US2939824A - Method and apparatus for the production of aluminum - Google Patents

Description

June 7, 1960 E. w. GREENFIELD 2,939,824

METHOD AND APPARATUS FOR THE PRODUCTION OF' ALUMINUM Filed July 26, 1957 2 Sheets-Sheet 1 (I 2 m s! Q LJ 5) 8er J 3 d w S I a: U 9 Si m N EUGENE W. GREENFIELD ATTORNEY June 7 1960 E. w. GREENFIELD 2,939,824

METHOD AND APPARATUS PDR THE PRODUCTION DP ALUMINUM Filed July 26, 1957 2 Sheets-Sheet 2 no ,g

IMPEDANCE IMPEDANCE INV ENTOR EUGENE W GREENFIELD ATTORNEY' 2,939,824 Patented June 7, 1960 METHOD AND APPARATUS FOR THE PRODUC- TION OF ALUMINUM Eugene W. Greenfield, Spokane, Wash., assignor to Kaiser Aluminum & Chemical Corporation, Oakland, Calif., a corporation of Delaware Filed July 26, 1957, Ser. No. 674,523

Claims. (Cl. 204-67) This invention relates to fused bath electrolytic cells and methods of operating :such cells. More particularly, this invention relates to methods of and apparatus for suppressing the phenomenon known as anode eiect in fused salt bath electrolytic cells susceptible thereto. A specific embodiment of the present invention contemplates a suppression system and method of suppression for use in conjunction with aluminum reduction electrolytic cells and the utilization of a detection device similar to that of my co-pending application Serial Number 614,961, filed October 9, 1956, for initiating the operation of said suppression device.

This application is a continuation-in-part` of my copending application, Serial Number 447,846, filed August 4, 1954 (now abandoned).

During :the normal operation of fused bath el'ectrolytic cells, the electrolytic action causes the conductive surface of the anode to be surrounded by gas bubbles which smoothly evolve and are removed from the reaction. The .phenomenon known as anode elfect results in a considerably higher net voltage drop between the electrodes of the electrolytic cell and consequent reduction in cell eiciency, and has been observed in electrolytic cells having fused salt electrolytes containing halides of lead, cadmium, silver, the alkali and alkaline earth metals, magnesium, cerium and aluminum; with complex electrolytes of aluminum uorides and with commercial fused salt electrolytes. It is theorized that anode effect is caused by the building up of a relatively high resistance ionized gas lilm or layer on the anode of the cell and that once such gas layer has become established, the anode effect tends to perpetuate itself since continued current flow is by arcing through such layer. 1 The disadvantages of anode eiect are many and vary with the material being electrolyzed. One of the `major disadvantages is that the high watt dissipation in the lm together with erosion caused by discharges, causes overheating which in turn causes very rapid consumption of the anode. `This sometimes burns off above the level of the electrolyte, and will cause a materially lower yield of product. Further, the large 'quantity of gas surrounding the anode may have a deleterious elfect on the anode such as in cells used for the production of fluorine. Another very important detrimental result of the anode eifect is a large unproductive power consump tion in the cell during :the anode etfect period.

It is known that a suitably high voltage discharge may be employed to burst` or dissipate a partially-ionized gas phase in an insulating liquid such asl oil. However, since most electrolytic cells are operated in series con` nected groups, the impression of a high D.C. voltage or conventional sixty` cycle A.C. voltage on one cell would havea `detrimental elfect on the remaining cells in the line which are not undergoing anode eifect.

In theoperation of a conventional cell for the produc-` tionpof aluminum, an electrolytic cell is formed between one or more carbon anodes,` an electrolyte consisting essentially of alumina dissolved in cryoliite and a carbon cathode. Direct current flow through such cell causes electrolytic reduction of the alumina to metallic aluminum.

Normally, a commercial electrolytic cell for production of aluminum operates at 50,000 to 60,000 amperes of direct current and a voltage drop through the electrolyte on the order of 4 to 6 volts. It has been observed that anode effect in such a cell is related to concentration of alumina in the electrolyte. As the alumina is electro- Y lytically reduced, the concentration of alumina in the fused electrolyte decreases until a crit-ical minimal concentration of alumina is reached at which time the overall resistance of the electrolyte suddenly increases by a factor of approximately ten times. In commercial installations for the production of aluminum the electrolytic cells are connected in a line or series so that the current ows from each cell to the next and a D C. voltage of 200 to 600 volts is impressed across the line, depending` on the design and the number of cells in the line. Since the cells rin a given line are all respectively in series,` increasing the resistance of one cell increases the Aproportion of the total voltage drop across that cell and decreases the voltage drop` across the remaining cells in the line. The voltage across the cell having depleted alumina concentration thus rises to approximately 50 volts, and the condition of anode effect is established. Counteraction of the anode effect and restoration of the low voltage drop is normally accomplished in prior practice with this :type of electrolytic cell by breaking the crust on top of the electrolyte and permitting additional alu- Vmina to enter the `molten bath. Also, anode elfect may be partially eliminated by periodic feeding of alumina to the cell to maintain its concentration above the critical value. However, if too much alumina is fed to the cell, the alumina falls to the bottom, intermingles with the metallic aluminum adversely alecting the normal thermal and` reduction process and the quality of the metal produced. For this reason, it has been conventional practice to allow each cell to undergo at least one anode eiiect per day as a safety precaution against overfeeding of alumina.l

Allowing each cell to undergo anode eifect periodically, intentionally or otherwise, has many disadvantages. In the lirst place, an electrolytic cell in anode eiect is unproductive while such condition exists. Further, in the case of commercial installations for production of aluminum, the cells in a given line are all respectively in series. Thus a sudden increase in resistance and voltage drop across one cell reduces the voltage available to the remaining cells inthe line since the voltage applied to `the line remains constant. This causes serious reduci tion of current through the entire line, and as a consequence production of the cells in the line which are not in nanode elect is reduced as Well. A further disadvan-` tage lies in the fact that a cell in anode eiect requires the complete attention of one or more operators for a period of from 3 to 5 minutes in order to restore normal operation to the cell. Additionally, `multiple anode effect occurring in the line of cells can cause serious surgesnin power load in the plant rectiiier and/or generator equipment. On occasion such deviation in power load can be severe enough to require removal of power from the entire line of cells, thereby necessitating a complete shutdown of the line. 3. i

. Accordingly, it is an object of this invention to provide a method of and apparatus for suppressing anode eifect increase in voltage across such cell, 4 A further ,object of this invention is to provide a method of and apparatus-forvsuppressing anode eet in one ,of

` in fused salt bath electrolytic cells prior to any substantial t. Several agria-connected fused,sslthathelestwlytic sells! without adversely affecting the operation of the remaining cells in the series.

A further object of this invention is to provide a methodof and apparatus for suppressing anode effect in a fused salt bath electrolytic cell by actuation of a device for suppression of anode effect by a device for detecting the Vonset of anode effect.

A further object ofV this invention is to provide a novel method of and vapparatus for suppressing anode effect prior to the actual increase in voltage drop across a given electrolytic aluminum reduction cell, whereby said suppression device suppresses the anode effect until additional alumina is fed to said cell, either manually or by operation of an automatic device for feeding alumina to said cell.

A further object of this invention is to avoid the periodic reduction in production of aluminum from an aluminum cell occasioned by periodic increase in voltage drop across said cell as Ya result of depletion of alumina in said cellrbelow a critical concentration. Y

A further object of this invention is'to avoid the periodic reduction in production from an electrolytic celloccasioned by periodic increase in voltage drop across said cell as a Vresult of anode effect.

A further object of this invention is to prevent reduced production from a series of aluminum cells occasioned by the periodic increase in voltage drop of one or more of said cells as a result of depletion of alumina in said cell below a critical concentration wherein the voltage in said cell increases to a considerable extent, thereby decreasing Vthe current in the line of V'aluminum cells and consequently decreasing production in said line of aluminum cells.Y

- A further object of this invention is to eliminate the possibility of Vbreakdown in rectifier and/or generator equipment for electrolytic cell lines occasioned by large variationsy in power drain resulting yfrom periodic increase in cell voltages occasioned by multiple anode effects. v

' The present 'invention contemplates suppression of anode effect in an electrolytic cell by applying a periodically varying electrical energy source characterized by high peak voltages and low amperage across the anode to electrolyte interface of the cell, preferably in pulses of rapid repetition rate. VBy the term high-voltage as used hereinafter is meant a voltage in excess of 1,000 volts. The voltage may range in value fromV about 1,000 volts to 10,000 volts. 'The repetition rate may range from about 180 to 15,000 cycles per second, the preferred range being from about 400 to 2,000 cycles per second.

Itis theorized that anode effect is the result of the formation of heavily ionized gas bubbles at the anode interface, `which normally rapidly evolve from the system. However, when the anode effect is established, examination reveals that the whole of the surface of contact between each anode and the electrolyte is covered by a Vcontinuous gaseous llm or envelope in a state of ionized discharge. This build up of gas on the anode occurs gradually, involving at first only a few gas bubbles at the anode areas. As the preliminary phases of anode effect advance, more and more of the totalv interface area becomes involved. When sufficient ionized gas has accumulated at the interface to withstand any appreciable potential, the condition of anode effect is suddenly established and the interfaceV gas complex can support a voltage'drop of'about 50 volts.

It has been found that application Yof a high voltage across the gas phase established at the anode interface will dissipate this gas phase instantly. It is believed that said-,high voltage changes the current conduction from partial ionization to full spark and arc conditions, the heat from which causes said dissipation of said gas phase permitting the ,current to pass directly from the (anode to the electrolyte rather'than through an ionized gas layer.

Continuous application ofthe voltage will continuously prevent gas formation and therefore will continuously prevent the iinal state of anode effect.

The use of periodically varying energy source having a repetition rate greater than cycles per second makes possible the use of an auxiliary'circuit arranged so that thevoltage will appear only :across that reduction cell whose anode electrolyte interface is approaching the onset of anode effect. By means of a suitable impedance which may consist of the natural self impedance of the exf ternal circuit to the energy source or suitable choke coils, the high voltage will not appear in the rest of the cell line circuit. Y d Y In the accompanying drawing, there is shown an illustrative embodiment of the invention and the preferred method of practicing the invention. In the drawing:

Figure l presents in schematic and diagrammatic form an electronic anode effect suppression system according to the presentV invention, wherein a blocking oscillator is uti=` lizedto deliver high-voltage, high-frequency energy pulses across the anode to electrolyte interface. l

' Figure 2 illustrates in schematic form the application of the anode effect suppression system of this invention to a series of aluminum reduction cells.

Figure 3 illustrates a pulse waveform, such as produced by a Ablocking oscillator, as employed in a preferred embodiment of the present invention.

Referring now to the accompanymg drawings, it will be apparent that the oscillator, amplifier, and power supply circuits are schematically represented, and that the specific nature of these components will be readily understood by those skilled in the art.

Referring now more particularly to Figure l, there is i illustrated an anode effect suppression system, as used in conjunction with an aluminum reduction cell. Aluminum reduction cell 1 is of generally conventional design, com` prising a carbon cathode 2 containing a molten aluminum pad, said cell further comprising a carbon anode 6, and an electrolyte 4, consisting Vessentially of alumina dissolved in cryolite. Current is delivered to the cell by conductor 14 through support rod 7 to anode 6,'frorn which it passes through the alumina and cryolite electro# lyte 4,-molte`n aluminum 3, to cathode 2 and out bus bar? 9. Passage of 4such direct current through said cell in the manner described enables electrolysis to proceed in such a manner as to reduce the alumina to metallic aluminum. The oxygen thus liberated ultimately reacts with the car bon electrode `6 to form carbon oxides which eventually' escape from the` system, Also, some fluorides are liberated as a result Vof thermal decomposition and second# ary Velectrolytic actions ofthe cryolite and these also eventually escape from the system. Y In commercial installations for the production of alumi numthe electrolytic cells are connected in a line or series so rthat the current flows from one cell to the next. such an instance the power for reduction cell 1 would be (supplied through the remaining cells in the series. Line 14 wouldthusbe connected'to the cathode of the next preceding cellA in the line Vwhile line 15 would ber con-- nected to the anode of the next subsequent cell of the line as shown in Figure 2. The power from the rectifier powerV supply would then be connected tothe anode'of the cell on one end of the lineV of reduction cells andrtoy the cathodeof the cell on the opposite end of the line. A separate source of high voltage pulses of high repetition rate could be employed for each cell or one source could be Vprovided for several cells along Vwith a suitable conventional switch-ing arrangement.

In accordance with. a specific embodiment of this Yin-V vention as illustrated in Figures l and 2, an impedance 11' is placed in series withvthe conductor 14 fromthe reduc?" cadena voltage drop across said cell is only about 4 to 6 volts, current doesnot pass through glow lamp 10. However, a sudden increase in voltage drop above 60-65 volts will cause glow lamp to discharge, providing a continuous conducting path from anode support rod 7 to cathode 2, thus effectively preventing such high voltage from being impressed across reduction'cell power supply lines 14 and In the specific embodiment of this invention illustrated by Figures l and 2 a high-frequency pulse oscillator 16 is employed as a source of high-voltage high repetition rate potential. More particularly, pulse oscillator 16 is of the blocking oscillator type, producing pulses having a repetition :rate ranging from 180 to 15,000 pulses per second. The preferred waveform produced by oscillator 16 is shown `in Figure 3. Anexample of such a wave-A form is one with positive polarity, a pulse duration 19 of to 40 microseconds and a rise time of 6 to 7 microseconds. These pulses are then amplified by a class A power amplifier 17 and further amplified by a class B power amplifier 18; The power for said oscillator and amplifier is provided by a variable D.C. power supply 13, capable of` delivering D.C. voltages `up to 10,000 volts and adapted to` deliver both a low votage and a high voltage simultaneously. Blocking oscillator- 16, class A power amplifier 17 and class B power amplifier 18 are ccnventional items of equipment well known to those skilled in the art. Suitable examples are shown and described in Radio Engineers Handbook, third edition, `by Frederick E. Termen, McGraw-Hill Book Company. A suitable blocking oscillator is described on pages 590 through 593 and shown in Figures 12-9. Suitable class A power ampliiiers are shown and described on pages 287-299. Suitable class B power amplifiers are described on pages 304-307 and a suitable circuit is shown in Figure 6-41 (a), Page305. A suitable power supply is described on page 5'57 and shown in Figure ll*8(a). Power supply 13 con sists of two such supplies, one for the Br low voltage and one for the B+ high voltage.

Operation of the invention according to the illustrated embodiment will now be described; When it is shown by a suitable indicating device such as that disclosed in my co-pending application Serial Number 614,961, filed October 9, 1956, that the onset of anode effect has developed, switch 8 is closed, thereby impressing the high-voltage pulses of high repetition rate across aluminum reduction cell 1. In such a case the high voltage pulses produced by the high-voltage, high repet- ition rate generator 13, 16, 17 and 18 is essentially prevented by the impedance 11 from appearing in the other cells and with only a small voltage drop from this source appearing across glow lamp 10 which small voltage drop is insufficient to cause glow lamp 10 to conduct.

While impedance 11 offers a high impedance to pulses of high repetition rate it offers little or no resistance to D.C. current from the reduction cell` power supply. The function of the impedance 11 and the glow lamp 10 is to prevent the high voltage pulses from entering the reduction cell power supply and causing possible damage to the rectifiers and/ or transformers and from adversely affecting the, other cells inthe line. The impedance 11 offers high impedance to the pulses of high repetition rate to prevent these pulsesV from impressing a dangerously v high voltage on the reduction cell power supply. The

glow lamp 10 is an additional precaution in that it limits the pulse voltage from ever increasing over 6065 volts across the reduction cell power supply. Normally this would not occur. However, it should be noted in this connection that if this should happen these high voltage pulses are of very short duration, for example 20 to 40 microseconds. While the voltage is high there is insufficient energy to burn out the glow lamp due to the short duration of the pulses. The circuit is opened upon expiration of each pulse and as can be seen from Figure 3, the time lapse between pulses is much greater than the 6. pulse duration. The value of impedance 1.1 is such as` to provide a sufficient impedance in parallel with reduction cell 1 at the selected repetition yrate to effectively impress a full 1,000 to 10,000 volts of high frequency pulses across the interface between anode 6 and molten alumina-cryolite mixture 4. Therefore, in accordance with the principles of this invention, the gas phase established at the anode interface will be discharged completely and thereby dissipated.

In electrolytic cells for `the reduction of alumina to produce aluminum, anode eifect is an indication that alumina has lbecome depleted in said cell. Therefore, in the operation of such cells, it is necessary in order to continue production to add more alumina. The `anode effect suppression device of this invention, when applied to cells for the production of aluminum may be employed to prevent establishment of anode effect, with the attending disadvantages, until alumina can be fed to the reduction cell.

As disclosed in my co-pending application Serial Num- Iber 614,961, filed October 9, 1956, said detection device may be employed to actuate heavy current relayswhich in turn would operate lalarm `and `signal systems. It is within the scope of this invention to utilize such relays actuated by said detection device to actuate the suppression device of this invention.

For example, in Ithe embodiment of Figures l and 2, relays actuated by said detection device may close switch `8 thereby impressing high voltage pulses of high repetition rate across cell 1. When used in conjunction with an automatic alumina feeder as disclosed in said `co-pending application, said high voltage pulses would be maintained across cell 1 until an automatic alumina feeder delivers a predetermined amount of alumina to the electrolyte, sufficient to eliminate the anode effect, at which point switch 8 may be opened by either manual or automatic means.

One example of the practice of this invention pertains to the suppression of anode effect in an electrolytic aluminum reduction cell employing four conventional prebake anodes. It is to be distinctly understood that this is by way of example rather than limitation.

The apparatus used yemployed a blocking oscillator 16- capable of producing pulses of positive polarity having a repetition rate ranging from 180 to l0,000 pulses per second, a pulse duration of 20 microseconds, and a rise time of 6 to 7 microseconds. The pulses from the blocking `oscillator 16 were fed into a class A power amplifier 17 having a gain of l5 and designed for a frequency range of to 10,000 cycles per second. The output of 'the class A amplifier 17 was fed into a class B power amplifier `18 which had a power amplifica-tion factor of 100 and designed for a frequency range of 100 to 10,000 cycles per second.` The D.C. power supplied `by power supply 13 was,300 volts for blocking oscillator 16 and class A power amplifier 17 and 3,000 volts for class B power amplifier 18. The peak voltage of the pulses delivered `by class B power amplifier 18 was 2,000 volts. The output was impressed across the anode to electrolyte interface of cell 1 as shown in Figure l. The impedance 11 employed was a choke coil having a value of l henry. The glow lamp 10 was designed -to conduct `at a voltage in excess of 65 volts.

An actual test for anode effect suppression was made by rst allowing the cell to go into a completed anode effect which is characterized by sudden high voltage across the cell. The anode effect suppression device was then placed lin operation `by closing switch with the result that the voltage drop returned to normal almost immediately. This was tried numerous times with various repetition rates for the pulses applied to .the reduction cell and it was found that the suppressor functioned best over a frequency range of from 400 to 2,000 pulses per second. Optimum operation for suppression of Ianode effect appeared at about 1,000 pulses per second. The `anode effect suppressor was turned on and off by opening and closing switch 8 about 12 times and maintained in the on position for periods of timeranging from several seconds to ten minutes. The reduction cell maintained normal voltage while the suppressor was in operation and immediately went into anode elfect characterized by voltages of 40-50 volts when the suppressor was turned off, i.e. switch 8 opened.

To demonstrate the value of the suppressor of this invention for preventing completed anode effect, i.e. abnormal voltage rise, an additional test was conducted. Tests were made `of the anode effect detection device of co-pending application `S.N. 614,961, filed October 9, 1956, wherein it was found that this device detected the onset of anode effect from 27-54 minutes in advance of the substantial voltage rise of a completed anode effect. Accordingly, this device was employed in connection with the test of the anode reffect suppressor of this invention. The anode effect detection device was connected tothe cell as described in co-pending application, S.N. 614,961. As soon as onset of anode effect was indicated on the oscilloscope screen, switch `8 of the anode effect suppressor was closed thereby impressing the high voltage pulses across the cell. As soon as switch 8 was closed, the abnormal size of the hash pattern and the spiked patterns of large amplitude and short duration disappeared and all that could be seen on the screen was the normal hash pattern. However, upon yopening switch `8 the abnormally large hash pattern and spiked patterns of large amplitude again appeared on the `oscilloscope screen. It was found that with switch 8 closed for a period `of two hours after initial indication of anode effect onset, the substantial voltage rise characteristic of completed anode eiect failed to appear. This test was repeated several times and in each case with switch 8 closed the voltage rise characteristic of a completed anode effect failed to appear within two hours after anode eEect was initially indicated on the oscilloscope screen of the anode effect detection device.

The results of these tests demonstrate that anode eiect can be suppressed by impressing a series of high voltage pulses of high repetition rate across the anode to electrolyte interface in accordance with this invention and further that a completed anode effect can be prevented by impressing the series of high voltage pulses across this interface as soon as indications are made by -an anode effect detection device as described in co-pending application, S.N. 614,961.

While specic embodiments of this invention have been shown and described, it is to be distinctly understood that the invention is not in any sense limited to the illustrative systems presented, but lthat many modiiications may be made without departing from the `scope thereof.

What is claimed is:

1. In the art of fused bath electrolysis wherein the problem of anode effect is present, the improvement for the suppression of said anode eiect comprising the steps of producing periodically varying electrical energy characterized by high peak voltages and a repetition rate of not less than 180 cycles per second, and impressing said energy across said electrolytic cell.

2. In the art of producing aluminum by the reduction o-f aluminum oxide in a fused bath electrolytic cell, said cell being subject to anode effect, the improvement for suppression of said anode effect comprising the steps of producing periodically varying electrical energy of positive polarity characterized by high peak voltages and 8 a repetition rate of not less than cycles per second, and impressing said energy across said electrolytic cell. 3. A method of suppressing anode elect in fused bath electrolytic cells comprising the steps of producing a periodically varying potential characterized by high peak voltages and a repetition rate ofnot less than 180 cycles per second, and impressing said energy across said electrolytic cell.

4. A method of suppressing anode effect in fused bath electrolytic cells comprising the steps of producing a series of high-voltage, pulses-of short duration, said pulses having a repetition rate of not less than 180 cycles per second and impressing said ser-ies of 4high-voltage pulses across the anode to electrolyte interface of said electrolytic cell. f y

5. A method of claim 4 wherein said pulses have a positive polarity, a repetition rate of 400-2,000 cycles per second, a pulse duration of 20 to 40 microseconds, a rise time of 6 to 7 microseconds, and a potential of 1,000 to 10,000 volts. Y

6. The method of claim 4 wherein the electrolytic cell is an aluminum reduction cell.

7. The method of claim 6 including the additional step of feeding alumina to said electrolytic aluminum reduction cell.

8. A method of suppressing anode elect in fused bath electrolytic cells comprising the steps of detecting the onset of anode effect, producing a series of high-voltage pulses of positive polarity and short duration, said pulses having a repetition rate of not less than 180 cycles per second, and impressing said series of high-voltage pulses across the anode to electrolyte interface of said electrolytic cell.

9. A fused bath electrolytic cell system comprising a cathode, an anode, an electrolyte, means for conducting low-voltage direct current energy through said electrolytic cell, a source of high-voltage pulses of short duration, said pulses having a repetition rate of not less than 180 cycles per second, means for impressing said pulses across the anode to electrolyte interface of said electrolytic cell with onset of anode effect therein, glow lamp means inV parallel with said electrolytic cell and the source of said low-voltage direct current, said glow lamp presenting an open circuit to a low voltage, but which discharges providing a conducting path when impressed with a highvoltage, and a suitable impedance in series with said low-voltage direct current energy and with said glow lamp and in parallel with said electrolytic cell with respect to said source of high voltage pulses whereby said low-voltage D.C. source is effectively isolated from said pulses.

10. The system of claim 9 wherein said pulses have a positive polarity, a repetition rate of 400-2,000 cycles per second, a pulse duration of 20 to 40 microseconds, a rise time of 6 to 7 microseconds, and a peak voltage of 1,000 to 10,000 volts.

References Cited in the file of this patent UNITED STATES PATENTS 1,428,049 Nickum Sept. 5, 1922 2,446,350 Wier Aug. 3, 1948 FOREIGN PATENTS 641,254 Germany Ian. 26, 1937

Claims (2)

1. IN THE ART OF FUSED BATH ELECTROLYSIS WHEREIN THE PROBLEM OF ANODE EFFECT IS PRESENT, THE IMPROVEMENT FOR THE SUPPRESSION OF SAID ANODE EFFECT COMPRISING THE STEPS OF PRODUCING PERIODICALLY VARYING ELECTRICAL ENERGY CHARACTERIZED BY HIGH PEAK VOLTAGES AND A REPETITION RATE OF NOT LESS THAN 180 CYCLES PER SECOND, AND IMPRESSING SAID ENERGY ACROSS SAID ELECTROLYTIC CELL.

9. A FUSED BATH ELECTROLYTIC CELL SYSTEM COMPRISING A CATHODE, AN ANODE, AN ELECTROLYTE, MEANS FOR CONDUCTING LOW-VOLTAGE DIRECT CURRENT ENERGY THROUGH SAID ELECTROLYTIC CELL, A SOURCE OF HIGH-VOLTAGE PULSES OF SHORT DURATION, SAID PULSES HAVING A REPETITION RATE OF NOT LESS THAN 180 CYCLES PER SECOND, MEANS FOR IMPRESSING SAID PULSES ACROSS THE ANODE TO ELECTROLYTE INTERFACE OF SAID ELECTROLYTIC CELL WITH ONSET OF ANODE EFFECT THEREIN, GLOW LAMP MEANS IN PARALLEL WITH SAID ELECTROLYTIC CELL AND THE SOURCE OF SAID LOW-VOLTAGE DIRECT CURRENT, SAID GLOW LAMP PRESENTING AN OPEN CIRCUIT TO A LOW VOLTAGE, BUT WHICH DISCHARGES PROVIDING A CONDUCTING PATH WHEN IMPRESSED WITH A HIGHVOLTAGE, AND A SUITABLE IMPEDANCE IN SERIES WITH SAID LOW-VOLTAGE DIRECT CURRENT ENERGY AND WITH SAID GLOW LAMP TO SAID SOURCE OF HIGH VOLTAGE PULSES WHEREBY SAID SPECT TO SAID SOURCE OF HIGH VOLTAGE PULSES WHEREBY SAID LOW-VOLTAGE D.C. SOURCE IS EFFECTIVELY ISOLATED FROM SAID PULSES.

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