US2984607A - Method of producing oxygen and hydrogen by electrolysis - Google Patents

Description

May 16, 1961 J. c. WHITE ETAL 2,984,507

METHOD OF PRODUCING OXYGEN AND HYDROGEN BY ELECTROLYSIS Original Filed June 5, 1957 IIELE I5 Weil La w an w 28 I Q i L -CYCLE A+CYCLE B -|OO 905 130 -70? 60E -50 o I 2 INVENTORj -200 JOSEPH c. WH'ITE IO GUY w. WORK 2.0 0 l K 0.5 L0 L5 2.0 2.5 3.0 3.5 4.0 g HOURS BY MWRNEYS United States Patent of America as represented by the Secretary of the Navy 6 1 Original application June 5, 1957, Ser. No. 663,856,

, now Patent No. 2,951,802, dated Sept. 6, 1960. Di-

.vided and this application Feb. 24, 1958, Ser. No. 717,279.

r 4 Claims. (Cl. 204-129 (Granted under Title 35, US. Code (1952), see. 266) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes Without the payment of any royalties thereon or therefor.

The present invention is a division of copending application Serial No. 663,856, filed June 5, 1957, now Patent No. 2,951,802, issued on September 6, 1960, and relates to electrolytic gas generators for electrolytic generation of oxygen without the accompanying generation ofhydrogen and more particularly to a method of producing oxygen and hydrogen by electrolysis.

Electrolysis of aqueous solutions of caustic alkalis or of oxygen-containing acids has been used as a method of obtaining very pure oxygen and hydrogen. The best known types of commercial cells for this purpose comprise electrodes of iron group metal, usually of nickelplated iron, separated by a diaphragm used to separate the oxygen from the accompanying hydrogen and as an electrolyte, a solution of sodium hydroxide or potassium hydroxide in a concentration between 10% and Another type makes use of a continuouslydepolarized cathode, suitably an air-depolarized porous carbon cathode in combination with aninsoluhle or passive anode in an aqueous electrolyte of potassium hydroxide or sodium hydroxide.

The prior art devices present several problems in adapting such devices for use on submarines and the devices presently used on submarines require periodic resurfacing for generation of oxygen which is stored in pressure tanks. The pressure type oxygen generators now used are very heavy, they require considerable space, and current and the pressures involved dictate to a great extent the configuration of the cell and limit the possibilities in cell design to a very narrow range. t It is an object of the present invention to provide an oxygen/hydrogen generator similar in structure to, an alkaline type of storage battery.

Another object is to provide'a method of generating oxygen orhydrogen by electrolysis.

Still another object 'is toprovide a system for generating oxygen in a device without drawing a continuous supply of oxygen gas from its immediate environs.

, Another object is to eliminate the need for a diaphragm a which is required in all electrolytic oxygen generators.

Another object is to provide a new type of electrolytic oxygen generator free from the usual accompanying generation of hydrogen. p i

Other and more specific objects of this invention will become apparent upon a more careful consideration of the following detailed description when taken together with the accompanying drawings, in which:

Fig. 1 illustrates a typical oxygen generator cell cut away to illustrate the plates therein;

Fig. 2 illustrates a system used for continuous generation of oxygen; and I Fig. 3 illustrates potential and gas concentration changes during two 90-ampere cycles ofa single gencrater cell. H t 1 l normal charge.

. Patented May 16,

The present invention comprises a storage battery type cell which has been "modified to include negative plates filled with cadmium activematerial and positive plates 'of sheet nickel to generate either oxygen or hydrogen by electrolysis depending on the direction of current flow through the cell. Two or more cells properly positioned and connected in a system will enable generation of oxygen from one cell and generation of hydrogen from another cell. This provides a means by which the cells will alternately produce oxygen and hydrogen to provide a system by which oxygen can be continuously produced and admitted to a device requiring a supply of oxygen. Such a system can be used to provide oxygen for a submarine such as a nuclear powered submarine where electrical energy is not at avhigh premium and where an unlimited supply of Water is available for replenishing the water dissipated duringelectrolysis.

The device and operation of this new type of oxygen generator is so similar to storage batteries that battery terminology will be used for descriptive purposes. The terms battery, charge and discharge are not to be taken to mean that electricity is stored in the battery but to be broadly construed as operating similar to a battery. As such, a charge will reduce the negative (cadmium) plate while producing oxygen at the sheet nickel electrode and a discharge'will oxidize the negative plate while producing hydrogen at the sheet nickel electrode.

Referring now to Fig. 1 there is shown by illustration a cellll made according'to the present invention which comprises positive plates 12 made of perforated sheet nickel and negative plates 13 made of any material ca.- pable of being charged without the evolution of hydrogen until almost completely charged for example, plates made of a plurality of pockets filled with cadmium active material or sintered nickel-cadmium plates made by impregnating sintered nickel plates with cadmium active material. The plates are alternately positioned within a suitable casing 14 made of nickel plated steel or any other suitble material and connected in parallel to outside terminals. .,,The cell as illustrated by Fig. 1 has fif.- teen positive and fourteen negative plates. The. nega-' tive plates are typically formedby a metal frame in which a plurality of flat tubes or nickel-plated steel pockets filled with cadmium active material having a length of about 7 inches, a width of about 0.5 inch, and a thickness of about 0.1'30inch. The PQ itive plates are, formedby perforated jsheetnickel having a height of about 7.7 inches, aifwidth of abfo'ut 4.7 inches, a thickness; of about 0.031 inch, with about 7,740 perforations perplate, each perforation having a diameterof about 0.04 3 inch. The plates are properlyjpositionedin the, cell and spaced from each other by about 0.062.,inch and thenfthe cell is sealed; A solution made up'to'abOut 'ZS ,percent ]K O I -I in distilled water is added to' the cell as an electrolyte through anbpeni'ng 15 in theftop' which alsoserves to permit escape of the 'gasesgcnerated and provided ameansby which water maybe added through appropriate tubes ,to replenish thefwateru'sed, 111p byele'ctrolysisa v Q r The unique characteristic of, a s'tandard negative cad mium platefin a nickel;-cadmium alkalinesto'rage battery is its abilityto'accept a. large'part of its charge before hy drogen is evolved. The amount ,of charge up to? the point of hydrogen evolution is referred tofasihe-platefs fhydroge'n free capa'cityf and is believed, to befattributed to the sufiiciently high hydrogen over voltage and ,theflat potential characteristic of the plate duringfr'nost of the A similar oxygen-free capacity, may be observed during discharge f 1 j In operation ofjthef'illustratedcell, Fig. represents the potentials and percent of hydrogen colli ifinttatior'i, for a single cell during two complete cycles of peraaqaai -amperes.- During" acharge, oxygen isproduced at a eell' potential of 1.6Voltsand during discharge the potential' changes to a negative "0.4' volt throughout "most of the discharge. Just betere the end of the discharge half cy le t po t a d ps q c ly t a uta n g ti'v' 6 jvo'lt s, "For continuous operation, thegpote'ntials repeat themselves throughout each hal f cycle and the1average 'fpotential throughout any complete cycle is about 24 ts",

In operation of the cell for evolution of gases, the cell must be 'connected'to a source of direct current which passes IhlfOllghihQ electrodes and solution which will thus evolve oxygen by electrolysis throughout a charge and hydrogen throughout a discharge.

, In "starting thefprocess, the positive lead of a power source is connected to the negative terminal and the negative lead is connected to thepositive terminal. The current flows through the solution to discharge the "cell oxidizing the negative (cadmium) electrode and 'producinghydrogen at the sheet nickel electrode. The reaction during discharge for production of hydrogen may be considered to be as follows:

It the charge is continued after the anon has been all reduced, hydrogen will also'be evolved in addition to Reaction VI.

The only maintenance as far as .the electrolytic part of the generator is concerned would, therefore, be the periodic addition of water to makeup for that used in e1erro1ysis.' 4 p To provide anelssentially continuoussupplyof oxygen, as [for a submarine or any other purpose, two 'cells or banks of cells'as represented by Fig. 12, could be operated simultaneously-cell 21 charging to evolve oxygenwhile cell 22' is discharging to evolve hydrogen and to condition that cell for charging? to produce oxygen. The oxygen produced by charging, cell '21 is discharged through appropriate tubing and through a three position valve .23 directly in to the desired space whereas the hydrogen produced by cell .22 is pumped overboard through appropriate tubing and the three position valve 24 by a compressor 25. I Valves23 and 2 4 control the outlet of the gases produced by the respective cells and after the respective cells have been simultaneously charged" or discharged through jtheir gas-free capacities, the current through the cellsis reversed by a reversing switch 28 and the cells produce the opposite gas. After the current has been reversed, cell 21 willproduce hydrogen and cell 22 produce oxygen. -During a, half-cycle reversal of the c r n n is h r n q eft e io s. :ot valves zdfand 24 must be" changed to discharge the gases through appropriate lines to the inside and outside of the desired space.

At the end of a half-cyclei;(the term cycle being used to denote a completion of either-a f discharge and charge; or, a fcharge and a dischargefjor each ,c e1l,)..before the directionof current flow through each cellis'reversed to produce the opposite gases in the'respective cells, the head-space of each cell and the line between the'cells and the valves must becleared ofthe gases "that thev cells were generating. For this purpose some means for 'ex ample, a vacuum pump 27 is provided to "clear the oxygen lines and the hydrogen pumping compressor 25 is, used to clear the hydrogen lines'from the respective cells. Valves 23 and 24 are positioned to connect respectively lines 29 and 30 to the outlets of cells'21 and 22. Lines 29 and 30 connect respectively to valves 41 and 42 which controls the passage of the gases to either the vacuum pump 27 or the hydrogen outlet line 34 which connects with compressor 25. When cell 21 is producing oxygen valve 41 would open to the vacuumpump 27 and valve '42 to the hydrogen line. If cell 22 is producing oxygen the reverse is done. Valves 23 and 24 are moved to their proper positions to connect each of the outlet pipes to the vacuum line and the pump is operated until the residual gases are removed. (Other methods than the vacuum method could be used.) After the residual gases havebeen removed, the vacuum pump 27 is stopped and the control valves 23 and 24 must be positioned at the properposition forconnecting the cells to the outlet line other than that to which it was connected during the last half cycle. This readies the system for generation of oxygenand-hydrogen by the opposite cells and the current is reversed to carry out the evolution of oxygen from the cell that formerly produced hydrogen, and hydrogen. from the cell which formerly produced oxygen. These cycles are continued for continuous oxygen generation by first one cell and then the other by first clearing the cells of residual gases at the end of each cycle, changingthe position of the valves and then reversing the current through the cells.

Operation of the control valves, reversing switch 28', and control of the vacuum and hydrogenipumps, may be carried out by hand; however, automatically shifting each cell ofthe generatorfrom oxygen production to hydrogen production may be vcarried out by suitable mechanical equipment not shown for simplification of the drawings Suitable oxygen and hydrogen detectors 31 and 32 are placed respectively in the hydrogen and oxygen outlet lines to detect the presence of the respective gases desired to be detected, and prevented from, passage into the wrong space, such as at theend of any half cycle. These detectors can be used for automatic, control of the various partsfor automatic operation of the system.

Suitable water lines 43 from a suitable source are connected between the outlet control valves 23qand24 and the cells 21 and 22, for the purpose of replenishing the water as it is used up. The water may be added at the end of any half cycle through'control valves 44.

In operation of, the system for instance in a submarine for continuous; generation of oxygen, one cell or bank of cells will be producing oxygen While charging whereas the other cell or bank of cells produces hydrogen while discharging. For instance, for the system illustrated in Fig. 2, cell 21 has been discharged previously and is nowin condition to evolve oxygen during charging, whereas cell 22 has been charged previously and is now ready to evolve hydrogen during discharge. Direct currentufrom a suitable source is connected with the cells such that the current flows .in opposite directions through each cell and cell 21 produces oxygen While cell 22 produces hydrogen. Valve 23 connects cell 21 to the oxygen outlet 33, while valve 24 is positioned 'to connect cell 22. with the hydrogen outlet 34. During operation with the valves in these positions, oxygen is' produced by cell 21 and carried directly into'the sub marine whereas hydrogen is produced by cell 22 and pumped overboard by compressor 25. As operation continues, cell 21 approaches polarization at which point it begins to give off a little hydrogen, this will be detected by hydrogen detector 32 in the oxygen outlet line to indicate that a shift in the cycle is required. The current is turned off simultaneously in both cells by reversing switch 28 and then valves 23 and 24 are positioned to connect the outlets respectively to lines 29 and 30. Valve 41 is positioned to connect with the vacuum pump 27 and valve 4-2 is positioned to connect with hydrogen outlet line 34, then the vacuum pump 27 and the compressor 25 are started to clear the residual gases from the respective outlet lines and the head spaces of each cell. After the residual gases have been cleared, the vacuum pump 25. and the compressor 27 are turned off and the position of valves 23 and 24 are now positioned such that valve 23 connects the outlet of cell 21 with the hydrogen outlet line and valve 24 connects the outlet of cell 22 to the oxygen outlet line. The current to the cells is now turned on but in the opposite direction through the cells and oxygen is now generated by cell 22 and hydrogen is generated by cell 21. When cell 22 approaches polarization at which time a little hydrogen is given off the hydrogen sensing instrument 32 will again indicate the presence of hydrogen and the current through the cells is turned 01? and the process reversed again.

The oxygen sensing instrument 31 in the hydrogen line will sense the presence of the generation of oxygen by the cell that is evolving hydrogen which indicates that the negative plates have completely oxidized and the current should be turned 01f in both cells and the process reversed as described above.

Obviously a bank of cells would be required to supply sufficient oxygen to the required space of a submarine and therefore the above system of two different cells is for illustrative purposes only. The size of the plates and the number of cells is completely flexible and can be made according to the need. For example, for a complement of 100 men, each requiring a cubic foot of oxygen per hour, two banks of the type of cells described above, each bank of 125 cells with the cells of each bank operating in series and alternately generating oxygen and hydrogen, would provide the desired continuous supply of oxygen from a 100ampere, 275-volt power source. Such a unit would occupy about 34.5 cubic feet and Weigh about 4100 pounds.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

We claim:

1. A method of alternately producing hydrogen and oxygen by electrolysis which comprises discharging a cadmium active material-sheet nickel plate battery by passing a direct current for a limited time through an aqueous electrolyte in the battery to oxidize the cadmium active material plates which produces hydrogen at the sheet nickel plates, removing from said battery the hydrogen produced during said discharging operation, then reversing the current for a limited time through the battery to reduce the cadmium active material plates which produces only oxygen at the sheet nickel plates and removing from said battery the oxygen produced by said oxygen producing step.

2. A method of alternately producing hydrogen and oxygen by electrolysis which comprises discharging" a cadmium active material-sheet nickel plate battery by passing a direct current for a limited time through an aqueous solution of KOH in the battery to oxidize the cadmium plates and release hydrogen at the sheet nickel plates, removing from said battery the hydrogen released during said discharging operation, then reversing the current for a limited time through the aqueous solution of the battery to charge the battery 'by reducing the cadmium active material plates and releasing only oxygen at the sheet nickel plates and removing from said battery the oxygen released during said charging operation.

3. A method of alternately producing hydrogen and oxygen by electrolysis which comprises discharging a cadmium active material-sheet nickel plate battery by passing a direct current for a limited time through an aqueous solution of up to about 25% KOH in the battery to oxidize the cadmium plates and release hydrogen at the sheet nickel plates, removing from said battery the hydrogen released during said discharging operation, then reversing the current for a limited time through the aqueous solution of the battery to charge the battery by reducing the cadmium active material plates and releasing only oxygen at the sheet nickel plates and removing from said battery the oxygen released during said charging operation.

4. A method of continuously producing hydrogen and oxygen by electrolysis in a system including at least one charged cadmium active material-sheet nickel plate battery and at least one discharged cadmium active material-sheet nickel plate battery which comprises discharging said charged battery by passing a direct current through an aqueous solution of KOH in the battery for a limited time to oxidize the cadmium plates and release hydrogen at the nickel plate, simultaneously charging said discharged battery by passing a direct current through an aqueous solution of KOH therein in an opposite direction to the current passed through said charged battery for a limited time to release oxygen at the sheet nickel plates of said discharged battery while charging said discharged battery, simultaneously pumping said oxygen released by said discharged battery into one chamber while pumping said hydrogen released by said charged battery into another chamber, after simultaneously charging said discharged battery to release oxygen and discharging said charged battery to release hydrogen, simultaneously reversing the current through each of said batteries to discharge said charged battery while releasing hydrogen and charging said discharged battery to release oxygen and alternately charging and discharging each of said batteries simultaneously to continuously produce oxygen and hydrogen while pumping said oxygen into one chamber and pumping said hydrogen into another chamber.

References Cited in the file of this patent UNITED STATES PATENTS 1,032,623 Reed July 16, 1912 1,218,584 Sanders Mar. 6, 1917 2,390,591 Ianes Dec. 11, 1945 2,433,871 Sutherland et al. Jan. 6, 1948 2,571,927 Neumann et al. Oct. 16, 1951 2,646,455 Iernnin July 21, 1953 2,708,211 Koren et al. May 10, 1955 2,798,110 Peters July 2, 1957

Claims (1)

1. A METHOD OF ALTERNATELY PRODUCING HYDROGEN AND OXYGEN BY ELECTROLYSIS WHICH COMPRISE "DISCHARGING" A CADMIUM ACTIVE MATERIAL-SHEET NICKEL PLATE BATTERY BY PASSING A DIRECT CURRENT FOR A LIMITED TIME THROUGH AN AQUEOUS ELECTROLYTE IN THE BATTERY TO OXIDIZE THE CADMIUM ACTIVE MATERIAL PLATES WHICH PRODUCES HYDROGEN AT THE SHEET NICKEL PLATES, REMOVING FROM SAID BATTERY THE HYDROGEN PRODUCED DURING SAID "DISCHARGING" OPERATION THEN REVERSING THE CURRENT FOR A LIMITED TIME THROUGH THE BATTERY TO REDUCE THE CADMIUM ACTIVE MATERIAL PLATES WHICH PRODUCES ONLY OXYGEN AT THE SHEET NICKEL PLATES AND REMOVING FROM SAID BATTERY THE OXYGEN PRODUCED BY SAID OXYGEN PRODUCING STEP.

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