JP5216660B2 - Dioxin-containing treated substance purification method and dioxin-containing treated substance purification apparatus - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a substance purification method and a purification apparatus, and in particular, a purification method for purifying a substance to be removed such as harmful substances (for example, dioxin) contained in an object to be removed by treatment in a gaseous state. The present invention relates to a purification device.

  In today's debate about global environmental issues, various studies are being conducted on methods for removing harmful substances emitted in various industrial processes. Among such harmful substances, dioxins are particularly toxic, and particular attention is paid to their removal measures. Dioxins in the narrow sense are polychlorinated dibenzodioxins. In general, dioxins are a general term for dibenzo pararadixin, dibenzofuran and coplanar PCB having chlorine in the molecule (hereinafter referred to as the present specification). The dioxins are simply called dioxins). None of these substances exist in nature, and they are contained in the flue gas of pulp bleaching plants, generated in the process of producing herbicides, etc., or in the flue gas due to reactions in the waste incinerator. May be included. In particular, polymer materials containing chlorine such as polyvinyl chloride are discarded as waste, and if the combustion temperature is not high enough when incinerated, dioxins are produced as intermediate products due to incomplete decomposition of the polymer material. It is known to occur easily. The amount of dioxins generated in Japan announced by the Environment Agency in 1998 is several tens to several hundred times that of Europe and the United States, and future measures centering on waste incinerators are becoming important.

  However, for example, in order to suppress the generation of dioxins in a waste incinerator or the like, the combustion temperature of the incinerator itself must be increased, and the renewal of equipment is required. In many cases, this is known to be indispensable for environmental measures, but it is often followed by financial problems of local governments that have treatment facilities.

  Another problem is that the frequency of analysis is rapidly increasing as regulations for harmful substances such as dioxins are regulated. There are many types of dioxin analysis such as soil, water, aquatic organisms, exhaust gas, general environment or work environment, all of which repeat solvent extraction-> concentration-> cleanup etc. according to each determined method. After being made into a concentrated analysis solution, it is used for analysis. However, the amount of the analysis solution used in the actual analysis is small, and the remaining analyzed waste solution is put in, for example, a sealed container and further stored in a freezer. Analytical laboratories have increased the amount of analysis liquids generated. However, in the case of dioxins, etc., there is an appropriate treatment method except for methods that require a large amount of cost and equipment, such as combustion decomposition at high temperatures. It has not been established, and it has been hurting to carry the increasing amount of analyzed waste liquid.

  An object of the present invention is to provide a substance purification treatment method capable of easily and inexpensively purifying a substance to be treated containing dioxin and a substance purification apparatus used therefor.

Means and actions / effects for solving the problems

In order to solve the above-described problems, the method (apparatus) for purifying a substance to be treated containing dioxin according to the present invention generates a plasma by applying a plasma generating voltage to a plasma generating electrode, and the plasma contains dioxin. A purification method (apparatus) for a dioxin-containing treated substance that reduces the dioxin content in the treated substance by introducing a gaseous treated substance and converting dioxin mainly into organic substances other than dioxin. , the plasma generating electrode, characterized a base material made of a metal, comprising a porous electrode layer made of the electrode surface forming a metal formed on the surface of the substrate, and the Rukoto porous electrode layer is disposed to face And

  According to the above method, plasma is generated by applying a plasma generation voltage to the plasma generation electrode, and dioxin is introduced into organic substances other than dioxin by introducing a gaseous substance to be treated containing dioxin into the plasma. Conversion can effectively reduce the dioxin content in the treated material. In addition, in conventional waste incinerators, etc., the temperature inside the furnace was raised to reduce the amount of dioxins emitted by complete decomposition into carbon dioxide, etc., so a very costly method such as increasing the output of equipment was used. I had to adopt it. However, according to the present invention, the substance to be treated is introduced into the plasma, and it is rendered harmless by converting it into an organic substance other than dioxin. It can be generated simply by applying a high frequency for plasma oscillation to the generating electrode. Furthermore, the main part of the apparatus for carrying out the above method is simple because it only needs to include the plasma generating part, and can be easily added to the discharge flow path of the gas to be processed. Therefore, it is possible to provide the removal target substance removal function at low cost without improving or updating the equipment side that is the source of the gas to be treated (or the substance to be treated). In the present invention, the dioxin in the substance to be treated may be partially converted into an inorganic compound such as carbon dioxide gas as long as the effect of the present invention is not significantly impaired.

  At least a part of the electrode surface for generating plasma of the plasma generating electrode can be a metal-based or non-metallic catalyst layer. By using such a catalyst layer, the conversion reaction of dioxy to an organic substance other than dioxin can be promoted, and as a result, dioxin in the substance to be treated can be more efficiently removed. On the other hand, the substance to be treated introduced into the plasma can be brought into contact with a metal-based or non-metallic catalyst provided separately from the plasma generating electrode.

  When a metal catalyst is used as the catalyst as described above, a metal having at least one selected from Cu, Ag, Au, Ni, Pd, Pt, Co, Rh, Ir, Ru, Os and Re as a main component When using what was formed in (3), the removal efficiency of the dioxin in a to-be-processed substance can be improved further. Of these, Cu, Ni, Pd, and Pt can be particularly preferably used. In the present specification, “main component” means a component having the highest weight content.

  In addition, as the plasma generating electrode, the electrode surface is formed of a metal whose main component is one or more selected from Cu, Ag, Au, Ni, Pd, Pt, Co, Rh, Ir, Ru, Os, and Re. By using what is done, the removal efficiency of the dioxin in a to-be-processed substance can be improved further.

  In the method or apparatus of the present invention, it is necessary to supply a plasma medium gas that forms a plasma forming medium around the plasma generating electrode. In this case, the plasma medium gas may be contained in the gas to be processed, or may be supplied separately from the gas to be processed.

  Next, the substance to be treated can be a substance obtained by vaporizing a liquid or solid substance at room temperature. As a result, even if the substance to be purified is liquid or solid at normal temperature, it can be easily removed or reduced by the method or apparatus of the present invention by vaporizing it by heating or the like. Can be purified. On the other hand, when the substance to be treated is gaseous at normal temperature, it can be treated as it is as the gas to be treated.

  The dioxin-containing material to be treated can be, for example, a solution containing dioxin, for example, a dioxin analysis waste liquid. The dioxin analysis waste liquid is obtained by dissolving dioxin in an organic solvent for dissolving / extracting the component to be analyzed. Such dioxin analysis waste liquid becomes a gas to be treated as an application target of the present invention by being vaporized by heating or the like. On the other hand, dioxin-containing exhaust gas generated in chemical synthesis processes such as herbicide production and chemical treatment processes such as pulp bleaching process, and dioxin-containing exhaust gas generated in combustion furnaces or incinerators are also applicable to the present invention. It becomes the target substance to be treated.

The schematic diagram which shows an example of the substance purification apparatus of this invention. The schematic diagram which shows and illustrates some electrode structures. The side surface fragmentary sectional view which shows the specific example of the purification | cleaning unit of the apparatus of FIG. The schematic diagram which estimates and shows the decomposition | disassembly and resynthesis process of dioxin. The schematic diagram which shows the modification of a purification | cleaning unit. The schematic diagram which shows the example which applies the substance purification apparatus of this invention to the process of combustion exhaust gas. The chart which shows the gas chromatography analysis result of the exhaust gas after the process in Experimental example 2. FIG.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 conceptually shows an example of a purification apparatus for a substance to be treated containing dioxins according to the present invention. In this apparatus 50, a plasma P is generated by applying a plasma generating voltage to the plasma generating electrodes 1 and 1 from the high frequency power source 3, and a gaseous target substance G (hereinafter, referred to as dioxin) contained in the plasma P. To be treated gas G). Thereby, the dioxin content in the to-be-processed substance G is reduced by converting the dioxin in the to-be-processed substance G into organic substance other than a dioxin.

  A predetermined gas introduction space 6 is formed around the plasma generating electrodes 1, 1, and a gas to be treated inlet 4 for introducing the gas G to be treated into the gas introduction space 6 and a purified exhaust gas are provided. A gas introduction space forming body 15 provided with an exhaust port 5 for exhausting from the gas introduction space 6 (communicating with the exhaust pipe 14) is disposed to form a purification unit. The gas to be treated G is circulated between the electrodes 1 and 1 in a state where the plasma P is generated between the pair of plasma generating electrodes 1 and 1 facing each other.

  The gas G to be processed is obtained by vaporizing the waste liquid to be processed by the vaporizer 9, and is led to the gas introduction space 6 through the valve 8, the gas supply pipe 7 to be processed and the main pipe 13. The vaporizer 9 has a built-in heater, and evaporates the waste liquid to be treated by heating. The waste liquid to be treated is an organic solvent waste liquid containing dioxin, which is a residual liquid after dioxin analysis here, and the gas introduction space 6 is intermittently vaporized by being divided into, for example, constant supply units.・ Supplied. On the other hand, a plasma medium gas (here, nitrogen) is supplied from the supply source 10 to the gas introduction space 6 through the valve 11 and the main pipe 13. That is, the to-be-treated gas supply pipe 7 serves as a supply pipe for supplying the vaporized substance to be treated into the plasma. The plasma medium gas is supplied to the gas introduction space 6 in a form mixed with the gas G to be processed. In order to prevent the gas to be treated G from condensing and returning to the liquid, the purification unit including the pipes 7, 13, and 14 and the gas introduction space forming body 15 includes a heater such as a band heater wound around the purification unit. Is heated by. In other words, a heater for heating the pipeline that heats the supply pipeline is provided.

  Next, the plasma generating electrode 1 is an electrode surface for generating plasma, here the whole is selected from Cu, Ag, Au, Ni, Pd, Pt, Co, Rh, Ir, Ru, Os and Re. It is formed of a metal having the above as a main component (hereinafter referred to as electrode surface forming metal), here Pt. As shown in FIG. 2 (a), the plasma generating electrode 1 may be formed of a metal mump material as described above, or a substrate surface made of another metal such as Fe or an iron alloy is used as the electrode. You may employ | adopt the structure lined with the layer of the surface formation metal.

  Moreover, the plasma generating electrode 1 can also be comprised as a porous electrode which consists of an electrode surface formation metal, as shown in FIG.2 (b). Such a porous electrode can be formed as a sintered porous member, for example. By doing in this way, the catalyst efficiency in case an electrode surface acts as a catalyst can be improved. In addition, as shown to (c), the structure which formed the porous electrode layer 1b which consists of an electrode surface formation metal in the electrode surface formation part of the base material 1a is employable.

  Returning to FIG. 1, plasma P is generated between the opposing electrode surfaces by igniting the high-frequency voltage on the opposing plasma generating electrodes 1 and 1. And by supplying the to-be-processed gas G between counter electrode surfaces in that state, the dioxin contained in this is converted into the organic substance different from a dioxin, and the dioxin content reduces. The exhaust gas in which the dioxin content is reduced is discharged from the exhaust port 5 through the exhaust pipe 14, and is collected in a trap or the like (not shown).

  FIG. 4 shows the process of decomposing dioxins in an estimated manner. Dioxin is decomposed and excited by being introduced into plasma, and various excited products having a lower molecular weight than dioxin are generated. Then, using the electrode surface forming metal layer constituting the surface layer portion of the plasma generating electrode 1 as a catalyst layer, the excited product is recombined to become a detoxified organic compound different from dioxin and discharged. Of course, the excited product also includes those derived from components other than dioxin, but even if this recombines with the excited product derived from dioxin, it eventually produces organic matter other than dioxin. Become.

  When nitrogen is used as the plasma medium gas, nitrogen radicals are generated when the nitrogen is excited in the plasma P, and the decomposition / removal reaction of dioxins may proceed more efficiently. In FIG. 1, air can be introduced instead of nitrogen as the plasma medium gas (for example, by the main pipe 13 via the valve 12). In this case, in addition to nitrogen radicals, oxygen radicals are similarly generated, which may contribute to the decomposition and removal of dioxins. Also, water vapor can be introduced together with the plasma medium gas. Specifically, there is a method of supplying air containing water vapor through the valve 12 through the main pipe 13. In this case, oxygen molecules containing active components such as ozone and OH radicals are generated by exciting water molecules in the plasma P, which may contribute to the decomposition / removal reaction of dioxins.

  FIG. 3 shows a specific example of the purification unit. The purification unit 41 includes a cylindrical inner cylinder electrode 42 that is a first plasma generation electrode and a cylindrical outer cylinder electrode 43 that is a second plasma generation electrode, which are opposed to each other, and the inner cylinder electrode 42 is an outer cylinder electrode. 43 is fixed substantially coaxially (that is, the electrodes 42 and 43 correspond to the electrodes 1 and 1 in FIG. 1). Both the inner cylinder electrode 42 and the outer cylinder electrode 43 are made of Pt metal. 1 is connected to the inner cylinder electrode 42 and the outer cylinder electrode 43, and a glass tube 44 (in the gas introduction space forming body 15 in FIG. 1) supporting the outer cylinder electrode 43 is connected. At both ends, a gas supply passage 45 to be processed corresponding to the gas inlet 4 to be processed and an exhaust passage 46 corresponding to the exhaust port 5 are formed.

  In the purification unit 41 as described above, when a high frequency high voltage is applied between the inner cylinder electrode 42 and the outer cylinder electrode 43 by the high frequency power source 3, the outer circumferential surface of the inner cylinder electrode 42 and the inner circumferential surface of the outer cylinder electrode 43 ( Plasma P is generated in the glass tube 44 between these and the counter electrode surface. In this state, when a mixed gas of a gas to be processed containing dioxin and nitrogen as a plasma medium gas is supplied from the gas supply passage 45 to be processed, nitrogen becomes plasma P, and decomposition of dioxin introduced therein The reaction will be promoted.

  As shown in FIG. 5, a catalyst made of the same material as the electrode surface forming metal can be provided separately from the plasma generating electrodes 1 and 1. Specifically, the gas to be treated that has passed between the plasma generating electrodes 1 and 1 can promote the conversion reaction of dioxins into harmless organic substances by contacting the catalyst. For example, in the case where the plasma generating electrodes 1 and 1 do not remarkably function as the catalyst, the resynthesis reaction of the excited product generated in the plasma P can be promoted by contact with the catalyst. It becomes like this. In this embodiment, the catalyst is configured as a catalyst packed bed filled with catalyst particles in a form allowing gas flow over the entire cross section of the gas flow conduit.

  In addition, as shown in FIG. 6, the apparatus of the present invention includes a purification unit on, for example, an exhaust pipe of a combustion furnace or a waste incinerator, and includes exhaust gas passing through the exhaust pipe as a gas to be treated. It can also be applied for the purpose of removing substances to be removed such as dioxins.

Experimental example

In order to confirm the effect of the present invention, the following experiment was conducted.
(Experimental example 1)
1, 2,3,4-tetrachlorodibenzo-p-dioxin, which is a kind of dioxin, using the purification unit shown in FIG. 3 (where the opposing distance between the inner cylinder electrode 42 and the outer cylinder electrode 43 is 1 mm). A purification experiment of a solution containing (hereinafter abbreviated as 1234TCDD) was conducted. First, a 1234TCDD toluene solution having a concentration of 100 ng / μl was prepared, and this was divided into 1 μl portions and injected into the purification unit while vaporizing so that 500 times, that is, 50 μg of 1234TCDD as a total amount was processed. In addition, the level of the high frequency applied voltage for plasma generation was adjusted to 10 to 16 kV, and the frequency was adjusted to various values of 1 to 5 kHz.

  The treated exhaust gas was trapped in 500 ml of toluene, the amount of 1234TCDD in the trapped toluene was measured, and the decomposition rate was obtained by dividing by the total amount of 1234TCDD charged. Table 1 shows the results.

  That is, by appropriately applying the level and frequency of the high frequency applied voltage, it is possible to decompose 1234TCDD of 50% or more, in particular, an applied voltage of 12 kV or higher, a frequency of 1 kHz or higher, 90% or higher, and an applied voltage of 14 kV or higher. It can be seen that a decomposition rate close to 100% can be achieved at a frequency of 1 kHz or higher.

(Experimental example 2)
Similar to Experimental Example 1 except that 2,3,7,8-tetrachlorodibenzo-p-dioxin (hereinafter referred to as 2378TCDD) was used as dioxin, and the high frequency applied voltage was fixed at 15 kV and the frequency was fixed at 2 kHz. The experiment was conducted. As a result, it was found that this could be purified with a decomposition rate of 99.1%.

FIG. 7 is a gas chromatographic analysis result of the benzene solution in which the exhaust gas after treatment is trapped. 2378TCDD peak was not observed, and it was found that many organic compounds other than dioxin, such as benzaldehyde, benzonitrile, dibenzyl, etc. were detected instead. All show distinct peaks from dioxin). This indicates that dioxin was decomposed and recombined with the organic compound and removed.

DESCRIPTION OF SYMBOLS 1 Plasma generating electrode 4 To-be-processed gas inlet 5 Outlet 6 Gas introduction space P Plasma G To-be-processed gas 50 Dioxin containing to-be-processed purification apparatus

Claims (10)

Plasma is generated by applying a plasma generating voltage to the plasma generating electrode,
Introducing a gaseous target substance containing dioxin into the plasma,
A dioxin-containing purification method for reducing a dioxin content in the material to be treated by mainly converting the dioxin into an organic substance other than dioxin,
The plasma generating electrode is
A base material made of metal ;
A porous electrode layer made of an electrode surface-forming metal formed on the surface of the substrate ,
A method for purifying a dioxin-containing substance to be treated, wherein the porous electrode layers are arranged to face each other .   The method for purifying a dioxin-containing material to be treated according to claim 1, wherein the porous electrode layer is a metal-based or non-metallic catalyst layer.   The method for purifying a dioxin-containing material to be treated according to claim 1 or 2, wherein the substrate is formed of a metal mainly composed of Fe.   The method for purifying a dioxin-containing substance to be treated according to any one of claims 1 to 3, wherein a plasma medium gas that forms a plasma forming medium is supplied around the plasma generating electrode.   The method for purifying a dioxin-containing substance to be treated according to claim 4, wherein the plasma medium gas is contained in the gaseous substance to be treated.   The substance to be treated is obtained by vaporizing a liquid or solid substance at normal temperature, and the liquid substance to be treated is divided into fixed supply units, and is vaporized and supplied intermittently. The purification method of the dioxin containing to-be-processed substance in any one of Claim 1 thru | or 5.   The dioxin is 1,2,3,4-tetrachlorodibenzo-p-dioxin, and the level of the high frequency applied voltage for generating the plasma is adjusted to 12 to 16 kV and the frequency is adjusted to various values of 1 to 5 kHz. The method for purifying a dioxin-containing substance to be treated according to any one of claims 1 to 6. By generating a plasma by applying a plasma generating voltage to the plasma generating electrode, introducing a gaseous material to be treated containing dioxin in the plasma, and converting the dioxin mainly into organic substances other than dioxin, A device for purifying a dioxin-containing treated substance that reduces the dioxin content in the treated substance,
The plasma generating electrode is
A base material made of metal ;
A porous electrode layer made of an electrode surface-forming metal formed on the surface of the substrate ,
A device for purifying a dioxin-containing substance to be treated, wherein the porous electrode layers are arranged to face each other . The porous electrodes layers, purifier dioxin-containing substance to be treated according to claim 8, characterized in that there is a catalyst layer of metallic or non-metallic. As the substrate, purifier dioxin-containing treated material according to claim 8 or 9, characterized in that what is formed of metal mainly composed of Fe is used.

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