JP2007268424A - Separation method of pcb-contaminated material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a separation method of PCB-contaminated material which effectively separates and removes PCB from water-containing PCB-contaminated material, such as sludge and soil, by a vacuum heating separation method. <P>SOLUTION: The separation method comprises a separation step for evaporating water and PCB from the water-containing PCB-contaminated material p by feeding the PCB-contaminated material p into a treatment container 10, inserting the treatment container 10 into a vacuum heating separation furnace 1, and heating the vacuum heating separation furnace 1 under reduced pressure, an adsorption step for condensing and adsorbing the separated water and PCB by introducing them into an oil shower tower 2 disposed between the vacuum heating separation furnace 1 and a vacuum pump 9, and bringing them into contact with oil, an oil-water separation step for separating water from the oil by an oil-water separation means 4, and a circulation step for returning the separated oil to the oil shower tower 2. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for separating PCB contaminants, and more particularly, to a method for removing PCBs by heating PCB contaminants containing moisture under reduced pressure.

  PCB (polychlorinated biphenyl) is a compound obtained by substituting one or more hydrogens of biphenyl with chlorine, and there are 10 types of homologues and 209 types of isomers depending on the number and position of chlorine to be substituted. PCB has high chemical stability and has characteristics such as high insulation, non-flammability, heat decomposability, and poor water solubility. Conventionally, PCB has been used as an insulating oil and heat medium for electrical equipment such as capacitors and transformers. Although it has been used, the production is discontinued because it is harmful to the human body and the environment, and a method for treating and disassembling the electrical equipment that contains the already produced PCB and the contaminants to which the PCB has adhered has been proposed.

  Patent Document 1 proposes a vacuum heating method for cleaning a member to which contaminants are attached by supplying a cleaning gas under reduced pressure. However, this vacuum heating cleaning method is effective for cleaning processing of electrical equipment and the like to which PCB is attached, but there is a problem in applying it to processing of sludge and soil contaminated with PCB. That is, since sludge and mud-like PCB contaminants contain a lot of moisture, the exhaust gas contains an overwhelming amount of moisture compared to PCB. In order to decompose this PCB, moisture and PCB are separated. Another process is required.

For example, a method is conceivable in which PCB is brought into contact with oil or the like and condensed and absorbed, and the PCB concentration of the oil is increased to decompose the PCB together with the oil. In this case, the oil absorbs moisture together with the PCB. Therefore, when the oil is circulated in the apparatus to repeat the contact with the PCB to increase the concentration of the PCB, cavitation occurs in the circulation pump if the oil contains moisture. There is a problem that foaming occurs when oil is sprayed, and that it takes a long time for the water in the oil to evaporate again to increase the degree of vacuum. Therefore, a method for effectively separating PCB from moisture-containing PCB contaminants has not yet been established.
JP 2004-99646 A

  An object of the present invention is to provide a method for separating and treating PCB contaminants by effectively separating and removing PCBs from PCB contaminants containing moisture such as sludge and soil by a vacuum heating separation method.

  In the method for separating PCB contaminants of the present invention that achieves the above object, PCB contaminants containing moisture are placed in a treatment vessel, the treatment vessel is charged into a vacuum heating separation furnace, and the vacuum heating separation furnace is placed under reduced pressure. A separation step of evaporating the moisture and PCB from the PCB contaminants, an absorption step of introducing the moisture and PCB into an oil shower tower and bringing them into contact with oil for condensation absorption; It includes an oil / water separation step of separating the water, and a circulation step of returning the separated oil to the oil shower tower.

  In the method for separating PCB contaminants of the present invention, PCB contaminants containing moisture such as sludge and soil are heated under reduced pressure, and the separated moisture and PCB are brought into contact with oil in an oil shower tower to be condensed and absorbed. The oil is separated and removed into oil, PCB and moisture by the oil / water separation means, and this oil is returned to the oil shower tower. Since this oil does not contain moisture, even if it is circulated through the oil shower tower, it prevents forming due to cavitation and spraying of the circulation pump, and the moisture in the oil does not evaporate again. The degree can be increased quickly. Therefore, since moisture and PCB are separated and removed from PCB contaminants containing moisture to regenerate the contaminants, and the separated moisture and PCB are effectively separated, the separation of PCB contaminants not containing moisture Similarly, oil with a high PCB concentration can be recovered and used for PCB decomposition.

  The present invention is described in detail below.

  The PCB contaminants treated in the present invention may be in the form of slurry or sludge such as soil or sludge containing water or other liquid materials. Specifically, the sludge, soil, or moisture contaminated by PCB is removed. Examples thereof include activated carbon, waste, heat-sensitive copying paper, wood, and mixtures thereof.

  FIG. 1 is an explanatory diagram schematically illustrating a vacuum heating separation apparatus used in the PCB contaminant separation processing method of the present invention. In FIG. 1, the vacuum heating separation apparatus includes a vacuum heating separation furnace 1, an oil shower tower 2, a vacuum condenser 8, and a vacuum pump 9.

  The PCB pollutant p is in the form of a slurry such as soil containing water or sludge, or in the form of mud, and is charged into the vacuum heating separation furnace 1 in a state of being put in the processing container 10. The vacuum heating / separation furnace 1 can be heated to a temperature equal to or higher than the boiling point of PCB by the heating means 12 and is reduced in pressure by the communicating vacuum pump 9. The PCB pollutant p placed in the vacuum heating separation furnace 1 is heated under reduced pressure, and the contained water and PCB are evaporated and separated and removed, and regenerated into soil or the like not containing PCB.

  The heating means 12 is preferably an external heating means such as an electric heater, a heat exchanger, a combustion burner, etc., and heats PCB contaminants by conduction heat transfer and radiation through the processing vessel 10. The processing container 10 is not particularly limited, but a metal container having high heat transfer efficiency may be used. By containing PCB contaminants in the processing vessel 10, the heating efficiency from the vacuum heating separation furnace 1 is improved, and particles such as sludge and soil are scattered from the PCB contaminants and diffused to downstream devices. Can be suppressed.

  The conditions for the vacuum heat separation are preferably a processing temperature of 180 to 600 ° C., more preferably 250 to 450 ° C., and a degree of vacuum of preferably 0.01 to 60 kPa, more preferably 0.1 to 10 kPa, The treatment time varies greatly depending on the treatment object and the treatment amount, but the treatment object needs to be treated so that the temperature of the treatment object reaches at least the treatment temperature, and preferably 0 hour or more after reaching the predetermined treatment temperature, It may be 24 hours or less, more preferably 1 to 6 hours. If the treatment temperature is less than 180 ° C., it is difficult to sufficiently separate and separate the PCB, and if it exceeds 600 ° C., the evaporation of impurities and the thermal decomposition of the combustible materials become violent, and the PCB recovery becomes complicated. Even if the degree of vacuum is higher than 0.01 kPa, the effect of evaporating and separating the PCB is low compared to the fact that the equipment becomes excessive, and if it does not reach 60 kPa, it is difficult and not preferable to sufficiently evaporate and separate the PCB. . With respect to the above processing time, PCB may not be sufficiently evaporated and separated unless it is processed for at least the time to reach the processing temperature. Even if processing is performed for longer than 24 hours after reaching the processing temperature, the PCB is evaporated and separated. The effect reaches its peak.

  The water and PCB evaporated and separated by the vacuum heating separation furnace 1 are sucked by the vacuum pump 9 and introduced into the oil shower tower 2. In the oil shower tower 2, oil is sprayed from the nozzle 7, moisture and PCB come into contact with the oil and condensed and absorbed, and the gas component from which moisture and PCB have been removed is introduced into the vacuum condenser 8 and subjected to condensation treatment. The oil that has absorbed moisture and PCB is preferably stored by flowing down to the oil tank 3 and transferred to the oil / water separation means 4.

  The oil / water separation means 4 is not particularly limited, and for example, specific gravity type oil / water separation tank, coalescer type oil / water separation device, filter type oil / water separation device, adsorption type oil / water separation device and the like are preferable, more preferably. , A specific gravity oil / water separation tank, a coalescer oil / water separator, a filter-type oil / water separator, and an adsorption-type oil / water separator, and two or more separation means may be combined. The oil discharged from the oil tank 3 is effectively separated into oil containing PCB and moisture by passing through these oil / water separation means 4.

  The specific gravity type oil / water separation tank is a separator that separates water and oil into two phases of an aqueous phase and an oil phase by utilizing a difference in specific gravity between them. As illustrated in FIG. 1, oil having a low specific gravity may be an upper separated phase, and the supernatant may be recovered in an adjacent oil tank so as to overflow. Further, moisture having a high specific gravity may be discharged from the drain pipe 11 after forming a lower separated phase and reaching a predetermined amount. The structure of the specific gravity oil / water separation tank is not limited to this. For example, the oil / water separation tank may be combined in multiple stages, or may be combined with other oil / water separation means.

  The coalescer oil-water separator is a separator that aggregates and coarsens particles of water suspended as fine droplets in oil and separates them by specific gravity difference. Note that a separation operation using a filter type separation membrane or the like may be performed instead of or in addition to the specific gravity difference separation in the latter stage.

  The filter-type oil / water separator is a separator that allows the surface of the filter-type separation membrane to have a water-repellent function and allows only oil to pass therethrough, and is highly effective when combined with specific gravity-type separation or coalescer-type separation.

  The adsorption type oil / water separator is an oil / water separator that collects and separates water dispersed in oil by an adsorption film. It is preferable to arrange the adsorption towers containing the adsorption film in parallel so that the adsorption operation and the desorption operation are performed in parallel.

  The water separated by the oil / water separation means 4 is in a state containing almost no PCB, and is discharged from the drain pipe 11 and subjected to appropriate treatment, and then reused or discarded. In addition, when PCB contaminant contains combustibles, such as paper and wood, in the water | moisture content discharged | emitted from the vacuum heating separation furnace 1, thermal decomposition products, such as a tar and a wood vinegar, may be contained. . These thermal decomposition products are unstable, and when they are absorbed by oil, circulate with the oil, cool and sprayed under reduced pressure, problems such as precipitation and adhesion occur due to rapid state changes. Therefore, separation of such a thermal decomposition product from oil together with moisture by the oil / water separation means 4 is also useful for stably performing the PCB separation treatment.

  In order to perform another decomposition process after increasing the PCB concentration in the oil, the oil separated by the oil / water separation means 4 is circulated and sprayed to the nozzle 7 through the cooler 6 by the circulation pump 5 and repeatedly contacted with the PCB. . Since this oil does not contain moisture, even if it is circulated through the circulation pump 5, it is possible to prevent cavitation from occurring in the circulation pump 5. Further, even if oil is sprayed from the nozzle 7 into the oil shower tower 2 in a reduced pressure state, it is possible to prevent forming. At the same time, it is possible to prevent bubbling from occurring in the oil tank 3 that stores oil.

  Furthermore, since there is no moisture having a low boiling point in the oil, it does not evaporate again in contact with the high-temperature gas component sucked from the vacuum heating separation furnace 1, so that the inside of the system is brought to a reduced pressure state with a high degree of vacuum. For example, when the time required for decompression is reduced from 2 hours to 1 hour, the processing capacity per hour of PCB contaminants can be improved by 5 to 10%.

  When the PCB concentration of the oil increases by repeating the circulation of the oil shower tower 2, a part or all of the PCB-containing oil is extracted from the oil discharge pipe 13 communicating with the oil circulation line 14, and a PCB decomposition treatment device (not shown) The PCB is decomposed. Since the extracted oil contains high-concentration PCB and does not contain moisture, it is possible to reduce the amount of PCB-containing oil to be processed in the decomposition processing step such as a PCB smelting reduction furnace, and to reduce the equipment cost. The processing cost can be reduced. Further, new oil corresponding to the extracted oil amount or oil containing almost no PCB is supplied from the oil supply pipe 15.

  In the present invention, it is preferable to add a heat transfer accelerator selected from a metal piece, a metal rod, a metal net, or a metal sphere to the PCB contaminant p before or after the PCB contaminant p is put into the processing container 10. By adding such a heat transfer accelerator and mixing with sludge and soil uniformly, the heat transfer accelerator fills the gaps between the sludge and soil particles after the water has evaporated. The heat transfer through the particles and the heat transfer promoter can be promoted, and the thermal conductivity of the entire PCB contaminant can be increased. For this reason, the thermal conductivity can be kept high until the predetermined processing temperature is reached, and the time required for heating can be greatly shortened.

  The addition amount of the heat transfer accelerator is preferably 10 to 90 parts by weight, more preferably 20 to 40 parts by weight with respect to 100 parts by weight of the PCB contaminant p. If the amount added is less than 10 parts by weight, the effect of increasing the thermal conductivity during vacuum heating cannot be sufficiently obtained. If the amount added exceeds 90 parts by weight, the proportion of PCB contaminants p decreases, and the heat transfer accelerator. The energy required to separate and recover is increased, which is not preferable. As a method for separating the heat transfer promoter from the PCB contaminant p after the treatment, a known method can be used, which can be separated and recovered by centrifugation, separation with a magnet, separation with a sieve, or the like.

It is explanatory drawing which shows typically an example of embodiment of the apparatus used for the separation processing method of the PCB contaminant of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Vacuum heating separation furnace 2 Oil shower tower 4 Oil-water separation means 9 Vacuum pump 10 Processing container p PCB contaminant

Claims (3)

  Separation step of placing PCB contaminants containing moisture in a processing container, charging the processing vessel into a vacuum heating separation furnace, and heating the vacuum heating separation furnace under reduced pressure to evaporate the moisture and PCB from the PCB contaminants An absorption step of introducing the moisture and PCB into an oil shower tower and bringing it into contact with the oil to condense and absorb; an oil-water separation step of separating the moisture from the oil by an oil-water separation means; and separating the oil into the oil A method for separating PCB contaminants, including a circulation step for returning to the shower tower.   2. The PCB contaminant separation process according to claim 1, wherein the oil / water separator is at least one selected from a specific gravity oil / water separator, a coalescer oil / water separator, a filter-type oil / water separator, and an adsorption-type oil / water separator. Method. Before or after the PCB contaminant is put into the processing vessel, a heat transfer promoter selected from a metal piece, a metal rod, a metal net, or a metal sphere is added to the PCB contaminant and the vacuum heating separation furnace is installed. 3. A method for separating PCB contaminants according to claim 1 or 2.

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