US1411530A - Electrolytic caustic-soda cell - Google Patents

Description

N. STATHAM.

ELECTROLYTIC CAUSTIC SODA CELL. APPLICATION FILED MAY 31.1917. RENEWED JUNE 30,1921.

UNITED sures PATENT- OFFICE}.-

NOEL STATHAM, 01'' HASTINGS 0N HUDSON, NEW YORK, ASSIGNOR TO INDUSTRIAL I CHEMICAL COMPANY, OF NEW YORK, N. Y., A CQRPO'RATION OF NEW YORK.

ELECTROLYTIC CAUSTIG-SODA CELL.

Application filed May 31, 1917, Serial No. 171,835.

made a certain new and useful invention Relating to Electrolytic Caustic Soda Cells, of which the following is a specification, taken in connection with the accompanying. drawing, which form part of the same.

This invention relates especially to cathode diaphragm electrolytic cells particularly adapted for use in producing caustic alkali, such as caustic soda, from salt, the cathode diaphragms being preferably constructed of special permeable material, so that the seepage of electrolyte therethrough occurs at such rate as to substantially overcome the back diffusion of the caustic soda through the small passages or interstices in the diaphragm. If desired also the diaphragm may in some cases have its permeability regulated preferably by forming adjacent the discharge side of the diaphragm a relatively impermeable layer of finer particles of asbestos or other material, which may be incorporated with the asbestos fibre or other material of which the body of the diaphragm may be formed.

In the accompanying drawing showing in a somewhat diagrammatic Way illustrative embodiments of this invention,

Fig. 1 is a longitudinal section through a cell, parts being removed for greater clea-rness.

Fig. 2 is a. transverse section thereof.

Fig. 3 is an enlarged horizontal section through one of the anode elements; and

Figs. 4 and 5 are diagrammatic sectional views of the cathode diaphragms which may be used.

The cell body 1 may with advantage be formed of concrete and provided with a suitable impervious lining 2 of vitreous tile, for instance. The concrete body may be strengthened and reenforced in suitable Ways, preferably by the use of stay rods or other strengthening devices arranged outside the cell, these rods 31 being bolted or otherwise connected, for instance, to the stay connectors 44 at the corners of the cell body so as to hold the parts together and strengthen the construct on while minimizing all undesirable electrolytic action on the stay rods and parts. As indicated in Figs. 1 and 2 suitable clamping plates, such as Specification of Letters Patent.

Patented Apr. 4, 1922.

Renewed J'uner30, 1921. Serial No. 481,708.

42, may be cast or embedded in the cell body so as to support the cathode elements in connection therewith and these clamping plates may be secured in position by suitable clamping bolts 11 which preferably pass through insulating protecting tubes 41 of hard rubber.

or the like to similarly protect these bolts against electrolytic action. The cathode elements which may be clamped upon both 1 sides of the cell body to cover the open rectangular sides thereof as by the clamping dogs 32 may comprise the channel iron frames 45 in which the concrete or other cathode backin 47 may be cast or otherwise formed, suitab e bearing bars, such as 23, being preferably cast into this backing so as to be substantially in line with the inner Y The cathodes in the edges of the frames. form of perforated plates 24 of steel or other suitable material may rest against these bearing bars and in turn support the cathode diaphragm 25 of suitable porous material, such as sheets of asbestos paper, preferably allowing substantially uniform seepage at the different levels in contact with the electrolyte within the cell, although this is not necessary in all cases. As is usual in the -'Hargreaves type of cell the cathode liquor entering the cathode chamber 33- by percolation or electrolytic action may run down into the caustic drip space 46 from which it may be continuously drained by the usual drain pipes or passages not shown.

The anode elements within thecell may with advantage comprise the anode posts l6 having bodies of raphite or other suit able material extending up through anode apertures 4 at the top of the cell body, and preferably permanently built into the cell body as by having the concrete or other calking 43 around their upper portions while their lower portions may be embedded in the cell lining or otherwise cast into or permanently secured to the cell body. It is advantageous to protect these anode posts against disintegration or other wasting influences in the cell and for this purpose they may be first coated with a protecting insulating covering as shown in Fig. 3, in which the graphite anode post bodies 20 are shown as enclosed in a: covering 16 of suitableinsulating material, wch, for instance, as hard rubber, which may be vulcanized in place on the posts before they are assembled. The thickness of this rotective covering is of course. considerab y exaggerated 1n the drawing since this coating need only be an eighth of an inch thick or less to give the desired permanence and elastic insulating properties. The anode plates are preferably removably mounted on these posts by suitable connecting devices, such, for instance, as the double tapered connecting pins 19 of graphite or similar material which may fit tightl into a tapered hole in the anode posts and a so into similarly taper-ed holes in the anode plates 17, 18,which are thus mounted on each side ofthe post so as to properly cooperate with the cathode diaphragins. it is, of course, understood that a suitable connector 15 may be cast upon or otherwise electrically connected to each anode post adjacent its top to conduct the current thereto and similar negative connections may be made with the cathode frames or plates, as is Well known in this art.

As indicated in Fig. 1, the cell may with advantage be formed with a draw-off outlet, such as 6, arranged in the bottom of the cell body so as to be opened from time to time so as to completely withdraw the elec trolyte from the cell, this outlet being, of course, normally closed by a suitable plug or other device. A brine inlet feed pipe 21 may be castinto the cell body so as to discharge brine through its inclined lower end 22, a transverse connection, such as 34, bein preferably provided at about the liquid evel of the cell, which may be normally closed by a removable plug or covering allowing observation of the level of the electrolyte from time to time. Another testing tube or opening 40 may be arranged in the top of the cell body, this tube preferably arranged adjacent one end of the cell, the

outlet pipe 10 preferably having a curved portion 7 in which a normally covered cleanout hole 8 ma be arranged adjacent the bend so as to al ow both sections of'the pipe to be cleared by suitable devices, the receiving end 14 of this chlorine discharge pipe preferabl communicating with the interior of the cel somewhat above the liquid level therein, which may be at about the-point indicated by the dotted line in Fig. 1. A brine drip discharge pipe, such as 12, may have a depending receiving end 13 within the cell and below the normal liquid level therein, the discharge end of this pipe 12 outside the cell being preferably arranged to drip into the trapped drip receiver 9 so that the amount of this brine drip which is discharged from the cell may be observed from time to time as it passes into the trapped connection with the chlorine discharge pipe and thus seals this connection iliane are used, so that considerable percolation of brine can take place through the diaphragms even when the current is not passing. For

this purpose the diaphragms may be formed.-

of asbestos board. or paper of a permeable character, the asbestos fibre being termed into heets of paper or cardboard of the do sired thickness, which of course provides numerous small diameter channels or capillary passages through. the diaphragm through which the electrolyte tends to flow under the static pressure the anode chamber. If desired, the amount of percolation occurring throughout the different parts of the diaphragm may be controlled by the use of more or less relatively impervious or finer grained material incorporated in or applied to the diaphragm preferably adjacent its discharge side. As shown in Fig. 4, the cathode diaphragm 26, the thickness of which is greatly exaggerated for the sake of clearness, may have incorporated. therewith a layer 27 of less permeable material, this layer varying in thickness more or less between the upper and lower parts of the diaphragm, so that at the bottom a greater thickness of this finer grain material is used which correspondingly cuts down the seepage of electrolyte and in this way a substantially uniform amount of seepage may take place throughout the entire diaphragm area. Another arrangement of diaphragm is shown in Fig. 5 in which the thickness of the diaphragm is also greatly exaggerated. The diaphragm, mainly composed of substantially uniform sized particles of asbestos fibre felted or laid together by paper makin methods may have a number of stepped or varying thickness portions of finer grained or less ermeable material 29, 30 arranged prefera 1y adjacent its discharge side so that the seepage of electrolyte is thereby limited and rendered more or less uniform throughout the diaphragm area. For these purposes particles of much finer grained asbestos fibre may be used and this material may be incorporated in any desired way with the fibrous material forming the body of the diaphragm, which is preferably composed of substantially uniform sized fibrous particles, during its manufacture, or if desired a coating of this or other relatively impervious material may be applied to the partly or completely formed diaphragm which is then preferably compacted so as to make a substantially uniform thickness layer or sheet which cooperates to best advantage with the diaphragm mounting used. It is advantageous to have these relatively impervious seepage regulat ing portions of the diaphragm at or adjacent its discharge side, since in this way solid particles or impurities carried into the diaphragm by the electrolyte in which they are suspended are usually stopped and embedded in the more porous open portions of the diaphragm where they exert comparativel little influence in cutting down its permeabi ity. y

In the use of a cell of this character for the productionof caustic soda from ordinary salt brine the seepage of brine through the diaphragm passages should preferably occur at such rate that undesirable diffusion of the caustic Soda formed adjacent the cathode cannot take place back through the diaphragm into the anode chamber. Caustic soda because of its much greater solubility has a much greater tendency to become dissolved in and diffused back through the electrolyte in the diaphragm than sodium carbonate would, for instance, and to prevent this undesirable action it seems necessary to have suflicient seepage or percolation of the electrolyte through the diaphragm so that the velocity at which the electrolyte passes through the small interstices or capillary passages in the diaphragm is greater than the velocity of back difiusion of the formed caustic soda electrolytically produced at thev surface of the cathode. The use of this cell has indicated that good results are secured when the cathode liquor seeping down through the cathode chamber 33 and into the drip space aG-at the bottom thereof contains about as much salt in solution as it contains of caustic. The cell is working at good efii- I ciency when there is about 110 grams per litre of caustic soda in the cathode liquor to 100 to 110 grams of dissolved salt therein. The salt'brine fed to the cell is preferably a fairly concentrated solution of about 4:0

degrees Twaddell and it is supplied to the cell in such quantities as to give a slight brine discharge at the sight drip provided on the cell giving a brine discharge of about th er square foot of diaphragm surface, alt ough of course somewhat greater brine discharge may occur without undesirable results. Under these conditions the cell runs efiiciently without undesirable amounts of wasteful chlorate decomposition in the anode chamber and for weeks at a time cells of this character have operated commercially with a current efficiency between 90 and 94 per cent of the theoretical current required for producing the caustic soda recovered. V

This invention has been described in connection with a number of illustrative embodiments, forms, proportions, shapes, parts, materials, arrangements and methods of operation and use, to the details of which disclosure the invention is not of course to be limited, since what is claimed as new and electrolysis of salt, an open sided .cell body formed of concrete and having an insulating vitreous lining, anodes mounted in said cell body vided with a hard rubber insulating protecting covering permanently embedded in the lining of the cell body and projecting through anode apertures in the top of the same, renewable anode plates cooperating with said posts and double tapered connector pins connecting said plates and posts, removable cathode frames secured to said cell body to cover the open sides thereof, perforated cathode plates and permeable cathode diaphragms in contact therewith clamped between said cell body and said cathode frames, said diaphragms being of varying permeability at different heights to make the seepage of electrolyte therethrough and comprising anode posts procathode plates and permeable cathode diaphragms in contact therewith clamped between said cell body and said cathode frames.

3.- In electrolytic cells adapted for'the electrolysis of salt, an open sided cell body,

anodes mounted in said cell body and comprising anode posts provided with an insulating protecting covering permanently embedded in-the bottom of the cell body and projecting through anode apertures in the top of the same, renewable anode plates cooperating with said posts, removable cathode frames secured to said cell body to cover the open sides thereof, perforated cathode plates and permeable cathode diaphragms in contact therewith clampedbetween said cell body and said cathode frames. 4. In electrolytic cells adapted for the electrolysis of salt, an open sided rectangular sectioned cell body formed of concrete, anodes mounted in said cell body, metallic strengthening members cooperating with said cell body and arranged outside of the same, clamping plates embedded in the said cell body and secured thereto by removing clamping bolts passing through said cell body and insulated therefrom by protecting tubes, removablecathode frames and clamping dogs secured to said clamping plates to clamp said cathode frames to said cell body to cover the opensides thereof and having bearing bars substantially flush with the inner faces of said frames, perforated cathode plates and permeable cathode diaphragms in contacttherewith clamped between said cell body and said cathode frames, said diaphragnis allowing seepage of electrolyte therethrough at such rate as to substantially prevent back diffusion of the formed caustic soda through said diaphragrns,

5. ln electrolytic cells adapted for the electrolysis of salt, an open sided rectangular sectioned cell body formed of concrete, anodes mounted in said cell body, metallic strengthening members cooperating with said cell body arranged outside of the same, clamping plates embedded in the said cell body and secured thereto by clamping bolts passing through said cell body and insulated therefrom, removable cathode frames and clamping dogs secured to said clamping plates to clamp said cathode frames to said cell body to cover the open sides thereof, perforated cathode plates and permeable cathode diaphragms in contact therewith clamped between said cell body and said cathode frames.

6. In electrolytic cells adapted for the electrolysis of salt comprising a cell formed of concrete, anodes mounted. in said cell and comprising carbon anode posts provided with an elastic insulating protecting covering permanently secured in the cell body and projecting through anode apertures in the same, renewable graphitic carbon anode plates cooperating with said posts and double tapered carbon connector pins connecting said plates and posts.

7. In electrolytic cells adapted for the electrolysis of salt, comprising a cell, anodes mounted in said cell and comprising carbon anode posts provided with an insulating protecting covering permanently secured in the cell body, renewable graphitic carbon anode plates cooperating with said posts and tapered carbon connector pins connecting said plates and posts.

v 8. In electrolytic cells adapted for the electrolysis of salt, comprising a cell, anodes mounted in said cell and comprising carbon anode posts provided with a protecting coverlng, renewable carbon anode plates cooperating with said postsand renewable Wedging carbon connecting portions electricall connectin said posts and plates.

9. In e ectrolytic cells adapted for the electrolysis of salt, comprising a cell, anodes mounted in said cell and comprising carbon anode posts provided with at protecting covering and renewable carbon anode'plates cooperating with said posts and tapered carbon connector pins connecting said plates and posts.

10. In electrolytic cells adapted for producing caustic soda by the electrolysis of salt, a cell body, anodes mounted in said cell body, removable cathode frames secured to said cell body to cover the open sides there of, perforated cathode plates and permeable cathode diaphragms in contact therewith clamped between said cell body and said cathode frames, said diaphragms being of substantially uniform thickness and com-- prising a variable-thickness layer of relatively impervious material on their discharge sides to give said diaphragms varying permeability at different heights to make the seepage of electrolyte therethrough substantially uniform throughout different parts of the diaphragms, said ,diaphragms allowing seepage of electrolyte therethrough at such rate as to substantially prevent back diffusion of the formed caustic soda through said diaphragms.

11. In electrolytic cells adapted for pro ducing caustic soda by the electrolysis of salt, a cell body, anodes mounted in said cell body, removable cathode frames secured to said cell body to cover the open sides there of, perforated cathode plates and permeable I cathode diaphragms in contact therewith clamped between said cell body and said cathode frames, said diaphragms being of substantially uniform thickness and com I prisin I a variable thickness layer to give said iaphragms varying permeability at different heights, said d-iaphragms allowin seepage of electrolyte therethrough at suc 100 rate as to substantially prevent back diffusion of the formed caustic soda through said diaphragms.

12. In electrolytic cells adapted for producing caustic soda by the electrolysis Of 105 salt, permeable cathode diaphragms of substantially uniform thickness and comprising a variable thickness layer of relatively impervious material to give said diaphragms varyin permeability at different heights, 110 said diaphragms allowing seepage of electrolyte therethrough at such rate as to substantially prevent back diffusion of the. formed caustic soda through. said diaphragms.

13. In electrolytic cells, permeable cathode diaphragms comprising a variable thickness layer of relatively impervious material to give said diaphragms varying permeability at different heights. 7

14. In electrolytic cells, permeable cathode diaphragms comprising a variable thickness layer of relatively impervious material on their discharge sides to give said diaphragms varying permeability at different 125 eights.

' NOEL STATHAM.

Witnesses: CHAS. H. DICKINSON, W. L. Comm.

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