Denitrification control device

Abstract

This denitrification control device is for controlling a denitrification device that denitrifies exhaust gas generated by combustion of ammonia fuel in a combustion device. The denitrification control device comprises: a first estimation unit for estimating the flow rate of the exhaust gas that is discharged from the combustion device, on the basis of the amount of the ammonia fuel that is supplied to the combustion device; a first prediction unit for predicting the NOx concentration of the exhaust gas on the basis of the amount of the ammonia fuel that is supplied to the combustion device; and a first calculation unit for calculating a first feedforward command value indicating the amount of denitrification ammonia that is supplied to the denitrification device during combustion of the ammonia fuel, on the basis of the flow rate of the exhaust gas estimated in the first estimation unit and the NOx concentration of the exhaust gas predicted in the first prediction unit.

Description

Denitration control device

[0001] This disclosure relates to a denitration control device. This application claims priority based on Japanese Patent Application No. 2025-009009 filed with the Japan Patent Office on January 22, 2025, and incorporates its content herein by reference.

[0002] NOx (nitrogen oxides) generated by the combustion of a combustion device such as a gas turbine is decomposed into nitrogen and water by the chemical reaction between ammonia supplied to the denitration device and a denitration catalyst. The supply amount of ammonia supplied to the denitration device is calculated based on the NOx ratio (NOx concentration) contained in the exhaust gas and the exhaust gas flow rate, and is sometimes controlled by feedback control that is finely adjusted by the deviation between the measured value and the target value of NOx after the denitration reaction (for example, Patent Document 1).

[0003] Japanese Patent Laid-Open No. 8-155267

[0004] The above-mentioned feedback control is applicable regardless of whether ammonia fuel or a fuel other than ammonia fuel (for example, natural gas) is burned in the combustion device. However, when ammonia fuel is burned in the combustion device, a large amount of NOx is generated compared to when natural gas is burned in the combustion device. Therefore, when the fuel of the combustion device is switched from natural gas to ammonia fuel, the supply amount of ammonia required for the denitration device may increase rapidly. In the feedback control described in Patent Document 1, since the supply amount of ammonia supplied to the denitration device is adjusted after detecting an increase in NOx at the inlet of the denitration device, a delay may occur in the control of the supply amount of ammonia to the denitration device, and appropriate control may be difficult.

[0005] In view of the above circumstances, at least one embodiment of this disclosure aims to provide a denitration control device that can suppress a delay in the control of the supply amount of ammonia for denitration to the denitration device.

[0006] A denitrification control device according to at least one embodiment of the present disclosure is a device for controlling a denitrification device that denitrifies exhaust gas generated by the combustion of ammonia fuel in a combustion device, comprising: a first estimation unit for estimating the flow rate of the exhaust gas discharged from the combustion device based on the amount of intake air supplied to the combustion device; a first prediction unit for predicting the NOx concentration of the exhaust gas based on the amount of ammonia fuel supplied to the combustion device; and a first calculation unit for calculating a first advance command value indicating the amount of ammonia for denitrification supplied to the denitrification device during the combustion of the ammonia fuel, based on the flow rate of the exhaust gas estimated by the first estimation unit and the NOx concentration of the exhaust gas predicted by the first prediction unit.

[0007] According to at least one embodiment of the present disclosure, a denitrification control device is provided that can suppress delays in controlling the amount of ammonia supplied to a denitrification device.

[0008] This is a schematic diagram illustrating the configuration of a denitrification system comprising a denitrification control device, a combustion device, and a denitrification device according to one embodiment of the present disclosure. This is a schematic diagram illustrating the configuration of a denitrification control device according to one embodiment of the present disclosure. This is a control block diagram showing an example of controlling the amount of ammonia supplied for denitrification to the denitrification device by a denitrification control device according to one embodiment of the present disclosure. This is a control block diagram showing an example of controlling the amount of ammonia supplied for denitrification to the denitrification device by a denitrification control device according to one embodiment of the present disclosure. This is a schematic diagram illustrating the configuration of a denitrification system comprising a denitrification control device, a combustion device, and a denitrification device according to one embodiment of the present disclosure.

[0009] Hereinafter, several embodiments of this disclosure will be described with reference to the attached drawings. However, the dimensions, materials, shapes, relative arrangements, etc., of the components described or shown in the drawings as embodiments are not intended to limit the scope of this disclosure, but are merely illustrative examples.

[0010] (Denitrification System) Figure 1 is a schematic diagram illustrating the configuration of a denitrification system 100 comprising a denitrification control device 1, a combustion device 3, and a denitrification device 4 according to one embodiment of the present disclosure. As shown in Figure 1, the denitrification system 100 comprises a combustion device 3 for burning fuel, a denitrification device 4 for denitrifying exhaust gas produced by the combustion of the combustion device 3, and a denitrification control device 1 for controlling the amount of ammonia for denitrification supplied to the denitrification device 4. In the following embodiments, the case in which the combustion device 3 is a gas turbine combustor will be described, but the combustion device 3 of the present disclosure is not limited to a gas turbine combustor.

[0011] In the embodiment shown in Figure 1, the combustion device 3 includes a combustor 30 for burning fuel and intake air, a compressor 31 for compressing the intake air (combustion gas, e.g., air) led to the combustor 30, a turbine 32 configured to be driven by the exhaust gas discharged from the combustor 30, and a rotating shaft 33 coaxially connecting the compressor 31 and the turbine 32. The compressor 31 is attached to one side of the rotating shaft 33, and the turbine 32 is attached to the other side, so that the compressor 31 and the rotating shaft 33 rotate together with the turbine 32. The combustion device 3 may also include a generator (not shown) mechanically connected to the rotating shaft 33 and configured to convert the rotational force of the turbine 32 into electricity.

[0012] As shown in Figure 1, the denitrification system 100 includes a denitrification ammonia supply device 5 configured to supply denitrification ammonia to the denitrification device 4, an ammonia fuel line 6 for leading ammonia fuel to the combustor 30 (combustion device 3), a nitrogen-free fuel line 7 for leading nitrogen-free fuel other than ammonia fuel to the combustor 30 (combustion device 3), an intake line 8 for leading intake air to the combustor 30 (combustion device 3), and an exhaust gas line 9 for leading exhaust gas discharged from the combustor 30 (combustion device 3). Nitrogen-free fuel is a fuel whose main combustion component consists of molecules that do not contain nitrogen atoms.

[0013] The denitrification device 4 is located downstream of the turbine 32 in the exhaust gas flow direction of the exhaust gas line 9. When the combustion device 3 is a fueler for a gas turbine, the denitrification device 4 is located inside a waste heat recovery boiler 40 located downstream of the turbine 32 in the exhaust gas line 9. The denitrification device 4 has a containment chamber 42 that houses an ammonia decomposition catalyst 41 for removing ammonia from the exhaust gas. The ammonia denitrification supply device 5 includes an ammonia denitrification line 52 that forms a flow path for guiding ammonia denitrification from a supply source 51 (for example, a tank for storing ammonia denitrification) to the containment chamber 42, and an ammonia denitrification control valve 53 for adjusting the amount of ammonia denitrification supplied to the containment chamber 42 (denitrification device 4) via the ammonia denitrification line 52.

[0014] The ammonia fuel line 6 forms a flow path for guiding ammonia fuel from an ammonia fuel supply source 61 (for example, a tank for storing ammonia fuel) to the combustor 30 (combustion device 3), and is formed, for example, by piping. The ammonia fuel line 6 is equipped with an ammonia fuel control valve 62 for adjusting the amount of ammonia fuel supplied to the combustor 30 (combustion device 3) via the ammonia fuel line 6, and an ammonia fuel supply amount meter 63 for measuring the amount of ammonia fuel supplied to the combustor 30 (combustion device 3) via the ammonia fuel line 6. In the illustrated example, the ammonia fuel supply amount meter 63 is a flow sensor configured to measure the flow rate of ammonia fuel flowing downstream of the ammonia fuel line 6 (towards the combustor 30) from the ammonia fuel control valve 62.

[0015] The nitrogen-free fuel line 7 forms a flow path for guiding nitrogen-free fuel from a nitrogen-free fuel supply source 71 (for example, a tank for storing nitrogen-free fuel) to the combustor 30 (combustion device 3), and is formed, for example, by piping. The nitrogen-free fuel line 7 is equipped with a nitrogen-free fuel control valve 72 for adjusting the amount of nitrogen-free fuel supplied to the combustor 30 (combustion device 3) via the nitrogen-free fuel line 7, and a nitrogen-free fuel supply amount measuring instrument 73 for measuring the amount of nitrogen-free fuel supplied to the combustor 30 (combustion device 3) via the nitrogen-free fuel line 7. In the illustrated example, the nitrogen-free fuel supply amount measuring instrument 73 is a flow sensor configured to measure the flow rate of nitrogen-free fuel flowing downstream of the nitrogen-free fuel line 7 (towards the combustor 30) from the nitrogen-free fuel control valve 72.

[0016] The intake line 8 forms a flow path for guiding intake air to the combustor 30 (combustion device 3), and is formed, for example, by an intake duct. The intake line 8 is provided with the compressor 31 described above and an intake air supply amount measuring instrument 81 for measuring the amount of intake air supplied to the combustor 30 (combustion device 3) via the intake line 8. In the illustrated example, the intake air supply amount measuring instrument 81 is a flow sensor configured to measure the flow rate of intake air flowing upstream of the compressor 31 in the intake line 8 (away from the combustor 30). Alternatively, the intake air supply amount measuring instrument 81 may be a flow sensor configured to measure the flow rate of intake air flowing downstream of the compressor 31 in the intake line 8 (towards the combustor 30).

[0017] The denitrification system 100 may include a load measuring instrument 34 for measuring the load of the combustion device 3 (in this embodiment, the gas turbine load; hereinafter referred to as the load), as shown in Figure 1. In the illustrated example, the load measuring instrument 34 is configured to calculate the load based on the measurement value of a temperature sensor configured to measure the temperature of the exhaust gas flowing upstream of the turbine 32 in the exhaust gas line 9 (on the combustor 30 side) and the discharge pressure of the compressor 31. The load measuring instrument 34 may also be configured to correct the load calculated using intake air temperature, atmospheric pressure, etc. Note that the load acquisition device in the denitrification system 100 is not limited to the load measuring instrument 34, as long as it is configured to acquire the load.

[0018] The exhaust gas line 9 forms a passage for guiding the exhaust gas discharged from the combustor 30 (combustion device 3), and is formed, for example, by an exhaust duct. The exhaust gas line 9 is equipped with the turbine 32 described above, the denitrification device 4 described above, and a facility 91 (a chimney in the illustrated example) for discharging exhaust gas, which is provided at the downstream end of the exhaust gas line 9.

[0019] As shown in Figure 1, the denitrification system 100 includes an ammonia concentration meter 92 (e.g., a concentration sensor) for measuring the concentration of unreacted ammonia in the exhaust gas flowing downstream of the denitrification device 4 in the exhaust gas line 9, and a NOx concentration meter 93 (e.g., a concentration sensor) for measuring the concentration of NOx in the exhaust gas flowing downstream of the denitrification device 4 in the exhaust gas line 9. Unreacted ammonia refers to ammonia (ammonia slip) that remains without being used for reduction in the ammonia decomposition catalyst 41.

[0020] (Denitrification Control Device) Figure 2 is a schematic diagram showing the configuration of a denitrification control device 1 according to one embodiment of the present disclosure. The denitrification control device 1 (controller) is an electronic control unit for controlling the amount of ammonia supplied to the denitrification device 4. The denitrification control device 1 may be configured as a microcomputer including an input device 101 (input interface), an output device 102 (output interface), a storage device 103 (memory such as ROM or RAM, an external storage device, etc.), and an arithmetic unit 104 (CPU), as shown in Figure 2.

[0021] The denitrification control device 1 is configured such that the CPU operates (for example, by performing calculations on data) according to the instructions of a program loaded into the main memory of the above-mentioned memory, thereby realizing the operation of each of the following parts (supply amount calculation unit 10, first estimation unit 11, first prediction unit 12, first calculation unit 13, first ratio calculation unit 14, first correction unit 15, first subtraction amount calculation unit 16, first increase / decrease amount calculation unit 17, first feedback correction unit 18, second estimation unit 21, second prediction unit 22, second calculation unit 23, second ratio calculation unit 24, second correction unit 25, second subtraction amount calculation unit 26, second increase / decrease amount calculation unit 27, second feedback correction unit 28).

[0022] The denitrification control device 1 receives various signals (measured values) from sensors (load meter 34, ammonia fuel supply meter 63, nitrogen-free fuel supply meter 73, intake air supply meter 81, ammonia concentration meter 92, NOx concentration meter 93) installed in the denitrification system 100, which are input to the storage device 103 and the arithmetic unit 104 via the input device 101. The storage device 103 stores the various signals (measured values) from the sensors installed in the denitrification system 100. The arithmetic unit 104 is configured to execute various controls (operations of each part) according to the control program stored in the storage device 103.

[0023] Figures 3 and 4 are control block diagrams showing an example of controlling the amount of ammonia supplied for denitrification to a denitrification apparatus 4 by a denitrification control device 1 according to one embodiment of the present disclosure. In some embodiments of the denitrification control device 1, as shown in Figures 3 and 4, the device comprises at least a first estimation unit 11, a first prediction unit 12, and a first calculation unit 13.

[0024] (First Estimation Unit) The first estimation unit 11 is configured to estimate the flow rate of exhaust gas discharged from the combustion device 3 (future emission GE1) based on at least the amount of intake air supplied to the combustion device 3 (current intake air supply amount AS). The first estimation unit 11 is configured to acquire the current intake air supply amount AS and to acquire the correlation between the current intake air supply amount AS and the future emission GE1.

[0025] The current intake air supply amount AS may be a value measured by the intake air supply amount measuring instrument 81. The first estimation unit 11 may obtain the current intake air supply amount AS from the intake air supply amount measuring instrument 81 or from the storage device 103. The future emission amount GE1 is an estimated value of the flow rate of exhaust gas discharged from the combustion device 3 when the fuel and the intake air at the current intake air supply amount AS are burned in the combustion device 3, and is an estimated value of the flow rate of exhaust gas to be introduced into the denitrification device 4 in the future.

[0026] The correlation between the current intake air supply amount AS and the future emissions GE1 may be represented by a map, table, function (as shown in the illustration), or machine learning model. The correlation between the current intake air supply amount AS and the future emissions GE1 may be pre-acquired based on at least one of steady-state test data, past performance values, past experimental values, or numerical analysis results and stored in the storage device 103. The first estimation unit 11 may acquire the correlation between the current intake air supply amount AS and the future emissions GE1 from the storage device 103.

[0027] As shown in the figure, the first estimation unit 11 may be configured to estimate the flow rate of exhaust gas discharged from the combustion device 3 (future emission amount GE1) based on the amount of intake air supplied to the combustion device 3 (current intake air supply amount AS) and the amount of ammonia fuel supplied to the combustion device 3 (current fuel supply amount FS1). The first estimation unit 11 is configured to acquire the current fuel supply amount FS1. The current fuel supply amount FS1 may be a value measured by the ammonia fuel supply amount measuring instrument 63. The first estimation unit 11 may acquire the current fuel supply amount FS1 from the ammonia fuel supply amount measuring instrument 63 or from the storage device 103.

[0028] In the illustrated embodiment, the first estimation unit 11 includes an exhaust gas flow rate calculation unit 111 for calculating the future emission GE1 corresponding to the current intake air supply amount AS by applying the current intake air supply amount AS to the correlation between the current intake air supply amount AS and the future emission GE1, and an exhaust gas flow rate correction unit 112 for correcting the future emission GE1 calculated in the exhaust gas flow rate calculation unit 111 by adding the current fuel supply amount FS1. The future emission GE1 is derived in the exhaust gas flow rate calculation unit 111, and the current fuel supply amount FS1 is added in the exhaust gas flow rate correction unit 112.

[0029] In some other embodiments, the first estimation unit 11 may obtain a correlation between the current intake air supply amount AS, the current fuel supply amount FS1, and the future emissions GE1, and apply the current intake air supply amount AS and the current fuel supply amount FS1 to this correlation to calculate the future emissions GE1 corresponding to the current intake air supply amount AS and the current fuel supply amount FS1.

[0030] (First Prediction Unit) The first prediction unit 12 is configured to predict the NOx concentration of exhaust gas (future NOx concentration C1) when ammonia fuel is burned, based on the amount of ammonia fuel supplied to the combustion device 3 (current fuel supply amount FS1). The first prediction unit 12 is configured to acquire the current fuel supply amount FS1 and to acquire the correlation between the current fuel supply amount FS1 and the future NOx concentration C1 when ammonia fuel is burned in the combustion device 3.

[0031] When ammonia fuel is burned in combustion device 3, fuel NOx derived from the fuel components becomes dominant because the chemical formula of ammonia is NH3. In contrast, when nitrogen-free fuels such as natural gas are burned in combustion device 3, thermal NOx (oxidation of N2 and O2 at high temperatures) becomes dominant. When ammonia fuel is burned in combustion device 3, the NOx concentration corresponding to the fuel supply amount is relatively higher compared to when nitrogen-free fuels such as natural gas are burned in combustion device 3, and a relatively larger supply amount of ammonia for denitrification is required. The current correlation between fuel supply amount FS1 and future NOx concentration C1 reflects the combustion state in which fuel NOx becomes dominant.

[0032] The first prediction unit 12 may obtain the current fuel supply amount FS1 from the ammonia fuel supply amount measuring instrument 63 or from the storage device 103. The future NOx concentration C1 is an estimated value of the NOx concentration of the exhaust gas discharged from the combustion device 3 when ammonia fuel and intake air at the current intake air supply amount AS are burned in the combustion device 3, and is an estimated value of the NOx concentration of the exhaust gas to be introduced into the denitrification device 4 in the future.

[0033] The correlation between the current fuel supply amount FS1 and the future NOx concentration C1 may be represented by a map (illustrated example), a table, a function, or a machine learning model. The correlation between the current fuel supply amount FS1 and the future NOx concentration C1 may be pre-acquired based on at least one of steady-state test data, past performance values, past experimental values, or numerical analysis results and stored in the storage device 103. The first prediction unit 12 may acquire the correlation between the current fuel supply amount FS1 and the future NOx concentration C1 from the storage device 103.

[0034] In the illustrated embodiment, the first prediction unit 12 is configured to derive the future NOx concentration C1 corresponding to the current fuel supply amount FS1 by applying the current fuel supply amount FS1 to the correlation between the current fuel supply amount FS1 and the future NOx concentration C1.

[0035] (First Calculation Unit) The first calculation unit 13 is configured to calculate a first advance command value CV1, which indicates the amount of ammonia for denitrification supplied to the denitrification device 4 during the combustion of ammonia fuel, based on the exhaust gas flow rate (future emission GE1) estimated in the first estimation unit 11 and the exhaust gas NOx concentration (future NOx concentration C1) predicted in the first prediction unit 12. The first calculation unit 13 is configured to acquire the future emission GE1 estimated in the first estimation unit 11 and the future NOx concentration C1 predicted in the first prediction unit 12.

[0036] The first calculation unit 13 is configured to obtain a first correlation, which is the correlation between future emissions GE1, future NOx concentration C1, and the first advance command value CV1. The first advance command value CV1 indicates the amount of ammonia for denitrification that will be supplied to the denitrification device 4 in the future.

[0037] The first correlation may be a map, table, function (as shown in the illustration), or machine learning model that shows the correlation between future emissions GE1, future NOx concentration C1, and the first advance directive value CV1. The first correlation may be acquired in advance based on at least one of steady-state test data, past performance values, past experimental values, or numerical analysis results and stored in the storage device 103. The first calculation unit 13 may acquire the first correlation from the storage device 103.

[0038] In the illustrated embodiment, the first calculation unit 13 is configured to calculate a first advance command value CV1 corresponding to the future emission GE1 and future NOx concentration C1 by applying the future emission GE1 estimated by the first estimation unit 11 and the future NOx concentration C1 predicted by the first prediction unit 12 to the first correlation.

[0039] In the illustrated embodiment, the denitrification control device 1 includes a first correction unit 15, a first subtraction amount calculation unit 16, and a first increase / decrease amount calculation unit 17. However, it may also be configured to include one or two of the first correction unit 15, the first subtraction amount calculation unit 16, or the first increase / decrease amount calculation unit 17, or it may be configured not to include the first correction unit 15, the first subtraction amount calculation unit 16, and the first increase / decrease amount calculation unit 17.

[0040] The denitrification control device 1 includes a supply amount calculation unit 10 for calculating the amount of denitrification ammonia to be supplied to the denitrification device 4 by the denitrification ammonia supply device 5. When the combustion device 3 is burning ammonia fuel, the supply amount calculation unit 10 sets the first supply amount command value SCV1 of denitrification ammonia determined based on the first prior command value CV1 as the supply amount SCV of denitrification ammonia to be supplied to the denitrification device 4 by the denitrification ammonia supply device 5.

[0041] The denitrification control device 1 is configured to control the operation of the ammonia denitrification supply device 5 so that the supply amount SCV of ammonia denitrification is supplied to the denitrification device 4 via the ammonia denitrification supply device 5. In one embodiment, the denitrification control device 1 is configured to control the opening degree and opening / closing operation of the ammonia denitrification control valve 53 according to the supply amount SCV of ammonia denitrification.

[0042] In the denitration control device 1 that does not include the first correction unit 15, the first subtraction amount calculation unit 16, and the first increase / decrease amount calculation unit 17, the first supply amount command value SCV1 is the first leading command value CV1 calculated by the first calculation unit 13. In the denitration control device 1 that includes at least one of the first correction unit 15, the first subtraction amount calculation unit 16, or the first increase / decrease amount calculation unit 17, the first supply amount command value SCV1 is the first leading command value CV1 calculated by the first calculation unit 13, to which at least one of addition of correction amounts (subtraction amount SU1, increase / decrease amount AS1) calculated in the first subtraction amount calculation unit 16 or the first increase / decrease amount calculation unit 17, or correction in the first correction unit 15, has been performed, and thus the first leading command value CV1 has been changed.

[0043] The denitration control device 1 can predict the NOx concentration (future NOx concentration C1) of the exhaust gas generated when the ammonia fuel of the supply amount (current fuel supply amount FS1) is burned in the combustion device 3 based on the relationship between the supply amount of the ammonia fuel to the combustion device 3 prepared in advance and the NOx concentration of the exhaust gas. The denitration control device 1 can obtain the supply amount (first leading command value CV1) of the ammonia for denitration to the denitration device 4 when the exhaust gas generated during the combustion of the combustion device 3 is introduced into the denitration device 4, based on the parameters (current intake supply amount AS, current fuel supply amount FS1) that can be obtained during the combustion of the combustion device 3. Therefore, the denitration control device 1 can suppress a delay in the control of the supply amount of the ammonia for denitration to the denitration device 4.

[0044] In the denitration control device 1 according to some embodiments, the above-described first calculation unit 13 is configured to calculate the first leading command value CV1 based on the flow rate of the exhaust gas (future discharge amount GE1) estimated in the first estimation unit 11, the NOx concentration of the exhaust gas (future NOx concentration C1) predicted in the first prediction unit 12, and the load (current load L1). The first calculation unit 13 is configured to obtain the current load L1.

[0045] The NOx concentration (future NOx concentration C1) of the exhaust gas may vary depending on the type of fuel and the load (current load L1) used in the combustion device 3. The load (current load L1) is a parameter that can be obtained during the combustion of the combustion device 3. The denitration control device 1 can obtain a more appropriate supply amount of ammonia for denitration by using the load (current load L1) when burning ammonia fuel as one of the parameters for obtaining the supply amount of ammonia for denitration (first leading command value CV1).

[0046] In the illustrated embodiment, the first calculation unit 13 includes a concentration conversion coefficient calculation unit 131 and a first leading command value calculation unit 132.

[0047] The concentration conversion coefficient calculation unit 131 is configured to calculate the conversion coefficient CF11 of the future NOx concentration C1 corresponding to the current load L1 by applying the current load L1 to the correlation between the load (current load L1) and the conversion coefficient CF11 of the future NOx concentration C1. The conversion coefficient CF11 is a coefficient for compensating for the increase in the future NOx concentration C1 corresponding to the increase in the current load L1. The above-described first correlation includes the correlation between the current load L1 and the conversion coefficient CF11 of the future NOx concentration C1.

[0048] The first leading command value calculation unit 132 is configured to calculate the first leading command value CV1 by multiplying the future emission amount GE1, the future NOx concentration C1, and the conversion coefficient CF11 of the future NOx concentration C1 calculated by the concentration conversion coefficient calculation unit 131.

[0049] Note that the first calculation unit 13 may be configured to calculate the first leading command value CV1 corresponding to the future emission amount GE1, the future NOx concentration C1, and the current load L1 by applying the future emission amount GE1 estimated by the first estimation unit 11, the future NOx concentration C1 predicted by the first prediction unit 12, and the current load L1 to the correlation between the future emission amount GE1, the future NOx concentration C1, the current load L1, and the first leading command value CV1.

[0050] (First Ratio Calculation Unit, First Correction Unit) In some embodiments of the denitrification control device 1, as shown in Figures 3 and 4, a first ratio calculation unit 14 and a first correction unit 15 are included. The first ratio calculation unit 14 is configured to calculate the ratio of NO2 to total NOx in the exhaust gas based on the load (current load L1). The first correction unit 15 is configured to correct the first preceding command value CV1 calculated in the first calculation unit 13 based on the NO2 ratio calculated in the first ratio calculation unit 14. The first ratio calculation unit 14 is configured to acquire the current load L1.

[0051] In the illustrated embodiment, the first ratio calculation unit 14 is configured to calculate the conversion coefficient CF12 for the ratio of NO2 according to the current load L1 by applying the current load L1 to the correlation between the load (current load L1) and the conversion coefficient CF12 for the ratio of NO2. The conversion coefficient CF12 is a coefficient for compensating for the decrease in denitrification efficiency in the denitrification device 4 in response to an increase in the current load L1, and is a coefficient for correcting the first pre-command value CV1. The first correction unit 15 corrects the first pre-command value CV1 by multiplying the first pre-command value CV1 calculated in the first calculation unit 13 by the conversion coefficient CF12 for the ratio of NO2 calculated in the first ratio calculation unit 14.

[0052] The ratio of NO2 to total NOx in the exhaust gas may change depending on the load. When the ratio of NO2 to total NOx in the exhaust gas is high, the denitrification efficiency of the denitrification device 4 may decrease compared to when the ratio of NO2 is low. For this reason, when the ratio of NO2 to total NOx in the exhaust gas is high, it is preferable to increase the amount of ammonia supplied to the denitrification device 4. The denitrification control device 1 can determine a more appropriate amount of ammonia supplied to denitrification by performing a correction in the first correction unit 15 to increase or decrease the first advance command value CV1 according to the ratio of NO2.

[0053] (First Subtraction Amount Calculation Unit) In some embodiments of the denitrification control device 1, as shown in Figures 3 and 4, a first subtraction amount calculation unit 16 is provided. The first subtraction amount calculation unit 16 is configured to calculate a subtraction amount SU1 relative to the first preceding command value CV1 calculated in the first calculation unit 13 by feedback control based on the deviation ΔV11 between the measured value MV11 of the unreacted ammonia concentration in the exhaust gas downstream of the denitrification device 4 and the set value SV11. The first subtraction amount calculation unit 16 is configured to acquire the measured value MV11 and the set value SV11 of the unreacted ammonia concentration.

[0054] The measured value MV11 of the unreacted ammonia concentration may be the value measured by the ammonia concentration meter 92. The first subtraction amount calculation unit 16 may obtain the measured value MV11 from the ammonia concentration meter 92 or from the storage device 103. The first subtraction amount calculation unit 16 may obtain the set value SV11 from the storage device 103.

[0055] In the illustrated embodiment, the first subtraction amount calculation unit 16 includes a deviation calculation unit 161 for calculating the deviation ΔV11 between the measured value MV11 and the set value SV11, and a feedback control unit (PID control unit) 162 for calculating the subtraction amount SU1 to the first preceding command value CV1 calculated in the first calculation unit 13 by feedback control based on the deviation ΔV11 calculated in the deviation calculation unit 161. The feedback control unit 162 may be provided with an output limit so that the subtraction amount SU1 having a negative value does not output a value below the lower limit threshold TL1, so that the first preceding command value CV1 (amount of ammonia supplied for denitrification) does not become excessively small due to the subtraction amount SU1.

[0056] The denitrification control device 1 may use the first pre-command value CV1, obtained by adding the subtraction amount SU1, as the amount of ammonia for denitrification to be supplied to the denitrification device 4. In the illustrated embodiment, the denitrification control device 1 includes a first feedback correction unit 18, which is an adder that adds at least one of the subtraction amount SU1 calculated in the first subtraction amount calculation unit 16 or the increase / decrease amount AS1 calculated in the first increase / decrease amount calculation unit 17 to the first pre-command value CV1. In the embodiments shown in Figures 3 and 4, the first feedback correction unit 18 adds the subtraction amount SU1 and the increase / decrease amount AS1 to the first pre-command value CV1 after correction in the first correction unit 15.

[0057] The denitrification control device 1, equipped with a first subtraction amount calculation unit 16, can determine the amount of denitrification ammonia supplied that can reduce the unreacted ammonia concentration in the exhaust gas downstream of the denitrification device 4 by using feedback control with the measured value MV11 of the unreacted ammonia concentration in the exhaust gas downstream of the denitrification device 4. When ammonia fuel is burned in the combustion device 3, fuel NOx is dominant. In order to ensure that the NOx contained in the exhaust gas reacts reliably in the ammonia decomposition catalyst 41, the amount of denitrification ammonia supplied may be excessive. The feedback control using the measured value MV11 of the unreacted ammonia concentration described above can suppress the supply of excessive denitrification ammonia.

[0058] In some embodiments of the denitrification control device 1, as shown in Figures 3 and 4, a first increase / decrease amount calculation unit 17 is included. The first increase / decrease amount calculation unit 17 is configured to calculate an increase / decrease amount AS1 relative to a first preceding command value CV1 calculated in the first calculation unit 13 by feedback control based on the deviation ΔV12 between the measured value MV12 and the set value SV12 of the NOx concentration in the exhaust gas downstream of the denitrification device 4. The first increase / decrease amount calculation unit 17 is configured to acquire the measured value MV12 and the set value SV12 of the NOx concentration.

[0059] The measured value MV12 of the NOx concentration may be the value measured by the NOx concentration measuring instrument 93. The first increase / decrease calculation unit 17 may obtain the measured value MV12 from the NOx concentration measuring instrument 93 or from the storage device 103. The first increase / decrease calculation unit 17 may also obtain the set value SV12 from the storage device 103.

[0060] In the illustrated embodiment, the first increase / decrease amount calculation unit 17 includes a deviation calculation unit 171 for calculating the deviation ΔV12 between a measured value MV12 and a set value SV12, and a feedback control unit (PID control unit) 172 for calculating the increase / decrease amount AS1 relative to the first preceding command value CV1 calculated in the first calculation unit 13 by feedback control based on the deviation ΔV12 calculated in the deviation calculation unit 171.

[0061] The denitrification control device 1 may use a first pre-command value CV1, obtained by adding the increase / decrease amount AS1, as the amount of ammonia for denitrification to be supplied to the denitrification device 4.

[0062] The denitrification control device 1, which includes a first increase / decrease calculation unit 17, can determine the amount of ammonia for denitrification that can reduce the NOx concentration in the exhaust gas downstream of the denitrification device 4 by using feedback control with the measured value MV12 of the NOx concentration in the exhaust gas downstream of the denitrification device 4.

[0063] In some embodiments, the combustion device 3 is configured to burn not only ammonia fuel but also nitrogen-free fuels other than ammonia fuel. In some embodiments of the denitrification control device 1, as shown in Figure 4, the device further comprises a second estimation unit 21, a second prediction unit 22, and a second calculation unit 23.

[0064] (Second Estimation Unit) The second estimation unit 21 is configured to estimate the flow rate of exhaust gas discharged from the combustion device 3 (future emission GE2) based on at least the amount of intake air supplied to the combustion device 3 (current intake air supply amount AS). The second estimation unit 21 is configured to acquire the current intake air supply amount AS and to acquire the correlation between the current intake air supply amount AS and the future emission GE2.

[0065] The current intake air supply amount AS may be a value measured by the intake air supply amount measuring instrument 81. The second estimation unit 21 may obtain the current intake air supply amount AS from the intake air supply amount measuring instrument 81 or from the storage device 103. The future emission amount GE2 is an estimated value of the flow rate of exhaust gas discharged from the combustion device 3 when nitrogen-free fuel and intake air at the current intake air supply amount AS are burned in the combustion device 3, and is an estimated value of the flow rate of exhaust gas to be introduced into the denitrification device 4 in the future.

[0066] The correlation between the current intake air supply amount AS and future emissions GE2 may be represented by a map, table, function (as shown in the illustration), or machine learning model. The correlation between the current intake air supply amount AS and future emissions GE2 may be pre-acquired based on at least one of steady-state test data, past performance values, past experimental values, or numerical analysis results and stored in the storage device 103. The second estimation unit 21 may acquire the correlation between the current intake air supply amount AS and future emissions GE2 from the storage device 103.

[0067] As shown in the figure, the second estimation unit 21 may be configured to estimate the flow rate of exhaust gas discharged from the combustion device 3 (future emission amount GE2) based on the amount of intake air supplied to the combustion device 3 (current intake air supply amount AS) and the amount of nitrogen-free fuel supplied to the combustion device 3 (current fuel supply amount FS2). The second estimation unit 21 is configured to acquire the current fuel supply amount FS2. The current fuel supply amount FS2 may be a value measured by the nitrogen-free fuel supply amount measuring instrument 73. The second estimation unit 21 may acquire the current fuel supply amount FS2 from the nitrogen-free fuel supply amount measuring instrument 73 or from the storage device 103.

[0068] In the illustrated embodiment, the second estimation unit 21 includes an exhaust gas flow rate calculation unit 211 for calculating the future emission GE2 corresponding to the current intake air supply amount AS by applying the current intake air supply amount AS to the correlation between the current intake air supply amount AS and the future emission GE2, and an exhaust gas flow rate correction unit 212 for correcting the future emission GE2 calculated in the exhaust gas flow rate calculation unit 211 by adding the current fuel supply amount FS2. The future emission GE2 is derived in the exhaust gas flow rate calculation unit 211 and the current fuel supply amount FS2 is added in the exhaust gas flow rate correction unit 212.

[0069] In some other embodiments, the second estimation unit 21 may obtain a correlation between the current intake air supply amount AS, the current fuel supply amount FS2, and future emissions GE2, and calculate the future emissions GE2 corresponding to the current intake air supply amount AS and the current fuel supply amount FS2 by applying the current intake air supply amount AS and the current fuel supply amount FS2 to the correlation.

[0070] (Second Prediction Unit) The second prediction unit 22 is configured to predict the NOx concentration of exhaust gas (future NOx concentration C2) when nitrogen-free fuel is burned, based on the amount of nitrogen-free fuel supplied to the combustion device 3 (current fuel supply amount FS2). The second prediction unit 22 is configured to acquire the current fuel supply amount FS2 and to acquire the correlation between the current fuel supply amount FS2 and the future NOx concentration C2 when nitrogen-free fuel is burned in the combustion device 3. The correlation between the current fuel supply amount FS2 and the future NOx concentration C2 differs from the correlation between the current fuel supply amount FS1 and the future NOx concentration C1, and reflects a combustion state in which thermal NOx is dominant.

[0071] The second prediction unit 22 may obtain the current fuel supply amount FS2 from the nitrogen-free fuel supply amount measuring instrument 73 or from the storage device 103. The future NOx concentration C2 is an estimated value of the NOx concentration of the exhaust gas discharged from the combustion device 3 when the nitrogen-free fuel and the intake air at the current intake air supply amount AS are burned in the combustion device 3, and is an estimated value of the NOx concentration of the exhaust gas to be introduced into the denitrification device 4 in the future.

[0072] The correlation between the current fuel supply amount FS2 and the future NOx concentration C2 may be represented by a map (illustrated example), a table, a function, or a machine learning model. The correlation between the current fuel supply amount FS2 and the future NOx concentration C2 may be pre-acquired based on at least one of steady-state test data, past performance values, past experimental values, or numerical analysis results and stored in the storage device 103. The second prediction unit 22 may acquire the correlation between the current fuel supply amount FS2 and the future NOx concentration C2 from the storage device 103.

[0073] In the illustrated embodiment, the second prediction unit 22 is configured to derive the future NOx concentration C2 corresponding to the current fuel supply amount FS2 by applying the current fuel supply amount FS2 to the correlation between the current fuel supply amount FS2 and the future NOx concentration C2.

[0074] (Second Calculation Unit) The second calculation unit 23 is configured to calculate a second advance command value CV2, which indicates the amount of ammonia for denitrification supplied to the denitrification device 4 during the combustion of nitrogen-free fuel, based on the exhaust gas flow rate (future emission GE2) estimated in the second estimation unit 21 and the exhaust gas NOx concentration (future NOx concentration C2) predicted in the second prediction unit 22. The second calculation unit 23 is configured to acquire the future emission GE2 estimated in the second estimation unit 21 and the future NOx concentration C2 predicted in the second prediction unit 22.

[0075] The second calculation unit 23 is configured to obtain a second correlation, which is the correlation between future emissions GE2, future NOx concentration C2, and the second advance command value CV2. The second advance command value CV2 indicates the amount of ammonia for denitrification that will be supplied to the denitrification device 4 in the future.

[0076] The second correlation may be a map, table, function (as shown in the illustration), or machine learning model that shows the correlation between future emissions GE2, future NOx concentration C2, and the second advance directive value CV2. The second correlation may be acquired in advance based on at least one of steady-state test data, past performance values, past experimental values, or numerical analysis results and stored in the storage device 103. The second calculation unit 23 may acquire the second correlation from the storage device 103.

[0077] In the illustrated embodiment, the second calculation unit 23 is configured to calculate a second advance command value CV2 corresponding to the future emission GE2 and future NOx concentration C2 by applying the future emission GE2 estimated in the second estimation unit 21 and the future NOx concentration C2 predicted in the second prediction unit 22 to the second correlation.

[0078] In the illustrated embodiment, the denitrification control device 1 includes a second correction unit 25, a second subtraction amount calculation unit 26, and a second increase / decrease amount calculation unit 27. However, it may also be configured to include one or two of the second correction unit 25, the second subtraction amount calculation unit 26, or the second increase / decrease amount calculation unit 27, or it may be configured not to include the second correction unit 25, the second subtraction amount calculation unit 26, and the second increase / decrease amount calculation unit 27.

[0079] The above-mentioned supply amount calculation unit 10 is configured such that, when the combustion device 3 is burning nitrogen-free fuel, the second supply amount command value SCV2 for denitrification ammonia determined based on the second prior command value CV2 becomes the supply amount SCV of denitrification ammonia to be supplied to the denitrification device 4 by the denitrification ammonia supply device 5.

[0080] In a denitrification control device 1 that does not include a second correction unit 25, a second subtraction amount calculation unit 26, and a second increase / decrease amount calculation unit 27, the second supply amount command value SCV2 is the second preceding command value CV2 calculated by the second calculation unit 23. In a denitrification control device 1 that includes at least one of the second correction unit 25, the second subtraction amount calculation unit 26, or the second increase / decrease amount calculation unit 27, the second supply amount command value SCV2 is the second preceding command value CV2 that has been modified by adding a correction amount (subtraction amount SU2, increase / decrease amount AS2) calculated by the second subtraction amount calculation unit 26 or the second increase / decrease amount calculation unit 27 to the second preceding command value CV2 calculated by the second calculation unit 23, or by performing a correction in the second correction unit 25.

[0081] The denitrification control device 1 can predict the NOx concentration (future NOx concentration C2) of the exhaust gas produced when the supplied amount (current fuel supply amount FS2) of nitrogen-free fuel is burned in the combustion device 3, based on a pre-prepared relationship between the amount of nitrogen-free fuel supplied to the combustion device 3 and the NOx concentration of the exhaust gas. The denitrification control device 1 can determine the amount of ammonia for denitrification supplied to the denitrification device 4 (second preceding command value CV2) when the exhaust gas generated during combustion in the combustion device 3 is introduced into the denitrification device 4, using parameters obtainable during combustion in the combustion device 3 (current intake air supply amount AS, current fuel supply amount FS2). Therefore, even when a nitrogen-free fuel other than ammonia fuel is burned in the combustion device 3, the denitrification control device 1 can suppress delays in controlling the amount of ammonia for denitrification supplied to the denitrification device 4.

[0082] In some embodiments of the denitrification control device 1, the second calculation unit 23 described above is configured to calculate a second advance command value CV2 based on the exhaust gas flow rate (future emission amount GE2) estimated by the second estimation unit 21, the exhaust gas NOx concentration (future NOx concentration C2) predicted by the second prediction unit 22, and the load (current load L2). The second calculation unit 23 is configured to acquire the current load L2.

[0083] The NOx concentration (future NOx concentration C2) of the exhaust gas may differ depending on the type of fuel used in the combustion device 3 and the load (current load L2). The load (current load L2) is a parameter that can be obtained during combustion in the combustion device 3. The denitrification control device 1 can determine a more appropriate supply amount of ammonia for denitrification by using the load (current load L2) when burning nitrogen-free fuel as one of the parameters for determining the supply amount of ammonia for denitrification (second preceding command value CV2).

[0084] In the illustrated embodiment, the second calculation unit 23 includes a concentration conversion coefficient calculation unit 231 and a second prior command value calculation unit 232.

[0085] The concentration conversion coefficient calculation unit 231 is configured to calculate the conversion coefficient CF21 for future NOx concentration C2 according to the current load L2 by applying the current load L2 to the correlation between the load (current load L2) and the conversion coefficient CF21 for future NOx concentration C2. The conversion coefficient CF21 is a coefficient for compensating for the increase in future NOx concentration C2 that corresponds to an increase in the current load L2. The second correlation described above includes the correlation between the current load L2 and the conversion coefficient CF21 for future NOx concentration C2.

[0086] The second advance command value calculation unit 232 is configured to calculate the second advance command value CV2 by multiplying the future emission GE2, the future NOx concentration C2, and the conversion coefficient CF21 of the future NOx concentration C2 calculated in the concentration conversion coefficient calculation unit 231.

[0087] The second calculation unit 23 may be configured to calculate the second preceding command value CV2 corresponding to the future emission GE2, future NOx concentration C2, and current load L2 by applying the future emission GE2 estimated in the second estimation unit 21, the future NOx concentration C2 predicted in the second prediction unit 22, and the current load L2 to the correlation between the future emission GE2, future NOx concentration C2, current load L2, and second preceding command value CV2.

[0088] (Second Ratio Calculation Unit, Second Correction Unit) In some embodiments of the denitrification control device 1, as shown in Figure 4, a second ratio calculation unit 24 and a second correction unit 25 are included. The second ratio calculation unit 24 is configured to calculate the ratio of NO2 to total NOx in the exhaust gas based on the load (current load L2). The second correction unit 25 is configured to correct the second preceding command value CV2 calculated in the second calculation unit 23 based on the NO2 ratio calculated in the second ratio calculation unit 24. The second ratio calculation unit 24 is configured to acquire the current load L2.

[0089] In the illustrated embodiment, the second ratio calculation unit 24 is configured to calculate the conversion coefficient CF22 for the ratio of NO2 according to the current load L2 by applying the current load L2 to the correlation between the load (current load L2) and the conversion coefficient CF22 for the ratio of NO2. The conversion coefficient CF22 is a coefficient for compensating for the decrease in denitrification efficiency in the denitrification device 4 in response to an increase in the current load L2, and is a coefficient for correcting the second pre-command value CV2. The second correction unit 25 corrects the second pre-command value CV2 by multiplying the second pre-command value CV2 calculated in the second calculation unit 23 by the conversion coefficient CF22 for the ratio of NO2 calculated in the second ratio calculation unit 24.

[0090] The ratio of NO2 to total NOx in the exhaust gas may change depending on the load. When the ratio of NO2 to total NOx in the exhaust gas is high, the denitrification efficiency of the denitrification device 4 may decrease compared to when the ratio of NO2 is low. For this reason, when the ratio of NO2 to total NOx in the exhaust gas is high, it is preferable to increase the amount of ammonia supplied to the denitrification device 4. The denitrification control device 1 can determine a more appropriate amount of ammonia supplied to denitrification by performing a correction in the second correction unit 25 to increase or decrease the second preceding command value CV2 according to the ratio of NO2.

[0091] (Second Subtraction Amount Calculation Unit) In some embodiments of the denitrification control device 1, as shown in Figure 4, a second subtraction amount calculation unit 26 is provided. The second subtraction amount calculation unit 26 is configured to calculate a subtraction amount SU2 relative to the second preceding command value CV2 calculated in the second calculation unit 23 by feedback control based on the deviation ΔV21 between the measured value MV21 and the set value SV21 of the unreacted ammonia concentration in the exhaust gas downstream of the denitrification device 4. The second subtraction amount calculation unit 26 is configured to acquire the measured value MV21 and the set value SV21 of the unreacted ammonia concentration.

[0092] The measured value MV21 of the unreacted ammonia concentration may be the value measured by the ammonia concentration meter 92. The second subtraction amount calculation unit 26 may obtain the measured value MV21 from the ammonia concentration meter 92 or from the storage device 103. The second subtraction amount calculation unit 26 may obtain the set value SV21 from the storage device 103.

[0093] In the illustrated embodiment, the second subtraction amount calculation unit 26 includes a deviation calculation unit 261 for calculating the deviation ΔV21 between the measured value MV21 and the set value SV21, and a feedback control unit (PID control unit) 262 for calculating the subtraction amount SU2 to the second preceding command value CV2 calculated in the second calculation unit 23 by feedback control based on the deviation ΔV21 calculated in the deviation calculation unit 261. The feedback control unit 262 may be provided with an output limit so that the subtraction amount SU2 having a negative value does not output a value below the lower limit threshold TL2, so that the second preceding command value CV2 (amount of ammonia supplied for denitrification) does not become excessively small due to the subtraction amount SU2.

[0094] The denitrification control device 1 may use the second lead command value CV2, obtained by adding the subtraction amount SU2, as the amount of ammonia for denitrification to be supplied to the denitrification device 4. In the illustrated embodiment, the denitrification control device 1 includes a second feedback correction unit 28, which is an adder that adds at least one of the subtraction amount SU2 calculated in the second subtraction amount calculation unit 26 or the increase / decrease amount AS2 calculated in the second increase / decrease amount calculation unit 27 to the second lead command value CV2. In the embodiment shown in Figure 4, the second feedback correction unit 28 adds the subtraction amount SU2 and the increase / decrease amount AS2 to the second lead command value CV2 after correction in the second correction unit 25.

[0095] The denitrification control device 1, which includes a second subtraction amount calculation unit 26, can determine the amount of ammonia for denitrification that can reduce the unreacted ammonia concentration in the exhaust gas downstream of the denitrification device 4 by using feedback control with the measured value MV21 of the unreacted ammonia concentration in the exhaust gas downstream of the denitrification device 4.

[0096] In some embodiments of the denitrification control device 1, as shown in Figure 4, a second increase / decrease amount calculation unit 27 is included. The second increase / decrease amount calculation unit 27 is configured to calculate an increase / decrease amount AS2 relative to the second preceding command value CV2 calculated in the second calculation unit 23 by feedback control based on the deviation ΔV22 between the measured value MV22 and the set value SV22 of the NOx concentration in the exhaust gas downstream of the denitrification device 4. The second increase / decrease amount calculation unit 27 is configured to acquire the measured value MV22 and the set value SV22 of the NOx concentration.

[0097] The measured value MV22 of the NOx concentration may be the value measured by the NOx concentration measuring instrument 93. The second increase / decrease calculation unit 27 may obtain the measured value MV22 from the NOx concentration measuring instrument 93 or from the storage device 103. The second increase / decrease calculation unit 27 may also obtain the set value SV22 from the storage device 103.

[0098] In the illustrated embodiment, the second increase / decrease amount calculation unit 27 includes a deviation calculation unit 271 for calculating the deviation ΔV22 between the measured value MV22 and the set value SV22, and a feedback control unit (PID control unit) 272 for calculating the increase / decrease amount AS2 relative to the second preceding command value CV2 calculated in the second calculation unit 23 by feedback control based on the deviation ΔV22 calculated in the deviation calculation unit 271.

[0099] The denitrification control device 1 may use a second pre-command value CV2, obtained by adding the increase / decrease amount AS2, as the amount of ammonia to be supplied to the denitrification device 4.

[0100] The denitrification control device 1, which includes a second increase / decrease calculation unit 27, can determine the amount of ammonia for denitrification that can reduce the NOx concentration in the exhaust gas downstream of the denitrification device 4 by using feedback control with the measured value MV22 of the NOx concentration in the exhaust gas downstream of the denitrification device 4.

[0101] In some embodiments, the nitrogen-free fuel mentioned above is natural gas. The denitrification control device 1 can suppress delays in controlling the amount of ammonia supplied to the denitrification device 4, regardless of whether ammonia fuel, natural gas, or both ammonia fuel and natural gas are supplied to the combustion device 3. Furthermore, the denitrification control device 1 can suppress delays in controlling the amount of ammonia supplied to the denitrification device 4 when switching the fuel supplied to the combustion device 3.

[0102] In some embodiments of the denitrification control device 1, as shown in Figure 4, a supply amount calculation unit 19(10) is provided. The supply amount calculation unit 19(10) is configured to calculate the supply amount SCV of denitrification ammonia to be supplied to the denitrification device 4 by a linear combination of a first supply amount command value SCV1 of denitrification ammonia determined based on a first precedent command value CV1, and a second supply amount command value SCV2 of denitrification ammonia determined based on a second precedent command value CV2, according to the ratio of the supply amounts of ammonia fuel and nitrogen-free fuel to the combustion device 3.

[0103] In the embodiment shown in Figure 4, the supply amount calculation unit 19 includes a second ratio calculation unit 190 configured to calculate the ratio (percentage) of the current fuel supply amount FS2 to the sum of the current fuel supply amount FS1 and the current fuel supply amount FS2, and a first ratio calculation unit 191 configured to calculate the ratio (percentage) of the current fuel supply amount FS1 to the sum of the current fuel supply amount FS1 and the current fuel supply amount FS2. The first ratio calculation unit 191 may calculate the ratio of the current fuel supply amount FS1 using the ratio of the current fuel supply amount FS2 calculated by the second ratio calculation unit 190 (illustrated example). The second ratio calculation unit 190 may also calculate the ratio of the current fuel supply amount FS2 using the ratio of the current fuel supply amount FS1 calculated by the first ratio calculation unit 191.

[0104] The supply amount calculation unit 19 includes a first ratio multiplier 192 configured to multiply the ratio of the current fuel supply amount FS1 calculated in the first ratio calculation unit 191 by the first supply amount command value SCV1; a second ratio multiplier 193 configured to multiply the ratio of the current fuel supply amount FS2 calculated in the second ratio calculation unit 190 by the second supply amount command value SCV2; and an adder 194 configured to calculate the supply amount SCV of ammonia for denitrification to be supplied to the denitrification device 4 by adding the output of the first ratio multiplier 192 and the output of the second ratio multiplier 193.

[0105] The denitrification control device 1 can determine the supply amount SCV of ammonia for denitrification to the denitrification device 4 from the first preceding command value CV1 and the second preceding command value CV2 when the combustion device 3 burns both ammonia fuel and nitrogen-free fuel. Therefore, even when the combustion device 3 burns both ammonia fuel and nitrogen-free fuel, the denitrification control device 1 can suppress delays in controlling the supply amount SCV of ammonia for denitrification to the denitrification device 4. Such a denitrification control device 1 can also suppress delays in controlling the supply amount SCV of ammonia for denitrification to the denitrification device 4 when the fuel supplied to the combustion device 3 is switched from ammonia fuel or nitrogen-free fuel to the other during the operation of the combustion device 3.

[0106] Figure 5 is a schematic diagram illustrating the configuration of a denitrification system 100 comprising a denitrification control device 1, a combustion device 3, and a denitrification device 4 according to one embodiment of the present disclosure. In some embodiments described above, the case in which the combustion device 3 is a gas turbine combustor was described, but the combustion device 3 may be a boiler (see Figure 5). The boiler may be configured to operate by switching between ammonia fuel and nitrogen-free fuel, or it may be a co-firing boiler that burns both ammonia fuel and nitrogen-free fuel together.

[0107] In the embodiment shown in Figure 5, the boiler furnace 35 corresponds to the combustor 30 of a gas turbine, and an ammonia fuel line 6, a nitrogen-free fuel line 7, and an intake line 8 are connected to the boiler furnace 35. A flue 94 for discharging exhaust gas from the boiler furnace 35 constitutes part of the exhaust gas line 9, and a denitrification device 4 is provided in the flue 94. The ammonia supply device 5 for denitrification is configured to supply ammonia for denitrification to the denitrification device 4.

[0108] In this specification, expressions describing relative or absolute arrangements such as "in a certain direction," "along a certain direction," "parallel," "orthogonal," "center," "concentric," or "coaxial" shall not only describe such arrangements strictly, but also describe states of relative displacement with tolerances or angles or distances sufficient to achieve the same function. For example, expressions describing things being in an equal state such as "identical," "equal," and "homogeneous" shall not only describe states of being strictly equal, but also describe states where tolerances or differences exist to the extent that the same function is achieved. Furthermore, in this specification, expressions describing shapes such as quadrilaterals or cylindrical shapes shall not only describe geometrically precise quadrilaterals or cylindrical shapes, but also describe shapes including concave and concave parts, chamfered parts, etc., to the extent that the same effect is achieved. In addition, in this specification, expressions such as "equipment," "includes," or "possesses" a component are not exclusive expressions that exclude the existence of other components.

[0109] This disclosure is not limited to the embodiments described above, but also includes modified forms of the embodiments described above, as well as forms that combine these forms as appropriate.

[0110] The contents described in some of the embodiments above can be understood, for example, as follows:

[0111] [1] A denitrification control device (1) according to at least one embodiment of the present disclosure is a device for controlling a denitrification device (4) that denitrifies exhaust gas generated by the combustion of ammonia fuel in a combustion device (3), and comprises: a first estimation unit (11) for estimating the flow rate of the exhaust gas discharged from the combustion device (3) based on the amount of intake air supplied to the combustion device (3); a first prediction unit (12) for predicting the NOx concentration of the exhaust gas based on the amount of ammonia fuel supplied to the combustion device (3); and a first calculation unit (13) for calculating a first advance command value (CV1) indicating the amount of ammonia for denitrification supplied to the denitrification device (4) during the combustion of the ammonia fuel, based on the flow rate of the exhaust gas estimated by the first estimation unit (11) and the NOx concentration of the exhaust gas predicted by the first prediction unit (12).

[0112] According to the configuration described in [1] above, the denitrification control device (1) can predict the NOx concentration of the exhaust gas generated when the supplied amount of ammonia fuel is burned in the combustion device (3), based on the relationship between the amount of ammonia fuel supplied to the combustion device (3) and the NOx concentration of the exhaust gas, which has been prepared in advance. The denitrification control device (1) can determine the amount of ammonia for denitrification supplied to the denitrification device (4) when the exhaust gas generated during combustion in the combustion device (3) is introduced into the denitrification device (4), based on parameters that can be obtained during combustion in the combustion device (3) (amount of intake air supplied, amount of ammonia fuel supplied). Therefore, the denitrification control device (1) can suppress delays in controlling the amount of ammonia for denitrification supplied to the denitrification device (4).

[0113] [2] In some embodiments, the denitrification control device (1) described in [1] above, wherein the first calculation unit (13) is configured to calculate the first advance command value (CV1) based on the flow rate of the exhaust gas estimated by the first estimation unit (11), the NOx concentration of the exhaust gas predicted by the first prediction unit (12), and the load of the combustion device (3).

[0114] According to the configuration described in [2] above, the NOx concentration of the exhaust gas may differ depending on the type of fuel used in the combustion device (3) and the load on the combustion device (3). The load on the combustion device (3) is a parameter that can be obtained when the combustion device (3) is burning. The denitrification control device (1) can determine a more appropriate amount of ammonia to supply for denitrification by using the load on the combustion device (3) when burning ammonia fuel as one of the parameters for determining the amount of ammonia to supply for denitrification.

[0115] [3] In some embodiments, the denitrification control device (1) described in [1] or [2] above comprises: a first ratio calculation unit (14) for calculating the ratio of NO2 to total NOx in the exhaust gas based on the load of the combustion device (3); and a first correction unit (15) for correcting the first advance command value (CV1) calculated in the first calculation unit (13) based on the ratio of NO2 calculated in the first ratio calculation unit (14).

[0116] According to the configuration of [3] above, when the ratio of NO2 to total NOx in the exhaust gas is high, the denitrification efficiency in the denitrification device (4) may decrease compared to when the ratio of NO2 is low. Therefore, it is preferable to increase the amount of ammonia supplied to the denitrification device (4). The denitrification control device (1) can determine a more appropriate amount of ammonia supplied to denitrification by performing a correction in the first correction unit (15) to increase or decrease the first advance command value (CV1) according to the ratio of NO2.

[0117] [4] In some embodiments, the denitrification control device (1) described in any of [1] to [3] above is further comprising a first subtraction amount calculation unit (16) for calculating a subtraction amount from the first preceding command value (CV1) calculated in the first calculation unit (13) by feedback control based on the deviation between the measured value and a set value of the unreacted ammonia concentration in the exhaust gas downstream of the denitrification device (4).

[0118] According to the configuration described in [4] above, the denitrification control device (1) can determine the amount of ammonia to be supplied for denitrification that can reduce the unreacted ammonia concentration in the exhaust gas downstream of the denitrification device (4) by using feedback control that utilizes the measured value of the unreacted ammonia concentration in the exhaust gas downstream of the denitrification device (4).

[0119] [5] In some embodiments, the denitrification control device (1) described in any of [1] to [4] above is further comprising a first increase / decrease calculation unit (17) for calculating an increase or decrease in the first preceding command value (CV1) calculated in the first calculation unit (13) by feedback control based on the deviation between the measured value and the set value of the NOx concentration in the exhaust gas downstream of the denitrification device (4).

[0120] According to the configuration described in [5] above, the denitrification control device (1) can determine the amount of ammonia for denitrification that can reduce the NOx concentration in the exhaust gas downstream of the denitrification device (4) by using feedback control that utilizes the measured value of the NOx concentration in the exhaust gas downstream of the denitrification device (4).

[0121] [6] In some embodiments, a denitrification control device (1) according to any of [1] to [5] above, wherein the combustion device (3) is configured to burn nitrogen-free fuel other than the ammonia fuel, and comprises: a second estimation unit (21) for estimating the flow rate of the exhaust gas discharged from the combustion device (3) based on the amount of intake air supplied to the combustion device (3); a second prediction unit (22) for predicting the NOx concentration of the exhaust gas based on the amount of nitrogen-free fuel supplied to the combustion device (3); and a second calculation unit (23) for calculating a second advance command value (CV2) indicating the amount of ammonia for denitrification supplied to the denitrification device (4) when the nitrogen-free fuel is burned, based on the flow rate of the exhaust gas estimated by the second estimation unit (21) and the NOx concentration of the exhaust gas predicted by the second prediction unit (22).

[0122] According to the configuration described in [6] above, the denitrification control device (1) can predict the NOx concentration of the exhaust gas generated when the supplied amount of nitrogen-free fuel is burned in the combustion device (3), based on the relationship between the amount of nitrogen-free fuel supplied to the combustion device (3) and the NOx concentration of the exhaust gas, which has been prepared in advance. The denitrification control device (1) can determine the amount of ammonia for denitrification supplied to the denitrification device (4) when the exhaust gas generated during combustion in the combustion device (3) is introduced into the denitrification device (4), based on parameters that can be obtained during combustion in the combustion device (3) (amount of intake air supplied, amount of nitrogen-free fuel supplied). Therefore, even when a nitrogen-free fuel other than ammonia fuel is burned in the combustion device (3), the denitrification control device (1) can suppress delays in controlling the amount of ammonia for denitrification supplied to the denitrification device (4).

[0123] [7] In some embodiments, the denitrification control device (1) described in [6] above includes a supply amount calculation unit (10) for calculating the supply amount (SCV) of denitrification ammonia to be supplied to the denitrification device (4) by a linear combination of a first supply amount command value (SCV1) of denitrification ammonia determined based on a first precedent value (CV1) and a second supply amount command value (SCV2) of denitrification ammonia determined based on a second precedent value (CV2), according to the ratio of the supply amounts of ammonia fuel and nitrogen-free fuel to the combustion device (3).

[0124] According to the configuration described in [7] above, the denitrification control device (1) can determine the supply amount of ammonia for denitrification (SCV) to the denitrification device (4) from the first preceding command value (SCV1) and the second preceding command value (SCV2) when the combustion device (3) burns both ammonia fuel and nitrogen-free fuel. Therefore, even when the combustion device (3) burns both ammonia fuel and nitrogen-free fuel, the denitrification control device (1) can suppress delays in controlling the supply amount of ammonia for denitrification (SCV) to the denitrification device (4). Such a denitrification control device (1) can also suppress delays in controlling the supply amount of ammonia for denitrification (SCV) to the denitrification device (4) when the fuel supplied to the combustion device (3) is switched from ammonia fuel or nitrogen-free fuel to the other during the operation of the combustion device (3).

[0125] [8] In some embodiments, the denitrification control device (1) described in [6] or [7] above, wherein the second calculation unit (23) is configured to calculate the second advance command value (CV2) based on the flow rate of the exhaust gas estimated by the second estimation unit (21), the NOx concentration of the exhaust gas predicted by the second prediction unit (22), and the load of the combustion device (3).

[0126] According to the configuration described in [8] above, the NOx concentration of the exhaust gas may differ depending on the type of fuel used in the combustion device (3) and the load on the combustion device (3). The load on the combustion device (3) is a parameter that can be obtained when the combustion device (3) is burning. The denitrification control device (1) can determine a more appropriate amount of ammonia to supply for denitrification by using the load on the combustion device (3) when burning nitrogen-free fuel as one of the parameters for determining the amount of ammonia to supply for denitrification.

[0127] [9] In some embodiments, a denitrification control device (1) according to any one of [6] to [8] above, comprising: a second ratio calculation unit (24) for calculating the ratio of NO2 to total NOx in the exhaust gas based on the load of the combustion device (3); and a second correction unit (25) for correcting the second lead command value (CV2) calculated in the second calculation unit (23) based on the ratio of NO2 calculated in the second ratio calculation unit (24).

[0128] According to the configuration described in [9] above, when the ratio of NO2 to total NOx in the exhaust gas is high, the denitrification efficiency in the denitrification device (4) may decrease compared to when the ratio of NO2 is low. Therefore, it is preferable to increase the amount of ammonia supplied to the denitrification device (4). The denitrification control device (1) can determine a more appropriate amount of ammonia supplied to denitrification by performing a correction in the second correction unit (25) to increase or decrease the second lead command value (CV2) according to the ratio of NO2.

[0129]

[10] In some embodiments, the denitrification control device (1) is as described in any of [6] to [9] above, wherein the nitrogen-free fuel is natural gas.

[0130] According to the configuration described in

[10] above, the denitrification control device (1) can suppress delays in controlling the amount of ammonia supplied to the denitrification device (4), regardless of whether ammonia fuel, natural gas, or both ammonia fuel and natural gas are supplied to the combustion device (3). Furthermore, the denitrification control device (1) can suppress delays in controlling the amount of ammonia supplied to the denitrification device (4) when switching the fuel supplied to the combustion device (3).

[0131] 1 Denitrification control device 3 Combustion device 4 Denitrification device 5 Ammonia supply device for denitrification 10 Supply amount calculation unit 11 First estimation unit 12 First prediction unit 13 First calculation unit 14 First ratio calculation unit 15 First correction unit 16 First subtraction amount calculation unit 17 First increase / decrease amount calculation unit 18 First feedback correction unit 21 Second estimation unit 22 Second prediction unit 23 Second calculation unit 24 Second ratio calculation unit 25 Second correction unit 26 Second subtraction amount calculation unit 27 Second increase / decrease amount calculation unit 28 Second feedback correction unit 100 Denitrification system

Claims

1. A denitrification control device for controlling a denitrification device that denitrifies exhaust gas generated by the combustion of ammonia fuel in a combustion device, comprising: a first estimation unit for estimating the flow rate of the exhaust gas discharged from the combustion device based on the amount of intake air supplied to the combustion device; a first prediction unit for predicting the NOx concentration of the exhaust gas based on the amount of ammonia fuel supplied to the combustion device; and a first calculation unit for calculating a first advance command value indicating the amount of ammonia for denitrification supplied to the denitrification device during the combustion of the ammonia fuel, based on the flow rate of the exhaust gas estimated by the first estimation unit and the NOx concentration of the exhaust gas predicted by the first prediction unit.

2. The denitrification control device according to claim 1, wherein the first calculation unit is configured to calculate the first advance command value based on the exhaust gas flow rate estimated by the first estimation unit, the NOx concentration of the exhaust gas predicted by the first prediction unit, and the load of the combustion device.

3. A denitrification control device according to claim 1 or 2, comprising: a first ratio calculation unit for calculating the ratio of NO2 to total NOx in the exhaust gas based on the load of the combustion device; and a first correction unit for correcting the first preceding command value calculated in the first calculation unit based on the ratio of NO2 calculated in the first ratio calculation unit.

4. The denitrification control device according to claim 1 or 2, further comprising a first subtraction amount calculation unit for calculating a subtraction amount from the first preceding command value calculated in the first calculation unit, based on feedback control based on the deviation between the measured value and a set value of the unreacted ammonia concentration in the exhaust gas downstream of the denitrification device.

5. The denitrification control device according to claim 1 or 2, further comprising a first increase / decrease calculation unit for calculating an increase / decrease amount relative to the first preceding command value calculated in the first calculation unit, by feedback control based on the deviation between the measured value and a set value of the NOx concentration in the exhaust gas downstream of the denitrification device.

6. The denitrification control device according to claim 1 or 2, wherein the combustion device is configured to burn a nitrogen-free fuel other than the ammonia fuel, and comprises: a second estimation unit for estimating the flow rate of the exhaust gas discharged from the combustion device based on the amount of intake air supplied to the combustion device; a second prediction unit for predicting the NOx concentration of the exhaust gas (introduced to the denitrification device) based on the amount of the nitrogen-free fuel supplied to the combustion device; and a second calculation unit for calculating a second advance command value indicating the amount of ammonia for denitrification supplied to the denitrification device during combustion of the nitrogen-free fuel, based on the flow rate of the exhaust gas estimated by the second estimation unit and the NOx concentration of the exhaust gas predicted by the second prediction unit.

7. The denitrification control device according to claim 6, further comprising a supply amount calculation unit for calculating the amount of denitrification ammonia to be supplied to the denitrification device by a linear combination of a first supply amount command value for denitrification ammonia determined based on the first prior command value and a second supply amount command value for denitrification ammonia determined based on the second prior command value, according to the ratio of the supply amounts of ammonia fuel and nitrogen-free fuel to the combustion device.

8. The denitrification control device according to claim 6, wherein the second calculation unit is configured to calculate the second advance command value based on the exhaust gas flow rate estimated by the second estimation unit, the NOx concentration of the exhaust gas predicted by the second prediction unit, and the load of the combustion device.

9. A denitrification control device according to claim 6, comprising: a second ratio calculation unit for calculating the ratio of NO2 to total NOx in the exhaust gas based on the load of the combustion device; and a second correction unit for correcting the second preceding command value calculated in the second calculation unit based on the ratio of NO2 calculated in the second ratio calculation unit.

10. The denitrification control device according to claim 6, wherein the nitrogen-free fuel is natural gas.

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