US3226199A - Apparatus for the flame decomposition of hydrocarbons and apparatus therefor - Google Patents

Description

UKl YANO ETAL 3,226,199 H DECOMPOSITION OF ARATUS THEREFOR Dec. 28, 1965 MASAY APPARATUS FOR '1 E FLAME HYDROCARBONS AND APP Filed Oct. 2.

United States Patent 3,226,199 APPARATUS FOR THE FLAME DECOMPOSITION gg IYDROCARBONS AND APPARATUS THERE- Masayuki Yano, Teruo Yasui, and Takashi Ueno, Kuraslriki, Japan, assignors to Kurashiki Rayon Company Limited, Kurashiki, Japan, a corporation of Japan Filed Oct. 2, 1961, Ser. No. 142,251 Claims priority, application Japan, Oct. 27, 1960, 35/ 42,742 1 Claim. (Cl. 23252) This invention relates to a method of manufacturing acetylene and ethylene by the thermal decomposition of hydrocarbons and also to the apparatus therefor.

The object of the invention is to provide an economical method for obtaining acetylene and ethylene by the thermal decomposition of hydrocarbons and a more effective and durable apparatus for carrying out the method.

In order to attain the object of the invention, it is desirable to suitably establish the conditions of the preheating temperature of the fuel and raw materials, reaction temperature and quenching temperature, flame velocity, reaction velocity as well as the state of flow of the flame and gases of raw materials. Moreover, the consumption of the fuel constituting the flame and oxygen should be possibly reduced and the loss of the heat quantity generated by the flame through the wall of the apparatus should be prevented and the heat should be effectively utilized for the decomposition of the raw materials and also to maintin the desired high temperatures.

Heretofore, the method generally used for the combustion of fuels has been of the so-called pre-mixing type, by which gaseous fuel and oxygen or oxygen containing gases are preheated and mixed and injected into a combustion chamber through a nozzle or a distributor to form the flame, and this type is used for many decomposition furnaces of similar type. However, said known method has the disadvantages that the nozzle is liable to cause back fire so that the perfect mixing of the combustion gases and oxygen or oxygen containing gases is difficult. Further, the flame is liable to be extinguished, and the flame after having been injected from the nozzle impinges on the wall of the combustion chamber prior to the reaction with the raw material gases so that the heat losses from the furnace wall are considerable, thereby resulting in burning loss of the wall material of the furnace.

In order to obviate the above disadvantages it has been proposed to introduce the fuel gases and oxygen into the combustion chamber separately at a constant rate of flow through small holes distributed on concentric circles for feeding fuel and through an oxygen supplying spinneret corresponding to each of said fuel nozzles. According to this method the flame constitutes, as a whole, a cylindrical form without making direct contact with the furnace wall so that the heat losses and high temperature burning loss of the furnace wall are avoided, but since the gases are introduced through small holes the quantity of gas flow and kind of gases and the range of application is very limited,

The above disadvantages can be avoided by the invention, wherein the entrance of the fuel gas and oxygen is formed of anular rings, so as to have mutual relation and entering speeds intimately depending on the shape of flame and by arranging the entrance openings at a definite relation and by adjusting the respective velocity of gases it is very effective to avoid the heat losses from the furnace wall and to prevent the burning loss of the furnace materials same as those of the burner consisting of a group of small holes as above described, yet, in the burner of annular nozzle type of the invention provides the excellent advantages as hereinafter explained.

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The invention will be better understood by referring to the accompanying drawings, in which:

FIG. 1 is a diagrammatic sectional elevation of an apparatus for carrying out the decomposition of hydrocarbons embodying this invention;

FIG. 2 is a sectional view through the line aa' in FIG. 1;

FIG. 3 is a partial elevation showing a modified form of the partition wall 9, and

FIG. 4 is a plan view of a nozzle disk provided with a number of nozzles.

Referring to FIG. 1, the reference numeral 1 represents a combustion chamber, and 2 a reaction chamber. According to the invention, concentric cylindrical passages 3 and 4 are formed by an adjustable cylindrical nozzle piece 8 located between the outer casing 7 and the central guide member 9 and at the entrance to the combustion chamber there are formed concentric openings 10 and 11 to inject fuel and oxygen, respectively, in suitable directions to intersect with each other for the purpose hereinafter explained. The middle portion 1' of the furnace between the combustion chamber 1 and the reaction chamber 2 is made narrower with a smaller diameter than that of the combustion chamber, and at this portion there are providde a number of feed pipes 5 for delivering the raw material hydrocarbon, and 6 represents the furnace wall of refractory material constituting an outer shell of the reaction furnace. 12 represents inlet pipes of water for quenching the thermally decomposed gases. The cylindrical nozzle walls 8 and if desired the central guide piece 9 may be so constructed that their positions can be shifted upwardly and downwardly independently with respect to 7, thereby regulating the gaps of openings 10 and 11. The preheated combustible gases and oxygen are supplied to the combustion chamber through the openings 10 and 11 of concentric cylindrical passages 3 and 4.

After various investigations about the relative positions of inlet openings 10 and 11 of fuel and oxygen respectively the inventors have found that the flame is generated in a direction of the resultant of the vector of the momentum of fuel passing through the opening 10 and the vector of momentum of oxygen passing through the opening 11. Accordingly, by suitably selecting the injection speeds and angles of the fuel and oxygen the flame thus formed may be made to a cylindrical shape parallel to the axis of the furnace without making contact with the wall. In addition, since the breadths of the openings 10 and 11 can be changed by shifting 8 relatively to 9 to a predetermined position, the flow speed of gases passing through the opening gaps 10 and 11 can be changed as desired so that the fuel gas of a suitable kind and also any desired quantity of fuel and oxygen can be used, thereby extending the range of using a set of furnace considerably. In designing the furnace it is a problem how to determine the inlet angles of the fuel and oxygen and distance between them.

The location of the oxygen nozzle in the inside position is effective to keep from the furnace wall the high temperature center caused by combustion. If the injection angles of both fuel and oxygen are made large and the distance between them is made small and the flow speed is increased, then the ignition point of the flame approaches the surface of the burner (FIG. 1, line a-a) so that the burning loss of the burner surface increases. In contrast to the above condition, if the injection angle of the fuel and oxygen is made small and the distance between them is made large, and the flow speed is made slower, then the gaps between the injection openings and the ignition point will become greater and in addition, mixing of oxygen and fuel becomes insuflicient, thereby necessitating to enlarge the combustion chamber, and

increasing undesirable heat losses. The optimum linear velocity is within the range of 50 to 350 m./sec. and the injection angle of 40 to 90.

In the cylindrical flame formed by the gases injected from nozzles of small holes as in the known apparatus, there are clearances between mutual unit flames so that the average density of the flame is dilute as compared with the cylindrical flame generated from the annular nozzle burners of the invention so that the capacity of the combustion chamber must be made correspondingly larger.

In addition, in order to complete the mixing of fuel and oxygen in a short time a screw 9 as shown in FIG. 3 may be provided in-the interior of the oxygen inlet tube for giving slow rotary motion to the flow of oxygen when entering into the combustion chamber, then it is more effective. When the combustion is effected under a severe condition there is tendency that the burner surface may be injured, then it is necessary to cool the parts 7, 8 and 9 by circulating cooling water through them.

The length of the combustion chamber should be sufficient to complete the combustion and depends on the speed of the flame and kind of gases. As the result of investigations made by the inventors about various fuels it has been ascertained that when the above nozzles are used the length of 100 to 250 mm. from the injecting surface of gases is suflicient.

The raw materials should be injected directly after the completion of combustion and under such condition that the mixing of the rawmaterials with the combustion gas can be completed in a short period. To this end, it is desirable to make the injection speed of raw material sufliciently high and to avoid the reverse flow of the raw material into the combustion chamber as far as possible. For this purpose, the injection openings of the raw material should be located at a portion 1 having a diameter smaller than that of the combustion chamber as shown in FIG. 1.

The above description shows the case when there is only one set of nozzles. A plurality of suitably distributed sets may be provided on the top cover of the combustion chamber, as illustrated in FIG. 4.

The invention will be explained by the following examples:

Example I .-Prpane fuel An apparatus as shown in FIG. 1, wherein the diameter of the combustion chamber is 70 mm., its length 165 mm., the diameter of the portion 1' where the raw materials are injected is 35 mm., and the diameter of the ring for flowing oxygen is 43.5 mm., that of flowing propane fuel 50.5 mm., the width of the annular nozzle for oxygen 1.5 mm., for fuel 1.0 mm. and the angle of intersection of two nozzles is 60, was used, and oxygen was supplied at the rate of 1.79 Nm. /min., the propane fuel at the rate of 0.358 Nm. /min., raw material naphtha 1.67 kg./min., water vapour supplied together with the raw material at the rate of 1.0 Nmfi/ min. and these substances were reacted and the composition of gases after the reaction consisted of CO 13.33%, C H 8.35%, C H 9.50%, CO 25.8%, H 32.76%, CH,

4 10.26%, and yield of C H +C H was 46.3%. All of the fed gases were preheated to 200 C.

Example 2.Propane-hydr0gen fuels With the same apparatus as in Example 1, the breadth of injection nozzle of fuel was adjusted to 1.5 mm. and the reaction was carried out. The quantities of gaseous flows were as follows:

Oxygen 1.434 Nrn. /min., hydrogen 1.673 Nm. /min., propane 0.1195 Nm. /min., raw material naphtha 1.34 kg./rnln., and water vapour 1.0 Nm. /min., all gases were preheated to a temperature of 200 C. The cornposi= tions of gases after the rea etion were CO; 6.03%, 11 10.49%, 62H. 9.63%, co 17.90%, H 46.14%, CH4 9.88% and yield of C H +C H was 51.9%.

Example 3.-Gases after reaction used as fuels With the same apparatus as in Example 1, a screw 9 as shown in FIG. 3 was used for the injection of oxygen to give rotary motion to the gas. The quantity of flow of each gas was as follows:

Oxygen 1.33 Nm. /min., fuel 2.33 Nm. /min., raw material naphtha 1.443 kg./min., water vapour 0.23 kg./

'min., and all gases were preheated to 250 C. The composition of gases after reaction were as follows:

CO 33.0%, CH, 5.61%, CO 11.38%, C H 10.35%, C H 3.91% and H 35.5%.

As a fuel use is made of the above gas by eliminating c02 C2H4 CZHZ, of C2H2+C2H4 was 46.38%.

What we claim is:

An apparatus for the flame decomposition of hydrocarbons, which comprises a combustion chamber for receiving oxygen containing gas and fuel, at least one set of concentric annular nozzles for separate introduction of said oxygen and fuel, said nozzles opening directly into said combustion chamber and forming with each other an angle of 40 to 2. reaction chamber communicating with said combustion chamber, and an inlet portion for the raw material hydrocarbons provided between said two chambers and having a diameter smaller than that of the said combustion and reaction chamber, said nozzles being formed by a stationary cylindrical outer wall member and movable members to adjust independently the width of each of the nozzle openings.

References Cited by the Examiner UNITED STATES PATENTS 1,517,183 11/1924 Waldron 239-417 X 2,219,119 10/1940 Schumann et al. 239-417 X 2,789,148 4/1957 Schutte 260679 X 2,945,074 7/1960 Elliott et a1. 260679 2,985,698 5/1961 Pechtold et a1. 260683 3,052,288 9/1962 Greco 48-196 3,055,957 9/ 1962 Braconier et al 260679 3,176,046 3/ 1965 Kondo et al. 260679 ALPHONSO D. SULLIVAN, Primary Examiner.

JOSEPH R. LIBERMAN, PAUL M. COUGHLAN,

Examiners.

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