US2343866A - Process for the pyrolysis of hydrocarbons - Google Patents

Description

March 14, 1944. w B HlNcKE 2,343,866

PROCESS FOR THE PYROLYSIS OF HYDROCRBONS Filed Oct. 7, 1938 FUE. Il. F0113 E. l HYDRQJBUN A 5 fQUARTZ TUBE j A50 I4 OXY-HYDROGEN L 43 WATER BURNER 41 44 47 53 coLGE;1 5cRAc/fEo INVENTOR w www BY MJCA/TOIEYS Patent M. i4,

misses SESS FOB u. B. liilincke, Kingsport, Tenn.. assigner, by

vmestre assignments,

Los cles, Calif., a

2 Claims.

This invention relates to the pyrolysis of hydrocarbon materials and more particularly to a thermal process for the manufacture of acetylene wherein at least a partY of the heating is obtained by mixing products of complete combustion with the hydrocarbon to be Pyrolyzed.

Unsaturated hydrocarbons and in particular acetylene, have many industrial uses. Acetylene is used directly or indirectly in the manufacture of aldehydes, acids, polymerization products and various other compounds. Acetylene has been manufactured from calcium carbide. This is rather an expensive source of acetylene and has other limitations. Various electrical processes, such as employing the heat of an electric arc, have been suggested but, likewise, many of these processes are not economical. It has also been proposed to produce acetylene by pyrolysis of hy-I drocarbons wherein the heating takes place indirectly through furnace walls or other barriers. In view of the high temperatures employed, deterioration of equipment is rapid in many instances or special equipment may be required.

It has also been proposed to produce acetylene by the partial combustion of hydrocarbons. In such incomplete combustion processes, a part of the hydrocarbon is burned to generate heat within the remainder, which exerts the pyrolysis or cracking effect producing the acetylene. It is apparent that such incomplete combustion processes subjects all of the cracking stock-to partial combustion and produces relatively low yields of acetylene, mixed with a variety of combustion products. Various miscellaneous processes have also been suggested for the manufacture of acetylene.

In general, it may be stated that the manufacture of acetylene requires large quantities of thermal energy at high temperatures, for example, greater than 1000 C. The transference of therto W Process Company,

corporation of California Application October 3, 1938, Serial No. 233,809

(Cl. 26o-679) the various disadvantages relative to heat trans fer have been minimized to a large extent. I have developed a simpliiled, and improved process land apparatus particularly adapted for the manufacture of acetylene. i

This invention has for one object to provide a process for the manufacture of unsaturated hydrocarbons and in particular acetylene. Still another object is to provide a pyrolysis process for the decomposition of saturated .hydrocarbon wherein at least a part of the heat is directly supplied to the hydrocarbon. Still another object is to provide a pyrolysis process wherein heat losses because of transference through furnace'walls or other barriers, is reduced to a minimum. Still another object is to provide a pyrolysis process wherein there is a particular type of combustion. Still another object is to provide a pyrolysis process wherein a substantial proportion of the heat may be supplied in a preheating step employing more or less conventional heating at relatively high mass velocities. A still further object is to provide apyrolysis process for the thermal decomposition of non-acetylenic hydrocarbons wherein undesirable catalytic eects are minimized. A still further object is to provide a m'al energy at high temperatures presents various problems, inasmuch as the use of ceramics may berequired. Transfer of heat through ceramics may reduce the eciency of the process to some extent as well as induce thermal distortion and deterioration of the apparatus. The use of metals at high temperatures, while more eilicient, is limited because at temperatures above 1000 C. for example, it presents a range wherein commercially available metal equipment is not particularly serviceable.

I have devised a process and apparatus for the manufacture of unsaturated hydrocarbons and particularly acetylene, wherein the efllciency of the various heating steps has been improved and pyrolysis process which is relatively simple and emclent. A

vStill another object is to provide a pyrolysis apparatus adapted for the direct heat transfer to the hydrocarbon to be heated. A still further 0bject is to provide a pyrolysis apparatus wherein both preheating and iinal heating may be carried out. Still another object is to provide a pyrolysis apparatus wherein thorough mixing may be caused to take place between at least a part of the heating medium and the hydrocarbon treated. Still another object is to provide a pyrolysis apparatus wherein an undesired catalytic effect may be minimized. Arstill further object is to provide a pyrolysis apparatus which is relatively simple in construction and operation.

A still further object is to provide novel construction materials which may be employed at least in part for the construction of pyrolysis apparatus. A still further object is to provide construction employing both novel alloy parts and ceramics. A still further object is to provide pary ticular composition alloys adapted for the use in pyrolysis apparatus. Other objects will appear hereinafter.

I have found a method for cracking hydrocarbons wherein an Oxy-hydrogen or Oxy-gas mixture is burned in such manner that the hot products of combustion either partially or entirely heatand crack .the hydrocarbons by mixing with them. In my process,.the iiame is preferably so placed that only the hot water vapor (hydrogen oxide) formed mixes with the stream` of hydrocarbon to be cracked.

'I'he combustion of the oxy-hydrogen or similar or equivalent) flame, should be complete so that very little hydrocarbon is subsequently reacted with the oxygen. The stream of `hydrocarbon gas to be pyrolyaed may. be so arrangedthat it prevents impingement of. the flame on any refractory surface.

After mixing the flame vapors with the hydrocarbon gas so that the sensible heat-in the ilame vapor heats up the mixture rapidly the mixed gas and steam are passed through a cracking zone where they become rapidly cracked to the desired degree at temperatures, for example 10001400 C. The reaction mixture may be then rapidly cooled in a quencher, the water condensed, the cracked gas separated and/or other procedure applied. Y

For a more complete understanding of my in- I vention, reference is made to the attached drawing forming a part of the present application. Fig. 1 is -a semi-diagrammatic side elevation view in the nature of a flow sheet showing the general arrangement of an apparatus for carrying out my process.

Fig. 2 is another view similar to Fig. 1 showing a slightly modified arrangement.

Fig. 3 is also a semi-diagrammatic side elevation view showing in greater detail an apparatus arrangement which might be employed for carrying out my process.

Figs. 4 and 5 are other semi-diagrammatic side elevation views oi' various different type apparatus constructions which might be employed for carrying out my process.

Fig. 6 is a side elevation view of a preferred type apparatus which might be employed for carrying out my process. In this view as well as in ycertain of the other views some of the parts have been shown on section and other parts in exaggerated scale for clarity.

'I'he functioning of the various parts of the apparatus and the operation of my'process may be understood to some extent from the legends appearing on the.various figures.` In Fig. l, A-B represents a quartz tube having a side tube C joined thereto. A portion of this quartz tube as at 2, functions as the combustion chamber, whereas another portion of the tube 3 functions as the hydrocarbon inlet. The side tube as at 4, may be connected yto a quencher orother type device (not shown) employed in the art.

Fig. 2 is substantially similar to Fig. 1 in that it comprises the quartz tube A--B with the side tube C. However, in this arrangement. the hydrocarbon inlet C in differently located than the hydrocarbon inlet 2. Likewise, the combustion chamber I is differently located than the combustion chamber 2.

The apparatus of Fig. 3 is to some extent similar to that already described, inasmuch as it comprises the elongated tube I and the side tube I. These various parts are substantially insulated as at Il and I2 to prevent heat losses. A hydrocarbon feed inlet may be provided at I3. Substantially opposite the hydrocarbon inlet and positioned at a proper distance therefrom is the burner construction I4. Preferably, the burner should be so disposed that the' hydrocarbon gas is mixed with the hot products of combustion iroin the flame only after substantially complete the burner on the refractory wall.

cilimbustion to hot hydrogen oxide has taken p ce.

The apparatus is equipped with various parts such as feed lines Il, I1 for conveying materials tothe burner. Ihe cooling device il may be provided to connect the cracking sone Il with a trap as at 2 I. Suitable draw-oil' conduits may be provided at 22 and 2l. The apparatus of Fig. 3, for

example, may be constructed loi' silicon carbide,

zirconium silicate or various ceramics which will withstand the temperature.

In the apparatus of Fig. 4 the shell of the heating chamber 4I may be constructed of any of the various refractories already mentioned or various fused or sintered aluminum oxides. The shell would be built up in order to provide an enlarged chamber 42. At one end of the chamber a suitable burner structure 43 would be inserted. At

-the other end of the chamber at 44` means are provided for introducing the hydrocarbon to be cracked.

n In the device shown this means comprises the concentric passageways 4I, 41. The passageways are separated by the walls 4l, 49. By this construction the hydrocarbon introduced at 5I ows on the outside of the walls 48, 49, thereby absorbing some heat and into the chamber 42. After becoming mixed with the products of complete combustion the materials leave the apparatus through passageway 41 which is connected to a quenching device l2.

The quenching device would include inlet 53 for the quenching medium, and an outlet 54 for the treated gas. Suitable drawoif arrangement may be provided at 50 for withdrawing the liquid components.

The modified apparatus of Fig. 5 is likewise constructed of high-grade refractory as at 6I. 'Ihis shell may be built up of refractory bricks or other such units. A suitable chamber is provided at 62. One or more oxy-hydrogen burners may be positioned at one end of the chamber 63. 'I'he other end of the chamber may be provided with an outlet passageway 44 leading to a suitable cooling device Il. Inasmuch as this cooling device is substantially similar to device 52, further description at this point is unnecessary.

In the apparatus of Fig. 5 the hydrocarbons to be pyrolyzed may be supplied through the plurality of inlet conduits 61, 68 andA 69. By this arrangement large capacity and thorough mixing may be obtained, as well as preventing the direct impinging of the hot products of combustion from Sudden and complete mixing of the gas to be cracked is very desirable, otherwise a portion of the process gas may become overcracked or deteriorate by reforming to CO. 'I'his may be avoided by reducing the whole of the mixed gas to a suitable cracking temperature by mixing all of the process gas as rapidly as possible with the heating gas. The contact time that the process gas holds the high cracking temperature is determined by the velocities used and the size of the outlet tube 64 going to the quencher.

It is to be understood that the apparatus described may be equipped with various ancillary devices. For example, fuel and/or air preheaters maybe connected to the Oxy-hydrogen burners. Suitable temperature recording devices and the like may be attached to the various parts of the apparatus.

The apparatus disclosed in Fig. 6 represents one of my preferred arrangements. This arrangement comprises the shell 1I which houses the preheating device and the adjacent shell 'l2 which houses the crackingchamber. As already discussed, these parts may be constructed of a suitable refractory, properly insulated. The various fittings would be constructed of suitable heat andcorrosionresistant metals.

Referring to the preheating shell, this portion of the apparatus comprises heating chamber 1l.

A metal tube preheater 'Il is positioned within The preheating coil M is connected to one of I the concentric passageways 1l of the concentric passageways l0, 19. These passageways are separated by the wallsnll, 82. This arrangement functions somewhat similarly to the device already described. The preheated gas is conducted through the eway 1I into the cracking chamber 83. The gas at this point becomes mixed with the heating medium u generated by the oxy-hydrogen burner It. The hot mixture is then conducted through the passageway '59 to the conduit l1 that leads to a suitable cooling device (not shown).

Although the operation of my apparatus is more or less apparent from the preceding description and the legends attached to the re- 'spective figures, further understanding of the operation will be apparent from the following disclosure relative to mv novel process.

.As already pointed out, the manufacture of acetylene requires high thermal input and high` temperatures of, for example, between il C.- 1600 C. The transfer of heat at such high temperatures through ceramic walls or other barriers for cracking a hydrocarbon involves thermal strains, distortion, heat losses and the like. While various metals transfer heat more by decomposition thereof to produce a reaction mixture containing acetylene. I have found that the steam (hydrogen oxide) resulting. from combustion of oxygen and hydrogen or other gas in any Oxy-hydrogen burner even at the high temperatures involved, does not materially dissociate. The dissociation of the products of combustion from the Oxy-hydrogen flame in my process and apparatus would probably be less than a few percent at the temperature of the gas mixture in the cracking zone,

' that is, at 1000 C.1400 C. For example at or less readily as compared with ceramics. the

metals do not satisfactorily withstand extremely high temperatures.

I have found that by the proper type com-'7 bustion, extremely high temperatures may be generated and the combustion materials injected directly into the hydrocarbon being thermally treated. vBy my Plocess employing the injection of the completely burned'materials into the hydrocarbon a number of disadvantages natural gas or any other gas burned with air before changing over to kciw-hydrogen fuel. The

burner would, of course, be operated to and yde signed to avoid iiash-back.

I have found that the products of combustion from an Oxy-hydrogen fiameor similar or equivalent flamecomprlsing a substantial amount of hydrogen oxide and the absence of substantial amounts of oxygen, may be introduced andA mixedv directly' with the hydrocarbon to be the temperature of the flame the dissociation of the products of combustion just after complete burning of the oxygen and hydrogen might .0025 atmosphere of oxygen and from about .04

to .005 atmosphere of hydrogen.

I have foundthat the effect upon the pyrolysis reaction of any small amount of oxygen which may be present through dissociation or otherwise, is to some extent dependent upon the surface or packing in the preheating. and/or combustion chambers. In my novel processwliere steam or water vapor may be present with the gas treated, the dissociation or reforming of the gas is counteracted to a great extent by the use of proper materials of construction for both the preheater and cracking chamber, as well as the preferred and controlled short times of contact, as will be set forth in further detail hereinafter.

For a further understanding lof my invention, reference will now be made to the following examples described in connection with the several.

ried out, the oxy-hydrogen flame was at B and the hydrocarbon gas passed into the apparatus at A. The gas and llame in this process actually mixed countercurrent-wise before leaving the hot zone through the tube C to be quenched. The quantity of acetylene formed was not as great by `this procedure as by the procedure diagrammatically indicated in the apparatus of Fig. 2. v

In Fig. 2 the gas'was fed to the tube at B and mixed with the hydrogen oxide from the more or less completely burned Oxy-hydrogen flame at l A. By this procedure the quantity of acetylene in the cracked gas was increased several percent and the carbon monoxide, carbon dioxide and hydrogen were considerably lower. In the aforementioned examples, as in other of the processes, saturated'hydrocarbons such as ethane, propane, butane and the like were employed. Sufcient oxygen and hydrogen were burned in the burner to cause the temperature of the hydrocarbon in the cracking zone to be raised to 1400l600fC. The hydrocarbons were caused to remain under cracking conditions for only a short residence period, for example, generally less than one- -hundredth of a second and the resultant cracked products were rapidly cooled.

Similar procedure was carried out in the appal ,ratus of Fig. 3. but on a larger soak with the cracked. Such procedure affects a high .tem-

perature rise in the hydrocarbon accompanied production of 6% or more acetylene per pass;

hence,'further description with respect to Fig. 3

is unnecessary.

In carrying out a process in accordance with Fig. 4, the hydrocarbon to be pyrolyzed was preheated v(by means of an economical and commercially obtainable fuel) outside of the cracking apparatus. The preheated hydrocarbon was fed yinto the cracking chamber through passageway .5| and passed in heat transfer relationship with the hot outgoing products through conduit I1.

The preheated hydrocarbon which may, if desired, be diluted with steam, nitrgen, mercury or various other diluents became mixed with hot hydrogen oxide in the chamber II. This additional heat input induced further thermal decomposition and formation of acetylene. 'I'he injection of the hot products of combustion from the oxy-hydrogen burner also caused increased velocity of flow of the reaction mixture through passageway 41 into the quenching device l! wherein the acetylene gas was rapidly cooled.

By first heating to about 900-1000" in a suitable preheater, the low temperature cracking takes place prior to mixing the gas with the hot products of combustion. By so heating a great saving in fuel for the Oxy-hydrogen flame is ducted throuehthe.

supplied from combustion of oxygen-hydrogen is reduced to a small amount.

As will be pointed out it is highly desirable that the heating period in this preheater be arelatively short time. The highly preheated hydrocarbon with or without a diluent is then coneway 'I8 into the pyrolysis chamber 8l. In a manner similar to that described with respect to Fig. 4, the incoming oxy-hydrogen burner.

effected. Moreover, the conditions of temperature and contact time in the high temperature reaction are more easily controlled with arbetter yield of acetylene in the cracked gas.

In the process as carried out in Fig. 5, procedure similar to that already described was followed. However, it will be noted with respect to Fig. 5, that the tempering of the heat in the combustion zone is accomplished by causing all.

or part of the hydrocarbon gas being cracked to enter at certain .points inthe refractory wall,

being careful that the gas is not exposed to direct llame lmpingement.

. By my procedure, since hydrogen and oxygen will burn very rapidly, the gases can be mixed in a suitable burner and caused to burn at a high velocity` and produce a short brush flame. This flame will be completely surrounded with azone. of hot steam. The apparatus arrangement of Fig. 6 will be described in' more detail, inasmuch as it represents one of my preferred apparatus'. arrangements.- As already set forth', in accordhydrocarbon is further heated by the outgoing acetylene containing reaction mixture.

The hot 4preheated hydrocarbon gases to be cracked, at a temperature generally less than 1000 C. and containing various unsaturated hy- Vcirocarbons such as ethylene. a small amount of acetylene under are rapidly heated by the I short contact time in pyrolyzing hydrocarbons in a ceramic apparatus, it has not been understood what procedure to applyin apreliminary heating. I have found that it is very important for optimum yields that the temperature, conance with my process itv is'desirablethatthe thermal treatment of the hydrocarbon should be. carried out in a refractory apparatus built-of a. lhigh-grade refractory material having as little surface as possible and such surface having little catalytic effecten the reforming reactions ofthe vsteam and hydrocarbon gas. Preferably, the flame from the Oxy-hydrogen burners should be .so dispersed that the hydrocarbon gas vis readily mixed with the hot products of combustion from the flame and after substantially complete combustion to hydrogen oxide.

In order to further render my process more eiiicient` and to economize on the'specialized cracking heat required from the oxygen and hydrogen, which is a more expensive fuel than other fuels commercially obtainable, I preferably subject `the hydrocarbon gas to a preliminary heating such as shown in Fig. 4 and more fully Ashown in Fig. 6.

The hydrocarbo gas .to be treated or the mixture of hydrocar thepreheating coil 14. Preferably, this preheating coil is of a particular composition and construction `as will be described in detail hereinafter. This `coil may be heated by any conventional and economical type fuel supplied to the burner 16; Temperaturesbetween 900" C. and

relatively eicient heat transfer thereby substantially raising the temperature of the hydrocarbon. By Ithis procedure the amount of heat 'to `be n and diluent is fed a't 15 intol 1100 C. may be appliedto the metaltube with y nary heating.

tact time and type of metal alloy tube used for the preheater be carefully adjusted; I have found that for optimum results thel preliminary heating should be at a temperature of over 850 C., that the 4contact time in the alloy tube should be very short, and that the alloy tube should contain little or no metals detrimental to the reaction. A

Many metals or alloys exert a-tendency which causes the sus being preheated to decompose into carbon and hydrogen.l I f the hydrocarbon gas being heated also contains some diluent such as steam. the reforming action is rapidand carbon monoxide, carbon dioxide and hydrogen would build up in the 88s I have found that i the decomposition or reforming reaction as little as many alloys. However, the use of iron at high temperatures and under oxidizing conditions presents structural difficulties. AI therefore have found that it is possible to use iron alloys containing little cr no nickel but containing one or more elements such as chromium, silicon, aluminum-tungsten, molybdenum and manganese.

Besides the selection of an alloy with the least detrimental catalytic effect on the hydrocarbon gas being treated, it is also desirable that the' volume and surface of the preliminary heating device besuch that the 4gas is heated rapidly to as high a temperature as possible without appreciable decomposition or reforming with any diluent, steam (or other diluent) which might be introduced4 with the hydrocarbon.

carbon feed gas are heated and cracked to gas high in voleilne content, this-content increases to a maximum and then decreases rapidly with in creasing temperatures. I have found that at highertemperatures the products 'of decomposition .and reforming may become appreciable. The amount ofthese products will lower the yield being subjected to'a prelimiordinary black iron catalyzes If ethane.' propane, -butane or other constituents in a hydroof oiefines produced in the preheater which in turnwill greatly lower the yields of acetylene from the final cracked gas. I have found that it is possible, using the proper alloy. to subject the gases to a preliminary heating at a higher temperature without reforming and decomposition and thus accomplish a high total of the crackingheat by transfer through a metal component of the apparatus. Aside from the catalytic eilect of the alloy preheater on the gas being cracked, I have found that the contact time of the gas in the preheater should be considerably shorter than has heretofore been used. It is not aumcient that thel contact time in the final decomposition step be kept short, but the total heating period in both the preliminary heating zone and high temperature zone should be effected in a short time interval.

If the contact time in the preheater is too long, even though the alloy has little catalytic effect on the degrading reactions it is possible to overcrack the gas even at low temperatures.

' For optimum yields of acetylene and for increasing the output, it is desirable that the alloy tube transfer a substantial part of the heat to the process gas in auch a time interval that the gas passed on to the high temperature cracking in ceramic equipment. is heated as `high as possible.

Under proper conditions the heated process gas will subsequentlyl produce better yields of acetylene.

Therefore. I propose a cracking process and apparatus involving the use of a series combination of a metal preliminary lheating apparatus followed by a ceramic high temperature heating arrangement. The heat resistant metal alloy is of such a composition as to have low catalytic effect on the unwanted side reactions. A variety of such alloyed compositions will be set forth hereinafter. The contact time in the preheat is so adjusted that it ls less than .020 minute. Contact time is here defined as the volume in cubic feet of the preliminary heating coil and connectlng pipes defined by the c. f. m. rate or iow of the gas plus a diluent such as steam, measured at 60 F. and '160 mm. For example,for heating a mixture of 25 c. f. m. of butane and 200 c. f. m. of steam diluent, I propose a maximum allowable preheater volume of 4 c. f. from the point where the gas and steam mix at 90-ll0 C. to the point of inlet to the nal cracking zone; The final temperature of the preheated gas for good final cracking and efdcient use would be from about 800\C. to 1000 C. The composition of the hot gas from the preliminary heating before entering the contacting chamber would contain a substantial oleflne content, for example, 35% or greater and a few percent acetylene.

For a rate of flow of gas and diluent, as indicated above, an alloy tube preheater of four cubic feet volume should have from 80-100 square feet of surface to produce the desired mass velocity for rapid heat transfer. The flue design should be countercurrent to the gas being heated.

As for suitable alloys for metal tube preheaters the following are suggested:

Carbon .16 1.6 .0'7 .25 Manganese .'75 20.8 .18 1.0 Silicon .70 .63 .22 .60 Chromium 30.0 24.75 38.8 28.0 Tungsten 3.5 Aluminum 6.2 5.28 8.01

Nickel It is to be understood that my invention relaexactly to the constructions shown. For example,

my novel preheating procedure, heating in the alloys specified, the short time of contact and other features, also might be employed in conjunction with an indirectly fired final cracking chamber. That is, hydrocarbon gases may be preheated in accordance with my invention prior to cracking in a regenerative furnace, elongated carborundum tube or various other type heating furnace.

Ceramic tubes do not transfer heat nearly as readily as do metals, but to obtain high yields of acetylene, cracking temperatures must be obtained above those which alloys will withstand. Inasmuch as the contact time of the gas, in the high heat lzone, must be very short in order to obtain the best yields from high temperature. indirect heat cracking in ceramic tubes, it is desirable to rst accomplish heat transfer to the gas above 800 C. in an alloy preheater. 'Ihe heattransferring-surfaces and volume oftube relationship cannot be obtained for the conditions of rapid high heat transfer without the use of such small gas passages through the ceramic tube that a small carbon deposit would obstruct the gas flow.

It is apparent from the preceding description that I have developed a novel process and apparatus for the production of acetylene from hydrocarbons. My process and apparatus may be ap'. plied to a large variety of hydrocarbons such as enumerated in Wulff Patents 1,800,308 and 1,800,309. The hydrocarbons may be treated either with or without dilution with steam, nitrogen or various other diluents. However, in my process of high heat cracking'diluents are not so necessary because the combustion products from the oxyhydrogen burners are injected directly into the hydrocarbon. My process may be operated under normal pressure or reduced pressure or at a slight positive pressure. A small degree of reduced pressure is preferred in many instances for increase in velocity.

As apparent from the preceding description, a high temperature preheat is desirable for optimum yields and efficient use of the ,ceramic ware in the succeeding higher temperature step. If I wish to transfer heat in the preheating step in such a manner that a large olenic content is obtained in the gas preheated to 1000 C., I have found that the solution to the problem is practically unique as far as the variables under control are concerned. As pointed out, the heat-transferring surfaces should be adequate to heat the gas without having too high a temperature drop in the l inside film.V The volume of the preheating equipment should be such that the contact time of the 60 gases in the preheater be as short as specified. Furthermore, the mass velocity (mass of gas flowing per unit time per unit cross section area) should preferably be such that the heat transfer through the inside gas film, with the low temperature difference between the tube wall and gas as described, can be eected with the surface available. After satisfying these'conditions, the only variance is in the use of smaller diameter conduits. However, the use of too small tubes, I have found, is more or less impractical'because this necessitates the use of excessive power to blow the gas mixture through such apparatus. II 'herefore, it is seen that I have described a particularly satisfactory preheater arrangement. u Larger preheating units may, for example, be obas is necessitated by the spirit ot the appended claims.

WhatIclaimiszi j 1. A process for the "manufacture oi' acetylene by the pyrolysis of hydrocarbons, which coml prises preheating non-acetylenic hydrocarbons ix a ferrous alloychamber comprising iron containing a combined content greater than 30% of the metals, aluminum and chromium, by externally contacting the chamber with combustion gases obtained by the combustion of hydrocarbons. for

a period not greater than .05 minute and-at a temperature greater than 800 C., but less than 1000" C., thereafter immediately subjecting the preheated hydrocarbons to thermal'decompositained by combining in parallel, units such as I tion .at a temperature between 1000'Cf-1600 C. by injecting directly into thepreheated hydrocar- 'bon to be decomposed a quantity of combustion products bumed out ofv contact withy the hydrocarbon and injected thereinto while said combustion products are still hot, in a direction opposed to the direction of ilow o! said hydrocarbon, the

combustion products containing little free oxygen and a large amount ot hydrogen oxide, resulting from the combustion of oxygen and hydrogen.

A2. A process for the manufacture o! acetylene, including direct heating of non-acetylenlc hydrocarbon which comprises injecting into and mixing with the hydrocarbons a. combustion mixture burned out of contact with the hydrocarbons and injected thereinto before any substantial cooling of the combustion mixture, in a direction opposed to the direction of ilowoi' said hydrocarbons, the

combustion products being injected in sumcient quantity and at sumciently high temperature to raise the temperature of the non-acetylenic hydrocarbons to be pyrolyzed to between 1000' C. and 1600" C. in less than .10 minute for causing the conversion oi' at least a part oi the hydrocarbon to acetylene, and withdrawing and utilizing l the acetylene. j y

WILLIAM B. HINCKE.

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