Gas turbine control device and control method

Abstract

This gas turbine control device (CL) comprises: an air-fuel ratio adjustment means (52) for adjusting, in accordance with the proportion of an auxiliary fuel in mixed air supplied to a combustor (2), an air-fuel ratio that is the volumetric flow rate ratio of air relative to the mixed air; and a fuel control means (53) for determining the amount of the mixed air and / or the air to be supplied to the combustor (2) on the basis of the air-fuel ratio adjusted by the air-fuel ratio adjustment means (52).

Description

Gas turbine control device and control method Related Applications

[0001] This application claims priority to Japanese Patent Application No. 2024-014449, filed February 1, 2024, the entire contents of which are incorporated herein by reference.

[0002] The present disclosure relates to a control device and a control method for a gas turbine fueled by a mixture of at least two types of fuel with different combustion rates.

[0003] In gas turbine engines, strict environmental standards have been established regarding the composition of exhaust gases emitted by combustion, and there is a demand for reducing harmful substances such as nitrogen oxides (hereinafter referred to as NOx). To address this, dry-type DLE (Dry Low Emissions) combustors are known, which inject a premixed gas mixture created by mixing fuel and compressed air into a combustion chamber to perform lean premix combustion at low temperatures.

[0004] To achieve even lower NOx emissions in a DLE combustor, a method has been proposed using two burners: a main burner with a premix burner and a supplementary burner located downstream of the main burner (see, for example, Patent Document 1). This main burner supplies fuel to control the local air-fuel ratio, and the remaining required fuel is supplied by the supplementary burner, controlling the power. The air-fuel mixture injected from the supplementary burner is supplied into the high-temperature combustion gas produced by the main burner's combustion flame, making it possible to combust even lean air-fuel mixtures that would normally be unburnable. Within a certain range of air-fuel mixtures, the supplementary burner produces almost no NOx emissions.

[0005] Furthermore, the DLE combustor in Patent Document 1 is a natural gas-fired combustor, but the recent CO ２ In response to growing interest in reducing CO2 emissions, natural gas is mixed with hydrogen. ２ Efforts are being made to reduce it.

[0006] JP 2012-141078 A

[0007] However, because hydrogen burns quickly, it is prone to high local combustion temperatures, which means that NOx emissions tend to be higher than when using only natural gas. This creates the problem that the desired NOx emissions cannot be achieved if the combustion adjustment settings are left unchanged for natural gas.

[0008] Furthermore, when a fuel with a high combustion speed, such as hydrogen, is burned, a backfire phenomenon occurs easily in which the flame generated in the combustion chamber returns to the burner side.

[0009] The disclosure of the present application has been made to solve the above-mentioned problems, and provides a gas turbine control device and control method that achieves NOx emissions at the same level as those achieved by mono-fuel combustion of natural gas, even when combusting a mixture of at least two types of fuel with different combustion speeds.

[0010] A gas turbine control device according to one embodiment of the present disclosure is a control device for a gas turbine equipped with a combustor that burns a mixture of a main fuel and a secondary fuel, and includes: air-fuel ratio adjustment means that adjusts an air-fuel ratio, which is a volumetric flow rate ratio of air to the mixture supplied to the combustor, in accordance with a secondary fuel ratio in the mixture; and fuel control means that determines the amount of at least one of the mixture and air to be supplied to the combustor based on the air-fuel ratio adjusted by the air-fuel ratio adjustment means.

[0011] According to a gas turbine control device according to one embodiment of the present disclosure, by increasing the air-fuel ratio in accordance with the proportion of secondary fuel in the mixture and reducing fuel, NOx emissions can be reduced to the same level as in the case of mono-fuel combustion of natural gas.

[0012] Any combination of at least two features disclosed in the claims and / or the specification and / or the drawings is included in the present disclosure. In particular, any combination of two or more of the claims is included in the present disclosure.

[0013] The present disclosure will be more clearly understood from the following description of preferred embodiments with reference to the accompanying drawings. However, the embodiments and drawings are merely for illustration and explanation purposes and should not be used to define the scope of the present disclosure. The scope of the present disclosure is defined by the appended claims. In the accompanying drawings, the same part numbers in multiple drawings indicate the same or corresponding parts. A schematic diagram showing a gas turbine power generation system using a gas turbine control device of the present disclosure. A longitudinal sectional view showing a combustor of the present disclosure. A schematic diagram showing a control circuit of the present disclosure.

[0014] First Embodiment An embodiment of the present disclosure will be described with reference to the drawings. FIG. 1 shows a schematic configuration of a gas turbine power generation system that uses a gas turbine GT control device CL according to an embodiment of the present disclosure. In the figure, the gas turbine GT includes, as main components, a compressor 1, a combustor 2, and a turbine 3. The combustor 2 includes a fuel supply device 5 and a fuel mixer 6 that mixes a main fuel F1 and a secondary fuel F2 supplied from the fuel supply device 5. A main fuel control valve B1, the valve opening of which is adjusted by the gas turbine control device CL in accordance with the combustion ratio of the main fuel F1 and the secondary fuel F2 supplied from the fuel supply device 5, is provided between the combustor 2 and the fuel mixer 6. Compressed air A supplied from the compressor 1 and a mixture F (F1 + F2) supplied from the fuel mixer 6 are combusted in the combustor 2, and high-temperature, high-pressure combustion gas G generated by the combustion is supplied to the turbine 3 to drive the turbine 3. Exhaust gas E is discharged from the turbine 3. The compressor 1 is driven by a turbine 3 via a rotary shaft 7 , and the turbine 3 also drives a load 9 such as a generator via a reducer 8 .

[0015] The main fuel F1 may be natural gas, city gas, or the like. City gas refers to an artificially produced gas that uses natural gas as the main raw material. The main fuel F1 is not limited to these, and may be any hydrocarbon-based fuel containing 60% or more by volume of hydrocarbons. The secondary fuel F2 may be hydrogen, by-product hydrogen, natural gas containing hydrogen or by-product hydrogen, or the like. The secondary fuel F2 is not limited to these, and may be any gas that has a high combustion temperature and a fast combustion rate. An example of such a fuel is ammonia. Note that the mixture F in this disclosure will be described as a mixture of two types of fuel, the main fuel F1 and the secondary fuel F2, which have different combustion rates, but it is not limited to this, and may be a mixture of three or more types of fuels.

[0016] In the following description, the compressor 1 side in the axial direction of the gas turbine GT will be referred to as the "upstream side," and the turbine 3 side will be referred to as the "downstream side." Furthermore, in the following description, unless otherwise specified, the terms "axial direction," "radial direction," and "circumferential direction" refer to the axial direction, radial direction, and circumferential direction of the gas turbine GT, respectively.

[0017] 2 shows the combustor 2. In this embodiment, the combustor 2 is a counter-flow can type combustor in which the flow direction of compressed air A supplied from the compressor 1 (FIG. 1) and the flow direction of combustion gas G are opposed to each other inside the combustor. The type of the combustor may be an annular type having a plurality of fuel injection valves arranged on the circumference.

[0018] The combustor 2 includes a combustion duct 34 and a casing 35 arranged concentrically on a central axis 302. A burner unit 30 is attached to the top of the combustion duct 34, and a combustion chamber 33 is formed inside the combustion duct 34 to combust fuel and the like injected from the burner unit 30. The combustion duct 34 is surrounded by a cylindrical casing 35, and an annular combustion air flow path 37 is formed between the combustion duct 34 and the casing 35, through which compressed air A supplied from the compressor 1 ( FIG. 1 ) flows. The casing 35 and the combustion duct 34 support a plurality of reheat burners 36 downstream of the burner unit 30.

[0019] In this embodiment, the burner unit 30 is arranged along a central axis 302 and includes a main burner 31 that injects a premixed gas, generated by mixing an air-fuel mixture F with compressed air A, into a combustion chamber 33, and a diffusion combustion type pilot burner 32 that directly injects the air-fuel mixture F into the combustion chamber 33. The main burner 31 is arranged concentrically around the pilot burner 32. The main burner 31 and the pilot burner 32 are in communication with the fuel mixing device 6 via a pipe 304.

[0020] In this embodiment, the main burner 31 has an outer cylinder 310 and an inner cylinder 312 concentrically arranged along the central axis 302. In this embodiment, as shown in the figure, the inner cylinder 312 also serves as a combustion air injection cylinder 322b of the pilot burner 32, which will be described later. The annular space between the outer cylinder 310 and the inner cylinder 312 is used as a premixing passage 314 for mixing the air-fuel mixture F and compressed air A. One end of the premixing passage 314 opens to the combustion chamber 33, and the other end opens radially outward to the combustion air passage 37 via a plurality of air intakes 315. A plurality of main fuel nozzles 316 that eject a first fuel are arranged radially outward of the air intakes 315. Although not shown, the plurality of air intakes 315 and the corresponding plurality of main fuel nozzles 316 are preferably arranged at equal intervals in the circumferential direction around the central axis 302. Although not shown, each main fuel nozzle 316 has a plurality of fuel injection holes (not shown) formed at a portion facing the air intake 315, which inject the air-fuel mixture F toward the air intake 315, and is connected to the fuel mixer 6 via a pipe 304a equipped with a flow control valve 201. By keeping the flow control valve 201 open during normal operation, the air-fuel mixture F supplied from the fuel mixer 6 is supplied from the air intake 315 to the premixing passage 314 together with the compressed air A supplied from the combustion air passage 37, and mixed in the premixing passage 314 to form a premixed air-fuel mixture that is injected into the combustion chamber 33. In this embodiment, the air intake 315 is provided with a plurality of swirl vanes (swirlers) 317 that impart a swirling force to the combustion air flowing into the premixing passage 314, thereby promoting premixing with the air-fuel mixture F.

[0021] The pilot burner 32 includes a fuel injection tube 322a extending along the central axis 302 and a combustion air injection tube 322b concentrically mounted on the fuel injection tube 322a. A fuel injection passage (not shown) formed in the fuel injection tube 322a is connected to the fuel mixer 6 via a pipe 304b equipped with a flow control valve 202. By opening the flow control valve 202 at startup, the air-fuel mixture F supplied from the fuel mixer 6 is injected into the combustion chamber 33. An annular air passage 324 is formed between the fuel injection tube 322a and the combustion air injection tube 322b. One end of the annular air passage 324 is connected to the combustion air passage 37 and the other end is connected to the combustion chamber 33, so that compressed air A supplied from the compressor 1 is injected into the combustion chamber.

[0022] The reheating burners 36 are attached to the casing 35 along four axes 360 that are included in a plane perpendicular to the central axis 302 and are arranged at equal intervals in the circumferential direction, and their inner tips pass through through-holes 340 formed in the combustion tube 34 and face the inside of the combustion chamber 33. The reheating burners 36 are connected to the fuel mixing device 6 via piping 306 equipped with a flow rate adjustment valve 203, and are configured so that the air-fuel mixture F can be injected into the combustion chamber 33 by opening the flow rate adjustment valve 203 during high-load operation.

[0023] The operation of the combustor 2 having the above-described configuration will be described below with reference to Fig. 2. As shown in Fig. 2, at the start-up of the gas turbine GT, the flow control valve 202 is opened, and the air-fuel mixture F supplied from the fuel mixing device 6 to the pilot burner 32 is injected into the combustion chamber 33. As a result, the air-fuel mixture F is diffused and mixed with the compressed air A injected into the combustion chamber 33 from the annular air passage 324 within the combustion chamber 33, and is ignited by an ignition source such as a spark plug (not shown), forming a pilot flame by diffusion combustion.

[0024] When the gas turbine GT shifts to normal operation, the premixed air-fuel mixture injected from the premixing passage 314 of the main burner 31 is ignited by the pilot flame in the combustion chamber 33 and combusts in the primary combustion zone S1 on the upstream side of the combustion chamber 33. By burning the lean premixed air-fuel mixture, the combustion flame temperature in the combustion chamber 33 drops, and the amount of NOx in the combustion exhaust gas from the main burner is suppressed.

[0025] When high-load combustion is required to increase the output of the gas turbine GT, the air-fuel mixture F is introduced into the combustion chamber 33 from the supplementary combustion burner 36, and is mixed with the combustion exhaust gas from the main burner 31 and combusted in the secondary combustion zone S2 downstream of the primary combustion zone S1.

[0026] Next, a control method for the gas turbine GT having the above configuration will be described. Here, the main fuel F1 is natural gas and the secondary fuel F2 is hydrogen. Figure 3 shows a part of the control circuit in the gas turbine control device CL of the present disclosure. The ratio of hydrogen to natural gas (mixed combustion ratio) is measured in advance. The gas turbine control device CL includes a combustion air flow rate estimation unit 50 that estimates the air flow rate in the gas turbine GT based on the intake-air temperature, gas turbine rotation speed, etc.; a main air-fuel ratio setting table 51 that sets an air-fuel ratio (hereinafter referred to as a standard air-fuel ratio) that is the volumetric flow rate ratio of compressed air A to natural gas during mono-fuel combustion based on the intake-air temperature, the load factor of the load 9 (FIG. 1), etc.; an air-fuel ratio adjustment means 52 (FIG. 3) that changes the air-fuel ratio (the volumetric flow rate ratio of compressed air A to mixture F supplied to the combustor 2 (FIG. 1)) in accordance with the hydrogen ratio (hydrogen blending ratio) of the mixture F of natural gas and hydrogen; and a fuel control means 53 that determines the amount of at least one of the mixture F and air to be supplied to the combustor 2 based on the air-fuel ratio adjusted by the air-fuel ratio adjustment means 52. The main air-fuel ratio setting table 51 sets the standard air-fuel ratio corresponding to mono-fuel combustion of natural gas. As described above, the hydrogen blending ratio is determined as the hydrogen ratio by measuring the volumetric flow rates of natural gas and hydrogen in advance.

[0027] The air-fuel ratio parameter is set to a known load factor for mono-fuel combustion of natural gas. During hydrogen-mixed combustion, the air-fuel ratio adjustment unit 52 corrects the air-fuel ratio so that it is larger by adding a correction value corresponding to the hydrogen-mixed combustion ratio to the air-fuel ratio parameter, which is the standard air-fuel ratio, using an adder 61. Since the air-fuel ratio is a value obtained by dividing the amount of air by the amount of the air-fuel mixture F, the correction value is a value added to the air amount. Then, the air amount estimated by the combustion air flow rate estimation unit 50 is divided by the air-fuel ratio corrected by the adder 61 using a divider 62 to calculate the amount of the air-fuel mixture F to be supplied to the combustor 2. In other words, because an air-fuel ratio larger than the standard air-fuel ratio is used, the air-fuel ratio adjustment unit 52 corrects the air-fuel ratio so as to reduce the amount of the air-fuel mixture F. The fuel control means 53 calculates the valve opening of the main fuel control valve B1 from the amount of fuel F supplied to the combustor 2, the gas specific gravity, the valve area, etc., and issues a command to the main fuel control valve B1 to achieve that valve opening, taking into account the gas density calculator 65 and the gas specific gravity 66 from the hydrogen proportion. The main fuel control valve B1 in Figure 1 controls the amount of mixture F supplied to the main burner 31 and the supplemental burner 36 in Figure 2.

[0028] In the above control, the fuel control means 53 controls the amount of fuel F supplied to the combustor 2, but NOx emissions can also be reduced by leaving the amount of fuel F supplied unchanged and increasing the amount of air supplied to the combustor 2. Therefore, the fuel control means 53 may determine the amount of air supplied to the combustor 2 instead of or together with the amount of fuel F supplied to the combustor 2.

[0029] According to the above-described configuration, the fuel control means 53 is provided, which determines the supply amount of at least one of the mixture F and air to the combustor 2 based on the air-fuel ratio adjusted by the air-fuel ratio adjusting means 52 in accordance with the proportion of secondary fuel in the mixture F. Therefore, it is possible to achieve the desired NOx emission amount and CO ２ The gas turbine GT can be controlled to achieve the desired exhaust gas volume.

[0030] The air-fuel ratio adjusting means 52 may have an air-fuel ratio correction table that corrects the air-fuel ratio with respect to the standard air-fuel ratio in accordance with the proportion of the secondary fuel F2. By using the air-fuel ratio correction table, the correction process can be easily performed, and the correction process circuit can be simplified.

[0031] The air-fuel ratio adjusting means 52 may make a correction by adding a correction value to the standard air-fuel ratio to reduce the air-fuel mixture F. By making a correction to reduce the air-fuel mixture F, it is possible to suppress NOx emissions to the same level as in the case of mono-fuel combustion of natural gas. Furthermore, when burning a fuel with a high combustion speed such as hydrogen, flashbacks are likely to occur, in which the flame generated in the combustion chamber returns to the burner, but by reducing the air-fuel mixture F, flashbacks are less likely to occur. Furthermore, by using hydrogen-mixed fuel, CO emissions are reduced compared to mono-fuel combustion of natural gas. ２ Emissions can also be reduced.

[0032] The air-fuel mixture F supplied based on the air-fuel ratio corrected by the air-fuel ratio correction table may be supplied to the main burner 31 and the supplementary combustion burner 36 arranged downstream of the main burner 31. Since the air-fuel mixture F based on the corrected air-fuel ratio is supplied not only to the main burner 31 but also to the supplementary combustion burner 36 arranged downstream of the main burner 31, NOx emissions can be further suppressed, and CO ２ Emissions can also be reduced in a similar manner.

[0033] A control method for a gas turbine GT equipped with a combustor 2 that burns a mixture F of a main fuel F1 and a secondary fuel F2 adjusts the air-fuel ratio, which is the volumetric flow rate ratio of air to the mixture F supplied to the combustor 2, in accordance with the secondary fuel ratio of the mixture F, and determines the supply amount of at least one of the mixture F and air to the combustor 2 based on the adjusted air-fuel ratio. Since the gas turbine GT is equipped with a fuel control means 53 that determines the supply amount of at least one of the mixture F and air to the combustor 2 based on the air-fuel ratio adjusted in accordance with the secondary fuel ratio of the mixture F, desired NOx emissions and CO ２ The gas turbine can be controlled to achieve the desired emissions.

[0034] As described above, the preferred embodiments of the present disclosure have been described with reference to the drawings, but various additions, modifications, and deletions can be made without departing from the spirit of the present disclosure. Therefore, such additions, modifications, and deletions are also included in the scope of the present disclosure.

Claims

1. A control device for a gas turbine equipped with a combustor that burns a mixture of main fuel and secondary fuel, comprising: air-fuel ratio adjustment means that adjusts the air-fuel ratio, which is the volumetric flow rate ratio of air to the mixture supplied to the combustor, in accordance with the secondary fuel ratio of the mixture; and fuel control means that determines the amount of at least one of the mixture and air to be supplied to the combustor based on the air-fuel ratio adjusted by the air-fuel ratio adjustment means.

2. A gas turbine control device according to claim 1, wherein the air-fuel ratio adjusting means has an air-fuel ratio correction table for correcting the air-fuel ratio in accordance with the proportion of the secondary fuel relative to the standard air-fuel ratio.

3. A gas turbine control device according to claim 1 or 2, wherein the air-fuel ratio adjusting means adds a correction value to the standard air-fuel ratio to correct the mixture so as to reduce it.

4. A gas turbine control device as described in claim 2, wherein the mixture supplied based on the air-fuel ratio corrected by the air-fuel ratio correction table is supplied to a main burner and a supplementary burner arranged downstream of the main burner.

5. A control method for a gas turbine equipped with a combustor that burns a mixture of main fuel and secondary fuel, the control method comprising: adjusting an air-fuel ratio, which is the volumetric flow rate ratio of air to the mixture supplied to the combustor, in accordance with the secondary fuel ratio of the mixture; and determining the amount of at least one of the mixture and air to be supplied to the combustor based on the adjusted air-fuel ratio.

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