US3677927A - Electrolyzer - Google Patents

Abstract

AN ELECTROLYZER FOR THE ELECTROLYSIS OF BRINE IS DISCLOSED. THE ELECTROLYZER COMPRISES A PLURALITY OF ELECTROLYTIC CELLS MECHANICALLY AND ELECTRICALLY CONNECTED IN SERIES. THE CATHODES OF ANY INDIVIDUAL CELL IN THE ELECTROLYZER ARE FINGERS CONNECTED TO OPPOSITE INTERIOR SURFACES OF THE CELL. THE ANODES ARE BLADES MECHANICALLY CONNECTED TO THE BACK WALL OF THE CELL AND ELECTRICALLY CONNECTED TO THE CATHODES OF THE PRIOR CELL IN THE CIRCUIT.

Description

y 1972 c. w. RAETZSCH ETAL 3,677,927

ELECTROLYZER Filed Nov. 23, 1970 5 Sheets-Sheet 1 F G 1 INVENTORJ' CARL W. RAE 726 CH Hum; cuMWn/G/Mm ATTORNEYS c. w. RAETZSCH ETAL 3,677,927

July 18, 1972 Filed Nov. 23, 1970 5 SheetsSheet 2 (\J J k r INVENTORS CfiRL w. )EAETZSCH #06 Gamma/MM y 1972 c. w. RAETZSCH ETAL 3,677,927

ELECTROLYZER 5 Sheets-Sheet 4 Filed Nov. 23, 1970 INVENTORS mm W, ,eAerzscH HUGH C NI /M oHAM W W M ATTORNEYS July 18, mm

Filed Nov. 23, 1970 C. W. RAETZSCH ETAL ELECTROLYZER 5 Sheets-Sheet 5 llllllll! INVE NTOR S CARL w. PAETZxH HUGH CUNNINGHAM.

A ORNEYS' United States Patent O 3,677,927 ELECTROLYZER Carl W. Raetzsch and Hugh Cunningham, Corpus Christi, Tex., assignors to PPG Industries, Inc., Pittsburgh, Pa. Filed Nov. 23, 1970, Ser. No. 91,911 Int. Cl. B01k 3/10 US. Cl. 204-258 8 Claims ABSTRACT OF THE DISCLOSURE An electrolyzer for the electrolysis of brine is disclosed. The electrolyzer comprises a plurality of electrolytic cells mechanically and electrically connected in series. The cathodes of any individual cell in the electrolyzer are fingers connected to opposite interior surfaces of the cell. The anodes are blades mechanically connected to the back wall of the cell and electrically connected to the cathodes of the prior cell in the circuit.

BACKGROUND OF THE INVENTION This invention relates to diaphragm cells for the electrolysis of brines. Diaphragm cells are characterized by the presence of two electrolyte compartments. One is the cathode electrolyte compartment or catholyte compart ment. The other compartment is the anode electrolyte compartment or anolyte compartment. These two compartments are separated by a semi-permeable diaphragm, typically of asbestos.

Economies of construction and operation, especially at high current densities, for example above about 125 amperes per square foot, may be obtained by constructing a plurality of diaphragm cells in series in a common housing with the anodes of one diaphragm cell being electrically in series with the cathodes of the prior cell in the circuit. One method by which this may be accomplished is in an electrolyzer having a bipolar configuration. In general, bipolar electrolyzers are characterized by the anodes of one cell in the circuit not only being electrically in series with the cathodes of the prior cell in the circuit but also mounted on a common structural member therewith.

Bipolar electrolyzers, when operated at high current densities, for example above about 125 amperes per square foot of anode area, are subject to a variety of problems.

One problem is associated with the electrolytic generation of hydrogen on the cathodic surface of the common structural member or backplate. This electrolytic hydrogen may diffuse into and through the backplate, thereby affecting the structural integrity of the electrolyzer.

Another problem associated with bipolar cells are limitations on the inter-electrode gap. For example, in an electrolyzer having substantially planar, sheet-like, nonperforate anodes, the anodes must typically be spaced at least A" from the diaphragm in order to prevent erosion of the diaphragm.

Furthermore, in order to avoid gas blinding in bipolar electrolyzers, operating at current densities above about 125 amperes per square foot, electrodes are restricted to a height of about four feet.

SUMMARY OF THE INVENTION It has now been found that the problem of cathodic hydrogen penetrating the cathodic face of the backplate may be substantially eliminated by eliminating the cathodic surface of the backplate and connecting the cathodes to opposite surfaces (as the tops and bottoms) of the individual cells thereby conducting current from the cathodes of one cell to the anodes of the next adjacent cell through the side Walls, the top, and the bottom of the 'ice individual cell thereby making the side walls, top, and bottom cathodic. In this way the atomic hydrogen is vented directly to the atmosphere.

It has also been found that gas blinding and the problems associated therewith can be substantially solved by providing a raceway or an anolyte gas circulation space containing no electrodes and extending substantially the entire height and width of the individual cell. In this way electrolyzers having cells of substantially greater height and width can be provided.

It has further been found that the provision of a raceway or electrode-free anolyte gas circulation space results in a lower volume fraction of gas in the anolyte. This reduces the IR voltage drop across the anolyte, thereby reducing power costs and electrolyte heating.

DESCRIPTION OF THE INVENTION In the drawings:

FIG. 1 is an exploded perspective view of an individual cell of the electrolyzer.

FIG. 2 is a partial cut-away plan view of the electrolyzer of this invention.

FIG. 3 is a partial cut-away front view, along plane IIIIII of FIG. 2 of the electrolyzer of this invention.

FIG. 4 is a partial cut-away side View, along plane IVIV of FIGS. 2 and 3, of the electrolyzer of this invention.

FIG. 5 is a cut-away view of the vertical anodic plate of the electrolyzer of this invention along plane V-V of FIG. 4.

FIG. 6 is one anode that may be used with the electrolyzer of this invention.

FIG. 7 is another anode that may be used with the electrolyzer of this invention.

FIG. 8 is another anode useful with the electrolyzer of this invention.

FIG. 9 is an end view of an exemplification of this electrolyzer having a non-perforate conduit.

FIG. 10 is a partial cutaway View along plane XX of FIG. 2 of the rod compressive means.

An electrolyzer comprising a plurality of individual cells 11, 12, and 13, mechanically and electrically connected in series and having common structural members therebetween is shown in exploded view in FIG. 1 and in partial cut-away in FIGS. 2 and 4.

Each individual cell, as cell 12, has a cathodic structure comprising a conductive peripheral body 21. Within the peripheral body 21 is a foraminous peripheral wall 31. The foraminous peripheral wall 31 is mechanically and electrically connected to the peripheral body 21. The foraminous peripheral wall 31 is, however, spaced from the peripheral body 21, defining a conduit or channel 38 therebetween. Extending vertically from the top to the bottom of the foraminous peripheral wall are a plurality of hollow foraminous fingers 41 electrically and mechanically connected to the foraminous peripheral wall. The hollow fingers 41 are in mechanical communication with the channel or conduit 38 between the foraminous wall 31 and the peripheral body 21. The hollow foraminous fingers 41 or cathode fingers are substantially parallel to each other.

Each cell 12 also has an anodic structure. The anodic structure comprises a substantially vertical plate 51 which is mechanically connected to the peripheral body 21 but electrically insulated therefrom. The plate 51 has one surface 53 facing the anolyte and another surface 52 facing the catholyte of the next cell 11 in the electrolyzer. Either or both of the surfaces 52 and 53 may be electrically insulated. A plurality of anodes 55 extend from the plate 51. The anodes 55 are substantially parallel to and interleaved between the cathode fingers 41.

On the opposite side of the peripheral body 21 is the vertical plate 61 of the next adjacent cell 13 in the electrolyzer, with one surface 62 of the vertical plate 61 facing cell 12 and the other surface 63 of vertical plate 61 facing the next adjacent cell 13 in the electrolyzer.

The electrolyzer comprises a plurality (up to 25, 30, or even more) of cells 11, 12, and 13. Thus, while only three cells are shown in the figures, electrolyzers with any number of individual cells are included within the contemplation of the invention, the number of such units being theoretically unlimited and, in fact, limited only by economic considerations.

The structural unit of the individual cell 12 is the peripheral body 21. The peripheral body 21 has a horizontal top 22, a horizontal bottom 23, and vertical walls 24 and 25. The peripheral body may be fabricated of any material that is suitably electrically conductive. It may be fabricated of iron or steel or copper. Most commonly, steel will be used. Whenever steel is referred to, it will be understood that iron, copper, and any other electrically conductive material may be used interchangeably therewith.

The steel plate used in fabricating the peripheral mem ber 21 should be heavy enough to maintain the structural rigidity of the peripheral member 21 and have a great enough thickness to minimize the IR voltage drop through the structural member 21. For this reason steel plate having a thickness in excess of about inch is preferred for the walls 24, 25, top 22, and bottom 23 of the peripheral member 21.

Openings are provided in the peripheral member 21 for feeding brine 71, recovering the catholyte 72, recovering the gaseous cathode product 73, and recovering the gaseous anode products 74.

Those areas of the interior surface of the peripheral member 21 that are exposed to the anolyte may be coated or lined in order to prevent corrosion. Suitable linings 27 include rubber, polyesters, and fluorocarbons. Typically, rubber is used.

A foraminous peripheral wall 31 is provided. The foraminous peripheral wall 31 is typically fabricated of wire mesh screen. Most commonly steel is used. The mesh must be large enough to present a large fraction of open area for unimpeded migration of the alkali metal ions, but small enough to be impervious to the diaphragm during diaphragm depositing procedures. The wire mesh may be of any electroconductive metal suitable for use in a cathodic environment. A suitable material is 6 by 6 mesh inch doubled, crimped .092 inch diameter steel screen.

Alternatively, a perforate material may be used to provide the inner peripheral wall. Where a perforate material is used in lieu of a foraminous material, the perforations provide fiuid transfer between the conduit or chamber and the cathode fingers. In order to avoid the formation of chlorates or hydrogen within the anolyte, such a perforate wall may be lined with asbestos, rubber, or plastic on those surfaces exposed to the anolyte.

The foraminous wall 31 is substantially parallel to and spaced from the top 22 and bottom 23 of the peripheral member with the edges 32 of the foraminous wall bent or shaped so as to touch the peripheral member 21, thereby forming a conduit or channel 38 therebetween as shown in FIGS. 1 and 2. The foraminous wall is also substantially parallel to and spaced from the side wall 24 and 25 of the peripheral member 21, with the edges of the foraminous wall 31 bent or shaped so as to also touch the peripheral member 21, thereby also forming a conduit or channel 38 therebetween.

In lieu of an inner peripheral wall, a rubber or plastic coated pipe or conduit 34 may be provided as shown in FIG. 9. The pipe or conduit has means for communicating with the hollow cathode fingers, and means whereby the catholyte and hydrogen may be recovered.

Extending vertically from the top of the foraminous wall 31 to the bottom of the foraminous wall 31 are a plurality of cathode fingers 41. The cathode fingers 41 are substantially perpendicular to the top 22 and bottom 23 of the peripheral member 21, the vertical anodic plate 51, and the vertical insulated plate 61, and substantially parallel to the sides 24 and 25 of the peripheral member 21. The cathode fingers are substantially parallel to each other.

The pitch of the electrodes is the center-to-center distance between electrodes of like polarity measured parallel to the top 22, bottom 23, and vertical plates 51 and 61 of the cell 12, and perpendicular to the plane of the electrodes. The pitch between adjacent cathodes is from about 1 /2 inches to about 2% inches. The pitch will depend on the thickness of the anode blades 55, the thickness of the diaphragm 49, the thickness of the cathode finger 41, and the gap between the anode blade 55 and the surface of the diaphragm.

The cathode fingers 41 are fabricated from the same wire mesh as the foraminous peripheral walls 31. Each finger 41 may be fabricated from one or two sheets of mesh, with welding performed so as to obtain wire-to-wire joints. The cathode fingers 41 are welded to the foraminous peripheral wall 31 at the top and bottom of the individual fingers 41.

The interior width of the cathode fingers must be such as to allow for the movement of the catholyte and catholyte gases substantially without frothing. Satisfactory results are obtained with an interior width from about A inch to about inch. Steel plugs 43 are spaced at intervals along the height of the cathode between the sides thereof. These plugs 43 are welded to the sides. They provide added rigidity to the cathodes and prevent the collapse of the cathodes while pulling the diaphragm.

Electrical connection is provided between the conducting peripheral member 21 and the cathode fingers 41 by two methods. One is by the actual metal-to-metal contact between the conducting peripheral member 21 and the foraminous peripheral wall 31, and then by the actual metal-to-metal contact between the foraminous peripheral wall 31 and the cathode fingers 41.

Additionally, electrical current is conducted between the peripheral member 21 and the cathode fingers 41 by providing electrical conductors therebetween. In one exemplification, shown generally in FIGS. 1, 2, 3, and 4, electroconductive bolts 45 extend from the top of the peripheral member 21 through the peripheral member 21 and through the channel or conduit 38 to the foraminous wall 31, and the ends of the cathode fingers 41. The bolt 45 is connected to the cathode finger by steel fittings 46 which may be welded or otherwise joined to the cathode finger 41. Similar fittings are provided at the bottom 23 of the peripheral member 21.

All of the foraminous surfaces, as the peripheral foraminous wall 31, and the cathode fingers 31, are covered with a diaphragm 49. The diaphragm 49 may be a permionic membrane, or asbestos, or any suitably pervious material that is non-reactive in the electrolytic cell environment. It is typically asbestos. The volume within the diaphragm 49, including the conduit or channel 38 and the volume within the cathode fingers 41, is the catholyte volume. The remainder of the volume of the cell is the anolyte volume.

The peripheral member 21 is bounded on its open sides by a pair of vertical plates 51 and 61, shown in particular detail in FIG. 5. Within any one particular cell, as cell 12 in FIGS. 1, 2, 3, and 4, one of the vertical plates as plate 61 has an insulated surface 62, thereby rendering it substantially electrolytically inactive and the other of the vertical plates, as plate 51, is anodic. It should be understood that in an assembled electrolyzer each of the vertical plates will have two faces, each face facing a different cell of the pair of adjacent cells separated by the said vertical plate. One of the faces will be anodic. The opposite face will be substantially electrolytically inactive.

The vertical plate may be fabricated out of any material that is electrically conductive and resistant to the anolyte. Typically, for reasons of cost, the vertical plate 51 is assembled as shown in FIG. 5. Shown therein is a plate comprising a steel plate 54 having linings 52 and 53 on both surfaces thereof.

The steel plate 54 is typically from about inch to about 1% inches thick. The lining 52 on the electrolytically inactive surface thereof may be plastic or rubber. Suitable plastics include polyvinylidene chloride, Teflon, Plexiglas, or any polyhalocarbon. The lining 53 on the anodic surface of the plate may be a valve metal such as titanium, tungsten, or tantalum. Alternatively, the lining 53 may be rubber or plastic as used in the electrolytically inactive surface 52.

The vertical plate 51 is physically separated from the adjacent peripheral members 21 by gaskets 81 and 82. The gaskets 81 and 82 must be electrically insulating and substantially non-reactive with the anolyte. The anodes 55 are physically and electrically connected to the vertical plate 51 on the surface 53 thereof facing the anolyte.

In one exemplification shown in FIG. 5, a plurality of connectors 86 embedded in the vertical plate 54 provide electrical and mechanical connection between the vertical plate 51 and the anodes 55.

The connectors 86, typically fabricated of iron, steel, copper, or titanium, comprise a bolt 87, a nut 88, and a stud 89. The bolt 87 and nut 88 are within the vertical plate 54, the nut 88 being countersunk within the vertical plate 54. The connectors 86 provide electrical and mechanical contact between the vertical plate 54 and a plurality of horizontal anode bars 90 through the studs 89 which are on the anodic surface 53 of the vertical plate 51. The anode bars 90 are typically from /2 inch to 1 inch thick and from 2 inches to 4 inches high, and extend substantially the entire width of the cell. They may be fabricated of any valve metal. Typically, they are fabricated of titanium.

The anodes 55 are bolted to the anode bars 90 by a titanium bolt 95. The length of the bolt 95 is less than the thickness of the anode bar 90 so that the bolt 95 does not contact the stud 89.

The anode blades 55 are substantially perpendicular to the top 22 and bottom 23 of the peripheral member 21 and to the vertical plate 51 and substantially parallel to the sidewalls 24 and 25 of the peripheral member 21, and to the cathode fingers 41. The individual anode blades 55 are interleaved between and substantially equidistant from a pair of cathode fingers 41. In this way the IR voltage drops for the current flowing from either surface of the anode are substantially equal. The inter-electrode gapthat is, the distance measured perpendicular to the electrodes between the anode 55 and the opposite cathode 41-is from about inch to about inch and is typically /2 inch. The inter-electrode gap should be narrow enough to minimize the IR voltage drop across the electrolyte between the anode and the adjacent cathode and thereby minimize power costs. The inter-electrode gaps should, however, be great enough to prevent abrasion or washing off of the diaphragm 49 by the chlorine liberated at the anodes 55.

Anodes used in the electrolyzer of this invention are dimensionally stable. That is, they do not change their size or shape after vigorous electrolysis.

The anode blades may be fabricated of any metal that, when subjected to an anodic medium, forms a protective oxide film conductive in the cathodic direction. Such metals are known as valve metals and include titanium, tantalum, and tungsten. Typically, for reasons of cost and availability, titanium is used. Whenever titanium is re ferred to, it will be understood that any of the valve metals are interchangeable with it and can be used in its place.

An electroconductive surface is applied to the anode blades. The electroconductive surface typically comprises a platinum group metal or metal oxide; it may also comprise other compounds of platinum group metals. Alternatively, it may comprise compounds of other metals.

Such dimensionally stable anodes are less than /2 inch in thickness; typically they have a thickness of from about inch to about 4; inch.

In one exemplification shown generally in FIGS. 1, 2, 3, 4, and 5, and in detail in FIG. 6, the anodes comprise a base member 56 and a pair of anode blades 57 and 58. Each of the anode blades 57 and 58 is interleaved between a pair of cathode fingers 41. Typically, both sides of each blade have an electroconductive coating thereon.

In another exemplification shown in detail in FIG. 7, the anodes comprise a single metal blade 59 having a base 56 for attaching the anode to the vertical plate 51. In the exemplification shown therein, electroconductive surfaces may be provided on one or both faces of the anode blade 59..

Alternatively, the anodic element may le in the form of two perforate or foraminous sheets, as shown in FIG. 8, and may be interposed between a pair of cathode fingers. In the exemplification shown in FIG. 8, either the pair of faces within the anodic element 60 or the pair of faces facing the cathode fingers 41, or both pairs of faces may be provided with an electroconductive surface. Typically, only the interior pair of faces will be provided with an electroconductive surface thereby reducing the abrasive effects of the evolved chlorine on the diaphragm and allowing a reduced inter-electrode gap.

In order to obtain economical operation of the electrolyzer, the inter-electrode gap should remain uniform across the surface of the anode. Accordingly, means are provided to keep the anode blades 57 and 58 in proper alignment with each other and with the cathode fingers 41 and to adjustably maintain the proper inter-electrode gap and anode pitch. In one exemplification of this inventron shown in FIGS. 2, 3 and 4, this takes the form of a threaded rod 101 passing laterally through and substantially perpendicular to the anode blades in a direction substantially parallel to the top 22 and bottom 23 of the peripheral member 21 and to the vertical plates 51 and 61, and substantially perpendicular to and through fittings 103 on the leading edge of each anode blade. Nuts 105 and washers 107 are on the threaded rod 101 on both sides of the fitting 103. Adjustment of the nuts 105 maintalns the pitch of the anode blades. In another exemplification where the anodes are wider in the horizontal directron than. the cathodes and extend beyond the cathodes, a notch can be provided in an edge of the blades of the anodes themselves. The rod then goes through the notches in the edge of the anode blades and laterally to the blades, across the cell from wall 24 to wall 25. The notch or opening is of sufiicient diameter to allow the rod 101 to pass through but of a sufliciently small diameter that the nuts 105 will maintain the blade in the desired position.

Mechanically and electrically connected to the peripheral body member 21 on the side opposite the first vertical plate 51 is a second vertical plate 61. This plate 61 is substantially parallel to the first or anodic vertical plate 51 of the cell 12.

The surface of the vertical plate 61 that is within the cell 12 has an insulating coating thereon 62. This coating may be a rubber or plastic as described previously for the electrolytically inactive surface 52 of the anodic vertical plate 51. The other surface 63 of the vertical plate 61 faces the anolyte of the next adjacent cell 13 in the electrolyzer.

Vertical plate 61 is displaced horizontally from the leading edges of the electrodes. The plate 61 is displaced from the electrodes 41 and 55 of cell 12 whereby it does not make electrical contact with the electrodes 41 and 55 of cell 12.

Additionally, the second vertical plate 61 may be spaced away from the electrodes upwards of from about 3 inches to about 6 inches. This provides an electrode free volume, thereby allowing for freer circulation of the anolyte and the chlorine. In this way the inter-electrode gap may be reduced; for example, to a gap of from about 95 inch to about ,4 inch. Furthermore, this electrode free gas circulation space results in a lower volume fraction of gas in the anolyte, reducing the IR voltage drop across the anolyte and thereby reducing power costs. Additionally, an electrode height in excess of about 4 feet at current densities in excess of 125 amperes per square foot may be provided; for example, from about 4 /2 feet to about 6 feet.

The second vertical plate 61 is electrically connected to the peripheral body member 21. This is done so that the flow of electrical current is from the first or anodic vertical plate 51 of the cell 12 substantially horizontally to and through the anodes 55 of the cell 12, thence from the anodes 55 of the cell 12 substantially horizontally and in a direction substantially perpendicular to the anodes through the anolyte to the cathodes 41 of the cell 12, thence substantially vertically through the cathode fingers 41 to the foraminous peripheral wall 31, and from the foraminous peripheral wall 31 of the cell 12 to the peripheral member 21. From the peripheral member 21 the current then flows to the next vertical Wall 61 which is the second or insulated vertical wall 62 of the first cell 12 which serves as the anodic vertical wall 63 of the next adjacent cell 13 in the electrolyzer. The peripheral body member 21 is electrically insulated from the anodic vertical wall 51 but electrically connected to the second or insulated vertical wall.

Electrical connection may be provided between the peripheral body member 21 and the insulated vertical plate 61 by conductors or bus connectors 111. Such conductors may be fabricated from copper or other suitable conducting material. Positive electrical contact is provided by studs 113 connecting the bus connector to the peripheral body member 21, and by suds 115 connecting the bus connector to the vertical plate 61 as shown in FIG. 2. The bus connector may also be used to provide additional structural support to the electrolyzer.

In the operation of the electrolyzer brine containing from about 310 grams per liter to about 325 grams per liter of sodium chloride is fed through the feed line 121. This feed mixes with chlorinated brine from tank 123 yielding a chlorinated brine containing from about 250 grams per liter to about 290 grams per liter of sodium chloride which is fed into the anolyte compartment through the brine inlet 71 at the side of the anolyte compartment The following reaction takes place at the anodes in the anolyte compartment:

Some of the chlorine liberated at the anode 55 bubbles up on the face of the anode 55 through the anolyte to the top of the anolyte compartment and thence out of the cell through the chlorine outlet 74 and through brine feed tank 123. The rest of the chlorine travels diagonally across the anode 55 into the raceway or electrode-free portion of the cell volume between the electrodes 41 and 55 and the insulated surface 62 of the vertical plate 61, and thence through the anolyte to the top of the anolyte compartment, and out of the cell through the chlorine outlet 74. The electrolyte permeates the diaphragm 49 and passes through it into the catholyte compartment. The following reaction takes place at the electrically active surfaces within the catholyte compartment:

Me+ +H O'+e-' MeOH+% H t where Me+ represents the alkali metal ion.

The hydrogen gas bubbles up through the cathode fingers 41 into the conduit 38 and out through the hydrogen outlet 73 into pipe 125 shown in FIGS. 1, 2, 3, and 4 in the top of the cell. The cell liquor containing from about 120 to about 150 grams per liter of sodium hydroxide and about 140 to about 170 grams per liter of sodium chloride is recovered from the conduit or catholyte compartment 38 through opening 72 in the side wall and discharged through the perc pipe 129. The perc pipe 129 is rotatably mounted on pipe 127 leading from opening 72.

Rotating the perc pipe 129 changes the hydrostatic pressure in the catholyte compartment, thereby changing the difference between the catholyte hydrostatic pressure and the anolyte hydrostatic pressure. In this way, as the permeability of the diaphragm decreases with service, the catholyte hydrostatic pressure may be made significantly less than the anolyte hydrostatic pressure thereby causing electrolyte to flow through the diaphragm.

In the normal operation of the electrolyzer, brine is fed into the anolyte compartment through a pipe 121 shown in FIGS. 2 and 3 to an opening 71 in the side wall of the cells. However, should the flow of brine to any cell in the electrolyzer be interrupted, the anolyte level could drop. This could cause abnormalities in the operation of the individual cell such as the anodes being exposed to the air, hydrogen entering the anolyte compartment, boiling of the anolyte, electrolytic attack of the backplate or anodes, or arcing across the electrodes. Any of these abnormalities could result in catastrophic failure of the electrolyzer. Accordingly, an equalizer 131 is provided. The equalizer, shown generally in FIGS. 2 and 4, serves to maintain a uniform head of anolyte in all of the individual cells. This is accomplished by providing hydraulic communication between a plurality of the individual cells in the electrolyzer. This hydraulic communication may be provided by an equalizer pipe or equalizer pipes as 131 in FIGS. 2 and 4 connecting the individual cells 11, 12, and 13 through openings in the walls of the cells.

The brine tank 123, the equalizer pipe 131, and the brine feed pipe 121 are steei and are lined with a material suitably resistant to saturated brine. Rubber, polyester, or fiuorocarbons may be used. Typically, polyester is used. Alternatively, the brine tank 123 and the equalizer pipe 131 and the brine feed pipe 121 may be fabricated from fiberglass reinforced polymers such as polyesters, polyvinylidene chloride, and other polyhalocarbons.

The total assembly of individual cells 11, 12, and 13 comprising the electrolyzer is held together by providing a compressive force on the two end cells 11 and 13. Specifically, a plurality of tie rods 186 shown generally in FIGS. 2, 4, and 10 apply a compressive force on the two end cells 11 and 13.

Each tie rod 186, enclosed in an insulating sleeve 187, passes through holes 188 in the vertical plates of the end cells 11 and 14. An insulating washer 189 and insulating cap 190 electrically insulate the plates 151 and 161 from nuts 191. Tightening the nuts 191 brings the individual cells into compression.

It is to be understood that although the invention has been described with specific reference to particular embodiments thereof, it is not to be so limited since changes and alterations therein may be made which are within the full intended scope of this invention as defined by the appended claims.

We claim:

1. An electrolyzer comprising a plurality of electrolytic cells in mechanical and electrical communication wherein the intermediate cells within said electrolyzer each comprise:

a first vertical plate having an insulating surface and an anodic surface, the said anodic surface being electrically in series with the prior electrolytic cell in the electrolyzer;

a plurality of anodes electrically and mechanically connected to the anodic surface of the said vertical plate;

a conductive metal peripheral body mechanically connected to and electrically insulated from said first vertical plate and having two side walls, a top, and a bottom;

a cathodic structure comprising:

a conduit, and

10 a plurality of vertical, hollow, foraminous cathodic electrically connected to said peripheral body, havfingers electrically and mechanically connected ing an electrically insulated first surface facing the to and communicating with said conduit; and said cell and the said first vertical plate and a sec a second vertical plate spaced from and substantially end surface facing the next adjacent cell in the parallel to said first plate, mechanically connected to electrolyzer. the said peripheral body, and having an insulating 3. The electrolyzer of claim 2 wherein the said inner facing the first vertical plate. peripheral wall is perforate. 2. An electrolyzer comprising a plurality of electrolytic 4. The electrolyzer of claim 2 wherein the said inner cells in mechanical and electrical communication, wherein peripheral wall is foraminous. an intermediate cell within said electrolyzer comprises: 5. The electrolyzer of claim 2 wherein the said cathodic a first Vertical plate having a pair of surfaces, the first of fingers are perforate.

said surfaces facing the prior cell in the electrolyzer, 6. The electrolyzer of claim 2 wherein the said cathodic and the second of said surfaces facing into the said fingers are foraminous. cell and being electrically in series with the prior elec' 7. The electrolyzer of claim 2 wherein the said anodes trolytic cell in the electrolyzer; are vertical and the said cathodic fingers are connected to a plurality of vertical anodes electrically and mechanithe top and bottom surfaces of the inner peripheral wall. cally connected to the said second surface of the said 8. The electrolyzer of claim 2 wherein the said second first vertical plate; vertical plate is spaced from the said electrodes whereby a a peripheral body mechanically connected to and elecraceway is provided.

trically insulated from said first vertical plate and having two side walls, a top, and a bottom; Re r n s Cit d 2. cathodic structure comprising:

UNITED STATES PATENTS an inner peripheral wall electrically and mechanically connected to and spaced inwardly of said 3342717 9/1967 Leduc 204266 peripheraldbodyl forming a conduit 2 332333133 $11353 $322 1"; 25311111111 333322 a gllffa lity of hollow, vertical cathodic fingers in 3390 072 6/1968 wiseman 204-286 communication with said conduit and electrically 2987463 6/1961 Baker et 204 286 and mechanically connected to said inner peripheral wall at opposite horizontal surfaces thereof JOHN MACK Pnmary Exammer whereby the said anodes are interleaved between W. I. SOLOMON, Assistant Examiner the said fingers; and a second vertical plate spaced from and substantially Us parallel to said first vertical plate, mechanically and 204-266 UNITED STATES PATENT @FFKCE I fiERTEHQATE @F RREGHN Patent No. 927 Dated July 18. 1972 In en Carl W. Raetzsch and Hugh Cunningham It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In Column 9, line 7, the Word surfaceshould be inserted before the Word "facing."

Signed and sealed this 29th day of May 1973.

CS EAL 1 Attestz EDWARD M.,FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents )RM PO-1050 (10-69) USCOMM-DC 50376-P69 Q U.$. GOVERNMENT PRINTING OFFICE: 1969 O366-334

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