CA1266059A - Control acr product yields by adjustment of severity variables - Google Patents

Abstract

CONTROL ACR PRODUCT YIELDS BY ADJUSTMENT OF
SEVERITY VARIABLES

ABSTRACT
Improved operation of the ACR process is achieved by regulating the reactions within a small area in the combustion feedstock mixing zone.
"Scorch Zone", by the addition of steam or other fluid such as ethane at the point of feed injection.

D-13,750

Description

5~ .

CONTROL ACR PRODUCT YIELDS BY ADJUSTMæNT OF
5EVERITY VARIABL~S

TECHNICAL FI~LD
Thi~ invention relateg to a method ~hich will enhan~e the practice o~ the Advanced Cracking Reaceor (ACR) pr~ees~. Hydro~arbo~ feed i8 in~rodu~ed into a high te~perature heat carrier such ~hat a modif ication of ~he yield spectru~ i~
achieved by the ~ddition of 6team or other fluid ~uch ~6 hydrogen or ethane at the point of feed injectlon. The amount and/or temperature of the added species ~an be u6ed to control the produc~
distribution.

The Advanced Cracking Reactor tACR~ proces~
i~ characterized by Khavarian, the~is for mast~rs degree in chemical e~gineering, ~e~t Virginia Collage of ~raduate Studie~O antitled: "Olefin~
Production by Crude Oil Cracking", April, 1977, as offerinq di~tinct advantage~: one being the Plexibili~y in the sel2ction of feedstocks, and another being, the ab~lity to alte~ produot compo~ition~ by changing proces~ variables. Ho~oi and Keister, Che~ical Engineering Progress, Volume 71, Number 11, No~ember, 197S, Page~ 63 67 discu~s many of the adv~ntage~ vf ACR proce~. Davis and K~ister, in a pap~r pre6ented before the Di~ision o~
Petroleum Chemi~try, Inc., of the American Chemi~l Society at the Philadelphia meeting, April 6 - 11, 1975 entitled "THE ADVANCED CRAC~I~G RE~CTOR ~ACR) A
PROCESS FOR RACKING HYDROCARBON LIQUIDS AT SHORT
D-13,750 ~126~

.
R~5IDENC~ TI~ES, HIGH ~EMPEaATURES A~D LO~ PARTIAL
PR~SSU~E5," add~e6s the i~sue of ~everity in the production of product6 and the flexihili~y which i6 ac~ieved in the u~e o~ the ACR proces6 to make a ~ariety of product com~ositions.
~ earns, ~ilks, and Kam~ ~Xearns, et al.) in a paper pre~e~t~d to the ~ympo~iu~ on Rec~nt Advances in the Prnduction and Utilization of Light Olefin~, Division of Petroleum Chemi~tEy of ~he American C~emical Soci~ty, at the 175th Na~ional Meeting, Anaheim, California, March 12 - 17. l97a~
"Development of S~aling ~ethods ~or a Crude Oil Cracking Reac~or U6ing Short Duration Test Technique~", give a thorough analysis of the ACR
proces6. The 8a~e ~earn~, et al. article, at page6 108 through 1280 in a test en~itled, "Thermal ~ydrocarbon Chemi~try", Oblad, e~ al., editors, of the Advances in Chemi~try Serie~ 183, published by the Am~rican Chemical Society, Washington, D. C...
1979, characterize6 the extreme flexibility with regard to feed~tock and product yields co~bined with intrin6ically high ~hemical yield~ that one can achieve in the practice o~ an ACR to produce e~hylene.
Kearns et al. give infor~ation on various critical s~ale-up condition~ for practicing the ACR
proces~ and ~peak in term~ of process variables which impact on the operation of the ACR. Of interast in re~pect to the instant invention i6 a statement at page 127 of the arti~le wherein the authors indicate that the "Oil Injection ~on~rol Volume~ is the "region of the highe6t process ~-13,750 temperatures which tend to generate high C2H2 yields."
The patent literature abounds in general descriptions of the ACR process and various embodiments of it. Illustrative of such patent literature are U. S. Patents Nos. 3,408,417, 3,419,632, 3,674,679, 3,795,713, 3,855,339, 4,134,824, 4,136,015, 4,142,963, 4,150,716, 4,240,898, 4,264,435, and 4,321,131.
As is evidenced by the substantial prior art, much is already known about the ACR process.
It is a process which combusts fuels in a combustion zone or chamber and regulates the temperature of the hot combustion gas stream with addition of steam. The regulated (or moderated) hot combustion gas (containing steam) is thereafter mixed with a fine droplet hydrocarbon feedstock stream. This hydrocarbon feedstock stream can be surrounded by a steam shroud which imparts additional momentum to the feedstock spray to achieve better intermixture with the hot combustion gas/steam stream. The mixture flows to th~
reaction zone where the desired cracking of the feedstock occurs. Refinement of this process has led to an understanding of the manner in which the process should be practiced in order to optimize the product distribution obtainable.
As pointed out in the Davis and Keister paper, I'severity'' is a factor which dictates the product mix. Severity is controllable in broad general terms through manipulation of reactor operating variables and it can be adjusted to D-13,750 ~r L~

1~60~

opti~ize a certain product di~tribution. I~ ha~
been determined however, ~hat there exi~t re~ion6 or area~ of higher reaction 3everi~y within the confine~ of the ~CR pro~e~ wherein a cra~kinq reaction occurs which can impact 6ignificantly upon the produ~t di~Sribution. In the~e ~one~, ultra-high cra~klDg ~eYerity o~curs and products ~uch a~ methane, acetylene, hydrogen, and their precursor~, predominate and contribute a di~proportionately large a~ount of ~u~h produ~t~ in the e~entual ACP~ product mi~c.
The aPore~entioned zone~ of ultra-high reaction ~everity occur where the combustion ga6/~tea~ rea~ from the combu ~ion zone fir6t make~ contact ~ith the plume of the injected hydrocarbon feed6tock ~pray. At ~age~ 116 through 11~ of the Kearn~ et al. article in "Thermal ~ydro~arbon Chemietry", suPra~ the inje~ted hydrocarbon feedstock i8 sprayed countercurrently into the interior of the cha~ber down~trea~ of the combusti~n zone and ~orm~ an arc-shaped ~tream or plume which converge~ with a combu6tion ga~Jsteam stream being rectilinearly pro3e~ted toward ~he ACR
throat into the ACR di~fuser/reac~or.
The ~patial 20ne6 of ultra-high reaction ~everity are ter~ed, ~or the purpose6 of ~he invention, as "S~or~h Zone". Thi~ means that in these zone~ there exi~t ~onditions wherein hydrocarbons are max~mally cracked to produce an inordinate quantity of lower-boiling species and gaseou~ produets such a~ methane, a~etylene, hydrogen, and the like. Thi~ oecur~ because the D-13,750 outer boundary of the hydrocarbon ~ray plu~e i8 not ~rotected ~ro~ eh~ extre~aly high te~peratures of ehe co~bustion gasJsteam ~tream. Sub~equent ~ixing of hydrocarbon feed with the eombustion gasJsteam 6tream therefore causes a temperature equilibration to occur ~hich ser~le~ t~ moderate temperature effest~ wit~lin the hydrocarbon feed. H~wever, at the outer edge of the plume ~hich Pir~t contact3 the combu6tion ga6/steam ~tream, no temperature moderation effects are available; consequently, the outer portion6 of the plume receive the Pull effect of th~ exereme temperatures of ~he combu6tion gas~stea~ stream and con~equently, there occurs a maximum deyree of cracking in such zones. ~uch cracking i~ deemed unde~irable ~or the proper practice of the ACR proce6~.
In the ~ast, ~o miti~ate the reactions occurring in ~uch zone ~a30r Ghanges ~ere made to variouæ process variables ~hich dramatically altered- ~
the composition o~ the ACR product mix. To change what wa6 being produced in such zoneæ required changes in major proce~s variable~ ~uch aæ burner t~mperatur~ and dilution mass flow rate. Thi6 adversely affect~ process economics and the co~position of the produ~t mix~
There is herein desc~ibed a proce~s which allows one to ~inimize the effeets ~hich are occurring within ehe Scorch Zones o~ the ACR in order to enhance the making of the desired reace~on products of the ACR proceææ. ~y knowing wher~ the Scorch Zone~ exiæt and what occur~ in the 20nes, one can vary the yield o~ products obtained in th~ ACR
D-13,750 :~L%~5~
_ 7 -proce~ without undertaki~g ma~or pro~es~ change~.
Con6equently, a minimal change in the operation of the ACR proce~s can impact ~igni~i~antly on the kind~ o~ product~ and their ~oncentrations, thereby mini~izing a significant negative effect bn the overall economics of the ~roce6~.
SUMMARY 0~ T~E INVENTI0 Ths pro~e~ of thig invention involve~
practicing the ACR pro~e6s by moderati~g the conditions of the Scorch Zone by adju~ing certain variables, within the hereinaft~r defined Scsrch Zone Variables, ~o produce a de~ired ACR product composition. Generally, "Scorching Zone~" are the s2atial zones within the Advanced Cracking Reactor a~ ~hich the plumet6) of ehe ~pray of hydrocarbon feed~tock first ~ontac~ the hot combu~tion gas/steam.
The proce~s of this ;nvention i6 an improvement in the ACR pro~e~ and involves, inter alia, the following`conventional ~CR procesR step~ -within an Adva~ced Cracking Reactor (ACR):
(a) the ~ormation of a combustion gas/~Qam ~ream having-a temperature of 1200C. to about 2400C: -(b) mi~ing of said ~tream (a~ defined in (a) abnve) w~th a countercurrent feed 6tream, in the form of a ~pray of atomized droplets o~
hydrocarbon feedstock shrouded by a stream or streams of ~team or other fluid;
(~) pa~ing the admixture of ~b) above to the ~hroatad portion of the reactor to a~hie~e a sonlc velo~i~y:

D-13.750 ~ d) ~assing the feed fror~ (c) above to an expanding difPuser/reaction zone wherein ~i) the fead accelerates to su~ersonic velocity th~n undergoe~ a ~hock and de~elerate~ to subsonic velocity and (ii) the temperature is from 600C to 1400C; thereby cracking ~he feedgtock into a ~tream in which e~hylene i~ a sig~ifi~ant produ~t; and (e3 quenching ~he produc~ from (d) above to stop the cracking reaction The i~proveme~t of ~his inYention involves a ~odification of the operatio~ of ~b) above, hereinafter termed the "~eedstock ~ixing 8tep".
The i~provement in the AC~ proces~ involve~
~oderatinq the condition~ of the ~cor~h Zone in the feed~o~k mixing step. The Scorch Zones are more readily identified as those zone~ wherein the initial ~racking of ~eedstock o~cur~ to form such hydrocarbons a~ acetylene, ~ethane, hydro~en, and their precur60rs. These exist ~here tha plumes of ..
the hydrocarbon spray Pir~ ~erge in~o contact with the combustion gase~ being ~ed through the throat to the cracking diffu~er/reactor portion of the ACR.
To control what oecur~ in ~he S~orch Zone which in turn controls th~ concentsation of product~ that ara produced, one can select a number of eroce~
variables, which are herainafter def;ned as the Scorch Zone variable~.
The S~orch Zone variables are de~ined 36 one or more o~ the ~ollowing: (1) ad3u~tment in the weight ratio of the shroud ~luid to the hydrocsrbon feedstock; (2) the temperature of the shroud fluid:
(3) the compo~i~ion of the shroud fluid; (4~ the D-13,750 , 5~

g ~ethod of feedstook introduction; (5) the ~eed~toc~
flashing behavior; (6) feedstock temperatur~ t7) the burner proce~s variable~, ~uch as the ma~ rate of ~he combu~ion ~a~ produc~ team ~trea~ to the ~as~ ra~e of the hydrocarbo~ feed~tock and the temperature and ~he ~o~position of the co~bust~on ~as~ætea~ strea~.
8RIEF D~scRIrrIoN oF o ~
Fi~. 1 and Fig. 2 are gra~h~ ~hich illus~rate the effect of injector shroud ~team and heat ca~rier t~mperature on ACR ga~ yield~ utili2ing a continuou~ reactor.
DETAILED DISCUSSION OF TH~ INVENTION
Aæ poin~ed out previously, this in~ention involves the modification of t~ ACR proces6 by changing the conditions which ex1st within the S~orch Zone to decreaæe the product6 therein formed 6uch a5 acetylene, methane, ~ydrogen, and their precursor~. The ~ucce~s of the proce6~ of thi~
inventio~ i~ re1e~ted by the concurrent reduction in the prQsence of tho6e products in the product strea~ which i~ r~oved from the diffuser/cracking rea~eor portion of the ACR.
As discus~ed above, ~mall severe reaction 20ne~ exi3t within t~e area where the combustion gas/~team ~tream ~i~es with the hydrocarbon ~eedstock and can have a significant i~pac~ on the yield of certain product~ of the ACR process. ~ith thie knowladge, one can deal directly with ~hat i8 ocaurring with~n those zone6 in order to change or control the yie~d of ~he ~roduct mix of the ACR
D-13,750 proce~. Conseqùently, the a~ount o~ propylQne and butenes that are obtained from the ACR process can be increased with ~inimum reduction in ~he ethyl~ne yield, simply by ~oderating the production wi~hin the Scorch Zone of ace~ylane, methane, hydrogen. and their precur~ors. The nu~ber of variables which one ca~ utilize to eontrol what i8 occurr~ng ~ithin the Scorch Zone are ~o diverfie, but it can be determined experimentally ~hich variablas can be modified to achieve the improvements, in accordance with the inve~tion.
ln order to more effectively define this invention, recour~s i~ made to the term ~Scorch Zone Variable6" to designate the choice6 of proces~
~odifications that are available for moderating the unde~irable effect~ of ~corchinq of a small portion oP the hydrocarbon feed ~roduced. Scorching, as defined h~rein, ~eans the subjection o~ the hydrocarbon Peed tQ in~an6e heat~ ~hen the .
hydrocarbon feed~tock i5 6ubjected ~o such intense heaS (6corching), a larga part of it is con~erted to acetylene, methane, hydrogen and their precursors.
The mo6t effective utilization of the ACR
~nvolves carrying out the proce~s as se~ forth in U.
S. Patent No. ~,136,015. Therein de~cribed i8 the improved operation of the ACR process by the ato~ization of the liquid petroleum ~eedstock into the ~tream of hot combu~tion ga6/steam in a chamber in ~hich the gas/vapor ~low i~ maintained at subsonic velocity. Thereaf~er. the completa ~ixing and vaporization is e~acted in a constricted throat zone wherein the combined stream exit6 at 60nic D-13,750 ~2~ S~

~elocity. The stream i8 thereafter pa~ed through a velocity accel~ration diffuser~reactor zone and achieves ~uper60nic velo~ity f 10~8 . The stream then passes through a sho~ region produced by the ~ros~-~ectional expansion of the dif~u~er/reactor zone and thi~ reduces the velocity to ~ub~onic.
Additional cracking occur~ in the reac~ion zone bef~re quenching.
A~ pointed ou~ in the patent, one o~ the method6 o~ mixing the hot co~bu~tion products witA
the feed~tock i6 to effect a~ atDmized form of the feed~tock wi~hin a mixing zone once combu~tion i8 achieved. Thi~ mixing o~ the feed~tock and combu~ion products i~ enhanced by using a steam shroud envelo~e about the hydro~arbon fesd. Such a ~hroud i8 de~cribed in U. S. Patent No. 4,142,963.
The purpose for which the ~hroud is employed i8 to enhance the overall penetration o~ the hydrocarbon feed ineo th~ ~ixing area wherein admixture with the co~bu6tion gas/steam ~trea~ i~ effected.
In the operation of the ACR, the hydrocarbon feed is typically 6prayed ~rom a small constriction under pre~sure into the ~ixing zone where the te~perature i6 extremely high, viz 1200C
- 2400C. ~hen this occur6, the 6pray of hydrocarbon being emi~ted i~ di~cretely atomi~ed and pro3ected ~orward towards the central axis of the mixin~ zone. A~ ~he s~ream i~ pro3ected for~ard, the upward and outermo~t extremes of the ~pray plume make fir~t contac~ with the combu~tion product gase~
and this generates the aforementioned Scorch Zones.
The Scorch Zone~ may not ex~t in any one particular D-13,750 (35~

. .
area but in a number of area~ within the mixing zone. The kinds and location~ of them are largely dete~mined by the nature of the spray pattern of the hydrocarbon fead plu~e within the interior of the mixing æone. I~ the hydrocarbon feed spray plume~
are ab~olutely uniPorm a~ amitted f~om $he port6 of their ~ntrodu~tion, then, of ~ourse, the location of the Scorc~ ~one~ are more ascurately determinable.
~ o alleviate the severe cracking ~f small increment6 of the hydrocarbon Peedstock which occurs within the ~i~ing zo~e when the outer extremitie~ of the ~pray plume of ~he hydro~arbon ~aed~tock first contact~ ~he combu~tion gas/6team mixture, a number of proce~s factor6 are available. For example, one can adju~t the we~ght ratio o~ the ~hroud fluid flow to that of hydrocarbon feedstoc~. ~y introducing a ~reater con~entration of shroud ~luid in the region of ~he oute~ extremitie~ of the ~pray plume, the temperature~ at ~uch extre~ities can be moderated and thereby reduced, and to ~ome extent, the adverse ~racking reaction moderated.
Ano~her method by ~hich the mixture of the s~orch zone can be controlled is Shrough the temperature of t~e shroud fluid. If the temperature of the ~hroud fluid i~ reduced by a value which would reduce tha temperature in the zones where the unde~ired cracking oc~ur~, the heat which would normally be utili~ed to ef~ect the cracking reaction would instead be par~ally utilized to bring the ~emperature of the gase~ in the mixing zone to the de~ired level.

D-13,750 Another variable for controlling the ~rob~ems ~hi~h occur in the Sco~ch Zone i5 the com~o~ition o~ the ~hroud fluid. 8Ome potential ~hroud fluid6, such a~ steam, are assentially chemically inert, and only have ther~al effect~ on the reaction. However, other po6sible ~hroud fluid~, ~articularly hydrogen or those compounds rich in hydrogen, can participate in the cracking reactions and have a beneficial effect on the yield pattern. ~ydrogen and methane would be par~icularly e~fective in this u~e. ~owever, other compound~
which are ga~eou6 at the injection temperature and are high in hydrogen, such a~ e~hane and pro~ane.
could al~o be u~ed. In addition to moderating the severe cracking in the Scorch Zone, compound~ ~uch a~ ethane and ~ropane will al~o c~ack ~o yield useful product~.
A number of methode of ~eeds~ock introduction can be utilized to ~oderate the condition~ which exist in the outer extremitie6 of the plume of the hydrocarbon ~eed6tock ~pray. The feed~tock should be injec~ed in such a way as to give quick and inti~ate mixing with the gaseou6 combustion produc~. In ~his way the mixture reach~ thermal equilibrium quickly, and ~he extent o~ the Scorch Zone is minimized. Thi~ is accompli~hed by atomizing the ~eed to extremely ~mall drople~, which have a high ~urface ar2a, 60 that they will ~ix and vaporize quickly. Such technique~ are well known in the prior ar~. In any ca~e, the feed nozzle6 should be ~laced and oriented, and the fe~d ~res~ure adjusted, to giYQ
D-13,750 S~

well-de~ined feed~tocls plumes which will penetrate well into the csnter of ehe f10wing stream o~ hot ~ombustlon p~oducts.
The fla~hing ~ehaYior of th~ fe~dstock ~ill also affec~ ~he condi~ions of the Scorch Zone, becau~e a feedsto~k which flashe~, or evaporate~
quickly, will ab~orb the heat of.vaporization and mix quickly with the g~eou6 com~u~tion product~.
Thu~, feea~tock which i~ evapora~ed quic~ly will minimize the extent of the Scorch Zone.
Fla&hing behavior can be controlled to 80~e degree~ Feedstoc~ which flash at a low ~emperature are preferred. Where it is not practical to use 6uch feed6tock~, flashing ~ay 60metime~ be induced by preheati~g the feed~ock above it~ normal boiling point at a high pres6ure, 80 that it remains in a liquid state; when the feed i~ injected ehrough the ~ozzles, the pres6ure drop~ and the feed will fla~h. If the Peed ha~ a ~ide range of boiling point~, only the lighte~ fractions may flash, However, thi~ i6 ~till u6eful since ~lashing aid~ in the breaku~ and atomization of the feedstock droplats, and promo~e~ good mixing with the ga~eou~
combustion eroduct~. If the feedstock con6ist~ of all heavy componentsO ~o that flashing cannot be induced by preheating, ~all amount~ of a lighter com~onent may be blended with the feedstock, ~o that this lighter component will fla6h upon injection.
Thi~ will improve the atomization and mixing of the feedstock, and thu~ reduce the extent Qf the Scorch Zone.

D-13,750 - 15 - ~

In contrast to whole di~tilla~e, certain haavy feedstock6, ~uch as hea~y vacuum gas oil, do not contain any ~omponents which would flash at reactor conditions, even after being preheated to 400C at the feed pressure. In this ca6e, it might be desirable to mix the feed~tock with a small a~ount of a ligh~ component to cau~e flashing and increase atomization. For example, a heavy vacuum ga~ oil could be mixed wlth about 10 to 20 weiqht ~er~ent naphtha or atmospheric gaz oil.
Other factor~ will have an effe~t on the extent and condition~ of the Scorch Zone. The gross reaction condition~ can be adju~ted to reduce the e~fect of the ~orch zone. However, economically it i8 much le~ de~irable to adju6t ~he major~ overall reactor conditions, rather than the local conditions ~8 de6cribed above.
FOE example, ~he temperature o~ the gaseous co~bu6tio~ product~ can be reduced to lower the .. ~ -tem~erature in the Scorch Zone. ~owever, this will directly reduca the net energy input to ~he reactor, and thu~ will lower the yield6 obtained from the feed~tock. Alternatively, the ma6s ratio of combustion product~ to ~eedstock can be incraased, to incrsase dilution and lower the partial ~res6ure of the feedstock. ~owever, t~is requires added ~uel, oxygen and 6team to be fed to the combustion cha~ber. The com~o~ition of the ga~eou6 combustion ~roduc~s may also be vaied, ~or example by feeding an ex~es~ of hydrogen to the burner, thus increasing the hydrogen content in the scorch~zone. However, this will al~o increase the fuel co~t6.
D-13,750 An i~portant ~dvantage of this invention is that local change6 in the critical Scorch Zone have 3 6trong and disproportionate e~fect on the final yield~, without incurring ~ajor C08~ due tO Change8 in the overall op~rating variables. By injecting the feed according to the ~rin2i~1e6 outlined above, ~he ext~nt and e~f ect of the Scorch Zone are minimi2ed: ~udiciou6 u~e of ~mall amoun~ o~ shroud 1uid will then have a stron~. po~i~ive effect on the yield pattern by further alleviatins the ~ffects of the Scorch Zone.
The actual desig~ of the a~paratus for i~jecting the shroud fluid i6 not critical. ~he concentric annular opening is simple and convenient to u~e, but other methods are possible. The only requiremen~ is that ~he shroud fluid ~hould be injected in such a way that a ~ub~tantial part o~ it flows to a region where it can moderate the re~ults of the ~corch zone.
In addition to steam, other fluids may be used in the shroud, 6uch a~ ethane. Ethane i8 one of the productæ re~ulting from the crac~ing of the fQed~tock. Thig e~hane i8 separated and preheated to abou~ the t~mperature of high ~ressure steam, then injected through ~he annular o2enings around the feed nozzle~, along with the 6hroud 6team. ~uch of the ethane crack6 to ~ive primarily ethylene, wi~h ~ome hydrogen and other products. The injection of the ethane further moderaee~ the effect of the Scorch Zone, both through thermal effects, and through the chemical participation of the ethane and hydrogen in the reactions occurring in the D-13,750 - 17 _ Scorch ZoneO This al80 ha~ the bene~it that the byproduct ethane iB e~f0ctively crack~d to useful products. I~ desired, the hydrogen, methane and ~ertain other ~roducts of the cracking proces6 ~an also be included in the ~hroud fluid in this way.
~AMPLES
EXA~PL~ 1 Table I indicate~ the experimen~al data obtained while utilizing a continuou~ reactor. The eontinuou~ reactor i~ approxi~ately one-four hundredth the size of a commercial reactor, and produces approxi~ately 250,000 lbs./yr. of ethylene.
T~o major variables ~ere s~reened in the ~ontinuous reactor, wi~h and ~ithout the addition of injector shroua steam. The re~ult8 of the experi~ents were adjusted ~lightly for the purpo~es of compar~son to a common set of variables u6ing available yield reg~es~ion models as follQw6: - ~

Steam dilution 8.74 lb. moles/100 lb. oil (without injector shroud steam) 9.56 lb. mole~/100 lb. oil (with in3~ctor ~hroud stea~) Feed Preheat Temperature 375C

The reactor pressure (40 ~sig) and the amount of excess fuel (approximately 10~) ~ere kept ~onstant. The re~ul~s of the experiments utilizing the continuous reactor which show the effec~ of injector shroud stea~ on ACR gas yield~ are shown in ~able I.
D-13,750 ~z~

A co~par~eon of the data in Table I
indicate~ ~hat injector ~hroud ~tea~ produce~
ffelectivity 6hifts in the yi~ldg of gaseou~
components by ~oderating the reaction severity.
~igh ~hroud steam re~ult~ in lower methana and acetylene yields ~it~ higher propylene and butene yields.
Pigures 1 and 2 represent the yields of ~elected component~ a~ a function of the heat carrier temperat~re. Figur~ 1 ~how~ that the et~ylene yield i8 ap~ro~ima~ely 1 pound higher in the ab~ence of injector ~hroud stea~ at les~ than 2100~C (low~r severitie~). Figure 1 further illustra~es that in the ab~ence of injector shroud steam, the pro~ylene and butadiene yield~ are ~igni~icantly lower over the range sf heat ~arrier temperature ~tudied.
Figure 2 6imilarly illu~trates that without injector shroud steam the ~ethane and ace~ylene yield~ are ~ignific~ntly higher.

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5~D

~AMPL~ 2 An ACR demonstra~ion unit, having an ethylene capaeity of approximately 5,000,000 lb~.~yr. was run (S~e Run 1~ Table II) with a naph~ha feed6tock ~low ra~e of about 1950 lb./hr.
hrough four in3~ctors. The lnjec~or~ which have ~oncentric annuli. have a total steam flo~ ra~e of approximately 200 lb./hr. The yield ~atte-~obtained i~ illustrated in Table II.
During ~un 2 (See Table II), ethane was added to the in3es~or annulus flows at a total rate of 150 lb./hr. The combined ethane plus naphtha cracking feed6tock flow rate ~as set at approximat01y l9S0 lb./hr. as in the previous run.
The in3ector annulus steam flow and all oeher opsrating variables remained constant. The yield pa~ern obtai~ed i8 illustrated in Table IIo ~ comparison of the data in Table II
indicate~ that the ethane has undergone significa~t endothermic cracking and has thus moderated the Scorch Zone cracking severity. The ethane decomposition to all products i6 approximately 58%.
The ethane cracki~ product mole selectivity to C2H~ i~ ap~roximately 78% of the total product ~ith the remaining products fro~ ethane consisting e~entially of C2Hz and ~2 These examples illustrate several important ~acets of the invention. The feedstoc~ is in~ected ~o a6 ~o give good atomization and mixing with the gaseous combustion product6, thus causing the total ~ixture to reach thermal equilibrium quickly and minimizing the extent of the Scorch Zone. A6 far as D-13,750 ~L2~ 5~

possible, flashin~ of the feedstock is encouraqed to aid the atomization and mixing. A ~hroud ~luid i8 also injec~ced in the region of the Scorch Zone to moderat~ ~he very severe cracking in the Scorch Zone. The ~hroud fluid i~ u~ed in relatively small quan~citie~ but i8 fed in a very localized area ~here it can have the mo~t benef it, and thus ~mproves the yield p~ttern to a degree dispro~o~tionate to the co~t of it8 u~e. In addition to thermal effect~, the ~hroud fluid ~ontains compound6 which have a chemi~al moderating effect on the reac~cions in the Scorch Zone.

D-13,750 TA~BLE3 I I
DE~SON5T ATION U~IT-NAPHTHA TESTS
WIT~ ETHANE IN ~HR INJECTOR ANNIJLUS
P~UN 1 R~UN 2 rilApHTHA
NATHTHA PLUS ETHANE
RUN NOS. _ ONLY I~3 ANNU~US
Naphtha ~ Ethan~ tlb.~hr. ) 1~4~ 1953 Ethane Annulus Plow llb. /hr. ) O 150 Steam Annulu~ Flow S lb . ~hr . ~ 200 200 Combu6tion Ga~ Flow (lb./hr. ) 3094 3124 Co~bustion Product Temp . ( C~ 2187 2156 Naphtha Feed Ter~p. (C) 241 240 Yield6 (lb./100 lb. ~racking feed~tock) }~2 1 . 44 1 . 78 C~4 , . 10 . 04 10 . 22. . - _ C2H2 2 . 97 3 . 49 C2H4 27 . 98 28 . 72 C2H6 2 . 44 5 . 47 C3H6 14 . 61 9 .15 C4~6 4.56 5.5 C,~,H~ 4 . 47 3 . 2 D- 1 3 , 7 50

Claims (10)

CLAIMS:

1. An advanced Cracking Reactor process wherein a fuel is oxidized in a combustion zone to affect a combustion reaction So produce combustion gases having temperatures in the range of from about 1200°C to about 2400°C, with optional addition of steam to moderate said combustion reaction, and passing a stream of said combustion gases to a Scorch Zone wherein a feedstock of shroud fluid and feedstock liquid mixes and impinges with said combustion gas stream to produce an admixture, passing a stream of said admixture through a throat wherein the velocity of the admixture is increased, and thereafter moving said stream more rapidly into a reaction zone wherein cracking occurs and the effluent from this zone is quenched, comprising the steps of moderating the conditions of said Scorch Zone to reduce the severity of reaction occurring thereat to reduce thereby the production of lower boiling species.

2. The process of claim 1 wherein the conditions of said Scorch Zone are modified by adjusting the right ratio of said shroud fluid to said feedstock liquid.

3. The process of claim 1 wherein the conditions of said Scorch Zone are modified by adjusting the temperature of said shroud fluid.

4. The process of claim 1 wherein the conditions of said Scorch Zone are modified by adjusting the composition of said shroud fluid.
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5. The processof claim 1 wherein said shroud fluid comprises hydrogen or a compound rich in hydrogen.

6. The process of claim 1 wherein said shroud fluid comprises ethane, methane, or propane.

7. The process of claim 1 wherein the conditions of said Scorch Zone are modified by adjusting the method of introducing said feedstock.

8. The process of claim 1 wherein the conditions of said Scorch Zone are modified by adjusting the flashing behavior of said feedstock.

9. The process of claim 1 wherein the conditions of said Scorch Zone are modified by adjusting the temperature of said feedstock.

10. In the process of practicing the ACR
using a shroud fluid about a feedstock liquid, the improvement which comprises analyzing the amount of reaction products formed, determining from said analysis that the amount of C4's and C3's in one cases are not sufficient and in another case determining that the C2's are not sufficient.
decreasing the temperature and/or raising the rate of the shroud fluid feed relative to the rate of feed of hydrocarbon feedstock to increase the production of C4's and C3's, or increasing the temperature and/or decreasing the shroud fluid rate relative to the feedstock whereby to increase production of the C2's.

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