|Title of Invention||
A SINGLE-CELL TYPE ELEMENT FOR AN ELECTROLYSIS DEVICE DELIMITED BY TWO SEMI-SHELLS (1,2)
|Abstract||The invention relates to a single-cell type element for an electrolysis device delimited by two semi- shells (1,2) each provided with a back-wall (9) and a peripheral flange (8) whereon insulation elements (10.3) are arranged and clamped by clamping elements (10) fitted in the flange area, characterized by comprising two electrodes (3,4) with a membrane (5) placed therebetween, the semi-shells (1,2) being free of bores or recesses for accommodating the bolting (10.1, 10.2) of the clamping elements (10) and the ratio between the flange surface overlapping said membrane (5) and the active membrane surface being less than 0.09.|
|Full Text||FIELD OF INVENTION
The invention relates to an electrolysis cell having the constructive form of the
single element, the so-called "single cell elements", said cells being exploited for
example for the production of chlorine, hydrogen and/or caustic soda solution
etc. and designed in such a manner that the portion of inactive membrane
surface is minimised with the aid of an optimised flange construction so that the
ratio between the semi-shell flange surface and the active membrane surface is
adjustable to provided with bores or recesses for passage of the clamping members.
BACKGROUND OF INVENTION
Electrolysis cells for the production of elemental chlorine, hydrogen and/or
caustic soda solution are well known and their state-of-the-art design has been
described sufficiently. In the conventional state-of-the-art technology, the use of
two types of cell is widespread in industrial applications: one of the filter press
design and the other of the said electrically series-connected "single cell
These electrolysis cells such as described in DE 19641 125, DE 19740637 or DE
19641 125 consist inter alia of one cathodic and one anodic semi-shell which
accommodate the anode or cathode, respectively, each having a different
surface structure. The ion-exchange membrane is arranged between the
electrodes and reaches far beyond the semi-shell flanges. The said semi-shell
flanges are sufficiently sized to ensure an adequate pressure surface in order to
avoid damage to the ion-exchange membrane.
According to the conventional state of the art, the semi-shell flanges and the
membrane placed in-between are provided with bores or openings for safe
positioning and fixing of the membrane, so that one bolted clamping member is
provided for each bore or opening. The seal pressure acting on the semi-shells
by means of the bolting is transferred via washer-type insulation elements placed
on either side of the semi-shell flanges.
In accordance with the known state of the art a multitude of such clamping
members are placed on the flange circumference of a single cell in order to
ensure tightness of the cell and an almost uniform seal pressure on the
A major disadvantage of this prior-art electrolysis device is the fact that more
than 10% of the ion-exchange membrane is inactive and does not take part in
the electrolysis process as the membrane is enclosed by the flange or even
extends beyond the flange to facilitate the assembly and because this very
expensive material is merely utilised to position said item during the assembly of
the single cell and to enhance the mechanical stability during operation.
The aim of the invention is to eliminate or minimise the inconvenience described
above and to provide for an optimisation of the surface area utilisation of the
OBJECT OF THE INVENTION
The aim of the invention is achieved by making the whole flange of the whole
electrolysis cell smaller, omitting bores and recesses normally required for the
passage of the bolting, the ratio between the semi-shell flange surface area
overlapping the membrane and the active membrane surface area being less
than 0.09 or preferably less than 0.07 or in an ideal embodiment less than 0.045.
SUMMARY OF THE INVENTION
According to a preferred embodiment of the electrolysis cell as specified in this
invention the membrane is shaped in such a manner that it has neither bores nor
recesses which normally serve to position the membrane in one or in both semi-
shells or to pass the clamping members.
The said device also has clamping members which are applied to the external
side of the flange or slipped onto the latter and which serve to clamp and seal
the anodic and cathodic semi-shells to form a single element.
In an advantageous embodiment of the invention the said clamping members
are individually bolted elements. An ideal variant is to use clamp-type or bolted
gibs as elements for fixing the semi-shells, the said elements being available on
the market as prefabricated elements. Further shapes of the said elements are
suitable for this purpose provided they have at least two parallel and opposite
insulation elements that are pressed against the flanges of the semi- shells.
Moreover, the electrolysis cell described in this invention comprises a device
which permits that only a part of the insulation elements arranged on the side
facing the flange of the semi-shell is directly supported by the said flange, a part
of the surface areas protruding from the flange. At least one spacer is arranged
between the insulation element faces that are not supported or one or both
insulating elements are shaped in such a manner that either the spacer itself or
in conjunction with the other insulating members fills the gap located in the area
above the flange. An insulation body shaped in this manner is provided with, for
example, protruding or cantilevered parts in the surface area facing the flange.
An advantageous embodiment of the invention provides for a spacer with a
thicker and a thinner section and upon assembly the thicker part protrudes from
the flange and the thinner section is clamped together with the membrane
between the flange of the semi-shells. An embodiment of the variant described
above provides for a spacer the protruding section of which has bores or
openings that can accommodate bolts or clamps. In this case the thickness of
the spacer section protruding from the flange approximately corresponds to the
thickness of the flange after assembly, i.e. the thickness of the components
inserted for the operation is included.
The essential advantage, hence, is a substantial reduction of the inactive
membrane surface area while the size of the active membrane area remains
A further important advantage in addition to the increased ratio of the active
membrane is the fact that the overall membrane surface area becomes smaller
and the membrane packaging is facilitated. It is imperative that any membrane
bore or opening be made prior to assembly. The bored membrane types should
be provided with bores prior to assembling, a step, which is now eliminated. This
step always represented danger for the membranes, as damages or pollution of
the coating or the base material of the membrane could never be completely
The reduction of the flange size also permits the semi-shells to be fabricated off
semi-finished products such as coils, which can be purchased in standard size on
the world market, a procedure which was not possible up to now. Hence, two
substantial and positive effects could be realised with regard to material costs of
the semi-shells, namely a simplified procurement and a reduced size.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 - shows a cross-sectional view of the electrolysis cell segment according
to the prior art
Figure 2 - shows the electrolysis cell of the invention without the clamping
Figure 3 - shows the electrolysis cell of the invention with the clamping device.
DETAIL DESCRIPTION OF THE INVENTION
The cross-sectional view in Figure 1 shows an electrolysis cell segment in
accordance with the present state of the art. Said view clearly illustrates the
anodic semi-shell 1 and the opposite cathodic semi-shell 2, anode 3 and cathode
4. Semi- shells 1 and 2 exhibit two sections, a wall 9 and a circumferential flange
8. Flange 8 has holes for fixing the clamping element 10, through which bolt
10.1 is inserted. Said clamping element also encompasses a spring washer 10.2,
which keeps the seal pressure constant, a detail required to compensate the
variation of the material characteristics due to different swelling conditions of the
membrane. Two annular insulation elements 10.3 are in direct contact with the
metallic surface of flange 8 and, hence, with the semi-shells, said elements
serving to transfer the forces. Moreover, bolt 10.1 located in the area of the
flange neck is inserted into insulation hose 10.4. Membrane 5 is arranged
between anode 3 and cathode 4.
The figurel illustrates that membrane 5 is sized such that it extends beyond the
section that accommodates the bores for the clamping elements. In a manner
similar to that of the flanges, the membrane is also provided with openings in
this section. Flange 8 is equipped with a flat spacer and insulation element 6 that
constitutes a frame and that is likewise provided with bores correlated with the
bores of flange 8. Two circumferential sealing cords 11 arranged between the
semi-shells in the area of flange 8 ensure the tightness of the semi-shells.
Internals 7 shown in Figures 1, 2 and 3 serve to ensure a calm flow in the upper
part of the cell.
Figure 2 shows the electrolysis cell of the invention without the clamping device.
Flange 8 is considerably smaller-sized and has neither holes nor bores. Spacer
variant 6 shown here protrudes from flange 8 and its upper part that extends
beyond flange frame 6.1 is provided with bores 6.2 into which bolts 10.1 of one
clamping element are inserted. The internal part of spacer 6, i.e. clamping area
6.3, is located between the flange parts of semi-shells 1 and 2. In this case
insulation hose 10.4 that protects bolts 10.1 as shown in Fig. 1 can be omitted
because the bolt cannot come into contact with the flange.
Figure 3 shows the electrolysis cell of the invention with the attached clamping
and sealing member 10, frame 6.1 and clamping area 6.3 of spacer 6 consisting
of two separate pieces which are not firmly linked with each other.
As a variant it is possible to shape one or both insulation elements in such a
manner that they have a protruding and a cantilevered part and the protruding
part located in the upper part forms the spacer itself. This variant, however, is
not shown in the figures.
It becomes evident that the device in accordance with the invention permits not
only a smaller membrane surface area which increases the portion of the active
membrane surface but also a certain degree of freedom in the design of the
clamping device and its matching elements thanks to the omission of bores.
Two electrolysis cells as specified in the invention were tested in a test bench
under genuine production conditions for a period of 5,000 operating hours. Two
industrial electrolysis cells had an active membrane surface area of 2.72 m2 each
and a flange width of 15.5 mm and, hence, said surface area was more than
60% smaller than that of the state-of-the-art electrolysis cells. The cell voltage
applied during the whole testing period was approx. 3.2 V at approx. 6 kA/m2
current density and a cell temperature of about 900C. The feed was 300 g per
litre NaCI solution.
The caustic soda solution has an average discharge concentration of 32% with a
NaCI residual concentration of produced, the average energy consumption being approx. 2,200 kWh per ton of
During the whole testing period it was possible to obtain high conversion rates,
product qualities, etc. by means of the single cells according to the present
invention, i.e. the figures equalled those of the larger and more expensive state-
of- the-art single cells with no disadvantages whatsoever with regard to the
safety, tightness or maintenance.
The design features described in this invention permitted to reduce the portion of
inactive membrane surface area from 11% obtained in the prior art technology
to less than 4.2 %.
The aim of the test series was to observe the membrane behaviour and
deterioration as well as the single cell tightness because the membrane is
subject to mechanical stresses generated by vibration and swelling or shrinking.
No anomalies were detected with regard to cell tightness and firm positioning of
the membrane. During the whole testing period no operational problems or
leakages were found and no adjustment or correction of the membrane or other
components in order to avoid disturbances were required.
It was a surprise to find that the cell maintenance was facilitated and that the
possibility of re-using a membrane already exploited in the process was
substantially improved. This is due to the fact that upon opening a single cell, a
membrane shrinking process is initiated, i.e. a criterion which formerly often
caused tearing of the membrane material in the deteriorated sections near the
bores and thus precluded a re-use of the membrane. As the electrolysis cell in
accordance with the invention is placed in a horizontal position prior to opening,
the membrane becomes free at once when a semi-shell is removed (no fixing) so
that a subsequent uniform shrinkage cannot cause membrane deformation or
It was also observed that the time required to assemble the single cells could be
shortened because the membrane adjustment is now facilitated in view of the
fact that no match with bores is necessary and the membrane ends only need be
roughly flush with the flange edge. This alignment is of considerably lower
importance because any deviation from being parallel with the edges is
Key to reference numbers
1 External semi-shell on anode side
2 External semi-shell on cathode side
6.3 Clamping area
8 Semi-shell flange
9 Elevated upper part of semi-shell
10 Clamping element
10.2 Spring washer
10.3 Insulation element
10.4 Insulation hose
11 Sealing cord
1. A single-cell type element for an electrolysis device delimited by two semi- shells
(1,2) each provided with a back-wall (9) and a peripheral flange (8) whereon
insulation elements (10.3) are arranged and clamped by clamping elements (10)
fitted in the flange area, characterized by comprising two electrodes (3,4) with a
membrane (5) placed therebetween, the semi-shells (1,2) being free of bores or
recesses for accommodating the bolting (10.1, 10.2) of the clamping elements
(10) and the ratio between the flange surface overlapping said membrane (5)
and the active membrane surface being less than 0.09.
2. The element as claimed in claim 1 wherein said ratio between the flange surface
and the active membrane surface is less than 0.045.
3. The element as claimed in claim 1 or 2 wherein said membrane is free of bores
or openings for its positioning in the semi-shells or for accommodating the
bolting of the clamping elements.
4. The element as claimed in any one of the preceding claims, wherein the
damping elements are slipped onto the flange or applied thereto.
5. The element as claimed in any one of the preceding claims, wherein the
clamping elements are designed as bolted single elements, clamp-type or bolted
gibs or as any other type or shape, said elements having at least two parallel and
opposite insulation elements that are pressed against the flanges of the semi-
6. The element as claimed in any one of the preceding claims, wherein only a part
of the insulation elements arranged on the side facing the surface of the flange
is directly supported by said flange, at least one spacer being fitted between the
insulation element faces that are not supported or one or both insulation bodies
being shaped in such a manner that they are provided with a protruding or
cantilevered section, so that the gap located beyond said flange is at least
7. The element as claimed in claim 6, wherein said at least one spacer has a thicker
and thinner section, the thicker section protruding from the flange, the thinner
section being clamped between the flanges of the two semi-shells together with
8. The element as claimed in claim 7 wherein said spacer section protruding from
the flange is provided with bores or openings.
9. The element as claimed in any one of claims 6 to 8, wherein the thickness of said
spacer protruding from the flange or of said protruding or cantilevered material
sections of the insulation element corresponds approximately to the thickness of
the flange in the assembled state, comprehensive of the thickness of the inserted
10.A single-cell type element for an electrolysis device substantially as herein
described with reference to the accompanying drawings.
The invention relates to a single-cell type element for an electrolysis device
delimited by two semi- shells (1,2) each provided with a back-wall (9) and a
peripheral flange (8) whereon insulation elements (10.3) are arranged and
clamped by clamping elements (10) fitted in the flange area, characterized by
comprising two electrodes (3,4) with a membrane (5) placed therebetween, the
semi-shells (1,2) being free of bores or recesses for accommodating the bolting
(10.1, 10.2) of the clamping elements (10) and the ratio between the flange
surface overlapping said membrane (5) and the active membrane surface being
less than 0.09.
|Indian Patent Application Number||3822/KOLNP/2006|
|PG Journal Number||49/2011|
|Date of Filing||19-Dec-2006|
|Name of Patentee||UHDENORA S.p.A.|
|Applicant Address||VIA BISTOLFI, 35 20134 MILAN|
|PCT International Classification Number||C25B 9/18|
|PCT International Application Number||PCT/EP2005/0006498|
|PCT International Filing date||2005-06-16|