US2114987A - Hydrocarbon oil conversion - Google Patents

Description

INVENTOR. l//CO/P STPLETON ATTORNEYS.

April 19, 1938. v. sTAPLE'roN HYDROCARBON OIL CONVERSION Filed July 3l, 1934 Patented Apr. 19, 1938 U r 'rares HYnnooAaoN oir CONVERSION Victor Stapleton, Jackson Heights, N. Y., assignor to The Texas Company, New York, N. Y., a corporation of Delaware appiicationuuly 31, 1934, serial No. 737,702

3 Claims.

My invention relates in general to the conversion of hydrocarbon oil to obtain a motor fuel in the gasoline boiling range, coke and fuel oil as final products.

In the usual combined coking and cracking operations heretofore practiced it has been customary to return the residuum, in the nature of cracked tar and other heavy tar-like products, resulting from the cracking of, a relatively clean m oil, together with unvaporized constituents Yof fresh oil directly to a coking chamber receiving a stream of oil at cracking temperature wherein they are retained and reduced to'coke. It has been foundthat suchI cracked'tars are not the most desirable coking stock and when mixed with unvaporized fresh charge, as well as with heavy condensate from the cracked vapors, they tend to out down the capacity of the entire system as well as produce a coke having certain disadvantages. This decrease in the capacity of the systern is due to the highly refractory nature of the cracked tar, hence a poor cracking stock, which results in the building up of a large quantity of heavy liquid in the coking chamber with the consequent frothing or foaming thereof.

Moreover, coke obtained in 'an operation of this character when using cracked tar as part of the coking stock has been found to be inferior to coke obtained from a less cyclic material.

30 In accordance with my invention, there is provided a combined coking and cracking operation in which cracked tars and other heavy tar-like products are not returned to the coking operation, thereby increasing the capacity of the operation and producing a superior coke. While vthe cracked tars deter from the overall efiiciency of the entire operation as well as from the quality of the coke produced, these materials if properly handled are quite satisfactory and possess qualities that enable a refiner to dispose of them as a readily marketable commercial fuel oil. When practicing my invention these tar-like products are withdrawn from the cracking system as fuel oil or they may be passed to a Zone maintained at a lower pressure than that maintained in the cracking system to thereby remove lighter vaporizable constituents therefrom. By flashing these products it is possible to obtain additional oil suitable as cracking stockin addition to an overhead naphtha fraction and a commercial My invention contemplates introducing a charge `oil into a'dephle'gmating tower receiving cracked vapors. The cracked vapors prior to being contactedwith the charge Aoil are dephleg- (Cl. IgG- 58) mated to separate therefrom the cracked tar and other heavy tar-like products these separated products being separately withdrawn from the clephlegmating tower. The charge oil introduced into the dephlegmating tower may be obtained from a fresh source extraneous to the system or if desired the charge may comprise condensate oil, resulting from flashing the cracked tars, and unvaporized constituents of fresh oil introduced into the flashing zone to Contact the Vaporous constituents therein.

The charge oil thus introduced into the dephlegmating tower receives heat from the upwardly rising cracked vapors therein thereby separating v'aporizable constituents therefrom. The unvaporized constituents of the charge oil, together with any heavy condensate condensed from the cracked vapors, are collected in the dephlegmating tower as a coking stock separately from the cracked tars. The thus collected coking stock is conducted to a coking chamber receiving cracked products and therein retained to be reduced to coke. i

From the foregoing it will be apparent that vthe cracked tars or heavy tar-like products, are notl returned to the coking chamber with the more desirable coking stock thereby improving the operation and producing a superior coke. This stock, is however, separately withdrawn from the cracking operation and recovered as a valuable commercial fuel oil.

In order to make my invention more clearly understood, I have shown in the accompanying drawing, means for carrying the same into practical eifect without limiting the improvements in their useful application to the particular constructions which, vfor the purpose of explanation, have been made the subject of illustration.

The single gure illustrates diagrammatically one form of apparatus for carrying out my invention.

Referring to the drawing there is shown a furnace I having a preheating coil 2 and a cracking coil 3 preferably heated preponderantly by radiant heat disposed therein. The cracking system may comprise in addition to the furnace I, a coking chamber d, a dephlegmating tower 5 divided into an upper portion 6 and a lower portion 'i by means of a trap-out tray 8, a fractionating tower 9, such as a conventional bubble tower, a condenser II and a distillate receiver I2 having a valved gas outlet I3 and a valved distillate withdrawal line I4.

A clean condensate oil resulting from fractionation of vapors in the fractionating tower 9,

2 as will be hereinafter explained, may be with# drawn from the lower portion of the fractionator 9through a line I5 and forced under super- Yatmospheric pressure, by means of a pump IB,

through the coils 2 Vand 3 wherein it is raised to Vthe desired cracking temperature.V The cracked 'products may be conducted from the cracking coil 3 through atransfer line I1 controlled by a suitable pressurer'eduction valve I8, two of which are shown but only o-ne of which is actually used n vfor any one particular operation, as will beV hereinafter explained, into-the coking chamber 4. The condensate oil passing throughV the heating coils 2 and 3 is preferably heated under Vapor phase cracking conditions Vand the vapors upon entering thek coking chamber 4 pass upwardly therein undergoing additional crackingarnd may Y be conducted through a line I9, controlled byra pressure reduction valve 2|, into the lower portion V1 of theA dephlegmatin'g tower 5.

The vapors introduced into the lower portion l into the upper portion 6 to contact the upwardly risingpvapors to separate relativelyheavy con# stituents as a condensate fromthe vapors and effect Yvaporization of pany light vaporizable constituents of the freslioil. These condensed con-v `stituents ofthe vapors and unvaporized portions Y ofthe charge oil arecollected on vthe trap-out Y'return to the heating coils through Vtheline I5.V

tray V8. The thus dephlegmated'vaporsv maybe conducted from Vthe dephle'ginator `5Athrough a line 22 intothe lower portionl ofthe fractionaltfr ing tower 9 and therein subjected to fractionation to separate out a clean reuX condensateY for 'Ihe fractionated. vapors leaving the fractionat-V ing. tower 9 may be conducted through the line 23 into the condenser II, wherein they are ccndensed, and then passed through aline vdistillate receiver I2. Y t Y Y In accordance with my invention, thefheavy 24 to. the

tar-like productsl collected inthe lower portion V1 ofthe dephlegmator 5 may be withdrawn from thecracking system through a line 25. YThis crackedvtar may be passed yto Asuitable storage. by opening a valve 26 in therline 25 or if desired maybeconductedto a flash chamber maintained f 21. VThe cracked tar' upon entering chamber is partially vaporized and the unvaporized'constituents comprising the desired fuel oil Y under reduced pressure. As shown, the cracked tar may be conducted through aline 2B, a valve 21 therein being openedand the valve V25 being Y closed, to a flash chamber 29 Yhaving anr upper portion 3I and a lowerpcrti'on 32 separated from -each other by means of a trap-'out tray 33.Y The pressure maintained on the cracked tar passing to the flash chamber-29 is reducedV by the valve the flash y are'collected in the lower portion 32 and withflash chamber 29 drawn therefrom through a line 32', Thevaporous constituents resulting from the vashing of the cracked tar pass upwardly in the Y through'ai passage in the trap-1 out tray 33 into the upperV portion 3 I 'wherein they .are'dephiegmated A' fresh charge oil,gi n `the nature of a heavy oiLsuch as a reduced crude The vapors passing through the upperY A fresh charge Yoil of a Y mator 5. o

valve 21 is closed and the valve 26 opened, thus Y f providing forwithdrawal ofthe cracked residuuin Y l f from the lower portion v1 through the line 25.

or a crude, preheated if desired, may be intrcduced into the upper portion 3I of theflash chamber 29 through a pipe 34 by, means of a pump 35. The fresh charge upon contacting the upwardly rising vapors is thus heated and the lighter orrlower boiling vaporizable constituents separated therefrom. The unvaporized portion Y of the fresh charge oil, together with condensateY n resulting Vfrom the dephlegmation of the up-Y wardly rising vapors, are collected'onthe trap-Y Y .out tray 33 to constitute thecharge Yoil for the dephlegmating tower 5.

The -vaporous constituents leaving the Vflash chamber 29 of a low boiling character in the nature of naphthamay be conducted througha line 36 to a condenser 31 wherein they are conkdensed and passed through a line 38 to a dis-V tillatev receiver 39 having a valved gas Youtlet 4I and valved distillate withdrawal lineV 42.` Under certain conditionsV of operation the stock Vcollected in receiver 39 may comprise kerosene,V Vand/or light gas oil, in addition to naphtha.

The unvaporized Vconstituents of [the fresh charge introducedY into the ash tower 29 and the condensate resulting from dephlegmation of the flashed vapors from the cracked tar whichY 'are collected oriV the trap-outvtray 33 maybe of a pump 44 through a line 45 into the upper` portion of the dephlegmating'tower 5. The ,de-y

Y phlegmating tower 5 vis las shown provided vwith suitable plates both above and belowthe trapout tray 8 for facilitating kthe Ydesired dephlegmation.V The ycharge oil thusv introduced rinto the upper portionY ofthedephlegmator 5 iiows downwardlyover the .plates in the `upper portion DOI'S.

suitable Yas chargingV stock "for the cracking coilrvr 3 are thus driven offland the unvaporized con-` stituents togetherrwith heavy condensate result;-

out tray 8 toeconstitute a coking stock.

As contemplated by my invention, andin carrying YYout the aforementioned objects, a vfresh charge oil from an extraneous source may be introduced vdirectly into the upper partV of ther Y dephlegrnator 5, this `o'iljbeing preheated, forl ex-` ample by passing it through apreheating coil withdrawn through a line 43-and forced by means I 6 and contactsvtheupwardly rising cracked va-V i Vaporizable constituents Yof thel charge Voil lio f ing from the dephlegmation ofthe cracked'vapors f' inthe upper portion Bare collected on the trapj positioned in the lower portion Tof-the dephleg-v Y When operating in'v this manneiy'the `The coking stock collected lon the trap-out l plate 8 which comprises unvaporized constituents of the fresh charge and condensate resulting from Vdephlegrnation ofthe cracked vapors but Vfree from cracked tar-like products may be Withdrawn through aline 46 and forced byfmeans of a pump Y 41 to the stream of clean condensate Vundergoing cracking. As shown, the coking stock may be.

introduced either on ythe higher 10W pressure side of -the pressurereductionvalve I8 therebyvcausing the stock so introduced to be raised to a cracking temperature and accomplishing sonic Y viscosity-breaking of this stock prior to its entry i into the coking cham-ber 4; If desiredthecoking.

stock may be passedv to an intermediate `point of the Ycracking'coil V3 in orderto impart more 'Y heat theretobefore being lpassed tothe coking chamber 4 -to cause even more cracking thereof of ya viscosity breakinglnature; or, vif desi-red, ajh f portion thereof may be passed directly to some intermediate point of the coking chamber 4, such as the upper part thereof and another portion of the coking stock merged with the highly heatedv condensate before this condensate is passed to the coking chamber 4 in any one of the ways already described.

The coking stock is thus intimately contacted with the highly cracked products and the Vaporizable constituents thereof separated and these together with cracked vapors are passed to the dephlegmator as before described. The liquid constituents of the coking stock are retained in the lower portion of the coking chamber 4 and are therein maintained at a coking temperature by the highly heated cracked products from coil 3 and reduced to coke. The coke produced in accordance with my invention is substantially free from cracked tar and other heavy tar-like products initially carried over from the coking Zone, and has been found to contain more lump and to be of a better granular structure than coke produced in accordance with prior processes. As the coke gradually builds vup in the coking chamber 4, the point of introduction of the cracked stream is correspondingly raised in a well known manner, and when the coking chamber 4 has the desired quantity of coke therein the charge to this particular coking chamber may be cut off and diverted to another similar coking chamber. The thus formed coke may be withdrawn from the coking chamber 4 through the manway 48.

To assist fractionation in the fractionator 9, the distillate, comprising naphtha, or other light distillate, collected in the receiver 39 may be withdrawn through the line 42 and forced by means of a pump 48 through a line 49 to the upper portion of the fractionator 9. This distillate which acts as a reuxing medium directly contacts the upwardly rising vapors and at least a portion thereof is vaporized, the unvaporized portion collecting with the reflux condensate in the lower portion of the fractionator 9 to constitute the charge for the coils 2 and 3.

The dephlegmator 5 and the flash tower 29 have been shown as being divided by means of suitable trap-out trays. It is to be understood that in lieu of using one vessel divided in the manner shown, two vessels may be used for each to accomplish the same results. Y

In carrying out a combined cracking and coking operation in accordance with my invention wherein a motor fuel of the gasoline boiling range is collected in the distillate receiver l2 and lump coke of an exceptionally good granular` structure produced in the coking chamber 4, as well as a heavy gravity fuel oil collected in the lower portion 1 of the dephlegmator 5 and either withdrawn through the line 25 by opening the valve 26 or through the line 32', the clean cycle condensate collected in the lower portion of the fractionator 9 at a temperature of from about 575-675 F. is forced while being maintained under a superatmospheric pressure of from 200 to 500 pounds per square inch through the coils 2 and 3 wherein it is raised to an outlet temperature of from about 975 to 1075 F. A coking stock comprising unvaporized constituents of the charge oil and condensate resulting from the dephlegmation of cracked vapors but substantially free from cracked heavy tar-like products is withdrawn from the trap-out tray 8 at a temperature of about 725 to 775 F. and forced to the transfer line il where it merges with the cracked stream. The pressure on the cracked stream either before or after the merging thereof with bined streams at the reduced pressure passed into the coking chamber4 maintained at a tem'- perature of about 830 to 900 F. Residual constituents of the oil introduced into the coking chamber 4 are retained therein and reduced'to coke, the vaporous constituents passing to the lower portion of the dephlegmator 5 which may be maintained at a pressure of from 75 to 250 pounds per square inch by manipulation of the valve 2l and are therein dephlegmated to produce a cracked residuum, such as a cracked tar in the lower portion 1 and the coking stock which is separately collected on the trap-out tray 8. The vapors passing through the line 22 at atem,

perature of about 650 to '7 50 F. are fractionated in the fractlonator 9 to obtain an overhead fraction having an end point within the rangel of4 about 325 to 425 F.

The cracked tar or heavy tar-like product which is at a superatmospheric pressure is introduced into the lower portion 32 of the ash chamber 29, maintained at a pressure of from about atmospheric to about pounds per square inch, and therein flashed to separate a heavy gravity fuel oil of from about 0 to 10 A. P. I. depending upon the charging stock which is withdrawn through the line 32. The vaporous constituents rising upwardly through the trapout plate 33 are contacted by freshfcharge, in the nature of a heavy oil, such as a reduced crude, introduced through the line 34 and preferably preheated to a. temperature about 200 to 500 F. and are therein dephlegmated. The unvaporized portion of the fresh charge together with cond-ensate resulting `-from dephlegmation of the flashed vapors are forced at a temperature of from about 500 to 650 F. through the lines 43 and 45 into the upper portion of the ydephlegmator 5 to constitute the charge oil therefor. This charge oil or fresh charge oil from an extraneous source is treated in the manner aforesaid to produce the products obtained in accordance with my invention.

The temperature-pressure conditionsmaintained on the oil passing through the cracking coils 2 and 3 are such as to accomplish vapor phase cracking, it being understood, of course, that higher or lower pressures and temperatures throughout the entire system may be maintained,

depending on the particular stock being treated. The relative amounts of cracked products from the heating coil 3 and coking stock from trap-out tr-ay 8 in dephlegmator 5, admixed with the cracked products in line l1, should be proportioned with respect to each other so that the temperature within the coking drum 4 will be adequate to form a solid coke residue. Y

While I have shown and described the pre ferred embodiment of my invention, I wish it to be understood that I do not confine myself to the precise details of construction herein set forth, by way of illustration, as it is apparent that many changes and variations may be made therein, by those skilled in the art, without departing from the spirit of the invention, or exceeding the scope of the appended claims.

I claim: I

1. In a method of treating petroleum oil to produce motor fuel and coke wherein a clean condensate stock is subjected to high-temperature cracking treatment in a tubular heating coil, the products thereafter transferred into an enlarged coking chamber atv atemperature ade- 4qua'tefto cokeadditional heavier hydrocarbon oil introduced therein andloverhead vaporous kprod- Y Iucts :resulting Yfrom the cracking and coking Vtreatment fractionated to separate a -desired disti'llate therefrom, theimprovement which comprisesinitiallyfractionating the overhead vaporousfproducts-in a primary fractionatingV Zonato separate a high-boiling fractionrthrerefr'om, sepa rately withdrawing the high-boiling fraction, subjecting said withdrawn fraction( toY further distillation toliberate 1owerboiling constituents Y therefrom, withdrawing unvaporized residue resulting frcmrsaid further .distillationas a Vfuel oilproduct, passing vapors `liberated during said 'further distillation in direct heat exchange with fresh I charging oillcontaining vaporizable and unvaporizable constituents to preheat said fresh charging oil andY condense higher-boiling cony .stituents of said liberated vapors, subjecting vaporsY remaining Vuncondensed in said primary fractionating zone to further fractionation in a secondary fractionatingzone, introducing the preheated fresh charging oil Aintorsaid secondary -fractionating Zone land passing the same in said ,'Zonej in directV countercurrent contact .with

cracked vapors therein to condense higher-boil-V ing .constituents of Y said cracked vapors and vto Vaporize lower-boiling'constituents of said'fresh charging oil, separately withdrawing a mixture of unvaporized'constituents of said charging oil and cracked condensate- `from said secondary fractionating zone, introducing said mixture into coking chamber at a temperature adequate to cokeV additional heavier hydrocarbon oil introduced therein and overhead vaporous products resulting from the cracking and c oking treat-A ment fractionated to separate a desired'distillate therefrom, the improvement which comprises initiallv4 fractionating the overhead vaporous products in a primary fractionating zone tov separate a high-boiling fraction therefrom,l separatelyY withdrawing the high-boiling fraction, subjecting said withdrawn fraction to further distillationfto liberate lower-*boiling constituents therefrom, withdrawing unvaporized residue resulting from said further distillation as a fuel oil product,pass i ing vapors liberated during said further distillation in direct'heat 'exchange with fresh charging oil containing vaporizable and unvaporizable constituents to preheat rsaid fresh charging oil and condense higher-boiling constituents of said liberated vapors, subjecting vapors remaining un- Y condensed in said primary fractionating zone to Vfurther fractionation ina secondary fraction-r atingzone, introducing theY preheated fresh charging oil into said secondary fractionating zone and passing the same in said zone lin direct countercurrent contact `with cracked vapors therein `to condense higher-boiling constituents of' said cracked vapors and to vaporize lowerboiling constituents of said fresh charging oil,-

separatelywithdrawing a mixture of unvaporized constituents of said charging oil and cracked condensate from said secondary fractionating zone, introducing said mixture into theenlarged coking chamber as coking Ystock therefor, subf- Vjecting vapors remaining uncondensed in said secondary fractionating zone to further fractionation in a tertiary fractionating zone to condense constituents boiling above the end point ofthe .1.

desired distillate, separately withdrawing the re-V A sulting condensategand passing it tosaid tubular heatingfcoil as charging stock therefor and "sub-YV jecting vapors remaining uncondensedlvin-said Ytertiaryfractionating zone'to further condensation to separate the desired distillate therefrom(VV In the methodof treatinggpetroleum oiltoiY produce motor fuel and coke wherein aclean condensate stock is subjected'to high-tempera ture cracking treatment 'in a tubular heating coil,` the products thereafter transferred'into an -enlarged ccking chamber at a temperature ade quate to coke additional heavier hydrocarbon oilv introduced therein and overhead Vaporous'products resulting from the cracking and coking tillate therefrom, the improverrtentv which comprises initially fractionatingV the overhead va porous products in a primary fractionating zone to'separate a high-boiling fraction therefrom,V

separately withdrawing the high-boiling frac- V`tion, subjecting said withdrawn fraction to further distillation to liberate 1ower-boiling constituents therefrom, withdrawing unvaporized residue resulting from said'further distillation as Va fuel oil productipassing vapors liberated dur? ing said'further distillation -iin direct heat ex- ,35' treatment fractionated to separate a desired disv change with fresh charging oil containing vapor-Y V.izable and .unvaporizable constituents to `preheat f said fresh charging oil and condense higher-1 T570 boiling constituents of said liberated vapors, with Y drawing a mixture of unvaporized constituents -of Vsaid charging oil and condensate resulting from contacting said rvapors liberated during said further distillation with fresh charging oil and.V

conducting said mixture into the enlarged coking vchamber toy be therein reduced to coke; subjecting vapors remaining uncondensed in saidprimary fractionating zone to further fractionation to 4separate a desired distillate product therefrom.

VICTOR STAPLETON. v

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