KR102476863B1 - Denitrification catalyst and exhaust gas treatment system for thermal power generation using the same - Google Patents

Abstract

The present invention relates to a denitration catalyst for a thermal power plant that maintains excellent denitration performance even under flue gas conditions containing a high concentration of nitrogen dioxide generated during initial operation of a thermal power plant, and a method for manufacturing the same. The present invention relates to the denitration catalyst for removing nitrogen oxides from exhaust gas, which satisfies NO_2/NO_x >= 0.5.

Description

Denitrification catalyst and exhaust gas treatment system for thermal power generation using the same}

The present invention relates to a denitrification catalyst and an exhaust gas treatment system for thermal power generation using the same, and more particularly, to a denitration catalyst applied to a selective catalytic reduction technology for removing nitrogen oxides contained in exhaust gas in the initial stage of operation of a thermal power plant and thermal power using the same It relates to an exhaust gas treatment system for power generation.

Electric power is generally produced in large-scale power generation facilities. In power plants, power is generated mainly by thermal power generation method by burning fuel, nuclear power generation method using nuclear energy, hydroelectric power generation method using fluid drop, etc. In other power generation facilities, power generation using solar heat, tidal power, wind power, etc. method is also used.

Among them, the thermal power generation method is a power generation method that is still being used very actively, and is a method of driving a turbine by burning fuel. In order to obtain electric power through thermal power generation, fuel must be continuously consumed, and the fuel is burned in a gas turbine to generate a large amount of exhaust gas (exhaust gas). This flue gas contains pollutants generated by a combustion reaction of a fuel and a high-temperature thermal reaction, and thus requires special treatment.

In particular, thermal power plants are operated and stopped frequently for the purpose of installation, and at the beginning of operation, various air pollutants such as NOx are emitted in larger amounts than during normal operation. In addition, a plan to reduce air pollutants discharged at the beginning of operation is required to minimize the effect when the concentration of fine dust is high.

Accordingly, Korean Patent Registration No. 10-2159082 discloses that a reducing agent including a hydrocarbon-based reducing agent and an ammonia-based reducing agent is brought into contact with nitrogen oxide-containing exhaust gas at the front of the denitrification catalyst to reduce high-concentration nitrogen dioxide-containing exhaust gas generated when a gas turbine of a thermal power plant is started. It describes how to handle it.

However, the treatment method may cause the emission of carcinogens such as formaldehyde by using a hydrocarbon-based reducing agent such as ethanol, and nitrogen dioxide in the exhaust gas forms solid ammonium nitrate (NH ₄ NO ₃ ) in the denitrification catalyst. There is a problem that the denitrification performance is lowered.

Therefore, there is a need for the development of a denitrification catalyst that is environmentally friendly and maintains denitrification performance for exhaust gas at the initial stage of operation.

Republic of Korea Patent Registration No. 10-2159082

The problem to be solved by the present invention is that manganese is added to the vanadium/tungsten/titania catalyst to achieve excellent denitrification performance even under exhaust gas conditions containing high concentrations of nitrogen dioxide generated during the initial operation of a thermal power plant, and in particular, ammonium nitrate (NH ₄ NO ₃ ) and suppress the generation of nitrous oxide (N ₂ O) to provide a denitrification catalyst for thermal power plants that does not reduce denitrification efficiency and a manufacturing method thereof.

As a means for solving the above problems,

The present invention is a denitration catalyst for removing nitrogen oxides of exhaust gas having NO ₂ /NO _x ≥ 0.5, wherein the denitration catalyst includes vanadium/tungsten/titania and manganese, wherein the manganese is α-Mn ₂ O ₃ and Mn ₃ O ₄ structure, thereby providing a denitration catalyst characterized in that the formation of ammonium nitrate (NH ₄ NO ₃ ) and the generation of nitrous oxide (N ₂ O) are suppressed.

In one embodiment of the present invention, the fraction of Mn ⁴⁺ in the surface Mn of the denitration catalyst is 60% or less, and the denitration catalyst for thermal power plants is prepared by calcining manganese nitrate as a precursor.

In one embodiment of the present invention, the denitration catalyst for thermal power plants uses anatase TiO ₂ , but the BET of vanadium-manganese/tungsten/titania is 45 m ² /g or more, the mean pore diameter is 32 nm or less, and the Vp is 0.35 It is produced by firing at less than cm ³ /g.

In one embodiment of the present invention, the final firing temperature of the denitration catalyst is 350 to 450 degrees Celsius, and the denitration catalyst has a nitrogen oxide conversion rate of 45% or more under the conditions of NO ₂ /NO _x =0.9 and 200 ° C or less. to be.

In one embodiment of the present invention, the vanadium is 2.0 to 8.0 parts by weight and the tungsten is 2.0 to 10.0 parts by weight based on 100 parts by weight of the titania. The manganese is 1.0 to 3.0 parts by weight.

The present invention is also an exhaust gas treatment system for thermal power generation, including a selective catalytic reduction (SCR) unit for reducing nitrogen oxides in exhaust gas discharged after thermal power generation,

The selective catalytic reduction (SCR) unit is the above-mentioned denitration catalyst.

The denitrification catalyst for thermal power plants according to the present invention has excellent nitrogen oxide removal efficiency even in the initial operating conditions of thermal power plants where high concentrations of nitrogen dioxide are generated due to incomplete combustion. There is an effect that the denitrification efficiency can be maintained.

1 is a graph showing the results of comparing the activity of the denitration catalyst according to Comparative Example 2 under conditions according to “Standard SCR” and NO ₂ ratio.
2a and 2b are graphs showing the results of FT-IR DRIFT analysis of the denitrification reaction using catalysts according to 350 ° C and 180 ° C of Comparative Example 2 under exhaust gas conditions with a high NO ₂ ratio, respectively.
3 is a graph comparing the activities of the denitration catalysts according to Preparation Example of the present invention and Comparative Example 2 under the condition of 90% NO ₂ .
4 is a graph comparing the activities of the denitration catalysts according to Preparation Example of the present invention and Comparative Example 1 under the condition of 90% NO ₂ .
5a to 5b are graphs showing the results of FT-IR DRIFT analysis of denitrification reactions using denitration catalysts according to Comparative Example 1, Comparative Example 2, and Preparation Example under exhaust gas conditions with a high NO ₂ ratio at 180 degrees Celsius, respectively.
6 is a graph showing the results of H ₂ -TPR analysis using denitration catalysts according to Preparation Example and Comparative Examples 1 and 2 of the present invention.
7 is a graph showing the results of Raman analysis using a denitrification catalyst according to a production example of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail. In describing the present invention, if it is determined that a detailed description of related known technologies may obscure the gist of the present invention, the detailed description will be omitted. Throughout the specification, when a part is said to "include" a certain component, it means that it may further include other components without excluding other components unless otherwise stated.

Currently, domestic thermal power plants are repeatedly operating and stopping according to power demand due to high power generation costs. The operation method of repeating operation and shutdown causes incomplete combustion at the beginning of operation (low power), that is, oxygen contained in the air supplied for combustion reacts with nitrogen instead of reacting with the raw material, resulting in nitrogen oxides, especially nitrogen dioxide (NO ₂ ). cause a phenomenon that occurs in large quantities.

In general, the nitrogen oxide decomposition reaction of SCR proceeds by a “Standard SCR” reaction that removes NO _x on a catalyst using ammonia (NH ₃ ) and urea as reducing agents, as shown in Reaction Scheme 1 below, or as shown in Reaction Scheme 2 below, The ratio of NO ₂ corresponds to 1:1 and proceeds by “Fast SCR” reaction that speeds up the catalytic reaction.

(Scheme 1) 4NO + 4NH ₃ + O ₂ -> 4N ₂ + 6H ₂ O

(Scheme 2) 2NH ₃ + NO ₂ + NO -> 2N ₂ + 3H ₂ O

NOx in flue gas discharged from most combustion devices exists as 90~95% nitrogen monoxide ( _NO ) and 5~10% nitrogen dioxide (NO ₂ ⁾ , so it can proceed with “Standard SCR” reaction or separate oxidation reaction. “Fast SCR” reaction is proceeding by oxidizing NO to NO ₂ by induction.

1 is a graph showing the results of comparing the activity of the denitration catalyst according to Comparative Example under conditions according to “Standard SCR” and NO ₂ ratio.

Referring to FIG. 1 , it can be seen that the NO _x conversion rate decreases as the NO ₂ ratio increases. In addition, it can be confirmed that the concentration of N ₂ O is increased. As such, in the denitrification reaction, controlling the NO ₂ /NO _x ratio is key, and in an environment where the ratio of NO ₂ in NO _x dominates, that is, in the initial operating conditions of the thermal power plant, high concentrations of nitrogen dioxide cause “Standard SCR” or “Fast SCR” reaction does not proceed, resulting in denitrification or paralysis.

In addition, a high concentration of nitrogen dioxide (NO ₂ ) in the flue gas generated at the beginning of operation reacts with ammonia (NH ₃ ), a reducing agent used in the denitrification reaction, to generate ammonium nitrate (NH ₄ NO ₃ ), as shown in Scheme 3 below. Since the melting point of ammonium nitrate (NH ₄ NO ₃ ) is approximately 170° C., the solid ammonium nitrate generated in the initial operating condition blocks the active site of the NOx removal catalyst, thereby reducing NOx removal performance.

(Scheme 3) 2NH ₃ + 2NO ₂ -> NH ₄ NO ₃ + H ₂ O + N ₂

2a and 2b are graphs showing the results of FT-IR DRIFT analysis of the denitrification reaction using catalysts according to 350 ° C and 180 ° C of Comparative Example 2 under exhaust gas conditions with a high NO ₂ ratio, respectively.

Referring to FIGS. 2A and 2B, after adsorbing 1000 ppm of NH ₃ for 30 minutes, 1000 ppm of NO ₂ and ₃ % of O ₂ were injected to confirm the reaction on the catalyst surface _. After that, it can be confirmed that NO ₂ peaks of 1346 cm ^-1 and NO ₂ peaks of 1620 cm ^-1 were generated (FIG. 2b).

On the other hand, even when the NO ₂ ratio was increased, no NO ₂ peak was generated at 350° C., which showed similar denitrification performance (FIG. 2a). Therefore, the formation of this NO ₂ peak is an ammonium nitrate (NH ₄ NO ₃ )-derived material produced by reacting with NH ₃ , and can be seen as a factor in reducing the activity of the denitration catalyst.

Therefore, the present invention has excellent denitrification performance even under the initial operating conditions of a thermal power plant, that is, exhaust gas conditions containing high concentrations of nitrogen dioxide, and in particular, suppresses the formation of ammonium nitrate (NH ₄ NO ₃ ) and the generation of nitrous oxide (N ₂ O). A denitrification catalyst capable of maintaining denitrification performance without a hydrocarbon-based reducing agent and a manufacturing method thereof are provided.

The denitrification catalyst for thermal power plants according to the present invention is a catalyst applicable to ammonia-based selective catalytic reduction technology for efficiently removing nitrogen oxides even under conditions of exhaust gas containing high concentrations of nitrogen dioxide. It may be a supported vanadium-manganese/tungsten/titania based catalyst.

Here, the exhaust gas containing a high concentration of nitrogen dioxide means that the NO _{2 /} NO _x ratio is 0.5 or more, and the ratio of nitrogen dioxide (NO ₂ ) among the nitrogen oxides contained in the exhaust gas is higher than the ratio of nitrogen monoxide (NO). and considering the initial operating conditions of a thermal power plant, the NO ₂ /NO _x ratio may preferably be 0.5 or more and 0.9 or less.

The amount of vanadium is preferably 2.0 to 8.0 parts by weight, preferably 3.0 to 5.0 parts by weight, based on 100 parts by weight of the titania support. In addition, the amount of tungsten is preferably 2.0 to 10.0 parts by weight, preferably 3.0 to 6.0 parts by weight, based on 100 parts by weight of the titania support. In one embodiment of the present invention, 4.0 parts by weight of vanadium and 5.0 parts by weight of tungsten were used, but the scope of the present invention is not limited thereto.

The manganese binds to the vanadium/tungsten/titania-based catalyst to suppress the conversion and adsorption of nitrogen dioxide (NO ₂ ) into ammonium nitrate-derived substances such as bidentate nitrate and monodentate coordinated nitrate, and as a result, ammonium nitrate (NH ₄ It suppresses the formation of NO ₃ ) to enhance the activity of the denitration catalyst, and is supported in an amount of 1.0 to 3.0 parts by weight, more preferably 1.5 parts to 2.5 parts by weight, and most preferably 2.0 parts by weight based on 100 parts by weight of the titania support. do.

In the present invention, in particular, when manganese is added as manganese nitrate, the fraction of Mn ⁴⁺ in Mn of the finally obtained catalyst is suppressed to 60% or less, and as a result, it is 180 degrees Celsius higher than other manganese materials such as NMO. It effectively inhibits the formation of ammonium nitrate (NH ₄ NO ₃ ) and suppresses the generation of nitrous oxide (N ₂ O) at a low temperature of the level.

Table 1 below shows the surface of the catalyst through XRS analysis of a catalyst made of manganese nitrate (Preparation Example) and a catalyst made of NMO (Natural Manganese Ore) (Comparative Example 1) according to an embodiment of the present invention described below. This is the result of measuring the Mn atomic concentration in

Mn ⁴⁺ / (Mn ⁴⁺ + Mn ³⁺ ) manufacturing example 45.0% Comparative Example 2 66.0%

According to an embodiment of the present invention, a mixed slurry is prepared by introducing manganese nitrate, a manganese precursor, into a titania carrier supported with a vanadium precursor and a tungsten precursor, and then drying and calcining the mixed slurry.

In the present invention, DT-51, which is anatase TiO ₂ , can be used as the titania carrier, ammonium metatungstate hydrate as the tungsten precursor, ammonium metavanadate as the vanadium precursor, and Manganess(II) nitrate hydrate as the manganese precursor, but is not particularly limited. .

Hereinafter, the manufacturing method of the denitrification catalyst for thermal power plants according to the present invention will be described in more detail.

The denitrification catalyst for thermal power plants prepared as described above has excellent nitrogen oxide removal efficiency even under flue gas conditions containing high concentrations of nitrogen dioxide generated during the initial operation of thermal power plants. The denitrification efficiency can be maintained.

On the other hand, the denitration catalyst for thermal power plants according to the present invention may be used in powder form or in a particle form with a small amount of binder, extruded in a monolith form, or manufactured in various forms such as slate, plate, or pellet.

In addition, when the NOx removal catalyst is actually applied, it can be used by coating on structures such as honeycomb, metal plate, metal fiber, ceramic filter, metal foam, and the like.

Hereinafter, the present invention will be described in more detail based on preferred embodiments of the present invention. However, it goes without saying that the technical idea of the present invention is not limited or limited thereto and can be modified and implemented in various ways by those skilled in the art.

manufacturing example

Ammonium metatugstate hydrate precursor is converted to 5.0 parts by weight of tungsten in 100 parts by weight of Anatase type TiO ₂ carrier, and then dissolved in distilled water at room temperature. Subsequently, a TiO ₂ carrier was added to the previously prepared tungsten aqueous solution to prepare a slurry form. Thereafter, the prepared slurry was dried at a temperature of 103° C. for more than 24 hours to completely remove moisture contained in the micropores, and then calcined at a temperature of 600° C. for 4 hours in an air atmosphere to prepare W/TiO ₂ . Then, Ammonium metavanadate and Manganess (II) nitrate hydrate were converted to 4.0 parts by weight of vanadium and 2.0 parts by weight of manganese, respectively, in 100 parts by weight of W / TiO ₂ carrier. dissolved in each. In the case of the vanadium aqueous solution, oxalic acid dehydrate was additionally added at a molar ratio of 1:1 to prevent elution. Subsequently, the prepared W/TiO ₂ carrier was prepared in the form of a slurry by adding an aqueous solution of vanadium and an aqueous solution of manganese. The prepared slurry was dried in the same manner as in the previous method and calcined at 400° C. for 4 hours in an air atmosphere to prepare V-Mn/W/TiO ₂ .

Comparative Example 1

Ammonium metatugstate hydrate precursor is converted to 5.0 parts by weight of tungsten in 100 parts by weight of Anatase type TiO ₂ carrier, and then dissolved in distilled water at room temperature. Subsequently, a TiO ₂ carrier was added to the previously prepared tungsten aqueous solution to prepare a slurry form. Thereafter, the prepared slurry was dried at a temperature of 103° C. for more than 24 hours to completely remove moisture contained in the micropores, and then calcined at a temperature of 600° C. for 4 hours in an air atmosphere to prepare W/TiO ₂ . Thereafter, Ammonium metavanadate is converted to 4.0 parts by weight of vanadium in 100 parts by weight of W/TiO ₂ carrier, and after quantification, it is dissolved in distilled water at 60 to 80 °C. In the case of the vanadium aqueous solution, oxalic acid dehydrate was additionally added at a molar ratio of 1:1 to prevent elution. Subsequently, the vanadium aqueous solution was added to the previously prepared W/TiO ₂ carrier to prepare a slurry form. The prepared slurry was dried in the same manner as in the previous method and calcined for 4 hours at a temperature of 400° C. in an air atmosphere to prepare V/W/TiO ₂ . Thereafter, after drying at 103 ° C. for 12 hours, natural manganese ore (NMO, Natural Manganese Ore) calcined under an air atmosphere at 400 ° C. for 4 hours is prepared. NMO/V/W/TiO ₂ was prepared by mixing the prepared V/W/TiO ₂ and NMO at a weight ratio of 10:1 and ball-milling.

Comparative Example 2

It was prepared in the same manner as in Comparative Example 1 except that the addition of manganese to the W/TiO ₂ carrier was excluded. A more detailed description of this is as follows.

Ammonium metatugstate hydrate precursor is converted to 5.0 parts by weight of tungsten in 100 parts by weight of Anatase type TiO ₂ carrier, and then dissolved in distilled water at room temperature. Subsequently, a TiO ₂ carrier was added to the previously prepared tungsten aqueous solution to prepare a slurry form. Thereafter, the prepared slurry was dried at a temperature of 103° C. for more than 24 hours to completely remove moisture contained in the micropores, and then calcined at a temperature of 600° C. for 4 hours in an air atmosphere to prepare W/TiO ₂ . Thereafter, Ammonium metavanadate is converted to 4.0 parts by weight of vanadium in 100 parts by weight of W/TiO ₂ carrier, and after quantification, it is dissolved in distilled water at 60 to 80 °C. In the case of the vanadium aqueous solution, oxalic acid dehydrate was additionally added at a molar ratio of 1:1 to prevent elution. Subsequently, the vanadium aqueous solution was added to the previously prepared W/TiO ₂ carrier to prepare a slurry form. The prepared slurry was dried in the same manner as in the previous method and calcined for 4 hours at a temperature of 400° C. in an air atmosphere to prepare V/W/TiO ₂ .

Comparative Preparation Example 3

The carrier of the denitration catalyst was prepared in the same manner as in Preparation Example, except that amorphous TiO ₂ was used.

Comparative Preparation Example 4

The support of the denitration catalyst was prepared in the same manner as in Preparation Example, except that TiO ₂ in which anatase TiO ₂ and rutile TiO ₂ were mixed was used.

Comparative Preparation Example 5

The support of the denitration catalyst was prepared in the same manner as in Preparation Example, except that anatase TiO ₂ was used, but TiO ₂ having physical properties different from those of Preparation Example was used.

Comparative Preparation Example 6

V-Mn/W/TiO ₂ was prepared by preparing and drying a catalyst slurry with the same configuration as in the preparation example, and then calcining the slurry at 300° C. for 4 hours in an air atmosphere.

Comparative Preparation Example 7

V-Mn/W/TiO ₂ was prepared by preparing and drying a catalyst slurry with the same configuration as in the preparation example, and then calcining the slurry at 500° C. for 4 hours in an air atmosphere.

Comparative Preparation Example 8

V-Mn/W/TiO ₂ was prepared by preparing and drying a catalyst slurry in the same configuration as in the above Preparation Example and firing it for 4 hours at a temperature of 600° C. in an air atmosphere.

Experimental Example 1

3 is a graph comparing the activities of the denitration catalysts according to Preparation Example of the present invention and Comparative Example 2 under the condition of 90% NO ₂ .

Referring to FIG. 3, the vanadium-manganese/tungsten/titania-based denitrification catalyst according to Preparation Example of the present invention showed higher activity than the vanadium/tungsten/titania-based denitration catalyst according to Comparative Example 2, and under “Standard SCR” conditions It was confirmed that the activity of the catalyst was similar to that of It is believed that the denitrification catalyst for thermal power plants according to the present invention suppresses the formation of ammonium nitrate, thereby maintaining excellent denitrification performance even under flue gas conditions containing a high concentration of nitrogen dioxide generated during the initial operation of a thermal power plant. In particular, as the vanadium-manganese/tungsten/titania-based denitrification catalyst according to the preparation example of the present invention showed less than 5 ppm of nitrous oxide in the entire temperature range (180 to 350° C.), generation inhibition was confirmed. Therefore, when the denitrification catalyst for thermal power plants according to the present invention is used, it is possible to maintain denitrification performance similar to that of “Standard SCR” without a separate hydrocarbon-based reducing agent for reducing nitrogen dioxide to carbon monoxide, thereby enabling an efficient and environmentally friendly denitration reaction. It is judged that there will be

Experimental Example 2

4 is a graph comparing the activities of the denitration catalysts according to Preparation Example of the present invention and Comparative Example 1 under the condition of 90% NO ₂ .

Referring to FIG. 4 , the vanadium-manganese/tungsten/titania-based denitrification catalyst according to Preparation Example of the present invention exhibited higher activity than the natural manganese ore/vanadium/tungsten/titania-based denitration catalyst according to Comparative Example 1. In particular, the vanadium-manganese/tungsten/titania-based denitrification catalyst according to the production example of the present invention confirmed the denitrification performance of 45% or more at 200 ° C or less, and the concentration of nitrous oxide was 5 ppm or less in the entire temperature range (180 to 350 ° C). It was confirmed that the occurrence was inhibited. It is believed that the denitrification catalyst for thermal power plants according to the present invention suppresses the formation of ammonium nitrate, thereby maintaining excellent denitrification performance even under exhaust gas conditions containing a high concentration of nitrogen dioxide generated during the initial operation of a thermal power plant. Therefore, when the denitrification catalyst for thermal power plants according to the present invention is used, it is possible to maintain denitrification performance similar to that of “Standard SCR” without a separate hydrocarbon-based reducing agent for reducing nitrogen dioxide to carbon monoxide, thereby enabling an efficient and environmentally friendly denitration reaction. It is judged that there will be

Experimental Example 3

5a to 5b are graphs showing the results of FT-IR DRIFT analysis of denitrification reactions using denitration catalysts according to Comparative Example 1, Comparative Example 2, and Preparation Example under exhaust gas conditions with a high NO ₂ ratio at 180 degrees Celsius, respectively.

5a to 5b, after adsorbing 1000 ppm of NH ₃ for 30 minutes, injecting 1000 ppm of NO ₂ and 3% of O ₂ to confirm the reaction on the catalyst surface, natural manganese ore/vanadium according to Comparative Example 1 / Tungsten / titania catalyst and vanadium / tungsten / tartania denitration catalyst according to Comparative Example 2 showed 1346 cm ^-1 NO ₂ peak and 1620 cm ^-1 NO after 45 minutes and 25 minutes after injection of NO ₂ and O ₂ It can be confirmed that ₂ peaks are generated, and this NO ₂ peak is ammonium nitrate (NH ₄ NO ₃ ) generated by reacting with NH ₃ , and can be seen as a factor in reducing the activity of the denitration catalyst.

On the other hand, it was confirmed that the vanadium-manganese/tungsten/titania-based denitration catalyst according to the preparation example of the present invention to which manganese was added did not generate NO ₂ peak of 1346 cm ^-1 and NO ₂ peak of 1620 cm ^-1 (Fig. see 5c). It is believed that the generation of ammonium nitrate (NH ₄ NO ₃ ) is suppressed due to the reactivity of the denitration catalyst for thermal power plants according to the present invention according to the addition of manganese.

Experimental Example 4

6 is a graph showing the results of H ₂ -TPR analysis using denitration catalysts according to Preparation Example and Comparative Examples 1 and 2 of the present invention.

Referring to FIG. 6, in the natural manganese ore/vanadium/tungsten/titania-based denitrification catalyst according to Comparative Example 1, reduction peaks from MnO ₂ to MnO and Mn ₂ O ₃ were confirmed. It was confirmed that 66% of Mn ⁴⁺ was present as the natural manganese ore, in which the β-MnO ₂ (pyrolusite) structure was dominant, was added. In addition, it was confirmed that the reduced peak was formed low by covering the natural manganese ore with vanadium, an active metal.

On the other hand, as the vanadium-manganese/tungsten/titania-based denitration catalyst according to the present invention uses manganese nitrate as a precursor of manganese, a low Mn reduction peak is formed through the combination of vanadium and manganese, and Mn ⁴⁺ is 60 % or less. In addition, it was confirmed that the vanadium reduction peak was formed at a different temperature than Comparative Example 1 and Comparative Example 2 according to the binding action of vanadium and manganese. These results suggest that manganese's high oxidizing power is partially suppressed by its combination with vanadium, thereby minimizing the generation of nitrous oxide by controlling the oxidation of ammonia, a reducing agent.

Therefore, the catalyst of this embodiment using manganese nitrate with a relatively low content of Mn ⁴⁺ reduces the formation of ammonium nitrate (NH ₄ NO ₃ ), which is more fatal to the SCR catalyst activity than natural manganese ore, especially during low-temperature processes. ₄ NO ₃ ) and nitrous oxide (N ₂ O), suggesting that it is very effective in inhibiting generation.

Experimental Example 5

Table 2 below shows the results of confirming the denitrification performance at 200 degrees of Preparation Example, Comparative Preparation Example 3, and Comparative Preparation Example 4 prepared by using different supports for vanadium-manganese/tungsten/titania catalysts made of manganese nitrate.

NOx conversion rate Amount of N2O manufacturing example 50 0 Comparative Preparation Example 3 19 11 Comparative Preparation Example 4 27 17

Referring to Table 2, NOx conversion rate of 30% or less and N2O generation of 10 ppm or more were confirmed at 200 degrees, except for the preparation example of the present invention using Anatase TiO ₂ . Table 3 below shows the results of confirming the denitrification performance at 200 degrees of Preparation Example and Comparative Preparation Example 5 prepared using Anatase TiO ₂ having different physical properties.

NOx conversion rate Amount of N2O manufacturing example 50 0 Comparative Preparation Example 5 63 11

Referring to Table 3, when Anatase TiO ₂ was used, both catalysts exhibited NOx conversion rates of 50% or more at 200 degrees. On the other hand, in Comparative Preparation Example 5, N ₂ O generation of 10 ppm or more was confirmed. Table 4 below shows the BET analysis results of Preparation Example and Comparative Preparation Example 5 prepared using Anatase TiO ₂ having different physical properties.

BET
(m ² /g) Mean pore diameter
(nm) Vp
(cm ³ /g) manufacturing example 59.018 23.572 0.3461 Comparative Preparation Example 5 44.068 32.662 0.3598

Therefore, a catalyst was prepared using anatase TiO ₂ and the final physical properties of the vanadium-manganese/tungsten/titania catalyst were BET 45 m ² /g or more, mean pore diameter 32 nm or less, and Vp 0.35 m ³ /g or less. It is suggested that it is very effective in inhibiting the formation of ammonium nitrate (NH ₄ NO ₃ ), which is fatal to the catalyst activity, especially the generation of ammonium nitrate (NH ₄ NO ₃ ) and nitrous oxide (N ₂ O) generated during low-temperature processes.
Experimental Example 6

7 is a graph showing the results of Raman analysis using the denitrification catalyst according to Preparation Example 5 and Comparative Preparation Example 5 of the present invention.

Referring to Comparative Preparation Example 1, it was confirmed that the natural manganese ore/vanadium/tungsten/titania-based denitrification catalyst mainly had a β-MnO ₂ (pyrolusite) structure as the natural manganese ore was added.

On the other hand, the vanadium-manganese/tungsten/titania-based denitration catalyst according to the preparation example of the present invention uses manganese nitrate as a manganese precursor, and thus has an α-Mn ₂ O ₃ structure (304, 396, 696cm ^-1 ) and Mn ₃ Growth of the O ₄ structure (283, 480 cm ⁻¹ ) was confirmed.

On the other hand, in Comparative Preparation Example 5, the α-Mn ₂ O ₃ structure (304, 396 cm ⁻¹ ) was confirmed, but the Mn ₃ O ₄ structure (283, 480 cm ⁻¹ ) was not confirmed.

Therefore, unlike natural manganese ores in which the β-MnO ₂ (pyrolusite) structure dominates, it contains both α-Mn ₂ O ₃ and Mn ₃ O ₄ manganese, and only the production example of the present invention in which these structures are mixed denitrifies. It is suggested that the catalyst is very effective in suppressing the formation of ammonium nitrate (NH ₄ NO ₃ ), which is fatal to the SCR catalyst activity, especially the generation of ammonium nitrate (NH ₄ NO ₃ ) and nitrous oxide (N ₂ O) generated during low-temperature processes.

Experimental Example 7

Table 5 below shows Preparation Examples, Comparative Preparation Example 6, Comparative Preparation Example 7, and Comparative Preparation Example 8 prepared according to different firing temperatures after drying the vanadium-manganese/tungsten/titania catalyst slurry prepared from manganese nitrate at 200 degrees. This is the result of confirming the denitrification performance in

NOx conversion rate Amount of N ₂ O generated manufacturing example 50 0 Comparative Preparation Example 6 32 2 Comparative Preparation Example 7 48 One Comparative Preparation Example 8 38 5

The above results show that the denitrification efficiency is very good when firing at a temperature of 350 ° C to 450 ° C.

The NOx removal catalyst according to the present invention may be used in a selective catalytic reduction (SCR) unit for reducing nitrogen oxides in exhaust gas discharged after thermal power generation in an exhaust gas treatment system for thermal power generation. In particular, the formation of ammonium nitrate (NH ₄ NO ₃ ) and the generation of nitrous oxide (N ₂ O) can be suppressed at a high NO ₂ /NO _x ratio occurring during initial startup.

Claims (8)

As a denitrification catalyst for the removal of nitrogen oxides from flue gas with NO ₂ /NO _x ≥ 0.5,
The denitrification catalyst includes vanadium/tungsten/titania and manganese, and the manganese includes both α-Mn ₂ O ₃ and Mn ₃ O ₄ structures, thereby forming ammonium nitrate (NH ₄ NO ₃ ) and nitrous oxide ( N ₂ O) generation is suppressed,
The fraction of Mn ⁴⁺ relative to Mn 4+ and Mn 3+ on the surface of the denitration catalyst is 60% or less,
2.0 to 8.0 parts by weight of the vanadium and 2.0 to 10.0 parts by weight of the tungsten based on 100 parts by weight of the titania. The denitration catalyst, characterized in that the manganese is 1.0 to 3.0 parts by weight. delete According to claim 1,
The denitration catalyst, characterized in that the denitration catalyst is prepared by calcining manganese nitrate as a precursor. delete According to claim 1,
The denitration catalyst, characterized in that the final firing temperature of the denitration catalyst is 350 degrees Celsius to 450 degrees Celsius. According to claim 1,
The denitration catalyst, characterized in that the NO ₂ /NO _x = 0.9, nitrogen oxide conversion rate of 45% or more under the conditions of 200 ℃ or less. delete As an exhaust gas treatment system for thermal power generation,
It includes a selective catalytic reduction (SCR) unit that reduces nitrogen oxides in exhaust gas discharged after thermal power generation,
The selective catalytic reduction (SCR) unit is an exhaust gas treatment system for thermal power generation, characterized in that the denitration catalyst according to any one of claims 1, 3, 5 and 6.

Images