US2144819A - Conversion of hydrocarbon oils - Google Patents

Description

Jan. 24, 1939. K. swAR'rwooD CONVERSION OF' HYDROCARBON OILS Original Filed Nov. 29

INVENTOR KENNETH SWARTWOOD Patented Jan. 24, 1939 UNITED STATES PATENT OFFICE CONVERSION OF HYDROCARBON OILS Application November 29, 1935, Serial No. 52,119 Renewed March 10, 1937 4 claims.

This invention particularly refers to an improved process for the treatment of hydrocarbon oils embodying the steps of fractional distillation, pyrolytic conversion, coking and reforming in which the Various steps are interdependent and mutually contribute to produce the desired hnal result, namely, the production of high yields of motor fuel of good antiknock value and minor yields of less desirable products, such as residual liquid and/or coke and gas.

One specific embodiment of the invention comprises subjecting hydrocarbon oil of relatively low-boiling characteristics, comprising intermediate liquid conversion products of the process, to conversion conditions of cracking temperature and superatmospheric pressure in a heating coil and communicating enlarged reaction chamber, withdrawing both vaporous and liquid conversion products from the reaction chamber and introducing the same into a separate enlarged chamber wherein vaporous and non-vaporous conversion products separate, removing the vaporous conversion products from said separate enlarged chamber, subjecting the same to further conversion under independently controlled heating conditions in a separat-e heating coil, passing the resulting heated products in indirect heat exchange with charging stock for the process, comprising an oil of relatively wide boiling range, whereby to partially cool the conversion products and heat the charging stock, introducing the heated charging stock into a distilling and fractionating column wherein its relatively low-boiling and high-boiling components are separated, supplying said low-boiling components of the charging stock, comprising vaporous products from the distilling and fractionating column, t0 said separate heating coil for conversion, supplying the partially cooled conversion products from said separate heating coil and said highboiling components of the charging stock from the distilling and fractionating column to a vaporizing and separating chamber wherein their vaporous .and liquid components Yare separated, recovering, when desired, a portion or all of the latter or returning the same to said separate enlarged chamber, subjecting vaporous products from said vaporizing and separating chamber to fractionation for the formation of said reflux condensate which is supplied for conversion to the first mentioned heating coil, subjecting fractionated vapors of the desired end-boiling point to condensation and recovering the resulting distillate.

The enlarged chamber to which vaporous and liquid conversion products from the reaction chamber are supplied and to which all or Aa portion of the non-vaporous liquids from the vaporizing and separating chamber may be supplied may be operated for the production of either liquid residue or relatively dry coke. In the latter case the heavy liquids supplied tothis zone from the vaporizing and separating chamber are preferably heated to a high conversion temperature under non-coking conditions, prior to their introduction into this zone, whereby suii'icient heat is supplied thereto to effect their reduction to coke upon introduction into said enlarged chamber.

The various novel features and advantages of the invention will be more apparent with reference to the accompanying diagrammatic drawing and the following description thereof. The drawing illustrates one specific form of apparatus embodying the features of the invention and in which the process of the invention may be acoomplished.

Referring vto the drawing, heating coil l is located Within a suitable furnace 2 and the relatively low-boiling oils, comprising intermediate liquid conversion products of the process, which are supplied to this zone as will be later described, are subjected therein to the desired conversion temperature, preferably at a substantial superatmospheric pressure. The heated products are discharged from heating coil l through line 3 and valve 4 into reaction chamber 5.

Chamber 5 is also preferably operated at a substantial superatmospheric pressure which may be substantially the same or somewhat'lower than that maintained at the outlet from heating coil I. Chamber 5 is also preferably insulated in order to conserve heat, although insulation is not indicated in the drawing, so that the hot conversion products supplied to this Zone, and more particularly their vaporous components, are subjected therein to appreciable continued conversion.y Vaporous and liquid conversion products are withdrawn in commingled state from the lower portion of chamber 5 and directed through line 6 and valve 'l into chamber 8 wherein their vaporous and non-vaporous components separate.

Chamber 8 may be operated as a zone of further vaporization for the liquid conversion products from chamber 5 and for the recovery therefrom of the resulting non-vaporous residual liquid, in which case the chamber is preferably operated at a, substantially reduced pressure relative to that employed in chamber 5, or chamber 8 may be utilized as a coking zone wherein the nonvaporous liquid conversion products supplied thereto are reduced to substantially dry coke. When coke is produced in chamber 8 it may be allowed to accumulate therein until the chamber is substantially filled, or until its operation is completed for any other reason, following which the coke may be removed in any well known manner, not illustrated, and the chamber prepared for further operation. A plurality of coking chambers may, of course,l be employed, when desired, although only a single chamber is shown in the drawing, and alternate operation of a plurality of coking chambers is specically contemplated by the present invention in order to permit continuous coking. When operated for the production of liquid residue such material may be removed from the lower portion of chamber 8 through line 9 and valve I8 to cooling and storage or elsewhere, as desired. This line may also serve, particularly in case the chamber is operated as a coking zone, as a means of introducing water, steam or any other suitable cooling material into the chamber after its operation has been completed and after it has been isolated from the rest of the system, in order to hasten cleaning and facilitate the removal of coke therefrom. When operated for the production of coke, any desired pressure ranging from substantially atmospheric up to a superatmospheric pressure substantially the same as that employed in chamber 5 may be utilized in the coking zone and preferably chamber 8 is, in any case, operated at a sufcient superatmospheric pressure to overcome the friction in the heating coil to which the vaporous products in this zone are supplied and the succeeding equipment, in order to avoid the use of a pump or compressor.

Vaporous products may be removed from the t upper portion of chamber 8 and directed through line I I and valve I2 to further conversion in heating coil I3. Preferably, however, in case chamber 8 is operated as a coking zone, a suitable tar separator, of any well known form, not illustrated, is interposed between chamber 8 and heating coil I3 tar and similar high-coke-forming materials removed from the vapors therein may be returned, by well known means, not shown, to chamber 8 or they may be supplied to heating coil 41 or to chamber 28. Heating coil I3 is supplied with heat from a furnace I4 of suitable form whereby the vaporous pro-ducts passing therethrough are subjected to further conversion under independently controlled heating conditions. The resulting heated products are discharged from heating coil I3 through line I5 and valve I6, preferably passing, as in the case here illustrated, through heat exchanger I1 wherein they are cooled appreciably by indirect heat exchange with hydrocarbon oil charging stock for the process, the partially cooled products passing from heat exchanger I'I through line I8 and valve I9 into vaporizing and separating chamber 28.

Charging stock for the process, which preferably comprises a hydrocarbon oil of relatively wide boiling range, specifically including crude petroleum or other oil containing a substantial proportion of materials within the boiling range of motor fuel but of poor antiknock value, but which may comprise any desired type of oil, is supplied through line 2l and valve 22 to pump 23 by means of which it is fed through line 24 and valve 25 into heat exchanger I1, wherein it serves to partially cool the hot conversion products passing through this zone, as previously described, and is heated sufficiently to effect substantial vaporization thereof in distilling and fractionating column 28 to which the heated charging stock is supplied' from heat exchanger I1 through line 26 and valve 21.

It will, of course, be understood that any other means of cooling the stream of hot conversion products from heating coil I3 sufficiently to prevent any substantial further conversion thereof may be utilized either alone or in conjunction with heat exchanger I1. One such additional means is illustrated in the drawing and will be later described. It is also Within the scope of the invention to utilize any other suitable means, not illustrated, of heating the charging stock for the purpose of effecting vaporization and fractional distillation thereof either alone or in conjunction with heat exchanger I1.

The charging stock is separated by vaporization and fractional distillation in column 28 into selected relatively low-boiling and high-boiling components. The low-boiling fractions, which include any motor fuel components of the charging stock and may also include any desired higher boiling components such as naphtha, kerosene or kerosene distillate, gas oil and the like, are withdrawn as fractionated vapors from the upper portion of column 28 through line 29 and may be directed through valve 38 in this line into chamber 8 or may be supplied directly to heating coil I3 for further conversion by means of line 3I, valve 32 and line I I. The higher boiling components of the charging stock which remain unvaporized or are condensed as reflux condensate in column 28 are Withdrawn from the lower portion of this zone through line 33 and Valve 34 to pump 35 by means of which they are directed through line 36 and 31 into vaporizing and separating chamber 28. In the particular case here illustrated the high-boiling components of the charging stock from column 28 commingle in line I8 with the stream of partially cooled conversion products from heat exchanger I1, serving to eiect additional cooling thereof, prior to the introduction of the commingled materials into chamber 28.

Chamber 28 serves as a zone wherein separation of the vaporous and liquid components of the materials supplied thereto is accomplished and may be operated at substantially the same or at a lower pressure than that employed at the outlet from heating coil I3. The non-vaporous liquids are removed from the lower portion of chamber 28 through line 38 and may be withdrawn, all or in part, through line 39 and valve 48 to cooling and storage or elsewhere, as desired, or they may be directed, all or in part, through valve 4I in line 38 to pump 42 by means of which they are directed through line 43 and may pass either through valve 44 in this line direct to chamber 8 or they may rst pass through heating coil 41 by means of lines 45 and 48 controlled by the respective valves 46 and 49.

When chamber 8 is operated for the production of coke the relatively heavy oils from chamber 28 are preferably passed through heating coil 41, prior to their introduction into the coking zone, and the conditions of temperature, pressure and time employed in heating coil 41 are preferably such as to quickly heat the relatively heavy oils to a conversion temperature sufliciently high to effect their subsequent reduction to coke in chamber 8 Without allowing them to remain in the heating coil and communicating lines for a sufficient length of time to permit any appreciable formation and deposition of coke therein. A

furnace- Sllof suitablefornrsuppliesathefrequired heatito heatingzcoil 4T.

Vaporous products are-Withdrawn fromthe upper portion of chamber 20 and directed through line 5| and valve 52 to fractionation .in fractionator 53 wherein their componentsboiling above the range. of the desired Vfinal motor fuel product of the process are condensed as reflux condensate. The reflux condensate. formedl in fractionator 53 is withdrawn fromthe lower portion thereof through line 54 and Valve 55 to pump 56 by means ofwhich itis returned through line 51 and valve` 58to `conversion in heating coil l, in the manner previously described.

Fractionated vapors of the desired end-boiling pointare withdrawn, together withuncondensable gas produced by the operation, from the upper portion of fractionator 53- and directed through line 59 and Valve 60 to condensation and cooling in condenserV 6|. The resulting distillate and gas passes through line 621- and valve 63 toy collection and separation in receiver 64. Uncondensed gases may be released from the receiver through line 65 and valve 66. Distillate may be withdrawn from receiver 64 through line 61 and valve 6B to storage or to any desired further treatment. When desired, regulated quantities of the distillate collected in receiver 64 may be recirculated by well known means, not illustrated in the drawing, into the upper portion of fractionator 53 to serve as a refluxing and cooling medium in this zone for assisting fractionation of the vapors and to maintain the desired vapor outlet temperature therefrom.

The preferred range of operating conditions which may be employed to accomplish the objects of the invention, in an apparatus such as illustrated and above described, may be approximately as follows: The heating coil to which the reflux condensate is supplied may utilize an outlet conversion temperature ranging, for example, from 850 to 950 F., or more, preferably with a superatmospheric pressure at this point in the system of from to 500 pounds, or thereabouts, per square inch. Substantially the same or somewhat lower pressure may be employed in the reaction chamber and the vaporizing or coking chamber may be operated at any desired pressure ranging from 50 pounds, or thereabouts, per square inch, superatmospheric pressure, up to substantially the same pressure as that employed in the reaction chamber. The heating coil to which the vaporous products from the Vaporizing or coking chamber and the low-boiling fractions of the charging stock are supplied may utilize an outlet conversion temperature of from 900 to 1100 F., for example, and the pressure employed in this zone preferably is substantially the same as that employed in the vaporizing or coking chamber. The vaporizing and separating chamber succeeding the vapor heating coil may employe a pressure substantially the same or somewhat lower than that employed in said heating coil and this pressure may be either substantially equalized or somewhat reduced in the succeeding fractionating, condensing and collecting portions of the system. The distilling and fractionating column to which the charging stock is supplied preferably employs a somewhat higher pressure than that utilized in the Vaporizing or coking chamber and the temperature to which the charging stock is heated for effecting fractional distillation thereof may range, depending upon its characteristics and the pressure employed in the distilling and fractionating column,

from 450`to-750'F.`, or more.L When a heating coil is employed for the heavy liquids supplied from the vaporizing andseparating chamber to the coking` chamber the temperature employed at the outlet-from this zone` may range, for example, from 800 to 10004 F. and the pressure employed vat this point in the system. is preferably of the order of 30 to 150 pounds per square inch, superatmospheric, although higher or lower pressures may be employed, when desired.

As a specific example of the operation of the process of the invention employing as charging stock a California crude of about 30 A. P. I. gravity containing approximately 26 per cent of straight-run gasolineboiling up to 400 F. which is of poor anti-knock value, the charging stock is subjected to fractional distillation, in the manner illustrated and above described, whereby its components boiling above and below approximately 600 F. are separated. The low-boiling components are supplied` together with vaporous products from the coking chamber of the system, to the vapor heating coil and its high-boiling components are commingled with the heated products supplied from this zone to the Vaporizing and separating chamber. The reflux condensate from the fractionator of the system is subjected in the heating coil to which it is supplied to an outlet conversion temperature of approximately 935 F. at a superatmospheric pressure of about 350 pounds per square inch which pressure is substantially equalized in the succeeding reaction chamber. The coking chamber to which vaporous and liquid products from the reaction chamber are supplied is operated at a superatmospheric pressure of approximately pounds per square inch. The heating coil to which the vaporous products from the coking chamber and the low-boiling components of the charging stock are supplied is operated at a temperature of approximately 950 F. and the pressure in this zone is substantially equalized with that in the coking chamber. The succeeding vaporizing and separting chamber is operated at a superatmospheric pressure of about 50 pounds per square inch which pressure is substantially equalized in the succeeding fractionating, condensing and collecting portions of the system. The heating coil to which the heavy liquids supplied from the vaporizing and separating chamber to the coking chamber are passed employs an outlet conversion temperature of approximately 1000o F. and a superatmospheric pressure of about 150 pounds per square inch. This operation will produce, per barrel of charging stock, approximately 68 per cent of motor fuel having an octane number of approximately 72 by the motor method and about 60 pounds of low volatile coke suitable as domestic fuel, the remainder being chargeable, principally, to uncondensable gas.

I claim as my invention:

l. In a process for the conversion of hydrocarbon oils wherein intermediate liquid conversion products of the process are subjected to conversion conditions of cracking temperature and superatmospheric pressure in a heating coil and communicating reaction chamber and the resulting vaporous and liquid conversion products introduced into a separate enlarged chamber wherein their vaporous and non-vaporous components separate, the improvement which comprises removing vaporous products from said separate enlarged chamber, subjecting the same to continued conversion under independently controlled heating conditions in a separate heating coil,

cooling the resulting heated products su'iciently to prevent any substantial further conversion thereof and introducing the same into a Vaporizing and separating chamber wherein their vaporous and residual liquid components separate, subjecting charging stock for the process, comprising a hydrocarbon oil of relatively wide boiling range, to fractional distillation whereby it is separated into selected relatively low-boiling and highboiling fractions, supplying said low-boiling fractions of the charging stock to said separate heating coil for conversion, introducing said highboiling fractions of the charging stock into the vaporizing and separating chamber, withdrawing non-vaporous residual liquids from the Vaporizing and separating chamber, subjecting vaporous products separately removed from the vaporizing and separating chamber to fractionation for the formation of said intermediate liquid products which are returned to the first mentioned heating coil for said conversion, subjecting fractionated vapors of the desired end-boiling point to condensation and recoveringthe resulting distillate.

2. A process such as claimed in claim 1 wherein the non-vaporous residual liquids withdrawn from the vaporizing and separating chamber are returned in regulated quantities to said separate enlarged chamber from which liquid residue is recovered.

3. A process such as claimed in claim 1 wherein regulated quantities of the non-vaporous residual liquid Withdrawn from the Vaporizing and separating chamber are heated to a high conversion temperature under non-coking conditions in a separate heating coil and introduced into said separate enlarged chamber wherein they are reduced, together with residual liquids supplied to this zone from the reaction chamber, to substantially dry coke.

4. A process such as claimed in claim 1 wherein at least a substantial portion of the heat required for said fractional distillation of the charging stock is recovered by passing the same in indirect heat exchange with the heated products from said separate heating coil, whereby partial cooling of said heated products is accomplished.

KENNETH SWARTWOOD.

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