EP0011886A1 - Preparation of oxy-halogenated acids and their salts by electrolysis - Google Patents

Preparation of oxy-halogenated acids and their salts by electrolysis Download PDF

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EP0011886A1
EP0011886A1 EP79200618A EP79200618A EP0011886A1 EP 0011886 A1 EP0011886 A1 EP 0011886A1 EP 79200618 A EP79200618 A EP 79200618A EP 79200618 A EP79200618 A EP 79200618A EP 0011886 A1 EP0011886 A1 EP 0011886A1
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unpurified
calcium
sea water
electrolysis
ions
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EP0011886B1 (en
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Karl Dipl.-Ing. Lohrberg
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GEA Group AG
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Metallgesellschaft AG
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    • 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
    • C25B1/00—Electrolytic production of inorganic compounds or non-metals
    • C25B1/01—Products
    • C25B1/24—Halogens or compounds thereof
    • C25B1/26—Chlorine; Compounds thereof

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  • the invention has for its object to achieve a reduction or control of the formation of deposits on the cathode during the electrolysis of seawater or salt solutions containing contaminating metal ions for the recovery of solutions of chlorine-oxygen acids or their salts, advantages of known methods being used without their disadvantages to have to put up with.
  • the invention now consists in operating the electrolysis cell with unpurified sea water or unpurified salt solution until a layer is formed on the electrodes
  • Compounds of the contaminating metal ions, in particular calcium and / or magnesium ions are deposited in a sufficient strength and effect a current efficiency of more than 90%, and that then the calcium and / or magnesium ions contained in the unpurified sea water or in the unpurified saline solution by adding sodium hydroxide solution and / or calcium hydroxide and sodium carbonate at a pH of more than 9 precipitates in whole or in part, if necessary separates and feeds the cleaned solution to the electrolysis cell.
  • Adequate layer thickness is understood in the sense of the invention to mean a layer thickness which is sufficient to achieve a current efficiency of more than 90%.
  • this is fed to the electrolyzer in carrying out the method according to the invention until a sufficient layer thickness is reached.
  • the current yield slowly increases over time until values of over 90% are reached. This increase generally takes place over a period of 5 to 30 hours, the cell voltage generally increasing by 0.2 to 0.3 volt with the same current density. After this deposition phase, the cell voltage continues to increase and this increase is 1 to 1.5 volts within 100 to 2000 hours, depending on the concentration of contaminating ions.
  • the supply of the unpurified salt solution is switched off by the method according to the invention and the purified salt solution is then fed to the electrolyte.
  • the impurities which are predominantly contained in the salt solution in the form of calcium and / or magnesium ions or iron ions, are precipitated by adding sodium hydroxide solution and / or calcium hydroxide and sodium carbonate or soda at a pH of more than 9.
  • the magnesium ions are precipitated by the hydroxyl ions of the calcium hydroxide, the calcium ions by the carbonate ions and magnesium hydroxide. Calcium carbonate precipitated.
  • the precipitation of the impurities is usually brought about completely. In some cases, depending on the local conditions of the electrolytic cells, it may be sufficient if the majority of the contaminants are precipitated.
  • the precipitation products can also remain wholly or partly in the finely divided state in the brine or saline solution.
  • impurities of, for example, calcium and magnesium salts in amounts of about 5 mg Ca ++ / 1 and 1 mg Mg ++ / 1 are deposited on the cathodes in the brine and gradually cause a layer to form.
  • electrolytic cells are used in the method according to the invention, for example electrolytic cells with alternating vertical anodes and cathodes.
  • the electrode spacing is, for example, 2 to 5 mm and the electrolyte with a flow rate of 0.3 to 2 m / s is electrolyzed at a current density of 2 to 25 A / dm 2 .
  • the temperature of the electrolyte can be 10 to 50 ° C and the pH can range from 7 to 10.
  • the cathodes are made of electrically conductive, wear-resistant metal materials, such as titanium, nickel, or iron and nickel alloys.
  • the anode material can be graphite.
  • anodes are titanium, niobium or tantalum electrodes coated with noble metal or noble metal oxide or so-called dimensionally stable anodes, in which the electrocatalytic effect is based on mixed oxides of noble metals and film-forming metals, in particular titanium.
  • the chlorine reacts with the sodium hydroxide solution to form sodium hypochlorite according to:
  • hypochlorous acid Sodium hypochlorite reacts with water to form hypochlorous acid
  • reaction (1) or reaction (2) depends on the pH of the environment. At a pH> 5, the entire active chlorine is in the form of hypochlorous acid and hypochlorite ions. The higher the pH value, the greater the proportion of hypochlorite ions.
  • the advantages of the method according to the invention can be seen in the fact that a targeted layer formation on the cathodes occurs uniformly in all electrolysis cells of the system.
  • the thin passive layer of a certain thickness deposited according to the invention prevents an excessive reduction of the hypochlorite ions, thus increases the yield of hypochlorite and makes cell cleaning unnecessary or reduces it to a very considerable extent.
  • FIG. 1 shows the efficiency of hypochlorite cells as a function of the running time.
  • a plant with 8 cells connected in series was operated with sea water at 28 ° C. at a rate of 20 m 3 / h.
  • the current strength was slowly increased from 500 A to 5000 A over a total of 30 hours.
  • the voltage rose from 25 to 35 V.
  • the content of active chlorine in the form of NaOCl rose from 0.2 g / l to 2.8 g / l in the same period.
  • the current yield ran according to the diagram in FIG. 1, ie without the addition of precipitation chemicals, the current yield would asymptotically approach the value of 100%, but at the same time the voltage would rise and the Pollution increase, so that after 2000 hours at the latest the plant would have to be shut down with acid washing.

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  • Chemical & Material Sciences (AREA)
  • Inorganic Chemistry (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)
  • Water Treatment By Electricity Or Magnetism (AREA)

Abstract

Bei Verfahren zur Gewinnung von Chlorsauerstoffsäuren bzw. deren Salze durch Elektrolyse von Meerwasser oder verunreinigende Metallionen enthaltenden Salzlösungen treten Schwierigkeiten durch anwachsende Abscheidungen auf. Zwecks Vermeidung der Ansatzbildung wird bei einem derartigen Verfahren die Elektrolysezelle so lange mit ungereinigtem Meerwasser oder ungereinigter Salzlösung betrieben, bis auf den Elektroden eine Schicht aus Verbindungen der verunreinigenden Metallionen, insbesondere Calciumcarbonat und/oder Magnesiumhydroxid, in einer hinreichenden und einen Stromwirkungsgrad von mehr als 90% bewirkenden Stärke abgeschieden ist, und dann werden die in dem ungereinigten Meerwasser oder in der ungereinigten Salzlösung enthaltenen Calcium- und/oder Magnesiumionen durch Zusatz von Natronlauge und/oder Calciumhydroxid sowie Natriumcarbonat bei einem pH-Wert von über 9 ganz oder teilweise ausgefällt, die Fällungsprodukte gegebenenfalls abgetrennt und die gereinigte Lösung der Elektrolysezelle zugeführt.In processes for the production of chlorine oxygen acids or their salts by electrolysis of sea water or salt solutions containing contaminating metal ions, difficulties arise due to increasing deposits. In order to avoid the formation of deposits, in such a method the electrolysis cell is operated with unpurified sea water or unpurified saline solution until a layer of compounds of the contaminating metal ions, in particular calcium carbonate and / or magnesium hydroxide, is present on the electrodes in a sufficient and current efficiency of more than 90 % effecting starch is deposited, and then the calcium and / or magnesium ions contained in the unpurified sea water or in the unpurified saline solution are precipitated, in whole or in part, by adding sodium hydroxide solution and / or calcium hydroxide and sodium carbonate at a pH of over 9, the Precipitation products are separated off if necessary and the cleaned solution is fed to the electrolysis cell.

Description

Magnesiumhydroxid neigt dazu, an der Kathode zu haften oder sich an den Wänden der Elektrolysekammer abzusetzen und dadurch die Strömung des Elektrolyten zu behindern und den Wirkungsgrad herabzusetzen. Die anwachsenden Ablagerungen verstopfen vor allem den Raum zwischen Anode und Kathode in der Elektrolysekammer, wodurch für längere Zeit ein kontinuierlicher Betrieb der Zelle unmöglich wird. Zur Vermei- dung dieser Schwierigkeiten hat man bereits nach bekannten Vorschlägen zur elektrolytischen Herstellung von Hypochlorit glatte, nicht unterbrochene Bleche als Kathoden verwendet und bei erhöhter Strömungsgeschwindigkeit ein bestimmtes Verhältnis von Strömungsgeschwindigkeit und Konzentration des Elektrolyten vorgesehen (DE-OS 26 19 497). Auch hat man in bekannten Elektrolysezellen zur Gewinnung von Hypochlorit aus Meerwasser durch bauliche Maßnahmen eine gerichtete Elektrolytströmung bestimmter Geschwindigkeit eingestellt (DE-AS 19 56 156). Bei der Herstellung von Alkalichloraten durch Elektrolyse von Alkalichloridlösungen ist es ferner bekannt, dem Elektrolyten Alkalihydroxid oder Carbonat zur Herabsetzung der Stromverluste zuzufügen. Bei derartigen Verfahren ist es ebenfalls bekannt, schwer lösliche Hydroxide, wie Calcium- oder Magnesiumhydroxid dem Elektrolyten zuzusetzen und diese Hydroxide während des ganzen Verlaufs der Elektrolyse in dem Elektrolyten suspendiert zu halten (DE-PS 90 060). Schließlich ist es bekannt, unerwünschte Metallionen aus Salzlösungen, die für die ChloralkaliElektrolyse bestimmt sind, durch Ausflockung der Eisen-, Magnesium- und Calciumionen als Carbonate bzw. Hydroxide zu entfernen (CH-PS 505 751).Magnesium hydroxide tends to adhere to the cathode or settle on the walls of the electrolysis chamber, thereby hindering the flow of the electrolyte and reducing the efficiency. The growing deposits mainly clog the space between the anode and cathode in the electrolysis chamber, making continuous cell operation impossible for a long time. For the avoidance du ng of these difficulties one has smooth after prior proposals for the electrolytic production of hypochlorite, uninterrupted plates used as cathodes and provided a specific ratio of flow rate and concentration of the electrolyte at elevated flow velocity (DE-OS 26 19 497). In known electrolysis cells for the extraction of hypochlorite from sea water, a directed electrolyte flow of a certain speed has been set by structural measures (DE-AS 19 56 156). In the production of alkali chlorates by electrolysis of alkali chloride solutions, it is also known to add alkali hydroxide or carbonate to the electrolyte in order to reduce the current losses. In such processes it is also known to add poorly soluble hydroxides, such as calcium or magnesium hydroxide, to the electrolyte and to keep these hydroxides suspended in the electrolyte throughout the course of the electrolysis (DE-PS 90 060). Finally, it is known to remove unwanted metal ions from salt solutions which are intended for chloralkali electrolysis by flocculating the iron, magnesium and calcium ions as carbonates or hydroxides (CH-PS 505 751).

Der Erfindung liegt die Aufgabe zugrunde, eine Verringerung bzw. Steuerung der Ansatzbildung auf der Kathode während der Elektrolyse von Meerwasser oder verunreinigende Metallionen enthaltenden Salzlösungen zur Gewinnung von Lösungen von Chlorsauerstoffsäuren bzw. deren Salze zu erzielen, wobei Vorteile bekannter Verfahren genutzt werden, ohne deren Nachteile in Kauf nehmen zu müssen.The invention has for its object to achieve a reduction or control of the formation of deposits on the cathode during the electrolysis of seawater or salt solutions containing contaminating metal ions for the recovery of solutions of chlorine-oxygen acids or their salts, advantages of known methods being used without their disadvantages to have to put up with.

Bei einem Verfahren der genannten Art zur Gewinnung von Chlorsauerstoffsäuren bzw. deren Salze durch Elektrolyse von Meerwasser oder verunreinigende Metallionen enthaltenden Salzlösungen besteht die Erfindung nun darin, daß man die Elektrolysezelle so lange mit ungereinigtem Meerwasser oder ungereinigter Salzlösung betreibt, bis auf den Elektroden eine Schicht aus Verbindungen der verunreinigenden Metallionen, insbesondere Calcium- und/oder Magnesiumionen, in einer hinreichenden und einen Stromwirkungsgrad von mehr als 90 % bewirkenden Stärke abgeschieden ist, und daß man dann die in dem ungereinigten Meerwasser oder in der ungereinigten Salzlösung enthaltenen Calcium-und/oder Magnesiumionen durch Zusatz von Natronlauge und/ oder Calciumhydroxid sowie Natriumcarbonat bei einem pH-Wert von über 9 ganz oder teilweise ausfällt, gegebenenfalls abtrennt und die gereinigte Lösung der Elektrolysezelle zuführt. Unter hinreichender Schichtstärke wird im Sinne der Erfindung eine Schichtdicke verstanden, die ausreicht, einen Stromwirkungsgrad von mehr als 90 % zu erreichen.In a method of the type mentioned for the production of chlorine oxygen acids or their salts by electrolysis of sea water or salt solutions containing contaminating metal ions, the invention now consists in operating the electrolysis cell with unpurified sea water or unpurified salt solution until a layer is formed on the electrodes Compounds of the contaminating metal ions, in particular calcium and / or magnesium ions, are deposited in a sufficient strength and effect a current efficiency of more than 90%, and that then the calcium and / or magnesium ions contained in the unpurified sea water or in the unpurified saline solution by adding sodium hydroxide solution and / or calcium hydroxide and sodium carbonate at a pH of more than 9 precipitates in whole or in part, if necessary separates and feeds the cleaned solution to the electrolysis cell. Adequate layer thickness is understood in the sense of the invention to mean a layer thickness which is sufficient to achieve a current efficiency of more than 90%.

Unabhängig von der Konzentration der Verunreinigungen in der Salzlösung wird diese in Durchführung des erfindungsgemäßen Verfahrens solange dem Elektrolyseur zugeführt, bis eine hinreichende Schichtdicke erreicht ist. Während des Aufbaus der Schicht aus insbesondere Calcium- und Magnesiumhydroxid und -carbonaten zu dieser Schichtstärke steigt die Stromausbeute langsam mit der Zeit an bis Werte von über 90 % erreicht werden. Dieser Anstieg erfolgt im allgemeinen in einem Zeitraum von 5 bis 30 Stunden, wobei die Zellenspannung bei gleicher Stromdichte in aller Regel um 0,2 bis 0,3 Volt ansteigt. Nach dieser Abscheidungsphase steigt die Zellenspannung weiter an und dieser Anstieg beträgt in Abhängigkeit von der Konzentration an verunreinigenden Ionen 1 bis 1,5 Volt innerhalb von 100 bis 2000 Stunden. Sobald Stromausbeuten von 90 erreicht sind, wird nach dem erfindungsgemäßen Verfahren die Zufuhr der ungereinigten Salzlösung abgestellt und nunmehr gereinigte Salzlösung dem Elektrolyten zugeführt. Die Verunreinigungen, die überwiegend in Form von Calcium-und/oder Magnesiumionen oder Eisenionen in der Salzlösung enthalten sind, werden durch Zusatz von Natronlauge und/ oder Calciumhydroxid sowie Natriumcarbonat bzw. Soda bei einem pH-Wert von über 9 ausgefällt. Bei Verwendung von Calciumhydroxid und Natriumcarbonat werden die Magnesiumionen durch die Hydroxylionen des Calciumhydroxids, die Calciumionen durch die Carbonationen niedergeschlagen und Magnesiumhydroxid bezw. Calciumcarbonat ausgefällt. Die Fällung der Verunreinigungen wird in aller Regel vollständig herbeigeführt. In manchen Fällen kann es in Abhängigkeit von den örtlichen Gegebenheiten der Elektrolysezellen ausreichend sein, wenn der überwiegende Teil der Verunreinigungen ausgefällt wird.Regardless of the concentration of the impurities in the salt solution, this is fed to the electrolyzer in carrying out the method according to the invention until a sufficient layer thickness is reached. During the build-up of the layer, in particular calcium and magnesium hydroxide and carbonates to this layer thickness, the current yield slowly increases over time until values of over 90% are reached. This increase generally takes place over a period of 5 to 30 hours, the cell voltage generally increasing by 0.2 to 0.3 volt with the same current density. After this deposition phase, the cell voltage continues to increase and this increase is 1 to 1.5 volts within 100 to 2000 hours, depending on the concentration of contaminating ions. As soon as electricity yields of 90 are reached, the supply of the unpurified salt solution is switched off by the method according to the invention and the purified salt solution is then fed to the electrolyte. The impurities, which are predominantly contained in the salt solution in the form of calcium and / or magnesium ions or iron ions, are precipitated by adding sodium hydroxide solution and / or calcium hydroxide and sodium carbonate or soda at a pH of more than 9. When using calcium hydroxide and sodium carbonate, the magnesium ions are precipitated by the hydroxyl ions of the calcium hydroxide, the calcium ions by the carbonate ions and magnesium hydroxide. Calcium carbonate precipitated. The precipitation of the impurities is usually brought about completely. In some cases, depending on the local conditions of the electrolytic cells, it may be sufficient if the majority of the contaminants are precipitated.

Im allgemeinen ist es zweckmäßig, die ausgefällten Verunreinigungen abzutrennen, beispielsweise durch Filtration unter gegebenenfalls Zusatz von Filtrierhilfsmitteln. In Fällen relativer Unempfindlichkeit von Elektrolysezellen gegen feinverteilte Feststoffe können die Fällungsprodukte jedoch auch ganz oder teilweise in feinverteiltem Zustand in der Speisesole bzw. Salzlösung verbleiben.In general, it is expedient to separate off the precipitated impurities, for example by filtration with the addition of filter aids where appropriate. In cases where electrolysis cells are relatively insensitive to finely divided solids, the precipitation products can also remain wholly or partly in the finely divided state in the brine or saline solution.

Es ist auch bekannt,' daß bereits Verunreinigungen von z.B. Calcium- und Magnesiumsalzen in Mengen von etwa 5 mg Ca++/1 bzw. 1 mg Mg++/1 in der Speisesole auf den Kathoden niedergeschlagen werden und allmählich eine Schichtbildung herbeiführen.It is also known that impurities of, for example, calcium and magnesium salts in amounts of about 5 mg Ca ++ / 1 and 1 mg Mg ++ / 1 are deposited on the cathodes in the brine and gradually cause a layer to form.

In dem erfindungsgemäßen Verfahren werden übliche Elektrolysezellen verwendet, beispielsweise Elektrolysezellen mit abwechselnd angeordneten vertikalen Anoden und Kathoden. Der Elektrodenabstand beträgt beispielsweise 2 bis 5 mm und der Elektrolyt mit einer Strömungsgeschwindigkeit von 0,3 bis 2 m/s wird bei einer Stromdichte von 2 bis 25 A/dm2 elektrolysiert. Die Temperatur des Elektrolyten kann 10 bis 50°C betragen und der pH-Wert kann im Bereich von 7 bis 10 liegen. Die Kathoden bestehen aus elektrisch leitenden, verschleißfesten Metallwerkstoffen, beispielsweise Titan, Nickel, oder Eisen- und Nickellegierungen. Das Anodenmaterial kann Graphit sein. Besonders geeignete Anoden sind jedoch mit Edelmetall oder Edelmetalloxid beschichtete Titan-, Niob- oder Tantal-Elektroden oder sogenannte dimensionsstabile Anoden, bei denen die elektrokatalytische Wirkung.von Mischoxiden von Edelmetallen und filmbildenden Metallen, insbesondere Titan, ausgeht.Conventional electrolytic cells are used in the method according to the invention, for example electrolytic cells with alternating vertical anodes and cathodes. The electrode spacing is, for example, 2 to 5 mm and the electrolyte with a flow rate of 0.3 to 2 m / s is electrolyzed at a current density of 2 to 25 A / dm 2 . The temperature of the electrolyte can be 10 to 50 ° C and the pH can range from 7 to 10. The cathodes are made of electrically conductive, wear-resistant metal materials, such as titanium, nickel, or iron and nickel alloys. The anode material can be graphite. Particularly suitable anodes, however, are titanium, niobium or tantalum electrodes coated with noble metal or noble metal oxide or so-called dimensionally stable anodes, in which the electrocatalytic effect is based on mixed oxides of noble metals and film-forming metals, in particular titanium.

Bei der elektrolytischen Herstellung von Hypochlorit aus Meerwasser oder Salzlösung laufen folgende chemischen Reaktionen an den Elektroden ab.The following chemical reactions take place at the electrodes in the electrolytic production of hypochlorite from sea water or saline.

An der Anode:

Figure imgb0001
At the anode:
Figure imgb0001

An der Kathode:

Figure imgb0002
Figure imgb0003
 On the cathode:
Figure imgb0002
Figure imgb0003

Das Chlor reagiert mit der Natronlauge unter Bildung von Natriumhypochlorit gemäß:

Figure imgb0004
The chlorine reacts with the sodium hydroxide solution to form sodium hypochlorite according to:
Figure imgb0004

Natriumhypochlorit reagiert mit Wasser unter Bildung von Hypochlorsäure

Figure imgb0005
Sodium hypochlorite reacts with water to form hypochlorous acid
Figure imgb0005

Hypochlorsäure dissoziiert gemäß

Figure imgb0006
Hypochlorous acid dissociates according to
Figure imgb0006

Das Überwiegen von Reaktion (1) oder Reaktion (2) hängt von dem pH-Wert des Milieus ab. Bei einem pH-Wert > 5 liegt das gesamte Aktivchlor in Form von Hypochlorsäure und Hypochlorit-Ionen vor. Dabei ist der Anteil an Hypochlorit-Ionen umso größer je höher der pH-Wert ist.The predominance of reaction (1) or reaction (2) depends on the pH of the environment. At a pH> 5, the entire active chlorine is in the form of hypochlorous acid and hypochlorite ions. The higher the pH value, the greater the proportion of hypochlorite ions.

Die Vorteile des erfindungsgemäßen Verfahrens sind darin zu sehen, daß in sämtlichen Elektrolysezellen der Anlage gleichmäßig eine gezielte Schichtbildung auf den Kathoden erfolgt. Die erfindungsgemäß abgeschiedene dünne Passivschicht bestimmter Stärke unterbindet eine zu starke Reduktion der Hypochloritionen, erhöht somit die Ausbeute an Hypochlorit und erübrigt die Zellenreinigung bzw. vermindert sie in einem ganz erheblichen Umfang.The advantages of the method according to the invention can be seen in the fact that a targeted layer formation on the cathodes occurs uniformly in all electrolysis cells of the system. The thin passive layer of a certain thickness deposited according to the invention prevents an excessive reduction of the hypochlorite ions, thus increases the yield of hypochlorite and makes cell cleaning unnecessary or reduces it to a very considerable extent.

Die Erfindung wird nachstehend und beispielhaft gemäß dem Diagramm der Figur 1 erläutert, worin der Wirkungsgrad von Hypochloritzellen in Abhängigkeit von der Laufzeit dargestellt ist.The invention is explained below and by way of example according to the diagram in FIG. 1, which shows the efficiency of hypochlorite cells as a function of the running time.

AusführungsbeispielEmbodiment

Eine Anlage mit 8 hintereinandergeschalteten Zellen wurde mit Meerwasser von 28°C mit einer Menge von 20 m3/h betrieben. Über insgesamt 30 Stunden wurde die Stromstärke langsam von 500 A auf 5000 A erhöht. Die Spannung stieg dabei von 25 auf 35 V. Der Gehalt an aktivem Chlor in Form von NaOCl stieg in demselben Zeitraum von 0,2 g/l auf 2,8 g/l. Die Stromausbeute verlief gemäß dem Diagramm der Fig. 1, d.h. ohne Zusatz von Fällchemikalien würde sich die Stromausbeute asymptotisch dem Wert 100 % nähern, gleichzeitig würde aber die Spannung ansteigen und die Verschmutzung zunehmen, so daß nach spätestens 2000 h eine Stillegung der Anlage mit anschließender Säurewäsche erforderlich werden würde. Während bei Normalbetrieb der Spannungsabfall pro Zelle ca. 4,5 V und die Stromausbeute 96 % beträgt, steigt die Spannung bei verschmutzten Zellen auf bis zu 6 V und die Stromausbeute kann fast 100 % betragen. Der Gleichstrom-Energieverbrauch beträgt im ersten Falle bei Normalbetrieb 3,6 kWh/kg C12, im zweiten Falle mit verschmutzten Zellen 4,5 kWh/kg C12. Dieser Anstieg im Energieverbrauch und die Notwendigkeit des regelmäßigen Waschens kann durch Fällung der Verunreinigungen verhindert werden, wenn man erfindungsgemäß mit dieser Fällung beginnt, nachdem sich eine Schutzschicht von hinreichender Stärke auf den Kathoden gebildet hat.A plant with 8 cells connected in series was operated with sea water at 28 ° C. at a rate of 20 m 3 / h. The current strength was slowly increased from 500 A to 5000 A over a total of 30 hours. The voltage rose from 25 to 35 V. The content of active chlorine in the form of NaOCl rose from 0.2 g / l to 2.8 g / l in the same period. The current yield ran according to the diagram in FIG. 1, ie without the addition of precipitation chemicals, the current yield would asymptotically approach the value of 100%, but at the same time the voltage would rise and the Pollution increase, so that after 2000 hours at the latest the plant would have to be shut down with acid washing. While during normal operation the voltage drop per cell is approx.4.5 V and the current yield is 96%, the voltage increases when the cells are dirty up to 6 V and the current yield can be almost 100%. The direct current energy consumption is 3.6 kWh / kg C1 2 in normal operation in the first case, and 4.5 kWh / kg C1 2 in the second case with dirty cells. This increase in energy consumption and the need for regular washing can be prevented by precipitating the impurities if, according to the invention, this precipitation starts after a protective layer of sufficient strength has formed on the cathodes.

Claims (2)

1. Verfahren zur Gewinnung von Chlorsauerstoffsäuren bzw. deren Salze durch Elektrolyse von Meerwasser oder verunreinigende Metallionen enthaltenden Salzlösungen, dadurch gekennzeichnet, daß man die Elektrolysezelle so lange mit ungereinigtem Meerwasser oder ungereinigter Salzlösung betreibt, bis auf den Elektroden eine Schicht aus Verbindungen der verunreinigenden Metallionen, insbesondere Calcium- und/oder Magnesiumionen, in einer hinreichenden und einen Stromwirkungsgrad von mehr als 90 % bewirkenden Stärke abgeschieden ist, und daß man dann die in dem ungereinigten Meerwasser oder in der ungereinigten Salzlösung enthaltenen Calcium- und/oder Magnesiumionen durch Zusatz von Natronlauge und/oder Calciumhydroxid sowie Natriumcarbonat bei einem pH-Wert von über 9 ganz oder teilweise ausfällt, gegebenenfalls abtrennt und die gereinigte Lösung der Elektrolysezelle zuführt.1. A process for the production of chlorine-oxygen acids or their salts by electrolysis of sea water or salt solutions containing contaminating metal ions, characterized in that the electrolysis cell is operated with unpurified sea water or unpurified salt solution until a layer of compounds of the contaminating metal ions on the electrodes, especially calcium and / or magnesium ions, is deposited in a sufficient and a current efficiency of more than 90% effecting strength, and that one then contains the calcium and / or magnesium ions contained in the unpurified sea water or in the unpurified saline solution by adding sodium hydroxide solution and / or calcium hydroxide and sodium carbonate precipitates in whole or in part at a pH of more than 9, if necessary separating them and feeding the cleaned solution to the electrolytic cell. 2. Verfahren nach Anspruch 1, dadurch gekennzeichnet daß Calciumhydroxid und Natriumcarbonat verwendet und die Calciumionen als Calciumcarbonat und die Magnesiumionen als Magnesiumhydroxid ausgefällt werden.2. The method according to claim 1, characterized in that calcium hydroxide and sodium carbonate are used and the calcium ions are precipitated as calcium carbonate and the magnesium ions as magnesium hydroxide.
EP79200618A 1978-11-22 1979-10-25 Preparation of oxy-halogenated acids and their salts by electrolysis Expired EP0011886B1 (en)

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DE19782850575 DE2850575A1 (en) 1978-11-22 1978-11-22 METHOD FOR THE ELECTROLYTIC PRODUCTION OF CHLORINE OXYGEN ACIDS OR. THEIR SALTS
DE2850575 1978-11-22

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EP0011886B1 EP0011886B1 (en) 1981-11-11

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EP79200618A Expired EP0011886B1 (en) 1978-11-22 1979-10-25 Preparation of oxy-halogenated acids and their salts by electrolysis

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US (1) US4238302A (en)
EP (1) EP0011886B1 (en)
JP (1) JPS5573882A (en)
BR (1) BR7907561A (en)
DE (2) DE2850575A1 (en)

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US5064514A (en) * 1990-03-30 1991-11-12 Olin Corporation Apparatus for the production of chloric acid
US5616234A (en) * 1995-10-31 1997-04-01 Pepcon Systems, Inc. Method for producing chlorine or hypochlorite product
US7611280B2 (en) * 2003-12-16 2009-11-03 Harco Laboratories, Inc. EMF sensor with protective sheath
WO2013131102A1 (en) * 2012-03-02 2013-09-06 Miox Corporation Waste to product on site generator
CN111039474A (en) * 2019-12-26 2020-04-21 西安泰金工业电化学技术有限公司 Power plant circulating water treatment system and method

Citations (2)

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Publication number Priority date Publication date Assignee Title
FR1406874A (en) * 1963-11-05 1965-07-23 Casson And Crane Improvements to the preparation of chlorine peroxide
US4088550A (en) * 1977-05-25 1978-05-09 Diamond Shamrock Corporation Periodic removal of cathodic deposits by intermittent reversal of the polarity of the cathodes

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US3799849A (en) * 1972-06-26 1974-03-26 Hooker Chemical Corp Reactivation of cathodes in chlorate cells
FR2244708B1 (en) * 1973-09-25 1977-08-12 Ugine Kuhlmann
US3974051A (en) * 1975-05-07 1976-08-10 Diamond Shamrock Corporation Production of hypochlorite from impure saline solutions
US4085014A (en) * 1977-04-21 1978-04-18 Diamond Shamrock Corporation Elimination of impurities from sea water cell feed to prevent anode deposits

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR1406874A (en) * 1963-11-05 1965-07-23 Casson And Crane Improvements to the preparation of chlorine peroxide
US4088550A (en) * 1977-05-25 1978-05-09 Diamond Shamrock Corporation Periodic removal of cathodic deposits by intermittent reversal of the polarity of the cathodes

Also Published As

Publication number Publication date
BR7907561A (en) 1980-07-08
DE2961328D1 (en) 1982-01-14
JPS5573882A (en) 1980-06-03
DE2850575A1 (en) 1980-06-04
EP0011886B1 (en) 1981-11-11
US4238302A (en) 1980-12-09

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