US2008480A - Treatment of hydrocarbon oils - Google Patents

Description

July i6, 1935 c. W. WATSQN ET AL TREATMENT OF HYDROCARBON OILS Filed sept. 9, 1931 mmm j 9m, Y K.

coke residue has been the inability to control the operation so as to Vobtainthe particular residual product desired. Thus, for example, if it isintended to produce a pitch, it has been diflicultto prevent the formation of large quantities of coke with the pitch, and similarly if it is intended to. c run to dry coke it has been impossible to controlv the operation so accurately that at least considerable portions of the coke product will not contain a largepitch or hydrocarbon component.

inV accordance with our invention the heavier or residual constituents are brought into contact with a stream' of condensate maintained at a highertemperature than that of the heavy ory residual constituents, in such a way that an accurate control of temperature may be had so as to obtain the productdesired. Inlsome cases the products from the primary fractionating zone, that is, the commingled fresh charging stock and reiiux condensate from that Zone, may be cooled and the stream of oil thus cooled merged with the highly heated cycle condensate undergoing cracking so as tothus obtain the exact composite temperature desired. The invention also .contem-V plat/es that in some cases, instead of introducing thefresh charging stock to the fractionating zone, that it may be introduced directly into the stream of` highly heated cycle condensate undergoing cracln'ng, the commingled stream being directed into the final lresidue forming zone to effect distillation and polymerization to produce the pitch or Ycoke product desired. In some cases a portion of the charging stock may-be introduced into the fractio-nating zone, while the other portion is directed into the stream of hotvcycle stock passing to the residue forming zone. c

In order to more fully' explain the invention reference will now be had to the accompanying drawing which is aflow diagram showing' apreferred embodiment of the invention. In the apparatus thus illustrated a furnace IIl adapted for supplying heat to the heatingcoils employed, a vaporizing or coking chamber II,` a primary fractionating tower I2 and a secondary fractionating tower I3 are shown. A pump I4 is adapted to introduce fresh charging stock through a line I5 having manifold branch lines as |501, and Ib to the primary fractionating tower I2. It is toy be understood that the fresh charging stock may be introduced into the tower I2 at any suitable point therein. The character of the charging stock employed and other Variable conditionsV will determine the precise point in the tower at which the charging stock is introduced. Thus, for example, in case the charge consists of a very heavy or dirty residuum, such as a crude residuum or cracked residue, it is generally preferable to introduce such a material at a mid-point or lower point in the tower and in such case it is preferable to `provide merelyvbaiiie plates in the lower portion of the towerover which .the liquid may flow, while if desired bubble traysV may be employed in the upper portions of the tower.' f

` A vapor line I6 conducts vapors from the tower '1 vI2 to the tower I3. A line I'I serves for withdrawing condensate from the tower I3 to a hot'I oil pump I8 havinga -discharge line I 9 extending to a coil 20, positioned in th-e furnace I 0. It is ordinarily preferable to subject the reux condensate as introduced by the line I9 to the maximum amount of cracking that can be obtainedin the heating coil Without danger of excessive coke formation, and to accomplish this it is preferable to provide the coil with a soaking section wherein the desired cracking temperature may be maintained.

In the apparatus illustrated the coil 2U is intende-d to be in a convection portion of the furnace and an extension or continuation of thisV coil is indicated comprising wall tubesV to form a radiant section 2l. It is to be understood that various coil heating arrangements may be employed in the practice of the invention. VA ra,- diant section ZI such as indicated is of advantage in maintaining the high cracking temperature desired while avoiding the danger 4of direct flame impingement or of excessive heating by direct current of convection gases. In general it is desirable that the latter portion of the coil in which the oilV is heated in the furnace IU beV disposed in a zone of comparative low heat density adapted to produce a more or Vless soaking effect. VA transfer line 22 extends from the coil 2| to a manifold line 23-having a plurality of Y branch lines as 23a, 23h, 23o, extending tothe coking drum Ii; transfer line which may be employed as a pressure reducingV valve as is hereinafter Ymore fully explained.

'A Vline 25Mis providedforrWithdrawingcom-V bined charging stock and redux condensate 'from the tower I 2 to a pump 26V having adischarge line 21.*',I'he `line`2`| is branched to `form one line` 28 having `further branches, such as 28a, 28h; extending directly to the coking drum II, and another branch line 29 which extends to the transfer line 22.

When introducing heat-ed condensate from the coil 2l mixed with bottoms from' the tower `I2 throughthe transfer line 22 it is preferable to distribute the charge entering the coking drum I2 through branch lines 23o and 23o, and when passing oil from tower I2 through line 28 -it is preferable tov introduce the oil from line 28 through Vthe upper branch line 28a while introducing hot oil from the transfer'line 22 through the iower'branch line 23e. Inother Words, We employ the upper lines 23a and 28a and the lower line 23o instead-of the intermediate lines 2Gb and 23h.

We' prefer that the streams of vapor or liquid entering the coke drum, more particularly those introduced to thel upper or intermediate sec-` tions thereof, he directed downwardly and thus may provid-e downwardly depending outlets 23:1: and 28x for the branch lines 23a and 23h, and 28a and 28h, respectively. The streams of entering fluid may thus be discharged downwardly toward the surface of the liqui-d in the coke drum thus tending to beat down or dissipate any ,foam produced in the coking operation `and cleanse the upwardly rising vapor of anyy foam that may be carried therewith'. In this way the constituentsin the coking drum II may be reduced to .a coke or pitchcresidue without priming.

'A cooling coil Bil is indicated having appropriate valved connections tothe line 21 so that when desired the hot products withdrawn from the tower I2, or a portion thereof, maybe cooled a predetermined degree before being introduced A valve 24 is indicated inV the r'5 "The charging line I5 isshownprovided with Vzo additional' branch 1ines'3`I and 32 communicating with a'coi133 positioned in an economizer section of the-furnace I0, so that aportion or-all of the fresh .charging stock may be .preheated toa predetermined degree.' Inflieu of the economiaer` coil 33 the fresh charging stock maybe.

preheated -in various other Ways,'such' for example as'bypassingit in heat exchange withv hot condensateswithdrawn `from the towers I2 or` I3.- 'The charging line I5 is also shown withfabranch line 3Il^Which`l extends directly to the transfer'lin'e 22,'so thatthe charging stock, instead of being admitted'tothe tower I2, may be passed directly toV the `.transfer line, or `so that afportion of the`4 fresh charger'maybe, passed directly.

tothe transfer linefwhile the otherportion-is introducedy to thetower` I2. A: branch line 35 iszalso indicatedfor'connecting the charging line lat'a' point therein ahead ofthe branch line 3| so that in cases wherecharging stock is being passed-'through theheatingcoil 337al portion of thecoolior unheated chargingstockmay `be passed'directly through the lines 35 and 34 to the transferline '22.\ `Itw`i1l Ythusbe seen that by means of`the connecting `lines shown all'of the `charging stock may Ybez introduced to the tower I2,or all of the charging stockm'ay be in.

troduced directlyrto the transfer line 22 through line 34,01-1 theacharging stock maybe apportioned lbetweenf the tower-kl2 Aand transfer line 22,V andinreither. case" a portionor all `of the charging stock may be heated in the economizer coil` 33` or otherwise, ashasfbeen indicated. i' f A'vaporline 36 is shown foi-'conducting vapors frorn` the` coking still I I jtoithe primary fractionating tower: I 2. lA lline 53:1." is :indicated for.V withdrawing a liquid residue from thestill I I. .l A. bottom manway 38sis shown for-the purpose of coke removal .when running togjcoke, and a well 39r is shown. adapted for suitable coke boring appara-l tus. When running to .ai pitch residuum` a .hot residue inliquid form.: may be withdrawnv through the line 3T during a run; the `pitch solidifiesupon' cooling and may befsubsequently.pulverized.and used as a powdered-fuel or .otherwise utilized. When running to cokeitispreferable to have a plurality; of cokedrums `I I.n Thusthe transfer line 22` may be manifolded to a plurality of drums which can .be cut fintoysuccession duringfa'run,` and while the coke is removed from one drum an-` other drum may be employed-for the formation ofcoke.-V N- I' Y AA `vapor lineA 40 is` shown extending fromithe fractionating tower I3-to a condenser coil 4I and a receiver 42 Yis indicated for collecting the final distillate. Y` Y A line' 43 is shownvinterconne'cting the lines 'II and 25 so that if Adesired a portion of the reflux ed to the liquid withdrawn from the tower I2 for introduction.tothe'transfer line 2 2 orto Athe cokingfstill II. The line`43 is shown as being connected to `a cooling coil 44 and reflux pump 45 so thatjf desired a portion ofl thecondensatewfrom the .tower I3 may becooled and employed as a reflux to the upper portion ofthetower I2 to control. the. fractionating Voperation in the tower. Coolingjmeans mayalso bel applied to the tower I3, such as forexamplea portion; of the final discondensate collected in the tower I3 maybe addtillate collected in the tower 42 maybe refluxed lto the top of the tower I3. i

` In Vaddition to the charging stock introduced bythe pump I4 provision is also made for introducing'additionalcharging stock as by means of may be` admitted directlyy to the fractionating` tower I2 or. may be passed. throughpthepreheating coil 33 before `being admitted to the frac-v tionating tower. When the preheating coil is used the degree of heating may be dependent upon the `.nature of the stock with respect to its'liability tofforniy coke and also may be limited by theextent of cooling thatit `maybe desired to apply'to the tower I2. Thuspfor example, charging stocks ,such'asgas oil and crude residuum may well be heated'to temperatures of 400J F. to 650 F..or Aeven higher in the preheating coil 33 before being admitted to the tower.4 In the:

case of cracked lbottoms withdrawn either from pressure stills, or from stripping stillsin which pressure still residues have been stripped, it @is 'particularly undesirable to apply any very high temperature heating to such oil While .flowing to the coking"k chamber.. These cracked residues contain polymer products of cracking which are readily converted to-coke and gas at temperatures even below those'at whichV any appreciable formation of gasoline may take` place and consequently I these residual oils should not besubjected to high 'enough temperature in the coil 33 as would engen- Yderthe formation of excessive `cokedeposits therein. `As a rule-,1 we prefer to introducethe cracked v residual.` oils directly Vinto the `tower I2 without passing themzthrough the preheating coil .33. In one method of operation ,contemplated the cracked stock may be drawn directly from running tanks receiving j residue .from cracking stills. or from stripping.` stills. and the residue 4vat temperatures sayof 200 `F.to 800 F. passed directly to the towerI2.` .i Y .V The charging stock introduced to the tower I2 operatesto` cool the hot vapors derived from the cokingA drum II and is subjected to fractionation or Vdistillation therein so that any lighter constituents present may be distilled` off-while the residual constituents,` which 5 may be combined with-.a certain amountv of condensed constituents fromthe vapors-.received from` the coking drum, collect. as a combinedresidue and condensate in the lower part of rtheitower and are withdrawn by the pump 26 by which the bottoms from the towerf-are introduceddirectly to the coking still I-I either through line 28 and'one or more of the branch-lines 28aand 28h orby the line 29 to the transfer line 22 ,tobe thus commingled with the s treamof highlyheated oil `flowing from the coil 2Ito1thecoking still II. `\The.vapors ythat pass from Athe' tower I2 to the tower I3 .are lsubjectedfto fractionation therein and the clean reflux condensate that is thus Vobtained inthe towerI3 is withdrawn by the pump 48 land is", subjected to cracking in passage throughthe coils in the furnace I0. The highly heated products from the heating coils are combined eitherin the coking still II, `orinV the .transfer line 22 before-enteringthe still, with theresidual yproducts' from the tower-d2. Itf is advantageous to pass the bottoms from thetowe'r I2 ythrough .the line-29 to the transfer line 222V sincesthis. method of operationfacilitates aivery accuratev control of conditions in the .,coking'still II. ,l Temperature indicating means "may be in-V- ser-ted in the transfer'line 22 beyond the point at. whichthe two streams are merged so that it isl thus` possible y to obtain an extremely accurate control cil 'the V'temperatureandwhence :of `the conditions under which distillationA and polymer` ization ,take'placein the drum II.` VVByvtyarying' the amount of oil introduced to the tower, I2 either as chargingstock'.through'the line-I5, or

lasadditional cooling supplied Vby the reflux con-5 densate pump: 45, ithequantity as Well as the temperatureof thefbottoms obtained in the tower |12 may be regulatedand consequently the extent oftcoolingxapplied to r,the cokingdrum may'fbe accurately controlled and: this cooling maybe further-controlled `by passing a Vportion or'all of the bottoms'lwithdrawn from the tower I 2 through the. cooling coil 3D or by the direct introduction of fresh'charging stock through-the line 34 to the transfer line 22; By these means, coupled vwith thercontroliofthe high temperature streamleavi-ng heating 4coils `in the, furnace I0, v anaccurate regulation Vof Ythe conditions of lpolymerization and vdistillation may be maintained in the coking dru'mII f L :When it isdesired to run to a pitchresidue the `proper.temperature conditions dependent upon the'character of the material introduced in the drum-,H- is maintained so that a pitch'residueof .desired Vmelting vpointis formed which may be continuously withdrawn through the line' =3`I by which'j the pitch may be Vconducted :to suitable cooling and collecting meansin'which the pitch issolidiiied.` i Ifr t When itis desired to' run to a coke residue the liquid: inthe drum II instead of being vwithdrawnfduringthe run is retained in'thefdrum Y and acoking temperature is maintained therein sol'thatsth'e mass is converted to a `coke residue. We have-found vthat it is desirable to distribute theroil' introduced to the coking drum instead of introducing all of the oil to the drum at one point. For example, incase the entire'charge'of oilto the drum is introduced at the bottom,particu" larly whenl charging heavyA cracked residues, there danger of priming tarry I materials through the `vapor line 36 into the-tower I2.v On the other f hand, 'When'introducingY all of the.

charge Atoth'e upper portion ofthe drurnfit` is practically impossible to' runr to'a' dry/ coke; When, Vhovveverjinv accordance withl our invention," the: material is distributed by introducing the'fr'naterial at different pointsin the drumthe y tendency to-'priming may be largely avoided and atV theV same time a dry Vcoke may be produced.

Thus, for example, when the stream of material ati the Sametime avoiding priming. It is advantageous-fand infact practically necessary if a dry coke is toV be produced to establish and maintain acurrent of upwardly rising vapors through the mass in the Vcoke drumVV which can well beaccomplished by the presence in the material introduced tothe lower'part of the drum of the highlyV heatedy cycle stock leavingthe coil When the bottoms that are withdrawn from the tower I2-L are vmixed in the transfer line. 22 with. the stream of .oil owing from the coil 2I` itis desirable to so regulatethe quantity and temperature; of' the'stream of bottoms flowingY through the line-29 :to tl'ietransifer line 22 that the-temperature" of the commingled stream will be suiiiciently reduced, dependent on the rate of flow through the transfer line, that cokingv mayV be avoidedinthe transfer'line. When the charg-f ing stock which` is introduced by the pump I4 to the. tower I.2 comprises anoil that is very readily coked,` such as 'crackedresidud and' whenV such an .oil'isrcommingle'dfwith the stream of highly heated oilV passing ,fromrthe coil 2lr to the trans-r ferfline 22;'care mustibe taken to keep the temperature of the commingled stream down below a'point atwhichrcoking would occur in the transfer line' and connections leading to the coke drum.

This reduction in temperature maybe facilitated bythe introduction of cool oil into the transfer line 22 through line 34. Y 1

One advantageousmethod ofoperation, par.-

tic'ulaily :when .treating 'crackedresidues,V is to introduce the bottoms withdrawn fromftheprimary tower I2through'theline 28 andxuppercurrentof upwardlyrlsing vapors throughrthe mass thercoking chamberis insured so that the heavier hydrocarbons which would otherondary tovverl `I3 and heating coils 2U and 2l` and thus' the establishment'and ina'intenancexot a" wise form pitch pockets in the coke mass as itis formed may 'be readily distilled out'while the mass inthe drum Amaintained at coking temperaturesis thus converted to a dry colte.V

By `retaining the' liquid in the coking drum II and maintaining the mass at colcing`V temperature, vapors areevolved and heavy complex hydro'- carbon constituents' are polymeized to form a coke residue. The'introduction to the lowerrpart of the coking drum of highly heated vaporizable constituentsV (which are present either in the combined stream of cracked vproducts from coil 2I and the bottoms from tower I2,1 when such bottoms areintroduced into the transfer line and a portion or all of the combined stream cli-1 V rected into the. lower part` of the coking chamber, or when the cracked'products' from the coil 2| are passed through 'the line 22 without -admixture with the bottoms from tower I2) serves the purpose not only of maintaining the4 necessary distilling and polymerizing temperature to form the cokevresidue butV also provides an upwardly rising current of vapor which facilitates the removalv of the` very heaviest hydrocarbon componentsjwhich would otherwise tend to form pitch pockets inthe coke mass and thus facili-V tatesl the, production of adry coke. The con-` trol of Athecoolingthat is applied to thecoking drum II may be accomplished by regulating the temperature and quantity of the bottoms that are withdrawn from the tower I2 and supplied tofthe colringv drum either through the Iines`28 or 29 or with such added coolingas the direct introduction of relatively cool oil tcthe transferrline 22 from the line 3G. The coking operation may thus beaccurately controlled in thedrum II so that whilea dry coke may be produced thecoke may not be so hard as to unduly impede the subsequent removal of the `coke from the drum at the end of a run to a given coking drum. Hitherto it has been difficult to produce al dry coke which would mee-t the testsrdesiredA as to volatile content without unduly baking thecoke residue to forni a, hard coke mass which was ex tremely difficult to remove from the coking chamber. The practice of our vinvention Vhas overcome this difficulty by providing for the pro, duction of a dry coke, which is yet of a suiliciente ly soft nature that it may bereadily removed from the coking drum. f

The oil which is heated in the :coils 26 andeZI maybe passed. through these coils under` any suitable super-atmospheric.pressure 'that may be`v desired for cracking, such for example, as a lpres-` sure of several hundred pounds and the. temperae tures may range within any suitable rangecfor cracking although we prefer to employltemperaE tures of the order of 900 to 1000 F. sincetem-f peratures of `this order are advantage'ousin im;-` parting thedesired anti-knock--quality to .-the nal distillate, are sufficiently7 high to maintain the desired pitch-forming or/cokeeformingtem.- perature in the still I I and by reason of the clean character of stock charged through these coils may be employedwithoutthe formation 'ofI ex. cessive coke deposits'in the coilV 2I. Thecoking or pitch-forming still II is held at a moderate superatmospheric pressure such as a pressure of the order'of 50er-100 pounds andwhen higher prssuresare employed` in thecoil 2I, Whichfis usually the case, the pressure should be corre.- spondingly reduced in the coking drum lII as :by means of the pressure reduction valve 24.

In the practice of our invention any suitable charging stock which Ymay be desired to crack may be introduced by' the charging pump I4 to the primary fractionating tower I2. Thus,-for example, algas oil charging 'stock maybe eme ployed and the `stock converted to a gasoline diss tillate and a coke or pitch residue as ultimate products. The practice of `our invention is, how, ever,-particularly adaptedfor the treatment of residual -petroleums having a high*` carbon con,

tent.' v v Y In further explanation Vof the invention, a'Spe.-.

ciic example may be given in whichl the charg.- Y

ing stock as introducednby the pump I4 isc-a crackedresidual` product derived from a previ-A ous cracking operation. In this example ofthe invention residue is'withdrawn from a pressure cracking still,v subjected to'astripping operation and then introduced by the pump rI4 through the linerI at the rate of iifty barrels per hour tothe' fractionating tower I2 at a temperature of about 200 F. The tower I2 is-refluxed with gas oil to maintain an overhead temperature` of about 700 F. while combined residue and con', densate is withdrawn from the bottom ofthe tower at a temperature-ofaboutBOil"` F. i. The tower I3 is vsupplied with a naphthareflux to maintain an overhead temperature of `about 400 F. and a bottom temperature of about 630"` F. Clean cycle condensate is withdrawnY from the bottom of towerIS at therateY of about V260 barrels per hour and subjected to cracking in the coils inthefurnace I0 under about 200 `pounds pressure with al temperature in the outlet of lthe coil-2l of about 9.25" F.' The bottoms from 'the tower I 2 and the stream of cracked products from the coil 2| are. directed into the coking drum II `wherein a. temperature of about 860 F. at 120 pounds Vpressure V.is maintained. Liquid is retaine'd'in the ydrum II and at that temperature 1'.

the mass is readily converted to a coke residue.

\ `In accordance with our invention it is not nec- 4 'essary to emplQy excessively high temperatures inrthe coking drum. We have found that with a wide range .of chargingmaterials satisfactory results may be obtained Within a temperature range extending from` a minimum of about 820 F.825 F. up to a. maximum of about 850 lit-860 F. or 875.911?.A While the practice of the inventionV does netpreclude the of higher temperatures we are able toproducc a marketable coke within the temperature range indicated so that there appearstchencnecessity for'goingto higher temperatures. Thus. at the minimum temperatures indicated (about 825 F.) such materials ascrude residual stocks (reduced crudes) and reduced sludge fuel (a product recovered from acid sludge produced in treating oil with sulphuric acid) may, infaccordance with our invention, be satisfactorily treatedto produce a coke substantially free from pitch'pockets and of a sufliciently lowlcontent of volatile combustible matter to meet market requirements. .The higher range of temperature mentionedis well adapted for the treatment of certain of the more refractory stocks such as a gas oil productderived fram a previous coke stilling operation. v

. We find that the higher the temperature employed in the .coke ,drum and the longer the length of' time employed in running to coke in agiven drum, the harder will be the resultant coke and the greater the .diiculty of removing the coke at the end of arun. We have, for example, produced ,a .coke having ,10% to `12% volatile 00mbustiblc matti?? Whhwas easily removed from the coking drum and produced an excellent pulverizediuel, l A coke containing a lower content of vala-tile combustible matter Will tend to be harder and sive Innere difficulty in removal from the coking drum vand furthermore is not so satisfactory A for use as a pulverlzed fuel. However, in accordance with our invention, the operating conditions in the coking drum may be accurately controlled andrnav be varied so as to obtain a coke prnduct having the particular characteristics.desited.A Wer'lprefer to carry onthefractionation in the secondarytower -I3 such a manner that the condensate l.that is drawn off through the line u II will be suitable for high temperature Cracking: By l c arfefully regulating `.the fractionating operation as carried on inthe fractionating towers I2 and I3, more particularly by properly refluxing the-tower I2 so| as t0 prevent the carrying over tothe toweraIS Lof potential cokefforming c-on-V stituer'its.l By the use `ofthe condensate or cycle stock from the tower I3 notl only may the gasoline yield be increased, but the increased temperature of the cracked productsy delivered to the .drum I I facilitates the maintenance of the desired pitchrunning eokgfiprmine temperature therein even admitting to the drum comparatively .large Yquantities of relatively low temperature heatfor coking being maintained by the stream of highly heated products'from vthe cracking coil.V It is advantageous to maintain a .relatively large reservo-ir of liquid condensate in the bottom of tower l3'in order to give a high degree of flexibility in the manipulation Yof pump I8.

A feature of our invention is the means of controlling the temperature not only in the coking drum I l 'but also in the transfer line 22 and connections leading to the coking drum. We have found that at temperatures usually around 975 F. and higher considerable difficulty may be encountered in operating valves in the lines through which the oil at this high temperature is o'wing. In accordance with our invention the stream of oil at temperatures for instance of thev order of 900 F. to 100 F. may enter the transfer'line 22 from the heating coil 2i but the temperature of the stream may be lowered, eitherby the stream of oil from the line 29 or by the stream of oil from the line 3d or by both such streams of oil, to lowerl the temperature sufficiently that the valves, such as those in lines 23a, 2311 and 23e may be readily operated. One great difhculty that has been encountered in Acoking operations has been in diverting the'stream of hot oil from one coking chamber into another coking chamber. In the practice of our invention, by1reason of the cooling oil admitted into the stream of hot oil ahead of the valves, this diversion of the stream may be readily accomplished; It maybe noted that the lines 34 and 29 are shown as being connected with the transfer line 22 rbeyond the valve 24. When there is a considerable drop in pressure through the pressure reducing 'valve 24 this arrangement may-be employed, since then liquid may be more easily introduced at this point than on the higher pressure side of the valve. However, our invention contemplates the introduction of the cooling liquid when necessary on the pressure side of the valve 24 as well.

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

' be made without departing from the spirit and scope thereof, and therefore, only such'limitations shouldbe imposed as `are indicated in the appended claims.V`

l. A combined cracking and coking process for converting hydrocarbon oil into ya light distillate and cokey as final products that comprises passing a stream of condensate oil through a heating coil Y to subjectv the oil to cracking temperature, passgpassing from said heating coil at a lower temperature than said streaml to thus Yreduce the temperature thereof, withdrawing condensate from the secondary fractionating zone and delivering it to said heating coil, maintaining the mass inthe coking chamber' at a coking temperature to thereby convert the same to a coke residue and taking off an overhead distillate from the secondary fractionating zone to iinal light distillate.

-. 2. A combined crackingv and coking process for converting hydrocarbon oil into alight distillate and coke as nal products that comprises pass#` s ing a stream of condensate oil through a heating coil to subject the'oil to cracking temperature; passing the thus heated stream of oil to a coking chamber where distillation takes placentemoving evolved vapors from the coking chamber while retaining the liquid therein, passing the vapors withdrawn from the coking chamber successively to primary and secondary fractionating zones, introducing fresh charging stock into the system,V passing a portion thereof into the primary fractionating zone, withdrawing combined condensate and unvaporized charging stock from the primary fractionatingrzoneV and introducing same into the stream of highly heated oil passing from said heating coil at a lower temperature than said stream to thusY reduce the temperature of the oil delivered to the coking chamber, passing another portion of the charging stock introduced into the system into the stream of oil passing from said heating coil at a lower teme perature than said stream to reduce the tempera-Y ture of the oil, withdrawing condensate from the secondary fractionating zone and delivering it to said heating coil,rmaintaining lthe mass VVin the coking chamber at a coking temperature to there'- by convert the same to a coke residue and taking off an overhead distillate from the secondary fractionating zone to constitute the final light distillate. Y

3. A combined cracking and-coking process for constituteY the converting hydrocarbon oil into a light distillate Y and coke as final products that comprises passing a stream of condensate oil through a heating coil to subject the oil to cracking temperature, passing the thus heated stream of oil to a coking chamber where distillation takes place, removing evolved vapors from the coking chamber while retaining the liquid therein, passing the va.- pors withdrawn from the coking chamber successively to primary and secondary fractionating zones, introducing fresh charging stock into the system, passing a portion thereof through a heating coil to raise its temperature and then into the primary fractionating zone, withdrawing combined condensate and unvaporizedchargng stock from the primary fractionating zone and introducing same into the coking chamber, vpassing another portion of the fresh charging stock introduced into the system into the stream of high-fV residue and taking off an overhead distillate from the secondary fractionating zone to con-v stitute the final light distillate. Y l Y 4. A combined cracking and coking process for converting hydrocarbon oil into a lightdistillate Y and coke as final products that comprises passing a stream of vcondensate oil through agheating coil to subject the oil to cracking temperature, passing the thus heated stream of oil toV a coking chamber where distillation takes place, removing evolved vapors from the coking chamber while retaining the liquid therein, Vpassingthe vapors withdrawn from the coking chamber sucstream of oil passing from'said heating coil at a lower temperature than said stream to reduce the temperature of the oi1,withdrawing condensate from the secondary fractionating zone and delivering it to the rst mentioned heating coil to`subject it to cracking, maintaining the mass in the coking chamber at av coking temperature to thereby convert the same to a coke residue and taking ofi an overhead distillate from the secondary fractionating zone to con- 10 stitute the final light distillate.

CLAUDE W. WATSON.

VICTOR STAPLE'I'O'N.V

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