US1747437A - Art of cracking hydrocarbon oils - Google Patents

Description

Feb. 18, 1930.

E. C. HERTHEL ET AL ART OF CRACKING HYDROCARBON OILS Filed Aug. l2, 1927 2 Sheets-Sheet Fb. 18, l 930. E. c. HERTHEL ET AL i 1,747,437

ART OF CRACKING HYDROGARBON OILS Filed Aug. 12, 1927 2 sheets-*sheet 2 INVENTORS "1 Eugene C. Hert/! LL v fhg/Yves de fo/an 'fft aras tutti? ENQ@ EUGENE C. HYERTHEL AND THOMAS DE COLON' TIFF'L,` 0F CHICAGO, TLLINOTS, AS-

SIGNORS TO SINCLAIR REFINING COMPANY, F NEW YORK,

0F MAINE N. Y., A. CORPORATION .ART 0F CRACKING HYDROCARBON OILS Application filed August 12, 1927. Serial No. 212,481.

This invent-ion relates to improvements in the cracking of heavier and higher boiling hydrocarbon oils, such as gas oil, fuel oil, and y topped crude oil, to produce therefrom lighter and lower boiling hydrocarbon oils, such as gasoline and gasoline-containing cracked distillates. The invention has several important advantages in heat economies, in features of control, in the treatment of particular stocks under particularly advantageous conditions, and in the maintenance of conditions which permit prolongation of the useful period of operation without sacrifice of efficiency.

In carrying out the present invention, the oil to be cracked is forced in a single pass through a heating zone into a vaporlzing Zone, being maintained under a superatmospheric pressure in both the heating zone and the vaporizing zone. In the heating zone, the oil is heated to a cracking temperature by heat exchange with heating gases, such as the hot 'products of combustion from a firebox in which fuel is burned. Unvaporized oil collecting in this vaporizing zone is withdrawn as a'liquid therefrom and discharged into a separate vaporizing zone maintained under a pressure lower than that prevailing in the first. Vapors, including vapors of the desired lighter and lower boiling oils, separatel in the first vaporizing zone and are taken ed therefrom. Due to the reduction in pressure, a further separation of vapors is effected in the second vaporizing zone, and these vapors are taken off and condensed. 'The resulting condensate, advantageously while still at a relatively high temperature, is forced in a single pass through a separate heating Zone into the first, high pressure, va-

porizing zone, being again heated to a crack- 40 ing temperature in the second heating zone.

The temperature at which the hot oil products are discharged from the second heating zone isadvantageously somewhat higher than that at which the hot oil products are discharged from the first heating zone. The unvaporized residue produced in the second vaporizing zone is not returned to either heating zone, but is discharged from the operation.

The vapors taken off from the first vaporizng zone, the high pressure vaporizing zone,

are advantageously subjected to a refluxing operation from which reflux condensate is returned to the first heating zone together with fresh oil. This refluxing operation, for example, may be carried out by introducing the fresh oil,-0r part of the fresh oil, into direct contact with the vapors from the first vaporizing Zone in a refluxing zone and forcing admixed reflux condensate and unvaporized fresh oil from this refluxing zone through the first heating zone. Part of the fresh oil may also be forced directly,y through the first heating zone. i

The vapors taken off from the second vaporizing Zone, are advantageously subjected to condensation in a refluxing operation for the separation of an)7 lighter and lower boiling oils suitable as components of the desired product from the heavier and higher boiling oils to be returned to the second heating zone. This refluxingoperation may be eected in a particularly advantageous way by introducing into direct contact with the vapors in a suitable refluxing zone a part of the distillate product. Or this refluxing operation may be effected by the introduction of fresh oil into the refluxing Zone, or Vby the introduction of fresh oil together with the reintroduction of a part of the distillate product. Thel reflux condensate from this refluxing operation is then forced through the second heating zone into the first vaporizing zone. Part of the fresh oil may also be forced directly through the second heating zone.

The first refluxing operation ris advantageously effected under substantially the pressure prevailing in the first vaporizing zone;

the second refluxing operation 1s carried out undera lower pressure, that prevailing in the second vaporizing zone or a lower pressure.

In carrying out the invention, it is advantageous to restrict the amount of .vapors taken off from the first vaporizing zone so that unvaporized constituents collect therein in the form of a freely flowing Huid residue. This restrictionv of the amount of vapors taken off can be effected by regulating the pressure maintained 1n the rst vaporizing zone, increasing the pressure to decrease the vaporization, vIt is also advantageous to maintain the unvaporized liquid oil constituents in the first vaporizing zone for a substantial period of time. Vaporization in the second vaporizing zone may be carried far enough to leave a, flux or heavy residue which can be removed as a liquid or it may be carried so far thatonly coke or a cokey mass remains. Vaporization in the second vaporizing zone also may be controlled by regulation of the. pressure maintained therein.,

.lustrate, diagrammatically and conventionally, one form. of apparatus adapted for carrying out the invention.

Referringto Fig. 2, the oil to be cracked is supplied from tank 1. This oil may be introduced into' the reflux tower'2 through connection 3 or it may be supplied directly to the heating coil 4 through connection 5 or it` may be supplied directly to the heating coil 6 through connection 7. Each of the heating coils 4'and 6 discharges into the high pressure vaporizing chamber 8, through 'connections9 and 10 respectively. Vapors from `the high pressure vaporizing chamber 8 pass through connection l1 to the reflux tower 2,'

and vapors remaining uncondensed escape from the reflux tower 2 through connection 12 to the condenser 13. Reflux condensate,

together with any admixed unvaporized fresh oil, from reflux tower 2 passes to tank' l4through connection 15. Reflux condensate, and any admixed unvaporized fresh oil, passes' from this tank through connection 16 to the pump 17 by which, together with any fresh oil supplied through connection 5, it is forced through the heating coil 4. Liquid residue collecting in the vaporizing chamber 8 is discharged through connection 18 to the vaporizing chamber 19 in which a lower pressure is maintained. Reduction of pressure between the two vaporizing chambers is effected by means of valve 20. This pressure reducing ,valve may be manually or automatically controlled, for example, it may be arranged to operate to maintain a fixed A liquid level in the high pressure vaporizing chamber 8. Where thevvaporization in the low pressure vaporizing 19 is carried to the' point where coke or a cokey mass remains, duplicate vaporizing receptaclesmay be provided so that the operation can be'carried out in a'continuous manner. Vapors from the low pressurev vaporizing chamber 19 pass through connection 21 to the reflux tower 22,

land vapors remaining uncondensed escape from the reflux tower 22 through connection 23 to the condenser 24. Reflux condensate from reflux tower 22 passes through connection 25 to tank 26. Reflux condensate from this tank passes through connection 27 to the through connections 32 and 30. Condenser 13 discharges into receiver 33 and condenser 24 discharges intoreceiver 35. In these receivers, the condensed product is separated from any gases and vapors remaining uncondensed. The gases and vapors are discharged through connections 34 and 36 respectively. The condensate from receiver 33' may be separately discharged through connection 37 and that from receiver 35 through `connection 38, or both condensates may be collected together in tank 39 and the composite condensate product, or so much of it as is not introduced into reflux vtower 22 by means of pumpv 31, -discharged through. .connection 40.` The pressure in the high pressure vaporizing chamber may be maintained and regulated bymeans ofvalve 41 in connection 12 between the reflux tower 2 and the condenser 13, or the reflux tower 2 may be operated at atmospheric pressure oran intermediate pressure and the pressure in the vaporizing chamber 8 maintained and regulated by means of valve 42.. The condenser 13 may be operated at atmospheric pressure or at substantially the same pressure prevailing in thev reflux tower 2, super-atmospheric pressure being maintained therein by means of valve 43 or by means of valves 44 and 45. Superatmospheric pressure may be maintained in the-low pressure vaporizing chamber, or the Apressure therein regulated, by

means of valve 46 or valve 47, or by means g of suitable valves beyond the condenser 24. Liquid residue may be discharged from the low pressure vaporizing .chamber 19 through connection 48.

The heating coils 4 and 6 are arranged in separate heating furnaces, 49 and 50 respec- 12| heating gases. The provision of separate heating furnaces makes possible the separate and independent regulation and control of sure vaporizing chamber, particularly where externally unheated, may

also be lagged or heat insulated in a similar manner. It is also advantageous to thoroughly lag or heat insulate the connections 9 and 10 'from the heating coils to the high pressure vaporizing chamber, and the return' connections 15 and 25 from the reflux towers 2 and 22, as well as the tanks 14 and 26, further to conserve heat.

In operation, liquid residue may be discharged from the high pressure vaporizing chamberV 8 to the low pressure vaporizing chamber 19 at a rate, for example, about 150% of the rate at which raw fresh oil is supplied to the operation, and, for example, about 80% of the liquid residue discharged into the-low pressure vaporizing chamber 19 vaporized 'therein and taken off asvapors therefrom. The 20% of the liquid residue from the high pressure vaporizing chamber 8 remaining unvaporized in the low pressure vaporizing chamber4 19, in such operation, would correspond to about 30% of the raw fresh oil supplied to the operation. The high pressure vaporizing chamber may be operated, for example, at pressures to 100 to 150 pounds per square inch or higher pressures, and the low pressure vaporizing chamber may be operated, for example, at pressures ranging from atmospheric pressure, or somewhat lower pressure, up to about 50 pounds per square inch or somewhat higher. Vaporization in the low pressure vaporizing chamber may be promoted by the introduction of steam. The .hotroil products may be discharged from the heating coils 4 and 6 at about the same temperature, or the hot oil products may with advantage be discharged from the heating coil 6 at a somewhat higher temperature than that at'which the hot oil products are discharged from the heating coil 4. The refluxing operation in the reflux tower 2 may be controlled by the regulated introduction of raw oil yto be cracked. The

raw oil may thus be utilized for effecting and controlling this refluxing operation and at the same time first subjected to the cracking conditions maintained in the heating coil 4. The refluxing operation in reflux tower 22 may be controlled by regulated introduction of raw oil to be cracked or by regulated reintroduction of a part of the distillate product. In general, it is more advantageous to supply the raw oil to be cracked to the refiuxing operation in reflux tower 2 or directly to the heat,-

Additional heat may be supand to effect the refluxing operation in reiux tower 22 by means of a returned portion of the distillate product. Additional raw oil may be supplied directly to either or both ofthe heating coils 4 and 6 as required.

rLlhe invention may be further illustrated by the following more specific example of an operation in accordance with the invention as carried out to produce a gasoline-containing cracked distillate ,from a gas oil characier charging stock in apparatus of the type ing coil 4,

illustrated. The heating furnace 49 is operated'tomaintain va discharge temperature from theheating coil 4 of about 750 to 800 F. and the heating furnace 50 to maintain a discharge temperature from the heating coil 6 in the neighborhood of 800 F. or somewhat higher. The head temperature of the reflux tower 2 is maintained in the neighborhood of 550 F. and the head temperature of the reflux tower 22 in the neighborhood of 400 F. The high pressure vaporizing chamber 8 is operated under a pressure 4of about 100 pounds per squaref inch, this pressure maintained through the reflux tower 2,

and reduced and regulated by means of valve' 41 between the reflux tower and the condenser. The low pressure vaporizing chamber 19 and the reflux tower 22, are operated under substantially atmospheric pressure. Raw oil, 31 rate of about 2,000 gallons per hour and at al temperature of about 80 F.; about 1,600 gallons per hour of rawv oil being introduced into the refiux tower 2 through connection 3, about 200 gallons per hour of raw 'oil being supplied directly to the heating coil 4 through connection 5, and about 200 gallons per hour of raw oil being supplied directly` to heating coil 6 through connection 7 fVapors, representing a Composite oil mixture of about 35 Baumwhen condensed, pass from the high pressure vaporizing chamber 8 to the reflux tower 2 at a temperature of about 760 F. and at a rate of about 4,000 gallons per hour. Liquid residue of about 24 Baume is discharged from the high pressure vaporizing chamber 8 to the low pressure vaporizing chamber 19 at a temperature of about 750 F. and at a rate of about 3,000 gallons per hour. Vapors representing a composite oil mixture of about 27 Baume when condensed, pass from the low pressure Vaporizing chamber 19 to the refiux tower 22 at a temperature of about 650 F. and at a rate of about 2,400 gallons per hour. The reflux condensate fresh oil mixture from reflux tower 2 is of about 33 Baume and passes through the connection 1,5 at a temperature of about 664 F, gallons per hour.v The reflux condensate from reflux tower 22 is of about 25.7 Baurn and passes through connection .25 at a temperature of about 550F. and at a rate of Baume gas oil, is supplied at a v and at a rate of about 4,390

about 2,250 gallons per hour. The oil mixture disc-harged by pump 17 is of about 33 Baume and enters the heating coil 4 at a temperature of about 650 F. and at a rate of about 4,590 gallons per hour. The oil mixture discharged by pump 28 is of about 25.8 Baume and enters the heating coil 6 a-t a temperature of about 540 F. and ata hour.

rate of about 2,450 gallons per hour. Liquid residue ofabout 12 Baume and at a temperature of about 600 F. is discharged from the low pressure vaporizing chamber 19 through connection 48 at a rate of about 600 gallons per hour. A distillate product of about 51 Baume is discharged from condenser 13 at a rate of about 1,210 gallons per Aboutv 1,550 gallons per hour of 51 Baume distillate is reintroduced into refiux tower 22 through connection 30 at a temperatiire of about 80 F., and about 1,700 gallons per hour of 51 Baume distillate is discharged from condenser 24. Where references to volumes per hour of vapors or vapor mixtures have been given in the foregoing ex- -ample it is to be understood that the amounts given are in terms of the amount of liquidequivalent to the amount of vapor or vapor mixture. It will also be understood that. the volumes per hour, gravities and temperatures given in the foregoing example are given only as representative approximate averages.

By recycling the oil separated as vapors in the low pressure vaporizing chamber from the Iliquid residue discharged from the high pressure vaporizing chamber, and by recycling this oil at relatively high temperature,

the present invention makes it possible to discharge from the high pressure vaporizing chamber a larger proportion of the oil entering the high pressure vaporizing chamber from the heating coils as a liquid residue Without interfering with the efficiency of the operation or the capacity of the apparatus. This in turn makes it possible to carry out the operation with a satisfactory production of the desired distillate product without the use of excessively high pressures in the high pressure vaporizing chamber or Without any necessityfor heating the oil to excessively Dhigh temperatures in the heating coils. The apparatus employed in carrying outthe present invention may thus be subjected to much less severe strains than are quite commonly imposed in cracking operations.l The discharge of a relatively large amount of liquid residue from the high pressure vaporizing chamber avoids the formation of excessive amounts of-solid or semi-solid coke or carbonaceous deposits in the high pressure vaporiz ing chamber, and-the less severe operating conditions made possible by the invention also assisti reduclng losses due to the for-` mation of pitch-h or-coke or carbon and fixed gases. The inventionalso enables the cracking operation to be carried o ut for prolonged Wards further cracking, and in carrying out the present invention is subjected to particularly advantageous cracking conditionsk in the heating coil through which it is recirculated. Raw fresh oil, and relatively less ref y fractory reflux condensate from the reflux tower on the high pressure vaporizing chamber, is also subjected to particularly advantageous cracking conditions in the separate heating coil through which itis circulated.

Ve claim:

1. An improved method of cracking hydrocarbon'oils, which comprises forcing raw oil in a single pass through a heating zone into avap'orizing zone and maintaining the oil under superatmospheric pressure in'both the heating zone and the vaporizing zone,' heating the oil to a cracking temperature in K,

the said heating zone, subjecting vapors from the said vaporizing zone to a reluxing operation and -forcing reflux condensate therefrom through the said heating zone in admixture with the raw oil, passing unvaporized loil from the said vaporizing zone'to a second vaporizing zone and maintaining the oil therein under a pressure lower than that -prevailing in the first vaporizing zone, subjecting vapors from the second vaporizing zone to a separate refluxing operation and forcing reflux condensate therefrom in a single pass through a separate heating zone into the first vaporlzing zone, heating'the oil to a cracking temperature in' the said separate heating zone, and taking off' vapors from both refiuxing operations and condensing themto form cracked distillate products.

2. An improved method of cracking hydrocarbon oils, which comprises forcing raw oil in a single pass through a heating Azone into a vaporizing zone and maintaining the oil under superatmospheric pressure in both the heating zone and the vaporizing zone, heating the oil to a cracking temperature in the said heating zone, subjecting'vapors from the said vaporizing zone to a refluxing operation and forcing reflux condensate therefrom through the said heating zone in admixture with the raw oil, passing unvaporized oil-from the said vaporizing zone to a second vaporizing zone and maintaining the oil therein under a pressure lower than-that prevailing in the first vaporizing zone, subv .jectlng vapors from the second vaporizing Ving the o il to av cracking j said heating Zone, subjecting vaporsv from the zone to a separate refiuxing operation and forcing reflux condensate therefrom ina single pass through a separate heating zone into the first vaporizin'g zone, heating 'the oi-l to a higher cracking temperature in the said separate heating zone, and taking off vapors from both refluxing operati-ons and condensing them to form cracked distillate products.

3. An improved method of cracking hydrocarbon oils, which comprises forcing raw oil in a single pass through a heating zone into a vaporizing Zone and maintaining the oil under superatmospheric pressure in both the. heating zone and the'vaporizing zone, heating the oil to a cracking temperature in the said heating zone, subj ectingvapors from the said vaporizing zone to a refluxing operation and forcing reflux condensate therefrom through the said heating zone in admixture with the raw oil, passing unvaporized ,oil from the` said vaporizing zone to a second vaporizing zone and maintaining the oil therein under a 'pressure lower' than y that revailing in the first vaporizing zone, sufijecting vapors lfrom the second vaporizing zone to a separaterefluxing operation and forcing reflux condensate therefrom in a single pass through a separate heating zone into the first vaporizing zone, heating the oil to a cracking temperature in the said separate heating zone, and taking off vapors from both reuxingoperations and condensing the`m to form cracked distillate products, the reflux condensate from both refluxing operations being returned to the said respective heating zones while still at relatively high temperature.

4. An improved methodof cracking hydrocarbo'n oils, which comprises forcing oil in a single pass through a heating Zone into a vaporizing zone and maintaining the oil under superatmospheric pressure in both the heating zone and the vaporizing Zone, 'heattemperature in the said vaporizing zone to a r'efluxing operation effected by heat exchangewith raw oil, forcing reiiux condensate/from the said reliuxing operation admixed with raw oil preheated thereby through the said heatinghzone, passing unvaporized oil from the saidvaporizing zone to a second vaporizing Zone and mainrtaining the oiltherein under apressure lower than thatprevailing in the first vaporizing zone, subjecting vapors from the second vaporizing zone to a separate Vrefluxing operation and forcing reflux condensate therefrom in a single pass through a separate. heating zone into the first vaporizing zone, heating the oil to a cracking temperature in the said separate heating zone, andtaking olf vapors from both reflux'ing operations and condensing them to form cracked distillate products.

5. An improved method of cracking hydro oil carbon oils, nwhich comprises forcing raw and forcing reflux condensate therefrom pressure in-both the through the said'heating Zone invadmixture with the raw oil, passing unvaporzed oil from thesaid vaporizing zone to a second vaporizing zone and maintaining the oil thereinunder a pressure lower than that prevailingin the first vaporizing zone, subjecting vapors from the second vaporizing Zone to a separate refluxing operationl and forcing reflux condensate together'with additional raw oil therefrom in a single pass through a separate heating Zone into the first vaporizing zone, heating the oil to a cracking temperature in the said separate heating zone, and taking off vapors from both refluxing operations and condensing distillate products.

6. An improved method of cracking hydrocarbon oils, which comprises forcing raw oil in a single pass through a heating zone into a vaporizing zone and maintaining the oil under superatmospheric pressure in both the heating zone and the vaporizing zone,r

heating the oil to a cracking temperature 1n the said heating zone, subjecting vapors from the said vaporizing zone to a refluxing operation and forcing reflux condensate therefrom through the said heating zone in admixture with the raw oil, passing -unvapo'rized oil from the said vaporizing zone to a second vaporizing zone and therein under a pressure lower than that prevailing in the first vaporizing zone, subjecting vapors from theV second vaporizing zone to a separate refluxing operation effected by introduction of a. part of the distillate product and forcing reflux condensate therefrom in a single pass through a separate heating zone into the first vaporizing zone, heating the oil to a cracking temperature in the said separate heating zone, and taking off vapors from both refluxing operati-ons and condensing them to form cracked distillate products.

7 An improved method of cracking hyvdrocarbon oils, which comprises forcingraw 'oil 'in a single pass through a heating zone into a vaporizing zone, maintaining -the oil under superatmospheric pressure in both the said yheating Zone and the said vaporizing zone, and heating the oil to a cracking temperature in the said heating zone, taking olf vapors from the said vaporizing zone and condensing them to form a cracked distillate product, passing unvaporized oil from the 4said vaporizing zone to a second vaporizing zone, maintaining the oil in the second vaporizing zone under a pressure lower than that them to form crackedmaintaining the oil prevailing in the first vaporizing'zone, taking ofi' vapors from the second vaporizing zone, condensing them and forcincondensate therefrom in a single pass `t rough a separate'heating zone into the first Vaporizing zone, heating the oil to a cracking temperature in the said separate heating zone, and discharging unvaporized residue from the second vaporizing zone.

8. An improved method of cracking hydrocarbon oils, which comprises forcing raw oil in a single pass through a heating zone into a vaporizing zone, maintaining the oil under superatmospheric pressure in both the said' heating zone and the said vaporizing zone, and heating the 'oil to a cracking temperlature in the said heating zone, taking off f vapors from the said vaporizing zone and condensing them to form a cracked distillate product, passing unvaporized oil from the said vaporizing zone to a second vaporizing l zone, maintaining the oil in the second vaporf izing zone under a pressure lower than that prevailing in the first vaporizing zone, taking of vapors from the second vaporizing zone, condensing them and forcing condensate therefrom 1n a single pass through a separate heating zone into the first Vaporizing Zone, heating /the oil to a higher crack'- ing temperature in the said separate heating zone, and discharging unvaporized residue from the second vaporizing zone.

9. In -the method of cracking petroleum oils in which a reflux condensate is produced from vapors from a cracking chamber and a distillateA is produced from residuum Withdrawn from the cracking chamber, the improvement Which comprises passing said condensate and said distillate under superatmospheric pressure through independent heaters, heating both said condensate and said distillate to cracking temperatures in said independent heaters and discharging the resulting ing chainber.

EUGENE C. HERTHEL. THOMAS COLON TIFFT.

heatedl products into the' crack-

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