JP2003148719A - Exhaust gas treatment device for melting furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust gas treatment device which reduces an operating cost and equipment expenses by feeding an exhaust gas including ash dust, NOx, and SO2 which is exhausted from a melting furnace such as ash melting furnaces to a dust collector and a denitration equipment to clean the gas. SOLUTION: The temperature of an exhaust gas is reduced by diluting with an external air fed to an exhaust pipe 2 of a melting furnace 1, and the exhaust gas is then fed to a dust collector 4. In addition, some amounts of the secondary exhaust gas of the dust collector are bypassed to a burner 5 in which the exhaust gas and a fuel is mixed and burned. By burning the fuel using oxygen including in the exhaust gas which is mixed with an external air, the temperature of the exhaust gas increases again, and the exhaust gas is then fed to a denitration equipment 7.

Description

DETAILED DESCRIPTION OF THE INVENTION [0001] The present invention relates to the passing dust discharged from the melting furnace ash melting furnace, NOx, and an exhaust gas containing SO ₂ in a dust collector and a denitration device The present invention relates to an exhaust gas treatment device for purifying and discharging exhaust gas. 2. Description of the Related Art 10 discharged from a melting furnace such as an ash melting furnace.
Exhaust gas at about 00 ° C. contains a large amount of dust and also contains irritating acidic gases such as NOx and SO ₂ . Conventionally, exhaust gas treatment equipment for removing these
As shown in FIG. 3, a cooling means 3 for introducing outside air into the exhaust path 2 of the melting furnace 1 to dilute the exhaust gas and spray water to remove heat of vaporization is provided to reduce the temperature of the exhaust gas by a bag filter. After the lime is blown into the exhaust gas as an absorbent, the exhaust gas is guided to a bag filter dust collector 4 to collect dust from the exhaust gas. Thereafter, the hot air generated by the hot air generating furnace 6 provided with the burner 5 for mixing and burning the fuel and the combustion air at an appropriate ratio is guided to the exhaust path to be mixed with the exhaust gas, thereby reducing the exhaust gas. Reducing denitration reaction is possible 2
It was reheated to about 10 ° C., guided to a denitration device 7 for denitration and desulfurization, and discharged from the chimney 8 to the atmosphere. Further, in the wet exhaust gas treatment apparatus shown in FIG. 4, a salt washing tower 9 is provided on the secondary side of the dust collector 4, and various salts are absorbed by sodium salts, ammonium salts, etc. Since the temperature of the exhaust gas drops to about 50 ° C. on the secondary side of the above, the temperature of the exhaust gas is raised again to about 210 ° C. by the hot air generated by the hot air generating furnace 6, and the exhaust gas is led to the denitration device 7. [0004] In the above-mentioned conventional exhaust gas treatment apparatus, the combustion air is added to the fuel by the burner 5 and the hot air generated thereby is mixed with the exhaust gas. Therefore, the amount of exhaust gas that needs to be treated increases, and the required treatment capacity of the denitration device 7 must be increased. Further, the fuel cost consumed by the burner 5 is also large. Note that the reheating may be in an environment where high-pressure steam or in-house generated power can be used as a heat source.However, when the melting furnace is installed alone, such an environment is not used. However, it is often not advisable to use it because the power selling ability etc. is reduced. SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above problems and to provide an exhaust gas treatment apparatus for a melting furnace which can reduce running costs and equipment costs. [0005] For this purpose, an exhaust gas treatment apparatus for a melting furnace according to the present invention reduces the temperature of the exhaust gas by introducing outside air into the exhaust path of the melting furnace and diluting the exhaust gas. Providing a burner that guides the dust collector and bypasses a part of the exhaust gas on the secondary side of the dust collector to mix and burn the exhaust gas and the fuel; and burns the fuel based on oxygen in the exhaust gas introduced by the outside air. After the temperature of the exhaust gas is raised again, the exhaust gas is guided to a denitration apparatus. Next, an embodiment of the present invention will be described with reference to FIG. In the figure, 1 is a melting furnace, 2 is an exhaust passage thereof, 3 is a cooling means for introducing outside air to dilute exhaust gas from the exhaust passage and spraying water to take away heat of vaporization. It is a bag filter dust collector provided for removing dust from exhaust gas cooled to ° C.
Reference numeral 6 denotes a hot-air generating furnace provided with a burner 5, which supplies a fuel such as city gas to the burner 5, and also provides a bypass 11 in an exhaust path 10 connecting the dust collector 4 and the denitration device 7, and A part of the exhaust gas is guided from the secondary side to the burner 5 and mixed with the fuel, and the fuel is burned in the hot air generator 6 by the oxygen contained in the exhaust gas. The exhaust gas contains sufficient oxygen necessary for combustion since the outside air is introduced for cooling as described above. Thus, the hot air generated in the hot air generating furnace 6 is returned to the exhaust path 10 by the bypass path 12 and mixed with other exhaust gas so that the exhaust gas temperature becomes about 210 ° C. at which reductive denitration reaction is possible. It is led to the denitration device 7 for denitration and desulfurization.
The chimney 8 discharges into the atmosphere. As described above, a part of the exhaust gas is guided to the burner 5 so as to substitute for the combustion air, so that the amount of the exhaust gas to be treated by the denitration device 7 is not unnecessarily increased, and the fuel is not increased. Is also saved. By the way, Table 1 is shown in FIG.
2 shows the calculation results of the heat balance between the conventional apparatus shown in FIG. 1 and the apparatus of the present invention shown in FIG. Here, the specific heat of each gas is set to 0.34 (kcal / Nm ³ · ° C.), and the fuel is city gas 13A (lower calorific value 9940 (kcal /
Nm ³ )) and the theoretical air amount is 10.95 (m ³ / m
³ fuel gas), a combustion product of 12.05 (m ³ / m ³ fuel gas), a treatment exhaust gas amount of 17000 (Nm ³ / h), and an air ratio of 1.2. After dust collection, the exhaust gas temperature was set at 150 ° C. in consideration of dioxin resynthesis, and the temperature at the denitration apparatus was set at a general denitrification enable temperature of 210 ° C. The room temperature was set to 20 ° C., which was used as a reference temperature for calculation. As a result, in this device, 3
Energy reduction of 3307 kcal / h (8.7%) was achieved. [Table 1] FIG. 2 shows an embodiment in which the present invention is applied to a wet exhaust gas treatment apparatus provided with a salt washing tower 9 on the secondary side of the dust collector 4. In this case, since the exhaust gas temperature on the secondary side of the salt washing tower 9 is as low as 50 ° C., the fuel saving rate in the burner 5 becomes more remarkable. Table 2 also shows the results of calculating the heat balance between the conventional apparatus shown in FIG. 4 and the apparatus of the present invention shown in FIG. 2 under the same conditions as in Table 1. As a result, in this apparatus, 88820 kcal / h (8.7)
%). [Table 2] In the embodiment shown in FIGS. 1 and 2, the hot air generator 6 is provided, but in the present invention, the burner 5 is directly attached to the exhaust path 10 without using the hot air generator, and You may make it burn. As described above, the exhaust gas treatment apparatus for a melting furnace according to the present invention is provided with a burner for bypassing a part of the exhaust gas on the secondary side of the dust collector and mixing and burning the exhaust gas and the fuel. Since the temperature of the exhaust gas is raised again by burning the fuel based on the oxygen in the exhaust gas introduced by the above, the fuel for reheating can be saved, the running cost can be reduced, and the denitration apparatus can be used. Since the amount of exhaust gas requiring treatment is not increased as in the conventional case, there is a beneficial effect such as a reduction in equipment costs.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an exhaust gas system diagram showing an embodiment of an exhaust gas treatment device for a melting furnace according to the present invention. FIG. 2 is an exhaust gas system diagram showing another embodiment of the exhaust gas treatment device for a melting furnace according to the present invention. FIG. 3 is an exhaust gas system diagram of a conventional exhaust gas treatment device for a melting furnace. FIG. 4 is an exhaust gas system diagram of a conventional exhaust gas treatment device for a melting furnace. [Description of Signs] 1 Melting furnace 2 Exhaust passage 3 Cooling means 4 Dust collector 5 Burner 6 Hot air generating furnace 7 Denitration device 9 Salt washing tower 10 Exhaust passage 11 Bypass passage

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Claims (1)

Claims 1. An outside air is introduced into an exhaust passage of a melting furnace to dilute the exhaust gas, thereby lowering the temperature of the exhaust gas, leading the exhaust gas to a dust collector, and extracting one of the exhaust gas on the secondary side of the dust collector. After providing a burner for bypassing the section and mixing and burning the exhaust gas and the fuel, the temperature of the exhaust gas is raised again by burning the fuel based on the oxygen in the exhaust gas introduced by the outside air, and then removing the exhaust gas. An exhaust gas treatment device for a melting furnace, which is led to a denitration device.