature, and another portion is heat exchange against a cooler fluid, preferably in a steam generation zone in order to extract the high temperature level heat from the solids, which are thereafter withdrawn from the process. Preferably, the flue gas produced at an elevated temperature is separated from entrained solid material and withdrawn from the heat generation zone for passage in indirect heat exchange with the oxygencontaining gas fed into the heat generation zone. Additional high temperature level heat available in the flue gas is most preferably employed to generate and superheat steam.

Sand having a layer of coke deposited thereon produced in the Coking zone is preferably treated in the lower part of the coking zone with a gaseous stripping agent, eg., steam, or other suitable stripping agent, in order to remove hydrocarbon vapors therefrom. A portion of the stripped sand is preferably passed into a feed preparation zone to prepare a iiuidizable mixture from the tar sands agglomerates, and the remaining portion is passed into the heat generation zone. It is also preferred to treat the portion of the hot sand which is passed from the heat generation zone back into the hydrocarbon conversion zone with a gaseous stripping agent, eg., steam, in order to remove inert material, eg., nitrogen, therefrom. Stripping at this point is particularly advantageous when a portion of the vaporous effluent of the coking zone is employed to generate hydrogen.

The carbonaceous residue on the solid material in the heat generation zone preferably is burned in two stages in order to reduce to a practical minimum the solid material withdrawn from the process. Accordingly, cokebearing sand passed from the coking zone is first contacted with a major portion of the oxygen-containing gas feed to burn coke in a first fluidized bed of solids. A portion of the thus-treated solid material is passed back to the coking zone and another portion is withdrawn to a second combustion zone maintained in a turbulent, uidized condition wherein additional oxygen-containing gas is employed to burn a further portion of the coke on the sand. The solid material treated in the second zone is heat exchange against cooler fluid and withdrawn from the system.

The solid material withdrawn from the heat generation zone is cooled prior to removal from the process by suitable heat exchange means to extract high temperature level heat therefrom. In accordance with another aspect of the present invention, finely divided solids material withdrawn from the heat generation zone after receiving one or 4more contacts with oxygen to burn coke there from is passed as a plurality of elongated confined streams of liuidized material through a multitubular heat exchange zone in indirect heat exchange relationship with suitable cooling fluid material maintained in external contact with the tubes. The tubes are preferably disposed vertically and in parallel arrangement within the heat exchange zone, and fluidization gas, preferably air, is supplied to the base of each tube to insure adequate liuidization. One of the problems of the past in achieving effective fluidized solids heat exchange involved the difficulty of obtaining equal distribution of solids material among the several tubes. This problem is overcome and substantially equal distribution of solids among the several tubes is achieved by passing the finely divided solids material withdrawn from the heat generation zone into an essentially unobstructed header zone situated immediately above the upper tube apertures and introducing fiuidization gas at a plurality of points located adjacent to and along side of the tube apertures, eg., between successive tube pairs in the lower portion of the header zone. At the bottom end of the heat exchange zone,

iiuidization gas is introduced directly into each tube at substantially the same rate for each tube. The rate of introduction of gas to each tube is preferably equalized in the following manner. A confined. stream of gas is flowed from a common source into the bottom aperture of each tube. A first relatively large pressure drop of essentially the same magnitude is introduced into each stream, eg., by means of a restricted orifice situated in the path ofthe confined stream. The stream is then diffused into the bottom tube aperture, eg., through a forarninous plate, such as a sintered metal cap, wherein the pressure drop is small relative to the tirst pressure drop. Since the confined streams passing to each tube aperture emanates from a common source, such as, e.g., a common gas chest or reservoir, by effecting substantially the same, relatively large pressure drop in each confined stream, the effect of variation in pressure drop at the point where the streams are diffused into the tube apertures is not a significant factor in determining the rate of fiow of iiuidizing gas into each tube, and, thus, the iiow rate into each tube is maintained at a substantially constant value.

The withdrawal of the coking zone effluent containing hydrocarbon vapors over a wide boiling range and the separation of such gaseous material from entraned fine particulate material e.g., in the cyclones, presents a serious problem, since coke has a tendency to be deposited in the withdrawal conduits. This problem is overcome by the introduction of superheated steam into the cyclone separation zone in admixture with the gaseous effluent to reduce the partial pressure of the heavy hydrocarbons from saturation to a condition at least about 30 F above dew point. The superheated gaseous mixture withdrawn from the separation Zone is then passed through a suitable conduit, preferably in indirect heat exchange relationship with super-heated steam being passed to the separation zone, and is discharged into the hydrocarbon recovery system.

For a better understanding of the present invention, reference is now made to the two figures of the drawings.

FIGURE l illustrates, diagrammatically, in elevation, a preferred embodiment of the fluid process of the present invention.

FIGURE 2 illustrates, also diagrammatically, in elevation, one embodiment of preferred means for recovering heat from fluidized solid material.

Reference is now made to FIGURE 1 which is described in conjunction with a working example of the operation thereof. Conveyor 10 introduces feed material into hopper 12 situated in an upper portion of mixing vessel 14. The feed material consists of tar sands agglomerates which have been reduced in size and screened such that the maximum diameter thereof is about 1 inch. The temperature of the feed is about 32 F. and the bulk density is about 100 pounds per cubic foot. The feed composition is about percent solids, 12 percent hydrocarbon and 3 percent free moisture on a weight basis. The diameters of the sand particles in the agglomerates range between about 1 200 microns, and clay particles in the feed may have diameters even below l micron.

The agglomerates are introduced into feed preparation zone 14 at the rate of 4,166,500 pounds per hour and are distributed about the periphery of a fixed bed 26 by means of a conical distributor plate 16. Solid particulate material comprising sand particles bearing a small amount of coke on the surfaces thereof is Withdrawn from a bottom portion of colting zone 42 at a temperature of 930 F., and is passed upwardly through risers 30 at a rate of 2,716,000 pounds per hour. The solid particulate material in conduit 30 pass into enlarged sections 30A for discharge at a reduced velocity above distributing plate 16. An opening is provided between conduits 30 and 30A to permit free movement of rake 24. The hot sand is mixed with agglomerates at the periphery of bed 26 which is maintained at a temperature of about 300 F. A vacuum of about 1 inch Hg. is maintained above bed 26 by the evacuation of gaseous material as hereinafter described. The water and some of the hydrocarbons in the agglomerates are vaporized by the contact of hot solids with the incoming feed in the feed preparation zone 14. Vaporized material, entrained solids, and air leakage from hopper 12 is withdrawn overhead of zone 14 by means of conduit 33 and passed into cyclone 39 wherein solids material is separated and returned to bed 26 by means of dipleg 40. Gaseous material separated from cyclone 39 is passed into condenser 127 in line 125 to condense water and hydrocarbons in the gaseous material. A gas-liquid mixture thus obtained is flowed into separator 130 operated at 140 F. and about 14 p.s.i.a. Gaseous material, which comprises inerts, is withdrawn from the separator in purge line 126, which can be connected to a steam jet ejector, for example, in order to maintain a slight vacuum. A water layer is separated and discarded in line 128 and the condensed hydrocarbon oil is recycled to coking zone 42 in line 132.

Returning to the description of feed preparation zone 14, rake 24 is provided for mixing the hot sand withdrawn from zone 42 with the cold feed. Prongs 24A depend from the rake and are preferably made plow-shaped in order to induce the material of bed 26 to ow inwardly toward standpipe 32. Rake 24 is rotated by means of motive force supplied by an electric motor connected to gear box 23 through rod 22. The rake 24 is rigidly attached to elongated rod 27 which is rotatably connected to gear box 23. Floor 25 is pitched toward the center of Zone 14 such that the material in bed 26 flows generally toward the center under the influence of prongs 24A. Shroud 18 is provided to protect the gear box 23. Zone 14 is 35 feet in diameter and bed 26 is maintained at a depth of about 4 feet. The average holding time in bed 26 is about 3.2 minutes which is sufficient to reduce the agglomerate feed material to a mixture of iluidizable particulate hydrocarbon materials. The mixture flows from bed 26 over the upper edge 28 of standpipe 32 for passage downwardly therethrough.

Standpipe 32 is centrally disposed within zone 14 and communicates between xed bed 26 and a dense bed of iiuidized particulate material 46 maintained in coking Zone 42. The standpipe comprises means for owing a pressure developing column of fluidized solids material from a feed mixing zone 14 operated at essentially atmospheric pressure into a fluid coking zone 42 operated at a relatively higher pressure. In this example, the standpipe has an inside diameter of about 4 feet. Elongated rod 27 rotatably connected to gear box 23 rotates within the standpipe 32. A plurality of bars 29 are angularly mounted on rod 27, although any suitable agitation means for the prevention of solids bridging of the standpipe can be employed such as, eg., a screw feeding means, The aforementioned uidizable tar sands mixture is discharged from standpipe 32 into dense uid bed 46. In this example, bed 46 is operated under coking conditions including a temperature of about 930 F., which is maintained by the introduction of solids material from two separate heat generation zones at the rate of 10,675,- 000 pounds per hour per generator through valved conduits 75. The temperature of the solids introduced from the heat generators is about 1200 F. The pressure above dense bed 46 in vessel 42 is maintained at about 10 p.s.i.g. while the pressure below baffies 48 is about 30.8 p.s.i.g. Residence time of about 5.2 minutes is provided in dense bed 46 and further residence time is provided in the section containing baffles 48 at the bottom of Zone 42. Fluidization gas is provided below baffles 48 by the introduction of steam through distributor rings 51. Additional uidization is provided in bed 46 by reason of the dry gas generated during the coking operation. Bafes 48 which can be made in any suitable shape and arrangement, such as the staggered, inverted V-shaped baftles shown in the drawing, aid in stripping hydrocarbon vapors from the outlet solids and in minimizing by-passing of fresh feed material to the outlet at the bottom of Zone 42.

Risers 30, preferably, depend into the lower baied portion of zone 42 which comprises means for conveying hot contact material to the feed preparation Zone such that the solids which are withdrawn for admixing with the cold feed agglomerates have been stripped of hydrocarbon vapors. Lift steam is supplied to the base of risers 30 by means of injection lines 47 situated at the bottom thereof. Vertical baie 49 is disposed within the bottom Central portion of zone 42 to divide the baffled section in essentially two equal parts. Stripped solid particulate material having coke deposited on the surface thereof is withdrawn to the heat generators 60 through valved standpipes 50 and transport lines 55. Aeration steam is introduced into standpipes 50 by means of lines 52 and lift air is introduced into transport lines 55 by means of lines 54.

Staged cyclones 43 are provided in the upper portion of Coking zone 42 to reduce the solids content of the gaseous effluent of the reactor. Solids material is returned to bed 46 by means of dipleg 44. Eiuent vapors and entrained solids material pass from cyclones 43 into plenum chamber 45 and then through withdrawal conduit 140 for passage to the vapor recovery system. Conduit is heated by means of steam jacket 142. Superheated steam is introduced into steam jacket 142 by means of line 144. To minimize the formation of coke in the cyclones and vapor outiet line 140, the superheated steam in jacket 142 is injected by means of line 146 into cyclone inlet 147. The steam injection is regulated such that steam introduced reduces the partial pressure of the heavy hydrocarbons in the efuent, i.e., the 850+ hydrocarbons in the coker effluent vapor, from saturation to a condition about 30 F. above the dew point. In this example, about 63,000 pounds per hour of steam at about 930 F. and 600 p.s.i.g. are introduced by means of line 144 into jacket 142 and then into the cyclones via line 146.

The coker efiiuent vapors are passed from conduit 140 into eluent scrubbing zone wherein the effluent is contacted with circulating oil introduced at about 600 F. in line 152 in order to cool the effluent and to remove soiids therefrom. The circulating oil consists essentially of 850`+ material. Scrubbing is achieved by owing the circulating oil downwardly over baffles 154 in intimate countercurrent contact with the upowing efiiuent vapors. Substantially all of the entrained solids are scrubbed from the efliuent and are withdrawn with the circulating oil fraction at the bottom of scrubber 150 in lines 156. The circulating oil which is heated to about 700 F. in scrubber 150 is cooled in a steam generator 160 which generates 600 p.s.i.g. saturated steam in line 161 from boiler feed water introduced in line 159. The cooled circulating oil is recycled to the scrubbing Zone in lines 162 and 152. Makeeup oil is added in line 163 as needed. Oil from line 156 is recycled for conversion into reactor 42 Iby means of lines 164 and 165. In this example, this quantity of recycle oil comprises 125,000 pounds per hour, and the solids content of this recycle oil is approximately 5 weight percent. Another portion of the 850+ oil is fed to the heat generators in line 166 for use as torch oil.

Product eiuent vapor is withdrawn from scrubber 150 by means of withdrawal conduit 170 and passed to line 172 into an electrostatic precipitator 174 to insure substantially complete removal of the solids from the product vapor feeding the product fractionator (not shown in the drawing). Water is introduced to the base of the electrostatic precipitator in line 178 at 70 F. and water con taining solids material is withdrawn from the base of the precipitator and passed to waste in line 180. Product vapors are withdrawn from precipitator 174 in line 176 at a temperature of about 600 F. and a pressure of about 9 p.s.i.g. The composition and flow rate of the feed to the product fractionator is shown `below in Table 1.

Table 1.-Prduct se'n't to final fractionation The coke make in reactor 42 is about 57,000 pounds per hour.

In this example, two heat generation zones 60 are employed to supply the heat requirements for coking zone 42. In order to supply the required heat for the process, the heat generators combust coke formed in the coker introduced in transport line 55, a portion of the 850-lliquid product introduced in line 166 and about 201% of the dry gas product introduced in line 79. The heat generators, in this example, are maintained at a temperature of about 1200" F. bythe combustion, and at a pressure of about 7 p.s.i.g. In order to provide uidization gas in dense lbed 64, and oxygen for combustion of coke and hydrocarbonaceous material in the hea-t generation zone, air is preheated to about 944 F. by indirect heat exchange with flue gas, as hereinafter described, and introduced by means of line 115 to distributor ring 66 situated in the bottom portion of the heat generators. The coke content of the solids is reduced to about 0.4 weight percent operating at an oxygen `concentration in the flue gas of about 0.5 mol percent. Since 0.4 weight percent of the solids represents about 25 percent of the total coke make, it is desirable to employ a secondary coke burner 81 to reduce coke loss to about .2 weight percent or about 12 weight percent of the total coke make. The air feed in line 116 to the secondary gas distributor ring 84 comprises about percent ofthe total combustion air while about 85 percent is fed to distributor 66. The remaining air is introduced into the heat exchangers, hereinafter described, and the transport lines 55. Entrance slots 82 are provided in the upper portion of the walls of secondary coke burner 61 to allow egress of the solids from bed 64 into secondary coke burner 81. Combustion gases rising from the second-ary coke blurner pass upwardly through grid 80 into the lower portion of dense bed 64. To control the temperature of the secondary burner at the desired temperature, which in this example, is about 1050 F., cooling coil 83 is provided in the secondary burner. Preferably coil 83 is employed to generate steam at an elevated temperature.

A portion of the solids in dense bed 64 are passed into stripping zone 70 through slot 71. Steam is introduced in line 76 through distributor ring 73 situated in a lower portion of the stripping zone and the steam passes upwardly through battles 72 to strip inerts from the solid material. Employing the above-described stripping operation, the concentration of inerts recycled with solids to the reactor are reduced such that they represent about 1 mol percent in the nal dry gas product. Hence, such stripping operation is advantageous where hydrogen production is contemplated.

Returning now to the description of the solids treated in secondary coke burner 81, spent solids ow by gravity downwardly therefrom through conduits 86 into fluidized solids heat exchan-gers 88 to recover high temperature level heat imparted to the solids. Referring to FIGURE 2, heat exchangers 88 are of the shell and tube type, cooling fluid being introduced into the shell side in line 89 and heated iluid being withdrawn in line 91. Tubes 90 which, in this example, have a 2 inch inside diameter, extend from the lower tube sheet 97 through upper tube sheet 92 and terminate at a point about 2 inches above the tube sheet. Gas sparger 96 is situated at an elevation below the upper apertures of tubes as a means of introducing fluidizing gas into a lower portion of header 86A to maintain the solid particulate material in a turbulent lluidized condition and to insure an equal distribution of solids among the tubes.

Gas chest 93 is situated in bottom header 88B and provide a common pressure source of uidization gas. Tubes 94 extend upwardly from gas chest 93 to points within the lower apertures of tubes 90. Each tube 94 is provided with a porous sintered metal cap 95 to diffuse lluidization gas into the solids within tubes 90. Orifice plates 94A are provided in tubes 94 as a means of creating a pressure drop of relatively l-ar-ge and equal magni tude for each tube as compared with the presure drop in caps 95. 1n this example, air is introduced by means of tubes 94 to maintain a supericial gas velocity in tubes 90 o-f about 0.7 foot per second and a net downward velocity of solids `of about 0.1 foot per second. Cooled solids are withdrawn from the base o-f exchanger 88 in valved discharge line 99 at a temperature of about 324 F. The solids can be further cooled by discharging them into slurry tanks, for example.

Referring again to FIGURE l, in heat generator 60 cyclone 62 having dipleg 63 depending therefrom is employed to separate solid material from flue gas. It is to be understood that any number of cyclones may be employed as needed in staged or parallel arrangement to reduce the solids contents of the ue gas to an acceptable level. Two separate trains of heat exchangers are employed for recovering the heat available in the l200 F. ue gas. Train A comprises heat exchangers 102A, 104A, and 106A arranged in series to recover heat from ilue gas in line A and, in this example, to preheat air feed to heat generator 60 from about 276 F. in line 114 to an outlet temperature of about 994 F. in line 115. Shell and tube heat exchangers are employed in each train. In this example, about 60 percent of the llue gas is passed from heat generators 60 through conduit 100A into train A and the remaining flue gas is passed through conduit 100B into train B, which is employed to superheat steam for process and power plant usage. Flue gas cooled in train A to about 490 F. and in train B to 495 F. is combined in line 112 and passed to gas scrubbing units, not shown in the drawing.

Many modifications and alterations will become apparent to those skilled in the art from the foregoing description and disclosure. For example, it is apparent that the fluid process described herein and vvarious elements thereof, particularly the fluidized solids and ue gas heat exchange methods, and the hydrocarbon etliuent withdrawal method may have wide application in hydrocarbon conversion processes of the catalytic as well as the non-catalytic variety. The breadth and scope of the present invention should thus be construed as limited only by the claims.

What is claimed is:

1. A method of extracting heat from uidizable solid material in substantially vertically disposed multitubular heat exchange zone having an essentially unobstructed header zone situated immediately above the upper apertures of the tubes which comprises: introducing into an upper portion of said header zone fluidizable solid material, introducing fluidization gas into a lower portion of said header zone adjacent said tube apertures to maintain the solids in a fluidized condition and to evenly distribute the solids flowing into the tubes, introducing fluidization gas into the bottom aperture of each tube at substantially the same rate for each tube and owing solid material downwardly as a plurality of confined streams of uidized solids in the tubes, passing relatively cool fluid in external contact with the tubes to extract heat from the iluidized solids.

2. The method of claim 1 in which the rate of introduction of uidization gas introduced into the bottom aperture of each tube is substantially equalized by maintaining a common reservoir of uidization gas and flowing from said reservoir into each tube aperture a separate confined stream of gas, introducing a rst relatively large pressure drop of substantially equal magnitude into the path of 110W of gas in each stream, and then passing the gas in each stream through a diffusion zone into the lower tube aperture, the pressure drop in the diffusion zone being small relative to said rst pressure drop.

References Cited UNITED STATES PATENTS yMalek 1 34-57 X ROBERT A. OLEARY, Primary Examiner.

10 A. W. DAVIS, JR., Assistant Examiner.

F0-1050 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 372 734 Dated March l2, 1968 Inventor) George C. Grubb and Marvin' F. Nathan It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

` O column 1, line 46, for 30%. read --300 F.-;

Column 2, line 43, for "reduct" read --reduce;

Column 2, line 58,- for "stream" read steam;

Column 5, lines 6 and 47', for "exchange" read --exchanged--7 Column 6, line 7l, for "distributing" read --distributor--7 Signed and .sealed this 28th day of 1December* 1971.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSGHALK Attestlng Officer Acting Commissioner of Patents

Claims (1)

1. A METHOD OF EXTRACTING HEAT FROM FLUIDIZABLE SOLID MATERIAL IN SUBSTANTIALLY VERTICALLY DISPOSED MULTITUBULAR HEAT EXCHANGE ZONE HAVING AN ESSENTIALLY UNOBSTRUCTED HEADER ZONE SITUATED IMMEDIATELY ABOVE THE UPPER APERTURES OF THE TUBES WHICH COMPRISES: INTRODUCING INTO AN UPPER PORTION OF SAID HEADER ZONE FLUIDIZABLE SOLID MATERIAL, INTRODUCING FLUIDIZATION GAS INTO A LOWER PORTION OF SAID HEADER ZONE ADJACENT SAID TUBE APERTURES TO MAINTAIN THE SOLIDS IN A FLUIDIZED CONDITION AND TO EVENLY DISTRIBUTE THE SOLIDS IN A FLUIDIZED CONDITION AND TO EVENLY DISTRIBUTE THE SOLIDS FLOWING INTO THE TUBES, INTRODUCING FLUIDIZATION GAS INTO THE BOTTOM APERTURE JOF EACH TUBE AT SUBSTANTIALLY THE SAME RATE FOR EACH TUBE AND FLOWING SOLID MATERIAL DOWNWARDLY AS A PLURALITY OF CONFINED STREAMS OF FLUIDIZED SOLIDS IN THE TUBES, PASSING RELATIVELY COOL FLUID IN EXTERNAL CONTACT WITH THE TUBES TO EXTRACT HEAT FROM THE FLUIDIZED SOLIDS.

Images