US2057401A

US2057401A - Conversion of hydrocarbon oils

Info

Publication number: US2057401A
Application number: US687944A
Authority: US
Inventors: Swartwood Kenneth
Original assignee: Universal Oil Products Co
Current assignee: Universal Oil Products Co
Priority date: 1933-09-02
Filing date: 1933-09-02
Publication date: 1936-10-13
Anticipated expiration: 1953-10-13

Description

Oct. 13, 1936. swA rrw 2,057,401

CONVERSION OF HYDROCARBON OILS Filed Sept. 2, 1935 VAPORIZING -AND FRACTIONATING CONDENSER FURNACE FURNACE RECEIVER FRACTIONA FURNACE 3B INVENTOR KEN T SWARTWOOD TORNEY Patented Oct. 13, 1936 CONVERSION OF HYDROCARBON OILS Kenneth Swartwood, Chicago, 111., assignor to Universal Oil Products Company, Chicago, 11]., a corporation of Delaware Application September 2, 1933, Serial No. 687,944

9 Claims.

This invention particularly refers to an improved process and apparatus for the conversion of hydrocarbon oils of relatively wide boiling range wherein the charging stock, together with insufficiently converted intermediate products of the process are separated into a plurality of selected fractions of progressively lower boiling characteristics, each of which is subjected to independently controlled conversion conditions.

As a feature of the present invention, each of the progressively lower boiling fractions is subjected to more severe conversion conditions, each in a separate heating coil and communicating reaction chamber constituting a separate stage of the process, and vaporous products from all but the final stage are subjected to continued conversion in the reaction chamber of the succeeding stage, together with more highly heated.

products from the communicating heating coil which serves .to increase the temperature of said vapors from the preceding stage, effecting their further conversion.

The advantages of separating oils of relatively wide boiling range into selected fractions of relatively narrow boiling range and subjecting each fraction to independently controlled conversion conditions of elevated temperature, superatmospheric pressure and suitable conversion time best suited for the particular boiling range fraction undergoing conversion are now well recognized. Probably the chief advantages in such a system reside in avoiding excessive conversion of the high coke-forming components of the highboiling fractions while permitting conversion of the lower boiling fractions at the higher temperatures required for the production of motor fuel of high antiknock value. By this method high yields of desirable low-boiling products such as motor fuel, may be obtained from each of the selected fractions of the charging stock without excessive yields of less desirable products, such as coke and gas.

motor fuel resulting from conversion of the highboiling fractions is ordinarily not as good, particularly with respect to its antiknock value, as that resulting from the conversion of the lower boiling fractions, due to the lower temperatures necessary for the conversion of said high-boiling fractions in order to avoid excessive coke and gas formation.

In the present invention provision is made for continued conversion, at a higher temperature, of the vaporous products resulting from said relatively low temperature conversion of the highboiling fractions bycommingling the same in However, in such operations the progressive stages of the cracking system with the more highly heated lower boiling fractions. In this manner all of the advantages of selective cracking are retained and its disadvantages are eliminated since all of the low-boiling vaporous products of the process are subjected to conversion conditions suitable for the production of motor fuel of high antiknock value while none of the high-boiling non-vaporous products or highboiling fractions of the charging stock are subjected to conversion conditions sufficiently severe to cause the excessive production of coke and gas. Residual liquid is separated from the lower boiling vaporous products in each stage of the process and intimate contact of the non-vaporous liquid with the incoming more highly heated products is carefully avoided.

One specific embodiment of the present invention may comprise subjecting hydrocarbon oil charging stock for the process to fractional distillation whereby it is separated into selected fractions comprising high-boiling fractions, intermediate fractions and low-boiling fractions. The high-boiling fractions may be subjected to conversion temperatures at superatmospheric pressure in a heating coil and communicating reaction chamber, the resulting vaporous andnon-vaporous conversion products may be separated in the reaction chamber and the vapors allowed more prolonged conversion time in this zone than that afforded the non-vaporous products. The intermediate fractions may be subjected to a higher conversion temperature at superatmospheric pressure in a separate heating coil and communicating reaction chamber, and the resulting vaporous and non-vaporous con version products may be separated in the reaction chamber. Said vaporous products may be commingled with the vaporous products from the preceding reaction chamber whereby to further heat the latter, the commingled vapors being subjected to more prolonged conversion time in said reaction chamber than that afforded the nonvaporous conversion products in this zone. Said low-boiling fractions may be subjected to a still higher conversion temperature at superatmospheric pressure in another separate heating coil and communicating reaction chamber, and the resulting vaporous and non-vaporous conversion products may be separated in the reaction chamber, commingling said vaporous products with the commingled vapors from the preceding reaction chamber to further heat the latter and subjecting the total commingled vapors to more prolonged conversion time in the last mentioned reaction chamber than that afforded the non-vaporous conversion products in this zone, subjecting the total commingled vapors to fractionation whereby their insufiiciently converted components are condensed as reflux condensate, subjecting frac tionated vapors of the desired end-boiling point to condensation, collecting the resulting products, separating the reflux condensate into selected fractions corresponding to said selected fraction of the charging stock and subjecting the same to further conversion, together with the correspond ing fraction of the charging stock.

The accompanying diagrammatic drawing illustrates one specific form of apparatus embodying the advantageous features of the present invention.

It will be understood, of course, that the invention is not limited to this specific form of apparatus, which is shown only for the purpose of more clearly illustrating the features of the present invention.

Referring to the drawing, raw oil charging stock for the process, comprising any desired hydrocarbon oil of relatively wide boiling range, such as, for example, crude petroleum, topped crude or the like, after being heated to a temp-erature sufficient to effect its substantial vaporization, in any well known manner not illustrated in the drawing, is supplied through line i and valve 2 into vaporizing and fractionating column 3 wherein its substantial vaporization occurs and it is separated by fractionation into a plurality of selected fractions. In the particular case here illustrated, the charging stock is separated into three fractions comprising an overhead vaporous product such as gasoline, naphtha or the like, an intermediate fraction comprising, for example, such material as naphtha, kerosene or kerosene distillate, gas oil and the like, and higher boiling fractions comprising the bottoms from the vaporizing and fractionating column which may include heavy gas oil, fuel oil and the like.

The low-boiling vaporous product from column 3 passes through line 4 and valve 5, to be subjected to condensation and cooling in condenser 6, from which the resulting distillate'and gas passes through line 1 and valve 8 to collection and separation in receiver 9. Gas may be released from receiver 9 through line H] and valve H. The distillate collecting in receiver 9 may be withdrawn therefrom through line l2 and valve I3, to storage or to any desired further treatment. Preferably, however, except when the distillate collected in receiver 9 comprises only gasoline components of the charging stock of satisfactory motor fuel characteristics, particularly with respect to antiknock value, at least a portion of this material is withdrawn from the receiver through line H! and valve 5 to pump l6 by means of which it is fed through line ill and valve [8 to further treatment in heating coil l9, as will be hereinafter more fully described. It is, of course, within the scope of the present invention, if desired, to return a regulated portion of the distillate from receiver 9 to the upper portion of column 3, by Well known means, not shown in the drawing, for the purpose of assisting cooling and fractionation of the vapors in this zone and to regulate the vapor outlet temperature from the column.

Intermediate fractions of the charging stock are withdrawn as one or a plurality of side streams from any suitable point in column 3, for example, through line 23 and valve 24 to pump 25, by means of which this material is fed through line 26 and valve 21 to conversion in heating coil 28, as will be later more fully described. It will be understood that it is within the scope of the present invention, instead of withdrawing only one intermediate fraction from column 3, as illustrated, to remove any desired number of selected intermediate fractions and to either subject each fraction to independently controlled conversion conditions in a separate heating coil, not shown in the drawing, or to withdraw any of the fractions from the system to storage or to any desired further treatment, with which the present invention is not specifically concerned, or to combine various fractions in any desired manner, subjecting the combined fractions to further treatment outside the system or to conversion within the system. The invention also contemplates reboiling of the intermediate fractions withdrawn from column 3, in any well known manner, for the purpose of freeing the same of light fractions or entrained gases, although means for accomplishing this well known step are not illustrated in the drawing.

High-boiling fractions of the charging stock, including, in the case illustrated, any components remaining unvaporized in column 3 as well as reflux condensate, formed in this zone, boiling above the desired intermediate fractions separately withdrawn from the column, as previously described, are withdrawn from the lower portion of column 3 through line 32 and valve 33 to pump 34 by means of which they are fed through line 35 and valve 36 to conversion in heating coil 31. In case the charging stock supplied to column 3 contains an appreciable quantity of high-boiling materials of a residual or pitchy nature, unsuitable for pyrolytic conversion on account of their high coke-forming tendencies, or when it is desired to recover high-boiling components of the charging stock such as fuel oil, asphaltic residue, lubricating stock or the like, a stream of such material may be withdrawn from the lower portion of column 3 to storage or to any desired further treatment, not illustrated, instead of directing the bottoms from the column to conversion in heating coil 31.

Heating coil 31 may be positioned within a furnace 38, of any suitable form, by means of which the required heat is supplied to the oil passing through the heating coil to bring it to the desired conversion temperature, preferably at a substan tial superatmospheric pressure and the heated conversion products are discharged through line 39 and valve 40 into reaction chamber 4i preferably entering the lower portion of the reaction chamber, as illustrated in the drawing.

Chamber 4| is also maintained at a substantial superatmospheric pressure which preferably is substantially the same as that maintained at the outlet from heating coil 31, although it may, if desired, be somewhat reduced relative thereto. Vaporous and non-vaporous conversion products are separated in chamber M, the latter preferably being quickly removed from the lower portion of the reaction zone to cooling and storage or elsewhere, as desired, through line 32 and valve 43 without being subjected to any extensive conversion time in chamber 4|. The vaporous conversion products from heating coil 37, after being substantially separated from the unvaporized residue in the lower portion of chamber 4|, in the case here illustrated, pass upwardly through the chamber and are subjected during their passage to appreciable continued conversion time in this zone. The vaporous products are then withdrawn from the upper portion of chamber 4 I t and pass lthroughtline 44 and valve 45 into reaction chamber 46.' 1: l

iHeatingrcoil' 28 is supplied with heat from a Lfi1rnaceu29', of any; suitable form, by means of which the intermediate fractionsv of the charging stock ..withdrawn from column 3, ,as previously described-are subjected preferably to a higher conversion temperature .than that employed for the treatment fof the high-boiling fractionsin this zone from, chamber ll and from heating coil 26, may .fcontinue therein. Non-vaporous conversion products supplied to this zone from heating coil ,28 substantially separate from the vapors in thelower portion of the chamberland are preferablypquickly...withdrawn therefrom through line 6 4'1 and valveliB. to cooling and storage or elsewhere,= as desired, withoutbeing allowed any ex-.'

tensive conversion time in .chamber 46; The vaporousproducts from heating coil 26, after the substantialzseparation therefrom of non-vaporous residual material; commingle with the vaporous conversionproducts supplied to chamber 46 from chamber 4|, as previously described. In this manner the vaporous conversion products, resulting .from relatively low temperature conversion of.-.the high boiling fractions of the charging stock inhe'atingcoil and chamber M; are subjected to continued conversion at a higher temperature inchamber. 46.-by commingling with the .more highly heated vaporous products from heating coil 28 after substantial separation of non-vaporous residualimaterial from both streams of conversion products. vThe commingled vapors .pass

upwardly through chamber 56, being thereby sub-,

jectedto appreciable continued conversion. time in this zone and are then withdrawn from the upper portion of chamber 46, passing through line 49 and valve 56into. reaction chamber The low-boiling fractions of the charging stock supplied to heating coil l9, as previously described, are subjected to conversion and/or reforming in this zone by means of heat supplied fromrfurnace 26of anysuitable form. Preferably a higher conversion temperature is employed i'nrthiszone than in either heating coil 28 or in heating coil 31 and a substantial superatmospheric pressureis also preferably maintained in thiszone; The highly heated conversion productsaredischarged from heatingcoil [9 through line 2| and'valve 22' into reaction chamber 5|, preferably entering the lower portion of this zone at a point below the point of introduction of the vaporous conversion products from chamber 46, as illustrated in thedrawing.

I, Chamber 5! is also preferably maintained at a substantial superatmospheric pressure so that appreciable continued conversion of the vaporous products supplied to this'zonefrom heating coil [Sand from chamber' lfi is effected therein. Any non-vaporousresidual componentsof the conversion prod ucts from heating coil 19 aresubstantially separated from the. vapors in thelower portion: oivcham-ber 5|, and preferably are quickly or elsewhere, as desired, through line 52 and valve 53 without allowing them sufficient time for any extensive continued conversion in chamber 5 I. The highly heated vaporous products from heating coil I9 then commingle in chamber 5| with the somewhat cooler vaporous products supplied to this zone from chamber 46, serving to increase the temperature of the latter and effect their further conversion in chamber 5!. The commingled vapors pass upwardly through chamber 5|, being subjected to appreciable continued conversion timeduring their passage therethrough, and. are

withdrawn from the upper portion of this zone through line 54 and valve 55, passing therefrom to fractionation in fractionator 56.

l Components of the vaporous products supplied to fractionator 56 boiling above the end-boiling point. ofjthe desired light distillate conversionv product of the process are condensed in this zone as reflux condensate. Reflux condensate may be withdrawn from the lower portion of fractionator. 56 through line 51 and valve 58 to pump 59 to be supplied therefrom through line 66 and valve 6! into vaporizing and fractionating column 3., In this case, the reflux condensate from fractionator 56. is subjected to vaporization and further fractionationin column 3, and is thereby separated into selected fractions corresponding to the se-' lected fractions of the charging stock so that the various fractions of the reflux condensate are subjected to the sametreatment as that afforded the selected fractions of the charging stock of corresponding boiling range. It is, of course, also within the scope of the present. invention, although not illustrated in the drawing, to separately withdraw selected fractions of the reflux condensate, of the desired boiling range from fractionator 56, withdrawing any desired portion thereof from the system or subjecting each or any withdrawn from this zone to cooling and storage of the various fractions to conversion in any of I the various heating coils I9, '28 or 3'1 employing the conversion conditions most suitable for the particular fraction of the reflux condensate or, when desired, a separate heating coil or coils, not shown in the drawing, may be employed for conversion of the total or selected fractions of the refluxcondensate. It is also within the scope of the invention, when desired, to supply the total or a regulated portion of the reflux condensate. from fractionator 56to any of the heating coils I6, 28 or 31 for further conversion, by well known means not illustrated in the drawing, although separation of the reflux condensate into selected frac tions for segregated conversion, as previously described, is ordinarily preferred.

Fractionated vapors of the desired end-boiling point, preferably comprising materials within the boiling range of motor fuel and of high antiknock value, are withdrawn together with uncondensable gas from the upper portion of fractionator 56 through line 62 and valve 63 and are subjected to condensation and cooling incondenser 64. The resulting distillate and gas passes through line-65 and valve 66 to collection and separation in receiver 61. Uncondensable gas may be released from the receiver through line 66 and valve. 69. Distillate is withdrawn from this zone through line 16 and valve H to storage or to any desired further treatment. A portion of the distillate collecting in receiver 61 may, when desired, be recirculated by well known and coolingmedium to; assist fractionation of the vapors and to maintain the desired vapor outlet temperature from the fractionator.

It is also within the scope of the present invention, although not illustrated in the drawing, to subject all or a portion of the non-vaporous conversion products of the process to further vaporization at substantially reduced pressure. Any well known type of flash distilling or coking equipment may be employed for this purpose and this stage of the process, when employed, may be operated for the production of either liquid residue, suitable, for example, as fuel oil or heavy cracking stock, or for the production of petroleum coke or asphaltic residue. The conditions necessary for these various types of operation and the equipment required for each are well known in the art and do not constitute a novel feature of the present invention except in combination with the other features described. Preferably, however, in case flash distillation, asphalt production or coking of any or all of the nonvaporous conversion products from the various reaction chambers is employed the evolved vapors are supplied by well known means, not

' shown in the drawing, to vaporizing and fractionating column 3 to be subjected to fractional distillation, together With the charging stock, the resulting selected fractions being subjected to further conversion, together with the corresponding fractions of the charging stock.

The temperature employed in the vaporizing and fractionating column will depend, primarily, upon the nature of the charging stock, the pressure conditions employed in this stage of the process and the desired separation of the stock and may range, for example, from 550 to 750 F., or thereabouts, in the lower portion of the column. Heating of the charging stock may be accomplished under any desired pressure ranging from subatmospheric to 150 pounds, or thereabouts, superatmospheric pressure and substantially the same or a somewhat reduced pressure may be employed in the vaporizing and fractionating column.

Preferred operating conditions in the cracking stage of a process such as illustrated and above described may be as follows: The temperature employed at the outlet from the heating coil to which the high-boiling fractions of the charging stock are supplied may range, for example, from 800 to 925 F., or thereabouts, and a substantial superatmospheric pressure is preferred at this point in the system within the range of 100 to 500 pounds, or more, per square inch. This pressure preferably is substantially equalized in the succeeding reaction chamber, although somewhat reduced pressure may be employed in the reaction chamber, when desired. The temperature employed at the outlet from the heating coil to which the intermediate fractions of the charging stock are supplied may range, for example, from 900 to 1000 F., or thereabouts, and a substantial superatmospheric pressure of the order of 200 to 800 pounds, or thereabouts, per square inch, is preferred at this point in the system. The reaction chamber to which the heated products from this zone are supplied may be maintained at substantially the same of somewhat reduced pressure which, however, is not in excess of that employed in the preceding reaction chamber. The heating coil to which the low-boiling fractions of the charging stock are supplied may employ an outlet temperature ranging, for example, from 950 to 1100 F., or thereabouts. A superatmospheric pressure of the order of 350 to 1000 pounds, or thereabouts, per

square inch, is preferred at this point in the.

system although, when desired, lower pressures down to substantially atmospheric may be employed in this zone. A substantially equalized or'somewhat reduced pressure relative to that employed at the outlet from this heating coil is employed in the communicating reaction chamber which pressure, however, does not exceed that in the preceding chamber. The fractionator as wall as the succeeding condensing and collecting portions of the cracking system may employ any desired pressure either substantially equalized with or somewhat reduced relative to the pressure employed in the final reaction chamber.

As a specific example of one of the many possible operations of the process of the present invention, the charging stock is a Wyoming crude of about 38 A. P. I. gravity containing about 5 percent of material boiling up to 248 F. and about 30 percent at 437 F. The charging stock is heated to a temperature of approximately 550 F. at substantially atmospheric pressure and introduced into the vaporizing and fractionating column, together with reflux condensate from the fractionator of the cracking system at a somewhat higher temperature, which latter serves to increase the temperature in the vaporizing and fractionating column. The charging stock and reflux condensate is separated in this zone into three fractions comprising an overhead product having an end-boiling point of approximately 500 F., an intermediate fraction having an end-boiling point of approximately 625 F., and a high-boiling fraction, including the remainder of the charging stock and reflux condensate. The high-boiling fraction is subjected to a conversion temperature of approximately 850 F. in a heating coil at an outlet pressure of approximately 400 pounds, per square inch and the heated products are introduced into a communicating reaction chamber maintained at approximately the same pressure. The intermediate fractions are supplied to a separate heating coil wherein they are subjected to an outlet temperature of approximately 950 F, at a superatmospheric pressure of about 400 pounds per square inch and are then introduced into a separate reaction chamber maintained under approximately the same pressure, to which vaporous products from the first reaction chamber are also supplied. The low-boiling fractions are subjected in another separate heating coil to a temperature of about 1000 F. at a superatmospheric pressure of approximately 600 pounds per square inch and the highly heated products are introduced into another separate reaction chamber maintained at approximately 400 pounds per square inch, to which vaporous products from the second chamber are supplied. The total vaporous conversion products are supplied from the last reaction chamber to the fractionator. An overhead vaporous product having an end-boiling point of approximately 400 F. is removed from the fractionator, condensed and collected. Reflux condensate from the fractionator of the cracking system is returned to the vaporizing and fractionating column td which the crude charging stock is supplied and there separated into fractions corresponding to said selected fractions of the charging stock. Nonvaporous residual liquid is withdrawn from each of the reaction chambers without being allowed appreciable conversion time therein and the total residue from the three chambers is subjected to flash distillation at a reduced pressure of approx- ,imatelySO pounds per square inch. The flashed residue is, cooled and collected and the total evolved vapors from the flashing stage of the of the charging stock for further conversion. This operation may yield, per barrel of raw oil charg irig'stock, about 60 percent of 400 end-point motorfuel having an antiknock value equivalent to ,an octane number of approximately78 and about f2,5, per cent of good qualityresidual oil, the remainder being chargeable principally to unconldensable gas and a negligible amount of coke.

I I 'claim as my invention: 7

l. 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 s'elected fractions compri'singhigh-boiling fractions, intermediate' fractions and low-boiling fractions, subjecting the high-boiling fractions to conversion temperature at superatrnospheric pressure in a heating coil and a first reaction chamber, separating the resulting vaporous and ,non-vaporous conversion products inthe reaction chamber and allowing the vapors more prolonged conversion time in this zone than that afforded the non-vaporous products, subjecting the intermediate fractions to a higher conversion temperature at superatmospheric pressure in a separate heating coil and a second reaction chamber, separating the resulting vaporous and non-vaporous conversion products in this reaction chamber, commingling said vaporous products with the vaporous products from the first reaction chamber whereby to further heat the latter, subjecting the commingled vapors to more prolonged conversion time in said second reaction chamber than that afforded the non-vaporous conversion prodnets in this zone, subjecting said low-boiling fractions to a still higher conversion temperature at superatmospheric pressure in another sep- .arate heating coil and a third reaction chamber, separating the resulting vaporous and non-vaporous conversion products in this reaction chamber, commingling said vaporous products with the commingled vapors from the second reaction chamber to further heat the latter and subjecting the total commingled vapors to more prolonged conversion time in'the last mentioned reaction chamber than that afforded the non-vaporous conversion products in this zone, subjecting the total commingl d vapors to fractionation whereby their insufficiently converted components are condensed as reflux condensate, subjecting fractionated vapors of the desired end-boiling point to condensation and collecting the resulting products.

2. A process'of the character defined in claim 4. A process of the character defined in claim 1 wherein the reflux condensate is commingled with the charging stock and subjected to fractional distillation therewith.

5. A hydrocarbon oil conversion process which comprises fractionating the charging oil and separating therefrom a relatively heavy fraction and aglighter fraction,1heating the heavy fraction to cracking temperature under pressure while flowing through a heating zone, discharging the heated heavy fraction into a reaction zone maintained under cracking conditions of temperature and pressure and effecting conversion therein, simultaneously heating the lighter fraction in a second heating zone to higher cracking temperature than the heavy fraction in the firstnamed heating-zone and then discharging same into a second reaction zone maintained under cracking conditions of temperature and pressure,

removing vapors from the first-mentioned reaction zone and introducing the same to said second ,reaction zone to commingle therein with vapors evolved from the lighter fraction, effecting further conversion of the commingled vapors in the second reaction zone and then removing and sub jecting them to fractionation to condense heavier comprises fractionating the charging oil and separating therefrom a relatively heavy fraction and a lighter fraction, passing said fractions under pressure through separate heating coils and heating the same therein to cracking temperatures, the lighter fraction being heated to higher temperature than the heavy fraction, then discharging the heavy fraction into a first reaction chamber and the lighter fraction into a second reaction chamber, both maintained under cracking conditions of temperature and pressure, separating vapors from residuein said first chamber and introducing such separated vapors into said second chamber to commingle therein with vapors evolved from the lighterfraciion, subjecting the commingled vapors to further conversion in the second chamber, then removing the vapors from the second chamber and subsequently fractionating the same to condense heavier fractions thereof, supplying resultant reflux condensate to the first-named fractionating step for fractionation therein together with the charging oil, and finally condensing the fractionated vapors.

7. A hydrocarbon oil conversion process which comprises fractionating the charging oil in a distilling and fractionating zone and separating therefrom a relatively heavy fraction, an intermediate fraction and a relatively light fraction, passing said fractions through independent heating zones and heating them therein to cracking temperatures, the intermediate fraction being heated to higher temperature than the heavy fraction and the light fraction being heated to higher temperature than the intermediate fraction, discharging the heated heavy, intermediate and light fractions, respectively, into a first reaction zone, a second reaction zone and a third'reaction zone, said reaction zones being independent of and maintained at higher temperature than the first-named zone, maintaining said reaction zones under cracking conditions of temperature and pressure and effecting further conversion therein, removing vapors from said first zone and introducing them to said second zone to commingle with vapors evolved in the latter, removing commingled vapors for said second zone and introducing the same to said third zone to commingle with vapors here evolved, and removing the vapors from the third zone and fractionating and condensing the same.

8. A hydrocarbon oil conversion process which comprises subjecting a relatively heavy hydrocarbon oil to conversion temperature under superatmospheric pressure in a heating coil and a first reaction chamber, separating the resulting vapors and unvaporized oil in the chamber and allowing the vapors more prolonged conversion time in the chamber than that afforded the unvaporized oil, simultaneously subjecting a lighter hydrocarbon oil to a higher conversion temperature at superatmospheric pressure in a separate heating coil and a second reaction chamber, separating the resulting vapors and unvaporized oil in said second chamber, commingling the last-named vapors with the vapors from the first reaction chamber whereby to further heat the latter, subjecting the commingled vapors to more prolonged conversion time in said second chamber than that afforded the unvaporized oil in this chamber, subsequently fractionating the commingled vapors to condense insufliciently converted components thereof as reflux condensate, and finally condensing and collecting the fractionated vapors.

9. A conversion process which comprises simultaneously passing relatively light, heavy and intermediate petroleum fractions through separating heating coils and heating the same therein to cracking temperatures under pressure, the intermediate fraction being heated to higher temperature than the heavy fraction and the light fraction being heated to higher temperature than the intermediate fraction, discharging the heated heavy, intermediate and light fractions, respectively, into a first reaction chamber, a second reaction chamber and a third reaction chamber, maintaining said chambers under cracking conditions of temperature and pressure and effecting further conversion therein, removing vapors from said first chamber and introducing them to said second chamber to commingle with vapors evolved in the latter, removing commingled vapors from said second chamber and introducing the same to said third chamber to commingle with vapors here evolved, and removing the vapors from the third chamber and fractionating and condensing the same.

KENNETH SWARTWOOD.