Exhaust gas treatment catalyst unit and exhaust gas treatment method

Abstract

To enhance catalytic performance even under fluctuation of exhaust gas components.SOLUTION: An exhaust gas treatment catalyst unit that promotes a reaction between nitrogen oxides and ammonia in a fluid in which ammonia is mixed with exhaust gas containing nitrogen oxides, the exhaust gas treatment catalyst unit comprising a first catalyst and a second catalyst disposed on a downstream side in an exhaust gas flow direction relative to the first catalyst, wherein the first catalyst is a catalyst containing zeolite, and the second catalyst is a catalyst containing titanium oxide as a main component.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to an exhaust gas treatment catalyst unit and an exhaust gas treatment method for treating nitrogen oxides contained in exhaust gas. [Background technology]

[0002] Combustion plants, such as gas turbines and boilers, that burn fossil fuels such as natural gas, oil, and coal, as well as fuels such as biomass, are equipped with exhaust gas treatment devices that treat the exhaust gas generated by combustion.The exhaust gas treatment devices have denitration equipment that reduces nitrogen oxides contained in the exhaust gas.The denitration equipment supplies urea or ammonia to the exhaust gas, causing ammonia to react with nitrogen oxides, thereby reducing the nitrogen oxides.The denitration equipment is equipped with a catalyst that promotes the reaction between ammonia and nitrogen oxides.

[0003] Patent Document 1 describes a denitration catalyst (exhaust gas treatment catalyst) that removes nitrogen oxides in exhaust gases where the NO2 / NO molar ratio is 1 or more, and that is a denitration catalyst that is made of a catalyst made of TiO2-V2O5-WO3 to which at least one of Cr, Cu, Mn, and Co is added in an amount of 0.1 to 10 wt% in terms of the oxide. Patent Document 2 also describes a denitration facility that includes an oxidation catalyst, a urea supply device, and a NO x A denitration system is described in which a reduction selective catalyst is arranged in sequence. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 04-18932 [Patent Document 2] International Publication No. 2007 / 102607 Summary of the Invention [Problem to be solved by the invention]

[0005] The catalyst described in Patent Document 1 can accelerate the reduction of nitrogen oxides. The denitration equipment described in Patent Document 2 oxidizes exhaust gas with an oxidation catalyst, then supplies urea (ammonia), and accelerates the reaction between ammonia and nitrogen oxides with a NOx selective reduction catalyst to treat the nitrogen oxides.

[0006] For example, gas turbines, boilers, and the like used in power generators may operate under variable load conditions to adjust the amount of power generated depending on the overall amount of power generated. When the load is varied, or when the device is operated at a low load, or when the device is operated at a load above a certain level, the components of the exhaust gas change. The same is true for engines, etc., whose combustion conditions fluctuate. Therefore, there is a demand for improved catalyst performance even when the components of the exhaust gas fluctuate.

[0007] The present disclosure is intended to solve the above-mentioned problems, and aims to provide an exhaust gas treatment catalyst unit and an exhaust gas treatment method that can improve catalyst performance even when the components of the exhaust gas fluctuate. [Means for solving the problem]

[0008] In order to achieve the above object, the present disclosure provides an exhaust gas treatment catalyst unit that promotes a reaction between nitrogen oxides and ammonia in a fluid in which ammonia is mixed with exhaust gas containing nitrogen oxides, and includes a first catalyst and a second catalyst that is arranged downstream of the first catalyst in the exhaust gas flow direction, wherein the first catalyst is a catalyst that contains zeolite, and the second catalyst is a catalyst that contains titanium oxide as a main component.

[0009] The exhaust gas treatment method of the present disclosure also includes the steps of introducing a fluid in which ammonia is mixed with exhaust gas containing nitrogen oxides, passing the fluid through a first catalyst containing zeolite, and passing the fluid through a second catalyst containing titanium oxide as a main component. [Effects of the Invention]

[0010] According to the present disclosure, the performance of the catalyst can be improved even when the components of the exhaust gas vary. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic diagram showing the configuration of a combustion plant to which the exhaust gas treatment catalyst unit of this embodiment is applied. [Figure 2] FIG. 2 is a table showing the results of measuring the denitration performance. [Figure 3] FIG. 3 is a table showing the results of measuring the denitration performance. [Figure 4] FIG. 4 is a table showing the results of measuring the denitration performance. [Figure 5] FIG. 5 is a table showing the results of measuring the denitration performance. [Figure 6] FIG. 6 is a table showing the results of measuring the denitration performance. DETAILED DESCRIPTION OF THE INVENTION

[0012] Preferred embodiments of the present disclosure will be described in detail below with reference to the drawings. Note that the present disclosure is not limited to these embodiments, and when there are multiple embodiments, the present disclosure also includes configurations that combine the embodiments. Furthermore, the components in the embodiments include those that can be easily imagined by a person skilled in the art, those that are substantially identical, and those that are within the so-called equivalent range.

[0013] FIG. 1 is a schematic diagram showing a combustion plant to which the exhaust gas treatment catalyst of this embodiment is applied. The combustion plant to which the denitration equipment of this embodiment is applied is a gas turbine that rotates the turbine with combustion gas obtained by burning gaseous fuel in a combustion chamber. Note that in this embodiment, the combustion equipment is a gas turbine, but the combustion equipment is not particularly limited, and the denitration equipment can be used as a denitration equipment for various combustion equipment that combusts fuel and emits exhaust gas containing nitrogen oxides. For example, the combustion equipment may be a boiler that burns fuel with a combustion burner and is capable of recovering heat generated by this combustion. In addition, the denitration equipment can also be used as a treatment equipment for exhaust gas discharged from a multi-fuel combustion equipment that burns a mixture of coal, liquid fuel, and gaseous fuel as fuel. In addition, the denitration equipment can also be used as a treatment equipment for exhaust gas discharged from a combustion equipment that burns biomass or the like.

[0014] The combustion plant 10 of this embodiment has a fuel supply unit 12, an air supply unit 14, a combustion device 20, a flue 30, and a denitration equipment 40. The combustion plant 10 may also include a heat exchanger that exchanges heat with the exhaust gas discharged from the combustion device 20, and an exhaust gas treatment device other than the denitration equipment 40. The fuel supply unit 12 supplies fuel, such as LNG or shale gas, to the combustion device 20. The air supply unit 14 supplies air to the combustion device 20.

[0015] The combustion device 20 is a gas turbine. The combustion device 20 has a combustor, a compressor, and a turbine, with the compressor and turbine connected by a shaft. The combustion device 20 compresses air supplied from the air supply unit 14 using the compressor, mixes the compressed air with fuel supplied from the fuel supply unit 12, and combusts the air in the combustor to generate high-temperature, high-pressure combustion gas. The combustion device 20 uses the energy of the combustion gas to rotate the turbine, and exhaust gas that rotates the turbine is discharged.

[0016] The flue 30 is connected to the combustion equipment 20, and the exhaust gas that has passed through the turbine of the combustion equipment 20 flows into the flue 30.

[0017] The denitration equipment 40 removes and reduces nitrogen oxides in the exhaust gas by supplying a reducing agent, such as ammonia or urea water, into the flue 30 and passing the exhaust gas to which the reducing agent has been supplied through a selective catalytic reduction catalyst that promotes a reaction between the nitrogen oxides and the reducing agent. The denitration equipment 40 includes a reducing agent supply device 42, a first denitration catalyst layer 50, and a second denitration catalyst layer 52. The denitration equipment 40 may further include a control device that measures the ammonia concentration, etc., and controls the amount of the reducing agent supplied.

[0018] The reducing agent supply device 42 has a reducing agent storage unit 42a and an injection unit 42b. The reducing agent storage unit 42a is a tank that stores a reducing agent. Examples of the reducing agent that can be used include ammonia water, gaseous ammonia, and urea water. The injection unit 42b is connected to the reducing agent storage unit 42a and has a supply port disposed inside the flue 30. The reducing agent supply device 42 supplies the reducing agent from the reducing agent storage unit 42a to the injection unit 42b, and discharges (injects) the reducing agent from the supply port of the injection unit 42b disposed inside the flue 40, thereby supplying the reducing agent into the flue 30. The reducing agent supplied from the reducing agent supply device 42 moves together with the exhaust gas and diffuses within the path through which the exhaust gas flows.

[0019] The first denitration catalyst layer 50 is disposed downstream of the reducing agent supply device 42 in the flow direction of the exhaust gas. The first denitration catalyst layer 50 has a catalyst and a support mechanism for fixing the catalyst to the flue 30. The shape of the catalyst is not particularly limited, and may be either a plate shape or a honeycomb shape. The components of the catalyst will be described later. The support mechanism may be any mechanism capable of supporting the catalyst, and the structure is not particularly limited.

[0020] The second Denitration catalyst layer 52 is disposed downstream of the first Denitration catalyst layer 50 in the flow direction of the exhaust gas. The second Denitration catalyst layer 52 has a catalyst and a support mechanism that fixes the catalyst to the flue 30. The second Denitration catalyst layer 52 is similar to the first Denitration catalyst layer 50 except for its location.

[0021] In the denitration equipment 40, a reducing agent supply device 42 supplies a reducing agent to the flue 30, and the exhaust gas mixed with the reducing agent passes through a first denitration catalyst layer 50 and a second denitration catalyst layer 52. The denitration equipment 40 removes nitrogen oxides from the exhaust gas by promoting a reaction between the nitrogen oxides and the reducing agent in the first denitration catalyst layer 50 and the second denitration catalyst layer 52. Although the denitration equipment 40 of this embodiment has two denitration catalyst layers, the total number is not particularly limited, and may be three or more layers or one layer. The denitration equipment 40 may also have a rectification layer upstream of the denitration catalyst layers.

[0022] Next, the catalysts of the first denitration catalyst layer 50 and the second denitration catalyst layer 52, that is, the exhaust gas treatment catalyst unit of this embodiment, will be described. The exhaust gas treatment catalyst unit of this embodiment has a first catalyst and a second catalyst. The second catalyst is arranged downstream of the first catalyst. In this embodiment, for example, the catalyst of the first denitration catalyst device 50 serves as the first catalyst, and the catalyst of the second denitration catalyst device 50 serves as the second catalyst. The first catalyst and the second catalyst can have various shapes, such as a plate shape or a honeycomb shape.

[0023] The first catalyst is a catalyst containing zeolite. The first catalyst is a catalyst in which zeolite is applied to the surface of a substrate. The first catalyst preferably further contains ruthenium.

[0024] The second catalyst is a catalyst whose main component is titanium oxide. The second catalyst preferably contains vanadium, tungsten, or the like as an active component. In other words, the exhaust gas treatment catalyst is a binary TiO2-WO3 catalyst, TiO2-V2O5 catalyst, or a ternary TiO2-V2O5-WO3 catalyst, and preferably contains manganese (Mn) in an amount of 1.0 mass % (wt.%) or less, calculated as Mn2O3, based on the total amount of the catalyst. The exhaust gas treatment catalyst may also contain molybdenum (Mo) as an active component. In other words, the exhaust gas treatment catalyst may be a TiO2-MoO3 catalyst, a TiO2-V2O5-MoO3 catalyst, or the like.

[0025] In the exhaust gas treatment catalyst unit, the first catalyst is disposed upstream of the second catalyst, so that exhaust gas supplied with NH3 as a reducing agent passes through the first catalyst containing zeolite and then the second catalyst containing titanium oxide. This allows the exhaust gas treatment catalyst unit to effectively reduce nitrogen oxides while reducing the outlet ammonia (NH3) component. Here, the outlet ammonia component is a component containing nitrogen (N) and hydrogen (H), and is a component that can generate NH3 in addition to NH3. Components that can generate NH3 are substances that can react with substances contained in the exhaust gas atmosphere to generate ammonia. For example, HCN may react with water in the exhaust gas in the following manner: HCN + 2H2O → CO2 + NH3 + H2. Therefore, HCN is included in the components that can generate NH3. Furthermore, HCONH2 may react with HCONH2 → CO + NH3. Therefore, HCONH2 is included in the components that can generate NH3.

[0026] Furthermore, the exhaust gas treatment catalyst unit can reduce the outlet ammonia component while maintaining a high denitration rate under NO2-rich conditions and in the presence of HCHO with a concentration equal to or greater than NO2. As a result, even if, for example, an oxidation catalyst for removing CO and VOCs is not installed upstream of the denitration equipment and HCHO (formaldehyde) emitted from a gas turbine flows directly into the denitration equipment, it is possible to suppress the generation of ammonia as an outlet component from HCHO and to perform the reduction treatment of nitrogen oxides appropriately. The same applies when an oxidation catalyst is installed but the removal of HCHO by the oxidation catalyst is insufficient. Specifically, the exhaust gas treatment catalyst unit can reduce the outlet ammonia component through the following reaction even when HCHO is contained in the exhaust gas. NH3+HCNO+1 / 2O2→HCONH2+H2O HCONH2 → CO+NH3 NH3+O2→N2+H2O

[0027] Furthermore, the exhaust gas treatment catalyst unit can reduce nitrogen oxides in exhaust gas even when the exhaust gas does not contain HCHO, while also reducing the outlet ammonia component.

[0028] The following describes the catalyst components used in the examples and comparative examples.

[0029] Example 1 In the exhaust gas treatment catalyst unit of Example 1, the first catalyst (first catalyst) was a catalyst containing ruthenium and zeolite, and the second catalyst (second catalyst) was a catalyst containing V2O5-WO3-TiO2. The zeolite of the first catalyst was of the MFI type, and the ruthenium (Ru) was 0.5 mass % (wt.%) relative to the total amount of the catalyst. The specific surface area of ​​Ru / zeolite in the first catalyst was 330 m 2 / g. The second catalyst contains 79.8 mass% TiO2, 2.6 mass% V2O5, and 6.2 mass% WO3 in terms of mass% relative to the total amount. In addition to the above components, binders and unavoidable impurities are also included. Furthermore, the active components do not contain manganese, chromium, copper, or cobalt. Here, "not containing target components" means that the amount is below the unavoidable impurity amount.

[0030] Example 2 In Example 2, the amount of ammonia supplied to the exhaust gas containing nitrogen oxides was reduced compared to Example 1. The configuration of the exhaust gas treatment catalyst unit was the same as in Example 1.

[0031] (Comparative Example 1) The exhaust gas treatment catalyst unit of Comparative Example 1 differs in that it does not include a first catalyst. In Comparative Example 1, the second catalyst (second catalyst) was a catalyst containing V2O5-WO3-Mn2O3-TiO2. The second catalyst (second catalyst) contained 2.5 mass% V2O5, 5.3 mass% WO3, and 0.53 mass% Mn2O3, based on the total mass. In addition to the above components, it also contained a binder and unavoidable impurities. Furthermore, it did not contain chromium, copper, or cobalt as active components.

[0032] (Comparative Example 2) The exhaust gas treatment catalyst unit of Comparative Example 2 differs in that it does not include a first catalyst. In Comparative Example 2, the second catalyst (second catalyst) was a catalyst containing V2O5-WO3-TiO2. The second catalyst (second catalyst) contained 2.6 mass% V2O5 and 6.2 mass% WO3 relative to the total mass. In addition to the above components, it also contained a binder and unavoidable impurities. Furthermore, it did not contain chromium, copper, or cobalt as active components.

[0033] (Comparative Example 3) In Comparative Example 3, the amount of ammonia supplied to exhaust gas containing nitrogen oxides was reduced compared to Comparative Example 2. The exhaust gas treatment catalyst unit of Comparative Example 3 differs in that it does not include a first catalyst. In Comparative Example 3, the second catalyst (second catalyst) was a catalyst containing V2O5-WO3-TiO2. The second catalyst (second catalyst) contained 2.6 mass% V2O5 and 6.2 mass% WO3 relative to the total mass. In addition to the above components, it also contained a binder and unavoidable impurities. Furthermore, it did not contain chromium, copper, or cobalt as active components.

[0034] (Measurement conditions) For the above catalyst, the first measurement was performed with a composition of NOx = 47 ppm, NO2 / NO x =0.85, NH3=54ppm, HCHO=179ppm, O2=15.1%, H2O=6.5%, CO2=4%, the remainder being N2. The temperature of the exhaust gas was 294°C, and the treated gas flow rate per catalytic gas contact area of ​​the second catalyst was AV21Nm 3 / m 2 / hr, treated gas flow rate AV19Nm per catalytic gas contact area of ​​exhaust gas treatment catalyst unit (first catalyst + second catalyst) 3 / m 2 / hr, the amount of nitrogen oxides after passing through the catalyst and the outlet ammonia content were measured, and the denitrification rate, which is the reduction rate of nitrogen oxides before and after the catalyst, and the amount of nitrogen oxides after passing through the catalyst (outlet NO x ) and the outlet ammonia content after passing through the catalyst was calculated. AV is the gas flow rate / catalyst gas contact area.

[0035] 2 and 3 are tables showing the results of measuring denitration performance. Fig. 2 and 3 are tables summarizing the catalyst components, denitration rate, amount of outlet ammonia component, and amount of ammonia at the outlet of the example and comparative example. Fig. 2 shows the measurement results. Fig. 3 shows the results of the same denitration performance, with a denitration rate of 90.7% and outlet NO 3. x 2 and 4, the exhaust gas treatment catalyst unit of the present disclosure can reduce the outlet ammonia component and outlet ammonia while improving the denitrification performance.

[0036] (Comparative Examples 4 and 5) The exhaust gas treatment catalyst units of Comparative Examples 4 and 5 differ in that they do not include the first catalyst. In Comparative Example 4, the amount of catalyst was the same as the amount of the first catalyst + the second catalyst in Example 1, and in Comparative Example 5, the amount of catalyst was the same as the amount of the first catalyst + the second catalyst in Example 2. In other words, the volume flow rate AV of the exhaust gas treatment catalyst unit (second catalyst) was 19 Nm 3 / m 2 The kinetic energy was measured as / hr. In Comparative Examples 4 and 5, the second catalyst (second catalyst) was a catalyst containing V2O5-WO3-Mn2O3-TiO2. The second catalyst (second catalyst) contained 2.5 mass% V2O5, 5.3 mass% WO3, and 0.53 mass% Mn2O3, based on the total mass. In addition to the above components, binders and unavoidable impurities were also included. Furthermore, chromium, copper, and cobalt were not included as active components.

[0037] (Comparative Examples 6 and 7) The exhaust gas treatment catalyst units of Comparative Examples 6 and 7 differ in that they do not include a first catalyst. In Comparative Example 6, the amount of catalyst was the same as the amount of the first catalyst + the second catalyst in Example 1, and in Comparative Example 7, the amount of catalyst was the same as the amount of the first catalyst + the second catalyst in Example 2. In other words, the volume flow rate AV of the exhaust gas treatment catalyst unit (second catalyst) was 19 Nm 3 / m 2The kinetic energy was measured as / hr. In Comparative Examples 6 and 7, the second catalyst (second catalyst) was a catalyst containing V2O5-WO3-TiO2. The second catalyst (second catalyst) contained 2.6 mass% V2O5 and 6.2 mass% WO3 relative to the total mass. In addition to the above components, binders and unavoidable impurities were also included. Furthermore, chromium, copper, and cobalt were not included as active components.

[0038] Fig. 4 is a table showing the results of measuring denitration performance. Fig. 4 is a table summarizing the catalyst components, denitration rate, amount of outlet ammonia component, and amount of ammonia at the outlet of the examples and comparative examples. Fig. 4 shows the results of Comparative Examples 4 and 5 and Comparative Examples 6 and 7, which have the same denitration performance, a denitration rate of 90.7% and an outlet NO x 4, the exhaust gas treatment catalyst unit of the present disclosure can reduce the outlet ammonia component and outlet ammonia even when the amount of ammonia at the unit inlet is set to the same denitration performance.

[0039] (Comparative Example 8) The exhaust gas treatment catalyst unit of Comparative Example 8 differs from Comparative Example 2 in that it includes a titanium oxide catalyst as the first catalyst. In Comparative Example 8, the first catalyst is a catalyst containing TiO2, and the second catalyst (second catalyst) is a catalyst containing V2O5-WO3-TiO2. The second catalyst (second catalyst) contains 2.6 mass% V2O5 and 6.2 mass% WO3, based on the total mass. In addition to the above components, it also contains a binder and unavoidable impurities. Furthermore, it does not contain chromium, copper, or cobalt as active components.

[0040] Comparative Example 9 The exhaust gas treatment catalyst unit of Comparative Example 9 differs from Comparative Example 3 in that it includes a titanium oxide catalyst as the first catalyst. In Comparative Example 9, the first catalyst is a catalyst containing TiO2, and the second catalyst (second catalyst) is a catalyst containing V2O5-WO3-TiO2. The second catalyst (second catalyst) contains 2.6 mass% V2O5 and 6.2 mass% WO3, based on the total mass. In addition to the above components, it also contains a binder and unavoidable impurities. Furthermore, it does not contain chromium, copper, or cobalt as active components.

[0041] 5 and 6 are tables showing the results of measuring denitration performance. Fig. 5 and Fig. 6 are tables summarizing the catalyst components, denitration rate, amount of outlet ammonia component, and amount of ammonia at the outlet of the example and comparative example. Fig. 5 shows the measurement results. Fig. 6 shows the results of the same denitration performance, with a denitration rate of 90.7% and outlet NO. x 5 and 6, the exhaust gas treatment catalyst unit of the present disclosure can reduce the outlet ammonia component and outlet ammonia more than when a titanium oxide catalyst is arranged as the first catalyst, and can also maintain a high denitrification rate.

[0042] Here, the first catalyst preferably has a smaller gas contact area that comes into contact with exhaust gas than the second catalyst. Specifically, it is preferable that 1 / 30≦(gas contact area of ​​first catalyst) / (gas contact area of ​​first catalyst)≦1. For example, (gas contact area of ​​first catalyst) / (gas contact area of ​​first catalyst)=1 / 12. By making the first catalyst smaller than the second catalyst, it is possible to reduce the outlet ammonia component and outlet ammonia while maintaining denitration performance.

[0043] Here, the second catalyst preferably contains titanium oxide in an amount of 60 mass % or more, more preferably 70 mass % or more, calculated as TiO2. It is preferable to use TiO2 as the titanium oxide. By keeping the titanium oxide content within the above range, the denitrification rate can be increased.

[0044] As described above, the second catalyst preferably contains at least one of tungsten oxide and vanadium oxide as an active component, thereby increasing the denitrification rate. Furthermore, the second catalyst may contain molybdenum as an active component.

[0045] The second catalyst preferably contains vanadium oxide in an amount of 0.1 to 10% by mass, more preferably 2 to 5% by mass, calculated as V2O5, of the total amount, which can increase the denitrification rate.

[0046] In the second catalyst, the tungsten oxide content is preferably 0.1% by mass to 20% by mass, more preferably 4% by mass to 8% by mass, calculated as WO3, of the total amount, which can increase the denitrification rate.

[0047] The second catalyst preferably contains manganese as an active component. The amount of manganese (Mn) added to the second catalyst is preferably 1.0% by mass (wt.%) or less, calculated as Mn2O3, relative to the total amount of the catalyst, and more preferably 0.2% to 1.0% by mass of the total amount. By setting the manganese content within the above range, the second catalyst can maintain catalytic activity under NO2-rich conditions, thereby improving denitration performance, and can maintain catalytic activity even under conditions where high concentrations of HCHO (formaldehyde) coexist, thereby improving denitration performance.

[0048] The second catalyst is composed primarily of titanium oxide and contains manganese as an active ingredient, and by adding 1.0% by mass (wt.%) or less of manganese (Mn) converted to Mn2O3 based on the total amount of catalyst, it is possible to remove a high percentage of nitrogen oxides from exhaust gases containing a large amount of nitrogen dioxide, regardless of the presence or absence of HCHO.Furthermore, the second catalyst is composed primarily of titanium oxide and contains manganese as an active ingredient, and by adding 1.0% by mass (wt.%) or less of manganese (Mn) converted to Mn2O3 based on the total amount of catalyst, it is possible to remove a high percentage of HCHO.

[0049] Furthermore, the exhaust gas treatment catalyst unit of the present disclosure can achieve a nitrogen oxide removal rate comparable to that of the comparative example even when no HCHO is contained, that is, even when combustion is performed under favorable conditions in a natural gas-fired gas turbine. In other words, the exhaust gas treatment method using the exhaust gas treatment catalyst unit of the present disclosure can achieve a NO2 / NO x is 0.5 or more and the HCHO concentration varies from the NO2 concentration or more to the HCHO concentration not being present, a high denitrification rate can be maintained, and even if HCHO is generated, it can be suitably removed.

[0050] The second catalyst preferably further contains sulfur trioxide in an amount of 0.1 wt% to 2% of the total amount, and more preferably 0.2 wt% to 2% of the total amount, which can increase the denitrification rate.

[0051] The second catalyst preferably does not contain chromium, copper, or cobalt as active components, which simplifies the catalyst configuration and prevents a decrease in the proportion of the main component.

[0052] [Effects of this embodiment] The present disclosure has the following features, but is not limited to the following. (1) An exhaust gas treatment catalyst unit that promotes the reaction between nitrogen oxides and ammonia in a fluid in which ammonia is mixed with exhaust gas containing nitrogen oxides, the exhaust gas treatment catalyst unit including a first catalyst and a second catalyst disposed downstream of the first catalyst in the exhaust gas flow direction, the first catalyst containing zeolite, and the second catalyst containing titanium oxide as a main component, thereby enabling exhaust gas treatment with a high denitrification rate and reducing outlet ammonia.

[0053] (2) The exhaust gas treatment catalyst unit according to (1), wherein the second catalyst contains titanium oxide in an amount of 60 mass % or more of the total amount calculated as TiO2, thereby making it possible to increase the denitrification rate.

[0054] (3) The exhaust gas treatment catalyst unit according to (1) or (2), which contains at least one of tungsten oxide and vanadium oxide as an active component, thereby enabling a high denitrification rate.

[0055] (4) The exhaust gas treatment catalyst unit according to (3), wherein the vanadium oxide is 0.1 mass % or more and 10 mass % or less of the total amount in terms of V2O5, thereby making it possible to increase the denitrification rate.

[0056] (5) The exhaust gas treatment catalyst unit according to (3) or (4), wherein the tungsten oxide is 0.1 mass % or more and 20 mass % or less of the total amount in terms of WO3, thereby making it possible to increase the denitrification rate.

[0057] (6) The exhaust gas treatment catalyst unit according to any one of (1) to (5), wherein the second catalyst contains manganese as an active component in an amount of 1.0 mass% or less of the total amount in terms of Mn2O3, thereby enabling a high denitrification rate even when VOC components are contained in the exhaust gas.

[0058] (7) The exhaust gas treatment catalyst unit according to any one of (1) to (5), wherein the second catalyst contains manganese, an active component, in an amount of 0.2% by mass to 1.0% by mass, calculated as Mn2O3, of the total amount, thereby enabling a high denitrification rate even when VOC components are contained in the exhaust gas.

[0059] (8) The exhaust gas treatment catalyst unit according to any one of (1) to (7), wherein the second catalyst further contains sulfur trioxide in an amount of 0.1 wt % to 2% of the total amount, thereby enabling an increase in the denitrification rate.

[0060] (9) The exhaust gas treatment catalyst unit according to any one of (1) to (8), which does not contain chromium, copper, or cobalt as an active component, thereby enabling a high denitrification rate.

[0061] (10) The exhaust gas treatment catalyst unit according to any one of (1) to (9), wherein the first catalyst contains ruthenium, thereby making it possible to increase the denitrification rate.

[0062] (11) The exhaust gas treatment catalyst unit according to any one of (1) to (9), wherein the first catalyst has a smaller gas contact area that comes into contact with the exhaust gas than the second catalyst, thereby enabling a higher denitrification rate.

[0063] (12) An exhaust gas treatment method comprising the steps of introducing a fluid in which exhaust gas containing nitrogen oxides and ammonia are mixed, passing the fluid through a first catalyst containing zeolite, and passing the fluid through a second catalyst containing titanium oxide as a main component, thereby enabling exhaust gas treatment with a high denitrification rate and reducing outlet ammonia. [Explanation of symbols]

[0064] 10 Combustion Plant 12 Fuel supply section 14 Air supply section 20 Combustion equipment 30 Flue (exhaust gas passage) 42 Reducing agent supply device 50 1st denitrification catalyst layer 52 2nd denitrification catalyst layer

Claims

1. An exhaust gas treatment catalyst unit that promotes a reaction between nitrogen oxides and ammonia in a fluid in which ammonia is mixed with exhaust gas containing nitrogen oxides, A first catalyst; a second catalyst disposed downstream of the first catalyst in the exhaust gas flow direction, the first catalyst is a catalyst containing zeolite, The second catalyst is a catalyst containing titanium oxide as a main component.

2. The second catalyst is characterized in that the titanium oxide is TiO ２ 2. The exhaust gas treatment catalyst unit according to claim 1, wherein the amount of the catalyst is 60 mass % or more of the total amount of the exhaust gas treatment catalyst unit.

3. 2. The exhaust gas treatment catalyst unit according to claim 1, wherein the second catalyst contains at least one of tungsten oxide and vanadium oxide as an active component.

4. The second catalyst is a catalyst in which vanadium oxide is V ２ O ５ 4. The exhaust gas treatment catalyst unit according to claim 3, wherein the amount of the catalyst is 0.1 mass % or more and 10 mass % or less of the total amount of the exhaust gas treatment catalyst unit.

5. The second catalyst is a catalyst in which tungsten oxide is WO ３ 4. The exhaust gas treatment catalyst unit according to claim 3, wherein the amount of the catalyst is 0.1 mass % or more and 20 mass % or less of the total amount of the catalyst unit.

6. The second catalyst has an active component of manganese, which is Mn ２ O ３ 2. The exhaust gas treatment catalyst unit according to claim 1, wherein the amount of the catalyst is 1.0 mass % or less of the total amount of the exhaust gas treatment catalyst unit.

7. The second catalyst has an active component of manganese, which is Mn ２ O ３ 2. The exhaust gas treatment catalyst unit according to claim 1, wherein the amount of the catalyst is 0.2 mass % or more and 1.0 mass % or less of the total amount of the exhaust gas treatment catalyst unit.

8. 2. The exhaust gas treatment catalyst unit according to claim 1, wherein the second catalyst further contains sulfur trioxide in an amount of 0.1 wt % or more and 2 wt % or less of the total amount.

9. 2. The exhaust gas treatment catalyst unit according to claim 1, wherein the second catalyst does not contain chromium, copper, or cobalt as an active component.

10. The exhaust gas treatment catalyst unit according to claim 1 , wherein the first catalyst contains ruthenium.

11. 2. The exhaust gas treatment catalyst unit according to claim 1, wherein the first catalyst has a smaller gas contact area that comes into contact with the exhaust gas than the second catalyst.

12. A step in which a fluid in which ammonia is mixed with exhaust gas containing nitrogen oxides flows in; passing the mixture through a first catalyst comprising a zeolite; and passing the exhaust gas through a second catalyst containing titanium oxide as a main component.

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