Combustion equipment and boilers

Abstract

To provide a combustion device having achieved down-sizing, and a boiler.SOLUTION: A combustion device 50 comprises a fuel channel 52 configured to allow liquified fuel to flow therethrough, an orifice 58 disposed in the fuel channel 52 to vaporize liquified fuel by depressurizing the same, and a heat transfer wall 57 configured to transfer heat of combustion air to the fuel channel 52 and disposed between a combustion air channel 23A and the fuel channel 52. According to the configuration, liquified fuel can easily be kept in a state of a liquid phase until reaching the orifice 58, and hence the fuel channel 52 disposed upstream of the orifice 58 can be downsized. The remaining liquified fuel having passed through the orifice 58 vaporizes in the downstream side of the orifice 58 by the heat of combustion air transferred from the heat transfer wall 57. An exclusive carburetor for vaporizing liquified fuel becomes unnecessary. Thereby, the combustion device 50 can be downsized.SELECTED DRAWING: Figure 2A

Description

[Technical field]

[0001] The present disclosure relates to combustion devices and boilers that use liquefied fuels. [Background technology]

[0002] The gas turbine combustion device disclosed in Patent Document 1 uses liquid ammonia, which is an example of a liquefied fuel, as fuel. In this document, the combustor liner is cooled during the process in which ammonia gas vaporized by the combustion heat of the combustor is supplied to the combustion chamber. In a separate supply line, the liquid ammonia is vaporized by a vaporizer and then injected into the combustion chamber from a burner. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-180303 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the above-mentioned patent document, the supply line between the vaporizer and the burner is passed through by ammonia gas in a gaseous state, which may lead to an increase in the size of the apparatus.

[0005] An object of the present disclosure is to provide a combustion device and a boiler that are compact. [Means for solving the problem]

[0006] A combustion device according to at least one embodiment of the present disclosure includes: a fuel flow path configured to allow a liquefied fuel to flow; a throttle provided in the fuel flow path for vaporizing the liquefied fuel by reducing pressure; a heat transfer wall provided between a combustion air flow path and the fuel flow path and configured to transfer heat of the combustion air to the fuel flow path; Equipped with.

[0007] A boiler according to at least one embodiment of the present disclosure includes: The combustion device; a furnace configured to combust the fuel gas vaporized in the combustion device; Equipped with. Effect of the Invention

[0008] According to the present disclosure, it is possible to provide a combustion device and a boiler that realize miniaturization. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram illustrating a boiler according to an embodiment of the present disclosure. [Figure 2A] 1 is a schematic diagram of a combustion device provided in a boiler according to a first embodiment. [Figure 2B] FIG. 6 is a schematic diagram of a combustion device provided in a boiler according to a second embodiment. [Figure 3A] 4 is a graph showing the relationship between the flow rate and supply pressure of fuel gas according to the first embodiment. [Figure 3B] 10 is a graph showing the relationship between the flow rate and supply pressure of fuel gas according to the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] An embodiment of the present disclosure will be described below with reference to the drawings. Note that the present invention is not limited to this embodiment, and when there are multiple embodiments, the present invention also includes a configuration in which each embodiment is combined. In the following description, up and above refer to the upper side in the vertical direction, and down and below refer to the lower side in the vertical direction, and the vertical direction is not precise and includes an error. Furthermore, the dimensions, materials, shapes, relative arrangements, and the like of the components described as the embodiments or shown in the drawings are merely illustrative examples and are not intended to limit the scope of the present disclosure. For example, expressions expressing relative or absolute configuration, such as "in a certain direction," "along a certain direction," "parallel," "orthogonal," "center," "concentric," or "coaxial," not only strictly express such a configuration, but also express a state in which there is a relative displacement with a tolerance or an angle or distance to the extent that the same function is obtained. For example, expressions indicating that things are in an equal state, such as "identical," "equal," and "homogeneous," not only indicate a state of strict equality, but also indicate a state in which there is a tolerance or a difference to the extent that the same function is obtained. For example, expressions describing shapes such as a rectangular shape or a cylindrical shape do not only refer to rectangular shapes, cylindrical shapes, etc. in the strict geometric sense, but also refer to shapes that include uneven portions, chamfered portions, etc., to the extent that the same effect is obtained. On the other hand, the expressions "comprise", "include", or "have" a certain element are not exclusive expressions excluding the presence of other elements. In addition, the same components are denoted by the same reference numerals and the description thereof may be omitted.

[0011] FIG. 1 is a schematic diagram showing the configuration of a boiler using solid fuel and liquefied fuel as main fuels according to this embodiment.

[0012] The boiler 10 of this embodiment is a boiler that can burn pulverized fuel obtained by pulverizing solid fuel and fuel gas obtained by vaporizing liquefied fuel using a burner, and exchange the heat generated by this combustion with feed water or steam to generate superheated steam. As the solid fuel, biomass fuel, coal, etc. are used. The liquefied fuel is a fuel that is in a gas phase at normal temperature under atmospheric pressure. The normal temperature in this specification is 35°C. The liquefied fuel is, for example, liquefied petroleum gas (LPG), liquefied natural gas (LNG), dimethyl ether (DME), liquid ammonia, etc. In the following description, unless otherwise specified, the liquefied fuel refers to liquid ammonia, and the fuel gas refers to ammonia gas.

[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 rectangular cylinder shape and is installed vertically. The furnace wall 101 constituting the inner wall surface of the furnace 11 is composed of a plurality of heat transfer tubes and fins connecting the heat transfer tubes, and recovers heat generated by the combustion of fuel by heat exchange with water and steam flowing inside the heat transfer tubes, while suppressing 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 this embodiment, the combustion device 20 is configured to inject pulverized coal fuel into the interior of the furnace 11, and the combustion device 50 is configured to inject fuel gas into the interior of the furnace 11.

[0015] The combustion device 20 has a plurality of burners 21A, 21B (hereinafter, sometimes collectively referred to as "burners 21") attached to the furnace wall 101, and the combustion device 50 has burners 51A, 51B, 51C, 51D (hereinafter, sometimes collectively referred to as "burners 51"). The burners 21, 51 are arranged at equal intervals along the circumferential direction of the furnace 11 (for example, four burners installed at each corner of the rectangular furnace 11) as one set (one stage), and are arranged in multiple stages along the vertical direction. For convenience of illustration, only two burners of one set are shown in FIG. 1, and each set is denoted by the reference numerals 21A, 21B, 51A, 51B, 51C, 51D. The shape of the furnace, the number of burner stages, the number of burners in one stage, the arrangement of the burners, and the like are not limited to this embodiment.

[0016] The combustion device 20 is outlined as follows. The burners 21A and 21B are 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 rollers and the pulverizing table is transported to a classifier (not shown) provided in the mill 31 by primary air (carrier gas, oxidizing gas) supplied to the mill 31. In the classifier, the fuel is classified into pulverized fuel having a particle size equal to or smaller than that suitable for combustion in the burner 21 and coarse pulverized fuel having a particle size larger than the particle size. The pulverized fuel passes through the classifier and is supplied to the burner 21 together with the primary air through the pulverized fuel supply pipe 22. The coarse pulverized fuel that does not pass through the classifier falls onto the grinding table by its own weight inside the mill 31 and is re-pulverized.

[0017] The combustion device 50 is outlined as follows. The burners 51A-51D are provided with fuel flow paths 52A-52D (hereinafter, sometimes collectively referred to as "fuel flow path 52"). In this embodiment, the liquefied fuel stored in the fuel tank 59 is vaporized (details will be described later) while flowing through the fuel flow path 52 by the drive of the pump 63, and fuel gas is obtained. The burner 51 is configured to blow this fuel gas into the inside of the furnace 11. Note that the fuel flow paths 52A-52D are provided with on-off valves 62A-62D (hereinafter, sometimes collectively referred to as "on-off valve 62"), respectively, so that the plurality of burners 51 can be selectively operated. Also, the amount (flow rate) of fuel gas blown by each burner 51 can be adjusted by changing the opening degree of a pressure regulating valve 68 provided between the on-off valve 62 and the pump 63. The flow rate (injection amount) of the fuel gas in the burner 51 is adjusted by adjusting the supply pressure of the fuel gas by changing the open / close state of the on-off valve 62 and the opening degree of the pressure regulating valve 68. In other embodiments, the combustion device 50 may not include the fuel tank 59 and the pump 63. The liquefied fuel may be supplied to the fuel flow passage 52 through a pipeline from, for example, a liquefied fuel production site or a large-scale storage facility.

[0018] An air register (wind box) 23 is provided on the outside of the furnace 11 at the mounting positions of the burners 21, 51, and one end of an air duct (air duct) 24 is connected to this air register 23. A forced draft fan (FDF: Forced Draft Fan) 32 is connected to the other end of the air duct 24. Air supplied from the forced draft fan 32 is heated by an air preheater 42 installed in the air duct 24 (details will be described later), and is supplied to the burner 21 via the air register 23 as secondary air (combustion air, oxidizing gas), and is introduced into the furnace 11.

[0019] The combustion gas passage 12 is connected to the vertical upper part of the furnace 11. The combustion gas passage 12 is provided with superheaters 102A, 102B, and 102C (hereinafter, sometimes collectively referred to as "superheaters 102"), reheaters 103A and 103B (hereinafter, sometimes collectively referred to as "reheaters 103"), and a coal economizer 104 as heat exchangers for recovering heat from the combustion gas, and heat is exchanged between the combustion gas generated in the furnace 11 and feed water or steam flowing inside each heat exchanger. The arrangement and shape of each heat exchanger are not limited to the form shown in FIG. 1.

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

[0021] Furthermore, a denitration device 43 may be provided in the flue 13 at a position upstream of the air preheater 42. The denitration device 43 supplies a reducing agent having an effect of reducing nitrogen oxides, such as ammonia or urea water, to the combustion gas flowing through the flue 13, and promotes a reaction between the nitrogen oxides (NOx) in the combustion gas to which the reducing agent has been supplied and the reducing agent by the catalytic action of a denitration catalyst provided in the denitration device 43, thereby removing and reducing the nitrogen oxides in the combustion gas. A gas duct 41 is connected to the flue 13 downstream of the air preheater 42. The gas duct 41 is provided with environmental equipment such as a dust collector 44, such as an electrostatic precipitator, for removing ash and the like from the combustion gas, a desulfurization equipment 46 for removing sulfur oxides, and an induced draft fan (IDF) 45 for directing the exhaust gas to these environmental equipment. The downstream end of the gas duct 41 is connected to a chimney 47, and the combustion gas treated in the environmental equipment is discharged to the outside of the system as exhaust gas.

[0022] In the boiler 10, when the multiple mills 31 are driven, pulverized and classified pulverized fuel is supplied to the burner 21 together with primary air via the pulverized fuel supply pipe 22. In addition, fuel gas obtained by vaporizing liquefied fuel is supplied to the burner 51. Furthermore, secondary air heated by the air preheater 42 is supplied to the burners 21 and 51 from the air duct 24 via the air register 23. The burner 21 blows a pulverized fuel mixture, which is a mixture of pulverized fuel and primary air, into the furnace 11, and also blows secondary air into the furnace 11. The pulverized 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 together with the fuel gas into the furnace 11. The fuel gas blown into the furnace 11 reacts with the secondary air and burns. High-temperature combustion gas generated by the combustion of pulverized fuel and fuel gas rises within the furnace 11 and flows into the combustion gas passage 12. The timing for injecting the fuel gas into the furnace 11 may be after the temperature inside the furnace 11 has risen to a certain temperature by the combustion of the startup fuel and the pulverized fuel. For example, after the boiler 10 is started using the startup fuel and the pulverized fuel is combusted, the fuel gas may be injected into the furnace 11 to perform mixed combustion of the fuel gas and the pulverized fuel. After that, the injection of the pulverized fuel may be stopped and the fuel gas may be exclusively combusted. In addition, in this embodiment, air is used as the oxidizing gas (primary air, secondary air), but the oxidizing gas may have a higher or lower oxygen content than air, and stable combustion in the furnace 11 can be achieved by adjusting the ratio of the amount of oxygen to the amount of fuel supplied within an appropriate range.

[0023] The combustion gas flowing into the combustion gas passage 12 exchanges heat with water and steam in a superheater 102, a reheater 103, and a coal economizer 104 arranged inside the combustion gas passage 12, and is then discharged into the flue 13, where nitrogen oxides are removed in a denitration device 43, and the combustion gas exchanges heat with primary air and secondary air in an air preheater 42, and is then discharged into a gas duct 41, where ash and the like are removed in a dust collector 44, and sulfur oxides are removed in a desulfurization device 46, and the combustion gas is then discharged to the outside of the system from a chimney 47. Note that the arrangement of the heat exchangers in the combustion gas passage 12 and the devices from the flue 13 to the gas duct 41 with respect to the combustion gas flow does not necessarily have to be in the order described above.

[0024] In the above-described embodiment, the boiler of the present disclosure has been described as a boiler that uses solid fuel as fuel. The solid fuel used in the boiler may be coal, biomass fuel, petroleum coke (PC), petroleum residue, or the like. The fuel for the boiler is not limited to solid fuels, but can also be petroleum such as heavy oil, light oil, and heavy oil, liquid fuels such as industrial wastewater, etc. Also, gaseous fuels such as natural gas, various petroleum gases, and by-product gases generated in the steelmaking process can also be used. Furthermore, the present invention can be applied to a multi-fuel boiler that uses a combination of these various fuels.

[0025] 2A is a schematic diagram showing a combustion device according to the first embodiment. A combustion device 50A (50) included in a boiler 10A (10) according to the first embodiment includes a burner 510. This burner 510 corresponds to at least one of the burners 51A to 51D shown in FIG.

[0026] The combustion device 50A includes, in addition to the above-mentioned fuel tank 59 (see FIG. 1), pump 63 (see FIG. 1), fuel flow passage 52, pressure regulating valve 68, on-off valve 62, and burner 510, a throttle 58 provided in the fuel flow passage 52, a heat transfer wall 57 provided between the combustion air flow passage 23A and the fuel flow passage 52, and a fuel nozzle 55 connected to the downstream end of the fuel flow passage 52. In the embodiment illustrated in FIG. 2A, the combustion air flow passage 23A is formed inside the air register 23. In other embodiments, the combustion air flow passage 23A may be formed by a component different from the air register 23. This component may be in communication with the air duct 24 (see FIG. 1). The fuel nozzle 55 is exposed to the internal space of the furnace 11 from a burner opening 15 formed in the furnace wall 101. In the example of Fig. 2A, the number of fuel nozzles 55 surrounded by the burner opening 15 is one.

[0027] The above-mentioned throttle 58 is configured so that the liquefied fuel flowing through the fuel flow passage 52 is vaporized by reducing the pressure. The throttle 58 is, for example, an orifice, a venturi, etc. At least a part of the liquefied fuel flowing through the throttle 58 is vaporized by reducing the pressure. For example, in an embodiment in which liquid ammonia is used as the liquefied fuel, the pressure and flow velocity of the liquefied fuel upstream of the throttle 58 are 1.5 MPa and 10 m / sec, respectively, and the pressure and flow velocity of the fuel gas (which may contain liquefied fuel) downstream are 0.15 MPa and 50 m / sec, respectively. 2A has an expanded diameter portion 64 provided downstream of the constriction 58. This allows the fuel flow passage 52 formed by the heat transfer wall 57 to accommodate the volumetric flow rate of the fuel gas vaporized as it passes through the constriction 58. In the example of FIG. 2A, the expanded diameter portion 64 is included in the heat transfer wall 57.

[0028] The heat transfer wall 57 of this embodiment is housed in the air register 23 that forms the flow path 23A of the secondary air (combustion air), and forms a part of the fuel flow path 52. The heat transfer wall 57 is configured to transfer heat of the combustion air to the fuel flow path 52. As illustrated in FIG. 2A, the heat transfer wall 57 is provided at least downstream of the throttle 58. Therefore, the remaining liquefied fuel that passes through the throttle 58 is vaporized by the heat of the combustion air transmitted through the heat transfer wall 57. In addition, the fuel gas vaporized by the throttle 58 is superheated by the heat transmitted from the heat transfer wall 57, so that condensation and re-liquefaction are suppressed. This allows the fuel nozzle 55 to blow the supplied fuel gas into the inside of the furnace 11. 2A, the inner diameter of heat transfer wall 57 is equal to the inner diameter of the downstream end of expanded diameter portion 64. This allows fuel flow passage 52 formed by heat transfer wall 57 to accommodate the volumetric flow rate of fuel gas. Note that the inner diameter of fuel flow passage 52 downstream of expanded diameter portion 64 is approximately three to four times larger than the inner diameter of fuel flow passage 52 upstream of constriction 58.

[0029] According to the above configuration, the liquefied fuel maintains its liquid phase state by maintaining the pressure in the system at or above the vapor pressure of the liquefied fuel until it reaches the orifice 58. This allows the fuel flow passage 52 upstream of the orifice 58 to be made smaller. Furthermore, downstream of the orifice 58, the remaining liquefied fuel that passes through the orifice 58 is vaporized by the heat of the combustion air transmitted from the heat transfer wall 57. Since the liquefied fuel is vaporized using the heat of the combustion air supplied to the furnace 11, a dedicated vaporizer for vaporizing the liquefied fuel is not required. This allows the combustion device 50A to be made more compact. 2A, the throttle 58 is disposed inside the air register 23, and the fuel flow passage 52 upstream of the throttle 58 is also formed by the heat transfer wall 57. In other embodiments, the throttle 58 may be disposed outside the air register 23. For example, the throttle 58 may be provided outside the air register 23 and downstream of the pressure regulating valve 68. In this case, the aforementioned expanded diameter portion 64 may also be disposed outside the air register 23.

[0030] The combustion device 50A of this embodiment includes a burner body 56 disposed inside the air register 23 including the combustion air flow path 23A. The above-mentioned fuel nozzle 55 is provided at the downstream end of the burner body 56. The burner body 56 constitutes at least a part of the heat transfer wall 57. In the illustrated embodiment, the burner body 56 is provided downstream of the orifice 58. According to the above configuration, the burner body 56 constituting at least a part of the heat transfer wall 57 is disposed inside the air register 23 including the flow path 23A of the combustion air, eliminating the need for a dedicated flow path for sending the combustion air to the heat transfer wall 57. Furthermore, even when the combustion device 50A is installed in an existing facility, construction is easy.

[0031] In this embodiment, the flow path length (dimension Lt) of the heat transfer wall 57 formed by the burner body 56 is half or more of the length (dimension La) of the air register 23 in the thickness direction of the furnace wall 101. The dimension Lt in this example corresponds to the flow path length of the burner body 56. According to the above configuration, the flow path length of the heat transfer wall 57 can be secured to a certain length or more, so that the remaining liquefied fuel flowing through the fuel flow path 52 formed by the heat transfer wall 57 can be sufficiently heated. Therefore, the liquefied fuel can be more reliably vaporized. In addition, the fuel gas vaporized in the orifice 58 can be sufficiently superheated, so that the condensation and re-liquefaction of the fuel gas can be suppressed.

[0032] In this embodiment, the orifice 58 is disposed inside the air register 23. Furthermore, in the illustrated embodiment, a part of the fuel flow passage 52 (hereinafter, may be referred to as the "upstream fuel flow passage 54") located upstream of the orifice 58 is also disposed inside the air register 23. According to the above configuration, the liquefied fuel increases in temperature as it passes through the orifice 58 by obtaining heat from the combustion air. Therefore, the combustion device 50A can reduce the liquefied fuel remaining in the orifice 58.

[0033] In this embodiment, the heat transfer wall 57 has a higher heat storage amount per unit flow path length than the fuel flow path 52 (upstream fuel flow path 54) located upstream of the throttle 58. As a first specific example, the inner diameter of wall portion 57A of heat transfer wall 57 is larger than the inner diameter of the wall portion that constitutes upstream fuel flow passage 54. As a result, the volume of wall portion 57A per unit flow passage length is larger than the wall portion that constitutes upstream fuel flow passage 54, and the amount of heat stored per unit length of heat transfer wall 57 is higher than that of upstream fuel flow passage 54. As a second specific example, wall portion 57A of heat transfer wall 57 is thicker than the wall portion that constitutes upstream fuel flow passage 54. Even in this case, the amount of heat stored per unit length of heat transfer wall 57 is higher than that of upstream fuel flow passage 54, for the same reason as above. As a third specific example, the heat transfer wall 57 includes a wall portion 57A and a sensible heat utilization type heat storage material (not shown) provided so as to surround the outer peripheral surface of the wall portion 57A. The heat storage density (amount of heat that can be stored per unit volume) of the heat storage material is preferably higher than the heat storage density of the wall portion constituting the upstream fuel flow path 54. One example of the material of such a heat storage material is ceramic. Note that the heat storage material may be a phase transition type (a more specific example is a solid phase transition type) heat storage material, and vanadium oxide, polyhydric alcohol, or a compound analogous thereto may be adopted as the material constituting the heat storage material. According to the above configuration, for example, before the liquefied fuel flows through the fuel flow passage 52, sufficient heat can be stored in the heat transfer wall 57 by using the combustion air, so that the liquefied fuel flowing through the fuel flow passage 52 formed by the heat transfer wall 57 can be more reliably vaporized. In addition, since the fuel gas can be sufficiently superheated, the fuel gas can be prevented from condensing and re-liquefying.

[0034] The heat transfer wall 57 of this embodiment further includes heat transfer promoters 53 for increasing the heat transfer area of ​​the heat transfer wall 57. The heat transfer promoters 53 are fins that protrude outward from the heat transfer wall 57 and are arranged at intervals along the extension direction of the heat transfer wall 57. The thickness direction of each fin is, for example, parallel to the extension direction of the fuel flow path 52. Examples of materials constituting the fins include metals such as aluminum, copper, stainless steel, and iron-based plated steel, and aluminum and copper are particularly preferable because of their good thermal conductivity. Although detailed illustration is omitted, the heat transfer promoter 53 may be provided so as to protrude inward from the wall portion 57A of the heat transfer wall 57. In other words, the heat transfer promoter 53 may be formed in the fuel flow passage 52. Even in this case, the heat transfer area of ​​the heat transfer wall 57 can be increased. According to the above-described configuration, the provision of the heat transfer promoter 53 promotes heat transfer from the combustion air to the fuel flow passage 52, so that the liquefied fuel can be vaporized in the fuel flow passage 52 more reliably. It is also possible to provide both the heat storage material (not shown) and the heat transfer promoter 53. For example, a plurality of heat transfer promoters 53 and a plurality of heat storage materials may be arranged alternately along the extension direction of the fuel flow path 52. Alternatively, a heat storage material may be provided on the outer side of the wall portion 57A, and a heat transfer promoter 53 may be provided on the inner side of the wall portion 57A.

[0035] The liquefied fuel in this embodiment is liquid ammonia. According to the above configuration, the emission of carbon oxides such as carbon dioxide accompanying the combustion in the furnace 11 is suppressed, so that the combustion device 50A can reduce the environmental load. In addition, the ratio of the latent heat of vaporization to the calorific value of ammonia is about 6%, which is higher than that of fuels such as propane (the ratio of the latent heat of vaporization to the calorific value is about 0.8%). Therefore, the amount of heat required to vaporize the liquid ammonia used as fuel tends to be large. In this regard, by adopting the above configuration, it is possible to vaporize the liquid ammonia without installing a dedicated vaporizer. As described above, a compact combustion device 50A for liquid ammonia is realized.

[0036] 2B is a schematic diagram showing a combustion device according to a second embodiment. A combustion device 50B (50) included in a boiler 10B (10) according to the second embodiment includes a plurality of burners 511 (51), and the plurality of burners 511 correspond to any of the burners 51A to 51D shown in FIG. 1. Alternatively, each of the burners 51A to 51D may be realized by a plurality of burners 511. Each burner 511 has a configuration similar to that of the burner 510 (see FIG. 2A). When any of the fuel nozzles 55 injects fuel gas, the opening / closing valve 62 corresponding to this fuel nozzle 55 is controlled. In some embodiments, after the injection amount of one burner 511 reaches an upper limit, the injection of fuel gas by the other burner 511 is started. 2B, the number of fuel nozzles 55 surrounded by the burner opening 15 is two, but the number of burners 511 surrounded by the burner opening 15 may be three or more. In other words, the number of burners 511 provided in the combustion device 50B may be three or more. In addition, in the example of Figure 2B, the two fuel nozzles 55 surrounded by the burner opening 15 are arranged so as to be aligned vertically, but as another example, they may be arranged so as to be aligned from the front side to the back side of the paper in Figure 2B. With the above-described configuration, even when the combustion device 50B is installed in an existing facility, construction work for modifying the burner opening 15 can be suppressed.

[0037] 3A and 3B, the difference between the variable ranges of the flow rate adjustment of the fuel gas in the boiler 10 shown in Fig. 2A and Fig. 2B will be described. In the following, for ease of understanding, it is assumed that the burner 51 of the boiler 10 is composed of four burners 51A to 51D. Fig. 3A is a graph showing a schematic relationship between the fuel gas flow rate Q and the supply pressure P in boiler 10A in which burners 51A-51D (see Fig. 1) are each constituted by burner 510 (see Fig. 2A). Fig. 3B is a graph showing a schematic relationship between the fuel gas flow rate Q and the supply pressure P in boiler 10B in which burners 51A-51D are each constituted by two burners 511 (see Fig. 2B). Here, the supply pressure P is the pressure upstream of the orifice 58. The flow rate Q of the fuel gas is determined by the supply pressure P depending on the pressure loss in the orifice 58, the burner body 56, and the fuel nozzle 55.

[0038] The straight line L1 in the graph shown in FIG. 3A shows the relationship between the flow rate Q and the supply pressure P when only the burner 51A is operating, and is created based on the assumption that the remaining burners 51B to 51D are not operating. The straight line L2 in the same figure shows the relationship between the total flow rate Q and the supply pressure P of each of the burners 51A and 51B when only the burners 51A and 51B are operating. The straight line L2 is created based on the assumption that the same supply pressure P is set for each of the burners 51A and 51B, and that the remaining burners 51C and 51D are not operating. Similarly, the straight line L3 shows the relationship between the total flow rate Q in the burners 51A to 51C and the supply pressure P of each of the burners 51A to 51C, and the straight line L4 shows the relationship between the total flow rate Q in the burners 51A to 51D and the supply pressure P of each of the burners 51A to 51D. 3A is a graph that shows a schematic relationship between the flow rate Q and the supply pressure P of the fuel gas, and the actual control of the supply pressure P in the boiler 10A is not necessarily performed so that the flow rate Q changes as shown in the graph in the figure. In other words, the burners 51A-51D are not necessarily controlled to have the same supply pressure P, and it is not necessarily controlled so that any of the burners 51A-51D is not in operation (the same applies to FIG. 3B).

[0039] 3B, the straight line L1A indicates the relationship between the flow rate Q and the supply pressure P when only one of the two burners 511 included in the burner 51A is operating, and the straight line L1B indicates the relationship between the total flow rate Q and the supply pressure P of each burner 511 when only the two burners 511 included in the burner 51A are operating. Also, the straight line L2A in the graph of the same figure indicates the relationship between the total flow rate Q and the supply pressure P of each burner 511 when only one of the two burners 511 included in the burner 51A and the two burners 511 included in the burner 51B is operating. The straight lines L2B, L3A, L3B, L4A, and L4B will be omitted to avoid duplication of explanation.

[0040] In this embodiment, representative values ​​of the fuel gas supply pressure P are, in ascending order, a lower limit pressure P1 for injecting fuel into the furnace 11, a vapor pressure P2 of the fuel gas, and a maximum supply pressure P max The following are some of the reasons: If the fuel used in the burner 51 is not liquefied fuel but liquid fuel such as heavy oil (fuel that is liquid at normal temperature and pressure), the supply pressure P can be reduced to the lower limit pressure P1. However, when liquefied fuel is used, it is necessary to maintain the supply pressure P at or above the vapor pressure P2 in order to suppress circulation problems (vapor lock) caused by vaporization of the liquefied fuel, for example, in the fuel flow passage 52 upstream of the throttle 58. In addition, since the maximum flow rate Qmax of the fuel gas is determined by the structure of the boiler 10, it is difficult to increase it. Therefore, when liquefied fuel is used, the flow rate variable range is limited. In FIG. 3A, the increase in the lower limit value of the flow rate Q due to the fuel being liquefied fuel when only the burner 51A is operating is indicated by ΔQ. It is understood that this ΔQ indicates the amount of decrease in the flow rate variable range in the burner 51A.

[0041] On the other hand, as shown in FIG. 3B, when each of the burners 51A to 51D is composed of two burners 511, the fuel flow passage 52, which is a supply line for the liquefied fuel, can be increased (divided), and it becomes possible to control the flow state of the liquefied fuel in each of the fuel flow passages 52. For example, as shown by the straight line L1A, when only one of the burners 511 included in the burner 51A is in operation, the flow rate Q of the fuel gas at the vapor pressure P2 is lim_y is the flow rate Q at vapor pressure P2 shown by line L1 lim_x Therefore, it can be seen that the boiler 10B (FIG. 2B) can widen the variable range of the fuel gas flow rate adjustment compared to the boiler 10A (FIG. 2A).

[0042] Returning to FIG. 2B, the boiler 10B further includes an exhaust gas passage 70 for guiding a portion of the exhaust gas from the furnace 11 (see FIG. 1) to the combustion air passage 23A. In the illustrated embodiment, the upstream end of the exhaust gas passage 70 is connected to the flue 13 between the economizer 104 and the denitration device 43, and the downstream end of the exhaust gas passage 70 is connected to the air register 23. This allows the combustion air and the exhaust gas to be mixed in the passage 23A formed by the air register 23 (the mixed air is blown into the furnace 11 from the burner 51). The flow direction of the exhaust gas in the flue 13 corresponds to the arrow R. According to the above configuration, exhaust gas from the furnace 11 is supplied to the combustion air flow path 23A, so that it is possible to prevent a shortage of the heat source required for vaporizing the liquefied fuel. This makes it possible to prevent the liquefied fuel from remaining in the fuel gas supplied to the fuel nozzle 55 and the fuel gas supplied to the fuel nozzle 55 from condensing and re-liquefying.

[0043] <Summary> The contents described in the above-mentioned embodiments can be understood, for example, as follows.

[0044] 1) A combustion device (50) according to at least one embodiment of the present disclosure comprises: a fuel flow passage (52) configured to allow a liquefied fuel to flow therethrough; a throttle (58) provided in the fuel flow path (52) for vaporizing the liquefied fuel by reducing pressure; a heat transfer wall (57) provided between the combustion air flow path (23A) and the fuel flow path (52) and configured to transfer heat of the combustion air to the fuel flow path (52); Equipped with.

[0045] According to the above configuration 1), the liquefied fuel tends to maintain a liquid state until it reaches the orifice (58), so the fuel flow path (52) upstream of the orifice (58) can be made smaller. Furthermore, downstream of the orifice (58), the remaining liquefied fuel that passes through the orifice (58) is vaporized by the heat of the combustion air transferred from the heat transfer wall (57). The heat of the combustion air supplied toward a predetermined location is used to vaporize the liquefied fuel, so that a dedicated vaporizer for vaporizing the liquefied fuel is not required. This allows the combustion device (50) to be made more compact. Furthermore, for example, when the combustion device (50) has a structure for injecting (spraying) liquefied fuel in a liquid phase, it is necessary to supply an atomizing medium, such as steam, to the combustion device (50) in order to promote atomization of the sprayed liquefied fuel. In addition, the heat of the atomizing medium is transferred to the liquefied fuel, which may cause the liquefied fuel before being injected to vaporize, resulting in unstable fuel injection. In this regard, in the above-described configuration, since it is fuel gas that is injected, the above-described atomizing medium is not required, and stable fuel injection is possible. In addition, piping and valves for supplying the atomizing medium are not required.

[0046] 2) In some embodiments, the combustion device (50) described in 1) above, a burner body (56) arranged inside an air register (23) including a flow path (23A) of the combustion air, At least a portion of the heat transfer wall (57) is formed by the burner body (56).

[0047] According to the above configuration 2), the burner body (56) constituting at least a part of the heat transfer wall (57) is disposed inside the air register (23) including the flow path (23A) of the combustion air, eliminating the need for a dedicated flow path (23A) for sending the combustion air to the heat transfer wall (57). Furthermore, even when the combustion device (50) is installed in an existing facility, construction is easy.

[0048] 3) In some embodiments, the combustion device (50) described in 2) above, The flow path length of the heat transfer wall (57) is equal to or greater than half the length of the air register (23) in the thickness direction of the furnace wall (101).

[0049] According to the above configuration 3), the flow path length of the heat transfer wall (57) can be ensured to be at least a certain length. Therefore, in the fuel flow path (52), the remaining liquefied fuel flowing through the fuel flow path (52) defined by the heat transfer wall (57) can be sufficiently heated. As a result, the liquefied fuel can be vaporized more reliably.

[0050] 4) In some embodiments, the combustion device (50) described in either 2) or 3) above, The restrictor (58) is disposed inside the air register (23).

[0051] According to the above configuration 4), since the throttle (58) is disposed inside the air register (23), the temperature of the liquefied fuel passing through the throttle (58) increases by obtaining heat from the combustion air. Therefore, the combustion device (50) can reduce the amount of liquefied fuel remaining in the throttle (58).

[0052] 5) In some embodiments, the combustion device (50) described in any one of 1) to 4) above, The heat transfer wall (57) has a higher heat storage amount per unit flow path length than the fuel flow path (52) located upstream of the throttle (58).

[0053] According to the above configuration 5), for example, before the liquefied fuel flows through the fuel flow path 52, it is possible to store sufficient heat in the heat transfer wall 57 by using the combustion air, so that it is possible to more reliably vaporize the liquefied fuel in the fuel flow path 52. In addition, it is possible to sufficiently superheat the fuel gas, so that it is possible to prevent the fuel gas from condensing and re-liquefying.

[0054] 6) In some embodiments, the combustion device (50) described in any one of 1) to 5) above, The heat transfer wall (57) further includes a heat transfer enhancer (53) for increasing the heat transfer area of ​​the heat transfer wall (57).

[0055] According to the above configuration 6), the provision of the heat transfer promoter (53) promotes heat transfer from the combustion air to the fuel flow path (52), so that the liquefied fuel can be vaporized more reliably in the fuel flow path (52).

[0056] 7) In some embodiments, the combustion device (50) described in any one of 1) to 6) above, The liquefied fuel is liquid ammonia.

[0057] According to the above configuration 7), since the liquefied fuel is liquid ammonia, carbon dioxide emissions due to combustion are suppressed, and therefore the combustion device (50) can reduce the environmental load. Furthermore, the ratio of the latent heat of vaporization to the calorific value of ammonia is about 6%, which is higher than that of fuels such as propane (the ratio of the latent heat of vaporization to the calorific value is about 0.8%). Therefore, the amount of heat required to vaporize the liquid ammonia used as fuel tends to be large, and the vaporizer also tends to be large. In this regard, by adopting the above configuration 1), the liquid ammonia can be vaporized without installing a dedicated vaporizer for vaporizing the liquid ammonia. As described above, the liquid ammonia combustion device (50) can be made smaller in size.

[0058] 8) At least one embodiment of the boiler (10) according to the present disclosure includes: A combustion device (50) according to any one of 1) to 7) above; a furnace (11) configured to combust the liquefied fuel vaporized in the combustion device (50); Equipped with.

[0059] According to the above configuration 8), the boiler (10) can be made smaller in size for the same reason as in the above configuration 1).

[0060] 9) In some embodiments, the boiler (10) according to 8) above, The combustion device (50) A plurality of the fuel passages (52); a plurality of fuel nozzles (55) provided at downstream ends of the plurality of fuel flow paths (52), respectively; a plurality of valves (62) provided in each of the plurality of fuel flow paths (52); Including, The furnace includes a burner opening (15) surrounding the plurality of fuel nozzles (55).

[0061] According to the above configuration 9), even when the combustion device (50) is installed in an existing facility, it is possible to suppress the need to modify the burner opening (15). In addition, since the fuel flow passage (52), which is the supply line of the liquefied fuel, can be increased (divided), it is possible to widen the variable range of the flow rate adjustment of the liquefied fuel.

[0062] 10) In some embodiments, the boiler (10) according to 8) or 9) above, an exhaust gas passage (70) for directing exhaust gas from the furnace (11) to the combustion air passage (23A); It further comprises:

[0063] According to the above configuration 10), exhaust gas from the furnace (11) is supplied to the combustion air flow path (23A), so that shortage of the heat source required for vaporizing the liquefied fuel can be suppressed. [Explanation of symbols]

[0064] 10: Boiler 11: Furnace 15: Burner opening 20: Combustion equipment 21: Burna 23: Air register 23A: Flow path 50: Combustion equipment 51: Burna 52: Fuel flow path 53: Heat transfer promoter 55: Fuel nozzle 56: Burner body 57: Heat transfer wall 58: Aperture 101: Furnace wall

Claims

1. a fuel flow path configured to allow a liquefied fuel to flow; a throttle provided in the fuel flow path for vaporizing the liquefied fuel by reducing pressure; a heat transfer wall provided between a combustion air flow path and the fuel flow path and configured to transfer heat of the combustion air to the fuel flow path; A combustion device comprising:

2. a burner body disposed inside an air register including the combustion air flow path; At least a portion of the heat transfer wall is constituted by the burner body. The combustion device of claim 1 .

3. The flow path length of the heat transfer wall is equal to or greater than half the length of the air register in the thickness direction of the furnace wall. The combustion device according to claim 2.

4. The restriction is disposed inside the air register. A combustion device according to claim 2 or 3.

5. The heat transfer wall has a higher heat storage amount per unit flow path length than the fuel flow path located upstream of the throttle. A combustion device according to any one of claims 1 to 4.

6. The heat transfer wall further includes a heat transfer promoter for increasing the heat transfer area of ​​the heat transfer wall. Combustion device according to any one of claims 1 to 5.

7. The liquefied fuel is liquid ammonia. Combustion device according to any one of claims 1 to 6.

8. A combustion device according to any one of claims 1 to 7; a furnace configured to combust the liquefied fuel vaporized in the combustion device; A boiler equipped with

9. The combustion device includes: A plurality of the fuel flow paths; a plurality of fuel nozzles provided at downstream ends of the plurality of fuel flow paths; a plurality of flow rate control valves provided in the plurality of fuel flow paths, respectively; Including, The furnace includes a burner opening surrounding the plurality of fuel nozzles. The boiler according to claim 8.

10. A combustion gas flow pipe for guiding exhaust gas from the furnace to the flow path of the combustion air. Further equipped 10. The boiler according to claim 8 or 9.

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