JP2000254552A - Method and facility for treating exhaust gas of refuse drying furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To almost completely remove harmful gases containing dioxins possible to be generated even though in a slight amount in a malodor removal and deodorization apparatus for an exhaust gas from a refuse drying furnace. SOLUTION: This method for treating an exhaust gas from a refuse drying furnace comprises a step of passing the exhaust gas generated in a refuse drying furnace through a deodorization furnace for thermal decomposition or combustion decomposition of malodorous components after dust removal and temperature increase for the exhaust gas is carried out and a step of decomposing remaining harmful substances after the exhaust gas passed through the deodorization furnace is cooled.

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 exhaust gas from a refuse drying furnace attached to a refuse drying apparatus, and more particularly to a method and apparatus for treating exhaust gas from a refuse drying furnace for drying municipal refuse. About.

[0002]

2. Description of the Related Art In treating municipal waste,
In some cases, a method of drying refuse to form a solid fuel is used. In this case, since the municipal solid waste generally contains a large amount of water and contains an odorous substance, the gas discharged from the refuse drying furnace is subjected to a deodorizing treatment. The general method is, as shown in a flow diagram in FIG. 5, a step of removing dust generated from a refuse drying furnace, a step of heating the exhaust gas, and a step of introducing the heated exhaust gas into a deodorizing furnace. Thermal decomposition or combustion decomposition of the odor component, and at this time, heat exchange is performed between the hot gas discharged from the deodorizing furnace and the exhaust gas generated from the refuse drying furnace, and the thermal decomposition is performed efficiently. It is often done.

A typical example is disclosed in JP-A-9-0520.
No. 23, but 1 at the drying furnace outlet
A gas of about 50 ° C. is burned at 600 to 700 ° C. in the deodorizer. This operation decomposes many offensive substances, but ammonia cannot be completely decomposed, and a small amount of ammonia may be released into the atmosphere. Further, since the gas generated from the drying furnace still contains dust even after dust removal, there is a possibility that dioxin may be generated in the deodorizing furnace, though the amount is small.

[0004] In order to prevent such a situation, it is conceivable to employ a means for removing the ammonia and offensive odor by bringing the gas discharged from the refuse drying oven into contact with the catalyst. However, a large amount of water vapor is contained in the exhaust gas from the refuse drying furnace, which may cause dew condensation. Therefore, a high-efficiency dust removing device such as a bag filter cannot be employed, and the catalyst is significantly deteriorated by residual dust. Therefore, the above means cannot be adopted.

[0005]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-mentioned problems of the prior art. It is an object of the present invention to provide a method and a facility for treating exhaust gas from a refuse drying oven, which can almost completely remove certain dioxins and harmful substances.

[0006]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a method for treating exhaust gas from a refuse drying furnace, which comprises removing dust generated from the refuse drying furnace, raising the temperature, and then passing the deodorizing furnace through a deodorizing furnace. After thermal decomposition or combustion decomposition of the odor component in the exhaust gas after passing through the deodorizing furnace,
Decomposing the remaining harmful gas components with a catalyst.

[0007] At this time, the temperature of the exhaust gas generated from the refuse drying furnace and the cooling of the hot gas discharged from the deodorizing furnace are performed by heat exchange between the two exhaust gases, thereby improving the thermal efficiency. Specifically, the dust removal temperature of the exhaust gas generated from the refuse drying furnace is 80 to 230 ° C, the temperature introduced into the deodorizing furnace after the temperature is raised is 250 to 550 ° C, and the thermal decomposition or combustion decomposition temperature in the deodorizing furnace is 600 to 800 ° C. And the temperature of the catalyst for decomposing the remaining harmful substances is 400 to 15
Preferably, the temperature is 0 ° C.

[0008] Further, a facility for carrying out the method for treating exhaust gas of a refuse drying furnace is provided with a dust collector connected to an exhaust gas discharge port of the refuse drying furnace, a gas which is removed by the dust collector, and a odor component is thermally decomposed. Or a deodorizing furnace for burning,
A heat exchanger for cooling the exhaust gas discharged from the deodorizing furnace and heating the exhaust gas removed by the dust collector;
And a catalyst treatment device for bringing remaining harmful substances in the exhaust gas cooled by the heat exchanger into contact with a catalyst and decomposing the catalyst.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings. As shown in FIG. 1, in treating the exhaust gas from the refuse drying furnace in the present invention, first, dust is removed from the exhaust gas generated from the refuse drying furnace. As a result, dust having a large particle size is removed from the dust discharged from the refuse drying furnace 1, and generation of harmful substances such as dioxin in a deodorizing furnace is suppressed. The gas discharged from the refuse drying furnace 1 is generally humid and easily condenses depending on the nature of the refuse to be treated. Therefore, the dust collector 3 for dust removal may be of a cyclone type, and may be of such a degree that only dust having a large particle diameter is removed. In addition, if the above-mentioned dust removal temperature is set to 80 to 230 ° C., smooth operation can be performed without worrying about dew condensation and without having to heat the dust collector at a high temperature.

The exhaust gas discharged from the dust collector 3 is heated, for example, by a heat exchanger 4 and then led to a deodorizing furnace 5 where thermal decomposition or combustion decomposition of odor components is performed. The temperature is 600 ~
The temperature is preferably set to 800 ° C. By setting the temperature to 600 ° C. or higher, dust in exhaust gas can be burned almost completely, and fine dust that cannot be collected by the dust collector 3 can also be eliminated. Further, it is possible to prevent the catalyst from deteriorating at an early stage due to the decomposition of harmful substances by the catalyst. On the other hand, the reason why the temperature is set to 800 ° C. or lower is that even if the temperature is higher than this, there is no possibility that the deodorization further progresses, and instead, the heat energy is simply wasted. To obtain the above temperature, an oil burner 11 may be used as shown in the figure.

It is preferable in terms of heat economy that the temperature is raised by exchanging heat between high-temperature exhaust gas discharged from the deodorizing furnace 5 and relatively low-temperature exhaust gas discharged from the dust collector 3. Therefore, in the apparatus according to the present invention, the heat exchanger 4 is placed so that the heat exchanger 4 raises the temperature of the exhaust gas from the dust collector 3 and cools the exhaust gas from the deodorizing furnace 5. in this case,
In order to obtain the operating temperature of the deodorizing furnace, the temperature of the exhaust gas discharged from the dust collector 3 after the temperature rise is preferably in the range of 250 to 550 ° C.

[0012] exhaust gas discharged from the deodorizing furnace 5 is not dust almost completely burn residual, NO _X or toxic substances dioxins are remained. In the present invention, utilizing the fact that no dust remains, the above gas is cooled and then passed through a catalyst treatment device 7 to remove the remaining harmful gas. As the catalyst, a titanium or vanadium-based catalyst can be used, and the following denitration reactions, 4NH ₃ + 4NO + O ₂ = 4N ₂ + 6H ₂ O dioxin decomposition reaction,

Embedded image As a result, N which is a harmful substance in the exhaust gas
O _X, or the removal of dioxins can be. In addition,
At this time, even if there is a trace amount of ammonia that cannot be decomposed in the deodorizing furnace, it can be rendered harmless by the above-described denitration reaction with nitrogen oxide or the like generated in the deodorizing furnace.

The above-described decomposition treatment with a catalyst is preferably carried out at a temperature having a high catalytic activity, for example, 200 ° C. or more as shown in FIG. Thus, NO _X or dioxins further can be converted into harmless substances such as CO _2, H ₂ O or N ₂ almost completely ammonia.

As shown in FIG. 2, it is possible to further increase the deodorizing efficiency by disposing a deodorizing device 8 further downstream of the catalyst treatment device 7. In this case, a catalyst that easily deteriorates with respect to dust can be used for the deodorizing device 8 to reduce costs. The detoxified substances and the deodorized gas in this way are discharged into the atmosphere via the exhaust pipe 9.
Further, a heat exchanger for preheating the combustion air for the deodorizing furnace 5 is provided between the heat exchanger 4 and the catalyst treatment device 7, so that the thermal efficiency of the entire device can be improved.

[0015]

EXAMPLE An exhaust gas from a refuse dryer was treated using the apparatus shown in FIG. The treatment capacity of the refuse dryer was 3 ton / hr, and a catalyst based on titanium and vanadium to which a small amount of a metal element was added was used. The capacity of the catalyst was SV = 2000 ^-1 . The operating temperature conditions in this example were as follows. Garbage drying furnace outlet: about 150 ° C After passing through a heat exchanger (after heating): about 450 ° C Deodorizing furnace temperature: about 700 ° C After passing through a heat exchanger (after cooling): about 400 ° C After passing through an air preheater: about 330 ° C Catalyst passage temperature: about 300 ° C

Table 1 shows the operation results. As shown here, as a result of the treatment with the apparatus of the present invention, harmful substances, odors and dust were almost completely removed, and even if they were released into the atmosphere, there was no problem in maintaining the environment.

[0017]

[Table 1]

[0018]

According to the present invention, as described above, the waste gas from a refuse drying furnace containing dust is burned and decomposed by a deodorizing furnace to obtain a gas containing no dust, and the remaining harmful components are removed by a catalyst treatment device. As a result, deodorization, denitration, and dioxins can be achieved very efficiently. Further, the life of the catalyst can be extended.

[Brief description of the drawings]

FIG. 1 is a flow diagram of a method for treating exhaust gas in a refuse drying furnace according to the present invention.

FIG. 2 is a flow diagram of a modification of the method for treating exhaust gas in a refuse drying furnace according to the present invention.

FIG. 3 is a diagram showing a relationship between a catalyst decomposition treatment temperature of harmful gas components and a removal rate.

FIG. 4 is a layout diagram of an apparatus according to the present invention.

FIG. 5 is a flow diagram of a conventional method for treating exhaust gas in a refuse drying furnace.

[Explanation of symbols]

 1: Garbage drying furnace 2: Hot blast furnace 3: Dust collector 4: Heat exchanger 5: Deodorizing furnace 6: Heat exchanger 7: Catalyst treatment device 8: Deodorizing device 9: Exhaust stack 11, 12: Oil burner

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B01D 53/74 B01D 53/34 134E 53/70 F term (Reference) 3K070 DA01 DA02 DA07 DA09 DA25 DA29 DA53 DA58 4D002 AA13 AA21 AB02 AC04 BA05 BA14 CA13 EA01 EA02 EA05 EA13 GB03 4D048 AA06 AA17 AA22 AB02 AB03 BA07X BA13X BA23X BA41X CC38 CC54 CD03 CD08 CD10 DA03 DA13 4D053 AA03 AB01 BA01 BB02 BC01 DA06 DA10

Claims (2)

[Claims] 1. Exhaust gas generated from a refuse drying furnace is removed, the temperature is raised, and then passed through a deodorizing furnace to thermally decompose or burn off odor components. Decomposing a harmful substance to be treated. 2. A dust collector connected to an exhaust gas outlet of a refuse drying furnace, a deodorizing furnace for receiving exhaust gas removed by the dust collector, and thermally decomposing or burning odor components; It has a heat exchanger that cools and heats the gas removed by the dust collector, and a catalyst treatment device that contacts and decomposes harmful substances remaining in the exhaust gas cooled by the heat exchanger with the catalyst. Waste gas treatment equipment for waste drying furnace.