Boiler

Abstract

To provide a boiler that can be controlled to continuously respond to a request load of a load apparatus, can suppress generation of ammonia unburned matters for stable combustion and enables mixed combustion of oil fuel and ammonia.SOLUTION: An ammonia mixed combustion boiler device 1 as a boiler includes: a burner 10 to which oil fuel F1 and ammonia fuel F2 are supplied; a can body 30 that recovers heat from combustion gas obtained by burning fuel jetting out from the burner 10; and a control section 70. The control section 70 includes a combustion control section 71 that enables combustion of the oil fuel F1 at a plurality of staged combustion positions and that enables combustion of the ammonia fuel F2 by continuously changing a combustion amount of the ammonia fuel F2 in a predetermined range.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a boiler.

Background Art

[0002] By replacing part of hydrocarbon fuels such as natural gas and oil fuel used as fuel for burners with ammonia that does not generate carbon dioxide, reduction of carbon dioxide emissions is expected (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Ammonia is known to be a fuel with low flammability, such as having a very slow combustion rate and a narrow flame retention range compared to other hydrocarbon fuels such as methane, which is the main component of city gas. Therefore, in a boiler that recovers heat from combustion gas to a heated medium, the combustion gas is quickly cooled in the heat exchanger, and unburned substances of ammonia are likely to occur due to changes in combustion conditions such as the combustion amount and air ratio.

[0005] Also, in industrial boilers that supply heat to demand sites in food factories, chemical plants, etc., in order to supply a heat amount corresponding to the load (demand), control is performed to increase or decrease the combustion amount. For example, in the case of a steam boiler capable of controlling the combustion amount at four combustion positions: combustion stop, low combustion position, medium combustion position, and high combustion position, when the steam pressure drops below a predetermined pressure during combustion at the low combustion position, the combustion amount is increased from the low combustion position to the medium combustion position. In such a transitional period, the combustion state becomes unstable and the generation of unburned substances increases.

[0006] In an ammonia co-firing boiler that controls the combustion amount of oil fuel stepwise, the problem is that the generation of unburned ammonia increases due to combustion instability when increasing or decreasing the combustion amount of oil fuel stepwise. Therefore, there is a need for a boiler that can quickly and flexibly supply heat in response to fluctuations in the required load, and can stably burn ammonia to suppress the generation of unburned substances.

[0007] An object of the present invention is to provide a boiler that co-fires oil fuel and ammonia, which can control the heat supply by ammonia combustion to continuously correspond to the required load of a load device, suppress the generation of unburned ammonia, and enable stable combustion.

Means for Solving the Problems

[0008] The present invention includes a burner to which oil fuel and ammonia fuel are supplied, a can body that recovers heat from combustion gas generated by burning the fuel ejected from the burner, a control unit, an oil fuel supply line that supplies the oil fuel to the burner, an ammonia supply line that supplies the ammonia fuel to the burner, a combustion air supply line that supplies combustion air to the burner, and an exhaust gas line connected to the can body through which combustion gas generated by burning the oil fuel and the ammonia fuel in the can body flows. The control unit includes a combustion control unit that enables combustion of the oil fuel at a plurality of stepwise combustion positions and enables combustion of the ammonia fuel by continuously changing the combustion amount of the ammonia fuel within a predetermined range. The present invention relates to a boiler.

[0009] Further, it is preferable that the combustion control unit changes the combustion position of the oil fuel after stopping the supply of the ammonia fuel.

[0010] Further, it is preferable that the combustion control unit changes the combustion position of the oil fuel after stopping the supply of the ammonia fuel when the total combustion amount of the oil fuel and the ammonia fuel reaches a combustion amount corresponding to a combustion rate set according to the combustion position.

[0011] Further, when the total combustion amount reaches the combustion amount corresponding to the combustion rate set according to the combustion position due to the increase in the combustion amount of the ammonia fuel, the combustion control unit preferably changes the combustion position of the oil fuel to a combustion position one stage higher.

[0012] Further, the upper limit value of the ammonia fuel mixing ratio in the range where the combustion amount of the ammonia fuel can be continuously changed at the combustion position with the maximum combustion rate for co-combustion with the ammonia fuel among the plurality of stepped combustion positions of the oil fuel is preferably larger than the upper limit value of the ammonia fuel mixing ratio in the range where the combustion amount of the ammonia fuel can be continuously changed at the combustion position with the minimum combustion rate for co-combustion with the ammonia fuel among the plurality of stepped combustion positions of the oil fuel.

[0013] Further, the ammonia supply line includes an ammonia flow rate adjustment valve and an ammonia shut-off valve, and when the combustion control unit changes the combustion position of the oil fuel, it is preferable to close the ammonia shut-off valve.

Advantages of the Invention

[0014] According to the present invention, it is possible to provide a boiler that can be controlled to continuously respond to the required load of a load device, suppress the generation of unburned substances of ammonia, and enable stable combustion, and that co-combusts oil fuel and ammonia.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0016] (First Embodiment) Hereinafter, the boiler according to the first embodiment of the present invention will be described with reference to the drawings. The ammonia co-firing boiler device 1 as the boiler of the present embodiment is a steam boiler that heats water to generate steam and supplies steam to a load device (not shown). FIG. 1 is a longitudinal sectional view of the ammonia co-firing boiler device 1 according to the first embodiment of the present invention.

[0017] As shown in FIG. 1, the ammonia co-firing boiler device 1 includes a can body 30, a burner 10, a control unit 70, a fuel supply line 100, and a combustion air supply line 200. The can body 30 includes a plurality of water pipes 40, a lower header 50, and an upper header 60. Further, a combustion chamber 32 surrounded by a plurality of water pipes 40 is formed inside the can body 30. The fuel supply line 100 includes an oil fuel supply line 130 and an ammonia supply line 140. In the present embodiment, the ammonia co-firing boiler device 1 ejects oil fuel and ammonia fuel from the burner 10 to which oil fuel and ammonia fuel are supplied, and co-fires the oil fuel and ammonia fuel in the combustion chamber 32. Further, the can body 30 recovers heat from the combustion gas in which the fuel ejected from the burner 10 is burned. As the oil fuel, heavy oil, light oil, kerosene, or the like can be used.

[0018] The can body 30 is configured in a cylindrical shape and constitutes a main part of the outer shape of the ammonia co-firing boiler device 1. Hereinafter, the shape and the like of the can body 30 of the present embodiment will be described, but this is only an example, and the shape of the can body 30 and the shape of the water pipes 40 provided in the can body 30 are not limited to this example. The can body 30 is arranged such that its height direction is along the vertical direction. An exhaust port 31 is formed at the upper part of the peripheral surface of the can body 30. The exhaust port 31 is connected to an exhaust gas line 33 through which combustion gas obtained by co-combusting oil fuel and ammonia fuel by the burner 10 flows.

[0019] A plurality of water pipes 40 extend vertically inside the can body 30. As shown in FIG. 1, the plurality of water pipes 40 constitute an inner water pipe group 41 and an outer water pipe group 42 arranged outside the inner water pipe group 41. The inner water pipe group 41 is configured to be annularly arranged such that the plurality of water pipes 40 are coaxial with the ejection central axis X of the burner 10 described later. In the present embodiment, the water pipes 40 constituting the inner water pipe group 41 are arranged such that adjacent water pipes 40 are in contact with each other. Further, the lower parts of the plurality of water pipes 40 constituting the inner water pipe group 41 have a small diameter, and gaps are formed between adjacent water pipes 40 at this lower part.

[0020] The outer water pipe group 42 is configured to be annularly arranged such that the plurality of water pipes 40 are coaxial with the ejection central axis X of the burner 10. Further, the outer water pipe group 42 is arranged such that a predetermined space is formed between the outer water pipe group 42 and the inner water pipe group 41. In the present embodiment, the water pipes 40 constituting the outer water pipe group 42 are arranged such that adjacent water pipes 40 are in contact with each other. Further, the upper parts of the plurality of water pipes 40 constituting the outer water pipe group 42 have a small diameter, and gaps are formed between adjacent water pipes 40 at this upper part.

[0021] The burner 10 extends in the vertical direction of the ammonia co-combustion boiler device 1 and is arranged at the upper part of the can body 30. As shown in FIG. 1, the burner 10 of the present embodiment includes an oil fuel flow path L1, a first air flow path L2, an ammonia flow path L3, and a second air flow path L4. Further, the burner 10 includes a wind box 28, and this wind box 28 includes a combustion air inlet 29 for introducing combustion air A0. The combustion air inlet 29 is connected to a combustion air supply line 200 described later, and the combustion air A0 is sent from the combustion air supply line 200.

[0022] The oil fuel flow path L1 includes two oil fuel supply pipes 11 (a first supply pipe 11a and a second supply pipe 11b), an oil fuel inlet 21 (a first inlet 21a and a second inlet 21b) for introducing the oil fuel F1, and an oil fuel ejection part 15 (a first ejection part 15a and a second ejection part 15b) for ejecting the oil fuel F1. In the present embodiment, an example will be described in which a total of two pipes, i.e., the first supply pipe 11a and the second supply pipe 11b, are arranged as the oil fuel supply pipes 11.

[0023] The oil fuel inlet 21 (the first inlet 21a and the second inlet 21b) is a part into which the oil fuel F1 flowing through the oil fuel supply line 130 is fed, and is provided at the end of the base end side (the side opposite to the combustion chamber 32) of the oil fuel supply pipe 11. As shown in FIG. 1, the first supply pipe 11a is provided with the first inlet 21a, and the second supply pipe 11b is provided with the second inlet 21b. At the tip of the oil fuel supply pipe 11 on the combustion chamber 32 side, an oil fuel ejection part 15 (a first ejection part 15a and a second ejection part 15b) for ejecting the oil fuel F1 that has flowed through the oil fuel flow path L1 and a baffle plate (not shown) are provided. As shown in FIG. 1, the first supply pipe 11a is provided with the first ejection part 15a, and the second supply pipe 11b is provided with the second ejection part 15b. This oil fuel ejection part 15 is, for example, a nozzle tip.

[0024] The first air flow path L2 includes a first combustion air inlet 22 for introducing the first combustion air A1, a first air flow path pipe 12, and a first air ejection part 16. The first combustion air inlet 22 is a part into which a part of the combustion air A0 fed into the wind box 28 is fed as the first combustion air A1. The first air flow path pipe 12 is a tubular member for allowing the first combustion air A1 to flow through. In the present embodiment, it has a larger diameter than the oil fuel supply pipe 11, has the same central axis as the oil fuel supply pipe 11, and is provided so as to enclose the oil fuel supply pipe 11. The first air ejection part 16 is arranged at the tip of the first air flow path L2 on the combustion chamber 32 side, and ejects the first combustion air A1 that has flowed through the first air flow path L2.

[0025] The ammonia flow path L3 includes an ammonia inlet 23 for introducing ammonia fuel F2, an ammonia flow path pipe 13, and an ammonia fuel ejection part 17. The ammonia inlet 23 is the part into which the ammonia fuel flowing through the ammonia supply line 140 is fed. The ammonia flow path pipe 13 is a tubular member through which the ammonia fuel F2 flows. In the present embodiment, it has a larger diameter than the first air flow path pipe 12, has the same central axis as the first air flow path pipe 12 and the oil fuel supply pipe 11, and is provided so as to house them therein. The ammonia fuel ejection part 17 is disposed at the tip of the ammonia flow path pipe 13 on the combustion chamber 32 side, and ejects the ammonia fuel F2.

[0026] The second air flow path L4 includes a second combustion air inlet 24 and a turning part 20 that serve as a second combustion air introduction part, a second air flow path pipe 14, and a second air ejection part 18. The second combustion air inlet 24 is the part that feeds a part of the combustion air A0 sent into the wind box 28 as the second combustion air A2. The turning part 20 is the part that turns the second combustion air A2. In the present embodiment, the second combustion air A2 that has flowed into the second air flow path L4 from the second combustion air inlet 24 is turned by the turning part 20 and becomes a swirling flow centered on the ejection central axis X from the second air ejection part 18, and flows through the second air flow path L4 and is ejected. The second air flow path pipe 14 is a tubular member through which the second combustion air A2 flows. In the present embodiment, it has a larger diameter than the ammonia flow path pipe 13, has the same central axis as the first air flow path pipe 12, the oil fuel supply pipe 11, and the ammonia flow path pipe 13, and is provided so as to house them therein. The second air ejection part 18 is disposed at the tip of the second air flow path pipe 14 on the combustion chamber 32 side, and ejects the second combustion air A2.

[0027] As shown in FIG. 1, the combustion chamber 32 is constituted by a space surrounded by the inner water pipe group 41 inside the can body 30. In this combustion chamber 32, the oil fuel F1 ejected from the oil fuel ejection section 15 of the burner 10, the first combustion air A1 ejected from the first air ejection section 16, the ammonia fuel F2 ejected from the ammonia fuel ejection section 17, and the swirling second combustion air A2 ejected from the second air ejection section 18 are mixed and burned. The combustion gas rises through the space formed between the inner water pipe group 41 and the outer water pipe group 42 through the gap formed between adjacent water pipes 40 at the lower part of the inner water pipe group 41 from the combustion chamber 32. Then, the combustion gas that has risen through the space formed between the inner water pipe group 41 and the outer water pipe group 42 flows through the gap formed between adjacent water pipes 40 at the upper part of the outer water pipe group 42 to the exhaust port 31 formed at the upper part of the can body 30, and is discharged to the outside through the exhaust gas line 33 connected to this exhaust port 31.

[0028] As described above, the fuel supply line 100 includes an oil fuel supply line 130 and an ammonia supply line 140. The oil fuel supply line 130 supplies the oil fuel F1 from an oil fuel supply source (not shown) to the burner 10. The upstream side of the oil fuel supply line 130 is connected to an oil fuel supply source (not shown), and the downstream side of the oil fuel supply line 130 is connected to the burner 10. The oil fuel supply line 130 includes a first oil fuel supply line 110 and a second oil fuel supply line 120. The first oil fuel supply line 110 and the second oil fuel supply line 120 include pumps (first pump 111, second pump 121), on-off valves (first on-off valve 112, second on-off valve 122), and fuel supply valves (first fuel supply valve 113, second fuel supply valve 123) from the upstream side. The first oil fuel supply line 110 is connected to the first supply pipe 11a of the burner 10, and the second oil fuel supply line 120 is connected to the second supply pipe 11b of the burner 10.

[0029] The first pump 111 and the second pump 121 respectively discharge the oil fuel F1 supplied from an oil fuel supply section (not shown) toward the first ejection section 15a and the second ejection section 15b of the oil fuel ejection section 15. The first on-off valve 112 and the second on-off valve 122, and the first fuel supply valve 113 and the second fuel supply valve 123 are constituted by electromagnetic valves or air-driven valves. The first on-off valve 112 and the first fuel supply valve 113 supply or cut off the oil fuel F1 between the first pump 111 and the first ejection part 15a, and can doubly cut off the supply of the oil fuel F1 from the first oil fuel supply line 110. Further, the second on-off valve 122 and the second fuel supply valve 123 supply or cut off the oil fuel F1 between the second pump 121 and the second ejection part 15b, and can doubly cut off the second oil fuel supply line 120.

[0030] The ammonia supply line 140 supplies ammonia fuel F2 to the burner 10 from an ammonia fuel supply source (not shown). The upstream side of the ammonia supply line 140 is connected to the ammonia fuel supply source, and the downstream side of the ammonia supply line 140 is connected to the burner 10. The ammonia supply line 140 includes, from the upstream side, an ammonia fuel flow rate sensor 141, a first shut-off valve 142 as an ammonia shut-off valve, a flow rate adjustment valve 143 as an ammonia flow rate adjustment valve, and a second shut-off valve 144 as an ammonia shut-off valve.

[0031] The ammonia fuel flow rate sensor 141 detects the flow rate of the ammonia fuel F2 flowing through the ammonia supply line 140. The first shut-off valve 142 and the second shut-off valve 144 are constituted by electromagnetic valves, open and close the flow path of the ammonia supply line 140, and supply or stop the ammonia fuel F2. The flow rate adjustment valve 143 is an adjustment valve that adjusts the flow rate of the ammonia fuel F2 supplied to the burner 10 by adjusting the opening degree of the valve based on the detection result of the ammonia fuel flow rate sensor 141.

[0032] The combustion air supply line 200 supplies combustion air A0 to the burner 10. In the present embodiment, the combustion air A0 is supplied to the windbox 28 of the burner 10. The upstream side of the combustion air supply line 200 is connected to the blower 201, and the downstream side of the combustion air supply line 200 is connected to the windbox 28. The combustion air supply line 200 includes, from the upstream side, a blower 201, an air flow rate sensor 202, and a damper 203.

[0033] The blower 201 supplies combustion air A0 to the burner 10. The blower 201 includes a fan and a motor that rotates this fan, and the rotational speed of the motor can be adjusted by controlling the frequency with an inverter 204. The air flow rate sensor 202 detects the flow rate of the combustion air A0 flowing through the combustion air supply line 200. The damper 203 adjusts the flow rate of the combustion air A0 supplied to the burner 10 by adjusting its opening degree. Specifically, the damper 203 is rotatably arranged between a closed state in which the flow path of the combustion air supply line 200 is blocked and an open state in which it rotates from this closed state by a predetermined angle (for example, 90 degrees) to open the flow path of the combustion air supply line 200.

[0034] The control unit 70 includes a combustion control unit 71 and a storage unit 72. The control unit 70 is composed of an arithmetic processor such as a PLC (Programmable Logic Controller), a DSP (Digital Signal Processor), or an FPGA (Field-Programmable Gate Array), for example. Various functions of the control unit 70 are realized by executing a predetermined software (program) stored in the storage unit 72, for example. Various functions of the control unit 70 may be realized by the cooperation of hardware and software, or may be realized by hardware (electronic circuit) only. The storage unit 72 stores various kinds of information. For example, the storage unit 72 may store a database of flow rates corresponding to the combustion rates of oil fuel F1 and a database of flow rates corresponding to the combustion rates of ammonia fuel F2.

[0035] The control unit 70 monitors the steam usage load based on the steam pressure of a steam header (not shown) and controls the ammonia co-firing boiler device 1 by steam pressure control. In the present embodiment, the combustion of the ammonia co-firing boiler device 1 is controlled by the combustion control unit 71 of the control unit 70. The combustion control unit 71 enables the combustion of the oil fuel F1 at a plurality of staged combustion positions, and controls to enable the combustion of the ammonia fuel F2 by continuously changing the combustion amount of the ammonia fuel F2 within a predetermined range.

[0036] In the ammonia co-firing boiler device 1 of the present embodiment, the combustion control unit 71 controls the oil fuel F1 in three staged combustion states (combustion position, combustion rate) shown in the following (A) to (C). The combustion rate indicates the ratio of the combustion amount (based on calorific value) when the maximum combustion amount of the ammonia co-firing boiler device 1 is 100%. (A) Combustion stop position (first combustion position: combustion rate 0%), (B) Low combustion position L (second combustion position: for example, set to a combustion rate of 25%), (C) Medium combustion position M (third combustion position: for example, set to a fuel rate of 50%).

[0037] In the ammonia co-firing boiler device 1 of the present embodiment, when the oil fuel F1 is burned at the low combustion position L (combustion rate 25%), the combustion control unit 71 continuously controls the co-firing rate of the ammonia fuel F2 within the range of 0% or more and 50% or less. When the oil fuel F1 is burned at the low combustion position L (combustion rate 25%) and the ammonia fuel F2 is burned at a co-firing rate of 50%, the combustion rate of the ammonia co-firing boiler device 1 becomes 50%. By continuously adjusting the co-firing rate of the ammonia fuel F2 by the combustion control unit 71, the ammonia co-firing boiler device 1 continuously controls the combustion amount within the combustion range that is equal to or higher than the low combustion position L and equal to or lower than the medium combustion position M. Note that the ammonia co-firing rate indicates the ratio of the combustion amount of the ammonia fuel F2 in the combustion amount of the ammonia co-firing boiler device 1.

[0038] Also, in the ammonia co-firing boiler device 1 of this embodiment, when the oil fuel F1 is burned at the mid-combustion position M (combustion rate 50%), the combustion control unit 71 continuously controls the co-firing rate of the ammonia fuel F2 in the range of 0% or more and 50% or less. When the oil fuel F1 is burned at the mid-combustion position M (combustion rate 50%) and the ammonia fuel F2 is burned at a co-firing rate of 50%, the combustion rate of the ammonia co-firing boiler device 1 becomes 100% (high combustion position H). By continuously adjusting the co-firing rate of the ammonia fuel F2 by the combustion control unit 71, the combustion amount of the ammonia co-firing boiler device 1 is continuously controlled in the combustion range from the mid-combustion position M to the high combustion position H (combustion amount 100%).

[0039] Further, when the total combustion amount of the oil fuel F1 and the ammonia fuel F2 reaches the combustion amount corresponding to the combustion rate set according to the combustion position, after stopping the supply of the ammonia fuel F2, the combustion control unit 71 changes the combustion position of the oil fuel F1. At this time, the total combustion amount of the oil fuel F1 and the ammonia fuel F2 before stopping the supply of the ammonia fuel F2 and the combustion amount of the combustion position of the oil fuel F1 changed after stopping the supply of the ammonia fuel F2 may be the same or the same combustion amount within a predetermined allowable range. For example, a difference in the combustion amount of about ±5% of the fuel rate during the combustion stop of the ammonia fuel F2 does not greatly affect the combustion state of the oil fuel F1, and the combustion amount can be set such that the combustion of the ammonia co-firing boiler device 1 is easily stabilized.

[0040] In the ammonia co-firing boiler device 1, when the combustion control unit 71 burns the oil fuel F1 at the low combustion position L, it controls to supply the oil fuel F1 only from either the first oil fuel supply line 110 or the second oil fuel supply line 120. For example, the combustion control unit 71 controls to supply the oil fuel F1 only from the first oil fuel supply line 110 and cut off the supply of the oil fuel F1 from the second oil fuel supply line 120. At this time, the combustion control unit 71 opens the first on-off valve 112 and the first fuel supply valve 113, closes the second on-off valve 122 and the second fuel supply valve 123, and operates the first pump 111. Thereby, the oil fuel F1 is injected from the first injection part 15a of the first supply pipe 11a to which the first oil fuel supply line 110 is connected. Also, when the combustion control unit 71 controls to supply the oil fuel F1 only from the second oil fuel supply line 120 and cut off the supply of the oil fuel F1 from the first oil fuel supply line 110, the combustion control unit 71 closes the first on-off valve 112 and the first fuel supply valve 113, opens the second on-off valve 122 and the second fuel supply valve 123, and operates the second pump 121. Thereby, the oil fuel F1 is injected from the second injection part 15b of the second supply pipe 11b to which the second oil fuel supply line 120 is connected.

[0041] When the combustion control unit 71 shifts the combustion position of the oil fuel F1 from the low combustion position L to the medium combustion position M, while maintaining the low combustion state, it opens the on-off valve and the fuel supply valve on the oil fuel supply line side where the supply of the oil fuel F1 has stopped, operates the pump, and injects the oil fuel F1 from the oil fuel injection part 15. For example, when the supply of the oil fuel F1 from the first oil fuel supply line 110 has stopped at the low combustion position L, the combustion control unit 71 opens the first on-off valve 112 and the first fuel supply valve 113, operates the first pump 111, and injects the oil fuel F1 from the first injection part 15a to control the combustion amount of the burner 10 to increase.

[0042] Furthermore, in the ammonia co-firing boiler apparatus 1, the combustion control unit 71 burns the oil fuel F1 at a predetermined combustion rate, and when a required load exceeding this predetermined combustion rate is requested from the load equipment, the combustion control unit 71 opens the first shut-off valve 142 and the second shut-off valve 144 of the ammonia supply line 140. At this time, based on the detection result of the ammonia fuel flow rate sensor 141, the combustion control unit 71 adjusts the opening degree of the valve of the flow rate adjustment valve 143 so that the combustion rate of the ammonia fuel F2 corresponds to the combustion rate of the difference between the combustion amount of the oil fuel F1 and the combustion amount of the required load. As a result, the combustion of the ammonia fuel F2 is started, and the combustion rate of the ammonia fuel F2 is continuously controlled according to the required load.

[0043] The combustion control unit 71 changes the opening degree of the damper 203 according to each combustion position to control the flow rate of the combustion air supplied to the combustion chamber 32. For example, the combustion control unit 71 injects the oil fuel F1 from the oil fuel injection unit 15 (the first injection unit 15a), and controls the opening degree of the damper 203 so as to increase the combustion air A0 with a delay of a predetermined time. The delay of the predetermined time for increasing the combustion air A0 is preset by experiments or the like.

[0044] FIG. 2 is a graph showing the combustion rate and the co-firing rate of the ammonia fuel of the ammonia co-firing boiler apparatus 1 according to the first embodiment of the present invention at a certain time. As shown in FIG. 2, in the first embodiment, the low combustion position L of the oil fuel F1 is set to a combustion rate of 25%, and the medium combustion position M is set to a combustion rate of 50%. As shown in FIG. 2, the combustion control unit 71 opens the first on-off valve 112 and the first fuel supply valve 113 of the first oil fuel supply line 110, closes the second on-off valve 122 and the second fuel supply valve 123 of the second oil fuel supply line 120, operates the first pump 111, injects the oil fuel F1 from the first injection unit 15a, and burns the oil fuel F1 at the low combustion position L. At this time, when a required load exceeding 25% of the combustion rate of the oil fuel F1 is requested from the load device, the combustion control unit 71 opens the first shut-off valve 142 and the second shut-off valve 144, and based on the detection result of the ammonia fuel flow rate sensor 141, adjusts the opening degree of the valve of the flow rate adjustment valve 143 so that the combustion amount of the ammonia fuel F2 corresponds to the combustion rate of the difference between the combustion rate of the required load and the combustion rate at the low combustion position L. Note that the opening degree of the valve of the flow rate adjustment valve 143 may be adjusted based on a database of flow rates corresponding to the combustion rate of the ammonia fuel F2 stored in the storage unit 72.

[0045] Further, until the total combustion amount of the oil fuel F1 and the ammonia fuel F2 reaches the medium combustion position M set to 50% (combustion rate 50%) of the maximum combustion amount of the ammonia co-firing boiler device 1, while maintaining the combustion position of the oil fuel F1 at the low combustion position L, the combustion control unit 71 adjusts the opening degree of the valve of the flow rate adjustment valve 143 to continuously increase the combustion amount of the ammonia fuel F2. At this time, the co-firing rate of the ammonia fuel F2 gradually increases up to 50%.

[0046] As a result, the fuel amount of the ammonia fuel F2 continuously changes within a predetermined combustion amount range, and the start and stop of the combustion of the ammonia fuel F2 to the burner 10 can be avoided. Therefore, it is possible to suppress the generation amount of unburned ammonia that increases when the combustion of the ammonia fuel starts and stops. Further, since the combustion amount of the ammonia co-firing boiler device 1 continuously changes according to the required load from the load device, it can quickly and flexibly respond to fluctuations in the required load.

[0047] Further, when the total combustion amount of the oil fuel F1 and the ammonia fuel F2 reaches the combustion amount corresponding to the combustion rate for changing the combustion position of the oil fuel F1, the combustion control unit 71 stops the supply of the ammonia fuel F2, and then changes the combustion position of the oil fuel F1. Further, when the total combustion amount of the oil fuel F1 and the ammonia fuel F2 reaches the combustion amount corresponding to the combustion rate for changing the combustion position of the oil fuel F1 due to the increase in the combustion amount of the ammonia fuel F2, the combustion control unit 71 changes the combustion position of the oil fuel F1 to a higher combustion position. Further, when changing the combustion position of the oil fuel F1, the combustion control unit 71 closes the first shut-off valve 142 and the second shut-off valve 144 serving as ammonia shut-off valves.

[0048] Specifically, the combustion control unit 71 performs the following control. As shown in FIG. 2, the combustion control unit 71 adjusts the opening degree of the valve of the flow rate adjustment valve 143 so as to increase the combustion amount of the ammonia fuel F2 while maintaining the combustion position of the oil fuel F1 at the low combustion position L. When the total combustion amount of the combustion amount of the oil fuel F1 and the combustion amount of the ammonia fuel F2 converted on the heat quantity basis of the oil fuel F1 reaches the combustion amount corresponding to the medium combustion position M set at a combustion rate of 50% by increasing the combustion amount of the ammonia fuel F2, the combustion control unit 71 closes the first shut-off valve 142 and the second shut-off valve 144, stops the supply of the ammonia fuel F2, and the combustion control unit 71 opens the first on-off valve 112 and the first fuel supply valve 113 so that the combustion amount of the oil fuel F1 corresponds to the medium combustion position M, and while the first pump 111 is operating, the second on-off valve 122 and the second fuel supply valve 123 of the second oil fuel supply line 120 where the supply of the oil fuel F1 is stopped are opened, the second pump 121 is operated, and the oil fuel F1 is injected from the second ejection unit 15b. Thereby, the combustion control unit 71 changes the combustion position of the oil fuel F1 to a higher combustion position. Here, the co-combustion rate of the ammonia fuel F2 when changing the combustion position of the oil fuel F1 from the low combustion position L to the medium combustion position M is 0%.

[0049] By changing the total combustion amount of the oil fuel F1 and the ammonia fuel F2, when the combustion rate corresponding to the combustion position of the oil fuel F1 is reached, the supply of the ammonia fuel F2 is temporarily stopped, and the combustion position of the oil fuel F1 is changed. Since the supply of the ammonia fuel F2 is restarted after changing the combustion position of the oil fuel F1, it is possible to avoid the ammonia fuel F2 from being burned and unburned ammonia from being generated during combustion instability due to the change in the combustion position of the oil fuel F1.

[0050] Further, when the total combustion amount of the oil fuel F1 and the ammonia fuel F2 reaches the combustion rate at which the combustion position of the oil fuel F1 is changed due to an increase in the combustion amount of the ammonia fuel F2, the combustion position of the oil fuel F1 is changed to a higher combustion position, so that the ammonia co-firing boiler device 1 can be continuously changed over a wide range of combustion amounts from the low combustion position L (combustion rate 25%) of the oil fuel F1 to the maximum combustion amount (combustion rate 100%) of the ammonia co-firing boiler device 1. Also, by closing the first shut-off valve 142 and the second shut-off valve 144 as the ammonia shut-off valves, it is not necessary to wait for the closing operation of the flow rate adjustment valve 143 as the ammonia flow rate adjustment valve, which takes time for the closing operation, and the combustion position of the oil fuel F1 can be changed in a short time.

[0051] As shown in FIG. 2, thereafter, the combustion control unit 71 continuously controls so as to maintain the combustion position of the oil fuel F1 at the medium combustion position M and continuously increase the combustion amount of the ammonia fuel F2 until the total combustion amount of the ammonia co-firing boiler device 1 corresponding to the required load reaches the combustion amount corresponding to 100% (combustion rate 100%) of the maximum combustion amount of the ammonia co-firing boiler device 1. At this time, the combustion rate of the ammonia fuel F2 gradually increases up to 50%, and accordingly, the co-firing rate gradually increases up to 50%.

[0052] Specifically, the combustion control unit 71 causes the combustion position of the oil fuel F1 to burn at the mid-combustion position M, and when a required load exceeding a combustion rate of 50% is requested from the load device, it opens the first shut-off valve 142 and the second shut-off valve 144. Further, the combustion control unit 71 adjusts the opening degree of the valve of the flow rate adjustment valve 143 based on the detection result of the ammonia fuel flow rate sensor 141 so that the combustion amount of the ammonia fuel F2 corresponds to the combustion rate of the difference between the combustion rate of the required load and the combustion rate of the mid-combustion position M. Note that the opening degree of the valve of the flow rate adjustment valve 143 may be adjusted based on a database of flow rates corresponding to the combustion rate of the ammonia fuel F2 stored in the storage unit 72. Also, until the total combustion amount of the oil fuel F1 and the ammonia fuel F2 reaches the combustion amount corresponding to a combustion rate of 100%, the combustion control unit 71 continuously increases the combustion amount of the ammonia fuel F2 by adjusting the opening degree of the valve of the flow rate adjustment valve 143 while maintaining the combustion position of the oil fuel F1 at the mid-combustion position M.

[0053] In FIG. 2, when the total combustion amount of the ammonia co-firing boiler device 1 corresponding to the required load decreases after reaching a combustion rate of 100%, the combustion control unit 71 maintains the combustion position of the oil fuel F1 at the mid-combustion position M until the combustion amount corresponding to a combustion rate of 50% is reached. Further, the combustion control unit 71 controls to continuously decrease the combustion amount of the ammonia fuel F2 by adjusting the opening degree of the valve of the flow rate adjustment valve 143. As a result, the combustion rate of the ammonia fuel F2 gradually decreases from 50% to 0%. When the total combustion amount of the ammonia co-firing boiler device 1 reaches a combustion rate of 50%, the combustion control unit 71 closes the first shut-off valve 142 and the second shut-off valve 144 to stop the supply of the ammonia fuel F2.

[0054] In Fig. 2, when the combustion control unit 71 further reduces the total combustion amount of the ammonia co-firing boiler device 1 from a combustion rate of 50% in response to a decrease in the required load, it maintains the opening of the first on-off valve 112 and the first fuel supply valve 113 and the operation of the first pump 111, and continues to supply the oil fuel F1 from the first injection unit 15a. On the other hand, the combustion control unit 71 closes the second on-off valve 122 and the second fuel supply valve 123, stops the second pump 121, and stops the supply of the oil fuel F1 from the second injection unit 15b.

[0055] At the same time, the combustion control unit 71 continuously controls the combustion amount of the ammonia fuel F2 so that the total combustion amount of the ammonia co-firing boiler device 1 becomes the combustion amount corresponding to the required load. As shown in Fig. 2, the combustion position of the oil fuel F1 is maintained at the low combustion position L so that the total combustion amount of the ammonia co-firing boiler device 1 reaches from a combustion rate of 25% to a combustion rate of 50%, and the control is performed so as to continuously increase the combustion amount of the ammonia fuel F2.

[0056] Specifically, when a required load exceeding a combustion rate of 25% is requested from the load device, the combustion control unit 71 opens the first shut-off valve 142 and the second shut-off valve 144. Further, the combustion control unit 71 adjusts the opening degree of the valve of the flow rate adjustment valve 143 based on the detection result of the ammonia fuel flow rate sensor 141 so that the combustion amount of the ammonia fuel F2 becomes the combustion amount corresponding to the combustion rate of the difference between the combustion rate of the required load and the combustion rate of the low combustion position L. Note that the opening degree of the valve of the flow rate adjustment valve 143 may be adjusted based on a database of the flow rate corresponding to the combustion rate of the ammonia fuel F2 stored in the storage unit 72. In Fig. 2, when the total combustion amount of the oil fuel F1 and the ammonia fuel F2 reaches the combustion amount corresponding to a combustion rate of 40%, the combustion control unit 71 maintains the opening degree of the valve of the flow rate adjustment valve 143 based on the detection result of the ammonia fuel flow rate sensor 141 so that the combustion amount of the ammonia fuel F2 becomes the combustion amount corresponding to 15% of the maximum combustion amount (combustion rate of 15%) of the ammonia co-firing boiler device 1.

[0057] When the total combustion amount of the ammonia co-firing boiler device 1 corresponding to the required load reaches the combustion amount corresponding to a combustion rate of 40%, the oil fuel F1 is the combustion amount corresponding to a combustion rate of 25%, and the ammonia fuel F2 is the combustion amount corresponding to 15% of the maximum combustion amount of the ammonia co-firing boiler device 1. At this time, the co-firing rate of the ammonia fuel F2 is 37.5%.

[0058] According to the ammonia co-firing boiler device 1 described above, the following effects are achieved.

[0059] (1) The ammonia co-firing boiler device 1 of the present embodiment includes a burner 10 to which the oil fuel F1 and the ammonia fuel F2 are supplied, a can body 30 that recovers heat from the combustion gas in which the fuel ejected from the burner 10 is burned, a control unit 70, an oil fuel supply line 130 that supplies the oil fuel F1 to the burner 10, an ammonia supply line 140 that supplies the ammonia fuel F2 to the burner 10, a combustion air supply line 200 that supplies the combustion air A0 to the burner 10, and an exhaust gas line 33 that is connected to the can body 30 and through which the combustion gas generated by burning the oil fuel F1 and the ammonia fuel F2 in the can body 30 flows. The control unit 70 includes a combustion control unit 71 that enables the combustion of the oil fuel F1 at a plurality of staged combustion positions and enables the combustion of the ammonia fuel F2 by continuously changing the combustion amount of the ammonia fuel F2 within a predetermined range. Thereby, since the fuel amount of the ammonia fuel F2 continuously changes within the range of a predetermined combustion amount, the supply amount of the ammonia fuel F2 to the burner 10 does not increase rapidly, so that the generation of unburned substances of ammonia in the burner 10 can be suppressed. In addition, since the combustion amount of the ammonia co-firing boiler device 1 continuously changes according to the required load from the load device, it can quickly and flexibly respond to fluctuations in the required load.

[0060] (2) In the ammonia co-firing boiler device 1 described in (1) above, after the combustion control unit 71 stops the supply of the ammonia fuel F2, it changes the combustion position of the oil fuel F1. Accordingly, when combustion is likely to become unstable as the combustion position of the oil fuel F1 changes step by step, since the ammonia fuel F2 is not combusted, generation of unburned matter of ammonia can be avoided.

[0061] (3) In the ammonia co-firing boiler device 1 described in (1) and (2) above, when the total combustion amount of the oil fuel F1 and the ammonia fuel F2 reaches the combustion amount corresponding to the combustion rate set according to the combustion position, after stopping the supply of the ammonia fuel F2, the combustion position of the oil fuel F1 is changed. By changing the total combustion amount of the oil fuel F1 and the ammonia fuel F2, when the combustion rate corresponding to the combustion position of the oil fuel F1 is reached, the supply of the ammonia fuel F2 is temporarily stopped, and the combustion position of the oil fuel F1 is changed. Accordingly, since the supply of the ammonia fuel F2 is restarted after changing the combustion position of the oil fuel F1, when combustion is likely to become unstable as the combustion position of the oil fuel F1 changes step by step, the ammonia fuel F2 is not combusted, so generation of unburned matter of ammonia can be avoided.

[0062] (4) In the ammonia co-firing boiler device 1 described in (1) to (3) above, when the combustion amount of the ammonia fuel F2 increases and the total combustion amount of the oil fuel F1 and the ammonia fuel F2 reaches the combustion amount corresponding to the combustion rate set according to the combustion position, the combustion position of the oil fuel F1 is changed to a combustion position one level higher. Accordingly, by changing the combustion position of the oil fuel F1 to a combustion position one level higher when the combustion amount of the ammonia fuel F2 increases and the total combustion amount of the oil fuel F1 and the ammonia fuel F2 reaches the combustion rate set according to the combustion position, the combustion amount of the ammonia co-firing boiler device 1 can be continuously changed within a wide range of combustion amounts.

[0063] (5) The ammonia co-firing boiler device 1 described in the above (1) to (4) is such that the ammonia supply line 140 includes a flow control valve 143 as an ammonia flow control valve, and a first shut-off valve 142 and a second shut-off valve 144 as ammonia shut-off valves. When the combustion control unit 71 changes the combustion position of the oil fuel F1, it closes the first shut-off valve 142 and the second shut-off valve 144 as ammonia shut-off valves. By closing the first shut-off valve 142 and the second shut-off valve 144 as ammonia shut-off valves, it is not necessary to wait for the closing operation of the flow control valve 143 as an ammonia flow control valve, which takes time for the closing operation, and the combustion position of the oil fuel F1 can be changed in a short time.

[0064] (Second Embodiment) Next, a second embodiment according to the present invention will be described. In this embodiment, the configuration of the ammonia co-firing boiler device 1 similar to that of the first embodiment is used. In the second embodiment, the combustion rates at the low combustion position L and the medium combustion position M of the oil fuel F1 are different from those of the first embodiment. Accordingly, in the second embodiment, the maximum value of the ammonia co-firing rate when the oil fuel F1 is burned at the combustion position of the medium combustion position M becomes larger than that of the first embodiment. In the following description, emphasis will be placed on the description of matters different from the first embodiment, and the description of matters common to the first embodiment may be omitted.

[0065] FIG. 3 is a graph showing the combustion rate and the co-firing rate of the ammonia fuel of the ammonia co-firing boiler device 1 according to the second embodiment of the present invention at a certain time. In the graph shown in FIG. 3, the combustion rate and the ammonia co-firing rate on the vertical axis are the same as the combustion rate and the ammonia co-firing rate on the vertical axis of the graph of FIG. 2 described above. Also, in the second embodiment, the low combustion position L of the oil fuel F1 is a combustion rate of 20%, and the medium combustion position of the oil fuel F1 is set to a combustion amount of 40%.

[0066] In this embodiment, when the oil fuel F1 is burned at the low combustion position L, the combustion control unit 71 continuously controls the co-combustion ratio of the ammonia fuel F2 in the range of 0% or more and 50% or less, and is 20% of the maximum combustion amount of the ammonia co-combustion boiler device 1 (corresponding to a combustion rate of 20% and the low combustion position L of the oil fuel F1) or more and 40% of the maximum combustion amount (combustion amount of 40%) or less. In the combustion range, continuous combustion amount control is performed. Here, the combustion amount of the ammonia fuel F2 refers to the combustion amount converted on the heat quantity basis of the oil fuel F1. Further, when the combustion control unit 71 burns the oil fuel F1 at the medium combustion position M and co-combusts it with the ammonia fuel F2, the co-combustion ratio of the ammonia fuel F2 is continuously changed in the range of 0% or more and 60% or less.

[0067] As shown in FIG. 3, when the combustion control unit 71 burns the oil fuel F1 at the low combustion position L and a required load exceeding a combustion rate of 20% is requested from the load device, the combustion of the ammonia fuel F2 is started so that the combustion amount of the ammonia fuel F2 corresponds to the combustion rate of the difference between the combustion rate of the required load and the combustion rate of the low combustion position L. Further, until the total combustion amount of the oil fuel F1 and the ammonia fuel F2 reaches the combustion amount corresponding to the medium combustion position M set to 40% (combustion rate 40%) of the maximum combustion amount of the ammonia co-combustion boiler device 1, while maintaining the combustion position of the oil fuel F1 at the low combustion position L, control is performed to continuously increase the combustion amount of the ammonia fuel F2. At this time, the combustion amount of the ammonia fuel F2 increases to the equivalent of 20% of the maximum combustion amount of the ammonia co-combustion boiler device 1, and the co-combustion ratio of the ammonia fuel F2 increases to 50%.

[0068] When the combustion amount of ammonia fuel F2 is increased and the total combustion amount of the combustion amount of oil fuel F1 and the combustion amount of ammonia fuel F2 reaches the combustion amount corresponding to the medium combustion position M where the combustion rate is set to 40%, the combustion control unit 71 stops the supply of ammonia fuel F2 and controls the supply of oil fuel F1 so that the combustion amount of oil fuel F1 becomes the combustion amount corresponding to the medium combustion position M. Thereby, the combustion control unit 71 changes the combustion position of the oil fuel F1 to a higher combustion position. Here, the co - combustion rate of ammonia fuel F2 when changing the combustion position of oil fuel F1 from the low combustion position L to the medium combustion position M is 0%.

[0069] Thereafter, the combustion control unit 71 maintains the combustion position of the oil fuel F1 at the medium combustion position M and continuously controls so as to continuously increase the combustion amount of the ammonia fuel F2 until the total combustion amount of the ammonia co - combustion boiler device 1 corresponding to the required load reaches the combustion amount corresponding to 100% of the maximum combustion amount of the ammonia co - combustion boiler device 1. At this time, the co - combustion rate of the ammonia fuel F2 increases up to 60%.

[0070] In FIG. 3, the upper limit of the co - combustion rate of ammonia fuel F2 when the oil fuel F1 is at the medium combustion position M is 60%, which is larger than the co - combustion rate of 50% of ammonia fuel F2 when the oil fuel F1 is at the low combustion position L. When the oil fuel F1 is at the medium combustion position M, compared with the case where it is at the low combustion position L, since the combustion amount of the oil fuel F1 and the total combustion amount of the ammonia fuel F2 combined are larger and the combustion state is stable, stable combustion can be performed even if the ammonia co - combustion rate is increased. Also, by increasing the ammonia co - combustion rate at the maximum combustion amount, the effect of reducing carbon dioxide emissions can be increased.

[0071] That is, in the second embodiment, the upper limit value of the ammonia fuel co - firing rate within the range where the combustion amount can be continuously changed is made larger at the combustion position (medium combustion position M) of the oil fuel F1 where the combustion rate is the maximum for co - firing with the ammonia fuel F2 than at the combustion position (low combustion position L) of the oil fuel F1 where the combustion rate is the minimum for co - firing with the ammonia fuel F2. According to this embodiment, the ammonia co - firing rate at the maximum combustion amount can be increased, and the effect of reducing carbon dioxide emissions can be enhanced.

[0072] Also, according to this embodiment, among the combustion positions of the oil fuel F1 set step - by - step, the combustion amount at the combustion position where the minimum combustion amount is obtained is reduced. For example, by setting the combustion amount at the low combustion position L to 10% of the maximum combustion amount, the TDR (turn - down ratio) can be increased, and the load - following performance and the stability of the ammonia fuel can be improved.

[0073] According to the ammonia co - firing boiler device 1 described above, the following effects are achieved.

[0074] (6) In the ammonia co - firing boiler device 1 described in (1) to (5) above, the ammonia fuel co - firing rate at the upper limit value of the range where the combustion amount of the ammonia fuel F2 can be continuously changed at the combustion position with the maximum combustion rate for co - firing with the ammonia fuel F2 among the plurality of step - by - step combustion positions of the oil fuel F1 is larger than the ammonia fuel co - firing rate at the upper limit value of the range where the combustion amount of the ammonia fuel F2 can be continuously changed at the combustion position with the minimum combustion rate for co - firing with the ammonia fuel F2 among the plurality of step - by - step combustion positions of the oil fuel F1. Thereby, the ammonia co - firing rate at the maximum combustion amount can be increased, and the effect of reducing carbon dioxide emissions can be enhanced. Also, among the combustion positions of the oil fuel F1 set step - by - step, by reducing the combustion amount at the combustion position where the minimum combustion amount is obtained, for example, setting the combustion amount at the low combustion position L to 10% of the maximum combustion amount, the TDR (turn - down ratio) can be increased, and both the load - following performance and the stable combustion of the ammonia fuel F2 can be realized simultaneously.

[0075] (Third Embodiment) Next, a third embodiment according to the present invention will be described. In this embodiment, the configuration of the ammonia co-firing boiler device 1 similar to that of the first embodiment is used. In the following description, emphasis will be placed on the description of matters different from the first embodiment, and the description of matters common to the first embodiment may be omitted. FIG. 4 is a graph showing the combustion rate and the co-firing rate of ammonia fuel of the ammonia co-firing boiler device 1 according to the third embodiment of the present invention at a certain time. In the graph shown in FIG. 4, the combustion rate and the ammonia co-firing rate on the vertical axis are the same as the combustion rate and the ammonia co-firing rate on the vertical axis of the graph in FIG. 2 described above. In this embodiment, the combustion control unit 71 controls the combustion position of the oil fuel F1 in three stages: a combustion stop position (combustion rate 0%), a medium combustion position M (combustion rate 50%), and a high combustion position H (combustion rate 100%).

[0076] In this embodiment, when the oil fuel F1 is at the medium combustion position M, the combustion control unit 71 continuously changes the ammonia fuel F2 within the range of a combustion amount of 0% or more and 50% or less of the maximum combustion amount of the ammonia co-firing boiler device 1 and causes it to burn. Here, the combustion amount of the ammonia fuel F2 refers to the combustion amount converted on the basis of the calorific value of the oil fuel F1. Further, when the combustion control unit 71 causes co-firing with the ammonia fuel F2 while burning the oil fuel F1 at the medium combustion position M, it continuously changes the co-firing rate of the ammonia fuel F2 within the range of 0% or more and 50% or less.

[0077] FIG. 4 shows an example when the cold-state ammonia co-firing boiler device 1 receives a boiler combustion start command. The combustion control unit 71 receives the boiler combustion start command and changes the combustion position of the oil fuel F1 from the combustion stop position to the high combustion position H. The combustion control unit 71 starts the combustion of the oil fuel F1 at the high combustion position H and continues it for a predetermined time. Here, when the combustion position of the oil fuel F1 is at the high combustion position H, the co-firing rate of the ammonia fuel F2 is 0%.

[0078] In FIG. 4, when attempting to control the total combustion amount of the ammonia co-firing boiler device 1 in a range of combustion rates lower than 100% in response to a decrease in the required load, the combustion control unit 71 changes the combustion position of the oil fuel F1 to a lower combustion position so that it becomes the combustion amount of the oil fuel F1 corresponding to the medium combustion position M (combustion rate 50%). When changing the combustion position of the oil fuel F1 from the high combustion position H to the medium combustion position M, the co-firing rate of the ammonia fuel F2 is 0%.

[0079] Thereafter, the combustion control unit 71 maintains the combustion position of the oil fuel F1 at the medium combustion position M and continuously controls the combustion amount of the ammonia fuel F2 so that the total combustion amount of the ammonia co-firing boiler device 1 corresponds to the required load. As a result, the total combustion amount quickly reaches the combustion rate corresponding to the previous decrease in the required load. Here, when the total combustion amount corresponding to the previous decrease in the required load is, for example, a combustion rate of 80%, if a constant required load continues, the total combustion amount is maintained at a combustion rate of 80%. At this time, the co-firing rate of ammonia is maintained at 37.5%. FIG. 4 shows the case where there is an increase in the required load after the previous decrease in the required load. The total combustion amount increases beyond a combustion rate of 80%, and the co-firing rate of ammonia increases beyond 37.5%. Note that the control of the flow rate of the ammonia fuel F2 by the combustion control unit 71 when a required load exceeding a combustion rate of 50% is requested from the load equipment is the same as that in the first embodiment and the like described above.

[0080] Also, in this embodiment, as shown in FIG. 4, the combustion control unit 71 has shown the case of controlling the combustion state of the oil fuel F1 at three combustion positions: the combustion stop position (combustion rate 0%), the medium combustion position M (combustion rate 50%), and the high combustion position H (combustion rate 100%). However, for example, it may be controlled in four stages: the combustion stop position (combustion rate 0%), the low combustion position L (25%), the medium combustion position M (combustion rate 50%), and the high combustion position H (combustion rate 100%). By increasing the combustion positions of the oil fuel F1, the difference in combustion rate between each combustion position becomes smaller, and the responsiveness of the required load can be enhanced.

[0081] According to the ammonia co-firing boiler device 1 of the present embodiment described above, the same effects as those of the ammonia co-firing boiler device 1 described in the aforementioned (1) to (5) are achieved. Further, according to the ammonia co-firing boiler device 1 of the present embodiment, the following effects can be achieved.

[0082] (7) In the ammonia co-firing boiler device 1, when combustion starts with the heat exchange part, heat insulating material, etc. cooled to the ambient temperature or a predetermined temperature or lower, the flame is cooled and unburned ammonia is likely to be generated. However, according to the present embodiment, since combustion occurs at a combustion rate of 100% of the oil fuel F1 during cold start-up, the preheating time required to stably start ammonia co-firing is shortened, and ammonia co-firing can be started earlier.

[0083] As described above, the preferred embodiment of the ammonia co-firing boiler device 1 as a boiler according to the present invention has been described. However, the present invention is not limited to the above-described embodiment and can be appropriately modified. Hereinafter, the modified forms of the boiler according to the present invention will be described.

[0084] (Modified Form) The ammonia fuel is a gaseous fuel mainly composed of ammonia, and may be an ammonia decomposition gas containing ammonia.

[0085] In each embodiment, an example is shown in which the flow rate of the ammonia fuel F2 and the flow rate of the combustion air A0 are detected by flow sensors (ammonia fuel flow sensor 141, air flow sensor 202). However, the present invention is not limited thereto, and the flow sensor may be a combination of a pressure loss part (such as an orifice) provided in each flow path and a pressure measurement part (such as a pressure gauge or a differential pressure gauge).

[0086] In each embodiment, the ammonia co-firing boiler device 1, which is a boiler according to the present invention, includes a burner 10, a plurality of water pipes 40, a lower header 50, and a can body 30 including an upper header 60, and an example was given in which the combustion chamber 32 is surrounded by a plurality of water pipes 40. Examples of such boilers include, for example, small once-through boilers, small-scale once-through boilers, etc., and in ships, marine water-tube boilers, marine composite boilers, etc. The boiler according to the present invention may also be a smoke-tube boiler that generates steam by arranging a plurality of pipes through which combustion gas burned in a combustion furnace flows in water and performing heat exchange between the plurality of pipes and water. Further, the present invention may be applied to furnaces without water-cooled walls such as heating furnaces and incinerators. In these boilers and combustion devices, since the combustion amount is controlled (the combustion amount fluctuates) according to fluctuations in the required load or control of heating conditions, etc., the generation of unburned substances accompanying changes in the combustion amount can be effectively suppressed.

[0087] In the first and second embodiments, the case of switching the combustion rate of the oil fuel F1 to the "combustion stop position", "low combustion position L", and "medium combustion position M" was shown, and in the third embodiment, the case of switching the combustion rate of the oil fuel F1 to the "combustion stop position", "medium combustion position M", and "high combustion position H" was shown. However, the setting of the combustion rate of the oil fuel F1 is not limited to this. The combustion rate of the oil fuel F1 may be switched in three or more stages. For example, by providing a third oil fuel supply line (not shown) and controlling the supply of oil fuel from these three supply lines, the combustion rate of the oil fuel F1 can be controlled in more stages. For example, when the combustion rates when burning only with the first to third oil fuel supply lines are 20%, 30%, and 50% respectively, the combustion rate of the oil fuel F1 can be set to 20%, 30%, 50%, and 100% by combining the opened oil fuel supply lines.

[0088] In each embodiment, when the oil fuel F1 burns at the low combustion position L, the oil fuel F1 is injected from only one of the two oil fuel injection parts 15. When the oil fuel F1 burns at the medium combustion position M, an example is shown in which the oil fuel F1 is injected from both of the oil fuel injection parts 15. However, the present invention is not limited to this. Even when the oil fuel F1 burns at the medium combustion position M, the oil fuel F1 corresponding to the combustion amount at the medium combustion position M may be injected from only one oil fuel injection part 15. In this case, at both the low combustion position L and the medium combustion position M, since a flame is formed from a single oil fuel injection part 15, compared with the case where a flame is formed from two oil fuel injection parts 15, a uniform flame without an overlapping part of the oil combustion flame is obtained, and unburned ammonia can be more effectively suppressed.

[0089] Since the present invention promotes the use of ammonia that does not emit carbon dioxide as a fuel, for example, it can contribute to Goal 7 of the Sustainable Development Goals (SDGs) led by the United Nations, "Ensure access to affordable, reliable, sustainable and modern energy for all."

Explanation of reference numerals

[0090] 1 Ammonia co-firing boiler device 10 Burner 15 Oil fuel injection part 17 Ammonia fuel injection part 30 Cylinder body 33 Exhaust gas line 70 Control unit 71 Combustion control unit 130 Oil fuel supply line 140 Ammonia supply line 200 Combustion air supply line A0 Combustion air F1 Oil fuel F2 Ammonia fuel L1 Oil fuel flow path L3 Ammonia flow path

Claims

1. a burner to which an oil fuel and an ammonia fuel are supplied; a can body that recovers heat from combustion gas in which the fuel ejected from the burner is burned; a control unit; an oil fuel supply line that supplies the oil fuel to the burner; an ammonia supply line that supplies the ammonia fuel to the burner; a combustion air supply line that supplies combustion air to the burner; an exhaust gas line that is connected to the can body and through which combustion gas generated by burning the oil fuel and the ammonia fuel in the can body flows, and the control unit is provided with a combustion control unit that enables combustion of the oil fuel at a plurality of stepwise combustion positions and enables combustion of the ammonia fuel by continuously changing the combustion amount of the ammonia fuel within a predetermined range. A boiler.

2. The combustion control unit changes the combustion position of the oil fuel after stopping the supply of the ammonia fuel. The boiler according to claim 1.

3. The combustion control unit When the total combustion amount of the oil fuel and the ammonia fuel reaches a combustion amount corresponding to a combustion rate set according to the combustion position, after stopping the supply of the ammonia fuel, the combustion position of the oil fuel is changed. The boiler according to claim 1.

4. The combustion control unit When the combustion amount of the ammonia fuel increases and the total combustion amount reaches a combustion amount corresponding to a combustion rate set according to the combustion position, the combustion position of the oil fuel is changed to a combustion position one level higher. The boiler according to claim 3.

5. The upper limit value of the ammonia fuel co - combustion rate in the range where the combustion amount of the ammonia fuel can be continuously changed at the combustion position with the maximum combustion rate for co - combustion with the ammonia fuel among the plurality of stepwise combustion positions of the oil fuel is larger than the upper limit value of the ammonia fuel co - combustion rate in the range where the combustion amount of the ammonia fuel can be continuously changed at the combustion position with the minimum combustion rate for co - combustion with the ammonia fuel among the plurality of stepwise combustion positions of the oil fuel. The boiler according to claim 1.

6. The ammonia supply line includes an ammonia flow rate adjustment valve and an ammonia shut - off valve, and the combustion control unit closes the ammonia shut - off valve when changing the combustion position of the oil fuel. The boiler according to claim 1.

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