EP1513634A2 - Method for reducing the corrosivity of cooling or process water - Google Patents

Method for reducing the corrosivity of cooling or process water

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Publication number
EP1513634A2
EP1513634A2 EP03735588A EP03735588A EP1513634A2 EP 1513634 A2 EP1513634 A2 EP 1513634A2 EP 03735588 A EP03735588 A EP 03735588A EP 03735588 A EP03735588 A EP 03735588A EP 1513634 A2 EP1513634 A2 EP 1513634A2
Authority
EP
European Patent Office
Prior art keywords
cooling
water
process water
soluble salt
buffering effect
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.)
Granted
Application number
EP03735588A
Other languages
German (de)
French (fr)
Other versions
EP1513634B1 (en
Inventor
Wolfgang Hater
Ulrich Kiedrowicz
Gerd Grelewitz
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.)
Henkel AG and Co KGaA
Original Assignee
Henkel AG and Co KGaA
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Filing date
Publication date
Application filed by Henkel AG and Co KGaA filed Critical Henkel AG and Co KGaA
Publication of EP1513634A2 publication Critical patent/EP1513634A2/en
Application granted granted Critical
Publication of EP1513634B1 publication Critical patent/EP1513634B1/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C22/05—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions
    • C23C22/06—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6
    • C23C22/34—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 containing fluorides or complex fluorides
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/12—Accessories for subsequent treating or working cast stock in situ
    • B22D11/124—Accessories for subsequent treating or working cast stock in situ for cooling
    • B22D11/1245—Accessories for subsequent treating or working cast stock in situ for cooling using specific cooling agents
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C22/05—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions
    • C23C22/06—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6
    • C23C22/48—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 not containing phosphates, hexavalent chromium compounds, fluorides or complex fluorides, molybdates, tungstates, vanadates or oxalates
    • C23C22/56—Treatment of aluminium or alloys based thereon
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C22/05—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions
    • C23C22/68—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous solutions with pH between 6 and 8

Definitions

  • the invention includes a method for reducing corrosion in cooling and process water, which can lead to an entry of acids into the system, e.g. B. in continuous casting plants of the steel industry.
  • the entry of silicon tetrafluoride and HF in the spray zones resulting from fluoride burn-off of the casting powder leads to a drop in the pH value in the spray water and to corrosion of system parts.
  • the object of the invention was to provide an effective method for reducing corrosion without having the disadvantages of the known methods.
  • a method should be made available which is not very critical with regard to a pH increase and at the same time allows a quick adaptation to changing operating conditions.
  • the invention relates to a method for reducing the corrosiveness of cooling or process water, in which there is a lowering of the pH due to an entry of acids, characterized in that at least one water-soluble salt with a buffering effect is added to the cooling or process water added.
  • water-soluble is understood to mean that at least 1 g of the salt dissolves in 1 liter of water at 20 ° C.
  • the water-soluble salt with a buffering effect is preferably used in the form of an aqueous solution, since this can simply be metered in via metering pumps.
  • the cooling or process water in the reservoir and in the piping system is at least 5 times as large, preferably at least 10 times as large and in particular at least 20 times as large as the amount of cooling or process water in the work area.
  • the method is particularly suitable for such a device.
  • the method can also be carried out in such a way that the cooling or process water is conducted in a continuous system which comprises a piping system and a working area.
  • the cooling or process water is not circulated, but is drained off after a single use.
  • “Working area” is understood to mean that area of the device in which the cooling or process water has its technically intended effect. This can be, for example, the area in which the cooling or process water exchanges heat or substances with the ambient air or with other substrates
  • it can be a cooling device in which the cooling or process water absorbs heat from this heat by direct or indirect contact with a medium to be cooled.An example of this is the evaporation zone of a cooling tower, but this can also be an area act by bringing the cooling or process water into contact with warm substrate surfaces in order to cool them, for example in the case of continuous casting plants in the steel industry, where the cooling or process water is sprayed onto metal surfaces to be cooled.
  • the cooling or process water In the work area, the cooling or process water usually not only comes into contact with the intended substrate, but also with the ambient air. Therefore, the cooling or process water in this area absorbs foreign matter either directly from the substrate surface or from the ambient air. These can be gaseous, solid or liquid in nature. This chemical absorption changes the chemical composition of the cooling or process water. In the example given above, the entry of acidic substances leads to a drop in the pH value in the cooling or process water. As a result, its corrosiveness to the materials of the device and possibly also to the substrate is undesirably increased.
  • the drop in pH is counteracted by metering a water-soluble salt with a buffering effect into the cooling or process water.
  • a water-soluble salt is buffered Effect metered into the pipe system at a point that is seen in the flow direction of the cooling or process water in front of the work area. Accordingly, it is not necessary to change the chemical composition of the entire cooling or process water, the main amount of which is in the reservoir, by adding the salt with a buffering effect. Rather, you only change the composition of that part of the cooling or process water that subsequently enters into a mass exchange with the environment in the work area.
  • the water-soluble salt with a buffering effect is dosed, based on experience, in proportion to the amount of water that flows through the work area. For example, per m 3 of cooling or process water that flows through the work area, a quantity of salt with a buffering effect determined by experience can be metered in. Accordingly, one embodiment of the method according to the invention is that the water-soluble salt with a buffering effect is metered in as a function of the amount of cooling or process water which flows through the working area within a predetermined time interval.
  • the dosage amount of the salt with a buffering effect can be made dependent on the currently determined need. This can apply to the entire addition of the salt with a buffering effect. However, one can also proceed in such a way that a basic amount of salt with a buffering effect is metered in proportion to the amount and additionally a fine metering is carried out on the basis of the currently determined need.
  • the procedure is preferably such that the value of at least one guide variable in the cooling or process water is measured continuously or discontinuously and the water-soluble salt with a buffering action is metered in as a function of the value of the guide variable.
  • the value of the guide variable is expediently measured either in the work area itself, in a sample of the cooling or process water taken in the work area or in that part of the line system which is located behind the work area in the direction of flow of the cooling or process water.
  • a sample can be taken in the work area by either draining off part of the cooling or process water and discarding it after measuring the guide variable or by returning it to the work area or the pipe system.
  • the guide variable can be selected, for example, from the pH value, the fluoride ion concentration and the acid capacity of the cooling or process water.
  • the water-soluble salt with a buffering effect is added when the pH value falls below a predetermined threshold value.
  • This threshold value to be determined depending on the material properties of the device and / or the substrate can be, for example, in the range from 4 to 7, in particular from 5 to 6. If the value falls below the threshold value, either salt with a buffering effect is added until the threshold value is exceeded again, or an amount of salt with a buffering effect is added, which depends on the difference between the threshold value and the pH actually measured.
  • the fluoride ion concentration can be selected as the guide variable. As mentioned in the introduction, this is the case, for example, with continuous casting plants in the steel industry.
  • the acid input is then proportional to the increase in the fluoride ion concentration.
  • the water-soluble salt with a buffering effect can be metered in if the fluoride ion concentration exceeds a predetermined threshold value, which can be, for example, in the range from 40 to 300 mg / 1, in particular in the range from 60 to 200 mg / 1. In this case, it is particularly advantageous to determine the deviation of the fluoride ion concentration from the predetermined threshold value and to add the salt with a buffering effect depending on the amount of this deviation.
  • the acid capacity of the cooling or process water is selected as the guide variable. This is defined by the amount (in millimoles) of strong monobasic acid that has to be added to one liter of the water in order to Lower the value to 4.3. It is expressed in millimoles of acid added per liter of water.
  • the water-soluble salt with a buffering effect is metered in when the acid capacity falls below a predetermined threshold. This can be, for example, in the range from 0.1 to 1 millimole / l, in particular from 0.3 to 0.7 millimole / l.
  • the proportionality factor is preferably determined empirically again.
  • any water-soluble salt (as defined above) that is known to have a buffering effect can be selected as the salt with a buffering effect.
  • the water-soluble salt with a buffering effect can be selected from hydrogen carbonates, carbonates, borates, orthophosphates and polyphosphates.
  • Such salts are preferably selected which are selected from alkali, alkaline earth and ammonium salts, preferably from sodium salts for reasons of cost and the environment.
  • preferred salts with a buffering action are, in particular, alkali or ammonium salts, especially the sodium salts, with hydrogen carbonate, carbonate, borate, orthophosphate or polyphosphate ions.
  • the method according to the invention is particularly suitable for reducing the corrosiveness of cooling or process water from continuous casting plants in the steel industry.
  • a preferred embodiment of the invention consists in additionally preventing the deposition of calcium fluoride in the cooling or process water by additionally adding to the cooling or process water at least one further water-soluble salt which contains at least one of the following ions: magnesium cations, cations trivalent metals, anions of oligo- or polyphosphate.
  • at least one further water-soluble salt which contains at least one of the following ions: magnesium cations, cations trivalent metals, anions of oligo- or polyphosphate.
  • magnesium cations cations trivalent metals
  • anions of oligo- or polyphosphate there is a water-soluble salt with magnesium cations to. More detailed information on special embodiments and preferred addition amounts can be found in the aforementioned DE 100 64412, to which reference is hereby expressly made.
  • additives known for this area of application can be added to the cooling or process water.
  • examples of these are scale inhibitors, corrosion inhibitors and dispersants.
  • examples of such additives are polymers or copolymers of unsaturated carboxylic acids, such as, for example, acrylic acid, methacrylic acid and / or maleic acid, which can additionally carry phosphonic or phosphinic acid groups.
  • polyamino acids such as polyaspartic acid are known.
  • polymeric molecules or ions such as aminoalkylenephosphonic acids, phosphonocarboxylic acids, geminal diphosphonic acids, which are not capable of forming chelate complexes are known for this purpose. Selected examples are contained in DE 10064412 already mentioned.
  • the pH value is continuously measured in the spray water of a continuous casting plant by means of a pH electrode, and the metering pump for the water-soluble, buffering salts is started when the temperature falls below a predetermined threshold. If the threshold value is exceeded, the metering is stopped again.
  • the threshold value here is usually in the pH range between 4 and 7, preferably in the pH range from 5 to 6.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Preventing Corrosion Or Incrustation Of Metals (AREA)
  • Non-Silver Salt Photosensitive Materials And Non-Silver Salt Photography (AREA)
  • Heat Treatments In General, Especially Conveying And Cooling (AREA)

Abstract

The invention relates to a method for reducing the corrosivity of cooling or process water, during which the pH value is lowered by introducing acids. The inventive method is characterized in that at least one water-soluble salt having a buffering effect is metered to the cooling water or process water. This preferably ensues either proportionally with regard to quantity or according to the measured value of a characteristic control value. The method can be applied to continuous flow systems or to circulation systems and, in particular, can be used in continuous casting installations utilized in the steel industry.

Description

"Verfahren zur Verringerung der Korrosivität von Kühl- oder Prozeßwasser""Process for reducing the corrosiveness of cooling or process water"
Die Erfindung beinhaltet ein Verfahren zur Verringerung der Korrosion in Kühl- und Prozesswässern, bei denen es zu einem Eintrag von Säuren in das System kommen kann, z. B. in Stranggussanlagen der Stahlindustrie. In diesem Fall führt der von Fluoridabbrand des Gießpulvers herrührende Eintrag von Siliciumtetrafluorid und HF in den Spritzzonen zu einem Abfall des pH-Wertes im Spritzwasser und zur Korrosion von Anlagenteilen.The invention includes a method for reducing corrosion in cooling and process water, which can lead to an entry of acids into the system, e.g. B. in continuous casting plants of the steel industry. In this case, the entry of silicon tetrafluoride and HF in the spray zones resulting from fluoride burn-off of the casting powder leads to a drop in the pH value in the spray water and to corrosion of system parts.
Nach dem Stand der Technik werden zur Anhebung des pH-Wertes in diesen Wässern starke Laugen, vor allem Natronlauge, in das Spritzwasser dosiert. Wegen der starken Schwankungen der Betriebsbedingungen kommt es jedoch häufig zu einer starken Erhöhung des pH-Wertes im Kühlwasser, so dass starke Ablagerungen von Calciumcarbonat im System die Folge sind.According to the state of the art, strong alkalis, especially sodium hydroxide, are dosed into the spray water to raise the pH in these waters. Due to the strong fluctuations in the operating conditions, however, there is often a sharp increase in the pH value in the cooling water, which results in heavy deposits of calcium carbonate in the system.
Der Erfindung lag die Aufgabe zu Grunde, ein effektives Verfahren zur Verringerung der Korrosion zur Verfügung zu stellen, ohne die Nachteile der bekannten Verfahren aufzuweisen. Insbesondere sollte ein Verfahren zur Verfügung gestellt werden, das hinsichtlich einer pH-Anhebung wenig kritisch ist, und gleichzeitig einen schnelle Anpassung an wechselnde Betriebsbedingungen erlaubt.The object of the invention was to provide an effective method for reducing corrosion without having the disadvantages of the known methods. In particular, a method should be made available which is not very critical with regard to a pH increase and at the same time allows a quick adaptation to changing operating conditions.
Die Erfindung betrifft ein Verfahren zur Verringerung der Korrosivität von Kühl- oder Prozesswasser, bei dem es aufgrund eines Eintrags von Säuren zu einer Absenkung des pH-Werts kommt, dadurch gekennzeichnet, dass man zu dem Kühl- oder Prozesswasser mindestens ein wasserlösliches Salz mit puffernder Wirkung zudosiert. Unter „wasserlöslich" wird hierbei verstanden, dass sich mindestens 1 g des Salzes bei 20 °C in 1 I Wasser lösen. Das wasserlösliche Salz mit puffernder Wirkung setzt man vorzugsweise in Form einer wässrigen Lösung ein, da diese einfach über Dosierpumpen dosiert werden kann.The invention relates to a method for reducing the corrosiveness of cooling or process water, in which there is a lowering of the pH due to an entry of acids, characterized in that at least one water-soluble salt with a buffering effect is added to the cooling or process water added. In this context, “water-soluble” is understood to mean that at least 1 g of the salt dissolves in 1 liter of water at 20 ° C. The water-soluble salt with a buffering effect is preferably used in the form of an aqueous solution, since this can simply be metered in via metering pumps.
In der Praxis trifft man häufig Einrichtungen, bei denen das Kühl- oder Prozesswasser in einem Kreislauf geführt wird, der ein Reservoir, ein Leitungssystem und einen Arbeitsbereich umfasst, und der Eintrag von Säure im Arbeitsbereich erfolgt, wobei die Menge des Kühl- oder Prozesswassers im Reservoir und im Leitungssystem mindestens 5 mal so groß, vorzugsweise mindestens 10 mal so groß und insbesondere mindestens 20 mal so groß ist wie die Menge des Kühl- oder Prozesswassers im Arbeitsbereich. Das Verfahren ist für eine derartige Einrichtung besonders geeignet.In practice, facilities are frequently found in which the cooling or process water is conducted in a circuit which comprises a reservoir, a piping system and a work area, and the entry of acid in the work area takes place, the The amount of cooling or process water in the reservoir and in the piping system is at least 5 times as large, preferably at least 10 times as large and in particular at least 20 times as large as the amount of cooling or process water in the work area. The method is particularly suitable for such a device.
Das Verfahren kann jedoch auch in der Weise ausgeführt werden, daß das Kühl- oder Prozeßwasser in einem Durchlaufsystem geführt wird, das ein Leitungssystem und einen Arbeitsbereich umfaßt. In dieser Ausführungsform wird das Kühl- oder Prozeßwasser also nicht im Kreis geführt, sondern nach einmaligem Gebrauch abgeleitet.However, the method can also be carried out in such a way that the cooling or process water is conducted in a continuous system which comprises a piping system and a working area. In this embodiment, the cooling or process water is not circulated, but is drained off after a single use.
Unter „Arbeitsbereich" wird dabei derjenige Bereich der Einrichtung verstanden, in dem das Kühl- oder Prozeßwasser seine technisch vorgesehene Wirkung entfaltet. Dies kann beispielsweise derjenige Bereich sein, in dem das Kühl- oder Prozeßwasser mit der Umgebungsluft oder mit anderen Substraten Wärme oder Stoffe austauscht. Beispielsweise kann es sich um eine Kühleinrichtung handeln, in der das Kühl- oder Prozeßwasser durch direkten oder indirekten Kontakt mit einem zu kühlenden Medium aus diesem Wärme aufnimmt. Ein Beispiel hierfür ist die Verdampfungszone eines Kühlturms. Es kann sich hierbei jedoch auch um einen Bereich handeln, in dem das Kühl- oder Prozeßwasser in Kontakt mit warmen Substratoberflächen gebracht wird, um diese zu kühlen. Dies ist beispielsweise bei Strangußanlagen der Stahlindustrie der Fall, wo das Kühl- oder Prozeßwasser auf abzukühlende Metalloberflächen aufgespritzt wird.“Working area” is understood to mean that area of the device in which the cooling or process water has its technically intended effect. This can be, for example, the area in which the cooling or process water exchanges heat or substances with the ambient air or with other substrates For example, it can be a cooling device in which the cooling or process water absorbs heat from this heat by direct or indirect contact with a medium to be cooled.An example of this is the evaporation zone of a cooling tower, but this can also be an area act by bringing the cooling or process water into contact with warm substrate surfaces in order to cool them, for example in the case of continuous casting plants in the steel industry, where the cooling or process water is sprayed onto metal surfaces to be cooled.
Im Arbeitsbereich kommt das Kühl- oder Prozeßwasser in der Regel nicht nur in Kontakt mit dem vorgesehenen Substrat, sondern auch mit der Umgebungsluft. Daher nimmt das Kühl- oder Prozeßwasser in diesem Bereich entweder direkt von der Substratoberfläche oder aus der Umgebungsluft Fremdstoffe auf. Diese können gasförmiger, fester oder flüssiger Natur sein. Durch diese Stoffaufnahme verändert sich die chemische Zusammensetzung des Kühl- oder Prozeßwassers. Im einleitend dargelegten Beispiel kommt es durch Eintrag sauer wirkender Substanzen zu einem Abfall des pH-Wertes im Kühl- oder Prozeßwasser. Hierdurch wird dessen Korrosivität gegenüber den Materialien der Einrichtung und ggf. auch gegenüber dem Substrat auf unerwünschte Weise erhöht.In the work area, the cooling or process water usually not only comes into contact with the intended substrate, but also with the ambient air. Therefore, the cooling or process water in this area absorbs foreign matter either directly from the substrate surface or from the ambient air. These can be gaseous, solid or liquid in nature. This chemical absorption changes the chemical composition of the cooling or process water. In the example given above, the entry of acidic substances leads to a drop in the pH value in the cooling or process water. As a result, its corrosiveness to the materials of the device and possibly also to the substrate is undesirably increased.
Erfindungsgemäß wirkt man dem Abfall des pH-Wertes dadurch entgegen, daß man dem Kühl- oder Prozeßwasser ein wasserlösliches Salz mit puffernder Wirkung zudosiert. Zweckmäßigerweise erfolgt dies nicht im Reservoir selbst, sondern im oder kurz vor dem Arbeitsbereich. Daher ist es bevorzugt, daß man das wasserlösliche Salz mit puffernder Wirkung in das Leitungssystem an einer Stelle zudosiert, die in Strömungsrichtung des Kühl- oder Prozeßwassers gesehen vor dem Arbeitsbereich liegt. Demnach ist es nicht erforderlich, durch Zugabe des Salzes mit puffernder Wirkung die chemische Zusammensetzung des gesamten Kühl- oder Prozeßwassers, dessen Hauptmenge sich im Reservoir befindet, zu ändern. Man ändert vielmehr nur die Zusammensetzung desjenigen Teils des Kühl- oder Prozeßwassers, der anschließend im Arbeitsbereich in einen Stoffaustausch mit der Umgebung tritt.According to the invention, the drop in pH is counteracted by metering a water-soluble salt with a buffering effect into the cooling or process water. This is expediently not done in the reservoir itself, but in or just before the work area. It is therefore preferred that the water-soluble salt is buffered Effect metered into the pipe system at a point that is seen in the flow direction of the cooling or process water in front of the work area. Accordingly, it is not necessary to change the chemical composition of the entire cooling or process water, the main amount of which is in the reservoir, by adding the salt with a buffering effect. Rather, you only change the composition of that part of the cooling or process water that subsequently enters into a mass exchange with the environment in the work area.
Im einfachsten Fall dosiert man das wasserlösliche Salz mit puffernder Wirkung, basierend auf Erfahrungswerten, mengenproportional zu derjenigen Wassermenge, die den Arbeitsbereich durchfließt. Beispielsweise kann man pro m3 Kühl- oder Prozeßwasser, der den Arbeitsbereich durchfließt, eine durch Erfahrung ermittelte Menge an Salz mit puffernder Wirkung zudosieren. Demnach besteht eine Ausführungsform des erfindungsgemäßen Verfahrens darin, daß man das wasserlösliche Salz mit puffernder Wirkung in Abhängigkeit von der Menge an Kühl- oder Prozeßwasser zudosiert, die innerhalb eines vorgegebenen Zeitintervalls den Arbeitsbereich durchfließt.In the simplest case, the water-soluble salt with a buffering effect is dosed, based on experience, in proportion to the amount of water that flows through the work area. For example, per m 3 of cooling or process water that flows through the work area, a quantity of salt with a buffering effect determined by experience can be metered in. Accordingly, one embodiment of the method according to the invention is that the water-soluble salt with a buffering effect is metered in as a function of the amount of cooling or process water which flows through the working area within a predetermined time interval.
Alternativ oder ergänzend hierzu kann man die Dosiermenge des Salzes mit puffernder Wirkung von dem aktuell ermittelten Bedarf abhängig machen. Dies kann für die gesamte Zugabe des Salzes mit puffernder Wirkung gelten. Man kann jedoch auch so verfahren, daß man eine Grundmenge an Salz mit puffernder Wirkung mengenproportional zudosiert und zusätzlich eine Feindosierung anhand des aktuell ermittelten Bedarfs durchführt. Für die Dosierung entsprechend dem aktuell ermittelten Bedarf geht man vorzugsweise so vor, daß man kontinuierlich oder diskontinuierlich den Wert mindestens einer Leitgröße im Kühl- oder Prozeßwasser mißt und das wasserlösliche Salz mit puffernder Wirkung in Abhängigkeit von dem Wert der Leitgröße zudosiert.As an alternative or in addition to this, the dosage amount of the salt with a buffering effect can be made dependent on the currently determined need. This can apply to the entire addition of the salt with a buffering effect. However, one can also proceed in such a way that a basic amount of salt with a buffering effect is metered in proportion to the amount and additionally a fine metering is carried out on the basis of the currently determined need. For the dosing according to the currently determined need, the procedure is preferably such that the value of at least one guide variable in the cooling or process water is measured continuously or discontinuously and the water-soluble salt with a buffering action is metered in as a function of the value of the guide variable.
Dabei kann man prinzipiell auf 2 unterschiedliche Weisen verfahren: Man kann entweder eine obere oder eine untere Wertgrenze für die Leitgröße definieren und bei Unter- bzw. Überschreiten dieses Grenzwerts so lange wasserlösliches Salz zudosieren, bis der Grenzwert wieder über- bzw. unterschritten wird. Oder man legt einen Sollwert für die Leitgröße fest, bestimmt die Abweichung des gemessenen Wertes von diesem Sollwert und dosiert eine Menge an Salz mit puffernder Wirkung, die proportional ist zur Differenz zwischen dem Sollwert und dem aktuellen Wert der Leitgröße. Der Proportionalitätsfaktor hängt beispielsweise von dem Volumen des zu behandelnden Wasserstroms ab und kann aus diesem berechnet oder vorzugsweise experimentell ermittelt werden. Zweckmäßigerweise mißt man den Wert der Leitgröße entweder im Arbeitsbereich selbst, in einer im Arbeitsbereich entnommenen Probe des Kühl- oder Prozeßwassers oder in demjenigen Teil des Leitungssystems, das sich in Fließrichtung des Kühl- oder Prozeßwassers hinter dem Arbeitsbereich befindet. Im Arbeitsbereich kann man dadurch eine Probe nehmen, daß man entweder einen Teil des Kühl- oder Prozeßwassers ableitet und nach Messung der Leitgröße verwirft oder wieder in den Arbeitsbereich oder in das Leitungssystem zurückführt.There are two main ways of doing this: You can either define an upper or a lower value limit for the guide variable and, if this limit value is exceeded or fallen short of, meter in water-soluble salt until the limit value is again exceeded or fallen below. Or you can set a target value for the master variable, determine the deviation of the measured value from this target value and dose an amount of salt with a buffering effect that is proportional to the difference between the target value and the current value of the master variable. The proportionality factor depends, for example, on the volume of the water flow to be treated and can be calculated therefrom or preferably determined experimentally. The value of the guide variable is expediently measured either in the work area itself, in a sample of the cooling or process water taken in the work area or in that part of the line system which is located behind the work area in the direction of flow of the cooling or process water. A sample can be taken in the work area by either draining off part of the cooling or process water and discarding it after measuring the guide variable or by returning it to the work area or the pipe system.
Die Leitgröße kann beispielsweise ausgewählt sein aus dem pH-Wert, der Fluoridionen- Konzentration und der Säurekapazität des Kühl- oder Prozeßwassers.The guide variable can be selected, for example, from the pH value, the fluoride ion concentration and the acid capacity of the cooling or process water.
Wählt man als Leitgröße den pH-Wert aus, so dosiert man das wasserlösliche Salz mit puffernder Wirkung dann zu, wenn der pH-Wert einen vorgegebenen Schwellenwert unterschreitet. Dieser je nach Materialeigenschaften der Einrichtung und/oder des Substrats festzulegende Schwellenwert kann beispielsweise im Bereich von 4 bis 7, insbesondere von 5 bis 6 liegen. Man gibt also bei Unterschreiten des Schwellenwerts entweder so lange Salz mit puffernder Wirkung zu, bis der Schwellenwert wieder überschritten wird, oder man gibt eine Menge an Salz mit puffernder Wirkung zu, die von der Differenz zwischen Schwellenwert und tatsächlich gemessenem pH-Wert abhängt.If the pH value is selected as the guide variable, the water-soluble salt with a buffering effect is added when the pH value falls below a predetermined threshold value. This threshold value to be determined depending on the material properties of the device and / or the substrate can be, for example, in the range from 4 to 7, in particular from 5 to 6. If the value falls below the threshold value, either salt with a buffering effect is added until the threshold value is exceeded again, or an amount of salt with a buffering effect is added, which depends on the difference between the threshold value and the pH actually measured.
Für denjenigen Fall, daß in das Kühl- oder Prozeßwasser Säure als HF oder als eine fluorhaltige Verbindung eingetragen wird, die in Wasser HF bildet, kann man als Leitgröße die Fluoridionen-Konzentration auswählen. Wie einleitend erwähnt, ist dies beispielsweise bei Stranggußanlagen der Stahlindustrie der Fall. Der Säureeintrag ist dann proportional zur Erhöhung der Fluoridionen-Konzentration. In diesem Fall kann man das wasserlösliche Salz mit puffernder Wirkung zudosieren, wenn die Fluoridionen- Konzentration einen vorgegebenen Schwellenwert überschreitet, der beispielsweise im Bereich von 40 bis 300 mg/1, insbesondere im Bereich von 60 bis 200 mg/1 liegen kann. In diesem Fall bietet sich insbesondere die Ausführungsform an, daß man die Abweichung der Fluoridionen-Konzentration von dem vorgegebenen Schwellenwert ermittelt und das Salz mit puffernder Wirkung in Abhängigkeit von der Höhe dieser Abweichung zudosiert.In the event that acid is introduced into the cooling or process water as HF or as a fluorine-containing compound which forms HF in water, the fluoride ion concentration can be selected as the guide variable. As mentioned in the introduction, this is the case, for example, with continuous casting plants in the steel industry. The acid input is then proportional to the increase in the fluoride ion concentration. In this case, the water-soluble salt with a buffering effect can be metered in if the fluoride ion concentration exceeds a predetermined threshold value, which can be, for example, in the range from 40 to 300 mg / 1, in particular in the range from 60 to 200 mg / 1. In this case, it is particularly advantageous to determine the deviation of the fluoride ion concentration from the predetermined threshold value and to add the salt with a buffering effect depending on the amount of this deviation.
In einer weiteren Ausführungsform wählt man als Leitgröße die Säurekapazität des Kühloder Prozeßwassers aus. Diese ist definiert durch diejenige Menge (in Millimol) an starker einbasischer Säure, die man zu einem Liter des Wassers zugeben muß, um dessen pH- Wert auf 4,3 abzusenken. Sie wird ausgedrückt in Millimol Säurezugabe pro Liter Wasser. Man dosiert das wasserlösliche Salz mit puffernder Wirkung zu, wenn die Säurekapazität einen vorgegebenen Schwellenwert unterschreitet. Dieser kann beispielsweise im Bereich von 0,1 bis 1 Millimol/I, insbesondere von 0,3 bis 0,7 Millimol/I liegen. Auch hierbei kann man entweder so lange Salz mit puffernder Wirkung zugeben, bis die Säurekapazität den Schwellenwert wieder überschreitet. Oder man bestimmt die Abweichung der tatsächlichen Säurekapazität vom Schwellenwert und gibt eine Menge an Salz mit puffernder Wirkung zu, die zu der Abweichung proportional ist. Der Proportionalitätsfaktor wird vorzugsweise wieder empirisch bestimmt.In a further embodiment, the acid capacity of the cooling or process water is selected as the guide variable. This is defined by the amount (in millimoles) of strong monobasic acid that has to be added to one liter of the water in order to Lower the value to 4.3. It is expressed in millimoles of acid added per liter of water. The water-soluble salt with a buffering effect is metered in when the acid capacity falls below a predetermined threshold. This can be, for example, in the range from 0.1 to 1 millimole / l, in particular from 0.3 to 0.7 millimole / l. Here too, you can either add salt with a buffering effect until the acid capacity again exceeds the threshold value. Or one determines the deviation of the actual acid capacity from the threshold value and adds an amount of salt with a buffering effect which is proportional to the deviation. The proportionality factor is preferably determined empirically again.
Als Salz mit puffernder Wirkung kann man jedes beliebige wasserlösliche (gemäß Definition weiter oben) Salz auswählen, von dem bekannt ist, das es eine puffernde Wirkung hat. Beispielsweise kann das wasserlösliche Salz mit puffernder Wirkung ausgewählt sein aus Hydrogencarbonaten, Carbonaten, Boraten, Ortho- und Polyphosphaten. Vorzugsweise wählt man solche Salze, die ausgewählt sind aus Alkali-, Erdalkali- und Ammoniumsalzen, aus Kosten- und Umweltgründen vorzugsweise aus Natriumsalzen. Demgemäß sind als Salze mit puffernder Wirkung insbesondere Alkalioder Ammoniumsalze, speziell die Natriumsalze, mit Hydrogencarbonat-, Carbonat-, Borat-, Ortho- oder Polyphosphationen bevorzugt.Any water-soluble salt (as defined above) that is known to have a buffering effect can be selected as the salt with a buffering effect. For example, the water-soluble salt with a buffering effect can be selected from hydrogen carbonates, carbonates, borates, orthophosphates and polyphosphates. Such salts are preferably selected which are selected from alkali, alkaline earth and ammonium salts, preferably from sodium salts for reasons of cost and the environment. Accordingly, preferred salts with a buffering action are, in particular, alkali or ammonium salts, especially the sodium salts, with hydrogen carbonate, carbonate, borate, orthophosphate or polyphosphate ions.
Das erfindungsgemäße Verfahren ist insbesondere zur Verringerung der Korrosivität von Kühl- oder Prozeßwasser von Stranggußanlagen der Stahlindustrie geeignet.The method according to the invention is particularly suitable for reducing the corrosiveness of cooling or process water from continuous casting plants in the steel industry.
Beim Eintrag von Fluoridionen in Kühl- oder Prozeßwasser, wie es insbesondere in dem genannten Anwendungsfall in der Stahlindustrie vorkommt, kann es neben den Korrosionserscheinungen auch zu einer Abscheidung von Calciumfluorid kommen. Dies ist unerwünscht, da hierdurch Leitungen, Ventile und Düsen verstopft werden können. Aus der DE 100 64412 ist ein Verfahren zur Verhinderung der Abscheidung von Calciumfluorid in Kühl- oder Prozeßwasser bekannt. Dieses bekannte Verfahren kann mit dem erfindungsgemäßen Verfahren zur Verringerung der Korrosivität kombiniert werden. Demnach besteht eine bevorzugte Ausführungsform der Erfindung darin, daß man zusätzlich die Abscheidung von Calciumfluorid in dem Kühl- oder Prozesswasser verhindert, indem man dem Kühl- oder Prozesswasser zusätzlich mindestens ein weiteres wasserlösliches Salz zugibt, das mindestens eines der folgenden Ionen enthält: Magnesiumkationen, Kationen dreiwertiger Metalle, Anionen von Oligo- oder Polyphosphat. Insbesondere gibt man ein wasserlösliches Salz mit Magnesiumkationen zu. Nähere Angaben zu speziellen Ausführungsformen und bevorzugten Zugabemengen sind der genannten DE 100 64412 zu entnehmen, auf die hiermit ausdrücklich Bezug genommen wird.When fluoride ions are introduced into cooling or process water, as is particularly the case in the mentioned application in the steel industry, calcium fluoride can also be separated in addition to the signs of corrosion. This is undesirable because it can clog pipes, valves and nozzles. DE 100 64412 discloses a method for preventing the deposition of calcium fluoride in cooling or process water. This known method can be combined with the method according to the invention for reducing the corrosiveness. Accordingly, a preferred embodiment of the invention consists in additionally preventing the deposition of calcium fluoride in the cooling or process water by additionally adding to the cooling or process water at least one further water-soluble salt which contains at least one of the following ions: magnesium cations, cations trivalent metals, anions of oligo- or polyphosphate. In particular, there is a water-soluble salt with magnesium cations to. More detailed information on special embodiments and preferred addition amounts can be found in the aforementioned DE 100 64412, to which reference is hereby expressly made.
Es versteht sich von selbst, daß man dem Kühl- oder Prozeßwasser weitere Additive zugeben kann, die für dieses Einsatzgebiet bekannt sind. Beispiele hierfür sind Scale- Inhibitoren, Korrosionsinhibitoren und Dispergatoren. Beispiele derartiger Additive sind Polymere oder Copolymere von ungesättigten Carbonsäuren wie beispielsweise Acrylsäure, Methacrylsäure und/oder Maleinsäure, die zusätzlich Phosphon- oder Phosphinsäuregruppen tragen können. Weiterhin sind Polyaminosäuren wie beispielsweise Polyasparaginsäure bekannt. Weiterhin sind für diesen Zweck nicht polymere, zur Bildung von Chelatkomplexen befähigte Moleküle bzw. Ionen wie beispielsweise Aminoalkylenphosphonsäuren, Phosphonocarbonsäuren, geminale Diphosphonsäuren bekannt. Ausgewählte Beispiele sind in der bereits genannten DE 10064412 enthalten.It goes without saying that other additives known for this area of application can be added to the cooling or process water. Examples of these are scale inhibitors, corrosion inhibitors and dispersants. Examples of such additives are polymers or copolymers of unsaturated carboxylic acids, such as, for example, acrylic acid, methacrylic acid and / or maleic acid, which can additionally carry phosphonic or phosphinic acid groups. Furthermore, polyamino acids such as polyaspartic acid are known. Furthermore, polymeric molecules or ions, such as aminoalkylenephosphonic acids, phosphonocarboxylic acids, geminal diphosphonic acids, which are not capable of forming chelate complexes are known for this purpose. Selected examples are contained in DE 10064412 already mentioned.
Beispiel:Example:
Der pH-Wert wird im Spritzwasser einer Strangussanlage kontinuierlich mittels einer pH- Elektrode gemessen, und bei Unterschreitung eines vorgegebenen Schwellenwertes wird die Dosierpumpe für die wasserlöslichen, puffernden Salze gestartet. Bei Überschreitung des Schwellwertes wird die Dosierung wieder gestoppt. Der Schwellenwert liegt hier üblicherweise im pH-Bereich zwischen 4 und 7, bevorzugt im pH-Bereich von 5 bis 6. The pH value is continuously measured in the spray water of a continuous casting plant by means of a pH electrode, and the metering pump for the water-soluble, buffering salts is started when the temperature falls below a predetermined threshold. If the threshold value is exceeded, the metering is stopped again. The threshold value here is usually in the pH range between 4 and 7, preferably in the pH range from 5 to 6.

Claims

Patentansprüche: claims:
1. Verfahren zur Verringerung der Korrosivität von Kühl- oder Prozesswasser, bei dem es aufgrund eines Eintrags von Säuren zu einer Absenkung des pH-Werts kommt, dadurch gekennzeichnet, dass man zu dem Kühl- oder Prozesswasser mindestens ein wasserlösliches Salz mit puffernder Wirkung zudosiert.1. A method for reducing the corrosiveness of cooling or process water, in which there is a decrease in the pH value due to the entry of acids, characterized in that at least one water-soluble salt with a buffering effect is added to the cooling or process water.
2. Verfahren nach Anspruch 1 , dadurch gekennzeichnet, dass das Kühl- oder Prozesswasser in einem Kreislauf geführt wird, der ein Reservoir, ein Leitungssystem und einen Arbeitsbereich umfasst, und der Eintrag von Säure im Arbeitsbereich erfolgt, wobei die Menge des Kühl- oder Prozesswassers im Reservoir und im Leitungssystem mindestens 5 mal so groß ist wie die Menge des Kühl- oder Prozesswassers im Arbeitsbereich.2. The method according to claim 1, characterized in that the cooling or process water is conducted in a circuit which comprises a reservoir, a piping system and a working area, and the entry of acid in the working area takes place, the amount of cooling or process water in the reservoir and in the pipe system is at least 5 times the amount of cooling or process water in the work area.
3. Verfahren nach Anspruch 1 , dadurch gekennzeichnet, dass das Kühl- oder Prozesswasser in einem Durchlaufsystem geführt wird, das ein Leitungssystem und einen Arbeitsbereich umfasst.3. The method according to claim 1, characterized in that the cooling or process water is guided in a continuous system which comprises a line system and a work area.
4. Verfahren nach Anspruch 2 oder 3, dadurch gekennzeichnet, dass man das wasserlösliche Salz mit puffernder Wirkung in das Leitungssystem an einer Stelle zudosiert, die in Strömungsrichtung gesehen in oder vor dem Arbeitsbereich liegt.4. The method according to claim 2 or 3, characterized in that the water-soluble salt with a buffering effect is metered into the line system at a point which, seen in the direction of flow, lies in or in front of the working area.
5. Verfahren nach einem oder mehreren der Ansprüche 2 bis 4, dadurch gekennzeichnet, dass man das wasserlösliche Salz mit puffernder Wirkung in Abhängigkeit von der Menge an Kühl- oder Prozesswasser zudosiert, die innerhalb eines vorgegebenen Zeitintervalls den Arbeitsbereich durchfließt.5. The method according to one or more of claims 2 to 4, characterized in that the water-soluble salt with a buffering effect is metered in as a function of the amount of cooling or process water which flows through the working area within a predetermined time interval.
6. Verfahren nach einem oder mehreren der Ansprüche 1 bis 5, dadurch gekennzeichnet, dass man kontinuierlich oder diskontinuierlich den Wert mindestens einer Leitgröße im Kühl- oder Prozesswasser misst und das wasserlösliche Salz mit puffernder Wirkung in Abhängigkeit von dem Wert der Leitgröße zudosiert.6. The method according to one or more of claims 1 to 5, characterized in that the value of at least one guide variable in the cooling or process water is measured continuously or discontinuously and the water-soluble salt with a buffering effect is metered in as a function of the value of the guide variable.
7. Verfahren nach Anspruch 6, dadurch gekennzeichnet, dass man den Wert der Leitgröße entweder im Arbeitsbereich selbst, in einer im Arbeitsbereich entnommenen Probe des Kühl- oder Prozesswassers oder in demjenigen Teil des Leitungssystems misst, das sich in Fließrichtung hinter dem Arbeitsbereich befindet.7. The method according to claim 6, characterized in that the value of the guide variable either in the work area itself, in a sample of the cooling or process water taken in the work area or in that part of the line system measures, which is located in the flow direction behind the work area.
8. Verfahren nach einem oder beiden der Ansprüche 6 und 7, dadurch gekennzeichnet, dass man die Leitgröße auswählt aus dem pH-Wert, der Fluoridionen-Konzentration und der Säurekapazität des Kühl- oder Prozesswassers.8. The method according to one or both of claims 6 and 7, characterized in that the guide variable is selected from the pH, the fluoride ion concentration and the acid capacity of the cooling or process water.
9. Verfahren nach einem oder beiden der Ansprüche 6 und 7, dadurch gekennzeichnet, dass man als Leitgröße den pH-Wert auswählt und das wasserlösliche Salz mit puffernder Wirkung zudosiert, wenn der pH-Wert einen vorgegebenen Schwellenwert im Bereich von 4 bis 7, insbesondere von 5 bis 6, unterschreitet.9. The method according to one or both of claims 6 and 7, characterized in that the pH value is selected as the guide variable and the water-soluble salt is added with a buffering effect if the pH value is a predetermined threshold value in the range from 4 to 7, in particular from 5 to 6.
10. Verfahren nach einem oder beiden der Ansprüche 6 und 7, dadurch gekennzeichnet, dass man für den Fall, dass in das Kühl- oder Prozesswasser als Säure HF oder eine fluorhaltige Verbindung eingetragen wird, die in Wasser HF bildet, als Leitgröße die Fluoridionen-Konzentration auswählt und das wasserlösliche Salz mit puffernder Wirkung zudosiert, wenn die Fluoridionen-Konzentration einen vorgegebenen Schwellenwert im Bereich von 40 bis 300 mg/l, insbesondere 60 bis 200 mg/l, überschreitet.10. The method according to one or both of claims 6 and 7, characterized in that in the event that HF or a fluorine-containing compound which forms HF in water is introduced as cooling water into the cooling or process water, the fluoride ion Select the concentration and meter in the water-soluble salt with a buffering effect if the fluoride ion concentration exceeds a predetermined threshold value in the range from 40 to 300 mg / l, in particular 60 to 200 mg / l.
11. Verfahren nach einem oder beiden der Ansprüche 6 und 7, dadurch gekennzeichnet, dass man als Leitgröße die Säurekapazität des Kühl- oder Prozesswassers auswählt und das wasserlösliche Salz mit puffernder Wirkung zudosiert, wenn die Säurekapazität einen vorgegebenen Schwellenwert im Bereich von 0,1 bis 1 mmol/l, insbesondere 0,3 bis 0,7 mmol/l, unterschreitet.11. The method according to one or both of claims 6 and 7, characterized in that the acid capacity of the cooling or process water is selected as the guide variable and the water-soluble salt with a buffering effect is metered in if the acid capacity has a predetermined threshold value in the range from 0.1 to Falls below 1 mmol / l, in particular 0.3 to 0.7 mmol / l.
12. Verfahren nach einem oder mehreren der Ansprüche 1 bis 11, dadurch gekennzeichnet, dass das wasserlösliche Salz mit puffernder Wirkung ausgewählt ist aus Hydrogencarbonaten, Carbonaten, Boraten, Ortho- und Polyphosphaten.12. The method according to one or more of claims 1 to 11, characterized in that the water-soluble salt with a buffering effect is selected from hydrogen carbonates, carbonates, borates, orthophosphates and polyphosphates.
13. Verfahren nach einem oder mehreren der Ansprüche 1 bis 12, dadurch gekennzeichnet, dass das wasserlösliche Salz mit puffernder Wirkung ausgewählt ist aus Alkali-, Erdalkali- und Ammoniumsalzen.13. The method according to one or more of claims 1 to 12, characterized in that the water-soluble salt with a buffering effect is selected from alkali, alkaline earth and ammonium salts.
14. Verfahren nach einem oder mehreren der Ansprüche 1 bis 13, dadurch gekennzeichnet, dass es sich bei dem Kühl- oder Prozesswasser um Kühl- oder Prozesswasser von Stranggussanlagen der Stahlindustrie handelt.14. The method according to one or more of claims 1 to 13, characterized in that it is cooling or process water in the cooling or Process water from continuous casting plants in the steel industry.
15. Verfahren nach einem oder mehreren der Ansprüche 1 bis 14, dadurch gekennzeichnet, dass man zusätzlich die Abscheidung von Calciumfluorid in dem Kühl- oder Prozesswasser verhindert, indem man dem Kühl- oder Prozesswasser zusätzlich mindestens ein weiteres wasserlösliches Salz zugibt, das mindestens eines der folgenden Ionen enthält: Magnesiumkationen, Kationen dreiwertiger Metalle, Anionen von Oligo- oder Polyphosphat. 15. The method according to one or more of claims 1 to 14, characterized in that one additionally prevents the deposition of calcium fluoride in the cooling or process water by additionally adding at least one further water-soluble salt to the cooling or process water, which at least one of the contains the following ions: magnesium cations, cations of trivalent metals, anions of oligo- or polyphosphate.
EP03735588A 2002-06-17 2003-06-10 Method for reducing the corrosivity of cooling or process water Expired - Lifetime EP1513634B1 (en)

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JPH0843586A (en) * 1994-04-08 1996-02-16 General Electric Co <Ge> Method for decreasing occurrence or growth of crack in surface of metal part
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