DE1027819B - Electrode arrangement for power transmission on salt baths - Google Patents

Description

GERMAN

The invention relates to an electrode for transmitting electricity to salt baths or the like Liquid baths. With such electrodes, the current is transferred from the electrode to the liquid salt not evenly. As is well known, the current transfer is important near the bath surface stronger than at the bottom of the electrode. At the point of highest surface loading, i.e. H. so close to the bath surface, the electrode is particularly stressed; also are at the transition area Strong corrosion effects exist between molten salt and air, so that at this point the electrode material is destroyed much more quickly than in the rest of the electrode.

This disadvantage is more noticeable in deep baths. In addition, as a result of the differently strong current transfer along the electrode undesired temperature differences between the upper and lower part of the bath. The temperature equalization through convection of the liquid But salt is only very imperfect in deep baths.

One knows electrode designs in which to avoid these disadvantages or to increase the Lifetime of the electrode insulates the power supply for the electrode from the top of the bath inserted and connected to the hollow electrode below the bath level, with the power supply is arranged within the electrode. In this way one achieves an upwardly decreasing one Surface loading, d. H. the highest current load and the highest chemical stress on the The separating layer between the molten salt and the outside air no longer coincide locally.

It is also known, in such electrode designs, the upper sleeve edges of the electrodes to connect permanently or only during the heating process or to connect them to one to connect the inner electrode of the sleeve in question opposite polarity, so that the The sleeve itself and its inner electrode act as an ohmic resistance and, when heated, the melting process can initiate.

Finally, there are also electrically heated salt bath stoves known with U-shaped or W-shaped electrodes, in which during operation the two upper ends of each U-shaped and the three upper ends of each W-shaped electrode through Parallel connection to the lead to the electrode are connected and the ends of the electrodes like this are connected to a switching device that the electrodes also serve as resistance heating elements can.

In this known electrode arrangement, in the electrode arrangement
for power transmission to salt baths

Applicant:

Brown, Boveri & Cie. Aktiengesellschaft, Mannheim-Käfertal, Boveristr. 22nd

Dipl.-Ing, Johannes Faltin, Dortmund-Aplerbeck,
has been named as the inventor

all connection points are above the bath level, the individual electrode legs will probably be the same heavily loaded. However, the disadvantage mentioned at the beginning remains that the places of the highest surface load due to the current transfer. all connection points near the bath surface lying, d. H. where the highest chemical stress occurs at the same time, so that Here, too, uneven wear of the electrode material occurs.

It is the object of the invention to provide an electrode arrangement for power transmission to salt baths or To create similar liquid baths, while avoiding the disadvantages mentioned as possible uniform current transfer from the electrode to the liquid takes place, so that a particularly favorable Distribution of the surface load is achieved.

In the case of an electrode arrangement in which, in a manner known per se, two or more connection points are provided along the electrode, at least one of which is below the bath level according to the invention, during normal operation at least one of the under the bath level lying connection points in parallel with at least one connection point above the bath level connected to the power source.

In the arrangement according to the invention, the operational parallel connection of upper and Connection points of the electrode lying below the bath level compared to the known arrangements a more even distribution of the surface load and thus a more even load or wear along the entire electrode.

You can make the electrode hollow and at least one power supply isolated through the hollow

7C9 959/356

room through to one below the bathroom mirror Lead connection point. According to a further embodiment of the invention, switching means can be used provide with which the connection points of the individual electrodes, which are connected in parallel in normal operation preferably connected to points of different potential while the bath is being heated up so that the electrode acts as a resistance heater. According to the invention, you can Form the electrode so that it is on part of its length, preferably in the middle part, between the power connection points a reduced cross-section and thus an increased ohmic resistance having.

In Figs. 1 to 3, an embodiment of the invention is shown.

Here, 2 denotes a hollow design, preferably made of iron or an iron alloy tubular electrode, 1 a power supply at the upper edge of the electrode. At 3 the electrode is with a second power supply line 4 made of a material that conducts electricity well, which is known per se Way is insulated through the cavity of the electrode.

The connection point 3 does not need to be at the lower end of the electrode, but it can also be located some distance from this end.

The conductor 4 lying within the electrode can be provided with a bore and through it conduct a coolant. You can see the space between the tubular electrode 2 and the Power supply bolt 4 with a heat insulating mass, for. B. Kieselguhr, fill in. By application With this thermal insulation, the heat losses caused by the cooling can be small being held. In particular, such a design of the electrode allows the conductor 4 also with Baths, the temperature of which is above the melting point of copper, are still made of this highly conductive material To manufacture material.

Fig. 3 shows the circuit arrangement of a salt bath furnace for heating up and normal operation. The electrode arrangement shown is suitable for connection to three-phase alternating current. The three electrodes 5, f>, 7 correspond in their design to FIGS. 1 and 2. They are connected to the secondary windings 11, 12, 13 of a transformer via a changeover switch 8, 9, 10 each. The fully extended position corresponds to the working position in which both connection points of each electrode are at the same potential. In this position, the switches 14, 15, 16, which establish the connection to the neutral point 17 of the transformer, are closed.

To start heating of the bath, the switches 8, 9, 10 brought into the position shown in broken lines, so that the inner and outer power supply, each electrode 5, 6, 7 to ^r \ erschiedenem potential will lie. Each of the individual circuits is then closed for itself via the corresponding electrode. The electrodes heat up, so that the neighboring salt melts.

In the heating position, switches 14 to 16 are open. This prevents during During the heating process, current also flows through the bath, which leads to an overload of the transformer could lead.

However, if the system is designed or the transformer is dimensioned so that the aforementioned additional load in the heating position during the melting of the salt is harmless, so can switches 14, 15, 16 can be dispensed with.

In order to increase the ohmic resistance of the tubular electrode, according to the invention the wall thickness of the tube in its central area be smaller without affecting the Working electrode or its resistance to wear and tear during normal operation is impaired is because when the working circuit is switched on, less current flows in the middle part of the electrode than at the electrode ends.

You can use the transformer circuit z. B. also according to Fig. 4 so that the electrodes in Heating up can be fed via the transformer taps during the heating up process to work with lower voltage.

To increase operational safety, it can be useful to switch over the electrodes from the heating circuit in the operating circuit serving switches 8 to 10 and 14 to 16 in such a way or to couple with each other that inevitably either only heating currents within the electrodes or only currents can flow through the bath.

The invention is not limited to the exemplary embodiment described. Above all, it can the electrode can be designed differently than shown in the drawing. There are also cases possible where another electrode material, e.g. carbon, silicon carbide or similar materials, can come into question. In the context of the invention, other circuits than those in the Fig. 3 and 4 shown possible. For example, the transformer can be on the secondary side in the operating position be connected in a triangle or alternatively in star or delta. Also leaves the number and Arrangement of the electrodes different variants too. The advantages of the invention come regardless of whether the electrodes or electrode arrangements are connected to single-phase or multi-phase alternating current networks or connected to a DC power source.

The invention can also be applied to any practically occurring temperature installation.

Claims (8)

Claims 1. Electrode arrangement for power transmission to salt baths or similar liquid baths with two or more connection points along the electrode, of which at least one is below of the bath level, characterized in that during normal operation at least one of the connection points (3) located under the bath level in parallel with at least a connection point located above the bathroom mirror is connected to the power source. 2. Electrode arrangement according to claim 1, characterized in that the electrode is hollow is formed and at least one power supply, isolated by the cavity, to a below the connection point located near the bathroom mirror. 3. Electrode arrangement according to claim 2, characterized in that the power supply to the connection point of the electrode located under the bath level and formed hollow a liquid is cooled. 4. Electrode arrangement according to claim 3, characterized in that the intermediate space between the hollow electrode and the current feed to the connection point below the bath level with a heat-insulating one Funds is filled. 5. Electrode arrangement according to one of the preceding claims with two connection points, characterized in that a power connection point at the end lying above the bathroom mirror and the other power connection point at or near the other end of the Electrode is arranged. 6. Electrode arrangement according to one of the preceding claims, characterized in that the electrode has a reduced cross-section over part of its length between the power connection points having. 7. Electrode arrangement according to one of the preceding claims, characterized in that Switching means (8 to 10, 14 to 16) are provided with which the connection points of the individual Electrodes - preferably while heating up the bath - with different points Potential and - preferably during normal operation - in parallel with Points of the same potential can be connected. 8. Electrode arrangement according to claim 7, characterized in that the switching means such are designed or coupled to each other that inevitably either only heating currents within the electrodes or only currents can flow through the bath. Considered publications:
German patent specifications No. 566 017, 896 836. 1 sheet of drawings