US3192280A - Preferred method for supplying reactants to a resonating shock tube machine - Google Patents

Description

0. R. LANDGREN June 29, 1965 PREFERRED METHOD FOR SUPPLYING REACTANTS TO A RESONATING SHOCK TUBE MACHINE Filed Dec. 27. 1960 FIGURE I WATER JACKET ELECTROCONDUCTIVE COATING FIGURE III INVENTOR Clarence Robert Lundgren BY /M.d.M

PATENT ATTORNEY United States Patent 0 PREFERRED METHOD FOR UPPLYHNG REACT- ANTS TO A RESONATING SHOCK TUBE MACHINE Clarence R. Landgren, Morristown, N.J., assignor to Esso Research and Engineering Company, a corporation of Delaware 7 Filed Dec. 27, 1960, Ser. No. 78,645 11 Claims. (Cl. 260-679) The present invention relates to an apparatus and process for high temperature and pressure, extremely short reaction time conversions of organic or inorganic materials. More particularly, this invention relates to improvements in (a) the configuration of, (b) supply of a reactant or reactants to, and (c) removal of a reactant or reactants from, a resonating shock tube wherein detonations (produced by ignition of an explosive mixture of gases) are employed to aid in the attainment of high reaction temperatures'for short reaction periods to chemically transform a reactant or reactants into a different compound or product. A cylindrical or spherical resonating shock tube reactor of this type is described in German Patent No. 1,016,376, which patent is hereby incorporated by reference. Yet more particularly, this invention relates to improved resonating shock tube reactor comprising a truncated cone, serving as a combined combustion chamber and reaction chamber, a combustion head located at the larger end of the truncated cone and in the immediate vincinity of both the explosive mixture feed and combustion products removal and a reactant heat located in the smaller end of the truncated cone and in the immediate vicinity of both the reactant feed and reaction product removal. The combustion products of the explosive mixture feed are removed adjacent the periphery of the combustion head, viz., at the larger end of the truncated cone. The reaction product(s) of the reactant(s) are removed adjacent to the periphery of the reactant head, viz., at the smaller end of the truncated cone, and the said reactants are supplied in a whirling motion from the center of the smaller end (reactant head) of the truncated cone shock tube opposite the combustion end. Due to the high tangential velocity of the reactants they form a thin well defined layer alongside the reactant face and exit uniformly at the peripheral wall adjacent to said reactant face. Thus, a constant residence time for the reactants is obtained with the present reactor. Most particularly in a preferred embodiment this invention relates to an apparatus and process for the pyrolysis of normally gaseous saturated hydrocarbons to produce high yields of desired unsaturates.

In German Patent No. 1,016,376 an apparatus has been described for producing shock waves in rapid succession within. a shock wave chamber. Thus, according to the said invention means are provided within a cylindrical or spherical shaped apparatus by which a thin layer of a flowing explosive mixture serving to form a shock wave is introduced continually or in periodic repetition to the combustion wall at one end of the said shock wave apparatus. This layer is periodically simultaneously ignited over its entire extent and thus provides a repeated formation of energy rich shock layers available at the opposite end of the tube. Additionally the shock wave upon reflection from said opposite end of the tube provides the energy for the ignition of a succeeding layer of explosive mixture at the combustion wall.-- In a specific example the order of magnitude of the time of ignition of a layer is between 10- and 10- seconds, the thickness of the layer being less than 10% of the distance to the opposite wall' of the tube.

In the patent above referred to although it is mentioned that the apparatus described may be used in addition to I amazes Patented June 29, 1965 its primary purpose, i.e. that of producing thermonculear reactions, for scientific investigations of matter at extremely high temperatures, densities and pressures no discussion is made of means for supplying reactants to the opposite end of the reaction tube where, of course, high pressures are obtained.

It has now surprisingly been discovered that an excellent control of reactants and unexpected process advantages as to uniform residence time are obtained specifically by the combination of employing a truncated cone serving as a combined (common) combustion chamber and reaction chamber wherein the combustion of an explosive mixture to produce detonations and the reaction of a reactants(s) to produce a compound or composition occur at opposite ends of the same truncated cone chamber, with the detonations being produced at the larger (combustion) end and the chemical product(s) prepared by the process'being produced at the smaller (reactant) end; feeding the explosive mixture and removing the combustion products thereof at the larger end; feeding the reactant(s) and removing the reaction product(s) at the smaller end; and supplying the reactants as described in this invention. Thus, the reactants are supplied at the center of the end of the reaction opposite the combustion end, in a whirling motion so as to form a thin layer parallel and adjacent to the said end as they spiral outward to a plurality of outlets in the reactor wall. This provides constant residence times for an individual molecule of gas as compared to other means for flowing gases across the reactant head, e.g. by introducing them at the reactor wall. In these other methods whether single or multiple introduction of reactants is used the length of the path taken by the individual molecules in travelling across the tube would necessarily vary.. Further, it should be noted that shorter flow paths for the gases are obtained which is advantageous in that the velocity required across the reactant head is reduced, i.e. each molecule of gas should be contacted with at least one, and preferably only one, shock wave to provide the necessary pressure and temperature for conversion.

The present invention will be more clearly understood from a consideration of the accompanying drawings, Figure I describing a preferred apparatus for carrying out the present invention and Figure II describing a section of an alternate preferred reactanthead particularly adapted for use where a large area reactant head is used. Thus, a truncated cone type of reactor is used so as toconcentrate the force of the shock wave at the reactant smaller end of the reactor. This provides higher temperatures and pressures at the reactant end than are obtained with a cylindrical reactor, e.g., as shown in German Patent 1,016,376.

Turning now to Figure I of the drawings, to initiate the formation of shock waves and thus place the tube in operation, tube truncated cone 1 is filledwith an explosive mixture. For example the means ordinarily used once the tube is operating for supplying the organic materials, to be converted to the reactant head may be utilized. Thus, the explosive mixture is passed through valved line 3 and/or line 4 to the reactant head 2 by opening the valves(s) for a short period of time and then closing it again.

At the combustion head 6, the gaseous components used for the formation of the successive explosions that drive the tube, for example oxygen and a hydrocarbon or hydrogen, are separately conducted tangentially intothe hollow spaces of the combustion head 6 through valved lines 7" and 8. The mixture emerging from'the openings shown in the combustion head 6 forms a thin uniform layer along the wall due to its whirling motion.

After this layer is set up the explosive mixture introduced at the opposite end of the tube is ignited by suittents of the shock wave tube.

. the mixture which is in the vicinity of the wall is ignited uniformly. This ignition propagates itself through the explosive chargev and leads dueto pressure and thermal effects to the combustion of the explosive layer at the wall of the combustion head 6; This explosion occurs simultaneously with reflection of the initial pressure wave at the wall of the end 6 so that a combined pressure wave travels to .the wall of the reactant distribution head 2 iwhere it is reflected back again. Duringthe time of the travel of this combined pressure wave, fresh mixture flows out of the openings in the combustion head 6 and forms a new explosive mixture layer there. This new explosive mixture layer is ignited by the combined pressure wave as it strikes the wall of the combustion head 6. By the ignition of the explosive mixture layer at the combustion head there is again developed a sudden increase in pressure of the ignited layer and thus a new shock wave travels down the tube to the reactant head 2. Thus, each successive explosive mixture layer atthe combustion head 6-is ignited by the preceding shock wave reflected from the reactant head of the shock tube.

The repetition of this process leads to the development of strong shock waves due to a resonance-like amplification .of the explosive energies of the layers introduced. The ignition of the explosive mixture layer by a shock wave gives short ignition times due to the high velocities of these waves. Furthermore, an ignition of the mixture layer through its entire extent is automatically produced thereby.

In some cases, it is desirable to obtain a faster sequence of shock waves than corresponds to the time .of the forward and returnztravel of a shock wave through the tube 1. The passage of a shock wave leads, for instance, in the case of a shock wave tube of a length of 100 mm. anda Velocity of the shock wave of 1000 meters per second to a travel time of 2-10 seconds. In order to obtain more than one ignition of a mixture layer within this period of time, it is possible to ignite the explosive mixture by heat radiation from the shock wave chamber. During the inward flowing of the explosive mixture against the wall of the tube end, the heat radiation from the shock wave tube acts ineach case on the. mixture layer. The. heating of the mixture layer produced thereby is slight at a relatively low temperature of the con- This is the case with the values indicated by way of example at a temperature of the contents of the, shock wave chamber of about 1000 K In the temperature range up to 1*0,000 K., the heat radiation increases with the fourth power of the temperature. Accordingly, a substantial control of the. heating of the inward flowing mixture can be obtained by an increase in the temperature of the contents of the shock wave chamber. By a proper control of this temperature it'is possible to achieve an ignition of the mixture layer before the aforementioned reflected shock wave ,arrives at the mixturelayer. By this heat radiation, there is thus produced an interim? ignition of the mixture layer. This ignition in its turn leads to an explosively producedpressure wave which travels through the shock wave tube, is reflected on the wall of the end 6,-producing the ignition of the mixture layer which has been formed in the meantime. The interim ignition of the mixture layer thus leads directly or after a few reflections of the wave formed therefrom to a plurality of shock waves travelling simultaneously in the shock wave tube.

By the selection of the temperature of the contents of the tube, it is possible to obtain a faster succession of the shock waves by increasing the number of shock waves travelling in the tube. As soon as a desired larger number of shock waves has been obtained by increasing the general temperatures in the shock wave chamber, the general temperature can again be reduced since the shock waves then, by themselves, eifect the ignitions of the mixture layers. It is known that shock waves penetrate substantially undisturbed in a manner similar to light waves, so that the travel of a plurality of shock waves in a shock wave chamber does not constitute any disturbance of the process.

A plurality of cylindrical cavities 9 are utilized in the combustion head 6 of the shock wavetube shown in FIGURE 1 so as to obtain a uniformly thin layer of the explosive mixture over the entire area of said head. The combustion components are preferably introduced separately into these cavities to thus obtain complete mixing.

The mixture components are preferably conducted through conduits 7 and 8 and branch lines 10 and 11 into the cavities 9 in end 6. The branch lines 10 and 11 discharge approximately tangentially into the cavities 9 so that the mixture components flow therein inan eddying motion. This eddying motion not only brings the explosive components together, but also effects the formation of a thin mixture layer adjacent the combustion head upon the flow of the explosive components out of the openings 12 of each eddy chamber. Thus, the spreading of the flowing material along the wall takes place with constant thickness of the layer. Particularly when a plurality of eddy chambers are provided, the formation of a flowing mixture layer along a wall of any extent is possible in a simple manner.

The introduction of the mixture components should, "as a rule, be conducted in such a manner that an explosive mixture is produced only at the outlet of the eddy chamber. It is therefore advantageous for this reason also to bring the components of the explosive mixture together in preferably a plurality of individual eddy chambers and to conduct separate mixtures through each outlet opening into the shock wave chamber.

The explosive mixture is continuously introduced into the shock Wave chamber and fiOWs outwardly to the wall of the reactor due to the tangential velocity produced by the whirling motion inthe cavities 9. In the wall of the reactor a plurality of outlets 12a are provided through which the combustion products pass into an outlet manifold 13 and thence, from the apparatus through line 14. Thus, a periodic ignition of the mixture layer as it flows to the manifold occurs due to the reflected shock wave from the opposite end of the reactor. In order to adapt the feeding of mixture to this periodic reaction, the tange'ntial velocity of the mixture in the cavities from which the mixture flows into the shock wave chamber can be attuned to the frequency of recurrence of the ignitions. It is therefore advantageous to introduce the components of the explosive mixture from preferably a plurality of individual cavities in the combustion head so as to reduce the length of the path to the .outlet manifold and thus reduce residence time. 1 It is, of course, preferred to utilize high frequencies of shock waves in the tube to obtain high throughputsfof reactants, and

therefore, of course, short residence times of the explosive mixture are desired. Such an adaptation of a large number of resonator chambers is particularly favorable if the travel of a plurality of shockwave-s in a shock wave chamber is to be obtained.

Turning now to the reactant head, the reactant or reactants are supplied separately (or together) through lines 3 and/or 4 to reactant head 2 containing a cavity 15. The gases are then transferred from this cavity through a port 16 to the reactor proper, where due to their whirling motion they form a thin mixture layer adjacent tov the end of the tube. Uniform reaction times for'an individual molecule of the gas are obtained as the gas passes radially to the peripheral wall of the tube. One or more successive shocks are applied to an individual molecule of the gas as it flows to the wall of the reactor to thus obtain the desired temperature and pressure and re is obtained due to the high tangential velocity of the gases introduced from cavity 15.

' Alternatively to the reactant head described in FIG,- URE I a reactant head containing a plurality of cavities and ports disposed in the central area of the reactant head may be used. Such an embodiment is described in FIG- URE H wherein for ease of illustration an end view of said reactant head is shown. Thus, referring to FIGURE II, the reactant head may comprise (for example, four cavities 20 disposed in a circular area 21. This circular arearepresents preferably less than 25%, specifically of the total area of the reactant head.

.It should be noted that the circular area within the group of cavities represents an area in which control of reaction time is poorer than the area outside that circular area. Therefore, it should be kept as small as possible and can easily bekept below 25% of the total reactant; head area particularly if the reactant head is smaller than 6 inches in diameter. The gases are introduced through lines 22 and 23 tangentially into said cavities and the gases exitthrough ports 24 with a whirling motion. Since the gases are introduced uniformly with either a clockwise or a counter-clockwise motion the desired tangential velocity to the periphery of the section is obtained. Thus, a similar fiow pattern to that obtained withthe single nozzle of FIGURE I is secured. It is preferred to use the reactant head described in FIGURE II particularly where larger reactors and specifically Where larger area reactant heads are utilized. Thus in these larger reactors a more even distribution of the reactants in a thin layer over the face of the said reactant head is obtained with a plurality of nozzles, e.g. 2 to 6 nozzles.

Suitable feed stocks to be supplied to the reactant head for conversion may be in general any material that may be supplied in vaporized form at temperatures below 1000 F. Thus, for example, hydrocarbons boiling below 1000 F. may be used. In a preferred embodiment such feed stocks are C to C preferably C to C paraffins, e.g. methane. These materials are reacted to produce selectively acetylenes, olefins and/or diolefins as desired, i.e. by using milder conditions olefins and diolefins rather than acetylenes may be produced. Additionally, in a preferred embodiment, inorganic materials may be reacted with other inorganic materials or organic materials may be reacted with other organic materials. All of these materials preferably must be gasifiable at temperatures below 1000 F., preferably at atmospheric pressure. For example, C -C paraflins, preferably C -C paratfins, e.g. methane may be reacted with 5-50 mol percent, preferably -30 mol percent, e.-g. mol percent of 0 based on paraffin feed to obtain aldehydes and/or ketones. Further, for example, by supplying air, a mixture of nitrogen and oxygen, as the reactant mixture nitrogen oxides are produced.

Reaction conditions in the above described conversions are: temperatures at the peakof the explosion wave at the reactant head 1,000 to 10,000 E, preferably 3,000 to 5,000 E, e.g. 3,500 F.; pressures of the inlet gases 1 to 100 atmospheres abs., preferably 1 to 10 atmospheres, e.g. 2 atmospheres, with peak pressures at the reactant head of 10 to 100 times these values; and reaction times .01 to 100 milliseconds, preferably .03 to .3 millisecond, e.g. .05 millisecond. In all of the conversions resonance frequencies in the tube may be 100 to 100,000 explosions per second, preferably 500 to 3,000 explosions per second, e.g. 1000 explosions per second. The length of the tube is chosen to obtain the desired frequency of explosions. Also, as previously mentioned more than one shock wave may be caused to travel in the tube. It should be noted that the pressures and temperatures at the reactant head are in general (adjusting for losses) proportional to the ratio of the area of the combustion head-.to the area of the reactant head. For example, ratios of the area of the combustion head to the area of the reactant head may be 20:1 to 1:1, preferably 10:1 to 4:1, e.g. 7:1. Thus, the higher the ratio the more concentration of'the shock wave occurring and the higher the temperature and pressure achieved'at the reactant head.

The present invention will be more clearly understood from a consideration of thefollowing example describing a preferred use of the present apparatus.

Example Methane is reacted to obtain a high yield of acetylene as follows. Methane is fed to the combustion or larger head of a truncated cone reactor. The said reactor is 200 cm. in length, the diameter of the larger end being 30 cm. and the diameter of the smaller end being 10 cm. Oxygen is also fed to the combustion head of the reactor. These gases are preheated to about 1000 to effect economies in fuel consumption. Methane reactant is fed to the reactant or smaller head of the re actorhaving first been preheated to about 900 F. to effect economies in fuel consumption. The gases are introduced to the combustion head and to the reactant head in a whirling motion through 4 nozzles for the former and 1 nozzle'for the latter of the type described in FIG- URE 1. Reactor residence times for the methane fed to the reactant head are about 1 millisecond, and for the combustion gases fed to the combustion head about 1 millisecond. The resonating shock waves (resonating at 1000 explosions per second) set up in the reactor by the combustion at the combustion end will develop pressures at the reaction head of above atmospheres. Temperatures sufficiently high to crack the methane to acetylene and ethylene are developed. The temperature is sufficiently high, 3000-3500" F., that acetylene is pro duced in large yield, e.g. 65 wt. percent yield on the CH feed. The gaseous product from the reactor is quenched to prevent the further decomposition of the acetylene product. The acetylene is then recovered in any of the usual type of acetylene purification plants, e.g. in a solvent absorption plant, an example of a solvent being dimethyl formamide.

In a similar way, olefins can be made by the use of other feed stocks and by operating under less severe cracking conditions.

It is to be understood that this invention is not limited to the specific example, which has been offered merely as an illustration, and that modifications may be made with out departing from the spirit of this invention.

What is claimed is:

1. Apparatus for reacting at least one organic material at high pressures and temperatures for a very short reaction time which comprises a truncated conical shock wave reactor, means by which a thin layer of flowing explosive mixture serving to develop a shock wave is introduced at the larger end of the truncated cone, means located at the small end of said cone for igniting the thin layer of flowing explosive mixture to thus initiate generation of shock waves, means for introducing a reactant mixture from the center of the small end of the truncated cone in a whirling motion having a low per-' pendicular velocity and a high tangential velocity and means for withdrawing reaction products at the wall of the reactor adjacent the said smaller end of the reactor.

2. The apparatus of claim 1 in which the means for introducing a reactant mixture comprises a single nozzle arranged perpendicularly to, and in the center of the small end of the reactor, the said nozzle having means for introducing reactant gases tangentially into the nozzle.

3. The apparatus of claim 2 in which means are provided within the nozzle for introducing at least two reactant gases separately in the same direction in said nozzle.

4. The apparatus of claim 1 in which the means for introducing the reactant mixture comprises a plurality of nozzles disposed perpendicularly to the small end of the shock wave chamber and located in a central area of the saidend containing less than 15% of the total area of the end and means for introducing reactant gases tangentially into each of the nozzles.

5. The apparatus of claim 4 in which means are provided within the nozzles for introducing at least two reactant gases separately tangentially in the same direction in said nozzle. 1

6. The apparatus of claim 1'in which the truncated conical shock wave chamber: is Water jacketed.

7. The apparatus of claim 1 in whichthe means for withdrawing reaction products comprises a perforated cylindrical wall of the reactor adjacent the smaller vend of the reactor head, the said wall being surrounded by a reaction manifold provided for the. withdrawal of reaction products from the apparatus.

8.'The process for reacting at least one organic material at high temperatures and pressures for very short reaction times which comprises continuously flowing a thin layer of organic material radially outwardly from a central point of the small end of a truncated conical reactor, applying a shock wave originating from the large end of said reactor periodically over the entire area of said thin layer thereby focusing shock wave energy at said small end, and withdrawing reaction products from the outer periphery of the thin layer at a position adjacent said small end. i

9. The process of claim 8 in which the application of each successive shock Wave occurs after the spreading of fresh material to the periphery of said small end.

10. The process of claim 9 in which at least two different reactants are supplied.

11. A process for reacting methane at high temperatures and pressures for very short reaction times which comprises continuously flowing a thin layer of methane outwardly from a central point of the small end of a truncated conical reactor, applying a shock wave originated from the large end of said reactor periodically over the entire area of said thin layer thereby focusing shock wave energy at said small end, the application of each successive shock wave occurring after the spreading of fresh methane to the vperiphery of said small end, and withdrawing reaction products from the; outer. periphery of the thin layer at a position adjacent said small end.

References. Cited by the Examiner UNITED STATES PATENTS 2,832,666 4/58 Hertzberg et a1 260-679 2,958,716' 11/60 Lahr et a1. 260679 3,047,371 7/62 Krause 61; a1. 260-679 FOREIGN PATENTS 1,016,376 9/57 Germany.

ALPHONSOD. SULLIVAN, Primary Examiner.

Claims (2)

1. APPARATUS FOR REACTING AT LEAST ONE ORGANIC MATERIAL AT HIGH PRESSURES AND TEMPERATURES FOR A VERY SHORT REACTION TIME WHICH COMPRISES A TRUNCATED CONICAL SHOCK WAVE REACTOR, MEANS BY WHICH A THIN LAYER OF FLOWING EXPLOSIVE MIXTURE SERVING TO DEVELOP A SHOCK WAVE IS INTRODUCED AT THE LARGER END OF THE TRUNCATED CONE, MEANS LOCATED AT THE SMALL END OF SAID CONE FOR IGNITING THE THIN LAYER OF FLOWING EXPLOSIVE MIXTURE TO THUS INITIATE GENERATON OF SHOCK WAVES, MEANS FOR INTRODUCING A REACTANT MIXTURE FROM THE CENTER OF THE SMALL END OF THE TRUNCATED CONE IN A WHIRLING MOTION HAVING A LOW PERPENDICULAR VELOCITY AND A HIGH TANGENTIAL VELOCITY AND MEANS FOR WITHDRAWING REACTION PRODUCTS AT THE WALL OF THE REACTOR ADJACENT THE SAID SMALLER END OF THE REACTOR.

8. THE PROCESS FOR REACTING AT LEAST ONE ORGANIC MATERIAL AT HIGH TEMPERATURES AND PRESSURES FOR VERY SHORT REACTION TIMES WHICH COMPRISES CONTINUOUSLY FLOWING A

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