JP2001074219A - Reduction of dioxins - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for reducing dioxins, of which the running cost is low and with which the discharge rate of dioxins can be readily reduced. SOLUTION: This method burns wastes in a combustion furnace or melting wastes in a melting furnace together with non-iron ore, sulfide mineral, sulfuric acid or gypsum based neutralized residue or the like having a characteristic of generating SO2 gas by combustion, and reduces dioxins in an exhaust gas discharged from the combustion furnace or the melting furnace. Further, the method directs non-iron pyrometallurgical exhaust gas containing SO2 gas to the combustion furnace or the melting furnace, combusts or melts the wastes, and reduces the concentration of dioxins in the exhaust gas discharged from the combustion furnace or the melting furnace.

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 dioxins, which reduces the amount of dioxins discharged from a waste incineration plant or the like.

[0002]

2. Description of the Related Art As a method of reducing the amount of dioxin in exhaust gas in a waste incineration plant or the like, dioxin is generated by taking measures such as shutting off from outside air at 800 ° C. or more and a residence time of 2 seconds or more in a combustion furnace or a secondary combustion furnace. How to suppress the
In the cooling equipment, a method of cooling the exhaust gas temperature to 200 ° C. or less, a method of blowing activated carbon or slaked lime in the exhaust gas treatment equipment, and the like can be mentioned. Further, JP-A-5-237339 and JP-A No. 10-211418, and at the same time the adsorption method for removing dioxins adsorption treatment of dioxins and SO ₂ if the SO ₂ is present is disclosed in the exhaust gas I have.

[0003]

In order to reduce dioxin in exhaust gas discharged from an incinerator or the like, exhaust gas regulations have been cleared at the expense of many running costs using the above method. Further, when the waste combustion treatment state becomes an incomplete combustion state, the amount of dioxins generated increases, and even if the above measures are taken, dioxins are resynthesized in the exhaust gas flue, further increasing running costs.

An object of the present invention is to provide a method for reducing dioxins, which has a low running cost and can easily reduce the amount of dioxins discharged.

[0005]

SUMMARY OF THE INVENTION The present invention relates to a method for burning waste in a combustion furnace together with at least one selected from the group consisting of nonferrous ore, sulfide mineral, sulfuric acid and gypsum-based neutralized slag. This is a method for reducing dioxins which melts in the furnace and reduces the concentration of dioxins in exhaust gas discharged from a combustion furnace or a melting furnace. In addition, the present invention introduces a non-ferrous smelting exhaust gas containing SO ₂ gas into a combustion furnace or a melting furnace, burns or melts waste, and removes waste gas from the exhaust gas discharged from the combustion furnace or the melting furnace. This is a method for reducing dioxins, which reduces the concentration of dioxins.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a combustion furnace refers to a furnace for burning general waste and industrial waste discharged from households and the like, and an example thereof is an incinerator. In addition, the melting furnace is a facility for melting automobile shredder dust and the like for the purpose of reducing the volume of waste and converting it into slag.
An example is a hot melt rotary kiln.

[0007] In these combustion furnaces and melting furnaces, chlorine generated from chlorine-containing compounds (eg, polyvinyl chloride) containing chlorine atoms in dirt is contained in dioxins (polychlorodibenzodioxin, polychlorodibenzofuran, etc.). Results in the generation of Two-stage reactions represented by the following formulas (1) and (2) have been pointed out as a reaction for producing dioxins. 2HCl + 1 / 2O ₂ → Cl ₂ + H ₂ O (1) Cl ₂ + aromatic compound → chlorinated aromatic compound (partially dioxins) (2)

[0008] HCl generated by combustion of waste is oxidized by O _{2 according} to the above formula (1). In the reaction of the formula (1), a transition metal compound such as copper chloride (cuprous chloride, cupric chloride, etc.) acts as a catalyst, and when these transition metal compounds are present in waste, dioxins are formed. It is known that the amount is large. Since Cl ₂ generated by the above formula (1) has high reactivity, the above formula (2) gives
Unburned aromatic compounds (aromatic compounds contained in wastes such as lignin) are chlorinated. At this time, a part of the reaction product becomes dioxins. In order to suppress the generation of dioxins, the reaction of the above formula (2) may be prevented. As a method, supply of SO ₂ generated by combustion of sulfur to a combustion field can be considered. The reason is,
Since SO ₂ reduces Cl ₂ to HCl according to the following formula (3), it suppresses the production of dioxins, or SO ₂
Is believed to be suppressed by the catalytic action of SO ₂ + Cl ₂ + H ₂ O → SO ₃ + 2HCl (3)

In the present invention, the waste is burned in a combustion furnace together with at least one sulfur atom-containing agent selected from the group consisting of nonferrous ore, sulfide mineral, sulfuric acid and gypsum-based neutralized slag, or in a melting furnace. Let melt. The sulfur atom-containing agent is converted into a sulfur dioxide gas (SO ₂
Gas). The generated SO ₂ is used for suppressing generation of dioxins. Examples of the non-ferrous ores include ores containing a sulfur atom, which are raw materials for non-ferrous metal smelting, and examples thereof include copper ores such as odorite ores and hand ores; zinc ores such as senaenite; and lead ores such as fauenite. It is. Examples of the sulfide minerals include nickel sulfide minerals such as nickel pyrite and the like, iron sulfide minerals such as pyrite, and silver sulfide minerals such as pyroxenite, which are (Ni, Fe) S, FeS
₂ , represented by Ag ₂ S. Gypsum can be mentioned as examples of gypsum-based neutralization slag, examples of which are CaSO ₄ · 2H ₂ O.

[0010] Nonferrous ore is introduced into a combustion furnace or a melting furnace. The particle size of the non-ferrous ore introduced into the combustion furnace or the like is appropriately selected. The amount of nonferrous ore used varies depending on the composition of the waste, but is, for example, about 5 kg to 100 kg per 1000 kg of waste. Further, in addition to the non-ferrous ore, another sulfur-containing substance having a property of generating SO ₂ by combustion (for example, coal, neutralized stone or the like) may be further added to the waste.

In order to suppress the generation of dioxins,
Non-ferrous smelting exhaust gas containing SO ₂ gas is introduced into a combustion furnace or a melting furnace. The nonferrous smelting exhaust gas is an exhaust gas discharged in a smelting process of a nonferrous metal such as copper, lead, and zinc. The non-ferrous smelting exhaust gas introduced into the combustion furnace or melting furnace
The concentration of the O ₂ gas is 1000 × 10 ⁻⁶ vol% (1000
ppm) to 20 vol%, preferably 1 vol% to 5 v
ol% is preferable. When the concentration of the SO ₂ gas is in the above range, the production of dioxins is easily suppressed, and the cost of desulfurizing SO ₂ is low.

FIG. 1 is a diagram for explaining an example of a method for reducing dioxins. As shown in FIG. 1, the waste incineration equipment includes an incinerator (primary incinerator 1) and a secondary combustion furnace (secondary incinerator 2) connected to the secondary side of the primary incinerator 1.
And a quenching reaction tower 3 connected to the secondary side of the secondary incinerator 2
And a filter 4 connected to the secondary side of the quenching reaction tower 3.
(Eg, a bag filter). The primary incinerator 1 burns waste using air, and the secondary incinerator 2 uses a quenching reaction to completely burn the combustion gas generated in the primary incinerator 1 using air and oil such as heavy oil. The tower 3 is used to reduce the temperature of the combustion gas passing through the secondary incinerator 2, and the filter 4 is used to remove dust contained in the combustion gas.

The non-ferrous smelting exhaust gas containing SO ₂ may be introduced into the secondary incinerator 2 as shown in FIG. 1 or may be introduced into the primary incinerator 1 as shown in FIG.

In the present invention, the use of a non-ferrous ore or a gypsum-based neutralized slag, the use of non-ferrous smelting exhaust gas, etc.
When the SO ₂ concentration in the primary incinerator 1 or the secondary incinerator 2 is 10
00ppm (1000 × 10 ^-6 vol%) to 20vo
1% (% by volume), preferably 1000 × 10 ⁻⁶ v
When the content is in the range of 5% by volume to 5% by volume, the generation of dioxin is easily suppressed, and the cost of desulfurization of SO ₂ is low.

The method of the present invention can be preferably carried out using an incinerator or a melting facility having a desulfurizer for removing sulfur compounds. That is, sulfur compounds such as SO ₂ or SO _{3 which} are brought along with combustion of waste, combustion of non-ferrous ore, or melting or introduction of non-ferrous smelting exhaust gas and not consumed in a combustion furnace, a melting furnace, etc. After removal,
It is preferable to discharge the exhaust gas into the atmosphere or the like. Examples of desulfurization methods for removing sulfur compounds include a caustic soda washing method and a calcium-based slurry method. The desulfurization device can be provided on the secondary side of the melting furnace or the secondary incinerator 2. As shown in FIG. 2, when provided on the secondary side of the filter 4, sulfur compounds such as SO ₂ can be efficiently removed from the combustion gas or the like.

[0016]

The present invention will be described below with reference to examples. Steps shown in Embodiment 1 Figure 1, i.e. by introducing SO ₂ gas into the secondary incinerator 2, were mixed in a SO ₂ gas in the combustion gas supplied from the primary incinerator 1 and the secondary incinerator 2, The combustion gas was burned. Then, the dioxin concentration in the gas was measured. The waste supplied to the primary incinerator 1 had a chlorine concentration of 5% by weight. The incinerators 1 and 2 used had an incineration capacity of about 1500 t / month. Further, as a gas containing SO ₂ gas (this gas was obtained from copper smelting exhaust gas), the concentration of SO ₂ was 15 vol%.
The supply amount of the gas containing SO ₂ gas into the secondary incinerator 2 was 5000 Nm ³ / hr. The dioxin concentration in the gas was measured for three types of gases: a gas collected at the outlet of the secondary incinerator 2, a gas collected at the inlet of the bag filter 4, and an exhaust gas collected at the exhaust gas outlet.
Table 1 shows the measurement results together with the gas amount and the gas temperature. In Tables 1 and 2, Nm ³ means normal cubic meter, ng means nanogram, TEQ means total dioxin amount, and wet means wet gas.

Comparative Example 1 According to the process shown in FIG. 3, waste was incinerated in the same manner as in Example 1, and the concentration of dioxin in the gas was measured. Table 2 shows the measurement results. 3 includes a primary incinerator 1, a secondary combustion furnace 2, a quenching reaction tower 3, a bag filter 4, and an activated carbon spraying device 5 for blowing activated carbon into exhaust gas.
And the SO ₂ gas was not supplied into the secondary incinerator 2.

[0018]

[Table 1]

[0019]

[Table 2]

From Tables 1 and 2, according to Example 1 in which SO ₂ gas was introduced into the incinerator, compared to Comparative Example 1, the gas passed through the quenching reaction tower 3 and the bag filter was used. The dioxin concentration of the gas collected at the entrance
It turns out that it was 1 /. That is, in the case of the first embodiment,
It has been found that the amount of dioxins in the gas discharged from the secondary incinerator 2 can be reduced. In the case of the first embodiment,
It has been found that the concentration of dioxins in exhaust gas can be reduced without using an activated carbon spray device.

[0021]

According to the present invention, the production of dioxins can be easily suppressed in a combustion furnace for treating waste. Further, since it is not always necessary to use activated carbon or extinguished coal for dioxin removal, cost can be reduced. Further, according to the present invention, the generation of dioxins can be suppressed even if the waste contains a transition metal-containing compound (compound containing a transition metal such as copper). Therefore, according to the present invention, industrial waste containing transition metal compounds such as precipitates (including copper chloride such as cuprous chloride and cupric chloride) generated in a plating tank is incinerated or melted. Can be disposed of.
According to the present invention, if an incineration facility is installed in or near a nonferrous metal smelter, the nonferrous smelting exhaust gas can be effectively used for dioxin removal.

[Brief description of the drawings]

FIG. 1 is a process chart for explaining an example of a dioxin reduction method of the present invention.

FIG. 2 is a process chart showing another example of the method for reducing dioxins of the present invention.

FIG. 3 is a process chart showing a conventional example of a method for reducing dioxins.

[Explanation of symbols]

1. Primary incinerator, 2. Secondary incinerator, 3. Quenching reaction tower, 4. Filter (bag filter), 5. Activated carbon spray device, 10. Desulfurization device

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B01D 53/70 B01D 53/34 134E (72) Inventor Fumihiko Ogino 4049-1 Naoshima-cho, Kagawa-gun, Kagawa Prefecture Mitsubishi Materi Al Co., Ltd. Naoshima Smelter F term (reference) 3K061 AA24 AB03 AC01 BA01 BA10 DA03 DA17 DA18 3K065 AA24 AB03 AC01 BA01 BA10 HA01 HA02 HA03 HA08 4D002 AA21 BA06 BA14 CA20 DA66 DA70 GA01 GB08

Claims (5)

[Claims] Claims: 1. Burning a waste together with at least one selected from the group consisting of a non-ferrous ore, a sulfide mineral, sulfuric acid and a gypsum-based neutralized slag in a combustion furnace or melting the waste in a smelting furnace; Alternatively, a method for reducing dioxins, which comprises reducing the concentration of dioxins in exhaust gas discharged from a melting furnace. _2. A non-ferrous smelting exhaust gas containing SO ₂ gas is introduced into a combustion furnace or a smelting furnace to burn or melt waste, and the waste gas is discharged from the combustion furnace or the smelting furnace. A method for reducing dioxins, comprising reducing the concentration of dioxins. 3. SO in a combustion furnace or a melting furnace._TwoGas concentration
But 1000 × 10^{- 6}vol% to 20vol%
3. The method for reducing dioxins according to claim 1 or 2. 4. The method for reducing dioxins according to claim 1, wherein the waste is a waste containing a transition metal compound. 5. The method for reducing dioxins according to claim 1, wherein the sulfur compound is removed from the gas discharged from the combustion furnace or the melting furnace by using a desulfurization apparatus.