JP3570885B2 - Exhaust gas treatment equipment for electric ash melting furnace - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an exhaust gas treatment facility of an electric ash melting furnace such as a resistance type, an arc type, and a plasma type.
[0002]
[Prior art]
When a bag filter, which is a dry-type smoke cleaning device, is used as a dust collector of an exhaust gas treatment facility of an ash melting furnace, it is conceivable to apply a conventional waste gas incinerator or a burner type ash melting furnace. That is, as shown in FIG. 2, for example, the exhaust gas discharged from the plasma type ash melting furnace 1 is introduced into the secondary combustion chamber 2, and the secondary air is supplied and burned by the burner 3. Since the temperature of the exhaust gas discharged from the secondary combustion chamber 2 is as high as 800 to 900 ° C. and cannot be directly introduced into the bag filter, the exhaust gas is introduced into the gas cooling tower 4, cooled down, and then introduced into the bag filter 5. The dust is then removed from the chimney 7 via the induction fan 6. On the upstream side of the bag filter 5, chemicals such as slaked lime and activated carbon for DXN removal and an auxiliary agent for preventing clogging are included in the exhaust gas by a dry method for desalination, denitration, and reduction of dioxin (hereinafter referred to as DXN). A chemical blowing device 8 for blowing is provided, and is blown into exhaust gas together with pneumatic air at room temperature.
[0003]
[Problems to be solved by the invention]
By the way, since the amount of exhaust gas discharged from the plasma type ash melting furnace is much smaller than that of the burner type ash melting furnace and the incinerator, the exhaust gas is cooled by the pneumatic air of the chemical. In the bag filter 5, since slaked lime deliquesces and solidifies when the exhaust gas temperature is lower than 160 ° C., it is necessary to maintain the temperature at 160 ° C. or higher, and the exhaust gas temperature before introduction into the bag filter 5 is set to 160 ° C. or higher. Then, the exhaust gas temperature at the outlet of the gas cooling tower 4 becomes about 300 ° C. However, the temperature around 300 ° C. is the temperature at which DXN is most easily generated, and there is a problem that the exhaust gas cannot be held at around 200 ° C.
[0004]
An object of the present invention is to solve the above-mentioned problems and to provide an exhaust gas treatment facility of an electric ash melting furnace capable of satisfactorily treating exhaust gas using a bag filter without generating DXN.
[0005]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a gas cooling means for cooling exhaust gas discharged from an electric ash melting furnace, and a chemical which reacts with and adsorbs harmful substances in the exhaust gas in the exhaust gas discharged from the gas cooling means. And a bag filter that removes dust and harmful substances by introducing exhaust gas after injecting the drug, and a part of the exhaust gas at around 160 ° C. discharged from the bag filter, An exhaust gas circulation line for supplying a chemical as a pneumatic fluid of the apparatus is provided, and the exhaust gas temperature is rapidly cooled to about 200 ° C. by the gas cooling means, and then supplied to a bag filter .
[0006]
According to the above configuration, since the exhaust gas at around 160 ° C. is used as the pneumatic fluid of the drug supply device via the exhaust gas circulation line after the dust removed from the bag filter, the amount of exhaust gas discharged from the ash melting furnace is reduced. At least, the temperature of the exhaust gas introduced into the bag filter from the exhaust gas cooling means does not significantly decrease. Therefore, the exhaust gas cooling means can rapidly cool the high-temperature exhaust gas to about 200 ° C., which is somewhat higher than the temperature at which the introduction of the bag filter is not hindered, thereby preventing the generation of DXN beforehand. Dust and harmful substances of the exhaust gas discharged from the melting furnace can be effectively removed. In addition, since a part of the exhaust gas discharged from the bag filter is circulated to the upstream side of the bag filter, the dust removal efficiency of the bag filter can be improved.
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
Here, an embodiment of a plasma type ash melting furnace according to the present invention will be described with reference to FIG. The same members as those described in the conventional example are denoted by the same reference numerals and described.
[0008]
In the plasma type ash melting furnace 1, a base metal 1a is accommodated as a conductor at the bottom, a working gas such as nitrogen gas is blown into the inside, and a power supply device (see FIG. (Not shown), a plasma arc is formed between the base metal 1a and the electrode 1b, and ash is supplied from the hopper 1c onto the molten base metal 1a to be heated and melted. The slag is discharged in an overflow format. The secondary combustion chamber 2 supplies secondary air to exhaust gas discharged from the ash melting furnace 1 and completely burns the exhaust gas with the burner 3.
[0009]
An exhaust gas duct 11 from the gas cooling tower 4, which is a gas cooling means for cooling the exhaust gas, to the bag filter 5 is connected to a drug supply pipe 12 from a drug blowing device 8, which is a drug supply means. Chemicals such as activated carbon for DXN removal and an auxiliary agent for preventing clogging are blown into the exhaust gas. The bag filter 5 removes dust and reactants with the medicine. An exhaust gas circulating line 14 for using a part of the exhaust gas as a pneumatic pumping fluid for the medicine is connected to a gas discharge duct 13 for discharging the exhaust gas from the bag filter 5. It is connected to the medicine blowing device 8 via the sending fan 15 and uses the exhaust gas after dust removal at around 160 ° C. which is slightly lower than the inlet temperature 160 to 200 ° C. of the exhaust gas of the bag filter 5 as the pneumatic fluid for the medicine. The temperature of the exhaust gas sent from the gas cooling tower 4 to the bag filter 5 is prevented from lowering. Thereby, in the gas cooling tower 4, the temperature of the exhaust gas can be rapidly cooled from 800 to 900 ° C. to about 200 ° C., and generation of DXN is prevented by extremely shortening the residence time at about 300 ° C.
[0010]
In the above configuration, the exhaust gas discharged from the plasma type ash melting furnace 1 is introduced into the secondary combustion chamber 2, to which secondary air is added, and completely burned by the burner 3. The exhaust gas discharged from the secondary combustion chamber 2 is introduced into the gas cooling tower 4, rapidly cooled from 800 to 900 ° C. to around 200 ° C., and then introduced into the bag filter 5 via the exhaust gas duct 11. During the transfer of the exhaust gas duct 11, chemicals such as slaked lime, activated carbon for DXN removal, and an auxiliary agent for preventing clogging are injected into the exhaust gas from the chemical injection device 8 via the chemical supply pipe 12, and the chemicals are exhausted. It reacts or is adsorbed with salts and heavy metals and DXN therein, and condensed reaction products and dust of these harmful substances are captured by the bag filter 5. At this time, a part of the exhaust gas after dust removal taken out from the gas exhaust duct 13 at the outlet of the bag filter 5 through the exhaust gas circulation line 14 is used as a fluid for pneumatically pumping the medicine. Also, the temperature of the exhaust gas introduced into the bag filter 5 does not drop significantly and does not become lower than 160 ° C. at which slaked lime deliquesces. The remaining exhaust gas is discharged from the chimney 7 via the attraction fan 6.
[0011]
According to the above-described embodiment, the exhausted gas discharged from the bag filter 5 and discharged at around 160 ° C. is used as the pneumatic fluid of the chemical supply device 8 through the exhaust gas circulation line 14, and thus is discharged from the ash melting furnace 1. Even if the amount of exhaust gas to be discharged is small, the temperature of the exhaust gas introduced from the exhaust gas cooling tower 4 to the bag filter 5 by the pneumatic fluid (gas) for injecting the medicine does not significantly decrease. Therefore, in the exhaust gas cooling tower 4, the exhaust gas can be rapidly cooled from 800 to 900 ° C. to approximately 200 ° C., which is slightly higher than 160 ° C. at which deliquescent of slaked lime occurs. For this reason, the residence time of the exhaust gas at around 300 ° C. can be instantaneous, and the generation of DXN can be prevented.
[0012]
In addition, since a part of the exhaust gas discharged from the bag filter 5 is circulated to the upstream side of the bag filter 5 by the exhaust gas circulation line 14, the dust removing effect of the bag filter 5 can be further improved.
[0013]
In the above embodiment, the plasma type ash melting furnace 1 is used, but the present invention can be applied to an electric type melting furnace having a small amount of exhaust gas, such as a resistance type ash melting furnace and an arc type ash melting furnace.
[0014]
【The invention's effect】
As described above, according to the first aspect of the present invention, the dust-exhausted exhaust gas discharged from the bag filter and having a temperature of about 160 ° C. is used as the pneumatic fluid of the drug supply device via the exhaust gas circulation line. Even if the amount of the exhaust gas discharged from the ash melting furnace is small, the temperature of the exhaust gas introduced into the bag filter from the exhaust gas cooling means does not significantly decrease. Therefore, the exhaust gas cooling means can rapidly cool the high-temperature exhaust gas to about 200 ° C., which is somewhat higher than the temperature at which the introduction of the bag filter is not hindered, thereby preventing the generation of DXN beforehand. Dust and harmful substances of the exhaust gas discharged from the melting furnace can be effectively removed. Further, since a part of the exhaust gas discharged from the bag filter is circulated to the upstream side of the bag filter, the dust removal efficiency of the bag filter can be improved.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing an exhaust gas treatment facility of a plasma ash melting furnace according to the present invention.
FIG. 2 is a configuration diagram when a conventional exhaust gas treatment facility using a bag filter is applied to a plasma type ash melting furnace.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Plasma ash melting furnace 2 Secondary combustion chamber 3 Burner 4 Gas cooling tower 5 Bag filter 6 Induction fan 7 Chimney 8 Chemical injection device 11 Exhaust gas duct 12 Chemical supply pipe 13 Gas exhaust duct 14 Exhaust gas circulation line

Claims (1)

Gas cooling means for cooling exhaust gas discharged from the electric ash melting furnace,
A drug supply device for blowing a drug that reacts with and adsorbs harmful substances in the exhaust gas into the exhaust gas discharged from the gas cooling means,
A bag filter that removes dust and harmful substances by introducing exhaust gas after injecting the medicine,
An exhaust gas circulation line that supplies a part of the exhaust gas at around 160 ° C. discharged from the bag filter as a pneumatic fluid of the drug of the drug supply device,
An exhaust gas treatment facility for an electric ash melting furnace, wherein the exhaust gas temperature is rapidly cooled to about 200 ° C. by the gas cooling means and then supplied to a bag filter .

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