US1234836A - Method and apparatus for electrically reducing refractory substances. - Google Patents

Description

L-G. WEBB.

METHOD AND APPARATUS FOR ELECTRICALLY REDUCING REFRACTORY SUBSTANCES.

APPLICATION FILED MAR. 16. 19]! Patented July 31, 1917.

JOHN G. WEBB, OF RICHMOND. VIRGINIA.

METHOD AND APPARATUS FOR ELECTRICALLY BEDUCIN 'G REFRACTORY SUBSTANCES.

Specification of Letters Patent.

Patented July 31, 1917.

Application filed March 18, 1917. Serial N 0. 155,297.

To all whom it may concern:

Be it known that 1, JOHN G. WEBB, a

.citizen of the United States, residing'at Richmond, in the county of Heurico, State of Virginia, have invented certain new and useful Improvements in Methods and Appaable others skilled in the art to which it appertains to make and use the same.

This invention relates to a method and; apparatus for reducing metals through the medium of an electric arc, the object of the invention being to utilize a maximum percentage of heat induced in the work'of reduction with a corresponding saving in heat units that are otherwise wasted and with also" a corresponding saving of the refractory lining of the furnace that has been previously burned out by these waste units.

Themethod embodies the maintenance of the reducing arcs in such relation to the mass operated upon as will form a depres sion in the mass into which the electrodes that sustain the arc, are gradually lowered as the fusing operation serves to deepen the depression, so'that the are or arcs as the case may be, are surrounded by a wall of the mass under reduction and thus the mass absorbs the heat units so that they are utilized in attaining the objective, instead of then passing to the refractory lining of the furnace with its resultant deterioration, as occurs in the usual practice of the electric reduction. The apparatus s designed to permit of the practice of the method referred to.

showing how the mass incloses the arcs so as to receive the im ingement of heat units that would be absor ed by the lining of the furnace if the arcs were not thus inclosed.

Fig. 3 is a view similar to Fig. 2 and hav-. ing added in dotted lines the relation of the electrodes to the charge in the ordinary electric furnace wherein the lowermost eleczrodes are in substantially horizontal posi- Fig. 4 is a detail view partly in section and partly in elevation and showing the mounting of one of 'the electrodes to permit of its longitudinal feed and to effect lateral swinging adjustment.

Fig. 5 is a detail sectional view taken transversely of an electrode and with the pivotal mounting of the electrode in plan View.

Referring now to the drawings, there. is shown at 10 the body of a furnace having a refractory lining indicated at 11. It will benoted that the greatest width of the receiving chamber 12 of the furnace is somewhat greater than its height, these propor: tions having been found best for concentrating the heat against the charge 13, it being understood that the higher the chamber of the furnace the greater the exposed area of lining above the charge and the greater l the consequent opportunity for heat absorption by the lining. Usually the top of the chamber is comparatively high above the charge and is so located, as to relieve it of the intense disintegrating effect of the heat from the arc. With the particular arrangementof electrodes and.in the practice of my particular method, however, the heat units from the are do not rise in sufficient quantity to the roof of the chamber to disintegrate its lining at anything near the rate resultant with the usual arrangement of electrodes hereinafter more particularly referred to.

Asillustrated, the top of the furnacefl l forming the roof of the chamber 12 is sprung on an arc'of considerable radius so as to make its higher portion little above V the upper edge ofthe side wall. I

The furnace illustrated is built to utilize a three phase current and includes three electrodes 15, 16 and 17'which d=-re brought each through an insulating bushing "18111 the top of-the furnace. is shown as coinciding with the vertical axis of the furnace while .the electrodes 15 and The electrode 16 17 converge downwardly at opposite sides of' the electrode 16' and at equal angles thereto. This particular arrangement of" the electrodes in the same transverse plane is a matter of convenience in the manipulation of the electrodes hereinafter explained and it will of course be understood that thef electrodes may be equidistant if preferred). Each electrode is longitudinally adjustable through its bushing 18 and each one is provided with a metallic collar 19 held thereon by a set screw 20 or in any other desired way and to each, is connected a bail 21 to which in turn is attached a cable 22 that passes over suitable direction pulleys 23 and24 to a Windlass 25 upon which the cable may be wound to raise its corresponding electrode, it being understood that the electrode will move downwardly by gravity when the Windlass is moved in an unwinding directiom Each electrode, it will be noted, is passed slidably through its insulating bushing 18 and the bushings of the electrodes 15 and 17 are each provided with an encircling band having trunnions 41 rockingly mounted in a'support 42. The

openings 43 in the furnace top -and the registering openings 14 in the furnace lining through which the electrodes enter the furnace, are of sufiicient size to permit of oscillatory movement of the electrodes 15 and 17 toward and away from the electrode 16'to maintain a determined length of are between each pair of electrodes at different elevations of the latter and to permit of distribution of the direct influence of the arcs over-different areas of the crater bottom.

'Any desired mechanism of course may be used for mounting the electrodes to permit of this adjustment. To swing the bushings on their trunnions, hand operated screws.

may be connected with collars -16 carried by thevbushings.

The feed wires 26,- 27 and 28 from a three phase generator 29 are in circuit with their corresponding electrodes 15, 16 and 17 through the medium of the collars 19 to Whichthey are connected.- 7

' Referring now'more particularly to Fig. 1 of the drawings, when the furnace is to be charged, with scrap iron, for instance, the chargeli's introduced through the door opening 30, at which time the electrodes are raised above the upper line of the door so as not to be struck and injured as the charge is thrown into the furnace, When the charge. indicated at 13, has been completed, the electrodes are thrown .into circuit with the generator 29 through the medium of a suitable switch 32 while the electrodes are then above the charge, the electrodesbeing so'spaced as that at this time they will not are across. Through the medium of the Windlass 25, the electrodes are then lowered simultantously to contact the charge and are then instantly raised to a degree to strike arcs between the electrodes and thelch arge, the ammeters 33, 34 and 35 in the circuits of being observed and the electrodes being manipulated-to th'row as even a load on the generator and to maintain the arcs as uniform as' may be.

Immediately the arcs are struck, the portions of the charge sustaining the arcs in connection with the electrodes, begin to melt and as they melt they settle with resultant craters. The electrodes are lowered gradually to compensateand the process continues until the individual craters merge and become one crater which grows deeper as the operation continues and into which the electrodes are further lowered.

When the electrodes shall have convergingly approached one another and the gases rising from the charge have in conjunction established the essential condition, the arcs swing to include the electrodes in multiple with the charge instead of in series as initially, so that the molten metal at the bottom of the crater is overspread with a flaming are which is held in close impingement against the molten metal by reason of theconductivity of the metal.

It will be noted that the angle of the electrodes 15, 16 and 17 to the vertical is less than the angle of repose of the charge. This, is of importance in order that diverggnce of the wall of the crator from the electrodes 15 and 17 may be insured and thus it may be possible that arcs may be maintained between the charge and the extremities of the electrodes only. It will be readily seen upon reference to Fig. 3 of the drawings that if the lower electrodes were arranged in the horizontal positions illustra d, as soon as a crater were formed benea h the terminals of the electrodes and the bed of that crater sunk to sucha degree that the resistance from the electrodes through the gasses to the bottom and wall of the'crater were greater than the resistance' between the electrodes and the top of the charge, arcs'would beestablished between the electrodes and the charge at correspondin points of the lengths of the electrodes. 11 other words, the arcs would cree wou d shift to different oints of the lengths of the electrodes as in uenced by varying he electrodes 15, 16 and 17 respectively,

resistances between the electrodes and charge at different points of'the lengths of the electrodes. Y When the angles of the lower electrodes to the vertical are less than the angle of repose of the charge, then that portion ofthe charge forming the wall of the crater will by gravitation retain its angle of divergence from the electrodes 15 and 17 and prevent creeping of the arcs up the electrodes.

U on reference to Fig.- 2 of the drawin it Wlll be noted that the charge incloses t e arcs and thus the heat units rising from the along the horizontal electrodes olr i of electrodes enteringithe h res are absorbed by that portion of the charge iorlning the crater wall and it is vfound in practice that the heat units that rise above the charge and impinge against the lining are so few as that the linin will stand a number of heats, a multiple 0 those of the lining of a furnace wherein this pariticular arrangement of the electrodes is not iad.

While there is shown the use of three electrodes in a three phase circuit, it will of course be understood that the number and arrangement of the electrodes may be varied at will and that they may be connectedelectrically as may be deemed best -so long as that the angle between each electrode and the horizontal is such that there will be a divergence of the wall of the resultant crater from the surface of each electrode, thus to permit of progressive deepening of the crater and a resultant inclosure of the are or arcs. It will of course be understood that when I know the angle at which I introduce the electrodes into the crater, I will know the critical voltage beyond which the arc will climb the electrodes and if I establish this angle between the electrodes less than I know by experimentation or otherwise, will be the angle of the crater wall, I insureagainst the arcs running up the crater wall and thus I hold the arc-s to the bottom oftthe crater, permitting the heat units to rise along the wall of thecrater and gradually reduce that wall with efficiency. a

It will benoted furthermore that the angle of the lower electrodes to the angle, is such that the action'of gravity exerts a greater tensile strain than a transverse strain, the

latter belng almost negligible with the consequent safety against fracture of the carbon of which the electrodes are formed.

What is claimed is:

'1. The method of melting a charge which consists in subjecting the charge to the action of an electric are sustained by electrodes disposed in such relation to the charge as that the impingement of the are against the charge will establish a crater, and introducing the electrodes into the crater as the latter deepens at an angle to each other less than the angle between an electrode andthefwall of the crater while maintaining the-arc, i

2. An apparatus for'reducing metals to a molten statcqcomprising a closable hollow body adapted to receive a char e, a plurality p y, means for feeding the electrodes into the bodyyand maintaining themflat such angle to each other and m-Qsuch location with respect to, the furnace body as to insurc-the'angle between the electrodes less than'the angle between either electrode and the wall of a crater that may be resultant in a charge within the furnace subject to an are between the terminals of the electrodes and means for maintaining an electric are between the electrodes.

3. The method of melting a charge which consists in subjecting the charge to the action of electric arcs sustained between the electrodes and the charge to establish a crater in the latter and introducing the elec trodes into the crater as it is formed and at an angle to each other and simultaneously approaching the electrodes toward each other to shift the are so that it will swing be tween the electrodes and between the electrodes and charge in multiple while maintaining the electrodes out of all physical contact.

4. The method of melting a charge which consists in subjecting the charge to the action of electric arcs sustained between the electrodes and the charge to establish a crater in the latter and introducing the elec' trodes into the crater as it is formed in such relation thereto as to maintain the arcs while maintaining the electrodes out of all physical contact.

5. The method of melting a charge which consists in subjecting the charge to the action ofa plurality of electric arcs sustained each between an electrode and the charge to establish a crater in the latter, introducing each electrode into its crater as it is formed and out of physical contact with thcchargc,

- tween the electrodes, an ammeter in the. circult of each electrode and means for adjust ing the electrodcswith respect to each other and with respect to a charge within the body a to insure the an 10 between the electrodes less than the ang e between either electrode and the wall of a crater that may be resultant inthe charge subject to the are between the terminals of the electrode, p

In testimony whereof, I aifix my signature in the presence of two witnesses.

JOHN G. WEBB.

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