US3910827A

US3910827A - Diaphragm cell

Info

Publication number: US3910827A
Application number: US348349A
Authority: US
Inventors: Carl W Raetzsch; Hoozer John F Van; Hugh Cunningham
Original assignee: PPG Industries Inc
Current assignee: PPG Industries Inc
Priority date: 1971-07-07
Filing date: 1973-04-05
Publication date: 1975-10-07
Anticipated expiration: 1992-10-07

Abstract

A novel diaphragm cell (electrolyzer) useful for electrolyzing brines to produce chlorine and sodium hydroxide is disclosed which is constructed of a plurality of single cells. Such single cells are made up from bipolar electrodes which have a plurality of finger-like, dimensionally stable anodes extending in one direction outwardly from a support wall and a plurality of finger-like cathodes extending in the opposite direction from the support wall. In its assembled state, the electrolyzer is made up of one or more single cells in which cathodes of one bipolar electrode are interleaved between anodes of the adjacent bipolar electrode to form a single cell. An especially effective bipolar electrode has hollow anodes having spaced pairs of anode surfaces. In a preferred embodiment the support wall (or backplate) has a titanium surface on its anode side and an iron surface on its catholyte side.

Description

[lll 3,910,827

[451 Oct.7,1975

United States Patent Raetzsch et al.

U.S. Patent Oct. 7,1975

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S8 INVENTORS CARL W. BETZS'CH :i Joy/J F. VnA/Hoozf w #06H cum/mom ATTORNEYJ DIAPHRAGM CELL RELATED APPLICATION This is a continuation of application Ser. No. 160,339, filed July 7, 1971, which is a continuation-inpart of application Ser. No. 54,816, filed July I4, 1970, and application Ser. No. 836,082, filed June 24, 1969, all now abandoned.

THE INVENTION The invention is concerned with an electrolytic cell (or electrolyzer) in which aqueous alkali metal salts (e.g., sodium chloride) are electrolyzed to form chlorine and alkali metal hydroxide (so called alkali chlorine cells) of the type which includes a succession of vertical electrodes in which dimensionally stable anodes alternate with cathodes carrying a diaphragm. It is particularly concerned with the arrangement and configuration of the anodes and cathodes on a support wall (or backplate) and with means for securing the electrodes to the support wall. It is also concerned with a special bipolar electrode configuration which among other things is characterized by hollow anodes having spaced pairs of anodic surfaces.

A variety of types of alkali-chlorine electrolytic cells employing a bipolar electrode assembly and a permeable diaphragm have been known in the past. The present trend in this type of cell is to provide within a single cell housing a plurality of individual cell units utilizing bipolar electrode structures. See U.S. Pat. Nos. 2,858,263 and 3,337,443. ln such an electrode structure, the anodes of one cell are positioned in a back-toback relationship with the cathodes of the adjacent cell and electrical Contact is maintained between the two. The supporting wall for the anodes and cathodes in the back-to-back relationship functions to physically sepa` rate the cells within the over-all cell housing.

The present invention provides an improved bipolar alkali-halogen diaphragm cell of the described type. The present invention provides a diaphragm cell which is particularly light in weight and easy to assemble and disassemble. lt provides a unique, highly advantageous bipolar electrode configuration which advantageously effects brine circulation within the cell, reduces (even substantially eliminates) the problems of gas binding in the interelectrode space and utilizes efficiently metallic anodes. The present invention furthermore provides a diaphragm cell having improved electrical connection between the cathode and anode.

Herein the term cell unit is used to describe the backto-back bipolar assembly of the anodes of one cell with the cathode of the adjacent cell. Each cell thus is made up of cathodes from one cell unit (i.e. the bipolar electrode thereof) interleaved and spaced from anodes of the next adjacent cell unit (i.e. the bipolar electrode thereof). Each cell unit thus includes as a principal component a bipolar electrode assembly. The cathodes characteristically have elongated hollow portions which are interleaved or interpositioned with and spaced from the anodes of the next adjacent cell unit. The cathodes are constructed of metal wire screening or the like perforated sheeting and are covered with a permeable diaphragm, for example asbestos. The metal wire screening may be of any suitable metal, for example, steel or, alternatively, nickel or chromium or other metal sufficiently resistant to corrosion under the conditions prevailing in the catholyte during electrolysis.

The finger-like anode elements may be provided by a single sheet or wall-like element or according to a particular preferred embodiment are hollow and cornprise a pair of laterallyspaced vertical walls. These walls, in one embodiment, may be open along the outer end of the elements or alternatively closed or substantially closed at the outer end. Electrolyzers with hollow anodes are constructed so as to provide for the presence of electrolyte in the hollow of the anode. Anodic products, notably gaseous chlorine can form and/or collect behind the anode surface directly facing the surface of the adjacent cathode. This is gases, notably elemental chlorine can and does collect in the hollow of the anode, and hence its accumulation in the interelectrode space is minimized or avoided. Electrolyte is also free to circulate in the electrolyzer and to move in the anode hollow. Such circulation of gas and electrolyte is especially noticeable (and enhanced) with metallic anode side walls of previous material, such as when the walls are of rods, screen, expanded metal mesh, perforated plate or louvered plate.

These anodes are constructed of any suitable chlorineresistant metal such as titanium or like valve metal, e.g., tantalum and tungsten, having an electroconductive surface of a platinum group metal or the oxide of a platinum group metal. one or both surfaces of the hollow anodes will have this electroconductive surface. Characteristically, the sheet or wall-like anodes are thin, eg., less than about a half inch thick. The term single-cell is used to describe the cell formed by the finger-like anodes from one bipolar electrode (or of one cell unit) which are interleaved with the finger-like cathodes from an adjacent bipolar electrode (or of the adjacent cell unit).

Another important component of the cell unit (and bipolar electrode) is the supporting wall or backplate. As shown in the specific embodiments hereinafter described, the backplate may serve one or more purposes including that of l) the prime structural element for supporting the plurality of anodes and cathodes which make up the cell unit, (2) the principal structure which divides the entire electrolytic cell (electrolyzer) into its component cells (single cells) and (3) the conductor by which the current flows from cell to cell. For the backplate to perform such functions it should be of appropriate construction and materials. One especially useful type of electroconductive backplate has its anodic side (or surface) of titanium (or like valve metal) and its cathodic surface of steel. These surfaces are each resistant enough to the respective cell environments to which they are exposed during cell operation to provide for long backplate life.

In the drawings:

FIG. l shows a perspective view illustrating generally the bipolar cell of the present invention with portions of the cell housing broken away.

FIG. 2 shows in cross-section an enlarged portion of the electrodes taken along the line lI-II in FIG. l illustrating the relationsip of the cell units to the cells in the cell housing.

FIGS. 3-12 illustrate various embodiments for mounting the electrodes to the support wall in the cell units of the bipolar cell.

FIGS. 13-15 show another preferred embodiment of the present invention.

Bipolar diaphragm cell l0 as shown in FIG. l is constructed of a plurality of cell units such as cell units l l,

l2, 13 and 14 which form

single cells

18, 19, and 20. The end cell unit l1 provides a cathode half cell and the end cell unit 14 provides an anodic half cell. The

intermediate cell units

12 and 13 are bipolar providing an anodic surface in the direction of cell unit ll and a cathodic surface in the direction of cell unit 14.

The bipolar cell l may be provided with only one intermediate cell unit having but one bipolar electrode such as cell unit 12. Alternatively, the cell unit l0 may include two or more (frequently 12 or l5) intermediate cell units, as desired. The intermediate cell units may be identically constructed.

The cell unit 13, for example, has a frame 21 including a backplate 22, which serves as a partition between

single cells

19 and 20, and

peripheral walls

23, 24, 25 and 26. The frame 21 may be constructed of iron and steel. However. the anodic side of the backplate 22 and the inner surfaces of

walls

23, 24, 25 and 26 Should have a suitable protective coating, such as of rubber, in order to prevent corrosion. Alternatively, the frame 21 may be of titanium plate or titanium clad steel plate. The peripheral walls, such as wall 24, each includes a pair of

flanges

27 and 28 that allow for bolting the cell unit 13 to similar flanges on the adjacent cell units l2 and 14. Of course, the bolts are suitably insulated electrically from the cell units and sealing gaskets are provided between the meeting surfaces of the adjacent flanges. Thus, the container for the single cell 19 is provided bythe backplate 22 of cell unit 13, the

peripheral walls

23, 24, 25 and 26 and the backplate 22 of cell unit l2.

The backplate 22 in the electrolytic cell illustrated in FIG. l has at least one opening 34 which allows brine to flow from one cell compartment to the next thereby providing an equal level of brine in each single cell. The backplate 22 further includes openings 33 for mounting of the cathode 16 and 17 thereon as hereinafter described. The upper portion of backplate 22 provides means for removing the cathodic gas product, for example, hydrogen, from the cell such means including a chamber 37 defined by wall 38 and the upper peripheral wall 25. The wall 38 has an opening 39 for passage of hydrogen formed in the hereinafter described cathodic zone in the cell into chamber 37. The hydrogen gas is removed from chamber 37 through pipe 41. A pipe 42 in the upper peripheral wall 25 is provided for removal of the anodic gas product, for example, chlorine gas which is formed in the anodic zone of the cell. A pipe 43 is provided in upper peripheral wall 25 for passage of brine into the single cell. The cell products such as caustic soda are removed from the cathodic zone of the cell through pipe 44 in the wall 24.

The cathode 16, as shown in FIGS. l and 2, includes a backscreen 47 spaced from plate 22 and finger-like cathode elements 46 which extend perpendicularly from the backscreen 47. The finger-like cathode elements are preferably wedge shaped as shown in FIGS, l and 2, thus facilitating achievement of near zero gap (or interelectrode space) between the anode and cathode fingers. However, the side walls comprising each cathode could be substantially parallel with each other. The cathode lingers 46 and the back screen 47 may be constructed of material conventionally used in diaphgram cell cathodes for example, the type of screen disclosed in U.S. Pat, No. 3,337,443. Cathode finger 46 includes the side walls 45 and 50 which are joined at their outermost end and at their upper and lower edge thus forming a chamber enclosed except for the end which open into the chamber defined by the backplate 22 and the backscreen 47. The chambers 70 and 75 of each of the multiplicity of cathode elements associated with the one cell unit together comprise the cathodic zone (in which the catholyte is contained) of the single cell 20. Each cathode element comprising cathode fingers 46 and the backscreen 47 is electrically interconnected to the backplate 22 and its corresponding anode 17 of the cell unit. The screen of the cathode fmgers 46 and backscreen 47 is covered with permeable diaphragm suitably of non-woven asbestos fabric. Alternatively, the permeable diaphragm may be a permionic membrane. The permeable diaphragm prevents undue mixing of the catholyte and anolyte and allows for the collection of anodic and cathodic gases. The chambers 70 and 75 communicate with the cathodic gas collection chamber 37 through the opening 39 in wall 38.

The cathode fingers 46 each have a plurality of horizontal bars 48 including laterally extending flanges 49 for supporting the screen forming the cathode fingers and for conducting electrical current to the cathodes. The bars 48 may be constructed of the same type of material as used in backplate 22, for example, iron or steel.

The anodes 17 (FIGS. l and 2) are finger-shaped and extend outwardly from the backplate 22. Anode 17 includes a pair of laterally-spaced walls 61 and 62 and a rear wall 63. The walls 61 and 62 may be solid plate or may be of a foraminous or louvered sheet material. Anode 17 has a horizontal bar 64 with laterallyextending flanges 66 for support ofthe walls 6l and 62. The walls 61 and 62 preferably are disposed so that their outer surfaces are at an angle which is complementary to the angle provided between the pair of adjacent cathode fingers 46. Thus, when the electrodes are in position of operation shown in FIG. 2, a uniform space (electrode gap) is provided between the outer, opposed, facing surfaces of the respective anodes and cathodes. The anode 17 including walls 6l, 62 and 63 as well as the horizontal bar 64 and flanges 66 and 67 may be constructed of any suitable anodically-resistant material, preferably titanium. The outer surfaces of solid walls 6l and 62 should be coated with a suitably anodically-resistant electroconductive surface Such as a platinum group metal or the oxide of a platinum group metal such as platinum, rhodium, palladium, ruthenium, rhenium, and osmium, mixtures and alloys of these metals, and/or one or more oxides of these metals. ln addition, the electroconductive surface may also contain oxides of other metals, some of which will improve the anodes performance including oxides of titanium, lead, manganese, cobalt, iron, chromium, tanta` lum and silicon. lf the walls 6l and 62 are foraminous sheets, then the outer and/or inner surfaces may be coated with such metal or metal oxide.

The cathode 16 and anode 17 are mounted on backplate 22 by electrode support means 52 (FIG. 2). The electrode support means 52 includes a block 53 which extends through opening 33 in backplate 22 and is Secured therein such as by welding. The block 53 may be constructed of iron rod or other electrically conductive, cathodically-resistant material and has an opening 54 there through for reception of screw S6. The screw 56 is threadedly engaged in opening 57 in the corresponding horizontal bar 48 of cathode finger 46. The

screw 56 holds the backscreen 47 and the cathode finger 46 snugly against a shoulder S8 of block 53 to provide good electrical contact. The opening 54 in block 53 has an enlarged portion 59 of sufficient size to permit the head of the screw S6 to be disposed there within. The rear wall 63 of anode 17 has an opening 68 through which anode mounting screw 69 extends for threaded engagement in the enlarged portion 59 of opening 54 in the block 53. The open outer end of anode 17 provides access to screw 69 for mounting and dismounting of anode 17. The screw 69 holds the anode 17 securely against block 53 and backplate 22 thus providing good electrical contact. The screw 69 should be of an anodically-resistant electrically conductive material such as titanium. Sealing gasket 71 may be provided between the anode 17 and the backplate 22, thereby preventing any anolyte from reaching the block 53 which, if it were to happen, might result in corrosion. Seal 73 is provided between screw 69 and the backwall 63, thereby preventing leakage of anolyte through opening 68 and into contact with the block 53.

The end cell unit 14 is constructed identical to cell unit 13 except that cell unit 14 does not include a cathode. In other words, the only electrodes mounted on cell unit 14 are anodes. The anodes may extend through the backplate and be welded or bolted to a copper bus bar.

Cell unit l1 is constructed of a backplate 77 which may be bolted to cell unit 12. Cell unit l1 has a cathode 78 including a backscreen 79 and finger-like cathodes 80. Cathode 78 may be mounted on plate 77 in a manner identical to the mounting of cathode 16 on backplate 22 of cell unit 13.

The cell units ll, 12, 13 and 14 are bolted together, forming

single cells

18, 19 and 20, and the bolts are suitably insulated to prevent shorting between cell units. Alternatively, the cell units may be secured together by tie rods in a manner conventionally used in filter press type cells. The

single cells

18, 19 and 20 are electrically connected in series. During a typical operation, brine is continuously added to each of the single cells through the corresponding pipe 43. The openings 34 between single cells permit equilization of the brine level in each single cell. The openings 34 further prevent any one of the single cells from going dry, for example, due to a stoppage in pipe 43. The brine is electrolyzed in the single cell with anodic products, such as chlorine gas being formed in the anodic zone and cathodic products, such as hydrogen gas and caustic soda being formed in the cathodic zone. ln those instances where each anode includes a pair of laterally spaced walls (e.g., as shown in some detail in FIGS. 3 and l2) of pervious material anodic gaseous products can and will collect in the hollow of the anode (bounded by the walls) and rise to the top of the cell for removal via pipe outlet 42. The diaphragm prevents back migration of the cathodic products into the anodic zone.

As illustrated in FIG. l, anodes 17 have their walls open and terminating above the bottom lower wall of the cell unit. This permits liquid communication between the interelectrode space and the hollow space within the anode. Electrolyte can thus also circulate behind the anode walls, and the anolyte in such cell configurations can be regarded as including electrolyte present both between the cathode and anode as well as within the hollow of the anode.

With perforate (pervious) anode walls, chlorine readily collects and rises in the hollow space defined by the space walls of the anode. As this chlorine collects and rises within the hollow, it will cause movement of electrolyte. With anode walls spaced close enough (usually spaced laterally less than 5 inches, more often between and 3 inches) and especially when the electrolyzer is operated with reasonably high current densities, the rising chlorine gas will lift upwardly electrolyte in the hollow. Electrolyte (anolyte liquor) circulation can primarily be provided in this fashion by the lift due to rising chlorine gas.

With those electrolyzers having bipolar electrodes with hollow electrodes as herein contemplated, brine feed to the electrolyzer need not be directly into the interelectrode gap. Brine, for example, can be introduced wherever convenient (other than to the catholyte); it can be fed into the hollow space of the anodes, if desirable.

It is found that with previous hollow anodes. electrolyzers of the type herein described function especially well and evidence ruggedness of performance. For example, shorting usually attributed heretofore in other cells to touching (or undue closeness) of anodic surface and diaphragm is no longer a frequent event even though there may be some slight misalignment or touching of anode to diaphragm (or cathode surface which has lost diaphragms.)

Further preferred embodiments of electrode support means are shown in FIGS. 3-12. The bipolar cell units 12A-121 shown in these Figures are constructed substantially like cell unit l2 except for the electrode dcsign and electrode support means.

The electrode support means 52A (FIGS. 3 and 4) includes an elongated bar or current gatherer 81 which is typical of the current gatherer used in cell units 12A through 12H. The current gatherer is welded to the cathode finger 46A and has openings (not shown) through which cathodic products formed in fingers 46A may pass to the chamber 75A. A metal block 82 is secured to bar 8l such as by welding. The metal block 82 extends through an opening 83 in backscreen 47A and is secured to backplate 22A by screw 84. The screw 84 extends through opening 87 in backplate 22A and is threadedly engaged in opening 88 in block 82. Preferably, the head 89 of screw 84 is countersunk into backplate 22A thereby providing a flat surface against which anode 16A (FIG. 4) may be mounted The electrode support means 52A further includes a screw 91 which secures the anode 16A (FIG. 4) or anode 17A (FIG. 3) to backplate 22A. The head 92 of screw 91 is preferably welded to backplate 22A. In the embodiment illustrated in FIG. 3 screw 91 is situated along the same axis as that of screw 84 whereas FIG. 4 shows an embodiment where screw 91 is offset from screw 84. In both embodiments, screw 91 extends through an opening 93 in backplate 22A and an opening 94 in the rear wall 63A of anode 17A (or 16A). The nut 96 is tightened down on screw 91 and draws anode 17A or 16A snugly and securely against backplate 22A. A seal 97 may be provided between anode 17A and backplate 22A, thereby preventing any leakage between the cathodic compartment and the anodic compartment. A seal 90, such as a Thred Seal (Trademark of Parker Seal Company), is provided between nut 96 and wall 63A.

The bipolar cell unit 12B (FIG. 5) includes an anode 17B, a backplate 22B, and a cathode 16B. The electrode support means 52B includes an enlongated bar 101 which is secured to cathode finger 46B, for example, by welding. Openings, not shown, are provided in bar 101 through which cathodic products may pass. A rod 102 which is threaded at one end is secured to bar 101, such as by welding. The rod 102 extends through opening 103 in backplate 22B. A nut 104 is threadedly engaged with rod 102, thereby securing cathode 16B in place. Preferably, a seal 106 such as a Thred Seal (Trademark of Parker Seal Company) is provided between nut 104 and backplate 22B. The seal 106 prevents leakage of catholyte through backplate 22B to its anodic side. The rear wall 63B of anode 16B in this em bodiment is a double wall including wall portions 107 and 108. The wall portion 107 may be of steel but the wall portion 108 must be of an anodically-resistant material such as titanium. The wall portion 107 has an opening 109 through which rod 102 extends. A nut 111 secures a wall portion 107 to the backplate 22B. The

side walls

61 B and 62B extend over wall portion 107 and are welded thereto. A screw 112 extends through opening 113 in wall portion 108. The screw 112 may be threadedly engaged in a suitable opening in rod 102. Alternatively, the screw 112 may be off set from rod 102, threadedly engaged in a suitable opening in wall portion 107, or screw 112 may be threadedly engaged in a nut disposed on the side of wall portion 107 toward backplate 22B. The screw 112 thereby secures wall portion or cover 108 to wall portion 107. A seal 114 is disposed between wall portion 108 and wall portion 107 and prevents arolyte from contacting wall portion 107. A further seal 116 is disposed between anode 16B and the backplate 22B.

The bipolar cell unit 12C (FIG. 6) includes an anode 17C` cathode 16C and backplate 22C. The anodes 17C and cathodes 16C are secured to the backplate 22C by the electrode support means 52C The electrode support means 52C includes an elongated bar 121 which is welded to the finger cathode 46C. Bar 121 has openings therein for passage of cathodic products. A rod 122 is secured to bar 121 and extends through an opening 123 in backplate 22C. The electrode support means 52C further includes a nut 124 which is threadedly engaged with rod 122. The nut 124 serves to hold the cathode 16C in spaced relationship to the backplate 22C. A nut 125 is threadedly engaged with rod 122 thereby securing cathode 16C to the backplate 22C. A seal 126 may be located between nut and backplate 22C. The anode 17C includes side walls 61C, 62C, and rear wall 63C. The rear wall 63C includes an opening 128 through which extends a screw 129. Screw 129 is threadedly engaged in rod 122 and secures the anode 17C to the backplate 22C. The screw 129 draws rear surface 127 of wall 63C into electrical contact with rod 122 and nut 125.

Seals

131 and 132 are provided to prevent leakage of anolyte into contact with parts which are of materials not resistant to the anolyte, notably steel parts such as rod 122 and backplate 22C,

The cell unit 12D (FIG. 7) includes an anode 17D. cathode 16D, and backplate 22D. The electrode support means 52D in this embodiment comprises an elongated bar 141 which is welded to the cathode finger 46D, the electrode support means 52D further includes the connecting block 142 which is attached to bar 141 such as by welding. Th block 142 extends through an opening 143 in backplate 22D. The anode 17D is secured in place by screw 144 which extends through opening 146 in rear wall 63D and is threadedly engaged in opening 147 in block 142. The block 142, if desiredl may be welded to the backplate 22D.

The electrode support means 52E of bipolar cell unit 12E (FIG. 8) includes an elongated bar or current gatherer 151 which is welded to the cathode t'mger 46E. The electrode support means 52E further includes a rod 152 which is welded to the bar 151 and extends through an opening 153 in backplate 22E. A nut 154 is threadedly engaged with rod 152 thereby holding cathode 16E in place. A seal 156 may be provided between nut 154 and the backplate 22E. The rod 152 extends through an opening 157 in the rear wall 63E of anode 17E. A threaded cap 158 is threadedly engaged with rod 152 thereby holding anode 17E in place. A seal 159 is provided between cap 158 and the rear wall 63E. A seal 160 is provided between the anode 17 E and the backplate 22E.

The electrode support means 521: of bipolar cell unit 12F (FIG. 9) includes an elongated bar 171 which is welded to cathode nger 46F, a block 172 which is welded to bar 171 is threaded to that the nut 173 may be tightened against the rear screen 47F. The block 172 has a portion 174 of reduced diameter which extends through the opening 176 in the backplate 22F. The block 172 has a shoulder 177 which abuts against the backplate 22F thereby holding the backscreen 47F at a point spaced from backplate 22F. The screw 178 secures anode 17F to the backplate 22F. The screw 178 extends through opening 179 in rear wall 63F and is threadedly engaged in opening 181 in the block 172. The screw 178 holds the meeting surfaces of wall 63F and block 172 in electrical contact with one another. A seal 182 is provided between the head of screw 178 and wall 63F and a seal 183 is provided between anode 1'7F and backplate 22F. The seals 182 and 183 may be of EPDM rubber (ASTM designation) which has excellent resistance to corrosion and remains resilient even after extended periods of cell operation at high temper atures.

The bipolar cell unit 12G (FIG. 10) has an electrode support means 52G including a current gatherer 191 which is welded to the cathode finger 46G. A threaded rod 192 is welded to the current gatherer 191. A nut 193 is threadedly engaged with rod 192 and securely holds the backscreen 47G against electrode finger 466. A nut 194 is threadedly engaged with rod 192 and holds the cathode 16G in a position spaced laterally from the backplate 22G. The rod 192 extends through opening 196 in the backplate 22G. The anode 17G in this embodiment is a single sheet or plate-like element, i.e., in contrast to the embodiments illustrated in FIGS. 2 to 9, includes only one side wall comprised of a plate of titanium or a titanium group metal having an electroconductive surface on both sides thereof. This side wall 61G, when the cell is operating, is disposed substantially equi-distant between opposed cathode lingers of each cathode of the appropriate cathode pair (not shown) of the adjacent cell unit. The anode 17G further includes a rear wall 63G which is welded to anode side wall 61G. The rear wall 63G has an opening 197 through which a screw 198 extends for threaded en gagement in an opening 199 in the rod 192. The screw 198 securely holds the anode 17G in place against the backplate 22G.

1n the embodiment illustrated in FIG. 10, the anode component of the cell unit is in the form of a thin anodicallyresistant vertically disposed sheet or plate having substantially parallel flat surfaces of appropriate electroconductive material upon which anolyte products of electrolysis (e.g., chlorine) form. When assembled in the electrolytic cell, each thin anode plate (of which there are a plurality in each cell unit) is interleaved between, but spaced laterally of opposed cathode fingers of adjacent cathodes extending outwardly from the adjacent cell unit.

The vertical edge of the sheet-like anode terminates parallel to and spaced from the backplate of the adjacent cell unit. The lateral distance (spacing) from this anode edge to the backplage cathodic face will be substantially greater (at least three times greater, but rarely more than times) than the space between the anode face and opposed cathode fingers (electrode gap), thus favoring current flow between opposed cathode and anode faces. A typical lateral space will be from 2 to 8 inches.

These anodes desirably are quite thin, usually considerably less than one inch in thickness (distance between the anodes parallel faces), notably about 0.5 inches or less (rarely less than 0.2 inch). When the sheet-like anodes are of mesh, thickness as herein intended considers the mesh as if it were a solid plate.

The cell unit 12H (FIG. l1) includes an electrode support means 52H having a current gatherer 211 which is welded to the finger cathode 46H. The current gatherer 211 may be a discontinuous bar, thus permitting cathodic products to pass from the finger to the space between the screws 47H and plate 22H. A threaded rod 212 is welded to the current gatherer 211. A nut 213 is threadedly engaged with rod 212 for purposes of holding the backscreen 47H securely against the fingered electrode 46H. The electrode support 52H further includes a nut 214 for controlling the extent to which the threaded rod 212 extends through the opening 216 in the backplate 22H` Ribs 223 are provided for spacing scren 47H from plate 22H. The ribs 223 may be of steel or other material chemically resistant to the catholyte conditions and are welded to plate 22H. The screen 47H is slightly flexible, thus permitting adjustment of rod 212 with respect to backplate 22H. The anode assembly 17H in this embodiment carries a narrow anode member 217, including a pair of side walls 61H and 662H which are welded to the rear wall 63H. A screw 219 extends through opening 221 in rear wall 63H and is threadedly engaged in the opening 222 in rod 212. The screw 219 securely retains the anode 17B against the backplate 22H and maintains excellent electrical Contact between the meeting surfaces of wall 63H and rod 212.

The cell unit 121 (FIG. 12) includes cathodes 161 and anodes 171 which are mounted on a backplate 221 such as by electrode support means 521. The cathodes 161 may be constructed substantially like cathodes 16 shown in FIGS. l and 2. However, in this instance the

rear portions

225 and 226 of side walls 451 and 501 are ared thereby providing lingers 461 with a wider base for resting against back screen 471 and permitting flexing of cathode 161 during adjustment of the block 228 with respect to backplate 221.

The electrode support means 521 includes a current gatherer 227 which is an elongated bar having openings therein through which cathode products may pass. The

current gatherer 227 is welded to side walls 451 and 501 of cathode 161. The electrode support means 521 includes a threaded rod 228 which is welded to the current gatherer 227 and extends through opening 229 in backscreen 471 and opening 230 in backplate 221. A nut 233 is threadedly engaged with rod 228 and retains cathode finger 461 securely against backscreen 471. Nut 234 is threadedly engaged with rod 228 and holds the cathode 161, including backscreen 471 and finger 461, securely against backplate 221. A screw 236, preferably of titanium metal, extends through opening 237 in rear wall 631 of anode 171 and is threadedly engaged in opening 235 in rod 228. A titanium thread seal washer 238 is provided between anode 171 and backplate 221. A plurality of spacer bars 241 are provided between backscreen 471 and backplate 221. The bars 241 hold the cathode 171 spaced from the backplate 221 and may be constructed of any material which is corrosion resistant in a cathode environment, for example, steel or copper. The ring nut 234 adjusts the distance rod 228 extends through plate 221, thus assuring proper contact between the surfaces of wall 631 and rod 228. Furthermore, use of ring nut 234 permits use of a smaller screw 236 than would otherwise be necessary. The rear wall 631 may be a continuous wall the full length of the anode 171 or may be comprised of a plurality of discontinuous wall portions, for example, one such wall portion being provided for each electrode support means. Alternatively, all of the anodes 171 for a cell unit could be mounted on a single rear wall 63|.

Furthermore, wall 221 could serve as the rear wall of anodes 171 in which case wall (backplate) 221 may ideally be a titanium clad steel plate and

anode walls

611 and 621 may be welded thereto. Wall 221 thus is provided on its anodic face with a titanium surface (an electroconductive material chemically resistant to the anolyte environment) and on its cathodic side with an iron surface (an electroconductive material resistant to the catholyte environment). Although, because of availability, cost and structural strength, backplates of titanium clad steel are specially preferred, backplates may have surfaces of other materials meeting certain electrical and corrosion resistant standards.

1n lieu of a steel cathodic surface, the backplate may be of other adequately electroconductive catholyte resistant materials such as ferrous metals (iron, alloys of iron including various steels), nickel, copper, gold, cobalt, platinum, silver lead and chromium, or mixtures thereof. Useful metals for the cathodic faces thus are those which do not readily form hydrides (by reaction with atomic hydrogen in the catholyte) and which are electroconductive. Metals whose resistivity is less than 50 microhms per cubic centimeter (at 20C.) are thus useful, while those with resistivities greater than l but less than about 20 microhms per cubic centimeter are especially useful.

On its side exposed to the anolyte, the backplates anodic surface may be of other so called valve metals or precious metals such as tantalum, niobium, platinum, zirconium, ruthenium, palladium, rhodium and irridium. The surface of titanium actually exposed to anolyte has thin protective titanium oxide film which usually develops in situ if not preformed. These metals and oxides are resistant to the anolyte conditions to which they are exposed, and particularly are resistant to chlorination, for example. Other oxides which have satisfactory corrosion resistant properties include magnetite and lead oxide.

As indicated, the respective anodic and cathodic sides of the backplate are of different materials, the most exemplary combination of which is titanium (on the anode side) and steel (on the cathode side) in the form of a single sheet, e.g., titanium clad steel. lt is however possible to use a structure in which a suitable electroconductive metal is sandwiched between the titanium and steel, such as a copper sheet having titanium on its anode side and steel on its cathode side.

The anodes 17| each include side walls 61| and 62| which are laterally spaced from one another and which may be secured such as by welding to a rear wall 63|. The side walls 61| and 62| of anode 17| are diverging rather than converging. ln other words, the space (and lateral distance) between walls 61| and 62| is less adjacent rear wall 63| than it is at the edge opposite rear wall 63|. The side walls 61| and 62| may have stiffening rods 242, if desired. The stiffcning rods 242 may be welded to the outer sides of walls 61| and 62|. ln this embodiment, the cathode linger 46| lies between the side walls 61| of one anode wall pair and 62| of the wall of the next adjacent anode. For further strengthening providing improved electrode spacing, the side wall 61| of one anode finger 17| may be secured at the forward edge thereof to the side wall 62| of that next adjacent anode finger, such as by connector 243. The connector 243 in this instance includes a screw 244 which extends through an opening in wall 61| and is threadedly engaged in nut 245. lt is possible to bring the forward edges of the anode walls substantially into touching contact by tightening this connecting means. The nut 245 is secured to side wall 62| such as by welding. The connector 243 alternatively may be a metal clip.

Although the walls of each anode diverge as they extend outwardly from rear wall 63| in this configuration, laterally spaced walls 62| and 61| each from one of two adjacent anodes which are interposed between adjacent cathode fingers converge as they extend towards cathodic backscreen 47|.

Cell J, shown in FlG. 13-15 is a further embodiment of the present invention. Cell 10J is constructed similar to cell 10 of FIG. l. Cell 10J has a cell container or frame 21J which. if desired, may be identical to frame 2| shown in FIG. l. Cell 10J further includes a plurality of wedge-shaped cathodes 16J and anodes 17j which are mounted on backplate 22.1 by an electrode support means 52j. ln this embodiment, the thin edge 255 of wedge-shaped electrodes lies in a horizontal plane or` in other words, the thin edge of the electrodes extends perpendicular to the vertical backplate 22]. The cathode 16J has a pair of side walls 45] and 50.1, a bottom wall 252, and an outer end wall 253. The walls 45.1, 50|, 252 and 253 may be constructed of screen. The walls 45| and 50], as shown in FIG. 14, converge upwardly. lf desired, baffles 254 (FlG. 13) may be provided in cathode 16J to force product gases from the cathode wedges into the space between the backstream 47j and the backplate 22]. The anode 17] includes a pair of side walls 61.| and 62j which are preferably constructed of foraminous plates. The anode 171 further includes a backplate 63|. The electrode support means 52], shown in detail in FIG. 15, is comprised of a current gathering bar 256 which is secured to walls 45.1 and 50] adjacent the open end of cathode 16J, for example, by welding. The electrode support means 52] further includes a rod 257 which is secured to bar 256 and extends through openings in the backplate 22j and rear wall 63] of anode 17J. A nut 258 is threadedly engaged with rod 257, thereby securing anode 17J and cathode 16J to the backplate 22].

The anodes 17 thorugh 171 have generally been described as being constructed of a titanium group metal with the walls 6l-61J and 62-62J being solid plates and the titanium plates being platinized on the side adjacent the cathode fingers 47-47.|. The anodes 17-17J may alternatively have side walls constructed of a pervious, anodically-resistant plate, for example, of rod material, screen, expanded metal mesh, perforated plate or louvered plate. The pervious plate may be of titanium metal. ln one preferred embodiment, the pervious titanium plate has an electroconductive surface, for example, of platinum, only on the side remote from the cathode fingers. By so doing, the titanium metal forms a non-conductive titanium oxide coating adjacent the diaphragm and gas evolution during cell operation takes place on the back side of the side walls, thus substantially reducing gas blinding and turbulence in the diaphragm. Both sides (surfaces) of the perforate anode may be provided with an electroconductive surface. When this is done, it is usually the better practice for the electroconductive surface facing the diaphragm to be thicker (1.5 to 5 times) than the coating 0n the other anode surface facing away from the cathode and toward the hollow of the anode.

Chlorine which evolves on the front side (and thicker electroconductive surface) of the anode wall nevertheless can move through the openings in the perforate anode walls into the hollow anode space. Louvered, perforate or expanded metal mesh or like materials with openings facilitate such gas movement and also permit anolyte to move from the electrode gap through the openings into the anode hollow. With the louvers (or like openings) tilted or fluted upwardly and inwardly toward the hollow space, gas and liquid movement through the anode walls has imparted thereto an upward movement component.

Furthermore` the side of the cathode backscreen and cathode fingers toward the anode may be electrically insulated such as with a rubber coating. By so doing, the cathodic gas products would be produced on the back side of the cathode which would further reduce gas blinding and back migration of caustic soda. This arrangment would provide a highly-efficient cell, particularly if the porosity of the diaphragm is slightly increased and the cell is operated at a high brine flow rate and a high current density such as in excess of 150, preferably in excess of 200, amperes per square foot of cathode surface, as defined by length and breadth measurements of the cathode. The cell of the present invention, especially when using wedge-shaped foraminous anodes and cathodes, operates in a very efficient manner when the anode-to-cathode gap (electrode gap) is near zero, for example, generally less than V2 inch, typically, fia to A inch and, preferably, the anode is directly against the diaphragm.

Although the present invention has been described with reference to specific details of particular embodiments thereof, it is not intended thereby to limit the scope of the invention except insofar as the specific details are recited in the appended claims. For example, one skilled in the art may replace the nonwoven asbestos fabric with a permionic membrane.

We claim:

l. A method of operating a bipolar electrolyzer having a plurality of individual bipolar units in back-toback bipolar configuration, with a peripheral wall around each individual bipolar unit; an anolyte chamber and a catholyte chamber in each individual bipolar unit, the anolyte chamber and catholyte chamber of an individual bipolar unit being separated from each other by a backplate having a surface of a ferrous metal on the catholyte side and titanium on the anolyte side; a plurality of hollow, wedge-shaped, inward and upward louvered, valve metal anodes in said anolyte chamber, said valve metal anodes having an electrically conductive surface thereon; valve metal conductors between the base of said valve metal anode wedges and the titanium surface of said backplate; the bases of said hollow, wedge-shaped, inward and upward louvered, valve metal anodes being held securely against said valve metal conductors; a plurality of hollow, wedge-shaped, metal cathodes in said catholyte chamber; said hollow, wedge-shaped metal cathodes being spaced from and electrically connected to the ferrous metal surface of said backplate; the hollow, wedge-shaped, valve metal anodes of one bipolar unit and the hollow, wedgeshaped cathodes of the next adjacent bipolar unit being interleaved between and uniformly spaced from each other and forming a single electrolytic cell therebetween; and a diaphragm therebetween dividing said single electrolytic cell into an anolyte chamber and a catholyte chamber; which method comprises feeding sodium chloride brine into each of the individual electrolytic cells; passing an electrical current through the electrolyzer from the cathodes of one cell through the backplate to the anodes of the next adjacent cell in the electrolyzer; evolving chlorine in the anolyte chamber; collecting the evolved chlorine within the hollow, wedge-shaped anodes between the inward and upward louvered metal walls thereof, thereby imparting an upward circulatory motion to anolyte liquor within the hollow, wedge-shaped anodes; recovering said chlorine at the top of said anolyte chamber; evolving hydrogen and caustic soda in said catholyte chamber; recovering said hydrogen at the top of said catholyte chamber; and recovering catholyte liquor from said catholyte chamber.

2. The method of operating a bipolar electrolyzer of claim 1 wherein said hollow, wedge-shaped, inward and upward louvered, valve metal anodes have an electrically conductive surface only on the interior surfaces thereof and wherein chlorine is evolved only within the hollow, wedge-shaped anodes.

3. The method of operating a bipolar electrolyzer of claim l comprising passing the electrical current from a cathode of one cell through an electrode support means which extends through an opening in the backplate, to an anode mounting means of the next adjacent cell of the electrolyzer, and from the anode mounting means to an anode mounted thereon.

4. The method of operating a bipolar electrolyzer of claim l comprising collecting the evolved hydrogen gas in a chamber in the upper portion of the bipolar unit and recovering catholyte liquor from a separate chamber in the lower portion of the bipolar unit.

5. A method of operating a bipolar electrolyzer having a plurality of individual bipolar units in back-toback bipolar configuration, with a peripheral wall around each individual bipolar unit; an anolyte chamber and a catholyte chamber in each individual bipolar unit, the anolyte chamber and catholyte chamber of an individual bipolar unit being separated from each other by a backplate having a surface of a ferrous metal on the catholyte side and titanium on the anolyte side; a plurality of hollow, wedge-shaped, inward and upward louvered, titanium anodes, in said anolyte chamber, said titanium anodes having an electrically conductive surface only on the interior surfaces thereof; titanium conductors between the base of said hollow, wedgeshaped, titanium anodes and the titanium surface of said backplate; the bases of said hollow, wedge-shaped, inward and upward louvered, titanium anodes being held securely against said titanium conductors; a plurality of hollow, wedge-shaped, metal cathodes in said catholyte chamber; said hollow, wedge-shaped metal cathodes being spaced from and electrically connected to the ferrous metal surface of said backplate; the hollow, wedge-shaped, titanium anodes of one bipolar unit and the hollow, wedge-shaped cathodes of the next adjacent bipolar unit being interleaved between and uniformly spaced from each other and forming a single electrolytic cell therebetween; and a diaphragm therebetween dividing said single electrolytic cell into an anolyte chamber and a catholyte chamber; which method comprises feeding sodium chloride brine into each of said individual electrolytic cells; passing an electrical current through said electrolyzer from the cathodes of one cell through the backplate to the anodes of the next adjacent cell in the electrolyzer; evolving and collecting chlorine within the hollow, wedge-shaped anodes between the inward and upward louvered walls thereof, thereby imparting an upward circulatory motion to anolyte liquor within the anode wedges; recovering said chlorine at the top of the anolyte chamber; evolving hydrogen and caustic soda in the catholytc chamber; recovering said hydrogen at the top of the catholyte chamber; and recovering catholyte liquor from the catholyte chamber.

6. The method of operating a bipolar electrolyzer of claim 5 comprising passing the electrical current from a cathode of one cell through an electrode support means which extends through an opening in the backplate, to an anode mounting means in the next adjacent cell, and from the anode mounting means to an anode mounted thereon.

7. The method of operating a bipolar electrolyzer of claim 5 comprising collecting the evolved hydrogen gas in a chamber in the upper portion of the bipolar unit and recovering catholyte liquor from a separate chamber in the lower portion of the bipolar unit.

8. A method of operating a bipolar electrolyzer having a plurality of individual bipolar units in back-toback bipolar configuration, with a peripheral wall around each individual bipolar unit; an anolyte chamber and a catholyte chamber in each individual bipolar unit, the anolyte chamber and catholyte chamber of an individual bipolar unit being separated from each other by a backplate having a surface of a ferrous metal on the catholyte side and titanium on the anolyte side; a plurality of hollow, wedge-shaped, inward and upward louvered, valve metal anodes in said anolyte chamber, said valve metal anodes having an electrically conductive surface only on the interior surfaces thereof; valve metal conductors between the base of said hollow. wedge-shaped, valve metal anodes, and the valve metal surface of said backplate; the bases of said hollow,

wedge-shaped, inward and upward louvered, valve metal anodes being held securely against said valve metal conductors; a plurality of hollow, wedge-shaped, metal cathodes in said catholyte chamber; said hollow, wedge-shaped, metal cathodes being spaced from and electrically connected to the ferrous metal surface of said backplate, the hollow, wedge-shapedl valve metal anodes of one bipolar unit and the hollow, wedgeshaped cathodes of the next adjacent bipolar unit being interleaved between and unformly spaced from each other and forming a single electrolytic cell therebetween; and a diaphragm therebetween dividing said single electrolytic cell into an anolyte chamber and a catholyte chamber; which method comprises feeding sodium chloride brine into each of said individual electrolytic cells; passing an electrical current through said electrolyzer from the cathode of one cell through an electrode support means which extends through an opening in the backplate, to an anode mounting means, in the next adjacent cell, and from the anode mounting means to an anode mounted thereon; evolving and collecting chlorine within the hollow, wedge-shaped, valve metal anodes between the inward and upward louvered walls thereof, thereby imparting an upward circulatory motion to the anolyte liquor within the hollow, wedgeshaped anodes; recovering said chlorine at the top of said anolyte chamber; evolving hydrogen and caustic soda in said catholyte chamber; collecting the evolved hydrogen gas in a chamber in the upper portion of the bipolar unit and recovering the hydrogen gas therefrom; and recovering catholyte liquor from a separate chamber in the lower portion of the bipolar unit.

9. A method of operating a bipolar electrolyzer having a plurality of individual bipolar units in back-toback bipolar configuration, with a peripheral wall around each individual bipolar unit; an anolyte charnber and a catholyte chamber in each individual bipolar unit, the anolyte chamber and catholyte chamber of an individual bipolar unit being separated from each other by a backplate having a surface of a ferrous metal on the catholyte side and titanium on the anolyte side; said bipolar unit having a chamber for the collection of gases in the upper portion thereof, in Communication with the catholyte side of the backplate, and a separate chamber for the collection of liquid in the lower portion thereof in communication with the catholyte side of the backplatc; a plurality of hollow, wedge-shaped, inward and upward louvered, titanium anodes in said anolyte chamber, said titanium anodes having an electrically conductive surface only on the interior surfaces thereof; internally threaded titanium conductors between the base of said titanium anode wedges and the titanium surface of said backplate; the bases of said hollow, inward and upward louvered, titanium anode wedges being held securely against said titanium conductors by a threaded, titanium screw; a plurality of hollow, wedge-shaped, ferrous metal cathodes in said catholyte chamber; said hollow, wedge-shaped ferrous metal cathodes being spaced from and electrically connected to the ferrous metal surface of said backplate; the hollow, wedge-shaped, titanium anodes of one bipolar unit and the hollow, wedge-shaped cathodes of the next adjacent bipolar unit being interleaved between and uniformly spaced from each other and forming a single electrolytic cell therebetween; and an asbestos diaphragm on said hollow, wedge-shaped cathodes dividing said single electrolytic cell into an anolyte chamber and a catholyte chamber; which method comprises continuously feeding sodium chloride brine into each of said individual electrolytic cells; passing an electrical current through said electrolyzer from the cathode of one cell through an electrode support means which extends through an opening in the backplate, to an anode mounting means, and from the anode mounting means to an anode of the next adjacent cell in the electrolyzer; evolving and collecting chlorine within the hollow, wedge-shaped, anodes between the inward and upward louvered walls thereof, thereby imparting an upward circulatory motion to anolyte liquor within the hollow, wedge-shaped anodes; recovering said chlorine at the top of said anolyte chamber; evolving hydrogen and caustic soda in said catholyte chamber; collecting the evolved hydrogen gas in the chamber in the upper portion of the bipolar unit; continuously recovering chlorine from said chamber, and recovering catholyte liquor from the separate chamber in the lower portion of the bipolar unit.

* lt Il* i 1k

Claims

1. A METHOD OF OPERATING A BIPOLAR ELECTROLYZER HAVING A PLURALITY OF INDIVIDUAL BIPOLAR UNITS IN BACK-TO-BACK BIPOLAR CONFIGURATION, WITH A PERIPHERAL WALL AROUND EACH INDIVIDUAL BIPOLAR UNIT: AN ANOLYTE CHAMBER AND A CATHOLYTE CHAMBER IN EACH INDIVIDUAL BIPOLAR UNIT, THE ANOLYTE CHAMBER AND CATHOLYTE CHAMBER OF AN INDIVIDUAL BIPOLAR UNIT BEING SEPARATED FROM EACH OTHER BY A BACKPLATE HAVING A SURFACE OF A FERROUS METAL ON THE CATHOLYTE SIDE AND TITANIUM ON THE ANOLYTE SIDE: A PLURALITY OF HOLLOW, WEDGE-SHAPED, INWARD AND UPWARD LOUVERD, VALVE METAL ANODES IN SAID ANOLYTE CHAMBER, SAID VALVE METAL ANODES HAVING AN ELECTRICALLY CONDUCTIVE SURFACE THEREON: VALVE METAL CONDUCTORS BETWEEN THE BASE OF SAID VALVE METAL ANODE WEDGES AND THE TITANIUM SURFACE OF SAID BACKPLATE: THE BASES OF SAID HOLLOW, WEDGE-SHAPED, INWARD AND UPWARD LOUVERED, VALUE METAL ANODES BEING HELD SECURELY AGAINST SAID VALVE METAL CONDUCTORS: A PLURALITY OF HOLLOW, WEDGE-SHAPED, METAL CATHODES IN SAID CATHOLYTE CHAMBER: SAID HOLLOW, WEDGE-SHAPED METAL CATHODES BEING SPACED FROM AND ELECTRICALLY CONNECTED TO THE FERROUS METAL SURFACE OF SAID BACKPLATE: THE HOLLOW, WEDGE-SHAPED, VALVE METAL ANODES OF ONE BIPOLAR UNIT AND THE HOLLOW, WEDGE-SHAPED CATHODES OF THE NEXT ADJACENT BIPOLAR UNIT BEING INTERLEAVED BETWEEN AND UNIFORMLY SPACED FROM EACH OTHER AND FORMING A SINGLE ELECTROLYTIC CELL THEREBETWEEN: AND A DIAPHRAGM THEREBETWEEN DIVIDING SAID SINGLE ELECTROLYTIC CELL INTO AN ANOLYTE CHAMBER AND A CATHOLYTE CHAMBER WHICH METHOD COMPRISES FEEDING SODIUM CHLORIDE BRINE INTO EACH OF THE INDIVIDUAL ELECTROLYTIC CELLS: PASSING AN ELECTRICAL CURRENT THROUGH THROUGH THE ELECTROL FROM THE CATHODES OF ONE CELL THROUGH THE BACKPLATE TO THE ANODES OF THE NEXT ADJACENT CELL IN THE ELECTROLYZER: EVOLVING CHLORINE IN THE ANOLYTE CHAMBER: COLLECTING THE EVOLVED CHLORINE WITHIN THE HOLLOW, WEDGE-SHAPED ANODES BETWEEN THE

3. The method of operating a bipolar electrolyzer of claim 1 comprising passing the electrical current from a cathode of one cell through an electrode support means which extends through an opening in the backplate, to an anode mounting means of the next adjacent cell of the electrolyzer, and from the anode mounting means to an anode mounted thereon.

4. The method of operating a bipolar electrolyzer of claim 1 comprising collecting the evolved hydrogen gas in a chamber in the upper portion of the bipolar unit and recovering catholyte liquor from a separate chamber in the lower portion of the bipolar unit.

5. A method of operating a bipolar electrolyzer having a plurality of individual bipolar units in back-to-back bipolar configuration, with a peripheral wall around each individual bipolar unit; an anolyte chamber and a catholyte chamber in each individual bipolar unit, the anolyte chamber and catholyte chamber of an individual bipolar unit being separated from each other by a backplate having a surface of a ferrous metal on the catholyte side and titanium on the anolyte side; a plurality of hollow, wedge-shaped, inward and upward louvered, titanium anodes, in said anolyte chamber, said titanium anodes having an electrically conductive surface only On the interior surfaces thereof; titanium conductors between the base of said hollow, wedge-shaped, titanium anodes and the titanium surface of said backplate; the bases of said hollow, wedge-shaped, inward and upward louvered, titanium anodes being held securely against said titanium conductors; a plurality of hollow, wedge-shaped, metal cathodes in said catholyte chamber; said hollow, wedge-shaped metal cathodes being spaced from and electrically connected to the ferrous metal surface of said backplate; the hollow, wedge-shaped, titanium anodes of one bipolar unit and the hollow, wedge-shaped cathodes of the next adjacent bipolar unit being interleaved between and uniformly spaced from each other and forming a single electrolytic cell therebetween; and a diaphragm therebetween dividing said single electrolytic cell into an anolyte chamber and a catholyte chamber; which method comprises feeding sodium chloride brine into each of said individual electrolytic cells; passing an electrical current through said electrolyzer from the cathodes of one cell through the backplate to the anodes of the next adjacent cell in the electrolyzer; evolving and collecting chlorine within the hollow, wedge-shaped anodes between the inward and upward louvered walls thereof, thereby imparting an upward circulatory motion to anolyte liquor within the anode wedges; recovering said chlorine at the top of the anolyte chamber; evolving hydrogen and caustic soda in the catholyte chamber; recovering said hydrogen at the top of the catholyte chamber; and recovering catholyte liquor from the catholyte chamber.

8. A method of operating a bipolar electrolyzer having a plurality of individual bipolar units in back-to-back bipolar configuration, with a peripheral wall around each individual bipolar unit; an anolyte chamber and a catholyte chamber in each individual bipolar unit, the anolyte chamber and catholyte chamber of an individual bipolar unit being separated from each other by a backplate having a surface of a ferrous metal on the catholyte side and titanium on the anolyte side; a plurality of hollow, wedge-shaped, inward and upward louvered, valve metal anodes in said anolyte chamber, said valve metal anodes having an electrically conductive surface only on the interior surfaces thereof; valve metal conductors between the base of said hollow, wedge-shaped, valve metal anodes, and the valve metal surface of said backplate; the bases of said hollow, wedge-shaped, inward and upward louvered, valve metal anodes being held securely against said valve metal conductors; a plurality of hollow, wedge-shaped, metal cathodes in said catholyte chamber; said hollow, wedge-shaped, metal cathodes being spaced from and electrically connected to the ferrous metal surface of said backplate, the hollow, wedge-shaped, valve metal anodes of one bipolar unit and the hollow, wedge-shaped cathodes of the next adjacent bipolar unit being interleaved between and unformly spaced from each other and forming a single electrolytic cell therebetween; and a diaphragm therebetween dividing said single electrolytic cell into an anolyte chamber and a catholyte chamber; which method comprises feeding sodium chloride brine into each of said individual electrolytic cells; passing an electrical current through said electrolyzer from the cathode of one cell through an electrode support means which extends through an opening in the backplate, to an anode mOunting means, in the next adjacent cell, and from the anode mounting means to an anode mounted thereon; evolving and collecting chlorine within the hollow, wedge-shaped, valve metal anodes between the inward and upward louvered walls thereof, thereby imparting an upward circulatory motion to the anolyte liquor within the hollow, wedge-shaped anodes; recovering said chlorine at the top of said anolyte chamber; evolving hydrogen and caustic soda in said catholyte chamber; collecting the evolved hydrogen gas in a chamber in the upper portion of the bipolar unit and recovering the hydrogen gas therefrom; and recovering catholyte liquor from a separate chamber in the lower portion of the bipolar unit.

9. A method of operating a bipolar electrolyzer having a plurality of individual bipolar units in back-to-back bipolar configuration, with a peripheral wall around each individual bipolar unit; an anolyte chamber and a catholyte chamber in each individual bipolar unit, the anolyte chamber and catholyte chamber of an individual bipolar unit being separated from each other by a backplate having a surface of a ferrous metal on the catholyte side and titanium on the anolyte side; said bipolar unit having a chamber for the collection of gases in the upper portion thereof, in communication with the catholyte side of the backplate, and a separate chamber for the collection of liquid in the lower portion thereof in communication with the catholyte side of the backplate; a plurality of hollow, wedge-shaped, inward and upward louvered, titanium anodes in said anolyte chamber, said titanium anodes having an electrically conductive surface only on the interior surfaces thereof; internally threaded titanium conductors between the base of said titanium anode wedges and the titanium surface of said backplate; the bases of said hollow, inward and upward louvered, titanium anode wedges being held securely against said titanium conductors by a threaded, titanium screw; a plurality of hollow, wedge-shaped, ferrous metal cathodes in said catholyte chamber; said hollow, wedge-shaped ferrous metal cathodes being spaced from and electrically connected to the ferrous metal surface of said backplate; the hollow, wedge-shaped, titanium anodes of one bipolar unit and the hollow, wedge-shaped cathodes of the next adjacent bipolar unit being interleaved between and uniformly spaced from each other and forming a single electrolytic cell therebetween; and an asbestos diaphragm on said hollow, wedge-shaped cathodes dividing said single electrolytic cell into an anolyte chamber and a catholyte chamber; which method comprises continuously feeding sodium chloride brine into each of said individual electrolytic cells; passing an electrical current through said electrolyzer from the cathode of one cell through an electrode support means which extends through an opening in the backplate, to an anode mounting means, and from the anode mounting means to an anode of the next adjacent cell in the electrolyzer; evolving and collecting chlorine within the hollow, wedge-shaped, anodes between the inward and upward louvered walls thereof, thereby imparting an upward circulatory motion to anolyte liquor within the hollow, wedge-shaped anodes; recovering said chlorine at the top of said anolyte chamber; evolving hydrogen and caustic soda in said catholyte chamber; collecting the evolved hydrogen gas in the chamber in the upper portion of the bipolar unit; continuously recovering chlorine from said chamber, and recovering catholyte liquor from the separate chamber in the lower portion of the bipolar unit.