MXPA94001386A - Electrode configuration for gas-forming electrolytic processes in membrane cells or diapragm cells - Google Patents

Abstract

An electrode plate of planar structure contains lamellar electrode elements, with adjacent electrode elements being separated from one another by a gap. For a better escape of the gas from the electrode/membrane area, the lamellar electrode elements are provided with an expanded-metal structure, the openings of which serve to improve the passage of gas. The electrode elements are provided with angled upper edge strips in order to facilitate the escape of gas in the vertical direction. The electrode configuration is particularly suitable as an anodically connected electrode in direct contact with an ion exchanger membrane, but can also be used as a cathode at a distance from the membrane.

Description

# • "ARRANGEMENT OF ELECTRODES FOR P30CES0S ELECTROLYTIC GAS FORMATORS IN MEMBRANE CELLS" # Inventors: BERND BUSSE, German, domiciled in Graupnerweg 40, 64287 Darmstadt, Germany and ROBERT SCANNELL, Irish, domiciled in Am Dautenberg 21, 64297 Darmstadt-Eberstadt, Germany.

• Causaire: HERAEUS ELEKTROCHEMIE GMBH, a German company, domiciled in Heraeusstr. 12-14, 63450 Hanau, Germany. . _i - * 4 ** »H, n« m, n?, lHtM.tMfc ?? fc »S- át REjyEN OF THE INVENTION # The present invention relates to an arrangement or arrangement of electrodes for gas-forming electrolytic processes in membrane cells, which has a flat electrode plate, which contains electrode elements in the form of lamellae, being; Separate the neighboring electrode elements by means of a slit. For the best gas conduction in the zone of the electrodes / membrane, the electrode elements in the form of lamellae are provided with a metallic structure in the form of a section, in which the holes serve for the best passage of the gas. The electrode elements are provided with angled upper edges, to facilitate gas extraction in the vertical direction. The arrangement or arrangement of electrodes is particularly suitable as anodically connected electrodes in direct support on the ion exchange membrane, however it can be placed as the cathode at a distance from the membrane.

Ajt. * ^, ^ *. ---. *. - -j-fil ... n,, trfit ^ Í? tá | fl ^^ i, j, DESCRIPTION OF THE INVENTION $ The invention refers to an arrangement of electrodes for gas-forming electrolytic processes, in particular processes in membrane cells, of a structure of plane-forming electrodes with at least two electrically conductive electrode elements and tightly connected to each other mechanically, a gap for the gas conduction being provided between them, the electrode elements present along the slit # laying plans for an ion exchange membrane or a diaphragm and the edges bordering the slit are shaped as a gas ejection device and the invention also refers to the use of the electrode array. German patent 32 19 704 discloses a membrane electrolytic cell of the filter press type with pairs of stackable electrodes, in which the electrodes contain at least one discontinuous active middle part and a membrane is placed between the electrode pairs; For this purpose, a joint is always placed between the edge of the electrodes and the edge of the membrane, the discontinuous half portion of the electrodes has a lattice-like construction, the bars of the lattice of the electrode pairs being located between each other. about half the width of the bar, in such a way That the distance between s1 is less than the projection of its * width; the bars of the lattice have at least on the active side a convex arc, the thickness of the joint being between the edge of the electrode and the edge of the membrane, equal to or less than the height of the portion of the protruding lattice bar on the edge of the electrodes. It is considered problematic that with such an arrangement there must be a lack of reach and gas bubbles in the laying surface, with which disadvantageous effects are obtained on the membrane and the coating of the electrodes. The electrolytic cells are provided for the electrolysis of an aqueous electrolyte containing halide, such as brine, to produce an aqueous solution of alkali metal hydride and hydrogen and hydride. With cells constructed in this way, it should be counted in the area of contact between electrode and membrane, with a chloride reduction, with which a decrease in long-term stability can be had. From the European patent 0 102 099 an arrangement of electrodes for gas forming electrolysis, especially electro '! isis of membrane, with plate electrodes placed vertically, a counter electrode and a membrane between both electrodes; plate electrodes , ***, **.,,. < This is divided into horizontal strips, whose total active electrode surface is placed parallel and at a short distance from the counter-electrode, however, it is provided between the membrane and the membrane. the electrode a slit for the expulsion of the gas formed by the electrochemical reactions; for the expulsion of the gases leaving the groove of the electrodes, horizontal strips are provided in the area of their upper edges with an inclined gas conduction member, in which the gas expands and is driven here partially backwards of the electrodes. Here the slit between the electrodes, necessary for the expulsion of the gas between the membrane and both electrodes, is considered problematic, resulting in proportionally greater proportionality between the electrodes, also an increase in cell stress. From the German patent 36 40 584 an arrangement of electrodes for gas-forming electrolysis is known, in particular for monopolar membrane electrolysis with vertically placed plate electrodes as well as counter-electrodes and a membrane between the plate electrode and counter-electrode; On the surface of the pl electrodes, in front of the membrane, conductive surface formations are placed and conductively connected in a ^ Electrical electrode with plate electrodes that are condWft as pre-electrodes, and run% n planes parallel to the plate electrodes. The flat formation that serves as electrodes has the shape of perforated plates, unfolded metals, metal mesh and wire lattice, the distance between the flat formations being between 1 and 5 mm; the flat electrodes are distributed in several horizontally separated units, to obtain an improvement in the distribution of current in the membrane and a reduction of the voltage drop on the surfaces that are in front of the membrane. In these electrodes, the decrease in chloride is considered problematic, especially at the point of contact between the electrodes and the ion exchange membrane, obtaining a reduction in long-term stability. It is also known from European patent 0 150 018 a method for the electrolysis of liquid electrolytes by means of discontinuous electrodes in electrolytic cells divided by an ion exchange membrane, where by reason of the formation in a lateral form to the main direction of the electrolysis. i t, a volume of gas is produced. The gas bubbles that form when bursting at the gas phase limit, give the gas to the volume of gas that limits laterally with the phase limit in the main direction of flow, which is formed in the electrodes in the form of plates, forming through space * which is behind the electrodes. The discontinuous electrodes may consist, among others, of unfolded metals or sheet strips. It is considered problematic of the known arrangement of European patent 0 150 018, the relatively complicated structure of electrodes with conductive elements of the gas stream, which are formed of individual strip strips. # The invention proposes the task of developing an array of electrodes with an open structure, possibly with a construction similar to a lattice, in which the structure must obtain a rapid emission of gas bubbles with an increased electrolytic exchange. in the area between the electrode and the membrane with a high degree of effectiveness; From this the electrode array must be easy to manufacture, its long-term stability must be increased and an increase in the catalytically active surfaces must be achieved. The task is solved by means of the characteristic attributes of the reference 1. Further advantageous characteristics of the invention as well as its application are given in claims 2 to 10. It is contemplated as particularly advantageous to carry out the arrangement of electrodes; furthermore * considers the variable capacity of * Place, as for example directly embedded in the membrane or also as a cathode at a distance from the membrane. From this it is possible to obtain a fast gas outlet due to the electrodes provided with expanded metal holes; In electrochemical cells with the electrode according to the invention a relatively low cell expansion can be obtained in comparison with the common membrane cells, whereby considerable energy savings are obtained. # The object is further described in detail with the aid of the figures la, Ib, le, 2 and 3. The figure shows a surface plan view of the arrangement of electrodes, while figure Ib represents a separate section A of the figure the; the figure shows a cross section in profile of the electrode arrangement. Figure 2 shows in a perspective representation a partially discontinuous array of electrodes, while Figure 3 shows the application of the arrangement of electrodes according to the invention in membrane electrolytic cells schematically in a fragmented partial representation. According to the figure the. the arrangement of the real electrodes 1 from a sheet of electrodes ; fej? • -? Ti ~ a 'A ** fcjAi «» «" jK iá¿m. ^ P1i able to form planes, shows a plurality of elements of * electrodes 2 placed in the form of lamellae, which are separated from each other by means of a slit 3; the upper edges 4 of the electrode elements 2, along a line 5 shown schematically are inclined on the side near the membrane, to enable a rapid gas outlet in the region of the gas bubbles formed in the electrodes. With the help of figure Ib, the holes 8 can be recognized essentially in the form of diamonds represented schematically, where despite the reductions an increase of the active surface in the range of 1.1 to 1.3 cm is obtained, this means that the Electrochemically effective electrode surface is increased by means of metal openings deployed in comparison with a closed surface, for example from 1 cm2 to a surface area of 1.15 cm2. Advantageously, expanded metal with a bridge width in the range of 1.5 to 4 mm is used. The long hole measurement (L D) is in the range of 2 to 4.5 mm, the short hole measurement (SWD) in the range of 1.2 to 3 mm. Due to the holes in the area of the catalytically active surface of the electrodes, a better mixing of the mixture of electrolyte gas bubbles can be achieved with a better expulsion of the air bubbles, thereby "* '> -' .T •",, f f ~ - ~. . . «. . , »-.« S? -íaf »6 - there is an improvement in long-term stability in the * area of the membrane and electrode connected anodlcamente; The anode connected electrode is directly on the membrane. As seen in FIG. 1, the angle between the upper edges 4 and the plane of the electrode arrangement 1 is approximately 30 °. An angle in the range of 20-35 ° has been regarded as advantageous. Suitable materials for the electrode arrangement are, in particular, titanium foil with a # Activation of noble metal and non-noble metal or nickel sheet with noble metal actlvation. The arrangement of electrodes has proven particularly useful when used as an anode and cathode in a membrane cell for chlor-alkali electrolysis or for obtaining hydrogen-oxygen. The edge strips 6 and 7 consist of either expanded metal or bonded sheet. With the aid of FIG. 2, in the holes 8 necessary for the expulsion of the gas inside the electrode elements 2 as well as through the slit 3 and the inclined upper edges 4, the possible separations of the mixture can be observed gas-electrolyte in a fraction of electrolytes and in a fraction of outgoing gas. In case the electrode is connected anodically, £? Is the membrane directly above the surface * flat designated with the 10th tariff, while the reg- • extends backwards in the electrolyte swath is open in order to extract the gas. In cases of a cathodic connection of the electrode, there are provided between the front part 10 of the electrode array 1 and the ion exchange membrane (not shown), which consist of an electrolyte-resistant material, but which # here They also are not represented. Figure 3 shows in a schematic representation in cross-section a membrane cell unit, in which mainly the ion exchange membrane is represented with cathode and anode in cross section, renouncing to a better view in reference to the expulsion of gas , in the representation of the corresponding peripherals as voltage elements, current conductors. As shown in FIG. 3, the electrode I connected anodically is directly with its front side 10 on the surface of the membrane II shown schematically, being recognized here, in view of the holes 8 shown only schematically in the area of the elements of FIG. electrodes the need for rapid expulsion of gas. Gas bubbles not shown here, due to their low weight l .. " . "• •"? "? 6 - * - specific in comparison to the 12 anolltos flow in * Vertical upwards and are collected and conducted by means of collecting devices not shown here. A corresponding process also takes place on the limiting side of the membrane 11, by means of the cathode-connected electrode 1 '; here, however, it should be noted that the cathode electrodes are placed at a distance from the membrane to allow the exchange of substances and the stability of the membrane, for example by means of distance elements 13 and that it is supported # against the ion exchange membrane 11, to obtain a distance in the range of 1 to 3 mm; however, it is also possible to form a substantial density between the membrane and the cathode electrode by means of a pressure difference. Here, too, a conduction of the gas bubbles in the vertical discharge is shown from the catholytes 14, a collector device not being provided here as well. • represented. The cell container represented fragmentarily, which contains the anolyte and cathode is designated with the dial 15. The arrangement of the membrane cells is particularly suitable for electrolytic cells for the generation of chlorine, however it can also be used for the generation of hydrogens / oxtgeno.

»* J ^ &méti * It is noted that in relation to this date, the best method known by the applicant to carry out the aforementioned invention, is the conventional one for the manufacture of the objects to which it refers. Having described the invention as above, property is claimed as contained in the following:

Claims (10)

14 .. £ * CLAIMS

1. - An arrangement or arrangement of electrodes for gas-forming electrolytic processes, especially processes in membrane cells, of an electrode structure capable of forming planes with at least two elements of electrically conductive electrodes and mechanically bound together mechanically, between which there is provided a slit for the expulsion of the gas, the electrode elements having along the slit laying planes for an Ion Exchanger membrane or a diaphragm and the edges bordering the slit are shaped as an ejector device of gas, the arrangement of electrodes is characterized because at least the planes of placement of the electrode elements have permeable areas to liquids and gases.

2. Arrangement of electrodes according to claim 1, characterized in that the positioning surfaces of the electrode elements are in a plane.

3. Arrangement of electrodes according to the re1v1nd1cac16n 1 or 2, characterized in that the electrode elements, in their total flat area have permeable areas to liquids and gases. J; U¿H «Í 5fó. '»« ^ AéÜk.? t #

4. Arrangement of electrodes according to one of claims 3, characterized in that the electrode element is formed of expanded metal.

5. Arrangement of electrodes according to claim 4, characterized in that the propulsion of the electrolytically active surface to the geometrical surface of the electrode element is in the range of 0.9: 1 to 2.0: 1.

6. Arrangement of electrodes according to one of claims 1 to 5, characterized in that the electrode elements are joined to each other by means of two front outer edge strips, wherein the electrode elements and the other edge strips The film consists of lamellae of plane forming electrodes.

7. Arrangement of electrodes according to one of claims 1 to 3, characterized in that the element Electrode consists of porous or microporous metal.

8. Arrangement of electrodes according to claim 7, characterized in that the electrode element consists of slurred titanium or nickel slit.

9. Arrangement of electrodes according to claim 7 or 8, characterized in that the maximum extension of the pores is in the range of the m8x1ma extension of the gas bubbles. XI

10. - Use of the electrode array according to one of claims 1 to 9 as anodes or cathodes of • a membrane cell. In testimony of which I sign this in this Mexico City, D.F. on February 23, 1994. By: HERAEOS ELEKTROCHEMIE GMBH. a »i» f * «fcWft« * s, »> , ft «*? fc. x &x ^ j? i