Methods of operating combustion systems and internal combustion engines

Abstract

To stabilize the operation of an internal combustion engine during load shedding when ammonia is used as fuel. [Solution] The combustion system comprises an internal combustion engine that uses at least ammonia as fuel, a fuel adjustment unit that adjusts the amount of fuel supplied to the internal combustion engine, an air adjustment unit that adjusts the amount of air supplied to the internal combustion engine, and a control device that controls the fuel adjustment unit and the air adjustment unit. The control device is configured to store in advance the amount of air and fuel necessary to maintain no-load operation of the internal combustion engine, and to perform a first adjustment step of adjusting the amount of air supplied to the internal combustion engine to the amount of air stored in the control device when the internal combustion engine is switched to no-load operation, and a second adjustment step of adjusting the amount of fuel supplied to the internal combustion engine to the amount of fuel stored in the control device.

Description

Technical Field

[0001] The present disclosure relates to a combustion system and a method for operating an internal combustion engine.

Background Art

[0002] Internal combustion engines may use ammonia as fuel. For example, Patent Document 1 discloses a gas turbine facility that uses ammonia as fuel.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Internal combustion engines such as gas turbines may be switched to unloaded operation under some circumstances. For example, a gas turbine may be required to continue operating without load during unloaded operation. However, when switching to unloaded operation, the internal combustion engine is disconnected from the load, so the rotational speed of the internal combustion engine increases. The increase in rotational speed can lead to over-rotation of the internal combustion engine. As an example of suppressing the increase in rotational speed, it is to reduce the supply of fuel to the internal combustion engine. However, ammonia is known as a fuel with low combustibility. Therefore, in an internal combustion engine using ammonia as fuel, reducing the supply of ammonia can cause problems such as misfires.

[0005] An object of the present disclosure is to provide a combustion system that can stabilize the operation of an internal combustion engine during load interruption when ammonia is used as fuel. Another object of the present disclosure is to provide a method for operating a related internal combustion engine.

Means for Solving the Problems

[0006] A combustion system according to one aspect of the present disclosure includes an internal combustion engine that uses at least ammonia as fuel, a fuel adjustment unit that adjusts the amount of fuel supplied to the internal combustion engine, an air adjustment unit that adjusts the amount of air supplied to the internal combustion engine, and a control device that controls the fuel adjustment unit and the air adjustment unit, wherein the control device stores in advance the amount of air and fuel necessary to maintain no-load operation of the internal combustion engine, and is configured to perform a first adjustment step of adjusting the amount of air supplied to the internal combustion engine to the amount of air stored in the control device when the internal combustion engine is switched to no-load operation, and a second adjustment step of adjusting the amount of fuel supplied to the internal combustion engine to the amount of fuel stored in the control device.

[0007] The internal combustion engine may also use a second fuel having higher combustibility than ammonia as fuel, and the fuel adjustment unit may include a first fuel adjustment unit that adjusts the amount of ammonia supplied to the internal combustion engine, and a second fuel adjustment unit that adjusts the amount of the second fuel supplied to the internal combustion engine, and the control device may store in advance the amount of the second fuel necessary to maintain no-load operation of the internal combustion engine, and the second adjustment step may include starting the supply of the second fuel to the internal combustion engine when the internal combustion engine is switched to no-load operation while burning only ammonia, adjusting the amount of the second fuel supplied to the internal combustion engine to the amount of the second fuel stored in the control device, and stopping the supply of ammonia to the internal combustion engine after the supply of the second fuel to the internal combustion engine has started.

[0008] The internal combustion engine may also use a second fuel having higher combustibility than ammonia as fuel, and the fuel adjustment unit may include a first fuel adjustment unit that adjusts the amount of ammonia supplied to the internal combustion engine, and a second fuel adjustment unit that adjusts the amount of the second fuel supplied to the internal combustion engine, and the control device may store in advance the amount of the second fuel necessary to maintain no-load operation of the internal combustion engine, and the second adjustment step may include adjusting the amount of the second fuel supplied to the internal combustion engine to the amount of the second fuel stored in the control device when the internal combustion engine is switched to no-load operation while the internal combustion engine is co-firing ammonia and the second fuel, and stopping the supply of ammonia to the internal combustion engine after the internal combustion engine has been switched to no-load operation.

[0009] The air conditioning unit may include an air venting mechanism for removing air used for combustion from the internal combustion engine.

[0010] The air conditioning unit may include an adjustment mechanism for adjusting the flow rate of air drawn into the internal combustion engine.

[0011] Another aspect of the present disclosure is a method for operating an internal combustion engine, comprising: a switching step for switching an internal combustion engine using at least ammonia as fuel to no-load operation; a first adjustment step for adjusting the amount of air supplied to the internal combustion engine to a predetermined amount of air when the switching step is performed; and a second adjustment step for adjusting the amount of fuel supplied to the internal combustion engine to a predetermined amount of fuel when the switching step is performed. [Effects of the Invention]

[0012] According to this disclosure, when ammonia is used as fuel, the operation of an internal combustion engine can be stabilized during load shedding. [Brief explanation of the drawing]

[0013] [Figure 1] Figure 1 is a schematic diagram of the combustion system according to the embodiment. [Figure 2] Figure 2 shows examples of air flow rate, fuel flow rate, ammonia flow rate, and LNG flow rate during load shedding. [Figure 3]Figure 3 shows examples of air flow rate, fuel flow rate, ammonia flow rate, and LNG flow rate during load shedding. [Figure 4] Figure 4 shows examples of air flow rate, fuel flow rate, ammonia flow rate, and LNG flow rate during load shedding. [Figure 5] Figure 5 shows examples of air flow rate, fuel flow rate, ammonia flow rate, and LNG flow rate during load shedding. [Modes for carrying out the invention]

[0014] Embodiments of this disclosure will be described in detail below with reference to the attached drawings. The specific dimensions, materials, and numerical values ​​shown in these embodiments are merely illustrative for ease of understanding and do not limit this disclosure unless otherwise specified. In this specification and drawings, elements having substantially the same function and configuration are denoted by the same reference numerals to avoid redundant explanations, and elements not directly related to this disclosure are omitted from the illustrations.

[0015] Figure 1 is a schematic diagram showing a combustion system 100 according to an embodiment. In this disclosure, the combustion system 100 may also be simply referred to as the "system". In Figure 1, solid arrows indicate fluid flow, and dashed arrows indicate signal flow.

[0016] For example, system 100 includes a first tank (first fuel source) 1, a second tank (second fuel source) 2, a gas turbine (internal combustion engine) 10, a generator 20, and a control device 90. System 100 may further include other components. Also, system 100 may not include at least one of the above components.

[0017] The first tank 1 stores ammonia (the first fuel). For example, the first tank 1 may store liquid ammonia. The first tank 1 is connected to the first fuel line L1. The first fuel line L1 connects the first tank 1 and the combustor 12 of the gas turbine 10. For example, the first fuel line L1 may supply liquid ammonia to the combustor 12. Alternatively, the system 100 may include a vaporizer (not shown) in the first fuel line L1, and the first fuel line L1 may supply gaseous ammonia, or a mixture of gaseous ammonia and liquid ammonia, to the combustor 12. In other embodiments, instead of the first tank 1, a device for producing ammonia may be used as the first fuel supply source.

[0018] The second tank 2 stores the second fuel. The second fuel has a higher combustibility than ammonia. For example, the second fuel may be a liquid fuel such as LNG (liquefied natural gas), heavy oil, light oil, or kerosene, or hydrogen. The second fuel is not limited thereto. In the present embodiment, LNG is used as the second fuel. The second fuel line L2 connects the second tank 2 and the combustor 12. For example, the second fuel line L2 may supply the second fuel to the combustor 12 in a liquid state. Alternatively, the system 100 may include a vaporizer (not shown) in the second fuel line L2, and the second fuel line L2 may supply the second fuel to the combustor 12 in a gaseous state, or as a mixture of gas and liquid. In other embodiments, instead of the second tank 2, a device for producing the second fuel may be used as the second fuel supply source.

[0019] The system 100 includes a fuel adjuster A0 that adjusts the supply amount of fuel to the gas turbine 10. Specifically, in the present embodiment, the system 100 includes a first fuel adjuster A1 and a second fuel adjuster A2.

[0020] The first fuel adjustment unit A1 adjusts the supply amount of ammonia to the gas turbine 10. For example, the first fuel adjustment unit A1 is provided in the first fuel line L1. For example, at least a part of the first fuel adjustment unit A1 may be connected to the control device 90 in a wired or wireless communication-capable manner. Also, at least a part of the first fuel adjustment unit A1 may be controlled by the control device 90.

[0021] For example, in the present embodiment, the first fuel adjustment unit A1 includes a first valve V1, a second valve V2, and a third valve V3. The first fuel adjustment unit A1 may further include other components. For example, in addition to or instead of the first valve V1, the second valve V2, and the third valve V3, the first fuel adjustment unit A1 may include a pump or a compressor (not shown) for sending the ammonia in the first tank 1 to the combustor 12. Also, the first fuel adjustment unit A1 may not include at least one of the first valve V1, the second valve V2, and the third valve V3.

[0022] The first valve V1 is provided in the first fuel line L1. For example, the first valve V1 may be an on-off valve. The first valve V1 is not limited to this, and may be other valves. The first valve V1 is closed when shutting off the supply of ammonia to the gas turbine 10 in an emergency.

[0023] The second valve V2 is provided in the first fuel line L1. For example, the second valve V2 may be a control valve. The second valve V2 is not limited to this, and may be other valves. The second valve V2 adjusts the flow rate of ammonia to the gas turbine 10.

[0024] The third valve V3 is provided in the first fuel line L1. For example, the third valve V3 may be an on-off valve. The third valve V3 is not limited to this, and may be other valves. The third valve V3 is closed to stop the supply of ammonia to the gas turbine 10 when the gas turbine 10 is shut off from the load.

[0025] In this embodiment, the second valve V2 is connected to the control device 90 via wired or wireless communication. In this embodiment, the second valve V2 is controlled by the control device 90. The control device 90 adjusts the ammonia flow rate supplied to the gas turbine 10 by controlling the opening degree of the second valve V2.

[0026] In Figure 1, the first valve V1 and the third valve V3 are not connected to the control device 90 by arrows, but the first valve V1 and the third valve V3 may be connected to the control device 90 via wired or wireless communication. Furthermore, the first valve V1 and the third valve V3 may be controlled by the control device 90.

[0027] The second fuel adjustment unit A2 adjusts the amount of LNG supplied to the gas turbine 10. For example, the second fuel adjustment unit A2 is located in the second fuel line L2. For example, at least a portion of the second fuel adjustment unit A2 may be connected to the control device 90 via wired or wireless communication. Also, at least a portion of the second fuel adjustment unit A2 may be controlled by the control device 90.

[0028] For example, in this embodiment, the second fuel adjustment unit A2 includes a fourth valve V4, a fifth valve V5, and a sixth valve V6. The second fuel adjustment unit A2 may further include other components. For example, the second fuel adjustment unit A2 may include a pump or compressor (not shown) for supplying LNG from the second tank 2 to the combustor 12. Also, the second fuel adjustment unit A2 does not have to include at least one of the fourth valve V4, the fifth valve V5, and the sixth valve V6.

[0029] The fourth valve V4 is located in the second fuel line L2. For example, the fourth valve V4 may be an on / off valve. The fourth valve V4 is not limited to this and may be any other valve. The fourth valve V4 is closed in an emergency to shut off the supply of LNG to the gas turbine 10.

[0030] The fifth valve V5 is located in the second fuel line L2. For example, the fifth valve V5 may be a control valve. The fifth valve V5 is not limited to this and may be any other valve. The fifth valve V5 adjusts the flow rate of LNG to the gas turbine 10.

[0031] The sixth valve V6 is located in the second fuel line L2. For example, the sixth valve V6 may be an on / off valve. The sixth valve V6 is not limited to this and may be any other valve. The sixth valve V6 is opened to start supplying LNG to the gas turbine 10 when the gas turbine 10 is disconnected from the load.

[0032] In this embodiment, the fifth valve V5 is connected to the control device 90 via wired or wireless communication. The fifth valve V5 is also controlled by the control device 90. The control device 90 adjusts the flow rate of LNG supplied to the gas turbine 10 by controlling the opening degree of the fifth valve V5.

[0033] In Figure 1, the fourth valve V4 and the sixth valve V6 are not connected to the control device 90 by arrows, but the fourth valve V4 and the sixth valve V6 may be connected to the control device 90 via wired or wireless communication. Furthermore, the fourth valve V4 and the sixth valve V6 may be controlled by the control device 90.

[0034] The gas turbine 10 may be any type of gas turbine, such as an industrial gas turbine, a mobile power supply gas turbine, or a mechanical drive gas turbine. The gas turbine 10 is not limited to these. The gas turbine 10 includes a compressor 11, a combustor 12, a turbine 13, and a shaft 14 connecting the compressor 11 to the turbine 13. The gas turbine 10 may further include other components.

[0035] The compressor 11 draws in air and pressurizes the drawn-in air. The pressurized air is supplied to the combustor 12.

[0036] The combustor 12 burns a gas containing at least one of ammonia from the first fuel line L1 and a second fuel from the second fuel line L2, and air from the compressor 11.

[0037] Combustion gases from the combustor 12 are supplied to the turbine 13. As the combustion gases pass through the impeller in the turbine 13, they rotate the impeller together with the shaft 14. The shaft 14 is connected to the generator 20, and the rotational force of the shaft 14 is used for power generation. In other embodiments, the shaft 14 may be connected to the generator 20 via a reduction gear. In other embodiments, the rotational force of the shaft 14 may be used in other devices (e.g., a compressor or pump). The rotational force of the shaft 14 is also used to pressurize air in the compressor 11. For example, exhaust gases from the turbine 13 may be supplied to a device not shown, such as a heat recovery steam generator (HRSG).

[0038] System 100 includes an air adjustment unit A3. The air adjustment unit A3 adjusts the amount of air supplied to the gas turbine 10, that is, the amount of air used for combustion in the gas turbine 10. For example, the air adjustment unit A3 includes a bleed line L3 and a seventh valve V7 as an air venting mechanism for removing the air used for combustion from the gas turbine 10.

[0039] In this embodiment, the bleed line L3 extends from the compressor 11. For example, the bleed line L3 may extend from an intermediate or final stage of the compressor 11. The bleed line L3 removes pressurized air from the compressor 11. In other embodiments, the bleed line L3 may extend from the combustor 12. In this case, for example, the bleed line L3 may extend from the inlet of the combustor 12 or from the inlet of a nozzle inside the combustor 12.

[0040] The seventh valve V7 is located in the bleed line L3. For example, the seventh valve V7 may be a control valve or an on / off valve. The seventh valve V7 adjusts the flow rate of air drawn from the compressor 11. By adjusting the flow rate of air drawn from the compressor 11, the amount of air supplied to the gas turbine 10, i.e., the amount of air used for combustion in the combustor 12, can be adjusted. The seventh valve V7 is not limited to this and may be any other valve.

[0041] In this embodiment, the seventh valve V7 is connected to the control device 90 via wired or wireless communication. The seventh valve V7 is also controlled by the control device 90. The control device 90 adjusts the flow rate of air drawn from the compressor 11 by controlling the opening degree of the seventh valve V7, thereby adjusting the amount of air supplied to the gas turbine 10.

[0042] In place of, or in addition to, the seventh valve V7 and the bleed line L3, the air conditioning unit A3 may include, for example, a variable stator vane (IGV) 15 provided on the compressor 11 as an adjustment mechanism for adjusting the flow rate of air drawn into the gas turbine 10. The IGV 15 adjusts the flow rate of air drawn into the compressor 11. The IGV 15 is communicated with the control device 90 by wire or wireless means. The IGV 15 is also controlled by the control device 90. The control device 90 adjusts the flow rate of air drawn into the compressor 11 by controlling the opening of the IGV 15, thereby adjusting the amount of air supplied to the gas turbine 10. The air conditioning unit A3 may further include other components. Also, the air conditioning unit A3 may not include at least one of the bleed line L3, the seventh valve V7, and the IGV 15. Alternatively or additionally, in yet another embodiment, the air conditioning unit A3 may employ a damper in the intake duct connected to the compressor 11 as an adjustment mechanism.

[0043] The control device 90 controls the system 100. For example, the control device 90 includes components such as a processor 90a, a storage device 90b, and a connector 90c, which are connected to each other via a bus. For example, the processor 90a includes a CPU (Central Processing Unit). For example, the storage device 90b includes a hard disk, a ROM for storing programs, and RAM as a work area. The control device 90 is connected to each component of the system 100 via the connector 90c so as to be able to communicate by wire or wirelessly. For example, the control device 90 may further include other components such as a display device such as a liquid crystal display or a touch panel, and an input device such as a keyboard, buttons, or a touch panel. For example, the operation of the control device 90 may be achieved by having the processor 90a execute a program stored in the storage device 90b.

[0044] Next, we will describe the operation of the system 100 when the gas turbine 10 is disconnected from the load.

[0045] The gas turbine 10 may be switched to no-load operation under certain circumstances. For example, if abnormal combustion is detected in the gas turbine 10, the gas turbine 10 is disconnected from the generator 20. In this case, the gas turbine 10 is immediately disconnected from the load. In this disclosure, “load disconnection” means that the internal combustion engine is disconnected from the load and switched to no-load operation. The circumstances requiring load disconnection are not limited to abnormal combustion.

[0046] In no-load operation, the gas turbine 10 is required to continue operating without load at a predetermined rotational speed in order to maintain a state where it can be reconnected to the generator 20. However, when switching to no-load operation, the gas turbine 10 is immediately disconnected from the load, so the rotational speed of the gas turbine 10 increases due to inertial force. This increase in rotational speed can lead to over-rotation of the gas turbine 10.

[0047] One way to suppress the increase in rotational speed is to reduce the fuel supply to the gas turbine 10. However, ammonia is known as a low-flammability fuel, and when ammonia is used as fuel, reducing the supply of ammonia can cause problems such as misfires.

[0048] In this disclosure, to address the above-mentioned problems, system 100 adjusts at least one of the ammonia supply, the LNG supply, and the air supply.

[0049] Figures 2 through 5 each show examples of air flow rate, fuel flow rate, ammonia flow rate, and LNG flow rate during load shedding. In the graphs of Figures 2 through 5, the horizontal axis represents time. In each of Figures 2 through 5, the vertical axis, from top to bottom, represents the air flow rate, fuel flow rate, ammonia flow rate, and LNG flow rate supplied to the gas turbine 10. In each of Figures 2 through 5, "fuel flow rate" refers to the sum of the ammonia flow rate and the LNG flow rate.

[0050] Figure 2 shows the case where the gas turbine 10 is switched to no-load operation while ammonia is being exclusively burned. Before time t1, the gas turbine 10 is operating at a certain rotational speed, and therefore the air flow rate is constant. Also, before time t1, the gas turbine 10 is exclusively burning ammonia, so the LNG flow rate is zero.

[0051] At time t1, the gas turbine 10 is switched to no-load operation. This increases the rotational speed of the gas turbine 10, and the amount of air drawn in by the compressor 11 increases. Therefore, the airflow rate increases from time t1.

[0052] The control device 90 controls the first fuel adjustment unit A1 and the second fuel adjustment unit A2 to reduce the fuel flow rate from time t1 in order to suppress an increase in the rotational speed of the gas turbine 10.

[0053] Specifically, in this example, the control device 90 controls the second valve V2 to reduce the ammonia flow rate from time t1 to time t2. The control device 90 also opens the sixth valve V6 at time t1 to begin supplying LNG, and controls the fifth valve V5 to increase the LNG flow rate from time t1 to time t2. The control device 90 controls the second valve V2 and the fifth valve V5 so that the rate of decrease in the ammonia flow rate exceeds the rate of increase in the LNG flow rate. Therefore, the fuel flow rate, including ammonia and LNG, decreases from time t1 to time t2. As the fuel flow rate decreases, the amount of combustion gas supplied from the combustor 12 to the turbine 13 decreases. Consequently, the force exerted on the turbine 13 by the combustion gas decreases.

[0054] In this example, the ammonia flow rate and the LNG flow rate are changed linearly from time t1 to time t2. In other examples, the ammonia flow rate and the LNG flow rate may be changed in steps. In yet another example, the ammonia flow rate and the LNG flow rate may be changed non-linearly from time t1 to time t2.

[0055] The fuel flow rate decreases to a value r0 at time t2. For example, the value r0 may be the lower limit of the fuel flow rate required to maintain the operation of the gas turbine 10. Alternatively, the value r0 may be obtained by multiplying the lower limit by a safety factor of 1 or more. For example, the value r0 may vary depending on the respective ratios of ammonia and LNG in the fuel flow rate. For example, the value r0 may be determined based on at least one of experiment, analysis, and calculation, and may be stored in the control device 90 beforehand.

[0056] The control device 90 maintains the opening of the second valve V2 and the fifth valve V5 from time t2 to time t3, thereby maintaining the fuel flow rate at value r0. As the effect of inertial force decreases, the rotational speed of the gas turbine 10 (i.e., air flow rate) begins to decrease between time t2 and time t3. The control device 90 controls the first fuel adjustment unit A1 and the second fuel adjustment unit A2 to increase the fuel flow rate in order to prevent an excessive decrease in the rotational speed of the gas turbine 10.

[0057] Specifically, in this example, the control device 90 controls the second valve V2 at time t3 to increase the ammonia flow rate. Also, the control device 90 controls the fifth valve V5 at time t3 to increase the LNG flow rate. Therefore, the fuel flow rate increases at time t3.

[0058] In this example, the ammonia flow rate and the LNG flow rate are each changed in a stepwise manner at time t3. In other examples, the ammonia flow rate and the LNG flow rate may each be changed linearly or nonlinearly from time t3.

[0059] At time t4, the control device 90 closes the third valve V3 to stop the supply of ammonia. Also at time t4, the control device 90 controls the fifth valve V5 to increase the LGN flow rate in order to prevent an excessive decrease in fuel flow rate.

[0060] In this example, the ammonia flow rate and the LNG flow rate are changed in a stepwise manner at time t4. In other examples, the ammonia flow rate and the LNG flow rate may be changed linearly or nonlinearly from time t4.

[0061] For example, the control device 90 may control the fifth valve V5 based on PID control so that the fuel flow rate (i.e., LNG flow rate) converges to the value r1 from time t5 onward. In other embodiments, the control device 90 may start PID control from another time, such as time t1. For example, the value r1 may be the LNG flow rate required to maintain no-load operation of the gas turbine 10.

[0062] For example, the value r1 may be determined based on at least one of experiments, analyses, and calculations, and may be stored in the control device 90 beforehand. Also, the opening degree of the fifth valve V5 for maintaining the LNG flow rate at value r1 may be stored in the control device 90 beforehand.

[0063] Through the above process, the gas turbine 10 is switched from ammonia-only combustion to no-load operation using LNG. In the example in Figure 2, the supply of LNG is started at time t1, and the supply of ammonia is stopped at time t4. Therefore, the supply of ammonia is stopped after the combustion has been stabilized by LNG. As a result, misfires during load shedding can be prevented. Also, in the example in Figure 2, over-rotation of the gas turbine 10 is prevented.

[0064] The switch from ammonia-only combustion to no-load operation using LNG is not limited to the example in Figure 2, and the ammonia flow rate and LNG flow rate may be changed by other means. For example, the ammonia flow rate and LNG flow rate may be changed by other means, insofar as the supply of ammonia is stopped after the supply of LNG is started. Also, for example, the supply of ammonia may be stopped before the supply of LNG is started, or simultaneously with the start of the supply of LNG, insofar as misfires are prevented.

[0065] In the example shown in Figure 2, system 100 does not adjust the airflow rate. Therefore, in the example shown in Figure 2, system 100 does not need to have the air adjustment unit A3.

[0066] Figure 3 shows the case where the gas turbine 10 is switched to no-load operation during co-firing of ammonia and LNG. Similar to Figure 2, before time t1, the gas turbine 10 is operating at a certain rotational speed, and therefore the air flow rate is constant. However, before time t1, the gas turbine 10 is performing co-firing of ammonia and LNG, so the LNG flow rate is not zero.

[0067] Similar to Figure 2, at time t1, the gas turbine 10 is switched to no-load operation. The control device 90 controls the first fuel adjustment unit A1 and the second fuel adjustment unit A2 to reduce the fuel flow rate from time t1 in order to suppress the increase in the rotational speed of the gas turbine 10.

[0068] Specifically, in this example, the control device 90 controls the second valve V2 so that the ammonia flow rate decreases to zero at time t2. The control device 90 also controls the fifth valve V5 so that the LNG flow rate increases from time t1 to time t2. The control device 90 controls the second valve V2 and the fifth valve V5 so that the rate of decrease in the ammonia flow rate exceeds the rate of increase in the LNG flow rate. Therefore, the fuel flow rate decreases from time t1 to time t2. As the fuel flow rate decreases, the amount of combustion gas supplied from the combustor 12 to the turbine 13 decreases. Therefore, the force applied to the turbine 13 by the combustion gas decreases.

[0069] In this example, the ammonia flow rate and the LNG flow rate are changed linearly from time t1 to time t2. In other examples, the ammonia flow rate and the LNG flow rate may be changed in steps. In yet another example, the ammonia flow rate and the LNG flow rate may be changed non-linearly from time t1 to time t2.

[0070] For example, the control device 90 may control the fifth valve V5 based on PID control so that the fuel flow rate (i.e., LNG flow rate) converges to the value r1 from time t2 onward. In other embodiments, the control device 90 may start PID control from another time, such as time t1. If PID control is started from time t1, the control device 90 controls valves V2 and V5 based on PID control so that the ammonia flow rate decreases and the LNG flow rate increases.

[0071] Through the above process, the gas turbine 10 switches from co-firing of ammonia and LNG to no-load operation using only LNG. In the example in Figure 3, at time t1, LNG is already supplied to the gas turbine 10. Therefore, the supply of ammonia is stopped while combustion is stabilized by LNG. As a result, misfires during load shedding can be prevented. Furthermore, according to the example in Figure 3, over-rotation of the gas turbine 10 is prevented.

[0072] The switch from co-firing of ammonia and LNG to no-load operation using only LNG is not limited to the example in Figure 3, and the ammonia and LNG flow rates may be changed according to other methods. For example, the LNG flow rate does not need to be increased as long as misfires are prevented.

[0073] Similar to Figure 2, in the example in Figure 3, system 100 does not adjust the airflow rate. Therefore, in the example in Figure 3, system 100 does not need to have the air adjustment unit A3.

[0074] Figure 4 shows the case when the gas turbine 10 is switched to no-load operation while ammonia is being exclusively burned. Similar to Figures 2 and 3, before time t1, the gas turbine 10 is operating at a certain rotational speed, and therefore the air flow rate is constant. Also, similar to Figure 2, before time t1, the gas turbine 10 is exclusively burning ammonia, so the LNG flow rate is zero.

[0075] Furthermore, in the example shown in Figure 4, system 100 does not use LNG. Therefore, the LNG flow rate remains 0 even after time t1.

[0076] Similar to Figures 2 and 3, at time t1, the gas turbine 10 is switched to no-load operation. The control device 90 controls the first fuel adjustment unit A1 to reduce the fuel flow rate (i.e., ammonia flow rate) from time t1 in order to suppress an increase in the rotational speed of the gas turbine 10. The control device 90 also controls the air adjustment unit A3 to reduce the air flow rate from time t1 in order to suppress an increase in the rotational speed of the gas turbine 10.

[0077] Specifically, in this example, the control device 90 may control the second valve V2 based on PID control so that the fuel flow rate (i.e., ammonia flow rate) converges to a value r2 after time t1. For example, the value r2 may be the ammonia flow rate required to maintain no-load operation of the gas turbine 10.

[0078] For example, the value r2 may be determined based on at least one of experiments, analyses, and calculations, and may be stored in the control device 90 beforehand. Also, the opening degree of the second valve V2 for adjusting the ammonia flow rate to the value r2 may be stored in the control device 90 beforehand.

[0079] Furthermore, the control device 90 opens the seventh valve V7 at time t1 to release pressurized air from the compressor 11. This reduces the airflow rate supplied from the compressor 11 to the combustor 12. The dashed line corresponds to the airflow rate in Figures 2 and 3 and shows the airflow rate when the air supply is not reduced. When the airflow rate and fuel flow rate decrease, the amount of combustion gas supplied from the combustor 12 to the turbine 13 decreases. Consequently, the force applied to the turbine 13 by the combustion gas decreases. As a result, the airflow rate is adjusted to converge to the value r3. For example, the value r3 may be the airflow rate required to maintain no-load operation of the gas turbine 10.

[0080] For example, the value r3 may be determined based on at least one of experiments, analyses, and calculations, and may be stored in the control device 90 beforehand.

[0081] Referring to Figure 1, for example, the system 100 may include a temperature sensor S in the intake duct connected to the compressor 11. The temperature sensor S is configured to measure the temperature of the air drawn into the compressor 11. The temperature sensor S is communicated with the control device 90 by wire or wireless means. The temperature sensor S also transmits measurement data to the control device 90. For example, the control device 90 may calculate the amount of air r3 required to maintain no-load operation of the gas turbine 10 based on the temperature received from the temperature sensor S. The calculated amount of air r3 may be stored in the control device 90 beforehand. The control device 90 may also adjust the airflow rate so that NOx levels fall within the target range.

[0082] For example, the control device 90 may store in advance a table showing the relationship between the rotational speed of the gas turbine 10 and the airflow rate. For example, the control device 90 may receive the current rotational speed of the gas turbine 10 from a rotational speed sensor (not shown) and determine the airflow rate corresponding to the current rotational speed based on the table. For example, the control device 90 may determine the amount of air to be reduced by the air adjustment unit A3 based on the current airflow rate and the value r3. The control device 90 may also determine the opening degree of the seventh valve V7 or IGV15 to adjust the amount of reduced air to the value r3.

[0083] Referring to Figure 4, the above process switches the gas turbine 10 from ammonia-only combustion to no-load operation using ammonia. In the example in Figure 4, both the ammonia flow rate and the air flow rate are reduced when the load is cut off. Therefore, the air-fuel ratio can be adjusted to a range where misfires do not occur. As a result, misfires during load cutoff can be prevented. Also, in the example in Figure 4, over-rotation of the gas turbine 10 is prevented.

[0084] In the example shown in Figure 4, system 100 does not use LNG. Therefore, in the example shown in Figure 4, system 100 does not need to include the second tank 2, the second fuel line L2, and the second fuel adjustment unit A2.

[0085] Figure 5 shows the case where the gas turbine 10 is switched to no-load operation while ammonia is being exclusively burned. The example in Figure 5 is a combination of the examples in Figure 2 and Figure 4. Specifically, in the example in Figure 5, the ammonia flow rate and LNG flow rate are adjusted according to the example in Figure 2, and the air flow rate is adjusted according to the example in Figure 4.

[0086] According to the above process, the gas turbine 10 is switched from ammonia-only combustion to no-load operation using LNG. In the example in Figure 5, similar to Figure 2, the supply of LNG is started at time t1, and the supply of ammonia is stopped at time t4. Therefore, the supply of ammonia is stopped after combustion has been stabilized by LNG. Also, according to the example in Figure 5, the ammonia flow rate, LNG flow rate, and air flow rate can be adjusted when the load is cut off. Therefore, if adjusting one of the air flow rate and fuel flow rate is insufficient to prevent misfire, misfire can be prevented by adjusting the other of the air flow rate and fuel flow rate. Also, according to the example in Figure 5, over-speeding of the gas turbine 10 is prevented.

[0087] In the example shown in Figure 5, the ammonia flow rate and LNG flow rate are adjusted according to the example in Figure 2 (ammonia-only combustion example), and the air flow rate is adjusted according to the example in Figure 4. In other examples not shown, the ammonia flow rate and LNG flow rate may be adjusted according to the example in Figure 3 (ammonia and LNG co-firing example), and the air flow rate may be adjusted according to the example in Figure 4.

[0088] As described above, from one perspective, the system 100 according to the embodiment comprises a gas turbine 10 that uses ammonia and LNG which has higher flammability than ammonia, and a control device 90. The control device 90 is configured to perform a first step of stopping the supply of ammonia to the gas turbine 10 and a second step of supplying LNG to the gas turbine 10 when the gas turbine 10 is switched to no-load operation (examples in Figures 2, 3 and 5). With this configuration, no-load operation of the gas turbine 10 is performed using LNG which has higher flammability than ammonia. Therefore, when ammonia is used as fuel, the operation of the gas turbine 10 can be stabilized when the load is cut off.

[0089] Furthermore, in the examples shown in Figures 2 and 5, when the gas turbine 10 is switched to no-load operation while burning ammonia exclusively, the second step includes starting the supply of LNG to the gas turbine 10, and the first step is performed after the supply of LNG to the gas turbine 10 has started. With this configuration, the supply of ammonia is stopped after the combustion has been stabilized by the LNG. As a result, misfires during load cutoff can be prevented.

[0090] Furthermore, in the example shown in Figure 3, when the gas turbine 10 is switched to no-load operation while co-firing ammonia and LNG, the first step is executed after the gas turbine 10 is switched to no-load operation, while the second step is already executed before the gas turbine 10 is switched to no-load operation and continues after the gas turbine 10 is switched to no-load operation. With this configuration, the supply of ammonia is stopped while the combustion is stabilized by LNG. As a result, misfires during load cutoff can be prevented.

[0091] Furthermore, the operation method of the gas turbine 10 includes a switching step of switching the gas turbine 10, which uses ammonia and LNG having higher combustibility than ammonia, to no-load operation; a first step of stopping the supply of ammonia to the gas turbine 10 when the switching step is performed; and a second step of supplying LNG to the gas turbine 10 when the switching step is performed. With this configuration, no-load operation of the gas turbine 10 is performed using LNG, which has higher combustibility than ammonia. Therefore, when ammonia is used as fuel, the operation of the gas turbine 10 can be stabilized during load shedding.

[0092] From another perspective, the system 100 according to the embodiment includes a gas turbine 10 that uses at least ammonia as fuel, an air adjustment unit A3 that adjusts the amount of air supplied to the gas turbine 10, and a control device 90 that controls the air adjustment unit A3. The control device 90 is configured to perform a step of reducing the amount of air supplied to the gas turbine 10 when the gas turbine 10 is switched to no-load operation (examples in Figures 4 and 5). With such a configuration, the air-fuel ratio can be adjusted to a range in which misfires do not occur. Therefore, misfires during load cutoff can be prevented. As a result, when ammonia is used as fuel, the operation of the gas turbine 10 during load cutoff can be stabilized.

[0093] Furthermore, the air adjustment unit A3 includes an air venting mechanism that removes air used for combustion from the gas turbine 10. With this configuration, the amount of air supplied can be reduced with a simple structure.

[0094] Furthermore, the air adjustment unit A3 may include an adjustment mechanism for adjusting the flow rate of air drawn into the gas turbine 10. This configuration also allows for a reduction in the amount of air supplied with a simple structure.

[0095] Furthermore, the control device 90 pre-stores the amount of air r3 required to maintain no-load operation of the gas turbine 10. With this configuration, there is no need to calculate the amount of air required to maintain no-load operation when the load is cut off. Therefore, the operation of the gas turbine 10 can be stabilized more quickly when the load is cut off.

[0096] Furthermore, the control device 90 stores in advance the amounts of fuel r1 and r2 required to maintain no-load operation of the gas turbine 10. With this configuration, there is no need to calculate the amount of fuel required to maintain no-load operation when the load is cut off. Therefore, the operation of the gas turbine 10 can be stabilized more quickly when the load is cut off.

[0097] Furthermore, the operation method of the gas turbine 10 includes a switching step of switching a gas turbine that uses at least ammonia as fuel to no-load operation, and a step of reducing the amount of air supplied to the gas turbine 10 when the switching step is performed. With this configuration, the air-fuel ratio can be adjusted to a range in which misfires do not occur. Therefore, misfires during load shedding can be prevented. As a result, when ammonia is used as fuel, the operation of the gas turbine 10 during load shedding can be stabilized.

[0098] From another perspective, the system 100 according to this embodiment includes a gas turbine 10 that uses at least ammonia as fuel, a fuel adjustment unit A0 that adjusts the amount of fuel supplied to the gas turbine 10, an air adjustment unit A3 that adjusts the amount of air supplied to the gas turbine 10, and a control device 90 that controls the fuel adjustment unit A0 and the air adjustment unit A3. The control device 90 stores in advance the amount of air r3 and the amounts of fuel r1,r2 necessary to maintain no-load operation of the gas turbine 10. The control device 90 is also configured to perform a first adjustment step of adjusting the amount of air supplied to the gas turbine 10 to the amount of air r3 stored in the control device 90, and a second adjustment step of adjusting the amount of fuel supplied to the gas turbine 10 to the amounts of fuel r1,r2 stored in the control device when the gas turbine 10 is switched to no-load operation (examples in Figures 4 and 5). With this configuration, since both the amount of air supplied and the amount of fuel supplied are adjusted, the air-fuel ratio can be adjusted in more detail within a range where misfires do not occur. Therefore, misfires during load shedding can be prevented. As a result, when ammonia is used as fuel, the operation of the gas turbine 10 during load shedding can be stabilized.

[0099] Furthermore, in the example shown in Figure 5, the gas turbine 10 also uses LNG, which has higher combustibility than ammonia, as fuel. The fuel adjustment unit A0 includes a first fuel adjustment unit A1 that adjusts the amount of ammonia supplied to the gas turbine 10, and a second fuel adjustment unit A2 that adjusts the amount of LNG supplied to the gas turbine 10. The control device 90 stores in advance the amount of LNG r1 necessary to maintain no-load operation of the gas turbine 10. The second adjustment step includes starting the supply of LNG to the gas turbine 10 when the gas turbine 10 is switched to no-load operation while burning ammonia exclusively, adjusting the amount of LNG supplied to the gas turbine 10 to the amount of LNG r1 stored in the control device 90, and stopping the supply of ammonia to the gas turbine 10 after the supply of LNG to the gas turbine 10 has started. With this configuration, the supply of ammonia is stopped after combustion has been stabilized by LNG. As a result, misfires during load cutoff can be prevented.

[0100] In another example not shown, the second adjustment step includes adjusting the amount of LNG supplied to the gas turbine 10 to the amount of LNG r1 stored in the control device when the gas turbine 10 is switched to no-load operation while co-firing ammonia and LNG, and stopping the supply of ammonia to the gas turbine 10 after the gas turbine 10 is disconnected from the load. With this configuration, the supply of ammonia is stopped while the combustion is stabilized by LNG. As a result, misfires during load cutoff can be prevented.

[0101] Furthermore, the air adjustment unit A3 includes an air venting mechanism that removes air used for combustion from the gas turbine 10. With this configuration, the amount of air supplied can be reduced with a simple structure.

[0102] Furthermore, the air adjustment unit A3 may include an adjustment mechanism for adjusting the flow rate of air drawn into the gas turbine 10. This configuration also allows for a reduction in the amount of air supplied with a simple structure.

[0103] Furthermore, the operation method of the gas turbine 10 includes a switching step of switching the gas turbine 10, which uses at least ammonia as fuel, to no-load operation; a first adjustment step of adjusting the amount of air supplied to the gas turbine 10 to a predetermined amount of air r3 when the switching step is performed; and a second adjustment step of adjusting the amount of fuel supplied to the gas turbine 10 to predetermined amounts of fuel r1 and r2 when the switching step is performed. With this configuration, since both the amount of air supplied and the amount of fuel supplied are adjusted, the air-fuel ratio can be adjusted in more detail within a range where misfires do not occur. Therefore, misfires during load shedding can be prevented. As a result, when ammonia is used as fuel, the operation of the gas turbine 10 during load shedding can be stabilized.

[0104] While embodiments have been described above with reference to the attached drawings, this disclosure is not limited to the embodiments described above. 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 fall within the technical scope of this disclosure.

[0105] For example, in the above embodiment, the system 100 includes a gas turbine 10 as an internal combustion engine. In other embodiments, the system 100 may include another internal combustion engine that can be shut off from the load instead of the gas turbine 10 (e.g., a gas engine).

[0106] Furthermore, for example, in the above embodiment, the method of operating the internal combustion engine according to the disclosure is performed by the control device 90. In other embodiments, the method of operating the internal combustion engine according to the disclosure may be performed manually by an operator.

[0107] Furthermore, in the above embodiment, for example, system 100 uses ammonia as the first fuel. In other examples, system 100 may use a low-flammability fuel other than ammonia as the first fuel (for example, by-product gases such as blast furnace gas (BFG), converter gas (LDG), and coke oven gas (COG)).

[0108] Furthermore, the operating patterns shown in Figures 2 to 5, particularly the times t1 to t5 and values ​​r0, r1, r2, and r3 in the figures, are merely illustrative examples, and operating patterns that do not use these are also included in this disclosure.

[0109] 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]

[0110] 10. Gas turbine (internal combustion engine) 20. Generator (Load) 90 Control device 100 Combustion Systems A0 Fuel adjustment section A1 1st fuel adjustment section A2 2nd fuel adjustment section A3 Air adjustment unit r1 Amount of LNG required to maintain no-load operation r2 Amount of ammonia required to maintain no-load operation r3 Amount of air required to maintain no-load operation

Claims

1. An internal combustion engine that uses at least ammonia as fuel, A fuel adjustment unit that adjusts the amount of fuel supplied to the internal combustion engine, An air adjustment unit that adjusts the amount of air supplied to the internal combustion engine, A control device for controlling the fuel adjustment unit and the air adjustment unit, Equipped with, The control device is The amount of air and fuel necessary to maintain the no-load operation of the internal combustion engine is stored in advance. When the internal combustion engine is switched to no-load operation, A first adjustment step of adjusting the amount of air supplied to the internal combustion engine to the amount of air stored in the control device, A second adjustment step of adjusting the amount of fuel supplied to the internal combustion engine to the amount of fuel stored in the control device, Configured to perform, Combustion system.

2. The aforementioned internal combustion engine further uses a second fuel having higher combustibility than ammonia as the fuel, The aforementioned fuel adjustment unit is A first fuel adjustment unit that adjusts the amount of ammonia supplied to the internal combustion engine, A second fuel adjustment unit for adjusting the amount of the second fuel supplied to the internal combustion engine, Includes, The control device pre-stores the amount of second fuel necessary to maintain the no-load operation of the internal combustion engine. The second adjustment step is performed when the internal combustion engine is switched to no-load operation while burning ammonia exclusively. To begin supplying the second fuel to the internal combustion engine, The amount of the second fuel supplied to the internal combustion engine is adjusted to the amount of the second fuel stored in the control device, After the supply of the second fuel to the internal combustion engine is started, the supply of ammonia to the internal combustion engine is stopped. including, The combustion system according to claim 1.

3. The aforementioned internal combustion engine further uses a second fuel having higher combustibility than ammonia as the fuel, The aforementioned fuel adjustment unit is A first fuel adjustment unit that adjusts the amount of ammonia supplied to the internal combustion engine, A second fuel adjustment unit for adjusting the amount of the second fuel supplied to the internal combustion engine, Includes, The control device pre-stores the amount of second fuel necessary to maintain the no-load operation of the internal combustion engine. The second adjustment step is performed when the internal combustion engine is switched to no-load operation while co-firing ammonia and the second fuel, The amount of the second fuel supplied to the internal combustion engine is adjusted to the amount of the second fuel stored in the control device, After the internal combustion engine is switched to no-load operation, the supply of ammonia to the internal combustion engine is stopped. including, The combustion system according to claim 1.

4. The air adjustment unit includes an air venting mechanism for removing air used for combustion from the internal combustion engine. The combustion system according to claim 1.

5. The air conditioning unit includes an adjustment mechanism for adjusting the flow rate of air drawn into the internal combustion engine. The combustion system according to claim 1.

6. A switching process for switching an internal combustion engine that uses at least ammonia as fuel to no-load operation, When the switching process is performed, a first adjustment process is performed to adjust the amount of air supplied to the internal combustion engine to a predetermined amount of air. When the switching step is performed, a second adjustment step is performed to adjust the amount of fuel supplied to the internal combustion engine to a predetermined amount of fuel. A method of operating an internal combustion engine, including [specific details omitted].

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