US874944A - Art of electric smelting. - Google Patents

Description

PATENTED DEC. 31, 1907 I. GREELMAN. ART OP BLEGTRIG SMBLTING.

APILIOATION FILED JAN. 5, 1904.

3 SHEETS-SHEET 1.

FIG. I.

INVENTOR: fime a m.

. By Attorneys,

No. 874,944. PATENTED DEC. 31, 1907. P. GRBELMAN.

ART 013 ELECTRIC SMBLTING.

APPLICATION FILED JAN. 6, 1904.

3 SHEETS-SHEET 2.

FIG. 4.

INVENTOR: Q L

By Altameys, mag/0 1Q WITNESSES:

No. 874,944. PATENTED DEC. 31, 1907. P. GREBLMAN. ART OF ELECTRIC SMBLTING APPLICATION IILBD JAN. 5, 1904.

3 sums-sum a m m V N E I, 8 w k k r F a a d n m m w W W TNESSES:

FRANK CREE'LMAN, or NEW YORK,

-1 UNITED STATES" PATENT OFFICE. 1

I COMPANY-F sr. CATHEBINES, *rron.

m'r'or ELECTRIC smam'me.

To all it may concern:

Be it known that I, FRANK CREELMAN, a

' citizen of the United States, residing in the new and useful Improvements in Electric smelting, of a s ecificationp smelting of a mixture 0 county, and York, have nvented certain.

the Art of which the following is borough off'Manhattan, city, State of New adapted to maintain an approximately constant or uniform electro-motive force, and

the effort is made to'maintain an approximationito uniformity of current or volume in each furnace by sp, manipulating the furnace as to maintain an approximation to a uniform internal resistance. The realization of these conditions in-actual practice is extremely difficult, because of the liability of the'formation of ashort-circuitfiwithin the furnace by the melting down of the material undergoingtreatment, or om other cause, so that a heavy rush of curr t occurs which is liable to injure the generating or transformingIelements, the furnace, and

makes the emeltingop'erationproceed in anirregular and fluctuating manner.

; cesslve rush An .exofcurrent' can beflimitedjo some extent by s the like, wit the accompaniment,however, of loss of en rgy I The nearest approximation to uniformity of [current volume heretofore I attained has been by the application of automatic regulating mechanisms governed by the varia tions of current and adapted to control the internal resistance of the furnace, by restormg the normal resistance when anychangle of conditions has disturbed it, and thereby to bring about either arg'approximately con stant volume (oriamperage), or the enpendie "turewithin the furnace of an approximately I constant energy, (or wattage).

These expedients, however, havev only ameliorated the difficulties, since such automatic regu- "lators cannot act instantly, because Lthey.

control the movements of heavy masses which require time to start or stop them.

.-]or exam le,in an" ordinary calcium carbid D furnace, teresistance 1's cdntrolled by mov- Specification Letter-irritant; Application and January 5.1904. sum Ho. 187.7942

ecial windings, choke-coils, or v OF ST. GATI IERI NES, CANADA,.A CORPORA- ing the carbon pencil or furnace, orby moving t e mass of reduced carbid in a continuous (or rotary) furnace. In some other types, of furnaces used in electric smelting, the control of. the internal resistance is even more difieiilt.

vide an electric furnace. of\an'y suitable or known kind, preferably mit a continuous-infeed of material to the arc and a continuous outfeed of the reduced tene'rgy from a source thereo whic is adapt- 1 ed to maintain in the practical operation of the furnace a constant flow or volume, that is to say, withiir number of amperes under anelectro-motive force varying 1n roportion to the-internal resistanceof the urnace; and I so regulate the furnace (by hand or automatically) as to restore the normal internal resistance when varied from, and hence to maintain an approximately uniform internal resistance, to thereby maintain an approximately uniform expenditure of energyor generation of heat. Thus in practical operation whenever the internal resistance varies, the current,- instead ofl-varying -in inverse proportion, remainsconstant, and a variation-involtage alone takes place, the normal 'oltage being soon restored by whichrestores the normal resistance. By the-regulation f the furnace Lmean the manipulation of such movingpartsas control its internal resistance; that is to say, ir; a crucible furnace the lifting of the carbon I vancement ofltheshell carrying the reduced horizontal incandescent fur- ,CilS. 1

eration-to be conducted with great precision and uniformity both in the rate at which the reduction proceeds and in the consumption of electrical energy, and results in a big degree of economy, while avoiding .the deterioration of the furnace elements and the liabilityto injury ofthe lectrical g'eneratingor cidental to the .violently' flu ctuating action heretofore encountered in electr c smelting operations.

Accprding" t9 further; feature of my in- Patented ne 31,1907.-

the regulation of the furnace,

product, commonly in the form of a pig or ingot; or in a N nace the separation of the conducting penencils in a crucible In practicing my-iniproved process I pro- -product;.I. rovide for supplyin electrical narrow limits a constant pencil or pencils; in a rotary furnace the ad I,

new process enables the smelting optransforming elements, -which have been 1n-.

vention I utilize, the constant current system hereinbefore set forth for the production of calcium carbid in a crustless pig. In the ordinary production of calcium carbid in the form of a pig or ingot, only the central portion of the powdered orbroken mixture of lime (or limestone) and carbon is reduced, and immediately surrounding the reduced product or pure carbid in the pig is a crust of the partially fused and unreduced or but partly reduced mixture, which is very low in carbid and hence practically worthless; and outside of this crust is a layer of the mixture which is entir ly unfused and practically unaltered. It is customary to chip off the crust from the pig, an operation which involves considerable expense. It is also customary to return the outer layer of mixture to the furnace to be resmelted. The formation of crust and the necessity of re-handling the hot unreduced mixture, are serious difficulties in the manufacture of calcium carbid. Efforts have been made to produce a crustless carbid bytapping the liquidproduct from the furnace at intervals, but this tapping process has been successful only with comparatively low grade carbid, which will not compete in the market with the ingot carbid. One serious difficulty with the tapping process is that the molten carbid is liable to congeal in the tap-hole; to avoid this it is necessary before tapping to force the pencil or pencils deep into the 'mass and heat it to a high temperature to insure the requisite fluidity, which is not only wasteful of energy, but results in dissociation of the elements, producing burned carbid of low gasproducing power.

According to my invention I produce cal cium carbid (or analogous material) in a crustless pig or ingot by a process differing from that practiced in the ordinary pig or ingot furnaces, and differing from that practiced in the tapping furnaces. may be said to be a continuous tapping process in which the zone of fusion is maintained in the tap-hole itself, the fused "material being supported immediately beneath the taphole to uphold therein the material undergoing fusion. In practicing this process I feed or pass the entire mixture through the zone of fusion and reduction maintained between two electrodes, the interspace between from the furnace.

the electrodes constituting the outlet or taphole of the furnace, and also constituting the zone of reduction. Preferably one electrode is formed'as a pencil projecting into and through an opening formed in the other or annular electrode, the annular space between the two forming the interspace or'taphole. Since none of the mixture can pass through this interspace or zone of reduction; without being reduced, no crust is formed, and no unreduced mixture is discharged The molten carbid is My process formed into a pig or ingot in a suitably shaped conveyer or trough beneath the outlet from the furnace. The application of a constantcurrent is practically important to the success of this process, since in this process the electrodes are normally stationary or are readjusted only at long intervals as they wear away, and wide but momentary fluctuations of resistance are liable to occur due to variations in the condition of the material filling the interspace or zone of reduction.

I will proceed to describe the practical application of my process and suitable apparatus for practicing it in connection with the accompanying drawings, wherein,

Figure 1 is an electric circuit diagram illustrating three furnaces .fed by an alternating current dynamo through transformers; Fig. 2 is a similar diagram showing three furnaces fed by an alternating current dynamo through a single transformer Fig. 3 is a similar diagram showing a furnace fed di rectly from a dynamo; Fig. 4 shows in seetional elevation a vertical type of furnace, the electric connections being shown in diagram; Fig. 5 shows in vertical section a form of double-pencil continuous furnace with its electrical connections; Fig. 6 is a vertical section of the form of furnace crustless carbid according to my complete invention, with its electrical connections; Fig. 7 is a transverse section of the furnace shown in Fig. 6; Fig. 8 is a plan showing the arrangement of the electrodcs.

In all the figures A designates an electric furnace and B a dynamo or generator, C 7 being transformers, and D D (in Fig. 2) being current regulating coils.

In the diagrams Figs. 1., 2 and 3, the furnace A is assumed to be of the single carbon crucible type shown in Fig. 4, E being the central carbon pencil, and F the pot or crucible, which constitute respectively the clec-- trodes. This is a well understo d type of furnace, the pencil E being'vertically adjustable to cause it to recede from the pool of reduced material which accumulates in the crucible. 1

In the preferred circuit arrangement shown in Fig. 1, the dynamo B is an alternating current generator, which may be adapted to maintain a normal constant potential or electro-motive force upon the main wires or leads G G. For each furnace A is provided a separate transformer C, of which a is the primary coil and b is the secondary. The primary coils are connected in nultiple with the main circuit'leads. Each transformer (I is of any construction adapted to maintain a constantcurrem in its secondaryroil b which feeds thefcircuit c d leading to the furnace. One suitable construction for these transformers is that in which the primary or secand so counterbalanced that as the. secondary current increases it causes the movable coil'to recede from the fixed coil and to maintain a" constant current. Such a transformer suitably fed by an alternating dynamo becomes a source of constant curstate that each current of 2,000 amperes under normally'-75 also feedin load upon the stant voltage.

branch circuits 0' volts difference of potentials/at the-furnace terminals, this voltage however varying 'constantly from time to time: I contemplate v a' series of furnaces from a smgle dynamo w ich,may have-a uniform voltage of-2,'200,'andmai1'1taining a mean or normal total current of 650' amperes; divided among the primaries' of any suitable number of transformers, sald primaries being arranged in parallel, forexample ten, each receiving amperes; the secondaries of these transformers being each in a se arate circuit including one furnace, and de ivering thereto a substantially uniform current approximating 1,000'amperes under a varying electro-mor, tive force.

tions' of load upon individual furnaces to some extent offset one another, so that the generator is the sum of the loads upon the respective furnaces.

With the arrangement shown in Fig. 2, the

whichfurna'cemay receive a normal;

By-this arrangement the varia thereby diminish the induction such proportion as the manner. shown in Fig.

ating operation is yternal resistance, instead of rent to the normal, acts to restore the noralternating dynamo B feeds the primary 0/ V 'ofinhe transformer C w ch feeds the'main leads H, H. In this case the transformer is not necessarily a constant current transformer, but 'will normally be adapted to maintain substantiallycon- The furnaces are fed. by (1 derived from the main leads II H, and in each of these branch circuits is introduced a current regulating coil.

D of any-suitable kind-adapted tomaintain a constant current within its own branch circuit. The coil D may be of that character the coil to introduce'moreor'less self induc tion or im edance, and thereby to prevent any rise 0 current above the normal, an

hence within narrow practical limits to keep the current constant. This arrangement,

however, is less desirable than that first'described.

In Fig. 3 is shown a dynamo B, whieh gy be either an alternating current or direct current generator connected directly to a fur- In this case the dynamo is itselfthe'secondary b" of f increase within the. furnace.

according toany known system.

In Figs. 4 and 5 two tgpesof furnace areshown, 1n' each case the mace being energized by a constant current transformerC in 1. With either type of furnace the regu performed either manually or mechanically, andis determined by the variatiofi of voltage or electre-motive force at the furnace terminals. That is to 'sa if a variation in resistance. occurs within t e furnace, of. causing a change in voltage; and the ensuing regulatingxnovement which restores the normal inrestoring the'curmal voltage; Preferably the regulating operation is made automatic under direct control of the variations in voltage. a.voltmeter- J is shown connected between the leads 0 d to show thevariations in -vol-' tage at the furnaceterminals by which an operator may be uided in manually regulating the furnace, t at is, with this type of nace in raising or lowering its pencil E In Fig.5 a regulating shunt magnetK isshown adapted to control the rate of feed offthe furnace body, (which in a furnace of this type moves the ingot or pool of reduced ma-v terialaway from the fixed carbon pencils). The magnet K may actuate any suitable reginrl 4 a furconstructed to maintain a constant current at instead 1 change in current,-1t causes a,

ulating mechanism; for exampleyit may pper te or control they regulating mechanism commonly appliedin rotary furnaces. An example of suitable mechanism is contained in my application filed January 7, 1904, Se+

rial'No. 188,038, the movable member or core of the ma net, K'being substituted for the part \E in 'g. f of said application. Whenthe proper-rate of passage of the material through the zone of fusion is deterthis rate of feed an it isnot necessary to vary it continually to correct trifling fluctuations ininternal resistance; because if fusion takes place 'too.

moment the reduction nre-f sistance reducesthe voltage and reduces the" rapidly at any rapidity of fusion so as to automatically check itself; or if the rateof fusion should be I retarded for a short time WheremIa core ,eis drawn more-or less into for any reason; the

resistance and the voltage and consequently the energy (or watts,- or heating effect) would so as to tend to makeup for the loss.

action tend to be regulator may be suitable sort Thus the irregularities of -selfcompensating. The controlled by a governorof any which responds to variations in the internal c resistance, and which 0 erates'to rectify after a certain interval o time an departure which has'occurred from norma conditions The self compensatlng action referred to being instantaneous, pre- &

cedes the necessarily slow action ofa regulator, which, even if automatic and very sensitive, requires an appreciable time to restore the normal internal resistance.

An important advantage of my invention 1s that it protects the electrodes. from injury I by excessive heat. In the ordinary furnaces, when the current becomes excessive, the heat due to the resistance of the electrodes increases with the square of the current, and as the resistance is greatest at-the'contact between the iron carbon holders and the carbon pencils, the holders are liable to be fused at this point, which would result in the dropping of the pencils. Since with my invention the increase of the current beyond the normal is impossible, such injury to the holders and destruction of the encils is avoided. My invention also avoids lieat loss (or C R loss) in the carbons due to anexcessive cur rent, which with carbons of high resistance becomes an appreciable waste.

I will now describe the furnace shown in Figs. 6, 7 and S. The electrode E is in the form of an upright pencil, having means for vertically adjusting it to compensate for wear. The electrode F is in the form of a plate or slab having a hole or opening f forming the inter-space in which the are or zone of fusion is maintained. The furnace chamber above this lower electrode .is fed" with the Ymixture to be smelted through chutes g gin the ordinary manner, Beneath the lower electrode is placed a receptacle L, preferably in the form of a trough made up of sections-as shown, these sections being movable in a direct line and horizontally, or down a suitable incline, as preferred, either by constructing them as cars running on a suitable track, or as slides moving on suitable slideways, or preferably by providing a succession of anti-friction wheels h h for carrying the trough sections. In Fig. 6 the trough sections travel from right to left, their left hand or outgoing end being closed by the solidified carbid within the trough, while their entering or right hand end is closed by a plate M, which serves primarily to prevent ingress of air, which would oxidize the electrodes, and also serves to limit any outflow of the molten carbid. Any suitable regulating mechanism serves to slowly or intermittently push forward the trough sections, a' new section being supplied from time to time, This regulating mechanism is controlled by a magnet or other electromotive device K adapted to respond to fluctuations in voltage. A suitable regulating mechanism is set forth in detail in another applicatfon executed dently herewith, namely, Serial No. 188,038-

f-iled January 7, 1904.

In starting the furnace, the trough section if beneath is'filled with a pile of suitable heat by me. 'coinci' resistant material, coarse carbon or' coke being introduced into the *interspace between the electrodesto complete the circuit, and the current being turned on, the zone of fusion is immediately instituted in .this in terspace; the raw material is then fed into I the furnace chamber above, and a portion thereof falls into the interspace, where it is fused and reduced, the fused carbid flowing down through the zone of fusion and" resting upon the material in the trough beneath. As the reduction proceeds, fresh material falls-into the arc or zone of fusion. As the fluid product descends below the zone of fusion, it eventually cools and hardens, forming a pig or ingot of carbid the shape of which is determined by the shape of the trough. Whenever the fluid material accmnulates too close to the interspace so that it reduces the resistance. between the electrodes, the consequent reduced voltage causes the regulating mechanism to act and push forward the trough sections, so that the molten product is permitted to overflow and restore the normal resistance. In this furnace there is no control of or readjustment of the electrodes by means of a regulating mechanism to maintain aconstant resistance, and therefore as in the ordinary stant current; but on the contrary the resistance in the interspace between the electrodes is subject to wide fluctuations aecompanied by corresponding fluctuations in voltage, the current remaining constant within the capacity of the generating and transforming apparatus. Such relatively fixed electrodes would be inadmissible in a furnace energized by the usual source of approximately constant potential.

-Heretofore (exce t in tapping furnaces) it has been practically necessary in order to produce a high grade carbid, to employ as the raw material an intimate mixture of I pulverized lime and carbon, the latter being usually in the form of coke or anthracite coal. My invention enables considerable economy to be attained as compared with other ingot furnaces by using limestone instead of lime, and by using the materials in granulated or lump form instead of pulverized. I My invention is not necessarily limited to the production of calcium carbid, but is appllcable so far as concerns the use of a constant current, to electric smelting generally, and so far as concerns the complete l process whereby a crustless product is produced by a continuous tapping operation, to 1 any roduct presenting difliculties analogous l to t ose encountered with calcium carbld. I do not claim to be the first inventor of the process whereby calcium carbid or analogous product is produced in a crustless furnaces an approximately 0011- l pig, or is produced by passing the entire mixture of raw material through a zone of w fusion and reduction from which the reduced materiahis' discharged as a crustless subjecting the mixture to the heat produced My invention may be greatly varied or modified in its application to Varying types or kinds of electric furnaces, and in its application to the roduction of different products, without eparting from its essential features or characteristics.

I do not herein claim the electric furnace shown in I the accomthe same'being claimed in my aforesaid application No. 183,038.

I claim as my invention: v

l, The process of electric smelting which consists in subjecting the materia to be smelted to the heat of an electric current of substantially uniform amperage notwithstanding variations in the internal resistance of the furnace, andregulating the furnace to restore the normal internal voltage and maintain an approximately uniform expenditure of energy. r

2. The process of electric smelting which consists in subjecting the material to be smelted to the heat of an electric arc maintained by electric energy of substantially uniform amperage notwithstanding variations in the internal resistance of the furnace, and regulating the furnace to restore thenormal internal resistance and thereby maintain and appurtenances an approximately uniform expenditure of energy. Y

3. The process of electric smelting which consists in subjecting. the material to be smelted to electric energy of substantially uniform amperage notwithstanding variations in the internal resistance of the furnace, and regulating the furnace by means of the variations in electromotive force occurring at charging the fused carbid as its terminals to restore the normal internal resistance.

4. The production of calcium carbid by by a current of electricity of substantially uniform amperage notwithstandin variations in the internal resistance of the urnace,

and regulating the furnace to restore the normal internal resistance and thereby restore the normal voltage and maintain an approximatelyuniform expenditure of energy. A i 5. The production of calcium carbid by fusing the entire mixture in. a zone of fusion produced by an source of energy of substantially uniform amperage notwithstanding variations in the internal resistance of the furnace, and disa-crustless pig. 6. The production of calcium carbid by fusing the mixture in a zone of fusion formed by an electric arc, and discharging the molten carhid; therefrom into a mass of carbid beneath the outlet from the furnace, which mass is held so closely adjacent to the zone offusion that it is maintained molten.

7. Electric smelting by passing the material to be smelted through a zone of fusion maintained in an lnterspace between electrodes,'-from which the fused material may freely flow, and continuously discharging the fused and reduced material therefrom into a receptacle beneath the outlet from the furnace, this receptacle being located so closely adjacent to the zone offusion that the material is maintained molten.

In witness whereof, I have hereunto signed my name in the presence of two subscribing witnesses.

FRANK CREELMAN.

' Witnesses:

ARTHUR C. ERAsEa, FRED WHITE.

electrlc arc maintained by a

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