GB2176497A - Electrochlorination device - Google Patents

Abstract

An electrochlorinator comprises an inner tubular anode 16, an outer tubular cathode 14, and a connector 46 for the inner anode, the connector including a tube, a portion of the outer periphery of which is closely fitted within the inner periphery of an end portion of the tubular anode such as to provide a good electrical connection between the two mating cylindrical surfaces. An electrochlorinator comprises an inner tubular anode and an outer tubular cathode, the inner tubular anode comprising titanium coated with platinum-iridium. An electrochlorinator comprises an inner tubular anode 16 and an outer tubular cathode 14 the electrodes defining an annular electrolyte gap 18 therebetween, the electrolyte entering and leaving the electrochlorinator by means of respective connectors at either end of the cathode, each connector having a first tubular portion 22 coaxial with the electrodes and a second tubular portion 24, extending perpendicularly to the first tubular portion, for connection of a pipe (54, figure 1) for flow of the electrolyte, the connectors joining with the cathode in a manner which allows a smooth flow path for electrolyte, free of any sharp electrode edges. <IMAGE>

Description

SPECIFICATION Electrochlorination device The present invention relates to electrochlorination devices.

Electrochlorination devices are used, inter alia, for the sterilisation of sea water or brine by the production of sodium hypochlorite. The presence of sodium hypochlorite prevents the growth of organic material which might otherwise come into contact with constructions, machinery and the like, and which can cause considerable problems such as blockage of passages, reduced efficiency and general inconvenient fouling due to build-up of organic material.

Electrochlorination has largely replaced the previous practice of dissolving chlorine gas in water, and has the advantage that chlorine, which is a highly toxic gas, is never produced as a gas, but is reacted in solution with sodium hydroxide almost instantaneously to form sodium hypochlorite.

Thus, an electrochlorinator relies only on the presence of an electric supply and is not dependent on an external supply of toxic chlorine, which is comparatively dangerous and expensive to transport.

Known electrochlorinators comprise essentially a cathode and an anode (plates, revolving plates or concentric tubes), between which sea water or brine is fed, producing sodium hypochlorite by the following reactions; 2Na + 2e-# < 2Na 2C 1-2e--, C12 2Na + 2H2O < 2NaOH + H2 2NaOH + C12 < 2NaOCl + H2 As can be seen, the electrolysis also produces hydrogen, and where the electrolyte is sea water, suspended salts such as magnesium hydroxide are also produced.

In accordance with a first aspect of the present invention there is provided an electrochlorinator comprising an inner elongate tubular anode electrode and an outer elongate tubular cathode electrode which coaxially surrounds the inner anode electrode along at least part of its length, and a current/ transferring connector means for introducing d.c. current to the inner anode electrode, said connector means including a tube made of a good electrical conductor, such as copper, a portion of the outer periphery of which is closely fitted within the inner periphery of an end portion of the tubular anode electrode such as to provide a good electrical connection between the two mating cylindrical surfaces, said tube carrying a terminal on its end portion projecting from the anode electrode for connection to an electrical supply.

The anode is preferably made of titanium coated with platinum iridium and the cathode is preferably of stainless steel.

The copper tube, which may have a longitudinal slot for ease of initial insertion into the anode electrode, is preferably force fitted into the anode electrode. The electrical connection between the tube and the anode electrode can be improved by the use of a conductive adhesive paste provided on either the outer periphery of the tube or the inner periphery of the anode, or both, prior to insertion of the tube.

By the use of such a tube, the area of contact with the inner periphery of the anode can be considerable, thus ensuring a low ohmic connection therebetween.

Advantageously, a connection as described above is provided at both ends of the tubular anode electrode, current thereby being introduced at both ends of the anode.

Preferably, the anode/cathode electrode pairs are arranged substantially vertically, and sometimes there is a plurality of sets of electrode pairs.

Preferably, the upper end of the one set of electrodes is connected to the base of an adjacent set of electrodes for example by a pipe.

Preferably each anode of a set of electrodes is connected to the cathode of an adjacent set of electrodes, both at the upper ends and at the lower ends of the sets of electrodes.

In accordance with a second aspect of the invention, an electroch-lorinator comprises an inner elongate tubular anode electrode and an outer elongate tubular cathode electrode which coaxially surrounds the inner anode electrode along at least part of its length, the inner tubular anode comprising titanium coated with platinum-iridium.

Preferably the outer tubular cathode comprises stainless steel.

In accordance with a third aspect of the invention, an electroch/ lorinator comprises an inner elongate tubular anode electrode and an outer elongate tubular cathode electrode which coaxially surrounds the inner anode electrode along at least part of its length, the electrodes defining an annular electrolyte gap therebetween, the electrolyte entering and leaving the electrochlorinator by means of respective connectors at either end of the cathode, each connector having a first tubular portion, coaxial with the electrodes and a second tubular portion, extending substantially perpendicularly to the first tubular portion, for connection of a pipe for flow of the electrolyte, the connectors joining with the cathode in a manner which allows a smooth flow path for electrolyte free of any sharp electrode edges.For this purpose, the cathode and the pipe are preferably secured in their respective positions by a bush having an annular projection which extends radially inwardly so as to lie over the annular end edge of the cathode and thereby prevent exposure of this end edge to the electrolyte.

By way of example only, a specific embodiment of the invention is now described, with reference to the accompanying drawings, in which; Figure 1 is a side elevation of one embodiment of electroch-lorinator according to the invention; Figure 2 is a plan view of the electrochlorinator of Figure 1; Figure 3 is an end elevation of the electrochlorinator of Figure 1, looking in the direction of arrow 111; Figure 4 is an end elevation of the electrochlorinator of Figure 1, looking in the direction of arrow IV; and Figure 5 is a side elevation, in cross-section, of one end of a cell of the electrochlorinator of Figure 1.

Referring to the drawings, the illustrated electrochlorinator comprises a plurality of elongate, tubular electrochlorination cells 10 (16 in this embodiment), arranged in two rows of eight on a metal framework 12. As best seen in Figure 5, each cell 10 comprises an outer, tubular, stainless steel cathode 14, and an inner, tubular anode 16, made from platinum-iridium-coated titanium, the two electrodes being arranged to lie concentrically, and defining an annulus 18 between them.

Referring to Figure 5, the ends of each cell are provided with a collar 20 comprising a first tubular portion 22 and a second tubular portion 24 branching from the centre of the portion 22 at a right angle. The cathode 14 extends into one end of the portion 22 sealingly, by means of a packing bush 26 and O-ring seal 28 which is seated in a recess in the bush. The end of the cathode 14 rests on a shoulder 30 at the junction of the portions 22, 24, which prevents the cathode from moving further into the collar 20. The anode passes out of the other end of the portion 22 sealingly by means of a packing bush 32 and O-ring seal 34, which is seated in a recess in the bush. The bush 32 rests on a shoulder 36, similar to shoulder 30, which prevents the bush from moving into the collar.

Similarly, the portion 24 is provided with a packing bush 38 which rests on a shoulder 40. The packing bush, in use, receives a pipe 42 which rests on a shoulder 44 provided in the bush.

Electrical connection to the anode is provided by a copper tube 46 which is normally about 25 cm long and which, in use, is positioned inside the anode. Two opposed slots (not shown) are machined in the copper tube 46 along the portion of the copper tube which is to fit inside the anode, to allow easier insertion of the copper tube into the anode.

Conductive adhesive is applied to the exterior of the copper tube and also to the interior of the titanium anode 16, to secure the copper tube to the titanium tube and to provide good electrical connection between the two. The current is conveyed to the copper tube by a metal bar 48 which is bolted to the copper tube as indicated at 50. The bar connects the copper tube to a lug 52 on the cathode of an adjacent cell 10, to which the bar is bolted. Both ends of the anode are connected to the cathode of an adjacent cell, as can best be seen in Figure 1.

The electrochlorination cells are positioned vertically, in this case in two rows. As best seen in Figures 1 and 2, pipes 54 interconnect the collar at the top of each cell with the collar at the bottom of an adjacent cell. The pipes are connected between an upper T-piece 56, which fits onto pipe 42 emerging from the collar 20 at the top of the cell, and a lower T-piece 58 which fits onto pipe 42 emerging from the collar 20 at the bottom of the cell. To one end of the lower T-piece 58 is connected a tap 60 for drainage purposes. To one end of the upper Tpiece 56 is connected a non-return valve 62 which allows the ingress of air when the tap 60 is opened to drain the system. When the system is drained, water flowing from the system collects in a trough 64 which guides the water to a drain hole 66, through which the water may flow.

The electrical supply for the electrochlorinator is produced by a unit 68 which houses a transformer, a rectifier and appropriate, conventional circuitry which produces a steady direct current.

In use, sea water or brine enters the electrochlorinator via inlet pipe 70. This pipe then bifurcates into two smaller pipes, 72,74 which are provided with a pressure gauge 76 and a flowmeter 78. Each pipe 72, 74 supplies water to one row of electrochlorination cells 10. The water flowing through the pipes 72, 74 flows into the upper end of end pipes 54. The water flows to the base of the first cell 10, upwardly through the cell and then downwardly to the base of the next cell via a further pipe 54. This flow continues through the cells 10 and pipes 54 until the water reaches the upper end of the final cells 10, where it flows out by means of outlet pipes 80,82, which are provided with a differential pressure switch 84 and a pressure gauge 86. The two outlet pipes combine to form a single main outlet pipe 88 which is provided with a temperature gauge 90, a temperature switch 92 and a discharge valve 94.

During its passage through the electrochlorination cells, the sea water or brine is cholorinated as described above to result in the formation of dilute sodium hypochlorite solution. The output of the elctrochlorinator may be used directly in industrial applications. The presence of the sodium hypochlorite in the water ensures that small plants and animals cannot survive and allows operation of water-containing apparatus without fear of blockage from living creatures in the water.

Claims (19)

1. An electrochlorinator comprising an inner elongate tubular anode electrode and an outer elongate tubular cathode electrode which coaxially surrounds the inner anode electrode along at least part of its length, and a current-transferring connector means for introducing DC current to the inner anode electrode, said connector means including a tube made of a good electrical conductor, a portion of the outer periphery of which is closely fitted within the inner periphery of an end portion of the tubular anode electrode such as to provide a good electrical connection between the two mating cylindrical surfaces, said tube carrying a terminal on its end portion projecting from the anode electrode for connection to an electrical supply.

2. An electrochlorinator as claimed in claim 1, wherein the tube forming part of the connector means comprises copper.

3. An electrochlorinator as claimed in claim 1 or claim 2, wherein the anode is made of titanium.

4. A electrochlorinator as claimed in claim 3, wherein the titanium is coated with platinum-iridium.

5. An electrochlorinator as claimed in any of claims 1 to 4, wherein the cathode comprises stainless steel.

6. An electrochlorinator as claimed in claim 2, or any of claims 3 to 5 when appendent to claim 2, wherein the copper tube is provided with at least one longitudinal slot for ease of initial insertion into the anode electrode.

7. An electrochlorinator as claimed in claim 6, wherein the copper tube is force-fitted into the anode electrode.

8. An electrochlorinator as claimed in any of claims 1 to 7, wherein conductive adhesive paste is provided between the tube and the anode electrode.

9. An electrochlorinator as claimed in claim 8, wherein conductive adhesive paste is provided at both ends of the tubular anode electrode.

10. An electrochlorinator as claimed in any of the preceding claims, wherein the current is introduced at both ends of the anode.

11. An electrochlorinator as claimed in any of claims 1 to 10, comprising a plurality of anode/ cathode electrode pairs.

12. An electrochlorinator as claimed in claim 11, wherein said electrode pairs are arranged substantially vertically.

13. An electrochlorinator as claimed in claim 11 or claim 12, wherein the upper end of one set of electrodes is connected to the base of an adjacent set of electrodes.

14. An electrnchlorinator as claimed in claim 13, wherein the connection is in the form of a pipe.

15. An electrochlorinator as claimed in claim 13 or 14, wherein each anode of a set of electrodes is connected to the cathode of an adjacent set of electrodes, both at the upper ends and the lower ends of the sets of electrodes.

16. An electrochlorinator comprising an inner elongate tubular anode electrode and an outer elongate tubular cathode electrode which coaxially surrounds the inner anode electrode along at least part of its length, the inner tubular anode comprising titanium coated with platinum-iridium.

17. An electrochlorinator comprising an inner elongate tubular anode electrode and an outer elongate tubular cathode electrode which coaxially surrounds the inner anode electrode along at least part of its length, the electrodes defining an annular electrolyte gap therebetween, the electrolyte entering and leaving the electrochlorinator by means of respective connectors at either end of the cathode, each connector having a first tubular portion, coaxial with the electrodes and a second tubular portion, extending substantially perpendicularly to the first tubular portion, for connection of a pipe for flow of the electrolyte, the connectors joining with the cathode in a manner which allows a smooth flow path for electrolyte, free of any sharp electrode edges.

18. An electrolyte as claimed in claim 17, wherein the cathode and the pipe are secured in their respective positions by a bush having an annular projection which extends radially inwardly so as to lie over the annular end of the cathode and thereby prevent exposure of this end edge to the electrolyte.

19. An electrochlorinator substantially as herein described, with reference to, and as illustrated in the accompanying drawings.