EP0723038A1 - Process and apparatus for regenerating a used etching solution for zirconium alloys - Google Patents

Process and apparatus for regenerating a used etching solution for zirconium alloys Download PDF

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Publication number
EP0723038A1
EP0723038A1 EP96400097A EP96400097A EP0723038A1 EP 0723038 A1 EP0723038 A1 EP 0723038A1 EP 96400097 A EP96400097 A EP 96400097A EP 96400097 A EP96400097 A EP 96400097A EP 0723038 A1 EP0723038 A1 EP 0723038A1
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Prior art keywords
solution
pickling
crystallizer
water
acid
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German (de)
French (fr)
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EP0723038B1 (en
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Bernard Furic
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Zircotube SNC
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Zircotube SNC
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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
    • C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
    • C23G1/00—Cleaning or pickling metallic material with solutions or molten salts
    • C23G1/36—Regeneration of waste pickling liquors
    • 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
    • C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
    • C23F1/00—Etching metallic material by chemical means
    • C23F1/46—Regeneration of etching compositions
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S423/00—Chemistry of inorganic compounds
    • Y10S423/01—Waste acid containing iron

Definitions

  • the invention relates to a method for regenerating a used acid pickling solution used for pickling zirconium alloy elements.
  • the fuel assemblies for nuclear reactors and in particular the fuel assemblies for pressurized water nuclear reactors generally consist of a bundle of fuel rods parallel to each other and held by a framework comprising in particular longitudinal guide tubes and spacer grids. transverse.
  • the fuel rods can consist of a zirconium alloy sheath into which pellets of combustible material are introduced.
  • the frame guide tubes can also consist of zirconium tubes.
  • the chemical pickling of zirconium alloy tubes such as Zircaloy 4 is carried out using a solution of hydrofluoric acid HF containing a certain proportion of nitric acid HNO 3 serving as catalyst for the attack of zirconium by hydrofluoric acid, according to the chemical reaction Zr + 4HF ⁇ ZrF 4 + 2H 2 .
  • Zirconium alloy pickling baths containing pollutants can be treated to separate most of the water from the solution of pollutants that must be destroyed, in approved treatment centers.
  • the zirconium alloy tube production units must therefore bear significant costs relating to the separation and destruction of polluting products in approved centers as well as the purchase of new acid to reconstitute the pickling solution.
  • the transport of the used solution to the treatment center is also accompanied by risks which are those of road transport of dangerous materials.
  • US-A-5,076,884 and EP-A-0331,231 disclose methods for the regeneration of pickling solutions of metals such as zirconium and hafnium. These methods use a precipitation reagent which is a sodium compound.
  • the object of the invention is therefore to propose a method for regenerating a used pickling solution consisting mainly of hydrofluoric acid, nitric acid and water, after use for the pickling of elements. made of zirconium alloy, this process making it possible to limit operating costs production lines for zirconium alloy components, the rejection of polluting materials into the environment and the risks linked to the transport of hazardous materials.
  • the usual pickling process consists in preparing a new pickling solution, by mixing in a container 3, hydrofluoric acid, nitric acid and water in the quantity desired to obtain good pickling efficiency.
  • the pickling solution is used in a pickling unit 4 in which the zirconium alloy tubes are brought into contact with the pickling solution.
  • the chemical characteristics of the pickling solution are checked and, when the solution no longer has the characteristics required for an effective implementation of the pickling process, the used pickling solution is discharged into a storage tank 5.
  • the used pickling solutions stored in a tank were destroyed in an approved center as represented by step 6 which does not is not implemented in the context of the regeneration process according to the invention.
  • the regeneration process according to the invention as shown inside the frame 2 is implemented by carrying out a separation treatment on the used pickling solution stored in the tank 5.
  • the solution stored in the tank 5 mainly contains water, hydrofluoric acid and nitric acid as well as zirconium fluoride ZrF 4 originating from the attack of the zirconium alloy tubes by hydrofluoric acid, catalyzed by nitric acid HNO 3 .
  • the separation operations necessary for the regeneration of the pickling solution by the process according to the invention are carried out successively in a vacuum evaporator 7 and in a vacuum-crystallizer evaporator 8.
  • the vacuum evaporators used have an evaporation chamber in which a low pressure is maintained, for example of the order of 40 mm of mercury.
  • the solution to be treated in the evaporation chamber is introduced and maintained at a moderate temperature, for example of the order of 35 ° C.
  • the heating of the solution to be treated is obtained by means of a heat pump.
  • Putting the evaporation chamber under reduced pressure makes it possible to separate at least one of the constituents of the solution whose treatment is carried out, in the form of a vapor, at a moderate temperature.
  • the vacuum evaporator 7 which can be constituted by a WTSE 1000 evaporator from the company LED ITALIA makes it possible to evaporate and condense a large part of the water contained in the used pickling solution which is introduced into the evaporator chamber of the evaporator 7, from the storage tank 5.
  • the crystallizer 8 which can be a vacuum evaporator operating according to the same principle as the vacuum evaporator 7 comprises, inside its condensation chamber, a container coated with a material resistant to concentrated acids and making it possible to collect the pollutant ZrF 4 in the form of solid crystals.
  • the crystallizer 8 preferably includes a plastic coating to allow it to resist the action of acids in concentrated form.
  • the titer of the pickling solution is adjusted at a processing unit 9 into which the mixture of concentrated acid and water supplied at the outlet of the crystallizer 8 and the evaporator 7 is introduced.
  • the solution is returned to the title, for example by reintroducing pure water or new acid into the mixture, at the level of the processing unit 9.
  • the regenerated acid reaching the storage tank 3 is freed from the polluting products formed during the pickling of the zirconium alloy tubes.
  • the regeneration treatment according to the invention makes it possible to recover hydrofluoric acid from the used pickling solution and almost all of the nitric acid from the fluonitric mixture. This avoids the use of large quantities of expensive new materials.
  • Pure water is therefore introduced into the crystallizer, which makes it possible to dissolve the ZrF 4 crystals.
  • the liquid obtained is withdrawn, so as to empty the crystallizer.
  • An acid solution of ZrF4 is obtained in which the ZrF 4 can precipitate as soon as the pH of the solution reaches a value of approximately 5. It is therefore possible to recover the ZrF 4 from the aqueous solution, by neutralizing this solution.
  • ZrF 4 zirconium fluoride obtained as a by-product in the regeneration process can be used as a base product in some manufacturing.
  • a complete or only partial recycling of the used treatment solution can be carried out and any type of installation can be provided to adjust the composition of the regenerated solution and to reintroduce the regenerated solution on the pickling line of the zirconium alloy elements.
  • the invention applies to the regeneration of any fluonitric acid solution used for the pickling of elements of zirconium alloy.

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Cleaning And De-Greasing Of Metallic Materials By Chemical Methods (AREA)
  • Heat Treatment Of Water, Waste Water Or Sewage (AREA)
  • Inorganic Compounds Of Heavy Metals (AREA)

Abstract

Regenerating a spent HF-HNO3 pickling soln., after being used for Zr alloy pickling, involves (a) vacuum evaporating and then condensing most of the water content of the soln. to obtain slightly acidic water and a conc. acid soln. contaminated by ZrF4; (b) vacuum evaporating the conc. acid soln. in a crystalliser to obtain ZrF4 crystals and a purified conc. acid soln.; and (c) mixing the slightly acidic water and the conc. acid soln. in the desired proportion to obtain a regenerated pickling soln. Also claimed is an appts. for carrying out the above process.

Description

L'invention concerne un procédé de régénération d'une solution de décapage acide usagée utilisée pour le décapage d'éléments en alliage de zirconium.The invention relates to a method for regenerating a used acid pickling solution used for pickling zirconium alloy elements.

Les assemblages combustibles pour réacteur nucléaire et en particulier les assemblages de combustible pour réacteur nucléaire à eau sous pression sont généralement constitués par un faisceau de crayons combustibles parallèles entre eux et maintenus par une ossature comportant en particulier des tubes-guides longitudinaux et des grilles-entretoises transversales.The fuel assemblies for nuclear reactors and in particular the fuel assemblies for pressurized water nuclear reactors generally consist of a bundle of fuel rods parallel to each other and held by a framework comprising in particular longitudinal guide tubes and spacer grids. transverse.

Les crayons de combustible peuvent être constitués par une gaine en alliage de zirconium dans laquelle sont introduites des pastilles de matériau combustible.The fuel rods can consist of a zirconium alloy sheath into which pellets of combustible material are introduced.

Les tubes-guides de l'ossature peuvent être également constitués par des tubes de zirconium.The frame guide tubes can also consist of zirconium tubes.

La fabrication des tubes en zirconium à partir d'ébauches nécessite plusieurs passes successives de laminage à froid qui sont suivies chacune d'un traitement thermique de recuit.The manufacture of zirconium tubes from blanks requires several successive cold rolling passes which are each followed by an annealing heat treatment.

Entre chacune des passes de laminage à froid et le traitement thermique consécutif, on effectue un dégraissage et un décapage chimique du tube laminé.Between each of the cold rolling passes and the subsequent heat treatment, degreasing and chemical pickling of the laminated tube are carried out.

Le décapage chimique des tubes en alliage de zirconium tel que le Zircaloy 4 est réalisé en utilisant une solution d'acide fluorhydrique HF contenant une certaine proportion d'acide nitrique HNO3 servant de catalyseur de l'attaque du zirconium par l'acide fluorhydrique, selon la réaction chimique Zr + 4HF → ZrF4 + 2H2.The chemical pickling of zirconium alloy tubes such as Zircaloy 4 is carried out using a solution of hydrofluoric acid HF containing a certain proportion of nitric acid HNO 3 serving as catalyst for the attack of zirconium by hydrofluoric acid, according to the chemical reaction Zr + 4HF → ZrF 4 + 2H 2 .

La solution de décapage usagée qui est récupérée dans un réservoir de stockage après le décapage renferme principalement de l'acide fluorhydrique, de l'eau et de l'acide nitrique ainsi que du fluorure de zirconium ZrF4 formé lors du décapage.The used pickling solution which is recovered in a storage tank after pickling mainly contains hydrofluoric acid, water and nitric acid as well as zirconium fluoride ZrF 4 formed during pickling.

Les bains de décapage d'alliage de zirconium contenant des produits polluants peuvent être traités pour séparer la plus grande partie de l'eau de la solution des produits polluants qui doivent être détruits, dans des centres de traitement agréés.Zirconium alloy pickling baths containing pollutants can be treated to separate most of the water from the solution of pollutants that must be destroyed, in approved treatment centers.

Les unités de production de tubes en alliage de zirconium doivent donc supporter des frais importants relatifs à la séparation et à la destruction des produits polluants dans les centres agréés ainsi qu'à l'achat d'acide neuf pour reconstituer la solution de décapage.The zirconium alloy tube production units must therefore bear significant costs relating to the separation and destruction of polluting products in approved centers as well as the purchase of new acid to reconstitute the pickling solution.

En outre, la destruction des solutions acides usagées produit des nitrates qui sont rejetés dans le milieu naturel.In addition, the destruction of used acid solutions produces nitrates which are released into the natural environment.

Le transport de la solution usagée vers le centre de traitement s'accompagne également de risques qui sont ceux d'un transport routier de matières dangereuses.The transport of the used solution to the treatment center is also accompanied by risks which are those of road transport of dangerous materials.

Un procédé de régénération des solutions de décapage d'alliage de zirconium peut donc présenter des avantages à la fois sur le plan économique et sur le plan écologique.A process for regenerating pickling solutions of zirconium alloy can therefore have advantages both economically and ecologically.

On connaît par le US-A-5.076.884 et le EP-A-0331.231 des procédés de régénération de solutions de décapage de métaux tels que le zirconium et le hafnium. Ces procédés utilisent un réactif de précipitation qui est un composé de sodium.US-A-5,076,884 and EP-A-0331,231 disclose methods for the regeneration of pickling solutions of metals such as zirconium and hafnium. These methods use a precipitation reagent which is a sodium compound.

Cependant, on ne connaissait pas jusqu'ici de procédé de régénération sans apport de réactif d'une solution de décapage fluonitrique utilisée pour le décapage d'éléments en alliage de zirconium tels que des tubes de gainage ou des tubes-guides d'assemblages de combustible pour réacteur nucléaire.However, no regeneration process has hitherto been known without the addition of a reagent of a fluonitric pickling solution used for the pickling of zirconium alloy elements such as cladding tubes or guide tubes for assemblies of fuel for nuclear reactor.

Le but de l'invention est donc de proposer un procédé de régénération d'une solution de décapage usagée constituée principalement par de l'acide fluorhydrique, de l'acide nitrique et de l'eau, après une utilisation pour le décapage d'éléments en alliage de zirconium, ce procédé permettant de limiter les coûts d'exploitation des lignes de production d'éléments en alliage de zirconium, le rejet de matières polluantes dans l'environnement et les risques liés au transport de matières dangereuses.The object of the invention is therefore to propose a method for regenerating a used pickling solution consisting mainly of hydrofluoric acid, nitric acid and water, after use for the pickling of elements. made of zirconium alloy, this process making it possible to limit operating costs production lines for zirconium alloy components, the rejection of polluting materials into the environment and the risks linked to the transport of hazardous materials.

Dans ce but, selon le procédé de l'invention :

  • on évapore sous vide puis on condense une partie substantielle de l'eau contenue dans la solution usagée de manière à obtenir de l'eau légèrement acide et une solution acide concentrée polluée par du fluorure de zirconium ZrF4,
  • on traite par évaporation sous vide dans un cristalliseur, la solution acide concentrée polluée, de manière à obtenir des cristaux de fluorure de zirconium ZrF4 et une solution acide concentrée épurée, et
  • on mélange l'eau légèrement acide et la solution acide concentrée en proportions voulues pour obtenir une solution de décapage régénérée.
To this end, according to the method of the invention:
  • it is evaporated under vacuum and then a substantial part of the water contained in the used solution is condensed so as to obtain slightly acidic water and a concentrated acidic solution polluted with zirconium fluoride ZrF 4 ,
  • the polluted concentrated acid solution is treated by vacuum evaporation in a crystallizer, so as to obtain crystals of zirconium fluoride ZrF 4 and a purified concentrated acid solution, and
  • the slightly acidic water and the concentrated acid solution are mixed in desired proportions to obtain a regenerated pickling solution.

Afin de bien faire comprendre l'invention, on va maintenant décrire, en se référant à la figure jointe en annexe, un mode de réalisation du procédé de régénération suivant l'invention.In order to clearly understand the invention, a description will now be given, with reference to the attached figure, of an embodiment of the regeneration process according to the invention.

La figure unique est un schéma fonctionnel montrant les différentes opérations successives mises en oeuvre pour effectuer la régénération d'une solution acide fluonitrique usagée, utilisée pour le décapage de tubes en alliage de zirconium.The single figure is a functional diagram showing the various successive operations implemented to effect the regeneration of a used fluonitric acid solution, used for the pickling of zirconium alloy tubes.

Sur la figure, on a représenté, à l'intérieur du cadre 1, les opérations mises en oeuvre de manière usuelle dans le cadre d'un procédé de décapage au moyen d'une solution d'acide et, à l'intérieur du cadre 2, les opérations de régénération d'une solution de décapage usagée après son utilisation dans le cadre du procédé habituel de décapage de tubes en alliage de zirconium.In the figure, there is shown, inside the frame 1, the operations carried out in the usual manner in the context of an etching process using an acid solution and, inside the frame 2, the operations of regenerating a used pickling solution after its use in the usual process of pickling zirconium alloy tubes.

Le procédé usuel de décapage consiste à préparer une solution de décapage neuve, en mélangeant dans un récipient 3, de l'acide fluorhydrique, de l'acide nitrique et de l'eau en quantité voulue pour obtenir une bonne efficacité du décapage. La solution de décapage est utilisée dans une unité de décapage 4 dans laquelle les tubes en alliage de zirconium sont mis en contact avec la solution de décapage.The usual pickling process consists in preparing a new pickling solution, by mixing in a container 3, hydrofluoric acid, nitric acid and water in the quantity desired to obtain good pickling efficiency. The pickling solution is used in a pickling unit 4 in which the zirconium alloy tubes are brought into contact with the pickling solution.

Dans le cadre d'un procédé de fabrication de tubes de gainage ou de tubes-guides pour assemblages de combustible pour réacteur nucléaire, on effectue successivement, sur les ébauches tubulaires, trois opérations de laminage suivies chacune d'un traitement thermique de recuit. Entre chacune des opérations de laminage et le recuit consécutif, on réalise un dégraissage et un décapage des ébauches tubulaires ou des tubes par le mélange fluonitrique.As part of a process for manufacturing cladding tubes or guide tubes for fuel assemblies for a nuclear reactor, three rolling operations are successively carried out on the tubular blanks, each followed by annealing heat treatment. Between each of the rolling operations and the subsequent annealing, degreasing and pickling of the tubular blanks or tubes is carried out with the fluonitric mixture.

On effectue un contrôle des caractéristiques chimiques de la solution de décapage et, lorsque la solution ne présente plus les caractéristiques voulues pour une mise en oeuvre efficace du procédé de décapage, on évacue la solution de décapage usagée dans un réservoir de stockage 5.The chemical characteristics of the pickling solution are checked and, when the solution no longer has the characteristics required for an effective implementation of the pickling process, the used pickling solution is discharged into a storage tank 5.

Dans le cadre de la mise en oeuvre industrielle du procédé de décapage selon l'art antérieur, les solutions de décapage usagées stockées dans un réservoir faisaient l'objet d'une destruction dans un centre agréé comme représenté par l'étape 6 qui n'est pas mise en oeuvre dans le cadre du procédé de régénération suivant l'invention.As part of the industrial implementation of the pickling method according to the prior art, the used pickling solutions stored in a tank were destroyed in an approved center as represented by step 6 which does not is not implemented in the context of the regeneration process according to the invention.

La destruction des solutions d'acide fluonitrique usagées en centre agréé présente l'inconvénient d'augmenter les coûts d'exploitation de la ligne de fabrication de tubes en alliage de zirconium, du fait des frais de transport et de traitement pour la destruction de la solution usagée et de l'obligation de préparer dans le réservoir de stockage 3 une solution d'acide neuf à partir de produits du commerce.The destruction of used fluonitric acid solutions in an approved center has the disadvantage of increasing the operating costs of the line for manufacturing zirconium alloy tubes, due to the transportation and treatment costs for the destruction of the used solution and the obligation to prepare in the storage tank 3 a new acid solution from commercial products.

En outre, le procédé de destruction en centre agréé s'accompagne d'une production de nitrates qui doivent être rejetés dans l'environnement.In addition, the destruction process in an approved center is accompanied by the production of nitrates which must be released into the environment.

Le procédé de régénération suivant l'invention tel que figuré à l'intérieur du cadre 2 est mis en oeuvre en effectuant un traitement de séparation sur la solution de décapage usagée stockée dans le réservoir 5.The regeneration process according to the invention as shown inside the frame 2 is implemented by carrying out a separation treatment on the used pickling solution stored in the tank 5.

La solution stockée dans le réservoir 5 renferme principalement de l'eau, de l'acide fluorhydrique et de l'acide nitrique ainsi que du fluorure de zirconium ZrF4 provenant de l'attaque des tubes en alliage de zirconium par l'acide fluorhydrique, catalysée par l'acide nitrique HNO3.The solution stored in the tank 5 mainly contains water, hydrofluoric acid and nitric acid as well as zirconium fluoride ZrF 4 originating from the attack of the zirconium alloy tubes by hydrofluoric acid, catalyzed by nitric acid HNO 3 .

Les opérations de séparation nécessaires pour la régénération de la solution de décapage par le procédé suivant l'invention sont réalisées successivement dans un évaporateur sous vide 7 et dans un évaporateur sous vide-cristalliseur 8.The separation operations necessary for the regeneration of the pickling solution by the process according to the invention are carried out successively in a vacuum evaporator 7 and in a vacuum-crystallizer evaporator 8.

Pour réaliser la mise en oeuvre industrielle du procédé de régénération, la société ZIRCOTUBE a utilisé un évaporateur sous vide commercialisé sous la dénomination WTSE 1000 par la société LED ITALIA et un évaporateur WTSE 150 de la même société modifié pour résister à l'agression par des acides concentrés et pour constituer un cristalliseur.To carry out the industrial implementation of the regeneration process, the company ZIRCOTUBE used a vacuum evaporator marketed under the name WTSE 1000 by the company LED ITALIA and a WTSE 150 evaporator from the same company modified to resist attack by concentrated acids and to constitute a crystallizer.

Les évaporateurs sous vide utilisés comportent une chambre d'évaporation dans laquelle on maintient une pression faible, par exemple de l'ordre de 40 mm de mercure.The vacuum evaporators used have an evaporation chamber in which a low pressure is maintained, for example of the order of 40 mm of mercury.

La solution à traiter dans la chambre d'évaporation est introduite et maintenue à une température modérée, par exemple de l'ordre de 35°C.The solution to be treated in the evaporation chamber is introduced and maintained at a moderate temperature, for example of the order of 35 ° C.

L'échauffement de la solution à traiter est obtenu par l'intermédiaire d'une pompe à chaleur.The heating of the solution to be treated is obtained by means of a heat pump.

La mise sous pression réduite de la chambre d'évaporation permet de séparer au moins l'un des constituants de la solution dont on effectue le traitement, sous forme d'une vapeur, à une température modérée.Putting the evaporation chamber under reduced pressure makes it possible to separate at least one of the constituents of the solution whose treatment is carried out, in the form of a vapor, at a moderate temperature.

L'évaporateur sous vide comporte un étage de condensation dans lequel on réalise la condensation de la vapeur séparée de la solution à traiter.The vacuum evaporator has a condensation stage in which the vapor separated from the solution to be treated is condensed.

L'évaporateur sous vide 7 et l'évaporateur cristalliseur 8 permettent d'obtenir un distillat qui est condensé dans un étage de condensation et un concentrat restant dans la chambre d'évaporation.The vacuum evaporator 7 and the crystallizer evaporator 8 make it possible to obtain a distillate which is condensed in a condensation stage and a concentrate remaining in the evaporation chamber.

L'évaporateur sous vide 7 qui peut être constitué par un évaporateur WTSE 1000 de la société LED ITALIA permet de réaliser l'évaporation et la condensation d'une grande partie de l'eau contenue dans la solution de décapage usagée qui est introduite dans la chambre d'évaporation de l'évaporateur 7, à partir du réservoir de stockage 5.The vacuum evaporator 7 which can be constituted by a WTSE 1000 evaporator from the company LED ITALIA makes it possible to evaporate and condense a large part of the water contained in the used pickling solution which is introduced into the evaporator chamber of the evaporator 7, from the storage tank 5.

On obtient en sortie de l'étage de condensation de l'évaporateur sous vide, de l'eau très légèrement acide et très légèrement polluée qui représente 70 % en volume de la solution initiale traitée. A l'intérieur de la chambre d'évaporation, il reste, après évaporation de l'eau, une solution d'acide concentrée représentant à peu près 30 % en volume de la solution de décapage initiale introduite dans la chambre d'évaporation.At the outlet of the condenser stage of the vacuum evaporator, very slightly acidic and very slightly polluted water which represents 70% by volume of the initial solution treated is obtained. Inside the evaporation chamber, there remains, after evaporation of the water, a concentrated acid solution representing approximately 30% by volume of the initial pickling solution introduced into the evaporation chamber.

La solution acide concentrée renferme de l'acide fluorhydrique HF, de l'acide nitrique HNO3, une faible quantité d'eau et un polluant constitué par du fluorure de zirconium ZrF4 provenant de l'attaque acide des tubes en alliage de zirconium, au cours du décapage.The concentrated acid solution contains hydrofluoric acid HF, nitric acid HNO 3 , a small amount of water and a pollutant consisting of zirconium fluoride ZrF 4 originating from the acid attack of the tubes of zirconium alloy, during stripping.

La solution d'acide concentrée pourrait être envoyée partiellement ou totalement à la destruction mais, selon le procédé de l'invention, on préfère effectuer un second traitement de cette solution concentrée dans le cristalliseur 8.The concentrated acid solution could be sent partially or totally for destruction but, according to the process of the invention, it is preferable to carry out a second treatment of this concentrated solution in the crystallizer 8.

Le cristalliseur 8 qui peut être un évaporateur sous vide fonctionnant suivant le même principe que l'évaporateur sous vide 7 comporte, à l'intérieur de sa chambre de condensation, un récipient revêtu d'un matériau résistant aux acides concentrés et permettant de recueillir le polluant ZrF4 sous la forme de cristaux solides.The crystallizer 8 which can be a vacuum evaporator operating according to the same principle as the vacuum evaporator 7 comprises, inside its condensation chamber, a container coated with a material resistant to concentrated acids and making it possible to collect the pollutant ZrF 4 in the form of solid crystals.

Le cristalliseur 8 comporte de préférence un revêtement en matière plastique pour lui permettre de résister à l'action des acides sous forme concentrée.The crystallizer 8 preferably includes a plastic coating to allow it to resist the action of acids in concentrated form.

On effectue à l'intérieur de l'évaporateur cristalliseur, de la même manière que dans l'évaporateur 7, une évaporation et une séparation d'une solution concentrée d'acide renfermant en substance, de l'acide fluorhydrique, de l'acide nitrique et une très faible quantité d'eau. L'acide concentré épuré par évaporation puis condensé représente à peu près 80 % en volume de l'acide concentré pollué introduit dans le cristalliseur 8.Is carried out inside the evaporator crystallizer, in the same manner as in the evaporator 7, an evaporation and a separation of a concentrated solution of acid containing substance, hydrofluoric acid, acid nitric and a very small amount of water. The concentrated acid purified by evaporation and then condensed represents approximately 80% by volume of the polluted concentrated acid introduced into the crystallizer 8.

La solution acide concentrée épurée récupérée dans l'étage de condensation du cristalliseur 8 renferme sensiblement l'intégralité de l'acide nitrique de la solution de décapage initiale, du fait que l'acide nitrique ne joue qu'un rôle de catalyseur lors du décapage de l'alliage de zirconium.The purified concentrated acid solution recovered in the condensing stage of the crystallizer 8 contains substantially all of the nitric acid from the initial pickling solution, because the nitric acid only plays a catalyst role during the pickling of the zirconium alloy.

A l'issue de l'évaporation de la solution acide concentrée épurée, il reste dans le fond du cristalliseur, des cristaux de ZrF4 constituant un extrait sec représentant approximativement 20 % en volume de la solution d'acide concentrée polluée de départ.At the end of the evaporation of the purified concentrated acid solution, there remain in the bottom of the crystallizer, ZrF 4 crystals constituting a dry extract representing approximately 20% by volume of the initial polluted concentrated acid solution.

L'acide concentré épuré obtenu à la sortie de l'étage de condensation du cristalliseur 8 est mélangé avec l'eau légèrement acide obtenue à la sortie de l'étage de condensation de l'évaporateur sous vide 7, pour obtenir une solution de décapage régénérée qui peut être renvoyée au réservoir de stockage 3 de la solution de décapage.The purified concentrated acid obtained at the outlet of the condensing stage of the crystallizer 8 is mixed with the slightly acidic water obtained at the outlet of the condensation stage of the vacuum evaporator 7, to obtain a regenerated pickling solution which can be returned to the storage tank 3 of the pickling solution.

Le titre de la solution de décapage est réglé au niveau d'une unité de traitement 9 dans laquelle on fait pénétrer le mélange d'acide concentré et d'eau fournis en sortie du cristalliseur 8 et de l'évaporateur 7.The titer of the pickling solution is adjusted at a processing unit 9 into which the mixture of concentrated acid and water supplied at the outlet of the crystallizer 8 and the evaporator 7 is introduced.

La remise au titre de la solution peut être réalisée par exemple en réintroduisant de l'eau pure ou de l'acide neuf dans le mélange, au niveau de l'unité de traitement 9.The solution is returned to the title, for example by reintroducing pure water or new acid into the mixture, at the level of the processing unit 9.

Le titre de la solution de décapage est vérifié par une unité de mesure 10 disposée sur la ligne de recyclage 11 de la solution de décapage régénérée à l'intérieur du réservoir de stockage 3.The titer of the pickling solution is checked by a measuring unit 10 placed on the recycling line 11 of the pickling solution regenerated inside the storage tank 3.

L'acide régénéré parvenant au réservoir de stockage 3 est débarrassé des produits polluants formés lors du décapage des tubes d'alliage de zirconium. De plus, le traitement de régénération suivant l'invention permet de récupérer de l'acide fluorhydrique de la solution de décapage usagée et la quasi totalité de l'acide nitrique du mélange fluonitrique. On évite ainsi l'utilisation de grandes quantités de matières neuves coûteuses.The regenerated acid reaching the storage tank 3 is freed from the polluting products formed during the pickling of the zirconium alloy tubes. In addition, the regeneration treatment according to the invention makes it possible to recover hydrofluoric acid from the used pickling solution and almost all of the nitric acid from the fluonitric mixture. This avoids the use of large quantities of expensive new materials.

Cependant, il reste nécessaire, pour éviter des phénomènes de concentration dans la solution régénérée et recyclée, d'effectuer des purges de la solution régénérée, de manière régulière, et de compenser ces purges par des appoints d'une solution acide fluonitrique neuve.However, it remains necessary, to avoid phenomena of concentration in the regenerated and recycled solution, to perform purges of the regenerated solution, on a regular basis, and to compensate for these purges with additions of a new fluonitric acid solution.

Les cristaux de ZrF4 constituant un extrait sec dans le cristalliseur peuvent être extraits facilement, du fait qu'ils sont solubles à l'eau.The ZrF 4 crystals constituting a dry extract in the crystallizer can be easily extracted, since they are soluble in water.

On introduit donc de l'eau pure dans le cristalliseur, ce qui permet de dissoudre les cristaux de ZrF4. Le liquide obtenu est prélevé, de manière à vider le cristalliseur. On obtient une solution acide de ZrF4 dans laquelle le ZrF4 peut précipiter dès que le pH de la solution atteint une valeur de 5 environ. On peut donc récupérer le ZrF4 de la solution aqueuse, en neutralisant cette solution.Pure water is therefore introduced into the crystallizer, which makes it possible to dissolve the ZrF 4 crystals. The liquid obtained is withdrawn, so as to empty the crystallizer. An acid solution of ZrF4 is obtained in which the ZrF 4 can precipitate as soon as the pH of the solution reaches a value of approximately 5. It is therefore possible to recover the ZrF 4 from the aqueous solution, by neutralizing this solution.

Le fluorure de zirconium ZrF4 obtenu comme sous-produit dans le procédé de régénération peut être utilisé comme produit de base dans certaines fabrication.ZrF 4 zirconium fluoride obtained as a by-product in the regeneration process can be used as a base product in some manufacturing.

Dans le cas où il n'est pas possible d'utiliser le ZrF4 produit par le procédé de régénération suivant l'invention, on peut le séparer de la solution aqueuse sur un filtre tel qu'un filtre-presse et le conditionner, par exemple, pour son évacuation dans un centre de stockage souterrain.If it is not possible to use the ZrF 4 produced by the regeneration process according to the invention, it can be separated from the aqueous solution on a filter such as a filter press and conditioned, by example, for its disposal in an underground storage center.

Le procédé suivant l'invention permet de limiter les coûts d'exploitation des unités de production d'éléments en alliage de zirconium tels que des tubes de gainage et d'éviter le transport de solutions de décapage usagées renfermant des produits polluants et le traitement coûteux de ces solutions usagées dans des centres de traitement spécialisés.The process according to the invention makes it possible to limit the operating costs of the units for producing zirconium alloy elements such as cladding tubes and to avoid the transport of used pickling solutions containing polluting products and the expensive treatment. of these solutions used in specialized treatment centers.

L'invention ne se limite pas au mode de réalisation qui a été décrit.The invention is not limited to the embodiment which has been described.

C'est ainsi qu'on peut utiliser, pour effectuer la séparation des produits de la solution usagée, des évaporateurs sous vide d'un type différent de ceux qui ont été décrits plus haut.Thus it is possible to use, to effect the separation of the products from the used solution, vacuum evaporators of a different type from those which have been described above.

On peut effectuer un recyclage total ou seulement partiel de la solution de traitement usagée et on peut prévoir tout type d'installation pour ajuster la composition de la solution régénérée et pour réintroduire la solution régénérée sur la ligne de décapage des éléments en alliage de zirconium.A complete or only partial recycling of the used treatment solution can be carried out and any type of installation can be provided to adjust the composition of the regenerated solution and to reintroduce the regenerated solution on the pickling line of the zirconium alloy elements.

L'invention s'applique à la régénération de toute solution d'acide fluonitrique utilisée pour le décapage d'éléments en alliage de zirconium.The invention applies to the regeneration of any fluonitric acid solution used for the pickling of elements of zirconium alloy.

Claims (9)

Procédé de régénération d'une solution de décapage usagée constituée principalement par de l'acide fluorhydrique, de l'acide nitrique et de l'eau, après une utilisation pour le décapage d'éléments en alliage de zirconium, caractérisé par le fait : - qu'on évapore sous vide puis qu'on condense une partie substantielle de l'eau contenue dans la solution usagée de manière à obtenir de l'eau légèrement acide et une solution acide concentrée polluée par du fluorure de zirconium ZrF4, - qu'on traite par évaporation sous vide dans un cristalliseur (8), la solution acide concentrée polluée, de manière à obtenir des cristaux de zirconium ZrF4 et une solution acide concentrée épurée, et - qu'on mélange l'eau légèrement acide et la solution acide concentrée en proportion voulue pour obtenir une solution de décapage régénérée. Method for regenerating a used pickling solution consisting mainly of hydrofluoric acid, nitric acid and water, after use for the pickling of elements made of zirconium alloy, characterized by the fact: - evaporated under vacuum and then condense a substantial part of the water contained in the used solution so as to obtain slightly acidic water and a concentrated acidic solution polluted by zirconium fluoride ZrF 4 , - which is treated by vacuum evaporation in a crystallizer (8), the polluted concentrated acid solution, so as to obtain zirconium crystals ZrF 4 and a purified concentrated acid solution, and - mixing the slightly acidic water and the concentrated acid solution in the desired proportion to obtain a regenerated pickling solution. Procédé suivant la revendication 1, caractérisé par le fait qu'on réalise une remise au titre de la solution régénérée obtenue par mélange de l'eau et de la solution acide concentrée épurée, avant sa réutilisation pour le décapage.Method according to claim 1, characterized in that a discount is made for the regenerated solution obtained by mixing water and the concentrated purified acid solution, before its reuse for pickling. Procédé suivant l'une quelconque des revendications 1 et 2, caractérisé par le fait qu'on effectue la dissolution par de l'eau des cristaux de fluorure de zirconium ZrF4 obtenus dans le cristalliseur (8) pour les évacuer du cristalliseur (8).Process according to either of Claims 1 and 2, characterized in that the crystals of zirconium fluoride ZrF 4 obtained in the crystallizer (8) are dissolved in water to remove them from the crystallizer (8) . Procédé suivant l'une quelconque des revendications 1 à 3, caractérisé par le fait que l'évaporation sous vide de l'eau contenue dans la solution usagée et de la solution acide concentrée polluée dans le cristalliseur (8) est réalisée sous une pression résiduelle de l'ordre de 40 mm de mercure.Process according to any one of Claims 1 to 3, characterized in that the evaporation under vacuum of the water contained in the used solution and of the polluted concentrated acid solution in the crystallizer (8) is carried out under a residual pressure of the order of 40 mm of mercury. Dispositif de régénération d'une solution de décapage usagée constituée principalement par de l'acide fluorhydrique, de l'acide nitrique et de l'eau, après une utilisation pour le décapage d'éléments en alliage de zirconium, caractérisé par le fait qu'il comporte un évaporateur sous vide (7) et un évaporateur sous vide cristalliseur (8) disposés en série, de manière que l'évaporateur sous vide cristalliseur (8) recueille le concentrat de l'évaporateur sous vide (7).Device for regenerating a used pickling solution consisting mainly of hydrofluoric acid, nitric acid and water, after use for pickling elements of zirconium alloy, characterized in that it comprises a vacuum evaporator (7) and a crystallizer vacuum evaporator (8) arranged in series, so that the crystallizer vacuum evaporator (8) collects the concentrate from the vacuum evaporator (7). Dispositif suivant la revendication 5, caractérisé par le fait que l'évaporateur sous vide (7) et l'évaporateur cristalliseur (8) comportent un étage de condensation de distillat, le dispositif comportant de plus des moyens de réalisation d'un mélange dosé des distillats produits dans l'évaporateur sous vide (7) et dans l'évaporateur cristalliseur (8).Device according to Claim 5, characterized in that the vacuum evaporator (7) and the crystallizer evaporator (8) have a distillate condensation stage, the device further comprising means for producing a metered mixture of distillates produced in the vacuum evaporator (7) and in the crystallizer evaporator (8). Dispositif suivant la revendication 6, caractérisé par le fait qu'il comporte de plus une unité de mélange et de remise au titre (9) de la solution de décapage régénérée.Device according to claim 6, characterized in that it further comprises a unit for mixing and returning to the title (9) the regenerated pickling solution. Dispositif suivant la revendication 7, caractérisé par le fait qu'il comporte de plus une ligne (11) de recyclage de la solution de décapage régénérée dans un réservoir de stockage de solution de décapage (3).Device according to claim 7, characterized in that it further comprises a line (11) for recycling the regenerated pickling solution in a pickling solution storage tank (3). Dispositif suivant la revendication 8, caractérisé par le fait qu'il comporte de plus sur la ligne de recyclage (11) de la solution de décapage régénérée, un dispositif de mesure (10) du titre de la solution régénérée.Device according to Claim 8, characterized in that it further comprises on the recycling line (11) of the regenerated pickling solution, a device (10) for measuring the titer of the regenerated solution.
EP96400097A 1995-01-24 1996-01-15 Process and apparatus for regenerating a used etching solution for zirconium alloys Expired - Lifetime EP0723038B1 (en)

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FR9500783 1995-01-24
FR9500783A FR2729676B1 (en) 1995-01-24 1995-01-24 METHOD AND DEVICE FOR REGENERATING A USED SOLUTION FOR STRIPPING ZIRCONIUM ALLOY ELEMENTS

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US7988946B2 (en) 2005-06-30 2011-08-02 Compagnie Europeenne Du Zirconium-Cezus Method for recycling zirconium tetrafluoride into zirconia
CN103241784A (en) * 2012-02-14 2013-08-14 库特勒自动化系统(苏州)有限公司 Method and device for treating solar battery etching waste system

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US6885845B1 (en) * 1993-04-05 2005-04-26 Ambit Corp. Personal communication device connectivity arrangement
FR2874220B1 (en) * 2004-08-10 2007-07-06 Snecma Moteurs Sa METHOD FOR REGENERATING CHEMICAL MACHINING ACIDS, INSTALLATION FOR IMPLEMENTING THE METHOD, AND METHOD FOR ASSOCIATED CHEMICAL MACHINING
FR2887868B1 (en) * 2005-06-30 2007-08-17 Cie Europ Du Zirconium Cezus S PROCESS FOR RECYCLING ZIRCONIUM ZIRCONIUM TETRAFLUORIDE

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FR2729676B1 (en) 1997-04-11
US5788935A (en) 1998-08-04
FR2729676A1 (en) 1996-07-26
EP0723038B1 (en) 2000-04-12
ES2145390T3 (en) 2000-07-01
DE69607660T2 (en) 2000-12-28
DE69607660D1 (en) 2000-05-18

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