EP0084478A2 - Process for continuously regenerating a flux bath in the hot tip galvanizing of steel work pieces - Google Patents

Process for continuously regenerating a flux bath in the hot tip galvanizing of steel work pieces Download PDF

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Publication number
EP0084478A2
EP0084478A2 EP83400049A EP83400049A EP0084478A2 EP 0084478 A2 EP0084478 A2 EP 0084478A2 EP 83400049 A EP83400049 A EP 83400049A EP 83400049 A EP83400049 A EP 83400049A EP 0084478 A2 EP0084478 A2 EP 0084478A2
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Prior art keywords
solution
iron
tank
zinc
sludge
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EP83400049A
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German (de)
French (fr)
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EP0084478B1 (en
EP0084478A3 (en
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Noel Dreulle
Alain Van Ceulen
Claude Eusebe
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Union-Miniere Sa Te Charleroi Belgie
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Asturienne France SA
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    • 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
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/30—Fluxes or coverings on molten baths

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  • the invention relates to a process for regenerating the content of fluxing tanks, consisting of zinc and ammonium chlorides in aqueous solution, into which steel parts are immersed before dip galvanizing.
  • the parts undergo preparative surface treatments including degreasing in an alkaline bath, pickling in an acid bath, and a so-called fluxing operation which consists in covering the pieces with a thin layer of zinc and ammonium chlorides (flux), by immersing them in a tank containing an aqueous solution of these salts, then optionally by evaporating the water in an oven of the solution.
  • a so-called fluxing operation which consists in covering the pieces with a thin layer of zinc and ammonium chlorides (flux), by immersing them in a tank containing an aqueous solution of these salts, then optionally by evaporating the water in an oven of the solution.
  • the bath contained in the fluxing tank is gradually enriched with iron, essentially in the divalent state, which comes from the transport of pickling bath, diluted by rinsing, and from the attack of the iron by the fluxing solution.
  • the entrainment of iron salts in the galvanizing tank causes a reaction of the molten zinc with these iron salts, with the formation of mattes, zinc / iron compounds, which precipitate in the molten zinc and tend to collect at the bottom of tank.
  • mattes can cause defects in the zinc coating, and cause loss of zinc.
  • the flux bath contains more than traces of dissolved iron
  • part of this iron in the divalent state accompanies the zinc and ammonium chlorides in the stream, while another part oxidizes in the state trivalent under the action of atmospheric oxygen, and precipitates as ferric hydroxide; ferric hydroxide is partially entrained by the fluxing solution.
  • the mattes which are formed by direct attack of the iron by the zinc in the presence of flux during galvanization are added, undesirably, the mattes resulting from the presence of dissolved iron in the bath of fluxing.
  • the subject of the invention is a process free from the aforementioned drawbacks, and for this purpose proposes a process for regenerating the content of fluxing tanks, consisting of zinc and ammonium chlorides in aqueous solution, into which steel parts are immersed.
  • the process implemented on a bath where the dissolved iron concentration remains low, since the elimination is permanent, makes it possible to add the reagents, hydrogen peroxide of oxidation and ammonia of pH adjustment, to the bath current of such so that the redox power and the pH are optimally adjusted in the reaction bath; the oxidation of iron (II) to iron (III) takes place with a consumption of hydrogen peroxide practically reduced to the minimum.
  • the speed of oxidation of iron is notably higher than that of precipitation of ferric hydroxide; thus the current, relatively faster in the injection phase of reagents, corresponding to the oxidation step, is slowed down to allow the ferric hydroxide flakes to mature, at a favorable pH.
  • the size of the flakes promotes the speed and efficiency of decantation.
  • ferric hydroxide sludge discharged by periodic purges from the decanter in reduced volumes, can easily be subjected to filtration, in order to recover the flux solution entrained by the purges.
  • the fluxing bath 10 an aqueous solution of zinc and ammonium chlorides is contained in a tank 1, with a capacity of approximately 40 cubic meters, which is conventionally part of a line of dip galvanizing.
  • This line includes degreasing tanks, first rinsing, acid pickling, second rinsing, the fluxing tank 1, followed by a drying oven and the galvanizing tank, which contains a bath of molten zinc.
  • the content of the tank 1 is withdrawn with regular current by a volumetric pump 12, through a suction pipe 11 which opens towards the bottom of the tank 10.
  • the flow rate of the pump 12 is approximately 100 liters per hour, or approximately 0.03 liters per second.
  • the pump 12 delivers the solution taken from a reactor 2, of 80 liters capacity, through a reaction tube 21 which enters the reactor as far as the bottom.
  • a reaction tube 21 which enters the reactor as far as the bottom.
  • At the upper part of the reaction tube 21 open two nozzles 22b and 23b, connected to two reservoirs 22 and 23 with reagents of 100 liters capacity, the reservoir 22 containing hydrogen peroxide and the reservoir 23 of ammonia, to usual concentrations.
  • Two metering pumps 22a and 23a take the reagents from the reservoirs 22 and 23 to send them to the nozzles 22b and 23b.
  • These metering pumps have flow rates controlled by sensors 22c and 23c, respectively for the redox potential and the pH, so that, in reactor 2, the pH is maintained at 4 (+ 0.1) and that, towards the surface of the reactor, the redox potential corresponds to an iron (II) concentration lower than a given value (0.5 g / 1), in presence of iron (III).
  • the reactor is provided with a peripheral gutter 31 into which the decanted liquid overflows, which returns to the fluxing tank 1 by the pipe 32, opening out in the vicinity of the surface of the bath 10.
  • a battery of 4 immersion heaters 34 with a unit power of 500 watts allows the surface heating of the contents of the settling tank 3.
  • the purge sludge extracted from the settling tank 3 can be, via a three-way valve 41, either sent directly to the evacuation of the workshop to a discharge treatment installation, or directed by a pump 42 on a filter 4, to recover the zinc and ammonium chlorides from the filtrate.
  • the period of purification of the contents 10 of the tank 1 is 400 hours for a volume of 40 cubic meters. Furthermore, the duration of mixing of the reactants with the solution stream in the tube 21 is of the order of ten seconds, and the residence time in the reactor 2 is approximately 50 minutes.
  • the rate of rise of the solution in this reactor is approximately 0.3 mm per second, which corresponds to an almost turbulence-free flow, where the reactions of redox between iron (II) and hydrogen peroxide occurs with the minimum of side reactions and spontaneous decomposition of oxygenated water, while nucleation of ferric hydroxide occurs in the mass of solution.
  • the composition of the withdrawn current corresponds to the composition of the contents of the tank, which varies slowly, while the returns through the pipe 32 are not likely to significantly alter the composition of the fluxing bath over a short period.
  • the residence time of the solution is 10 hours, which corresponds to an ascending speed of 0.04 mm / sec. approximately, for the reactor dimensions specified above.
  • the maturation of the ferric hydroxide flakes have time to be complete, but also these flakes have an apparent density such that their rate of fall can greatly exceed the rate of rise of the liquid. It will be noted that, in reactor 2, where the flakes have barely exceeded the nucleation stage, while the rate of rise of the liquid is almost eight times greater, the entrainment of ferric hydroxide is substantially complete.

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Coating With Molten Metal (AREA)

Abstract

1. A process for regenerating the content of fluxing tanks, which is formed by chlorides of zinc and ammonium in aqueous solution in which steel components are dipped prior to galvanisation, the process comprising, in order to remove the harmful dissolved iron, taking off in a closed circuit the content of the tank which is maintained at a pH-value of between 3 and 6 and adding oxygenated water to the material taken off so as to cause all the iron present to go to the trivalent state and form insoluble sludge of ferric hydroxide oxide which is removed prior to returning the solution to the tank, characterised by taking off a flow at a practically constant flow rate, simultaneously adding to said flow flows of oxygenated water and ammonia which are respectively regulated in such a way that the oxygenated water is substantially in stoichiometric equilibrium with the iron to be oxidised and the pH-value is maintained at between 3,9 and 4,1, allowing the formation of flakes of ferric hydroxide to be concluded in the flow in a practically non-turbulent flow condition, and transferring the flow into a settlement zone where it circulates upwardly in such a way that the hydroxide sludge accumulates at the bottom from which it is discharged, and collecting at the surface the solution of chloride of zinc and ammonium from which iron has been removed, said solution being heated in the settlement zone by the application of heat at the surface at a temperature which is at least equal to that of the solution in the tank.

Description

L'invention a trait à un procédé de régénération du contenu de cuves de fluxage, constitué de chlorures de zinc et d'ammonium en solution aqueuse, où sont plongées des pièces en acier avant galvanisation au trempé.The invention relates to a process for regenerating the content of fluxing tanks, consisting of zinc and ammonium chlorides in aqueous solution, into which steel parts are immersed before dip galvanizing.

Au cours du processus de galvanisation au trempé, c'est-à-dire par immersion des pièces dans un bain de zinc en fusion, les pièces subissent des traitements de surface préparatoires comprenant un dégraissage en bain alcalin, un décapage en bain acide, et une opération dite fluxage qui consiste à recouvrir les pièces d'une mince couche de chlorures de zinc et d'ammonium (flux), en les plongeant dans une cuve contenant une solution aqueuse de ces sels, puis éventuellement en évaporant en étuve l'eau de la solution.During the dip galvanizing process, that is to say by immersion of the parts in a bath of molten zinc, the parts undergo preparative surface treatments including degreasing in an alkaline bath, pickling in an acid bath, and a so-called fluxing operation which consists in covering the pieces with a thin layer of zinc and ammonium chlorides (flux), by immersing them in a tank containing an aqueous solution of these salts, then optionally by evaporating the water in an oven of the solution.

Pour réduire les transports de bain de dégraissage dans le bain de décapage, et de ce bain de décapage dans le bain de fluxage, on effectue des rinçages intermédiaires. Néanmoins le bain contenu dans la cuve de fluxage s'enrichit progressivement en fer, essentiellement à l'état divalent, qui provient du transport de bain de décapage, dilué par le rinçage, et de l'attaque du fer par la solution de fluxage.To reduce the transport of degreasing bath in the pickling bath, and of this pickling bath in the fluxing bath, intermediate rinses are carried out. However, the bath contained in the fluxing tank is gradually enriched with iron, essentially in the divalent state, which comes from the transport of pickling bath, diluted by rinsing, and from the attack of the iron by the fluxing solution.

L'entraînement de sels de fer dans la cuve de galvanisation provoque une réaction du zinc en fusion avec ces sels de fer, avec formation de mattes, composés zinc/fer, qui précipitent dans le zinc fondu et ont tendance à se rassembler en fond de cuve. Ces mattes peuvent provoquer des défauts dans le recouvrement de zinc, et provoquent des pertes de zinc.The entrainment of iron salts in the galvanizing tank causes a reaction of the molten zinc with these iron salts, with the formation of mattes, zinc / iron compounds, which precipitate in the molten zinc and tend to collect at the bottom of tank. These mattes can cause defects in the zinc coating, and cause loss of zinc.

Lorsque le bain de fluxage contient plus que des traces de fer dissous, une partie de ce fer à l'état divalent accompagne les chlorures de zinc et d'ammonium dans le flux, tandis qu'une autre partie s'oxyde à l'état trivalent sous l'action de l'oxygène atmosphérique, et précipite à l'état d'hydroxyde ferrique ; l'hydroxyde ferrique est partiellement entraîné par la solution de fluxage. Aux mattes qui se forment par attaque directe du fer par le zinc en présence de flux lors de la galvanisation viennent s'ajouter, de façon indésirable, les mattes provenant de la présence de fer dissous dans le bain de fluxage.When the flux bath contains more than traces of dissolved iron, part of this iron in the divalent state accompanies the zinc and ammonium chlorides in the stream, while another part oxidizes in the state trivalent under the action of atmospheric oxygen, and precipitates as ferric hydroxide; ferric hydroxide is partially entrained by the fluxing solution. To the mattes which are formed by direct attack of the iron by the zinc in the presence of flux during galvanization are added, undesirably, the mattes resulting from the presence of dissolved iron in the bath of fluxing.

Pour remédier à cette difficulté, il est classique d'effectuer périodiquement une régénération des bains de fluxage. Pour ce faire on ajoute au contenu de la cuve de l'eau oxygénée, jusqu'à ce que pratiquement tout le fer contenu passe à l'état trivalent, et précipite sous forme d'hydroxyde ferrique, qui se présente sous forme de flocons. On laisse se former en fond de cuve des boues d'hydroxyde, que l'on évacue ensuite par pompage. Le bain clair qui subsiste est complété en niveau et en teneur.To remedy this difficulty, it is conventional to periodically perform a regeneration of the flux baths. To do this, hydrogen peroxide is added to the contents of the tank, until practically all of the iron contained passes to the trivalent state, and precipitates in the form of ferric hydroxide, which is in the form of flakes. Hydroxide sludge is left to form at the bottom of the tank, which is then removed by pumping. The clear bath that remains is completed in level and content.

On comprend aisément que cette opération de régénération qui bloque l'exploitation de la ligne de galvanisation pendant une durée importante, n'est exécutée que lorsque la teneur du bain de fluxage en fer dissous atteint des valeurs prohibitives entraînant une baisse sensible de la qualité de la galvanisation. Par ailleurs le prélèvement des boues en fond de cuve provoque un entraînement de bain de fluxage important ; les boues sont volumineuses, et relativement riches en zinc et chlorure. Il est onéreux de traiter ces boues pour éviter des pollutions. La pratique courante présente encore un inconvénient : l'oxydation du fer à l'état trivalent par l'eau oxygénée ne doit pas être conduite sous agitation, sous peine de voir l'hydroxyde ferrique se former en flocons de taille réduite qui ne sont pas susceptibles de décanter en un temps raisonnable. Il s'ensuit que l'eau oxygénée ne peut être répartie rapidement dans la masse du bain pour oxyder le fer. Au cours de la diffusion lente, une quantité importante d'eau oxygénée. se décompose spontanément, et la consommation de ce réactif est excessive.It is easy to understand that this regeneration operation, which blocks the operation of the galvanizing line for a significant period, is only carried out when the content of the fluxing bath in dissolved iron reaches prohibitive values resulting in a significant reduction in the quality of galvanizing. Furthermore, the removal of sludge from the bottom of the tank causes a significant flux bath to be entrained; the sludge is bulky, and relatively rich in zinc and chloride. It is expensive to treat this sludge to avoid pollution. Current practice still has a drawback: the oxidation of iron in a trivalent state by hydrogen peroxide should not be carried out with stirring, otherwise the ferric hydroxide will form in small flakes which are not likely to settle in a reasonable time. It follows that the hydrogen peroxide cannot be rapidly distributed in the mass of the bath to oxidize the iron. During the slow diffusion, a significant amount of hydrogen peroxide. breaks down spontaneously, and consumption of this reagent is excessive.

L'invention a pour objet un procédé exempt des inconvénients précités, et propose à cet effet un procédé de régénération du contenu de cuves de fluxage, constitué de chlorures de zinc et d'ammonium en solution aqueuse, où sont plongées des pièces en acier avant galvanisation au trempé, procédé d'élimination du fer dissous nuisible suivant lequel on ajoute au contenu de la cuve de l'eau oxygénée de façon à faire passer pratiquement tout le fer dissous à l'état trivalent et former des boues insolubles d'hydroxyde ferrique, et on élimine ces boues insolubles, caractérisé en ce que l'on prélève de la cuve un courant à débit pratiquement constant de son contenu, on ajoute à ce courant des débits d'eau oxygénée et d'ammoniaque réglés respectivement en sorte que l'eau oxygénée soit sensiblement en équilibre stoechiométrique avec le fer à oxyder et que le pH soit maintenu sensiblement à 4, on laisse s'achever. la formation d'hydroxyde ferrique en milieu calme, et on évacue par décantation les boues d'hydroxyde en renvoyant à la cuve la solution de chlorures de zinc et d'ammonium débarrassée de fer.The subject of the invention is a process free from the aforementioned drawbacks, and for this purpose proposes a process for regenerating the content of fluxing tanks, consisting of zinc and ammonium chlorides in aqueous solution, into which steel parts are immersed. dip galvanizing, process for removing harmful dissolved iron by which hydrogen peroxide is added to the contents of the tank so as to pass practically all of the dissolved iron to the trivalent state and form insoluble ferric hydroxide sludges , and we eliminate these insoluble sludge, characterized in that a current is drawn from the tank at a practically constant flow rate of its content, there is added to this flow rates of hydrogen peroxide and of ammonia adjusted respectively so that the hydrogen peroxide is substantially in stoichiometric equilibrium with the iron to be oxidized and the pH being maintained substantially at 4, it is allowed to complete. the formation of ferric hydroxide in a calm environment, and the hydroxide sludge is removed by decanting, returning the solution of zinc and ammonium chlorides stripped of iron to the tank.

Le procédé, mis en oeuvre sur un bain où la concentration en fer dissous reste faible, puisque l'élimination est permanente, permet d'ajouter les réactifs, eau oxygénée d'oxydation et ammoniaque de réglage de pH, au courant de bain de telle sorte que le pouvoir oxydoréducteur et le pH soient ajustés de façon optimale dans le bain en réaction ; l'oxydation du fer (II) en fer (III) se fait avec une consommation d'eau oxygénée pratiquement réduite au minimum. En outre on profite de ce que la vitesse d'oxydation du fer est notablement supérieure à celle de la précipitation d'hydroxyde ferrique ; ainsi le courant, relativement plus rapide dans la phase d'injection de réactifs, correspondant à l'étape d'oxydation, est ralenti pour laisser venir à maturation, au pH favorable, les flocons d'hydroxyde ferrique. La grosseur des flocons favorise la rapidité et l'efficacité de la décantation.The process, implemented on a bath where the dissolved iron concentration remains low, since the elimination is permanent, makes it possible to add the reagents, hydrogen peroxide of oxidation and ammonia of pH adjustment, to the bath current of such so that the redox power and the pH are optimally adjusted in the reaction bath; the oxidation of iron (II) to iron (III) takes place with a consumption of hydrogen peroxide practically reduced to the minimum. In addition, it takes advantage of the fact that the speed of oxidation of iron is notably higher than that of precipitation of ferric hydroxide; thus the current, relatively faster in the injection phase of reagents, corresponding to the oxidation step, is slowed down to allow the ferric hydroxide flakes to mature, at a favorable pH. The size of the flakes promotes the speed and efficiency of decantation.

Diverses dispositions viennent améliorer le processus ; ainsi après introduction des réactifs, le courant de bain est conduit au fond d'un réacteur par une canalisation, en sorte que la durée d'oxydation soit voisine du temps de parcours du bain dans la canalisation, tandis que dans le réacteur où le courant est presque imperceptible, l'hydroxyde peut venir à maturation. Après cela le bain, où l'hydroxyde s'est développé pour sa majeure partie, est envoyé dans un décanteur où l'hydroxyde se rassemblera en partie inférieure. Il sera judicieux de chauffer en surface le décanteur, pour éviter des turbulences de convection qui pourraient ramener en surface de l'hydroxyde si les couches superficielles dans le décanteur, se refroidissant, devenaient plus denses que les couches profondes.Various provisions improve the process; thus after introduction of the reactants, the bath stream is led to the bottom of a reactor by a pipe, so that the oxidation time is close to the time taken by the bath to run in the pipe, while in the reactor where the stream is almost imperceptible, the hydroxide can mature. After that the bath, where the hydroxide has developed for the most part, is sent to a decanter where the hydroxide will collect in the lower part. It will be advisable to heat the decanter on the surface, to avoid convection turbulence which could bring hydroxide to the surface if the surface layers in the decanter, cooling, become denser than the deep layers.

Enfin les boues d'hydroxyde ferrique évacuées par des purges périodiques du décanteur, par volumes réduits, peuventaisé- ment être soumises à filtration, pour récupérer la solution de flux entraînée par les purges.Finally, the ferric hydroxide sludge discharged by periodic purges from the decanter, in reduced volumes, can easily be subjected to filtration, in order to recover the flux solution entrained by the purges.

Les caractéristiques et avantages de l'invention ressortiront d'ailleurs dela description qui va suivre à titre d'exemple, en référence au dessin annexé qui représente schématiquement la disposition du matériel utilisé pour la mise en oeuvre du procédé.The characteristics and advantages of the invention will also emerge from the description which will follow by way of example, with reference to the appended drawing which schematically represents the arrangement of the equipment used for implementing the method.

Selon le mode de réalisation choisi et représenté, le bain de fluxage 10, solution aqueuse de chlorures de zinc et d'ammonium est contenu dans une cuve 1, d'une contenance de 40 mètres cubes environ, qui fait partie classiquement d'une ligne de galvanisation au trempé. Cette ligne comprend des cuves de dégraissage, de premier rinçage, de décapage acide, de second rinçage, la cuve de fluxage 1, suivie d'une étuve de séchage et de la cuve de galvanisation, qui contient un bain de zinc fondu.According to the embodiment chosen and shown, the fluxing bath 10, an aqueous solution of zinc and ammonium chlorides is contained in a tank 1, with a capacity of approximately 40 cubic meters, which is conventionally part of a line of dip galvanizing. This line includes degreasing tanks, first rinsing, acid pickling, second rinsing, the fluxing tank 1, followed by a drying oven and the galvanizing tank, which contains a bath of molten zinc.

Pour éliminer le fer dissous dans le bain de fluxage 10, fer qui provient des entraînements de la cuve de décapage acide, et de l'attaque superficielle des pièces par le bain de fluxage, le contenu de la cuve 1 est prélevé en courant régulier par une pompe volumétrique 12, à travers une canalisation d'aspiration 11 qui débouche vers le fond de la cuve 10. Le débit de la pompe 12 est d'environ 100 litres à l'heure, soit à peu près 0,03 litre seconde.To remove the iron dissolved in the fluxing bath 10, iron which comes from the drives of the acid pickling tank, and from the surface attack of the parts by the fluxing bath, the content of the tank 1 is withdrawn with regular current by a volumetric pump 12, through a suction pipe 11 which opens towards the bottom of the tank 10. The flow rate of the pump 12 is approximately 100 liters per hour, or approximately 0.03 liters per second.

La pompe 12 refoule la solution prélevée dans un réacteur 2, de 80 litres de contenance à travers un tube de réaction 21 qui pénètre dans le réacteur jusqu'au voisinage du fond. A la partie supérieure du tube de réaction 21 débouchent deux ajutages 22b et 23b, reliés à deux réservoirs 22 et 23 à réactifs de 100 litres de contenance, le réservoir 22 contenant de l'eau oxygénée et le réservoir 23 de l'ammoniaque, à des concentrations usuelles. Deux pompes doseuses 22a et 23a prélèvent les réactifs dans les réservoirs 22 et 23 pour les envoyer aux ajutages 22b et 23b. Ces pompes doseuses sont à débits asservis par des capteurs 22c et 23c, respectivement pour le potentiel d'oxydoréduction et le pH, en sorte que, dans le réacteur 2, le pH soit maintenu à 4 (+ 0,1) et que, vers la surface du réacteur, le potentiel d'oxydoréduction corresponde à une concentration en fer (II) inférieure à une valeur donnée (0,5 g/1), en présence de fer (III).The pump 12 delivers the solution taken from a reactor 2, of 80 liters capacity, through a reaction tube 21 which enters the reactor as far as the bottom. At the upper part of the reaction tube 21 open two nozzles 22b and 23b, connected to two reservoirs 22 and 23 with reagents of 100 liters capacity, the reservoir 22 containing hydrogen peroxide and the reservoir 23 of ammonia, to usual concentrations. Two metering pumps 22a and 23a take the reagents from the reservoirs 22 and 23 to send them to the nozzles 22b and 23b. These metering pumps have flow rates controlled by sensors 22c and 23c, respectively for the redox potential and the pH, so that, in reactor 2, the pH is maintained at 4 (+ 0.1) and that, towards the surface of the reactor, the redox potential corresponds to an iron (II) concentration lower than a given value (0.5 g / 1), in presence of iron (III).

Une canalisation de trop plein 24 piquée sur le réacteur 2, et qui définit le niveau de surface, débouche au centre et vers le fond d'un décanteur cylindrique-23, d'un diamètre de 1 mètre et une hauteur de 1,300 mètre (volume 1 mètre cube environ). Le réacteur est muni d'une gouttière périphérique 31 dans laquelle vient déborder le liquide décanté, qui retourne à la cuve de fluxage 1 par la canalisation 32, débouchant au voisinage de la surface du bain 10. Du fond du décanteur 3 part une canalisation de purge 33, pour évacuer les particules solides qui se sont rassemblées au fond du décanteur 3. Une batterie de 4 thermoplongeurs 34 de puissance unitaire 500 watts permet le chauffage superficiel du contenu du décanteur 3.An overflow pipe 24 pitted on the reactor 2, and which defines the surface level, opens out in the center and towards the bottom of a cylindrical decanter-23, with a diameter of 1 meter and a height of 1,300 meters (volume About 1 cubic meter). The reactor is provided with a peripheral gutter 31 into which the decanted liquid overflows, which returns to the fluxing tank 1 by the pipe 32, opening out in the vicinity of the surface of the bath 10. From the bottom of the decanter 3 there is a pipe of purge 33, to evacuate the solid particles which have collected at the bottom of the settling tank 3. A battery of 4 immersion heaters 34 with a unit power of 500 watts allows the surface heating of the contents of the settling tank 3.

Les boues de purge extraites du décanteur 3 peuvent être, par l'intermédiaire d'une vanne à trois directions 41, soit envoyées directement à l'évacuation de l'atelier vers une installation de traitement des rejets, soit dirigées par une pompe 42 sur un filtre 4, pour récupérer les chlorures de zinc et d'ammonium du filtrat.The purge sludge extracted from the settling tank 3 can be, via a three-way valve 41, either sent directly to the evacuation of the workshop to a discharge treatment installation, or directed by a pump 42 on a filter 4, to recover the zinc and ammonium chlorides from the filtrate.

Si l'on porte son attention sur le cycle d'épuration de solution de fluxage, on remarque que, avec un débit d'extraction de 100 litres à l'heure, la période d'épuration du contenu 10 de la cuve 1, est de 400 heures pour un volume de 40 mètres cubes. Par ailleurs la durée de mélange des réactifs au courant de solution dans le tube 21 est de l'ordre de la dizaine de seconde, et le temps de séjour dans le réacteur 2 est d'environ 50 minutes. Avec une hauteur de réacteur 2 d'environ 0,80 mètre, la vitesse ascensionnelle de la solution dans ce réacteur est d'environ 0,3 mm à la seconde, ce qui correspond à un écoulement pratiquement sans turbulences, où les réactions d'oxydoréduction entre fer (II) et eau oxygénée se produisent avec le minimum de réactions secondaires et de décomposition spontanée de l'eau oxygénée, tandis que la nucléation de l'hydroxyde ferrique se produit dans la masse de solution. On remarquera en outre que, en raison du peu d'importance relative du prélèvement de solution de fluxage dans la cuve 1 vis-à-vis du volume total de solution, la composition du courant prélevé correspond à la composition du contenu de la cuve, qui varie lentement, tandis que les retours par la canalisation 32 ne sont pas susceptibles d'altérer sensiblement la composition du bain de fluxage sur une courte durée. Aussi les apports de réactifs, eau oxygénée et ammoniaque, par les pompes doseuses 22a et 23a, varient également très lentement, de sorte que les mesures des capteurs 22c et 23c s'effectuent sur des grandeurs, potentiel d'oxydoréduction et pH, en régime sensiblement permanent.If we pay attention to the purification cycle of fluxing solution, we notice that, with an extraction rate of 100 liters per hour, the period of purification of the contents 10 of the tank 1, is 400 hours for a volume of 40 cubic meters. Furthermore, the duration of mixing of the reactants with the solution stream in the tube 21 is of the order of ten seconds, and the residence time in the reactor 2 is approximately 50 minutes. With a height of reactor 2 of approximately 0.80 meters, the rate of rise of the solution in this reactor is approximately 0.3 mm per second, which corresponds to an almost turbulence-free flow, where the reactions of redox between iron (II) and hydrogen peroxide occurs with the minimum of side reactions and spontaneous decomposition of oxygenated water, while nucleation of ferric hydroxide occurs in the mass of solution. It will also be noted that, due to the relatively small importance of the sample flow of fluxing solution in the tank 1 vis-à-vis the total volume of solution, the composition of the withdrawn current corresponds to the composition of the contents of the tank, which varies slowly, while the returns through the pipe 32 are not likely to significantly alter the composition of the fluxing bath over a short period. Also the contributions of reagents, hydrogen peroxide and ammonia, by the metering pumps 22a and 23a, also vary very slowly, so that the measurements of the sensors 22c and 23c are carried out on quantities, redox potential and pH, in steady state. substantially permanent.

A l'étape suivante, dans le décanteur 3, le temps de séjour de la solution est de 10 heures, ce qui correspond à une vitesse ascensionnelle de 0,04 mm/sec. environ, pour les dimensions de réacteur précisées plus haut. Non seulement la maturation des flocons d'hydroxyde ferrique a le temps d'être complète, mais encore ces flocons ont une densité apparente telle que leur vitesse de chute peut excéder largement la vitesse ascensionnelle du liquide. On notera que, dans le réacteur 2, où les flocons ont peu dépassé encore le stade de nucléation, tandis que la vitesse ascensionnelle du liquide est près de huit fois plus grande, l'entraînement de l'hydroxyde ferrique est sensiblement complet.In the next step, in the decanter 3, the residence time of the solution is 10 hours, which corresponds to an ascending speed of 0.04 mm / sec. approximately, for the reactor dimensions specified above. Not only does the maturation of the ferric hydroxide flakes have time to be complete, but also these flakes have an apparent density such that their rate of fall can greatly exceed the rate of rise of the liquid. It will be noted that, in reactor 2, where the flakes have barely exceeded the nucleation stage, while the rate of rise of the liquid is almost eight times greater, the entrainment of ferric hydroxide is substantially complete.

Par ailleurs, il est de pratique courante d'effectuer le fluxage à une température supérieure à l'ambiante, afin d'opérer avec des bains plus concentrés en chlorures, amenés à une viscosité acceptable. La solution qui séjourne 10 heures dans le décanteur 3 se refroidirait, tant par les parois du décanteur qu'en surface. Les inégalités de température dans le décanteur 3 engendreraient des mouvements de convection dans le liquide, du fond en partie centrale vers la surface en partie périphérique, entraînant en conséquence l'hydroxyde ferrique vers la cuve 1. C'est la raison pour laquelle on prévoit le chauffage des couches superficielles du décanteur 3, en sorte de former une couche chaude en surface, stable et capable de protéger contre le refroidissement les couches sous-jacentes.Furthermore, it is common practice to carry out the fluxing at a temperature above ambient, in order to operate with baths more concentrated in chlorides, brought to an acceptable viscosity. The solution which stays 10 hours in the decanter 3 would cool, both by the walls of the decanter and on the surface. The temperature inequalities in the decanter 3 would cause convection movements in the liquid, from the bottom in the central part to the surface in the peripheral part, consequently causing the ferric hydroxide towards the tank 1. This is the reason why it is planned heating the surface layers of the decanter 3, so as to form a hot layer on the surface, stable and capable of protecting the underlying layers against cooling.

Bien entendu l'invention n'est pas limitée à l'exemple décrit, mais en embrasse toutes les variantes d'exécution, notamment en s'adaptant au volume de bains de fluxage à épurer.Of course, the invention is not limited to the example described, but embraces all the variant embodiments thereof, in particular by adapting to the volume of flux baths to be purified.

De plus, lorsque les cadences de travail sont régulières, on peut faire l'économie de réglage asservi des débits de réactifs, en vérifiant périodiquement les conditions de pH et d'oxydoréduction.In addition, when the work rates are regular, it is possible to save on controlled adjustment of the reagent flow rates, by periodically checking the pH and redox conditions.

Claims (5)

1. Procédé de régénération du contenu de cuves de fluxage, constitué de chlorures de zinc et d'ammonium en solution aqueuse, où sont pbngées des pièces en acier avant galvanisation au trempé, procédé d'élimination du fer dissous nuisible suivant lequel on ajoute au contenu de la cuve de l'eau oxygénée de façon à faire passer pratiquement tout le fer dissous à l'état trivalent et former des boues insolubles d'hydroxyde ferrique, et on élimine ces boues insolubles, caractérisé en ce que l'on prélève de la cuve un courant à débit pratiquement constant de son contenu, on ajoute à ce courant des débits d'eau oxygénée et d'ammoniaque, réglés respectivement en sorte que l'eau oxygénée soit sensiblement en équilibre stoechiométrique avec le fer à oxyder et que le pH soit maintenu sensiblement à 4, on laisse s'achever la formation d'hydroxyde ferrique en milieu calme, et on évacue par décantation les boues d'hydroxyde en renvoyant à la cuve la solution de chlorures de zinc et d'ammonium débarrassée de fer.1. Process for regenerating the contents of fluxing tanks, consisting of zinc and ammonium chlorides in aqueous solution, where steel parts are coated before dip galvanizing, process for removing harmful dissolved iron, which is added to the contents of the tank of hydrogen peroxide so as to pass practically all of the dissolved iron to the trivalent state and to form insoluble ferric hydroxide sludge, and this insoluble sludge is eliminated, characterized in that the tank a current at a practically constant flow rate of its content, to this current are added hydrogen peroxide and ammonia flow rates, regulated respectively so that the hydrogen peroxide is substantially in stoichiometric equilibrium with the iron to be oxidized and that the pH is maintained substantially at 4, the formation of ferric hydroxide is allowed to end in a calm environment, and the hydroxide sludge is removed by decantation, returning the solution of zinc and ammonium chlorides to the tank. ssée of iron. 2. Procédé suivant la revendication 1, caractérisé en ce qu'on maintient en circulation le courant de solution de chlorures après ajout d'eau oxygénée et d'ammoniaque sur un parcours suffisamment long pour que l'oxydation du fer soit sensiblement complète, avant de laisser s'achever en milieu calme la formation d'hydroxyde.2. Method according to claim 1, characterized in that the current of chlorine solution is kept in circulation after addition of hydrogen peroxide and ammonia over a sufficiently long course so that the oxidation of iron is substantially complete, before to allow the formation of hydroxide to end in a calm environment. 3. Procédé suivant la revendication 1 ou la revendication 2, caractérisé en ce qu'on transfère la solution de chlorures, après formation de la majeure partie de l'hydroxyde ferrique, dans une zone de décantation.3. Method according to claim 1 or claim 2, characterized in that the chlorides solution is transferred, after formation of most of the ferric hydroxide, in a settling zone. 4. Procédé suivant la revendication 3, caractérisé en ce que l'on chauffe la solution de chlorures en surface dans la zone de décantation.4. Method according to claim 3, characterized in that the chlorides solution is heated on the surface in the settling zone. 5. Procédé suivant une quelconque des revendications 1 à 4, caractérisé en ce que les boues évacuées par décantation sont soumises ultérieurement à une opération de filtrage en sorte de récupérer de la solution de chlorures de zinc et d'ammonium entraînée par ces boues.5. Method according to any one of claims 1 to 4, characterized in that the sludge discharged by decantation is subsequently subjected to a filtering operation so as to recover from the solution of zinc and ammonium chlorides entrained by these sludges.
EP83400049A 1982-01-15 1983-01-10 Process for continuously regenerating a flux bath in the hot tip galvanizing of steel work pieces Expired EP0084478B1 (en)

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AT83400049T ATE31557T1 (en) 1982-01-15 1983-01-10 CONTINUOUS REGENERATION PROCESS FOR FLUX BATHS IN HOT-DIP GALVANIZING OF STEEL WORKPIECES.

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FR8200605 1982-01-15
FR8200605A FR2520007B1 (en) 1982-01-15 1982-01-15 PROCESS FOR THE CONTINUOUS REGENERATION OF FLUXING BATHS IN STEEL GALVANIZATION OF STEEL PARTS

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EP0084478A2 true EP0084478A2 (en) 1983-07-27
EP0084478A3 EP0084478A3 (en) 1983-08-24
EP0084478B1 EP0084478B1 (en) 1987-12-23

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AT (1) ATE31557T1 (en)
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Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1994011542A1 (en) * 1992-11-06 1994-05-26 Um Engineering S.A. Method for sustaining a fluxing bath in a galvanising line
US5810946A (en) * 1997-02-04 1998-09-22 Metals Recycling Technologies Corp. Method for the production of galvanizing fluxes and flux feedstocks
EP1277849A1 (en) * 2001-07-17 2003-01-22 Goldschmidt AG Flux composition, which removes iron from flux baths
EP2674507A3 (en) * 2012-06-15 2016-04-27 RAM Engineering + Anlagenbau GmbH Apparatus for the continuous preparation of flux containing iron
US10316400B1 (en) * 2017-05-11 2019-06-11 Beta Control Systems, Incorporated Systems and methods for removing impurities from galvanizing flux solution
EP3530773A1 (en) * 2018-02-23 2019-08-28 RAM Engineering + Anlagenbau GmbH Installation for the treatment of flux for steel pretreatment and method for operating the installation

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FR2095281A1 (en) * 1970-06-16 1972-02-11 Didier Werke Ag
FR2277910A1 (en) * 1974-07-09 1976-02-06 Degremont Sa Removing iron salt contaminants from galvanising baths - by oxidn. at acid pH and filtering off ferric hydroxide
DE2633872B1 (en) * 1976-07-28 1977-07-28 Preussag Ag Metall Process for producing an aqueous flux lye for hot-dip galvanizing

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BE840955A (en) * 1976-04-21 1976-08-16 PROCESS FOR REGENARATION OF GALVANIZATION BATHS AND INSTALLATION FOR ITS IMPLEMENTATION

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Publication number Priority date Publication date Assignee Title
FR2095281A1 (en) * 1970-06-16 1972-02-11 Didier Werke Ag
FR2277910A1 (en) * 1974-07-09 1976-02-06 Degremont Sa Removing iron salt contaminants from galvanising baths - by oxidn. at acid pH and filtering off ferric hydroxide
DE2633872B1 (en) * 1976-07-28 1977-07-28 Preussag Ag Metall Process for producing an aqueous flux lye for hot-dip galvanizing

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Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1994011542A1 (en) * 1992-11-06 1994-05-26 Um Engineering S.A. Method for sustaining a fluxing bath in a galvanising line
BE1006337A3 (en) * 1992-11-06 1994-07-26 Mechim Engineering Sa Method for maintaining a bath fluxing a line galvanizing.
US5810946A (en) * 1997-02-04 1998-09-22 Metals Recycling Technologies Corp. Method for the production of galvanizing fluxes and flux feedstocks
EP1277849A1 (en) * 2001-07-17 2003-01-22 Goldschmidt AG Flux composition, which removes iron from flux baths
EP2674507A3 (en) * 2012-06-15 2016-04-27 RAM Engineering + Anlagenbau GmbH Apparatus for the continuous preparation of flux containing iron
US10316400B1 (en) * 2017-05-11 2019-06-11 Beta Control Systems, Incorporated Systems and methods for removing impurities from galvanizing flux solution
US11091828B2 (en) 2017-05-11 2021-08-17 Beta Control Systems, Incorporated Systems for removing impurities from galvanizing flux solution
EP3530773A1 (en) * 2018-02-23 2019-08-28 RAM Engineering + Anlagenbau GmbH Installation for the treatment of flux for steel pretreatment and method for operating the installation
WO2019162450A1 (en) * 2018-02-23 2019-08-29 Ram Engineering + Anlagenbau Gmbh Flux processing system for processing flux used for pretreating steel, and method for operating said system

Also Published As

Publication number Publication date
DE3375026D1 (en) 1988-02-04
ATE31557T1 (en) 1988-01-15
FR2520007A1 (en) 1983-07-22
FR2520007B1 (en) 1990-11-02
EP0084478B1 (en) 1987-12-23
EP0084478A3 (en) 1983-08-24

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