US2206135A - Conversion of hydrocarbon oils - Google Patents

Description

y 2, 1940- K. SWARTWOOD 2,205,135 I CONVERSION OF HYDROCARBON OILS Original Filed Oct. 5, 1935 FRACTIONATOR REA GTION CHAMBER VA POR 3 EPA RATOR FURNACE l8 FRACTIONATOR FURNACE 6| INVENTCR KENNETH I w TOOD Patented July 2, 1940 UNITED STATES CONVERSION OF HYDROCARBON OI LS Kenneth Swartwood, Chicago, 111., assignor to Universal Oil Products Company, Chicago, 111., a corporation of Delaware Application October 5, 1935, Serial No. 43,665 Renewed January 27, 1939 1 Claim.

This invention particularly refers to animproved process for the fractional distillation of hydrocarbon oils of relatively wide boiling range, comprising the charging stock for the system, ac-

companied by conversion of relatively low-boiling {15 intermediate conversion products of the process subjected to further conversion within the same system.

In one embodiment, the invention comprises 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 high-boiling fractions, subjecting the highboiling fractions to conversion conditions of cracking temperature and superatmospheric .pressure in a heating coil and communicating reaction chamber, separating the resulting vaporous and liquid conversion products. and subjecting the latter to further vaporization in the reduced pressure vaporizing chamber, withdrawing nonvaporous residual liquid from the vaporizing chamber and introducing the same into a coking chamber wherein it is reduced to substantially dry coke, subjecting vaporous products from the 35 vaporizing chamber to fractionation whereby their insufficiently converted components are condensed as reflux condensate, returning the reflux condensate to said heating coil for further conversion, subjecting vaporous products of the desired end-boiling point resulting from the last mentioned fractionating step to condensation, recovering the resulting distillate, subjecting said selected low-boiling fractions of the charging stock to independently controlled conditions of relatively higher cracking temperature at superatmospheric pressure in a separate heating coil, introducing the resulting highly heated products into the coking chamber wherein they commingle with and assist coking of the residual liquidsupplied thereto, commingling vaporous products from the coking chamber with the charging stock undergoing said fractional distillation, subjecting the resulting fractionated vapors comprising low-end point motor fuel of good antiknock value to condensation and recovering the resulting distillate. i As a modification of the specific embodiment of the invention above outlined, the reflux condensate formed by said fractionation of the vaporous products from the reduced pressure vaporizing chamber may be separated into selected relatively low-boiling and high-boiling fractions, the high-boiling fractions returned for further conversion to the same heating coil to which said high-boiling fractions of the'charging stock are supplied and the selected lower boiling fractions subjected to independently controlled conditions of relatively higher cracking temperature at superatmospheric pressure in a separate heating coil, the highly heated products from which are introduced into the reaction chamber together with the products from the first mentioned heat ing coil.

The cooperative nature and advantages of the various features of the present invention will be apparent to those familiar'with the cracking art. The selected low-boiling fractions of the charging stock normally contain highboiling motor fuel fractions of poor antiknock value including, frequently somewhat higher boiling materials such as heavy naphtha fractions, kerosene, kerosene distillate and the like. When such relatively lowboiling oils are subjected to conversion for the production of high yields of good quality motor fuel there is ordinarily a large amount of excess heat in the resulting products which, in accordance with the best present day practice, is dissipated in order to prevent excessive further conversion thereof. In the present invention'i'nstead of being cooled in the usual manner (by indirect heat exchange with cooler oil and/or the introduction of a cooling medium) this excess heat is utilized to effect coking of the residual liquid conversion products of the process'by being in-, 40 troduced into direct contact with thematerials undergoing coking in the coking chamber. Another feature of the'invention which is cooperative with the feature above outlined resides in the use of the hot vaporous products from the coking zone'for effecting fractional distillation of the charging stock whereby the charging stock is separated into the selected relatively low-boiling and high-boiling fractions desired for selective conversion while, at the same time, the charging stock serves as a cooling and refluxing medium for assisting fractionation of the hot vaporous products from the coking zone whereby their insufi'iciently converted components are condensed and also separated into corresponding selected relatively low-boiling and high-boiling fractions which commingle with the corresponding selected fractions of the charging stock and are subjected to further conversion therewith.

Further features and advantages of the present 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 present invention and in which the process of the invention may be accomplished.

Referring to the drawing, hydrocarbon oil charging stock for the process, preferably comprising an oil of relatively wide boiling range, although any desired type of charging stock which does not contain any substantial quantity of lowboiling motor fuel fractions of poor antiknock value or of high-boiling residual materials of a high coke-forming nature, is supplied through line and valve 2 to pump 3 by means of which it is introduced through line 4 and valve 5 into fractionator 5 wherein it is subjected to fractional distillation by means of heat recovered from the hot vaporous products from the coking stage of the system, as will be later more fully described.

The charging stock is separated by said fractional distillation in column 6 into selected relatively low-boiling and high-boiling fractions. The high-boiling fractions are removed from the lower portion of column 6 through line I and valve 8 to pump 9 by means of which they are fed through line Ill and may be directed, all or in part, through valve II in this line and thence through line l2 to conversion in heating coil M or they may be directed, all or in part, from line I through line l and valve l6 into fractionator I"! wherein theycommingle with and assist fractionation of the vaporous conversion products supplied to this zone.

The oil supplied to heating coil I4 is subjectet therein to the desired conversion temperature, preferably at a substantial superatmospheric pressure, by means of heat supplied from a furnace l8 of any suitable form and the heated products are discharged through line |9 and valve into reaction chamber 2|.

Chamber 2| is also preferably maintained at a substantial superatmospheric pressure which may be substantially the same or somewhat lower than that employed at the outlet from the heating coil. Chamber 2| is also preferably insulated in order to prevent the excessive loss of heat therefrom by radiation so that the heated produc'ts supplied to this zone and particularly their vaporous components are subjected to further conversion therein. In the particular case here illustrated both vaporous and liquid conversion products are withdrawn from the lower portion of chamber 2| through line 22 and valve 23 and are introduced into reduced pressure vaporizing chamber 24. It is, however, entirely within the scope of the invention to effect partial or substantially complete separation of vaporous and liquid conversion products in chamber 2 l, in which case the liquid conversion products, either alone or together with a regulated portion of the vapors, may be supplied to chamber 24, in the manner described, while substantially all or the remaining portion of the vaporous conversion products are separately removed from any suitable point in chamber 2| above the point of removal of the liquid conversion products and may be separately supplied, all or in part, to chamber 24 at any desired point in this zone or they may be directed, all or in part, to fractionation in fractionator H. The well known means for accomplishing this alternative method of operation are, for the sake of simplicity, omitted from the drawing.

Chamber 24 is operated at a substantially reduced pressure relative to that employed in reaction chamber 2| by means of which appreciable further vaporization of the liquid conversion products supplied to this zone is accomplished. The residual liquid remaining unvaporized in chamber 24 is withdrawn from the lower portion of this zone through line 25 and valve 26 to pump 2'! by means of which it is supplied through line 28 and valve 29 to coking chamber 30 wherein it is reduced to substantially dry coke, as will be later more fully described. Pump 21 may, of course, be eliminated or by-passed in case a substantially higher pressure is employed in chamber 24 than in the coking chamber.

vaporous conversion products are withdrawn from the upper portion of chamber 24 and directed through line 3| and valve 32 to fractionation in fractionator either alone or together with vaporous conversion products separately supplied to this zone from chamber 2|, in the manner previously indicated. The components of the vapors supplied to fractionatorl'l boiling above the range of the desired motor fuel prodnot of this stage of the system are condensed in this zone as reflux condensate. The total reflux condensate may be removed from the lower portion of fractionator I! through line 33 and valve 34 to pump 35 by means of which it is returned through line l2 and valve |3 to further conversion in heating coil H or, as an alternative method of operation, the reflux condensate formed in fractionator I'l may be separated into selected relatively low-boiling and high-boiling fractions which are separately subjected to independently controlled conversion conditions. In case the latter method of operation is employed,

the high-boiling fractions of the reflux condena sate recovered from the lower portion of the fractionator may be returned, as previously described, to heating coil l4 while the selectedlower boiling fractions are separately removed from one or a plurality of suitable intermediate points in the fractionator to be directed through line 36 and valve 31 to pump 38 by means of which they are supplied through line 39 and valve 40 to heating coil 4| for further conversion.

The relatively low-boiling reflux condensate supplied to heating coil 4| is subjected therein to the desired independently controlled conversion conditions of cracking temperature and superatmospheric pressure by means of heat supplied from a furnace 42 of any suitable form and the highly heated products are discharged through line 43 and valve 44 into reaction chamber 2|, wherein they are subjected to continued conversion together with the heated products from heating coil l4.

Fractionated vapors of the desired end-boiling point, preferably comprising motor fuel of good anti-knock value, are withdrawn, together with uncondensable gas produced by the cracking operation, from the upper portion of fractionator H and are directed through line 45 and valve 46 to condensation and cooling in condenser 41. The resulting distillate and gas passes through line 48 and valve 49 to collection and separation in receiver 50. Uncondensable gas may be released from receiver 50 through line 5| and valve 52. Distillate may be withdrawn from receiver 50 through line 53 and valve 54 to storage or elsewhere, as desired. Then desired, a regulated portion of-the distillate collected in receiver 50 may be recirculated by well known means, not shown in the drawing, to the upper portion of fractionator IT to serve as a cooling and refluxing medium in this zone for assisting fractionation of the vapors and to maintain the desired vapor outlettemperature from the fractionator.

The selected low-boiling fractions of the charging stock, preferably containing any high-boiling motor fuel fractions thereof of poor antiknock value as well as, when desired, somewhat higher boiling materials such as heavy naphtha fractions, kerosene, kerosene distillate and the like, are removed from one or a plurality of suitable intermediate points in fractionator B and are directed through line 55 and valve 56 to pump 57, by means of which they are supplied through line 58 and valve 59 to heating coil 60, wherein they are subjected to independently controlled conversion conditions of cracking temperature and superatmospheric pressure suitable for reforming the high-boiling motor fuel fractions to produce therefrom high yields of good antiknock motor fuel and suitable for converting any higher boiling components of the oil supplied to this zone to produce high yields of good quality motor fuel.

A furnace 6! of any suitable form supplies the required heat to the oil passing through heating coil 60 to subject the same to the desired conversion conditions and the highly heated products are discharged from the heating coil through line 62 and valve 63 into coking chamber 30. The hot conversion products supplied to the coking chamberv are preferably directly commingled in this zone with the materials undergoing coking, whereby to furnish heat thereto for efiecting their reduction to coke, and, although only one point of introduction is shown in the drawing, the hot conversion products from heating coil 60 may be supplied to the coking chamber at'a plurality of points or the point of introduction may be varied to suit requirements as coke accumulates within the chamber.

Coking chamber 30 is preferably operated at substantially atmospheric or a relatively low superatmospheric pressure although, when desired,

superatmospheric pressures up to 150 pounds or more per square inch may be employed in this zone. lowed to accumulate in this zone to be removed therefrom in any well known manner, not illustrated, after the chamber has been substantially filled or after its operation is completed. Chamber 3E3 is provided with a suitable drain-line 64 controlled by valve 65 which may also serve as a means of introducing steam, water or any other suitable cooling medium 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 cooling and facilitate the removal of coke. It will be understood, of course, that although only one coking chamber is illustrated in the drawing, any desired number of a plurality of such zones may be employed and, when a plurality is employed, the chambers preferably are alternately operated, cleaned and prepared for further operation in order that the coking stage, in common with the rest of the system, may be operated continuously.

Vaporous conversion products are withdrawn from the upper portion of the chamber through line 66 and are directed through valve 6'! into The coke produced in chamber 30 is al-' fractionator 6,'wherein they commingle with and supply to the charging stock the heat required for its fractional distillation. The vaporous conversion products from the coking chamber are also subjected to fractionationin fractionator 6 and their insufficiently converted components, which are condensed as reflux condensate in this zone, are separated, together with the charging stock,

into selected relatively low-boiling and highboiling fractions which are subjected to the conditions of further treatment already described.

Fractionated vapors of the desired end-boiling point, preferably comprising low-boilingmotor fuel fractions of good antiknock value, are withdrawn together with uncondensable gas from the upper portion of fractionator 6 and are directed through line 68 and valve 69 to condensationand cooling in condenser 10. The resulting distillate and gas passes through line H and valve 12 to collection and separation in receiver 13. Uncondensable gas may be released from the receiver through line 14 and valve 15. Distillate may be withdrawn from receiver 13 through line 16 and valve 11 to storage or to any desired further treatment and this material may, when desired, be commingled with the distillate withdrawn from receiver 50, the commingled distillates forming the-final motor fuel product of the process, in which case either or both of the separately recovered distillates from receiver 50 and receiver may be separately subjected to independently controlled conditions of treatment for the purpose of improving their quality with respect to gum and sulfur content, vapor pressure, etc.

The preferred range of operating conditions which may be employed to accomplish the objects of the present invention in an apparatus such. as illustrated and above described may be approximately as follows: The heating coil to which the high-boiling fractions of the charging stock and the total or high-boiling fractions of the reflux condensate from the fractionator of the cracking stage are supplied may range, for example, from 850 to 950 F., preferably witha superatmospheric pressure at this point in the system of from I 100 to 500 pounds, or more, per square inch. A superatmospheric pressure within substantially the same range is preferred in the reaction chamber and, when a separate heating coil is employed for conversion of selected low-boiling fractions of the reflux condensate from the fractionator of the cracking stage, the conversion temperature employed at the outlet therefrom may range, for example, from 900 to 1000 F., preferably with a superatmospheric pressure measured at the outlet from the heating coil of from 200 to 800 pounds, or more, per square inch. The vaporizing chamber, as previously mentioned, is preferably operated at a substantially reduced pressure relative to that employed in the reaction chamber ranging, for example, from 100 pounds, or thereabouts, per square inch down to substantially atmospheric pressure. The pressure employed in the vaporizing chamber may be substantially equalized or reduced in the succeeding fractionating, condensing and collecting equipment of this stage of the system. The heating coil to which the selected low-boiling fractions of the charging stock and the corresponding fractions of the reflux condensate recovered from the vaporous products from the coking zone are supplied may employ an outlet conversion temperature ranging, for example, from 950 to 1100 F., preferably with a superatmospheric pressure of from 300 to 1000'pounds, or thereabouts, per square inch, at the outlet from this zone although, when desired, and particular- 1y with the higher conversion temperatures, pressures down to substantially atmospheric may be employed in this zone. The coking chamber may be operated at any desired pressure ranging from substantially atmospheric up to substantially the same as that employed in the communicating light oil heating coil, the preferred range being from 25 to 75 pounds, or thereabouts, per square inch. The fractionating, condensing and collecting equipment of the coking stage of the system may be operated at substantially the same or at lower pressure than that employed in the coking chamber.

As a specific example of one of the many possible operations of the process of the present invention as it may be accomplished in an apparatus of the character illustrated and above described, the charging stock is a crude oil of about 2G.6 'A. P. I. gravity having an initial boiling point of approximately 176 F. and containing approximately 5 per cent of material boiling up to 274 F. and about 10 per cent at 335 F. The charging stock is subjected to fractional distillation in the fractionator of the coking stage of the system wherefrom a motor fuel of about 300 F. end-boiling point is recovered and Wherein the higher boiling components of the charging stock and vaporous products from the coking chamber are condensed and separated into fractions boiling above and below approximately 550 F. The high-boiling fractions of the charging stock are subjected, together with reflux condensate from the fractionator of the cracking stage, to a conversion temperature, measured at the outlet from the heating coil to which these materials are supplied, of approximately 940 F. at a superatmospheric pressure of about 350 pounds per square inch. This pressure is substantially equalized in the reaction chamber and is reduced in the vaporizing chamber to approximately 50 pounds per square inch. The vaporous products from the vaporizing chamber are supplied to the fractionator of this stage of the system wherefrom a motor fuel of approximately 400 F. end-boiling point is recovered. The selected low-boiling fractions from the fractionator of the coking stage are subjected in a separate heating coil to an outlet conversion temperature of approximately 970 F. at a superatmospheric pressure of about 750 pounds per square inch and the resulting highly heated products are introduced into the coking chamber which is maintained at a superatmospheric pressure of approximately 30 pounds per square inch. This operation Willproduce, per barrel of charging stock, approximately 62 per cent of motor fuel comprising a blend of the low end-point and higher endpoint motor fuel products of the process having an octane number of approximately '72 by the motor method, and approximately '15 pounds of low volatile coke of uniform quality and good structural strength, the remainder being chargeable, principally, to uncondensable gas.

I claim as my invention:

A conversion process which comprises subjecting hydrocarbon oil to cracking conditions of temperature and pressure in a heating zone and separating resultant vapors from unvaporized oil in a separating zone, removing the unvaporized oil from the separating zone and distilling the same in a distilling zone, removing vapors from said distilling zone and fractionating the same together with charging oil for the process and independently of the first-named vapors, removing from the last named fractionating stage relatively heavy and light liquid fractions and a gasoline vapor fractionating the first-named vapors in contact with the heavy liquid fraction from said fractionating stage, thereby combining reflux condensate with said heavy fraction, supplying the resultant mixture to said heating zone, subjecting the lighter liquid fraction from said fractionating stage to independently controlled cracking conditions of temperature and pressure in a second heating zone and discharging resultant heated products into the distilling zone to assist the distillation of said unvaporized oil therein, and finally condensing and collecting said gasoline vapor.

KENNETH SWARTWOOD.

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