MXPA99004297A - Electrochemical gaseous diffusion half cell - Google Patents

Abstract

An electrochemical half cell based on a gaseous diffusion electrode (5) as a cathode or anode, comprising a gas space for a gaseous diffusion electrode (5) formed by one or several gas pockets (2a, 2b, 2c, 2d), an ion exchanger membrane (40), a retaining element (11), a gas inlet (21) and a gas outlet (22), an electrolyte feed pipe (20), an electrolyte discharge pipe (22) and a housing (13). Said half-cell is characterized in that the gas diffusion electrode (5) is connected to one or more of the gas pockets (2a, 2b, 2c, 2d) thereby forming one or several modules (1a, 1b, 1c, 1d) which are removably secured to the retaining element (11), wherein the gas inlet (21) and the gas outlet (22) are removably connected to the gas pockets (2a, 2b, 2c, 2d).

Description

ELECTROQUÍMICA SEMICELDA WITH GASEOUS DIFFUSION.

FIELD OF THE INVENTION.

The use of electrodes with gaseous diffusion in electrochemical cells with pressure compensation requires, in the case of large construction heights, a division of the gaseous enclosure into superposed segments called gas pockets, which have to be electrically contacted and closed off. gas-tight manner in the marginal zone with the electrode.

DESCRIPTION OF THE PREVIOUS TECHNIQUE.

A half-cell, showing a basic construction of this type, has been described, for example, in published German patent application DE 44 44 114 A1. A drawback of the construction form shown in DE 44 44 114 consists of the contacted in the hermetic seal of the electrodes with comparatively cumbersome gas diffusion. It is desirable to be able to contact and seal the electrodes with the gas bags in as narrow a space as possible to maintain REF. : 30080 as small as possible the inactive surface of the electrodes with respect to the reaction of the electrodes.

OBJECT OF THE INVENTION.

The aim of the invention is to provide the electrochemical system with gaseous diffusion that allows as much use as possible of the active surface of the electrodes, the electrodes being configured, together with the gas bag, if necessary in form of removable module, so that a previous assembly of the electrodes is possible on the gas bag, gas-tight in the marginal contacts, and that the electric contact for the operation of the electrodes with gas diffusion in the half-cell is simplified . Another object of the invention is especially to configure the half cell and the module of the electrodes and the gas bag in such a way that modules of the half cell can be exchanged in a simple manner even by a conventional electrode, for example a nickel electrode producing hydrogen .

DETAILED DESCRIPTION OF THE INVENTION.

The object is solved according to the invention in that the gas pockets, equipped with gas diffusion electrodes, can be removed from the half-cell, if necessary individually, and have been detachably configured from gas supply or from pressure compensation as well as of the electrical connections. In this case the gas bags are manufactured as compact flat elements, the front side of which is closed by the gas diffusion electrodes in such a way that, when the electrodes are mounted on the half cell, no electrolyte can escape to the cavity gas can not escape any gas, in the opposite direction, from the gaseous bag. The present invention relates to an electrochemical semi-cell based on an electrode with gaseous diffusion as a cathode or as an anode with a gaseous enclosure for the gas diffusion electrodes, which is formed from one or several gas pockets with an exchange membrane of ions, a support structure for the assembly of the electrodes electrical connections for the electrodes, a gas supply to the gas bags and a gas discharge, pressure compensator, from the gas bags an electrolyte feed and a discharge of electrolyte as well as a housing for the reception of the components of the cell, characterized in that the gaseous diffusion electrodes are joined to the gas bag to form a module, which is detachably fixed on the support structure, forming the gas supply and the gas discharge a removable connection with the gas bag. In a preferred embodiment, the gaseous enclosure is subdivided into several gas pockets, optionally supplied, each with gas from the electrodes, which are compensated in pressure, if necessary, with respect to the electrolyte chamber in front of the gaseous diffusion electrodes. Particularly preferred is a half cell in which the individual modules are detachably fixed to the support structure independently of one another., in the case of several gas bag modules. Also particularly preferred are embodiments in which the gaseous diffusion electrodes are sanded in an easily removable manner on the gas bag in order to allow a replacement of the aged electrodes. Preferably, the gas supply or the discharge of gas as a hose connection with which the gas bag is attached, which facilitates a removal of the gas bags after the release of the ion exchange membrane, will be carried out. Alternatively, it is also possible to use gas feeds manufactured as an overlap, made in the upper part as bubble channels and corresponding pressure compensating divers. In another embodiment of the half-cell according to the invention, the modules of the gas bags are positioned with the aid of structural elements in the half-cell, electrically connected to the external current supplies and, if necessary, a hermetic sealing is carried out. that the electrolyte can not overflow uncontrollably from the interstitium for the electrolyte traveled to the preceding room compensated in pressure, of the gas bag, positioning the structural elements of the gas bag modules in such a way that the electrodes with diffusion gas can simultaneously serve as a gap for the electrolyte for the passage of the electrolyte in the electrolyte chamber between the gaseous diffusion electrodes and the ion exchange membrane. The electrical contact of the gas bag modules with an external electric power source, for example connected to the half-case housing, can be improved if the modules are electrically contacted, in addition to the contacts under pressure in the marginal zone, with support of a substructure, which is pressed for example with the housing of the half-cell, on its rear side, the side directed in the opposite direction to that of the gas diffusion electrodes, through elastic and electrically conductive contact elements (for example contacts of spring). By means of the electrical contacts in the marginal zone and by means of the contact of the electrodes distributed on the surface of the electrodes, a power supply of the reduced ohmic electric current to the electrodes is made possible. In another preferred variant of the half cell according to the invention, the electrode has been electrically contacted with gas diffusion, on its side directed towards the gaseous chamber of the gas bag, with the help of a support grid on its surface. In this case, the support grid has electrical contact with the rear wall of the gas bag. A possible additional channel, which is formed at the lower edge between the gas diffusion electrodes and the gas bag, can be used to collect the condensate that is formed, if necessary. The condensate can be discharged, together with the excess gas, through the gas discharge, located at the lowest point, to the preceding electrolyte chamber. A lack of homogeneity in the feeding of the room for the electrolyte located in front of the gaseous diffusion electrodes with fresh electrolyte can be avoided in a preferred variant if the half cell has, behind the electrolyte feed, an additional electrolyte distributor, which regularizes the electrolyte current over the width of the half cell. The rear enclosure offset in pressure will not be traversed in this case in this case. The above room compensated under pressure will not be traversed in this case in this case. The preceding room, compensated under pressure, is not covered in this case in this case. The preceding room is in communication with the electrolyte current only at the upper edge of the half cell. A special advantage of the constitution of the half cell according to the invention consists in the possibility of operating the half cell, even when exchanging the modules of the gas bags, simply with conventional electrodes, especially with hydrogen products electrodes for example nickel electrodes. In a preferred variant, the gas bag modules are thus interchangeably configured with. conventional electrodes, the supply of gases up to the gas bags being optionally lockable or removable The object of the invention is also the use of the electrochemical half cells according to the invention in an electrochemical cell, especially in an electrolyte cell, for operation , optionally, with gas bag modules or with conventional electrodes, especially with hydrogen producing electrodes, first of all with activated nickel electrodes.

DRAWINGS The invention will now be explained in more detail by means of the figures. In these figures they show: FIG. 1 a cross-section through half-cells according to the invention seen from the ion exchange membrane towards the gas diffusion electrodes and the supports for the gas pockets located between them. Figure 2 shows a broken longitudinal section with the closed half cell corresponding to line AA 'in figure 1. Figure 3 shows a broken longitudinal section corresponding to line AA' in figure 1, with the open half cell with the ion exchange membrane detached from the cell housing and with gas bag module. Figure 4 shows a detail of figure 2, to explain the electrical contact of the gas bag. Figure 5a shows a cross section corresponding to the line B-B 'with view on the gas supply 21 of the half-cell. Figure 5b shows a partial section corresponding to the line CC in the upper part of the half cell according to figure 1. Figure 6 presents a partial cross section corresponding to the line D-D1 in figure 1 through the half cell, in which the modules of the gas bags have been replaced by a conventional nickel electrode 30 with the supporting structure 31. Figure 7 shows a longitudinal section corresponding to the line AA 'according to figure 1, for the variant of the half-cell according to Figure 6 in operation with a nickel electrode 30.

EXAMPLES Example 1.

An electrochemical half cell is constituted as follows: In a housing 13 (see FIG. 3) resistant to electrolytes, a frame structure 11 is fixedly anchored in the form of a semi-capsule, as well as a substructure 12, which is connected to a power supply. external current (not shown). A gas line 21 (see FIG. 1), an electrolyte feed 20 as well as a combined electrolyte and gas discharge 22 are passed through the housing 22. The bag unit is fixed on the support structure 11. of gas 1 with the gaseous diffusion electrode 5 in the housing 13 with the help of vertical terminal strips A and horizontal terminal strips 9. The half cell is closed by the membrane 40, which is supported on the peripheral edge of the housing 13 by means of a seal 41 (see Figure 2) and pressed, for example by clamping another half cell, not shown, in an electrolyte-tight manner on the peripheral edge of the housing 1. The conduits 6a, 6b, 6c, 6d (see Figure 1) flexible starting from the gas distributor, are connected by flange connections respectively with tubing 6e on the unit of the gas bags. The embodiment according to Figure 1 shows a distribution in four gas bags 2a, 2b, 2c, 2d respectively with compensation of the pressure by means of gas overflow conduits 7. The gas bag 1 is constituted by a metal casing 2, which is in communication by means of current contacts, for example spring contacts 14, brush contacts 15 or direct contact, with the current-carrying substructure 12, on the pre-baffled parts of the structure 16 (see the detail in FIG. figure 4). The further supply of current is carried out by means of metal process contacts between the terminal strips 8, 9 and the support structure 11 on the marginal region of the casing 2. The contact resistance can be reduced by surface ennoblement (for example by plating with gold). The gas bag unit 1 also has supply and discharge ducts 6e and 7 for the electrode gas, a support structure 3 for supporting the gaseous diffusion electrodes 5 as well as a support grid for the electrodes 4, on which the gaseous diffusion electrodes lie with all their surface 5. Each of the four gas bags, Ib, lc, ld presents a gaseous diffusion electrode 5 connected in a gas-tight manner in the edge area of the gas bag module, which in this case is electrically connected simultaneously. In the case of gaseous diffusion electrodes with conductive rear side, a complete electrical contact is made through the electrode support grille. During operation, as shown in FIG. 5a, the electrolyte enters from the electrolyte supply conduit 20, through the electrolyte distributor 23, through the holes 24 and other holes 10 in the horizontal terminal strips, to the enclosure for electrolyte 27 in front of the gaseous diffusion electrodes 5. The electrolyte travels through the electrolyte chamber 27 along four gas bag modules up to ld and penetrates through holes in the upper horizontal terminal strip 9, into the channel for the electrolyte accumulation 26. From there the electrolyte is discharged through holes 25 in the preceding room behind the gaseous diffusion electrode and is discharged through a drop tube 22 together with the excess electrode gas from the half cell (see figure 5b). The half cell is connected during operation as an electrolytic cell on the front side with an ion exchange membrane 40, which is responsible for passing the ions, according to the corresponding electrolytic reaction, from the half cell according to the invention to another connected half cell. if necessary, in the opposite direction. The electrode gas enters the supply conduit 21 in the half-cell and is distributed by means of a gas distributor 19 in the throttled conduits 6a, 6b, 6c and 6d for a better distribution of the gases in the individual modules of the bags of gases, up to the four modules of gas bags la, Ib, lc, ld (see figure 1). The gas of the electrodes travels through the gas pockets in the longitudinal direction and the unconsumed excess as well as eventually the condensate formed exits at the opposite end through gas overflow tubes 7 from the gas pockets to the electrolyte in the gas. interstitium of the electrolyte. In this way, pressure compensation is achieved. From the gas overflow conduits 7 the gas bubbles through the enclosure behind the gas bag modules, upwards and accumulates in the enclosure located above the end of the connection 22. From there it is remove the gas from the half cell through the drop tube 22.

Example 2 For operation with a conventional electrode, the gas bag modules can be removed up to ld together with the terminal strips 8 and 9 as indicated in FIG. 3 and replaced by a nickel cathode 30 with a substructure 31, which serves as power supply and support. The gas supplies 6a to 6d are conveniently closed. The conventional electrode, for example an activated nickel cathode, is fixed with threaded connections 32 on the frame structure 11 of the half cell (see FIGS. 6 and 7). The discharge of the hydrogen formed during the reaction at the electrodes can be carried out together with the electrolyte projecting through the drop tube 22. It is noted that in relation to this date, the best method known to the applicant to carry out the practice said invention is that which is clear from the present description of the invention. Having described the invention as above, property is claimed as contained in the following:

Claims (11)

1. Electrochemical semi-cell based on a gaseous diffusion electrode as a cathode or anode, with a gas enclosure for the gas diffusion electrodes, which is formed by one or several gas pockets, with an ion exchange membrane a structure of support, a gas supply, a gas discharge, an electrolyte feed, an electrolyte discharge and a housing, characterized in that the gaseous diffusion electrode is connected to the gas bag (s) to form a module or modules, which it is detachably fixed on the support structure by forming the gas supply and the gas discharge, a releasable connection with the gas bags.

2. Semi-cell according to claim 1, characterized in that the gaseous enclosure is subdivided into several gas-bag modules, possibly supplied with gas independently of each other, which are compensated in pressure with respect to the electrolyte enclosure.

3. Semi-cell according to claim 2, characterized in that the gas bag modules are detachably fixed independently to one another on the support structure.

4. Semicell according to the claims 1 to 3, characterized in that the gas feeds are configured as flexible pipe joints with the gas bags.

5. Semi-cell according to claims 1 to 4, characterized in that the modules of the gas pockets are electrically contacted by structural elements positioned in the half-cell and, where appropriate, they are hermetically sealed with respect to the flow, the structural elements forming at the same time a active gap for the electrolyte travel.

6. Semicell according to the claims 1 to 5, characterized in that the modules of the gas bags are electrically in contact with the substructure through contact elements,

7. Semi-cell according to claims 1 to 6, characterized in that the gaseous diffusion electrodes are electrically contacted in a surface manner on a support grid in the internal space of the gas pockets.

8. Semi-cell according to claims 1 to 7, characterized in that the cell has a distributor for the electrolyte for the homogeneous supply of the electrolyte chamber with electrolyte.

9. Semi-cell according to claims 1 to 8, characterized in that the modules of the gas bags are interchangeable by conventional electrodes.

10. Semi-cell according to claims 1 to 9, characterized in that the gaseous diffusion electrodes are removably connected to the modules.

11. Use of the half-cell according to one of claims 1 to 10 in an electrochemical cell for operation, optionally, with gas bag modules or with conventional electrodes.