US2107509A - Conversion of hydrocarbon oils - Google Patents

Description

Feb. 8, 1938. J D SEGUY 2,107,509

CONVERSION OF HYDROCARBON OILS Filed May 10, 1953 Condenser fimdenser \pfforizey Patented Feb. 8, 1938 UNiTED STATES PATENT OFFICE CGNVERSION OF HYDROCARBON OILS Application May 10, 1933, Serial No. 670,375

6 Claims.

This invention particularly refers to an improved process and apparatus for the conversion of relatively high-boiling hydrocarbon oils for the production of. high yields of lower boiling products wherein the raw oil charging stock is first subjected to relatively mild conversion conditions, high-boiling and low-boiling conversion products arbitrarily separated, the low-boiling products subjected to more severe conversion in 10 a conjointly operated cracking system while said high-boiling conversion products are subjected to less severe conversion conditions than those imposed upon the low-boiling products in, the same conjointly operated cracking system.

A more specific embodiment of the present invention may comprise subjecting a relatively high-boiling hydrocarbon oil such as heavy crude petroleum, topped crude, fuel oil or the like to relatively mild conversion in a heating coil, introducing the heated oil into a vaporizing chamber wherein the low-boiling products, comprising a substantial proportion of the gas oil produced, are separated from the higher boiling products which remain unvaporized in this zone, subjecting a portion of said low-boiling products to more severe conversion conditions of elevated temperature and superatmospheric pressure in a separate heating coil, introducing the heated oil into a separate vaporizing chamber, preferably maintained at substantially reduced pressure relative to that employed in the heating coil, wherein the vaporous and residual conversion products are separated, subjecting the vapors 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 and gas, returning reflux condensate produced by fractionation of the vaporous conversion products to the last mentioned heating coil for further conversion,

together with said low-boiling fractions from the first described cracking operation, and commingling the unvaporized high-boiling fractions from 5 the first described cracking operation with the hot conversion products passing from the last mentioned heating coil to the reduced pressure vaporizing chamber.

The present invention permits the ultimate 50 conversion of relatively high-boiling oils into high yields of desirable low-boiling products, such as motor fuel of high anti-knock value, without the excessive production of undesirable products such as coke and gas and also permits a flexi- 55 'bility of operation whereby intermediate products, such as gas oil of the desired quality may be recovered, when desired, as well as permitting the production, when desired, of good quality residual oil, suitable, for example, as fuel. By use of the two-stage method of. conversion provided 5 by the present invention, the first or relatively mild stage produces high yields of intermediate oils, such as gas oil, for further conversion in the second stage to produce high yields of good quality motor fuel. More severe conversion con- 10 ditions may be employed for the production of the motor fuel in the second stage than permissible, without excessive yields of coke and gas, in the conversion of higher boiling oils such as supplied to the first cracking stage of the process. 15 By this method of operation a product of better motor fuel characteristics, particularly with respect to anti-knock value, may be produced than could be accomplished by cracking the heavy charging stock in one operation. Also by the 20 method ofv operation of the present invention the high-boiling products of the first cracking stage are subjected to further conversion under milder conversion conditions than those employed for the treatment of lower boiling products, whereby additional yields of good quality motor fuel and minimum yields of coke and gas are produced.

Other advantages and features of the present invention will be more apparent with reference to the accompanying diagrammatic drawing and 30 the following description thereof. The drawing illustrates one specific form of apparatus embodying the features of. the present invention and the description of the drawing includes a more detailed description of the operation of the 35 process as it may be practiced in the apparatus illustrated.

Referring to the drawing, the raw oil charging stock tobe treated is supplied through line I and valve 2 to pump 3 by means of which it is fed 40 through line 4 and valve 5 to heating coil 6 wherein it is subjected to the desired relatively mild conversion temperature, preferably at superatmospheric pressure, by means of heat supplied from a furnace l of any suitable form.

The charging stock may of course, be preheated when desired in any well known manner, not illustrated, prior to its introduction into heating coil 5. The hot conversion products are discharged from heating coil 6 through line 8 and valve 9 into vaporizing and separating chamber H] which may be operated at substantially the same pressure as that maintained at the outlet from heating coil 6 but is preferably operated at reduced pressures in order to assist vaporiza- However, at least a portion of this product is preferabiy diverted from line it through line l6 valve l! to pump l8by means of which it is tied through line i9, passing preferably, all or in part, through valve 28 in this line into fractionator 2! or, when desired, from line l9 through line 22, valve 23 and line 24 direct to heating a coil 25. V f

Ordinarily, although relatively mild conversion conditions are preferably employed in heating coil 6, some materials within the boiling range; of gasoline will normally'be produced in the first 'conve rsion stage of the process and these will' vary in 'quality and quantity with the nature of the charging stock and the conversion conditions to which it is subjectech When this motor fuel product is of good character itmay be collected,

together with the other motor'fuel conversion products of the process of similar end-boiling point, liy'supplying the distillate from condenser E3 to fractionator 2!, as previously described.

1 However, when these fractions of the distillate product from chamber it) are of inferior motor fuel quality, particularly with: respect to their anti-knock value, the distillateg'may be supplied directly to heating can 25, by means already "described, wherein it may be subjected to further conversion under conditions suitable to effect a substantial improvement in itsanti-knock value.

Line 23 containing valve 21, communicating through line iii with pump it, permits the intro- "duction of suitable oil'from any desired external source'to the second crackinggstage of the process. This oil from an externalsource, which may be considered secondary charging stock, preferably comprises an oilgsimilar in cracking char- 'acteristics"tof the distillate from the first and previously deseribedcracking stage of the process and may be supplied, all or in part, either to fractionator 2 or to heating coil 25 or, in part, toboth, as. described in connection with the in vtroduction of the distillate from condenser l3 into this portion of the system. The low-boiling charging oil for the second cracking stage of the process, when supplied to fractionator 2|, as illustrated and described} serves to assist fractionation of the vaporous conversion products with which it is. directly commingled in the fractionator by means of which the charging stock: is preheated. Any charging stock introduced into fractionator 2i, as well as vaporous conversion products supplied to this zone, boiling above the end-boiling point of the desired overhead stream of fractionated vapors comprisingthe light distillate product of the process, are condensed as reflux condensate within the fractionator and collect within its lower portion fromwhich they are withdrawn through line 28 and valve '29 to pump 30 by means of which they are supplied through line 24 and valve 3| toheating coil 25, commingling, in'line 26, with any charging stock supplied thereto through line 22 and valve 23, as previously described,

Heating coil 25 is located within a furnace32 of any suitable form, by means of whichthe oil supplied to the heating coil is brought to the desired conversion temperature, preferably more :5 severe than that employed in heating coil 6 and preferably at a substantial superatmospheric pressure. The heated oil is discharged from heating coil 25 through line 33 and valve 34 into vaporizing chamber 35, which is preferably maintained at a substantially reduced pressure relative to that employed at the outlet from the heating coil, accomplished by the manipulation of pressure control valve 34, whereby the heated conversion products are cooled and their vaporization in chamber 35 assisted;

Simultaneous with the introduction of heated oil from heating coil 25 into" chamber 35, the high-boiling conversion products from heating coil 6 which remain unvaporized in chamber in are withdrawn therefrom through line 36 and valve tl to pump 38 by means of which they are fed through line 39 and valve 66 into line 33, commingling therein with the highly fheated oil from heating coil 25, serving to cool the hot cohversion products further than that accomplished by reduction of the pressure imposed thereon, the

heavy oil from chamber 38 being thereby heated to a milder *conversion temperature than that employed in heating coil 25.

Residual 'oil remaining unvaporized in chamber 35 may be withdrawn therefrom through line" 4| and valve d2 to cooling and storage or to any desired further treatment. The vaporous conversion products pass from chamber 35 through line 33 and valve id to fractionation in fractionator 2! wherein their insufiiciently converted components are condensed and returned, as previously described, to further conversion in heating coil 25.

Fractionated vapors of the desired end-boiling 7 point, preferably comprising conversion products within the boiling range of gasoline and of high anti-knock value, are withdrawn, together with uncondensable gas produced by the operation, from the upper portion of the fractionator through line 45 and valve 56 to be subjected to condensation and cooling in condenser 41. The resulting distillate and gas passes from condenser 4'! through line lfl and valve 49 t0 collection in receiver 50. Uncondensable gas may be released from the receiver through line H and valve 52. The distillate is withdrawn from this 'zone through line 53 and valve 5Q to storage or to any desired further treatment. When desired, a regulated portion of the distili ate'from receiver 50 may be recirculated, by well known means not shown in the drawing, to the upper portion of fractionator 2! to assist fractionation of the vapcrs in this zone and maintain the desired vapor outlet temperature from the fractionator, thereby controlling the end-boiling point of the final light distihate product of the process.

The conditions in chamber ii! are preferably such that the vapors leaving said chamber will contain a major portion or all of the gas oil frac-, tions and will be substantially freeof heavier fractions. When desired, separation of the heavier products from the gas oil and lighter vapors in chamber i ii may be improved by providing said chamberwith fractionating means of any well known form such as baffles, perforated pans, bubble trays, cooling coils, reboiling coils and the like, not shown.

The conversion temperature-to which the high boiling charging stock for the first described cracking stage of the process is subjected in the,

heating coil may-range, for example, from 758 to the succeeding vaporizing chamber.

let from the heating coil of from 150 pounds, or thereabouts, per square inch down to substantially atmospheric pressure. A pressure substantially equalized with or reduced relative to that employed in the heating coil may be utilized in A higher conversion temperature, preferably within the range of 900 to 1050 F., is preferred at the outlet from the heating coil of the second conversion stage of the process, preferably with a substantial superatmospheric pressure measured at this point of from. 200 to 800 pounds, or more, per square inch. The heated products from this heating coil are preferably cooled by pressure reduction and by the introduction of high-boiling conversion products from the separator of the first conversion stage of the process to a temperature of the order of 800 to 900 F., or thereabouts, and a substantially reduced pressure of from 100 pounds, or thereabouts, per square inch down to substantially atmospheric pressure is preferred in the vaporizing chamber of this stage of the process and this pressure may be substantially equalized or somewhat reduced in the succeeding fractionating, condensing and collecting portions of the system.

As an example of one specific operation of the process of the present invention, as it may be practiced in an apparatus such as illustrated and above described, the charging stock is a Mid-Continent topped crude of about 23 A. P. I. gravity which is subjected in the heating coil of the first conversion stage to an outlet temperature of approximately 765 F., at a superatmospheric pressure of about 50 pounds per square inch. This pressure is substantially equalized in the succeeding vaporizing chamber from which liquid conversion products are withdrawn at a temperature of about 675 F., the vaporous products from this zone being condensed and supplied to the fractionator of the second conversion stage of the process from which the major portion thereof is withdrawn, together with reflux condensate formed in this zone, to the heating coil of this portion of the system. A conversion temperature of about 930 F., and a superatmospheric pressure of about 550 pounds per square inch is maintained at the outet from the second heating coil. The unvaporized oil from the first conversion stage of the process is introduced into the stream of heated oil from the second heating coil after the pressure thereon has been reduced to approximately 40 pounds per square inch which is maintained in the succeeding vaporizing chamber. Residual liquid is withdrawn from this zone to cooling and storage and the vaporous products passed to the fractionator which is maintained at a pressure substantially equalized with that in the vaporizing chamber. This operation may produce, per barrel of topped crude supplied to the system, about 56% of motor fuel having an anti-knock value equivalent to an octane number of approximately '75, about 37% of residual oil suitable for use as fuel and about 600 cubic feet of uncondensable gas.

I claim as my invention:

1. A process for producing motor fuel which comprises subjecting hydrocarbon oil heavier than gas oil in a heating zone to relatively mild cracking conditions of temperature and pressure such as to produce gas oil therefrom, separating the thus treated oil into a residue heavier than gas oil and a distillate containing the gas oil, passing such distillate through a second heating zone and heating the same therein to higher cracking temperature than the oil in the first-mentioned heating zone to produce gasoline therefrom,v then commingling the thus heated distillate with residue from the first-named cracking treatment, separating vaporous from unvaporized reaction products, and fractionating and condensing the separated vapors.

2. A process for producing motor fuel which comprises subjecting hydrocarbon oil heavier than gas oil in a heating zone to relatively mild cracking conditions of temperature and pressure such as to produce gas oil therefrom, separating the thus treated oil into a residue heavier than gas oil and a distillate containing the gas oil, passing such distillate through a second heating zone and heating the same therein to higher cracking temperature than the oil in the firstmentioned heating zone to produce gasoline therefrom, then commingling the thus heated distillate with residue from the first-mentioned cracking treatment, separating vaporous from unvaporized reaction products, fractionating the separated vapors to condense insufficiently cracked fractions thereof, returning resultant reflux condensate to said second heating zone in admixture with an additional quantity of said distillate, and finally condensing the fractionated vapors.

3. A process which comprises subjecting heavy hydrocarbon oil in a heating zone to relatively mild cracking conditions of temperature and pressure, separating the heated oil in a separating zone into vapors and unvaporized oil and condensing the vapors, simultaneously passing a lighter oil through a second heating zone and heating the same therein to higher cracking temperature than the heavy oil in the first-mentioned heating zone, then discharging the thus heated lighter oil into a second separating zone and also introducing to this zone unvaporized oil from the first-named separating zone, separating the resultant mixture in the second separating zone into vapors and residue and introducing the former to a fractionating zone, introducing to the fractionating zone condensate formed by the condensation of the first mentioned vapors and fractionating the second mentioned vapors in contact therewith independently of the first-named vapors, supplying liquid products from the fractionating zone to said second heating zone to constitute at least a part of said lighter oil, and finally condensing the fractionated vapors.

4. A process for producing motor fuel which comprises subjecting hydrocarbon oil heavier than gas oil in a heating zone to relatively mild cracking conditions of temperature and pressure such as to produce gas oil therefrom, separating the heated oil into vapors and a residue heavier than gas oil, subjecting the vapors to condensation to form a condensate containing the gas oil, introducing such gas oil condensate into a fractionating zone containing cracked vapors and fractionating the latter in contact with the condensate to condense insufliiciently cracked fractions thereof, passing the resultant mixture of reflux condensate and gas oil condensate from the fractionating zone through a second heating zone and heating the same therein to higher cracking temperature than the oil in the firstmentioned heating zone to produce gasoline therefrom, separating the resultant vapors and introducing the same to the fractionating zone for fractionation in contact with said gas oil condensate, and separately condensing the vapors uncondensed in the fractionating zone.

5. A process for producing motor fuel which comprises subjecting hydrocarbon oil heavier than gas oil in a heating zone to relatively mild cracking conditionsof'temp'erature and pressure such as to produce gas oil therefrom, separating the heated oil into vapors and a residue heavier than gas oil, subjecting the vapors to condensation to form a condensate containing the gas oil, introducing such gas oil condensate into a fractionating zone containing cracked vapors and fractionating the latter in contact with the condensate to condense insufii'ciently cracked fractions thereof, passing the resultant mixture of reflux condensate and gas oil condensate from the fractionating zone through a second heating zone and heating the same therein to higher cracking temperature than-the oil in the first-mentioned heating Zone to produce gasoline therefrom, then commingling a substantial quantity of said residue with-the thusheated mixture, separating I vaporous from unvaporized reaction products and introducing the former to the fractionating zone for fractionation'in contact with said gas oil condensate, and separately condensing the Vapors uncondensed in the fractionating zone.

6. A process for producing motor fuel which comprises subjecting hydrocarbon oil heavier than gas oil to relatively mild conversion conditions of temperature and pressure such as to produce therefrom a major proportion of gas oil and a minor proportion of gasoline, separating gas oil and gasoline hydrocarbons thus formed

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