GB2101632A - Electrolysis cell - Google Patents

Abstract

An electrolysis cell consisting of a housing 1 with one inlet 4 and one outlet 5 for the electrolyte passing through the cell, said housing accommodating monopolar electrodes, 7, 8, 9, each electrode consisting of parallel plates 13, 15, fixed to a common carrier element, the electrodes being arranged in a staggered pattern so that the plates of one polarity extend into the gaps formed by the plates of the opposite polarity and that at least one median electrode stack 9 of one polarity with central electric power supply input is arranged between two electrode stacks of the opposite polarity, is characterized in that the median electrode stack 9 consists of a plurality of electrode plates 13 and a current supply plate 14 of a length substantially equal to that of the electrode plates and a width substantially equal to that of the cell, the electrode plates 13 being directly fixed e.g. welded along one longitudinal side to the power supply plate 14. The power supply plate 14 is optionally joined to a side wall 17 of the cell housing 1, the wall 17 being optionally provided externally with at least one power input connection 12. <IMAGE>

Description

SPECIFICATION Electrolysis cell The present invention relates to an electroylsis cell consisting of a housing with one inlet and one outlet for the electrolyte passing through the cell, said housing accommodating monopolar electrodes, each electrode consisting of a number of parallel plates fixed to a common carrier element, the electrodes being arranged in a staggered pattern so that the plates of one polarity extend into the gaps formed by the plates of the opposite polarity and that at least one median electrode stack of one polarity with central electric power input is arranged between two electrode stacks of the opposing polarity.

German Auslegeschrift No. 26 45 121 describes a monopolar cell having such a design through which the electrolyte passes in a vertical direction and in which a plurality of electrode plates is arranged vertically in a monopolar pattern. The two outer electrode stacks are connected to the negative pole of a power source and thus serve as cathodes. These outer electrode plates are fixed to 2 carrier plates which serve as two side walls of the cell. The plates are arranged in a vertical direction, equally spaced and parallel to one another. The inner electrode plates which constitute the median electrode stack are connected to the positive pole of a power source to serve as anodes.

The individual anode plates of the desired design are rectangular and are provided with 2 circular openings located symmetrically on the centre line. The anode plates are fixed to two sleeves extending through the openings and are equally spaced, parallel to one another and perpendicular to the longitudinal centre lines of the sleeves. The cathode plates are rectangular and their free longitudinal edge is provided with 2 semi-circular openings; the plates are arranged so that a small annular gap is left between the sleeves and the cathode plates fixed to the two opposite carrier plates.

All cathode components are of steel while all anode components are of titanium. The anode plates are coated with an activating layer of a known type on one or both sides. The anode plates are lined up on one or preferably several threaded rods and are fixed in place by means of threaded sleeves and threaded rings. According to one embodiment described, in the central electrode stack the threaded sleeves are provided with annular crowns to which the anode plates with corresponding openings are welded.

While the cathode plate of the electrolysis cell of the described design is free of mechanical problems, the cell is affected by certain disadvantages concerning the anode plates, i.e.

the median electrode stack. The latter consists of a multitude of bolted components with more or less precise electric contact points which are sensitive to corrosion with consequent increased electrical resistance and voltage drops. The long threads and the areas of thin wall thickness of the threaded sleeve require complex fabrication procedures and are subject to distortion. The concentric power supply, for example through 2 or 3 power supply bolts, is bound to entail an unfavourable distribution of current density across the rectangular electrode plate. Welding of the electrode plates to the threaded sleeve with annular crowns may easily cause warping because of the multiple concentric welded joints and this may, consequently result in an irregular spacing of anode and cathode plates.

There is a need for a simplified design of such a central electrode stack in order to achieve, for example, a more uniform current distribution from the power input element.

The present invention provides an electrolysis cell which comprises a housing having an inlet port and an outlet port and accommodating at least one group of monopolar electrode stacks comprising an inner stack centrally arranged between at least two outer stacks, each stack able to be attached to a suitable power supply and each stack comprising a plurality of electrode plates fixed to a central carrier member, the inner electrode stack of a group being of one polarity in use and the outer electrode stacks being of opposite polarity in use, with the electrode plates on each electrode stack of a group being arranged such that plates of one polarity extend into gaps between plates of opposite polarity, wherein the electrode plates of the inner electrode stack of a group are each directly fixed along a- side edge of the central carrier member of the inner electrode stack and extend outwardly therefrom.

Each electrode plate of the inner electrode stack, suitably acting as the anode, is affixed to the central carrier member along one of its side edges. Suitably the electrode plates are fixed by direct means without the use of any intermediate connecting members such that the plates and the electrode stack become unitary or integral in nature. It is preferred that the plates are attached by welding them onto the stack. By such a fixed direct join the plates can be held rigidly in position and difficulties caused by the presence of bolts, for example, are avoided.

The electrode plates of the inner electrode stack are suitably, indeed preferably, rectangular and require no apertures or specially fashioned joints for attachment to the carrier member. The plates are generally arranged parallel to one another on the carrier member, each extending in the same direction therefrom. Of course, the carrier member may bear more than one array of electrode plates, the plates in each array being parallel to each other and extending outwardly in the same direction into gaps existing between the plates of one of the outer electrode stacks.

An electrolysis cell of the present invention incorporates substantial advantages. The inner electrode stack no longer needs bolted joints and, therefore, no bolted contact points. Changes in electrical resistance with a consequent voltage drop across corroding contact areas no longer occurs. The number of components to be fabricated and shaped by metal-cutting operations is drastically reduced. The flow of electric current from the sole power input plate into the anode plates is unifonn, and there is no increase in current density at any point An electrolysis cell of the present invention permits cost-effective fabrication, is less subject to disturbances and provides an improved energy yield because of the reduced voltage drop.

An electroylsis cell according to the present invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 shows, in diagrammatic form, a side elevation of the electrolysis cell with a part crosssectional view along line I-I of Figure 2; Figure 2 shows, in diagrammatic form, a plan view of the electrolysis cell; Figure 3 shows, in diagrammatic form, a crosssectional view along line Il-Il, of Figure 1.

Referring to the drawings, the electrolysis cell comprises a cell housing 1 of, for example, titanium having a truncated-pyramid-shaped base 2 and a truncated-pyramid-shaped cover 3. The lower part of the base 2 terminates in an inlet nozzle 4. The top part of the cover 3 terminates in an outlet nozzle 5 for the electrolyte which may pass through the cell from bottom to top. Inlet nozzle 4 and outlet nozzle 5 are each provided with a flange 6 to aid connection with feed and discharge lines for the electrolyte and the electrolysis products, respectively. The cell housing 1 accommodates three electrode stacks, 7, 8, 9 two of which are of the same polarity.The two outer electrode stacks, 7, 8 are connected to the negative pole of a power source by means of connectors 10, 11, suitably made of copper, to serve as cathodes while the median electrode stack 9 located between the two cathodes 7, 8 is connected to the positive pole of the power source by means of conductors 12 to serve as an anode.

The central electrode stack 9 is a compact anode stack comprising a plurality of anode plates 13 assembled on a power input plate 14. The cathode stacks 7 8 also consist of a number of cathode plates 1 5. The cathode plates are arranged in a vertical direction and attached to one side of a carrier plate 16, and are equally spaced and parallel to one another. The carrier plates 16 also serve as side walls of cell housing 1. The carrier plates 16 are electrically insulated from the other components of cell housing 1 to which they are attached, the joint being normally liquid-tight. Power input conductors 10, 11 are fixed to the outside surfaces of carrier plates 1 6.

All other parts of cell housing 1 are electricaily connected with anode stack 9.

The anode plates 13 are rectangular and are welded to current input plate 14 on their longitudinal side. They are spaced so that cathode plates 1 5 fit into the gaps while some clearance is maintained. The cathode plates 15 also have straight internal sides without any recess. The current input plate 14 crosses the electrolysis cell and extends over the full height of the electrodes, this means that the current transition from the input plate to the electrode is free of any restriction and, consequently, the current density is not subject to an increase.

It is preferred that the internal side of wall 17 is also provided with an activating layer so that another anode side is incorporated.

All cathode components are suitably made of steel while all anode components are suitably made of titanium. The anode plates may be provided with a customary activating layer on one side or on both sides. The power input plate may be made of copper and is suitably provided with titanium coating throughout the entire internal part within the cell. The titanium coating is normally welded to the cell housing at the point where the plate enters the cell, to form a liquidtight seal between plate and cell wall. Outside the housing, the power input plate may be connected to one or more current conductors.

Claims (12)

1. An electrolysis cell which comprises a housing having an inlet port and an outlet port and accommodating at least one group of monopolar electrode stacks comprising an inner stack centrally arranged between at least two outer stacks, each stack able to be attached to a suitable power supply and each stack comprising a plurality of electrode plates fixed to a central carrier member, the inner electrode stack of a group being of one polarity in use and the outer electrode stacks being of opposite polarity in use, with the electrode plates on each electrode stack of a group being arranged such that plates of one polarity extend into gaps between plates of opposite polarity, wherein the electrode plates of the inner electrode stack of a group are each directly fixed along a side edge to the central carrier member of the inner electrode stack and extend outwardly therefrom.

2. An electrolysis cell as claimed in claim 1, wherein the central carrier member of the inner electrode stack of a group is a current supply plate which extends from one wall of the housing to the opposite wall of the housing.

3. An electrolysis cell as claimed in claim 2, wherein the power supply plate extends through the housing wall and the power supply plate is provided with at least one external power input connection.

4. An electrolysis cell as claimed in claim 2 or claim 3, wherein the power supply plate extends beyond the wall of the cell housing and is provided with more than one power supply connection.

5. An electrolysis cell as claimed in any one of claims 2 to 4, wherein the power supply plate is a coated copper plate extending to at least all areas inside the cell such that the surfaces wetted by the electrolyte are protected.

6. An electrolysis cell as claimed in any one of claims 2 to 5, wherein the power supply plate is seal-welded to the housing at the point of penetration through the housing wall.

7. An electrolysis cell as claimed in any one of claims 1 to 6, wherein the inner surface of a side of the housing is activated to obtain an additional electrode surface.

8. An electrolysis cell as claimed in any one of claims 1 to 7, wherein only one group of electrode stacks is present.

9. An electrolysis cell as claimed in claim 1 which is substantially as described herein with reference to, and as illustrated by, the accompanying drawings.

10. An electrolysis cell consisting of a housing with one inlet and one outlet for the electrolyte passing through the cell, said housing accommodating monopolar electrodes, each electrode consisting of a plurality of parallel plates fixed to a common carrier element, the electrodes being arranged in a staggered pattern so that the plates of one polarity extend into the gaps formed by the plates of the opposite polarity and that at least one median electrode stack of one polarity with central electric power input is arranged between two electrode stacks of the opposite polarity, characterized in that the median electrode stack consists of a plurality of electrode plates and a power supply plate of a length substantially equal to that of the electrode plates and a width substantially equal to that of the cell, the electrode plates being welded along one longitudinal side to the power supply plate in a toothed pattern and the power supply plate being joined to a side wall of the cell housing, the side wall being provided with at least one power input connection.

11. An industrial plant incorporating an electrolysis cell as claimed in any one of claims 1 to 10.

12. Electrolysis whenever performed using an electrolysis cell as claimed in any one of claims 1 to 10.