US2091437A - Conversion of hydrocarbon oil - Google Patents

Description

Aug. 31, 1937. A. ENGELSTEIN CONVERSION OF HYDROCARBON OIL Filed Feb. 27, 1936 Patented Aug. 3l, 1937 UNITED STATS sarai res CONVERSION F HYDROCARBON OIL Application February 27, 1936, Serial No. 65,995

2 Claims.

This invention particularly refers to an improved process wherein selected fractions of a crude oil, containing a substantial amount of straight-run gasoline, are selectively cracked to 5 produce high yields of motor fuel of good antiknock value, in, an economic manner.

A feature of the invention comprises reforming motor fuel fractions contained in the charging stock, for the purpose of improving their antiknock value, utilizing the excess heat contained in the resulting hot conversion products for distilling the charging stock by commingling the same therewith and thereby cooling the 1re-formed products to the desired degree by the heat exchange with the charging stock.

In combination with the fractional distillation of crude oil containing low boiling hydrocarbons within the boiling range of motor fuel, the invention contemplates selectively cracking various fractions of charging stock and intermediate 0 D liquid conversion products of the process of selected boiling point range, to produce high yields of motor fuel of good anti-knock value and minor yields of marketable fuel oil and uncondensable gas. As an alternative, the process may be oper- 35 as gasoline, an intermediate fraction such as gas oil and/ or kerosene, and heavy topped crude. The low boiling fractions are removed as fractionated vapors from said column, subjected to condensation, the resulting distillate supplied in regulated quantities to the reforming coil wherein it is subjected to relatively severe conversion conditions of cracking temperature and substantial superatmospheric pressure, the highly heated products discharged from the reforming coil,

5 commingled with the crude charging stock, and

the commingled materials introduced into the separating and fractionating column. The heat for effecting fractional distillation of the crude oil is derived from the heated products of the 50 reforming operation and the charging stock serves to cool the reformed products sufficiently to prevent any excessive further conversion thereof. As can readily be seen, any desired quantity of gasoline from the topping and reforming operation 55 may be recycled to the reforming coil to obtain suflicient heat for topping and to produce a final motor fuel product of the desired anti-knock value.

Reflux condensate, comprising intermediate fractions of the crude and components of the vaporous conversion products boiling above the range of the desired reformed motor fuel product, is removed from the fractionating column, subjected to conversion conditions of cracking temperature and superatmospheric pressure in a separate heating coil and communicating reaction chamber, both vapors and liquid products withdrawn in ccmmingled state from the reaction chamber and introduced into a reduced pressure vaporizing Zone, the resulting non-vaporous residual liquid recovered from the vaporizing chamber, vaporous products separately withdrawn from the vaporizing chamber and introduced into` a separate fractionating column wherein their insufficiently converted components are condensed as reux condensate, fractionated vapors of the desired end boiling point removed from the last mentioned fractionating column, subjected to condensation and the resulting distillate recovered, reflux condensate separately withdrawn from the last mentioned fractionating column and returned to said separate heating coil for cracking together with said intermediate fractions from the reforming and topping operation. High boiling oils comprising the high boiling components of the crude and residual liquid conversion and polymerization products from the reforming operation are removed from the lower portion of the separating column, subjected to relatively mild conversion conditions of cracking temperature and superatmospheric pressure in another separate heating coil and the heated products therefrom introduced, all or in part, into the vaporizing chamber or the reaction chamber or, in part, to both.

The accompanying diagrammatic drawing illustrates one specific form of apparatus in which the invention may be carried out. Charging stock for the process, preferably comprising crude petroleum or similar wide-boiling range oil containing a substantial quantity of motor fuel or motor fuel fractions, is supplied through line I and valve 2 to pump 3 by means of which it is fed through line 1i, Valve 5 and line 2l into separating and fractionating column 5. The charging stock is commingled in line 2l with hot conversion products from heating coil i9 whereby it is heated sufficiently to effect its substantial vaporization in column 6 and serves to partially cool and retard or arrest conversion of the products from heating coil I9. The commingled materials supplied to column 6 are separated therein,

in the case here illustrated, into three selected fractions, the nature of which will be later 5 described.

The overhead fractionated product from column 5 comprises components of the charging stock and conversion products from heating coil i9 boiling within the range of the desired final l motor fuel product of this stage of the system and is directed, together with the gaseous products of this stage of the system, through line I and valve 8 to condensation and cooling in ccndenser 9, whereirom the resulting distillate and l gas pass through line I9 and valve Il to collection .and separation in receiver I2. The uncondensed gas may be released from receiver I2 through line I 4' and valve I5'. Distillate is withdrawn from the receiver through line I3 and is 2O directed, in part, through valve I4 to storage or elsewhere, as desired. A regulated portion of the distillate removed from receiver I2 is diverted from line I3 through line I3 and Valve I5 to pump it by means of which it is supplied through line Il' and valve I8 to heating coil I9.

When desired, regulated quantities of the distillate collected in receiver I2 may be recirculated by Well known means (not shown) to the upper portion of column 6 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.

Heat is supplied to coil I9 from a suitable furnace 25 by means of which the oil passing through the heating coil is heated to a sufficiently high cracking temperature to effect a substantial improvement in its motor fuel characteristics, particularly with respect to anti-knock value, Without excessively altering its boiling range. A relatively high superatmospheric pressure is preferably employed at the outlet from heating coil I9 and the highly heated products from this Zone are directed through line 2| and valve 2I to column 6. Preferably, the pressure imposed upon the stream of heated products from heating coil I9 is substantially reduced as they pass through valve 2l. This pressure reduction serves to assist cooling and retard conversion of the heated products and preferably, as previously indicated, additional 'cooling of the heated products is obtained by commingling the same in line 2I with the charging stock supplied to column 6.

Selected intermediate fractions of the charging stock and conversion products from heating coil I9 supplied to column 6 are withdrawn as one or a plurality of side streams from a suitable intermediate point or points in column 6, provision being made, in the case here illustrated, for removing this material from column 6 through line 22 wherefrom it is directed through valve 23 to pump 24. Pump 24 supplies these intermediate fractions through line 25, valve 2'6 and line 21 to heating coil 54.

Reflux condensate from fractionator 48 is also supplied to heating coil 54, as will be later more fully described, and the commingled oils passing through this zone are heated to the desired cracking temperature preferably at a substantial superatmospheric pressure by means of heat supplied from furnace 55. The heated products are discharged from heating coil 54 through line 56 and valve 51 into reaction chamber 4I.

Chamber 4I is also preferably maintained at a substantial superatmospheric pressure and, al-

though not indicated in the drawing, this zone is preferably insulated in order to prevent the excessive loss of heat by radiation so that the heated products supplied thereto, and more particularly their vaporous components, are subjected therein to appreciable further conversion. In the par- 5 ticular case here illustrated, both vaporous and liquid conversion products are withdrawn in commingled state from the lower portion of chamber 4I and directed through line 58 and valve 59 into chamber 45. It is, however, also Within the scope 10 of the invention, although not illustrated, to separately remove vaporous and liquid conversion products from chamber 4I, supplying the latter either alone or together with a regulated portion of the vapors to chamber 4B, in the manner dei5 scribed, while the vaporous products may be separately supplied, all or in part, to chamber 49 or supplied, all or in part direct to fractionator 48.

Chamber [i9 is preferably maintained at a substantially reduced pressure relative to that ern- 20 ployed in reaction chamber 4I by means of which appreciable further vaporization of the liquid product supplied to this Zone from the reaction chamber is accomplished. Residual liquid remaining unvaporized in chamber ill may be withdrawn through line 60 and valve tl to cooling and storage or elsewhere, as desired. It is also Within the scope of the invention, when desired, to operate chamber 40 as` a coking zone wherein the heavy residual components of the conversion products supplied thereto are reduced to coke. When this method of operation is -employed the coke may be allowed to accumulate within chamber 4e to. be removed therefrom after opera.- tion of the chan'ibei` is completed and, when desired, a plurality of coking chambers may be employed for this purpose, although not illustrated, and preferably are alternately operated, cleaned and prepared for further operation. Vaporous products are removed from the upper por- 4.0 tion of chamber iii and directed through line t2 and valve 63 to fractionation in fractionator 4&1.

The components ofthe vaporous products supplied vto fractionator 48 boiling above the range of the desired final light distillate product of this 4.5 stage of the system are condensed within the fractionator as reflux condensate which may be removed from the lower portion thereof through line t9; and valve 59 to pump 5I by means of which it is returned through line 2'! and valve 52 to 50 further cracking in heating coil 54,.

Fractionated vapors of the desired vend boiling point are removed, together with uncondensable gas, from the upper portion of fractionator 43 and directed'through line 64 and valve 65 to condensation and cooling in condenser 65. The resulting distillate and uncondensed gases pass through line El! and valve B8 to collection and separation in'receiver '69. Distillate may be withdrawn from receiver 59 through line 'lli and valve ll to storage, 00 or elsewhere, as desired. The gases may be released from receiver 69 through line i2 and valve '13. When desired, regulated quantities of the distillate collected in receiver 69 may be recirculated by well known means (not shown) to the upper portion of fractionator 43 to serve as a refluxing and cooling medium in this zone for assisting fractionation of the vapors and to raintain the desired vapor outlet temperature therefrom.

The high boiling fractions of the commingled oils suppliedto column 5, including high boi components of the charging stock and any residual liquid conversion products and heavy polymerization products from heating coil I9, are75 removed from the lower portion of column 6 through line y28 and valve 29- to pump 30 by means of which they are fed through line 3| and may be directed, all or in part, either through valve 32, in this line, to heating coil 33 or, all or in part, through line 44, valve 41 and either through valve 45 in this line into reaction chamber 4 I or through line 42, valve 43, line 36 and valve 38 into the upper portion of chamber 4|] or from line 36 through line 3l and valve 39 into the lower portion of chamber 40 or, when desired, regulated quantities of the relatively high bo-iling oils may be supplied to any two or more of the points mentioned. l5 When supplied to reaction chamber 4l the high boiling oils from column 6 commingle with the heated products from heating coil 54 and are subjected therewith to relatively mild cracking in the reaction chamber. When supplied to cham- O ber 40 the high boiling oil from column 6 may be subjected to further vaporization in this zone either by virtue of a reduced pressure in chamber 40 relative to that employed in column 6 or, due to the heat recovered by the heavy oils from the conversion products supplied to chamber 40 from reaction chamber 4I, or in part by both. In the latter case non-vaporous high boiling components of the heavy oils supplied to chamber 40 will be recovered from this zone, together with the resi- 30 dual liquid conversion productsremoved therefrom as previously described, without being subjected to appreciable cracking.

When heating coil 33 is employed the relatively high boiling oil supplied thereto from column E,

35 as previously described, is heated to the desired cracking temperature, preferably at a substantial superatmospheric pressure by means of heat supplied from a furnace 34. The heated products are directed from heating coil 34 through line 36 and may be directed either through valve 33 in this line into the upper portion of chamber 40 or through line 3l and valve 39 into the lower portion of chamber 40 or, when desired, they may pass, all or in part, from line 36 through line 42,

i5 valve 43, line 44 and valve 45 into reaction chamber 4l.

Two general methods of operation may be employed in heating coil 33, depending primarily upon the characteristics of the relatively heavy oils supplied thereto and the residual conversion product of the process which it is desired to produce. When the oil supplied from heating coil 33 from column 6 is of a relatively high boiling nature and it is desired to produce coke as the final residual product of the process, the oil is preferably heated in coil 33 to a high conversion temperature and, although illustrated in a conventional manner in the drawing, coil 33 and furnace 34 are preferably of such form, which is now well known, that the oil is quickly heated without allowing it to remain in the heating coil and communicating lines for a sufficient length of time to permit any substantial formation and deposition of coke therein. When this method of operation is employed the heated products from coil 33 are supplied to chamber 40, wherein the coke is allowed to accumulate.

When it is desired to produce good quality fuel oil as the residual product of the process but the high boiling oils removed from the lower portion of column 6 are too viscous to meet the desired market specifications, heating coil 33 may be operated as a viscosity breaking coil, in which case a relatively low cracking temperature and a relatively long conversion time is preferably employed in this zone. In such cases the heated products from coil 33 may be supplied either to vaporizing chamber 40 or to reaction chamber 4l, as desired. When supplied to the reaction chamber the heavy oils from coil 33 are subjected to additional conversion time, under the relatively mild cracking conditions maintained in this zone, before being supplied therefrom to chamber 4 l.

The preferred range of operating conditions which may be employed to produce the desired results in an apparatus such as illustrated and above described are approximately as follows: Th-e heating coil to which reflux condensate and intermediate fractions of the liquid conversion products and of the charging stock are supplied may employ an outlet conversion temperature ranging, for example, from 850 to 975 F., preferably with a superatmospheric pressure at this point in the system of from to 500 pounds, or thereabouts, per square inch. The succeeding reaction chamber may utilize a superatmospheric pressure substantially the same or somewhat lower than that emyployed at the outlet from the heating coil. The vaporizing or coking chamber is preferably operated at a substantially reduced pressure relative to that employed in the reaction chamber which may range, for example, from a superatmospheric pressure of 100 pounds, or thereabouts, per square inch, down to substantially atmospheric pressure. The fractionating, condensing and collecting equipment of this stage of the system may employ pressures substantially the same or somewhat lower than that employed in the vaporizing or coking chamber. The reforming coil to which regulated quantities of the motor fuel product from the distilling and reforming operations are supplied preferably ernploys an outlet conversion temperature of the order of 925 to 1000 F., or more, and a superatmospheric pressure of from 200 to 1000 pounds, or thereabouts, per square inch. The succeeding separating and fractionating Zone is preferably operated at a substantially reduced pressure relative to that employed at the outlet from the reforming coil which may range, for example, from 100 pounds, or more, per square inch, superatmospheric, down to substantially atmospheric pressure and this zone may be operated at substantially the same or at a higher or lower pressure than that employed in the vaporizing or coking chamber. When the process is operated for the production of coke the temperature employed at the outlet from the heating coil to which the relatively high boiling oils are supplied may range, for example, from 900 to l000 F., preferably with a superatmo-spheric pressure of from 30 to 150 pounds, or thereabouts, per square inch. When operated for the production of good quality fuel oil residue the heating coil to which the relatively high boiling oils are supplied may utilize a conversion temperature ranging, for example, from '775 to 875 F. with any desired superatmospheric pressure ranging from 100 to 500 pounds, or more, per square inch.

As a specific example of the operation of the process, a Mid-continent crude of about 30 A. P. I. gravity containing approximately 18% of material boiling up to 400 F. is subjected to fractional distillation by commingling the same in the separating and fractionating column of the system with heated products from the reforming coil. The light distillate product from the topping and reforming operations is a motor fuel of approximately 4:00L7 F. end boiling point and a sufficient quantity of this product is recycled through the Cil reforming coil to bring the anti-knock Value of this product up to an octane number of 70 or better. A cracking temperature of approximately 985 F. and a superatmospheric pressure of about 80() pounds per square inch is employed at the outlet from the reforming coil. The heated products from the reforming coil passing to the separating and fractionating column are cooled by commingling therewith a suiicient quantity of the charging stock to reduce their temperature to approximately 750 F. Intermediate fractions from the separating and fractionating column, which have an end boiling point of approximately 690 F., are supplied to a separate cracking coil wherein they are heated to an outlet conversion temperature of approximately 940 F. at a superatmospheric pressure of about 350 pounds per square inch. This pressure is substantially equalized in the succeeding reaction chamber and the products from this zone are supplied to a coking chamber wherein their high boiling components are reduced to coke. Vaporous products from the last mentioned cracking and coking operation are subjected to fractionation for the formation of reiiux condensate which is returned to the last mentioned cracking coil and the light distillate product from this stage of the system comprises a motor fuel of approximately 390 F. end boiling point having an octane number of approximately 70. The high boiling oils from the separating and fractionating column are quickly heated in another separate cracking coil to an outlet conversion temperature of approximately 950 F. at a superatmospheric pressure of about 100 pounds per square inch and are introduced into the coking chamber which is maintained at a superatmospheric pressure of approximately 30 pounds per square inch. This pressure is substantially equalized in the succeeding fractionating, condensing and collecting portions of the system and substantially the same pressure is employed in the separatingv and fractionating column. The yield of motor fuel from this operation is approximately 63% based on the charging stock, and the coke produced, which is of low volatility and good structural strength, amounts to approximately 75 pounds per barrel of crude charging stock, the remainder being chargeable, principally, to uncondensable gas.

I claim as my invention:

1. In a conversion process wherein hydrocarbon oil is heated to cracking temperature under pressure in a heating coil, the heated products separated in a separating chamber into vapors and residue and the former fractionated in a` fractionating zone to condense heavierr fractions thereof, the method which comprises simultaneously topping and fractionating crude oil containing straight-run gasoline in a'second fractionating zone to separate the' gasoline therefrom and to form topped crude and an intermediate fraction heavier than gasoline, passing a portion of the gasoline through a second heating coil and heating the same therein suciently to enhance its anti-knock Value, introducing resultant products to the second fractionating' zone to supply heat for the topping and fractionation of the crude, removing said intermediate fraction from the second fractionating zone and combining the same with reflux condensate formed in the firstnamed fractionating Zone, vsupplying the resultant mixture to the first-named coil, removing topped crude from the second fractionating Zone and combining the same with said heatedl products from the rst-named coil for separation therewith in the separating chamber into vapors and residue,

2. The method as defined in claim 1 further characterized in that the topped crude is heated to cracking temperature in a third heating coil prior to its commingling with said heated products from the first-named coil.

ALVIN ENGELSI'EIN.

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