US2130408A

US2130408A - Conversion of hydrocarbon oils

Info

Publication number: US2130408A
Application number: US725880A
Authority: US
Inventors: Charles H Angell
Original assignee: Universal Oil Products Co
Current assignee: Universal Oil Products Co
Priority date: 1934-05-16
Filing date: 1934-05-16
Publication date: 1938-09-20
Anticipated expiration: 1955-09-20

Description

\ ep 20, 1938. H. ANGELL- 2,130,408

CONVERSION OF HYDROCARBON OILS Filed May 16, 1934 COKING CHAMBER INVENTOR H. ANGELL AND COLUMN H TTORNEY Patented Sept. 20, 1938 umrso STATES PAT OFF IZCJE CONVERSION OF HYDROCA'RBON OILS Application May 16, 1934, Serial No. 725,880

'7 Claims.

The invention particularly refers to an improved'process for the fractional distillation of hydrocarbon oils of relatively wide boiling range,

n suchas crude petroleum, for example, accompanied by the pyrolytic conversion of selected low-boiling fractions of the charging stock, including any motor fuel components of inferior quality, under conditions regulated to produce high yields of motor fuel of good anti-knock value and the use of the resulting highly heated products to coke residual liquid resulting from the conversion, under independently controlled conditions, of the higher boiling fractions of the charging stock.

In operations of the general character above outlined wherein use is made of the available excess heat in the products resulting from conversion of the relatively low-boiling oils to effect or assist coking of residual oil, the vaporous products from the coking zone normally contain a considerable quantity of excess heat over that required for their fractionation. The present invention makes use of the excess heat in the vaporous products from the coking zone to effect or assist fractional distillation of the charging stock for the process by indirect heat exchange between the charging stock and the vaporous products from the coking zone, prior to fractionation of the vaporous products. This partial cooling of the vaporous products from the coking zone, prior to their fractionation also serves as a method and means of facilitating their subsequent fractionation and removing therefrom high-boiling components of a high coke-forming nature, including any particles of tar, pitch and the like entrained in and carried over with the vapors from the coking operation, thus preventing the inclusion of such materials in the reflux condensate formed by fractionation of the vaporous products of the process. Such high cokeforming materials would contaminate the reflux condensate and cause excessive coking in the heating coil to which the reflux condensate is returned for further conversion.

In one specific embodiment, the invention comprises subjecting hydrocarbon oil charging stock of relatively wide boiling range to fractional distillation whereby it is separated into selected relatively low-boiling and high-boiling fractions, subjecting high-boiling fractions of the charging stock to conversion conditions of elevated temperature and superatmospheric pressure, separating the resulting vaporous and liquid conversion products and subjecting the latter to further vaporization at substantially reduced pressure relative to that at which they are formed, withdrawing the non-vaporous residual liquid from the vaporizing zone and subjecting the same to coking in a separate low-pressure coking zone, subjecting the vaporous products from the cracking and coking operation to fractionation whereby their insufiiciently converted components are condensed as reflux condensate and separated into selected relatively low-boiling and high-boiling fractions, subjecting fractionated vapors of the desired end-boiling point fromthe last mentioned fractionating stage to condensation and recovering the resulting distillate, returning high-boiling fractions of the reflux condensate to further conversion, together with said high-boiling fractions of the charging stock, subjecting selected lowboiling fractions of the charging stock, including any components within the boiling range of motor fuel but of poor anti-knock value, together with said low-boiling fractions of the reflux condensate, to independently controlled conversion conditions of elevated temperature and superatmospheric pressure regulated to produce high yields of motor fuel of good anti-knock value, introducing the conversion products from the last mentioned conversion stage, while still in highly heated state, into direct contact with the residual materials undergoing coking, for the purpose of assisting the coking operation, and heating the charging stock, for the purpose of effecting said fractional distillation thereof, by indirect contact with hot vaporous products from the coking zone, prior to theirfractionation.

It will be apparent from the foregoing that the various features of the invention are cooperative and mutually contribute to produce the desired final results; for example, charging stock for the process is heated to effect its fractional distillation and desired separation into various components by exceses heat available from the vapors resulting from coking of the residual liquid conversion products of the process which, in turn, is accomplished by the use of highly heated selected low-boiling oils, said low-boiling oils as well as higher boiling oils which are converted to produce the residue for coking being made available, at least in part,-by-the'fractional distillation of the charging stock.

The accompanying diagrammatic drawing illustrates one specific form of apparatus in which the process may be carried out. The drawing and the accompanying description thereof will serve to more clearly illustrate the specific embodiment of the invention above outlined as well as some of the many possible modifications thereof which are entirely within the scope of the present invention.

Referring to the drawing, hydrocarbon oil charging stock for the process is supplied through line I and valve 2 to pump 3 by means of which it may be fed through line 4, valve 5, heat exchanger 6, line 1 and valve 8 into distilling and fractionating column 9. Heat exchanger 6 serves the purpose of heating the charging stock by indirect contact with hot vaporous products of the process, as will be later more fully described. Ordinarily all of the heat required for distillation of the charging stock may be supplied in this manner, but it is within the scope of the invention, when desired, to supply additional heat thereto in any suitable well known manner, not illustrated.

The charging stock supplied to column 9 is separated by fractionation into selected relatively low-boiling and high-boiling fractions. The latter may be withdrawn from the lower portion of column 9 through line In and valve H' to pump l2 by means of which they are supplied through line l3, valve l4 and line to conversion in heating coil l6.

When the charging stock contains an appreciable quantity of desirable low-boiling components, such as, for example, motor fuel or motor fuel fractions of satisfactory anti-knock value,

they may be withdrawn as fractionated vapors from the upper portion of column 9, together with gas produced by the distilling operation, and supplied through line H and valve [8 to condensation and cooling in condenser I9. The resulting distillate and gas passes through line and valve 2| to collection and separation in receiver 22. Uncondensable 'gas may be released from the receiver through line 23 and valve 24. Distillate may be withdrawn from receiver 22 through line 25 and valve 26 to storage or to any desired treatment. When desired, a regulated portion of the distillate collected in receiver 22 may be recirculated by well known means, not illustrated, to the upper portion of column 9 to serve as a, refluxing and cooling medium to assist cooling and fractionation of the vapors.

In case the charging stock contains no appreciable quantity of desirable low-boling components, such as motor fuel or motor fuel fractions of satisfactory anti-knock value, any other selected low-boiling components, including poor anti-knock motor fuel or motor fuel fractions as well as, when desired, somewhat higher boiling materials such as naphtha, kerosene or kerosene distillate and the like, may be recovered in receiver 22, in the manner previously described, to be withdrawn therefrom, all or in part, through line 21 and valve 28 to pump 29 by means of which they are supplied through line 30, valve 3| and line 32 to further conversion or reforming in heating coil 33.

In case desirable low-boiling components of the charging stock, such as previously mentioned, are collected in receiver 22, other selectedlowboiling components, including any motor fuel or motor fuel fractions of poor anti-knock value as well as, when desired, somewhat higher boiling materials such as naphtha, kerosene or kerosene distillate and thelike, may be withdrawn from one or a plurality of suitable intermediate points in column 9, such as, for example, through line 34 and valve 35, to pump 36 by means of which they aresupplied through line 31, valve 38 and line 32 to conversion or reforming in heating coil 33.

The oil supplied to heating coil I6 is subjected therein to the desired conversion temperature, preferably at a substantial superatmospheric pressure, by means of heat supplied from a furnace 39 of any suitable form and the stream of heated oil is discharged from the heating coil through line 40 and valve 4| into reaction chamber 42.

Chamber 42 is also preferably maintained at a substantial superatmospheric pressure and, although not indicated in the drawing, is preferably well insulated against the excessive loss of heat so that conversion of the heated products supplied to this zone, and particularly their vaporous components, may continue in the reaction chamber. In the case here illustrated, both vaporous and liquid conversion products are discharged in commingled state from the lower portion of chamber 42 through line 43 and valve 44 into vaporizing chamber 45. It is, however, within the scope of the invention to separately withdraw a regulated portion or all of the vaporous products from chamber 42 at any desired point or plurality of points in this zone, in which case the vapors separately withdrawn from the reaction chamber may be supplied directly to fractionator 59 or to heat exchanger 6 or they may be introduced at any desired point or plurality of points into chamber 45, although well known means for accomplishing this are not illustrated in the drawing.

Chamber 45 is preferably operated at a substantially reduced pressure relative to that employed in reaction chamber 42, by means of which further vaporization of the liquid conversion products supplied to-this zone from the reaction chamber is accomplished. The vapors evolved by further distillation of the liquid conversion products in chamber 45, as Well as any vapors supplied to this zone from the reaction chamber, are withdrawn from the upper portion of the vaporizing chamber and supplied, as will be later more fully described, to fractionation in fractionator 59.

Residual liquid conversion products remaining unvaporized in chamber 45 are withdrawn from the lower portion of this zone through line 46 and supplied through valve 41 coking chamber 48 wherein they are reduced to substantially dry coke.

. The oil supplied to heating coil 33 is subjected therein to the desired conversion temperature,

preferably at a substantial superatmospheric pressure, by means of heat supplied from furnace 49 of any suitable form. Preferably, the relatively low-boiling oil supplied to heating coil 33 is subjected therein to more severe conversion conditions than the higher boiling oil supplied to heating coil I6 and when motor fuel or motor fuel fractions are included in the low-boiling oils supplied to heating coil 33 the conversion conditions maintained in this zone are regulated to materially improve their motor fuel characteristics, particularly with respect to anti-knock value, without excessively altering their boiling range. The highly heated products are discharged from heating coil 33 through line 50 and are introduced through one or a plurality of suitable lines 5| controlled by valves 52 into coking chamber 48 at any desired point or plurality of points in this zone. Preferably, however, the heated products from heating coil 33 come into direct and intimate contact in chamber 48 with the residual material undergoing coking in this zone or, when desired, the residual liquid from chamber 45 may be commingled with the stream of heated products from 75;

heating coil 33and the commingled materials introduced into the coking chamber, by well known means not illustrated. In any case, the highly heated products from heating coil 33 furnish heat required to effect reduction of the residual liquid from chamber 45 to substantially dry coke in coking chamber 48. The invention is, however, not limited to the introduction of the total products from heating coil 33 into the coking zone inasmuch as any excess of such materials over the quantity required for producing coke of the desired characteristics in the coking zone may, when desired, be supplied to reaction chamber 42, vaporizing chamber 45, or heat exchanger 6, by well known means not illustrated.

Coking chamber 48 is preferably operated at substantially atmospheric or relatively low superatmospheric pressure although, when desired, superatmospheric pressures up to 150 pounds, or more, per square inch may be employed in this zone, in which case a suitable pump, not illustrated, may be employed for introducing residual liquid from chamber 45 into chamber 48. When desired, a plurality of coking chambers similar tochamber 48, but not illustrated, may be utilized and may be simultaneously operated or, preferably, are alternately operated, cleaned and prepared for further operation so that the coking stage of the process as well as the cracking stages is continuous. Coke may be allowed to accumulate within the coking chamber to be removed therefrom in any suitable well known manner after its operation is completed. Chamber 48 is provided with a drain-line 53 controlled by valve 54. This line may also serve as a means of introducing steam, water or other suitable cooling medium into the coking chamber, after it has been substantially filled -with coke and isolated from the rest of the system, so as to hasten cooling and facilitate cleaning of the chamber.

Hot Vaporous products are removed from the upper portion of coking chamber 98 through line 55 and valve 56 and pass through heat exchanger 9, line 51 and valve 58 to fractionation in fractionator 59. The relatively hot vapors passing through heat exchanger 6 come into indirect contact in this zone with hydrocarbon oil charging stock for the process, thereby supplying to the charging stock a portion, at least, of the heat required for its fractional distillation. Heat exchange between the vaporous products from the coking chamber and the charging stock also serves to remove from the vapors, by cooling and partial condensation, high-boiling components of a high coke-forming nature, including entrained particles of tar, pitch and the like, which would contaminate the reflux condensate produced in fractionator 59. These high-boiling materials removed as condensate in heat exchanger 9 may be withdrawn from the lower portion of this zone through line 99 and valve 5! to pump 92 and may be discharged from the system by well known means, not illustrated, or may be returned to exchanger 6 to vaporizing chamber 45 or direct to coking chamber 48, or, when desired, this material may be returned to reaction chamber 42 at any desired point-in this zone. H

Vaporous products maybe withdrawn, as'previously mentioned, from the upper. portion of chamber .45 and may be directed through line 65 and valve 66' to heat exchanger 6 or they may pass, by well known means not illustrated in the drawing, direct to fractionator 59. v

The components of the Vaporous products of the process supplied tofractionator 59 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, when desired, as a single stream from the lower portion of this zone through line 61 and valve 68 to pump 69 to be returned therefrom through line l5and valve ill to further conversion in heating coil 96, or the reflux condensate may, when desired, be separated in column 59 into selected relatively low-boiling and high-boiling fractions, in which case only the latter are supplied, as described, to heating coil [6 while selected low.- boiling fractions, comprising, for example, such materials as high-boiling motor fuel fractions or naphtha, pressure distillate bottoms, kerosene or kerosene distillate and the like may be withdrawn from one or a plurality of suitable intermediate points in column 59, for example, through line H and valve 72, to pump 73 by means of which they are returned through line I4, valve and line 32 to further conversion in heating coil 33, together with the selected low-boiling fractions of the charging stock, supplied to this zone as previously described.

Fractionated vapors of the desired end-boiling point, preferably comprising motor fuel of good anti-knock value, are withdrawn, together with uncondensable gas from the upper portion of fractionator 59 through line 79 and valve ll to be subjected to condensation and cooling in condenser '19. The resulting distillate and gas passes through line 8i) and valve 8| to collection and separation in receiver 82. Uncondensable gas may be released from the receiver through line 83 and valve 84. Distillate may be Withdrawn from receiver 82 through line 85 and valve 86 to storage or to any desired further treatment. A regulated portion of the distillate collected in receiver 82 may, when desired, be recirculated, by Well known means, not illustrated, to the upper portion of fractionator 59 to serve as a refiuxing and coo-ling medium to assist fractionation of the vapors and to maintain the desired vapor outlet temperature from the fractionator.

It will be understood that the invention is not limited to the specific form of apparatus illustrated and above described since many modifications other than those above mentioned are possible within the scope of the invention. For example, vaporizing chamber 45 may be eliminated, in which case the residual liquid from reaction chamber 92 may be supplied direct to the coking chamber and Vaporous products from the reac-' tion chamber subjected to fractionation with or without first passing through heat exchanger 6. On the other hand the high-pressure reaction chamber 42 may be eliminated, when desired, without departing from the scope of the invention, in which case the conversion products from heating coil 16 are introduced into vaporizing chamber 45. In such cases a substantial reduction in pressure is preferably employed between the heating coil and the vaporizing chamber and, when desired, additional well known means may be employed for cooling the stream of hot conversion products from the heating coil to any desired degree, prior to its introduction into the vaporizing chamber. It is also'entirely Within the scope of the present invention, when desired, to subject the vaporous products from the coking zone to fractionation separate from the vaporous products resulting from conversion of the relatively high-boiling oils and to separately condense and collect the desired overhead product of such separate fractionation, in which case the reflux condensate resulting from such separate fractionation is preferably separated into selected relatively low-boiling and high-boiling fractions which are, respectively, subjected to conversion, together with the selected low-boiling and highboiling fractions of the charging stock or, when desired, the total reflux condensate from the coking operation may be subjected to further conversion, together with the high-boiling fractions of the charging stock.

In an apparatus such as illustrated and above described, the preferred operating conditions for accomplishing the process of the present invention may be approximately as follows: The heating coil to which the relatively high-boiling oils are supplied may employ an outlet conversion temperature ranging, for example, from 850 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. Substantially the same or a somewhat reduced superatmospheric pressure may be employed in the reaction chamber and preferably a substantially reduced pressure ranging, for example, from 100 pounds, or thereabouts, per square inch to substantially atmospheric pressure is employed in the vaporizing chamber. The pressures employed in the fractionating, condensing and collecting portions of the cracking system may be substantially equalized or somewhat reduced relative to the pressure employed in the vaporizing chamber. The temperature to which the charging stock is heated to effect its fractional distillation may range, depending upon its characteristics, for example, from 450 to 700 F., or thereabouts, and heating of the charging stock may be accomplished at any desired pressure from substantially atmospheric to 150 pounds, or more, per square inch. The distilling and fractionating column to which the heated charging stock is supplied is preferably operated at substantially atmospheric pres- 'sure, although sub-atmospheric or superatmospheric pressures may be employed in this zone, when desired. The heating coil to which the relatively low-boiling oils are supplied may utilize a conversion temperature, measured at the outlet therefrom, ranging, for example, from 925 to 1050 F., or more, preferably with a superatmospheric pressure at this point in the system of from 300 to 1000 pounds, or thereabouts, per square inch. The coking chamber is preferably operated at substantially atmospheric or a relatively low superatmospheric pressure up to pounds, or thereabouts, per square inch, although higher superatmospheric pressures up to that employed at the outlet from the light oil heating coil will be employed in the coking zone, when desired.

The following is 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 of the character illustrated and above described: A California crude of about 25 A. P. I. gravity containing about 5% of material boiling below 276 F., and about 22% boiling below 437 F. is heated to a temperature of approximately 600 by heat exchange with hot vaporous products from the coking stage of the system and is subjected to fractional distillation at substantially atmospheric pressure. The relatively high-boiling fractions (i. e. its components boiling above approximately 550 F.) are subjected in a heating coil to an outlet conversion temperature of approximately 940 F., at a superatmospheric pressure of about 375 pounds per square inch. The heated products are introduced into a reaction chamber operated at substantially the same pressure, from which vaporous and liquid conversion products are withdrawn in commingled state and introduced into a reduced pres sure vaporizing chamber operated at a superatmospheric pressure of about 60 pounds per square inch. Non-vaporous residual liquid is Withdrawn from the vaporizing chamber and introduced into a coking chamber operated at a superatmospheric pressure of about 50 pounds per square inch, wherein it is reduced to coke. The vaporous conversion products, including vapors from the coking operation after removal of their heavy components by indirect heat exchange with the charging stock, are subjected to fractionation at substantially the same pressure as that employed in the coking chamber, whereby their insufficiently converted components are condensed as reflux condensate and fractionated vapors having an end-boiling point of approximately 387 F., are condensed and collected as the final motor fuel product of the process. High-boiling fractions of the reflux condensate, boiling above approximately 550 R, are returned to the heating coil for further conversion, together with the high-boiling fractions of the charging stock. Low-boiling components of the charging stock, boiling below approximately 550 F., are subjected, together with low-boiling fractions of the reflux condensate, boiling between approximately 385 and 550 F., to a conversion temperature of approximately 970 F., at a superatmospheric pressure of about 800 pounds per square inch and the resulting heated products are introduced into direct contact with the residual material undergoing .coking in the coking chamber. This operation will yield, per barrel of charging stock, about 72% of motor fuel having an octane number of approximately 70 and about 60 pounds of low volatile coke, the remainder being chargeable principally to uncondensable gas.

I claim as my invention:

1. A conversion process which comprises heating hydrocarbon oil to cracking temperature under pressure in a heating zone and subsequently separating the same into vapors and unvaporized oil, distilling the unvaporized oil to coke and passing the vapors thus formed, prior to any previous fractionation thereof, in indirect heat exchange relation with fresh charging oil for the process to preheat the latter and to separate high coke-forming constituents from these vapors, distilling the thus preheated charging oil and separating therefrom a relatively heavy fraction and a lighter fraction, supplying the relatively heavy fraction to said heating zone, heating said lighter fraction in a second heating zone to higher cracking temperature than the oil in the first-named heating zone and discharging resultant heated products into contact with said unvaporized oil to assist the coking thereof, fractionating the vapors uncondensed by said heatexchange independently of the charging oil to form relatively heavy and light reflux condensates, returning such heavy and light reflux condensates respectively to the first-named heating zone and said second heating zone, and finally condensing the fractionated vapors.

2. A conversion process which comprises heating hydrocarbon oil to cracking temperature under pressure in a heating zone and subsequently separating the same into vapors and unvaporized oil, distilling the unvaporized oil to coke and passing the vapors thus formed, prior to any previous fractionation thereof, in indirect heat exchange relation with fresh charging oil for the process to preheat the latter and to separate high coke-forming constituents from these vapors, returning such separated constituents to the coking operation, distilling the thus preheated charging oil and separating therefrom a relatively heavy fraction and a lighter fraction, supplying the relatively heavy fraction to said heating zone, heating said lighter fraction in a second heating zone to higher cracking temperature than the oil in the first-named heating zone and discharging resultant heated products into contact with said unvaporized oil to assist the coking thereof, fractionating the vapors uncondensed by said heat exchange independently of the charging oil to form relatively heavy and light reflux condensates, returning such heavy and light reflux condensates respectively to the first-named heatmg zone and said second heating zone, and finally condensing the fractionated vapors.

3. A conversion process which comprises heating hydrocarbon oil to cracking temperature under pressure in a heating zone and subsequently separating the same into vapors and. unvaporized oil in a separating zone, removing the unvaporized oil from the separating zone and distilling the same to coke in a coking zone, combining the vapors evolved in the coking zone with the first-named vapors and passing the resultant mixture, prior to any previous fractionation thereof, in indirect heat exchange relation with fresh charging oil for the process to heat the latter and to separate high coke-forming constituents from the vapors, distilling the thus heated charging oil and separating therefrom a relatively heavy fraction and a lighter fraction, supplying the relatively heavy fraction to said heating zone, heating said lighter fraction in a second heating zone, to higher cracking temperature than the oil in the first-named heating zone and discharging resultant heated products into the coking zone to assist the coking of the unvaporized oil therein, fractionating the vapors uncondensed by said heat exchange independently of the charging oil and returning resultant reflux condensate to the process for retreatment, and finally condensing the fractionated vapors.

4. A conversion process which comprises heating hydrocarbon oil to cracking temperature under pressure in a heating zone and subsequently separating the same into vapors and unvaporized oil in a separating zone, removing the. unvaporized oil from the separating zone and distilling the same to coke in a coking zone, combining the vapors evolved in the coking zone with the flrstnamed vapors and passing the resultant mixture, prior to any previous fractionation thereof, in indirect heat exchange relation with fresh charging oil for the process to heat the latter and to separate high coke-forming constituents from the vapors, introducing such separated constituents to the coking zone for further treatment therein, distilling the thus heated charging oil and separating therefrom a relatively heavy fraction and a lighter fraction, supplying the relatively heavy fraction to said heating zone, heating said lighter fraction in a second heating zone, to higher cracking temperature than the oil in the first-named heating zone and discharging resultant heated products into the coking zone to assist the coking of the unvaporized oil therein, fractionating the vapors uncondensed by said heat exchange independently of the charging oil and returning resultant reflux condensate to the process for retreatment, and finally condensing the fractionated vapors.

5. The process as defined in claim 4 further characterized in that at least a portion of said reflux condensate is returned to the first-named heating zone.

' 6. The process as defined in claim 4 further characterized in that at least a portion of said reflux condensate is returned to the secondnamed heating zone.

7. A conversion process which comprises heating hydrocarbon oil to cracking temperature under pressure in a heating zone and subsequently separating the same into vapors and unvaporized oil in a separating zone, removing the unvaporized oil from the separating zone and distilling the same to coke in a coking zone, combining the vapors evolved in the coking zone with the firstnamed vapors and passing the resultant mixture, prior to any previous fractionation thereof, in indirect heat exchange relation with fresh charging oil for the process to heat the latter and to separate high coke-forming constituents from the vapors, introducing such separated constituents to the coking zone for further treatment therein, distilling the thus heated charging oil and separating therefrom a relatively heavy fraction and a lighter fraction, supplying the relatively heavy fraction to said heating zone, heating said lighter fraction in a second heating zone, to higher cracking temperature than the oil in the firstnamed heating zone and discharging resultant heated products into the coking zone to assist the coking of the unvaporized oil therein, fractionating the vapors uncondensed by said heat exchange independently of the charging oil to form a relatively heavy reflux condensate and a lighter reflux condensate, supplying such heavy and lighter reflux condensates respectively to the first-named heating zone and said second heating zone, and finally condensing the fractionated vapors.

CHARLES H. ANGELL.