Gas turbine cogeneration system and its operating method

Abstract

To provide a gas turbine cogeneration system capable of quickly responding to an increase in an amount of NOx discharged from a gas turbine and performing a denitrification operation when a hydrogen gas fuel mixed combustion ratio in the gas turbine increases, and an operation method therefor.SOLUTION: A gas turbine cogeneration system comprises a denitration control unit that outputs a control command to the denitration device to set a NOx emission at an exhaust heat recovery boiler outlet to a boiler outlet target value or less. The denitration control unit is configured to generate the control command by referring to at least a first addition amount of a reductant obtained by calculation based on a NOx parameter, which is a parameter that correlates with the NOx emission at a turbine outlet.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present disclosure relates to a gas turbine cogeneration system including a combustor that is supplied with hydrogen gas fuel, and an operating method thereof. [Background technology]

[0002] The gas turbine cogeneration system disclosed in Patent Document 1 includes a gas turbine, a heat recovery boiler that generates steam using exhaust gas from the gas turbine, a process system that supplies steam discharged from the heat recovery boiler to a steam consuming facility, a first steam system that supplies steam extracted from the process system to the upstream side of a flame zone in a combustor of the gas turbine, and a second supply system that supplies steam extracted from the process system to the downstream side of the flame zone. In the combustor, it is possible to mix a normal fuel such as natural gas with a gasification gas fuel such as coal gas or biomass gas. In the above gas turbine cogeneration system, the amount of steam supplied by the first supply system and the second supply system is controlled based on the mixed combustion ratio of the normal fuel and the gasification gas and the amount of steam required in the steam facility. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2014-173572 A Summary of the Invention [Problem to be solved by the invention]

[0004] When the gasification gas is hydrogen gas fuel containing hydrogen gas as a main component, a change in the supply amount of hydrogen gas fuel changes the flame temperature in the combustor and the concentration of nitrogen oxides discharged from the gas turbine. As the hydrogen gas fuel mixed combustion ratio, which is the mixed combustion ratio of hydrogen gas fuel and other fuel, changes, it is preferable to quickly perform a denitrification operation to remove nitrogen oxides (hereinafter sometimes referred to as "NOx") from the exhaust gas discharged from the gas turbine.

[0005] An object of the present disclosure is to provide a gas turbine cogeneration system and an operating method thereof that can perform denitration operation in response to an increase in the amount of NOx emitted from the gas turbine when the hydrogen gas fuel co-combustion ratio in the gas turbine is increased. [Means for solving the problem]

[0006] A gas turbine cogeneration system according to at least one embodiment of the present disclosure includes: a gas turbine including a compressor, a combustor, and a turbine; a hydrocarbon fuel supply facility for supplying a hydrocarbon gas fuel to the combustor; a hydrogen gas fuel supply facility for supplying hydrogen gas fuel, which is a fuel mainly composed of hydrogen gas, to the combustor; a heat recovery steam generator for generating steam using exhaust gas from the turbine; an upstream steam line for supplying the steam discharged from the heat recovery steam generator to a head end side of the combustor; a denitration device for denitrifying the exhaust gas by adding a reducing agent to the exhaust gas flowing through the exhaust heat recovery boiler; a denitration control unit for outputting a control command to the denitration device so as to make the NOx emission amount at the exhaust heat recovery boiler outlet equal to or less than a boiler outlet target value; Equipped with The denitration control unit is configured to generate the control command with reference to at least the first addition amount of the reducing agent obtained by a calculation based on a NOx parameter which is a parameter correlated with the amount of NOx emissions at a turbine outlet.

[0007] A method for operating a gas turbine cogeneration system according to at least one embodiment of the present disclosure includes: The gas turbine cogeneration system includes: a gas turbine including a compressor, a combustor, and a turbine; a hydrocarbon fuel supply facility for supplying a hydrocarbon gas fuel to the combustor; a hydrogen gas fuel supply facility for supplying hydrogen gas fuel, which is a fuel mainly composed of hydrogen gas, to the combustor; a heat recovery steam generator for generating steam using exhaust gas from the turbine; an upstream steam line for supplying the steam discharged from the heat recovery steam generator to a head end side of the combustor; a denitration device for denitrifying the exhaust gas by adding a reducing agent to the exhaust gas flowing through the exhaust heat recovery boiler; Including, a denitration control step of outputting a control command to the denitration device so as to make the NOx emission amount at the exhaust heat recovery boiler outlet equal to or less than a boiler outlet target value; In the denitration control step, the control command is generated with reference to at least the first addition amount of the reducing agent obtained by a calculation based on a NOx parameter which is a parameter correlated with the amount of NOx exhausted at a turbine outlet. Effect of the Invention

[0008] According to the present disclosure, it is possible to provide a gas turbine cogeneration system and an operating method thereof that can perform denitrification operation in response to an increase in the amount of NOx emitted from the gas turbine when the hydrogen gas fuel mixed combustion ratio in the gas turbine is increased. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram illustrating a gas turbine cogeneration system according to an embodiment. [Diagram 2] FIG. 1 is a schematic diagram illustrating a combustor according to an embodiment. [Diagram 3] FIG. 1 is a schematic diagram illustrating a water recovery system according to one embodiment. [Figure 4] FIG. 2 is a schematic diagram illustrating a controller according to an embodiment. [Diagram 5] FIG. 2 is a schematic diagram showing characteristics of NOx emissions at a turbine outlet. [Figure 6] FIG. 2 is a schematic diagram showing characteristics of NOx parameters. [Figure 7] FIG. 4 is another schematic diagram showing characteristics of NOx parameters. [Figure 8] 4 is a flowchart of a cogeneration system control process according to an embodiment. [Figure 9] 9 is a flowchart of the cogeneration system control process following FIG. 8. [Figure 10] 4 is a flowchart of a denitration control process according to an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, some embodiments of the present disclosure will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of components described as the embodiments or shown in the drawings are merely illustrative examples and are not intended to limit the scope of the present disclosure. For example, expressions expressing relative or absolute configuration, such as "in a certain direction," "along a certain direction," "parallel," "orthogonal," "center," "concentric," or "coaxial," not only strictly express such a configuration, but also express a state in which there is a relative displacement with a tolerance or an angle or distance to the extent that the same function is obtained. For example, expressions indicating that things are in an equal state, such as "identical," "equal," and "homogeneous," not only indicate a state of strict equality, but also indicate a state in which there is a tolerance or a difference to the extent that the same function is obtained. For example, expressions describing shapes such as a rectangular shape or a cylindrical shape do not only refer to rectangular shapes, cylindrical shapes, etc. in the strict geometric sense, but also refer to shapes that include uneven portions, chamfered portions, etc., to the extent that the same effect is obtained. On the other hand, the expressions "comprise", "include", or "have" a certain element are not exclusive expressions excluding the presence of other elements. In addition, the same components are denoted by the same reference numerals and the description thereof may be omitted.

[0011] <Outline of Gas Turbine Cogeneration System 100> FIG. 1 is a schematic diagram showing a gas turbine cogeneration system 100 (hereinafter, sometimes referred to as "cogeneration system 100") according to an embodiment of the present disclosure. The cogeneration system 100, which may be, for example, a power plant, includes a gas turbine 9 and a heat recovery steam generator 14. The gas turbine 9 includes a compressor 1 for generating compressed air 7 from compressor inlet air 6, a combustor 3 for burning a fuel using oxygen in the compressed air 7 as an oxidizer and raising the temperature of the compressed air 7 to generate a combustion gas 12, a turbine 2 for rotating using the combustion gas 12 discharged from the combustor 3 as a driving source, and a generator 5 connected to the turbine 2. The fuel supplied to the combustor 3 includes a hydrocarbon gas fuel and a hydrogen gas fuel (details will be described later). The heat recovery steam generator 14 is configured to generate steam from boiler feed water by utilizing heat recovered from exhaust gas 13 discharged from the turbine 2. The boiler feed water is water to be supplied to the heat recovery steam generator 14.

[0012] The cogeneration system 100 includes a steam supply line 21 for supplying steam discharged from the heat recovery steam generator 14 to the steam consumer 10. The steam supply line 21 includes a steam pipe 21A connected to the heat recovery steam generator 14 and the steam consumer 10, and a steam flow control valve 21B provided on the steam pipe 21A. The opening degree of the steam flow control valve 21B is controlled by a controller 90 described later, whereby a consumer steam supply amount, which is the amount of steam supplied to the steam consumer 10, is controlled. The steam consumer 10 is, for example, a steam turbine. The steam consumer 10 may be a steam turbine of a combined cycle power plant, an industrial process device, or the like. Furthermore, the cogeneration system 100 includes a steam extraction line 130 for supplying steam extracted from the steam supply line 21 to the combustor 3. The configuration of the steam extraction line 130 will be described in detail later.

[0013] Although not essential components of the present disclosure, the cogeneration system 100 includes a water recovery system 40 for recovering moisture contained in the exhaust gas 13 discharged from the heat recovery boiler 14, a make-up water tank 17 for storing the water containing moisture recovered from the water recovery system 40 as boiler feed water, a feed water line 15 for supplying the boiler feed water to the make-up water tank 17, a feed water line 19 connected to the make-up water tank 17 and the heat recovery boiler 14, and a feed water pump 18 provided on the feed water line 19. When the feed water pump 18 is driven, the boiler feed water stored in the make-up water tank 17 flows through the feed water line 19 and is supplied to the heat recovery boiler 14. It is preferable that the temperature of the boiler feed water supplied to the heat recovery boiler 14 is high. This is because the amount of heat required for the heat recovery boiler 14 to generate steam is reduced, and the efficiency of the cogeneration system 100 is improved.

[0014] Although not an essential component of the present disclosure, the cogeneration system 100 includes an exhaust gas supply line 57 which is a supply line for the exhaust gas 13 from the exhaust heat recovery boiler 14 to the water recovery system 40, an exhaust line 29 which is provided branching off from the exhaust gas supply line 57, and an exhaust damper 31 which is provided in the exhaust line 29. The exhaust gas 13 flowing through the exhaust line 29 is exhausted to the outside from the exhaust tower 30. In one embodiment of the present disclosure, when the exhaust gas 13 is supplied from the cogeneration system 100 to the water recovery system 40, the exhaust damper 31 is closed and the exhaust gas 13 does not flow through the exhaust line 29.

[0015] <Schematic configuration of combustor 3> FIG. 2 is a schematic diagram showing a combustor 3 according to an embodiment of the present disclosure. The combustor 3 includes a combustor casing 23 formed in a cylindrical shape, a head end 24 provided at one end of the combustor casing 23, a fuel nozzle 25 provided at the head end 24, a cylindrical combustor liner 26 separating unburned air from burned combustion gas 12, and a combustor transition piece 27 connected to the downstream side of the combustor liner 26. Compressed air 7 is supplied to the combustor casing 23. In the combustor casing 23, the compressed air 7 flows toward the head end 24 through an annular space formed outside the combustor liner 26. The compressed air 7 flowing through the annular space flows into the inside of the combustor liner 26 and mixes with fuel injected from the fuel nozzle 25 into the inside of the combustor liner 26. The fuel is combusted inside the combustor liner 26, and a flame 28 is generated inside the combustor liner 26. The combustion gas 12 generated inside the combustor liner 26 is discharged from a combustor transition piece 27 and flows into the turbine 2 .

[0016] <Fuel supply system for combustor 3> Returning to FIG. 1, the fuel supplied to the combustor 3 includes a hydrocarbon gas fuel and a hydrogen gas fuel. The cogeneration system 100 includes a hydrocarbon fuel supplying device 51 for supplying the hydrocarbon gas fuel to the combustor 3, and a hydrogen gas fuel supplying device 52 for supplying the hydrogen gas fuel to the combustor 3. The hydrocarbon fuel supplying device 51 includes a first supply source 53 which is a supply source of the hydrocarbon gas fuel, a first pipe 151 for guiding the hydrocarbon gas fuel from the first supply source 53 to the fuel nozzle 25 (see FIG. 2) of the combustor 3, and a first flow adjustment valve 153 provided on the first pipe 151. Similarly, the hydrogen gas fuel supplying device 52 includes a second supply source 54 which is a supply source of the hydrogen gas fuel, a second pipe 152 for guiding the hydrogen gas fuel from the second supply source 54 to the fuel nozzle 25, and a second flow adjustment valve 154 provided on the second pipe 152. The opening degree of the first flow regulation valve 153 and the opening degree of the second flow regulation valve 154 are controlled by a controller 90 described later, whereby the hydrocarbon gas fuel supply amount, which is the supply amount of the hydrocarbon gas fuel, and the hydrogen gas fuel supply amount, which is the supply amount of the hydrogen gas fuel, are adjusted. In other words, the controller 90 can adjust the hydrogen gas fuel mixing ratio in the combustor 3. The hydrogen gas fuel mixing ratio is the ratio of the hydrogen gas fuel to the fuel supplied to the combustor 3. The ratio is a value calculated on a calorific value basis or a weight basis. Note that the hydrocarbon gas fuel in this embodiment is off-gas. The hydrocarbon gas fuel in other embodiments may be natural gas. Also, the hydrogen gas fuel is a fuel containing hydrogen gas as a main component.

[0017] As the hydrogen gas fuel supply amount increases and the hydrogen gas fuel mixed combustion ratio increases, the amount of carbon dioxide gas generated in the combustor 3 decreases, but the temperature of the flame 28 in the combustor 3 increases, resulting in an increase in the amount of NOx generated. Therefore, when the hydrogen gas fuel mixed combustion ratio changes, the denitrification device 120 described below must operate to maintain a state in which the NOx emission amount at the outlet of the exhaust heat recovery boiler 14 (exhaust heat recovery boiler outlet) is equal to or less than the boiler outlet target value. The boiler outlet target value is a fixed value that reflects a certain margin of error above the regulated value in the area where the cogeneration system 100 is installed.

[0018] <Configuration of the steam extraction line 130> 1 and 2 is configured to supply steam bleed from the steam supply line 21 to the head end 24 side of the combustor 3 and the turbine 2 side of the combustor 3. The head end 24 side of the combustor 3 refers to the upstream side in the combustion gas flow direction of a region where a flame 28 is formed in the combustor casing 23. The combustion gas flow direction refers to the direction in which the combustion gas 12 flows in the combustor liner 26, and is exemplified by the arrow C (see FIG. 2). Furthermore, the turbine 2 side of the combustor 3 refers to the downstream side in the combustion gas flow direction of a region where a flame 28 is formed in the combustor casing 23.

[0019] As shown in FIG. 2, the steam extraction line 130 includes an upstream steam line 131 for supplying steam extracted from the steam piping 21A of the steam supply line 21 to the head end 24 side of the combustor 3, and a downstream steam line 132 for supplying the extracted steam to the turbine 2 side of the combustor 3.

[0020] The upstream steam line 131 has an upstream steam pipe 131A for supplying the extracted steam between the head end 24 and the combustor liner 26, and an upstream steam flow control valve 131B provided on the upstream steam pipe 131A. The opening degree of the upstream steam flow control valve 131B is controlled by a controller 90 described later, and thereby the upstream steam supply amount, which is the flow rate of steam guided to the combustor 3 by the upstream steam pipe 131A, is adjusted. The more the upstream steam supply amount increases, the greater the effect of lowering the temperature of the flame zone, and therefore the amount of nitrogen oxides generated in the combustor 3 decreases. Therefore, it is preferable that the upstream steam supply amount increases as the hydrogen gas fuel mixed combustion ratio increases. However, the upstream steam supply amount needs to be equal to or less than the allowable upper limit supply amount to avoid misfire of the flame 28 of the combustor 3. If the upstream steam supply amount exceeds the allowable upper limit supply amount, the oxygen concentration in the combustor 3 decreases significantly, and the possibility of the flame 28 disappearing increases.

[0021] The downstream steam line 132 has a downstream steam pipe 132A for supplying the extracted steam to the downstream side of the combustor liner 26, and a downstream steam flow control valve 132B provided in the downstream steam pipe 132A. The opening degree of the downstream steam flow control valve 132B is controlled by a controller 90 described later, and thereby the downstream steam supply amount, which is the flow rate of steam guided to the combustor 3 by the downstream steam pipe 132A, is adjusted. The more the steam supply amount to the combustor 3, i.e., the total amount of the upstream steam supply amount and the downstream steam supply amount, increases, the more the flow rate of steam that flows into the turbine 2 to do work increases, and the power generation amount of the generator 5, which is the output of the gas turbine 9, increases. On the other hand, if the total amount of the steam supply amount decreases, the output of the gas turbine 9 decreases unless the fuel supply in the combustor 3 changes. The total amount of the upstream steam supply amount and the downstream steam supply amount needs to be equal to or less than the limit supply amount to avoid surging of the compressor 1. If the total steam supply exceeds the limit supply, the pressure at the outlet of compressor 1 increases, increasing the likelihood that compressor 1 will surge.

[0022] Returning to Fig. 1, although it is not an essential component of the present disclosure, the steam extraction line 130 further includes a desuperheater 22 for lowering the temperature of the steam extracted from the steam supply line 21. The desuperheater 22, which is disposed upstream of the upstream steam pipe 131A and the downstream steam pipe 132A in the steam flow direction, is configured, for example, so that a part of the boiler feedwater supplied to the heat recovery steam generator 14 flows in as cold water (see arrow B), and the cold water is injected inside the desuperheater 22 to cool the steam. The cooled steam flows through the upstream steam pipe 131A and the downstream steam pipe 132A.

[0023] <Denitration equipment 120> As shown in FIG. 1, the cogeneration system 100 includes a denitration device 120 for denitrifying the exhaust gas 13 by adding a reducing agent to the exhaust gas 13 flowing through the exhaust heat recovery boiler 14. In this example, the reducing agent is ammonia gas. The denitration device 120 injects the reducing agent into a denitration region R, which is a part of a flow passage space formed inside the exhaust heat recovery boiler 14 through which the exhaust gas 13 flows. More specifically, a catalyst is disposed in the denitration region R, and ammonia gas as a reducing agent is injected into the exhaust gas upstream of the catalyst, so that the exhaust gas and the ammonia gas are mixed. Then, nitrogen oxides in the exhaust gas 13 are decomposed into moisture and nitrogen components by an ammonia catalytic reduction decomposition method via the catalyst.

[0024] The denitration device 120 includes a supply device 122 for supplying a reducing agent, a reducing agent supply conduit 124 connected to the supply device 122 and the heat recovery boiler 14, a reducing agent supply flow control valve 126 provided in the reducing agent supply conduit 124, and an injection nozzle 128 for injecting the reducing agent guided by the reducing agent supply conduit 124 into the denitration region R. One end of the reducing agent supply conduit 124 is disposed inside the heat recovery boiler 14, and the injection nozzle 128 is provided at one end of the reducing agent supply conduit 124. The opening degree of the reducing agent supply flow control valve 126 is controlled by a controller 90 described later, whereby the flow rate of the reducing agent flowing through the reducing agent supply conduit 124 is adjusted, and the amount of reducing agent added to the flue gas 13 is adjusted.

[0025] <Measuring instruments for Cogeneration System 100> 1 includes a generator output meter 65 for measuring the amount of power generated by the generator 5, a compressor inlet air flowmeter 64 for measuring the flow rate of the compressor inlet air 6 flowing into the compressor 1, a compressor inlet air pressure meter 62 for measuring the pressure at the inlet of the compressor 1, a compressor outlet air pressure meter 63 for measuring the pressure at the outlet of the compressor 1, a steam flowmeter 66 for measuring the amount of steam supplied to a consumer, an upstream steam flowmeter 67 for measuring the amount of steam supplied upstream, a downstream steam flowmeter 68 for measuring the amount of steam supplied downstream, a turbine outlet NOx meter 69 for measuring the amount of nitrogen oxides at the outlet of the turbine 2, and a heat recovery boiler outlet NOx meter 70 for measuring the amount of nitrogen oxides contained in the exhaust gas 13 discharged from the heat recovery boiler 14. All of the measurement results of these meters are sent to a controller 90, which is a component of the cogeneration system 100 and will be described later. Hereinafter, the compressor inlet air pressure measuring instrument 62 and the compressor outlet air pressure measuring instrument 63 may be collectively referred to as "air pressure measuring instrument 61." The heat recovery steam generator outlet NOx measuring instrument 70 and the turbine outlet NOx measuring instrument 69 are configured to measure the concentration of NOx.

[0026] <Water Recovery System 40> FIG. 3 is a schematic diagram showing a water recovery system 40 according to an embodiment of the present disclosure. The water recovery system 40 is outlined as follows. The water recovery device 33, which is a component of the water recovery system 40, is configured to recover moisture in the exhaust gas 13 as recovered water by bringing the exhaust gas 13 and the refrigerant water introduced by the exhaust gas supply line 57 into gas-liquid contact. As a more detailed example, the water recovery device 33 includes a heat exchange vessel 135 into which the exhaust gas 13 and the refrigerant water flow, a sprinkler device 34 for sprinkling the refrigerant water inside the heat exchange vessel 135, and a filler 35 located below the sprinkler device 34 inside the heat exchange vessel 135. The exhaust gas 13 introduced by the exhaust gas supply line 57 flows into the heat exchange vessel 135. The refrigerant water sprinkled by the sprinkler device 34 adheres to the filler 35 and exchanges heat with the exhaust gas 13 flowing into the heat exchange vessel 135. As a result, the moisture in the exhaust gas 13 is condensed. The recovered water, which contains the condensed moisture and the refrigerant water that has completed the heat exchange, falls and is stored in the water tank 136 that constitutes the lower part of the heat exchange container 135.

[0027] The water recovery system 40 further includes a recovered water cooling device 110 for cooling the recovered water discharged from the water tank 136 of the water recovery device 33, a recovered water discharge line 39 for guiding the recovered water discharged from the water tank 136 of the water recovery device 33 to the recovered water cooling device 110, and a recovered water supply line 42 for guiding the cooled recovered water discharged from the recovered water cooling device 110 to the heat exchange vessel 135 as refrigerant water. The recovered water cooling device 110 of this example is configured to cool the recovered water with cooling water which may be seawater, for example. A cooling water supply pump 55 is provided in a cooling water supply line 41 for supplying cooling water to the recovered water cooling device 110.

[0028] The water recovery system 40 further includes a water supply line 4 for guiding the recovered water to the make-up water tank 17, and the water supply line 4 includes a high-temperature water supply line 44 and a low-temperature water supply line 47. The high-temperature water supply line 44 is connected to the recovered water discharge line 39 and configured to guide the recovered water taken out from the recovered water discharge line 39 to the make-up water tank 17. The recovered water taken out from the recovered water discharge line 39 has a relatively high temperature because it contains heat recovered from the exhaust gas 13. The low-temperature water supply line 47 is connected to the recovered water supply line 42 and configured to guide the recovered water taken out from the recovered water supply line 42 to the make-up water tank 17. The recovered water taken out from the recovered water supply line 42 has been subjected to a cooling process by the recovered water cooling device 110 and therefore has a relatively low temperature.

[0029] The low-temperature feed water line 47 is provided with a water treatment device 46, which is a component of the water recovery system 40. The water treatment device 46 is configured to perform a process for removing impurities, such as sulfur, from the recovered water flowing through the low-temperature feed water line 47. The impurities are generated during combustion in the combustor 3 (see FIG. 1) and may be mixed into the exhaust gas 13. At least a part of the impurities is dissolved in the recovered water by heat exchange between the exhaust gas 13 and the refrigerant water in the water recovery device 33. The water treatment device 46 removes the impurities contained in the recovered water, thereby suppressing the impurities from being contained in the boiler feed water stored in the make-up water tank 17. In general, the lower the temperature of the water to be treated, the higher the processing capacity of the water treatment device 46 for removing impurities. If the temperature of the recovered water is high, the ion exchange resin 146 constituting the water treatment device 46 may be damaged, and the processing capacity for removing impurities may be reduced.

[0030] A high-temperature feed water valve 48 is provided on the high-temperature feed water line 44, and a low-temperature feed water valve 45 is provided on the low-temperature feed water line 47, and both valves are controlled by the controller 90. For example, when the amount of hydrocarbon gas fuel, which may be off-gas, supplied to the combustor 3 is large (i.e., when the hydrogen gas fuel mixed combustion ratio is low), and the sulfur component mixed in the exhaust gas 13 is higher than the allowable value and is equal to or lower than the allowable upper limit, the controller 90 closes the high-temperature feed water valve 48 and opens the low-temperature feed water valve 45 because there is a large amount of sulfur component mixed in the exhaust gas 13. As a result, low-temperature recovered water that requires impurity removal processing flows into the make-up water tank 17 via the water treatment device 46 provided on the low-temperature feed water line 47. This prevents impurities from adhering to the equipment constituting the cogeneration system 100, such as the feed water line 19 and the heat recovery boiler 14, and can suppress deterioration of the cogeneration system 100. On the other hand, when the hydrogen gas fuel mixed combustion ratio is relatively high, that is, when the sulfur components mixed in the exhaust gas 13 are equal to or lower than the allowable value, the controller 90 opens the high-temperature feed water valve 48 and closes the low-temperature feed water valve 45. This allows high-temperature recovered water that does not require impurity removal treatment to flow into the make-up water tank 17 via the high-temperature feed water line 44. Since the temperature of the boiler feed water supplied from the make-up water tank 17 to the heat recovery boiler 14 can be increased, the efficiency of the cogeneration system 100 is improved. In this way, in the water recovery system 40 of this example, it is possible to switch the supply line of recovered water sent to the make-up water tank 17 depending on the hydrogen gas fuel mixed combustion ratio.

[0031] <Configuration of controller 90> FIG. 4 is a schematic diagram showing a controller 90 according to an embodiment of the present disclosure. The controller 90 is configured by a computer and includes a processor, a memory, and an external communication interface. The processor is a CPU, a GPU, an MPU, a DSP, or a combination thereof. The processor according to another embodiment may be realized by an integrated circuit such as a PLD, an ASIC, an FPGA, or an MCU. The memory is configured to temporarily or non-temporarily store various data, and is realized by at least one of a RAM, a ROM, and a flash memory, for example. The processor executes various control processes according to instructions of a program loaded into the memory. The controller 90 may also be a DCS board constituting one of a plurality of control boards constituting the cogeneration system 100.

[0032] The controller 90 having such a hardware configuration executes control for denitrifying the exhaust gas 13 generated in the combustor 3. More specifically, the controller 90 executes upstream steam supply control and reducing agent supply control. These controls are realized by the controller 90 sending control signals for changing or maintaining the valve opening to the first flow regulation valve 153, the second flow regulation valve 154, the upstream steam flow regulation valve 131B, the downstream steam flow regulation valve 132B, and the reducing agent supply flow regulation valve 126. Each of these flow valves is configured to detect its own opening after performing an operation for changing or maintaining the valve opening in response to the input control signal, and to return the detection result to the controller 90.

[0033] The controller 90 includes a power increase command acquisition unit 94 for acquiring a power increase command for increasing the amount of power generation, which is the output of the cogeneration system 100, a fuel supply control unit 99 for controlling the amount of hydrogen gas fuel supplied and the amount of hydrocarbon gas fuel supplied in accordance with the acquired power increase command, and a hydrogen gas fuel mixing ratio setting unit 95 for setting the hydrogen gas fuel mixing ratio after being controlled by the fuel supply control unit 99.

[0034] The power increase command acquisition unit 94 acquires a power increase command, for example, while the combustor 3 is burning the hydrocarbon gas fuel and the hydrogen gas fuel. The fuel supply control unit 99 of this example sends control signals to the first flow regulation valve 153 and the second flow regulation valve 154 so that the hydrogen gas fuel burning ratio increases in response to the power increase command. For example, a control signal for reducing the opening degree of the first flow regulation valve 153 and a control signal for increasing the opening degree of the second flow regulation valve 154 are sent, and the hydrogen gas fuel burning ratio increases. Note that the present disclosure is not limited to the increase in the hydrogen gas fuel burning ratio being triggered by the acquisition of the power increase command. As another example, the control for increasing the hydrogen gas fuel burning ratio may be executed in response to the acquisition of a command for reducing the carbon dioxide gas emission amount of the cogeneration system 100. The hydrogen gas fuel burning ratio setting unit 95 sets (updates) the hydrogen gas fuel burning ratio to a current value after the fuel supply control unit 99 executes the control. The set hydrogen gas fuel mixing ratio is stored in the memory of the controller 90 and is referred to when calculating NOx parameters, which will be described later.

[0035] The controller 90 further includes an upstream steam control unit 81 for controlling the upstream steam line 131. The upstream steam control unit 81 sends a control signal to the upstream steam flow control valve 131B to change the valve opening so that the actual NOx emission at the turbine outlet is equal to or less than the turbine outlet target value. The turbine outlet target value is a value higher than the above-mentioned boiler outlet target value. The turbine outlet target value is determined as follows. That is, first, the hydrogen gas fuel mixing ratio is set, and the upstream steam supply amount according to the hydrogen gas fuel mixing ratio is determined. The temperature of the flame 28 is calculated based on these two parameters, and the turbine outlet target value is determined based on a software module described later.

[0036] The upstream steam control unit 81 includes a supply control unit 810. The supply control unit 810 determines an upstream steam supply amount based on a turbine outlet target value, and controls the upstream steam flow adjustment valve 131B so as to realize a target upstream steam supply amount, which is the determined upstream steam supply amount. For example, when the hydrogen gas fuel control unit 92 updates the hydrogen gas fuel mixed combustion ratio to a higher value in response to an increase in power output command, the amount of NOx generated in the combustor 3 increases, and therefore a target upstream steam supply amount larger than the current upstream steam supply amount is set. Then, the supply control unit 810 sends a control signal to the upstream steam flow adjustment valve 131B to increase the opening degree.

[0037] Moreover, the upstream steam control unit 81 is configured to satisfy a condition that the upstream steam supply amount is equal to or less than an allowable upper limit supply amount for avoiding misfire in the combustor 3. Specifically, the upstream steam control unit 81 includes an upstream steam reduction control unit 811 for reducing the upstream steam supply amount when it is determined that the upstream steam supply amount exceeds the allowable upper limit supply amount. The upstream steam reduction control unit 811 sends a control signal to the upstream steam flow adjustment valve 131B to reduce the opening degree.

[0038] In addition, the upstream steam control unit 81 is configured to control the upstream steam line so that the upstream steam supply rate exceeds the target upstream steam supply rate and is equal to or lower than the allowable upper limit supply rate when the above-mentioned target upstream steam supply rate, which is the upstream steam supply rate for keeping the NOx emissions at the turbine outlet below the turbine outlet target value, falls below the allowable upper limit supply rate. Specifically, the upstream steam control unit 81 includes an upstream steam supply amount resetting unit 813 for resetting the upstream steam supply amount to a predetermined supply amount that is greater than the target upstream steam supply amount and equal to or less than the allowable upper limit supply amount when the target upstream steam supply amount falls below the allowable upper limit supply amount. The upstream steam supply amount resetting unit 813 in this example sets the upstream steam supply amount to a value close to the allowable upper limit supply amount, and transmits a control signal to the upstream steam flow adjustment valve 131B to increase the opening degree. As a result, the actual upstream steam supply amount increases to the reset upstream steam supply amount, exceeding the initial target upstream steam supply amount.

[0039] The upstream steam control unit 81 also includes an upstream steam increase control unit 812 for increasing the upstream steam supply amount when it is determined that the actual NOx emission amount exceeds the turbine outlet target value. The upstream steam increase control unit 812 transmits a control signal for increasing the opening degree to the first flow regulation valve 153. The upstream steam control unit 81 also includes an upstream steam supply amount determination unit 814 for determining a final upstream steam supply amount. The upstream steam supply amount determination unit 814 acquires an actual upstream steam supply amount at a timing when it is determined that the actual NOx emission amount is equal to or less than the turbine outlet target value based on at least one of the measurement result of the upstream steam flow meter 67 and the opening degree measurement result of the upstream steam flow regulation valve 131B. The acquired actual upstream steam supply amount is determined as a final upstream steam supply amount and stored in the memory of the controller 90. This upstream steam supply amount is referred to when calculating a NOx parameter described later.

[0040] The controller 90 further includes a downstream steam control unit 82 for controlling the downstream steam line 132. The downstream steam control unit 82 includes a supply control unit 820 for controlling the downstream steam flow adjustment valve 132B so as to realize the output of the power increase command acquired by the power increase command acquisition unit 94. As described above, the total amount of the upstream steam supply amount and the downstream steam supply amount contributes to an increase in the output of the gas turbine 9. However, the control of the upstream steam supply amount is restricted by the trade-off between the allowable upper limit supply amount and the amount of denitrification required in the combustor 3. Therefore, in this embodiment, after the final upstream steam supply amount is determined, the shortage of steam to be supplied to the turbine 2 is compensated for by the supply control of the downstream steam by the supply control unit 820.

[0041] Furthermore, the downstream steam control unit 82 is configured to control the downstream steam line 132 while satisfying a condition that the total steam supply amount, which is the sum of the upstream steam supply amount determined by the upstream steam supply amount determination unit 814 and the downstream steam supply amount, is equal to or less than the limit supply amount for avoiding surging of the compressor 1. When the total steam supply amount reaches the limit supply amount, the pressure ratio of the compressor 1 reaches the allowable upper limit pressure ratio for avoiding surging, so it is preferable that the total steam supply amount is equal to or less than the limit supply amount. Therefore, the downstream steam control unit 82 further includes a pressure ratio determination unit 97 configured to determine whether the pressure ratio calculated based on the measurement result of the above-mentioned air pressure measuring instrument 61 for measuring the pressure ratio of the compressor 1 is equal to or lower than the allowable upper limit pressure ratio, and a downstream steam reduction control unit 821 for reducing the downstream steam supply amount when it is determined that the pressure ratio exceeds the allowable upper limit pressure ratio. The downstream steam reduction control unit 821 sends a control signal to the downstream steam flow adjustment valve 132B to reduce the opening degree.

[0042] The controller 90 further includes a denitration control unit 93 for outputting a control command to the denitration device 120 so that the amount of NOx emissions at the exhaust heat recovery boiler outlet is equal to or less than a boiler outlet target value.

[0043] The denitration control unit 93 includes a NOx parameter acquisition unit 935 for acquiring a NOx parameter that is a parameter correlated with the amount of NOx emissions at the outlet (turbine outlet) of the turbine 2. The NOx parameter in this example is an estimated value of the amount of NOx emissions at the turbine outlet (hereinafter also referred to as "estimated NOx emissions"), which is determined by calculation based on the hydrogen gas fuel co-combustion ratio, the head-end steam injection rate, and the temperature of the flame 28. The estimated NOx emissions may be treated as a target value of the amount of NOx emissions at the turbine outlet. The head end steam injection rate is the ratio of the upstream steam supply amount to the flow rate of the compressor inlet air 6. The flow rate of the compressor inlet air 6 can be determined based on the measurement results of the air pressure gauge 61 and the compressor inlet air flow meter 64. The temperature of the flame 28 may be an estimated value obtained by calculation based on the hydrogen gas fuel supply amount, the hydrocarbon gas fuel supply amount, and the compressor inlet air 6 flow rate.

[0044] FIG. 5 is a schematic diagram showing the characteristics of NOx emissions at the turbine outlet, and shows the characteristics of NOx emissions obtained by experiments. As shown in the figure, the steam injection rate (head-end steam injection rate, which is the ratio of the upstream steam supply amount to the flow rate of the compressor inlet air 6), the hydrogen gas fuel mixed combustion rate, the temperature of the flame 28, and the amount of NOx generated in the combustor 3 have a specified relationship with each other. In this embodiment, the NOx emissions on the vertical axis of the graph are treated as estimated NOx emissions. Specifically, the relationship shown in the figure is stored in the software module as a function formula, a data table, or a learning model, and the NOx parameter acquisition unit 935 can acquire NOx parameters as the estimated NOx emissions. The software module is a calculation device that stores the function formula, the data table, or the learning model after machine learning, and the calculation device may be incorporated in the controller 90. The steam injection rate, the hydrogen gas fuel mixed combustion rate, and the temperature of the flame 28 are input to the software module as input parameters, and the NOx parameter acquisition unit 935 acquires the estimated NOx emissions output from the software module as output parameters.

[0045] FIG. 6 is a schematic diagram showing the characteristics of the NOx parameters (estimated NOx emissions) according to one embodiment of the present disclosure. The figure shows a graph of the predicted characteristics of the NOx parameters based on experimental results (similar to FIG. 7). As shown in the figure, the higher the head-end steam injection rate, the lower the NOx parameters, and the higher the hydrogen gas fuel co-firing rate, the higher the NOx parameters. The head-end steam injection rate A% is the steam injection rate equivalent to the above-mentioned allowable upper limit supply amount.

[0046] FIG. 7 is another schematic diagram showing the characteristics of the NOx parameters (estimated NOx emissions) according to an embodiment of the present disclosure. As shown in the figure, regardless of the hydrogen gas fuel co-combustion ratio, the higher the head-end steam injection rate is, the lower the NOx parameters are, and the amount of the reducing agent (ammonia) required for denitration in the denitration device 120 is reduced. Also, as shown in the figure, the head-end steam injection rate (A%), which corresponds to the allowable upper limit supply amount, is the same regardless of the hydrogen gas fuel co-combustion rate. The reason is as follows. The head-end steam injection rate (A%) is an injection rate determined based on combustion stability, and is determined by the water vapor partial pressure and oxygen partial pressure in the combustion region, so the influence of the gas components to be oxidized is small.

[0047] 4, the denitration control unit 93 further includes a first addition amount calculation unit 931 for acquiring (calculating) a first addition amount of the reducing agent by calculation based on the NOx parameters, and a control command generation unit 936 for outputting a control command to the reducing agent supply flow adjustment valve 126 of the denitration device 120 with reference to at least the calculated first addition amount. The calculation performed by the first addition amount calculation unit 931 is a feedforward calculation based on the NOx parameters obtained by the NOx parameter acquisition unit 935, and the above control command generated by the control command generation unit 936 is a feedforward control command.

[0048] The first addition amount calculated based on the NOx parameters at the turbine outlet upstream of the heat recovery boiler 14 indicates the amount of reducing agent (amount of ammonia supplied for denitration) required in the future for the denitration device 120. According to the configuration in which the denitration control unit 93 generates a feedforward control command, the control command generation unit 936 of the denitration control unit 93 generates a control command to be input to the reducing agent supply flow adjustment valve 126 as a feedforward control command, with reference to the first addition amount of reducing agent based on the NOx parameters. This allows the denitration device 120 to start an operation for denitrifying the NOx generated in the turbine 2 before the NOx reaches the denitration area R inside the heat recovery boiler 14. Therefore, when the hydrogen gas fuel mixed combustion ratio in the gas turbine 9 increases, the cogeneration system 100 is realized that can perform a denitration operation by quickly following the increase in the amount of NOx discharged from the gas turbine 9. The NOx parameter is not limited to the estimated NOx emission amount. For example, the NOx parameter may be the actual NOx emission amount measured by the turbine outlet NOx measuring instrument 69. Even in this case, the above-mentioned advantages can be obtained as long as the first addition amount calculation unit 931 performs a feedforward calculation based on the NOx emission amount to calculate the first addition amount.

[0049] Moreover, according to an embodiment in which the NOx parameter is the estimated NOx emission amount, it is also possible to calculate the estimated NOx emission amount at the time when a control command (valve opening command) for controlling the hydrogen gas fuel supply amount and the upstream steam supply amount is generated. Before the hydrogen gas fuel supply amount and the upstream steam supply amount indicated by this control command actually start to be supplied, the control command generating unit 936 of the denitration control unit 93 can generate a control command to be input to the denitration device 120 by referring to the first addition amount of the denitration agent. Therefore, the denitration device 120 can perform a denitration operation that quickly follows an increase in the amount of NOx discharged from the gas turbine 9.

[0050] The denitration control unit 93 shown in Fig. 4 is further configured to perform feedback control of the amount of reducing agent added. Specifically, the denitration control unit 93 further includes a boiler outlet NOx deviation acquisition unit 934 for acquiring a boiler outlet NOx deviation, which is a deviation between the boiler outlet target value and the actual NOx emission amount at the exhaust heat recovery boiler outlet obtained by measurement by the exhaust heat recovery boiler outlet NOx measuring instrument 70, and a second addition amount calculation unit 932 for acquiring (calculating) a second addition amount of reducing agent by calculation based on the boiler outlet NOx deviation acquisition unit 934. The calculation executed by the second addition amount calculation unit 932 is a feedback calculation. The boiler outlet target value is a value that reflects a certain margin of error in the regulation value regulated in the area where the cogeneration system 100 is installed, and is a constant value.

[0051] The control command generating unit 936 is configured to generate a control command by referring to the second adding amount, in addition to generating a control command by referring to the first adding amount. The control command generated based on the second adding amount is a feedback control command, and is a control signal for the valve opening degree input to the reducing agent supply flow adjustment valve 126. According to the configuration in which the control command generating unit 936 generates a feedback control command, it is possible to reliably keep the NOx emission amount at the exhaust heat recovery boiler outlet at or below the boiler outlet target value.

[0052] Furthermore, according to a configuration in which the upstream steam control unit 81 controls the upstream steam line 131 while satisfying the condition that the upstream steam supply rate is equal to or less than the allowable upper limit supply rate, it is possible to suppress the upstream steam supply rate from exceeding the allowable upper limit supply rate, thereby suppressing the occurrence of misfire in the combustor 3.

[0053] Moreover, according to a configuration in which the upstream steam control unit 81 includes the upstream steam supply amount resetting unit 813, it is possible to increase the upstream steam supply amount flowing into the head end 24 side of the combustor 3 while avoiding misfire in the combustor 3. Since the denitration amount in the combustor 3 can be increased to the maximum, it is possible to reduce the denitration amount in the denitration device 120, and it becomes possible to reduce the amount of additive of the reducing agent.

[0054] Furthermore, according to a configuration in which the downstream steam control unit 82 controls the downstream steam line 132 while satisfying the condition that the total steam supply amount is equal to or less than the limit supply amount for avoiding surging of the compressor 1, after the upstream steam supply amount for keeping the NOx emission amount equal to or less than the turbine outlet target value is determined, the downstream steam control unit 82 controls the downstream steam supply amount while satisfying the condition that the total steam supply amount is equal to or less than the limit supply amount. This makes it possible to increase the denitration amount in the combustor 3 while also avoiding surging of the compressor 1.

[0055] Furthermore, the amount of moisture contained in the combustion gas 12 discharged from the gas turbine 9 increases as the hydrogen gas fuel co-combustion ratio increases. In this regard, when the cogeneration system 100 is configured to include the water recovery system 40 and the makeup water tank 17, the moisture in the exhaust gas 13 at the gas turbine outlet consists of the moisture in the compressor inlet air 6 of the compressor 1, the moisture due to steam injection in the gas turbine 9, and the moisture generated by combustion. The moisture in the compressor inlet air 6 is discharged to the outside of the system from the exhaust tower 30 or the outlet of the water recovery device 33, but the moisture from the steam injection and the moisture generated by combustion are recovered by the water recovery system 40, the steam injection moisture is reused as boiler feed water, and the moisture generated by combustion becomes surplus water, so that the cogeneration system 100 can also function as a water production plant.

[0056] <How to operate the Cogeneration System 100> 8 and 9 are flowcharts showing a cogeneration system control process according to an embodiment of the present disclosure, and show an example of a method of operating the cogeneration system 100. The cogeneration system control process is a control process for changing the upstream steam supply amount and the reducing agent supply amount when the hydrogen gas fuel mixed combustion ratio increases. The control process is executed by the processor of the controller 90. In the following description, the "processor of the controller 90" may be abbreviated to "processor" and "step" may be abbreviated to "S". Note that before the cogeneration system control process is started, mixed combustion of hydrocarbon gas fuel and hydrogen gas fuel has already occurred in the combustor 3.

[0057] First, the processor acquires a power increase command (S1). The processor that executes S1 is an example of the power increase command acquisition unit 94 described above. Next, the processor controls the amount of hydrogen gas fuel supply and the amount of hydrocarbon gas fuel supply in accordance with the power increase command acquired in S1 (S3). Specifically, a control signal for the valve opening corresponding to the power increase command is sent to the first flow regulation valve 153 and the second flow regulation valve 154. In this example, a control signal for reducing the opening of the first flow regulation valve 153 and a control signal for increasing the opening of the second flow regulation valve 154 are sent, and the hydrogen gas fuel mixed combustion ratio increases. The processor that executes S3 is an example of the fuel supply control unit 99 described above.

[0058] Next, the processor sets the hydrogen gas fuel mixing ratio (S5). For example, after S3 is executed, the hydrogen gas fuel mixing ratio is calculated based on the opening degree of the first flow regulation valve 153, the opening degree of the second flow regulation valve 154, the measurement result of the first flow meter 71, and the measurement result of the second flow meter 72, and the processor stores the calculated hydrogen gas fuel mixing ratio in the memory of the controller 90 (S5). The processor that executes S5 is an example of the hydrogen gas fuel mixing ratio setting unit 95 described above.

[0059] Next, the processor controls the upstream steam supply amount (S7). The processor that executes S7 is an example of the supply control unit 810 described above. Next, the processor determines whether the upstream steam supply amount is equal to or less than the allowable upper limit supply amount, for example, based on the measurement result of the upstream steam flow meter 67. If it is determined that the upstream steam supply amount exceeds the allowable upper limit supply amount (S11: NO), the processor executes control to reduce the upstream steam supply amount (S13). The processor that executes S13 is an example of the upstream steam reduction control unit 811 described above.

[0060] If it is determined that the upstream steam supply rate is equal to or lower than the allowable upper limit supply rate (S11: YES), the processor resets the upstream steam supply rate to a value higher than the current upstream steam supply rate measured by the upstream steam flow meter 67 (S15). Then, the processor sends a control signal to the upstream steam flow adjustment valve 131B so that the reset value of the upstream steam supply rate is realized. This increases the upstream steam supply rate (however, this upstream steam supply rate is equal to or lower than the allowable upper limit supply rate). The processor that executes S15 is an example of the upstream steam supply rate resetting unit 813 described above.

[0061] Next, the processor determines whether the actual NOx emission amount at the turbine outlet is equal to or less than the turbine outlet target value (S17). For example, the NOx amount measured by the turbine outlet NOx measuring instrument 69 is compared with the turbine outlet target value to determine which is larger. If it is determined that the actual NOx emission amount exceeds the turbine outlet target value (S17: NO), the processor executes control to increase the upstream steam supply amount (S19). However, the upstream steam supply amount after the increase is equal to or less than the allowable upper limit supply amount. The processor executing S19 is an example of the upstream steam increase control unit 812 described above.

[0062] When it is determined that the actual NOx emission amount at the turbine outlet is equal to or less than the turbine outlet target value (S17: YES), the processor determines the upstream steam supply amount at the determination timing (S21). More specifically, the upstream steam supply amount is determined based on the upstream steam flow meter 67 and the opening degree of the upstream steam flow control valve 131B at the timing, and the upstream steam supply amount is stored in the memory of the controller 90 (S21). The processor that executes S21 is an example of the upstream steam supply amount determination unit 814 described above.

[0063] Next, the processor executes denitration control for controlling the denitration device 120 (S23). The processor executing S23 is an example of the above-mentioned denitration control unit 93. The denitration control will be described in detail later.

[0064] 9, the processor controls the downstream steam supply amount (S31). Specifically, the processor controls the downstream steam flow adjustment valve 132B so that the power increase command acquired in S1 is realized. The processor that executes S31 is an example of the supply control unit 820 described above.

[0065] Next, the processor judges whether the pressure ratio is equal to or lower than the allowable upper limit pressure ratio (S33). The processor executing S33 is an example of the pressure ratio judgment unit 97 described above. If it is judged that the pressure ratio exceeds the allowable upper limit pressure ratio (S33: NO), the processor executes control to reduce the downstream steam supply amount (S35). The processor executing S35 is an example of the downstream steam reduction control unit 821 described above. If it is judged that the pressure ratio is equal to or lower than the allowable upper limit pressure ratio (S33: YES), the processor judges whether the output of the gas turbine 9 has reached the target output indicated by the power increase command acquired in S1 (S37). If it is judged that the power generation amount measured by the generator output measuring instrument 65 has not reached the target power generation amount (S37: NO), the processor executes control to increase the downstream steam supply amount (S39). In S39, a control signal to increase the valve opening degree is sent to the downstream steam flow adjustment valve 132B. If it is judged that the power generation amount measured has reached the target power generation amount (S37: YES), the processor ends the cogeneration system control process.

[0066] The denitration control process will be described with reference to Fig. 10. The denitration control process is a process for controlling the denitration operation by the denitration device 120. The processor acquires NOx parameters based on the hydrogen gas fuel mixed combustion ratio set in S5 and the upstream steam supply amount determined in S21 (S51). More specifically, the upstream steam supply amount, the steam injection rate based on the flow rate of the compressor inlet air 6, the hydrogen gas fuel mixed combustion ratio, and the temperature of the flame 28 are input to the above-mentioned software module, and an estimated NOx emission amount is acquired. The processor that executes S51 is an example of the above-mentioned NOx parameter acquisition unit 935.

[0067] The processor calculates the first addition amount by feedforward calculation based on the NOx parameters acquired in S51 (S53). The processor that executes S53 is an example of the above-mentioned first addition amount calculation unit 931. Next, the processor generates a control command indicating a valve opening corresponding to the first addition amount as a feedforward control command, and sends it to the reducing agent supply flow adjustment valve 126 (S55).

[0068] Next, the processor acquires the boiler outlet NOx deviation (S57). The processor that executes S57 is an example of the boiler outlet NOx deviation acquisition unit 934 described above. Then, the processor determines the second addition amount for making the boiler outlet NOx deviation acquired in S57 0 or a value that can be regarded as 0 by feedback calculation (S59). The processor that executes S59 is an example of the second addition amount calculation unit 932 described above. Next, the processor generates a control command indicating a valve opening corresponding to the second addition amount as a feedback control command, and sends it to the reducing agent supply flow adjustment valve 126 (S61). The processor that executes S55 and S61 is an example of the control command generation unit 936 described above. After that, the processor ends the denitration control process.

[0069] <Summary> The contents described in the above-mentioned embodiments can be understood, for example, as follows.

[0070] 1) A gas turbine cogeneration system (100) according to at least one embodiment of the present disclosure includes: a gas turbine (9) including a compressor (7), a combustor (3), and a turbine (2); a hydrocarbon fuel supply facility (51) for supplying a hydrocarbon gas fuel to the combustor; a hydrogen gas fuel supply facility (52) for supplying hydrogen gas fuel, which is a fuel mainly composed of hydrogen gas, to the combustor; a heat recovery steam generator (14) for generating steam using exhaust gas from the turbine; an upstream steam line (131) for supplying the steam discharged from the heat recovery steam generator to a head end (24) side of the combustor; a denitration device (120) for denitrifying the exhaust gas by adding a reducing agent (ammonia gas) to the exhaust gas flowing through the exhaust heat recovery boiler; a denitration control unit (93) for outputting a control command to the denitration device so as to keep the NOx emission amount at the exhaust heat recovery boiler outlet equal to or less than a boiler outlet target value; Equipped with The denitration control unit is configured to generate the control command with reference to at least the first addition amount of the reducing agent obtained by a calculation based on a NOx parameter which is a parameter correlated with the amount of NOx emissions at a turbine outlet.

[0071] If the amount of NOx emissions at the turbine outlet of the turbine located upstream of the heat recovery boiler is known, the amount of denitration that will be required in the future for the denitration device can be identified. According to the configuration of 1) above, the denitration control unit generates a control command by referring to the first amount of reducing agent added based on the NOx parameter, so that the denitration device can start operation to denitrify the NOx generated in the turbine before the NOx reaches the denitration area inside the heat recovery boiler. This realizes a gas turbine cogeneration system that can quickly follow the increase in the amount of NOx emitted from the gas turbine and perform denitration operation when the hydrogen gas fuel co-combustion ratio in the gas turbine increases.

[0072] 2) In some embodiments, the gas turbine cogeneration system according to 1) above, The control command is configured to generate the control command by referring to the second adding amount of the reducing agent obtained by a calculation based on the deviation between the boiler outlet target value and the amount of NOx emissions at the exhaust heat recovery boiler outlet obtained by measurement.

[0073] According to the above configuration 2), the denitrification control unit generates a control command by referring to the second addition amount of reducing agent based on the deviation between the boiler outlet target value of NOx emissions at the exhaust heat recovery boiler outlet and the NOx emissions at the exhaust heat recovery boiler outlet determined by measurement, so that it is possible to reliably keep the NOx emissions at the exhaust heat recovery boiler outlet below the boiler outlet target value.

[0074] 3) In some embodiments, the gas turbine cogeneration system according to 1) or 2) above, The NOx parameter is an estimated NOx emission amount at the turbine outlet obtained by a calculation based on the hydrogen gas fuel supply amount, which is the supply amount of the hydrogen gas fuel supplied by the hydrogen gas fuel supply equipment, and the upstream steam supply amount, which is the supply amount of the steam supplied by the upstream steam line.

[0075] The configuration of 3) above makes it possible to calculate the estimated NOx emission amount at the time when a control command for controlling the hydrogen gas fuel supply amount and the upstream steam supply amount is generated. Before the hydrogen gas fuel supply amount and the upstream steam supply amount indicated by the control command actually start to be supplied, the denitration control unit can generate the control command by referring to the first addition amount of the denitration agent based on the estimated NOx emission amount. Therefore, the denitration device can perform a denitration operation that quickly follows an increase in the amount of NOx discharged from the gas turbine.

[0076] 4) In some embodiments, the gas turbine cogeneration system according to any one of 1) to 3) above, The system further includes an upstream steam control unit (81) for controlling the upstream steam line such that an actual NOx emission amount at the turbine outlet is equal to or less than a turbine outlet target value that is higher than the boiler outlet target value, while satisfying a condition that an upstream steam supply amount, which is the supply amount of the steam supplied by the upstream steam line, is equal to or less than an allowable upper limit supply amount.

[0077] According to the above configuration 4), it is possible to suppress the occurrence of misfires in the combustor of the gas turbine due to the upstream steam supply amount exceeding the allowable upper limit supply amount.

[0078] 5) In some embodiments, the gas turbine cogeneration system according to 4) above, The upstream steam control unit is configured to control the upstream steam line so that, when a target upstream steam supply rate, which is the upstream steam supply rate for keeping the NOx emissions at the turbine outlet below the turbine outlet target value, falls below the allowable upper limit supply rate, the upstream steam supply rate exceeds the target upstream steam supply rate and is below the allowable upper limit supply rate.

[0079] According to the above configuration 5), since the upstream steam supply rate is set to a value equal to or less than the target upstream steam supply rate and the allowable upper limit supply rate, the flow rate of steam flowing into the combustor can be increased while avoiding misfire in the combustor. Since the amount of denitration in the combustor can be increased, the amount of denitration in the denitration device can be reduced, and the amount of reducing agent added can be reduced.

[0080] 6) In some embodiments, the gas turbine cogeneration system according to 4) or 5) above, the upstream steam control unit has an upstream steam supply amount determination unit (814) for determining the upstream steam supply amount for making the actual NOx emission amount at the turbine outlet equal to or less than the turbine outlet target value, The gas turbine cogeneration system includes: a downstream steam line (132) for supplying the steam discharged from the heat recovery steam generator to the turbine side of the combustor relative to the head end; a downstream steam control unit (82) for controlling the downstream steam line while satisfying a condition that a total steam supply amount, which is a sum of a downstream steam supply amount that is a supply amount of the steam supplied by the downstream steam line and the upstream steam supply amount determined by the upstream steam supply amount determination unit, is equal to or less than a limit supply amount for avoiding surging of the compressor; It further comprises:

[0081] According to the above configuration 6), after the upstream steam supply amount for keeping the NOx emission amount equal to or less than the turbine outlet target value is determined, the downstream steam control unit controls the downstream steam supply amount while satisfying the condition that the total steam supply amount is equal to or less than the limit supply amount. This makes it possible to increase the amount of denitration in the combustor while also avoiding compressor surging.

[0082] 7) In some embodiments, the gas turbine cogeneration system according to any one of 1) to 4) above, a water recovery system (40) for recovering moisture from the exhaust gas by heat exchange between the exhaust gas of the heat recovery boiler and refrigerant water; a make-up water tank (17) for storing boiler feed water for supplying the recovered water by the water recovery system to the heat recovery boiler; It further comprises:

[0083] The higher the hydrogen gas fuel co-firing ratio, the greater the amount of moisture contained in the combustion gas discharged from the gas turbine. In this regard, according to the configuration of 7) above, the moisture recovered from the exhaust gas by the water recovery system can be reused as boiler feed water supplied to the heat recovery steam generator, and the gas turbine cogeneration system can also function as a water production plant.

[0084] 8) A method of operating a gas turbine cogeneration system (100) according to at least one embodiment of the present disclosure, comprising: The gas turbine cogeneration system includes: a gas turbine (9) including a compressor (7), a combustor (3), and a turbine (2); a hydrocarbon fuel supply facility (51) for supplying a hydrocarbon gas fuel to the combustor; a hydrogen gas fuel supply facility (52) for supplying hydrogen gas fuel, which is a fuel mainly composed of hydrogen gas, to the combustor; a heat recovery steam generator (14) for generating steam using exhaust gas from the turbine; an upstream steam line (131) for supplying the steam discharged from the heat recovery steam generator to a head end side of the combustor; a denitration device (120) for denitrifying the exhaust gas by adding a reducing agent (ammonia gas) to the exhaust gas flowing through the exhaust heat recovery boiler; Including, A denitration control step (S23) is provided for outputting a control command to the denitration device to make the NOx emission amount at the exhaust heat recovery boiler outlet equal to or less than a boiler outlet target value; In the denitration control step, the control command is generated with reference to at least the first addition amount of the reducing agent obtained by a calculation based on a NOx parameter which is a parameter correlated with the amount of NOx exhausted at a turbine outlet.

[0085] According to the configuration 8) above, for the same reason as in 1) above, when the hydrogen gas fuel co-combustion ratio in the gas turbine increases, a gas turbine cogeneration system is realized that can perform denitration operation in quick response to an increase in the amount of NOx emitted from the gas turbine. [Explanation of symbols]

[0086] 1: Compressor 2: Turbine 3: Combustor 5: Generator 6: Compressor inlet air 7: Compressed air 9: Gas turbine 10: Steam consumers 12: Combustion gas 13: Exhaust gas 14: Waste heat recovery boiler 17: Water supply tank 24: Headend 40: Water recovery system 51: Hydrocarbon fuel supply equipment 52: Hydrogen gas fuel supply equipment 81: Upstream steam control section 82: Downstream steam control section 93: Denitrification control section 100: Cogeneration system (gas turbine cogeneration system) 120:Denitration equipment 131: Upstream steam line 132: Downstream steam line 814: Upstream steam supply amount determination unit R: Denitrification area

Claims

1. a gas turbine including a compressor, a combustor, and a turbine; a hydrocarbon fuel supply facility for supplying a hydrocarbon gas fuel to the combustor; a hydrogen gas fuel supply facility for supplying hydrogen gas fuel, which is a fuel mainly composed of hydrogen gas, to the combustor; a heat recovery steam generator for generating steam using exhaust gas from the turbine; an upstream steam line for supplying the steam discharged from the heat recovery steam generator to a head end side of the combustor; a denitration device for denitrifying the exhaust gas by adding a reducing agent to the exhaust gas flowing through the exhaust heat recovery boiler; a denitration control unit for outputting a control command to the denitration device so as to reduce the amount of NOx emissions at the outlet of the exhaust heat recovery boiler to a boiler outlet target value or less; Equipped with the denitration control unit is configured to generate the control command by referring to at least a first addition amount of the reducing agent obtained by a calculation based on a NOx parameter that is a parameter correlated with a NOx emission amount at a turbine outlet, The NOx parameter is an estimated NOx emission amount at the turbine outlet obtained by a calculation based on a hydrogen gas fuel supply amount, which is a supply amount of the hydrogen gas fuel supplied by the hydrogen gas fuel supply facility, and an upstream steam supply amount, which is a supply amount of the steam supplied by the upstream steam line. Gas turbine cogeneration system.

2. The control command is generated by referring to the second addition amount of the reducing agent obtained by a calculation based on a deviation between the boiler outlet target value and the amount of NOx emission at the outlet of the exhaust heat recovery boiler obtained by measurement. The gas turbine cogeneration system according to claim 1 .

3. A gas turbine including a compressor, a combustor, and a turbine; a hydrocarbon fuel supply facility for supplying a hydrocarbon gas fuel to the combustor; a hydrogen gas fuel supply facility for supplying hydrogen gas fuel, which is a fuel mainly composed of hydrogen gas, to the combustor; a heat recovery steam generator for generating steam using exhaust gas from the turbine; an upstream steam line for supplying the steam discharged from the heat recovery steam generator to a head end side of the combustor; a denitration device for denitrifying the exhaust gas by adding a reducing agent to the exhaust gas flowing through the exhaust heat recovery boiler; a denitration control unit for outputting a control command to the denitration device so as to reduce the amount of NOx emissions at the outlet of the exhaust heat recovery boiler to a boiler outlet target value or less; Equipped with the denitration control unit is configured to generate the control command by referring to at least a first addition amount of the reducing agent obtained by a calculation based on a NOx parameter that is a parameter correlated with a NOx emission amount at a turbine outlet, The boiler further includes an upstream steam control unit that controls the upstream steam line so that an actual NOx emission amount at the turbine outlet is equal to or less than a turbine outlet target value that is higher than the boiler outlet target value while satisfying a condition that an upstream steam supply amount, which is a supply amount of the steam supplied by the upstream steam line, is equal to or less than an allowable upper limit supply amount. Gas turbine cogeneration system.

4. The upstream steam control unit is configured to control the upstream steam line so that, when a target upstream steam supply rate, which is the upstream steam supply rate for making the NOx emission amount at the turbine outlet equal to or less than the turbine outlet target value, falls below the allowable upper limit supply rate, the upstream steam supply rate exceeds the target upstream steam supply rate and is equal to or less than the allowable upper limit supply rate. The gas turbine cogeneration system according to claim 3 .

5. the upstream steam control unit has an upstream steam supply amount determination unit configured to determine the upstream steam supply amount for reducing an actual NOx emission amount at the turbine outlet to equal to or less than the turbine outlet target value, The gas turbine cogeneration system includes: a downstream steam line for supplying the steam discharged from the heat recovery steam generator to a turbine side of the combustor relative to the head end; a downstream steam control unit that controls the downstream steam line while satisfying a condition that a total steam supply amount, which is a sum of a downstream steam supply amount that is a supply amount of the steam supplied by the downstream steam line and the upstream steam supply amount determined by the upstream steam supply amount determination unit, is equal to or less than a limit supply amount for avoiding surging of the compressor; Further equipped The gas turbine cogeneration system according to claim 3 .

6. a water recovery system for recovering moisture from the exhaust gas by heat exchange between the exhaust gas of the exhaust heat recovery boiler and refrigerant water; a make-up water tank for storing boiler feed water for supplying the recovered water recovered by the water recovery system to the heat recovery boiler; Further equipped The gas turbine cogeneration system according to claim 1 or 2.

7. A method for operating a gas turbine cogeneration system, comprising: The gas turbine cogeneration system includes: a gas turbine including a compressor, a combustor, and a turbine; a hydrocarbon fuel supply facility for supplying a hydrocarbon gas fuel to the combustor; a hydrogen gas fuel supply facility for supplying hydrogen gas fuel, which is a fuel mainly composed of hydrogen gas, to the combustor; a heat recovery steam generator for generating steam using exhaust gas from the turbine; an upstream steam line for supplying the steam discharged from the heat recovery steam generator to a head end side of the combustor; a denitration device for denitrifying the exhaust gas by adding a reducing agent to the exhaust gas flowing through the exhaust heat recovery boiler; Including, a denitration control step of outputting a control command to the denitration device so as to make the NOx emission amount at the exhaust heat recovery boiler outlet equal to or less than a boiler outlet target value; In the denitration control step, the control command is generated with reference to at least the first addition amount of the reducing agent obtained by a calculation based on a NOx parameter which is a parameter correlated with a NOx emission amount at a turbine outlet; The NOx parameter is an estimated NOx emission amount at the turbine outlet obtained by a calculation based on a hydrogen gas fuel supply amount, which is a supply amount of the hydrogen gas fuel supplied by the hydrogen gas fuel supply facility, and an upstream steam supply amount, which is a supply amount of the steam supplied by the upstream steam line. A method for operating a gas turbine cogeneration system.

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