EP0060746B1 - Electrolyser with temperature-stable structure - Google Patents

Abstract

An electrolyzer cell of the filter-press type intended to operate under high pressure and at high temperature is constructed of spacing frames (4) for supporting and joining the electrodes and the diaphrams (1). Each frame is constituted by several portions (41 to 44), each held at a fixed point (61 to 64) and slidingly joined to one another.

Description

The present invention relates to the construction of an electrolyser of the filter press type, and more particularly to an electrolyser intended to operate under high pressure and at high temperature, for example an electrolyser which is the subject of French patent No 2448583.

In general, an electrolyser of the filter press type consists of a stack of several hundred elementary electrolysis cells, this stack appearing as an alternating succession of electrodes and diaphragms delimiting spaces in which circulates the 'electrolyte. Also conventionally, and in order to obtain maximum power, this stack is placed in a sealed enclosure filled with an inert gas and brought into operation at high pressure and temperature.

Depending on the operating cycles, the temperature inside the pressurized enclosure can vary considerably, being for example of the order of 160 ° C during operating hours and 20 ° C during operating hours. Eve. However, the stacking of cells being mounted at room temperature, it is necessary, to ensure the proper functioning of the electrolyser at its operating temperature, that the geometric shapes of the initial stacking are kept at working temperature in despite the expansions due to the rise in temperature. In general, the electrodes are made of a metallic material, generally nickel, with a low coefficient of expansion. Similarly, the diaphragms are formed either by an asbestos cloth or by a nickel or Tefton reps ", materials with a low coefficient of expansion, and are often crimped in a rigid frame made of nickel or other material which also expands very little. On the other hand, it is necessary, for reasons of resistance to corrosion due to the electrolyte, to constitute the insulating connections forming spacers and joint between electrodes and diaphragms by frames in a material resistant to corrosion, such as a fluoropolymer, possibly loaded with nickel or asbestos, for example polytetrafluorethylene, known as PTFE. This type of material, if it has excellent qualities of creation of sealing, electrical insulation, and resistance to corrosion , unfortunately has the disadvantage of expanding five to ten times more than the other constituent materials of the stack, so that it is found that, in the case of use of non-crimped diaphragms in a nickel frame, many tears occur in the diaphragms, and in addition in all cases the stack does not keep its initial geometric shape so that the performance of the electrolyser is deeply affected.

The present invention overcomes these drawbacks. The electrolyser of the filter press type of which it is the object is characterized in that it is equipped with bracing frames each consisting of at least two frame portions, each of these portions comprising a fixed point and being assembled to the adjacent portion or to the two adjacent portions by sliding junctions.

• la fig. 1 est une vue schématique en coupe transversale de l'électrolyseur de l'invention, faite au ras d'un diaphragme,
• la fig. 2 est une vue agrandie du détail entouré en traits mixtes sur la fig. 1,
• la fig. 3 montre, en coupe partielle selon la direction AA de la fig. 1, un premier exemple possible de réalisation d'un point fixe,
• la fig. 4 montre de même un second exemple de réalisation d'un point fixe,
• la fig. 5 est une coupe schématique transversale d'une variante de réalisation, destinée à s'appliquer à un électrolyseur de grandes dimensions.

The invention will be better understood with the aid of the following description of a preferred embodiment, applied to the construction of an electrolyser as concerned by the aforementioned French patent No. 2448583, with reference to the appended drawings in which:

• fig. 1 is a schematic cross-sectional view of the electrolyser of the invention, made flush with a diaphragm,
• fig. 2 is an enlarged view of the detail surrounded by broken lines in FIG. 1,
• fig. 3 shows, in partial section along the direction AA of FIG. 1, a first possible example of making a fixed point,
• fig. 4 likewise shows a second embodiment of a fixed point,
• fig. 5 is a schematic cross section of an alternative embodiment, intended to be applied to a large size electrolyser.

Referring first to all of FIGS. 1 to 3, the electrolyser of the invention is equipped with diaphragms 1 in nickel reps, each crimped in a rigid frame 2, also in nickel. Each frame 2 is engaged with the possibility of sliding in a corresponding groove made in the spacer frame 4 made of PTFE which, in a very conventional manner, serves both as a joint and as a support for the electrodes 5 and the diaphragm 1.

As seen in fig. 1, each bracing frame 4 consists of four portions (41,42,43,44) which are mounted end to end so as to form said frame, using sliding assemblies of which FIG. 2 shows in more detail and by way of example that surrounded by dashed lines at the bottom left of FIG. 1. Furthermore, each frame portion is provided in its central part with a fixed point, respectively 61, 62, 63, 64, having the role of preventing at this location any deformation by expansion of the frames 4 relative to the electrodes 5.

For example, as seen in fig. 3, a fixed point 62 is constituted by a set of nickel washers 7 force-fitted into a channel 8 previously pierced longitudinally in the cell stack.

In the example considered, the fixed points 61 and 63 are located respectively between the evacuation channels 91 and 92 and the supply channels 101 and 102, and the fixed points 62 and 63 are located respectively at the other two angles of the square formed by a frame 4.

In particular in the enlarged view of FIG. 2, it can be seen that two successive frame portions (42 and 43) are slidably fitted into one another. Furthermore, in order to perfect the seal at their joint, springs 11 are placed as appearing in FIG. 2, so as to spread the U-shaped male ends of the portion 42 by pressing them against the corresponding female walls of the portion 43. Finally, FIG. 2 shows that it is possible to make the electrolyser of the invention by providing, with formally to the teaching of the aforementioned French patent No 2448583, the frames 4 thereof of distributing grooves 212 and collecting collectors 211, using the terms and references of said patent, the distributing grooves 212 being supplied with demineralized water as explained in detail in said French patent. The junction between the successive sections of a groove 212 or 211 is then made respectively using the sliding spaces 121 and 122, as shown in the drawing. It can be seen that with the aid of the construction according to FIGS. 1 to 3, no differential expansion can occur between the frames 4 and the electrodes 5, at the location of the fixed points 61 to 64. The frame portions 41 to 44 therefore expand by sliding one inside the other so that the geometric shape of each frame 4 is preserved. For this, care has been taken to produce the frame portions such as 42 and 43 so that at room temperature they leave between them sliding spaces, such as 121 and 122 for example, sufficient to allow sliding up to maximum operating temperatures.

Furthermore, as can be seen in FIG. 3, the rigid frames 2 are fitted into the grooves 3 so as to leave, at room temperature, a sufficient sliding space 31.

The fixed points such as 62 can be produced in a manner other than that described with reference to FIG. 3. They can for example be simply constituted each by a screw and nut assembly or be made, as shown in FIG. 4, simply by riveting using the electrodes themselves, then slightly folded along the orifice 8 so as to firmly hold the frames 4.

The embodiment which has just been described with reference to FIGS. 1 to 4 rather relates to an electrolyser equipped with small cells, 50 cm side for example. In the case where larger frames are used, the side of which may for example be of the order of 150 cm, it will be preferable to match the stack of frames each consisting of more than four sliding portions, one in the other, each of these portions also being equipped with a fixed point preferably located in its median plane.

Fig. 5 shows an embodiment of such an electrolyser of larger dimensions. As can be seen in the drawing, each frame 4 is constituted by eight sliding portions 411 to 418, each of these portions being provided in its median plane with a fixed point, respectively 611 to 618. In the case of even larger frames , each of these could be made up of a number of sliding portions with fixed point according to the invention which may be equal to 12 or more.

Claims (5)

1. Electrolyser of the filter-press type equipped with spacing frames (4) forming a support and seal for the electrodes (5) and diaphragms (1), characterised in that each of the said frames consists of at least two parts (41,42,43,44), each of the said parts comprising a fixed point (61, 62, 63, 64) and being assembled with the adjacent part or with the two adjacent parts by sliding connections.

2. Electrolyser according to Claim 1, characterised in that the said fixed point is situated in the median plane of the corresponding part.

3. Electrolyser according to Claim 1 or 2, of the type equipped with diaphragms (1) crimped in a stiff frame (2), characterised in that each stiff frame is mounted to slide in a groove (3) of the corresponding spacing frame (4).

4. Electrolyser according to Claim 1, characterised in that the said sliding connections are equipped with sealing components (11).

5. Electrolyser according to any one of Claims 1 to 4, of the type equipped with distributing grooves (212) and collecting grooves (211) according to French Patent No. 2448583, characterised in that the connection of two adjacent parts of a groove is made across the sliding spaces (121, 122) between the two corresponding parts (42, 43) of a frame.

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