US1145748A - Electric furnace. - Google Patents

Description

P; BU NET.

' ELECT APPLICATION RIL FYURNACEp -F|LED NOV. 24, I814.

Patented Jul 6, 1915. 2 SHEETS-SHEET 1'.

- wwhm P BUNE'T.

ELECTRIC FURNACE.

1 N FILED NOV 24 194' APPLIC 1 1; 11 1:5348. Patented July 6;1915 mum's-spin 2.

UNITED STATES PAUL ome, or WHITNEY, NORTH mm, 'AssIGu'oR To soomrr': .GEHERALE Dnsi NITRURES, OF PARIS, FRANCE.

EL'nornIc rummcn,

i Specification of Letters Patent.-

. j.- -i q1:app lieation fi led m 9,- 1 913, Seria1 Nb. 766,461. .Divided and this application filed November 24,

To all it may concern:

Be it known thatI, PAUL'B NEnpf Whitney, Stanly county, North Carolina, and a I vcitizenof the Republic of-France, have invented certain new and useful Improvements, iii-Electric Furnaces, of which the following is'aspecification. I

4 This invention relates to'a revolving electric furnace, more particularly adapted. to carry out a process for. the manufacture of aluminium nitrid by the methodcwhich con- 'sists in heating-in presence of nitrogen or of gases containing the latter, amixture of alumina or aluminous substances and carhon 1n electrical reslstance furnace in which thematerial under treatment ltself serves as the heating resistanc My IHVGIIl ZiOII COIISi StS in the construction? v of the continuous electrical furnace'so as to above substances containing an excess ofv carbon or other conductivesubstances in sufficientquantity to insure the passage of ourrent-in'spite of the reactionary losses ofcaralumina into aluminium nitrid.

effect the advance of the mixture of the bon ,'necessaryfto the transformation of the 7 My invention. may be embodied in fur- .naces of diiferent types, such as hereinafter described. ,The first type of furnace is arranged in such a waythat the thickness of the layer of material goes on increasing in proportion as the latter advances through I 1 the furnace. In this'way the sectional area increases in the parts of the'furnace Where the mixture becomes poor in carbon inconsequence of the reactlon, andthere 1s, therefore, always at -ever y cross-section of the furnace a-suflic1entquant1tyof conductive 1 material to insure the regular passage of the current. The second type of furnace is a so arranged that at intervals along its length thereg .are connections or'electrodes for conveying the current, which are connected alternately to the two poles of the generator or supply. divided into In this way the I furnace is a number of elements or sections through which the material under treatment: passes successively; the'length of each section can be selected in accordance with the state of conductivity of the material treated therein. These two types of furnace can evidently be combined.

21912., "The gas direction to the 'm'atenal 1914. Serial N0.873,781'.

The accomp ny-il furnaces for carrying out the process. lgure 1 1s a longitudinal section, .illus-fl' trating'anr inclined revolving. electric fink;

" PatentedJuly6,1915 j 1 nace, acco'rding'to my invention Fig.1 2 is a I (vertical section" of a'istationary form' of-fur- 'nace;rF1g's. 3 and} are diagrammatic sec-f fied forms' of revolvingtions of'two" d electric furnaces Fig-ll shows a revolving'furnace which is slightly inclined so to allow the-substances introduced; into "the furnace to ad,

" nte h f th QtIglimin a continuous manner, after the-general," methdd described in the Serpek Pat ontainmg nitrorent is led to two annul conductors A and B of which the lower (in-e Theielectric cur iprojectsins'ide the furnace so asto form a diaphragm and to retain the material C traveling through the furnace. Asezgplained abovei in proportion as the materialadvances through the furnace and' the transformation into-.nitridbecomes very complete, the thiclmes'sfo'fthe layer is 'increased in; this way'allowing of maintaining at every cross-section the quantity of carbon sufiicient to insure theregular passage of the current inspite of the losses resulting from. the reaction; Matters can, therefore, be so arranged that the resistance,

'the furnace and to facilitate the passage of the current at the start, the operation may be commenced by passing carbon alone and consequently the evolution of heat are I through the furnace; the mixture to be treated is then gradually'added. There may be arranged in the furnace at certain intervals conductive rings D fitted in the refractory lining, E, and projecting ornot. In

this way there are formed in the furnace zonesofless resistance which facilitate the I passagefof the current. This arrangement allows the furnace to be madefof'any length,

jection of the conductive rings D.

greater in proportion to the size of the pro- I Fig. 2 of the drawing shows a stationary furnace based upon the same prmclple; the

I trode B The electrode A is insulated on its underside by an insulating support A in furnace is vertical and the current is led to the two electrodes A and B The material poured upon the side of the electrode A falls upon the lateral walls of the furnace forming a sloping bank, the sectional area of which increases toward the lower eleccreasing or decreasingthe separation of the the mixture.

electrodes and the areas for the passage of Openings F, closed by plugs F are formed at the bottom of the furnace at various points in the periphery to allow the material to be withdrawn. 1

Fig.3 is a longitudinal section of a furnace of the second type, in which an intermediate electrode or terminal B is arranged between the extreme electrodes A A, all

- these electrodes being formed as conductive rings or annuli. Fig. fl is a longitudinal section of a similar furnace, having two intermediate electrodes; in this case some of the conductive rings forming terminals have been'arranged to project internally of the furnace so as to afford walls or diaphragms according to the principle of the first type of furnace above described. In the arrangement of Fig. 4, the conductive rings A, .A are connected to one of the-poles of the-electrical generator while the alternate rin s B B* are connected to the other pole. n

these-two figures, E still indicates the refractory lining. of the furnace and The current of nitrogen circulates in the opposite'direction as usual.

The use of intermediate electrodes and the possibility of selecting their separation as desired, form a practical method which al- 1 lows latitude for regulating in accordance tion of the furnace, proportion of the con-' ductive material added to the mass in reaction, total expenditure of energy and of heat and division of the matter along the various elementary sections of the furnace In par-" ticular, by reducing the length of the path traveled by the material between two successive electrodes, the resistance is diminished. It becomes possible,- therefore, to reduce the quantity of conducting material added to the materials in reaction in order to insure the passage of the current; this allows of diminishing the expenditure of ener devoted to the heating of these conductlve materials and to obtain at the end The electrode A and its support A the ma-. terial in course of its advance therethrough.-

of the operation a product which is not surcharged with inert material and is, thereforeyricher in nitridi.

Instead of reducing the proportion of conductive matter added, the length of the furnace may be increased without reaching. aresistance deleterious to the satisfactory carrying out of the operation. In this way there is obtained a result analogous to that whichis produced by theconductive rings D, 'which are not connected tothe poles of the generator in the furnace shownin Fig. 1. Again, by bringing closer together-two consecutive electrodes, the heat may be concentrated in'a given zone as desired, for example in the final zone which is the poorest in carbon'and. in whichthe current has most difiiculty in passing.

Another peculiarity of the type of furmice, which presents an important practical advantage, lies inthe fact that itrealizes au-' tomatically the regulation of the intensity of the current, and, therefore, of the quantity of heat which passes through the different elementary sections of the furnace. Indeed, if for any reason the intensity of thec'urrent increased abnormally at one of the sections of the furnace, to the detriment of the others, there would be produced at that point a larger quantity of heat; this would increase the reaction of the carbon and alumina. There would result an elimination of carbon in the state of carbon monoxid and the reacting mixture would become less conductive; this would cause a reduction in the intensity of the current in this section and so reestablish the general equilibrium.

As has been said before, it is advanta geous to combine the useof intermediate electrodes with the system of furnace-diaphragms as shown in Fig. 1; such an arrangement is illustrated in Fig. 4. In this way it becomes possible to combine the useful effects of the methods of regulation of the two systems, according to different requirements; In particular, it becomes possible to vary as desired in each elementary section of the furnace, the thickness of the layer ofmaterial under treatment, and'the extent which it occupies between the consecutive electrodes.

As stated above, the material delivered to the furnace may be a mixture of alumina and carbon with an excess of the latter over or above the quantity necessary to the reaction. By way of example, it may be stated that there may be introduced into the mixture a quantity of carbon double that which -is necessary to the reaction. A part. or the whole of this excess of carbon may, however, equally well be replaced by one or more substances which are good electrical conductors, the metals for example. Among these substances, it is of advantage to select those which possess at the same time the 5. lower crown projecting internally o furnace,in such a way as' to increase the thickness of the layer of material treated toward the outlet end.- I i property of actifying the reaction of forma- I nace having conductiverings and means for, supplying current thereto and intermediate tionof 'niti'id. ,One may, for -example, use 1ron, copper,fn1ckel, manganese of then: ores "or again alloys .of, these metals, such as.

5 ferro-nickel, ferro-s'ilicon, ferro-manganese,

etc. The-use of iron or of certain of its alloyshas the further.- special advantage of allowin it to be se arated eticall from th e-aluminum n'i trid at tli bi d of thz 5 operation. Since iron oxid isalready'foundin greater or less proportions in certain aluminium ores, (in particular the ferrm,

ginous bauxites, for example), it fwill be sufficient in case ofthe useof these ores to" complete by additions the quantity of iron,

requiredto obtain the desired conductivity of the mass under treatment. "I he material introduced into the furnace" whatever be its composition and whatever a the type of furnace employedfmay. be in the pulverulent "state or. in thezform jof agglomerates; it may again be in'the form 'or'agglomerates containing onlyvthe alumina or aluminous .material'and the carbonnecessary to the reaction, whilethe carbon or other conductive material intended'to insure the desired conductivit'} .is added separately. In case'the conductivematerial' added consists Wholly or in-parttgof carbon, the atmospheric air 3. may be useddirectly as the gas of the reac- 'tion; the excess of carbon contained in the material may then serve .at the end of the voperationf andbeyond the electrical=zone to deprivethia air of its oxygen.

66,461, the present application being a divi "J sion offsaid' prior application.

nace, having two conductlve crowns, and

means for I supplying current theretot the the i source, to, divide the i g I for the rings."

, Theprocesses which I have above de-'. -1 scribed as capable'of being carried out. in my I furnaces, form the subject of a separate ap-' licationfiled by me Mayj9, 1913, Serial No.'

conductive rin s interposed at difi'erent :points in there ractorywall ofthe furnace.

3'. An inclined revolving' electrical furnace in the length ofwhich are arranged electrodes which are connected alternately to eachv of the two ipioles of a generating of elementary sections, the length of each of which can'be selected. according to the state conductivity possessed by the material at the time of passing this-section.

rnace into a'number :4. A, slightly inclined revolving continuopsfiirnac'e, having electrodes spaced along th'el'ength of the furnace, and in which the separatlon of the-electrodes diminishes in the direction of'the advance of the material,

'that is .to-say, according as the latter be-- comes less conductive asthe reactions go on.

5. An inclined revolving electric furnace having ,jelectr'odes in the form of diaphragms with decreasing orifices for the pas,- sage of the material, to vary the-thickness of the layer of material under treatment and the extent whichit occupies between the electrodes. t

6. In an inclined rotary electric furnace, a lining composed of refractory conducting rings and refractory nonconducting' material between the rings to insulate thesame from each other; and electrical connections 7 V -7.- In an inclined'rotary electric furnace,

a lining composed of carbon ringsand re- ,f ractory non-conducting material between the carbon rings to insulate the same from each other; a conductive char e bridging the rings and electrical connectlons for the rings. j

.In testimony whereof I have signed my name to this specification two subscribing witnesses.

.Witnesses: y I W. F. ROCKWELL, W. P. MARs'nnmns.

PAUL BUNET.

in the presence of. 1

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