US2165820A - Manufacture of acetylene - Google Patents

Description

Patented July il, i3

Standard ration of Delaware William E. Smyers, Westfield, N. J., asslgnor to Oil Development Company, a. corpo- Application December 29, 1934, Serial No. 759,601 5 Claims. (Cl. 20M- 31) 'I'his invention relates to improved methods of manufacturing acetylene and to novel apparatus therefor.

There have been many attempts in the past to devise cheap methods of manufacturing acetylene from hydrocarbon gases or vapors,.but none of the methods used heretofore have been successful in giving economical yields above 25% on a commercial scale.

According to the present invention, a nely comminuted, preferably highly preheated, solid carbonaceous material consisting chiefly of carbon, e. g. coke dust, is fed directly into an electric arc simultaneously, and preferably pre-mixed, with hydrocarbon gases or vapors, such as methane or higher hydrocarbons, in order Ito carry out in an efficient manner chemical reactions of which the following equations are typical:

saturated or unsaturated normally gaseous hy- I drocarbons, such as ethane, butane, ethylene, butylene, etc., or higher normally liquid hydrocarbon fractions, such as naphtha, gas oil, tars, etc. or mixtures of those or equivalent hydrocarbon gases or vapors. The invention is applicable particularly to the use of methane, or gases containing large amounts of same, such as natural gas or petroleum refinery gases (obtained from cracking higher hydrocarbons), because these lighter gases are generally much cheaper and available in much larger quantities than the higher hydrocarbons, and because these gases contain a much higher proportion of hydrogen and a lower proportion oi carbon than the higher hydrocarbons.

The solid carbonaceous material to be used is preferably one having a H/C (hydrogenzcarbon) molar ratio less than 1.0 and preferably less than about 0.75. Suitable materials include soft and hard coal (which have a H/C ratio of usually between the limits of about .75 and .25), and coke, charcoal, lamp black, etc. which have an even lower H/C ratio. Asphaltenes (with a H/C ratio of about 0.85) could also be used, as well as highly aromatic polynuclear materials, such as anthracene, uorescein, etc., or their derivatives or crude commercial products containing the same, such as certain vfractions obtained upon destructive distillation of coal, oil-shale or other carbonaceous material,

In carrying out the invention, the solid carbonaceous material is comminuted by any suitable means, such as a ball mill, roll crusher. gyratory crusher or roll and pan crusher, or abrasion with a toothed wheel or drum, the comminution being carried out to such an'extent that the resultant powder will stay in suspension for whatever time is required by the design of the arc equipment used. Ordinarily, it is preferable to have all of the powder or dust fine enough to pass a mesh sieve, and preferably, a 200 mesh sieve, and even more efficient chemical reaction will be obtained with material that is so fine that it would pass a 500 mesh sieve, this latter material being ordinarily obtained by air-or waterclassilcation, rather than by screening. The carbonaceous material is also preferably preheated, either before or after comminution, to as high a temperature as is consistent with the materials and design of the equipment to be used. For instance, soft coal could not be pre-heated much above several hundred degrees centigrade without decomposing and liberating tarry materials which would have a tendency to clog up the apparatus. On the other hand, a. high temperature coke dust could be heated to a glowing red or even yellow temperature. The carbonaceous dust, with or without pre-heating such as described above, is then fed into an electric arc, either simultaneously with or preferably premixed with the hydrocarbon gases or vapors to be used, which have also preferably been pre-heated to just below their decomposition temperature. Various specific means of carrying out the invention are illustrated in the accompanying drawing where Figure 1 is a sketch of an entire plant layout for manufacturing acetylene, and Figures 2, 3, 4, 5 and 6 represent alternative methods of feeding the finely divided solid carbonaceous material and the hydrocarbon gases or vapors, into an electric arc.

As is already known in the art, it is highly desirable to use an exceedingly high temperature for the reactions in question, and therefore the temperature of the arc and of the reacting materials passing through the same should be maintained at least above 700 C. and preferably above 1500 or 2000 C., and perhaps even as high as 5000 C. or more. It is likewise important that the time of contact should be short, e. g., 1.0 to .0005 second. Generally, the higher the temperature the shorter the time of contact. Usually, for temperatures ranging from 2000 to 5000 C., the time of contact should be between the approximate limits of 0.2 and .001 second.

I'he pressure to be used is preferably atmospheric or slightly below or above atmospheric. For instance, it may be desirable to operate under a super-atmospheric pressure of several atmospheres in order to be able to carry out the pneumatic transfer of gases and vapors through the different parts of the plant equipment used, and on the other hand, it may be desirable to operate under a reduced pressure (as low as is practicable) inasmuch as the chemical reactions concerned are facilitated by the use of vacuum, or at least a partial vacuum.

It is also necessary, for obtaining high yields of acetylene, that the gaseous products issuing from the electric arc should be immediately cooled at least to below the decomposition temperature of acetylene. This may conveniently be done by quenching the gaseous products with water, as by injecting many fine jets, or a spray, of water directly into the gaseous products. It is thus possible to cool the gases from, for instance, an

average temperature of about 3000 C. to about.

500 C. or below, in a small fraction of a second, such as .01 to .0001 second. The gases which now contain a large proportion of acetylene may then be still further cooled as by passing through vertical Water cooled tubes, and are then preferably freed from any residual suspended carbon or other finely divided solids, such as mineral ash, and are then preferably purified as by solvent scrubbing in order to remove impurities of the nature of di-acetylene. Suitable methods for accomplishing this purification are described in the copending application of E. V. Murphree, Serial No. 577,285 led November 25, 1931, which covers the purification of acetylene-containing gases by scrubbing with a solven't, such as gas-oil, having a selective solvent action for impurities of the nature of di-acetylene.

'I'he Water used for quenching of the hot reaction gaseous products issuing from the electric arc, may contain in suspension some unburned and some partially burned carbon or solid carbonaceous matter, as Well as a large proportion of the mineral ash of the original solid carbonaceous material used. This water may be recycled as such if desired, or is preferably allowed to settle in a suitable settling tank where the finely divided solids settle out at the bottom and are either wasted or, if they still contain substantial amounts of available carbon, are dried and recycled for repassage through the electric arc.

The invention possesses several advantages, chief of which is that a high yield of acetylene (generally 30 to 80% or more compared to the 5 to 30%, or usually l0 to 15% obtained in the prior art) is obtained with a. relatively low cost. In other words, high yields of acetylene are obtained, expressed in liters of acetylene per kilowatt hour of electricity consumed. The eciency of the process is believed to be at least partially due to the high reactivity of nascent hydrogen formed by the decomposition of the methane or other hydrocarbon gases or vapors, as well as to the high reactivity of the solid carbonaceous matter when passed, preferably in a highly preheated condition, directly into the electric arc. Other advantages will be apparent to those skilled in the art from the forgoing description, as well as from the following explanation of the specific embodiments of the invention illustrated in the accompanying drawing.

Referring to Figure 1, a solid carbonaceous' material, such as coke or coal, is fed into crusher I, and the ne coke dust is drawn by blower 2 through line 3 into settling bin 4, from which it isl fed into pre-heater 5, into supply bin B, from which it is fed by means of screw conveyor 'I into the hydrocarbon gas inlet line I, and the two materials passed together through pre-heater 9, into electric arc I0. Electrodes Il and I2 may be arranged in any convenient manner within the arc chamber I3 in order to obtain the optimum dispersion of the hydrocarbon gas and solid carbonaceous material within the field of the electric arc. The hot reaction gases issuing from arc I0 pass upward through a water spray I4, thence through cooler I5, dust separator I6, blower I1, and finally into scrubber I8 from which the purified gases, rich in acetylene, are discharged through line I9 to storage, or used directly for manufacturing chemical products, such as acetaldehyde, acetic acid, vinyl compounds, etc. The scrubbing liquid used in scrubber I8 may suitably be gas oil or some other liquid having a selective solvent action for impurities of the nature of di-acetylene, as described in co-pending application 577,285 previously referred to. Finely divided solids suspended in the wash water coming from spray I4 accumulate in the bottom of settling tank 2l, and are slowly worked toward the center by suitable scraper blades 2I, caused to rotate through gears 22 by suitable means not shown. 'I'he resultant sludge 23 is then either discharged through ash hopper 24 and wasted, or is carried by screw conveyor 25 into dryer 26, from which it is drawn by blower 2 back into the solid carbonaceous dust feed line 3. Clear water is decanted from settling tank 20 through line 21, and recycled by means of pump 28 into cold water line 29, from which it goes through the water cooler Hi,l and is again used in the water4 spray Il.

In Figure 2 the electric arc Il is composed of arc chamber I3, hollow positive electrode IIa, and a hollow annular negative electrode I2a. The hydrocarbon gases are fed in through hollow electrode Ila and the solid carbonaceous mate-z rial, preferably in the form of a solid rod $0 (preferably pre-heated to glowing temperature),` is fediagainst a suitable abrading meanssuch as a rapidly rotating, preferably water-cooled; toothed wheel or drum I I thereby showering fine carbonaceous material directly into the electric arc I0. The abrading surface itself, such as the teeth on a toothed wheel or drum are preferably made out of suitable refractory material, such as carbides of silicon, aluminum, boron, etc., suitably mounted on a circular metal base.

Figure 3 provides a similar arc construction, except that positive electrode II is solid and a suitable hydrocarbon liquid, such as gas-oil (preferably pre-heated) containing finely divided solid carbonaceous material in suspension, is fed through nozzles 32 directly into electric arc Il.

Figure 4 shows an electric arc construction somewhat similar to that shown in Figure 2, except that the arc chamber I3 and hollow positive electrode IIa are in a vertical position, and hydrocarbon gases or vapors containing finely divided solid carbonaceous material, are fed through the electrode IIa directly into electric arc I 0, the hot gaseous products being immediately quenched by water spray I4. Instead of feeding the hydrocarbon gases and carbonaceous dust into the arc through the hollow electrode IIa, the reacting materials might be fed tangentially into the arc chamber in such a way as to produce what is known in the art as a swirling arc.

In Figure 5 electric arc l0 is formed by electrodes IIb and I 2b, 4both of which are composed of nely divided carbonaceous material loosely packed together in stick form (with or without a binder), and hydrocarbon gases or vapors are fed in through inlet 8 and pre-heater 9. If desired, the arc may be struck between two conventional tightly packed solid carbon electrodes (not shown), and loosely packed rods, such as l lb and |2b, could be used merely as a source of iinely cmminuted solid carbonaceous material without using them as electrodes. These rods may be prepared by mixing together coke dust (fine enough that or more of it passes a 200 mesh sieve) with an amount of binder small enough that when the powder is packed lightly into stick form (as by shaking down 'or vibrating it in a suitable container, or by the application of a few pounds pressure by mechanical means), the particles of dust will stick together tight enough to maintain the shape into which they were molded, and if desirable, tight enough to conduct electricity so that the sticks may be used as electrodes, but at the same time loosely enough that when one end of these sticks is projected into an electric arc the fine dust particles will be rapidly disengaged from the end of the stick resulting in the production of a shower of dust particles in the arc. For instance, 5 or 10% of water may be used, or preferably water containing a small amount of glue, or similar binder in solution, so that the amount of such binder is between the approximate limits of l to 5%, based on the weight of the coke dust. The amount of the binder used and the amount of pressure, or other means used for packing the powder, should not in any case, be such as to completely ll the voids or air spaces between the particles of coke dust; in other words, the finished packed rod should be substantially porous. Small amounts of water-insoluble binders, such as tar, may be used.

In Figure 6 electric arc l0 is formed by conventional electrodes il and l2, while hydrocarbon gases (preferably pre-heated) are fed in through inlet 8 and solid carbonaceous material in the form of rod 30 (preferably pre-heated to `glowing temperature) is fed against the toothed wheel or drum 3|, thereby feeding a. shower of highly pre-heated carbonaceous dust into the hydrocarbon gases, and the mixture is fed directly into electric arc l0.

It is apparent that other modifications can be made without departing from the broader scope oi the invention, and it is not intended that the invention be limited by any of the specific embodiments shown, nor examples given, nor by any theories suggested as to the mechanism of the operation of the invention, but only by the appended claims in which it is intended to claim all inherent novelty in the invention as broadly as the prior art permits.

I claim:

l. A process for producing acetylene which comprises reacting together two carbonaceous materials by feeding a solid finely divided carbonaceous material having a hydrogen/carbon ratio less than 1.0 simultaneous with a gas consisting essentially of normally gaseous hydrocarbon not less saturated than olefins directly into an electric arc whereby a reaction ternperature of above about 700 C. is maintained, said solid carbonaceous material having been preheated to a glowing temperature and said solid carbonaceous material being suspended in said gaseous hydrocarbons during 'exposure in the reaction zone, maintaining an acetylene forming time of contact between the approximate limits of 1.0 and .0005 second, the proportions of said materials being controlled to carry out in an efficient manner the chemical reactions between the gaseous hydrocarbon and the solid carbonaceous material to produce acetylene, and immediately cooling the reaction products below the decomposition temperature of acetylene.

2. A process for producing acetylene which comprises feeding a pulverized solid carbonaceous material simultaneously with gaseous hydrocarbons directly into an electric arc at an acetyleneforming temperature and time of exposure, and immediately cooling the reaction products below the decomposition temperature of acetylene, in which process a solid rod of carbonaceous material preheated to a glowing temperature is fed against a rapidly rotating abrading means in such a position that a shower of finely comminuted glowing particles of carbonaceous material is injected directly into the arc.

3. A process for producing acetylene which comprises reacting together two carbonaceous materials by feeding a solid carbonaceous material fine enough to pass a mesh sieve having a hydrogen/carbon ratio less than .25 and preheated to a glowing temperature, simultaneously with a gas consisting essentially of normally gaseous hydrocarbons not less saturated than olefins, said hydrocarbons having been preheated to an elevated temperature below their decomposition temperature, directly into an electric arc whereby a reaction temperature at least above 1500 C. is maintained, said solid carbonaceous material being suspended in said gaseous hydrocarbons during exposure to the arc, maintaining an acetylene-forming time of contact between the approximate limits of 1.0l and .0005 second, the proportions of said materials being-controlled to carry out in an efficient manner, the chemical reactions between the gaseous hydrocarbon and the solid carbonaceous material to produce acetylene, and immediately cooling the reaction products below the decomposition temperature of acetylene.

4. A process for' producing acetylene whichI comprises feeding coke dust ne enough to substantially all pass a 200 mesh sieve and preheated to a glowing temperature, simultaneously with a gas consisting essentially of normally gaseous hydrocarbons not less saturated than olens, containing a large amount of methane, said hydrocarbons having been preheated to an elevated temperature just below their decomposition temperature, directly into an electric arc maintained at a temperature above about 2000 C., said solid carbonaceous material being suspended in said gaseous hydrocarbons during exposure to the arc, maintaining an acetyleneforming time of contact between the approximate limits of .2 and .001 second, the proportions of said materials being controlled to carry out in an eiiicient manner, the chemical reactions between the gaseous hydrocarbon and the solid carbonaceous material to produce acetylene, and immediately quenching the acetylene-containing reaction products with water from the reaction temperature down to a temperature below about 500 C. in less than about .0l second to prevent decomposition of the acetylene.

5. A process for producing acetylene which comprises reacting together two carbonaceous materials by feeding 'a solid carbonaceous material fine enough to pass a 100 mesh sieve having a hydrogen/carbon ratio less than .25 and preheated to a glowing temperature, simultaneously with a gas consisting essentially of normally gaseous hydrocarbons not less saturated than oleflns, said hydrocarbons having been preheated to an elevated temperature below their decomposition temperature, directly into an electric arc whereby a, reaction temperature at least above 1500 C; is maintained, said solid carbonaceous material being suspended in said gaseous hydrocarbons during exposure to the arc, maintaining an acetylene-forming time of contact between the approximate limits of 1.0 and .0005 seconds, the proportions of said materials being WILLIAM H. SMYERS.

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