JP7046770B2 - Method for treating carbon-containing fly ash containing mercury - Google Patents

Description

The present invention relates to a method for treating carbon-containing fly ash containing mercury.

Fly ash generated during the incineration of municipal waste and industrial waste may contain a large amount of heavy metals such as mercury that are harmful to the human body. Although the separate collection of household waste is progressing, it is inevitable that dry batteries, thermometers, fluorescent lamps, etc. will be mixed in, and the fly ash generated when incinerated in an incinerator contains heavy metals such as mercury. The problem is that when this heavy metal elutes into groundwater, rivers and seawater, it causes serious environmental pollution.

The Minamata Convention on Mercury was adopted and signed in 2013 with the aim of protecting human health and the environment from the anthropogenic emissions of mercury and mercury compounds, and came into effect in 2017. Air, soil and water. There is increasing momentum to regulate mercury emissions to.

Incinerator fly ash is a specially controlled general waste, and intermediate treatment such as chemical treatment is obligatory. Since the incinerated fly ash contains heavy metals and the heavy metals are eluted by rainwater or the like after the landfill treatment, a method of immobilizing and suppressing the elution is generally used.

The method by chemical treatment is a method of kneading chemicals, water and incinerator fly ash to immobilize harmful heavy metals. Agents used for this purpose include organic chelating agents such as dithiocarbamate and inorganic agents such as iron compounds. A triazole compound has also been proposed as a fly ash immobilization agent for mercury (Patent Document 1). In incinerators, as a measure against dioxins, activated carbon is also blown into the entrance of a filter-type dust collector in a waste incinerator (Patent Document 2), but in recent years, the technique of blowing activated carbon has been to remove mercury in fly ash. It is also studied from the aspect of immobilizing and reducing mercury contained in exhaust gas (Patent Document 3).

Fly ash containing carbon, such as fly ash containing activated carbon, has characteristics different from those of conventional fly ash in the adsorption and re-eluting of heavy metals due to the porous structure of carbon and the behavior when mixed with water. Even if the conventional organic chelating agent is applied as it is, it is difficult to stably suppress the elution of mercury. Therefore, in consideration of the characteristics of fly ash containing carbon such as activated carbon, a new technique capable of stably suppressing the elution of mercury by an organic chelating agent has been desired.

In particular, in the case of carbon-containing fly ash, considering the properties of adsorption and re-eluting of heavy metals due to its porous structure, there is a risk that mercury may not be well immobilized under the same amount of water content as general fly ash treatment conditions. After kneading chemicals, water and fly ash, if the treated ash is stored in a place exposed to changes in ambient temperature and humidity, wind and rain, mercury may not be immobilized well, and in a waste incineration facility. There is a concern that the elution of mercury cannot be stably suppressed after the elution test conducted for inspection and the elution test after being carried out from the waste incineration facility and landfilled. Further, Patent Documents 4 and 5 propose a technique for suppressing the elution of heavy metals by kneading a chemical, water, and incinerator fly ash and then curing them at a high temperature. It is desirable that mercury can be immobilized without adding such special conditions.

Japanese Unexamined Patent Publication No. 2013-193039 Japanese Unexamined Patent Publication No. 2003-1221 Japanese Unexamined Patent Publication No. 2004-160306 Japanese Unexamined Patent Publication No. 2006-150339 Japanese Unexamined Patent Publication No. 2005-118617

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a treatment method capable of stably suppressing the elution of mercury from carbon-containing fly ash.

In order to solve the above-mentioned problems, the method for treating carbon-containing fly ash of the present invention is a method for treating carbon-containing fly ash containing mercury, and has a mass of 20 mass with respect to dithiocarbamate and the carbon-containing fly ash. The treated ash obtained by kneading% or more and 150% by mass or less of water together with the carbon-containing fly ash is post-treated at a temperature of more than 0 ° C. and lower than 80 ° C. and a humidity of 10% or more to stably suppress the elution of mercury. It is supposed to be.

According to the present invention, elution of mercury from carbon-containing fly ash can be stably suppressed.

Hereinafter, the present invention will be described in detail.

The flying ash that is the subject of the present invention is not particularly limited, but is, for example, incinerated flying ash and incinerated ash that are generated along with the combustion exhaust gas when incinerating municipal waste, industrial waste, sewage sludge, etc. in an incinerator. Examples include molten flying ash generated when the flying ash is melted in a melting furnace, electric furnace dust generated from a metal smelting electric furnace, and the like. These are collected in a partition type bag filter, a distribution type electrostatic precipitator, a cyclone, etc. in an incineration facility.

In the present invention, the "carbon-containing fly ash" is fly ash containing carbon generated in an incinerator, and the origin of carbon is not particularly limited, but for example, adsorption of activated carbon, unburned carbon, etc. blown into the incinerator. Capable carbon substances and the like are included. The carbon-containing fly ash includes, for example, fly ash containing 1% by mass or more of carbon with respect to the total amount of fly ash, and the carbon content may be 3% by mass or more, and further 7% by mass or more. It may be present, and in particular, it may be 9% by mass or more.

The effect of the present invention becomes even more remarkable when the amount of mercury eluted from the treated ash immediately after kneading with dithiocarbamate and water is 0.0005 mg / L or more.

In the present invention, the action of stably suppressing the elution of mercury from carbon-containing fly ash is not intended to be limited to this, but it is considered as follows from the cause of mercury elution and the mechanism of immobilization.
(1) Form of mercury The mercury in flying ash is Hg ⁰ , Hg ²⁺ (HgCl ₂ , HgO), Hg ⁺ (HgCl), Hg (OH) ₂ (colloidal), HgCl ₂ · HgO (double salt), etc. It exists in the form of. Of these, Hg ²⁺ can be immobilized with dithiocarbamate. Others (0-valent, monovalent, double salt) cannot be immobilized with dithiocarbamate, but are immobilized by adsorption to activated carbon or the like or solidification of ash. However, in the case of adsorption or the like, there is a risk of re-elution due to changes in the environment or the like. In the present invention, 0-valent and monovalent mercury is oxidized to divalent mercury due to the change with time after kneading, and thus it is considered to be immobilized in the presence of a dithiocarbamic acid group. In addition, the double salt mercury stabilizes the bond between the carboxyl group on the carbon surface and calcium in the flying ash, and the calcium carbonate adsorbed on the surface becomes a hydroxide, thereby stabilizing the adsorbed mercury.
(2) Carbon surface structure and adsorbed material Carboxyl groups and calcium carbonate are adsorbed on the surface of carbon and activated carbon contained in flying ash. Mercury reacting with the carboxyl group on the surface of activated carbon may ion-exchange with calcium and the like in the ash over time and re-elute. However, in the presence of the dithiocarbamic acid group, the re-eluting mercury reacts with the dithiocarbamic acid group, so that the re-eluting mercury is immobilized.

As the dithiocarbamate used in the present invention, a compound obtained by a general production method can be used. For example, carbon disulfide is reacted with amines in the presence of a base, and dithioate is added to nitrogen of amines. Examples thereof include compounds obtained by introduction.

In the present invention, for example, the following amines can be used.
(Alkyl type)
Examples of alkyl-based amines include monoalkylamines and dialkylamines.
Examples of the monoalkylamine include monomethylamine, monoethylamine, monopropylamine, monoisopropylamine, monobutylamine, monoisobutylamine, amylamine, 2-ethylhexylamine and the like.
Examples of the dialkylamine include dimethylamine, diethylamine, dipropylamine, diisopropylamine, dibutylamine, diisobutylamine, ethylmethylamine, methylpropylamine, isopropylmethylamine, butylmethylamine, isobutylmethylamine, ethylpropylamine and ethyl. Examples thereof include isopropylamine, butylethylamine, ethylisobutylamine, isopropylpropylamine, butylpropylamine, butylisobutylamine, diamylamine, di-2-ethylhexylamine and the like.
In addition, alkyl-based amines include alicyclic-type amines such as cyclohexylamine and compounds having a hydrocarbon-based substituent on an alkyl group such as benzylamine.

(Alkylphenyl type)
Examples of alkylphenyl amines include methylphenylamine, ethylphenylamine, phenylpropylamine, isopropylphenylamine, butylphenylamine, isobutylphenylamine and the like.

(Alcohol)
Examples of alcohol-based amines include monoalcohol amines and dialcohol amines.
Examples of the monoalcohol amine include monomethanolamine, monoethanolamine, monopropanolamine, monoisopropanolamine, monobutanolamine, monoisobutanolamine and the like.
Examples of the dialcohol amine include dimethanolamine, diethanolamine, dipropanolamine, diisopropanolamine, dibutanolamine, diisobutanolamine and the like.

(Aromatic)
Examples of aromatic amines include phenylenediamine, o-, m-, p-xylylenediamine, 3,5-diaminochlorobenzene, aniline and the like.

(Heterocyclic system)
Examples of the heterocyclic amines include piperazine type, piperidine type, morpholine type, thiomorpholine type, imidazolidine type, pyrazolidine type, pyrrolidine type, imidazole type, pyrazole type, pyrrole type and the like.
[Piperazine system]
Examples of piperazine-based amines include piperazine, monoalkylpiperazine, dialkylpiperazine, trialkylpiperazine, tetraalkylpiperazine, homopiperazine and the like.
Examples of the monoalkylpiperazine include 1-methylpiperazine, 1-ethylpiperazine, 1-propylpiperazine, 1-isopropylpiperazine, 1-butylpiperazine, 2-methylpiperazine, 2-ethylpiperazine, 2-propylpiperazine, 2-. Examples thereof include isopropylpiperazine, 2-butylpiperazine, 2-isobutylpiperazine and the like.
Examples of the dialkylpiperazine include 2,3-dimethylpiperazine, 2,5-diethylpiperazine, 1,3-diethylpiperazine and the like.
Examples of the trialkylpiperazine include 2,3,5-trimethylpiperazine, 1,2,5-trimethylpiperazine, 2,3-dimethyl-5-ethylpiperazine and the like.
Examples of the tetraalkylpiperazine include 2,3,5,6-tetramethylpiperazine, 1,3,5,6-tetrapropylpiperazine, 3-ethyl-2,5,6-trimethylpiperazine and the like.
[Piperidine]
Examples of piperidine-based amines include piperidine, monoalkyl piperidine, dialkyl piperidine, trialkyl piperidine, tetraalkyl piperidine, pentaalkyl piperidine and the like.
Examples of the monoalkylpiperidine include 2-methylpiperidine, 2-ethylpiperidine, 2-propylpiperidine, 2-isopropylpiperidine, 2-butylpiperidine, 2-isobutylpiperidine, 3-methylpiperidine, 3-ethylpiperidine, and 3-. Propylpiperidine, 3-isopropylpiperidine, 3-butylpiperidine, 3-isobutyltipiperidine, 4-methylpiperidine, 4-ethylpiperidine, 4-propylpiperidine, 4-isopropylpiperidine, 4-butylpiperidine, 4-isobutylpiperidine, etc. Can be mentioned.
Examples of the dialkylpiperidine include 2,3-dimethylpiperidine, 2,5-diethylpiperidine, 2,4-dipropylpiperidine, 2-methyl-4-propylpiperidine and the like.
Examples of the trialkylpiperidine include 2,4,6-trimethylpiperidine, 2,4-ethyl-6-propylpiperidine and the like.
Examples of the tetraalkylpiperidine include 2,3,5,6-tetramethylpiperidine, 2,3,4,6-triethylpiperidine and the like.
Examples of the pentaalkyl piperidine include pentaalkyl piperidines such as 2,3,4,5,6-pentamethyl piperidine and 2,3,4,5,6-pentaethyl piperidine.
[Morpholine]
Examples of morpholine-based amines include morpholine, monoalkyl morpholine, dialkyl morpholine, trialkyl morpholine, tetraalkyl morpholine and the like.
Examples of the monoalkyl morpholine include 2-methyl morpholine, 2-ethyl morpholine, 2-propyl morpholine, 2-isopropyl morpholine, 2-butyl morpholine, 2-isobutyl morpholine, 3-methyl morpholine, 3-ethyl morpholine, 3-. Examples thereof include propyl morpholine, 3-isopropyl morpholine, 3-butyl morpholine, 3-isobutyl morpholine and the like.
Examples of the dialkyl morpholine include 2,3-dimethylmorpholine, 2,5-diethylmorpholine, 2-ethyl-5-methylmorpholine and the like.
Examples of the trialkylmorpholine include 2,3,5-trimethylmorpholine and 2,3-dimethyl-6-ethylmorpholine.
Examples of the tetraalkylmorpholine include 2,3,5,6-tetraethylmorpholine and 2-ethyl-3,5,6-trimethylmorpholine.
[Thiomorpholine]
Examples of thiomorpholine-based amines include thiomorpholine, monoalkylthiomorpholine, dialkylthiomorpholine, trialkylthiomorpholine, tetraalkylthiomorpholine and the like.
Examples of the monoalkylthiomorpholine include 2-methylthiomorpholine, 2-ethylthiomorpholine, 2-propylthiomorpholine, 2-isopropylthiomorpholine, 2-butylthiomorpholine, 2-isobutylthiomorpholine, 3-methylthiomorpholine and 3-. Examples thereof include ethylthiomorpholine, 3-propylthiomorpholine, 3-isopropylthiomorpholine, 3-butylthiomorpholine, 3-isobutylthiomorpholine and the like.
Examples of the dialkylthiomorpholine include 2,3-dimethylthiomorpholine, 2,5-diethylthiomorpholine, 2,6-dipropylthiomorpholine, 2-ethyl-3-methylthiomorpholine, and 2-methyl-6-propylthio. Examples include morpholine.
Examples of the trialkylthiomorpholine include 2,3,5-trimethylthiomorpholine and 2,3,6-triethylthiomorpholine.
Examples of the tetraalkylthiomorpholine include 2,3,5,6-tetramethylthiomorpholine, 2-ethyl-3,5,6-trimethylthiomorpholine and the like.
[Imidazolidine]
Examples of the imidazolidine-based amines include imidazolidine, monoalkyl imidazolidine, dialkyl imidazolidine, trialkyl imidazolidine, tetraalkyl imidazolidine and the like.
Examples of monoalkyl imidazolines include 1-methylimidazolidine, 1-ethyl imidazolidine, 1-propyl imidazolidine, 1-isopropyl imidazolidine, 1-butyl imidazolidine, 1-isobutyl imidazolidine, and 2-methyl imidazolidine. , 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-isobutyl Examples thereof include imidazolidine, 5-methylimidazolidine, 5-ethylimidazolidine, 5-propylimidazolidine, 5-isopropylimidazolidine, 5-butylimidazolidine, 5-isobutylimidazolidine and the like.
Examples of the dialkyl imidazoline include 2,3-dimethylimidazolidine, 2,5-diethyl imidazolidine, 4,5-dipropyl imidazolidine, 1-methyl-4-propyl imidazolidine and the like.
Examples of the trialkylimidazolidine include 2,4,5-trimethylimidazolidine, 3,4-diethyl-5-propylimidazolidine and the like.
Examples of the tetraalkylimidazolidine include 2,3,4,5-tetramethylimidazolidine, 1,2,4,5-tetramethylimidazolidine and the like.
[Pyrazolidine]
Examples of pyrazolidine-based amines include pyrazolidine, monoalkylpyrazolidine, dialkylpyrazolidine, trialkylpyrazolidine, tetraalkylpyrazolidine and the like.
Examples of the monoalkyl pyrazolysine include 1-methylpyrazolidine, 1-ethylpyrazolidine, 1-propylpyrazolidine, 1-isopropylpyrazolidine, 1-butylpyrazolidine, and 1-isobutylpyrazoline. Lysine, 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-isobutylpyrazolidine and the like can be mentioned.
Examples of the dialkylpyrazolidine include 3,4-dimethylpyrazolidine, 3,5-diethylpyrazolidine, 2,5-dipropylpyrazolidine, 3-methyl-5-propylpyrazolidine and the like. Be done.
Examples of the trialkylpyrazolidine include 3,4,5-trimethylpyrazolidine, 2,4-diethyl-5-propylpyrazolidine and the like.
Examples of the tetraalkylpyrazolidine include 2,3,4,5-tetramethylpyrazolidine, 1,4-diethyl-3,5-dipropylpyrazolidine and the like.
[Pyrrolidine system]
Examples of pyrrolidine-based amines include pyrrolidine, monoalkylpyrrolidin, dialkylpyrrolidin, trialkylpyrrolidine, tetraalkylpyrrolidin and the like.
Examples of the monoalkylpyrrolidine include 2-methylpyrrolidine, 2-ethylpyrrolidine, 2-propylpyrrolidin, 2-isopropylpyrrolidine, 2-butylpyrrolidine, 2-isobutylpyrrolidine, 3-methylpyrrolidin, 3-ethylpyrrolidine, 3-. Examples thereof include propylpyrrolidine, 3-isopropylpyrrolidine, 3-butylpyrrolidine, 3-isobutylpyrrolidine and the like.
Examples of the dialkylpyrrolidine include 2,3-dimethylpyrrolidine, 2,4-diethylpyrrolidine, 2-ethyl-3-methylpyrrolidine and the like.
Examples of the trialkylpyrrolidine include 2,3,4-trimethylpyrrolidine, 2,3-dimethyl-5-ethylpyrrolidine and the like.
Examples of the tetraalkylpyrrolidine include 2,3,4,5-tetramethylpyrrolidine, 2-ethyl-3,4,5-trimethylpyrrolidin and the like.
[Imidazole system]
Examples of the imidazole-based amines include imidazole, monoalkyl imidazole, dialkyl imidazole, trialkyl imidazole and the like.
Examples of the monoalkyl imidazole include 2-methyl imidazole, 2-ethyl imidazole, 2-propyl imidazole, 2-isopropyl imidazole, 2-butyl imidazole, 2-isobutyl imidazole, 4-methyl imidazole, 4-ethyl imidazole, 4-. Examples include propylimidazole, 4-isopropylimidazole, 4-butylimidazole, 4-isobutylimidazole, 5-methylimidazole, 5-ethylimidazole, 5-propylimidazole, 5-isopropylimidazole, 5-butylimidazole, 5-isobutylimidazole and the like. Will be.
Examples of the dialkylimidazole include 2,4-dimethylimidazole, 2,5-diethylimidazole, 2,4-dipropylimidazole, 2-ethyl-4-methylimidazole, 2-methyl-5-propylimidazole and the like. ..
Examples of the trialkylimidazole include 2,4,5-trimethylimidazole, 2,4,5-triethylimidazole and the like.
[Pyrazole system]
Examples of the pyrazole-based amines include pyrazole, monoalkylpyrazole, dialkylpyrazole, and trialkylpyrazole.
Examples of the monoalkylpyrazole include 3-methylpyrazole, 3-ethylpyrazole, 3-propylpyrazole, 3-isopropylpyrazole, 3-butylpyrazole, 3-isobutylpyrazole, 4-methylpyrazole, 4-ethylpyrazole, 4-. Examples include propylpyrazole, 4-isopropylpyrazole, 4-butylpyrazole, 4-isobutylpyrazole, 5-methylpyrazole, 5-ethylpyrazole, 5-propylpyrazole, 5-isopropylpyrazole, 5-butylpyrazole, 5-isobutylpyrazole and the like. Will be.
Examples of the dialkylpyrazole include 3,4-dimethylpyrazole, 3,5-diethylpyrazole, 3,4-dipropylpyrazole, 3-ethyl-5-methylpyrazole and the like.
Examples of the trialkylpyrazole include 3,4,5-trimethylpyrazole and 3,4,5-triethylpyrazole.
[Pyrrole]
Examples of pyrrole-based amines include pyrrole, monoalkylpyrrole, dialkylpyrrole, trialkylpyrrole, tetraalkylpyrrole and the like.
Examples of the monoalkylpyrrole include 2-methylpyrrole, 2-ethylpyrrole, 2-propylpyrrole, 2-isopropylpyrrole, 2-butylpyrrole, 2-isobutylpyrrole, 3-methylpyrrole, 3-ethylpyrrole and 3-. Examples thereof include propylpyrrole, 3-isopropylpyrrole, 3-butylpyrrole, 3-isobutylpyrrole and the like.
Examples of the dialkylpyrrole include 2,3-dimethylpyrrole, 2,5-diethylpyrrole, 2,4-dipropylpyrrole, 2-ethyl-4-methylpyrrole, 2-methyl-3-propylpyrrole and the like. ..
Examples of the trialkylpyrrole include 2,3,4-trimethylpyrrole, 2,3,5-triethylpyrrole and the like.
Examples of the tetraalkylpyrrole include 2,3,4,5-tetramethylpyrrole, 2-ethyl-3,4,5-trimethylpyrrole and the like.

(Polyamine type)
Examples of polyamine-based amines having two or more amino groups include aliphatic amine-based, cycloalkane-based, cyclic imine polymers, unsaturated amine polymers, and the like, in addition to the compounds exemplified above.
Examples of aliphatic amine-based amines include ethylenediamine, propylenediamine, butylene diamine, hexamethylenediamine, diethylenetriamine, dipropylenetriamine, dibutylenetriamine, triethylenetetramine, tripropylenetetramine, tributylenetetramine and tetraethylenepentamine. , Tetrapropylene pentamine, tetrabutylenepentamine, pentaethylenehexamine, hexaethyleneheptamine, heptaethyleneoctamine, iminobispropylamine, monomethylaminopropylamine, methyliminobispropylamine, 1,3-propanediamine, 1, Examples thereof include 4-butanediamine, hexamethylenediamine, octamethylenediamine, N, N'-dimethylethylenediamine, N, N'-diethylpropylenediamine, N, N'-diethylethylenediamine, N, N'-diethylpropylenediamine and the like. ..
Examples of cycloalkane-based amines include 1,3-bis (aminomethyl) cyclohexane and the like.
Examples of the cyclic imine polymer include polyethyleneimine, polypropyleneimine, poly-3-methylpropylimine, poly-2-ethylpropylimine and the like.
Examples of the unsaturated amine polymer include polyvinylamine and polyallylamine.
Examples of polyamine-based amines include unsaturated amines such as vinylamine and allylamine, dimethylacrylamide, styrene, methyl acrylate, methyl methacrylate, acrylic acid, methacrylic acid, styrene sulfonic acid and the like, and salts thereof. , Copolymers with other monomers having unsaturated bonds copolymerizable with unsaturated amines, polyethyleneimine-benzyl chloride condensates and the like.

The above amines may be used alone or in combination of two or more.

Among the above amines, piperazine-based, alkyl-based, and polyamine-based are preferable, piperazine-based and polyamine-based are more preferable, and piperazine-based is particularly preferable, because the effect of the present invention tends to be more remarkable. Among the piperazine type, piperazine is preferable, among the alkyl type, diethylamine is preferable, among the polyamine type, diethylenetriamine, triethylenetetramine, tetraethylenepentamine and polyethyleneimine / benzyl chloride condensate are preferable, and among the polyamine type, tetraethylenepentamine is more preferable. ..

Dithiocarbamate is a compound (salt-type functional group) in which a salt of a dithioic acid group is bonded to a nitrogen atom of amines. Further, two or more dithioic acid group salts may be introduced into one molecule of amines. Examples of the salt-type functional group include sodium salt, potassium salt, magnesium salt, calcium salt, barium salt, amine salt and the like, but sodium salt and potassium salt are usually preferable. Such a compound can be obtained by reacting amines with carbon disulfide, and the reaction between amines and carbon disulfide can be carried out with an alkali such as a metal hydroxide as exemplified above as a salt. A compound having a salt-type functional group can be obtained by carrying out in the presence or by treating with an alkali after the reaction. Dithiocarbamate may be used alone or in combination of two or more.

In the present invention, the amount of dithiocarbamate used is not particularly limited, but is preferably 0.05% by mass or more, more preferably 0.1% by mass or more, and more preferably 0.5% by mass or more with respect to the carbon-containing fly ash. More preferably, 1% by mass or more is particularly preferable. Further, 30% by mass or less is preferable, 20% by mass or less is more preferable, 15% by mass or less is further preferable, and 10% by mass or less is particularly preferable. When the amount used is within this range, it is suitable for obtaining the effect of the present invention. Excessive use of dithiocarbamate may re-elute the mercury immobilized by dithiocarbamate. Further, when the total amount with water increases, the appearance of the treated ash does not become lumpy but becomes slurry, and there is a possibility that the immobilization of mercury becomes insufficient.

From the viewpoint of the reaction efficiency of heavy metal and dithiocarbamate, if the treated ash is in the form of a dry powder, the heavy metal ion and dithiocarbamate cannot move smoothly, and the contact frequency decreases, so that the reaction does not proceed sufficiently. In powdered fly ash, the zero-valent, monovalent, double-salt mercury that does not react with dithiocarbamate elutes without being oxidized. When the treated ash is liquid, the concentration of heavy metal ions and dithiocarbamic acid becomes low, and the contact frequency decreases, so that the reaction probability (frequency) decreases. Therefore, in order to properly treat mercury, it is desirable to add an optimum amount of water to form a lump or slurry having an appropriate amount of water, and it is more desirable to form a lump.

In the present invention, the amount of water used is 20% by mass or more, preferably 25% by mass or more, and more preferably 30% by mass or more with respect to the carbon-containing fly ash. Further, it is 150% by mass or less, preferably 100% by mass or less, more preferably 80% by mass or less, further preferably 60% or less, and particularly preferably 40% by mass or less with respect to the carbon-containing fly ash. Carbon-containing fly ash is more difficult to mix uniformly with water than normal fly ash, but by adding more than a specific amount, dithiocarbamate, which is a chelating agent, is more efficient than mercury in carbon-containing fly ash. Good contact promotes complex formation. As a result, the effect of the present invention can be obtained without reducing the effect of suppressing the elution of mercury by the post-treatment after kneading or excessively delaying the immobilization. If the amount of water used is excessive, it may become a slurry instead of a lump, and the immobilization of mercury may be insufficient. When the amount of water used is 20% by mass or more and 60% by mass or less with respect to the carbon-containing fly ash, the effect of the present invention tends to be remarkable, and when it is 25% by mass or more and 40% by mass or less, more. It tends to be noticeable.

In the present invention, when dithiocarbamate and water are kneaded with carbon-containing fly ash, dithiocarbamate and water may be added to the carbon-containing fly ash at the same time, or these may be added separately. Normally, dithiocarbamate and water are added to carbon-containing fly ash, but the procedure for adding and mixing dithiocarbamate, water, and carbon-containing fly ash is optional. When dithiocarbamate and water are added to the carbon-containing fly ash, the method is not particularly limited, and examples thereof include a spraying method.

In the present invention, other components can be used together with dithiocarbamate and water as long as the effect is not impaired. Examples of such other components include, but are not limited to, a flocculant, a pH adjuster, a rust preventive, and the like.

In the present invention, the elution amount of mercury from fly ash after post-treatment may be set to 0.005 mg / L or less of the landfill standard value in accordance with Notification No. 13 of the Environment Agency of 1973 from the viewpoint of the landfill standard value. It is more preferably 0.002 mg / L or less, further preferably 0.001 mg / L or less, and particularly preferably 0.0005 mg / L or less. From the viewpoint of the environmental standard value in Notification No. 46 of the Environment Agency of 1991, it is desirable that the elution amount is 0.0005 mg / L or less.

In the present invention, the post-treatment after kneading the fly ash with dithiocarbamic acid, water or the like stably suppresses the elution of mercury by allowing it to stand or stirring. For example, the post-treatment time is not particularly limited, but from the viewpoint of stably suppressing mercury elution, 1 day or more is preferable, 4 days or more is more preferable, 7 days or more is further preferable, and 14 days or more is particularly preferable. , 30 days or more is particularly preferable. When the post-treatment time is 1 day or more, the decrease in the mercury elution concentration becomes remarkable. If the post-treatment time is further extended, the effect of re-elution becomes smaller and the mercury elution concentration decreases more stably. When the post-treatment time is within the above range, mercury is sufficiently immobilized by the post-treatment, and it is possible to dispose of it by landfill or the like without storing it for a long period of time. Dithiocarbamate is a compound obtained from piperazine as amines, and when post-treated for 30 days or more after kneading, the effect of the present invention tends to be more remarkable.

In the present invention, the temperature of the post-treatment is more than 0 ° C and less than 80 ° C. As described above, an appropriate amount of water is required for the reaction between dithiocarbamic acid and heavy metal ions to proceed. When the temperature of the post-treatment is 80 ° C. or higher, the water content evaporates and drying proceeds. Therefore, when the temperature is 0 ° C. or lower, the reaction between dithiocarbamate and heavy metal ions does not proceed due to freezing. Since the post-treatment can be left to stand near room temperature, it is possible not to use special equipment for heating and cooling, and mercury is sufficiently fixed by leaving it in an indoor pit or container. Can be changed. In this respect, the post-treatment temperature may be 5 ° C. or higher, 10 ° C. or higher, 20 ° C. or higher, or 25 ° C. or higher. In terms of the effect of the present invention, the temperature of the post-treatment is preferably more than 0 ° C. and 60 ° C. or lower, and more preferably more than 0 ° C. and 40 ° C. or lower. When the temperature of the post-treatment is within this range, mercury can be more stably immobilized. After kneading, post-treatment at a temperature of 25 ° C. or higher and 60 ° C. or lower, and further at 25 ° C. or higher and 40 ° C. or lower tends to make the effect of the present invention remarkable.

The present invention can stably suppress the elution of mercury in carbon-containing fly ash, but it can also suppress the elution of other heavy metals such as lead.

In the present invention, the humidity of the post-treatment is 10% or more, preferably 30% or more, more preferably 40% or more, still more preferably 60%, in order to bring the treated ash into an appropriate wet state. In the present invention, the humidity is a relative humidity (RH), which is the ratio of the actual water vapor pressure of air to the saturated water vapor pressure at a certain temperature. When the humidity of the post-treatment is within this range, mercury can be stably immobilized. Since the post-treatment can be left in the atmosphere, it is possible not to use special equipment for adjusting the humidity, and the mercury can be sufficiently fixed by leaving it in an indoor pit or container. Can be changed. The upper limit of the humidity of the post-treatment is not particularly limited, but if it is exposed to excessive moisture due to wind and rain or the like, mercury may not be treated stably.

The carbon in the carbon-containing fly ash of the present invention is a carbon substance having an adsorptive ability such as activated carbon and unburned carbon. The effect of the present invention is remarkable when the carbon-containing fly ash in the present invention contains more activated carbon than ordinary fly ash.

Maintaining the moist state of the treated ash in the above temperature and humidity environment promotes elution from carbon, further oxidation reaction and chelation reaction between dithiocarbamate and mercury, so that mercury is faster and better. Can be processed. Since the reaction between dithiocarbamate and mercury proceeds by the post-treatment under the above temperature and humidity environment, the post-treatment under specific conditions may be performed continuously or intermittently. When post-processing is performed intermittently under specific conditions, the total time is used as the post-processing time.

In a waste incinerator, fly ash generated by incinerator incinerator is transferred to a partition type bag filter, a distribution type electrostatic precipitator, a cyclone, etc. together with exhaust gas and collected. The collected fly ash is stored in a silo, for example, and then transferred to a batch or continuous kneader, to which dithiocarbamate and water are added, and the ash is uniformly kneaded. The kneaded material from the kneader is carried out by a conveyor and sent to the pit. The post-treatment of the kneaded material can be performed in indoor equipment such as a conveyor or a pit where the kneaded material from the kneading machine is transferred and stored indoors, or in a container or the like. After the post-treatment, it is transferred to a final disposal site by a truck or the like and then landfilled. However, the carbon-containing fly ash treated by the method of the present invention is exposed to moisture such as rainwater and temperature changes such as high temperature. However, the post-treatment stably immobilizes mercury and suppresses elution.

Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples.

The agents used in the following examples and comparative examples are as follows.
(Dithiocarbamate)
Piperazine system Piperazine N, N'-potassium dithiocarbamate diethyl system diethyldithiocarbamate potassium polyamine system N (1), N (2), N (3), N (5) -tetra (dithiocarboxy) tetraethylenepentamine Sodium salt (inorganic drug)
Ferric chloride (40 Baume)
Aluminum sulfate band (8% aluminum oxide equivalent)

Test method Using a porcelain mortar as a container, add the chemicals and water shown in Tables 1 and 2 in the amounts shown in the same table per 100 g of fly ash generated in the waste incinerator, knead for 10 minutes, and mix uniformly. did. Furthermore, the fly ash after kneading was allowed to stand at the temperature, humidity, and time shown in the same table. For the fly ash after the treatment, the elution amounts of mercury and lead were measured based on the Environmental Agency Notification No. 13 test method. At the same time, the pH of the fly ash after the treatment was also measured.

The environmental quality standard for soil is that total mercury is 0.0005 mg / L or less, the elution amount standard is 0.0005 mg / L or less for mercury and its compounds, and alkylmercury is not detected. Lead is 0.3 mg / L in the criteria for specially controlled industrial waste.

For fly ash A to C from waste incineration facilities in various parts of Japan shown in Tables 1 and 2 having different carbon contents, the elution amounts of mercury and lead were measured after kneading the chemical and water. The results are shown in the columns of Tables 1 and 2 on the 0th day after standing. The carbon content is measured according to the measurement method of ignition loss of JIS A 6201 "fly ash for concrete", and the mercury content is measured in 1988 Environmental water pipe No. 127 "sediment survey method" 5.1, total. It was measured according to the mercury analysis method.

Fly ash with a low carbon content has the elution amount of mercury and lead immediately below the standard value after kneading, and can be sufficiently immobilized without being allowed to stand, whereas fly ash A to C containing carbon contains carbon. After kneading, the lead elution amount immediately fell below the standard value, but the mercury elution amount did not fall below the standard value. Immediately after kneading, since it cannot be sufficiently immobilized with a dithiocarbamic acid-based drug, a large amount of mercury (zero-valent, monovalent, double salt) other than Hg ²⁺ is contained, and these mercury are sufficiently immobilized on fly ash. However, it was suggested that it would elute into the filtered water in the elution test. In particular, fly ash A, which has a high carbon content and mercury content, was confirmed to have a large amount of mercury elution immediately after kneading, and may contain a larger amount of mercury (zero-valent, monovalent, double salt) other than Hg ²⁺ . It was suggested. From this, even if activated carbon is used instead of dithiocarbamate, it is considered difficult to sufficiently immobilize mercury because it elutes when it changes to Hg ²⁺ over time.

Next, using fly ash A to C, the amounts of chemicals and water shown in Tables 1 and 2 were added and kneaded, and then allowed to stand under the conditions of the same table, and mercury and lead from the treated fly ash were added. Elution amount was measured. The results are shown in Tables 1 and 2.

In Example 1, a piperazine-based agent was used, the water content was 40% by mass, the standing conditions were a temperature of 25 ° C. and a humidity of 60%. After 15 hours of kneading, there was no change in the amount of mercury eluted. The mercury elution concentration decreased after 1 day of standing, further decreased at 4 and 7 days, and became less than the standard value at 7 to 14 days of standing. It was less than the standard value even after standing for 30 days, and it can be seen that it was stably immobilized without re-eluting. From this result, the effect of standing still was confirmed. The amount of lead elution was less than the standard value immediately after kneading.

In Example 2 of the diethyl system, the elution amount of mercury was 0.002 mg / L from 1 to 30 days of standing, and although it did not fall below the standard value, the elution amount was higher than the elution amount of the raw ash shown in Table 1. Has become low.

In Example 3 of the polyamine system, similarly to Example 1, the mercury elution concentration decreased after 1 day or more of standing, and further decreased to near the reference value by standing for a long time.

In Example 4, the standing temperature was changed from Example 1 to 40 ° C. Although the mercury elution concentration tended to decrease by standing, it took time to fix the mercury elution concentration below the reference value as compared with Example 1. Considering that the amount of elution immediately after kneading is higher than that of Example 1, it is suggested that the effect of standing still is high.

In Example 5, when the standing temperature was changed from Example 1 to 60 ° C., the elution amount decreased in 1 day of standing, and the elution amount did not change until 7 days after that, but it was 0 after 14 days. It was .0006 mg / L, which was less than 0.0005 mg / L after 30 days, and it took time to fix it below the reference value as compared with Example 1. It was suggested that the reaction did not proceed efficiently because the treated ash dried and the frequency of contact between dithiocarbamate and Hg ²⁺ decreased when the ash was allowed to stand at 60 ° C. Contrast of temperature conditions in the post-treatments of Examples 1, 4 and 5 suggests that a moderately wet state is necessary for an efficient reaction.

In Example 6, when a diethyl system was used and the standing temperature was changed from Example 2 to 60 ° C., the elution amount decreased in one day of standing, but no change was observed in the elution amount thereafter.

In Example 7, the humidity of standing still was changed from Example 1 to 30%. Although the mercury elution concentration tended to decrease by standing still, the result was that it took time to decrease the elution amount as compared with Example 1.

In Example 8, when the water content was changed to 25% by mass from Example 1, it took more time to fix the water content below the reference value as compared with Example 1.

In Example 9, when the water content was changed from Example 1 to 100% by mass, the amount of mercury elution decreased by standing, but the amount of elution after 7 days was 0.0019 mg / L, which was higher than that of Example 1. there were.

In Example 10, when the water content was changed from Example 1 to 150% by mass, the amount of mercury elution decreased by standing, but the amount of elution after 7 days was 0.0017 mg / L, which was higher than that of Example 1. there were. The appearance of fly ash after kneading was slurry-like. Therefore, it was suggested that the reaction did not proceed efficiently because the concentration of dithiocarbamate and Hg ²⁺ decreased and the contact frequency decreased, and it took time to decrease the elution amount.

Example 11 using fly ash B (carbon content 7.2% by mass) was treated under the same treatment and post-treatment conditions as in Example 1 using fly ash A (carbon content 9.3% by mass) for 4 days. Later, mercury fell below the standard value.

Example 12 using fly ash C (carbon content 3.3% by mass) was subjected to the same treatment and post-treatment conditions as in Example 1 using fly ash A (carbon content 9.3% by mass) for one day. Later, mercury fell below the standard value.

From Examples 1, 11 and 12, in fly ash having a carbon content of 3% or more, the elution amount of mercury can be treated to a reference value or less in one day or more after the post-treatment, and the carbon content is 7% or more. Fly ash could be treated in 4 days or more, and with a carbon content of 9% or more, it could be treated in 14 days or more. From this result, it was confirmed that in terms of the reduction rate of the elution amount of mercury per hour, the effect of the post-treatment of the present invention becomes more remarkable as the fly ash has a higher carbon content.

In the treatment of fly ash A using piperazine-based dithiocarbamate, among Examples 1, 4, 5, 7 to 10, in Examples 1, 4, 5, and 7, the fly ash during the post-treatment has an appropriate amount of water. It was in the form of a lump, and Example 8 was in the form of powder, and Examples 9 and 10 were in the form of slurry. Therefore, it was suggested that in Examples 1, 4, 5, and 7, the dithiocarbamate and mercury reacted more efficiently than in Examples 8, 9, and 10, and the immobilization proceeded faster.

Inorganic agents were used in Comparative Examples 2 and 3. Although the amount of mercury elution decreased to some extent by standing, the decrease was small and unstable compared to the dithiocarbamine-based drug, and lead could not be immobilized below the standard value.

From Tables 1 and 2, in Examples 1 to 10 using dithiocarbamate, the mercury elution concentration immediately after the treatment and after standing was lower than in Comparative Examples 2 and 3 using the inorganic agent. .. From this, it was confirmed that dithiocarbamate has higher mercury immobilization performance immediately after treatment and after standing than an inorganic drug.

It was confirmed that Example 1 using a piperazine system can fix the mercury elution concentration below the standard value in a shorter number of standing days as compared with Examples 2 and 3 using a diethyl system or a polyamine system. ..

Of Examples 1, 8, 9, and 10 using the piperazine system, Example 1 in which the added water content is 40% by mass includes Example 8 (25% by mass in water content) in which the amount of water added is less than that, and water content. It was confirmed that mercury can be immobilized below the standard value in a shorter number of standing days as compared with Example 9 (water content 100% by mass) and 10 (moisture 150% by mass). From these results, in the present invention, the water content of the fly ash treatment is 20% by mass or more, preferably 25% by mass or more, and 30% by mass, from the viewpoint of efficient reaction between dithiocarbamate and mercury. It was confirmed that the above is better, 150% by mass or less, 100% by mass or less is better, and 40% by mass or less is better.

Of Examples 1 and 7 using the piperazine system, Example 1 having a humidity of 60% had a lower mercury concentration after 4 days of standing as compared with Example 7 having a low humidity of 30%. From this, it was confirmed that mercury was immobilized faster when it was allowed to stand at a humidity of 60% rather than a humidity of 30%, and it was suggested that the reaction proceeded efficiently when there was an appropriate amount of water during the post-treatment. ..

Of Examples 1, 4 and 6 using the piperazine system, Example 1 having a temperature of 25 ° C. was compared with Example 4 (40 ° C.) and Example 6 (60 ° C.) at a higher temperature. It was confirmed that mercury was immobilized below the standard value in a short standing time. Further, when the examples 4 and 6 were compared, the mercury concentration in the example 4 having a temperature of 40 ° C. was lower after 4 days of standing. From this result, it is suggested that mercury can be immobilized by performing post-treatment at a temperature of 25 ° C or higher and 60 ° C or lower, and that mercury immobilization proceeds more efficiently by suppressing the drying of fly ash during post-treatment. Was done.

In Examples 1, 4, 5, 7 to 12 using the piperazine system, the mercury elution concentration decreased from 1 to 4 days of standing, further decreased from 4 to 7 days, and further decreased from 7 days or more. .. Furthermore, it was confirmed that mercury was immobilized without re-elution even after 14 days or more and 30 days or more. From these results, in the immobilization of mercury in carbon-containing fly ash, it is better to set the post-treatment time to 1 day or more, 4 days or more is better, 7 days or more is even better, and 14 days or more is particularly good. It was confirmed that 30 days or more was particularly good.

Claims (5)

A method for treating carbon-containing fly ash having a carbon content of 7% by mass or more and containing mercury.
Without the use of chemicals containing aluminum sulphate bands
A drug containing dithiocarbamate as a main component, which is either a piperazine-based compound or a polyamine-based compound, and 25% by mass or more and 150% by mass or less of water with respect to the carbon-containing fly ash are added together with the carbon-containing fly ash. A method for treating carbon-containing fly ash, in which the kneaded treated ash is allowed to stand or stirred at a temperature of more than 0 ° C. and lower than 80 ° C. and a humidity of 10% or more for 4 days or more to stably suppress the elution of mercury. .. A method for treating carbon-containing fly ash having a carbon content of 7% by mass or more and containing mercury.
Without the use of chemicals containing aluminum sulphate bands
A chemical containing diethyldithiocarbamate as a main component and treated ash obtained by kneading 25% by mass or more and 150% by mass or less of water with the carbon-containing fly ash with respect to the carbon-containing fly ash are mixed at a temperature of more than 0 ° C and less than 80 ° C. A method for treating carbon-containing fly ash, which stably suppresses the elution of mercury by performing a post-treatment of standing or stirring at a humidity of 10% or more for 30 days or more. The method for treating carbon-containing fly ash according to claim 1 or 2, which is post-treated at a humidity of 30% or more after kneading. The method for treating carbon-containing fly ash according to any one of claims 1 to 3, which is post-treated at a temperature of 25 ° C. or higher and 60 ° C. or lower after kneading. The method for treating carbon-containing fly ash according to claim 1, wherein the dithiocarbamate is a piperazine-based compound and is post-treated for 30 days or more after kneading.