US3270077A

US3270077A - Process for the production of acetylene-and ethylene-containing gases by the incomplete combustion of liquid hydrocarbons

Info

Publication number: US3270077A
Application number: US249014A
Authority: US
Inventors: Tsutsumi Shigeru; Nagao Shiro; Ohashi Kumao
Original assignee: Toa Kagaku Kogyo KK
Current assignee: Toa Kagaku Kogyo KK
Priority date: 1962-01-08
Filing date: 1963-01-02
Publication date: 1966-08-30
Anticipated expiration: 1983-08-30
Also published as: BE626824A; DE1468731A1

Description

Aug. 30, 1966 SHIGERU TSUTSUMI ETAL 3,270,077

PROCESS FOR THE PRODUCTION OF ACETYLENE-AND ETHYLENE-CONTAINING GASES BY THE INCOMPLETE COMBUSTION OF LIQUID HYDROCARBONS Filed Jan. 2, 1963 SmGERu TsuT sumo NAGA qhd KUMAO OHASHI IN VENTOR5 E Say- 41 United States Patent PROCESS FUR THE PRODUCTION OF ACE'IYLENE- AND lETHYLENE-CONTAINING GASES BY THE INCOMPLETE (ZOMBUSTION 0F LIQUID IIY- DRUCARBQNS @lrigeru Tsutsurni, Hirakata-shi, Osaka-fir, Shir-o Nagao, fialrai-shi, Osaka-fa, and Kumao Uhashi, I-Iigashi-ku, Nagoya-shi, Japan; said 'Isutsumi 'assignor to Toa Isiagaku Kogyo Kabushiki Kaislia, Tokyo, Japan Filed Ian. 2, I963, Ser. No. 24?,014 Claims priority, application Japan, Jan. 8, 1962, 37/256, 37/257;1Feb. 27, 1962, 37/6341, 37/6,942 7 Claims. (Cl. 26t)679) This invention relates to a process for the production of unsaturated hydrocarbons and particularly of acetylene and ethylene by the thermal cracking of liquid hydrocarbons.

Hitherto, various processes have been known for the production of acetylene and/ or ethylene by the thermal cracking of the hydrocarbons. These known processes include a partial combustion method wherein a part of hydrocarbons to be cracked is burned with an insufficient amount of oxygen in order to crack the remaining part of the hydrocarbons as well as a complete combustion method wherein the entire quantity of hydrocarbons to be cracked is decomposed by subjection to a higher temperature which is produced by burning other fuel gases. Both of the above methods supply the hydrocarbons to be cracked with the maximum permissible amount of heat energy during a short time interval and recover the available cracking products while preventing the over-cracking of them.

As a result of our researches on the thermal cracking of hydrocarbons under reduced pressure, we have previously discovered that the thermal cracking of hydrocarbons under reduced pressure is much more favourable for the production of acetylene and ethylene than cracking conducted under an ordinary or elevated pressure. Based on this discovery, We have previously developed many processes in this field of technique as be disclosed in Japanese patent publication Nos. 3,479/61, 3,471/61, 3,472/61, 3,473/61 and 3,474/61.

On the basis of the above-mentioned processes we have previously developed, we have recently begun to make a fundamental study in order to obtain a commercial process which is suitable for the production of acetylene and ethylene by the partial combustion of liquid hydrocarbons under reduced pressure. As a result of research concerning fundamental matters relating to the design of the cracking furnace'and the operating conditions thereof to obtain increased yields for the thermal cracking of liquid hydrocarbons, we have now found that the total yield of acetylene and ethylene may be considerably improved when a first refractory reaction chamber of a relatively smaller volume is placed directly above a second refractory reaction chamber of a relatively larger volume in such a way that these two reaction chambers communicate directly with each other and when vaporized hydrocarbons are partially burned with substantially pure oxygen in the upper or first reaction chamber without the usual pre-mixing of the hydrocarbons With the oxygen. We have further investigated the operating conditions and have found that a stable partial combustion of hydro- 3,273,077 Fatented August 30, 1966 carbons may be maintained under subatmospheric pressure in the two reaction chambers.

According to the invention, there is provided a process for the production of acetyleneand ethylene-containing gases by the incomplete combustion of liquid hydrocarbons, which comprises vaporising the liquid hydrocarbons, introducing the vaporised hydrocarbons and oxygen separately, namely without pre-mixing of the hydrocarbons with the oxygen, into a first refractory reaction chamber of a relatively small cross-sectional area which is mounted directly on top of a second refractory reaction chamber of a relatively large cross-sectional area in such a way that these first and second reaction chambers communicate directly with each other, the combustion flame being formed at that point in the first reaction chamber at which the vaporised hydrocarbons and oxygen are simultaneously introduced into said chamber, and maintaining the average total retention time of the gaseous cracking products Within the reaction chambers at a duration not exceeding 0.2 second and keeping the pressure prevailing in the second reaction chamber at a value not exceeding 460 mm. Hg absolute. This pressure of 460 mm. Hg absolute, of course, means the pressure which is determined on the basis of Torricellian vacuum.

As distinguished from the present invention, it is generally conventional in the prior art that the fuel gas and oxidant shall have been previously mixed together in a separate pre-mixing chamber before introduction into the combustion chamber. The combustion of the fuel gas pre-mixed with the oxidant however, usually requires the use of a special burner and involves such risks that, in the event of incomplete combustion of methane and other hydrocarbons with the oxygen, unless the pressure and flow velocity of the mixture of the fuel and oxygen are kept constant, the flame of the combustion of the fuel gas may backfire into the pre-rnixing chamber, resulting in a considerable reduction in the total yield of acetylene and ethylene and possibly even in a break-down of the burner employed.

The present invention is essentially characterized in that the partial combustion is carried out in a furnace having the aforesaid special construction under the specific operating conditions and without any pre-mixing of the vaporised hydrocarbons with the oxygen prior to combustion. In this way, the process of this invention not only avoids the above-mentioned drawbacks and risks but also provides a significantly higher total yield of acetylene and ethylene which is not obtained by the pre-mixing of the prior art. This is probably due to the synergistic effect which is involved in the process of the invention. The process of the invention is particularly suitable for the production of acetylene and ethylene and readily increases the total yield of these products to 40-45% by weight of the hydrocarbons introduced.

As to the construction of the cracking furnace used in the process of the invention, a first reaction chamber of a relatively small cross-section area is vertically aligned immediately above a second reaction chamber of a relatively large cross-section area in such a way that they communicate directly with each other. The reason for the employment of the cracking furnace of this vertical type through which the gas stream. passes downward according to the invention is that the total yield of acetylene 6 and ethylene is higher and the removal of carbon deposit can be much more easily effected in such a vertical furnace than in a horizontal one. The removal of carbon deposit is one of the important problems in a thermal cracker for commercial use.

The process of the invention will be described below with reference to the accompanying drawing which shows diagrammatically a sectional view in elevation of one embodiment of the cracking furnace suitable for carrying out the process of the invention.

Referring to the drawing, the cracking furnace shown is provided with the surrounding layers of refractory materials and mainly comprises a conduit for the supply of the vaporised hydrocarbons 1, a conduit for the supply of the oxygen 2, a pipe for the introduction of the vaporised hydrocarbons 3, a pipe for the introduction of the oxygen 4, a hole for insertion of a pilot burner 5, a first reaction chamber 6, a second reaction chamber 7 and a cooling chamber for the gaseous cracking products 8, the longitudinal axes of conduits 1 and 2 intersecting each other downwardly convergently in the shape of the letter V in the upper part of the first reaction chamber 1. The intersecting angle a of the conduits 1 and 2 shown may be any angle in the vicinity of 90. In order to check whether the flame of the combustion of the hydrocarbons is formed at the point of mixing of the hydrocarbons and oxygen in the first reaction chamber in the course of the cracking reaction, the pipe for the introduction of oxygen 4 is provided with an observation window 9 which may be formed from a heat-resistant glass plate.

The first reaction or cracking chamber 6 represents that portion of the furnace which is in the shape of a long and narrow cylinder extending between a and b. The second reaction chamber 7 represents that portion of the furnace which is in the shape of a frustum of a cone extending between b and c. The angle [3 formed at the apex of the cone may preferably be between 6 and 20. The first reaction chamber 6 is particularly exposed to higher temperatures during the cracking reaction, and therefore the wall 10 of this chamber is made from a highly refractory material such as zirconia and the like. The outside of the chamber wall 10 is further covered by a refractory aluminous layer 11 in order to effect the heatinsulation of the furnace. The second reaction chamber 7 is also exposed to elevated temperatures but relatively lower than the first reaction chamber 6, and therefore the wall 12 of the second reaction chamber may be made from a highly aluminous material. The outside of the second reaction chamber wall 12 is further covered by a refractory layer 13 in a suitable manner similarly to the first reaction chamber 6 in order to effect the heat-insulation of the furnace.

The bottom of the. refractory material layers surrounding the two reaction chambers are supported on a supporting member 14 fitted with a water-cooled jacket which is cooled by passing the cooling water therethrough from an inlet 15 to an outlet 16.

The wall of cooling chamber 8 is made of a metal and protected from higher temperatures by being wetted with the cooling water which is fed through an annular conduit 17 and perforations 18.

The cracking reaction of the hydrocarbons is carried out in the following way: liquid hydrocarbons to be cracked are first vaporised and the vaporised hydrocarbons which may have been properly pre-heated and, if desired, added with a quantity of steam are then supplied through the pipe 3 into the first reaction chamber 6. At the same time, oxygen is supplied through the pipe 4 separately into the first reaction chamber 6. The vaporised hydrocarbons and oxygen are ignited by means of a pilot burner which may be inserted through the hole 5, so that the flame is formed at the point of mixing of said gases within the first reaction chamber 6. Substantially all of the hydrocarbons supplied can be cracked at higher temperatures and for an extremely short time within the first reaction chamber 6. The gaseous cracking products formed therein and unreacted hydrocarbons are subsequently passed down into the second reaction chamber 7 which is kept at relatively lower temperature of order of 600-l000 C. The reaction for the formation of acetylene and ethylene is substantially completed in this second reaction chamber 7. The gaseous cracking products are further passed down into the cooling chamber 8 and then recovered therethrough.

It may be regarded that the first and second reaction chambers used according to this invention are corresponding to the mixing chamber and the combustion chamber according to the prior art, respectively. According to the process of the invention, however, it is essential that the cracking reaction of the hydrocarbons should be carried out in such a way that the flame is formed in the interior of the first reaction chamber while the vaporised hydrocarbons and oxygen are introduced into this chamber without premixing of them. The temperature prevailing in the first reaction chamber and the retention time of the gaseous cracking products within the first reaction chamber have a large influence on the total yield of acetylene and ethylene and particularly on the yield of acetylene. In the thermal cracking, it is necessary to take such measure to insure that the cross-section area of the first reaction chamber may be reduced as small as possible in order to keep the inevitable loss of heat due to the radiation as low as possible and also that a large amount of heat energy may be fed to the reactants for a very short time while preventing the over-cracking of the useful gaseous cracking products. For this purpose, it is also necessary to relevantly select the dimensions and shapes of the first and second reaction chambers in which the retention time of the gaseous cracking products in the furnace and the pressure prevailing in the furnace can be stably maintained at their optimum values.

According to the invention, the configuration of the transverse cross-section of the first reaction chamber may be either circular or triangular, quadrangular or other proper polygonal. The first reaction chamber may be also in the form of a slightly tapered tube. In any case, however, it is essential to the invention that the crosssection area of the first reaction chamber should be smaller than that of the second.

As to the second reaction chamber 7, this chamber is primarily provided in order to complete the cracking reaction which has not been yet completed in the first reaction chamber 6. The second reaction chamber 7 may be generally maintained at temperatures of 600- 1000 C. as it is influenced by the highly endothermic reaction of formation of acetylene which takes place more vigorously than in the lower part of the first reaction chamber 6.

It is necessary that the retention time of the gaseous cracking products in the second reaction chamber should be substantially about 10-1000 times longer than that in the first reaction chamber and that the second reaction chamber should have a capacity enough to permit such a longer retention time of the cracking products to be obtained therein. The second reaction chamber may be in the shape of frustum of a cone as shown in the accompanying drawing or may be properly polygonal in the configuration of its transverse cross-section. It is preferable, however, that the second reaction chamber has such a structure the transverse cross-section area of which gradually increases downwards, in order to reduce the resistance of the gases flowing therethrough and facilitate the removal of carbon deposit. For this reason, it is appropriate that the first reaction chamber is e.g. in the shape of a cylinder While the second reaction chamber is substantially in the shape of a frustum of a cone. It is most preferable for the second reaction chamber to have the shape of a frustum of such a cone which forms an angle 5 of 6-20 at the apex thereof. In general, this apex angle has a large influence on the total yield of acetylene and ethylene as well as on the consumption of oxygen. With an apex angle of more than 20, it has been found that a part of the gaseous cracking products flows in whirls and there is involved the formation of carbon deposit, resulting in an increase in the unfavourable tendency to reduce the yield of acetylene and the effective consumption of oxygen. With an apex angle of less than 6, on the other hand, it has been found that the process becomes disadvantageous from the view-point of economy not only because the quantity of uncracked hydrocarbons is increased involving a reduction in the total yield of acetylene and ethylene but also because the operation can be largely adversely affected by a small amount of carbon deposit.

According to a preferred embodiment of the invention, the second reaction chamber is substantially in the shape of a frustum of such a cone which forms an angle of 6-20 at the apex. It is not necessary, however, that the second reaction chamber is exactly in the shape of a frustum of such a cone. The second reaction chamber in the shape of a frustum of a polygonal pyramid initially may be used, since the chamber in this shape becomes the chamber substantially having the shape of a frustum of a cone due to the wearing of the refractory material of the chamber wall which occurs during the service of the furnace.

According to another embodiment of the invention, the second reaction chamber also may have such a construction that the upper part of this chamber is substantially in the shape of a frustum of a cone but the lower part of said chamber, namely that portion of said chamber near to the cooling chamber is substantially in the shape of a cylinder as shown in the accompanying drawing. According to a further embodiment of the invention, the second reaction chamber also may have such a construction that the cross-section area of the lower end of this chamber is somewhat constricted downwards. It is also possible that the lower extremity of the second reaction chamber is provided with such a means which is able to prevent the heat radiations from taking place from the reaction chambers to the cooling chamber in order to keep the interior of the second reaction chamber at higher temperatures.

The first and second reaction chambers should be formed from refractory materials so that the heat loss of the furnace due to radiation may be reduced and the temperatures prevailing in the furnace may be kept high enough to carry out the thermal cracking of hydrocarbons and give a higher total yield of acetylene and ethylene.

The refractory materials available for building the reaction chambers of the cracking furnace used in the process of the invention include special refractory bricks of titania, zi-rconia .and/ or alumina. However, it is necessary to carefully select the refractory material used because the first reaction chamber and particularly the upper part thereof near to the conduits for the introduction of the vaporised hydrocarbons and oxygen can be exposed to higher temperature of 2000 C. or above. While, the second reaction chamber may be built up in practice by a refractory material which is able to be resistant to higher temperature of about 1000 C.

Any of hydrocarbons which are liquid at normal temperature may be used in the process of the present invention but the use of extremely high boiling point hydrocarbons is not preferred since it is necessary to vaporise them before introducing them into the cracking furnace. It is appropriate that the hydrocarbons used have a dry point of 70180 C., a higher content of paraffins and lower contents of naphthenes and olefins. The use of a hydrocarbon fraction mainly consisting of straight chain hydrocarbons of 6-11 carbon atoms is preferred. It is desirable that the oxygen used for the partial combustion of the hydrocarbons be of a high purity. However, the

oxygen is permitted to contain a small quantity of an inert gas such as nitrogen etc.

The vaporised hydrocarbons to be cracked and oxygen may be properly pre-heated, if desired, before their supply to the first reaction chamber. In order to improve the total yield of acetylene and ethylene, it is effective to preheat the hydrocarbons to be cracked to C.-500 C. and particularly to about 400 C.

According to further embodiments of the invention, a quantity of steam may be added to the vaporised hydrocarbons to be cracked and/ or the oxygen. In any case, it is necessary that the quantity of steam added should be up to 30% by weight of the hydrocarbons fed. The quantity of steam added may preferably be in the range of 1025% by weight. When the quantity of steam added is less than 5% 'by weight of the hydrocarbons, the effect of the addition of steam is negligible. When the quantity of steam added is more than 30% by weight of the hydrocarbons, the yield of the useful cracking products is reduced although the deposit of carbon may be suppressed.

The addition of a quantity of steam to the vaporised hydrocarbons to be cracked and/ or the oxygen substantially prevents the over-cracking of acetylene and the deposit of carbon, so that the cracking furnace may be run for a long period of time. When a quantity of steam is added to the oxygen, the yield of acetylene is somewhat reduced but the yield of ethylene may be considerably enhanced. When a quantity of steam is added to the hydrocarbons to be cracked, the yield of acetylene remains substantially unchanged. When the steam is added to both the hydrocarbons and oxygen, the yield of ethylene may be increased.

The vaporised hydrocarbons to be cracked and oxygen which, if desired, may have properly pro-heated and/or added with a quantity of steam, are then separately introduced into the first reaction chamber through their introduction pipes and supply conduits which may intersect in the shape of the letter V as shown in the drawing. According to further embodiments of the invention, it is also possible to arrange that the hydrocarbons are introduced through both the conduits 1 and 2 of the accompanying drawing and the oxygen through the conduit 5 of the drawing. In the latter case, of course, it becomes necessary to provide a hole for the insertion of the pilot burner elsewhere in the furnace.

According to a further embodiment of the invention, it is possible to feed a part of the vaporised hydrocarbons to be cracked supplementally into a zone at or near to the tip of the flame formed in the first reaction chamber through a tube (not shown) which is provided in the side wall of the second reaction chamber. The part of the hydrocarbons supplementally introduced in this way may be the same as or different from the hydrocarbons which are supplied through the main supply conduit into the first reaction chamber.

In general, it is necessary that the ratio by weight of the oxygen to the hydrocarbons supplied in the furnace should be properly varied depending on the operating conditions of the furnace, the composition of the gaseous cracking products desired and other considerations. In order to obtain a maximum total yield of acetylene and ethylene, it ispreferable to keep said ratio in a range of 0.50.8. When the cracked gases rich in ethylene are to be produced, this object generally may be achieved by adjusting said ratio in a range of 0.4-0.7. On the other hand, when the cracked gases rich in acetylene are to be produced, it is generally desired to adjust said ratio in a range of 0.6-1.0.

As stated above, the process of the invention is essentially characterized in that the vaporised hydrocarbons to be cracked and oxygen are separately introduced into the first reaction chamber without pre-mixing of them and that the hydrocarbons are ignited to form the flame at that point in the first reaction chamber at which the hydrocarbons and oxygen are introduced into this chamber. As a result of our research, it has been found that the flame can be formed at said introduction point, if the flow velocity of the gases is kept at a value of up to 100 m./scc. within the first reaction chamber. In general, however, the formation of the flame at said introduction point is largely influenced by the ratio of the oxygen to the hydrocarbons, the degree of pre-heating of the starting materials, the temperature and pressure prevailing in the reaction chambers, the dimensions and shapes of the reaction chambers and the sort of the refractory materials used. Even when the flow velocity of the gases is higher than 100 m./sec. a stabilised flame can be maintained in the first reaction chamber if the above-mentioned factors are appropriately combined.

According to the invention, it is necessary that the average total retention time of the gaseous cracking products in the first and second reaction chambers should not exceed 0.2 second. This average retention time is calculated on the basis of the volume of the gaseous cracking products which are at a temperature of 800 C. and under the pressure prevailing in the cracking furnace. It is particularly desirable that the average retention time is in a range of 0.05-0.005 second.

It is to be appreciated that the above-mentioned average retention time does means the time of the gaseous cracking products staying in both the first and second reaction chambers. In this connection, it is necessary that the retention time in the first reaction chamber should be in a range of one-tenth to one-thousandth of said average total retention time of the cracking products in the first and second reaction chambers. In this Way, the gaseous cracking products may be exposed to very much higher temperatures for an extremely short time in the first reaction chamber, so that the reaction for the formation of acetylene and ethylene can advantageously proceed and the acetylene once produced may be re covered smoothly without being subjected to the overcracking.

The cracking reaction of the vaporised hydrocarbons involves an increase in the volumes of the gases, and it is theoretically advantageous that the partial pressures of acetylene and ethylene produced are reduced. In accordance with the invention, the pressure prevailing in the second reaction chamber should be substantially up to 460 mm. Hg absolute. However, an extreme reduction in the prevailing pressure is not economic in practice due to an increase in the power cost required therefor, although it is favorable for the total yield of acetylene and ethylene. If the pressure prevailing in the second reaction chamber is higher than 460 rrnn. Hg. absolute, there are increased unfavourable tendencies to form the carbon deposit and reduce the total yield of acetylene and ethylene.

In accordance with the process of the invention, the portion of the furnace heated to very much higher temperatures is limited to a small area and the temperature of the gases leaving the furnace is relatively lower, so that particular water-quenching of the gaseous cracking products is not necessary. Of course, however, it is possible to quench the cracking products by spraying water and/ or flowing over water-film, if desired. That is to say, a cooling chamber of any type may be employed in the process of the invention.

Thus, the process of the invention is advantageous for the effective production of acetylene and ethylene over the processes of the prior art.

Furthermore, the by-product gases formed in the process of the invention are rich in hydrogen and carbon monoxide, and they are suitable for use in the synthesis of methanol. Accordingly, the process of the invention may advantageously be combined with a process for the synthesis of methanol.

The process of the invention will be now illustrated with reference to the following examples.

8 EXAMPLE 1 A cnacking furnace as shown in the accompanying drawing is employed. 45 l./hour of liquid hydrocarbons which have been obtained from a crude petroleum oil from Kuwait are vaporised and pre-heated to 225 C. and then introduced into the first reaction chamber of the furnace. At the same time, 23.26 kg./hour of oxygen are introduced separately into the same reaction chamber to partially combust the hydrocarbons in the first reaction chamber. The reaction for the formation of acetylene and ethylene takes place. For comparison, the position of the point where the flame is formed is transferred out of the first reaction chamber into the second reaction chamber by varying the supply rates and temperatures of the vaporised hydrocarbons and oxygen. The results obtained are tabulated in Table I below. As will be clear from Table I below, it has been found that the yield of acetylene is remarkably increased when the flame is formed at that point in the first reaction chamber at which the hydrocarbons and oxygen are introduced into this chamber.

The dimensions of the cracking furnace used in this example are as follows: The intersecting angle a formed between the conduit for the supply of the vaporised hydrocarbons 1 and the conduit for the supply of oxygen 2 as shown in the accompanying drawing is The first reaction chamber is in the shape of a cylinder of 240 mm. in the length and 25 mm. in the inner diameter. The second reaction chamber is substantially in the shape of a frustum of a cone having an apex angle 3 of 12.5". The inner diameter of this frustum is 25 mm. at the upper end and mm. at the lower end. The height of this frusturn is 740 mm. The conduits for the supply of the hydrocarbons and oxygen are 27 mm. in their inner diameters. In order to determine the pressure prevailing in the second reaction chamber, there is arranged a pressure gauge aperture (not shown) in the chamber wall located midway between the top and bottom of the second reaction chamber.

Table I Flame formed Flame formed in the first reaein the second tion chamber reaction according to chamber the invention (comparative) Ratio oxygen/hydrocarbons, by weight. 0. 767 O. 767 Pressure in mm. Hg absolute 200 200 Retention time in sec 0.033 0. 033 Concentration of acetylene in vol.

percent. 10. 1 7. 4 Concentration of ethylene in vol. percent 8. 6 6.0 Gasification rate in NM per litre of liquid hydrocarbons 1. 20 1. 22 Yield of acetylene in percent by weight 20. 0 15. 5 Yield of ethylene in percent by weight. 19. 1 13. 6 Total yield of acetylene and ethylene 40. 0 29. 1

When the flame is formed in the first reaction chamber, the gaseous cracking products show the following composition.

The process of Example 1 is repeated in the same way except that 70 l./hour of liquid hydrocarbons of specific gravity of 0.674 are supplied in the vapor phase into the first reaction chamber of the furnace with a ratio of oxygen/hydrocarbon of 0.7 and the cracking reaction is carried out under such diiferent pressures as set out in Table III below.

The results obtained are tabulated in Table III. From these results, it appears that the total yield of acetylene and ethylene is much increased as the pressure is reduced.

Table III Example No 2 3 4 l 5 6 I 7 Reaction pressure in mm. Hg absolute 460 420 380 320 260 200 Retention time in sec 0.080 Concentration of acetylene 8.4 8 .4 8 .5 8. 8.6 8 .5 Concentration of ethylene in vol. percent.-- 8.6 8 .7 9.2 9. 10.6 11 .9 Yield of acetylene in percent by weight 14.5 14.6 .0 15. 15 .8 16.2 Yield of ethylene in percent by weight". 16.0 16.3 17 .5 18. 21.0 24.6 Total yield of acetylene and ethylene 30.5 30.9 32.5 34. 36.8 .8 Gasification rate in N M /l. of liquid hydrocarbons 1 .005

EXAMPLES 8-12 The process of Example 1 is repeated in the same way except that an oxygen/hydrocarbon ratio of 0.7 is employed and the average retention time of the gaseous cracking products in the furnace is varied with-in a range tion for the formation of acetylene and ethylene. In this process, the hydrocarbons and/or oxygen fed are added with steam in a quantity of 16.5% by weight of the hydrocarbons. The results obtained are shown in Table V below.

Table V Example No 13 14 15 Steam is added to Oxygen Hydrocarbons Oxygen and hydrocarbon Ratio oxygen/hydrocarbons 0.70 0.70 0.70 Pressure in mm. Hg absolute. 200 200 200 Retention time in sec 0.026 0.026 0.026 Concentration of acetylene in vol. percent 7. 9 8. 5 7. 8 Concentration of ethylene in vol. perceut 12. 8 12.0 13.0 Yield of acetylene in percent by weight- 15. 1 16. 2 14. 9 Yield of ethylene in percent by weight 26. 3 24. 7 26. 8 Total yield of acetylene and ethylene 41. 4 40. 9 41. 7 Gasification rate in N M per litre of liquid hydrocarbons 1. 10 1. 10 1. 11

EXAMPLE 16 of 0.020.2 second by changing the rate of supply of the hydrocarbons. The results obtained are tabulated in Table IV below.

The process of Example 14 is repeated in the same Way except that the ratio of oxygen/hydrocanbons fed is Table IV ample No 8 l 9 10 11 12 Supplied rate of hydrocarbons in 1./hour 80 33 18 9 .5 Retention time in sec 0 02 0 03 0.05 0.1 0.2 React-ion pressure in mm. Hg absolute." 200 Concentration of acetylene in vol. percent. 8 .8 8.6 8.3 7 .8 6.9 Concentration of ethylene in vol. percent. 11.9 11.8 11.7 10.9 9 .3 Yield of acetylene in percent by weight. 16 .7 1G .3 15 .6 14.6 12.6 Yield of ethylene in percent by weight 24.3 24.1 23 .8 21.9 18 .3 Total yield of acetylene and ethylene 41.0 40.4 39 .4 36.5 30.9 Ggsifieation rate in NM /l. of liquid hydrocar- 1 10 ons In the above Examples 1-9, it is observed that the temperature is about 2000 C. in the upper part of the first reaction chamber and about 1000-1500 C. in the lower part and that the temperature is 800-900 C. in the middle part of the second reaction chamber.

varied within a range of 0.65-0.90 by properly changing the supplied rate of oxygen while keeping the supplied rate of the hydrocarbons constant. The carbon balance between the starting hydrocarbons and the gaseous cracking products is calculated from the experimental data.

meters of mercury, absolute; withdrawing the combustion products from the bottom of said second zone; cooling said combustion products; and obtaining from the cooled combustion products a gaseous mixture containing acetylene and ethylene.

Table VI Ratio of oxygen/hydrocarbons 0. 0. 0. 0. 0. 0. Carbon balance in percent by weight 93. 6 92. 9 92. 4 91. 9 91. 4 91. 0

The definition of the carbon balance is given by the following equation:

Sum of carbon contents of C H C H C0, C0 and CH present in the gaseous cracking products Sum of carbon contents in the starting hydrocarbons What we claim is:

1. A process of the class described, comprising the steps of: vaporizing and preheating a mixture of normally liquid hydrocarbons to form a supply of a first gaseous reactant; providing substantially pure oxygen to form a supply of a second gaseous reactant; separately introducing said supplies of reactants into a first combustion zone; igniting said supplies of reactants within said first zone to form a sustained flame therein; confining said reactants in a generally cylindrical configuration open at its lower end and having a vertical axis, said configuration preventing upward and lateral movement of said reactants out of said first zone; maintaining a temperature in the upper portion of said first zone which is of the order of 2,000" C. and of the order from 1,000 C. to 1,500 C. in the lower portion thereof; guiding said reactants downwardly directly from said first zone into a second combustion zone; confining said reactants laterally in said second zone in a downwardly divergent frusto-eonical configuration open at both ends and coaxial with said cylindrical configuration, said frusto-conical configuration having an apex angle in the range from 6 to 20 degrees, the upper base of said frustoconical configuration being coextensive with the bottom of said cylindrical configuration; introducing said reactants into said first zone at a flow rate providing a total retention time for said reactants in said two zones of from 20 to 200 milliseconds; maintaining a temperature in the central portion of said second zone in the range from 600 C. to 1,000 C.; maintaining a pressure in said second zone in the range from 200 to 400 milli- X =carbon balance percent 2. The process according to claim 1, in which said hydrocarbons consist essentially of straight chain hydrocarbons having from 6 to 11 carbon atoms.

3. The process according to claim 2 wherein said oxygen and said hydrocarbons are separately introduced into said first combustion zone at rates which provide a weight ratio of oxygen to hydrocarbons in the range from 0.5 to 0.8 for said reactants prior to combustion.

4. The process according to claim 1, wherein said supplies of reactants are separately introduced into said first combustion zone in convergent streams which intersect at the axis of said cylindrical configuration.

5. The process according to claim 1, in which said gaseous mixture obtained from said cooled combustion products contains acetylene and ethylene in substantially equimolar amounts.

6. The process of claim 1, comprising the further step of introducing a supply of steam into said first combustion zone with said supplies of reactants.

7. The process according to claim 6, wherein said steam is introduced at a rate which provides a ratio of steam to hydrocarbons in the range from 10% to 25% by weight.

References Cited by the Examiner UNITED STATES PATENTS 7/1960 'Elliott et a1. 260679 5/1961 Pechtold ct al. 260679 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,270,077 August 30, 1966 Shigeru Tsutsumi et a1.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below In the heading to the printed specification, lines 8 and for "said Tsutsumi assignor to Toa Kagaku Kogyo Kabushiki Kaisha," read said Ohashi assignor to Toa Gosei Kagaku Kogyo Kabushiki Kaisha,

Signed and sealed this 1st day of August 1967.

(SEAL) Attest:

EDWARD M. FLETCHER, JR. EDWARD J. BRENNER Attesting Officer Commissioner of Patents

Claims

1. A PROCESS OF THE CLASS DESCRIBED, COMPRISING THE STEPS OF: VAPORIZING AND PREHEATING A MIXTURE OF NORMALLY LIQUID HYDROCARBONS TO FORM A SUPPLY OF A FIRST GASEOUS REACTANT; PROVIDING SUBSTANTIALLY PURE OXYGEN TO FORM A SUPPLY OF A SECOND GASEOUS REACTANT; SEPARATELY INTRODUCING SAID SUPPLIES OF REACTANTS INTO A FIRST COMBUSTION ZONE; IGNITING SAID SUPPLIES OF REACTANTS WITHIN SAID FIRST ZONE TO FORM A SUSTAINED FLAME THEREIN; CONFINING SAID REACTANTS IN A GENERALLY CYLINDRICAL COFIGURATION OPEN AT ITS LOWER END AND HAVING A VERTICAL AXIS, SAID CONFIGURATION PREVENTING UPWARD AND LATERAL MOVEMENT OF SAID REACTANTS OUT OF SAID FIRST ZONE; MAINTAINING A TEMPERATURE IN THE UPPER PORTION OF SAID FIRST ZONE WHICH IS OF THE ORDER OF 2,000*C. AND OF THE ORDER FROM 1,000*C. TO 1,500*C. IN THE LOWER PORTION THEREOF; GUIDING SAID REACTANTS DOWNWARDLY DIRECTLY FROM SAID FIRST ZONE INTO A SECOND COMBUSTION ZONE; CONFINING SAID REACTANTS LATERALLY IN SAID SECOND ZONE IN A DOWNWARDLY DIVERGENT FRUSTO-CONICAL CONFIGURATION OPEN AT BOTH ENDS