EP0396174B1 - Verfahren zum Einstellen eines Anodensatzes in einer Elektrolysezelle mit Quecksilberkathode, in der Chlor hergestellt wird - Google Patents

Verfahren zum Einstellen eines Anodensatzes in einer Elektrolysezelle mit Quecksilberkathode, in der Chlor hergestellt wird Download PDF

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Publication number
EP0396174B1
EP0396174B1 EP90201008A EP90201008A EP0396174B1 EP 0396174 B1 EP0396174 B1 EP 0396174B1 EP 90201008 A EP90201008 A EP 90201008A EP 90201008 A EP90201008 A EP 90201008A EP 0396174 B1 EP0396174 B1 EP 0396174B1
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EP
European Patent Office
Prior art keywords
anode
anode unit
cathode
measured
process according
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP90201008A
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English (en)
French (fr)
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EP0396174A1 (de
Inventor
Mauro Filippone
Stefano Bigini
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Solvay SA
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Solvay SA
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Filing date
Publication date
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Priority to AT90201008T priority Critical patent/ATE93550T1/de
Publication of EP0396174A1 publication Critical patent/EP0396174A1/de
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Classifications

    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B15/00—Operating or servicing cells
    • C25B15/04—Regulation of the inter-electrode distance

Definitions

  • the present invention relates to a method for adjusting the position of the anodes in electrolysis cells with a horizontal mercury cathode, used for the production of chlorine by electrolysis of an aqueous solution of sodium chloride.
  • the distance between the anodes and the cathode is an important parameter in the operation of electrolysis cells with a horizontal mercury cathode. Excessive distance damages the energy balance of the electrolysis operation, causing an unnecessary loss of electrical energy by the Joule effect in the electrolyte. Too small a distance also harms the energy balance, causing a drop in the electrochemical yield of the electrode reactions (the drop in yield being due to a reduction, in contact with mercury, of part of the chlorine generated at the anodes). It should also be avoided that one or the other anode occasionally comes into contact with the mercury cathode, because the short-circuit which would result therefrom could cause serious degradation at the anode, mainly in the case of titanium anodes carrying an active coating based on noble metal oxide.
  • the causes of an untimely variation of the anode-cathode distances or of a fortuitous contact between an anode and mercury are numerous; they may reside in particular in a deformation or wear of the anode, the formation of agglomerates of large mercury (sometimes called "mercury butter") adhering to the bottom of the cell or floating on the surface of mercury, an untimely variation of the level of mercury in the cell, a fortuitous turbulence occurring in the flow of mercury.
  • agglomerates of large mercury sometimes called "mercury butter”
  • the invention provides a method which improves on the known method described above, by involving the anode imperfections in the adjustment of the anode-cathode distances of the mercury cells.
  • the invention therefore relates to a method for positioning an anode unit in a mercury cathode electrolysis cell in which chlorine is produced on an active area of the anode unit by electrolysis of a sodium chloride brine; according to the invention, the anode unit is brought into a reference position for which the electrical resistance of the brine layer located between the active area of the anode unit and the cathode is equal to a set value, we temporarily set aside the anodic unit of the reference position, from a defined distance, the corresponding variation of the electrical resistance of the brine layer is measured and the position of the anodic unit is corrected when the measured variation exceeds a threshold value.
  • the anode unit can be an individual anode or a group of anodes displaceable together with respect to the mercury cathode, for example a group of anodes fixed together, in derivation, to a rigid and displaceable current collector.
  • the active zone of the anode unit is the zone thereof, which effectively participates in the electrochemical reaction of oxidation of chloride ions during electrolysis.
  • the reference position of the anode unit is a physically indeterminate position, defined by an imposed value (set value) of the electrical resistance of the brine layer located directly above its active area.
  • the set value is the magnitude of the electrical resistance of the electrolyte layer under the active area of a reference anode during electrolysis, when this reference anode occupies a predetermined theoretical position for which the user of the cell electrolysis considers that its operation is optimum.
  • the reference anode is an ideal anode, free from flatness defects and strictly parallel to the sheet of mercury forming the cathode.
  • a new anode of the cell is chosen for the reference anode.
  • the theoretical position therefore depends on the geometry of the reference anode and the density of the electrolysis current, and it must be determined in each particular case by a routine experimental study, depending on the operating conditions of the cell. electrolysis.
  • the electrical resistance of the brine layer between the active area of the anode unit and the cathode is measured, and the position of the anode unit is adjusted so that the resistance measured equals the setpoint defined above.
  • the measurement of the electrical resistance can be obtained by any suitable means, for example by means of an ohmmeter or from a measurement of the intensity of the electric current passing through the anode unit during the operation of the cell and of a measure of the difference in electrical potential between this unit anode and the mercury cathode.
  • the technique described in patent BE-A-668236 is advantageously used.
  • the corresponding variation in the electrical resistance of the brine layer is measured under the active zone of the anode unit and it is compared to a threshold value.
  • the threshold value is the electrical resistance that a layer of brine free of chlorine bubbles would have, located under the active zone of the anode unit and whose thickness is equal to the aforementioned defined distance.
  • the process according to the invention is based on the observation that, all other things remaining equal, the electrical resistivity of the layer of brine interposed between an anode and the cathode increases when this layer of brine is charged with a substantial amount of chlorine gaseous.
  • the measurement of the variation in resistance (consecutive to a momentary separation of the anode unit from its reference position) and its comparison with the threshold value are therefore an indication of the density of bubbles.
  • chlorine in the brine layer under the anode unit and thus constitute a control of the position of the anode unit in the electrolysis cell.
  • the position of the anode unit is corrected by increasing the anode-cathode distance by an imposed value, generally arbitrary.
  • the anode unit after having corrected the position of the anode unit in the manner described above, it is subjected to a second control. For this purpose, it is temporarily removed from its corrected position, by a distance equal to the aforementioned defined distance, the corresponding variation in resistance is measured and an additional correction is made to the position of the unit. anodic, if the measured variation exceeds the threshold value. If necessary, the anode unit can thus be subjected to several successive corrections, until the resistance variation no longer exceeds the threshold value.
  • the observation that after several successive corrections, it is not possible to reach a resistance variation less than the threshold value, is an indication that the anode unit subjected to the adjustment has reached an excessive level of imperfection.
  • a defined number of successive corrections is fixed, beyond which the anode unit is put out of service, if the measured resistance variation remains greater than the threshold value.
  • the cell was equipped with a mixture of new and used anodes.
  • electrolysis of a brine containing approximately 230 g was carried out.
  • sodium chloride per kg the temperature in the cell being about 50 to 70 ° C. It has been calculated that at this temperature, the electrical resistance of a brine layer with a surface area of 1 m2 and a thickness of 1 mm (above the mercury) was approximately 30 ⁇ Ohm. This value was therefore chosen as the resistance threshold value, in the application of the method according to the invention.
  • each anode was positioned individually in the cell, by means of the method and of the adjustment installation described in patent BE-A-668236.
  • each anode was gradually lowered towards the cathode, the electrical resistance of the underlying brine layer was simultaneously measured and the anode (reference position) was stabilized as soon as the resistance measured was equal to a predetermined set value.
  • the average energy consumption and the average anode current efficiency were calculated.
  • the electrolysis voltage has been corrected to bring the temperature in the cell back to the normalized value of 60 ° C.
  • the setpoint value selected corresponded to the resistance of a 2 mm layer of brine, under a new anode.
  • the cell operated continuously with the anodes set to this setpoint.
  • the control test revealed 28 anodes for which the increase in electrical resistance was greater than the threshold value. These 28 anodes were therefore raised by 1 mm from the initial reference position.
  • Example 7 The test of Example 7 was repeated with a cathode current density of 4.3 kA / m2.
  • Table I relates to the electrolysis tests at a current density of 7.6 kA / m2 (examples 1, 3, 5, 7), and Table II relates to the electrolysis tests at a current density of 4, 3 kA / m2 (examples 2, 4, 6, 8).

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Electrolytic Production Of Non-Metals, Compounds, Apparatuses Therefor (AREA)
  • Electrolytic Production Of Metals (AREA)

Claims (8)

  1. Verfahren zum Einstellen eines Anodensatzes in einer Elektrolysezelle mit Quecksilberkathode, in der Chlor hergestellt wird auf einer aktiven Zone des Anodensatzes durch Elektrolyse einer Natriumchloridsalzlösung, gemäß dem man den Anodensatz in eine Bezugseinstellung bringt, für die der elektrische Widerstand der zwischen der aktiven Zone des Anodensatzes und der Kathode liegenden Salzlösungsschicht gleich einem Einstellwert ist, dadurch gekennzeichnet, daß man den Anodensatz provisorisch aus der Bezugseinstellung um einen bestimmten Abstand entfernt, die entsprechende Abweichung des elektrischen Widerstands der Salzlösungsschicht mißt und die Einstellung des Anodensatzes korrigiert, wenn die gemessene Abweichung einen Schwellenwert übersteigt.
  2. Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß man die Einstellung des Anodensatzes durch Vergrößerung des ihn von der Kathode trennenden Abstandes korrigiert.
  3. Verfahren nach Anspruch 1 oder 2, dadurch gekennzeichnet, daß zum Anbringen des Anodensatzes in der Bezugseinstellung der elektrische Widerstand der zwischen ihrer aktiven Zone und der Kathode liegenden Salzlösungsschicht gemessen wird und die Einstellung des Anodensatzes bis zu einer Bezugseinstellung eingestellt wird, für die der gemessene Widerstand dem Einstellwert entspricht.
  4. Verfahren nach Anspruch 3, dadurch gekennzeichnet, daß man zum Messen des elektrischen Widerstandes die Intensität des elektrischen Stromes der Elektrolyse, der den Anodensatz durchfließt und die elektrische Potentialdifferenz zwischen dem Anodensatz und der Kathode mißt.
  5. Verfahren nach einem der Ansprüche 1 bis 4, dadurch gekennzeichnet, daß der Schwellenwert dem elektrischen Widerstand entspricht, den eine chlorblasenfreie Salzlösungsschicht hätte, die unter dem Anodensatz angebracht ist, und deren Dicke gleich dem oben genannten bestimmten Abstand ist.
  6. Verfahren nach einem der Ansprüche 1 bis 5, dadurch gekennzeichnet, daß nach dem Korrigieren der Einstellung des Anodensatzes man diesen provisorisch aus seiner korrigierten Einstellung entfernt, um einen Abstand, der gleich dem oben genannten bestimmten Abstand ist, man die entsprechende Abweichung des Widerstandes mißt und eine zusätzliche Korrektur der Einstellung des Anodensatzes vornimmt, wenn die gemessene Abweichung den Schwellenwert übersteigt.
  7. Verfahren nach einem der Ansprüche 1 bis 6, dadurch gekennzeichnet, daß man zum provisorischen Entfernen des Anodensatzes aus seiner Bezugseinstellung ihn von der Kathode entfernt.
  8. Verfahren nach einem der Ansprüche 1 bis 7, dadurch gekennzeichnet, daß der Anodensatz eine einzelne Anode der Elektrolysezelle ist.
EP90201008A 1989-05-03 1990-04-23 Verfahren zum Einstellen eines Anodensatzes in einer Elektrolysezelle mit Quecksilberkathode, in der Chlor hergestellt wird Expired - Lifetime EP0396174B1 (de)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT90201008T ATE93550T1 (de) 1989-05-03 1990-04-23 Verfahren zum einstellen eines anodensatzes in einer elektrolysezelle mit quecksilberkathode, in der chlor hergestellt wird.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
IT2036289 1989-05-03
IT8920362A IT1229328B (it) 1989-05-03 1989-05-03 Procedimento per posizionare un'unita' anodica in una cella elettrolitica con catodo di mercurio, nella quale si produce cloro.

Publications (2)

Publication Number Publication Date
EP0396174A1 EP0396174A1 (de) 1990-11-07
EP0396174B1 true EP0396174B1 (de) 1993-08-25

Family

ID=11166056

Family Applications (1)

Application Number Title Priority Date Filing Date
EP90201008A Expired - Lifetime EP0396174B1 (de) 1989-05-03 1990-04-23 Verfahren zum Einstellen eines Anodensatzes in einer Elektrolysezelle mit Quecksilberkathode, in der Chlor hergestellt wird

Country Status (6)

Country Link
EP (1) EP0396174B1 (de)
AT (1) ATE93550T1 (de)
BR (1) BR9002048A (de)
DE (1) DE69002857T2 (de)
ES (1) ES2045757T3 (de)
IT (1) IT1229328B (de)

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4004989A (en) * 1974-04-18 1977-01-25 Olin Corporation Method for automatic adjustment of anodes based upon current density and current
FR2491958A1 (fr) * 1980-10-13 1982-04-16 Costes Jean Procede de reglage de la distance entre les deux electrodes des cellules d'electrolyse a cathode de mercure

Also Published As

Publication number Publication date
ES2045757T3 (es) 1994-01-16
DE69002857T2 (de) 1994-03-17
IT8920362A0 (it) 1989-05-03
DE69002857D1 (de) 1993-09-30
BR9002048A (pt) 1991-08-13
ATE93550T1 (de) 1993-09-15
IT1229328B (it) 1991-08-08
EP0396174A1 (de) 1990-11-07

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