Ammonia fuel supply unit, power generation plant, and boiler operation method

Abstract

To provide an ammonia fuel supply unit that secures heat quantity for vaporizing liquid ammonia and suppresses an impact on thermal efficiency of a heat cycle, a power generation plant, and an operating method for a boiler.SOLUTION: An ammonia fuel supply unit 60 for supplying ammonia fuel to a boiler 10 includes a first vaporizer 81 and a second vaporizer 82. The first vaporizer 81 is configured to vaporize liquid ammonia serving as fuel by using a heat source having a temperature equal to or higher than a boiling point of the liquid ammonia. The second vaporizer 82 is provided between the first vaporizer 81 and the boiler 10, and is configured to vaporize the liquid ammonia remaining in the vaporization processing in the first vaporizer 81, by using hot air generated by using exhaust heat of the boiler 10 as a direct or indirect heat source.SELECTED DRAWING: Figure 3A

Description

[Technical Field]

[0001] The present disclosure relates to ammonia fuel supply units, power plants, and methods of operating boilers. [Background technology]

[0002] Conventionally, power plants that supply ammonia fuel to a boiler are known. For example, the power plant disclosed in Patent Document 1 includes a vaporizer that vaporizes liquid ammonia to produce ammonia gas. The ammonia gas produced by the vaporizer is supplied to the boiler as fuel. The vaporizer uses hot water sent from a heat recovery boiler as a heat source. After heat exchange with the liquid ammonia, the hot water returns to the heat recovery boiler via a circulation flow path. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6245404 Summary of the Invention [Problem to be solved by the invention]

[0004] In the above-mentioned patent documents, hot water circulating between a heat recovery boiler and a vaporizer is used as a heat source for vaporizing liquid ammonia, which may affect the efficiency of a thermal cycle formed by a turbine, a condenser, etc. of a power plant. Also, in the above-mentioned patent documents, the vaporization process using hot water as an indirect heat source is performed only once, which may result in a failure to ensure the amount of heat required for vaporizing liquid ammonia.

[0005] An object of the present disclosure is to provide an ammonia fuel supply unit, a power generation plant, and a boiler operation method that ensures the amount of heat required for vaporizing liquid ammonia while suppressing the impact on the thermal efficiency of the thermal cycle. [Means for solving the problem]

[0006] In accordance with at least one embodiment of the present disclosure, an ammonia fuel supply unit includes: 1. An ammonia fuel supply unit for supplying ammonia fuel to a boiler, comprising: a first vaporizer for vaporizing liquid ammonia as fuel using a heat source having a temperature equal to or higher than the boiling point of the liquid ammonia; A second vaporizer that is provided between the first vaporizer and the boiler and that vaporizes the liquid ammonia remaining in the vaporization process by the first vaporizer using hot air generated by using exhaust heat from the boiler as a direct or indirect heat source; Equipped with.

[0007] In accordance with at least one embodiment of the present disclosure, a power plant includes: the ammonia fuel supply unit; the boiler that generates steam using combustion gas generated by combustion of fuel supplied from the ammonia fuel supply unit as a heat source; a turbine that rotates using the steam from the boiler as a driving source; a generator for generating electricity by rotation of the turbine; Equipped with.

[0008] A method of operating a boiler according to at least one embodiment of the present disclosure includes: 1. A method for operating a boiler supplied with ammonia fuel, comprising: a first vaporization process for vaporizing liquid ammonia as fuel using a heat source having a temperature equal to or higher than the boiling point of the liquid ammonia; a second vaporization process for vaporizing the liquid ammonia remaining in the first vaporization process using hot air generated by using exhaust heat from a boiler as a direct or indirect heat source; Equipped with. [Effects of the Invention]

[0009] According to the present disclosure, it is possible to provide an ammonia fuel supply unit, a power generation plant, and a boiler operation method that ensure the amount of heat required for vaporizing liquid ammonia while suppressing the impact on the thermal efficiency of the thermal cycle. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram illustrating a boiler according to an embodiment of the present disclosure. [Figure 2] 1 is a schematic diagram of a power plant according to an embodiment of the present disclosure. [Figure 3A] FIG. 1 is a schematic diagram illustrating an ammonia fuel supply unit according to an embodiment of the present disclosure. [Figure 3B] FIG. 1 is a schematic diagram illustrating an ammonia fuel supply unit according to an embodiment of the present disclosure. [Figure 4] 1 is a flowchart illustrating a method for operating a boiler according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0011] Preferred embodiments of the present disclosure will be described below with reference to the drawings. The present invention is not limited to these embodiments, and when there are multiple embodiments, the present invention also includes configurations that combine the embodiments. In the following description, "upper" and "upper" refer to the upper side in the vertical direction, and "lower" and "lower" refer to the lower side in the vertical direction, and the vertical direction is not precise and may include errors. Furthermore, the dimensions, materials, shapes, relative arrangements, etc. of the components described as 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 arrangement such as "in a certain direction," "along a certain direction," "parallel," "orthogonal," "center," "concentric," or "coaxial" not only express such an arrangement exactly, 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 such as "identical," "equal," and "homogeneous" that indicate that something is in an equal state 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 representing shapes such as a square shape or a cylindrical shape not only represent shapes such as a square shape or a cylindrical shape in the strict geometric sense, but also represent shapes including uneven portions, chamfered portions, etc., to the extent that the same effect can be obtained. On the other hand, the expressions "comprise," "include," or "have" one element are not exclusive expressions that exclude the presence of other elements. Note that the same components will be denoted by the same reference numerals and the description thereof will be omitted.

[0012] <Outline of Boiler 10 and Power Plant 1> FIG. 1 is a schematic diagram illustrating a boiler according to one embodiment of the present disclosure.

[0013] A boiler 10 according to one embodiment of the present disclosure is a coal-fired (pulverized coal-fired) boiler that uses pulverized coal obtained by pulverizing coal (carbon-containing solid fuel) as pulverized fuel, burns this pulverized fuel with a burner, and is capable of exchanging heat generated by this combustion with feedwater or steam to generate superheated steam. In addition to the pulverized fuel, the boiler 10 of this embodiment also burns ammonia gas generated by vaporizing liquid ammonia with the burner. Therefore, the boiler 10 of this embodiment performs mixed combustion of pulverized coal and ammonia gas. In the following description, when liquid ammonia and ammonia gas are collectively referred to or no distinction is made between them, they may be referred to as ammonia fuel. Note that liquid ammonia may be ammonia in a liquid phase as a pure substance, or may be a mixed liquid in which a small proportion of water is mixed into liquid ammonia.

[0014] In this embodiment, as shown in Fig. 1, a boiler 10 has a furnace 11, a combustion device 12, and a combustion gas passage 13. The furnace 11 has a hollow rectangular cylindrical shape and is installed vertically. A furnace wall 101 constituting the furnace 11 is composed of a plurality of heat transfer tubes and fins connecting these, and exchanges heat generated by the combustion of at least one of pulverized fuel and ammonia gas with water or steam flowing inside the heat transfer tubes, thereby suppressing a temperature rise in the furnace wall 101.

[0015] The combustion device 12 is provided on the lower side of the furnace wall 101 that constitutes the furnace 11. In this embodiment, the combustion device 12 has a plurality of burners (e.g., 21, 22, 23, 24, 25) attached to the furnace wall 101. For example, the burners 21, 22, 23, 24, 25 are arranged at equal intervals along the circumferential direction of the furnace 11 as one set, and are arranged in multiple stages (e.g., five stages in FIG. 1) along the vertical direction. However, the shape of the furnace, the number of burners in one stage, the number of stages, the arrangement, etc. are not limited to this embodiment.

[0016] An ammonia fuel supply unit 60 for supplying ammonia fuel to the boiler 10 is connected to the burners 21, 22, and 23 via an ammonia gas supply pipe 69. The ammonia fuel supply unit 60 is configured to vaporize liquid ammonia as fuel using seawater and hot air generated using the exhaust heat of the boiler 10. In this embodiment, the ammonia gas generated by the vaporization process is supplied to the burners 21, 22, and 23. The hot air may serve as a direct or indirect heat source for vaporizing the liquid ammonia. Details of the ammonia fuel supply unit 60 will be described later.

[0017] The burners 24, 25 are connected to multiple pulverizers (mills) 34, 35 via pulverized coal supply pipes 29, 33 (hereinafter, the pulverizers 34, 35 may be collectively referred to as the pulverizer 3). In the pulverizer 3, for example, a pulverizer table (not shown) is supported in a housing so that it can be driven and rotated, and multiple pulverizer rollers (not shown) are supported above the pulverizer table so that they can rotate in conjunction with the rotation of the pulverizer table. When coal is introduced between the multiple pulverizer rollers and the pulverizer table, it is pulverized and transported by a carrier gas (primary air, oxidizing gas) to a classifier (not shown) in the housing of the pulverizer 3. The pulverized fuel classified into particles within a predetermined particle size range can be supplied to the burners 24, 25 via the pulverized coal supply pipes 29, 33. The carrier gas also serves to dry the pulverized fuel.

[0018] The above-mentioned conveying gas is delivered to the pulverizer 3 from a primary air fan (PAF) 31, which takes in outside air, via an air pipe 30. The air pipe 30 includes a hot air induction pipe 30A through which hot air heated by an air heater 42 flows from the primary air fan 31; a cold air induction pipe 30B through which cold air at near room temperature flows from the primary air fan 31 without passing through the air heater 42; and a conveying gas flow path 30C through which the hot air and cold air merge and flow. The hot air induction pipe 30A and the cold air induction pipe 30B are provided with a hot air damper 30D and a cold air damper 30E, respectively. The opening degrees of these dampers are adjusted according to the supply conditions of pulverized coal fuel, thereby adjusting the flow rate and temperature of the conveying gas flowing through the conveying gas flow path 30C. In this embodiment, the carrier gas flowing through the carrier gas passage 30C contains hot air from the hot air induction pipe 30A. In other words, the hot air induction pipe 30A and the carrier gas passage 30C are configured to guide hot air heated by the air heater 42 to the pulverizer 3 that pulverizes coal as fuel. In the following description, the hot air induction pipe 30A and the carrier gas passage 30C may be collectively referred to as a pulverizer hot air pipe 39.

[0019] The pulverizer hot air pipe 39, which is connected to the air heater 42 and the pulverizer 3, includes a branching section 63 that is a portion that connects to a hot air pipe 62 that is a component of the ammonia fuel supply unit 60. A pulverizer adjusting damper 49 is provided in the pulverizer hot air pipe 39 between the branching section 63 and the pulverizer 3, and a heat source adjusting damper 68 is provided in the hot air pipe 62. The pulverizer adjusting damper 49 is configured to adjust the flow rate of the carrier gas (i.e., the flow rate of the hot air) supplied to the pulverizer 3, and the heat source adjusting damper 68 is configured to adjust the flow rate of the hot air supplied to the ammonia fuel supply unit 60. Both the pulverizer adjusting damper 49 and the heat source adjusting damper 68 of this embodiment are dampers whose opening degree can be adjusted. Although details will be described later, the opening degrees of the pulverizer adjusting damper 49 and the heat source adjusting damper 68 are adjusted according to the combustion conditions of the boiler 10, such as the ammonia co-firing ratio, so that surplus hot air that does not need to be supplied to the pulverizer 3 is supplied to the ammonia fuel supply unit 60. This ensures a heat source for the ammonia fuel supply unit 60 to vaporize the liquid ammonia. In the embodiment illustrated in Fig. 1, the hot air pipe 62 is connected to the carrier gas flow path 30C, but in other embodiments, the hot air pipe 62 may be connected to the hot air induction pipe 30A or to the outlet of the air heater 42.

[0020] Furnace 11 is also provided with a wind box 36 at the mounting positions of burners 21, 22, 23, 24, and 25, and one end of an air duct (airway) 37 is connected to this wind box 36. Air duct 37 has a forced draft fan (FDF) 38 attached to the other end.

[0021] 1, the combustion gas passage 13 is connected to the vertical upper part of the furnace 11. The combustion gas passage 13 is provided with superheaters 102, 103, 104, reheaters 105, 106, and an economizer 107 as heat exchangers for recovering heat from the combustion gas, and heat is exchanged between the combustion gas generated in the furnace 11 and the feedwater or steam flowing inside each heat exchanger.

[0022] As shown in FIG. 1 , the combustion gas passage 13 is connected downstream to a flue 14 through which the combustion gas that has undergone heat exchange is discharged. An air heater 42 is provided in the flue 14 for heating the air flowing through the air duct 37 and the air pipe 30. In the air heater 42, heat exchange occurs between the outside air flowing through the air duct 37 and the combustion gas flowing through the flue 14, thereby raising the temperature of the combustion air supplied to the burners 21, 22, 23, 24, and 25. Furthermore, in the air heater 42, heat exchange occurs between the outside air flowing toward the hot air induction pipe 30A and the combustion gas flowing through the flue 14, thereby converting the outside air into hot air. Therefore, it can be understood that the air heater 42 is configured to heat the outside air using the exhaust heat of the boiler 10.

[0023] Furthermore, a denitration device 43 is provided in the flue 14 at a position upstream of the air heater 42. The denitration device 43 supplies a reducing agent, such as ammonia or urea water, that has the ability to reduce nitrogen oxides into the flue 14, and removes and reduces the nitrogen oxides in the combustion gas by promoting the reaction between the nitrogen oxides in the combustion gas to which the reducing agent has been supplied and the reducing agent through the catalytic action of a denitration catalyst provided in the denitration device 43. A gas duct 41 connected to the flue 14 is provided with a dust collector 44, such as an electrostatic precipitator, an induced draft fan (IDF) 45, a desulfurization device 46, and the like, at a position downstream of the air heater 42, and a chimney 50 is provided at the downstream end.

[0024] Meanwhile, when the multiple pulverizers 34, 35 (3) are driven, the generated pulverized fuel is supplied to the burners 24, 25 together with carrier gas (primary air, oxidizing gas) through the pulverized coal supply pipes 29, 33. Furthermore, the exhaust gas discharged from the flue 14 exchanges heat with the air heater 42, and heated combustion air (secondary air, oxidizing gas) is supplied to the burners 21, 22, 23, 24, 25 from the air duct 37 via the wind box 36. The burners 24, 25 inject a pulverized fuel mixture, which is a mixture of the pulverized fuel and carrier gas, into the furnace 11, and also inject combustion air into the furnace 11. At this time, the pulverized fuel mixture is ignited, forming a flame. A flame is generated in the lower part of the furnace 11, and high-temperature combustion gas rises within the furnace 11 and is discharged into the combustion gas passage 13. At the same time as the start of injection of the pulverized fuel mixture (or after the ignition of the pulverized fuel mixture), burners 21, 22, and 23 inject ammonia gas into the furnace 11, causing combustion of the ammonia gas and co-firing of pulverized coal and ammonia. In this embodiment, air is used as the oxidizing gas. Gases with a higher or lower oxygen content than air may also be used, provided that the fuel flow rate is optimized.

[0025] 1, the combustion gas undergoes heat exchange in a second superheater 103, a third superheater 104, a first superheater 102 (hereinafter sometimes simply referred to as superheaters), a second reheater 106, a first reheater 105 (hereinafter sometimes simply referred to as reheaters), and an economizer 107, which are arranged in a combustion gas passage 13, and then nitrogen oxides are reduced and removed in a denitration device 43, particulate matter is removed in a dust collector 44, and sulfur oxides are removed in a desulfurization device 46, before being discharged into the atmosphere from a chimney 50. Note that the heat exchangers do not necessarily have to be arranged in the order described above with respect to the combustion gas flow.

[0026] Note that Figure 1 does not accurately show the positions of each heat exchanger (superheaters 102, 103, 104, reheaters 105, 106, and economizer 107) in the combustion gas passage 13, and the arrangement order of each heat exchanger relative to the combustion gas flow is not limited to that shown in Figure 1.

[0027] FIG. 2 is a schematic diagram of a power plant according to an embodiment of the present disclosure. The power plant 1 of this embodiment includes, for example, a boiler 10 including the heat exchangers described above, a turbine 110 that rotates using steam from the boiler 10 as a power source, a generator 115 that generates electricity by the rotation of the turbine 110, a condenser 114 that condenses the steam discharged from the turbine 110, a boiler feedwater pump 123 that sends the condensed water condensed by the condenser 114 to the boiler 10, and an ammonia fuel supply unit 60. The boiler 10, the turbine 110, the condenser 114, and the boiler feedwater pump 123 form a specified heat cycle (e.g., a Rankine cycle). The generator 115 generates electricity by using work extracted from the turbine 110 in this heat cycle. The circulating heat medium in this heat cycle is water circulating at a pressure and temperature above the triple point. In one embodiment, all of the above-mentioned components of the power plant 1 except for the ammonia fuel supply unit 60 are existing facilities, and the ammonia fuel supply unit 60 is added to these existing facilities.

[0028] The turbine 110 of this embodiment is composed of, for example, a high-pressure turbine 111, an intermediate-pressure turbine 112, and a low-pressure turbine 113, and the high-pressure turbine 111 and the intermediate-pressure turbine 112 are connected to each other via reheaters 105 and 106 that recover heat from the combustion gas flowing through the combustion gas passage 13 (see FIG. 1). A condenser 114 is connected to the low-pressure turbine 113. The condenser 114 houses heat transfer tubes 117 configured so that cooling water flows inside. The cooling water is, for example, seawater, fresh water, or brackish water. The steam that has driven the low-pressure turbine 113 to rotate flows into the condenser 114 and is cooled by the cooling water to become condensed water.

[0029] The condenser 114 is connected to the economizer 107 via a feedwater line L1. The feedwater line L1 is provided with, for example, a condensate pump (CP) 121, a low-pressure feedwater heater 122, a boiler feedwater pump (BFP) 123, and a high-pressure feedwater heater 124. A portion of the steam that drives the turbines 111, 112, 113 (110) is extracted into the low-pressure feedwater heater 122 and the high-pressure feedwater heater 124 and is supplied as a heat source to the high-pressure feedwater heater 124 and the low-pressure feedwater heater 122 via an extraction line (not shown), and the feedwater supplied to the economizer 107 is heated.

[0030] The fuel used in the boiler 10 may be a solid fuel such as biomass fuel, PC (Petroleum Coke) fuel generated during oil refining, or petroleum residue. Furthermore, the fuel is not limited to solid fuels; petroleum products such as heavy oil, light oil, and heavy oil, and liquid fuels such as industrial wastewater can also be used. Furthermore, gaseous fuels (natural gas, by-product gas, etc.) can also be used. Furthermore, the present invention can be applied to a multi-fuel boiler that uses a combination of these fuels.

[0031] <Example of Details of Ammonia Fuel Supply Unit 60 According to One Embodiment> 3A is a schematic diagram showing an ammonia fuel supply unit 60A (60) according to one embodiment of the present disclosure. The ammonia fuel supply unit 60A is configured to vaporize liquid ammonia using the above-mentioned hot air as a direct heat source. Note that in FIG. 3A, the hot air damper 30D, the cold air induction pipe 30B, and the cold air damper 30E conceptually illustrated in FIG. 1 are omitted (the same applies to FIG. 3B).

[0032] Ammonia fuel supply unit 60A includes a first vaporizer 81 for vaporizing liquid ammonia as fuel using seawater, and a second vaporizer 82A (82) provided between first vaporizer 81 and boiler 10. Seawater is an example of a heat source having a temperature equal to or higher than the boiling point of liquid ammonia. The heat source is located outside the thermal cycle system that includes boiler 10 as a component. Ammonia fuel supply unit 60 of this embodiment further includes an ammonia tank 71 provided upstream of first vaporizer 81. Liquid ammonia stored in ammonia tank 71 is supplied to first vaporizer 81 by driving an ammonia supply pump 75. The supply pressure at this time is adjusted by a pressure regulating valve 109.

[0033] The first vaporizer 81 of this embodiment includes a first container 91 accommodating a plurality of first heat transfer tubes (not shown) extending vertically. Liquid ammonia flowing into the first vaporizer 81 flows inside the first heat transfer tubes. Seawater is supplied to the first container 91 by a seawater pump (not shown). The seawater flowing into the first container 91 exchanges heat with the liquid ammonia flowing inside the first heat transfer tubes. As a result, the liquid ammonia is vaporized to produce ammonia gas. However, there are cases where the temperature of the seawater exceeds the boiling point of the liquid ammonia but is lower than the dew point temperature of the liquid ammonia when moisture is mixed with the liquid ammonia, and therefore liquid ammonia remains in the vaporization process of the first vaporizer 81. The ammonia fuel (ammonia gas and liquid ammonia) discharged from the first vaporizer 81 is supplied to the second vaporizer 82A via a connecting pipe 89. The liquid ammonia remaining in the first vaporizer 81 includes liquid ammonia that did not vaporize while flowing through the first heat transfer tube and liquid ammonia that vaporized while flowing through the first heat transfer tube and then re-condensed. The heat source of first vaporizer 81 may be other than seawater, for example, water (industrial water) or steam, as long as it has a temperature equal to or higher than the boiling point of liquid ammonia. These heat sources are also preferably outside the heat cycle system that includes boiler 10 as a component.

[0034] The second vaporizer 82A is configured to vaporize the liquid ammonia remaining after the vaporization process in the first vaporizer 81, using hot air generated using the exhaust heat of the boiler 10 as a direct heat source. The second vaporizer 82A of this embodiment includes a second container 92 accommodating a second heat transfer tube (not shown) through which the ammonia fuel flows. A hot air tube 62A (62), which is a component of the ammonia fuel supply unit 60, is connected to the second vaporizer 82A. The hot air introduced into the second vaporizer 82 by the hot air tube 62A exchanges heat with the ammonia fuel flowing through the second heat transfer tube. The temperature of the hot air is sufficiently higher than the evaporation temperature and dew point temperature of the liquid ammonia. Therefore, of the ammonia fuel flowing into the second vaporizer 82A, the liquid ammonia remaining in the first vaporizer 81 is vaporized, and the remaining ammonia gas that has already vaporized at the time of flow is heated. The ammonia gas discharged from the second vaporizer 82A of this embodiment is supplied to the boiler 10 via the ammonia gas supply pipe 69 in a state of having a certain degree of superheat. The second container 92 of the second vaporizer 82A may house a fan (not shown) for promoting the flow of hot air. This promotes heat exchange between the hot air and the ammonia fuel.

[0035] In other embodiments, ammonia fuel supply unit 60A may not include ammonia tank 71, ammonia supply pump 75, and pressure regulating valve 109. For example, instead of ammonia tank 71, liquid ammonia may be supplied to first vaporizer 81 from a large tank truck or a ship that stores liquid ammonia. Furthermore, liquid ammonia such as ammonia mist may be mixed into the ammonia gas discharged from second vaporizer 82.

[0036] According to the above configuration, since multiple heat sources, namely seawater (or other heat source with a temperature equal to or higher than the boiling point of liquid ammonia) and hot air, are used to vaporize liquid ammonia, the amount of heat required to vaporize liquid ammonia is easily ensured. Furthermore, since the seawater and hot air as heat sources are outside the specified thermal cycle system constituted by the boiler 10, turbine 110, condenser 114, boiler feed pump 123, etc., their impact on the thermal efficiency of the thermal cycle is suppressed. As described above, an ammonia fuel supply unit 60A is realized which ensures the amount of heat required to vaporize liquid ammonia and suppresses the impact on the thermal efficiency of the thermal cycle. Furthermore, by connecting hot air pipe 62A to second vaporizer 82A, second vaporizer 82A vaporizes liquid ammonia using hot air as a direct heat source. Since the heat contained in the hot air is directly transferred to the liquid ammonia in second vaporizer 82A, it is easier to ensure the amount of heat required to vaporize the liquid ammonia.

[0037] Ammonia tank 71 of this embodiment stores liquid ammonia in which liquid-phase ammonia is mixed with water at a specified ratio. Water is mixed with the liquid-phase ammonia at a ratio of, for example, several mol %. According to the above configuration, since liquid ammonia contains water, stress corrosion cracking of steel and the like constituting ammonia tank 71 can be suppressed. This makes it possible to suppress leakage of liquid ammonia from ammonia tank 71. Furthermore, although the dew-point temperature of liquid ammonia containing water tends to be higher than that of liquid-phase ammonia as a pure substance, sufficient vaporization processing by first vaporizer 81 and second vaporizer 82A can suppress the inclusion of ammonia mist in the ammonia fuel discharged from second vaporizer 82A. This makes it possible to suppress misfires in boiler 10 during ammonia co-firing.

[0038] The ammonia fuel supply unit 60A includes a hot air pipe 62A that guides hot air from the air heater 42 to the second vaporizer 82A, and a heat source adjustment damper 68 provided on the hot air pipe 62A. The heat source adjustment damper 68 is configured to adjust the flow rate of the hot air flowing through the hot air pipe 62A (i.e., the direct heat source of the second vaporizer 82A in the embodiment illustrated in FIG. 3A). The amount of hot air is adjusted by adjusting the opening degree of the heat source adjustment damper 68. The opening degree of the heat source adjustment damper 68 may be changed depending on the amount of ammonia fuel supplied to the second vaporizer 82A. This ensures that the heat source required by the second vaporizer 82A to perform the vaporization process of the ammonia fuel is available. The amount of ammonia fuel supplied to the second vaporizer 82A correlates with the ammonia co-firing ratio.

[0039] In another embodiment, in addition to (or instead of) the flow rate of the ammonia fuel supplied, the opening degree of heat source adjustment damper 68 may be adjusted according to the pressure in second vaporizer 82. The evaporation temperature of liquid ammonia and the amount of heat required for the vaporization process of liquid ammonia are determined according to the pressure in second vaporizer 82A. The pressure in second vaporizer 82A may be determined by a pressure gauge (not shown) provided at the inlet or outlet of second vaporizer 82A, or may be determined by the internal pressure of ammonia tank 71 and the opening degree of pressure adjustment valve 109. Furthermore, the adjustment of the opening degree of heat source adjustment damper 68 may be performed by a controller 90 described below, or may be performed by an operator.

[0040] According to the above configuration, second vaporizer 82A can use, as a heat source, hot air according to the flow rate of the supplied ammonia fuel by adjusting the opening degree of heat source adjustment damper 68. Furthermore, because hot air pipe 62A guides hot air from air heater 42, even if equipment including boiler 10 and air heater 42 is already installed, a configuration in which second vaporizer 82A can use hot air as a heat source can be realized by performing additional installation work on this existing equipment.

[0041] Second vaporizer 82A is configured to heat the ammonia fuel discharged from first vaporizer 81 to a temperature equal to or higher than the dew point temperature to generate ammonia gas. As a specific example, the openings of pulverizer adjustment damper 49 provided in pulverizer hot air pipe 39 and heat source adjustment damper 68 provided in hot air pipe 62A are adjusted to adjust the flow rate of hot air flowing through hot air pipe 62A, thereby adjusting the heat source available to second vaporizer 82A. At this time, the openings of hot air damper 30D and cold air damper 30E shown in FIG. 1 may also be adjusted together to control the temperature of the hot air. Furthermore, the opening degrees of the pulverizer adjusting damper 49 and the heat source adjusting damper 68 may be adjusted according to the pressure in the second vaporizer 82A (the method for specifying the pressure is as described above). Furthermore, the opening degrees of the pulverizer adjusting damper 49 and the heat source adjusting damper 68 may be adjusted by the controller 90 described below, or may be adjusted by an operator. According to the above configuration, it is possible to prevent ammonia mist from being mixed into the ammonia gas discharged from the second vaporizer 82A, and therefore, it is possible to prevent misfires in the boiler 10.

[0042] The ammonia fuel supply unit 60 includes a controller 90 configured to control the opening degree of the heat source adjustment damper 68 in accordance with the flow rate of the ammonia fuel supplied to the second vaporizer 82A. The flow rate of the ammonia fuel supplied to the second vaporizer 82A may be obtained based on the ammonia co-firing ratio. The controller 90 includes a processor that executes various arithmetic processes and a memory that stores various data processed by the processor non-temporarily or temporarily. The processor may be implemented by a CPU, GPU, MPU, DSP, or other arithmetic device, or a combination of these. The memory may be implemented by a ROM, RAM, flash memory, or a combination of these.

[0043] The controller 90 of this embodiment is configured to control not only the ammonia fuel supply unit 60 but also the power plant 1, and acquires a command indicating the ammonia co-firing ratio in the boiler 10. Based on this ammonia co-firing ratio, the controller 90 specifies the amount of ammonia fuel to be supplied to the boiler 10. The specified amount of ammonia fuel to be supplied can be considered as the flow rate of ammonia fuel to be supplied to the second vaporizer 82A. Based on this flow rate of ammonia fuel, the controller 90 adjusts the opening degree of the heat source regulating damper 68. According to the above configuration, the flow rate of the hot air used as a heat source for the second vaporizer 82A can be automatically adjusted in accordance with the supply amount of ammonia fuel.

[0044] The controller 90 may also adjust the opening of the pulverizer adjustment damper 49 when adjusting the opening of the heat source adjustment damper 68. In this case, the hot air generated by the air heater 42 can be appropriately and automatically distributed between the hot air supplied to the pulverizer 3 and the hot air used directly in the second vaporizer 82A according to the supply amount of ammonia fuel.

[0045] In the present embodiment, the hot air pipe 62A is provided by branching off from the pulverizer hot air pipe 39. According to the above configuration, even if equipment including the boiler 10, the air heater 42, and the pulverizer 3 is already installed, the hot air pipe 62A branches off from the pulverizer hot air pipe 39, which makes it possible to easily install the ammonia fuel supply unit 60B in the existing equipment.

[0046] The above describes the details of ammonia fuel supply unit 60A, but the number of each of first vaporizer 81 and second vaporizer 82A (82) may be either one or more (the same applies to ammonia fuel supply unit 60B illustrated in FIG. 3B and described below). As a specific example, multiple first vaporizers 81 may be arranged in series or parallel, and multiple second vaporizers 82A (82) may also be arranged in series or parallel. This allows a larger amount of liquid ammonia to be vaporized, thereby increasing the amount of ammonia gas supplied to boiler 10.

[0047] <Example of ammonia fuel supply unit 60B according to another embodiment> 3B is a configuration diagram showing an ammonia fuel supply unit 60B (60) according to another embodiment of the present disclosure. The ammonia fuel supply unit 60B is configured to vaporize liquid ammonia using the above-mentioned hot air as an indirect heat source. In the following, configurations similar to those of the ammonia fuel supply unit 60A are given the same reference numerals in the drawings, and descriptions thereof will be omitted in part or in whole.

[0048] Ammonia fuel supply unit 60B includes a hot air pipe 62B (62), a heat exchanger 65, piping 66, and a second vaporizer 82B (82). Hot air pipe 62B is connected to branching portion 63 and heat exchanger 65, and hot air pipe 62B guides hot air into heat exchanger 65. The hot air introduced into the heat exchanger 65 exchanges heat with the heat transfer liquid circulating between the heat exchanger 65 and the second vaporizer 82, heating the heat transfer liquid. The piping 66 constitutes a part of the heat transfer liquid circulation path 77. The piping 66 introduces the heat transfer liquid discharged from the heat exchanger 65 by driving the pump 55 provided in the circulation path 77 to the second vaporizer 82B. The second vaporizer 82B (82) is configured to vaporize the liquid ammonia remaining in the vaporization process in the first vaporizer 81 using the heated heat transfer liquid as a direct heat source. That is, the second vaporizer 82B is configured to vaporize the liquid ammonia using the hot air generated using the exhaust heat of the boiler 10 as an indirect heat source. The second vaporizer 82B is, for example, a hot water bath type vaporizer, and the temperature of the hot water serving as the heat transfer medium flowing into the second vaporizer 82B is higher than the evaporation temperature and dew point temperature of the liquid ammonia. The ammonia gas discharged from the second vaporizer 82B is supplied to the boiler 10 via an ammonia gas supply pipe 69.

[0049] According to the above configuration, ammonia fuel supply unit 60B, like ammonia fuel supply unit 60A, can ensure the amount of heat required to vaporize liquid ammonia and suppress the influence on the thermal efficiency of the thermal cycle. Furthermore, the heat transfer liquid heated by the hot air in heat exchanger 65 flows into second vaporizer 82B via pipe 66. Second vaporizer 82B vaporizes the liquid ammonia using the heated heat transfer liquid, that is, using hot air as an indirect heat source. Because the specific volume of the heat transfer liquid is smaller than that of hot air, second vaporizer 82, which houses the second heat transfer tube, can be made smaller. Therefore, second vaporizer 82B can be made smaller.

[0050] A heat source adjustment damper 68 provided in the hot air pipe 62B is configured to adjust the flow rate of hot air flowing through the hot air pipe 62B (i.e., the indirect heat source of the second vaporizer 82A in the embodiment illustrated in FIG. 3B). In this embodiment, a controller 90 adjusts the opening degree of the heat source adjustment damper 68 according to the flow rate of ammonia fuel supplied to the second vaporizer 82A (i.e., according to the ammonia co-firing ratio of the boiler 10). At this time, the controller 90 according to this embodiment also adjusts the opening degree of the heat source adjustment damper 68 provided in the pulverizer hot air pipe 39. The advantages of adopting the above configuration have been described above with reference to FIG. 3A, and therefore will not be described in detail to avoid duplication.

[0051] <Example of how to operate the boiler 10> Fig. 4 is a flowchart showing a method for operating a boiler according to an embodiment of the present disclosure. The flowchart shown in Fig. 4 is executed by the controller 90, as an example. The flowchart in Fig. 4 is applicable to both the ammonia fuel supply units 60A and 60B (see Fig. 3A and Fig. 3B).

[0052] First, the boiler 10 is set to coal combustion (S11). For example, the controller 90 sends control signals to the pulverizer 3, the hot air damper 30D, the cold air damper 30E, the pulverizer adjusting damper 49, the primary air ventilator 31, the forced draft fan 38, and the like. The burners 24 and 25 inject a pulverized fuel mixture, which is a mixture of pulverized fuel and carrier gas, into the furnace 11, and also inject combustion air into the furnace 11. The pulverized fuel mixture is ignited, and a flame is formed in the boiler 10. Note that, in this embodiment, the burners 21, 22, and 23 are not operating at this time, the heat source adjusting damper 68 is closed, and hot air is not supplied to the ammonia fuel supply unit 60.

[0053] Next, it is determined whether or not to start ammonia co-firing (S13). For example, the controller 90 determines whether or not a co-firing start condition is satisfied. The co-firing start condition may be that the temperature inside the furnace 11 has reached a certain temperature or higher, that a co-firing start command has been input by an operator, or a combination of these. In this embodiment, mono-fuel combustion of coal is performed until the co-firing start condition is satisfied (S13: NO).

[0054] When the co-firing start condition is satisfied (S13: YES), the ammonia co-firing ratio is acquired (S13). The co-firing ratio may be a value indicated by a command written in advance in the program, or may be a value input by the operator as a command.

[0055] Next, a first vaporization process is performed to vaporize liquid ammonia using seawater (S17). For example, controller 90 determines the flow rate of liquid ammonia to be supplied from ammonia tank 71 based on the ammonia co-firing ratio obtained in S13. Controller 90 controls ammonia supply pump 75, a seawater pump, and pressure control valve 109 so that the determined liquid ammonia is vaporized in first vaporizer 81. Seawater flows into first vaporizer 81, and liquid ammonia flows from ammonia tank 71 into first vaporizer 81, and heat exchange occurs between the liquid ammonia and seawater. This completes the first vaporization process. Note that, if there is a sufficient amount of seawater available as a heat source in the first vaporization process, the seawater pump may supply a constant flow rate of seawater to first vaporizer 81 regardless of the ammonia co-firing ratio obtained in S13.

[0056] Next, a second vaporization process is carried out using hot air generated using the exhaust heat of the boiler 10 as a direct or indirect heat source to vaporize the liquid ammonia remaining in the first vaporization process (S19).

[0057] In the second vaporization treatment step (S19) of this embodiment, the controller 90 controls the opening degree of the heat source adjustment damper 68 according to the ammonia co-firing ratio acquired in S15 (i.e., according to the ammonia fuel supplied to the second vaporizer 82). As a result, hot air according to the ammonia co-firing ratio is used as a heat source by the second vaporizer 82. As a result, the liquid ammonia remaining in the first vaporizer 81 is vaporized, and the temperature of the ammonia gas vaporized in the first vaporizer 81 is increased. The ammonia gas discharged from the second vaporizer 82 is supplied to the burners 21, 22, and 23 via the ammonia gas supply pipe 69. These burners inject the ammonia gas into the furnace 11, causing combustion of the ammonia gas and starting the co-firing of coal and ammonia. According to the above configuration, the flow rate of the hot air used as a heat source in the second gasification process can be adjusted according to the ammonia co-firing ratio, and therefore ammonia gas according to the ammonia co-firing ratio can be supplied to the boiler 10.

[0058] Furthermore, in the second vaporization treatment step (S19) of this embodiment, the controller 90 controls the aperture of the heat source adjustment damper 68 according to the ammonia co-firing ratio acquired in S15. As the ammonia co-firing ratio increases, the amount of coal supplied to the boiler 10 decreases, thereby reducing the amount of hot air to be supplied to the pulverizer 3, and the aperture of the heat source adjustment damper 68 can be reduced. As a result, at least a portion of the hot air generated by the air heater 42 becomes surplus. The controller 90 of this embodiment controls the aperture of the heat source adjustment damper 68 so that this surplus hot air flows through the hot air pipe 62. In other words, the amount of hot air obtained by subtracting the amount of hot air to be supplied to the pulverizer 3 from the amount of hot air generated by the air heater 42 flows through the hot air pipe 62 and is used directly or indirectly as a heat source for the second vaporizer 82. The amount of excess hot air determined according to the ammonia co-firing ratio is sufficiently greater than the minimum required amount of hot air that is determined based on the amount of ammonia fuel supplied and that should be used in second vaporizer 82. In other words, a sufficient amount of hot air required for the second vaporization treatment step is secured, and it is possible to prevent ammonia gas discharged from second vaporizer 82 from containing ammonia mist. According to the above configuration, the hot air generated by the air heater 42 can be appropriately and automatically distributed between the hot air supplied to the pulverizer 3 and the hot air used directly or indirectly in the second vaporizer 82 according to the ammonia co-firing ratio. In still another embodiment, the hot air pipe 62 and the hot air pipe 39 for the pulverizer may be connected separately to the air heater 42, in which case the opening degree of the heat source adjustment damper 68 may be set independently of the opening degree of the hot air pipe 39 for the pulverizer.

[0059] After S19 is executed, it is determined whether the ammonia co-firing ratio is to be changed (S21). For example, the controller 90 determines whether the program being executed includes a command to change the ammonia co-firing ratio, or whether the operator has input a command to change the ammonia co-firing ratio. If the ammonia co-firing ratio is to be changed (S21: YES), the controller 90 repeats S15 to S21.

[0060] If the ammonia co-firing ratio is not changed (S21: NO), it is determined whether the temperature of the ammonia gas supplied to the boiler 10 has fallen below a specified value (S23). For example, the controller 90 acquires the temperature of the ammonia gas based on the detection result of the temperature sensor 88 (see FIGS. 3A and 3B) provided in the ammonia gas supply pipe 69, and determines whether the acquired temperature has fallen below a specified value. The specified value is a value higher than the evaporation temperature and dew point temperature of liquid ammonia. If the temperature of the ammonia gas is equal to or higher than the specified value (S23: NO), S27, which will be described later, is executed.

[0061] On the other hand, if the ammonia gas temperature falls below the specified value (S23: YES), there is a possibility that the heat source used by the second vaporizer 82 will become insufficient in the future for some reason, causing ammonia mist to be emitted from the second vaporizer 82. In this case, a notification process is executed (S25). For example, the controller 90 notifies the operator that the temperature of the ammonia gas has fallen below the specified value. The operator can then determine whether or not to terminate the operation of the boiler 10.

[0062] Thereafter, it is determined whether or not to terminate the operation of the boiler 10 (S27). For example, the controller 90 determines whether or not an end command to terminate the operation of the boiler 10 has been input by the operator. If an end command has not been input (S27: NO), the controller 90 returns the process to S21. If an end command has been input (S27: YES), the controller 90 executes a specified process and then terminates the operation of the boiler 10.

[0063] In S11 according to other embodiments, for example, coal and oil may be combusted instead of the mono-combustion of coal. Alternatively, ammonia gas and other fuel may be mixed and combusted from the start of operation of the boiler 10, and S11 and S13 may not be performed.

[0064] <Summary> The contents of the above-described embodiments can be understood, for example, as follows.

[0065] 1) At least one embodiment of the ammonia fuel supply unit (60) according to the present disclosure includes: An ammonia fuel supply unit (60) for supplying ammonia fuel to a boiler (10), a first vaporizer (81) for vaporizing liquid ammonia as fuel using a heat source having a temperature equal to or higher than the boiling point of the liquid ammonia; a second vaporizer (82) provided between the first vaporizer (81) and the boiler (10), for vaporizing the liquid ammonia remaining after the vaporization in the first vaporizer (81) by using, as a direct or indirect heat source, hot air generated by using exhaust heat from the boiler (10); Equipped with.

[0066] When liquid ammonia is supplied as fuel to the boiler (10), the supply rate tends to be higher than when liquid ammonia is used as a reducing agent for removing or reducing nitrogen oxides emitted from the boiler (10). The ratio of the latent heat of vaporization of ammonia to its calorific value is approximately 6%, which is higher than that of fuels such as propane (whose ratio of the latent heat of vaporization to its calorific value is approximately 0.8%). Therefore, the amount of heat required to vaporize liquid ammonia used as fuel tends to be large. In this regard, the configuration described in 1) uses a heat source having a temperature equal to or higher than the boiling point of liquid ammonia and hot air as multiple heat sources for vaporizing liquid ammonia, making it easier to ensure the amount of heat required to vaporize liquid ammonia. Furthermore, since all of the heat sources are located outside the thermal cycle that includes the boiler (10) as a component, their influence on the thermal efficiency of the thermal cycle is suppressed. As described above, an ammonia fuel supply unit (60) is realized that ensures the amount of heat required to vaporize liquid ammonia while suppressing the influence on the thermal efficiency of the thermal cycle.

[0067] 2) In some embodiments, the ammonia fuel supply unit (60) described in 1) above, a hot air pipe (62) for guiding the hot air from an air heater (42) that heats outside air using the exhaust heat of the boiler (10); a heat source adjustment damper (68) provided in the hot air pipe (62) for adjusting the flow rate of the hot air serving as the heat source for the second evaporator (82); Further provided are:

[0068] According to the configuration 2), the opening of the heat source adjustment damper (68) is adjusted, so that hot air corresponding to the flow rate of the supplied ammonia fuel can be used as a heat source. Furthermore, since the hot air pipe (62) guides the hot air from the air heater (42), even if an equipment including the boiler (10) and the air heater (42) is already installed, a configuration in which the second vaporizer (82) uses hot air as a heat source can be realized by adding an additional installation to the existing equipment.

[0069] 3) In some embodiments, the ammonia fuel supply unit (60) described in 2) above, The system further includes a controller (90) configured to control the degree of opening of the heat source adjustment damper (68) in accordance with the flow rate of the ammonia fuel supplied to the second vaporizer (82).

[0070] According to the above configuration 3), the flow rate of the hot air used as a heat source for the second vaporizer (82) can be automatically adjusted in accordance with the amount of ammonia fuel supplied.

[0071] 4) In some embodiments, the ammonia fuel supply unit (60) described in 2) or 3) above, The hot air pipe (62) is a pulverizer hot air pipe (3) for guiding the hot air heated by the air heater (42) to a pulverizer (3) for pulverizing coal as fuel. 9 ) and is provided by branching off from

[0072] According to the configuration of 4) above, even if the equipment including the boiler (10), the air heater (42), and the pulverizer (3) is an existing equipment, the hot air pipe (3) for the pulverizer can be easily installed. 9 ) from which the hot air pipe (62) branches. Therefore, the ammonia fuel supply unit (60) can be easily installed in an existing facility.

[0073] 5) In some embodiments, the ammonia fuel supply unit (60) described in any one of 2) to 4) above, the hot air pipe (62) is connected to the second vaporizer (82); The second vaporizer (82) is configured to vaporize the liquid ammonia using the hot air as the direct heat source.

[0074] According to the above configuration 5), the heat contained in the hot air is directly transferred to the liquid ammonia, so that the amount of heat required for vaporizing the liquid ammonia can be more easily ensured.

[0075] 6) In some embodiments, the ammonia fuel supply unit (60) described in any one of 2) to 4) above, a heat exchanger (65) configured to heat the heat transfer medium liquid by heat exchange between the hot air guided by the hot air pipe (62) and the heat transfer medium liquid; a pipe (66) for guiding the heat transfer liquid discharged from the heat exchanger (65) to the second vaporizer (82); Furthermore, The second vaporizer (82) is configured to vaporize the liquid ammonia using the hot air as the indirect heat source.

[0076] According to the above configuration 6), the heat transfer medium liquid heated by the hot air in the heat exchanger (65) flows through the pipe into the second vaporizer (82). The second vaporizer (82) vaporizes the liquid ammonia using the heated heat transfer medium liquid. Since the specific volume of the heat transfer medium liquid is smaller than that of the hot air, the size of the second vaporizer (82) can be reduced.

[0077] 7) In some embodiments, the ammonia fuel supply unit (60) described in any one of 1) to 6) above, The system further includes an ammonia tank (71) provided upstream of the first vaporizer (81) for storing the liquid ammonia in which liquid phase ammonia is mixed with water at a specified ratio.

[0078] According to the above configuration 7), the liquid ammonia contains water, which can suppress stress corrosion cracking in the ammonia tank (71) and can suppress leakage of the liquid ammonia from the ammonia tank (71). Furthermore, although the dew-point temperature of liquid ammonia containing water tends to be higher than that of ammonia in the liquid phase as a pure substance, for example, sufficient vaporization by the first vaporizer (81) and the second vaporizer (82) can suppress inclusion of ammonia mist in the ammonia fuel discharged from the second vaporizer (82).

[0079] 8) In some embodiments, the ammonia fuel supply unit (60) described in any one of 1) to 7) above, The second vaporizer (82) is configured to heat the ammonia fuel discharged from the first vaporizer (81) to a temperature equal to or higher than the dew point temperature, to generate ammonia gas.

[0080] According to the above configuration 8), it is possible to prevent ammonia fuel discharged from the second vaporizer (82) from containing ammonia mist.

[0081] 9) At least one embodiment of the power plant (1) according to the present disclosure includes: an ammonia fuel supply unit (60) according to any one of 1) to 8) above; the boiler (10) that generates steam using, as a heat source, combustion gas generated by combustion of fuel supplied from the ammonia fuel supply unit (60); a turbine (110) that rotates using the steam from the boiler (10) as a driving source; a generator (115) for generating electricity by rotation of the turbine (110); Equipped with.

[0082] According to the configuration of 9) above, for the same reason as in 1), a smoke generating plant can be realized that ensures the amount of heat required for vaporizing liquid ammonia while suppressing the impact on the thermal efficiency of the thermal cycle.

[0083] 10) In some embodiments, the power plant (1) according to 9) above, an air heater (42) that heats outside air by using the exhaust heat of the boiler (10); a pulverizer (3) configured to pulverize coal as fuel; a pulverizer adjusting damper (49) provided in a pulverizer hot air pipe (39) for guiding the hot air generated by the air heater (42) to the pulverizer (3), for adjusting the flow rate of the hot air supplied to the pulverizer (3); Furthermore, The ammonia fuel supply unit (60) a heat source adjusting damper (68) provided in a hot air pipe (62) branching from the pulverizer hot air pipe (39) upstream of the pulverizer adjusting damper (49), for adjusting a flow rate of the hot air serving as the heat source for the second vaporizer (82), The power plant (1) comprises: The system further includes a controller (90) configured to control the pulverizer adjusting damper (49) and the heat source adjusting damper (68) so that the flow rates of the hot air in the pulverizer hot air pipe (39) and the hot air pipe (62) are adjusted based on the ammonia co-firing ratio in the boiler (10).

[0084] According to the configuration 10), as the ammonia co-firing ratio increases, the amount of coal supplied to the boiler (10) decreases, and therefore the amount of hot air required by the pulverizer (3) decreases, and the aperture of the pulverizer adjusting damper (49) decreases. This results in excess hot air being generated. On the other hand, as the ammonia co-firing ratio increases, the amount of heat required by the second vaporizer (82) increases, and therefore the aperture of the heat source adjusting damper (68) increases. This allows the excess hot air to be effectively used as a heat source for the second vaporizer (82). Therefore, the hot air generated by the air heater (42) can be appropriately and automatically distributed between the hot air supplied to the pulverizer (3) and the hot air used in the second vaporizer (82) according to the ammonia co-firing ratio.

[0085] 11) A method of operating a boiler (10) according to at least one embodiment of the present disclosure, comprising: A method of operating a boiler (10) supplied with ammonia fuel, comprising: A first vaporization process (S17) for vaporizing liquid ammonia as fuel using a heat source having a temperature equal to or higher than the boiling point of the liquid ammonia; a second vaporization treatment step (S19) for vaporizing the liquid ammonia remaining in the first vaporization treatment step (S17) by using hot air generated by using exhaust heat from a boiler (10) as a direct or indirect heat source; Equipped with.

[0086] According to the configuration 11), for the same reason as in the configuration 1), a method for operating the boiler (10) is realized in which the amount of heat required for vaporizing the liquid ammonia is ensured and the influence on the thermal efficiency of the heat cycle is suppressed.

[0087] 12) In some embodiments, a method for operating the boiler (10) described in 11) above, comprising: In the second vaporization treatment step (S19), A heat source adjustment damper (68) is provided in a hot air pipe (62) for guiding the hot air from an air heater (42) that heats outside air by using the exhaust heat of the boiler (10). The damper adjusts the flow rate of the hot air. The degree of opening of the damper is controlled in accordance with the ammonia co-firing ratio in the boiler (10).

[0088] According to the above configuration 12), the flow rate of the hot air used as a heat source in the second vaporization treatment step (S19) can be adjusted depending on the ammonia co-firing ratio, and therefore, the ammonia fuel according to the ammonia co-firing ratio can be supplied to the boiler (10).

[0089] 13) In some embodiments, a method for operating the boiler (10) described in 12) above, comprising: In the second vaporization treatment step (S19), A pulverizer hot air pipe (39) includes a branch portion (63) that is a connection portion with the hot air pipe (62), and is connected to the pulverizer (3) configured to pulverize coal as fuel and the air heater (42). The pulverizer hot air pipe (39) has an opening degree of a pulverizer adjusting damper (49) provided between the branch portion (63) and the pulverizer (3), the pulverizer being configured to pulverize coal as fuel, and the opening degree of the pulverizer adjusting damper (49) is controlled in accordance with the ammonia co-firing ratio.

[0090] According to the configuration 13), as the ammonia co-firing ratio increases, the amount of coal supplied to the boiler (10) decreases, and therefore the amount of hot air required by the pulverizer (3) decreases, and the aperture of the pulverizer adjusting damper (49) decreases. This results in excess hot air being generated. On the other hand, as the ammonia co-firing ratio increases, the amount of heat required by the second vaporizer (82) increases, and therefore the aperture of the heat source adjusting damper (68) increases. This allows the excess hot air to be effectively used as a heat source for the second vaporizer (82). Therefore, the hot air generated by the air heater (42) can be appropriately distributed between the hot air supplied to the pulverizer (3) and the hot air used in the second vaporizer (82) according to the ammonia co-firing ratio. [Explanation of symbols]

[0091] 1: Power plant 3: Crusher 10: Boiler 30: Air pipe 34: Crusher 39: Hot air pipe for crusher 42: Air heater 49: Adjustable damper for crusher 60: Ammonia fuel supply unit 62: Hot air pipe 63: Branch 65:Heat exchanger 66: Piping 68: Heat source adjustment damper 71: Ammonia tank 81: First vaporizer 82: Second vaporizer 90: Controller 110: Turbine 115: Generator

Claims

1. 1. An ammonia fuel supply unit for supplying ammonia fuel to a boiler, comprising: a first vaporizer for vaporizing liquid ammonia as fuel using a heat source having a temperature equal to or higher than the boiling point of the liquid ammonia; A second vaporizer that is provided between the first vaporizer and the boiler and that vaporizes the liquid ammonia remaining in the vaporization process by the first vaporizer using hot air generated by using exhaust heat from the boiler as a direct or indirect heat source; a hot air pipe for guiding the hot air from an air heater that heats outside air using the exhaust heat of the boiler as the heat source of the second vaporizer; An ammonia fuel supply unit comprising:

2. a heat source adjusting damper provided in the hot air pipe for adjusting the flow rate of the hot air serving as the heat source of the second vaporizer; 10. The ammonia fuel supply unit of claim 1.

3. Further comprising a controller configured to control the opening degree of the heat source adjustment damper in accordance with the flow rate of the ammonia fuel supplied to the second vaporizer.

3. The ammonia fuel supply unit of claim 2.

4. The hot air pipe is provided branching off from a pulverizer hot air pipe for guiding the hot air heated by the air heater to a pulverizer that pulverizes coal as fuel.

4. An ammonia fuel supply unit according to claim 2 or 3.

5. the hot air pipe is connected to the second vaporizer; The second vaporizer is configured to vaporize the liquid ammonia using the hot air as the direct heat source.

4. An ammonia fuel supply unit according to claim 2 or 3.

6. a heat exchanger configured to heat the heat transfer medium liquid by heat exchange between the hot air guided by the hot air pipe and the heat transfer medium liquid; a pipe for guiding the heat transfer liquid discharged from the heat exchanger to the second vaporizer; Furthermore, The second vaporizer is configured to vaporize the liquid ammonia using the hot air as the indirect heat source.

4. An ammonia fuel supply unit according to claim 2 or 3.

7. The system further includes an ammonia tank provided upstream of the first vaporizer and configured to store the liquid ammonia in which liquid phase ammonia is mixed with water at a specified ratio.

3. An ammonia fuel supply unit according to claim 1 or 2.

8. The second vaporizer is configured to heat the ammonia fuel discharged from the first vaporizer to a dew point temperature or higher to generate ammonia gas.

3. An ammonia fuel supply unit according to claim 1 or 2.

9. The method further comprises an ammonia gas supply pipe for guiding the ammonia gas discharged from the second vaporizer to the boiler while substantially maintaining the pressure of the ammonia gas.

2. The ammonia supply unit of claim 1.

10. An ammonia fuel supply unit according to any one of claims 1 to 9; the boiler that generates steam using combustion gas generated by combustion of fuel supplied from the ammonia fuel supply unit as a heat source; a turbine that rotates using the steam from the boiler as a driving source; a generator for generating electricity by rotation of the turbine; A power plant comprising:

11. an air heater that heats outside air using the exhaust heat of the boiler; a pulverizer configured to pulverize coal as fuel; a pulverizer adjusting damper provided in a pulverizer hot air pipe for guiding the hot air generated by the air heater to the pulverizer, the pulverizer adjusting damper adjusting the flow rate of the hot air supplied to the pulverizer; Furthermore, The ammonia fuel supply unit comprises: a heat source adjusting damper provided in a hot air pipe branching from the pulverizer hot air pipe upstream of the pulverizer adjusting damper, for adjusting the flow rate of the hot air serving as the heat source for the second vaporizer; The power generation plant comprises: The system further includes a controller configured to control each of the pulverizer adjusting damper and the heat source adjusting damper so that the flow rates of the hot air in the pulverizer hot air pipe and the hot air pipe are adjusted based on the ammonia co-firing ratio in the boiler. The power plant of claim 10.

12. 1. A method for operating a boiler supplied with ammonia fuel, comprising: a first vaporization process for vaporizing liquid ammonia as fuel using a heat source having a temperature equal to or higher than the boiling point of the liquid ammonia; a second vaporization process for vaporizing the liquid ammonia remaining in the first vaporization process using hot air generated by using exhaust heat from a boiler as a direct or indirect heat source; Equipped with In the second vaporization treatment step, hot air from an air heater that heats outside air using the exhaust heat of the boiler is used as the heat source for vaporizing the liquid ammonia.

13. In the second vaporization treatment step, a heat source adjusting damper provided in a hot air pipe for guiding the hot air from the air heater, the damper adjusting the flow rate of the hot air, and the degree of opening of the damper is controlled in accordance with an ammonia co-firing ratio in the boiler. A method for operating a boiler according to claim 12.

14. In the second vaporization treatment step, a pulverizer hot air pipe including a branch portion that is a connection portion with the hot air pipe, the pulverizer hot air pipe being connected to a pulverizer configured to pulverize coal as fuel and the air heater, wherein the opening degree of a pulverizer adjusting damper provided between the branch portion and the pulverizer is controlled according to the ammonia co-firing ratio; A method for operating a boiler according to claim 13.

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