JP2006281148A - Dioxin contaminant treating method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of safely and inexpensively treating dioxin contaminants at site in a normal temperature and a normal pressure. <P>SOLUTION: In this dioxin contaminant treating method, in an original position where dioxin contaminants generate, a decomposing agent mainly consisting of inorganic powder having dioxin decomposing property is added to the contaminants at a normal temperature to reduce dioxin concentration to less than 3 ng-TEQ/g. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for treating dioxin contaminants, and more particularly, to a method for treating the dioxin contaminants in a simple and inexpensive manner at the position where the dioxin contaminants are generated.

  Dioxins generically named polychlorinated dibenzopararadioxin (PCDD), polychlorinated dibenzofuran (PCDF), coplanar polychlorinated biphenyl (coplanar PCB) are mainly incinerators, waste heat utilization equipment, exhaust gas for general waste and industrial waste It is an organochlorine substance that is unintentionally generated from equipment such as processing equipment. In addition to the equipment, it may be accumulated in facilities and soil contaminated with dioxins due to accidents, and incinerated landfills. If these dioxins are contained in soil, incineration ash, fly ash, etc., even in a trace amount of several hundred pg-TEQ / g to 1 ng-TEQ / g, there is a possibility of affecting the human body and the environment. high. The reason is that dioxins are fat-soluble and chemically stable, and when they are released into the environment such as air, soil, and rivers, they are concentrated in the organism through the food chain.

In recent years, pollution caused by dioxins discharged from waste incineration facilities has become a major problem nationwide. Rehabilitation of dioxin generation facilities, removal of dioxins accumulated in the facilities, and restoration of soil contaminated with dioxins Has been done. When emissions standards dioxins than incineration capacity 4t, there also reinforced with 0.1ng-TEQ / m ³ or less, many incinerators becomes operation stop is dismantled.

  A large amount of industrial waste is generated at the time of dismantling and removal of the incinerator, but waste containing dioxins of 1 ng-TEQ / g or more is subject to disposal as industrial waste. In particular, high-concentration contaminants of 3 ng-TEQ / g or more must be designated as specially controlled industrial waste and must be strictly controlled or treated at specific facilities. The processing cost of this special management waste is very expensive.

Rather than storing dioxin pollutants as specially managed industrial waste, techniques for detoxifying them are being actively proposed. Listed below are typical detoxification methods.
(1) Melt-solidification method Melt-solidification method is a method in which waste such as incineration ash is exposed to high-temperature conditions of about 1200 ℃ or higher to burn harmful organic substances, melt inorganic substances, and cool the products. This is a technology for making glassy solidified products and molten slag. This is an extremely effective method for preventing the elution of heavy metals and for the decomposition and reduction of dioxins.
(2) Kiln incineration method The kiln incineration method is a direct or indirect heating method using a reaction tank, in which dioxin contaminants are heated in a reducing atmosphere of 500-600 ° C in a container and dechlorinated to make them harmless. Is the method.
(3) Low-temperature reductive decomposition method Dioxins contaminated by dehydration are dried and heated to about 350 ° C to decompose dioxins. At this time, the decomposition rate is increased by making the inside of the reaction vessel a reducing atmosphere and adding a catalyst or the like. In this method, it is possible to almost completely decompose dioxins.
(4) Hot metal extraction method This method repeats the process of mixing and separating the contaminant and the extractant, and in the final stage, it is extracted with a pure extractant.
(5) Iron powder mixed decomposition method This method uses highly reactive powders such as iron powder to purify dioxin contaminants.

  The methods (1) to (3) for thermally decomposing contaminants require equipment for heating and exhaust, and the equipment and management costs are extremely high. If the pollutant has a high water content, it cannot be decomposed unless it is once dried. The chemical treatment (4) is costly in chemicals and generates secondary contaminants. The method using iron powder of (5) is difficult to handle such as iron powder, and there is a risk of dust explosion. Therefore, considerable safety equipment and caution are required when working on site.

  In any of the above methods, it is difficult to provide heat treatment or chemical treatment facilities at individual sites where contaminants are generated from the viewpoint of facility costs and securing land. On the other hand, due to concerns about the environmental impact of the discharge destination and the intermediate processing plant, it is strongly required to treat dioxins pollutants, particularly high-concentration pollutants, in-situ.

In response to these demands, several methods have been proposed for detoxifying dioxin pollutants under the conditions as close to normal pressure and room temperature as possible.
JP 2001-293103 A JP 2001-310163 A JP2003-300037 JP 2004-313912 A

  The object of the present invention is directed to a method for treating dioxins pollutants in the field under normal environmental conditions, as well as the invention described in the above-mentioned patent publication. The purpose is to provide a safe, inexpensive and highly practical method.

  As a result of intensive studies on the above problems, the present inventors have found that the following problems can be solved. That is, in the present invention, a dioxin concentration is 3 ng-TEQ / g or less by adding a decomposing agent mainly composed of dioxin-decomposable inorganic powder at normal temperature to the contaminant at the original position where the dioxin contaminant is generated. This is a method for treating dioxin contaminants.

  The inorganic powder is preferably an alkaline earth metal or a compound thereof, more preferably magnesium or a compound thereof.

  It is desirable to contain at least one decomposition aid of iron salt, zeolite, platinum, and titanium oxide together with the decomposition agent.

  The treatment method of the present invention is performed in a wet manner without removing moisture. Further, by adding water or a moisture adjusting agent together with the decomposing agent, it is possible to efficiently perform the treatment under the most suitable moisture.

  In the treatment method of the present invention, the reduced dioxin contaminants are transported to a management-type disposal site outside the site, or the reduced and harmless ones are buried in-situ. Build a safe, inexpensive and highly practical treatment method.

The treatment method of the present invention purifies dioxins contaminants in-situ (also referred to as on-site) to a relatively mild level in a wet manner. This feature has the following effects.
(1) The method of the present invention that treats high-concentration dioxins at the site where the high-concentration dioxins are generated significantly reduces the risk of dissipating the high-concentration dioxins out of the system.
(2) The wet treatment method of the present invention covers a wide range from pollutants with a high water content such as drainage, sludge, sludge, and slurry to soil with a low water content. Moreover, even a dried product can be applied to the method of the present invention by adding moisture. It can also be used for complex contamination such as oils, volatile organic compounds (VOC), heavy metals. The treatment method of the present invention is particularly suitable for the treatment of high moisture content dioxin contaminants such as sludge and sediment.
(3) The treatment method of the present invention can be carried out with a simple apparatus and does not require a large-scale apparatus like conventional heat treatment equipment. Also, it is not necessary to consume a great deal of energy used for conventional drying and heating. Therefore, this method is very advantageous in terms of both equipment cost and operation cost.
(4) Since the treatment method of the present invention does not require activated carbon or resin generally used in chemical treatment methods, it does not produce secondary contaminants. Since the pH of the reaction is in the neutral range, neutralization is not necessary after wet processing.
(5) The final product obtained by the method of the present invention has a diokine concentration of 3 ng-TEQ / g or less and can be easily disposed of. That is, even if it is stored in a management-type disposal site, its management cost is lower than that in the case of high-concentration contaminants. Therefore, the processing method of the present invention is advantageous in comprehensive evaluation including the management cost of the final processed product.

  First, dioxins contaminants to be treated by the treatment method of the present invention and chemicals used in the treatment method will be described. Dioxins contaminants to be treated by the treatment method of the present invention are not particularly limited as long as they contain or adhere to dioxins. Specifically, incineration ash and fly ash collected in the incinerator demolition work, contaminated soil generated by renewal work such as factory sites, managed disposal sites, and sludge containing diosins with high water content generated by these works And dioxin-containing sludge collected in the bottom sediment purification work such as drainage, rivers and harbors. The treatment method of the present invention is advantageous over the prior art involving a drying step in that a high water content diosin-contaminated sludge is treated as it is by a wet process.

  The dioxin decomposing agent for use in the treatment method of the present invention is not particularly limited as long as it is made of an inorganic powder that is dioxin decomposable at room temperature. A typical inorganic powder is an alkaline earth metal or a compound thereof.

  Examples of alkaline earth metals are magnesium, calcium, etc., and specific examples of alkaline earth metal compounds include magnesium compounds such as magnesium oxide, magnesium hydroxide, magnesium carbonate, magnesium sulfate; calcium oxide, calcium hydroxide Calcium compounds such as calcium carbonate and calcium sulfate; complex metal compounds such as calcium carbonate / magnesium carbonate and calcium oxide / magnesium oxide.

  The inorganic powder is in the form of powder or particles. The particle size is usually 1-1000 μm, preferably 1-30 μm, more preferably 3.5-10 mm. If the particle size of the inorganic powder is too large, the decomposition (redox) reaction of dioxins cannot be performed advantageously in terms of contact rate, reaction rate, reaction time, etc. Conversely, if it is too small, This is disadvantageous in that it tends to be non-uniform because the reaction of

  As the inorganic powder, it is also possible to use a carrier such as zeolite or activated carbon or a carrier supported on a dispersion medium.

  The amount of the inorganic powder added to the dioxins contaminant can vary depending on the concentration of the dioxins. Typically, the inorganic powder is 1 to 200 g, preferably 1 to 100 g, especially 1000 g of the contaminant. Preferably it is 5-20g.

  In the treatment method of the present invention, at least one of iron salts such as ferrous sulfate, iron sulfide, ferrous chloride, and iron oxide, zeolite, platinum, and titanium oxide can be added as a decomposition aid. Although the usage-amount of a decomposition aid may change with chemical compositions, generally it is 1-100g with respect to 100g of usage-amounts of a decomposition agent, Preferably it is 1-20g, More preferably, it is 3-5g.

  Dioxins pollutants generated in the field are various, including dried products, moderately water-containing products, and high water-containing products. The method of the present invention can accommodate all forms of dioxin contaminants through the use of water or moisture modifiers. Water may be added to the dried contaminants. Addition means include spraying, pouring, and spraying.

  On the other hand, the moisture content of the high moisture content contaminants is moderately maintained by the water absorbing moisture adjusting agent. Water-absorbing moisture regulators include starch-acrylic acid copolymer cross-linked products, starch-acrylonitrile copolymer hydrolysates, cross-linked polyacrylic acid salts, saponified copolymers of vinyl esters and unsaturated carboxylic acids. , Isobutylene-maleic anhydride copolymer crosslinked product, crosslinked carboxymethylcellulose derivative, acrylic acid-acrylamide copolymer crosslinked product, partial hydrolysis product of acrylamide copolymer, sulfonated polystyrene, polyvinyl alcohols, polyethylene oxides, polyvinyl Water-absorbing resins (gels) such as pyrrolidones, acrylic acid / sodium acrylate polymers; dry silica sand, zeolite, calcium carbonate, and gypsum. Of these, gypsum is preferable in that it has high reactivity and raises the temperature by reaction heat.

  The water | moisture content of the dioxin contaminant after adding a water | moisture-content regulator is 0-100% normally, Preferably it is 20-75%, More preferably, it manages to 30-55%. By adjusting the moisture within this range, the reactivity between dioxins and inorganic powder can be maximized.

  A surfactant may be appropriately added to the treatment method of the present invention. Examples of surfactants include polyoxyethylene alkyl ether carboxylates, polyoxyethylene alkyl phenyl ether sulfates, polyoxyethylene alkyl ether sulfates, apolyoxyethylene alkyl ether phosphates, polyoxyethylene alkyl phenyl ether phosphates Anionic surfactants such as salts, alkyl sulfonates, alkyl benzene sulfonates, alkyl phosphates, higher alcohol sulfates; cations such as aliphatic quaternary ammonium salts, aliphatic amine salts, pyridinium salts Surfactants: polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene polyoxypropylene alkyl ether, polyoxyethylene sorbitan fatty acid ester, polyethylene glycol Fatty acid esters, nonionic surfactants such as sucrose fatty acid ester; carboxy betaine, aminocarboxylate, and ampholytic surfactants such as lecithin.

  These surfactants have a function of controlling the decomposition rate of dioxins. That is, the surfactant improves the retention of dioxin contaminants, particularly air in the sludge, and if the reaction rate between the dioxin contaminants and the decomposition agent is too high, a film is formed between the two. If the reaction rate is too low, it will help to improve the affinity between the dioxin contaminants and the decomposing agent to speed up the reaction.

  In the purification method of the present invention, in addition to the above-described decomposing agent, decomposing aid, moisture adjusting agent, and surfactant, other auxiliary agents may be used as long as they do not impair the object of the invention. Examples thereof are cement, chelating agent, pH adjuster (sodium hydroxide, sulfuric acid, etc.).

  Although the mechanism of decomposition of dioxins is considered as follows, it does not limit the present invention. That is, when a decomposition agent such as magnesium oxide is added to a high water content dioxin contaminant, the magnesium hydroxide produced by the reaction between magnesium oxide and moisture first reduces 2,3,7,8-tetrachlorodioxin. And 3,4-dichlorophenol dioxin is produced. Next, the phenolic hydroxyl group of 3,4-dichlorophenol dioxin reacts with magnesium to form a salt, which turns into a harmless and insoluble 3,4-dichlorophenol dioxin magnesium salt.

で表現することができる。 The above reaction system includes the following redox reaction:

Can be expressed as

  In the treatment method of the present invention, it is preferable to supply oxygen to the redox reaction system in order to promote the redox reaction. The oxygen may be air or oxygen enriched air. The concentration of oxygen in the oxygen-enriched air is preferably 21.1% to 30% or more, particularly preferably 21 to 25%. Oxygen is usually supplied through a vent pipe or the like.

  In the treatment method of the present invention, the oxidation-reduction reaction is performed at room temperature, but heating at about 30 to 70 ° C. is also included in the present invention.

  In the treatment method of the present invention, in order to reduce the dioxin concentration to a simple treatment level (3 ng-TEQ / g or less), a reaction time of 24 hours or more is usually required after adding the decomposition agent. The treatment method of the present invention reduces the contamination concentration of dioxin contaminants to 3 ng-TEQ / g or less that can be safely transported out of the system at the original position, and transports the transported low-concentration contaminants in a simple storage facility or the like. By storing, a comprehensive, simple, safe and inexpensive processing method is constructed.

  Next, the aspect of the purification method of the present invention will be described with reference to the accompanying drawings. FIG. 1 schematically shows a method for treating dioxin contaminants in an incinerator and its flue. Dioxins are often unevenly distributed near the inner wall of the incinerator and the surface layer of the flue, and this aspect is a method of adding the decomposition agent in situ to the surface layer portion having a high dioxin concentration. Addition methods include spraying, spraying, pouring and coating.

  Next, the surface layer portion containing (or detoxified) the low-concentration contaminants is washed with high-pressure water or mechanically removed with high-pressure air or the like. Preferably, the surface layer portion that has been contaminated is further removed to a depth of about 10 mm. The collected low-concentration contaminants may be collected in one place and then transported to a simple storage area.

  Next, another embodiment of the purification method of the present invention will be described. In this aspect, it is a method of batch processing dioxin pollutants contained in contaminated soil of factory ruins, sediments contaminated with dioxins in rivers and harbors, specially controlled industrial waste stored at disposal sites, etc. . In FIG. 2, the schematic of the reaction tank used for another embodiment of this invention is shown.

  The reaction container 1 in FIG. 2 is for purifying dioxin contaminants (soil and sludge) excavated in the field, and may have any shape and size (in FIG. 2, a drum can). The reaction vessel 1 is made of, for example, iron, stainless steel, glass fiber reinforced plastic, or the like. Steel is better when the pressure inside the reaction vessel is increased or reduced.

  The reaction vessel 1 is provided with a stirring means 2 in order to increase the contact frequency between the dioxins and the decomposition agent. The stirring means 2 is usually a paddle, a biaxial kneader, a disc turbine blade, a mixer, a homogenizer, or the like.

  Reference numeral 3 denotes a dioxin contaminant supply means 2 to the reaction vessel. In FIG. 2, a belt conveyor is used, but a bucket conveyor, an excavator, or the like may be used.

  The finer the contaminants to be treated, the better the reaction efficiency. As the pulverizing means (not shown), stirring, crushing, ball mill and the like are arbitrarily selected. Furthermore, in order to prevent intrusion of gravel, pebbles and other foreign substances into the reaction vessel 1, a filter means 4 such as a sieve (10 to 20 mm) or a lattice net shown in FIG. 2 is suitably attached to the supply means. .

  The decomposition agent supply means 5 for adding the decomposition agent to the reaction vessel 1 is not particularly limited and is usually a pump or a sprayer. In the case of a plurality of decomposing agents, they may be added separately or may be mixed and added in an appropriate combination.

  In the same manner as in the above embodiment, it is preferable to appropriately supply oxygen to the dioxin decomposition reaction field in order to promote the oxidation-reduction reaction in the reaction system. In FIG. 2, the stirring means 2 also serves as oxygen supply means. The oxygen enrichment concentration in the reaction system is the same as in the above embodiment.

  Even in this embodiment, the reaction is carried out at room temperature, but also includes heating to about 30 to 70 ° C. In addition, the reaction proceeds under normal environmental conditions at normal pressure, but it can also be carried out at a pressure of 0.5 to 3 atm.

  The time for which the system is allowed to stand after adding and mixing the decomposing agent is the same as in the above embodiment. For example, after standing for about 24 hours, a purified product having a dioxin concentration reduced to 3 ng-TEQ / g can be obtained.

  The purified product discharging means 6 is an outlet for taking out the purified soil from the container after the reaction is completed.

  The oxidation-reduction reaction is carried out in a neutral pH range (usually 5 to 9, preferably 6 to 8). Therefore, the treatment method of the present invention does not require the preparation of a corrosion-resistant reaction vessel, and does not require neutralization of the treated sludge and waste water.

EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not restrict | limited by these.
[Example 1]
(Preparation of decomposition agent composition)
80 g of commercially available magnesium oxide (reagent, particle size 10 μm) and 60 g of ferrous sulfate (reagent, particle size 10 μm) were mixed to prepare a dioxin decomposer composition.

  As high-concentration dioxin contaminants, contaminated soil (water 0%) containing dioxins (2,3,7,8-tetrachlorodioxin) at a concentration of 10 ng-TEQ / g was prepared.

  15 g of the decomposition agent blended with the above composition was added to 100 g of the contaminated soil at a time and mixed at room temperature. The water content of the soil after mixing was 25%.

  After mixing and leaving for about 7 days, the concentration of dioxins in the contaminated soil was measured and found to be 2.6 ng-TEQ / g (reduction rate 74%).

It is the figure which showed the process based on the processing method of the dioxin contaminant of this invention. It is the schematic of the reaction tank used for another embodiment of the processing method of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Reaction container 2 Agitation means 3 Contaminant supply means 4 Filter means 5 Decomposition agent supply means 6 Purified substance discharge means

Claims (6)

  It consists of adding a decomposing agent mainly composed of dioxin-decomposable inorganic powder at normal temperature to the contaminants at the place where dioxin contaminants are generated to reduce the dioxin concentration to 3 ng-TEQ / g or less. , Dioxin contamination treatment method.   The method for treating a dioxin contaminant according to claim 1, wherein the inorganic powder is an alkaline earth metal or a compound thereof.   The method for treating a dioxin contaminant according to claim 1 or 2, wherein the inorganic powder is magnesium or a compound thereof.   4. The method for treating a dioxin contaminant according to claim 1, wherein a decomposition aid comprising at least one of iron salt, zeolite, platinum, and titanium oxide is added together with the decomposition agent.   The processing method of the dioxin contaminants as described in any one of Claims 1-4 which adds water or a water | moisture-content regulator with the said decomposition agent.   The processing method of the dioxin contaminants as described in any one of Claims 1-5 which further includes conveying the reduced dioxin contaminants to the management type | mold disposal site etc. outside a field.

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