US1701477A - Treatment of mineral oils by heat - Google Patents

Description

Feb. 5, 1929.

` W. J. PERELIS TREATMENT oF MINERAL oILs BY HEAT 'Filed June 24, 1925 Patented Feb. 5, 1929.

AUNITE-D sTATEs WALTER JAMES I'EmiLIs,` or EVEEETT, MASSACHUSETTS, AssIGNoE'Io SHELL 13E-` I vELoIMEN'I' COMPANY, or vl-IDELAWARE 'f w'. .r

. .'.raEA'rNIEN'r or MINERAIioILs BYy HEAT.

SAN FRANcIsc'o, CALIFORNIA, A ooEroItA'rIoN` 011'l L i Application filed June 24, 1925.. Serial No'. 39,280.

.I This invention relates lto thetreatment ofv mineral oils by heat, includes a process for converting the material treated into a more volatile fraction and valuable heavier fractions suitable for further use; and relates to apparatus suitable for practice of the process. One object of this invention is to provide a process for the cracking or conversion by heat of mineral oils, their derivatives. and mixtures, to provide suitable apparatus for this purpose; and particularly to provide apparatus and a process to'be practiced by the aid of the apparatus which shall be capable of subjecting different fractions of the material for example, in respect to the temperature, thc time, or the pressure) characteristic of the treatment of one component fraction as compared with treatment of the other component fraction. y

A further obj ect of theinvention is to provide a process, and apparatus for practicing it, which is capable in use to permit a continuous vinflow of a heterogeneous mixture,

l or of crude materials, or of a Wide fraction having therein hydrocarbon materials of many different boiling points, the processl being characterized by operations upon-the material Which will result in separating the flowing material into fractions in respect to which optimum conversion into gasoline` or naphtha, light gas oil, `and fuel oil should be accomplished by dilferentkinds of .heat treatment; and by the provision of a mode of l treating the fractions severally v-accordingrto the optimum kind of treatment for suchc'onversion.

" `A further obj ect of the invention to provide a continuous process for the heat treatment of mineral oils comprising as `steps cracking the mineral oil by subjecting-it in v stages severally to conditions `of treatment adapted respectively for heavier and less volatile mineral oils, and for lighter'andymore volatilev mineral oils.

A further object of the invention comprises theprovision of steps, and suitable apparatus for use inpracticing these steps, characterized by. consevationof the heat of one stage of tlie process for use -in performing the other st-agesofthe process.

' I have heretofore describedy and claimed in niy application Serial No. 16,952, filed March Q0, 1925, a process of general application `to treated toA heat treatments differing in degree mineral oils for converting them into a motorspirit, naphtha or gasoline fraction, a light gasoil andkerosene fraction, and a fueloil fraction, containing in common 'with this invention an improved genus of treatments for cracking the oil by turbulenty flovv in a tubular heater under conditions tending to prolong the time of iowfunder reactive conditions of heat and during maintenance of a maximum fluidity of the oil underV treatment, such as is induced by creating a condition'of mixed vapor and liquid, the vapor being in finely divided bubblysuspension in the liquid.

The present invention comprises improvements in the process, and in the apparatus for carrying out' the process, disclosed in my said application, 'said improvementshaving for their general object facilitation of treatment of oils which lack homogeneit of contents, and to avoid any necessity or alter-` native treatment of fractions of the same oil in-tWo di'erent units of apparatus; or at koil under different conditions of heat and pressure from the heavier fractions, and pro-- :vides for this purpose a method of, and apparatus for, lso treating the mineral oils `as totconserve the heat and conserve the energy required to move the oil through the respec- 'tive'stages of the operations upon it.

ingfrom rectify'ing .the naphthas and,` gasolines or other light fractions of thefcracked One o f the chief advantages ofthe present processus related to the economy of heat flowoutput of.v a cracking' operation conjointly with carryingon the crackingoperation in relation tofthe Whole 'raw material.; lIn, a-

rectifying operation it is necessary to provide heat, and for a high recoveryt is invention rovidesfor crackingthe-b'ottom frac` tion rom the rectifying column continuously,

in order thoroughly to convert all of the coni vertible hydrocarbon materials into the valuable naphtlia `and gasoline range of products; A typical example of practicev of .the proe-,...

ess ofthe invention will nowY be described in connection with one formrof apparatus suitable to practice the process.

In 'the accompanying drawings, the figure isa flow-sheet in'diagram of a complete unit of the apparatus.A .f

. able form of heavy vapor separator 10. Heat .v

The raw material, which rmay be aerude petroleum or a mixture of crude roductsor fractionsfis fed from any surta le storage receptacle'throughthe pipe 1 with the aid of any suitable pump 2 lthrough a heat exchanger 4 interposed anywhere in the pipe line 3, 5 leading to a jet tower or other suitexchangerll may, as shown, be in a loopof the feed pipe 3, 5 vsurrounded by a by-pa'ss 6, pipelines beingprovided with suitable valves to regulate the proportion of oil iowing through the heat exchanger 4. The hot side of the heat exchanger 4 may be suitably heated vby eilux from other parts of the apparatus.

The preliminary heat (for one example only, 200 F.) given the material flowing in pipe 5 and delivered in the jets 9 of the vapor separator tank may. be of any degree desired,

` but preferably is such as to render the incoming hetero eneous material sufficiently lluid to How rea ily in the separator 10 andto give up a part of its most volatile constituents on Contact in the separator 10 with effluent hot vapors from a vaporizer presently mentioned.

The feed stock notvaporized in the separator 10 (i. e. thefgreater part of the feed stock) Hows through the pipe 12 into a tank 13,*preferably heat-insulated, whence it is pumped l out through ,a h ot feedv line 14: bythe pressure pumps 15, lwhichv may comprise'a ybooster a and hi h pressure unit The pipe 14 carries the in'ux oil through a heat exchanger 16 in Which the owing streamattains a temperature of the order' of about 740 F. The effort of the booster pump a and the high pressure pump of the pumping unit at 15 maintains the pressure inv and beyond heat exchanger 16 as far as a pressure reducing valve 25 presently mentioned of about 250'to-350 pounds per square inch, when handling heavy oil in the recommended practice. The routflow pipe 17, which may besuitablyheat insulated, leads the oil under treatment (comprising at this stage all of the Iorigina-l contents of the oil except the most volatile fractions delivered up as vapor on the Islight elevation of temperature of the-oil in the separator 10) into a primary or low-pressure cracking unit A.

The cracking unit A. may comprise any l suitable convoluted arrangement of tubular sharp angular bends.-

takes place in a part 20 passages, for example comprising a relatively great length of round steel tubing'of substantially uniform internal diameter built up v considerable length of flow in coil 20.. During flow in coil 20, the oil will have attained a maximum fluidity and optimum temperature.

The efflux throul h pipe 21 from the heater element of the crac ing unitin which the temperature of the oil is raised to a temperature of from 860 F. to 900 F., is carried into a timecoil, which may be a mere continuation of the coil 20 and comprise, for example, a coil 22 and a coil 23, is preferably subjected to cooling in the coil 22 and to heating again 'in the coil 23. For example, the coil 23 is mounted in a furnace, not shown, whereas the coil 22 is merely in a closed chamber permitting some loss of heat; for example the temperature may be allowed to recede through about 50 F. in coil 22, and the temperature may be raised again in coil 23 to about 880 Fpto 910 F.

The relative temperatures attained during flow are import-ant to correct practice. In the entrance coil 20 the oil passes to its maxi- `mum fluidity or lack of viscosity and attains a cracking temperature during increasing rate and turbulence of flow due to expansion, the impressed pressure and the internal disintegration of its components. The rate of heating to this point, if much higher than that recommended, would cause coking because the rate of input of heat would be too great for oil not yet in a state of minimum viscosity or maximum fluidity, so that the oil particles close to the tube wall would be overheated. and the center of the stream of oil would remainv relatively cool. Coking would then occur in the oil in contact with the tube walls. But when the temperature is permitted to recede somewhat in the second coil 22, the material has already been subjected to heat during sufficiently long a time to permit the development in it of minute vesicles of vapor, which are kept in a state of thorough distribution and individual separation by the rate and turbulence of flow of the stream. The temperature in coil 22 is still suiiicient for continued development by heat of the more volatile products of conversion, and by the time the material passes out of coil 22, its condition is such as to ensure inability to overheat its liquid contents by heated pipe-walls which, at

an earlier stage, would have resulted in heating the liquid in conta ct with them to too high a temperature, so high as to result in too much permanent gas and too much carbon in the products. In other words, the' fluid stream has now been brought to a state of flow, lack of viscosity, and contents of entrained vapor in which state it is a good vehicle for the con vection of heat away from the walls of the tubular heater, as contrasted with greatly` less eiciency in this respect in the entrance portions of the first coil 20. l y,

The fluid stream may therefore bedetained during rapid and turbulent flow ,in` coil'23 under higher temperatures for a suiicient time to complete the conversion of the hydrocarbon material to the degree desired without endangering the formation of too much permanent gas and carbon. Coil 23 may therefore be of such length and maintained at suchA relatively high temperatures throughout as to effect the thorough conversion of the material.

These steps are effective to cause a higher efficiency in cracking in relation both to the volume of material treated in a given time and in the use of heat for the conversion. A still greater advantage, however, arises from the effect of the relationship of condition of the flowing stream to the heating walls. The temperatures to which the material may be subjected without coking are much increased by the recommended procedure, with corresponding increase in the production of gasoline.

The pressures at which cracking is carried out may vary from 250 pounds to 350 pounds to the square inch at exit. The cracking unit A is therefore, relatively speaking, ,a

low-pressure cracking unit adapted to deal With heavy oils. The described mode of.

feeding the material through the heavy vapor separator 10 is such as to cause the material to be stripped of its light volatile constituents and to be enriched by the heavy materials of vapors entering through the pipe 31 from a closed pressure vaporizer 30. These heavy vapors, and the light vapors which accom-V pany them, are the product of cracking in the low pressure unit A from which an outflow pipe 24 leads through the heat exchanger 16 to a pressure-reducing valve 25, whence the cracked out-flow enters the vaporizer 30 through a pipe 26. A part of the effect of the heat exchanger 16 is to lower the temperature of the efflux through valvel 25 and pipe 26 to a temperature of from 750 F. to 550 F. prior to partial release of pressure at the valve 25 and in the vaporizer 30. As pointed out and claimed in my said application Serial No. 16,952, filed March 20, 1925, such precooling of the cracked efflux,V conduces to the separation of vapors from a fuelvoil residue without causing the formation of coke, carbon or sediment in the residue, which is drawn off from vaporizer throughv valve 28, pipe 29, and' cooler 32, and comprises a product of fuel oil typically containing less than one percent of suspended free carbon or sediment.

If'desired, all or a part of the heat delivered in cooler 32 may be utilized to pre-heat the incoming flow in pipe 1, instead of or in aid of other sources of heat on the hot side of heat-exchanger 4. V

As mentioned above the unaltered condensate formed in flow through the heavy vapor separator 10 has been dealt with in the cracking unit A.

The vaporous elux from the heavy vapor separator 10 may be introduced through the pipe 39 to the proper stage of the rectifying column 40, whichv delivers a gasoline or motor-spirit fraction through the pipe 41, the cooler 42, and a gas separator 43 to a rectified gasoline storage'tank 44,v whence a pump 45 may recireulate a part of the gasoline through the feed line 46 into the top of the column 40.

The bottom fraction from the rectifying column is capable of further conversion into the motor spirit by cracking. vCracking under optimum conditions of this frac tion of the -product necessarily involves 2 higher pressure, and sometimes a higher temperature, than the optimum conditions for cracking the material treated in the cracking unitA. The proper operation of the rectifying column 40 necessitates added heat. It is therefore provided that the bottom fraction from the. rectifying column 40 shall be taken out of the system 40, 41, and 46 only as a surplus or overflow, which passes through the pipe 47 to the heat exchanger 4 as above explained and may flow to storage through pipe andcoolc1z61. A continuous withdrawal from the bottom of the recti't'ying column 40 is provided by flow vthrough the pipe 48 from- Whicha pump 49 and booster 49` vforce the material through a heat exchanger 50 and into a secondary cracking unit B under suitable pressure. The optimum pressure is that at which the cfa-cking temperature employed in the cracking `unit B results in a mixed liquid and vapor flow. This pressure is higher than the pressure in cracking unit A, and may be from 500 to 600 pounds per square inch at exit. The temperature of the liquid efflux at 48 from the bottom of the rectifying column 40 may be between 450 F. and 500 F: for example, in the neighborhood of 470 F. i

The cracking unit B may comprise an entrance coil,v similar to that employed in connecticnwith the unit A, for example as indicated at 52, comprising runs of uniform diameter tubing frequently. `reversing in direction and housed -in a heating'vfurnace, not shown', the end of the heating coil 52 communicating at 53 with a cooling coil 54 (which may comprise merely a few runs tubular .coil 1n a closed chamber) continuous with a secondary heating coil 55,` whichy may be c heated by Waste heat from the furnace heating the coil 52.v The effect of these disposi-` tions is to raise the temperature of the efflux from the rectifying column 40 at 48 to a predetermined maximum, for example, at 870 F., then to permit the flow to cool, and then again to raise the temperature to from 890 to 910. This heating is accomplished during rapid and turbulent flow induced by the, pressure pumps 49, 4QF-and controlled by pressure reduction valve 56 in an outflow pipe f 57 leading through-one side-ofthe heat-exchanger 50. The cracked material is reduced in temperature in the heat-exchanger by preheating the incoming stream to a temperature in the neighborhood of 600o F., which may, if necessary, be adjusted or coriected by use of a Water-flow cooler 59 through Which the pipe 58 leads into the lower part of the rectifier 40. c

By the described operation employing a mixed or heterogeneous feed material in contact with the cracked product of this same material as a preliminary to the supply of a rectifying column with the vapor of the niotor spirit, naphtha and gasoline orkerosene an-d light fuel oil, or other volatile fractions being made, the rectifying column can be operated as a source of a bottom fraction classifiable as a light gas oil, and it is highly desirable to operate upon this fraction by further cracking to develop in the product a larger product of the` naphtha or gasoline range. By the described device, only the surlus of the bottom fraction from the rectifying tower is taken out of the system as light gas oil, the remainder being recycled With continuous accretions of the motor-spirit or gasoline fraction produced by treatment in the light oil cracking unit B. The bottom of the rectifier should operate at a temperature between 450 F. and 500o F. By having the accumulations in the bottom of the rectifier in continuons circulation through and out of the light oil cracking unit, this temperature may be maintained `by the waste heat of' the cracking there performed, and conversely thecracking itself is performed with only slight additions of heat to the feed material collected from the bottom of the rectifier tower. So long as heat has to be supplied in any event at the bottom of the rectifying column to produce rectified gasoline, the production of gasoline at this point is effected at practically no expense at all by the installation described; in this Way the proportional output as gasoline of the raw oil charges is considerably increased, and the overall fuel consumption is proportionally reduced.

I claim:

1. Process for the conversionby heat of a heavy heterogeneous mineral oil feed stock into gasoline and higher boiling point products comprising separating the more volatile 'from the less volatile constituents of the feed stock, subjecting said less volatile constituents to a cracking reaction and separating a heavier fraction of the more volatile products of said cracking, mixing said heavier `fraction with a heavier fraction of the more volatile constituents of the feed stock, separately cracking said mixture concomitantly With but under different conditions than said first named cracking reaction, and collecting the products of said cracking reactions which have a boiling point Within the gasoline range. i

2.- Processfor the conversion by heat of a heterogeneous heavy feed stock of mineral oils under pressure into gasoline, light gas j oil and fuel oil comprising as steps uniting and subjecting to a separate. liquid-vapor phase cracking treatment a heavier fraction of the more volatile constituents of the feed stock and a heavier fraction -of the more volatile products of a cracking treatment carried out upon the less volatile constituents of the feed stock.

3. Process for the conversion by heat of a heterogeneous heavy feed stock of mineral oils into gasoline, light gas oil and fuel oil comprising as steps uniting and subjecting a heavier fraction of the more volatile constituents of the feed stock and a heavier fraction of the more volatile products of a cracking treatment carried out upon the less volatile constituents of the feed stock to a separate cracking treatment, said separate cracking treatment comprising heat treatment in the liquid-vapor phase under flow under pressures respectively suitable to the development in a more volatile oil of derivatives in the gasoline range.

4. Process for the conversion by heat of a heterogeneous heavy feed stock of mineral oils into gasoline, light gas oil and fuel oil comprising as steps uniting and subjecting a heavier fraction of the more volatile constit.

uents of the feed stock and a heavier fraction of the more volatile products of a cracking- 5. Process for the heat treatment of mineral oils comprising as steps subjecting heterogeneous feed stock to heat, and separating the more volatile from the less volatile consti-tuents, subjecting the less volatile constituents to cracking for conversion into more volatile constituents, separating a fuel oil fraction,a heavy condensate and more volatile constituents, returning the heavy condensate to the same cracking and subjecting the more volatile constituents of the results of the said operations to treatment including separate cracking of the less volatile fractions of the said more volatile constituents and separately collecting the products of higher and lower boiling-point ranges.

6. Process for the heat treatment of mineral oils comprising as steps subjecting heterogeneous feed stock to primary heating by exchange With the eiilux from a cracking operation, and separating the more volatile from the less volatile constituents, subjecting'the less volatile constituents to cracking for conversion into more volatile constituents, septhe results of the said operations to treatment including continuous separate cracking of the less volatile fractions of the said more volatile constituents and separately collect-y ing the'products of higher and lower boilingpoint ranges.

7. Process for the heat treatment of mineral oils comprising as steps subjecting heterogeneous feed stock to heat, and separating the more volatile from the less volatile constituents, subjecting the less volatile constituents to cracking for conversion into more volatile derivatives during flow in a tubular heater under relatively loW pressure, mixing the vapors of themore volatile fractions of the feed stock and of the 'efiiux of the relatively low pressure cracking, subjecting the mixture to fractionation, and continuously cracking the condensate produced by the fractionation in a tubular heater, using higher' pressure.

8. Process for the heat treatment of mineral oilscoinprising as steps subjecting heterogeneous feed stock to heat, and separating the more volatile from the less volatile cn' stituents, subjecting the less volatile constit' into gasoline and higher boiling point products comprising separating the more volatile from the less volatile constituents in the feed stock, subjecting said less volatile constituents to a cracking reaction and separating a heavier fraction of the more volatile products of said cracking, heavier fraction of the more volatileproducts and permitting vaporization of the eiilux of the cracking of said fraction of the more volatile products at a suitable temperature in the bottom part of a suitable rectifying column. 10. Process for the conversion by heat of a heavy heterogeneous feed stock of mineralI f oils into gasoline and products of higher boil-'- ing point comprising as steps concomitantly subjecting the less volatile constituents only ofsaid feed stock to a lower pressure cracking and separately subjecting a fraction of the more volatile products of said lcracking to a higher` pressure liquid-vapor phase cracking treatment, cooling the 'efflux of said higher pressure cracking treatment to a, temperature above the temperature suitable-for the vaporization of products'within the gasoline range, and subjecting the vapors containing the gasoline constituents to rectification in a. suitable column apparatus.

11. Process for the conversion by heat of a heavy heterogeneous feed stock of mineral oils intorgasoline and products of higher boiling pointfcomprising as steps concomitantly subjecting the less vola-tile ,constituents only of said'feedstock to lower pressure cracking and a fraction of theinorevolatile products of said cracking to 'a higher pressure cracking treatment, cooling the vefflux of said higher pressurecrackiiig treatment to a temperature above the temperaturev suitable for the vaporilzation'fof products within the gasoline range, and .subjecting the produced gasoline containing vapo-'rs and 'other vvapors containing "gasoline from va separating treatment and safidf lower pressure cracking treatment to rectification together in a suitable column apparatus. v

l2." Process for the conversion by heat of a heavy heterogeneous feed stock of mineral loils into gasoline and products of higher boiling point comprising as steps concomitantly subjecting the less volatile constitutents only of said feed stock to lower pressure cracking and a fraction vofthe more volatile products of said cracking to a higher pressure cracking` treatment, cooling the efflux of said higher pressure cracking treatment to a temperature above the temperature suitable for the vaporization of products within the gasoline range by heat interchange with said aforementioned fraction of the more volatile products prior to the cracking thereof 'and subjecting the gasoline containing vapors to rec-v tification in a suitable column apparatus.

13. Process for the conversion by heat of a heavy heterogeneous feed stock of mineral oils into gasoline and products of higher boiling point'comprising as steps concomitantly subjecting the less volatile constituents only of saidl feed stockto a-lower pressure cracking and a fraction of vthe more volatile prodiol ucts of said cracking to ajliigher'pressure cracking treatment, coolingth'e eiiiux of said higher pressure cracking treatment to a temperaturelabove the temperature suitable for the vaporizationof products Within the gaso line 'r ang`e, and subjecting the gasoline containingvaporsyto.rectification in a suit-able column apparatus adaptedto deliver as a bottileproducts. i l..

114.- 'I' Process the heat treatment of mineral oils comprising as steps subjecting heavy vfeed oil to cracking during turbulent flow in a -tubularheaterat a suitable maximum teinperaturje van-dja suitable maximurn pressure, resulting 11n the production of unconverted heavy oil-andv fuel oil as well as of more volatilev derivatives, lcooling' and' permitting vatom fraction said fraction of the morevolal' is'oA porization of the efiux at a reduced pressure, subjecting the vapors to fractionating condensation, returning the heavier condensate to the same cracking heater, subjecting the lighter condensate to cracking in another suitable tubular heater at a suitable maximum temperature and a pressure higher than the pressure of said heavy oil cracking and cooling, releasing the pressure, and subjecting the vapors to condensation.

15. Process for the heat treatment of mineral oils comprising as steps subjecting heavy feed stock to separation treatment toseparate off light fractions, subjecting the heavier fraction to lower pressure cracking during turbulent flow in a tubular heater at a suit-able maximum temperature and a suitable maximum pressure, resulting in the production of more volatile derivative products, cooling and permitting vaporization of the efflux at a. reduced pressure, subjecting the vapors to frac-` tionating condensation in a suitable apparatus, subjecting the lighter one of the tvvo condensates made to higher pressure cracking in asuitable tubular heater at a suitable maximum temperature and a pressure higher than the pressure of said lower pressure cracking, and cooling, releasing the pressure, and separating constitutents of different boiling points in the said apparatus.

16. Continuous process for the conversion of a heterogeneous heavy7 feed stock of mineral oils into gasoline, light gas oil and fuel oil comprising as steps preheating the feed stock by Waste heat of a cracking operation, separating olf the more volatile constituents, subjecting the residue to cracking under optimum conditions yfor heavy oils, separating the more volatile constituents of the .cracked efliux from heavy oil and a fuel-oil residue, subject-ing said more volatile constituents and the volatile constituents of the feed stock together to rectifying treatment in suitable apparatus, and subjecting the less volatile products of rectification toA cracking under optimum conditions for lighter oils, the rectification being conducted by the heat of the cracked eiiux from the last named cracking operation returned to the rectifying apparatus.

17. Continuous processfor the conversion of a heterogeneous heavy feed stock of mineral oils into gasoline, light gas oil and fuel oil comprising as steps preheating the feed stock by Waste heat of a cracking operation, separating olf the more volatile constituents, subjecting the residue to cracking during turbulent flow at temperatures and pressures suitable to mixed liquid and vapor phase cracking, cooling the elilux to from 550 F. to 7 50 F., reducing the pressure, and separating the residual fuel oil fraction, separating the heavy oil, subjecting the remaining vapors and the vapors of the volatile cons tit-uents of the feed stock together to rectifying treatment in suitable apparatus, and subjecting the less volatile products of rectilication to crackingunder optimum conditions for lighter oils, the rectification being conducted by the heat of the cracked eiux from the last named cracking operation returned to the bottom part of the rectifying apparatus.

'18. Process for the treatment of mineral oils by heat comprising as steps causing a preheated feed stream of the oil to pass in contact with the vapors of a cooled eiux of a cracking heater, separating the vapors ensuing from this operation, and 'rectifying these vapors, the rectifying operation including continuous ycracking of the bottom fraction collecting in a suitable rectifying tower, and the return of the efflux from said last named cracking to the bottom part of the tovver.

19. Process for the treatment of mineral voils by heat comprising separation of constituents of the feed stock by distillation, cracking the heavier fraction, and rectifying the vapors comprising the lighter fraction of the feed stock constituents, and the more volatile derivatives of the cracking operation, the rectifying operation including continnous cracking of the bottom fraction collecting in a suitable rectifying tower, and the return of the eliiux from said last named cracking to the bottom part of the tower. I

20. Process for the heat treatment of mlneral oils comprising as a step rectifying light i continuously subjecting the bottom con-` densate from suitable rectifying apparatus to cracking temperatures for a substantial time in a liquid-vapor phase under flow and pressure, positively reducing the pressure and temperature, and introducing the cracked efflux into the bottom part of the rectifying apparatus.

21. Process for the heat treatment of mineral oils comprising as a step rectifying lightoil vapors of distillation of a cracked product of a heavy-oil feed stock, the rectification step including continuously subjecting the bottom condensate from suitable rectifying apparatus to cracking temperatures for a substantial time in the liquid-vapor phase under flow and pressure, positively cooling the cracked eiilux to a temperature above the boilino point of its more volatile liquid products of cracking, reducing the pressure, and introducing the cracked efflux into the bottom part of the rectifying apparatus.

2Q.. Process for the heat treatment of mineral oils comprising as a step rectifying lightoil vapors of distillation from a cracked product of a heavy-oil feed stock, the rectication apparatus to crackin by heat-interchange with the eliiuX from the' rectifying apparatus to a temperature above the boilmg points of its more volatile liquid products of cracking, reducing the pressure,

vand introducing thecracked efflux into the bottom partof therectifying apparatus. i

23. In a process for rectifying the volatile derivatives from the heat-treatment of a mineral oil, that step comprising heating the materialsr forrectification by continuously sub-y jecting the condensate in the bottom `of a suitable rectifying column under pressure to flow maintained in a tubular heater for a substantial time at a cracking temperature in the liquid-vapor phase, coolingthe cracked efflux, and returning the cooled efflux to the K bottom part of the rectifying column.

24. In a process for rectifying the volatile derivatives from the heat treatment of a mineral oil, that step comprising heating the materials for rectification by continuously subjecting the condensate in the bottom of a suitable rectifying column to flow maintainedl in a tubular heater under pressure fora substantial time at a cracking temperature in the liquid-vapor phase, positively 'reducing the temperature and pressure and returning the efflux to the bottom part of the rectifying column at a temperature above the vaporization end-pointv of the desired rectified con-y densate.

25. In a process for rectifying the volatile derivatives. from the heat treatment of a 'mineral oil,thatstep comprising heating the materials for rectification by continuously subjecting the condensate in the bottom of a suitable rectifying column to iiow maintained in a tubular heater under pressure at a cracking temperature, reducing the temperature by heatexchange with the said bottom condensate of the rectifying column and then reducing the pressure, and returning the efiiux to the bottom part of the rectifyn'g column at a temperature above the vaporization endpoint of the desired rectified condensate.

26. Apparatus for use in making rectified gasoline comprising a rectifying column,y a

cracking unit, and means for causing the condensate from the bottoni of the rectifying column to flow through the cracking unit in which the condensate is in a li uid state under pressure and to attain and to eep for a substantial time a cracking temperature suitable for light oils, posit-ive means for reducing the vtemperature and pressure of the eiHuX, and means for returning the efflux to the bottom part of the'rectifying column at a temperachanger for exchanging heat between said condensate and the cracked efflux, and means for returning the efflux to the bottom part of the rectifying column at a temperature suficient to cause a rectifying flow of vapors in the rectifying column.

28. In a process for making rectied gasoline from a heterogeneous heavy mineral oil ,feed stock, subjecting the feed stock to fractional distillation, cracking under predetermined conditions of heat and pressure the higher boiling fraction, including the less volatile constituents of the feed stock and the heavy reflux, fractionating together the more volatile derivatives of cracking, and the more Avolatile constituents of the feed stock, eracking the higher boiling fraction of this last named mixture under predetermined conditionsof temperature and at a higher pressure than/fthe said first-mentioned cracking and condensing and collecting together the vapors resulting from the said operations having boiling points in the gasoline range.

29. An apparatus" comprising a cracking unit for handling higher boiling constituents separately under lower pressures and another cracking unit to handle lower boiling constituents only at higher pressures, a vaporizer adapted to handle the cooled efliux of the lower pressure cracking unit and to separate the fuel residue from vapors, a heavy vapor separator, means to conduct such vapors to the bottom part of the heavy vapor separator, means for delivering raw material 'to the top of the heavy vapor separator, means to feed the bottom condensate of the heavy vapor separator to the lower pressure cracking unit, means to conduct the vapors from the'top of the heavy vapor separator to the bottom of a rectifier, means to spray the top of the rectif-ler with gasoline, means to feed conden` sate accumulated at the bottom of the recti fier through the higher pressure cracking unit and through a heat exchanger back to the bottom of the rectifier, means to preheat the raw material before entering the top of the

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