Combustion system

Abstract

To provide a combustion system comprising a boiler capable of running on liquid ammonia.SOLUTION: A combustion system comprises: a boiler that has a furnace including a furnace wall, an injection nozzle for emitting a jet of liquid ammonia into the furnace, and a combustion gas passage; and NOx removal equipment that is provided downstream of the combustion gas passage. The injection nozzle is constituted to be capable of emitting the jet of liquid ammonia into the furnace by atomizing the liquid ammonia as-is.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present disclosure relates to a combustion system.

Background Art

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

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] An object of the present disclosure is to provide a combustion system including a boiler capable of using liquid ammonia as a fuel.

Means for Solving the Problems

[0005] The combustion system according to at least one embodiment of the present disclosure includes a boiler having a furnace including a furnace wall, an injection nozzle for injecting liquid ammonia into the furnace, and a combustion gas passage, a denitration device provided downstream of the combustion gas passage, and is provided with the injection nozzle is configured to be able to atomize liquid ammonia in a liquid state and inject it into the furnace.

[0006] The combustion system according to at least one embodiment of the present disclosure includes a boiler having a furnace including a furnace wall, an injection nozzle for injecting liquid ammonia into the furnace, and a combustion gas passage, A denitration device provided downstream of the combustion gas passage, comprises, The injection nozzle is configured to mix liquid ammonia with water vapor and inject it into the furnace interior.

[0007] A combustion system according to at least one embodiment of the present disclosure, a furnace including a furnace wall, a first injection nozzle that injects any one of petroleum coke fuel, other petroleum residues, heavy oil, light oil, heavy fuel oil, other petroleum oils, industrial waste liquid, coal, biomass fuel, natural gas, petroleum gas, and by-product gas generated in the ironmaking process, or a fuel combining these various fuels, into the furnace interior, a second injection nozzle that injects liquid ammonia into the furnace interior, a combustion gas passage, a boiler having, a denitration device provided downstream of the combustion gas passage, comprises, The second injection nozzle is configured to atomize liquid ammonia in a liquid state and inject it into the furnace interior.

Advantages of the Invention

[0008] According to the present disclosure, a combustion system capable of using liquid ammonia as a fuel can be provided.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Embodiments for Carrying Out the Invention

[0010] Hereinafter, an embodiment according to the present disclosure will be described with reference to the drawings. Note that the present invention is not limited by this embodiment, and when there are multiple embodiments, those configured by combining each embodiment are also included. In the following description, "up" or "upper" indicates the upper side in the vertical direction, and "down" or "lower" indicates the lower side in the vertical direction. The vertical direction is not strict and includes errors. Also, the dimensions, materials, shapes, relative arrangements, etc. of the components described as embodiments or shown in the drawings are not intended to limit the scope of the present disclosure, but are merely illustrative examples. For example, expressions representing relative or absolute arrangements such as "in a certain direction", "along a certain direction", "parallel", "orthogonal", "center", "concentric", or "coaxial" not only strictly represent such arrangements, but also represent states where there are tolerances or relative displacements with angles or distances that can obtain the same function. For example, expressions representing that things such as "identical", "equal", and "homogeneous" are in an equal state not only strictly represent an equal state, but also represent states where there are tolerances or differences that can obtain the same function. For example, expressions representing shapes such as a rectangular shape or a cylindrical shape not only represent the shapes such as a rectangular shape or a cylindrical shape in a geometrically strict sense, but also represent shapes including concave and convex portions, chamfered portions, etc. within a range where the same effect can be obtained. On the one hand, the expressions "comprising", "including", or "having" a component do not exclude the presence of other components. For the same components, the same reference numerals may be used and the description may be omitted.

[0011] <1. Overall Configuration of Combustion System 1> FIG. 1 is a schematic configuration diagram showing a combustion system including a boiler that uses solid fuel and liquefied fuel as main fuels. The liquefied fuel is a fuel that becomes a gas phase at normal temperature under atmospheric pressure. The normal temperature referred to in this specification is 35°C. The liquefied fuel is, for example, petroleum (light oil and liquefied petroleum gas), liquefied natural gas, dimethyl ether, and liquid ammonia. In the following description, unless otherwise specified, the liquefied fuel shall refer to liquid ammonia.

[0012] The boiler 10 included in the combustion system 1 of the present embodiment is a boiler capable of burning pulverized fuel obtained by pulverizing solid fuel and liquefied fuel with a burner, and exchanging heat between the heat generated by this combustion and feed water or steam to generate superheated steam. As the solid fuel, biomass fuel, coal, etc. are used.

[0013] The boiler 10 has a furnace 11, combustion devices 20 and 50, and a combustion gas passage 12. The furnace 11 has a hollow shape of a rectangular cylinder and is installed along the vertical direction. 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 to each other, and recovers the heat generated by the combustion of the pulverized fuel by exchanging heat with water or steam flowing inside the heat transfer tubes, and suppresses the temperature rise of the furnace wall 101.

[0014] The combustion devices 20 and 50 are installed in the lower region of the furnace 11. In the present embodiment, the combustion device 20 is configured to inject pulverized fuel into the furnace 11. Further, the combustion device 50 is configured to atomize liquefied fuel with an atomizing fluid (spray medium) and inject it into the furnace 11. The atomizing fluid of the present embodiment is atomizing steam.

[0015] 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. At the tip of each burner 21, an injection nozzle (not shown) configured to inject pulverized fuel into the furnace 11 is provided. Further, at the tip of each burner 51, a two-fluid injection nozzle 59 (see FIG. 4) configured to atomize liquefied fuel with an atomizing fluid and inject it into the furnace 11 is provided. The burners 21 and 51 are arranged at equal intervals along the circumferential direction of the furnace 11 (for example, four burners installed at each corner of a square furnace 11 are taken as one set) and are arranged in a plurality of stages along the vertical direction. In the example of FIG. 1, two sets of burners 21 are arranged in two stages and four sets of burners 51 are arranged in four stages. In FIG. 1, for the sake of illustration, only two of the burners in one set are shown, and the reference numerals 21 and 51 are attached to each set. The shape of the furnace, the number of stages of the burners, the number of burners in one stage, the arrangement of the burners, etc. are not limited to this embodiment.

[0016] Each burner 21 of the combustion device 20 is connected to a plurality of mills (pulverizers) 31A and 31B (hereinafter sometimes collectively referred to as "mills 31") via a plurality of pulverized fuel supply pipes 22A and 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 roller and the pulverizing table is conveyed to a classifier (not shown) provided in the mill 31 by primary air (transport gas, oxidizing gas) supplied to the mill 31. In the classifier, it is classified into pulverized fuel having a particle size suitable for combustion in the burner 21 and coarse powder fuel having a particle size larger than the above particle size. The pulverized fuel passes through the classifier and is supplied to the burner 21 through the pulverized fuel supply pipe 22 together with the primary air. The coarse powder fuel that has not passed through the classifier falls onto the pulverizing table inside the mill 31 by its own weight and is pulverized again.

[0017] The burner 51 of the combustion device 50 is connected to the supply unit 90. The supply unit 90 includes an atomizing fluid supply unit 60 for a two-fluid injection nozzle configured to supply atomizing fluid to the combustion device 50 (hereinafter sometimes simply referred to as "atomizing fluid supply unit 60"), and a liquefied fuel supply unit 70 for a two-fluid injection nozzle configured to supply liquefied fuel to the combustion device 50 (hereinafter sometimes simply referred to as "liquefied fuel supply unit 70"). The controller 110 acquires the required injection flow rate of the liquefied fuel at the burner 51 determined according to the combustion load in the boiler 10. By sending a control command corresponding to the required injection flow rate from the controller 110 to the supply unit 90, the atomizing fluid supply unit 60 and the liquefied fuel supply unit 70 can respectively adjust the supply amounts of the atomizing fluid and the liquefied fuel. Details of the configuration of the supply unit 90 will be described later. Note that the required injection flow rate of the liquefied fuel is the required injection flow rate of the liquefied fuel per two-fluid injection nozzle 59 (see FIG. 4) of each burner 51.

[0018] An air register 23 is provided outside the furnace of the furnace 11 at the mounting positions of the burners 21 and 51, and one end of an air duct (air duct) 24 is connected to this air register 23. A forced draft fan (FDF) 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), supplied as secondary air (combustion air, oxidizing gas) to the burner 21 through the air register 23, and introduced into the interior of the furnace 11.

[0019] The combustion gas passage 12 is connected to the upper part of the furnace 11 in the vertical direction. In the combustion gas passage 12, as heat exchangers for recovering the heat of the combustion gas, there are a superheater 102A, 102B, 102C (hereinafter, may be collectively referred to as "superheater 102"), a reheater 103A, 103B (hereinafter, may be collectively referred to as "reheater 103"), and a carbon saver 104. Heat exchange is performed between the combustion gas generated in the furnace 11 and the feed water or steam flowing inside each heat exchanger. Note that the arrangement and shape of each heat exchanger are not limited to the form described in FIG. 1.

[0020] On the downstream side of the combustion gas passage 12, a flue 13 through which the combustion gas from which heat has been recovered by the heat exchanger is discharged is connected. An air preheater (air heater) 42 is provided in the flue 13 between the flue 13 and the air duct 24. Heat exchange is performed between the air flowing through the air duct 24 and the combustion gas flowing through the flue 13 to heat the primary air supplied to the mill 31 and the secondary air supplied to the burner 21, thereby further recovering heat from the combustion gas after heat exchange with water or steam.

[0021] Also, 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 action of reducing nitrogen oxides such as ammonia and aqueous urea to the combustion gas flowing through the flue 13, and promotes the reaction between the nitrogen oxides (NOx) in the combustion gas supplied with the reducing agent and the reducing agent by the catalytic action of the denitration catalyst installed in the denitration device 43, thereby removing and reducing the nitrogen oxides in the combustion gas. A gas duct 41 is connected to the downstream side of the air preheater 42 in the flue 13. In the gas duct 41, there are provided a dust collection device 44 such as an electrostatic precipitator for removing ash and the like in the combustion gas, an environmental device such as a desulfurization device 46 for removing sulfur oxides, and an induced draft fan (IDF) 45 for guiding the exhaust gas to these environmental devices. The downstream end of the gas duct 41 is connected to a chimney 47, and the combustion gas treated by the environmental device is discharged to the outside of the system as exhaust gas.

[0022] In the boiler 10, when a plurality of mills 31 are driven, the pulverized and classified fine powder fuel is supplied to the burner 21 together with the primary air through the fine powder fuel supply pipe 22. Further, the atomizing fluid and the liquefied fuel are respectively supplied from the atomizing fluid supply unit 60 and the liquefied fuel supply unit 70 to the burner 51. Furthermore, the secondary air heated by the air preheater 42 is supplied to the burners 21 and 51 from the air duct 24 through the air register 23. The burner 21 blows the fine powder fuel mixture in which the fine powder fuel and the primary air are mixed into the furnace 11, and also blows the secondary air into the furnace 11. The fine powder fuel mixture blown into the furnace 11 ignites and reacts with the secondary air to form a flame. The burner 51 blows the secondary air into the furnace 11 together with the liquefied fuel atomized by the atomizing fluid. The liquefied fuel blown into the furnace 11 vaporizes into fuel gas and reacts with the secondary air to burn. The high-temperature combustion gas generated by the combustion of the fine powder fuel and the fuel gas rises in the furnace 11 and flows into the combustion gas passage 12. Note that the timing at which the liquefied fuel is blown into the furnace 11 may be after the temperature in the furnace 11 has risen to a certain temperature due to the combustion of the fine powder fuel. For example, after exclusive combustion of the fine powder fuel at the start of the boiler 10, the liquefied fuel may be blown into the furnace 11, and co-combustion of the fuel gas vaporized from the liquefied fuel and the fine powder fuel may be performed. Further, thereafter, the blowing of the fine powder fuel may be stopped, and exclusive combustion of the liquefied fuel may be performed. Also, in this embodiment, air is used as the oxidizing gas (primary air, secondary air), but it may be one with a higher oxygen ratio or conversely a lower oxygen ratio than air, and by adjusting the ratio of the oxygen amount to the fuel amount supplied to an appropriate range, stable combustion is achieved in the furnace 11.

[0023] The combustion gas that has flowed into the combustion gas passage 12 exchanges heat with water and steam in the superheater 102, reheater 103, and carbon saver 104 disposed inside the combustion gas passage 12, and then is discharged into the flue 13. Nitrogen oxides are removed by the denitration device 43, and after exchanging heat with the primary air and secondary air in the air preheater 42, it is further discharged into the gas duct 41. Ash and the like are removed by the dust collection device 44, and sulfur oxides are removed by the desulfurization device 46, and then it is discharged outside the system from the chimney 47. Note that the arrangement of each heat exchanger in the combustion gas passage 12 and each device from the flue 13 to the gas duct 41 does not necessarily have to be arranged in the order described above with respect to the combustion gas flow.

[0024] 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. As the solid fuel used in the boiler, coal, biomass fuel, petroleum coke (PC) fuel, petroleum residue, etc. are used. Note that as the fuel of the boiler combined with the liquefied fuel, not only solid fuel but also liquid fuels such as heavy oil, light oil, and heavy oil, and liquid fuels such as factory waste liquid can be used. Also, gaseous fuels such as natural gas, various petroleum gases, and by-product gases generated in the iron-making process can be used. Furthermore, it can also be applied to a co-firing boiler that uses a combination of these various fuels.

[0025] <2. Configuration of the Liquefied Fuel Supply Unit 70> Referring to FIG. 2, the configuration of the liquefied fuel supply unit 70, which is a component of the supply unit 90 described above, 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, for the convenience of viewing the drawing, the illustration of the combustion device 20 (see FIG. 1) is omitted.

[0026] The liquefied fuel supply unit 70 includes a storage unit 79 that stores liquefied fuel, a liquefied fuel supply line 75 that supplies the liquefied fuel stored in the storage unit 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 unit 78 provided in the liquefied fuel supply line 75.

[0027] The storage unit 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 path 57, which is a component of the two-fluid injection nozzle 59 provided in each of the plurality of burners 51. A return path 752 for returning a part of the supplied liquefied fuel to the storage unit 79 is provided in the upstream part of the liquefied fuel supply line 75. The heater 76 is configured to heat the liquefied fuel to a constant temperature that does not vaporize the liquefied fuel. The heat source of the heater 76 is, as an example, auxiliary steam, which is a part of the steam generated in the combustion system 1. Due to the heating by the heater 76, the liquefied fuel blown into the furnace 11 is easily vaporized, and misfire in the furnace 11 can be suppressed. Based on the measurement result of the thermometer 175 for measuring the temperature of the liquefied fuel heated by the heater 76, the control valve 81 provided in the flow path of the auxiliary steam is adjusted, and the heating amount of the liquefied fuel in the heater 76 is adjusted. In this example, this adjustment is executed by the controller 110.

[0028] The liquefied fuel adjustment 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 adjustment unit 78 of the present embodiment includes 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 regulating valve, and the control valve 782 is, for example, a flow regulating valve. In this example, based on the measurement results of the pressure gauge 173 provided on the downstream side of the branch point between the return path 752 of the liquefied fuel supply line 75 and the flow meter 176 provided on the upstream side of the branch point with the liquid fuel supply path 57, respectively, the plurality of control valves 781 and the control valve 782 are controlled by the controller 110. As a more specific example, the controller 110 controls the plurality of control valves 781 and the control valve 782 based on the measurement results of the pressure gauge 173 and the flow meter 176, respectively, so that liquefied fuel with a flow rate corresponding to the required injection flow rate is supplied to the burner 51.

[0029] In other embodiments, the liquefied fuel supply unit 70 may not include the storage unit 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 manufactures liquefied fuel.

[0030] <3. Configuration of the atomizing fluid supply unit 60> Referring to FIG. 2, the configuration of the atomizing fluid supply unit 60, which is a component of the supply unit 90 described above, is illustrated. The atomizing fluid supply unit 60 includes an atomizing fluid supply line 55 for supplying atomizing fluid to the two-fluid injection nozzle 59 of the burner 51, a desuperheater 53 provided in the atomizing fluid supply line 55, and an atomizing fluid adjustment unit 58 provided in the atomizing fluid supply line 55. The atomizing fluid supply line 55 is connected to an atomizing fluid supply passage 52, which is a component of the two-fluid injection nozzle 59 provided in each of the plurality of burners 51.

[0031] The desuperheater 53 is configured to cool the atomizing fluid to a constant temperature using a cooling medium having a lower temperature than the atomizing fluid. In the present embodiment, the atomizing fluid is steam, and in the desuperheater 53, spray water is mixed to cool the atomizing fluid. For example, a spray water control valve 54 provided in a spray water pipe is controlled by a controller 110 based on the measurement result of a thermometer 161 provided downstream of the desuperheater 53.

[0032] The atomizing fluid adjustment unit 58 is configured to adjust the supply pressure of the atomizing fluid according to the required injection flow rate of the liquefied fuel described above. The atomizing fluid adjustment unit 58 of the present embodiment includes a plurality of control valves 581 having different capacities provided in parallel downstream of the desuperheater 53. In this example, based on the measurement result of a pressure gauge 182 provided downstream of the atomizing fluid adjustment unit 58, the plurality of control valves 581 are controlled. 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 atomizing fluid having a pressure corresponding to the required injection flow rate of the liquefied fuel is supplied to the burner 51.

[0033] <Flow control of liquefied fuel in the two-fluid injection nozzle 59> Referring to FIG. 3, the details of the flow control of the liquefied fuel in the two-fluid injection nozzle 59 are illustrated. FIG. 3 is a graph conceptually showing the 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 indicates the flow rate (Q) of the liquefied fuel injected from the two-fluid injection nozzle 59. The vertical axis of the same graph indicates the supply pressure (Pf) of the liquefied fuel. Pf on the vertical axis 0 and Pf 1 are, respectively, the burner lower limit pressure and the burner upper limit pressure of the liquefied fuel for realizing stable combustion in the burner 51. Also, Pf V is the supply lower limit pressure for stably supplying the liquefied fuel to the burner 51, and is a value corresponding to the vapor pressure of the liquefied fuel at the temperature of the liquefied fuel heated by the heater 76.

[0034] The graph line A conceptually drawn in the same graph shows the relationship between the flow rate and the supply pressure of the liquefied fuel when the supply pressure (Pa) of the atomizing fluid is Pa1. Also, the 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 atomizing fluid is Pa2 and Pa3, respectively. Regarding the supply pressure (Pa) of the atomizing fluid, the following formula (1) holds. Pa1 > Pa2 > Pa3 ···(1) Note that it is not necessarily required that the atomizing supply pressure (Pa) be three pressures, and it is also possible to control with more pressures or fewer pressures. Also, the minimum pressure of Pa may be zero, that is, the atomizing fluid may not be supplied.

[0035] In the present embodiment, by changing the supply pressure of the liquid fuel and the supply pressure of the atomizing fluid, the flow rate of the liquefied fuel injected from the two-fluid injection nozzle 59 is adjusted. Hereinafter, the details will be described by taking as an example the case where the flow rate of the liquefied fuel decreases from the state shown by the point J1 to the state shown by the point J4 in the graph.

[0036] First, while the liquefied fuel adjustment unit 78 maintains the supply pressure (Pf) of the liquefied fuel at Pf 1 the atomizing fluid adjustment unit 58 increases the supply pressure (Pa) of the atomizing 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, since the supply pressure of the liquefied fuel is maintained, the flow of the liquefied fuel is likely to be stabilized. Thereafter, while the atomizing fluid adjustment unit 58 maintains the supply pressure of the atomizing fluid at Pa2, the liquefied fuel adjustment unit 78 reduces the supply pressure of the liquefied fuel from Pf 1 to Pf d to Pf d (Pf is larger than Pf V described later). As a result, the flow rate of the liquefied fuel decreases (point J3). Furthermore, while the liquefied fuel adjustment unit 78 maintains the supply pressure of the liquefied fuel at Pf d the atomizing fluid adjustment unit 58 increases the supply pressure of the atomizing fluid from Pa2 to Pa1. As a result, the flow rate of the liquefied fuel decreases (point J4).

[0037] 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, when the required injection flow rate of the liquefied fuel in the two-fluid injection nozzle 59 decreases and it is necessary to reduce the flow rate of the liquefied fuel, 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 is likely to fall below Pf V which is the supply lower limit pressure. As a result, the supply pressure of the liquefied fuel becomes equal to or lower than the vapor pressure of the liquefied fuel, and vapor lock may occur, for example, in the liquefied fuel supply line 75 or the two-fluid injection nozzle 59, and the flow of the liquefied fuel may become unstable. This is particularly likely to occur when a relatively low-boiling liquid such as liquid ammonia rather than an oil with a relatively high boiling point is used as the liquefied fuel. In this regard, according to the above configuration, even when maintaining the supply pressure of the liquefied fuel above the vapor pressure of the liquefied fuel by adjusting the supply pressure (Pa) of the atomizing fluid by the atomizing fluid adjustment unit 58 according to the required injection flow rate of the liquefied fuel, the injection flow rate of the liquefied fuel can be adjusted over a wide range. Thereby, the occurrence of the above-described vapor lock caused by the supply pressure of the liquefied fuel dropping below the vapor pressure of the liquefied fuel is suppressed. 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.

[0038] Also, the following advantages can be obtained. That is, when the supply pressure (Pa) of the atomizing fluid is maintained at, for example, Pa2 and the supply pressure (Pf) of the liquefied fuel is adjusted, even if Pf is adjusted within the maximum variable range (Pf V ≦Pf≦Pf 1 ), the amount of change in the flow rate remains within the range indicated by ΔQ 0 , and the flow rate adjustment range of the liquefied fuel is narrow. In this regard, when adjusting the flow rate by changing both the supply pressure (Pf) of the liquefied fuel and the supply pressure (Pa) of the atomizing fluid, even if Pf is adjusted within a range (Pf d ≦Pf≦Pf 1 ) narrower than the maximum variable range, the amount of change in the flow rate can be adjusted within the range indicated by ΔQ 1 , and the flow rate adjustment range of the liquefied fuel can be widened.

[0039] Note that 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 other embodiments, the supply pressure of the atomizing fluid may be increased from Pa3 to Pa1 first, and then the supply pressure of the liquefied fuel may be decreased from Pf 1 to Pf d . Even in this case, the above advantages can be enjoyed. Also, according to 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 described as the "first range". Also, 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 described as the "second range".

[0040] In the present embodiment, in the first range of the required injection flow rate of the liquefied fuel, the controller 110 changes the supply pressure of the atomizing fluid according to the required injection flow rate of the liquefied fuel by the atomizing fluid adjustment unit 58. Also, in the second range of the required injection flow rate of the liquefied fuel, the controller 110 changes the supply pressure of the liquefied fuel according to the required injection flow rate by the liquefied fuel adjustment unit 78. According to the above configuration, since the controller 110 is suppressed from simultaneously controlling the atomizing fluid adjustment unit 58 and the liquefied fuel adjustment unit 78, the control of the injection flow rate of the liquefied fuel by the controller 110 is simplified. Also, since the control by the atomizing fluid adjustment unit 58 and the liquefied fuel adjustment unit 78 is suppressed from interfering with each other, the flow rate of the liquefied fuel to be controlled is also stabilized.

[0041] Also, in the present embodiment, in the first range, the controller 110 causes the supply pressure of the liquefied fuel to be constant by the liquefied fuel adjustment unit 78 (in the example of FIG. 3, the supply pressure becomes Pf 1 or Pf d ), and controls the supply flow rate (supply amount) of the liquefied fuel. That is, the opening degrees of the plurality of control valves 781 (see FIG. 2) are controlled by the controller 110 so that the supply pressure of the liquefied fuel becomes constant. According to the above configuration, since the supply pressure of the liquefied fuel is maintained constant when the supply pressure of the atomizing fluid is adjusted, the pressure fluctuation of the liquefied fuel when the liquefied fuel and the atomizing fluid are mixed can be stabilized. Therefore, the two-fluid injection nozzle 59 can stably inject the liquefied fuel.

[0042] Also, in the present 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 the range of the required injection flow rate corresponding to the flow rate between point J3 and point J4, and the high flow rate range is the range of the required injection flow rate corresponding to the flow rate between point J1 and point J2. Further, 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 frequency is relatively high 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 frequency is relatively high, the flow rate of the liquefied fuel can be adjusted with higher accuracy.

[0043] Also, in the present embodiment, as described above, the atomizing fluid adjustment unit 58 (see FIG. 2) includes a plurality of control valves 581 with different capacities provided in parallel. Then, the controller 110 controls the supply pressure of the atomizing fluid by controlling the opening degree of each of the plurality of control valves 581, and controls the flow rate of the liquefied fuel. According to the above configuration, a rough adjustment of the supply pressure of the atomizing fluid is made by the control valve 581 with a relatively large capacity, and a fine adjustment of the supply pressure is made by the control valve 581 with a relatively small capacity. Therefore, even when the adjustment range of the required injection flow rate becomes wide, the supply pressure of the atomizing fluid can be controlled with high accuracy within the range of the supply pressure of the atomizing fluid corresponding to the adjustment range.

[0044] Also, in the present embodiment, as described above, the liquefied fuel adjustment unit 78 includes a plurality of control valves 781 with different capacities provided in parallel (see FIG. 2). Then, the controller 110 controls the supply pressure of the liquefied fuel by controlling the opening degree of each of the plurality of control valves 781, and controls the flow rate of the liquefied fuel. According to the above configuration, the relatively large-capacity control valve 781 roughly adjusts the supply pressure of the liquefied fuel, and the relatively small-capacity control valve 781 finely adjusts the supply pressure. Therefore, within the supply pressure range of the liquefied fuel corresponding to a wide range of liquefied fuel flow rates, the supply pressure of the liquefied fuel can be controlled with high precision. And in this embodiment, high-precision control of the supply pressure of the liquefied fuel can be performed in the second range with a high demand frequency.

[0045] Also, in this embodiment, the storage unit 79, which is a component of the liquefied fuel supply unit 70, functions as a liquid ammonia storage unit for storing liquid ammonia. That is, liquid ammonia is adopted as the liquefied fuel supplied to the two-fluid injection nozzle 59. Thereby, it contributes to carbon neutrality and can reduce the environmental load.

[0046] <5. Exemplification of the Outline of the Burner 51> Referring to FIG. 4, the outline of the configuration of the burner 51 is exemplified. FIG. 4 is a schematic configuration 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 hole 591 and the second injection hole 592 are each configured to inject a mixed fluid of the liquefied fuel and the atomizing fluid. In other words, from each of the first injection hole 591 and the second injection hole 592, the liquefied fuel atomized by the atomizing fluid is injected. In this embodiment, the supply paths to which the liquefied fuel and the atomizing fluid are supplied are independent of each other at the first injection hole 591 and the second injection hole 592. The details of this supply path will be described below.

[0047] The supply path of the liquefied fuel is as follows as an example. The two-fluid injection nozzle 59 includes a liquefied fuel supply passage 57 connected to the liquefied fuel supply line 75 described above. 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 the first injection hole 591 and the second injection hole 592, respectively. Further, 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 are provided in the liquefied fuel supply passage 57. And the plurality of liquefied fuel valves 157 have 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. By controlling the first liquefied fuel on-off valve 157A and the second liquefied fuel on-off valve 157B by the controller 110, the supply of liquefied fuel to each of the first injection hole 591 and the second injection hole 592 is independently performed.

[0048] The supply passage of the atomizing fluid is as follows as an example. The two-fluid injection nozzle 59 includes an atomizing fluid supply passage 52 connected to the atomizing fluid supply line 55 described above. This atomizing fluid supply passage 52 has a first atomizing fluid supply passage 521 and a second atomizing fluid supply passage 522 for guiding atomizing fluid to the first injection hole 591 and the second injection hole 592, respectively. Further, a plurality of atomizing fluid valves 152 configured to independently change the supply of atomizing fluid in each of the first atomizing fluid supply passage 521 and the second atomizing fluid supply passage 522 are provided in the atomizing fluid supply passage 52. And the plurality of atomizing fluid valves 152 have a first atomizing fluid valve 152A provided in the first atomizing fluid supply passage 521 and a second atomizing fluid valve 152B provided in the second atomizing fluid supply passage 522. By controlling the first atomizing fluid valve 152A and the second atomizing fluid valve 152B by the controller 110, the supply of atomizing fluid to each of the first injection hole 591 and the second injection hole 592 is independently performed.

[0049] In this embodiment, the atomizing fluid supply passage 52 and the liquefied fuel supply passage 57 are provided at positions offset from each other in the circumferential direction with respect to the axis in the two-fluid injection nozzle 59. More specifically, the first atomizing fluid supply passage 521, the second atomizing fluid supply passage 522, the first liquefied fuel supply passage 571, and the second liquefied fuel supply passage 572 are provided at positions offset from each other in the circumferential direction (see the right view of FIG. 6). The radial distances from the axis of the two-fluid injection nozzle 59 to these four supply passages may be the same or different.

[0050] According to the above configuration, since the atomizing fluid supply passage 52 and the liquefied fuel supply passage 57 are separated from each other in the circumferential direction, heat input from the atomizing fluid flowing through the atomizing fluid supply passage 52 to the liquefied fuel flowing through the liquefied fuel supply passage 57 is suppressed. More specifically, the liquefied fuel in each of the first liquefied fuel supply passage 571 and the second liquefied fuel supply passage 572 is separated from the atomizing fluid in each of the first atomizing fluid supply passage 521 and the second atomizing fluid supply passage 522 in the circumferential direction, thereby suppressing heat input from the atomizing fluid to the liquefied fuel. Therefore, vapor lock inside the two-fluid injection nozzle 59 due to vaporization of the liquefied fuel can be suppressed.

[0051] Further, in this embodiment, the space between the atomizing fluid supply passage 52 and the liquefied fuel supply passage 57 shown in FIG. 4 is thermally insulated. More specifically, either the first liquefied fuel supply passage 571 or the second liquefied fuel supply passage 572 and either the first atomizing fluid supply passage 521 or the second atomizing fluid supply passage 522 are thermally insulated from each other. Thermal insulation means that heat transfer from the atomizing fluid to the liquefied fuel is blocked at least in a part in the axial direction of the two-fluid injection nozzle 59. In this embodiment, these four supply passages are thermally insulated from each other, and more specifically, they are thermally insulated 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 at least half of the total length of the two-fluid injection nozzle 59, and more preferably at least three-quarters. 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.

[0052] According to the above configuration, the atomizing fluid flowing through the atomizing fluid supply passage 52 and the liquefied fuel flowing through the liquefied fuel supply passage 57 are thermally insulated. 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 and the atomizing fluid in at least one of the first atomizing fluid supply passage 521 or the second atomizing fluid supply passage 522 are thermally insulated. Thereby, the heat input from the atomizing fluid to the liquefied fuel is further suppressed, so that the vapor lock in the two-fluid injection nozzle 59 can be further suppressed.

[0053] Also, in the present embodiment, the above-described storage portion 79 is connected to the liquefied fuel supply passage 57 via the liquefied fuel supply line 75. The storage portion 79 of the present embodiment is a liquid ammonia storage portion that stores liquid ammonia as the liquefied fuel. In the example of FIG. 3, the first liquefied fuel supply passage 571 and the second liquefied fuel supply passage 572 are connected to a single storage portion 79, but two storage portions 79 may be provided corresponding to these two supply passages. According to the above configuration, it can contribute to carbon neutrality and reduce the environmental load.

[0054] As described above, the liquefied fuel valve 157 and the atomizing 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 atomizing fluid valve 152A, and the second atomizing fluid valve 152B are each independently controlled by the controller 110. Thereby, the supply presence / absence control of the liquid ammonia and the atomizing fluid is independently controlled at each of the first injection hole 591 and the second injection hole 592.

[0055] According to the above configuration, in each of the first injection hole 591 and the second injection hole 592, the variable flow rate range of the liquefied fuel is expanded. That is, even if the variable flow rate ranges of the liquefied fuels in the first liquefied fuel supply passage 571 and the second liquefied fuel supply passage 572 are not set overly wide, a wide variable flow rate range of the liquefied fuel as a whole of the combustion system 1 can be realized by selecting the presence / absence of the supply of the liquefied fuel in each of the first liquefied fuel supply passage 571 and the second liquefied fuel supply passage 572. Therefore, a wide variable flow rate range 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.

[0056] In the present embodiment, when the required injection flow rate of the liquefied fuel is relatively small, the liquefied fuel valve 157 and the atomizing 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 operates. Then, when the required injection flow rate of the liquefied fuel exceeds the upper limit of the injection amount of the liquefied fuel in the first injection hole 591, the liquefied fuel valve 157 and the atomizing fluid valve 152 are controlled so that the second injection hole 592 operates in addition to the first injection hole 591. More specifically, when the required injection flow rate is included in the first set range of the variable flow rate range of the liquefied fuel, the controller 110 opens 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. At this time, only the first atomizing fluid valve 152A of the first atomizing fluid valve 152A and the second atomizing fluid valve 152B may be opened. And when the required injection flow rate of the liquefied fuel is included in the second set range having a higher flow rate than the first set range, the controller 110 further 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 atomizing fluid valve 152B may be opened in addition to the first atomizing fluid valve 152A.

[0057] FIG. 5 is a graph conceptually showing the relationship between the supply pressure and the injection flow rate of the liquefied fuel when the above control is performed. The horizontal axis of the graph indicates the supply pressure (Pf) of the liquefied fuel, Pf d and, Pf 1This is as described above with reference to FIG. 3. The vertical axis of this graph indicates the total flow rate of the liquefied fuel injected from the first injection hole 591 and the second injection hole 592. In this graph, the supply pressure of the atomizing fluid is Pa2. The straight line L1 shown in the graph indicates the flow rate characteristics when only the first liquefied fuel on-off valve 157A is opened. Therefore, the dimension R1 shown in the graph corresponds to the first setting range. And the first setting range corresponds to the second range described above with reference to FIG. 3. The straight line L2 shown in the graph indicates the flow rate characteristics when, in addition to the first liquefied fuel on-off valve 157A, the second liquefied fuel on-off valve 157B is further opened. Therefore, the dimension R2 corresponds to the second setting range.

[0058] According to the above configuration, when the required injection flow rate of the liquefied fuel in the combustion system 1 is within the first setting range, only the first liquefied fuel supply path 571 out of the first liquefied fuel supply path 571 and the second liquefied fuel supply path 572 is used. Also, when the required injection flow rate of the liquefied fuel is within the second setting range, which is a higher flow rate than the first setting range, in addition to the first liquefied fuel supply path 571, the second liquefied fuel supply path 572 is also used. Thus, by selecting whether or not to supply the liquefied fuel in each of the first liquefied fuel supply path 571 and the second liquefied fuel supply path 572, a wide variable range of the flow rate of the liquefied fuel as a whole of the combustion system 1 can be realized. That is, a wide variable range of the 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 or the two-fluid injection nozzle 59.

[0059] <Details of the configuration of the two-fluid injection nozzle 59> With reference to FIGS. 6 and 7, the details of the configuration of the two-fluid injection nozzle 59 are illustrated. FIG. 6 is a schematic explanatory view of a two-fluid injection nozzle according to an embodiment of the present disclosure. FIG. 7 is a schematic explanatory view of a back plate according to an embodiment of the present disclosure. The two-fluid injection nozzle 59 according to an embodiment of the present disclosure includes a burner can 560 provided with a liquefied fuel supply passage 57 and an atomizing fluid supply passage 52, a spray plate 590 provided with a first injection hole 591 and a second injection hole 592, and a back plate 550 that connects the burner can 560 and the spray plate 590.

[0060] In the burner can 560 of the present embodiment, the liquefied fuel supply passage 57 and the atomizing fluid supply passage 52 are thermally blocked by a heat insulating material 88. In the spray plate 590 of the present embodiment, a plurality of first injection holes 591 are arranged along the circumferential direction with respect to the axis of the two-fluid injection nozzle 59. A mixing chamber 601 in which the supplied liquefied fuel and atomizing fluid are mixed is formed upstream of each first injection hole 591. Also, a plurality of second injection holes 592 are arranged along the circumferential direction inside the plurality of first injection holes 591 in the axial direction view of the two-fluid injection nozzle 59. A mixing chamber 602 in which the supplied liquefied fuel and atomizing fluid are mixed is formed upstream of each second injection hole 592.

[0061] The back plate 550 of the present embodiment connects the flow paths (mixing chambers 601, 602) between the first liquefied fuel supply passage 571, the first atomizing fluid supply passage 521, the second liquefied fuel supply passage 572, and the second atomizing fluid supply passage 522, and 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 the first liquefied fuel supply passage 571, a first atomizing fluid connection passage 511 connected to the first atomizing fluid supply passage 521, a second liquefied fuel connection passage 502 connected to the second liquefied fuel supply passage 572, and a second atomizing fluid connection passage 512 connected to the second atomizing fluid supply passage 522. In the present embodiment, these connection passages exhibit an asymmetric shape at the tip side (injection side) and the base side of the back plate 550. Specifically, the base side of these connection passages defines a columnar flow path that is parallel or inclined with respect to the axial direction of the two-fluid injection nozzle 59, while each connection passage at the tip side defines an annular flow path in the axial direction view.

[0062] According to the above configuration, even in a complex 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 atomizing fluid can flow smoothly without leakage.

[0063] <7. Exemplification of supply method> Referring to FIG. 8, a method for supplying a liquefied fuel and an atomizing fluid to the two-fluid injection nozzle 59 will be described. FIG. 8 is a flowchart showing a method for supplying a liquefied fuel and an atomizing 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.

[0064] First, the controller 110 acquires the combustion load of the boiler 10 (S11). Thereby, 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 atomizing fluid according to the acquired required injection flow rate, and controls the liquefied fuel adjustment unit 78 and the atomizing fluid adjustment 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 atomizing fluid adjustment unit 58 to change the supply pressure of the atomizing fluid. At this time in the present embodiment, the controller 110 controls the liquefied fuel adjustment unit 78 so that the supply pressure of the liquefied fuel becomes constant. According to the above configuration, the flow of the liquefied fuel is stabilized.

[0065] Next, the controller 110 determines whether or not the required injection flow rate of the liquefied fuel acquired with the execution of S11 is included in the first set range (S15). When 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 atomizing fluid valve 152A so that only the first injection hole 591 out of the first injection hole 591 and the second injection hole 592 operates (S17). On the other hand, when 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 atomizing fluid valve 152B in addition to the first liquefied fuel on-off valve 157A and the first atomizing fluid valve 152A so that the second injection hole 592 operates in addition to the first injection hole 591 (S19). That is, by executing either S17 or S19 according to the required injection flow rate, the supply of the liquefied fuel in each of the first liquefied fuel supply path 571 and the second liquefied fuel supply path 572 is independently changed. After the execution of S17 or S19, the controller 110 ends the process.

[0066] <8. Summary> The content described in some of the above-described embodiments is grasped as follows, for example.

[0067] 1) The two-fluid injection nozzle (59) according to at least one embodiment of the present disclosure is a two-fluid injection nozzle (59) including at least one or more first injection holes (591) and at least one or more second injection holes (592) for injecting a liquefied fuel and an atomizing fluid, a first liquefied fuel supply path (571) and a first atomizing fluid supply path (521) for guiding the liquefied fuel and the atomizing fluid to the first injection hole (591), respectively, and a second liquefied fuel supply path (572) and a second atomizing fluid supply path (522) for guiding the liquefied fuel and the atomizing fluid to the second injection hole (592), respectively. Either the first liquefied fuel supply passage (571) or the second liquefied fuel supply passage (572) is thermally insulated from either the first atomizing fluid supply passage (521) or the second atomizing fluid supply passage (522).

[0068] According to the configuration of 1) above, the liquefied fuel flowing through at least one of the first liquefied fuel supply passage (571) or the second liquefied fuel supply passage (572) and the atomizing fluid flowing through at least one of the first atomizing fluid supply passage (521) or the second atomizing fluid supply passage (522) are thermally insulated. As a result, the heat input from the atomizing fluid to liquid ammonia is suppressed, so that vapor lock inside the two-fluid injection nozzle (59) can be suppressed. Therefore, the two-fluid injection nozzle (59) can stabilize the flow of the liquefied fuel.

[0069] 2) In some embodiments, it is the two-fluid injection nozzle (59) described in 1) above, the first liquefied fuel supply passage (571), the first atomizing fluid supply passage (521), the second liquefied fuel supply passage (572), and the second atomizing fluid supply passage (522) are provided at positions offset from each other in the circumferential direction with respect to the axis of the two-fluid injection nozzle.

[0070] According to the configuration of 2) above, the liquefied fuel in each of the first liquefied fuel supply passage (571) and the second liquefied fuel supply passage (572) is separated from the atomizing fluid in each of the first atomizing fluid supply passage (521) and the second atomizing fluid supply passage (522) in the circumferential direction, so that the heat input from the atomizing fluid to the liquefied fuel can be suppressed. Therefore, vapor lock inside the two-fluid injection nozzle (59) can be further suppressed.

[0071] 3) In some embodiments, it is the two-fluid injection nozzle (59) described in either 1) or 2) above, The combustion system (1) according to at least one embodiment of the present disclosure includes a back plate (550) that connects the flow paths of the first liquefied fuel supply path (571), the first atomizing fluid supply path (521), the second liquefied fuel supply path (572), and the second atomizing fluid supply path (522) to the flow paths of the first injection hole (591) and the second injection hole (592).

[0072] According to the configuration of 3) above, even when a complex flow path that is asymmetric between the tip side and the base end side, which is the injection hole side of the back plate (550), is formed, the liquefied fuel and the atomizing fluid can flow smoothly without leakage.

[0073] 4) The combustion system (1) according to at least one embodiment of the present disclosure includes the two-fluid injection nozzle (59) according to any one of 1) to 3) above, a plurality of liquefied fuel valves (157) for independently changing the supply of the liquefied fuel in each of the first liquefied fuel supply path (571) and the second liquefied fuel supply path (572), and a plurality of atomizing fluid valves (152) for independently changing the supply of the atomizing fluid in each of the first atomizing fluid supply path (521) and the second atomizing fluid supply path (522).

[0074] According to the configuration of 4) above, even if the variable flow rate range of the liquefied fuel in the first liquefied fuel supply path (571) and the second liquefied fuel supply path (572), which are the supply paths of the liquefied fuel corresponding to the first injection hole (591) and the second injection hole (592), respectively, is not set overly wide, by selecting the presence / absence of the supply of the liquefied fuel in each of the first liquefied fuel supply path (571) and the second liquefied fuel supply path (572), a wide variable flow rate range of the liquefied fuel as a whole of the combustion system (1) can be realized. Therefore, while suppressing the risk of vapor lock inside the liquefied fuel supply path (57) or the two-fluid injection nozzle (59), etc., a wide variable flow rate range of the liquefied fuel in the combustion system (1) can be realized.

[0075] 5) In some embodiments, the combustion system (1) described in 4) above Comprising a controller (110) for controlling the plurality of liquefied fuel valves (157), The plurality of liquefied fuel valves (157) are, A first liquefied fuel on-off valve (157A) provided in the first liquefied fuel supply path (571), And a second liquefied fuel on-off valve (157B) provided in the second liquefied fuel supply path (572), The controller (110) is, When the required injection flow rate of the liquefied fuel per one of the two-fluid injection nozzles is included in the first set range of the 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 set range that is a higher flow rate than the first set range of the flow rate variable range, the first liquefied fuel on-off valve (157A) and the second liquefied fuel on-off valve (157B) are configured to be opened.

[0076] According to the configuration of 5) above, 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). Further, when the required injection flow rate of the liquefied fuel is within a second set range that is a higher flow rate than the first set range, the second liquefied fuel supply path (572) is also used in addition to the first liquefied fuel supply path (571). Therefore, since the timing at which the first liquefied fuel on-off valve (157A) and the second liquefied fuel on-off valve (157B) are used simultaneously is limited, 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.

[0077] 6) In some embodiments, the combustion system (1) described in 4) or 5) above, Further including at least one liquid ammonia storage unit (storage unit 79) connected to each of the first liquefied fuel supply path (571) and the second liquefied fuel supply path (572) and storing liquid ammonia as the liquefied fuel.

[0078] According to the configuration of 6) above, it contributes to carbon neutrality and can reduce the environmental load.

[0079] 7) The method for controlling the supply amount of liquefied fuel according to at least one embodiment of the present disclosure is a method for controlling the supply amount of liquefied fuel using the combustion system (1) according to any one of 4) to 6) above, including steps (S17, S19) of independently changing the supply of the liquefied fuel in each of the first liquefied fuel supply path (571) and the second liquefied fuel supply path (572).

[0080] According to the configuration of 7) above, for the same reason as 4) above, while suppressing the risk of vapor lock in the liquefied fuel supply path (57) or the two-fluid injection nozzle (59), etc., a wide flow rate variable range of the liquefied fuel in the combustion system (1) can be realized.

Explanation of reference numerals

[0081] 1: Combustion system 52: Atomizing fluid supply path 57: Liquefied fuel supply path 59: Two-fluid injection nozzle 79: Storage part 110: Controller 152: Atomizing fluid valve 157: Liquefied fuel valve 157A: First liquefied fuel on-off valve 157B: Second liquefied fuel on-off valve 521: First atomizing fluid supply path 522: Second atomizing fluid supply path 550: Back plate 571: First liquefied fuel supply path 572: Second liquefied fuel supply path 591: First injection hole 592: Second injection hole

Claims

1. A boiler having a furnace including a furnace wall, an injection nozzle for injecting liquid ammonia into the inside of the furnace, and a combustion gas passage; a denitration device provided downstream of the combustion gas passage; Equipped with The injection nozzle is configured to atomize liquid ammonia while it is in a liquid state and inject it into the inside of the furnace. A combustion system comprising:

2. A boiler having a furnace including a furnace wall, a combustion device having a plurality of burners each having an injection nozzle at its tip for injecting liquid ammonia into the furnace, and a combustion gas passage having a heat exchanger for recovering heat of the combustion gas; a denitration device provided downstream of the combustion gas passage for removing or reducing nitrogen oxides in the combustion gas; Equipped with The burners are attached to the furnace wall, The combustion device is configured to atomize liquid ammonia while it is still in liquid form and inject it into the furnace. A combustion system comprising:

3. A boiler having a furnace including a furnace wall, an injection nozzle for injecting liquid ammonia into the inside of the furnace, and a combustion gas passage; a denitration device provided downstream of the combustion gas passage; Equipped with The injection nozzle is configured to mix liquid ammonia with water vapor and inject the mixture into the interior of the furnace. A combustion system comprising:

4. A boiler having a furnace including a furnace wall, a combustion device having a plurality of burners each having an injection nozzle at its tip for injecting liquid ammonia into the furnace, and a combustion gas passage having a heat exchanger for recovering heat of the combustion gas; a denitration device provided downstream of the combustion gas passage for removing or reducing nitrogen oxides in the combustion gas; Equipped with The burners are attached to the furnace wall, The combustion device is configured to mix liquid ammonia with water vapor and inject the mixture into the furnace. A combustion system comprising:

5. a furnace including a furnace wall; a first injection nozzle for injecting fuel into the furnace, the fuel being any one of petroleum coke fuel, other petroleum residues, heavy oil, light oil, heavy oil, other petroleum products, industrial wastewater, coal, biomass fuel, natural gas, petroleum gas, by-product gas generated in a steelmaking process, or a combination of these various fuels; A second injection nozzle that injects liquid ammonia into the furnace; A combustion gas passage; A boiler having a denitration device provided downstream of the combustion gas passage; Equipped with The second injection nozzle is configured to atomize liquid ammonia while it is in a liquid state and inject it into the inside of the furnace. A combustion system comprising:

6. a furnace including a furnace wall; a first combustion device having a plurality of first burners each having a first injection nozzle at its tip for injecting fuel into the furnace, the fuel being any one of petroleum coke fuel, other petroleum residues, heavy oil, light oil, heavy oil, other petroleum products, industrial wastewater, coal, biomass fuel, natural gas, petroleum gas, by-product gas generated in a steelmaking process, or a combination of these various fuels; A second combustion device having a plurality of second burners each having a second injection nozzle at its tip for injecting liquid ammonia into the furnace; a combustion gas passage provided with a heat exchanger for recovering heat from the combustion gas; A boiler having a denitration device provided downstream of the combustion gas passage for removing or reducing nitrogen oxides in the combustion gas; Equipped with The first burners and the second burners are mounted on the furnace wall, The second combustion device is configured to atomize liquid ammonia while it is in a liquid state and inject it into the furnace. A combustion system comprising:

7. 3. The combustion system according to claim 1, wherein the liquid ammonia injected from the injection nozzle is vaporized into ammonia gas inside the furnace and combusted.

8. 7. The combustion system according to claim 5, wherein the liquid ammonia injected from the second injection nozzle is vaporized into ammonia gas inside the furnace and combusted.

9. A desulfurization device is provided downstream of the denitration device and removes sulfur oxides from the combustion gas. A combustion system according to any one of claims 1 to 8.

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