US2090504A - Method and apparatus of heating hydrocarbon oils - Google Patents

Description

Aug. 17, 1937. H. c. scHuTT Er AL METHOD AND APPARATUS OF HEATING HYDROCARBON OILS Filed OOt. 9. 1955 3 Sheets-Sheet lv Aug.v 17, 1937. 2,090,504

- METHOD AND APPARATUS oF 'HEATING HYnnocARaoN oILs H. Y 3. scHUT'r ET A1.

Filed oct. 9. 19:55

3 Sheets-Sheet 2 RS Herma/zn @SMU/f5?,

Illy h' kmkw kil Aug. 17, 1937. H. c. scHuT-r Er AL METHOD AND APPARATUS OF HEATING HYDROCARBON ILS Filed oct. s, 1953 s sheets-sheet 5 NOQ n 5mm mh y V5 A x mv w @SW mwuv .wunvl mam A 1. Nom. MNO@ Non, Non NQ@ No, Nom. NON kg wm M m Q .A e n HM QOO\ MaJ my QQQN QQOM. .\.I.\|I||.\I.!W^ M||I|I| Il.: l QON@ j lill! QQSv A QQQM. @Skub )bulobw M MQUG @Skoh .CWQU wSO wml Patented Aug. 17, 1937 A "mamon AND APPARATUS' 0F HEATING HYDRQCARBON OILS 3. Hermann c. schonend John w. Throckmrton, A New York, N. Y., -asslgnorsto 4Alco Products Incorporated, New York,

l' of Delaware I Application October 9,

' -14 Claims.

Our inventionrelates to a method and appara-l tus for heating hydrocarbon oils, and more particularly to a furnace havingscctlons for heatf ing, moderate low temperature cracking and/or viscosity breaking andhigh temperature cracking.

In cracking operations the oil to be charged to the cracking still is either topped,l heated sufticiently to reduce its viscosity and/or mildly cracked'lbefore it is passed to the cracking still in; which`it1is" subjected to' high temperatures'. In the A'tivi-o process, foregrarnpie', the oil-to `be cracked is heated-toaporiaing temperatures.` then flashed 'in a iiash'evaporator and 'the vapors subsequently cracked inthe-vapor 4phase in a high temperaturec0115 im j VIt.has beenlthe :practicejlfreduently to -employ` separate pipe stills-FiordiiIerent duties depending upon whether or not high temperature --or lowV temperature-heat requirements" 'were necessary Iorthe operation.

One object of-our invention is' to' 'provide a furnace which will perform the heating' functions oi two stills in e. novel andv emcient manner.

'Anotherobiect of our invention is to provide 'si' furnace in which'both higher temperatureand lowerttemperature loperations may Abe performedj with a high eii'iciency.

Other and further objects of our invention will' be seen fromthe following description.- .I

In the accompanying drawings, which form par oi the instantspecitlcation and are to be read in conjunction therewith and in which like reference numerals refer to like parts'in the several views;

Figure 1 isa'schematic sectional elevation' of one mode of carrying out our invention.

Figure 2 is a schematic sectional elevation of another mode ofl carrying out ourinvention.

. Figure 3 is Aadiagrammatic showing oi the relationship of temperature to excess air in the embodiment shown in Figures 1 'and 2.

In general, our invention comprises. the provision of a furnace setting having a bridge wall dening a pair of combustion chambers. The

d gases of combustion from the combustion chambers are discharged at separated points into a gas 4 passageway which may be positioned underneath or at the side of the furnace setting and enclosed therewithin. Radiant heat absorbing sections are positioned in each of the combustion chambers. A series of convection heat absorb'ing sections are disposed in the gas passageway, such that some are exposed only to the gases from the high` temperature treating section while the remainder are exposed to a mixture of the gases issued from N. Xs a corporation 1933, serial No. 692,304

(ci. 19e- 49;

thehigh temperature and the lower temperature treating sections. The combustion gases from the lower temperature section are discharged into the gas passageway and admixed with the combustion gases froml the high temperature section having passed through the series of high temperature'convection heat absorbing tubes and reached' a'.temperature approximately the sarne as that of the gases escaping from the combustion'ohamber of'the lower temperature section. 'I'h'e'l-c'om'bined streams 'of flue gases are then passd'through another section of convection tubes these being at lower temperature and posiof thellower-t'emperature side. then' through a con.

v'ection' section of the higher temperature side', then-through a radiant section of the 'higher temperature side and iinally through a soakingsec'tion or the-higher temperature side. Portions of the convection section or the radiant sectionlof either side or a combination of portions of the convection section and radiant section may be used as soaking' sections depending upon the purpose to be accomplished and the character of the hydrocarbon undergoing treatment. In the case of a vapor'phase process; a ash evaporator is interposed between' the sections oi the lower temperature and the higher temperature sections. The section of the'lower temperature side may then be used for viscosity breaking and'the vapors from the'ash evaporator may be cracked in the sections of the higher temperature' side.

More particularly. referring to Figure l, a furnace setting l, which may be of any suitable approved` construction is provided with a partition wall 2 dividing the setting into a pair of combustion chambers 3 and 4. Suitable burners 5 and 6' are positioned within the combustion chambers. Horizontal bridge walls l and 8 cooperate with partition wall 2. to define the combustion chambers 3 and l. A passageway 9 is positioned within the settingi underneath the combustion chambers 3 and 4. Ii desired, this passageway may be positioned at either side. The passageway 9 terminates with an opening l0 which is connected to a stack or fiue to conduct the waste gases to any suitable point, such as a smoke preventer or the atmosphere.

rows indicate the direction of1-the ilow of the 1 15 combustion gases. The hot combustion'jgases from combustion chamber 4 are 'discharged into passageway 9 and pass therethrough to the ilue connection lila. 'Ihe combustion from combustion chamber 3 discharge into the gas 20 passageway 9 at a separated point therein from that of the entrance of the gases from the combustion chamber 4. A series of convection tube sections are positioned'within the. passageway 9 as can be readily seen by reference to the draw- The oil to be heated is charged through line i5 through the tubes .of a bank i6 of the lower temperature convection section. This section has a main bank IG of the lower vtemperature convec- 30 tion section.

and an auxiliary bank will be hereinaftermore fully described. The oil from bank 'i6 passes throughv linefiBb .to :bank

ia of the convection section. then through linev i1. throught the tubes oi.' the radiantheat banki of the lowerv temperature section, then intothe tubes of the soaking bank i8 of the lower temperature convection section. and then into the tubes of the' radiant soaking bank ila of the lower vternperature section. In order to guard against carbon deposition which might be occasioned-by the overheating-of the oil ,within the tubes, soaking b'ank it is positioned vbehind bank lia of the lower temperature convection section and soaking bank 45 la is positioned abo've radiant bank lil. It -.will be observed that bank I8 is a convection bank and that gasesl of combustion passing over the bank must first pass over bankA IGa., In this manner,

it is insured that the cil within bank-I8 will not 50 be overheated resulting in a partial decomposition with danger of carbon -formation and deposition.

The oil leaves the tubes of bank ila through line is and in the case'of a vapor phase process,

55 goes to ilash evaporator 20 from which the unvaporized oil is withdrawn through line 2i and the oil vapors through line 22. It is to be understood, of course, that our furnace may be employed also in liquid phase cracking operations in which case the ilash evaporator may be replaced by a ,topping tower and the cracking stock withdrawn from the topping tower; may be charged throgh the line 22.

The oil fromlne 22 passesthroughabank 35 of the higher temperature convection section. In-

thls convection bank 23 which in case of a vapor phase cracking process is usually termed a drying tube section. the reactant is further heated under moderate heat transfer conditions and up 70 to temperatures where pyrolytic reaction takes place only at a low rate. Thus the vapors are dried and all liquid particles completely vaporized under conditions which do not permit the formation and deposition of coke. The dried, or super- 75 heated, oil vapors leave bank 23 through line 24,

This section has a mainbankil i6a, .the purpose v:tn lyvhicli tube wall and medium in the tubes in spite of the higher -heat absorption rate,'thereby reducing the danger of overheating. The vapors now pass vthrough'the tubes of the radiant heating bank il ci the higher temperature section where at a 'high rate of heat absorption they attain rapidly the desired reaction temperature and subsequently through the tubes of soaking convection bank 25 of4 this section and iinally through the tubes oi the shielded radiant soaking bank 25a. The oil from the shielded radiant soaking bank 25a leaves through line 26 and passes to the quenching chamber in the case of a vapor phase process, or to the reaction chamber in the case of a liquid phase process.

In operation, the oil enters the tubes of the convection banks i6 and i6a of the lower temperature section and passes through a series, of radiant heating tubes ID disposed-within the combustion chambervci the lower temperature section, and then passes to the tubes ot. the soakingbanks IBa and it in. which .the desired low-temperature heattreatment is completed the case volf a vapor .phaser processfor example, :the vapors enter thedryingtube bank23-which is characterized by a moderatel and uniform rate of convection heat absorption, and consequently low tube wall temperatures. The oil vapors then pass iiaof the radiant tube section of the her temperature section, and thence through the tubes of the radlantbankl l. r

It will be observed that the vaporsare heated A at progressively increasing vaporxiilm rates. avoiding high tube wall temperatures with its inherent danger of illm carbonization. After these preliminaryheatingstages, as represented by tube banks 23 and lia., the .vapors are sufciently super-heated that coke `formation in the high transfer rate heating tubes il at the proper vaporillm rate is unlikely. Highly superheated hydrocarbon vapors in a process of thermochemical decomposition at;.high temperatures will form some carbon but this carbon will be in vdeilociculated form, known as lamp black carbon, which. will be carried away by the vapors passing through the tubes at high velocities and will not deposit on the tube walls if these are not overheated. 'I'he vaporsleave the-radiant heat tube section and pass into the tubes of the soaking bank 25 which is a convection bank maintained at the desired reaction temperature. The vapors leave the tubes of the convection soaking bank and pass through the tubes oi' the shielded radiant heat soaking'- bank 25u` from 'whence they are led off through line 26 for quenching and further processing. The feature of importance in the soaking tube banks 25 and 25a is that the heat absorption rate of the soaking tubes be equal to the heat consumed by the endothermic reaction of cracking so that a uniform temperature is maintained.

The burners and i may be oil or gas burners so that they may be readily controlled. By controlling burner B it is possible to obtain an adjustment which will achieve an even soaking temperature ln the soaking banks 25-25a as will be apparent by reference to Figure 3. The diagram there shown is illustrative of the manner in which the rate of heat absorption adjusts itself when a combination ofl radiant and con- 6 vection heat absorbing soaking tubes are employed as shown in Figure 1.

.The figure shows that the rate of heat absorption whichis principally a function ofthe tem perature for the radiant heat tubesvdecreases in l the radiant section with an increase in the amount of air in excesszoi' that required for complete combustion. This is due to the lowered mean temperature in the radiant section. At the same time. howeverI the excess air' causes an increase in the flue gas velocity with a resultant more efficient transfer of heat from'the flue gas t o the convection heat tubes and a consequent rise in the. rate of -heat absorption. Obviously, therefore, a furnace designed with a soaking bank formed by a second row of roof tubes and another soaking section formed las a convection bank may be efiiciently operated according tov the requirements of the particular charging stock and its characteristics as far as the reaction rate isconcerned. Figure 3 shows that with a rate of heat absorption of around 3700 B. t. u./sq. ftJhr. in the radiant and convection soaking sections; substantially 60% excess air is required. As moreor less air is supplied, the rate of heat 3 absorption? in the radiant and convection sections changes in amanner whichliscieariy shown in the diagram of Figure 3.@ It is thus' clear that considerable variation in vtheoperating condi? tions for the radiant and convection soaking tube .sections can'behad by a regulation of the' amount ofexcess-air.

- The flue gases emanating from `the high tem.

perature section are ordinarily not tempered by the gases escaping from the low temperature ra- 40 dient section. The latter may'be as high in temperature as the former. Howevenin such A cases where extreme high temperature treatment is performed-in the high temperature section. and the nue gas temperature of the combustion gasesie'aving this section is still so high that a high heat absorption rate is forced on the front rows of tubes in the lower temperature convection section. and the material in these tubes (liquid oil in most cases) will carbonize at the overheated tube wall, then the combustion in the lower temperature radiant section can be so ad- :usted that the nue gases leaving this combustion chamber will be of lower temperature and actually temper the combustion gases leaving the,

higher temperature section. It will be observed that the hot gases from combustion chamber 4 are cooled by passing through the soaking bank 25 and the drying bank 23. They will in some cases. however, still be too 'hot for the 'convec- 00 tion tubes of the lower temperature section of the furnace. Before they are allowed to contact the convection banks of the lower temperature section, the combustion gases from the lower temperature section are admixed therewith. The

temperature of the flue gas mixture can be readily controlled by the firing conditions of burners 5 determining the temperature of the flue gases leaving the combustion chambers of the lower temperature section. Adjustments can be made so that the resulting gases passing through the convection section of the lower temperature section will be at that temperature desired for the process being conducted.

It will be observed that our arrangement makes for a very flexible design, in that the duties of the two sections may be varied at will without impairing the performance of either individual section. A maximum of economy is thus obtained and uniform results achieved in a process involving a multitude of separate phases of operation. An economizer tube b ank may be positioned in the gas passage before the gases go to the ue to effect the highest possible furnace economy. The section may be used to heat a circulating medium for use in evaporator-s, heaters. reboilers.or for the generation of Vsteam As an example of the operation of our furnace, the topped crude, gas oil or a. mixture of gas oil, a relatively heavier oil at a temperature between 550? F. and 600 F. is charged through line, i5, to the. convection -preheating banks iS--lta where the oil is heated to around 700 F. The heated oil from bank ISG. is raisedin the radiant heated tubes of combustion chamber 3 to a temperature ranging between 850 and 800"l F. which is maintained in the convection heated and radiant heated soaking banks I 8i8a. The heated oil from the moderate low temperature cracking or viscosity breaking section of the furnace is then charged through the line i8 to the evaporator 20 from which the oil vapors at a temperature of approximately 800A F; are led through the convection drying section 23 where then temperature is raised-toi 850 F. oil vapors are then'passedthrough the radiant heated bank (in wherethe temperature is raised to'875400iF.: before the nal heating'nf the oil vapors takes'place .in-radiant heated banks ii wherefthe temperature is raised to 1100-1300. F. The nal=`pyrolytic treatment or high temperature cracking takes place inthe soaking sections y25=2.a.iv\rl1ere I'the oil -vapors still at a temperature of between d-1300*l F.are subiected to the* iinal cracking. The flue gases leave combustion chamber 4 at a between, 1700' to 1800*"F. and arecooled by passage through the convection banksZS and 23 to a. temperature of about 13004 'E'. The combustion gases from the -low temperature treating section 3 leave at a temperature between HOT-1300' F. and are commingled with the gasfroxn the high temperature treating or cracking section such that the resultant temperature of the commingled 'gases prior to passage through theconvection banks lia, I8 and IG is between 1250-1300 F. The gases in passing through the convection banks Isa, Il'and li are reduced in temperature to .between 800'900 F. A further reduction in temperature is effected as the resuit of the passage of the gases through the economiser bank 3U wherein the temperature falls to around 600 F. before passage into the stack. It is to be observed. that the eoonomizer bank llimay be used to heat a charging stock which may be raised from 300 F. to 890 F. by passage therethrough. The heated stock could then be flashed into an evaporator tower from which the vapors could be withdrawn at a temperature between 550600 F. and charged to the convection preheating bank i6 as before.

Referring now more particularly to Figure 2, a modification is disclosed in which one section of the furnace is used for preliminary drying and heating to the desired cracking temperature and the other is used for soaking.

Oil is charged through the line 29 t the economizer bank 30 where the temperature is raised by convection heat and the heated oil then led by line i9 to the evaporator 20. The vapors sep `grated in the evaporator 20 are charged through The dried the line l5 to a preliminary drying bank formed by convection heated sections iG--lGa from which the vapors are led by the line l1 to the radiant hea't bank- I0 in the combustion cham- 5 ber 3 which may comprise roof, iioor and wall tubes in which the vapors are rapidly 'brought up to the desired cracking temperature. The heated vapors are 'led by a line Ila. to the radiantly heated bank II in the combustion chamber l0 4 where the iinal pyrolytic reaction takes place. The radiant soaking bank Il is supplemented' by a convection heated, soaking bank positioned in the passageway 9 and from which the vapors are led by line 26 for further processing or cool- 151mg. In the vevent that 'it is desired to utilize the furnace forliquid phase cracking, a distillate or a topped crude'from a topping tower may be charged through the economizer bank 30 and then led directly -into the convection preheating 20 banks IE--lla from which the oil is led for heating as in the vapor phase operation.

. It is to' be observed that our furnace permits of separate control .of the temperatures in the radiant heating and soaking sections by the 25 ring of the burners 5 and G located respectively in the chambers 3 and 4. Extreme flexibility of control of the cracking temperatures is thus provided and forms an important feature of our invention.

The diagram of Figure 3 is particularly applicable to the furnace of-Figure 2. A proper control'of .therexcess air -in the combustioncham-T- ber 4 wi11:permitof considerable -variation in the rate-of heat transferA to the radiant heated and to the' convection heated tubesofathe soaking section independently ofthe temperature in the cracking section 3. It is to .-be further observed that thismodiiication-ls `illustrativefof a of operation in 40 which the gases from the extreme high 4temperature soaking sectionrare tempered and cooled by the Vcooler gases from the combustion chamber 3 before they are allowed to contact the Aconvectlonvheated section IG-ia. The formation of and deposition .of carbon within.: the tubes. of these sections as the result of too rapid heating is thus-prevented. For example,` assuming a naphtha reforming operation. the reactant after initial' heat exchange is charged through the economizer bank 30 and is :raised intemperature from 250 to 650 F. and then passed to the evaporator 20 through the `line I9. `The vapors from the evaporator at a temperature of between S50-600 F. are heated in the convection sections IG-lGa of the lower temperature section, to approximately 80G-900 F. before entrance into the radiant heated bank i0 of the heating section 3. The vapors are rapidly heated in the tubes l0 to a temperature between 1100-1300 F. for high temperature cracking and then passed to the soaking banks Il and 25 of the higher temperature section where the final reaction takes place. It will be understood that certain features and sub-combinations are of utility and may be cmployed Without reference to other features and sub-combinations. This is contemplated by and is within the scope of our claims. It is further .n obvious that various changes may be made in details within the scope of our claims without departing from the spirit of our invention. It is, therefore, to be understood that our invention is not to be limited to the specific details shown and described.

mainly byiconvection heat part of the convection heat of thegases'of combustion issuing from one of said combustion chambers by hydrocarbon oil passing to said combustio'n chamber in a confinedl stream, vs/hereby. to reduce the temperature voi? said gases, commingling said -gases thus reduced in temperature with the gases of combustion issuing from the'otherpf said 'combustion chambers and absorbing in a zone heated mainly by convection heat partei -the convection heat from the resultingmixture of combustion gases by'hydrocarbon oil passinginaconiined streamto said last mentioncdecm'oustion chamber.

A furnace for heating hydrocarbon oils com'- prising in combination, a unitary setting, a verical partition wall and ,a-par of horizontal bridge walls within said setting defining' therewith a pair of combustion chambersnmeans for burning fuel disposed-in eachfof said chambers; .oil circulating means positioned-:in eacharof' said 'ehambers adapted toibe hcatedmainly by -theradiant heat of eombustomoil circulating means adapted to be heatedmanlybytconvection heat-:from thegases of comtn istion,I issuing Iromonly oneof said chambers andconnected to the;- oil circulating means insaidfone of said chambers, andseparate oil circulating means adapted to be-heatedmain-A ly by convectionheatrom the combined wmbustion 4gases -I rom'bothpf said chambers:con-' nected tothe-oil circulating-means in the-other of said chambers.- u

tive oil circulating means are connected in series.

.4. Afurnace for heating l'iydrocarbon oils corntherealong, apair of tube banks positioned in said passage adapted to be .heated mainlyf by convection heat of the gases from oneof said chambers, a pair of tube banks positioned in said passage adapted to be heated by convection heat of the gases from both of said chambers, respective tube banks adapted to be heated mainly by radiantheat positioned in said chambers, and means for passing hydrocarbon oil through one of the banks of said last mentioned pair of convection tubesbanks, then through a radiant tube bank, then through the other bank of the said last mentioned pair of convection tube banks. then through a convection tube bank of said first mentioned pair of convection tube banks, then through the other of said respective radiant tube banks and then through the remaining convection tube bank.

5. Heating hydrocarbon oil by passing it through tube banks and heating it in succession as follows: heating the oil mainly by convection heat; heating the oil mainly by radiant heat; heating the oil mainly by a second convection heat; heatingthe oil mainly by shielded radiant heat; heating the oil mainly by convection heat f higher temperature than said nrst convection heat; heating the oil mainly by radiant heat oi higher temperature than said first radiant heat; heating the oil mainly by convection heat of higher temperature than said second convection heat; heating the oil mainly by shielded radiant heat, of higher temperature than said first shielded radiant heat.

6. A process of heating hydrocarbon oil comprising the steps of progressively f'passing'it in an elongated, connned stream throughs. ilrst coil of a pair of serially connected coils disposed in a gas passage. through an intermediate coil disposed in a gas generating zone. and through the second coil of the pair, generating hot gases oi combustion in a ilrst gas generating zone; subjecting the oil stream in the second coil of the pair to the convection heatingaction 'of said gases, independently and simultaneously generating further hot gases oi combustion in a second gas generating zone, effecting absorption by the 'eil during passage of the stream through the intermediate coil ot part of the radiant heat of combustion ofthe hot gases generated in said second zone, after the stream-has passed of seriauy connected coils and. -before it has :throughthe second of said pair of coils.

and introducing thescombustion gases generated insaidsecondgugeneratingzone intosaidgas and heating it in succession in a convection heating zone, in a radiant heating-zone ofloneteniin a radiant heating zone .of a-higher temperature, and -in a convection heating zone of a higher temperature than said first convection heating zone. generating -of.combustion 4o in a nrst gas generating' zone,

gasesof combustion in a second gas generating zone, said iixst convection heating step being performed by the hot gases of combustion from both zones. said nrst radiant heating step being performed only by the radiant heat of second radiant the radiant heat ot combustion in said second gas generating zone, and said second convection heat- 5o ins .step being performed by the hot gasesoi combustion from said second gas generating zone only.

8. A process of heating hydrocarbon oil comprising the steps ot'passing oil in an elongated. streamina sexiesofheating zonesand heating the oil in succession in a convection heating zone. in a radiant heating zone, in a second convection heating zone. in a third convection heating zone, in a second radiant heating zone, and in a fourth convection heating zone, generating hot gases oi combustion in a rst gas generating zone, generating hot gases of combustion in a second gas generating zone. said ilrst radiant heating step being performed by the radiant heat of combustion in said first gas generating zone. said second radiant heating step being performed by the hot gases of combustion in said second gas generating zone. said rst and second convection heating steps being perfumed by the hot gases of combustion from both said gas generating zones, and said third and fourth convection heating steps being perfumed by the hot gases of combustion from one of said gas generating zones.

9. A process of heating hydrocarbon oils comprisms the steps of burning iuel in a rst comthrcughthe iirst'oi said pail' f, Passing the oil oonnned Smm thmuh a sexies of heatingzones A hot gases issuing generating hot bustion zone to generate radiant heat and hot gases of combustion, independently burning fuel in a second lower temperature combustion zone to generate 'radiant heat and hot gases of combustion, separately withdrawing the hot gases from each combustion zone, tempering the gases withdrawn from the ilrst combustion zone bycommingling them with the cooler gases withdrawn from the second combustion zone, simultaneously passing hydrocarbon oil in an elongated coriiincd stream through the zone containing the tempered commingled gases to thereby heat the oil mainly by the convection heat of the gases and then passing the oil in a conilned stream through the combustion zones of successively higher temperature to thereby progressively heat the oil mainly by the radiant heat generated in each.

10. A process of heating hydrocarbon oils comprising the steps of passing the oil in heat interchange relationship with hot gases in a convection heat absorption zone, simultaneously converting energy in a second heating zone to cause radiant heat and the formation of hot gases, withdrawing' the hot gases from the second heating zone and passing them through the convection heat absorption zone, passing the oil in a confined stream through the second heating zone and heatingthe oil-mainly by radiant heat,A separately and independently converting energy in a third higher temperature heating zone to-cause radiant heat and the formation of hot gases, from the second heating zone .through -the third heating zone and absorbing a portion of the radiant heat therein, withdrawing the hot fromthe lastmentioned zone cool- Y. ing said gases to'substantialLv the temperature of .the gases ,issuing from said 'second heating zone and then commingling the cooled gases -with the from the second heating zone.

A 'process 'oi converting hydrocarbon oils into hydrocarbon oils of lower molecular weight comprising the steps of independently generating hot gases of combustion in a ilrst combustion zone and in a second lcombustion zone. withdrawing the gases from each of said zones. passing the gases from the second zone in heat exchange relationship with cooler hydrocarbon oil, commlngling the cooled gases with the gases withdrawn from the first zone, passing hydrocarbon oil to be converted in heat exchange relationship with the commingled gases to eiect a ilrst gradual temperature rise in the oil, passing the then heated oil in heat exchange relationship with the radiant heat in the ilrst combustion zone to secure a second rapid temperature rise in the oil and a mild cracking reaction, passing the partially cracked oil in heat exchange relationship with the gases issuing from the second combustion zone to effect the cooling of said gases and a further gradual temperature rise in the oil and then passing the oil in heat exchange relationship with the radiant heat in the second combustion zone to raise the oil to the final cracking temperature.

12. A process of converting hydrocarbon oil comprising independently generating hot gases oi combustion and radiant heat in separate combustion zones. separately withdrawing and then combining the gases from each zonel passing hydrocarbon oil to be cracked in heat exchange relationship with the combined gases as a preliminary heating step. subjecting the heated oil to a viscosity breaking reaction by passing it in heat exchange relationship with the radiant heat in one of said combustion zones, separating the vaporized from the unvaporized oil, passing the vapors in heat exchange relationship with the gases issuing from the other of said combustion zones whereby the gases are cooled before being commingled with the gases issuing from the other zone, and the vapors are dried. and raising the dn'ed vapors to the desired cracking temperature by passing them in heat exchange relationship with the radiant heat generated in said last mentioned combustion zone.

1 3. A process of converting hydrocarbon `oils comprising the steps of independently generating both hot gases of combustion and radiant heat in separate'cracking and soaking z ones, separately withdrawing the gases of. combustion 'from each of said zones, combining the gases, passing hydrocarbon oil to be .cracked in heat. exchange relationship with-the'combined gases whereby the oil is initially heated, subjecting the heated oilto heat exchange with radiant heat in said cracking zone to eiect a rapid temperature rise to a predetermined cracking temperature, passing the oil at'the cracking temperature to the soaking zone and there subjecting it to radiant heat for a predetermined time interval suilicient to eiIect a substantial 4cracking of the oil, then passing the oil in convective heat exchange relationship with the hot gases issuing fromthe soaking zone to effect a cooling of said gases, and withdrawing the cracked oil from the process.

14. A tube still for converting hydrocarbon oils comprisingin combination. a furnace setting. a partition wall within said setting defining therewith a pair of combustion chambers, a bridge wall in each chamber, said bridgevwalls deiining with said setting a passageway for the combustion gases issuing from both of said chambers, means for burning fuel disposed in a portion of each of said chambers, atube bank positioned in said passageway and adapted to be heated mainly by convection' heat of the gases from one .of said chambers, a pair of tube banks positioned in said passagewayand adapted'to ,be heated mainly by convection heat of he-gases from both of. said chambers, one of the banks of said pair serving as a hottest gas shield for the other, tube banks adapted to be heated mainly by radiant heat positioned in said chambers, and means for passing hydrocarbon o il through thev shielded bank of said pair'of convection heated tube banks, then through the shield bank of said pair, then through a radiant heated tube bank in one of said chambers,then through aradiant heated tube bank in the other of said chambers, and then through the rst mentioned convection heated tube bank.

. 1 .DISCLAIMER- 2,090,504r-H-ermamtf-.Schutt and-John W. cw York,lNu.f,Y. IVIi-rrnon AND APRARATUB or HEATING lHxmaocluuaou OILS.

filed December '30, 41939, by theassignee,-

August 17, 1937. Disclaimer lAfnerican Locomotive Company.

-Patent dated ent-ea this disclaimer reclaim 9 of Sanitaer; Bag-iii. j'

in one of said combustion zones, separating the vaporized from the unvaporized oil, passing the vapors in heat exchange relationship with the gases issuing from the other of said combustion zones whereby the gases are cooled before being commingled with the gases issuing from the other zone, and the vapors are dried. and raising the dn'ed vapors to the desired cracking temperature by passing them in heat exchange relationship with the radiant heat generated in said last mentioned combustion zone.

1 3. A process of converting hydrocarbon `oils comprising the steps of independently generating both hot gases of combustion and radiant heat in separate'cracking and soaking z ones, separately withdrawing the gases of. combustion 'from each of said zones, combining the gases, passing hydrocarbon oil to be .cracked in heat. exchange relationship with-the'combined gases whereby the oil is initially heated, subjecting the heated oilto heat exchange with radiant heat in said cracking zone to eiect a rapid temperature rise to a predetermined cracking temperature, passing the oil at'the cracking temperature to the soaking zone and there subjecting it to radiant heat for a predetermined time interval suilicient to eiIect a substantial 4cracking of the oil, then passing the oil in convective heat exchange relationship with the hot gases issuing fromthe soaking zone to effect a cooling of said gases, and withdrawing the cracked oil from the process.

14. A tube still for converting hydrocarbon oils comprisingin combination. a furnace setting. a partition wall within said setting defining therewith a pair of combustion chambers, a bridge wall in each chamber, said bridgevwalls deiining with said setting a passageway for the combustion gases issuing from both of said chambers, means for burning fuel disposed in a portion of each of said chambers, atube bank positioned in said passageway and adapted to be heated mainly by convection' heat of the gases from one .of said chambers, a pair of tube banks positioned in said passagewayand adapted'to ,be heated mainly by convection heat of he-gases from both of. said chambers, one of the banks of said pair serving as a hottest gas shield for the other, tube banks adapted to be heated mainly by radiant heat positioned in said chambers, and means for passing hydrocarbon o il through thev shielded bank of said pair'of convection heated tube banks, then through the shield bank of said pair, then through a radiant heated tube bank in one of said chambers,then through aradiant heated tube bank in the other of said chambers, and then through the rst mentioned convection heated tube bank.

. 1 .DISCLAIMER- 2,090,504r-H-ermamtf-.Schutt and-John W. cw York,lNu.f,Y. IVIi-rrnon AND APRARATUB or HEATING lHxmaocluuaou OILS.

filed December '30, 41939, by theassignee,-

August 17, 1937. Disclaimer lAfnerican Locomotive Company.

-Patent dated ent-ea this disclaimer reclaim 9 of Sanitaer; Bag-iii. j'

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