Combustion system and control method

Abstract

Suppresses the decline in energy efficiency. [Solution] The combustion system 1 comprises a combustor 12 to which ammonia is supplied, an intake passage 101 connected to the combustor 12, an exhaust passage 102 connected to the combustor 12, a recirculation passage 108 connecting the exhaust passage 102 and the intake passage 101, and a control device 400 that controls the temperature of the exhaust gas circulating from the exhaust passage 102 to the intake passage 101 via the recirculation passage 108.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a combustion system and a control method.

BACKGROUND ART

[0002] As a combustion system for burning fuel in a combustor, a gas turbine system or the like is used. In combustion systems such as gas turbine systems, for example, as disclosed in Patent Document 1, ammonia may be used as fuel. By using ammonia as fuel, carbon dioxide emissions are suppressed.

PRIOR ART DOCUMENTS

PATENT DOCUMENTS

[0003]

PATENT DOCUMENT 1

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

[0004] Here, when ammonia is used as fuel, nitrogen oxides (hereinafter also referred to as NOx) are likely to be generated due to the nitrogen atoms contained in ammonia. During partial load operation in which the combustion system is operated at a load smaller than that during steady operation, in addition to an increase in NOx emissions, energy efficiency, which is the generation efficiency of energy obtained from combustion in the combustor, may decrease.

[0005] An object of the present disclosure is to provide a combustion system and a control method capable of suppressing a decrease in energy efficiency.

MEANS FOR SOLVING THE PROBLEMS

[0006] To solve the above problems, the combustion system of the present disclosure comprises a combustor to which ammonia is supplied, an intake passage connected to the combustor, an exhaust passage connected to the combustor, a recirculation passage connecting the exhaust passage and the intake passage, and a control device for controlling the temperature of exhaust gas circulating from the exhaust passage to the intake passage via the recirculation passage.

[0007] The control device may control the temperature based on the energy efficiency, which is the efficiency of energy generation obtained by combustion in the combustor.

[0008] The gas turbine includes a compressor provided in the intake passage and a turbine provided in the exhaust passage, and a generator connected to the gas turbine, and the energy efficiency may be the power generation efficiency of the combustion system.

[0009] The recirculation channel is equipped with a heat exchanger through which the refrigerant channel passes, and the control device may control the temperature by controlling the flow rate of the refrigerant flowing through the refrigerant channel.

[0010] A denitrification device may be provided in the exhaust flow path.

[0011] A demister may be provided at the connection point between the recirculation passage and the intake passage.

[0012] The control device may control the flow rate of exhaust gas circulating from the exhaust passage to the intake passage via the recirculation passage based on parameters relating to nitrogen oxide emissions.

[0013] In addition to ammonia, the combustor is supplied with a nitrogen-free fuel, and the control device may control the ratio of the amount of ammonia supplied to the combustor to the amount of nitrogen-free fuel supplied to the combustor based on a parameter relating to nitrogen oxide emissions.

[0014] The combustor is supplied with ammonia in both liquid and gaseous forms, and the control device may control the ratio of the amount of liquid ammonia supplied to the combustor to the amount of gaseous ammonia supplied to the combustor based on a parameter relating to nitrogen oxide emissions.

[0015] To solve the above problems, the control method of the present disclosure is a control method for a combustion system, the combustion system comprising a combustor to which ammonia is supplied, an intake passage connected to the combustor, an exhaust passage connected to the combustor, and a recirculation passage connecting the exhaust passage and the intake passage, wherein a control device controls the temperature of exhaust gas circulating from the exhaust passage to the intake passage via the recirculation passage. [Effects of the Invention]

[0016] According to this disclosure, the decrease in energy efficiency can be suppressed. [Brief explanation of the drawing]

[0017] [Figure 1] Figure 1 is a schematic diagram showing the configuration of a combustion system according to an embodiment of this disclosure. [Figure 2] Figure 2 is a flowchart showing an example of the flow of the first process performed by the control device according to the embodiment of this disclosure. [Figure 3] Figure 3 is a flowchart showing an example of the flow of the second process performed by the control device according to the embodiment of this disclosure. [Figure 4] Figure 4 is a flowchart showing an example of the flow of a third process performed by the control device according to the embodiment of this disclosure. [Figure 5] Figure 5 is a flowchart showing an example of the flow of the fourth process performed by the control device according to the embodiment of this disclosure. [Modes for carrying out the invention]

[0018] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. The dimensions, materials, and other specific numerical values shown in the embodiments are merely examples for facilitating understanding, and do not limit the present disclosure unless otherwise specified. Note that, in the present specification and the drawings, elements having substantially the same functions and configurations are denoted by the same reference numerals to omit redundant description, and elements not directly related to the present disclosure are omitted from the drawings.

[0019] Figure 1 is a schematic diagram showing the configuration of a combustion system 1 according to the present embodiment. The combustion system 1 is a gas turbine system corresponding to an example of a combustion system that generates energy by burning fuel. In particular, the combustion system 1 uses ammonia as fuel. Thereby, carbon dioxide emissions are suppressed.

[0020] As shown in Figure 1, the combustion system 1 includes a gas turbine 11, a combustor 12, a generator 13, a filter housing 14, an exhaust heat recovery boiler 15, a denitration device 16, an exhaust tower 17, a fan 18, a heat exchanger 19, a first damper 20, and a second damper 21.

[0021] Further, the combustion system 1 includes, as flow paths through which fluid flows, an intake flow path 101, an exhaust flow path 102, a liquid ammonia flow path 103, a gaseous ammonia flow path 104, a natural gas flow path 105, a water flow path 106, a reducing agent flow path 107, a recirculation flow path 108, and a refrigerant flow path 109.

[0022] Further, the combustion system 1 includes, as flow rate control valves that adjust the flow rate of the fluid flowing through the flow paths, a first flow rate control valve 201, a second flow rate control valve 202, a third flow rate control valve 203, a fourth flow rate control valve 204, and a fifth flow rate control valve 205.

[0023] Further, the combustion system 1 includes, as sensors, a first gas analyzer 301, a second gas analyzer 302, a third gas analyzer 303, a first thermometer 304, and a second thermometer 305.

[0024] Furthermore, the combustion system 1 includes a control device 400 that controls each device within the combustion system 1.

[0025] The gas turbine 11 includes a compressor 11a and a turbine 11b. The compressor 11a and turbine 11b rotate as a single unit. The compressor 11a and turbine 11b are connected to each other by a shaft.

[0026] The compressor 11a is located in the intake passage 101, which is connected to the combustor 12. Air supplied to the combustor 12 flows through the intake passage 101. As will be described later, exhaust gas can also be sent from the recirculation passage 108 to the intake passage 101, and this exhaust gas can be supplied to the combustor 12 in addition to the air.

[0027] The filter housing 14 is located upstream of the compressor 11a in the intake air passage 101. The filter housing 14 is a housing that houses a filter for removing substances from the gas. The filter housing 14 is equipped with an air filter 14a and a demister 14b as such filters. The air filter 14a removes foreign matter from the air that is taken into the intake air passage 101 and flows through the intake air passage 101. The demister 14b will be described later. The air that has passed through the air filter 14a is sent to the combustor 12. The compressor 11a compresses the air and discharges it downstream. The filter housing 14 may also be equipped with other components not shown (for example, a heat exchanger).

[0028] The turbine 11b is located in the exhaust passage 102, which is connected to the combustor 12. Exhaust gas discharged from the combustor 12 flows through the exhaust passage 102. The exhaust gas discharged from the combustor 12 passes through the turbine 11b and is sent to the downstream side of the exhaust passage 102 from the turbine 11b. The turbine 11b generates rotational power by being rotated by the exhaust gas.

[0029] The generator 13 is connected to the gas turbine 11 (specifically, the compressor 11a and the turbine 11b). The rotational power generated by the gas turbine 11 is used to generate electricity with the generator 13.

[0030] Compressed air from the compressor 11a is supplied to the combustor 12 through the intake passage 101, and fuel is supplied through the liquid ammonia passage 103, the gaseous ammonia passage 104, and the natural gas passage 105. As will be described later, the type of fuel supplied to the combustor 12 and the amount of each fuel supplied to the combustor 12 are controlled by the control device 400 according to the situation.

[0031] The liquid ammonia flow path 103 is a flow path that supplies liquid ammonia to the combustor 12. The liquid ammonia flow path 103 connects an ammonia supply source (not shown) to the combustor 12. Liquid ammonia supplied from the ammonia supply source flows through the liquid ammonia flow path 103. For example, liquid ammonia is stored in the ammonia supply source. Then, liquid ammonia is supplied from the ammonia supply source to the liquid ammonia flow path 103.

[0032] A first flow control valve 201 is provided in the liquid ammonia flow path 103. The first flow control valve 201 adjusts the flow rate (i.e., the amount supplied) of liquid ammonia that passes through the liquid ammonia flow path 103 and is supplied to the combustor 12. Specifically, the amount of liquid ammonia supplied to the combustor 12 is adjusted by adjusting the opening degree of the first flow control valve 201.

[0033] The gaseous ammonia flow path 104 is a flow path that supplies gaseous ammonia to the combustor 12. The gaseous ammonia flow path 104 connects an ammonia supply source (not shown) to the combustor 12. Gaseous ammonia supplied from the ammonia supply source flows through the gaseous ammonia flow path 104. For example, liquid ammonia is stored in the ammonia supply source. The liquid ammonia supplied from the ammonia supply source is vaporized by a vaporizer, and the gaseous ammonia thus produced is sent to the gaseous ammonia flow path 104.

[0034] A second flow control valve 202 is provided in the gaseous ammonia flow path 104. The second flow control valve 202 adjusts the flow rate (i.e., the amount supplied) of gaseous ammonia supplied to the combustor 12 through the gaseous ammonia flow path 104. Specifically, the amount of gaseous ammonia supplied to the combustor 12 is adjusted by adjusting the opening degree of the second flow control valve 202.

[0035] The natural gas flow path 105 is a flow path that supplies natural gas to the combustor 12. Natural gas is an example of a fuel that does not contain nitrogen atoms. However, the fuel that does not contain nitrogen atoms supplied to the combustor 12 may be a fuel other than natural gas. For example, the fuel that does not contain nitrogen atoms supplied to the combustor 12 may be natural gas, hydrogen, kerosene, or a combination thereof. The natural gas flow path 105 connects the combustor 12 to a natural gas supply source (not shown). Natural gas sent from the natural gas supply source flows through the natural gas flow path 105.

[0036] A third flow control valve 203 is provided in the natural gas flow path 105. The third flow control valve 203 adjusts the flow rate (i.e., the amount of natural gas supplied) of the natural gas that passes through the natural gas flow path 105 and is supplied to the combustor 12. Specifically, the amount of natural gas supplied to the combustor 12 is adjusted by adjusting the opening degree of the third flow control valve 203.

[0037] The waste heat recovery boiler 15 is located downstream of the turbine 11b in the exhaust passage 102. The waste heat recovery boiler 15 is equipped with a water passage 106. The water passage 106 is a passage through which water flows. The water flowing through the water passage 106 is heated by the exhaust gas flowing through the exhaust passage 102 and vaporizes into a gas (i.e., steam). For example, the water passage 106 is connected to a steam turbine (not shown). The steam generated in the waste heat recovery boiler 15 is then sent to the steam turbine. As described above, the outlet side of the water passage 106 of the waste heat recovery boiler 15 corresponds to the steam passage through which steam flows. The steam then rotates the steam turbine, generating rotational power. For example, the rotational power generated by the steam turbine is used for power generation.

[0038] The denitrification device 16 is installed downstream of the turbine 11b in the exhaust flow path 102. For example, the denitrification device 16 is installed inside the waste heat recovery boiler 15. However, the denitrification device 16 only needs to be installed in the exhaust flow path 102 and may be installed outside the waste heat recovery boiler 15.

[0039] The reducing agent channel 107 is a channel for supplying a reducing agent to the denitrification device 16. The reducing agent is, for example, gaseous ammonia, liquid ammonia, aqueous ammonia, aqueous urea, etc. However, the reducing agent is not particularly limited as long as it can cause the denitrification reaction described later. The reducing agent channel 107 connects a reducing agent supply source (not shown) to the denitrification device 16. The reducing agent supplied from the reducing agent supply source flows through the reducing agent channel 107.

[0040] A fourth flow control valve 204 is provided in the reducing agent flow path 107. The fourth flow control valve 204 adjusts the flow rate (i.e., the amount supplied) of the reducing agent that passes through the reducing agent flow path 107 and is supplied to the denitrification device 16. Specifically, the amount of reducing agent supplied to the denitrification device 16 is adjusted by adjusting the opening degree of the fourth flow control valve 204.

[0041] As described above, a reducing agent is supplied to the denitrification unit 16. The denitrification unit 16 reacts NOx in the exhaust gas flowing through the exhaust passage 102 with the reducing agent to decompose it into nitrogen and water. This reaction is also called a denitrification reaction.

[0042] The exhaust tower 17 is located downstream of the heat recovery boiler 15 in the exhaust flow path 102. The exhaust gas discharged from the combustor 12 passes through the turbine 11b and the heat recovery boiler 15, is sent to the exhaust tower 17, and is discharged from the exhaust tower 17. As will be described later, a portion of the exhaust gas discharged from the exhaust tower 17 is sent to the recirculation flow path 108.

[0043] The recirculation passage 108 is a passage for circulating exhaust gas from the exhaust passage 102 to the intake passage 101. This technology for recirculating exhaust gas is also called EGR (Exhaust Gas Recirculation). The recirculation passage 108 is also called the EGR passage. In this disclosure, the exhaust gas that circulates from the exhaust passage 102 to the intake passage 101 via the recirculation passage 108 is also referred to as the circulating gas. The recirculation passage 108 connects the exhaust passage 102 and the intake passage 101. Specifically, the recirculation passage 108 connects the exhaust passage 102 and the intake passage 101, bypassing the combustor 12.

[0044] In the example shown in Figure 1, the recirculation passage 108 connects the exhaust tower 17 and the filter housing 14. Hereafter, the side of the recirculation passage 108 that is on the exhaust tower 17 side relative to the filter housing 14 will be referred to as the upstream side, and the side of the recirculation passage 108 that is on the filter housing 14 side relative to the exhaust tower 17 will be referred to as the downstream side. However, the connection point between the recirculation passage 108 and the exhaust passage 102 may be other than the exhaust tower 17. Also, the connection point between the recirculation passage 108 and the intake passage 101 may be other than the filter housing 14.

[0045] Fan 18 is installed on the upstream side of the recirculation channel 108. Fan 18 pressurizes the circulating gas flowing through the recirculation channel 108 and sends it downstream.

[0046] The heat exchanger 19 is located downstream of the fan 18 in the recirculation channel 108. A refrigerant channel 109 passes through the heat exchanger 19. The refrigerant channel 109 is a channel through which the refrigerant flows. The refrigerant flowing through the refrigerant channel 109 is, for example, water. In the heat exchanger 19, heat exchange takes place between the circulating gas flowing through the recirculation channel 108 and the refrigerant flowing through the refrigerant channel 109.

[0047] A fifth flow control valve 205 is provided in the refrigerant flow path 109. The fifth flow control valve 205 adjusts the flow rate of refrigerant flowing through the refrigerant flow path 109. Specifically, the flow rate of refrigerant flowing through the refrigerant flow path 109 is adjusted by adjusting the opening degree of the fifth flow control valve 205.

[0048] The above describes an example where the refrigerant flowing through the refrigerant channel 109 is water. However, the refrigerant flowing through the refrigerant channel 109 may be something other than water. For example, the refrigerant flowing through the refrigerant channel 109 may be liquid ammonia. In this case, the liquid ammonia flowing through the refrigerant channel 109 may be heated by the circulating gas flowing through the recirculation channel 108 to the extent that it does not vaporize, and then supplied to the combustor 12 through the liquid ammonia channel 103. Alternatively, the liquid ammonia flowing through the refrigerant channel 109 may be heated by the circulating gas flowing through the recirculation channel 108, vaporize, and then supplied to the combustor 12 through the gaseous ammonia channel 104.

[0049] The first damper 20 is installed downstream of the heat exchanger 19 in the recirculation passage 108. The first damper 20 adjusts the flow rate of the fluid at the installation location, for example, by adjusting the cross-sectional area of ​​the passage at the installation location. Specifically, the first damper 20 is installed in the section that branches off from the recirculation passage 108 and communicates with the atmosphere. The first damper 20 can adjust the flow rate of the circulating gas discharged from the recirculation passage 108 to the atmosphere. In this way, the first damper 20 can adjust the flow rate of the circulating gas sent from the recirculation passage 108 to the intake passage 101. If the diameter of the passage at the installation location of the first damper 20 is small, a valve may be used instead of the first damper 20.

[0050] The second damper 21 is installed downstream of the first damper 20 in the recirculation passage 108. The second damper 21 adjusts the flow rate of the fluid at the installation location, for example, by adjusting the cross-sectional area of ​​the passage at the installation location. Specifically, the second damper 21 can adjust the flow rate of the circulating gas flowing through the recirculation passage 108. As a result, the second damper 21 can adjust the flow rate of the circulating gas sent from the recirculation passage 108 to the intake passage 101. If the diameter of the passage at the installation location of the second damper 21 is small, a valve may be used instead of the second damper 21.

[0051] As described above, a filter housing 14 is provided at the connection point between the recirculation passage 108 and the intake passage 101. A demister 14b is provided in the filter housing 14. The demister 14b removes moisture contained in the circulating gas sent from the recirculation passage 108 to the intake passage 101. The circulating gas sent from the recirculation passage 108 to the filter housing 14 is sent to the intake passage 101 after the moisture in the circulating gas has been removed by the demister 14b.

[0052] The first gas analyzer 301 is installed downstream of the filter housing 14 and upstream of the compressor 11a in the intake passage 101. The first gas analyzer 301 measures the concentration of each component in the gas in the intake passage 101 (specifically, at the installation location of the first gas analyzer 301). For example, the first gas analyzer 301 measures the concentration of oxygen in the intake passage 101.

[0053] The second gas analyzer 302 is installed in the exhaust passage 102 downstream of the turbine 11b and upstream of the waste heat recovery boiler 15. The second gas analyzer 302 measures the concentration of each component in the gas in the exhaust passage 102 (specifically, at the installation location of the second gas analyzer 302). For example, the second gas analyzer 302 measures the concentration of NOx and the concentration of oxygen in the exhaust passage 102.

[0054] The third gas analyzer 303 is installed inside the exhaust tower 17 or downstream of the exhaust tower 17 in the exhaust passage 102. The third gas analyzer 303 measures the concentration of each component in the gas in the exhaust passage 102 (specifically, at the installation location of the third gas analyzer 303). For example, the third gas analyzer 303 measures the concentration of NOx and the concentration of oxygen in the exhaust passage 102.

[0055] The first thermometer 304 is installed downstream of the second damper 21 in the recirculation channel 108. The first thermometer 304 measures the temperature of the gas in the recirculation channel 108 (specifically, at the location where the first thermometer 304 is installed).

[0056] The second thermometer 305 is installed in the intake air passage 101 downstream of the filter housing 14 and upstream of the compressor 11a. The second thermometer 305 measures the temperature of the gas in the intake air passage 101 (specifically, at the installation location of the second thermometer 305).

[0057] The control device 400 includes, for example, a processor 401 and a memory 402. The processor 401 includes, for example, a central processing unit (CPU). The memory 402 includes, for example, a ROM in which programs are stored and RAM as a work area. The functions of the control device 400 are realized, for example, by the execution of a program stored in the memory 402 by the processor 401.

[0058] The control device 400 controls each device within the combustion system 1. For example, the control device 400 can control the flow rate of the circulating gas by controlling the fan 18, the first damper 20, and the second damper 21. The control device 400 can also control the flow rate of each fluid by controlling the first flow control valve 201, the second flow control valve 202, the third flow control valve 203, the fourth flow control valve 204, and the fifth flow control valve 205. Furthermore, the control device 400 can acquire detection results from the first gas analyzer 301, the second gas analyzer 302, the third gas analyzer 303, the first thermometer 304, and the second thermometer 305.

[0059] As explained above, combustion system 1 uses ammonia as fuel. This suppresses carbon dioxide emissions. However, when ammonia is used as fuel, NOx is easily generated due to the presence of nitrogen atoms in ammonia. Furthermore, during partial load operation, where combustion system 1 is operated at a lower load than during steady-state operation, in addition to an increase in NOx emissions, the energy efficiency, which is the efficiency of energy generation obtained from the combustion of combustor 12, may decrease.

[0060] Therefore, in this embodiment, the above-mentioned problems can be solved by particularly devising the process related to the recirculation of the circulating gas from the exhaust passage 102 to the intake passage 101 using the recirculation passage 108. The first, second, third, and fourth processes performed by the control device 400 will be described below with reference to Figures 2 to 5.

[0061] For example, the control device 400 repeatedly executes the processing flow in Figure 2, the processing flow in Figure 3, the processing flow in Figure 4, and the processing flow in Figure 5 in sequence. Each processing flow may be repeated, for example, at a predetermined time interval. However, the control device 400 does not have to perform any part of the first, second, third, and fourth processes described below. For example, the control device 400 may perform only one type of process from the first, second, third, and fourth processes, or it may perform any multiple types of processes from the first, second, third, and fourth processes.

[0062] Figure 2 is a flowchart showing an example of the flow of the first processing performed by the control device 400. When the processing flow shown in Figure 2 starts, in step S101, the control device 400 acquires parameters related to the NOx emissions from the combustion system 1.

[0063] The parameters described above are specifically correlated with NOx emissions. Below, we will explain an example where the above parameters have a positive correlation with NOx emissions. In other words, we will explain an example where the above parameters increase as NOx emissions increase. However, the above parameters may also have a negative correlation with NOx emissions. In other words, the above parameters may decrease as NOx emissions increase.

[0064] The above parameters may, for example, be the NOx concentration in the exhaust flow path 102. For example, the control device 400 may acquire the NOx concentration detected by the second gas analyzer 302 or the NOx concentration detected by the third gas analyzer 303 as the above parameters.

[0065] The above parameter may be, for example, the oxygen concentration in the intake passage 101. For example, the control device 400 acquires the oxygen concentration detected by the first gas analyzer 301 as the above parameter.

[0066] The above parameters may be, for example, the oxygen concentration in the exhaust passage 102. For example, the control device 400 may acquire the oxygen concentration detected by the second gas analyzer 302 or the oxygen concentration detected by the third gas analyzer 303 as the above parameters.

[0067] The above parameter may be, for example, the amount of reducing agent supplied to the denitrification device 16. Here, the control device 400 controls the amount of reducing agent supplied to the denitrification device 16 so that the amount of NOx reduced in the denitrification device 16 becomes a predetermined value. Therefore, the control device 400 can determine the amount of reducing agent supplied to the denitrification device 16.

[0068] For example, the control device 400 obtains a value corresponding to the amount of NOx actually reduced in the denitrification device 16, which is obtained by subtracting the concentration of NOx detected by the second gas analyzer 302 from the concentration of NOx detected by the third gas analyzer 303. Then, if the amount of NOx actually reduced in the denitrification device 16 is less than a predetermined value, the control device 400 increases the amount of reducing agent supplied to the denitrification device 16 by increasing the opening of the fourth flow control valve 204. On the other hand, if the amount of NOx actually reduced in the denitrification device 16 is greater than a predetermined value, the control device 400 decreases the amount of reducing agent supplied to the denitrification device 16 by decreasing the opening of the fourth flow control valve 204. Thus, the control device 400 can obtain the amount of reducing agent supplied to the denitrification device 16 based on, for example, the opening of the fourth flow control valve 204.

[0069] The above parameter may, for example, be the output of the gas turbine 11. Here, the control device 400 controls the supply of fuel to the combustor 12 so that the output of the gas turbine 11 becomes the required value. Therefore, the control device 400 can determine the output of the gas turbine 11.

[0070] Following step S101, in step S102, the control device 400 determines whether the above parameter is greater than the target value.

[0071] The target values ​​for the above parameters are those that result in NOx emissions from combustion system 1 reaching the target emission level. The target emission level is a predetermined value for NOx emissions. Combustion system 1 is required to keep NOx emissions below the target emission level.

[0072] Specifically, target values ​​are set for each type of parameter mentioned above. For example, target values ​​are set separately for the NOx concentration in the exhaust passage 102, the oxygen concentration in the intake passage 101, the oxygen concentration in the exhaust passage 102, the amount of reducing agent supplied to the denitrification device 16, and the output of the gas turbine 11.

[0073] If the above parameters are greater than the target values, it corresponds to a situation where NOx emissions are greater than the target emissions. In the first treatment shown in Figure 2, as will be described later, NOx emissions are reduced by increasing the flow rate of the circulating gas in such cases.

[0074] For example, a NOx concentration in the exhaust flow path 102 being greater than the target value directly indicates that the NOx emissions are greater than the target emissions.

[0075] Furthermore, if the amount of oxygen supplied to the combustor 12 is large, NOx is more likely to be generated during combustion in the combustor 12 due to the reaction of nitrogen atoms and oxygen atoms. Therefore, if the oxygen concentration in the intake passage 101 or the exhaust passage 102 is greater than the target value, it indicates that the amount of NOx emitted will be greater than the target amount.

[0076] Furthermore, as mentioned above, the greater the amount of NOx reduced by the denitrification unit 16, the greater the amount of reducing agent supplied to the denitrification unit 16. Therefore, a supply of reducing agent to the denitrification unit 16 that is greater than the target value also indicates that the amount of NOx emitted is greater than the target emission level.

[0077] Furthermore, when the output of the gas turbine 11 is high, the amount of fuel supplied to the combustor 12 is also high, making it easier for NOx to be generated by combustion in the combustor 12. Therefore, an output of the gas turbine 11 greater than the target value also indicates that NOx emissions will be higher than the target emission level.

[0078] If the above parameters are not determined to be greater than the target values ​​(step S102 / NO), the processing flow shown in Figure 2 ends. On the other hand, if the above parameters are determined to be greater than the target values ​​(step S102 / YES), the process proceeds to step S103.

[0079] If the result in step S102 is determined to be YES, in step S103 the control device 400 increases the flow rate of the circulating gas, and the processing flow shown in Figure 2 is terminated.

[0080] For example, in step S103, the control device 400 increases the flow rate of the circulating gas by increasing the rotational speed of the fan 18, decreasing the opening degree of the first damper 20, or increasing the opening degree of the second damper 21. However, the control device 400 may also increase the flow rate of the circulating gas by controlling any multiple types of devices among the fan 18, the first damper 20, and the second damper 21.

[0081] As described above, in the first treatment, if the above parameters are greater than the target values ​​and the NOx emissions are greater than the target emissions, the control device 400 increases the flow rate of the circulating gas. This increases the proportion of circulating gas with a lower oxygen concentration than the atmosphere in the gas supplied to the combustor 12, thereby reducing the amount of oxygen supplied to the combustor 12. Consequently, the amount of NOx generated by combustion in the combustor 12 can be reduced, thus suppressing NOx emissions. As a result, the above parameters will move closer to the target values. In this way, the control device 400 can suppress NOx emissions by controlling the flow rate of the circulating gas so that the above parameters move closer to the target values.

[0082] As explained above, in the first process described above, the control device 400 controls the flow rate of exhaust gas (i.e., circulating gas) that circulates from the exhaust passage 102 to the intake passage 101 via the recirculation passage 108, based on parameters related to NOx emissions. As a result, as described above, the amount of NOx generated by combustion in the combustor 12 can be reduced, thereby suppressing NOx emissions.

[0083] Here, the combustion system 1 includes a denitrification device 16 installed in the exhaust passage 102. As a result, the amount of NOx emitted from the combustor 12 is reduced, and the amount of NOx that needs to be reduced by the denitrification device 16 can also be reduced. Therefore, the denitrification device 16 can be made smaller. Alternatively, the amount of reducing agent supplied to the denitrification device 16 can be reduced.

[0084] Furthermore, in the first process described above, the above parameters include, for example, the NOx concentration in the exhaust flow path 102. This allows for appropriate control of the circulating gas flow rate, taking into account the need to increase the circulating gas flow rate in order to reduce NOx emissions.

[0085] Furthermore, in the first process described above, the above parameters include, for example, the oxygen concentration in the intake passage 101. This allows for appropriate control of the circulating gas flow rate, taking into account the need to increase the circulating gas flow rate in order to reduce NOx emissions.

[0086] Furthermore, in the first process described above, the above parameters include, for example, the oxygen concentration in the exhaust flow path 102. This allows for appropriate control of the circulating gas flow rate, taking into account the need to increase the circulating gas flow rate in order to reduce NOx emissions.

[0087] Furthermore, in the first treatment described above, the above parameters include, for example, the amount of reducing agent supplied to the denitrification device 16. This allows for appropriate control of the circulating gas flow rate, taking into account the need to increase the circulating gas flow rate in order to reduce NOx emissions.

[0088] Furthermore, in the first process described above, the above parameters include, for example, the output of the gas turbine 11. This allows for appropriate control of the circulating gas flow rate, taking into account the need to increase the circulating gas flow rate in order to reduce NOx emissions.

[0089] In the above, examples of the parameters given were the NOx concentration in the exhaust passage 102, the oxygen concentration in the intake passage 101, the oxygen concentration in the exhaust passage 102, the amount of reducing agent supplied to the denitrification device 16, and the output of the gas turbine 11. However, the control device 400 may use all of these types of parameters, or it may use only some of these types of parameters.

[0090] Furthermore, the combustion system 1 includes a demister 14b provided at the connection point between the recirculation passage 108 and the intake passage 101. This allows for the removal of moisture contained in the circulating gas sent from the recirculation passage 108 to the intake passage 101. Therefore, it is possible to suppress the unnecessary supply of moisture to the intake passage 101 or the combustor 12. As a result, for example, if water vapor and ammonia gas in the intake air sent to the gas turbine 11 change to a liquid phase, the demister 14b can remove those droplets.

[0091] In the above description, an example was given in which the control device 400 increases the flow rate of the circulating gas when the above-mentioned parameters are greater than the target values. However, the control device 400 may also decrease the flow rate of the circulating gas when the above-mentioned parameters are smaller than the target values. Furthermore, the control device 400 may control the flow rate of the circulating gas to a value corresponding to the above-mentioned parameters, without comparing the above-mentioned parameters with the target values.

[0092] Figure 3 is a flowchart showing an example of the flow of the second processing performed by the control device 400. When the processing flow shown in Figure 3 starts, in step S201, the control device 400 acquires parameters related to the NOx emissions from the combustion system 1. The processing in step S201 is the same as the processing in step S101 described above.

[0093] Following step S201, in step S202, the control device 400 determines whether the above parameter is greater than the target value. The process in step S202 is the same as the process in step S102 described above.

[0094] If the above parameters are not determined to be greater than the target values ​​(step S202 / NO), the processing flow shown in Figure 3 ends. On the other hand, if the above parameters are determined to be greater than the target values ​​(step S202 / YES), the process proceeds to step S203.

[0095] If the result in step S202 is determined to be YES, in step S203 the control device 400 reduces the ratio of the amount of ammonia supplied to the combustor 12 to the amount of natural gas supplied to the combustor 12, and the processing flow shown in Figure 3 ends.

[0096] For example, in step S203, the control device 400 reduces the ratio of ammonia supply to natural gas supply by decreasing the opening of at least one of the first flow control valve 201 and the second flow control valve 202 and increasing the opening of the third flow control valve 203. For example, the control device 400 may gradually change the ratio of ammonia supply to natural gas supply over time. The control of the ratio between the supply of liquid ammonia and the supply of gaseous ammonia to the combustor 12 will be described later.

[0097] As described above, in the second treatment, if the above parameters are greater than the target values ​​and the NOx emissions are greater than the target emissions, the control device 400 reduces the ratio of ammonia supply to natural gas supply. This reduces the proportion of ammonia in the fuel supplied to the combustor 12. Therefore, the amount of NOx generated by combustion in the combustor 12 can be reduced, thus suppressing NOx emissions. As a result, the above parameters will move closer to the target values. In this way, the control device 400 can suppress NOx emissions by controlling the ratio of ammonia supply to natural gas supply so that the above parameters move closer to the target values.

[0098] As explained above, in the second process described above, the control device 400 controls the ratio of the amount of ammonia supplied to the combustor 12 to the amount of nitrogen-free fuel (natural gas in the above example) supplied to the combustor 12 based on the above parameters. As a result, as described above, the amount of NOx generated in conjunction with combustion in the combustor 12 can be reduced, and thus NOx emissions can be suppressed.

[0099] In the above, an example was described in which the control device 400 reduces the ratio of ammonia supply to natural gas supply when the above-mentioned parameter is greater than the target value. However, the control device 400 may increase the ratio of ammonia supply to natural gas supply when the above-mentioned parameter is smaller than the target value. Furthermore, the control device 400 may control the ratio of ammonia supply to natural gas supply to a value corresponding to the above-mentioned parameter, without comparing the above-mentioned parameter with the target value.

[0100] Figure 4 is a flowchart showing an example of the flow of the third process performed by the control device 400. When the process flow shown in Figure 4 starts, in step S301, the control device 400 acquires parameters related to the NOx emissions from the combustion system 1. The process in step S301 is the same as the process in step S101 described above.

[0101] Following step S301, in step S302, the control device 400 determines whether the above parameter is greater than the target value. The process in step S302 is the same as the process in step S102 described above.

[0102] If the above parameters are not determined to be greater than the target values ​​(step S302 / NO), the processing flow shown in Figure 4 ends. On the other hand, if the above parameters are determined to be greater than the target values ​​(step S302 / YES), the process proceeds to step S303.

[0103] If the result in step S302 is determined to be YES, in step S303 the control device 400 reduces the ratio of the amount of liquid ammonia supplied to the combustor 12 to the amount of gaseous ammonia supplied to the combustor 12, and the processing flow shown in Figure 4 ends.

[0104] For example, in step S303, the control device 400 reduces the ratio of the supply of liquid ammonia to the supply of gaseous ammonia by decreasing the opening of the first flow control valve 201 and increasing the opening of the second flow control valve 202. For example, the control device 400 may gradually change the ratio of the supply of liquid ammonia to the supply of gaseous ammonia over time. Depending on the situation, the control device 400 may supply only gaseous ammonia to the combustor 12, only liquid ammonia to the combustor 12, or both to the combustor 12.

[0105] As described above, in the third treatment, if the above parameters are greater than the target values ​​and the NOx emissions are greater than the target emissions, the control device 400 reduces the ratio of the supply of liquid ammonia to the supply of gaseous ammonia. Here, the liquid ammonia supplied to the combustor 12 evaporates and vaporizes in the combustor 12 before combustion. Therefore, when liquid ammonia is supplied to the combustor 12, NOx tends to be generated more easily compared to when gaseous ammonia is supplied to the combustor 12, due to reasons such as the amount of energy required for combustion and the longer time until combustion starts. Therefore, by reducing the ratio of the supply of liquid ammonia to the supply of gaseous ammonia, the amount of NOx generated by combustion in the combustor 12 can be reduced, thereby suppressing NOx emissions. As a result, the above parameters will move closer to the target values. In this way, the control device 400 can suppress NOx emissions by controlling the ratio of the supply of liquid ammonia to the supply of gaseous ammonia so that the above parameters move closer to the target values.

[0106] As explained above, in the third process described above, the control device 400 controls the ratio of the amount of liquid ammonia supplied to the combustor 12 to the amount of gaseous ammonia supplied to the combustor 12 based on the above parameters. As a result, as described above, the amount of NOx generated in conjunction with combustion in the combustor 12 can be reduced, and thus NOx emissions can be suppressed.

[0107] In the above, an example was described in which the control device 400 reduces the ratio of the supply of liquid ammonia to the supply of gaseous ammonia when the above-mentioned parameter is greater than the target value. However, the control device 400 may increase the ratio of the supply of liquid ammonia to the supply of gaseous ammonia when the above-mentioned parameter is smaller than the target value. Furthermore, the control device 400 may control the ratio of the supply of liquid ammonia to the supply of gaseous ammonia to a value corresponding to the above-mentioned parameter, without comparing the above-mentioned parameter with the target value.

[0108] As described above, the control device 400 may perform both the second process described with reference to Figure 3 and the third process described with reference to Figure 4 as processes related to controlling the amount of fuel supplied to the combustor 12. In other words, the control device 400 may control the ratio of the amount of ammonia supplied to the combustor 12 to the amount of nitrogen-free fuel (natural gas in the above example) supplied to the combustor 12 based on the above parameters, while also controlling the ratio of the amount of liquid ammonia supplied to the combustor 12 to the amount of gaseous ammonia supplied to the combustor 12 based on the above parameters.

[0109] Figure 5 is a flowchart showing an example of the flow of the fourth process performed by the control device 400. When the processing flow shown in Figure 5 starts, in step S401, the control device 400 obtains the power generation efficiency of the combustion system 1.

[0110] For example, the control device 400 calculates and obtains the power generation efficiency of the combustion system 1 based on the amount of fuel input to the gas turbine 11 and the amount of power output from the generator 13. The above power generation efficiency corresponds to an example of energy efficiency, which is the efficiency of generating energy obtained by the combustion of the combustor 12. For example, the above describes an example in which the gas turbine 11 is connected to the generator 13. However, the gas turbine 11 may not be connected to the generator 13, and the energy generated by the gas turbine 11 may be used for purposes other than power generation. In this case, the above energy efficiency will be a parameter other than the power generation efficiency.

[0111] Following step S401, in step S402, the control device 400 determines whether the power generation efficiency is lower than the target value.

[0112] The target value for power generation efficiency mentioned above is, for example, predetermined. In the fourth process shown in Figure 5, the power generation efficiency is controlled to be above the target value in order to suppress a decrease in power generation efficiency. Specifically, as will be described later, if the power generation efficiency is lower than the target value, the decrease in power generation efficiency is suppressed by increasing the temperature of the circulating gas.

[0113] If the power generation efficiency is not determined to be lower than the target value (step S402 / NO), the processing flow shown in Figure 5 ends. On the other hand, if the power generation efficiency is determined to be lower than the target value (step S402 / YES), the process proceeds to step S403.

[0114] If the result in step S402 is determined to be YES, in step S403 the control device 400 increases the temperature of the circulating gas, and the processing flow shown in Figure 5 is terminated.

[0115] For example, in step S403, the control device 400 increases the temperature of the circulating gas by reducing the opening of the fifth flow control valve 205 and decreasing the flow rate of the refrigerant flowing through the refrigerant passage 109. The control device 400 may increase the temperature of the circulating gas so that the temperature of the circulating gas reaches a desired target value. In this case, the control device 400 may use, for example, the temperature detected by the first thermometer 304 or the temperature detected by the second thermometer 305 as the temperature of the circulating gas to be controlled.

[0116] As described above, in the fourth process, if the power generation efficiency is lower than the target value, the control device 400 increases the temperature of the circulating gas. This increases the temperature of the gas supplied to the combustor 12, so that even during partial load operation, the combustion environment in the combustor 12 can be brought closer to that of steady-state operation. Therefore, the decrease in power generation efficiency can be suppressed. In this way, the control device 400 can suppress the decrease in power generation efficiency by controlling the temperature of the circulating gas so that the power generation efficiency approaches the target value.

[0117] As explained above, in the fourth process described above, the control device 400 controls the temperature of the exhaust gas circulating from the exhaust passage 102 to the intake passage 101 via the recirculation passage 108. As a result, as described above, even during partial load operation, the combustion environment in the combustor 12 can be brought closer to that of steady-state operation, thereby suppressing a decrease in energy efficiency.

[0118] Furthermore, in the fourth process described above, the control device 400 controls the temperature based on the energy efficiency (power generation efficiency in the above example), which is the energy generation efficiency obtained by the combustion of the combustor 12. This effectively suppresses the decrease in energy efficiency.

[0119] Furthermore, the control device 400 may control the temperature based on information other than energy efficiency. For example, the control device 400 may control the temperature based on information that can be substantially converted into energy efficiency. This also helps to suppress a decrease in energy efficiency.

[0120] Furthermore, in the fourth process described above, the control device 400 controls the temperature by controlling the flow rate of the refrigerant flowing through the refrigerant flow path 109 that passes through the heat exchanger 19 provided in the recirculation flow path 108. This ensures that the temperature is properly controlled.

[0121] The control device 400 may control the temperature in a manner other than controlling the flow rate of the refrigerant through the refrigerant passage 109. For example, the control device 400 may control the temperature using a device that directly injects refrigerant into the recirculation passage 108.

[0122] In the above, an example was described in which the control device 400 increases the temperature of the circulating gas when the power generation efficiency is lower than the target value. However, the control device 400 may also decrease the temperature of the circulating gas when the power generation efficiency is higher than the target value. Furthermore, the control device 400 may control the temperature of the circulating gas to a value corresponding to the current power generation efficiency, regardless of the comparison between the power generation efficiency and the target value.

[0123] While embodiments of this disclosure have been described above with reference to the attached drawings, it goes without saying that this disclosure is not limited to such embodiments. It will be obvious to those skilled in the art that various modifications or alterations can be conceived within the scope of the claims, and these will naturally also fall within the technical scope of this disclosure.

[0124] The configuration of the combustion system 1 was described above with reference to Figure 1. However, some components of the combustion system 1 may be omitted, and components may be added. For example, a device that directly injects water or steam into the inside of the combustor 12 or into the upstream flow path of the combustor 12 may be added to the combustion system 1. These devices are provided, for example, to suppress NOx emissions.

[0125] Furthermore, the above description omits details regarding equipment provided in conjunction with the combustion system 1. However, additional equipment may be provided in conjunction with the combustion system 1. For example, the combustion system 1 may be used as part of a cogeneration system or as part of a combined cycle system.

[0126] Furthermore, the above description explains an example in which, in addition to ammonia, a fuel that does not contain nitrogen atoms (natural gas in the above example) is supplied to the combustor 12 in the combustion system 1. However, it is not necessary for a fuel that does not contain nitrogen atoms to be supplied to the combustor 12.

[0127] Furthermore, the above describes an example in which both liquid ammonia and gaseous ammonia are supplied to the combustor 12 as ammonia in the combustion system 1. However, only one of either liquid ammonia or gaseous ammonia may be supplied to the combustor 12.

[0128] This disclosure can promote the use of ammonia, which leads to a reduction in CO2 emissions, and thus can contribute, for example, to Sustainable Development Goal (SDG) 7, "Ensure access to affordable, reliable, sustainable and modern energy," and Goal 13, "Take urgent action to combat climate change and its impacts." [Explanation of symbols]

[0129] 1. Combustion System 11 Gas Turbine 11a Compressor 11b Turbine 12 Combustor 13 Generators 16 Denitration equipment 19 Heat exchanger 101 Intake passage 102 Exhaust passage 108 Recirculation channel 109 Refrigerant flow path 400 Control Unit

Claims

1. A combustor supplied with ammonia, The intake passage connected to the aforementioned combustor, An exhaust passage connected to the aforementioned combustor, A recirculation passage connecting the exhaust passage and the intake passage, A control device that controls the temperature of exhaust gas circulating from the exhaust passage to the intake passage via the recirculation passage, Equipped with, Combustion system.

2. The control device controls the temperature based on the energy efficiency, which is the energy generation efficiency obtained by the combustion of the combustor. The combustion system according to claim 1.

3. A gas turbine including a compressor provided in the intake passage and a turbine provided in the exhaust passage, A generator connected to the aforementioned gas turbine, Equipped with, The aforementioned energy efficiency is the power generation efficiency of the combustion system. The combustion system according to claim 2.

4. The recirculation channel is provided with a heat exchanger through which the refrigerant channel passes, The control device controls the temperature by controlling the flow rate of the refrigerant flowing through the refrigerant passage. The combustion system according to claim 1.

5. The exhaust passage is equipped with a denitrification device, The combustion system according to claim 1.

6. A demister is provided at the connection point between the recirculation passage and the intake passage. The combustion system according to claim 1.

7. The control device controls the flow rate of exhaust gas circulating from the exhaust passage to the intake passage via the recirculation passage based on parameters relating to nitrogen oxide emissions. The combustion system according to any one of claims 1 to 6.

8. In addition to ammonia, the combustor is supplied with a fuel that does not contain nitrogen atoms. The control device controls the ratio of the amount of ammonia supplied to the combustor to the amount of nitrogen atom-free fuel supplied to the combustor, based on a parameter relating to nitrogen oxide emissions. The combustion system according to any one of claims 1 to 6.

9. The combustor is supplied with both liquid ammonia and gaseous ammonia. The control device controls the ratio of the amount of liquid ammonia supplied to the combustor to the amount of gaseous ammonia supplied to the combustor, based on a parameter relating to nitrogen oxide emissions. The combustion system according to any one of claims 1 to 6.

10. A method for controlling a combustion system, The aforementioned combustion system, A combustor supplied with ammonia, The intake passage connected to the aforementioned combustor, An exhaust passage connected to the aforementioned combustor, A recirculation passage connecting the exhaust passage and the intake passage, Equipped with, The control device controls the temperature of the exhaust gas circulating from the exhaust passage to the intake passage via the recirculation passage. Control method.

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