JP2005081287A - Method for treating stack gas - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for treating stack gas which solves such a problem that harmful organic halogenated substances such as dioxins and heavy metals might be contained in stack gas and fly ash exhausted from a waste incineration plant, and the like, and when being released to the natural world, might cause environmental pollution, thus which method is capable of efficiently reducing the concentration of the organic halogenated substances in the stack gas and fly ash and efficiently treating the stack gas containing fly ash so that heavy metals are not eluted from the fly ash separated from stack gas even in relatively low temperature conditions without using such a specific apparatus as to perform heating in an oxygen-deficient state. <P>SOLUTION: In the method for treating stack gas, the stack gas containing the fly ash is brought into contact with a reductant, a metal trapping agent and a porous body (adsorbent), and thereafter, the fly ash is separated from the stack gas. The stack gas is preferably brought into contact with the reductant, the metal trapping agent and the adsorbent at a temperature of the stack gas of 120 to 400°C. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for treating flue gas capable of safely treating harmful substances in flue gas including fly ash generated during waste incineration.

  In recent years, it has been pointed out that extremely toxic organic halides such as dioxins (PCDDS, PCDFS, etc.) are produced when waste is incinerated at a garbage incineration plant or the like. Organic halides generated during the incineration of waste are a major social problem in some cases where they are contained in smoke at high concentrations. Organic halides generated by incineration of wastes not only cause air pollution problems when released into the atmosphere together with smoke, but also may accumulate in the soil. Organic halides accumulated in the soil There is a risk of causing widespread environmental pollution problems such as being absorbed in agricultural products or flowing out by rainwater to contaminate groundwater and rivers. In addition, organic halides generated when incinerating waste may be contained in a large amount in the fly ash separated from the flue gas, and there is a risk that the environment will be polluted by burying the fly ash. It was.

  Organic halides such as dioxins are very stable substances that do not dissolve in water and do not disappear semi-permanently in the natural environment. Therefore, they are regarded as important chemical substances for environmental pollution countermeasures due to their strong toxicity.

  On the other hand, with the recent diversification of garbage, smoke and fly ash may contain a large amount of heavy metals, and organic halogens such as dioxins that are also contained in the smoke. Along with chemicals, harmful heavy metals may be accumulated, which is a problem.

  In order to reduce the amount of dioxins that are likely to be generated when incineration of waste, especially plastic waste, etc. at a garbage incineration plant, the flue gas generated by incineration of waste is activated carbon, etc. It is said that the method of contacting with is effective to some extent. For this reason, it has been attempted to remove dioxins from the flue gas by contacting the flue gas with activated carbon and then passing it through a bag filter.

  According to the guidelines on the operation of incinerators issued by the Ministry of Health and Welfare in December 2000, in the newly installed incinerator, the smoke emission temperature at the dust collector inlet is lowered to 200 ° C or lower, and the concentration of dioxins in the smoke at the outlet is The international equivalent equivalent concentration should be 0.5 ng / Nm3 or less. In existing incinerators, the smoke emission temperature at the dust collector inlet should be as low as 250 to 280 ° C. Is required to be 1/10 or less of the conventional value. However, in these methods, the removal rate of dioxins is 99.5% or more even when the temperature of flue gas passing through the bag filter is reduced to 150 ° C., which is the lowest practical temperature. It is difficult to ensure at all times, and even if dioxins in the flue gas can be removed effectively, organic halides such as dioxins are contained in the fly ash separated from the flue gas by the bag filter. There was a fear of remaining.

  In recent years, as a method for reducing the amount of dioxins and the like, a method of decomposing dioxins by heating fly ash containing dioxins in a non-through system in an oxygen-deficient state (Patent Document 1), activated carbon, silica-based materials, An adsorbent that adsorbs dioxin precursors such as zeolite, and a suppressant that suppresses dioxin formation reaction such as silicic acid compounds such as sodium silicate, phosphoric acid compounds, ammonium compounds such as diammonium hydrogen phosphate, and amine compounds. A method of adding to flue gas (Patent Document 2), a method of adding amine compounds such as monoethanolamine, triethanolamine and methanolamine to fly ash and the like (Patent Document 3) In a process in which the temperature is 500 ° C. or lower, a method of bringing flue gas into contact with a reducing agent (Patent Document 4), the temperature of the flue gas is 500 ° C. While in the above, after spraying an aqueous solution containing a reducing agent to the flue gas, a method of quenching the flue gas (Patent Document 5) it has been proposed.

Japanese Patent Publication No. 6-38863 JP-A-10-296050 Japanese Patent Laid-Open No. 10-272440 Japanese Patent Laid-Open No. 11-137952 JP 2002-102650 A

  However, in the method described in Patent Document 1, the dioxins cannot be effectively decomposed unless they are in an oxygen-deficient state, and in order to obtain an oxygen-deficient state, working in a closed system or in an inert gas atmosphere There is a problem that it is necessary to adopt a method such as elimination of intrusion, and a high airtight structure is required for the heating device used for the heat treatment, so that there is a problem that high costs are required for equipment investment, equipment maintenance, and the like. Further, in this method, there is a possibility that even if chlorinated aromatic compounds such as dioxins are thermally decomposed, there is a possibility that they are decomposed only to the stage of chlorine and aromatic compounds. There was also a possibility that dioxins and the like may be generated again by binding under heating conditions.

  Moreover, although the method of patent document 2 and patent document 3 can process dioxins etc., without requiring special facilities like the method of patent document 1, it processes heavy metals. Therefore, the treatment of dioxins and the immobilization treatment of heavy metals must be performed separately, and there is a problem that the treatment work becomes complicated. On the other hand, the methods described in Patent Documents 4 and 5 are used to reduce dioxins in the flue gas and reduce the heavy metals from the fly ash easily without using special processing equipment. Is possible. However, in the method of Patent Document 4 in which flue gas is treated at 500 ° C. or less, if the content of dioxins and their precursors and the content of heavy metals are large, the amount of reducing agent used must be increased, There was a possibility that it would be difficult to sufficiently treat heavy metals. In addition, the method of Patent Document 5 may generate dioxins again if it is not rapidly cooled after the treatment, and all of them still have room for improvement.

  As a result of diligent research to solve the above-mentioned problems, the present inventors have treated exhaust gas in combination with a reducing agent, a metal scavenger, and a porous material, thereby producing organic halogens such as dioxins in the exhaust gas. The present inventors have found that the concentration of the compound can be reduced and that an efficient treatment can be performed so that heavy metals are not easily eluted from the fly ash, and the present invention has been completed.

That is, the present invention
(1) A method for treating flue gas, comprising separating fly ash from fly ash after bringing the flue gas containing fly ash into contact with a reducing agent, a metal scavenger and a porous body,
(2) The method for treating flue gas according to (1), wherein the flue gas is brought into contact with a reducing agent, a metal scavenger and a porous body at a flue gas temperature of 120 to 400 ° C.
Is a summary.

  According to the method of the present invention, the concentration of organic halides such as dioxins in flue gas can be efficiently reduced even if treatment is performed at a relatively low temperature without the need for special treatment equipment. The heavy metals can be reliably insolubilized so that the heavy metals are not eluted from the fly ash separated from the smoke.

  Examples of the reducing agent used in the present invention include phosphorous acids, hypophosphorous acids, metal hydrides, metal hydrogen complex compounds, boranes, hydrazines, and the like. The reducing agent is not limited to one type, and two or more types of the same type and / or different types can be used.

  As the phosphorous acid, phosphorous acid and phosphite are used. Examples of phosphites include sodium phosphite, potassium phosphite, calcium phosphite, magnesium phosphite, ammonium phosphite, sodium hydrogen phosphite, potassium hydrogen phosphite, calcium hydrogen phosphite, Examples thereof include magnesium phosphate. Of these, phosphorous acid, sodium phosphite, and calcium phosphite are preferable.

  As hypophosphorous acid, hypophosphorous acid or hypophosphite is used. Examples of hypophosphites include sodium hypophosphite, potassium hypophosphite, calcium hypophosphite, magnesium hypophosphite, ammonium hypophosphite, etc. Sodium phosphite and calcium hypophosphite are preferred.

  Examples of metal hydrides include alkylaluminum hydrides (such as diisobutylaluminum hydride), trialkyl (or aryl) ammonium having 1 to 18 carbon atoms (such as trimethylammonium and triisobutylaluminum), and alkyltin hydride compounds ( For example, tri-α-butyltin hydride, triphenyltin hydride, etc., alkylhydrasilane having 1 to 18 carbon atoms (eg, triethylsilane, phenyldimethylsilane, triethoxysilane, tri-n-butylsilane, diphenylsilane, diethyl) Silane etc.).

  Metal hydride complex compounds include metal borohydride salts of metals such as lithium, potassium, sodium, calcium, zinc, and aluminum (for example, sodium trimethoxyborohydride, sodium triacetoxyborohydride, zinc borohydride, etc.) And alkyl borohydride metal salts of metals such as lithium, potassium, sodium, calcium, zinc and aluminum, aluminum hydride metal salts, alkyl aluminum hydride metal salts and the like. Boranes include boron tribromide, alkylboranes such as texylborane and diciamylborane, and amine complexes of boranes such as diborane and trimethylborane. Hydrazines include hydrazine, hydrazine dihydrochloride, hydrazine hydrate, hydrazine hydrochloride, And hydrazine sulfate.

  The metal scavenger is a compound having a functional group containing an atom having coordination ability to a metal such as oxygen, nitrogen, sulfur, etc., for example, a dithiocarbamic acid group, a phosphoric acid group, a carboxylic acid group, a carbamic acid group, a dithioic acid. And a compound having at least one group such as a group, an aminophosphate group, a thiol group, and a xanthate group. When it has two or more functional groups, it may have the same functional group or different functional groups. As the metal scavenger, those having water solubility and water dispersibility are preferred, and those having a dithiocarbamic acid group or a salt thereof as a functional group are preferred.

  Examples of the metal scavenger having a dithiocarbamic acid group or a salt thereof as a functional group include compounds obtained by reacting carbon disulfide with amines such as monoamine and polyamine. Examples of amines used for obtaining a compound having a dithiocarbamic acid group as a functional group include monoalkylamines such as monomethylamine, monoethylamine, monopropylamine, monoisopropylamine, monobutylamine, monoisobutylamine; dimethylamine, diethylamine , Dipropylamine, diisopropylamine, dibutylamine, diisobutylamine, ethylmethylamine, methylpropylamine, isopropylmethylamine, butylmethylamine, isobutylmethylamine, ethylpropylamine, ethylisopropylamine, butylethylamine, ethylisobutylamine, isopropyl Dialkylamines such as propylamine, butylpropylamine, butylisobutylamine; ethylenediamine, propylene di Min, butylenediamine, hexamethylenediamine, diethylenetriamine, dipropylenetriamine, dibutylenetriamine, triethylenetetramine, tripropylenetetramine, tributylenetetramine, tetraethylenepentamine, tetrapropylenepentamine, tetrabutylenepentamine, pentaethylenehexamine, Aliphatic amines such as iminobispropylamine, monomethylaminopropylamine, methyliminobispropylamine; monoalcoholamines such as monomethanolamine, monoethanolamine, monopropanolamine, monoisopropanolamine, monobutanolamine, monoisobutanolamine Dimethanolamine, diethanolamine, dipropanolamine, diisopropanolamine, dibuta Ruamin include dialcohol amines such as diisobutyrate ethanolamine.

  Further, alkylphenylamines such as methylphenylamine, ethylphenylamine, phenylpropylamine, isopropylphenylamine, butylphenylamine, isobutylphenylamine; morpholine; 2-methylmorpholine, 2-ethylmorpholine, 2-propylmorpholine, 2-isopropylmorpholine Monoalkylmorpholine such as 2-butylmorpholine, 2-isobutylmorpholine, 3-methylmorpholine, 3-ethylmorpholine, 3-propylmorpholine, 3-isopropylmorpholine, 3-butylmorpholine, 3-isobutylmorpholine; Dialkylmorpholines such as dimethylmorpholine, 2,5-diethylmorpholine, 2-ethyl-5-methylmorpholine; 2,3,5-trimethylmorpholine, 2,3-dimethyl- -Trialkylmorpholine such as ethylmorpholine; Tetraalkylmorpholine such as 2,3,5,6-tetraethylmorpholine, 2-ethyl-3,5,6-trimethylmorpholine; Piperazine; 1-methylpiperazine, 1-ethylpiperazine, Monoalkylpiperazines such as 1-propylpiperazine, 1-isopropylpiperazine, 1-butylpiperazine, 2-methylpiperazine, 2-ethylpiperazine, 2-propylpiperazine, 2-isopropylpiperazine, 2-butylpiperazine, 2-isobutylpiperazine; Dialkylpiperazines such as 2,3-dimethylpiperazine, 2,5-diethylpiperazine, 1,3-diethylpiperazine; 2,3,5-trimethylpiperazine, 1,2,5-trimethylpiperazine, 2,3-dimethyl-5 -Ethyl Trialkylpiperazines such as perazine; tetraalkylpiperazines such as 2,3,5,6-tetramethylpiperazine, 1,3,5,6-tetrapropylpiperazine, 3-ethyl-2,5,6-trimethylpiperazine; pyrrolidine 2-methylpyrrolidine, 2-ethylpyrrolidine, 2-propylpyrrolidine, 2-isopropylpyrrolidine, 2-butylpyrrolidine, 2-isobutylpyrrolidine, 3-methylpyrrolidine, 3-ethylpyrrolidine, 3-propylpyrrolidine, 3-isopropylpyrrolidine Monoalkylpyrrolidines such as 3-butylpyrrolidine and 3-isobutylpyrrolidine; dialkylpyrrolidines such as 2,3-dimethylpyrrolidine, 2,4-diethylpyrrolidine and 2-ethyl-3-methylpyrrolidine; 2,3,4-trimethyl Pyrrolidine, Trialkylpyrrolidines such as 2,3-dimethyl-5-ethylpyrrolidine; tetraalkylpyrrolidines such as 2,3,4,5-tetramethylpyrrolidine and 2-ethyl-3,4,5-trimethylpyrrolidine; piperidine; Methylpiperidine, 2-ethylpiperidine, 2-propylpiperidine, 2-isopropylpiperidine, 2-butylpiperidine, 2-isobutylpiperidine, 3-methylpiperidine, 3-ethylpiperidine, 3-propylpiperidine, 3-isopropylpiperidine, 3- Monoalkyl piperidines such as butyl piperidine, 3-isobutyl tipiperidine, 4-methyl piperidine, 4-ethyl piperidine, 4-propyl piperidine, 4-isopropyl piperidine, 4-butyl piperidine, 4-isobutyl piperidine; 2,3-dimethyl Dialkylpiperidines such as piperidine, 2,5-diethylpiperidine, 2,4-dipropylpiperidine, 2-methyl-4-propylpiperidine; 2,4,6-trimethylpiperidine, 2,4-ethyl-6-propylpiperidine, etc. Trialkylpiperidine of 2,3,5,6-tetramethylpiperidine, tetraalkylpiperidine such as 2,3,4,6-triethylpiperidine; 2,3,4,5,6-pentamethylpiperidine, 2,3 , 4,5,6-pentaethylpiperidine, and the like; thiomorpholine; 2-methylthiomorpholine, 2-ethylthiomorpholine, 2-propylthiomorpholine, 2-isopropylthiomorpholine, 2-butylthiomorpholine, 2- Isobutylthiomorpholine, 3-methylthiomorpholine, 3 Monoalkylthiomorpholine such as ethylthiomorpholine, 3-propylthiomorpholine, 3-isopropylthiomorpholine, 3-butylthiomorpholine, 3-isobutylthiomorpholine, 2,3-dimethylthiomorpholine, 2,5-diethylthiomorpholine, 2 , 6-dipropylthiomorpholine, 2-ethyl-3-methylthiomorpholine, dialkylthiomorpholine such as 2-methyl-6-propylthiomorpholine; 2,3,5-trimethylthiomorpholine, 2,3,6-triethylthio Trialkylthiomorpholine such as morpholine; tetraalkylthiomorpholine such as 2,3,5,6-tetramethylthiomorpholine, 2-ethyl-3,5,6-trimethylthiomorpholine; imidazolidine; 1-methylimidazolidine, 1-ethyl Imidazoli Gin, 1-propylimidazolidine, 1-isopropylimidazolidine, 1-butylimidazolidine, 1-isobutylimidazolidine, 2-methylimidazolidine, 2-ethylimidazolidine, 2-propylimidazolidine, 2-isopropylimidazolidine, 2-Butylimidazolidine, 2-Isobutylimidazolidine, 3-Methylimidazolidine, 3-Ethylimidazolidine, 3-Propylimidazolidine, 3-Isopropylimidazolidine, 3-Butylimidazolidine, 3-Isobutylimidazolidine, 4- Methylimidazolidine, 4-ethylimidazolidine, 4-propylimidazolidine, 4-isopropylimidazolidine, 4-butylimidazolidine, 4-isobutylimidazolidine, 5-methylimidazolidine, 5-ethylimidazole Monoalkylimidazolidines such as zolidine, 5-propylimidazolidine, 5-isopropylimidazolidine, 5-butylimidazolidine, 5-isobutylimidazolidine; 2,3-dimethylimidazolidine, 2,5-diethylimidazolidine, 4, Dialkylimidazolidines such as 5-dipropylimidazolidine and 1-methyl-4-propylimidazolidine; trialkylimidazolidines such as 2,4,5-trimethylimidazolidine and 3,4-diethyl-5-propylimidazolidine; Tetraalkylimidazolidines such as 2,3,4,5-tetramethylimidazolidine, 1,2,4,5-tetramethylimidazolidine; pyrazolidine; 1-methylpyrazolidine, 1-ethylpyrazolidine, 1- Propylpyrazolidine, 1-isopropylpyra Lysine, 1-butylpyrazolidine, 1-isobutylpyrazolidine, 2-methylpyrazolidine, 2-ethylpyrazolidine, 2-propylpyrazolidine, 2-isopropylpyrazolidine, 2-butylpyrazolidine 2-isobutylpyrazolidine, 3-methylpyrazolidine, 3-ethylpyrazolidine, 3-propylpyrazolidine, 3-isopropylpyrazolidine, 3-butylpyrazolidine, 3-isobutylpyrazolidine, 4-methylpyrazolidine, 4-ethylpyrazolidine, 4-propylpyrazolidine, 4-isopropylpyrazolidine, 4-butylpyrazolidine, 4-isobutylpyrazolidine, 5-methylpyrazolidine, 5 -Ethylpyrazolidine, 5-propylpyrazolidine, 5-isopropylpyrazolidine, 5-butylpyrazolidine, 5-isobuty Monoalkylpyrazolidines such as tilpyrazolidine; dialkyls such as 3,4-dimethylpyrazolidine, 3,5-diethylpyrazolidine, 2,5-dipropylpyrazolidine, 3-methyl-5-propylpyrazolidine Pyrazolidine; trialkylpyrazolidine such as 3,4,5-trimethylpyrazolidine, 2,4-diethyl-5-propylpyrazolidine; 2,3,4,5-tetramethylpyrazolidine, 1 , 4-diethyl-3,5-dipropylpyrazolidine and the like; pyrrole; 2-methylpyrrole, 2-ethylpyrrole, 2-propylpyrrole, 2-isopropylpyrrole, 2-butylpyrrole, 2 -Isobutylpyrrole, 3-methylpyrrole, 3-ethylpyrrole, 3-propylpyrrole, 3-isopropylpyrrole, 3- Monoalkyl pyrroles such as til pyrrole and 3-isobutyl pyrrole; 2,3-dimethyl pyrrole, 2,5-diethyl pyrrole, 2,4-dipropyl pyrrole, 2-ethyl-4-methyl pyrrole, 2-methyl-3-propyl Dialkyl pyrrole such as pyrrole; trialkyl pyrrole such as 2,3,4-trimethylpyrrole and 2,3,5-triethylpyrrole; 2,3,4,5-tetramethylpyrrole, 2-ethyl-3,4,5 -Tetraalkylpyrrole such as trimethylpyrrole; imidazole; 2-methylimidazole, 2-ethylimidazole, 2-propylimidazole, 2-isopropylimidazole, 2-butylimidazole, 2-isobutylimidazole, 4-methylimidazole, 4-ethylimidazole 4-propylimidazo Monoalkyl such as 4-propylimidazole, 4-butylimidazole, 4-isobutylimidazole, 5-methylimidazole, 5-ethylimidazole, 5-propylimidazole, 5-isopropylimidazole, 5-butylimidazole, 5-isobutylimidazole Dialkylimidazoles such as imidazole, 2,4-dimethylimidazole, 2,5-diethylimidazole, 2,4-dipropylimidazole, 2-ethyl-4-methylimidazole, 2-methyl-5-propylimidazole; Trialkylimidazoles such as 5-trimethylimidazole and 2,4,5-triethylimidazole; pyrazole; 3-methylpyrazole, 3-ethylpyrazole, 3-propylpyrazole, 3-isopropylpyrazole 3-butylpyrazole, 3-isobutylpyrazole, 4-methylpyrazole, 4-ethylpyrazole, 4-propylpyrazole, 4-isopropylpyrazole, 4-butylpyrazole, 4-isobutylpyrazole, 5-methylpyrazole, 5-ethyl Monoalkylpyrazoles such as pyrazole, 5-propylpyrazole, 5-isopropylpyrazole, 5-butylpyrazole, 5-isobutylpyrazole, 3,4-dimethylpyrazole, 3,5-diethylpyrazole, 3,4-dipropylpyrazole, 3 A dialkylpyrazole such as ethyl-5-methylpyrazole; a trialkylpyrazole such as 3,4,5-trimethylpyrazole, 3,4,5-triethylpyrazole; phenylenediamine, o-, m-, p-xylylenediamine, 3,5 Aromatic amines such as diaminochlorobenzene and aniline; cycloalkane polyamines such as 1,3-bis (aminomethyl) cyclohexane; polyethyleneimine, polypropyleneimine, poly-3-methylpropylimine, poly-2-ethylpropylimine, etc. Cyclic imine polymers; polymers of unsaturated amines such as polyvinylamine and polyallylamine. Furthermore, unsaturated amines that can be copolymerized with unsaturated amines such as vinylamine and allylamine and unsaturated amines such as dimethylacrylamide, styrene, methyl acrylate, methyl methacrylate, acrylic acid, methacrylic acid, styrene sulfonic acid, and salts thereof. Copolymers with other monomers having a saturated bond are also included. A mixture of two or more of these can also be used.

  A compound having a dithiocarbamate group or a salt thereof as a functional group may be a compound having only a dithiocarbamate group (acid type functional group) or a dithiocarbamate group (salt type functional group) in one molecule, Any of those having both a functional group of the mold type and a functional group of the salt type can be used as the metal scavenger. Also, a compound having only an acid type functional group, a compound having only a salt type functional group, and a mixture of two or more of an acid type functional group and a salt type functional group can be used. Examples of the salt-type functional group include barium salt, sodium salt, potassium salt, calcium salt, magnesium salt, amine salt and the like, but sodium salt and potassium salt are usually preferable.

  Examples of the compound having a phosphate group as a functional group include compounds obtained by reacting the same amines as described above with aldehydes and phosphorous acids. In the compound having a phosphoric acid group as a functional group, the phosphoric acid group may be an acid type (terminal is a hydrogen atom), a salt type, or a compound containing both. Examples of the salt-type phosphate group include barium salt, sodium salt, potassium salt, calcium salt, magnesium salt, and amine salt, and sodium salt and potassium salt are usually preferable. As a compound having a phosphate group as a functional group, a compound having both an acid type and a salt type phosphate group in one molecule, a compound having only an acid type phosphate group, and a salt type phosphate group only. One kind or a mixture of two or more kinds of the compounds having them can be used.

  Examples of the compound having a carboxylic acid group as a functional group include compounds having a carboxylic acid group obtained by reacting the same amines as described above with a monohalogenated carboxylic acid or an ester thereof. In the compound having a carboxylic acid group as a functional group, the carboxylic acid group may be an acid type (terminal hydrogen atom), a salt type, or a compound containing both. Examples of the salt-type carboxylic acid group include barium salts, sodium salts, potassium salts, calcium salts, magnesium salts, and amine salts, but sodium salts and potassium salts are usually preferable. As a compound having a carboxylic acid group as a functional group, a compound having both an acid type and a salt type carboxylic acid group in one molecule, a compound having only an acid type carboxylic acid group, and a salt type carboxylic acid group only. One kind or a mixture of two or more kinds of the compounds having them can be used.

  In this invention, a commercially available thing can also be used as a metal scavenger. Commercially available metal scavengers include, for example, Ashclean C-500, Ashclean C-508, Ashclean C-505 (Ebara Corporation), Ashnite S-803 (Kurita Industry Co., Ltd.), TX-10 , TS-500, TS-600, TS-800, (Tosoh Corporation), Alcite L-105 (Fuji Sash Corporation), Koei Chelate 200 (Lassa Soei Co., Ltd.), Ash Ace L-5000 (Hitachi) Shipbuilding Co., Ltd.), UML-7200, UML-8100, UML-8100A (Unitika Co., Ltd.), ALM-648HG, Heidion-VG (Nippon Soda Co., Ltd.), Miyoshi Yushi Co., Ltd. Epoflock series (Epoch Lock L-1) , Epoflock L-2, etc.), Epolba series (NEW Epolva 800, NEW E) Luba 800A, NEW Eporuba 810 etc.) include Epoasshu M-1 and the like.

  As the porous material used in the present invention, dimethylsiloxane, calcium silicate, sodium silicate, aluminum oxide, alumino-silica gel, alumina white, aluminum silicate, aluminum hydroxide, synthetic hydrotalcite, magnesium metasilicate aluminate, Slaked lime, calcium carbonate, gypsum, hydroxyapatite, silica gel, colloidal silica, ultrafine anhydrous silica, zeolite, activated carbon, titanium oxide, titanium silicide, magnesium silicate, magnesium oxide, magnesium hydroxide, magnesium carbonate, silicon carbide, Examples thereof include titanium carbide, aluminum nitride, silicon nitride, titanium nitride, ilmenite, kaolin, activated clay, silica sand, diatomaceous earth, talc, perlite, bentonite, meteorite, bauxite and the like. Among these, activated carbon, clay, silica gel, aluminum oxide, titanium oxide, and magnesium silicate are preferable.

  In the method of the present invention, as a method of bringing flue gas containing fly ash into contact with the reducing agent, the metal scavenger and the porous body, there is a method of spraying the reducing agent, the metal scavenger and the porous body onto the flue. Adopted. The reducing agent, the metal scavenger, and the porous material may be sprayed separately or mixed and sprayed at the same time, but are preferably mixed and sprayed at the same time. Usually, an aqueous solution, aqueous dispersion or powder Used as The amount of reducing agent, metal scavenger, and adsorbent used for flue gas is the type of reducing agent and metal scavenger, the amount of dioxins and precursors contained in the flue gas, the amount of heavy metals, etc. For example, when the reducing agent is phosphorous acid or hypophosphorous acid, it is preferably 1 to 10,000 mg / m3 in terms of solid content with respect to the amount of flue gas. In the case of hydrazines, the reducing agent is solid with respect to the amount of flue gas. It is preferably 1 to 10000 mg / m3 in terms of minute. The amount of metal scavenger used is usually preferably 0.01 to 30% in terms of solid content with respect to the amount of fly ash in the flue gas, and the amount of porous material used is preferably 10 to 100,000 mg / m3.

  In the method of the present invention, when the flue gas containing fly ash is treated by bringing it into contact with a reducing agent, a metal scavenger and a porous body, if the flue gas temperature is too high, the metal scavenger is thermally decomposed. There is a possibility that not only the ability to immobilize heavy metals is lowered, but also the reducing ability of the reducing agent is lowered. The temperature of the flue gas when treating the flue gas is preferably 120 to 400 ° C, particularly preferably 150 to 300 ° C. After the flue gas containing fly ash is brought into contact with the reducing agent, the metal scavenger, and the porous body, the fly ash in the flue gas is separated by a dust collector. As the dust collector, a known dust collector such as an electric dust collector (EP), a filtration dust collector, a centrifugal dust collector, a gravity dust collector, or an inertial dust collector is used. The flue gas separated from the fly ash can be directly discharged from the chimney. The separated fly ash can be solidified with cement or the like as needed.

  The method of the present invention can reduce the concentration of organic halides such as dioxins, their precursors, and PCBs in flue gas and fly ash or suppress resynthesis, and lead, cadmium, hexavalent chromium, arsenic, selenium, mercury , Nickel, molybdenum, antimony, copper, zinc, manganese and other heavy metals can be treated so that they are difficult to elute from the fly ash.

Hereinafter, the present invention will be described in more detail with reference to examples.
Examples 1-5, Comparative Examples 1-5
A treatment liquid containing a reducing agent, a metal scavenger, and a porous material (the comparative example does not include one or two of these) is sprayed on the flue at the ratio shown in Table 1, and garbage is removed in an incinerator. It was made to contact with the flue gas generated by incineration (amount of smoke discharged 20000Nm3 / hr-wet). Table 1 shows the smoke emission temperature when the treatment liquid and the smoke emission are brought into contact with each other. The treatment liquid is continuously sprayed so that each spray amount (solid equivalent amount) of the reducing agent, the metal scavenger, and the porous body per 1 Nm3 of the flue gas becomes the amount shown in Table 1, and the flue gas and the treatment liquid Then, the smoke was passed through the bag filter, and the concentration of dioxins contained in the smoke was measured at the bag filter outlet. The results are shown in Table 2. The lead elution test from the fly ash separated by the bag filter was conducted according to the Environmental Agency Notification No. 13 test method. The lead elution amount from the fly ash during the flue gas treatment and the dioxin concentration in the fly ash are shown together in Table 2.

The metal scavengers used in Examples and Comparative Examples are as follows.
Metal scavenger a: NEW Epolva 800A (Metal scavenger manufactured by Miyoshi Oil & Fat Co., Ltd.)
Metal collector b: NEW Epolva 810 (metal collector made by Miyoshi Oil & Fat Co., Ltd.)
Metal scavenger c: Epoash M-1 (Metal scavenger manufactured by Miyoshi Oil & Fat Co., Ltd.)

* 1 Value measured by sampling the flue gas continuously for 4 hours after 2 hours from the start of treatment liquid spraying.
* 2 Value measured by sampling the flue gas continuously for 4 hours from 2 hours after stopping the treatment liquid spray.
* 3 The value of fly ash collected 4 hours after the start of treatment liquid spraying.
* 4 Value of fly ash collected after 4 hours from stopping treatment liquid spray.

Claims (2)

A method for treating flue gas, comprising separating flue gas containing fly ash from flue gas after contacting the flue gas containing fly ash with a reducing agent, a metal scavenger and a porous body. The method for treating flue gas according to claim 1, wherein the flue gas is brought into contact with a reducing agent, a metal scavenger and a porous body at a flue gas temperature of 120 to 400 ° C.