US468148A - Aluminium - Google Patents

Description

(No Model.)

2 Sheets-Sheet 1.

G. S. BRADLEY. PROCESS OF SEPARATING ALUMINIUM.

. Patented Feb. 2, 1892.

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2 Sheets-Sheet 2.

(No Model.)

0. S. BRADLEY. rnocs ssor SEPARATING ALUMINIUM.

No. 468,148. Patented Feb. 2, 1892.

WITNESSES: 3

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UNITED STATES CHARLES S. BRADLEY, OF NEW YORK, N.

I PATENT OFFICE.

PROCESS OF SEPARATING ALUMINIUM.

SPECIFICATION forming part of Letters Patent No. 468,148, dated February 2, 1892.

Application filed February 23, 1883. Serial No. 85,957. (No specimensl To all whom, it may con/cent.-

Be it known that I, CHAnLEs S. BRADLEY, of the city, county, and State of New York, have invented a new and useful Improvement in Processes for Separating Aluminium, of which the following is a specification.

My invention relates to a process of effecting by the electric current the separation or disassociation of aluminium from its ores or compounds,'or the decomposition in a similar manner of other like highly-refractory metallic compounds of which aluminium may be considered a type and which have been classed together by reason of the great diiiiculty in their reduction.

Hitherto this process has been carried on by subjecting the fused ore to the action of the current in a crucible or other refractory vessel placed in a heating-furnace where the temperature is sufficiently high to keep the ore in a melted condition; but the greatest difficulty is encountered in preventing the destruction of the crucible with this mode of working the process, for it has been found that, in the case of cryolite especially, which is a double fluoride of aluminium and sodium, the fused ore unites or fluxes with the crucible itself, and that the gas liberated in the process of reduction (fluorine gas) attacks the material of which the crucible is composed, and the consequence is that the crucible is quickly destroyed. This destructive fluxing action takes place to a greater or less extent in treating almost any material,'and is greatly aggravated by the fact that the crucible is subjected to heat from without; but even in the case of materials which do not exert a fiuxing action the mere mechanical action of the external heat is sufficient to make it almost impossible to prevent the cracking of the crucibles.

The main object of my invention, therefore, is to dispense with the external application of heat to the ore in order to keep it fused. In order to accomplish this object, I employ an electric current of greater strength or intensity than what would be required to produce the electrolytic decomposition alone, and I maintain the ore or other substance in a state of fusion by the heat developed by the passage of the current through the melted mass, so that by my invention the electric current is employed to perform two distinct functions, one of these being to keepthe ore melted by having a portion of its electrical energy converted into heat by the electrical resistance offered by the fused ore, and the other being to effect the desired electrolytic decomposition, by which means the heat, be-

the ore and in employing a body or heap of f the ore itself to constitute the vessel or cell in which the reduction takes place which is not destroyed by the chemical action of the fused ore and the gas liberated, and which therefore admits of the process being perfectly continuous, nothing being required but the charging of fresh ore as fast as the reduction goes on, either from without or from the sides or walls of the heap itself.

To enable others to carry out my process, I will proceed to describe as applied in one particular case to the extraction of aluminium from its ore cryolite.

In the accompanying drawings, Figure 1 is a sectional view of a pile of ore with the electrodes in position in the basin and connected to a source of electric current. Figs. 2, 3, and i are modified arrangements.

Upon a hearth. of brick 1 or other suitable material is piled a heap or body 2 of the ore, more or less pulverized, in the shape of a truncated cone, and a cavity or basin 3 is excavated in the top of the heap to contain the fused portion of the ore which is to be treated electrolytically. In order to fuse the ore at the start, I take two electrodes 4 of a suitable material, such as already used in like proccsses where fusion has been effected by an external furnace and connected, respectively, to the two poles of a dynamo-electric machine 5 or other source of current, bring, the said electrodes into contact, separate them suiiiciently to produce an electric arc, and then thrust them into the ore lying at the bottom of the cavity or basin,where the ore soon fuses by the heat of the arc and becomes a conducting electrolyte, through which the current from the electrodes continues to flow. The are of course ceases to exist as soon as there is a conducting-liquidthe fused orebetween the electrodes, and the passage of the current then takes place through the fused ore by conduction and the heat is produced as it is in an incandscent lamp. The are is merely used to melt the ore in the beginning and the ore is kept melted by incandescence, so to speak, the metallic aluminium being gradually deposited at the cathode and the fluorine gas being set free at the anode so long as'the ore is maintained in a state of fusion. As soon as the actionis properly started the electrodes should be moved a little farther apart, in or der that the metal set free at the cathode shall not form a short circuitbetween the electrodes or be attacked by the fluorine set free at the anode.

I have spoken several times of fluorinebeing set free although I am aware that it is considered to be almost impossible to isolate that element. I use the term fluorine merely for convenience, meaning thereby whatever is set free at the anode, which may be fluorine or some compound of fluorine, with the substance composing the anode, moisture of the air, 820. As a-matter of fact, when the process is worked fumes arise at the anode; but the anode is not attacked or eaten away very rapidly, provided it is made of pure carbon, such as gas-retort carbon, which. I prefer in preference to carbon containing silica or alumina.

In working my process I employ, as I have already stated, an electric current sufficiently powerful not only to effect the electrolytic decomposition of the ore treated, but also to develop by its passage the heat required to keep the ore fused. I have found that by using an electric current about twiceas strong as would be employed to perform a given amount of electrolytic work in the ordinary Way in externally-heated crucibles, I am enabled to keep the ore fused according to my invention without the application of any external heat whatever.

For the purpose of perfectly managing and controlling my process, I have my electric generator or source of current so arranged that the strength of the electrolytic current may be properly regulated and the mass of ore thereby kept at the proper temperature. The most efficient way to accomplish this is to raise or lower the electro-motive force of the generator by any of the well-known methods employedfor example, in incandescent electric lighting. One of the well-known methods for accomplishing this is illustrated in Fig. 2, and consists in the employment of an adjustable resistance R in the field-circuit of the generator. By these means I am enabled to dispense with the necessity of keeping the ore in a fused state by the application of heat from without through the walls of the refractory vessel and to concentrate the heat required for this purpose just where it is needed between the two electrodes, and by the use of a vessel or cavity formed of the ore itself I avoid its destruction by the ac-' tion of the melted ore and by the gas or acid set free during decomposition.

The body of unfused ore may either be formed into an unconfined pile, as in Fig. 1, or it may be contained in a receptacle or box 6 of any desired shape, so as practically to form a tank or holder lined with the ore itself, as in Fig. 2. Such a lining willprevent the destruction of the holder, and the process may go on indefinitely without interruption. As fast as the reduction proceeds-and the metal is set free fresh ore may be supplied to the bath andthe metal removed therefrom, if desired, in any desired way. The fresh ore may be introduced on the top by shoveling it in or by means of a hopper, which may be regulated to feed the ore at a constant rate, or it may be introduced intermittently by hand. The metal set free may likewise be drawn off, as frequently as desirable,'byladling it out by hand or by boring a tap-hole through to the molten metal and allowing it to run off.

It is evident that various forms of furnace and built of various materials may be employed without departing from my invention. Instances of two such modifications are illustrated by Figs. 3 and 4C. In Fig. 3 the body 2 of ore is heaped upon a slab of carbon 7, which is connected to one of the poles of the dynamo-electric machine 5. The electrodes 4 and 4: are first brought together and inserted in the basin 3 into the contained ore and then separated to form the are, as previously described and when the heat has melted down a portion of the ore so as to form: a conductor the electrode 4. may be withdrawn and the operation thereafter continued between the electrode 4 and the carbon slab 7. In Fig. 4 the arrangement is the same, except that the electrode 4' is omitted, and in this instance the operation is started by first establishing contact between the electroded and the carbon slab 7, and then the former is withdrawn as soon as a sufficient quantity of fused ore is present to conduct the current and effect the required results.

I have described my process as preferably carried on by employing a body of the ore itself to form the basin or receptacle in which the electrodes are situated, between which the current flows through the ore for heating and electrolyzing the same. That specific invention, however, is not claimed herein, since it forms the subject-matter of Patent No. 464,933, dated December 8, 1891.

My present invention is not limited to the specific character of the receptacle nor the upon it rather than by an external furnace and as it becomes fused efiecting electrolysis by passing an electric current therethrough between terminals which are maintained in circuit with the fused bath, whereby the process is rendered continuous, substantially as set forth.

2. The continuous process of separating or dissociating metals from aluminous or like highly-refractory ores or compounds, non-conductors in an unfused state, which consists in progressively fusing the refractory ore or compound and as it becomes fused electrolyzing it by passing an electric current therethrough of sufficient volume to continue and maintain the fusion and effect electrolysis and adding fresh material from time to time to preserve the bath constant, as set forth.

3. The process of redncin g metals from that class of highly-refractory ores and compounds, non-conductors in an unfused state, of which the ores and compounds of aluminium are a type, which consists in fusing a portion of the refractory ore orcompound to be treated, in establishing an electric current through said fused portion, and by such current producing simultaneously progressive fusion of such ore or compound and continuous electrolysis of the same as fused.

4.. The process of separating or dissociating 3o aluminium from its ores or compounds, consisting in fusing and maintaining the fusion and electrolytically decomposing the ore or compound by the passage of the electric current therethrough, substantially as set forth.

5. The continuous process of separating or dissociating aluminium from its ores or compounds, consisting in fusing and maintaining the fusion and electrolytically decomposing the ore or compound by the passage of the electric current therethrough and charging the bath with fresh quantities of the ore or compound as the reduction proceeds, substantially as set forth.

6. The process of separating or dissociating aluminium from its ores or compounds, consisting in fusing and maintaining the fusion and electrolytically decomposing the ore or compound by the passage of the electric current therethrough and regulating the strength of said current in accordance with the requirements of the fused mass, substantially as set forth.

CHARLES S. BRADLEY.

Witnesses:

CHAs. G. CURTIS, FRANCIS B. Onocnnn.

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