CA2062739A1 - Electrolysis cell for gas-producing electrolytic processes - Google Patents
Electrolysis cell for gas-producing electrolytic processesInfo
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- CA2062739A1 CA2062739A1 CA002062739A CA2062739A CA2062739A1 CA 2062739 A1 CA2062739 A1 CA 2062739A1 CA 002062739 A CA002062739 A CA 002062739A CA 2062739 A CA2062739 A CA 2062739A CA 2062739 A1 CA2062739 A1 CA 2062739A1
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- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
- C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
- C25B11/02—Electrodes; Manufacture thereof not otherwise provided for characterised by shape or form
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
- C25B9/00—Cells or assemblies of cells; Constructional parts of cells; Assemblies of constructional parts, e.g. electrode-diaphragm assemblies; Process-related cell features
- C25B9/17—Cells comprising dimensionally-stable non-movable electrodes; Assemblies of constructional parts thereof
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Electrolytic Production Of Non-Metals, Compounds, Apparatuses Therefor (AREA)
- Electrodes For Compound Or Non-Metal Manufacture (AREA)
- Electrolytic Production Of Metals (AREA)
- Electroluminescent Light Sources (AREA)
- Medicines Containing Material From Animals Or Micro-Organisms (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
An electrolysis cell for electrolytic processes that generate gas bubbles comprises at least one electrode with parallel electrode elements. The electrode elements are of a thickness that is up to three times the average bubble separation diameter and include a capillary gap that causes the gas bubbles to move through the electrode essentially in line with the direction of the electrical field between the reaction surfaces of the anode and the cathode.
An electrolysis cell for electrolytic processes that generate gas bubbles comprises at least one electrode with parallel electrode elements. The electrode elements are of a thickness that is up to three times the average bubble separation diameter and include a capillary gap that causes the gas bubbles to move through the electrode essentially in line with the direction of the electrical field between the reaction surfaces of the anode and the cathode.
Description
~2~3~
The present invention relates to an electrolysis cell for electrolytic processes that produce gas, in particular for water and chlor-alkali electrolysis, using at least one electrode with parallel electrode elements that form the anode and the cathode.
Electrolytic processes that produce gas are extremely important for the production of different and important basic chemical materials such as caustic soda, chlorine, hydrogen, or hydrogen peroxide. The electrodes that are used during the electrolysis of alkaline solutions, water, hydrochloric acid or sulfuric acid, which includes both anodes and cathodes, must meet a number of service parameters that are in part contradictory. A very important demand is for the rapid removal of the gases that are developed from the space between the anodes and the cathodes in order to avoid a large build up of gas, which increases the electrical resistance of the electrolyte. This, however, is contrary to efforts to make maximally effective use of the structural surfaces that are available for an electrochemically effective electrode surface.
Furthermore, attempts are being made to arrive at the most even and finely structured electrode surface that is possible, in order to provide the conditions for an homogeneous electrical field. Discontinuities such as, for example, edges, lead to increases in the field strength and thus to uneven loading of the electrodes, which causes not only energy losses, but also premature wear of the electrode material or the electro-catalytic coating.
Membranes or diaphragms are used to separate the gases that form on the electrodes. These separator elements are of relatively high ohmic resistance so that gas separation is achieved at the cost of high energy consumption.
The present invention relates to an electrolysis cell for electrolytic processes that produce gas, in particular for water and chlor-alkali electrolysis, using at least one electrode with parallel electrode elements that form the anode and the cathode.
Electrolytic processes that produce gas are extremely important for the production of different and important basic chemical materials such as caustic soda, chlorine, hydrogen, or hydrogen peroxide. The electrodes that are used during the electrolysis of alkaline solutions, water, hydrochloric acid or sulfuric acid, which includes both anodes and cathodes, must meet a number of service parameters that are in part contradictory. A very important demand is for the rapid removal of the gases that are developed from the space between the anodes and the cathodes in order to avoid a large build up of gas, which increases the electrical resistance of the electrolyte. This, however, is contrary to efforts to make maximally effective use of the structural surfaces that are available for an electrochemically effective electrode surface.
Furthermore, attempts are being made to arrive at the most even and finely structured electrode surface that is possible, in order to provide the conditions for an homogeneous electrical field. Discontinuities such as, for example, edges, lead to increases in the field strength and thus to uneven loading of the electrodes, which causes not only energy losses, but also premature wear of the electrode material or the electro-catalytic coating.
Membranes or diaphragms are used to separate the gases that form on the electrodes. These separator elements are of relatively high ohmic resistance so that gas separation is achieved at the cost of high energy consumption.
2 ~ ~ 2 7 ~, ~
An even and small distance between the electrodes is also important for ensuring an optimal process without imposing excessive mechanical stress when these membranes are used, or even damaging them. It should also be ensured that electrode elements that are of greater thickness do not exert a high levsl of contact pressure on the membrane and thus hinder the flow of electrolyte or the ion transport through the pore system of the membrane.
Two important basic types of gas-generating metal electrodes are known: first, one uses parallel profile rods that are supported by current distributors, these being of circular, tear-drop, or rectangular cross section (DE-OS
3008 116, DE-OS 3325 187, DE-PS 3519 272, DE-OS 3519 573).
However, U-shaped rails that are arranged in spaced rows, as described in DE-AS 1271 093, are also known. On the other hand, perforated sheets with vertical and horizontal slits with segments that are angled with reference to the plane of the electrode, or deep drawn, perforated sheet metal electrodes, and metal mesh electrodes are also known (DE-PS
250 026, DE-OS 3625 506, DE-OS 2735 238).
Representatives of the first-named basic type use electrode elements that are arranged in parallel, and which are rigidly connected to the current distribution rails and are of tear-drop cross section (DE-OS 3325 187) or an almost circular cross section (DE-OS 3008 116). The circular cross sections have been modified by removing segments that lie in the plane of the electrodes. Both electrodes are intended to be used preferably for chlor-alkali electrolysis in amalgam cells. These electrodes display no significantly reduced degree of coverage by gas bubbles. The gases are carried off exclusively by fluid flow and buoyancy. The particular cross section geometries are not suitable for assuming an active role during the movement of gas through the electrodes. It is true that they hinder any overloading 20~27 ?~
of the catalytic coating by avoiding discontinuities, although this is done by accepting the disadvantages that result from the uneven spacing of the electrode surfaces that is caused by their radii.
DE-OS 3519 272 describes an electrode structure that uses a plurality of parallel electrode elements of rectangular cross section. A plate-like carrier with bulges on both sides is used to secure the electrode elements and as a current distributor. The cross section of the rectangular electrode elements have in ratio of 1:5. In order that the trails of gas that is removed do not come into contact with each other in the area of the gap and cause turbulence, there is a relatively large gap between adjacent electrode elements. This leads to a relatively low use of the available structural surface and to irregular loading of the electrodes, in particular in the area of the edges of the rectangular profiles, where increased wear of the catalytic coating can be anticipated. The selected shape of the carrier for the electrode elements, which is simultaneously a current distributor, prevents the concentration of gas in the space on the far side of the reactive electrode surface. As a consequence of this, there is a large amount of gas in the area of the reaction surface, and there are associated increased electrical losses.
The electrode that is described in DE-OS 3519 573 is very similar to the electrode structure described heretofore. This also consists of electrode elements of rectangular cross section that are arranged parallel, and arranged on a current distributor and the spaces between these electrode elements is in the order of a few millimetres. In addition, the face sides of the electrode elements that face the membrane incorporate a plurality of recesses. The bridge pieces located between these are not - . .
2Q~27~9 :
electro-catalytically coated and lie upon the membrane.
Thus, the reactive surface that is available only amounts to approximately 10 per cent of the membrane surface. Because of the relative movement between the electrode and the membrane, the bridge pieces can cause localized damage to the membrane.
- It is an object of the present invention to develop an electrolysis cell for electrolytic processes that generate gas, which has significantly altered performance parameters.
It is intended to provide for greatly reduced ohmic power losses and thus an increase of the specific electrical loading of the electrodes. However, it is also intended that the degree of gas enrichment on the electrode surfaces be greatly reduced, despite the fact that more gas is produced.
In particular, it is intended to achieve the following:
A reduction of the gas-bubble loading of the electrolyte between the electrodes and of the degree of gas-bubble coverage on the reaction surfaces of the electrodes;
The structure of the electrodes is intended to ensure an appropriately directed movement of the gas during the process;
Improvement of the ratio of active electrode surface to the structural surface;
- A reduction of local increases in f eld strength and the formation of an almost homogeneous electrical field in order to even out the loading of the electrode surfaces that are available for the reaction;
The new electrolysis cell is to have gas-separating characteristics, which will render the use of gas separating means (membranes, diaphragms, or the like) unnecessary. When this is done, the spacing between the electrodes is not to be increased.
According to the present invention, the electrode elements are of a thickness that is up to three times the average bubble separation diameter and forms a capillary gap such that the direction of movement of the gas bubbles through the electrodes lies essentially either in the direction or the reverse direction of the electrical field between the reaction surfaces of the anode and the cathode, and in that the electrode elements incorporate profilings to fix the capillary gap. The present invention is also intended to include electrolysis cells that are built up from electrode structures with quasi-parallel electrode elements that form a capillary gap, such as this applies, for example, to a spiral-wound electrode.
The bubble separation diameter is understood to be the diameter of a bubble that leaves its formative nucleus under the given actual process conditions, on an electrode of the type according to the present invention. The bubbles that move as a consequence of the adhesion on the electrode surface are also to be regarded as bubbles that are leaving their formative nucleus.
As is known, the separation diameters of the gas bubbles depend to a very considerable extent on the type of electrolysis and the conditions of the process. According to Elektrochimika Acta, Vol. 33, No. 6, pp 769 to 779, 1988, the following bubble diameters can be expected under the usual conditions of electrolysis:
- for hydrogen: approximately 8 ~m - for oxygen: approximately 17 ~m - for chlorine: approximately 110 ~m Proceeding from the area between the electrode elements, an electrolysis cell according to claim 1 ensures that the capillary effect of the electrodes also affects the bubbles that are formed on the face surfaces, which are ,, 2 ~ 3 ~
mostly rounded, and this then draws them into the capillary gap if a gap is left between the electrode and the membrane.
It is advantageous that the electrode elements are plates, bands, or foils with a thickness of at most 450 ~m. The width of the electrode elements is significantly greater than their thickness and amounts to at least ten times the width of the capillary gap. This creates a capillary system that is effective in two dimensions in the electrode and this in turn prevents the introduction of turbulence from the degassing chamber of the electrolyte into the reaction space between the electrode and the membrane. Thus any effect on or disruption of the bubble formation process and the movement of the bubbles into the capillary gap is precluded. The movement of gas through the electrodes is effected directionally, essentially transversely to the plane of the electrodes over the very small distance corresponding to the width of the electrode elements. The cause for this is the considerable relative increase in the volume of the reaction space as a consequence of the bubble formation process. This leads to an increase of pressure at this point and a displacement reaction. Electrolyte flows through the capillary gap without any turbulence to the reactive surfaces of the electrode to the same extent as the gas is forced out of the reaction space and the electrode.
The high level of electrolyte exchange prevents ionic depletion of the electrolyte, even in its boundary layer, for the movement of liquid caused by capillary forces is effected directly on the surface of the electrode. The characteristic flow conditions in the capillary gap prevent any vertical movement of the gas bubbles to a very large extent.
Two versions of the electrodes have been found to be particularly advantageous in order to realize the principle of the electrolysis cell according to the present invention.
Thus, the alternating folding of continuous sheet material ~27~
permits economic production of capillary gap electrodes, this being done, most expediently, after all the necessary work processes such as perforation, profiling, and coating have been completed in a continuous operation. It is expedient that these perforations in the area of the fold edges be evenly distributed. In order to fix the capillary gap, the electrode elements incorporate profiling. Those that have a structure that is web-like, and that is transverse to the plane of the electrode, have also proved satisfactory; button-surface profiles have also been found to be useable. But stacking the electrode elements according to the present invention is also suitable for producing capillary gap electrodes. The profiling that is produced in the original shaping process, or by subsequent shaping, fixes the capillary gap and renders separate spacers unnecessary.
The lower limit of the thickness of the electrode elements is determined only by the mechanical stability and ease of handling of the material, ease with which they can be machined, which ultimately means the type of material.
In order to be able to exploit the advantages of the new type of electrolysis cell to its fullest extent, it is advantageous to seal off the electrode elements that border the electrode at the sides and the lower end of the electrode to the inner wall of the cell housing to form a gap which at most corresponds to the capillary gap. In addition, the degassing spaces in the upper area of the cell are to be hermetically sealed by a bulkhead that reaches to the lowest possible level of the electrolyte within the reaction space. This prevents any mixing of the gases that rise into the degassing spaces of the electrolysis cell. If such a cell construction is used for water electrolysis, which is to say in a process that requires no separation of anolyte and catholyte the use of a gas separation system ~&2~
such as, for example, a diaphragm, may be unnecessary or it may permit the use of a comparatively large-pored element with a negligible ohmic resistance that, optionally, only serves to fix the electrode spacing.
In order to prevent coagulation of the gas bubbles that are formed on the electrode of opposite polarity, a gap that is equal to at least three times the bubble separation diameter is to be left between the electrodes. This feature counteracts any contamination of the gas bubbles that rise into the degassing spaces and the formation of a mixture of gases in the reaction space by coagulation of the gas bubbles.
An advantageous variation of the present invention for use in water electrolysis, which is to say with identical anolyte and catholyte, uses a dielectric distance piece that is resistant to the electrolyte between the anode and the cathode; in particular, this can be in the structure of a net, honeycomb or a coarse fabric. Depending on its thickness, this distance piece guarantees that the anode and ~0 the cathode can be spaced closely together without any danger of short-circuiting. The great flexibility of the electrode structure, which can be subjected to extremely large mechanical loads, ensures electrode spacing that is even on all sides. In addition, the reaction space is divided into numerous small reaction cells by this distance piece. For all practical purposes, no more disruptions caused by flow conditions and no formation of mixed gas can occur.
The advantages of electrodes made up of electrode elements according to the present invention, with a capillary gap arrangement, are as follows:
~ery little gas-bubble loading of the electrolyte within the reaction space because of directional gas bubble 2~2~
movement within the capillary gap electrode;
- Even and finely structured gas and liquid permeable electrode structure at a high packing density;
- Because of the foregoing, even current loading and utilization of the available reaction surface no local erosion of the electrode surface or, in particular, of the electro-catalytic coating;
- Mechanically loadable, nevertheless flexible, electrode structure;
- No great demands with respect to evenness, distortion, and the like.
The invention will now be described in more detail, by way of example only, with reference to the accompanying drawings in which:-Figure 1 is a cross section through an electrolysis cell with a capillary gap electrode according to the present inventlon;
Figure 2 is a perspective and detailed drawing of twocapillary gap electrodes as cathode and anode with an interposed separating element;
Figure 3 is an enlarged section A of figure 2 (scale approximately 10:1);
Figure 4 is an enlarged section A of figure 2 (scale approximately 20:1);
Figure 5 is an electrode coil element in section;
Figure 6 is a cross section through a capillary gap electrode, consisting of a plurality of electrode coil elements;
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Figure 7 is an enlarged perspective view of electrode elements of undulating structure (scale approximately 10:1);
Figure 8 is a part of a capillary gap electrode (scale approximately 10:1) formed from a foil material folded on alternating sides, in an enlarged perspective view;
Figure 9 is a an enlarged section B of the capillary gap electrode shown in figure 8;
Figure 10 is an enlarged perspective view of an electrode element with horizontal bar-like profiling (on one side);
Figure 11 is an enlarged perspective view of an electrode element with essentially horizontal bar-like profiling (on both sides);
Figure 12 is an enlarged perspective view of an electrode element with local profiling that is made up of non-directional, staggered button-like elements;
Figure 13 is a section of an electrode having unprofiled and undulating electrode elements;
Figure 14 is an enlarged perspective view of an electrode element with grooves arranged on both sides;
Figure 15 is an enlarged perspective view of an electrode element with grooves arranged on one side; and Figure 16 is a perspective detailed drawing of two capillary gap electrodes as cathode and anode with an interposed distance piece (scale approximately 1:1).
For reasons of clarity, Figures 2 to 16 show only the 2~2~
electrode elements or the electrodes formed therefrom that are used in an electrolysis cell.
As can be seen from Figures 1 to 8 and Figure 16, the electrode is made up of parallel or quasi-parallel electrode elements 1, la, 28, 29, the thickness 3 of these, and the distance 4 between them, being one to two orders of magnitude less than in known electrodes.
According to the present invention, the thickness 3 of the electrode elements 1, la, lb, lc, ld, 15, 16, 28, 29, 30, 31, which can be bands, foils, or plates, amounts to at most three times the mean bubble separation diameter.
Between the electrode elements 1, la, lb, lc, ld, 15, 16, 28, 29, 30, 31, there is a gap 4 that causes a capillary effect. The electrode elements can be fixed to each other, for example, by a plurality of wires that pass through the electrode elements. Distance pieces that ensure the capillary gap can be arranged on the wires between the electrodes. The use of profiled electrode elements 1, la, lb, lc, ld, 15, 16, 28, 29, 30, 31 is more advantageous.
These measures permit the simple manufacture of a capillary gap electrode that is of easily adaptable width, and that is simple to transport and install.
The production of electrode elements from glass-metal foil bands that have been produced by the melt-spinning process is particularly economical. They have smooth surfaces and edges and are of a thickness 3 of 20 ~m to 100 ~m. The preferred range of electrode element thickness lies about 40 ~m; the bands are approximately 5 mm wide. When some 40 electrode elements per centimetre are used, there is an average capillary gap 4 of 200 ~m. An electrode made up of a number of very flexible single elements represents a structure that can withstand high mechanical loads and which is nevertheless completely adaptable to a flat surface and 2 ~ 3? :~
which is in the form of a dense package. No great demands with regard to flatness, distortion, and the like need be imposed on these surfaces.
Figure 2 shows two electrodes 8 with electrode elements 1; of these, one forms the cathode and the other forms the anode, with an interposed separating element 7 such as, for example, a membrane in the so-called null interval. The electrode structure permits a constant and small electrode interval over a large area and this corresponds to the thickness of the separating element 7. The adaptability of the electrodes 8 also ensures an even distribution of pressure across the separating element 7. This does not restrict the ion flow or the flow of electrolyte, and it also prevents the separating element 7 from becoming damaged. The spaces that are adjacent to the electrode surfaces that are remote from the separating element 7 serve as degassing spaces for the electrolyte.
Figures 3 and 4 show, at larger scale, the detail A of the electrode 8 in figure 1. The electrode elements 1 that are used have a thickness 3 of approximately 30 ~m and a width 5 of approximately 5 mm. The capillary gap 4 between the electrode elements 1 is approximately 200 ~m.
The surfaces 2 of the electrode elements 1 (see figure 4) represent the areas of high electrolytic reactivity. Their mass-area conversion corresponds approximately to that on the face surfaces of the electrode elements 1. These surfaces 2, which are highly reactive and which play a significant part in the conversion, extend transversely to the plane of the electrodes at a depth that corresponds approximately to the width of the gap 4. For purposes of improved clarity, the width of the gap 4 has been increased three-fold in comparison to the thickness and width of the electrode elements 1.
2~7~
Figure 5 shows another variation of an electrode structure with a capillary gap, which acts in the same way.
Because of the spiral winding of one pair of electrode elements, consisting of a smooth electrode element 29 and an undulating electrode element 28, this is a quasi-parallel electrode structure. The desired capillary gap can also be fixed by electrode elements that are profiled in a different manner; this will be discussed below.
Figure 6 shows an electrode section that consists of a plurality of electrode coil elements 53. This electrode is enclosed by a current feed 51. The electrode coil elements 53 are supported by a current distributor 52. Any structure that ensures sufficient electrical conductivity and which can be mechanically loaded can be used as a current distributor 52. In the simplest case, one can use a perforated metal plate.
Figure 7 shows electrode elements la that are of undulating structure. The axes 18 of their profiling are inclined relative to the horizontal. By folding a foil 19 that is profiled in this way on alternate sides on its fold axes 20 that lie on the vertical axis 17, the profiling on adjacent electrode elements 15, 16 lie one on top of the other in point contact. The perforations 21 that are arranged along the fold axes 20 are of a width 22 that is oriented to the width of the capillary gap 4 to the degree of deformation of the foil 19.
Figures 8 and 9 show details of such an electrode. The foil that is used has a thickness 3 of approximately 25 ~m;
the electrode elements la that are produced by the alternate-sided folding of the profiled foil 19 have a width 5 of approximately 5 mm and fix the width of the gap 4 at approximately 200 ~m. The surfaces 2 of the elements la once again represent areas of a high level of electrolytic ~3~ 2 ~ ? ~
activity. Electrodes that are produced by perforation, profiling, and folding, are rational to produce, easily manipulated, and are of a very even and fine structure.
Whereas the electrode element lb that is shown in figure 10 has horizontal ridge-like profiling 23 on only one side, on the electrode element lc shown in figure 11 there are ridge-like profilings 24', 24'' on both sides. The profiling 24', with the axis 26, on one side, are not parallel to the profilings 24'', with axis 27, on the other side of the same electrode element lc. Thus, it is possible to double the capillary gap between adjacent electrode elements lc. When electrode elements lc as in figure 11 are stacked, the profiles 24', 24'' that cross over each other are in point contact. However, an alternating arrangement of electrode elements lc with profiling on both sides with smooth, non-profiled electrode elements is also possible.
Figure 12 shows non-directional button-like profiling 25 on one side of the electrode element ld. However, it is also possible to provide profiling 25 on both sides of the electrode element ld. Profilings 23, 24', 24'', 25 shown in figures 10 to 12 can be made by stamping tools. The production of the electrode elements lb, lc, ld by the melt-spin process to form glass-metal foil bands is particularly economical. These are mostly of a thickness 3 of 20 ~m to 100 ~m and can be produced in the desired width. The surfaces of the rollers are suitably prepared in order to generate the profiles 23, 24, 24'', 25.
Figure 13 shows the cross section of part of an electrode that consists of a package with alternating profiled and non-profiled electrode elements 28, 29. The profilings of the electrode elements 28 are of an undulating structure, which gives rise to a constantly varying capillary gap. The half gap 34 between two adjacent non-2~27~
profiled electrode elements 29 can be regarded as the mean capillary gap width. Because of the spring effect of the undulating electrode elements 28, the use of this package permits a very simple variation of the width of the capillary gap 4, for electrodes can be produced for different electrolytic processes by using one and the same profiling.
Figures 14 and 15 show electrode elements 30, 31 with creased profiling 32 on both or one side, respectively, the axes 36 of these extending orthogonally to the longitudinal axis 35 of the electrode elements 30, 31. The electrode element 30 can be used in this form with non-profiled electrode elements 1, 29. A combination of these electrode elements 30 with the axes 36 of the creased profilings 32 that are inclined relative to the horizontal results in electrode structures that are very similar to those shown in figures 7 and 8.
The advantages of the electrode elements lie in the fact that these can be combined to form dense, fine, and evenly structured packages without separate distance pieces.
The capillary gap between adjacent electrode elements, fixed by their profilings, ensures a directional movement of the gas and an intensive electrolyte exchange.
Figure 16 shows two electrodes 8, of which one serves as the anode, and the other as a cathode, with an interposed coarse mesh distance element 14. The electrode structure permits a constant and small electrode interval across a large surface, this corresponding to the thickness of the distance element 14. In addition, the adaptability of this electrode structure ensures that any damage to the distance element 14 is prevented. The electrodes 8 consist of electrode elements 1. The bulkhead 13 separates the gases in the upper area of the cell housing 40.
2~2~
Figure 1 shows the construction of an electrolysis cell. It incorporates electrodes 8 that are formed from the electrode elements according to the present invention. In order to provide for a clearer representation of the gas-bubble distribution, the path of the gas bubbles has beensimplified in the form of the beaded lines 41 and the electrolysis cell has a relatively large electrode interval as well as wide degassing spaces 10, 11. One of the important requirements for the functioning of the electrolysis cell according to the present invention are the electrodes 8 that are formed from the electrode elements according to the present invention.
The following are indicated by the arrows in figure 1:
- the electrolyte feed 37;
- removal of the gas 38;
- the removal of the mixed gas 39.
The connections between the reaction space 9 and the degassing spaces 10, 11 are at most of the size of a capillary gap; complete sealing between these spaces is better so that no interference caused by the flow can result from the movement of the electrolyte between the electrodes 8 and the cell housing 40, for such interference would possibly lead to the separation of gas bubbles 6 from the electrode reaction surface into the reaction space 9.
This provides a cell structure that divides the electrolysis cell hydraulically into a common reaction space 9, and separate degassing spaces 9, 10.
The purity of the gases that are generated depends substantially on the quality of the electrodes. The distance between the electrodes can also have an effect on the purity of the gases. In order to prevent any coagulation of the gas bubbles, a distance that is at least 2~27i~
three times the bubble separation diameter must be left between the electrodes 8. Coagulation of the gas bubbles leads to the formation of mixed gas in the reaction space 9.
Thus, every effort must be made to achieve the smallest possible distance between the electrodes since this reduces ohmic resistance. Electrolytic exchange between the degassing spaces 10, 11 and the reaction space 9 is more intensive the smaller (narrower) the reaction space 9 (electrode interval).
Gas bubbles 6 which leave the electrodes 8 and migrate into the reaction space 9 lead to the above-discussed insignificant formation of mixed gas. These bubbles cannot cause contamination of the pure gas, because, before reaching the opposite electrode, they would coagulate with the bubbles that are formed there. Their bubble diameter would then be too great for movement through the capillary gap 4 of the electrode 8 or in the sealed area of the housing wall. The separation of pure gases in the upper cell area is effected by one or more bulkheads 12 that extend below the level of the liquid.
Optimal functioning of the electrode 8 is then ensured if its structure is fine and even. Such properties are best achieved by tightly packed and evenly profiled electrode elements 1, la, lb, lc, ld, 28, 29, 30, 31.
An electrolysis cell that is fitted with an electrode made up of electrode elements according to the present invention functions as follows:
The large number of electrode elements 1, la, lb, lc, ld, 28, 29, 30, 31 of the electrode 8 (approximately 40 to 50 electrode elements pex centimetre) represents a high level of smoothing of the electrode surface. Connected with :
.
~ ~ ~ 2 7 ~ ~
this is an adequate smoothing of the electrical field and of the current density loading. Consequently, overloading and thus premature wear of the electro-catalytic coating is prevented. Furthermore, it has been made possible to increase the surface involved in the reaction by a value greater than the design surface. Under favourable conditions, the ratio of active reaction surface to construction surface can lie at a value of approximately 2.
The gas bubbles that are formed on the face surfaces and on the reactive surfaces 2 of the electrode elements 1, la, lb, lc, ld, 28, 29, 30, 31 are located in the sphere of influence of the capillary gap 4. Because of the gas bubble formation there is a pressure build-up in the reaction space 9, which is the reason for movement of the gas transverse to the plane of the electrode. Figure 4 shows the path of a gas bubble 6 through the capillary gap 4 between the electrode elements 1. To the same extent, the electrolyte is exchanged between the degassing space 10, 11 and the reaction space 9. For all practical purposes, there are no free-moving gas bubbles in the electrolyte of the reaction space 9. Because of the action of the capillary effect, they are moved onto the electrode surface and "drawn" into the capillary gap 4. This results in a significant reduction of the electrical resistance of the electrolyte.
It should also be pointed out that the width 5 of the electrode elements 1 can be adapted to the requirements with reference to the smallest possible ohmic voltage drop in the electrode material. The same applies to the dimensions of the capillary gap 4 in order to achieve undisturbed hydraulic conditions within the reaction space of the electrolysis cell.
-- 1~ --
An even and small distance between the electrodes is also important for ensuring an optimal process without imposing excessive mechanical stress when these membranes are used, or even damaging them. It should also be ensured that electrode elements that are of greater thickness do not exert a high levsl of contact pressure on the membrane and thus hinder the flow of electrolyte or the ion transport through the pore system of the membrane.
Two important basic types of gas-generating metal electrodes are known: first, one uses parallel profile rods that are supported by current distributors, these being of circular, tear-drop, or rectangular cross section (DE-OS
3008 116, DE-OS 3325 187, DE-PS 3519 272, DE-OS 3519 573).
However, U-shaped rails that are arranged in spaced rows, as described in DE-AS 1271 093, are also known. On the other hand, perforated sheets with vertical and horizontal slits with segments that are angled with reference to the plane of the electrode, or deep drawn, perforated sheet metal electrodes, and metal mesh electrodes are also known (DE-PS
250 026, DE-OS 3625 506, DE-OS 2735 238).
Representatives of the first-named basic type use electrode elements that are arranged in parallel, and which are rigidly connected to the current distribution rails and are of tear-drop cross section (DE-OS 3325 187) or an almost circular cross section (DE-OS 3008 116). The circular cross sections have been modified by removing segments that lie in the plane of the electrodes. Both electrodes are intended to be used preferably for chlor-alkali electrolysis in amalgam cells. These electrodes display no significantly reduced degree of coverage by gas bubbles. The gases are carried off exclusively by fluid flow and buoyancy. The particular cross section geometries are not suitable for assuming an active role during the movement of gas through the electrodes. It is true that they hinder any overloading 20~27 ?~
of the catalytic coating by avoiding discontinuities, although this is done by accepting the disadvantages that result from the uneven spacing of the electrode surfaces that is caused by their radii.
DE-OS 3519 272 describes an electrode structure that uses a plurality of parallel electrode elements of rectangular cross section. A plate-like carrier with bulges on both sides is used to secure the electrode elements and as a current distributor. The cross section of the rectangular electrode elements have in ratio of 1:5. In order that the trails of gas that is removed do not come into contact with each other in the area of the gap and cause turbulence, there is a relatively large gap between adjacent electrode elements. This leads to a relatively low use of the available structural surface and to irregular loading of the electrodes, in particular in the area of the edges of the rectangular profiles, where increased wear of the catalytic coating can be anticipated. The selected shape of the carrier for the electrode elements, which is simultaneously a current distributor, prevents the concentration of gas in the space on the far side of the reactive electrode surface. As a consequence of this, there is a large amount of gas in the area of the reaction surface, and there are associated increased electrical losses.
The electrode that is described in DE-OS 3519 573 is very similar to the electrode structure described heretofore. This also consists of electrode elements of rectangular cross section that are arranged parallel, and arranged on a current distributor and the spaces between these electrode elements is in the order of a few millimetres. In addition, the face sides of the electrode elements that face the membrane incorporate a plurality of recesses. The bridge pieces located between these are not - . .
2Q~27~9 :
electro-catalytically coated and lie upon the membrane.
Thus, the reactive surface that is available only amounts to approximately 10 per cent of the membrane surface. Because of the relative movement between the electrode and the membrane, the bridge pieces can cause localized damage to the membrane.
- It is an object of the present invention to develop an electrolysis cell for electrolytic processes that generate gas, which has significantly altered performance parameters.
It is intended to provide for greatly reduced ohmic power losses and thus an increase of the specific electrical loading of the electrodes. However, it is also intended that the degree of gas enrichment on the electrode surfaces be greatly reduced, despite the fact that more gas is produced.
In particular, it is intended to achieve the following:
A reduction of the gas-bubble loading of the electrolyte between the electrodes and of the degree of gas-bubble coverage on the reaction surfaces of the electrodes;
The structure of the electrodes is intended to ensure an appropriately directed movement of the gas during the process;
Improvement of the ratio of active electrode surface to the structural surface;
- A reduction of local increases in f eld strength and the formation of an almost homogeneous electrical field in order to even out the loading of the electrode surfaces that are available for the reaction;
The new electrolysis cell is to have gas-separating characteristics, which will render the use of gas separating means (membranes, diaphragms, or the like) unnecessary. When this is done, the spacing between the electrodes is not to be increased.
According to the present invention, the electrode elements are of a thickness that is up to three times the average bubble separation diameter and forms a capillary gap such that the direction of movement of the gas bubbles through the electrodes lies essentially either in the direction or the reverse direction of the electrical field between the reaction surfaces of the anode and the cathode, and in that the electrode elements incorporate profilings to fix the capillary gap. The present invention is also intended to include electrolysis cells that are built up from electrode structures with quasi-parallel electrode elements that form a capillary gap, such as this applies, for example, to a spiral-wound electrode.
The bubble separation diameter is understood to be the diameter of a bubble that leaves its formative nucleus under the given actual process conditions, on an electrode of the type according to the present invention. The bubbles that move as a consequence of the adhesion on the electrode surface are also to be regarded as bubbles that are leaving their formative nucleus.
As is known, the separation diameters of the gas bubbles depend to a very considerable extent on the type of electrolysis and the conditions of the process. According to Elektrochimika Acta, Vol. 33, No. 6, pp 769 to 779, 1988, the following bubble diameters can be expected under the usual conditions of electrolysis:
- for hydrogen: approximately 8 ~m - for oxygen: approximately 17 ~m - for chlorine: approximately 110 ~m Proceeding from the area between the electrode elements, an electrolysis cell according to claim 1 ensures that the capillary effect of the electrodes also affects the bubbles that are formed on the face surfaces, which are ,, 2 ~ 3 ~
mostly rounded, and this then draws them into the capillary gap if a gap is left between the electrode and the membrane.
It is advantageous that the electrode elements are plates, bands, or foils with a thickness of at most 450 ~m. The width of the electrode elements is significantly greater than their thickness and amounts to at least ten times the width of the capillary gap. This creates a capillary system that is effective in two dimensions in the electrode and this in turn prevents the introduction of turbulence from the degassing chamber of the electrolyte into the reaction space between the electrode and the membrane. Thus any effect on or disruption of the bubble formation process and the movement of the bubbles into the capillary gap is precluded. The movement of gas through the electrodes is effected directionally, essentially transversely to the plane of the electrodes over the very small distance corresponding to the width of the electrode elements. The cause for this is the considerable relative increase in the volume of the reaction space as a consequence of the bubble formation process. This leads to an increase of pressure at this point and a displacement reaction. Electrolyte flows through the capillary gap without any turbulence to the reactive surfaces of the electrode to the same extent as the gas is forced out of the reaction space and the electrode.
The high level of electrolyte exchange prevents ionic depletion of the electrolyte, even in its boundary layer, for the movement of liquid caused by capillary forces is effected directly on the surface of the electrode. The characteristic flow conditions in the capillary gap prevent any vertical movement of the gas bubbles to a very large extent.
Two versions of the electrodes have been found to be particularly advantageous in order to realize the principle of the electrolysis cell according to the present invention.
Thus, the alternating folding of continuous sheet material ~27~
permits economic production of capillary gap electrodes, this being done, most expediently, after all the necessary work processes such as perforation, profiling, and coating have been completed in a continuous operation. It is expedient that these perforations in the area of the fold edges be evenly distributed. In order to fix the capillary gap, the electrode elements incorporate profiling. Those that have a structure that is web-like, and that is transverse to the plane of the electrode, have also proved satisfactory; button-surface profiles have also been found to be useable. But stacking the electrode elements according to the present invention is also suitable for producing capillary gap electrodes. The profiling that is produced in the original shaping process, or by subsequent shaping, fixes the capillary gap and renders separate spacers unnecessary.
The lower limit of the thickness of the electrode elements is determined only by the mechanical stability and ease of handling of the material, ease with which they can be machined, which ultimately means the type of material.
In order to be able to exploit the advantages of the new type of electrolysis cell to its fullest extent, it is advantageous to seal off the electrode elements that border the electrode at the sides and the lower end of the electrode to the inner wall of the cell housing to form a gap which at most corresponds to the capillary gap. In addition, the degassing spaces in the upper area of the cell are to be hermetically sealed by a bulkhead that reaches to the lowest possible level of the electrolyte within the reaction space. This prevents any mixing of the gases that rise into the degassing spaces of the electrolysis cell. If such a cell construction is used for water electrolysis, which is to say in a process that requires no separation of anolyte and catholyte the use of a gas separation system ~&2~
such as, for example, a diaphragm, may be unnecessary or it may permit the use of a comparatively large-pored element with a negligible ohmic resistance that, optionally, only serves to fix the electrode spacing.
In order to prevent coagulation of the gas bubbles that are formed on the electrode of opposite polarity, a gap that is equal to at least three times the bubble separation diameter is to be left between the electrodes. This feature counteracts any contamination of the gas bubbles that rise into the degassing spaces and the formation of a mixture of gases in the reaction space by coagulation of the gas bubbles.
An advantageous variation of the present invention for use in water electrolysis, which is to say with identical anolyte and catholyte, uses a dielectric distance piece that is resistant to the electrolyte between the anode and the cathode; in particular, this can be in the structure of a net, honeycomb or a coarse fabric. Depending on its thickness, this distance piece guarantees that the anode and ~0 the cathode can be spaced closely together without any danger of short-circuiting. The great flexibility of the electrode structure, which can be subjected to extremely large mechanical loads, ensures electrode spacing that is even on all sides. In addition, the reaction space is divided into numerous small reaction cells by this distance piece. For all practical purposes, no more disruptions caused by flow conditions and no formation of mixed gas can occur.
The advantages of electrodes made up of electrode elements according to the present invention, with a capillary gap arrangement, are as follows:
~ery little gas-bubble loading of the electrolyte within the reaction space because of directional gas bubble 2~2~
movement within the capillary gap electrode;
- Even and finely structured gas and liquid permeable electrode structure at a high packing density;
- Because of the foregoing, even current loading and utilization of the available reaction surface no local erosion of the electrode surface or, in particular, of the electro-catalytic coating;
- Mechanically loadable, nevertheless flexible, electrode structure;
- No great demands with respect to evenness, distortion, and the like.
The invention will now be described in more detail, by way of example only, with reference to the accompanying drawings in which:-Figure 1 is a cross section through an electrolysis cell with a capillary gap electrode according to the present inventlon;
Figure 2 is a perspective and detailed drawing of twocapillary gap electrodes as cathode and anode with an interposed separating element;
Figure 3 is an enlarged section A of figure 2 (scale approximately 10:1);
Figure 4 is an enlarged section A of figure 2 (scale approximately 20:1);
Figure 5 is an electrode coil element in section;
Figure 6 is a cross section through a capillary gap electrode, consisting of a plurality of electrode coil elements;
~Q~7~'~
Figure 7 is an enlarged perspective view of electrode elements of undulating structure (scale approximately 10:1);
Figure 8 is a part of a capillary gap electrode (scale approximately 10:1) formed from a foil material folded on alternating sides, in an enlarged perspective view;
Figure 9 is a an enlarged section B of the capillary gap electrode shown in figure 8;
Figure 10 is an enlarged perspective view of an electrode element with horizontal bar-like profiling (on one side);
Figure 11 is an enlarged perspective view of an electrode element with essentially horizontal bar-like profiling (on both sides);
Figure 12 is an enlarged perspective view of an electrode element with local profiling that is made up of non-directional, staggered button-like elements;
Figure 13 is a section of an electrode having unprofiled and undulating electrode elements;
Figure 14 is an enlarged perspective view of an electrode element with grooves arranged on both sides;
Figure 15 is an enlarged perspective view of an electrode element with grooves arranged on one side; and Figure 16 is a perspective detailed drawing of two capillary gap electrodes as cathode and anode with an interposed distance piece (scale approximately 1:1).
For reasons of clarity, Figures 2 to 16 show only the 2~2~
electrode elements or the electrodes formed therefrom that are used in an electrolysis cell.
As can be seen from Figures 1 to 8 and Figure 16, the electrode is made up of parallel or quasi-parallel electrode elements 1, la, 28, 29, the thickness 3 of these, and the distance 4 between them, being one to two orders of magnitude less than in known electrodes.
According to the present invention, the thickness 3 of the electrode elements 1, la, lb, lc, ld, 15, 16, 28, 29, 30, 31, which can be bands, foils, or plates, amounts to at most three times the mean bubble separation diameter.
Between the electrode elements 1, la, lb, lc, ld, 15, 16, 28, 29, 30, 31, there is a gap 4 that causes a capillary effect. The electrode elements can be fixed to each other, for example, by a plurality of wires that pass through the electrode elements. Distance pieces that ensure the capillary gap can be arranged on the wires between the electrodes. The use of profiled electrode elements 1, la, lb, lc, ld, 15, 16, 28, 29, 30, 31 is more advantageous.
These measures permit the simple manufacture of a capillary gap electrode that is of easily adaptable width, and that is simple to transport and install.
The production of electrode elements from glass-metal foil bands that have been produced by the melt-spinning process is particularly economical. They have smooth surfaces and edges and are of a thickness 3 of 20 ~m to 100 ~m. The preferred range of electrode element thickness lies about 40 ~m; the bands are approximately 5 mm wide. When some 40 electrode elements per centimetre are used, there is an average capillary gap 4 of 200 ~m. An electrode made up of a number of very flexible single elements represents a structure that can withstand high mechanical loads and which is nevertheless completely adaptable to a flat surface and 2 ~ 3? :~
which is in the form of a dense package. No great demands with regard to flatness, distortion, and the like need be imposed on these surfaces.
Figure 2 shows two electrodes 8 with electrode elements 1; of these, one forms the cathode and the other forms the anode, with an interposed separating element 7 such as, for example, a membrane in the so-called null interval. The electrode structure permits a constant and small electrode interval over a large area and this corresponds to the thickness of the separating element 7. The adaptability of the electrodes 8 also ensures an even distribution of pressure across the separating element 7. This does not restrict the ion flow or the flow of electrolyte, and it also prevents the separating element 7 from becoming damaged. The spaces that are adjacent to the electrode surfaces that are remote from the separating element 7 serve as degassing spaces for the electrolyte.
Figures 3 and 4 show, at larger scale, the detail A of the electrode 8 in figure 1. The electrode elements 1 that are used have a thickness 3 of approximately 30 ~m and a width 5 of approximately 5 mm. The capillary gap 4 between the electrode elements 1 is approximately 200 ~m.
The surfaces 2 of the electrode elements 1 (see figure 4) represent the areas of high electrolytic reactivity. Their mass-area conversion corresponds approximately to that on the face surfaces of the electrode elements 1. These surfaces 2, which are highly reactive and which play a significant part in the conversion, extend transversely to the plane of the electrodes at a depth that corresponds approximately to the width of the gap 4. For purposes of improved clarity, the width of the gap 4 has been increased three-fold in comparison to the thickness and width of the electrode elements 1.
2~7~
Figure 5 shows another variation of an electrode structure with a capillary gap, which acts in the same way.
Because of the spiral winding of one pair of electrode elements, consisting of a smooth electrode element 29 and an undulating electrode element 28, this is a quasi-parallel electrode structure. The desired capillary gap can also be fixed by electrode elements that are profiled in a different manner; this will be discussed below.
Figure 6 shows an electrode section that consists of a plurality of electrode coil elements 53. This electrode is enclosed by a current feed 51. The electrode coil elements 53 are supported by a current distributor 52. Any structure that ensures sufficient electrical conductivity and which can be mechanically loaded can be used as a current distributor 52. In the simplest case, one can use a perforated metal plate.
Figure 7 shows electrode elements la that are of undulating structure. The axes 18 of their profiling are inclined relative to the horizontal. By folding a foil 19 that is profiled in this way on alternate sides on its fold axes 20 that lie on the vertical axis 17, the profiling on adjacent electrode elements 15, 16 lie one on top of the other in point contact. The perforations 21 that are arranged along the fold axes 20 are of a width 22 that is oriented to the width of the capillary gap 4 to the degree of deformation of the foil 19.
Figures 8 and 9 show details of such an electrode. The foil that is used has a thickness 3 of approximately 25 ~m;
the electrode elements la that are produced by the alternate-sided folding of the profiled foil 19 have a width 5 of approximately 5 mm and fix the width of the gap 4 at approximately 200 ~m. The surfaces 2 of the elements la once again represent areas of a high level of electrolytic ~3~ 2 ~ ? ~
activity. Electrodes that are produced by perforation, profiling, and folding, are rational to produce, easily manipulated, and are of a very even and fine structure.
Whereas the electrode element lb that is shown in figure 10 has horizontal ridge-like profiling 23 on only one side, on the electrode element lc shown in figure 11 there are ridge-like profilings 24', 24'' on both sides. The profiling 24', with the axis 26, on one side, are not parallel to the profilings 24'', with axis 27, on the other side of the same electrode element lc. Thus, it is possible to double the capillary gap between adjacent electrode elements lc. When electrode elements lc as in figure 11 are stacked, the profiles 24', 24'' that cross over each other are in point contact. However, an alternating arrangement of electrode elements lc with profiling on both sides with smooth, non-profiled electrode elements is also possible.
Figure 12 shows non-directional button-like profiling 25 on one side of the electrode element ld. However, it is also possible to provide profiling 25 on both sides of the electrode element ld. Profilings 23, 24', 24'', 25 shown in figures 10 to 12 can be made by stamping tools. The production of the electrode elements lb, lc, ld by the melt-spin process to form glass-metal foil bands is particularly economical. These are mostly of a thickness 3 of 20 ~m to 100 ~m and can be produced in the desired width. The surfaces of the rollers are suitably prepared in order to generate the profiles 23, 24, 24'', 25.
Figure 13 shows the cross section of part of an electrode that consists of a package with alternating profiled and non-profiled electrode elements 28, 29. The profilings of the electrode elements 28 are of an undulating structure, which gives rise to a constantly varying capillary gap. The half gap 34 between two adjacent non-2~27~
profiled electrode elements 29 can be regarded as the mean capillary gap width. Because of the spring effect of the undulating electrode elements 28, the use of this package permits a very simple variation of the width of the capillary gap 4, for electrodes can be produced for different electrolytic processes by using one and the same profiling.
Figures 14 and 15 show electrode elements 30, 31 with creased profiling 32 on both or one side, respectively, the axes 36 of these extending orthogonally to the longitudinal axis 35 of the electrode elements 30, 31. The electrode element 30 can be used in this form with non-profiled electrode elements 1, 29. A combination of these electrode elements 30 with the axes 36 of the creased profilings 32 that are inclined relative to the horizontal results in electrode structures that are very similar to those shown in figures 7 and 8.
The advantages of the electrode elements lie in the fact that these can be combined to form dense, fine, and evenly structured packages without separate distance pieces.
The capillary gap between adjacent electrode elements, fixed by their profilings, ensures a directional movement of the gas and an intensive electrolyte exchange.
Figure 16 shows two electrodes 8, of which one serves as the anode, and the other as a cathode, with an interposed coarse mesh distance element 14. The electrode structure permits a constant and small electrode interval across a large surface, this corresponding to the thickness of the distance element 14. In addition, the adaptability of this electrode structure ensures that any damage to the distance element 14 is prevented. The electrodes 8 consist of electrode elements 1. The bulkhead 13 separates the gases in the upper area of the cell housing 40.
2~2~
Figure 1 shows the construction of an electrolysis cell. It incorporates electrodes 8 that are formed from the electrode elements according to the present invention. In order to provide for a clearer representation of the gas-bubble distribution, the path of the gas bubbles has beensimplified in the form of the beaded lines 41 and the electrolysis cell has a relatively large electrode interval as well as wide degassing spaces 10, 11. One of the important requirements for the functioning of the electrolysis cell according to the present invention are the electrodes 8 that are formed from the electrode elements according to the present invention.
The following are indicated by the arrows in figure 1:
- the electrolyte feed 37;
- removal of the gas 38;
- the removal of the mixed gas 39.
The connections between the reaction space 9 and the degassing spaces 10, 11 are at most of the size of a capillary gap; complete sealing between these spaces is better so that no interference caused by the flow can result from the movement of the electrolyte between the electrodes 8 and the cell housing 40, for such interference would possibly lead to the separation of gas bubbles 6 from the electrode reaction surface into the reaction space 9.
This provides a cell structure that divides the electrolysis cell hydraulically into a common reaction space 9, and separate degassing spaces 9, 10.
The purity of the gases that are generated depends substantially on the quality of the electrodes. The distance between the electrodes can also have an effect on the purity of the gases. In order to prevent any coagulation of the gas bubbles, a distance that is at least 2~27i~
three times the bubble separation diameter must be left between the electrodes 8. Coagulation of the gas bubbles leads to the formation of mixed gas in the reaction space 9.
Thus, every effort must be made to achieve the smallest possible distance between the electrodes since this reduces ohmic resistance. Electrolytic exchange between the degassing spaces 10, 11 and the reaction space 9 is more intensive the smaller (narrower) the reaction space 9 (electrode interval).
Gas bubbles 6 which leave the electrodes 8 and migrate into the reaction space 9 lead to the above-discussed insignificant formation of mixed gas. These bubbles cannot cause contamination of the pure gas, because, before reaching the opposite electrode, they would coagulate with the bubbles that are formed there. Their bubble diameter would then be too great for movement through the capillary gap 4 of the electrode 8 or in the sealed area of the housing wall. The separation of pure gases in the upper cell area is effected by one or more bulkheads 12 that extend below the level of the liquid.
Optimal functioning of the electrode 8 is then ensured if its structure is fine and even. Such properties are best achieved by tightly packed and evenly profiled electrode elements 1, la, lb, lc, ld, 28, 29, 30, 31.
An electrolysis cell that is fitted with an electrode made up of electrode elements according to the present invention functions as follows:
The large number of electrode elements 1, la, lb, lc, ld, 28, 29, 30, 31 of the electrode 8 (approximately 40 to 50 electrode elements pex centimetre) represents a high level of smoothing of the electrode surface. Connected with :
.
~ ~ ~ 2 7 ~ ~
this is an adequate smoothing of the electrical field and of the current density loading. Consequently, overloading and thus premature wear of the electro-catalytic coating is prevented. Furthermore, it has been made possible to increase the surface involved in the reaction by a value greater than the design surface. Under favourable conditions, the ratio of active reaction surface to construction surface can lie at a value of approximately 2.
The gas bubbles that are formed on the face surfaces and on the reactive surfaces 2 of the electrode elements 1, la, lb, lc, ld, 28, 29, 30, 31 are located in the sphere of influence of the capillary gap 4. Because of the gas bubble formation there is a pressure build-up in the reaction space 9, which is the reason for movement of the gas transverse to the plane of the electrode. Figure 4 shows the path of a gas bubble 6 through the capillary gap 4 between the electrode elements 1. To the same extent, the electrolyte is exchanged between the degassing space 10, 11 and the reaction space 9. For all practical purposes, there are no free-moving gas bubbles in the electrolyte of the reaction space 9. Because of the action of the capillary effect, they are moved onto the electrode surface and "drawn" into the capillary gap 4. This results in a significant reduction of the electrical resistance of the electrolyte.
It should also be pointed out that the width 5 of the electrode elements 1 can be adapted to the requirements with reference to the smallest possible ohmic voltage drop in the electrode material. The same applies to the dimensions of the capillary gap 4 in order to achieve undisturbed hydraulic conditions within the reaction space of the electrolysis cell.
-- 1~ --
Claims (12)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. An electrolysis cell for electrolytic processes that generate gas bubbles, in particular for water and chlor-alkali electrolysis, comprising at least one electrode, forming the anode or cathode of the cell, comprising electrode elements arranged in parallel, said electrode elements being of a thickness that is up to three times the average bubble separation distance and having a capillary gap therebetween to constrain the direction of movement of the gas bubbles through the electrode to be essentially in line with the direction of the electrical field between the reaction surfaces of the anode and cathode; and profiled protrusions on said electrode elements to defined said capillary gap.
2. An electrolysis cell as claimed in claim 1, wherein the electrode elements are plates, bands or foils with a thickness of at least 450 µm.
3. An electrolysis cell as claimed in claim 1, wherein the width of the electrode elements is at least ten times the width of the capillary gap.
4. An electrolysis cell as claimed in any one of claims 1 to 3, wherein the electrode elements are in the form of a spiral.
5. An electrolysis cell as claimed in any one of the claims 1 to 3, wherein the electrode elements are components of a surface structure that is folded on alternate sides, and which includes perforations in the area of its fold edges.
6. An electrolysis cell as claimed in claim 5, wherein the perforations are evenly distributed.
7. An electrolysis cell as claimed in claim 7, wherein the profilings are raised areas of the material forming the electrode elements.
8. An electrolysis cell as claimed in claim 7, wherein the profilings are in the form of a bar-like structure that is transverse to the plane of the electrode elements.
9. An electrolysis cell as claimed in claim 7, wherein the profilings are in the form of buttons or bumps.
10. An electrolysis cell as claimed in claim 1, wherein the electrode elements at the sides and lower end of the electrode are sealed to an inner wall of the cell to form a gap that corresponds to at least said capillary gap between the electrode elements, and degassing spaces in the upper area of the cell are separated so as to be gas-tight by a bulkhead at least to the surface level of electrolyte in the cell.
11. An electrolysis cell as claimed in claim 11, wherein the distance between the anode and the cathode is fixed by means of one or more dielectric distance elements that are resistant to the electrolyte and which are of a net, honeycomb or textile structure.
12. An electrolysis cell as claimed in any one of claims 1 to 5, wherein the electrode elements are produced from a glass-metal foil strip.
Applications Claiming Priority (10)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DEWPC25B/329905-8 | 1989-06-23 | ||
| DD32990289A DD285122B5 (en) | 1989-06-23 | 1989-06-23 | Electrolysis cell for gas-producing electrolytic processes |
| DEWPC25B/329902/5 | 1989-06-23 | ||
| DEWPC25B/329903/3 | 1989-06-23 | ||
| DEWPC25B/329901/7 | 1989-06-23 | ||
| DD32990589A DD285128B5 (en) | 1989-06-23 | 1989-06-23 | Electrode for gas-developing electrolytic processes |
| DD32990189A DD285125B5 (en) | 1989-06-23 | 1989-06-23 | Electrode for gas-developing electrolytic processes |
| DEWPC25B/329904-4 | 1989-06-23 | ||
| DD32990389A DD285126B5 (en) | 1989-06-23 | 1989-06-23 | Electrode for gas-developing electrolytic processes |
| DD32990489A DD285127B5 (en) | 1989-06-23 | 1989-06-23 | Electrode element of an electrode for gas-developing electrolytic processes |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2062739A1 true CA2062739A1 (en) | 1990-12-24 |
Family
ID=27509744
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002062739A Abandoned CA2062739A1 (en) | 1989-06-23 | 1990-06-20 | Electrolysis cell for gas-producing electrolytic processes |
Country Status (12)
| Country | Link |
|---|---|
| EP (1) | EP0479840B1 (en) |
| AT (1) | ATE127168T1 (en) |
| AU (1) | AU5920190A (en) |
| BR (1) | BR9007455A (en) |
| CA (1) | CA2062739A1 (en) |
| DE (1) | DE59009595D1 (en) |
| DK (1) | DK0479840T3 (en) |
| ES (1) | ES2079476T3 (en) |
| FI (1) | FI915971A0 (en) |
| NO (1) | NO307574B1 (en) |
| RU (1) | RU2073071C1 (en) |
| WO (1) | WO1991000379A1 (en) |
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6336430B2 (en) | 1998-06-29 | 2002-01-08 | Fatpower Inc. | Hydrogen generating apparatus |
| US7240641B2 (en) | 2001-01-19 | 2007-07-10 | Hy-Drive Technologies Ltd. | Hydrogen generating apparatus and components therefor |
| US8282812B2 (en) | 2009-02-24 | 2012-10-09 | John Christopher Burtch | Apparatus for producing hydrogen from salt water by electrolysis |
| US20150200401A1 (en) * | 2012-06-20 | 2015-07-16 | Solvay Sa | Bipolar electrode and method for producing same |
| US10577700B2 (en) | 2012-06-12 | 2020-03-03 | Aquahydrex Pty Ltd | Breathable electrode structure and method for use in water splitting |
| US10637068B2 (en) | 2013-07-31 | 2020-04-28 | Aquahydrex, Inc. | Modular electrochemical cells |
| US11005117B2 (en) | 2019-02-01 | 2021-05-11 | Aquahydrex, Inc. | Electrochemical system with confined electrolyte |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE4119836A1 (en) * | 1991-06-12 | 1992-12-17 | Arnold Gallien | ELECTROLYSIS CELL FOR GAS DEVELOPING OR GAS-CONSUMING ELECTROLYTIC PROCESSES AND METHOD FOR OPERATING THE ELECTROLYSIS CELL |
| DE4120679C2 (en) * | 1991-06-22 | 1995-11-09 | Grimma Masch Anlagen Gmbh | Electrolysis process and electrolysis cell for gas-developing or gas-consuming electrolytic processes |
| DE19540012A1 (en) * | 1995-10-27 | 1997-04-30 | Elwatec Elektrolyse Und Wasser | Plant for the very fine distribution of a gas in a liquid, preferably for the hydrogenation of liquids, and method for operating the plant |
| US5911859A (en) * | 1997-07-15 | 1999-06-15 | Exxon Research And Engineering Co. | Three-dimensional electrode (Law464) |
| RU2530892C2 (en) * | 2012-11-15 | 2014-10-20 | Федеральное государственное бюджетное образовательное учреждение высшего профессионального образования "Кубанский государственный аграрный университет" | Electrolytic cell |
| CN116853411B (en) * | 2023-06-29 | 2023-12-08 | 中国船舶集团有限公司第七一九研究所 | Surface microstructure with drag reduction function and forming method thereof |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB128436A (en) * | 1918-07-17 | 1919-06-26 | Alexander Thomas Stuart | Improvements in and relating to Electrolytic Cells. |
| US4013525A (en) * | 1973-09-24 | 1977-03-22 | Imperial Chemical Industries Limited | Electrolytic cells |
| US4097346A (en) * | 1974-04-01 | 1978-06-27 | Peter Murday Robertson | Electrochemical oxidation of diacetone-L-sorbose to diacetone-L-ketogulonic acid |
| CH597371A5 (en) * | 1975-04-25 | 1978-03-31 | Battelle Memorial Institute |
-
1990
- 1990-06-20 AU AU59201/90A patent/AU5920190A/en not_active Abandoned
- 1990-06-20 DK DK90909653.9T patent/DK0479840T3/en active
- 1990-06-20 ES ES90909653T patent/ES2079476T3/en not_active Expired - Lifetime
- 1990-06-20 CA CA002062739A patent/CA2062739A1/en not_active Abandoned
- 1990-06-20 RU SU905010723A patent/RU2073071C1/en active
- 1990-06-20 EP EP90909653A patent/EP0479840B1/en not_active Expired - Lifetime
- 1990-06-20 BR BR909007455A patent/BR9007455A/en unknown
- 1990-06-20 WO PCT/EP1990/000972 patent/WO1991000379A1/en active IP Right Grant
- 1990-06-20 DE DE59009595T patent/DE59009595D1/en not_active Expired - Fee Related
- 1990-06-20 AT AT90909653T patent/ATE127168T1/en not_active IP Right Cessation
-
1991
- 1991-12-03 NO NO914748A patent/NO307574B1/en unknown
- 1991-12-18 FI FI915971A patent/FI915971A0/en not_active Application Discontinuation
Cited By (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6336430B2 (en) | 1998-06-29 | 2002-01-08 | Fatpower Inc. | Hydrogen generating apparatus |
| US7240641B2 (en) | 2001-01-19 | 2007-07-10 | Hy-Drive Technologies Ltd. | Hydrogen generating apparatus and components therefor |
| US8282812B2 (en) | 2009-02-24 | 2012-10-09 | John Christopher Burtch | Apparatus for producing hydrogen from salt water by electrolysis |
| US10577700B2 (en) | 2012-06-12 | 2020-03-03 | Aquahydrex Pty Ltd | Breathable electrode structure and method for use in water splitting |
| US20150200401A1 (en) * | 2012-06-20 | 2015-07-16 | Solvay Sa | Bipolar electrode and method for producing same |
| US9972846B2 (en) * | 2012-06-20 | 2018-05-15 | Solvay Sa | Bipolar electrode and method for producing same |
| US10637068B2 (en) | 2013-07-31 | 2020-04-28 | Aquahydrex, Inc. | Modular electrochemical cells |
| US11018345B2 (en) | 2013-07-31 | 2021-05-25 | Aquahydrex, Inc. | Method and electrochemical cell for managing electrochemical reactions |
| US11005117B2 (en) | 2019-02-01 | 2021-05-11 | Aquahydrex, Inc. | Electrochemical system with confined electrolyte |
| US11682783B2 (en) | 2019-02-01 | 2023-06-20 | Aquahydrex, Inc. | Electrochemical system with confined electrolyte |
Also Published As
| Publication number | Publication date |
|---|---|
| EP0479840B1 (en) | 1995-08-30 |
| AU5920190A (en) | 1991-01-17 |
| WO1991000379A1 (en) | 1991-01-10 |
| DK0479840T3 (en) | 1996-01-02 |
| FI915971A0 (en) | 1991-12-18 |
| ATE127168T1 (en) | 1995-09-15 |
| NO914748D0 (en) | 1991-12-03 |
| NO914748L (en) | 1991-12-03 |
| ES2079476T3 (en) | 1996-01-16 |
| BR9007455A (en) | 1992-06-16 |
| NO307574B1 (en) | 2000-04-25 |
| EP0479840A1 (en) | 1992-04-15 |
| RU2073071C1 (en) | 1997-02-10 |
| DE59009595D1 (en) | 1995-10-05 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| FZDE | Discontinued |