US2511686A - Tank for aqueous electrolysis - Google Patents

Description

June 13, 1950 J. ANDRE 2,511,686 TANK FOR AQUEOUS ELECTROLYSIS Filed April 30, 1948 r s Sheets-Sheet 1 In venfor- June 13, 1950 J ANDRE 2,511,686

TANK FOR AQUEOUS ELECTROLYSIS Filed April 30, 1948 a 3 Sheets-Sheet Z June 13, 1950 J. ANDRE TANK FOR AQUEOUS ELECTROLYSIS 3 Sheets-Sheet 3 Filed April 30, 1948 .271 Veda (Liv/20% 'w Patented June 13, 1950 TANK FOR AQUEOUS ELECTROLYSIS Jean Andr, Paris, France, assignor to Compagnie de Produits Chimiques et Electrometallur- ,giques Alais, Froges et Camargue, Paris, France,

a corporation of France Application April 30, 1948, Serial No. 24,291

In France May 14, 1947 3 Claims.

The present invention relates to electrolysis tanks for aqueous solutions and more especially alkali chlorates and perchlorates. Its objects is the provision of such a tank arrangement wherein the distribution of the electric current among the various active pole elements is as uniform as possible, this leading to a more highly uniform wear on the anode elements.

According to a feature of the invention the positive elements in the tank are comprised of spaced strips of graphite fitted at each end thereof in graphite bars which form potential distributors and placed at the bottom of the tank, current being led to said bars through substantially vertical conductor members.

This arrangement makes it possible to construct independent and removable anode pole units adapted to be mechanically prefabricated and facilitates the construction of electrolysis units having as high a current capacity as may be desired, through a simple juxtaposition of said pole units in parallel relationship within a common tank permanently installed in the electrolysis plant. The arrangement further makes it possible quickly to remove a used or worn out anode group and replace it witha fresh one.

According to a further feature of the invention the cathode elements are so arranged as to permit of their being cooled and thereby to make it possible to cool the electrolyser. rangement is found to be particularly desirable especially in connection with the electrolysis of alkali chlorides for the manufacture of chlorates and perchlorates, inasmuch as it makes it possible to maintain at a low and uniform temperature the body of the cathode elements themselves in graphitic anode electrolysers, and thereby in a very great measure to increase the current density over the anode elements without incurring the danger of a breakdown or excessive wear on said elements.

In practice said arrangement makes it possible to double the maximum current density heretofore considered permissible without provision of any cooling means other than thegeneral .coolattained where the cathode elements are refrigerated with cool water.

Other features and advantages of the invention will appear from 'the ensuing description Such arwhich relates to some forms of embodiment thereof given by way of example. In the description reference is made to the accompanying drawing wherein:

Fig. 1 is a View in vertical cross section of a tank according to the invention.

Fig. 2 is a view in vertical cross-section on a plane transverse to the foregoing figure.

Fig. 3 is a detailed view of the mounting of the anode elements.

Fig. 4. is a detailed view of an anode plate or strip.

Fig. 5 shows another embodiment of a multielement block or brick used as a support for the anode strips.

Fig. 6 is a view drawn to a larger scale of an end of said brick.

Fig. 6b shows a modification.

Fig. 7 is a detailed showing of a conductive member for leading current to the bricks.

Fig. 8 shows the manner in which said current conveying members are mounted.

Fig. 9 is a detailed view of a modification of the current conveying means for the anode elements.

The tank I is made of welded steel sheeting or cast iron. The cathode assembly or bundle is provided in the form of a plurality of tubes 2 of flattened cross-section which in the example shown are welded in parallel spaced relationship with each other to the opposite longitudinally extending walls of the tank, or else they may be embedded on casting in said walls where the latter of cast iron. The tubes at both their ends open outwardly of the tank.

' tween the pole surfaces.

The current from the anodes is divided among .the cathode strips and flows towards the side walls of the tank. through the tubes 2. Connections 4 are appropriately spaced along the longitudinal walls of the tank to draw 01f said current. Moreover in order to facilitate the current distributween the connections 4.

Cooling of the electr'olyser isefiected by the cathodes themselves which form a radiating unit, by means of a forced flow of water circulated through the tubes 2 of the bundle. For that purpose both ends of the tubes 2 are made to issue into water jackets or headers 5v and 6 provided with baille means therein. Pressure water is conveyed through an inlet pipe I to the tank and is discharged through an outlet pipe 8.

The active portion of the positive unit or bundle comprises a plurality of graphite strips 9 arranged in parallel spaced relationship and maintained in such condition by being fitted or inserted in a pair of graphite blocks or bricks ill extending parallel with each other and at right angles with the strip 9. The opposite ends, II. and. i2 of each strip are machined to the form of a wedge having a predetermined angle of taper. Both bricks l0 comprise slots l3 therein formed to the same angle of taper. The Whole assembly s m unt s hown in s- Electric current is conveyed to the graphite bricks, It through graphite rods [at inserted by means of a tapered connection into the bricks.

The Whole arrangement forms an undeformable unitary pole assembly which is easy to handle. This assembly is lowered into the tank in such a way that the raphite strips 9 will alternate with the cathode strips 3 placed opposite thereto as particularly shown in Fig. 2.

The aboye arrangement makes it possible to immerse the active portions of the bundle as deep as desired under the surface level of the bath,

I thus providing the possibility of increasing the Faraday efiiciency factor of the system.

Supports 15 of dielectric material as narrow "as practicable in their transverse dimension enable the assembly thus constructed to rest upon the tubes 2 while providing the necessary clearance for free unitary expansion of the strips.

The bricks ID are encased in a casing [6 of ebonite or any other suitable dielectric material impervious to the solution in operation. Said casing prevents a. direct iiow of current as between the bricks HI and the adjacent negative elements. ing current to the bricks are encased throughout Likewise the rods l4v used for leadflat paralellopipedic blocks of graphite assembled with each other so as to form the brick of the desired initial shape. A metal rod which may be made of steel extends through a central aperture throughout the entire brick longitudinally thereof and provides for the possibility of firmly clamping all of its elements together through the use of clamping plates and rubber members. Said metal clamping rod and the'related metal bearing members should not participate in the electrolyte process. They are completely insulated from the graphite structure which is at the positive terminal and are directly connected with the negative terminal through a connectionmade of a metal similar thereto in character such as iron.

The system is so arranged that the path of loss between the negative metallic portion and the adjacent positive graphite elements will be long enough to avert the occurrence of any parasitic electrolytic side efiects. It should be observed however that in practice such parasitic electrolytic side effects would not actually be very injurious, except for slow gradual wear of the thicker graphite parts. They would simply cause both parts to play a similar function to that of the active elements in the remainder of the assembly.

However, for considerations involving the evolution of gas, among other reasons, it is desirable to avert the production of such effects within the central bore in the bricks and for this reason the specific mounting arrangements to be described hereinafter by way of example are provided.

As concerns the downward positive current leads into the depth of the electrolysis bath, rather than usingas in the foregoing arrangements graphite rods fitted through a tapered connection paralellopipedic graphite blocks of ordinary form are used, that is blocks that do not possess any particularly great mechanical strength and the ends of which are cut to the shape of paralellopipedic teeth fitted into the composite brick assembly thereby both imparting mechanical rigidity to the assembly and providing an excellent electric contact for the distribution of current into the brick.

In the examples shown the graphite plates comprising the brick are of two different types 30 and 3! which difi'er as to thickness. The plates 3t. which are the thicker ones form the, teeth of the general mounting assembly, while the plates 3| define the gaps therebetween. All of the plates are formed with a central bore 32. Said plates assembled in juxtaposed relation may bemounted in any one of various ways and in particular according to the arrangements shown.

In the arrangement shown in Fig. 6 a tube 33 made of a semi fiex ibl'e dielectric substance'chemi'cally impervious to the electrolysis solutions, for instance plasticized polyvinyl chloride is inserted through the general longitudinal bore of the asrod 38, extends through the entire arrangement.

, Said rod is preliminarily coated with a coat of polyvinyl chloride varnish or any other suitable dielectric varnish impervious to chemical attack from the electrolyte solution. Said steel clamping rod is formed with screw threads at both ends thereof and a nut 35 firmly clamps the whole assembly against each of the washers member 42 serving to. convey current thereto.

The lowermost end of said current conveying member 42 (Figs. 5, 7 and 8') 1s machined so as to form teeth 43 (Fig. 7) said teeth also being formed with a central bore which thus extends all along the brick throughout its entire length. Insertion is effected as shown in detail in Fig. 8, the teeth 43 of the member 42' taking the place of the plates 3| at this point.

After the assembly has been suitably clamped the composite brick thus formed may be milled, the milled portions occurring accurately opposite to the plates 4|. It'will be understood that the positive graphite current leads 42 may of course be machined to any other suitable form, and the connections therewith may be accomplished in any appropriate manner.

A modification of a mounting assembly is shown in Fig. 62).

According to this modification, the inner dielectric tube 33 is a tube made of a hard dielectric substance such as glass, ceramic material, hard polyvinyl chloride and the like. Such substance, although considered to be more fragile than that of which is made the tube in the previously described arrangement, has the advantage however of showing less tendency to be modified with time and is less liable to have objectionable cracks or fissures appear therein. In order to mount it however it is necessary to modify the ends in the manner described. The resilient bearing-washer 34 and the ebonite coated steel clamp plate 35 should be formed with a larger recess than in the previously described device so as to enable the end of the tube 33 to pass therethrough; in order to increase the length of the loss path, the ebonite-coated steel clamp plate 35 is provided with increased thickness. In other respects the mounting assembly is identical with the one described hereinabove.

Fig. 9 shows a modified conductive rod for leading current into tanks having a high anode current density. To avoid an excessive voltage drop through the rod, the latter is provided hollow and within the recess I8 therein there is inserted a copper rod [9 immersed in a mass of mercury. The graphite forming the rod 14 is specially impregnated to ensure its imperviousness to the liquid of the surrounding bath.

It is essential that both tapers II and I2 of the strip 9 be identical, their opposite pairs of faces as seen from a common side of the strip not only being parallel but also coplanar. This condition is a requisite in order that the insertion of the potential distributing member into the bricks II) should not create any abnormal stress in the teeth of said bricks and moreover in order that the positioning of each strip 9 of the anode bundle with respect to the negative bundle should be accurately defined.

It will of course be understood that the present invention is not restricted to the specific forms of embodiment shown and described and that it may be carried out in a large number of modified forms.

What I claim is:

1. An electrolysis tank which comprises in combination a container, a cathodic structure including a plurality of parallel tubes extending across the lower inner part of the container and adapted to conduct electrolysis current to the side walls of said container, a plurality of perforate metallic plates in parallel spaced relationship, each of said plates being secured along its bottom longitudinal edge with one of said tubes, means to circulate a cooling fluid through said tubes, electric insulators carried by said tubes near the ends thereof, and an anodic structure which comprises a pair of oppositely arranged parallel blocks extending above said tubes at right angles thereto and set upon said insulators within said container, and a plurality of parallel vertical spaced anodic strips, extending across said blocks in alternating relationship with said plates and having their opposite ends inserted in recesses formed in said blocks, and vertical conducting members, adapted to convey positive current, fitted into the top face of said blocks.

2. An electrolysis tank, which comprises in combination a container, a fixed cathodic structure comprising a plurality of parallel tubes passing through two opposite side walls of the container and through its lower inner part, and electrically connected with the side walls of the container, electric insulators carried by said tubes near the ends thereof, means for circulating a cooling through said tubes, a set of parallel spaced perforated metal plates, one edge of each of said plates being welded to one of said tubes, and a movable unitary anodic structure, which comprises a pair of oppositely arranged, parallel spaced blocks and a plurality of parallel vertical spaced anodic strips extending across said blocks and inserted at their opposite ends into recesses of said blocks, vertical conducting members adapted to convey positive current fitted into the top face of said blocks, the entire unitary anodic structure being arranged in said container at a predetermined depth therein in such a way that said blocks are set upon said tubes at right angles thereto through the electric insulators carried by the same, the said metallic plates being positioned in spaced alternating relationship with said anodic strips.

3. An electrolysis tank as claimed in claim 1, in which each of said blocks comprises a number of juxtaposed strip shaped elements clamped together forming a plurality of parallel vertical recesses on one side of the block.

JEAN ANDRE.

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

UNITED STATES PATENTS Number Name Date 507,374 Lyte Oct. 24, 1893 674,927 Mauran May 28, 1901 1,053,266 Barstow Feb. 18, 1913 1,359,716 Le Sueur Nov. 23, 1920 2,177,453 Donald Oct. 24, 1939 FOREIGN PATENTS Number Country Date 13,690 Great Britain of 1896 118 Great Britain of 1902 121,460 Great Britain June 19, 1919 444,709 Great Britain Nov. 23, 1920

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