JPH11123317A - Device for removing dioxin in exhaust combustion gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a novel device for removing dioxin which can effectively decompose and remove organic chlorine compounds such as deadly poisonous dioxin, etc., contained in an exhaust combustion gas. SOLUTION: Combustion gas and incineration ash containing organic chlorine compounds such as dioxin, etc., is produced in an incinerator 1. A smoke stack 2, through which the combustion gas and incineration ash is passed through in two or more seconds, is connected to the incinerator 1. And a photocatalyst layer 3 comprising a mixture of alumina, n-type titanium oxide (anatase), strontium oxide, platinum, palladium, and rhodium is formed on the inner wall surface of the stack 2. A microwave generator 4 is connected to the vicinity of a combustion gas inlet of the stack 2 to irradiate microwaves into the stack 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dioxin removing apparatus for decomposing and removing dioxin, which is a highly toxic organic chlorine compound contained in flue gas, into harmless components.

[0002]

2. Description of the Related Art Generally, when industrial waste and household waste are burned at a low temperature of 300 to 600 ° C., dioxins, which are highly toxic organochlorine compounds, are generated. Are known. Especially,
2,3,7,8-TCDD-tetrachlorodibenzoparaoxin, which is said to be the most toxic of the dioxins, converts benzene-type gas generated during combustion and activated chlorine gas into approximately It is said to be produced most by passing through a furnace at 500 ° C.

[0003] Therefore, conventionally, the combustion method has been devised, for example, the generation of dioxins is suppressed by operating the combustion temperature of the incinerator at a high temperature (1000 ° C or higher) at which dioxin can be destroyed. However, it is difficult to completely suppress the generation of dioxins by 100%.

[0004] The dioxins are contained not only in exhaust gas but also in incineration ash and fly ash generated by incineration, and a method for effectively removing dioxins contained in these is also included. There is no present.

Accordingly, the present invention has been devised in order to effectively solve such a problem, and an object thereof is to provide an organic chlorine compound such as highly toxic dioxin contained in combustion exhaust gas and incinerated ash. The present invention provides a novel dioxin removing device capable of effectively decomposing and removing dioxin.

[0006]

Heretofore, organic chlorine compounds such as dioxins have been used as raw materials in the presence of carbon-based compounds, especially benzene-based compounds and aromatic-based compounds, and chlorinated hydrochloric acid-based compounds, and have a certain amount of oxygen (about 3%). It is known to form at moderate temperatures between 300 ° C and 600 ° C, provided that they are present. For example, 2,3,7,8TCDD, which is considered to be the most toxic among dioxins, has a chemical structure as shown in FIG. 3 (A).
It is known that DD is partially generated when a benzene-based gas, activated chlorine gas, and activated oxygen (present in air) gas are passed through a furnace at a temperature of about 500 ° C. Have been. FIG. 3 (B) shows the chemical structure of dioxin, 1,3,6,8TCDD tetrachlorodibenzoparadioxin, which is less toxic than this.

[0007] However, even such highly toxic dioxins are a kind of organic substance, so that harmless carbon dioxide (CO ₂ ) and water vapor (H ₂ ) may be used at an extremely high incineration temperature (1000 ° C. or higher). O) and hydrogen chloride gas (H
Cl) and sulfur dioxide (SO ₂ ). In particular, when the incineration temperature is 900 to 1200 ° C., 300 ° C. to 6
It has also been reported that a breaking speed 1000 times or more as high as that at a medium temperature of 00 ° C. can be exhibited.

Further, in addition to such high temperature incineration conditions,
The residence time in the furnace is required to be at least 2 seconds or more, preferably 3 seconds or more. For example, furnace volume 1m
³ is a furnace per 100,000 kcal / H or less of the thermal load is required.

On the other hand, in the case of a conventional refuse incinerator, since various components are mixed and burned, not only the raw materials for dioxin are included, but also
It is extremely difficult to raise the incineration temperature to 1000 ° C. or higher due to the furnace structure and the suppression of generation of nitrogen oxides (NO _x ). At present, it is almost impossible to suppress the generation of dioxin only by the combustion conditions because a low-temperature portion may be generated.

[0010] For this reason, for example, an apparatus having a structure completely different from that of a conventional incinerator, such as an ultra-high-temperature molten gas, is installed, or a decomposition catalyst device made of an extremely expensive material is provided. Although it has been proposed to suppress such a problem, according to this method, there is a problem in that the cost is too high and the burden is not only large on the local public entities but also on general processors.

In view of the above situation, the present inventor has conducted intensive studies for many years. As a result, using the existing incinerator as it is, economically and effectively, an organic chlorine compound such as dioxin can be effectively used. A novel dioxin removal apparatus capable of decomposing and removing dioxin has been proposed.

That is, the present invention does not suppress the generation of dioxin depending on the combustion conditions, but also effectively uses not only organochlorine compounds in the combustion exhaust gas generated by the conventional combustion method but also those contained in the incineration ash. It is possible to decompose and remove.

Specifically, in order to achieve the above object, a first aspect of the present invention is to provide an incinerator which generates a combustion gas and an incineration ash containing an organic chlorine compound such as dioxin, by adding at least two combustion gases and the incineration ash to the incinerator. At the same time as connecting a chimney flowing for more than a second, a photocatalytic layer composed of a mixture of alumina, titanium oxide N-type (anatase), strontium oxide, platinum, palladium and rhodium is formed on the inner wall of the chimney, and the combustion gas of the chimney A microwave generator that irradiates microwaves into the chimney is connected near the entrance.

When a microwave is irradiated from the microwave generator into the chimney, the surface of the photocatalyst layer formed on the inner wall of the chimney by the microwave is oxidized as strongly as when heated to about 70,000 to 100,000 ° C. Generate force. Then, by flowing a combustion gas containing an organic chlorine compound such as dioxin into the chimney in such a state for at least 2 seconds or more, not only dioxin in the combustion exhaust gas but also in the incineration ash scattered with the combustion exhaust gas. Dioxin and all toxic organic chlorine compounds such as cyanide are instantaneously decomposed, and harmless carbon dioxide (CO ₂ ) and water vapor (H ₂ O), hydrogen chloride gas (HCl) and sulfur dioxide gas (SO ₂ ) ₂ ) Completely destroyed.

This is presumed to be due to the following phenomenon.

First, a microwave having a wavelength of 1 m or less, which is an ultra-high frequency, is converted into the above-mentioned alumina, titanium oxide N-type (anatase), strontium oxide, platinum, palladium,
When the photocatalyst layer made of a mixture of rhodium is irradiated, electron-hole pairs are generated on the surface of the photocatalyst layer, and the electrons move inside the holes to the surface. At this time, the holes are photoreacted with the moisture of the fine particles and fine particles on the surface and become hydroxyl groups (hydroxyl radicals) having a strong oxidizing power, which breaks and destroys any chemical bond of any toxic organic substance.

Furthermore, since the hydrogen chloride gas (HCl) and the sulfur dioxide gas (SO ₂ ) generated by the destruction of the microwaves directly cause air pollution, if necessary, they are neutralized by a conventional desulfurization device or the like. You only have to disassemble.

A second invention is directed to a chimney for flowing combustion gas and incinerated ash containing an organic chlorine compound such as dioxin,
A residence zone is formed in which the combustion gas and incineration ash are retained for at least 2 seconds to flow, and a mixture of alumina, titanium oxide N-type (anatase), strontium oxide, platinum, palladium and rhodium is formed on the inner wall surface of the retention zone. And a microwave generator for irradiating the staying zone with microwaves in the staying zone.

That is, according to the present invention, a residence zone provided with the photocatalyst layer and the microwave generator is provided in the middle of the chimney in which the flue gas flows. It is led into a stagnation zone where the organic chlorine compounds contained in the combustion exhaust gas and the incineration ash are destroyed at once. In particular, by forming such a stagnation zone, the incineration ash is stored, so that a sufficient destruction effect on the incineration ash can be obtained.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a preferred embodiment of the present invention will be described with reference to the accompanying drawings.

FIG. 1 shows an embodiment of an apparatus for removing dioxin in combustion exhaust gas according to the first invention.

As shown in the figure, the dioxin removing apparatus includes an incinerator 1 for generating a combustion gas containing dioxin.
Is connected to the chimney 2 through which the flue gas flows.
A photocatalyst layer 3 is formed over the entire inner wall surface of the device, and a microwave generator 4 is connected near the combustion gas inlet of the chimney 2.

The length of the chimney 2 is set such that the flue gas exhausted from the incinerator 1 flows over at least two seconds. Specifically, the length is determined by the discharge amount and the flow rate of the combustion exhaust gas exhausted from the incinerator 1. As shown in the figure, by extending the exhaust gas in the horizontal direction, the exhaust gas pressure loss is increased. In this case, the residence time can be made longer than in the case of extending vertically.

The microwave generator 4 includes a microwave power source,
A casing 5 accommodating microwave generating means including an isolator, a power monitor, a transfer device, and the like is mounted on the upstream side of the chimney 2 and a microwave radiating tube 6 for radiating microwaves is coaxially arranged substantially at the axis of the chimney 2. The microwave is applied to the photocatalyst layer 3 on the downstream side of the chimney 2 with a wavelength of 1 m or less.

As shown in FIG. 2, the photocatalyst layer 3 comprises alumina powder (Al ₂ O ₃ ) and titanium oxide (Ti).
A mixture of ₂ O ₃ ) N-type (anatase) powder, strontium oxide (Sr ₂ O ₃ ) powder and a noble metal raw material such as platinum (Pt), palladium (Pd), rhodium (Rd) is mixed in a slurry with an organic binder. The combined material is coated, and exhibits a high oxidizing power with respect to the combustion exhaust gas flowing in the chimney 2 and the incineration ash flowing with the combustion exhaust gas.

The operation of the present invention will be described above.

As shown in FIG. 1, the microwave generator 4 is activated to continuously irradiate the chimney 2 with microwaves. Then
As described above, the photocatalyst layer 3 in the chimney 2 which has been irradiated with the microwave generates the same strong oxidizing power as when its surface is heated to about 70,000 to 100,000 ° C.

When the flue gas discharged from the incinerator 1 flows into the chimney 2 in such a state, the dioxin in the flue gas as well as the dioxin in the incineration ash scattered with the flue gas and the toxicity are reduced. The chemical bonds that make up all the organochlorine compounds that have are broken at a stretch,
It is completely destroyed by harmless carbon dioxide gas (CO ₂ ) and water vapor (H ₂ O) and hydrogen chloride gas (HCl) and sulfur dioxide gas (SO ₂ ) as shown in FIG. Although the destruction of the organochlorine compound by such an action is usually almost completed if it is usually 2 seconds or less, as described above, the length of the chimney 2 is set so that the residence time is at least 2 seconds or more. Since it is set, the object can be sufficiently achieved.

Next, FIG. 5 shows an embodiment of the dioxin removing apparatus according to the second invention.

As shown in the figure, the dioxin removing apparatus includes a stagnation zone in which the combustion gas and incinerated ash are allowed to stay for at least 2 seconds or more in a chimney 2 through which a combustion gas containing an organic chlorine compound such as dioxin and incinerated ash flows. 7, a photocatalyst layer 3 made of the above-described raw material is formed on the inner wall surface of the retention zone 7, and a microwave generator 4 for irradiating the retention zone 7 with microwaves is provided. .

That is, in the case of the first invention, the photocatalyst layer 3 is formed over the entire inner surface of the chimney 2 and the microwave generator 4 is provided upstream of the chimney 2. A retention zone 7 provided with the photocatalyst layer 3 and the microwave generator 4 is provided in the middle of the chimney 2 through which the exhaust gas flows, and the combustion exhaust gas and the incineration ash flowing through the chimney 2 are guided into the retention zone 7. The organic chlorine compound contained in the combustion exhaust gas and the incineration ash is destroyed at once.

Therefore, in the present invention, similarly to the first invention, not only the organic chlorine compounds in the combustion exhaust gas but also the organic chlorine compounds in the combustion ash can be effectively decomposed and removed.
In addition, once the combustion exhaust gas flows into the stagnation zone 7, the stagnation time can be increased, so that the overall length of the chimney can be shortened and made compact. Furthermore, once flowing into the retention zone 7, separation of incineration ash in combustion exhaust gas like a cyclone is promoted,
The effect of separating incinerated ash can be obtained at the same time.

[0033]

In summary, according to the present invention, the following excellent effects can be exhibited.

It is possible to almost completely decompose all organochlorine compounds, including highly toxic dioxins, contained in combustion exhaust gas and combustion ash into harmless components such as carbon dioxide gas and water vapor.

Therefore, it is possible to prevent the deterioration of the local environment due to highly toxic organic chlorine compounds such as dioxin.

Further, since the apparatus of the present invention can be used by being attached to an existing incinerator, the existing facility can be effectively used as it is without constructing a new incinerator, and it is necessary to remove organic chlorine compounds. Significant reduction in equipment costs can be achieved.

Moreover, once the device of the present invention is constructed, it can exert its effects almost permanently with a small amount of electric power only for generating microwaves. Economic efficiency.

Since the photocatalyst layer is composed of a microwave and a special component, a large installation space is not required, and the surrounding environment is not adversely affected during operation.

[Brief description of the drawings]

FIG. 1 is a partially broken whole view showing an embodiment of the first invention.

FIG. 2 is a sectional view taken along line XX in FIG.

FIG. 3 (A) is a view showing the chemical structure of 2,3,7,8TCDD which is a highly toxic dioxin in combustion exhaust gas. (B) shows the chemical structure of 1,3,6,8TCDD tetrachlorodibenzoparadioxin.

FIG. 4 is a conceptual diagram showing a state of destruction of dioxin by microwaves.

FIG. 5 is a partially broken whole view showing an embodiment of the second invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Incinerator 2 Chimney 3 Photocatalyst layer 4 Microwave generator 5 Casing 6 Microwave radiation tube 7 Retention zone

Claims (2)

[Claims] An incinerator that generates a combustion gas and an incineration ash containing an organic chlorine compound such as dioxin is connected to a chimney for flowing the combustion gas and the incineration ash over at least two seconds, and is connected to an inner wall surface of the chimney. Microwave generation to form a photocatalyst layer composed of a mixture of aluminum, alumina, titanium oxide N-type (anatase), strontium oxide, platinum, palladium, and rhodium, and to irradiate microwaves into the chimney near the combustion gas inlet of the chimney A device for removing dioxin in flue gas, wherein a device is connected. 2. In a chimney through which a combustion gas containing an organic chlorine compound such as dioxin flows, a retention zone is formed in which the combustion gas and incinerated ash are retained for at least 2 seconds or more, and on the inner wall surface of the retention zone, A photocatalytic layer composed of a mixture of alumina, titanium oxide N-type (anatase), strontium oxide, platinum, palladium, and rhodium was formed, and a microwave generator for irradiating microwaves in the retention zone was provided in the retention zone. A device for removing dioxin in combustion exhaust gas, characterized in that: