US2941021A - Process and device for carrying out chemical reactions at high temperatures - Google Patents

Description

June 14, 1960 w. KRAUSE ETAL 2,941,021

PROCESS AND DEVICE FOR CARRYING OUT CHEMICAL REACTIONS AT HIGH TEMPERATURES Filed May 8, 1956 i Figl2 5' 1 7 \Eh Fig.3

Walter Krouse Werner Fischer Rudolf Wirrz Hormur Schilken INVENTORS BY chnfi 4yonah r sa%ad ilnited States iatent G raocnss AND DEVICE non CARRYING our gHEMICAL REACTIONS AT HIGH TEMPERA- Walter Krause, Frankfurt am Main, Werner Fischer, Bad Soden am Taunus, and Rudolf Wirtz and Hartmut Schilken, Frankfurt am Main, Germany, assignors to Farbwerke Hoechst Aktiengesellschaft vormals Meister Lucius & Briining, Frankfurt am Main, Germany, a corporation of Germany Filed May 8, 1956, Ser. No. 583,567

Claims priority, application Germany May 13, 1955 11 Claims. (Cl. 260-679) The present invention relates to a process and to a device for carrying out chemical reactions at high temperatures.

It is known that the production of acetylene, ethylene and higher olefins from methane, ethane or higher bydrocarbons requires supplying Within the shortest possible time the hydrocarbons to be reacted with great amounts of energy.

Thus, for example, the energy may be supplied indirectly by passing the gases to be cracked through outsideheated pipes or heat exchangers. This method involves the disadvantage that the Walls of the pipes are superheated and thus give rise to pronounced formation of coke and soot. Furthermore, the process referred to above is restricted to the use of small diameter pipes, since a pipe of greater size in diameter enables only too slow and incomplete a heat transfer from the walls to the gas. The gases in the border zones become too hot contrary to the gases in the middle zones which become insufiiciently hot and, therefore, do not participate in the reaction.

For the indirect supply of heat there are also used so called regenerative furnaces heated with a gas mixture obtained by combustion of fuel with air; heating is then interrupted, the furnace is cleansed with an inert gas and then charged with the hydrocarbons to be cracked at the hot filling material of the furnaces. The furnace is again heated with heating gas after a minimum temperature has been reached. This operation is continually repeated by automatic commutation in intervals of some minutes. Detrimental to this process is, in addition to the complicated reversing automatic, the inevitable deposition of tarry substances in the regenerative furnace and the constantly changing temperature of the furnace which jeopardize economy and the yields obtained.

According to another process the energy required for cracking is supplied direct by subjecting part of the hydrocarbon to be cracked to a combustion process in a special combustion device with oxygen, whereby the hydrocarbon itself furnishes the energy for pyrolizing the hydrocarbon in excess. This process is however not applicable when it is desired to prevent the hydrocarbon to be cracked from partial combustion.

Therefore, it has repeatedly been proposed to supply the energy by means of a carrier gas, for example hydrogen or combustion gases such as steam heated to a high temperature, which is then mixed in suitable manner with the hydrocarbons to be cracked. In this case, it is especially advantageous to use as fuel hydrogen and to subject this substance together with oxygen to a combustion process since, after the reaction, the steam formed can be easily separated from the resulting gas by condensation and since the subsequent separation of the gas is thereby rendered less ditficult. As combustion gas there may also be used all products obtained by combustion of any combustible substance. Furthermore, it is particularly advantageous to perform the combustion of the fuel within a fairly small space and to provide for as short a distance as possible between the end of the combustion zone and the inlet for the hydrocarbon to be cracked, so that the inevitable heat losses caused by dissipation are kept as small as possible. As results therefrom, a fairly short flame shall be produced which furnishes great amounts of energy but burns only on a short distance.

To this end, the fuel and the oxidizing agent are often premixed in a separate mixing chamber before they are introduced into the combustion chamber proper for combustion. The combustion devices which aresupplied with pre-mixed gases involve however the risk that the flame flashes back into the mixing chamber and destroys the. combustion device unless the gas supply lines are provided with very sensitive and in most cases technically complicated control devices which maintain constant pressure and velocity of flow of the mixture of oxygen and vaporized or gaseous fuel, such as hydrogen, as is the case with combustion devices used for the incomplete combustion of methane or earth gas with oxygen.

All these disadvantages are overcome by our present invention which comprises a combustion chamber for performing any pyrolytic reaction; more particularly, our present invention relates to the production of acetylene and/ or ethylene and/ or higher olefinic hydrocarbons, wherein fuel and oxidizing agent are completely mixed only after the components have reached the flame so that just as short a flame is produced as in the case where the flame is produced by the supply of pre-mixed gases. According to the process of this invention finely divided liquid, vaporized or gaseous fuel and at least one oxidizing gas are introduced separately into the combustion chamber at a velocity corresponding to a Mach-number of at least 0.8, preferably at sonic speed, via at least one tangential bore hole arranged in at least one plane in or opposite to the direction of rotation and then subjected to a combustion process. In this case one of the reactants may be introduced wholly or partially via radial bore holes. =By mixing and whirling in the manner described above, fuel and oxidizing agent undergo so rapid a combustion that the resulting flame ceases to burn after a very short distance. It is, therefore, possible to operate the combustion chamber with very high charges. Industrially, it is especially advantageous to operate the combustion chamber with charges of 1 billion or more Kcal/mFh (10 Kcal) The combustion chamber as used in the process of this invention involves the particular advantage that the whole combustion process is performed Within the smallest space-as is the case of flames produced with premixed gasesso that the heat losses caused by dissipation are small in relation to the energy produced; contrary to the known devices, a combustion chamber as used herein prevents the flame from flashing back into the mixing chamber and requires no complicated control mechanism.

The term Mach-number used herein is to define the gas velocity applied in relation to the sonic speed at the corresponding temperature.

The operating procedure according to'this invention involves the further advantgae that the combustion gases leaving the combustion chamber at flame temperature possess such a high turbulence-due to their having been whirled in said chamberthat they are practically instantaneously mixed with the reactant to be pyrolized. Thus, the heat is especially Well transferred from the combustion gas to the reactants, whereby it is possible to perform a practically complete reaction.

The reactant to be pyrolized can be introduced into the combustion chamber radially or tangentially either of the oxidizing agent and reversely. The fuel and the oxidizing agent may, howevenalso be' introduced through proper-:bore rings."

' When his desired to prepare acetylene 'and/ or ethylene and/or higher olefin-containing' gases, iLe. gases which in addition to acetylene and/or ethylene contain propylene, n-butylene, iso-butylene, etc. that is chiefly o lefins with 3 or 4 carbon atoms, it is especially suitable t adv mix between the flame end and the place where the reactant isintroduced asecondary gas, preferably steam and/or hydrogen in order to reduce the proportion of oxygen-containing radicals, oxygen atoms and oxygen molecules as it is described in copending patent application Serial No. 578,581, filed'April 17, 1956 for Mann-.

facture of Low Molecular Unsaturated Hydrocarbons. This operating procedure is especially suitable if fuels are used that produce flames and combustion gases, such' as have very high temperatures, for example hydrogen. In this case, the secondary gas can be introduced into the combustion gas radially or tangentially and both" in and opposite to the direction of rotation.

For the production of acetylene and/ or ethylene and/or other olefins containing 2 to 4 carbon atoms using a combustion device according to this invention-,jaliphatic' hydrocarbons which may have been pre-heated areintroduced in gaseous or liquid. form-which term here 4 r ethylene and/0r higher hydrocarbons there may be used any gaseous or other hydrocarbons as. far as they are liquid or can be liquefied by heating. Such fuels are used in a finely divided form for operating the combustion chamber according to this invention and for the production of the aforesaid unsaturated hydrocarbons. The term finely dividedjform as used herein shall comprise fine atoririzationofliq'uid hydrocarbons and shall 'alsocomprise th e use of gaseous and vaporous hydrocarbons. As fuels there may also be'used hydrogen, carbon monoxide or water gas which contains an excess of hydrogen and/0r carbon monoxide. 'Insome cases it is advisable V to use commerciallhydrogeu.

. As' oxidizing :agent there mayadyarita'geohsly be used commercial, pure oxygen, if desired .in' admixture with air, the oxidizing agent b ing always employed in a theoretically insufficient-quantity. i

A combustion device suitable for use in carryinggout the process of this invention is shown diagrammatically in the accompanying drawing, wherein:

Figure 1 is a schematic view in elevation; and

Figures Zand 3 are sections taken through section line AA and BB, respectively, of Figure 1.

In the drawing the numerals designate the following parts:

. Metal chamber 1 surrounded by a coolinguagent, for example water, is supplied through tangential borehole 2 with hydrogen and through tangential bore hole 3 with oxygen. As shown in Figure 2, hydrogen and oxygen are supplied alternately in one or several superimposed planes. Steam is introduced through holes 4- radially or tangentially'by way of inlet 4 at the end of the flame.

, The hydrocarbons to be cracked are also introduced radiand below shall include the vapo-urized' state-either radi ally or tangentially or in any other knownmanner into thecurrent of combustion gases in order to be mixed action chamber, "for example the reaction tube, with ceramic material to suppress undesirable soot formation which is favored by metal surfaces.

For designing the combustion chamber it is expedient I to use a metal which is cooled by means of a cooling agent,

for example water; however, there may also be used ceramic materal or metal lined with ceramic material. In the'caseoffa cooled metal combustion chamber, the heat taken up by the cooling agent can be recovered and used for other purposes.

As starting materifls suitable'for use in the process of this invention there can housed the knownihydrocarbons, for example saturated or unsaturated hydrocarbons containing up to 30 or more carbon atoms. It is. particularly advantageous to employ saturated hydrocarbons, such as methane, ethane, propane, butane, pentane,- heptane, octane, decane dodecane, especially in the form of liquid commercial mixtures, such as petroleum distiilates or hydrocarbon oils, for example topped I iuweit oil, aswell as in :the form of technical gases such as earth gas. Instead of aliphatic'saturated hydrocarbons'containing from 1 to about 30 or more carbon. atoms, therernay also he used unsaturated hydrocarbons and hydrocarbons having a branched chain: As branched" hydrocarbons there are concerned, "for example isobutane, isooctane,-isoheptane, isohexane, etc. It is not advisable to use unsaturated hydrocarbons per se unIess it is desired to produce acetylene or unless they are contained inesmall amounts inotherhydrocarbons. Thus, for example; ethylene, propyleneynor iso-butylene-may be used for the production'of acetylene;

As fuels suitable in the production of 'acetylene-and/or ally or tangentially by Way of inlets 5 as; shown in Figure 3. After a short residence time in reactor 6, depending on. the dimensions of the reactor, the gases farechilled by means of a cooling agent, for example finely divided water introduced by way of lines 7, and separated in a siphon 8 from the liquid ingredients. The reactor, which is advantageously constructed of metal resistant to high temperature, is lined with ceramic material 9. e

We claim: 7 W

1. A process for the manufacture of C -C unsaturated hydrocarbons which comprises continuously forming a rotating stream of hot combustiongas in a a combustion zone by introducing an excess of atomized fuel and an oxidizing gas therefor separatelyand tangentially with a velocity corresponding to a Machnumberof at least 0.8 into the combustion zone, contacting said combustion gas with an atomized aliphatic hydrocarbon for pyrolysis-thereof, and chilling the effluent mixture of pyrolyzed hydrocarbon and combustion gas.

2. 'A process for the manufacture of C -C unsaturated hydrocarbons which comprises continuously-form ing a rotating stream of hot combustiongasin a. comb ustion'zone by introducing an excess of atomized fuel and an oxidizing gas therefor separately into thecombustion zone, at least one of said reactants being'introduced tangentially with a velocity corresponding to a Mach number of at least 0.8, conducting the combusti'on gas through a constricted opening or acceleration thereof, contacting said accelerated combustion gas with an atomized aliphatic hydrocarbon for pyrolysis thereof, and chilling the effluent mixture of pyrolyzedhydrocarbon and'combustion gas.

3. A process'for the manufacture of C -C unsaturated hydrocarbons which comprises coritinuouslyforming a rotating stream of hot combustion: gas in acombustion zone by introducing an excess 'of atomizedufuel' and an oxidizing gas therefor separately into the .C01I1-' bustion zone, at leastione of said reactants being'intro duced tangentially: with a velocity correspondingitoia Mach number of at least, 0.8, adding a secondary gas selected fromthe group consisting of steam, hydrogen and mixtures thereof to the rotating stream of hot combustion gas, contacting an atomized aliphatic hydrocarbon with the gas mixture thus obtained for pyrolysis of said hydrocarbon, and chilling the effiuent reacted mixture.

4. A process for the manufacture of a product selected from the group consisting of acetylene, ethylene and a mixture thereof which comprises continuously forming a rotating stream of hot combustion gas by introducing, separately and at about sonic speed, commercial oxygen and an excess of commercial hydrogen tangentially into a combustion zone; adding a secondary gas selected from the group consisting of steam, hydrogen and mixtures thereof to said rotating stream; thereafter introducing into the rota-ting stream an aliphatic hydrocarbon in gaseous form for pyrolysis therein; and chilling the reacted mixture.

5. In a process for the manufacture of C -C unsaturated hydrocarbons by continuously forming a stream of hot combustion gas in a combustion zone, contacting said combustion gas with an atomized aliphatic hydrocarbon for pyrolysis thereof and chilling the efiluent mixture of pyrolyzed hydrocarbon and combustion gas, the improvement which comprises forming a rotating stream of hot combustion gas by introducing an excess of atomized fuel and an oxidizing gas therefor separately into the combustion zone, at least one of said reactants being introduced tangentially with a velocity corresponding to a Mach number of at least 0.8.

6. A process as defined in claim 5 wherein the fuel a and oxidizing gas are introduced at a rate, in relation to the size of the combustion zone, such as to generate at least about a billion kilo calories per hour per cubic meter of combustion chamber.

7. A process as defined in claim 5 wherein at least one of the reactants is introduced at sonic speed.

8. A process as defined in claim 5 wherein the fuel is hydrogen.

9. A process as defined in claim 5 wherein the oxidizing gas is oxygen.

10. A process as defined in claim 5 wherein the atomized aliphatic hydrocarbon is introduced into the combustion gas in a direction coincident with the direction of rotation of the stream of combustion gas.

11. A process as defined in claim 5 wherein the atomized aliphatic hydrocarbon is introduced into the combustion gas in gaseous form.

References Cited in the file of this patent UNITED STATES PATENTS 2,343,866 Hincke Mar. 14, 1944 2,599,981 Ekholm June 10, 1952 2,706,210 Harris Apr. 12, 1955 2,750,434 Krejci June 12, 1956 2,767,233 Mullen et a1 Oct. 16, 1956 2,813,138 MacQueen Nov. 12, 1957 2,816,941 Goins Dec. 17, 1957 2,868,856 Hale et a1. Ian. 13, 1959

Claims (1)

1. 4. A PROCESS FOR THE MANUFACTURE OF A PRODUCT SELECTED FROM THE GROUP CONSISTING OF ACETYLENE, ETHYLENE AND A MIXTURE THEREOF WHICH COMPRISES CONTINUOUSLY FORMING A ROTATING STREAM OF HOT COMBUSTION GAS BY INTRODUCING, SEPARATELY AND AT ABOUT SONIC SPEED, COMMERCIAL OXYGEN AND AN EXCESS OF COMMERCIAL HYDROGEN TANGENTIALLY INTO A COMBUSTION ZONE, ADDING A SECONDARY GAS

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