US2071087A - Electrolytic cell - Google Patents

Description

Feb. 16, 1937. H. PHlLlPP ELECTROLYTIC CELL Filed Jan. 29, 1951 ATT Parental Feb. 1s, 1937.--

UNITED STATES PATENT OFFICE Solvay Process poration of New York Company, Syracuse, N. Y., a cor- Application January 29, 1931', serial No. 512,058

15 Claims.

This invention relates tol an apparatus and process for the electrolytic dissociation -of materials. The invention particularly relates to the electrolysis of fused alkali metal halides, such as sodium chloride, to obtain alkali metal and gaseous halide therefrom.

Electrolytic cells and the' methods employed in operating such cells have presented many problems ,diilicult of solution. especially when electrolyzing a fused salt, such as'sodiumchloride or other alkali metal halide. These problems have arisen primarily from two sources. One great source of trouble has been due to failures of elements or materials used in the cell by reason of the high temperatures employed during operation and because of the corrosive action of the products of electrolysis upon the cell walls, metallic diaphragms, conduits for removing the products from-the cell and the electrical conductors leading to the electrodes. The second important source of difficulty arises from the decreased emclency of the operation due to the recombination of products liberated at the anode and cathode and lto the sluggish movement of the electrolyte and products of electrolysis away from the electrodes and out of the cell. 'I'he relatively slow movement of the liberated products results in excessive corrosion of the diaphragm and other elements of the cell and allows the products to diffuse through the melt. Diusion of the products through the melt alters the bath resistance and temperature, whereas recombination of the liberated products decreases the yield. Each of these factors tends to lower the efficiency of the cell and render the operation diihcult to control. A

I'he principal objects of the present invention are to diminish or eliminate these diiculties and to provide apparatus and process for the elec- 40 trolysis of fused salts characterized by durability,

high emciency and stability of operation.

These and other. objects of the invention are attained by providing new apparatus and process by means of which the electrolyte is circulated through the cell and between'the electrodes in such a manner that fresh electrolyte is continually suppliedto the zone of electrolysis between the anode and cathode and the products liberated in said zqne are carriedaway` from the e so v'faces of the electrodes and away from the intervening diaphragm so' as to prevent excessive corrosion of these elements and-to diminish the vent the product liberated at one electrode from coming into contact with that liberated at the other electrode or with the electrical conductors or members by which the other product is liberated and collected and removed from the cell. 5

In accordance with the present invention, the electrolyte, preferably in a fused condition, is introduced into a cell and into a chamber isolated from the products of electrolysis. The fused electrolyte is circulated between suitably ener- 10 gized electrodes and about an intervening perforated diaphragm, ilowing upwardly and c arrying the liberated products away from the zone of electrolysis and out of contact with the diaphragm and electrodes. The products liberated 15 at the anode and cathode are separated in the melt by the diaphragm and collected in suitable chambers isolated from each other by the electrolyte. The electrolyte freed from the products of electrolysis is discharged from the cell through 20 a spillway to maintain a constant level of the electrolyte in the cell. and to induce circulation thereof through the cell. The process may b'e carried out in any suitable type of cell but it is preferred to employ an electrolytic cell such as that illustrated inthe accompanying ilgures of the drawing and hereinafter described.

In the drawing, Fig. 1 is a vertical sectional view of a preferred form of electrolytic cell for carrying out the procesa-and 30 Fig. 2 is a sectional view of the cell illustrated in Fig. l taken on the line 2 2.

In the form ofthe invention illustrated in the drawing, a cylindrical electrolytic cell is provided having cell walls 2 formed of rebrick or other 35 suitable material and provided with a centrally located anode 4, supported above the bottom of the cell upon firebrick orothersuitable supports 6 spaced or provided with openings l. The anode is provided with vertical passages Ill communi- 40 eating with the space between the bottom of the anode and the bottom of the cell. 'I'he conductor I2 which is connected to the centrally located anode 4 passes upwardly fromthe anode and out of th fused electrolyte in the cell. Current is' 45 supplied to the conductor I2 through 4a suitable electrical conductor connected to a source of current.

'I'he cathode I6 abuts the wall of the cell and is annular in form surrounding the anode Land separated therefrom by the space I 8. The pors ,tion Il of the cell wall adjacent to the cathode is formed of suitable refractory material to re- A. sist the action ofthe electrolyte and sodium or other vmaterial liberated at the cathode. The 5s conductor 20 for supplying current to the cathode passes laterally through the cell wall and is not exposed to the action of the salt melt at any point.

The upper portion of the cell is divided into three concentric chambers. The central chamber 22 surrounds the conductor I2 and is adapted to receive the electrolyte. This chamber is formed by the member 24 which rests upon the upper' surface of the anode 4. The member 24 is constructed of 'material capable of resisting the action of the molten electrolyte and the product liberated at the anode, such as materialcommonly known as shamotte. A second chamber 26 surrounding and concentric with the central chamber 22 is formed by the member 24 and the member 28 which is formed of material similar to that of the member 24. The chamber 26 is located above the outer portion of the anode and in position to receive and collect the products of electrolysis liberated at the face of the anode.

An outer concentric chamber is formed by the annular member 30, spaced from the member 28 and positioned above the cathode I6 for collecting the products of electrolysis liberated at the cathode. The member 30 is formed of iron or other material capable of resisting the action of the cathode product. This member is secured to and carried by the wall of the cell so as to be maintained in proper position with reference to the cathode. The inner edge of the annular member 30 is spaced slightly from the lower edge of the member 28 to provide an opening 33 through which the electrolyte may flow from the space I8 between the electrodes to the outlet or spillway 34 through which -it is discharged from the cell.y A porous diaphragm 32 is secured to the inner edge of the annular member Y 30 and extends downwardly in the space I8 between the active or outer face of the anode 4 and the inner face of the cathode I6. The product liberated at the cathode is confined by the diaphragm 32 and collected by the member 38. An outlet 36 for the cathode product is connected to the annular member 30 for discharging the product from the cell as it is collected.

The member 28 which forms the outer wall of the chamber 26 is carried by and is a. depending part of a cover 38 which closes the upper end of the chamber 26. The lower end of the member 28 is beveled to direct the product liberated at the anode and passing upward adjacent the diaphragm 32 into the chamber 26. An outlet 44 for the product liberated at the anode is provided in the cover 38. Sodium or other product liberated at the cathode and discharged through the outlet 36 is collected in the vessel 46. The electrolyte discharged from the cell through the spillway 34 may be collected and recirculated through the cell in a cyclic manner.

The operation of the cell described in the electrolysis of sodium chloride is as follows: The sodium chloride is charged into the central chamber 22 of the cell preferably in a molten condition until the level of the salt reaches thehelght of the spillway 34 through which the excessvsalt is discharged. The electrodes'are energized and dissociation of the salt effected with the liberation of chlorine at the anode and sodium at the cathode. Additional .salt is introduced into the central chamber 22 to maintain circulation of the salt from the chamber 22 downwardly through the vertical passages III in the anode into the space beneath the anode and through the openings 8. The salt then flows upwardly through the space I8 over the active faces of the anode and cathode and over the intervening diaphragm in co-current iiow with the liberated sodium and chlorine, carrying these products away from the surfaces of these members and bringing fresh salt containing no diffused products into the space between the electrodes. The sodium liberated at the cathode does not pass through the diaphragm 32, but is collected by the member 30 and, being lighter than the melt, floats on the top thereof and is discharged through the outlet 36 to the vessel 46. The chlorine liberated at the anode also passes upwardly with the salt and is collected in the chamber 26 from which it is removed through the outlet 44 as strong, dry, chlorine gas. The salt freed from both the chlorine and sodium continues to pass upwardly passing through space 33 to the spillway 34 from which it is discharged to be recirculated through the cell.

From the foregoing description of the invention, it is apparent that the process may be carried out in a continuous and uniform manner and that the preferred type of cell described is durable and free from the defects inherent in electrolytic apparatus heretofore employed. However, the invention may be carried out in other electrolytic cells and may be varied in many respects. Therefore, it is not intended that the invention should be limited to the particular construction and process steps described except as defined by the claims.

I claim:

1. A cell for the electrolysis of a fused electrolyte having in combination a centrally located anode, a cathode positioned externally of the anode and spaced therefrom, a chamber for the electrolyte positioned centrally of the cell and communicating with the space between the anode and the cathode, and an outlet for the electrolyte also communicating with the space between the anode and the cathode whereby circulation of a fused electrolyte through said space and in the same direction in contact with both the anode and the cathode is effected.

2. A cell for the electrolysis of a fused electrolyte having spaced concentric electrodes and means for circulating a fused electrolyte through the cell, one of said electrodes being provided with an aperture through which the electrolyte passes into the space between the electrodes.

3. A cell for the electrolysis of a fused electrolyte having a central anode and a spaced concentric cathode, and means for circulating a fused electrolyte through the cell, said anode being provided with an aperture through which the electrolyte passes into the space between the anode and the cathode.

4. A cell for the electrolysis of a fused electrolyte having in combination cell walls, a central anode, a submerged cathode surrounding said anode and adjacent the wall of the cell and means located below the surface of the bath above the cathode and supported by the wall of the cell for collectingthe product liberated at the cathode.

5. An electrolytic cell for the electrolysis of fused sodium chloride having in combination a central anode, a submerged cathode adjacent the Y walls of the cell, a sodium collector located above and separate from the cathode and supported by the wallsl of the cell and means separated by a. space from thesodium collector for collecting the chlorine liberated at the anode, said space serving as an outlet for fused sodium chloride.

6. An electrolytic cell for the electrolysis of fused sodium chloride having in combination a central ano'de, a cathode adjacent the walls of the cell and surrounding the anode, said anode and cathode having their outer and inner surfaces respectively in contact with fused sodium chloride, a sodium collector positioned above and separate from the cathode, said sodium collector being supported by the walls of the cell and a porous diaphragm secured to the sodium collector and positioned between the anode and the cathode.

7. An electrolytic cell comprising electrodes. a central chamber for the reception of electrolyte, an adjacent chamber concentric with the central chamber for collecting the product liberated at one of the electrodes, and an outer chamber forcollecting the product liberated at the other electrode and a conductor passing through the central chamber and leading to one of the electrodes which is submerged in the electrolyte adjacent the central chamber, said conductor being isolated from the products of electrolysis by said central chamber.

8. An electrolytic cell comprising an anode and a cathode, a central chamber for receiving the electrolyte, a concentric chamber positioned externally of the central chamber and located above the anode for receiving the product liberated at the anode, lan outer concentric chamber positioned above and separate from the cathode for collecting the product liberated at the cathode,

and a conductor connected to the anode and isolated from the products of electrolysis by the central chamber.

9. A cell for the electrolysis of fused salt comprising chambers for collection of the products of electrolysis, a separate chamber for reception of the electrolyte, oppositely poled electrodes in contact with the fused salt and a conductor connected to one of said electrodes extending within said last mentioned chamber upwardly out of the salt and isolated from the products of electrolysis by fused salt in said chamber.

10. A cell for the electrolysis of fused alkali metal halides comprising a centrally located submerged anode, an annular cathode surrounding said anode, said anode and cathode having their outer and inner surfaces respectively in contact with fused alkali metal halide, a diaphragm between said anode and said cathode, a conductor connected to said anode and extending upwardly out of the bath ofv fused material and a chamber for the electrolyte surrounding said conductor.

11. A cell for the electrolysis of fused alkali metal halides comprising chambers for collection of the products of electrolysis, a separate chamber for the reception of the electrolyte, a central anode, a conductor leading to said anode and extending within said last mentioned chamber upwardly out of the; bath, and isolated from the products of electrolysis by fused salt in said chamber, a cathode surrounding said anode, said anode and cathode having opposed active faces where the products of electrolysis arelliberated in contact with and completely submerged in the fused material.

12. A cell for the electrolysis of a fused electrolyte comprising a centrally located anode, an annular cathode surrounding the anode and spaced' therefrom, an electrical conductor leading to the anode, a. central chamber surrounding said conductor for receiving an electrolyte, said chamber communicating with the space between the anode and cathode, chambers external of the central chamber for receiving the products liberated at the anode and cathode, and a spillway also communicating with the space between the anode and cathode for discharging fused electrolyte from` the cell.

13. A cell for the electrolysis of fused sodium i chloride comprising a centrally located anode, an

- the same through which the fused sodium chloride passes upwardly over the surfaces of the anode and cathode to said outlet.

14. A cell for the electrolysis of a fused salt comprising a centrally located anode, an annular cathode surrounding and spaced from the anode,

a central chamber into which fused salt is introduced, chambers concentric with the central chamber for separately receiving the products of. electrolysis which are liberated at both the anode and cathode. an outlet located above the anode and cathode through which fused salt is discharged from the cell and a passageway leading from the central chamber to the' space between the anode and cathode below the same through which the fused salt passes upwardly over the lsurfaces of the anode and cathode to said outlet.

15. A cell for the electrolysis of a fused electrolyte, an anode and a cathode, a chamber for electrolyte, an outlet through which electrolyte may be discharged from the cell, a conduit open at the ends only through said cell, said conduit connecting said chamber and outlet, whereby a positive flow of electrolyte may be maintained through said conduit, said lanode and cathode defining in part the wall of said conduit whereby electrolyte flowing through the conduit flows' along the surfaces of said anodeand cathode.

HERBERT PrmJPP.

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