US2079168A - Conversion of hydrocarbon oils - Google Patents

Description

May 4, 1937. J. B. HElD CONVERSION 0F HYDROCARBON OILS Filed June 7, 1934 (oke fila??? M, m, m4@

`30 resulting vaporous and liquid PatentedMay 4,VA 1937Y UNITED STATES PATENT ortis 2,079,168 CONVERSION OF HYDROCARBON OILS Jacob Benjamin Heid, Chicago,

Ill., assigner to Universal Oil Products Company, Chicago, Ill., a corporation of Delaware Y This invention particularly refers to am improved process for the pyrolytic conversion of hydrocarbon oils accompanied by reduction of the residualliquid conversion products to coke.

. More specifically the invention embodies a selective cracking operation wherein hydrocarbon oil charging stock for the process, preferably of a relatively high-boiling nature, and selected low-boiling fractions of the reflux condensate (intermediate products recovered by fractionation of the vaporous conversion products) are subjected to independently controlled conversion conditions and wherein residual liquid resulting from conversion of the charging stock is subjected to coling and high-boiling fractions of the reflux condensate subjected to further conversion without being passed through a heating coil; the highly heated products resulting from conversion of the selected low-boiling fractions of the reflux condensate serving as a heat `carrying medium for coking of the residue and conversion of the high-boiling fractions of the reflux condensate.

In one specific embodiment, the invention comprises subjecting a hydrocarbon oil charging stock of relatively high-boiling characteristics to conversion conditions of elevated temperature and superatmospheric pressure in a heating coil and communicating reaction chamber, separating the conversion products, subjecting the vapors to fractionation `whereby 'their insumciently converted components are condensed as reflux condensate, subjecting fractionated vapors of the desired end boiling point to condensation, recovering the resulting distillate, separating the reflux condensate into selected relatively low-boiling and highboiling fractions, subjecting the low-boiling frac- Ytions to independently controlled conversion con- 40 ditions of elevated temperature and superatmospheric pressure in a separate heating coil, intro- I ducing the4 resulting products into a coking chamber, commingling the aforementioned residual liquid and the high-boiling fractions of the reflux condensate with the `heated products supplied from said separate heating coil to the coking chamber, for the purpose of effecting further `conversion of the high-boiling reflux condensate and reducing the residue to coke, and subjecting vaporous products from the coking zone to said fractionation.

The featuresv of the present invention and their advantages will be more apparent with reference to the accompanying diagrammatic drawingand the following descriptionthereof.

in chamber The drawing illustrates one specific form of apparatus in which the process of the present invention maybe accomplished.

Referring to the drawing, hydrocarbon Voil charging stock for ,the process, which may be any desired type of oil but preferably comprises an oil ofrelatively high-boiling characteristics such as, for example, crude petroleum, topped crude, fuel oil, gas oil and, in general, heavy distillates and residual oils may be supplied through line l and valve 2 to pump 3 wherefrom it may be directed through line 4 and valve 5 to heating coil 6. The charging stock may, of course, be preheated in any suitable well known manner, not illustrated, prior to its introduction into the heating coil such as, for example, by indirect contact and heat exchange with hot vaporous and/or liquid products of the process.

A furnace' 'l of any suitable form supplies the required heat to the oil passing through heating coil 6 to bring it to the desired temperature, preferably at a substantial superatmospheric pressure, and the stream of heated oil is discharged fromthe heating coil through line 8 and valve 9 into reaction chamber I0.

Chamber I0 is also preferably maintained at a substantial superatmospheric pressure, which may be the same n orrsomewhat lower' than that vemployed at the outlet from the heating coil and,

although not indicated in the drawing, the reaction chamber is preferably insulated to prevent the excessive loss of heat so that conversion of the heated products supplied to this Zone from heating coil 6 may continue therein. Separation of vaporous and residual ucts is accomplished, in the case here illustrated, l0. The residual liquid is withdrawn from the lower portion of this zone through line II and valve I2 and is subjected to coking, as will be laterA more fully described, while the vaporous conversion products pass from the upper portion of the reaction chamber through line I3 and valve lll toffractionation in fractionator l5.

The vaporous products from the coking operation are also'supplied to fractionator l5, in the case here illustrated, as will be later more fully described, and the components of the total vaporous products supplied to this zone boiling above the range of the desired final light distillate prodp uct of the process are condensed as reflux condensate. Fractionated vapors of the desired endboiling point are withdrawn, together with uncondensable gas produced by the operation, from the upper portion of fractionator l5 through line I6 and valve I'l and are subjected to condensaliquid conversion prod- 3 tion and cooling in condenser I8. The resulting distillate and gas passes through line I9 and valve 20 to collection and separation in receiver 2I. Uncondensable gas may be released from the receiver through line 22 and valve 23. The distillate may be withdrawn from receiver 2 I through line 24 and valve 25 to storage or to any desired further treatment. When desired, a regulated portion of the distillate collected in receiver 2I may be recirculated, by Well known means, not

shown in the drawing, to the upper portion of fractionator I5 to serve as a reuxing and cooling medium to assist fractionation of the vapors and maintain the desired vapor outlet temperature from the fractionator.

The reflux condensate formed in fractionator I5 is separated into selected relatively low-boiling and high-boiling fractions. The `former may be withdrawn from any suitable intermediate point or plurality of points in the fractionatorr passing, for example, through line 26 and valve `2I tozpump 28 by means of which they .are supplied through line 29 and valve 30 to furtherconversion in heating coil 3l.

Heating coil 3| is located in a furnace 32 of any suitable form by means-of which the oil supplied to the heating coil is brought to the desired conversion temperature, preferably at a substantial superatmospheric pressure. Preferably the relatively low-boiling oil supplied to heating lcoil 3l is subjected therein to more severe conversion conditions than the charging stock supplied to heating coil 5. The highly heated products from heating coil 3| are discharged-therefrom through line 33 and valve 34 and are introduced into coking chamber 35, entering this zone at any desired point or plurality of points such as, for example, through valve 36 in line 33 into the lower yportion of the coking chamber or from -line 33 through line 31, valve 38, line 39 and valve 40 into the upper portion of the chamber.

High-boiling fractions of the reuxcondensate recovered in fractionator I5 may be withdrawn from the lower portion of this zone through line 4I and valve 42 to pump 43 by means of which they may be directed through line 44 and valve 45 into line 41, commingling therein with residual liquid withdrawn from chamber I0, as previously described, through line II and valve I2 to pump 46 wherefrom it is discharged through line -41 and valve 48. The stream of commingled residual liquid and high-boiling reflux condensate may then be directed into coking chamber 35, entering this zone Yat any desired point or plurality of points, either alone or together lwith the stream of highly heated products supplied to "this zone from heating coil 3|. The drawing indicates provision for supplying the commingled residual liquid and high-boiling reflux condensate to coking chamber 35 through ,line l39 and valve 40 or through line''l, valve 38, line 33 and valve 36. It is also within the scope of the invention to .commingle either the stream of residual liquid from chamber Ill nr the stream -of high-*boiling reflux condensate from fractionator I5 with the stream of highly heated products passing :from :heating coil 3l into cokingfchamber ..35 :and to supply Vthe other stream `direct to Athe coking :chamber :at vany desired point, although :means 'for accomplishing this are not illustratedin the'drawing. Whenth'e stream of residual liquid or the streamof .highboiling reflux condensate, or both, `are commingled Ywith the stream of iheatedproducts from heating Vcoil 3| in line .'33 `they serve to reduce the vtemperature of the `conversion products and retard their further conversion, prior to their introduction into the coking chamber and, in any case, regardless of the method employed for supplying the various materials to the coking chamber, the products from heating coil 3I serve as a heat carrying medium to effect further conversion of the high-boiling reux condensate from fractionator I5 and to effect reduction of the residual materials in chamber 35 to coke.

The coke formed in chamber 35 may be allowed to accumulate in this zone to be removed therefrom, in any suitable manner not illustrated,

after the voperation Aof the chamber is completed and, when desired, a plurality of coking chambers similar to chamber 35, but not illustrated, may be employed and may be simultaneously opy'erated 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 may be continuous. Chamber 35 lis provided lwith a suitable drain-line 49, controlled by valve 50 which may lalso serveas means for introducing steam, water or any other ysuitable cooling medium into -chamber 35, after its .operation has been completed and it has been isolated from the rest of the system, in order to hasten cooling and facilitate lcleaning of the chamber. Vaporous products vare directed from the coking chamber through line 5I, valve 52 and line I3 vto fractionation in fractionator I5, to-

gether with the vaporous conversion products from chamber IIJ. Itis, however,entire1y Within the scope of the present invention, when desired, to separately fractionate the vaporous products from chambers I0 and 35, although .means for rf accomplishing this are not illustrated.

In an apparatus such as illustrated and above described, the preferred range of operating conditions may be approximately as follows: The charging stock may be subjected in the heating coil to which it is supplied, to an outlet conversion temperature ranging, for example, 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 thereabouts, per sq. in. The reaction chamber following the charging stock heating coil may employ substantially the same or somewhat lower Superatmospheric pressure than that employed at the outlet from the heating coil. Conversion conditions more severe than those employed for the charging stock are preferably utilized for conversion of the low-boiling fractions of the reflux condensate, the outlet conversion temperature from the heating coil to which the light reflux condensate is supplied ranging, forexample, from 925 to 1050 F., or thereabouts, preferably with a superatmospheric pressure, measured at the outlet from the heating coil, of from 200 to 800 pounds, or more, per sq. in. 'I'he coking chamber may be operated at any desired pressure ranging from substantially atmospheric up to the pressure employed at the outlet from the light reflux heating coil and may be varied to suit requirements, depending upon the characteristics of the coke desired and upon the nature of the high-boiling reflux condensate supplied to this zone and the degree of conversion to which it is desired to subject the same. The fractionating, condensing and collecting portions of the system may employ pressures substantially the same or somewhat lower than the pressure employed in the coking chamber.

As a specific example of the operation of the process of the present invention as it may be practiced in an apparatus of the character illustrated and above described; the charging stock, comprising a Mid-Continent topped crude of about 25 A. P. I. gravity, is subjected to a conversion temperature, measured at the outlet from the heating coil to which it is supplied, of approximately 900 F. at a superatmospheric pressure of about 275 pounds per sq. in. Substantially lthe same pressure is employed in the succeeding reaction chamber. LoW-boiling fractions of the reflux condensate resulting from fractionation of the vaporous products of the process, which fractions boil below approximately 650 F., are subjected in a separate heating coil to an outlet conversion temperature of approximately 950 F. at a superatmospheric pressure of about 400 pounds per sq. in. The stream of heated products from the light oil heating coil is commingled with residual liquid withdrawn from the reaction chamber and the remaining higher boiling fractions of the reflux condensate, the commingled materials being introduced into a coking chamber which is operated at a superatmospheric pressure of about 150 pounds per sq. in. This operation will produce, per barrel of charging stock, about percent of good quality motor fuel and about pounds of petroleum coke having a volatile content of approximately 7 percent and of substantially uniform quality and good structural strength; the remainder being chargeable, principally, to uncondensable gas.

I claim as my invention:

1. In a process for the conversion of hydrocarbon oils wherein hydrocarbon oil charging stock for the process is subjected to conversion conditions of elevated temperature and superatmospheric pressure in a heating coil and communicating reaction chamber, the resulting vaporous conversion products and the residual liquid separated, the vapors subjected to fractionation, whereby their insufficiently converted components are condensed as reflux condensate, fractionated vapors of the desired end-boiling point subjected to condensation and the resulting distillate recovered, the improvement which comprises separating the reflux condensate into selected relatively low-boiling and high-boiling fractions, subjecting the low-boiling fractions to independently controlled conversion conditions of elevated temperature and superatmospheric pressure in a separate heating coil, introducing the resulting products into a coking chamber, commingling said residual liquid and said high-boiling fractions of the reflux condensate with the heated products from said separate heating coil supplied to the coking chamber, the high boilized oil in a separating zone, fractionating the vapors to separate a relatively heavy reflux condensate and a lighter reflux condensate therefrom, passing the lighter reflux condensate through a second heating zone and heating the same therein to higher cracking temperature n than the oil in the first-named heating zone, removing said unvaporized oil from the separating zone and introducing the same to a reduced pressure coking zone, also introducing said heavy reflux condensate, without prior substantial cracking thereof, into the coking zone, discharging heated products from the second heating zone into the coking zone and therein distilling the unvaporized oil and heavy reflux condensate to coke by the heat of said products, combining vapors thus formed in the coking zone with the first-named vapors for fractionation in admixture with the latter, and finally condensing the fractionated vapors.

JACOB BENJAMIN HEID.

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