US2105561A - Conversion of hydrocarbon oils - Google Patents

Description

' Jan. 18, 1938. K. SWARTWOOD 2,105,561

CONVERSION OF HYDROCARBON OILS v Fiipd June 29, 1936 DISTILLING AND FRACTIONATING F RACTIONKI'OR COLUMN RECEIVER FURNACE 6| |NVENTOR I KENNETH SWARTWOQD ORNEY Patented Jan. 18, 1938 STATES PATENT OFFICE CONVERSION OF HYDROCARBON OILS Application June 29, 1936, Serial No. 87,943

6 Claims.

This invention refers to an improved process and apparatus for the fractional distillation of hydrocarbon oils of relatively wide boiling range accompanied by the selective conversion of rela- .'tively low-boiling and high-boiling fractions of the charging stock and the intermediate conversion products of the process and reduction of the residual liquid conversion products to substantially dry coke.

In one specific 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 said lowboiling fractions to pyrolytic conversion in a heating coil, commingling with the resulting heated products said high-boiling fractions of the charging stock, introducing the commingled materials into a separating chamber wherein separation of vaporous and liquid products is accomplished, subjecting the vapors to fractionation whereby their insufficiently 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 to condensation, collecting and separating the resulting distillate and gas, returning the low-boiling fractions of the reflux condensate to said heating coil for further conversion, subjecting the high-boiling fractions of the reflux condensate to independently controlled conversion conditions of elevated temperature and superatmospheric pressure in a sepa- -n=rate heating coil and communicating enlarged reaction chamber, withdrawing vaporous and liquid conversion products from the reaction chamber in commingled state and introducing the same into a coking zone, withdrawing non-vaporous residual liquid from said separating chamber, heating the same to a conversion temperature at superatmospheric pressure in another separate heating coil under non-coking conditions, introducing the resulting heated oil into either the reaction chamber or the coking zone or, in part, to both and supplying the vaporous products from the coking zone to said first mentioned fractionating step for fractionation together with the charging stock, and recovering from said fractionating step any desirable lowboiling components of the commingled fractionated vapors within the boiling range of motor fuel and of satisfactory antiknock value.

The advantages and the cooperative nature of the various features of the present invention will be apparent to those familiar with the cracking art from the following description of the accompanying diagrammatic drawing. It will be understood, of course, that the various alternative features of the invention are'not equivalent but may be selected to suit requirements in order to render the process more flexible.

Referring to the drawing, which diagrammatically illustrates one specific form of apparatus embodying the features of the invention, hydrocarbon oil charging stock for the process, which may be of any desired type but preferably comprises an oil of relatively wide boiling range, such as crude petroleum, topped crude, or the like, is supplied from any suitable source, not illustrated, through line I and valve 2 to distilling and fractionating column 3 wherein it commingles with vaporous products from the coking stage of the process, supplied to this zone as will be later more fully described, and is thereby subjected to vaporization and fractionation. The commingled materials in column 3 are separated into selected relatively low-boiling and high-boiling fractions. Selected low-boiling fractions, comprising fractionated vapors of the desired end-boiling point and uncondensable gas, are withdrawn from the top of column 3 through line 4 and valve 5 and are subjected to condensation in condenser E. The resulting distillate and. gas passes through line I and valve 8 to collection and separation in receiver 9. Uncondensable gas may be released from the receiver through line It] and valve H. Distillate, preferably comprising or containing materials within the boiling range of motor fuel which are of good antiknock value, may be withdrawn from receiver 9 through line [2 and valve l3 to storage or to any desired further treatment. In case the commingled vapors in column 3 contain no appreciable quantity of motor fuel or motor fuel fractions of good antiknock value the distillate collected in receiver 9 is preferably Withdrawn therefrom through line I4 and valve Hi to pump l6 by means of which it is supplied through line I9 and valve to conversion in heating coil 2 I.

In case a desirable product such as motor fuel or motor fuel fractions of good antiknock value is collected in receiver 9, in the manner previously described, the material supplied to heating coil 2| for further conversion may comprise somewhat higher boiling fractions of the commingled materials in column 3, such as naphtha, kerosene or kerosene distillate, pressure distillate bottoms, light gas oil or the like, which may be withdrawn as a side stream or streams from one or a plurality of suitable intermediate points in column 3,.

In the case here illustrated provision is made for removing a low-boiling side stream from column 3 through line H and valve IE to pump I6 by means of which it may be supplied through line i9 and valve 20 to conversion in heating coil 2 l.

A furnace 22 of any suitable form supplies the required heat to the oil passing through heating coil 2| to subject the same to the desired conversion temperature at any desired pressure ranging from substantially atmospheric to a, high superatmospheric pressure and the resulting products are discharged from -hating coil 2! through line 23 and valve into separating chamber 25.

High-boiling fractions of the commingled materials in column 3 are withdrawn from the lower portion of this zone through line'26 andvalve 2'! to pump 28 by means of which they arefed through line 29 and valve 30 and commingled in line 23 with the stream of heated products from heating coil 2|, serving to cool the heated. products sufii'ciently to prevent'their excessivefurther conversion and being heated sufficiently to effect their appreciable vaporization in chamber Separation of vaporous and liquid products is accomplished in chamber 25 which may be operated at any desired pressure ranging from substantially atmospheric to a high superatmospher ic pressure. When it is desired to effect only further vaporization of the high-boiling fractions from column 3 in chamber 25 the separating chamber is preferably operatedzlat substantially atmospheric or a relativelylow-superatmospheric pressure. When, on the other hand, it is desired to subject the high-boiling fractions from column 3 to mild conversion in chamber 25 by means of the heat recovered frcmthe highly heated products from heating coil 2! chamber 25 may be operated at a substantial superatmospheric pressure, in which casesubstantially the same or somewhat higher pressure is maintained at the outlet from heating coil 2|. Non-vaporous residual liquid products are withdrawn from the lower portion of chamber 25 through line. 3! and valve 32 to pump 33 by means of which they are supplied through line 34 and valve 35 to heating coil as for further treatment, as will be later more fully described. vaporous products are withdrawn from chamber 25 through line 37! and valve 33 and are subjected to fractionation in fractionator 39. v v

The components .of the vaporous products: supplied tofractionator 39 boiling abovethe range of the desired motor fuel product of this'stage of the process are condensed in this zone as reflux condensate. Fractionated vapors of the desired end-boiling point are withdrawn, together with uncondensable gas, from the upper portion of fractionator 39 through line 40 and valve 41 and are subjected-to condensation and cooling in condenser 42. The resulting distillate and gas passes through line 43 and valve 44 to collection and separation in receiver 45. Uncondensable gas may be released from the receiver through line 46 and valve 41; Distillate may be withdrawn from receiver 45 through line 48 and valve 49 to storage or to any desired further treatment. When desired, a regulated portion of the distillate collected in receiver 45 may be recirculated by well known means, not illustrated in the draw-. ing, to the upper portion of fractionator 39 to serve as a cooling and refluxing medium for assisting fractionation of the vapors and to maintain the desired vapor outlet temperature from the fractionator,

The reflux condensate formed in fractionator 39 may be separated by fractional condensation in this zone into selected relatively low-boiling and high-boiling fractions in which case the low boiling fractions may be withdrawn from one or a plurality of suitable intermediate points in the fractionator and, in the case here illustrated, this material is directed through line 59 and valve iii to pump 52 by means of which it is returned through line 53, valve 5 5 and line 19 to further conversion in heating coil 2! together with the low-boiling oil from column 3, supplied to this zone as previously described. The high-boiling fractions of the reflux condensate formed in fractionatcr 39 or the total reflux condensate, in case its separation into low-boiling and highboiling fractions is not accomplished in the fractionator, are withdrawn from the lower portion of this zone through line 55 and valve 56 to pump 51 by means of which this material is fed through line 58 and valve 59 to further conversion in heating coil E9.

Heating coil 68 is located within a furnace 61 of any suitable form by means of which the required heat is supplied to the oil passing through this zone to subject the same to the desired conversion temperature preferably at a substantial superatmospheric pressure and the stream of heated products is discharged from the heating coil through line 62 and valve 53 into reaction chamber 54.

Chamber is aiso preferably maintained at a substantial superatrncspheric pressure and, although not indicated in the drawing, this zone is preferably insulated in order to prevent the excessive loss of heat therefrom by radiation so that conversion of the heated products supplied thereto, and particularly their vaporous components, may continue in this zone. In the particular case here illustrated, both vaporous and liquid conversion products are withdrawn in commingled state from the lower portion of chamber 64 through line 65 and valve 56 and are discharged into coking chambers 6i and 51' through the respective lines 58 and E33 controlled, respectively by valves 69 and 58'.

The residual liquid products from chamber 25 supplied, as previously described, to heating coil 36 are subjected to additional heating in this zone by means of heat supplied from a furnace 10 of any suitable form and the heated products are discharged therefrom through line H, being directed either through line '52 and valve 13 into reaction chamber 54 or through line is and valve l5 into coking chambers E? and 5? through the respective lines it; and 76' controlled respectively by valves ii and if, or the heated products from heating coil as may be directed, in part, to both the reaction chamber and the coking zone.

The conditions of treatment afforded the residual liquid products from chamber 25 in heating coil 36 will depend upon the nature of this material, particularly with respect to its cokeforming tendencies. In case the residual liquid is capable of withstanding appreciable additional conversion without excessive coke formation this may be accomplished in heating coil 3% and reaction chamber 5'3. When, on the other hand, the residual liquid is of such nature that it will not withstand appreciable additional conversion without substantial coke formation the heat transfer conditions in heating coil 36 and the velocity of the oil passing through this zone is such that the oil may be quickly heated-to a high conversion temperature in this zone without allowing it to remain in the heating coil and communicating lines for a sufficient length of time to permit the excessive formation and deposition of coke in this zone, in which latter case the heated oil is preferably discharged into the coking chambers instead of into the reaction chamber. It is also within the scope of the invention to employ a relatively mild temperature in heating coil 36 below the cracking range or at least below the temperature at which any appreciable formation and deposition of coke will occur in this zone, in which case the heated oil from heating coil 36 may be discharged either into the reaction chamber or the coking chambers, the method of treatment being selected to suit the particular requirements.

In case the nature of the charging stock and the operating conditions in heating coil 2! and chamber 25 are such that the quantity of residual liquid withdrawn from chamber 25 is relatively small it is entirely within the scope of the present invention to eliminate heating coil 36 and to supply the residual liquid from chamber 25 direct to reaction chamber 64 or to the coking chambers, by well known means not illustrated in the drawing.

Coking chambers 61 and 5'! are similar coking zones, preferably operated at a substantially reduced pressure relative to that employed in reaction chamber 64, wherein reduction of the liquid conversion products supplied thereto to substantially dry coke is accomplished. It will be understood, of course, that although two coking chambers are shown in the drawing a single coking chamber or any desired number of a plurality of such zones may be employed, when desired. When a plurality is employed the coking chambers may be simultaneously operated or, 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. Chambers 6! and El" are provided with suitable drain lines '58 and 78 respectively, controlled by the respective valves l8 and 19 which may also serve as a means of introducing steam, water or any other suitable cooling medium into the chambers, after their operation has been completed and after they have been isolated from the rest of the system, in order to hasten cooling and facilitate the removal of coke from the chambers. Vaporous products are withdrawn from the upper portion of chambers El and 6'! through the respective lines 83 and 88' controlled respectively, by valves 8! and 8| and are directed through line 82 into distilling and fractionating column 3 wherein they commingle with the charging stock supplied to this zone, as previously described, and are subjected therewith to fractionation and further treatment, in the manner already described.

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 temperature employed at the outlet from the cracking coil to which the low-boiling oils are supplied may range, for example, from 925 to 1100 F. and the pressure employed at the outlet from this zone may range, for example, from substantially atmospheric to 1000 pounds, or more, per square inch, theihigher temperatures above 1000 F., or thereabouts, normally being employed with a relatively low pressure. The separating chamber following the light oil heating coil may employ substantially the same or lower pressure than that employed in the heating coil ranging, for example, from 500 pounds, or thereabouts, per squareinch down to substantially atmospheric pressure and the pressure employed in the separating chamber may be substantially equalized or reduced in the succeeding fractionating, condensing and collecting equipment. The heating coil to which the reflux condensate or high-boiling fractions of the reflux condensate are supplied may utilize a conversion temperature measured at the outlet therefrom ranging, for example, from 850 to 950 F., preferably with a superatmospheric pressure at this point in the system of from 100 to 500 pounds, or thereabouts, per square inch. Substantially the same or a somewhat lower superatmospheric pressure may be employed in the succeeding reaction chamber. The heating coil to which the residual liquid from the separating chamber is supplied, when such a zone is utilized, may employ a temperature ranging, for example, from 800 to 1000 F., preferably with a low superatmospheric pressure of the order of 25- to 100 pounds, or thereabouts, per square inch at the outlet from this zone although lower or higher pressures may be employed, when desired. A substantially re duced pressure relative to that employed in the reaction chamber is preferred in the coking zone and may range, for example, from substantially atmospheric to 150 pounds, or thereabouts, per square inch superatmosphericpressure. Any desired pressure from substantially atmospheric to 150 pounds, or thereabouts, per square inch but no greater than that employed in the coking zone may be utilized in the distilling and fractionating stage of the system wherein the charging stock is subjected to fractional distillation.

As a specific example of one of the many possible operations of the process which may be accomplished in an apparatus such as illustrated and above described but which is only illustrative and should not be considered a limitation; the charging stock is a crude oil of about 25 A. P. I. gravity which is subjected to fractional distillation, together with vaporous products from the coking zone of the system in a distilling and fractionating column operated at a superatmospheric pressure of approximately 30 pounds per square inch. The overhead condensate from the distilling and fractionating column, which has an end boiling point of approximately 300 F. and amounts to approximately 20 per cent by volume of the charging stock, is recovered as good quality gasoline. An intermediate fraction from the distilling and fractionating column having an initial boiling point of approximately 288 F. and an end-point of approximately 550 F. is subjected, together with low-boiling reflux condensate from the fractionator of the first cracking stage of the system, to a conversion temperature of approximately 1050 F. at a superatmospheric pressure of approximately 800 pounds per square inch, as measured at the outlet from the heating coil to which these materials are supplied. The heated products from this zone are commingled with hottoms from the distilling and fractionating column and the commingled materials are introduced into a separating chamber maintained at a superatmospheric pressure of approximately pounds per square inch. The vaporous products from the separating chamber are subjected to fractionation for the formation of said low-boiling and a higher boiling reflux condensate and for the recovery therefrom of a motor fuel product of approximately 400 F. end-boiling point, by condensation of the fractionated vapors. The high-boiling reflux condensate from this fractionator is subjected in a separate heating coil to an outlet conversion temperature of approximately 920 F. at a superatmospheric pressure of about 350 pounds per square inch and substantially the same pressure is maintained in the succeeding reaction chamber to which the heated products are supplied. vaporous and liquid conversion products are withdrawn in commingled state from the reaction chamber and supplied to alternately operated coking chambers maintained at a superatmospheric pressure of approximately 50 pounds per square inch. Residual liquid products are withdrawn from the separating chamber and passed through a separate heating coil wherein they are quickly heated to an outlet temperature of approximately 900 F. at a superatmospheric pressure of about pounds per square inch and the heated products are introduced into the coking zone. This operation will produce, per barrel of charging stock, approximately '70 per cent of gasoline, including that recovered from the distilling and fractionating column, having an octane number of approximately 68 by the motor method. In addition approximately 70 pounds of low volatile petroleum coke, suitable for sale as domestic or industrial fuel, is recovered and the remainder is chargeable, principally, to uncondensable gas.

I claim as my invention:

1. A process for the treatment of hydrocarbon oils which comprises, subjecting hydrocarbon oil charging stock for the process to fractional distillation whereby it is separated into selected relatively low boiling and high boiling fractions, subjecting selected low boiling fractions of the charging stock to conditions of pyrolytic conversion in a heating coil, discharging the resulting products from the heating coil into a separating chamber and commingling therewith selected high boiling fractions of the charging stock, subjecting vaporous products from the separating chamber to fractionation whereby their insufficiently convert ed components are condensed as reflux condensate, subjecting fractionated vapors of the desired end boiling point to condensation, collecting the resulting distillate, subjecting said reflux condensate to further conversion at cracking temperature and superatmospheric pressure in a separate heating coil and communicating reaction chamber, withdrawing non-vaporous residual liquid from said separating chamber, subjecting the same to additional heating under non-coking conditions in another separate heating coil, introducing the heated residual oil into said reaction chamber, withdrawing vaporous and liquid conversion products from the reaction chamber, introducing the same into a coking zone wherein their residual components are reduced to substantially dry coke, supplying vaporous products from the coking zone to the first mentioned fractionating step for fractionation together with the charging stock, and recovering from said first mentioned fractionating step any motor fuel fractions of the commingled charging stock and vaporous products from the coking zone which are of satisfactory antiknock value.

2. A process for the treatment of hydrocarbon oils which comprises, subjecting hydrocarbon oil charging stock for the process to fractional distillation whereby it is separated into selected relatively low boiling and high boiling fractions, subjecting the selected low boiling fractions of the charging stock to conditions of pyrolytic conversion in a heating coil, discharging the resulting products from the heating coil into a separating chamber and commingling therewith selected high boiling fractions of the charging stock, subjecting vaporous products from the separating chamber to fractionation whereby their insufliciently converted components are condensed as reflux condensate, subjecting fractionated vapors of the desired end boiling point to condensation, collecting the resulting distillate, separating the reflux condensate formed by said fractionation of the vaporous products from the separating chamber into selected relatively low boiling and high boiling fractions, returning said low boiling fractions to the heating coil for further cracking, subjecting said high boiling fractions of the reflux condensate to further conversion at cracking temperature and superatmospheric pressure in a separate heating coil and communicating reaction chamber, withdrawing non-vaporous residual liquid from said separating chamber, subjecting the same to additional heating under non-coking conditions in another separate heating coil, introducing the heated residual oil into the reaction chamber, withdrawing vaporous and liquid conversion products from the reaction chamber, introducing the same into a coking zone wherein their residual components are reduced to substantially dry coke, supplying vaporous products from the coking zone to the first mentioned fractionating step for fractionation together with the charging stock and recovering from said first mentioned fractionating step any motor fuel fractions of the commingled charging stock and vaporous products from the coking zone which are of satisfactory antiknock value.

3. A process for the treatment of hydrocarbon oils which comprises, subjecting hydrocarbon oil charging stock for the process to fractional distillation whereby it is separated into selected relatively low boiling and high boiling fractions, subjecting the selected low boiling fractions of the charging stock to conditions of pyrolytic conversion in a heating coil, discharging the resulting products from the heating coil into a separating chamber and commingling therewith selected high boiling fractions of the charging stock, subjecting vaporous products from the separating chamber to fractionation whereby their insufficiently converted components are condensed as reflux condensate, subjecting fractionated vapors of the desired end boiling point to condensation, collecting the resulting distillate, subjecting said reflux condensate to further conversion at cracking temperature and superatmospheric pressure in a separate heating coil and communicating reaction chamber, withdrawing vaporous and liquid conversion products from the reaction chamber, introducing the same into a coking zone, withdrawing non-vaporous residual liquid from said separating chamber, subjecting the same to additional heating under non-coking conditions in another separate heating coil, introducing the heated residual liquid into the coking zone wherein it is reduced to coke, supplying vaporous products from the coking zone to the first-mentioned fractionating step for fractional distillation together with the charging stock and recovering from said first mentioned fractionating step any motor fuel components of the commingled charging stock and vaporous products from the coking zone which are of satisfactory antiknock value.

4. A process for the treatment of hydrocarbon oils which comprises, subjecting hydrocarbon oil charging stock for the process to fractional distillation whereby it is separated into selected relatively low boiling and high boiling fractions, subjecting the selected low boiling fractions of the charging stock to conditions of pyrolytic conversion in a heating coil, discharging the resulting products from the heating coil into a separating chamber and commingling therewith selected high boiling fractions of the charging stock, subjecting vaporous products from the separating chamber to fractionation whereby their insufilciently converted components are condensed as reflux condensate, subjecting fractionated vapors of the desired end boiling point to condensation, collecting the resulting distillate, separating said reflux condensate into selected relatively low boiling and high boiling fractions, returning said low boiling fractions to the heating coil for further cracking, subjecting said high boiling fractions of the reflux condensate to further conversion at cracking temperature and superatmospheric pressure in a separate heating coil and communicating reaction chamber, withdrawing vaporous and liquid conversion products from the reaction chamber, introducing the same into a coking zone, withdrawing non-vaporous residual liquid from said separating chamber, subjecting the same to additional heating under non-coking conditions in another separate heating coil, introducing the heated residual liquid into the coking zone wherein it is reduced to coke, supplying vaporous products from the coking zone to the first-mentioned fractionating step for fractionation together with the charging stock, and recovering from said first mentioned fractionating step any motor fuel components of the commingled charging stock and vaporous products from the coking zone which are of satisfactory antiknock value.

5. A hydrocarbon oil conversion process which comprises fractionating the charging oil together with hydrocarbon vapors, formed as hereinafter set forth, to form a relatively light fraction and a heavier fraction, heating the light fraction to cracking temperature in a heating coil and commingling said heavier fraction with the resultant heated products, separating the resultant mixture into vapors and unvaporized oil in a separating zone, fractionating these vapors independently of the charging oil and the first-named vapors and supplying resultant reflux condensate to said coil, removing unvaporized oil from the separating zone and distilling the same to coke in a coking zone, and supplying vaporous products from the coking zone to the first-named fractionating step as said hydrocarbon vapors.

6. A hydrocarbon oil conversion process which comprises fractionating the charging oil together With hydrocarbon vapors, formed as hereinafter set forth, to form a relatively light fraction and a heavier fraction, heating the light fraction to cracking temperature in a heating coil and commingling said heavier fraction with the resultant heated products, separating the resultant mixture into vapors and unvaporized oil in a separating zone, fractionating these vapors independently of the charging oil and the first-named vapors and separating therefrom a relatively light reflux condensate and a heavier reflux condensate, supplying the light reflux condensate to said coil, removing unvaporized oil from said separating zone and distilling the same to coke in a coking zone, subjecting said heavier reflux condensate to independently controlled cracking conditions in a second heating coil and introducing resultant products to the coking zone, and supplying vaporous products from the coking zone to the first-named fractionating step as said hydrocarbon vapors.

KENNETH SWARTWOOD.

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