US3522015A - Direct conversion chemical processing arc heater - Google Patents

Description

y &1970 D. A. MANIERO ET AL 3,522,015

DIRECT CONVERSION CHEMICAL PROCESSING ARC HEATER Filed Feb. 16, 1966 2 Sheets-Sheet 1 M258 N2 @E om mm A INVENTORS Dunlel A.M0niero 0nd l Ch %;(s 8. Wolf mm mm 5 mm mm mm ATTORNEY July 28, 1970 D, MANIERO ET AL 3,522,015

DIRECT CONVERSION CHEMICAL PROCESSING ARC HEATER Filed Feb. 16, 1966 2 Sheets-Sheet 2 mioww Q21 od} vw mm om w. o w w o o NINQ w wm w \ul 9 ON on ow om United States Patent US. Cl. 23277 Claims ABSTRACT OF THE DISCLOSURE An arc heater has a pair of axially spaced annular electrodes forming a gap with a generally axially extending arc therebetween, the electrodes having magnetic field coils therein for generating a magnetic field which exerts a force on the arc and cause it to move substantially continuously around and between the electrodes and to describe a generally annular or cylindrical path. Process gas to be pyrolized is substantially continuously admitted under pressure into the arc heater through a substantially circumferential admission path radially external to the electrodes from which it passes rapidly in a generally radial direction through the gap between electrodes and through the annular path described by are movement and into an arc chamber. The arc describes its annular path at such a fast repetitive rate that pyrolysis with substantially uniform heating of the process gas are obtained. The arc chamber is elongated providing a long path for process gas between arc pyrolysis area and exhaust area; cooling of the pyrolized gas to a temperature at which a a desired recombination product is present in substantial proportion may occur within the arc chamber. Quenching gas may be introduced into the arc chamber at one or more axially spaced positions along the path of the process gas. The volumetric capacity of the arc chamber is increased by having the upstream end of the arc chamber closed in a substantial axial distance from the upstream electrode.

This invention relates to improvements in arc heaters, and more particularly to an improved arc heater for the processing of one gas and the conversion thereof to another desired product gas, or carbon.

It has been known for some years that an electric arc may be used to pyrolyze a gas, and after the gas has been decomposed into atoms and free radicals, the atoms and free radicals may recombine to produce a different and desired product gas, depending upon the temperature to which the decomposed gas is quenched or cooled and the speed with which it is cooled after pyrolysis takes place. Sometimes an auxiliary gas may be added to assist in rapid cooling.

The arc heater of our invention utilizes an arcto pyrolyze the process gas or feed stock, for example OH; or C H which is thereafter quenched and cooled, so that a substantial yield of the product gas, for example C H is obtained. The arc heater of our invention is especially suitable for handling high flow rates of the process gas, and for producing the product gas with a minimum of kilowatt hours of electricity to the arc per pound of the product gas. For example, in one experimental test run of our arc heater, methane (CH was utilized as a process gas with a flow rate of 0.275 lbs. per second. The power to the arc electrodes was 840 kilowatts, and the acetylene, C H yield was 5.03 kilowatt hours of electricity utilized by the arc, per pound of acetylene C H a figure which compares very favorably with other processes now in general use, such as the Du Pont process and Huels process.

Accordingly a primary object of our invention is to 3,522,015 Patented July 28, 1970 MIC provide a new and improved direct conversion chemical processing arc heater.

Another object is to provide a new and improved chemical processing are heater in which large flow rates of a process gas may be employed.

Still a further object is to provide a new and improved arc heater for chemical processing in which the kilowatt hours per pound of a product gas are maintained at a low value.

These and other objects will become more clearly apparent after a study of the specification, when read in connection with the accompanying drawings, in which:

FIG. 1 is a cross-section through the direct conversion chemical processing are heater according to the preferred embodiment of our invention; and

FIG. 2 is a graph illustrating the operation of the apparatus of FIG. 1.

Referring now to the drawing of FIG. 1 for a more detailed understanding of the invention, a pair of fluid cooled electrodes 11 and 12 have an are 13 therebetween. It is seen that the electrodes 11 and 12 are annular in shape, and that each of the electrodes has an annular magnetic field producing coil therein, these being designated 14 and 15 respectively. If desired, field coils 14 and 15 are energized by direct current, the leads to the coil 14 being shown at 16 and 17 passing through a passageway 18, the leads to coil 15 being shown at 21 and 22 passing through passageway 23. Coils 14 and 15 may be energized by direct current with their fields in opposition so that a magnetic field is produced between electrodes which is substantially transverse to the path of the are 13 and which exerts a force on the are 13 which causes it to rotate substantially continuously around the annular arcing surface of the electrodes in a conventional manner. The rotation of an are by a magnetic field has been described elsewhere in the literature of the art and in prior art patents and need not be described in detail.

Coil 14 is seen to be mounted in an annular housing 24 composed of insulating material, the housing 24 being disposed within an annular cup-shaped member 25 which is generally U-shaped in cross section, which has ends 26 and 27 thereof abutting against annular shoulders 28 and 29 of an electrode supporting and fluid channeling member 30. The cup-shaped member 25 is seen to be spaced from the inner wall of the generally U-shaped electrode 11 providing fluid passageways 31, 32 and 33. It is seen that the portion of the fluid passageway 31 at the lefthand end thereof communicates with a fluid header 34, which may be a fluid inlet header, and which has fluid inlet 35. Passageway 33 around the other side of the coil and coil housing communicates by way of a plurality of circumferentially spaced passageways 36 and 37 with a fluid header 38 which may be a fluid outlet header. In actual practice in the construction of the arc heater of the figure, two fluid inlets spaced apart are provided for the fluid inlet header 34, there being an inlet in addition to the inlet shown at 35; and in addition there are two fluid outlets 39, only one being shown for simplicity of illustration for the fluid outlet header 38, the fluid outlets being preferably spaced 180 apart.

The internal construction of the other electrode 12 is similar to that of the electrode 11 and need not be described in detail. Fluid passageways 41, 42, and 43 around the three sides of the field coil 15 communicate, one with fluid outlet header 44 and another with fluid inlet header 45. Fluid inlet header 45 is seen having the inlet passageway 46 communicating therewith, and outlet header 44 has outlet 47.

Between the two electrodes 11 and 12 there is a heat shield enclosing the chamber in which the arc takes place, this heat shield including two generally annular ring members 51 and 52, separated by a center ring 53. The

two annular L-shaped ring members generally designated 51 and 52 each has a plurality of annular fingers 54 and 55 respectively extending from ring inside wall portions 48 and 49 respectively forming in each ring member a plurality of spaced annular passageways 62 and 63 respectively. Within 360 annular grooves 19 and of ring members 51 and 52 respectively are disposed ring members 9 and 10 respectively having short fluid inlet headers 56 and 57 respectively, fluid header 56 having inlet 58, and fluid header 57 having inlet 60. Disposed 180 from the aforementioned inlets 58 and 60, are two outlets 59 and 61 communicating with fluid outlet headers 165 and 166 in rings 9 and 10 respectively, so that fluid flows in two semicircular paths in passageways 62 and 63.

Between the aforementioned ring member 51 and the adjacent electrode 11 there is disposed means for introducing gas, either a process gas or a quenching gas or some auxiliary gas, at a plurality of circumferentially spaced points around the electrode 11, the gas entering the chamber 50 through the annular passageway 64. The annular passageway or opening 66 constitutes a gas header, and in actual practice the arc heater would employ two gas inlets to this gas header 66, one of these gas inlets being shown at 67, it being understood that another gas inlet spaced if desired at 180 therefrom would also be provided. From the gas header 66 gas passes through a plurality of circumferentially spaced passageways 68 and into annular space 69, thence through gaps or spaced Adjacent the aforementioned electrode 12 is a similar into the portion of the chamber 50 Where the arc rotates. bores 70 into the aforementioned annular space 64 and gas header 71 having gas inlet 72, gas from the gas header 71 entering the arc chamber through the annular space 73.

It is noted that electrode 11 is separated from annular ring 51 by annular insulating means including annular insulating members 74 and 75, and that electrode 12 is electrically insulated from ring member 52 by means including annular insulating members 77 and 78.

It is noted that the remainder of the arc heater includes sectionalized arc chamber walls, these including a heat shield generally designated 80, which section may be eliminated if desired, a heat shield generally designated 81, and a heat shield generally designated 82. It is further noted that the right-hand end of the arc chamber 50 is closed by an end plug generally designated 84 and that on the left-hand of the arc heater as seen in the figure there is a nozzle generally designated 86.

It is seen that the aforementioned cylindrical heat shield 82 is fluid cooled by fluid flowing in passageways 88 and 89, passageway 88 connecting with fluid header 91 and thence with fluid inlet 92, passageway 89 communicating with fluid header 94 and thence with fluid outlet 95.

It is further to be noted that gas is admitted into the chamber 50 at a plurality of circumferentially spaced positions around the heat shield 82, there being an annular insulating member 97 with spaced bores 98 communicating with an annular passageway 99 which communicates by way of spaced bores 101 with an annular gas header 100 which has a gas inlet, not shown for convenience of illustration, disposed at a convenient position on the arc heater.

Gas is also admitted at a plurality of circumferentially spaced positions around the end plug generally designated 84 and near the inner chamber wall of the heat shield 82. There is an annular space 102 which serves as an auxiliary gas header, and an annular gasket of insulating material 103 having a plurality of bores 104 at spaced intervals therearound to permit a quenching gas or an auxiliary gas or a process gas to be introduced into the chamber 50. The annular space 102 communicates with annular gas header 106. It is further seen that the heat shield generally designated 82 is electrically insulated from the electrode 12 by means 107, 108, and that the heat shield generally designated 82 is electrically insulated from the end plug 84 by means 111 and 112 composed of insulating material. End plugs 84 is seen to be fluid cooled, having a conical passageway 113 extending from fluid header 114 connected to fluid inlet 115. The conical passageway 113 communicates with a fluid header 116 connected to fluid outlet 117.

The aforementioned heat shield 81 is similar to the heat shield 82 and need not be described in detail. Suffice it to say regarding the heat shield 81 that the surface thereof which faces the arc chamber 50 is fluid cooled by fluid passageways having fluid inlet and fluid outlet headers communicating with fluid inlets and fluid outlets. A gas is admitted at a plurality of circumferentially spaced positions between heat shield 81 and heat shield and a gas is admitted at, or can be admitted at, a plurality of circumferentially spaced positions between heat shield 81 and electrode 11, the last named gas passing through the passageway 119 and through spaced bores 120 in an annular ring of insulating material 121. The gas header for the last named gas is designated 122 having inlet 124, while the gas header for gas admitted by way of annular space 155 the heat shields 80 and 81 is designated 123, having a gas inlet, not shown, for convenience of illustration.

Particular attention is directed now to the heat shield 80, which is electrically insulated from heat shield 81 by insulating means 125 and 126 and electrically insulated from nozzle 86 by insulating means 128 and 129. Heat shield 80 is cooled by fluid passing through annular passages 131 communicating by way of holes 127 With a fluid header 132 having fluid inlet 133, and communicating by holes with outlet header 144 having fluid outlet 134, spaced from inlet 133 so that fluid flows through two semicircular paths. Passageways 136 and 137 may be used for seeding or sampling or quenching or mixing purposes, but may be plugged up by plugs 138 and 139, which may be secured thereto by bolts, not shown for convenience of illustration.

If desired, the heat shield 80 may be entirely eliminated from the arc heater, and the arc chamber wall may comprise an up-stream heat shield 82, and a downstream heat shield 81.

Gas may be injected between the aforementioned heat shield 80 and the aforementioned nozzle 86 by way of gas header 141 having inlet 142, header 141 communicating by spaced passageways 161 with annular space 162.

The aforementioned nozzle 86 is seen to include a fluid cooled inner surface 146 having fluid flow passageway 147 near the inner surface, the passageway 147 communicating with a fluid inlet header 148 and a fluid outlet header 149, these communicating with inlets and outlets respectively, not shown for convenience of illustration.

It is seen, then, that there is provided an arc heater with means for supplying a large electrical current to the electrodes, symbolized by leads 151 and 152 connected to source of potential 153 to produce and sustain the arc 13; magnetic field coils 14 and 15 are energized to set up a magnetic field which causes the arc to rotate at a predetermined speed which is neither too fast nor too slow, the arc moving from any particular position before the intensely hot are spot has burned through the electrode, the are not returning to the same position until that area or that point on the electrode has had a chance to cool down to a safe temperature. It is further seen that gas may be admitted into the arc chamber at a plurality of points depending upon the process gas used and the desired product. As will be readily understood, the process gas is pyrolized or decomposed by the heat of the arc and thereafter it is cooled to a temperature at which some desired recombination product is present in substantial proportion, the exact temperature of cooling determining in part the proportion of the desired recombination product.

It will be understood that the gap between electrodes 11 and 12 is adjustable, if desired by having a number of rings 51-52 of various widths available for use.

Particular reference is made now to Tables I, H, III, and IV which show the results of tests runs. In all of Particular reference is made now to Graph No. 1, where variations in some of the products are charted for various flow rates.

In the curves of FIG. 2, the quantities of H CH C, and C H expressed in mole percentage are shown varythese test runs, the arc was powered by alternating cur- 5 ing with variations in the reciprocal of the flow rate of rent, and the electrode gap was inch. CH supplied to the arc chamber, and the curves corre- To insure purity of process gas and accurate measspond generally to the values of Tables I and II. urements of the recombination products, the arc chamber Particular reference is made now to Table No. III, was flushed before process gas was admitted by supwhere the process gas employed was C H and the complying chemically pure nitrogen to the chamber for several position of the product is analyzed with respect to the seconds. At the conclusion of the supplying of process gas three different flow rates and three diflFerent input powto the arc heater, nitrogen was again supplied to the arc ers to the arc heater. heater for several seconds. Particular reference is made now to Table No. IV, The tables show results for various flow rates of the where product values obtained during the same test runs,

process gas and various powers to the electric arc.

that is runs 4, 5 and 6, are shown with percent reference TABLE I.COMPOSITION INVOLUME PERCENT OF PRODUCT GAS IN CH; FLAME Composition, percent CH4, Power to Kw. hr./ Run No lbs./sec. gas, kw. Hz 00 CH4 CgHz CzHz 04111 Other lb. CzHg Percent reference to total carbon Run No CzHz C2H4 04H: 00 O her a process gas may be introduced at one or more of a num- 234 269 ber of points up-stream and down-stream of an arc to 5.2% 38 2.3} assist in providing maximum production of the desired product for a given kilowatt hours of power to the arc.

Tables I and H show a chemical analysis of the gas in the arc heater where methane is used as the process gas, and the desired recombination product is acetylene C H Further, although an auxiliary quenching gas was not employed in the test runs described, out apparatus provides that a quenching gas or an auxiliary gas may be introduced at a number of points up-stream and down-stream In obtaining test samples of gas for chemical analysis, a 3 of an are or substantially in the area of the arc path.

TABLE IIL-COMPOSITION IN VOLUME PERCENT OF PRODUCT GAS IN CsHe FLAME Composition, percent probe consisting of a water cooled concentric copper tube with a 4; inch bore was employed, the bore opening of the probe being at the nozzle, preferably of the axis thereof. Runs 1, 2 and 3 are the same runs in Tables I and II with their results analyzed in different manners and show the results for different flow rates of the matane, and different input powers to the arc heater, together with the quantity of the desired output (Table I), measured in kilowatt hours per pound of the desired recombination product gas. Test run number 3 shows that TABLE IV.CONVERSION OF CaHe TO PRODUCTS Percent reference to total carbon for a certain flow rate and are input power, the yield Run No Soot can on. 02H; can, C3H4 0.11. of acetylene, measured in kilowatt hours per pound of Q27 Q31 0.27 41 acetylene, compares very favorably with presently used 13.83 5.48 1.56 0. 33

processes. In test run No. 3 which produced such efficiency in the conversion of Methane to acetylene, Methane was introduced at the following points in the arc heater:

40% by gas inlet 67. 40% by gas inlet 72. 4% by gas inlet 124 and gas header 122. 4% by the corresponding gas inlet (not shown).

for gas header 100. 4% by the gas inlet (not shown) for gas header 106. 4% by gas header 123 and gas inlet 110. 4% by gas inlet 142 and gas header 141.

Particular references made now to Table II, where test runs 1, 2 and 3 are analyzed with respect to, or with reference to, the total carbon, and it is seen that the electrical and flow rate conditions which produce the most efiicient conversion to acetylene are also accompanied by the production of the least carbon in the arc heater.

This invention constitutes a further development and advance in the chemical processing art, as described in the copending application of Messrs. Bruning, Kienast, Kemeny and Hirayama for Cross-Flow Arc Heater Apparatus and Process for the Synthetic of Carbon, Acetylene and Other Gases, filed Nov. 12, 1965, Ser. No. 507,- 345; to that of C. Hirayama et al. for Method and Equipment for the Pyrolysis and Synthesis of Hydrocarbons and Other Gases and Arc Heater Apparatus for Use Therein, Ser. No. No. 446,012, filed Apr. 6, 1965, now issued Pat. 3,389,189; that of P. F. Kienast et al. for Arc Heater Apparatus for Chemical Processing, Ser. No. 471,914, filed July 14, 1965, now Pat. No. 3,345,191; and that of D. A. Maniero et al. for Process for Hydrogen Cyanide and Acetylene Production in an Arc Heater Having a Rotating Arc, Ser. No. 657,867, filed Aug. 2, 1967, now Pat. No. 3,460,902, all of the above-identified patents and the above-identified application being assigned to the assignee of the instant invention.

Whereas we have shown and described our invention with respect to an embodiment thereof which gives satisfactory results, it is intended that all matter contained in the foregoing description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense; changes may be made and equivalents substituted without departing from the spirit and scope of the invention.

We claim as our invention:

1. Arc heater apparatus for chemical processing comprising generally cylindrical means forming an arc chamber, first and second axially spaced annular electrodes disposed in the arc chamber with an annular gap therebetween, the second electrode being the downstream electrode, means for producing and sustaining an are between the first and second electrodes, the arc extending generlly in an axial direction, means for causing the arc to move substantially continuously around and between the first and second electrodes and to describe a generally annular path, means for introducing a process gas into the arc chamber through a substantially circumferential path radially external to the electrodes from which the process gas passes in a generally radial direction through the gap between electrodes and through the annular path described by are movement, said are pyrolizing the process gas, and means located downstream of the second electrode a distance substantially equal to the distance between the arcing surfaces of the first and second electrodes for introducing a quenching gas into the chamber, the quenching gas acting to cool the pyrolized gas, and nozzle exhaust means for the arc chamber.

2. An arc heater for chemical processing comprising generally cylindrical means forming an arc chamber, first and second axially spaced annular electrodes disposed in the arc chamber with an annular gap therebetween and assisting in defining the arc chamber, the second electrode being the downstream electrode, means for producing and sustaining an are between the first and second electrodes, the are extending generally in an axial direction, means for causing the arc to move substantially continuously around and between the first and second electrodes and to describe a generally annular path, means for introducing a process gas into the are chamber peripherally spaced positions between the first and second through a substantially circumferential path radially external to the electrodes from which the rocess gas passes in a generally radial direction through the gap between electrodes and through the annular path described by are movement and is pyrolized by the arc, nozzle exhaust means for the arc chamber, and heat shield means extending between the second electrode and the nozzle exhaust means, the heat shield means being at least several times greater in length than the distance between the first and second electrodes whereby sufiicient time is provided for the process gas after being pyrolized to be substantially cooled as it moves away from the arc zone before being exhausted from the nozzle means.

3. Are heater apparatus according to claim 2 additionally characterized as including means for injecting a quenching fluid into the pyrolized process gas at some position along the length of the heat shield means and before the process gas is exhausted through the nozzle exhaust means.

4. Arc heater apparatus according to claim 3 in which the heat shield means is composed of tWo elongated sections and the quenching fluid may be injected at a plurality of peripherally spaced points between the two sections of the heat shield means.

5. Are heater apparatus according to claim 1 in which the means forming an arc chamber includes a closing plug for the upstream end of the arc heater and an elongated heat shield interposed between the first electrode and the closing plug, the space enclosed by the last-named elongated heat shield increasing the volumetric capacity of the arc chamber thereby increasing the conversion effiency of the arc heater where methane is the process gas and the desired recombination product is acetylene.

References Cited UNITED STATES PATENTS 3,343,019 9/1967 Wolf et al. 313-32 3,182,176 5/1965 Bunt et a1 2l9-121 3,389,189 6/1968 Hirayama et a1. 23277 XR J. H. TAYMAN JR., Primary Examiner US. Cl. X.R.

23l, 209.3, 259.5; 20431l, 323; 219-75, 121, 123; 260-679g 31332, 231

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