US2356019A - Conversion of hydrocarbon oils - Google Patents

Description

J. W. WARD CONVERSION oF HYDROCAHBON o'Ls Filed Feb. 24, 1941 Aug. 15, 1944.

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Patented Aug. 15, 14944 V umrizov STATES PATENT oFFlcE John W. Ward, Chicago, Ill., assignor to Universal ,Oil Products Company, Chicago, `I1l., -a`

Y corporation ofDelaware Y y -Y Application February 24, 1941,SerialfNo`.` 380,127 solaims. (c1. 19e-48)",

This invention relates to an V'improved process for the pyrolytc conversion ofrhydrocarbon oils and is more particularly directed to a com` bination lprocess in which relatively heavy oils are cracked and light distillates reformed,` to produce therefrom high yields of good' antiknock gasoline. l

lOne yspecific embodiment of the invention provided by the process comprises, crackingrelatively high-boiling components at elevated temperature and substantial superatmospheric pressure, separating vapors and non-vaporous residue from the resulting product, fractionating said vapors to separate relatively high-boiling components therefrom as reflux condensate, returning said reflux condensate to the `aforementioned cracking step, lighter hydrocarbon oil, such as distillate comlprising poor antiknock gasoline fractions, to reform and convert the same into highyields of gasoline of `im-proved antiknock value, cooling the resulting reformed products sufficiently to prevent substantial further cracking thereof and in a second fractionating step fractionating the cooled products in commingled state with frac# tionated vapors from the first mentioned fractionating step to condense from the mixture, as a secondary Vreflux condensate, components thereof boiling above range of the desiredgasoline product, Asubjecting fractionated vapors kof the desired end-boiling point from `the second mentioned fractionating step to condensation, recovering the resulting distillate and cooling and commingling'regulated 'quantities of said secondary reflux condensate with'the heated products of the reforming step to effect' said cooling of the latter.

As a special feature of the invention, that portion fof said secondary reflux condensate, which is not required for cooling the reformed products, as abovedescribed, is subjected to flash distillation to substantially free the same of undesired low-boiling components to leave as the unvaporized residue a product meeting market specifications for furnace oil, the evolved vapors from kthis flash distilling step being subjected to condensation and the resulting condensate returned in regulated quantities to one or both of 1 the aforementioned fractionating steps wherein it serves as a refiuxing and cooling medium. This feature cooperates With the feature of subjecting the vaporous products of the heavy oilcracking operation to primary and secondary fractionation in successive. fractionating zones and the .feature of supplying the reseparately heating a' formed products .to said secondary fractionating zone in that, by this method of operation, materials of the generalnature of pressure distillate bottoms in the products of the heavy oil cracking operation and thetot'al componentsr of the reformed products boiling above the range of gasoline are recovered as an intermediate [product meeting the flash point and other specifications for good quality furnace oil.' These featuresV are also cooperative with that of employing regulated quantities of said secondary reflux condensate as a medium for cooling the hot reformed products prior to fractionation thereof. The secondary reflux condensate is ideal for this purpose in that it 'is relatively refractory for cracking, Will not contaminate the reformed products in any respect and in that, since it is not materially converted into lighter and heavier productsby recycling in the manner described and an unlimited quantity thereof is available for cooling the reformed products. Due to these characteristics, its use inthe manner described does not appreciably decrease th'e quantity of furnace oil recovered.

Another special and coperative feature of the invention resides in subjecting a regulated portion. of the fractionated vaporous stream from the primary fractionating zone to partial con. densation to form a distillate which is returned as cooling and reuxing medium to the primary fractionating step, the uncondensed components of the lpartially condensed stream being commingled and subjected vto further condensation with thefractionated vapors-from the secondary fractionatingzone. L This is not only a'convenient method of obtaining reluxing material for the primary fractionator; but also materially decreases the load and required size of the secondary fractionator as compared with an operation in which uncondensed components .of said partially condensed stream are supplied to the secondary fractonator or an operation in which the total fractionated vapors from the primary fractionator are supplied to the secondary fractionator. In order to obtain full advantage of this feature, I operate the partial condensing and succeeding separating step under temperature and pressure conditions regulated to give acondensate `for recycling to the primary, fractionator as a cooling and refluxing mediumwhi'ch is substantially free of Vdissolvedigases and" give an uncondensed fraction consisting predominantly of light gasoline and gases andfsubstantially. free of components boiling above the range of the desired final gasoline product. kBy this'meth'odof operation, said uncondensed fractions will notl Referring to the drawing, charging stock for the process, which may comprise an oil `of high--V boiling characteristics or of relatively wide boiling range, such as, for example, crude petroleum",

topped crude or the like, is supplied vthrough line I and valve 2 to pump 3 by means of which it is fed through line 4 and may be directed there-Y from, all or in part, through line `and valve 6 into fractionator 1 or, allor in part, through' lineV 3, valve `9 and line I0 to heating coil II.

Y .When the charging oil isY supplied, as described, tofractionator 1, it serves as aI cooling and reuxin-g medium in this zone for the vaporous conversion products with which it is commingled therein and is subjected to fractionation with the vapors. Any components of the charge oil supplied to fractionator l, which corresponds in boiling characteristics to the reflux condensate formed in this Zone, is supplied with the latter, as will be laterdescribed, to cracking treatment in heating coil II, while any components thereof within the range of the overhead vaporous stream removed from fractionator 'I will be commingled therewith and directed to further fractionatin treatment, as will be later described. .The oil supplied to heating coil I I is therein heated to thev desired cracking temperature at substantial superatmospheric pressure by means of .heat supplied from furnace I2 within which the heating coil is disposed. The resulting heated products are directed from coil I I through line I3 and valve I4 into the upper portion of reaction chamber I5 wherein the cracking reaction is continued.

Y Chamber I5 is also .preferably operated at a substantial superatmospheric pressure which may besubstantially the same or lower than that employed-at the outlet of coil II. Preferably, the reaction chamber is insulatedto conserve heat, although insulation is not indicated in the drawing.

. In the case here illustrated, both vaporous andliquid conversion products are withdrawn in commingled state from the lower portion of chamber I5 and directed therefrom through line I6 and valve. II to vaporizing and separating cham-Y ber E8 which is operated ata substantially reduced pressure relative to that employed in the reaction chamber. The liquid conversion products supplied to chamber I8 are appreciably further vaporized in this zone by virtue of the reduced pressure employed therein, leaving a nonvaporous residue in this zone which, depending upon the particular conditions of operation employed, may be either a liquid residue or substantially dry coke. When liquid residue is produced in chamber I8 it may be directed from the lower portion thereof through line I9 and valve to cooling and storage or tov any desired further treatment, not illustrated. When the process is operated for the production of coke in chamber I8, a plurality of such. chambers are preferably employed, although only one is illustrated in the drawing, so that they may be al,

Y previously described. Fractionator 'I is operated kto condense high-boiling components of the vaporouvsconversion products supplied thereto and to separate therefrom as fractionated vapors, a lower boiling stream comprising normally gaseous products, gasoline and also including, in this "particular instance, higher boiling fractions of the nature of light furnace oil. Redux condensate formed in fractionator 'I is directed, together with corresponding fractions of any charging oil supplied to this zone, from the lower portion of thel fractionator through line 23 and valve 24 to pump 25 by means of which this material is supplied, in the case here illustrated, through line I!) and valve 26 to cracking treatment in coil VI I.

It is also entirely within the scope of the invention to supply only charging oil to heating coil II and to employ a separate heating coil for selective cracking treatment of the reflux condensate formed in fractionator 'I, although this modification is not illustrated in the drawing. The system so far described, in conjunction with the drawing, is not considered novel per se and the advantages of the novel features provided -by the invention are not dependent upon the specilc form of cracking equipment employed therein nor its specific method of operation, except with respect to the aforementioned operation of the fractionating step. Many other modifications of the system so far described may, therefore, be employed without departing from within the scope of the invention.

Fractionated vapors of the general character above mentioned are directed from the upper portion of fractionator I through line 2l and supplied, at least in part,'through valve 28 in this line to further fractionation in fractionator 29, a portion of the fractionated vaporous stream preferablybeing diverted from line 2l and subjected to further treatment, including partial condensation, Vas'will be subsequently described.

Simultaneous with Vtheoperation above described, another charging oil of lower boiling characteristics than that supplied to pump 3 and derived from the same or separate source is separately subjected to cracking treatment within the system. This secondary charging oil may be, for example, straight-run or cracked gasoline, naphtha or the like comprising gasoline fractions of inferior antiknock value which will be materially improved by the type of cracking operation generally known as reforming. It -is supplied through line 3! and valve 3| to pump 32 and fed therefrom through line 33 and valve 34 to reforming in heating coil 35. It is, vof course, within the scope of the invention to preheat either the relatively light or relatively heavy charging oil or both to below active cracking temperature by any well known means, notv illustrated, prior to their introduction into the cracking zone. v

-Heating coil 35 is disposed'in a furnace 36 byY means of which heat is supplied 'to the oil passing through the coil to heat it to the desired relatively high cracking temperature, preferably at a substantial superatmosphericrpressure. The resulting highly heated reformed products are directed from. coil `.35 through line 3T and valve 38 and after preferably being cooled, as will be later described, .to a temperaturebelow that at which substantial further cracking thereof will occur, they are directed through line 39 into fractionator 29, together -with Vfractionated vapors from fractionator 1.V Y j, Fractionator 29 is operated to produce as a fractionated overhead vaporous stream from this zone, the vapors having an end-boilingpoint corresponding to that of the desired gasoline product of the process and to condense therein as reflui; condensate,.higher boiling 'components of the reformed products from coil 35,'andY the fractionated vapors from fractionatorl Reflux condensate thus vformed in fractionator 29 is withdrawn from( the lower portion thereof through line 4I and is preferably directed in regulated amounts through valve. 4.21m this line to pump 43V wherefrom. itis returned to fractio-nator 29 via line. 94, coolorS, line 4B and line 39. The oil thus recycled commingles in line 39 with the hot reformed productsY from coil 35 and serves as a means of reducing their temperature to the desired value. 'I'he function of cooler 45 is to reduce the temperature of the recycled reflux condensate in order to limit thev quantity thereof which will be required to ac-A complish the desired cooling. of the reformed products in line 39.

Fractionated vapors fof the desired end-boil;` ing point are directed `from the upper portion of fractionator` 29 through Valve 41, line 48 and line 49 to condenser 59 wherein they are cooled suf-V iiciently to form a gas-containing distillate including substantially all of the gasoline fractions whereinl they are cooled sufficiently to form as the resultingdistillate, gasoline containing substantial quantities of dissolved high-boiling gases. The Aresulting distillate is directed, together With the remaining uncondensed and undissolved gases through line l and valve 52 to collection and separation in receiver 53. Distillate is Withdrawn from this zone through line 54 and valve 55 to storage or to any desired further treatment, not illustrated, such as, for example, stabilization to reduce its vapor presl sure to the desired value. Uncondensed and un'- dissolved gases-collected in receiver 53 are di-f` rected therefrom through line 56 and valve 51 to storage or to absorption treatment or elsewhere, as desired. When desired, regulated quantities of the distillate collected in receiver 53 may b'e returnedbymeans of line 58, valve 59, pump 6D, line El'and valve 62 to the upper portion of fractionator 29 to servetherein as a cooling and refluxingmedium.

Preferably, as previously mentioned, regulated quantities of the overhead vaporous stream from` fractionator 1, instead of being supplied to fractionator 29, are subjected to separate treatment for the purpose and in the manner which will now be described. These vapors are directed in the desired quantity from line 21 through line 63 and valve 84 to cooling and partial condensation in condenser 65- wherefrom the resulting distillate and uncondensed vapors and gases'are directed through line '66 and valve 61 to separa` tion in accumulator 68'. i

One of the purposes of subjecting regulated quantities cfr-'the fractionated vapors from fractionator I ltopartial condensation, as above (1e-'- scribed, to form a distillate for' use as" cooling and refluxing medium in fractionator 1 and, for this purpose, distillate collectedv in accumu-` lator 68 is directed therefrom inregulated quamA titles through line 69, valve 18, pump 1I,` line 12 and valve 13 to the upper portion of frac-:. tionator 1.

Anotherpurpose of the partial condensation treatment to which fractionated vapors from fractionator 1 are subjected is to decrease the load which would otherwise be imposed upon the secondary fractionator 29 if all of the fractionated vapors from primary fractionator 1 were sup'aV plied thereto. This is accomplished by socontrolling the temperature and pressure conditions employed in partial condenser. and accumu-A lator 68 that a substantial quantity of theA vae pors remain uncondensed in the accumulator and that the uncondensed 'materials will not includeany appreciable quantity of fractions boiling above the range of the desired gasoline prod-z uct recovered in receiver 53. It will be understood that the features of the invention, last described, may be employed to' advantage in many cracking systems wherein the vaporous conversion products are subjected to primary and secondary fractionation and that this aspect of the invention` is not limited to use in the combination cracking an-d reformingsystem. That portion of the secondary reflux condena sate formed in fractionator 29 which is not-recycled to this zone, in the manner `previously described, after being used as acooling and reiluxingmedium `for the reformed products from coil 35 is directed lfrom line 4| and through line 11 and may be directed therefrom, all or in part, through line 18 and valve 19 tov cooling and storage or to separate cracking treatment Within the same or a separate system or elsewhere, as desired. Preferably, however, this material is directed, all or in part, from line 11 through line 88 and valve 8| into vaporizing chamber 82 which is preferably operated at a reduced` pressure relative to that employed in fractionator 29. Chamber 82 is operated to effect sucient vaporization of the oil supplied thereto that undesired light fractions, which would give it an especiallylow flash point for use as fur' nace oil, are liberated therefrom. In case the reduction in pressure employed in chamber 82 is not sufficient to accomplish this, additional heat may be supplied to the unvaporized oil in chamber 82 in any suitable welll known manner and, in the particular case here illustrated, a closed coil 83 `through which a suitable heating medium, `such as steam or hot oil derived from within or external to the system may be passed, is provided in the lower` portion of chamber` 82 to reboil the oilsupplied to this zone. remaining unvaporized in .chamber 82 isV directed through the lower portion thereof through line .84 and valve 85 and, in the specific opera-A tion under consideration, this product is .cooled and recovered as specification furnace oil. Light vapors and gases evolved in chamber 82 from the oil supplied to this Zone are directed from the' upper portion thereof through line 86 and valve 8,1 to condenser 88 wherein substantially all of removed from the accumulator through line 9|- and valve 92 and may be directed to storage `or The oir toabsorption equipment, not illustrated, or elsewhere, as desired. Distillate collected in accumulator 90 is `directed therefrom through line 93 and valve 9# to pump- 95-wherefrom it isv fed through `line 96 and may be thence directed in regulated quantities through line 91 and valve 98 into fractionator 29 wherein it comm-ingles with the vapors undergoing fractionation in this zone, serves as a cooling and refluxing medium therefor and is therein subjected to refractionation. When desired, ydistillate from accumulator 96 may also be employed in regulated quantities as a cooling and refluxing medium in primary fractionator l. To accomplish this it is directed from line 96 through line 9,9 and valve I to pump H and therefrom through line l2 and Valve 'I3 to fractionator 1.

As an example of one specific operation of the process provided by the invention, as it may be conducted in an apparatus such as illustrated and above described, the charging oil amounts to 3160 barrels per stream day of which 2660 barrels is an Illinois reduced crude of approximately 24" A. P. I. gravity, while the remaining 500' barrels is a straight-run naphtha of approximately 51 A. P. I. gravity. f

The topped crude is supplied to fractionator 'I and passed therefrom with the reflux condensate formed in this Zone to heating coil l I the total feed supplied to this zone amounting to approximately 10,000 barrels per day and being supplied thereto at a temperature of approximately 765 F'. Conversion products are discharged from coil Il at a temperature of approximately 935 F. and a superatmospheric pressure of approximately 2'75 pounds per square inch and are passed through reaction chamber l5 which is operated at substantially the same pressure.

The total products from the reaction chamber are supplied to Vaporizing and separating chamber IB at a temperature of approximately 860 F. The pressure employed in chamber I8 is approximately 270 pounds per square inch, superatmospheric. The succeeding primary fractionator is operated at substantially the same pressure and a reduced superatmospheric pressure of approximately 150 pounds per square inch is employed in the secondary fractionator and the succeeding condensing and -collecting equipment.

In this particular operation the residual liquid removed from chamber I8 is flash distilled at reduced pressure to produce specification fuel oil in flash distilling equipment of suitable well known form not illustrated in the drawing.

A top temperature of approximately 500 F. is maintained in the primary fractionator and approximately 48 weight per cent of the overhead vaporous stream is supplied directly to the secondary fractionator. The remaining portion of this stream is supplied to condenser 65 wherein it is cooled to a temperature of approximately 150 F., the resulting condensed and uncondensed materials being collected and separated in accumulator 68 which is operated at approximately the same pressure as that employed in the primary fractionator and a temperature of about 150 F. Distillate from accumulator 68 is returned in regulated quantities to the upper portion of fractionator 1 to serve as a refluxing and cooling medium and the uncondensed materials from accumulator B8 are commingled with the stream of ,fractionated vapors being,

supplied from secondary fractionator 29 to condenser 50.

The naphtha charging stock is supplied to heating coil 35and therein reformed, the outlet temperature from this coil being approximately .10.25 F. and the outlet pressure approximately 450 pounds per square inch, superatmospheric. The reformed products are cooled to a temperature of approximately '700 F. and introduced into the secondary fractionator which is operated at a superatmospheric pressure of about 150 pounds per square inch.

' A top `temperature of about 400 F. is maintained in the vsecondary fractionator and the fractionatedvapors from this zone, together with the uncondensed materials from accumulator 69, are cooled in condenser 59 to a temperature of approximately F., the resulting gas-containing distillate and uncondensed and undissolved gases being supplied to receiver 53 wherein they are separated. The distillate from this Zone is supplied to suitable stabiliz'mg equipment of well known form, notI illustrated, wherein its vapor pressure is reduced to approximately 10 pounds Reidy by liberating therefrom regulated quantities of the dissolved gases. A regulated quantity of the distillate collected in receiver 53 is returned to the upper portion of fractionator 29 to serve as cooling and reuxing medium in this zone.

Reflux condensate formed in the secondary fractionator is withdrawn from the lower portion of this zone at a temperature of approximately 550 F. and at the rate of approximately 530 barrels per day. Approximately 290 barrels per day of this material is cooled in cooler 45 to a temperature of approximately F. and then commingled in line 39 with the reformed products discharged from coil 45. The remainder is supplied without cooling to vaporizing chamber 82 which is operated at a superatmospheric pressure of approximately l0 pounds per square inch and wherein the secondary reflux condensate is reboiled at a temperature of about 500 F. The remaining unvaporized material, amounting to approximately barrels per day, is recovered as specification furnace oil and the evolved vapors are subjected to condensation in condenser 88 at a temperature of about 95 F., the resulting distillate being returned from receiver 90 to a mid-.point in the secondary fractionator wherein it serves as a cooling and refluxing medium.

The yields of the various products which may be expected from an operation such as above described are approximately as follows: The gasoline produced will amount to approximately 50.5 volume per cent of the total charging oil and constitutes a blend of reformed and cracked gasoline having an end-point of approximately 400 F., a Reid vapor pressure of approximately l0 pounds and an octane number of approximately 69 as determined by the motor method. The reformed gasoline in this blend may amount to approximately 85 volume per cent of the naphtha charging stock and the cracked gasoline may amount to approximately 44 volume per cent of the topped crude. The fuel oil residue produced may amount to approximately 41 volume per cent of the topped crude of 33.4 volume per cent of the total charging stock and, in this particular operation, has a viscosity of approximately 250 seconds Saybolt Furol at 122 F. The furnace oil recovered from chamber 82 has a flash point of approximately 150v F. and also meets market specifications for light furnace oil in other respects. It may amount to approximately 5.4 volume per cent cf the total charging oil. The remainder or approximately 10.7 volume per cent of the total charging oil is accountable for as gas and loss.

It will, of course, be understood that operating conditions may be varied considerably, depending upon the specific charging stock undergoing treatment and the desired characteristics of the products, Without departing from the scope of the invention and the foregoing example should, therefore, not be construed as a limitation.

I claim as my invention:

1. The hydrocarbon oil conversion process which comprises cracking a charging oil of relatively high boiling characteristics to convert the same into high yields of gasoline, separating resulting conversion products into vapors and nonvaporous residue, fractionating the vapors in a primary fractionating zone to condense relatively high boiling components thereof as primary reflux condensate, returning the latter to the aforesaid cracking step, subjecting at least a portion of the resulting primary fractionated vapors including componentsl boiling above the range of gasoline to cooling and condensation under temperature and pressure conditions such that gases and light gasoline fractions remain uncondensed and to form a substantially gas-free distillate, returning the latter to the primary fractionating step as a cooling and refluxing medium, simultaneously subjecting a second charging oil of relatively loW boiling characteristics to conditions of high cracking temperature at substantial superatmospheric pressure to produce therefrom high yields of good antiknock gasoline, partially cooling the resulting heated products to a temperature at which substantial further cracking thereof is prevented and commingling the same with the remaining portion of the fractionated vapors from the primary fractionating step which include components boiling above the range of the desired gasoline product, subjecting the mixture to fractionation in a secondary fractionating step to condense therefrom as secondary reflux condensate components boiling above the range of the desired gasoline product, cooling and commingling regulated quantities of said secondary reflux condensate with said highly heated products of the second mentioned cracking step to effect said partial cooling of the latter, combining said uncondensed gases and light gasoline fractions with the resulting fractionated vapors from the secondary fractionating step and subjecting the mixture to cooling and condensation, and recovering the resulting distillate.

2. The hydrocarbon oil conversion process which comprises, cracking a charging oil of relatively high-boiling characteristics to convert the same into high yields of gasoline, separating re-` sulting conversion products into vapors and nonvaporous residue, fractionating the vapors in a primary fractionating step to condense relatively high-boiling components thereof as primary reflux condensate, returning the latter to the aforesaid cracking step, simultaneously subjecting a second charging oil of relatively low-boiling characteristics to conditions of high cracking temperature at substantial superatmospheric pressure to produce therefrom high yields of good antiknock gasoline, partially cooling the resulting heated products to a temperature at which substantial further cracking thereof is prevented and commingling the same with fractionated vapors from said primary fractionating step which include components boiling above the range of the desired gasoline product, subjecting the mixture to fractionation in a secondary fractionating step to condense therefrom as secondary reflux condensate components boiling above the range of the desired gasoline product, cooling and commingling regulated quantities of said secondary reflux condensate with said highly heated products of the second mentioned cracking step to effect said partial cooling of the latter, subjecting another portion of said secondary reflux condensate to further vaporization to substantially free the same of undesired light ends and leave an unvaporized portion meeting market specifications for furnace oil, recovering the latter, cooling and condensingsaid vaporzed portion and supplying resulting distillate to the secondary fractionating step as a cooling and refluxing medium, and subjecting fractionated vapors of the desired end-boiling point from said secondary fractionating step to condensation and recovering the resulting distillate.

3. The hydrocarbon oil conversion process which comprises, cracking a charging oil of relatively high-boiling characteristics to convert the same into high yields of gasoline, separating resulting conversion products into vapors and nonvaporous residue, fractionating the vapors in a primary fractionating step to condense relatively high-boiling components thereof as primary reflux condensate, returning the latter to the aforesaid cracking step, simultaneously subjecting a second charging cil of relatively low-boiling characteristics to conditions of high cracking temperature at substantial superatmospheric pressure to produce therefrom high yields of good antiknock gasoline, partially cooling the resulting heated products to a temperature at which substantial further cracking thereof is prevented and commingling the same with fractionated vapors from said primary fractionating step which include components boiling above the range of the desired gasoline product, subjecting the mixture to fractionation in a secondary fractionating step to condense therefrom as secondary reflux condensate components boiling above the range of the desired gasoline product, cooling and commingling regulated quantities of said secondary reflux condensate with said highly heated products of the second mentioned cracking step to effect said partial cooling of the latter, subjecting another portion of said secondary reflux condensate to further vaporization to substantially free the same of undesired light ends and leave an unvaporized portion meeting market specifications for furnace oil, recovering the latter, cooling and condensing said vaporized portion and supplying resulting distillate, in part, to the primary fractionating and, in part, to the secondary fractionating step, as a cooling and reluxing medium, and subjecting fractionated vapors of the desired end-boiling point from the secondary fractionating step to cooling and condensation and recovering the resulting distillate.

JOI-DIW. WARD.

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