JP2011025123A - Exhaust gas treatment method and exhaust gas treatment equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust gas treatment method which can inhibit the adsorption of ammonia by a catalyst for mercury oxidation reaction and simplify treatment steps as a whole, as well as exhaust gas treatment equipment. <P>SOLUTION: This exhaust gas treatment equipment 1 is for sending an exhaust gas to a denitrification device 5 from a fire furnace 2, and the denitrification device 5 includes a first catalyst 10 which brings about mercury oxidation reaction and a second catalyst 11 which generates a denitrification reaction downstream of the first catalyst 10. In addition, an ammonia adding line 12 which adds ammonia, is arranged between the first catalyst 10 and the second catalyst 11. When the exhaust gas is treated, a halogenated gas is kept in such a state that it coexists in the exhaust gas from the fire furnace 2, and a hardly soluble metallic mercury contained in the exhaust gas is transformed to a water-soluble divalent mercury with the help of the first catalyst 10. Next, the exhaust gas is denitrified by the second catalyst 11 with the addition of ammonia supplied from the ammonia adding line 12. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an exhaust gas treatment method and exhaust gas treatment equipment for treating exhaust gas from a furnace.

  In general, a coal-fired boiler exhaust gas treatment facility is provided with a denitration device, a dust collector, and a desulfurization device in order from the upstream side in a flow path through which exhaust gas flows from a furnace to a chimney.

  The denitration apparatus is configured to include a predetermined catalyst, and NOx in the exhaust gas is reduced and removed by the catalyst in the presence of ammonia in the presence of ammonia. The dust collector is an electric dust collector, a bag filter or the like, and removes soot and dust in the exhaust gas. Further, the desulfurization apparatus is provided with a spraying means for spraying a reaction liquid containing calcium carbonate, and SOx in the exhaust gas is removed as calcium sulfate by spraying the reaction liquid.

On the other hand, when coal is burned in a coal-fired boiler, it may contain slightly soluble metal mercury Hg ^{0 in} the exhaust gas. Therefore, hydrogen chloride HCl is added to the exhaust gas and mercury oxidation reaction is performed. It is considered that a catalyst is provided, and that the hardly soluble metal mercury Hg ⁰ is converted into a water-soluble divalent mercury Hg ²⁺ [formula 1] and dissolved and removed by a wet desulfurization apparatus.
[Formula 1]
Hg ⁰ + 2HCl + 1 / 2O ₂ → HgCl ₂ + H ₂ O
Here, divalent mercury Hg ²⁺ is represented by HgCl ₂ .

  As another example of the exhaust gas treatment facility, a denitration device, an ammonia decomposition catalyst, an air heater, a dust collector, and a desulfurization device are arranged in order from the upstream side in the flow path for flowing exhaust gas from the boiler to the chimney. There is a type in which a mercury oxidation catalyst is disposed between the air heater, between the air heater and the dust collector, or between the dust collector and the desulfurizer (see Patent Document 1).

JP 2004-237244 A

  However, ammonia that reduces NOx in the exhaust gas is adsorbed on the catalyst for mercury oxidation reaction, so that the reaction between hydrogen chloride and the hardly soluble metal mercury on the catalyst for mercury oxidation reaction is inhibited, and the hardly soluble metal There was a problem that mercury could not be properly transformed. Further, when the ammonia decomposition catalyst is arranged as in other examples to eliminate the influence of ammonia, there is a problem that the entire configuration becomes complicated and the manufacturing cost increases.

  In view of such circumstances, the present invention is intended to provide an exhaust gas treatment method and an exhaust gas treatment facility that prevent ammonia from being adsorbed on a catalyst for mercury oxidation reaction and simplify the overall configuration.

The exhaust gas treatment method of the present invention includes a first catalyst that generates a mercury oxidation reaction in a flow path for flowing exhaust gas from a furnace, and an exhaust gas treatment method that includes a second catalyst that generates a denitration reaction downstream of the first catalyst. Because
In the exhaust gas from the furnace, a halogenated gas is allowed to coexist, and the hardly soluble metal mercury contained in the exhaust gas is converted into water-soluble divalent mercury by the first catalyst, and then the first catalyst and Ammonia is added between the two catalysts and denitration is performed with the second catalyst.

The exhaust gas treatment facility of the present invention is an exhaust gas treatment facility for flowing exhaust gas from a furnace to a denitration device,
The denitration apparatus includes a first catalyst that generates a mercury oxidation reaction, and a second catalyst that generates a denitration reaction downstream of the first catalyst.
An ammonia addition line for adding ammonia is disposed between the first catalyst and the second catalyst,
When treating the exhaust gas, make the halogenated gas coexist in the exhaust gas from the furnace, and convert the hardly soluble metal mercury contained in the exhaust gas into water-soluble divalent mercury with the first catalyst. Then, denitration is performed with the second catalyst by adding ammonia from the ammonia addition line.

  In the exhaust gas treatment facility of the present invention, it is preferable to provide a halogen addition line for adding halide or halogen gas in the furnace.

  In the exhaust gas treatment facility of the present invention, it is preferable to provide a halogen addition line for adding a halide or halogen gas to the flow path from the furnace to the first catalyst.

  According to the exhaust gas treatment method and the exhaust gas treatment facility of the present invention, ammonia is added between the first catalyst that generates the mercury oxidation reaction and the second catalyst that generates the denitration reaction. Prevents adsorption to the catalyst and appropriately reacts the hardly soluble metal mercury with the halogenated gas on the first catalyst, converting the hardly soluble metal mercury into water-soluble divalent mercury with high efficiency. Can be made. In addition, since ammonia is added to the downstream side of the first catalyst for mercury oxidation reaction through the ammonia addition line, the arrangement of the ammonia decomposition catalyst is not required, the overall configuration is simplified, and the manufacturing cost can be suppressed. The effects can be achieved.

1 is an overall schematic configuration diagram showing a first example of an exhaust gas treatment method and an exhaust gas treatment facility of the present invention. It is a graph which shows progress of mercury oxidation reaction and denitration reaction. It is a whole schematic block diagram which shows the 2nd example of the waste gas processing method of this invention, and waste gas processing equipment. It is a whole schematic block diagram which shows the other structure of the 2nd example of the waste gas processing method of this invention, and waste gas processing equipment.

  Hereinafter, a first example of an embodiment of the present invention will be described with reference to FIGS.

  An exhaust gas treatment method and an exhaust gas treatment facility 1 as a first example of an embodiment are a denitration device 5, a dust collector 6, and a flow path 4 through which exhaust gas flows from a furnace 2 of a coal fired boiler to a chimney 3, in order from the upstream side. A desulfurization apparatus 7 is installed.

  The furnace 2 includes a coal supply line 8 for supplying coal pulverized by a pulverized coal machine and a halogen addition line 9 for supplying a halide of a chlorine compound so that the coal and the halide are mixed and burned at 300 ° C. It has become. Here, the halogen of the halide is selected from F, Cl, Br, I, and the like, and the halogen addition line 9 may supply a halogen gas instead of the halide, or HCl or the like as the halide. The halogenated gas may be supplied.

The denitration device 5 includes a first catalyst 10 that generates a mercury oxidation reaction, and a second catalyst 11 that generates a denitration reaction on the downstream side of the first catalyst 10. It flows at a temperature of 500 ° C., and exhaust gas flows through the second catalyst 11 at 200 ° C. to 500 ° C., preferably 300 ° C. to 400 ° C. Here, in the first catalyst 10 and the second catalyst 11, the carrier is selected from TiO ₂ , Al ₂ O ₃ , ZrO ₂ , SiO _2, etc., and the carrier is a simple substance such as V, Cu, W, oxide, compound The active ingredient selected from is carried.

  Further, a flow path 4a having a predetermined distance L (see FIG. 2) is disposed between the first catalyst 10 and the second catalyst 11, and an ammonia addition line for adding ammonia to the flow path 4a. 12 is connected. Here, the predetermined distance L is set such that the temperature of the exhaust gas does not decrease excessively so as to maintain an appropriate temperature of the exhaust gas in the second catalyst 11. Further, the distance from the ammonia addition position to the second catalyst 11 is set to a distance at which ammonia is sufficiently diffused.

  On the other hand, the dust collector 6 is an electric dust collector, a bag filter, or the like, and the desulfurization device 7 includes spraying means for spraying a reaction liquid containing calcium carbonate, and SOx in the exhaust gas is converted into calcium sulfate by spraying the reaction liquid. To remove it.

  The operation of the first embodiment of the present invention will be described below.

When treating the exhaust gas from the furnace 2 of the coal-fired boiler, first, the coal 2 and a halide such as a chlorine compound are mixed and burned in the furnace 2, and a halogenated gas (halogen) such as HCl coexists in the exhaust gas. In this state, a catalytic reaction between the hardly soluble mercury Hg ⁰ and the halogenated gas is performed under the first catalyst 10 to convert the hardly soluble mercury Hg ⁰ into divalent mercury Hg ²⁺ [Formula 2].
[Formula 2]
Hg ⁰ + 2HCl + 1 / 2O ₂ → HgCl ₂ + H ₂ O
Here, the halogenated gas is indicated by HCl, and the divalent mercury Hg ²⁺ is indicated by HgCl ₂ . Further, the mercury oxidation rate is processed to be about 70% or more.

Next, ammonia is added to the flow path 4a between the first catalyst 10 and the second catalyst 11 from the ammonia addition line 12, the exhaust gas and the ammonia gas are mixed in the flow path 4a, and the NO under the second catalyst 11 is mixed. Denitration is performed by the reaction of ammonia with ammonia gas [Formula 3].
[Formula 3]
NO + NH ₃ + 1 / 4O ₂ → N ₂ + 3 / 2H ₂ O
Here, the denitration rate is processed to be about 70% or more.

  Thereafter, ash and soot are removed by the dust collector 6 of the exhaust gas treatment facility 1, and desulfurization is performed by the desulfurization device 7, and the exhaust gas is discharged from the chimney 3 to the outside air.

  Thus, according to the first example of the embodiment, since ammonia is added between the first catalyst 10 that generates the mercury oxidation reaction and the second catalyst 11 that generates the denitration reaction, the ammonia is used for the mercury oxidation reaction. The first catalyst 10 is prevented from adsorbing, and the catalytic reaction of the hardly soluble metal mercury with the halogenated gas is appropriately performed on the first catalyst 10 to convert the hardly soluble metal mercury into water-soluble divalent mercury. Can be transformed with high efficiency. Further, denitration can be performed with high efficiency. Furthermore, since ammonia is added to the downstream side of the first catalyst 10 by the ammonia addition line 12, the arrangement of an ammonia decomposition catalyst or the like is not required, the overall configuration is simplified, and the manufacturing cost can be suppressed.

  Further, in the first example of the embodiment, when the halogen addition line 9 for adding a halide or halogen gas is provided in the furnace 2, the catalytic reaction between the hardly soluble metal mercury and the halogenated gas is performed on the first catalyst 10. It is possible to suitably perform the transformation of the hardly soluble metal mercury into the water-soluble divalent mercury with higher efficiency.

  A second example of the embodiment of the present invention will be described below with reference to FIG. Here, the exhaust gas treatment method and the exhaust gas treatment facility 1a of the second example are obtained by changing the supply position of the halide or halogen, and in FIG. 3, the same reference numerals as those of the first example are the same. Yes.

  The exhaust gas treatment method and the exhaust gas treatment facility 1a, which are the second example of the embodiment, are connected to the flow path 4 through which the exhaust gas flows from the furnace 2 of the coal-fired boiler to the chimney 3 in order from the upstream side in the same manner as in the first example. A dust collector 6 and a desulfurization device 7 are installed.

  The furnace 2 includes a coal supply line 8 that supplies coal pulverized by a pulverized coal machine, and burns the coal. Here, the furnace 2 may be provided with a halogen addition line 9 for supplying a halide of a chlorine compound similar to the first example as shown in the exhaust gas treatment facility 1b having another configuration shown in FIG.

Similar to the first example, the denitration device 5 includes a first catalyst 10 that generates a mercury oxidation reaction, and a second catalyst 11 that generates a denitration reaction downstream of the first catalyst 10. The exhaust gas flows at a temperature of 200 ° C. to 500 ° C., and the exhaust gas flows through the second catalyst 11 at 200 ° C. to 500 ° C., preferably 300 ° C. to 400 ° C. Here, in the first catalyst 10 and the second catalyst 11, the support is selected from TiO ₂ , Al ₂ O ₃ , ZrO ₂ , SiO _2, etc., and the support is made of a simple substance such as V, Cu, W, an oxide, or a compound. The selected active ingredient is supported.

  A flow path 4b having a predetermined distance is disposed between the furnace 2 and the first catalyst 10, and a halogen addition line 13 for supplying a halide of a chlorine compound is connected to the flow path 4b. ing. Here, the halogen of the halide is selected from F, Cl, Br, I, and the like, and the halogen addition line 13 may supply halogen instead of the halide, and the halide such as HCl may be supplied. A halogenated gas may be supplied. The predetermined distance (not shown) is set such that the distance from the addition position of the halide or the like to the first catalyst 10 is a distance at which the halogenated gas is sufficiently diffused.

  Further, a channel 4a having a predetermined distance L (see FIG. 2) is arranged between the first catalyst 10 and the second catalyst 11, as in the first example. An ammonia addition line 12 for adding ammonia is connected. Here, the predetermined distance L is set such that the temperature of the exhaust gas does not decrease excessively so as to maintain an appropriate temperature of the exhaust gas in the second catalyst 11. Further, the distance from the ammonia addition position to the second catalyst 11 is set to a distance at which ammonia is sufficiently diffused.

  On the other hand, the dust collector 6 and the desulfurization device 7 are configured in the same manner as in the first example.

  The operation of the second embodiment of the present invention will be described below.

When the exhaust gas from the furnace 2 of the coal fired boiler is treated, a halide or a halogen gas is added to the flow path 4b from the halogen addition line 13, and HCl or the like is contained in the exhaust gas at 200 ° C to 500 ° C from the furnace 2. In a state in which a halogenated gas (halogen) coexists, a catalytic reaction between the hardly soluble mercury Hg ⁰ and the halogenated gas is performed under the first catalyst 10, and the form of the hardly soluble mercury Hg ⁰ is converted to divalent mercury Hg ^2+. [Formula 4]
[Formula 4]
Hg ⁰ + 2HCl + 1 / 2O ₂ → HgCl ₂ + H ₂ O
Here, the halogenated gas is indicated by HCl, and the divalent mercury Hg ²⁺ is indicated by HgCl ₂ . Further, the mercury oxidation rate is processed to be about 70% or more.

Next, similarly to the first example, ammonia is added to the flow path 4a between the first catalyst 10 and the second catalyst 11 from the ammonia addition line 12, and the exhaust gas and the ammonia gas are mixed in the flow path 4a. Denitration is performed by the reaction of NO and ammonia gas under the catalyst 11 [Formula 5].
[Formula 5]
NO + NH ₃ + 1 / 4O ₂ → N ₂ + 3 / 2H ₂ O
Here, the denitration rate is processed to be about 70% or more.

  Thereafter, ash and soot are removed by the dust collector 6 of the exhaust gas treatment facility 1a, and desulfurization is performed by the desulfurization device 7, and the exhaust gas is discharged from the chimney 3 to the outside air.

  Thus, according to the second example of the embodiment, the same operation and effect as the first example can be obtained.

  Further, in the second example of the embodiment, when a halogen addition line 13 for adding a halide or a halogen gas is provided in the flow path 4 b from the furnace 2 to the first catalyst 10, a hardly soluble metal on the first catalyst 10. A catalytic reaction between mercury and a halogenated gas is suitably performed, and the hardly soluble metallic mercury can be converted into water-soluble divalent mercury with higher efficiency.

  The exhaust gas treatment method and exhaust gas treatment equipment of the present invention are not limited to the illustrated examples described above, and it is needless to say that various modifications can be made without departing from the scope of the present invention.

DESCRIPTION OF SYMBOLS 1 Exhaust gas treatment equipment 1a Exhaust gas treatment equipment 1b Exhaust gas treatment equipment 2 Furnace 4a Flow path 5 Denitration device 9 Halogen addition line 10 First catalyst 11 Second catalyst 12 Ammonia addition line 13 Halogen addition line

Claims (4)

An exhaust gas treatment method comprising a first catalyst that generates a mercury oxidation reaction in a flow path for flowing exhaust gas from a furnace, and a second catalyst that generates a denitration reaction downstream of the first catalyst,
In the exhaust gas from the furnace, a halogenated gas is allowed to coexist, and the hardly soluble metal mercury contained in the exhaust gas is converted into water-soluble divalent mercury by the first catalyst, and then the first catalyst and An exhaust gas treatment method comprising adding ammonia between two catalysts and performing denitration with a second catalyst. An exhaust gas treatment facility for flowing exhaust gas from a furnace to a denitration device,
The denitration apparatus includes a first catalyst that generates a mercury oxidation reaction, and a second catalyst that generates a denitration reaction downstream of the first catalyst.
An ammonia addition line for adding ammonia is disposed between the first catalyst and the second catalyst,
When treating the exhaust gas, make the halogenated gas coexist in the exhaust gas from the furnace, and convert the hardly soluble metal mercury contained in the exhaust gas into water-soluble divalent mercury with the first catalyst. Next, an exhaust gas treatment facility characterized in that denitration is performed with a second catalyst by adding ammonia from an ammonia addition line.   The exhaust gas treatment facility according to claim 2, further comprising a halogen addition line for adding a halide or a halogen gas in the furnace.   The exhaust gas treatment facility according to claim 2 or 3, further comprising a halogen addition line for adding at least one of a halide or a halogen gas to a flow path from the furnace to the first catalyst.

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