Plant control device, plant, plant control method, and program

Abstract

A plant control device according to the present invention comprises: a signal reception unit that receives a signal including at least one of a power demand, a hydrogen demand, and a steam demand of a production process; and a control unit that, on the basis of the received signal, adjusts at least one of the amount of steam generated by a boiler, the amount of steam supplied to a steam turbine, the amount of steam supplied to an ammonia decomposition device, and the amount of steam supplied to the production process, such that a decrease in the load of the boiler is suppressed.

Description

Plant control device, plant, plant control method, and program

[0001] This application claims priority to Japanese Patent Application No. 2024-099517, filed on June 20, 2024, the contents of which are incorporated herein by reference.

[0002] Boilers have traditionally been used for a variety of purposes. Steam generated in industrial boilers is sent to factories and used in the production process of industrial products. In addition, in cogeneration plants, steam generated in boilers is also used to generate electricity, separate from being sent to factories. The generated electricity is used in the factory's production process and sold to an external grid (external sales).

[0003] Furthermore, ammonia, which can reduce carbon dioxide emissions, is sometimes used as fuel for power plants. For example, Patent Document 1 describes the configuration of a thermal power plant in which steam generated in a boiler is supplied to an ammonia decomposition device, and hydrogen decomposed from ammonia by the heat of the steam is supplied to the boiler as fuel. Furthermore, Patent Document 2 describes the configuration of a gas turbine system in which high-temperature compressed air is supplied from a compressor to an ammonia decomposition catalyst, and hydrogen decomposed from ammonia by the heat of the compressed air is supplied to a combustor as fuel.

[0004] JP 2018-96616 A International Publication No. 2022 / 209562

[0005] Demand for steam used in production processes and electricity used in production processes and for external sales fluctuates seasonally, monthly, weekly, and daily. Plant control devices must adjust the plant's power output and boiler steam generation in response to these demand fluctuations.

[0006] FIG. 13 is a diagram illustrating fluctuations in demand and boiler load factor in a cogeneration plant according to conventional technology. The vertical axis of FIG. 13 represents the boiler's steam generation rate (load factor) and boiler efficiency, and the horizontal axis represents time. FIG. 13 is a stacked graph showing the transition of the amount of steam generated by the boiler in response to the power demand and steam demand over a day. Of the amount of steam generated by the boiler, a represents the amount of steam supplied to the steam turbine to meet the power demand, and b represents the amount of steam supplied to the production process. Furthermore, of the amount of steam supplied to the steam turbine, a1 represents the amount of steam used for in-house power generation, and a2 represents the amount of steam used for external sales of power. The dashed line E represents the boiler efficiency.

[0007] In conventional plants, as shown in the example of Figure 13, the amount of steam generated by the boiler (load factor) fluctuates depending on the daily fluctuations in power and steam demand. For example, if the boiler load drops due to a decrease in power and steam demand at time t1 in Figure 13, the excess air ratio increases, resulting in increased gas loss and increased radiation heat loss, reducing boiler efficiency and lowering economic efficiency. Furthermore, boilers with load factors below their minimum load factor are shut down. Therefore, particularly in plants using boilers that are difficult to operate at low loads (e.g., minimum load factors of around 50%), lowering the boiler load factor in response to a decrease in demand can result in a decrease in the boiler's operating rate, further reducing economic efficiency.

[0008] An object of the present disclosure is to provide a plant control device, a plant, a plant control method, and a program that enable boiler steam to be used for hydrogen generation in addition to production processes and power generation, and that can operate the plant efficiently by suppressing a decrease in boiler load due to demand fluctuations.

[0009] According to one aspect of the present disclosure, a plant control device includes a boiler that generates steam, a steam turbine that is rotationally driven by the steam, a generator that converts the rotational power of the steam turbine into electric power, an ammonia decomposer that decomposes ammonia using the heat of the steam to produce hydrogen, and steam supply piping that supplies the steam to the steam turbine, the ammonia decomposer, and a production process that utilizes the steam for production, and includes a signal receiving unit that receives a signal including at least one of an electric power demand, a hydrogen demand, and a steam demand of the production process, and a control unit that adjusts at least one of the steam generation amount of the boiler, the flow rate of the steam supply piping of the steam turbine, the flow rate of the steam supply piping of the ammonia decomposer, and the flow rate of the steam supply piping of the production process based on the received signal so as to suppress a decrease in the load of the boiler.

[0010] According to one aspect of the present disclosure, a plant includes a boiler that generates steam, a steam turbine that is rotationally driven by the steam, a generator that converts the rotational power of the steam turbine into electric power, an ammonia decomposition device that decomposes ammonia using the heat of the steam to produce hydrogen, steam supply piping that supplies the steam to the steam turbine, the ammonia decomposition device, and a production process that utilizes the steam for production, and the above-mentioned control device.

[0011] According to one aspect of the present disclosure, a plant control method includes a boiler that generates steam, a steam turbine that is rotationally driven by the steam, a generator that converts the rotational power of the steam turbine into electric power, an ammonia decomposer that decomposes ammonia using the heat of the steam to produce hydrogen, and steam supply piping that supplies the steam to the steam turbine, the ammonia decomposer, and a production process that utilizes the steam for production, the plant control method including the steps of: receiving a signal including at least one of an electric power demand, a hydrogen demand, and a steam demand of the production process; and adjusting, based on the received signal, at least one of an amount of steam generated by the boiler, a flow rate of a steam supply piping of the steam turbine, a flow rate of a steam supply piping of the ammonia decomposer, and a flow rate of a steam supply piping of the production process so as to suppress a decrease in the load of the boiler.

[0012] According to one aspect of the present disclosure, a program causes a control device of a plant including a boiler that generates steam, a steam turbine that is rotationally driven by the steam, a generator that converts the rotational power of the steam turbine into electric power, an ammonia decomposer that decomposes ammonia using the heat of the steam to produce hydrogen, and steam supply piping that supplies the steam to the steam turbine, the ammonia decomposer, and a production process that uses the steam for production, to execute the steps of receiving a signal including at least one of an electric power demand, a hydrogen demand, and a steam demand of the production process, and adjusting, based on the received signal, at least one of an amount of steam generated by the boiler, a flow rate of the steam supply piping of the steam turbine, a flow rate of the steam supply piping of the ammonia decomposer, and a flow rate of the steam supply piping of the production process so as to suppress a decrease in the load of the boiler.

[0013] According to the above aspect, the boiler steam can be used for hydrogen generation in addition to the production process and power generation, and the plant can be operated efficiently by suppressing a decrease in the boiler load due to fluctuations in demand.

[0014] 1 is a schematic diagram showing the overall configuration of a plant according to a first embodiment. FIG. 2 is a schematic process flow diagram of an ammonia decomposition apparatus according to the first embodiment. FIG. 3 is a block diagram showing the functional configuration of a control device according to the first embodiment. FIG. 4 is a first flowchart showing an example of processing by the control device according to the first embodiment. FIG. 5 is a second flowchart showing an example of processing by the control device according to the first embodiment. FIG. 6 is a first diagram illustrating fluctuations in demand and boiler load factor of the plant according to the first embodiment. FIG. 7 is a second diagram illustrating fluctuations in demand and boiler load factor of the plant according to the first embodiment. FIG. 8 is a first schematic diagram showing the overall configuration of a plant according to a second embodiment. FIG. 9 is a second schematic diagram showing the overall configuration of a plant according to the second embodiment. FIG. 10 is a first flowchart showing an example of processing by the control device according to the second embodiment. FIG. 11 is a second flowchart showing an example of processing by the control device according to the second embodiment. FIG. 12 is a schematic diagram showing the overall configuration of a plant according to a third embodiment. FIG. 13 is a diagram illustrating fluctuations in plant demand and boiler load factor in the prior art.

[0015] First Embodiment Hereinafter, a first embodiment will be described in detail with reference to FIGS.

[0016] (Overall Configuration of Plant) FIG. 1 is a schematic diagram showing the overall configuration of a plant according to a first embodiment. As shown in FIG. 1, the plant 1 includes a boiler 3, a steam turbine system 4, an ammonia decomposition device 5, and a control device 10. The plant 1 of this embodiment is, for example, a cogeneration plant that generates steam for use in a production process at a facility and generates electricity for use at the facility and for sale to an external grid, to which the ammonia decomposition device 5 has been added to enable hydrogen production. A vaporizer or the like may be installed in the ammonia supply pipe L2 from the ammonia tank 51 to the ammonia decomposition device 5, but this is not shown in FIG. 1. Furthermore, although the hydrogen in the hydrogen tank 52 is in the form of gas or liquid, hydrogen liquefaction equipment is not shown in FIG. 1.

[0017] The boiler 3 generates steam to be used in the steam turbine system 4, the factory's production process, and the ammonia decomposition unit 5. The steam turbine system 4 includes a steam turbine 41 and a generator 42. The steam turbine 41 is driven by steam supplied from the boiler 3. The generator 42 is connected to the rotor of the steam turbine 41 and converts the power of the steam turbine 41 into electricity. The electricity generated by the generator 42 is used within the facility. In addition, surplus electricity may be sold (externally sold) to an external grid. The ammonia decomposition unit 5 decomposes ammonia (NH3) supplied from the ammonia tank 51 using the heat of the steam to produce hydrogen (H2). The hydrogen produced by the ammonia decomposition unit 5 is stored in a hydrogen tank 52. The hydrogen stored in the hydrogen tank 52 may be used as fuel for the boiler 3 or for the facility's production process, or may be sold externally to hydrogen consumers outside the facility.

[0018] A header pipe L1 that delivers steam generated by the boiler 3 is connected to the boiler 3. The header pipe L1 is provided with at least a pressure gauge P4 and a thermometer T4. Steam supply pipes L11, L12, and L13 that deliver steam to the steam turbine 41, the production process, and the ammonia decomposition unit 5, respectively, branch off from the header pipe L1. The steam supply pipe L11 is provided with at least a flow control valve V1, a flow meter F1, a pressure gauge P1, and a thermometer T1 that adjust the flow rate of steam supplied to the steam turbine 41. The steam supply pipe L12 is provided with at least a flow control valve V2 and a flow meter F2 that adjust the flow rate of steam supplied to the production process. The steam supply pipe L13 is provided with at least a flow control valve V3, a flow meter F3, a pressure gauge P3, and a thermometer T3 that adjust the flow rate of steam supplied to the ammonia decomposition unit 5. The ammonia tank 51 and the ammonia decomposition unit 5 are connected by an ammonia supply pipe L2. The ammonia supply pipe L2 is provided with at least a flow control valve V4 that adjusts the flow rate of ammonia supplied to the ammonia decomposition apparatus 5, and a flow meter F4. The measured values ​​of each sensor (flow meter, pressure gauge, thermometer) are sequentially transmitted to the control device 10. Note that, in this embodiment, an example in which a flow meter, pressure gauge, and thermometer are provided as sensors will be described, but measuring instruments that measure various other measured values, such as ammonia concentration and pump rotation speed, may also be provided. Furthermore, in order to measure the amount of hydrogen supplied, a flow meter may be installed in the hydrogen pipe between the ammonia decomposition apparatus 5 and the hydrogen tank 52 or in the hydrogen pipe from the hydrogen tank 52 to a consumer facility, or a level gauge may be provided in the hydrogen tank 52.

[0019] The control device 10 controls the amount of steam generated by the boiler 3 and the flow rate of steam supplied to each part based on a signal D1 indicating the power demand of the power demander, a signal D2 indicating the steam demand of the steam demander, and a signal D3 indicating the hydrogen demand of the hydrogen demander. At this time, the control device 10 adjusts the flow rate of steam supplied to each part so as to suppress a decrease in the load of the boiler 3 due to fluctuations in demand. The power demander includes at least one of the facility in which the plant 1 is installed and an external grid. The steam demander includes a production process in the facility in which the plant 1 is installed. The hydrogen demander includes at least one of the boiler 3 of the plant 1, the production process in the facility in which the plant 1 is installed, and hydrogen demanders outside the facility.

[0020] (Functional Configuration of Ammonia Decomposition Apparatus) Fig. 2 is a schematic process flow diagram of the ammonia decomposition apparatus according to Embodiment 1. As shown in Fig. 2, the ammonia decomposition apparatus 5 includes a decomposition reactor 53, an absorption tower 54, a regeneration tower 55, and a hydrogen purification unit 56.

[0021] The decomposition reactor 53 decomposes ammonia supplied from the ammonia tank 51 by a pump 501 into a cracked gas containing nitrogen and hydrogen through an endothermic reaction using steam supplied from the boiler 3 as a heat source (NH3 + 46 kJ → 3 / 2H2 + 1 / 2N2). The ammonia supplied from the ammonia tank 51 is liquid, and is vaporized in an evaporator 502, heated in a heat exchanger 503, and introduced into the decomposition reactor 53. A cracked gas pipe L21 is connected to the outlet of the decomposition reactor 53. The cracked gas delivered from the decomposition reactor 53 is cooled in the heat exchanger 503 and a condenser 504 and introduced into the absorption tower 54.

[0022] A cracked gas pipe L21 is connected to the bottom of the absorption tower 54, and cracked gas is introduced therein. A water pipe L22 is connected to the top of the absorption tower 54, and water (H2O) supplied from the water pipe L22 is sprayed into the inside of the absorption tower 54. In the absorption tower 54, residual ammonia in the cracked gas is dissolved in the sprayed water, thereby removing the residual ammonia from the cracked gas. The treated gas (H2, N2) from which the residual ammonia has been removed rises inside the absorption tower 54 and is sent to the hydrogen purification unit 56 through a treated gas pipe L23 connected to the top end of the absorption tower 54. The ammonia water in which the residual ammonia has been dissolved is stored in the bottom of the absorption tower 54 and sent to the regeneration tower 55 through an ammonia water pipe L24 connected to the bottom end of the absorption tower 54.

[0023] An ammonia water pipe L24 is connected to the top of the regeneration tower 55, and ammonia water containing dissolved residual ammonia is introduced therein. A circulation pipe L25 is provided to the regeneration tower 55. A reboiler 507 is provided in the circulation pipe L25, and the ammonia water extracted from the bottom of the regeneration tower 55 is heated to separate and distill the ammonia in the ammonia water as gaseous ammonia. The water in the ammonia water is stored in the bottom of the regeneration tower 55. A portion of the water stored in the regeneration tower 55 is sent to the absorption tower 54 via the water pipe L22 by a pump 505. At this time, a heat exchanger 506 exchanges heat between the water sent from the regeneration tower 55 and the ammonia water sent from the absorption tower 54, thereby cooling the water and heating the ammonia water. An ammonia recovery pipe L26 is connected to the top end of the regeneration tower 55, and a gas containing gaseous ammonia separated from the ammonia water is sent to the ammonia supply pipe L2 by a pump 509. A condenser 508 is provided in the ammonia recovery pipe L26, which cools the gas flowing through the ammonia recovery pipe L26 and returns the moisture in the gas to the regeneration tower 55.

[0024] The hydrogen purification unit 56 separates and purifies hydrogen from the treated gas delivered from the absorption tower 54. The hydrogen purification unit 56 has adsorption towers 561 and 562 each equipped with an adsorbent Ad. While FIG. 2 shows an example in which the hydrogen purification unit 56 has two adsorption towers 561 and 562, the number of adsorption towers may be changed as desired. The treated gas pipe L23 is connected to the inlets of the adsorption towers 561 and 562, and the hydrogen pipe L27 is connected to the outlets. The adsorbent Ad adsorbs or desorbs impurities other than hydrogen contained in the treated gas depending on changes in pressure. The adsorption towers 561 and 562 adsorb nitrogen in the treated gas using the adsorbent Ad and discharge hydrogen with a purity equal to or higher than a reference value (e.g., 99.9% or higher). If the treated gas contains ammonia, the adsorbent Ad also adsorbs the ammonia. The hydrogen discharged from the absorption tower 54 is stored in the hydrogen tank 52 via the hydrogen pipe L27. Furthermore, the remaining off-gas containing nitrogen, hydrogen and ammonia is discharged through the off-gas pipe L28.

[0025] (Functional Configuration of Control Device) Fig. 3 is a block diagram showing the functional configuration of the control device according to embodiment 1. As shown in Fig. 3, the control device 10 includes a processor 11, a memory 12, a storage 13, and a communication interface 14.

[0026] The processor 11 operates in accordance with a predetermined program to function as a signal receiving unit 111 and a control unit 112 .

[0027] The signal receiving unit 111 receives signals indicating measurement values ​​from each sensor (at least a flow meter, a pressure gauge, and a thermometer). The signal receiving unit 111 receives a signal D1 indicating the electricity demand of an electricity consumer, a signal D2 indicating the steam demand of a steam consumer, and a signal D3 indicating the hydrogen demand of a hydrogen consumer. The signal receiving unit 111 also receives a signal D4 indicating the amount of steam generated by the boiler 3, a signal D5 indicating the power generated by the generator 42, and a signal D6 indicating the amount of hydrogen produced by the ammonia decomposition device 5.

[0028] Based on the various signals received by the signal receiving unit 111, the control unit 112 adjusts at least one of the steam generation amount of the boiler 3, the flow rate of the steam supply pipe L11 of the steam turbine 41, the flow rate of the steam supply pipe L13 of the ammonia decomposition device 5, and the flow rate of the steam supply pipe L12 of the production process so as to suppress a decrease in the load of the boiler 3. At this time, the control unit 112 transmits a signal D4 that instructs the boiler 3 to generate steam, a signal D5 that instructs the steam turbine system 4 to generate power, a signal D6 that instructs the ammonia decomposition device 5 to generate hydrogen, and signals S1 to S4 that instruct the flow rate to each of the flow control valves V1 to V4, thereby adjusting the steam generation amount, steam supply amount, etc.

[0029] The memory 12 has a memory area necessary for the operation of the processor 11 .

[0030] The storage 13 is a so-called auxiliary storage device, such as a hard disk drive (HDD), a solid state drive (SSD), etc. The storage 13 stores data that each part of the processor 11 acquires, generates, and references during processing.

[0031] The communication interface 14 is an interface for transmitting and receiving signals including measurement values, commands, etc. between each unit.

[0032] (Processing Example 1 of the Control Device) Fig. 4 is a first flowchart showing an example of processing of the control device according to the first embodiment. Fig. 4 shows a processing example when the power demand of a power consumer increases. The signal receiving unit 111 receives a signal D1 indicating the power demand of the power consumer at each predetermined control period. When the signal receiving unit 111 receives the signal D1 indicating an increase in power demand (e.g., the power demand amount of the previous signal D1 < the power demand amount of the current signal D1) (step ST101), the control unit 112 determines whether the amount of steam generated by the boiler 3 can be increased (step ST102).

[0033] For example, if the load factor of boiler 3 has not reached the upper limit (100%) and the amount of steam generated can be increased (step ST102; YES), control unit 112 sends signal D4 to boiler 3 including an instruction to increase the amount of steam generated in accordance with the increase in power demand based on signal D1 (step ST103).

[0034] Furthermore, the control unit 112 transmits a signal S1 including a command to the flow rate control valve V1 of the steam supply pipe L11 to the steam turbine 41 to increase the amount of steam supplied to the steam turbine 41 in accordance with an increase in the amount of steam generated by the boiler 3 (step ST104). The flow rate control valve V1 increases its opening in accordance with the signal S1. This increases the amount of steam supplied to the steam turbine 41, and the amount of power generated by the generator 42 increases accordingly.

[0035] On the other hand, if the control unit 112 determines that it is not possible to increase the amount of steam generated by the boiler 3 (step ST102; NO), it determines whether it is possible to reduce the amount of steam supplied to the production process (step ST105). For example, the control unit 112 inquires of the production process, and when it receives a response that it is possible to reduce the amount of steam supplied to the production process, it determines that it is possible to reduce the amount of steam supplied to the production process (step ST105; YES). Furthermore, the control unit 112 may automatically determine whether it is possible to reduce the amount of steam supplied to the production process based on a steam usage plan for each time period of the production process that has been notified in advance.

[0036] If it is determined that the amount of steam supplied to the production process can be reduced (step ST105; YES), the control unit 112 transmits a signal D2 to the production process, including a command to reduce the amount of steam supplied in response to the increase in power demand based on the signal D1 (step ST106). The control unit 112 also transmits a signal S2 to the flow control valve V2 of the steam supply pipe L12, including a command to reduce the amount of steam supplied to the production process (step ST107). The flow control valve V2 reduces its opening in accordance with the signal S2.

[0037] Next, the control unit 112 monitors the measurement value of the flow meter F2, and if the flow rate through the steam supply pipe L12 (i.e., the amount of steam supplied to the production process) has not decreased to the supply rate commanded by signal S2 (step ST108; NO), the control unit 112 waits until the flow rate decreases. If the flow rate through the steam supply pipe L12 has decreased to the supply rate commanded by signal S2 (step ST108; YES), the control unit 112 transmits a signal S1 to the flow control valve V1, including a command to increase the amount of steam supplied to the steam turbine 41 by the amount of the decrease in the amount of steam supplied to the production process (step ST104). The flow control valve V1 increases its opening in accordance with signal S1. This increases the amount of steam supplied to the steam turbine 41, and the amount of power generated by the generator 42 increases accordingly.

[0038] On the other hand, if the control unit 112 determines that it is not possible to reduce the amount of steam supplied to the production process (step ST105; NO), it transmits a signal D6 to the ammonia decomposition device 5 including a command to reduce the amount of hydrogen produced in accordance with the increase in power demand based on the signal D1, and also transmits a signal D3 to hydrogen consumers notifying them of the reduction in the amount of hydrogen produced (step ST109).

[0039] The control unit 112 also transmits a signal S4 to the flow rate control valve V4 of the ammonia supply pipe L2, the signal S4 including a command to reduce the amount of ammonia supplied in response to the decrease in the amount of hydrogen produced (step ST110). The flow rate control valve V4 reduces its opening in accordance with the signal S4.

[0040] Next, the control unit 112 monitors the measurement value of the flow meter F4. If the flow rate through the ammonia supply pipe L2 (i.e., the ammonia supply amount) has not decreased to the supply amount commanded by the signal S4 (step ST111; NO), the control unit 112 waits until the flow rate decreases. If the flow rate through the ammonia supply pipe L2 has decreased to the supply amount commanded by the signal S4 (step ST111; YES), the control unit 112 transmits a signal S3 to the flow control valve V3, including a command to reduce the steam supply amount to the ammonia decomposer 5 by the amount of the decrease in the hydrogen production amount (step ST112). The flow control valve V3 reduces its aperture in accordance with the signal S3. If the temperature, flow rate, and pressure of ammonia and steam are not maintained in appropriate states, the success rate and production amount of hydrogen production will be affected. Therefore, by reducing the steam supply amount after the ammonia supply amount has decreased to the command value, it is possible to prevent the temperature and pressure of the ammonia decomposer 5 from being unable to be maintained in appropriate states due to a lack of steam. In other words, it is possible to prevent a decrease in the productivity and quality of hydrogen produced in the ammonia decomposer 5.

[0041] The control unit 112 monitors the measurement value of the flow meter F3, and if the flow rate through the steam supply pipe L13 (i.e., the amount of steam supplied to the ammonia decomposer 5) has not decreased to the supply rate commanded by signal S3 (step ST113; NO), the control unit 112 waits until the flow rate decreases. If the flow rate through the steam supply pipe L13 has decreased to the supply rate commanded by signal S3 (step ST113; YES), the control unit 112 transmits a signal S1 including a command to the flow control valve V1 to increase the amount of steam supplied to the steam turbine 41 by the amount of the decrease in the amount of steam supplied to the ammonia decomposer 5 (step ST104). The flow control valve V1 increases its opening in accordance with signal S1. This increases the amount of steam supplied to the steam turbine 41, and the amount of power generated by the generator 42 increases.

[0042] In this way, the control device 10 can increase the amount of steam supplied to the steam turbine 41 and increase the amount of power generation in response to an increase in power demand by increasing the amount of steam generated by the boiler 3 or adjusting (reducing) the amount of steam supplied to the production process or the ammonia decomposition device 5. Furthermore, as described above, the steam supplied to the production process is handed over to the steam turbine 41 only when it is possible to reduce the amount of steam supplied to the production process, so that an increase in power demand can be met while minimizing the impact on the production process. Furthermore, even if the amount of steam supplied to the ammonia decomposition device 5 is temporarily reduced, the hydrogen demand can be met using the hydrogen stored in the hydrogen tank 52. Therefore, an increase in power demand can be met while minimizing the impact on hydrogen consumers caused by adjusting the amount of steam supplied.

[0043] (Processing Example 2 of the Control Device) FIG. 5 is a second flowchart showing an example of processing of the control device according to the first embodiment. FIG. 5 shows a processing example when the power demand of a power consumer decreases. The signal receiving unit 111 receives a signal D1 indicating the power demand of the power consumer at each predetermined control period. When the signal receiving unit 111 receives the signal D1 indicating a decrease in power demand (e.g., the power demand amount of the previous signal D1 is greater than the power demand amount of the current signal D1) (step ST201), the control unit 112 transmits a signal S1 to the flow rate control valve V1, the signal S1 including a command to reduce the amount of steam supplied to the steam turbine 41 in response to the decrease in power demand (step ST202). The flow rate control valve V1 reduces its opening in accordance with the signal S1.

[0044] Next, the control unit 112 transmits a signal D6 to the ammonia decomposition device 5, which includes a command to increase the amount of hydrogen produced in response to the decrease in power demand based on the signal D1, and also transmits a signal D3 to hydrogen consumers notifying them of the increase in the amount of hydrogen produced (step ST203).

[0045] Furthermore, the control unit 112 transmits a signal S3 to the flow rate control valve V3, which includes a command to increase the amount of steam supplied to the ammonia decomposition device 5 in accordance with the increase in the amount of hydrogen produced (step ST204). The flow rate control valve V3 increases its opening in accordance with the signal S3.

[0046] Next, the control unit 112 monitors the measured values ​​of the thermometer T3 and the flow meter F3 and determines whether the temperature and flow rate (steam supply rate) of the steam supplied to the ammonia decomposition unit 5 satisfy the conditions (step ST205). The temperature condition is set based on the temperature at which the thermal decomposition efficiency of ammonia is equal to or greater than a predetermined value. For example, the temperature condition is considered to be satisfied when the steam temperature at the inlet of the ammonia decomposition unit 5 is equal to or greater than 300°C. Furthermore, the flow rate condition is considered to be satisfied when the flow rate in the steam supply pipe L13 increases to the steam supply rate commanded by signal S3. If at least one of the temperature and flow rate does not satisfy the condition (step ST205; NO), the control unit 112 waits until both conditions are satisfied.

[0047] On the other hand, if both the temperature and flow rate satisfy the conditions (step ST205; YES), the control unit 112 transmits a signal S4 to the flow rate control valve V4 of the ammonia supply pipe L2, including a command to increase the ammonia supply rate in accordance with the increase in the hydrogen production rate (step ST206). The flow rate control valve V4 increases its aperture in accordance with the signal S4. As described above, if the temperature, flow rate, and pressure of ammonia and steam are not maintained at appropriate levels, the success rate and production rate of hydrogen production will be affected. Therefore, by increasing the ammonia supply rate after the conditions for the steam used in ammonia decomposition are satisfied, the hydrogen production rate in the ammonia decomposition device 5 can be increased while suppressing a decrease in the ammonia thermal decomposition efficiency. In other words, the hydrogen production rate can be increased while suppressing a decrease in the productivity and quality of the hydrogen produced in the ammonia decomposition device 5.

[0048] In this way, by adjusting the amount of steam supplied to the ammonia decomposition device 5, the control device 10 can respond to fluctuations (decrease) in power demand without reducing the load factor of the boiler 3. In addition, excess hydrogen produced is stored in the hydrogen tank 52. As a result, even if, for example, power demand or steam demand is high and a sufficient amount of steam cannot be secured for the ammonia decomposition device 5, the hydrogen demand can be met with the hydrogen stored in the hydrogen tank 52.

[0049] 6 and 7 are diagrams illustrating fluctuations in demand and boiler load factors in a plant according to the first embodiment. FIGS. 6 and 7 show examples in which the amount of steam generated by the boiler 3 and the amount of steam supplied to each component are adjusted in accordance with daily demand fluctuations according to the processes shown in FIGS. 4 and 5 . FIGS. 6 and 7 also show examples in which the load factor of the boiler 3 is controlled to always be maintained at 100%. FIG. 6 also shows an example in which control is performed to prioritize power generation (external sales of electricity) when, for example, the price of electricity is high, while FIG. 7 shows an example in which control is performed to prioritize hydrogen generation (external sales of hydrogen) when, for example, the price of hydrogen is high.

[0050] 6, the control device 10 increases the steam supply amount c to the ammonia decomposition device 5 by the amount corresponding to the decrease in the steam supply amounts a and b to the steam turbine 41 and the production process, without reducing the load factor of the boiler 3, thereby utilizing the excess steam for hydrogen production. In this way, it is possible to suppress the decrease in the boiler load factor and boiler efficiency E due to fluctuations in demand, and to suppress a decrease in economic efficiency, compared to the prior art (FIG. 13).

[0051] 4 illustrates an example in which the amount of steam generated by the boiler 3 is increased and the amount of steam supplied to each component is adjusted in response to an increase in power demand, but the present invention is not limited to this. For example, when a signal D2 indicating an increase in steam demand in the production process is received in step ST101 of FIG. 4, the control unit 112 increases the amount of steam generated by the boiler 3 in steps ST102 and ST103, and transmits a signal S2 including a command to the flow control valve V2 to increase the amount of steam supplied in step ST104. If it is not possible to increase the amount of steam generated by the boiler 3 (step ST102; NO), the control unit 112 reduces the amount of steam supplied to the ammonia decomposition unit 5 in steps ST109 to ST113, and increases the amount of steam supplied to the production process accordingly.

[0052] Furthermore, when signal D3 indicating an increase in hydrogen demand is received in step ST101 of FIG. 4 , control unit 112 increases the amount of steam generated by boiler 3 in steps ST102 and ST103, and performs steps ST203 to ST206 of FIG. 5 instead of step ST104, thereby increasing the amount of ammonia and steam supplied to ammonia decomposer 5. If it is not possible to increase the amount of steam generated by boiler 3 (step ST102; NO), control unit 112 reduces the amount of steam supplied to the production process in steps ST105 to ST108, and increases the amount of steam supplied to ammonia decomposer 5 accordingly. Note that if it is not possible to reduce the amount of steam supplied to the production process (step ST105; NO), as in the example of FIG. 7 , the sale of hydrogen may be prioritized over the sale of generated electricity. In this case, the following processing is performed instead of steps ST109 to ST113. First, the control unit 112 transmits a signal D5 to the steam turbine 41, including a command to reduce the amount of power generated for external sale in response to an increase in hydrogen demand, and also transmits a signal D1 notifying the reduction in power for external sale. Next, the control unit 112 transmits a signal S1 to the flow control valve V1, including a command to reduce the amount of steam supplied to the steam turbine 41. After the flow rate in the steam supply pipe L11 is reduced, the control unit 112 performs the processing of steps ST203 to ST206 in FIG. 5 to increase the amount of ammonia supplied and the amount of steam supplied to the ammonia decomposition unit 5. In this manner, for example, if hydrogen can be sold at a higher price than electricity, the amount of power generated for external sale can be reduced and the amount of hydrogen produced can be increased accordingly, thereby increasing the profits of the plant 1 while economically operating the boiler 3.

[0053] Similarly, although an example in which the amount of steam supplied to the ammonia decomposition device 5 is adjusted (increased) in response to a decrease in power demand to increase the amount of hydrogen produced has been described in Fig. 5 , the present invention is not limited to this. For example, when a signal D2 indicating a decrease in steam demand in the production process is received in step ST201 of Fig. 5 , the control unit 112 transmits a signal S2 including a command to the flow rate adjustment valve V2 to decrease the amount of steam supplied to the production process in step ST202, and then executes steps ST203 to ST206 to increase the amount of hydrogen produced.

[0054] Even when the sale of hydrogen is prioritized over the sale of generated power as shown in FIG. 7 , there are cases where the amount of hydrogen produced (hydrogen demand) must be reduced, for example, when the free capacity of the hydrogen tank 52 is insufficient. In this case, in step ST201 of FIG. 5 , a signal D3 indicating a decrease in hydrogen demand is received. The control unit 112 then executes steps ST109 to ST113 of FIG. 4 instead of step ST202 to reduce the amount of ammonia supplied and the amount of steam supplied to the ammonia decomposer 5. Thereafter, the amount of steam supplied to the steam turbine 41 is increased to increase the amount of power sold by the amount corresponding to the decrease in the amount of steam supplied to the ammonia decomposer 5. Specifically, instead of steps ST203 to ST206, the control unit 112 performs the following processing. First, the control unit 112 transmits a signal D5 to the steam turbine 41, which includes a command to increase the amount of power sold in response to the decrease in hydrogen demand, and also transmits a signal D1 notifying the increase in power sold. Next, the control unit 112 transmits a signal S1 including a command to the flow rate control valve V1 to increase the amount of steam supplied to the steam turbine 41. In this way, when it is necessary to reduce the amount of hydrogen produced, the amount of power generated for external sales can be increased accordingly, thereby enabling economical operation without reducing the load on the boiler 3 and preventing a decline in the profits of the plant 1.

[0055] (Operation and Effect) As described above, the plant 1 according to this embodiment includes the boiler 3 that generates steam, the steam turbine 41 that is rotationally driven by the steam, the generator 42 that converts the rotational power of the steam turbine 41 into electric power, the ammonia decomposer 5 that decomposes ammonia using the heat of the steam to produce hydrogen, steam supply pipes L11, L12, and L13 that supply steam to the steam turbine 41, the ammonia decomposer 5, and the production process that uses the steam for production, and the control device 10. The control device 10 includes a signal receiving unit 111 that receives a signal including at least one of an electric power demand, a hydrogen demand, and a steam demand of the production process, and a control unit 112 that adjusts, based on the received signal, at least one of the amount of steam generated by the boiler, the flow rate through the steam supply pipe L11 of the steam turbine 41, the flow rate through the steam supply pipe L13 of the ammonia decomposer 5, and the flow rate through the steam supply pipe L12 of the production process so as to suppress a decrease in the boiler load.

[0056] In this way, the plant 1 can produce hydrogen in addition to the generated electricity and steam used in the production process. By using carbon-neutral or carbon-free fuels such as biomass or ammonia as fuel for the boiler 3, the generated hydrogen can be sold externally as green hydrogen.

[0057] Furthermore, the control device 10 can appropriately adjust the amount of steam supplied to the steam turbine 41, the ammonia decomposition device 5, and the production process in accordance with demand fluctuations while suppressing a decrease in the load factor of the boiler 3 due to demand fluctuations. In other words, it is possible to suppress a decrease in the boiler load factor and boiler efficiency due to demand fluctuations, and to suppress a decrease in the economic efficiency of the plant 1.

[0058] In addition, when the control unit 112 receives a signal indicating an increase in electricity demand, hydrogen demand, or steam demand, it determines whether it is possible to increase the amount of steam generated by the boiler 3, and if it is possible to increase the amount of steam generated, it instructs the boiler 3 to increase the amount of steam generated in accordance with the increase in electricity demand, hydrogen demand, or steam demand.

[0059] In this way, when, for example, electricity demand increases, the control device 10 can increase the amount of steam generated by the boiler 3, thereby increasing the amount of steam supplied to the steam turbine 41, and increasing the amount of power generation, while suppressing the impact (reduction in the amount of steam supplied) on other ammonia decomposition devices 5 and the production process. Similarly, when hydrogen demand or steam demand increases, it becomes possible to respond to the increase in hydrogen demand or steam demand without affecting other consumers.

[0060] Furthermore, when the control unit 112 receives a signal indicating an increase in electricity demand or hydrogen demand and it is not possible to increase the amount of steam generated by the boiler 3, it determines whether it is possible to reduce the amount of steam supplied to the production process, and if it is possible to reduce the amount of steam supplied to the production process, it reduces the flow rate of the steam supply pipe L12 of the production process in accordance with the increase in electricity demand or hydrogen demand, and increases the flow rate of the steam supply pipe L11 of the steam turbine 41 or the steam supply pipe L13 of the ammonia decomposition unit 5.

[0061] In this way, if the steam generation rate of the boiler 3 cannot be increased, the control device 10 can respond to increases in electricity demand and hydrogen demand by transferring the steam supply rate to the production process to the steam turbine 41 or the ammonia cracker 5. Although the steam and electricity used in the production process fluctuate over time, the time and amount of fluctuation are generally consistent and less variable than the electricity and hydrogen sold. This makes it easier to develop a control plan for boiler steam allocation. For example, solar power generation, for example, fluctuates depending on the weather on that day. Therefore, when electricity demand is high and the power generated by solar power generation, for example, is low, the power sold from the plant 1 (power generated by the generator 42) can contribute to grid power stability as backup power. Similarly, sudden increases in hydrogen demand can also be accommodated. If demand for both electricity and hydrogen increases, steam allocation may be adjusted to prioritize either power generation or hydrogen production depending on the prices of electricity and hydrogen.

[0062] Furthermore, when the control unit 112 receives a signal D1 indicating an increase in power demand and it is not possible to reduce the amount of steam supplied to the production process, it reduces the amount of ammonia supplied to the ammonia decomposition unit 5 in accordance with the increase in power demand, and after the amount of ammonia supplied has decreased, it reduces the flow rate of the steam supply pipe L13 of the ammonia decomposition unit 5 in accordance with the increase in power demand, and increases the flow rate of the steam supply pipe L11 of the steam turbine 41.

[0063] In this way, the control device 10 can respond to an increase in power demand by increasing the amount of steam supplied to the steam turbine 41 by the amount corresponding to the decrease in the amount of steam supplied to the ammonia decomposer 5. Furthermore, by reducing the amount of ammonia supplied to the ammonia decomposer 5 and then reducing the amount of steam supplied, it is possible to suppress a decrease in the efficiency of thermal decomposition of ammonia due to insufficient steam flow rate, temperature, or pressure, and a decrease in the quality and productivity of hydrogen. Note that by storing hydrogen generated when demand for power or steam is low in the hydrogen tank 52, the impact of such a decrease in the amount of hydrogen produced (shortage of hydrogen supply) can be suppressed.

[0064] Furthermore, when the control unit 112 receives a signal D1 indicating a decrease in power demand, it reduces the flow rate of the steam supply pipe L11 of the steam turbine 41 in accordance with the decrease in power demand, increases the flow rate of the steam supply pipe L13 of the ammonia decomposition device 5, and increases the amount of ammonia supplied to the ammonia decomposition device 5 after the flow rate and temperature of the steam supplied to the ammonia decomposition device 5 satisfy predetermined conditions.

[0065] In this way, the control device 10 can respond to a decrease in power demand without reducing the load on the boiler 3, and can effectively utilize the surplus steam for hydrogen production. Furthermore, by increasing the ammonia supply amount after the flow rate and temperature of the steam supplied to the ammonia decomposition device 5 satisfy predetermined conditions, it is possible to prevent a decrease in the efficiency of ammonia thermal decomposition due to insufficient flow rate, temperature, or pressure of the steam, and a decrease in the quality and productivity of hydrogen.

[0066] Second Embodiment Next, a second embodiment will be described in detail with reference to Figures 8 to 11. Components common to the above-described embodiment will be assigned the same reference numerals and detailed description thereof will be omitted.

[0067] FIG. 8 is a first schematic diagram showing the overall configuration of a plant according to a second embodiment. For example, as shown in FIG. 8 , the ammonia decomposition unit 5 may use steam extracted or exhausted from a steam turbine 41, instead of steam generated by a boiler 3. In the example of FIG. 8 , a pipe L3, through which exhaust steam from the steam turbine 41 flows, is connected to the outlet of the steam turbine 41. A steam supply pipe L13, which supplies steam to the ammonia decomposition unit 5, branches off from the pipe L3. Note that the pipe L3 may be connected to an intermediate stage of the steam turbine 41 and may pass steam extracted from the steam turbine 41. The steam supply pipe L12, which supplies steam to the production process, may branch off from the main pipe L1 as in the example of FIG. 1 or from the pipe L3 as in the example of FIG. 8 . Note that if the temperature of the exhaust steam (or extracted steam) from the steam turbine 41 is too high, a temperature reducing spray 43 may be provided on the pipe L3, as in the example of FIG. 8 . Although not shown in FIGS. 1 and 8 , the main pipe L1 may be provided with a temperature reducing spray 43 if necessary.

[0068] Fig. 9 is a second schematic diagram showing the overall configuration of a plant according to the second embodiment. As shown in Fig. 9, the steam supply pipe L13 to the ammonia decomposition apparatus 5 may branch off from the steam supply pipe L12 to the production process.

[0069] 8 and 9, a return pipe L29 may be added to return the steam used in the ammonia decomposition apparatus 5 to the upstream side. For example, as shown in Fig. 8, the return pipe L29 is connected upstream of the steam supply pipe L12 to the production process, and returns the steam used in the ammonia decomposition apparatus 5 to the gas supply system of the production process. Alternatively, as shown in Fig. 9, the return pipe L29 may be connected to the main pipe L1. Although not shown, the return pipe L29 may be connected upstream of the steam supply pipe L11 to the steam turbine 41, and return the steam used in the ammonia decomposition apparatus 5 to the gas supply system of the steam turbine 41.

[0070] In addition, in a configuration in which exhaust steam from the outlet of the steam turbine 41 (or extracted steam from the intermediate stage) is supplied to the production process and the ammonia decomposition unit 5 as shown in FIG. 8 , the control device 10 adjusts the amount of steam supplied to the ammonia decomposition unit 5 in accordance with the steam demand.

[0071] FIG. 10 is a first flowchart showing an example of the processing of the control device according to the second embodiment. For example, when the signal receiving unit 111 receives a signal D2 indicating an increase in steam demand in the production process (step ST301), the control unit 112 reduces the ammonia supply amount and the steam supply amount to the ammonia decomposition unit 5 (steps ST302 to ST306) and executes a process of increasing the steam supply amount to the production process accordingly (step ST307). The processing of steps ST302 to ST306 in FIG. 10 is the same as the processing of steps ST109 to ST113 in FIG. 4. In this way, the steam supply amount to the ammonia decomposition unit 5 can be adjusted to accommodate the increase in steam demand in the production process while maintaining the load factor of the boiler 3 constant.

[0072] 11 is a second flowchart showing an example of the processing of the control device according to the second embodiment. For example, when the signal receiving unit 111 receives a signal D2 indicating a decrease in steam demand in the production process (step ST401), the control unit 112 reduces the amount of steam supplied to the production process (step ST402) and executes processing to increase the amount of steam supplied to the ammonia decomposer 5 by that amount (steps ST403 to ST406). The processing of steps ST403 to ST406 in FIG. 11 is the same as the processing of steps ST203 to ST206 in FIG. 5. In this way, the amount of steam supplied to the ammonia decomposer 5 can be adjusted to respond to the decrease in steam demand in the production process while maintaining the load factor of the boiler 3 constant.

[0073] As described above, the configuration of the steam supply pipes L11 to L13 may be changed as desired. This allows efficient reuse of the thermal energy of the steam generated in the boiler 3 and the steam exhausted (bleed) from the steam turbine 41, thereby improving the economic efficiency of the plant 1. A temperature-reducing spray 43 for lowering the steam temperature may be provided upstream of the steam supply pipe L12 for the production process. Furthermore, a return pipe L29 may be provided to return the steam used in the ammonia decomposition unit 5 to the mother pipe L1, the steam supply pipe L11 to the steam turbine 41, or the steam supply pipe L12 to the production process. This allows efficient reuse of the steam used in the ammonia decomposition unit 5, thereby improving the economic efficiency of the plant 1.

[0074] Third Embodiment Next, the second embodiment will be described in detail with reference to Fig. 12. Components common to the above-described embodiments are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0075] Fig. 12 is a schematic diagram showing the overall configuration of a plant according to the third embodiment. As shown in Fig. 12, the off-gas pipe L28 of the ammonia decomposition apparatus 5 is connected to the boiler 3. The off-gas contains hydrogen. That is, in this embodiment, the off-gas of the ammonia decomposition apparatus 5 is reused as fuel for the boiler 3.

[0076] In this way, by reusing the off-gas from the ammonia decomposition device 5, it is possible to improve the thermal efficiency of the boiler 3. Furthermore, it is possible to use the resource (ammonia) input into the ammonia decomposition device 5 without waste.

[0077] <Other Embodiments> Although one embodiment has been described in detail above with reference to the drawings, the specific configuration is not limited to the above, and various design modifications are possible. That is, in other embodiments, the order of the above-described processes may be changed as appropriate. Furthermore, some processes may be executed in parallel.

[0078] <Additional Notes> The above-described embodiment can be understood, for example, as follows.

[0079] (1) According to a first aspect, the control device 10 of the plant 1 includes a boiler 3 that generates steam, a steam turbine 41 that is rotationally driven by the steam, a generator 42 that converts the rotational power of the steam turbine 41 into electric power, an ammonia decomposer 5 that decomposes ammonia using the heat of the steam to produce hydrogen, and steam supply pipes L11, L12, and L13 that supply steam to the steam turbine 41, the ammonia decomposer 5, and a production process that uses the steam for production, respectively. The control device 10 includes: a signal receiving unit 111 that receives a signal including at least one of an electric power demand for electric power generated by the generator 42, a hydrogen demand for hydrogen produced by the ammonia decomposer 5, and a steam demand for the production process; and a control unit 112 that adjusts, based on the received signal, at least one of the amount of steam generated by the boiler 3, the flow rate of the steam supply pipe L11 of the steam turbine 41, the flow rate of the steam supply pipe L13 of the ammonia decomposer 5, and the flow rate of the steam supply pipe L12 of the production process so as to suppress a decrease in the load of the boiler 3.

[0080] In this way, the control device 10 can appropriately adjust the amount of steam supplied to the steam turbine 41, the ammonia decomposition device 5, and the production process in accordance with the demand fluctuation, while suppressing a decrease in the load on the boiler 3 due to a demand fluctuation. In other words, it is possible to suppress a decrease in the boiler load and boiler efficiency due to a demand fluctuation, and to suppress a decrease in the economic efficiency of the plant 1.

[0081] (2) According to the second aspect, in the control device 10 of the plant 1 relating to the first aspect, when the control unit 112 receives a signal indicating an increase in electricity demand, hydrogen demand, or steam demand, it determines whether it is possible to increase the amount of steam generated by the boiler 3, and if it is possible to increase the amount of steam generated, it instructs the boiler 3 to increase the amount of steam generated in accordance with the increase in electricity demand, hydrogen demand, or steam demand.

[0082] In this way, when, for example, electricity demand increases, the control device 10 can increase the amount of steam generated by the boiler 3, thereby increasing the amount of steam supplied to the steam turbine 41, and increasing the amount of power generation, while suppressing the impact (reduction in the amount of steam supplied) on other ammonia decomposition devices 5 and the production process. Similarly, when hydrogen demand or steam demand increases, it becomes possible to respond to the increase in hydrogen demand or steam demand without affecting other consumers.

[0083] (3) According to the third aspect, in the control device 10 of the plant 1 related to the second aspect, when the control unit 112 receives a signal indicating an increase in electricity demand or hydrogen demand and when it is not possible to increase the amount of steam generated by the boiler 3, it determines whether it is possible to reduce the amount of steam supplied to the production process, and if it is possible to reduce the amount of steam supplied to the production process, it reduces the flow rate of the steam supply pipe L12 of the production process in accordance with the increase in electricity demand or hydrogen demand, and increases the flow rate of the steam supply pipe L11 of the steam turbine 41 or the steam supply pipe L13 of the ammonia decomposition unit 5.

[0084] In this way, when the amount of steam generated by the boiler 3 cannot be increased, the control device 10 transfers the amount of steam supplied to the production process to the steam turbine 41 or the ammonia decomposition device 5, thereby enabling it to respond to increases in electricity demand and hydrogen demand.

[0085] (4) According to the fourth aspect, in the control device 10 of the plant 1 related to the third aspect, when the control unit 112 receives the signal D1 indicating an increase in power demand and it is not possible to reduce the amount of steam supplied to the production process, the control unit 112 reduces the amount of ammonia supplied to the ammonia decomposer 5 in accordance with the increase in power demand, and after the amount of ammonia supplied has decreased, the control unit 112 reduces the flow rate of the steam supply pipe L13 of the ammonia decomposer 5 in accordance with the increase in power demand, thereby increasing the flow rate of the steam supply pipe L11 of the steam turbine 41.

[0086] In this way, the control device 10 can respond to an increase in power demand by increasing the amount of steam supplied to the steam turbine 41 by an amount corresponding to the reduction in the amount of steam supplied to the ammonia decomposition device 5. Furthermore, by reducing the amount of ammonia supplied to the ammonia decomposition device 5 and then reducing the amount of steam supplied, it is possible to suppress a decrease in the efficiency of thermal decomposition of ammonia due to insufficient steam flow rate, temperature, or pressure, and a decrease in hydrogen quality and productivity.

[0087] (5) According to the fifth aspect, in the control device 10 of the plant 1 according to any one of the first to fourth aspects, when the control unit 112 receives a signal D1 indicating a decrease in power demand, the control unit 112 reduces the flow rate of the steam supply pipe L11 of the steam turbine 41 in accordance with the decrease in power demand, increases the flow rate of the steam supply pipe L13 of the ammonia decomposer 5, and increases the amount of ammonia supplied to the ammonia decomposer 5 after the flow rate and temperature of the steam supplied to the ammonia decomposer 5 satisfy predetermined conditions.

[0088] In this way, the control device 10 can respond to a decrease in power demand without reducing the load on the boiler 3, and can effectively utilize the surplus steam for hydrogen production. Furthermore, by increasing the ammonia supply amount after the flow rate and temperature of the steam supplied to the ammonia decomposition device 5 satisfy predetermined conditions, it is possible to prevent a decrease in the efficiency of ammonia thermal decomposition due to insufficient flow rate, temperature, or pressure of the steam, and a decrease in the quality and productivity of hydrogen.

[0089] (6) According to a sixth aspect, the plant 1 includes a boiler 3 that generates steam, a steam turbine 41 that is rotationally driven by the steam, a generator 42 that converts the rotational power of the steam turbine 41 into electric power, an ammonia decomposition device 5 that decomposes ammonia using the heat of the steam to produce hydrogen, steam supply pipes L11, L12, and L13 that supply steam to each of the steam turbine 41, the ammonia decomposition device 5, and a production process that utilizes steam for production, and a control device 10 related to any one of the first to fifth aspects.

[0090] In this way, the plant 1 can produce hydrogen in addition to the generated power and steam used in the production process. Furthermore, the plant 1 can appropriately adjust the amount of steam supplied to the steam turbine 41, the ammonia decomposition unit 5, and the production process in accordance with demand fluctuations, while suppressing a decrease in the load on the boiler 3 due to demand fluctuations. In other words, it is possible to suppress a decrease in the boiler load and boiler efficiency due to demand fluctuations, and to suppress a decrease in the economic efficiency of the plant 1.

[0091] (7) According to a seventh aspect, the plant 1 according to the sixth aspect further includes an off-gas pipe L28 that connects the boiler 3 and the ammonia decomposer 5 and circulates off-gas discharged after hydrogen is produced in the ammonia decomposer 5 as fuel for the boiler 3.

[0092] In the plant 1, by reusing the off-gas from the ammonia decomposition unit 5 in this manner, the thermal efficiency of the boiler 3 can be improved. In addition, the resource (ammonia) input to the ammonia decomposition unit 5 can be used without waste.

[0093] (8) According to an eighth aspect, the plant 1 according to the sixth or seventh aspect further includes a return pipe L29 that returns the steam used in the ammonia decomposition unit 5 to the steam supply pipe L11 that supplies steam to the steam turbine 41, the steam supply pipe L12 that supplies steam to the production process, or the mother pipe L1 that delivers steam from the boiler 3 to the steam supply pipes L11, L12, and L13.

[0094] In this way, the steam used in the ammonia decomposition unit 5 can be efficiently reused, and the economic efficiency of the plant 1 can be improved.

[0095] (9) According to a ninth aspect, the plant 1 according to any one of the sixth to eighth aspects further includes a pipe L3 that extracts steam from an intermediate stage of the steam turbine 41 or exhausts steam from an outlet of the steam turbine 41, and a steam supply pipe L13 of the ammonia decomposition unit 5 branches off from the pipe L3 and supplies the steam extracted or exhausted from the steam turbine 41 to the ammonia decomposition unit 5.

[0096] In this way, the thermal energy of the steam extracted or exhausted from the steam turbine 41 can be efficiently reused in the ammonia decomposition unit 5, thereby improving the economic efficiency of the plant 1.

[0097] (10) According to a tenth aspect, a control method for a plant 1 includes a boiler 3 that generates steam, a steam turbine 41 that is rotationally driven by the steam, a generator 42 that converts the rotational power of the steam turbine 41 into electric power, an ammonia decomposer 5 that decomposes ammonia using the heat of the steam to produce hydrogen, and steam supply pipes L11, L12, and L13 that supply steam to the steam turbine 41, the ammonia decomposer 5, and a production process that utilizes the steam for production, the control method comprising the steps of: receiving a signal including at least one of an electric power demand for electric power generated by the generator 42, a hydrogen demand for hydrogen generated by the ammonia decomposer 5, and a steam demand for the production process; and adjusting, based on the received signal, at least one of an amount of steam generated by the boiler 3, a flow rate through the steam supply pipe L11 of the steam turbine 41, a flow rate through the steam supply pipe L13 of the ammonia decomposer 5, and a flow rate through the steam supply pipe L12 of the production process so as to suppress a decrease in the load on the boiler 3.

[0098] (11) According to an eleventh aspect, the program causes a control device 10 of a plant 1 including a boiler 3 that generates steam, a steam turbine 41 that is rotationally driven by the steam, a generator 42 that converts the rotational power of the steam turbine 41 into electric power, an ammonia decomposer 5 that decomposes ammonia with the heat of the steam to produce hydrogen, and steam supply pipes L11, L12, and L13 that supply steam to the steam turbine 41, the ammonia decomposer 5, and a production process that uses the steam for production, to receive a signal including at least one of an electric power demand for electric power generated by the generator 42, a hydrogen demand for hydrogen produced by the ammonia decomposer 5, and a steam demand for the production process; and a step of adjusting, based on the received signal, at least one of an amount of steam generated by the boiler, a flow rate through the steam supply pipe L11 of the steam turbine 41, a flow rate through the steam supply pipe L13 of the ammonia decomposer 5, and a flow rate through the steam supply pipe L12 of the production process so as to suppress a decrease in the load on the boiler 3.

[0099] According to the above aspect, the boiler steam can be used for hydrogen generation in addition to the production process and power generation, and the plant can be operated efficiently by suppressing a decrease in the boiler load due to fluctuations in demand.

[0100] REFERENCE SIGNS LIST 1 Plant 3 Boiler 4 Steam turbine system 41 Steam turbine 42 Generator 43 Reduced temperature spray 5 Ammonia decomposition device 51 Ammonia tank 52 Hydrogen tank 53 Decomposition reactor 54 Absorption tower 55 Regeneration tower 56 Hydrogen purification unit 10 Control device 11 Processor 111 Signal receiving unit 112 Control unit 12 Memory 13 Storage 14 Communication interface L1 Main pipe L11, L12, L13 Steam supply piping L2 Ammonia supply piping L28 Off-gas piping L29 Return piping

Claims

1. A plant control device comprising: a boiler that generates steam; a steam turbine that is rotationally driven by the steam; a generator that converts the rotational power of the steam turbine into electricity; an ammonia decomposition device that decomposes ammonia using the heat of the steam to produce hydrogen; and steam supply piping that supplies the steam to the steam turbine, the ammonia decomposition device, and a production process that utilizes the steam for production, the plant control device comprising: a signal receiving unit that receives a signal including at least one of electricity demand, hydrogen demand, and steam demand of the production process; and a control unit that adjusts at least one of the amount of steam generated by the boiler, the flow rate of the steam supply piping of the steam turbine, the flow rate of the steam supply piping of the ammonia decomposition device, and the flow rate of the steam supply piping of the production process, based on the received signal, so as to suppress a decrease in the load of the boiler.

2. A plant control device as described in claim 1, wherein the control unit, when receiving a signal indicating an increase in electricity demand, hydrogen demand, or steam demand, determines whether it is possible to increase the amount of steam generated by the boiler, and if it is possible to increase the amount of steam generated, commands the boiler to increase the amount of steam generated in accordance with the increase in electricity demand, hydrogen demand, or steam demand.

3. The plant control device according to claim 2, wherein the control unit receives a signal indicating an increase in electricity demand or hydrogen demand and, when it is not possible to increase the amount of steam generated by the boiler, determines whether it is possible to reduce the amount of steam supplied to the production process, and, when it is possible to reduce the amount of steam supplied to the production process, reduces the flow rate in the steam supply piping of the production process in accordance with the increase in electricity demand or hydrogen demand, and increases the flow rate in the steam supply piping of the steam turbine or the steam supply piping of the ammonia decomposition unit.

4. The plant control device according to claim 3, wherein the control unit, when receiving a signal indicating an increase in electricity demand and when it is not possible to reduce the amount of steam supplied to the production process, reduces the amount of ammonia supplied to the ammonia decomposition unit in accordance with the increase in electricity demand, and after the amount of ammonia supplied has decreased, reduces the flow rate in the steam supply piping of the ammonia decomposition unit in accordance with the increase in electricity demand, and increases the flow rate in the steam supply piping of the steam turbine.

5. The plant control device according to claim 1, wherein, when the control unit receives a signal indicating a decrease in power demand, the control unit reduces the flow rate of the steam supply pipe of the steam turbine in accordance with the decrease in power demand, and increases the flow rate of the steam supply pipe of the ammonia decomposition device, and increases the amount of ammonia supplied to the ammonia decomposition device after the flow rate and temperature of the steam supplied to the ammonia decomposition device satisfy predetermined conditions.

6. A plant comprising: a boiler that generates steam; a steam turbine that is rotationally driven by the steam; a generator that converts the rotational power of the steam turbine into electricity; an ammonia decomposition device that decomposes ammonia using the heat of the steam to produce hydrogen; steam supply piping that supplies the steam to the steam turbine, the ammonia decomposition device, and a production process that utilizes the steam for production; and a control device according to any one of claims 1 to 5.

7. The plant according to claim 6, further comprising an off-gas pipe connecting the boiler and the ammonia decomposition unit, through which off-gas discharged after hydrogen is produced in the ammonia decomposition unit flows as fuel for the boiler.

8. The plant according to claim 6, further comprising a return pipe for returning the steam used in the ammonia decomposition unit to the steam supply pipe for supplying steam to the steam turbine, the steam supply pipe for supplying steam to the production process, or a mother pipe for sending the steam from the boiler to the steam supply pipe.

9. The plant according to claim 6, further comprising a pipe for extracting the steam from an intermediate stage of the steam turbine or for exhausting the steam from an outlet of the steam turbine, wherein the steam supply pipe for the ammonia decomposer branches off from the pipe and supplies the steam extracted or exhausted from the steam turbine to the ammonia decomposer.

10. A method for controlling a plant comprising: a boiler that generates steam; a steam turbine that is rotationally driven by the steam; a generator that converts the rotational power of the steam turbine into electricity; an ammonia decomposition unit that decomposes ammonia using the heat of the steam to produce hydrogen; and steam supply piping that supplies the steam to the steam turbine, the ammonia decomposition unit, and a production process that utilizes the steam for production, the method comprising the steps of: receiving a signal including at least one of an electricity demand, a hydrogen demand, and a steam demand of the production process; and adjusting, based on the received signal, at least one of the amount of steam generated by the boiler, the flow rate of the steam supply piping of the steam turbine, the flow rate of the steam supply piping of the ammonia decomposition unit, and the flow rate of the steam supply piping of the production process so as to suppress a decrease in the load of the boiler.

11. A program causing a control device of a plant including: a boiler that generates steam; a steam turbine that is rotationally driven by the steam; a generator that converts the rotational power of the steam turbine into electricity; an ammonia decomposition device that decomposes ammonia using the heat of the steam to produce hydrogen; and steam supply piping that supplies the steam to the steam turbine, the ammonia decomposition device, and a production process that uses the steam for production, to execute the steps of receiving a signal including at least one of electricity demand, hydrogen demand, and steam demand of the production process; and adjusting, based on the received signal, at least one of the amount of steam generated by the boiler, the flow rate of the steam supply piping of the steam turbine, the flow rate of the steam supply piping of the ammonia decomposition device, and the flow rate of the steam supply piping of the production process so as to suppress a decrease in the load of the boiler.

Images