|Title of Invention||
AN ELECTROCHEMICAL CELL FOR THE MEMBRANE ELECTROLYSIS PROCESS
|Abstract||ELECTORCHMICAL CELL FOR ELECTROLYSERS WITH SINGLE-ELEMENT TECHNOLOGY The invention describes an electrochemical cell for the members electroysis process for electrolyers with single-element technology. The cell consists of at least of 2 half-shell (8,10), which suround an anolyte chember (16) and a cathode chamber (22) with a membrane (5) arranged in between, and an anode (6) in the anlyte chamber (16), with the cathode chamber (22) being provided with an oxygen-consuming cathode (4), with a plurality of pressure-compensated gas pockets (15) arranged one above the other, a catholyte gap (14) and optionally a back chamber (19), where electrically conducting supporting elements (7) are provide in the anolyte chamber (16) and supporting elements (3,2,1)n are provided in the cathode chamber (22) at the same opposite one anthoer.|
|Full Text||FORM 2
THE PATENTS ACT 1970 [39 OF 1970]
THE PATENTS RULES, 2003 COMPLETE SPECIFICATION
[See Section 10; rule 13]
"AN ELECTROCHEMICAL CELL FOR THE MEMBRANE ELECTROLYSIS PROCESS"
BAYER AKTIENGESELLSCHAFT, a body corporation organized under the laws of Federal Republic of Germany of D-51368 Leverkusen, GERMANY
The following specification particularly describes the invention and the manner in which it is to be performed:
The present invention relates to an electrochemical cell for the membrane electrolysis process.
The invention relates to an electrochemical cell for electrolysers with single-element
technology for the membrane electrolysis process in accordance with the preamble to
5 claim 1. The cell consists of at least 2 half-shells which surround an anolyte chamber
and a cathode chamber with a membrane arranged in between, and an anode in the
anolyte chamber, with the cathode chamber being provided with an oxygen-
consuming cathode, with a plurality of pressure-compensated gas pockets arranged
one above the other, a catholyte gap and optionally a back chamber, with electrically
10 conducting supporting elements being provided in the anolyte chamber and
supporting elements being provided in the cathode chamber at the same positions opposite one another.
Electrolysers, for example for NaCl electrolysis, are known in two fundamentally
known basic technologies for the bipolar method.
In the filter press technology, the cell elements are arranged within the frame in the
manner of half-shells welded back to back, with the anode and cathode each being
located on the outside in a free-standing manner, and the ion exchanger membrane
20 inserted between two elements forming the electrochemical cell. The current from
cell to cell flows via the weld seams between the half-shells.
In the single-element technology, the electrochemical cell is formed by two
individual electrode half-shells, between which a membrane is placed and which are
25 then bolted together to form a single element. The electrical contacting from single
element to single element takes place by pressing together a pack of single elements, which are electrically connected to one another via suitable contact strips. The externally acting pressing forces have to be passed on within the element structures.
30 The use of oxygen-consuming cathodes in pressure compensation operation with so-
called gas pockets, as described in US Patent Specification 5,963,202 in basic prin-
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ciple and in DE-A 196 22 744 Al for gas pockets through which gas flows, actively,
takes place with an electrolyte gap between the oxygen-consuming cathode and the
membrane. At the same time, the gas pocket itself represents an empty volume. Both
structures, which are undefined for force transmission, have to be bridged by means
5 of a system which is suitable for the transmission of stress forces. At the same time,
the aim is to utilize the stress force for a further improvement in the current distribution into the oxygen-consuming cathode via press contacts.
The gas pockets containing the oxygen-consuming cathodes usually extend over the
10 entire width of the electrolysis cell. The structures for transmitting the stress forces
are, for hydraulic reasons, arranged vertically, as in the case of hydrogen-producing electrolysis. For the crossing functions here, a pragmatically simple solution had to be found which can be integrated both into new electrolysis elements from the outset and also enables retrofitting of electrolyses currently working in hydrogen operation.
The object is achieved in accordance with the invention by an electrochemical cell for the membrane electrolysis process, consisting at least of 2 half-shells, which surround an anolyte chamber and a cathode chamber with a membrane arranged in between, and an anode in the anolyte chamber, with \he cathode chamber being
20 provided with an oxygen-consuming cathode, with a plurality of pressure-
compensated gas pockets arranged one above the other, a catholyte gap and optionally a back chamber, which is characterized in that electrically conducting supporting elements are provided in the anolyte chamber and further supporting elements are provided in the cathode chamber at the same positions opposite one
25 another, which absorb the pressing forces acting on the half-shell walls.
A preferred embodiment of the electrochemical cell is characterized in that the
support in the cathode chamber takes place by means of a multi-part supporting
element, where one supporting part is arranged in the catholyte gap, a further
30 supporting part is arranged in the gas pocket and, if a back chamber is present, a third
supporting part is arranged in the back chamber behind the gas pockets.
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The back of the gas pockets is, in particular, welded to the vertical supporting ele¬
ments for force and current transmission. Structural beams, for example, or vertically
running structural bridges of other types are preferably welded into the gas pockets
5 via these weld seams as supporting elements, which are so high that they have the
same level as the peripheral outer edge of the gas pocket.
Irrespective of the embodiment selected, these internal fittings must facilitate hori¬
zontal passage of gas through the gas pocket and also horizontal outflow of any
10 condensate at the lower edge.
After the oxygen-consuming cathodes have been installed, these are located, for
example, flat on the structural beams or bridges and on the edge of the gas pockets
and form a planar surface over the full width and the respective height of the gas
In order to bridge the catholyte gap between the oxygen-consuming cathode and the
membrane, a supporting element is, in particular, installed as supporting element
made from electrolyte- and heat-resistant material as counterpart to the above-
20 mentioned structural beams or bridges and is itself supported via the oxygen-
consuming cathode and on the other hand via the membrane at the anode structure, which is likewise supported in this region, and thus facilitates force transmission " through the electrochemical cell,
25 The supporting element (spacer) is preferably not installed in one piece in the cell, for
the following reasons. Firstly, reliable positioning relative to the above-mentioned structural beams or bridges is not ensured over the full height, even small lateral deformations potentially resulting in slipping, with the risk of destruction of the oxygen-consuming cathode, and secondly the coefficients of thermal expansion differ
30 so much that lateral bending out is probable, favored by the sliding effect through the
catholyte. For this reason, it is advantageous to split the supporting element into
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pieces and to divide it into segments which correspond to the height of the respective
individual gas pockets. The segments of the supporting elements are, in particular,
attached or guided at the top and bottom in accordance with the following scheme: at
the upper end, they are attached to the edge of the gas pocket. This can take place
5 either via a pin or a type of snap fastener either at the spacer or, however, at the upper
edge of the gas pocket, it being necessary for the respective opposite part to contain a corresponding hole.
A preferred variant of the invention is consequently characterized in that the sup-
10 porting part in the catholyte gap is formed from a plurality of bars arranged one
above the other, which are optionally attached at their upper end via a detachable connecting means, for example a snap-fit connector, to cross-braces which carry the electrode.
15 At the lower end, the supporting element terminates in a dovetail-shaped structure
which surrounds the pointed upper end of the next supporting element beneath and thus ensures the horizontal positioning of the supporting element. The gap between these two segments is advantageously selected in such a way that the greater thermal expansion of the supporting element compared with the metallic structures is
In a preferred variant of the electrochemical cell, the respective adjoining ends of the
supporting parts are therefore designed as a tongue-and-groove combination, with the
upper end of the respective lower supporting part being designed, in particular, as the
Good force distribution occurs in the cell if the supporting elements extend over the entire height of the half-shells.
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The second supporting part in the gas pockets has openings or leaves passages open, particularly preferably at selected points, in particular in its upper and lower region of the respective gas pocket.
5 The second supporting part is particularly preferably designed in the form of solid
electrically conductive bars or as a TJ-profile, or, however, as corresponding vertical embossing of the back of the gas pocket.
In order to ensure even more reliable positioning of the supporting element, the
10 structural beams or bridges can be provided with slight vertical arching either to the
right or left or, however, in the center, which corresponds to a corresponding shaping of the supporting elements, so that the latter is always re-centered on the opposite structure on distortion of the electrolyser.
15 The oxygen-consuming cathode should be, in particular, electrically conductive on its
back. Besides the metallic connection of the oxygen-consuming cathode to the edge of the gas pocket, this provides a further electrical connection through press contact via the electrically conductive supporting elements, which results in a further minimization of the resistance losses. In addition, the use of the supporting element
20 prevents the oxygen-consuming cathode from bulging into the catholyte gap over a
large area, with the risk of local blockage of the catholyte flow through contact with the membrane. This applies, in particular, in the case of the above-mentioned structuring of the supporting elements by means of which the oxygen-consuming cathode is stressed.
The supporting elements in the catholyte gap are, in particular in the case of chloralkali electrolysis, advantageously made of ECTFE, FEP, MFA or PFA, while the electrically conducting supporting elements, for example structural beams or bridges, should consist of nickel or another caustic lye-resistant metal alloy or are
30 embossed directly out of the back wall of the gas pocket.
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In the case of an oxygen-consuming cathode which is metallic or "electrically conducting on its front, the supporting elements in the catholyte gap may be metallic on the side facing the oxygen-consuming cathode in order to obtain an improvement in the current distribution into the oxygen-consuming cathode via the press contact. In this case, the supporting elements preferably have a two-layered structure, with the side facing the membrane consisting of ECTFE, FEP, MFA or PFA, while the metallic part consists of caustic lye-resistant metal.
The use of the force transmission described in the single-element technology is not restricted just to chloralkali electrolysis, but can also be used for all electrolyses with gas-diffusion electrodes in direct contact with liquid electrolytes which require pressure compensation, such as, for example,
hydrogen peroxide production with an oxygen-consuming cathode,
sodium dichromate electrolysis with a hydrogen-consuming anode and an
alkaline fuel cells for enrichment of sodium hydroxide solution
hydrochloric acid electrolysis with an oxygen-consuming cathode
The invention is explained in greater detail by way of example below with reference to the figures, in which:
Fig. 1 shows a longitudinal section through a cathode half-shell of a cell
according to the invention as a detail of the top left corner
Fig. 2 shows a cross section corresponding to line A-A" in Fig. 1 through the
Fig. 3 shows a longitudinal section through a cathode half-shell corre-
sponding to line B-B" in Fig. 1
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Figure 1 shows the view of the cathode half-snell witn the top left corner as detail,
and Figure 2 shows a horizontal section A-A" through a gas pocket 15. In the cathode
5 half-shell 10, the gas pocket structure with back wall 11 and lateral frame 9 is
supported via the supporting structure 3.
The vertical structural beams 2a or [lacuna], according to a variant shown in the same Fig. 2 or 3, the vertical structural bridge 2b is welded into the gas pocket 15. In order
10 to ensure cross-transport of oxygen in the gas pocket 15, the two structures are open
and are not on the horizontal limit 12 of the gas pocket 15 in order to facilitate outflow of any condensate formed from the oxygen-consuming cathode. The oxygen-consuming cathode 4 is attached in an electrically conductive and gas-tight manner on and to the lateral frame 9 and the horizontal limit 12 and is situated on the
15 structural beams or bridges. The catholyte gap -14 between the membrane 5 and the
oxygen-consuming cathode 4 is defined by the spacer elements 1, which are in turn supported via the membrane at the anode 6, which is held in a defined manner in the anode half-shell 8 via the supporting structure 7 (cf. Fig. 2).
20 The anode half-shell 8 and cathode half-shell 10 are connected to one another in a
liquid-tight manner and form a single element (electrolysis cell). When the electrolyser is pressed together, a large number of such single elements are pressed -together, with the respective next anode half-shell 8" of adjacent single elements being pressed onto the cathode half-shell 10 and the next cathode half-shell 10" of an
25 adjacent single element on the other side of the single element being pressed onto the
anode half-shell 8. The pressing together of the single element places a load, via the cathode half-shell 10, on the supporting structure 3, the vertical structural beam 2a or the vertical structural bridge 2b and the spacer 1, which presses on the one hand against the oxygen-consuming cathode 4 and on the other hand via the membrane 5
30 against the anode 6. This transmits stress forces via the supporting structure 7 to the
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anode half-shell 8. The electrical contacting of single element to single element takes place by pressing against the contact strips 21a and 21b.
The spacer elements la, lb themselves are designed with a taper to a point at the top and are provided at the bottom with a corresponding dovetail structure (Fig. 1). They are attached to the top to the horizontal limit 12 of the gas pocket 15 by means of a pin or a snap fastener-like holding device 13. The dovetail of the spacer element lb engages over the tip of the next spacer element la beneath and is thus positioned unequivocally. At the same time, a defined gap between the spacer elements la, lb facilitates their free thermal expansion, which, due to the material, is greater than that of the metallic structures.
1. Electrochemical cell for the membrane electrolysis process, consisting at least of 2 half-shells (8, 10), which surround an anolyte chamber (16) and a cathode chamber (22) with a membrane (5) arranged in between, and an anode (6) in the anolyte chamber (16), with the cathode chamber (22) being provided with an oxygen-consuming cathode (4), with a plurality of pressure-compensated gas pockets (15) arranged one above the other, a catholyte gap (14) and optionally a back chamber (19), characterized in that there are provided electrically conducting supporting elements (7) in the anolyte chamber (16) and supporting elements (3, 2, 1) in the cathode chamber (22) at the same position op¬posite one another which support each other the supporting in the cathode chamber (22) being effected by means of a multi-part supporting element (3,2,1) with one supporting part (1) in the catholyte (14), a further supporting part (2a; 2b) in the gas pocket (15) which has openings (22a, 22b, 23a) or leaves passages (24) open at selected points, in particular in their upper and lower region of the respective gas pocket (15) and, if a back chamber (19) is present, a third supporting part (3) is arranged in the back chamber (19) behind the gas pockets (15).
2. Electrochemical cell as claimed in Claim 1, wherein in that the supporting part (1) in the catholyte gap (14) is formed from a plurality of bars (1) arranged one above the other which are optionally attached at their upper end via a detachable connecting means (13), for example a snap-fit connector (13), to cross-braces (12) which carry the electrode (4).
3. Electrochemical cell as claimed in Claim 2, wherein the respectively adjoining ends of the supporting parts (la, lb) are designed as a tongue-and-groove combination, with the upper end of the respective lower supporting part (1 a) being designed, in particular, as the tongue.
4. Electrochemical cell as claimed in one of Claims 1 to 3, wherein that the supporting elements (3, 2, 1) extend over the entire height of the half-shell (10) and are located opposite a continuous supporting element (7) in the second half-shell 8.
5. Electrochemical cell as claimed in one of claims 1 to 4, wherein the
second supporting part (2) is designed either as a solid electrically con¬
ductive bar (2a) or as a U-profile (2b).
6. Electrochemical cell as claimed in Claim 5, wherein that the U-
profile (2b) has been embossed out of the back wall of the gas pocket,
and the supporting element (3) extends into the base of the embossed U-
profile (2b) and thus directly causes the transmission of force.
7. Electrochemical cell as claimed in one of Claims 1 to 6, wherein the supporting elements (7, 3 and 2) are made of caustic lye metals or alloys, in particular from nickel, or from acid-resistant metals or alloys, in particular from titanium or alloys of titanium and palladium.
8. Electrochemical cell as claimed in one of Claims 1 to 7, wherein the supporting elements (1, la or lb) consist of a heat and electrolyte-re¬sistant plastic.
9. Electrochemical cell as claimed in one of Claims 1 to 8, wherein the supporting elements (1, la, lb) are made metallically conducting on the side facing the oxygen-consuming cathode (4).
Dated this 15th day of May, 2002.
OF REMFRY & SAGAf?
ATTORNEY FOR THE APPLICANTS
in-pct-2002-00619-mum-petition under rule 137-5-12-2005.pdf
in-pct-2002-00619-mum-petition under rule 138-9-12-2005.pdf
|Indian Patent Application Number||IN/PCT/2002/00619/MUM|
|PG Journal Number||12/2008|
|Date of Filing||15-May-2002|
|Name of Patentee||BAYER AKTIENGESELLSCHAFT|
|Applicant Address||D-51368 LEVERKUSEN, GERMANY|
|PCT International Classification Number||C25B9/00|
|PCT International Application Number||PCT/EP00/11531|
|PCT International Filing date||2000-11-20|