US2328665A

US2328665A - Electrolytic cell

Info

Publication number: US2328665A
Application number: US301582A
Authority: US
Inventors: Horace D Munson
Original assignee: Mathieson Alkali Works Inc
Current assignee: Mathieson Alkali Works Inc
Priority date: 1939-10-27
Filing date: 1939-10-27
Publication date: 1943-09-07
Anticipated expiration: 1960-09-07

Description

Sept. 7, 1943. H, D. MUNSON ELECTROLYTIC CELL Filed Oct. 27, 1939 INVENTOR flora C6 0. Mums ATTORNEYS involving the hazard of Patented Sept. 7, 1943 2,328,665 ELECTROLYTIC CELL Horace D. Munson, Nia

to The Mathieson Alk York, N. Y., a corporation of Virginia a Falls, N. Y., assignor all Works. Inc., New

Application October 27, 1939, Serial No. 301,582 7 Claims. 204-286) This invention relates to electrolytic cells in which gas is generated and particularly to alkalichlorine cells of the mercury cathode type. The

invention is concerned particularly with the ad- Justment of the distance between a mercury layer in the bottom of the cell which acts as one electrode and a second electrode which is su ported above it in a pool of electrolyte.

In the electrolytic decomposition of alkali metal halides, for example sodium chloride, an aqueous solution thereof is introduced into the anode compartment of a mercury cell overlying a mercury layer which acts as cathode in this compartment. An anode of graphite or the like is disposed within a pool of the solution (electrolyte) in the compartment. Passage of current between anode and cathode brings about decomposition of the electrolyte with resulting evolution of chlorine gas, which rises to the top of the compartment in a vapor space overlying the pool 01 electrolyte; alkali metal, for example sodium, goes to the mercury cathode and amalgamates therewith.

In such cells high current densities are employed so that it is economical to place the anode member connected to the second electrode and extending upwardly through an aperture in the cover, means for adjusting the height of said u supporting member with respect to the cover comprising. a clamp on said supporting member and a shim of substantially uniform thickness interposed between the clamp and the cover, and sealing means connected to the cover and to the supporting member to permit relative movement of the two without escape of gas through the aperture.

The sealing means may comprise an annular hydraulic seal disposed around the supporting member adjacent the cover to permit relative movement between the cover and the supporting member without permitting escape of gas. This hydraulic seal maycomprise an annular container attached to the cover and adapted to contain a pool of liquid and a cap disposed around the supporting member and projecting into the annular container to a point below the level of liquid therein. Another type or hydraulic seal close to the mercury cathode. I have observed that for every inch of brine between the anode and the mercury cathode there is an increase of cell voltage of approximately 0.1 volt. Graphite anodes and, in fact, anodes of other resistant materials tend to erode with relative rapidity under the conditions of electrolysis. With graphite anodes, the anode surface recedes from the mercury layer at a rate such that in one month the cell voltage'increases about 0.1 volt. In order to maintain high electrical efilciency and low resistance in the cell, it is therefore desirable to adjust the height of the anode with respect, to the mercury layer from time to time.

As a result of my investigations, I have developed a means for suspending the anode in the cell so that its height with respect to the mercury layer can be quickly and accurately adjusted to have the anode spaced at an optimum distance above the mercury cathode and without gas leaks from the cell, which in the case of halogen gases is extremely perilous. My inventioncontemplates (in an electrolytic cell in which gas is generated), the comblnation which comprises a compartment, an electrode (for example, a mercury layer) disposed in the lower portion of the compartment, a pool of electrolyte in the compartment in contact with said electrode, a second electrode disposed in the pool, a cover on said compartment, a supporting which may be employed comprises an annular container attached tothe supporting member and through which the supporting member passes, and a ring attached to the cover and projecting into the annular container, said container being filled with liquid to a point above the lower edge of the ring. However, my preferred form of sealing means for preventing escape of gas at the aperture (in which the supporting member passes through the cover) comprises an annulus of flexible, and preferably resilient, material, for example rubber, fastened at its outer edge to the cover and at its inner edge to the supporting member. As the supporting member is moved relative to the cover a sealing means of this type gives without permitting leakage. Rubber is a useful material, especially in mercury cells, because oi its high dielectric and relative inertness to attack by wet halogens.

These and other features of my invention will be more readily understood in the light of the following detailed description taken in conjunc-v tion with the accompanying drawing, in which: Figure 1 is a cross section through the anode compartment of a mercury cell equipped with -means of my invention for adjusting the disnular container of the seal being fastened to' the cover with the sealing ring-fastened to the supporting member; and

Fig. 3 illustrates a further modification of the apparatus of my invention employing a hydraulic seal in place of the flexible annulus but in this case with the annular container of the seal fastened to the supporting member and with the sealing ring fastened to the cover.

Referring now to Fig. l, which illustrates the presently preferred structure of my invention, it will be observed that a conventional anode compartment H) of a mercury cell having a substantially horizontal bottom IDA and vertical sides ll, l2 contains a layer or cathode l3 of mercury, which rests upon and covers the bottom. Conventional means (not'shown) are provided for conducting current to the mercury cathode. The mercury layer is overlain by a pool I of electrolyte, such, for example, as aqueous solution of sodium chloride, which rises to a level MA. The compartment is closed by a cover iii of material, such as concrete, which is resistant to attack by wet chlorine and has a relatively high electrical insulating value or dielectric strength. The space It between the cover and the upper level of the electrolyte pool serves for the collection of chlorine or other gas generated in the compartment.

An anode l1 comprising one or more graphite bars is immersed in the pool of electrolyte and is suspended therein by means of a supporting member I8 or lead-in which passes through an aperture IS in the cover of the compartment and fits loosely therein.

The supporting member should be fastened in good electrical contact with the anode and either made of a material which resists attack by wet chlorine or protected against attack by means of a sleeve. The supporting member is made of electrically conductive material and at its upper end is attached to abus clamp IRA to which direct current is supplied from a conventional source (not shown), the other pole of said source being connected to the mercury layer through the bottom of the compartment.

The bus clamp is connected to the power source through a flexible conductor 20 which has sufflcient slack to permit vertical movement of the supporting member or lead-in.

An annular sealing member or diaphragm 21 of flexible and preferably resilient material, such as rubber, is disposed around the supporting member immediately above the cover and fas tened therewith with a gastight joint. The outer edge of this diaphragm is fastened by a gastight joint to the cover around the supporting member. The diaphragm may be made of molded rubber with a substantial wall thickness, say inch and should have sufiicient slack" to permit substantial vertical movement of the supporting member with respect to the cover. This is especially true if the diaphragm is merely flexible and not capable of great stretch, but is desirable even when the diaphragm is made of resilient rubber or the like. As shown in Fig. l, the diaphragm may be bell-shaped with its lower edge fastened to the cover and with a central aperture through which the supporting member is tightly fitted.

At a point relatively high up on the supporting member but below the bus clamp is disposed an annular clamp 22 which is slidable upwardly and downwardly on the supporting membar but may be fixed by means of a set screw 23 'timum cell performance.

or other clamping means. A rest member 24 fastened to the cover around the aperture outside the diaphragm and projecting upwardly is provided. The rest has an aperture in its upper portion through which the supporting member passes and has a substantially horizontal flat top 25. Between the clamp and the rest, a spacer 26 or shim is interposable. This shim is Y- or U-shaped in construction so that it can be slid into place between the rest and the clamp from the side. The thickness of the spacer preferably corresponds to that distance between the bottom of the cell and the anode which gives op- In the operation of a mercury cell of the modern type this distance is about inch, but is, of course, dependent upon the thickness of the mercury layer and upon other cell conditions.

If desired, in order to provide further assur- I ance against short circuits from the supporting member to the cover an insulator sleeve or bushing assembly 21 may be provided around that portion of the supporting member that passes through the aperture in the cover and clamped or threaded to the conductive inner tubular portion I8B of the supporting member l8. In any event, there should be substantial clearance between the walls of the aperture and the supporting member and the supporting member should be insulated against short-circuiting of current through the walls of the compartment to the mercury cathode.

To adjust the height of the supporting member relative to the cover, and consequently to adjust the distance between the anode and the bottom of the cell or the upper level of the mercury, the adjusting clamp is loosened and the spacer is removed. Due to the flexibility of the flexible seal or diaphragm the anode can then be pushed down to touch the bottom of the cell. With the anode in this position and with the clamp disposed upon the upper surface of the rest, the clamp is tightened; then the Y- or U-shaped spacer is inserted. As indicated hereinbefore, the thickness of the spacer is such as to give the optimum distance between the bottom of the anode and the mercury level under the particular conditions of operation. This is usually about inch.

It is desirable in the construction of the appa ratus herein illustrated to machine the top surface of the rest so that this is parallel with the bottom of the cell so that the anode will be suspended parallel to the mercury surface.

WhileI prefer to employ the flexible diaphragm or seal 1n the position shown in Fig. 1, it may be clamped to the top of the cell cover but extend down into the cell through a larger aperture in the cover and be clamped at its lower end around the supporting member or to the anode.

Referring now to Fig. 2, it will be observed that the flexible diaphragm or sealing member of Fig. 1 has been replaced by a hydraulic seal 28. This. hydraulic seal comprises an annular container 29 resting on the cover around the supporting member and spaced substantially therefrom. On the supporting member there is fastened a. downwardly projecting cap or bell 30 which extends into the annular container. The annular container is filled with oil 3| or other suitable liquid and the heights of both the contamer and the walls of the cap are such as to permit substantial vertical movement of the supporting member with respect to the cover without breaking the liquid seal.

In Fig. 3 an alternative form of hydraulic seal structure 32 is shown. This seal structure like that of Fig. 2 may be employed in place or the flexible diaphragm of Fig. 1. However, in this instance, an annular container 33 is fastened to spacer of substantially uniform thickness disposed between the cover and the clamp and sup porting the clamp, and a vertically adjustable sealing means between the supporting member and the cover.

2. In an electrolytic cell having a compartment which gas is generated, a cover on the compartment, a first electrode disposed inthe bottom of the compartment, a second electrode dis posed in the compartment above the first electrode' and a pool of electrolyte in the compartment in contact with both electrodes, the combination which comprises a supporting member attached to the second electrode and projecting spacer of substantiallyuniform thickness corresponding approximately to that distance between the bottom of the cell and the second electrode which give optimum cell performance, and a vertically adjustable sealing means between the supporting member andthe cover.

3. In an electrolytic cell having a compartment in which gas is generated, a cover on the compartment. a first electrode disposed in the bottom of the compartment, a second electrode disposed in the compartment above the first electrode and a pool of'electrolyte in the compartment in contact with both electrodes. the combination which comprises a supporting member attached to the second electrode and projecting through an aperture in the cover, a vertically adjustable clamp on the supporting member above the cover, a open-sided laterally removable spacer 01' substantially uniform thickness disposed between the cover and the clamp and supporting the clamp, and avertically adjustable sealing means of flexible material between the supporting member and the cover.

4. In an electrolytic cell having a compartment in which gas is generated, a cover on the compartment, a first electrode disposed in the bottom of the compartment, a second electrode disposed in the compartment above the first electrode and comprises a supporting member attached to the 'the supporting member and a sealing cap 34 is the compartment. j

5. In an electrolytic cell having a compartment in which gas is generated, a cover on the compartment, a first electrode disposed in the bottom of the compartment, a second electrode disposed in the compartment above the first electrode and adjustable clamp on slack to permit vertical movement ing member with respect to the cover.

6. In an electrolytic cell having in which gas is generated, a cover on the compartment, a first electrode disposed in the bottom of the compartment, a second electrode disposed in the compartment above the first electrode and comprises a supporting member attached to the second electrode and projecting through an aperture in the cover, a vertically adjustable clamp on the supporting member above the cover, a open-sided laterally removable spacer of substantially uniform thickness disposed between the cover and the clamp and supporting the clamp, and sealing means comprising an annulus oi flexible resilient material fastened at its outer edge to the cover and at its inner edge to the supporting member.

7. In an electrolytic cell having a compartment in which gas is generated, a cover on the compartment, a first electrode disposed in the bottom 01' the compartment, a second electrode disposed in the compartment above the first electrode and a pool of electrolyte in the compartment in contact with both electrodes, the combination which comprises a supporting member attached to the second electrode and projecting through an aperture in the cover, a vertically adjustable clamp on the supporting member above the cover, a opensided laterally removable spacer of substantially uniform thickness disposed between the cover and the clamp and supporting the clamp, and sealing means comprising a resilient rubber bell fastened at its lower edge to the-cover and having a central aperture through which the supporting member passes with a gastight fit.

v HORACE D. MUN-SON.