US2212023A

US2212023A - Conversion of hydrocarbon oils

Info

Publication number: US2212023A
Application number: US166263A
Authority: US
Inventors: Lyman C Huff
Original assignee: Universal Oil Products Co
Current assignee: Universal Oil Products Co
Priority date: 1937-09-29
Filing date: 1937-09-29
Publication date: 1940-08-20
Anticipated expiration: 1957-08-20

Description

Aug. 2o, 1940. y L, C, HUFF 2,212,023

CONVERSION OF HYDROCARBON OILS Filed Sept. 29, 1937 ffznvzace 7 3 Patented Aug. 20, 1940 PATENT vori-mE CONVERSION OF HYDROGARBON OILS Lyman C. Huff, Chicago, Ill., assigner to Universal Oil Products Company, Chicago, Ill., a corporation of Delaware Application September 29, 1937, Serial No. 166,263

4 Claims.

This application is a continuation-in-part of my co-pending application led on November 30, 1936, Serial No. 113,424, now Patent No. 2,177,829.`

The invention relates to improvements in the type of process wherein hydrocarbon oils of different boiling range characteristics are separately cracked to produce high yields of good quality gasoline and minor yields of less valuable prod- ',ucts comprising petroleum coke, light normally gaseous products and, when desired, heavy residual liquid suitable, for example, as fuel oil.

Y The process herein provided comprises twov major and independently controlled but coop- 1 erative steps, the first of which is devoted to the separate pyrolytic conversion of selected relatively low-boiling and high boiling fractions of the charging stock and intermediate liquid conversion products of the process, while the second is den voted to the coking of heavy residual liquid products Aproduced in each of the two major steps, intermediate liquid products of the second step being returned to the fractionator and thence to the selective cracking stages of the first step, light distillate produced in the second step being also returned as a Cooling and reluxing medium to the fractionator of the rst step wherefrom it is recovered together with Igasoline produced in the first step, the total gasoline product being stabilized to the desired vapor pressure and the gaseous =products of the process being subjected to absorption to recover desirable high-boiling components therefrom. When desired, liquid residue may be recovered from either or both steps of the system. Charging stock for the process which may be any desired type of hydrocarbon oil but is preferably an oilof relatively wide boiling range,.is preferably supplied as a cooling and reuxing medium to the fractionator of the second step of the system wherefrom it is subsequently supplied, together with the reflux condensate produced in the fractionator of said second step, to the fractionator of the first step.

. The above outlined major features of the invention, as well as other features of a minor nature, are described more fully in conjunction with the following description of the accompanying drawing. The cooperative and interdependent nature of the various features of the invention and their advantages will be readily apparent to those familiar with the art by referring to the drawing and the following description thereof.

' The drawing is diagrammatic and illustrates o ne specific form of apparatus in which the process of the invention may be conducted .to t

produce` the desired results.y

Referring to the drawing, an oil of relatively high-boiling characteristics is supplied, as will be later described, 'to heating coil l wherein it is he'ated to the desired cracking temperature, preferably at a substantial superatmospheric pressure by means of heat supplied from furnace 2, the'heated products being discharged from4 coil l through. line V3 and valve llr into reaction chamber5.

Simultaneously, an oil of relatively low-boiling characteristics is supplied, as will be later'described, to heating coil-6 wherein it is .heated preferably to a higher cracking temperature than that employed in heating coil l. Heat is supplied to heating coil 6 from furnace l; A substantial superatmospheric pressure is also preferably employed in heating coil' and the highly heated. products are discharged therefrom through line l8 and valve 9 into reaction cham-` ber5. f

ChamberV 5 is also preferably maintained at` a substantial superatmospheric pressure which may be substantially the same or somewhat lower than that employed in the communicatingheating `coil utilizing the lowest outlet pressure. Continued cracking of the heated products supplied to chamber. 5 from coils l and 6 is accomplished Atherein and preferably the reaction chamber isfinsulatedl to conserve heat, although insulation is not shown in the drawing. In 'the particular case here illustrated, both vaporous and liquid conversion products are withdrawn in commingledlA state from the lower portionl of chamber 5 and directed therefrom throughl line Hl and valveV Il into vaporizing and separating chamber l2. The products passing from chamber 5 to chamber l2may be diluted and/or cooled by introducing any suitable diluent and/or coolingmedium into line l0 on either or both sides of valve II, lines I3 controlled by valves I4 being provided for this purpose, vin the case here il lustrated.

Chamber I2 is preferably maintained at a substantially reduced pressure relative to that employed in chamber 5. The reduction in pressure being accomplished as the heated products pass through valve Il in line Il). This reduction in pressure also serves to partially cool the conversion products,` prior-.to their introduction into chamber, I2, and the heat liberated by the pressure reduction serves to effect further vaporization of the liquid' products in chamber I2. Separationof-,the heavy liquid conversion products, which remain unvaporized in chamber I2, from the lighter, vaporous components of the conversion products, is accomplished in this Zone. 'Ihe residual liquid is withdrawn from the lower portion of chamber I2 through line I5 and, when desired, may be removed in part, from the system to cooling and storage, or elsewhere, as a final residual liquid product of the process by means of line I3 and valve I1. However, at least a portion of the residual liquid is directed through valve I8 in line I5 to pump I9 by means of which it is fed through line 20 and may be directed through valve 2| in this line to further treatment, as will be later described, in heating coil 22, or it may be rst supplied, all or in part, from line 20 through line 23 and valve 24 into separating chamber 25 wherefrom it is directed, together with other heavy liquid products from this zone, through line 26 and valve 21 to pump 28 and thence through line 29 and valve 30 to further treatment in heating coil 22.

Vaporous conversion products are removed from the upper portion of chamber I2 and directed through line 3| and valve 32 to fractionation in fractionator 33, wherein their components boiling above the range of the desired final gasoline product of the process are condensed as reflux condensate. The reflux condensate formed in fractionator 33 is separated therein into selected relatively low-boiling and higher boiling fractions. The latter are removed from the lower portion of the fractionator and are directed through line 34 and valve 35 to pump 36 by means of which they are supplied through line 31 and valve 38 to conversion, as previously described, in heating coil I. The selected relatively low-boiling fractions of the reflux condensate formed in fractionator 33 may be removed from one or a plurality of suitable intermediate points in `this zone and, in this case here illustrated, are directed through line 39 and valve 40 to pump 4| by means of which they are fed through line 42 and may be supplied, all or in part, through line 43 and valve 44 to conversion, as previously described, in heating coil 6.

Fractionated vapors of the desired end-boiling point are removed, together with normally gaseous products, from the upper portion of fractionator 33 and directed through line 45 and valve 45 to cooling and partial condensation in condenser 41, wherefrom the resulting distillate and the remaining uncondensed vapors and gases are directed through line 48 and valve 49 to collection in accumulator 50. Distillate thus collected in accumulator 50 may be recirculated in regulated quantities by means of line 5|, valve 52, pump 53, line 54 and valve 55 to the upper portion of fractionator 33, to serve therein as a cooling and reuxing medium for assisting fractionation of the vapors and to maintain the desired vapor outlet temperature from the fractionator. The uncondensed vapors and gases are directed from accumulator 50 through line 56 and valve 51 to sub-cooler 58 wherein they are further cooled suiiciently to condense substantially all of their normally liquid components by circulating any suitable cooling medium through the sub-cooler by means of lines 59 and 6| controlled, respectively,by valves 60 and 62. The resulting distillate and uncondensed normally gaseous products are directed from sub-cooler 58 through line 53 and valve 64 to collection and separation in receiver 65. The uncondensed gases are withdrawn from receiver 65 through line 66 and, when desired, may be directed therefrom, all or in part, through line 81 and valve 68 to storage, or elsewhere, as desired, or they may be passed through valve 69 in line 66 to absorption in absorber 10, the operation of which will be later described.

The high-boiling residual oil supplied to heating coil 22, as previously described, from chamber 25 and/or chamber I2, is heated in this zone preferably at a rapid rate to a su'iciently high temperature to induce subsequent reduction of its high-boiling components to substantially dry coke in coking chamber |00. Furnace 80 supplies the required heat to the oil passing through heating coil 22 and the highly heated residual liquid is discharged therefrom through line 95, Wherefrom it is directed into coking chamber at any desired point or plurality of points in this zone; lines 96 and 98 controlled, respectively, by valves 91 and 99 being shown in the drawing for the introduction of heated residual oil into the upper and lower portions, respectively, of the reaction chamber.

The coke formed in chamber |00 is allowed to accumulate therein and may be removed from this zone by any well known means, not illustrated, after the chamber is substantially filled or after its operation has been completed,` for any other reason. Preferably, a plurality of coking chambers is provided, although only a single coking chamber is illustrated in the drawing, and, preferably, the various chambers are alternately operated, cleaned and prepared for further operation in order that the coking stage, in common with the rest of the system, may be operated continuously. Chamber |00 is provided with a suitable drain line Il controlled by valve |02 and this line may also serve, when desired, as a means of introducing water, steam, or any other suitable cooling medium into the chamber, after its operation has been completed and preferably after it has been isolated from the rest of the system, in order to hasten cooling andI facilitate removal of the coke.

The vapors evolved from the residue undergoing coking in chamber |00 will normally contain a substantial quantity of entrained and/or dissolved heavy liquids unsuitable for further cracking in heating coils I or 6. These vaporous products are therefore directed from chamber |00 through line |03 and valve |04 into separating chamber 25 wherein they are partially cooled and washed to effect the removal therefrom of said undesirable high-boiling components. 'I'he latter are removed from the lower portion of chamber 25, either alone or together with the non-vaporous components of any residual liquid supplied to this zone, as previously described, from chamber i2, and are directed through line 2G and Valve 21 to pump 28 wherefrom they are fed through line 29 and may be supplied through valve' 3E! in this line directly to heating coil 22 or they may be diverted from line 29 through line and valve |06 into chamber I2, in which case, residual liquid from the latter zone is supplied directly, as previously described, to heating coil 22. When desired a regulated quantity of the heavy liquid products withdrawn from the lower portion of chamber 25 may be removed from the system to cooling and storage or elsewhere, as desired, as a final residual liquid product of the process by means of line |01 and valve |08.

Relatively clean components of the vaporous products supplied to and evolved in chamber 25, which remain uncondensed in this zone, are drected therefrom through a suitable partition or liliy tray |09, which separates chamber 2-5` from fractionator H0, into the latter zone.

The high-boiling components of the vaporous products supplied, as described, to fractionator H0, are condensed in this zone as reflux condensate and, in orderto assist fractional condensation of the vapors, charging stock of the process is preferably directly commingled with the vaporous products underoging fractionation in fractionator H0. In the case here illustrated, the charging stock is supplied from any suitable source through line and valve II2 to pump H3 by means of which it is fed through line I |4 and may be introduced into fractionator 0 at any desired point or plurality of points in this zone by means of branch lines ||5 controlled by valves I6. The high-boiling fractions condensed as reflux condensate fromthe vapors in fractionator |10 as well as any high-boiling components of the charging stock, which remain unvaporized in fractionator H0, are directed from the lower portion of Ythis zone throughl line ||1 and valve |18 to pump ||9 by means of which these commingled oils are supplied through line |20 to fractionator 33, entering the latter zone at any desired point or plurality of points therein by means of branch lines |2| controlled by valves |22. The commingled charging stock and reflux condensate thus supplied from fractionator |10 to fractionator 33, is separated in the latter zone into selected relatively low-boiling and higher boiling fractions which are supplied, respectively, to conversion in heating coils 6 and I, together with the corresponding relatively lowboiling and high-boiling fractions of the reuX condensate formed, as previously described, in fractionator 33.

In the particular case here illustrated, in order to partially cool the Vaporous products in chamber 25 and eifect the separation of undesired heavy liquid components therefrom, a relatively low-boiling fraction of materials condensed in fractionator ||0 is withdrawn as a sidestream from the upper portion of this zone and directed through line |23 and valve |24 to pump |25 b-y means of which it is introduced in regulated quantities through line |26 and valve |21 into i the upper portion of chamber 25, preferably being sprayed or otherwise intimately contacted with the vapors in this zone by means, for example, of a suitable spreader flange or spray arrangement |28. l

Low-boiling components of the materials supplied to fractionator ||0, which remain uncondensed in this zone, are directed in Vaporous state from the upper portion thereof through line |3'0 and valve |3| to condensation and cooling iny condenser |32. The resulting distillate and uncondensed gases are directed through line |33 and valve |34 to collection and separation in receiver |35. The uncondensed gases are withdrawn from receiver |35 through li-ne |36 and may be directed therefrom, all or in part, when desired, through line |31 and valve |38 to storage or elsewhere, as desired, or they may be directed through valve |39 in line |36 and through line |40 to absorber 10. The distillate collected in receiver |35 is directed therefrom through line |4| and valve |42 to pump |43' by means of which it is fed through line |44, and regulated quantities of this material may be diverted from line |44 through line |45 and valve |46 into the up-` per portion of fractionator ||0 to lserve as a cooling and refluxing medium in this zone, while the remaining portion of the distillate isdirected througlnvalvel 41 in line, |44. into fractionator 33, wherein it serves asa cooling and reiluxing medium and wherein the components thereof boiling within the range of the vdesired nal gasoline vproductor the process are revaporized and directed, ,together with the gasoline formed in this stage of the system, through line 45 and valvev 46 to the subsequent treatment previously described.

:The distillatecollected in receiver 65 which comprises the total net gasoline production of the system, is withdrawn therefrom through line |50 and valve. |5| to pump 4|52 by means of which it is supplied through line |53, valve |54, heat ex' changer |55, line |56 and valve |51 to stabilizer |58. .Thepurpose 4of heat exchanger |55 is `to reheat the distillate sufciently to effect partial vaporization thereof and,`in the yparticular case here illustrated, this heat is recovered from withing the system, as will be later described.

.Regulated quantities of dissolved gases are lib-` erated from the distillate in stabilizer |58, whereby to reduce its vapor pressure to the desired degree. To assist in establishing -equilibrium conditions in the stabilizer, cooling is provided in the upper portion thereof, as will lbe llater described, and the distillate collected in the lower portion of the stabilizer is reboiled. The reboiling is accomplished, in the case here illustrated, by directing the distillate from the lower portion of the stabilizer through line |59 and valve |60 to a suitable heat exchanger or reboiling druml 10, wherein heat for reboiling is supplied to the distillate b-y circulating regulated quantities of the light reux condensate formed in fraction-v ator 33 Lin indirect heat exchange therewith, as will be later described. The vapors and -gases evolved in reboiler |10 are returned therefrom through line |1| and valve |12 to stabilizer |58.

'Ihe stabilized and reboiled distillate is withdrawn from the lower portion of reboiler |10 and, in the casev here illustrated, is directed through line |13 'and valve |14 to and through heat exchanger |55, wherein it supplies heat to the distillate passing through this zone to stabilizer |58, as previously described, and wherefrom the resulting partially cooled distillate is directed through line |15 and valve |16 to further cooling and storage or to any desired further treatment, not illustrated.

Light `refluxcondensate for effecting reboiling of the distillate in reboiler |10 is supplied thereto from pump 4| and line 42 through line |11 and valve |18. |Ifhe resulting partially cooled light reflux condensate is discharged from reboiler |10 through line |18 and, in the particular case here illustrated, is directed through valve in this line into the upper portion of vaporizing and separating chamber I2, wherein itv serves asl a cooling and reuxing medium for assisting the desired separation of vaporous and residual liquid products in this zone.

The gases liberated from the distillate and remaining. uncondensed in the stabilizer |58 are directed from the upper portion thereof through line I 8| and Valve |82 to condenser |83' wherein these'materials are cooled sufficientlyk to effect partial condensation thereof by passing the same in indirect heat exchange with any suitable cooling medium, which is circulated through *conf denser |83, by means of lines |84 and |86 controlled, respectively, by valves |85 and |81. The

condensed components of `the products released from the upper portionof stabilizer |58 are directed from condenser |83 through line |88. and

The gaseous products supplied, as described, to absorber 10 contain a substantial quantity of high-boiling components such as butane, butenes and a portion of the propane and propene, a high proportion of which high-boiling gases may be concentrated in the nal gasoline product without excessively increasing its vapor pressure.

The purpose of absorber 10 and stabilizer |58 and their appurtenances herein provided is to separate substantially all of the low-boiling gases from the final gasoline product of the process and concentrate therein substantially only the relatively high-boiling normally gaseous products. This is accomplished by absorbing the desirable highboiling components from the gases in absorber 10 in an absorber oil comprising selected relatively low-boiling fractions of the intermediate liquid conversion products of the process, returning the enriched absorber oil to fractionator 33 to increase the concentration of high-boiling gases in the overhead vaporous stream from this zone and thereby increase the concentration thereof in the distillate collected in receiver 65, stabilizing the distillate to the desired vapor pressure and returning the gases liberated from the distillate by said stabilization to absorber lil.

The absorber oil utilized, in the particular case illustrated, is a regulated quantity of the lowboiling reflux condensate recovered from iractionator 33. This material is diverted from line 42 through line 200 and valve 20| to heat exchanger 203 wherein it is partially cooled, as will be later described, and wherefrom it is directed through line 200 and valve 205 to further cooling in cooler 206, through which any suitable cooling medium is passed by means of lines 29? and 209 controlled, respectively, by valves 208 and 2 I0.

The resulting cool absorber oil is directed from cooler 205 through line 2|| and valve 2|2 into the upper portion of absorber '10, wherein it passes in direct counter-current contact with the ascending gases in this zone and absorbs desirable highboiling components therefrom. The low-boiling gaseous products which remain unabsorbed in absorber 'I0 are released from the upper portion of this zone through line 2|3 and valve .2M to storage or elsewhere, as desired. The enriched absorber oil is withdrawn from the lower portion of absorber 70 through line 2|5 and valve 2|0 to pump 2 by means of which it is fed through line 2|8 and valve 2|9 to heat exchanger 203, wherein it is heated by indirect heat exchange with the light reflux condensate supplied to this zone, as previously described, and wherefrom the resulting enriched hot absorber oil is directed through line 220 and valve 22| into fractionator 33.

The preferred conditions of operation Which may be employed, in an apparatus such as illustra-ted and above described, to produce the desired results, may be as follows: A temperature of the order of 850 to 950 F. and a superatmospheric pressure of from to 350 pounds, or more, per square inch, is preferably employed at the outlet of heavy oil heating coil Light oil heating coil 0 preferably employs a higher temperature which may range, as measured at the outlet, from 900 to l000 F., or thereabouts, preferably with a superatmospheric pressure at this point in the system .of from 200 to 500 pounds, or more, per square inch. The reaction chamber is also maintained at an active cracking temperature and at a substantial superatmospheric pressure which may be approximately the same or somewhat lower than that employed in the communicating heating coil utilizing the lowest pressure. Vaporizing and separating chamber |2 preferably employs a substantially reduced pressure relative to that utilized in the reaction chamber, the reduced pressure ranging, for example, from 100 pounds, or thereabouts, per square inch, superatmospheric, down to substantially atmospheric pressure, the preferred pressure in this zone being of the order of 25 to 75 pounds per square inch, superatmospheric. Fractionator 33 and the succeeding condensing and collecting equipment may be operated at any desired pressure from substantially atmospheric up to substantially the same pressure as that employed in vaporizing and separating chamber |2. Heating coil 22 of the coking stage of the system, in which high rates of heating and a high oil velocity are preferably employed, may utilize an outlet temperature ranging, for example, from 850 to 1000 F. and a superatmospheric pressure of from 25 to 200 pounds, or more, per square inch, the preferred conditions at the outlet of heating coil 22 being 900 to 950 F. and 50 to 150 pounds per square inch, or thereabouts, superatmospheric pressure. rhe coking chamber may employ any desired pressure ranging from substantially atmospheric up to approximately the same as that employed at the outlet of heating coil 22. The separating and fractionating column to Which vaporous products of the coking operation are supplied and the succeeding condensing and col lecting equipment may employ pressures ranging from substantially atmospheric up to substantially the same pressure as that employed in the coking chamber. Absorber 'l0 is preferably operated at a superatmospheric pressure of from 50 to 175 pounds, or more, per square inch and a superatmospheric pressure of the order of 50 to 250 pounds, or thereabouts, per square inch, is preferred in stabilizer |58.

As an example of one specic operation of the process, as it may be conducted in an apparatus such as illustrated and above described: The charging stock is a Bahrein Island reduced crude of approximately 17.5 A. P. I. gravity which contains approximately 6% of fractions boiling up to 572 F., approximately 50% at 698 F., with an end-boiling point of approximately '750 F. and containing approximately 10% of coke by weight. In this operation, the temperature employed at the outlet of heavy oil heating coil is approximately 915 F., with a superatmospheric pressure at this point in the system of approximately 200 pounds per square inch. Light oil heating coil E employs an outlet conversion temperature of approximately 955 F. and a superatmospheric pressure of approximately 260 pounds per square inch. The reaction chamber is operated at a superatmospheric pressure of approximately 200 pounds per square inch, which is reduced in the succeeding vaporizing and separating chamber to approximately 75 pounds per square inch, superatmospheric. Approximately the same pressure is employed in the succeeding condensing and collecting equipment of this stage of the system. Residue heating coil 22 employs an `outlet temperature of approximately 950 F. and the pressure `employed in this zone, as measured at the outlet thereof, is approximately pounds per square inch, superatmospheric. The coking chamber is operated at a superatmospheric pressure of approximately 50 pounds per square inch and this pressure is substantially equalized in the succeeding separating, fractionating, condensing and collecting equipment.

In the above operation, the charging stock is supplied to the fractionating column of the coking stage of the system and reflex condensate from this zone is returned to fractionator 33, as is also distillate resulting from condensation of the overhead vaporous stream from the fractionator of the coking stage. Residual liquid from vaporizing and separating chamber l2 is supplied to separating chamber 25 of the coking stage lof the system and non-vaporous residual liquid from the latter Zone is supplied to heating coil 22 of the coking stage. A portion of the light reflux condensate from fractionator 33 is utilized as absorber oil in absorber 70 and the resulting enriched absorber oil is returned to fractionator 33.

This operation will yield per barrel of charging stock approximately 60% of 400 F. end-point gasoline having an octane number of approximately 68, as determined by the motor method. The only other products of this operation are relatively light gases and about 88 pounds ofA low volatile coke per barrel of charging stock.

I claim as my invention:

1. A conversion process which comprises subjecting hydrocarbon oil to cracking conditions in a cracking Zone and separating the resultant products into vapors and unvaporized oil in a separating chamber, removing unvaporized oil from said chamber and reducing the same to coke in a coking zone, introducing the vaporous products from the coking zone into a second separating chamber and therein separating highboiling components of these products, then fractionating the remainder of said vaporous products independently of therst-mentioned vapors to separate therefrom a relatively heavy reflux condensate and a lighterreflux condensate, introducing the latter into contact with the vaporous products in said second chamber to assist the separation of said high-boiling components, introducing the first-mentioned vapors and said heavy reiiux condensate into a fractionating zone and therein fractionating the former in contact with the latter, supplying reflux condensate from the fractionating zone to said cracking zone, and nally condensing the fractionated vapors.

2. A conversion process which comprises subjecting hydrocarbon oil to cracking conditions in a cracking zone and separatingthe resultant products into vapors and unvaporized oil in a separating chamber, removing unvaporized oil from said chamber and reducing the same to coke in a coking Zone, introducing the vaporous products from the coking zone into a second separating chamber and therein separating highboiling components; of these products, then fractionating the remainder of said vaporous products independently of the rst-mentioned vapors to separate therefrom a relatively heavy reflux condensate and a lighter reux condensate, introducing the latter into contact with the vaporous products in said second chamber to assist the separation of said high-boiling components, introducing the mst-mentioned vapors and said heavy reflux condensate into a vfractionating zone and therein fractio-nating the former in contact with the latter, separating from the contacting vapors and condensate in the fractionating zone relatively 'heavy and light cracking stocks, supplying the heavier cracking stock to said cracking zone, subjecting the lighter cracking stock to independently controlled cracking conditions and introducing resultant products to the rst-mentioned separating chamber, and iinally condensing the fractionated vapors.

3. In a process wherein vaporous and liquid products resulting from the pyrolytic conversion of hydrocarbon oils are supplied in commingled state from an enlarged reaction chamber maintained at substantial super-atmospheric pressure to a reduced pressure vaporizing and separating chamber wherein said liquidsl are appreciably further vaporized and Wherefrom the vapors and resultant liquid residue are separately removed, the vapors fractionated to form reflux condensate which is returned to said pyrolytic conversion and a distillate boiling Within the range of gasoline recovered from the fractionated vapors, the improvement which comprises introducing residual liquid removed from said vaporizing and separating chamber into a coking chamber wherein its high-boiling components are reduced to coke, supplying vaporous products of the coking operation to another separating chamber wherein high-boiling components, comprising entrained heavy liquids, are removed therefrom,`

removing said high-boiling components as residual liquid from said separating chamber, reducing their heavy components to coke in said coking chamber, indeqendently fractionating the remaining relatively clean components of the vaporous products of the coking operation in Contact with charging oil for the process to form a mixture of unvaporized charging oil and reiiux condensate, supplying this mixture to the firstmentioned fractionating step and then to said pyrolytic conversion, together with the firstnamed reiiux condensate and recovering from the lower-boiling components of said relatively clean vapors additional fractions boiling Within the range of gasoline, and introducing into contact with thev vapors in the second-mentioned separating chamber a light reflux condensate from said independent fractionating step.

4. `A conversion process which comprises subjecting hydrocarbon oil to cracking conditions in a cracking zone and separating the resultant productsl into vapors and unvaporized oil in a separating chamber, removing unvaporized oil from said chamber and reducing the same to coke in a coking zone, introducing the vaporous products from the coking zone into a second separating chamber and therein separating highboiling compo-nents of these products, then fractionating the remainder of said vaporous products to separate therefrom a relatively heavy reflux condensate and a lighter reflux condensate, introducing the latter into contact with the vaporous products in said second chamber to assist the separation of said high-boiling components, independently fractionating the first-mentioned vapors and combining reflux condensate thus formed with at least a portion of said heavy reiiuX condensate, supplying the resultant mixture to said cracking zone, and finally condensing the fractionated vapors.

LYMAN C. HUFF.