JP2000288351A - Exhaust gas treatment equipment for electric furnaces - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To effectively remove dioxin in exhaust gas. SOLUTION: A bag house 23 is provided in a direct drawing system exhaust path 2 for directly sucking exhaust gas from an electric furnace 1, and dust in the exhaust gas is collected by an internal bag filter 231.
A catalyst reaction tower 25 is provided downstream of the baghouse 23,
Dioxin in exhaust gas is oxidatively decomposed and removed by the catalyst layer provided inside. The catalyst layer is made of titanium oxide, vanadium pentoxide, tungsten or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas treatment device for an electric furnace, and more particularly to an exhaust gas treatment device for removing dioxin contained in exhaust gas from an electric furnace.

[0002]

2. Description of the Related Art Conventionally, many exhaust gas treatment apparatuses for electric furnaces such as arc furnaces mainly aim at collecting dust discharged during the operation of the furnace. The dust inside is collected and removed.

[0003]

However, in recent years, there has been a problem that dioxin is discharged from an arc furnace, particularly in the early stage of melting, and it has been desired to provide an effective exhaust gas treatment apparatus for removing dioxin. I have.

Accordingly, an object of the present invention is to solve such a problem, and an object of the present invention is to provide an exhaust gas treatment apparatus for an electric furnace which can effectively remove dioxin in exhaust gas.

[0005]

In order to achieve the above object, an exhaust gas treatment apparatus for an electric furnace according to the first invention is provided with a bag filter (2) in an exhaust path (2) for directly sucking exhaust gas from the electric furnace (1). 231) and a bag filter (23)
A catalyst layer (25) for decomposing dioxin in exhaust gas is provided downstream of 1). Note that the catalyst layer is made of titanium oxide, vanadium pentoxide, tungsten, or the like.

In the first invention, the exhaust gas discharged from the electric furnace is collected by a bag filter to collect dust.
Dioxin contained in the exhaust gas is decomposed and removed by the catalyst layer and purified.

In the second invention, a reducing agent is added to the exhaust gas upstream of the catalyst layer. In addition, as the reducing agent, ammonia or the like can be used. According to the second invention, NOx in the exhaust gas can be removed in addition to the dioxin according to the first invention.

[0008] The reference numerals in parentheses indicate the correspondence with specific means described in the embodiments described later.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) FIG. 1 shows the overall configuration of an exhaust gas treatment device for an arc furnace. The exhaust path of the exhaust gas treatment device is connected to the exhaust gas outlet 11 of the arc furnace 1 and directly sucks the exhaust gas, and is connected to the ceiling hood 31 above the arc furnace 1 and indirectly sucks the exhaust gas. Two exhaust systems 3 are provided for the building system.

The exhaust gas outlet 11 is provided with an openable / closable outside air inlet 12, to which a direct drawing system exhaust path 2 is connected. The combustion tower 21,
A cooling tower 22 provided with a heat exchanger 221 therein and a bag house 23 provided with a plurality of bag filters 231 are provided, and a heater 24 and a catalyst reaction tower 25 are provided downstream of the bag house 23, respectively. ing. The catalyst reaction tower 25 has a known structure, in which a catalyst layer made of titanium oxide, vanadium pentoxide, tungsten, or the like is supported on a porous catalyst carrier such as a plate or honeycomb.

A booster blower 26 is provided downstream of the catalytic reaction tower 25. The direct drawing exhaust passage 2 is connected to the building exhaust passage 3 at a position downstream of the booster blower 26 and communicates therewith, and selectively communicates with an exhaust duct 28 leading to a chimney by a switching damper 27 provided on the way. Let me do. On the other hand, an opening / closing damper 32 is provided in the base opening of the hood 31 in the building exhaust passage 3, and a blower 33 and a plurality of bag filters 341 are built in a position downstream of the connection point with the direct drawing exhaust passage 2. A bag house 34 is provided.

In such an exhaust gas treatment apparatus, when the operation of the arc furnace 1 is started, the blowers 26 and 33 are activated, and the exhaust gas from the arc furnace 1 is passed through the direct exhaust line 2 and the building exhaust line 3 respectively. Is started. Direct pulling exhaust path 2
In the above, after the exhaust gas discharged at a temperature of 800 to 1200 ° C. flows into the combustion tower 21, the exhaust gas passes through the cooling tower 22 and is cooled to 250 ° C. or lower, which is the heat-resistant temperature of the bag filter 231, The dust is mainly collected by the bag filter 231.

The temperature of the exhaust gas leaving the baghouse 23 is 15
Since the temperature is 0 ° C. or lower, the heater can be reheated by the heater 24 to maintain the activity of the catalyst layer of the catalyst reaction tower 25.
Raise temperature to 0-200 ° C. The heated exhaust gas flows into the catalytic reaction tower 25, and dioxin contained in the exhaust gas is oxidatively decomposed and removed by the catalyst layer while passing through the catalytic reaction tower 25.

The exhaust gas that has passed through the catalytic reaction tower 25 flows into the building exhaust passage 3 via the blower 26 and mixes with the exhaust gas flowing through the building exhaust passage 3. As a result, the temperature of the exhaust gas is greatly reduced to around 60 ° C., and the solidification of dioxin remaining in the exhaust gas proceeds. The exhaust gas that has flowed into the bag house 34 is purified by collecting the solidified dioxin and dust contained in the bag house 34 with the bag filter 341 and then discharging the exhaust gas into the outside air.

(Second Embodiment) The exhaust gas treatment apparatus of the present invention can be applied to a scrap preheating type arc furnace as shown in FIG. In FIG. 2, the arc furnace 1
A scrap furnace top preheating tower 4 is provided above the inside, and support shelves 41 and 42 which can be developed downward in two stages vertically.
Are disposed, and a scrap M is placed on the support shelves 41 and 42. A scrap catcher 29 is provided at the uppermost stream of the direct exhaust path 2 connected to the exhaust gas outlet 11, and a U-shaped curved flow path P is provided inside the scrap catcher 29 by a baffle plate 291 extending downward. Are formed. Scrap catcher 29
At the subsequent stage, a combustion tower 21 and a cooling tower 22 having a heat exchanger 221 provided therein are provided. Further, a heater 24 and a catalyst reaction tower 25 similar to those described in the first embodiment are provided downstream of the cooling tower 22. Other structures are the same as those of the first embodiment already described.

The high-temperature exhaust gas discharged from the arc furnace 1 heats the scrap M on the lower support shelf 42 while going to the exhaust gas outlet 11, and also heats the scrap M on the upper support shelf 41 via the bypass passage 43. I do. Exhaust gas outlet 1
Exhaust gas flowing out of 1 flows through the flow path P of the scrap catcher 29, and during this circulation, the scrap flying with the exhaust gas is separated downward by inertia.

After the exhaust gas flows into the combustion tower 21 in the next stage,
It flows into the cooling tower 22 and is cooled to 250 ° C. or lower, which is the heat-resistant temperature of the bag filter 231. The cooled exhaust gas flows into the baghouse 23, where dust is mainly collected by the bag filter 231, and after the temperature is increased by the heater 24, the exhaust gas passes through the catalytic reaction tower 25, where dioxin in the exhaust gas is oxidized and decomposed and removed. Is done. Subsequent exhaust gas treatment is the same as in the first embodiment.

(Other Embodiments) The First and Second Embodiments
In the embodiment, if a reducing agent such as ammonia is added to the exhaust gas before passing through the catalyst layer of the catalytic reaction tower 25, NOx in the exhaust gas can be removed in addition to dioxin. Further, since the dust and dioxin in the exhaust gas have been almost completely removed and the exhaust gas has been rendered harmless when passing through the catalytic reaction tower 25, it is necessary to always join the direct exhaust system 2 to the building exhaust system 3. There is no.

[0019]

As described above, the exhaust gas treating apparatus for an electric furnace according to the present invention can effectively remove dioxin in exhaust gas.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an entire configuration of an exhaust gas treatment apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing an overall configuration of an exhaust gas treatment device according to another embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Electric furnace, 2 ... Exhaust passage, 23 ... Bag house, 231 ...
Bag filter, 25: catalytic reaction tower.

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Claims (2)

[Claims] 1. An exhaust gas treatment for an electric furnace, wherein a bag filter is provided in an exhaust passage for directly sucking exhaust gas from the electric furnace, and a catalyst layer for decomposing dioxin in the exhaust gas is provided downstream of the bag filter. apparatus. 2. The exhaust gas treatment device for an electric furnace according to claim 1, wherein a reducing agent is added to the exhaust gas upstream of the catalyst layer.