US1515967A

US1515967A - Electric furnace

Info

Publication number: US1515967A
Authority: US
Publication date: 1924-11-18
Anticipated expiration: 1941-11-18

Description

Nov. 18, 1924- 1,515,967

H'. c. REAGAN ELECTRIC FURNACE Filed Feb. 24, 1920 4 Sheets$heet 1 49 47 50 I l- I 46 INVENTOR.

Nov. 18, 1924. 1,515,967

H. C. REAGAN ELECTRIC FURNACE Filled Feb., 24, 1920 4 Sheets-Sheet 2 4 ,6 2: :2: i W/Z INVENTOR. H .C. R EAGA N.

ATTORNEY.

Nov. 18, 1924. 1,515,967

H. c. REAGAN ELECTR I C FURNACE Filed Feb. 24. 1920 4 Sheets-Sheet 5 INVENTOR. H c. REAGA H. C. REAGAN ELECTRIC FURNAC E Nov. 18, 1924- Filed Feb. 24 1920 4 Sheets-Sheet 4 INVENTOR.

H .C. REAGA Patented Nov. 18, 1924.

PATENT OFFICE.

HARRY C. REAGAN, OF BOULDER, COLORADO.

ELECTRIC FURNACE.

Application filed February 24, 1920.

To all whom it may concern."

Be it known that I, HARRY C. REAGAN, a citizen of the United States, residing at Boulder, in the county of Boulder and State of Colorado, have invented certain new and useful Improvements in Electric Furnaces, of which the following is a specification.

My invention relates to electric furnaces and its primary object is to provide a fur naee of novel construction in' which ores and other fusible materials may be' rapidly smelted at a low cost ofjgop'erationfi Another object of the invention is .toprovide in an electric furnace, oneworimore hearths of conductive material which "in the operation thereof function. in ;conjunction with each other or with ordinaryrelectrodes to cause the passage of an electriccurient through a resistant mass of material under treatment.

A further object of'the invention: is to provide novel means for preheating. the charge fed into an electric furnace, and still other objects reside in the provision of novel features of construction, and arrangement of parts by which a maximum effi- :ciency is combined with simplicity of 'con-' struction and economy in-installation, maintenance and operation. 'i a With the above and other objects in vie w all of which will fully appear-in. the courseof the following description, my invention consists of the construction and'combinations of parts shown in theaccompanying drawings in the several vie'ws'of which corresponding parts are similarly designated and in which w Figure 1 is a vertical sectional view of my improved furnace in its preferred form;

n the line Serial No. 360,567.

coil employed to preheat the charge to the furnace;

Figure 7, a sectional elevation of a furnace of modified construction, and

Figure 8, a sectional elevation of a furnace in which two melting units constructed in accordance with my invention are arranged for conjunctive operation.

Referring first to Figure 1 of the drawings, my improved furnace consists of a body structure 2 the walls of which are preferably made of brick lined with a suitable refractory material of high heat resisting qualities, such as silica brick.

The structure is'divided into upper and lower crucibles or smelting

chambers

3 and 4 connected by a narrow passage 5. Atopposite sides of this passage in the upper crucible, are channels or depressions 6 containing'conductive hearths 9 of a construction which will hereinafter be described in:

detail.

The channels adjoin the outer walls of the furnace and they are separated from the passage between them by bridge walls 7 pro vided with longitudinal passages 8 for the circulation of air. I

The lower crucible has a hearth 10 of conducting material which extends across its bottom and directly beneath the central passage between the hearths of the upper chamber. The lower chamber is preferably made narrower than the upper one and the projecting portions of the upper part of the structure 2 are supported upon walls 12 which are spaced from the walls of the lower part of the same to provide archways 13 for the circulation of air and to afford access to the terminals of the conductive hearths of the upper chamber as will hereinafter be more fully explained.

The central portion of the structure as above described is supported upon piers 1 1 which are separated from each other to provide a space giving access to the terminal of the hearth in the lower melting chamber.

The hearths of the upper crucible are each composed of a hollow metal base 15 laid upon the bottom of the depression upon which the hearth is formed and provided with a multitude of upwardly projecting pins 16 and with a terminal 17 which exfit) tends through an opening in the bottom of the depression into the archway 13 beneath the same.

The terminal of the base has suitable means for the attachment: of one or more conductors of electricity forming part of a circuit in which the hearth is connected.

The hollow base is connected. with a source of water supply by means of a pipe 18 and' it. has an outlet. pipe 19 for the discharge of the water after it has performed its function of cooling the parts withwhich it comes in contact.

The hearth proper is composed of a body 20 of refractorv and conductive material "preferably of the kind whose conductivity for electricit" increases in proportion to ts in operations The surface of the hearth flares upwardly along the outer wall of the furnace toprovide a protect-ire coating which preventsthe' accunu'ilationof molten metal in direct contact wit-hi its lining.

The construction of the hearth o l the lower melting chamber is similar to that. of the upper one in tlhat it consists of. a body of conductive and iefractory material sup ported upon' a metal base which: is provided with a terminal. for its connection in an electric circuit.

The; base in this construction is composed of a plate 22 placed betweenthe walls of the lower part of the furnace and the piers upon which they are supported and pro vi'd'ed with a central opening to receive the ter minal by which: it is connected in the circuit.

This terminal is preferably composed of a. flanged open box 23 rigidly connected to the plate by bolts passing. through openings in its flanges and' provided with binding screws 2+ for the attachmentof conductors of electricity at itsbottom portion with-hr the spacebetween the piers.

The box has a filling 25 of conductive material preferably composed of carbon blocks and the plate is covered by a layer 26 of noncond'uctive material such as silica bricks, which extends in a plane with. the upper edges of the box.

Formed upon this base is the body portion 21 of the hearth made as before of dolomite, magnesite or other similar substance and having its upper surface. concaved to fonn a cup or basinfor the metal melted in the operationof the furnace-.-

In order to prevent the communicatioir of heat generated in either crucible to the walls of the other, the structure may be composed of two sections which are insulated from each other by an interposed gasket 27 of nonconduoting material.

Thereof 28-of the furnace; which may be flat or arched. hasa central opening 29 for the passage of the charge from a superposed feed stack 30. The joint between the roof and the walls of the body structure of the furnace, upon which it is loosely supported, is sealed with a packing 31 of nonconduct ing material such as asbestos, wool and soapstone placed in a trough or gutter 32 set along the dividing line.

The opening in the rootof the furnace which is vertically alined with the narrow passagebetween the two crucibles is divided by a'- wedge shi'aped' partition which in the o oration of'the furnaceserves to distribute tie ch'a'rge: passing from the stack through the opening, so that part or it will fall directly onto the two healrt li's of the upper chamber which project horizontally in wardly fromthe opposite walls thereof.

The feed stack of the furnace is sus pended above the roof of its body portion in air-tightconnection. with the central open ing'of' the sa'me from IbeRlllS 34' which are supported: upon a: suitable structure, as for example the walls of a building in whichthefurnace is erected.-

A hopper 35 at the upper end of the stack is contracted to provide a seal 36* for a cone-shaped valve 37 which may be raised orlowered by any suitable means. not. shown in the drawings,- to regulate the passage: oll material fed into the hopper from a conveniently located: source of supply,- to the stack.-

Movably suspended above the hearths of the upper crucible are two ordinary carbon on graphite electrodes 38- wlrich pass through openings in the roof of the furnace.-

The carbons are suspended by means of non-conductive cables 39 from sheaves 4 0' mounted at opposite sides of the stark and their cables may if so desired be connected with a suitable winding lllfltllfllllilll not shown in the drawings.

The openings in the roof of the furnace through which the electrodes extend are sealed by a packing 41 similar to that employed to cover the joint betweenthe roof and the walls of the furnace and placed in nonconducting cups 42 which are: fastened to the roof around the openings.

The pamages 8 of the bridge walls which Separate the hearths of the upper settling chamber from the narrow passage between them, are connected at one of their ends by aconduit 43 to a source of air under pres sure such as ablower or other similar d evicet and air passing through their opposite ends is by means of a pipe- A conducted to two manifolds or bus pipes 45 and 46 placed around the stack and the hopper. with which Ill they are connected by a plurality of

tuyeres

47 and 48.

Valves

49 and 50 controlling the flow of air to the two manifolds are placed to permit the passage of air to either one separate from the other as may be desired.

The hopper of the. stack has a gas-escape opening 51 which may be connected with a condenser or a receiver in case it is desired to save the gases for the recovery of any of their elements or of matter held in suspension therein.

The material charged into the furnace may be further dried and preheated before it enters the upper melting chamber, by an induction coil 52 placed aroundthe stack.

When the stack is made of a brick-lined metal shell as is usualin furnaces of this type, the shell is omitted at'the point at which the induction coil is located to permit of the formation of'a' magnetic field in the interior of the stack."-' i Referring to Figure 6' of the drawings, the primary windings 53 of the induction coil are asusual connected in an electric (fircuit. p

The charge falling through the stack from the superposed hopper'passes through the magnetic field of the coil=and being highly resistant; to the current created in the m ass as it passes through the magnetic field, generates heat which iscmnm'unicated to its metal constituents" before they enter the melting'chamber.

The efiect of the primary coils may be increased by providing one or mole second ary c'ils54; fandthe coils are by'means of conductors of 'electricity= '55 connected to contacts at bpposit'e "sid'es'"df* one of the hearths' "of the furnace preferably at a dis tance belowthe normal level of the molten mass which congregates thereon, so that the current induced in; the secondary coils must pass'through s aid mas's to complete the circuit.

In the operation of the furnace as above described, the three conductive'hearths function as electrodes in conjunction with each other and with the carbon electrodes 38 for the passage of a current of electricity through the material in the melting chamb'ers, which forms a resistance and is rapidly heated to a high temperature by the arc passing'through it.

The carbon electrodes are in the preferred form of the invention used merely for priming purposes to heat the material initially until its temperature is sufliciently high to permit of a constant passage of electric current between two of the conductive hearths connected in opposite sides of the circuit.

The hearths and the electrodes are to this end connected in an electric circuit together with one or more switches which are adjustable to either produce a flow of current through the carbon electrodes and the hearths of the furnace above which they are suspended or to cut the carbon electrodes out of the circuit and connect the upper and lower hearths in opposite sides of the circuit for the passage of electricity be- In Figure of the drawings the conduc- 1 tive hearths 9 and and the carbon clec trodes 38 of the furnace have been shown connected in a three-phase system, the referenoe characters 56, 57 and 58 designating the contact rings of a generator of electricity and the

reference characters

59 and 60 the switches to transfer the current from one part of the circuit to another.

In the operation of the furnace the ore fed into the hopper passes past the open valve 37 and through the stack into the upper crucible 3, part falling upon the hearths 9 and part passing through the opening 5 onto the hearth 10 of the lower crucible 4. 1

-To"prime or start the furnace the electrodes 38 are lowered to a distance from the hearths; of the upper crucible above which they aresuspended, sufficient for the passage of current through the resistance of the material with which the chambers are filled, and the switches 59 and are adjusted for a. current flow along the following path:

Commencing at the first phase ring 58 ofjthe generator, the conductors 61 and 62 connected by the switches 59, one of the carbon electrodes 38, the hearth 9 above which it is suspended, conductors 62- and 64 connected in the switch 59, the second phase ring 57 of the generator,

conductors

65 and 66 connected in the switch (311 the other hearth 9 of the upper crucible. the corresponding electrode 18. the conductor 67, the switch 60 and a conductor 8 connected with the third phase ring 56 of the generator.

The current passing between the electrodes and the respective hearths rapidly heats the material in the upper crucible beyond the melting temperature of its me tallic constituents and the molten metal congregating on the hearth either flows across the bridge walls 7 into the lower crucible or is drawn from the furnace through tap holes 69.

The heat generated by the high resistance of the material in the furnace rapidly increases the conductivity of the material and of the conductive and refractory substance Til lit)

of which the hearths are composed and by the time enough metal has been molten to cover the surfaces of the hearths the material has been rendered sufiiciently non-resistant to conduct a current of electricity between the hearths of the upper chamber and that in the lower one.

At this point in the operation the position of the switches 59 and (i0 is reversed and the current is transferred to flow through the following circuit:

Commencing at the phase ring 58 of the generator, the conductors 61 and- 70 connected in the switch 59, the conductor 68, the corresponding conductivehearth, 9 of the upper melting chamber, the conductive hearth 10 of the lower melting chamber connected by

conductors

71 and 65 with the second-phase ring of the generator, through the

switches

59 and 60, the second hearth 9 of the upper chamber, the conductor 66, the switch 60 and the conductor 68 connecting with the third-phase ring of the generator.

The different hearths of the furnace now function as electrodes to heat the material in the chambers by its own resistance independent of the carbon electrodes whichare raised above the heated and melting mass.

The molten metal congregating on the three hearths, being of very low resistance, forms a conductive medium between the material under treatment and the conductive substance of which the heartlis are composed and being constantly renewed it lengthens the life of the hearth by facilitating the passage of the current to the; conductive constituents of the material.

The molten metal may be constantly discharged from the lower melting chamber through a. tap-hole 72 or it may bemade to rise to any desired level in the chamber-and maintained at that level by proper regulation of its discharge in order to decrease the distance of current travel. in case the material is of low conductivity or low metallic value, or in case the current is not sufficiently strongv to pass between the hearth-electrodes through the material and heat the latter to the required temperature by its own resistance.

The operation may under any of the above-mentioned circumstances be expedited by permitting the molten metal to overflow the bridge walls of the upper hearths into the lower crucible, but it will be understood that under normal conditions the material as it is fed into the furnace and before it is melted, forms the resistant body through which the current passes between the hearths.

Inasmuch as all the current must flow through the narrow passage connecting the two crucibles, the zone of greatest heat is directly in line with the feed opening in the roof of the furnace and it follows that the material which falls directly into the lower melting chamber must pass through said zone and is thereby heated as rapidly as that which first falls onto the hearths of the. upper chamber.

The air constantly circulating through the passages in the bridge walls prevents overheating of the materials of which the walls a re composed and thereby lengthens the life of the structure, it being understood that the walls being located in the zone of heat of greatest intensity are more rapidly destroyed than those remote therefrom.

The position of the hearths in projecting relation to the outer walls of the furnace and the cupped form of their upper surfaces which permits the molten metal to flow away from said walls, greatly aid in lengthening the period of effective condition of the outer parts of the structure.

The air which while passing through the bridge walls is heated to a high temperature, is employed in drying and preheating the charge by its admission to the interior of the hopper and the stack through the tuyeres of the buspipes 45 and 46.

The

valves

49 and 50 provide a convenient means to proportionate the quantity of air admitted at the two points of entrance to the material, according to its temperature or volume and other variable conditions, and the induction coil placed and connected as hereinbefore described further preheatsthe material as it passes through its magnetic field.

The construction of the electrode-hearths which must necessarily be of very refractory character, is designed to give them a maxi-- mum degree of conductivity compatible with the refractory quality necessary to resist the intense heat generated in the furnace. The metal pins projecting from the terminal plates of the upper hearths distribute electric current through the bod of refractory conductive material in \vhici they are embedded and the carbon bricks of the lower hearth perform a similar function.

The water jackets of the terminal plates of the hearth reduce the temperature of the conductive parts with which they are in contact and the manner in which the hearths are arranged permits of their ready removal and renewal in case of wear or breakage without disturbing the walls of the structure.

A furnace of the character hereinbefore described is not only adapted for melting ores and other materials at a low cost of operation, but may also be employed in refining steel by charging the upper hearths with raw material exclusive of the other and permitting the molten metal to overflow into the lower crucible in which it is refined.

The very limited period during. which the carbon-electrodes an: actively employed in the operation of the furnace is an important factor in reducing the cost of operation, it being understood that the electrodeahearths constructed as described are well adapted to resist the heat and are not consumed by the electric cur'rent'and that except under'unusual circumstances the carbons are not used in the continuous operation of the furnace.

In'the form oflmy-invention sl own-in Figure 7 a single melting chamber 73 has three hearths 74 arranged with'the central one beneath the feed opening of itsroof and intermediate of the others. The central hearth is placed at a higher elevation than the others between two hollow bridge walls 75 and the carbon electrodes 76 are'movably suspended above the other hearths'as before.

' -The'o'peration of'the furnaceissubstam -tially-the'same as'that of the first-described construction. The structural form of -the furnace is changed in I accordance with the different; arrangenient of the hearths, and

-- its walls are made in three sections -7 7 and 78 divided by interposed gaskets 79 z of nonconductin-g material. I r

This Cteature of the construction-aside from its insulating qualities hasfl the' 'adwantage of providing a convenient method of dismantling thefurnace in case of repairs or removal.

, The-upper section 77 of the furnace is suspended by means f of bars 79 from a suitable-support such as the walls of a building iii which the furnace is erected and the lower sections 78 are held in-i-cooperative relation totthe oth'erupon liftingljacksi80 which are preferably. mounted on railway trucksSL For purposes :of repair or replacement the lower sections of the furnacexcanbe removed from the upper one by lowering the jacks and moving the trucks along the rails upon which they are supported.

A man-hole 82 in the walls of the furnace normally closed by an air-tight door, gives access to the interior of the structure for minor repairs and adjustments.

In Figure 8 of the drawings, two separate furnace-units 83 each having its individual feed-stack 84:, can be connected for separate orsimultaneous operation with one and the same source of electricity. Each unit has two electrode hearths '85.,placed one above 'the :other and one movable. electrode 86 which sis suspended above the upperhearth.

. By connecting the corresponding hearths of the two furnace units in multiple, the two units may be simultaneously operated by the current flow in a circuit suchas that hereinbefore described, or by placing an-' other switch in the circuit, one unit may be operated independent of the other if so desired.

It will be seen that in a duplex furnace-of t-his character all danger of $119M Cilouiting between two hearths in one side of an elec tric circuit is avoided and that if necessary two different materials may be treatedat one and the same time;

f The illustration furthermore shows a Silliphtied method of constructing 'a single furnace 11108.88 the'desired capacity renders the use of a singleupper hearth sufficient. I

I desire it understood that while 'Lhave shown and'described an arrangement of conductive hearths in which oneuis disposed above another, it is possible: iwithinfithe principle of my invention'to place one or more conductive hearths connected in. an electric circuit as/before oulsubstantially the same leveLand I'desire'ithfurtherunderstood that other modifications in'tthe construction and arrangement; ofi #1116 parts. of

the furnaceiiin anynof itsi formsiiherein shown .and described nnay be jresorted to within the spirit ofthe" inventioncas defined in the following claims;

o VVhat I claim anddesire toisecureibyd et ters-Patent is:

.F f I -1. In an; electric. furnace,-ai broken circu t,

' and two I conductive hearths 1; placed. mini; a

chamber-of the. furnace ondiofowhichis cupped-:etoretain a portion of'the'material under treatment and disposed vwithrirelation to the Mother ltobovetflownthereinto, :tll8 hearths. being: connected at, opposite sides l of a break in. thecircuit to permit of material on one overflowing-onto .theothernandcon- :nected in'the circuit ifor the-zapassage-of electricity between ;them.

2. In an electric. furnace, a circuit, a plurality. of conductive hearths adapted to retain a quantit'y of the material under. treatment upon; the; same and; an electrode 5 in a chamber of thezfurnace said hearths and said electrode being connected in the circuitfor the.passage of electricity; between them, and means to transfer the current flow through the circuit to either pass between the electrode and one of the hearths, orbetween one hearth and another.

;3. In an electric furnace, a plurality of conductive hearths and an electrode in a chamber of the furnace, circuits in which said hearths and said electrode are connected, rand current-controlling means to produce a flow of electricity either between said electrode and one of said hearths or structure composed of insulated sections, conductive hearths in said sections, and a circuit in which said hearths are connected for the passage of electricity between them.

(5. In an electric furnace, a chambered struc ture composed of insulated sections one of which is removably mounted with relation to the other, conductive hearths in said sections, and a circuit in which said hearths are connected for the passage of electricity between them.

7. -An electric furnace having upper and lower crucibles connected by a narrow passage, a conductive hearth in the lower cruoible, a conductive hearth in the upper crucible at aside of the passage, and a circuit in which the hearths are connected for the passage of electricity between them.

8. An electric furnace having upper and lower crucibles connected by a narrow passage, a conductive hearth in the lower crucible, a conductive hearth in the upper crucible at a side of the passage, a hollow bridge wall separating the hearth in the up per crucible from the passage, and a circuit in which the hearths are connected for the passage of electricity between them.

9. An electric furnace having upper and lower crucibles connected by a narrow pasu sage, a. conductive hearth in the lower crucible, conductive hearths in the upper crucible at opposite sides of the passage, and a circuit in which the hearths are connected for the passage of electricity between them.

10. An electric furnace having upper and lower crucibles connected by a narrow pas sage, a conductive hearth in the lower cruoible, conductive hearths in the upper crucib'le at opposite sides of the'passage, hol- 40 low bridge-walls separating the hearths in the upper crucible from the passage, and a circuit in which the hearths are connected for the passage of electricity between them.

11. An electric furnace having a feed-opening, a health in vertical alinement therewith,

hearths at opposite sides of the other, and means to direct material fed through said opening onto said hearths.

'12. An electric furnace having a feedopening and upper and lower crucibles con nected by a passage in vertical alinement ith the feed-opening, a conductive. hearth in the lower crucible, a conductive hearth in the upper crucible at a side of the passage,

a vertically movable electrode above the an air-conduit extending through a crucible of the furnace, a bus-pipe in connection with said passage, and tuyeres connecting the buspipe with the stack.

15. In a melting furnace, a feed-stack and a dividing-bridge wall in a crucible of the furnace having an air passage in connection with the stack.

16. In a melting furnace, a feed-stack, and an air-passage extending through a crucible of the furnace in valve-controlled connection with the stack at separated points thereof.

17. In a melting furnace, a chambered structure, a roof removably sealed thereon and having a feed opening, and a separately supported feed stack connecting with said opening.

18. In a melting furnace, a crucible, a non-conductive feedconduit connected there- :ivit-h, and an induction coil around said con uit.

19. In a melting furnace, a crucible, a nonconductive feedconduit connected therewith, and an induction .coil around said conduit having secondary windings electrically connected at separated points of the crucible.

20. In a melting furnace, a'crucible, a

feed conduit connected therewith, a hearth 1n the crucible, andan induction coil around the feed-conduit, having secondarywindings electrically connected at separated :points of the crucible adjacent the hearth.

21. In. an electricv furnace, a .-melting chamber, metal retaining conductive hearths disposed therein for'the passage of molten material from one to the other, a broken circuit in which said hearths are terminals, and means for feeding material to the chamher so as to occupy-the hearths-and the space between them.

22. In an electric furnace, a-melting chamber, a metal retaining conductive hearth therein, a second conductive hearth disposed to receive an overflow from the other, a.

broken circuit in which said hearths are terminals, and means for feeding material to the chamber so as to occupy-the hearths and the space between them.

23. In an electric furnace, a reduction chamber, a conductive hearth, metal-retaining conductive hearths separated by a passage above the first-mentioned hearth and adapted to overflow into said passage, means for causing material fed into said chamber to continuously fill said passage, anil a circuit in which the hearths are termina 9.

24. In an electric furnace, a reduction chamber, a conductive hearth, conductive hearths'separated by a passage above the first-mentioned hearth, means for causing material fed into said chamber to continuously fill said passage, and a circuitin which the hearths are terminals,

25. In an electric" furnace, a conductive loo hearth having an overflow for the discharge of melted matter, at a distance above its bottom surface, and means for connecting the hearth in an electric circuit.

26. An electric furnace having a melting chamber, and upper and lower electric hearths therein, the chamber having in its top, a feed opening positioned with relation to said hearths to cause material fed into the chamber to pass onto the lower hearth and fill the chamber to above the upper hearth.

27. In an electric furnace having a melting chamber, and upper and lower electric I hearths therein, the chamber having in its top, a feed opening positioned with relation to said hearths to cause material fed into the chamber to pass onto the lower hearth and fill the chamber to above the upper hearth, and means to direct part of the material passing through the feed-opening, to the upper hearth.

28. In an electric furnace, a melting chamber, upper and lower conductive hearths ar- 1 ranged in the chamber for the passage of molten material from the one to the other, conductive material in said chamber, occupying the hearths and the space between them,

and an electric circuit of which the hearths are terminals.

30. In an electric furnace, a melting chamber, and upper and lower conductive hearths therein, connected by a passage, the chamber having an opening for feeding material to the hearths by filling the passage between them.

In testimony whereof I have affixed my signature.

HARRY C. REAGAN.