DE20204142U1 - Short-circuiting device for electrolysis cells - Google Patents

Description

drying. Ernst Stratmann

Patent Attorney
D-40212 Düsseldorf · Schadowplatz 9

13 March 2002

0203 Gm

Ritter Starkstromtechnik GmbH & Co. KG
57234 Wilnsdorf

Short-circuiting device for electrolysis cells

The invention relates to a short-circuiting device for the maintenance of electrolysis cells, with a frame having short-circuitable contact devices, which can be placed on a cell or a group of cells in such a way that the contact devices of the frame come into electrical contact with connection contacts of the cell or the group of cells, wherein the frame comprises contact arms supported by a support device and switching devices connected thereto.

Such a short-circuiting device is already known from the magazine "Minerales Revista", February 2000, pages 35 - 42.

This journal article describes the development of a new type of short-circuiting frame equipment for electrolysis cells used to produce pure copper. The short-circuiting arrangement can be used to shut down cells that have to be taken out of service for maintenance purposes, for example, whereby the short-circuiting arrangement

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allows the unaffected cells to continue working, i.e. the electrical current does not have to be interrupted. This makes the copper electrolysis process more effective and optimal. However, the arrangement is very heavy and therefore difficult to handle.

From DE 198 13 557 A1 a disconnector is known which operates by means of a pneumatic drive and can switch high currents.

European patent specification 0 012 752 (corresponding to WO 79/00670) describes a high direct current short-circuiter and enables one cell in a series of electrolytic cells intended for the production of chlorine or aluminium to be isolated and dismantled, for example, without interrupting the operation of the other cells. The short-circuiter described in the specification is equipped with two sets of moving contacts controlled by a common shaft and cooperating with two current-carrying assemblies comprising a deformable part and cooled by water circulating in housings.

The object of the invention is to improve the short-circuiting device for electrolysis cells known from the first-mentioned publication, in particular in such a way that the weight of the short-circuiting device is reduced and the device is therefore easier to handle, but also cheaper to manufacture. In a further development, the current losses should be reduced, which serves to save energy. Furthermore, the short-circuiting device itself should require less maintenance and provide a longer service life for the contact devices.

The main object of the present invention is achieved by connecting the contact arms to a fluid cooling device. This allows the cross-section of the contact arms, which are made of copper for example, to be drastically reduced, for example to 25%.

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The weight of the short-circuiting device designed according to the invention is lower, which improves mobility and other handling. In addition, the risk of damage to the connection contacts of the cell(s) is reduced. In addition, it is cheaper to manufacture, and above all less copper material is required.

According to a further development of the invention, the switching devices comprise pre-contacts and main contacts, and at least the main contacts are in thermal connection with the fluid cooling device. This also creates the possibility of working with smaller copper cross-sections and thus making do with a lower weight, apart from the fact that the combination of pre-contacts and main contacts enables particularly high switching rates.

Preferably, the switch devices are arranged at one end of the contact arms, which also makes handling easier. However, switch devices can also be provided at both ends of the contact arms, which in turn serves to reduce weight, since the cross-sections of the copper contact arms can be reduced (also towards the other end).

Maintenance work can be accelerated by arranging several contact devices along the length of the contact arms according to a further development of the invention. This means that entire groups of cells can be short-circuited simultaneously.

According to yet another development of the invention, the current-carrying cross section of the contact arms is designed to increase with each contact device in the direction of the switching devices, which means an adaptation to the actual current load and thus in turn represents a construction that is as effective and thus as weight-saving as possible.

The frame can have electrically insulating spacers between the contact arms

which increases the stability of the overall arrangement without the risk of operational disruptions due to misdirected currents.

For better handling, according to yet another embodiment of the invention, the frame has fastening devices, such as crane lifting eyes, for a transport device.

Funnel-shaped inlets on the frame and/or the cells serve the same purpose. In particular, four guide pins are used to precisely position the frame on the edge of the cell.

The frame preferably comprises a steel structure as a supporting element, as well as a contact arm arrangement made of copper, which is attached to the steel structure via electrically insulating connecting devices.

Springy metal strips made of copper or similar have proven to be effective for the contact devices that come into contact with the cell.

With regard to the switching devices, pneumatic drives are preferred, as they are particularly robust in environments filled with corrosive gases. However, manual drive or drive by means of an electric motor is also possible.

Sensor devices for the temperature of the fluid, such as cooling water, can be arranged in the frame, the measuring signals of which are fed to a central control and monitoring device.

Likewise, sensor devices for current and/or voltage or voltage drop can also be arranged on the frame, the measuring signals of which can also be fed to a central control and monitoring device.

This central control and monitoring device can be located on the frame or remotely from it and could also control the fluid circulation, e.g. a circulation pump for cooling water.

This central control and monitoring device can also time the movement of the main switching contacts as well as any pre-switching contacts present in order to extend the service life of these contacts.

The invention is explained in more detail below using embodiments shown in the drawings.

It shows:

Fig. 1 shows a top view of a

Short-circuiting device for the maintenance of electrolysis cells, at one end of which a switch device is provided;

Fig. 2 in a front view of the short-circuiting device according to Fig. 1

to explain the switch device.

Fig. 3 and Fig. 4

in similar views to Fig. 1 and Fig. 2, a short-circuiting device for the maintenance of electrolytic cells, which is provided with two switch devices at both ends;

Fig. 5 in an enlarged view compared to Fig. 4 the pneumatic

operable switch device with four pre-contacts and six main contacts;

Fig. 6 is a further illustration to explain the contact arrangement; and

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Fig. 7 is a cross-sectional view taken along line VII-VII of Fig. 1.

In Fig. 1, a plan view of a short-circuiting device 10 for the maintenance of electrolysis cells, not shown, can be seen, which is provided with a frame 16 having short-circuitable contact devices 14, which can be placed on a cell or on a group of cells in such a way that the contact devices 14 come into electrical contact with the terminals of the cell(s), the frame 16 comprising contact arms 20 supported by a support device 18 and a switch device 22 connected to them. As the enlarged sectional view along the section line VII-VII of Fig. 1 in Fig. 7 shows, the contact arm 20, which has an angular profile shape in cross section, for example, comprises a pipe 24 welded or soldered into the angle, through which a cooling fluid, such as cooling water 26, can flow. The soldering material between the pipe 24 and the angle 20, or 28, 30, establishes an intimate thermal contact between the wall of the pipe 14 on the one hand and the material of the angle 20 on the other hand, so that heat generated by current flow within the angle 20 can be transferred via the pipe wall 24 to the coolant, such as cooling water 26, and thus dissipated.

The connection contact 32 of an electrolysis cell, which is indicated schematically in Fig. 7, is connected to the angle profile of the contact arm 20 via a contact lug 34 consisting of resilient copper material, which, by spring pressure, establishes a secure contact between itself and the connection contact 32 when the frame 16 is lowered.

In addition, Fig. 7 shows angle stiffeners 35, which also hold the tube 24 and provide heat conduction to the lower end of the angle.

The contact arm 20 shown on the right in Fig. 1 has, for example, according to the illustration therein 64 contact lugs 34, which are connected to corresponding contact terminals or connecting lines 32 of the

electrolysis cells not shown in detail. Accordingly, on the left-hand side of Fig. 1 there is a contact arm 120 which is connected to electrolysis cell contact connections via suitably designed contact lugs, whereby, for example, the positive connections of electrolysis cells are contacted via the contact arm 20, while the contact arm 120 engages the corresponding negative connection contacts of these electrolysis cells with its lugs. Two connection rails 36 and 136 lead from the contact arms 20, 120 to a high-current switch device 22 which can be seen in a view from above according to Fig. 2 in Fig. 5 and is shown in a perpendicular representation in Fig. 6.

The switch device 22 shown in Fig. 5 and 6 comprises one or more, here four, pre-contacts 38 and one or more, here for example six, main contacts 40. The switch device 22 can in principle represent the construction which is described in more detail in DE 198 13 557. For example, a pneumatic drive 42 is provided which can rotate a shaft 44 back and forth, for example. The shaft 44 is in turn connected to lever or eccentric devices not shown in detail here, which can move contact disks 48, 148 up and down by means of slotted guides 46, 146 according to Fig. 6, which are screwed to the end 52, 152 of the connecting rail 36, 136 via flexible connecting lines 50, 150, see reference number 154. This end piece 52, 152 can also have a cooling water bore 56, 156 through which cooling water, generally: cooling fluid, see arrow 58, 158, can be supplied in order to cool both the connecting lines 50, 150 and then, when passing into the connecting rod or rail 36, 136, see arrow 57, 157, this current-carrying connecting rod and then the contact arms 20, 120. to cool, see arrow 26.

On the right side according to Fig. 5 and 6 there are rigid connecting lines 51, 151 which connect fixed contact disks 49, 149 in an analogous manner to the end 52 of the connecting rail 36.

Here, there is a coolant circuit via the arrow 58, 158 through a bore 56, 156 arranged in the end 52, 152, which opens into the pipe 36, 136.

If the switch 22 is actuated (e.g. by the pneumatic drive 42), it rotates the shaft 44 and displaces, for example, the contact carriers 60, 160 and thus the movable contact disks 148, 48 carried by it outwards, whereby a gap is created between the contact disks 48, 49 and 148, 149, which interrupts the flow of current.

If the shaft 44 is rotated again, e.g. in the opposite direction, the two contacts close again.

The pre-contacts 38, which are connected to the end pieces 52, 152 via lines 64, 164 or 66, 166 via corresponding screw connections, designated 65, operate accordingly.

The switch shown in Figs. 5 and 6 is used in the embodiment according to Figs. 1 and 2, wherein in Fig. 1 the three flexible connecting lines 50, 150 and the associated three fixed connecting lines 51, 151 can be seen, which can switch, for example, 3 x 12 kA, thus a total of 36 kA.

In Fig. 3 and 4, this load is distributed over two switches 122 and 222, respectively, so that these switches with their three main contact pairs only have to switch half the amperage (3 x 6 kA) and can be designed accordingly smaller or with fewer contact pairs.

These two switches 122, 222 are switched alternately to ensure even wear, so sometimes switch 122 is switched first, other times switch 222 is switched first.

With the possibility of short-circuiting 36 kA, 64 connection contacts can be connected to

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562.5 A can be switched per connection contact.

The size of the frame is adapted to the size of the electrolysis cell(s) to be bridged, for example the length of the frame is approx. 7 m and the width approx. 3 m.

Since the two contact arms 20, 120 have different potentials when the short-circuit switches are open, the spacers 68, 70, which are made of metal for example, are attached to them via insulating devices 72. In the embodiment shown in Fig. 1, the current within the contact arm 20, 120 is greater the closer one is to the switch 22. It can therefore be advantageous to increase the current-carrying cross-section of the contact arm as one approaches the switch 22.

Accordingly, in the embodiment according to Fig. 3, the cross-section could be increased starting from the center of the contact arms in the direction toward the two switches.

For better handling of the support structure of the frame 16, the support device 18 can be equipped with crane eyelets 74, which enable the attachment of a crane hook, see Fig. 7, where a further insulation 76 is also arranged between the support structure 16 consisting of a steel frame on the one hand and the current-carrying angle copper arms 20 on the other hand.

Not shown in detail here are any sensor devices that may be present for the temperature of the cooling water that flows through the frame, whereby the sensor devices will feed their measurement signal to a central control and monitoring device, which also senses the current or voltage or the voltage drop in the frame via other sensor devices. For example, the flow rate of the cooling water can be adapted to the current strength that the short-circuiter must transmit.

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The short-circuiting device according to the figure works as follows:
If a cell has to be cleaned after a certain time, the construction according to the invention is arranged by means of a hall crane on the electrolysis cell arranged in this hall and - for example supported by guide bolts and/or funnel-shaped guide devices - aligned in such a way that its contacts 34 rest on the corresponding connection contacts 32 of the electrolysis cell to be serviced. At this time, the switch devices 22, 122 are still open.

By means of a control device, for example, the switch 22 is now operated in such a way that the pre-contacts 38 and then the main contacts 40 are closed one after the other at intervals of a few milliseconds. The current no longer flows through the cell, but rather through the short-circuiting device due to the much lower contact resistance. The necessary maintenance work can now be carried out on the electrolysis cell, for example the cell can be cleaned of harmful deposits.

The connection contact 32 of an electrolysis cell shown in Fig. 7 is usually present several times per cell. For example, an electrolysis cell has 32 anode contacts and 32 cathode contacts inside. The cathodes are initially made of copper or stainless steel, on which copper is then deposited as a result of the electrolysis process. The anodes, which are made of lead, undergo an oxidation process (wear), whereby particles dissolve and a deposit forms, which must be removed every few months. This takes place during the short-circuited state, so that no disruptive current flow occurs within the electrolysis cell during cleaning.

Usually, two cells with their 32 contacts for the anode and 32 contacts for the cathode are short-circuited for maintenance purposes using the short-circuit frame according to Fig. 1 or Fig. 3, so that the current, indicated by the arrows 78, 80, no longer flows through the cells, but via the rails and arms 20, 36,

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the switch 22 and the rails and arms 136, 120.

In order to initiate the electrolysis process in the cell, a minimum voltage must be present between the cell terminals (anode, cathode). A specific switching sequence - when closing, first the pre-contacts, then the main contacts, when opening, first the main contacts, then the pre-contacts - reduces the amount of arcing. In addition, the cell and the rectifier connected to the cells as a power supplier are subjected to less load.

In addition, the energy stored in the magnetic field created by the frame current changes as the switch opens and closes. This cannot happen suddenly, but takes time.

These magnetic fields also generate strong forces that the frame construction must absorb. A hybrid construction made of steel and copper is therefore particularly suitable.

Claims (15)

1. Short-circuiting device ( 10 ) for the maintenance of electrolysis cells, with a frame ( 16 ) having short-circuitable contact devices ( 14 ) which can be placed on a cell or a group of cells in such a way that the contact devices ( 14 ) of the frame ( 16 ) come into electrical contact with connection contacts ( 32 ) of the cell or the group of cells, the frame ( 16 ) comprising contact arms ( 20 ) supported by a carrier device ( 18 ) and switching devices ( 22 ) connected thereto, characterized in that the contact arms ( 20 ) are connected to a fluid cooling device ( 26 ). 2. Short-circuiting device for the maintenance of electrolysis cells according to claim 1, characterized in that the switching devices ( 22 ) comprise pre-contacts ( 38 ) and main contacts ( 40 ), and that at least the main contacts ( 40 ) are in thermal connection with a fluid cooling device ( 56 , 156 ). 3. Short-circuiting device for the maintenance of electrolysis cells according to claim 1 or 2, characterized in that the switch devices ( 22 ) are arranged at one end of the contact arms ( 20 ) ( Fig. 1, 2). 4. Short-circuiting device for the maintenance of electrolysis cells according to claim 1 or 2, characterized in that switch devices are arranged at both ends of the contact arms ( 20 ) ( Fig. 3, 4). 5. Short-circuiting device for the maintenance of electrolysis cells according to claim 3 or 4, characterized in that several contact devices ( 14 ) are arranged along the longitudinal extension of the contact arms ( 20 ). 6. Short-circuiting device for the maintenance of electrolysis cells according to claim 5, characterized in that the electrically effective cross-section of the contact arms ( 20 ) increases with each contact device ( 14 ) in the direction of the switching devices ( 22 ). 7. Short-circuiting device for the maintenance of electrolysis cells according to one of claims 1-6, characterized in that the frame ( 16 ) has electrically insulating spacers ( 68 , 70 ) between the contact arms ( 20 ). 8. Short-circuiting device for the maintenance of electrolysis cells according to one of claims 1-7, characterized in that the frame ( 16 ) has fastening devices, such as crane eyelets ( 74 ), for a transport device. 9. Short-circuiting device for the maintenance of electrolysis cells according to one of claims 1-8, characterized in that the frame ( 16 ) comprises a steel structure ( 18 ) as a supporting structure, and a contact arm arrangement ( 20 ) made of copper, which is fastened to the steel structure via electrically insulating connecting devices ( 76 ). 10. Short-circuiting device for the maintenance of electrolysis cells according to one of claims 1-9, characterized in that the contact devices ( 34 ) coming into contact with the cells are resilient metal strips made of copper or the like. 11. Short-circuiting device for the maintenance of electrolysis cells according to one of claims 1-10, characterized in that the switching devices ( 22 ) are operated manually, electrically or pneumatically ( 42 ). 12. Short-circuiting device for the maintenance of electrolysis cells according to one of claims 1-11, characterized in that sensor devices for the temperature of the fluid, such as water, are arranged on the frame ( 16 ), the measuring signals of which are fed to a central control and monitoring device. 13. Short-circuiting device for the maintenance of electrolysis cells according to one of claims 1-12, characterized in that sensor devices for current and/or voltage or voltage drop are arranged on the frame ( 16 ), the measuring signals of which are fed to a central control and monitoring device. 14. Short-circuiting device for the maintenance of electrolysis cells according to one of claims 1-13, characterized in that a central control and monitoring device is provided on the frame ( 16 ) or remotely therefrom, which controls the fluid circulation. 15. Short-circuiting device for the maintenance of electrolysis cells according to one of claims 1-14, characterized in that a central control and monitoring device is provided on the frame or remotely therefrom, which controls the movement of the main switching contacts ( 40 ) and/or pre-switching contacts ( 38 ) in time.