US 3055821 A
Description (OCR text may contain errors)
Se t. 25, 1962 A. J. HOLMES ETAL 3,055,821
DIAPHRAGMLESS MONOPOLAR ELECTROLYTIC CELL Filed March 7, 1960 2 Sheets-Sheet 1 FIG.I
INVENTORS ARTHUR J. HOLMES By WILLIAM C.GARD|NER %WMM1/ AGENT Sept. 25, 1962 A. J. HOLMES ETAL 3,055,821
DIAPHRAGMLESS MONOPOLAR ELECTROLYTIC CELL Filed March 7, 1960 2 Sheets-Sheet 2 24 23 I? F 34 ooooooooooo I I I v 36 3 I 000000000000 I [I [I [I [I L44 I8 '9 25 w FIG.2
VINVENTORS ARTHUR J. HOLMES y WILLIAM C.GARD|NER AGENT 3,055,821 DIAPI-RAGMLESS MONOPULAR ELECROLYTIC CELL Arthur J. Holmes, Tonawanda, and William C. Gardiner,
Niagara Falls, N.Y., assignors to fllin Mathieson Chemical Corporation, a corporation of Virginia Filed Mar. 7, 1960, Ser. No. 13,021 3 Claims. (Cl. 204--270) This invention relates to improvements in electrolytic cells. More particularly it relates to diaphragmless, monopolar electrode cells useful for a variety of electrochemical purposes.
The electrolytic cell of the present invention generally comprises a cell container, anode and cathode assemblies and suitable accessory parts.
The cell container is a rectilinear box with three closed sides and a fourth side in which is formed a rectangular anode port which is appropriately flanged to receive the anode assembly. The two sides perpendicular to the anode port side can be single sheets but preferably are double walled sides with suitable internal baflles and fittings to provide cooling water jackets. The cell container is open and flanged at the top to receive the cell cover. A feed inlet is provided at a convenient point in the cell container, suitably through the single walled cathode side or anode port side. A valved drain is advantageously provided in the bottom of the cell container to permit removal of the liquid contents of the cell when necessary. The cell is supported on insulating legs attached to the bottom of the cell container.
The cathode assembly consists of a plurality of vertically disposed steel sheets integrally attached, suitably by welding, to the inside surface of the side of the cell container which is opposite the anode side. The cathode sheets extend across the cell and partly through the opening in the anode side and are supported by welding to the lower and upper ledges of the port in the anode side of the cell container. The cathode sheets are suitably spaced to receive an anode between each adjacent pair of cathode sheets. The thickness of the cathode sheets may vary from about 0.1 to 0.5 inch. Standard 0.25 inch steel plates are particularly suitable. Using anodes of a thickness of 0.1 to 0.125 inch, the spacing between the cathode sheets is appropriately about 0.5 inch. The cathodes and entire cell container are cathodically protected against corrosion since in use they are covered by electrolyte. Thus, ordinary iron or mild steel is suitable for cathode sheets and cell container.
The cathode assembly has a width less than that of the cell container and an electrolyte mixing and circulation zone is provided around the sides of the cathode assembly.
The anode assembly consists of a series of vertically arranged titanium sheets coated with a platinum metal. The individual plates are mounted perpendicularly on a heavier titanium sheet into which the electrodes are press-fitted or welded. Press-fitted anodes are particularly advantageous in that they are easily removed and replaced when re-plating becomes necessary. The anode sheets are suitably from about .05 to 0.5 inch in thickness. In this range commercially available sheets 0.1 and 0.125 inch in thickness are particularly suitable. The cathode spacing is selected to accommodate the anode thickness and desired inter-electrode spacing. For example, when the anodes are 0.1 inch thick, and the cathodes are 0.25 inch thick the cathodes are appropriately 0.75 inch between centers. It is convenient to arrange the dimension of the cell to utilize sheets of commercially available size, for example, 4 x 8 feet. Alloys consisting principally of titanium may also be used as the base metal of the anodes.
3,fl55,82l Patented Sept. 25, 1962 ice The platinum may be applied to the titanium anodes in any suitable manner, for example by the process described in Australian application 36,758, of 1958 by Jansen, opened to public inspection April 1, 1958, or by the process described in Australian application 49,837 of 1958 by Imperial Chemical Industries, Ltd., opened to public inspection July 23, 1958, or by other suitable methods. Other metals of the platinum group may also be used. The platinum coating on the anodes appropriately covers an area of the anodes equal to that overlapped by the cathodes. The coating need not be applied to the stubs of the anodes or to the titanium base plate to which they are attached.
The anode assembly is inserted into the cell container containing previously fitted cathodes, interleaving the anodes and cathodes and bolting the titanium base plate of the anode assembly to the flanges defining the rectangular port of the anode side of the cell container. The titanium plate is insulated from the flanged surfaces by means of a non-conducting gasket which may be soft rubber or any other suitable material. The bolts are insulated by any suitable means, for example, by Micarta sleeves and washers.
The anodes and cathodes are separated and spaced by means of depending spacers suitable in the form of bars or rods of insulating material, for example, glass or Teflon. The spacers are supported by means of retainers lying transversely across the top of the anodes and cathodes and fabricated of similar non-conductive materials. The retainers are suitably Teflon sheets slotted or punched to receive the bars or rods which depend between the electrodes. The retainers and spacers are suitably held in place by means of bolts welded to the top end of the cathode plates.
The cell cover is also a rectilinear box suitably flanged to fit on the cell container and to provide ample space for cell gas to disengage from the cell liquor. An opening at the top of the cell cover permits the removal of cell gas and an outlet near the bottom of one side is provided for eflluent cell liquor. The cell cover may be made of plastic or other corrosion resistant material, for example, titanium or glass lined steel. include polytetrafluoethylene or polytrifluovinyl chloride. A plastic coating may be applied to steel using Kel-F (polytrifluovinylchloride) dispersion or by an other suitable means.
Since titanium is only a fair conductor of electricity, a thin sheet of copper or aluminum is advantageously applied, for example, by silver brazing to the titanium anode base plate to improve current distribution. A similar current distributing sheet is advantageously applied to the cathode side of the cell container. Bus connections, for example, copper bars, are applied by similar means to the copper sheets covering the titanium anode base plate and the cathode side of the cell container.
The cells of this invention are constructed very simply and effect a considerable saving of space over known monopolar cells of the same capacity. The-particular design of this invention also effects an important saving in the cost of expensive titanium over designs in which the anodes extend to or through the gas-disengaging space in the top of the cell. All of the surface of the anodes of the present design'are below electrolyte level and are working surfaces. However, the base plate to which the anodes are fitted is necessarily titanium which resists the corrosive action of the electrolyte and evolved gases even though not cathodically protected. The cells are particularly advantageous when a group of them are arranged in series with bus bars between the cathode assembly of one cell and the anode assembly of the adjacent cell. The cells can be closely spaced and the bus bars are then Suitable plastics very short. An external source of current is applied to the cathodes of one terminal cell and the anodes of the other terminal cell. Advantageously connections for cooling water, electrolyte feed, electrolyte efiluent and gas effiuent are arranged to permit easy access. One cell can be shorted out by appropriate bus connections and removed as a unit without interrupting operations.
The cells of this invention are especially suitable for the electrolysis of sodium chloride to sodium chlorate. They are particularly designed for operation at temperatures higher than usual in the art of producing chlorates. In use, strong sodium chloride brine which may also contain dissolved sodium chlorate (recycle brine, refortified with sodium chloride), is introduced through the feed inlet near the bottom of the cell container. The brine circulates in the cell, being lifted upward between the electrodes by evolved hydrogen gas and flows downward near the sides of the cell. Mixing is excellent. The brine, enriched in chlorate is removed through the brine outlet in the cell top and treated to recover sodium chlorate. Hydrogen and any other evolved gases are disengaged in the cell top and leave by the gas outlet in the top.
In chlorate service, the novel cells operate at approximately three times the current density of conventional graphite anode chlorate cells. The platinum coated titaninum is extraordinarily resistant to oxidation, corrosion and erosioneven at temperatures above 100 C. Whereas graphite anodes wear away and inter-electrode distances and, therefore, resistance increase in use, the platinum-on-titanium anodes maintain the original close spacing between electrodes indefinitely. High conductivity is maintained and the cell retain their original high efiiciency. Because of their high, constant current density, space requirements for the novel cells are about onethird that for conventional cells. Operating costs are markedly reduced.
A particular embodiment of the invention is described in the accompanying drawings. FIGURE 1 is a side view, partly in elevation and partly in section of the electrolytic cell of this invention and FIGURE 2 is section 2--2 of FIGURE 1 taken just above the electrodes. The cell box 11 has a drain 12 and a flange 13 at the top. Two opposite sides have inner walls 14 and outer walls 15. The outer walls are fitted with inlets 16 at the bottom and outlets 17 near the top thus providing jackets for cooling water. The cell also has a brine inlet 18 near the bottom of one side. Flanged surfaces 19 define the port in the anode side of the cell container 11. The port defined by flange 19 is partially covered by titanium base plate 20 of the anode assembly and fastened thereto by bolts 21. Soft rubber gasket 25 is applied between the flange 19 and the titanium plate 20 to insulate the anode base plate from the cathodic container. The bolts are insulated from the flange 18 by Micarta sleeves and gaskets (not shown). In FIGURE 1, titanium plate 20 is cut away revealing cathodes 22 and anodes 33.
A sheet of copper 23 is bonded to the major portion of the surface of the titanium base plate of the anode assembly. A similar sheet of copper 23 is applied to the opposite side of the cell for current distribution to cathode 22. Bus connections 24 are applied to the copper sheet 23 covering the titanium base plate 20 and the cathodic side wall opposite. The cell is supported on insulating pedestals 37.
FIGURE 1 shows cell top 26 with gas outlet 27 and liquor outlet 28. The lower edge of cell top 26 carries flange 29 which is bolted to flange 13 at the top of the cell container '11 by means of bolts 30 and nuts 31. A soft rubber gasket 32 is applied between flanges 29 and 13. Electrical insulation is not necessary between these surfaces. i
Example A cell, designed and constructed as described above has 20 platinum coated titanium sheets 2 by 2.5 feet by 0.1 inch thick spaced 0.75 inch on centers. They are press-fitted into slots in a 0.375 inch thick titanium anode base plate 19 by 36 inches bolted to the flanges of a rectangular port of the same dimensions in the side of the cell container. Cathode sheets 0.25 inch thick by 2 by 2.7 feet are welded to the inside of the opposite side of the cell container. The spacing is 0.75 inch on centers. The overall dimensions of this cell excluding bus bars are 2.1 by 2.3 by 4 feet 6 inches high. A typical conventional chlorate cell to produce the same amount of chlorate, requires a cell about 3 feet by 8 feet by 4 feet high. The floor space actually occupied by the cell of the present example is about 4.8 square feet while the area occupied by a conventional cell with the same daily chlorate capacity is thus about 24 square feet. The sidemounted anodes require about one-third less titanium than top-mounted anodes would.
What is claimed is:
1. An electrolytic cell comprising a ferrous rectilinear cell container, an anode assembly and a cathode assembly, the cell container having a bottom, three closed sides and a fourth side having an anode port defined by a rectangular flange in a plane parallel to the plane of the fourth side, a cathode assembly integral with and perpendicular to the side of the cell container opposite the fourth side and formed of vertically disposed steel cathode sheets spaced to receive an anode sheet between each adjacent pair of cathode sheets, an assembly of vertically arranged, platinum coated titanium anode sheets integral with a titanium anode base plate cloisng the port in the fourth side of the cell container and electrically insulated therefrom, insulating spacers between each pair of adjacent anode and cathode sheets and a top attached by fluid-tight means to the cell container, a gas outlet and a liquor outlet in the top and a liquor inlet in the cell container.
2. The electrolytic cell of claim 1 in which the two sides perpendicular to the fourth side are double walled sides with cooling water inlets and outlets.
3. A series of electrolytic cells comprising a plurality of the cells of claim 1, the cathode assembly of each cell being electrically connected to the anode assembly of the adjacent cell with the proviso that the cathode assembly of one terminal cell of the series and the anode assembly of the other terminal cell of the series are electrically connected to an external source of electric current.
References Cited in the file of this patent UNITED STATES PATENTS 728,440 Boucher May 19, 1903 1,477,099 Baum Dec. 11, 1923 FOREIGN PATENTS 508,487 France July 26, 1920 OTHER REFERENCES Cotton: Platinum Metals Review, volume 2, April 1958, pages 45 through 47.