US2661324A - Conversion of heavy hydrocarbonaceous materials in the presence of subdivided coke - Google Patents

Description

Patented Dec. 1, 1.953

CONVERSION OF HEAVY HYDROCARBNA- CEOUS MATERIALS IN THE PRESENCE F SUBDIVIDED COKE Frederick W. LeHer, Riverside, Ill., assigner to Universal Oil Products Company, Chicago, Ill., a corporation of Delaware Application February 25, 1950, Serial N o. 146,286

(-Cl. Zim- 14) 12 Claims. 1

This invention relates to an improved method and means for effecting the conversion of heavy hydrocarbonaceous materials and particularly the eoking of relatively heavy hydrocarbon oil streams in the presence of subdividedv coke', to produce more desirable lighter hydrocarbon fractions and net usable*` coke. More specifically, the present invention isy directed to the cracking and coking of heavy residual petroleum oils and tars in a moving or fluidized bed type of operation, with heat being supplied tothe coking zone by a continuous recycle.l stream of heated coke particles, and it provides an improved methodk and means for effecting the separation of the resulting coke particlesI so that. only thev liner coked particles are returned to: thefeoking zone.y to, supply heat thereto. and; to provide nuclei for the formation of additional coke.

Many of the recentlyfdisclosed' continuous types of coking operations of the moving' or uidized bed type, have been designed: in a manner which provides for transfer ofrboth hotcombustion gases andcoke particles to the coking'zone toaid inzthe" distillation and coking` of the charge stream. The hot combustion gaseswithin the cokingzzone. give rise to the contaminationzof thedesired'condensable conversion products'v byf undesired Oxy:-V genated impurities,` aswell as considerablequantitles of uncondensable'gases. Also', many of: the processes. make use off mechanical crushing or: other mechanical sizingI and separatingv meansto provide for the.returnofnely-'divided particles to the coking zone, with thel disadvantages aci-- companying thel continuous operation of theA mechanical apparatus; aswell ashigh installa'- tion costs.

It is a principal object of the present invention to provide a simple and efficient method and' means for effecting the separationv of thecoke produced and thelreturn of only the liner'of'the particles to the coking zone' as nuclei and as a heat supplying medium.-

It-isalso an objectpfthepresent invention to' provide for'thecontinuous separation ofthe coke assures a continuously1replenished"accumulation of heated `liner coke particlesfin a collecting zone or reservoir wherefroma streamofithe het liney coke particles may be returned -to thecolz'ingzone aty a rate controllableindependently ottlieerate of :introduction of frea'ctant'fluids VtothisV zone:

It-is-a further object of: thepresentinvention 55 to provide a method and means for effecting the transfer of the ne coke particles and combustionl gases, resulting from the coke separation and heating in the combustion and burning zone, from this zone to a line coke collecting zone in a manner permitting. maximum preservationy and' utilization of the heat contained in these com bustion gases and line particles simultaneously with theV feeding of the separated hot fine ,pare ticles substantially by gravity ow to an elevated portion of the cokng zone;

It is still another object of this invention to provide an improved method and means for simultaneously minimizing: the cokev combustion and controlling the:A separation in the combustion' zone by supplying toA thevv latter an oxygen-'containing gas' streamcontaining regulated amountsl of a hot' relatively inert gas vproduced andseparated within the system.

Principally,. the improved method for' eiectingA the' conversion of a. heavy hydrocarbonaceousL charge stream' int-oi more valuable lower boiling` products and coke according to this invention comprises, introducing' a stream of heated line coke particles into a1 conned' coking zone and therein contactingv themwith the heavy hydro-V carbonaceous charge stream at a temperature'at' which thisichargeistreamis converted into lower boilingv vaporous products and' coke with the transformationof at least some of ne'cokelparticles into coarser particles, continuously withdrawing resulting vaporous conversion products from-thecokingzoneland-passingthem to a frac'- tionating zone;v discharging a. streamofl mixed fine-and coarser cokeparticles from thev coking` zone into a-.il'u-idized bed off-'coke particles main# tained in the lower portieri-ora separate conned combustion zone, introducing a-gas'stream containing free oxygen"` in't'o the?v lower! portion of the luidizedfbed andthere'in burning: a portionv ofthe coke and heatingtlie residual portion ofy` the* cokel particles while' simultaneously passing: the oxidizingv gas stream and resultingv combusv tion'l gases upwardly fthroug'h' the fluidized beda't a rate at vwhich `fine icokel'particl'es-are elutriat'e'd from thev c'oar'sr particlesiand are entraine'd in the gas mixture" disengaglng' from ther uidized bed into the upper portionof the' combustion zone, passing the're'sulting lhot-fine coke suspension into a separate@ruined-:collecting zoneot perature maintained in# the? cokinga zone-` intev` combustion gases which' are continuously with? drawn from the upper portion of the collecting zone and into fine coke particles which are collected in the lower portion thereof, passing a stream f the separated iine coke particles from the lower portion of the collecting zone substantially by gravitational flow as the aforesaid heated fine coke particles into the coking zone, and withdrawing a stream of relatively coarse particles from the lower portion of the iiuidized bed and the combustion zone as net coke production of the process.

In a preferable operation,"the heavy hydrocarbonaceous feed stream is preheated to a high temperature, precluding cracking or coking within the transfer line to the coking zone, say to the order of 825 F. for a reduced crude charge and generally within the range offrom about '750c to about 850 F., and is commingled with the hot finely divided coke particles in the top portion of a descending bed of coke particles maintained within the cracking and coking Zone. At the desired high temperature conditions, the heavy hydrocarbonaceous charge stream is Substantially non-viscous and is cracked and coked with a minimum of agglomeration of particles. Additional coke may be formed by the deposition of a thin nlm-like layer over the coke nuclei introduced to the zone, while in addition new nuclei or particles may be formed during the ensuing conversion and the descent of the dense bed of particles through the conversion andcoking zone. Where the heavy charge stream is introduced to the upper portion of a descending relatively compact moving bed of coke particles extending through substantially the entire height of the coking zone, the resulting vaporous fractions are preferably withdrawn from an intermediate or lower portion of the descending bed of particles. However, when operating with a fluidized dense phase bed of coke particles in the conversion zone, the heavy charge stream is introduced preferably at an elevated point of such bed below the upper level of the latter and the vaporous conversion products are discharged from the iiuidized bed into the upper portion of the conversion zone to be thereafter directed from the latter to fractionation.

' In accordance with a preferred operation, the ne coke particles are introduced to the upper portion of the coking zone to maintain the descending bed of particles, and are supplied thereto at a high temperature within the range of from about 1000* to about 1100 F., while the average bed temperature in the conversion zone is maintained at about 9225"-965o F., and all or at least a considerable portion of the necessary heat for effecting the cracking and coking of the charge stream is introduced in this manner by the supply of heated fine coke particles. However, a desirable operation also utilizes a light high temperature gaseous or vaporous stream within the lower portion of the coking and conversion zone to supplement the supply of reaction heat and to aid in the deasphalting and drying of the resulting coke formation and in the substantially complete removal of valuable low boiling hydrocarbon fractions absorbed or entrained with the descending bed of particles so that a substantially asphalt-free hard coke reaches the bottom portion of the coking zone in a freely flowing particulated state. A gasiform material which will not combine with the desired vaporous product stream in a detrimental manner, and more particularly a gasiform material practically devoid of free oxygen, or a vapor stream which may be readily condensed and sep-t arated from the desired product fractions, is preferably used as the high temperature fluid stream within the lower portion of the conversion zone and may be introduced thereto at a suitable temperature of from about 950 to about 1100" F. Superheated steam may be used to advantage for this purpose, or alternatively, a light refractory hydrocarbon fraction, such as a distillate or light reflux condensate recovered from the fractionating zone receiving the vapors from the coking and vcracking step provides a desirable light charge material for this purpose.

Inasmuch as the continuous coking operation of the present Vtype eifects coke deposition, at least in part, as an additional layer to coke particles present in the coking zone, and there is net coke production in addition to the formation of desired lower boiling fractions which are particularly suitable for the subsequent conversion to gasoline and fuel oil by catalytic cracking processing, the substantially ideal operation provides for the withdrawal of coarser particles from the unit and the return of the finer particles to the coking and conversion zone as the heat carrying material and as nuclei for the formation and deposition of the additional coke. An exacting separation of the ne from coarse particles would, in general, require the utilization of automatic mechanical sizing or screening of particles or other equivalent step or steps in a continuous cyclic system. The present invention utilizes advantageously a combined method of burning and heating and elutriation of particles within a separate confined combustion zone, such that the ner of the coke particles that are elutriated from the bed in the combustion zone are suspended and entrained with the resulting combustion gases for elevation to a point above the coking zone, whereby they may be subsequently introduced to the upper portion of the latter zone continuously and at a rate controllable independently of the rate of supply of the heavy hydrocarbonaceous charge to the coking zone, and also independently of the supply of gasiform high temperature fluid to the lower portion of the latterr to permit therein the aforedescribed preferable' operation of the coking and cracking step.

In order to effect the desired elutriation within the combusion zone, gas must be passed through.l

the descending bed of particles therein in a sufficient quantity and at a sufcient velocity to separate and entrain the desired finer particles in a fluidized transfer to the elevated ne coke collecting zone. Thus, in accordance with a more specic embodiment of the present invention, hot combustion gas used for carrying fine coke particles to the elevated collecting zone isf separated from the particles therein and is then recycled in controlled amounts and substantially without intentional cooling to the lower end of the combustion zone to become admixed with the air or other oxygen-containing stream supplied from an extraneous source so as to provide the desired quantity of a hot gaseous oxidizing, uidizing and entraining medium without unduly increasing the oxygen content of the burning an elutriating stream. A stream of regulated low oxygen content is, of course, necessary to in turn control and regulate the amount of oxidation or burning effected Within the fluidized bed of the combustion zone, so that only so much of the carbon is burned therein as is necessary to heat the remaining particles to a desired temperature for subsequent introduction into the cok- 'accuses ing sand vcrackingtone. Thereby, the lhot recycle combustion gases also =provide for an economical vutilization of heat produced withintheunit'.

'Excess hot 4combustion gases vmay be passed `from thelfinecoke collecting -zone :through a vheat exchanger to produce .or heat steam; vor.alternatively Aexcess hot .combustion .gases may 'be `used to advantage `for the :preheating of acharge stream. fIihe present .operation kalso .effects :the .combustion of a .portionof the .coke vas Wellas zthe .eluitriation, in a .zoneenti-rely separate .from vthe ook.- 'inggzona Wherebythe .mixing of. combustion gases .and other .contaminating :gases :with `,the .desired `-vaporous .hydrocarbon .product 4fractions .is ipre.n cludediand the :formationlof .roxygenated products ein .the .coking 'zone .is .substantially avoided.

ln .a more speci-fic .and desired embodiment of .the present invention, :there is .provided .an improved method sfor :cracking .and .cohing .a 'hea-Vy .hydrocarbon .charge stream, .which .com- -prises,.supplying `-a stream .ofheatednely divided ookeparticles tothe upper portion of Aadescending Jaedioflcoke particles maintained .Within a .cracking .and .coking zone, the .nely .divided coke particles being introduced into the .ooking zone .at a tem.- l ;oerature .above fthe .average .bed .temperature atherein, `ilfltroducing Iheavy hydrocarbon charge stream ,at Ya temperature below the aver- :age bed:.temperature into the upperportionof the `bedarrd effecting therein the conversion of `the .chargel'stream into .-desredlower boiling vaporous products .and icolte with the transformation of `at Aleast ;a :portion of the ne coke particles into .coarsor particles, 'withdrawing .resulting vaporcus .conversion .products ffrom the ldescending .coke :bed .atan ir.xtermeci-iat@ -fnoint .and passing them :to ia traotionating sone, discharging a stream `of .coke vparticles ,from the bottom nor.- ftionofthedescendingbedand-passing .them sub- .:stantially by Vgravity into :a fluidized v:bed Vof coke particles tirolo-Wer portion of .a separate conned `oo nrlloust ion .zone rmaintained ,directly v:below Athecuisine zone, :introducing a VVgas stream .oontaininafree oxygen :to the :lower portion of .the fnuidizedrloed vWithin .the .combustion zone. burn- --ine a portion of the .coketherein .and heating the remaining `.coke particles While simultaneously passing ...the .gaseous :stream and resulting comffbustionigasos upwardly ethrouehfthe iiuidized bed .at rato at which vthe ,iiner coke particles are `elutriated .from theicoarser particles .and are erid .tr nedin the gasmixture -diseneasirie from @the f dined bed into the Iupperportion of the oom- .bustion y.zone passing the .resulting .hot .une coke :suspension upwardly from the combustion zone in .la substantially vertical coni-inedpath in indirect ,heat exchange ,relationship with the .descending flied of yparticles maintained Within the coking `zone, discharging the suspension from the oongfined path into a .collecting ,zone superimposed ldireiztly above the coking `Zone and therein sepa.-

ratingthe suspension at atemperatureabove the ayeragebed ltemperature in :the ooki-ng zone vinto `lcomloustion gases @which uare continuously dis- :chargedif-rom the upper portionof the collecting A@zone and-into fine coke particles l#wliichfare collooted in lthe lower portion thereof, ,passing a stream of ttl-1e separated fhot 4-1"ir.1e-.oo.1 e particles iltromthe lowerportion of the collecting zonefsub- `s tantially by .gravity ,as `the aforesaid stream .of heated nel-ydi-videdooke particles tothe upper tportion of the .c oking zone, and withdrawing a ,stream of relatively .coarse particles yfrom the .lower portion-.of fthe luidized bedand :the oom- .pustion ,zone .the .het vv,coke production of .the

process.

Preferably, .a substantially yvertical .straight transfer conduit kis provided from the .upper .end ofthe combustion zone Adirectly .through thecen- .ter portion of the .coking zone .to an elevated point in the collecting zone, which in turn lis superimposed over the .coking zone, so that the entrained fine coked particles passing liflwardly with the combustion gases may `pass in asubstantia'lly straight rline oW through Vthe .Cokng zoneand in heat exchange relationshiptherewith, .whereby loss of heat from the unit is reduced to a minimum. A portion of the heat from the het combustion .gases and .ne particlesmay be transmitted through .the wall of .the vertical ftranslter yconduit .to the surrounding descending bed Aof coke within the coking and cracking zone; however, the combustion and elutriation operation effected inthe combustion zone in a manner per.- mitting finely divided coke .particles to reach the upper portion of the coking zone, after vpassage through the vertical transfer conduit and theonllecting Zone, at a temperature which is higher than the .average bed temperature in thecoking zone and suiciently high .to eect, or at least materially aid in, the .desiredcracking and coking. of the heavy hydrocarbon charge stream.

Also, in connection with a preferred embodiment of the coking operation, a light `high temeperature gasiform stream, vsuch as superheated steam or heated hydrocarbon distillate, is intro,- duced into the lower .portion of ,the ookingzone'to pass upwardly countercurrently through at least the lower portion `of .the 4descending bed .therein and provide such portion. of :theheat Irequirement of the cracking Vand Vcoking reactions Vas is not furnished by the heatediine coke particles sup.- plied to the elevated .portion of the coking Zone, and moreover to electthe Vheatingand .dry ,distillation of the coke particles :prior to thedisoharge of the latter into the `combustion zone, as Wellas to effect the stripping of .desired low boiling-hydrocarbon fractions.fromfthecokematerial. The latter embodiment .is vparticularly desirable in order to preclude the fagglomeration of particles .where the heavy'hydrocarbon chargehas a tondency to form a heavy tarry .or asphalt-likegdeposition Von the coke .particles in the descending bed.

The operation of the Ypresent improved cracking and coking process as .well .as additional .advantages, will be more apparent upon reference to 'the accompanying drawing-andthe.followingdescription thereof.

Figure 1 .of the drawing, iis :an elevational ,diafgrammatic View of the contacting zones and transfer lines permitting the 1improved'.elutriation operation in combination with the combustion of a portion of the coke particles to heat the recycled coke.

Figure "2 of the drawing is a diagrammatic elevational View of a preferred .construction and arrangement of the contacting zones, with a substantially straight conduit from the upper portion of thecombustion zone passinginternally through the coking cone, precluding the loss .of heat `fromthe system duringfthe transfer of the finely divided `coke particles :to an Velevated .collecting zone or hopper, from Ywhich the'hightem.- Aperature finely divided `material is `subsequently passed to the coking zone.

Referring now to vFigure 11 vof the drawing,

there is indicated line VI, having control valve 2,

connecting Vwith a suitable distributing header or `ring ,31, which Yin 'turn is adapted Yto distribute a heavy 7hydrocarbonaceousl charge stream to the upper portion of the contact chamber 4 serving as cracking and coking zone. This heavy charge stream may be a heavy residual petroleum such 1 as reduced crude, topped crude, Bunker C fuel,

or the like, which does not ordinarily provide a good charging stock to a catalytic cracking unit or it may be a heavy tar or an asphalt liqueable by moderate heating. A continuously descending mass of particles is maintained either as a fluidized bed or as a compact moving bed in the coking zone or contact chamber 4, the particles being supplied at a high temperature from an upper elevated hopper or collecting chamber by a line 6, having a valve or feeding mechanism 1, suitable to supply a continuous stream of heated coke particles to the descending bed in the coking zone. In accordance withthe present cracking and coking operation, the particles are supplied at a high temperature, of the order of 950 to 1l00 F., suitable to effect the desired cracking and coking of the heavy charge stream being introduced by way of the distributor 3. The particles are heated prior to their introduction into the collector or hopper 5, as will hereinafter be more fully described, and since the particles in the preferred method of operation furnish at least a major portion of the heat being supplied to the coking zone, they are at a temperature substantially above that of the average temperature in the bed of descending particles of the coking zone. Resulting vaporous products from the cracking and distillation of the heavy charge stream are continuously removed from the coking zone 4 by way of an intermediately positioned outlet line 8 and control valve 9. Suitable baiiiing IU permits the collecting of the resulting vapors from the descending bed for removal through line 8.

In the present embodiment, the lower portion of the coking zone 4 is utilized as a dry distilling zone for conversion of asphalt-like components on the coke particles into hard coke and volatile products, as well as a stripping zone for the removal of low boiling Vaporous hydrocarbon fractions adsorbed in the descending bed of particles. The high temperature uid medium, suitable for stripping and drying the coke is introduced to the lower portion of the coking chamber 4 by way of line il and control valve l2, with a suitable header or distributing ring I3 utilized to uniformly distribute the gasiform medium throughout the descending bed of particles. The high temperature medium being introduced by way of line Il has still another desirable function in that it maintains coke material in the lower portion of the descending bed in a freely flowing or loose, particulated state, preventing the agglomeration of particles While effecting the drying and stripping operations.

As hereinbefore noted, this uid medium may be a light hydrocarbon distillate which will commingle with the vaporous products resulting from the cracking and coking step within the upper portion of the coking zone 4, or alternatively, the iluid medium may be superheated steam which may be later condensed and removed from the hydrocarbon product fractions without unduly elaborate separation steps. The stream is preferably charged to the lower portion of the coking zone at a high temperature above the average bed temperature in order to be more effective in the dry distilling and stripping functions.

The resulting and newly formed coke material, reaching the lower end of the coking chamber 4 in a substantially asphalt-free state, is passed by `way of conduit i4 and regulator or feeder l5 to an elutriating chamber IB, which serves also as combustion chamber and wherein there is maintained a uidized and elutriated bed of coke particles, the upper extremity of the fluidized dense phase bed being indicated by the dotted line l1. An oxidizing and elutriating gas stream is introduced to the lower portion of the chamber I6 by way of line I8, pump I9, and line 20 having control valve 2 l. In accordance with the present invention, the gaseous stream introduced into the lower portion of the elutriating or combustion chamber IB is in sufficient quantity and at a suitable velocity to effect the elutriation of the finer from coarser particles within the fiuidized bed therein, while simultaneously effecting the burning of a portion of the coke to effect the heating of the residual coke particles within the bed. Thus, the finer particles are transported as a suspension in hot combustion gases to the collector 5, at the aforementioned high temperature, vto supply heat to the coking zone, and the elutriation eifected within the combustion and elutriation chamber I6, is such as to carry a su'icient quantity of fine particles by Way of conduit 22 to the eleva-ted hopper and collector 5 to maintain the continuously descending bed of particles within the coking chamber 4. The hot fine coke particles carried from the fluidized bed I1 in suspension by the resulting combustion gases and through the conduit 22 into the collecting chamber 5, are separated from the gases by means of the enlarged area zone and the mechanical or centrifugal separator 23. The freed combustion gases are discharged from the separator 23 by way of outlet line 24, while recovered entrained particles are passed to the lower portion of the collector 5 by gravitational settling and by a return leg of the centrifugal separator 23. Also in accordance with the present invention, hot combustion gases from the collecting chamber 5 are recycled by way of the conduit 24, control valve 25, pump 26 and line 21 to the lower portion of the combustion and elutriation chamber i6. 'Ihe combustion gases provide a suitable high temperature diluent medium for mixing with the air stream in line I8, whereby a suflicient volume of gaseous medium containing free oxygen is made available to effect the desired elutriation of the ner from coarse coke particles in that zone as well as the desired burning and heating therein. The recirculated hot combustion gas and air charged to the combustion zone are blended in such regulated proportions that the resultant mixture has the desired oxygen content for effecting the burning of coke within the combustion zone to supply the desired amount of heat to the finer particles being recycled to the conversion zone Excess hot ue gas is withdrawn from line 24 by way of line 28 and valve 29, being utilized to generate or superheat steam, or for other heating purposes prior to being discharged to the atmosphere by way of a suitable stack.

A particle withdrawal standpipe 30 and regulating valve 3l provide means for withdrawing excess cokey primarily the coarser particles, from the combustion and elutriation zone IB, such coke being a net product of the conversion operation. Although not indicated in the present drawing, excess heat may be recovered from the withdrawn stream of coarser particles, for example, by contacting this stream with an aqueous medium in a quenching zone to generate steam. Steam from such a quenching zone may be superheated by indirectnheat exchange with a stream of the excess hot combustion gases'anl moet S24 :may thereafter be utilized to advantage as the light gaseous medium being introduced .to rthe Alower portion of the -coking .zone 'in chamber v4. "as Well fas for stripping stearnat various points in the present unit. As noted in the drawing, aerating .and stripping steam is preferably introducedfinto each of the principal particle trans- .fer lines or conduits. Line 32 and control valve 33 suppl-ies steam or v.other stripping medium to the particle conduit E; line 3d and valve 35 conneet with and control the introduction o'I stripping steam into line i4; and line .36 with `valve 311 .provides means to introduce steam into the coarse coke withdrawal line 30.

vFigure 2 of the drawing provides-a somewhat more-compact and preferable arrangement of the various contacting zones and means for transaferring particles with a minimum yloss of heat from `the system. The preheated heavy charge stream 4is introduced by Way of line All, control valve til and distributing head 42 into the kdescending bed of particles `maintained within "the contact or colnng zone 43 of a single `elongated lvertically disposed chamber de. Theheavycharge stream is supplied at a temperature and Vrate of iiow vat which line fit, valve 4l and `distributing head 42 remain clean and free from coke deposits. High temperature nnely divided vcoke particles are continuously introduced to the upper portion of lthe'colzing zone 43 from a cokelhopper or collecting zone d5 maintained in the upper portion oi` chamber 4d. The collecting `zone is separated from the coking zone by suitable partitioning it and a U shaped baiting 4l, which in combination with the lower depending -portion of the baiile 45 provides a U tube or `U trap arrangement for the transfer of finely divided particles from the upper collecting zone 45 into the coking zone s3 and for precluding access of vaporous material from the latter to the former. The high temperature ne coke particles are continuously passed by gravity through annular zones 48 and 49 of the U trap arrangement, with a suitable fluid medium being introduced `by way of line 50 and valve 5I to the lower portion 'of the particle transfer zone to 'act a's a Asealing uid and at the same time to regulate the continuous yflow of particles essentially by gravity from the collecting zone 45 through "the U trap arrangement to the descending fluidized bed Yof particles in the coking zone 43.

As described in connection with Figure v1 of the drawing, the coke particles are continuously `in- I troduced to the upper portion of the descending bed in the coking zone ata high temperature suitable to eect the conversion and coking of the heavy hydrocarbon charge `stream to desired lower 'boiling fractions and into coke depositing at least partly on the particles being "continuously introduced into that zone. The resulting vaporous products or hydrocarbon fractions Aare withdrawn from an intermediate portion of the descending bed of particles in the coking none 43 byway of an outlet line 52 Iand control valve "53, and may be passed to a suitable fractionating equipment for the separation or recovery ofthe desiredproducts. Also, in accordance with-'a desirable operation, the descending bed-of coke particles in the lower portion of the chamber v41! is subjected to contact with a high tempera-ture l-i'ght'fluid medium, such `'as steam or a 'lig-ht :hydrocarbon fraction, so that there maybe "dry distillation, hardening `and Stripping of theV coke prior to its withdrawal from the coking zone, The 'light fluid medium is 'introduced to 'theilower :portion foi? fthe 'descending -bed of cokev particles `of -chamberfJM by way of line 151i, valve Y55, land distributinghead, and at a high temperature 1aitleast-about equal to and preferably substantially rabove that of -the average bed temperature withinfthe-cnamber-M. This light `fluid medium lis advantageously supplied at a temperature land rateio'fv flow adequate -to furnish the balance of the heat- 4required 'in the coking zone 43 as far as not furnished by the heated lne coke parti- `cles entering Vvthis zone through the U trap arrangement. The resulting asphalt-free coke paritidlesreach-ing ithe lower portion -of the bed in chamber H4 are continuously passed by wayof conduit i'5l 4valve or regulating mechanism '58 to aiseparate'coniined chamber 59.

Afluidized `andelutriated bed of coke lparticles iis'maintainedlwithin the lower portion ofthe lutrialting and-combustion chamber 59, as indicated -hy the bed t0, iwith an oxygen-containing stream lbe'ing Aintroduced lto the lower 'end of the chamberg leyway of line 6l, pump 62 and line BBl'havingcontrol valve 65. Burning of a portion of'theca-rbonaceous:matter is eiected to yin turn provide a heating of lthe entire bed 4of particles such that Aa -recycle stream of the nner particles will supply to the conversion or coking zone '43 allor 'atlleasta majoriportion of theheat required in `tl-iis zone. In accordance vwith `the present invention, @the lburning operation is carried out in combination with an elutria'tion operation, whereby only the nner-'of the coked `particles are returned -to the collecting zone d5 'for subsequent return to the coking zone. Thus, the oxygencontaining 'or air stream is introduced Ato the lower portion of the chamber 5B at `a suiiicient velocity-and in suflicient quantity to effect the removal *of iine 4coke vparticles from the b'ed'of the combustion zone 60 and carry them in suspension in the Yresu'ltant hot combustion Agas vmixture through the -internal conduit t5 to the upper portion of the collecting Zone 25.

lit a particularly desirable feature of the present apparatus arrangement to have the Yinternalftrans'fer conduit -65 extend substantially vertically -and concentrically upwardly through the compact Ikor leoking zone 43 and collecting zone 45 to an elevated portion within the latter. Thus, fthe' ii-necoke particles are carried in suspension ithe 'resulting hot flue gases to the yelevated hopper `and collecting zone with little or noloss'pheat from the system and with a minimum of friction and -erosive action in the transfer conduit-65. 'The combustion chamber 59 located directlylbelowthe coking chamber e4, and conduit'f6'5 .is provided with a suitable expansion joint't `@positioned between the two chambers 'to accommodate A5differential expansions, due tothe high temperature operating conditions and linear expansions resulting therefrom. The gaseous charge stream to the combustion chamber 5S and resulting flue gases enc-ect the transporting of the lnecokeparticles tothe chamber 45, and as hereinbeforenoted, is .regulated and controlled to assure thetransperting of suinc-ient iine material to maintain the continuously descending bed of particles in the coking and conversion zone `43.

'Flue -gas yfrolrrthe upper portion of lthe collecting fzone .45 is passed by way of conduit 61, and :separators-v f58 and 69 `to a transfer line "lil, while-recovered Aentrained particles are Vreturned tofthe lower portion .of the collecting zone 45 `by suitable Areturn "legs 'll and '12. Also, in accordance with the 4present invention, atleast aportionfoflthe separated hotfflue gas lis recycled 'without intentional cooling by way of the conduit and control valve 13, pump 14 and line 15 to the charge line 6| and the lower portion of the combustion chamber 59. Thus, a hot gaseous medium is provided for blending with the oxygencontaining gas stream supplied from an external source vand for aiding in furnishing the desired quantity of elutriating gas utilized within the fluidized bed 60 of the combustion and elutriation chamber 59. Excess hot flue gas from line 10 may be withdrawn by way of line 16 and valve 11 and transferred to suitable heat exchanger equipment for conversion of heat from the hot combustion gases. The coarser coke particles which represent net coke production from the unit, are continuously withdrawn from the lower portion of the combustion zone 59 by way of standpipe or outlet conduit 18 and regulating means 19. This coke may be passed to cooling and processing zones for further treating as may be desired. Provision is also made in this embodiment of the unit, for the introduction of steam or other stripping uid into each of the coke withdrawal conduits by way of line 8U and control valve 8l communicating with standpipe 18, and by way of conduit 82 and valve 83 communicating with the withdrawal conduit 51.

The elevational arrangement of the contacting zones, in accordance with the accompanying drawing, is advantageous in that the coke particles have a descending gravity ow through all zones but the burning zone and there is required but a single uidized lift of the finer coke particles to maintain a continuous cyclic flow of coke particles through the entire system. Also, the elutriation in combination with the burning operation eliminates the need of any additional equipment for sizing operations to effect the classication of particles. The control of the elutriating and oxydizing gas stream by the blending of suitable proportions of :air and recycled hot combustion gases and the action of the blended gas stream in a simple straightthrough type of combustion chamber, substantially free of internal structures or obstructions, materially contribute to the high efficiency and economy of the operation of the present invention.

The cracking and coking operation, within the conversion or coking zone, may be carried out under any suitable pressure conditions, including atmospheric pressure; however, it is preferably effected at a relatively moderate super-atmospheric pressure, within the range of from 8 to 150 pounds per square inch, with temperatures correlated to the particular operating pressure to provide the desired lower boiling conversion products. The pressure in the elutriating and combustion zone and in the elevated fine particle collecting zone is substantially balanced with the pressure in the conversion zone so that the substantially gravitational flow of coke particles from the collecting zone into and downwardly through the conversion zone and from the latter into the elutriating and combustion zone is assured.

I claim as my invention:

1. An improved method for converting a heavy hydrocarbonaceous charge stream in the presence of subdivided coke, which comprises introducing aistream of heated fine coke particles into a conned coking zone and contacting them therein with said heavy charge stream at a temperature at which said heavy charge is converted into lower boiling vaporous products and coke with the transformation of at least a portion of said fine coke into coarser particles, continuously withdrawing resulting vaporous conversion products from said coking zone and passing them to a fractionating zone, discharging a stream of mixed ne and coarser coke particles from said coking zone into a iiuidized bed of coke particles maintained in the lower portion of a separate conned combustion zone, introducing a gas stream containing free oxygen into the lower portion of said fluidized bed and therein burning a portion of the coke and heating the residual coke particles while simultaneously passing said oxygen-containing gas and resulting combustion gases upwardly through said fluidized bed at a rate at which iine coke particles are elutriated from the coarser particles and are entrained in the gas mixture disengaging from said fluidized bed into the upper portion of said combustion zone, passing the resulting hot ne coke suspension from said combustion zone into a separate conned collecting zone of higher elevation than said coking zone, separating said suspension in said collecting zone at a temperature substantially above the average temperature maintained in the coking zone into combustion gases which are continuously discharged from the upper portion of said collecting zone and into fine coke particles which are collected in the lower portion thereof, passing a stream of the separated fine coke particles from the lower portion of said collecting zone substantially by gravitational flow as said heated line coke particles into said coking zone, and withdrawing a stream of relatively coarse coke particles from the lower portion of said iluidized bed and said combustion zone as net coke production.

2. An improved method for converting a heavy hydrocarbonaceous charge stream in the presence of subdivided coke, which comprises introducing a stream of heated fine coke particles into an elevated portion of a confined coking zone, passing said particles downwardly through said zone and contacting them therein with said heavy charge stream at a temperature at which said heavy charge is converted into lower boiling vaporous products and coke with the transformation of at least a portion of said fine coke into coarser particles, continuously withdrawing resulting vaporous conversion products from said coking zone and passing them into a fractionating zone, discharging a stream of mixed fine and coarser coke particles from the bottom portion of said coking zone substantially by gravitational flow into a fluidized bed of coke particles maintained in the lower portion of a separate confined combustion zone of lower elevation than said coking zone, introducing a gas stream containing free oxygen into the lower portion of said fluidized bed and therein burning a portion of the coke and heating the residual coke particles while simultaneously passing said oxygen-containing gas and resulting combustion gases upwardly through said uidized bed at a rate at which ne coke particles are elutriated from the coarser particles and are entrained in the gas mixture disengaging from said iiuidized bed into the upper portion of said combustion zone, passing the resulting hot ne coke suspension from said combustion zone into a separate coniined collecting zone of higher elevation than said coking zone, separating said suspension in said collecting zone at a temperature substantially above the average temperature maintainedl ini. the coking zonet into combustion gaseswhich are continuously.v discharged from: the* upper portion of said' collecting: zone into ne coke particles which. are collected.'in` the" lowerL portion thereof, passing a. stream' oi the separated iinc coke particlesuirom. the lower portion oi said collecting. Zone.substantially by gravitational flow as said heated nne cose; particles into said'c'olring: zone', and withdrinsing,'a` stream of relatively coarse coke particies: from the lower portion of said iiuidized bed: andA said; combustion zone as net coke production;

3; An improved method for. cracking."and.:` ook:n ing aheavy hydrocarbon charge stream. in .the presence of heated subdivided solid material which comprises, supplying a stream of heated ne. cokeparticles to the upper portion of a. conned cracking and coking zone and maintaining a descending bed of ine coke particles therein, introducing said heavy charge stream at a temperatureflower. than the average'hed temperature an4 elevated portion. of saidvbed and enacting therein the conversion of said heavy charge stream into lower boiling vaporousl products and coke with the. transformation. off a portionL ofa the fine colteV into. coarser particles, withdrawing resu'lting vaporous, conversion products from'. said coke bed and` passing themi to a ractionating zone, discharging a stream of coke particles from thel bottom portion of. said.` descending bed into a iluidized bed` of. coke. particles maintained. in the lower portionof. a separate connned. combustion Zone, introducing a gas stream containing free oxygen into the lower portion of said iiuidized bed and therein burning aportion of the coke .1

and heating the residual coke particles while simultaneously passing said oxygen-containing gas and resulting combustionl gases upwardly through said fluidized bed at a rate at which ne coke particles are elutriated from the coarser particles and are entrained in the ascending gas mixture disengaging from said fduidized bed into the upper portion of said combustion zone, passing the resulting hot fine coke suspension substantially without intentional cooling into a confined collecting zone superimposed above said cracking and coking Zone, separating said suspension in said collecting zone at a temperature substantially above the average bed temperature maintained in said coking zone into combustion gases which are continuously discharged from said collecting zone and into fine coke particles which are collected in the lower portion thereof, passing a stream of the separated iine coke particles from the lower portion of said collecting zone substantiallj,1 by gravitational flow as said heated ne coke particles into said coking zone, and Withdrawing a stream of relatively7 coarse coke particles from the lower portion of said uidized bed and said combustion zone as net coke production.

4,. The method of claim 3 further characterized in that said oxygen-containing gas stream being introduced into said combustion and elutriation zone comprises air in admixture with a controlled portion of hot combustion gases recycled from said collecting zone.

5. An improved method for cracking and coking a heavy hydrocarbon charge stream in the presen-ce of subdivided solid material, which comprises, supplying a stream of heated fine coke particles to the upper portion of a descending bed of coke particles maintained Within a cracking and coking zone, said coke particles being introduced into said zone at a temperature above the average coke bed temperature therein, introducing said: heavy hydrocarbon chargefstreamiinto: an;

stantially by gravity into a fluidized: bed. of cokeI particles maintained' within the lower` portion of a. sepa-rate coniined combustion zone underneath said coking zone; introducing a gas stream con.- taining free oxygenii'nto the lower-portion of said fluidized bedI andftherein burning a portionof the coke and heating 'the remaining coke particles.

while simultaneously passing said. oxygen-containing gas streamy and resulting combustion gases upwardly through said uidized bed at a rate at which fine colte particles are elutriated from the' coarser particles and are entained' in the gas mixture disengaging from said l'uidized` bed into the upper portion of said combustion zone, passing the resulting hot fine coke suspension from saidl combustion zone upwardly in aconnned path through said coking zone andv in indirect heat exchange relationship with said descending bed and thereupon discharging it at a temperature substantiallyabove the average temperature ofV said descending hed into a collooting zone superimposed on coking zone, separating said suspension substantially without intentional cooling in said collecting zone into combustion gases which are continuously withdrawn from the upper portion of* said collecting zone and into ne coke particles which are collected in the lower portion thereof, passing a stream of the separated fine coke particles from said collecting zone substantially by gravity now as said heated fine coke particles to the upper portion of said descending bed in said coking zone, and withdrawing a stream of relatively coarse particles from the lower portion of said uidized bed and said combustion zone as net coke production of the process.

6. The method of claim 5 further characterized in that said oxygen-containing gas stream introduced to the lower portion of the fluidized bed maintained within said combustion zone consists essentially of a mixture of a regulated portion of the hot combustion gases discharged from said collecting zone and air in a proportion assuring controlled heating of the coke in the combustion zone and entrainment of hot line coke in the resulting combustion gas mixture at a rate suflicient to maintain said descending bed in said coking zone.

7. The method of claim 5 further characterized in that a light vaporous stream substantially devoid of free oxygen at a higher temperature than the average bed temperature in the ooking zone is introduced into the lower portion thereof and passed upwardly through at least a substantial portion of the descending bed of coke particles therein, whereby to aid in the conversion of said heavy hydrocarbon charge stream to desired lower boiling products and a hard dry coke.

8. The method of claim 7 further characterized in that said light vaporous stream comprises superheated steam produced by passing an aqueous fluid stream in heat exchange relationship with hot coarse coke particles withdrawn from 10. Apparatus suitable for effecting the con-V version of heavy hydrocarbonaceous material in the presence of subdivided coke, which comprises in combination a vertically elongated conned contact chamber disposed inbetween and vertically aligned with an upper conned collecting chamber and a lower conned elutriating chamber, said contact chamber having fluid inlet and outlet ports, a particle transfer conduit containing ow regulating means and connecting the bottom portion of said contact chamber with the lower portion of said elutriating chamber, particle passageway means connecting the bottom portion of said collecting chamber with an elevated portion of said contact chamber, a substantially vertical particle suspension transfer conduit extending upwardly from the top portion-0f said elutriating chamber substantially along the axis oi alignment of said chambers through said contact chamber and centrally through said particle passageway means into an elevated portion of said collecting chamber, a fluid inlet and a particle outlet at the lower portion of said elutriating chamber, and a fluid outlet at the upper portion of said collecting chamber.

11. The apparatus of claim 10 further characterized by a fluid recirculation conduit connecting the fluid outlet at the upper portion of said collecting chamber with said fluid inlet at 16 the lower portion of said elutriating chamber and containing means for forcing huid discharged from said collecting chamber into the lower portion of said elutriating chamber.

12. The apparatus of claim 10 further characterized in that said particle passageway means is arranged to discharge into the top of the contact chamber and comprises a U trap arranged annularly around said particle suspension transfer conduit, and fluid inlet and distributing means are positioned at the lower end of said U trap for the introduction of a fluid stream thereto and the regulation of particle flow from said collecting chamber to said contact chamber.

FREDERICK W. LEFFER.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 2,304,128 Thomas Dec. 8, 1942 2,340,974 Myers Feb. 8, 1944 2,362,270 Hemminger Nov. 7, 1944 2,393,636 Johnson Jan. 29, 1946 2,401,739 Johnson June 11, 1946 2,409,353 Giuliani et al Oct. 15, 1946 2,412,667 Arveson Dec.'17, 1946 2,464,812 Johnson Mar. 22, 1949 2,493,911 Brandt Jan. 10, 1950 2,506,307 Martin May 2, 1950 2,541,077 Leffer Feb. 13, 1951 2,546,625 Bergstrom Mar. 27, 1951 2,600,078 Schutte June 10, 1952 2,623,010 Schutte Dec. 23, 1952 FOREIGN PATENTS Number Country Date 574,892 Great Britain J an. 24, 1946

Claims (1)

1. AN IMPROVED METHOD FOR CONVERTING A HEAVY HYDROCARBONACEOUS CHARGE STREAM IN THE PRESENCE OF SUBDIVIDED COKE, WHICH COMPRISES INTRODUCING A STREAM OF HEATED FINE COKE PARTICLES INTO A CONFINED COKING ZONE AND CONTACTING THEM THEREIN WITH SAID HEAVY CHARGE STREAM AT A TEMPERATURE AT WHICH SAID HEAVY CHARGE IS CONVERTED INTO LOWER BOILING VAPOROUS PRODUCTS AND COKE WITH THE TRANSFORMATION OF AT LEAST A PORTION OF SAID FINE COKE INTO COARSER PARTICLES, CONTINUOUSLY WITHDRAWING RESULTING VAPOROUS CONVERSION PRODUCTS FROM SAID COKING ZONE AND PASSING THEM TO A FRACTIONATING ZONE, DISCHARGING A STREAM OF MIXED FINE AND COARSER COKE PARTICLES FROM SAID COKING ZONE INTO A FLUIDIZED BED OF COKE PARTICLES MAINTAINED IN THE LOWER PORTION OF A SEPARATE CONFINED COMBUSTION ZONE, INTRODUCING A GAS STREAM CONTAINING FREE OXYGEN INTO THE LOWER PORTION OF SAID FLUIDIZED BED AND THEREIN BURNING A PORTION OF THE COKE AND HEATING THE RESIDUAL COKE PARTICLES WHILE SIMULTANEOUSLY PASSING SAID OXYGEN-CONTAINING GAS AND RESULTING COMBUSTION GASES UPWARDLY THROUGH SAID FLUIDIZED BED AT A RATE AT WHICH FINE COKE PARTICLES

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