NO863296L - PROCEDURE FOR MANUFACTURING A UNIQUE ELECTRIC POWER TRANSMISSION ELEMENT FOR MONOPOLAR OR BIPOLAR FILTER PRESSURE TYPE ELECTROCHEMICAL CELL UNITS. - Google Patents

Description

The invention relates to a method for manufacturing

of a cell unit for one of the repeated units in a "bipolar" electrode series in electrolytic cells arranged in a form normally called filter press type cell series. Surprisingly, this invention also relates to a method for using practically the same cell unit as one of the repeated units in a "monopolar" electrolysis cell. Monoplar cells arranged in a filter press type mold are well known to those skilled in the art. What is not well known is the possibility of using a fluid-impermeable structural element, i.e. an electrical current transmission element in either a biplar or monoplar cell form. This is surprising because the various electrical current transmission characteristics necessarily required for an electrode used in a monopolar or bipolar cell device.

The structure of bipolar cells relates to cells which employ substantially hydraulically impermeable planar ion exchange membranes placed between substantially parallel perforated electrodes with flat surfaces, i.e. metal anodes and cathodes when the electrodes are mounted at a distance from the fluid impermeable structure that physically separates adjacent electrolysis cells. Such cells are particularly useful in the electrolysis of aqueous solutions of alkali metal chlorides, especially in the electrolysis of aqueous sodium chloride solutions. The cell structure can also be used by electrolysis of other solutions to produce products such as potassium hydroxide, iodine, bromic acid, persulfuric acid, hydrochloric acid, adiponitrile and other organic compounds produced by electrolysis.

Use of an electrical current transmission element in the present invention reduces the manufacturing cost of the ceile units, reduces the work required to

putting them together simplifies their manufacture, greatly reduces the warping of the components of a cell unit, and provides a much more stable cell structure than the similar previously known bipolar filter press type cells.

Reducing the warping of the components in a cell unit allows the cell to be operated more efficiently; i.e. produce more electrolysis products per electricity unit. Reducing the warp reduces the deviation from the construction of the span between the electrodes of each electrolytic cell. Ideally, this span is uniformly the same between the anode and the cathode in order to have a uniform current density spread between the electrode rafts. Among other things, structural warping causes deviations from this opening which causes some parts of the anode and cathode to be closer together than others. In these places, the electrical resistance is smaller, the electrical current flow is higher, and thus the electrical heating is greater. This electrical heating is in many cases sufficient to damage the membrane in these places. These places with unacceptably high electrical current concentration and high heat are called here "hot spots".

To avoid these heat spots, the cell structures have previously been constructed with larger than that. desired span between the anode and the cathode in each electrolysis cell.

This of course increases the cell operating voltage and reduces the cell's operating efficiency. Complex construction and manufacturing is another disadvantage of these cells.

Apart from the structures used for the end cells

in a bipolar cell series, the structures of the intermediate cells in the series are similar cell structural units pressed together. Examples of such cells operated in series see described in U.S. Pat. Patent No. 4,111,779; 4,017,375; 4,364,815; 4,111,779; 4,115,236; 4,017,375; 3,960,698; 3,859,197; 3,752,757; 4,194,670; 3,788,966; 3,884,781; 4,137,144 and 3,960,699.

Monopolar cells first differ from bipolar ones

cells in that each anode and each cathode of the cells in the series are electrically connected, respectively in parallel and not in an electrical series as bipolar cells are. I.e. that in a typical monopolar cell series, the anode of each cell is electrically connected through its cell edge structure to the same positive electrical energy supply source as each of the other anodes

in the cells in series, so that each anode has essentially the same absolute voltage potential. Likewise, catho-

it in each monopolar cell connected through its cell's edge structure to the same negative electrical energy supply source as each of the other cell cathodes in the series, so that each cathode in the monopolar cell series has essentially the same absolute voltage potential. Although the cells in a monopolar form are thus physically arranged in a face-to-face series form, they nevertheless have their like electrodes connected in an electrically parallel form. A monopolar unit cell can be called a stack or a series. Two or more monopolar cell assemblies can be electrically connected in series. Conversely, the electrodes in a bipolar cell series are connected in an electrical series arrangement instead of an electrical parallel arrangement. In a bipolar cell series, the positive electrical current-carrying conductor is only connected to the anode of one of the two end cells of the bipolar series, and the negative electrical current-carrying conductor is connected to the cathode of the other end cell located at the opposite end of the bipolar cell series . A big D.C. voltage potential is applied from a source to the conductors so that the electric current will pass from cell to cell in the bipolar cell series.

Two or more bipolar cell series can be electrically connected in parallel.

This different electrical connection arrangement forces a monopolar cell series to be different on

other ways from a bipolar cell series. E.g. serves a monopolar anode unit located in the inner part of a monopolar cell series as anodes for its.two adjacent cells. Likewise, the internal monopolar cathode cell unit acts as cathodes for two adjacent cells.

Further description of the monopolar electrodes used

in a filter press type series of electrolytic, cells are provided in the U.S. Patent No. 4,056,458 and U.S. Patent No. 4,315,810.

Both of these patents describe the use of one structure type

to carry a monopolar cell unit and they indicate the use of other structures (multiple conductor rods or .rails) to for-

share electricity from an electrical source that is located

outside the cells to monopolar electrode elements inside the cell. Other complications in the monopolar cell series which may require many parts and many connections can be found in a study of these two patents.

The present invention enables the construction

of monopolar cell series that are very simple, very solid, yet economical to manufacture and operate.

The present invention relates to the manufacture and composition of electrolysis cell units which are used as repeated units in filter press type cell series. Such cell units include an electrical current transmission element (hereinafter referred to as an ECTE) comprising a general planar carrier portion, several lugs projecting from opposite sides of the carrier portion, and a frame-like flange portion that extends around the outer edges of the carrier portion. The ECTE is applicable to both monopolar and bipolar cell units. It is applicable in salt water electrolysis and in other electrochemical processes. Application of an integrally shaped electrical current transmission element in a monopolar or bipolar cell unit as a fundamental building block is a fundamental goal of the invention.

The invention lies particularly in a method of manufacturing an electric current transmission element useful as a main component in one of several repeated cell units located between two end-standing cells in a filter press type series of electrochemical cells, which method comprises the step of: forming the electric current transmission element from an electrically conductive metal in a mold, where the mold inside is shaped so that the transmission element has a planar support part, a frame-like flange part that goes around an outer edge of the planar support part which constitutes the outer limits of the electrode spaces which are located on opposite sides of the planar support part,

and a plurality of lugs projecting from opposite sides of the planar carrier portion, which electric current transmission element comprises an integrally formed, one-piece structural element, characterized in that the electric current transmission element is suitable for use in a monopolar or bipolar cell unit and

contains connection devices for at least one electric current carrying conductor arranged on the flat part or the flange part of the electric current transmission element, in which the connection devices are exclusively used for the end cells of a bipolar cell series or used for all cells in a monopolar cell series.

The preferred method for integrally forming a uniform ECTE is by sand casting of molten metal, preferably an iron (II) metal. Other methods for integrally forming a uniform ECTE are mold casting, powdered metal pressing and sintering, hot isostatic pressing, hot forging and cold forging.

Furthermore, it is within the scope of the invention to integrally shape a uniform or one-piece ECTE by using inserts, molds and cores. In fact, the specific placement of molds in specific metals has led to the surprising result that you not only get a smoother cast, but at the same time produce an ECTE with better electrical conduction properties. By doing so, these molds:: then turn into inserts of course.

In order to establish the definition, the meaning of molds, inserts and cores in metal structure forming will now be stated, as these terms are generally used in the field. Molds are objects that are placed in a mold and act as an aid when casting the part. Their primary purpose is to control the cooling rate of the molten metal at specific locations in the mold. By controlling the cooling of the molten metal, metal shrinkage can be more controlled. accurately and thereby improve part quality through reduced weaknesses and defects. Molds can, but do not have to become an integral part of the casting and can in some cases also act as inserts.

Inserts are objects that are placed in a mold to help the function of the mold, help shape the part, or that will become a functional part of the finished object. They retain their identity to varying degrees after the formation has ended. They are normally metallic, although other suitable materials may be used. Deposits can i

some cases also act as moulds.

Cores are objects that are placed in a mold and serve to exclude metal in unwanted areas of a casting. Cores are used in the mold where it would be impractical or impossible to form the mold in such a way as to avoid the unwanted metal. A typical example would be a core used to form

an internal cavity in a cast metal body. In some cases, cores can also act as molds.

The particularly useful molds which become inserts to increase the electrical conductivity of an ECTE are located across the planar carrier part and enter the lugs. Preferred . inserts or molds are made of a solid metal that has the mass of the metal of the molded ECTE around it. Preferably, the metal is shaped round

them formed by casting it into a molten state in a sand mold.

Cores can also be used to form openings that run all the way through the planar carrier portion of the ECTE in a monoplar cell unit to improve circulation. Such cores would have no appreciable advantage in a bipolar cell unit as long as the ECTE has at least one flange or pan on one of its sides to prevent mixing of anolyte or catholyte from adjacent bipolar compartments.

The procedure for composition of. the cell unit may further comprise the fitting of a suitable lining to one of the sides of the ECTE to protect the metal of the ECTE from corrosive attack by the electrolyte in which it is expected to be used.

The procedure for assembling the cell unit further preferably includes electrical and mechanical connection of plane-placed electrode components indirectly to each side of the ECTE by welding these electrode components to the fringing which itself is welded directly or indirectly through an intermediate metal wafer or coupon to the ECTE . These electrode components can be electrodes in themselves or they can be electrically conductive elements for further conduction of electricity to the actual electrodes themselves. Normally, the electrodes have a catalytically active metal deposited on them.

After the cell units are fabricated individually, they are shaped

then in a filter press type cell series by compressing them together with a hydraulic press, bolts, tension rods, etc.

The present invention is suitable for use with the newly developed solid polymer electrolyte electrodes. Solid polymer electrolyte electrodes are an ion exchange membrane with an electrically conductive material embedded in or bonded to the ion exchange membrane. Such electrodes are well known in the field and are e.g. described in the U.S. Patent Nos. 4,457,815 and 4,457,823.

In addition, the present invention is suitable for use as a zero aperture cell. A zero aperture cell is one in which at least one electrode is in physical contact with the ion exchange membrane. Optionally, both electrodes can be in physical contact with the ion exchange membrane. Such cells are described in U.S. Pat. Patent No. 4,444,639; 4,457,822 and 4,448,662.

Electrode components that can be used are preferably perforated structures that are essentially flat and can be made from a sheet of expanded metal perforated sheet, punched sheet or woven metal wire. Optionally, the electrode components can be current collectors in contact with an electrode. Electrodes may optionally have a catalytically active coating on their surface. The electrode components may be welded to the lugs or to the liner, if a liner is used. Preferably, the electrode components are welded because the electrical contact is better.

Other electrode components that can be used in connection with the present invention are current collectors, spacers, mats and other elements known to a person skilled in the art. Special elements or compositions for zero aperture shapes or solid polymer electrolyte membranes can be used. Also, the electrolytic units of the present invention can be adapted for a gas chamber for use in connection with a gas fumigating electrode, sometimes called a depolarized electrode. The gas chamber is required in addition to the liquid-electrolyte drums. A number of electrode components that can be used in the present invention are well known to the person skilled in the art and are e.g. described in the U.S. Patent No. 4,444,623; 4,350,452 and 4,444,641.

A better understanding of this invention will be

easier to obtain by mentioning its bipolar and monopolar aspects

separately as follows.

In forming and composing an improved unit cell used in forming a bipolar cell, the unit cell is separated from an adjacent unit cell by a separator such as a substantially hydraulically impermeable ion exchange membrane or a hydraulically permeable porous asbestos diaphragm, except in a chlorate cell where no separator is used when an alkali metal chloride (salt water), such as sodium chloride is electrolysed to the respective alkali metal chlorate, e.g. sodium chlorate. Although this invention also applies to cell units that use no separator between the anode and the cathode, it is nevertheless primarily referred to in connection with cell units that use permeability-selective ion exchange membranes to show where the membranes would go. The membranes are sealably placed between each of the cell units so that more cells are formed. Each of the cell units preferably, but not necessarily, has at least one flat membrane which delimits and separates the anolyte space from the catholyte space in each cell unit. The cell unit has an ECTE which physically separates the anolyte space in a cell unit located on one side of the ECTE from the catholyte space of an adjacent cell unit located on the opposite side of the ECTE. The ECTE has a planar placed perforated "flat plate" anode component located in its adjacent anolyte compartment and has a planar placed perforated "flat plate" cathode component located in its adjacent catholyte compartment. Both electrode component surfaces are substantially parallel to the membrane placed planarly between them and the ECTE. The ECTE has the anode component of the adjacent anolyte compartment electrically connected through it to the cathode component of the adjacent catholyte compartment.

The anolyte and catholyte compartments near the ECTE have a structure around their edges to terminate their physical boundaries. This cell unit also has an electrical current conductor associated with it to provide electrical current flow through the ECTE from its adjacent catholyte compartment to its adjacent anolyte compartment. This cell assembly includes spacer components to keep the anode and cathode of the two cells adjacent to the ECTE at predetermined distances from the ECTE.

The invention uses a castable metal as part of the ECTE which transfers electricity through the ECTE from the catholyte compartment to the adjacent anolyte compartment. Preferably, this metal is malleable iron (hereafter called wrought iron).

The ECTE is shaped in such a way as to provide the necessary structural integrity to physically support the adjacent electrolyte compartments when filled with electrolyte, as well as support the associated cell accessories.

The anode component spacer devices and the portion of the electrical current conductor located in the ECTE on the anolyte side of the ECTE are combined into several anode lugs that protrude a predetermined distance from the carrier portion of the ECTE in the anolyte space near the carrier portion. These anode lugs can be mechanically and electrically connected either directly or indirectly to the anode component through at least one compatible metal intermediate piece placed in a butt-like manner between the anode compartment and the anode lugs. Preferably, all the anode cams have flat end surfaces which preferably lie in the same geometric plane.

The cathode component spacers and that part of

the electrical current conductor located on the catholyte side of the planar carrier part is combined into a series of cathode cams which protrude a predetermined distance from the carrier part in the catholyte space near the carrier part. These cathode cams can be mechanically and electrically connected either directly or indirectly to the cathode component through at least one weldable compatible metal intermediate piece placed in a butt-like manner between the cathode component and the cathode cams. Preferably, all cathode cams have flat end surfaces which preferably lie in the same geometric plane.

The invention further includes anode cams which are separated in such a way that anolyte can circulate freely through the entirety of the otherwise unoccupied adjacent anolyte space, and likewise the cathode cams are separated in such a way that the catholyte can circulate freely through the entirety of the otherwise unoccupied

adjacent catholyte compartment.

Preferably, the material of the unit ECTE is selected from ferrous metals such as iron, steel, stainless steel or from nickel, aluminium, copper, chromium, magnesium, tantalum, cadmium, molybdenum, zirconium, lead, zinc, vanadium, tungsten, iridium , rhodium, cobalt, alloys of each and alloys thereof. Even better, the metal in the ECTE is selected from iron(II) metals whose primary constituent is iron.

The invention preferably includes an anolyte side lining made of a metal plate which is fitted over the surfaces of the anolyte space side of the ECTE which would otherwise be exposed to the corrosive environment of the anolyte.

Preferably, the metal in the anolyte side liner is resistant to corrosion of the anolyte and is formed with covers that fit over and around the anode lugs, the liner being connected to the flat ends of the anode lugs of the ECTE.

Preferably, according to the invention, the ring is also sufficiently pressed down around the separated anode cams against the flat carrier part in the spaces between the cams, so that free circulation of the anolyte is obtained between the cammed ECTE and the membrane of the adjacent anolyte chamber. Note that the liner replaces the ECTE surface near the anolyte chamber as one boundary in contact with the anolyte.

The metal liner is preferably connected to the anode lugs by welding, soldering, brazing or film forming, through a metal spacer which is placed between the lugs and the liner with the metal of the metal spacer weldably compatible with both the metal of the anolyte side liner and the metal of which the ECTE is made, i.e. weldably compatible with both metals to the point that it is capable of forming a solid solution with them by welding them after their welding.

The anolyte side lining is made of a metal selected from titanium, tantalum, niobium, hafnium, zirconium, alloys of each and alloys thereof.

Another way to connect an anolyte side liner to the ECTE when these metals are weldably incompatible is. that no metal spacer is used, but where the anolyte side ring is directly bonded to the anode nodes by explosion bonding or diffusion bonding.

In most cases, it is desired that the anolyte sidewall extends over the entire side surface of the anolyte space's edge-frame-like flange part of the ECTE so that a sealing surface is formed with this for the membrane when the cell segments are clamped together and form a cell series.

In most cases, it is desired that the anolyte side filter is connected to the ECTE at the ends of the anode branches. However, this invention includes connection of the liner to the sides of these lugs and also connection of the liner to the planar support portion between the lugs. Preferably, however, the anolyte side filter is welded to the ends of the anode lugs through an intermediate metal coupon or wafer.

A catholyte side deflation is required less often than an anolyte side deflation. However, there are cases such as in rooms with high caustic catholyte concentration, where a catholyte side discharge is required. Thus, this invention also includes a catholyte side shield made of a metal plate adapted over the surfaces of the ECTE which would otherwise be exposed to the catholyte of the adjacent cell. Preferably, the catholyte side coating is made of nickel.

Plastic firings can be used in some cases where electrical contact is provided from the cathode component to the cathode cams through the plastic. Combinations of plastic and metal fittings can also be used. The same applies to anolyte cidefferines.

The catholyte side deflation is sufficiently pressed down around the separated cathode cams against the plane carrier part in the spaces between the cams so that there is free circulation of the catholyte between the lined ECTE and the membrane of the adjacent catholyte chamber. Note that the liner replaces the ECTE surface near the catholyte chamber as one boundary in contact with the catholyte.

Unlike the anolyte side filter, it is not normally necessary for the catholyte side filter to be connected to the cathode cams through a metal spacer. Accordingly, it is preferred that the catholyte side lining is directly connected to the cathode lugs by welding without a metal spacer placed between the lugs and the liner. However, a metal spacer can be used. If this is the case, the metal spacer must be weldably compatible with both the metal of the catholyte side plating and the metal of which the ECTE is made.

The metal for the catholyte side coating is selected from iron (II) metals, nickel, chromium, magnesium, tantalum, cadmium, zirconium, lead, zinc, vanadium, tungsten, iridium, molybdenum, cobalt, alloys of each or alloys thereof.

In many cases it is desired that the metal in the ECTE, the catholyte side coating and in the cathode component of the adjacent cell are all selected from ferrous metals.

In some cases it is preferred to have the metal spacers located between the cathode lugs and the adjacent catholyte side discharge. The metal spacers are similar. which is discussed when attaching the anolyte side filter. However, in most cases the metal in the catholyte side coating can be welded directly to the planar carrier part without the need for a metal spacer.

The catholyte side filter is shaped so that it fits over

and around the ends of the cathode lugs and is welded directly on one side of the fringing to the lugs in such a way as to provide an electrical connection between the ECTE and the cathode component. The cathode component itself is directly welded to the opposite side of the cathode side liner.

As with the anolyte side filtration, it is preferred that the catholyte side filtration also extends over the side surface of the edge flange part of the catholyte compartment so that a sealing surface is formed at this for the membrane when the cell segments are pressed together to form a cell series.

In most cases it is desired that the catholyte side discharge is connected to the ECTE at the ends of the cathode cams. However, this invention includes connection of the wire to the carrier part between the lugs.

The present invention also provides a method for the manufacture and assembly of cell units for monopolar cells assembled in a filter press mold.

The ECTE for the monopolar cell unit is the same as that described above for the bipolar cell unit, with the exception that each monopolar ECTE also has means for electrically connecting it to an external power source. These devices can be added as a separate element

to the ECTE or may be integrally formed with it. Otherwise, the monopolar ECTE can have the same physical appearance as the bipolar ECTE and is made of the same metals. It is also made in the same way, e.g. by a simple casting to produce an integral unit of the carrier part, the edge flange and the electrode component lugs on opposite sides of the carrier part.

Of course, the lugs are on opposite sides of the carrier part

in the monopolar unit cell as opposed to the bipolar unit cell of the same type, i.e. the lugs on opposite sides are all anode lugs or they are all cathode lugs. They are not such that they will be anode terminals on one side and cathode terminals on the other side as in the case of bipolar cell units. The end cells for a monopolar cell series are end cell units where only one side requires an electrode component.

The single electrical polarity of the monopolar unit cell also forces the electrolyte space on both sides of the ECTE to be of the same type, i.e. these adjacent compartments will either both be anolyte compartments or they will both be catholyte compartments.

The ECTE is designed in such a way that you get structural integrity

to support the weight of the cell. It also provides the electrical current path to the two electrode components that are electrically connected on opposite sides of it if it is electrically connected as an anode or vice versa if it is electrically connected as a cathode.

They referred to liners for bipolar electrode cell units

are largely the same as those for monopolar electrode cell units. They may be similar in appearance and they may serve the same function of protecting the ECTE from electrochemical attack.

Of course, it differs from monopolar ECTE

the bipolar anolyte and catholyte side effects which are. discussed above where each ECTE had an anolyte side lining on one of its sides and. a catholyte side ring on the other hand, either ano-

listening side linings or catholyte side linings on both sides depending on whether the monopolar ECTE is to be used as an anode or as a cathode. Note that if the catholyte concentration is below approx. 22% at a temperature below approx. 85°C, it is not necessary to have a catholyte side filter. These monopolar anolyte and catholyte side rings are made of the same materials and by the same methods as those described above for the bipolar cell unit. The monopolar anolyte and catholyte side liners are also connected to the monopolar ECTE in the manner described above for their counterpart bipolar anolyte and catholyte side liners.

The monopolar electrode components are similar to those described for the bipolar electrode cell assembly described above and are connected in the same manner. Like the bipolar electrode components, the monopolar electrode components do not necessarily have to be electrodes themselves, since electrodes are defined as the place where the electrochemical reactions are initiated. The electrode components can be elements that themselves conduct electricity to the anodes and from the cathodes.

Nozzles are preferably a cast of titanium or nickel and of a shape that fits into channels or notches in the frame-like edge flange part.

Bipolar cells use both catholyte and anolyte nozzles, while monopolar cells use one or the other.

The invention can be better understood with reference to the drawings which illustrate the preferred embodiments produced by the method according to the invention, and where like reference numbers refer to like parts in different drawing figures. Figure 1 is a partially broken away perspective view of a bipolar electric current transmission element taken apart shown with the associated parts forming one bipolar filter press type electrode cell assembly; Figure 2 is a cross section of three bipolar filter press type cell units using the electrical current transmission elements. The cell units shown as they would appear in a filter press series; Figure 3 is a cross-section of a cell unit taken apart; Figure 4 is a partially broken away: perspective view of a monopolar unitary electric current transmission element and associated components forming one monopolar anode type filter press cell unit of a cell array taken apart; Figure 5 is a cross-section of three monopolar cell units shown in the same way as they would appear if they were taken as the three bipolar cell units of Figure 2 are taken, i.e. the cell units are shown in a filter press assembly showing a monopolar anode cell unit fitted between two identical monopolar cathode cell units;

Figure 6 is a cross-section of the cell unit used

in the formation of a monopolar anode cell unit manufactured according to the method of the present invention taken apart, which cross-section is taken along the line 8-8 of Figure 8 and which shows only such parts as are actually in contact with the image cross-sectional cutting plane taken along the line 8-8 of Figure 8 for not to obscure these elements by showing the other parts which are behind the image cross-sectional cutting plane and which are normally shown in a cross-section;

Figure 7 is a partially broken away elevational view of a monopolar cathode cell unit using elements made according to the method of this invention; Figure 8 is a partially broken away elevational view of a monopolar anode cell assembly using elements made according to the method of this invention; and Figure 9 is a cross-section of the cell structure used in forming a monopolar cathode cell unit produced according to the method used in this invention. from each other, the cross-section being taken along the line 11-11 in figure 7 and the image only showing such parts which are actually in contact with the image cross-section cutting plane taken along the line 11-11 in figure 7 in order not to obscure these elements by showing other parts which are behind image cross section cutting plane dg which

is normally shown in a cross-section.

Figures 1, 2 and 3 show a "flat plate" bipolar electrode type, filter press type electrolysis cell unit 10

using the preferred embodiment of an electric current transmission element (ECTE) 12 made according to the method of this invention.

In the preferred embodiment, ECTE 12 is made of cast wrought iron. It has one. compact planar carrier portion 14, a frame-like edge flange portion 16 extending laterally from opposite sides of the edges of carrier portion 14, projecting and spaced anode lugs 18, and projecting and spaced cathode lugs 20.

By having these parts all molded into a single unitary element, many problems are avoided or greatly reduced at the same time. E.g. greatly mitigates most warping problems, fluid leakage problems, electrical current misdistribution problems and complications in cell construction on a mass production basis. This simple cell construction makes it possible to construct ECTEs that are more reliable and that are constructed much more economically.

An anolyte compartment 22 of an adjacent cell can be seen on the right side of the ECTE 12. On the left side of the ECTE 12

one can see a catholyte compartment 24 of an adjacent cell unit. Thus ECTE 12 separates one cell from another. One very important feature of cells of this type is to conduct electricity from one cell to another. One very important feature of cells of this type is to conduct electricity from one cell to another as cheaply as possible.

On the anolyte compartment side of the ECTE 12 is a liquid impermeable anolyte side baffle 26 preferably made from a single sheet of titanium, although it may be made from two or more sheets. This ffiring 26 is hot-formed with a press in such a way that it fits over and substantially against the surfaces of the ECTE 12 on its anolyte space side. This is done to protect the wrought iron in the ECTE 12 against the corrosive environment of the anolyte compartment 22. Ffiring 26 also forms the left boundary of anolyte space 22, as an ion exchange membrane 27 forms the right boundary (as shown in figure 3). The ECTE 12 is molded so that its edge structure forms the frame-like flange portion 16 which serves not only as a carrier for the edge boundary of the anolyte compartment 22, but also as a carrier for the edge boundary of the catholyte compartment 24. Preferably, the titanium ring 26 is formed without stresses in it to provide a liner that atomically hydrogen cannot attack as quickly and give brittle, electrically non-conducting titanium hydrides. Atomic hydrogen is known to attack titanium with stresses faster. Avoidance of these stresses in the ring is achieved by hot forming the ring in a press at a higher temperature from 482°C to 704°C. Both the forming metal and the press are heated to this higher temperature before pressing the forming into the desired shape. The firing can be kept in the heated press for approx. 15 min. to prevent the formation of stresses in it as it cools. Other methods that can be used to form a liner can be vacuum, hydraulic, explosion, cold forming and other previously known methods.

The titanium anolyte sidewall 26 is connected to the wrought iron ECTE 12 by resistance or capacitor discharge welding. Such welding is achieved indirectly by welding the liner 26 to

the flat ends 28 of the cylindrically shaped, compact anode cams 18 through vanadium wafers 30 and titanium wafers 31 which are themselves welded to the vanadium wafers 30. Vanadium is a metal which is weldable in itself and which is weldably compatible with titanium and iron. Weldable compatible means that a joint with sufficient mechanical strength and electrical conductivity is formed. This is often done by welding two or more metals together so that they form a wrought iron solution. Titanium and iron are not weldably compatible with each other, but both are weldably compatible with vanadium. Consequently, the vanadium wafers 30 are used as a metal spacer between the iron anode cams 18 and the titanium fring 26 to achieve their welding together forming an electrical connection between the fring 26 and the ECTE 12, as well as to form a mechanical support device for the ECTE 12 to support the anolyte side defring 26. For better welding of a thin titanium ring 26 to the iron anode cams 18, the second wafer 31 which is made of titanium is welded to the outside of the vanadium wafers 30 before welding the ring 26 to the anode

the knobs 18 on the ECTE 12.

The preferred fit of the anolyte side liner 26 against the ECTE 12 can be seen from the drawing (Fig. 2). The liner 26

have undercut hollow covers 32 pressed into them. These covers 32 are conical in shape, but are hollow rather than compact as the anode lugs 18 are. The covers 32 are sized and spaced to fit over and around the anode cams 18. The covers 32 are sized in the recess depth so that their inner ends 34 abut the titanium wafers 31 after the titanium wafers 31 and vanadium wafers 30 have been welded to the flat ends 28 of the anode cams 18 The particular shape of these knobs and covers is not decisive. They could be square shaped or have any other suitable shape. However, preferably their ends 28 are all flat and preferably they all lie in the same imaginary geometric plane. In fact, the anode cams 18 and the covers 32 can be shaped and placed so that they lead the anolyte and gas circulation in the anolyte space 22.

The anolyte side deflation 26 is resistance or capacitor discharge welded at the inner ends 34 of its undercut covers 32 to the flat ends 28 of the anode lugs 18 through the interposed weldable compatible vanadium wafers 30 and titanium wafers 31.

Anode component 3 6 is a mainly flat plate of expanded metal, punched plate, metal strips or woven wire made of titanium. In this preferred embodiment, the anode component 36 has a catalyst coating containing an oxide of ruthenium. It is welded directly to the outside of the flat ends 38 of uncut wooden covers 32 in the side ring 26. These welds form an electrical connection and a mechanical support device for the anode component 36. Other catalyst coatings can be used.

Again, it should be emphasized that the anode component 36 need not be the anode itself, but it may contain a current-distributing planar surface which conducts electricity to the anode either directly or indirectly through a mat or other electrode elements.

In Figure 2, membrane 27 can be seen to be placed in a flat

plane between the anode component 36 of one cell unit 10 and the cathode component 46 of the next adjacent cell unit 10, so that the anolyte and catholyte space in the cell which is located between the planar carrier part 14 of each of two adjacent ECTEs 12 is strongly delimited.

Representative types of permeability-selective ion exchange membranes prescribed for use with structural

purely prepared according to this invention are those described in U.S. Pat. Patent No.: 3,909,378; 4,329,435; 4,065,366;

4,116,888; 4,126,588; 4,209,635; 4,212,713; 4,251,333; 4,270,996; 4,123,336; 4,151,053; 4,176,215; 4,178,218; 4,340,680; 4,357,218; 4,025,405; 4,192,725; 4,330,654; 4,337,137; 4,337,211; 4,358,412 and 4,358,545.

Of course, it is within the scope of this invention to use multiple cells using more than one membrane, e.g. a three-compartment cell with two membranes separated from each other so that they form a space between them, as well as the space formed on the opposite sides of each membrane between each. membrane and its respective adjacent unit cell 10.

The location of the anode 36 in the anolyte compartment 22 in relation

to the titanium-lined carrier part 14 is determined by the conditions between

lom the lateral extent of the flange part 16 from the carrier part 14, the extent of the anode cams 18 from the carrier part 14, thick-

the thickness of the vanadium wafers 30, the thickness of the anolyte side ring 2 6 oyl.. It can easily be seen that the anode space 36 can be moved by changing the extent of the anode lugs 18 from the carrier part 14. However, it is preferred that the flange part 16

on the anolyte side of the carrier part 14 extends the same distance as the anode lugs 18 from the carrier part 14. This contributes to simplifying the construction of the ECTE 12 because a metal processing planer can plan both end surfaces .28 of the anode lugs 18, as well as the side surface 16a of the flange part 16 simultaneously on a such a way that these surfaces all lie in the same geometric plane. The same preference applies to similar surfaces 16c on the catholyte side of the ECTE 12. Deviating from this preference can be used to create significant spacing between an electrode component and the membrane, e.g. to accommodate a mat

or to form an electrolytic opening.

For fluid sealing purposes between the membrane 27 and the flange surface 16a, it is preferred that the anolyte side lining 26 is shaped like a pan with a retracted lip 42 that goes around its edge. The lip 42 fits tightly against the side surface 16a of the flange part 16. The edge part of membrane 27 fits tightly against a first can lining strip 44 which itself fits against the side ffiring lip 42. A second edge lining strip 45 fits tightly against the other side of the edge part of membrane 27. a series of cells shown in Figure 2, the sealing strip 45 fits snugly against a retracted lip 72 on the catholyte side liner or against the side face 16c of the flange portion 16 on the catholyte side of the next adjacent ECTE 12 and snugly against the membrane 27 when there is no side facing 48. One can choose different sealing strips to possibly accommodate a mat or form an electrolyte opening.

Although membrane 27 is shown with two sealing strips 44, 45 on each of its sides around the edge portion, this cell construction allows the use of only one sealing strip on each side of the membrane.

Sometimes you want to have the side lining 48, but often

it is not necessary for it to be there. E.g. by electrolysis of sodium chloride salt water which produces caustic in the catholyte compartment with concentrations below approx. 22% at catholyte temperatures below approx. 85°C, a ferrous metal ECTE 12 would not normally require a nickel plating 4 8 to protect it from the catholyte. But for salt water electrolysis at catholyte temperatures above approx. 85°C and caustic concentrations above approx. 22%, a nickel plating 48 is normally required to protect the metal in the ECTE 12 against corrosion by the catholyte.

In figures 2 and 3, the catholyte side (the left side) of the ECTE 12 appears as a mirror image of its anolyte side in this most preferred embodiment. The flange part 16 forms the boundary edge of the catholyte space 24, while the catholyte side ring 48 and membrane 27 form the remaining boundaries. Separate cathode cams 20 may be compact, cylindrical or conical.Le-conical-shaped projections extending outwards from the carrier portion 14 in the catholyte space 24. The preferred cone glass truncations will closely approximate a straight cylinder. The shape of these cathode cams 20 is not critical. They are preferably flat at their ends 40,

and these ends 40 are preferably all in the same geometric plane. This also applies to the undercut covers 70

of the catholyte side ring 48 as discussed below. These cathode cams 20 and side firing covers 70 can be shaped and positioned so that they guide the catholyte and the gas circulation.

When a side ring is desired on the catholyte compartment side of the ECTE 12, it can be readily provided in the same manner as the anolyte compartment side ring 26. The catholyte side ring 48 is made of a metal that is highly resistant to corrosive attack from the catholyte in the catholyte compartment 24. The metal must also be sufficiently tough and machinable. to be able to be pressed from a simple sheet of metal in the non-planar shape shown. This includes being able to have the cone-conical shaped covers 70 pressed into the plate. Of course, these covers 70 must be spaced so as to fit over and around the spaced cathode lugs 20, as well as the other portions of the side of the ECTE 12 that would otherwise be exposed to the catholyte in compartment 24. It is preferred that this side fairing 48 has an incised lip 72 which goes around its edge in such a way as to abut against the side surface 16c of the flange portion 16 of

the side of the ECTE 12 which faces the catholyte space 24. The side ring 48 is preferably connected to the ECTE 12 by resistance or capacitor discharge welding of the internal ends 74 directly in a butted manner to the flat ends 40 of cathode lugs 20. I.e. this is preferable if the metal in the fringing 48 and the ECTE 12 are weldably compatible with each other. If these metals are not weldably compatible, metal spacers or combinations of metal spacers should

ker is used which is weldably compatible with the metal of the fringing 48 and the ECTE 12. Such spacers (not shown) are placed between the flat ends 40 and the internal ends 74. However, r~..z.no such spacers are necessary when The fringing 48 is made of nickel and the ECTE 12 is made of a wrought iron as is preferred.

It will be noted that both the anode component 36 and the cathode component 46 have their outer edges rolled inward toward the ECTE 12 and away from the membrane 27. This is done to prevent the sometimes jagged edges of these electrode components from contacting the membrane 27 and tear it up.

Cathode components are preferably a perforated, substantially flat sheet of nickel and are attached to the nickel side ring 48 by welding the cathode 46 to the outside 76 of the covers 70 formed in the side ring 48. In this preferred embodiment, the nickel cathode component 46 has a catalytic coating with itself and thus serves as a cathode in itself. It can be pressed against the membrane 27 in the same way as the adjacent titanium anode component 36 is pressed against the membrane so that there is practically no opening between the membrane 27 and its adjacent electrodes.

A preferred catalytic coating for nickel cathode component 4 6 is a heterogeneous mixture of nickel oxide and ruthenium oxide. A preferred method for depositing this coating is described in U.S. Pat. Patent Application No. 499,626 dated May 31, 1983. Of course, the nickel cathode component 46 could be without a catalytic coating, or the cathode component could simply be an electrical transfer means for electricity

which comes from the cathode formed by other elements (not shown) embedded in or pressed against the membrane.

Both the anolyte and catholyte drums 22 and 24 have inlet

and outlet devices for introducing raw materials and removing product gases and liquids. These inlet and outlet devices pass through the flange portion 16 of the ECTE 12. The preferred inlet and outlet devices are best illustrated by anolyte compartment outlet devices whose various parts (80-85 in Figure 1 and 180-185 in Figure 4). is shown. An open side channel 80 is formed in the flange portion 16 on its anolyte side;

an opening 81 is cut in the titanium side ring 26. Opening 81 in the side ring 26 coincides with the boundaries of channel 80. The nozzle 82 is then sealingly welded to. the opening 81 in the flange of the side ring 26 in such a manner. that the bottom of the nozzle 82 at least reaches the anolyte space 22 and the top of the nozzle 82

at least extends to the top of the flange channel 80 so that no anolyte products can contact the iron in the flange

the channel 80. Bolt ear holders 83 extend from the side of the nozzle 82 so that the nozzle 82 can be attached to the flange part 16 with bolts 84 screwed into drilled and threaded holes 85 formed in the flange part 16.

An anolyte compartment inlet (not shown) similar to the anolyte compartment outlet just described is formed on the anolyte bottom side of the flange portion 16. Catholyte compartment inlet and outlet devices (not shown) are formed in the same manner as the anolyte compartment outlet with the exception that inlet and outlet devices are formed in the flange portion on the catholyte side of the ECTE 12 and with the further exception that the catholyte nozzles are made of nickel instead of titanium.

The bipolar cell works as follows. The added salt water is continuously introduced into the anolyte space 22 through the anolyte space inlet, while fresh water or diluted caustic solutions can be introduced into the catholyte space 24 through the catholyte space inlet. Electrical energy (D-C.) is applied through the series of cells in such a way that the anode 36 in each cell is positive relative to the cathode 46 in that cell; i.e., the positive electrical conductor of the energy source is electrically connected to the anode of the last cell unit at one end of the cell series, and the negative electrical conductor of the energy source is electrically connected to the cathode of the last cell unit at the other end of the cell series. Disregarding depolarized cathodes or anodes, the electrolysis proceeds as follows. Chlorine gas is continuously formed at the anode 36, sodium cations are transported through membrane 2 7 to the catholyte compartment. Hydrogen gas and an aqueous solution of sodium hydroxide are continuously formed in the catholyte compartment 24. The chlorine gas and used salt water continuously flow from the anolyte chamber 22 through the anolyte chamber outlet, while hydrogen gas and sodium hydroxide continuously exit from the catholyte compartment 24 through the catholyte chamber outlet. Depolarized electrodes can be used to suppress the production of hydrogen or chlorine or both if desired.

The side fairings 26 and 48 can be formed from several plates which

are tightly welded together and form an impenetrable single

disc. This includes the ability to be pressed so that they have conically shaped covers 32 and 70. It should also be clear that the invention is not limited to the covers 32, 70 being conically shaped or limited to the anode and cathode cams 18 and. 20 which is cylindrical or cone-conical in shape. The ends 28 and 40 of the lugs 18 and 20 should provide sufficient surface area for electrical connections to their respective electrodes to provide an electrical path of sufficiently low electrical resistance. The lugs 18 and 20 should be separated so that they provide a fairly even and fairly low electrical potential gradient across the side of the electrode to which they are connected. They should be so separated as to allow free electrolyte circulation from any unoccupied point within their respective electrolyte space to any other unoccupied point within that space. Thus, the knobs will be fairly evenly separated from each other in their respective rooms. It should be noted here that although the anode and cathode cams 18 and 20 are shown in a back-to-back relationship on carrier part 14, they need not be this way.

They may be offset from each other.

The materials of which the anode and cathode cams 18 and 20 are made are preferably the same as in the ECTE 12, as part of this invention is to form them as an integral part of this cell element.

The metals of which the anolyte and catholyte sidewalls 26 and 48 are made are normally different due to the different electrolyte corrosion and electrolytic corrosion conditions to which they are exposed. This is true not only in chlor-alkali cell electrolytes, but also in other electrolytes. However, some materials may be useful in both electrolytes. Thus, the selected metals must be chosen so that. they fit the conditions to which they are to be subjected. Titanium is often the preferred metal for the anolyte drum ring 26.

The preferred embodiment of the monopolar cell unit produced by the method of this invention is. illustrated in Figure 4. Apart from the arrangement and location of these cell elements, the primary difference between them. and the bipolar cell units essentially their electrical connections

sharing devices. A further difference is that a bipo-

lar unit cell has its longest dimension oriented in the horizontal direction, while a monopolar unit cell has its longest dimension in the vertical direction. This longest dimension difference is only preferred, and is not critical for cells produced by the present invention.

Thus, it can be seen that the method according to this invention provides cell unit parts for the composition of a monopolar cell unit that can be used as a bipolar cell unit by simply repositioning the side plates and electrode components and providing all necessary electrical connections. The carrier portion not only provides the thickness to support the weight of any monopolar or bipolar cell unit, but it is also sufficiently thick (at least one centimeter) to provide a very low electrical resistance path for the monopolar cell units. This combination of features leads to a new, simple, replaceable ECTE

which is economical to manufacture, economical to assemble with other cell parts to produce either a monopolar or bipolar cell unit, which is economical to operate and which has a very long service life.

In the monopolar cell unit illustrated in Figure 4, the same reference numerals are used for like parts in the bipolar cell unit 10 in Figures 1-3.

In the monopolar anode cell unit. as illustrated in Figure 4, the unitary ECTE 12 is equipped with anode side filters 26 on opposite sides thereof which thus form the anolyte chambers on the opposite sides of the carrier part 14. The cell unit is further provided with anode components 36 and membranes 27 for in the essential to complement the structural components of the anode cell unit. If the cell unit is a cathode cell unit,

are the electrical connection devices such that ECTE 12

is made cathodic in that the electrodes on opposite sides of ECTE 12 are cathodes and form catholyte chambers on opposite sides of carrier part 14.

Of course they have monopolar anode and cathode ECTEs

an electrical connection device such as anode or cathode collector terminal 190. These connection devices are connected

to the flange portion 16. Otherwise, the primary important structural differences between monopolar and bipolar cell units are that in a bipolar cell unit one side has parts adapted for use in an anolyte environment, while the opposite side has parts adapted for use in a catholyte environment but in a monopolar cell unit,

both sides are adapted for the same electrolyte. However, if the parts are designed to be interchangeable between monopolar and bipolar cell units, all one has to do before assembling these parts is to determine the type of cell units desired in the particular cell series before assembling parts taken from the group of parts produced according to the method in this invention and consequently the method of composition of this invention.

Thus, when a monopolar anode cell unit for this invention is desired, a titanium side ring 26 is attached to each side of the ECTE 12 followed by the attachment of the anode 36 to each of the side rings. For cathode cell units for this cell series, a nickel side ring 4 8 is connected to each side of the ECTE 12 followed by the attachment of a cathode component 46 to each of the side rings 48.

Thus is a generic method of manufacture

and composition of a cell unit for each filter press cell series for both dei^Koriapsla^erxxj'bipolar filter press type of electrochemical cell series described.

The necessary step to complete the assembly of any filter press cell series is that the cell series be connected to electrical power. A bipolar cell series is formed by the connection of a positive electrical energy source conductor with one end of a cell series and a negative electrical energy source conductor with the other end of this cell series, as the potential difference between these two conductors is superimposed on the intermediate cell units in the series . A monopolar filter press type electrochemical cell series is completely defined when alternating cell units in the series are connected to a positive and a negative energy source. I.e. every other unit cell in a monopolar cell series will be connected to a positive electrical energy source with the other unit cells connected to a negative

electrical energy source.

Anode or cathode collector terminal 190 used to connect the energy source to the monopolar anode cell unit or monopolar cathode cell unit, respectively, are preferably integrally molded with their respective ECTEs 12, but need not be.

EXAMPLE 1

Four (4) electrical current transmission elements were cast for a nominal 61 cm x 61 cm monopolar electrolyzer.

All electrical power transmission elements were cast

of ASTM A536, GRD65-45-12 wrought iron and were similar in terms of as-cast dimensions. Finished castings were inspected and found to be structurally sound and without any surface defects. Primary dimensions were: nominal 61 cm x 61 cm external dimensions, a 2 cm thick carrier section, sixteen 2.5 cm diameter lugs located on each side of the carrier section and directly opposite each other, a 2.5 cm wide sealing device area 6.4 cm thick around the edge of the cell cast. Treated areas including sealing device sides (both sides parallel)

and the top of each knob (each side treated in a single plane and parallel to the opposite side). There were sixteen knobs on each side.

The cathode cell contained 0.9 mm thick protective nickel fringings on each side of the cell unit. Inlet and outlet valves, which were also constructed of nickel, were welded to the f fours before spot welding the f fours to the cell unit. Finished assembly included spot welding of catalytically coated nickel electrodes to the bushings at each cam point.

The distance between the planes of the ends of the lugs was 58.2 mm

for the monopolar cathode cell, which corresponds to the ECTE thickness. The total cell thickness from the outside of one nickel electrode component to the outside of the other nickel electrode component was 69.2 mm. Thus the ECTE thickness was 92%

of the total thickness.

The cathode end cell was similar to the cathode cell with the exception of

that a protective nickel plating was not required on one side,

as well as the lack of an accompanying nickel electrode.

The anode cell contained 0.9 mm thick protective titanium rings on either side of the ECTE. Inlet and outlet nozzles,

also constructed of titanium, was pre-welded to the frings before spot welding the frings to the ECTE. Finished assembly included spot welding of titanium electrodes to the ffirings by. each cam point through intermediate vanadium and titanium wafers.

The anodes were coated with a catalytic layer of mixed oxides of ruthenium and titanium.

The anode end cell was similar to the anode cell with the exception that a protective fSring was not required on one side, and the lack of an accompanying titanium electrode.

Claims (7)

1. A method of manufacturing an electric current transmission element useful as a main component in one of several repeated cell units located between two end cells of a filter press type series of electrochemical cells, which method comprises the steps of: forming the electric current transmission element from an electrically conductive metal in a mold, which shape has the inside so shaped that the transmission element has a planar carrier part, a frame-like flange part that goes around the outer edge of the carrier part that forms the edge boundaries for electrode spaces located on opposite sides sides of the carrier part, and several lugs projecting from opposite sides of the carrier part, which transmission element comprises an integrally formed, one-piece structural element, characterized in that the transmission element is suitable for use in a monopolar or a bipolar cell unit and contains connection devices for at least one electrical current-carrying conductor located on the carrier part or the flange part of the transmission element, in which the connection devices are used exclusively for the end cell units of a bipolar cell series or are used for each of the cell units in a monopolar cell series. 2. Method according to claim 1, characterized in that it includes the steps: forming a side facing for at least one side of the opposite sides of the electric current transmission element from at least one metal plate impermeable to and chemically non-reactive with the electrolyte to which it is to be exposed, which side facing is so shaped as to cover the side and substantially fits the shape of the electric power transmission element and has covers pressed into the side ring in such a way that the ring can be attached electrically and mechanically to the lugs on this side of the electric power transmission element by welding, and welding of at least several of the covers in the side fairing to the knobs. 3. Method according to claim 1 or 2, characterized in that it includes the step of welding the side firing to the lugs in the electric current transmission element through a metal intermediate piece placed between the lugs and the side firing, wherein the metal intermediate piece is a metal that is weldably compatible with both metals in the electric current transmission element and the side firing. 4. Method according to claim 1, 2 or 3, characterized in that the electric current transmission element is made of a ferrous metal, and the side ring is made of a metal selected from titanium and nickel. 5. Method for manufacturing and assembling a cell unit that can be placed between two end cells in a filter press type electrolysis cell series, which method comprises: (A) forming an integral compact cast of an electric current transmission element for the cell unit from an electrically conductive metal by pouring the molten metal into a mold, which mold has the interior so shaped that the electric current transmission element has: (1) a planar support portion, (2) ) a frame-like flange portion around the edge of the casting forming the outer boundaries of the electrode spaces located on opposite sides of the planar support portion, and (3) compact lugs projecting from opposite sides of the planar support portion; (B) removing the electrical current transmission element from the mold; (C) welding a substantially planar electrode component to the ends of the lugs, characterized in that the cell unit contains attachment devices for at least one electrically current-carrying conductor located on the planar carrier part or the flange part of the electrical current transmission element and is suitable for use in a monopolar cell series. 6. Method according to claim 5, characterized in that a) the side frame is attached to at least one side of the electric current transmission element between the transmission element and the electrode component and thereby the electrode component remains attached to the side frame instead of the transmission element. 7. Procedure for the manufacture and assembly of a cell unit that can be placed between two end cells in a filter press electrolysis cell series> which procedure includes: (A) forming an integral compact cast of an electrical current transmission element for the cell unit by pouring a molten electrically conductive metal into a mold, cooling the metal until it becomes sufficiently rigid to retain the shape given to it by the mold after it is removed from the mold , which shape has the inside so shaped that the transmission element has: (1) a planar carrier portion, (2) a frame-like flange portion around the outer edges of the carrier portion that forms the outer boundaries of the electrode spaces located on opposite sides of the carrier portion, and (3) compact lugs projecting outwardly from opposite sides of the carrier part; (B) removing the transmission member from the mold; (C) attaching a side shield to each side of the transmission member, which side shield has previously been formed from at least one metal plate impermeable to and chemically non-reactive with the electrolyte to which it is to be exposed and which is formed to cover the sides of the transmission member and shaped to substantially conform to the shape of the side of the transmission member, which side flange has recesses in the plate such that the recesses fit over the lugs, which connection of the side flanges to the sides of the transmission element is accomplished by welding at least half of the recesses to the lugs located on each side of the transmission element; (D) welding substantially planar electrode components to the ends of the recesses of the two side firings, and is characterized in that the cell unit contains attachment means for at least one electrically current-carrying conductor located on the planar carrier portion or the flange portion of the electrical current transmission element and is suitable for use in a monopolar cell series.