US2166787A - Hydrocarbon oil conversion - Google Patents

Description

July 18, 1939. J. G. ALTHER 2,156,787

HYDROGARBON OIL CONVERSION i Filed Jan. 15, 1937 fezvzate Patented July 18,1939 2,166,787

UNITED STATES PATENT oFFlca HYDBOCARBON OIL CONVERSION Joseph G. Alther, Chicago, Ill., assigner to Universal O il Products Company, Chicago, Ill., a corporation oi' Delaware Appucation January 15, 1937, serial No. 120,981 14 claims. (ci. 19e-49) This application is a continuation-in-part of also effects reduction of the latter to coke, the my lcci-pending application Serial No. 516,021, coking zone being separate and apart from other Vfiled February 16, 1931, which has now become portions of the system to the extent that only abandoned. heated products from said separate heating coil The 'invention relates to an 'improved process are supplied thereto. 5 for the cracking of hydrocarbon oils to produce The relatively low-boiling oil commingled with high yields of good quality gasoline and minor the high-boiling residual liquids subjected tosaid yields of high-boiling residual liquids accom-v coking comprises selected relatively low-boiling panied by the reduction of all or a portion of the fractions of the reflux condensate resulting from l0 latter to substantially dry coke, said coking being fractionation of lthe vaporous conversion products 10 accomplished, in the present invention, by quickly of the first mentioned cracking step and, when heating said residual oil, following its separation desired, may also include selected low-boiling from lower boiling vaporous products and in com-` fractions of the charging stock and/or selected i mingled state with a selected substantially lower low-boiling fractions of the reflux condensate re- 15 boiling hydrocarbon oil derived from Within the sulting from fractionation of the vaporous prodl5 system, to a high cracking temperature under ucts of the coking step, the components and the non-coking conditions and introducing the renature of this materialbeing selected to suit resultant highly heated mixture into a coking zone quirements and being in any case of such nature wherein their high-boiling components are rethat it will be substantially vaporized under the duced to coke by the contained heat of the mixconditions and treatment to which it is subjected ture. a in said heatingcoil and coking zone and pref- 20 My aforementioned coa-pending application diserably such that it is further cracked under these closes a combination cracking and coking system conditions to produce additional yields of desirwherein heavy residual oils. resulting from the able low-boiling products within the range of reduced pressure or flash distillation of liquid gasoline. t

conversion products, resulting from the cracking Components of the reux condensate which 25 y of lower boiling hydrocarbon oils, are reduced are of a higher boiling nature than the selected to coke in one of several alternatively non-equivfractions subjected to treatment with the highalent manners, each of which involves further boiling residual liquids are preferably supplied to Y 80 heating of the ashed residual liquid, either by the first mentioned cracking step of the system passing the same through a heating coil or by for further cracking, and hydrocarbon oil charg- 30 commingling the same with a' heat carrying meing stock of the process, depending upon its chai'- dium'comprising relatiuely light intermediate liqacteristics, may be either cracked in commingled uid products of the process, to a suiiiciently high state with said high-boiling components of the 3i temperature to induce to its further vaporization reflux condensate, or it maybe separated, when and reduction of the resultant non-vaporous desired, into selected relatively low and high-boilv componentsto coke 'in a coking zone separate `ing fractions, such separation being preferably from the zone of said ash distillation. effected by subjecting the charging stock to frac- This continuation-impart is directed speciiitionation together with said vaporousconversion 4o cally to that embodiment of the parent applicaproducts, in which latter case, the high-boiling tion wherein all or a regulated portion'of thev fractions of the charging stock are supplied to 40 flashed residual liquid from the vaporizing or the initial cracking step for conversion together flash distilling zone of the cracking system is with the high-boiling components of the reflux commingled with a selected relatively low-boilcondensate, while the selected low-boiling fracing oil derived from within the system, the comtions of the charging stock are supplied to said.

mingled materials passed through a heating coil separate heating coil together with said high- 45 separate from that of the primary cracking zone boiling residual liquids and said selected lowand therein subjected to a relatively high crack- A`boiling fractions `ol the reflux condensate. l ing temperature. under conditions which pre- .I am fully aware that the teachings of this in- 5o clude the formation and deposition 0f any sub" vention appear contrary to the previously estabstantial quantity of coke in the heating coil, and lished concepts of the best methods of cracking ,50 the resultant highly heated commingled mateand/or `colrlng heavy oils. The best previous rials passed 4into a .coking zone wherein their methods of cracking have all tended toward -the contained heat eifects vaporization of all but selective segregation of relatively low-.boiling yand their undesirable high-boiling components and high-boilingoils accompanied-,fbx the crackingy of u,

each selected fraction under independently controlled conditions of temperature, pressure and time and have distinctly voided mixing of relatively low-boiling and relative high-boiling oils in the cracking .coil. Previous attempts at cracking oils of widely different boiling range in cornmingled state have resulted in the excessive formation and deposition of coke. in the heating coil with its attendant hazards and severe penalties with respect to the useful life of the equipment and the duration of the operating cycle of the process. However, I now believe that those previous concepts of the advantages of selective cracking are only partially correct and while they are almost universally applicable as applied to the usual run of cracking stocks, they do not necessarily apply to the further cracking and coking of heavy residual oils such as those resulting from the iiash distillation of the liquid conversion products of a modern cracking operation. The failure of previous attempts have been explained by the theory that the presence of lowboiling oils in the same cracking coil with relatively high-boiling oils, results in excessive va porization in this zone, leaving a thin film of exceptionally high-boiling oil on the inner surface of the tubular heating coil through which the mixture is passed, which film tends to adhere to the surface of the tube and is readily reduced thereon to coke under the high temperature condtions normally employed in the cracking furnace. However, by selecting as the only components of the mixture, an oil of exceptionally high-boiling characteristics and an oil of much lower boiling characteristics, by blending the same in such proportions that the high-boiling oil comprises a substantial proportion of the mixture and by quickly heating the mixture to the desired relatively high temperature, I have found it possible to heat the mixture to a sufficiently high temperature to induce subsequent coking of its non-vaporous components and appreciable cracking of its vaporous components and still avoid coking difficulties in the heating coil and communicating lines, while producing a good quality coke and substantial additional yields of desirable lowboiling products, such as good antiknock gasoline.

While it is not the purpose of this application to offer a theoretical explanation for the success of this operation, I believe that it can be accounted for, at least in part, by the fact that I employ a suflicient quantity of sufficiently heavy oil in the mixture supplied to the heating coil to maintain a substantial body of liquid on the surface of the tubular elements of the heating coil, which heavy liquid acts as a wash for the walls of the tubes, keeping the same relatively clean and free from carbon deposits and functioning in much the same manner as the heavy liquid supplied to the walls of a high pressure reaction chamber, the value of the latter expedient being well recognized in the art. The relatively high oil velocity which I preferably em'ploy in this coil increases the efficiency of the heavy liquid as a washing or scrubbing medium and these factors, in combination with the relativelyA short time and high pressure preferably employed'in a heatingcoil, are believed to account to a large extent f orthe success of the operation. I also believe that the wide difference `in boiling characteristics between the light I,and heavy components of the mixture is ,an important factor, the result being a truly tioned are essential and cooperate to produce the desired result. It also seems probable that there is some interaction of a chemical nature between the light and heavy components of the mixture, during and/or subsequent to their passage through the heating coil, which accounts, at least in part, for the improved yields of gasoline obtained, and I have found that the antiknock quality of the gasoline produced is improved when fairly high superatmospheric pressure is employed in the coking zone. This is, no doubt, due to the additional conversion time afforded the mixture and, more particularly, its low-boiling vaporous components, in the coking zone. However, when high pressure is employed in the coking zone, the volatility of the coke produced is normally somewhat higher and it is therefore a matter of choice as to whether the coking zone is operated at relatively low pressure, depending in part upon the nature of the charging stock and in part upon the other operating conditions employed, as well as the desired quality of the nal products.

The accompanying diagrammatic drawing illustrates one specific form of apparatus employing the feature of the invention and in which the process of the invention may be successfully conducted.

Referring to the drawing, the charging stock which may be an oil of any desired characteristics but is preferably of relatively high-boiling nature or relatively wide boiling range, such as for example, crude petroleum', topped crude and the like, is supplied through line I and valve 2 to pump 3 wherefrom it is fed from line 4 and may pass all or in part through line 6 and valve 1 into fractionator 8, to commingle therein with the vaporous conversion products in this zone and be subjected to fractionation therewith, or the charging stock may be passed all or in part through valve 9 in line 4 into,a suitable closed coil or other heat exchange apparatus I0 disposed within fractionator 8, wherein it is heated by indirect heat exchange with the relatively hot vaporous products undergoing fractionation and wherefromit is directed through line Il, valve I2, line I3 and valve I8 to conversion in heating coil I9. It is, of course, also within the scope of the invention to preheat the charging stock to any desired degree in any other well known manner not illustrated prior to its introduction into heating coil I9, or it may be supplied thereto, all or in part, without being preheated.

I-Iigh-boiling fractions of the reflux condensate formed in fractionator 8 are also supplied to heating coil I9, as will be later described and the mixture passing through this zone is heated to desired cracking temperature `preferably at a substantial superatmospheric pressure by means of heat supplied from furnace 20. The heated products are discharged from coil I9 through line 2| and valve 22 into reaction chamber 23.

' Reaction chamber 23 is also preferably maintained at a substantial superatmospheric pressure and although not indicated in the drawing, it is preferably insulated to conserve heat, so that the hot conversion products supplied to this zone are subjected to appreciable continued conversion therein.

In the particular case here illustrated, both vaporous and liquid conversion y*products are discharged from the lower portion chamber 23 through line 24 and valve 25 into vaporizing and "the scope of the invention to separate the vaporous and liquid products in chamber 23, in which case, the liquid products, either alone or together with a minor portion of the vapors, are supplied through line 24 and valve 25 to chamber 26 while all or the remaining portion of the vapors are withdrawn from any other suitable point in the reaction chamber and directed, by well known means not illustrated, either to fractionator l or to chamber 26 or in part to both. When all or a portion of the vaporous products separately withdrawn from chamber 23 are supplied to chamber 26, they may be either commingled with line 24 with the liquid products passing to chamber 26, or they may be separately supplied to this zone at any desired point therein.

Chamber 26 is preferably operated at a substantially reduced pressure relative to that employed in the reaction chamber by means of which appreciable further vaporization of the liquid products supplied to this zone is accomplished, leaving a relatively heavy liquid residue in this zone which is withdrawn from the lower portion thereof through line 39- and subjected all or in part to further treatment, as will be later described.

The vaporous products supplied to chamber from the reaction chamber as well as the vapors evolved from the liquid products in this zone, are directed therefrom through line 21 and valve 2 8 to fractionation in fractionator 6, commingling therein with the charging stock or any portion thereof which is supplied to the fractionator as previously described. The components of the materials supplied to fractionator 6 boiling above the range of the desired nal light distillate product of the process, which is normally gasoline, are separated by fractionation in this zone into se# lected relatively low-boiling and high-boiling fractions which, for the sake of convenience, will hereinafter be termed low-boiling and high-boiling reflux condensates, although either or each (of the fractions may include componentsof the V2charging stock when all or a portion of the latter is supplied to the fractionator.

Fractionated vapors of the desired end-boiling point are withdrawn together with normally gaseous products from the upper portion of fractionator 8 and directed through line 29 and valve 30 to condensation and cooling in condenser 3 I. The resulting distillate and uncondensed gases pass through line 32 and valve 33 to collection and separation in receiver 34. The uncondensed gases may be released from the receiver through line 35 and valve 36. The distillate products may be withdrawn through line 31 and valve 38 to storage or to any desired further treatment.

When desired, regulated quantities of the distillate collected in receiver 34 may be recirculated, by well known means not illustrated, to the upper portion of fractionator 8 to serve as a cooling and refluxing medium in this zone.

The selected high-boiling components of the reflux condensate formed in fractionator 3 are directed from the lower portion of this zone through' line I4 and valve I5 to pump I6 by means of which they are returned through line I3, valve I1 and valve I8 to further cracking in heating coil I9.

The heavy residual liquids remaining unvaporized in chamber 26 are withdrawn, as previously mentioned, from the lower portion of this zone through line 39 and a regulated portion of this material may, when desired, be removed from the system as a nal product thereof through line 4I and valve 42 to cooling and storage, or elsewhere, as desired. However, at least a portion of the heavy liquid residue is directed through valve 40 in line 39 to pump 43 by means of which it is directed through line 44 and Valve 45 to heating 5 coil 46.

The low-boiling fractions of the reflux condensate selected for blending and treatment with the heavy residual liquid, may be Withdrawn from one or a plurality of suitable intermediate points in the fractionator, lines 41 and valves 48 being provided for this purpose and directed through line 49 to pump 50 by means of which this mate` rial is directed through line 5I and valve 52.into line 44 to commingle therein with the residual l5 liquid from chamber 26, passing therewith to treatment in heating coil 45. These lower boiling fractions of the reflux condensate may comprise such materials as light gas oil, kerosene or kerosene distillate, pressure distillate bottoms, naph` .0 tha, high-boiling gasoline fractions of unsatisfactory antiknock value, or any desired mixture of such materials.

The commingled stream of low-boiling and high-boiling oils is heated in coil 46 preferably to e a relatively high cracking temperature, by means of heat supplied from furnace 53, the heating coil preferably being of such design, several forms of which are now Well known, as to permit the use of high velocity in the heating coil with rates of heating adequate to bring the oil quickly to the desired temperature without allowing it to remain in the heating coil for a sufficient length of time to permit any substantial formation or deposition of coke therein. A sulciently high pressure to keep at least a substantial portion of the heavy liquids supplied to heating coil 46 in liquid-phase during theirpassag'e through this zone,is also preferably employed and this high pressure also favors conversion of the low-boiling components of the mixture into additional yields of good quality4 gasolinewithout excessive coke and gas formation.

The highly heated mixture is discharged from heating coil 46 through line 54 and is directed through line 55 and valve 56'into coking chamber 51 and/or through line 55' and valve 56' into coking chamber 51', wherein the high-boiling non-vaporous components of the mixture are reduced by its containing heat to substantiallyf dry coke. 5.0

Coking chambers 51 and 51' are similar zones which may be operated at substantially the same or lower pressure than that employed at the outlet of heating coil 46. A single coking chamber or any desired number of a plurality of such i. zones may, of course, be employed and when two or more chambers are utilized they preferably are alternately operated, cleaned and prepared for further operation, in order that the operating cycle will not be limited by the capacity of the coking zone. The coke producedis allowed to accumulate in chambers 51 and 51 and may be removed therefrom in any well known manner, not illustrated, after their operation has been completed and preferably after they have'been er, isolated from the rest of the system. Chambers 51 and 51' are provided with suitable drain lines 58 and 58', respectively controlled by the respective valves 59 and 59 -and this facility may also 'serve as a means Vof introducing steam, water or any other suitable cooling medium into the chambers after their operation has been completed products are withdrawn from the upper portion of chambers 51 and 51 through lines 60 and 50 respectively controlled by the respective valves 6I and 6I' and are thence directed through line 62 and either through valves 63 in this line and through line 21 into fractionator 8, or preferably through line 64 and valve 65 into chamber 26.

The vaporous products of the coking operation are preferably directed to chamber 2B for the reason that they will normally contain entrained or dissolved high-boiling materials unsuitable as components of the redux condensate supplied to heating coil I9. By supplying the vapors to chamber 26 at least a major portion of any undesirable high-boiling materials in the vapors may be removed therefrom and collected with the residual liquid in this zone, to be returned therewith to further treatment in heating coil 46. Suitable fractionating means of any well known form, not illustrated, such as baflles, bubble trays, perforating pans, liquid sprays or the like, may be employed, when desired, in the upper portion of chamber 26 to assist in removing any un-l desirable heavy components from the vaporous products supplied from this zone to fractionator 8,` thereby keeping thegreilux condensate relatively clean and substantially free of high cokeforrning components.

In order to better regulate the proportions of light and heavy oils in the mixture supplied to heating coil 46, provision is made, in the case here illustrated, for supplying only a regulated portion of the low-boiling reflux to heating coil 46 and removing the remainder, all or in part, from the system through line 61 and valve 68 to cooling and storage, or elsewhere as desired, or directing the same, all or in part to further cracking in heating coil I9 by means of lin'e 65, valve l0, line I3 and valve I8.

The preferred range of operating conditions which may be employed to successfully conduct the process, in an apparatus such as illustrated and above described, may be approximately as follows: The heating coil to which the highboiling refluxA condensate and/or high-boiling fractions of the charging stock are supplied for conversion, may employ an outlet temperature of from 650 to 950 F. or thereabouts, preferably with a superatmospheric pressure, measured at the outlet from the heating coil, of from 100 to 500 pounds or more per square inch. A superatmospheric pressure of substantially the same order is preferably employed in the succeeding reaction chamber, although this zone may be operated at a lower superatmospheric pressure than that employed in the heating coil, the vaporizing and separating chamber, as previously mentioned, preferably employing a substantially reduced pressure relative to that utilized in the reaction chamber which may range for example from 150 pounds or thereabouts per square inch down to substantially superatmospheric pressure, the preferred range being a superatmospheric pressure of from,25 to pounds or thereabouts per square inch.

The heating coil of the coking stage of the system preferably employs an outlet temperature of the order of from 900 to l000 F. and preferably a superatmospheric pressure of from 100 to 800 pounds per square inch, or thereabouts, is employed in this .zone although lower pressure may be employed when desirable. The coking zone may employ substantially the same pressure as that maintained at the outlet from the heating coil of the coking stage of the system,

or any desired lower pressure down tosubstantially atmospheric. The fractionating condition and collecting portions of the system may be operated at substantially the same or somewhat lower pressure than that employed in the vaporizing chamber.

As an example of one specic operation of the process, as it may be conducted in an apparatus such as illustrated and described, the charging stock, which is a fuel oil of about 18 A. P. I. gravity, Vafter being preheated by indirect heat exchange with the vaporous products in the fractionator is supplied to the heating coil of the cracking ysystem together with high boiling fractions of the reflux condensate; wherein the commingled oils are heated to an outlet conversion temperature of approximately-940 F. at a superatmospheric pressure of about 350 pounds per square inch, substantially the same pressure is maintained in the reaction chamber and both vaporous and liquid conversion products are supplied from the reaction chamber to the Vaporizing and separating chamber which is maintained at a superatmospheric pressure of approximately 50 poundsper square inch. This pressure is substantially equalized in the fractionating conditions and collecting equipment. In this operation the total liquid residue from the vaporizing and separating chamber is commingled with about an equal amount, by volume, of low-boiling reflux condensate, which latter has a boiling range of approximately 390 to 560 F., and the resultant mixture is quickly heated in the heating coil of the coking stage of the system to an outlet temperature of approximately 970 F. at a super atmospheric pressure of about 400 pounds per square inch. Relatively short time high velocity is employed in this heating coil and the heated materials are quickly transferred therefrom to alternately operating coking chambers maintained at superatmospheric pressure of approximately 250 pounds per square inch. Vaporous products from the coking chambers are supplied to the vaporizing and separating chamber. This operation will produce, per barrel of charging stock, approximately 65% of 400 F. yield point gasoline having an octane number of approximately 70 by the motor method and approximately pounds of good quality petroleum coke, the remainder being chargeable principally to normally gaseous products.

I claim as my invention:

1. In a process for the conversion of hydrocarbon oils wherein an oil, comprising essentially charging stock for the process and selected highboiling fractions of the reflux condensate formed in the process, is cracked at cracking temperature and substantial superatmospheric pressure, thereby forming vaporous and liquid conversion products, the latter reduced to high-boiling residual oil by ilash distillation, the vaporous products, including those resulting from said iiash distillation, subjected to fractionation for the formation of reux condensate, fractionated vapors of the desired end-boiling point condensed and resulting distillate recovered, the improvement which comprises commingling at least a substantial portion of said high-boiling residual oilI with a regulated portion of said reflux condensate, passing the resultant mixture through a heatingcoil and quickly heating the same therein under independently controlled, non-coking conditions sufficiently to veffect subsequent coking of its high-boiling components and appreciable cracking of its low-boiling components, in-

troducing the heated material from the last mentioned heating step into an enlarged coking zone wherein vaporous and non-vaporous components of the heated mixture are separated and the latter reduced to coke without additional heating, and fractionating vaporous products of the coking step in admixture with the first-mentioned vaporous products.

2. In a process for the conversion of hydrocarbon oils wherein an oil .is cracked at cracking temperature and substantially superatmospheric pressure, thereby forming vaporous and liquid conversion products, the latter reduced to highboiling residual oil by ash distillation, the vaporous products, including those resulting from said flash distillation, subjected to fractionation for the formation of reflux condensate, fractionated vapors of the desired end-boiling point condensed and resulting distillate recovered, the improvement which comprises supplying at least a portion of the hydrocarbon oil charging stock for the process to said iractionating step wherein it is subjected to fractionation in commingled state with said vaporous conversion products, com'- mingling at least a substantial portion of said high-boiling residual oil with a regulated portion of said redux condensate, passing the resultant mixture through a heating coil and quickly heating the same therein under independently controlleti,y non-coking conditions suiiciently to effeet subsequent coking oi' its high-boiling components and appreciable cracking of its low-boil- 11,18 COmpOnents, introducing the heated material from the last mentioned heating step into an enlarged coking zone wherein vaporous and nonvaporouscomponents of the heated mixture are separated and the latter reduced to coke without additional heating, and fractionating vaporous products of the coking step in admixture with the first-mentioned vaporous products.

l 3. A process such as defined in claim 2 wherein the portions of said charging stock which remain unvaporized in the fractionating step are supplied, together with high-boiling fractions of the reilux condensate, to the first mentioned cracking step.

4. A process such as defined in claim 2 whereinl the portions of said charging stock which remain unvaporized in the i'ractionating step are supp d, together with high-boiling fractions of the re ux condensate, to the first mentioned cracking step and wherein said portion of the reilux condensate commingled with said high-boiling residuai oil includes selected fractions of the charging stock.

5. In `a process for the conversion of hydrocarbon oils wherein an oil is cracked at cracking temperature and substantial super-atmospheric pressure, thereby forming vaporous and liquid conversion products, the latter reduced to highboiling residual liquid by flash distillation, the vaporous products, including those resulting from said flash distillation, subjected to fractionation for the formation of reflux condensate, fractionated vapors oi' the desired end-boiling point condensed and the resulting distillate recovered, the improvement which comprises separating selected low-boiling fractions from the reflux condensate commingling at least a substantial portion of said high-boiling residual liquid with regulated quantities of selected low-boiling fractions or the reux condensate, supplying the resultant mixture to a heating coil and quickly heating the same` therein, under independently controlled, nonooking conditions, to a temperature sufficient to effect subsequent coking of its high-boiling components and appreciable cracking of its low-boiling components, supplying the heated materials from said heating coil to an enlarged coking zone, wherein separation of their vaporous and non-vaporous components is accomplished and the latter reduced .to coke without additional heating, and fractionatlng vaporous products of the coking stage in admixture with the first-v mentioned vaporous products.4

6. A process such as defined in claim 5 wherein high-boiling fractions of the reux condensate are returned to the iirst mentioned cracking step.

'1. A process such as defined in claim 5 wherein that portion of the reflux condensate which is not commingled with said high-boiling residual oil is returned for further cracking to the irst mentioned cracking step.

8. A process such as defined in claim 5 wherein at least a portion of the hydrocarbon oil charging stock for the process is supplied to said frac-5 tionating step and subjected to fractionation therein, in commingled state with said vaporous products, and wherein at least a portion of said charging stock is cracked in the iirst mentioned cracking step.

9. A process such as defined in claim 5 wherein high-boiling fractions of the reflux condensate and high-boiling fractions of the charging stock are supplied to the iirst mentioned cracking step and whereinv said selected low-boiling fractions of the reflux condensate which are commingled with said high-boiling residualoil include selected low-boiling fractions of the charging stock.

l0. In a process for the conversionof hydrocarbon oils which comprises heating an oil to cracking temperature at substantial superatmospheric pressure in a heating coil, supplying the heated products to an enlarged reaction chamber, also maintained at substantial superatmospheric pressure, wherein appreciable further crackingthereoi' is accomplished, supplying both vaporous and liquid conversion products from the reaction chamber to a reduced pressure vaporizing and separating chamber, wherein appres ciable further vaporization of said liquid products is accomplished and wherein vaporous products are separated from the resultant residual liquid, fractionating the vaporous lproducts from said vaporizing and separating chamber for the formation of reflux condensate, separating said reflux condensate into selected relatively low-boiling and high-boiling fractions, returning said high-boiling fractions of the reflux condensate to the heating coil for further cracking, subjecting fractionated vapors of the desired end-boiling point to condensation, recovering the resulting distillate, commingling at least a substantial portion of said residual liquid with regulated quantities of said selected low-boiling fractions of the reflux condensate, passing the resultant mixture through a separate heating coil and heating the same therein at substantial superatmospheric pressure to a sufliciently high temperature to induce subsequent coking of its high-boiling components and appreciable cracking of its lowboiling components, regulating the conditions of treatment in said separate' heating coil to main- .tov

tain said mixture in a mixed-phase condition attained temperature in this zone and wherein the non-vaporous high-boiling components of the mixture are reduced to coke, removing undesirable high-coke forming components from the vaporous products of the coking step, returning the same to the coking step for further treatment, subjecting the remaining relatively clean vaporous products of the coking step to fractionation for the formation of redux-condensate, returning the latter to further cracking within the system, condensing fractionated vapors of the desired end-boiling point from the last mentioned Iractionating step, and recovering the resultant distillate. y

11. In a process for the conversion of hydrocarbon oils which comprises heating an oil to cracking temperature at substantial superatmospheric pressure in the heating coil, supplying the heated products to an enlarged reaction chamber, also maintained at substantial superatmospheric pressure, wherein appreciable further cracking thereof is accomplished, supplying both vaporous and liquid conversion products from the reaction chamber to a reduced pressure vaporizing and separating chamber, wherein appreciable further vaporization of said liquid products is accomplished and wherein vaporous products are separated from the resultant residual liquid, fractionating the vaporous products from said vaporizing and separating chamber for the formation of reflux condensate, separating said reiiux condensate into selected relatively low-boiling and high-boiling fractions, returning said high-boiling fractions of the reiiux condensate to the heating coil for further cracking, subjecting fractionated vapors of the desired end-boiling point to condensation, recovering the resulting distillate, commingling at least a substantial portion of said residual liquid with regulated quantities of said selected low-boiling fractions of the redux con-.

densate, passing the resultant mixture through a separa-te heating coil and heating the same therein at substantial superatmospheric pressure to a sumciently high temperature to induce subsequent coking of its high-boiling components and appreciable cracking oi its low-boiling components, regulating the conditions of treatment in said separate heating coil to maintain said mixture in a mixed-phase condition therein, discharging the resultant highly heated mixture from said separate heating coil and introducing the same into an enlarged coking zone, also maintained at a sufficiently high superatmospheric pressure to effect appreciable cracking of the vaporous components of the mixture at their attained temperature in this zone and wherein the non-vaporous high-boiling components of the mixture are reduced to coke, removing resultant vaporous products1 including any entrained highcoke forming materials, from the coking zone, and supplying the same to said vaporizing and separating chamber.

12. A process such as defined in claim 11 wherein charging stock for the process, comprising a hydrocarbon oil of relatively wide boiling range, is supplied to said fractionating step wherein relatively low-boiling and high-boiling components thereof commingie, respectively, with said selected low-boiling and high-boiling fractions of the reflux condensate.

13. A process such as dened in claim 1l wherein charging stock for the process, comprising essentially an oil of higher boiling characteristics than said selected low-boiling fractions of the reflux condensate, is supplied for cracking to the iirst mentioned heating coil.

14. In a process of hydrocarbon oil conversion wherein the oil is heated in a heating zone, the

heated oil discharged into an enlarged reaction zone, superatmospheric pressure maintained on the heating zone and enlarged reaction zone, all of the products of reaction being withdrawn from the enlarged reaction zone and discharged into an enlarged reduced pressure zone wherein vapors separate from non-vaporous residue, the` vapors being fractionated to form primary and secondary redux condensates and the primary reflux condensate resulting from such fractionation being returned to the heating zone admixed with fresh charging stock, the improvement which comprises withdrawing regulated portions.

of the non-vaporous residue from the reduced pressure zone and combining the same with said secondary reflux condensate, subjecting the resultant mixture to heat, discharging said heated mixture into an enlarged coking zone, the temperature conditions in the residue heating zone being controlled to reduce the residue in said coking zone to coke.

JOSEPH G. ALTHER.

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