US2361891A

US2361891A - Conversion of hydrocarbon oils

Info

Publication number: US2361891A
Application number: US358408A
Authority: US
Inventors: Kenneth M Watson
Original assignee: Universal Oil Products Co
Current assignee: Universal Oil Products Co
Priority date: 1940-09-26
Filing date: 1940-09-26
Publication date: 1944-10-31
Anticipated expiration: 1961-10-31

Description

Oct. 3l, 1944. K. M. wATsoN CONVERSION OF HYDROOARBON OILS Filed Sept. 26, '1940 2 Sheets-Sheet 1 5% INV ENTOR.

K. M. WATSON CONVERSION oF HYDRocARBoN oILs INV ENT OR.

1e/ 777. Malsvz ygzarvzeoll LII' ' oct. 31, 1944.

Patented Oct. 3l, 1944 CONVERSION HYDROCARBON OILS Kenneth M. Watson, Chicago, Ill., assignor tol Universal Oil Products Company, Chicago, Ill., a corporation of Delaware Application September 26, V1940, Serial No, 358,408

2 Claims.

The invention relatesV to an improvedprocess for the pyrolytic conversion o f relatively highboiling hydrocarbon oil such as heavy crude petroleum, topped crude and the like, to produce therefrom high yields of light distillate such as good antiknock gasoline and minor yields of petroleum coke. Normally gaseous products containing a high percentage of readily polymerizable olefins, suchvas propene and butenes, are also produced within the system and, in the preferred embodiment of the invention, intermediate liquid products such as good quality furnace oil, naphtha and the like are recovered as separate products of the process.

A number of novel features are provided by the invention which represent advantageous 'departures from prior practice, particularly in view of their interdependent and cooperative relationship. The invention also resides in various combinations of these features involving less than the entire combination disclosed and it is therefore not intended to limit the invention to this entire combination.

In accordance with one specic embodiment of the invention, the hydrocarbon oil charging stock to be cracked is preheated, as will be later described, and thence supplied to and through a heating coil wherein it isbrought to the desired cracking temperature at substantial superatmospheric pressure and wherein a` portion of the cracking reaction occurs.` The resulting heated products are passed downwardly through an elongated vertically disposed reaction chamber also maintained at a cracking temperature and substantial superatmospheric pressure wherein the desired cracking reaction is substantially completed- Vaporous and liquid conversion products are separated` in the lower portion of the reaction chamber and separately removed therefrom. The charging oil is passed in indirect heat transfer relation with said vaporous products and then in indirect heat transfer relation with said lliquid products to preheat the same prior to its introduction into the heating coil and the resulting partially cooled products are supplied to a vaporizing and fractionating column, maintained at a super-atmospheric pressure lower thanthat employed in the reaction chamber, from which fractionating column the overhead vaporous stream consisting essentially of gasoline and normally gaseous fractions is supplied to condensing and recovery equipment. Unvaporized components of the conversion products and condensate formed in the fracizing and` fractionating column operated at substantially reduced pressure from which `latter column a light overhead distillate, such as naphtha, and a select intermediate fraction, such as 'i' furnace oil, are separately recovered, while the bottoms comprising higher boiling components of the materials supplied to this zone are directed to a third fractionating column from which an-` other overhead distillate product and a select side-stream comprising goodquality light fuel oil are separately recovered. The bottoms from the third fractionating column are supplied to another heating coil wherein they are quickly heated under non-Coking conditions to a temperature adequate to induce their `subsequent reduction to coke in alternately operated enlarged coking chambers to which the heated products from this coil'are supplied. Vapors evolved in the coking chamber are supplied to a separating chamber wherein high coke-forming components unsuitable for treatment in the last named heating coil are separated from 'the lighter vapors, these heavy components being returned directly to the coking chambers while vapors from the separating chamber are supplied to the last named fractionating column.

Referring to Figs.Y l and 2 of the drawings, which diagrammatically illustrate means for carrying out the invention, the preheated charging stock is supplied, as will be later described, to heating coil I disposed in furnace 2 and in passing therethrough is heated to the desired cracking temperature at substantial superatmospheric pressure.,` The resulting heated products are directed from' coil I through line 3 and valve 4 into reaction chamber 5 which is also maintained at substantial superatmospheric pressure and which is preferably insulated to conserve heat, although insulation is not shown in the drawings, so'that cracking of the heated products from coil 2 is continued in the reaction chamber. p

The rough separation of vaporous and liquid conversion products is effected in thelower portion of chamber 5 and the liquid products are directed from the bottom of the chamber through line B, valve l, heat exchanger 3, line 9 and valve Il] into the vaporizingand separating section II,

of column I2, `of which the upper portion I3 is a iractionator. The vaporous conversion products are separately removed from chamber 5 above the point of removal of the liduidproducts in this zone and are directed through line I4, heat exchanger l5, line I6 and valve Il also into zone Il. In the case here illustrated, the streams of vaporsand liquid products separately removed from chamber 5 are commingled after they have passed through heat exchangers I5 and 8, respectively, and before they are introduced into zone II, although it is entirely within the scope of the invention to separately supply the vaporous and liquid products to the latter zone when desired.

The function of heat exchangers 8 and I5 is to separately cool the vaporous and liquid streams supplied, respectively, to these zones to a temperature at which no substantial further cracking of these materials will occur, this being accomplished, in the case here illustrated, by passing the separate streams in indirect heat transfer relation with the charging oil which is thereb-y preheated. I have found that the feature of separating the vaporous and liquid conversion products in the reaction chamber and separately cooling the same in transit to the subsequent vaporizing and separating step is particularly advantageous as compared with removing them in commingled state from the reaction chamber and effecting their cooling in commingled state. Due to this separation and separate cooling, the formation and deposition of coke during the transfer of the conversion products from the reaction chamber to the subsequent vaporizing and separating step is practically eliminated, thus greatly prolonging the duration of the operating cycle of the process.

A substantial superatmospheric pressure is also employed in column I2 but is preferably somewhat lower than the pressure utilized in the reaction chamber. The vapors supplied to and evolved in zone II pass therefrom through vapor riser II into fractionating section I3 of column I2 wherein they are fractionated to form light and heavy condensates and fractionated vapors of the desired end boiling point. The heavy condensate formed by fractionation of the vapors and collected above the tray or deck I8, which forms a partition between zones II and I3, is directed through line I9 and valve 20 to pump 2I wherefrom it is supplied through line 22 and valve 23 to heat exchanger 24, cooled in the latter zone, as will be later described, and thence directed through line 25 wherefrom it is supplied, in part, through valve 26 into fractionator I3 wherein it serves as a cooling and refluxing medium and, in part, through line 21, valve 28 and a suitable spray device indicated at 29 into the lower section II of the column wherein it contacts and acts as a coolingl medium for the vapors supplied to and evolved in this zone and, in part, commingles with the liquid products removed from the lower portion of zone I I. Relatively heavy liquid conversion products which remain unvaporized in zone II are directed therefrom through line 30 and valve 3I to fractionator 34.

The vapors remaining uncondensed in the lower portion of fractionator I3 are further fractionated in the upper portion of this zone to form a lighter condensate which is removed therefrom through line 32 and may be directed, al1 or in part, through valve 33 in this line to fractionator 34 or returned, all or in part, via line 35, valve 36, pump 31, line 38 and valve 39 to heating coil I for further cracking in this zone in commingled state with the charging oil.

Fractionated vapors of the desired end-boiling point, which preferably consist predominantly of gasoline and normally gaseous products, are directed from the upper portion of fractionator I3 through line 40 and valve 4I to cooling and condensation in condenser 42 wherefrom the resulting distillate and uncondensed gases and vapors are directed through line 43 and valve 44 to accumulator 45. Condensate collected in accumulator 45 is returned in regulated quantities through line 46, valve 4'I, pump 48, line 49 and valve 50 to the upper portion of fractionator I3 to serve as a cooling and reuxing medium in this zone. Vapors and gases which remain uncondensed in accumulator 45 Iare directed therefrom through line 5I and valve 52 to sub-cooler 53, wherein condensation of substantially all of the normally liquid components of the vapors is completed. The resulting distillate and uncondensed gases are directed from sub-cooler 53 through line 54 to receiver or separating drum 55 wherefrom the gases are released through line 56 and valve 5'I to storage or suitable absorption equipment, not illustrated, or elsewhere as desired, while the distillate which will normally contain substantial quantities of dissolved gases is supplied through line 58 and valve 59 to suitable stabilizing equipment, not illustrated, or to any other required further treatment or storage.

Due to the relatively high pressure employed in column I2, the stream removed therefrom through line 32 will contain substantial quantities of gasoline or heavy gasoline fractions and will also contain heavy fractions undesirable as components of the light furnace oil product of the operation. Also, the heavier liquid fractions removed from the lower portion of zone II will normally include some gasoline or heavy gasoline fractions and a substantial quantity of lowboiling fractions desirable for inclusion in the light furnace oil. By substantially reducing the pressure in chamber 34 and supplyingT both of these streams from column II to this zone, they are subjected to revaporization and fractionation in this zone to effect a better segregation of the desired products and, in addition to the vaporization elfected in this zone by the pressure reduction, heat in the vapors evolved from the hot heavy fractions from zone II serves to effect vaporization of the lighter condensate from fractionator I3 by intimate countercurrent contact therewith in fractionator 34, while the lighter condensate serves to partially cool and assist fractionation of said vapors evolved from the heavier oil. The bottoms which remain unvaporized in fractionator 34, together with the heavy condensate collected in the lower portion of this zone, are removed therefrom through line 60 and directed through valve 6I in this line into column H2, the function of which will be later explained.

A side-stream comprising the desired light fur nace oil and some undesired lower boiling components is removed from a suitable intermediate point in fractionator 34 through line 65 and is directed, in part, through valve 66 in this line to heat exchanger I wherein it is cooled and wherefrom it is thence returned through line 68 and valve 69 to fractionator 34 to serve as a cooling and refluxing medium in this zone. The remaining portion of the side-stream from line 65 is directed through lines 'I0 and valve 1I to stripping column 'I2 wherein it is reboiled in any suitable well known manner for the purpose of substantially freeing the same of undesired light fractions. Reboiling and stripping is accomplished, in the particular -casehere illustrated, by supplying open steam to column 'I2 through line 'I3 and valve I4, although reboiling may be accomplished, when desired, by the use of an indirect heat exchange medium such assteam or hot oil. The vapors evolved in column 12 are returned therefrom through line 15 to fractionator34 and the desired light furnace oil product is directed from the lower portion of this zone through line 16 and valve 11 to cooling and storage or elsewhere, as desired.

Fractionated vapors of the desired end-boiling point, which, in addition to any normally gaseous fractions, may constitute a special naph-' tha productor additional yields of gasoline or heavy gasoline fractions, are directed from the upper portion of fractionator 34 through line 18 and valve 19 to cooling and condensation in condenser 80 wherefrom the resulting distillate and uncondensed gases are directed through line 8| and valve 82 to collection and separation in receiver 83. The uncondensed gases are released from the receiver through line 84 and valve 85 to storage or elsewhere, as desired, andregulated quantities of the distillate collected in the receiver are preferably returned by means of line 86, valve 81, pump 88, line 89 and valve 90 to the upper'portion of fractionator 34 to serve as a cooling and refluxing medium in this zone.

The net make of the distillate collected inreceiver 83 is directed therefrom through line 9| and valve 92 to pump`93 and when this material is desired as a separate productl ofthe process it may be directed. through line 94, line 95 and valve 96 to storage or to any desired further treatment or, when this material comprises gasoline or gasoline fractions suitable forinclusion with the gasoline inthe overhead vaporousv stream from fractionator I3, it may be supplied from pump 93 through line 94, line 98 and valve 91 to sub-cooler 53 wherein it commingles with the uncondensed stream from accumulator `45 and wherein the distillate from receiver 83 will normally serve as an absorbent for some ofthe heavy gases in saiduncondensed stream, the resulting commingled distillate being collected in receiver 55 and therein separated from the uncondensed and undissolved gases.

Charging stock for the process, which may comprise anyl desired type of oil but preferably consists of relatively heavy petroleum fractions, such as topped or reduced crude, is supplied through line |00 and valve I0I to pump |02 Wherefrom it is supplied to heating coil I after first passing, in the particular case here illustrated, through each of the

heat exchangers

61, 24, I5 and 8, in series, and serves in each of these zones `as a cooling medium for the relatively hot ma-` terials supplied thereto, as previously described,`

,by passing in indirect heat exchange relation therewith. From pump |02, the charging oill is directed, in the particular case here illustrated,

` It will, of course, be understood, that any`other desired method `and means of preheating the charging oil may be employed Within the scope of the invention or that it may, when desired, be supplied to coil I without preheating or that any of the heat exchangers 8, I5, 24 and 61 may be employed for preheating the charging stock without necessarily using all of them for this purpose. For any of the heat exchangers not utilized to preheat `the charging oil a suitable cooler of any conventional form may be substituted or another cooling medium may be utilized therein Without departing from the scope invention'.

The bottoms supplied from fractionator 34 to the fractionating section I|0 of column I I2 commingle in this zone with vaporous products of the coking operation which are supplied to fractionator |I0, as will be later described, and the mixture is separated into relatively light, relatively heavy and intermediate fractions. The relatively light fractions which comprisethe overhead vaporous stream from fractionator I|0, consisting essentially of gasoline and normally gaseous fractions, are derived predominantly from the vaporous products of the coking operation, while the heavy and intermediate liquid fractions are derived from both the vaporous products of the coking operation and the bottoms from fractionator 34.

The intermediate fractions, which preferably comprise a good quality fuel `or furnace oil, are removed from an` intermediate point in fractionator I I0 through line I I3 and are directed, all or` in part, through line IIII and valve II5 to stripping column ||6 wherein they are substantially freed of undesired light fractions, this being accomplished, in the case here illustrated, by reboiling with open steam which is supplied to the lower portion of the column through line I I1 `and valve I I8. The stripped product is removed from `the lower portion of the column through line I9 and valve I 20 to cooling and storage or elsewhere, as desired, and the evolved vapors and gases may be returned directly from column I I6 to fractionator I I0 by well known means, not illustrated, or, preferably, in order that a reduced dissolved gases are released from accumulator.

|24 through line |25 and valve |26 and the dis. tillate from this zone is returned by means of line |21,=valve |28, pump |29, line |30, valve |3I and lline |32 to a suitable intermediate point in fractionator I|0 above the point of removal of said intermediate fraction therefrom, to serve as a cooling and fluxing medium in'this zone. To augment the distillate supplied from accumulator |24 to fractionator I0 and provide additional cooling and refluxing in the latter zone, when desired, provision is made for directing a regulated portion of the unstripped'side-stream from fractionator I I0 through valve |33 in line II 3 to pump |34 by means of `which it is returned via line |35, valve |38, cooler |31, line |32 and valve |38 to fractionator I|0. A portion or all of the side stream removed from column I|0 may, when desired, be recovered without rst stripping the same in column II6, this being accomplished by directing the same, after cooling v in cooler`l31, to storage or elsewhere as desired,

fthroughline |90 and valve I 9| communicating with line |32.

The liigh-boilingcomponents of the materials supplied to fractionator ||0 constitute a heavy but relatively clean oil suitable for further crack-` of the and is directed therefrom through line |42 and valve |43 to pump |44 by means of which it is supplied through line |45 and valve |46 to heating coil |41.

Coil |46 is disposed in furnace |48 which, although illustrated in a conventional manner in the drawings, preferably consists of one of the several well known forms of heaters designed to transfer heat to the oil at high rates so that the heavy oil may be quickly heated in coil |41 to a high temperature which will induce cracking and effect subsequent reduction of the heavy conversion products to coke without allowing the oil to remain in the heating icoil for a suicient length of time to cause coking diiiicunlties therein. A substantial superatmospheric pressure is preferably employed at the outlet of coil |41 and the highly heated oil from this zone is directed through line |49 and valve |50 into a plurality of alternately operated coking chambers.

Two substantially identical coking chambers |53 and |53 are illustrated in the drawings, but it will, of course, be understood that any desired number of such zones may be utilized. Heated oil from line |49 is supplied to chamber |53 through line and valve |52 and to chamber |53 through line |5|' and valve |52. The coking chambers are `preferably unheated and insulated, although insulation is not indicated in the drawings, and the coke which forms in these zones as the result of distillation and cracking of the heated oil therein is allowed to accumulate in the coking chamber in operation until it is substantially filled or until its operation is completed for any other reason, following which the heated oil stream is diverted t0 the other chamber and the accumulated coke is removed from the first mentioned chamber" in any well known manner, not illustrated, preferably after it has been isolated from the rest of the system. Coking chambers |53 and |53 are provided with drain lines |54 and |54', respectively, controlled by the respective valves |55 and |55' and theselines may also serve as a means of introducing steam, water or other suitable cooling material into each of the chambers after its operation has been completed in order to hasten cooling and facilitate removal of the coke.

Vapors evolved in chambers |53 and |53 are removed therefrom through the respective lines |56 and |56', controlled by the respective valves |51 and |51', and are thence directed through line |58 to separating zone of column ||2 wherein heavy pitch or tar-like materials carried over with the vapors from the coking Zone are removed therefrom prior to their fractionation for the formation of the heavy condensate supplied to coil |41. The vapors substantially freed of entrained, undesirable heavy materials pass from zone through vapor riser |4| into fractionator ||0. The heavy tar or pitch-like materials removed from the vapors are, due to their high coke-forming characteristics, unsuitable for treatment in coil |41 and are, therefore, returned directly to the coking chambers for further treatment Without passing through coil |41, this being accomplished by removing the same from the lower portion of zone through line |59 and valve |60 to pump 6| wherefrom they are returned through line |62 and valve |63 to line |49 and thence to the coking chamber in operation.

The fractionated vaporous stream removed from the upper portion of fractionator ||0 is in this zone.

directed through line and Valve |66 to cooling and partial condensation in condenser |61 wherefrom the resulting distillate and uncondensed vapors and gases are directed through line |68 to accumulator |69, wherefrom the condensate is returned in regulated quantities by means of lines |10, |1|, pump |12, line |13 and valve |14 to the upper portion of fractionator ||0 to serve as a cooling and reuxing medium The vapors and gases which remain uncondensed in accumulator |69 are directed therefrom through line |15 to sub-cooler |16 wherein condensation of substantially al1 of their normally liquid components is completed to form a distillate boiling within the range of gasoline and containing substantial quantities of dissolved heavy gases. The resulting distillate and remaining uncondensed and undissolved gases are directed from sub-cooler |16 through line |11 and Valve |18 to collection and separation in receiver |19 wherefrom the uncondensed gases are directed to storage or to suitable absorption equipment, not illustrated, through line |80 and valve |8|, while the distillate from this zone is removed through line |82 and valve |83 to stabilization and /or to any other desired treatment, not illustrated, or to storage.

The operating conditions employed in various portions of the system will vary considerably depending upon the nature of the charging stock employed and the desired characteristics of the products. In general, however, when the charging stock is a relatively heavy oil, such as topped or reduced crude, a cracking temperature of from 850 to 950 F., or thereabouts, is employed at the outlet of coil preferably with a superatmospheric pressure at this point in the system of 200 pounds, or more, per square inch. A pressure of substantially the same magnitude or somewhat lower is preferably employed in reaction chamber 5 and the vaporous and liquid conversion products separately removed from this zone are preferably cooled to a temperature of .from 800 to 850 F., prior to their introduction into column |2. A substantial superatmospheric pressure of from 150 to 200 pounds, or thereabouts, per square inch is preferably employed 1n column I2, but to assist vaporization in the lower portion of this zone the pressure employed therein is preferably somewhat lower than that utilized in the reaction chamber. A still lower pressure ranging, for example, from 30 to 150 pounds or thereabouts, per square inch, superatmospheric, is preferably employed in fractionator 34. A temperature of from 900 to 950 F'. is preferably employed at the outlet of heating coil |41, preferably with a superatmospheric pressure at this point in the system of from to 150 pounds, or thereabouts, per square inch. Substantially the same or somewhat lower superatmospheric pressure may be employed in the succeeding coking chambers and column ||2 is preferably operated at substantially the same pressure as that employed in the coking zoney this pressure preferably also being substantially equalized in the succeeding condensing and collecting equipment for the overhead vaporous stream from column ||0, while substantially the same or, preferably, a somewhat lower pressure may be employed in stripping column I6.

As an example of one specic operation of the process herein provided, as it may be conducted in an apparatus of the character illustrated and above described, the charging stock is a West Asuperatmospheric pressure at the outlet of this coil of approximately 265 pounds per square inch. Substantially the same pressure is employed in the reaction chamber and the vaporous and liquid conversion products separately withdrawn from this zone are each separately cooled by indirect heat exchange with the charging stock to a temperature of approximately 830 F., at which they enter section II of column I2.

A superatmospheric pressure of approximately 160 pounds per square inch'is employed in column I2 and condensate removed from the lower portion of fractionator I3 at a temperature of approximately 700 F. is cooled to a temperature of approximately 500 F. and returned. in part, to section II and, in part, to fractionating section I3 of column I2 in the manner illustrated.

Approximately 12,000 barrels per day of approximately A. P. I. gravity liquid conversion products are removed from the lower portion of section II of column l2 at a temperature of approximately 790 F. and supplied to fractionator 34 at a relatively low point in this zone. Approximately 2450 barrels per day of condensate having a gravity of approximately 38.5 A. P. I. is removed from an intermediate point in fractionator I3 `at a temperature of approximately 625 F. and also supplied to fractionator 34 at a relatively high point in this zone. The overhead vaporous stream from fractionator I3 is cooled in condenser 42 to a temperature of about 180 F. and resulting condensate is returned from accumulator 45 to the upper portion of fractionator I3. A temperature of approximately 100 F. is employed in sub-cooler 53 and receiver 55 is operated at a superatmospheric pressure of about 150 pounds per square inch.

Fractionator 34 is operated at a superatmospheric pressure of about 40 pounds per square inch and bottoms of approximately 16 A. P. I. gravity are removed from this zone at a temperature of approximately 710 F. and supplied therefrom to fractionator IIO at the rate of apf proximately 9600 barrels per day. The stripped side-stream recovered from column 12 is a furnace oil of about 32 A. P. I. gravity and amounts to approximately 5400 barrels per day. The gas removed from receiver 83 amounts to approximately 300 pounds per hour and approximately 1050 barrels per day of 48 A. P. I. gravity naphtha are recovered from receiver 83.

Heating coil I4I employs an outlet cracking temperature of approximately 945 F. with a superatmospheric pressure at this point in the system of approximately 150 pounds per square inch. Substantially the same pressure is employed in the succeeding. alternately operated coking chambers and the vapors which leave the cokingzone at a temperature of approximately 885 F. are supplied to the lower portion o'f column II2 at the rate of approximately 218,000 pounds per hour. The heavy oil supplied from the lower portion of fractionator IIO to heating coil I4'I amountsyto approximately 16,800 barrels of column II2 to the coking zone has an A. P. I. gravity of approximately 5 and amounts to approximately 800 barrels per day. The sidestream removed from fractionator III] has an A. P. I. gravity of approximately 29 and is withdrawn from this zone at a temperature of approximately 625 F. A portion of this material is cooled to a temperature of approximately 200 F. and returned to an immediate point in fractionator IIIJ, while the remaining portion which amounts to approximately 40,00 barrels per day is recovered as stock for further cracking in another cracking unit. The overhead vaporous stream from fractionator IIIU is cooled in condenser IGI to a temperature of about 180 F., the temperature being reduced in sub-cooler |16 to approximately F. and a superatmospheric pressure of about pounds per square inch being employed in receiver |19. Distillate from accumulator |69 is returned from the upper portion of fractionator III) as a cooling and reiluxing medium. Approximately 11,500 pounds per hour of uncondensed gases are recovered from receiver |19 and the unstabilized gasoline recovered from this zone amounts to approximately 3,460 barrels per day and has an' A. P. I. gravity of approximately 69.5.

The yields of the various products, based on reduced crude charged to the system, are approximately as follows:

Cracking section Yields Product Per cent Per cent by wt. by vol.

Gasoline (400 F. E. P.-10 #R. V. P.) 14. 2 17. Furnace oil (stripped side stream from col. 72) 28. 0 29. Residuum (to cooking sect.) 54. 9 52. 7 Gas and loss-; 2.9

Colcing section Yields Product Per cent Per cent by wt. by vol.

Gasoline (400 F. E. P.-10 #R. V. P.).. 12.6 15, 7 Unstrlpped side stream from Fract. 112 21. 4 22.0 Coke 14. 3 Gas and loss 6. 6

I claim as my invention:

1. A process of hydrocarbon oil conversion which comprises treating said oil at a cracking temperature and substantial superatmospheric pressure in a heating' coil and communicating enlarged reaction chamber, supplying resulting vaporous and liquid conversion products to a vaporizing and fractionating zone operated at reduced superatmospheric pressure and therein separating them into heavy liquid fractions,

lighter condensate and a fractionated vaporous stream consisting essentially of gasoline and gases, subjecting the vaporous stream to condensation and the resulting distillate and uncondensed gases to separation, separately supplying per day and has an A. P. I.- gravity of approximately 12. The heavier high coke-forming materials supplied directly from the lower portion said heavy liquid fractions and lighter condensate, each without intentional cooling thereof, to another vaporizing and fractionating zone operated at substantially lower pressure than that employed in the irst mentioned vaporizing and fractionating zone, therein eiecting further vaporization of said residual liquid by virtue of its contained heat and the reduced pressure and distilled and reduced residual liquid from the last f described vaporizing and fractionating Zone to a third fractionating step, supplying bottoms from the third fractionating step to a separate heating coil, therein heating the same to cracking temperature under non-coking conditions, introducing heated products from the last named coil into a coking zone and therein reducing their high'- boiling components to coke, separating any undesirable heavy components from the vaporous products of the coking operation, supplying resulting relatively clean vaporous products of the coking operation to said third fractionating step, therein separating from the materials supplied thereto said bottoms supplied to the heating coil of the coking system, a lighter condensate suitable for further cracking and a fractionated vaporous stream consisting essentially of gasoline and gases, subjecting the latter to condensation and recovering lthe resulting distillate and uncondensed gases.

, 2. The process of hydrocarbon oil conversion which comprises cracking an oil at a cracking temperature and substantial superatmospheric pressure in a heating coil, passing resulting heated products downwardly through an enlarged vertically disposed reaction chamber also maintained at cracking temperature and substantial superatmospheric pressure, separating the resulting products into predominantly va porous and predominantly liquid fractions in the lower portion of the reaction chamber and removing the same as separate streams therefrom, separately cooling each of said streams to a temperature at which substantial further cracking thereof is prevented, supplying both of the cooled streams to a vaporizing and fractionating zone operated at lower pressure than that employed in the reaction chamber, therein separating the vaporous and liquid fractions into residual liquid, lighter condensate containing high boiling gaso line fractions and a fractionated vaporous stream consisting essentially of gasoline and gases, subjecting the latter to condensation and recovering the resulting distillate and uncondensed gases, supplying said lighter condensate to a second vaporizing and fractionating zone, separately supplying said residual liquid, without intentional loss of heat, to a lower point in the second vaporizing and fractionating zone, substantially reducing the pressure employed in the latter zone relative to that employed in the first mentioned vaporizing and fractionating zone, therein effecting further vaporization of the residual liquid and supplying heat from the evolved vapors to said lighter condensate to further vaporize the same and evolve said heavy gasoline fractions therefrom, recovering from an intermediate point in the second fractionating zone a heavier condensate substantially devoid of fractions boiling within the range of the desired gasoline product of the process, removing as fractionated vapors from the second vaporizing and fractionating zone an overhead stream comprising gasoline of higher end-boiling point than that recovered from the i'lrst mentioned fractionating Zone, condensing and recovering the same, removing the resulting flash distilled and reduced residual liquid from the lower portion ofthe second vaporizing and fractionating zone and supplying the same to a third fractionating zone, supplying bottoms from the third fractionating zone to a separate heating coil, therein heating the same to cracking temperature under non-coking conditions, discharging the resulting heated products into an enlarged coking zone and therein reducing their high boiling components to coke, separating undesirable heavy components from the vaporous products of the coking operation and supplying the remaining relatively clean vaporous products to said third fractionating zone, separating. from the materials supplied to the latter zone said bot toms supplied to the heating coil of the coking system, a light condensate suitable for further cracking and a fractionated vaporous stream consisting essentially of gasoline and gases, subjecting the latter to condensation and recovering the resulting distillate and uncondensed gases.

KENNETH M. WATSON.