EP0240419A1 - Verfahren zur Einbettung von pulverigen und/oder körnigen, radioaktiven oder toxischen Abfällen in granuliertem Bitumen - Google Patents

Verfahren zur Einbettung von pulverigen und/oder körnigen, radioaktiven oder toxischen Abfällen in granuliertem Bitumen Download PDF

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Publication number
EP0240419A1
EP0240419A1 EP87400681A EP87400681A EP0240419A1 EP 0240419 A1 EP0240419 A1 EP 0240419A1 EP 87400681 A EP87400681 A EP 87400681A EP 87400681 A EP87400681 A EP 87400681A EP 0240419 A1 EP0240419 A1 EP 0240419A1
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EP
European Patent Office
Prior art keywords
bitumen
extruder
waste
radioactive
powders
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP87400681A
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English (en)
French (fr)
Inventor
Jean Raibaud
Pascal Cirasse
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
TechnicAtome SA
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TechnicAtome SA
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Filing date
Publication date
Application filed by TechnicAtome SA filed Critical TechnicAtome SA
Publication of EP0240419A1 publication Critical patent/EP0240419A1/de
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    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21F—PROTECTION AGAINST X-RADIATION, GAMMA RADIATION, CORPUSCULAR RADIATION OR PARTICLE BOMBARDMENT; TREATING RADIOACTIVELY CONTAMINATED MATERIAL; DECONTAMINATION ARRANGEMENTS THEREFOR
    • G21F9/00—Treating radioactively contaminated material; Decontamination arrangements therefor
    • G21F9/28—Treating solids
    • G21F9/30—Processing
    • G21F9/301—Processing by fixation in stable solid media
    • G21F9/307—Processing by fixation in stable solid media in polymeric matrix, e.g. resins, tars

Definitions

  • the present invention relates to the coating in bitumen of radioactive or toxic waste.
  • the coating in bitumen of radioactive or toxic waste constituted for example by an aqueous suspension is generally carried out by mixing the aqueous suspension with bitumen in the fluidized state, then carrying out an evaporation of the water from the suspension and pouring the mixture thus obtained into a container to solidify it.
  • French patent 2052093 of the CEA filed on 7/15/1969 describes an installation for coating an aqueous suspension of radioactive products using bitumen, which uses a thin film evaporator and a gear pump to extract the coated products obtained at the base of the evaporator. To achieve this coating, it is also possible to use continuous coating installations, using twin or quadruple screw extruders in which the waste is mixed with the bitumen and the suspension is dried.
  • Patent DE-C-2 240 119 also describes an installation for coating waste in bitumen, which uses an extruder in which the mixing and drying of the waste takes place.
  • Patent FR-A-2 418 387 describes, on the contrary, a process for coating radioactive waste such as ion exchange resins in bitumen, which comprises a preliminary stage of drying the waste making it possible not to exceed a temperature of 120 ° C in the mixer; this prevents chemical decomposition of the resins in the mixer from occurring, releasing toxic or explosive gases.
  • bitumen must be brought beforehand to a temperature sufficient to present the fluidity necessary for its transfer and its metering by means of a pump. Therefore, very fluid bitumens which do not have good mechanical strength are used, for example a direct distillation bitumen such as the product sold under the name MEXPHALT 40/50, which has a penetration index at 25 ° C of 4 at 5mm, a softening point of 47 at 60 ° C and a pumpability temperature of 125 ° C.
  • the coating is carried out in an extruder, it is possible to use more viscous bitumens, obtained by blowing, the characteristics of which have been modified by partial dehydrogenation and oxidation.
  • the generally chosen bitumen which is for example MEXPHALT 90/40, has a penetration index at 25 ° C of 3.5 to 4.5mm, a softening point of 95 ° C and a pumpability temperature of 165 ° vs.
  • bitumens have excellent waste confinement properties, but they pose mechanical resistance problems because they are in a visco-elastic state at ambient temperature. In addition, their resistance to irradiation for an integrated dose of 108 rad is insufficient. Furthermore, in order to obtain correct evaporation of the water present in the waste suspension, it is necessary to use in these installations temperatures of the order of 160 ° C., which involves considerable fire risks.
  • the present invention specifically relates to a method of coating waste in bitumen, which overcomes the drawbacks of the methods mentioned above.
  • the process according to the invention for coating radioactive or toxic waste in bitumen consists in introducing radioactive or toxic waste in powders and / or grains into granules of a bitumen containing at least one radioactive or toxic waste. 25% asphaltene and at least one fluxing liquid, and heating the extruder so as to obtain at the outlet thereof a pasty or liquid mixture containing said waste.
  • bitumen melting circuits can be eliminated since it must no longer be introduced in the molten state into the mixing apparatus.
  • the heating is only intended to fluidize the bitumen, it is possible to limit the high temperature zone to the last part of the extruder only to facilitate the flow of the mixture when it is desired to obtain a liquid mixture.
  • the addition of a fluxing liquid to the bitumen in granules makes it possible to lower the temperature necessary to obtain a liquid or pasty mixture and to reduce the mechanical energy necessary for the mixing operation.
  • bitumens having better characteristics for example solid asphalt in granules such as "C5 asphalt” obtained by selective extraction with pentane, which contains a fraction of the order 30% asphaltene.
  • This asphalt has a zero penetration index at 25 ° C, a softening point of 150 ° C, a pumpable temperature of 250 ° C and it is hardly flammable.
  • its high content of aromatic products (oils and resins) and heterocyclic compounds (asphaltene) gives it excellent resistance to irradiation.
  • bitumen with more than 25% of asphaltene a natural rock such as gilsonite which has substantially the same characteristics as asphalt to C5 and which is a solid easily convertible into granules.
  • the fluxing liquids which can be used in the invention are liquids capable of lowering the softening point of the bitumen used.
  • Aromatic oils can be of the LCO (Light Cycle Oil) type, they are 90% distillation residues of cyclic hydrocarbons. Paraffinic oils are generally conventional mechanism lubrication oils, for example contaminated radioactive oils from pumps and compressors in nuclear installations.
  • the process of the invention can be implemented in different ways depending on whether a pasty mixture or a liquid mixture is collected at the outlet of the extruder.
  • the extruder is heated so as to recover at the outlet of the latter a liquid mixture.
  • the liquid mixture is introduced into a container and the mixture is allowed to harden in the container, the bitumen then serving as a waste containment barrier.
  • the mixture of bitumen, fluxing liquid and waste leaving the extruder contain at most 50% of radioactive or toxic waste.
  • the inlet of the extruder is heated to 100 ° C, then the middle part to about 120 ° C and the last part to a temperature of 140 to 160 ° C.
  • the extruder is heated so as to recover a paste mixture at the outlet of the extruder.
  • This pasty mixture is then transformed into profiles which are then cut into pieces such as cylindrical pellets having for example a diameter of 20 mm and a height of 20 mm.
  • bitumen does not serve as a containment barrier for radioactive or toxic waste but only as a binder to agglomerate this waste.
  • the pieces or pellets obtained at the outlet of the extruder cannot be stored as is. Also, it is necessary to coat them in thermosetting resins or in concrete to form around them a concrete or resin confinement barrier having the desired properties.
  • the entire extruder can be heated to a relatively low temperature not exceeding 120 ° C, for example heating the inlet to 100 ° C and the rest at 120 ° C.
  • the process of the invention can be used for the treatment of liquid waste provided, of course, that this waste is transformed into powders and / or grains before introducing them into the extruder.
  • the method of the invention comprises a preliminary step consisting in transforming the liquid waste into powders and / or grains. This can be done by heat treatment in a separate installation, which allows the temperature and duration of the treatment to be adjusted according to the type of waste treated. This treatment may consist of drying carried out by introducing the liquid waste into a reactor with a stream of hot gas.
  • This heat treatment can also consist of incineration of the waste, which leads to obtaining waste dry powders such as ash.
  • the powders and / or the grains are then introduced into a conventional extruder with the bitumen granules introduced cold and the fluxing liquid.
  • the heating of the mixture to the desired temperature is then carried out in the extruder.
  • bitumen into the extruder at a temperature above room temperature to promote the mixing operation, but this temperature is generally less than 100 ° C. and does not require bitumen melting installations as in l prior art.
  • the fluxing liquid for example aromatic or paraffinic oils
  • the fluxing liquid can be introduced at the inlet of the extruder at the same time as the bitumen and the waste; it can also be introduced separately at one or more points of the extruder cage.
  • the quantity of fluxing liquid used represents from 25% to 40% by weight of the mixture formed by the bitumen and the fluxing liquid.
  • the powders and / or the grains of radioactive or toxic waste are obtained by heat treatment of liquids
  • the powders and / or grains thus obtained are preferably transferred by means of a gas stream, then at least one is separated. part of the powders and / or grains present in the gas stream and the part thus separated is introduced into the extruder.
  • This separation of the powders and / or of the grains from the gas stream is preferably carried out by carrying out the following treatment cycle: - first separate a portion of the powders and / or grains present in the gas stream to deplete it in powders and / or grains, - circulating the gas thus depleted in powders and / or grains in the first compartment of a filtration device separated into first and second compartments by at least one porous and permeable wall having pores of dimensions smaller than that of the powders and / or grains for obtaining at the outlet of this first compartment gas enriched in powders and / or grains and diffusing in the second compartment purified gas, - recover the purified gas which has diffused in the second compartment, and - Recycle the gas enriched in powders and / or grains leaving the first compartment to subject it to a new treatment cycle with the gas stream to be treated.
  • the powders and / or grains are separated from the gas stream in a cyclone separator and introduced directly into the extruder from the separator.
  • This method of introducing the powders and / or grains obtained during drying is particularly advantageous since there is no rupture of the confinement between the drying installation and the coating installation. In addition, it avoids having to store the powders and / or the grains and then dosing them at the entrance to the extruder. This prevents radioactive dust from being released into the atmosphere.
  • Radioactive or toxic waste capable of being treated by the process of the invention can thus be obtained by heat treatment of liquid waste such as aqueous effluents from nuclear power plants, nuclear plants and many industrial installations.
  • these effluents can be constituted solely by solutions or else by suspensions of particles of insoluble matter such as fine powders, for example metal oxide powders, colloidal particles, etc. In all cases, during the heat treatment of these effluents, particles are obtained which may consist of powder, ash, etc.
  • the waste treated by the process of the invention may also consist of grain products such as ion exchange resins which are preferably subjected to drying before introducing them into the extruder with the bitumen granules. and the fluxing liquid.
  • grain products such as ion exchange resins which are preferably subjected to drying before introducing them into the extruder with the bitumen granules. and the fluxing liquid.
  • an installation which comprises: a liquid waste drying reactor comprising means for introducing liquid waste, means for introducing a hot gas and means for collecting the particles obtained in the drying reactor, and an extruder provided with heating means, means for introducing bitumen granules, means for introducing fluxing liquid and means for introducing the particles (powders and / or grains) collected in the drying reactor.
  • the installation further comprises means for transferring the particles collected in the drying reactor by means of a gas stream and means for separating the particles transferred by the gas stream.
  • the means for separating the transferred particles by the gas stream comprise: a treatment loop successively comprising a filtration device separated into a first and a second compartment by at least one porous and permeable wall having pores of dimensions smaller than those of the particles, a particle separation device connected to the two ends of the first compartment of the filtration device, and means for circulating the gas stream in the treatment loop, - means for introducing the gas stream into the loop treatment, means for extracting the gas having diffused in the second compartment of the filtration device, and - Means for collecting the separated particles in the separation device and introducing them into the extruder.
  • the separation device is a cyclone separator and the porous walls of the filtration device consist of tubes internally delimiting the first compartment.
  • the process of the invention can also be used to coat particles coming from a drying reactor or from an incinerator after these have been stored.
  • the stored particles are taken up either directly by a mechanical extraction device or by a gas stream and they are introduced into the treatment loop described above to separate the particles and introduce them directly into the extruder.
  • FIG. 1 there is shown an installation for continuously coating radioactive effluents implementing the method of the invention.
  • the effluents to be treated are stored in a tank 1 which is equipped with a pipe 3 and a circulation pump 5, with a system of on-line pH regulation 7 and of a device for injecting insolubilization products 9.
  • a pipe 11 provided with a positive displacement pump 13 makes it possible to inject the effluents coming from the reservoir 1 into a flash drying reactor 15.
  • this reactor 15, hot air is introduced via line 17 which is sucked through a filter 19 by a booster 21 and is heated in a heater 23.
  • the liquid effluents are evaporated by the hot air and they are cooled at the outlet of the reactor in the dilution box 25 by quenching air which is introduced through line 27 after being cooled in an exchanger 29.
  • the mixture leaving the dilution box 25 is therefore consisting of air loaded with powders and / or grains.
  • This mixture is then treated in the loop 31 provided with a cyclone separator 33, a circulation fan 35 and a filtration device 37 separated into a first compartment 37a and a second compartment 37b by porous and permeable tubes 37c , the direction of circulation in the treatment loop being indicated on the diagram.
  • the air laden with powders and dust is thus first introduced into the cyclone 33 where a part of the powders is separated and collected in the lock 39 while the gas depleted in particles is taken up by the fan 35, then introduced in the filtration device 37.
  • this filtration device 37 a pressure difference has been established between the compartments 37a and 37b in order to be able to extract from this device by passage through the wall of the porous tubes 37c of the purified air and recover at the outlet of the first compartment air enriched with particles.
  • the purified air is evacuated via the pipe 41, and the air enriched in particles is recycled in the cyclone 33 with an additional air loaded with particles (powders and / or grains) coming from the flash reactor 15.
  • the air purified leaving the filtration device through the pipe 41 is sucked by the pump 43 and it can be discharged into the atmosphere after passing through safety filters 45.
  • the powders and / or the separated grains are continuously treated in the cyclone 33 by introducing them directly through the lock 39 into an extruder 47.
  • Bitumen granules are also introduced into this extruder from a hopper 49 and the quantity of bitumen introduced by means of the extractor 51 is metered.
  • a metering pump 59 is provided for injecting a determined quantity of fluxing liquid coming from the tank 60 at one or more points of the extruder cage .
  • the extruder is provided with heating sleeves and the bitumen is if necessary heated in this extruder before the introduction of the particles coming from the separator 33. In the last part of the extruder 47, it is possible to continue heating the mixture to a higher temperature.
  • This installation therefore makes it possible to continuously treat liquid effluents in order to coat them in bitumen. This allows the volume of waste to be limited and its packaging to be carried out continuously under good conditions.
  • FIG 2 there is shown a variant embodiment of the installation of Figure 1 more particularly suitable for the deferred coating of powders, grains or ash from incineration.
  • the installation comprises a storage hopper 26 for the particles, and the particles stored in the hopper 26 are then introduced into the treatment loop 31 by a pneumatic transport assembly comprising a fan 61, a heater 63, a can of introduction 65 supplied by a dosing screw 67.
  • the particles are taken up by a gas stream, then introduced into the treatment loop 31 in which they are separated at 33, then introduced continuously into the extruder 47, with the bitumen granules coming from the hopper 49 and the fluxing liquid coming from the tank 60.
  • an installation such as those shown in FIGS. 1 and 2 was used to treat powders having an average particle size of 1 to 5 micrometers using for coating a two-screw extruder of 55 cm in diameter with streaks after the product introduction area and before the final heating area.
  • the speed of rotation of the screws was 120 rpm, the flow rate in the extruder 10 kg / h.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • High Energy & Nuclear Physics (AREA)
  • Processing Of Solid Wastes (AREA)
  • Working-Up Tar And Pitch (AREA)
EP87400681A 1986-04-04 1987-03-26 Verfahren zur Einbettung von pulverigen und/oder körnigen, radioaktiven oder toxischen Abfällen in granuliertem Bitumen Withdrawn EP0240419A1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8604844A FR2596908B1 (fr) 1986-04-04 1986-04-04 Procede et installation d'enrobage de dechets liquides radioactifs ou toxiques dans du bitume
FR8604844 1986-04-04

Publications (1)

Publication Number Publication Date
EP0240419A1 true EP0240419A1 (de) 1987-10-07

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EP87400681A Withdrawn EP0240419A1 (de) 1986-04-04 1987-03-26 Verfahren zur Einbettung von pulverigen und/oder körnigen, radioaktiven oder toxischen Abfällen in granuliertem Bitumen

Country Status (3)

Country Link
EP (1) EP0240419A1 (de)
JP (1) JPS62294999A (de)
FR (1) FR2596908B1 (de)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5582572A (en) * 1993-11-12 1996-12-10 Bianchi; Alessio Method and plant for rendering solid waste inert and for its subsequent definite storage

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR3080707B1 (fr) * 2018-04-25 2020-05-01 Seche Eco Services Procede de traitement de dechets bitumines radioactifs

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2240119B1 (de) * 1972-08-16 1974-01-03 Werner & Pfleiderer, 7000 Stuttgart Verfahren und vorrichtung zum beseitigen von in kleineren mengen anfallenden, mittel bis stark strahlenden festen abfaellen
FR2318487A1 (fr) * 1975-07-15 1977-02-11 Kraftwerk Union Ag Procede d'elimination de dechets de matieres synthetiques radioactifs et installation pour sa mise en oeuvre

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2240119B1 (de) * 1972-08-16 1974-01-03 Werner & Pfleiderer, 7000 Stuttgart Verfahren und vorrichtung zum beseitigen von in kleineren mengen anfallenden, mittel bis stark strahlenden festen abfaellen
FR2318487A1 (fr) * 1975-07-15 1977-02-11 Kraftwerk Union Ag Procede d'elimination de dechets de matieres synthetiques radioactifs et installation pour sa mise en oeuvre

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5582572A (en) * 1993-11-12 1996-12-10 Bianchi; Alessio Method and plant for rendering solid waste inert and for its subsequent definite storage

Also Published As

Publication number Publication date
FR2596908B1 (fr) 1992-06-05
JPS62294999A (ja) 1987-12-22
FR2596908A1 (fr) 1987-10-09

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