JP3730251B2 - Purification method and apparatus for solid substances contaminated with organic halogen compounds - Google Patents

Description

  The present invention relates to a method and apparatus for purifying solids contaminated with organic halogen compounds, and more particularly, to purify solids such as soil and sludge contaminated with organic halogen compounds such as polychlorinated biphenyls, dioxins and agricultural chemicals. The present invention relates to a purification method and an apparatus for detoxifying and detoxifying.

  As is well known, polychlorinated biphenyl, a kind of organic halogen compound, is very stable and difficult to be decomposed, and has high insulation (electrical resistance), so in the past, insulation materials such as transformers and capacitors, and heat media Or it was used for carbonless copy paper, but now it is prohibited to use for environmental reasons. However, there are cases where traces remain in solids such as soil and sludge even if they have been used for some time, and how to decompose and treat them is an important issue. It has become.

  In recent years, the treatment of organic halogen compounds such as dioxins has also become a problem from the viewpoint of environmental destruction and safety, and such dioxins also remain as trace components in solids such as soil and sludge. There may be.

  As a method for purifying contaminants contaminated with such an organic halogen compound, a thermal decomposition method in which the object to be purified is heated to 300 to 400 ° C. or more and oxygen is supplied for combustion, or a temperature higher than the evaporation temperature of the organic halogen compound (for example, 300 ° C. or higher), evaporating and then cooling, heat desorption method, heating to 300 to 400 ° C. or higher, mainly adding an alkaline compound such as NaOH or KOH, and in the presence of a hydrocarbon solvent, A chemical method (BCD method) for detoxification is performed.

  However, since both methods are heated at a high temperature, the organic halogen compound is evaporated by the heating. As a result, there is a problem that the influence on the surrounding environment cannot be ignored and the environment is destroyed. Although it is not impossible to prevent such scattering of the organic halogen compound, a large-scale apparatus is required for that purpose. In addition, since any method is processed at a high temperature, a great amount of heat energy is required.

  The present invention has been made in order to solve such problems, and it is possible to lower the treatment temperature for purification below the vapor pressure of the organic halogen compound, thereby preventing the surroundings due to the scattering of the organic halogen compound. The issue is to prevent environmental destruction.

In order to solve such problems, the present invention has been made as a purification method and apparatus for a solid substance contaminated with an organic halogen compound. The purification method is characterized by a solid substance contaminated with an organic halogen compound. After removing moisture in the product by distillation under reduced pressure , an alkali metal is added to the solid material contaminated with the organic halogen compound, and the organic halogen compound is decomposed to purify the solid material.

  The purification device is characterized by supplying a solid substance contaminated with an organic halogen compound and adding an alkali metal to react the organic halogen compound in the solid substance with the alkali metal, Before the reaction apparatus 1 reacts the organic halogen compound and the alkali metal in the solid with each other, a water removal apparatus for removing the water in the solid is provided.

The water removal apparatus for removing moisture solids in the distillation apparatus 2 is used to perform the reduced pressure distillation.

  In the present invention, an alkali metal such as sodium metal that reacts at a heating temperature of normal temperature or higher, preferably 60 ° C. or higher and 200 ° C. or lower, is added to solids such as soil and sludge containing organic halogen compounds, so that the boiling point is the above. There is no possibility that organic halogen compounds such as polychlorinated biphenyl and dioxin which are much higher than the temperature will evaporate, and therefore there is an effect that the surrounding environment is not affected and the environment is not destroyed.

  As a result, there is no need to provide a large-scale device for capturing the evaporated organic halogen compound as in the conventional case, and there is an effect that the facility can be reduced in size.

  Moreover, since it can process at low temperature compared with the conventional method, much heat energy is not required unlike the past.

  Furthermore, since the moisture in the solid is removed in advance before adding the alkali metal to the solid, there is no possibility that the sodium metal reacts with the moisture in the soil to become caustic soda, such as sodium metal and polychlorinated biphenyl. There is an effect that the reaction with the organic halogen compound is not hindered.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
First, a solid purification device contaminated with an organic halogen compound as one embodiment will be described.

  In FIG. 1, 1 supplies a soil containing polychlorinated biphenyl as an example of an organic halogen compound, and also adds a sodium dispersant in which metal sodium powder is dispersed in insulating oil, so that polychlorinated biphenyl and metal are added. In this reaction apparatus 1 for reacting sodium, isopropyl alcohol which is a reaction promoting substance is further added.

  2 is a distillation apparatus for removing moisture in the soil in advance by vacuum distillation before the sodium dispersant is added, and is provided in the preceding stage of the reaction apparatus 1. 3 shows an adsorption device for adsorbing the water removed by the distillation device 2 with activated carbon.

  4 is a separator for separating unreacted sodium dispersant from the soil among the sodium dispersant added in the reactor 1, and for returning the separated sodium dispersant to the reactor 1. The return line 5 is connected to the reactor 1 and the separator 4.

  6 is a distillation apparatus for separating isopropyl alcohol from the soil after separating the sodium dispersant by vacuum distillation, and a return line 7 for returning the separated isopropyl alcohol to the reaction apparatus 1 comprises the reaction The apparatus 1 and the distillation apparatus 6 are connected.

  Next, a method for purifying a solid substance contaminated with an organic halogen compound using such a purification apparatus will be described with reference to FIGS.

  First, contaminated soil containing polychlorinated biphenyl is supplied to the distillation apparatus 2, and the soil is distilled under reduced pressure by the distillation apparatus 2. As a result, moisture in the soil evaporates and a certain amount of moisture is removed.

  In other words, if the soil contains a large amount of water, metal sodium added later may react with the water in the soil to become caustic soda, which hinders the reaction between metal sodium and polychlorinated biphenyl. Since there exists a possibility, a water | moisture content is previously removed by the said vacuum distillation. The removed water vapor is adsorbed by the activated carbon of the adsorption device 3 and processed.

  Next, the soil after vacuum distillation is supplied to the reactor 1 and heated at about 100 ° C., a sodium dispersant in which metal sodium powder is dispersed in insulating oil is added to the reactor 1, and isopropyl alcohol is further added. Add. As a result, polychlorinated biphenyl in the soil reacts with metallic sodium in the sodium dispersant to dechlorinate the polychlorinated biphenyl. Further, by adding isopropyl alcohol, the reaction between polychlorinated biphenyl and metallic sodium is promoted.

  Furthermore, since polychlorinated biphenyl contained in soil is generally contained in insulating oil, the affinity is improved by dispersing the alkali metal added in the insulating oil as described above. The reaction with the compound will be carried out more reliably.

  After the reaction as described above, the soil is supplied to the separation device 4, and only the sodium dispersant is separated by the separation device and is returned to the reaction device 1 through the return line 5. The sodium dispersant after the separation is unreacted and is returned to the reactor 1 for reuse. On the other hand, the separated soil is supplied to the distillation apparatus 6 and is distilled under reduced pressure by the distillation apparatus 6 to separate isopropyl alcohol. The isopropyl alcohol separated in this vacuum distillation is returned to the reaction apparatus 1 via the return line 7.

  This isopropyl alcohol is returned to the reactor 1 and reused as a reaction accelerator between polychlorinated biphenyl and metallic sodium. The soil separated by the distillation apparatus will be obtained as a detoxified dry matter.

  As described above, in the present embodiment, the sodium dispersant in which metallic sodium powder is dispersed in insulating oil is reacted with polychlorinated biphenyl to dechlorinate polychlorinated biphenyl. The polychlorinated biphenyl having a boiling point of about 300 degrees is not evaporated and scattered from the soil and does not affect the surroundings. It is.

(Example)
The PCB was subjected to a decomposition treatment in the reactor at room temperature, 60 ° C., 75 ° C., 90 ° C., and 110 ° C., and the changes in the residual PCB rate over time were tested. Here, the residual PCB rate is expressed by the following equation.
Residual PCB rate (%) = (post-reaction PCB concentration) / (pre-reaction PCB concentration) × 100

  The initial PCB concentration was 360 ppm. The test results are shown in FIG. As is apparent from FIG. 3, PCB is completely decomposed in about 5 minutes at 110 ° C., completely decomposed in about 10 minutes at 90 ° C., decomposed in about 15 minutes at 75 minutes, and about 95 at 60 ° C. Decomposed in minutes.

  Even at room temperature, the residual PCB rate could be reduced to about 75% in about 120 hours, and it was confirmed that the PCB decomposition reaction was possible even at room temperature. From these, decomposition treatment is possible even at room temperature, but it is preferable to perform the treatment at 60 ° C. or higher in consideration of the time required for the treatment. In addition, if the treatment temperature is increased, the treatment can be performed in a short time. However, if the temperature exceeds 200 ° C., the PCB will evaporate significantly. Therefore, the decomposition treatment is preferably performed at 200 ° C. or less.

  The metal sodium used in the above embodiment has an advantage that it is inexpensive and generally easily available. However, the present invention is not limited to this, and metal potassium, metal strontium, metal lithium and alloys thereof can also be used. The point is that a dispersant in which an alkali metal is dispersed in a dispersion medium such as oil may be used.

  Further, in this embodiment, isopropyl alcohol is used as a reaction accelerator, and this isopropyl alcohol has many functional groups (reactive groups) and is excellent in reactivity due to low viscosity, and is used for pharmaceuticals such as disinfectants. Therefore, there are advantages such as excellent safety and biodegradability, but the type of reaction accelerator is not limited to this, and ethanol, methanol, and the like can also be used, for example.

  Furthermore, in the above embodiment, since the sodium dispersant after separation and the isopropyl alcohol after distillation are returned, there is an advantage that they can be reused. However, such return and reuse are also included in the present invention. This is not a requirement.

  Furthermore, in the above embodiment, since metallic sodium is dispersed in a dispersion medium such as insulating oil, the affinity is improved, and a favorable effect that the reaction between the alkali metal and the organic halogen compound is performed more reliably is obtained. The dispersion in such a dispersion medium is not an essential condition for the present invention.

  In addition to this, the solid material such as soil to which alkali metal has been added is heated in the object to be treated by the method of stirring while heating above the melting point of the alkali metal, the method of pulverizing and mixing, or the method of applying alkali metal vapor to the solid material. It is also possible to disperse sodium.

  Furthermore, in the above embodiment, the case where polychlorinated biphenyl is treated has been described. However, the type of the organic halogen compound to be treated is not limited to the polychlorinated biphenyl of the above embodiment, for example, dioxin. It may be. Moreover, pesticides, such as DDT and BHC, may be sufficient. In short, it is only necessary that the soil to be treated contains an organic halogen compound.

  Furthermore, although the said Example demonstrated the case where the soil containing an organic halogen compound was processed, it is also possible to apply this invention when processing not only soil but the sludge containing an organic halogen compound, for example. is there. Furthermore, the present invention can also be applied to the treatment of containers, fabrics and the like to which organic halogen compounds are attached. In short, the present invention can be applied to any solid matter containing an organic halogen compound or contaminated by adhering to it.

The schematic block diagram of the purification apparatus of the solid substance as one Example. The schematic block diagram which shows the purification | cleaning process of the solid substance as one Example. The graph which shows the correlation of reaction time and residual PCB rate.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Reaction apparatus 2 ... Distillation apparatus 4 ... Separation apparatus

Claims (2)

After removing moisture in the solid contaminated with the organic halogen compound by distillation under reduced pressure , an alkali metal is added to the solid contaminated with the organic halogen compound, and the organic halogen compound is decomposed to purify the solid. A method for purifying a solid substance contaminated with an organic halogen compound. While supplying the solid substance contaminated with the organic halogen compound and adding an alkali metal, the reaction apparatus (1) for reacting the organic halogen compound and the alkali metal in the solid substance is solid in the reaction apparatus (1). An organic halogen compound comprising a distillation apparatus (2) for performing distillation under reduced pressure to remove moisture in a solid before reacting an organic halogen compound and an alkali metal in the product. Purification equipment for contaminated solids.

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