US2361066A - Coking hydrocarbon oils - Google Patents

Description

24, 1944- A. H. SCHUTTE 5 COKING-HYDROGARBON OILS Filed Ndv. 1S, 1941 INVENTOR ATTO I Patented oer. 24, 1944 COKING HYDROCARBON OILS August Henry Schutte, Hastings on Hudson, N. Y., assignor to The Lummus Company, New York, N. Y., a corporation of Delaware Application November 15, 1941, Serial No. 419,277

15 Claims.

This invention relates to an improved method of and an apparatus for coking hydrocarbon material. More particularly, this invention is concerned with the continuous production of coke from liquid or semiliquid hydrocarbon or hydrocarbon-containing materials, especially heavy residual liquids resulting from the pyrolytic conversion or distillation of hydrocarbon oils.

The manufactureof coke by the pyrolytic re: duction or distillation of heavy petroleum residues and the like is well known. In the past, however, it has been customary to coke suchpetroleum residues in a discontinuous manner requiring the use of a plurality of coking drums or chambers and resulting in cyclic operation because of the necessity of periodic removal of the coke formation from each chamber.

To overcome the disadvantages of this periodic operation, several methods of continuously coking petroleum residues have been proposed or suggested. These methods, which usually provide for the formation of coke on a continuously moving surface or receptacle, have not been generally successful inasmuch as the resulting coke mass can not be conveniently, quickly, and entirely dislodged from the coking surface after passage through the coking zone. Furthermore, difliculty is encountered in these methods in continuous removal of the dislodged and broken coke mass from the coking apparatus, which may be maintained under a super atmospheric pressure.

It is an object of my invention to provide a continuous method for coking hydrocarbon materials such-as petroleum residues, tars, and the like whereby the disadvantages of prior continuous coking methods are avoided.

Another object of my invention is to provide a readily controlled method of coking residual hydrocarbon material whereby such hydrocarbon material is formed into a continuous layer which is passed through a coking zone for reduction to coke and subsequently subjected to a disrupting force for disintegration of the solidified coke mass.

It is a further object of my invention to provide an improved continuous coking apparatus having means to form a continuously moving layer or film of hydrocarbon material to be coked, means to convert such hydrocarbon material to coke, and means to dislodge and break up the resulting continuous coke mass by suitable disruption thereof.

Still another object of my invention is the provision of a method and an apparatus wherein the hydrocarbon material to be coked is formed into a continuously moving layer having a con-- vex -lower surfaceand wherein the resulting coke mass is disintegrated by distortion or. flexing of the convex lower surface of the coke layer.

It is also within the purview. of my invention to provide for the discharge of the dislodged and broken coke mass from the coking zone. Accordingly, it is also an object of my invention to provide for use with my continuous coking apparatus an improved liquid seal through which the disintegrated coke mass is continuously discharged preferably without being wet by or undergoing reaction with the sealing liquid while the pressure within the apparatus is maintained at the desired level.

Further. objects and advantages of my invention will be apparent from the following description thereof taken in connection with the at tached drawing, wherein:

Fig. 1 is a plan view, partly broken away and partly in section, of a form of apparatus for carrying out my improved method of continuously coking hydrocarbon material .in layer form.

Fig. 2 is a vertical cross section taken on line 22 of Fig. 1 showing the liquid seal through which the dislodged coke mass is discharged from the coking apparatus.

Fig. 3 is a vertical cross section taken on line 3-3 of Fig. 1 showing the arrangement of the flexible coking means and the heating means therefor.

Fig. 4 is a fragmentary vertical cross section taken on line 4-4 of Fig. 1 showing the provision made for driving the flexible coking means.

In the preferred form of embodiment of my invention, the hydrocarbon material to be coked is continuously deposited as a layer on an endless belt having a concave upper surface, which belt moves the hydrocarbon material through a coking zone wherein it is subjected to temperatures sufiicient for conversion thereof to coke. The resulting coke layer is then disintegrated and dislodged from the'belt by suitably flexing the belt so that its upper surface is leveled or flattened as by passing the belt over a cylindrical roller. The disrupted coke mass is discharged from the coking apparatus by'passage through aseal comprising a nonwetting, nonreactive liquid which simultaneously prevents the escape of gases and vapors from the coking zone through the coke discharge outlet.

In the drawing, numeral i denotes an elongated vessel fabricated from metal of suitable thickness to withstand the pressures and temperatures required for converting hydrocarbon material to coke. This vessel preferably is cytioned a pair of spaced, horizontal cylindrical rollers 2 and 3, mounted respectively on shafts I and 5, which are in turn respectively supported by side bearings 6 and I secured in the vessel wall. Rollers 2 and 3 preferably lie in the same horizontal plane, and the shafts and bearings therefor are desirably constructed in such a manner as to prevent leakage of gases and vapors from vessel I.

According to my invention, a thin, endless, resilient, and flexible belt III is carried by the spaced rollers and is positively driven as by means of the motor II connected to shaft 5 of roller 3. Belt III iscontinuous and nonsegmental for reasons more fully disclosed hereinafter. So that positive movement of the belt can be assured and the possibility of slippage substantially eliminated, belt I0 is desirably provided with a series of spaced openings I2 along each edge thereof for engagement with drive pins or sprockets I3 extending radially from the peripheral edges of drive roller 3. Roller 2 may be similarly constructed in order to assist in the continuous movement of belt III.

To accomplish the objects of my invention, I construct belt III of a suitable metal, desirably a heat-resistant alloy, that will maintain its characteristics of resiliency and flexibility upon continued subjection to the relatively high temperatures required to effect the coking operation. The composition of this alloy is: desirably such that the belt, when repeatedly deformed at the operating temperatures, continues to resume its original shape. At the same time the metal of the'belt should be able to withstand the normal corrosive action of the hydrocarbon material being treated. A suitable metal for this purpose may comprise a ferrous alloy containing molybdenum and/or nickel, for example, or a nonferrous or substantially nonferrous alloy containing nickel such as Inconel (a product of The International Nickel 00., Inc. containing approximately80% nickel, 14% chromium, and 6% iron).

The belt is made thin enough so that, as it com tinuously passes between the two rollers, it forms, because of its resiliency, a longitudinal, troughlike structure having a concave upper surface upon which the formation of the coke mass can take place. .At thesame time the thin structure of the belt permits it to be flexed so that its concave upper surface is substantially fiattened as it passes over each roller. It will be appreciated, of course, that the thickness of the belt and its tensile strength should be such that it can readily support the coke mass that forms thereon.

Vessel or chamber I is maintained at the desired coking temperature by means of hot gases flowing through longitudinal flue I5. These gases may enter flue I5 through inlet passage I6 and may discharge therefrom through exhaust passage I1. For this purpose, the hot combustion gases from a cracking heater or the like may be used. Supplementary firing (not shown) to produce a separate suppb of hot flue gases may be provided if such is necessary or if such is desired to control the heating within chamber I.

Flue I5 is preferably so constructed that its upper surface I8 is concave and has the same general configuration as that assumed by the flexible belt III in its continuous movement between the rollers 2 and 3. In this manner, belt lindrical in shape as shown but may have anyother shape desired. Within this vessel is posi- III is supported by the upper surface of flue II as it continuously moves thereover. The contact between belt I0 and the upper surface ofthe'fiue is made as close and as complete as the speed with which belt III moves permits, and graphite may be used to facilitate the'movement of the belt. The directionof movement of the belt is preferably countercurrent to that of the hot gases as shown, although both may move concurrently.

In operation, the hydrocarbon material tobe coked such as a heavy residue, star, or the like is introduced into vessel I-tlirough line I 9 and nozzle 20 and is continuously deposited on the moving belt III. The coking feed may comprise, for example, the heavy, tarry bottoms from the fuel oil flash tower of a combination cracking system, which feed may be charged directly to chamber I from such tower. The feedis preferably preheated to some extent before being introduced into the coking vessel and is desirably at a temperature between 600 and 900 F. Where hot fuel oil bottoms comprises the feed, its tem-' perature may be in the neighborhood of 750 F. When the temperature'of the feed is at the desired coking temperature, the purpose of the hot gases in flue I5 is to supply primarily the endothermic heat necessary to effect coking of the residual hydrocarbons. When the temperature of the feed is below the desired coking temperature, however, the hot flue gases also supply the heat necessary to raise the residual'hydrocarbon material to the operating temperature. In the countercurrent operation shown, the residual material to be coked is subjected to gradu ally increasing temperatures, and progressive coking of such material thereby results. The rate of heating may also be so controlled that the resulting coke can have substantially any desired degree of volatility.

The volatile hydrocarbons formed and vaporized from the residual material during the coking operation are withdrawn from vessel I through nozzle 2I and line 2Ia. These hydrocarbons may be condensed in condenser 22, and the resulting condensate may be collected in accumulator 23, from which it may be withdrawn, if desired, by pump 24 for discharge through line 25. Preferably, these volatile hydrocarbons are subjected to suitable conditions for further conversion thereof into gasoline and other desired products.

As the residual material is discharged onto belt I 0, it forms a continuous layer or film, the lower surface of which becomes convex and assumes the configuration of the upper surface of the belt. The residual material retains this layer form as it undergoes conversion into coke so that a continuous layer of coke having a convex lower surface is moved towards roller 3. Although the layer of residual material may be made as thick as desired, the desired volatility of the resulting coke and the coking temperature employed are important factors to be considered in the determination of the layer thickness in a particular operation.-

One of the salient features of the present invention is the provision for the disintegration of the solid coke layer formed on the continuously moving belt into fragments or lumps which are subsequently discharged from the coking vessel at the end opposite the residual material inlet. According to my invention, this breaking up of the coke layer is entirely automatic and is accomplished by flexing or exerting a pressure on tinuously subjected to a disrupting force.

2,861,066 the belt as it reaches the drive roller 3 whereby the belt lsflattened and the-coke mass is con- As the belt is carried over theroller, it is flexed or forced upwardly so that it becomes substantially flat; and this action causes the cokelayer to break up and disintegrate into fragments. I

At the same time, the belt passes around roller 3, and the disintegrated coke mass iscontinuously dislodged'frombelt l0. During passage of the belt over roller 3, there isa simultaneous radial and transverse action which shears the layer of coke from the .beltat the plane of adherence .of the cokemass to the belt and causes the coke mass to crackand subsequently to break into fragments. Substantially complete freeing or separation of the coke layer from the moving belt is thereby accomplished. It will be appreciated that conditions may be so controlled as to obtain the coke in fragments of predetermined size. 1

The pieces of coke are discharged through opening 30 in vessel I-and pass through conduit 3| into the sealed conveyor 32, which discharges the broken coke from coking chamber I. In this discharge conveyor I make provision for maintaining a column of liquid through which the coke fragments must pass, which column-has a height suflicient to balance the differencein pressure, if any, between the coking chamber I and the discharge side of conveyor 32. To accomplish this object, I prefer to construct conveyor 32 so that it has a substantially U-shaped configura tion as shown and to provide a quantity of sealing liquid 33 in the lower portion of the U-tube.

and are discharged therefrom through conduit 42 fordisposal as'desired. If the coke fragments are to be stored, they may be subjected to a quenching operation after-discharge from con- .veyor32 and prior to'storage Discharge leg '40 is preferably, outwardly-and upwardly flared as shown in order to prevent arching of the cokefragments with subsequentnplugging of the-leg as the coke fragmentsrise through the sealing n um In order to maintain the'liquid seal at the desired operating temperature; I provide-a jacket 44 which surrounds vat-lea'st the lower portion of the sealed conveyor 32. A suitable heating medium such as a flue gasor the like may be circulated through this heating jacket as by inlet 48 and outlet 41.

The liquid used to effect the seal should have certain characteristics and should be selected with regard to the particular operating conditions employed. It should have a freezing point sumciently below and a boiling point sufilciently above the coking temperature so that slight temperature variations Within the coking chamber will not alter its physical state. The specific gravity of the liquid should be such that the necessary liquid head to balance the differential pressure can be maintained within a reasonable height. In addition, the specific gravity of the liquid should be greater than that of the coke so that the coke does not accumulate at the low point of the seal. The liquid should have a high surface tension so that it does not wet or adhere to the coke fragments in any way, and it should not react chemically with the coke; otherwise, the discharge of the coke fragments through the sealed conveyor may not be satisfactorily accom plished. It is also preferable that gases dissolve in the sealing liquid to a negligible extent.

In order to move the coke fragments through the resulting seal, I provide means to convey them from conduit 3| down through the seal-33. The conveying means may comprise any suitable conveying device, but I find that a continuous device such as an articulated link conveyor as shown at 35' is preferable. A motor 36 or the like is provided to drive the continuous conveying device 35.

As the coke fragments are brought to the low point of the seal by the conveying device, they are freed therefrom and rise through the sealing liquid because of their much lower s ecific gravity. The well portion 38 is preferably enlarged at 39 as shown to facilitate the freeing of the coke fragments from the conveying device. The coke fragments rise vertically through the liquid maintained in leg ill of the U-tube conveyor 32 Molten metals are especially suitable as the sealing liquid since the coking operation must be carried out at an elevated temperature. Because of their higher specific gravity, molten metals such as lead are particularly to be preferred when the coking operation must be carried out at a. pressure in excess of atmospheric. Molten alloys,

normally liquid metals such as mercury, or the like may also be used.

Molten lead is particularly satisfactory in that it has a specific gravity such that excessive heights of liquid are not required to withstand operating pressures below about pounds per square inch gage. Furthermore, it has a high surface tension so that it does not wet the coke fragments, and it does not react chemically therewith. In addition, it does not materially vaporize at coking temperatures within the range of 700 to 1000 F,

It will be apparent that I have provided a process and an apparatus wherein residual hydrocarbon material to be coked is formed into a layer on a continuously moving carrying medium preferably having a concave upper surface, from which the resulting coke mass is sheared at its planeof adherence to the carrying medium by flexing thereof, and wherein the disintegrated coke mass is discharged from the coking zone without disturbance of the continuous coking operating conditions.

It will be appreciated that certain features of my invention are not necessarily limited to the coking of residual hydrocarbon materials. For example, my invention may also be applied to the coking of other types of carbonaceous materials.

While I'have shown and described a preferred form of embodiment of my invention, I am aware that modifications may be made thereto; and I, therefore, desire a broad interpretation of my invention within the scope and spirit of the description herein said of the claims appended hereinafter.

What I claim is:

1. The method of continuously coking residual carbon material, which includes an elongated.

coking chamber, spaced rollers within said chamher, a continuously moving endless resilient metal belt carried by said rollers, the outer surface of said belt assuming a concave configuration between said rollers. means to deposit hydrocarbon material to be coked in continuous layer form on the concave outer surface of said endless belt. said rollers flexing and flattening said belt as it passes thereover whereby the resulting coke layerformed on the belt is disintegrated and dislodged, and a heating medium conduit positioned between said rollers to contact the convex under surface of .in fragments of coke are continuously discharged from the coking zone, the steps of sealing said coking zone against pressure leakage at the point of coke discharge, comprising maintaining at said point a volume of liquid nonwetting and nonreactive with respect to the coke, constraining said volume of liquid to form a column with a head suilicient to balance the differential pressure between the coking zone and the external atmosphere, temperature-conditioning said liquid by circulation of temperature-conditioned fluid therearound, and passing the fragments of coke through said column.

5. In a continuous coking process wherein the coking zone is maintained under predetermined pressure and temperature conditions and wherein fragments of coke are continuously discharged from the coking zone, the steps of sealing said coking zone against pressure leakage at the point of coke discharge, comprising maintaining at said point a volume of molten lead, constraining said volume of lead to form a column with a head sufflcient to balance the pressure differential between the coking zone and the external atmosphere, temperature-conditioning said volume of lead by circulation of temperature-conditioned fluid therearound, and passing the fragments of coke to the lower end of said column for flotation by the lead to the upper end of the column. 6. Apparatus for continuously coking hydrocarbon material, comprising means defining an elongated gas-tight coking chamber, a pair of rollers within and spaced along said chamber and mounted for rotation on parallel horizontal axes, an endless resilient belt formed of a band of sheet metal trained around said rollers, means for driving one of said rollers to move the belt continuously. the outer surface of said belt assuming a concave cross-sectional configuration between said rollers, to form a shallow trough of the upper run of the belt, means to continuously deposit fluid hydrocarbon material upon the belt at the trailing end of said trough to form a layer of the material within the trough, and means for supplying heat to the said material upon the belt to coke the material as it is transported by the belt, the roller at the leading end of said trough being formed to flatten the belt as it passes thereover to thereby disintegrate the coke layer for subsequent dislodgment of the coke from the belt as the direction of the belt is changed by said roller.

7. Apparatus for continuously coking hydrocarbon material, comprising means defining an elongated gas-tight coking chamber, a pair of rollers within said chamber and spaced therealong and mounted for rotation upon parallel horizontal axes, an endless resilient belt formed of a band of sheet metal trained around said rollers, means for driving one of said rollers to move the belt continuously, the outer surface of said belt assuming a concave cross-sectional configuration between the said rollers to form a shallow trough of the upper run of the belt, means to continuously deposit fluid hydrocarbon material upon the belt at the trailing end of said trough to form a layer of said material within the trough, and a conduit for heating material extending along the under side of said run of the belt and having a transversely curved upper surface conforming to the convex under surface of the belt and in contact therewith for supplying heat to said layer of material as it is transported by the belt, the one of said rollers at the leading end of said beltrun being formed to flatten the belt asit passes thereover to thereby disintegrate the coke layer for subsequentdislodgment of the coke from the belt as the direction of the belt is changed by said roller.

8. In an apparatus for continuously coking residual hydrocarbon material and including a coking chamber wherein coking is performed under predetermined pressure and temperature conditions and wherein fragments of coke are continuously discharged through an outlet from said chamber, means for sealing said outlet against loss of pressure from said chamber, comprising an approximately U-shaped conduit having one leg thereof in gas-tight connection with said outlet to receive the coke fragments therefrom, a

volume of liquid in said conduit nonwetting and nonreactive with respect to the coke and heavier than coke, the other leg of said conduit having a coke-discharging outlet, the volume of said liquid and said conduit outlet being correlated to form of the liquid a column in said other leg with a head suflicient to balance the differential pressure between the coking chamber and the external atmosphere, and a'conveyor within said conduit for passing the coke from the receiving leg to the discharge leg of the conduit for flotation in said liquid column to said conduit outlet.

9. In an apparatus for continuously coking residual hydrocarbon material and including a coking chamber wherein coking is performed under predetermined pressure and temperature conditions and wherein fragments of coke are continuously discharged through an outlet from said chamber,

means for sealing said outlet against loss of pressure from said chamber, comprising an approximately U-shaped conduithaving one leg thereof in gas-tight connection with said outlet to receive the coke fragments therefrom, a volume of liquid in said conduit nonwetting and nonreactive with respect to the coke, the other leg of said conduit having a coke-discharging outlet, the volume of said liquid and said conduit outlet being correlated to form of the liquid a column in said other leg with a head suflicient to balnace the differential pressure between the coking chamber and the external atmosphere, a conveyor within said conduit for passing the coke from the receiving leg to the discharge leg of the conduit for fiotation in said liquid column to said conduit outlet, and means for circulating temperatureconditioning fluid around the exterior of said conduit for temperature-conditioning said liquid.

10. The method of coking hydrocarbon material, comprising the steps of depositing said material upon a concave supporting surface to form a layer upon said surface, moving said layer, by advance of said surface, through a coking zone, maintaining said zone under conditions to convert the material to coke and cause the coke to adhere to said surface, flexing said surface transversely of the direction of its advance to disintegrate the resulting coke layer, and flexing said surface longitudinally of said direction to dislodge the so-disintegrated coke from said surface.

11. The method of coking hydrocarbon material, comprising the steps of depositing said material upon a concave supporting surface to form a layer upon said surface, moving said layer, by advance of said surface, through a coking zone, conducting, within said zone, a constrained stream of heating fluid beneath said surface and in indirect heat exchange relation to the latter to convert said material to coke and cause the coke to adhere to said surface, flexing said surface transversely of the direction of its advance to disintegrate the resulting coke layer, and flexing said surface longitudinally of said direction to dislodge the so-disintegrated coke from said surface.

12. The method of continuously coking hydrocarbon material, comprising the steps of continuously depositing said material from a fixed point and upon a concave supporting surface to form a layer thereon, continuously moving said surface past said point to advance said layer through a coking zone, maintaining said zone under conditions to convert said material to coke, continuously flexing said moving surface transversely of its direction of movement at a point advanced from said point of deposit to disintegrate the coke, and, at a point farther advanced from said fixed point, continuously flexing said surface longitudinally of its direction of movement to dislodge the so-disintegrated coke from said surface.

13. The method of continuously coking residual hydrocarbon material, comprisingthe steps of forming a continuous layer of said material having a convex lower surface, continuously advancing said layer through a coking zone maintained under conditions to convert said material to coke, and flexing the convex under surface of the resulting coke layer transversely of said movement of the coke layer to disintegrate the latter.

14. In a continuous coking process wherein the coking zone is maintained under predetermined pressure and temperature conditions and wherein fragments of coke are continuously discharged from the coking zone, the steps of sealing said coking zone against pressure leakage at the point of coke discharge, comprising maintaining at said point a volume of liquid, non-wetting and nonreactive with respect to the coke, constraining said volume of liquid to form a column with a head suflicient to balance the differential pressure between the coking zone and the external atmosphere, temperature-conditioning said liquid by circulation of temperature-conditioned fluid in indirect heat exchange relation to said liquid, and passing the fragments of coke through said column,

15. In a continuous coking process wherein the coking zone is maintained under predetermined high pressure and temperature conditions and wherein fragments of coke are continuously discharged from the coking zone, the steps of sealing said zone against pressure leakage at the point of coke discharge, comprising maintaining at said point a volume of molten material, nonwetting and non-reactive with respect to the coke and heavier than the coke, constraining said molten material to form a column with a head sufiicient to balance the pressure differential between the coking zone and the external atmosphere, passing the coke from the coking zone to the base of said column free from the external atmosphere, and then passing the coke upwardly through said' column by flotation.

AUGUST HENRY SCHUT'I'E.

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