US2081347A - Conversion of hydrocarbon oils - Google Patents

Description

( H. ANGELL 2,081,347

CONVERSION OF HYDROCARBON OILS Filed June 8. i934 May 25, 1937.

' FRACTIONATOR VAPORIZING CHAMBER COLUMN FURNACE 26 v RECEIVER Patented May 25, 1 937 PATENT OFFICE CONVERSION OF HYDROCARBON OILS Charles H. Angeli, Chicago, HlL, assignor to Uniyersal Oil Products Company, Chicago, 111., a corporation of Delaware Application June8, 1934, Serial No. 729,542

Claims.

This invention particularly refers to an improved process for the fractional distillation of hydrocarbon oils of relatively wide boiling range accompanied by the pyrolytic conversion of in- .3 term'ediate or high-boiling fractions of the charging stock and intermediate conversion products of the process; coking of the residual liquid conversion products, either alone or together with high-boiling fractions of the charging stock, and reforming of any inferior motor fuel fractions of the charging stock and of the vaporous prod- 'ucts of the coking operation for the purpose of producing, primarily, high yields of motor fuel of good antiknock value.

Many processes have been proposed, some of which are now in use, for the coking, at relatively low pressure, of residual liquids resulting from the pyrolytic conversion of hydrocarbon oils atrelatively high pressure. Many such coking operations are accomplished simultaneous and in direct cooperation with the cracking process wherein the residual oil is produced and such operations are of great economic importance at thepresent time, due to the ability to produce, by their use, high yields of desirable light liquid products, such as motor fuel, with-relatively low yields of residue, which is in the form of substantially dry coke and is marketable as domestic fuel. It has been found, however, that the motor fuel recovered by fractionation of the va-- porous products from such low-pressure coking operations is often of inferior quality, particulariy with respect to its antiknock value. Furthermore, it is readily apparent that, due to the high temperatures required for reduction of residual oil to low volatile coke, the resulting vaporous products contain a considerably greater quantity of heat than is necessary for their fractionation and this excess heat is ordina ily'dlssipated without being employed to advantage.

In the present invention the excess heat from the low-pressure coking operation, such as above mentioned, is utilized to advantage by employing the same to effect fractional distillation of hydrocarbon oil charging stock for the process and the unsatisfactory motor fuel components of the vaporous products fromthe coking operation, together with any motor fuel components of the charging stock of poor antiknock value, are subjected to reforming for the purpose of materially improving their motor fuel characteristics without-excessively altering their boiling range, thereby obviating both of the disadvantages above mentioned which ordinarily attend the coking of residual liquid conversion products at low temperature.

Another disadvantage ordinarily encountered in low-pressure coking operations is the presence of appreciable amounts of relatively heavy high coke-forming materials, including entrained tars, pitches and the like in the vaporous products from the coking operation. These materials contaminate the reflux condensate unless removed from the vapors prior to their fractionation for the formation of reflux condensate, and ordinarily cause excessive coking if returned to a heating coil for further consersion, together with the reflux condensate. The present invention provides for theremoval of such highcoke-forming materials from the vaporous prod ucts of the coking operation by contact with hydrocarbon oil charging stock for the process accompanied by collection of such materials, together with any similar high coke-forming components of the charging stock, separate from the lower boiling reflux condensate and lower boiling components of the charging stock and further provides for the return of the high coke-forming materials to the coking stage of the process.

The present invention embodies numerous other coperative features and advantages which will be more apparent with referencev to the subsequent description. It will be understood, however, that the invention is not limited to any one or any combination of the minor features described but is directed, primarily, to the cooperative relation between the coking, topping and reforming operations whereby the charging stock is subjected to fractional distillation by means of heat recovered from the coking operation and unsatisfactory motor fuel components of the charging stock and of the vaporous products from the coking operation are commingled and subjected to reforming.

In one specific embodiment, the invention com prises subjecting a hydrocarbon oil charging stock of relatively wide boiling range to fractional distillation, recovering any desirable components of the charging stock such as motor fuel fractions of satisfactory antiknock value, sub-, jecting high-boiling fractions of the charging stock boiling above the range of motor fuel and selected low-boiling fractions of the charging stock, including any motor fuel components of unsatisfactory antiknock value, each to independently controlled conversion conditions of elevated temperature and superatmospheric pressure for the production of high yields of motor fuel of good antiknock value, separating the resulting vaporous and liquid conversion products, subjecting the latter to further vaporization at,substantially reduced pressure relative to that at which they are formed, subjecting the vaporous conversion products to fractionation whereby their insufllciently converted components are condensed as reflux condensate, returning the reflux condensate to further conversion in the same system, subjecting fractionated vapors of the desired endboiling point to condensation and recovering the resulting distillate, subjecting the residual liquid conversion products remaining unvaporized by said further vaporization to further heating and to coking in a zone of relatively low pressure, subjecting vaporous products from the coking zone to fractionation together with the hydrocarbon oil charging stock and returning high coke-forming materials removed from the vaporous products of the coking operation, together with any similar high coke-forming components of the charging stock to the coking stage.

Many modifications of the above specific embodiment are possible within the scope of the present invention. Some of these, as well as the operation above outlined, are described in connection with the following description of the accompanying diagrammatic drawing. The drawing illustrates one specific form of apparatus in which the process of the invention may be accomplished.

Referring to the drawing, hydrocarbon oil charging stock for the process, preferably comprising oil of relatively wide boiling range, such as, for example, crude petroleum or the like, containing a substantial quantity of materials within the boiling range of motor fuel which are of unsatisfactory antiknock value, may be supplied through line I and valve 2 to pump 3 by means of which it may be fed through line 4 and valve 5 into distilling and fractionating column 6, wherein it is subjected to fractional distillation, together with vaporous products from the coking stage of the process supplied to this zone as will be later more fully described. The charging stock may, of course, be preheated by any well known means, not illustrated, prior to its introduction into column 6, however, the major portion of the heat required for fractional distillation of the charging stock may ordinarily be recovered from the vaporous products of the coking operation and use of the charging stock, in the manner illustrated and described, serves to cool and assist fractionation of said vapors.

Fractionated vapors of the desired end-boiling point, preferably comprising materials within the boiling range of motor fuel and, when desired, somewhat higher boiling materials such as naphtha, kerosene or kerosene distillate, pressure distillate bottoms and the like, are withdrawn, together with uncondensable gas, from the upper portion of column 6 through line I and valve 8 to be subjected to condensation and cooling in condenser 9. The resulting distillate and gas pass through line I0 and valve I I to collection and separation in receiver l2. Uncondensable gas may be released from the receiver through line I3 and valve l4. Distillate may be withdrawn from receiver I2 through line l5 and valve 16 to storage or to any desired further treatment.

In case the materials subjected to fractionation in column 6, comprising the charging stock and vaporous products of the coking operation, contain no appreciable quantity of materials within the boiling range of motor fuel which are of satisfactory antiknock value, a regulated portion or all of the condensate collected in receiver I2 is preferably withdrawn therefrom through line I! and valve l8 to pump l9 by means of which it is supplied through line 20, valve 2| and line 22 to heating coil 23.

In case the materials subjected to fractionation in 'column 6 contain an appreciable quantity of materials within the boiling range of motor fuel having sat'.factory motor fuel characteristics, particularly with respect to their antiknock value, these materials may be collected in receiver I2, as previously described, while'somewhat high er boiling materials, including motor fuel fractions of unsatisfactory antiknock value or of otherwise inferior motor fuel quality as well as, when desired, somewhat higher boiling materials such as, for example, naphtha, kerosene or kerosene distillate, pressure distillate bottoms and the like may be separately withdrawn as one or a plurality of side streams from column 6 at any suitable intermediate point or points in this zone, passing, for example, through line 24, valve 25 and line I! to pump I9 to be supplied therefrom to heating coil 23, in the manner previously described.

It is, of course, also within the scope of the present invention, in case the overhead product from column 6 is supplied to heating coil 23, to supply the overhead vaporous product, including uncondensable gas, direct to the heating coil by suitable well known means, not illustrated, without first condensing the distillate and separating the gases in receiver I2, as previously described.

A furnace 26 of any suitable form supplies the required heat to the oil passing through heating coil 23 to bring it to the desired conversion temperature, preferably at a substantial superatmospheric pressure and, in the preferred embodiment of the invention, the heating coil and furnace arrangement is such that the relatively light oil supplied to heating coil 23 is brought to or near the maximum desired conversion temperature and then maintained at a temperature near the maximum to, which it is subjected for a predetermined time. The stream of highly heated products is discharged from heating coil 23 through line 21 and may pass through valve 28 and valve 29 in this line into reaction chamber 30, being cooled, when desired, by means which will be later described, to a temperature at which its conversion is materially retarded or arrested, prior to its introduction into the reaction chamber, particularly in case a soaking section is employed in heating coil 23. Also, when desired, instead of introducing all of the heated products from heating coil 23 into reaction chamber 30 a regulated portion or all of this material may be supplied from line 21 through line 3i and valve 32 into vaporizing chamber 33. Further reference to this particular feature of the invention will be made later.

Reaction chamber 30 is also preferably maintained at a substantial superatmospheric pressure and, although not indicated in the drawing, is preferably insulated to prevent the excessive loss of heat so that conversion of relatively highboiling oils, supplied to this zone as will be later described, as well as, when desired, the heated products from heating coil 23, may continue in the reaction chamber. In the case here illustrated, both vaporous and liquid conversion products are withdrawn from the lower portion of chamber 30 through line 34 and valve 35 and are introduced into vaporizing chamber 33 wherein further vaporization of the liquid conversion vaporous and liquid conversion products from the reaction chamber bywell known means, not lllustrated, in which case the liquid products, either alone or together with a regulated portion 01' the vapors, may be introduced into chamber 33 or the liquid conversion products may be supplied direct to heating coil Mi for further heating and subsequent reduction to cokewhile the vaporous products may be supplied, all or in part, to chamber 33 or to fractionator 88, although well known means for accomplishing these alternate operations are not illustrated in the drawing.

Chamber 33 is preferably operated at a substantially reduced pressure relative to that employed in chamber 3%, whereby appreciable further vaporization of the liquid conversion products supplied to this zone is accomplished. In-

troduction of a regulated portion or all of theheated products from heating coil 23 into chamber 33, as previously described, may serve to assist further vaporization of the liquid conversion products in this zone and it is within the scope of the invention to supply heated products from Residual liquid conversion products remaining unvaporized in chamber 33 are withdrawn from the lower mrtion of this zone through line 39 and valve at to pump it by means of which they may be supplied through line t2 and valve ii to heating coil M.

Heating coil M is located within a furnace at of any suitable form by means or which sumclent heat is imparted to the residual liquid passim throuahthis zone to eflect its subsequent reduction to substantially dry coke in coking chamber 56. to which the heated oil from heating coil M is supplied by means of line M and branch lines t8 controlled by valves as, which permit the introduction of the hot-residual oil into the coking chamber at any desired point or plurality of points in this zone. Preierably, the residual oil passing through heating coil M is subjected to relatively high rates of heating so that it may be brought quickly to the relatively high temperature required for its reduction to coke in-the cokmg zone without allowirm it to remain in heating coil it for a sumcient length of time to permit tion, although it will be understood that otherwell known methods of coking may be employed, either alone or in conjunction with the method above described, without departing from the scope of the present invention.

It is, ior example, specifically within the concept oiv thepresent" invention to externally heat the coking chamber or to supply a suitable heat carrying medium thereto. The invention also contemplates the use of coking retorts employe ing'a refractory heat conducting floor or wall and also the use of rotary coking retorts of the type wherein the coke is deposited on the internal surface of the retort walls or o! the type wherein it is deposited on the-external surface.

Coking chamber 46 is preferablyoperated at substantially atmospheric or a relatively low superatmospheric pressure, as low pressures favor the production 01 low volatile coke, and in case a substantially lower pressure is employed in the coking chamber than in vaporizing chamber 33 the use of pump at may be obviated. The coke produced in chamber it may be allowed to'accumulate within this zone to be removed-therefrom in any well known manner, not illustrated, alter the operation of the chamber is completed. When desired, a

plurality of coking chambers similar to chamber 46 may be employed, although not illustrated,

and may be operated simultaneously or, preferably, are alternately operated, cleaned and prepared ior further operation, so that the comng stage of the process, as well as the distilling and cracking stages, is continuous. Chamber to is provided with a suitable drain line 5d controlled by valve 58 which may also serve as a means of introducing suitable cooling material such as, for example, water and/or steam into the coking chamber, after its operation is completed and it has been'isolated from the rest of the system, in order to hasten cooling and facilitate cleaning of the chamber. I

The vaporous products of the coking operation may pass from the upper portion of chamber it through line 52 and valve ES to fractionation in distilling and fractionating column d, together with the charging stock supplied to this zone as previously described, the heat in the vaporous products from the coking zone serving as a means of eflecting vaporization and fractionation of the charging stock while the charging stock serves as a cooling means to assist fractionation of the vaporous products from the col;- ing zone. Thecomponents oi the vaporous products from the coking chamber condensed in column 6, together with the high-boiling components of the charging stock which are condensed or remain unvaporized in the distilling and fractionating column, maybe withdrawn from the lower portion of this zone through line at and valve at to pump at by means oi which they are fed through line 57 and may be supplied through valve m to vaporizing chamber it.

By this method of operation any high, coke- :torming materials contained in the vaporous products from the coking zone, including entrained particles oi tar, pitch and the like as .well as any similar high boiling components of the charging stock, are included in the condensate withdrawn from the lower portion of column d but are separated in chamber 33 from the lower boiling components of the condensate, which latter are vaporized in this mne and supplied therefrom to fractionation in iractionator id. The high coke-forming materials in the condensate supplied from column a to chamber 33 commingle in the vaporizing chamber with] no appreciable quantity of "heavy high cokeforming materials, to separate the heavy componentsot the vapors from the com some, in-

.cluding entrained tars, pitches and the like,

condensate from the heat exchanger or partial.

condenser may be returned either to vaporizing chamber 33, heating coil 44 or coking chamber 46, as desired. In case the latter type 01' operation is employed (separate removal of the high cokeforming materials from the vaporous products of the coking operation, prior to their fractionation in column 5) the condensate from column B may be returned, all or in part, to vaporizing chamber 33, as previously described, or may be supplied to fractionator 38 or commingled with the reflux condensate from iractionator 8S3 externai to the fractionator and subjected to further treatment therewith, as will be later more fully described, although for the sake of simplicity the well known lines and valves for accomplishing these alternatives are not illustrated in the drawing.

By supplying all or a regulated portion of the condensate from column 6 to vaporizing chamber 38 this material may be utilized as a means of effecting condensation of some of the heavy vapore evolved from the residual liquid undergoing vaporization in chamber 33 and baiiles or fractionating means or any suitable form, not illustrated, may be employed, when desired, in the upper portion of chamber 33 to assist rough fractionation oi the evolved vapors. By regulation of the quantity of relatively cold condensate supplied irom column to chamber 33 and the quantity of relatively hot products from heating coil 23 supplied to this zone, the degree of vaporization in chamber 33 and the characteristics of the residual liquid withdrawn from this zone for col:- ing may be accurately controlled and, when desired, the condensate supplied to chamber 33 may be cooled to any desired degree, by well known means not shown, prior to its introduction into the vaporizing chamber.

The components of the vaporous materials supplied, as previously described, to iractionator I8, boiling above the range of the desired final light distillate product of the process. are condensed in this zone as reflux condensate, which may be withdrawn as a single product from the fractionator or may be separated therein, as will be later more fully described, into selected relatively lowboiling and high-boiling fractions. Fractionated vapors of the desired end-boiling point, preferably comprising materials within the boiling range of motor fuel and of good antiknock value, are withdrawn, together with uncondensable gas, from the upper portion of i'ractionator 38 through line 59 and valve 60 to be subjected to condensation and cooling in condenser Bl. The resulting distillate and gas passes through line 62 and valve 63 to collection and separation in receiver H. Uncondensable gas may be released from the receiver through line 65 and valve 88. Distillate may be withdrawn from receiver 84 through line 67 and valve 68 to storage or to any desired further treatment.

The usual well known expedients for assisting fractionation oi the vapors in column 6 and fractionator 38, such as, for example, returning regulated portions of the distillate from receivers l2 and N to the respective i'ractionating zones, may

be employed, although not illustrated in the drawing.

when the reflux condensate formed in fractlonator 38 is separated, as previously mentioned, into selected relatively low-boiling and high-boiling fractions, selected high-boiling fractions may be withdrawn from any suitable intermediate point or plurality oi! points in the fractionator and supplied, for example, through line 69 and valve I0 topl p H by means of which they are fed through line 12 and may be directed through valve 13 in this line and through line 22 to further conversion in heating coil 23, together with low-boiling distillate from the distilling and coking operations, supplied to heating coil 23 as previously described, or the selected low-boiling condensate from iractionator 88 may be diverted from line 12 through line H and directed through valve 15 to further conversion in heating coil 16.

The high-boiling iractions of the reflux condensate formed in tractionator 38 or the total reflux condensate, in case selected low-boiling fractions are not separately withdrawn from this zone, may be withdrawn from the lower portion of the iractionator through line TI and valve 18 to pump 80 by means of which this material is fed through line 8| and may be directed through valve 88 and line 14 to further conversion in heating coil 16 or, when desired, a regulated portion or all of this material may be directed from line at through line 89 and valve 80 into line 21 to commingle therein with the stream of hot conversion products from heating coil 23. When the latter method of operation is employed the temperature to which the reflux condensate from iractionator 38 is heated by commingling with the stream or heated products from heating coil 23 may be sumcient to effect appreciable further conversion 01' the reflux condensate but preferably the temperature of the resulting stream of commingled materials is sufliciently low to prevent excessive conversion of the reflux condensate as well as excessive further converslon of the heated products from heating coil 23. The commingled materials are preferably directed through line 27 and valve 28 into reaction chamber 30 but may, when desired, be directed all or in part from line 21 through line 3| and valve 32 into vaporizing chamber 38.

-I n case reflux condensate from fractionator I8 is commingled, as described, with thestream oi' 'highly heated products from heating coil 23,

heating coil 18 or reaction chamber 30, or both or these zones may be eliminated, although it is specifically within the scope oi the invention to supply only high-boiling fractions of the reflux condensate to line 21 and to subject selected lowboiling fractions of the reflux condensate from fractionator 38 to further conversion in heating coil 16 and reaction chamber 38.

The oil supplied to heating coil 16. comprising the total or regulated portions of the total reflux condensate from iractionator I! or selected lowboiiing fractions of the reflux condensate from fractionator 3B. is subjected, by means of heat supplied from a furnace 9| 0! any suitable form,

to the desired conversion temperature, preferably at a substantial superatmospheric pressure, and the heated products from heating coil 10 may be directed through line 02 and valve 83 into reaction chamber 30 or may, when desired, be supplied by well known means not illustrated, to vaporizing chamber 23.

It will be understood that the many alternative methods oi operation above described are not to be considered equivalent but maybe selected to suit requirements, depending upon the type of oil being treated, the desired results and the particular operating conditions employed. The alternative features mentioned are, in many cases, not

new in themselves but are complementary to the readily apparent and may be employed without departing from the spirit and scope of the invention.

In an apparatus suchas illustrated and above described, the preferred range of operating conditions may be approximately as follows:

The heating coil to which the selected relatively lowboiling fractions of the charging stock and of the vaporous products from the coking operation are supplied may utilize a maximum conversion temperature ranging, for example, from 950 to 1050 F.,'preferably with a superatmospheric pressure, measured at the outlet from the heating coil, of

from 300 to 1000 pounds, or thereabouts, per sq.

in. The heating coil to which the total reflux condensate or regulated portions of the total reflux condensate or selected low-boiling fractions of the reflux condensate from the fractionator of the cracking system are supplied, when this heating coil is employed, may utilize a conversion temperature, measured at the outlet from this zone, of from 800 to 950 F., or thereabouts, preferably with a superatmospheric pressure at this point in the system of from 100 to 500 pounds, or

- more, per sq. in. The reaction chamber when utilized may employ any desired pressure ranging from 100 to 500 pounds, or more, per sq. in., while the vaporizing chamber may be operated at a pressure ranging, for example, from substantially atmospheric to 100 pounds, or thereabouts, per sq. in., with substantially equalized or somewhat reduced pressures in the succeeding fractionating, condensing and collecting equipment. The temperature to which the residual liquid is heated to affect its reduction to coke may range, for example, from 900 to 975 R. or thereabouts, preferably with a superatmosphelic pressure of from 50 to 150 pounds, or

thereabouts, in the heating coil and, as previously mentioned, relatively rapid rates of heating and a relatively short time factor are preferred in this zone. The comng chamber is preferably operated at a relatively low pressure ranging, for example, from substantially atmospheric to 100 pounds, or thereabouts, per sq. in. while the succeeding fractionating and distilling equipment may be operat ed at substantially the same or somewhat lower pressure than that employed in the coking cham- As a specific example of one of. the many possible operations of the process of the present invention, as it may be accomplished in an apparatus such as illustrated and above described,

- the charging stock, which comprises a California crude of about 27.5" A. P. I. gravity, containing about percent of materiai boiling up to 220 F.

and about 2'! percent at 437 F., is subjected to fractionation, together with vaporous products from the coking stage of the process. Fractions of the crude and of the vaporous products of the coking operation boiling up to approximately 500 F., are subjected in a. reforming coil to a conversion temperature of approximately 980 F. at a superatmospheric pressure of about 1000 pounds per sq. in. The resulting products are cooled to a temperature of about 900 F. by commingling therewith selected high-boiling fractions of the reflux condensate from the fractionator of the cracking stage of the system and by reduction in pressure to about 350 pounds per sq. in., the commingled materials being introduced into a reaction chamber operated at about this pressure.

Selected low-boiling fractions of the refiux'condensate from the fractionator of the cracking stage are subjected in a separate heating coil to an outlet conversion temperature of approximate-' 1y 950 F. at a superatmospheric pressure of about 400 pounds per sq. in. and the heated products from this coil are also supplied to the reaction chamber. Vaporous and liquid conversion products are withdrawn from the reaction chamber in commingled state and areintroduced into a vaporizing chamber operated at a reduced superatmospheric pressure of about 60 pounds per sq. in. Higher boiling components of the charging stock and of the vaporous products from the coking zone, including high coke-forming materials contained in the vapors from the coking zone, are supplied to the vaporizing chamber wherein the high-boiling materials commingle.

with the residual liquid conversion products remaining unvaporized in this zone. Vaporous products from the vaporizing chamber are subjected to fractionation for the formation of said low-boiling and high-boiling reflux condensates and fractionated vapors, which latter are subjected to condensation and the resulting distillate, comprislng the final motor fuel product of the process, is recovered. The residual liquid from the vaporizing chamber is quickly heated in a separate heating coil to a'temperature of approximately 935 F. at a superatmospheric pressure of about 100 pounds per sq. in. and the heated residue is introduced into the coking chamber which is operated at a superatmospheric pressure of about 30 pounds per sq. in. This operation may yield, per barrel of charging stock, approximately 67 percent of motor fuel having an. octane number of about '70 and about 60 pounds of petroleum coke of uniformly good structure, having a volatile content of less than five percent, the remainder-being chargeable, principally, to uncondensable gas.

I claim asvmy invention:

1. In a process forthe conversion of hydrocarbon oils wherein hydrocarbon oil is subjected to conversion conditions of elevated temperature and superatmospheric pressure in a cracking zone, the resulting residual liquid and vaporous conversion products separated in a reduced pressure separating zone, the vapors subjected to fractionation for the formation. of reflux condensate and the recovery of desirable low-boiling components and the residual liquid subjected to additional heating, to effect its reduction to coke in a zone separate from that wherein the aforementioned residual liquid and vaporous conver- .ing the vaporous products of the coking opera:

tion to fractionation, subjecting selected relatively high-boiling components of the charging stock and of the vaporous products of the coking operation to said conversion in said cracking zone subjecting selected relatively low-boiling components comprising the total motor fuel boiling component of the charging stock and of the vaporous products of the coking operation to independently controlled more severe conversion conditions, and commingling products of the lastnamed conversion stage with products of the firstmentioned conversion stage.

2. A process of the character defined in claim 1 wherein the selected low-boiling fractions of the charging stock and of the vaporous products of the coking operation supplied to the last men-' tioned conversion stage also include materials boiling somewhat above the range of motor fuel.

3. In a process for the conversion of hydrocarbon oils wherein the oil is subjected to conversion temperature at superatmospheric pressure in a heating coil and communicating reaction chamber, the resulting vaporous and liquid conversion products separated, the latter subjected to further vaporization in a vaporizing chamber operated at substantially reduced pressure, the vaporous conversion products, including those resulting from said further vaporization, subjected to fractionation for the formation of reflux condensate which is subjected to further conversion in the same system, fractionated vapors of the desired end-boiling point subjected to condensation, the resulting distillate recovered, non-vaporous residual liquid withdrawn from said vaporizing chamber and subjected to additional heating to effect its reduction to coke, the improvement which comprises directly commingling the vaporous products of the coking operation with hydrocarbon oil'charging stock for the process. subjecting the commingled materials to fractionation, separate from the aforementioned vaporous conversion products, whereby they are separated into components comprising low-boiling motor fuel fractions of satisfactory antiknock value, selected somewhat higher boiling fractions, including motor fuel components of unsatisfactory antiknock value, intermediate fractions, boiling substantially entirely above the range of motor fuel,

and still higher boiling components including tars and similar high coke-forming materials, returning the high-boiling components, including tars and similar high coke-forming materials, to the coking operation, returning the intermediate fractions boiling substantially entirely above the range of motor fuel to the heating coil for further conversion, recovering the low-boiling motor fuel fractions of satisfactory antiknock value, subjecting the selected fractions including motor fuel components of unsatisfactory antiknock value to independently controlled conversion conditions, in aseparate heating coil regulated to materially improve their motor fuel characteristics and commingling the products from said separate heating coil with the aforementioned vaporous conversion products, prior to their fractionation.

4. A process of the character defined in claim 3 wherein the reflux condensate resulting from the first mentionedfractionation is separated into selected relatively low-boiling and high-boiling fractions, the high-boiling fractions returned to the first mentioned heating coil for further conversion and the low-boiling fractions returned for further conversion to said separate heating coil.

5. A process of the character defined in claim 3 wherein therefiux condensate resulting from the first mentioned fractionation is separated into selected relatively low-boiling and high-boiling fractions, the low-boiling fractions returned for further conversion to the first mentioned heating coil and the high-boiling fractions commingled with the stream of heated products discharged from said separate heating coil.

6. A process of the character defined in claim 3 wherein the reflux condensate resulting from the first mentioned fractionation is returned for further conversion to the first mentioned heating coil.

7. A process of the character defined in claim 3 wherein the reflux condensate resulting from the first mentioned fractionation is commingled with the stream of heated products discharged from said separate heating coil;

8. A process of the character defined in claim 3 wherein the products from said separate heating coil are discharged into the reaction chamber.

9. A process of the character defined in claim 3 wherein the products from said separate heating coil are discharged into the vaporizing chamber.

10. A process of the character defined in claim 3 wherein said intermediate fractions of the commingled charging stock and vapor-ous products of the coking operation and their high-boiling components, including tars and similar high cokeforming materials, are returned to the vaporizing chamber.

11. In a process for the conversion of hydrocarbon oils wherein a relatively low-boiling oil recovered from within the system is subjected to a high conversion temperature at superatmospheric pressure in a heating coil, the resulting highly heated products cooled sufficiently to retard their excessive further conversion by commingling cooler hydrocarbon oil therewith, the commingled materials subjected to vaporization, the resulting residual liquid and vaporous products separated, the vapors subjected to fractionation for the formation of reflux condensate which is subjected to further conversion in the same system, fractionated vapors of the desired end-boiling point subjected to condensation, the resulting distillate recovered, and the non-vaporous residual liquid subjected to additional heating to effect its reduction to coke, the improvement which comprises commingling vaporous products from the coking operation with hydrocarbon oil charging stock for the process, separating the commingled materials into components comprising any low-boiling motor fuel fractions of satisfactory antiknock value, selected low-boiling fractions including any motor fuel components of unsatisfactory antiknock value, intermediate fractions boiling substantially entirely above the boiling range of motor fuel and any higher boiling components including tars and similar high coke-forming materials, returning the high-boiling components, including tars and similar high coke-forming materials, to the coking operation, recovering the low-boiling motor fuel fractions of satisfactory antiknock value, supplying the selected low-bolling fractions to said heating coil and commingling the intermediate fractions with the stream of highly heated products discharged from the heating coil.

12. A process of the character defined in claim 11 wherein said reflux condensate is commingled with the stream of highly heated products discharged from the heating coil.

13. A process of the character defined in claim 11 wherein said reflux condensate is separated into selected relatively low-boiling and high-boilproducts of the coking operation.

14. A conversion process which comprises heating hydrocarbon oil to cracking temperature under pressure in a heating coil and subsequently introducing the same to an enlarged separating zone, separating vapors from unvaporized oil in the separating zone. removing the unvaporized. a oil and subjecting the same to further distillation in a second enlarged zone, fractionating vapors mixture of condensate and unvaporized charging oil, separating from the contacting charging oil and vapors undergoing fractionation a fraction of lower boiling point than said mixture, heating this fraction in a second heating coil to higher cracking temperature. than theoil in the firstnamed coil and subsequently introducing the same into the first-named separating zone, introducing said mixture into the first-named separating zone and distilling a substantial portion thereof in this zone, removing resultant vapors from the first-named separating zone in admixture with the first-mentioned vapors, fractionating these vapors and supplying resultant reflux condensate to the first-named heating coil, and

finally condensing the vapors uncondensed in the last-mentioned fractionating step.

15. A hydrocarbon oil conversion process which comprises separating cracked products, formedas hereinafter set forth, into vapors and residual liquid in a separating zone, distilling the residual liquid to coke in a coking zone, fractlonating the.

vapors from the coking zone in contact with charging oil for the process thereby forming a mixture of heavy condensate and unvaporized charging oil, separating from the contacting charging oil and vapors undergoing fractionation a fraction of lower boiling point than said mixture, introducing said mixture to the separating zone and therein distilling a substantial portion thereof, passing said fraction of lower boiling point than the mixture through a heating coil and heating the same therein to cracking temperature under pressure, removing the vapors from the separating zone and fractionating the same to form a relatively heavy reflux condensate and a lighter reflux condensate, subjecting the latter to independently controlled cracking coirditions of temperature and pressure in a second heating coil, subjecting the heavy reflux conden sate to cracking conditions bycommingling the same with the heated products from said coils,

introducing the resultant mixture to the separating zone as said cracked products, and finally condensing the fractionated vapors.

omnms' H. ANGELL.

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