JP2006000558A - Method and apparatus for detoxifying harmful organic substances - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and apparatus for decomposing a harmful organic compound into a harmless compound without discharging any harmful compound into the environment in the course of treatment.
SOLUTION: A harmful organic compound 7 is decomposed and rendered harmless by reacting in a gas phase with a mist 9 or vapor of a molten salt 12 containing an alkali metal hydroxide, carbonate or nitrate. , A vapor-phase detoxification treatment method for harmful organic substances, and a vapor-phase detoxification treatment apparatus for harmful organic substances using the same.
[Selection] Figure 1

Description

  The present invention relates to various harmful organic compounds such as harmful organic halogen compounds such as polychlorodibenzo-p-dioxins and / or polychlorobenzofurans, harmful organic nitrogen compounds, harmful organic sulfur compounds, harmful organic phosphorus compounds, especially incineration. The present invention relates to a gas-phase detoxification treatment method and treatment apparatus for these harmful organic compounds present in exhaust gas, incinerator bottom ash, fly ash, or soil.

Polychlorodibenzo-p-dioxins and polychlorobenzofurans (hereinafter abbreviated as dioxins) are highly toxic compounds that have not been consciously manufactured or used at all, but incineration of waste, etc. As a by-product, it is present in exhaust gas, incineration ash, and fly ash at a high concentration. From there, it has further moved into the soil, and high concentrations of dioxins have been revealed in various soils.
Polychlorinated biphenyls (hereinafter abbreviated as PCB) have been widely used in the past as insulating oils for electrical equipment, heat media, copy paper, etc., but they have strong toxicity (carcinogenicity, mutagenicity, etc.). It became clear that there was persistence and accumulation in organisms, and both production and use were prohibited.

  Hexachlorocyclohexane (hereinafter abbreviated as BHC), 1,1,1-trichloro-2,2-bis (p-chlorophenyl) ethane (hereinafter abbreviated as DDT), aldrin, dieldrin, and chlordane have been used as insecticides and pesticides in the past. Although they were widely used, their production and use were prohibited due to their strong toxicity and accumulation in the human body, as with PCB.

  In addition, various halogenated aliphatic hydrocarbons represented by trichloroethane and tetrachloroethane were previously widely used as cleaning solvents in the semiconductor industry and dry cleaning, but they are still used because of their carcinogenic properties. It was banned.

  Furthermore, chlorofluorocarbons and hydrochlorofluorocarbons (hereinafter abbreviated as chlorofluorocarbons) are widely used as refrigerants, cleaning agents, foaming agents, etc., and bromofluorocarbons (hereinafter abbreviated as halons) are widely used as fire extinguishing agents. It was. However, once they are released into the atmosphere, it becomes clear that they have the effect of destroying the stratospheric ozone layer. However, the types that are still approved for use are required to be promptly replaced with other substances (compounds not containing halogen).

  All of these harmful organic halogen compounds are chemically stable and are not easily decomposed by water, acid, alkali, etc., but they are also thermally stable and difficult to decompose even at considerably high temperatures. There is a nature. Therefore, things that have been used in the past even after production and use are banned remain, and some of them leak into the environment (air, soil, rivers, ocean, groundwater, etc.) and accumulate in them. ing.

  Because of such problems, it is required to decompose and detoxify these harmful organic halogen compounds into organic compounds containing no halogen or inorganic compounds.

  In addition to organic halogen compounds, there are many harmful compounds in organic nitrogen compounds, organic sulfur compounds, and organic phosphorus compounds as well as organic halogen compounds. Examples of harmful organic nitrogen compounds include organic cyan compounds such as nitriles, cyanohydrins and isocyanates, organic nitro compounds such as nitrobenzenes, and organic amino compounds such as benzidine and naphthylamine. Examples of harmful organic sulfur compounds include dimethyl sulfate. Furthermore, the harmful organophosphorus compounds include most of various organophosphorus pesticides including parathion and methylparathion, which are already banned due to their toxicity.

  It is well known that some of these compounds exist in the environment for a long time because they are hardly decomposable, and there is a concern that they may be taken into the human body. Yes. Especially in the case of agricultural chemicals, the level of contamination in soil and water is considerably high because they are not intentionally leaked but consciously sprayed. In addition, there is a high risk of being ingested by humans through agricultural crops, and it is desired to make the treatment harmless immediately.

  The following examples are known as methods for decomposing and detoxifying harmful organic compounds.

  First, as shown in Patent Document 1 or 2, for example, a harmful organic halogen compound is burned at a very high temperature of about 1200 ° C. or more under a sufficient oxygen atmosphere to produce carbon dioxide, water, and halogenation. This method completely decomposes to hydrogen (incineration method).

  When the harmful organic compound is, for example, dioxins, the harmful organic compound itself is often not contained alone but contained in gas or water. Therefore, a method of incinerating the adsorbent after adsorbing it on a combustible adsorbent such as activated carbon and removing it from gas or water is also well known.

  In the second method, for example, as shown in Patent Document 3 or the like, a harmful organic compound is heated to a temperature that is the same as or slightly lower than that of the incineration method described above in an oxygen-free or oxygen-deficient atmosphere. This is a method of performing decomposition. The decomposition product in this case is an inorganic compound such as carbon and hydrogen, or an organic compound (such as methane) having a very simple structure that decomposes even the basic skeleton of the original compound (the benzene ring in the case of dioxins). Become.

  By applying this technology, the dioxins contained in incineration ash and fly ash are heat-treated at about 300-400 ° C in an oxygen-deficient atmosphere, resulting in almost complete decomposition from the ash. (See, for example, Patent Document 4 or 5).

  The third method is a method of converting a halogen atom of a harmful organic compound with a hydrogen atom or the like by a chemical reaction to convert it into a harmless organic compound containing no halogen (chemical decomposition method). Therefore, the following three kinds of specific techniques have been reported. That is, (1) a technique in which high-pressure hydrogen gas is allowed to act in the presence of a catalyst in the absence of a solvent as shown in, for example, Patent Document 6 or 7, and (2) disclosed in, for example, Patent Document 8 or 9. Similarly, a technique of heating to about 100 ° C. without a solvent in a nitrogen gas atmosphere together with a decomposing agent comprising a mixture of an alkali metal or a hydroxide thereof and polyethylene glycol, and (3) disclosed in, for example, Patent Document 10 or 11 As described, this is a technique of irradiating ultraviolet rays, radiation, and the like in a solution of alcohol or the like in the presence of an alkali metal hydroxide at normal temperature and normal pressure.

  The fourth method is, for example, as shown in Patent Document 12, by causing a certain type of microorganism to take in a harmful organic chlorine compound and decompose (metabolize) it in the body, so that the product carbon dioxide, water and It is a method of changing to hydrogen chloride.

  For example, as shown in Patent Document 13, a fifth method uses supercritical water having a temperature of 380 ° C. or more and a pressure of 22 MPa or more to convert harmful organic halogen compounds to carbon dioxide and water (hydrohalic acid). It is a technology that decomposes the

Each of the above methods is a technology for decomposing and detoxifying harmful organic halogen compounds, but most of them are not effective only for harmful organic halogen compounds, and harmful organic nitrogen compounds and harmful organic sulfur compounds. Alternatively, it is a technique that can also be applied when decomposing and detoxifying harmful organic phosphorus compounds and the like.
Japanese Patent Publication No. 01-8242 Japanese Patent Laid-Open No. 02-241586 Japanese Patent Publication No. 02-5100 Japanese Patent Application Laid-Open No.5-168728 Japanese Patent Laid-Open No. 8-141547 JP 49-13155 A JP-A 51-26852 JP 59-131373 A Japanese Unexamined Patent Publication No. 60-114278 Japanese Patent Publication No.52-47459 Japanese Patent Publication No.53-17582 Japanese Unexamined Patent Publication No. 01-68281 JP 09-327678 A

  However, according to the study by the present inventors, it has been found that there is room for improvement in each of the above prior arts as follows.

  First, the incineration method requires a large amount of energy to maintain a very high combustion temperature, and if the temperature drops during the process, highly toxic dioxins may be produced as a by-product. In addition, harmful heavy metals with low boiling points such as mercury, lead, and cadmium may volatilize in a considerable amount and migrate into exhaust gas. Furthermore, since the furnace wall material of the incinerator may be corroded by high-temperature hydrogen halide gas, the furnace wall material is limited.

  The second pyrolysis method also requires a large amount of energy, the risk of dioxin formation, the migration of mercury, lead, cadmium, etc. into the exhaust gas, the corrosion of the furnace wall material of the incinerator by hydrogen halide gas, etc. In this respect, the same improvement as in the incineration method remains. In addition, equipment for secondary combustion of the cracked product gas is required, and the apparatus configuration becomes very large.

  In the case of the report that the dioxins in the ash described above are removed by thermal decomposition, dioxins are re-synthesized when the ash after heat treatment is slowly cooled, so to prevent this, the ash after heat treatment is removed. It is said that it needs to be cooled quickly. From this, it is clear that dioxins in fly ash are not completely decomposed into harmless inorganic compounds. In other words, dioxins are decomposed only to a mixture of various organic compounds with a simpler structure (naturally, some or all of them contain chlorine) by heat treatment. It seems to be insufficient.

  Among harmful organic compounds, especially organic halogen compounds have many extremely toxic substances as represented by PCBs and dioxins, but in the case of such compounds, after decomposition and detoxification treatment Residual amount is required to be ng to pg level. However, in the case of chemical decomposition methods, it is very difficult to decompose to reach such a low residual level.

  In the case of the fourth microbial decomposition method, it is effective when it is present at a relatively low concentration, but is not suitable for processing a high concentration sample or a large amount of sample. Also, even if there are microorganisms suitable for decomposing certain harmful organic compounds, there is no microorganism effective against all kinds of harmful organic compounds, so this method is not general.

  Furthermore, in the case of the fifth supercritical water oxidation method, a large amount of energy is required to bring water into a supercritical state, and there is a danger due to decomposition under ultrahigh pressure. In particular, when the harmful organic compound is a harmful organic halogen compound typified by PCBs or dioxins, the high-temperature and high-pressure aqueous solution containing hydrohalic acid generated by decomposition has a very strong corrosive action. Therefore, the materials that can be used for the apparatus are limited to special and expensive materials having very strong corrosion resistance.

  The present invention has been completed by examining the points to be improved by the prior art as described above, and does not release harmful organic compounds into the environment at all during the treatment process. It is an object of the present invention to provide a method and apparatus for decomposing and detoxifying a harmful organic compound characterized by decomposing to the point of.

  The method of detoxifying a harmful organic substance according to the present invention is characterized in that the harmful organic compound is decomposed by reacting with a molten salt mist or vapor in the gas phase.

  Further, the gas phase detoxification treatment apparatus for harmful organic substances according to the present invention includes a reaction vessel comprising a reaction tower, a heater for heating or keeping the reaction tower, and a treatment comprising a harmful organic compound in the reaction vessel. A treatment gas injection part for injecting a gas; and a molten salt introduction part for introducing a molten salt into the reaction vessel, wherein harmful organic compounds and the molten salt contained in the treatment gas are removed from the reaction vessel. It is characterized by decomposing harmful organic compounds by contacting and reacting in a phase state.

  According to the present invention, harmful organic compounds can be almost completely decomposed and detoxified with relatively little input energy without discharging any harmful substances into the environment during the process. Separation of the product and the salt after treatment is easy, and the reaction product can be easily recovered.

  Embodiments of the present invention will be described below.

  This embodiment relates to a method for decomposing and detoxifying harmful organic compounds. In the present invention, the harmful organic compound means a substance harmful to the human body or the environment. For example, “Law Concerning Chemical Substances Review and Manufacturing Regulations”, “Occupational Safety and Health Act”, “Law for Understanding the Release of Specific Chemical Substances to the Environment and Promoting Improvement of Management”, “ The organic compounds included in the “hazardous chemical substances” defined in the “Law Concerning Protection of the Ozone Layer by Regulations”, “Law Treatment and Cleaning Law”, etc. are the harmful organic compounds in the present invention.

Although such a compound is not specifically limited, For example, the following can be mentioned.
(1) Organic halogen compounds such as dioxins, polyhalogenated biphenyls, halogenated benzenes, halogenated phenols, halogenated toluenes, halogenated aliphatic hydrocarbons,
(2) Organic nitrogen compounds such as organic cyanide compounds, organic nitro compounds, organic amino compounds (3) harmful organic sulfur compounds such as alkyl sulfates (4) harmful organic phosphorus compounds such as parathions.

  In the present embodiment, the above-mentioned harmful organic compound is brought into contact with a molten salt made of mist or vapor in the gas phase to decompose and render it harmless.

The typical molten salt of inorganic salt has a density of about 2 g / cm ³ and a viscosity of about 10 ^-3 Ns / m ² , all in the same order as water at room temperature, and a conductivity of 20-50 S / m, thermal conductivity of about 1 W / m · K, about the same as that of metal, melting point is about 500-1000 ° C, lower than most metals, chemical stability is large compared to molten metal, and chemical change It has properties such that it is difficult to cause oxidization, is almost completely uniform as a whole, and is soluble in many other inorganic salts and metals. Due to such properties, the molten salt may be used as a solvent or heat medium for chemical reaction.

In the present invention, the molten salt also acts as a solvent and a heat medium, but the harmful organic compound in the molten salt is represented by the following formulas (1) to (4) in the presence of an oxidizing agent such as oxygen gas. The chemical reaction shown in Fig. 1 is caused, and it is easily oxidatively decomposed into inorganic compounds such as carbon dioxide, water, hydrogen halide, sulfur dioxide and the like.
C _l H _m X _n + (l + m / 4) O ₂ = lCO ₂ + (m / 2) H ₂ O + nHX (1)
_{C l H m S n + (} l + m / 4 + n) O 2 = lCO 2 + (m / 2) H 2 O + nSO 2 .................. (2)
C _l H _m N _n + (l + m / 4) O ₂ = lCO ₂ + (m / 2) H ₂ O + (n / 2) N ₂ (3)
_{C l H m (PO 4)} n + (l + m / 4) O 2 = lCO 2 + (m / 2-3n / 2) H 2 O + nH 3 PO 4 ......... (4)

The molten salt used in the present embodiment is preferably a hydroxide, carbonate, or nitrate, and these molten salts have the property of dissociating and releasing oxygen ions, so that oxygen gas is not newly supplied. However, the molten salt itself acts as an oxygen supply source and accelerates the decomposition reaction of harmful organic compounds. For example, carbonate liberates oxygen ions as shown in the following formula (5).
^{_{CO 3 2- (l) = CO}} 2 (g) + O 2 - (l) .................. (5)

  When the molten salt is alkaline, acidic inorganic gases such as hydrogen halide gas and sulfur dioxide gas generated by decomposition of harmful organic compounds are neutralized by the molten salt, which is stable and harmless. It is changed into a halogenated alkali salt (for example, sodium chloride) or sodium sulfate, and is retained in an excess alkali molten salt, and is not released into the environment at all. Accordingly, the molten salt to be used is preferably an alkaline inorganic salt having a property capable of forming a harmless neutral inorganic alkali salt by combining with an acidic inorganic gas generated by decomposition of a harmful organic compound. In view of reactivity with hydrogen halide gas and the stability of neutral inorganic alkali salt formed, it is an alkali metal or alkaline earth metal hydroxide or carbonate, or a mixture of both. It is more preferable. Furthermore, in order to keep the operating temperature as low as possible, relatively low melting point hydroxides or carbonates such as sodium hydroxide (melting point 328 ° C.), potassium hydroxide (melting point 360 ° C.), sodium hydroxide-potassium hydroxide Crystalline salt (melting point 218 ° C.), sodium hydroxide-sodium carbonate eutectic salt (melting point 286 ° C.), lithium carbonate-sodium carbonate-potassium carbonate ternary eutectic salt (melting point 397 ° C.) and the like are most preferable. However, if the temperature of the molten salt is too low, the decomposition reaction rate of harmful organic compounds will be slow. Therefore, the temperature of the molten salt is generally in the range of 300 to 600 ° C. From the relationship between the heat input and the decomposition rate, the temperature is 400 to 500 ° C. It is particularly preferable in terms of efficiency.

  In the present invention, these alkali metal hydroxides and carbonates do not necessarily have to be pure, and these salts are combined as a main component with their melting points or hydrogen halide gas generated by decomposition of harmful organic compounds. It does not prevent any other inorganic salt (for example, nitrate, chloride, sulfate) from being mixed in a small amount within a range that does not particularly affect the properties capable of forming the inorganic halide salt.

  As described above, this embodiment is effective for decomposing and detoxifying harmful organic compounds, but its effectiveness is limited to the case where the harmful organic compounds are present alone. It is most suitable for decomposing and detoxifying harmful organic compounds contained in various wastes and environmental samples.

  Specifically, for example, it is a well-known fact that exhaust gas from incinerators, incineration ash, fly ash, etc. contain high concentrations of dioxins. Dioxins contained in incineration ash, fly ash, etc. can be easily decomposed and detoxified.

  Incineration exhaust gas, incineration ash, and fly ash contain various low boiling point hazardous heavy metals (for example, arsenic, lead, cadmium, mercury, etc.) contained in the waste before incineration due to high temperatures when incinerated. It is often volatilized and contained at a high concentration. In the case of the treatment method according to the present invention, all of these heavy metals are dissolved or precipitated in the molten salt and stably held, and are not released into the environment.

  Dioxins released in exhaust gas, incineration ash, fly ash, etc., organic chlorine pesticides such as DDT and BHC used in the past, PCB leaked from storage, storage or use containers , Various organic chlorinated solvents such as trichlorethylene, or chlorofluorocarbons are often accumulated in soil at high concentrations. By applying the present invention to soil contaminated with these harmful organic compounds, it is possible to purify the soil by selectively decomposing and detoxifying the harmful organic compounds that are pollutants.

In the present embodiment, as described above, when harmful organic compounds are contained in wastes such as incineration exhaust gas, groundwater, fly ash, and soil, these wastes are supplied as they are into the molten salt. However, if necessary, it may be fed into the molten salt after some pretreatment is performed so that the decomposition reaction easily occurs. As such pre-processing, for example,
(1) Granulation treatment of incineration ash, fly ash, or soil,
(2) Incineration ash, fly ash, or treatment to heat and gasify harmful organic compounds contained by heating the soil,
(3) A process of extracting and separating only harmful organic compounds contained in gaseous, liquid, or solid waste using an organic solvent,
(4) A treatment for adsorbing harmful organic compounds contained in gaseous or liquid waste to an appropriate adsorbent,
Etc. Note that these pretreatments are not limited to only one type, and two or more types of pretreatment operations can be performed in combination, such as heating gasification and adsorption or solvent extraction and adsorption. Each pre-processing will be briefly described as follows.

  Incinerated ash, fly ash, or soil usually has an apparent density as small as about 0.2 to 0.4, and as such cannot be supplied well into molten salt. Therefore, when pre-granulation treatment is performed on incinerated ash, fly ash, or soil containing a harmful organic compound, the apparent density increases and supply into the molten salt becomes easy. In addition, this granulation pretreatment may be performed not only with waste such as incineration ash, fly ash, or soil, but also with a granulating agent that acts as a binder. As the granulating agent used in this case, it is most preferable to use one kind or two or more kinds selected from inorganic salt components, particularly each inorganic salt component forming a molten salt, but it is never limited to them. Any substance can be used as long as it does not adversely affect the reaction of decomposing and detoxifying harmful organic compounds.

  When solid waste such as incinerated ash, fly ash, or soil containing a toxic organic compound is heated above the boiling point of the toxic organic compound contained therein, the toxic organic compound evaporates. At this time, incinerated ash, fly ash, or oxides of inorganic elements such as potassium, calcium, and silicon, which are main constituents of the soil, remain unchanged without causing evaporation or chemical change. This facilitates the supply to the molten salt. In addition, it is possible to separate and concentrate harmful organic compounds dispersed at a low concentration in waste such as ash.

  When the harmful organic compound is an organic chlorinated solvent or chlorofluorocarbon, its boiling point is 150 ° C. or less (mostly 100 ° C. or less), and a pretreatment temperature of about 100 to 200 ° C. is sufficient. These organic chlorinated solvents and chlorofluorocarbons have a high vapor pressure despite their relatively low boiling point, and if the pre-heating operation is carried out in an inert gas stream such as nitrogen or argon, the temperature is below the boiling point. However, the entire amount can be easily evaporated. In addition, when the harmful organic compound is a relatively high boiling point compound such as PCB or dioxins, it is not always necessary to completely evaporate the harmful organic compound in this heating pretreatment operation. It may be gasified.

  As described above, a method or apparatus for heating ash or the like in an inert gas stream and pyrolyzing dioxins contained therein, as reported in, for example, Patent Document 4 or 5 so far In this case, decomposition and detoxification are insufficient.

  On the other hand, in the case of the present invention, the heat gasification is performed for the purpose of separating harmful organic compounds contained in the waste such as fly ash and supplying them into the molten salt together with the carrier gas. Pre-processing operations can be performed. Therefore, the purpose of this pretreatment for heating is to gasify the organic harmful compounds, and even if the harmful organic compounds are only partially decomposed to the organic compounds containing chlorine, they are simply evaporated without further decomposition. You may just do it. The gasified organic compound is further decomposed and detoxified by treatment with molten salt. Therefore, as compared with the case of the above reported example, the preheating treatment that can be used in the present invention is sufficient with a lower heating temperature and a shorter heating time, and dioxins are not re-synthesized.

  Harmful organic compounds generally have great solubility in various organic solvents. Therefore, various types of waste containing toxic organic compounds (not only solid waste such as incineration ash, fly ash and soil, but also various types of waste water, ground water, river water and other liquid waste, or incineration exhaust gas, etc. Gas wastes) can be separated and concentrated in low-concentration hazardous organic compounds by performing pre-extraction separation treatment using an appropriate organic solvent. .

  As the solvent for extraction, any solvent can be used as long as it is sufficiently soluble in these harmful organic compounds and does not adversely affect the decomposition / detoxification reaction in the molten salt. In particular, when the harmful organic compound is a high boiling point compound such as PCB or dioxins in the soil, a halogenated hydrocarbon organic solvent having a relatively low boiling point, such as trichloroethylene or chlorofluorocarbons, may be used as the extraction solvent. Most preferred. In this case, since the solvent itself used as the solvent is a harmful organic compound, that is, a substance to be decomposed / detoxified, it is not necessary to use a new solvent only for the pre-extraction treatment. Since it is a boiling point, the possibility of remaining in the soil after the extraction operation is low.

  The method of supplying the solution after extracting and separating harmful organic compounds into the molten salt is most commonly the method of supplying the solution as it is. However, depending on the case, a method of supplying only the harmful organic compound remaining after evaporating and removing the solvent, or a method of heating the solution and gasifying and supplying the solvent and the harmful organic compound together can be used.

  Furthermore, when the waste to be decomposed / detoxified is in liquid or gaseous form, it is possible to separate harmful organic compounds contained in the low concentration by pre-adsorption treatment. It can be concentrated. As the adsorbent, any adsorbent is used as long as it has a sufficiently large adsorption capacity for these harmful organic compounds and does not adversely affect the decomposition / detoxification reaction of the harmful organic compounds in the molten salt. be able to. However, the adsorbent is preferably a substance that is easily decomposed together with harmful organic compounds in the molten salt.

  As described above, activated carbon acts on organic chlorinated solvents (both liquid and vapor) such as dioxins contained in incinerator exhaust gas or trichrene contained in groundwater and air. Then, it is a well-known fact that dioxins can be efficiently adsorbed and removed from them, and many application examples have already been reported.

  Since activated carbon is carbon, it is obvious that it is easily oxidized to carbon dioxide in a molten salt under an oxidizing atmosphere. Based on the facts described above, adsorbents used for pretreatment for the adsorption of harmful organic compounds contained at low concentrations in various solid or liquid wastes such as incinerator exhaust gas and groundwater Is most preferably activated carbon. However, in the present invention, this adsorbent is not limited to activated carbon.

  Activated carbon that adsorbs harmful organic compounds such as dioxins and organic chlorinated solvents is generally incinerated. In this case, dioxins are re-synthesized in the exhaust gas system as described above. It is not a proper processing method.

  On the other hand, in the case of the present invention, harmful organic compounds (eg, dioxins) adsorbed on the activated carbon are completely decomposed into carbon dioxide, water, and hydrogen chloride in the molten salt, and hydrogen chloride is a solvent. It reacts with certain alkaline molten salts to form alkali chloride and is stabilized.

  In addition, it is more effective when this pretreatment for adsorption of harmful organic compounds is used alone or in combination with another pretreatment method. Specifically, for example, a method in which a harmful organic compound is first gasified by heating and separated and concentrated, then the gasified harmful organic compound is adsorbed on activated carbon and the activated carbon is supplied into the molten salt. Alternatively, the toxic organic compound is first extracted and separated and concentrated, and then the toxic organic compound is adsorbed on the adsorbent such as activated carbon directly or after the solution is heated and gasified. And the like, and the like.

  Furthermore, when decomposing and detoxifying a harmful organic compound in a molten salt according to the present invention, it is not always necessary to adopt a method of supplying a harmful organic compound or the like into the molten salt as described above. It may be a system in which the salt is supplied to contact around the harmful organic compound or the harmful organic compound, or a system in which the molten salt is further heated to evaporate or vaporize and contact with the harmful organic compound or the like. . In the case of contact with molten salt vapor, decomposition / detoxification reaction is a gas phase-gas phase reaction if the harmful organic compound or the like is originally in a gaseous state or is in a gaseous state in the pretreatment by heating gasification. It is most preferable because it proceeds with However, the present invention is not limited to this, and the harmful organic compound may be liquid or solid.

  By the way, as described above, in the present invention, a part of the alkaline molten salt is combined with carbon dioxide, hydrogen halide, sulfur dioxide, phosphoric acid and the like produced by oxidative decomposition of the harmful organic compound, and carbonate ( Only when hydroxide is used as the molten salt), halides, sulfates, and phosphates. When the concentration of these reaction product salts is increased, precipitation may occur, the melting point may increase, the decomposition of the decomposition-generated acid gas, the decomposition rate, etc. may occur. Therefore, it can be reused by extracting the used salts and regenerating them into alkaline salts such as the original hydroxides and carbonates.

As a method for regenerating the salt, any existing technique such as a molten salt electrolysis method using β-alumina as a partition wall or ion exchange after forming an aqueous solution can be used alone or in combination. If a loss occurs due to the salt regeneration process and the amount of salt required for the decomposition process is insufficient, a new salt can be supplemented separately.
Or it can also refine | purify as an original salt by isolate | separating and removing only the reaction product salt which is an impurity, without regenerating | regenerating the salt after use. As this purification method, for example, fractional crystallization can be applied based on the difference in solubility of each salt in water. Of course, a solvent other than water may be used as the crystallization solvent, and a purification method other than the fractional crystallization method may be used. Even when the salt is merely purified, a new salt can be supplemented separately as necessary.

The present invention also relates to an apparatus for treating harmful organic compounds using the method for treating harmful organic compounds described above. The gas phase detoxification treatment apparatus for harmful organic substances according to the present invention,
A reaction vessel comprising a reaction tower, a heater for heating or keeping the reaction tower, a treatment gas injection part for injecting a treatment gas containing a harmful organic compound into the reaction vessel, and an alkali metal in the reaction vessel A molten salt introduction section for introducing a molten salt containing a hydroxide, carbonate or nitrate of the above, and in the reaction vessel, the harmful organic compound contained in the processing gas and the molten salt are vapor-phased. It is characterized by decomposing and detoxifying harmful organic compounds by contacting and reacting in a state.

  The treatment gas containing the hazardous organic compound to be treated is gasified by the pretreatment as described above in addition to the gas containing the harmful organic compound, for example, incineration exhaust gas, and the like, or the waste containing the organic compound or the organic compound. It may be made.

  The molten salt introduction part may be any one as long as it can introduce molten salt mist or vapor into the reaction vessel. Here, the apparatus for misting or vaporizing the molten salt, for example, the molten salt mist generating apparatus may be inside or outside the reaction vessel. For example, as shown in FIG. 1, a molten salt bath is disposed at the bottom of the reaction vessel, a bubbling nozzle is inserted into the molten salt, and a gas, preferably an inert gas such as nitrogen gas, is blown, Mist can be generated. Further, a mist generating device equipped with a molten salt bath and a bubbling nozzle can be arranged outside the reaction vessel, and the generated mist can be introduced into the reaction vessel through a mist injection tube (FIG. 2). Further, it is possible to generate molten salt vapor by heating the molten salt to the boiling point without using a bubbling nozzle. Thus, when the apparatus which produces | generates mist is outside reaction container, a collection | recovery container can be provided in the lower part of reaction container. Of the reaction products produced by the reaction of the toxic organic compound and the molten salt, the solid component often settles, and the solid component is deposited in the recovery container.

  Usually, the reaction vessel is provided with an exhaust gas outlet pipe. The exhaust gas outlet pipe contains a harmless gas, for example, carbon dioxide, water vapor, or the like generated as a result of a reaction between a harmful organic compound and a molten salt. This exhaust gas can be discharged into the environment after removing a gas such as carbon dioxide or removing a finely divided solid as required. The gas discharged from the exhaust gas outlet pipe can also be used when generating a mist of molten salt. That is, moisture is removed from the gas discharged from the exhaust gas outlet pipe by a moisture removing device, and the gas after moisture removal is sent to the bubbling nozzle using a gas circulation pump or the like to generate mist ( FIG. 3). By setting it as such a mode, the gas discharged | emitted in an environment can be reduced. Furthermore, it is also possible to construct a substantially exhaustless closed system by supplementing consumed oxygen or the like with another means.

  In another embodiment, the liquid molten salt and the processing gas can be mixed using a two-fluid nozzle, and the mixture can be introduced into the reaction vessel as mist or vapor (FIG. 4). At this time, another gas, for example, an inert gas such as nitrogen can be mixed with the processing gas. A gas containing a molten salt in a mist or vapor state can also be used.

  In yet another embodiment, the molten salt introduction part can be arranged to spray molten salt mist or vapor at the top of the reaction vessel, while the processing gas injection part can be arranged at the bottom of the reaction vessel (FIG. 6). By adopting such a configuration, the mist or vapor of molten salt is sprayed from above into the reaction vessel, and the gas containing harmful organic compounds is supplied from the bottom, so that the reaction is promoted at the position where both are mixed. Near the reaction tower.

  The reaction tower promotes the reaction between the harmful organic compound pretreated as necessary and the molten salt mist or vapor. The shape of the reaction tower can be arbitrarily selected from those commonly used for gas reactions. In order to proceed the reaction more advantageously, fins may be provided in the reaction column. This reaction tower is heated or kept at a temperature at which the above reaction proceeds by a heater arranged outside or inside the reaction vessel. The temperature at which the reaction tower is maintained varies depending on the molten salt used and the harmful organic compound to be treated, but is generally in the range of 300 to 600 ° C. From the relationship between the heat input and the decomposition rate, the temperature is 400 to 500 ° C. It is particularly preferable in terms of efficiency.

  The method for detoxifying a harmful organic substance according to the present invention and a treatment apparatus using the same will be described as follows. These examples are for explaining the present invention, and the present invention is not limited to these examples.

  FIG. 1 shows one embodiment of a processing apparatus for harmful organic compounds according to the present invention.

  The reaction vessel 1 includes a molten salt bath for holding a molten salt 12, a reaction tower 5, a heater 4 for heating the reaction tower, a processing gas injection pipe 6, a nitrogen gas injection pipe 8, a bubbling nozzle 10, an exhaust gas outlet pipe 2, A mist trap 3 is provided. Nitrogen gas 11 is injected into molten salt 12 such as sodium hydroxide through nitrogen gas injection pipe 8 and bubbling nozzle 10, and mist 9 is generated when the generated bubbles 11 a burst. On the other hand, a processing gas 7 containing a harmful organic compound is introduced into the reaction vessel 1 through the processing gas injection pipe 6. These molten salt 12 and the harmful organic compound are mixed in the gas phase 1a and reacted in the reaction tower 5 heated to 500 to 600 ° C. in consideration of, for example, the decomposition rate at the upper part of the reaction vessel 1 to decompose the harmful organic compound.・ Detoxified. The exhaust gas 30 is discharged from the exhaust gas outlet pipe 2.

  In this embodiment, the heating is performed at 500 to 600 ° C. in consideration of the decomposition rate. However, when the heat input is taken into consideration, the heating can be performed more efficiently when the temperature is controlled at 400 to 500 ° C.

  FIG. 2 shows one embodiment of a processing apparatus for harmful organic compounds. In this example, the mist generator 14 is provided outside the reaction vessel, and the mist 9 of the molten salt 12 is introduced into the reaction vessel 1 through the mist injection tube 15. A recovery container 16 is provided in the lower part of the reaction container 1, and solid components of the reaction product 13 generated in the reaction container 1 are recovered in the recovery container 16. Further, the exhaust gas is discharged from the exhaust gas outlet pipe 2.

  FIG. 3 shows one embodiment of a processing apparatus for harmful organic compounds. In this example, the moisture removing device 17 and the gas circulation pump 18 are connected to the exhaust gas outlet pipe 2, and the gas 31 generated in the reaction vessel 1 is used for generating the mist 9 in the mist generating device 14. In this case, since the exhaust gas is again introduced into the mist generator 14, no exhaust can be achieved, and a closed system can be configured.

  FIG. 4 shows one embodiment of a processing apparatus for harmful organic compounds. In this example, the molten salt 12 and the mixed gas 32 of the processing gas 7 and the nitrogen gas 11 are mixed in the two-fluid nozzle 19, and the mixed gas containing the harmful organic compound 7 and the mist 9 of the molten salt 12 is added to the reaction vessel 1. Supply. Although two two-fluid nozzles 19 are shown in FIG. 3, the number of the two-fluid nozzles 19 may be one or three or more because of the capacity of the reaction vessel 1 and the nature of the fluid flow inside.

  FIG. 5 shows one embodiment of a processing apparatus for harmful organic compounds. In this example, the heater for heating the reaction tower 5 is an interpolated heater 22 to improve the heating efficiency. The reaction tower 5 is provided with fins 23 for improving the reaction efficiency.

  FIG. 6 shows one embodiment of a processing apparatus for harmful organic compounds. In this example, the molten salt storage tank 25 holding the molten salt 12 in a molten state is supplied to the molten salt injection pipe 26 by the salt transport pump 24. The molten salt 12 is sprayed from a salt spray nozzle 27 provided at the upper part in the reaction vessel 1. The sprayed molten salt 12 is mixed with the processing gas 7 injected from the lower part of the reaction vessel 1 and reacts in the reaction tower 5.

The conceptual diagram which shows the harmful organic substance detoxification processing apparatus by this invention. The conceptual diagram which shows the harmful organic substance detoxification processing apparatus by this invention. The conceptual diagram which shows the harmful organic substance detoxification processing apparatus by this invention. The conceptual diagram which shows the harmful organic substance detoxification processing apparatus by this invention. The conceptual diagram which shows the harmful organic substance detoxification processing apparatus by this invention. The conceptual diagram which shows the harmful organic substance detoxification processing apparatus by this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Reaction container 2 Exhaust gas outlet piping 3 Mist trap 4 Heater 5 Reaction tower 6 Processing gas injection pipe 7 Processing gas 8 Nitrogen gas injection pipe 9 Mist 10 Bubbling nozzle 11 Nitrogen gas 12 Molten salt 13 Reaction product 14 Mist generator 15 Mist injection pipe 16 Recovery container 17 Cooler 18 Gas circulation pump 19 Two-fluid nozzle 22 Interpolated heater 23 Fin 24 Salt transport pump 25 Molten salt storage tank 26 Molten salt injection pipe 27 Molten salt spray nozzle 30 Exhaust gas 31 Gas 32 Mixed gas

Claims (13)

  A method of detoxifying a harmful organic compound by reacting the harmful organic compound with a molten salt mist or vapor in a gas phase to decompose the compound.   The method for detoxifying a harmful organic substance in a gas phase according to claim 1, wherein the harmful organic compound is selected from the group consisting of an organic halogen compound, an organic nitrogen compound, an organic sulfur compound, and an organic phosphorus compound. .   3. The method for detoxifying a harmful organic substance in a gas phase according to claim 1 or 2, wherein the molten salt comprises an alkali metal hydroxide, carbonate or nitrate.   4. The method for detoxifying a harmful organic substance according to any one of claims 1 to 3, wherein the molten salt contains an alkali metal hydroxide.   A processing gas containing the harmful organic compound and a molten salt mist or vapor are injected into a reaction vessel having a reaction tower, and the harmful organic compound is decomposed in a gas phase portion in the reaction tower. The vapor-phase detoxification method for harmful organic substances according to any one of claims 1 to 4, wherein   A reaction vessel comprising a reaction tower, a heater for heating or maintaining the reaction tower, a treatment gas injection part for injecting a treatment gas containing a harmful organic compound into the reaction vessel, and the reaction vessel A molten salt introduction part for introducing a molten salt into the reaction vessel, bringing the harmful organic compound contained in the processing gas into contact with the molten salt in a gas phase and reacting them in the reaction vessel, A gas phase detoxification treatment apparatus for harmful organic substances characterized by decomposing harmful organic compounds.   The molten salt introduction part is composed of a molten salt bath provided in the lower part of the reaction vessel and a bubbling nozzle provided in the molten salt, and is melted by injecting gas from the bubbling nozzle into the molten salt in a molten state. 7. The apparatus for detoxifying a harmful organic substance in a gas phase according to claim 6, wherein a salt mist is generated.   The molten salt introduction part comprises a molten salt bath provided outside the reaction vessel, a bubbling nozzle provided in the molten salt, and a mist introduction tube for introducing mist into the reaction vessel. The molten salt mist is generated by injecting gas into the molten salt in the molten state, and the generated mist is introduced into the reaction vessel through the mist introduction tube, and the reaction product is recovered in the lower part of the reaction vessel. An apparatus for detoxifying a harmful organic substance in a gas phase according to claim 6, wherein a recovery container is provided.   The exhaust gas outlet pipe is further provided in the upper part of the reaction vessel, and the exhaust gas outlet pipe is coupled to the bubbling nozzle through a moisture removing device and a gas circulation pump. Gas-phase detoxification equipment for harmful organic substances.   The molten salt introduction unit and the processing gas injection unit are connected to a two-fluid nozzle, and the molten salt and the processing gas are mixed and introduced into the reaction vessel in the two-fluid nozzle. The gas-phase detoxification treatment apparatus for harmful organic substances according to claim 6.   The molten salt introduction section sprays molten salt mist or vapor, and is disposed in the upper part of the reaction container, and the processing gas injection part is disposed in the lower part of the reaction container. The gas-phase detoxification treatment apparatus for harmful organic substances according to claim 6.   The harmful organic substance vapor phase detoxification treatment apparatus according to any one of claims 6 to 11, wherein the heater is an interpolated heater inserted into the reaction tower.   The apparatus for vapor phase detoxification of harmful organic substances according to any one of claims 6 to 12, wherein the reaction tower further comprises fins.

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