US2100414A

US2100414A - Conversion of hydrocarbon oils

Info

Publication number: US2100414A
Application number: US680556A
Authority: US
Inventors: Swartwood Kenneth
Original assignee: Universal Oil Products Co
Current assignee: Universal Oil Products Co
Priority date: 1933-07-15
Filing date: 1933-07-15
Publication date: 1937-11-30
Anticipated expiration: 1954-11-30

Description

Nov. 30, 1937. K. swARTwooD CONVERSIONy OF HYDROCARBON OILS Filed July l5, 1933 bers f 71710 ce 1.9 INVENTOR.

enne /z zffarfzaam BY ATTORNEY,

Patented Nov. 30, 1937 i Y, n i i i Y UNITED STATES PATENT cerros coNvERsIo-N oF HYDROCARBON oms Kenneth Swartwood, Chicago, Ill., assigner to Universal Oil Products Company, Chicago, Ill., a corporation of Delaware Application July 15, 1933, SerialNmV 680,556 8 claims. `(CI. 19e- 49) This invention particularly refers vto` an iming fractions in the same crackingsystem under proved process of the type wherein a hydrorelatively mild or even non-cracking conditions, carbon oil charging stock of relatively wide boilbut the present invention differs from such ,proc-v ing range, such as crude petroleum, is separated esses in that, in the present invention, the heavy by distillation into low-boiling and high-boiling residual components of thehigh-boiling fractions fractions, each of which are subjected to indeof the charging stock which are unsuitable vfor pendently controlled selected conversion condiconversion at high-temperature and pressurejare tions in the same cracking system and wherein subsequently reduced VVto coke, together with the the` residual conversion products of the process residual productsV of the cracking operation.

0 are reduced to coke; the process being operated Vaporous products from thefcoking operation Vas 10? for the production, primarily, of 'high yields-cf well asthe vaporous conversion products of the' light liquid products such as motor fuel of high process vand the vapors resulting from .saidfurantiknock value and minor yields of coke and ther distillation of thehigh-boiling fractions `of gas. the chargingfstock are subjectedfto `fractionation The distinguishing feature of thepresent inand the resulting reiluxfcondensate, comprising l'g5l Y( vention resides in the novel and advantageous the insuciently converted -components of thetreatment of the high-boiling fractions of the total rVaporous products*ofthe-:processare sub.- charging stock, which, after being separated from jected Vto further 'conversion in -the same system, the lower boiling fractions, are subjected to fur-v preferably under milder heatingconditions than ther distillation in a low-pressure vaporizing those employedfor the conversion of the low- 215 zone of the cracking system wherein the heavy boiling fractions'of the charging stock, which components of said high-boiling fractions of the l latterl are `rutil-ized as Aa fheatcarrying medium for charging stock are separated from its lighter thecoking operation.' This method Tof :operation f vaporous components and commingled with the permits` the production of high yields of light` residual liquid conversion products of the process liquid productssuch -as `motorffuel of high .anti-V 25A' while the vapors from this zone, including Vapor knock--value with minimum yields-of heavyresidous conversion products of the'process and said ual productsgand gas and itwill be apparent thatV vaporous components of the high-boiling fracthe various steps of the process'all cooperateV to tions of the charging stock, are subjected to frac- Yproduce-the final desiredfresultsthe :novelty of 30. tionation for the formation of reflux condensate the present invention residing in Uthe-advanta 30';V

which is returned to a heating coil of the -crackgeous'combination-of the various Yfeatures vproing system for further conversion. vided. t Y

The process of the present invention is par- One embodiment ofthe'present invention comticularly advantageous for the treatment of prises subjecting a hydrocarbon oil of relativelyl charging stocks -of relatively wide boiling range, Wide boiling range to distillation whereby it is 35i for example such as crude petroleum or other loils separated into low-boiling and high-boiling fraccontaining appreciable quantities of bothV lowtions, subjecting the latterto further -vaporiza` boiling fractions and high-boiling materials ofA aV tion, subjecting the Vunvaporized residual oil to heavy residual nature, since, in accordance with coking, subjecting Ylow-boiling .fractions ofetheY 40 the features of the present invention, I avoidV charging stock tozpyrolytic conversion and ut-i- 401Y passage `of the heavy residual components of the lizing the resulting highly heated conversion charging stock through a cracking coil, thus products as a heat carrying medium to. assist the Y, avoicng the excessive coke and gas formation coking operation, subjectingthe vaporous prod. which would result from the conversion of these uctsrvof the process -resulting from conversion,Y

materials under the high temperature and preS- coking and-saidfurther vaporizationof the high- 45 sure conditions required for the production of boiling fractions of -the charging stock to fracmaximum yields of desirable light liquid prodtionation whereby components boilinglabover the ucts from the lowerrboilingfractions of the chargrange ofk the desired .final lightrdistillate 'product Y ing stock. of the processare condensed vas reflux conden-A V5U I am aware that other processes have been sate,-subjecting Ythereflux vcondensate toindeproposed for the separation of oils of relatively pendently controlledconversion conditionsof-e1ewide boiling range' into low-boiling andliighvated temperature and superatmosphericrpresl z boiling fractions, conversion of the low-boiling sure and v'commingling the resulting `products at fractions under relatively severe conversion con-lV substantially reduced pressure with .said high-k ditions and further distillation of the highboilboiling fractions of the chargingstock *wherebyV 55 to effect said further vaporization of the latter and the liquid conversion products.

The accompanying diagrammatic drawing illustrates one specific form of apparatus in which the process may be accomplished. It will be understood that the invention is not limited to this nor to any other specific form of apparatus.

Referring to the drawing, raw oil charging stock for the process, preferably comprising an oil of relatively wide boiling range containing an appreciable quantity of both low-boiling and highboiling fractions such as crude oil, is supplied in heated state through line I and valve 2 to distilling and fractionating column 3. Heating of the charging stock to the temperature required for its distillation may be accomplished in any well known manner, not illustrated, for example, by heat recovered from hot vaporous and/ or liquid products of the process or by heat from an external source. Heating of the charging stock may be accomplished at any desired pressure and column 3 is preferably operated at substantially atmospheric pressure although superatmospheric pressure or partial vacuum may be employed in this Zone, when desired. The charging stock is separated in column 3 into low-boiling and highboiling fractions.

When the charging stock contains any appreciable quantity of motor fuel or vmotor fuel fractions of satisfactory antiknock value they may be removed, together with any gas from the distilling operation, from the upper portion of column 3 through line 4 and valve 5 to condenser The resulting distillate and gas passes through ine 'I and valve 8 to collection and separation in receiver 9. Gas may be released from the receiver through line I and valve Il. Distillate may be Withdrawn through line I2 and valve I3 to storage or elsewhere, as desired. In this case any higher boiling motor fuel fractions of inferior antiknock value and/o1', when desired. other light oils such as naphtha, kerosene,lkerosene distillate, light gas oil and the like are separately removed as one or a plurality of side streams from any suitable point in column 3, for example, through line I4 andvalve I5 toY pump IG to be supplied therefrom to conversion in heating coil 2l, as will be later more fully described. When no appreciable quantity of motor fuel or motor fuel fractions of satisfactory antiknock value are contained in the charging stock, the low-boiling oils to be supplied to heating coil 2l may be removed from the upper portion of column 3 through line 4 and collected as distillate in receiver 9, in the manner previously described, to be withdrawn therefrom through line I'I and valve I8 to pump I6. 1n the latter case it is also within the scope of the present invention, instead of subjecting the overhead. vaporous product from column 3 to condensation and separating the resulting distillate and gas, to supply the total vaporous products directto heating coil 2| by means of a suitable pump or compressor and the required connecting lines which for the sake of simplicity, are not shown in the drawing.

High-boiling fractions of the charging stock, comprising its components boiling above the range of the lighter oils supplied to pump IE and including any components of the charging stock of a heavy residual nature, are withdrawn from the lower portion of column 3 through line 22 and valve 23 to pump 24 by means kof which they are fed through line 25 and valve 26 into vaporizing chamber 21. commingling, in the case illusf trated, in line 25 with hot

conversion products 4chambers

33 and 33.

from reaction chamber 28, as will be later more fully described, although it is within the scope of the present invention to separately introduce these materials into chamber 21 at any desired point. Further vaporization of the high-boiling fractions of the charging stock is accomplished in chamber 21 by means of heat derived from the hot conversion products from chamber 28 supplied to this zone and, when desired,by othermeans which will be later more fully described. The residual liquid remaining unvaporized in chamber 2T, comprising both the heavy residual components of the charging stock and residual liquid conversion products of the process remaining unvaporized in this Zone are withdrawn therefrom through line 3l and valve 32 and are supplied through lines 34 and 34 controlled, respectively, by

valves

35 and 35 into the respective coking The vapors from chamber'21, including vaporous conversion products from chamber 28 supplied to this zone and vapors derived by further vaporization of the highboiling fractions of the charging stock from column 3 and liquid conversion products from chamber 28, pass from chamber 2'I through line 36 and valve 3'! to fractionation in fractionator 38, together with vaporous products from the coking zone, as will be later more fully described.

The low-boiling oils supplied topump I6 are fed therefrom through line I9 and valve 20 to heating coil 2| wherein they are heated to the desired conversion temperature, preferably at a substantial superatmospheric pressure by means of heat supplied from a furnace 39 of any suitable form. When the oil supplied to heating coil ZI comprises a substantial proportion of materials within the boiling range of motor fuel the conditions of conversion temperature, pressure and time employed in the heating coil are preferably such as to effect a substantial improvement in the motor fuel characteristics of this material, particularly with respect to its antikncck value, without excessively altering its boiling range. Such conditions may be selected which Aare also suitable for the conversion of higher boiling oils such as naphtha, kerosene or kerosene distillate, light gas oil and the like and it is also within the scope of the invention to include any such components of the charging stock with the motor fuel or motor fuel fractions supplied to heating coil 2l or to supply thereto only materials boiling above the range of motor fuel, such as previously indicated. Regardless of the specific low-boiling oil supplied to heating coil 2l and the specific conversion conditions employed therein, the nature of the heated products discharged therefrom and the temperature to which they are heated, Within the scope of the present invention, it is necessary to select conditions which will be satisfactory for accomplishing coking of the residual oils supplied to the coking chambers.

The highly heated products are discharged through heating coil 2| through line 4B and valve 4I and are introduced through lines 42 and 42' controlled, respectively, by

valves

33 and 43 into the respective coking chambers 33 and 33' entering the coking chambers at one or a plurality of any desired points therein, although only a single point of introduction to each chamber is shown in the drawing. The heated low-boiling oils preferably enter below the level of residual material in the coking zone and come into direct contact with the residual liquid supplied thereto, heating the latter to a sufficiently high temperature to effect its reduction to coke under the lowpressure conditions employed in this Zone.` Although two coking chambers are shown in the drawing it will be understood that one or any number of a plurality of such zones may be ernployed within the scope of the invention. A 'plurality of alternately operated coking chambers is preferredin order that oneor more such zones may be cleaned and prepared for'further operation While another or others are Vin use, although simultaneous operation of a plurality of coking lchambers may be employed. Chambers 33 and 33' are provided withdrain-lines `44 and 44', respectively, controlled by the respective valves 45 and 45'. These lines may also serve as a means of introducing steam, water or other suitable cooling medium into the bed of residual material in the coking zone after the operation of the chamber is completed in order to hasten cooling and facilitate cleaning of the chamber.

Vapors evolved by the cokin-g operation as well as vaporous products resulting from conversion of lthe low-boiling oils in heating coil 2| are withdrawn from

chambers

33 and 33 through the respective lines 45 and 46 controlled, respectively, by valves 41 and'41 and may pass through line 43 and valve 68 to fractionation in fractionator 38 or, when desired, a regulated portion orall of the relatively hot vapors from the coking chambers may be introduced into vaporizing chamber 21, for example, through line 69 and valve 10 orat any other desired point, preferably co-ming into direct contact with the residual liquid in chamber 21 for the purpose of increasing its temperature and assisting its vaporization to the desired degree.

Components of the vaporous products supplied to fractionator 38, boiling above the range of the desired iinal light distillate product of the processA are condensed in this zone as reiiux condensate.

Fractionated vapors of the desired end-boiling',

point are withdrawn, together with uncondensable gas, from the upper portion of fractionator 38 through line 49 and valve 5l] and are subjected to condensation and cooling in condenser 5I. The resulting distillate and gas passes through line 52 and valve 53 to collection and separation in receiver 54. Uncondensable gas may be released from receiver 54 through line 55 and valve 56. The distillate may be withdrawn from this Zone through line 51 and Valve 58 to `storage or to any desired further treatment and it may, when desired, be blended with any motor fuel components of the charging stock of satisfactory antiknock Value collec-ted, as previously described, in receiver 5, in which case the blended material comprises the final motor fuel product 'of the Y process.

The usual method oicontrolling fractionation in' fractionator 38 and column 3, forV example, such as recirculating a portion of the distillate from the

receivers

54 and 5` to the upper portion of the respective fractionating zones are entirely within the scope of the present invention, although the well known means whereby this may be accomplished are not illustrated in the drawing. Y

The reflux condensate formed in fractionator 38, comprising insumciently converted components of the total vaporous conversion products of the process and components of the highboiling fractions of the charging stock which are vaporized in chamber 21 and subsequently sub- `jected to fractionation in iractionator 38, `are Withdrawn from the lower portion of thisY Zone through line 59 and valve 65 to pump v6| bymeans of Whichthey arefed'through line 62 Vand valve l3rto conversion in heating coil 64.

Heatingcoil 64 is located in a furnace `65 vof any suitable form by means of which sufficient heat is supplied to the oil to vbring it Ytothe desired conversion temperature, preferably ata substantial super-'atmospheric pressureV and the'` heatedioill is discharged through line 56 and valvei-61 into reaction chamber 28.

ChamberrZil is also :preferably maintained at a substantial. superatmospheric pressure and', althoughv not illustrated in Vthe drawing, Vis preferably well insulatedto prevent the 'excessive loss of heat by radiation so,thatconVersion'-of the heated products from heating coilA 64, and more Iparticularly their vaporous components, may .continue in the reaction chamber. In .the casehere illustra-tedVboth Vaporous and liquid conversion.. product-'sV are withdrawn. in commingledstate fromtheiower portion of chamber 28:through line v29 and valve 30 .and `are introduced. through line 25 into vaporizing chamber 21, which `is preferably maintained at a substantially'xreduced pressure relative to that employed inthe reaction chamber in order to effect further vaporizationlin this `Zone of the liquid conversion productszfrom chamber 28andthe highboiling fractionsof the chargingstock from .oo l- Y umn 3.

In an apparatus such as illustrated land above described, ,preferred operating conditions for the process may be as follows: Heating of thecharging stock, priorto its introduction into the distillingfand fractionating column may be accomplished at any vdesired pressure ranging, forexample, from substantiallyy atmospheric to 150 poundsorzthereabouts',I per square .inch and theV temperature -to which` it is heated may range, 'Y

depending uponthe :nature of the Vcharging stock, thevpressure employed `and the desired separation of the-lowboiling and high-boiling fractions, from 450 lto 750 -or thereabouts. Substantially atmospheric, subatmospheric or a superatmospheric pressure, preferably not in excess of pounds, or thereabouts, per square inchV may be employed inthe distilling and frac-Y tionating Ycolumn Vand may be substantially equalizedfor reduced in the succeeding condensing and collecting equipment. The heating coil to which'the low-boiling fractions of the charging stock are supplied vmay utilize a conversion temperaturemeasured at the outlet therefrom Within the range -of 900 to Y F., `or thereabouts, preferably with a substantial superatv Y pounds perV square inch.'Y ThisV pressure prefer- ,ablyV is substantially equalized in the succeeding,V reaction chamber, nalthough .a vsomewhat reduced se A pressure may be employed Yin .this zone, when desired. The vaporizingchamber is preferably operated at .substantially reduced pressure relative to that employed in the reaction chamber.andV

may range, for example, from 100 pounds, or thereabouts, per square inch, to substantially atmospheric. Pressures of from 100 pounds to substantially atmospheric may be employed in the fractionatlng, condensing and collecting portions of the crackingsystem.

As a specic example of one of the many possible operations of the process of the present invention as it may be practiced in an apparatus of the type illustrated and above described, the charging stool; may comprise a California crude of about 33 A. P. I. gravity containing less than 5 percent of material boiling up to 200 F., and approximately 30 percent of 400 F. which is subjected to distillation at substantially atmospheric pressure and thereby separated into fractions boiling above and below approximately 620 F. The low-boiling fractions which comprise approximately 60 percent of the charging stock are subjected to a conversion temperature of approximately 970 F. at a superatmospheric pressure of about 500 pounds per Square inch and are introduced into direct Contact with the residual material in the coking Zone of the sys- The high-boiling fractions of the charging stock are supplied to the vaporizing chamber and rciux condensate from the fractionator, is subjected to a conversion temperature of approximately 930C F. at a superatmospheric pressure of approximately 350 pounds per Square inch in a separate heating coil. The succeeding reaction chamber' is maintained at about the same pressure and a reduced pressure of approximately 30 pounds per square inch is employed in the vaporizing chamber as well as in the coking chambers and the succeeding fractionating, condensing and collecting portions of the system. This operation may produce, per barrel of charging stock, about 65 percent of motor fuel having an antiknock value equivalent to an octane number of approximately 75 and about 60 pounds of low volatile coke, the remainder being chargeable principally to uncondensable gas.

I claim as my invention:

1. A process for the conversion of hydrocarbon oils which comprises separating, by distillation, hydrocarbon oil charging stock for the process into low-boiling and high-boiling fractions, further separating from the high-boiling fractions any heavy components of a residual nature unsuitable for conversion at elevated temperature and superatrnospheric pressure, subjecting the latter to coking at low-pressure, subjecting the remaining lower boiling components of said highboiling fractions of the charging stock to conversion at elevated temperature and superatmospheric pressure, separating the resulting vaporous and residual liquid conversion products, subjecting the latter to coking together with said heavy residual components of the high-boiling fractions of the charging stock, subjecting low-boiling fractions of the charging stock to indep-endently controlled more severe conversion conditions and contacting the resulting highly heated products with the residual materials undergoing coking for the purpose of assisting their reduction to coke.

2. A process for the conversion of hydrocarbon oils which comprises separating, by distillation, hydrocarbon oil charging stock for the process into low-boiling and high-boiling fractions, further separating from the high-boiling fractions any heavy components of a residual nature unsuitable for conversion at -elevated temperature and superatrnospheric pressure, subjecting the latter to coking at low-pressure, subjecting the remaining lower boiling components of said highboiling fractions of the charging stock to conversion at elevated temperature and superatmospheric pressure, separating the resulting vaporous and residual liquid conversion products, subjecting the latter to coking together with said heavy residual components of the high-boiling fractions ofthe charging stock, subjecting lowboiling fractions of the charging stock to independently controlled more severe conversion conditions, contacting the resulting highly heated products with the residual materials undergoing coking for the purpose of assisting their reduction to coke, subjecting the vaporous products of the cracking and coking operations to fractionation whereby their insufficiently converted components are condensed as reflux condensate, subjecting fractionated vapors of the desired endboiling point to condensation, recovering the resulting distillate and returning the reflux condensate to further conversion, together with said remaining lower boiling components of the high-boiling fractions of the charging stock.

3. A process for the conversion of hydrocarbon oils which comprises subjecting hydrocarbon oil charging stock for the process to fractional distillation whereby it is separated into low-boiling and high-boiling fractions, introducing the latter into a vaporizing chamber whereby its heavy components which remain unvaporized in this zone are separated from its lower boiling components, subjecting the latter to conversion temperature at superatmospheric pressure in a heating coil and communicating reaction chamber, separating the resulting vaporous and liquid conversion products and subjecting the latter to further vaporization at substantially reduced pressure in said vaporizing chamber, withdrawing unvaporized residual oil from said vaporizing chamber and introducing the same into a lowpressure coking zone, subjecting low-boiling fractions of the charging stock to independently controlled more severe conversion conditions in a separate heating coil, introducing the highly heated products into direct Contact with the residual material in the coking zone for the purpose of assisting its reduction to coke, subjecting the' vaporous products of the process to fractionation whereby their insufficiently converted components are condensed as reiiux condensate, subjecting fractionated vapors of the desired endboiling point to condensation, recovering the resulting distillate and returning the reflux condensate to the first mentioned heating coil for further conversion.

4. A process for the conversion of hydrocarbon oils which comprises subjecting hydrocarbon oilv charging stock for the process to fractional distillation whereby it is separated into low-boiling and high-boiling fractions, introducing the latter into a vaporizing chamber whereby its heavy components which remain unvaporized in this zone are separated from its lower boiling components, subjecting the latter to conversion temperature at superatmospheric pressure in a heating coil and communicating reaction chamber, withdrawing both vaporous and liquid products from the reaction chamber and introducing them at reduced pressure into said vaporizing chamberwhereby to effect said further vaporization of the high-boiling fractions of the charging stock as well as the liquid conversion products, withdrawing unvaporized residual oil from said vaporizing chamber and introducing the same into.

a low-pressure coking zone, subjecting low-boil- 'rect contact with the residual material ing fractions of the charging stock to independently controlled more severe conversion conditions in a separate heating coil, introducing the highly heated products into direct contact with the residual material in the coking zone for the purpose of assisting its reduction to coke, subjecting the vaporous products of the process to fractionation whereby their insufficiently con- Verted components are condensed as reflux condensate, subjecting fractionated vapors of the desired end-boiling point to condensation, recovering the resulting distillate and returning the reux condensate to the rst mentioned heating coil for further conversion.

5. A process for the conversion of hydrocarbon oils which comprises subjecting hydrocarbon oil charging stock for the process to fractional distillation whereby it is separated into lowboiling and high-boiling fractions, introducing the latter into a vaporizing chamber whereby its heavy components which remain unvaporized in this zone are separated from its lower boiling components, subjecting the latter to conversion temperature at superatmospheric pressure in a heating coil and communicating reaction chamber, separating the resulting vaporous and liquid conversion products and subjecting the latter to further vaporization at substantially reduced pressure in said'vaporizing chamber, withdrawing unvaporized residual oil from said vaporizing chamber and introducing the same into a lowpressure coking zone, subjecting low-boiling fractions of the charging stock to independently controlled more severe conversion conditions in a separate heating coil, introducing the highly heated conversion products into di- 1n the coking zone for the purpose of assisting its reduction to coke, introducing a regulated portion of the hot vaporous products from the coking zone into direct contact with the liquid in said vaporizing chamber for the purpose of assisting its vaporization, subjecting the vapcrous products of the process to fractionation whereby their insufficiently converted components are condensed as reflux condensate, subjecting'fractionated vapors of the desired end-boiling point to condensation, recovering the resulting distillate and returning the reflux condensate to the rst mentioned heating coil for further con- Version.

6. A conversion process which comprises subjecting reflux condensate, formed as hereinafter set forth, to cracking conditions of temperature and pressure in a heating coil and separating the same into vapors and unvaporized oil, in an enlarged chamber simultaneously partially distilling fresh charging oil for the process and sep-Y arating a relatively light fraction therefrom,

combining residual fractions of the charging oil Y,

with said unvaporized oil and subjecting the resultant mixture to distillation in a second enlarged chamber, subjecting said light fraction to independentlyl controlled cracking conditions'of temperature and pressure in a second heating coil and then'contacting the same with said mixture.

to assist the Vdistillation thereof, combining resultant vapors from said second chamber with vapors separated in the first-named chamber and fractionating the commingled vapors to condense heavier fractions thereof, supplying such condensed heavier fractions to the first-mentioned heating coil as said reux condensate, and finally condensing the fractionated vapor Y 7. A conversion process whichrcomprises subjecting reiiux condensate, formedY as hereinafter set forth, to cracking conditions of temperature and `pressure and separating the same intovapors and unvaporized oil, simultaneously partially distilling fresh charging oil forthe process and separating a relatively light fraction therefrom, com-Y bining the `unvaporized portion of the charging oil with said unvaporized oil and reducing the resultant mixture to coke, heating said light fraction to higher cracking temperature than the reflux condensate and then contacting the same with said mixture to assist Ythe coking thereof, combining the vapors evolved from said mixture with the first-mentioned vapors and fractionating the thus commingled vapors to condense heavier fractions thereof, supplying such condensed heavier fractions to the first-named cracking step as said reflux condensate, and nally condensing the fractionated vapors.

8. A conversion process which comprises sub-Y jecting reflux condensate, formed as hereinafter set forth, to cracking conditions of temperature and pressure in a cracking zone and separating the same into vapors and residual oil in a separating zone, simultaneously partially distilling fresh charging oil for the process and separating a relatively light fraction therefrom, introducing they unvaporized portion of the charging oil into the separating zone and commingling the same therein with said residual oil, heating said light fractionl to higher cracking temperature than said reflux condensate and then contacting Y the same with the commingled residual oil and unvaporized charging oil to distil this mixture to Y coke, subjecting the vapors thus formed and the first-named vapors to common fractionation to condense heavier fractions thereof, supplying such condensed heavier fractions to said crack-A ing zone as said reflux condensate, and finally condensing 'the fractionated vapors.

KENNETH SWARTWOOD. Y