Boiler

Abstract

To provide a boiler that can stabilize a flow of liquid ammonia in an injection nozzle.SOLUTION: A boiler comprises: a furnace including a furnace wall; and a combustion device comprising a liquefied fuel supply line, an injection nozzle constituted so as to inject liquid ammonia in a liquid state into the furnace, and a liquefied fuel supply passage for guiding the liquid ammonia supplied through the liquefied fuel supply line, to the injection nozzle. The combustion device may comprise heating means for heating the liquid ammonia, and may heat the liquid ammonia to inject it into the furnace.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present disclosure relates to boilers. [Background technology]

[0002] Conventionally, there is known a two-fluid injection nozzle that atomizes liquid fuel with steam and injects it. For example, in Patent Document 1, oil is used as the liquid fuel, and the oil and steam are mixed at the tip of the two-fluid injection nozzle and injected. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Microfilm of Utility Model Application No. 59-007564 (Utility Model Application No. 60-122623) Summary of the Invention [Problem to be solved by the invention]

[0004] From the viewpoint of stabilizing the flow of liquid fuel, it is preferable to suppress vapor lock, in which liquid fuel vaporizes inside the two-fluid injection nozzle, but the above-mentioned patent documents do not disclose a configuration for achieving this.

[0005] An object of the present disclosure is to provide a boiler that can stabilize the flow of liquid ammonia within the injection nozzle. [Means for solving the problem]

[0006] A boiler according to at least one embodiment of the present disclosure includes: a furnace including a furnace wall; A combustion device having a liquefied fuel supply line, an injection nozzle configured to inject liquid ammonia into the inside of the furnace while it is in a liquid state, and a liquefied fuel supply path that guides the liquid ammonia supplied through the liquefied fuel supply line to the injection nozzle; Equipped with. Effect of the Invention

[0007] According to the present disclosure, a boiler capable of stabilizing the flow of liquid ammonia within an injection nozzle can be provided. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic configuration diagram of a combustion system according to an embodiment of the present disclosure. [Diagram 2] FIG. 2 is a conceptual configuration diagram of a supply unit according to an embodiment of the present disclosure. [Diagram 3] 4 is a graph conceptually showing a relationship between a flow rate of liquefied fuel injected from a two-fluid injection nozzle according to an embodiment of the present disclosure and a supply pressure of the liquefied fuel. [Figure 4] FIG. 1 is a schematic diagram of a burner according to an embodiment of the present disclosure. [Diagram 5] 4 is a graph conceptually illustrating a relationship between the supply pressure and the injection flow rate of the liquefied fuel according to an embodiment of the present disclosure. [Figure 6] FIG. 1 is a schematic explanatory diagram of a two-fluid jet nozzle according to an embodiment of the present disclosure. [Figure 7] FIG. 2 is a schematic illustration of a backplate according to an embodiment of the present disclosure. [Figure 8] 1 is a flow chart illustrating a method for delivering liquefied fuel and atomized fluid according to one embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] An embodiment of the present disclosure will be described below with reference to the drawings. Note that the present invention is not limited to this embodiment, and when there are multiple embodiments, the present invention also includes a configuration in which each embodiment is combined. In the following description, up and above refer to the upper side in the vertical direction, and down and below refer to the lower side in the vertical direction, and the vertical direction is not precise and includes an error. Furthermore, the dimensions, materials, shapes, relative arrangements, and the like of the components described as the embodiments or shown in the drawings are merely illustrative examples and are not intended to limit the scope of the present disclosure. For example, expressions expressing relative or absolute configuration, such as "in a certain direction," "along a certain direction," "parallel," "orthogonal," "center," "concentric," or "coaxial," not only strictly express such a configuration, but also express a state in which there is a relative displacement with a tolerance or an angle or distance to the extent that the same function is obtained. For example, expressions indicating that things are in an equal state, such as "identical," "equal," and "homogeneous," not only indicate a state of strict equality, but also indicate a state in which there is a tolerance or a difference to the extent that the same function is obtained. For example, expressions describing shapes such as a rectangular shape or a cylindrical shape do not only refer to rectangular shapes, cylindrical shapes, etc. in the strict geometric sense, but also refer to shapes that include uneven portions, chamfered portions, etc., to the extent that the same effect is obtained. On the other hand, the expressions "comprise", "include", or "have" a certain element are not exclusive expressions excluding the presence of other elements. In addition, the same components are denoted by the same reference numerals and the description thereof may be omitted.

[0010] <1. Overall configuration of combustion system 1> FIG. 1 is a schematic diagram showing a combustion system including a boiler using solid fuel and liquefied fuel as main fuels according to this embodiment. The liquefied fuel is a fuel that is in a gas phase at room temperature under atmospheric pressure. The room temperature referred to in this specification is 35°C. The liquefied fuel is, for example, petroleum (light oil or liquefied petroleum gas), liquefied natural gas, dimethyl ether, liquid ammonia, etc. In the following description, unless otherwise specified, the liquefied fuel refers to liquid ammonia.

[0011] The boiler 10 of the combustion system 1 of this embodiment is a boiler that can burn pulverized fuel made by pulverizing solid fuel and liquefied fuel with a burner and exchange the heat generated by this combustion with feed water or steam to generate superheated steam. Biomass fuel, coal, etc. are used as the solid fuel.

[0012] The boiler 10 has a furnace 11, combustion devices 20 and 50, and a combustion gas passage 12. The furnace 11 has a hollow rectangular cylinder shape and is installed vertically. The furnace wall 101 constituting the inner wall surface of the furnace 11 is composed of a plurality of heat transfer tubes and fins connecting the heat transfer tubes, and recovers heat generated by the combustion of pulverized fuel by heat exchange with water and steam flowing inside the heat transfer tubes, while suppressing the temperature rise of the furnace wall 101.

[0013] The combustion devices 20 and 50 are installed in the lower region of the furnace 11. In this embodiment, the combustion device 20 is configured to inject pulverized fuel into the inside of the furnace 11. In addition, the combustion device 50 is configured to atomize liquefied fuel with an atomizing fluid (atomizing medium) and inject the atomized fuel into the inside of the furnace 11. The atomizing fluid in this embodiment is atomizing steam.

[0014] The combustion device 20 has a plurality of burners 21 attached to the furnace wall 101, and the combustion device 50 has a plurality of burners 51. An injection nozzle (not shown) configured to inject pulverized fuel into the furnace 11 is provided at the tip of each burner 21. In addition, a two-fluid injection nozzle 59 (see FIG. 4) configured to atomize liquefied fuel with an atomizing fluid and inject the atomized fuel into the furnace 11 is provided at the tip of each burner 51. The burners 21, 51 are arranged at equal intervals along the circumferential direction of the furnace 11 (for example, four burners installed at each corner of the rectangular furnace 11) as one set, and are arranged in multiple tiers along the vertical direction. In the example of FIG. 1, one set of burners 21 is arranged in two tiers, and one set of burners 51 is arranged in four tiers. Note that, for convenience of illustration, FIG. 1 shows only two burners of one set, and each set is given the reference numerals 21, 51. The shape of the furnace, the number of burner tiers, the number of burners in one tier, the arrangement of the burners, etc. are not limited to this embodiment.

[0015] The burners 21 of the combustion device 20 are connected to a plurality of mills (pulverizers) 31A, 31B (hereinafter, sometimes collectively referred to as "mills 31") via a plurality of pulverized fuel supply pipes 22A, 22B (hereinafter, sometimes collectively referred to as "pulverized fuel supply pipes 22"). The mill 31 is, for example, a vertical roller mill in which a pulverizing table (not shown) is supported inside so as to be rotatable and a plurality of pulverizing rollers (not shown) are supported above the pulverizing table so as to be rotatable in conjunction with the rotation of the pulverizing table. The solid fuel pulverized by the cooperation of the pulverizing rollers and the pulverizing table is transported to a classifier (not shown) provided in the mill 31 by primary air (carrier gas, oxidizing gas) supplied to the mill 31. In the classifier, the fuel is classified into pulverized fuel having a particle size equal to or smaller than that suitable for combustion in the burner 21 and coarse pulverized fuel having a particle size larger than the particle size. The pulverized fuel passes through the classifier and is supplied to the burner 21 via the pulverized fuel supply pipe 22 together with the primary air. The coarse fuel powder that does not pass through the classifier falls under its own weight onto the grinding table inside the mill 31 and is re-ground.

[0016] The burner 51 of the combustion device 50 is connected to the supply unit 90. The supply unit 90 includes an atomized fluid supply unit 60 for a two-fluid injection nozzle configured to supply an atomized fluid to the combustion device 50 (hereinafter, may be simply referred to as the "atomized fluid supply unit 60"), and a liquefied fuel supply unit 70 for a two-fluid injection nozzle configured to supply a liquefied fuel to the combustion device 50 (hereinafter, may be simply referred to as the "liquefied fuel supply unit 70"). A controller 110 acquires a required injection flow rate of the liquefied fuel in the burner 51, which is determined according to the combustion load in the boiler 10. The controller 110 sends a control command according to the required injection flow rate to the supply unit 90, so that the atomized fluid supply unit 60 and the liquefied fuel supply unit 70 can adjust the supply amount of the atomized fluid and the liquefied fuel, respectively. The configuration of the supply unit 90 will be described in detail later. The required injection flow rate of the liquefied fuel is the required injection flow rate of the liquefied fuel per one two-fluid injection nozzle 59 (see FIG. 4) of each burner 51.

[0017] An air register 23 is provided on the outside of the furnace 11 at the mounting positions of the burners 21, 51, and one end of an air duct (air duct) 24 is connected to the air register 23. A forced draft fan (FDF: Forced Draft Fan) 32 is connected to the other end of the air duct 24. The air supplied from the forced draft fan 32 is heated by an air preheater 42 installed in the air duct 24 (details will be described later), and is supplied to the burner 21 via the air register 23 as secondary air (combustion air, oxidizing gas), and is introduced into the furnace 11.

[0018] The combustion gas passage 12 is connected to the vertical upper part of the furnace 11. The combustion gas passage 12 is provided with superheaters 102A, 102B, and 102C (hereinafter, sometimes collectively referred to as "superheaters 102"), reheaters 103A and 103B (hereinafter, sometimes collectively referred to as "reheaters 103"), and a coal economizer 104 as heat exchangers for recovering heat from the combustion gas, and heat is exchanged between the combustion gas generated in the furnace 11 and feed water or steam flowing inside each heat exchanger. The arrangement and shape of each heat exchanger are not limited to the form shown in FIG. 1.

[0019] A flue 13 is connected to the downstream side of the combustion gas passage 12, and discharges the combustion gas whose heat has been recovered by the heat exchanger. An air preheater (air heater) 42 is provided between the flue 13 and the air duct 24, and heat is exchanged between the air flowing through the air duct 24 and the combustion gas flowing through the flue 13, thereby heating the primary air supplied to the mill 31 and the secondary air supplied to the burner 21, thereby recovering further heat from the combustion gas after heat exchange with water and steam.

[0020] Furthermore, a denitration device 43 may be provided in the flue 13 at a position upstream of the air preheater 42. The denitration device 43 supplies a reducing agent having an effect of reducing nitrogen oxides, such as ammonia or urea water, to the combustion gas flowing through the flue 13, and promotes a reaction between the nitrogen oxides (NOx) in the combustion gas to which the reducing agent has been supplied and the reducing agent by the catalytic action of a denitration catalyst provided in the denitration device 43, thereby removing and reducing the nitrogen oxides in the combustion gas. A gas duct 41 is connected to the flue 13 downstream of the air preheater 42. The gas duct 41 is provided with environmental equipment such as a dust collector 44, such as an electrostatic precipitator, for removing ash and the like from the combustion gas, a desulfurization equipment 46 for removing sulfur oxides, and an induced draft fan (IDF) 45 for directing the exhaust gas to these environmental equipment. The downstream end of the gas duct 41 is connected to a chimney 47, and the combustion gas treated in the environmental equipment is discharged to the outside of the system as exhaust gas.

[0021] In the boiler 10, when the multiple mills 31 are driven, pulverized and classified pulverized fuel is supplied to the burner 21 together with primary air via the pulverized fuel supply pipe 22. In addition, the atomized fluid supply unit 60 and the liquefied fuel supply unit 70 supply the atomized fluid and liquefied fuel to the burner 51, respectively. Furthermore, secondary air heated by the air preheater 42 is supplied to the burners 21 and 51 from the air duct 24 via the air register 23. The burner 21 injects a pulverized fuel mixture, which is a mixture of pulverized fuel and primary air, into the furnace 11, and also injects secondary air into the furnace 11. The pulverized fuel mixture injected into the furnace 11 ignites and reacts with the secondary air to form a flame. The burner 51 injects the secondary air into the furnace 11 together with the liquefied fuel atomized by the atomizing fluid. The liquefied fuel injected into the furnace 11 vaporizes into fuel gas, which reacts with the secondary air and burns. High-temperature combustion gas generated by the combustion of pulverized fuel and fuel gas rises within the furnace 11 and flows into the combustion gas passage 12. The timing for injecting the liquefied fuel into the furnace 11 may be after the temperature inside the furnace 11 has risen to a certain temperature by the combustion of the pulverized fuel. For example, after the pulverized fuel is exclusively burned at the start of the boiler 10, the liquefied fuel may be injected into the furnace 11, and the pulverized fuel may be mixed with the fuel gas vaporized from the liquefied fuel and the pulverized fuel. After that, the injection of the pulverized fuel may be stopped, and the liquefied fuel may be exclusively burned. In addition, in this embodiment, air is used as the oxidizing gas (primary air, secondary air), but the oxidizing gas may have a higher or lower oxygen content than air, and stable combustion in the furnace 11 can be achieved by adjusting the ratio of the amount of oxygen to the amount of fuel supplied within an appropriate range.

[0022] The combustion gas flowing into the combustion gas passage 12 exchanges heat with water and steam in a superheater 102, a reheater 103, and a coal economizer 104 arranged inside the combustion gas passage 12, and is then discharged into the flue 13, where nitrogen oxides are removed in a denitration device 43, and the combustion gas exchanges heat with primary air and secondary air in an air preheater 42, and is then discharged into a gas duct 41, where ash and the like are removed in a dust collector 44, and sulfur oxides are removed in a desulfurization device 46, and the combustion gas is then discharged to the outside of the system from a chimney 47. Note that the arrangement of the heat exchangers in the combustion gas passage 12 and the devices from the flue 13 to the gas duct 41 with respect to the combustion gas flow does not necessarily have to be in the order described above.

[0023] In the above-described embodiment, the boiler of the present disclosure has been described as a boiler that uses solid fuel and liquefied fuel as fuel. The solid fuel used in the boiler may be coal, biomass fuel, petroleum coke (PC), petroleum residue, or the like. The fuel for the boiler combined with liquefied fuel is not limited to solid fuel, but can also be liquid fuel such as petroleum such as heavy oil, light oil, and heavy oil, and industrial waste liquid. In addition, gaseous fuels such as natural gas, various petroleum gases, and by-product gases generated in the steelmaking process can also be used. Furthermore, the present invention can be applied to a multi-fuel boiler that uses a combination of these various fuels.

[0024] 2. Configuration of the liquefied fuel supply unit 70 With reference to Fig. 2, a configuration of a liquefied fuel supply unit 70, which is a component of the above-mentioned supply unit 90, is illustrated. Fig. 2 is a conceptual configuration diagram of a supply unit according to an embodiment of the present disclosure. Note that in Fig. 2, the combustion device 20 (see Fig. 1) is omitted for ease of viewing.

[0025] The liquefied fuel supply unit 70 includes a storage section 79 for storing liquefied fuel, a liquefied fuel supply line 75 for supplying the liquefied fuel stored in the storage section 79 to the two-fluid injection nozzle 59 of the burner 51, a heater 76 provided in the liquefied fuel supply line 75, and a liquefied fuel adjustment section 78 provided in the liquefied fuel supply line 75.

[0026] The storage section 79 stores liquid ammonia, which is an example of liquefied fuel. The downstream end of the liquefied fuel supply line 75 is connected to the liquefied fuel supply passage 57, which is a component of the two-fluid injection nozzle 59 provided in each of the burners 51. A return passage 752 is provided in the upstream portion of the liquefied fuel supply line 75 to return a portion of the liquefied fuel supplied to the storage section 79. The heater 76 is configured to heat the liquefied fuel to a certain temperature that does not vaporize the liquefied fuel. As an example, the heat source of the heater 76 is auxiliary steam, which is a portion of the steam generated in the combustion system 1. The liquefied fuel injected into the furnace 11 is easily vaporized by the heating by the heater 76, and misfire in the furnace 11 can be suppressed. In addition, based on the measurement result of the thermometer 175 for measuring the temperature of the liquefied fuel heated by the heater 76, the adjustment valve 81 provided in the flow path of the auxiliary steam is adjusted, and the amount of heat of the liquefied fuel in the heater 76 is adjusted. In this example, this adjustment is performed by the controller 110.

[0027] The liquefied fuel adjusting unit 78 is configured to adjust the supply pressure and flow rate of the liquefied fuel according to the required injection flow rate of the liquefied fuel described above. The liquefied fuel adjusting unit 78 of this embodiment is a plurality of control valves 781 with different capacities provided in parallel in the return path 752 and a control valve 782 provided in the liquefied fuel supply line 75. The control valve 781 is, for example, a pressure adjustment valve, and the control valve 782 is, for example, a flow rate adjustment valve. In this example, the plurality of control valves 781 and the control valve 782 are controlled by the controller 110 based on the respective measurement results of the pressure gauge 173 provided downstream of the branch point of the liquefied fuel supply line 75 with the return path 752 and the flow meter 176 provided upstream of the branch point with the liquid fuel supply path 57. As a more specific example, the controller 110 controls the plurality of control valves 781 and the control valve 782 based on the respective measurement results of the pressure gauge 173 and the flow meter 176 so that the liquefied fuel is supplied to the burner 51 at a flow rate corresponding to the required injection flow rate.

[0028] In other embodiments, the liquefied fuel supply unit 70 does not need to include the storage section 79. For example, the liquefied fuel supply line 75 may be connected by a pipeline to a ship such as a large tank truck that stores liquefied fuel or a facility that produces liquefied fuel.

[0029] 3. Configuration of atomizing fluid supply unit 60 2, the configuration of the atomized fluid supply unit 60, which is a component of the above-mentioned supply unit 90, is illustrated. The atomized fluid supply unit 60 includes an atomized fluid supply line 55 for supplying an atomized fluid to the two-fluid injection nozzle 59 of the burner 51, a desuperheater 53 provided in the atomized fluid supply line 55, and an atomized fluid adjustment unit 58 provided in the atomized fluid supply line 55. The atomized fluid supply line 55 is connected to an atomized fluid supply passage 52, which is a component of the two-fluid injection nozzle 59 provided in each of the multiple burners 51.

[0030] The desuperheater 53 is configured to desuperheat the atomized fluid to a certain temperature using a cooling medium having a lower temperature than the atomized fluid. In this embodiment, the atomized fluid is steam, and the desuperheater 53 desuperheats the atomized fluid by mixing it with spray water. For example, the spray water adjustment valve 54 provided in the spray water pipe is controlled by the controller 110 based on the measurement result of a thermometer 161 provided downstream of the desuperheater 53.

[0031] The atomized fluid adjusting unit 58 is configured to adjust the supply pressure of the atomized fluid in accordance with the required injection flow rate of the liquefied fuel described above. The atomized fluid adjusting unit 58 in this embodiment is a plurality of control valves 581 with different capacities that are arranged in parallel downstream of the desuperheater 53. In this example, the plurality of control valves 581 are controlled based on the measurement result of a pressure gauge 182 that is arranged downstream of the atomized fluid adjusting unit 58. More specifically, as an example, the controller 110 controls each of the plurality of control valves 581 based on the measurement result of the pressure gauge 182 so that the atomized fluid having a pressure corresponding to the required injection flow rate of the liquefied fuel is supplied to the burner 51.

[0032] <4.2 Flow rate control of liquefied fuel in fluid injection nozzle 59> 3, a detailed example of flow rate control of the liquefied fuel in the two-fluid injection nozzle 59 will be illustrated. Fig. 3 is a graph conceptually showing a relationship between the flow rate of the liquefied fuel injected from the two-fluid injection nozzle according to an embodiment of the present disclosure and the supply pressure of the liquefied fuel. The horizontal axis of the graph in FIG. 3 represents the flow rate (Q) of the liquefied fuel injected from the two-fluid injection nozzle 59. The vertical axis of the graph indicates the supply pressure (Pf) of the liquefied fuel. Pf0 and Pf1 on the vertical axis are the lower limit pressure and the upper limit pressure of the liquefied fuel for realizing stable combustion in the burner 51, respectively. V is the lower limit supply pressure for stably supplying the liquefied fuel to the burner 51, and is a value according to the vapor pressure of the liquefied fuel at the temperature of the liquefied fuel heated by the heater 76.

[0033] Graph line A, which is conceptually drawn in the graph, shows the relationship between the flow rate and the supply pressure of the liquefied fuel when the supply pressure (Pa) of the atomized fluid is Pa1. Graph lines B and C show the relationship between the flow rate and the supply pressure of the liquefied fuel when the supply pressure (Pa) of the atomized fluid is Pa2 and Pa3, respectively. Note that the following formula (1) holds for the supply pressure (Pa) of the atomized fluid. Pa1>Pa2>Pa3 (1) The atomizing supply pressure (Pa) does not necessarily have to be three pressures, and it is possible to control with more or less pressures. Also, it is acceptable for the minimum pressure Pa to be zero, that is, for no atomizing fluid to be supplied.

[0034] In this embodiment, the supply pressure of the liquid fuel and the supply pressure of the atomizing fluid are changed to adjust the flow rate of the liquefied fuel injected from the two-fluid injection nozzle 59. Details of this will be described below using as an example a case in which the flow rate of the liquefied fuel decreases from the state indicated by point J1 on the graph to the state indicated by point J4.

[0035] First, the liquefied fuel adjusting unit 78 maintains the supply pressure (Pf) of the liquefied fuel at Pf1, while the atomized fluid adjusting unit 58 increases the supply pressure (Pa) of the atomized fluid from Pa3 to Pa2. As a result, the flow rate Q of the liquefied fuel decreases from Q4 to Q3 (point J2). At this time, the supply pressure of the liquefied fuel is maintained, so the flow of the liquefied fuel is likely to be stabilized. Thereafter, the atomized fluid adjusting unit 58 maintains the supply pressure of the atomized fluid at Pa2, while the liquefied fuel adjusting unit 78 changes the supply pressure of the liquefied fuel from Pf1 to Pf d (Pf d is Pf V This reduces the flow rate of the liquefied fuel (point J3). Furthermore, the liquefied fuel adjusting unit 78 adjusts the supply pressure of the liquefied fuel to Pf d While maintaining the pressure at the nozzle 51 at point J2, the atomized fluid adjusting unit 58 increases the supply pressure of the atomized fluid from Pa2 to Pa1, thereby decreasing the flow rate of the liquefied fuel (point J4).

[0036] The advantages of controlling the flow rate of the liquefied fuel by changing both the supply pressure (Pf) of the liquefied fuel and the supply pressure (Pa) of the atomizing fluid are as follows. The injection amount of the liquefied fuel correlates with the supply pressure of the liquefied fuel. Therefore, for example, in order to reduce the flow rate of the liquefied fuel in response to a decrease in the required injection flow rate of the liquefied fuel in the two-fluid injection nozzle 59, if the supply pressure (Pa) of the atomizing fluid is maintained at, for example, Pa3 and only the supply pressure (Pf) of the liquefied fuel is reduced, the supply pressure (Pf) of the liquefied fuel will be lower than the lower limit supply pressure Pf V As a result, the supply pressure of the liquefied fuel becomes equal to or lower than the vapor pressure of the liquefied fuel, which may cause vapor lock in the liquefied fuel supply line 75 or the two-fluid injection nozzle 59, for example, and may cause the flow of the liquefied fuel to become unstable. This is particularly likely to occur when liquid ammonia, which has a relatively low boiling point, is used as the liquefied fuel, rather than oil, which has a relatively high boiling point. In this regard, according to the above configuration, the supply pressure (Pa) of the atomized fluid is adjusted by the atomized fluid adjusting unit 58 in accordance with the required injection flow rate of the liquefied fuel, so that the injection flow rate of the liquefied fuel can be adjusted over a wide range even when the supply pressure of the liquefied fuel is maintained at or above the vapor pressure of the liquefied fuel. This suppresses the occurrence of the above-mentioned vapor lock caused by the supply pressure of the liquefied fuel dropping to or below the vapor pressure of the liquefied fuel. Therefore, the flow of the liquefied fuel in the supply path of the liquefied fuel and the two-fluid injection nozzle 59 can be stabilized.

[0037] In addition, the following advantages are obtained: That is, when the supply pressure (Pa) of the atomized fluid is maintained at, for example, Pa2, and the supply pressure (Pf) of the liquefied fuel is adjusted, Pf is adjusted within the maximum variable range (Pf V Even if the flow rate is adjusted within the range of ΔQ0, the amount of change in the flow rate is limited to the range indicated by ΔQ0, and the range of adjustment of the flow rate of the liquefied fuel is narrow. In this regard, if the flow rate is adjusted by changing both the supply pressure of the liquefied fuel (Pf) and the supply pressure of the atomizing fluid (Pa), the range of Pf is narrower than the maximum variable range (Pf d Even if the flow rate is adjusted within the range of Pf≦Pf1), the amount of change in the flow rate can be adjusted within the range indicated by ΔQ1, and the flow rate adjustment range of the liquefied fuel can be expanded.

[0038] The procedure for changing the flow rate from the state indicated by point J1 to the state indicated by point J4 is not limited to the above description. In another embodiment, the supply pressure of the atomized fluid is increased from Pa3 to Pa1, and then the supply pressure of the liquefied fuel is increased from Pf1 to Pf2. d Even in this case, the above-mentioned advantages can be obtained. Also, depending on the required injection flow rate of the liquefied fuel, the flow rate may change from the state indicated by point J1 to the state indicated by point J2, and then return to the state indicated by point J1. Similarly, the flow rate may be changed between the state indicated by point J2 and the state indicated by point J3, or between the state indicated by point J3 and the state indicated by point J4. In the following description, the range of the required injection flow rate of the liquefied fuel corresponding to the flow rate from point J1 to point J2 and the range of the required injection flow rate of the liquefied fuel corresponding to the flow rate from point J3 to point J4 may both be referred to as a "first range." Moreover, the range of the required injection flow rate of the liquefied fuel corresponding to the flow rate from point J2 to point J3 may be referred to as a "second range."

[0039] In this embodiment, in a first range of the required injection flow rate of the liquefied fuel, the controller 110 changes the supply pressure of the atomized fluid in accordance with the required injection flow rate of the liquefied fuel by the atomized fluid adjusting unit 58. In addition, in a second range of the required injection flow rate of the liquefied fuel, the controller 110 changes the supply pressure of the liquefied fuel in accordance with the required injection flow rate by the liquefied fuel adjusting unit 78. According to the above configuration, the controller 110 is prevented from simultaneously controlling the atomized fluid adjustment unit 58 and the liquefied fuel adjustment unit 78, which simplifies control of the injection flow rate of the liquefied fuel by the controller 110. In addition, mutual interference between the controls by the atomized fluid adjustment unit 58 and the liquefied fuel adjustment unit 78 is prevented, which also stabilizes the controlled flow rate of the liquefied fuel.

[0040] In the present embodiment, the controller 110 controls the liquefied fuel adjusting unit 78 to keep the supply pressure of the liquefied fuel constant in the first range (in the example of FIG. 3, the supply pressure is Pf1 or Pf d In other words, the openings of a plurality of control valves 781 (see FIG. 2) are controlled by the controller 110 so that the supply pressure of the liquefied fuel is constant. According to the above configuration, the supply pressure of the liquefied fuel is maintained constant when the supply pressure of the atomized fluid is adjusted, so that the pressure fluctuation of the liquefied fuel when the liquefied fuel and the atomized fluid are mixed can be stabilized. Therefore, the two-fluid injection nozzle 59 can stably inject the liquefied fuel.

[0041] In this embodiment, the first range includes a low flow rate range of the required injection flow rate and a high flow rate range that is higher than the low flow rate range. The low flow rate range is a range of the required injection flow rate corresponding to the flow rate between points J3 and J4, and the high flow rate range is a range of the required injection flow rate corresponding to the flow rate between points J1 and J2. The second range is a medium flow rate range between the low flow rate range and the high flow rate range. According to the above configuration, in the medium flow rate range where the required injection flow rate of the liquefied fuel is required relatively frequently among the variable range of the required injection flow rate of the liquefied fuel, the controller 110 changes the supply pressure of the liquefied fuel. Therefore, in the medium flow rate range where the required injection flow rate is required relatively frequently, the flow rate of the liquefied fuel can be adjusted with higher accuracy.

[0042] In this embodiment, as described above, the atomized fluid adjusting unit 58 (see FIG. 2) includes a plurality of control valves 581 with different capacities arranged in parallel. The controller 110 controls the opening degree of each of the plurality of control valves 581 to control the supply pressure of the atomized fluid and the flow rate of the liquefied fuel. According to the above configuration, the supply pressure of the atomized fluid is roughly adjusted by the control valve 581 having a relatively large capacity, and the supply pressure is finely adjusted by the control valve 581 having a relatively small capacity. Therefore, even if the adjustment range of the required injection flow rate is wide, the supply pressure of the atomized fluid can be controlled with high accuracy within the range of the supply pressure of the atomized fluid corresponding to the adjustment range.

[0043] In this embodiment, as described above, the liquefied fuel adjusting unit 78 includes a plurality of control valves 781 with different capacities arranged in parallel (see FIG. 2). The controller 110 controls the opening degree of each of the plurality of control valves 781 to control the supply pressure of the liquefied fuel and the flow rate of the liquefied fuel. According to the above configuration, the supply pressure of the liquefied fuel is roughly adjusted by the control valve 781 having a relatively large capacity, and the supply pressure is finely adjusted by the control valve 781 having a relatively small capacity. Therefore, the supply pressure of the liquefied fuel can be controlled with high accuracy within the supply pressure range of the liquefied fuel corresponding to a wide range of the flow rate of the liquefied fuel. In this embodiment, the supply pressure of the liquefied fuel can be controlled with high accuracy within the second range, which is frequently required.

[0044] In this embodiment, the storage section 79, which is a component of the liquefied fuel supply unit 70, functions as a liquid ammonia storage section that stores liquid ammonia. That is, liquid ammonia is adopted as the liquefied fuel supplied to the two-fluid injection nozzle 59. This contributes to carbon neutrality and reduces the environmental load.

[0045] <5. Example of Burner 51 Overview> An outline of the configuration of the burner 51 is illustrated with reference to FIG. 4. FIG. 4 is a schematic diagram of a burner according to an embodiment of the present disclosure. The two-fluid injection nozzle 59, which is a component of the burner 51, includes at least one or more first injection holes 591 and at least one or more second injection holes 592. The first injection holes 591 and the second injection holes 592 are each configured to inject a mixed fluid of liquefied fuel and atomized fluid. In other words, the liquefied fuel atomized by the atomized fluid is injected from each of the first injection holes 591 and the second injection holes 592. In this embodiment, the supply passages through which the liquefied fuel and the atomized fluid are supplied are independent of each other for the first injection hole 591 and the second injection hole 592. Details of these supply passages will be described below.

[0046] An example of the supply path for the liquefied fuel is as follows. The two-fluid injection nozzle 59 includes a liquefied fuel supply passage 57 connected to the above-mentioned liquefied fuel supply line 75. This liquefied fuel supply passage 57 has a first liquefied fuel supply passage 571 and a second liquefied fuel supply passage 572 for guiding liquefied fuel to a first injection hole 591 and a second injection hole 592, respectively. The liquefied fuel supply passage 57 is provided with a plurality of liquefied fuel valves 157 configured to independently change the supply of liquefied fuel in each of the first liquefied fuel supply passage 571 and the second liquefied fuel supply passage 572. The plurality of liquefied fuel valves 157 include a first liquefied fuel on-off valve 157A provided in the first liquefied fuel supply passage 571 and a second liquefied fuel on-off valve 157B provided in the second liquefied fuel supply passage 572. The first liquefied fuel on-off valve 157A and the second liquefied fuel on-off valve 157B are controlled by the controller 110, so that the supply of liquefied fuel to the first injection hole 591 and the second injection hole 592 is carried out independently.

[0047] An example of the supply path of the atomizing fluid is as follows. The two-fluid injection nozzle 59 includes an atomized fluid supply passage 52 connected to the above-mentioned atomized fluid supply line 55. The atomized fluid supply passage 52 has a first atomized fluid supply passage 521 and a second atomized fluid supply passage 522 for guiding the atomized fluid to the first injection hole 591 and the second injection hole 592, respectively. The atomized fluid supply passage 52 is provided with a plurality of atomized fluid valves 152 configured to independently change the supply of the atomized fluid in each of the first atomized fluid supply passage 521 and the second atomized fluid supply passage 522. The plurality of atomized fluid valves 152 include a first atomized fluid valve 152A provided in the first atomized fluid supply passage 521 and a second atomized fluid valve 152B provided in the second atomized fluid supply passage 522. The first atomizing fluid valve 152A and the second atomizing fluid valve 152B are controlled by the controller 110, so that the atomizing fluid is supplied independently to the first injection hole 591 and the second injection hole 592, respectively.

[0048] In this embodiment, the atomized fluid supply path 52 and the liquefied fuel supply path 57 are provided at positions offset from each other in the circumferential direction based on the axis of the two-fluid injection nozzle 59. More specifically, the first atomized fluid supply path 521, the second atomized fluid supply path 522, the first liquefied fuel supply path 571, and the second liquefied fuel supply path 572 are provided at positions offset from each other in the circumferential direction (see the right diagram in FIG. 6). The radial distances from the axis of the two-fluid injection nozzle 59 to these four supply paths may be the same or different.

[0049] According to the above configuration, the atomized fluid supply passage 52 and the liquefied fuel supply passage 57 are spaced apart in the circumferential direction, thereby suppressing heat input from the atomized fluid flowing through the atomized fluid supply passage 52 to the liquefied fuel flowing through the liquefied fuel supply passage 57. More specifically, the liquefied fuel in each of the first liquefied fuel supply passage 571 and the second liquefied fuel supply passage 572 is spaced apart in the circumferential direction from the atomized fluid in each of the first atomized fluid supply passage 521 and the second atomized fluid supply passage 522, thereby suppressing heat input from the atomized fluid to the liquefied fuel. Therefore, vapor lock inside the two-fluid injection nozzle 59 caused by vaporization of the liquefied fuel can be suppressed.

[0050] In this embodiment, the atomized fluid supply path 52 and the liquefied fuel supply path 57 shown in FIG. 4 are thermally insulated from each other. More specifically, either the first liquefied fuel supply path 571 or the second liquefied fuel supply path 572 is thermally insulated from either the first atomized fluid supply path 521 or the second atomized fluid supply path 522. The thermal insulation means that the heat transfer from the atomized fluid to the liquefied fuel is prevented in at least a part in the axial direction of the two-fluid injection nozzle 59. In this embodiment, these four supply paths are thermally insulated from each other, and more specifically, the four supply paths are thermally insulated from each other by providing a heat insulating material 88 (see FIG. 6). In the axial direction of the two-fluid injection nozzle 59, the length of the heat insulating material 88 is preferably half or more of the total length of the two-fluid injection nozzle 59, and more preferably three-quarters or more. However, in other embodiments, thermal insulation may be achieved by arranging a cooling air flow path between the atomizing fluid supply passage 52 and the liquefied fuel supply passage 57 .

[0051] According to the above configuration, the atomized fluid flowing through the atomized fluid supply passage 52 is thermally insulated from the liquefied fuel flowing through the liquefied fuel supply passage 57. More specifically, the liquefied fuel in at least one of the first liquefied fuel supply passage 571 or the second liquefied fuel supply passage 572 is thermally insulated from the atomized fluid in at least one of the first atomized fluid supply passage 521 or the second atomized fluid supply passage 522. This further suppresses the heat input from the atomized fluid to the liquefied fuel, thereby further suppressing vapor lock in the two-fluid injection nozzle 59.

[0052] In this embodiment, the above-mentioned storage section 79 is connected to the liquefied fuel supply path 57 via the liquefied fuel supply line 75. The storage section 79 in this embodiment is a liquid ammonia storage section that stores liquid ammonia as the liquefied fuel. In the example of Fig. 3, the first liquefied fuel supply path 571 and the second liquefied fuel supply path 572 are connected to a single storage section 79, but two storage sections 79 may be provided corresponding to these two supply paths. The above configuration contributes to carbon neutrality and reduces the environmental impact.

[0053] As described above, the liquefied fuel valve 157 and the atomized fluid valve 152 are controlled by the controller 110. More specifically, the first liquefied fuel on-off valve 157A, the second liquefied fuel on-off valve 157B, the first atomized fluid valve 152A, and the second atomized fluid valve 152B are each independently controlled by the controller 110. As a result, the supply / non-supply of liquid ammonia and atomized fluid is independently controlled for each of the first injection hole 591 and the second injection hole 592.

[0054] According to the above configuration, the flow rate variable range of the liquefied fuel is expanded in each of the first injection hole 591 and the second injection hole 592. In other words, even if the flow rate variable range of the liquefied fuel in each of the first liquefied fuel supply passage 571 and the second liquefied fuel supply passage 572 is not set excessively wide, a wide range of flow rate variable of the liquefied fuel can be realized in the entire combustion system 1 by selecting whether or not the liquefied fuel is supplied in each of the first liquefied fuel supply passage 571 and the second liquefied fuel supply passage 572. Therefore, a wide range of flow rate variable of the liquefied fuel in the combustion system 1 can be realized while suppressing the risk of vapor lock inside the liquefied fuel supply passage 57 and the two-fluid injection nozzle 59.

[0055] In this embodiment, when the required injection flow rate of liquefied fuel is relatively small, the liquefied fuel valve 157 and the atomized fluid valve 152 are controlled so that only the first injection hole 591 of the first injection hole 591 and the second injection hole 592 is operated. Then, when the required injection flow rate of liquefied fuel exceeds the upper limit of the injection amount of liquefied fuel from the first injection hole 591, the liquefied fuel valve 157 and the atomized fluid valve 152 are controlled so that in addition to the first injection hole 591, the second injection hole 592 is operated. More specifically, when the required injection flow rate is included in the first set range of the flow rate variable range of the liquefied fuel, the controller 110 opens only the first liquefied fuel on-off valve 157A among the first liquefied fuel on-off valve 157A and the second liquefied fuel on-off valve 157B. At this time, only the first atomized fluid valve 152A may be opened among the first atomized fluid valve 152A and the second atomized fluid valve 152B. When the required injection flow rate of the liquefied fuel is included in a second set range that is higher than the first set range, the controller 110 opens the second liquefied fuel on-off valve 157B in addition to the first liquefied fuel on-off valve 157A. At this time, the second atomized fluid valve 152B may be opened in addition to the first atomized fluid valve 152A.

[0056] FIG. 5 is a graph conceptually showing the relationship between the supply pressure of the liquefied fuel and the injection flow rate when the above control is performed. The horizontal axis of the graph shows the supply pressure (Pf) of the liquefied fuel, and Pf dand Pf1 are as described above with reference to Fig. 3. The vertical axis of the graph indicates the total flow rate of the liquefied fuel injected from the first injection hole 591 and the second injection hole 592. In the graph, the supply pressure of the atomized fluid is Pa2. A straight line L1 shown in the graph indicates the flow rate characteristics when only the first liquefied fuel on-off valve 157A is open. Therefore, the dimension R1 shown in the graph corresponds to the first setting range. The first setting range corresponds to the second range described above with reference to FIG. 3. A straight line L2 shown in the graph indicates the flow rate characteristics when the second liquefied fuel on-off valve 157B is further opened in addition to the first liquefied fuel on-off valve 157A. Therefore, the dimension R2 corresponds to the second setting range.

[0057] According to the above configuration, when the required injection flow rate of the liquefied fuel in the combustion system 1 is within the first set range, only the first liquefied fuel supply path 571 is used among the first liquefied fuel supply path 571 and the second liquefied fuel supply path 572. When the required injection flow rate of the liquefied fuel is within a second set range that is higher than the first set range, the second liquefied fuel supply path 572 is used in addition to the first liquefied fuel supply path 571. Thus, by selecting whether or not the liquefied fuel is supplied to each of the first liquefied fuel supply path 571 and the second liquefied fuel supply path 572, a wide range of variable flow rate of the liquefied fuel can be realized as a whole of the combustion system 1. In other words, a wide range of variable flow rate of the liquefied fuel in the combustion system 1 can be realized while suppressing the risk of vapor lock inside the liquefied fuel supply path 57 and the two-fluid injection nozzle 59.

[0058] <6.2 Details of the configuration of the fluid injection nozzle 59> 6 and 7, the detailed configuration of the two-fluid ejection nozzle 59 is illustrated. Fig. 6 is a schematic explanatory diagram of the two-fluid ejection nozzle according to an embodiment of the present disclosure. Fig. 7 is a schematic explanatory diagram of a back plate according to an embodiment of the present disclosure. A two-fluid injection nozzle 59 according to one embodiment of the present disclosure comprises a burner gun 560 in which a liquefied fuel supply passage 57 and an atomized fluid supply passage 52 are provided, a spray plate 590 in which a first injection hole 591 and a second injection hole 592 are provided, and a back plate 550 connecting the burner gun 560 and the spray plate 590.

[0059] In the burner gun 560 of this embodiment, the liquefied fuel supply passage 57 and the atomized fluid supply passage 52 are thermally insulated from each other by a heat insulating material 88 . In the spray plate 590 of this embodiment, a plurality of first injection holes 591 are arranged along the circumferential direction based on the axis of the two-fluid injection nozzle 59. A mixing chamber 601 in which the supplied liquefied fuel and atomized fluid are mixed is formed upstream of each of the first injection holes 591. In addition, a plurality of second injection holes 592 are arranged along the circumferential direction on the inner side of the plurality of first injection holes 591 when viewed in the axial direction of the two-fluid injection nozzle 59. A mixing chamber 602 in which the supplied liquefied fuel and atomized fluid are mixed is formed upstream of each of the second injection holes 592.

[0060] The back plate 550 of this embodiment connects the first liquefied fuel supply passage 571, the first atomized fluid supply passage 521, the second liquefied fuel supply passage 572, and the second atomized fluid supply passage 522 to the flow paths (mixing chambers 601, 602) of the first injection hole 591 and the second injection hole 592. Specifically, the back plate 550 includes a first liquefied fuel connection passage 501 connected to a first liquefied fuel supply passage 571, a first atomized fluid connection passage 511 connected to a first atomized fluid supply passage 521, a second liquefied fuel connection passage 502 connected to a second liquefied fuel supply passage 572, and a second atomized fluid connection passage 512 connected to a second atomized fluid supply passage 522. In this embodiment, these connection passages have asymmetric shapes on the tip side (ejection side) and base side of the back plate 550. Specifically, the base side of these connection passages defines a cylindrical flow path parallel or inclined to the axial direction of the two-fluid injection nozzle 59, while each connection passage on the tip side defines an annular flow path when viewed in the axial direction.

[0061] According to the above configuration, even in a complicated flow path that is asymmetric between the front end side and the rear end side of the back plate 550, the liquefied fuel and the atomized fluid can flow smoothly without leakage.

[0062] <7. Examples of supply methods> A method for supplying liquefied fuel and atomized fluid to the two-fluid injection nozzle 59 will be described with reference to FIG. 8. FIG. 8 is a flowchart showing a method for supplying liquefied fuel and atomized fluid according to an embodiment of the present disclosure. In the following description, "step" may be abbreviated as "S". The supply method of this example is executed by the controller 110 as an example.

[0063] First, the controller 110 acquires the combustion load of the boiler 10 (S11). As a result, the controller 110 acquires the required injection flow rate of the liquefied fuel according to the combustion load. Next, the controller 110 acquires the supply pressure of the liquefied fuel and the supply pressure of the atomized fluid according to the acquired required injection flow rate, and controls the liquefied fuel adjusting unit 78 and the atomized fluid adjusting unit 58 so that these supply pressures are realized. The control of this step is as described above with reference to Fig. 3. For example, when the required injection flow rate of the liquefied fuel is included in the first range, the controller 110 controls the atomized fluid adjusting unit 58 to change the supply pressure of the atomized fluid. At this time, in this embodiment, the controller 110 controls the liquefied fuel adjusting unit 78 so that the supply pressure of the liquefied fuel becomes constant. According to the above-mentioned configuration, the flow of the liquefied fuel is stabilized.

[0064] Next, the controller 110 judges whether the required injection flow rate of the liquefied fuel acquired by executing S11 is included in the first set range (S15). If the required injection flow rate is included in the first set range (S15: YES), the controller 110 opens the first liquefied fuel on-off valve 157A and the first atomized fluid valve 152A so that only the first injection hole 591 of the first injection hole 591 and the second injection hole 592 is operated (S17). On the other hand, if the required injection flow rate is included in the second set range (S15: NO), the controller 110 opens the second liquefied fuel on-off valve 157B and the second atomized fluid valve 152B in addition to the first liquefied fuel on-off valve 157A and the first atomized fluid valve 152A so that the second injection hole 592 is operated in addition to the first injection hole 591 (S19). In other words, by executing either S17 or S19 depending on the required injection flow rate, the supply of liquefied fuel in each of the first liquefied fuel supply passage 571 and the second liquefied fuel supply passage 572 is changed independently. After executing S17 or S19, the controller 110 ends the process.

[0065] <8. Summary> The contents described in the above-mentioned embodiments can be understood, for example, as follows.

[0066] 1) The two-fluid jet nozzle (59) according to at least one embodiment of the present disclosure is A two-fluid injection nozzle (59) including at least one first injection hole (591) and at least one second injection hole (592) for injecting a liquefied fuel and an atomizing fluid, a first liquefied fuel supply passage (571) and a first atomized fluid supply passage (521) for guiding the liquefied fuel and the atomized fluid to the first injection hole (591), respectively; a second liquefied fuel supply passage (572) and a second atomized fluid supply passage (522) for respectively guiding the liquefied fuel and the atomized fluid to the second injection hole (592), Either the first liquefied fuel supply path (571) or the second liquefied fuel supply path (572) is thermally insulated from either the first atomized fluid supply path (521) or the second atomized fluid supply path (522).

[0067] According to the above configuration 1), the liquefied fuel flowing through at least one of the first liquefied fuel supply path (571) and the second liquefied fuel supply path (572) is thermally insulated from the atomized fluid flowing through at least one of the first atomized fluid supply path (521) and the second atomized fluid supply path (522). This reduces heat input from the atomized fluid to the liquid ammonia, thereby preventing vapor lock inside the two-fluid injection nozzle (59). Therefore, the two-fluid injection nozzle (59) can stabilize the flow of the liquefied fuel.

[0068] 2) In some embodiments, the two-fluid injection nozzle (59) described in 1) above, The first liquefied fuel supply passage (571), the first atomized fluid supply passage (521), the second liquefied fuel supply passage (572), and the second atomized fluid supply passage (522) are provided at positions offset from each other in the circumferential direction based on the axis of the two-fluid injection nozzle.

[0069] According to the above configuration 2), the liquefied fuel in each of the first liquefied fuel supply passage (571) and the second liquefied fuel supply passage (572) is separated in the circumferential direction from the atomized fluid in each of the first atomized fluid supply passage (521) and the second atomized fluid supply passage (522), thereby suppressing heat input from the atomized fluid to the liquefied fuel. This makes it possible to further suppress vapor lock inside the two-fluid injection nozzle (59).

[0070] 3) In some embodiments, the two-fluid injection nozzle (59) according to either 1) or 2) above, The fuel cell further includes a back plate (550) that connects the first liquefied fuel supply passage (571), the first atomized fluid supply passage (521), the second liquefied fuel supply passage (572), and the second atomized fluid supply passage (522) to the first injection hole (591) and the second injection hole (592).

[0071] According to the above configuration 3), even when a complex flow path is formed that is asymmetric between the tip end side, which is the injection hole side of the back plate (550), and the base end side, the liquefied fuel and the atomized fluid can flow smoothly without leakage.

[0072] 4) At least one embodiment of the combustion system (1) according to the present disclosure includes: A two-fluid jet nozzle (59) according to any one of 1) to 3) above; a plurality of liquefied fuel valves (157) for independently varying the supply of the liquefied fuel in each of the first liquefied fuel supply passage (571) and the second liquefied fuel supply passage (572); The device includes a plurality of atomizing fluid valves (152) for independently changing the supply of the atomizing fluid in each of the first atomizing fluid supply passage (521) and the second atomizing fluid supply passage (522).

[0073] According to the configuration of 4) above, a wide range of variable flow rate of the liquefied fuel can be realized in the entire combustion system (1) by selecting whether or not the liquefied fuel is supplied in each of the first liquefied fuel supply passage (571) and the second liquefied fuel supply passage (572), without setting an excessively wide range of variable flow rate of the liquefied fuel in the first liquefied fuel supply passage (571) and the second liquefied fuel supply passage (572), which are the supply passages of the liquefied fuel corresponding to the first injection hole (591) and the second injection hole (592), respectively. Thus, a wide range of variable flow rate of the liquefied fuel in the combustion system (1) can be realized while suppressing the risk of vapor lock inside the liquefied fuel supply passage (57) or the two-fluid injection nozzle (59), etc.

[0074] 5) In some embodiments, the combustion system (1) described in 4) above, a controller (110) for controlling the plurality of liquefied fuel valves (157); The plurality of liquefied fuel valves (157) include a first liquefied fuel on-off valve (157A) provided in the first liquefied fuel supply passage (571); a second liquefied fuel on-off valve (157B) provided in the second liquefied fuel supply passage (572), The controller (110) When the required injection flow rate of the liquefied fuel per one of the two-fluid injection nozzles is within a first setting range of a flow rate variable range of the liquefied fuel, only the first liquefied fuel on-off valve (157A) of the first liquefied fuel on-off valve (157A) and the second liquefied fuel on-off valve (157B) is opened, When the required injection flow rate is included in a second setting range that is higher than the first setting range of the flow rate variable region, the first liquefied fuel on-off valve (157A) and the second liquefied fuel on-off valve (157B) are configured to be opened.

[0075] According to the configuration of 5) above, when the required injection flow rate of the liquefied fuel in the combustion system (1) is within a first set range, of the first liquefied fuel supply path (571) and the second liquefied fuel supply path (572), only the first liquefied fuel supply path (571) is used. When the required injection flow rate of the liquefied fuel is within a second set range that is higher than the first set range, the second liquefied fuel supply path (572) is used in addition to the first liquefied fuel supply path (571). Thus, the timing when the first liquefied fuel on-off valve (157A) and the second liquefied fuel on-off valve (157B) are used simultaneously is limited, and therefore, the control of the first liquefied fuel on-off valve (157A) and the second liquefied fuel on-off valve (157B) by the controller (110) can be simplified.

[0076] 6) In some embodiments, the combustion system (1) according to 4) or 5) above, The fuel cell further includes at least one liquid ammonia storage section (storage section 79) that is connected to each of the first liquefied fuel supply passage (571) and the second liquefied fuel supply passage (572) and stores liquid ammonia as the liquefied fuel.

[0077] The above configuration 6) contributes to carbon neutrality and reduces the environmental impact.

[0078] 7) A method for controlling a supply amount of liquefied fuel according to at least one embodiment of the present disclosure, A method for controlling a supply amount of liquefied fuel using any one of the combustion systems (1) described in 4) to 6), The method includes the steps (S17, S19) of independently changing the supply of the liquefied fuel through the first liquefied fuel supply path (571) and the second liquefied fuel supply path (572), respectively.

[0079] According to the configuration of 7) above, for the same reason as in 4) above, it is possible to realize a wide variable range of the flow rate of the liquefied fuel in the combustion system (1) while suppressing the risk of vapor lock in the liquefied fuel supply passage (57) or the two-fluid injection nozzle (59), etc. [Explanation of symbols]

[0080] 1: Combustion system 52: Atomization fluid supply path 57:Liquid fuel supply path 59:2 Fluid Injection Nozzle 79: Storage section 110: Controller 152: Atomizing fluid valve 157: Liquid fuel valve 157A: First liquefied fuel on-off valve 157B: Second liquefied fuel on-off valve 521: First atomizing fluid supply passage 522: Second atomizing fluid supply passage 550: Back plate 571: 1st liquefied fuel supply path 572:Second liquefied fuel supply path 591: 1st injection hole 592:Second injection hole

Claims

1. a furnace including a furnace wall; A combustion device having a liquefied fuel supply line, an injection nozzle configured to inject liquid ammonia into the inside of the furnace while it is in a liquid state, and a liquefied fuel supply path that guides the liquid ammonia supplied through the liquefied fuel supply line to the injection nozzle; A boiler comprising:

2. 2. The boiler according to claim 1, wherein the combustion device includes a heating means for heating liquid ammonia, and the liquid ammonia is heated and injected into the inside of the furnace.

3. A boiler as described in claim 1 or 2, characterized in that the combustion device is provided with a fluid supply passage that guides the atomized fluid supplied from an atomized fluid supply line to the injection nozzle, and liquid ammonia is mixed with the atomized fluid and injected from the injection nozzle.

4. The boiler according to claim 3, further comprising: a first regulating valve for regulating an amount of liquid ammonia supplied to the injection nozzle through the liquefied fuel supply line; a second regulating valve for regulating the supply of the atomizing fluid supplied to the injection nozzle through the fluid supply path; and a controller for controlling the first regulating valve and the second regulating valve.

5. 5. The boiler according to claim 1, wherein the combustion device is provided with a heat insulating means for insulating the liquefied fuel supply passage.

6. 6. The boiler according to claim 1, wherein the liquid ammonia injected by the injection nozzle is vaporized into ammonia gas inside the furnace and combusted.

7. 7. The boiler according to claim 1, further comprising a burner for mixing biomass fuel or natural gas with air and injecting the mixture into the furnace to be combusted in the furnace.

8. 8. The boiler of claim 7, wherein the air is heated prior to said mixing.

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