MXPA00009965A - Electrolysis apparatus for producing halogen gases - Google Patents

Abstract

The invention relates to an electrolysis apparatus for producing halogen gases from an aqueous alkali halogen solution, comprising several electrically connected plate-shaped electrolysis cells arranged in a pile and respectively provided with a housing consisting of two half shells made of an electro-conductive material and fitted with outer contact strips on at least one rear wall of said housing, also including two respective planar electrodes (anode and cathode), whereby the anode and cathode are provided with louver-like orifices so that the electrolytic feed material and products can flow though, said anode and cathode are separated from each other by means of a partition wall, are arranged parallel to each other and are electroconductively connected to the associated rear wall of the housing by means of metal reinforcements. The aim of the invention is to provide an apparatus which can operate at flow densities of more than 4 kA/m2 with correspondingly higher production of gas in the boundary layer while maintaining a sustainable service life for the membrane and requiring few pulses. This is achieved by slanting the louver-like orifices (8B, 9B) of the anode (8) and cathode (9) towards the horizontal.

Description

ELECTROLYSIS APPARATUS TO PRODUCE HALOGEN GASES DESCRIPTIVE MEMORY The invention relates to an electrolysis apparatus for producing halogen gases from an aqueous alkaline halogen solution with several electrolysis cells in the form of plates arranged in stack next to one another and which are in electrical contact, which respectively have a housing of two half-shells of electrically conductive material with external contact strips at least on a rear wall of the housing, the housing having devices for feeding the electrolysis stream and the electrolysis starting materials and devices for discharging the electrolysis stream and the electrolysis products and respectively two electrodes (anode and cathode) essentially flat, the anode and the cathode being provided with lattice-shaped grooves for a continuous flow of the starting materials, the electrolysis products and separated one from the other by a dividing wall and arranged parallel one to another and being connected in a conductively electrical way to the respectively arranged wall of the housing by means of metallic reinforcements. The unique electrolysis cells are produced in such a way that the respective housings of two half-shells are assembled respectively, interconnecting the necessary devices and the cathode and the anode as well as the dividing wall and fixing them by means of metallic reinforcements, and they hold the anode and the housing or the cathode and the housing, then the electrolysis cells in the form of plates thus produced are electrically electrically arranged and tighten against each other in a stack in order to establish long-lasting contact. The electrolysis current is fed to the stack of cells in the single external cell of the stack, impregnates the stack of cells in an essentially vertical direction to the middle planes of the electrolysis cells in the form of plates and is discharged to the other external cell of the pile. With respect to the average plane, the electrolysis current reaches average values of current density of at least 4 kA / m2. Such an electrolysis apparatus is known from DE 196 41 125 A1 of the applicant. In this known electrolysis apparatus, the anode or the cathode are connected to the respective rear wall of the housing halves by vertical metal reinforcements of the bridge type.

On the back of the anodes or of the half-shell, respectively, a vertical contact strip is placed for the electrical contact to the adjacent electrolysis cell, uniformly shaped. The current flows through the contact strip through the rear wall to the vertical metal reinforcements of the bridge type and from there it is distributed from the contact points (reinforcement / anode) through the anode. After the current has passed through the dividing wall (the membrane), it is received by the cathode to flow through the vertical reinforcements of the bridge type to the rear wall of the cathode side and to then enter the terminal again of contact and from there to the next electrolysis cell. The connection of the conductive components of the • current in this case by welding. At the welding points, the electrolysis current is concentrated at maximum current densities. The vertical metal reinforcements of the bridge type are designed as bridges aligned with the contact strips, whose side edges are in contact by the total height of the rear wall and the anode or cathode in the rear wall and the anode or • 10 cathode. The vertical bridges subdivide the back space of the electrodes within the respective housing halves into single segments that conduct the electrolytes. So that a completely irregular subdivision of concentration in the electrolyte is not made along the For the depth of the respective housing halves, there is provided below in each housing half an inlet manifold, on which they can be • feed the electrolysis starting materials to the only ones formed by the bridges in the half-shells. By means of an electrolyzer shaped in such a way, it is carry out electrolysis processes that produce gas, such as for example the electrolysis of alkaline chloride, the electrolysis of hydrochloric acid or the alkaline electrolysis of water. In the alkali metal electrolysis, aqueous solutions of alkali halide, for example sodium and potassium chloride, are decomposed in the electrolysis cell by the influence of electric current to an alkaline liquor, for example sodium hydroxide solution or potassium hydroxide solution, and to a halogen gas, for example chlorine and hydrogen. In the electrolysis of water, • Water is broken down and hydrogen and oxygen are formed at the electrodes. 5 The spatial separation of the spaces of the electrodes occurs by means of the wall mentioned at the beginning, in general a diaphragm or a so-called ion exchanger membrane. The diaphragm consists of a porous material, which is chemical, thermal and mechanically stable with respect to the media, temperatures and pressures present in the cell. • 10 In the case of the ion exchanger membrane, it is generally perfluorinated hydrocarbons. These membranes are gas tight and partly liquid, but allow ion transport in the electric field. A particular feature of these electrolysis processes consists of the fact that the diaphragm or the ion exchanger membrane is compressed against one of both electrodes. This is necessary because the wall is thus fixed and is therefore effortless from the mechanical point of view. Often, the dividing wall probably rests only on one of the two electrodes, since in this way a useful life can be achieved. more possibly long of all the components (electrodes and dividing wall). With the direct contact of the dividing wall with the electrodes, in some cases a chemical reaction may take place between the dividing wall and the electrodes or the gases produced in the electrodes. A distance between the membrane and the cathode is thus established in the alkaline chloride electrolysis, since otherwise the electrocatalyst, or in non-activated nickel cathodes, nickel is released from the electrode. Another example is nickel oxide diaphragms, which are used in alkaline water electrolysis. With too small a distance to the hydrogen-producing electrode, the nickel oxide is reduced to nickel and becomes conductive, which results in a short circuit. The support of the membrane or the diaphragm on at least one electrode results in a gas retention in the electrolyte delimiting layer between the electrode and the membrane or the diaphragm with processes in which gas is produced. Of these are involved the electrodes claimed at the beginning which are shaped such that they may be flowing from the electrolysis starting materials or from the electrolysis products. Such electrodes are preferably provided with perforations (perforated plate, expanded metal, braided with lattice-shaped grooves), so that, despite their flat arrangement in the electrolysis cell, the gases formed during electrolysis in the layer delimiter can more easily enter the posterior space of the electrolysis cell. The gas bubbles rising in the electrolyte agglomerate in particular at the ends or edges of the grooves facing downwards in the cell and remain there permanently in the noses between the adjacent dividing wall (membrane) and the perforation edges.

These bubbles disturb the current transport, ie the transport of material through the dividing wall, because they block the exchange surface of the membrane and make it inaccessible, or active. In an electrode configuration, which was created by the applicant for the reduction of this gas retention and which is described in the German patent specification DE 44 15 146 C2, the electrodes are outlined, while these are provided for example of slots and holes. In this way, on the one hand the gas can escape more easily and on the other hand new electrolyte can reach the boundary layer again • 10 electrolytically active between the electrode and the membrane. During the admission of electrodes profiled in such a manner with current densities above 4 kA / m2, however, the gas evolution still increases and the profiled electrode then reaches the limit of its discharge capacity. In electrolysis reactions in which gas is released As in the anodic evolution of chlorine from the alkaline chloride electrolysis in the anodic oxygen release from the electrolysis of the alkaline water electrolysis, for example, a separation problem arises, ie the gas evolved is not separated from the electrolyte, which results in a foaming. This problem results in the distribution of current densities are inhomogeneous with current densities above 4 kA / m2. In this way, the useful life is restricted by a portion of the active cell components, such as membranes, diaphragms and electrode activations. On the other hand, the electrolysers are thus limited also with respect to the maximum current density at approximately 4 kA / m2. In addition, foaming gives rise to pressure fluctuations within the electrochemical cell, since the foam clogs the cell outlet at least for a short time to the gas formed. The entrance is blown freely again by means of a negligible pressure rise inside the cell, which gives rise to the known effect of torrential flow and the so-called pressure fluctuations. This is disadvantageous for the operation of the electrolyser. In addition, the useful duration in particular of the membranes is affected by the distribution of concentrations. The more homogeneous, for example, the concentration of common salt in the anode space of an alkaline chloride electrolyzer, the longer the useful life of the membrane. In order to achieve a more homogeneous electrolyte distribution, either an additional circulation is produced by externally arranged pumps, or an internal circulation is caused by a difference in densities by installing a guide plate to the cell. It is an object of the invention to provide an electrolysis apparatus that can also be operated with current densities above 4 kA / m2 and the gas production correspondingly increased in the delimiting layer, conserving long and poorly pulsed residence times.

This object is solved according to the invention with an electrolysis apparatus indicated at the beginning, by appropriately arranging the lattice-like grooves of the anode and the cathode against the horizontal.

• By this configuration according to the invention, it is possible to improve, as has been shown, the gas conduction from the delimiting layer of the electrolyte near the membrane, in such a way that current densities of up to 6% can be reached for the first time. at 8 kA / m2, preserving long residence times of the membrane. The gas bubbles that form roll along due to the inclination of • 10 the electrode rods with respect to the horizontal at the lower end of the electrode, collide with the gas bubbles still adhered to the electrode end and join together growing. This also results, because of the increased volume, that the bubbles are accelerated, ie the effect accelerates itself. At the same time, the volume found in the electroactive zone, whereby a lower cell voltage is achieved. A suction effect, which originates with the movement of the gas bubbles along the electrode end, ensures that the new electrolyte is sucked into the electroactive zone between the membrane or the diaphragm and the electrode, which is for example in the electrolysis of chloride alkaline is a prerequisite for a long service life of the membrane. further, a directed flow arises, since all gas bubbles are forced in one direction. In this way, the density of the electrolyte / gas mixture decreases on the one hand because of the increasing gas content, which results in an internal circulation which, compared to the entrance to the electrolysis stream, is greater in a factor from 10 to 100. In this way, an excellent electrolyte homogenization is achieved. As a particularly advantageous feature, it has been shown that the inclination angle 5 of the grooves with respect to the horizontal is between T and 10 °. In a particularly preferred configuration from the construction point of view, it is provided that the lower part of the respective housing is arranged parallel to the horizontal and the grooves in the form of The lattice of the anode and the cathode are arranged inclined against the lower part of the respective housing. It is then necessary to modify the electrolysis apparatus with respect to the electrolysis apparatus only insignificantly, nothing more than that the anode and the cathode must be installed inclined and conveniently configured with the side end, for that can be installed conveniently. As a result, it can be provided that the lower part of the respective housing is arranged inclined with respect to the horizontal. Therefore, the particular accommodations must not be modified with respect to the dwellings hitherto known, only that they must be installed inclined with respect to the horizontal, whereby automatically also the grooves in the form of lattice of the cathode and the anode are arranged inclined with respect to the horizontal.

The invention is explained below in more detail by way of example based on the drawings. These show in: Figure 1, a section through two electrolysis cells arranged side by side, Figure 2, a section of Figure 1 in perspective and Figure 3, also in perspective an enlarged cut of the figure 1. An electrolysis apparatus generally designated 1 to produce halogen gases from an aqueous solution of alkaline halogen has several electrolysis cells in the form of plates arranged in stack next to one another and which are in electrical contact, which in figure 1 are represented two such electrolysis cells 2 arranged next to each other. Each of these electrolysis cells 2 has a housing of two half-shells 3, 4, which are provided with edges of the type of flange, between which a dividing wall (membrane) 6 pp is mediated respectively of the packings 5. The clamping of the membrane 6 can be carried out optionally in another way. Through the total depth of the rear receiving doors 4A of the respective electrolysis cell 2, a plurality of contact strips 7 are arranged parallel to one another, which are fixed or incorporated by welding or similar to the outer part of the respective rear housing wall 4A. These contact strips 7 establish the electrical contact with the adjacent electrolysis cell 2, namely with the rear housing wall 3A, in which no contact strip is properly provided. Within the respective housing 3, 4, a flat anode 8 and a flat cathode 9 are respectively provided in the membrane 6 adjacent to each other, the anode 8 or the cathode 9 being respectively connected with reinforcements arranged in alignment with the contact strips 7, which are shaped as bridges 10. Thus, the bridges 10 are fixed in a metal-conducting manner, preferably along their entire lateral edge 10A to the anode or cathode 8, 9. In order to make possible the • 10 feeding the electrolysis starting materials and the discharge of the electrolysis products, the bridges 10 end in tip from the side edges 10A through their total width to the adjacent side edge 10B and have a certain height there, which corresponds to the height of the contact strips 7. They are conveniently fixed with their edges 10B to through the total height of the contact strips 7 at the rear opposite the contact strips 7 of the rear housing wall 12A • Ó 4A. For the feeding of the electrolysis products, a device is provided for the respective electrolysis cell 2; such a device is indicated with the 11. Also, a device for discharging the electrolysis products is provided in each electrolysis cell, but it is not shown.

The electrodes (anode 8 and cathode 9) are formed in such a way that the electrolysis input product or the outlet products 3 can pass or flow without interruption, for which the anode 8 or the cathode 9• they are formed in the form of a lattice, that is they consist respectively of 5 particular electrode bars in the form of a lattice, and are present between the grooves in the form of a lattice. This applies to both the anode 8 and the cathode 9, with only one electrode 8, 9 being represented in FIGS. 2 and 3 respectively. Here the particular electrode plates are designated with 8A or 9A, while the grooves in shape from lattices are designated with 8A or 9B. It is essential for the invention that these lattice-like grooves 8B, 9B are arranged inclined with respect to the horizontal, preferably at an angle between T and 10 °. This angle is designated in Figure 2 with the. As inferred from figures 2 and 3, the posterior space of the electrode 8 or 9 is provided with chambers (ie subdivided into several chambers) by vertical bridges 10. As has been demonstrated, this configuration results in the gas bubbles formed rolling along the inclined arrangement of the electrode rods 8A, 9A at the lower end of the anode 8 or the cathode 9, are then with the bubbles that are adhered at the electrode end and grow together. This causes the gas bubbles to accelerate because of the increasing volume, so that the effect itself is accelerated. At the same time, the volume of gas that is in the electroactive zone decreases, whereby a reduced cell voltage is achieved. A suction effect, which originates with the movement of the gas bubbles along the electrode end, ensures that the new electrolyte is sucked into the electroactive zone between the membrane 6 or the diaphragm and the electrode 8, 9, which is for example in the alkaline chloride electrolysis a prerequisite for a long useful life of the membrane. In addition, a directed flow occurs, since all gas bubbles are forced in one direction. This current is indicated by the arrow in figure 2. In this way, the density of the electrolyte / gas mixture decreases on the one hand because of the increasing gas content, which results in an internal circulation which, compared to the incoming electrolysis current is greater by a factor of 10 to 100. In this way, excellent electrolyte homogenization is achieved. The construction of the electrolysis apparatus is in no way different from known electrolysis apparatuses. The juxtaposition of several electrolysis cells 2 in the form of plates occurs in a matrix, the so-called cell framework. The electrolysis cells 2 are hung in the form of plates between the two upper longitudinal supports of the cell frame so that the plane of the plate remains vertical to the axis of the longitudinal support. In order that the plate-shaped electrolysis cells 2 can transmit their weight on the upper flange of the longitudinal support, they have a carrier in the form of a cantilever arm at the upper plate end on each side. The carrier extends horizontally in the direction of the plane of the plate and protrudes over the edge of the flange. In the electrolysis cells in the form of plates hung on the frame, the lower end of the carrier in the form of a cantilever arm remains on the upper flange. • The electrolysis cells 2 in the form of plates hang 5 comparatively as folders in a hanging file in the cell frame. In the cell frame, the plate surfaces of the electrolysis cells are in mechanical and electrical contact, as if they were stacked. The electrolysers of this form of construction are called electrolysers as a construction of hanging piles. By the juxtaposition of several electro cells 2 of construction of hanging cells by means of known voltage devices, the electrolysis cells 2 are electrically connected in stack through the contact strips 7 respectively with adjacent electrolysis cells. . Of the strips of contact 7 the current then flows through the half-shells through the bridges 10 at the anode 8. After passing through the embryo rr 6, the current is received by the cathode to flow through the bridges 10. to the other half shell or its rear wall 3A and to end here to the contact strip. In this way, the electrolysis current impregnates the full battery of electrolysis cells, entering in an outer cell and deriving in the other outer cell. Not represented in particular in the figures, the configuration of the electrolysis cells 2 is in the lower area with the electrolyte input.

The entrance of the electrolyte can be carried out both on time and with a so-called input distributor. The inlet distributor is configured here so that a tube is arranged in the element having openings. Since a half shell is segmented by the bridges 10, 5 representing the connection between the rear walls 3A or 4A and the electrodes 8, 9, an optimum concentration distribution is achieved, when both half-shells 3, 4 are equipped with a distributor, corresponding the length of the distributor of entrances arranged in the average shell to the width of the average shell and being provided of the respective one • 10 electrolyte each segment at least through an opening in the inlet distributor. The sum of the transverse surface of the openings in the inlet manifold should thus be less than or equal to the inner cross-section of the distribution pipe. As can be seen from figure 1, they are provided with flanges both half-shells 3, 4 in the flange area, which are bolted. The cells thus constructed are hung or put in a cell frame not • represented. The suspension or incorporation into the cell frame is effected by means of arresting devices (not shown) located on the flanges. The electrolysis apparatus 1 may consist of a cell or preferably by a juxtaposition of several electrolysis cells 2 in the form of construction of hanging piles. If several individual cells are compressed according to the principle of hanging piles, the individual cells must be straightened in parallel planes, before the voltage device is closed, otherwise the current conduction of a particular cell to the The following can not take place through all the contact strips 7. In order to be able to straighten the cells in parallel after being hung or incorporated into the cell frame, it is necessary that the elements in the unloaded state usually of approximately 210 kg. weight move easily. To meet this requirement, fixing devices (not shown) or support surfaces located in the cell frame and the cell frame are provided with coverings intended. In this case, the fixing devices that are in the element flange frame are lined internally with a plastic, for example PE, PP, PVC, PFA, FEP, E / TFE, PVIF or PTFE, while the support surfaces in the cell frame they are also coated with one of these plastics. The plastic can thus only be superposed or driven through a slot, adhered, welded or screwed. It is essential only that the plastic support be fixed. With two plastic surfaces in contact, the particular elements found in the frame are so easily movable that they can be straightened in parallel by hand without an additional lifting or pushing device. When closing the tension device, the elements are supported laminarly because of their easy mobility in the cell frame on the entire rear wall, which is a requirement for a uniform current distribution. In addition, the cell is electrically isolated in this manner with respect to the cell frame.Naturally, the invention is not limited to the embodiments shown in the drawings. Other configurations are possible, without abandoning the fundamental idea. Thus, the respective electrode 8, 9 can be installed in a suitably oblique manner to the respective cell 2, around the inclination of the lattice-like grooves 8B, 9B or of the electrode rods 8A, 9B of both electrodes 8, 9 with with respect to the horizontal, as represented. Alternatively, it can also be provided, however, that the electrolysis cell be disposed obliquely, in such a way that the lower part of the respective half housing shell is arranged inclined with respect to the horizontal, so that necessarily also the grooves in the form of lattice 8A, 9B are arranged inclined and the effect described with respect to Figures 2 and 3 is incorporated.

Claims (4)

NOVELTY OF THE INVENTION CLAIMS

1. - Electrolysis apparatus for producing halogen gases from an aqueous solution of alkaline halogen with several electrolysis cells in the form of plates arranged in stack next to one another and which are in electrical contact, which respectively have a housing of two means shields of electrically conductive material with external contact strips at least on a rear wall of the housing, the housing having devices for feeding the electrolysis stream and the electrolysis starting materials and devices for discharging the electrolysis stream and the electrolysis products and respectively two essentially flat electrodes (anode and cathode), the anode and the cathode being provided with lattice-shaped grooves for a continuous flow of the starting materials and the electrolysis products and separated from one another by a dividing wall and arranged parallel to each other and being connected in a conductively electrical manner with the respectively disposed wall of the housing by means of metallic reinforcements, characterized in that the lattice-like grooves (8B, 9B) of the anode (8) and the cathode (9) are arranged inclined with respect to the horizontal.

2. - Electrolysis apparatus according to claim 1, further characterized in that the inclination angle of the lattice-shaped grooves (8B, 9B) is between and 10 ° with respect to the horizontal.

3. Apparatus for electrolysis according to claim 1 or 2, further characterized in that the lower part of the respective housing (3, 4) is arranged parallel to the horizontal and the lattice-shaped grooves (8B, 9B) of the anode ( 8) and the cathode (9) are arranged inclined with respect to the horizontal.

4. Electrolysis apparatus according to claim 1 or 2, further characterized in that the lower part of the respective housing (3, 4) is arranged inclined with respect to the horizontal.