JPH11156157A - Method and apparatus for treatment of exhaust gas of incinerator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and an apparatus for treatment of an exhaust gas of an incinerator wherein maintenance and control are easy without making its equipment and apparatus large-scaled and they are free from influence from fly ash. SOLUTION: An exhaust gas discharged from an incineration ash separator 4 is passed through a photocatalytic device 5 provided by combining a photocatalytic carrier supporting a catalyst having titanium oxide as a principal constituent, and an ultraviolet lamp to remove hazardous material contained in the exhaust gas by decomposition. An exhaust line of an incineration furnace 1 is provided by arranging a cooling device 3, an incineration ash separator 4 and the photocatalytic device 5 in this order, and the photocatalytic device 5 is provided by combining a zigzag pohocatalytic carrier for carrying a catalyst having titanium oxide as main component, and an ultraviolet lamp.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for treating an exhaust gas of an incinerator for removing harmful substances such as organic chlorine compounds containing dioxins contained in the exhaust gas generated from the incinerator.

[0002]

2. Description of the Related Art Dioxins contained in exhaust gas generated from incinerators are highly toxic, and it is required to reduce the amount of dioxins generated. In general, dioxin is a general term for PCDDs (polychlorinated dibenzo-p-dioxins) having 75 types of isomers and PCDFs (polychlorinated dibenzofurans) having 135 types of isomers, and is a highly toxic substance. Precursors of PCDDs and PCDFs such as CP (chlorophenol) and CB (chlorobenzene) are also included. In the present invention, these are referred to as dioxins.

In a waste incineration plant, fly ash such as ash collected from a gas cooler or a reaction tower or ash collected from an electric dust collector or a bag filter contains a trace amount of dioxins. Is a problem.
Fly ash is known to act as a catalyst for these dioxin-forming reactions and promote the production of dioxins.

Conventionally, in an incinerator, a combustion temperature of 85
The amount of dioxins generated is suppressed by incineration stably at 0 ° C or higher, and the exhaust gas is quenched to 350 ° C or lower to prevent regeneration in the exhaust gas and further removed together with dust by a dust filter. . But
Even with this method, the amount of dioxins released into the environment was not satisfactory.

[0005] Therefore, it has been proposed to blow activated carbon before the dust filter to adsorb and remove dioxins by the activated carbon, or to provide an activated carbon adsorption tank after the dust filter to perform adsorption treatment, and then regenerate and reuse the activated carbon. (For example, JP-A-7-75720). or,
A catalyst using a titanium oxide catalyst has also been proposed (for example, JP-A-2-35914, JP-A-5-3373).
Japanese Patent Publication No. 36, Japanese Patent Publication No. 7-75656 and Japanese Patent Publication No. 7-75656
No. 106299, Japanese Patent No. 2542290, Japanese Patent No. 2609393).

[0006]

However, for example, in the invention described in Japanese Patent Application Laid-Open No. 7-75720, it is necessary to regenerate or dispose of activated carbon, so that the apparatus is large and complicated. In the invention described in JP-A-2-35914, since the exhaust gas from which dust has been removed is introduced into the reaction vessel at a temperature of 150 ° C. or higher, preferably 170 to 300 ° C., operation management is troublesome.

In the invention described in Japanese Patent Application Laid-Open No. 5-337336, NH ₃ is continuously or intermittently added as an auxiliary agent, so that there is a problem that equipment costs and operation costs are increased and operation management is troublesome. . In the invention described in Japanese Patent Publication No. 7-75656, the operating temperature range is 250 ° C. or more, the space velocity is 50000 or less, and the catalyst surface area is 1 m.
^Since the gas amount per ² is 250 m ³ / hr (at temp.) Or less, operation management is troublesome.

[0008] In the invention described in Japanese Patent Publication No. 7-106299, since the treatment is performed before being introduced into the dust collecting portion, fly ash easily adheres to the catalyst, and maintenance and management are difficult. In the invention described in Japanese Patent No. 2542290, since ammonia is continuously or intermittently added as an auxiliary agent, there is a problem that equipment costs and operation costs are increased and operation management is troublesome.

In the invention described in Japanese Patent No. 2609393, the operating temperature range is 150 to 450 ° C. or more, the space velocity is 20,000 or less, and the gas amount per 1 m ^{2 of the} catalyst surface area is 100 m ³ / hr (at temp. ) Operation management is troublesome because: The present invention has been made to solve such a conventional problem, and an object of the present invention is to provide an exhaust gas treatment method for an incinerator that is easy to maintain without increasing the size of facilities and equipment and is not affected by fly ash. And an apparatus therefor.

[0010]

According to the first aspect of the present invention,
Exhaust gas discharged from the incineration ash separation device is passed through a photocatalyst device combining a photocatalyst carrier carrying a catalyst containing titanium oxide as a main component and an ultraviolet lamp to decompose and remove harmful substances contained in the exhaust gas. It is characterized by.

According to a second aspect of the present invention, in the exhaust gas treatment method for an incinerator according to the first aspect, the harmful substance is an organic chlorine compound containing dioxins.
The invention according to claim 3 is characterized in that a cooling device, an incineration ash separation device, and a photocatalyst device are sequentially arranged in an exhaust gas line of an incinerator, and the photocatalyst device has a concavity-like shape that carries a catalyst containing titanium oxide as a main component. Characterized in that the photocatalyst carrier is combined with an ultraviolet lamp.

According to a fourth aspect of the present invention, in the exhaust gas treatment device for an incinerator according to the third aspect, the photocatalyst device comprises a photocatalyst carrier comprising titanium oxide supported on a honeycomb-like material or a filter-like material in which sheets are woven. And an ultraviolet lamp provided with a reflector on the upstream side and arranged on the upstream side of the photocatalyst carrier, while being arranged in a container in a distorted manner. According to a fifth aspect of the present invention, in the exhaust gas treatment device for an incinerator according to the third aspect, the reflecting plate has a double structure, a passage for clean air is formed therein, and a flow of exhaust gas in the photocatalytic device. A jet port for jetting clean air in a direction is formed.

(Function) According to the first to third aspects of the present invention, the exhaust gas from which fly ash has been removed by the incineration ash separation device is supplied to a photocatalyst carrier carrying a catalyst mainly composed of titanium oxide and an ultraviolet lamp. The harmful substances contained in the exhaust gas can be decomposed and removed by the photocatalyst by passing through a photocatalyst device comprising a combination of the above.

When ultraviolet rays are applied to the surface of the photocatalyst (TiO _{2 of the} anatase type), electrons e ⁻ and holes h ⁺ are generated. The electrons e ⁻ and the holes h ⁺ decompose water in the air to generate hydrogen peroxide and hydroxyl radicals. This hydroxyl radical has strong oxidizing power, and its energy is 120 kcal / mol.
It is. Many binding energies are 120 kcal / mo
l, it is decomposed by the photocatalyst.

As representatives of dioxins, 2,3
There is 7,8-TCDD. This is the most toxic. The chemical structural formula is, as shown in Chemical Formula 1, where two benzene rings are 2
Two oxygens in between and two chlorines each. Here, the C—O binding energy 70.0 k
cal / mol, C-Cl binding energy 66.5 kca
1 / mol, CH bond energy 99.5 kcal / m
ol, the oxidation energy of each of the hydroxyl radicals is lower than 120 kcal / mol, and it can be considered that they are decomposed.

Embedded image In the invention according to claim 4, the photocatalyst device disposes a photocatalyst carrier in which a photocatalyst made of a titanium oxide catalyst is supported on a honeycomb-like material or a filter-like material in which a sheet is woven, and the photocatalyst device is arranged in a container in a cross-shaped manner Since an ultraviolet lamp provided with a reflection plate on the upstream side is arranged on the upstream side of the photocatalyst carrier, the exhaust gas can be surely decomposed by hydroxyl radicals at the stage of contact with the photocatalyst carrier.

According to the fifth aspect of the present invention, since clean air is ejected from the inside of the reflector in the flow direction of the exhaust gas in the photocatalyst device, even if a small amount of fly ash is mixed, the fly ash is discharged by the ultraviolet lamp. Can be discharged along the exhaust flow without touching the air.

[0017]

Embodiments of the present invention will be described below with reference to the drawings.

FIGS. 1 to 3 show a first embodiment of an incinerator exhaust gas treatment method and apparatus according to the present invention (corresponding to the first to fourth aspects of the present invention). In the exhaust gas line 2 of the incinerator 1, a cooling device 3, an incineration ash separation device 4 such as a bag filter, a photocatalyst device 5, a blower 6, and a chimney 7 are arranged in this order. Here, since the incinerator 1, the cooling device 3, the incineration ash separation device 4, the blower 6, and the chimney 7 are known, their description is omitted.

The photocatalyst device 5 includes a reaction vessel 10 comprising a cylindrical vessel having an exhaust gas inlet 11 and an exhaust gas outlet 12, which carries a catalyst containing titanium oxide as a main component so as to block the exhaust gas passage of the reaction vessel 10. Folded photocatalyst carrier 20
Are arranged in two rows at an interval, and an ultraviolet lamp 30 is disposed opposite to the upstream side of each of the photocatalyst carriers 20 and has a reflection plate 31 disposed on the upstream side.

Here, in the photocatalyst carrier 20 having a skewed shape, a supporting member 21 made of a honeycomb-like material or a filter-like material in which a sheet is woven is formed so that the pressure loss for flowing the exhaust gas does not become higher than 100 mmAq. ing. In the photocatalyst carrier 20, titanium oxide is supported on a support member 21 made of a honeycomb-like material or a filter-like material in which a sheet is woven according to a known method such as vapor deposition (CVD or the like), coating, and dipping.

[0021] As the photocatalyst, using a TiO _2, TiO ₂
To which at least one selected from the group consisting of Pt, Ag, Pd, RuO ₂ , and Co ₃ O ₄ is preferably used. Incidentally, the photocatalyst is usually preferable because a semiconductor material is effective and easily available. In terms of effect and economy, Se, Ti, Zn, Cu, Sn, Al, Ga, I
n, P, As, Sb, Bi, Cd, S, Te, Ni, F
Compounds, alloys or oxides such as e, Co, Ag, Mo, Sr, W, Cr, and Pb are preferable, and these can be used alone or in combination of two or more. For example,
Compounds include AlP, AlAs, GaP, AlS
b, GaAs, InP, GaSb, InAs, InS
b, CdS, CdSe, ZnS, MoS ₂ , WS ₂ , and oxides such as TiO ₂ , Bi ₂ O ₃ , CuO, CuO ₂ , Z
nO, MoO ₃ , InO ₃ , Ag ₂ O, PbO, SrTi
O ₃ , BaTiO ₃ , Co ₃ O ₄ , Fe ₂ O ₃ , NiO, Ru
There are O ₂ , WO ₃ and ZrO.

The ultraviolet lamp 30 is covered with a quartz tube 32, and is connected to a power supply via a connector on the wall surface of the reaction vessel 10. Here, the ultraviolet lamp 30 is not particularly limited as long as it emits light including ultraviolet light, and specifically, a low-pressure mercury lamp is desirable.
In particular, those that emit ultraviolet light having a wavelength of 400 nm or less with high efficiency are preferable.

Cooling air is passed between the ultraviolet lamp 30 and the quartz tube 32 to keep the lamp temperature low.
The reflection plate 31 is arranged on the upstream side of each photocatalyst carrier 20 facing the ultraviolet lamp 30. The reflection plate 31 allows the ultraviolet light emitted from the ultraviolet lamp 30 to efficiently reach the photocatalyst carrier 20 in a skewed shape.

Further, the reaction container 10 is provided with an inspection port 13. Next, a treatment method using the thus configured incinerator exhaust gas treatment apparatus according to the present invention according to the present embodiment will be described. When the incinerator 1 is operated according to a conventional method, exhaust gas of about 800 ° C. is discharged through the exhaust gas line 2 of the incinerator 1. Where dioxins are 800
Since it is regenerated in the temperature range of ~ 300 ° C, it is rapidly cooled by the cooling device 3 and the inlet temperature of the incineration ash separation device 4 is set to 200 ° C. The incineration ash separation device 4 removes solids such as fly ash in the exhaust gas.

After that, the exhaust gas flows into the photocatalyst device 5 through the exhaust gas inlet 11. In the photocatalyst device 5, ultraviolet light is irradiated from the ultraviolet lamp 30 to the quasi-shaped photocatalyst carrier 20 that carries a catalyst containing titanium oxide as a main component,
Electrons e ⁻ and holes h ⁺ are generated on the photocatalyst carrier 20. When the exhaust gas flows into the photocatalyst carrier 20, dioxins in the exhaust gas generate CO ₂ , H ₂ by the action of electrons emitted by the irradiation of the photocatalyst carrier 20 with ultraviolet rays.
Dioxins decomposed and removed into ₂ O and HCl and not decomposed by the action of electrons are decomposed and removed on the surface of the photocatalyst carrier 20 when passing through the photocatalyst carrier 20.

After this process has been performed twice, the exhaust gas is discharged from the exhaust gas outlet 12 and then discharged from the chimney 7 through the blower 6 to the atmosphere. As described above, in the present embodiment, dioxins in the exhaust gas are removed by the photocatalyst device 5 after removing solids such as fly ash in the exhaust gas by the incineration ash separation device 4, so that activated carbon can be used.
Compared with the conventional method in which an auxiliary agent such as NH ₃ or ammonium is added, there is no unnecessary post-treatment, the apparatus does not increase in size, and operation management is simple.

The operation management and maintenance are performed by the ultraviolet lamp 3.
The replacement of 0 is mainly performed, and the operation amount is reduced. Incidentally, the life of the ultraviolet lamp 30 is about one year. In addition, since the photocatalyst carrier 20 is in a distorted shape, the contact time with the exhaust gas can be long. Also, since the processing is performed in two stages,
Dioxins in exhaust gas can be reliably decomposed and removed.

Further, since the reflection plate 31 is provided on the upstream side of the photocatalyst carrier 20, it is possible to prevent fly ash which may be slightly mixed from adhering to the ultraviolet lamp 30. Therefore, the effect of fly ash can be minimized. In this embodiment, the case where two sets of the photocatalyst carriers 20 are provided is described, but the photocatalyst carriers 20 may be further provided.

FIG. 4 shows a second embodiment of an incinerator exhaust gas treatment method and apparatus according to the present invention (corresponding to the first to fifth aspects of the present invention). In the present embodiment, a fly ash adhesion preventing mechanism is provided on the reflection plate 31 in order to make it difficult for fly ash, which may be slightly mixed, to adhere to the ultraviolet lamp 30. Since the photocatalyst device 5 is provided on the downstream side of the incineration ash separation device 4 such as a bag filter, basically, fly ash does not adhere, but there is a possibility that the fly ash may be slightly mixed.

However, the fly ash has a very small particle diameter, is hardly affected by inertial force or gravity, and flows with the flow of air. Therefore, in the present embodiment, the reflection plate 3
1 has a double structure, and clean air is blown into the outside of the reaction vessel 10 at the same flow rate as the flow of the exhaust gas. That is,
By forming a passage 33 for clean air supplied from the outside between the two reflecting plates 311 and 312, the reflecting plate 3
Spouts 34 were formed over and under one over the longitudinal direction. Here, the upstream reflecting plate 311 is set to be longer than the reflecting plate 312, and a jet port 34 is formed between the two so as to face the downstream side of the flow of the exhaust gas.

As a result, the exhaust gas does not come into direct contact with the periphery of the ultraviolet lamp 30, and the ultraviolet lamp 30
There is no risk of fly ash adhering to the surface.

[0032]

As described above, according to the first to fifth aspects of the present invention, after removing solid matter such as fly ash in the exhaust gas by the incineration ash separation device, harmful substances in the exhaust gas are removed by the photocatalytic device. Since the substance is decomposed and removed, maintenance and management are easy without increasing the size of the facilities and equipment, and there is no influence from fly ash.

According to the fifth aspect of the present invention, it is possible to reliably prevent fly ash, which may be slightly mixed, from adhering to the ultraviolet lamp.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a first embodiment of an incinerator exhaust gas treatment method and apparatus according to the present invention.

FIG. 2 is an explanatory diagram of the photocatalyst device in FIG.

FIG. 3 is an explanatory view showing a main part of the photocatalyst device in FIG. 2;

FIG. 4 is an explanatory view showing a second embodiment of the method and apparatus for treating exhaust gas in an incinerator according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Incinerator 2 Exhaust gas line 3 Cooling device 4 Incineration ash separation device 5 Photocatalyst device 6 Blower 7 Chimney 10 Reaction container 20 Photocatalyst carrier 30 Ultraviolet lamp 31, 311, 312 Reflector 33 Passage 34 Spout

Claims (5)

[Claims] An exhaust gas discharged from an incineration ash separation device is passed through a photocatalyst device comprising a combination of a photocatalyst carrier carrying a catalyst containing titanium oxide as a main component and an ultraviolet lamp, and harmful substances contained in the exhaust gas. A method for treating exhaust gas in an incinerator, comprising decomposing and removing the waste gas. 2. The exhaust gas treatment method for an incinerator according to claim 1, wherein the harmful substance is an organic chlorine compound containing dioxins. 3. An incinerator exhaust gas line comprising a cooling device, an incineration ash separation device, and a photocatalyst device arranged in this order, wherein the photocatalyst device has a concavity-shaped photocatalyst carrier carrying a catalyst containing titanium oxide as a main component. And an ultraviolet lamp. 4. The exhaust gas treatment device for an incinerator according to claim 3, wherein the photocatalyst device comprises a photocatalyst carrier comprising titanium oxide supported on a honeycomb-like material or a filter-like material in which a sheet is woven.
An exhaust gas treatment device for an incinerator, comprising: an ultraviolet lamp having a reflection plate provided on an upstream side and disposed in an upstream side of a photocatalyst carrier while being disposed in a container in a skewed manner. 5. The exhaust gas treatment device for an incinerator according to claim 3, wherein the reflection plate has a double structure, has a passage for clean air therein, and cleans in a flow direction of the exhaust gas in the photocatalyst device. An exhaust gas treatment device for an incinerator, wherein an exhaust port for ejecting air is formed.