US1941816A

US1941816A - Electrolytic method and cell for the decomposition of water

Info

Publication number: US1941816A
Application number: US446311A
Authority: US
Inventors: Stuart Alexander Thomas
Original assignee: Individual
Current assignee: Individual
Priority date: 1930-04-22
Filing date: 1930-04-22
Publication date: 1934-01-02
Anticipated expiration: 1951-01-02

Description

A. T. STUART 1,941,816

ELECTROLYTIC METHOD AND CELL FOR THE DECOMPOSITION OF WATER Jan. 2, 1934.

Filed'April 22, 1930 2 Sheets-Sheet 1 Jan. 2, 1934. A T. STUART 1,941,316

ELECTROLYTIC METHOD AND CELL FOR THE DECOMPOSITION OF WATER Filed April 22, 1930 2 Sheets-Sheet 2 Patented Jan. 2, 1934 UNITED STATES ELECTROLYTIC METHOD AND CELL FOR THE DECOMPOSITION OF WATER Alexander Thomas Stuart, Toronto, Ontario, Canada Application April 22, 1930. Serial No. 446,311

12 Claims.

It is known that when certain acids and bases are dissolved in water for electrolytic purposes, the resulting solution is a conductor of electricity, that it has the property of suffering chemical decomposition by the passage of a uni-directional electric current, that such solutions are called electrolytes, and that the process of decomposition'is referred to as electrolysis.

It is also knownz-that the solution when electrolyzed is split into its radicals which migrate towards the anodes and cathodes and which, if they do not interact with the water, are set free; that during the decomposition of certain electrolytes hydrogen is liberated at the negative pole and oxygen is liberated at the positive'pole of the current.

It is also knownz-that one type of cell suitable for the electrolytic decomposition of water comprises a plurality of anodes and cathodes alternately arranged and connected in parallel and pforous diaphragms for separating the anodic and cathodic products of the electrolysis and dividing the cell into a corresponding number of anode and cathode compartments; that this type of cell is commonly referred to as the tank or separate unit type of cell to contradistinguish it from the commonly known filter press or bipolar type; that when the electrolyte is decomposed the positive radicals accumulate at the cathodes and the negative radicalsaccumulate at the anodes as the electrolysis progresses; and that this accumulation is due to the ionic migration of the radicals under the influence of the electric current; that the ionic migration towards the cathodes withdraws the positive radicals from the anolyte and concentrates them in the catholyte, thereby impoverishing the electrolyte at the anodes and enriching it at the cathodes; that the migration towards the anodes withdraws the negative radicals from the catholyte and concentrates them in the anolyte, thereby impoverishing the electrolyte at the cathodes and enriching it at the anodes; that in both cases the ionic migration creates an unbalanced condition of the strength, or positive ion concentration of the electrolyte throughout the cell; that this unbalanced condition is partly but not wholly corrected by a backward diffusion of the electrolyte through the diaphragms; that without this backward diffusion a basic electrolyte would rapidly become, during the operation of the cell process, pure water at the anodes, and an acid electrolyte would rapidly become pure water at the cathodes; that it is only by the partial corrective resulting from this backward difiusion trodes when suitable ducts are provided for removing the electrolyte from the top of and out of. the cell and for returning it to the bottom of the cell after the offtake of the gases; that in the filter press type of cell this principle is utilized and that it is common practice with batteries of filter press cells to so remove the anolyte and catholyte from the top of each cell in the battery by a pair of ducts, one common to all the anolyte compartments and the other common to all the catholyte compartments of all the cells; that the electrolyte from all the cells is led to an apparatus exterior of the cells for separating the gases and for remixing the anolyte and catholyte; that the remixed electrolyte is then returned to the several cells by a common duct; that, in this circulatory system, shunt currents follow the common ducts and generate hydrogen in the oxygen duct and oxygen in the hydrogen duct, thereby delivering impure gases at the ofitakes. It is also kn0wn:that, heretofore, in the operation of tank types of cells, no provision has been made for a positive circulatory system within the cell itself whereby the anolyte and catholyte, free from gases, are returned from the top of the several electrode compartments to the bottom of the cell, and thoroughly mix before again being admittedto the various electrode compartments. According to this invention the method is adapted to a tank type of cell and is characterized by the electrolyte in each cell being unmixed with the electrolyte from the other cells and a positive cyclic circulation of the electrolyte within each cell createdfor maintaining all the electrolyte therein at uniform normal strength; this cyclic circulation being effected by collecting the electrolyte from the top of the electrode compartments of one polarity; maintaining its separation from the electrolyte of the compartments of the other polarity; and returning itto the bottom of the same cell through a channel separate from the electrode compartments to V recirculate therethrough. It is further characterized by regulating the speed of the circulation for ensuring the offtake of pure gas.

Various methods and means may be devised for creating and maintaining this cyclic circulation and intermixing the anolyte and catholyte during the cell operation without departing from the principle of the invention. One method which I have satisfactorily employed consists of providing separate channels of circulation for the anolyte and catholyte from the top of the anode and cathode compartments, respectively, to the bottom of the cell, and intimately mixing them to restore the normal strength of the electrolyte before re-entering the several cell compartments. Another method which I have satisfactorily employed consists of a positive cyclic circulation of the anolyte from the anode compartments into the cathode compartments and the catholyte from the cathode compartments into the anode compartments, when the gases have been separated from it, thereby utilizing the enriched electrolyte of one set of compartments for restoring the impoverishedelectrolyte in the other set of compartments to substantially normal strength throughout the several cell compartments, and maintaining the electrolyte at substantially uniform strength throughout the cell.

In both of the above methods the speed of the circulation may be regulated by valves or dampers suitably installed in the cyclic system, to control the rate of movement of the electrolyte and prevent the gas being carried to the bottom of the cell during the circulation.

For an understanding of the invention reference'is to be had to the following description and to the accompanying drawings, in which:

Fig. 1 represents a vertical section of an oxygenhydrogen cell showing a preferred method of elec trode assembly, this section being taken on the line BB, Fig. 2.

Fig. 2 is a vertical section on the line A-A, Fig. 1. I

'Figs. 3 and 4 are similar views to Figs. 1 and 2 of a modification of the cell, with the electrodes omitted.

Like characters of reference refer to like parts throughout the specification and drawings.

The cell comprises a tank A, a plurality of electrodes numbered 1 to 5, inclusive, alternately arranged as cathodes and anodes, and porous diaphragms D interposed between them for separating the oxygen and hydrogen liberated during the decomposition of the electrolyte. Any number of electrodes may be used and the general construction'and assembly of the electrodes and the interposed diaphragms hereinafter described and shown in the accompanying drawings are similar to the electrodes shown and described in my Letters Patent 'of the United States of America 1,597,553 dated August 24th, 1926, but any other type of electrodes and'diaphragms suitable for oxygemhydrogen cells may be employed.

Each electrode comprises a current feeder and a group of thin, narrow strips, arranged vertically in substantially parallel planes, individually separated, and directly connected collectively with the current feeder. The current feeders 16 of the odd numbered electrodes are connected with the negative pole of the current and consequently all the odd numbered electrodes are cathodes. The current feeders 17 of the even numbered electrodes are connected with the positive pole of the current and consequently all the even numbered electrodes are anodes. The feeders. 16 and 1'7 are shown to be located above the strips but they may be located below the strips at a position which will intercept their vertical axes. In the assembly of the cell the anodes are positioned between the cathodes. The strips forming the electrodes are set edgewise towards each other with the surfaces of the electrodes in the same direction as the circuit of the current across the intervening spaces or electrolytic gaps between the anodes and cathodes, and each of these gaps is of a width approximately equal to the thickness of the diaphragms.

Above and overhanging each cathode is a channelled hood 20, and secured to the perimeter of the entire group of hoods are four skirts or plates 22 for suspending the hoods from the cover 22a of the cell. The skirts 01' plates 22, together with the group of hoods 20, form a header 220 above the electrodes. Interjacent the hoods 20 are openings 2217, located one above each anode, for the circulation of the anolyte and anodic products into the header. Surrounding each anode is a diaphragm D, which is of a tubular formation, open at the top and'bottom, and extends from the hoods 20 to below the bottom of the electrodes for separating the anodic and cathodic products of the electrolysis. 'Each diaphragrn is secured to thecontiguous walls of two adjacent hoods 20 and the thickness of the diaphragm corresponds to the widthof the'electrolytic gaps between the anodes and cathodes. The diaphragms divide the cell into a plurality of al ternately arranged anode and cathode compartments, A and C, respectively, and in conjunction with the channelled hoods maintains the separae tion of the anolyte and catholyte and the anodic and cathodic products in their respective coinpartments. The width of each electrolytic gap, by corresponding approximately to thethickness of the diaphragm, permits of the edges of the anodes and cathodes in the cell assembly being in contact, or substantially so, with the diaphragms. The current from the positive, 01? is distributed uniformly to all the anodes and flows outwardly from the edges of each interposed anode stripand across the electrolytic gaps to the edges of the corresponding interposed cathode strips, from the edges of which it flows inwardly. In this arrangement each strip'of each electrode has two active ed es forming re acting areas with currents of equal intensity flowing inopposite directions from the edges of eachinterposed electrodewhereby equalquantities of gas are evolved at each edge of each interposed electrode. The maximum current intensity exists at the edges and the minimum current intensity exists interiacent the edges and this differential of intensity providesa path be; I

tween the edges of each strip for the unimpeded and rapid uplift'of the electrolyte and gases, and reduces to a negligible amountrthe gasesin suspension between the electrodes and adhering to the electrodes and diaphragms and tends to prevent polarization of the cell. The oxygen and anolyte rise to the top ofthe anode compartments and pass through the openings 221) into thejheader 22c formed by the skirts 22 and channell'edhoods, and these skirts and hoods keep the' anolyte and oxygen separated from the catholyte and hydrogen. The hoods 20 extend lengthwise of the celland beyon d the ends of the header 220. The catholyte fills the cathode compartments andthe upper partof the cell, exterior of the header to within a few inches of the cell'cover. The cathodic products rise through the cathode compartments to the hoods and are conducted by them to the ends of the cell, exterior of the header, from which they pass-tov .lects under the cell cover.

the hydrogen ofitake 23. .The catholyte circulates upwardly through the cathode compartments to the hoods, by which .itis deflected to-the ends and from the header passes down the tube 26 and structed with a rod or rods 31 extendingabove the cell cover and fitted with a lock nut or nuts 32 by which it is adjusted. By completely closing the valve-or damper the cyclic circulation of the anolyte can be arrested. By fully opening it a rapid circulation may be maintained, and the speed or rapidity of circulation can be regulated between these extremes by the adjustment of the valve or damper.

During the operation of the cell process the current circuiting from the feeders 1'7 to the anodes activates the edges of those electrode strips and results in the liberation of oxygen, which rises through the anode compartments and passes into the header, from which it escapes through the oxygen offtake 27. The current circuits outwardly from the edges of the anode strips to the edges of the cathode strips, from which it circuits inwardly and passes to the feeder 16. The hydrogen generated in the cathode compartments passes upwardly to the hoods and is directed by them to the ends of the cell, from which it escapes through the hydrogen ofitalre 23. In Figs. 3 and 4 a positive circulation of the electrolyte is maintained by connecting the bottom of the tube 26 with a manifold 50, and connecting the manifold with the bottom of each cathode compartment by a pipe 51, so that the anolyte passing down the tube 26 and through the manifold 50 will be compelled to pass into the cathode compartments C. The tops of the cathode compartments C are connected by pipes 52 with a tube 53 provided with a hydrogen ofitake 54. The bottom of the tube 53 is connected to a manifold 55, which in turn is connected by pipes 56 with the anode compartments A and the catholyte is thus compelled to pass into the anode compartments. Controlling the circulation through the pipes 52 is a valve or damper 5'7 similar to the valve or damper 30 for the purpose of regulating the speed of the circulation. By closing the dampers and thereby preventing circulation, the voltage of the cell immediately rises, with a consequent lowering of thecell efficiency. By opening the damper the circulation is renewed, the voltage falls to normal, and the cell efficiency is restored.

Having thus fully described my invention, what I claim as new and desire to secure by Letters Patent is:

1. An electrolytic method for the decomposition of water which, in addition to the electrolysis and ofitake of the gases, comprises a positive cyclic circulation of the electrolyte within the cell created by returning the anolyte and catholyte, free of oxygen and hydrogen, from the top to the bottom of the cell, intermixing them for restoring the electrolyte to and maintaining it at substantially uniform strength throughout the alternately arranged as anodesand cathodes,

cell, and regulating the speed of the circulation for ensuring the offtake of pure gases. v

2. An electrolytic cell for the decomposition of water which comprises a plurality of electrodes 8 and porous'diaphragms interposed between them for'dividing the cell into a corresponding num ber of anode and cathode compartmentain combination with means within the cellseparate from the anode and cathode compartments for returning the anolyte and the catholyte from the tops of the anode and cathode compartments,

respectively, to the bottom ofthe cell and inter- -mixing them below the electrodes for maintaining the electrolyte at substantially the same strength throughout the cell, and, means for controlling the speed. of the circulation through the cell. I

3. An electrolytic cell as claimed in claim 2 having means for the return of- ,the anolyte from all the anode compartments, and, other means for the return of the catholyte from all of the cathode compartments to the bottom of the cell.

4. An electrolytic cell as claimed in claim 2 having means for the return of the anolyte from all the anode compartments, and other means for the return of the catholyte from all of the cathode compartments to the bottom of the cell, and means for regulating the speed of the circulation.

5. An electrolytic cell for the decomposition of water including a plurality of electrodes alternately arranged as anodes and cathodes, and porous diaphragms interposed between them for dividing the cell into a corresponding number of anode and cathode compartments, in combination with means for creating a cyclic circulation of the electrolyte by returning the anolyte and catholyte from the top of the anode and cathode compartments to the bottom of the cell and intermixing them below the electrodes for maintaining the electrolyte at substantially the same strength throughout the cell, which comprises a header located above the electrodes in circulation with all the anode compartments, and a duct extending from the header for the return of the anolyte to the bottom of the cell, and means for regulating the speed of the circulation for ensuring the ofitake of pure gas.

6. An electrolytic cell as claimed in claim 5 having valves for controlling the flow from the header through the duct and regulating the speed of the circulation of the anolyte.

7. An electrolytic method for the decomposition of water in a tank type cell characterized by a positive cyclic circulation of the electrolyte within each cell for maintaining all the electrolyte therein at uniform normal strength effected by collecting the electrolyte from the top of the electrode compartments of one polarity; maintaining its separation from the electrolyte of the compartments of the other polarity and returning it to the bottom of the same cell separately from the electrode compartments, mixing it with the electrolyte from the electrode compartments of the other polarity and then recirculating the mixed electrolyte through the electrode compartments.

8. An electrolytic method for the decomposition of water in a tank type cell characterized by a positive cyclic circulation of the electrolyte within each cell for maintaining all the electrolyte therein at uniform normal strength effected. by collecting the electrolyte from the top of the electrode compartmentsof one polarity; maintaining its'separation from the electrolyte of the compartments of the other polarity and re- 'turning it to the bottom of thesame cell to reof the circulationfor ensuring the'offtake of pure circulate therethrough, and regulating the speed -9. An electrolytic method for the decomposiing the enriched electrolyte of one set of 00mpartments for restoring the impoverished electrol'yte of the other set of compartments to substantially normal strengh throughout the cell.

10. The electrolytic-method for the decompm sition of water as claimedin claim 9 inwhich the electrolyte from both sets of compartments is returned separately to the bottom of the cell through diflerent channels.

11. An electrolytic method for the decomposition of water as claimed in claim 9 in which the speed of the circulation is regulated to control the rate of movement for the return of the electrolyte from the top to the bottom of the cell.

12. An electrolytic method for the decomposition of water as claimed in claim -'I in which the speed of the circulation is regulated for ensuring the oiftake of pure'gases by preventing them being carried in suspension in the anolyteand catholyte returning from the anode and cathode compartments to the bottom of the cell.

ALEXANDER '1'. STUART.