EP0946790B1 - Electrolysis apparatus for producing halogen gases - Google Patents

Description

The invention relates to an electrolysis apparatus for production of halogen gases from aqueous alkali halide solution with several arranged side by side in a stack and plate-shaped electrolytic cells in electrical contact, each made up of two half-shells electrically conductive material with outside contact strips have on at least one rear wall, wherein the housing means for supplying the electrolysis current and electrolysis input materials and facilities for discharging the electrolysis current and the electrolysis products and a substantially planar anode and cathode has, wherein the anode and the cathode by a Partition separated and arranged parallel to each other are and by means of metallic stiffeners with the each assigned rear wall of the housing electrically conductive are connected, the metallic stiffeners as webs aligned with the contact strips are, the side edges over the height of the rear wall and the Anode or cathode on the rear wall and the anode or cathode issue.

The invention further relates to a method of manufacture of electrolysis cells for an electrolysis apparatus of the above Type in which the respective housing from each two half shells with the interposition of the required Facilities and the cathode and anode as well as the partition by fixing them by means of webs metallic stiffeners and the anode and Housing or cathode and housing electrically conductive to each other be attached.

From documents US-A-4,108,752, GB-A-2,135,696, EP-A-172 495 and JP-A-08 04 084 electrolysis apparatus are known, which are made up of single cells, the anode or Contain half-shell-shaped vessel parts arranged on the cathode side. In the solution according to JP-A-08 04 084, the Backs of neighboring vessel parts, plating pads, on their Place the mutually opposite parts of the vessel be firmly connected by laser welding.

An electrolysis apparatus is known from EP 0 189 535 B1, at the the anode or the cathode with the respective rear wall the housing halves via truss-like metallic stiffeners connected is. On the back of the anode or Half of the cathode is a contact strip for each electrical contact to the neighboring, identical structure Electrolysis cell attached. The current flows through the contact strip through the back wall into the half-timbered metallic stiffeners and from there it spreads starting from the metallic contact points - stiffening / anode - via the anode. After the flow through the Membrane has passed through, it is taken up by the cathode, to find out about the framework-like stiffeners in the Back wall to flow on the cathode side and then back in the contact strip and from there to the next electrolytic cell to enter. The connection of the current-carrying components is done by spot welding. In the The electrolysis current bundles welding spots to form peak current densities.

It has the disadvantage of this known electrolysis apparatus it turned out above all that the current did not exceed the entire area of the contact strip flows because of the current starting from the metallic connection between the truss-like Stiffening and the back wall of the cathode selectively is introduced into the contact strip. With decreasing current-carrying area of the contact strip increases but the voltage required for current flow, the so-called Contact voltage, on. Because the specific energy requirement, necessary for the manufacture of the electrolysis products is, linearly increases with the tension, the production costs decrease to.

Another disadvantage of the known electrolysis apparatus is that the framework-like stiffeners that the Connect the back wall and the electrodes together Flexibility reasons not perpendicular between the rear wall and Are arranged, resulting in an extension of the Leads to current paths, which also results in an increase in cell voltage results. In addition, the current comes from the framework-like Stiffening in the electrode only selectively, which on the one hand has an uneven power distribution and on the other hand in turn leads to an increase in cell voltage. The uneven current distribution on the electrodes leads moreover to a non-uniform depletion of electrolytes, resulting in a reduction in electricity yield and results in a reduction in membrane life.

The object of the invention is to provide an electrolysis apparatus create, in which the current-carrying areas as possible are large in order to provide only a selective introduction into the electrodes and the contact strips and thus an uneven current distribution to avoid.

This task is done with an electrolysis machine at the beginning designated type solved according to the invention in that the Contact strips are U-shaped in cross section and each rest with their U-web on the back wall and in the middle area of the U-web across the entire height the back wall and the respective web in one electrically conductive triple composite are joined, the triple composite cross-sectionally goblet-shaped starting from the U-bridge extends inwards.

Through this inventive design of the electrolysis apparatus uneven current-carrying areas become largely avoided and the electricity is not only selective, but largely over the entire surface in the electrodes and the Contact strips initiated. The current paths themselves are short, since the stiffening webs are perpendicular between the respective Rear wall and the respective electrode can be arranged. Due to this design, the required Cell voltage significantly compared to the known electrolysis apparatus less.

Due to the integral joining of the triple composite the joining surfaces between the web and the rear wall on the one hand and between the rear wall and the contact strip on the other hand or between Bridge and electrode. The electrolysis current flow needs no longer the electrical ones present in the joining surfaces Overcoming surface contact resistances.

Another advantage of the integrally joined is surprising Triple association has been established. The triple network increases the rigidity of the rear walls of the half-shells considerably. Because between the back walls of the electrolytic cells both the prestressing force in the stack and the electrolysis current is transmitted, - both are simultaneously via the respective contact strips of the neighboring ones Electrolysis cell back walls directly transferred - must Contact strips under the influence of the clamping force so stay between the adjacent contact strips current flow as possible can take place. The higher one Bending stiffness of the triple composite reduces the electrical Contact resistance between the individual electrolytic cells in the stack.

It is preferably provided that the webs over their entire Height electrically connected to the anode or cathode are.

The cathodes can be made of iron, cobalt, nickel or chrome or one of their alloys and the anodes made of titanium, niobium or tantalum or an alloy of these metals or from consist of a metal or oxide ceramic material. About that in addition, the electrodes are preferably catalytic effective coating. Here are the electrodes preferably provided with perforations (perforated sheet, Expanded metal, wattle or thin sheets with blind-like Breakthroughs), so that due to their arrangement in the electrolysis cell, the gases formed during electrolysis easily can enter the back of the electrolytic cell. By this gas discharge is achieved that the electrolyte between the electrodes have the lowest possible gas bubble content and thus has maximum conductivity.

The partition, the so-called membrane, is preferably an ion exchange membrane, generally from a copolymer of polytetrafluoroethylene or one of its derivatives and a perfluorovinyl ether sulfonic acid and / or perfluorovinyl carboxylic acid. She cares to ensure that the electrolysis products do not mix and because of their selective permeability for Alkali metal ions the current flow. Also come as a partition also diaphragms in question. A diaphragm is one fine-porous partition that prevents the gases from mixing and an electrolytic connection between cathodes and Represents anode space and thus allows current flow.

The webs forming the metallic stiffeners can be formed over the entire surface or with openings or Slots.

To achieve an optimal feed of the electrolytes it is advantageously provided that an inlet distributor is provided via which the electrolytes can be fed into the half-shells are. This inlet distributor is preferably like this designed that each segment of a half-shell over at least an opening in the inlet manifold with fresh electrolyte can be supplied and the sum of the areas of the openings in the inlet manifold less than or equal to the cross-sectional area of the inlet distributor.

The anode half-shells preferably consist of a counter Halogens and saline resistant material while the cathode half-shells preferably from one against alkali eyes resistant material.

A generic method for producing the above Electrolysis apparatus is distinguished according to the invention characterized in that the metallic, electrically conductive Connection of the stiffeners designed as webs with the respective rear wall and the respective contact strip as well the anode or cathode using a reductive sintering process or is produced using a welding process.

If a reductive sintering process is used, an adhesive consisting essentially of an oxidic material, for example NiO, and an organic binder is used. This adhesive is spread on the web and the component to be connected to it, for example the rear wall, and the two parts are pressed together using a holding device. After the organic binder has hardened, the oxidic component of the adhesive is reductively sintered in a reducing atmosphere (eg H ₂ , CO, etc.).

If a welding process is used, a is preferred Laser beam welding process used. It becomes special preferably the laser beam is perpendicular to the welding direction polarized to a significantly reduced ratio to reach from the upper track width to the connection width.

The laser beam can preferably be by means of mirror optics be shaped so that by means of a special beam shaping two or more at a time selectable Amount of offset focus points are generated.

It is also advantageously provided that the laser beam by means of a high-frequency scanner drive, preferably a piezo quartz, by a selectable amount is scanned across the welding direction.

Fig. 1

einen Schnitt durch zwei nebeneinander angeordnete Elektrolysezellen eines Elektrolyseapparates,

Fig. 2

perspektivisch einen Ausschnitt aus Fig. 1,

Fig. 3A bis 3D

verschiedene Varianten der als Steg ausgebildeten Versteifungen und

Fig. 4A bis 4C

in vergrößerter Detaildarstellung in verschiedenen Varianten einen metallischen Dreifachverbund zwischen Kontaktstreifen, Gehäuserückwand und Steg.

The invention is explained below with reference to the drawing, for example. This shows in:

Fig. 1

2 shows a section through two electrolysis cells of an electrolysis apparatus arranged side by side,

Fig. 2

in perspective a section from FIG. 1,

3A to 3D

different variants of the stiffeners and

4A to 4C

In an enlarged detail in different versions, a metallic triple bond between the contact strip, the rear wall of the housing and the web.

A generally designated 1 electrolysis apparatus for Production of halogen gases from aqueous alkali halide solution has several, side by side in a stack arranged and in electrical contact plate-shaped Electrolysis cells 2, of which in Figure 1 exemplary two such electrolysis cells 2 side by side are shown arranged. Each of these electrolytic cells 2 has a housing made of two half-shells 3, 4, which are provided with flange-like edges, between which by means of seals 5 each have a partition (membrane) 6 is clamped. Clamping the membrane 6 can be done in another way if necessary.

Over the entire depth of the rear walls 4A of the respective Electrolysis cell 2 are parallel to each other A plurality of contact strips 7 arranged through Welding or the like. What is described in more detail below on the outside of the rear wall in question 4A are attached or applied. These contact strips 7 make the electrical contact to the neighboring Electrolysis cell 2, namely the one in question Housing rear wall 3A, forth, on which no separate contact strip is provided.

Within the respective housing 3, 4 are each on the membrane 6 is adjacent to a flat anode 8 and a flat cathode 9 is provided, the anode 8 or the cathode 9 in each case in alignment with the contact strips 7 arranged stiffeners are connected, the are designed as webs 10. The webs are 10 preferably along its entire side edge 10A the anode or cathode 8, 9 is attached in a metallically conductive manner. To feed and discharge the electrolysis input materials to allow the electrolysis products to rejuvenate the webs 10, starting from the side edges 10A, across its width to the adjacent side edge 10B and have a height there that corresponds to the height of the contact strips 7 corresponds. Accordingly, they are with their margins 10B over the entire height of the contact strips 7 on the rear sides opposite the contact strips 7 the rear walls 3A and 4A attached.

A suitable one is to supply the electrolysis products Device provided for the respective electrolysis cell 2, such a device is indicated by 11. There is also a device in every electrolysis cell provided for removing the electrolysis products, these is not indicated, however.

The electrodes (anode 8 and cathode 9) are designed such that they are the electrolysis input product or the Flow through raw materials or let them flow freely, for which purpose corresponding slots 8A or the like are provided are, as can also be seen in Fig. 2. The Stringing together several plate-shaped electroyse cells 2 happens in a framework, the so-called cell framework. The plate-shaped electrolytic cells are between the two upper side members of the cell frame suspended in such a way that their plate plane is perpendicular to the longitudinal beam axis stands. So that the plate-shaped electrolysis cells 2 their weight on the upper flange of the side member can transfer, they have on the upper plate edge a cantilever-like holder on each side.

The holder extends horizontally in the direction of the Plate level and protrudes over the edges of the flanges out. With the plate-shaped ones suspended in the scaffold Electrolysis cells lie the lower edge of the cantilever-like Holder on the upper flange.

The plate-shaped electrolysis cells 2 hang comparatively like folders in a hanging file in the cell structure. The plate surfaces of the electrolysis cells are in the cell frame in mechanical and electrical contact, as if they were stacked. Electrolysers this Design are called electrolysers in a hanging stack type.

By lining up several electrolytic cells 2 in a hanging stack design using known tensioning devices become the electrolytic cells 2 over the contact strips 7 each with adjacent electrolytic cells in one Stack electrically connected. From the contact strips 7 the current then flows through the half-shells over the webs 10 into the anode 8. After passing through the membrane 6 the current is absorbed by the cathode 9, to cross over the webs 10 into the other half-shell or the back wall 3A to flow and here in the contact strip 7 to cross the next cell. In this manner and way the electrolysis current passes through the whole Electrolysis cell stack, being on the one outer cell initiated and derived on the other outer cell becomes.

In the detail shown in Figure 2 from a Electrolysis cell is a section of a rear wall of the housing 4A of the half-shell 4, on which a U-shaped contact strip 7 is attached. It is good too recognize that on the back aligned with the contact strip 7 is attached to the rear wall 4A a web 10 is, the web 10 is approximately in the center of the U-shaped profiled contact strip 7, which is related 4A to 4C explained in more detail below becomes. On the other side edge 10A of the web 10 this attached to the anode 8, which in the area of Connection with the webs 10 is formed over the entire surface, while adjacent to these areas to pass through Electrolysis input and output products slots 8A are provided. The connection is the same between the respective web 10 and the cathode 9 educated.

As can be seen from FIGS. 3A to 3D, the Web 10 have a different design. At In the embodiment according to FIG. 3A, the webs 10 are full-surface formed, only the two side edges 10A and 10B different for the reasons mentioned above are long.

In the embodiment according to FIG. 3B, the webs 10 Open slots 13. The embodiment according to Figure 3D, in which the web 10 is shown in a side view according to FIG. 3C is also has slots, which from angled Die cuts 15 are formed.

As already shown with reference to FIG. 2, through the connections between the electrodes (anode 8 or cathode 9) to the housing rear walls 3A or 4A the webs 10 have a maximum cross-sectional area for the Current flow provided because of this in principle along its entire length with both the rear wall of the housing 3A or 4A as well as with the respective electrode 8 or 9 is metallically connected. In addition, the current path is minimized, since the web 10 is the vertical connection between the housing rear wall 3A or 4A and the electrode 8 or 9 represents.

The connection of the web 10 to the electrode 8 or 9 or with the rear wall 3A or 4A is preferred designed in such a way that no joining surfaces are created, the additional Surface contact resistors for current flow would form. It is therefore preferred between the a metallic double or Triple composite manufactured, preferably by a laser beam welding process, although basically also conventional Welding processes, e.g. Resistance welding, can be used. Beyond that too reductive sintering process possible. The welded joint can possibly, in order to minimize the welding process To ensure heat input and thus minimal warpage, also done selectively. There is also a welded joint possible over the entire individual cell height, whereby a continuous connection is preferable because therefore an optimal current distribution, minimal contact resistance and thus a minimum possible cell voltage is achieved.

Different embodiments of a triple composite in Laser welding processes are shown in FIGS. 4A to 4C, in each of which a contact strip 7, a Part of a rear wall 4A and the side edge 10B of a web are shown.

The embodiment according to FIG. 4A shows laser welding with a laser beam source with a beam index of K = 0.5 with a beam power of P = 2 KW and a focusing optics with the focusing number of F = 10. The weld seam 16 which is produced forms a pronounced one Chalice shape. A typical relationship results from top track width to connection width of 2.5.

With a laser beam of the same beam power and the same Focus indicator, but with a particularly high one Beam index of K = 0.8, the in Figure 4A was Solid lines 16 'shown in solid lines receive. Here was a ratio of the upper bead width reached to the connection width of 2.0. However this more favorable ratio with less tub warpage with a connection width between Bridge 10 and rear wall 4A bought.

In the embodiment according to FIG. 4B, a seam shape was used with the same laser beam source and focusing optics as in the embodiment of Figure 4A, but using one polarized perpendicular to the welding direction Laser beam reached, so that as a result of the seam flanks acting increased beam coupling through the Brewster effect resulted in a significant widening of the seam is. This seam is labeled 16 ''. Here is the ratio of the upper track width to the connection width at about 1.6. The seam volume was in this case in the same order of magnitude as for welding Figure 4A, but the port width is almost 25% elevated.

A particularly good ratio of top track width the welded joint shows the connection width of 1.5 according to Figure 4C, which is designated there with 16 '' '. The In this case, the connection width is 50% higher than with the welded connection according to FIG. 4A. The one shown here Seam shape 16 '' 'was created using a special Beam shaping with the same laser beam source as in of the welded connection according to FIG. 4B. Here was the laser beam with special mirror optics shaped so that two were offset by about 0.5 mm at the same time Focus points were created. Such a seam shape can also be done by high-frequency scanning of the focusing mirror with an amplitude of e.g. 0.5 mm realized become.

The figures are not shown in detail Design of the electrolysis cells 2 in the lower area with the electrolyte entry. The electrolyte entry can both selectively and with a so-called inlet distributor respectively. The inlet distributor is designed so that a tube is arranged in the element that over Openings. Since a half-shell through the webs 10, the connection between the rear walls 3A and 4A and represent the electrodes 8, 9, is segmented you get an optimal concentration distribution if both Half-shells 3, 4 equipped with an inlet distributor are, the length of which is arranged in the half-shell Inlet distributor corresponds to the width of the half-shell and each segment through at least one opening in the inlet manifold supplied with the respective electrolyte becomes. The sum of the cross-sectional area of the openings in the Inlet manifold should be smaller than or equal to that Inner pipe cross section of the distributor pipe.

As can be seen from Figure 1, the two half-shells 3, 4 provided with flanges in the flange area, that are screwed. The cells thus constructed are in a cell structure, not shown, is either attached or posed. Hooking or placing in the cell structure takes place on the flanges, not shown holding devices located. The electrolysis machine 1 may consist of a single cell, or preferably by stringing together several electrolysis cells 2 in hanging stack design. Become several single cells pressed together according to the hanging stack principle the individual cells are aligned plane-parallel before the clamping device is closed, otherwise the No current transfer from one single cell to the next can take place over all contact strips 7. Around the cells after hanging or placing in the cell structure To be able to align in parallel, it is necessary that which usually weigh around 210 kg when empty Let elements move easily. To meet this requirement meet, the brackets or not shown contact surfaces on the cell frame and cell frame provided with assigned coatings. Are there the brackets located on the element flange frame a plastic, e.g. PE, PP, PVC, PFA, FEP, E / TFE, PVDF or PTFE relined, while the contact surfaces on Cell structure also coated with one of these plastics is. The plastic can only be put on and guided over a groove, glued, welded or be screwed on. It is only essential that the Plastic pad is fixed. Because two Touching plastic surfaces are those in the scaffolding Individual elements so easily movable that they without additional lifting or sliding device by hand in parallel can be aligned. When closing the tensioning device lay out the elements due to their im Cell structure easy to move across the entire Back wall flat, which is the prerequisite for one uniform current distribution. It is also on this way the cell is electrically opposite the cell framework isolated.

Claims (11)

1. An electrolysis apparatus for the production of halogen gases from aqueous alkali halide solution comprising a plurality of plate-shaped electrolysis cells which are arranged in mutually juxtaposed relationship in a stack and which are in electrical contact and which each have a housing comprising two half-shell portions of electrically conductive material with external contact strips on at least one rear wall of the housing, wherein the housing has devices for feeding the electrolysis current and the input electrolysis substances and devices for carrying away the electrolysis current and the electrolysis products and a substantially flat-surfaced anode and cathode, wherein the anode and the cathode are separated from each other by a partition and are arranged in mutually parallel relationship and are electrically conductively connected by means of metal stiffeners to the respectively associated rear wall of the housing, wherein the metal stiffeners are in the form of plates (10) which are aligned with the contact strips (7) and whose side edges (10A, 10B) bear over the height of the rear wall (3A, 4A) and the anode (8) or cathode (9) against the rear wall (3A, 4A) and the anode (8) or cathode (9), characterised in that the contact strips (7) are of a U-shaped configuration in cross-section and each bear with the web portion of their U-shape against the rear wall (4A) and in the central region of the web portion of the U-shape are joined over the entire height to the rear wall (4A) and the respective plate (10) in an electrically conductive triple composite assembly, wherein starting from the web portion of the U-shape the triple composite assembly extends inwardly in a bell-shaped cross-sectional configuration.
2. An electrolysis apparatus according to claim 1 characterised in that the plates (10) are electrically conductively connected over their entire height to the anode or cathode respectively.
3. An electrolysis apparatus according to claim 1 or claim 2 characterised in that the plates (10) have a solid surface.
4. An electrolysis apparatus according to claim 1 or claim 2 characterised in that the plates (10) are provided with openings or slots (13, 14, 15).
5. An electrolysis apparatus according to claim 1 or one of the following claims characterised in that there is provided an intake distributor by way of which the electrolytes can be fed into the half-shell portions (3, 4).
6. An electrolysis apparatus according to claim 5 characterised in that the intake distributor is of such a design that each segment of a half-shell portion can be supplied with fresh electrolyte by way of at least one opening in the intake distributor and the sum of the areas of the openings in the intake distributor is smaller than or equal to the cross-sectional area of the intake distributor.
7. A process for the production of electrolysis cells for an electrolysis apparatus according to one or more of claims 1 to 6 in which the respective housing is assembled from two respective half-shell portions with the interposition of the required devices and the cathode and the anode and the partition by fixing thereof by means of metal stiffeners in the form of plates and the anode and the housing and the cathode and the housing respectively are electrically conductively fixed to each other, characterised in that the metallic, electrically conducting connection of the stiffeners which are in the form of plates to the respective rear wall and the respective contact strip and the anode or cathode respectively is made by way of a reductive sintering process or by way of a welding process.
8. A process according to claim 7 characterised in that a laser beam welding process is used.
9. A process according to claim 8 characterised in that in the laser beam welding process the laser beam is polarised perpendicularly to the welding direction in order to achieve a markedly reduced relationship of the upper welding pass width to the connection width.
10. A process according to claim 8 or claim 9 characterised in that the laser beam is so formed by means of a mirror optics that two or more focal points which are displaced by a selectable amount are produced simultaneously by means of a special beam formation.
11. A process according to claim 8 or claim 9 characterised in that the laser beam is scanned transversely to the welding direction by a selectable amount by means of a scanner drive operating at high frequency, preferably a piezoelectric quartz.

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