JP3397089B2 - Prevention method of dioxins release - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for reducing the amount of dioxins released along with exhaust gas from an incinerator and preventing the elution of heavy metals from the fly ash collected.

[0002]

2. Description of the Related Art In an incinerator such as a refuse incinerator, organic compounds such as phenol, benzene and acetylene, chlorinated aromatic compounds such as chlorophenol and chlorobenzene, and dioxin precursors such as chlorinated alkyl compounds are combusted during combustion. Occurs. When the fly ash coexists, these dioxin precursors become dioxin by a reaction as shown in the following formula by the catalytic action thereof and become present in the exhaust gas (in the present invention, the dioxin and the dioxin precursor are collectively referred to as " Sometimes referred to as "dioxins").

[0003]

[Chemical 1]

This dioxin formation reaction is 40
It does not easily occur at high temperatures of 0 ° C. or higher, and occurs when the temperature drops to around 200 to 400 ° C.

That is, Karasek (Science 237: 754, 1987),
Stieglitz (Chemosphere 18: 1219,1989), Hutzinger
According to a study by (Chemosphere 14: 581, 1985), the production of dioxin in an incinerator is mainly due to the conversion of dioxin precursor contained in exhaust gas into dioxin by the catalytic action of fly ash. The optimum temperature for this reaction is around 300 ° C. When a dioxin precursor such as chlorophenol or chlorobenzene is adsorbed on the dioxin-forming catalytic active site of fly ash particles and exposed to a temperature condition of 200 to 400 ° C, the dioxin precursor is catalytically acted on by the fly ash. React to produce dioxin.

Conventionally, as a method for preventing the release of dioxins contained in exhaust gas to the outside of the system, a method of contacting an amine compound or ammonia with exhaust gas to suppress the generation of dioxins, or fly ash collected There is a method of decomposing dioxin produced by kneading (hereinafter referred to as "dust ash") and an amine compound or ammonia and heating.

That is, the amine compound and ammonia are adsorbed on the fly ash in the exhaust gas to reduce the catalytic ability of the fly ash and inhibit the dioxin forming reaction. Further, amine compounds and ammonia decompose dioxins contained in dust ash and the like at a temperature of 200 ° C. or higher.

[0008]

Fly ash in the exhaust gas of an incinerator contains heavy metals such as lead (Pb) and cadmium (Cd). Therefore, conventionally, it is necessary to prevent the elution of heavy metals from the exhaust gas from dust ash of bag filters, electrostatic precipitators, and the like (immobilization of heavy metals). However, when exhaust gas or dust collecting ash is treated with an amine compound or ammonia to prevent the release of dioxins, the amount of heavy metals eluted from the dust collecting ash is increased as compared with the case of no treatment.

An object of the present invention is to provide a method for preventing the release of dioxins that reduces the amount of dioxins released along with exhaust gas and prevents the elution of heavy metals from dust ash.

[0010]

A method for preventing the release of dioxins according to claim 1 is directed to a dioxins and a heavy metal-containing substance such as a fly ash-containing gas and / or a dust ash containing dioxins and a heavy metal, an amine compound, ammonia. And an ammonium salt (excluding ammonium persulfate), the method for preventing dioxin release by adding one or more dioxin release inhibitors selected from the group consisting of the dioxin and the heavy metal- containing substance. It is characterized by the addition of a heavy metal immobilizing agent that has a stronger affinity for heavy metals than the release inhibitors and insolubilizes the heavy metals.

The method for preventing the release of dioxins according to claim 3 is one or more selected from the group consisting of amine compounds, ammonia and ammonium salts for fly ash in exhaust gas containing dioxins and heavy metals. 0.5 to 10% by weight of the dioxin release inhibitor as an active ingredient
Exhaust and 1 to 20% by weight heavy metal immobilizing agent as an aqueous solution and
It is characterized by spraying on gas .

A method for preventing the release of dioxins according to claim 4 is one or more dioxins selected from the group consisting of amine compounds, ammonia and ammonium salts, for dust ash containing dioxins and heavy metals. It is characterized in that 0.1 to 10% by weight of a release inhibitor as an active ingredient and 1 to 20% by weight of a heavy metal fixing agent as an aqueous solution are added to the dust collecting ash and kneaded.

A dioxin release inhibitor such as an amine compound enhances metal elution because it forms a water-soluble complex compound by coordinate-bonding with a metal contained in fly ash. Also has a high affinity with metals, and since a heavy metal immobilizing agent that insolubilizes heavy metals is added, it is possible to stably immobilize heavy metals and prevent their elution.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below.

In the present invention, among amine compounds, ammonia and ammonium salts added as a dioxin release inhibitor, the amine compounds include alkylamines such as trimethylamine, alkanolamines such as triethanolamine and monoethanolamine, and the like. Amine salts such as hydrochlorides, sulfates and carbonates of these amine compounds can be mentioned. Examples of the ammonium salt include ammonium bicarbonate, ammonium sulfate, diammonium hydrogen phosphate and the like. Of these, triethanolamine is particularly preferable.

These dioxin release inhibitors may be used alone or in combination of two or more. Also,
The form of addition may be any of gaseous, liquid and aqueous solutions, but it is particularly preferred to add it as an aqueous solution of 0.5 to 50% by weight.

When a dioxin release inhibitor is added to the exhaust gas, for example, in the case of an incinerator, the dioxin release inhibitor is added to the exhaust gas at the exhaust gas flue from the incinerator to the dust collector, especially at the exhaust gas temperature of 300 ° C. or higher. It is preferable to spray an aqueous solution. That is, as described above, since the dioxin-forming reaction occurs at a temperature of about 300 ° C., the dioxin-releasing inhibitor is added at the upstream of the point where the dioxin-producing reaction easily occurs at 300 ° C. The effect of suppressing can be effectively obtained.

In this case, the amount of the dioxin release inhibitor added is 0.5 to 0.5 as an active ingredient amount with respect to the fly ash in the exhaust gas.
It is preferably 10% by weight, particularly preferably 2 to 5% by weight.

When the dioxin release inhibitor is added to the dust ash, it is preferable to knead an aqueous solution of the dioxin release inhibitor with the dust ash. In this case, the amount of the dioxin release inhibitor added to the dust ash is On the other hand, the amount of active ingredient was 0.
It is preferably 1 to 10% by weight, particularly preferably 0.5 to 3% by weight.

Examples of the heavy metal immobilizing agent include phosphoric acid heavy metal immobilizing agents, chelating heavy metal immobilizing agents such as piperazine dithiocarbamic acid and piperidine dithiocarbamic acid, and other sulfide heavy metal immobilizing agents and silicic acid heavy metal immobilizing agents. There are various agents, and among these, a phosphate-based heavy metal fixing agent is particularly preferable.

Phosphoric acid or a salt thereof is used as the phosphoric acid-based heavy metal fixing agent. Among these, phosphoric acid is orthophosphoric acid, hypophosphorous acid, metaphosphorous acid, pyrophosphorous acid, orthoacoustic acid. Examples thereof include phosphoric acid, hypophosphoric acid, metaphosphoric acid, pyrophosphoric acid, triphosphoric acid, and condensed phosphoric acid. Examples of phosphoric acid salts include salts of these phosphoric acids, primary phosphoric acid salts, and secondary phosphoric acid salts. To be

In the present invention, orthophosphoric acid (H ₃ P
O ₄ ), sodium dihydrogen phosphate (NaH ₂ PO ₄ ),
Disodium hydrogen phosphate (Na ₂ HPO ₄ ), potassium dihydrogen phosphate (KH ₂ PO ₄ ), dipotassium hydrogen phosphate (K ₂ HPO ₄ ), condensed phosphoric acid and the like can be preferably used, and these Is preferably used as an aqueous solution of about 20 to 75% by weight.

When a heavy metal fixing agent is added to exhaust gas,
For example, in the case of an incinerator, it is preferable to spray an aqueous solution of a heavy metal immobilizing agent into the exhaust gas in the exhaust gas flue that goes from the incinerator to the dust collector.

In this case, the amount of the heavy metal immobilizing agent added is 1 to 20% by weight as an active ingredient amount with respect to the fly ash in the exhaust gas,
In particular, it is preferably 5 to 10% by weight.

When the heavy metal fixing agent is added to the dust collecting ash, it is preferable to knead an aqueous solution of the heavy metal fixing agent to the dust collecting ash. In this case, the amount of the heavy metal fixing agent added is to the dust collecting ash. On the other hand, the amount of the active ingredient is 1 to 20% by weight, particularly 5 to 10%.
It is preferably set to wt%.

Since the heavy metal fixing effect of the phosphoric acid-based heavy metal fixing agent is effectively exhibited at pH 8 to 12, when the heavy metal fixing agent is added to the exhaust gas and / or the dust collecting ash, it may be necessary. Acids such as hydrochloric acid as pH adjusters,
It is preferable to adjust the pH of fly ash or dust ash by using an alkali such as sodium hydroxide or potassium hydroxide together.

In this case, phosphoric acid can serve both as a heavy metal fixing agent and a pH adjusting agent.

In the present invention, the procedure for adding the dioxin release inhibitor and the heavy metal fixing agent is not particularly limited, but the following method is preferable. Mixing dioxin release inhibitor and heavy metal fixing agent or separately, flue or electrostatic precipitator, bag filter,
Spray into other dust collecting equipment. In this case, a kneading machine is not required and the equipment is simple. The dioxin release inhibitor is sprayed onto the flue, and the heavy metal fixing agent is kneaded with the dust collecting ash taken out from the dust collecting equipment. In this case, the heavy metal fixing effect can be reliably obtained by directly kneading the heavy metal fixing agent with the dust collecting ash.

In the present invention, activated carbon may also be used in combination, and in this case, the dioxin in the exhaust gas is adsorbed and removed by the adsorbing action of the activated carbon to further reduce the dioxin concentration in the exhaust gas. it can. in this case,
Activated carbon is preferably added at an exhaust gas flue heading from the incinerator to the dust collector, particularly at a point where the exhaust gas temperature is 150 to 300 ° C.

Further, the dust collecting ash (including incineration ash (bottom ash)) obtained by treatment with the dioxin release inhibitor and the heavy metal immobilizing agent according to the present invention is heated to decompose dioxin of the dioxin release inhibitor. It is preferable to decompose the dioxin thus produced. The heating temperature varies depending on the type of dioxin release inhibitor used, but the heating temperature when alkanolamine is used is preferably 200 to 300 ° C. The heating may be performed by once taking out the dust collecting ash from the dust collecting equipment, or by heating the dust collecting equipment itself to such a temperature.

The method for preventing the release of dioxins of the present invention should be applied to various municipal waste incinerators, as well as various waste gases from industrial waste incinerators, medical waste incinerators, incinerator ash melting furnaces, RDF furnaces, etc. You can Further, it is applicable to the treatment of exhaust gas from various furnaces regardless of the type of furnace such as a stoker furnace, a rotary kiln, a fluidized bed furnace, and the type of furnace such as a continuous furnace, a quasi-continuous furnace, and a batch furnace.

[0032]

EXAMPLES The effects of the present invention will be shown below with reference to Examples and Comparative Examples.

Example 1 Municipal solid waste was incinerated in a laboratory incinerator consisting of a stoker furnace, a waste heat boiler, a bag filter and a scrubber, and 1% by weight aqueous triethanolamine solution was added to the exhaust gas and triethylamine was mixed with fly ash in the exhaust gas. 3 as pure ethanolamine
Exhaust gas temperature in front of the bag filter is about 30% by weight
It was injected at a point of about 0 ° C. In addition, a 50 wt% phosphoric acid aqueous solution was added to H ₃ PO ₄ to the dust collecting ash discharged from the bag filter.
Was added and kneaded so as to be 8% by weight with respect to the collected ash (pH of the kneaded product was 8.5). The dioxin concentration and the elution amounts of lead and cadmium in this dust ash were measured by the following measuring methods, and the results are shown in Table 1.

The amount of waste incinerated is 150t / 24h.
r, the flow rate of exhaust gas is about 40,000 Nm ³ / hr, and the fly ash concentration in the exhaust gas flowing into the bag filter is 2.0 g / Nm.
Is ^3, the average gas temperature in the bag filter was 220 ° C..

Method for measuring dioxin concentration Sampling and analysis were carried out in accordance with the "Dioxins Analysis Manual" of the Waste Research Foundation.

Method of measuring heavy metal elution amount Sample preparation and analysis were carried out in accordance with the Environmental Agency Notification No. 13 test.

Comparative Example 1 Dioxin concentration and heavy metal elution amount were measured in the same manner as in Example 1 except that the triethanolamine aqueous solution was not injected, and the results are shown in Table 1.

Comparative Example 2 Dioxin concentration and heavy metal elution amount were measured in the same manner as in Example 1 except that the phosphoric acid aqueous solution was not added, and the results are shown in Table 1.

[0039]

[Table 1]

As is clear from Table 1, according to the present invention, it is possible to prevent the release of dioxins and the elution of heavy metals.

[0041]

As described above in detail, according to the method for preventing the release of dioxins of the present invention, by preventing the generation of dioxin and the decomposition reaction in the flue and the dust collecting equipment of the incinerator,
It is possible to reduce the concentration of dioxins in exhaust gas and the concentration of dioxins in dust ash, and to fix heavy metals in dust ash to prevent elution of heavy metals from dust ash.

─────────────────────────────────────────────────── ─── Continued front page (72) Inventor Noboru Fujiwara 3-4-7 Nishishinjuku, Shinjuku-ku, Tokyo Kurita Industry Co., Ltd. (72) Inventor Takashi Tanabe 3-4-7 Nishishinjuku, Shinjuku-ku, Tokyo No. Kurita Industry Co., Ltd. (56) Reference JP-A-6-265133 (JP, A) JP-A-9-879 (JP, A) JP-A-10-33939 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) B01D 53/34 B09B 3/00

Claims (4)

(57) [Claims] 1. A substance containing dioxins and heavy metals,
In the method for preventing the release of dioxins, which comprises adding one or more dioxin release inhibitors selected from the group consisting of amine compounds, ammonia and ammonium salts (excluding ammonium persulfate), said dioxins and heavy metal- containing substances A method for preventing dioxin release, comprising adding a heavy metal immobilizing agent that has a stronger affinity for heavy metals than the dioxin release inhibitor and insolubilizes heavy metals. 2. The method for preventing release of dioxins according to claim 1, wherein the heavy metal fixing agent is a phosphoric acid-based, chelate-based, sulfide-based, or silicic acid-based heavy metal fixing agent. 3. One or two or more dioxin release inhibitors selected from the group consisting of amine compounds, ammonia and ammonium salts for fly ash in exhaust gas containing dioxins and heavy metals as an active ingredient. .5-
A method for preventing the release of dioxins, comprising spraying 10% by weight and 1 to 20% by weight of a heavy metal fixing agent as an aqueous solution onto the exhaust gas . 4. For dust ash containing dioxins and heavy metals, 0.1 or more kinds of dioxin release inhibitors selected from the group consisting of amine compounds, ammonia and ammonium salts as an active ingredient. 10% by weight and heavy metals immobilization agent 1 to 20% by weight and said as an aqueous solution
A method for preventing the release of dioxins, which comprises adding to the collected ash and kneading.