US2195227A - Production of acetylene - Google Patents

Description

March 26, 1940. s c ssz 2,195,227

PRODUCTION OFACETYLENE Filed March 4, 1937 Hans Sachss e INVENTOR QQ a.

ms ATTORNEY Patented Mar. 26, 1940 PATENT OFFICE PRODUCTION OF ACETYIENE Hans Sachsse, Mannheim, Germany,

assignor to I. G. Farbenindustrle Akticngesellschaft, Franhfort-on-the-Main, Germany Application March 4, 1937, Serial No. 128,957 In Germany March 6, 1936 8 Claims.

This invention relates to the production of acetylene by incomplete combustion of hydrocarbons or gases containing the same.

It is already known that acetylene can be obtained by the incomplete combustion of slightly unsaturated or saturated hydrocarbons; for example up to 4.5 per cent of acetylene is obtained in the flnal gas when the combustion of methane with the aid of oxygen is allowed to proceed in 10 the form of an inverted flame. A mixture of oxygen and methane may also be charged through long, externally heated tubes at a gas speed exceeding the speed of the flame. In this arrangement, the reaction is caused by the hot walls of the tubes. In another process for the prepara- 'tion of acetylene by incompletecombustion of hydrocarbons, the ignition of the mixture, which again flows in this case at a gas speed exceeding the speed of the flame, is effected by obstacles introduced in the current of gas which cause whirling. At these places 01' reduced gas speed, an ignition takes place which is then'transmitted to the whole of the gas moving at a speed greater than the speed of the flame. I have now found that acetylene can be obtained by incomplete combustion of gaseous or vaporous hydrocarbons which are saturated or less saturated than acetylene or gas mixtures containing the same, in particular methane 80 and/or its homologues, mixed with oxygen, air

or other suitable gases at gas speeds which in thepath to the reaction zone are greater than, but in the reaction zone itself and behind the same are equal to or even smaller than, the speed of 36 the flame, thus causing the formation of a freely burning flame extending over the cross-section of the reaction vessel. The term freely burning flame means a flame which forms in the free space of the reaction vessel at a certain region 40 without external heating or without localization by means of obstacles. It is advisable to construct the reaction vessel in such a manner that the gases in all parts of it move progressively and that no regions occur in the reaction vessel in 45 which this progressive motion of the gases is essentially hindered, e. g. by the formation of Windless regions or of regions with prevailing eddying motion of the gases as they occur in the lee-side of obstacles in the flow of the gases. o Windless regions or regions with prevailing eddying motion often cause the periods within which single parts of the reaction mixture are present in the reaction zone to deviate considerably from the average reaction time and accordingly formation of soot or coke occurs. 1

The amount of the oxidizing gas is appreciably less than half the amount necessary for complete combustion, it is so chosen that incomplete combustion with the formation of a flame is secured without transfer of heat to the reaction zone 5 from other sources, except preheating the gases before entering the reaction zone.

A special advantage of this method of working consists in the fact that it permits of the maintenance of the flame by ignition in the gas cham- 10 her by reason of homogeneous transference of heat from the flame to the incoming fresh gas, i. e. by transference only within the gaseous mixture. It is not therefore necessary to use superheated walls in the form of narrow tubes or bu'nll dles of tubes for the purpose of ignition when carrying out the process and this is of advantage because the said walls favour the undesirable deposition of carbon in some cases.

When working in apparatus, in which the smallest diameter of the cross-section over which the flame is extending does not exceed about millimeters preferably care is to be taken that the flow of the gases is substantially non-turbulent, especially during the reaction, because with. 3| turbulent motion the formation of soot in such small apparatus can scarcely be avoided. In apparatus with greater diameter excellent results are obtained with turbulent as well as with nonturbulent flow of the gases. go

Simple apparatus for carrying out the process according to this invention are shown in the accompanying drawing, but the invention is not restricted to the apparatus shown.

Referring to Figure 1, A is a relatively narrow ,5 tube which is joined to a coaxial, wider tube B by a gradual transition. The mixture of the participants in the combustion flows through A at a speed exceeding the speed of the flame, while the cross-section of B is such that the gas speed 40 therein is less than the speed of the flame. 'At the portion of the conical portion between A and B at which the gas speed is equal to the speed of the flame, a quiet and stable flame burns extending over the whole cross-section of the said 5 conical portion. The relative proportions of the cross-sections of the narrow and wider portions of the tube may be varied within wide limits. For example proportions of from 1:4 to 1:12 may be successfully used. In some cases rectangular, o elliptical or other cross-sections may be used instead of a circular cross-section and the gas may be allowed to pass downwards through the combustion zone without impairing the yield.

In the apparatus shown in Figure 2 there are which end in long points. In this case also the flame burns in the portion at .which the free cross-section varies and in which the gas speed falls from a value above the speed of the flame to a value below the same.

Theposition of the flame in the widening may be regulated by'regulating the speed of the gas and the speed of the flame. The speed of the flame may be influenced by the oxygen content in the freshiasjhe increase of the same within the permissible mixture range effecting an increase in the speed of the flame; preheating of the fresh gas also effects a considerable increase in the speed of the flame. A special advantage of an increase in the speed of the flame produced by preheating consists in the fact that when using preheated gas a quietly burning flame may be maintained even with small oxygen contents, as for example with a ratio of CH4 to 02 of 1.7 and more, up to about 2.0. It is important that the preheating need not reach such temperatures as lead to spontaneous ignition of the reaction mixture. In this way it is possible to avoid overheating of the walls. A great variety of substances may be used as constructional'materials, as for example ceramic masses, quartz, poreclain or steels, as for example chromium steels.

Another suitable arrangement essentially consists. of a tube in which a sieve plate is inserted through which the gases are passed at a speed exceeding the speed of the flame; after leaving the sieve plate they enter the reaction space while extending over the whole cross-section of the tube and reducing their speed below that of the flame forming. Such a sieve plate may be built up from a bundle of small tubes cemented together; the ends of the small tubes at which the reaction mixture is leaving them are preferably somewhat widened in order to avoid the formation of essentially windless regions between the small tubes.

For the production of a high yield of acetylene it is preferable to chill the gases after they have left the reaction zone. This may be effected in known manner, as for example by spraying in liquids, such as water, by mixing with cold gases or also by cooled surfaces.

' The following examples will further illustrate the nature of this invention but the invention is not restricted to these examples. The percentages are by volume.

-' 9 Example 1 A gas mixture of 58.6 per cent of methane, 4 per cent of nitrogen and 37.4 per cent of oxygen preheated to 550 C. is burnt in the apparatus shown in the drawing in an amount of 250 liters per hour. The cross-section of the supply pipe is for example 0.25 square centimeter. The composition of the final gas obtained is 3 per cent of CO2, 8.2 per cent of C2H2, 0.7 per cent of 02, 23.4

per cent of CO, 55.4 per cent of H2, 6 per cent of CH4 and 3.3 per cent of N2. After condensation of the steam formed, the volume of the final gas measured under normal conditions is 18 per cent greater than that of the initial mixture.

Example 2 volume ascertained in the manner described in Example 1 is 20 per cent.

Example 3 A mixture of 65 per cent of methane and 35 per cent of oxygen preheated to 640 C. is burnt under the conditions specified in Example 1. The composition of the final gas obtained is: 3 per cent of CO2, 8.8 per cent of Cal-I2, 0.2 per cent of O2, 23 per cent of CO, 56 per cent of H2, 9 per cent of CH4. The increase of volume is 19 per cen Example 4 A mixture of 63 per cent of methane and 37 per cent of oxygen is led into a flre clay tube 4 centimeters in diameter in strongly whirling motion. The inlet tube is so narrow that the gas speed therein exceeds the speed of 'the flame; within the fire clay tube, in the contrary, it is below the speed of the flame. Therefore the flame, once ignited, is burning quietly. After leaving the reaction zone the gases are chilled by water sprayed therein. A gas is obtained consisting of 9 per cent of C2H2, 3.5 per cent of CO2, 24 per cent of CO, 56 per cent of Hz, 6.5 per cent of CH4 and 1 per cent of nitrogen. Its volume is about twice that of the methane introduced. Formation of soot can scarcely be detected and no coke is formed even after long periods of reaction.

Example 5 A mixture of 44 per cent of propane and 56 per cent of oxygen is converted in the apparatus used in Example 4. After chilling with water a gas is obtained which consists of 10 per cent of CzHz, 3.5 per cent of CO2, 27 per cent of CO, 52 per cent of Hz, 6.5 per cent of methane and 1 per cent of nitrogen. No coke is formed.

What I claim is:

1. A process for the production of acetylene by partial combustion of gases essentially comprising hydrocarbons which are not highly un saturated which comprises leading a mixture of such gases with the oxidizing gases in an amount appreciably less than one-half the amount necessary for complete combustion, to a reaction zone extending over the whole cross section of the reaction vessel at gas speeds which in the path leading to the reaction zone are greater than, but

in all parts of the reaction zone itself, and behind the same, are at most equal to, but not greater than the speed of the flame, thus causing the formation of a freely burning flame.

2. A process for the production of acetylene by partial combustion of gases essentially comprising at least one aliphatic saturated hydrocarbon which comprises leading a mixture of such gases with the oxidizing gases in an amount appreciably less than one-half the amount necessary for complete combustion, to a reaction zone extending over the whole cross section of the reaction vessel at gas speeds which in the path leading to the reaction zone are greater than, but in all parts of the reaction zone itself, and behind the same, are at the most equal to, but not greater than the speed of the flame, thus causing the formation of a freely burning flame.

3. The process for the production of acetylene by partial combustion of gases essentially consisting of methane which comprises leading a mixture of methane and oxygen in an amount appreciably less than one-half the amount necessary for complete combustion, to a reaction zone extending over the whole cross section of the reaction vessel at gas speeds which in the path leading to the reaction zone are greater than, but in all parts of the reaction zone itself, and behind the same, are at the most equal to, but not greater than, the speed of the flame, thus causing the formation of a freely burning flame.

4. A process for the production of acetylene by partial combustion of gases essentially comprising hydrocarbons which are not highly unsaturated which comprises leading a mixture of such gases with the oxidizing gases in an amount appreciably less than one-half the amount necessary for complete combustion, to a reaction zone extending over the whole cross section of the reaction vessel at gas speeds which in the path leading to the reaction zone are greater than, but in all parts of the reaction zone itself, and behind the same, are at most equal to, but not greater than the speed of the flame, thus causing the formation of a freely burning flame, and taking care than the flow of the gases is substantially non-turbulent.

5. A process for the production of acetylene by partial combustion of gases essentially consisting of hydrocarbons which are not highly unsaturated which comprises leading a mixture of such gases with oxidizing gases in an amount appreciably less than one-half the amount necessary. for complete combustion, to a reaction zone extending over the whole cross section of the reaction vessel at gas speeds which are greater than the speed of the flame while gradually expanding the gases over the entire section comprising the reaction zone, and providing for gas speeds in all parts of the reaction zone itself, and behind the same, which are at the most equal to, but not greater than the speed of the flame itself, thus causing the formation of a freely burning flame.

6. A process for the production of acetylene by partial combustion of gases essentiallyconsisting of hydrocarbons which are not highly unsaturated which comprises leading a preheated mixture of such gases with oxidizing gases in an amount appreciably less than half the amount necessary for complete combustion to a reaction zone extending over the whole cross section of the reaction vessel at gas speeds which in the path leading to the reaction zone are greater than, but in all parts of the reaction zone itself, and behind the same, are at the most equal to, but not greater than the speed of the flame, thus causing the formation of a freely burning flame.

7. A process for the production of acetylene by partial combustion of gases essentially comprising hydrocarbons which are not highly unsaturated which comprises leading a mixture of such gases with the oxidizing gases in an amount appreciably less than one-half the amount necessary for complete combustion, to a reaction zone extending over the whole v,cross section of the reaction vessel at gas speeds which in the path leading to the reaction zone are greater than, but in all parts of the reaction zone itself, and behind the same, are at the most equal to, but not greater than the speed of the flame, thus causing the formation of a freely burning flame, and chilling the reaction products.

8. A process for the production of acetylene by partial combustion of gases essentially consisting of methane which comprises leading a mixture of about 1.5 to 2 volumes of methane and 1 volume of oxygen to a reaction zone extending over the whole cross section of the reaction vessel at gas speeds which in the path leading to the reaction zone are greater than, but in all parts of the reaction zone itself, and behind the same, are at the most equal to, but not greater than the speed of the flame, thus causing the formation of a freely burning flame, and chilling the reaction products.

HANS SACHSSE.

Images