DE1588192A1 - Switching arrangement for reporting and eliminating short circuits on electrolytic cells - Google Patents

Description

FARBENFABRIKEN BAYER AG

LE VIRKU S E N -ieyerwerk Patcot Abbey Mr / rh

Switching arrangement for reporting and eliminating short circuits

on electrolysis cells

The invention is directed to a switching arrangement for the prevention and automatic elimination of short circuits Electrolysis cells, in particular chlorine electrolysis cells, the change in cell voltage as it arises and as it disappears Short circuit is exploited.

When producing chlorine in electrolysis cells, e.g. that work according to the amalgam process, the yield depends on the individual on the use of electrical energy, essentially the distance between the graphite or metal anodes and the mercury cathode away. So if one strives for economic reasons to keep this distance small, the J inevitably increases Number of short circuits that occur as a result of individual anodes being immersed in the mercury level. Such short circuits lead to local overheating and must therefore be eliminated at short notice.

In Belgian patent specification No. 642.974 it is proposed that the very rapid voltage change on the one in operation Electrolytic cell, which in each case in the opposite direction

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Occurrence and disappearance of a short circuit occurs, to make visible and the voltage jump as an auxiliary feature to the optimal Setting the anodes to use. It is also proposed to observe the voltage change with an arrangement which consists of a capacitor and a galvanometric relay connected in series. For the purpose of reporting and Eliminating short circuits, this arrangement has several disadvantages. For example, certain operational processes, such as rapid load changes or the like, misleading short-circuit messages trigger. Electroplating systems are also used by the strong magnetic ones that are present in the vicinity of the electrolytic cells Fields affected. They must therefore either be shielded in a complex manner or housed at a sufficient distance from the cells will. The voltage potential of the electrolysis cells towards the end, which is sometimes high, depending on the size of the system, is therefore easy dragged to other parts of the system, for which special safety precautions are required. Sudden increases in voltage are not a sure sign that in the cell in question no longer has a short circuit. For example, touch two or more in the same cell in quick succession If the anode rods the mercury surface, the voltage increase occurs when the anode group is raised, as soon as only one of the anodes from which mercury emerges. If you ended the superscript at this point, you could not recognize further short circuits caused serious damage and malfunctions will.

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It has now been found that these disadvantages can be overcome according to the invention can be remedied by detecting the change in cell voltage with a monostable or bistable electronic circuit.

According to a special embodiment of the switching arrangement the cell voltage from the electronic signaling and control device by interposing a direct current transformer galvanically isolated. Preferably the electronic circuit the difference voltage between the cell voltage and a reference voltage is supplied, with the mean value as the reference voltage the voltages of all the electrolysis cells in the same circuit are used. Ale has proven particularly suitable

1.

a switching arrangement in which the secondary sides of all resemble which are rom transformative tor en assigned to the electrolytic cells lying in the same circuit, single-pole (eg minus-sei tig) are guided on a common reference point, while each of the other pole (for example plus- side) tapped cell voltages are led via resistors with the same, sufficiently high and closely tolerated resistance value to a common star point, the voltage of which represents the mean value compared to the reference point, and that this mean value is fed to the individual signaling and control circuits via an electronic impedance converter as a reference value . The contribution of those electrolysis cells for which a short-circuit message is present is preferably taken out of the mean value formation by means of suitable switching elements, for example relay contacts. According to a further particular embodiment of the invention, the short-circuit message

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with a smaller difference between cell voltage and reference voltage (Ut, - U "approx. 0.5 volts) triggered by the change in the voltage difference over time, but with a larger difference (U _R - U ₂ approx. 0.5 volts) occurring during normal operation Maintain response to the absolute value of the voltage difference in a reliable manner. In a further development of the invention , the monostable or bistable electronic circuit controls a remotely controllable device for adjusting electrodes or groups of electrodes in the event of a short circuit in such a way that the electrode causing the short circuit is lifted from the mercury surface by a length that can be set or during a predeterminable running time of the adjustment drive.

Between the electrolysis cells 1 connected in series, the busbars are each as far as possible at the same point Taken from the voltage potential and fed to the commercially available DC voltage transformer 3 via fuses 2. This enables a safe separation of the downstream switching and control devices from the potential of the electrolysis circuit. the Minus-side connections of the transformer secondary side are with the Samne! rail 4 connected, while the plus-side connection each via the capacitor 5 with the control input of a monostable or bistable electronic switching stage 6 is connected. The monostable executed switching stage 6 is through a rapid voltage drop from the idle state to the working state reversed. It then automatically tips back into retirement after a specified period of time - regardless of whether the short circuit still exists or not. The bistable one

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Switching stage, on the other hand, remains in the working position after the short-circuit-induced cell voltage drop until it is controlled back into the rest position by the rapid voltage increase associated with the disappearance of the short circuit. DC transformer and electronic switching stage are insensitive to magnetic DC fields, so that the installation location in this respect can be freely granted. The signal unit 7 and later are to be described on the electronic switching stage 6 Bende control stage 8 for the anode adjustment device 9 connected. The signal unit 7 is set up so that the signaling regardless of the duration of the input pulse up to Acknowledgment by the system personnel is retained.

In order to make the arrangement insensitive to operationally-related rapid changes in the cell voltage, such as those during a Load changes can occur, the input of each switching stage 6 is not the respective cell voltage, but the difference between the cell voltage and one on busbar 10 Reference voltage applied. This reference voltage is the span * Average value of all electrolysis cells in the same circuit 1 and therefore changes with the system load like the individual voltages, so that even with rapid load changes there is no sufficient voltage difference for a signaling and control device to respond incorrectly.

The individual cell voltages are used to calculate the mean value the opening contact 11 controlled by the switching stage 6 and one closely tolerated high resistance 12 of e.g. 10 ohms to the

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Busbar 13 out. From there the mean is about a Impedance converter 15 is supplied to busbar 10 with a ratio of 1: 1.

As soon as a switching stage 6 is in the working position as a result of a short circuit is controlled, the contact 11 opens, and the voltage of the disturbed cell is removed from the averaging. This is especially important for the Pail that has an electrolytic cell is de-energized for operational reasons by bridging the power supply lines. So in such a case the Switching stage 6 cannot jump back into the rest position, the capacitor 5 is bridged by a silicon diode H. As soon the row voltage in question is lower than about 0.5 volts is than the reference voltage, the diode becomes conductive and thus prevents the switching stage from falling back into standby.

The control stage 8 has the following mode of operation for the anode adjustment device: As soon as an electrode short circuit brings the switching stage 6 into the working position, a self-holding system is excited in the control stage 8. Independently of the length of the output pulse of the switching stage 6, this controls the anode adjustment system belonging to the cell concerned in the upward direction until a predeterminable height difference or an adjustment time approximately corresponding to this height difference has been reached. Difference in height or adjustment time are selected to be so large that an anode short-circuit after the adjustment has been completed is, according to experience, safely eliminated. Further interventions, such as returning the anodes to the economically optimal setting, can preferably be left to the operating personnel. 909383/1014 Le A 10 565

Claims (7)

Patent claims: 1.) Circuit arrangement for the heating and automatic elimination of short circuits on electrolysis cells, especially chlorine electrolysis cells, whereby the change in cell voltage is used when a short circuit occurs and disappears, characterized by the detection of the cell voltage change with a monostable or bistable electronic circuit. 2. Switching arrangement according to claim 1, characterized in that the cell voltage from the electronic signaling and control device is galvanically isolated by interposing a DC transformer. , 3. Switching arrangement according to claim 1 or 1 and 2, characterized in that that the electronic circuit the differential voltage between the cell voltage and a reference voltage is supplied, with the mean value of the voltages of all electrolysis cells lying in the same circuit as the reference voltage serves. 4. Switching arrangement according to Claims 1 to 3, characterized that the secondary sides of all DC transformers, which are assigned to the electrolysis cells lying in the same circuit are single-pole (e.g. on the minua side) at a common reference point are guided, while each at the other pole (e.g. positive side) tapped cell voltages via resistors with 909883/1014 Le A 10 565 always the same, sufficiently high and closely tolerated resistance value are led to a common star point, the voltage of which represents the mean value compared to the reference point, and that this mean value is fed to the individual reporting and control circuits as a reference value via an electronic impedance converter will. 5. Switching arrangement according to claim 1 to 4, characterized in that by means of suitable switching elements such as relay contacts the contribution of such electrolysis cells for which a short-circuit message exists, from which averaging is taken 6. Switching arrangement according to claim 1 to 5, characterized in that the short-circuit message is _{triggered with a smaller difference between cell voltage and reference voltage (Ug - U 2} approx. 0.5 volts) by the temporal change in the voltage difference, with a larger difference that does not occur in normal operation (U _R - U "approx. 0.5 volts), however, is reliably maintained by responding to the absolute value of the voltage difference. 7. Switching arrangement according to claim 1, characterized in that the monostable or bistable electronic circuit is a remotely controllable device for adjusting electrodes or groups of electrodes controls when a short circuit occurs in such a way that the electrode causing the short circuit around a predeterminable Amount of length or is lifted from the mercury surface during a predeterminable running time of the adjustment drive. τ α, λ c »809883/1014 Le A 10 565