Exhaust gas treatment device, and exhaust gas treatment method

Abstract

An exhaust gas treatment device for treating exhaust gas generated by burning fuel, wherein: the exhaust gas treatment device comprises one or more catalyst units, each of which includes a first denitration catalyst for reducing nitrogen oxides in the exhaust gas, an ammonia decomposition catalyst that is provided downstream of the first denitration catalyst in an exhaust gas flow and is for decomposing ammonia in the exhaust gas, and a second denitration catalyst that is disposed downstream of the ammonia decomposition catalyst in the exhaust gas flow and is for reducing nitrogen oxides in the exhaust gas; and the ratio (CNH3_FSCR / CN2O_SYS) of the concentration of ammonia (CNH3_FSCR) at the outlet of the first denitration catalyst to the concentration of dinitrogen monoxide (CN2O_SYS) at the outlet of the one or more catalyst units is 10.0 or greater.

Description

Exhaust gas treatment device and exhaust gas treatment method

[0001] This application claims priority to Japanese Patent Application No. 2023-090194, filed with the Japan Patent Office on May 31, 2023, the contents of which are incorporated herein by reference.

[0002] Denitration catalysts are sometimes used to reduce nitrogen oxides (NOx) contained in combustion exhaust gas from combustion equipment. When treating exhaust gas, ammonia is usually added to the exhaust gas upstream of the denitration catalyst. In the presence of the denitration catalyst, the nitrogen oxides in the exhaust gas react with ammonia as a reducing agent and are broken down into harmless substances (nitrogen and water).

[0003] In addition, an ammonia decomposition catalyst may be used to reduce unreacted ammonia in the exhaust gas after passing through the denitration catalyst. By bringing the ammonia-containing exhaust gas after passing through the denitration catalyst into contact with the ammonia decomposition catalyst, the ammonia is oxidized and decomposed, producing mainly nitrogen.

[0004] Patent Documents 1 and 2 describe treating exhaust gas containing nitrogen oxides using a reactor in which a denitration catalyst layer is installed upstream of the exhaust gas flow and an ammonia catalyst layer is installed downstream of the reactor.

[0005] Japanese Patent No. 3462580 Japanese Patent Laid-Open No. 2000-93749

[0006] In the oxidative decomposition reaction of ammonia using an ammonia decomposition catalyst, nitrogen is mainly produced, and nitrous oxide (N2O), a greenhouse gas, is also usually produced as a by-product. ２ In particular, when exhaust gas with a high concentration of nitrogen oxides (for example, combustion exhaust gas of a fuel containing ammonia) is to be treated, a large amount of ammonia is added as a reducing agent to sufficiently reduce the nitrogen oxides in the exhaust gas, which tends to result in a large amount of dinitrogen monoxide, a by-product of the oxidative decomposition reaction of ammonia, being produced.

[0007] In view of the above circumstances, at least one embodiment of the present invention aims to provide an exhaust gas treatment device and an exhaust gas treatment method that can reduce nitrogen oxides and ammonia in exhaust gas while effectively suppressing the amount of nitrous oxide produced.

[0008] An exhaust gas treatment device according to at least one embodiment of the present invention is an exhaust gas treatment device for treating exhaust gas generated by burning fuel, comprising: a first denitration catalyst for reducing nitrogen oxides in the exhaust gas; and one or more catalyst units each including an ammonia decomposition catalyst disposed downstream of the first denitration catalyst in the exhaust gas flow for decomposing ammonia in the exhaust gas, and a second denitration catalyst disposed downstream of the ammonia decomposition catalyst in the exhaust gas flow for reducing nitrogen oxides in the exhaust gas, wherein a concentration of nitrous oxide (C Ｎ２Ｏ＿ＳＹＳ ) the ammonia concentration (C ＮＨ３＿ＦＳＣＲ ) ratio (C ＮＨ３＿ＦＳＣＲ / C Ｎ２Ｏ＿ＳＹＳ ) is 10.0 or more.

[0009] Moreover, in at least one embodiment of the present invention, an exhaust gas treatment device is an exhaust gas treatment device for treating exhaust gas generated by burning fuel, comprising: a first denitration catalyst for reducing nitrogen oxides in the exhaust gas; and one or more catalyst units each including: an ammonia decomposition catalyst provided downstream of the first denitration catalyst in the exhaust gas flow for decomposing ammonia in the exhaust gas; and a second denitration catalyst provided downstream of the ammonia decomposition catalyst in the exhaust gas flow for reducing nitrogen oxides in the exhaust gas, wherein a length of the first denitration catalyst in the direction of the exhaust gas flow is three times or more the length of each of the ammonia decomposition catalysts.

[0010] Furthermore, an exhaust gas treatment method according to at least one embodiment of the present invention is a method for treating exhaust gas generated by burning fuel, the method comprising the step of treating the exhaust gas using an exhaust gas treatment device including: a first denitration catalyst for reducing nitrogen oxides in the exhaust gas; and one or more catalyst units each including an ammonia decomposition catalyst provided downstream of the first denitration catalyst in the exhaust gas flow for decomposing ammonia in the exhaust gas, and a second denitration catalyst provided downstream of the ammonia decomposition catalyst in the exhaust gas flow for reducing nitrogen oxides in the exhaust gas, wherein in the step, a concentration of nitrous oxide (C Ｎ２Ｏ＿ＳＹＳ ) the ammonia concentration (C ＮＨ３＿ＦＳＣＲ ) ratio (C ＮＨ３＿ＦＳＣＲ / C Ｎ２Ｏ＿ＳＹＳ The exhaust gas is treated so that the value of the saturation energy (saturation energy) is 10.0 or more.

[0011] According to at least one embodiment of the present invention, an exhaust gas treatment device and an exhaust gas treatment method are provided that can reduce nitrogen oxides and ammonia in exhaust gas while effectively suppressing the amount of dinitrogen monoxide produced.

[0012] FIG. 1 is a schematic diagram of an example of combustion equipment to which an exhaust gas treatment device according to some embodiments is applied. FIG. 1 is a schematic diagram of an exhaust gas treatment device according to an embodiment. FIG. 2 is a graph showing the relationship between the concentration of nitrous oxide at the outlet of an exhaust gas treatment device and the ratio of the concentration of ammonia at the outlet of a first Denitration catalyst to the concentration of nitrous oxide at the outlet of the exhaust gas treatment device when combustion exhaust gas is treated with an exhaust gas treatment device according to an embodiment. FIG. 3 is a graph showing the relationship between the concentration of nitrous oxide at the outlet of an exhaust gas treatment device and the concentration of ammonia at the outlet of a first Denitration catalyst when combustion exhaust gas is treated with an exhaust gas treatment device according to an embodiment. FIG. 4 is a schematic diagram showing the arrangement of catalysts included in the exhaust gas treatment device shown in FIG. 2. FIG. 5 is a graph showing the relationship between the concentration of nitrous oxide at the outlet of an exhaust gas treatment device and the ratio of the length of a first Denitration catalyst to the length of an ammonia decomposition catalyst when combustion exhaust gas is treated with an exhaust gas treatment device according to an embodiment. ＦＳＣＲ / L ＡｍＤ 1 is an example of a graph showing the relationship between the temperature and the humidity (ordinate) (ordinate).

[0013] Hereinafter, several embodiments of the present invention will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of components described as embodiments or shown in the drawings are merely illustrative examples and are not intended to limit the scope of the present invention.

[0014] (Configuration of Combustion Facility) Fig. 1 is a schematic diagram of an example of combustion facility to which an exhaust gas treatment device according to some embodiments is applied. Fig. 2 is a schematic diagram of an exhaust gas treatment device according to one embodiment. In some embodiments, the combustion facility 1 includes a combustion device 100 (see Fig. 1) configured to combust fuel, and an exhaust gas treatment device 102 (see Fig. 2) configured to treat combustion exhaust gas from the combustion device 100.

[0015] The combustion facility 1 shown in FIG. 1 is a gas turbine combined cycle (GTCC) power generation facility including a gas turbine facility 2 including a combustor 12 as the combustion device 100 described above, a steam turbine facility 4, and a heat recovery steam generator (HRSG) 6.

[0016] The gas turbine facility 2 includes a compressor 10, the above-described combustor 12, and a turbine 14. The compressor 10 is configured to compress air to generate compressed air. The combustor 12 is configured to generate combustion gas through a combustion reaction between the compressed air from the compressor 10 and fuel. The turbine 14 is configured to be rotationally driven by the combustion gas from the combustor 12. A generator 18 is connected to the turbine 14 via a rotating shaft 16, and the generator 18 is driven by the rotational energy of the turbine 14 to generate electricity. The combustion gas that has completed its work in the turbine 14 is discharged from the turbine 14 as combustion exhaust gas. Note that the fuel supplied to the combustor 12 (combustion device 100) may include a carbon-containing fuel such as natural gas or coal gasification gas and / or a nitrogen-containing fuel such as ammonia.

[0017] The heat recovery steam generator 6 is configured to generate steam using the heat of the combustion exhaust gas from the gas turbine equipment 2. As shown in Fig. 2, the heat recovery steam generator 6 has a duct 30 into which the combustion exhaust gas from the gas turbine equipment 2 is introduced, and a heat transfer tube 34 provided in a flow path 32 of the combustion exhaust gas defined by the duct 30. Condensate from the condenser 26 of the steam turbine equipment 4 is introduced into the heat transfer tube 34, and steam is generated in the heat transfer tube 34 by heat exchange between the combustion exhaust gas flowing inside the duct 30 and the condensate. The exhaust gas that has passed through the duct 30 of the heat recovery steam generator 6 is discharged from a chimney 38.

[0018] The steam turbine facility 4 includes a turbine 20 configured to be driven by steam from the heat recovery boiler 6. A generator 24 is connected to the turbine 20 via a rotating shaft 22, and the generator 24 is driven by the rotational energy of the turbine 20 to generate electricity. The steam that has completed its work in the turbine 20 is guided to a condenser 26, where it is condensed to become condensed water, which is then supplied to the heat recovery boiler 6.

[0019] (Configuration of Exhaust Gas Treatment Device) As shown in Fig. 2, the exhaust gas treatment device 102 includes a first Denitration catalyst 50 and one or more catalyst units 52 (catalyst units 52A to 52C in Fig. 2) provided downstream of the first Denitration catalyst 50 in the exhaust gas flow. Each of the one or more catalyst units 52 includes an ammonia decomposition catalyst 54 and a second Denitration catalyst 56 provided downstream of the ammonia decomposition catalyst 54 in the exhaust gas flow. The exhaust gas treatment device 102 shown in Fig. 2 also includes a reducing agent supply unit 40.

[0020] The reducing agent supply unit 40 reduces nitrogen oxides (NOx; NO and NO) contained in the combustion exhaust gas from the combustion device 100. ２ The combustion exhaust gas flowing through the flow path 32 is configured to supply a reducing agent for reducing nitrogen oxides (e.g., nitrogen oxides) to the combustion exhaust gas flowing through the flow path 32. By supplying the reducing agent to the combustion exhaust gas containing nitrogen oxides, the nitrogen oxides in the combustion exhaust gas can be reduced, thereby reducing the amount of nitrogen oxides contained in the combustion exhaust gas. The reaction between the nitrogen oxides and the reducing agent decomposes the nitrogen oxides in the combustion exhaust gas into nitrogen and water, thereby reducing the amount of nitrogen oxides in the combustion exhaust gas.

[0021] The reducing agent supply unit 40 may be provided upstream of the first denitration catalyst 50 in the flow path 32 for the combustion exhaust gas of the fuel. As shown in Fig. 2, the reducing agent supply unit 40 may include a nozzle 42 configured to spray a liquid or gas containing a reducing agent into the flow path 32. The liquid or gas containing a reducing agent stored in a reducing agent storage unit 44 may be supplied to the nozzle 42 via a supply line 46. The supply line 46 may be provided with a valve 48 for adjusting the amount of reducing agent supplied via the reducing agent supply unit 40.

[0022] The reducing agent supplied from the reducing agent supply unit 40 is a substance that has the effect of reducing nitrogen oxides, and may include, for example, ammonia or urea. The reducing agent may be supplied to the combustion exhaust gas in the form of an aqueous solution (e.g., ammonia water or urea water).

[0023] The first denitration catalyst 50 may be provided downstream of the reducing agent supply unit 40 in the flow path 32. The first denitration catalyst 50 is configured to promote a reduction reaction between nitrogen oxides in the combustion exhaust gas and a reducing agent containing ammonia (including ammonia originally contained in the fuel and / or a reducing agent supplied by the reducing agent supply unit 40). The first denitration catalyst 50 may contain a metal or a metal compound containing, for example, titanium, vanadium, tungsten, or molybdenum.

[0024] The ammonia decomposition catalyst 54 has a function of promoting the decomposition reaction of ammonia in the combustion exhaust gas. When the exhaust gas flowing through the flow path 32 comes into contact with the ammonia decomposition catalyst 54, the ammonia contained in the exhaust gas (i.e., unreacted ammonia that has not been consumed by the first DeNOx catalyst 50) is decomposed. The ammonia decomposition catalyst 54 may contain a metal or a metal compound including platinum, copper, iron, cobalt, palladium, iridium, nickel, or ruthenium.

[0025] The second Denitration catalyst 56, which constitutes the catalytic unit 52 together with the ammonia decomposition catalyst 54, is provided in the flow path 32 downstream of the corresponding ammonia decomposition catalyst 54. The second Denitration catalyst 56 is configured to promote a reduction reaction between nitrogen oxides in the combustion exhaust gas and a reducing agent containing ammonia (including ammonia originally contained in the fuel and / or a reducing agent supplied by the reducing agent supply unit 40). The second Denitration catalyst 56 may contain a metal or metal compound containing, for example, titanium, vanadium, tungsten, or molybdenum.

[0026] The number of catalyst units 52 constituting the exhaust gas treatment device 102 is not particularly limited as long as it is one or more.

[0027] In some embodiments, exhaust gas treatment device 102 may include multiple (i.e., two or more) catalytic units 52. In the exemplary embodiment shown in Figure 2, exhaust gas treatment device 102 includes three sets of catalytic units 52.

[0028] 2, the exhaust gas treatment device 102 may include a first ammonia concentration measurement unit 72 for measuring the ammonia concentration at the outlet of the first denitration catalyst 50 in the combustion exhaust gas flow path 32. The exhaust gas treatment device 102 also measures the ammonia concentration, the concentration of nitrogen oxides (NOx) and / or the concentration of nitrous oxide (N) at the outlet of one or more catalyst units 52 in the combustion exhaust gas flow path 32 (i.e., at the outlet of the exhaust gas treatment device 102). ２ a second ammonia concentration measuring unit 74, a NOx concentration measuring unit 76, and / or a N ２ The exhaust gas supply system may also include an O concentration measuring unit 78. The outlets of the one or more catalytic units 52 are located downstream of the catalytic unit 52 located most downstream among the one or more catalytic units 52 (catalytic unit 52C in FIG. 2).

[0029] The nitrogen oxide concentration in the combustion exhaust gas can be measured using, for example, a chemiluminescence NOx meter (JIS B 7982), a non-dispersive infrared absorption method (NDIR method), or a zinc-reduced naphthylethylenediamine absorptiometry method (Zn-NEDA method) in accordance with JIS K 0104. The NOx concentration measurement unit 76 may be configured to measure the NOx concentration using any of these methods.

[0030] Here, the reactions occurring in the first denitration catalyst 50 and one or more catalyst units 52 (the ammonia decomposition catalyst 54 and the second denitration catalyst 56), and the decomposition of nitrogen oxides (NOx), ammonia (NH ３ ) and nitrous oxide (N ２ In the following description, FSCR refers to the first Denitration catalyst 50, and AmD_i and RSCR_i refer to the ammonia decomposition catalyst 54 and the second Denitration catalyst 56 that constitute the i-th catalyst unit 52 from the upstream side.

[0031] In the first denitration catalyst 50 and the second denitration catalyst 56 of the catalyst unit 52, nitrogen oxides are reduced by ammonia to produce nitrogen and water mainly through the reaction of the following formula (A): 4NO + 4NH ３ +O ２ → 4N ２ +6H ２ O...(A)

[0032] Therefore, in the first denitration catalyst 50 (FSCR) and the second denitration catalyst 56 (RSCR_i), NOx and NH ３ is consumed, reducing these concentrations.

[0033] In the ammonia decomposition catalyst 54, ammonia is oxidatively decomposed to produce nitrogen and water mainly through the reaction of the following formula (B): ３ +30 ２ → 2N ２ +6H ２ O ... (B) In addition, in the ammonia decomposition catalyst 54, ammonia is oxidized and decomposed into nitrogen monoxide (NO), dinitrogen monoxide (N ２ O) is produced as a by-product. ３ +5O ２ → 4NO+6H ２ O... (C) 2NH ３ +20 ２ → N ２ O+3H ２ O... (D)

[0034] Therefore, in the ammonia decomposition catalyst 54 (AmD_i), NH ３ is consumed and NH ３ The concentration of NOx and N ２ The concentration of O increases.

[0035] NOx and NH in the exhaust gas discharged from the exhaust gas treatment device 102 ３ and N ２ Although there are cases where limit values ​​such as management values ​​and regulation values ​​are set for the concentration of O, NOx, NH ３ and N ２The final concentration of O varies depending on the composition of the exhaust gas introduced into the exhaust gas treatment device 102 and the combination of catalysts in the exhaust gas treatment device 102. ２ There is a possibility that the amount of O etc. produced will increase. ２ While suppressing the by-production and increase in concentration of O, NOx and NH ３ It is necessary to devise ways to reduce emissions (concentration).

[0036] In this regard, in the exhaust gas treatment device 102 according to some embodiments, the concentration of nitrous oxide (C Ｎ２Ｏ＿ＳＹＳ ) (i.e., N ２ N at the measurement position of the O concentration measurement unit 78 ２ O concentration) at the outlet of the first denitration catalyst 50 ＮＨ３＿ＦＳＣＲ ) (i.e., NH ３ concentration) ratio (C ＮＨ３＿ＦＳＣＲ / C Ｎ２Ｏ＿ＳＹＳ ) is 10.0 or more.

[0037] Here, FIG. 3 shows the concentration of nitrous oxide (C ) at the outlet of one or more catalytic units 52 (the outlet of the exhaust gas treatment device 102) when combustion exhaust gas is treated by the exhaust gas treatment device 102 according to one embodiment (including three catalytic units 52). Ｎ２Ｏ＿ＳＹＳ ) and the above ratio (C ＮＨ３＿ＦＳＣＲ / C Ｎ２Ｏ＿ＳＹＳ 3 is a graph showing the relationship (test results) between the catalyst type and catalyst length, or test conditions such as the reaction temperature at the catalyst and the contact time between the exhaust gas and the catalyst, are included among the plots in the graph of FIG.

[0038] As a result of intensive research by the present inventors, when an exhaust gas treatment device 102 including the first denitration catalyst 50 and one or more catalyst units 52 (a combination of an ammonia decomposition catalyst 54 and a second denitration catalyst 56) is used, as shown in the graph of FIG. 3, ＮＨ３＿ＦＳＣＲ / C Ｎ２Ｏ＿ＳＹＳBy setting the ratio of NOx to a value equal to or greater than 10.0, the concentration of nitrogen oxides (NOx) and the concentration of ammonia at the outlet of the exhaust gas treatment device 102 can be set to respective predetermined limit values ​​(for example, 10 ppmvdc and 5 ppmvdc, respectively) or less, and the concentration of dinitrogen monoxide (N ２ Therefore, according to the above-described embodiment, it is possible to suppress the concentration of dinitrogen monoxide (N ２ The amount of nitrogen oxides (NOx) and ammonia (NH ３ ) can be reduced.

[0039] According to the exhaust gas treatment device 102 of the above embodiment, even when the nitrogen oxide concentration in the exhaust gas introduced into the exhaust gas treatment device 102 is relatively high (for example, 500 ppm or more), the concentration of nitrogen oxides (NOx) and the concentration of ammonia at the outlet of the exhaust gas treatment device 102 can be reduced to or below predetermined limit values ​​(for example, 10 [ppmvdc] and 5 [ppmvdc], respectively). ２ The concentration of nitrogen oxides (NO) can be suppressed to a low value (for example, 10 ppmvdc or less). An example of exhaust gas with a relatively high concentration of nitrogen oxides is combustion exhaust gas of a fuel containing ammonia.

[0040] In some embodiments, the above ratio (C ＮＨ３＿ＦＳＣＲ / C Ｎ２Ｏ＿ＳＹＳ ) is 100.0 or less.

[0041] According to the above embodiment, the above ratio (C ＮＨ３＿ＦＳＣＲ / C Ｎ２Ｏ＿ＳＹＳ ) is set to 100.0 or less, the ammonia concentration in the exhaust gas before it is introduced into one or more catalyst units 52 including the ammonia decomposition catalyst 54 is relatively low. ２ O) can be easily kept low.

[0042] In some embodiments, the ammonia concentration (C ＮＨ３＿ＦＳＣＲ) is 150 ppmvdc or less.

[0043] Here, FIG. 4 shows the concentration of nitrous oxide (C ) at the outlet of one or more catalytic units 52 (the outlet of the exhaust gas treatment device 102) when combustion exhaust gas is treated by the exhaust gas treatment device 102 according to one embodiment (including three catalytic units 52). Ｎ２Ｏ＿ＳＹＳ ) and the ammonia concentration (C ＮＨ３＿ＦＳＣＲ 4. Note that the plots in the graph of FIG. 4 include plots in which the type or length of the catalyst, or test conditions such as the reaction temperature at the catalyst and the contact time between the exhaust gas and the catalyst are different.

[0044] From the graph of FIG. 4, when the combustion exhaust gas is treated by the exhaust gas treatment device 102 according to one embodiment, the ammonia concentration (C ＮＨ３＿ＦＳＣＲ ) is 150 ppmvdc or less, the amount of dinitrogen monoxide (N ２ According to the above-described embodiment, the ammonia concentration (C ＮＨ３＿ＦＳＣＲ ) was set to 150 ppmvdc or less, so that the dinitrogen monoxide (N ２ O) can be effectively reduced.

[0045] In some embodiments, as shown in FIG. 2 , for example, the exhaust gas treatment device 102 includes the above-described reducing agent supply unit 40 and a reducing agent supply amount adjustment unit 58 configured to adjust the amount of reducing agent supplied from the reducing agent supply unit 40 based on the nitrogen oxide concentration or the ammonia concentration at the outlet of the first denitration catalyst 50 and the nitrous oxide concentration at the outlet of one or more catalyst units 52.

[0046] The reducing agent supply amount adjusting unit 58 is configured to measure the NOx concentration by the NOx concentration measuring unit 76 or the second ammonia concentration measuring unit 74 and the N ２ The nitrogen oxide concentration or ammonia (NH ３ ) concentration and nitrous oxide (N ２The control device 60 may be configured to adjust the amount of reducing agent (ammonia, etc.) supplied by the reducing agent supply unit 40 based on the measurement result of the NOx concentration. ２ A signal indicating the measurement result by the O concentration measurement unit 78 may be sent to the control device 60.

[0047] The control device 60 includes a computer equipped with a processor (such as a CPU or a GPU), a storage device (such as a memory device such as a RAM), an auxiliary storage device, an interface, etc. The processor is connected to the NOx concentration measurement unit 76 or the second ammonia concentration measurement unit 74 and the N ２ The processor is configured to process signals received from the NOx concentration measurement unit 76 or the second ammonia concentration measurement unit 74 and the N ２ An opening command value to be given to the valve 48 may be calculated based on the concentration measurement value by the O concentration measurement unit 78. The control device 60 may be configured to give the calculated opening command value to an actuator that changes the opening of the valve 48. In this manner, the amount of reducing agent supplied from the reducing agent supply unit 40 may be adjusted by the control device 60.

[0048] According to the above-described embodiment, the nitrogen oxide concentration or the ammonia concentration (C ＮＨ３＿ＦＳＣＲ ) and the concentration of nitrous oxide (C Ｎ２Ｏ＿ＳＹＳ ) based on the ratio of the above concentrations (C ＮＨ３＿ＦＳＣＲ / C Ｎ２Ｏ＿ＳＹＳ Therefore, according to the above-described embodiment, it is easy to adjust the amount of nitrous oxide (N ２ This facilitates reducing nitrogen oxides and ammonia in exhaust gases while effectively suppressing the amount of generated nitrogen oxides and ammonia.

[0049] FIG. 5 is a schematic diagram showing the arrangement of catalysts (first denitration catalyst 50 and one or more catalyst units 52 (ammonia decomposition catalyst 54 and second denitration catalyst 56)) included in the exhaust gas treatment device 102 shown in FIG. 2. In the drawing, LＦＳＣＲ indicates the length of the first denitration catalyst 50 in the flow direction of the exhaust gas in the exhaust gas treatment device 102, and L ＡｍＤ＿ｉ and L ＲＳＣＲ＿ｉ indicate the lengths of the ammonia decomposition catalyst 54 and the second denitration catalyst 56 of the i-th catalyst unit 52 from the upstream side, respectively.

[0050] In some embodiments, in the exhaust gas treatment device 102, the length of the first denitration catalyst 50 in the direction of exhaust gas flow is expressed as follows: ＦＳＣＲ and the length L of each ammonia decomposition catalyst ＡｍＤ The ratio (L ＦＳＣＲ / L ＡｍＤ ) is y[-], the structure is configured to satisfy the relational expression expressed as y≧0.003x.

[0051] The concentration of nitrogen oxides in the exhaust gas introduced into the exhaust gas treatment device 102 is the concentration of nitrogen oxides in the exhaust gas discharged from the combustion device 100. The concentration of nitrogen oxides can be measured in the exhaust gas path between the combustion device 100 and the exhaust gas treatment device 102, for example, at the outlet of the combustion device 100 or the inlet of the exhaust gas treatment device 102 (for example, the inlet of the duct 30 shown in FIG. 2 ).

[0052] Here, FIG. 6 shows the concentration of nitrous oxide (C ) at the outlet of one or more catalytic units 52 (the outlet of the exhaust gas treatment device 102) when combustion exhaust gas is treated by the exhaust gas treatment device 102 according to one embodiment (including three catalytic units 52). Ｎ２Ｏ＿ＳＹＳ ) and the length (L ＦＳＣＲ ) and the length (L ＡｍＤ ) and the ratio (L ＦＳＣＲ / L ＡｍＤ ) (calculated values). The lengths of the three ammonia decomposition catalysts 54 included in the three catalyst units 52 in this exhaust gas treatment device 102 are all L ＡｍＤ6 include plots based on different calculation conditions, such as the concentration of nitrogen oxides in the exhaust gas introduced into the exhaust gas treatment device 102.

[0053] 7 shows the relationship between the concentration of nitrogen oxides in the exhaust gas introduced into the exhaust gas treatment device 102 (hereinafter referred to as the inlet NOx concentration of the exhaust gas treatment device 102; horizontal axis) and the length L of the first denitration catalyst in the direction of the exhaust gas flow. ＦＳＣＲ and the length L of each ammonia decomposition catalyst ＡｍＤ The ratio (L ＦＳＣＲ / L ＡｍＤ 7 is an example of a graph showing the relationship between the concentration of nitrous oxide (C) at the outlet of the exhaust gas treatment device 102 and the inlet NOx concentration. Ｎ２Ｏ＿ＳＹＳ ) is the minimum catalyst length ratio at which the NOx concentration at the inlet is equal to or less than the specified value (10 ppm). The line L1 in the graph of FIG. 7 is an approximation line of these plots, and is the minimum catalyst length ratio (L ＦＳＣＲ / L ＡｍＤ ) is expressed as y[-], the relation is y=0.003x.

[0054] That is, from the graphs of FIGS. 6 and 7, when the relationship of y≧0.003x is satisfied, the concentration of nitrous oxide (C Ｎ２Ｏ＿ＳＹＳ ) becomes equal to or less than the specified value (10 ppm), and the nitrogen monoxide (N ２ This is because when the inlet NOx concentration is low (for example, 100 ppmvdc), the length L of the first denitration catalyst 50 is ＦＳＣＲ and the length L of each ammonia decomposition catalyst 54 ＡｍＤ The ratio (L ＦＳＣＲ / L ＡｍＤ ) is close to 1, but when the inlet NOx concentration is high (for example, 2000 ppmvdc), the length L ＦＳＣＲ and the length L of each ammonia decomposition catalyst 54 ＡｍＤ The ratio (L ＦＳＣＲ / L ＡｍＤ) becomes larger, and it is considered that when the relationship y≧0.003x is satisfied, it becomes easier to keep the ratio of the ammonia concentration to the nitrogen oxide concentration at the outlet of the first-stage ammonia decomposition catalyst 54 (AmD_1) (i.e., the inlet of the first-stage second denitration catalyst 56 (RSCR_1)) within an appropriate range (for example, 0.6 or more and 2.0 or less).

[0055] According to the above-described embodiment, in an exhaust gas treatment device 102 including a first denitration catalyst 50 and one or more catalyst units 52 (a combination of an ammonia decomposition catalyst 54 and a second denitration catalyst 56), the length of the first denitration catalyst 50 in the direction of the exhaust gas flow is determined by the ratio of the concentration x [ppmvdc] of nitrogen oxides in the exhaust gas introduced into the exhaust gas treatment device 102 to the length L of the first denitration catalyst 50 in the direction of the exhaust gas flow. ＦＳＣＲ and the length L of each ammonia decomposition catalyst 54 ＡｍＤ Since the ratio y[-] of the ammonia concentration to the nitrogen oxide concentration at the outlet of the first-stage ammonia decomposition catalyst 54 (AmD_1) (i.e., the inlet of the first-stage second denitration catalyst 56 (RSCR_1)) is easily kept within an appropriate range (for example, 0.6 to 2.0). ２ It is possible to reduce nitrogen oxides and ammonia in exhaust gases while effectively suppressing the amount of generated nitrogen oxides and ammonia.

[0056] The contents described in each of the above embodiments can be understood, for example, as follows.

[0057] [1] An exhaust gas treatment device (102) according to at least one embodiment of the present invention is an exhaust gas treatment device for treating exhaust gas generated by burning fuel, comprising: a first denitration catalyst (50) for reducing nitrogen oxides in the exhaust gas; and one or more catalyst units (52) each including an ammonia decomposition catalyst (54) disposed downstream of the first denitration catalyst in the exhaust gas flow for decomposing ammonia in the exhaust gas, and a second denitration catalyst (56) disposed downstream of the ammonia decomposition catalyst in the exhaust gas flow for reducing nitrogen oxides in the exhaust gas, wherein a concentration of nitrous oxide (CＮ２Ｏ＿ＳＹＳ ) the ammonia concentration (C ＮＨ３＿ＦＳＣＲ ) ratio (C ＮＨ３＿ＦＳＣＲ / C Ｎ２Ｏ＿ＳＹＳ ) is 10.0 or more.

[0058] As a result of intensive research by the present inventors, when an exhaust gas treatment device including a first denitration catalyst and one or more catalyst units (a combination of an ammonia denitration catalyst and a second denitration catalyst) is used, the concentration of dinitrogen monoxide (C Ｎ２Ｏ＿ＳＹＳ ) the ammonia concentration (C ＮＨ３＿ＦＳＣＲ ) ratio (C ＮＨ３＿ＦＳＣＲ / C Ｎ２Ｏ＿ＳＹＳ ) is 10.0 or more, the concentration of nitrogen oxides (NOx) and the concentration of ammonia at the outlet of the exhaust gas treatment device can be made equal to or less than the respective predetermined limit values, and the concentration of dinitrogen monoxide (N ２ Therefore, according to the configuration [1], it is possible to reduce the amount of nitrogen oxides and ammonia in the exhaust gas while effectively suppressing the amount of dinitrogen monoxide produced.

[0059] [2] In some embodiments, in the configuration of the above [1], the ratio (C ＮＨ３＿ＦＳＣＲ / C Ｎ２Ｏ＿ＳＹＳ ) is 100.0 or less.

[0060] According to the configuration [2] above, the above ratio (C ＮＨ３＿ＦＳＣＲ / C Ｎ２Ｏ＿ＳＹＳ ) is set to 100.0 or less, the ammonia concentration in the exhaust gas before it is introduced into one or more catalyst units containing an ammonia decomposition catalyst is relatively low, which makes it easier to keep the nitrous oxide concentration at the outlet of the exhaust gas treatment device low.

[0061] [3] In some embodiments, in the configuration of the above [1] or [2], the ammonia concentration (C ＮＨ３＿ＦＳＣＲ ) is 150 ppmvdc or less.

[0062] According to the above configuration [3], the ammonia concentration (CＮＨ３＿ＦＳＣＲ ) was set to 150 ppmvdc or less, so the nitrogen monoxide (N ２ O) can be effectively reduced.

[0063] [4] In some embodiments, in the configuration of any one of [1] to [3] above, the exhaust gas treatment device includes: a reducing agent supply unit (40) for supplying a reducing agent capable of reducing nitrogen oxides to the exhaust gas; and a reducing agent supply amount adjustment unit (58) configured to adjust the amount of the reducing agent supplied from the reducing agent supply unit based on the ammonia concentration at an outlet of the first denitration catalyst and the nitrous oxide concentration at an outlet of the one or more catalyst units.

[0064] According to the configuration [4] above, the ammonia concentration (C ＮＨ３＿ＦＳＣＲ ) and the concentration of nitrous oxide (C) at the outlet of one or more catalytic units (i.e., the outlet of the exhaust gas treatment device). Ｎ２Ｏ＿ＳＹＳ ) based on the ratio of the above concentrations (C ＮＨ３＿ＦＳＣＲ / C Ｎ２Ｏ＿ＳＹＳ Therefore, according to the above-mentioned configuration [4], it is easy to reduce nitrogen oxides and ammonia in the exhaust gas while effectively suppressing the amount of dinitrogen monoxide produced.

[0065] [5] An exhaust gas treatment device (102) according to at least one embodiment of the present invention is an exhaust gas treatment device for treating exhaust gas generated by burning fuel, comprising: a first denitration catalyst (50) for reducing nitrogen oxides in the exhaust gas; and one or more catalyst units (52) each including an ammonia decomposition catalyst (54) disposed downstream of the first denitration catalyst in an exhaust gas flow for decomposing ammonia in the exhaust gas, and a second denitration catalyst (56) disposed downstream of the ammonia decomposition catalyst in the exhaust gas flow for reducing nitrogen oxides in the exhaust gas, wherein the length of the first denitration catalyst in the direction of the exhaust gas flow is expressed as a length L of the first denitration catalyst in the direction of the exhaust gas flow, where x [ppmvdc] is a concentration of nitrogen oxides in the exhaust gas introduced into the exhaust gas treatment device. ＦＳＣＲand the length L of each of the ammonia decomposition catalysts ＡｍＤ The ratio (L ＦＳＣＲ / L ＡｍＤ ) is y[-], the structure satisfies the relational expression y≧0.003x.

[0066] According to the configuration [5] above, in an exhaust gas treatment device including a first denitration catalyst and one or more catalyst units (a combination of an ammonia decomposition catalyst and a second denitration catalyst), the length of the first denitration catalyst in the direction of exhaust gas flow is determined by the ratio of the concentration x [ppmvdc] of nitrogen oxides in the exhaust gas introduced into the exhaust gas treatment device to the length L of the first denitration catalyst in the direction of exhaust gas flow. ＦＳＣＲ and the length L of each ammonia decomposition catalyst ＡｍＤ Since the ratio y[-] of the ammonia concentration to the nitrogen oxide concentration at the outlet of the first-stage ammonia decomposition catalyst (i.e., the inlet of the first-stage second Denitration catalyst) is configured to satisfy the relational expression expressed as y≧0.003x, it is easy to keep the ratio of the ammonia concentration to the nitrogen oxide concentration at the outlet of the first-stage ammonia decomposition catalyst (i.e., the inlet of the first-stage second Denitration catalyst) within an appropriate range. Therefore, according to the configuration [5] above, it is possible to reduce nitrogen oxides and ammonia in the exhaust gas while effectively suppressing the amount of dinitrogen monoxide produced.

[0067] [6] An exhaust gas treatment method according to at least one embodiment of the present invention is a method for treating exhaust gas generated by burning fuel, the method comprising: treating the exhaust gas using an exhaust gas treatment device comprising: a first denitration catalyst (50) for reducing nitrogen oxides in the exhaust gas; and one or more catalyst units (52) each including an ammonia decomposition catalyst (54) disposed downstream of the first denitration catalyst in the exhaust gas flow for decomposing ammonia in the exhaust gas, and a second denitration catalyst (56) disposed downstream of the ammonia decomposition catalyst in the exhaust gas flow for reducing nitrogen oxides in the exhaust gas, wherein the step of treating the exhaust gas using an exhaust gas treatment device comprises measuring a concentration of nitrous oxide (C Ｎ２Ｏ＿ＳＹＳ ) the ammonia concentration (C ＮＨ３＿ＦＳＣＲ ) ratio (C ＮＨ３＿ＦＳＣＲ / C Ｎ２Ｏ＿ＳＹＳ The exhaust gas is treated so that the value of the saturation energy (saturation energy) is 10.0 or more.

[0068] As a result of intensive research by the present inventors, when an exhaust gas treatment device including a first denitration catalyst and one or more catalyst units (a combination of an ammonia denitration catalyst and a second denitration catalyst) is used, the concentration of dinitrogen monoxide (C Ｎ２Ｏ＿ＳＹＳ ) the ammonia concentration (C ＮＨ３＿ＦＳＣＲ ) ratio (C ＮＨ３＿ＦＳＣＲ / C Ｎ２Ｏ＿ＳＹＳ ) is 10.0 or more, the concentration of nitrogen oxides (NOx) and the concentration of ammonia at the outlet of the exhaust gas treatment device can be made equal to or less than the respective predetermined limit values, and the concentration of dinitrogen monoxide (N ２ Therefore, according to the method of [6] above, it is possible to reduce the amount of nitrogen oxides and ammonia in the exhaust gas while effectively suppressing the amount of dinitrogen monoxide produced.

[0069] [7] An exhaust gas treatment method according to at least one embodiment of the present invention is an exhaust gas treatment method for treating exhaust gas generated by burning fuel, the method comprising: treating the exhaust gas using an exhaust gas treatment device comprising: a first Denitration catalyst (50) for reducing nitrogen oxides in the exhaust gas; and one or more catalyst units (52) each including an ammonia decomposition catalyst (54) disposed downstream of the first Denitration catalyst in the exhaust gas flow for decomposing ammonia in the exhaust gas, and a second Denitration catalyst (56) disposed downstream of the ammonia decomposition catalyst in the exhaust gas flow for reducing nitrogen oxides in the exhaust gas, wherein in the step, a concentration of nitrogen oxides in the exhaust gas introduced into the exhaust gas treatment device is defined as x [ppmvdc], and a length L of the first Denitration catalyst in the direction of the exhaust gas flow is defined as ＦＳＣＲ and the length L of each of the ammonia decomposition catalysts ＡｍＤ The ratio (L ＦＳＣＲ / L ＡｍＤ When y[-] is used, the exhaust gas is treated at least using the first denitration catalyst that satisfies the relational expression y≧0.003x.

[0070] According to the method [7] above, in an exhaust gas treatment device including a first denitration catalyst and one or more catalyst units (a combination of an ammonia decomposition catalyst and a second denitration catalyst), the concentration x [ppmvdc] of nitrogen oxides in the exhaust gas introduced into the exhaust gas treatment device and the length L of the first denitration catalyst in the direction of exhaust gas flow are ＦＳＣＲ and the length L of each ammonia decomposition catalyst ＡｍＤ Since the first denitration catalyst is used in which the ratio y[-] of the ammonia concentration to the nitrogen oxide concentration at the outlet of the first-stage ammonia decomposition catalyst (i.e., the inlet of the first-stage second denitration catalyst) satisfies the relational expression y≧0.003x, it is easy to keep the ratio of the ammonia concentration to the nitrogen oxide concentration at the outlet of the first-stage ammonia decomposition catalyst (i.e., the inlet of the first-stage second denitration catalyst) within an appropriate range. Therefore, according to the configuration [5] above, it is possible to reduce nitrogen oxides and ammonia in the exhaust gas while effectively suppressing the amount of dinitrogen monoxide produced.

[0071] The above describes an embodiment of the present invention, but the present invention is not limited to the above-described embodiment, and also includes forms in which the above-described embodiment is modified, or forms in which these forms are appropriately combined.

[0072] In this specification, expressions expressing relative or absolute arrangements, such as "in a certain direction," "along a certain direction," "parallel," "orthogonal," "center," "concentric," or "coaxial," not only strictly express such arrangements, but also express a state in which there is a relative displacement with a tolerance or an angle or distance to the extent that the same function is obtained. For example, expressions expressing that things are in an equal state, such as "identical," "equal," and "homogeneous," not only express a state in which there is a strict equivalence, but also express a state in which there is a tolerance or a difference to the extent that the same function is obtained. Furthermore, in this specification, expressions expressing shapes such as a rectangular shape or a cylindrical shape not only express shapes such as a rectangular shape or a cylindrical shape in the strict geometric sense, but also express shapes including concave and convex portions, chamfered portions, etc., to the extent that the same effect is obtained. Furthermore, in this specification, the expressions "comprise," "include," or "have" a component are not exclusive expressions that exclude the presence of other components.

[0073] REFERENCE SIGNS LIST 1 Combustion equipment 2 Gas turbine equipment 4 Steam turbine equipment 6 Heat recovery boiler 10 Compressor 12 Combustor 14 Turbine 16 Rotating shaft 18 Generator 20 Turbine 22 Rotating shaft 24 Generator 26 Condenser 30 Duct 32 Flow path 34 Heat transfer tube 38 Chimney 40 Reducing agent supply section 42 Nozzle 44 Reducing agent storage section 46 Supply line 48 Valve 50 First denitration catalyst 52 Catalytic unit 52A Catalytic unit 52B Catalytic unit 52C Catalytic unit 54 Ammonia decomposition catalyst 56 Second denitration catalyst 58 Reducing agent supply amount adjustment section 60 Control device 72 First ammonia concentration measurement section 74 Second ammonia concentration measurement section 76 NOx concentration measurement section 78 N ２ O concentration measuring unit 100 Combustion device 102 Exhaust gas treatment device

Claims

1. An exhaust gas treatment device for treating exhaust gas generated by burning fuel, comprising: a first denitration catalyst for reducing nitrogen oxides in the exhaust gas; and one or more catalyst units each including an ammonia decomposition catalyst disposed downstream of the first denitration catalyst in the exhaust gas flow for decomposing ammonia in the exhaust gas; and a second denitration catalyst disposed downstream of the ammonia decomposition catalyst in the exhaust gas flow for reducing nitrogen oxides in the exhaust gas; wherein a concentration of nitrous oxide (C Ｎ２Ｏ＿ＳＹＳ ) to the ammonia concentration (C ＮＨ３＿ＦＳＣＲ ) ratio (C ＮＨ３＿ＦＳＣＲ / C Ｎ２Ｏ＿ＳＹＳ ) is 10.0 or more.

2. The above ratio (C ＮＨ３＿ＦＳＣＲ / C Ｎ２Ｏ＿ＳＹＳ 2. The exhaust gas treatment device according to claim 1, wherein the value of the stoichiometric ratio is 100.0 or less.

3. The ammonia concentration (C ＮＨ３＿ＦＳＣＲ 3. The exhaust gas treatment device according to claim 1 or 2, wherein the concentration of 150 ppmvdc or less is 150 ppmvdc or less.

4. An exhaust gas treatment device as described in claim 1 or 2, comprising: a reducing agent supply unit for supplying a reducing agent capable of reducing nitrogen oxides to the exhaust gas; and a reducing agent supply amount adjustment unit configured to adjust the amount of the reducing agent supplied from the reducing agent supply unit based on the nitrogen oxide concentration or ammonia concentration at the outlet of the first denitrification catalyst and the nitrous oxide concentration at the outlet of the one or more catalyst units.

5. An exhaust gas treatment device for treating exhaust gas generated by burning fuel, comprising: a first denitration catalyst for reducing nitrogen oxides in the exhaust gas; and one or more catalyst units each including an ammonia decomposition catalyst disposed downstream of the first denitration catalyst in the exhaust gas flow for decomposing ammonia in the exhaust gas, and a second denitration catalyst disposed downstream of the ammonia decomposition catalyst in the exhaust gas flow for reducing nitrogen oxides in the exhaust gas, wherein the length of the first denitration catalyst in the direction of the exhaust gas flow is expressed as x [ppmvdc], and the length L of the first denitration catalyst in the direction of the exhaust gas flow is expressed as ＦＳＣＲ and the length L of each of the ammonia decomposition catalysts ＡｍＤ Ratio to (L ＦＳＣＲ / L ＡｍＤ ) is y[-], the exhaust gas treatment device is configured to satisfy a relational expression expressed as y≧0.003x.

6. An exhaust gas treatment method for treating exhaust gas generated by burning fuel, comprising a step of treating the exhaust gas using an exhaust gas treatment device including: a first denitration catalyst for reducing nitrogen oxides in the exhaust gas; and one or more catalyst units each including an ammonia decomposition catalyst disposed downstream of the first denitration catalyst in the exhaust gas flow for decomposing ammonia in the exhaust gas, and a second denitration catalyst disposed downstream of the ammonia decomposition catalyst in the exhaust gas flow for reducing nitrogen oxides in the exhaust gas, wherein the step includes measuring a concentration of nitrous oxide (C Ｎ２Ｏ＿ＳＹＳ ) to the ammonia concentration (C ＮＨ３＿ＦＳＣＲ ) ratio (C ＮＨ３＿ＦＳＣＲ / C Ｎ２Ｏ＿ＳＹＳ The exhaust gas is treated so that the ratio of the total amount of the exhaust gas to the total amount of the exhaust gas is 10.0 or more.

7. An exhaust gas treatment method for treating exhaust gas generated by burning fuel, comprising: a step of treating the exhaust gas using an exhaust gas treatment device comprising: a first denitration catalyst for reducing nitrogen oxides in the exhaust gas; and one or more catalyst units each including an ammonia decomposition catalyst disposed downstream of the first denitration catalyst in the exhaust gas flow for decomposing ammonia in the exhaust gas, and a second denitration catalyst disposed downstream of the ammonia decomposition catalyst in the exhaust gas flow for reducing nitrogen oxides in the exhaust gas, wherein in the step, a concentration of nitrogen oxides in the exhaust gas introduced into the exhaust gas treatment device is defined as x [ppmvdc], and a length L of the first denitration catalyst in the direction of the exhaust gas flow is defined as ＦＳＣＲ and the length L of each of the ammonia decomposition catalysts ＡｍＤ Ratio to (L ＦＳＣＲ / L ＡｍＤ ) is y[-], the exhaust gas is treated by using at least the first Denitration catalyst which satisfies a relational expression expressed by y≧0.003x.

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