WO2002098514A1

WO2002098514A1 - Method for decontamination and decomposition of polychlorobiphenyls (pcb's)

Info

Publication number: WO2002098514A1
Application number: PCT/FR2001/001766
Authority: WO
Inventors: Yves Guibert; Roger Gilbert; Georges Ceresoli
Original assignee: Aprochim
Priority date: 2001-06-07
Filing date: 2001-06-07
Publication date: 2002-12-12
Also published as: EP1432477B1; ATE459394T1; HU228885B1; HUP0401688A2; ES2344139T3; EP1432477A1; DE60141484D1

Abstract

The invention concerns a decontamination method using vacuum distillation of PCB's at temperature less than 500 °C in a vessel (1), and optionally heat treatment of the distillate in a mass furnace (12) under inert gas and in the absence of oxygen, at a temperature higher than 1200 °C, preferably in the form of submicronic micelles obtained by means of an ultrasonic transducer (11), as well as basic neutralisation in a chamber (15) of the gaseous chlorine generated by the decomposition of the PCB molecule, and subsequent thermal decomposition in a combustion tube (17) of the chlorine-free gaseous by-products.

Description

PROCESS FOR DECONTAMINATION AND DECOMPOSITION OF PCBs

FIELD OF THE INVENTION

The present invention relates to the field of decontamination of materials soiled by polychlorinated biphenyls, hereinafter referred to as "PCB". The invention relates more particularly to a method and an apparatus for the treatment of materials soiled by PCBs, in order to decontaminate these materials and optionally to decompose the PCB molecule.

PCBs are indeed chemicals known to be carcinogenic, the decomposition of which itself most often generates dioxins and / or furans.

TECHNOLOGICAL BACKGROUND OF THE INVENTION

Processes are known for the decontamination of materials contaminated with PCBs, in which a solvent is used in the vapor phase or in the liquid phase, working under low vacuum or at atmospheric pressure.

There is also known a process for decomposing the PCB molecule by heat treatment, with loading of the PCB in liquid form, in the presence of ambient air, in a heat treatment enclosure.

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.

Document EP 0887087 describes a process for destroying polychlorinated biphenyls by contact with hydrogen gas at temperatures between 250 and 400 ° C.

Document WO 9852648 discloses a biological process intended to allow the dechlorination of PCBs by anaerobic methanogenic inoculation. There was therefore a need for a more efficient process for decontamination and / or decomposition of materials contaminated by PCBs.

SUMMARY OF THE INVENTION

The first object of the invention is a process for the decontamination of materials soiled by PCBs, and optionally for the decomposition of PCB molecules, in which said decontamination is carried out thermally in the absence of oxygen, advantageously under vacuum pushed, and said decomposition is carried out by heat treatment under inert gas, advantageously by treatment of PCB previously brought to the state of mist comprising submicronic micelles of PCB molecules.

The subject of the invention is also an apparatus for implementing this method. The method and the means according to the invention make it possible to decontaminate all types of materials contaminated by PCBs and to decompose them without producing dioxins or furans, which are highly contaminating products.

Compared with current methods for decontamination of materials soiled by PCBs and those for the decomposition of PCBs, the method according to the invention is distinguished by a shorter extraction time, by a lower residual PCB content in the material. treated, and by obtaining a concentrated product which is directly destructible, in the form of a mist produced under an inert atmosphere, in the absence of oxygen, by a short-term heat treatment and under a neutral atmosphere, making it possible to guarantee the absence of dioxins and furans formation in the gaseous emissions.

Thus, in total opposition to the state of the art described above, the method according to the invention does not use a solvent for extracting the PCB from its support, nor a chemical reaction such as hydrogenation or biological degradation for its decomposition.

The object of the present invention is to provide an efficient technique from several points of view, for the decontamination of materials soiled by PCBs and, optionally, for the decomposition of PCBs extracted from said materials. This objective, as well as others which will emerge from the rest of the present description, have been achieved by means of a method and a device which will be detailed below.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is illustrated below in more detail, with reference to the accompanying drawing board, in which FIG. single represents a block diagram of the operation of the method according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

In the method according to the invention for the decontamination of materials and / or materials soiled by PCBs and the optional decomposition of the collected PCBs, said operations are carried out in the absence of oxygen. Thus, according to the invention, the production of dioxins or furans is avoided.

In the present text, the term "material to be decontaminated" means any material containing PCBs and / or other pollutants / volatile contaminants, in particular an electrical transformer containing PCBs.

As for the terms "materials to be decontaminated", they designate materials impregnated with PCBs and / or other pollutants / contaminants, such as those used in the composition of electrical equipment, such as, for example, dunnage, copper coils, between others, as well as aluminum, paper and other materials used in the composition of electrical capacitors. Although the present description essentially relates to PCBs, it should be noted that all other polluting agents and / or contaminants having a volatility similar or comparable to that of PCBs can also be extracted and collected, or even broken down by the process according to the invention; a person skilled in the art is capable of proceeding, on a case-by-case basis and with simple routine tests, to the possible adjustments of the operating conditions which the implementation of the method according to the invention might require for pollutants other than PCBs and / or mixtures of pollutants / contaminants with PCBs. By way of nonlimiting examples of such pollutants / contaminants, mention may be made of halogen or non-halogen complexes distilled under vacuum, chlorinated compounds and / or volatile bromines, as well as more generally all the dielectric fluids conventionally contained in electrical appliances.

In general, the invention therefore relates to a decontamination process, and optionally thermal decomposition, as described below and which is applicable to the elimination of dielectric fluids contained in electrical devices.

The method according to the invention advantageously comprises the following steps: 1 - loading of materials and / or materials soiled by PCBs in an enclosure equipped to operate in the absence of oxygen, advantageously in an enclosure suitable for being placed under vacuum, preferably with a high residual vacuum, and creation of a high vacuum in said enclosure, advantageously up to a reduced pressure of less than 0.1 millimeter of mercury (ie 0.1 × 133.322 Pa) in said enclosure; 2 - distillation of pollutants / contaminants, in particular PCBs, by heating the equipment and / or materials loaded in the enclosure, in which a high vacuum has been produced, preferably by heating to a temperature below about 500 ° C inside said enclosure, advantageously until a residual PCB content of less than 50 pp is obtained, and

3 - optionally, recovery and decomposition of PCBs and / or other pollutants / contaminants collected by condensation after step 2, by heat treatment under inert gas, advantageously by heating to a temperature above 1200 ° C., for a period of at least 2 seconds, preferably of ^~ by such heat treatment of submicronic micelles of PCBs and / or other pollutants / contaminants, advantageously obtained by means of an ultrasonic transducer.

As a variant, said thermal decomposition of PCBs and / or other pollutants / contaminants can be dissociated from the decontamination operation which made it possible to extract them or even can be the subject of a treatment independent of the latter.

By way of example, it is possible, according to the invention, to treat materials of the type of electrical transformers containing PCBs, or materials impregnated with PCBs, such as for example dunnage, windings of copper and / or capacitors, the latter comprising aluminum, paper and other materials.

According to a preferred embodiment, the pressure is brought into said enclosure to a value less than 0.1 millimeter of mercury and the enclosure is heated to a maximum temperature below 500 ° C, without introducing inert gas in said enclosure.

The distillate obtained in step 2 above is sent to a receiver, which is placed under inert gas.

In the embodiment of the method according to the invention which includes thermal decomposition of the PCBs, the liquid PCB distillate is introduced, advantageously after transformation of the properly liquid phase into a submicron mist, preferably by a sound transducer, in an oven decomposition where it is left to stay for a minimum duration of 2 seconds, the adjustment of this duration being combined on a case-by-case basis with the injection of inert gas which also ensures the total absence of oxygen in this thermal decomposition step .

According to a preferred embodiment, the method according to the invention comprises the introduction into the heat treatment furnace of a divided material which is electrically conductive and insensitive to chlorine gas resulting from the decomposition of the PCB molecule, advantageously composed pieces of about 10-15 millimeters in side or diameter, and the application of an appropriate induction heating to bring the temperature of said material to a minimum of 1200 ° C, thus providing an eminent contact between the fog of PCB in the form of submicron micelles and said divided conductive material filling the oven enclosure.

The products resulting from this thermal decomposition of PCBs and / or other pollutants / contaminants are then sent to a basic neutralization chamber, into which an appropriate neutralizing agent is injected into the gas circuit, itself advantageously in the form of submicron micelles.

For example, the difference in contact area of the same amount of basic neutralizing solution, in particular with chlorine, between a conventional spraying by micro-nozzles generating micelles of about 2 micrometers and a spraying by mist obtained by ultrasound generating micelles of about 0.1 micrometer, is of a ratio of 1 to 400 in favor of ultrasonic mist, with the result of an exhaustive neutralization of the chlorine in sodium, potassium or calcium salts depending on the neutralizing agent chosen. These salts are considered acceptable for the environment. In an optional step of the process according to the invention, those of the obtained by-products which are combustible can be thermally decomposed by means of a combustion torch.

The subject of the invention is also an apparatus for implementing the said method, said apparatus comprising: 1 - an enclosure for loading materials and / or materials soiled by PCBs, equipped to operate in the absence of oxygen , advantageously with vacuum means, preferably with a high residual vacuum, while the high vacuum advantageously corresponds to a reduced pressure of less than 0.1 millimeter of mercury in said enclosure;

2 - means for heating the equipment and / or materials loaded in the enclosure, in which a high vacuum has been produced, for expelling it by distillation and evacuation by an appropriate outlet, the pollutants / contaminants, in particular the PCBs and other pollutants / volatile contaminants, advantageously until a residual PCB or similar content of less than 50 ppm is obtained, as well as means for condensing them, and

3 - optionally, means for the recovery and decomposition of PCBs and / or other pollutants / contaminants collected by condensation after step 2, comprising means for heat treatment under inert gas, advantageously by heating to a temperature above 1200 ° C, for a short time, and advantageously means for producing submicronic micelles of PCBs and / or other pollutants / contaminants, such as for example an ultrasonic transducer. In one embodiment of the device for implementing the method according to the invention, as shown diagrammatically in the appended figure, an enclosure 1, for example a cylindrical tank provided with opening / closing means 2 on at least l 'one of its horizontal ends, and designed to resist vacuum and a temperature below about 500 ° C, is loaded by opening 2 with material and / or materials to decontaminate PCBs and any other pollutants / contaminants found there.

Opening 2 must be designed to withstand the distillation temperature of PCBs and a pressure of less than 0.1 millimeter of mercury. In operation, the tank 1 loaded with the equipment and / or materials to be decontaminated is evacuated by means of a vacuum group 3, having a capacity to create the vacuum adapted to the volume of the installation, so as to reach a final vacuum of around 0.1 mm of mercury, preferably. The interior of the enclosure 1 thus evacuated is heated by an appropriate means, such as for example an electrical resistance, an electromagnetic induction system and / or a heat transfer fluid (not shown) until the PCBs are distilled and / or other pollutants / contaminants. The boiling temperature of volatile products such as in particular PCBs, under a pressure of less than 0.1 millimeter of mercury is lower than the boiling temperature of the same compounds or mixtures of compounds under atmospheric pressure.

Heating of the interior of said vacuum enclosure is undertaken so that the temperature inside the enclosure 1 is less than about 500 ° C. Under these conditions, PCB extraction was obtained up to a residual value of a few ppm (parts per million), and even up to a few ppb (parts per billion) only.

In a variant of the process according to the invention, the tank 1 loaded with the equipment and / or materials to be decontaminated, previously placed under vacuum, unheated corn, is returned to atmospheric pressure by introduction into said tank of an appropriate inert gas. by a pipe 4, for example nitrogen, using the valve 5. The latter, when in the closed position, also seals the part of the installation which is under vacuum for the PCB distillation phase. Then, said charged tank is again placed under vacuum via a vacuum group 3 and heated by one or more electrical resistances, by induction and / or by a heat-transfer fluid, until the PCBs and other pollutants / possible contaminants begin to distill and the heating is continued as long as desired so that the decontamination reaches a high rate, as indicated above. Generally, the receiver containing the distillate is put under inert gas during the breaking of the vacuum.

The trapping of PCBs and / or other pollutants / contaminants thus extracted in the vapor state from the equipment and / or materials to be treated is then carried out, advantageously by evacuation by an appropriate outlet and condensation by means of a descending refrigerant 6, and the PCB or any other distilled liquid pollutant / contaminant is collected in a receiver 7.

In order to avoid any contamination of the vacuum group 3, the few traces of vapor entrained by the vacuum are preferably trapped by a refrigeration unit 8.

The end of the distillation process for PCBs and other pollutants / contaminants is indicated by the vacuum limit displayed by the vacuum group 3 and the known temperature at the end of the operation announcing a residual content of PCBs and / or other pollutants / contaminants a few ppm (parts per million), and even advantageously only a few ppb, in decontaminated equipment and / or materials.

In the embodiment of the method according to the invention comprising the option of decomposing PCBs, the liquid PCB condensed in the receiver 7 under the effect of the descending refrigerant 6, and preferably also by the cold plant 8, is directed via line 9, after opening the valve 10, on an ultrasonic transducer 11, which transforms the liquid PCB in the form of submicron micelles, for its introduction in the form of a mist, into the furnace 12 for heat treatment. The latter has previously been placed under inert gas 13 or is placed under inert gas 13 simultaneously with the injection of the PCB submicron mist into the oven 12 heated to a temperature above 1200 ° C.

In a preferred embodiment, the oven 12 receiving the PCB to be destroyed is filled with pieces, advantageously about 10 to 15 millimeters in side or in diameter, of a material which is electrically conductive and insensitive to chlorine gas , which is a gas produced by the decomposition of the PCB molecule and / or other pollutants / halogen contaminants, and said oven is brought to an internal temperature of at least 120 ° C., for example by induction heating, in order provide close contact between the PCB fog under form of submicron micelles and the conductive body filling the interior volume of the oven 12.

The products resulting from this breakdown of PCBs and / or other pollutants / contaminants under inert gas and in the absence of oxygen are directed, under the slight pressure of inert gas 13, through line 14 to a chamber 15 for basic neutralization. In this basic neutralization enclosure 15, an appropriate neutralizing agent, which a person skilled in the art is able to choose from among conventional neutralizing agents, if necessary after iterative tests, is preferably injected into the gas circuit of the products resulting from the decomposition of the PCB molecule, in the form of submicron micelles preferably obtained by means of an ultrasonic transducer 16 integrated into the neutralization enclosure 15. It is thus possible to carry out an exhaustive neutralization of the chlorine into sodium, potassium or calcium salts, which are then received in a tank 19, drawn off by gravity using a valve 20 located at the low point of the tank 19, and are deemed to be environmentally acceptable.

If desired, the combustible by-products obtained, being free of chlorine, can be thermally decomposed, for example by means of a combustion torch 17, before being discharged into the atmosphere 18.

The PCB distillation tank (1) and the combustion torch (17) can be heated by electrical energy or by conventional combustible, liquid and / or gaseous products.

By way of nonlimiting examples, the process according to the invention has treated, on the one hand, a capacitor core, and, on the other hand, a block of wood from an electrical transformer.

For these two examples of PCB extraction according to the present invention, a pilot laboratory installation was used comprising a 2000 cm ^ stainless steel heat treatment chamber. To treat a part of a raw, unground milled capacitor core made of paper, aluminum and PCB, the following operating conditions were applied:

- vacuum limit during extraction between 6, lxl0 ^~ 3 and 4.4xl0 "2 millibar (1 millibar = 10 ² Pa); - external resistance heating (reactor heater); - distillation temperature between 103 and 155 ° C;

- duration of distillation: approximately 2 hours;

- gross weight entered: 263.61 grams;

- weight of the distillation residue: 154.80 grams; - weight loss on the product used: 108.81 grams, or 26.36%;

- residual PCB content on the treated product: <1 ppb (part per billion).

To treat part of an electrical transformer wooden block saturated with PCBs, the following operating conditions were applied:

- limit vacuum during extraction between 6.8x10 "^ and 3.2x10"! millibar; - external resistance heating (reactor heater);

- distillation temperature between 148 and 241 ° C;

- duration of the distillation: approximately 10 hours;

- gross weight entered: 295.27 grams;

- weight of the distillation residue: 56.18 grams; - weight loss on the product used: 239.09 grams, or 80.97%;

- residual PCB content on the treated product: <1 ppb (part per billion).

The invention described above can also be used for the decontamination of equipment and / or materials contaminated with halogen complexes distilled under vacuum.

Furthermore, it goes without saying that the invention is not limited to the sole embodiments described here; it encompasses all their variant embodiments and applications. Thus, for example, one would not depart from the scope of the invention by placing the tank 1 vertically, or by using a heating source other than electricity, both for the distillation tank 1 and for for the combustion torch 17.

Claims

1. Method for the decontamination of materials soiled by PCBs and / or other pollutants / volatile contaminants and, optionally, the decomposition of these PCBs and / or pollutants / contaminants, characterized in that the decontamination steps and the optional decomposition step are carried out in the absence of oxygen.

2. Method according to claim 1, characterized in that it comprises decontamination by distillation carried out under vacuum.

3. Method according to claim 2, characterized in that the distillation is carried out under a reduced pressure less than 0.1 millimeter of mercury.

4. Method according to one of claims 2 or 3, characterized in that the distillation is carried out by heating the equipment and / or materials loaded in a chamber under high vacuum, to a temperature in said chamber below 500 ° vs.

5. Method according to claim 1, characterized in that the decomposition of the PCB molecule is carried out by heat treatment under inert gas.

6. Method according to claim 5, characterized in that said heat treatment is carried out by heating to a temperature above 1200 ° C for a period of at least 2 seconds.

7. Method according to one of claims 5 or 6, characterized in that subject to said thermal treatment of submicron micelles

PCB and / or other pollutants / contaminants, preferably by means of an ultrasonic transducer.

8. Method according to claim 1, characterized in that it comprises the following steps: 1 - loading of materials and / or materials soiled by PCBs in an enclosure equipped to operate in the absence of oxygen, advantageously in an enclosure capable of being placed under vacuum, preferably with a high residual vacuum, and production of a high vacuum in said enclosure, advantageously up to a reduced pressure of less than 0.1 millimeter of mercury (ie 0.1 × 133.322 Pa) in said enclosure;

2 - distillation of pollutants / contaminants, in particular PCBs, by heating the equipment and / or materials loaded in the enclosure, in which a high vacuum has been produced, preferably by heating to a temperature below about 500 ° C inside said enclosure, advantageously until a residual PCB content of less than 50 ppm is obtained, and

3 - optional, recovery and breakdown of PCBs and / or other pollutants / contaminants collected by condensation after the step

2, by heat treatment under inert gas, advantageously by heating to a temperature above 1200 ° C., for a period of at least 2 seconds, preferably by such heat treatment on submicronic micelles of PCBs and / or others pollutants / contaminants, advantageously obtained by means of an ultrasonic transducer.

9. Method according to claim 8, characterized in that it further comprises a basic neutralization step of the chlorine gas resulting from the decomposition of the PCB molecule according to step 3 and, optionally, a thermal decomposition step of the sub -Chlorine-free gaseous products from said basic neutralization step.

10. Apparatus for the decontamination of materials soiled by PCBs and / or other pollutants / volatile contaminants and, optionally, the decomposition of these PCBs and / or pollutants / contaminants, characterized in that it comprises:

1 - an enclosure (1) for loading equipment and / or materials soiled by PCBs, equipped to operate in the absence oxygen, advantageously with means (3) for evacuating, preferably with a high residual vacuum;

2 - means for heating the equipment and / or materials loaded in the enclosure to expel, by distillation and evacuation by an appropriate outlet, pollutants / contaminants, in particular PCBs and other pollutants / volatile contaminants, as well as means (6) for condensing them, and

3 - optionally, means (7, 12, 13) for the recovery and decomposition of PCBs and / or other pollutants / contaminants collected by condensation after step 2, comprising means for heat treatment under inert gas, advantageously by heating at a temperature above 1200 ° C.

11. Apparatus according to claim 10, characterized in that the enclosure (1) comprises means (3) suitable for placing under vacuum at a reduced pressure less than 0.1 millimeter of mercury in said enclosure.

12. Apparatus according to claim 10, characterized in that it comprises a mass furnace (12) for heat treatment, advantageously filled with pieces, preferably 10 to 15 millimeters on the side or in diameter, of a material which is conductive electricity and insensitive to chlorine gas. ^~~

13. Apparatus according to claim 10, characterized in that it comprises a basic neutralization enclosure (15), as well as an inlet pipe (14) and means (13) for ensuring in said enclosure a slight pressure of inert gas, for the neutralization of breakdown products of PCBs and / or other pollutants / contaminants.

14. Apparatus according to claim 10, characterized in that it comprises an ultrasonic transducer (16) integrated into the enclosure (15) for the production of submicron micelles of the products resulting from the breakdown of PCBs.

15. Apparatus according to claim 10, characterized in that it comprises a combustion torch (17), for the thermal decomposition of gaseous by-products free of chlorine.

16. Application of the method according to any one of claims 1 to 9 to the decontamination of materials and / or materials soiled with halogen complexes distilled under vacuum.

17. Equipment and / or material, characterized in that it is obtained by decontamination, and optionally decomposition, according to any one of claims 1 to 9 of a material and / or material initially soiled with PCBs and / or other pollutants / contaminants, and that it has a residual PCB content of less than 50 ppm.