US1814700A - Art of cracking hydrocarbon oils - Google Patents

Description

July 14, 1931. E. w. lsoM ART OF CRACKING HYDROCARBON OILS Filed April 9. 1927 kg@ Es EHR INVENTOR BY ma, L ATTORNEYS Patented July 14,l 1931 UNITED STATES PATENT OFFICE EDWARD W. ISOM, 0F SCARSDALE, NEW YORK, ASSIGNOR TO SINCLAIB. REFINING COM- PANY, OF NEW YORK, N. Y., A CORPORATION OF MAINE ARTOF CRACKING HYDROCAR-BON OILS i Application mea April a, 1927. serial No. 182,355.

This invention relates to improvements in the cracking of-heavier hydrocarbon oils, such as gas oil or kerosene to produce therefrom lighter hydrocarbon oils, such as gasoline or gasoline-containing distillates.

Lighter hydrocarbon -oilsv are usually more refractory with respect to elevated temperatures than are heavier oils. Gas oil, for example, will crack more rapidly at a lower temperature than will a lighter kerosene. If subjected to higher temperatures, however, heavier'oils tend to be overcracked with accompanying losses. A

. This invention relates particularly to improvements ina combined cracking operation in which various oils of different characters are subjected to cracking conditions advantageous with respect to the individual oils.

Thisv application is in part a continuation of' .successively through reflux towers 4 and 5.

Vapors from the reflux tower 5 pass through connection 6 to'y a condenser (not shown).

The condenser is of ordinary construction Aand 1s connected toga recelver 1n the usual way. The reflux tower 4 is provided interiorly with baffles, oil for refluXing the vapors being introduced into direct contact with the vapors through connection 7 Reflux tower 5 is provided interiorly with tubes through which the vapors pass, the refluxing medium being circulated about the tubesin indirect heat exchanging relation with the vapors passing through the tubes.

In referring to single pass operation, reference is intended to operation in which the oil supplied to the heating conduit is circu lated but once therethrough. VI intend to include operations in whichl vaporized fractlons may be refluxed and recirculated from the oil heating conduit, but to exclude operations in which unvaporized portions 'of the oil supplied are recirculated through the heating conduit.

The heating conduit 1 is arranged in a. heating furnace 8. This furnace, as illustrated, is advantageously provided with means for recirculating over the heating condult in admiXture with fresh hot products of combustion -a portion" of the heating gases whlch have previously passed thereover.

duit the oilis heated to a cracking temperature, for example, to a temperature of about 8.000 F. to 1200o F., as it is discharged from the heating conduit. In the enlarged chamber 2, the @vapors of the cracked oil sepa-rate These va.-

from any unvaporized ortions.

pors then pass successive y-through the reux f towers 4 and 5 ineach of which heavier portions of the vapors are condensed. In the iirst refluxing operation, that carried out in tower 4, fresh oil, supplied by means'of pump 11, is introduced into direct contact with the vapors. The fresh oil is thus heated and the vapors thus cooled and condensed. Likewise, any intermediate constituents which the fresh oil may contain are vaporized and escape from the refluxing operation together with the vapors from the cracking operation remaining uncondensed. The fresh oil so supplied to the first refluxing operation is advantageously of a leavier character, although' it may contain intermediate constituents. The present invention is of special value and application, in connection with the treatment of such relatively heavy oil containing intermediate constituents. The vapors from this lirst reuxing operation are then subjected to a second refluxing operation, that effected in tower 5. ,Here the vapors are cooled and condensed by indirect heat exchan e with oil supplied through connectionA ond refluxing operation effected by some ex- A ternal means. It is advantageous, however, to employ this fresh oil, previous to introduction into reflux tower 4, for effecting the cooling requisite to the reluxing operation carried out intower 5. The fresh oil, particularly fresh, heavier `oil, may thus be with the vapors in reflux tower 5, by means of connection 12 and then conveyed to reflux tower 4 by means of connections 14, 15 and 7. In the latter procedure, the reiluxing in ltower 5 may be regulated by bypassing a part of the fresh oil through connection 13. Likewise the reiluxing in tower 4 may be regulated by bypassing part of the fresh oil Supplied through either 0r both connections 13 and 14 through connection 16. Fresh oil bvpassed through. connection 16 may be dis- 'c arged into the chamber 2 throughconnections 17 and 18 or returned to storage through connection 19.

and admixed, unvaporized, fresh oil, from reflux tower 4 is advanta eously returned to the enlarged chamber 2 through connections 20, 21 and 18. Part of this mixture, however, may be supplied to the receptacle 22 through connections 23 and 24. The relatively lighter condensate from the reflux tower 5 is conveyed to the receptacle 22 through connections 25 and 24. The receptacle 22, as well as the connections for returning hpt condensates from the reflux towers thereto, isl advantageouslyinsulated against heat loss. In carrying out the inventin the reflux condensate collecting in this receptacle may thus be returned to the operation at temperaturesI as high as 500 F. or even somewhat higher. In the second refluxing operation, that carried out in tower 5, intermediate constituents vaporizedfrom the fresh oil introduced into tower 4 are cm1- densed and flow to the receptacle 22 with the reflux condensate.

The oil collecting in receptacle 22 is forced into the heatingI conduit 1 by means of the pump 10. Additionahfresh oil, particularly fresh, li hter oil, may also be supplied to this reeeptace 22 throughconnection 26. Fresh foil supplied through connection 26 mingles with the hot reflux condensate in receptacle y B5 22, being thereby preheated, and is supplied this body, either continuously or intermitpassed in indirect heat exchanging relation The relatively heavier reflux condensate,

to the heating conduit 1 in admixture therewith.

The operation carried out in the enlarged chamber 2 may be one of several. A body of oil may be maintained therein and subjected to cracking either by the heat supplied internally by the hot products discharged from the heating conduit 1 or by this heat supplemented by additional heat supplied by the furnace'9. This is a par- 75 ticularly advantageous operation for cracking heavier oils or oils which crack with an excessive formation of carbon and pitch. In such operation, oil may be discharged from 8O tently, through connection 27. In addition to thefresh oil supplied to this chamber 2A through connection 16 and, in admixturewith the relatively heavymcondensat-e, through connection 21, additional fresh oil, particularly very heavy oil or easily cracked oil, may be supplied thereto through connections 19, 17 and 18. Or, the operation carried out in chamber 2 may be such as toreduce to coke the'oil residues 'collecting therein. In such operation, it is advntageous to do away with external heating o this/chamber. In such operation, the discharge of oil through con- Jnection 27 inay be omitted, or oil maybe discharged through this connection during an initial period ofoperation and this discharge stopped and the operation carried out for the production of coke in a subsequent period of operation.

In the operation of the invention, lighter loo and more refractory oils are subjected to ad- I vantageous cracking conditions in the heating conduit 1 andheavier and 'less refractory oils are subjected to advantageous cracking conditions in thev enlarged chamber 2. By maintaining less severe cracking conditions in the enlarged chamber 2, overcracking of such heavier and less refractory oils is avoided while the operation of enlarged chamber 2 is adapted to accommodate cracking of 110 such oils as results in formation of fairly large amounts of carbon and pitch. To illustrate, in the operation of the present invention, the charging stock supplied to the tower 4 through connection 7 may be an average 115 gas oil. Lighter charging stock, such as a light gas oil orkerosene, is advantageously supplied tothe receptacle 22 through connection 26. Verylheav'y oilsGto be cracked, such as heavy gas oils, fuel oils or residues,`or 120 oils which tend to form large amounts of u,carbon or pitch when subjected to cracking,

may bepsupplied directly to the enlarged chamber 2 through connection 19. The operation of the invention is particularly ad-l 193 vantageous in the treatment of oils containing intermediate as well as heavier constituents. Such oils are supplied to the reflux tower 4 through connection 7, the intermediate constituents being vap'orized by the heat 129 exchange with the vapors in this tower and I The enlarged chamber 2 is advantageously l maintained under elevated pressure to repress vaporization of constituents undergoing cracking for the production of dcomponents desired in the product under the conditions' prevailing therein. Forthe production of gasoline or gasoline-containing pressure dis-v tillates, for example, the pressure in the enlarged chamber may, for example, be maintained in the neighborhood of 50 to 150v pounds per square inch. The oil supplied vto the heating conduit 1 may be forced into this heat-ing conduit unde'r pressure just suficient to driveit therethrough and discharge the resuting products into the` enlarged chamber'J 2, or the heating conduit 1 may be maintained under a higher pressure than vthat prevailing lin the enlarged chamber 2 and 4the pressure reduced between the heating conduit and the enlarged chamber. The reflux tower Liis advantageouslyl operated undersubstantially the same pressure as that prevailing in the enlarged chamber 2, to avoid the necessity of using a -pump for returning admixed reflux 4o condensate and unvaporized fresh oil from this reflux tower to the enlarged chamber. Where a part of the admixed reux conden-` sate and unvaporized fresh oil from reflux tower 4`is supplied to the receptacle 22, it is also advantageous to operate the reux tower 5 under substantially the same pressure. The reux tower 5 may, however, be operated un- 'der a lower intermediate pressure or atsubstantially atmospheric pressure and the pressure reduced betwe/enA the two reflux towers, 'or the 'pressure may be maintained on the system through both reflux towers and reduced between the second refiux tower and the condenser, or the pressure on the system may be pl'ace of supplying fresh oil to receptacle 22,k

I .es

maintained through the final condenser. In

fresh oil to be forced through the heating conduit 1 may be supplied directly to the suction of the pump operating for this'purpose,

or a separate pump may be used for forcing such fresh oil through the heating conduit. .Iclaimz A* i 1. An .improved method of cracking hydrocarbonl oils, which comprises forcing oil in a single pass through ay heating conduit and heating it to a` cracking temperature therein, discharging the hot oil from the heating conduit into an enlarged chamber, taking off vapors of the cracked oil from the enlarged chamber and` subjecting these vapors succes sively to a first and second refluxing operation, passing fresh oil first in indirect heat exchangin relation with the vapors in the second re uxing operation and then introducing the thus heated fresh oil into direct contact with the vapors in the rst refiuxing operation, supplying admixed reflux condensate and unvaporized fresh oil from the first refluxing operation to the enlarged chamber,

fand supplying reflux condensate from the second refluxing operation'to the heating conduit. I

2. I.Animproved method of cracking hydrocarbon oils, which comprises forcing oi in a single pass through a heating conduit and heating it to a cracking temperature therein,

. discharging the hot oil from the heating conduit into an enlarged chamber, taking off vapors of the cracked oil from the enlarged chamber and subjecting these vapors successively to a first and .second reiuxingoperation, passing fresh oil rst in indirect heat exchangin relation with the vapors in the second re uxing operation and then introducing the thus heated fresh `oil into direct contact with the vapors'in the first refiuxing atY operation, supplying admixed reflux condensate andunvaporized fresh oil from the first refluxing operation to the enlarged chamber, "su plying reux condensate from the second re uxing operation to the heating conduit and supplying additional fresh oil to the heating conduit.

3. An improveA carbon oils,.whi`ch comprises forcing-oil in a single pass through a heating conduit and heating it toa cracking temperature therein,

d methodof cracking hydrodischarging the hot oil from the heating conduit into an enlarged chamber, taking '0E vapors of the icracked oil from the er1- larged chamber and subjecting these vapors successively to a first and second refluxing operation, passing fresh oil containing heavy and intermediate constituents 'first-in indirect heat` exchanging relation with the vapors in the second refluxing operation and then introducing the thus heated fresh oil into direct contact with the vapors in the rst reuxing operation, vaporizing intermediate constitu` ents from the fresh oil in the first reflux ing operation and condensing heavier vapors therein, condensing in/the second refluxing operation intermediate constituents vapor- .ized from the fresh oil in the first refluxing operation, supplying admixed reux con- 'densate and unvaporized fresh oil from the rst reuxing operation to the enlarged chamber, and supplying reiux condensate and condensed intermediate oil con- 50 name.

' stituents from the second reiuxing operation-to the heatin conduit. v

4. An improve method of cracking hydrocarbon oils, which comprises forcing oil 5 in a single pass through a heating conduitv and heating it to a cracking temperature therein, discharging the hot oil from the heating conduit into an enlarged chamber, taking olf'vapors of the cracked oil from the enlarged chamber and subjecting thesev vapors successively to a first and second refluxing operation, introducing fresh oil containing heavy and intermediate constituents into direct contact with the vapors in the first refiuxing operation, vaporizing intermediate constituents from the fresh oil in the first reluxing operation and condensing heavier vapors therein, condensing in the second refluxing operation intermediate constituentsvaporized 'from the fresh oil in the first reiluxing operation, supplying admiXed reflux condensate and unvaporized fresh oil from the first reuxing operation to the enlarged chamber, and supplying reflux condensate 21" and condensed .intermediate fresh oil con- .stituents from the second refluxing opera-y tion to the heating conduit.

5. A process of cracking hydrocarbon oil, consisting in passing oil through a coil disposed within ay heating zone wherein the oil is raised to aconversion temperature, in discharging the highly heated oil from said coil into an enlarged reaction chamber wherein conversion occurs, in passing the evolved vapors through a primary dephlegmator wherein only the less refractory constituents of the vapors are condensed, in introducing in the sa-idprimary dephlegmator a second oil differing in characteristics from the oil passing through the coil to act as a dephlegmating medium for the vapors therein, 1n passing the reflux condensate collected in said primary dephlegmator together with the unvaporized portions of the second oil intro- 457 duced thereto into said reaction chamber,

and in further dephlgmatiilg and condensf ing the vapors issuing `from said primary dephlegmator. 1

n Witness whereof, I have subscribed my EDWARD w. IsoM.

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