US837277A - Electric furnace. - Google Patents

Description

No. 837,277. PATENTED DEC. 4, 1906. K. BIRKELAND 8: S. EYDE.

ELECTRIC FURNACE. APPLICATION IIL'BD NOV. 10. 1904.

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N0- 83'7,277. PATENTED DEC. 4, 1906. K. BIRKELAND & S. EYDB.

ELECTRIC FURNACE.

APPLICATION FILED NOV.10. 1904.

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KRISTIAN BIRKELAND AND EYDE, or OHRISTIANIA, NORWAY.

ELECTRIC FURNACE.

Specification of Letters Patent.

Patented Dec. 4, 1906.

Application filed November 10, 1904. Serial No. 232.232.

To all whom it may concern:

Be it known that we, KRISTI'AN'BIRKE- LAND and SAMUEL EYDE, subjects of the King of Sweden and Norway, residing at Christiania, Norway, have invented certain new and useful Improvements in Electric Furnaces; and we 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 to make and use the same, reference being had to the accompanying drawings, and to letters of reference marked thereon, which form a part of this specification.

This invention relates to electrical furnaces used in the chemical industry to create chemical reactions under the influence of the electrical arcs.

The invention relates more especially to the class of electrical furnaces described in United States Letters Patent No. 775,123, dated November 15, 1904, in which an arc is made use of which is dispersed by means of a ma netic field.

he object of the present invention is to improve this class of furnaces, so that they may advantageously be run with alternating currents, either for the electrodes or for the field-magnet windings, or in both.

It is also an object of this invention to provide means whereby it is made possible to increase the ratio between the furnace tension and the tension of the electric machinery, or, more correctly, to increase the ratio between the kilowatts and the kilovoltamperes.

In the drawings, Figure 1 is a diagram showing .the form of a current curve in a Birkeland furnace fed with alternating current. Fig; 2 shows an arrangement of the electrodes, and Fig. 3 a detail of a modified form of the electrode-points, the electrode being hollow. Fig. 4 illustrates another form of electrode arrangement. Fig. 5 shows the general arrangement of the furnace.

Referring more particularly to Fig. 5, a 11 indicate the electrodes e, the furnace, through the walls of which the electrodes project into the reaction-chamber. f is an electromagnet disposed so as to create a field in the chamber around the electrodes. In this instance the electrodes are for the matter of convenience shown disposed axially in relation to the magnetic field. They may be so dis osed,

althou h it'is' generally foundprefera 'le to' have t em disposed at right angles to the lines of force. The electrode b is shown rotatably mounted and may be provided with a small motor 9, which keeps it in rotation, as will be hereinafter explained more fully.

In the following it is supposed that the generator h for elivering current to the electrodesis an alternating-current enerator.

In the furnace workin with alternating current the current curve as about the form indicated in the dia ram, Fig. 1.

If it is attempte to increase the tension for the purpose of obtaining an increase of energy as well as arcs with increased surface by increasi the relative distance between the electrodes,t care will soonbe extinguished i. e., a certain intensity of current and of magnetic filed corresponds to a certain maximum distance between the electrodes. It is derived from observations that the extinction will always take place when the current is about zero. to avoid extinction at this point, it might be possible to increase the tension materially without having to fear an extinction of the arc. This result may be obtained by running the furnace with a resistance in the are,

which alternates in synchronism with thecurrent hase and in such way that the resistance as its minimum when the current value is passing zero, or the variations in the resistance may be of so much greater freuency than the frequency of the current t at an extinction is practically excluded.

We may obtain the aim of the invention in several ways and we shall here explain three different ways, one of which may be termed mechanical, one a magnetical, and one an electrical method. We may, for instance, obtain such a result by varying the relative distance between the points of the electrodes in synchronism with the current phases so as to obtain the shortest distance at the zero-points of the current curve and longer ones at the intermediate parts of the curve. Hereby is obtained an increased average tension and an increased factor of energy, or, in other words, the ratio between the kilowatts and the kilovoltamperes is increased.

If therefore it was possible corresponding number of'poles.

, call an As it would not be suitable to have the electrodes moving to and from each other n their axial direction, in carrying out this method we prefer usin electrodes or roups of electrodes rotating a )out an axis, w ereby the necessary synchronism may be obtained by aid of a synchronous motor rotating the said electrodes or groups of electrodes.

When using electrodes of the form illustrated in Fig. 2, the electrode a is or may be stationary, while the electrode bis rotatable about its longitudinal axis, the minimum distance between the electrode points being only a fraction of their maximum distance, and we may easily rovide for any desired degree of variation this distance simply by altering the form of the points of the electrodes.

It is advantageous to provide one or both electrodes with a plurality of points and to have the rotating electrode actuated by a synchronous motor (not shown) having a Such an arrangement is especially suitable when tubular electrodes, as illustrated in Fig. 3, are used.

It is sometimes advantageous to make use of these tubular electrodes for the purpose of leading the gases or part of them into the furnace through the interior of the electrodes, whereby the latter are cooled. Y We may also provide for an arrangement where both electrodes are stationary, but

where there is placed a conductive pointed body d or arc-former between'the said points, I

as illustrated in Fi 4, the said conductive body being rotate or otherwise moved in synchronism with the current phases. The body is shown to have four points, but it may have any other form and any number of points.

The herein-described devices may also be used for furnaces running with direct current both on the electrodes and on the magnets.

In the foregoing it has been supposed that the magnetic field has a constant intensity. It is, however, possible to carry out this invention with a pulsating or variable magnetic field, such pulsation having an efi'ect on the factor of energy substantially equivalent with the variation of the distance between the electrode.

The furnace may be worked with stationary electrodes and alternating currents both in the electrodes and in the field-magnet, obtaining thereby substantially the same result as with moving electrodes.

We may, as hereinbefore mentioned, obtain the result aimed at by way of what we electrical method. This may be done by-connecting the electrodes with an auxiliary circuit 7c, supplied from a source Z through condensers m n, producing a spark discharge of high frequency with high tens1on and low current strengthfor instance, a Tesla current. Such discharges may be sald to act as a bridge for the arc of the Workmg current.

Having thus described our invention, what we claim as new therein, and desire to secure by Letters Patent, is

1. In an electric furnace, the combination of means for creating a ma netic field, electrodes placed within said eld, a source of alternating electric current capable of forming dispersed arcs between said electrodes, and means to vary the resistance of the current in passing between the electrodes in synchronism with the phases of the working current. I

2. In an electric furnace, the combination of means for creating a magnetic field, elec-' trodes placed within said field, a source of alternating electric current capable of form ing dispersed arcs between said electrodes, and means to vary the distance between the electrodes in synchronism with the phases of the working current.

3. In an electric furnace, the combination of means for creating a variable ma netic field, electrodes placed within the said eld, a source of alternating electric current capable of forming dispersed arcs between said electrodes, and means to vary the distance between the electrodes in synchronism with the phases of the field current.

4. In an electric furnace, an electrode formed of a tubular piece of electrically-conducting material and having its ends serrated to form one or more points.

5. In an electric furnace, the combination with means for creating a variable magnetic field, a stationary and a movable electrode placed Within the field, a source of alternating current capable of forming dispersed arcs between said electrodes and means to vary the distance between the electrodes in synchronism with the phases of the working current, substantially as described.

6. In an electric furnace, the combination with means for creating a variable magnetic field, hollow electrodes having eccentric arcforming points within the field, a source of alternating current capable of forming dispersed arcs between said electrodes and means to vary the distance between the arcforming oints of the electrodes in synchronism wit the phases of the working current, substantially as described.

7. In an electric furnace, the combination with means for creating a variable magnetic field, a fixed electrode whose arc-forming end. is out of alinement with the axis of the electrode, a second rotatable electrode in alinement therewith and whose arc-forming end is also out of alinement with the axis thereof, a

source of alternating current capable of formas our invention we have signed our names in mg dispersed arcs between said electrodes presence of two subscnbm witnesses.

and means to rotate the second electrode to KRISTIAN 'IRKELAND. vary the distance between the ends of the SAMUEL EYDE.

5 electrodes in synchronism with the working Witnesses:

current, substantially as described. MICHAEL ALGER,

In testimony that we claim the foregoing HENRY BoRDEwIcH.

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