JPS6311436B2 - - Google Patents

Description

[Detailed description of the invention]

FIELD OF THE INVENTION The present invention relates to an electrolytic cell for the anodic deposition of electrolytic brownstone, in which anode plates consisting of a plurality of sintered titanium strips are suspended between two flat cathodes. Prior Art Over the past few years, titanium has gradually attracted attention as an anode material in the production of electrolytic brownstone (electrolytic manganese dioxide, or EMD). This is because titanium shows no wear phenomena compared to the frequently used graphite, and compared to the similarly used lead it practically does not corrode and can therefore be used repeatedly. . A particular disadvantage of titanium is that during anodic loading it has a tendency to passivate, i.e. to form a layer of poorly conductive oxide on its surface in the case of a certain current density. Therefore, there is a tendency to cause an increase in terminal voltage. However, electrolytes containing manganese ions form a highly conductive coating of titanium due to EMD, so that even at high electrolytic densities, which are possible in manganese-free electrolytes, such as dilute sulfuric acid, the terminal voltage does not increase. However, the protection provided by the EMD layer is not complete, and under certain conditions the titanium anode can still become passivated. Such phenomena have been variously described, and it has been shown that in addition to the current density, sulfuric acid concentration and temperature also play an important role as limiting barometers for electrolysis. (Chemie-Inganieur-
Technik) Vol. 49, p. 347 (1977) and British Patent No. 977569]. Many attempts have been made to overcome such electrolytic limitations. This also includes the provision of an active layer on the titanium surface at high cost in order to avoid passivation, thus ensuring high current densities and thus high economic efficiency of the existing equipment. One important method is to increase the effective surface area of the electrodes and thus reduce the true current density for a given bath current strength. It has therefore been proposed to roughen and thus increase the surface roughness of titanium by sandblasting. At the same time, good adhesion of the deposited EMD coating on the anode is thereby achieved (US Pat. No. 3,436,323). Attempts were also made to achieve the same objective with expanded metal (U.S. Patent No.
3654102 specification). Already in 1952 and 1953 it was known that anodes made of titanium sintered in manganese sulfate baths allow higher current densities than anodes made of titanium sheets (U.S. Pat. No. 2,608,531 and U.S. Pat. Patent No. 2631115 specification). Nevertheless, perhaps for technical reasons, sintered titanium is EMD
It was not used in practice for a long time in the manufacture of.
Industrial electrodes based on sintered titanium were first described in 1976 (West German Patent Application Publication No.
2645414 specification). At the same manufacturing cost, this electrode is significantly more rigid than a thin titanium plate. Currently, there is a trend in EMD production to use even lower current densities, so titanium activation is less important than the use of large anode surfaces. “Journal of Metals, Vol. 34 (1982), No. 37-
For technical reasons, the mechanical and electrical properties of sintered titanium produced in the form of plates are more important than those of rolled titanium sheets or solid titanium plates. Use a suitable anode material. This is because, for the same cost, a thicker anode can be produced and at the same time a surface roughness advantageous for the deposition of the EMD to be deposited is obtained. Previously known forms of anodes for EMD electrolysis are:
These are plates made of graphite or titanium, or rods or tubes made of expanded titanium metal or sintered titanium and lead or graphite (DE 2853820). An anode consisting of two titanium sheets has also been proposed. Anodes have also been proposed in which these two titanium sheets are corrugated by grooving and welded together, thus resulting in a tube connected to each other by a web. This provides good rigidity of the anode. Two practical demands must always be made on anodes for producing EMDs. a Good adhesion during electrolysis b Easy separation of the EMD after electrolysis These two requirements are contradictory to each other, so
Compromise is necessary. The EMD coating is easily removed from the anode with a flat surface by hammer impact.
The adhesion of the coating to the anode is extremely poor. A tube in which crystals can grow freely from all sides is an EMD
The smaller the diameter, the better the substrate for adhesion. However, since these tubes are placed at a small distance from each other, EMD
It also grows into the interstices, so if you want to extract the EMD from there, you can only remove it with difficulty.
In the case of deformable lead anodes, this is not a problem, but if the anode component is rigid and fixed, EMD removal is a tedious process. Problems to be Solved by the Invention The problem of the present invention is to combine the advantages of good EMD adhesion during electrolysis and its easy peelability by using sintered titanium as a main material, and to combine a large anode area with a specified tank volume. The object of the present invention was to provide a titanium anode that could be loaded into a sintered titanium alloy and combined in such a way as to fully exploit the advantages of sintered titanium compared to solid titanium. Means for Solving the Problem The problem was solved by replacing the wide sintered metal plate with a narrow sintered titanium strip of dimension abL (a=width, b=thickness and L=length). The problem was solved by arranging the longitudinal axis of the anode plate group in the longitudinal direction of the main plane of the anode plate group, and the elongated strip being pivoted from the main plane of the electrode by a fixed mounting angle α about the longitudinal axis.
This mounting angle is between 10 and 90°. The strips may lie parallel to each other or at an angle to each other; in the latter case the mounting angles are alternately α° and 180°-α°. Advantageously, the strips should not touch each other and should maintain a mutual distance. Although it is advantageous to fix the strip in such a way that it is suspended from the top down due to its length, the invention also provides an arrangement pivoted through 90°, ie an arrangement in which the strip is fixed horizontally into the container. Within range. The sintered titanium strip as the anode plate is fixed in a manner known per se, generally at its upper end, vertically suspended from the transverse connecting rod, which serves as the anode. The sintered titanium elongated plate is pivoted outward from the main plane of the anode plate group about its longitudinal axis, and is in contact with the plane from 0 to 0.
angle α of 90°, and is characterized in that the width of the sintered titanium strip is greater than twice its thickness, but less than half the cathode-to-cathode distance. Furthermore, the electrolytic cell according to the invention is selectively and advantageously characterized in that: a the sintered titanium strips are arranged parallel to each other, measured by the projection of the strips onto the anode plane;
the distance d between the sintered titanium strips is <0;0; or >0; b the sintered titanium strips alternately form angles α and 180−α with the anode plane in a zigzag arrangement and extend onto the anode plane; the distance d between the sintered titanium strips, measured in the projection of the strips, is ≧0; c the angle α is between 30 and 70°; d the sintered titanium strips of the anode each have two It is fixed vertically between vertically arranged flat cathodes. Embodiments Next, the anode system according to the present invention will be described in detail with reference to embodiments shown in the accompanying drawings. FIG. 1 shows a sintered titanium strip 1 of an anode system arranged in a zigzag manner between two flat cathodes 2, which sintered titanium strip 1 is arranged in a zigzag manner between two flat cathodes 2.
, alternately turning outward by an angle α or 180−α. Figure 2 shows a sintered titanium strip 1 of the anode system arranged parallel between two flat cathodes 2, which sintered titanium strip 1 extends outward at an angle α from the plane 3 of the anode system. It is turning to FIG. 3 shows two sintered titanium strips as a partial view from FIG. 1. FIG. In this case a=width of the strip; b=thickness of the strip; d=distance between the strips in their projection onto the plane of the anode system.
The angle β between the strip edge a and the strip diagonal is important in the following equation. FIG. 3 shows the case where d>0. FIG. 4 shows two sintered titanium strips as a partial view from FIG. 2 for the case d<0. The width and angle α of the strips and the number of strips per anode system depend respectively on the electrolyzer dimensions present and the desired total current load of the anode system. Below, given the dimensions of the strip, the thickness D and the effective surface area (Oeff) of the anodic system and the ratio Q of the effective surface area (Oeff) to the formal surface area (Oform) of the anodic system are expressed as angle α We have written the formulas that can be calculated accordingly. However, on the contrary, from the diagrams prepared according to these formulas it is also possible to know at least how large the angle α must be selected if one wants to obtain a certain effective surface area of the anode system. . D=√ ² + ²・sin(α+β) () O _eff =n・(a+b). L.2 () Q=O _eff /O _fprn (); O _fprn = 2B.L () (n = number of strips per anode system; a = width of the strip; b = thickness of the strip 1 = length of the strips; d = distance between the strips in their projection onto the plane of the anode system; B = width of the anode system). The available cathode-to-cathode distance in the electrolytic cell determines the maximum thickness D of the anode system, which also includes the thickness of the EMD deposit and the electrodeposited anode from the flat cathode. The minimum distances of the system are added. Furthermore, D is a function of the strip width a and the angle α, and also of the strip thickness b and the angle β [see equation () and FIG. 3]. The anode system according to the invention proves to be superior to a planar arrangement. This is because more than 100% of the additional anode area can be accommodated in the electrolytic cell, and the geometry of the arrangement can be adjusted on the anode system.
This is because it induces good adhesion of EMD. Example 1 Zigzag arrangement of sintered titanium strips in the anodic system Width of the strips a = 4 cm Thickness of the strips b = 0.8 cm Distance between the strips d = 0.2 cm Formal width of the anode system: 100 cm, anodic system Formal length: 100 cm, formal surface area on both sides of the anode system (O _fprn ): 2 m ² , O _eff = effective surface area of the anode system, Q = O _eff / O _fprn ,
n = number of strips per anode system, D = thickness of the anode system

[Table] Table 1 shows that turning outward up to α=20° means
It is shown that the distance between the strips d = 2 mm does not offer any appreciable advantage over the planar arrangement of sintered titanium strips (α = 0°). The reason for this is that the gaps between the strips are quickly bridged by EMD, so that the anode system continues to work like a planar anode system, which in this case is under internal stress. On the other hand, it is also disadvantageous to turn outward by more than α=70°. This is because the gaps between the strips become smaller and smaller, so that it becomes more and more difficult to remove the EMD from it, until finally at α = 90° the zigzag shape is abandoned and it becomes, as it were, a plane again. This is because an unreasonably thick anode is obtained. The optimum angle of rotation α of the sintered titanium strip around its longitudinal axis from the plane of the anode system is therefore from 30° to 70° or alternatively from 150° to 110°. Table 1 also shows that the thickness of the anode system is greater than 4 cm in the angular range below about 70° to 90°. This is because the diagonal width of the sintered titanium strip plays a role here. Example 2 The dimensions of the inclined parallel arrangement of the sintered titanium strips of the anode system are the same as in Example 1 with the following exceptions. Width of the strip a = 3 cm, thickness b of the strip = 0.6 cm,
Distance between strips d=0

[Table] If the need for effective surface area is small, the number n can of course be lowered. That is, it is possible to increase the distance d in the anode system and arrange a smaller number of strips.

[Brief explanation of the drawing]

The accompanying drawings show an embodiment of the anode system of the present invention; FIG. 1 is a plan view of an anode system in which sintered titanium strips are arranged in a zigzag pattern between two flat cathodes; The figure is a plan view of an embodiment in which sintered titanium strips are arranged in parallel between two flat cathodes; FIG. 3 shows two sintered strips, d>0
FIG. 4 is a partial view from FIG. 2 for d<0, also showing two sintered strips. 1... Sintered titanium strip, 2... Cathode, 3...
Plane of the anode system, a... Width of the strip, b... Thickness of the strip, d... Distance between the strips when projected onto the plane of the anode system, D = Thickness of the anode system difference.

Claims (1)

[Claims] 1. An anode plate group consisting of a plurality of sintered titanium strips is suspended between two flat cathode plates, each with a longitudinal axis of the sintered titanium strips parallel to the cathode plates. In an electrolytic cell for anodic precipitation of electrolytic brownstone, which is present in the extending main plane of the anode plate group, the sintered titanium strip is pivoted outward from the main plane of the anode plate group about its longitudinal axis, each forming an angle α of 0 to 90° with said plane, and characterized in that the width of the sintered titanium strip is greater than twice its thickness, but less than half the cathode-to-cathode distance. 2
An electrolytic cell for anodic deposition of electrolytic brownstone, in which an anode plate group consisting of a plurality of sintered titanium strips is suspended between two flat cathodes. 2. The electrolytic cell according to claim 1, wherein the sintered titanium strips are arranged parallel to each other. 3. The distance d between the sintered titanium strips, measured by projection of the strips onto the anode plane, is <0;0; or >
The electrolytic cell according to claim 2, wherein the electrolytic cell is 0. 4. Electrolytic cell according to claim 1, in which the sintered titanium strips make alternating angles .alpha. and 180.degree.-.alpha. in a zigzag arrangement with the anode plane. 5. Electrolytic cell according to claim 4, in which the distance d between the sintered titanium strips, measured by projection of the strips onto the anode plane, is ≧0. 6. The electrolytic cell according to any one of claims 1 to 5, wherein the angle α is between 30 and 70°. 7. The method according to claim 1, wherein the sintered titanium strips of the anodes are each fixed vertically between two vertically arranged flat cathodes. electrolytic cell.