US919165A - Electric smelting-furnace. - Google Patents

Description

H. 0. HARRISON. ELECTRIC SMELTING FURNACE. ABPLIOATION FILED MAY 4. 1908.

919 1,65 Patented Apr. 20, 1909.

ZSHBETS-SHEET 1.

H. G. HARRISON.

'ELBGTRIG SMBLTING FURNACE. APPLIOATION FILED MAY 4, 1908.

i9 1 9, 1 65. Patented Apr. 20, 1909.

. 2 SHEETS-SHEET 2.

hum Joslain.) an. .in 4k) Parr-ma orrion.

HERBERT C AMPION HARRISON, OF EXTOX, PENNSYLVANIA.

ELLE CTRIC SME LTING-FURNACE Application filed May e,

To all whom it may concern:

Be it known that I, Hnnnnn'r CHAMILOII HARRISON, o. SUbJBCl of the King of Great Britain, residing at Exton, in the county of Chester and State of Pennsylvania, have invented certain new and useful improvements in Electric Smelting-Furnaces; and i do hereby declare the following-to be a full,

-- clear, and exact description of the invention,

such as will enable others skilled in the art to which it appertains tomake and use the same.

My invention relates to smelting'furnaces of the arc type and to methods of operating the same, and has for its object the produc- ,tion of a furnace and a method which will be more efficient in action then heretofore; and a furnace that will be easy to repair and the cost of which, for a given output will be a minimum.

To these ends my invention consists in. a furnace of the are type and a method of operating the same, employing polyphase currents for the purpose of smelting the charge, and using reducing agents whereby the products of reduction are obtained continuously in the form required by tapping the same, all as more fully hereinafter disclosed and particularly pointed out in the claims.

Referring to the accompanying drawings forming a part of this specification :Figure 1, is a, plan View of a furnace employing three packets of electrodes. Fig. 2, a sectional View of the same, showing the elect-rode packets in side elevation. Fig. 3, a sectional View taken at right angles to the view of Fig. 2, showing one packet of electrodes in end elevation. Fig. 4, a plan view of a smaller furnace employing only single else-- trodes. Fig- 5, a sectional view of this smaller furnace showing the single electrodes in side elevation, and Fig. 6, a like view taken at right angles to Fig. 5, showing such electrodes in end elevation.

Like numerals refer to like parts in all the views:

It is well known that electric smelting furnaces are made of various sizes, and that when they becomeso large that electrodes in one piece cannot take care of the power required it'is necessary to build up the electrodes of a plurality of a thereby forming packets, in order to accommodate large units of pow r. in Figs. 3., 8 illustrated e furnace empl 1 units of no Specification of Letters Patent.

1908. Serial No.430,712.

on very large Patented April 20, 1909.

} illustrated a furnace ca able of employing only the power that can e carried by single electrodes, all as will appear more fully hereinaft er. I p

Referring to Figs. 1, 2 and 3:-l, rcpresents the furnace proper which is rectanguls in shape; 3 the molten bath; and 4, an opening through which the products may be continuously tapped. 5, re )resents an outer metal covering; 6, a metal bottom; and 7, a suitable refractory bottom lining of carbon conducting material. 2, represents any suitable charge. In the case of the manufacture of ferro alloys, such as ferro silicon, this charge may consist of a mixture of silica, iron, or iron ore, and charcoal or coke, in such proportions as the required product of reduction may determine. Such a charge is of a relatively low conductivity when compared with a )rcduct of reduction, such as molten ferro silicon which collects at the bottom of the furnace, and this fact is taken advantage of, as will resently appear. The disposition of the ellictrode packets 9, and their connections, however, is such that the arcs are always maintained between each electrode and the bath, and never between the electrodes themselves. That is to say, the bath is grounded through the refractory bottom lining"7, and metal bottom 6, as shown at 10 and the neutral point 11, of the star connection 12, of the polyphase genera tor, is likewise grounded; so that the bath itself is always neutral.- The holders or other supports 13, for the electrode packets, are likewise joined to the point 11 of the star connection by the lead wires 14, as shown, and the said packets 9, are spaced just far enough apart to cause the molten bath to be always one and not three separate baths, so

one electrode to the other through the unreduced charge,- which, as above stated, is relatively highly resisting. In such a furnace, if the highest efficiency is to be attained, the parts must be all so proportioned as to cause the electrode packets, which are oblon in cross section, to be symmetrically placec as shown in Fig. 1. When single electrodes are employed, evidently a narrower furnace 1s required for the best results. Therefore, in such cases the parts should be disposed, as shown in Figs. 4, 5 and 6, wherein the furnace 15, is still rectangular, but is made nar: rower than the and illustrated in Fig. 1. .In these figures the electrodes 16, are spaced apart and disposed relatively to the bath as in the previous figures the leads are likewise disposed, and the hath made neutral in the same way.. In both cases itis desirable, in

fact practically essential, to provide a lifting and regulating means 17, for the electrodes,

as shown. In Working such furnaces, the charge 2 may be continuously fed in from the to while the reduced product may be tapped ofr from the bottom as required; and to start u such a furnace, a charge relatively hi h in t e metallic element should be employe un-' til the molten bath, mentioned above, is formed, when the ordinary charge is substituted. i My invention should be carefully distinguished fromthose prior polyphase furnaces acting upon the resistance principle, wherein the electrodes must essentially be placed symmetrically in regard to the neutral point, and which itself must be of the nature of an electrode. Such an arrangementpractically presupposes acircular furnace-which is more ex ensive to build and complicates the. regulation of the electrodes. In my furnace on the otherE-hand itis not essential'to arrange the electrodes symmetrically with the neutral 1point, which is in reality the molten bath itse it is only necessary to balance the 3;) phases by a'careful regulation of the arcs maintained between each electrode and this neutral bath. My invention should likewise be carefully distinguished from those polyphase furnaces,fsulch as are disclosed in Gersaman Patent No. 150,262, June 12, 1903, to -Seemen. Inj'this furnace the electrodes are inclined, thereby necessitating that they be moved greater distances, than would bethe case if they were vertically disposed, -when. 40 ever the length of thei arcs is adjusted. Furthermore, the length; and weight of the electrodes, when large furnaces are employed, must be such that inclined electrodes would be liable to break with their own weight; especially when adjusted by cranes or power .as they must be in practice. Again, such electrodes in large furnaces would tend to burn unevenly, owing to the varying distances between their surfaces and the molten bath. Also owing to their inclined and circular disposition, it would be exceedingly difficult to keep the phasesbalanced. In addition to this, it wouldlbe impossible to combine the electrolysisfeature of this German patent to my furnace, on account'of the fact that my electrodesbeing arranged in a 'row of packets or row ofs': le electrodes, the middle electrode will li neessarily occupy the place which the fourth or electrolyzing electrode in "this German patent must occupy,-

which is the central position with regard to the molten bath. In fact the furnace of this Germanpatent is necessarily a small one,

sary for ,a given amount of power.

' form of poly I avoid all the foregoing objections in prior polyphase furnaces, by,.amo n otherthings, making my furnaces rectang ar and so proportioned as to be able to place my rectan: gular electrodes all in a row. At the same time, I secure the advantages .of being able to save current over ordinary directcurrent'," and single phase furnaces, employin a plurality of electrodes in line, because a .of my arcs are efficient; owing to the fact that I obtain a maximum periphery to each are for a given amount of power. Furthermoral save over a single phase furnaceof similar capacity, half the weight of conductors neces- This. is becauseboth the neutral point .of the star connection on the generator, and the neutral bath in the furnace are grounded, thus doing away with a fourth return wire which woul have to be large enough to carry the whole 85 of the current. Moreover, commercial electrio power is now generally delivered in the hase currents, and instead of being compel ed to use. three separate single phase furnaces, which necessaril entails greater maintenance charges an greater labor costs, I am enabled-to use this power directly in my furnace without converting it into any other form, thereby effecting a great saving over the employment of three separate furnaces, and also saving the expense of conversion, and the losses incident thereto when a single phase current is emloyed. Another important advantage my rnace possesses over the direct, or single 100 phase type, is the ability to put very much more power into a furnace of a given size, and thereby securing all the benefits flowing from such fact.

The above difierences, while of little or no 10E consequence in thosefurnaces using only a few horse power, are nevertheless of the highest importance in furnaces using thousands of horse power. For in such larger furnaces, every objection inherent in the small furnace 110 becomes enormously magnified; and unless remedied, efiicient results will be dereated and largesums of money wasted.

Of course I do not wish to be understood as limiting myself to the exact details and1l5 arrangement above disclosed, since it is evident that both may be varied by those skilled in the art, without departing from the spirit of my invention.

What I claim is 1. The method of utilizing polyphase currents to effect reductions in electric furnaces l of the arc type, which consists in vertically disposing arc electrodes inthe furnace; in connecting each electrode to one ofthe branches of the star connection of a polyphase generator; in so spacing the electrodes that a single bath is formed and an are beand it would not be possible to employ large tween each electrode and said bath is also 65 units of power on this principle,

'. formed; and in placing resisting charge material between said electrodes to prevent any substantialleakage of current from electrode to electrode, substantially as described.

2. The method of utilizing polyphase currents to effect reductions in electric furnaces of the arc type, which consists in first charg: ing said furnaces with a charge relatively high in metal until a molten bath is formed, then charging said furnaces with a charge of a lower conductivity than said first charge; vertically disposing arc electrodes in the furnace connecting each electrode to one of the branches of the star connection of a polyphase generator; and placing resisting charge material between said electrodes to prevent any substantial leakage of current from electrode to electrode, substantially as described.

3. An electric furnace of the arc type rectan ular in shape, ada ted to use polypnase currents, provided with a plurality of vertical arc electrodes, laced in a row, and having a metal bottom e ectrically connected with the molten bath of said furnace; in combination with a polyphase generator provided with a-star connection and suitable electric connections between said star connection and the ground, between said metal plate and the ground, and betweensaid star connection and each of said electrodes, substantially as de scribed.

4. In a polyphase electric furnace of the are type having a rectangular shape, the com:

bination of three are electrode packets, each packet of an oblong rectangular shape, vertically disposed in a row; means to adjust said packets up and down; a metal bottom for said furnace a ground connection for HERBERT CHAMPION HARRlSOh.

lNitnessesz' WM. H. CAREY, J. T. CARPENTER.

Images