DE2432691A1 - PROCEDURE FOR FINDING SHORT CIRCUITS IN MERCURY CELLS AND CALIBRATING THE CURRENTS - Google Patents

Description

Patent Attorney H / E / D (693)

Dr. Michael Hann 2432O3 I.

63 casting
Ludwigstrasse 67

PPG Industries, Inc., Pittsburgh, Pennsylvania, USA

PROCEDURE FOR FINDING SHORT CIRCUITS IN MERCURY CELLS AND CALIBRATING THE AMOUNTS

Priority: July 10, 1973 / USA / Ser. No. 377 993

According to one of the known processes for the electrolytic decomposition of saline solutions into sodium hydroxide and chlorine electrolysis is carried out in mercury cells. It is characteristic of mercury cells that they are conductive Surface is arranged slightly inclined from its horizontal. About this usually about 3.175 to about 6.35 mm thick plate, a film of mercury amalgam flows in its direction of inclination. That liquid mercury amalgam film is the cathode.

The electrolyte flows on the amalgam, ie the aqueous saline solution »The electrolyte normally has a layer thickness of around β ₉ 35 ram to around 5 cm at the beginning of the inclined plate ' and as a layer thickness of up to 25 or 30 cm at its end»

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Anodes, for example carbon anodes or metal anodes, are usually at a distance of 3.175 to Placed 4.762 mm above the surface of the mercury amalgam film. In this way, electricity can flow from the anodes through the electrolyte to the liquid mercury amalgam cathode flow. Constructively, a group of anodes is electrically movable on one against the cell body mounted on an insulated frame or carrier of another type. Several connected to a single power rail and anodes side-by-side across the width of the cell are referred to as an anode row. A group rows of anodes mounted on a frame or other carrier are referred to as an anode bank.

Normally in an electrolytic cell there is a selection of such anode banks along the longitudinal axis of a cell lined up. For example, between 12 and 30 rows of anodes can be used in a cell with a length of 18 to 21 ra be arranged in about 4 to 8 banks along the cell.

Several cells are usually arranged in series in a cell circle. Normally, two or more rows of cells are arranged side by side, the positive pole of an energy source being connected to the anodes of the last cell of the first row of cells and the negative pole of the energy source being connected to the cathode of the last cell of the last row of cells. Within a series, the cathodes of one cell are connected to the anodes of the next cell. With a margin upwards and downwards, 30 to 80 cells can be arranged in several rows of cells, connected in a cell circle,

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In a normally working electroysis cell with a mercury amalgam cathode, there is chlorine at the anode and sodium at the! cathode, whereby the sodium forms an amalgam with the mercury.

One has such with mercury amalgara cathodes when operating equipped cells, each of which contains several vertically movable rows of anodes, found that the current " flow from each individual anode to the cathode shows deviations from the total current flow through the cell Changes in the physical and electrical properties of amlagam, the formation of mercury compounds at the bottom of the cell, the formation of so-called "cell butter", the decrease in the electrolyte content the saline solution and the thermal expansion of the cell body and the material used for the cell. The anode banks can also get out of alignment due to various processes during operation of the cell.

Each of these factors or the interaction of several or all of the factors can cause a cell short circuit when the anode comes into contact with the mercury cathode. The consequence is an excessive current flow through the anode, which can be damaged as a result.

If *, furthermore, the anodes should get out of alignment , the current flow through the cell will be inconsistent,

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i.e. one row of anodes can carry significantly more current than an adjacent row of anodes. This leads to a uneven and sporadic cell operation and voltages higher than required for cell operation.

Short circuits can be eliminated by placing a single anode at a greater distance from the cathode increases as soon as the current flowing through it reaches or exceeds a preselected strength. Described is this way of working in German patent specification 2 107 305 and in Canadian patent specification 909 720. Other methods of eliminating short circuits in electrolysis cells with a liquid mercury cathode are in U.S. Patent Nos. 3,574,073, 3,644,190 and 3 689 398. In all of these procedures, the anode is removed from the cathode as soon as a short circuit begins has been determined by suitable measuring devices; however, there is neither a rearrangement of the anode in it In the working position, the cell is still being calibrated.

Several methods are known that aim at this are to arrange anodes in such a way that the current flow through the individual anodes is balanced when the cell is put into operation will. Thus, according to this method, all anodes can be arranged in such a way that they are kept lowered onto the cathode until the beginning of a short circuit is indicated, after which they are raised again slightly. Reference is made to this See, for example, U.S. Patents 3,361,654 and 3,396,090. Similarly, one has the anodes in a cell with a Arranged mercury cathode, and after measuring the resistance or conductivity of the saline solution, the electrodes

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adjusted accordingly. Corresponding processes are described in U.S. Patents 3,464,903 and 3,476,660.

It is also known to arrange individual anodes independently of other anodes in the cell in such a way that each anode a predetermined current flow passes through it. U.S. Patents 3,556,973 and 3,627,666 are cited in this regard.

It has now surprisingly been found that the first display shows one between a single anode and a individual cathode beginning short circuit in the busbar, which is assigned to the anode row with the anode in question the current flow is gradual compared to the other rows of anodes, i.e. compared to the average Current flow through the cell increases.

It was also surprisingly found that an electrolysis cell operated with a liquid mercury amalgam cathode with a lower average cell voltage when the current flow passing through each bank of adjustable anodes is within a preselected average s range of the currents flowing through each row of anodes is continuously measured and maintained.

According to the invention, a cell circuit consisting of several electrolysis cells with liquid mercury amalgam cathodes is provided operated in such a way that the current flow passing through each anode row of a cell is within a preselected Average range of the individual currents passing through all anode rows of the cell during a longer period

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Electrolysis time is maintained continuously. In this way, namely by having the currents flow through each individual Keeps the anode rows within a preselected average range, the anodes of the electrolysis cell in the Maintained balance, recognized the occurrence of short circuits and prevented them.

"Continuous maintenance" means the monitoring and regulation of a certain anode current flow with such a frequency that changes in the current flow are detected and corrected before they reach an undesirable level. For this purpose, each current flow is measured and regulated at time intervals that are less than the time constant of the anode flows. The time constant of each individual anode is the physical parameter represented by the "" in the LaPlace-Trans format ion of the anode transfer function (1 / ΐΓ. _D S + l ^ J "). A single row of anodes in a cell with a liquid Mercury amalgam cathode has a time constant of several minutes to several hours for measuring and regulating the current flow through the anode row. Therefore, if the current flow through each individual anode row to the liquid mercury amalgam cathode at intervals of less than twenty seconds, for example every two seconds to once in 20 seconds is measured and regulated, the current flow through an anode bank to the cathode is considered to be continuously controlled.

By "prolonged electrolysis time ¹¹ is the time duration of the electrolysis, which is to be sized, as a rule so that the operations which in the cell at the commissioning

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Show drive, have time to balance yourself, and that Processes associated with long-term operation of the cell, such as changes in the concentration of the electrolyte and other processes that may occur and take effect. For example, one works with electrolysis times of longer than one day, for example 3 days, 5 days or several months.

According to the invention, short circuits can be prevented and the individual cells through the use of a control element be matched. Short circuits occur when the anode comes into direct contact with the liquid mercury cathode and result in a strong reduction in voltage and an increase in the flow of current. In one of the possible embodiments of the invention, in which the supplied to the control organ If the signal corresponds to the current flow in the anode busbar, the control unit regulates the current flow in each row of anodes associated busbar by increasing the space between the anode and the cathode when the current is the preselected Exceeds the setpoint and decreases it when the current falls below the preselected setpoint. Usually that is Setpoint depends on the average current flow, i.e. the average current flow plus or minus a constant Fixed value or a constant multiple of the mean current flow. According to the invention, the anode row is when, for example through an increase in the flow of electricity, the emergence indicating a short circuit, raised vertically to a greater distance from the cathode until the current flows either can again correspond to the comparison value that is present in the controller.

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is set or from the respective instantaneous Operating condition of the cell, e.g. measured as average Current flow through each of the rows of anodes in the row, or below the comparison value.

The individual cells are also kept in equilibrium by the control organ. A cell is considered balanced if each of the cells has an equal voltage drop from the anode to the cathode or if the current flow through each anode row of a cell is approximately the same. This means that the actual voltage drop between the anode and the cathode of a cell differs from the average voltage drop between the anode and the cathode of a cell by less than a predetermined amount, or that according to a preferred embodiment of the invention, the actual current flow through an anode row differs by less than the predetermined amount from the average current flow through the anode row. The measure _? by which an actual tension differs from the average tension or the selected tension, or the dimension _? by which, in a preferred embodiment of the invention, the current flowing through a row of anodes differs from the average current flow, ie the degree of deviations between the two values indicates the accuracy of the regulation.

Even if it is a regulation of the circuit, a prevention short circuits and balancing of the cell using the voltage drop from the anode to the cathode are possible, so one uses according to the invention for the same purpose preferably

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supplies the current flowing through the busbar of an anode row. The reason for this is that there is a difference of less than 25% of the measured total voltage between the possible maximum voltage values, but a difference of 100 % is possible between the maximum values of the current carried by the busbars.

One of the possible embodiments of a device which can be used for carrying out the invention is shown in the accompanying sheet Drawing shown. In the drawings show:

1 shows a schematic representation of a single mercury cell;

FIG. 2 shows an isometric illustration and partially in section, a mercury cell; FIG.

3 shows a schematic representation of a multiple coupling circuit suitable for the purposes of the invention;

FIG. 4 shows a schematic representation of the switching elements for the multiple coupling circuit according to FIG. 3; FIG.

5 shows a schematic representation of a magnetic barrier matrix suitable for the purposes of the invention (magnetic latching matrix) and

6 shows a block diagram of a control method according to the invention.

According to one of the possible embodiments of the invention the voltage drop measured on an unbranched section of the busbar of an anode. Since this voltage drop corresponds to the

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is proportional to the current flowing through the busbar after the anode row, a first signal is generated, which is proportional to the current flowing in the anode busbar. Then a second electrical signal namely a setpoint signal, preset or generated. This second signal is proportional to the current flow when a short circuit occurs. By comparing the First, a third signal, an error signal, is generated with the second signal. When the first electric Signal is greater than the second electrical signal, i.e. when the current flowing through the anode busbar the maximum permissible level, i.e. exceeds the control current, means are actuated by which the anode bank moves vertically in proportion to the magnitude of the error signal will. Currents more than twice the average current indicate short circuit conditions given are. In general, the setpoint current is about 1.1 to about 1.5 times, preferably 1.1 to 1.2 times as strong as the average current. Control currents that are less than 1.05 times as strong are for the control purposes according to the invention are unsuitable. At the same time, a short-circuit situation that arises can also affect one Control desk can be registered with a typewriter. In the manner described, short circuits can arise detected and prevented. Furthermore, at the request of the operating staff, with the aid of a cathode ray oscillograph and / or an automatic writing machine, the operating conditions of the cells can be queried.

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As soon as short-circuit conditions or emerging short-circuits have been eliminated _P the current flowing to each individual cell can be adjusted. When balancing a cell, the current flowing through the busbar of each anode row is measured in the manner described. Thereafter, a signal proportional to the current flowing through the anode currents is generated. The same happens with each anode busbar of a ZeIIe ₀ Further, an electrical signal is generated _9, the bus bar of an anode row by fließenen average current is proportional. This signal can be the sum of all the anode busbar signals divided by the total number of signals. It can also be the current flow from the energy source to the cell circuit divided by the number of busbars or rows of anodes in a cell. Wherever an average _{current is mentioned 9 it} can be a current obtained according to one of the mentioned types of calculation.

The average of the electrical busbar signals of an anode row determined for an anode bank is compared with this average signal of the current flowing through the busbar of an anode bank, and an error signal is generated for each anode bank. If the error signal exceeds a threshold value ₉ means are actuated which move the anode bank vertically.

After the cell has been calibrated, the cell voltage can be set. «The minimum cell voltage depends on the total current of the cell and can then be determined or preset

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will. The average voltage drop in the cell can be determined by measuring, and the minimum voltage drop be compared with it. If the average voltage drop is greater than the minimum voltage drop, actuates the means provided for vertical adjustment of the anode for all anode banks at the same time. To this In this way, the voltage drop can be reduced without disturbing the adjusted current intensity.

When controlling a cell circuit according to the method of the invention, a controller receives electrical signals from the individual anode rows or anode banks of the electrolysis cells of the cell circuit and gives them as electrical control? signals back to the individual anode rows or anode banks.

This is made clear in Figures 1 and 2 of the drawing, in which a mercury cell 1 with a mercury aralgam cathode 72 flowing over a steel surface 70, metal _{anodes 74 S} busbars 8O ₉ through which the anodes 74 current is supplied, and rods 76 through which the Bus bars 80 are connected to the anodes 74 and which pass through a cover plate 78 made of rubber, plastic or other flexible material. The anodes 74 and the anode bars 76 are supported by frames 82. Double-T beams or beams with assembled scaffolding are used as the frame 82. The anode frame 82 and the anode rows 74 can be moved vertically on threaded rods 84. The vertical movement can be carried out by a motor 88 via a gearbox 86 . According to the invention, through the busbars

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in the anode rows 74 flowing current measured, whereupon the measured values are fed to a controller and in this with can be compared to a target value. In doing so, an error signal is generated which actuates the motor 88.

According to one of the possible embodiments of the invention, an analog computer is used as the controller. The ones in the Values entered by analog computer are the currents measured on each individual anode busbar and the currents between each individual anode and its associated cathode measured voltages. These currents and voltages are selective in arbitrary distributed (randomly) or in successive manner (sequentially) via a multiple coupler (multiplexer) and an amplifier is fed to the analog computer.

The analog computer supplies error signals corresponding to the values entered for each row of anodes. the Error signals are passed through a multiple coupler to the mechanism that actuates the vertical movement of each anode bank forwarded.

In a preferred embodiment of the invention is the controller is a digital computer with programmed memory. You work with a digital computer with programmed Storage is preferred if more than 450 anode busbars, for example up to 2 100 anode busbars and above, must be guarded.

The values entered into the digital computer are the amperages measured on the busbar of each row of anodes and the measured values for those between each row of anodes

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and the associated cathode voltages. These Single currents and single voltages are generated by a multiple coupler and an amplifier selectively inputted to the digital computer. It will be from the digital computer Receive error signals for each individual row of anodes. The error signals are sent to the vertical movement of each anode bank actuating mechanism is passed.

A control system using a digital computer with programmed memory is shown schematically in FIG. 3 in connection with a single cell. As shown, the voltage drop across a unitary section of the anode bus bars 80 of a cell 1 is measured by leads 90. Triggered by relay 241, contacts 221 to 232 close so that electrical signals pass through primary multiple coupler 201, ie contacts 221 to 232, and are present at the secondary multiple coupler, ie at contacts 321 to 332. The secondary multiplexer 301 is controlled by the digital computer 431 in such a way that two selected contacts can close and the corresponding associated current and voltage signals are converted into digital values. So that the electrical signal can be input into the digital computer in a digital form, the weak signal is amplified by an amplifier 411 and converted in the analog-to-digital converter 421. From here the signal is fed to the digital computer 431.

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The digital computer operates the output matrix (output matrix) 450 with the latching relays to 463. An alarm device 95 and light signals 96 can be triggered by the output matrix 450 and sent to the Motors 88 located in rows of anodes are set in motion. Output matrix switch 464 controls relay switch 241 and selects by closing contacts 221 to 232 the cell whose operating status is to be queried.

The signal entered into the controller is proportional to the current flowing through each anode busbar. It is possible to connect a shunt to an unbranched section of an anode busbar. The length of the shunt in relation to the strength of the current flowing through the busbar is such that a voltage drop of about 30 to 40 millivolts occurs in it.

For the cell control according to the invention it is not necessary that all cells of a cell circuit are continuously monitored. It is only necessary that the cells are monitored at time intervals that are less than the time constants of each individual cell. For this purpose, one proceeds in the manner that it sends to the controller of each individual anode row of a given cell Eingangesignale via a multiplexer (multiplexing the input signal).

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The current flow and voltage signals to be sent to the controller can be selected using various methods with multiple coupling. For example, they can be entered into the amplifier in one step one after the other via parallel switching contacts. A multiple coupler with a coded addressing system can be used for the purposes of the invention (coded addressing system multiplexer). In a multiplexer of this type, a signal is generated, usually by the computer. This signal activates an input selector, which closes the switch by means of which the address corresponding to the signal can be read from the sensor or from a sensor group. The input selector on each busbar has its own n-digit address and an ^M AND ^M (AND-gate) pulse. If the address of the input selector of an individual busbar has been selected, this input selector then forwards its measured values to the controller. The millivolt signal generated by the shunt described above can be used as the input selector of a busbar.

When using a multiple coupler with a coded addressing system, the reading obtained when a busbar signal is requested is passed on to the controller. This can be done electromechanically with the help of reed relays. However, a solid-state element, for example a transistor or a field effect transistor, can also be used for this purpose. However, for the purposes of the invention, a field effect transistor must have a large on / off impedance ratio and gate pulse isolation (gate isolation), but no EMF through pn junction (EMF junction) .

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On the other hand, a rotatable switch can also be used for a rotary sequential scanning switch. It is also possible to use a magnetic latching switch matrix, with the relay corresponding to each of the anode series shunts can be closed sequentially, so that the current of each row of anodes from the regulator is sequential can be read.

A parallel arrangement of multi-stage multiple coupling systems (multiple multi-level multiplexing system) is preferably used as the multiple coupling system. In a two-stage system, a first primary multiple coupler (first first level multiplexer) simultaneously receives the signals coming from the busbars of a cell in their entirety. A first (first second level multiplexer) secondary multiple coupler, in turn, as part of the controller, receives all of the signals coming from the first primary multiple coupler. Then another primary multiple coupler is connected to another secondary multiple coupler. This in turn picks up all incoming signals from the second primary multiple coupler _o In the meantime, the first of the secondary multiple couplers has separated from the first primary multiple coupler and connected to a further primary multiple coupler.

In a usual sixty-four cell circle, each of which is equipped with four anode busbars, the sensors are connected to the controller through a system of sixty-four Primary multiple couplers (201-208) and four secondary multiple couplers (301 - 304) connected ·. In a cell circuit of this structure there are sixteen relays, viz

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four relays per cell multiplied by the number of secondary multiplexers, namely the four secondary multiplexers, simultaneously switched on. The signals from the first primary multiplexer (201), i.e. of the first four Signals coming in from the anode busbars are received consecutively by the secondary multiple couplers (301). Once the incoming signals from the four anode bus bars have been input to controller 431, the first primary multiple coupler (201) switched off. Then a second primary multiplexer (205) is attached to the secondary multiplexer (301) connected. During this time, the incoming from the next primary multiplexer 202 becomes Signal input to controller 411 through the next secondary multiplexer 302 in the same manner. This continues in the same order through all cells of the cell circle away.

In a multi-stage multiple coupling method, the contacts are connected in parallel and in series, with the second contact stage, for example steps 321 to 332, being connected in series with the first contact stage, for example steps 221 to 232. The multiple coupling stage only needs to contain as many contacts zn as are necessary so that all current and voltage signals coming from a single cell can be received. The first multiple coupler stage contains as many contacts as is required so that all signals coming in from a cell and multiplied with the total number of cells can be recorded. A contact switch controls the output switching matrix,

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For example, the contact switch 464, the relay 241, which in the primary multiple coupler all contacts 221 to 232 for operated a single cell. The computer then reads the cell's current and voltage signals that are in the primary multiplexer have been selected by actuating contacts 321 to 332. The computer can read the signals in read randomly or in succession. As soon as all signals of a single cell are read are, the contacts 221 to 232 are opened for this cell by activating the relay via the contact switch 464 turns off. After the contacts of the cell just read in the primary multiplexer have opened, you can for a further cell the contacts 221 to 233 are closed in a further primary multiple coupler, and the reading process through contacts 321 to 332 are repeated. Both in the primary multiple coupler and in the secondary multiple coupler The contacts can be solid-state elements, tongue relays, electromechanical ^ relays or combinations thereof be.

The primary multiple coupler can consist of mercury wetted reed relays. Man sees a relay and a relay group for each anode power rail for a cell. The secondary multiplexer can be part of the computer and can also be wetted with mercury Tongue relays exist.

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The preferred multiple coupling system for the purposes of the invention Figure 3 is a two-stage multiplexer of Figure 3 showing a single such system. as For control purposes, tongue relays wetted with mercury are preferably used in the multiple coupler. In a preferred However, the multiple coupling system does exist from a variety of two-stage multiple couplers with a common output on amplifier 411. By the If a large number of two-stage multiple couplers are used, they can overlap one another in their activity. This speeds up the operating process because the time that would normally be needed for switching breaks is gained must be expended when switching. A system made up of a large number of two-stage multiple couplers is illustrated in the example shown in Figure 4, in which two primary multiple couplers each with a secondary multiple coupler are connected. For example, the primary multiplexers 201 and 205 are with the secondary multiplexer 302, the primary multiplexers 203 and 207 with the secondary multiplexer 303 and the primary multiplexers 204 and 208 connected to the secondary multiplexer 304. As shown in Figure 4, all cells of the Cell circuit connected in series, with each cell having its own primary multiplexer. Every fourth cell and as a result, every fourth primary multiplexer will be connected to a single secondary multiplexer.

The two-stage or appropriate according to the invention The secondary multiple coupling system is shown in FIG.

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At the start of operation, the contacts 221 to each of the primary multiple couplers 201 to 208 and the contacts 321 to 332 of the secondary multiple couplers 301 to 301 are open. Then the contacts 221 to 232 of the first four primary multiple couplers 201 to 204, for example via the coil 241 (coil) are closed -Multiplier 301 connected. The controller reads the electrical signals fed to the contacts 321 to 332 of the secondary multiple coupler 301 one after the other. At this point, all of the contacts 221-232 of the first primary multi-coupler 201 are opened and all of the contacts in the primary multi-coupler 205 are closed. While the contacts in the primary multi-coupler 201 are open and the contacts in the primary multi-coupler 205 are closed, the electrical signals supplied by the primary multi-coupler 202 from each of the contacts of the secondary multi-coupler are received one after the other by the controller 431. After the input of all of the signals emitted by the primary multiplexer 202 via the secondary multiplexer 302, all contacts in the primary multiplexer 202 open and all contacts in the primary multiplexer 206 close at the same time. While this is happening, the contacts of the secondary -Multiplier coupler 303 emitted electrical signals recorded successively by the controller 431. After all of the signals output at the secondary multiple coupler 303 have been entered, all the contacts of the primary multiple coupler 203 and 203 open

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all contacts of the primary multiple coupler close at the same time 207. While this is happening, the controller takes over from the contacts of the primary multiplexer 204 the secondary multiplexer 304 on electrical signals outputted. When all from the primary multiplexer 204 over the secondary multiplexer 304 received signals output all contacts of the primary multiple coupler open 204 and all contacts in the secondary multiplexer 208 close at the same time. When the contacts in the primary multiplexer 204 open and the contacts in the primary multiplexer 208 close, grounding those of the contacts of the multiplexer 205 outputted electrical signals successively via the secondary multiplexer 301 recorded. When all of the signals fed to the multiplexer 205 have been passed, the contacts open this multiple coupler 205, and thus the next following primary multiple coupler 209 closes.

While the method according to the invention has been explained in the drawings on a cell circuit with four secondary multiple couplers, three secondary multiple couplers can also be used and one third of the cells can be assigned to each secondary multiple coupler. However, two secondary multiple couplers can also be used and half of the cells assigned to each secondary multiple coupler x ^ earth _e That means that η secondary multiple couplers can also be used and each secondary multiple coupler η + 1 cells can be assigned. The number of multiple couplers is determined by economic considerations and also depends on the number of secondary contacts or switches available in the controller.

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In the circuit used according to the invention in an electrolysis cell to regulate the current intensity, between the output point of the current signals in the cells and the controller a filter can be installed. This filter is supposed to the interference noise arising in the process to be monitored is attenuated to a minimum, for example the alternating current pulsation, which occurs in electrolysis used direct current, or the noise generated by the control circuit, in particular that noise associated with the multiplexers. The filter is placed between the individual anode busbars and the Regulator arranged. In a multi-stage or multi-stage multiple coupler system, for example in a two-stage system, the filter must be used in an arrangement between a primary multiple coupler and the corresponding secondary multiple coupler a filter with a short start-up time (low settling time filter), while with an arrangement of the filters between a primary multiple coupler and the process room a larger and consequently a cost-increasing number of filters is required. In a certain type of circuit regulation according to the invention in an electrolysis cell the secondary multiple coupler is equipped with capacitors above each of its inputs. As soon as the receipt is read is, the capacitor is disconnected from the input and with an amplifier and further connected to an analog-to-digital converter. In this way, no interfering noise gets into the Regulator.

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It can also be useful to build an amplifier into the control circuit, with which the incoming signal is amplified so that it can be processed by the analog-to-digital converter.

The analog-to-digital converter converts the incoming signal into digital form and also includes a sample and holding element (a sample and hold element, lock & hold). This is in the block diagram of Figure 6 as

. (1 - e " ^Ts ) / s
shown.

If a digital computer with a programmable memory is used as a controller, then the process is controlled given considerable leeway. A computer with a programmable controller is preferably used as the controller Memory with more than 10,000 words at 16 bits per word (16 bit per word memory), preferably with more than 12,000 words at 16 bits per word.

When using a computer with programmable memory, the control characteristic can be proportional / integral (PI behavior), i.e. the proportional behavior corresponds to equation

P = Ke -e J + ^ t e,

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in which e the error signal, η the interval or sample number, K is the proportionality factor, t is a measuring interval, TR restoration or time interval constant and P denote the output signal.

The measurement time or Δ T has a duration of about 0.5 to about 120 seconds. With an electrolysis cell circuit of of the type used, Δ T generally has a duration of about 4 to about 10 seconds. The longer measurement times relate to the approximate time constant when the average line voltage or the average cell current drift, while the shorter. Time constant the approximate time constant of the beginning of short circuits or drifting of the individual Concern anodes.

The output signal of the controller can be made visible with a cathode ray oscilloscope, written with automatic typists, used as a control signal for motors or in a combination of these possibilities _. or the equilibrium state of the cell can be visualized graphically or the like *

The output signal can also be used as a control signal to the motors 88, which control the vertical movement of the rows of anodes 82. The electrical signal gives both the size as well as the direction of movement of the rows of anodes.

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Since most digital computers are limited by the number of contact closures they can accommodate and a system for detecting shorts in mercury amalgam cells requires a large number of contacts, the number of contacts must be over that the computer can have. For example, a relay matrix is arranged for this purpose in such a way that it is operated by the contacts available in the computer. The relay coils are arranged according to the matrix pattern shown in FIG. In their relationship to the control circuit, they are shown as relays in FIG. Contacts 701-710 are arranged to actuate either a column or a row of the matrix. Each relay has a closed coil (c) and an open coil (o), each with opposite magnetic flux. When the closed coil and the open coil are energized at the same time, the magnetic flux generated by the closed coil will be greater than that generated by the open coil. The relays are magnetically blocked so that they remain in the closed or open state even if their coils are de-energized. The relay located at the intersection of a column and a row is blocked in the closed state when the computer contacts for this column and row are closed . For example, when computer contacts 703 and 709 are closed, relay 553 blocks and remains closed even when computer contacts 703 and 709 are opened. If, in general, a relay is not to be blocked in the matrix, the computer contact in the row in which the relay is located should be closed and the computer contact in the column in

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to which the relay is located, can be opened. As a result, the open coil is excited without the closed coil at the same time Coil is energized. For example, if relay 553 is to be opened, computer contact 703 becomes opened and the computer contact 709 closed. The contacts of the matrix relays can be used to control the motors to move the anodes, to switch on light signals indicating short circuits and analog input relays or a To operate the signal horn.

The locking relay matrix 450 contains contacts 701 to 708, which, forming a matrix, are arranged in rows and columns. Preferably they are alike, forming a barrier matrix Arranged in rows and columns. By closing the contacts in each row or column, this will be on Intersection of the two locking relays locked in the closed state. Without blocking a contact in each row all relays in the same row are opened.

Cell equilibrium is maintained by keeping the anode bank in relation to the error signal emotional. Particularly suitable for the purposes of the invention is a cell control in which the speed the movement of the anode is constant, but the duration of the movement is proportional to the size of the error signal and shorter than the measuring time can be maintained. If the anode bank does not move to the desired extent within a measuring interval has been, the current is measured, a new error signal is generated and the anode again during the next measurement interval emotional. For every anode bank motor, stable mo-

A 0 9 8 8 5/1 0 1 0

Use gate relays with a single bearing and a double cranked axis (single pole double center stable motor relays). There are several alternatives for raising and lowering the anodes. For example, an anode bank in the event of a short circuit being increased until the current has reached zero or a fraction of the average current strength, for example by a tenth or half, or until the current strength falls below a preselected one Alarm value drops. The anode bank can then be slowly lowered again, as described above, and the current in the cell be adjusted again. You can also quickly lift all the anode banks and adjust the amperage in the Lower the cell slowly again. You can run the anodes at a continuous speed, with a gradual speed or with speed increase over the entire Move the setting range.

In order to equalize the current in a cell or to return the cell to a minimum voltage, one can use the Anode banks during a measurement interval over the greatest possible distance or a constant distance or a multiple this distance, but not beyond the necessary maximum distance. The maximum distance that the anode bank can be moved, on the other hand it can also be a fraction of the amount required for the current adjustment, so that one gradually approaches the cell balance and does not over-regulate it.

The following example further illustrates the invention.

409885/1010

example

A mercury cell circuit consisting of 68 cells and operated at 300,000 amperes was fitted with a system equipped to find short circuits and to balance the cell current. The 68 cells were divided into four Groups of 17 cells each divided. The cell control equipment included four secondary multiplexers, from each with 17 primary multiple couplers with 30 relays each was connected.

Each mercury cell in the cell circuit had six anode frames and each frame had four rows of anodes, im Whole as equipped with 24 rows of anodes. The was measured and passed on as signals from the four cells Current rail flowing through each anode and the voltage in the cell from the anode frame to the cathode. The signals emanating from each cell were transmitted via a bipolar relay contact wetted with mercury The primary multiplexer containing the associated secondary multiplexer is supplied.

The secondary multiple coupler was with 125 IBM analog input relays equipped «, These were, according to the number of contacts in the primary multiplexers, in 4 groups of 30 relays each subdivided. A zero balancing voltage source was also directly connected to the secondary multiple couplers (zero reference voltage), a reference voltage source (calibration reference voltage), the total current flowing through the cell circuit, the total voltage present in the cell circuit and

409885/1010

the energy supply for the coils of the switching relays.

The signals from the secondary multiplexer were connected to the IBM computer via a programmable broadband amplifier and an analog-to-digital converter System 7 forwarded.

The IBM computer has a memory of 12,000 words of 16 bits per word. The one coming from the computer Signal drives a magnetic switch matrix with single-pole two-coil relays. The locking relay matrix had the double function, to open and close the two-pole contacts at the input of the signals supplied from the anode row close as well as trigger the control of an emerging short circuit and a cell synchronization.

When operating according to the test system, the thirty signals emanating from each primary multiplexer became alternating switched into the secondary multiple coupler and in its Output read from IBM Computer System 7. The critical point was 1.2 times the average current. The these Anode rows exceeding the value were detected by visual and acoustic alarms and by printing out the error values in displayed on a typewriter. To make the Error signaling was also a cathode ray oscillograph used.

The results obtained are given in the table below.

409885/1010

Tabel

Electrolysis Duration (Days)

average Voltage drop between anode rod and cathode; not with a reg-

r connected cells oltT avg. Voltage drop between the anode rod
and cathode; with a
Computer connected
Cells (volts)

Voltage difference between regulated and unregulated cells (Volt)

3
7th

14th
17th
21
28

4.25 4.33 4.31 4.19 4.24 4.29 4.02
4.08
4.04
4.02
4.03
4.12

0.23 0.25 0.27 0.17 0.21 0.17

-C - OO

ro

cn

CD

Claims (28)

Patent claims 1. Procedure for * performing electrolysis in one Cell circuit consisting of a large number of electrolysis cells, each of which has a liquid mercury amalgam cathode and a plurality of anode banks connected together in a plurality of vertically movable anode banks Contains rows of anodes, and in which a current flows from the anodes of the anode banks to a cathode, thereby through characterized by having each of the through each of the anode rows of a single cell flowing individual currents during longer electrolysis times constantly within a preselected range of a Control current. 2. The method according to claim 1, characterized in that that the preselected control current is the average of the anode rows flowing through a cell Is single streams. 3. The method according to claim 2, characterized in that that one generates the first electrical signals that the individual rows of anodes of a cell • Individual currents flowing through are proportional to one A second electrical signal is generated which is proportional to the average of the individual currents flowing through these rows of anodes and one generates error signals to control the cell, which is the difference between the first signals and are proportional to the second signal. 4098 85/1010 4. The method according to claim 3 _S characterized in that all anode banks are moved vertically away from their cathode when one of the first signals
exceeds a value at which a short circuit begins. 5. The method according to claim 3, characterized in that one moves each of the anode banks in relation to a transition of the error signal to
maintain cell balance. 6. The method according to claim 3, characterized in that one for generating the second
Signal measures the total amount of current flowing in the cell circuit, the second signal being proportional to the total amount of current flowing in the cell circuit
is. 7 «, method according to claim 6, characterized marked It is necessary to produce an electrical signal which is the average of the flow through each row of anodes Current is proportional, the second signal through the number of the first electrical signals divided " 8. The method according to claim 5, characterized denotes that one represents a function of the first individual signals «, 9. The method according to claim 5, characterized in that that the function of the first individual signals was stored 409885/1010 10. The method according to claim 5, characterized in that that to generate the first electrical signals, the current flow through the busbar of each row of anodes. 11. The method according to claim 5, characterized in that that the cells are monitored by a common control organ. 12. The method according to claim 11, characterized in that that one monitors the output of a relay matrix. 13. The method according to claim 12, characterized in that that one establishes contact closures through which a blocking relay matrix is operated. 14. The method according to claim 13, characterized in that the contact connections are lined up in columns and rows of the same number, _{or the like} 15. The method according to claim 13, characterized in that there is a contact in a row and closes in a column, whereby one in the closed state blocks a relay at the intersection of the row with the column. 16. The method according to claim 13, characterized in that that one closes a contact in a row and thereby all relays in this row locks in its open position. 409885/101 (1 17. The method according to claim 11, characterized in that that the cells are controlled in a sequential manner. 18. The method according to claim 11, characterized in that that one controls the cell in an arbitrarily distributed manner. 19. The method according to claim 11, characterized in, that all the first electrical signals of each individual cell via a primary switch stage a secondary switch. 20. The method according to claim 19, characterized in that that one each first electrical signal individually from the secondary switch stage to the control element feeds. 21. The method according to claim 11, characterized in that that all the first electrical signals of a single cell of a primary switch stage and passes through these and that one of these first electrical signals individually from a secondary switch stage forwards to the control element. 22. The method according to claim 21, characterized in that that all the first electrical signals of a single cell are sent simultaneously to a first group of Supplies primary switches and forwards them to a first group of secondary switches; one all first 409885/101 f) electrical signals simultaneously from a second single cell from a second group of primary switches leads to and through them; one of these first electrical signals separately from the first Group of secondary switches from the common control element feeds the electrical connection between the first group of secondary switches and the first group of primary switches interrupts the first group the secondary switch electrically connects to the next group of primary switches and each of the first electrical ones Signals from the second group of primary switches individually through the second group of secondary switches common control element. 23. Cell circuit with a large number of series-connected, Electrolysis cells equipped with a liquid mercury amalgam cathode, each of which is connected to the neighboring cells is electrically connected, and a control circuit in which a digital computer with programmable Connected memory is characterized by shunts that affect the flow of electricity in each Address busbar, and primary and secondary multiple coupler devices, which are arranged between the bus bars and the digital computer with programmable memory. 24. Cell circuit according to claim 23, characterized in that that one primary multiplexer is used per mercury cell. 409885M010 25. Cell circuit according to claim 24, characterized in that that secondary multiplexer between the primary multiplexers and the digital computer are arranged with programmable memory. 26. Cell circuit according to claim 25, characterized in that that more than one primary multiplexer is used per secondary multiple coupler. 27. Cell circuit according to claim 23, characterized in that that the digital computer with programmable memory to operate the multiplexer is equipped with means, including a locking relay that can be triggered by contact closure. 28. Cell circuit according to claim 27, characterized in that that the contact connections are lined up in an equal number of columns and rows are.