JP3837862B2 - Electric melting furnace operation method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for operating an electric melting furnace that prevents discharge of harmful substances such as dioxin from an electric melting furnace such as an arc furnace in a steel factory, a waste melting facility, and the like.
[0002]
[Prior art]
For example, in a steel mill where an arc furnace is installed, a direct exhaust system that sucks exhaust gas generated during the melting period directly from the furnace body and directs it to the bag filter dust collector to collect dust, and at the time of scrap charging and steel output. Conventionally, there has been provided a building exhaust system that sucks exhaust gas discharged from the arc furnace into the building from a ceiling hood and leads it to a baghouse type dust collector. And since the exhaust gas of the direct exhaust system directly sucked from the furnace body has a high temperature, it is cooled through a cooling tower and then passed through a bag filter to collect dust.
[0003]
[Problems to be solved by the invention]
However, the above conventional dust collectors sufficiently capture harmful substances such as dioxins (a general term for isomers such as polychlorinated dibenzopararadixin and polychlorinated dibenzofuran) and heavy metals contained in exhaust gas. There is a problem that cannot be collected, and therefore development of a technique for improving the removal efficiency has been awaited.
[0004]
In addition, it has been conventionally performed to adsorb harmful substances in exhaust gas using an adsorbent such as activated carbon. However, since a large amount of adsorbent is required to maintain high adsorption efficiency, the cost increases. At the same time, there is a problem of how to treat a large amount of used adsorbent, and if the treatment method is poor, there is a risk that the environment will be further deteriorated due to secondary contamination.
[0005]
[Means for Solving the Problems]
The present invention has been made to solve the above-described problems in operation of the conventional electric melting furnace, and at least two bag filters are provided in series in the exhaust path of the exhaust gas discharged from the electric melting furnace. , together with the blowing carbonaceous adsorbent between the upstream side of the bag filter and the downstream side of the bag filter of the exhaust path, collecting the adsorbent by the downstream side of the bag filter, the electric melting furnace the adsorbent It is characterized by being charged and treated as a pre-fill material or a carbon injection material.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
Next, an arc type electric melting furnace for melting iron scrap will be described with reference to FIG. In the figure, 1 is an arc type electric melting furnace in which an electrode 3 is suspended in a furnace body, 10 is an exhaust gas outlet through which exhaust gas generated in the electric melting furnace 1 is discharged, and 11 is an upper side of the electric melting furnace 1. It is a ceiling hood provided on the ceiling of the building. The exhaust gas outlet 10 is provided with a combustion tower 13, a cooling tower 14, a bag filter 15, a charging device 16, a bag filter 17, and a booster blower 18 in order from the upstream, and the top hood 11 has a blower 19 via a duct 5, and A bag filter 20 is provided downstream thereof.
[0007]
The combustion tower 13 combusts and decomposes unburned components such as CO in the exhaust gas while flowing the exhaust gas downward. The cooling tower 14 has a built-in radiator for passing cooling water, and cools the temperature of the exhaust gas to 250 ° C. or less, which is the heat resistant temperature of the bag filter.
[0008]
The bag filter 15 includes a plurality of bag houses 25. The bag filter 15 collects dust in the exhaust gas, removes the dust attached to the bag filter, and discharges it to the dust transport conveyor 27. Similarly, the bag filter 17 is composed of a plurality of bag houses 28, and is configured to collect dust in the exhaust gas, remove the dust adhering to the bag filter, and discharge the dust to the dust transfer conveyor 30.
[0009]
The charging device 16 includes a hopper 31 in which powdered activated carbon is stored, a blower 32, and a charging throat 33 provided so that the front end faces the exhaust gas duct 26 between the bag filter 15 and the bag filter 17, The activated carbon in the hopper 31 is pumped to the charging throat 33 by the blower 32, and the activated carbon can be blown into the exhaust gas duct 26 from the tip of the charging throat 33. The amount of the activated carbon added is, for example, 100 to 500 mg per 1 Nm ^{3 of} exhaust gas.
[0010]
A booster blower 18 is provided on the downstream side of the bag filter 17, a flow path switching damper 34 is provided on the downstream side of the blower 18, and the blower 19 of the duct 5 of the building exhaust system is provided on the downstream side of the damper. The exhaust gas is joined to the building exhaust system, and the other is connected to an exhaust duct 35 connected to a chimney (not shown).
[0011]
The bag filter 20 includes a plurality of bag houses 36, and is configured to collect dust in the exhaust gas, remove the dust attached to the bag filter, and discharge the dust to the dust transfer conveyor 37. And it is discharged | emitted from the upper part of this bag filter 20 to air | atmosphere as clean gas.
[0012]
Therefore, the exhaust gas at 800 to 1200 ° C. sucked from the electric melting furnace 1 by the operation of the blower 18 is subjected to CO combustion or the like through the combustion tower 13 and is cooled to 250 ° C. or less by passing through the cooling tower 14. After that, fine dust containing dioxins, heavy metals and the like is collected by the bag filter 15. The temperature of the exhaust gas downstream of the bag filter 15 is 150 ° C. or lower.
[0013]
Then, when activated carbon is blown from the charging device 16, harmful substances such as dioxins and heavy metals are adsorbed to the activated carbon, and the activated carbon can be collected by the bag filter 17 downstream thereof. In this manner, the amount of activated carbon added can be reduced by adding activated carbon downstream of the bag filter 15 as compared to adding activated carbon upstream of the bag filter 15. In addition, the addition at the downstream side of the bag filter 15 has an advantage that the temperature of the exhaust gas is sufficiently lowered and the risk of dust explosion, fire, etc. is reduced because the fire type is trapped by the bag filter 15.
[0014]
In addition, acidic gas such as HCl and SO4 in the exhaust gas can be neutralized by filling the hopper 31 with a mixture of activated carbon and slaked lime and blowing slaked lime with the activated carbon. It is also possible to suppress the regeneration of harmful substances such as.
[0015]
The exhaust gas discharged from the bag filter 17 through the booster blower 18 can be discharged into the atmosphere as it is through the exhaust duct 35. By combining the damper 34 with the exhaust gas of the building exhaust system, Since the concentration can be greatly diluted and the temperature is lowered to about 60 ° C., the solidification of harmful substances such as dioxins further proceeds and can be reliably collected by the bag filter 20.
[0016]
In the present invention, the activated carbon collected by the bag filter 17 and collected on the dust conveyor 30 is pre-filled into the electric melting furnace 1 by pneumatic transportation or the like as indicated by the broken line 6 in FIG. Or, it is charged as a carbon injection material. The charged activated carbon is used for heating the molten metal, or can be effectively used as a reducing agent for the molten metal and a component adjusting material. In addition, harmful substances such as dioxin adsorbed on the activated carbon are thermally decomposed by being heated to a high temperature of 800 ° C or higher in the furnace, so that the environment deteriorates due to secondary pollution as when the activated carbon is discarded as it is. There is no risk of causing any problems.
[0017]
The activated carbon collected by the bag filter 20 as well as the activated carbon collected by the bag filter 17 may be charged into the electric melting furnace 1.
In addition to the combustion tower 13 and the cooling tower 14 shown in the embodiment, a scrap bucket preheating chamber, a twin bucket preheating chamber, and the like may be provided between the electric melting furnace 1 and the bag filter 15.
[0018]
In the embodiment of FIG. 1, the activated carbon blown into the duct is collected by the bag filter. However, as shown in FIG. 2, the adsorption tower 40 storing the activated carbon is used as the exhaust gas exhaust system of the electric melting furnace 1. The exhaust gas may be passed through the adsorption tower to adsorb harmful substances such as dioxins. That is, the adsorption tower 40 shown in FIG. 2 is provided with an exhaust gas inlet 41 on the lower side wall and an exhaust gas outlet 42 on the upper side wall, and a funnel-shaped low wall 44 is formed in a double bottom so that a ventilation gap 43 is formed, Activated carbon 46 flowing down from the hopper 45 is stored on the low wall 44, and the exhaust gas flowing in from the exhaust gas inlet 41 enters the activated carbon storage part through the ventilation gap 43 as shown by the arrow in the figure, and toward the exhaust gas outlet 42. While rising, harmful substances are adsorbed on the activated carbon.
[0019]
The activated carbon that has adsorbed the harmful substances is discharged by releasing the lower gate valve 47, and the activated carbon is similarly charged into the electric melting furnace 1 as a pre-fill material or a carbon injection material. The adsorption tower 40 can adsorb fine dust containing chromium, tin, manganese, and the like, and organic chlorine compounds such as dioxin, sulfur compounds, nitrogen oxides, and the like that cannot be collected even by bag filters. The cleaned exhaust gas is released into the atmosphere. In addition to activated carbon, carbon-based adsorbents such as lignite can be used for the adsorption tower.
[0020]
【The invention's effect】
As described above, in the operation method of the electric melting furnace according to the present invention, harmful substances such as dioxin contained in the exhaust gas of the electric melting furnace can be removed with high efficiency, and the carbon-based adsorbent adsorbing the harmful substances can be electrically melted. By charging and treating the furnace, there is no risk of environmental deterioration due to secondary contamination, and there is a beneficial effect that the adsorbent can be used effectively.
[Brief description of the drawings]
FIG. 1 is an exhaust gas system diagram showing an embodiment of an electric melting furnace operating method according to the present invention.
FIG. 2 is a longitudinal sectional view of an adsorption tower used for carrying out the method for operating an electric melting furnace according to the present invention.
[Explanation of symbols]
1 Electric melting furnace 10 Exhaust gas outlet 13 Combustion tower 14 Cooling tower 15 Bag filter 16 Loading device 17 Bag filter 20 Bag filter 40 Adsorption tower

Claims (1)

At least two bag filters are provided in series in the exhaust path of the exhaust gas discharged from the electric melting furnace , and a carbon-based adsorbent is blown between the upstream bag filter and the downstream bag filter in the exhaust path, collecting the adsorbent with the downstream side of the bag filter, charged to the process operation method for an electro-melting furnace, characterized in that the adsorbent as first-material or carbon injection material into the electric melting furnace.

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