US2525938A

US2525938A - Electrochemical apparatus with adjustable electrode

Info

Publication number: US2525938A
Application number: US707066A
Authority: US
Inventors: Lee H Peck
Original assignee: Koppers Co Inc
Current assignee: Beazer East Inc
Priority date: 1946-11-01
Filing date: 1946-11-01
Publication date: 1950-10-17
Anticipated expiration: 1967-10-17

Description

Get. 17, 1950 Fil d Nov. 1, 1946 5 an E L. H. PECK ELECTROCHEMICAL APPARATUS WITH ADJUSTABLE ELECTRODE 2 Sheets-Sheet 1 .z -5. ia

Oct. 17, 1950 H. PECK 5, 38

ELECTROCHEMICAL APPARATUS WITH C ADJUSTABLE ELECTRODE FilQ -Noy. 1-, 1946 2 Sheets-Sheet 2 3 HAM/MM Zee/Zfka',

Patented Oct. 17, 1950 ELECTROCHEMICAL APPARATUS WITH ADJUSTABLE ELECTRODE Lee H. Peck, Chagrin Falls, Ohio, assignor, by mesne assignments, to Koppers Company, Inc., a corporation of Delaware Application November 1, 1946, Serial'No. 707,066

12 Claims.

The present invention relates to an automatic or semi-automatic device for use in the striking or initiating of electrical discharges.

In the electrochemical transformation of a gas eous medium in the presence of an electrical discharge between a single pair of electrodes, it is necessary to strike or initiate the discharge using an appropriate striking voltage; for example, with a high frequency discharge of 2.1 megacycles, the striking voltage for a 17 mm. (millimeter) gap may be approximatel 18,000 volts; whereas, after the discharge has been struck the active operating voltage is only about thereof or about 1800 volts. The figures given are for the production of hydrazine from ammonia in which the electrochemical transformation of the ammonia is carried out at super-atmospheric pressures, as for example, 770 mm.

In the manufacture of nitric oxide from atmospheric air at sub-atmospheric pressures, as for example, at 335 mm. pressure, for a 1'? mm. gap, the striking voltage may approximate 25% to 3000 volts. After the discharge is-once struck, the active operating voltage. may vary approximately between 1000 and 1200 volts.

It is well known that other conditions remaining constant, the striking voltage or breakdown voltage in a gaseous discharge is approximately proportionate to the gap distance, that is, the distance between cooperating electrode terminals between which the discharge is initiated. Therefore, if the gap between a cooperating pair of electrodes can be temporarily decreased at the time the discharge is struck, the striking voltage may be proportionately decreased, and if the gap be decreased so that the striking voltage does not exceed the normal operating voltage, the electrode discharge gap after the discharge is struck may be lengthened or drawn out to a desired predetermined gap which is the original electrode the electrochemical transformation of a gaseous medium' comprising the combination of a reactor vessel, a pair of electrode terminals positioned.

able electrode terminal to its initial position or any other predetermined position, means being provided for introducing a' gaseous medium into said casing while maintaining a relatively higher pressure above the plunger than therebelow to move the piston and its electrode terminal closer v to the cooperating electrode and shorten the electrode: gap between the electrode terminals so that the discharge therebetween maybe effected under operating voltage instead of under higher striking voltage, there also being provided means" for reducing the' press'ure diiieren'tialbetween the pressures above and below the plunger to substantially zero, whereupon the returning means returns the reciprocating electrode to a prede.

termined position. i

It is an additional object of the invention to provide means to leak gaseous medium from, above the plunger to below the plunger to equalize the pressure'above and below the plunger whereupon th'e returning means returns the recipro cating electrode to a predetermined position;

While spring means may be employed to return the adjustable or reciprocating electrode other equivalent means maybe employed.

It is an additional object of the present inven tion to provide an apparatus of the character set forth wherein the adjustable electrode is caused to reciprocate to shorten the electrode gap be tween its cooperating electrode by the applica-, tion of a super-atmospheric pressure which may be just slightly above atmospheric pressure or may be considerably higher.

It is an additional-object of the present invention to utilize a pressure lower than atmospheric to cause the adjustable electrode of the apparatus to reciprocate to shorten the electrode gap.

The invention will be described in connection with the accompanying drawing wherein Figure 1 isthe-frontelevation of the electrode gap adjusting device;

Figure 2 is a plan view thereof. 1 1

Figure 3 is a longitudinal cross sectional view taken on line 33 of Figure 2.

Figure 4 is a detail view of the plunger of the electrode gap adjusting device.

Figure 5 is a longitudinal sectional view showing the piston member of the electrode gap adjustor in its depressed condition adapted to position the electrode for the shortest electrode gap.

Figure 6 is a view partly in section of the electrode gap adjustor assembled with an electrical discharge reactor adapted to eifect electrochemical transformation of a gaseous medium under super-atmospheric pressure.

Figure '7 is a similar view wherein the electrochemical transformation of the gaseous medium is effected. at sub-atmospheric pressure.

Referring to the drawing, the electrode adjustor comprises a casing It] provided with a member II which functions as an inlet member when operating under super-atmospheric pressure and as an outlet member when operating at sub-atmospheric pressure. The casing I0 is provided with an inner wall l2, and at its lower extremity, it is rovided with a bottom wall l3, the latter acting to limit the travel stroke of the plunger l4 in a manner as hereinafter set forth. The casing adjacent its lower extremity is provided with a series of apertures l 5, l6, l1, and I8, adapted to allow the gaseous medium which operates the device to escape from the casing while the piston l4 has been depressed. The casing at its upper portion is provided with a conductive cap l9 provided with a top wall '20 and a lower wall 2|, the latter functioning to limit the upward stroke of the piston 14. The cap, which is externally threaded at 22 is screwed into the upper end of the casing which is provided with threads 23. A binding post 24 adapted to receive the electrical connector 25 is connected with the upper wall member 20.

The piston rod 14 is provided with a lower cylindrical portion 26, an intermediate enlarged cylindrical portion 21, and a top cylindrical portion 29. The cylindrical portion 2'! is provided with a shoulder 28 at its juncture with the piston rod portion 26. The shoulder portion 28 serves as a stop to limit the downward stroke of the piston rod [4.

Adjustably mounted on the piston rod I4 is the piston or plunger 30 which is held in a predetermined position by the screw nut 32. The piston rod l4 below the plunger 30 is provided with a coil spring 33. It is to be noted that the coils of the spring 33 are not of the same diameter throughout the spring, but that the coils of smaller diameter are at the top portion of the spring, and the coils gradually increase in diameter from the upper portion of the spring towards the lower portion of the spring. This is the preferred type of spring as it operates to exert its pressure at and adjacent the center of the plunger 30 instead of adjacent the periphery of the plunger 30. When the spring pressure is exerted at and adjacent the periphery portion of the piston or plunger 30 there is a tendency for the piston to jam in the casing, and this is eliminated by the employment of a spring of the character set forth.

It is to be noted that preferably there is a small clearance between the outer surface 3| and the interior wall of the casing III. This clearance should be sumcient to allow the escape or leakage of gases past the piston plunger after the gas has acted to effect movement of the piston either in a downwardly or upwardly direction, depending on whether the activating gas is at superatmospheric pressure or at sub-atmospheric pressure, respectively.

The lower portion of the piston member 26 is threaded at 31 and is adapted to receive the electrode terminal 38. The piston rod l4, including the lower portion 26, acts as one electrode for the reactor 40 in which there is positioned a cooperating electrode terminal 39 and an electrode 4 I.

The upper end of the reactor 40 is provided with an apertured closure member 42 preferably of a non-conducting material in which the electrode adjustor E is mounted. The lower end of the reactor is provided with a non-conducting closure member 43.

Means are provided to introduce the gaseous medium to be electrochemically transformed into the reactor 40, a suitable inlet means such as the conduit 44 being provided.

Connected to the inlet conduit 44 are

branch lines

45 and 43. At the junction of

conduits

44, 45, and 46, there is provided a three-way valve 41. The conduit 45 is connected to the conduit H of the electrode adjustor E.

For operation under super-atmospheric conditions the hookup set forth in Fig. 6 is suitable. In starting operations the normal operation voltage, as for example 1800 volts, suitable for the production of hydrazine from ammonia is applied to the

electrode terminals

38 and 39. Thereafter the valve 41 is positioned so asto allow the gas to be transformed, such as ammonia, to pass by the way of the conduit 45 and conduit H into the interior of the electrode adjustor E where it acts upon the plunger 30 causing the piston rod 26 to move downwardly to the position shown in Figure 5 where the electrode terminal 38 is closely adjacent the electrode terminal 39.

In the specific case set forth the electrode terminal 38 has been moved 16 mm. inwardly to within 1 mm. of the terminal 39. With this shortened electrode gap the discharge strikes at a very low voltage, as for example, for the production of ammonia from hydrazine, at 1800 volts instead of 18,000 volts. As soon as the discharge has been effected the valve 41 is turned to cause the incoming gas to fiow through the conduit 46 into the interior of the reactor 40 whereupon the pressure within the reactor causes the gas to flow through the small apertures I5, 16, H, and I8 into the interior of the casing [0 below the plunger 30, thereby equalizing the pressures below and above the plunger 30. When this occurs, the spring 33 forces the plunger upwardly and thereby causes the rod 26 to move upwardly and restore the electrode terminal 38 to its original predetermined position 17 mms. from the electrode terminal 39, or to any other desired position.

In the above form of the invention when utilizing super-atmospheric pressure the operation is semi-automatic, and it is not necessary to have any substantial clearance between the exterior surface 3| of the plunger 30 and the interior wall of the casing l0. However, in the form of the invention shown in Figure '7, the electrode gap adjustor may be made to function fully automatically by providing and utilizing a clearance space. The electrochemically transformed product passes from the reactor 40 through the conduit 50.

Referring to Figure '7, the electrochemical transformation of the gaseous medium is carried out under sub-atmospheric pressure, as for example, under a pressure of 335 mm. when electrochemically transforming atmospheric air to nitrogen oxide.

The reactor 30 is provided with an inlet conduit 49 and an outlet conduit 50 connected to the vacuum pump P. A by-pass conduit 52 is connected to the conduit l l of the electrode adjuster E and to the outlet 50 via the valve 5|.

In operation the normal operating voltage, as

for example, 1000 to 1200 volts, is applied to the electrode connector 25 and the electrode 4|. The applied voltage is, as stated, the operating voltage of 1000 to 1200 volts, and not the striking voltage of 5000 to 6000 volts which would be required if the electrode adaptor E were not u ilized.

Thereafter, the vacuum generated by the vacuum pump P is applied to the conduit 50, the valve 5! being so set as to disconnect the by-pass conduit 52. As soon as this vacuum is established, atmospheric air to b transformed enters the reactor 40 by means of the conduit 49, and the vacuum is communicated to the interior of the casing in via the apertures l5, l6, l1, and I8. The gaseous medium under a vacuum pulls the plunger downwardly compressing the spring 33 and forcing electrode terminal 33 inwardly 16 mms. to within 1 mm. of the electrode terminal 39. After the discharge has been struck, the electrode 38 is brought back to its predetermined normal position in the following manner which is automatic.

As previously stated, there is a clearance between the periphery of the piston 30 and the interior wall of the casing Hi. The air in the easing I above the plunger 30 before the plunger moved downwardly under the action of the vacuum is at atmospheric pressure and is at all times at a pressure higher than that existing in the gaseous medium below the plunger. As soon as the plunger 30 is pulled downwardly on application of the vacuum the discharge strikes, and the leakage of the gaseous medium from the space above the plunger to the space below the plunger is initiated, thus starting the reverse or upward movement of the plunger. The time for the reverse] is dependent upon the tension of the spring and the clearance of the plunger.

When operating as herein set forth, the time of reversal may take about 10 seconds. It is desired to point out, however, that it is not desired to be limited to this time period as the time period can be adjusted to any desired reversal time by the tension of the spring and the clearance between the plunger 30 and the interior wall of the casing l0.

It is to be noted that the operation as above set forth is fully automatic and the valve remains positioned as shown in Fi ure '7. If a quick reversal is required the valve 5|, which is normall closed, is momentarily opened, whereupon the pressures above and below the plunger are rapidly equalized as, for example, in a fraction of a second. In this case the operation is semiautomatic.

Referring to Figure 6, a gaseous medium under a pressure varying from 770 mm. to 800 mm. is introduced into the casing in above the plunger 30, and then the arc is struck at the normal operating voltage which as stated, is much lower than the usual striking voltage. Thereafter, the same gas or a different gas is introduced by a conduit 36 and passes through the openings I5, l6, l1, and I8 into the casing below the piston. Upon the pressure being equalized, the piston 30 is caused to travel upwardly under the influence of the spring 33 which has been compressed duringthe downward stroke of the piston. Instead of using the same pressures above and below the piston 30 to operate the piston in the manner above set forth after the plunger 30 has oncebeen depressed, the gas introduced below the piston may have a higher pressure in pounds per sq. in. than pheric pressure, and the valve 5| is closed. Theoperations are started, and the normal operating voltage is applied between the

electrode terminals

38 and 39. Thereafter with the valve 5! closed,

the vacuum is applied in the manner hereinbefore set forth.

It is desired to point out that in the form of the apparatus shown in Figure 7, instead of having a gas at atmospheric pressure in the casing l0 above the plunger 30, the gas may be at below atmospheric pressure and a gas at a pressure still lower than the pressure of the gas in the casing abovev the piston may be introduced into the casing below the piston to cause the piston to operate. The point, again, is that even when operating under a vacuum all that is necessary is that there be a" difference in pressure above and below the piston in order to activate the piston and shorten the electrode gap. After the electrode gaphas been shortened, the pressure is equalized, and upon equalization, the spring 33 effects return of the adjustable electrode to a predetermined position.

The difference in pressures must be suflicient to overcome the pressure exerted by the upward thrust of the spring.

I claim:

1. In an electrode gap adjustor, the combina tion of a casing having an interior chamber, a

top end wall, and an-aperturedlower end wall, a piston carrying a plunger intermediate its upper and lower end, the latter being provided with an electrode terminal, said piston reciproeating, in said chamber through the 'apertured' lower end member, stop means on said pistonv and reciprocating therewith, auxiliary cooperat-' ing stop means in said casing for limiting the forwardstroke of the piston to the. distanceit is desired to move the electrode terminal, spring means in said casing positioned to assist in re turning the plunger, the piston, and the electrode terminal after completion of the forwardstroke of the piston, means tolimit the upward travel u of the piston and the electrode terminal, and means for effecting reciprocation of the plunger in the chamber casing including an opening in' the casing below the plunger;

2. In an electrode gap adjuster, the combination of a casing having an interior chamber, a top end wall, and an apertured lower end wall,

a piston carrying a plunger intermediate its,

upper and lower end, the latterbeing provided with an electrode terminal, said piston reciprocating in said chamber through the apertured lower end, a clearance space between said plunger and the interior wall of the casing chamben'stop,

means on said piston and reciprocatingtherewith, auxiliary cooperating stop means in said casing for limiting the forward stroke of the V The p piston to the distance it is desired to move the electrode terminal, spring means in said casing positioned to assist in returning the plunger, the piston, and the electrode terminal after completion of the forward stroke of the piston, means to limit the upward travel of the piston and the electrode terminal, and means for effecting reciprocation of the plunger in the chamber casing including an opening therein.

3. In an electrode gap adjustor, the combination of a casing having an interior chamber, a removable upper cap having an interior bottom wall and an apertured lower end wall, the interior wall of which acts as a stop member, a piston carrying plunger intermediate its upper and lower end, the latter being provided with an electrode terminal, said piston reciprocating in said chamber through the apertured lower end wall, stop means on the piston and reciprocating with the piston, said stop means abutting the interior lower end wall and limiting the forward stroke of the piston the distance it is desired to move the electrode terminal, spring means positioned in said casing below said plunger to assist in returning the plunger, the piston, and the electrode terminal after completion of the forward stroke of the piston, means to limit the upward travel of the piston and electrode terminal comprising the interior bottom wall of the cap member, and means for eifecting reciprocation of the plunger in the chamber casing, including an opening in the casing below the plunger.

4. In an electrode gap adjustor, the combination of a casing having an interior chamber, a removable upper cap having an interior bottom wall and an apertured lower end wall, the interior wall of which acts as a stop member, a piston carrying a plunger intermediate its upper and lower end, the latter being provided with an electrode terminal, said piston reciprocating in said chamber through the apertured lower end wall, stop means on the piston and reciprocating with the piston, said stop means abutting the interior lower end wall and limiting the forward stroke of the piston the distance it is desired to move the electrode terminal, spring means positioned in said casing below said plunger to assist in returning the plunger, the piston, and the electrode terminal after completion of the forward stroke of the piston, means to limit the upward travel of the piston and electrode terminal comprising the interior bottom wall of the cap member, and means for effecting reciprocation of the plunger in the chamber casing, including a plurality of small openings positioned circumferentially of the casing adjacent its lower end.

5. In an electrode gap adjustor, the combination of a casing having an interior chamber, a removable upper cap having an interior bottom wall and an apertured lower end wall, the interior wall of which acts as a stop member, a piston carrying a plunger intermediate its upper and lower end, the latter being provided with an electrode terminal, said piston reciprocating in said chamber through the apertured lower end wall, stop means on the piston and reciprocating with the piston, said stop means abutting the interior lower end wall and limiting the forward stroke of the piston the distance it is desired to move the electrode terminal, spring means positioned in said casing below said plunger to assist in returning the plunger, the piston, and the electrode terminal after completion of the forward 8 stroke of the piston, means to limit the upward travel of the piston and electrode terminal comprising the interior bottom wall of the cap member, means for effecting reciprocation of the plunger in the chamber casing, including an opening in the casing below the plunger, and means to leak gaseous medium from above the plunger to below the plunger to equalize the pressure above and below the plunger.

6. In an electrode gap adjustor, the combination of a casing having an interior chamber, a removable upper cap having an interior bottom wall and an apertured lower end wall, the interior wall of which acts as a stop member, a piston carrying a plunger intermediate its upper and lower end, the latter being provided with an electrode terminal, said piston reciprocating in said chamber through the apertured lower end wall, stop means on the piston and reciprocating with the piston, said stop means abutting the interior lower end wall and limiting the forward stroke of the piston the distance it is desired to move the electrode terminal, spring means positioned in said casing below said plunger to assist in returning the plunger, the piston, and the electrode terminal after completion of the forward stroke of the piston, means to limit the upward travel of the piston and electrode terminal comprising the interior bottom wall of the cap member, means for effecting reciprocation of the plunger in the chamber casing, including a plurality of small openings positioned circumferentially of the casing adjacent its lower end, and means to leak gaseous medium from above the plunger to equalize the pressure above and below the plunger.

7. In a gas-discharge apparatus for effecting electrochemical transformation of a gaseous medium under super-atmospheric pressure, the combination of a reactor vessel, a pair of electrode terminals positioned respectively on a pair of lectrode members, eaid electrode terminals being capable of effecting an electrical discharge in said reactor, one of said electrode members and its electrode terminal being mounted on a piston reciprocating in a casing to vary the electrode gap between said electrode terminals, means for introducing a gaseous medium under pressure into said casing to move said piston and its electrode terminal closer to the cooperating terminal and initiate a discharge between the electrode terminals at a lower operating voltage than is required in the absence of the shortening of the electrode gap, means for introducing a gaseous medium to be transformed into the reactor vesselunder super-atmospheric pressure, means including an opening in the casing for returning the reciprocating electrode to a predetermined position, and means for removing the transformed reaction product from the reactor vessel.

8. In the gas-discharge apparatus for effecting the electrochemical transformation of a gaseous medium under super-atmospheric pressure, the combination of a reactor vessel, a pair of electrode terminals positioned respectively on a pair of electrode members, said electrode members being capable of effecting an electric discharge in said reactor, one of said electrode members and its electrode terminals being mounted on a piston provided with a plunger held in an initial predetermined position by spring means, said piston and plunger reciprocating in a casing to shorten the electrode gap between said electrode terminals, means including an opening in the casing for introducing a gaseous medium under pressure into said casing to move said piston and its electrode terminal closer to its cooperatingterminal, and shorten the electrode gap between said terminals and initiate a discharge between the electrode terminals at a lower operating voltage than is required in the absence of the shortening of the electrode gap, means including an opening in the casing for introducing a gaseous medium into the reactor vessel under super-atmospheric pressure and into the casing below said plunger whereupon the pressure below and above the plunger becomes equalized and the spring means returns the reciprocating electrode to a predetermined position, and means for removing a gaseous product from the reaction vessel.

9. In the gas-discharge apparatus for effecting the electrochemical transformation of a gaseous medium, the combination of a reactor vessel, a pair of electrode terminals positioned respectively on a pair of electrode members, said electrode members being capable of effecting an electric discharge in said reactor, one of said electrode members and its electrode terminals being mounted on a piston provided with a plunger held in initial predetermined position by spring means, said piston and plunger reciprocating in a casing to shorten the electrode gap between said electrode terminals, means for introducing a gaseous medium under a vacuum into the reactor vessel, an opening in said casing for introducing gaseous medium therein to move said piston and its electrode terminal closer to the cooperating electrode terminal and shorten the electrode gap between said electrode terminals and initiate a discharge between the electrode terminals at a lower operating voltage than is required in the absence of the shortening of the electrode gap, means for equalizing the pressure of the gaseous medium above and below the piston plunger, means acting upon said equalization of pressure for returning the reciprocating electrode terminal to a predetermined position, and means for removing the gaseous product from the reactor vessel.

10. In a gas-discharge apparatus for effecting the electrochemical transformation of a gaseous medium, the combination of a reactor vessel, a pair of electrode terminals positioned respectively on a pair of electrode members, said electrode members being capable of effecting an electric discharge in said reactor, one of said electrode members and its electrode terminals being mounted on a piston provided with a plunger held in an initial predetermined position by spring means, said piston and plunger reciprocating in a casing, to shorten the electrode gap between said electrode terminals, means for introducing a gaseous medium under a vacuum into the reactor vessel, an opening in said casing for introducing gaseous medium therein, to move said piston and its electrode terminal closer to the cooperating electrode terminal and shorten the electrode gap between said electrode terminals and initiate a discharge between the electrode terminals at a lower operating Voltage than is required in the absence of the shortening of the electrode gap, means for removing the gaseous product from the reactor vessel, means to leak gaseous medium from above the plunger to below the plunger to equalize the pressure above and below the plunger whereupon the spring means returns the reciprocating electrode to a predetermined position, and -means for removing the gaseous product from. the reactor vessel.

11. In a gas-discharge apparatus for effecting the electrochemical transformation or" a gaseous medium, the combination of a reactor vesseha pair of electrode terminals positioned respectively on a pair of electrode members, said electrode members being capable of effecting an electric discharge in said reactor, one of said electrode members and its terminals being mounted on a piston provided with a plunger held in an initial predetermined position by spring means, said piston and plunger reciprocating in a casing to shorten the electrode gap between said electrode terminals, an opening in said casing, means for introducing a gaseous medium through said opening into said casing, while maintaining a relatively higher pressure above the plunger than below, to move the piston and the electrode terminals against the spring means and bring'said electrode terminal closer to its cooperating terminal, to thereby shorten the electrode gap between said terminals and initiate a discharge between the electrode terminals at a lower operating voltage than is required in the absence of the shortening of the electrode gap, means for reducing the pressure differential above and below the plunger to substantially zero, whereupon the spring means returns the reciprocating electrode to a predetermined position, and means for removing the gaseous product from the reactor vessel.

12. In the gas-discharge apparatus for efiecting the electrochemical transiormation of agaseous medium, the combination of a reactor vessel, a pair of electrode terminals positioned respectiveiy on a pair of electrode members, said electrode members being capable oi efi'ecting an electric discharge in said reactor, one of said electrodemembers and its electrode terminals being mounted on a piston provided with a plunger held in initial predetermined position by spring means, said piston and plunger reciprocating in a casing to shorten theelectrode gapbetween said elecating voltage than is required in the absence of a shortening of the electrode gap, means for equalizing pressure or" the gaseous medium above and below the piston plunger, means acting upon said equalization of pressure for returning therecipro-p eating electrode terminal to predetermined position and means for removing a gaseous product from the reactor vessel.

LEE H. PECK.

REFERENCES CITED' I The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 758,884 Alsop May 3, 1904 1,039,851

Wagener a. Oct. 1, 1912,

Claims

11. IN A GAS-DISCHARGE APPARATUS FOR EFFECTING THE ELECTROCHEMICAL TRANSFORMATION OF A GASEOUS MEDIUM, THE COMBINATION OF A REACTOR VESSEL, A PAIR OF ELECTRODE TERMINALS POSITIONED RESPECTIVELY ON A PAIR OF ELECTRODE MEMBERS, SAID ELECTRODE MEMBERS BEING CAPABLE OF EFFECTING AN ELECTRIC DISCHARGE IN SAID REACTOR, ONE OF SAID ELECTRODE MEMBERS AND ITS TERMINALS BEING MOUNTED ON A PISTON PROVIDED WITH A PLUNGER HELD IN AN INITIAL PREDETERMINED POSITION BY SPRING MEANS, SAID PISTON AND PLUNGER RECIPROCATING IN A CASING TO SHORTEN THE ELECTRODE GAP BETWEEN SAID ELECTRODE TERMINALS, AN OPENING IN SAID CASING, MEANS FOR INTRODUCING A GASEOUS MEDIUM THROUGH SAID OPENING INTO SAID CASING, WHILE MAINTAINING A RELATIVELY HIGHER PRESSURE ABOVE THE PLUNGER THAN BELOW, TO MOVE THE PISTON AND THE ELECTRODE TERMINALS AGAINST THE SPRING MEANS AND BRING SAID ELECTRODE TERMINAL CLOSER TO ITS COOPERATING TER-