KR20230067406A - Exhaust gas treatment system for liquefied natural gas combined cycle power generation - Google Patents

Abstract

Provided is an exhaust gas treatment system for liquefied natural gas combined cycle power generation, comprising: a selective catalytic reduction (SCR) unit for reducing nitrogen oxides in the exhaust gas discharged after the combined cycle power generation; and a carbon monoxide (CO) treatment unit disposed after the selective catalytic reduction (SCR) unit and equipped with a catalyst to remove carbon monoxide, wherein the NO_2/NO_x ratio in the exhaust gas is 0.5 or more.

Description

Exhaust gas treatment system for liquefied natural gas combined cycle power generation}

The present invention relates to an exhaust gas treatment system for a liquefied natural gas combined cycle power plant, and more particularly, to an exhaust gas treatment system for a liquefied natural gas combined cycle power plant capable of effectively removing both nitrogen oxides and carbon monoxide emitted during initial start-up operation. It's about the system.

LNG combined cycle power generation generates almost no air pollutants during normal operation of the generator, but pollutants are temporarily generated during start-up. When the generator is started, it is difficult to remove air pollutants due to the low reactivity with the reducing agent due to the lower exhaust gas temperature (200 ° C) than during operation.

In the past, there was a grace period for NOx removal from various harmful substances emitted from start-up to normal operation mode. However, there is a problem that NOx removal (denox) must be performed from the beginning.

Therefore, it is necessary to develop a new technology capable of effectively removing hydrocarbons such as CO, NOx, and CH4 that are initially emitted.

Therefore, the problem to be solved by the present invention is to provide a new exhaust gas treatment system in consideration of the characteristics of exhaust gas discharged when starting a liquefied natural gas combined cycle power plant.

In order to solve the above problems, the present invention is an exhaust gas treatment system for a liquefied natural gas combined cycle power plant, a selective catalytic reduction (SCR) unit for reducing nitrogen oxides in exhaust gas discharged after the combined cycle power plant; A carbon monoxide (CO) processing unit disposed at the rear end of the selective catalytic reduction (SCR) unit and equipped with a catalyst for removing carbon monoxide; and a liquefied natural gas characterized in that the NO ₂ /NO _x ratio in the exhaust gas is 0.5 or more. An exhaust gas treatment system for combined cycle power generation is provided.

In one embodiment of the present invention, the catalyst of the selective catalytic reduction (SCR) unit is an NO ₂ SCR catalyst in which a selective catalytic reduction reaction occurs even at a NO 2 / NOx ratio of 0.5 or more, and the exhaust gas treatment system for liquefied natural gas combined cycle power generation , Further comprising an ammonia injection unit coupled to the selective catalytic reduction (SCR) unit and directly injecting ammonia into the selective catalytic reduction (SCR) unit.

In one embodiment of the present invention, the exhaust gas treatment system for the liquefied natural gas combined cycle power plant further includes a hydrocarbon processing unit provided in front of the selective catalytic reduction (SCR) unit to treat hydrocarbons with a catalyst.

In one embodiment of the present invention, the NO ₂ SCR catalyst includes vanadium/tungsten/titania and manganese, and the manganese includes both α-Mn ₂ O ₃ and Mn ₃ O ₄ structures, whereby ammonium nitrate (NH ₄ NO ₃ ) formation and nitrous oxide (N ₂ O) generation are inhibited.

In the present invention, denox is performed from the exhaust gas by the FAST SCR process considering the high NO2 content at the time of initial start-up. In addition, in order to minimize the poisoning effect of NOx on the CO removal catalyst, an oxidation process of CO and NH3 removal is performed at the rear end of the SCR catalyst, which reacts from the start, to solve the problems of ammonia slip and harmful carbon monoxide emission. Furthermore, by performing a CH4 removal process prior to the SCR process in which ammonia is injected, the problem of ammonia oxidation by the CH4 catalyst is solved.

1 is a schematic diagram of an exhaust gas treatment system for a liquefied natural gas combined cycle power plant according to an embodiment of the present invention.
2 is a schematic diagram of an exhaust gas treatment system for a liquefied natural gas combined cycle power plant according to another embodiment of the present invention.
1 is a schematic diagram of a liquefied natural gas combined cycle power plant exhaust gas treatment system according to an embodiment of the present invention).
3 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.
4 is a graph showing the results of FT-IR DRIFT analysis of the denitrification reaction using catalysts according to 180 ° C and 350 ° C of Comparative Example 2 under flue gas conditions with a high NO ₂ ratio.
5 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 .
6 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 .
7 is a graph showing the results of FT-IR DRIFT analysis of the denitrification reaction using the denitration catalysts according to Preparation Example of the present invention and Comparative Examples 1 and 2 under flue gas conditions with a high NO ₂ ratio.
8 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.
9 is a graph showing the results of Raman analysis using a denitrification catalyst according to a preparation example of the present invention.

Since the present invention can apply various transformations and have various embodiments, specific embodiments will be exemplified and described in detail in the detailed description. However, this is not intended to limit the present invention to specific embodiments, and should be understood to include all conversions, equivalents, or substitutes included in the spirit and scope of the present invention.

Terms used in the present invention are only used to describe specific embodiments, and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise. In the present invention, terms such as include or have are intended to designate that a feature, number, step, operation, component, part, or combination thereof described in the specification exists, but one or more other features, numbers, or steps However, it should be understood that it does not preclude the possibility of existence or addition of operations, components, parts, or combinations thereof.

The present invention provides a new exhaust gas treatment system in consideration of the characteristics of the exhaust gas generated during the above-described liquefied natural gas combined cycle power plant.

1 is a schematic diagram of a liquefied natural gas combined cycle power plant exhaust gas treatment system according to an embodiment of the present invention).

1, the exhaust gas discharged from the liquefied natural gas combined cycle power engine is injected into the selective catalytic reduction (SCR) unit 100 equipped with a selective catalytic reduction reaction (SCR) catalyst. A "NO ₂ SCR catalyst" is used, which does not slow down the SCR process even in nitrogen oxides (NO ₂ /NO _x ratio of 0.5 or more) containing a high content _of nitrous oxide (NO ₂ ). "SCR catalyst" is described in more detail below.

In this way, the present invention takes into account the peculiar components of the exhaust gas generated during initial startup, and removes nitrogen oxides from the initial startup.

Thereafter, the exhaust gas that has passed through the SCR process is again introduced into the CO controller 200 equipped with a CO removal catalyst (oxidation catalyst). In the present invention, in order to prevent poisoning of the oxidation catalyst for removing CO by ammonia introduced into the reducing agent, a catalyst for removing CO is provided at the rear end of the SCR reaction. As a result, it is possible to simultaneously solve the problem of 1) oxidation of CO and 2) trace emission of NH3, a reducing agent (NH3 slip).

In one embodiment of the present invention, the selective catalytic reduction (SCR unit 100) is provided with a reducing agent direct injection unit 300 for directly injecting ammonia, which is a reducing agent. In one embodiment of the present invention, the reducing agent is ammonia, This may be decomposed from urea water by a catalytic reaction or diluted ammonia water itself.

In particular, by applying the urea water decomposition catalyst vaporization method, the size of the device is smaller than that of the general vaporization method, and it has advantages in installation site size and equipment cost, and it has the advantage that relatively safe urea water can be used compared to ammonia.

2 is a schematic diagram of an exhaust gas treatment system for a liquefied natural gas combined cycle power plant according to another embodiment of the present invention.

Referring to FIG. 2, the system further includes a hydrocarbon removal unit 400 equipped with a catalyst for removing hydrocarbons such as CH4 in front of the selective catalytic reduction (SCR unit 100). That is, NH3 to treat CH4. Ammonia oxidation is prevented by installing a CH4 decomposition catalyst in front of the Ammonia Injection Grid (AIG).

In particular, in the present invention, the concentration of CH4 discharged from LNG is within about several hundred to 1,000 ppm, and the oxidation reaction temperature of the CH4 catalyst is about 400 degrees or more. It is not converted to CO2 and has no effect on the SCR reaction.

In one embodiment of the present invention, the SCR catalyst not only causes a selective reduction reaction when the NO2 ratio in NOx is less than 0.5, but also selective reduction reaction occurs even when the NO2 ratio in NOx is greater than 0.5. In particular, by suppressing the formation of ammonium nitrate (NH ₄ NO ₃ ) and the generation of nitrous oxide (N ₂ O), the denitrification efficiency is not lowered. This will be described in more detail below.

3 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.

4 is a graph showing the results of FT-IR DRIFT analysis of the denitrification reaction using catalysts according to 180 ° C and 350 ° C of Comparative Example 2 under flue gas conditions with a high NO ₂ ratio.

5 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 .

6 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 .

7 is a graph showing the results of FT-IR DRIFT analysis of the denitrification reaction using the denitration catalysts according to Preparation Example of the present invention and Comparative Examples 1 and 2 under flue gas conditions with a high NO ₂ ratio.

8 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.

9 is a graph showing the results of Raman analysis using a denitrification catalyst according to a preparation example of the present invention.

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.

3 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. 3 , 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

4 is a graph showing the results of FT-IR DRIFT analysis of the denitrification reaction using catalysts according to 180 ° C and 350 ° C of Comparative Example 2 under flue gas conditions with a high NO ₂ ratio.

Referring to FIG. 4, 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, 1346 25 minutes after NO ₂ and O ₂ were injected It can be seen that cm ^-1 NO ₂ peak and 1620 cm ^-1 NO ₂ peak were generated.

On the other hand, even when the NO ₂ ratio increased, it was not possible to confirm the generation of such a NO ₂ peak at 350° C., which showed similar denitrification performance. 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 used 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. are supported

In the present invention, in particular, when manganese is added as manganese nitrate (Mn nitrate), the fraction of Mn4+ in the 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 low temperatures.

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 1 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

5 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. 5, 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

6 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. 6 , 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

7 is a graph showing the results of FT-IR DRIFT analysis of the denitrification reaction using the denitration catalysts according to Preparation Example and Comparative Examples 1 and 2 under exhaust gas conditions with a high NO ₂ ratio at 180 degrees Celsius.

Referring to FIG. 7, 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/tungsten according to Comparative Example 1 / Titania-based catalyst and vanadium / tungsten / titania-based denitrification catalyst according to Comparative Example 2 showed 1346 cm ^-1 NO ₂ peak and 1620 cm ^-1 NO ₂ peak after 45 minutes and 25 minutes after injection of NO ₂ and O ₂ It can be confirmed that is generated, and this NO ₂ peak is ammonium nitrate (NH ₄ NO ₃ ) generated by reacting with NH ₃ , which 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 peaks of 1346 cm ⁻¹ and NO ₂ peaks of 1620 cm ⁻¹ . 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

8 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. 8, 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, except for the production example of the present invention using Anatase TiO ₂ , NOx conversion rate of 30% or less and generation of N 2 O of 10 ppm or more at 200 degrees were confirmed. 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, generation of N ₂ O 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 (cm ³ /g) Mean pore size
(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 cm ³ /g or more, mean pore diameter 32 nm or less, and Vp 0.35 cm 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

9 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, only the manufacturing example of the invention containing both α-Mn ₂ O ₃ and Mn ₃ O ₄ manganese is generated in exhaust gas with a high NO2 ratio. It suggests that it 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 N ₂ O generation amount 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 indicate that the catalyst firing temperature is preferably at the level of 400 degrees Celsius, that is, in the range of 350 degrees Celsius to 450 degrees Celsius.

Claims (5)

As an exhaust gas treatment system for liquefied natural gas combined cycle power plants,
a selective catalytic reduction (SCR) unit for reducing nitrogen oxides in the exhaust gas discharged after the combined cycle power plant;
A carbon monoxide (CO) treatment unit disposed after the selective catalytic reduction (SCR) unit and equipped with a catalyst for removing carbon monoxide; includes,
An exhaust gas treatment system for a liquefied natural gas combined cycle power plant, characterized in that the NO ₂ / NO _x ratio in the exhaust gas is 0.5 or more. According to claim 1,
The catalyst of the selective catalytic reduction (SCR) unit is an exhaust gas treatment system for a liquefied natural gas combined cycle power plant, characterized in that the NO ₂ SCR catalyst in which a selective catalytic reduction reaction occurs even at a NO 2 / NOx ratio of 0.5 or more. The method of claim 1, wherein the exhaust gas treatment system for the liquefied natural gas combined cycle power plant,
The exhaust gas treatment system for a liquefied natural gas combined cycle power plant further comprising an ammonia injection unit coupled to the selective catalytic reduction (SCR) unit and directly injecting ammonia into the selective catalytic reduction (SCR) unit. The method of claim 3, wherein the liquefied natural gas combined cycle power plant exhaust gas treatment system,
The exhaust gas treatment system for a liquefied natural gas combined cycle power plant, characterized in that it further comprises a hydrocarbon processing unit provided in front of the selective catalytic reduction (SCR) unit to treat hydrocarbons with a catalyst. According to claim 2,
The NO ₂ SCR catalyst includes vanadium/tungsten/titania and manganese, and manganese includes both α-Mn ₂ O ₃ and Mn ₃ O ₄ structures, thereby forming ammonium nitrate (NH ₄ NO ₃ ) and suboxidation. An exhaust gas treatment system for a liquefied natural gas combined cycle power plant, characterized in that the generation of nitrogen (N ₂ O) is suppressed.

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