US2027014A - Process for making gasoline - Google Patents

Description

Jan. 7, 1936. o, BEHlMER PRocEss FOR MAKING GAsoLIuE Filed Nov. 21

liuc no Patented Jan. 7, 1936 UNITED STATESI PATENT OFFICE 2,027,014 PROCESS FOR MAKING GASOLINE Application November 21, 1918, Serial No. 263,5@ In Canada December 3, 1921 23 Claims. ('Cl. 196-58) This invention relates to methods of making condensable light oils, such as gasoline. More particularly it relates to certain novel improvements in the cracking of hydrocarbons whereby higher boiling hydrocarbons are decomposed into those of lower boiling p'oint.

In prior methods of cracking hydrocarbon oils, considerable difficulty has been experienced on account of carbon formations, which occur on the sides of tubes and stills exposed to the heat required to carry on the cracking operation.

It is a broad novel feature of the herein disclosed process, that substantially all of the cracking operation occurs in a vessel to which no external heat is applied, except at such times and in such quantities as are necessary to compensate for heat losses, the oil prior to its introduction to such vessel having been subjected to a high degree of cracking heat and the excess heat of the oil itself being used to effect its own decomposition. As a consequence, I avoid substantial carbon formations of the destructive character which have proved such an impediment to prior systems. The removal of the cracking operation from the heating zone. also reduces the danger from fires such as frequently occur where cracking is carried on in highly heated stills and coils exposed to direct heat.

More specically my process preferably embodies a novel cyclic system in which a circuit of oil is constantly maintained under Varying liquid and vapor phases. The oil to be treated en entering this circuit is subjected to a high degree of heat, but the time element, is so controlled with respect thereto that there is comparatively littlev decomposition and deposition of carbon while it is exposed to this external heat, the oil being rapidly removed from the heating zone and conducted to the cracking zone, where without necessarily being subjected to additional heat, it undergoes a molecular decomposition whereby carbon and light products are formed -and liberated. It will bev understood that oil cracking or conversion is dependent not only upon the relative conditions of pressure and tempcrature but aso upon the time element with respect thereto, that is,-the necessary pressure and temperature must be maintained for a suflicient period of time to enable the molecular decomposition or conversion to take place.v According to the present invention, this time factoris so controlled by regulating the rate of heating the oil passing through the heating zone that the temperature thereof is progressively raised in transit and reaches the desired cracking teinperature near the end of the heating coil at about the time or a little before the oil emerges therefrom. Thus, although the oil is subjected to cracking heats in the heating zone, this temperature is attained only just previous to the 5 exit -of the oil therefrom, and therefore the oil leaves the heating coil before any substantial decomposition and incident deposition of carbon takes place. Subsequently, the highly heated oil in a state of incipient decomposition, is delivered 10 to the cracking zone, where the desired temperature and pressure conditions are continuously sustained and the cracking of the oil and the incident deposition of carbon are effected. The bulk of the carbon is removed from the circuit by withdrawing from the cracking zone, portions of the residual oil. Although the process, in its broad conception, is complete at this ,stagey of the operation, the light products preferably continue the cycle, leaving the cracking zone in the form of vapor and gas. These vapors and gases are then subjected to a reduction in temperature, whereby the heavier constituents thereof, such as kerosene, are condensed. The condensate is preferably combined with the charging oil entering the heating zone, thus completing the cycle. The constituents of the desired volatility are removed from the circuit and condensed. The outlets from the circuit are so controlled that the entire system is maintained under a pressure sufcient to insure the desired molecular transformation.

My process is to be distinguished from those of the prior art, in which a circuit of liquid residuum is kept in circulation. When such oil is kept in circulation, considerable quantities of carbon are formed, owing to the readiness with which this type of oil carbonizes when exposed to high temperatures, the carbon forming in fine particles in the oil, and wherever it comes in Contact with heated metal surfaces, it attaches itself thereto and builds up deposits, which ofte-n cause the choking of tubes and coils. It also crystallizes the metal surfaces, thereby decreasing the tensile strength of the metal and causing the bulging and breaking of such surfaces. Any residual oil resulting from the cracking operation will necessarily contain a considerable amount of heavy polymerization products and carbon held in susension in the oil, and to circulate such a residue through heated tubes is to continually pass into or produce in such tubes a large amount of free carbon. In my system I do not circulate a residuum, but instead keep the residual oil removed from the application of external heat and withthe bulk of the carbon, from the cycle at the cracking zone, and continue the cycle by means of the vapor generated, which contains the condensable product desired and also certain heavier vaporous constituents which are used to complete the cycle. By removing the heavier residuum from the cycle, I keep the circuit free from this source of carbon formation, and since I conduct substantially all of the cracking in a vessel to which either no external heat is applied or only a small quantity of heat is applied to maintain the requisite temperature conditions, I am thus able to effectively remove the carbon formed.

In cracking oil for gasoline, there is generally formed a considerable quantity of vapors heavier than gasoline, which may be generally designated by the term, kerosene. I preferably employ these heavier vapors as a carrier for the lighter vapors; they assist in maintaining a current of vapor by which the gasoline is removed from the cracking zone to a separatorwhere the kerosene vapors are condensed and removed from the gasoline vapors which pass on to the condenser. The kerosene condensate, preferably at atemperature, not materially below its boiling point, is injected or otherwise suitably forced under mechanical pressure into the heavy oil charge entering and flowing through the heating tubes whereby a foamy agitated mixture is produced by the acceleration of the circulation in the heating tubes resulting from the increased volume of oil therein, thereby preventing the settling and flow of the heavier portions of the oil along the bottom of the highly heated tubes and the consequent local overheating and carbonization of the oil, thus keeping the tubes substantially free from any slight carbon formations.

These kerosene constitutents are an excellent mechanical conductor of heat, and there is thus produced a heat cycle which materially assists in maintaining the proper temperatures in the heating and cracking zones. By maintaining these bodies in constant circulation, the kerosene constituents, which under existing methods have been found so diicult to decompose into lighter products, are, in my system, ultimately reduced to gasoline.

I have devised certain novel apparatus which is adapted for carrying out my process, and illustrate the preferred form thereof in the drawing in which:

Figure 1 is a diagrammatic elevation of -said apparatus.

Figure 2 is a diagrammatic View of a modiied cracking drum which may be substituted for that of Figure 1.

It will be understood that other apparatus besides that illustrated may be used in carrying out my process.

Referring to Fig. 1 of the illustrative drawing, a tubular heating coil I is located in a furnace 2, having a burner 3 and a stack 4. As Shown for illustrative purposes, the coil I comprises a plurality of horizontally disposed rows of tubes extending through the furnace and placed the one above the other. The adjacent ends of each alternate pair of tubes in each horizontal row are conveniently connected together by horizontally positioned return bends or fittings to form horizontal coils. The several horizontal coils thus arranged are conveniently connected together at their right-hand ends by vertically disposed return bends or ttings, as shown in Fig. 3 to form a single elongated and continuous hea.tingA coil l draw the heavier portions thereof, which contain through which the oil flows and is heated to the required degree. This coil is of extended length and restricted cross-section and has a relatively large and effective heating surface whereby the stream of oil passing therethrough is enabled to efiiciently absorb heat and reach a high temperature with rapidity. A checkered brick baie 5 having openings 6 may serve to distribute the heat evenly over the coil. A fresh oil charging line 1, having a jet or injector Ta, extends to a pump 10 8, which is connected to a suitable source of oil supply (not shown). The pipe 9, having a valve I II, extends from the heating coil I to an enlarged cracking drum or chamber II, within which it may terminate ina distributor 9a. This dlstribl5 utor 9= may be of any suitable form to thoroughly distribute and diffuse the charging oil throughout the body of oil in the drum whereby an intimate contact of the highly heated charging oil with the body of voil in the drum is effected. The cracking 20 drum is preferably provided with a jacket II of suitable insulating material to protect it against heat radiation and is equipped with a valved draw-off I2, a vapor outlet I3, and an oil gauge I4. The vapor outlet I3 extends to a separator 25 I 5, having a vapor outlet I 6, and a condensate outlet I1. The Vapor line I6 terminates in a water-cooled condenser coil I8, having an outlet I9 equipped with a regulatable pressure valve 20. If desired the valve 20 may be placed in the vapor 30 line I6, but I prefer to maintain the pressure in the heating coil, cracking drum and separator through the condenser. The outlet I9 terminates in a collecting tank ZI, having a. valved gas outlet 22 and a valved distillate outlet 23. The 35 condensate line I1, which is, preferably insulated as indicated at I'Ib is equipped with a valve |11,

and is connected to the charging line 1 at the jet 1B. Y

In conducting the process with the apparatus 4o illustrated, the oil to be treated is forced through the charging line 1 under considerable pressure, and is rapidly flowed through the heating coil I, where it is heated to the desired cracking temperature. Preferably this temperature is some- 45 what higher than the temperature at which it is desired to conduct the cracking operation and may or may not result in substantial vaporization. The oil on being forced through the coil acquires a high cracking temperature, but on ac- 5o count of the rapidity of its flow, decomposition Is only in the incipient stages when the oil is discharged through the pipe 9 into the heat insulated cracking drumI I where a constant body of oil is maintained at ,a cracking temperature and under 55 pressure. The distributor 9, if employed, serves to discharge the oil into the cracking drum in a wide stream, thus thoroughly mixing the hot oil with the liquid body of oil maintained in the drum and diffusing the heat therethrough. This heat 60 diifusion is materially aided by using a distributor with serrated edges. The rapid fl'ow of the oil through the coil where it is closely confined, is here suddenly retarded, as the oil enters the drum which is of ample volume. Thus' excess 65 heat of the oil operates to maintain the body of oil at the desired cracking temperature and molecular decomposition and distillation are carried on vigorously, the higher boiling hydrocarbons continually breaking up into hydrocarbons of lower boiling point. The vapors and gas generated gather in the upper part of the cracking drum and pass out through the vapor outlet I3 to the separator I5, where there is effected a separation of hydrocarbons of desired volatility from those of less volatility. The hydrocarbons of the desired volatility pass out through the vapor line I 6, by which they are conducted to the condenser I8, where they are condensed and the condensed distillate is either intermittently or preferably continuously allowed to run into the collecting tank 2I.

The temperature in the air'condenser I5 is such that the less volatile hydrocarbons are condensed and dropped into the conduit I'I, by which they are conducted while still hot to the jet in the charging line or other suitable forced or applied mechanical pressure device for forcing the condensate into the charging stream. The separator is preferably somewhat elevated so as to give a considerable head of liquid in the pipe I1, which preferably contains a U bend, as illustrated, in order to form a liquid seal therein. This head of liquid, together with the high pressure at which the oil in the charging line passes the jet, this pressure being ordinarily from 50 to 100 pounds higher than the pressure in the drum, insures that the condensate shall be constantly and positively drawn into the charging line and forced under applied mechanical pressure into the coil I. The introduction of this hot condensate into the charging line increases the volume of oil in the heating coil thereby accelerating the flow therein and producing a f oamy mixture so that local overheating is prevented and the coil is kept substantially free from any slight carbon formations. This condensate consists in a type of hydrocarbons which when decomposed does not yield any great amount of carbon so that the oil charge is constantly being diluted with oil capable of being decomposed into lighter products without the production of large amounts of. carbon. This condensate reaches the jet in a heated condition, preferably at a temperature not materially below its boiling point. so as to heat the charge of oil entering the heating coil. The heat cycle formed by the kerosene constituents contributes to the maintenance of the proper temperatures in the heating coil and the cracking drum. By injecting or otherwise suitably forcing this condensate under applied mechanical pressure into the heating coil I increase the volume of oil flowing therein Without increasing the total amount of oil charged into the system at any given time.

A considerable pressure is maintained throughout the system, which pressure is regulated by means of the valve 20 or the valve on the gas outlet 22. The pressure used varies with the character of the oil operated on and the character of the product desired, Ordinarily the decomposition in the cracking drum is carried on under a pressure of from 100 to 400 pounds. In utilizing oils of the type commonly employed for decomposition into products of the nature of gasoline a temperature in the drum II of from 700 F. to 850 with a temperature in the coil I of from '700o F. to 950 F. is ordinarily used. For example, in cracking a paraffin base gas oil of a Baume gravity of about 34, a temperature of 850 F` in the coil and of '775 F. in the drum with a pressure of approximately 200 pounds has been used to advantage.

'I'he oil to be decomposed is constantly forced into the heating coil thereby causing a steady stream of heated oil to enter the cracking chamber. The residuum is withdrawn preferably at such a rate that there is maintained a constant body of oil in the crackingzone.

, It is desirable to equip the apparatus with the valves I and IIaL so that in case there is a ess these valves are open.

Auxiliary heat may be supplied to the crack- -ing drum in any suitable manner if desired and a convenient method of providing this auxiliary heat is, as shown in Fig. 2, to insulate only the upper part of the drum and apply heat at a moderate temperature or in a relatively small quantity from any suitable heater such as is designated 30. The lower portion of the drum may be enclosed in a furnace. In the early stages of a run, since there is no danger of overheating a carbon-free surface, the drum may be heated freely until the necessary heat cycle has been generated and decomposition has begun. For this reason the arrangement of Fig. 2 pos- 20 sesses certain advantages overthat of Fig. 1. But when decomposition begins, with a consequent deposition of carbon, the heat must be reduced, as otherwise the carbon would accumulate on the hot surfaces and build up tenacious formations thereon, thus preventing the effectual removal of the carbon and asphaltic bodies. As the run continues only a moderate heat is applied, suicient only to oiset the loss of heat due to radiation and distillation. 1f desired the 3o drum may be heated by means of waste heat from the furnace 2 or in any other suitable manner. The product obtained by the herein disclosed process is, for a cracked product, remarkably sweet, in other words, low in unsaturated com 35 l pounds.

It is understood that I use the terms gasoline and kerosene in this application by Way of example and that these terms are taken as types of other similar distillates which may be produced by my process. I use the term gasoline as an example of the volatile product desired which under the temperatures and pressures used is a vapor in the separator I5 and is condensable in the cooling coil I8. I use the term kerosene as an example of those constitutents which under the temperatures and pressures used is a Vapor in the vapor line I3 but is condensable in the separator I5. It is to be noted that the gravity and boiling point of the products which will condense in the separator I5 depends upon the temperature therein under the pressure used.

Although for illustrative purposes the invention has been shown and described in connection with apparatus of more or less specific details of construction, arrangement and location of parts, and as embodying in its mode of operation a certain series and sequence of somewhat denite steps and voperating conditions; it will be understood that many of the objects and y advantages .of the invention may be obtained,

to a greater or less extent, through the employment of apparatus of modified character or, in fact, through variations or, in some cases, omissions, of certain of the component steps, without departing from the spirit and scope of the invention.

Having thus described the invention what is claimed as new and desired to be secured by Letters Pat-ent is:-

l. The process of cracking oil which comprises forcing oil through a coil into an enlarged drum under pressure in which a body of liquid oil is maintained at a cracking temperatufe, raising the oil as it passes through the coil to a decomposing temperature without substantial cracking and effecting decomposition of the oil in the drum while positively insuring that none of the oil which has remained unvaporized in the cracking drum shall be returned to the heating coil.

2. The process of oil conversion that comprises passing hydrocarbon oil through an elongated passageway subjected to high external temperature whereby it is brought to a decomposing temperature without being extensively converted, passing the oil from said passageway into an enlarged chamber in which a body of liquid oil and a decomposing temperature is maintained whereby the oil is largely cracked therein, and maintaining superatmospheric pressure throughout the system, the oil passing through the elongated passageway being substantially free of residual oil fromthe enlarged chamber.

3. A process of oil conversion which comprises preliminarily subjecting oil free from residual carbon to cracking heat sufficient to produce a condition of incipent conversion but without substantial decomposition, delivering the highly heated oil to a cracking zone where superatmospheric pressure and cracking temperature are maintained whereby the oil is converted therein, said cracking temperature being no higher than that of said oil delivered to the cracking zone, and removing the residuum including carbon from the cracking zone without returning residuum to the system.

4. The process of oil conversion that comprises continuously supplying oil at a comparatively high cracking temperature but substantially free from decomposition to a heat-insulated drum maintained under pressure and where a body of oil is maintained at a cracking temperature by the contained heat of said oil supplied thereto for a suiiicient period to effect decomposition thereof.

5. 'I'he process of oil conversion that comprises forcing oil through an elongated heating coil, heating the oil in transit through the coil to a cracking temperature without any substantial amount of cracking therein, and delivering the highly heated oil in a state of incipient conversion into an enlarged heat-insulated drum where a body of liquid oil is maintained at a cracking temperature by the contained heat of said oil delivered thereto and under superatmospheric pressure and is materially decomposed therein.

6. A process of oil conversion that comprises passing the oil under pressure through an elongated heating coil, heating the oil in transit .to a cracking temperature without substantial decomposition, delivering the highly heated oil at a cracking temperature to an enlarged drum where a body of oil is maintained under pressure and at a cracking temperature without supplying additional, internal heat thereto and carbon resulting from the cracking operation is deposited, and withdrawing the residual oil from said drum and preventing the recirculation of residual oil through the system.

7. A process of oil conversion thatI comprises rapidly passing the oil through a heating coil of restricted cross-section under such regulated conditions of pressure, temperature and rate of flow as to heat'the oil up to a cracking temperature while preventing carbon from forming therein, removing the highly heated oil free from residual carbon from the heating coil and delivering it at the cracking temperature attained in said coil to a seperate enlarged cracking chamber Where a body of liquid oil is maintained under superatmospheric pressure and at an effective cracking temperature no higher than that obtained in said coil for a sufficient time to effect the desired amount of cracking and resultant formation of 5 carbon.

8. A process of oil conversion which comprises heating the oil in a heating coil under such coordinated operating conditions of temperature, pressure and time as to heat the oil up to a 10 cracking temperature while preventing carbon from forming Within the heating coil, passing the highly heated oil at cracking temperature and free from residual carbon into a body of liquid oil in an enlarged cracking chamber maintained 15 at an effective cracking temperature no higher than that obtaining at the exit of the heating coil and under superatmospheric pressure substantially corresponding to that obtaining at the exit of the heating coil wherein cracking of the oil is 20 largely effected and the formation of carbon is localized.

9. A process of oil conversion comprising cracking a body of liquid oil in an enlarged cracking chamber, to which not more than moderate ex- 25 ternal heat is applied and where cracking conditions of temperature, pressure and time are maintained and carbon is formed and deposited under safe conditions, and supplying heat to said chamber to maintain the body of oil at an et- 30 fective cracking temperature by delivering into said body of oil a stream of hot oil free from residual carbon after passage through a heating coil under such regulated conditions of temperature, pressure and time as to heat the oil up 5 to a. cracking temperature while preventing carbon from forming therein.

10. The process of oil conversion which com-l prises passing oil under superatmospheric pressure'and at a rapid rate of flow through an elon- 40 gated Vheating coil, heating the oil in transit therethrough by passing hot combustion gases in heat exchange relation with the oil flowing through the heating coil and in countercurrent passage with respect thereto to heat the oil up to a cracking temperature only as it reaches or approaches the exit thereof, while preventing carbon from forming therein, passing the highly heated oil free from residual carbon into a body of oil in an enlarged cracking chamber maintained at an effective cracking temperature and under superatmospheric pressure wherein the bulk of the cracking is effected and carbon formed.

11. The process of cracking oil that comprises subjecting oil in single transit through a heating zone to such regulated conditions of temperature, pressure and velocity of flow as to heat the oil up to a cracking temperature while preventing carbon from forming therein, then delivering the heated oil free from residual carbon into a cracking zone in which liquid oil is maintained under pressure and at an effective cracking temperature without supplying additional internal heat thereto, to crack the oil therein to the desired extent with resultant formation of carbon therein, and removing carbon-containing residual oil from said cracking zone while preventing the recirculation of any carbon-containing residual oil through the heating and cracking zones.

l2. A process of oil conversion that comprises maintaining a body of oil under pressure at a cracking temperature in a drum by continuously supplying oil at a comparatively high cracking temperature but substantially free from decomposition into the body of oil in said drum to be cracked therein, preventing loss of heat from said drum, distilling and condensing the gasoline and kerosene fractions, separating out the kerosene fractions and returning them to the drum commingled with the incoming supply.

13. A process of oil conversion that comprises passing the oil through an extended heating zone of restricted cross-section Where it is heated to a cracking temperature without substantial decomposition, delivering -the heated oil into a cracking and'distilling zone, separating the heavier constituents of the evolved vapors and returning them to the heating Zone for retreatment, removing the residue from the cracking Zone without recirculating residue through the heating zone, and maintaining superatmospheric pressure through the heating and cracking zones.

14. The process of cracking oil that comprises forcing oil through a heating zone under such regulated conditions of pressure, -temperature and rate of flow as to heat the oil up to a cracking temperature while preventing carbon from forming therein, delivering the heated oil free of residual carbon into a separate cracking zone where it is maintained at superatmospheric pressure and supplying sufficient additional heat to the oil in said cracking zone to maintain it at a cracking temperature no higher than that of the oil delivered to said cracking zone for a time sufficient to effect the desired cracking and resultant for-- mation of carbon therein. l

15. A process of oil conversion comprising -cracking .a body of liquid oil in an enlarged cracking chamber, to which not more than moderate external heat is applied and where cracking conditions of temperature, pressure and time are maintained and carbon is formed and deposited under safe conditions, supplying heat to said chamber to maintain the. body of oil at an effective cracking temperature -by delivering into said body of oil a stream of hot oil free from residual carbon after passage through a heating coil under such regulated conditions of temperature, pressure and time as to heat the oil up to a cracking` temperature while preventing carbon from forming-therein, withdrawing vaporous products of conversion from a high point in said chamber and discharging*carbon-containing residual oil from a low point therein.

16. A process of oil conversion that comprises forcing the oil at high speed through a coil into a cracking drum, applying high temperature heat to the coil to raise the temperature of the oil lso that it is delivered to the drum at a cracking temperature but without substantial decomposition, maintaining a body of liquid oil under pressure and .at a cracking temperature in said drum to produce decomposition thereof, continuously withdrawing the vapors from the drum, separating the kerosene-like constituents from the lighter vapors and reintroducing the kerosenelike constituents into the coil with the charge, and condensing the lighter vapors.

17. A process of oil conversion that comprises passing the oil through an extended heating zone of restricted cross-section under such regulated conditions of pressure, temperature and rate of heavier constituents of the separated vaporous.

products to form a clean condensate and recycling the clean condensate free of residual oil to the heating and cracking zones for further treatment,

while continuously supplying charging stock to the system.

18. A process of oil conversion that comprises heating the oil in a heating coil under such coordinated operating conditions of temperature, pressure and time as to heat the oil up to a cracking temperature while preventing formation of carbontherein, passing the highly heated oil at a cracking temperature and free' from residual carbon into a separate cracking zone maintained at an effective cracking temperature and under superatmospheric pressure wherein a material amount of cracking is effected.

19. A process of oil conversion that comprises heating the oil under superatmospheric pressure to a cracking temperature in its passage through an elongated heating zone without extensively convertingthe oil therein, passing the highly heated oil into a separate cracking zone maintained under superatmospheric pressure, subjecting the cracking Zone to moderate external heat to maintain the voil therein at a cracking temperature of the general order of that attained in the heating Zone whereby the oil is largely cracked therein, effecting a separation by distillation of the lighter products produced from the heavier residual oil formed in the process, and removing the residual oil from the system While preventing the return of residual oil to the heating and cracking zones.

20. A process of oil conversion which comprises to a cracking temperature in transit through a heating coil While preventing carbon formation therein, delivering the heated oil free from residual carbon into a. separate cracking zone maintained under superatmospheric pressure, moderately heating the oil in said cracking Zone to effeet substantial cracking of the oil therein, separating the lighter products as vapors from the unvaporized residual oil formed in the process, discharging the residual oil from' the process While preventing the recirculation of residual oil through the heating coil and cracking zone, and continuously supplying charging stock to the process.

21. A process of oil conversion that comprises passing oil i un'der superatmospheric pressure through an elongated heating coil, heating the oil in transit therethrough by passing hot combustion'jgases in heat-exchange relation with the oil flowing through the heating coil and in countercurrent passage with respect thereto to heat the oil up to a cracking temperature only as it approaches the exit thereof, while preventing carbo'n formation therein, passing the highly heated oil free from residual carbon into a separate cracking zone subjected to superatmospheric pressure and to vrelatively moderate additional heat to maintain an eiective cracking temperature therein and effect material cracking of the oil therein.

22. The ,steps of a process of cracking hydro-j carbon oilgthat comprise forcing oil free from residual products through an extended heating zone of restricted cross-section under a pressure of substantially to 500 pounds and regulating the rate of heating so as to remove the oil from the heating zone after it has been heated at least to its cracking temperature but before any ma,- terial decomposition has taken place.

23. The process of cracking oil that comprises passing a stream of hydrocarbon oil free from residual products once through a. heating coil under pressure in which the oil is not substantially decomposed and from which it is discharged at a. cracking temperature, .and utilizing the heat supplied to the oil in passing through the coil to effect material decomposition of the oil after it emerges therefrom.

` OTTO BEHIMIER.

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