US2952604A

US2952604A - Electrolysis apparatus

Info

Publication number: US2952604A
Application number: US510415A
Authority: US
Inventors: Nora Vittorio De
Original assignee: Oronzio de Nora Impianti Elettrochimici SpA
Current assignee: De Nora SpA
Priority date: 1955-05-23
Filing date: 1955-05-23
Publication date: 1960-09-13
Anticipated expiration: 1977-09-13
Also published as: GB834005A; BE548036A; FR1153516A; CH352660A

Description

Sept. 13, 1960 v. DE NORA 2,952,604

ELECTROLYSIS APPARATUS Filed May 23, 1955 8 Sheets-Sheet l INVENT R VlTTOR/O ell ORA BY I I ATTO EYS a 8 Sheets-Sheet 2 Filed May 23, 1955 INVENTOR V/TTOR/O de/VORA Sept. 13, 1960 v. DE NORA ELECTROLYSIS APPARATUS 8 Sheets-Sheet 3 Filed May 23, 1955 IN.VENT R V/rro /o J/VORA Sept. 13, 1960 v. DE NORA ELECTROLYSIS APPARATUS 8 Sheets-Sheet 4 Filed May 23, 1955 INVENT R V/TroR/o a e/Vow 4/ ATTOR Sept. 13, 1960 v. DE NORA 2,952,604 ELECTROLYSIS APPARATUS Filed May 23, 1955 8 Sheets-Sheet 5 INVENT R V/TTOR/O 0 NORA Sept. 13, 1960 v. DE NORA 2,952,604

ELECTROLYSIS APPARATUS Filed May 23, 1955 8 Sheets-Sheet 6 Mil mm: H

V. DE NORA Sept. 13, 1960 ELECTROLYSIS APPARATUS 8 Sheets-Sheet 7 Filed May 23, 1955 INVENTOR V/TTORIO deli/0AA ATT Sept. 13, 1960 v. DE NORA ELECTROLYSIS APPARATUS 8 Sheets-Sheet 8 Filed May 25, 1955 A R o N e INVENT V/TTOR/O m? E In O A United States Patent Ofiice 2,952,604 Patented Sept. 13, 1960 ELECTROLYSIS APPARATUS Vittorio de Nora, Milan, Italy, Nora Impianti Elettrochimici, tion of Italy assignor to Oronzio de Milan, Italy, a corpora- This invention relates to an apparatus for carrying out the electrolysis of solutions from which cations can be discharged onto a mercury cathode by forming an amalgam therewith. Typical examples of such metals are sodium, potassium, lithium, zinc, lead, and cadmium. The most widespread use of the mercury cathode type electrolytic cell up to the present time is in the alkali chlorine industry where mercury cells are used in the decomposition of sodium chloride solutions to release chlorine at the anode and form an amalgam of sodium at the cathode which amalgam is later decomposed to release the sodium in the form of sodium hydroxide, or other sodium compounds, and the mercury returned to the cell for further use in the electrolysis process.

The mercury cells most commonly employed up to the present time consist of an elongated trough in which the film of mercury flows along the sloping bottom of the trough forming a continuous layer. A set of anode plates which are usually of graphite are suspended a small fraction of an inch above the flowing mercury layer and a stream of brine is electrolyzed by applying a proper voltage between the graphite anode and the mercury cathode.

The above described arrangement requires considerable floor space because the cell structure develops in a horizontal plane. Furthermore, cells of this type are not suitable for carrying out some special processes which have been recently developed in which amalgam metallurgy is used and by which the metal amalgamated in the first electrolysis stage is then plated out of the mercury in a second electrolysis stage during which the amalgam is acting as an anode in order to deposit the metal to be recovered on a rigid metallic cathode in a high state of purity.

Various attempts have been made heretofore to produce electrolytic cells in which the mercury flows substantially vertically over the cathode surface. These attempts, however, have not been successful in that they either require the use of a moving cathode support, such as rotating disks or movable belt surface, which moving parts are diflicult to maintain under the conditions encountered in an electrolytic cell, or require the flow of mercury along a vertical steel plate of special configuration to prevent the thinning mercury stream from breaking up and exposing the underlying plate and in which it is extremely difi'lcult to maintain the ideal flow arrangements required. The use of rods, pipes or strips to serve as guides to the downward flow of mercury has also been suggested, but no commercial applications thereof have been made.

It is the object of this invention to provide an electrolytic cell using a fluent amalgam cathode in which the mercury amalgam flows vertically downward over the cathode base surfaces.

Another object of the invention is to provide a vertical fluent amalgam cell which will be compact in floor arrangement and will have a high capacity for the floor area and cost of the cell.

Y and auxiliary equipment required,

Another object of the invention is to provide a vertical fluent amalgam cell in which the amount of mercury in circulation can be materially reduced below the amount of mercury required in horizontal mercury cells of equivalent capacity.

Another object of the invention is to provide a vertical mercury or fluent amalgam cell with a cathode surface on which the mercury tends to spread and adhere in the operation of the cell, whereby thinning of the mercury or amalgam film and exposure of the underlying surface is avoided.

Another object of the invention is to provide a fluent amalgam cell in which a diaphragm separates the anode compartment from the cathode compartment to reduce mixing of the products produced therein and the electrolytes in said compartments and increase the current efliciency of the electrolysis.

Another object of the invention is to provide a vertical fluent amalgam cell in which an amalgam of sodium or of other metals may be recirculated over the cathode base surface to promote better adherence of the mercury or amalgam film to the supporting cathode base, without reducing the output of the cell or the purity of the products produced therein.

A more specific object of the invention is to provide a cathode base in the form of a metal surface provided With open spaces therethrough, such as a net, screen or perforated plate, over both sides of which the mercury amalgam flows and which has the property of forming perfectly continuous films over the whole surface, including the holes, even when the open fraction of the total area is large.

Various other objects and advantages of the invention will become apparent as this description proceeds.

While the cell constituting the subject matter of this invention will be referred to frequently as a vertical mercury or vertical fluent amalgam cell, it is understood that the cathode and anode surfaces of the cell need not be exactly vertical but may occupy a sloping position anywhere between 30 and to the horizontal.

The vertical fluent amalgam cell of this invention has many advantages over horizontal mercury cells as they have been used up to the present time. The horizontal mercury cell requires a large floor space as the capacity of the cell is proportional to the surface area of the electrodes and in a horizontal mercury cell, the floor space required for each cell depends upon the capacity of the cell unless the cells are located one on top of the other. This makes the cost of horizontal mercury cells very high, not only because of the floor space involved, but because of the lengths of piping, bus bar connections, as well as the amount of mercury involved. However, it has been difiicult heretofore to provide suitable flow of mercury over a vertical or substantially vertical cathode surface Without undue exposure of the cathode to electrolysis conditions which would bring about the formation of hydrogen on the cathode surface, which reduces the capacity of the cell and also creates conditions of potential danger through explosion in the event the hydrogen becomes mixed with the chlorine.

Mercury, because of its high inward tension, is one of the most difiicult of liquids to cause to spread uniformly in a thin layer over a flat surface Whether the flat surface is in horizontal or vertical plane or intermediate between a horizontal and vertical plane.

I have found, however, that, contrary to the usual practice, if mercury previously amalgamated with sodium or other metals is used for the cathode surface, the adherence between the amalgam and the metal constituting the base of the cathode under electrolysis conditions is greater than the adherence of relatively pure mercury, so

that instead of stripping the mercury Substantially free of sodium, or other metal being deposited. I prefer to circulate a sodium amalgam back to the cell which has not been stripped completely of sodium but. has approximately 0.01% or more of sodium amalgamated therein. For economical operation, the range of sodium content of the recirculated amalgam may,.however, vary between substantially and 0.1% of sodium or other metal being deposited as the amalgam quickly picks up additional sodium when it starts its flow through the cell. While the sodium amalgamated in the mercury may thus be varied, for example between .002% to .2%, a substantial amount of sodium amalgamated in the mercury substantially improves the performance of the cells. This provides a. further advantagein the operation of the cells, for, as the decomposition of the amalgam formed in the cell can be compared to a first order reaction, Where complete decomposition is not required, the size of the decomposer for a cell of given capacity may be substantially reduced. With amalgams of other metals than sodium the same advantages are present to a greater or lesser degree, dependent upon the particular amalgamating metal.

Whereas a modern horizontal mercury cell used for chlorine-caustic soda production dischargm an amalgam containing up to 0.2% of sodium and in which, for satisfactory operation, the sodium content should be reduced to .001% in the decomposer, in the operation of the cell of the present invention smaller decomposers may be used and greater efiiciency obtained if the amalgam recirculated to the cell contains .0l% or more of sodium.

The cathode supports, when in the form of plates, should preferably be of such construction that the amalgam can be caused to flow over both sides of the plates and through perforations in the plates so that the amalgam layer communicates from one side of the plate to the other, which also provides better adherence of the amalgam to the supporting base plates. The cathode plates should also be provided with means to hold back and retard the flow of the amalgam so that the amalgam tends to gather in pools along the surfaces of the vertical cathode plate which pools are constantly replenished from above and overflow down the surface of the cathode plate to maintain fresh amalgam surfaces and yet prevent rapid flow of the amalgam over the cathode plate, since rapid flow tends to thin the amalgam column and cause it to lose adherence with the surface of the cathode plate so as to expose parts of the base surface of the cathode plate to the electrolyte and the electrolysis action.

I have found that a perforated net or wire screen, which has preferably been rolled under heavy rolls to flatten the same and which provides many open spaces between the meshes, forms a very satisfactory cathode plate on which a perfectly continuous film of amalgam may be maintained throughout the whole surface, including the spaces between the metal as well as the metal itself even when the open spaces between the wires are large with reference to the diameter of the wires used. While the size of mesh of such a screen may be varied within wide limits, I have found that a rolled steel wire screen having 4 wires per linear centimeter and a wire diameter of 2 millimeters provides a very satisfactory surface. Such a cathode surface is not only highly dependable as regards the capability of forming a'continuous amalgam layer thereon, but is also easy to produce and of sturdy construction and easy to assemble.

I have also found that a vertical mercury cell embodying a plurality of vertical anodes, having cathodes assembled therebetween in the form' of a filter press construction with diaphragms between the anodes and cathodes, provides a cell of large capacity in a relatively small floor space which has the additional advantage of reducing the piping to the cell and the length of the connections by which chlorine is conducted from the cells.

Theme of diaphragrns separating the anodes from the cathodes prevents flow of chlorine into the cathode 4 compartments and of hydrogen into the anode compartments and promotes better operation of the cell in various ways. By such arrangement, secondary reactions between chlorine and the products of the electrolysis at the cathode will not take place, hydrogen cannot form an explosive mixture with chlorine and the pH values in the cathode and anode compartments can be maintained at different levels.

Referring now to the drawings which illustrate preferred forms of embodiment of-the invention, Fig. 1 is a perspective' view with parts broken away to show the assembled construction of the improved vertical mercury cell.

Fig. 2 is a part vertical sectional .view approximately through the center of Fig. 1, with some parts shown in elevation.

Fig. 3 is a sectional view along the line 3-3 of Fig. 2. Fig. 4 is a sectional view substantially along the line 44 of Fig. 2.

Fig. 5 is a sectional view along the line 5-5 of Fig. 2.

Fig. 6 is a perspective view of one of the spacing elements forming the cathode compartment.

Fig. 7 is a detailed view of one of the electrolyte distributors.

Fig. 8 is a section view partially broken away of one of the anode compartments taken approximately on the line 88 of Fig. 3.

Fig. 9 is an enlarged detail section of one of the cathode plates showing the mercury distributor.

Fig. 10 is adetailed view showing the gasket connection between two of the anode frames and the spacing element.

Fig. 11 is an enlarged detail showing the preferred construction of the rolled wire cathode plate.

Fig. 12 is a diagrammatic view of a cell and decomposer unit.

Fig. 13 is a diagrammatic sectional view and Fig. 14 is a diagrammatic plan view of a modified type of vertical mercury cell construction. 7

Fig. 15 is a diagrammatic section view, Fig. 16 is a plan view, Fig. 17 is a sectional view approximately on the line 17-17 of Fig. 15, and Fig. 18 is a detail of a further modification of a vertical mercury cell construction, and

Figs. 19, 20 and 21 are sectional views of a further modified form of vertical fluent amalgam cell.

'While the mercury cell of this invention may be built and used as a single cell consisting of an anode and a cathode or of two anodes and one cathode, to combine the advantages of reduced floor space and reduced cost with high output, it is preferable to embody the invention in a multiple unit cell or cell bank of the filter press type as illustrated in Figs. 1 to 12.

The cell will be described herein as used for the electrolysis of sodium chloride brine to produce chlorine and caustic soda, but it will be understood that other electrolytes maybe used and other products produced.

In this particular embodiment of the invention. the cell consists of a plurality of anode compartments 1 and cathode compartments 2, there being one more anode compartment than there are cathode compartments. The anode compartments 1 and cathode compartments 2 are assembled together between end plates 3 and 4 which are held in assembled fluid tight relationship by the rods 5 which may be provided with nuts 5a and spring washers 6. 7

Each anode compartment consists of a rectangular frame'10 shown in greater detail in Figs. 3 and 4, having a passage 11 in one lower corner for the flow of the electrolyte solution (brine) therethrough and a passage 12 at the diagonallyopposite corner for the flow of spent brine and chlorine, or other product gas, from the anode compartments. The passages 11 and 12 are in alignment with corresponding passages in the other anode frames and in the separators forming the cathode compartments, and when assembled together will conduct the incoming fresh electrolyte and the outgoing spent electrolyte and product gas along the entire banks of frames from end to end of the cell. The frames may be made of any suitable insulating or insulated material resistant to attack by the electrolyte and the electrolysis products. For example, in the electrolysis of sodium or potassium chloride the frames may be rubber lined steel, hard rubber, or any chlorine proof plastic material.

From the passage 11 the brine flows through the openings 11a into each anode compartment and into a distributor 13 which fits into the bottom of each anode compartment and is provided with a plurality of holes 13a for distributing the fresh brine along the anode compartment. Openings 12a conduct the outgoing spent brine and chlorine from each anode compartment into the passage 12.

The tops of the anode frames are provided with a plurality of holes for receiving graphite bars 14, the tops of which are connected in parallel by

connectors

15 and 16 with the positive bus bar A.

The anode frames are provided with rabbets 10a around each inner edge (Figs. 9 and 10), into which diaphragms 17 of the type used in diaphragm chlorine cells are fitted and held when the cell is assembled. The diaphragms 17 preferably consist of a permeable asbestos layer 17:: suspended against a net or screen 17b of chlorine resistant plastic material. A passage or duct 18 is provided at approximately the center of the bottom of each of the anode frames 10, except the end frames, through which duct the mercury amalgam from the cathode compartments flows to the center of the cell bank and is discharged to the decomposer.

Each anode frame 19 is also provided with a slot 10b (Figs. 9 and 10) across the top thereof to receive a plastic gasket or cover, of Plexiglas or the like, which forms the seal of the top of cathode compartment. The center anode frame is also provided with a discharge outlet 19 at the bottom thereof through which the mercury amalgam from the cathode compartments flows to the decomposer.

The cathode compartments are formed between the anode frames by U-shaped spacers 29 (Fig. 6) provided with passages 21 for the fresh electrolyte and passages 22 for the spent electrolyte and product gas, and a slot 23 which registers with the ducts 18 in the bottom of the anode frames to permit the amalgam to flow from the cathode compartments to the center discharge outlet 19 for the cell bank. The bottom of the U-shaped spacers 20 slopes toward the center slot 23 so that the amalgam dripping from the ctahode surfaces will flow into the center discharge slots 23. The spacer 21} in Fig. 6 is shown as it appears when viewed from the right-hand side of Fig. l.

The cathode plates 25 may be formed of any perforated material which is wetted by mercury and will withstand the electrolysis conditions. It is preferable, however, to use a rolled Wire screen such as illustrated in Fig. ll. 1 have found that a rolled steel wire screen, having 4 wires per linear centimeter and a wire size of 2 mm., forms a cathode surface which is highly dependable in its capability for amalgamation and is of sturdy construction and easy to assemble. Obviously other forms of cathode supports and cathode plates, such as described later herein, and other sizes of wire or flat perforated plates, or other mesh characteristics may be used. In the form of construction illustrated in Fig. 11, the mercury amalgam flowing over the screen 25 gathers in pockets along the tops of the horizontal wires 25a, and particularly at 25c, where the vertical Wires 25b cross the horizontal wires. The horizontal wires thus constitute hold-back means while the holes in the screen provide through communication between the amalgam films on each side of the cathode base plate which tend to hold or rivet the mercury films on the cathode base plates. The bottom of the cathode plates 25 is sloped similar to the slope of the bottom of the spacers 20, and the plates 25 extend substantially to the bottom of the spacers 20, so that the bottom of the cathode plates extend into and make electrical contact with the amalgam flowing above the sloping bottom of the spacers 20 at all times.

The amalgam is distributed to the cathode plates 25 from a manifold 26 running along one side of the cell bank. Headers 27, which may be copper clad steel pipes slitted along their center line, spread the amalgam from side to side of the plates 25 and it trickles through slots 27a in the bottoms of the headers 27. A plastic sheath 28, of Plexiglas or the like, surrounds the headers 27 and extends downward along the cathode plates 25 into the cathode compartment to below the electrolyte level in the cell to cause the amalgam to spread onto the cathode plates.

The plates 25 extend above the headers 27 and into a machined slot 29 (Fig. 9) in connectors 30 which connect the cathode plates to the negative bus bar B. A cover 32 of Plexiglas or other suitable material, preferably integral with the sheaths 28, is secured to the cathode plate assembly and rests in slots 10b in the top of the anode frames 10. The covers 32 seal the tops of the cathode compartments. When a cathode assembly is removed from a cell bank for inspection or repair the cover 32 moves with the cathode assembly. When in place, the covers 32 may be sealed around the edges by any suitable sealing compound. By this arrangement, the cathode plates are freely suspended in the cathode compartments and may be removed and reinserted therein without disassembling the anode frames or the filter press assembly.

When the anode and cathode frames are assembled as described, the space between the graphite anode bars 14 and the diaphragms 17 may be filled with small lumps of graphite 35, which may be introduced through holes 36 in the top of the anode frames 10, suitable plugs being provided to close the holes 37 when the cell is in operation. The chlorine ions migrating toward the anode bars will discharge on these loose graphite lumps before reaching the anode bars, which will thus be saved from oxidation side reactions, While the loose graphite lumps consumed by such oxidation may be easily replaced by adding more granular graphite lumps 35 through the holes 36. In place of granular graphite lumps 35 other loose granular conducting material such as magnetite or the like may be used. In this way, the gap between the anode and cathode may be kept substantially constant. It will be obvious, however, that the granular packing 35 may be omitted and the chlorine ions discharged directly on the anode bars 14, or that block graphite anodes of the type normally used in horizontal mercury cells may be used in the anode compartments.

In the operation of a cell bank of the type described, fresh brine flows into the passages 11 from the line 40 and is distributed to the anode compartments through the openings 11a, passages 13 and openings 13a. Spent brine and chlorine or other product gas flow from the passages 12 into the discharge conduit 41 to the chlorine or product gas recovery system. Mercury amalgam flows through the manifold 26 and into the various headers 27 from which it flows beneath the plastic sheaths 28 and down the cathode plates 25, drips into the amalgam pool on the sloping bottom of the spacers 20 and flows into the slots 23, through the ducts 18 in the anode frames and out of the opening 19 in the center anode frame to the conduit 42 leading to the decomposer.

Current flows from the positive bus bar A, through the anode bars 14 and granular packing 35 (if a granular packing is used), and through the brine to the mercury amalgam flowing along the cathode plates 25, which are connected with the negative bus bar B. Electrolysis of the brine takes place in the usual manner of electrolytic mercury cells with chlorine being released at the anodes and sodium migrating to the cathode, where it is amalgated with the mercury flowingalong the cathode plates. The diaphragms 17 keep the chlorine from escaping into the cathode compartments and keep the granular packing (if used) in position around the anode bars 14. While the cell of Fig. 1 has been shown as a single cell with a positive bus bar along one side and a negative bus bar along the other side for simplicity of illustration, it will be understood that in practicea plurality of these cells will be connected in series.

' While I prefer to feed fresh brine into the anode compartments from the passages 11 as illustrated and described above, it is also possible to feed the fresh brine to the cathode compartments instead of to the anode compartments. In this case, openings are provided from the passages 21 of the cathode frames into the cathode compartments. Brine, after going through the diaphragms 17, reaches the anode compartments and from there flows with chlorine, or other product gas, through holes 12a and passages 12 into the discharge conduit 41, as described above. By this type of circulation, the flow of fresh brine towards the anode compartments prevents the diffusion of anode products into the cathode compartments.

The amalgam flows from the center discharge outlet 19 through the conduit 42 to a reservoir 4212 which discharges into the well of pump 43 (Fig. 12) driven by a suitable motor 44. The reservoir 42a is locatedsufliciently above the level of the bottom of the cells 1 to maintain a layer of amalgam at the desired level in the cell to maintain contact with the bottoms of the cathode plates 25 and prevent brine from flowing out of the amalgam outlet. The pump 43 pumps the mercury amalgam, received from the reservoir 42a, through the conduit 45 to a header 46 from which part of it flows through the line 47 to the amalgam reservoir 48, which feeds amalgam to the manifold 26, and another part flows into the decomposer 49 where it is decomposed by water in contact with a suitable catalytic mass in a manner well known in the industry to produce sodium hydroxide, and the sodium-depleted amalgam flows from the line 50 back into a reservoir 50a and then into the well of the pump 43. The depleted amalgam which is fed back to the well of pump 43 dilutes the concentrated amalgam flowing from the cell bank. By the use of suitable valves (not shown) in the header 46, the amount of the amalgam passed to the cell banks is controlled so as to keep the content of the amalgamating metal within the range which promotes wetting and adherence to the cathode plates on first coming in contact therewith. As stated previously, the amount of sodium in the amalgam returned to the cells is preferably .0l% or more but may vary between .002 and .2%.

The mixing of the amalgam flowing out of the cell bank through the conduit 42 with the depleted amalgam flowing from the decomposer 49 provides a sufliciently rich amalgam for operation of the cell bank, and in the operation of the cell, amalgam adheres better to the cathode plates 25 than pure mercury would adhere. At the same time, the fact that the amalgam does not need to be as completely decomposed, as in the operation of a horizontal type mercury cell, in order to provide relatively pure mercury for the cathode, permits the use of smaller decomposer units and greater efliciency in the decomposition.

In practice, the amalgam discharged through the conduit 42 from a cell bank used for the electrolysis of sodium chloride, to produce chlorine and caustic soda, normally contains between .1% and 2% of sodium and the amalgam fed to the cell bank may contain from 002% to .2% of sodium. I have found, however, that a minimum sodium content of about .Ol% in the mercury amalgam fed to the cells is desirable in order to promote adherence of the mercury layer to the cathode plates 25, whereas in the operation of a horizontal mercury cell it is considered undesirable to feed mercury containing over .00l% of sodium to the cells.

As'will be obvious to persons skilled in the art, the principles of this invention may be applied in other ways and to other forms of electrolytic cells than the cells illustrated in Figs. 1 to 12.

Figs. 13 and 14 illustrate somewhat diagrammatically the application of my invention to a Hooker-type electrolytic cell. In this embodiment, the cell is enclosed in a housing 51, mounted in a suitable base 52 ,and the anodes 53 are embedded in a conducting base 54 of lead, or the like, which is connected to the positive side of bus bar at 55. Mercury amalgam flows into the housing 51 through the manifolds 56, and is distributed by the headers 57 to the cathode plates 58 in a manner similar to that illustrated in Fig. 9. Diaphragms 58a,'extending over the top of headers 57- and down the sides of cathode plates 58, separate the anode compartments from the cathode compartments in the manner described in connection with Figs. 1 to12. Fresh brine enters the cell at 59 and spent brine flows out at 61}, chlorine escapes to the top of the cell and flows out of the opening 61, while the amalgam flowing down the cathode plates flows along the sloping bottom of the cell to an amalgam outlet 62 and from there to a decomposer. Negative bus bar connections are made at 63 to the amalgam manifolds 56. A mastic insulation 64 covers the conducting base 54 between the anodes 53 and is shaped to provide troughs 65 into which the amalgam flows from the cathode 58 to the amalgam outlet 62. Vents not shown in the drawings are provided for the escape of hydrogen or other gases which may collect in the cathode compartments. The operation of this embodiment of the invention is similar to the operation of the embodiment illustrated in Figs. 1 to .12.

In the modifications illustrated diagrammatically in Figs. 15, 16, 17 and l8, the cell, which is similar to the Nelson diaphragm cell, is enclosed in a housing 70 formed of side members 71 and U-shaped member '72 suitably secured together. Anodes 73, with slots 74a as indicated in Fig. '16 for the escape of chlorine, suitably enclosed in diaphragms 73a, are supported in the housing 70 and provided with connectors 74 for connection with a positive bus bar. The connectors 74, which are preferably made of graphite, are fixed to the tops of the graphite anodes 73 as illustrated in Figs. 17 and 18. Cathodes 75, of perforated wire screen or other perforated metal construction, receive amalgam from a header 76. Fresh brine enters the cell through the pipe 77 and spent brine flows from outlet 78. Chlorine flows out through inverted U-shaped outlets 79 and the mercury amalgam flows out through outlet 80. A suitable mercury level is maintained in the cell as previously described. The operation of this cell is the same in principle as the operation of the cell described in greater detail in connection with Figs. 1 to 12.

In another form of construction illustrated in Figs. 19, 20 and 21, the cathode compartment consists of a rectangular frame 81 having a passage 82 in one lower corner for the flow of the diluted amalgam therethrough. From the passage 82 the diluted amalgam flows into each cathode compartment through a distributor 83 in the 5 bottom of eachcathode compartment which is provided with a plurality of holes 83a for distributing the diluted 'j amalgam to a series of vertical metal pipes 84 constituting the cathode support of which only some are shown in Fig. 119. The amalgam overflows through openings 85 of pipes 84 and flows downwardly along said pipes to the bottom of the cathode frame which is provided with a slot 86 which registers with the ducts 1 8 in the bottom of the anode frames (Fig. 3) to permit the amalgam to flow from the cathode compartments to the center discharge outlet 19 for the cell bank. The bottom of the cathode frames 81 slopes towards the .center slot 86 as in the case of cathode frames illustrated in Fig. 6. If desired, the pipes 84 may be located sufliciently close 9 together so that the amalgam will spread from one pipe to another to maintain a substantially unbroken sheet or film of amalgam between the pipes, although this is not necessary for the operation of this embodiment of my invention.

The cathode compartments are provided with passages 87 for the fresh electrolyte, passages 88 for the spent electrolyte and product anode gas and passages 89 for the product cathode gas. When this type of cathode supports is used, the anode frames are provided with passages for the diluted amalgam and the product cathode gas which register with the

ducts

82 and 89 of the cathode frames. The cathode frames are made of steel or other metal and protected against corrosion on the surfaces exposed to corrosive conditions by rubber lining or the like. Connectors 90 are provided to connect the cathode supports and the amalgam to the negative bus bar in a similar way as illustrated in Fig. l. The cathode frames 81 are provided with rabbets 91 around each inner edge to fit with the corresponding rabbets 10a provided around each inner edge of the anode frames 10, as illustrated in Figs. 9 and 10, and to hold the diaphragms l? in place when the cell is assembled.

While a preferred embodiment of the invention and some modifications thereof has been illustrated and described, it will be understood that various other modifications and changes may be made Within the spirit of the invention and the scope of the following claims.

I claim:

1. In an electrolytic cell, a substantially vertical perforated metal plate cathode support, a flowing film of mercury amalgam on said support forming a cathode, an anode parallel therewith, a diaphragm between the anode and the cathode, surrounding fluid-tight walls enclosing said cathode and anode, means to flow a mercury amalgam downwardly over said cathode support, comprising an amalgam distribution header spaced on each side of said perforated metal plate cathode support and extending from side to side of said plate and means to protect said amalgam from contact with all gases between the point Where it leaves said header and enters the electrolyte, means to flow an electrolyte through said cell, means to maintain a substantially constant level of electrolyte in said cell means to vent gases therefrom, and means to impress an electrolysis current between said anode and said cathode.

2. In an electrolytic cell, a substantially vertical perforated rolled flat metal screen cathode support, a flowing film of mercury amalgam on said support forming a cathode, an anode parallel therewith, a diaphragm between the anode and the cathode, means enclosing said anode and cathode in a fluid-tight enclosure, means to flow a mercury amalgam downwardly over said cathode support, comprising a slotted metal header pipe, through which said rolled metal screen cathode support extends, the spaces between said slotted metal header pipe and said screen cathode support forming slits through which amalgam flows over the surface of said cathode support, a plastic covering surrounding said header pipe and extending downward on each side of said metal screen cathode support and adjacent thereto to below the electrolyte level in said cell, means to flow an electrolyte through said cell, means to maintain a substantially constant level of electrolyte in said cell, means to vent gas therefrom, and means to impress an electrolysis current between said anode and said cathode.

3. In an electrolytic cell, a plurality of substantially vertical metal cathode supports, an anode on each side of each cathode support and parallel therewith, a diaphragm between each anode and each cathode support, means forming a fluid-tight enclosure around said anodes and said cathode supports, means to flow a mercury amalgam downwardly over each side of each of said cathode supports to form a cathode, comprising a plurality of slotted metal header pipes through which said cathode supports extend, the spaces between said metal 1O cathode supports and said slotted metal header pipes forming slits through which amalgam flows over the surface of said cathode supports, means to protect said amalgam from contact with all gases between the point where it leaves said header and enters the electrolyte, means to flow an electrolyte through said cell, means to maintain a substantially constant level of electrolyte in said cell means to vent gases therefrom, and means to impress an electrolysis current between each of said anodes and its adjacent cathode.

4. In an electrolytic cell, a plurality of substantially vertical perforated metal plate cathode supports, an anode on each side of each cathode support, a diaphragm between each anode and each cathode support, means forming a fluid-tight enclosure around said anodes and the operative surface of said cathode supports, means to maintain a substantially constant electrolyte level in said cell, means to flow a mercury amalgam downwardly over each side of each of said cathode supports comprising an upwardly extending portion of said metal plate cathode supports, an amalgam distributing header spaced on each side of said upwardly extending portion of said cathode supports, a plastic covering surrounding said header and extending in close adjacency to said cathode support to below the electrolyte level, means to how an electrolyte through said cell, means to vent gas therefrom, and means to impress an electrolysis current between each of said anodes and its adjacent cathode.

5. In a vertical mercury electrolysis cell of the filterpress type, a plurality of substantially rectangular open anode frames, a brine inlet conduit adjacent one corner of each frame, a brine outlet conduit adjacent the diagonally opposite corner of each frame, means to support a diaphragm on each side of each anode frame, anodes in each anode frame, a cathode spacer element between each of two adjacent anode frames, conduits in said cathode spacer elements corresponding with said brine inlet and outlet conduits in said anode frames, a metal cathode support in each cathode spacer element, means to secure said anode frames and cathode spacer elements together in fluid-tight relationship with said conduits in registry to form brine inflow and outflow passages along the entire cell, a diaphragm bet-ween each anode frame and each cathode support, means to flow mercury amalgam downward over each cathode support, comprising a slotted metal header pipe above each cathode spacer through which each cathode plate extends and means to protect said amalgam from contact with all gases between the point where it leaves said header and enters the electrolyte, means to flow mercury amalgam from the bottom of each cathode spacer element, means to flow brine into each anode frame from said brine inlet conduit, means to flow brine out of each anode frame, means to maintain a substantially constant level of electrolyte in said cell electrical connections to each of said anodes and cathodes, and means to cause an electrolysis current to flow through the electrolyte between each anode and its adjacent cathode.

6. In a vertical mercury electrolysis cell of the filterpress type, a plurality of substantially rectangular open anode frames, a brine inlet conduit adjacent one corner of each frame, a brine outlet conduit adjacent the diagonally opposite corner of each frame, anodes in the rectangular opening of said frames, a diaphragm on each side of each anode, a U-shaped cathode spacer element between each of two adjacent anode frames, conduits in said cathode spacer elements corresponding with said brine inlet and outlet conduits in said anode frames, a perforated fiat metal plate cathode support in each cathode spacer element and extending above the top thereof, means to secure said anode frames and cathode spacer elements together in fluid-tight relationship with said conduits in registry to form brine inflow and outflow passages along the entire cell, means to flow mercury amalgam downward over each cathode plate comprising 11 a slotted metal header pipe above each cathode spacer through which each cathode plate extends and a plastic covering surrounding said each header pipe and extending downwardly adjacent to each side of said cathode plates to below the top of said cathode spacers and carrying closing member for closing the top of said U-shaped cathode spacer elements, means to flow mercury amalgam from the bottom of each cathode spacer element, means to flow brine into each anode frame from said brine inlet conduit, means to flow brine out of each anode frame, means to maintain a substantially constant level of electrolyte in said cell electrical connections to each of said anodes and cathodes, and means to cause an electrolysis current to flow through the electrolyte between each anode and its adjacent cathode.

7. In a vertical mercury electrolysis cell of the filterpress type, a plurality of substantially rectangular open anode frames, a brine inlet opening adjacent one corner of each frame, a brine outlet opening adjacent the diagonally opposite corner of each frame, and passages through said anode frames communicating with said inlet and outlet openings, a plurality of cylindrical anode rods in the rectangular opening of said frames, means to support a diaphragm on each side of each anode frame, granular electrical conductive packing between said anode rods and said diaphragms, a cathode spacer element between each of two adjacent anode frames, passages in said cathode spacer elements registering with the passages through said anode frames, metal cathode supports in each cathode spacer element, means to secure said anode frames and cathode spacer elements together in fluid-tight relationship with said passages in registry, means to flow mercury amalgam downwardly over each cathode support to form a cathode, means to flow mercury amalgam from the bottom of each cathode spacer element, means to flow brine into and out of said anode frames, electrical connections to said anodes and cathodes, and means to cause an electrolysis current to flow through the electrolyte between each anode and its adjacent cathode.

8. In a vertical mercury electrolysis cell of the filterpress type, a plurality of substantially rectangular open anode frames, a brine inlet opening adjacent one corner of each frame, a brine outlet opening adjacent the diagonally opposite corner of each frame and passages through said frames communicating with said inlet and outlet openings, a plurality of cylindrical anode rods in the rectangular opening of said frames, means to support a diaphragm on each side of each anode frame, granular electrical conductive packing between said anode rods and said diaphragms, a U-shaped cathode spacer element between each of two adjacent anode frames, passages in said cathode spacer elements registering with the passages through said anode frames, a perforated flat rolled metal screen cathode plate in each cathode spacer element and extending above the top thereof, means to secure said anode frames and cathode spacer elements together in fluid-tight relationship with said passages in registry, means to flow mercury amalgam downwardly over each cathode plate comprising a slotted metal header pipe above each cathode spacer element through which the upwardly extending portion of each metal screen cathode plate extends and a plastic covering surrounding each header pipe and extending downward on each side of each cathode plate to below the top of said cathode spacer elements, means to flow mercury amalgam from the bottom of each cathode spacer element, means to flow brine into and out of said anode frames, electrical connections to said anode rodsandtsaid cathodes, and means to cause an electrolysis current to flow through the electrolyte between each anode and its adjacent cathode.

9. In a vertical mercury electrolysis cell of the filter press type, a plurality of substantially rectangular open anode frames, a brine inlet opening adjacent one corner of each frame, a brine outlet opening adjacent the diagonally opposite corner of each frame and passages through said frames communicating with said inlet and outlet openings, a plurality of cylindrical anode rods in the rectangular opening of said frames, a brine distributor along the bottom of each anode frame and openings in said brine distributors between each anode rod, means to support a diaphragm on each side of each anode frame, granular electrical conductive packing between said anode rods and said diaphragms, a U-shaped cathode spacer element between each of two adjacent anode frames, passages in said cathode spacer elements registering with the passages through said anode frames, a perforated flat rolled metal screen cathode plate in each cathode spacer element and extending above the top thereof, means to secure said anode frames and cathode spacer elements together in fluid-tight relationship with said passages in registry, means to flow mercury amalgam downwardly over each cathode plate comprising a slotted metal header pipe above each cathode spacer element through which the upwardly extending portion of each metal screen cathode plate extends and a plastic covering surrounding each header pipe and extending downward on each side of each cathode plate to below the 'top of said cathode spacer elements, means to flow mercury amalgam from the bottom of each cathode spacer element, means to flow brine into and out of said anode frames, electrical connections to said anode rods and said cathodes, and means to cause an electrolysis current to flow through the electrolyte between each anode and its adjacent cathode.

10. As an article of manufacture, a mercury cell for the manufacture of chlorine and other purposes comprising two anodic end sections each having an anode compartment and means to seal said end sections with intermediate cathode sections having a cathode compartment, a plurality of intermediate anode sections each carrying an anode and each having means at each side to seal with a cathode section having a cathode compartment, a cathode section between each of said anode sections and a middle cathode section having an outlet for mercury therein, means to secure said sections together and to form a liquid-tight seal therebetween a diaphragm between each of said section, means to circulate mercury amalgam through the cathode sections, comprising a slotted metal header pipe, a flat metal plate cathode support having its upper end within said slotted header pipe and its lower portion within said cathode compartment, and a plastic covering surrounding said header pipe and extending downward adjacent to each side of said cathode support into said cathode compartment means to circulate an electrolyte through said cell, means to maintain a substantially constant level of electrolyte in said cell means to cause an electrolysis current to flow through said electrolyte from said anodes to said cathodes, means to remove chlorine from said cell, and means to flow spent electrolyte from said cell.

11. As an article of manufacture, a mercury cell for the manufacture of chlorine and other purposes comprising two anode sections each having an anode compartment and a cathode section having a cathode compartment, means to sealsaid anode sections with said cathode section therebetween, means to secure said sections together and to form a liquid-tight seal therebetween, a diaphragm between each anode and cathode, means to circulate mercury amalgam'through the cathode sections, comprising a slotted metal header pipe, a flat metal plate cathode support having its upper end within said slotted header pipe and its lower portion within said cathode compartment, and a plastic'covering surrounding said header pipe and extending downward adjacent to each side of 'said cathode supportinto said cathode compartment means to circulate an electrolyte through said anode sections, means to maintain a substantially constant level of 'an electrolyte in said cell means to cause an electrolysis current to flow through said electrolyte from said anodes to said cathodes, means to remove chlorine from said cell,

means to flow spent electrolyte from said cell, and means to remove the mercury amalgam fiom said cell.

12. In a vertical mercury electrolysis cell, a rectangular open anode frame, a rabbet around each inside edge of said frame, a diaphragm held in each rabbet, passages through diagonally opposite corners of said frame for the flow of electrolyte from one anode frame to the adjacent anode frame, said frame having an opening from each passage into the rectangular open portion of said anode frame, vertical openings through the top of said frame, anode connections extending through said openings and anodes in the hollow central section of said anode frame.

13. In a vertical mercury electrolysis cell, a rectangular open anode frame, a rabbet around each inside edge of said frame, a diaphragm held in each rabbet and extending across the open center of said frame, passages 1 through diagonally opposite corners of said frame, for the flow of electrolyte from one anode frame to the adjacent anode frame, said frame having an opening from each passage into the rectangular open portion of said anode frame vertical openings through the top of said frame, anode rods extending into said frame through said openings and a loose granular conductive packing between said anode rods and said diaphragms.

14. In a vertical mercury electrolysis cell, comprising a bottom and four sides, an amalgam distributor comprising a rolled metal screen cathode support plate extending above the top of said sides of said cell, a slotted metal header pipe through which said cathode support plate extends with approximately one half of said pipe on each side of said cathode plate support, an opening between the bottom of each one half of said pipe and said cathode plate support for the flow of amalgam therethrough and a plastic covering around said pipe adjacent to each side of said plate and extending down the plate into said cell.

15. In an electrolytic cell, a substantially vertical metal cathode support, a flowing film of mercury amalgam on said support forming a substantially vertical mercury cathode sheet, an anode parallel therewith, a diaphragm between the anode and the cathode, surrounding fluid tight walls enclosing said cathode and anode, means to flow a mercury amalgam downwardly over said cathode support, comprising an amalgam distributing header having a slot on the underside through which said cathode support extends forming slits on either side thereof to feed mercury amalgam to each side of said cathode support along the entire Width of said cathode support, means to protect said amalgam from contact with all gases between the point where it leaves said header and enters the electrolyte, means to flow an electrolyte through said cell, means to maintain a substantially constant level of electrolyte in said cell, means to vent gases therefrom and means to impress an electrolysis current between said anode and cathode.

16. In a vertical mercury electrolysis cell of the filterpress type, a plurality of substantially rectangular open anode frames, a brine inlet conduit adjacent one corner of each frame, a brine outlet conduit adjacent the diagonally opposite corner of each frame, means to support a diaphragm on each side of each anode frame, anodes in each anode frame, a cathode spacer element between each of two adjacent anode frames, conduits in said cathode spacer elements corresponding with said brine inlet and outlet conduits in said anode frames, a metal cathode support in each cathode spacer element, means to secure said anode frames and cathode spacer elements together in fluid-tight relationship with said conduits in registry to form brine inflow and outflow passages along the entire cell, a diaphragm between each anode frame and each cathode support, means to flow mercury amalgam downward over each cathode support, comprising an amalgam distributing header adapted to feed mercury amalgam to each side of said cathode support, means to protect said amalgam from contact with all gases between the point where it leaves said header and enters the electrolyte, means to flow mercury amalgam from the bottom of each cathode spacer element, means to flow brine into each anode frame from said brine inlet conduit, means to flow brine out of each anode frame, means to maintain a substantially constant level of electrolyte in said cell, electrical connections to each of said anodes and cathodes, and means to cause an electrolysis current to flow through the electrolyte between each anode and its adjacent cathode.

References Cited in the file of this patent UNITED STATES PATENTS 835,329 Snodgrass Nov. 6, 1906 1,738,372 Edgeworth-Iohnstone Dec. 3, 1929 1,970,975 Palmaer et al Aug. 21, 1934 2,226,784 Sorensen Dec. 31, 1940 2,544,138 De Nora Mar. 6, 1951 2,597,545 Taylor May 20, 1952 2,669,542 Dooley Feb. 16, 1954 FOREIGN PATENTS 204,518 Switzerland Aug. 1, 1939 16.358 Great Britain July 23, 1902

Claims

1. IN A ELECTROLYTIC CELL, A SUBSTANTIALLY VERTICAL PERFORATED METAL PLATE CATHODE SUPPORT, A FLOWING FILM OF MERCURY AMALGAM ON SAID SUPPORT FORMING A CATHODE, AN ANODE PARALLEL THEREWITH, A DIAPHRAGM BETWEEN THE ANODE AND THE CATHODE, SURROUNDING FLUID-TIGHT WALLS ENCLOSING SAID CATHODE AND ANODE, MEANS TO FLOW A MERCURY AMALGAM DOWNWARDLY OVER SAID CATHODE SUPPORT, COMPRISING AN AMALGAM DISTRIBUTION HEADER SPACED ON EACH SIDE OF SAID PERFORATED METAL PLATE CATHODE SUPPORT AND EXTENDING FROM SIDE TO SIDE OF SAID PLATE AND MEANS TO PROTECT SAID AMALGAM FROM CONTACT WITH ALL GASES BETWEEN THE POINT WHERE IT LEAVES SAID HEADER AND ENTERS THE ELECTROLYTE, MEANS TO FLOW AN ELECTROLYTE THROUGH SAID CELL, MEANS TO MAINTAIN A SUBSTANTIALLY CONSTANT LEVEL OF ELECTROLYTE IN SAID CELL MEANS TO VENT GASES THEREFROM, AND MEANS TO IMPRESS AN ELECTROLYSIS CURRENT BETWEEN SAID ANODE AND SAID CATHODE.