DE2735059A1 - ANODE ARRANGEMENT - Google Patents

Description

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Folder 24300

ICI CASE MD.28988 / 29049

IMPERIAL CHEMICAL INDUSTRIES LIMITED London, United Kingdom

Anode arrangement

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Your invention is concerned with improvements in the field of the diaphragm cells for the electrolysis of aqueous alkali halide solutions.

In recent years, the conventional graphite anodes have been used for electrolytic diaphragm cells displaced by permanent anodes made of electrolyte-resistant metals (e.g. titanium). In the case of the consumable graphite anodes, the lower ends of the anodes were usually attached to copper feed bars connected or poured into a lead plate forming part of the cell base. To protect the feed rails or the cast lead plate from the corrosive effect of the chlorine-containing liquor during operation of the A protective coating made of e.g. concrete or bitumen was then applied to the cell.

The advent of having an electrocatalytically active coating provided metal anodes led to considerable changes in the construction of the anode assemblies or units for diaphragm cells. These changes were due in part to the fact that the coated metal anodes had a considerably longer service life than comparable graphite anodes. More important, however, was the fact that a graphite anode is consumed during the operation of the cell and replaced at the end of its life must, whereas you only need to equip a metal anode with a new coating if you are electrocatalytic active coating has become unusable. The ones used to protect the power supply devices for graphite anodes, Complex methods are therefore not suitable for metal anodes, which can easily be removed from the cells for regeneration stratification had to be removable. At the same time, however, the facilities for power supply to the lower had to be installed

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Ends of the metal anodes still before the corrosion whirlcun ■; of the electrolyte. At Ketal anodes were the best results obtained by providing the cell with a base made up of an electrically conductive and The metal was unassailable due to the electrolyte used in the cell. Because of its easy availability and its reasonable price, titanium has proven to be the most suitable metal for such cell bases. In such a construction, the metal anodes are attached to one side of the titanium base and at least one Conductor is connected to the other side of the Ba3is in this way » that it conducts the current to the metal anodes.

Examples of diaphragm cells equipped with metal bases are described in British Patents 1,125,493 and 1,127,484. In both cases, coated titanium anodes are releasably attached to ribs, which act as anode carriers and are attached to one side of a titanium base plate. Will be adjacent to the other surface of the base plate mechanically and electrically connected to the metal anodes copper, aluminum or steel conductors. It will several forms of training for the ladder as well as several methods of achieving the bond between the titanium base plate and the ladders. The ladder can, for example, take the form of a single »with the whole Base plate have joined sheet metal; on the other hand, several parallel strips of the conductor metal with the lower surface of the baseplate immediately below the anode support must be connected. You can connect steel or copper circuit boards to titanium »by using a Intermediate layer made of a binding metal or a corresponding alloy produced »and the metals rolled together. The metals can also be welded by explosion welders: unite or also locally by resistance welding

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tie. If the conductors are made of copper, they will be vo. zu ^ cwoir.e with the titanium base; Latte soft or hard soldered If aluminum is used as a conductor material »you can bond finally achieved by pouring molten aluminum onto the titanium bases.

The inventors have now found that for the Achieving an effective mechanical and electrical bond between a titanium base plate and one or more Ladders from a technical and economic point of view on a method based on an ultrasonic tinning and joining technique is best. The procedure overcomes the difficulties encountered in bonding metals to titanium caused by the normally found on the Oxide layer present on the surface of titanium metal.

The invention thus creates an anode arrangement or a Anode assembly kit for an electrolytic cell, the (the) a base plate made of an electrically conductive metal, the not attacked by the electrolyte to be used in the cell is »several attached to a surface of the base plate and connected to this in electrical contact Comprises anodes and one or more current conductors connected to the other surface of the base plate and are in electrical contact with it, with the other surface of the base plate prior to connection with the conductor (s) by contacting with a molten tin-plating metal or equivalent Alloy and pre-tinned with a probe excited by ultrasound.

The metal base can be equipped with several, spaced apart, parallel anode supports, which are connected to the base and in electrical contact

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and consist of a material that is electrically conductive and different from that to be used in the cell Electrolyte is not attacked. The anodes can be connected to the carriers in this way (e.g. welded or screwed) that they are in electrical contact with the carriers.

Optionally, the anodes can be connected directly to the upper surface of the metal base plate (e.g. welded).

In a preferred embodiment, the anode trays have τ r but the form of rows of spaced bolts or pins which are friction welded Capacitor discharge stud welding with the metal base plate can be connected. Capacitor discharge stud welding Arc pressure welding has the advantage that it is the bond between the base plate and the conductor (s) are not affected.

The base plate and the anode carrier are also preferably made of titanium. However, tantalum or niobium can also be used be used for this purpose. Alloys of the aforementioned metals are also suitable.

The anodes are preferably made of titanium or a titanium alloy » which have similar anode polarization properties like titanium has.

The anodes can be electrocatalytic with any conventional active coating. For example, coatings based on platinum group metalloids » s.B. Use ruthenium oxide. The coating can also be a platinum group metal or an alloy thereof »e.g. Contain platinum or platinum-iridium ».

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The anodes can have a suitable construction. You can r..E. 13 "; och ·, n ;: 1 jnloursiearti ^ eη elements (louvre :;) or strips h- betw. B1: ^; . Tt cm. The anodes are preferably non-detachably attached to the spaced-apart, parallel anode supports.

Is the conductor or conductors _t which (r) with the tin-plated by means of ultrasound lower surface of the Ketalltasisplatte connected (are) "consists (consist) of a metal with higher electrical conductivity ale that of the base plate" is preferably made of copper "aluminum or steel .

The conductor can be a single sheet of metal which is connected to the (preferably entire) lower surface of the base plate; alternatively, several parallel strips of the conductor metal can also be connected to the lower surface the metal base plate directly below the anodes or the anode support (depending on the existing construction).

The conductor or conductors can have a conical cross section which decreases in the direction of the decreasing current.

The ultrasonic pre-tinning of the base plate can be carried out according to the ultrasonic tinning method described in GB-FS 1 236 997. In this process, a The surface of the base plate is pre-tinned »by using an ultrasound-excited probe and a molten tin-plating metal (or an equivalent Alloy) and moves the probe over the surface of the base plate. The ultrasound probe is used to remove the »

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natural oxide film (wrs especially for one made of titanium existing Baaisplatte applies); at the same time wild the metal surface tinned. Examples · of suitable tin-plating metals or alloys are tin, zinc and cadmium, binary Alloys of tin with lead, antimony and bismuth εο-wle Ternary tin-containing alloys, e.g. tin / zinc / lead alloys. A preferred alloy is a tin / zinc alloy.

The probe excited by ultrasound can have a suitable resonance at a frequency of, for example, about 20 kHz / s; the temperature of the molten tinning rivets. (or the corresponding alloy) may be up to 45O ⁰ C suitably in the range of 350th Further details regarding the ultrasonic pre-tinning method can be found in GB-PS 1,236,997.

The base plate, pre-tinned with ultrasound, can be attached to the conductor (e.g. a mild steel sheet) using conventional methods. get connected. The connection can for example. done by soldering. A soldering process is preferably carried out below Vacuum carried out so that the surfaces to be connected are held in mutual contact by a force become »which corresponds to the reduced pressure achieved in relation to atmospheric pressure; this procedure is called Referred to as "vacuum connection method".

The pre-tinned base plate can thus be in a vacuum chamber, which contains a flexible membrane, with the (the) electrical conductor (s) are connected. During the connection process, the chamber is evacuated so that the membrane is pressed directly or indirectly against the base plate or the conductor (s), thereby putting pressure on these parts is exercised.

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The connection kxnn between ^ c: ulluici at a pressure of 10 Lic 10 mi.) Hg, e.g. Lei about '0 "nia Hg. Has been carried out. Jurcr. I; Λ rr; -? I tor: at.' er '/aki.i'. ei ie vor to L ihrift.r: "/ '.' ruinier -;:, ir. . L rvir.biliuru ·, -in ler verbi.-iii-i: -fu. ■ achieved between the base plate and the electrical conductor (s), whereby the strength of the connection is increased.

The compound is typically carried out at a temperature of 120 to 25O ⁰ C. Conventional solder, such as bismuth / Bxei alloys, can be used for this.

The vacuum connection can be carried out in an evacuable chamber as follows: The printed circuit board, for example made of mild steel, is placed on a heating plate in the chamber and pre-tinned with a tin-plating metal (or a corresponding alloy). The plate is then allowed to cool down and a base plate (e.g. made of titanium), pre-tinned with the aid of ultrasound, is placed on the circuit board, with π ^r m providing additional solder between the two plates to create the connection. Then you put heat insulating material (e.g. in the form of a decree or board) on the basic plate and seal the assembly of heating plate, circuit board, solder rivet, base plate and heat insulating material located in the canoe by closing the chamber with a flexible membrane (e.g. a rubber membrane) away. The chamber is then evacuated, which removes the air from the joint. The negative pressure (e.g. 10 "mm Hg) causes the flexible membrane to press the base plate into close contact with the circuit board. The temperature is then increased to the connection temperature. The chamber can also be evacuated after heating or heating and evacuating at the same time. Furthermore, instead of the or

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in addition to using eir; r hotplate V / low with the help of the above i Basieplatte;; _t ccidneten carry flexible heating elements.

The invention also relates to an electrode equipped with an anode arrangement of the type described above. lyee cell.

In the following an exemplary Aui, -führungfonii explained with reference to the accompanying drawings. Show it:

Pig. 1 shows a pictorial representation of a device according to the invention Anode assembly;

Fig. 2 is a front view of a portion of the anode assembly of Fig. 1; and

3 shows a cross section through a device for vacuum connection from Titan Dit mild steel.

Referring to the drawings, the cell contains several Pairs of plate anodes 1 made of titanium, one electrocatalytically have active coating (e.g. of ruthenium oxide / titanium dioxide) and at their lower ends by Wideret at the seam carbonisation with titanium bridge parts 2 will. For example, perforated or louvres-like elements are used as anodes Plate anodes. The bridge parts 2 are made by argon arc welding connected to the titanium studs 3, which in turn are connected by capacitor discharge stud welding are connected to the titanium sheet serving as the base plate 4 of the cell. The titanium base plate 4 is used pre-tinned by ultrasound and then in the

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in Pig. 3 shown (and described in more detail below) device with the mild steel plate 5 connected. The mild steel plate serves as a conductor which creates a low resistance current path between the anodes 1 and copper connections (not shown) screwed to a side edge of the mild steel plate 5. The titanium base plate is equipped with at least one drainage hole (not shown).

To pre-tin the titanium base plate, create a »3.175 mm (1/8 in.) High wall surrounding the edges of a titanium sheet» place the titanium sheet on a heating plate »heat the sheet and add a zinc / tin alloy (25 % Zn> 75 ° Sn) on the dam until the alloy just fills the dam after melting. The temperature of the alloy is in the range of 350 to 45O ⁰ C.

Subsequently, a »ultrasound-excited probe connected to a magnetostrictive transducer» consists of a steel probe resonating at half the wavelength with a natural frequency of 20 kHz / s »so far into the molten alloy» until it comes into contact with the titanium surface . Then move the probe from side to side until the entire surface has been touched in this way. The probe is kept in contact with the surface and immersed in the molten alloy during this process. The probe is then removed and the excess alloy is allowed to run off the sheet metal or plate. After cooling down, scrape the treated area with a flat iron so far that only a thin alloy film remains attached to the sheet metal.

The pre-tinned titanium plate obtained is shown in FIG shown vacuum connection device connected to a current conductor.

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The vacuum connection device comprises a mild steel chamber having the base 6 and the side walls 7. The chamber is supported by the mild steel frame 8. The side walls 7 have the outlet pipe 9 which is equipped with the flange 10 for connection to a vacuum pump (not shown). The mild steel plate 11 (part of the cell base) is placed on the heating plate equipped with the heating elements 13 12 of mild steel. The plate 11 and the heating plate 12 are supported by the supports 14 made of insulating material. The pre-tinned by means of ultrasonic titanium plate 18, which forms the cell base plate is placed on the upper surface of the mild steel 11, wherein the pre-tinned side of mild steel is zugo- versa. Then the solder 16 (for example a lead / tin or lead / bismuth alloy) is placed between the titanium plate 15 and the mild steel plate 11. The titanium plate 15 is covered with a layer of insulating material 17 t which also serves to distribute the load evenly. Finally, the vessel is covered with the flexible rubber diaphragm 18, which is tightly fastened between the flange 19 on the side walls 7 and the cover flange 20.

The vessel is evacuated to a pressure in the range of 10 to 10 "* ^ mm Hg (e.g. 10 mm Hg), which is a pressure

2 corresponds to the top surface of the titanium plate 15 of about 1.05 kgf / cm (about 15 psi) (exerted by the diaphragm 18 and the insulating material 17).

The arrangement is then heated to approximately 200 ^° C. in order to solder the titanium plate 15 to the mild steel plate 11; then the assembly is allowed to cool.

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Claims (12)

PATENT CLAIMS 1. Anode assembly for a slectrolysis cell with a Base plate (4) made of an electrically conductive electrolyte to be used in the cell non-vulnerable metal, several attached to a surface of the base plate and with this in electrical contact wound anodes (1) and one or more with the other surface of the base plate connected and aiit this in electrical Contact standing current conductors (5) »whereby the other surface of the base plate before connecting with the (the) current conductor (s) by bringing it into contact with a molten tin-plating metal or an equivalent Alloy and was pre-tinned with an ultrasound excited probe. 2. Anode arrangement according to claim 1t, characterized in that that the anodes (1) are provided with an electrocatalytically active coating. 3. anode arrangement according to claim 1 or 2, characterized in that daö the anodes (1) of several, located at a distance, Parallel TrMrern (_j) are worn u: vl with lenses verbunia are uni in electrical contact :, v.obei the beams with the ba:; ii: plate (4) varbunia:; ir. 1 r id are in electrical contact with this and consist of a material that is electrically conductive and cannot be attacked by the electrolyte to be used in the cell. 70988R / 0922 BATH ORIGINAL - Χι - 4. Anode arrangement according to claim 3 »characterized in that the anodes tr-trc ·: ( \) consist of rows of spaced-apart pins or bolts. 5. Anode arrangement according to claim 1 to 4 »characterized» that the base plate (4) consists of titanium. 6. Anode arrangement according to claim 1 to 5 »characterized» that the anodes (1) are made of titanium. 7. anode arrangement according to claim 3 to 6 »characterized that the anode support (3) are made of titanium. 8. Anode arrangement according to claim 1 to 7 »characterized in that the current conductor (5) consists of a single» with the surface of the base plate (4) connected metal plate or a metal sheet. 9. Anode arrangement according to claim b, characterized in that that the 5 troir.l ei t he (5) a,; tüil plate or a steel sheet int .. 10. Anode arrangement according to claim 1 to 9 »characterized in that that the pre-tinned base plate (4) is soldered to the conductor (s) (5). 11. A method for producing an anode assembly according to Claim 1 to 10, characterized in that the pre-tinned base plate is made into a flexible one Membrane-having vacuum chamber with the (the) current conductor) connects, whereby the chamber is evacuated in such a way, that the membrane is pushed against the base plate or the conductor (s) and thereby pressure is applied exercises these parts. 12. Use of the anode arrangement according to claim 1 to 10 in an electrolytic cell. PATENT LAWYERS DIt.-INQ. H. riNCKE. DIPL. -INQ. H. BOHK "• Pt -IMO. S. STAEGER. OR. Rar. To the left R. KNtISS. 709886/0922 BATH ORIGINAL