Exhaust gas processing device, and method for designing exhaust gas processing device

Abstract

Provided is an exhaust gas processing device (100) for processing an exhaust gas discharged from a combustion device (200) that combusts a fuel containing ammonia, the exhaust gas processing device (100) comprising: an ammonia decomposition part (10) having an ammonia decomposition catalyst with which ammonia contained in the exhaust gas is decomposed; and a nitrogen oxide decomposition part (20) having a second catalyst with which nitrous oxide and NOx contained in the exhaust gas in which ammonia has been decomposed by the ammonia decomposition part (10) are decomposed.

Description

Exhaust gas treatment device and design method for the same

[0001] The present disclosure relates to an exhaust gas treatment device and a method for designing an exhaust gas treatment device.

[0002] In recent years, there has been a demand for carbon neutrality to curb global warming, and the application of ammonia fuel as a fuel that does not emit carbon dioxide when burned is being considered. When ammonia fuel is used, not only NOx but also ammonia (NH ３ ) and nitrous oxide (N ２ O), etc., so it is necessary to remove these from the exhaust gas to reduce their impact on the environment.

[0003] BACKGROUND ART Conventionally, there has been known an ammonia treatment apparatus that decomposes ammonia into nitrogen and water by oxidizing the ammonia using an ammonia decomposition catalyst (see, for example, Patent Document 1).

[0004] Japanese Patent Application Laid-Open No. 2006-26529

[0005] However, although Patent Document 1 can decompose ammonia, it cannot decompose nitrous oxide when nitrous oxide is contained in the gas to be treated, for example.

[0006] Furthermore, selective catalytic reduction (SCR) has been known in the past to decompose NOx contained in exhaust gases emitted from combustion equipment, in which a reducing agent such as ammonia or urea water is sprayed into the exhaust gas to reduce the NOx. However, while selective catalytic reduction can decompose NOx, it cannot decompose nitrous oxide.

[0007] The present disclosure has been made in consideration of the above circumstances, and aims to provide an exhaust gas treatment device and a design method for an exhaust gas treatment device that are capable of appropriately decomposing ammonia, nitrous oxide, and NOx contained in exhaust gas emitted from a combustion device that burns fuel containing ammonia.

[0008] In order to solve the above problems, the present disclosure employs the following means: An exhaust gas treatment device according to the present disclosure is an exhaust gas treatment device that treats exhaust gas emitted from a combustion device that combusts fuel containing ammonia, and includes a first treatment device having a first catalyst that decomposes the ammonia contained in the exhaust gas, and a second treatment device having a second catalyst that decomposes nitrous oxide and NOx contained in the exhaust gas after the ammonia has been decomposed in the first treatment device.

[0009] A design method for an exhaust gas treatment device according to the present disclosure is a design method for an exhaust gas treatment device that treats exhaust gas discharged from a combustion device that combusts a fuel containing ammonia, wherein, when the concentration of ammonia contained in the exhaust gas is higher than the sum of a first concentration obtained by multiplying the concentration of nitrous oxide contained in the exhaust gas by a first coefficient and a second concentration obtained by multiplying the concentration of NOx contained in the exhaust gas by a second coefficient, the exhaust gas treatment device is designed so that a first treatment device having a first catalyst that decomposes the ammonia contained in the exhaust gas is arranged downstream of the combustion device, and a second treatment device having a second catalyst that decomposes the nitrous oxide and NOx contained in the exhaust gas after ammonia has been decomposed in the first treatment device is arranged downstream of the first treatment device, and when the concentration of ammonia contained in the exhaust gas is equal to or lower than the sum of the first concentration, the exhaust gas treatment device is designed so that the first treatment device is not arranged downstream of the combustion device, but the second treatment device is arranged

[0010] According to the present disclosure, it is possible to provide an exhaust gas treatment device and a method for designing an exhaust gas treatment device that can appropriately decompose ammonia, nitrous oxide, and NOx contained in exhaust gas emitted from a combustion device that burns fuel containing ammonia.

[0011] FIG. 1 is a schematic configuration diagram showing an exhaust gas treatment device according to a first embodiment of the present disclosure. FIG. 2 is a graph showing the decomposition characteristics of an ammonia decomposition catalyst. FIG. 3 is a graph showing the relationship between ammonia concentration and temperature rise in an ammonia decomposition catalyst. FIG. 4 is a graph showing the decomposition characteristics of nitrous oxide versus exhaust gas temperature. FIG. 5 is a graph showing the decomposition characteristics of NO versus exhaust gas temperature. FIG. 6 is a flowchart showing a supply process of a reducing agent in an exhaust gas treatment device according to a first embodiment of the present disclosure. FIG. 7 is a flowchart showing a switching process of a bypass valve in an exhaust gas treatment device according to a first embodiment of the present disclosure. FIG. 8 is a schematic configuration diagram showing an exhaust gas treatment device according to a second embodiment of the present disclosure. FIG. 9 is a flowchart showing a switching process of a bypass valve in an exhaust gas treatment device according to a second embodiment of the present disclosure. FIG. 10 is a flowchart showing a design method of an exhaust gas treatment device according to a fourth embodiment of the present disclosure. FIG. 11 is a schematic configuration diagram showing an exhaust gas treatment device according to a fifth embodiment of the present disclosure. FIG. 12 is a graph showing the decomposition rate of nitrous oxide versus exhaust gas temperature in a nitrogen oxide decomposition unit, comparing the cases where the NO concentration is 0 ppm and 450 ppm. FIG. 13 is a flowchart showing a supply process of fuel and a reducing agent in an exhaust gas treatment device according to a fifth embodiment of the present disclosure. 10 is a flowchart showing a fuel and reducing agent supply process in an exhaust gas treatment device according to a fifth embodiment of the present disclosure. 11 is a schematic configuration diagram showing an exhaust gas treatment device according to a modified example of the fifth embodiment of the present disclosure.

[0012] First Embodiment An exhaust gas treatment device 100 according to a first embodiment of the present disclosure will be described below with reference to the drawings. The exhaust gas treatment device 100 of this embodiment is a device that treats exhaust gas discharged from a combustion device 200 that combusts fuel containing ammonia, and reduces the amounts of ammonia, nitrous oxide, and NOx discharged to the outside.

[0013] The combustion device 200 is a device that burns fuel containing ammonia, and is, for example, a marine diesel engine that generates propulsive power for a ship. The combustion device 200 of this embodiment, for example, mixes ammonia with other fuels (heavy oil, LNG (liquefied natural gas), LPG (liquefied petroleum gas)). Furthermore, the combustion device 200 may be, for example, a device that uses only ammonia as fuel.

[0014] Since the combustion device 200 uses ammonia as fuel, the exhaust gas discharged from the combustion device 200 contains unburned ammonia. The exhaust gas discharged from the combustion device 200 also contains NOx (NO, NOx) generated by the combustion of ammonia and other fuels. ２ ) and nitrous oxide (N ２ The exhaust gas treatment device 100 of this embodiment reduces the ammonia, NOx, and nitrous oxide contained in the exhaust gas discharged from the combustion device 200.

[0015] Fig. 1 is a schematic diagram showing the configuration of an exhaust gas treatment device according to a first embodiment of the present disclosure. As shown in Fig. 1, an exhaust gas treatment device 100 of this embodiment includes an ammonia decomposition unit (first treatment unit) 10, a nitrogen oxide decomposition unit (second treatment unit) 20, an ammonia decomposition unit (third treatment unit) 30, a detection unit 40, a first supply unit 50 that supplies ammonia or urea water as a reducing agent, a temperature sensor 60, a bypass valve 70, and a control unit 80.

[0016] Exhaust gas discharged from the combustion device 200 is supplied to the ammonia decomposition unit 10 via pipe L1. The exhaust gas that has passed through the ammonia decomposition unit 10 is supplied to the nitrogen oxide decomposition unit 20 via pipe L2. The exhaust gas that has passed through the nitrogen oxide decomposition unit 20 is supplied to the ammonia decomposition unit 30 via pipe L3. The exhaust gas that has passed through the ammonia decomposition unit 30 is discharged to the outside via pipe L4. When the bypass valve 70 is open, part of the exhaust gas that has passed through the nitrogen oxide decomposition unit 20 is guided from pipe L3 to pipe L4 via pipe L5 without passing through the ammonia decomposition unit 30.

[0017] Although the exhaust gas treatment device 100 of this embodiment is provided with the pipe L5 and the bypass valve 70, a modified example may be adopted in which these are not provided. In this modified example, the entire amount of exhaust gas that has passed through the nitrogen oxide decomposition unit 20 is led to the ammonia decomposition unit 30.

[0018] The ammonia decomposition unit 10 has an ammonia decomposition catalyst (first catalyst) that decomposes ammonia contained in exhaust gas discharged from the combustion device 200. The ammonia decomposition catalyst is a multi-functional catalyst that not only decomposes ammonia but also decomposes NOx and suppresses the production of nitrous oxide. The ammonia decomposition catalyst of this embodiment is a catalyst comprising a first component that is silica and / or zeolite supporting one or more noble metals selected from platinum (Pt), palladium (Pd), iridium (Ir), and rhodium (Rh), and a second component that is a composition comprising an oxide of one or more elements selected from titanium (Ti), tungsten (W), and vanadium (V). Examples of the ammonia decomposition catalyst will be described later.

[0019] The ammonia decomposition catalyst of the ammonia decomposition unit 10 converts NH ３ Decompose 4NH ３ +30 ２ →2N ２ +6H ２ O (1) 4NH ３ +5O ２ → 4NO + 6H ２ O (2)

[0020] The ammonia decomposition catalyst of the ammonia decomposition unit 10 converts the second component into NH ３ and removes at least a portion of the NO by-produced in formula (2). ３ +4NO+O ２ →4N ２ +6H ２ O (3)

[0021] In addition, in the ammonia decomposition catalyst of the ammonia decomposition unit 10, NH ３ is oxidized according to formula (4) to produce NO２ From the formula (5), nitrous oxide (N ２ In the ammonia decomposition catalyst, a small amount of noble metal catalyst is uniformly present on the denitration catalyst, so NO generated on the noble metal catalyst is ２ reacts immediately with the NO produced in equation (2) on the denitration catalyst as shown in equation (6) to produce N ２ This is highly likely to occur, which can reduce the by-production of NO. ３ +7O ２ →4NO ２ +6H ２ O (4) 4NH ３ +4NO ２ +O ２ →4N ２ O+6H ２ O (5) NO+NO ２ +2NH ３ →2N ２ +3H ２ O (6)

[0022] The nitrogen oxide decomposition section 20 has a nitrogen oxide decomposition catalyst (second catalyst) that decomposes nitrous oxide and NOx contained in the exhaust gas after ammonia has been decomposed in the ammonia decomposition section 10. The nitrogen oxide decomposition catalyst is a catalyst containing SiO ２ and Al ２ O ３ The carrier contains SiO ２ and Al ２ O ３ may be contained as a mixture or a composite. ２ O ３ Examples of composites of these include aluminosilicate (xM ２ O.yAl ２ O ３ zSiO ２ ・nH ２ Examples of nitrogen oxide decomposition catalysts will be described later.

[0023] The nitrogen oxide decomposition catalyst in the nitrogen oxide decomposition unit 20 converts nitrous oxide into NH３ It is decomposed by a reduction reaction with 3N ２ O + 2NH ３ →4N ２ +3H ２ O (7)

[0024] The nitrogen oxide decomposition catalyst in the nitrogen oxide decomposition unit 20 converts NOx into NH ３ It is decomposed by the reduction reaction: 4NO + 4NH ３ +O ２ →4N ２ +6H ２ O (8) NO+NO ２ +2NH ３ →2N ２ +3H ２ O (9) 6NO ２ +8NH ３ →7N ２ +12H ２ O (10)

[0025] The ammonia decomposition section 30 has an ammonia decomposition catalyst (third catalyst) that decomposes ammonia contained in the exhaust gas that has passed through the nitrogen oxide decomposition section 20. The ammonia decomposition catalyst is a multi-functional catalyst that not only decomposes ammonia but also decomposes NOx and suppresses the production of nitrous oxide. The ammonia decomposition catalyst is a catalyst comprising a first component that is silica and / or zeolite supporting one or more precious metals selected from platinum (Pt), palladium (Pd), iridium (Ir), and rhodium (Rh), and a second component that is a composition comprising an oxide of one or more elements selected from titanium (Ti), tungsten (W), and vanadium (V). The configuration of the ammonia decomposition section 30 is similar to that of the ammonia decomposition section 10, and therefore will not be described below.

[0026] The detection unit 40 is a device that detects the concentrations of nitrous oxide and NOx contained in the exhaust gas that has passed through the ammonia decomposition unit 10. The detection unit 40 detects the concentrations of nitrous oxide and NOx contained in the exhaust gas that passes through the pipe L3. The concentrations of nitrous oxide and NOx detected by the detection unit 40 are transmitted to the control unit 80.

[0027] The first supply unit 50 is a device that supplies ammonia or urea water as a reducing agent to the exhaust gas supplied from the ammonia decomposition unit 10 to the nitrogen oxide decomposition unit 20. The first supply unit 50 supplies the reducing agent to the pipe L2 via the pipe L6 and mixes it with the exhaust gas flowing through the pipe L2. The pipe L6 mixes the reducing agent with the exhaust gas, for example, by spraying the reducing agent into the pipe L2. The first supply unit 50 adjusts the amount of reducing agent supplied to the pipe L2 in response to a control signal transmitted from the control unit 80.

[0028] When urea water is supplied as a reducing agent, the urea water mixed with the exhaust gas in the pipe L2 is hydrolyzed in the exhaust gas to generate ammonia. Then, the nitrogen oxide decomposition catalyst of the nitrogen oxide decomposition unit 20 converts NOx into ammonia (NH ３ ) and decomposes it by reduction reaction.

[0029] The temperature sensor 60 is a device that detects the temperature of the exhaust gas flowing through the pipe L2. The temperature sensor 60 transmits the detected temperature of the exhaust gas to the control unit 80.

[0030] The bypass valve 70 is an on-off valve disposed in the pipe L5. The open / close state of the bypass valve 70 is controlled by the control unit 80. When the bypass valve 70 is in an open state, the exhaust gas is guided from the pipe L3 to the pipe L4 via the pipe L5. When the bypass valve 70 is in a closed state, the exhaust gas is not guided to the pipe L5, and the entire amount of the exhaust gas flowing through the pipe L3 is guided to the pipe L4 via the ammonia decomposition unit 30.

[0031] The control unit 80 is a device that controls each part of the exhaust gas treatment device 100. The control unit 80 controls each part of the exhaust gas treatment device 100 by reading and executing a control program stored in a storage unit (not shown).

[0032] The control unit 80 controls the amount of reducing agent supplied to the pipe L2 by the first supply unit 50 in accordance with the concentrations of nitrous oxide and NOx detected by the detection unit 40 and the temperature of the exhaust gas detected by the temperature sensor 60. The control unit 80 also controls the open / close state of the bypass valve 70 in accordance with the concentrations of nitrous oxide and NOx detected by the detection unit 40 and the temperature of the exhaust gas detected by the temperature sensor 60.

[0033] Next, the decomposition characteristics of the ammonia decomposition catalyst of the ammonia decomposition unit 10 of this embodiment will be described with reference to Figure 2. Figure 2 is a graph showing the decomposition characteristics of the ammonia decomposition catalyst. As shown in Figure 2, as the temperature of the exhaust gas containing ammonia increases from 350°C to 450°C, the ammonia decomposition rate [%] by the ammonia decomposition catalyst of the ammonia decomposition unit 10 increases.

[0034] Next, the relationship between the ammonia concentration and the temperature rise in the ammonia decomposition catalyst of the ammonia decomposition unit 10 of this embodiment will be described with reference to Fig. 3. Fig. 3 is a graph showing the relationship between the ammonia concentration and the temperature rise in the ammonia decomposition catalyst.

[0035] 3, the ammonia decomposition catalyst of the ammonia decomposition unit 10 generates heat when decomposing ammonia, and as the concentration of unburned ammonia contained in the exhaust gas discharged from the combustion device 200 increases, the temperature of the exhaust gas increases. By burning the unburned ammonia with the ammonia decomposition catalyst of the ammonia decomposition unit 10, the temperature of the ammonia decomposition unit 10 can be increased, and the ammonia decomposition rate can be increased. In addition, the temperature of the exhaust gas discharged from the ammonia decomposition unit 10 can be increased.

[0036] Next, the decomposition characteristics of nitrous oxide relative to the temperature of exhaust gas will be described with reference to Figure 4. Figure 4 is a graph showing the decomposition characteristics of nitrous oxide relative to the temperature of exhaust gas. Catalysts A to F shown in Figure 4 correspond to catalysts A to F described in the examples of nitrogen oxide decomposition catalysts described below. As shown in Figure 4, in all of catalysts A to F, the decomposition rate of nitrous oxide increases as the temperature of exhaust gas increases. Therefore, when the temperature of exhaust gas is increased by decomposing ammonia using the ammonia decomposition catalyst in the ammonia decomposition unit 10, the decomposition rate of nitrous oxide increases as the temperature of the exhaust gas increases.

[0037] Next, the decomposition characteristics of NO versus exhaust gas temperature will be described with reference to Figure 5. Figure 5 is a graph showing the decomposition characteristics of NO versus exhaust gas temperature. Catalysts A to F shown in Figure 5 correspond to catalysts A to F described in the examples of the nitrogen oxide decomposition catalyst described below. As shown in Figure 5, in all of catalysts A to F, the decomposition rate of NO increases as the exhaust gas temperature increases. Therefore, when the ammonia decomposition catalyst in the ammonia decomposition unit 10 decomposes ammonia to increase the exhaust gas temperature, the decomposition rate of NO increases as the exhaust gas temperature increases.

[0038] In this embodiment, the ammonia decomposition section 10 is provided upstream of the nitrogen oxide decomposition section 20 because it is assumed that the supply amount of unburned ammonia contained in the exhaust gas discharged from the combustion device 200 will exceed the amount of ammonia required to decompose nitrous oxide and NOx in the nitrogen oxide decomposition section 20. In the exhaust gas treatment device 100 of this embodiment, the ammonia decomposition section 10 decomposes excess ammonia, and the heat generated when the ammonia is decomposed increases the temperature of the exhaust gas, thereby increasing the decomposition rate of nitrous oxide and NOx in the nitrogen oxide decomposition section 20.

[0039] The exhaust gas treatment device 100 of this embodiment is assumed to have the concentrations of ammonia, nitrous oxide, and NOx contained in the exhaust gas discharged from the combustion device 200 satisfy the following formula (11): ammonia concentration>α×nitrous oxide concentration+β×NOx concentration (11)

[0040] Here, α and β are coefficients, and for example, α = 1.0 and β = 1.5. α = 1.0 is the value obtained by multiplying the molar ratio of ammonia to nitrous oxide in the reaction of equation (7) (ammonia / nitrous oxide = 2 / 3) by 1.5. β = 1.5 is the value obtained by multiplying the molar ratio of ammonia to NO in the reaction of equation (8) (ammonia / NO = 1 / 1) by 1.5. Note that the values ​​by which α and β are multiplied are not limited to 1.5, and may be set to any value between 1.2 and 2.0, for example, depending on the properties of the exhaust gas from the combustion device 200.

[0041] On the other hand, for example, if the amount of exhaust gas emitted from the exhaust gas treatment device 100 or the amount of ammonia contained in the exhaust gas is less than expected, all of the unburned ammonia will be decomposed in the ammonia decomposition unit 10, resulting in a shortage of ammonia required as a reducing agent in the nitrogen oxide decomposition unit 20. Therefore, in this embodiment, if there is a shortage of ammonia required as a reducing agent in the nitrogen oxide decomposition unit 20, the shortage of ammonia in the nitrogen oxide decomposition unit 20 is made up for by supplying a reducing agent from the first supply unit 50.

[0042] Next, a reducing agent supply process in the exhaust gas treatment device 100 of this embodiment will be described with reference to Fig. 6. Fig. 6 is a flowchart showing the reducing agent supply process in the exhaust gas treatment device 100 of this embodiment. The process of each step in Fig. 6 is executed by the control unit 80 controlling each part of the exhaust gas treatment device 100. The process of this flowchart is started in response to the start of combustion operation by the combustion device 200.

[0043] In step S101, the control unit 80 determines whether the temperature Ta of the exhaust gas flowing through the pipe L2, which is transmitted from the temperature sensor 60, is equal to or higher than the supply temperature (e.g., 350°C) at which the reducing agent can be supplied to the nitrogen oxide decomposition unit 20. If the determination is YES, the process proceeds to step S102. If the determination is NO, the process proceeds to step S108.

[0044] In step S108, the control unit 80 controls the first supply unit 50 to stop supplying the reducing agent because the temperature Ta of the exhaust gas flowing through the pipe L2 is lower than the supply temperature at which the reducing agent can be supplied to the nitrogen oxide decomposition unit 20.

[0045] In step S102, the control unit 80 determines whether the NOx concentration detected by the detection unit 40 is equal to or lower than a first predetermined concentration (e.g., 200 ppm), and if YES, proceeds to step S103, and if NO, proceeds to step S105.

[0046] In step S103, the control unit 80 determines whether the nitrous oxide concentration detected by the detection unit 40 is equal to or lower than a second predetermined concentration (e.g., 50 ppm), and if the answer is YES, the process proceeds to step S104, and if the answer is NO, the process proceeds to step S105.

[0047] In step S104, the control unit 80 determines that the reduction process of NOx and nitrous oxide by ammonia is being performed appropriately because the NOx concentration is equal to or less than the first predetermined concentration and the nitrous oxide concentration is equal to or less than the second predetermined concentration, and controls the first supply unit 50 to reduce the amount of reducing agent supplied.

[0048] In step S105, the control unit 80 determines that the reduction process of NOx and nitrous oxide by ammonia is not being performed sufficiently because the NOx concentration is higher than the first predetermined concentration or the nitrous oxide concentration is higher than the second predetermined concentration, and controls the first supply unit 50 to increase the amount of reducing agent supplied, and proceeds to step S101.

[0049] In step S106, the control unit 80 determines whether the combustion device 200 is stopped, and if the determination is YES, the process proceeds to step S107, but if the determination is NO, step S101 is executed again. The combustion device 200 transmits the operating state, including the state in which the combustion operation is stopped, to the control unit 80.

[0050] In step S107, the control unit 80 determines that the reduction process of NOx and nitrous oxide by ammonia is unnecessary because the combustion device 200 is stopped, stops the supply of reducing agent by the first supply unit 50, and ends the process of this flowchart. When the combustion device 200 starts combustion operation, the control unit 80 resumes the process of this flowchart.

[0051] Next, the switching process of the bypass valve 70 in the exhaust gas treatment device 100 of this embodiment will be described with reference to Fig. 7. Fig. 7 is a flowchart showing the switching process of the bypass valve 70 in the exhaust gas treatment device 100 of this embodiment. The process of each step in Fig. 7 is executed by the control unit 80 controlling each part of the exhaust gas treatment device 100. The process of this flowchart is started in response to the start of combustion operation by the combustion device 200.

[0052] In the exhaust gas treatment device 100 of this embodiment, an ammonia decomposition section 30 is arranged downstream of the nitrogen oxide decomposition section 20. The ammonia decomposition section 30 is provided to reliably decompose the excess ammonia and prevent it from being discharged to the outside when, for example, the ammonia concentration contained in the exhaust gas discharged from the combustion device 200 is higher than a predetermined concentration and the ammonia cannot be completely decomposed by the ammonia decomposition section 10 and the nitrogen oxide decomposition section 20.

[0053] On the other hand, when the concentration of ammonia contained in the exhaust gas discharged from the nitrogen oxide decomposition unit 20 is equal to or lower than a predetermined allowable concentration, there is no need to treat the exhaust gas in the ammonia decomposition unit 30, and a pressure loss occurs when the exhaust gas passes through the ammonia decomposition unit 30. Therefore, in this embodiment, when the concentration of ammonia contained in the exhaust gas discharged from the nitrogen oxide decomposition unit 20 is equal to or lower than a predetermined allowable concentration, a part of the exhaust gas discharged from the nitrogen oxide decomposition unit 20 is guided to the pipe L5, thereby preventing the occurrence of a pressure loss when the exhaust gas passes through the ammonia decomposition unit 30.

[0054] In step S201, the control unit 80 determines whether the temperature Ta of the exhaust gas flowing through the pipe L2, which is transmitted from the temperature sensor 60, is equal to or higher than the supply temperature (e.g., 350°C) at which the reducing agent can be supplied to the nitrogen oxide decomposition unit 20. If the determination is YES, the process proceeds to step S203. If the determination is NO, the process proceeds to step S202.

[0055] In step S202, the control unit 80 controls the bypass valve 70 to be in a closed state because the temperature Ta of the exhaust gas flowing through the pipe L2 is below the supply temperature at which the reducing agent can be supplied to the nitrogen oxide decomposition unit 20 and the temperature of the exhaust gas discharged from the combustion device 200 has not risen to an appropriate temperature.

[0056] In step S203, the control unit 80 determines whether the load of the combustion device 200 is equal to or less than a predetermined load (for example, 50% load). If the determination is YES, the process proceeds to step S204. If the determination is NO, the process returns to step S201. The combustion device 200 transmits the load of the combustion operation to the control unit 80.

[0057] In step S204, the control unit 80 controls the bypass valve 70 to be in an open state because the load on the combustion device 200 is equal to or less than a predetermined load. When the load on the combustion device 200 is equal to or less than the predetermined load, the concentration of ammonia contained in the exhaust gas discharged from the nitrogen oxide decomposition unit 20 is equal to or less than a predetermined allowable concentration (e.g., 5 ppm), and the exhaust gas does not need to be treated in the ammonia decomposition unit 30. Therefore, in order to reduce pressure loss that occurs when the exhaust gas passes through the ammonia decomposition unit 30, a portion of the exhaust gas flowing through the pipe L3 is guided from the pipe L5 to the pipe L4.

[0058] In step S205, the control unit 80 determines whether the combustion device 200 is stopped, and if the determination is YES, the process proceeds to step S206, but if the determination is NO, step S201 is executed again. The combustion device 200 transmits the operating state, including the state in which the combustion operation is stopped, to the control unit 80.

[0059] In step S206, the control unit 80 closes the bypass valve 70 because the combustion device 200 is stopped, and ends the processing of this flowchart. When the combustion device 200 starts combustion operation, the control unit 80 resumes the processing of this flowchart.

[0060] In the above description, the detection unit 40 detects the concentrations of nitrous oxide and NOx contained in the exhaust gas that has passed through the ammonia decomposition unit 10, but other embodiments are also possible. The detection unit 40 may detect the concentration of either nitrous oxide or NOx contained in the exhaust gas that has passed through the ammonia decomposition unit 10. When the detection unit 40 detects the concentration of nitrous oxide, the process of step S102 in Fig. 6 is omitted. When the detection unit 40 detects the concentration of NOx, the process of step S103 in Fig. 6 is omitted.

[0061] [Examples of Ammonia Decomposition Catalyst] The ammonia decomposition catalyst of the ammonia decomposition section 10 of this embodiment can be obtained, for example, by any of the following examples.

[0062] Example 1 1.33 × 10 -２ wt% chloroplatinic acid (H ２ [PtCl ６ 〕・6H ２ O) 100 g of fine silica powder (manufactured by Tomita Pharmaceutical Co., Ltd., silicic anhydride) was added to 1 liter of the aqueous solution, and the mixture was evaporated to dryness on a sand bath and baked in air at 500°C for 2 hours to obtain a 0.05 wt% Pt.SiO ２ was prepared to obtain a catalyst composition powder of the first component.

[0063] On the other hand, titanium oxide powder (manufactured by Ishihara Sangyo Kaisha, Ltd., trade name: MCH, SO ４ 46.7 kg of ammonium paratungstate ((NH ４ ) １０ ・W １２ O ４１ ・5H ２ 7.43 kg of ammonium metavanadate (W / V) and 3.0 kg of ammonium metavanadate were added and kneaded using a kneader. The resulting paste was granulated, dried, and calcined at 550°C for 2 hours. The resulting granules were pulverized to obtain a catalyst composition powder, which is the second component. The composition was Ti / W / V = 91 / 5 / 4 (atomic ratio).

[0064] A paper honeycomb carrier (manufactured by Nichias Corporation, product name: Honeycle 3722, 150 mm x 150 mm square, 50 mm long) was immersed in a slurry obtained by suspending 20 g of the first component and 2.02 kg of the second component in 3.06 kg of water to impregnate the carrier, and then the liquid was drained off with an air blower to obtain the catalyst of this example. This was air-dried in the atmosphere for 12 hours and then calcined at 500°C for 2 hours. The first component / second component ratio of this catalyst was 1 / 99 (weight ratio, the same applies hereinafter), the Pt content in the catalyst components was equivalent to 5 ppm, and the catalyst loading amount of the first and second components combined was 150 g / m per carrier surface area. ２ A test piece having 5 rows x 8 cells (11 x 14 mm) and a length of 50 mm was cut out from the obtained honeycomb catalyst.

[0065] Example 2 A catalyst of this example was obtained in the same manner as in Example 1, except that the amount of the first component was changed to 10 g, the amount of the second component to 2.02 kg, and the amount of water to 3.04 kg. The first component / second component ratio of the first component to the second component in this catalyst was 0.5 / 99.5, the Pt content in the catalyst component was equivalent to 2.5 ppm, and the amount of the catalyst supported, in total, of the first component and the second component per carrier surface area was 150 g / m ２ It was.

[0066] Example 3-5 The first and second components obtained in Example 1 were used, and the amount of water added during slurry preparation was changed to 476 and 816 kg. The resulting slurry was supported on a paper honeycomb carrier (manufactured by Nichias Corporation, product name: Honeycle 3319, 150 mm x 150 mm square, 50 mm long) in the same manner as in Example 1 to obtain the catalyst of this example. The first component / second component ratio of the first component to the second component in this catalyst was 1 / 99, and the Pt content in the catalyst component was equivalent to 5 ppm. The supported amounts of the catalyst in Example 3-5, in total, of the first component and the second component per carrier surface area were 100, 80, and 50 g / m, respectively. ２ It was.

[0067] Example 6 A catalyst of this example was obtained in the same manner as in Example 1, except that the paper honeycomb carrier of Example 1 was replaced with a metal lath (SUS304, plate thickness 0.2 mmt, 150 mm x 150 mm square). The first component / second component ratio of the first component to the second component in this catalyst was 1 / 99, and the Pt content in the catalyst component was equivalent to 5 ppm. The catalyst loading amount of the first component and the second component combined was 200 g / m per carrier surface area. ２ It was.

[0068] Example 7 The water for preparing the slurry in Example 1 was replaced with colloidal silica (manufactured by Nissan Chemical Industries, Ltd., trade name: OS Sol, SiO ２ The catalyst of this example was prepared in the same manner as above, except that the ratio of ethanol to water was changed to 3 / 7 (20%).

[0069] Example 8 20 g of the first component prepared in Example 1 was suspended in 1000 g of a liquid of colloidal silica / water = 3 / 7, and a paper honeycomb carrier was immersed in this suspension to impregnate the carrier with the slurry, and then the liquid was drained with an air blower, air-dried in the air for 12 hours, and then calcined for 2 hours at 500°C. The obtained catalyst was immersed in a slurry obtained by suspending 2.02 kg of the second component of Example 1 in 3.06 kg of water, and then the liquid was drained, air-dried, and calcined for 2 hours at 500°C to prepare the catalyst of this example.

[0070] [Examples of Nitrogen Oxide Decomposition Catalyst] The nitrogen oxide decomposition catalyst of the nitrogen oxide decomposition section 20 of this embodiment is, for example, any one of the following catalysts A to E.

[0071] Catalyst A (supporting step (ion exchange)) BEA type zeolite (SiO ２ / Al ２ O ３ Iron (III) nitrate nonahydrate (Fe) (ratio = 25) 60 g heated to 80 ° C. ２ (NO ２ ) ２ ・9H ２The resulting mixture was poured into 2000 ml of an aqueous solution containing 13.2 g of Fe-supported zeolite catalyst A, and then stirred for 3 hours while maintaining the temperature at 80°C to obtain a slurry. The slurry was dehydrated using a suction funnel equipped with filter paper (No. 5C). A predetermined amount of pure water was poured onto the cake on the filter paper and washed. The washed cake was dried at 110°C for 12 hours and calcined at 500°C for 5 hours. The calcined product was pulverized in a planetary ball mill to obtain a powdered Fe-supported zeolite catalyst A.

[0072] (Honeycomb coating process) The Fe-supported zeolite catalyst A was added to pure water and stirred to obtain a catalyst slurry. The catalyst slurry was applied to a honeycomb substrate at a coating amount of 70 g / m. This was dried at 120°C for 2 hours and then fired at 500°C for 2 hours to obtain a honeycomb catalyst A.

[0073] Catalyst B BEA type zeolite (SiO ２ / Al ２ O ３ ratio = 25) was added to BEA type zeolite (SiO ２ / Al ２ O ３ Powdered Fe-supported zeolite catalyst B and honeycomb catalyst B were obtained in the same manner as catalyst A, except that the Fe-supported zeolite catalyst B was replaced with a zeolite catalyst B (ratio = 28).

[0074] Catalyst C BEA type zeolite (SiO ２ / Al ２ O ３ ratio = 25) was added to BEA type zeolite (SiO ２ / Al ２ O ３ Powdered Fe-supported zeolite catalyst C and honeycomb catalyst C were obtained in the same manner as catalyst A, except that the Fe-supported zeolite catalyst C was changed to a catalyst having a ratio of 7.5.

[0075] Catalyst D CHA type zeolite (SiO ２ / Al ２ O ３ Iron (III) nitrate nonahydrate (Fe) (ratio = 24) 60 g heated to 80 ° C. ２ (NO ３ ) ３ ・9H ２The resulting mixture was poured into 2000 ml of an aqueous solution containing 13.2 g of ammonium nitrate (Isopropyl Alcohol), and then stirred for 3 hours while maintaining the temperature at 80°C to obtain a slurry. The slurry was filtered using a suction funnel equipped with filter paper (No. 5C). A predetermined amount of pure water was poured onto the cake on the filter paper to wash it. The washed cake was dried at 110°C for 12 hours and calcined at 500°C for 5 hours. The calcined product was pulverized in a planetary ball mill to obtain a powder.

[0076] This powder was treated with iron(III) nitrate nonahydrate (Fe ２ (NO ３ ) ３ ・9H ２ The resulting honeycomb catalyst was poured into 2000 ml of an aqueous solution containing 13.2 g of Fe-supported zeolite catalyst A, and the above procedure was repeated two more times (a total of three ion exchange steps) to obtain a powdered Fe-supported zeolite catalyst D. The honeycomb catalyst D was obtained by the same production method as for catalyst A, except that the Fe-supported zeolite catalyst A was replaced with the Fe-supported zeolite catalyst D.

[0077] Catalyst E BEA type zeolite (SiO ２ / Al ２ O ３ ratio = 25) was added to MFI type zeolite (SiO ２ / Al ２ O ３ Powdered Fe-supported zeolite catalyst E and honeycomb catalyst E were obtained in the same manner as catalyst A, except that the Fe-supported zeolite catalyst E was replaced with a zeolite catalyst E (ratio = 30).

[0078] Catalyst F BEA type zeolite (SiO ２ / Al ２ O ３ ratio = 25) was added to BEA type zeolite (SiO ２ / Al ２ O ３ Powdered Fe-supported zeolite catalyst F and honeycomb catalyst F were obtained in the same manner as catalyst A, except that the catalyst A was changed to a catalyst containing 24% Fe.

[0079] The following describes the actions and effects of the exhaust gas treatment device 100 of the present embodiment described above. According to the exhaust gas treatment device 100 of the present disclosure, ammonia contained in exhaust gas discharged from the combustion device 200 is appropriately decomposed by the ammonia decomposition catalyst when passing through the ammonia decomposition section 10. Furthermore, nitrous oxide and NOx generated when ammonia is combusted in the combustion device 200 are appropriately decomposed by the nitrogen oxide decomposition catalyst when passing through the nitrogen oxide decomposition section 20. In this way, according to the exhaust gas treatment device 100 of the present disclosure, ammonia and nitrous oxide contained in exhaust gas discharged from the combustion device 200 that burns fuel containing ammonia can be appropriately decomposed.

[0080] According to the exhaust gas treatment device 100 of this embodiment, even if ammonia remains in the exhaust gas that has passed through the nitrogen oxide decomposition unit 20, the ammonia can be decomposed in the ammonia decomposition unit 30, thereby preventing the ammonia from being discharged to the outside.

[0081] According to exhaust gas treatment device 100 of this embodiment, when detection unit 40 detects that the concentration of nitrous oxide contained in the exhaust gas that has passed through nitrogen oxide decomposition unit 20 is higher than the first predetermined concentration, or that the concentration of NOx contained in the exhaust gas that has passed through nitrogen oxide decomposition unit 20 is higher than the second predetermined concentration, a reducing agent is supplied from first supply unit 50 to the exhaust gas supplied to nitrogen oxide decomposition unit 20 in order to make up for the shortage of ammonia for reducing nitrous oxide and NOx. As a result, the shortage of ammonia supplied from ammonia decomposition unit 10 to nitrogen oxide decomposition unit 20 is made up, and the concentrations of nitrous oxide and NOx contained in the exhaust gas that has passed through nitrogen oxide decomposition unit 20 can be reduced.

[0082] Second Embodiment An exhaust gas treatment device 100A according to a second embodiment of the present disclosure will be described below with reference to the drawings. The exhaust gas treatment device 100A according to this embodiment is a modified example of the exhaust gas treatment device 100 according to the first embodiment, and is the same as the first embodiment except as otherwise specifically described below, and therefore further description thereof will be omitted.

[0083] The exhaust gas treatment device 100B of this embodiment differs from the exhaust gas treatment device 100 of the first embodiment in that it is equipped with a pipe (bypass pipe) L7 that directs a portion of the exhaust gas flowing through pipe L1 to pipe L2, and a bypass valve 90 that is arranged in pipe L7.

[0084] 8 is a schematic configuration diagram showing an exhaust gas treatment device 100A according to a second embodiment of the present disclosure. As shown in Fig. 8, the exhaust gas treatment device 100A of this embodiment includes a pipe L7 that guides a portion of the exhaust gas flowing through a pipe L1 to a pipe L2, and a bypass valve 90 disposed in the pipe L7.

[0085] The bypass valve 90 is an on-off valve disposed in the pipe L7. The open / close state of the bypass valve 90 is controlled by the control unit 80. When the bypass valve 90 is in an open state, the exhaust gas is guided from the pipe L1 to the pipe L2 via the pipe L7. When the bypass valve 90 is in a closed state, the exhaust gas is not guided to the pipe L7, and the entire amount of the exhaust gas flowing through the pipe L1 is guided to the pipe L2 via the ammonia decomposition unit 10.

[0086] In the exhaust gas treatment device 100A of this embodiment, when the supply amount of unburned ammonia contained in the exhaust gas discharged from the combustion device 200 exceeds the amount of ammonia required to decompose nitrous oxide and NOx in the nitrogen oxide decomposition section 20, the bypass valve 90 is closed and the entire amount of exhaust gas flowing through the pipe L1 is directed to the ammonia decomposition section 10, where the excess ammonia is decomposed.

[0087] On the other hand, in the exhaust gas treatment device 100A of this embodiment, when the supply amount of unburned ammonia contained in the exhaust gas discharged from the combustion device 200 is equal to or less than the amount of ammonia required to decompose nitrous oxide and NOx in the nitrogen oxide decomposition section 20, the bypass valve 90 is opened and a portion of the exhaust gas flowing through the pipe L1 is directed to the pipe L2 without passing through the ammonia decomposition section 10.

[0088] Next, the switching process of the bypass valve 90 of the exhaust gas treatment device 100A according to this embodiment will be described with reference to Fig. 9. Fig. 9 is a flowchart showing the switching process of the bypass valve 90 of the exhaust gas treatment device 100A according to this embodiment. The process of each step in Fig. 9 is executed by the control unit 80 controlling each part of the exhaust gas treatment device 100A. The process of this flowchart is started in response to the start of combustion operation by the combustion device 200.

[0089] In step S301, the control unit 80 determines whether the temperature Ta of the exhaust gas flowing through the pipe L2, which is transmitted from the temperature sensor 60, is equal to or higher than the supply temperature (e.g., 350°C) at which the reducing agent can be supplied to the nitrogen oxide decomposition unit 20. If the determination is YES, the process proceeds to step S302. If the determination is NO, the process proceeds to step S305.

[0090] In step S302, the control unit 80 calculates the concentrations of each of the components of ammonia, nitrous oxide, and NOx in the exhaust gas emitted from the combustion device 200 based on the load of the combustion device 200. The combustion device 200 transmits the load of the combustion operation to the control unit 80. The control unit 80 stores in a memory unit (not shown) a map of the concentrations of each of the components of ammonia, nitrous oxide, and NOx associated with each of the multiple loads of the combustion device 200. The control unit 80 calculates the concentrations associated with the load transmitted from the combustion device 200 by referring to the map stored in the memory unit.

[0091] In step S303, the control unit 80 determines whether the ammonia concentration calculated in step S302 is equal to or lower than a predetermined concentration. If the determination is YES, the process proceeds to step S304. If the determination is NO, the process proceeds to step S305. Here, the predetermined concentration is the concentration expressed by the following equation (12): α·nitrous oxide concentration+β·NOx concentration (12) Here, α and β are coefficients, and for example, α=1.0, which is the same as that described in equation (11) of the first embodiment.

[0092] In step S304, the control unit 80 opens the bypass valve 90 because the ammonia concentration is below the predetermined concentration and there is no need to supply the entire amount of exhaust gas to the ammonia decomposition unit 10 in order to decompose the excess ammonia in the ammonia decomposition unit 10.

[0093] In step S305, the control unit 80 closes the bypass valve 90 because the temperature Ta of the exhaust gas is below the supply temperature at which the reducing agent can be supplied to the nitrogen oxide decomposition unit 20, or the ammonia concentration is higher than a predetermined concentration. This is because the temperature of the exhaust gas discharged from the combustion device 200 is not sufficiently high, or the ammonia concentration contained in the exhaust gas is higher than a predetermined concentration, and therefore the entire amount of the exhaust gas needs to be supplied to the ammonia decomposition unit 10.

[0094] In step S306, the control unit 80 determines whether the combustion device 200 is stopped, and if the determination is YES, the process proceeds to step S307, but if the determination is NO, step S301 is executed again. The combustion device 200 transmits the operating state, including the state in which the combustion operation is stopped, to the control unit 80.

[0095] In step S307, the control unit 80 closes the bypass valve 90 because the combustion device 200 is stopped, and ends the processing of this flowchart. When the combustion device 200 starts combustion operation, the control unit 80 resumes the processing of this flowchart.

[0096] The following describes the functions and effects of the exhaust gas treatment device 100B of this embodiment described above. According to the exhaust gas treatment device 100A of this embodiment, when the concentration of ammonia contained in the exhaust gas discharged from the combustion device 200 is higher than the concentration required as a reducing agent when the nitrogen oxide decomposition unit 20 decomposes nitrous oxide and NOx, the bypass valve 90 can be closed to decompose the excess ammonia in the ammonia decomposition unit 10. Furthermore, when the concentration of ammonia contained in the exhaust gas discharged from the combustion device 200 is the same as or lower than the concentration required as a reducing agent when the nitrogen oxide decomposition unit 20 decomposes nitrous oxide and NOx, the bypass valve 90 can be opened to guide the ammonia to the nitrogen oxide decomposition unit 20 without decomposing the ammonia in the ammonia decomposition unit 10.

[0097] Third Embodiment An exhaust gas treatment device 100B according to a second embodiment of the present disclosure will now be described with reference to the drawings. The exhaust gas treatment device 100B according to this embodiment is a modified example of the exhaust gas treatment device 100 according to the first embodiment, and is the same as the first embodiment except where specifically described below, and therefore will not be described below.

[0098] In the exhaust gas treatment device 100 of the first embodiment, the ammonia decomposition section 10 is arranged upstream of the nitrogen oxide decomposition section 20. In contrast, in the exhaust gas treatment device 100B of the present embodiment, the ammonia decomposition section 10 is not arranged upstream of the nitrogen oxide decomposition section 20.

[0099] Fig. 10 is a schematic diagram showing an exhaust gas treatment device 100B according to a third embodiment of the present disclosure. As shown in Fig. 10, in the exhaust gas treatment device 100B of this embodiment, an ammonia decomposition unit 10 is not arranged upstream of the nitrogen oxide decomposition unit 20, and the exhaust gas discharged from the combustion device 200 is supplied to the nitrogen oxide decomposition unit 20 via a pipe L1.

[0100] In this embodiment, the ammonia decomposition unit 10 is not provided upstream of the nitrogen oxide decomposition unit 20 because it is assumed that the supply amount of unburned ammonia contained in the exhaust gas discharged from the combustion device 200 is equal to or less than the amount of ammonia required to decompose nitrous oxide and NOx in the nitrogen oxide decomposition unit 20. The exhaust gas treatment device 100B of this embodiment compensates for any shortage of ammonia required as a reducing agent for decomposing nitrous oxide and NOx contained in the exhaust gas by supplying it from the first supply unit 50.

[0101] The exhaust gas treatment device 100B of this embodiment is assumed to have the concentrations of ammonia, nitrous oxide, and NOx contained in the exhaust gas discharged from the combustion device 200 satisfy the following formula (13): ammonia concentration≦α·nitrous oxide concentration+β·NOx concentration (13) where α and β are coefficients, and are the same as those described in formula (11) of the first embodiment.

[0102] The reducing agent supply process in the exhaust gas treatment device 100B of this embodiment is similar to the process shown in Fig. 6 of the first embodiment. Moreover, the bypass valve 70 switching process in the exhaust gas treatment device 100A of this embodiment is similar to the process shown in Fig. 7 of the first embodiment.

[0103] The actions and effects achieved by the exhaust gas treatment device 100B of this embodiment described above will now be described. According to the exhaust gas treatment device 100B of this embodiment, ammonia contained in exhaust gas discharged from the combustion device 200 is decomposed by reacting with nitrous oxide and NOx as a reducing agent by the nitrogen oxide decomposition catalyst as it passes through the nitrogen oxide decomposition unit 20. Furthermore, nitrous oxide and NOx generated when ammonia is combusted in the combustion device 200 are appropriately decomposed by the nitrogen oxide decomposition catalyst as it passes through the nitrogen oxide decomposition unit 20. In this way, according to the exhaust gas treatment device 100B of this embodiment, ammonia, nitrous oxide, and NOx contained in exhaust gas discharged from the combustion device 200 that burns fuel containing ammonia can be appropriately decomposed.

[0104] [Fourth Embodiment] A design method for an exhaust gas treatment device according to a fourth embodiment of the present disclosure will now be described. The design method of this embodiment is a method for determining whether to design an exhaust gas treatment device in which the ammonia decomposition unit 10 is arranged upstream of the nitrogen oxide decomposition unit 20, as in the exhaust gas treatment devices 100 and 100A described in the first and second embodiments, or in which the ammonia decomposition unit 10 is not arranged upstream of the nitrogen oxide decomposition unit 20, as in the exhaust gas treatment device 100B described in the third embodiment.

[0105] 11 is a flowchart showing a method for designing an exhaust gas treatment device according to this embodiment. In step S401, the concentrations of each of the components, ammonia, nitrous oxide, and NOx, in the exhaust gas emitted from the combustion device 200 are calculated. The concentrations of each component are determined by assuming that the combustion device 200 operates at a predetermined constant load, and the concentrations of each of the components, ammonia, nitrous oxide, and NOx, in the exhaust gas at that load are specified.

[0106] In step S402, it is determined whether the ammonia concentration calculated in step S401 is equal to or lower than a predetermined concentration. If the result is YES, the process proceeds to step S403, and if the result is NO, the process proceeds to step S404. Here, the predetermined concentration is the concentration shown in equation (12) of the second embodiment, which is α·nitrous oxide concentration+β·NOx concentration.

[0107] In step S403, because the ammonia concentration in the exhaust gas discharged from the combustion device 200 is equal to or lower than the predetermined concentration, the exhaust gas treatment device 100B of the third embodiment is designed so that the ammonia decomposition unit 10 is not arranged upstream of the nitrogen oxide decomposition unit 20. The reason for this design is that there is no need to arrange the ammonia decomposition unit 10 upstream of the nitrogen oxide decomposition unit 20 to decompose excess ammonia.

[0108] In step S404, because the ammonia concentration in the exhaust gas discharged from the combustion device 200 is higher than a predetermined concentration, the exhaust gas treatment device 100 of the first embodiment or the exhaust gas treatment device 100A of the second embodiment is designed to place the ammonia decomposition unit 10 upstream of the nitrogen oxide decomposition unit 20. The reason for such a design is that, because the ammonia concentration contained in the exhaust gas is higher than a predetermined concentration, it is necessary to supply the entire amount of the exhaust gas to the ammonia decomposition unit 10 to decompose the excess ammonia.

[0109] According to the design method for an exhaust gas treatment device of this embodiment, when the concentration of ammonia contained in the exhaust gas is higher than the sum of a first concentration obtained by multiplying the concentration of nitrous oxide contained in the exhaust gas by α (first coefficient) and a second concentration obtained by multiplying the concentration of NOx contained in the exhaust gas by β (second coefficient), the exhaust gas treatment device is designed so that the ammonia decomposition unit 10 is located downstream of the combustion device 200 and the nitrogen oxide decomposition unit 20 is located downstream of the ammonia decomposition unit 10 in order to prevent the concentration of ammonia supplied from the ammonia decomposition unit 10 to the nitrogen oxide decomposition unit 20 from becoming excessive.

[0110] On the other hand, when the concentration of ammonia contained in the exhaust gas is equal to or less than the sum of a first concentration obtained by multiplying the concentration of nitrous oxide contained in the exhaust gas by α (first coefficient) and a second concentration obtained by multiplying the concentration of NOx contained in the exhaust gas by β (second coefficient), the concentration of ammonia supplied from the ammonia decomposition unit 10 to the nitrogen oxide decomposition unit 20 does not become excessive, so the exhaust gas treatment device is designed so that the nitrogen oxide decomposition unit 20 is located downstream of the combustion device 200 without the ammonia decomposition unit 10. This makes it possible to design an exhaust gas treatment device with an appropriate configuration according to the concentration of ammonia contained in the exhaust gas discharged from the combustion device 200.

[0111] Fifth Embodiment Next, an exhaust gas treatment device 100C according to a fifth embodiment of the present disclosure will be described with reference to the drawings. The exhaust gas treatment device 100C according to this embodiment is a modified example of the exhaust gas treatment device 100 according to the first embodiment, and is the same as the first embodiment except where specifically described below, and therefore further description thereof will be omitted.

[0112] The exhaust gas treatment device 100C of this embodiment differs from the exhaust gas treatment device 100 of the first embodiment in that it includes a second supply unit 55 that supplies ammonia or urea water as fuel for heating the ammonia decomposition catalyst (first treatment unit) of the ammonia decomposition unit 10 to the exhaust gas supplied from the combustion device 200 to the ammonia decomposition unit 10. The exhaust gas treatment device 100C of this embodiment also differs from the exhaust gas treatment device 100 of the first embodiment in that it does not include an ammonia decomposition unit 30.

[0113] Fig. 12 is a schematic configuration diagram showing an exhaust gas treatment device 100C according to this embodiment. As shown in Fig. 12, the exhaust gas treatment device 100C according to this embodiment includes an ammonia decomposition section (first treatment section) 10, a nitrogen oxide decomposition section (second treatment section) 20, a detection section 40, a first supply section 50, a second supply section 55, a temperature sensor 60, and a control section 80. The configuration other than the second supply section 55 is the same as that of the first embodiment, and therefore will not be described below.

[0114] The second supply unit 55 is a device that supplies ammonia or urea water as fuel for heating the ammonia decomposition catalyst to the exhaust gas supplied from the combustion device 200 to the ammonia decomposition unit 10 when the temperature detected by the temperature sensor 60 is equal to or lower than a predetermined temperature. The second supply unit 55 supplies urea water to the pipe L1 via the pipe L8, and generates ammonia by a hydrolysis reaction of the urea water.

[0115] The ammonia introduced into the ammonia decomposition unit 10 is decomposed by the action of the ammonia decomposition catalyst according to the reactions of formulas (1) and (2) in the first embodiment. The exothermic reaction occurring when the ammonia is decomposed heats the exhaust gas passing through the ammonia decomposition unit 10. Furthermore, instead of supplying urea water from the second supply unit 55, ammonia may be supplied from the second supply unit 55 to the pipe L2.

[0116] The inventors conducted experiments to confirm the relationship between the properties of the exhaust gas emitted from the combustion device 200 and the decomposition rate of nitrous oxide, and discovered that there is a temperature range in which the decomposition rate of nitrous oxide changes depending on the concentration of NO contained in the exhaust gas. If the decomposition rate of nitrous oxide changes depending on the concentration of NO contained in the exhaust gas, it may be impossible to obtain the desired decomposition rate of nitrous oxide in the exhaust gas treatment device 100 of the first embodiment. Therefore, the exhaust gas treatment device 100C of the present embodiment is configured to operate the nitrogen oxide decomposition unit 20 within a temperature range in which the decomposition rate of nitrous oxide does not change depending on the concentration of NO contained in the exhaust gas.

[0117] Fig. 13 is a graph showing the decomposition rate of nitrous oxide versus exhaust gas temperature in the nitrogen oxide decomposition unit 20, comparing cases where the NO concentration is 0 ppm and 450 ppm. Fig. 13 shows an example in which catalyst A was used as the nitrogen oxide decomposition catalyst in the nitrogen oxide decomposition unit 20. The example shown by the solid line and the example shown by the dotted line in Fig. 13 differ in that the NO concentration in the exhaust gas is 450 ppm and 0 ppm, respectively. On the other hand, the example shown by the solid line and the example shown by the dotted line in Fig. 13 are common in that the nitrous oxide concentration in the exhaust gas is 180 ppm, the ammonia concentration in the exhaust gas is 570 ppm, the oxygen concentration in the exhaust gas is 13%, the sulfur dioxide concentration in the exhaust gas is 15 ppm, the moisture concentration in the exhaust gas is 15%, and the remainder is nitrogen.

[0118] As shown in Figure 13, when the exhaust gas temperature is around 450°C, there is almost no difference in the decomposition rate of nitrous oxide even when the NO concentration in the exhaust gas is 450 ppm or 0 ppm. On the other hand, as the exhaust gas temperature falls below 450°C, the difference in the decomposition rate of nitrous oxide increases. Specifically, at the same exhaust gas temperature, the decomposition rate of nitrous oxide when the NO concentration in the exhaust gas is 0 ppm is lower than the decomposition rate when the NO concentration in the exhaust gas is 450 ppm.

[0119] The reason why Figure 13 shows the above tendency is presumably because, in the temperature range below 450°C, oxygen bound to the nitrogen oxide decomposition catalyst in the following formula (11) is removed by oxygen bound in the formula (12) and / or nitrous oxide is reduced in the reaction of formula (13). In other words, it is presumed that the decomposition rate of nitrous oxide is higher when NO exists together with nitrous oxide in the exhaust gas. ２ O → 2N ２ +30 ２ (11) 4NO+4NH ３ +O ２ →4N ２ +6H ２ O (12) N ２ O + NO → N ２ +NO ２ (13)

[0120] 13, the inventors set the temperature range so that the temperature of the exhaust gas discharged from ammonia decomposition unit 10 would be 450°C or higher, so that the decomposition rate of nitrous oxide would not change depending on the concentration of NO contained in the exhaust gas. Furthermore, the inventors set the temperature range so that the temperature of the exhaust gas discharged from ammonia decomposition unit 10 would be 530°C or lower, in order to reduce thermal stress on the catalytic reactor and suppress thermal deterioration of the catalyst.

[0121] Next, the fuel and reducing agent supply process in the exhaust gas treatment device 100C according to this embodiment will be described with reference to Figures 14 to 16. Figures 14 to 16 are flowcharts showing the fuel and reducing agent supply process in the exhaust gas treatment device 100C according to this embodiment. The process of each step in Figures 14 to 16 is executed by the control unit 80 controlling each part of the exhaust gas treatment device 100C. The process of this flowchart is started in response to the start of combustion operation by the combustion device 200.

[0122] In step S401, the control unit 80 determines whether the temperature Ta of the exhaust gas flowing through the pipe L2, which is transmitted from the temperature sensor 60, is equal to or higher than a fuel supply temperature (e.g., 300°C) at which fuel for heating the ammonia decomposition catalyst (first processing unit) can be supplied from the second supply unit 55 to the ammonia decomposition unit 10; if the determination is YES, the process proceeds to step S402; if the determination is NO, the process proceeds to step S403.

[0123] In step S402, the control unit 80 controls the second supply unit 55 to increase the amount of fuel supplied to the pipe L1 from the second supply unit 55. When step S402 is executed for the first time after step S401, the control unit 80 increases the amount of fuel supplied by the second supply unit 55 from 0 to a predetermined supply amount.

[0124] In step S403, the control unit 80 controls the second supply unit 55 to stop supplying fuel because the temperature Ta of the exhaust gas flowing through the pipe L1 is lower than the fuel supply temperature at which fuel can be supplied to the ammonia decomposition unit 10.

[0125] In step S404, the control unit 80 determines whether the temperature Ta of the exhaust gas is equal to or higher than the reducing agent supply temperature (e.g., 450°C) at which the reducing agent can be supplied to the nitrogen oxide decomposition unit 20. If the determination is YES, the process proceeds to step S405. If the determination is NO, the process proceeds to step S402, where the amount of fuel supplied from the second supply unit 55 is increased.

[0126] In step S405, the control unit 80 controls the first supply unit 50 to increase the amount of reducing agent supplied to the pipe L2 from the first supply unit 50. When step S405 is executed for the first time after step S404, the amount of reducing agent supplied by the first supply unit 50 is increased from 0 to a predetermined supply amount.

[0127] In step S406, the control unit 80 determines whether the NOx concentration detected by the detection unit 40 is equal to or lower than a first predetermined concentration (e.g., 200 ppm), and if YES, proceeds to step S407, and if NO, proceeds to step S414.

[0128] In step S407, the control unit 80 determines whether the nitrous oxide concentration detected by the detection unit 40 is equal to or lower than a second predetermined concentration (e.g., 10 ppm), and if the answer is YES, the process proceeds to step S408, and if the answer is NO, the process proceeds to step S414.

[0129] In step S408, the control unit 80 controls the combustion device 200 to release the load limit on the combustion device 200. Until the load limit is released in this step, the control unit 80 controls the combustion device 200 to maintain a predetermined load or less. This is because, when the combustion device 200 is operated without a load limit, if the amount of reducing agent supplied from the first supply unit 50 to the nitrogen oxide decomposition unit 20 to reduce the NOx concentration and nitrous oxide concentration becomes excessive, there is a possibility that unreacted ammonia will be discharged from the nitrogen oxide decomposition unit 20 to the outside via the pipe L3.

[0130] By controlling the combustion device 200 to maintain a predetermined load or less until the load restriction is released in this step, it is possible to prevent unreacted ammonia from being discharged from the nitrogen oxide decomposition section 20 to the outside via the pipe L3, and to reduce the NOx concentration and nitrous oxide concentration to below the threshold value, thereby reducing the environmental load.

[0131] In step S409, the control unit 80 determines whether the temperature Ta is equal to or lower than a first upper limit temperature (for example, 480° C.), and if YES, proceeds to step S410, and if NO, proceeds to step S411.

[0132] In step S410, the control unit 80 reduces the amount of fuel supplied from the second supply unit 55 to the pipe L1 so that the temperature Ta falls below the first upper limit temperature. After executing step S410, the control unit 80 proceeds to step S404.

[0133] In step S411, the control unit 80 determines that the temperature Ta is lower than the first upper limit temperature, and therefore decreases the amount of reducing agent supplied from the first supply unit 50 to the pipe L2, and proceeds to step S412.

[0134] In step S412, the control unit 80 determines whether the combustion device 200 is stopped, and if the determination is YES, the process proceeds to step S413, but if the determination is NO, step S404 is executed again. The combustion device 200 transmits the operating state, including the state in which the combustion operation is stopped, to the control unit 80.

[0135] In step S413, since the combustion device 200 is stopped, the control unit 80 stops the supply of reducing agent by the first supply unit 50 and the supply of fuel by the second supply unit 55, and ends the processing of this flowchart. When the combustion device 200 starts the combustion operation, the control unit 80 resumes the processing of this flowchart.

[0136] In step S414, the control unit 80 calculates the amount of reducing agent required to reduce NOx and nitrous oxide based on the NOx concentration and nitrous oxide concentration calculated in step S302 of Fig. 9, and determines whether the amount of reducing agent being supplied is greater than the amount obtained by multiplying the required amount of reducing agent by a predetermined coefficient γ. If the answer is YES, the process proceeds to step S415, and if the answer is NO, the process proceeds to step S405. Here, the predetermined amount of reducing agent supplied is the amount of reducing agent required to reduce NOx and nitrous oxide contained in the total nitrogen oxide concentration multiplied by a predetermined coefficient γ. The coefficient γ is set to a value, for example, greater than or equal to 0.8 and less than or equal to 1.2.

[0137] In step S415, the control unit 80 determines whether the temperature Ta is equal to or lower than a second upper limit temperature (for example, 530° C.), and if YES, proceeds to step S416, and if NO, proceeds to step S417.

[0138] In step S416, the control unit 80 increases the amount of fuel supplied to the pipe L1 from the second supply unit 55. After executing step S416, the control unit 80 proceeds to step S419.

[0139] In step S417, the control unit 80 reduces the amount of fuel supplied from the second supply unit 55 to the pipe L1 so that the temperature Ta falls below the second upper limit temperature. In step S418, the control unit 80 reduces the output of the combustion device 200 (for example, a 10% load reduction), and the process proceeds to step S404.

[0140] In step S419, the control unit 80 determines whether the combustion device 200 is stopped, and if the determination is YES, the process proceeds to step S420, but if the determination is NO, step S405 is executed again. The combustion device 200 transmits the operating state, including the state in which the combustion operation is stopped, to the control unit 80.

[0141] In step S420, since the combustion device 200 is stopped, the control unit 80 stops the supply of reducing agent by the first supply unit 50 and the supply of fuel by the second supply unit 55, and ends the processing of this flowchart. When the combustion device 200 starts the combustion operation, the control unit 80 resumes the processing of this flowchart.

[0142] In the above description, fuel is supplied from the second supply unit 55 to generate ammonia through an exothermic reaction in the ammonia decomposition catalyst of the ammonia decomposition unit 10, but other embodiments are also possible. For example, ammonia or urea water may be supplied from the first supply unit 50 to the pipe L1.

[0143] According to the exhaust gas treatment device 100C of this embodiment, by supplying ammonia or urea water to the exhaust gas supplied from the combustion device 200 to the ammonia decomposition unit 10, it is possible to promote the exothermic reaction caused by the oxidation of ammonia in the ammonia decomposition unit 10. This makes it possible to appropriately increase the temperature of the exhaust gas guided from the ammonia decomposition unit 10 to the nitrogen oxide decomposition unit 20, and to operate the nitrogen oxide decomposition unit 20 within a temperature range in which the decomposition rate of nitrous oxide does not change depending on the concentration of NO contained in the exhaust gas.

[0144] Furthermore, according to the exhaust gas treatment device 100C of this embodiment, by setting the predetermined temperature to 450°C or higher and 530°C or lower, it is possible to operate the nitrogen oxide decomposition unit 20 within an appropriate temperature range in which the decomposition rate of nitrous oxide does not change depending on the concentration of NO contained in the exhaust gas.

[0145] In the exhaust gas treatment device 100C of this embodiment, the exhaust gas that has passed through the nitrogen oxide decomposition unit 20 is discharged to the outside via the pipe L3, but other configurations are also possible. For example, as in a modified exhaust gas treatment device 100D shown in Fig. 17, the exhaust gas that has passed through the nitrogen oxide decomposition unit 20 may be introduced into the ammonia decomposition unit 30, and the exhaust gas that has passed through the ammonia decomposition unit 30 may be discharged to the outside via the pipe L4.

[0146] Fig. 17 is a schematic configuration diagram showing an exhaust gas treatment device 100D according to a modified example of the fifth embodiment of the present disclosure. The ammonia decomposition unit 30 shown in Fig. 17 has a configuration similar to that of the ammonia decomposition unit 30 of the first embodiment. According to the exhaust gas treatment device 100D shown in Fig. 17, even if ammonia is contained in the exhaust gas that has passed through the nitrogen oxide decomposition unit 20, the ammonia can be appropriately decomposed in the ammonia decomposition unit 30 so that the ammonia is not discharged to the outside.

[0147] 17, ammonia is appropriately decomposed in the ammonia decomposition unit 30, so that load restriction on the combustion device 200 before step S408 in Fig. 15 is unnecessary or the frequency with which the load restriction is performed can be reduced. In order to eliminate the need for load restriction or reduce the frequency with which the load restriction is performed, in step S414, the amount of reducing agent required to perform reduction treatment on NOx and nitrous oxide is calculated for the NOx concentration and nitrous oxide concentration calculated in step S302 in Fig. 9, and the coefficient γ by which the required amount of reducing agent is multiplied is set to a value (e.g., 1.5) larger than that in the fifth embodiment.

[0148] The exhaust gas treatment device and the design method of the exhaust gas treatment device described in each of the above-described embodiments can be understood, for example, as follows: The exhaust gas treatment device (100) according to the present disclosure is an exhaust gas treatment device (100, 100A) that treats exhaust gas discharged from a combustion device (200) that combusts fuel containing ammonia, and includes a first treatment device (10) having a first catalyst that decomposes ammonia contained in the exhaust gas, and a second treatment device (20) having a second catalyst that decomposes nitrous oxide and NOx contained in the exhaust gas after the ammonia has been decomposed in the first treatment device.

[0149] According to the exhaust gas treatment device of the present disclosure, ammonia contained in exhaust gas discharged from a combustion device is appropriately decomposed by the first catalyst as it passes through the first treatment section. Furthermore, nitrous oxide and NOx produced when ammonia is combusted in the combustion device are appropriately decomposed by the second catalyst as it passes through the second treatment section. Thus, the exhaust gas treatment device of the present disclosure can appropriately decompose ammonia, nitrous oxide, and NOx contained in exhaust gas discharged from a combustion device that burns a fuel containing ammonia.

[0150] In the exhaust gas treatment device according to the present disclosure, the first treatment unit may be configured to remove NOx generated when ammonia contained in the exhaust gas is decomposed by the first catalyst. According to the exhaust gas treatment device configured as above, NOx generated when ammonia is decomposed in the first treatment unit is removed by the first catalyst, so that it is possible to appropriately prevent an increase in NOx contained in the exhaust gas emitted from the combustion device when the exhaust gas passes through the first treatment unit.

[0151] The exhaust gas treatment device according to the present disclosure may be configured to include a bypass pipe (L7) that guides the exhaust gas discharged from the combustion device to the second treatment device without passing through the first treatment device, and a bypass valve (90) disposed in the bypass pipe. According to this configuration, when the concentration of ammonia contained in the exhaust gas discharged from the combustion device is higher than the concentration required as a reducing agent for decomposing nitrous oxide and NOx in the second treatment device, the bypass valve can be closed to decompose the excess ammonia in the first treatment device. Furthermore, when the concentration of ammonia contained in the exhaust gas discharged from the combustion device is equal to or lower than the concentration required as a reducing agent for decomposing nitrous oxide and NOx in the second treatment device, the bypass valve can be opened to guide the ammonia to the second treatment device without decomposing it in the first treatment device.

[0152] The exhaust gas treatment device according to the present disclosure may be configured to include a third treatment section (30) that decomposes ammonia contained in the exhaust gas that has passed through the second treatment section. According to the exhaust gas treatment device of this configuration, even if ammonia remains in the exhaust gas that has passed through the second treatment section, the ammonia can be decomposed in the third treatment section, thereby preventing the ammonia from being discharged to the outside.

[0153] The exhaust gas treatment device according to the present disclosure may include a detection unit (40) that detects the concentration of nitrous oxide and / or NOx contained in the exhaust gas that has passed through the second treatment unit, and a first supply unit (50) that supplies ammonia or urea water to the exhaust gas that is supplied from the first treatment unit to the second treatment unit when the concentration of nitrous oxide contained in the exhaust gas is higher than a first predetermined concentration or the concentration of NOx contained in the exhaust gas is higher than a second predetermined concentration, and the second catalyst may be a catalyst that reduces and decomposes the nitrous oxide and NOx contained in the exhaust gas with ammonia.

[0154] According to the exhaust gas treatment device of this configuration, when the detection unit detects that the concentration of nitrous oxide contained in the exhaust gas that has passed through the second treatment unit is higher than a first predetermined concentration, or that the concentration of NOx contained in the exhaust gas that has passed through the second treatment unit is higher than a second predetermined concentration, ammonia or urea water is supplied as a reducing agent from the first supply unit to the exhaust gas that is supplied to the second treatment unit in order to make up for the shortage of ammonia for reducing nitrous oxide and NOx. As a result, the shortage of ammonia supplied from the first treatment unit to the second treatment unit is made up, and the concentrations of nitrous oxide and NOx contained in the exhaust gas that has passed through the second treatment unit can be reduced.

[0155] The exhaust gas treatment device according to the present disclosure may be configured to include a temperature detection unit that detects the temperature of the exhaust gas discharged from the first treatment unit, and a second supply unit (55) that supplies ammonia or urea water to the exhaust gas supplied from the combustion device to the first treatment unit when the temperature detected by the temperature detection unit is equal to or lower than a predetermined temperature. According to the exhaust gas treatment device of this configuration, by supplying ammonia or urea water to the exhaust gas supplied from the combustion device to the first treatment unit, it is possible to promote the exothermic reaction caused by the decomposition of ammonia in the first treatment unit. This allows the temperature of the exhaust gas guided from the first treatment unit to be appropriately increased, and the nitrogen oxide decomposition unit to operate within a temperature range in which the decomposition rate of nitrous oxide does not change depending on the concentration of NO contained in the exhaust gas.

[0156] The exhaust gas treatment device according to the present disclosure may be configured to include a third treatment section (30) that decomposes ammonia contained in the exhaust gas that has passed through the second treatment section. According to the exhaust gas treatment device of this configuration, even if ammonia is contained in the exhaust gas that has passed through the second treatment section, the ammonia can be appropriately decomposed in the third treatment section to prevent the ammonia from being discharged to the outside.

[0157] In the exhaust gas treatment device according to the present disclosure, the predetermined temperature may be set to a temperature of not less than 450° C. and not more than 530° C. According to the exhaust gas treatment device of this configuration, by setting the predetermined temperature to not less than 450° C. and not more than 530° C., it is possible to operate the nitrogen oxide decomposition unit within an appropriate temperature range in which the decomposition rate of nitrous oxide does not change depending on the concentration of NO contained in the exhaust gas.

[0158] The exhaust gas treatment device according to the present disclosure is an exhaust gas treatment device (100B) that treats exhaust gas discharged from a combustion device that burns a fuel containing ammonia, and includes: a first supply unit (50) that supplies ammonia as a reducing agent to the exhaust gas discharged from the combustion device; a nitrogen oxide decomposition unit (20) having a decomposition catalyst that reduces nitrous oxide and NOx contained in the exhaust gas with ammonia supplied from the ammonia supply unit; and an ammonia decomposition unit (30) that decomposes ammonia contained in the exhaust gas that has passed through the nitrogen oxide decomposition unit.

[0159] According to the exhaust gas treatment device of the present disclosure, ammonia contained in exhaust gas emitted from a combustion device is decomposed by reacting with nitrous oxide and NOx as a reducing agent in the decomposition catalyst as it passes through the nitrogen oxide decomposition section. Furthermore, nitrous oxide and NOx generated when ammonia is combusted in the combustion device are appropriately decomposed by the decomposition catalyst as it passes through the nitrogen oxide decomposition section. Thus, the exhaust gas treatment device of the present disclosure can appropriately decompose ammonia, nitrous oxide, and NOx contained in exhaust gas emitted from a combustion device that burns fuel containing ammonia.

[0160] A design method for an exhaust gas treatment device according to the present disclosure is a design method for an exhaust gas treatment device that treats exhaust gas discharged from a combustion device that combusts a fuel containing ammonia, wherein, when the concentration of ammonia contained in the exhaust gas is higher than the sum of a first concentration obtained by multiplying the concentration of nitrous oxide contained in the exhaust gas by a first coefficient and a second concentration obtained by multiplying the concentration of NOx contained in the exhaust gas by a second coefficient, the exhaust gas treatment device is designed so that a first treatment device having a first catalyst that decomposes the ammonia contained in the exhaust gas is arranged downstream of the combustion device, and a second treatment device having a second catalyst that decomposes the nitrous oxide and NOx contained in the exhaust gas after ammonia has been decomposed in the first treatment device is arranged downstream of the first treatment device, and when the concentration of ammonia contained in the exhaust gas is equal to or lower than the sum of the first concentration, the exhaust gas treatment device is designed so that the second treatment device is arranged downstream of the combustion device without the first treatment device.

[0161] According to the design method of an exhaust gas treatment device disclosed herein, when the concentration of ammonia contained in the exhaust gas is higher than the sum of a first concentration obtained by multiplying the concentration of nitrous oxide contained in the exhaust gas by a first coefficient and a second concentration obtained by multiplying the concentration of NOx contained in the exhaust gas by a second coefficient, the exhaust gas treatment device is designed so that the first treatment device is located downstream of the combustion device and the second treatment device is located downstream of the first treatment device in order to prevent the concentration of ammonia supplied from the first treatment device to the second treatment device from becoming excessive.

[0162] On the other hand, when the concentration of ammonia contained in the exhaust gas is equal to or less than the sum of a first concentration obtained by multiplying the concentration of nitrous oxide contained in the exhaust gas by a first coefficient and a second concentration obtained by multiplying the concentration of NOx contained in the exhaust gas by a second coefficient, the concentration of ammonia supplied from the first treatment unit to the second treatment unit does not become excessive, so the exhaust gas treatment device is designed so that the second treatment unit is located downstream of the combustion device instead of the first treatment unit. This makes it possible to design an exhaust gas treatment device with an appropriate configuration according to the concentration of ammonia contained in the exhaust gas discharged from the combustion device.

[0163] REFERENCE SIGNS LIST 10 Ammonia decomposition section (first processing section) 20 Nitrogen oxide decomposition section (second processing section) 30 Ammonia decomposition section (third processing section) 40 Detection section 50 First supply section (reducing agent supply section) 55 Second supply section (fuel supply section) 60 Temperature sensor 70 Bypass valve 80 Control section 90 Bypass valve 100, 100A, 100B, 100C, 100D Exhaust gas treatment device 200 Combustion device L1, L2, L3, L4, L5, L6, L7, L8 Piping

Claims

1. An exhaust gas treatment device for treating exhaust gas discharged from a combustion device that burns a fuel containing ammonia, A first treatment section having a first catalyst that decomposes ammonia contained in the exhaust gas; a second treatment section having a second catalyst that decomposes nitrous oxide and NOx contained in the exhaust gas from which ammonia has been decomposed in the first treatment section; a detection unit that detects a concentration of nitrous oxide contained in the exhaust gas that has passed through the second treatment unit; a first supply unit that supplies ammonia or urea water to the exhaust gas supplied from the first treatment unit to the second treatment unit when a concentration of nitrous oxide contained in the exhaust gas is higher than a first predetermined concentration, The second catalyst is a catalyst that reduces and decomposes nitrous oxide contained in the exhaust gas with ammonia.

2. The exhaust gas treatment device according to claim 1 , wherein the first treatment section removes NOx produced when ammonia contained in the exhaust gas is decomposed by the first catalyst.

3. a bypass pipe for guiding the exhaust gas discharged from the combustion device to the second treatment unit without passing through the first treatment unit; The exhaust gas treatment device according to claim 1 or 2, further comprising: a bypass valve disposed in the bypass piping.

4. 3. The exhaust gas treatment device according to claim 1, further comprising a third treatment device that decomposes ammonia contained in the exhaust gas that has passed through the second treatment device.

5. The detection unit detects a concentration of NOx contained in the exhaust gas that has passed through the second treatment unit, the first supply unit supplies ammonia or urea water to the exhaust gas supplied from the first treatment unit to the second treatment unit when a concentration of NOx contained in the exhaust gas is higher than a second predetermined concentration; 3. The exhaust gas treatment device according to claim 1, wherein the second catalyst is a catalyst that reduces and decomposes NOx contained in the exhaust gas with ammonia.

6. a temperature detection unit that detects the temperature of the exhaust gas discharged from the first treatment unit; 6. The exhaust gas treatment device according to claim 5, further comprising: a second supply unit that supplies ammonia or urea water to the exhaust gas supplied from the combustion device to the first treatment unit when the temperature detected by the temperature detection unit is equal to or lower than a predetermined temperature.

7. The exhaust gas treatment device according to claim 6 , further comprising a third treatment device that decomposes ammonia contained in the exhaust gas that has passed through the second treatment device.

8. The exhaust gas treatment device according to claim 6, wherein the predetermined temperature is a temperature of 450°C or more and 530°C or less.

9. An exhaust gas treatment device for treating exhaust gas discharged from a combustion device that combusts a fuel containing ammonia, an ammonia supply unit that supplies ammonia as a reducing agent to the exhaust gas discharged from the combustion device; a nitrogen oxide decomposition unit having a nitrogen oxide decomposition catalyst that reduces nitrous oxide and NOx contained in the exhaust gas with ammonia supplied from the ammonia supply unit; an ammonia decomposition section that decomposes ammonia contained in the exhaust gas that has passed through the nitrogen oxide decomposition section.

10. A method for designing an exhaust gas treatment device for treating exhaust gas discharged from a combustion device that combusts a fuel containing ammonia, comprising: when the concentration of ammonia contained in the exhaust gas is higher than the sum of a first concentration obtained by multiplying the concentration of nitrous oxide contained in the exhaust gas by a first coefficient and a second concentration obtained by multiplying the concentration of NOx contained in the exhaust gas by a second coefficient, the exhaust gas treatment device is designed so that a first treatment section having a first catalyst that decomposes ammonia contained in the exhaust gas is disposed downstream of the combustion device, and a second treatment section having a second catalyst that decomposes nitrous oxide and NOx contained in the exhaust gas after the ammonia has been decomposed in the first treatment section is disposed downstream of the first treatment section; A design method for an exhaust gas treatment device, the design method including the step of: when a concentration of ammonia contained in the exhaust gas is equal to or less than the total concentration, designing the exhaust gas treatment device so that the second treatment device is disposed downstream of the combustion device without disposing the first treatment device.