US2330404A - Electrolytic alkali chlorine cell - Google Patents

Description

Filed Sept. 4, 1940 4,Sheets-Sheet 1 N VE N TOR Y E W .T T A p 1943- s. L. BURNS ET-AL 2,330,404

ELECTROLYTIC ALKALI CHLORINE CELL Filed Sept. 4, 1940 4 Sheets-Sheet 2 \Hymaes/v ATTO NEY Sept. 28, 1943, s. L. BURNS ET AL ELECTROLYTIC ALKALI CHLORINE CELL Filed Sept. 4, 1940 4 Sheets-Sheet 3 Hun @1151,

A TTOR E Y p 1943- s. L. BURNS ET AL 2,330,404

ELECTROLYTIC ALKALI CHLORINE CELL Filed Sept. 4, 1940 4 Sheets-Sheet 4 V I Z INVENTOR WE Y Patented Sept. 28, 1943 ELECTROLYTIC ALKALI CHLORINE CELL Samuel L. Burns and Martin Chesterfield, Niagara Falls, N. Y., assignors to Hooker Electrochemical Company, Niagara Falls, N. Y., a corporation of New York Application September 4, 1940, Serial No. 355,346

6 Claims.

Our invention relates more particularly to an alkali chlorine cell for production of caustic alkali, chlorine and hydrogen from alkali metal chlorides.

Our invention is a modification of the alkali chlorine cell disclosed in Patent No. 1,866,065. One object of our invention is to provide a cell having certain of the characteristics of the cell disclosed in this patent but having no concrete in its construction. Another object of our invention is to provide a cell of the general type referred to but having only one joint to be sealed against leakage.

Referring to the drawings:

Fig. 1 is a plan view of our cell, partly cut away to show the interior construction.

Fig. 2 is a side elevation of our cell, in section along line a-a of Fig. 1.

Fig. 3 is an end elevation of our cell, in section along the line bb of Fig. 1.

Figs. 4, 5 and 6 are perspective views of a number of cathodic electrode elements, illustrating one method of constructing and assembling them.

Fig. '7 is a plan view of a modified embodiment of our invention, in section along line d-d of Fig. 8. I

Fig. 8 is an elevation of this modification, in section along line e-e of Fig. '7.

Fig. 9 is a perspective view of a portion of the foraminous'cathodic electrode structure, in perspective, looking upward from below.

Referring to the figures:

Our cell comprises a cathode assembly forming a liquid-tight base member and an anode assembly resting upon and making a liquid-tight joint therewith.

The cathode assembly comprises a rectangular container or tank I, preferably of steel, housing. the cathodic electrode structure. Inside the rim of tank I, along each of its four sides, is a member 2, of angle sect on, the horizontal leg of the angle being welded to the rim to form a passage 3 extending all around the rim. The purpose of this passagewill be discussed later. The bottom of tank I is reinforced by ribs 4, extending transversely of the cell, and staggered ribs 5, 6 and l 8, extending longitudinally of the cell. Pads 9 and web i0 complete three points of support upon which the cell may rest,

cathodic electrode members ll, having fiat, versupported from tical faces. These cathodic electrode members are adapted to alternate with the anodic electrodes, .to be described later. In the preferred embodiment of the invention. they are parallel with each other and arranged in two groups or banks. The members of each bank are perpendicular to a side wall of tank I. Between the two banks is a clearance or passage l2, to facilitate circulation of electrolyte (see Figs. 1 and 3). Between each bank of cathod c electrode members and the side wall with which the members are perpendicular is a clearance or passage l3, which communicates with passage 3. Between the bottom of tank I and the banks of cathodic electrode members is a clearance or passage M, with 'which the open bottom edges 0f the clearance between these members communicate. The two banks of cathodic electrode members are joined together along their lower inner edges by a strip of foraminous metal similar to that from which the electrode members themselves are formed. Each bank of cathodic electrode members is also conductively joined to the angle member 2, to which it is adjacent, by

strips of similar foraminous metal.

The form of these cathodic electrode memhem will be better understood from Figs. 4, 5

and 6 which illustrate one method of constructing these members. A long sheet of foraminous metal, preferably of steel wire screen, having a width slightly greater than the" height of the finished electrodes, is first bent into wide corrugations separated by narrow corrugations. Ihe wide corrugations are of a width equal to the distance which is to separate the active cathodic surfaces, between which surfaces the anodic electrodes ai e later to be installed, clearance being provided between the anodic and cathodic electrode surfaces for circulation of electrolyte. The narrow corrugations are of a sufficient width to provide passages between the active cathodic electrode surfaces for removal of hydrogen and liquid products resulting from the electrolysis. The edges of the screen are then peened toward each other until they meet. At one, side of the sheet the edges of the wide corrugations are pcened toward each other until they iect in seam l5, where the wires are butted and welded. At the other side the edges of the narrow corrugations are peened toward each other. preferably over a semi-circular mandrel, until they meet in seam l6. where the wires are likewise butted and welded. The screen is also peened outward at the roots of both the narrow and wide corrugations, as illustrated at ll, Fig,

4. Strips of wire screen are then scalloped along one edge. the other edge being left straight. A portion of such a strip is illustrated at l8, Fig. 6. Other strips are scalloped along both edges. A portion of such a strip is illustrated at l9, Fig. 5. The radii and pitch of these scallops are those of the peened roots l1. These strips are butted and welded along their scallops to roots ll of the cathodic electrode members ii. Two banks of cathodic electrode members are thus assembled into units. The number of cathodic electrode members ii, formed and assembled in each bank depends upon the current under which the cell is intended to perate, and other practical considerations. Strips i8 are then continued around the ends of the cell as illustrated at and strips [9 are carried up the ends of the cell as illustrated at 2i. After the cathodic electrode members Ii and strips l8, i9, 20 and 2i have been assembled in i this way, a steel supporting structure is inserted between the walls of these electrodes, behind their roots and below their lower edges. This structure is made up of members 23, 24 and 25. Members 23- are fiat strips of steel of a width to slide freely into the clearances between the electrodes H but wide enough to support their walls against collapsing pressures. Members 24, to which members 23 are welded at their intersections, form with. members 23 a rake like structure, the pitch of the teeth of the rake being exactly that which it is desired that the series of parallel cathodic electrode members should finally have. Vertical members 25, to which members 23 and 24 are welded at their intersections, space the two rake-like structures on each side of the cell at the desired distance apart and height from the bottom of the cell. Members 26, mounted upon legs 21, support the bottom edges of each bank of cathodic electrodes. Members 23 complete the supporting structure. These are horizontal fiat strips welded to the lower free edge of angle member 2, and also welded to each other at the corners of the cell, so that they form a shelf extending inward from angle member 2. Strips l8 and 20 of wire screen overlap and rest upon this shelf.

Strips l8 and 20 are conductively welded to angle member 2 and members 28. The outer ends of members 23 and the lower ends of members 25 are welded to the shell of tank I. Members 25 are also welded to the horizontal wires of the screen itself at the root of the cathodic electrode.

Cathodic electrode members H are covered with a permeable diaphragm as indicated by the speckled surfaces, dividing the cell into an anode compartment and a cathode compartment. This is preferably of asbestos fiber. It will be noted that the active cathode surface is formed by two or more sheets of wire screen which is corrugated in both the vertical and horizontal planes, hence has warped e. g., quarter sphericall surfaces where the convolutions intersect. Such surfaces could not be covered. by a sheet of paper. The diaphragm can therefore best be applied by the method disclosed in U. S. Patents Nos. 1,855,497 and 1.862.244 and 1,865,152. The diaphragm formed in this way will cover strips i8 and 20 and will therefore be overlapped and have its edges scaled by non-conducting coating 39.

The anode as embly comprises a rectangular main frame 33. of angle section, formed of four pieces welded a. the corners, supporting a series of graphite anodic electrodes 3l'. The proportions and dimensions of frame conform to the inner wall formed by angle member 2, with however a suitable clearance for insulation. Frame 30 rests upon insulating blocks 32 which in turn rest upon strips 18 and 20, which of course are supported by the rigid shelf formed by members 28.

Frame 30 is covered by rectangular plate 33, to which the vertical leg of its angle section is welded all around the frame, except where bus bar 34 enters through a slot in the vertical leg of the angle to make contact with the under surface of plate 33. Beneath cover 33 is a slab 35 of low melting metal or alloy, preferably lead, extending between the end members of frame 33 and retaining members 36, which are parallel to a side member of frame 30. In lead slab 35 are embedded, for a short distance at their upper ends, the graphite blades which constitute anodic electrodes 3i. These blades are thin, fiat, elongated plates adapted to alternate with cathodic electrode members II, with however, sufficient clearance between to permit of circulation of the electrolyte. In the particular embodiment of our invention illustrated, these blades are arranged in groups of three, placed edge to edge, each group of blades being in parallel alignment with a series of other similar groups, the entire series forming two banks of electrodes, leaving clearance l2 open for circulation of electrolyte. The anodic electrodes thus depend from the top or cover of the cell and extend nearly to the bottoms of the cathodic electrode members. a clearance being, however, provided at the bottom for circulation of electrolyte. Each anode blade has two holes drilled through it near the end which is to be embedded in lead. Each blade is also notched where it is contiguous with the adjoining blade. The lead is introduced in a molten condition, and as it flows through the holes and notches the blades are anchored to the lead securely.

The inner surfaces of frame 30, cover 33. lead slab 35 and members 36 is protected against electrolysis by a non-conducting layer 38, preferably of bitumen or asphalt. This is likewise poured in while molten and flows through the notches between contiguous blades. When the anode assembly is in place and resting upon insulating blocks 32 the joint between it and the cathode assembly is sealed by pouring in bituminous material 33.

At a point above passage l2, preferably at the geometrical center of the cell, an exit 40 is provided for chlorine. This comprises a section of ceramic pipe 4| in an envelop 42 of steel, the bitumen of non-conducting layer 38 being allowed to fill the space between. Between the upper edges of cathodic electrode members H and the lower surface of non-conducting layer 38, sufficient clearance is provided for circulation of electrolyte and to permit the chlorine liberated on anodic electrodes 3| to find its way to passage i2 and thence to exit 40.

Hydrogen liberated on the cathodic side of the diaphragm finds its way beneath the top walls of the cathodic electrodes to and through passage 3 to exit 44.

The liquid products of electrolysis, together with undeco-mposed electrolyte, find their way through the open outer ends and bottoms of the cathodic electrodes to the cathode compartment, whence they are discharged through pipe 45, which, although connected to tank I near its bottom is preferably formed with a high point slightly below the level of the upper edge of cathodic electrode members ll, so that the oathode compartment of the cell is normally nearly filled with liquid.

In order that the discharge passages from the cathodic electrodes may be more clearly visualized. aportion of the foraminous cathodic electrode structure, in perspective, looking upward from below, is shown in Fig. 9, the supporting structure being omitted for simplicity. In this figure the discharge of hydrogen and liquid products from the open outer ends and bottoms of the cathodic electrodes is clearly indicated by the arrows.

Electrolyte may be supplied to the cell in the form of a jet (not shown) directed downwardly into chlorine exit 40. The level of the electrolyte within the cell is indicated by a. stem 41 attached to float 48, which floats in tube 49. The

lower end of tube 49 is upturned to prevent escape of chlor ne. Stem 41, float 48 and tube 49 are preferably of glass.

Bus bar 46, which is conductively connected to tank I, together with bus bar 34, already referred to, serves to complete the electrical connections to the cell.

Figs. '7 and 8 illustrate a modification of our cell in which-the shape in plan is circular. In

- these figures, parts that are analogous to parts illustrated in Figs. 1 to 3 are indicated by the same reference numbers, followed by the suffix 11. Thus, the tank is la, the cathodic electrode members Ha, the central, peripheral and bottom clearances or passages l2a. I311 and [4a respectively, the shelf 28a. the frame of the anode assembly 30a, the anodic electrodes 3la, the cover 33a, the lead slab 3511, the bitumen covering 38a, the chlorine exit 40a, the ceramic dome Ma, the hydrogen exit 44a and the exit for liquid products 45a. In this case the side walls of the cathode electrode members Ha are of course radial. The particular advantage of this embodiment of our invention is that it permits the electrolyte to be introduced at the exact geometrical center of the cell, thus securing equal distribution to all the electrodes.

While we have illustrated and described one method'of forming the cathodic electrodes, we do not wish to be strictly limited thereto, as other methods of forming these electrodes will suggest themselves to persons skilled in the art. We claim as our invention: 1. In an electrolytic alkali-chlorine cell. a cathode assembly comprising an open, liquidtight, metal tank adapted to carry the cell current and housing a foraminous, caustic alkali resistant, metal structure, said foraminous structure comprising spaced, horizontally-aligned, cathodic electrodes extending from opposite sides filler strips to the rim of said tank, the lower edges of the inner cathodic electrode end walls and inner edges of the bottom bridge walls being conductively joined to a central fitted filler member similarly joincdto similar edges of opposite cathodic electrodes, joining all the cathodic electrodes into a unitary structure having discontinuous bottom and side walls paralleling the bottom and side walls of said tank with corridors between into which the cathodic electrodes may freely deliver products of electrolysis through their open bottoms and ends; and means for withdrawing gaseous and liquid products of electrolysis from said corridors.

2. In an electrolytic alkali-chlorine cell, a cathode assembly comprising an open, liquidtight, rectangular metal tank adapted to carry the cell current and housing a foraminous, caustic alkali-resistant, metal structure comprising two banks of thin, parallel, spaced, horizontally- V aligned, cathodic electrodes extending from opposite sides of said tank perpendicularly with respect thereto and with respect to the bottom of said tank and adapted to alternate and co-operate with chlorine-resistant anodic electrodes extending downwardly from above; said foraminous structure being adapted to be covered on its anode facing surfaces with permeable, chlorineresistant diaphragm material, each of said cathodic electrodes comprising a. top wall, an inner end wall and two side walls and being open at its bottom and outer end, the spaces between adjacent cathodic electrodes being bridged at their bottoms and outer ends, the outer edges of said top walls and upper edges of the outer'bridge walls being conductively joined through fitted filler strips to the rim of said tank, the lower edges of the inner cathodic electrode end walls and inner edges of the bottom bridge walls being conductively joined to acentral fitted filler strip similarly joined to similar edges of the opposite bank of cathodic electrodes, joining the two banks into a unitary structure having discontinuous bottom and side walls paralleling the bottom and side walls of said tank with corridors between intowhich the cathodic electrodes may freely deliver products of electrolysis through their open bottoms and ends; and means for withdrawing gaseous and liquid products of elecof said tank perpendicularly with respect thereto and with respect to the bottom of said tank and adapted to alternate and co-operate with chlorine-resistant anodic electrodes extending downwardly from above; said foramin'ous strum ture being adapted to be covered on its anode facing surfaces with permeable, chlorine-resistant diaphragm material, each of said cathodic electrodes comprising a top wall, an inner end wall and two side walls and being open at its bottom and outer end, the spaces between adjacent cathodic electrodes being'bridged at their bottoms and outer ends, the outer edges of said top walls and upper edges of the outer bridge wallsbeing conductively joined through fitted trolysis from said corridors.

3. In an electrolytic alkali-chlorine cell, a cathode assembly comprising an open, liquidtight, rectangular metal tank adapted to carry the cell current and housing a foraminous, caustic alkali-resistant, metal structure comprising two banks of thin, parallel, spaced. horizontallyaligned, cathodic electrodes extending from opposite sides of said tank perpendicularly with respect thereto and with respect to the bottom of said tank and adapted to alternate and cooperate with chlorine-resistant anodic electrodes extending downwardly from above; said foraminous structure being adapted to be covered on its anode facing surfaces with permeable, chlorineresistant diaphragm material, each of said cathodic electrodes comprising a top wall, an inner end wall and two side walls and being open at its bottom and outer end, the spaces between adjacent cathodic electrodes being bridged at their bottoms and outer ends, walls paralleling the end walls of said tank, with corridors between, the spaces between cathodic electrodes at the extremities of said banks and said Walls paralleling the end walls of said tank being bridged at the bottoms and outer ends of said cathodic electrodes, the outer edges of said top walls and upper edges of the outer bridge walls and end Walls paralleling the end walls of the tank, being conductively joined through fitted filler strips to the rim of said tank, t'ze lower edges of the inner cathodic electrode and walls and inner edges of the bottom bridge walls being conductively joined to a central fitted filler strip similarly joined to similar edges of the opposite bank of cathodic electrodes, said central fitted filler strip being likewise joined at its ends to the lower edges of said walls paralleling the end walls of the tank, joining the LWO banks into a complete unitary basket-like structure having discontinuous bottom and side walls paralleling the bottom and side walls of said tank with corridors bet-ween into which the cathodic electrodes may freely deliver products of electrolysis through their open bottoms and ends; and means for withdrawing gaseous and liquid products of electrolysis from said corridors.

4. In an electrolytic alkali-chlorine cell, a cathode assembly comprising an open, liquid-tight, rectangular metal tank provided with an inwardly extending shelf around its rim, said tank being adapted to carry the cell current and housing a foraminous, caustic alkali-resistant. metal structure comprising two banks of thin, parallel, spaced, horizonta ly-aligned, cathodic electrodes extending from opposite sides of said tank perpendicularly with respect thereto and with respect to the bottom of said tank and adapted to alternate and co-operate with chlorine-resistant anodic electrodes extending downwardly from above; said foraminous structure bein adapted to be covered on its anode facing surfaces with permeable. chlorine-resistant diaphragm material, each of said cathodic electrodes comprising a top wall, an inner end wall and two side walls and being open at its bottom and outer end, the spaces between adjacent cathodic electrodes being bridged at their bottoms and outer ends, the outer edges of said top walls and upper edges of the outer bridge Walls being conductively joined through fitted filler strips to the edge of said shelf. the lower edges of the inner cathodic electrode end walls and inner edges of the bottom bridge walls bein conductively joined to a central fitted filler strip similarly joined to similar edges of the opposite bank of cathodic electrodes, joining the two banks into a unitary structure havine; discont nuous bottom and side Walls paralleling the bottom and side walls of said tank with corridors between into which the cathodic electrodes may freely deliver products of electrclvsis through their open bottoms and ends, and means for withdrawing gaseous and liquid products of electrolysis from said corridors.

5. In an electrolytic alkali-chlorine cell, a cathode assembly comprising an open, liquid-tight, rectangular metal tank provided with an inwardly extending flange around its rim, inner walls joined to said flan e and paralleling the walls of said tank, forming therewith and with said flange a gas-tight passage extending around the rim of said tank. and an inwardly extending shelf around the lower edge of said inner paralleling Wall and making a gas-tight joint therewith, said tank being adapted to carry the cell current and housing a foraminous, caustic alkali-resistant. metal structure comprising two banks of thin, parallel, spaced, horizontally-aligned,

cathodic electrodes extending from opposite sides of said tank, perpendicularly with respect thereto and with respect to the bottom of said tank and adapted to alternate and co-operate with chlorine-resistant anodic electrodes extending downwardly from above; said foraminous structure being adapted to be covered on its anode facing surfaces with permeable, chlorine-resistant diaphragm material, each of said cathodic electrides comprising a top wall, an inner end wall and two side walls and being open at its bottom and outer end, the spaces between adjacent cathodic electrodes being bridged at their bottoms and outer ends, the outer edges of said top walls and upper edges of the outer bridge walls being conductively joined through fitted filler strips to the edge of said shelf, the lower edges of the inner'cathodic electrode and walls and inner edges of the bottom bridge walls being conductively joined to a central fitted filler strip similarly joined to similar edges of the opposite bank of cathodic electrodes, joining the two banks into a unitary structure having discontinuous bottom and side walls paralleling the bottom and side walls of said tank with corridors between into which the cathodic electrodes may freely deliver products of electrolysis; and means for withdrawing liquid products of electrolysis from said corridors at a level substantially above the bottom of said tank but below the level of said shelf and gaseous products of electrolysis from said gas tight passage.

6. In an electrolytic alkali-chlorine cell, a cathode assembly comprising an open, liquid-tight, rectangular metal tank adapted to carry the cell current and housing a foraminous, caustic alkaliresistant, metal structure comprising two banks of thin, parallel, spaced, horizontally-aligned, cathodic electrodes extending downwardly from above; said cathodic electrode comprising clan-- ated sheets of foraminous metal flexed into convolutions having straight side, constituting the active faces of the cathodic electrodes, joined by fillets constituting the ends and roots of the cathodic electrodes, the top and bottom edges of said sheets being peene d in opposite directions to form filleted flanges continued around the ends of the cathodic electrodes at the bottom and around the roots of the cathodic electrodes at the top. the top flanges being joined to form the top walls of the cathodic electrodes, the bottom flanges being joined to bridge the spaces between adjacent cathodic electrodes, the scalloped edges thus left free along the upper outer edge of each of the resulting structures being conductively joined through fitted filler strips to the rim of said tank, constituting a bank of cathodic electrodes, the scalloped edges thus left free along the lower inner edge of said resulting structure being conductively joined through a fitted filler strip to the similarly scalloped edge of the opposite bank of electrodes, joining the two bunks of cathodic electrodes into a unitary structure havin discontinuous bottom and side walls paralleling the bottom and side walls of said tank respectively, with corridors between into which the cathodic electrodes may freely deliver products of electrolysis through their open bottoms and ends: and means for withdrawing gaseous and liquid products of electrolysis from said corridors.

SAMUEL L. BURNS. MARTIN CHESTERFIELD.

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