US2082224A - Process for treating hydrocarbon oil - Google Patents

Description

Patented .lune` 1, 1937 UNITED STATES PATENT OFFICE PBOQESS FOR TRElTLING HYDRCARBON Application May 3, 1933, Serial No. 669,081

12 Claims.

This invention relates to improvements in processes for the thermal conversion of heavy hydrocarbon oil into lighter products and relates more specifically to processes according to which the oil to be converted is subjected to a plurality of successive heating and vaporizing steps.,

In accordance with my invention fresh charging stock, such as crude oil, is stripped successively by vapors derived froma tar dashing operation, vapors from a viscosity breaking cracking operation and vapors from a vapor phase cracking operation, the fully stripped charging stock ythen being` subjected to the viscosity breaking y operation' alreadygmentioned. A ilnal A`desired distillate' such as "gasoline, g as well as a heavier clean condensate isformed from the lighter vapors of the vapor phase cracking operation combined with the lighter vapors from the.

stripped crude and this condensate is used as the charging stock for the vapor phase cracking operation. Other condensate products are also segregated as a result of the crude stripping operation, a particular advantage being that the tarry residues produced by the vapor phase cracking operation and the viscosity breaking operation are separately collected for individual disposal.

My invention will be explained more fully in the followingl description taken in conjunction with the accompanying drawing.

The drawing shows diagrammaticallya system for treating hydrocarbon oil in accordance with my invention.

In the drawing reference numeral I indicates a crude oil ash tower; 2 an evaporator tower; 3 a fractionator tower; l a fuel oil flash tower; 5 a viscosity breaking heater or furnace; 6 a vapor phase heater or furnace; and I a vapor phase soaking drum. Fresh charging stock, such for example as 36 A. P. I. Mid-Continent crude, is forced by action of pump Il through charging line 8 and heat exchanger coils 9 and Ill located in the tops of the fractionator tower and dash tower respectively, into the primary or light naphtha ash drum II of crude ashtower I. In this tower, because of the rise in temperature secured by passage through the heat exchanger coils, light naphtha vapors are separated from the rest of the crude charge. 'I'hese vapors are removed from the top of the drum through vapor line I2 and condenser I3 for storage in receiver IQ# after being subjected to a certain amount of fractionation as a result 0I passage through the bubble trays or other fractionating devices I5, which are supplied with any necessary cooling medium through conduit I6. When the charging stock` is a'topped crude or other oil low in naphtha content the ash drum II may be eliminated and the preheated charge may be introduced directly into secondary ilash drum I8.

The unvaporlzed portion of the fresh charging stock is removed from the bottom of iiash drum II and introduced into an intermediate point in a secondary iiash drum I8 through pipe I9. The oil enters the drum I8 at an intermediate point in a series of baille plates 23, and is therein partly vaporized by the aid of heat derived from hot products introduced through line 2| into the lower portion of the ash drum I8. The resulting vapors risel in the drum, being subjected to partial lcondensation by the action of the bubble trays or other fractionating devices 22 and any necessary kcooling uid introduced through the conduit 23. The light vapors remaining uncondensed pass oiI from the drum I8 through vapor line 24 and condenser 25. the resulting condensate being collected in receiver 26. The iiash drum I8 is also provided with trap out trays 21 and 28, aswell as with additional baille plates 29 located below the latter trap out tray. Light gas oil collects on trap out tray 21 and is withdrawn through conduit 30 for storage in receiver- 3l, or for any further treatment desired. A heavier condensate and unvaporized residue of the crude chargeis collected on trap out tray 28, removed through pipe line 32, and forced by action of pump 33 into an intermediate point in the evaporator tower 2, above a series of lbaille plates 34. 4

'I'he evaporator tower has also bubble trays or other fractionating devices 35, located above the baille plates first mentioned, as well as a trap out tray 36. Below this trap out tray is arranged a series of baille plates 3l and a conduit 38 is provided for introducing a suitable cooling agent on top of these baille plates. The reduced crude and condensate oil introduced into the evaporator 2 through line 32 flow downwardly over baille plates 34 and meet a rising vcurrent of vapors produced by the introduction of hot cracked products into the base of the evaporator through conduit 39, with the result that the rising vapors are cooled and partially condensed, while the introduced oil is heated. Unvaporized portions of the introduced oil and condensed portions of the rising vapors are caught on trap out tray 36, removed through pipe line 40 and introduced into tank 6I,

preferably insulated, which serves as a source of supply for the viscosity breaking heater 5. The preheated stock contained in the tank 4I is withdrawn through pipe line 42 and introduced,

by action of the pump 48, into the viscosity breaking heater 5, from which it emerges at a moderate cracking temperature, e. g. 860 F., and passes through the line 2|, already mentioned,

5 into the lower` part of flash drum I8, as described hereinbefore.

- by passage upwardly through the evaporator pass off from the top thereof through vapor line 44 l into the lower part offractinnator tower 3. A cooling coil 45 is positioned in the top of the \evaporator tower to control the character of the emerging vapors, fresh charging stock or any v.other desired 'cooling medium being passed l through the coil in the well known manner. In the fractionator tower 3 the introduced vapors undergo fractionation to separate vapors of products in the gasoline boiling point range, the resulting condensate, beingciean and suitable for I vapor phase cracking, is withdrawn from the base of the fractionator tower through pipe line 53 and introduced by action of pump 46 into the vapor phase heater 8, from which the products emerge at a relatively high cracking temperature, for example 925 to 935 F., and are preferably 'transferred through conduit 41 into the soaking drum 1, but if desired the vapors may be bypassed around the drum 1 through pipe 41, by proper manipulation of valves 48 and 49. In this drum further cracking and digestion of the products take place, the temperature being subing the vapor phase heater. The digested products then travel through conduit 89 into the lower -part of the evaporator tower as already men'- tioned. 'I'he gasoline vapors remaining uncondensed by the fractionating action of tower 3 emerge from the top thereof and passv through vapor line 48 and condenser 49, the condensate 0 formed being collected in receiver 50, from which any necessary portion of the distillate can be returned through pipe 5I, .by action of pump 52, into the top of the fractionator tower, as a refiuxing medium. The coil 9, through which the relatively cool fresh charging stock passes,` also aids in the fractionating operation in the well known manner.

Tar is withdrawn from the bottom of evaporator 2 through drawoi line. 54 having rreducing l0 valve 5 5 therein and preferably is introduced into the ash tower- 4. which is maintained under a lowerpressure, such as atmospheric pressure for example. In the ash tower the tar separates into vapors which move upwardly through fracu tionating devices 5B, such as bale plates, partial condensation occurring, and the vapors remaining uncondensed pass oif from the top of the tower through vapor line 51 into the secondary flash drum I8, below the baille plates 20. Coil I0 in the top of the flash tower provides the necessary cooling for effecting the partial condensation mentioned. Unvaporized portions of the tar, which may be suitably between 5 and 20 A. P. I. gravity, are withdrawn from the base of the flash tower 4 through drawoiI line 58 and sent to storage. 'I'he flashing operation may be dispensed with and the tar may be withdrawn from the system through line 54' if desired. Unvaporized crude residue, which may be betweenli and 12 secondary flash drum I8 through draw-011l line 59 and passed to storage. This residuumis especially suitable for manufacturing certain types of 'nl ssphalts and. paving materials and it may also 'I'he vaporous products remaining uncondensed i stantially the same as that of the products leav- A. P.,I. gravityis withdrawn fromv the bottom of be employed for flushing the vapor line Ia as will be described hereinafter. Also, it may be blended with cracked tar and other oils to meet Bunker C fuel oil specications. This residue may be steam stripped prior to withdrawal. if desired, steam inlet pipe 59' being provided for this purpose.

The conditions in ash tower l are subject to variation depending on the particular charging stock used. For the charging stock specifically mentioned hereinbefore, i. e. 36 A. P. I. Mid-Continent crude, the temperature of the preheated stock entering flash drum I I might be, for example, about 450" F., while the temperature of combined condensate and residue drawn o from tray 28 might be about 570 F. andthe lightgas oil drawn from tray 21 might have a temperature of about 475 F. Under these conditions the combined condensate and residue drawn from tray 28 might have a gravity approximating 22 A. P. I.

The viscosity breaking heater may be operated under such conditions that the oil emergesv therefrom at a temperature of, for example, 860 F. and a pressure of 200 pounds per square inch, while the vapor phase heater may be-so controlled as to discharge the oil therefrom at a temperature of, for example, 960 F. and a pressure of 200 pounds per square inch. The soaking drum 1, evaporator tower 2 and fractionator tower 8. may be operated. under substantially the same pressure, the only difference in pressure being that necessary to cause a flow of the products through these chambers and their pipe lines. However, if desirable the vapor phase cracking operation may be carriedout at a lower or even somewhat higher pressure, but 200 pounds will generally be found to be preferable where the temperature mentioned is maintained. The viscosity breaker need not operate under the same pressure as that of the vapor phase heater, higher or lower pressure may be used to secure best .results with different charging stocks. 'Ihe pressure desired can be maintained by proper manipulation of the pressure reducing valve 80. Light naphtha ash drum I I and secondary ash drum I8 are preferably maintained at substantially atmospheric pressure, whereby the desired products are readily separated in vapor form, but "l somewhat higher pressures might be maintained with a corresponding lesser amount of vaporization. The amount of cracking per pass attained in the viscosity breaker and vapor phase heater may be varied to suit the characters of different charging stocks, however, with a charging stock such as that mentioned hereinbefore the specific temperatures and pressure already mentioned are suitable. The cracking per pass of the vapor phase heater, in terms of end point gasoline, may be 13 to 15%, while the total cracking per pass, including that attained in the soaking drum 1, might be 18 to 19%. The viscosity breaker onV the other hand is advantageously operated to produce only a moderate amount of cracking such as to convert from 8 to 10% of the lstock charged thereto into gasoline and into a product suitable as vapor phase charging stock.

I have found that if,`when employing vapor phase soaking drum 1, there is a tendency for coke to deposit in the vapor line 1a leading to the evaporator tower 2, such deposition may be obviated by flushing the line continuously with a 'drum I8 is particularly adapted for this purpose.

\ is then forced by pump 14 and line 15 thru cooler I6 to the vapor line 'Ea where it may be introduced at one point as shown or at a plurality of points along the line. A y

While I have described a .particular embodiment of my invention for the purposes of illustration it should be understood that various modications and ,adaptations .thereof may be made within the spirit of the invention as set forth in the appended claims.

v1. The vprocess of treating hydrocarbon oils which comprises introducing hot lightly cracked heavy oilinto a first vapor separating zone wherein vapors are separated from said oil, introducing a hot cracked tar into a second vapor separating zone wherein vapors are separated, cornbining, in a third zone, vapors, produced in said vapor separating 'zones and forming a reflux condensate therefrom, removing uncondensed vapors from said third zone and condensing them, introducing said redux condensate into a fourth zone, separately introducing hot vapor phase cracked products into said fourth zone in countercurrent contact with said condensate whereby a portion f said condensate is Avaporized, removing uncondensed vapors from said fourth zone and forming a final desired product therefrom, and removing liquid residual constituents of said vapor phase cracked products from said fourth zone and utilizing them as a source of said hot cracked tar rst mentioned.

2. A process in accordance with claim 1 where-4 in said iirst and second vapor separating zones are maintained under substantially atmospheric pressure and said fourth zone is maintainedunder a pressure in the order of 200 pounds per square'inch. 3. A process in accordancewith claim 1 where- 'in the uncondensed vapors in the fourth zone are subjected to fractionation to form an uncondensed vapor of the desired end point and reux condensate. said uncondensed vapor being withdrawn to form a nnal desired product while said reflux condensate is cracked in the vapor phase to form said vapor phase cracked products.

4. A process in accordance with claim l Wherein said tar is withdrawn from said fourth zone.

' 5. Aprccess in accordance with claim i wherein charging stock for the system is contacted with the combined vapors from the first and second vapor separating zones and introduced with said condensate into said fourth zone. l

6. The process of treating hydrocarbon oil which comprises introducing relatively heavy charging oil into a vapor separating zone wherein said oil is partially vaporized by contact with hot oil vapors, leaving unvaporized liquid` oil, introducing said liquid oil into an intermediate point in a second zone containing hot vapors, to be heated by countercurrent contact with said vapors, removing heated liquid oil from an intermediate point in said second zone, lower than said point nrst mentioned, cracking the rmovedy second zone.

7. The process of treating hydrocarbon oil liquid oil, separating resulting cracked products into vapors and a residue, withdrawing said residue from the system, introducing said vapors into said-vapor separating zone rst mentioned, re-

moving vapors froxn'said second zone, partially condensing the removed vapors in afractionating zone, leaving uncondensed light 'vapors-and a reux condensate, forming a final desired product from said light vapors, separately cracking said reflux condensate in the vapor phase, introducing resulting cracked'pr'oducts into a low point in said second zone. and 'separately withdrawing unvaporized residue from the bottom of said which comprises introducing relatively heavy hydrocarbon oil into a vapor separating zone. separately introducing hot vapors into said zone in counter-current contact with said heavy oil, removing from said zone as a mixture unvaporized portions of said heavy oil ami condensed portions of said vapors, heating the removed mixture to a moderate cracking temperature, separating iight vaporous fractions from theresultinglightly cracked products, in a second zone, leaving liquid residue. withdrawing said liquid residue from the process, fractionating said light vaporous fractions in a third zone, out of contact with the vapors liberated in said vapor separating zone, to form a heavy condensate, condensing resulting fractionated vapors as a desired product, introducing said heavy condensate into said vapor separating zone as said heavy oil rst-mentioned, and removing uncondensed vapors from the top of the mst-mentioned vapor separating zone and forming a desired product therefrom.

8. A process in accordance with claim 7 wherein heavy charging oil is contacted with the light vaporous fractions separated from said lightly cracked heavy oil in said third zone, and unvaporlzed portions of said charging stock are introduced into said vapor separating' zone firstmentioned mixed with said heavy condensate.

9. The process of treating hydrocarbon oil which comprises separating from crude oil by aid of heat derived from cracked vapors, Without cracking, light gas oil and topped crude. introducing the resulting topped crudedirectly into an intermediate point in a vapor separating vzone containing hot vapors, to'be heated by contact with said vapors, causing said topped crude and hot vapors to flow countercurrent to one another in said separating zone, removing resulting vapers from a high point in said separating zone and fractionating them out of contact with vapors from said crude oil, to form e. lnal desired light distillate and a reflux condensate, removing the heated topped crude from an intermediate point in said separatingr zone lower than said point nrst-xnentioned, cracking the removed topped crude, separating the resulting cracked products, in a second vapor separating zone, into vapors and liquid residue, preventing passage of said vapors last mentioned into said vapor separating zone rst mentioned, withdrawing said residue from the process and utilizing vapors so obtained as a source of said hot vapors rst mentioned. v

l0. A process in accordance with claim 9 wherein said redux condensate from said fractionating step is cracked separately from said topped crude, the resulting hot cracked products are introduced into said separating zone rst mention@ at Aa point below said intermediate Cil point and liquid residue is withdrawn from the base thereof. l

11. The process of treating hydrocarbon oil which comprises introducing heavy oil containing lighter vaporizable constituents into a stripping zone in countercurrent contact with highly heated vapors from a ilrst source and a second source, whereby said heavy oil is partially vaporized, removing resultingA residual -oll from said stripping zone and passing it into a second zone in' countercurrent contact with highly heated cracked vapors whereby additional vaporization of said residual oil and partial condensation of said cracked vapors occurs, removing a mixture r of unvaporized residue and condensate from said 1 second zone and passing it through va first cracking zone wherein it is raised to a cracking temperature and subjected to conversion, introducing the resulting cracked products into a third zone wherein vapors separate from liquid residue, withdrawing resulting residue from the process, utilizing resulting vapors as said vapors from -said ilrst source, fractionating vapors from said second zone in a fourth fractionating zone to form a ilnal desired distillate and a reilux condensate, passing reflux condensate so obtained through a second cracking zone wherein itis raised to a cracking temperature and subjected g to conversion. separating resulting cracked prod- 30 ucts into vapors and a liquid residue. utilizing f aosaaaa said vapors from said second source and separately withdrawing the flashed residue vfrom vthe process.

12. The process of treating hydrocarbon oil which comprises stripping crude charging stock of lighter products by contact with hot vapors n in a stripping zone, forming reduced crude, introducing resulting reduced crude into a dephlegmating zone in contact with hot vapors, removing liquid oil comprising unvaporized constituents of said reduced crude from said dephlegmating zone, cracking the removed liquid oil, separating the resulting cracked product into vapors and residue, isolating said residue from the process, directing vapors thus separated into saidvstripping zone, separately cracking a clean condensate stock, introducing resulting hot cracked products into a separating zone wherein separation of vapors from residue takes place. passing separated vapors from the separating zone to aforesaid dephlegmating zone, withdrawing residue from said separating zone, removing vapors from said dephle'gmating zone and forming'a desired product therefrom. f* i HAROLD R. SNOW. 3.

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