FI56557C - DIAFRAGMACELL MED ETT FLERTAL AVDELNINGAR FOER FRAMSTAELLNING AV KLOR OCH ALKALIMETALLHYDROXID - Google Patents

Description

- [B] (11) ADVERTISEMENT rfirr? LJ VUTLÄGGN I NGSSKRIFT 9099 / i C (45) Patent granted 11 02 1930, Patent oeddelat T (51) Kv.lk • / Int.CI. * C 25 B 9/00 FINLAND —EN NLAND (21) p * Mflttlh »K» mu * - P »tent« n »eknlnf 1395/71 (22) H» k «nl * ptlvt - Ansaknlngsdag 21.05-71 (23) AlkupUvl — Giltl | h« ttdag 21.05.71 (41) Interpreters for public - Bllvtt offwttllg 27.11.71

Patent and Registration Office .... ......... ,,. .....

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Patent and regulatory authorities Amukut uttagd och utUkiiftm publicerad 31.10.79 (32) (33) (31) Stuolkeu * —Bsglri prlorlttt 26.05-70

England-England (GB) 25201/70 (71) Imperial Chemical Industries Limited, Imperial Chemical House, Millbank, London SW1, England-England (GB) (72) Alan Brian Emsley, Runcorn, Cheshire, Colin Jackson, Runcorn, Cheshire , England-England (GB) (7M Oy Kolster Ah (5 * 0 Multi-compartment diaphragm cell for the production of chlorine and early metal hydroxide) by electrolysis of an aqueous solution of an alkali metal chloride, the cell comprising at least one bipolar electrode arranged between the terminal anode and the terminal cathode to form at least two unit electrolytic cells connected in series, each bipolar electrode being a unit comprising (a) an anode forming an anode , preferably titanium, on a plate (1) having on one surface 1a is a coating of an active electrode material, preferably platinum metal and / or platinum oxide, which is electrically conductively connected to a plate of iron or steel over a substantial area of its opposite surface, and (b) a cathode consisting of a perforated iron or steel plate preferably woven 2 56557 mesh and located parallel to and spaced from said iron or steel plate but electrically connected thereto, forming a cathode solution compartment between the plate and the perforated plate, the end cathode being a perforated iron or steel plate forming the end cathode box a single-walled iron plate as the end wall and opposite the bipolar unit, the cathode solution compartments and end cathode box of the bipolar units having a gas outlet and a liquid outlet, the end anode being an anode metal, preferably titanium, plate with a functional, electrode on one surface a platinum metal and / or platinum metal oxide coating, wherein the terminal cathode, bipolar units and end anode are arranged in series so that each perforated cathode plate is parallel to the coated anode surface of an adjacent bipolar electrode but electrically insulated and spaced apart from the porous arranged between each cathode and an adjacent coated anode surface, whereby an anode solution compartment is formed between the film and the coated anode surface, and wherein each anode solution compartment has an electrolyte inlet and a liquid and / or gas outlet.

The term "perforated sheet" as used herein means a perforated or reticulated sheet, such as a multi-hole or perforated sheet, gauze, woven mesh, or expanded metal sheet, which may be flattened if desired. Most preferably, this perforated sheet is in the form of a woven mesh.

Anode metal means a metal which is titanium, zirconium, niobium, tantalum, tungsten or an alloy consisting mainly of these metals and having anodic polarization properties similar to those metals themselves. These are also known as film-forming metals. The more preferred metal is titanium.

The active electrode material may be any material that actively transfers electrons from the electrolyte to the anode metal below and that is capable of resisting electrochemical phenomena under the conditions acting in the cell in which that anode is to be used. For use in highly corrosive conditions, e.g. in the case of chlorine electrolyte, this active electrode material may preferably consist of one or more platinum group metals, i.e. platinum, rhodium, iridium, ruthenium, osmium and palladium and / or their oxides or other metal or metal , which acts as an anode and is capable of providing the electrochemical dissolving effect of this cell, such as, for example, rhenium, rhenium trilium, magnetite, titanium nitride and borides, phosphides and silicic acid salts of platinum group metals. The coating consisting of the active electrode material may also contain electrically non-conductive oxides, in particular oxides of anode metals such as titanium and / or other metals such as tin, as is known in the art to more firmly anchor this active electrode material to a supportive anode metal structure. resistance to the dissolving effect of this working cell.

In particular, it is preferred to use a platinum coating which may have been formed, for example, by electroplating on a substrate, as described, for example, in French Patent Publication No. 159-758.

Other coatings that can also be used include, for example, those described in Belgian Patent 7 ^ + 0 2k2, Belgian Patent No. Jh2 89 ^, or British Patent Publications 1,29h,373, 1,352,872 and 1,35 ^ 897 · When an oxide coating is used, it is most preferred that this coating be composed of ruthenium oxide.

The cathode is most preferably made of melt steel. Accordingly, said iron plate may most preferably be formed of melt steel.

According to a preferred embodiment of the present invention, the iron plate and the perforated plate form opposite end surfaces of a cathode box adapted to contain a cathode solution. This box is most suitably provided with an outlet for gases and an outlet for liquids. If desired, the same outlet can be used for both gases and liquids.

Most preferably, this perforated plate is supported by transverse supports attached to said iron plate. These supports may be electrically conductive and are usually spot welded onto this perforated plate.

The cell according to the invention is characterized in that the anode metal plate of each bipolar unit has channels along the entire circumference of the plate on the opposite side of the roof plate of the same unit, the channels communicating with the anode solution compartment close to the perforated cathode plate of the adjacent unit.

Preferably, said channels are formed by bending the edges of the anode metal plate. The anode metal plates are preferably rectangular, with at least one liquid and / or gas outlet in the channel at one edge and at least one electrolyte inlet in the channel at the opposite edge.

U.S. Patent No. 5,655,734 discloses a bipolar cell without a membrane in each cell unit suitable for the production of chlorate, perchlorate or hypochlorite. Each bipolar electrode may consist of an anode plate made of platinum-plated titanium and a cathode surrounding and open at the top and bottom, the anode closest to the cathode steel plate being connected to the titanium anode plate by "coating" could flow into the connecting cathode to provide cathodic protection on the inner steel surfaces. Such a bipolar electrode must be immersed in a container containing the electrolyte.

The cell according to the invention makes it possible to omit the container when connecting the electrodes into a multielectrolytic cell, by means of channels along the entire circumference of the anode plate.

U.S. Patent No. 2,786 θ11 discloses the use of peripheral channels to recycle electrolyte in and out of cells and to remove gases generated in electrolysis used in filter press type cells. The bipolar electrode is formed by a flat metal plate with a nickel plating on the anode side and peripheral peripheral channels formed of rectangular steel channels welded to both the anode and cathode sides of the plate. There is no separate cathode with an opening and the film is therefore self-supporting except for the edges insulated from said rectangular steel channels, between which the edges are pressed with insulated elements.

U.S. Pat. No. 3,312,611, on the other hand, discloses cells in which both the anode and the cathode are provided with horizontal channels at the bottom (to supply electrolyte) and at the top (to remove liquid and gases). In comparison, the present invention relates to a multielectrolytic cell having bipolar units in which only the anode of each bipolar unit is provided with channels, in addition to which channels are arranged on the entire circumference of the anode, i. both horizontally and vertically. The channels according to the invention are formed much more simply, preferably by bending. Furthermore, as also mentioned in connection with U.S. Patent 3 1 + 51 91 * +, the arrangement of channels around the entire circumference of the anode allows the container to be omitted when assembling electrodes into a multielectrolytic cell, whereas U.S. Patent 3,312,611 restricts to a single cell with two cell wall metal electrodes .

5,565S7

It is preferred that at least the channel containing the outlet and in general also the channel containing the inlet is widened in cross-section so that liquids and / or gases can pass through them without too much shrinkage.

This channel of expanded cross-section may consist of a tube whose axis is substantially parallel to the edge portion adjacent to which it is located. The outlets and inlets may preferably be coaxial with these tubes.

Most preferably, a certain grooved plate, e.g. titanium, is inserted into these troughs to support the shaped bodies of this channel.

An anode metal plate may be attached to the former plate by suitable means which provide an electrically conductive connection. Most preferably, the coating of the working electrode material is applied to the plate of this anode metal after this joining operation.

This joining can be performed e.g. by soldering or brazing these plates together and a particularly suitable method for soldering is described in Belgian Patent No. 737 207 · In this method an anode metal plate is coated with "tin" metal or alloy by heating this plate while the surface to be coated is covered with a tin metal or alloy in a molten state, in addition to which the ultrasonically fed tester is moved along substantially the entire surface to be coated, this tester being in contact with this surface as well as with the molten metal or alloy. which has already been tinned in advance.

This "tin" metal or alloy is a metal or metal alloy which forms a coating on a plate of anode metal or this alloy and as a result of which it is possible that the plate thus obtained is used in a conventional soldering process. Suitable tin metals include tin, zinc and cadmium. Suitable alloys of tin metals include bimetallic alloys containing tin, and the other metal is zinc, lead, antimony or bismuth, or tin-containing alloys containing tin, such as an alloy of tin, zinc and lead. It is preferred to use an alloy of zinc and tin.

Pre-tinning of the first-mentioned plate can most conveniently be carried out in a conventional manner by heating the surface to be joined, e.g. using an alloy of lead and tin using e.g. an alloy containing 30% lead and 70% tin or using an alloy of lead and bismuth. If desired, this tin metal or alloy may be the same metal as that used to tin both the anode plate and the first-mentioned plate.

A wide range of alloys can be used to solder these plates together. Suitable solder alloys include, for example, alloys of lead and tin or alloys of lead and bismuth.

6 56557

Another means of joining the first-mentioned plate and the anode plate together is to use an electrically conductive adhesive. Any suitable adhesive may be used and includes epoxy resins using a powder of a conductive metal, e.g. silver or zinc, as the filler. In general, this epoxy resin consists of Bisphengol A sealants with epichlorohydride and can be cured with suitable crosslinking agents such as an amine. These adhesives most preferably contain between 50-90% by weight of metal. When such adhesives are used, it is desirable that they be applied to these adhesive sheets, which are then held together under a certain pressure of, for example, between 1.4 and 3.5 kp / cm, while this adhesive hardens, which occurs e.g. at a temperature between 100 ° C and 180 ° C.

Said film may be any suitable film material, but it is most preferred that this film be made of polytetrafluoroethylene (PTFE) using e.g. the method described in British Patent Publication 1,081 01 + 6. Other suitable film materials include asbestos, which can be placed, for example, on this perforated plate by immersing this plate in an asbestos slurry and using a vacuum to suck asbestos onto this plate.

It is also preferred that the outlets from the anode solution compartment be connected to a defoaming space located away from the compartments of this anode solution, e.g. as described in British Patent 1,123,321. In such arrangements, the defoaming space is connected to the inlets of the anode solution compartment. channels for this purpose.

The present invention is illustrated in the accompanying drawings, in which Figure 1 is a side view of a bipolar unit taken along line BB 'in Figure 2.

Figure 2 is a section taken along line AA 'in Figure 1.

Figure 3 is a top view of this unit.

Fig. 4 is a top side view of an alternative structure of this bipolar unit shown in Fig. 1, viewed in this case along the line DD 'in Fig. 5 ·

Fig. 5 is a section taken along the line CC 'in Fig. 1 *.

Fig. 6 is a partial side view of the bipolar unit taken along line EE 'in Fig. 5 and showing various fasteners not shown in Fig. 4.

Figure 7 is a sectional view of a cell incorporating the two bipolar units shown in Figures 1, 2 and 3.

Fig. 8 is a schematic representation of a cell as shown in Fig. 7 when used for saline electrolysis.

Referring now to these drawings, the bipolar unit shown in Figure 1-7 is made of a titanium plate 1 electrically connected to a molten steel plate 2.

These plates are joined together using the ultrasonic welding to the sound end method as follows. The titanium plate was pre-tinned using 75% 56557 tin and $ 25 zinc as solder at 400 ° C with the aid of an ultra sound head. This plate was kept at this temperature for 50 minutes after tinning to allow the solders to diffuse to the inner surface. Melt steel was pre-tinned using a "plumber solder" (containing $ 70 lead and $ 50 tin) at 500 ° C using an ammonium chloride flux. The tinned titanium was then coated with a thin layer of plumber solder at 500 ° C. A certain layer of this plumbing solder was made to flow over the melt steel at 300 ° C and a titanium plate was made to adhere to it. This structure was then held together and allowed to cool until the plates were joined together. The platinum coating was then galvanized on the uncoated side of this titanium. In the units shown in Figures 1 to 5 and 7, the horizontal plates of this titanium sheet are bent at 3 to form a trough supported by grooves 4 made of titanium. This chute is provided with inlets 5 and outlets 6. The bipolar units shown in Figures 4,5 and 6 have channels at the horizontal edges, the shape of which is extended from 40 and 41. These have inlets 42 and outlets 43. In Figure 6, the outlets 43 are connected to vessels 44 »which act as a defoaming space where the gas and liquid forming foam may separate so that gas may exit the outlets 45 and liquid may pass through the inlet 42. Further liquid may be added to these vessels 44 through inlets 46 and gas may escape from these vessels 44 through outlets 45. The vertical edges of this titanium plate are also bent twice in all figures to form channels, but for clarity this is not shown in the sectional figures.

The sheet steel plate 2 is equipped with yellow steel walls? » which are welded onto this plate. This steel plate has vertical wall-edge edges (not shown for clarity) which, together with the walls 7, form the sides of an open box with a base plate 2.

These walls are provided with edge portions 8 to which are attached the wire mesh portions 9 »of melt steel, which form a cathode. These plates 2 and 9 form dreaded end surfaces of the cathode box. The upper and lower side walls of each box shown in Figures 2,3 and 7 are provided with outlets 10 and 11. The units shown in Figures 5 and 6 have outlets 47 »connected to vessels 48 each having an outlet for gases 49 and an outlet for liquids. for 50 ·

Figures 7 and 8 show two of the bipolar units of Figures 1-3 incorporated in an electrolytic cell. The end anode 12 and the end cathode 13 are similar in structure to the anode and cathode parts in the bipolar unit, respectively. Thus, the terminal anode 20 has a platinum surface similar to surface 1 and an inlet 21 corresponding to the inlets 5 and in addition an outlet 8 56557 corresponding to the outlets o. The wood cathode consists of a wire mesh plate 25 * of melt steel, which is similar to the plates 9 * with the outlet 23 corresponding to the outlets 10 and the inlet 24 corresponding to the inlets 11.

Each of the perforated cathodes is spaced apart from its adjacent active anode surface. A particular intermediate separator 14 electrically separates adjacent anodes and cathodes. This separator can be made of any suitable material, such as a formaldehyde resin mixture, e.g. Tufnol, or polytetrafluoroethylene, which is generally capable of resisting the electrolyte and electrolytic products. to ensure that no liquid can escape between adjacent anodes and cathodes.

A certain porous polytetrafluoroethylene film 15 * containing titanium dioxide as a filler is placed next to this perforated cathode.

This membrane and the anode form opposite end surfaces of an anode box which, with its various separators and seals, is suitable for containing anode liquid.

It is now desirable that the gap between the electrodes be as small as possible in order to reduce the ohmic losses that occur during electrolysis. It is preferred that this opening be between 5 and 10 mm. In the cell shown in Fig. 7, the distance between the anode surface and the adjacent cathode is 7 mm.

The end anode and end cathode are equipped with power supply rails 16 and 17. · This cell is assembled by the system in the correct order into a suitable frame (not shown in the figures) and then applying sufficient pressure to its end faces so that the whole cell stays together and no leaks occur at adjacent junctions. between units and between terminal electrodes and adjacent units.

Although there are only two units in the cell shown, one may contain any number that is compatible with the voltages at which it is desired to operate. Thus, such a cell usually contains at least 10 units and e.g. always up to 100 units.

Figure 8 is a schematic representation of the cell shown in Figure 7 for use in saline electrolysis. The brine enters the cell along channel 35, releasing chlorine at anodes 1 and 20 and releasing hydrogen at cathodes 9 and 25. At the same time, sodium hydroxide is formed in the cathode compartments of this cell.

This chlorine is produced in such an amount and at a rate of production that a foam is formed which is formed from the chlorine in brine as it forms in the anode compartments in this cell. The force of these chlorine bubbles causes the foam to pass out of the cell along the channel 30 into the defoaming space 32 where the chlorine is separated from the brine. Chlorine exits here through the defoamer 32 outlet 34. ' 9 and 56557

Spent replacement saline is added through channel 55. The surface height 37 of the brine solution in the foam remover 32 is high enough to ensure that the brine circulates, back to the bottom of the cell along the channel 35 ·

The hydrogen formed in the cathode compartments exits through passage 51 and the formed sodium hydroxide exits mixed with saline along passage} 6 The cells shown in Figures 7 and 8 can be converted by replacing one or more of these bipolar units in Figures 1-5 with one or more of Figures 4-6. In such an arrangement, the end anode and end cathodes are generally similar in structure to the anode and cathode portions in the bipolar units 4-6, Foam Removal Space 57, respectively. 8 consists of vessels 44 These vessels 44 may be common to all of these cells. Most preferably, each unit is provided with its own individual container 44 although if desired a common container for two or more units or even an entire cell may be used. Alternatively, bulkheads may be placed in the common container so that it may function effectively as a number of smaller containers, thereby reducing leakage danger between units. When electrolysing the brine, chlorine foam in the brine enters vessels 44 with pitch outlets 45 »and. then the chlorine here separates from this brine. Chlorine exits the vessels along the outlets 45 and the brine is recycled back to the bottom of this anode box through the inlets 42. Consumption replacement saline is added through inlets 46. Hydrogen, sodium hydroxide, and saline exit the cathode boxes along outlets 47 as they enter vessels 48, where hydrogen exits through outlets 49 and sodium hydroxide and saline exit through outlets 50.

Although these cells have now been described for the electrolysis of an aqueous solution of sodium chloride, other alkali metal halides, such as potassium chloride, can also be electrolysed in these cells.

The present invention can be further illustrated by the following example:

Example

A suitable cell is made of the two bipolar units shown in Figures 4-6 and is used for electrolysis of saline! o o its operating temperature is between 80 C and 85 C for a period of five days. The following results were obtained: 10 2 5 6 5 S 7

Voltage acting over one module

(i.e. from the anode to the cathode of the adjacent unit) 3 * 24 V

Anode current density 2 kA / m

Sodium chloride feedstock content 307 g / l NaCl

The concentration of the cathode solution is 122.8 g / l NaOH

0.55 g / l NaClO5 180.2 g /. NaCl

Anode gas collection analysis Clg 98 i by volume oo2 1 56 o2 1% h2 0 io n2 0 $>

Cell current efficiency 96.5 i

Conversion efficiency 49 * 9 i>

It can now be seen that the cell thus gives the value of good chlorine efficiency and good conversion efficiency as well as an exceptionally good voltage to current ratio. This cell is very compact in structure and can completely eliminate the need for a cell housing.

Claims (3)

56557 A multi-compartment diaphragm cell for producing chlorine and alkali metal hydroxide by electrolysis of an aqueous alkali metal chloride solution, the cell comprising at least one bipolar electrode arranged between an end anode (12) and an end cathode (13) to form at least two unit electrolytic cells, each connected in series, a unit comprising (a) an anode consisting of a plate (1) of anode metal, preferably titanium, with a coating (20) on one surface of an active electrode material, preferably platinum metal and / or platinum metal oxide, and electrically connected to the opposite from a substantial area of its surface to an iron or steel plate (2), and (b) a cathode consisting of a perforated iron or steel plate (9), preferably a woven mesh, parallel to said iron or steel plate (2), and at a distance from it, but tel connected to it, whereby a cathode solution compartment is formed between the plate (2) and the perforated plate, the end cathode being a perforated iron or steel plate (25) forming one wall of the end cathode box with the iron plate (13) as the end wall and opposite the bipolar unit, the cathode solution compartments and end cathode box of the bipolar units having a gas outlet (10, 23) and a liquid outlet (11, 2U), the end anode (12) being a plate of anode metal, preferably titanium, with an active electrode material on one surface, preferably a coating of platinum metal and / or platinum metal oxide, wherein the terminal cathode, bipolar units and the terminal anode are arranged in series so that each perforated cathode plate is parallel to the coated anode surface of an adjacent bipolar electrode but electrically insulated and spaced apart therefrom, wherein the porous film (15) is fitted to each cathode and adjacent coated between the anode surface, whereby an anode solution compartment is formed between the membrane (15) and the coated anode surface, and wherein each anode solution compartment has an electrolyte inlet (5, 21) and a liquid and / or gas outlet (6, 22), characterized in that each bipolar unit has channels (3) along the entire circumference of the plate on the opposite side of the cathode plate of the same unit, the channels communicating with the anode solution compartment close to the perforated cathode plate of the adjacent unit. Diaphragm cell according to claim 1, characterized in that said channels (3) are formed by bending the edges of the anode metal plate. Diaphragm cell according to Claim 1, characterized in that the anode metal plates are rectangular, that the channel (3) on one edge has at least one liquid and / or gas outlet (6, 22) and that the channel on the opposite edge has at least one electrolyte inlet (5, 21). 12 56557