JP2020044513A - Treatment method of fly ashes containing carbon involving mercury - Google Patents

Abstract

To provide a treatment method capable of stably suppressing elution of mercury from fly ashes containing carbon.SOLUTION: The treatment method of fly ashes containing carbon involving mercury is characterized by that treated ashes obtained by kneading the fly ashes containing carbon together with a dithiocarbamic acid salt and water of 20 mass% or over and 150 mass% or under with respect to the fly ashes containing carbon is subjected to a post treatment at a temperature of over 0°C and under 80°C and a humidity of 10% or over to stably suppress elution of mercury.SELECTED DRAWING: None

Description

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

  Fly ash generated during the incineration of municipal solid waste and industrial waste may contain a large amount of heavy metals harmful to the human body, such as mercury. Separation and collection of household waste is progressing, but the incorporation of batteries, thermometers, fluorescent lights, etc. cannot be completely avoided, and heavy metals such as mercury are contained in fly ash generated when incinerated in incineration facilities. When this heavy metal is eluted into groundwater, rivers, and seawater, serious environmental pollution is caused.

  The Minamata Convention on Mercury was adopted and signed in 2013 with the aim of protecting human health and the environment from anthropogenic emissions of mercury and mercury compounds. There is growing momentum to regulate mercury emissions into the country.

  Incinerated fly ash is a specially managed municipal waste, and requires intermediate treatment such as chemical treatment. Since incineration fly ash contains heavy metals, and after being subjected to landfill treatment, heavy metals are eluted by rainwater or the like. Therefore, a method of immobilizing and suppressing elution is generally used.

  The method by chemical treatment is a method in which a chemical, water and incinerated fly ash are kneaded to fix harmful heavy metals. Drugs used for this purpose include organic chelating agents such as dithiocarbamates and inorganic drugs such as iron compounds. A triazole compound has also been proposed as an agent for fly ash immobilization treatment for mercury (Patent Document 1). At incineration plants, as a measure against dioxin, activated carbon is also blown into the inlet of a filter-type dust collector in a garbage incineration facility (Patent Document 2). In recent years, activated carbon blowing technology has reduced mercury in fly ash. It is also studied from the aspect of immobilization and reduction of mercury contained in exhaust gas (Patent Document 3).

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

  In particular, in the case of carbon-containing fly ash, considering the properties of heavy metal adsorption and re-elution due to its porous structure, mercury may not be immobilized satisfactorily under the same amount of water as general fly ash processing conditions. If the treated ash is stored in a place exposed to changes in the surrounding temperature and humidity and exposed to wind and rain after kneading the chemical, water and fly ash, mercury may not be fixed well, and There is a concern that the elution of mercury cannot be stably suppressed after an elution test performed for inspection or after being transported from a waste incineration facility and landfilled. Patent Literatures 4 and 5 propose a technique in which a chemical, water, and incineration fly ash are kneaded and then cured at a high temperature to suppress elution of heavy metals. However, equipment for raising the temperature from room temperature is proposed. It is desirable that mercury can be immobilized without adding such special conditions.

JP 2013-193039 A JP-A-2003-1221 JP 2004-160306 A JP 2006-150339 A JP 2005-118617 A

  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 problem, a method for treating a carbon-containing fly ash of the present invention is a method for treating a carbon-containing fly ash containing mercury, and comprises a dithiocarbamate and 20 mass% of the carbon-containing fly ash. % To 150% by mass of water is kneaded with the carbon-containing fly ash, and the treated ash is post-treated at a temperature of more than 0 ° C and less than 80 ° C and a humidity of 10% or more to stably suppress the elution of mercury. And

  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.

  Fly ash targeted by the present invention is not particularly limited, for example, when incineration of municipal solid waste, industrial waste, sewage sludge, and the like in an incinerator, incineration fly ash, incineration ash generated accompanying the combustion exhaust gas And fly ash generated when melting ash and fly ash in a melting furnace, electric furnace dust generated from an electric furnace for refining metal, and the like. In an incineration facility, these are collected by a partition-type bag filter, a flow-type electric dust collector, a cyclone, or the like.

  In the present invention, "carbon-containing fly ash" is fly ash containing carbon generated in an incineration facility, and the origin of carbon is not particularly limited. For example, activated carbon blown in an incineration facility, adsorption of unburned carbon, etc. Carbon materials and the like having the ability. The carbon-containing fly ash includes, for example, fly ash containing 1% by mass or more of carbon based on the total amount of fly ash, and the carbon content may be 3% by mass or more, and more preferably 7% by mass or more. May be present, in particular at least 9% by weight.

  The effect of the present invention becomes more remarkable when the treated ash immediately after kneading with dithiocarbamate and water has a mercury elution amount of more than 0.0005 mg / L.

The action of stably suppressing the elution of mercury from the carbon-containing fly ash in the present invention is not intended to be limited to this, but is considered as follows from the cause of the elution of mercury and the mechanism of immobilization.
(1) Form of mercury Mercury in fly 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 (zero-valent, one-valent, double salts) cannot be immobilized by 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 possibility that the substance is eluted again due to a change in environment or the like. In the present invention, it is considered that zero-valent and monovalent mercury are oxidized to divalent mercury due to a change with time after kneading, and thus are fixed in the presence of a dithiocarbamic acid group. The double salt mercury also stabilizes the adsorbed mercury by binding the carboxyl groups on the carbon surface to the calcium in the fly ash and converting the calcium carbonate adsorbed on the surface to a hydroxide.
(2) Carbon surface structure and adsorbed substances Carboxy groups and calcium carbonate are adsorbed on the carbon and activated carbon surfaces contained in fly ash. Mercury reacting with carboxyl groups on the activated carbon surface may ion-exchange with calcium and the like in the ash over time and elute again. 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 fixed.

  As the dithiocarbamate used in the present invention, a compound obtained by a general production method can be used.For example, an amine is reacted with carbon disulfide in the presence of a base, and the dithiocarbamate is added to the nitrogen of the amine. Compounds obtained by introduction are mentioned.

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

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

(Alcoholic)
Examples of alcohol-based amines include monoalcoholamine and dialcoholamine.
Examples of the monoalcoholamine include monomethanolamine, monoethanolamine, monopropanolamine, monoisopropanolamine, monobutanolamine, monoisobutanolamine and the like.
Examples of the dialcoholamine include dimethanolamine, diethanolamine, dipropanolamine, diisopropanolamine, dibutanolamine, diisobutanolamine, and the like.

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

(Heterocyclic system)
Examples of the heterocyclic amines include piperazine, piperidine, morpholine, thiomorpholine, imidazolidine, pyrazolidine, pyrrolidine, imidazole, pyrazole, pyrrole, and the like.
[Piperazine type]
Examples of the 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, 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, and 2,3-dimethyl-5-ethylpiperazine.
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 type]
Examples of piperidine-based amines include piperidine, monoalkylpiperidine, dialkylpiperidine, trialkylpiperidine, tetraalkylpiperidine, and pentaalkylpiperidine.
Examples of the monoalkylpiperidine include 2-methylpiperidine, 2-ethylpiperidine, 2-propylpiperidine, 2-isopropylpiperidine, 2-butylpiperidine, 2-isobutylpiperidine, 3-methylpiperidine, 3-ethylpiperidine, and 3-ethylpiperidine. Propyl piperidine, 3-isopropyl piperidine, 3-butyl piperidine, 3-isobutyl tipiperidine, 4-methyl piperidine, 4-ethyl piperidine, 4-propyl piperidine, 4-isopropyl piperidine, 4-butyl piperidine, 4-isobutyl piperidine, etc. No.
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 pentaalkylpiperidine include pentaalkylpiperidines such as 2,3,4,5,6-pentamethylpiperidine and 2,3,4,5,6-pentaethylpiperidine.
[Morpholine type]
Examples of the morpholine-based amines include morpholine, monoalkyl morpholine, dialkyl morpholine, trialkyl morpholine, and tetraalkyl morpholine.
Examples of the monoalkylmorpholine include 2-methylmorpholine, 2-ethylmorpholine, 2-propylmorpholine, 2-isopropylmorpholine, 2-butylmorpholine, 2-isobutylmorpholine, 3-methylmorpholine, 3-ethylmorpholine, and 3-ethylmorpholine. Examples thereof include propyl morpholine, 3-isopropyl morpholine, 3-butyl morpholine, and 3-isobutyl morpholine.
Examples of the dialkylmorpholine 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 the thiomorpholine amines include thiomorpholine, monoalkylthiomorpholine, dialkylthiomorpholine, trialkylthiomorpholine, and tetraalkylthiomorpholine.
Examples of the monoalkylthiomorpholine include 2-methylthiomorpholine, 2-ethylthiomorpholine, 2-propylthiomorpholine, 2-isopropylthiomorpholine, 2-butylthiomorpholine, 2-isobutylthiomorpholine, 3-methylthiomorpholine, and 3-methylthiomorpholine. Examples include ethylthiomorpholine, 3-propylthiomorpholine, 3-isopropylthiomorpholine, 3-butylthiomorpholine, and 3-isobutylthiomorpholine.
Examples of the dialkylthiomorpholine include 2,3-dimethylthiomorpholine, 2,5-diethylthiomorpholine, 2,6-dipropylthiomorpholine, 2-ethyl-3-methylthiomorpholine, and 2-methyl-6-propylthio Morpholine and the like.
Examples of the trialkylthiomorpholine include 2,3,5-trimethylthiomorpholine and 2,3,6-triethylthiomorpholine.
Examples of the tetraalkylthiomorpholine include 2,3,5,6-tetramethylthiomorpholine and 2-ethyl-3,5,6-trimethylthiomorpholine.
[Imidazolidine type]
Examples of imidazolidine-based amines include imidazolidine, monoalkyl imidazolidine, dialkyl imidazolidine, trialkyl imidazolidine, tetraalkyl imidazolidine, and the like.
Examples of the monoalkyl imidazolidine include 1-methyl imidazolidine, 1-ethyl imidazolidine, 1-propyl imidazolidine, 1-isopropyl imidazolidine, 1-butyl imidazolidine, 1-isobutyl imidazolidine, and 2-methyl imidazolidine. , 2-ethylimidazolidin, 2-propylimidazolidin, 2-isopropylimidazolidin, 2-butylimidazolidin, 2-isobutylimidazolidin, 3-methylimidazolidin, 3-ethylimidazolidin, 3-propylimidazolidin, 3- -Isopropyl imidazolidine, 3-butyl imidazolidine, 3-isobutyl imidazolidine, 4-methyl imidazolidine, 4-ethyl imidazolidine, 4-propyl imidazolidine, 4-isopropyl imidazolidine, 4-bu Le imidazolidine, 4-isobutyl-imidazolidine, 5-methyl-imidazolidine, 5-ethyl-imidazolidine, 5-propyl-imidazolidine, 5-isopropyl imidazolidine, 5-butyl imidazolidine, 5-isobutyl-imidazolidine and the like.
Examples of the dialkyl imidazolidine include 2,3-dimethyl imidazolidine, 2,5-diethyl imidazolidine, 4,5-dipropyl imidazolidine, 1-methyl-4-propyl imidazolidine, and the like.
Examples of the trialkyl imidazolidine include 2,4,5-trimethyl imidazolidine, 3,4-diethyl-5-propyl imidazolidine and the like.
Examples of the tetraalkyl imidazolidine include 2,3,4,5-tetramethyl imidazolidine and 1,2,4,5-tetramethyl imidazolidine.
[Pyrazolidine type]
Examples of pyrazolidine-based amines include pyrazolidine, monoalkylpyrazolidine, dialkylpyrazolidine, trialkylpyrazolidine, tetraalkylpyrazolidine, and the like.
Examples of the monoalkylpyrazolidine include 1-methylpyrazolidine, 1-ethylpyrazolidine, 1-propylpyrazolidine, 1-isopropylpyrazolidine, 1-butylpyrazolidine, 1-isobutylpyrazolidine. 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, - methyl pyrazolidine, 5-ethyl-pyrazolidine, 5-propyl pyrazolidine, 5-isopropyl-pyrazolidine, 5-butyl-pyrazolidine, and 5-isobutyl pyrazolidine and the like.
Examples of the dialkylpyrazolidine include 3,4-dimethylpyrazolidine, 3,5-diethylpyrazolidine, 2,5-dipropylpyrazolidine, 3-methyl-5-propylpyrazolidine and the like. Can be
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]
Examples of pyrrolidine-based amines include pyrrolidine, monoalkylpyrrolidine, dialkylpyrrolidine, trialkylpyrrolidine, and tetraalkylpyrrolidine.
Examples of the monoalkylpyrrolidine include 2-methylpyrrolidine, 2-ethylpyrrolidine, 2-propylpyrrolidine, 2-isopropylpyrrolidine, 2-butylpyrrolidine, 2-isobutylpyrrolidine, 3-methylpyrrolidine, 3-ethylpyrrolidine, and 3-methylpyrrolidine. Examples thereof include propylpyrrolidine, 3-isopropylpyrrolidine, 3-butylpyrrolidine, and 3-isobutylpyrrolidine.
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-trimethylpyrrolidine and the like.
[Imidazole type]
Examples of the imidazole-based amines include, for example, imidazole, monoalkylimidazole, dialkylimidazole, and trialkylimidazole.
Examples of the monoalkyl imidazole include 2-methylimidazole, 2-ethylimidazole, 2-propylimidazole, 2-isopropylimidazole, 2-butylimidazole, 2-isobutylimidazole, 4-methylimidazole, 4-ethylimidazole, and 4-methylimidazole. Propylimidazole, 4-isopropylimidazole, 4-butylimidazole, 4-isobutylimidazole, 5-methylimidazole, 5-ethylimidazole, 5-propylimidazole, 5-isopropylimidazole, 5-butylimidazole, 5-isobutylimidazole and the like. Can 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 and 2,4,5-triethylimidazole.
[Pyrazole type]
Examples of the pyrazole-based amines include, for example, 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-ethylpyrazole Propyl pyrazole, 4-isopropyl pyrazole, 4-butyl pyrazole, 4-isobutyl pyrazole, 5-methyl pyrazole, 5-ethyl pyrazole, 5-propyl pyrazole, 5-isopropyl pyrazole, 5-butyl pyrazole, 5-isobutyl pyrazole, and the like. Can be
Examples of the dialkylpyrazole include 3,4-dimethylpyrazole, 3,5-diethylpyrazole, 3,4-dipropylpyrazole, and 3-ethyl-5-methylpyrazole.
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, and tetraalkylpyrrole.
Examples of the monoalkylpyrrole include 2-methylpyrrole, 2-ethylpyrrole, 2-propylpyrrole, 2-isopropylpyrrole, 2-butylpyrrole, 2-isobutylpyrrole, 3-methylpyrrole, 3-ethylpyrrole, and 3-ethylpyrrole. 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 and 2,3,5-triethylpyrrole.
Examples of the tetraalkylpyrrole include 2,3,4,5-tetramethylpyrrole and 2-ethyl-3,4,5-trimethylpyrrole.

(Polyamine type)
Examples of the polyamine-based amines having two or more amino groups include, in addition to the compounds exemplified above, aliphatic amine-based, cycloalkane-based, cyclic imine polymers, and unsaturated amine polymers.
Examples of the aliphatic amine-based amines include, for example, ethylenediamine, propylenediamine, butylenediamine, hexamethylenediamine, diethylenetriamine, dipropylenetriamine, dibutylenetriamine, triethylenetetramine, tripropylenetetramine, tributylenetetramine, and tetraethylenepentamine. , Tetrapropylenepentamine, tetrabutylenepentamine, pentaethylenehexamine, hexaethyleneheptamine, heptaethyleneoctamine, iminobispropylamine, monomethylaminopropylamine, methyliminobispropylamine, 1,3-propanediamine, 1, 4-butanediamine, hexamethylenediamine, octamethylenediamine, N, N'-dimethylethylenediamine, N, N'-diethylprodiamine Diamine, N, N'-diethyl ethylenediamine, N, N'-diethyl propylene diamine and the like.
Examples of cycloalkane-based amines include 1,3-bis (aminomethyl) cyclohexane.
Examples of the cyclic imine polymer include polyethylene imine, polypropylene imine, poly-3-methylpropyl imine, poly-2-ethylpropyl imine, and the like.
Examples of unsaturated amine polymers include polyvinylamine, polyallylamine, and the like.
Examples of polyamine-based amines include, for example, unsaturated amines such as vinylamine and allylamine, and dimethylacrylamide, styrene, methyl acrylate, methyl methacrylate, acrylic acid, methacrylic acid, styrene sulfonic acid, and salts thereof. And a copolymer with another monomer having an unsaturated bond copolymerizable with an unsaturated amine, and a polyethyleneimine / benzyl chloride condensate.

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

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

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

  In the present invention, the amount of the dithiocarbamate used is not particularly limited, but is preferably 0.05% by mass or more, more preferably 0.1% by mass or more, and preferably 0.5% by mass or more based on the carbon-containing fly ash. More preferably, it is particularly preferably 1% by mass or more. Further, it is preferably at most 30% by mass, more preferably at most 20% by mass, further preferably at most 15% by mass, particularly preferably at most 10% by mass. When the amount is within this range, it is suitable for obtaining the effects of the present invention. If the dithiocarbamate is used in excess, the mercury immobilized by the dithiocarbamate may be re-eluted. In addition, when the total amount with water increases, the appearance of the treated ash becomes a slurry instead of a lump, and there is a possibility that the fixation of mercury becomes insufficient.

  From the viewpoint of the reaction efficiency between the heavy metal and the dithiocarbamate, if the treated ash is in the form of a dry powder, the heavy metal ion and the dithiocarbamate cannot move smoothly, and the contact frequency decreases, so that the reaction does not proceed sufficiently. In the powdery fly ash, mercury of zero valence, one valence and double salt which does not react with dithiocarbamate is eluted without being oxidized. When the treated ash is in a liquid state, the concentrations of heavy metal ions and dithiocarbamic acid decrease, and the frequency of contact decreases, so that the probability (frequency) of the reaction decreases. Therefore, in order to properly treat mercury, it is desirable to add an optimal amount of water to form a lump or slurry having an appropriate amount of water, and more desirably 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 based on the carbon-containing fly ash. Further, the content is 150% by mass or less, preferably 100% by mass or less, more preferably 80% by mass or less, still more preferably 60% or less, particularly preferably 40% by mass or less based on the carbon-containing fly ash. Carbon-containing fly ash is more difficult to mix uniformly with water than ordinary fly ash, but by adding more than a certain amount, the chelating agent dithiocarbamate is less efficient than mercury in carbon-containing fly ash. Good contact promotes complex formation. Thereby, the effects of the present invention can be obtained without reducing the effect of suppressing the elution of mercury by the post-treatment after kneading or without excessively delaying the immobilization. If the amount of water used is excessive, there is a possibility that the slurry does not become a lump but becomes a slurry and the fixation of mercury becomes insufficient. When the amount of water 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 the amount is 25% by mass or more and 40% by mass or less, Tends to be noticeable.

  In the present invention, when kneading the dithiocarbamate and water with the carbon-containing fly ash, the dithiocarbamate and water may be added simultaneously to the carbon-containing fly ash, or they may be added separately. Usually, dithiocarbamate and water are added to the carbon-containing fly ash, but the procedure of adding and mixing the dithiocarbamate, water, and the carbon-containing fly ash is optional. When the dithiocarbamate and water are added to the carbon-containing fly ash, the method is not particularly limited, and examples thereof include a method of spraying.

  In the present invention, other components can be used together with dithiocarbamate and water as long as the effects are not impaired. Such other components are not particularly limited, but include, for example, a flocculant, a pH adjuster, and a rust inhibitor.

  In the present invention, the amount of mercury eluted from the fly ash after the post-treatment is set at 0.005 mg / L or less of the landfill standard value in accordance with the Notification of the Environment Agency of 1973, from the viewpoint of the landfill standard value. Preferably, it is 0.002 mg / L or less, more preferably 0.001 mg / L or less, and particularly preferably 0.0005 mg / L or less. From the viewpoint of environmental standard values in Notification No. 46 of the Environment Agency in 1991, it is desirable that the elution amount be 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 or stirs to stably suppress the elution of mercury. For example, the post-treatment time is not particularly limited, but is preferably 1 day or more, more preferably 4 days or more, still more preferably 7 days or more, and particularly preferably 14 days or more, from the viewpoint of stably suppressing the elution of mercury. And more preferably 30 days or more. When the time of the post-treatment is 1 day or more, the decrease in the mercury elution concentration becomes remarkable. When the post-treatment time is further increased, the effect of re-elution is reduced, and the mercury elution concentration is more stably reduced. When the time of the post-treatment is in the above range, the post-treatment can sufficiently fix the mercury, and can be disposed of by landfill or the like without being stored for a long period of time. The dithiocarbamate is a compound obtained from piperazine as an amine, and the effect of the present invention tends to be more remarkable when post-treated for 30 days or more after kneading.

  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. If the temperature of the post-treatment is 80 ° C. or higher, moisture evaporates and drying proceeds. If the temperature is 0 ° C. or lower, the reaction between the dithiocarbamate and the heavy metal ion does not proceed due to freezing. Since the post-treatment can be allowed to stand at around room temperature, it is possible to use no special equipment for heating or cooling, and the mercury can be sufficiently fixed by leaving it in an indoor pit or container. Can be In this regard, the post-treatment temperature may be 5 ° C or higher, 10 ° C or higher, 20 ° C or higher, or 25 ° C or higher. From the viewpoint of the effects of the present invention, the temperature of the post-treatment is preferably higher than 0 ° C and 60 ° C or lower, more preferably higher 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. When the post-treatment is performed at a temperature of 25 ° C. or more and 60 ° C. or less, and further at a temperature of 25 ° C. or more and 40 ° C. or less after the kneading, the effect of the present invention tends to be significant.

  The present invention can stably suppress the elution of mercury in carbon-containing fly ash, but 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, and still more preferably 60% in order to make the treated ash in an appropriate wet state. In the present invention, humidity refers to relative humidity (RH), which is the ratio of the actual water vapor pressure to the saturated water vapor pressure at a certain air temperature. When the humidity of the post-treatment is within this range, mercury can be stably immobilized. Since the post-treatment can be allowed to stand in the atmosphere, it is possible to use no special equipment for adjusting humidity, and it is possible to fix mercury sufficiently by leaving it in indoor pits or containers. Can be Although the upper limit of the humidity of the post-treatment is not particularly limited, there is a possibility that mercury may not be stably treated when exposed to excessive moisture due to wind and rain.

  The carbon in the carbon-containing fly ash of the present invention is a carbon substance having an adsorption 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.

  If the wet state of the treated ash is maintained in the above temperature and humidity environment, elution from carbon, oxidation reaction and chelation reaction between dithiocarbamate and mercury are promoted, so mercury is more quickly and favorably. Can be processed. From the viewpoint that the reaction between dithiocarbamate and mercury proceeds by performing 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 refuse incineration facility, fly ash generated by incineration in an incinerator is transported together with exhaust gas to a partition-type bag filter, a flow-type electric dust collector, a cyclone, etc., and collected. The collected fly ash is stored in, for example, a silo, and then transferred to a batch or continuous kneader, to which dithiocarbamate and water are added and uniformly kneaded. The kneaded material discharged from the kneader is carried out by a conveyor and sent to a pit. Post-processing of the kneaded material can be performed in indoor equipment such as a conveyor and a pit, or in a container or the like where the kneaded material discharged from the kneader is transferred and stored indoors. After the post-treatment, the carbon-containing fly ash treated by the method of the present invention is exposed to moisture such as rainwater or a temperature change such as high temperature after being transferred to a final disposal site or the like by a truck or the like. Also, the post-treatment stably fixes the mercury and suppresses the elution.

  Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

The drugs used in the following examples and comparative examples are as follows.
(Dithiocarbamate)
Piperazine type Piperazine N, N'-dipotassium potassium dithiocarbamate diethyl system Diethylamine dithiocarbamate polyamine system N (1), N (2), N (3), N (5) -tetra (dithiocarboxy) tetraethylenepentamine sodium salt (Inorganic drug)
Ferric chloride (40 Baume)
Sulfuric acid band (8% aluminum oxide equivalent)

Test method Using a mortar made of porcelain as a container, per 100 g of fly ash generated in a garbage incineration plant, add the chemicals and water shown in Tables 1 and 2 in the amounts shown in the same table, knead for 10 minutes, and mix uniformly did. Further, the fly ash after kneading was allowed to stand at the temperature, humidity, and time shown in the same table. With respect to the fly ash after the treatment, the elution amounts of mercury and lead were measured based on the Environment Agency Notification No. 13 test method. In addition, the pH of the fly ash after the treatment was also measured.

  The environmental standard for soil is 0.0005 mg / L or less for total mercury, the standard for elution is 0.0005 mg / L for mercury and its compounds, and no alkylmercury is detected. The standard for lead is 0.3 mg / L in the criteria for specially controlled industrial waste.

  With respect to fly ashes A to C having different carbon contents from waste incineration facilities in various parts of Japan shown in Tables 1 and 2, after kneading the chemicals and water, the elution amounts of mercury and lead were measured. The results are shown in the column on day 0 after standing in Tables 1 and 2. The carbon content was measured in accordance with the method for measuring ignition loss of JIS A 6201 “Fly ash for concrete”, and the mercury content was measured in 1988, Environmental Water Pipe No. 127, “Methods for Examining Sediment”, 5.1. It was measured according to the mercury analysis method.

Fly ash with a low carbon content immediately after kneading, the elution amount of mercury and lead becomes less than the reference value, and sufficient fixation is possible without standing, whereas carbon-containing fly ash A to C After kneading, the elution amount of lead immediately fell below the reference value, but the elution amount of mercury did not fall below the reference value. Immediately after kneading, since the dithiocarbamic acid-based drug cannot be sufficiently immobilized, a large amount of mercury other than Hg ²⁺ (zero-valent, monovalent, double salt) is contained, and the mercury is sufficiently fixed to fly ash. However, it was suggested by the dissolution test that the compound eluted into the filtered water. In particular, fly ash A, which has a high carbon content and a high mercury content, has been confirmed to have a large amount of mercury eluted immediately after kneading, and may contain more mercury (0-valent, monovalent, double salt) other than Hg ^2+. It was suggested. From this, even if activated carbon is used in place of dithiocarbamate, it is considered difficult to sufficiently immobilize mercury because Hg ²⁺ elutes when it is changed over time.

  Next, after using the fly ashes A to C to add and knead the chemicals and water in the amounts shown in Tables 1 and 2, the mixture was allowed to stand still under the conditions shown in the table, and mercury and lead from the treated fly ash were added. Was eluted. The results are shown in Tables 1 and 2.

  In Example 1, a piperazine-based drug was used, the water content was 40% by mass, and the stationary conditions were a temperature of 25 ° C. and a humidity of 60%. After 15 hours of kneading, there was no change in the elution amount of mercury. The mercury elution concentration decreased after 1 day or more of standing, and further decreased on 4 days and 7 days, and became lower than the reference value between 7 days and 14 days of standing. It is less than the reference value even after 30 days of standing, and it can be seen that it is stably immobilized without re-elution. From these results, the effect of standing was recognized. The amount of lead eluted was below the reference value immediately after kneading.

  In Example 2 of the diethyl series, the elution amount of mercury was 0.002 mg / L from 1 to 30 days of standing and did not fall below the reference value, but the elution amount was higher than the elution amount of raw ash shown in Table 1. Became lower.

  In the case of the polyamine-based Example 3, as in Example 1, the concentration of mercury eluted decreased after standing for one day or more, and decreased to near the reference value by standing for a longer period of time.

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

In Example 5, when the standing temperature was changed to 60 ° C. from Example 1, the amount of elution decreased after one day of standing, and no change was observed in the amount of elution after 7 days. 0006 mg / L, after 30 days, it was less than 0.0005 mg / L, and compared with Example 1, it took time to fix it below the reference value. When left at 60 ° C., the treated ash dried and the frequency of contact between dithiocarbamate and Hg ²⁺ decreased, suggesting that the reaction did not proceed efficiently. Comparison of the temperature conditions in the post-treatments of Examples 1, 4, and 5 suggested that an appropriate wet state was necessary for an efficient reaction.

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

  In Example 7, the static humidity was changed from Example 1 to 30%. The mercury elution concentration tended to decrease with standing, but as compared with Example 1, it took longer to reduce the elution amount.

  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 to the reference value or less than in Example 1.

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

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

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

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

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

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

  Comparative Examples 2 and 3 used inorganic drugs. The amount of mercury eluted by standing still decreased to some extent, but the decrease was small and unstable compared to dithiocarbamine drugs, and lead could not be fixed below the standard value.

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

  It was confirmed that in Example 1 using a piperazine system, the mercury elution concentration could be immobilized below the reference value in a short period of standing compared to Examples 2 and 3 using a diethyl system or a polyamine system. .

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

  Among 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 than that of Example 7 having a low humidity of 30%. From this, it was confirmed that the mercury was fixed more quickly when left standing at a humidity of 60% than at a humidity of 30%, and it was suggested that the reaction proceeded efficiently if there was appropriate moisture during the post-treatment. .

  Among Examples 1, 4, and 6 using the piperazine system, Example 1 at a temperature of 25 ° C. was compared with Examples 4 (40 ° C.) and Example 6 (60 ° C.) at higher temperatures. It was confirmed that the mercury was fixed below the reference value in a short standing time. Further, when comparing Examples 4 and 6, Example 4 at a temperature of 40 ° C. had a lower mercury concentration after 4 days of standing. From these results, it is suggested that mercury can be immobilized when post-treatment is performed at a temperature of 25 ° C. or more and 60 ° C. or less, and the immobilization of mercury proceeds more efficiently when the drying of fly ash during the post-treatment is suppressed. Was done.

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

Claims (8)

A method for treating carbon-containing fly ash containing mercury,
A treated ash obtained by kneading dithiocarbamate and 20% by mass or more and 150% by mass or less of water with respect to the carbon-containing fly ash together with the carbon-containing fly ash at a temperature exceeding 0 ° C. and less than 80 ° C. and a humidity of 10% or more A method for treating carbon-containing fly ash, which is treated to stably suppress the elution of mercury.   The method for treating carbon-containing fly ash according to claim 1, wherein post-treatment is performed at a humidity of 30% or more after kneading.   The method for treating carbon-containing fly ash according to claim 1 or 2, wherein after-kneading is carried out at a temperature of from 25 ° C to 60 ° C.   The method for treating carbon-containing fly ash according to any one of claims 1 to 3, wherein post-treatment is performed for one day or more after kneading.   The method for treating carbon-containing fly ash according to any one of claims 1 to 3, wherein after-kneading is carried out for at least 4 days.   The method for treating carbon-containing fly ash according to any one of claims 1 to 3, wherein after-kneading is performed for at least 7 days.   The method for treating carbon-containing fly ash according to any one of claims 1 to 6, wherein the dithiocarbamate is a compound obtained from piperazine as an amine, and post-treatment is performed for 30 days or more after kneading.   The method for treating carbon-containing fly ash according to any one of claims 1 to 7, wherein the carbon content of the carbon-containing fly ash is 1% or more.