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IMPROVEMENTS TO TUBULAR ELECTROLYSERS
Field of the Invention
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The invention relates to improvements to concentric tubular electrolysers and in particular to electrolysers using sea water
for the production of sodium hypochlorite.
Background to the invention
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Concentric tubular electrolysers are well known in the market place. These often incorporate inner tubular electrodes and
outer tubular electrodes co-axially disposed to form an annular cavity through which, in use, the electrolyte (eg. seawater)
flows. The tubular electrodes are disposed as a succession of tubular electrodes where a portion of the inner electrodes
are inserted into a portion of the outer electrodes. The polarity of the outer electrodes alternates along the flow path of the
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electrolyte; the polarity of the inner electrodes alternates along the flow path of the electrolyte. The polarity of the portions
of the outer electrodes is opposite to the polarity of the corresponding portions of the inner electrodes. The electrolyser
further comprises an inlet for receiving pressurised fluid and an outlet allowing the fluid to exit from the cavity. These
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electrolysers are often disposed in a serpentine path with a number of turns and lengths of tubular electrodes. Electrical
connections are provided between the power terminals and an electrolyser whilst further electrical connections are
provided between adjacent lengths of tubular electrodes. Outer electrode portions are connected by localised unions
which provide the necessary electrical insulation between adjacent outer electrodes and prevent pressurised fluid from
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escaping the electrolyser.
A number of drawbacks arise from the prior art configuration, these are at least the following;
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The outer electrodes being electrified are substantially exposed along the length of the electrolyser and are
therefore electrically hazardous;
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
Due to the requirement of incorporating unions for both sealing and insulating adjacent electrode portions, the
assembly of the various components is particularly complex and prone to failure (in particular leaking);
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
The complex, costly and time consuming titanium fabrication; which often requires flange collars or threaded
“over-rings” to enable union;
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
The location of the electrical connections might not be precise and/or consistent;

The relative position of the various lengths of the electrolyser might not be precisely maintained over time.
The invention seeks to address at least some of these drawbacks when considering various improvements over the prior art
electrolysers.
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Summary of the Invention
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In a first broad independent aspect, the invention provides an electrolyser comprising inner tubular electrodes and outer
tubular electrodes co-axially disposed to form an annular cavity through which, in use, the electrolyte flows; said tubular
electrodes being disposed as a succession of tubular electrodes where a portion of the inner electrodes are inserted into a
portion of the outer electrodes; wherein the polarity of the outer electrodes alternates along the flow path of the electrolyte;
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and the polarity of the inner electrodes alternates along the flow path of the electrolyte; the polarity of the portions of the
outer electrodes is opposite to the polarity of the corresponding portions of the inner electrodes; said electrolyser further
comprising an inlet for receiving pressurised fluid; and an outlet allowing said fluid to exit said cavity; electrical connections
being provided between adjacent lengths of tubular electrodes; wherein said electrolyser further comprises electrically
insulating members located on the outside of said outer tubular electrodes which extend along the length of said tubular
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electrodes between said electrical connections. The electrolyser may form a serpentine path with a number of turns and
lengths of tubular electrodes.
In a subsidiary aspect, a first spacer of insulating material is provided between adjacent outer electrodes.
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In a further subsidiary aspect, a seal is provided between said electrically insulating members and said outer electrodes;
said seal being separate from said spacer.
In a further subsidiary aspect, the electrolyser further comprises a second spacer of insulating material located between
adjacent inner electrodes.
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This configuration is particularly advantageous because it provides an alternative means of joining portions of electrodes.
There is no requirement for unions of the kind envisaged in the prior art. Instead, the process of assembling lengths of the
electrolyser is much simplified. It also provides a configuration which is much safer to operate.
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In a subsidiary aspect, the electrically insulating members incorporate one or more tubes which fit around said outer
electrodes. This is particularly advantageous when the tubes are tightly fitted around the outer electrodes so as to improve
the assembly and operation of the electrolyser.
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In a further subsidiary aspect, said electrically insulating members incorporate flanges located at their extremities which are
adjacent to said electrical connections; and facilitate the incorporation of fasteners which fasten adjacent flanges together.
This configuration allows the electrical connections to take place whilst at the same time minimising the exposure of
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electrically conductive components. The provision of flanges also provides for a particularly robust form of water tight
“access” window for electrical connections.
In a further subsidiary aspect, a flange incorporates a reinforcing web located between the laterally projecting portion of the
flange and the outer surface of its corresponding tube. This configuration is particularly advantageous in terms of its
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mechanical strength and the likely achievable longevity of the electrolyser.
In a further subsidiary aspect, the flanges are rectangular; and the flanges of a first length of the serpentine path abut
against the flanges of an adjacent second length of the serpentine path. This configuration is particularly advantageous in
terms of precisely locating the lengths of the electrolyser in the desired serpentine path formation.
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In a further subsidiary aspect, an additional housing is provided to house the electrical connections. By covering the
electrical connections with a housing, the serpentine path is effectively entirely insulated and therefore any hazard is further
minimised.
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In a further subsidiary aspect, a seal is provided between said electrically insulating members and said outer electrodes.
This provides for water tight junctions without the use of the union bodies of the prior art.
In a further subsidiary aspect, said electrically insulating members incorporate an internal annular groove for receiving a
seal in the form of an O-ring. This configuration is particularly advantageous in terms of providing the necessary water tight
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characteristic.
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In a further subsidiary aspect, said electrically insulating members incorporate a distal extremity which is chamfered to
locate against said seal. This configuration further improves the seal.
In a further subsidiary aspect, a compression ring is provided with a chamfered extremity to abut against the seal. This
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configuration is particularly advantageous because it further strengthens the seal.
In a further subsidiary aspect, said electrical connection incorporates a collar extending around said outer electrodes; said
collar being configured so that when compressed it clamps onto said outer electrode. This configuration is particularly
advantageous because it provides a distributed contact surface for optimum conduction of electricity.
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In a further subsidiary aspect, adjacent electrodes are separated by a cylindrical spacer. This allows the necessary
separation between adjacent electrodes to provide for the necessary succession of portions with the appropriate polarity.
Brief description of the figures
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Figure 1 is a side elevation of a first embodiment of the electrolyser assembly.
Figure 2 shows the electrical and hydraulic connections in a side view as in figure 1.
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Figure 3A shows in part a cross-sectional view of a tubular portion of an electrolyser.
Figure 3B shows the outer tubular electrodes in a cross-sectional view along their length.
Figure 3C shows the inner tubular electrodes in a longitudinal cross-sectional view.
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Figure 3D shows a longitudinal cross-sectional view of a length of the electrolyser in its
assembled form.
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Figure 4 shows an extremity of an electrolyser with a corner junction member (for example a U-bend).
Figure 5 shows a flange junction portion.
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Figure 6 shows an embodiment of the electrolyser with a number of flange junction members.
Figures 7A & 7B show cross-sectional views of the water tight “access” window for terminal connections between the
anodes/cathodes of concentric tube electrolysers.
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Figures 8A & 8B show cross-sectional views of water tight “access” windows for terminal connections both in an
uncompressed configuration (figure 8A) and in a compressed configuration (figure 8B).
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Detailed description of the figures
Figure 1 shows an electrolyser assembly generally referenced 1. The electrolyser comprises an inlet 2 for receiving
seawater. The inlet in this embodiment is disposed at a lower portion of the electrolyser. An outlet 3 is provided at an
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upper portion through which the products of the electro-chlorination exit. These products are primarily hypochlorite and
hydrogen. In order to control the flow out of the electrolyser a titanium flange and a titanium ball valve are provided. A
titanium threaded spigot is screwed into a cPVC union. A beam of support frame 6 is cladded by uPVC cladding 7. At the
base of the serpentine electrolyser configuration, a sliding plinth 8 with lateral support PVC provides support for the lower
flanges such as flange 9 of the electrolyser. A base square cross-section beam 10 is located across the lower extremity of
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the support frame. A uPVC floor 11 covers the square beam and provides a support surface against which the sliding
plinth rests. Beams 6, 10, 12 and 13 are joined together to form a framework which can be used to at least partially enclose
the electrolyser.
The serpentine configuration incorporates a lower first bend portion 14 which is of an electrically insulating material such as
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an appropriate polymer. The electrolyser incorporates at the opposite extremity of a first length of the serpentine
configuration a second bend portion 15 which is also of electrically insulating material. A succession of outer covering
electrically insulating tube portions 16, 17 and 18 substantially covers the entire length of electrolyser apart from a first
“access” window 19 and a second “access” window 20. “Access” window 20 incorporates flange 9 and 21 respectively
provided at an extremity of tube portions 17 and 18. A water tight seal is provided at close proximity to both flanges 9 and
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21. In window 20 a tubular electrode portion is sufficiently exposed to allow an electrical connection to be established
between neighbouring windows such as windows 20 and 22. An upper extremity of flange 9 abuts against a lower
extremity of flange 23 whilst an upper extremity of flange 21 abuts against a lower extremity of flange 24.
The electrolyser’s serpentine configuration incorporates ten lengths of tubular electrodes or rows of tubular electrodes
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joined together by bend portions. Each row incorporates two pairs of flanges located respectively at opposite ends of the
rows. The flanges of the various rows at one extremity are aligned so that the electrical connections can be aligned. The
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electrical connections can be housed or boxed in, in order to provide an entirely electrically insulated serpentine
configuration.
Figure 2 shows a succession of electrode portions such as electrode portion 25. If electrode portion 25 is connected to the
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negative terminal it will itself be negative. The various electrical connections between neighbouring electrode portions are
shown as thick black lines such as electrical connection 26. No electrodes are provided in the bend region. Line 27 simply
indicates the flow between the last electrode of the first row and the first electrode of the second row. In this embodiment,
there are two pairs of terminal connections 28 and 29 which respectively provide power for an upper half and a lower half
portion of the electrolyser assembly.
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Figure 3 shows one of the rows of the serpentine configuration in further detail. The electrodes are formed from a
succession of tubular portions. Each tubular portion may be a titanium tube. The first row of the serpentine configuration
may incorporate electrodes of either a relatively short or a relatively long configuration. There might for example be a short
outer titanium tube 30 followed by a long titanium tube 31 and a short titanium 32. Located within these outer tubes two
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long inner titanium tubes 33 and 34 are provided. The diameter of the inner tubes and the diameter of the outer tubes are
selected to provide an annular channel 35 through which the fluid flows. In order to separate the various tubular portions
spacers are provided. Two kinds of spacers are envisaged. The first kind such as spacer 36 incorporates a flange
corresponding in diameter to the outer diameter of inner tubular portions with diametrically oppositely located bosses 37
and 38 which project inside at least part of the inner tube portions. The bosses and flange precisely locate the inner
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tubular portions whilst centralising projections or tabs which extend radially outwards from the flange fit snugly against the
inner diameter of the outer tubular portion. In order to allow the passage of fluid across spacer 36, one or more
passageways 39 are provided. The second kind of spacer such as spacer 40 is a collar which slides inside the PVC tube
over the inner tubular portions whilst providing a surface against which neighbouring outer tubular portions abut; the outer
tubular portions being in alignment with the spacer so that the spacers appear as an extension of the outer tubular portions.
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Whilst providing the necessary separation between outer tubular portions, this spacer does not obstruct the flow of fluid.
The spacer 40 corresponds in dimensions to the dimensions of the outer electrode. An annular cavity 41 is therefore
provided between the spacer and the inner tubular portion. End pieces 42 and 43 are provided to maintain the spacing
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between inner and outer tubular portions whilst allowing the passage of the fluid into the bend portions of the serpentine
configuration. These end portions 42 and 43 incorporate a boss sized and shaped to fit within the inner tubular portions
and a flange portion 44 with a passageway.
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On the outside of the outer tubular portions, an electrically insulating tube 45 covers one or more of the electrodes. The
electrically insulating sleeve may be of a polymer such as PVC. A spacing between the electrically insulating tube and the
outer electrode is present although its dimensions are kept to a minimum. Since there is no seal provided between spacer
40 and the outer tubular portions, any clearance between the outer tubular portions and the electrically insulating tube will
be filled by fluid. Consequently, in order to provide the necessary electrical connections to the outer electrode portions, a
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seal is provided. These may take a number of forms; figures 4 and 5 show a first embodiment of an arrangement for
sealing whilst figures 7 and 8 show an alternative configuration for sealing the clearance between the outer electrically
insulating tube and the outer electrode.
Figure 4 shows a bend portion 46 which is provided with an end piece 47. End piece 47 incorporates a boss 48 with a
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chamfered inner extremity 49 to facilitate the insertion of an extremity of an inner tubular portion 50. Outer electrode tubular
portion 51 abuts against flange 52 at one extremity and against spacer 53 at its opposite extremity. An outer electrically
insulating tubular portion 54 and an outer electrically insulating tubular portion 55 are provided at either side of an “access”
window 56 which facilitates the attachment of an electrical connection either to a terminal or to an adjacent electrode. An
annular trough 57 is provided in the outer electrically insulating portion 54 to accommodate an O-ring 58 which is sized to
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provide a water tight seal against the outer surface of the outer tubular portion 51. A flange 59 extends around the annular
groove. This provides not only the necessary reinforcement of what would otherwise be a weak point of the outer tube but
also allows a fastener to be provided between flange 59 and flange 60 located at the other side of the window. The
fastener may, for example, be a bolt and screw to prevent the flanges from separating apart as the electrolyte is under
pressure. Instead of providing for a flange, the invention envisages the use of any kind of projection which is sufficient to
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attach the necessary fastener. The fastener may incorporate a single bolt of sufficient length for either a pair of flanges or
to provide the requisite tightening of several flanges across a length of the electrolyser.
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Figure 5 shows the embodiment of figure 4 as a closer view of the “access” window region. This view is particularly
interesting in terms of comparing the clearance between outer electrode 51 and outer electrically insulating tubular portion
54 with the annular cavity 61 between the inner and outer electrodes. Furthermore, this figure shows the tight engagement
of the O-ring on the outer surface of the electrode 51.
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Instead of providing an electrolyser with necessarily a serpentine configuration, the electrolyser might incorporate a
succession of tubular electrodes as shown in figure 6. A plurality of “access” windows 62, 63 and 64 are provided. Instead
of simply providing perpendicularly extending flanges 65 and 66, the invention envisages further reinforcements between
the flange and the outer electrically insulating portion 67. These extra reinforcements may take the form of a web 68.
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Figure 7A shows an “access” window 69 with the following components: an outer PVC tube 71, an outer titanium tube
(anode or cathode) 72, an inner titanium tube (cathode or anode) 73, a flange 74, a collar 75, an O-ring 76, a compression
ring 77, flange nuts and bolts 78, copper bus bar 79, a compression ring 80, an O-ring 81, a collar 82, a flange 83, an outer
PVC tube 84, seawater flow (electrolyte) 85, a copper bus bar extension to a next pipe section 86.
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Figure 7A shows a concentric tubular electrolyser pipe section 87 of n (outer anode).
Figure 7B shows a concentric tubular electrolyser pipe section 88 of n (outer cathode).
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Figure 8B shows how the copper bus bar collar 79 is secured against the outer titanium tube 72. The copper bus bar
incorporates a collar or loop with lateral chamfered surfaces 89 and 90 which abut against compression rings 77 and 80
which likewise incorporate chamfered sides such as sides 91 and 92 in figure 8A. The compression ring engages at
chamfered side 92, an O-ring 93 which is forced against a chamfered surface 94 located at the extremity of the outer PVC
tube. This configuration is particularly advantageous in order to avoid weakening of the area immediately adjacent to the
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flange 74. The collar 95 is provided between the outer PVC tube and the flange in order to further strengthen this
configuration.
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CLAIMS
1. An electrolyser comprising inner tubular electrodes and outer tubular electrodes co-axially disposed to form an annular
cavity through which, in use, the electrolyte flows; said tubular electrodes being disposed as a succession of tubular
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electrodes where a portion of the inner electrodes are inserted into a portion of the outer electrodes; wherein the polarity of
the outer electrodes alternates along the flow path of the electrolyte; and the polarity of the inner electrodes alternate along
the flow path of the electrolyte; the polarity of the portions of the outer electrodes is opposite to the polarity of the
corresponding portions of the inner electrodes; said electrolyser further comprising an inlet for receiving pressurised fluid;
and an outlet allowing said fluid to exit said cavity; electrical connections being provided between a power source and the
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electrolyser; and further electrical connections being provided between adjacent lengths of tubular electrodes; wherein
said electrolyser further comprises electrically insulating members located on the outside of said outer tubular electrodes
which extend along the length of said tubular electrodes between said electrical connections.
2. An electrolyser according to claim 1, wherein a first spacer of insulating material is provided between adjacent outer
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electrodes.
3. An electrolyser according to claim 2, wherein a seal is provided between said electrically insulating members and said
outer electrodes; said seal being separate from said spacer.
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4. An electrolyser according to any of the preceding claims, further comprising a second spacer of insulating material
located between adjacent inner electrodes.
5. An electrolyser according to any of the preceding claims, wherein said electrically insulating members incorporate one
or more tubes which fit around said outer electrodes.
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6. An electrolyser according to any of the preceding claims, wherein said electrically insulating members incorporate
flanges located at their extremities which are adjacent to said electrical connections; and facilitate the incorporation of
fasteners which fasten adjacent flanges together.
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7. An electrolyser according to claim 6, wherein a flange incorporates a reinforcing web located between the laterally
projecting portion of said flange and the outer surface of its corresponding tube.
8. An electrolyser according to either claim 6 or claim 7, wherein the electrolyser forms a serpentine path with a number of
turns and lengths of tubular electrodes; and wherein the flanges are rectangular; and the flanges of a first length of the
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serpentine path abut against the flanges of an adjacent second length of the serpentine path.
9. An electrolyser according to any of the preceding claims, wherein an additional housing is provided to house the
electrical connections.
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10. An electrolyser according to any of the preceding claims, wherein said electrically insulating members incorporate an
internal annular groove for receiving a seal in the form of an O-ring.
11. An electrolyser according to any of the preceding claims, wherein said electrically insulating members incorporate a
distal extremity which is chamfered to locate against said seal.
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12. An electrolyser according to claim 11, wherein a compression ring is provided with a chamfered extremity to abut
against said seal.
13. An electrolyser according to any of the preceding claims, wherein said electrical connection incorporates a collar
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extending around said outer electrode; said collar being configured so that when compressed it clamps onto said outer
electrode.
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14. An electrolyser according to any of the preceding claims, wherein adjacent electrodes are separated by a cylindrical
spacer.
15. An electrolyser substantially as hereinbefore described and/or illustrated in any appropriate combination of the
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accompanying text and/or figures.
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IMPROVEMENTS TO TUBULAR ELECTROLYSERS
ABSTRACT
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An electrolyser comprises inner tubular electrodes and outer tubular electrodes co-axially disposed to form an annular
cavity through which, in use, the electrolyte flows; said tubular electrodes being disposed as a succession of tubular
electrodes where a portion of the inner electrodes are inserted into a portion of the outer electrodes; wherein the polarity of
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the outer electrodes alternates along the flow path of the electrolyte; and the polarity of the inner electrodes alternates
along the flow path of the electrolyte; the polarity of the portions of the outer electrodes is opposite to the polarity of the
corresponding portions of the inner electrodes; said electrolyser further comprising an inlet for receiving pressurised fluid;
an outlet allowing said fluid to exit said cavity; said electrolytes forming a serpentine path with a number of turns and
lengths of tubular electrodes; electrical connections being provided between a power source and the electrolyser; further
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electrical connections being provided between adjacent lengths of tubular electrodes; wherein said electrolyser further
comprises electrically insulating members located on the outside of said outer tubular electrodes which extend along the
length of said tubular electrodes between said electrical connections.
Figure 7A illustrates the invention.
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