EP1673491A2

EP1673491A2 - Constructional unit for bipolar electrolysers

Info

Publication number: EP1673491A2
Application number: EP04765737A
Authority: EP
Inventors: Fritz Gestermann; Andreas Bulan
Original assignee: Bayer MaterialScience AG
Current assignee: Covestro Deutschland AG
Priority date: 2003-10-14
Filing date: 2004-10-01
Publication date: 2006-06-28
Also published as: WO2005038090A3; TW200523403A; CN1867701A; US20050077068A1; JP2007508456A; WO2005038090A2; DE10347703A1

Abstract

The invention relates to a constructional unit for bipolar electrolysers of the filter press type, comprising at least a first shell (12), a second shell (14) and a frame support element (10), whereby at least one of the shells (12, 14) contains plastic, both shells (12, 14) are arranged within the support element (10), such that the back wall of the first shell (12) and the back wall of the second shell (14) are adjacent, the support element (10) and both shells (12, 14) comprise at least two openings (16, 19) for the introduction and withdrawal of electrolyte and/or gas and both shells (12, 14) have opposing openings (15, 15') in the base (11, 13), for accommodating at least one electrically-conducting connector element (30) to which a first electrode (42) in the first shell (12) and a second electrode (44) in the second shell (14) are fixed.

Description

Design unit for bipolar electrolysers

The invention relates to a construction unit for bipolar electrolysers according to the filter press technology, in particular for the electrolysis of an aqueous solution of hydrogen chloride according to the membrane process. As described, for example, in EP-A 0 785 294, electrochemical cells for the electrolysis of aqueous solutions of hydrogen chloride (hydrochloric acid) usually consist of titanium or a titanium alloy, for example a titanium-palladium alloy. In EP-A 0 785 294, an oxidizing agent with a redox potential of preferably 0.3-0.6 V compared to the normal hydrogen electrode is added to the hydrochloric acid as corrosion protection. Trivalent iron is chosen as the preferred oxidizing agent. However, the corrosiveness in the presence of hydrochloric acid is only a disadvantage of titanium as a material for electrochemical cells. Another disadvantage is the poor conductivity, which leads to voltage losses in the current supply to the electrodes and in the current distribution within the cell. In addition, titanium is a very expensive material. The object of the present invention is therefore to provide a design unit for bipolar electrolysers for the electrolysis of aqueous solutions of hydrogen chloride by the membrane process, which is less susceptible to corrosion, leads to less voltage losses and at the same time consists of less expensive materials. Is ben operated with bipolar circuit are the Konstrul tion unit is according to the ^'filter press technology incorporated into an electrolyzer.

The invention relates to a construction unit for bipolar electrolyzers according to the filter press technology, at least comprising a first half-shell, a second half-shell and a frame-shaped support element, at least one of the half-shells containing plastic, the two half-shells being arranged within the support element such that the rear wall of the first th half-shell and the rear wall of the second half-shell lie against one another, the support element and the two half-shells have at least two openings for the supply and discharge of electrolyte and / or gas, and the two half-shells have openings in the bottom one above the other for receiving at least one electrically conductive Have a connecting element to which a first electrode is fastened in the first half-shell and a second electrode in the second half-shell,

While in single element technology an electrochemical cell consisting of an anode half element, a cathode half element and one of the two half elements from each other separating ion exchange membrane, form a construction unit for the construction of an electrolyser, the construction unit in filter press technology is formed from an anode half-element of an electrochemical cell and a cathode half-element of an adjacent electrochemical cell, the two half-elements being arranged back to back to each other. In the Filteψressentechnik an electrochemical cell is therefore formed from a half element of one Konsuτiktionsemheit and a half element of the adjacent construction unit, the two half elements, which form an electrochemical cell, are separated from each other with an ion exchange membrane.

The frame-shaped support element, into which the two half-shells of two adjacent electrochemical cells are inserted and which together with the two half-shells and the connecting elements and the two electrodes, which serve as cathode and anode, form the constructional unit according to the invention, preferably consists of metal, in particular made of steel or one with plastic, e.g. Polyvinylidene fluoride (PVDF) or polyvinyl chloride (PNC), coated steel.

The half-shells each consist of a base and a circumferential, preferably angled, edge with which they are inserted into the carrier element. The peripheral edge lies on the support element. The two half-shells, the anode half-shell and the cathode half-shell, are inserted into the carrier element in such a way that the half-shells lie back to back to one another, i.e. the bottoms of the half-shells lie against one another with their outer sides (rear walls). The half-shells can be manufactured as two separate components, which are connected to one another either releasably or non-releasably. Alternatively, the half-shells can also be formed in one piece. The half-shells are preferably releasably connected to one another.

The bottoms of the half-shells have openings for receiving the connecting elements. If the half-shells are placed together with their rear walls, the openings in the half-shells come to lie on top of one another. This makes it possible to guide the connecting elements through the half shells. The openings can be of any shape, e.g. to be round, angular.

To form the two half-elements of a constructional unit according to a preferred embodiment by means of two half-shells and to connect them by means of a detachable connection has the advantage over a simple partition between the two half-elements, as is known, for example, from EP-A 0 999 294, that a single half-shell can be removed from the design unit and exchanged for another. This makes retrofitting or repair easier if the electrolyser is damaged. The two half-shells of the half elements can be identical. But they can also have different depths. A gas diffusion electrode is preferably used as the cathode in the construction unit. In this case, the cathode half-shell is preferably less deep than the anode half-shell, which saves material on the one hand and space for the electrolyzer on the other.

If different materials are used for the half-shells and the support element, the different thermal expansion of the materials must be taken into account. This applies in particular to the selection of the dimensions of the two half shells made of plastic in relation to the dimensions of the metal support element made of metal and their openings for receiving the connection elements made of metal in relation to the diameter of the connection elements. The electrolysis of an aqueous solution of hydrogen chloride is preferably carried out at temperatures from 30 to 70 ° C.

According to the invention, at least one of the half-shells contains plastic. Both half shells are preferably made of plastic, in particular polyvinyl fluoride (PVDF), polytetrafluoroethylene (PTFE) or chlorinated polyvinyl chloride (CPVC). The advantage of the present invention is therefore that essential structural components of the electrolyzer consist of corrosion-resistant, in particular hydrochloric acid-resistant and at the same time inexpensive materials.

The connecting elements can be bolts, pins, screws or the like. his. The two half-shells are preferably on at least one end of the connecting elements, e.g. releasably connected by means of a screw-nut connection. The connecting elements are preferably bolts, pins or the like, which have an external thread on at least one end and are connected with a threaded nut to the anode half-shell on the one hand and the cathode half-shell on the other.

The connecting elements also take over the function of the StiOm supply to the electrodes in the two half-elements. The connecting elements are therefore electrically conductive. In particular, the connecting elements are made of titanium, an acid-resistant titanium alloy or coated with an acid-resistant titanium alloy. The connecting elements preferably have a core made of a metal with high electrical conductivity, in particular copper, and a sleeve made of titanium or a titanium alloy, in particular a titanium-palladium alloy or titanium-ruthenium alloy. This embodiment of the connecting elements advantageously uses the high conductivity of the copper. The two electrodes, which serve as an anode and cathode, are attached to the connecting elements with low resistance. For example, they can be welded to the connecting elements, ie they cannot be releasably connected. This can be done, for example, by using a screw-like or bolt-like connecting element, in which the screw head fits into one of the half shells, for example. the anode half-shell, and the other end of the threaded connection element with the threaded nut in the other half-shell, for example the cathode half-shell, protrudes. Then the electrode, for example the anode, can be welded to the screw head of the connecting element. In a preferred embodiment, the electrodes are detachably attached to the connecting elements, for example by screwing. For this purpose, the connecting elements have a thread on at least one end. The detachable connection of the electrodes to the connecting elements is advantageous because the electrodes can be installed and removed with relatively little effort if they have to be replaced due to wear of the electrochemically active coating or damage. In a further preferred embodiment, the electrode serving as the anode is not detachably connected to the connecting elements, for example by means of welding, while the electrode serving as the cathode, in particular a gas diffusion electrode, is detachably connected to the connecting elements, for example by means of screws.

The number of connecting elements depends on the material and thickness they are made of and the transverse conductivity of the anode and cathode. The higher the electrical conductivity of the material and the transverse conductivity of the electrodes, the fewer bolts are required. In addition, the thinner the connecting elements, the more connecting elements are used. The distance between two adjacent connecting elements is in the range of 10 to 20 cm.

The anode consists, for example, of titanium, a titanium alloy, in particular a titanium-palladium alloy, which consists, for example, with an acid-resistant coating based on a ruthenium-titanium mixed oxide or ruthenium-titanium-iridium oxide. The cathode can be constructed similarly to the anode. However, it can also be equipped with other ^coatings' depending on the application. In the case of a gas diffusion electrode as the cathode, a material corresponding to the anode can be used as a carrier for the coating containing the catalyst. For example, a gas diffusion electrode can be used which contains a platinum group catalyst, preferably platinum or rhodium. Examples include gas diffusion electrodes from E-TEK (USA), which have 30% by weight platinum as a catalyst on a carbon substrate with a noble metal coating of 1.2 mg Pt / cm ² . In a preferred embodiment, the gas diffusion electrode is operated as an oxygen consumable cathode. In addition to the connecting elements, pin-shaped spacer elements are preferably provided between the anode half-shell and the anode and / or between the cathode half-shell and the cathode. These spacer elements prevent any deformation of the electrodes or the half-shells, so that the distance between the anode and cathode remains constant. The spacer elements can, for example, be pin-shaped or the like as T or Z profiles. be trained. For example, they can consist of plastic and be made in one piece with the half-shells. However, they can also be connected to the half-shells on the one hand and the electrodes on the other hand in any other way. If the spacer elements are also used for better current distribution, they are electrically conductive. The spacer elements can be connected to one another by means of cross-connection elements. The cross-connection elements can be wires, nets, fabrics or the like. his. The cross-connection elements can be electrically conductive in order to improve the current distribution.

The frame-shaped support element has e.g. channel-shaped openings for the supply and discharge of electrolyte and / or gas. In the case of conventional electrodes as cathodes and anodes, a supply and discharge of electrolyte as well as a discharge of the chlorine is required for each half-shell and in the anode half-element. If necessary, the chlorine can also be removed together with the electrolyte. If a gas diffusion electrode is used as the cathode, gas must be fed into the cathode half element and excess gas and liquid must be removed from the cathode half element. In the e.g. channel-shaped openings in the carrier element are e.g. Pipes introduced, which are either releasably or non-releasably connected to the respective half-shell. For example, the tube can be flanged at the end lying inside the half-shell, so that it is pushed into the opening from the inside of the half-shell.

When assembling several construction units according to the invention into an electrolyzer according to the filter press principle, the frame-shaped carrier elements are pressed against one another. In addition, the construction units can be sealed off from one another with commercially available media-resistant seals, such as PTFE or PTFE-containing sealing materials.

The invention is explained in more detail below with reference to the accompanying drawings. Show it:

Fig. 1 shows a schematic cross section through the coristruction element according to the invention

FIG. La shows an enlarged detail from FIG. 1 2 shows a schematic section of the design element according to FIG. 1, which shows in cross section the half shells, a first preferred embodiment of a connecting element and the electrodes.

FIG. 1 shows in cross section a frame-shaped support element 10 and two half-shells 12, 14 which are inserted back to back into the support element 10 in the area of the base 11, 13. The circumferential, angled edge 17, 18 of the half-shells 12, 14 lies on the carrier element 10. Openings 16, 19 in the carrier element and openings in the half-shells are provided for the supply and / or discharge of electrolyte and / or gas. 1 shows a channel-shaped opening 16 in the carrier element 10 and an opening 19 in the edge 18 of the half-shell 14. In the opening 16 and the opening 19 there is a tube 23 for the supply or discharge of electrolyte and / or Arranged gas. In the embodiment shown, the two half-shells 12, 14 are detachably connected to one another with the aid of connecting elements 30. The connecting elements 30 pass through openings 15, 15 'lying one above the other in the bottoms 11, 13 of the half-shells 12, 14 and protrude into the half-cells which are formed by the half-shells 12, 14. Electrodes 42, 44 are attached to the connecting elements.

FIG. 1 a shows an embodiment of a supply or discharge of electrolyte and / or gas in an enlargement of a section from FIG. 1. A channel-shaped opening 16 is arranged in the carrier element 10. The half-shell 14 has an opening 19 in its edge 18, which coincides with the opening 16. In the opening 16 and the opening 19 there is a, in particular metallic, tube 23. The tube 23 has a flange 25 at the end which points into the half-shell. The tube 23 is at the edge 18 of the half-shell 14 by means of a screw 22 attached. A seal 24 is provided between the screw 22 and the edge 18 of the half-shell 14.

FIG. 2 shows an exclusion from the construction element according to the invention according to FIG. 1. The half-shells 12, 14 lie against one another in the area of the bases 11, 13 and have openings 15, 15 'which overlap. The openings 15, 15 'accommodate a connecting element 30. The embodiment of the connecting element 30 shown in FIG. 2 is similar to a screw. The two ends of the screw-like connecting element 30 protrude into the space formed by the respective half-shells 12, 14. The two half-shells 12, 14 are detachably connected to one another with the aid of the connecting elements 30. In the embodiment shown in FIG. 2, the connecting element 30 has an external thread 32 at one end 31, so that the connection is made at this end 31 by means of a screw-nut connection 34. The other end 33 of the connecting element 30 has a head 35, whose diameter is larger than the diameter of the openings 15, 15 '. It prevents the connecting element 30 from sliding through the openings 15, 15 'of the half-shells 12, 14. A seal 52 is provided between the half-shell 12 and the nut 34. ^• In an analogous manner, there is a seal 54 between the half-shell 14 and the head 35 of the connecting element 30. It is also possible, both ends 31, 33 of the connecting element 30 analog with an external thread to provide 32 and the two half shells 12, 14 by means of a Screw-nut connection analog 34 to connect. In the embodiment shown, the connecting element 30 has a core 38 made of copper and a shell 39 made of titanium or a titanium alloy, which completely surrounds the core 38.

FIG. 2 also shows an embodiment of a detachable connection of the electrodes 42, 44 to the connecting element 30. The connecting element 30 has an internal thread 36, 37 at both ends 31, 33, so that the electrodes 42, 44 are connected to the Connecting element 30 are connected. Alternatively, at least one of the electrodes 42, '44 can also be connected to the connecting element 30 by welding. The electrode serving as the anode is preferably connected to the connecting element 30 by means of welding. .

In FIG. 2, spacer elements 52, 54 and cross-connection elements 53, 55 are also shown. The, for example, electrically conductive spacer elements 52, 54 are each located between the half-shells 12, 14 and the electrodes 42, 44. They are essentially perpendicular to the half-shells 12, 14 and the electrodes 42, 44. They prevent the electrodes 42 from bending, 44 between the connecting elements 30 and thus ensure a uniform distance between the half-shells 12, 14 and the electrodes 42, 44. The spacing elements 52, 54 are pin-shaped in the embodiment shown. The cross-connection elements 53, 55 can e.g. also be electrically conductive and connect the spacing elements 52, 54 to one another. This increases the current distribution. The cross-connection elements are wires, nets, fabrics or the like.

Claims

claims

1. construction unit for bipolar elelctiolysers according to the Filteipressentechnik, at least comprising a first half-shell (12), a second half-shell (14) and a ralxmeniform carrier element (10), at least one of the half-shells (12, 14) containing plastic, the two half-shells (12, 14) are arranged within the carrier element (10) such that the rear wall of the first half-shell (12) and the rear wall of the second half-shell (14) lie against one another, the carrier element (10) and the two half-shells (12 , 14) have at least two openings (16, 19) for the supply and discharge of electrolyte and / or gas and the two half-shells (12, 14) in the bottom (11, 13) are overlapping openings (15, 15 ') for receiving at least one electrically conductive connecting element (30) to which a first electrode (42) is fastened in the first half-shell (12) and a second electrode (44) in the second half-shell (14).

2. Construction unit according to claim 1, characterized in that the two half-shells (12, 14) are detachably connected.

3. Construction unit according to claim 2, characterized in that the two half-shells (12, 14) are releasably connected to at least one end of the connecting elements (30) by means of a screw-nut connection (34).

4. Consumption unit according to claim 1, characterized in that the two half-shells (12, 14) are formed in one piece.

5. Constuction unit according to one of claims 1-4, characterized in that the first electrode (42) and / or the second electrode (44) are detachably connected to the connecting elements (30).

6. Construction unit according to claim 5, characterized in that the connecting elements (30) have an internal thread (36) on at least one end and the first electrode (42) and / or second electrode (44) with screws (43, 45) are releasably connected to the connecting elements (30).

7. Construction unit according to one of claims 1-6, characterized in that spacer elements (52, 54) between the first half-shell (12) and the first electrode (42) and / or between the second half-shell (14) and the second electrode ( 44) are provided.

8. Construction unit according to claim 7, characterized in that the spacer elements (52, 54) are electrically conductive and are connected to one another by means of electrically conductive cross-connection elements (53, 55).

9. Construction unit according to one of claims 1-8, characterized gekennzeiclmet that both half-shells (12, 14) contain plastic, preferably polytetrafluoroethylene, PVDF or CPVC.

10. Construction unit according to one of claims 1-9, characterized in that the carrier element (10) made of metal, in particular steel.

11. Construction unit according to one of claims 1-10, characterized in that the connecting elements (30) made of a core (38) made of copper and a shell (39) made of titanium or a titanium alloy, in particular a titanium-palladium alloy or Titanium-ruthenium alloy.

12. Construction unit according to one of claims 1-11, characterized in that one of the two electrodes (42; 44) is a gas diffusion electrode.