EP2588256B1 - Method and device for decontaminating polluted materials - Google Patents

Description

FIELD OF THE INVENTION

The present invention relates to the field of depollution. It relates more particularly to the decontamination of polluted materials of various types and categories, in particular to extract PCBs and / or other pollutants / contaminants.

The term "other pollutants / contaminants" is understood to mean products of contaminants and / or pollutants vaporizable by heating under vacuum, and in particular having a volatility similar or comparable to that of PCBs. Such pollutants / contaminants are most often polychlorinated biphenyls proper, polychlorobenzyltoluenes, or polychloroterphenyls. But it may also be, more generally, all low volatility compounds, such as VOCs (volatile organic compounds) such as halogenated or non-halogenated complexes distillable under vacuum, or chlorinated compounds and / or volatile brominates, or more generally all dielectric fluids conventionally contained in electrical equipment, as well as organochlorine compounds from the pesticide industry.

It is indeed now required by the authorities, and by current or future standards, to lower the residual content of contaminants in polluted materials of all types below a content of 50 ppm, and preferably below 20 ppm.

TECHNOLOGICAL BACKGROUND

Methods are known for the decontamination of PCB-contaminated materials in which a vapor phase or liquid phase solvent is used which operates under low vacuum or even at atmospheric pressure.

In addition, the document FR 2743801 describes a process for the destruction of polychlorinated biphenyls by catalytic hydrogenation carried out on polychlorinated biphenyls dissolved or suspended in an aqueous solution.

The document WO 9552648 discloses a biological method for allowing dechlorination of PCBs by anaerobic methanogenic inoculation.

The document EP 0098811 discloses a process for extracting PCBs from electro-mechanical apparatus containing them by immersion in a closed chamber fed with vapors of a suitable solvent.

The document EP 1432477 B1 discloses a method for the decontamination of PCB contaminated materials, wherein the decontamination is carried out thermally in the absence of oxygen, preferably under high vacuum. Such a process makes it possible to decontaminate all types of materials soiled by PCBs and to decompose them without the production of dioxins or fiurannes, which are highly contaminating products.

There was still a need for a high-performance decontamination process capable of providing decontamination without producing dioxins or furans over a wider field of contaminants (such as PCBs in the strict sense and the like, PCBTs, PCTs, and the like). other volatile organic compounds), and for a variety of different materials and / or materials.

SUMMARY OF THE INVENTION

It has now been found that these objectives, as well as others, can be achieved with a method and an apparatus using a confined enclosure into which the soiled material is introduced and where: a first evacuation of about 20 mbar followed by an injection of inert gas and heating to a temperature not exceeding about 220 ° C, with forced convection, and then the pressure is lowered to about 0.1 mbar, a bypass (or bypass or dual pumping flow) is established, and an inert gas is introduced to bring the pressure back above about 950 mbar, then forced convection cooling is performed. The contaminants are then separated during the process as a distillate.

An object of the present invention is thus to provide a technique and apparatus that perform well according to several points of view, for decontamination of soiled materials with PCBs and other contaminants.

Another objective is to provide such a technique and such equipment providing a decontamination without producing dioxins or furans.

These and other objectives, which will be apparent from the remainder of the present description, have been achieved through a method and apparatus which will be detailed later.

DETAILED DESCRIPTION OF THE INVENTION

• on charge les matériaux à traiter dans une enceinte apte à être mise sous vide poussé;
• on met l'enceinte sous un premier vide inférieur à 20 mbar et on injecte ensuite un gaz d'inertage (ou gaz destiné à rendre inerte l'atmosphère entourant le matériau à traiter dans l'enceinte), notamment de l'azote, jusqu'à ce que la pression dans l'enceinte remonte au-dessus de 950 mbar environ;
• on chauffe le contenu de l'enceinte, sous convection forcée, à une température maintenue inférieure ou égale à environ 220°C,
  tandis que:
  • on opère une nouvelle mise sous vide jusqu'à une pression résiduelle d'environ 0,1 mbar, tout en maintenant le chauffage;
  • on injecte ensuite un gaz inerte, notamment de l'azote, jusqu'à ce que la pression remonte à environ 950 mbar; et ensuite
• on refroidit le contenu de l'enceinte sous convection forcée; et
• on décharge de l'enceinte les matériaux ainsi décontaminés,

tandis que les produits polluants/contaminants extraits ont été évacués sous forme de distillat, pour être stockés sur site, traités/décomposés sur site, ou expédiés à un centre de traitement par décomposition.It has indeed been found that the above and other objectives can be achieved with a method and an apparatus in which:

• the materials to be treated are loaded into an enclosure capable of being placed under high vacuum;
• the enclosure is placed under a first vacuum of less than 20 mbar and then an inerting gas (or gas intended to render the atmosphere surrounding the material to be treated in the enclosure) inert, in particular nitrogen, until the pressure in the chamber rises above about 950 mbar;
• the contents of the enclosure are heated, under forced convection, to a maintained temperature of less than or equal to about 220 ° C.,
  while:
  • a new evacuation is carried out to a residual pressure of about 0.1 mbar, while maintaining the heating;
  • an inert gas, especially nitrogen, is then injected until the pressure rises to approximately 950 mbar; and then
• the contents of the enclosure are cooled under forced convection; and
• the materials thus decontaminated are discharged from the enclosure,

while the extracted pollutants / contaminants were removed as a distillate, stored onsite, processed / decomposed on site, or shipped to a decomposition treatment center.

The invention can be implemented for the decontamination treatment of electrical and electronic equipment and waste from such equipment, within the meaning of the decree French No. 2005-829 of 20.07.2005, both in the field of industrial equipment and in that of electrical appliances, computer, office and other. In particular, the polluted materials to be treated according to the invention may be those used in the composition of electrical equipment such as transformers or capacitors, such as dunnage, copper windings, aluminum, paper and others. .

• la cuve constituant l'enceinte est de préférence parallélépipédique; elle comporte avantageusement une convection forcée, notamment par au moins un ventilateur approprié;
• la porte de l'enceinte chargée est fermée au moyen d'un joint d'étanchéité approprié, de préférence un joint gonflable;
• une fois le joint susdit gonflé, on pratique une mise sous vide initiale jusqu'à un vide correspondant à une pression interne se situant en dessous de 20 mbar (ou 20 mPa) environ;
• le gaz d'inertage est l'azote, l'argon et/ou le CO₂ ou un mélange d'azote avec un ou plusieurs autres gaz procurant classiquement une atmosphère inerte;
• la mise en chauffe des matériaux à dépolluer peut être poursuivie sur une durée à déterminer par une méthode d'essais itératifs; elle peut être d'environ 15 heures en pratique, pour une pression interne après inertage d'environ 950 mbar;
• l'étape ultérieure peut consister en une mise sous vide à petit débit, jusqu'à une pression interne (c'est-à-dire pression dans l'enceinte) d'environ 700 mbar;
• une fois atteinte une pression de cet ordre de grandeur, la pression dans l'enceinte est avantageusement abaissée jusqu'à environ 100 mbar par un pompage à grand débit;
• l'abaissement de la pression jusqu'à moins de 2 mbar, avantageusement jusqu'à environ 1 mbar, peut s'effectuer selon l'invention par une mise sous vide à grand débit, notamment au moyen d'un système de pompage de type Roots, actionné pendant environ 8 heures;
• un bypass (ou double flux de pompage) permet ensuite , en option, l'optimisation de l'extraction des polluants/contaminants des matériaux traités; il est avantageux de mettre en oeuvre ce bypass sur une durée d'environ 10 heures;
• l'injection d'azote subséquente, avec ou sans l'étape de bypass susdite, est effectuée jusqu'à ce que l'on constate un retour de la pression interne à environ 950 mbar;
• le refroidissement des matériaux dans l'enceinte est ensuite effectué par des moyens traditionnels, jusqu'à ce que leur température soit inférieure à environ 90°C;
• une ventilation à l'air pendant environ 30 min permet d'effectuer, en option, un nettoyage des matériaux traités;
• le joint d'étanchéité de l'enceinte de mise sous vide est dégonflé et on peut ensuite ouvrir l'enceinte pour en extraire, par déchargement classique, les matériaux dépollués; la teneur résiduelle de ceux-ci en polluants/contaminants peut être déterminée en option, à titre de vérification, de préférence sur des prélèvements aléatoires.

In advantageous embodiments, one or more of the following provisions are implemented optionally, in combination or separately, if this is technically possible:

• the tank constituting the enclosure is preferably parallelepipedic; it advantageously comprises a forced convection, in particular by at least one appropriate fan;
• the door of the charged enclosure is closed by means of a suitable seal, preferably an inflatable seal;
• once the aforesaid seal is inflated, an initial vacuum is applied to a vacuum corresponding to an internal pressure of less than about 20 mbar (or 20 mPa);
• the inerting gas is nitrogen, argon and / or CO ₂ or a mixture of nitrogen with one or more other gases conventionally providing an inert atmosphere;
• the heating of the materials to be cleaned up can be continued over a period to be determined by an iterative test method; it can be about 15 hours in practice, for an internal pressure after inerting of about 950 mbar;
• the subsequent step may consist of a vacuum at low flow rate, up to an internal pressure (that is to say pressure in the chamber) of about 700 mbar;
• once a pressure of this order of magnitude is reached, the pressure in the chamber is advantageously lowered to about 100 mbar by high-volume pumping;
• the lowering of the pressure to less than 2 mbar, advantageously up to approximately 1 mbar, can be carried out according to the invention by high-volume evacuation, in particular by means of a pumping system of the type Roots, operated for about 8 hours;
• a bypass (or double pumping flow) then allows, as an option, the optimization of the extraction of pollutants / contaminants from the treated materials; it is advantageous to implement this bypass over a period of about 10 hours;
• the subsequent nitrogen injection, with or without the above-mentioned bypass step, is carried out until a return of the internal pressure to about 950 mbar is observed;
• the cooling of the materials in the enclosure is then carried out by conventional means, until their temperature is below about 90 ° C;
• an air ventilation for about 30 minutes allows an optional cleaning of the treated materials;
• the seal of the evacuation chamber is deflated and can then be opened to extract, by conventional unloading, the cleaned materials; the residual content of these pollutants / contaminants can be determined optionally, as verification, preferably on random samples.

1. a. chargement des matériaux à décontaminer,
2. b. mise sous vide à environ 20 millibars,
3. c. injection d'azote à environ 950 millibars,
4. d. chauffage avec convection forcée à environ 220°C,
5. e. mise sous un vide d'environ 0,1 millibars,
6. f. injection d'un gaz d'inertage à 950 millibars,
7. g. refroidissement avec convection forcée,
8. h. déchargement des matériaux dépollués.

Thus, in a preferred embodiment of the method according to the invention, the aforesaid steps may comprise the following phases:

1. at. loading of the materials to be decontaminated,
2. b. evacuation to about 20 millibars,
3. vs. nitrogen injection at about 950 millibars,
4. d. heating with forced convection at about 220 ° C,
5. e. put under a vacuum of about 0.1 millibars,
6. f. injection of an inerting gas at 950 millibars,
7. boy Wut. cooling with forced convection,
8. h. unloading of the cleaned materials.

The method according to the invention evaporation of PCBs, PCBT, PCT, and other pollutants / contaminants by vacuum distillation and temperature, while reducing the necessary heating time compared to known processes implemented.

The inerting above allows to operate in the absence or substantially in the absence of oxygen.

There is no or essentially no chemical reaction, biological decomposition or even thermal decomposition on pollutants / contaminants extracted by conventional distillation, after the implementation of the process according to the invention.

Forced convection promotes heat transfer in materials and material to the dewaxing dew point. Advantageously used for this purpose a finned exchanger with fluid at about 5 ° C, in combination with forced convection mentioned above.

PCBs and their counterparts do not decompose below 300 ° C, even in the presence of flames, hot surfaces or arcing.

The invention thus has as its first object a method for the decontamination of polluted materials as described herein.

It also relates to an apparatus for the decontamination of polluted materials by implementing this method.

1. a. chargement des matériaux à décontaminer dans une enceinte à vide,
2. b. mise sous vide à environ 20 millibars,
3. c. injection d'azote à environ 950 millibars,
4. d. chauffage avec convection forcée à environ 220°C,
5. e. mise sous un vide d'environ 0,1 millibars,
6. f. injection d'un gaz d'inertage à 950 millibars,
7. g. refroidissement avec convection forcée,
8. h. déchargement des matériaux dépollués.

In the most general embodiment of the apparatus according to the invention, the aforementioned devices comprise appropriate means, arranged and operatively connected to each other so as to allow the following operations:

1. at. loading the materials to be decontaminated in a vacuum chamber,
2. b. evacuation to about 20 millibars,
3. vs. nitrogen injection at about 950 millibars,
4. d. heating with forced convection at about 220 ° C,
5. e. put under a vacuum of about 0.1 millibars,
6. f. injection of an inerting gas at 950 millibars,
7. boy Wut. cooling with forced convection,
8. h. unloading of the cleaned materials.

• une enceinte étanche et supportant un vide poussé, ladite enceinte étant de préférence de forme parallélépipédique et étant de préférence munie d'un joint gonflable;
• des moyens pour le chargement des matériaux à traiter dans ladite enceinte;
• des moyens de pompage pour mettre l'enceinte sous un premier vide inférieur à 20 mbar et des moyens pour injecter ensuite un gaz d'inertage (ou gaz destiné à rendre inerte l'atmosphère entourant le matériau à traiter dans l'enceinte), notamment de l'azote, jusqu'à ce que la pression dans l'enceinte remonte au-dessus de 950 mbar environ;

• des moyens pour chauffer le contenu de l'enceinte, sous convection forcée, à une température maintenue inférieure ou égale à environ 220°C, tandis qu'on prévoit également des moyens pour:
  • opérer une nouvelle mise sous vide jusqu'à une pression résiduelle d'environ 0,1 mbar, tout en maintenant le chauffage;
  • injecter ensuite un gaz inerte, notamment de l'azote, jusqu'à ce que la pression remonte à environ 950 mbar; et
• des moyens pour refroidir le contenu de l'enceinte sous convection forcée; et
• des moyens pour décharger de l'enceinte les matériaux ainsi décontaminés,

tandis qu'on dispose de moyens pour évacuer et condenser les produits polluants/contaminants extraits sous forme de distillat, afin que ceux-ci puissent être stockés sur site, traités / décomposés sur site, ou expédiés à un centre de traitement par décomposition, et
tandis que l'appareillage comprend également des moyens accessoires et de connectique, et éventuellement un automate de pilotage, utiles pour le bon fonctionnement de l'ensemble.Said apparatus preferably comprises, essentially:

• a sealed enclosure supporting a high vacuum, said enclosure preferably being of parallelepipedal shape and preferably being provided with an inflatable seal;
• means for loading the materials to be treated in said enclosure;
• pumping means for putting the enclosure under a first vacuum of less than 20 mbar and means for subsequently injecting an inerting gas (or gas intended to render the atmosphere surrounding the material to be treated inert the chamber), in particular nitrogen, until the pressure in the chamber rises above about 950 mbar;

• means for heating the contents of the enclosure, under forced convection, to a maintained temperature of less than or equal to about 220 ° C, while also providing means for:
  • re-evacuate to a residual pressure of approximately 0.1 mbar while maintaining the heating;
  • then inject an inert gas, especially nitrogen, until the pressure rises to about 950 mbar; and
• means for cooling the contents of the enclosure under forced convection; and
• means for discharging the materials thus decontaminated from the enclosure,

while there is a means to evacuate and condense the pollutants / contaminants extracted as distillate, so that they can be stored on site, treated / decomposed on site, or shipped to a processing center by decomposition, and
while the apparatus also comprises accessory means and connectors, and possibly a controller, useful for the proper functioning of the whole.

Those skilled in the art are able to select and possibly adapt known devices to use them in the above functions and make them operational in the method according to the present invention.

In an advantageous embodiment, the pumping assembly may include two parallel-mounted vane pumps and a Roots depressor, or alternatively a dry primary pump and a Roots depressant to allow descent to 10 ^-4 atm (1 atm). = 101.325 Pa), or even 10 ^-5 atm with a higher pumping rate.

In any case, and all other things being equal, the lower the treatment temperature, the shorter the duration of treatment.

In parallel, it appeared important to properly evacuate the condensates, including forced convection proposed according to the invention, to maximize the extraction by evaporation of pollutants / contaminants. To this end, one can also provide optional minimize the re-evaporation of some of the recovered condensates by supplementing the recovery recipe of the condenser of an additional recipe with a system of valves to allow to purge continually recovered condensate.

In the apparatus according to the invention, the temperature and / or pressure measurements are carried out inside the enclosure with appropriate probes.

By way of example of particularly remarkable decontamination results obtained by the process according to the invention, mention may be made of a residual content of PCBs or equivalents of the order of only a few ppm, and even of only about 1 ppm, both for a large electrical transformer than for an electrical capacitor, initially contaminated on average by about 250,000 ppm PCB or equivalent.

The person skilled in the art is able to choose and / or adapt the devices, their dimensions and their constituent materials, as well as their accessories and connection elements to the different needs and specific operating conditions that he can select for convenience in the frame of the method according to the invention.

Those skilled in the art will readily understand that the practice of the present invention provides undeniable advantages and significant progress over currently known and practiced techniques.

Thus, by means of the technique according to the invention, it is possible to achieve substantial savings, to simplify the procedures involved in the process phases, and to achieve particularly remarkable decontaminations.

Such a system provides very significant advantages over traditional decontamination techniques. In particular, it possibly avoids the prior dismantling of equipment to be decontaminated, such as transformers, capacitors, and others. The method according to the invention allows a very precise temperature control and excellent control of the operation of the process and the conduct of the equipment.

Claims (10)

1. Method for the decontamination of polluted materials, characterized in that it comprises the operations consisting of:

   loading the materials to be treated into a chamber capable of being placed under high vacuum;

   placing the chamber at a first vacuum below 20 mbar, and then injecting an inerting gas, in particular nitrogen, until the pressure in the chamber increases to above approximately 950 mbar;

   heating the contents of the chamber, under forced convection, to a temperature that is maintained at less than or equal to approximately 220°C, while:

   evacuation is again carried out, to a residual pressure of approximately 0.1 mbar, while the heating is continued; then an inert gas, in particular nitrogen, is injected, until the pressure increases to approximately 950 mbar; and then

   cooling the contents of the chamber under forced convection; and

   unloading the thus-decontaminated materials from the chamber,

   while the extracted polluting/contaminating products have been removed in the form of a distillate.
2. Method according to claim 1, characterized in that a chamber including an inflatable sealing gasket is used.
3. Method according to claim 1, characterized in that it includes, separately or in combination, one or more of the following provisions:

   the tank constituting the chamber is parallelepipedal and includes a forced convection;

   the door of the loaded chamber is closed by means of an inflatable sealing gasket;

   once said gasket has been inflated, an initial evacuation is carried out to a vacuum corresponding to an internal pressure of below 20 mbar (or 20 mPa) approximately;

   the inerting gas is nitrogen, argon and/or CO₂ or a mixture of nitrogen with one or more other gases conventionally providing an inert atmosphere;

   heating of the materials to be decontaminated is continued for a duration of approximately 15 hours, for an internal pressure after inerting of approximately 950 mbar;

   the subsequent step consists of evacuation at a low flow rate until reaching an internal pressure of approximately 700 mbar;

   once this pressure is reached, the pressure in the chamber is reduced to approximately 100 mbar by pumping at a high flow rate;

   reducing the pressure to less than 2 mbar, advantageously to approximately 1 mbar, is carried out by evacuation at a high flow rate, in particular by means of a Roots-type pumping system, actuated during approximately 8 hours;

   a bypass is implemented for a duration of approximately 10 hours;

   a subsequent injection of nitrogen is carried out until it is observed that the internal pressure has returned to approximately 950 mbar;

   cooling of the materials in the chamber is then carried out until their temperature is less than approximately 90°C;

   ventilation with air during approximately 30 min makes it possible to carry out cleaning of the treated materials;

   the sealing gasket of the evacuation chamber is deflated and the chamber opened in order to extract the decontaminated materials therefrom by unloading.
4. Method according to claim 1, characterized in that it includes the following phases:

   a. unloading of the materials to be decontaminated,

   b. evacuation to approximately 20 millibars,

   c. injection of nitrogen to approximately 950 millibars,

   d. heating with forced convection to approximately 220°C,

   e. evacuation to approximately 0.1 millibars,

   f. injection of an inerting gas at 950 millibars,

   g. cooling with forced convection,

   h. unloading of the decontaminated materials.
5. Method according to claim 1, characterized in that the PCBs, PCBTs, PCTs, and other pollutants/contaminants that can be distilled under vacuum are evaporated.
6. Method according to claim 1, characterized in that a fin tube exchanger is used with fluid at approximately 5°C, in combination with forced convection.
7. Method according to claim 1, characterized in that it is implemented for the decontamination treatment of electrical and electronic equipment and waste originating from these items of equipment.
8. Equipment for the implementation of the method according to any one of claims 1 to 7, characterized in that it includes essentially:

   a sealed chamber supporting a high vacuum, said chamber being preferably parallelepipedic in shape and preferably being equipped with an inflatable gasket;

   means for loading the materials to be treated into said chamber;

   pumping means for placing the chamber under a first vacuum below 20 mbar and means for injecting an inerting gas, in particular nitrogen, until the pressure in the chamber increases to above 950 mbar approximately;

   means for heating the contents of the chamber, under forced convection, to a temperature maintained at less than or equal to approximately 220°C,

   while means are also provided for:

   carrying out a fresh evacuation to a residual pressure of approximately 0.1 mbar, while continuing the heating;

   then injecting an inert gas, in particular nitrogen, until the pressure increases to approximately 950 mbar; and

   means for cooling the content of the chamber under forced convection; and

   means for unloading the thus-decontaminated materials from the chamber,

   while having available means for draining and condensing the pollutant/contaminant products extracted in the form of distillate, so that these can be stored on site, treated/decomposed on site, or sent to a centre for treatment by decomposition, and

   while the equipment also comprises .accessory and connectivity means, and optionally automated control means, useful for the correct operation of the whole.
9. Equipment according to claim 8, characterized in that the pumping unit includes two vaned pumps, mounted in parallel, and a Roots depressor, or as a variant a primary dry pump and a Roots depressor in order to make it possible to bring the pressure down to 10-4 atm, or even 10-5 atm with a higher pumping rate.
10. Equipment according to any one of claims 8 or 9, characterized in that it includes moreover means for limiting the re-evaporation of a portion of the condensates recovered in operation, by adding to the condenser recovery station an additional station equipped with a system of vanes in order to allow the continuous purging of the recovered condensates.