Boiler

Abstract

To provide a boiler capable of promptly starting combustion of ammonia while reducing unburned ammonia remaining in combustion gas due to lowering of a temperature of combustion gas when starting mixed combustion of ammonia fuel.SOLUTION: An ammonia mixed combustion boiler 1 includes: a burner 20 to which at least either of first fuel F1 having combustion speed higher than ammonia or ammonia fuel F2 and combustion air A1 are supplied and that burns fuel; a can body 10; a steam pressure detection section 14 that detects steam pressure inside the can body 10; an exhaust gas temperature detection section 401 that is a heating state detection section for detecting a heating state of the can body 10; and a control section 40. The control section 40 includes a combustion control section 42 and a reference temperature evaluation section 43 that determines a reference temperature for starting mixed combustion. After combustion of the first fuel F1 is started, if a detection result from the heating state detection section exceeds the reference temperature, the combustion control section 42 performs control to start the mixed combustion of the first fuel F1 and ammonia fuel F2.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a boiler.

Background Art

[0002] By replacing a part of hydrocarbon fuels such as natural gas and oil fuel used as fuel for burners with ammonia fuel that does not generate carbon dioxide, reduction of carbon dioxide emissions is expected. On the other hand, ammonia has a slower combustion rate than general hydrocarbon fuels and is known as a difficult-to-burn fuel. In Patent Document 1, in an ammonia fuel combustion device that has many disadvantages in terms of very difficult initial ignition of the fuel and stabilization of the ignition state, a combustion device for a difficult-to-burn fuel that contributes to ignition and stabilization of the difficult-to-burn fuel has been devised. However, in the combustion device of Patent Document 1, the vicinity of the inner wall of the combustor body becomes low temperature due to the external temperature, the flame is quenched, the combustion reaction stops, and incomplete combustion gas is generated. Therefore, in Patent Document 2, a special burner has been devised for the problem that a stable flame cannot be formed by ammonia.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a boiler using an ammonia co-firing burner, when starting the combustion of ammonia fuel, the temperature of the combustion gas decreases, resulting in unstable combustion of the ammonia fuel, an increase in the amount of unburned ammonia in the combustion gas, and ultimately, the combustion of the ammonia co-firing burner not being stable. It has been an issue to stabilize the combustion of the ammonia co-firing burner, promptly start the co-firing of ammonia fuel, and effectively reduce the carbon dioxide generated by the combustion of hydrocarbon fuel.

[0005] Therefore, an object of the present invention is to provide a boiler that can promptly start the combustion of ammonia while reducing the unburned ammonia in the remaining combustion gas due to the decrease in the temperature of the combustion gas when starting the co-firing of ammonia fuel.

Means for Solving the Problem

[0006] The present invention includes a burner that supplies at least one of a first fuel with a faster combustion rate than ammonia and ammonia fuel, and combustion air, and burns the fuel; a can body that recovers heat from the combustion gas generated by the combustion of the fuel by the burner and generates steam; a steam pressure detection unit that detects the steam pressure inside the can body; a heating state detection unit that detects the heating state of the can body; and a control unit. The control unit includes a combustion control unit that controls the combustion of the burner, and a reference temperature evaluation unit that determines a reference temperature for starting the co-firing of the first fuel and the ammonia fuel based on the combustion amount of the first fuel and the detection result of the steam pressure detection unit. The combustion control unit controls to start the co-firing of the first fuel and the ammonia fuel when the detection result of the heating state detection unit exceeds the reference temperature after starting the combustion of the first fuel. This relates to a boiler.

[0007] Further, it is preferable that the combustion control unit controls to start the co-firing of the first fuel and the ammonia fuel when the detection result of the steam pressure detection unit exceeds a predetermined value and the detection result of the heating state detection unit exceeds the reference temperature.

Effect of the Invention

[0008] According to the present invention, it is possible to provide a boiler that can quickly start the combustion of ammonia while reducing the unburned ammonia in the remaining combustion gas due to the decrease in the temperature of the combustion gas when starting the co-firing of ammonia fuel.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0010] Hereinafter, the ammonia co-firing boiler 1 as a boiler according to an embodiment of the present invention will be described with reference to the drawings. The ammonia co-firing boiler 1 of the first embodiment is a steam boiler that burns fuel and heats water to generate steam, and supplies steam to a load device (not shown).

[0011] FIG. 1 is a diagram schematically showing the configuration of the ammonia co-firing boiler 1 according to the embodiment. As shown in FIG. 1, the ammonia co-firing boiler 1 includes a can body 10, a burner 20, an exhaust pipe 400, and a control unit 40. The ammonia co-firing boiler 1 also includes a first fuel supply line 100, an ammonia fuel supply line 200, a combustion air supply line 300, a water supply line 500, and a steam supply line 600. The "line" in this specification is a general term for a flow path, a route, a pipeline, etc.

[0012] The can body 10 recovers heat from the combustion gas generated by the combustion of fuel by the burner 20 and generates steam. The can body 10 includes a lower header 11, a plurality of water pipes 12, an upper header 13, a steam pressure detection unit 14, a water pipe temperature detection unit 15, a scale monitor 16, a combustion chamber B, etc., and heats the water W1 supplied to the can body 10 to generate steam S1. The plurality of water pipes 12 are arranged to extend vertically inside the can body 10.

[0013] The lower header 11 is arranged at the lower part of the can body 10. The lower ends of the plurality of water pipes 12 are connected to the lower header 11. The upper header 13 is arranged at the upper part of the can body 10. The upper ends of the plurality of water pipes 12 are connected to the upper header 13. Water W1 is supplied to the lower header 11 from a water supply line 500 described later. The water W1 supplied to the lower header 11 fills up to a predetermined height of the plurality of water pipes 12. The water W1 in the plurality of water pipes 12 is heated by the combustion gas generated by the combustion of fuel by the burner 20 to generate steam S1. The generated steam S1 flows into the upper header 13. There may be a state where water W1 and steam S1 exist in the upper header 13. Also, it may be in a form where water can be supplied from the upper header 13 to the water pipes 12.

[0014] The steam pressure detection unit 14 detects the steam pressure inside the can body 10 (hereinafter also referred to as "the pressure inside the can"). In the present embodiment, the steam pressure detection unit 14 is connected to the upper header 13 and detects the pressure inside the can. The steam pressure detection unit 14 is electrically connected to a control unit 40 described later, and the detection result of the steam pressure detection unit 14 can be acquired by the control unit 40. Note that the steam pressure detection unit 14 may be attached to a water level control cylinder (not shown) or a separator that separates steam and water, and may detect the steam pressure of the separator instead of the pressure inside the can. The water pipe temperature detection unit 15 is arranged at the upper part of at least one water pipe 12 and detects the temperature of the upper part of the water pipe 12. The water pipe temperature detection unit 15 is electrically connected to a control unit 40 described later, and the detection result of the water pipe temperature detection unit 15 can be acquired by the control unit 40.

[0015]

[0015] The scale monitor 16 is disposed at a position lower than the water level in the water pipe 12, that is, on the lower side of the water pipe 12, in at least one water pipe 12. When the water pipe temperature rises excessively due to the adhesion of scale to the inner surface of the water pipe 12, the water pipe 12 may be damaged due to the decrease in material strength at high temperatures. To prevent this, the scale monitor 16 is provided for the purpose of indirectly observing the scale adhesion situation inside the water pipe 12 based on the water pipe temperature. The scale monitor 16 is electrically connected to a control unit 40 described later, and the detection result of the scale monitor can be acquired by the control unit 40. In the case where two or more rows of water pipes 12 are arranged along the radial direction of the can body 10, it is preferable from the viewpoint of suppressing the temperature rise of the water pipe itself of the water pipe 12 that the scale monitor 16 is disposed at the lower side of the outer row of water pipes 12 and at a position inside the can body 10 in the radial direction.

[0016] The burner 20 burns fuel by supplying at least one of a first fuel F1 having a combustion speed faster than ammonia and an ammonia fuel F2 and combustion air in a combustion chamber B of the can body 10. The burner 20 is disposed at the upper part of the can body 10. The burner 20 includes a burner body 21 and a wind box 22. A first fuel supply line 100 and an ammonia fuel supply line 200 are connected to the burner body 21. A combustion air supply line 300 is connected to the wind box 22.

[0017]

[0016] In the present embodiment, first, the first fuel F1 and the combustion air A1 are supplied to the burner 20 to start combustion. Next, the ammonia fuel F2 is supplied toward the combustion region of the first fuel F1. At this time, a predetermined amount of combustion air A1 corresponding to the total amount of the first fuel F1 and the ammonia fuel F2 is supplied to the burner 20. In addition, in this embodiment, the first fuel F1 with a combustion speed faster than that of ammonia can use either liquid fuel or gaseous fuel. As the liquid fuel, oil fuel, alcohol fuel, etc. can be used. As the gaseous fuel, LNG, LPG, city gas (13A), etc. can be used.

[0018] The control unit 40 controls the combustion of the burner 20 of the ammonia co-firing boiler 1. Details of the control unit 40 will be described later.

[0019] The first fuel supply line 100 supplies the first fuel F1 from a first fuel supply source (not shown) to the burner 20. The upstream side of the first fuel supply line 100 is connected to the first fuel supply source, and the downstream side of the first fuel supply line 100 is connected to the burner 20. The first fuel supply line 100 includes, from the upstream side, a main valve 101, a first fuel flow sensor 102 as a first fuel detection unit, a first shut-off valve 103, a flow rate adjustment valve 104, and a second shut-off valve 105.

[0020] The main valve 101 is constituted by a manual valve and opens and closes the flow path of the first fuel supply line 100. The first fuel flow sensor 102 detects the flow rate of the first fuel F1 flowing through the first fuel supply line 100. The first fuel flow sensor 102 is electrically connected to the control unit 40, and the detection result of the first fuel flow sensor 102 can be acquired by the control unit 40. The first shut-off valve 103 and the second shut-off valve 105 are constituted by electromagnetic valves, open and close the flow path of the first fuel supply line 100, and supply or stop the first fuel F1. The first shut-off valve 103 and the second shut-off valve 105 are electrically connected to the control unit 40 and are controlled by a signal transmitted from the control unit 40. The flow rate adjustment valve 104 is an adjustment valve that adjusts the flow rate of the first fuel F1 supplied to the burner 20 by adjusting the opening degree of the valve. The flow rate adjustment valve 104 is electrically connected to the control unit 40 and is controlled by a signal transmitted from the control unit 40.

[0021] The ammonia fuel supply line 200 supplies ammonia fuel F2 from an ammonia fuel supply source (not shown) to the burner 20. The upstream side of the ammonia fuel supply line 200 is connected to the ammonia supply source, and the downstream side of the ammonia fuel supply line 200 is connected to the burner 20. The ammonia fuel supply line 200 includes, from the upstream side, a main valve 201, an ammonia fuel flow sensor 202 as an ammonia fuel detection unit, a first shut-off valve 203 as an ammonia fuel shut-off valve, a flow rate adjustment valve 204, and a second shut-off valve 205 as an ammonia fuel shut-off valve.

[0022] The main valve 201 is constituted by a manual valve and opens and closes the flow path of the ammonia fuel supply line 200. The ammonia fuel flow sensor 202 detects the flow rate of the ammonia fuel F2 flowing through the ammonia fuel supply line 200. The ammonia fuel flow sensor 202 is electrically connected to the control unit 40, and the detection result of the ammonia fuel flow sensor 202 can be acquired by the control unit 40.

[0023] The first shut-off valve 203 and the second shut-off valve 205 are constituted by electromagnetic valves, open and close the flow path of the ammonia fuel supply line 200, and supply or stop the ammonia fuel F2. The first shut-off valve 203 and the second shut-off valve 205 are electrically connected to the control unit 40 and are controlled by a signal transmitted from the control unit 40. The flow rate adjustment valve 204 is an adjustment valve that adjusts the flow rate of the ammonia fuel F2 supplied to the burner 20 by adjusting the opening degree of the valve. The flow rate adjustment valve 204 is electrically connected to the control unit 40 and is controlled by a signal transmitted from the control unit 40.

[0024] The combustion air supply line 300 supplies combustion air A1 to the burner 20. In this embodiment, the combustion air A1 is supplied to the windbox 22 of the burner 20. The upstream side of the combustion air supply line 300 is connected to the blower 301, and the downstream side of the combustion air supply line 300 is connected to the windbox 22. The combustion air supply line 300 includes, from the upstream side, the blower 301, the combustion air flow rate sensor 303, and the damper 304 as the combustion air adjustment unit.

[0025] The blower 301 supplies the combustion air A1 to the burner 20. The blower 301 includes a fan and a motor that rotates the fan, and the rotational speed of the motor can be adjusted by controlling the frequency with the inverter 302. In this embodiment, the inverter 302 is electrically connected to the control unit 40 and is controlled by a signal transmitted from the control unit 40.

[0026] The combustion air flow rate sensor 303 detects the flow rate of the combustion air A1 flowing through the combustion air supply line 300. The combustion air flow rate sensor 303 is electrically connected to the control unit 40, and the detection result of the combustion air flow rate sensor 303 can be obtained by the control unit 40. The damper 304 adjusts the supply amount of the combustion air A1 supplied to the burner 20 by adjusting the opening degree of the damper. Specifically, the damper 304 is rotatably arranged between a closed state in which the flow path of the combustion air supply line 300 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 300. The damper 304 is electrically connected to the control unit 40 and is controlled by a signal transmitted from the control unit 40.

[0027] The exhaust pipe 400 discharges the exhaust gas E1 generated by burning the first fuel F1 and the ammonia fuel F2 in the burner 20 to the outside of the can body 10. The upstream side of the exhaust pipe 400 is connected to the upper part of the peripheral surface of the can body 10, and the downstream side of the exhaust pipe 400 is open to the atmosphere. The exhaust pipe 400 includes an exhaust gas temperature detector 401 as a heating state detector.

[0028] The exhaust gas temperature detection unit 401 detects the temperature of the exhaust gas E1 flowing through the exhaust pipe 400. The exhaust gas temperature detection unit 401 is electrically connected to the control unit 40, and the detection result of the exhaust gas temperature detection unit 401 can be obtained by the control unit 40.

[0029] The water supply line 500 supplies water W1 from a water supply source (not shown) to the can body 10. The upstream side of the water supply line 500 is connected to the water supply source, and the downstream side of the water supply line 500 is connected to the lower header 11. The water supply line 500 is provided with an original valve 501. The original valve 501 is constituted by a manual valve and opens and closes the flow path of the water supply line 500.

[0030] The steam supply line 600 supplies steam S1 from the can body 10 to a load device (not shown). The upstream side of the steam supply line 600 is connected to the upper header 13 of the can body 10, and the downstream side of the steam supply line 600 is connected to the load device. The steam supply line 600 is provided with an original valve 601. The original valve 601 is constituted by a manual valve and opens and closes the flow path of the steam supply line 600.

[0031] As shown in FIG. 1, the control unit 40 includes a storage unit 41, a combustion control unit 42, and a reference temperature evaluation unit 43. The control unit 40 is constituted by 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 40 are realized by executing a predetermined software (program) stored in the storage unit 41, for example. Various functions of the control unit 40 may be realized by the cooperation of hardware and software, or may be realized only by hardware (electronic circuit). The storage unit 41 stores various kinds of information. In the present embodiment, the storage unit 41 stores a graph of the relationship between the internal pressure and the reference temperature of the can body 10 for each combustion amount.

[0032] Figure 2 is a graph showing the relationship between the in-cylinder pressure and the reference temperature for each combustion amount in the ammonia co-firing boiler 1 according to the embodiment, and shows the result of theoretical calculation under the condition of an air ratio of 1.31 (oxygen concentration in the exhaust gas: 5%). In the graph shown in Figure 2, the vertical axis represents the reference temperature [°C], and the horizontal axis represents the in-cylinder pressure [MPaG] of the cylinder body 10. The ammonia co-firing boiler 1 of the present embodiment is a boiler that can be set to a combustion amount of 25%, 50%, or 100% with respect to the maximum combustion amount, as shown in the graph of Figure 2. The reference temperature is the temperature at which the co-combustion of the first fuel and the ammonia fuel starts, and it is suitable to use the temperature of the exhaust gas at the outlet of the cylinder body under the condition that the cylinder body 10 has reached thermal equilibrium as the reference temperature. The temperature of the exhaust gas at the outlet of the cylinder body is detected by the exhaust gas temperature detection unit 401. Note that the graph shown in Figure 2 shows the relationship between the in-cylinder pressure and the reference temperature for each combustion amount in the ammonia co-firing boiler 1 of the present embodiment, and shows an example of the boiler of the present invention. Also, the air ratio used for calculating the reference temperature is preferably set according to the operating conditions of the ammonia co-firing boiler.

[0033] Here, the heat transfer amount Q [W] generated in the ammonia co-firing boiler 1 and the temperature Tg of the exhaust gas at the outlet of the cylinder body out can be expressed by the following formula. Q = G × cp × (Tg in - Tg out ) Q = K × A × ΔTm In the above formula, G is the exhaust gas flow rate [kg / s], cp is the specific heat of the exhaust gas [J / (kg·°C)], Tg in is the initial temperature of the combustion gas [°C], K is the overall heat transfer coefficient between the combustion gas and the water pipe 12 [W / (m 2 × °C)], A is the heat transfer area [m 2 , and ΔTm is the logarithmic mean temperature difference [°C].

[0034] Here, the heat transfer area A is constant for the same can body. The specific heat cp of the exhaust gas is almost constant regardless of the combustion amount if the composition of the exhaust gas E1 is the same. Also, due to the decrease in the combustion amount, the exhaust gas flow rate G decreases, and the overall heat transfer coefficient K between the combustion gas and the water pipe 12 decreases due to the decrease in the heat transfer performance accompanying the decrease in the combustion gas flow velocity. At this time, since the influence of the decrease in the exhaust gas flow rate G is greater than the influence of the decrease in the overall heat transfer coefficient K between the combustion gas and the water pipe 12, at low combustion amounts, the can body outlet temperature Tg out becomes lower. That is, due to the decrease in the exhaust gas flow rate accompanying the decrease in the combustion amount, the exhaust gas temperature becomes lower, and it is necessary to set the exhaust gas reference temperature lower. Note that the specific heat cp of the exhaust gas is almost constant regardless of the combustion amount if the exhaust gas composition is the same, but it slightly decreases as the temperature decreases. That is, due to the decrease in the combustion amount, the average temperature of the exhaust gas inside the ammonia co-firing boiler 1 decreases, and the specific heat cp of the exhaust gas also slightly decreases. Therefore, here, since the decrease amount of the specific heat cp of the exhaust gas is small, it is assumed to be almost constant as described above.

[0035] The reference temperature evaluation unit 43 determines the reference temperature at which the co-combustion of the first fuel F1 and the ammonia fuel F2 starts based on the combustion amount of the first fuel F1 and the detection result of the steam pressure detection unit 14. In the present embodiment, the reference temperature evaluation unit 43 determines, based on the set combustion amount of the first fuel F1 and the detection result of the steam pressure detection unit 14, from a graph showing the relationship between the in-can pressure and the reference temperature for each combustion amount as shown in FIG. 2, the reference temperature at which the co-combustion of the first fuel F1 and the ammonia fuel F2 starts.

[0036] The combustion control unit 42 controls the combustion of the burner 20. Also, the combustion control unit 42 starts the blower 301, adjusts either the inverter 302 or the damper 304, and supplies combustion air A1 with a predetermined flow rate to the burner 20. Further, after starting the combustion of the first fuel F1, the combustion control unit 42 controls to start the co-combustion of the first fuel F1 and the ammonia fuel F2 when the detection result of the exhaust gas temperature detection unit 401 exceeds the reference temperature. In this embodiment, the combustion control unit 42 starts the blower 301, adjusts either the inverter 302 or the damper 304, and supplies combustion air A1 with a predetermined flow rate to the burner 20. Further, the combustion control unit 42 opens the first shut-off valve 103 and the second shut-off valve 105, adjusts the flow rate adjustment valve 104, and supplies the first fuel F1 with a predetermined flow rate to the burner 20. Thereby, the burner 20 starts the combustion of the first fuel F1.

[0037] After the combustion control unit 42 starts the combustion of the first fuel F1, when the detection result of the exhaust gas temperature detection unit 401 exceeds the reference temperature determined by the reference temperature evaluation unit 43, the first shut-off valve 203 and the second shut-off valve 205 are opened, the flow rate adjustment valve 204 is adjusted, and ammonia fuel F2 with a predetermined flow rate is supplied to the burner 20. Thereby, the burner 20 starts the co-combustion of the first fuel F1 and the ammonia fuel F2. Therefore, the ammonia co-combustion boiler 1 can promptly start the combustion of ammonia while suppressing the generation of unburned substances.

[0038] Note that instead of the above-described exhaust gas temperature detection unit 401, the water pipe temperature detection unit 15 or the scale monitor 16 may be used as the heating state detection unit. At this time, individual references corresponding to the detection results of the water pipe temperature detection unit 15 or the scale monitor 16 are set as the reference temperature. After the combustion control unit 42 starts the combustion of the first fuel F1, when the detection result of the water pipe temperature detection unit 15 or the scale monitor 16 as the heating state detection unit exceeds the reference temperature, the combustion control unit 42 may control to start the co-combustion of the first fuel F1 and the ammonia fuel F2. Thereby, when the detection result of the water pipe temperature detection unit 15 or the scale monitor 16 exceeds the reference temperature and further the internal pressure of the ammonia co-combustion boiler 1 exceeds a predetermined value, by determining that ammonia co-combustion is possible, the remaining of unburned ammonia in the combustion gas can be suppressed.

[0039] Figure 3 is a graph schematically showing changes in the internal pressure of the can, the exhaust gas temperature, the water pipe temperature (superheat thermo), and the scale monitor temperature after combustion starts in a boiler that burns city gas (13A). In the graph shown in Figure 3, the "internal pressure of the can" is the internal pressure of the can body 10 detected by the vapor pressure detection unit 14, the "water pipe temperature" is the temperature detected by the water pipe temperature detection unit 15, the "scale monitor temperature" is the temperature detected by the scale monitor 16, and the "exhaust gas temperature" is the temperature of the exhaust gas E1 detected by the exhaust gas temperature detection unit 401. When the burner 20 starts combustion at high combustion from a situation where the can body 10 has not reached thermal equilibrium, such as during cold start-up, the internal pressure of the can, the temperature of the can body represented by the water pipe temperature and the scale monitor temperature, and the exhaust gas temperature rise rapidly. The water pipe temperature and the scale monitor temperature are affected by the increase in the heat transfer rate on the water side due to the start of boiling of the water in the water pipe, and the gradient of the temperature rise becomes slightly gentler. Then, as time passes, first the internal pressure of the can approaches a steady state and the rise becomes gentle, and then the rising speed of the water pipe temperature and the scale monitor temperature decreases. Even after the water pipe temperature and the scale monitor temperature reach equilibrium, the temperature of a caster or the like with a large heat capacity continues to rise, so the exhaust gas temperature continues to rise for a while.

[0040] Therefore, in order for the can body 10 to be in a sufficiently preheated state and stably start the combustion of ammonia, it is preferable to start the ammonia co-combustion after the exhaust gas temperature reaches the reference temperature. As shown in Figure 3, the exhaust gas temperature detected by the exhaust gas temperature detection unit 401 is affected by the water supply, decreases during water supply, and then repeats the fluctuation of rising. For this reason, the determination of the start of ammonia co-combustion is preferably performed based on the average value of the exhaust gas temperature detected by the exhaust gas temperature detection unit 401 for a predetermined time, or the exhaust gas temperature detected by the exhaust gas temperature detection unit 401 after a predetermined time has elapsed since the water supply.

[0041] Further, when the water pipe temperature detection unit 15 or the scale monitor 16 is used as the heating state detection unit and the start of co-combustion of ammonia is determined based on the detected temperatures thereof, it is desirable that the combustion control unit 42 perform control so as to start ammonia co-combustion after a predetermined time has elapsed since the temperature detected by the water pipe temperature detection unit 15 or the scale monitor 16 has reached the reference temperature. Further, the exhaust gas temperature detected by the exhaust gas temperature detection unit 401 varies depending on the fuel amount. Therefore, when starting ammonia co-combustion when the first fuel F1 is in low combustion, the combustion control unit 42 performs control so as to start ammonia co-combustion based on the reference temperature for low combustion.

[0042] In addition, in the above-described embodiment, the combustion control unit 42 may be configured to perform control so as to start co-combustion of the first fuel F1 and the ammonia fuel F2 when the detection result of the steam pressure detection unit 14 exceeds a predetermined value and the detection result of the exhaust gas temperature detection unit 401 exceeds the reference temperature. Even in such a configuration, the combustion control unit 42 starts the blower 301, adjusts either the inverter 302 or the damper 304, and supplies combustion air A1 having a predetermined flow rate to the burner 20. Further, the combustion control unit 42 opens the first shut-off valve 103 and the second shut-off valve 105, adjusts the flow rate adjustment valve 104, and supplies the first fuel F1 having a predetermined flow rate to the burner 20. Thereby, the burner 20 starts combustion of the first fuel F1.

[0043] After starting the combustion of the first fuel F1, when the detection result of the steam pressure detection unit 14 exceeds a predetermined value and the detection result of the exhaust gas temperature detection unit 401 exceeds the reference temperature determined by the reference temperature evaluation unit 43, the combustion control unit 42 opens the first shut-off valve 203 and the second shut-off valve 205, adjusts the flow rate adjustment valve 204, and supplies ammonia fuel F2 with a predetermined flow rate to the burner 20. Thereby, the burner 20 starts the co-combustion of the first fuel F1 and the ammonia fuel F2. When the detection result of the exhaust gas temperature detection unit 401 exceeds the reference temperature and further when the internal pressure of the ammonia co-combustion boiler 1 exceeds a predetermined value, by determining that the ammonia co-combustion can be started by the combustion control unit 42, it is possible to more reliably suppress the remaining unburned substances of ammonia in the combustion gas.

[0044] According to the ammonia co-combustion boiler 1 described above, the following effects are achieved.

[0045] (1) The ammonia co-combustion boiler 1 of the present embodiment is supplied with at least one of the first fuel F1 and the ammonia fuel F2 having a combustion rate faster than that of ammonia, and combustion air A1, and includes a burner 20 that burns the fuel, a boiler body 10 that recovers heat from the combustion gas generated by the combustion of the fuel by the burner 20 and generates steam, a steam pressure detection unit 14 that detects the steam pressure (internal pressure of the boiler body) inside the boiler body 10, a heating state detection unit that detects the heating state of the boiler body 10, and a control unit 40. The control unit 40 includes a combustion control unit 42 that controls the combustion of the burner 20, and a reference temperature evaluation unit 43 that determines a reference temperature for starting the co-combustion of the first fuel F1 and the ammonia fuel F2 based on the combustion amount of the first fuel F1 and the detection result of the steam pressure detection unit 14. After starting the combustion of the first fuel F1, when the detection result of the heating state detection unit exceeds the reference temperature, the combustion control unit 42 controls to start the co-combustion of the first fuel F1 and the ammonia fuel F2. In a situation where the temperature of the burner 20 and the temperature inside the ammonia co-firing boiler 1 are low, the temperature of the combustion gas from the co-firing of the first fuel F1 and the ammonia fuel F2 does not rise sufficiently, and there is a high possibility that unburned substances of ammonia remain in the combustion gas. In order to suppress the remaining unburned substances of ammonia, it is effective to start the co-firing of the first fuel F1 and the ammonia fuel F2 after the temperature of the burner 20 and the temperature inside the ammonia co-firing boiler 1 have risen. In order to determine whether the temperature of the burner 20 and the temperature inside the ammonia co-firing boiler 1 have risen, the reference temperature evaluation unit 43 determines a reference temperature based on the combustion amount of the first fuel F1 and the detection result of the steam pressure detection unit 14. When the detection result of the heating state detection unit exceeds the reference temperature determined by the reference temperature evaluation unit 43, it is determined that ammonia co-firing is possible, and the co-firing of the first fuel F1 and the ammonia fuel F2 is started. Thereby, while reducing the unburned substances of ammonia in the remaining combustion gas due to the decrease in the temperature of the combustion gas from the co-firing of the first fuel F1 and the ammonia fuel F2, it is possible to effectively reduce carbon dioxide generated from fuels with a higher combustion rate than ammonia. Also, thereby, the ammonia co-firing boiler 1 can promptly start the combustion of ammonia while suppressing the generation of unburned substances.

[0046] (2) The ammonia co-firing boiler 1 described in (1) is controlled by the combustion control unit 42 to start the co-firing of the first fuel F1 and the ammonia fuel F2 when the detection result of the steam pressure detection unit 14 exceeds a predetermined value and the detection result of the exhaust gas temperature detection unit 401 exceeds the reference temperature. Thereby, it is possible to more reliably suppress the remaining unburned substances of ammonia in the combustion gas.

[0047] (Modified form) As described above, the preferred embodiments of the ammonia co-firing boiler 1 according to the present invention have been described. However, the present invention is not limited to the above-described embodiments and can be appropriately modified.

[0048] (1) The ammonia fuel F2 may be ammonia or a gas fuel mainly composed of ammonia.

[0049] (2) In the above-described embodiment, an example was shown in which the flow rates of the first fuel F1 and the ammonia fuel F2 are detected by the flow sensors (the first fuel flow sensor 102 and the ammonia fuel flow sensor 202). However, this flow sensor may detect the mass flow rate, or may be a flow sensor that detects the flow rate using other flow measurement methods, for example, a flow sensor that detects the flow rate using the differential pressure before and after a pressure loss portion provided in the flow path.

[0050] (3) In the above-described embodiment, an example was shown in which the ammonia co-firing boiler 1 controls the opening degree of the flow rate adjustment valve by a signal from the control unit 40 to adjust the combustion amounts of the first fuel F1 and the ammonia fuel F2. However, the present invention is not limited to this. For example, the combustion air flow rate may be controlled by a signal from the control unit 40, the pressure of the combustion air and the pressure of each fuel may be made equal, and the combustion amounts of the first fuel F1 and the ammonia fuel F2 may be adjusted by the equal pressure valve method in which the mixing ratio is made constant. In this case, since the flow rate of the first fuel F1 can be controlled without going through the control unit 40, there is an effect that the control of the fuel flow rate can be simplified.

[0051] (4) In the above-described embodiment, an example was shown in which the combustion control unit 42 starts the blower 301 and adjusts either the inverter 302 or the damper 304 to supply combustion air A1 having a predetermined flow rate to the burner 20. However, the present invention is not limited to this. The combustion control unit 42 may adjust both the inverter 302 and the damper 304. Further, the ammonia co-firing boiler 1 is provided with an exhaust gas oxygen concentration detection unit (not shown), and the combustion control unit 42 adjusts at least one of the inverter 302 or the damper 304 so that the detection result of the exhaust gas oxygen concentration detection unit becomes a predetermined oxygen concentration, and may control the combustion air amount.

[0052] (5) In the above-described embodiment, the reference temperature evaluation unit 43 determines the reference temperature for starting the co-combustion of the first fuel F1 and the ammonia fuel F2 from the graph showing the relationship between the internal pressure of the can body 10 and the reference temperature for each combustion amount as shown in FIG. 2 based on the set combustion amount of the first fuel F1 and the detection result of the vapor pressure detection unit 14. However, the present invention is not limited to this. For example, the storage unit 41 stores a calculation formula corresponding to the relationship between the internal pressure of the can body 10 and the reference temperature for each combustion amount, and the reference temperature evaluation unit 43 calculates and determines the reference temperature from the calculation formula corresponding to the relationship between the internal pressure of the can body 10 and the reference temperature for each combustion amount based on the combustion amount of the first fuel F1 and the detection result of the vapor pressure detection unit 14. Alternatively, the storage unit 41 stores a data table of the relationship between the internal pressure of the can body 10 and the reference temperature for each combustion amount, and the reference temperature evaluation unit 43 determines the reference temperature from a graph or data table corresponding to the relationship between the internal pressure of the can body 10 and the reference temperature for each combustion amount based on the combustion amount of the first fuel F1 and the detection result of the vapor pressure detection unit 14. Note that the reference temperature evaluation unit 43 is not limited to the example of determining the reference temperature from a graph, data table, or calculation formula corresponding to the relationship between the internal pressure of the can body 10 and the reference temperature for each combustion amount. The reference temperature may also be determined by multiplying a constant coefficient by a graph, data table, or calculation formula corresponding to the relationship between the internal pressure of the can body 10 and the reference temperature for each combustion amount. Thereby, the remaining unburned ammonia in the combustion gas can be more reliably suppressed. Furthermore, the reference temperature evaluation unit 43 may calculate the heat balance of the ammonia co-firing boiler 1 to determine the reference temperature.

[0053] (6) In the above-described embodiment, the ammonia co-firing boiler 1 is exemplified as a steam boiler, but it is not limited thereto, and other boilers may be used. For example, the ammonia co-firing boiler 1 of the present invention may be a hot water boiler or a heat medium boiler. In addition, the present invention stably starts ammonia co-firing and is particularly effective in boilers that have a higher frequency of starting and stopping combustion in normal use compared to power generation boilers, such as small-scale once-through boilers and small-scale once-through boilers. Further, the present invention may be a furnace tube smoke tube boiler. Furthermore, in the above-described embodiment, the ammonia co-firing boiler 1 is shown as using gaseous fuel as the first fuel, but it is not limited thereto, and liquid fuel such as A heavy oil may be used.

[0054] In addition, since the present invention promotes the use of ammonia that does not emit carbon dioxide as 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".

Explanation of Signs

[0055] 1 Ammonia co-firing boiler 10 Can body 14 Steam pressure detection unit 20 Burner 40 Control unit 42 Combustion control unit 43 Reference temperature evaluation unit 401 Exhaust gas temperature detection unit (heating state detection unit) A1 Combustion air F1 First fuel F2 Ammonia fuel

Claims

1. A burner that is supplied with at least one of a first fuel having a combustion rate faster than ammonia and an ammonia fuel, and combustion air, and burns the fuel; A can body that recovers heat from the combustion gas generated by the combustion of the fuel by the burner and generates steam; A steam pressure detection unit that detects the internal steam pressure of the can body; A heating state detection unit that detects the heating state of the can body; A control unit, and is provided with: The control unit: A combustion control unit that controls the combustion of the burner; A reference temperature evaluation unit that determines a reference temperature for starting co-combustion of the first fuel and the ammonia fuel based on the combustion amount of the first fuel and the detection result of the steam pressure detection unit; And is provided with: The combustion control unit: After starting the combustion of the first fuel, when the detection result of the heating state detection unit exceeds the reference temperature, it controls to start co-combustion of the first fuel and the ammonia fuel, a boiler.

2. The combustion control unit: When the detection result of the steam pressure detection unit exceeds a predetermined value and the detection result of the heating state detection unit exceeds the reference temperature, it controls to start co-combustion of the first fuel and the ammonia fuel, The boiler according to Claim 1.

Images