US2003776A - Treatment of hydrocarbon oils - Google Patents

Description

June 4, 1935. w. M. STRATFORD 2,003,776

J TREATMENT OF HYDROCARBON OILS Filed Feb. 12, 1951 STILL INVENTOR BY Arrwzfdw Patented June 4, 1935 TREATMENT OF HYDROCABBON OILS William M. Stratford, New York, N. Y., assignor to The Texas Company, New York, N. Y.,a corporation of Delaware Application February 12, 1931, Serial No. 515,189

12 Claims.

,This invention relates to the treatment of hydrocarbon oils and has particular reference to the conversion of higher boiling hydrocarbon oils intdi-lower boiling hydrocarbon oils.

The invention contemplates a process involving the distillation of fresh charging stock in contact with hqt-rgapors from a cracking still, the formation of a condensate from the vapors thus evolved and the utilization of this condensate as a clean cracking stock. The process is particularly adapted'for utilizing crude petroleum or residues thereof since it provides forthe production of a condensate obtained from the crude orresidue as a result of heat exchange with the hot vapors from a cracking still which condensate is freed of residual oil and may thus be used as a cracking stock without the danger of excessive coke formation.

In my co+pending application, Serial No. 273,885,, there is described a method in which a charging stock such as crude petroleum is subjected to distillation by contact with the hot vapors from a pressure or so-called liquid phase cracking operation. The resultant residue is drawn off and the vapors, comprising the vaporized charging stock commingled with the cracked vapors received from the cracking still, are subjected to dephlegmation to thereby form a vapor fraction (from which a distillate is obtained that constitutes the desired gasoline or naphtha) and a reflux condensate consisting essentially of intermediate constituents from the crude charging stock combined with constituents obtained from the cracked vapors which are of higher boiling point than desired for the final naphtha or gasoline distillate,'and this reflux condensate is introduced as charging stock to the cracking still.

In the present invention the fresh charging stock is subjected to distillation by contact with hot vapors from a vapor phase cracking opera- .tion. The resultant residue is withdrawn from the system and the vapors dephlegmated to form a vapor fraction and a reflux condensate, d consisting essentially of the higher boiling products of the vapors from the vapor phase cracking operation and the bulk of the heavier constituents vaporized from the fresh charging stock, and this reflux condensate is introduced as a charging stock to a pressure or liquid phase cracking operation. The lower boiling products from the liquid phase cracking operation are vaporized .and the unvaporized residue withdrawn from-the system. The vapors are subjected to dephlegmation to form a vapor fraction and a reflux condensate, which may be used either as a charge to the vapor phase cracking operation or as acycle' stock for recharging to the liquid phase cracking operation.

erably carried out under considerable superstmospheric pressure and likewise the resultant vapors are dephlegmated under high pressure. The vapor phase cracking operation is preferm ably carried out under lower superatmospheric pressure. preferably near atmospheric pressure. The fractionation of the vapors from the vapor phase cracking operation is carried out in a fractionating tower likewise maintained under 15 low pressure. The low boiling products from the low pressure fractionating tower of the vapor phase cracking operation are preferably returned to the high pressure tower of the liquid phase cracking system where they are combined with the vaporstherein and subjected to fractionation. This return of the cracked products may be conveniently done by condensing the condensible vapors from the low pressure tower, u separating the incondensible gases and, then, pumping the condensate to the high pressure tower. If desired, however. all the vapors be returned directly to the tower without'condensation. '0

In the preferred form of operation the reflux condensate in the high pressure tower is separated into a lower and a higher boiling'fraction. The lower boiling fraction may be taken off as a side stream from the high pressure a tower. and used as a charge for the vapor phase cracking operation. The higher boiling fraction is taken from the bottom of: the same tower and may be used as a. cycle stock for rechar ing to the liquid phase cracking 0 operation. I I

In one method of operation the reflux condensate may be withdrawn as a single fraction from the bottom of the high pressure tower. This single fraction may then be named entirely or in' part to either the vapor phase cracking operation or the liquid phase crack ing operation. I

In order to more fully disclose the invention reference will now be had to the accompanying w drawing which illustrates the preferred em;- bodiment of the invention.

In the apparatus a high temperature heating coil l is connected. by a transfer line! to a cracking still 3. The heating coil is located in The liquid phase cracking operation is prefthe high pressure tower II a furnace 4 having a burner or heating means 5. The still 3 may be insulated so that the body of oil therein may be maintained at the desired cracking temperature by means of the highly heated oil delivered from the coil I by the transfer line 2 or, if desired, the still may be mounted in a furnace in order that the proper temperature may be maintained therein.

A vapor line I0 serves to conduct vapors from the cracking still 3 to a high pressure fractionating tower or dephlegmator II. Baffles I2 are indicated'in the tower II for the purpose of insuring adequate contact of the vapors with the liquids passing therethrough. A vapor line I3 serves to conduct vapors from the fractionating tower II to a condenser I4. A line I5 conducts the products from the condenser I4 to a receiver I6, .the latter having a gas release pipe I! and a liquid draw-off line I8. A line 20 leading from the bottom of the high pres- "sure tower II conducts reflux condensates to a pump 2]. The pump 2I then forces the condensates through line 22 to the heating coil I. A portion of the condensates, if desired, may be by-passed through the by-pass line 23 to the accumulator tank 25.

' In the preferred method of operation the condensates collecting in the high pressure tower I I are separated into a higher boiling fraction and into a lower boiling fraction. The lower boiling fraction maybe collected at an intermediate point in the tower and withdrawn as a side stream through the line 24 to the accumulator tank 25.

"The accumulator tank 25 may also be provided with an inlet line in order that an extraneous oil may be charged thereto to be used as a charging stock when all the condensates collected in the high pressure tower II are recycled to the heating coil I throughline 20, or when only a portion of the condensates from are bypassed through the line 23, in which case the condensates may be insufficient to maintain the desired volumein the accumulator tank 25.

The liquid from the accumulator tank 25 which may be, as indicated heretofore, an extraneous oil introduced through the line 30,

. in'g coil 32 is located within a furnace 36 which may receive heat from a burner 3! or other heating means. The low pressure tower is provided with bafIle plates 38 to insure adequate contact between the vapors and the liq uids therein.

In the preferred manner of practicing the invention the fresh charging stock, such as crude petroleum or a residuum thereof, is withdrawn by the pump 40 from a charge tank 4| and is passed, through the line 42 and suitable connection, either directly to the low pressure tower 35 where it comes in contact with the hot vapors, or first mixed with the cracked products from the vapor phase heating coil and the mixture then introduced into the tower. A connection 43 may be used to pass the fresh charging stock directly to an intermediate point in the low pressure tower 35 by suitable regulation of the valve 44. A connection 45 may be used to pass the fresh charging stock in contact with the vapor phase cracked products prior to entrance to the low pressure'tower by suitable regulation of the valve 46. In either method of operation the cracked products from the heating coil 32 and the fresh charge are intimately contacted and the lower boiling constituents from the crude oil are vaporized and combined with the vapors from the vapor phase cracking operation to be fractionated in the fractionating tower 35.

A vapor line conducts vapors from the low pressure tower to a condenser 5|. A line 52 conducts the products from the condenser 5| to a receiver 53 which is equipped with the usual gas release line 54 and a liquid draw-off line 55. A pump 56 serves to withdraw the liquid from the receiver 53 and may conduct any or all of it to the high pressure fractionating tower by way of the line 51.

The reflux condensates collecting in the low pressure tower consisting of the higher boiling constituents of the vapor phase cracked products and the vaporized constituents of the fresh charging stock are withdrawn from the low pressure tower through the line 60 to an accumulator tank 6|. A line 52 serves to supply an extraneous oil to the accumulator tank 6| if desired. The liquids in the accumulator tank BI may be withdrawn through a line to a pump 66. The pump 66 then forces these liquids through the line 61 to the heating coil I of the liquid phase cracking system.

The unvaporizedliquids or tar collectingin the lower pressure tower 35 may be withdrawn from the bottom thereof through the tar line 68 and sent to storage or otherwise disposed of along with the residue from the still 3 which likewise is withdrawn from the bottom thereof through the residue line 69.

In practicing the invention the cracking operation in the heating coil I and still 3 is preferably carried out in substantially the liquid phase. The cracking system may be any of the common or preferred types in which the temperatures andpressures are well known. I prefer, however, to maintain a body of oil in the still 3 and to maintain the still at a temperature of approximately 750 to 900 F. therein under pressures of, for example, 100 to 500 pounds per square inch. The oil is delivered to the still 3 from the coil I at temperatures of about 750 to 900 F. and it is ordinarily preferable to maintain the coil I and still 3 at substantially the same pressure, there being only the differences involved in the frictional drop due to forcing the oil through' the heating coil. In some cases, however, a pressure .-reducing valve may be employed in the transfer line 2 so that the pressure in the still 3 and tower II may be dropped a predetermined amount. The fractionating tower I I, however, is always maintained under a substantial superatmospheric pressure. In'this way the fractionation of the vapors in the high pressure fractionating tower II is carried out under a pressure sufliciently high to produce sufficient fractionation and at the same time efiect a polymerization'or stabilization of the unstable constituents of the vapors therein."

The vapors withdrawn through the line I3 are gasoline preferably with a -maximum boiling point in the neighborhood of 400 F. The gasoline produced by the condensation of these vapors, as will be observed, consists not only of liquid phase cracked products but also vapor phase cracked constituents whereby a gasoline of high anti-knock quality is obtained.

In the preferred method of operation the lower boiling fraction of the reflux condensates is withdrawn as a side stream through the line 24 and accumulated in the tank 25 for a charging stock to the vapor phase cracking system. It is to be understood, however, that other'types of charging stock may be used in the vapor phase cracker such, for example, as an extraneous oil supplied through the line or a portion or all of the combined condensates received through the by-pass line 23. In case a lower boiling fraction is taken off as a side stream through the line 24, the heavier fraction of the reflux condensate is preferably conducted to the liquid phase cracking coil I where it may be introduced at an intermediate point in the coil as indicated in the drawing.

The vapor phase heating coil 32 is preferably maintained under a low pressure in the neighborhood of atmospheric pressure. The type of vapor phase cracker and the operating conditions may vary depending on the type of cracking system and the nature of the charging stock. The temperature, however, will ordinarily be maintained at approximately 900 to 1050 F.

The cracked products from the vapor phase heating coil are suddenly cooled by contact with the fresh charging stock from the tank 4|.

In this way the charging stock is heated and a substantial amount thereof vaporized. The average temperature of the oil maintained in the bottom of the low pressure tower may be in the neighborhood of 600 F. The liquid drawn off from the low pressure tower through the line 68 may be termed fuel oil. It consists essentially of the unvaporized portion of the fresh charging stock although there may be minor .amounts of the higher boiling constituents of the vapor phase-products.

The reflux condensates from the low pressure tower consisting of a clean all of intermediate boiling point, such as gas oil, is withdrawn through the line 60 to an accumulator tank where a body of clean oil is maintained for a charging stock to the heating coil I of the. liquid phase cracking operation. If desired, an extraneous clean oil, such as gas oil, maybe supplied to the accumulator tank through the line The vapors passing from the low pressure tower 35 consist essentially of all the gasoline constituents from the vapor phase products together with a small fraction of heavy boiling omitted and the vapors passed directly to the.

high pressure tower without intervening condensation.

Obviously many modifications and variations of the invention, as hereinbefore set forth, may

be made without departure from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

I claim:

1. The process of treating hydrocarbon oils that comprises subjecting hydrocarbon oil in a first cracking zone to a substantially liquid phase cracking temperature to effect conversion of the high boiling hydrocarbon oils into lower boiling hydrocarbon oils, vaporizing the lower boiling hydrocarbons of the cracked products, withdrawing the unvaporized oil from the system, fractionating the evolved vapors in a first fractionating zone to form a gasoline-like vapor fraction, a lighter reflux condensate and a heavier reflux condensate, returning the heavier condensate to said liquid phase cracking operation, subjecting said lighter condensate to a vapor phase cracking temperature in a second cracking zone, contacting relatively heavy fresh charging stock with the resulting vapors from the vapor phase cracking operation to thereby vaporize a portion of the fresh charging stock, withdrawing the unvaporized portion of the "charging stock from the system, dephlegmating the combined vapors from. the vapor phase cracking operation and the vapors from the fresh charging stock in a. second fractionating zone to produce a vapor fraction suitable for the production of gasoline and a reflux condensate suitable as a clean cracking stock and charging said clean cracking stock to the liquid phase cracking operation.

2. The process of treating hydrocarbon oil that comprises subjecting hydrocarbon oil in a first cracking zone to a substantially liquid phase cracking temperature, under relatively high pressure, to effect conversion of higher boiling hydrocarbons into lower boiling hydrocarbons, separating the resulting cracked products into vapors and liquid residue, withdrawing said residue from the process, passing vapors so obtained to a fractionating zone and therein fractionating the vapors into a lighter fraction containing gasoline hydrocarbons and a heavier fraction suitable for vapor phase cracking, removing said lighter fraction as desired product, subjecting said heavier fraction suitable for vapor phase cracking to a vapor phase cracking temperature in a second cracking zone, under relatively low pressure, to effect conversion thereof into lower boiling products, contacting fresh relatively heavy charging stock comprising crude oil constituents, with the resulting vapors from the vapor phase cracking operation, in a separating zone, to thereby vaporize, a substantial portion of the charging stock, isolating from the process the unvaporized portion of said charging stock, passing the vapors from the vapor phase cracking operation and the vapors from said charging stock to a second fractionating zone and therein fractionating these vapors into a lighter fraction suitable for the production of gasoline and a heavier fraction suitable for liquid phase cracking, and charging said last mentioned heavier fraction to said flrst cracking zone.

3. The process of treating hydrocarbon oils which comprises mixing relatively heavy fresh charging stock, comprising residual crude constituents, with the hot products from a relatively low pressure vapor phase cracking operation, separating the resulting mixture into vapors and residual liquid, in a separating'zone, removing said residual liquid from the process, passing said vapors to a first fractionating zone and therein dephlegmating them to form a vapor fraction containing lighter hydrocarbons and a liquid condensate fraction containing heavier hydrocarbons suitable as a clean cracking stock, subjecting said clean cracking stock, free from said residual liquid, to conversion conditions of temperature and relatively high superatmospheric pressure, in a first cracking zone, to effect conversion of the high boiling hydrocarbons substantially in the liquid phase into lower boiling hydrocarbons, passing the resulting cracked products to a second separating zone and therein separating the lower boiling hydrocarbons as vapors, removing remaining unvaporized products from the process, fractionating said vapors in a second fractionating zone into a fraction containing gasoline-like hydrocarbons and a heavier fraction suitable for cracking in the vapor phase, removing said fraction containing gasoline-like hydrocarbons, as a desired product, and charging said heavy fraction to said vapor phase cracking operation.

4. The process of treating hydrocarbon oils that comprises subjecting a heavy hydrocarbon oil in a liquid phase cracking zone to cracking temperature, under relatively high pressure, to effect conversion of higher boiling hydrocarbons substantially in the liquid phase into lower boiling hydrocarbons, separating the lower boiling hydrocarbons as vapors, and removing the higher boiling unvaporized hydrocarbons from the process, simultaneously subjecting a light hydrocarbon oil in a vapor phase cracking zone to cracking temperatures, under relatively low pressure, to effect conversion thereof substantially in the vapor phase, contacting relatively heavy fresh charging stock comprising residual crude constituents, with the resulting vapor phase cracked products, in a separating zone, to vaporize a. substantial portion of the fresh charging stock, separating the vaporized portion of the fresh charging stock and the products resulting from the vapor phase cracking operation into vapors and a liquid residue, removing said liquid residue from the process, passing said vapors to a first fractionating zone and therein separating them into a lighter fraction containing gasoline-like hydrocarbons and a heavier condensate fraction suitable for a clean cracking stock, charging said clean cracking stock to said liquid phase cracking zone uncontaminated by unvaporized' portions of said charging stock, combining said lighter fraction with said vapors separated from the oil undergoing liquid phase cracking and fractionating the resulting mixture, in a second fractionating zone, under higher pressure than that of said vapor phase cracking zone, to form a desired stabilized gasoline distillate and reflux condensate of higher boiling point.

5. A process in accordance with claim 4 wherein reflux condensate from said second fractionating zone is utilized as a source of said light hydrocarbon oil subjected to vapor phase crackmg.

6. The process of treating hydrocarbon oil which comprises heating clean charging stock to a cracking temperature in the vapor phase to produce conversion thereof into lighter products, introducing the resulting cracked products into a separating zone wherein separation of vapors from liquid occurs, introducing fresh relatively heavy charging stock, comprising residual crude oil constituents, into said zone, separately removing from said zone light fractions in vapor form, an intermediate condensate free from unvaporized portions of said heavy charging stock and a heavy residue, removing said residue from the process, condensing said light fractions as a desired product, cracking said condensate, separating from the resulting cracked products a liquid residue and a clean condensate stock, utilizing the clean condensate stock so obtained as said charging stock first mentioned, and withdrawing said liquid residue from the process.

'7. A process according to claim 6 wherein said fresh relatively heavy charging stock is combined with the vapor phase cracked products prior to their introduction into said separating zone, in quantities suflicient to reduce the temperature of said cracked products below an active cracking value.

8. In the conversion of higher boiling hydrocarbon oils into lower boiling oils, the process that comprises subjecting a hydrocarbon oil in a cracking zone to cracking temperature under superatmospheric, pressure to effect cracking and vaporization; subjecting evolved vapors to fractionation in a fractionating zone while under a superatmospheric pressure in the neighborhood of 500 pounds per square inch, to form a reflux condensate and a vapor fraction comprising gasoline, removing said reflux condensate and heating it in a separate cracking zone to a vapor phase cracking temperature under a pressure approximating atmospheric to subject the oil to vapor phase cracking, fractionating the products of the vapor phase cracking to separate out a heavier fraction thereof and a lighter fraction thereof comprising gasoline, introducing said lighter fraction into the high pressure fractionating zone to thereby subject said fraction to reconditioning and refractionation under the high pressure therein, and condensing the vapor fraction from the high pressure fractionating zone to form a final gasoline distillate.

9. The process of treating hydrocarbon oil which comprises heating clean relatively heavy oil to a cracking temperature under relatively high pressure, separating the resulting cracked products into vapors and liquid residue, passing said vapors to a relatively high pressure fractionating zone, and therein separating heavier fractions as condensate from lighter products as vapors, removing and condensing the fractionated vapors as a desired product, removing condensate formed in the fractionating zone and passing it in a stream of restricted cross sectional area through a heating zone under relatively low pressure wherein it is heated to a cracking temperature and subjected to conversion in the vapor phase, mixing fresh relatively heavy charging stock with the resulting cracked products immediately upon their emergence from the heating zone, in such quantities that the temperature of the resulting mixture is below an active cracking value, passing the resulting low temperature mixture into a separating zone wherein vapors separate from liquid residue, passing resulting vapors through a fractionating zone wherein condensation of the heavier constituents thereof occurs, removing resulting condensate, free from residual constituents of the fresh relatively heavy charging stock and utilizing it as said clean charging stock first mentioned. removing fractionated vapors from said fractionating zone second mentioned, condensing them andzintroducing the resulting condensate into the iractionating zone first mentioned whereby they are subjected to redistillation and beneficial polymerization under a pressure higher than that of their formation.

10. A process in accordance with claim 9 wherein additional reflux condensate formed in said fractionating zone first mentioned is recycled through said heating zone first mentioned.

11. The process-of treating hydrocarbon oil which comprises passing fresh relatively heavy charging stock through a cracking zone wherein it israised to a temperature in the range of 750 to 900 F. under-relatively high pressure and is subjected to conversion, separating the resulting cracked products into vapors and a liquid residue, passing said vapors through a fractionating zone wherein heavier constituents thereof arecondensed as reflux condensate,

- removing resulting fractionated vapors' and condensing them as a desired product, removing resulting reflux condensate from said fraction ating zone and passing it in a stream of restricted cross sectional area through a heating zone wherein it is raised to a cracking temperature of at'least 1000 pressure, directly admixing crude oil charging still in a stream of restricted cross sectional area the amount of crude oil charging stock so admixed being sumcient to reduce the temperature of the mixture below an active cracking value, passing the low temperature mixture so obtained into a, separating zone wherein vapors separate from liquid residue, passing resulting vapors through a second fractionating zone wherein partial fractionation thereof takes place with the formation of a reflux condensate, removing the fractionated vapors from said second fractionating zone, said vapors compris- F., under relatively low the resulting cracked products while '5 ing gasoline constituents, c'ondensingithe vapors so removed and introducing resulting condensate into said fractionating zone first mentioned for redistillation under higher pressure, whereby beneficial polymerization and stabilization thereof occurs.

12. The process of treating hydrocarbon oil.

which comprises passing-fresh relatively heavy clean charging stock in a stream of restricted cross sectional area through a heating zon'e wherein it is raised-to a crackingQtemp'erature, of at least 1000 F. under relatively low pressure, admixing with the resulting cracked products, while still in a stream of restricted cross sectional area crude oil charging stock inquantities sufiicient to reduce the temperature of the mixture below an active cracking value, passing the low temperature mixture so obtained into a separating zone wherein vapors separate from liquid residue, passing resulting vapors through a fractionating zone wherein heavier constituents thereof are condensed as reflux condensate, removing resulting fractionated vapors, comprising light; gasoline constituents, from said ffactionating zone and condensing them, passing condensate so formed into a .second fractionating zone wherein fractionation thereof 00- I curs under pressure considerably higher than that in said first'fractionating zone, removing reflux condensate formed in said second fractionating zone and passing it through a separate cracking zone wherein itis raised to a cracking temperature in the range of 750 to 900 E, un'der relatively high pressure and conversion thereof occurs, separating the resulting cracked products into vapors and a liquid residue, passing said vapors into said fractionating zone 'sec-.--

0nd mentioned, and removing fractionated vapors from said second mentioned fractionating zone andcondensing them as a desired gasoline distillate.

WHLIAM M. STRATFORD.

.DISGLAIMEIR 2,003,776..William' ltl. Stratfcrd, New York, N. Y. TREATMENT or HYDRbChRBON OILs. Patent dated June- 4, 1935. 'Disclaimer filed' May 20,1937, bythe assignee, The Texas Company. a

Hereby enters this disclaimer to the subject matter of claim 1 thereof,except as said claim a plies to-a process in which the relativelyheavy fresh charging stock which is contacts with the resulting vaporsfrom the vapor hase cracking 0 eration 1s a relatively heavj stock; with respect to stocks employe for conversion mto gasohne by cracking, and contains unvaporizable constituents which'are not vaporized under the conditlons of said contacting with the resulting vapors from the 'vapor phase cracking operation, and in which the resultant unvaporized portion of the charging stock is withdrawn from the system. y

[Ojimal Gazette Jun .15, 1937.]

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