Boiler, power generation facility, and method for controlling boiler

Abstract

Provided is a method for controlling a boiler, the boiler including: a solid fuel burner that uses a solid fuel in a furnace to form a flame; a solid fuel adjustment unit that adjusts a supply amount of the solid fuel supplied to the solid fuel burner; an ammonia fuel burner that uses an ammonia fuel in the furnace to form a flame; and an ammonia fuel adjustment unit that adjusts a supply amount of the ammonia fuel supplied to the ammonia fuel burner, said method comprising a control step for controlling the solid fuel adjustment unit and the ammonia fuel adjustment unit, wherein, in the control step (S102), when a load increase operation for increasing the load of the boiler is performed, the ammonia fuel adjustment unit is controlled so as to increase the supply amount of the ammonia fuel supplied to the ammonia fuel burner during an operation period from the start of the load increase operation to the completion thereof.

Description

Boiler, power generation facility, and boiler control method

[0001] The present disclosure relates to a boiler, a power generation facility, and a method for controlling a boiler.

[0002] Conventionally, boilers that perform combined combustion of pulverized coal and ammonia are known (see, for example, Patent Document 1). In the boiler disclosed in Patent Document 1, when a load increasing operation is performed to increase the load, only fuel other than ammonia fuel is supplied to the burner unit at the start of the load increasing operation, and thereafter, when the air ratio of the burner unit and the temperature inside the furnace satisfy the determination conditions, the supply of ammonia fuel is started.

[0003] Japanese Patent Application Laid-Open No. 2022-155820

[0004] When ammonia fuel is mixed with a solid fuel such as pulverized coal, if the ammonia fuel mixing ratio (the ratio of the heat input of ammonia fuel to the total heat input of fuel) is lower than the solid fuel mixing ratio (the ratio of the heat input of solid fuel to the total heat input of fuel), the solid fuel becomes the primary fuel. In this case, when changing the boiler load, the heat input to the boiler is generally changed by changing the supply amount of the solid fuel, which is the primary fuel. Therefore, the rate of change of the boiler load is limited by the rate of change of the amount of solid fuel supplied to the boiler.

[0005] On the other hand, when comparing ammonia fuel, which is liquid or gaseous, with solid fuel, it is known that ammonia fuel (particularly liquid ammonia) has the characteristic of being easier to change the supply amount. In Patent Document 1, ammonia fuel is not supplied to the burner unit at the start of the load increase operation, and only other fuels such as pulverized coal are supplied, so there is room for improvement in order to increase the load change speed of the boiler.

[0006] The present disclosure has been made in consideration of the above circumstances, and aims to provide a boiler, a power generation facility, and a boiler control method that are capable of increasing the load change rate of a boiler when performing a load change operation that changes the load of a boiler that burns both solid fuel and ammonia fuel in a furnace.

[0007] In order to solve the above problems, a boiler, a power generation facility, and a boiler control method according to an aspect of the present disclosure employ the following means: The boiler according to an aspect of the present disclosure includes a solid fuel burner that injects solid fuel into a furnace to combust it, a solid fuel adjustment unit that adjusts the supply amount of the solid fuel supplied to the solid fuel burner, an ammonia fuel burner that injects ammonia fuel into the furnace to combust it, an ammonia fuel adjustment unit that adjusts the supply amount of the ammonia fuel supplied to the ammonia fuel burner, and a control unit that controls the solid fuel adjustment unit and the ammonia fuel adjustment unit, wherein when a load changing operation that changes the load of the boiler is performed, the control unit controls the ammonia fuel adjustment unit to change the supply amount of the ammonia fuel supplied to the ammonia fuel burner during an operation period from the start to the completion of the load changing operation.

[0008] In a boiler control method according to one aspect of the present disclosure, the boiler has a solid fuel burner that forms a flame in a furnace using solid fuel, a solid fuel adjustment unit that adjusts the supply amount of the solid fuel supplied to the solid fuel burner, an ammonia fuel burner that forms a flame in the furnace using ammonia fuel, and an ammonia fuel adjustment unit that adjusts the supply amount of the ammonia fuel supplied to the ammonia fuel burner, and includes a control step of controlling the solid fuel adjustment unit and the ammonia fuel adjustment unit, wherein the control step controls the ammonia fuel adjustment unit to change the supply amount of the ammonia fuel supplied to the ammonia fuel burner during an operation period from the start to the completion of a load changing operation when a load changing operation that changes the load of the boiler is performed.

[0009] According to the present disclosure, it is possible to provide a boiler, a power generation facility, and a boiler control method that can increase the load change rate of a boiler when performing a load change operation that changes the load of a boiler that burns both solid fuel and ammonia fuel in a furnace.

[0010] 1 is a schematic configuration diagram showing a boiler according to a first embodiment of the present disclosure; FIG. 2 is a front view of the combustion burner shown in FIG. 1; FIG. 3 is a cross-sectional view of an ammonia fuel burner provided in the combustion burner shown in FIG. 1; FIG. 4 is a cross-sectional view of a pulverized fuel burner of the combustion burner of the boiler shown in FIG. 1; FIG. 5 is a flowchart showing a method for controlling a boiler according to the first embodiment of the present disclosure; FIG. 6 is a graph showing the time change in the load of the boiler; FIG. 7 is a graph showing the time change in the supply amount of pulverized fuel; FIG. 8 is a graph showing the time change in the supply amount of ammonia fuel; FIG. 9 is a flowchart showing a method for controlling a boiler according to a second embodiment of the present disclosure; FIG. 10 is a graph showing the time change in the supply amount of pulverized fuel;

[0011] [First Embodiment] A boiler 10 according to a first embodiment of the present disclosure will be described below with reference to the drawings. The boiler 10 according to this embodiment is an apparatus that combusts pulverized fuel (solid fuel) and ammonia fuel using a combustion burner and recovers heat generated by this combustion.

[0012] Fig. 1 is a schematic diagram showing a boiler 10 according to a first embodiment of the present disclosure. As shown in Fig. 1, the boiler 10 of this embodiment has a furnace 11, a combustion device 12, and a flue 13. The furnace 11 has a hollow rectangular cylindrical shape and is installed vertically. The combustion device 12 is provided below the furnace wall that constitutes this furnace 11.

[0013] The combustion device 12 has a plurality of combustion burners 100A, 100B, 100C, 100D, and 100E attached to the furnace wall. In this embodiment, the combustion burners 100A, 100B, 100C, 100D, and 100E are arranged in five sets (five stages) along the vertical direction, with four burners arranged at equal intervals around the circumferential axis of the vertical direction of the furnace 11. Although five sets are used here, six sets or any other number of sets may be used.

[0014] The combustion burners 100A, 100B, 100C, 100D, and 100E are connected to pulverizers 31, 32, 33, 34, and 35 via pulverized fuel supply pipes 26, 27, 28, 29, and 30, respectively. The pulverizers 31, 32, 33, 34, and 35 pulverize solid carbonaceous fuel such as coal into pulverized fuel, and supply the pulverized fuel together with a carrier gas such as air to the pulverized fuel supply pipes 26, 27, 28, 29, and 30. The pulverized fuel is supplied from the pulverized fuel supply pipes 26, 27, 28, 29, and 30 to the combustion burners 100A, 100B, 100C, 100D, and 100E.

[0015] The pulverizers 31, 32, 33, 34, and 35 are connected to flow rate adjusters (solid fuel adjustment units) 31 a, 32 a, 33 a, 34 a, and 35 a via solid fuel supply pipes 31 b, 32 b, 33 b, 34 b, and 35 b, respectively. The supply amounts of pulverized fuel supplied to the combustion burners 100A, 100B, 100C, 100D, and 100E via the pulverized fuel supply pipes 26, 27, 28, 29, and 30 are controlled by adjusting the amounts of solid carbonaceous fuel supplied to the pulverizers 31, 32, 33, 34, and 35 by the flow rate adjusters (solid fuel adjustment units) 31 a, 32 a, 33 a, 34 a, and 35 a.

[0016] 1 shows an example in which a belt conveyor is applied to the flow rate adjusting units (solid fuel adjusting units) 31 a, 32 a, 33 a, 34 a, and 35 a. For example, the amount of solid carbonaceous fuel supplied to the pulverizers 31, 32, 33, 34, and 35 is adjusted by the moving speed of the belt of the belt conveyor. Here, since unpulverized solid carbonaceous fuel remains inside the pulverizers 31, 32, 33, 34, and 35, the adjustment of the amount of solid carbonaceous fuel supplied by the moving speed of the belt is reflected in the amount of pulverized fuel supplied to the combustion burner with a certain delay time.

[0017] Each of the combustion burners 100A, 100B, 100C, 100D, and 100E is connected to an ammonia fuel supply unit 50 via ammonia fuel supply pipes 51, 52, 53, 53, and 55. The ammonia fuel supply unit 50 supplies liquid or gaseous ammonia fuel containing ammonia as a component to the ammonia fuel supply pipes 51, 52, 53, 54, and 55. The ammonia fuel is supplied from the ammonia fuel supply pipes 51, 52, 53, 54, and 55 to the combustion burners 100A, 100B, 100C, 100D, and 100E.

[0018] The ammonia fuel supply pipes 51, 52, 53, 54, and 55 are provided with flow rate adjusters (ammonia fuel adjusters) 51 a, 52 a, 53 a, 54 a, and 55 a, respectively. The flow rate adjusters (ammonia fuel adjusters) 51 a, 52 a, 53 a, 54 a, and 55 a use, for example, control valves that adjust the amount of fuel supplied by changing the opening degree. The flow rate adjusters 51 a, 52 a, 53 a, 54 a, and 55 a adjust the amount of ammonia fuel supplied from the ammonia fuel supply pipes 51, 52, 53, 54, and 55 to the combustion burners 100A, 100B, 100C, 100D, and 100E.

[0019] The boiler 10 includes a control unit 60 that controls each unit of the boiler 10, including the flow rate adjustment units 31a, 32a, 33a, 34a, and 35a and the flow rate adjustment units 51a, 52a, 53a, 54a, and 55a. The control unit 60 controls the belt movement speeds of the flow rate adjustment units 31a, 32a, 33a, 34a, and 35a to control the amount of solid carbonaceous fuel supplied to the pulverizers 31, 32, 33, 34, and 35, thereby indirectly adjusting the supply amount of pulverized fuel supplied from the pulverized fuel supply pipes 26, 27, 28, 29, and 30 to the combustion burners 100A, 100B, 100C, 100D, and 100E. Furthermore, the control unit 60 controls the opening degrees of the flow rate adjustment units 51a, 52a, 53a, 54a, and 55a to adjust the supply amounts of ammonia fuel supplied to the combustion burners 100A, 100B, 100C, 100D, and 100E from the ammonia fuel supply pipes 51, 52, 53, 54, and 55. That is, the flow rate adjustment units 51a, 52a, 53a, 54a, and 55a directly control the supply amounts of ammonia fuel.

[0020] The furnace 11 is provided with a wind box 36 at the mounting position of each of the combustion burners 100A, 100B, 100C, 100D, and 100E, and one end of an air duct 37 is connected to this wind box 36. A blower 38 is attached to the other end of this air duct 37. Furthermore, the furnace 11 is provided with additional air nozzles 39 vertically above the mounting positions of each of the combustion burners 100A, 100B, 100C, 100D, and 100E.

[0021] An end of a branch air duct 40 branching off from the air duct 37 is connected to the additional air nozzle 39. Therefore, combustion air sent by the blower 38 can be supplied from the air duct 37 to the wind box 36, and then from the wind box 36 to each of the combustion burners 100A, 100B, 100C, 100D, and 100E. In addition, combustion air sent by the blower 38 can be supplied from the branch air duct 40 to the additional air nozzle 39.

[0022] A flue 13 is connected to the furnace 11 at the top in the vertical direction, and this flue 13 is provided with superheaters 41, 42, reheaters 43, 44, and economizers 45, 46, 47, which are heat exchangers for recovering heat from the combustion gas, and heat is exchanged between the combustion gas generated by combustion in the furnace 11 and water or steam.

[0023] An exhaust gas pipe 48, through which the combustion gas that has undergone heat exchange is discharged as exhaust gas, is connected to the downstream side of the flue 13. An air heater 49 is provided between this exhaust gas pipe 48 and the air duct 37, so that heat exchange occurs between the air flowing through the air duct 37 and the exhaust gas flowing through the exhaust gas pipe 48, thereby raising the temperature of the combustion air to be supplied to the combustion burners 100A, 100B, 100C, 100D, and 100E. A chimney (not shown) is provided at the downstream end of the exhaust gas pipe 48.

[0024] The combustion burners 100A, 100B, 100C, 100D, and 100E inject pulverized fuel and ammonia fuel into the furnace 11, and also inject combustion air into the furnace 11, which is ignited at this time to form a flame. In the furnace 11, the pulverized fuel, ammonia fuel, and combustion air combust to generate a flame, and when the flame is generated in a vertically lower region within the furnace 11, combustion gas (exhaust gas) rises within the furnace 11 and is discharged into the flue 13.

[0025] Water supplied from a water supply pump (not shown) is preheated by economizers 45, 46, and 47, and then introduced into superheaters 41 and 42 through heat transfer tubes (not shown) that form the furnace walls, where superheated steam is generated by heat exchange with the combustion gas.

[0026] The superheated steam generated in the superheaters 41, 42 is supplied to a steam turbine (not shown) of a power plant (power generation facility). The steam turbine is connected to a generator, and generates electricity by driving the generator with the steam generated in the boiler 10. The steam turbine may be a multi-stage turbine including a low-pressure turbine that introduces steam discharged from the high-pressure turbine into reheaters 43, 44 of the boiler 10 and utilizes the resuperheated steam.

[0027] Next, the combustion device 12 will be described in detail. However, since each of the combustion burners 100A, 100B, 100C, 100D, and 100E that make up this combustion device 12 has a substantially similar configuration, only the combustion burner 100A located at the top will be described.

[0028] FIG. 2 is a front view showing the combustion burner 100A shown in FIG. 1 . As shown in FIG. 2 , the combustion burner 100A has an ammonia fuel burner 110, a pair of pulverized fuel burners (solid fuel burners) 120, and a pair of air nozzles 130. The ammonia fuel burner 110, the pulverized fuel burner 120, and the air nozzles 130 are arranged along the vertical direction VD at the same position in the horizontal direction HD. The ammonia fuel burner 110 is a device that injects ammonia fuel into the furnace 11 to combust it. The pulverized fuel burner 120 is a device that injects pulverized fuel into the furnace 11 to combust it. The air nozzle 130 is a device that supplies combustion air to the furnace 11. Note that the configuration of the combustion burner 100A is not limited to this. For example, the number of each of the ammonia fuel burner 110, the pulverized fuel burner 120, and the air nozzles 130 may be one or three or more. Furthermore, the order of the ammonia fuel burner 110, the pulverized fuel burner 120, and the air nozzle 130 may be set arbitrarily.

[0029] Fig. 3 is a cross-sectional view showing the ammonia-fuel burner 110 of the combustion burner 100A of the boiler 10 shown in Fig. 1. As shown in Fig. 3, the combustion burner 100A has ammonia-fuel burners 110a, 110b, 110c, and 110d attached to four wall surfaces 11a, 11b, 11c, and 11d that form the furnace 11. The wall surfaces 11a, 11b, 11c, and 11d are each installed along the vertical direction.

[0030] Ammonia fuel burners 110a, 110b, 110c, and 110d are respectively connected to branch pipes 51A, 51B, 51C, and 51D branched from an ammonia fuel supply pipe 51. In addition, branch pipes 37a, 37b, 37c, and 37d branched from an air duct 37 are respectively connected to ammonia fuel burners 110a, 110b, 110c, and 110d.

[0031] The ammonia fuel burner 110a is installed on the wall surface (first wall surface) 11a, and is installed at a position close to the wall surface 11b among the wall surfaces (second wall surface) 11b and (third wall surface) 11d, which are arranged opposite to the wall surface 11a at positions adjacent to the wall surface 11a. The ammonia fuel burner 110b is installed on the wall surface 11b, and is installed at a position close to the wall surface 11c among the wall surfaces 11a and 11c, which are arranged opposite to the wall surface 11b at positions adjacent to the wall surface 11b.

[0032] The ammonia fuel burner 110c is installed on the wall surface 11c, and is installed at a position close to the wall surface 11d among the wall surfaces 11d and 11b which are arranged opposite to the wall surface 11c at a position adjacent to the wall surface 11c. The ammonia fuel burner 110d is installed on the wall surface 11d, and is installed at a position close to the wall surface 11a among the wall surfaces 11a and 11c which are arranged opposite to the wall surface 11d at a position adjacent to the wall surface 11d.

[0033] Therefore, each of the ammonia-fuel burners 110a, 110b, 110c, and 110d on each wall surface of the furnace 11 can inject ammonia fuel into the furnace 11 at a slight deflection angle with respect to the center Ct of the furnace 11, thereby forming four flames F1, F2, F3, and F4. The flames F1, F2, F3, and F4 become swirling flames that swirl counterclockwise when viewed from above the furnace 11. Here, the flames swirl counterclockwise, but the ammonia-fuel burners 110a, 110b, 110c, and 110d may be arranged to form swirling flames that swirl clockwise.

[0034] Fig. 4 is a cross-sectional view showing the pulverized fuel burner 120 of the combustion burner 100A of the boiler 10 shown in Fig. 1. As shown in Fig. 4, the combustion burner 100A has pulverized fuel burners 120a, 120b, 120c, and 120d attached to four wall surfaces 11a, 11b, 11c, and 11d that form the furnace 11.

[0035] The pulverized fuel burners 120a, 120b, 120c, and 120d are respectively connected to branch pipes 26a, 26b, 26c, and 26d branched from the pulverized fuel supply pipe 26. In addition, the pulverized fuel burners 120a, 120b, 120c, and 120d are respectively connected to branch pipes 37a, 37b, 37c, and 37d branched from the air duct 37.

[0036] The pulverized fuel burner 120a is installed on the wall surface (first wall surface) 11a, and is installed at a position close to the wall surface 11b among the wall surfaces (second wall surface) 11b and (third wall surface) 11d, which are arranged opposite the wall surface 11a at a position adjacent to the wall surface 11a. The pulverized fuel burner 120b is installed on the wall surface 11b, and is installed at a position close to the wall surface 11c among the wall surfaces 11a and 11c, which are arranged opposite the wall surface 11b at a position adjacent to the wall surface 11b.

[0037] The pulverized fuel burner 120c is installed on the wall surface 11c, and is installed at a position close to the wall surface 11d among the wall surfaces 11d and 11b which are arranged opposite to the wall surface 11c at a position adjacent to the wall surface 11c. The pulverized fuel burner 120d is installed on the wall surface 11d, and is installed at a position close to the wall surface 11a among the wall surfaces 11a and 11c which are arranged opposite to the wall surface 11d at a position adjacent to the wall surface 11d.

[0038] Therefore, the pulverized fuel burners 120a, 120b, 120c, and 120d on each wall surface of the furnace 11 inject pulverized fuel into the furnace 11 at a slight angle relative to the center of the furnace 11, thereby forming four flames F1, F2, F3, and F4. The flames F1, F2, F3, and F4 become swirling flame flows that swirl counterclockwise when viewed from above the furnace 11. Here, the flames swirl counterclockwise, but the pulverized fuel burners 120a, 120b, 120c, and 120d may also be arranged to create swirling flame flows that swirl clockwise.

[0039] 3 and 4, the ammonia fuel burner 110a and the pulverized fuel burner 120a are arranged at the same position on the wall surface 11a when the furnace 11 is viewed in a plan view along the vertical direction VD. Furthermore, the ammonia fuel burner 110b and the pulverized fuel burner 120b are arranged at the same position on the wall surface 11b when the furnace 11 is viewed in a plan view along the vertical direction VD. Furthermore, the ammonia fuel burner 110c and the pulverized fuel burner 120c are arranged at the same position on the wall surface 11c when the furnace 11 is viewed in a plan view along the vertical direction VD. Furthermore, the ammonia fuel burner 110d and the pulverized fuel burner 120d are arranged at the same position on the wall surface 11d when the furnace 11 is viewed in a plan view along the vertical direction VD.

[0040] Next, a control method for the boiler 10 of this embodiment will be described with reference to Fig. 5 to Fig. 8. Fig. 5 is a flowchart showing a control method for the boiler 10 according to the first embodiment of the present disclosure. Fig. 6 is a graph showing the time change in the load of the boiler 10. Fig. 7 is a graph showing the time change in the supply amount of pulverized fuel. Fig. 8 is a graph showing the time change in the supply amount of ammonia fuel. Figs. 7 and 8 show the supply amount of pulverized fuel and the supply amount of ammonia fuel when the mixed combustion ratio of ammonia fuel is 20%.

[0041] 5 is executed by the control unit 60. The control unit 60 of this embodiment controls the flow rate adjustment units 31 a, 32 a, 33 a, 34 a, and 35 a and the flow rate adjustment units 51 a, 52 a, 53 a, 54 a, and 55 a so that the load on the boiler 10 corresponds to the command value.

[0042] 5 is a process that is started in response to the control unit 60 increasing the load of the boiler 10 from the current load L1 toward a target value L2. Here, the load of the boiler 10 refers to, for example, the ratio of the actual evaporation rate of the main steam to the evaporation rate of the main steam generated when the boiler 10 is operated at rated capacity. Furthermore, instead of the evaporation rate of the main steam, other indicators such as the temperature of the main steam, the pressure of the main steam, or the generator output may be used as the indicator of the boiler load.

[0043] As shown in Fig. 6, the load of the boiler 10 is constant at L1 from time t0 to time t1. The load of the boiler 10 is increased at a specified rate of change from time t1, when a target value L2 is given, to time t4. The processing of the flowchart in Fig. 5 starts at time t1 and ends at time t4. The comparative example shown in Fig. 6 shows the actual measured value of the boiler load when only the pulverized fuel is increased when the load of the boiler 10 is increased from L1 to L2.

[0044] In step S101, the control unit 60 determines whether the ammonia fuel co-firing ratio is 20% or more, and if YES, the process proceeds to step S102, and if NO, the process proceeds to step S103. Here, the ammonia fuel co-firing ratio refers to the ratio of the heat input amount of ammonia fuel to the total heat input amount, which is the sum of the heat input amount of the solid fuel supplied to the boiler 10 and the heat input amount of the ammonia fuel.

[0045] The control unit 60 presets the ammonia fuel co-combustion ratio and controls the flow rate adjusters 31a, 32a, 33a, 34a, 35a and the flow rate adjusters 51a, 52a, 53a, 54a, 55a so that the ammonia fuel co-combustion ratio is the preset value. For example, the control unit 60 controls the flow rate adjusters 31a, 32a, 33a, 34a, 35a and the flow rate adjusters 51a, 52a, 53a, 54a, 55a so that the ammonia fuel co-combustion ratio is 20% or more and 80% or less. The control unit 60 may also control the flow rate adjusters 31a, 32a, 33a, 34a, 35a and the flow rate adjusters 51a, 52a, 53a, 54a, 55a so that the ammonia fuel co-combustion ratio is 20% or more and 50% or less.

[0046] In step S102, the control unit 60 controls the apertures of the flow rate adjustment units 51 a, 52 a, 53 a, 54 a, and 55 a so as to increase the supply amount of ammonia fuel at a specified rate of change. As shown in Fig. 8 , the control unit 60 gradually increases the supply amount of ammonia fuel from Qa1 at time t1 at a specified rate of change from time t1 to time t2.

[0047] The control unit 60 executes step S102 when the ammonia fuel co-combustion ratio is 20% or more. This is because if the ammonia fuel co-combustion ratio is less than 20%, and ammonia fuel is used to increase the load on the boiler 10, the ammonia fuel co-combustion ratio may significantly deviate from a preset value.

[0048] In step S103, the control unit 60 controls the flow rate adjusting units 31a, 32a, 33a, 34a, and 35a to increase the supply amount of pulverized fuel at a specified rate of change. The control unit 60 executes step S103 both when the ammonia fuel co-combustion ratio is 20% or more and when it is less than 20%. As shown in Fig. 7, the control unit 60 gradually increases the supply amount of pulverized fuel from Qc1 at time t1 to Qc2 at time t4 at a specified rate of change, from time t1 to time t4.

[0049] In step S104, the control unit 60 determines whether the absolute value of the difference between the command value Lt and the actual measured value La of the load of the boiler 10 at the current time is equal to or greater than a predetermined value, and if the result is YES, the process proceeds to step S105, and if the result is NO, the process proceeds to step S106. When the evaporation rate of the main steam is used as the load index indicating the load of the boiler 10, the actual measured value of the load of the boiler 10 is measured by a measurement unit (not shown) that measures the flow rate of the main steam.

[0050] In step S105, since the absolute value of the difference between the command value Lt and the actual measured value La of the load of the boiler 10 deviates by more than the predetermined value Lpr, the control unit 60 changes the rate of change of the supply amount of ammonia fuel so that the actual measured value La approaches the command value Lt. The control unit 60 changes the rate of change of the supply amount of ammonia fuel by controlling the opening degrees of the flow rate adjustment units 51 a, 52 a, 53 a, 54 a, and 55 a.

[0051] The control unit 60 reduces the rate of change of the amount of ammonia fuel supplied when the actual measurement value La is higher than the command value Lt by a predetermined value Lpr or more. Furthermore, the control unit 60 increases the rate of change of the amount of ammonia fuel supplied when the actual measurement value La is lower than the command value Lt by a predetermined value Lpr or more. Fig. 6 shows an example in which the actual measurement value La becomes lower than the command value Lt by a predetermined value Lpr or more at time t2, and becomes higher than the command value Lt by a predetermined value Lpr or more at time t3.

[0052] As shown in Fig. 8, the control unit 60 increases the rate of change of the supply amount of ammonia fuel from time t2 when the actual measurement value La becomes lower than the command value Lt by at least a predetermined value Lpr, to time t3 when the actual measurement value La becomes higher than the command value Lt by at least the predetermined value Lpr. Furthermore, the control unit 60 decreases the rate of change of the supply amount of ammonia fuel from time t3 to time t4. The comparative example shown in Fig. 8 is an example in which the specified rate of change of the supply amount of ammonia fuel from time t1 to time t2 is maintained from time t2 to time t4.

[0053] In step S106, the control unit 60 determines whether the command value for the load of the boiler 10 has reached the target value L2. If YES, the control unit 60 proceeds to step S107, and if NO, the control unit 60 returns to step S104.

[0054] In step S107, in response to the command value of the load of the boiler 10 reaching the target value L2, the control unit 60 controls the opening degrees of the flow rate adjustment units 51a, 52a, 53a, 54a, and 55a so that the supply amount of ammonia fuel supplied to the ammonia fuel burner 110 is maintained at a supply amount Qa2 that results in a specified mixed combustion ratio.

[0055] In step S108, in response to the command value of the load of the boiler 10 reaching the target value L2, the control unit 60 controls the flow rate adjustment units 31a, 32a, 33a, 34a, and 35a so that the amount of pulverized fuel supplied to the pulverized fuel burner 120 becomes a specified mixed combustion ratio. After executing step S108, the control unit 60 ends the processing of this flowchart.

[0056] 5 , when executing a load increasing operation (load changing operation) for increasing the load of the boiler 10 from L1 to L2, the control unit 60 controls the apertures of the flow rate adjusting units 51a, 52a, 53a, 54a, and 55a so as to gradually increase the supply amount of ammonia fuel supplied to the ammonia-fuel burner 110 during an operation period from time t1 when the load increasing operation starts to time t4 when the load increasing operation stops. The load increasing operation is an operation that is executed in an operating state after the boiler 10 is started.

[0057] In the flowchart shown in Figure 5, when performing a load increase operation to increase the load of the boiler 10 from L1 to L2, the control unit 60 controls the flow rate adjustment units 31a, 32a, 33a, 34a, and 35a to gradually increase the amount of pulverized fuel supplied to the pulverized fuel burner 120 during the operation period from time t1 when the load increase operation starts to time t4 when the load increase operation stops.

[0058] In the above, an example has been described in which the control unit 60 executes a load increasing operation (load changing operation) to increase the load of the boiler 10 from L1 to L2, but the control unit 60 can also execute a load decreasing operation (load changing operation) to decrease the load of the boiler 10 from L2 to L1. When the control unit 60 executes a load decreasing operation, the process of "increasing the supply amount of ammonia fuel at a specified rate of change" in step S102 becomes a process of "decreasing the supply amount of ammonia fuel at a specified rate of change". Furthermore, the process of "increasing the supply amount of pulverized fuel at a specified rate of change" in step S103 becomes a process of "decreasing the supply amount of pulverized fuel at a specified rate of change".

[0059] The boiler 10 of this embodiment described above provides the following actions and effects. According to the boiler 10 of this embodiment, when a load-increasing operation is performed to increase the load of the boiler 10, the supply amount of ammonia fuel supplied to the ammonia-fuel burner 110 increases during the operation period from time t1 to time t4, which is the period from the start to the completion of the load-increasing operation. Comparing ammonia fuel with solid fuel, ammonia fuel (particularly liquid ammonia) has the characteristic of being easier to change in supply amount. Therefore, by increasing the supply amount of ammonia fuel supplied to the ammonia-fuel burner 110, the boiler 10 can more easily follow changes in load compared to when only the supply amount of solid fuel is increased.

[0060] Furthermore, according to the boiler 10 of this embodiment, when a load-increasing operation is performed to increase the load of the boiler 10, the supply amount of pulverized fuel supplied to the pulverized fuel burner 120 increases during the operation period from the start to the completion of the load-increasing operation. Since the supply amounts of both ammonia fuel and pulverized fuel are increased, the boiler 10 can improve its ability to follow changes in load while maintaining a relatively constant mixed-fuel ratio, compared to when only the supply amount of pulverized fuel is increased.

[0061] According to the boiler 10 of this embodiment, by setting the ammonia fuel co-firing ratio to 20% or more and 80% or less, the amount of carbon dioxide generated can be reduced compared to when the ammonia fuel co-firing ratio is less than 20%. Furthermore, because the ammonia fuel co-firing ratio is relatively high, even when ammonia fuel is used when performing a load increase operation to increase the load of the boiler 10, the ammonia fuel co-firing ratio can be maintained in an appropriate range of 20% or more and 80% or less.

[0062] [Second embodiment] Hereinafter, a boiler 10 according to a first embodiment of the present disclosure will be described with reference to the drawings. The second embodiment is a modified example of the first embodiment, and is the same as the first embodiment except where specifically described below, and therefore, description thereof will be omitted below.

[0063] The control unit 60 in the first embodiment controls the flow rate adjusting units 31a, 32a, 33a, 34a, and 35a so as to increase the amount of pulverized fuel supplied to the pulverized fuel burner 120 when the load on the boiler 10 is increased. In contrast, the control unit 60 in the present embodiment controls the flow rate adjusting units 31a, 32a, 33a, 34a, and 35a so as to keep the amount of pulverized fuel supplied to the pulverized fuel burner 120 constant when the load on the boiler 10 is increased.

[0064] A control method for the boiler 10 according to the present embodiment will be described with reference to Fig. 9 to Fig. 11. Fig. 9 is a flowchart showing a control method for the boiler 10 according to the second embodiment of the present disclosure. Fig. 10 is a graph showing the time change in the supply amount of pulverized fuel. Fig. 11 is a graph showing the time change in the supply amount of ammonia fuel. Figs. 10 and 11 show the supply amount of pulverized fuel and the supply amount of ammonia fuel when the ammonia fuel co-firing ratio is 20%. It is also assumed that the time change in the load of the boiler 10 is the same as that shown in the graph in Fig. 6.

[0065] In FIG. 9, steps S201, S202, S203, S204, S205, S208, and S209 are similar to steps S101, S102, S104, S105, S106, S107, and S108 in FIG. 6 of the first embodiment, and therefore will not be described below.

[0066] In the boiler 10 of the first embodiment, the control unit 60 increases the supply amount of pulverized fuel at a specified rate of change in step S103. On the other hand, in the boiler 10 of the present embodiment, the control unit 60 does not increase the supply amount of pulverized fuel at a specified rate of change. In the boiler 10 of the present embodiment, the control unit 60 controls the flow rate adjustment units 31 a, 32 a, 33 a, 34 a, and 35 a so that the supply amount of pulverized fuel is constant when the load of the boiler 10 is increased.

[0067] In step S206, the control unit 60 controls the apertures of the flow rate adjustment units 51 a, 52 a, 53 a, 54 a, and 55 a so that the supply amount of ammonia fuel supplied to the ammonia fuel burner 110 decreases at a specified rate of change in response to the lapse of a certain time since the command value of the load of the boiler 10 reached the target value L2. Fig. 11 is a graph showing the change over time in the supply amount of ammonia fuel.

[0068] 11 , the control unit 60 controls the apertures of the flow rate adjusters 51 a, 52 a, 53 a, 54 a, and 55 a so that the supply amount of ammonia fuel decreases at a specified rate of change during the period from time t5 to time t6, which is a certain time period after time t4, when the command value of the load of the boiler 10 reaches the target value L2. The reason for decreasing the supply amount of ammonia fuel is to reduce the supply amount of ammonia fuel used to increase the load of the boiler 10 from L1 to L2, thereby achieving a set mixed-firing ratio.

[0069] In step S207, the control unit 60 controls the flow rate adjusting units 31a, 32a, 33a, 34a, and 35a so that the supply rate of pulverized fuel supplied to the pulverized fuel burner 120 increases at a specified rate of change when a certain time has elapsed since the command value of the load of the boiler 10 reached the target value L2. Fig. 10 is a graph showing the change over time in the supply rate of pulverized fuel.

[0070] 10, the control unit 60 controls the flow rate adjusting units 31a, 32a, 33a, 34a, and 35a so that the supply amount of pulverized fuel increases at a specified rate of change during a period from time t5 to time t6, which is a certain time period after time t4 when the command value of the load of the boiler 10 reaches the target value L2. The reason for increasing the supply amount of pulverized fuel is to offset the gradual decrease in the supply amount of ammonia fuel during the period from time t5 to time t6, and to maintain the load of the boiler 10 constant.

[0071] If the ammonia fuel mixed combustion ratio is less than 20% in step S201, the process proceeds to step S210, and the control unit 60 controls the flow rate adjustment units 31a, 32a, 33a, 34a, and 35a to increase the supply amount of pulverized fuel at a specified rate of change.

[0072] In step S211, the control unit 60 determines whether the absolute value of the difference between the command value Lt and the actual measured value La of the load of the boiler 10 at the current time is equal to or greater than a predetermined value Lpr, and if the result is YES, the process proceeds to step S212, and if the result is NO, the process proceeds to step S213. When the evaporation rate of the main steam is used as the load index of the boiler 10, the actual measured value of the load of the boiler 10 is measured by a measurement unit (not shown) that measures the flow rate of the main steam.

[0073] In step S212, since the command value Lt of the load of the boiler 10 and the actual measured value La deviate from each other by a predetermined value Lpr or more, the control unit 60 changes the rate of change of the supply amount of pulverized fuel so that the actual measured value La approaches the command value Lt. The control unit 60 changes the rate of change of the supply amount of pulverized fuel by controlling the flow rate adjustment units 31a, 32a, 33a, 34a, and 35a.

[0074] In step S213, the control unit 60 determines whether the command value for the load of the boiler 10 has reached the target value L2. If YES, the control unit 60 proceeds to step S214, and if NO, the control unit 60 returns to step S211.

[0075] In step S214, the control unit 60 controls the opening degrees of the flow rate adjustment units 51a, 52a, 53a, 54a, and 55a so that the amount of ammonia fuel supplied to the ammonia fuel burner 110 increases at a specified rate of change, depending on whether a certain amount of time has elapsed since the load command value of the boiler 10 reached the target value L2.

[0076] In step S215, the control unit 60 controls the flow rate adjusting units 31a, 32a, 33a, 34a, and 35a so that the supply rate of pulverized fuel supplied to the pulverized fuel burner 120 decreases at a specified rate of change when a certain time has elapsed since the command value of the load of the boiler 10 reached the target value L2. The reason why the supply rate of ammonia fuel is increased while the supply rate of pulverized fuel is decreased is to reduce the supply rate of pulverized fuel used to increase the load of the boiler 10 from L1 to L2 and achieve a set mixed combustion ratio.

[0077] According to the boiler 10 of this embodiment, when a load increasing operation is performed to increase the load of the boiler 10, the supply amount Qc1 of the pulverized fuel is constant during the operation period from time t1 to time t4 from the start to the completion of the load increasing operation, so that the load of the boiler 10 is increased only by the ammonia fuel. Therefore, compared to the case where the supply amount of the pulverized fuel is increased, fluctuations in the heat input amount to the boiler 10 can be suppressed, and the ability of the boiler 10 to follow changes in the load can be improved.

[0078] Although the above has described an example in which the control unit 60 executes a load increasing operation (load changing operation) to increase the load of the boiler 10 from L1 to L2, the control unit 60 can also execute a load decreasing operation (load changing operation) to decrease the load of the boiler 10 from L2 to L1. When the control unit 60 executes a load decreasing operation, the process of "increasing the supply amount of ammonia fuel at a specified rate of change" in steps S202 and S214 becomes a process of "decreasing the supply amount of ammonia fuel at a specified rate of change". Furthermore, the process of "increasing the supply amount of pulverized fuel at a specified rate of change" in steps S210 and S207 becomes a process of "decreasing the supply amount of pulverized fuel at a specified rate of change".

[0079] Moreover, the process of "decreasing the supply amount of ammonia fuel at a specified rate of change" in step S206 becomes a process of "increasing the supply amount of ammonia fuel at a specified rate of change". Moreover, the process of "decreasing the supply amount of pulverized fuel at a specified rate of change" in step S215 becomes a process of "increasing the supply amount of pulverized fuel at a specified rate of change".

[0080] The boiler, the power generation facility, and the boiler control method described in the above-described respective embodiments can be understood, for example, as follows: A boiler according to a first aspect of the present disclosure is a boiler including: a solid fuel burner (120) that injects solid fuel into a furnace (11) and burns it; a solid fuel adjustment unit (31a to 35a) that adjusts the supply amount of the solid fuel supplied to the solid fuel burner; an ammonia fuel burner (110) that injects ammonia fuel into the furnace (11) and burns it; an ammonia fuel adjustment unit (51a to 55a) that adjusts the supply amount of the ammonia fuel supplied to the ammonia fuel burner; and a control unit that controls the solid fuel adjustment unit and the ammonia fuel adjustment unit, wherein, when a load changing operation that changes the load of the boiler is performed, the control unit controls the ammonia fuel adjustment unit to change the supply amount of the ammonia fuel supplied to the ammonia fuel burner during an operation period from the start to the completion of the load changing operation.

[0081] According to the boiler according to the first aspect of the present disclosure, when a load change operation is performed to change the boiler load, the amount of ammonia fuel supplied to the ammonia-fueled burner is increased during the operation period from the start to the completion of the load change operation. Comparing ammonia fuel with solid fuel, ammonia fuel (particularly liquid ammonia) has the property of more easily increasing the heat input. Therefore, by changing the amount of ammonia fuel supplied to the ammonia-fueled burner, the boiler load change speed can be increased compared to when only the amount of solid fuel supplied is changed.

[0082] A boiler according to a second aspect of the present disclosure is the first aspect, further comprising the following configuration. That is, the control unit controls the solid fuel adjusting unit to change the supply amount of the solid fuel supplied to the solid fuel burner when changing the load of the boiler. According to the boiler according to the second aspect of the present disclosure, when performing a load change operation to change the load of the boiler, the supply amount of the solid fuel supplied to the solid fuel burner increases during the operation period from the start to the completion of the load change operation when performing a load change operation to change the load of the boiler. Because the supply amounts of both ammonia fuel and solid fuel are changed, the load change rate of the boiler can be increased compared to when only the supply amount of solid fuel is changed.

[0083] A boiler according to a third aspect of the present disclosure is the first aspect, further comprising the following configuration. That is, when changing the load of the boiler, the control unit controls the solid fuel adjusting unit so that the supply amount of the solid fuel supplied to the solid fuel burner remains constant. According to the boiler according to the third aspect of the present disclosure, when performing a load change operation to change the boiler load, the supply amount of solid fuel remains constant throughout the operation period from the start to the completion of the load change operation, so the boiler load is changed using only ammonia fuel. Therefore, the boiler load change speed can be increased compared to when the supply amount of solid fuel is changed.

[0084] A boiler according to a fourth aspect of the present disclosure is any one of the first to third aspects, further comprising the following configuration. That is, during a predetermined operating period in which the boiler is in an operating state, the control unit controls the solid fuel preparation unit and the ammonia fuel preparation unit so that a ratio of the heat input of the ammonia fuel to a total heat input, which is the sum of the heat input of the solid fuel and the heat input of the ammonia fuel, is 20% or more and 80% or less. According to the boiler according to the fourth aspect of the present disclosure, by setting the ammonia fuel co-combustion ratio to 20% or more and 80% or less, the amount of carbon dioxide generated can be reduced compared to when the ammonia fuel co-combustion ratio is less than 20%. Furthermore, because the ammonia fuel co-combustion ratio is relatively high, even when ammonia fuel is used when performing a load increase operation to increase the boiler load, the ammonia fuel co-combustion ratio can be maintained in an appropriate range of 20% or more and 80% or less.

[0085] A boiler according to a fifth aspect of the present disclosure is the third aspect, further comprising the following configuration. That is, during a predetermined operating period in which the boiler is in an operating state, the control unit controls the solid fuel preparation unit and the ammonia fuel preparation unit so that the ratio of the heat input of the ammonia fuel to the total heat input, which is the sum of the heat input of the solid fuel and the heat input of the ammonia fuel, is 20% or more and 50% or less. According to the boiler according to the fifth aspect of the present disclosure, by setting the ammonia fuel co-combustion ratio to 20% or more and 50% or less, the amount of carbon dioxide generated can be reduced compared to when the ammonia fuel co-combustion ratio is less than 20%. Furthermore, because the ammonia fuel co-combustion ratio is relatively high, the ammonia fuel co-combustion ratio can be maintained in an appropriate range of 20% or more and 50% or less, even when ammonia fuel is used when performing a load increase operation to increase the boiler load.

[0086] A boiler according to a sixth aspect of the present disclosure is any one of the first to third aspects, further comprising the following configuration: the load change operation is an operation executed in an operating state after startup of the boiler. According to the boiler according to the sixth aspect of the present disclosure, the load change rate of the boiler can be increased in an operating state after startup of the boiler.

[0087] A power generation facility according to a seventh aspect of the present disclosure includes the boiler according to any one of the first to third aspects, a steam turbine driven by steam generated in the boiler, and a generator connected to the steam turbine. According to the power generation facility according to the seventh aspect of the present disclosure, by changing the supply amount of ammonia fuel supplied to the ammonia-fuel burner, it is possible to increase the load change rate of the boiler compared to when only the supply amount of solid fuel is changed.

[0088] In a boiler control method according to an eighth aspect of the present disclosure, the boiler has a solid fuel burner that forms a flame in a furnace using solid fuel, a solid fuel adjustment unit that adjusts the supply amount of the solid fuel supplied to the solid fuel burner, an ammonia fuel burner that forms a flame in the furnace using ammonia fuel, and an ammonia fuel adjustment unit that adjusts the supply amount of the ammonia fuel supplied to the ammonia fuel burner, and includes a control step of controlling the solid fuel adjustment unit and the ammonia fuel adjustment unit, wherein the control step controls the ammonia fuel adjustment unit to change the supply amount of the ammonia fuel supplied to the ammonia fuel burner during an operation period from the start to the completion of a load changing operation when a load changing operation that changes the load of the boiler is performed.

[0089] According to the boiler control method according to the eighth aspect of the present disclosure, when a load change operation is performed to change the boiler load, the supply amount of ammonia fuel supplied to the ammonia-fueled burner is changed during the operation period from the start to the completion of the load change operation. Comparing ammonia fuel with solid fuel, ammonia fuel (particularly liquid ammonia) has the characteristic of being more susceptible to changes in heat input. Therefore, by changing the supply amount of ammonia fuel supplied to the ammonia-fueled burner, the boiler load change rate can be increased compared to when only the supply amount of solid fuel is changed.

[0090] DESCRIPTION OF SYMBOLS 10 Boiler 11 Furnace 12 Combustion device 13 Flue 26 Pulverized fuel supply pipe 31, 32, 33, 34, 35 Pulverizer 31a, 32a, 33a, 34a, 35a Flow rate adjustment unit (solid fuel adjustment unit) 50 Ammonia fuel supply unit 51, 52, 53, 54, 55 Ammonia fuel supply pipe 51a, 52a, 53a, 54a, 55a Flow rate adjustment unit (ammonia fuel adjustment unit) 60 Control unit 100A, 100B, 100C, 100D, 100E Combustion burner 110 Ammonia fuel burner 120 Pulverized fuel burner 130 Air nozzle Lt Command value L2 Target value La Actual measurement value Lpr Predetermined value VD Vertical direction

Claims

1. A boiler comprising: a solid fuel burner which injects solid fuel into a furnace for combustion; a solid fuel adjustment unit which adjusts the amount of the solid fuel supplied to the solid fuel burner; an ammonia fuel burner which injects ammonia fuel into the furnace for combustion; an ammonia fuel adjustment unit which adjusts the amount of the ammonia fuel supplied to the ammonia fuel burner; and a control unit which controls the solid fuel adjustment unit and the ammonia fuel adjustment unit, wherein when a load changing operation which changes the load of the boiler is performed, the control unit controls the ammonia fuel adjustment unit so as to change the amount of the ammonia fuel supplied to the ammonia fuel burner during an operation period from the start of the load changing operation to the completion of the load changing operation.

2. A boiler as described in claim 1, wherein the control unit controls the solid fuel adjustment unit to change the amount of solid fuel supplied to the solid fuel burner when the load of the boiler is changed.

3. A boiler as described in claim 1, wherein the control unit controls the solid fuel adjustment unit so that the amount of solid fuel supplied to the solid fuel burner is constant when the load of the boiler is changed.

4. A boiler as described in any one of claims 1 to 3, wherein the control unit controls the solid fuel adjustment unit and the ammonia fuel adjustment unit so that, during a specified operating period during which the boiler is in an operating state, the ratio of the heat input of the ammonia fuel to the total heat input, which is the sum of the heat input of the solid fuel and the heat input of the ammonia fuel, is 20% or more and 80% or less.

5. A boiler as described in claim 3, wherein the control unit controls the solid fuel adjustment unit and the ammonia fuel adjustment unit so that the ratio of the heat input of the ammonia fuel to the total heat input, which is the sum of the heat input of the solid fuel and the heat input of the ammonia fuel, is 20% or more and 50% or less during a specified operating period during which the boiler is in an operating state.

6. A boiler as claimed in any one of claims 1 to 3, wherein the load change operation is an operation executed in an operating state after start-up of the boiler.

7. A power generation facility comprising: a boiler according to any one of claims 1 to 3; a steam turbine driven by steam generated in the boiler; and a generator connected to the steam turbine.

8. A method for controlling a boiler, the boiler having: a solid fuel burner that forms a flame in a furnace using solid fuel; a solid fuel adjustment unit that adjusts the supply amount of the solid fuel supplied to the solid fuel burner; an ammonia fuel burner that forms a flame in the furnace using ammonia fuel; and an ammonia fuel adjustment unit that adjusts the supply amount of the ammonia fuel supplied to the ammonia fuel burner, the method comprising a control step of controlling the solid fuel adjustment unit and the ammonia fuel adjustment unit, the control step controlling the ammonia fuel adjustment unit to change the supply amount of the ammonia fuel supplied to the ammonia fuel burner during an operation period from the start of a load changing operation to the completion of the load changing operation when a load changing operation that changes the load of the boiler is performed.

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