Combustion device

Abstract

To provide a combustion device capable of reducing generation of greenhouse gas.SOLUTION: A CFB boiler (circulating fluidized bed boiler) for supplying and burning fuel in a furnace 11 in which a fluidizing material flows includes carbon-free fuel supply parts 16A to 16D for supplying ammonia and hydrogen as carbon-free fuel into the furnace 11. The carbon-free fuel supply section 16A supplies carbon-free fuel to the windbox 122, the carbon-free fuel supply section 16B supplies carbon-free fuel to the fluidized bed A, the carbon-free fuel supply section 16C supplies carbon-free fuel to the fluidized bed A, and the carbon-free fuel supply section 16D supplies carbon-free fuel to the freeboard B.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a combustion device and a boiler that combusts fuel. [Background technology]

[0002] Known boilers that generate steam from water using heat generated by the combustion of fuel include bubbling fluidized bed (BFB) boilers and circulating fluidized bed (CFB) boilers, which burn fuel using a fluidized bed formed by a fluidizing material such as silica sand flowing in a combustion chamber. Patent Document 1 discloses a CFB boiler. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-255612 Summary of the Invention [Problem to be solved by the invention]

[0004] BFB and CFB boilers achieve high combustion efficiency by using a high-temperature fluidized material flowing within the combustion chamber. This makes them ideal for burning unstable or non-flammable fuels, such as biomass (biofuels), sludge, and waste materials (waste paper, plastics, tires, etc.). However, because these fuels are primarily carbon-based, they emit greenhouse gases such as carbon dioxide during combustion, potentially exacerbating global warming. The recent trend toward decarbonization has led to increased demand for biomass fuels, which can be considered carbon-neutral in the long term. However, procuring stable, stable biomass fuels at low cost has become increasingly difficult. While BFB and CFB boilers have traditionally primarily been designed to burn non-flammable carbon-containing fuels such as coal and waste-derived fuels, the challenge is to utilize biomass fuels and develop combustion methods that do not emit greenhouse gases such as carbon dioxide.

[0005] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a combustion device and a boiler that can reduce the generation of greenhouse gases. [Means for solving the problem]

[0006] In order to solve the above problems, one embodiment of the combustion device of the present invention is a combustion device that supplies fuel into a combustion chamber in which a fluid material flows and burns it, and is equipped with a carbon-free fuel supply unit that supplies carbon-free fuel into the combustion chamber.

[0007] Another aspect of the present invention is a boiler comprising: a combustion section that supplies fuel into a combustion chamber in which a fluid material flows and burns the fuel; a carbon-free fuel supply section that supplies a carbon-free fuel that does not contain carbon into the combustion chamber; and a steam generation section that generates steam from water by heat generated in the combustion section.

[0008] Any combination of the above components, and any transformation of the present invention into a method, device, system, recording medium, computer program, etc., are also valid aspects of the present invention. [Effects of the Invention]

[0009] According to the present invention, greenhouse gas emissions can be reduced by supplying carbon-free fuel. [Brief explanation of the drawings]

[0010] [Figure 1] The overall configuration of a CFB boiler (circulating fluidized bed boiler) is shown below. [Figure 2] 10A and 10B are schematic diagrams illustrating an example of the configuration of a start-up burner as a hybrid fuel supply unit. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the description and drawings, identical or equivalent components, parts, and processes are designated by the same reference numerals, and redundant explanations will be omitted as appropriate. The scale and shape of each part shown in the drawings are set for convenience to facilitate explanation, and should not be interpreted as limiting unless otherwise specified. The embodiments are merely examples and do not limit the scope of the present invention in any way. All features and combinations thereof described in the embodiments are not necessarily essential to the invention.

[0012] The combustion apparatus of the present invention is any apparatus that supplies fuel to a combustion chamber in which a fluidized material flows and burns it. For example, when the combustion apparatus is configured as a boiler, the combustion apparatus can be configured as a BFB boiler or CFB boiler that burns fuel using a fluidized bed or fluidized bed formed by a fluidized material such as silica sand flowing in the combustion chamber. In this embodiment, an example in which the combustion apparatus is configured as a CFB boiler will be mainly described.

[0013] Figure 1 shows the overall configuration of a CFB boiler (circulating fluidized bed boiler) as a combustion device. A CFB boiler is equipped with a combustion section 1, which supplies fuel to a furnace 11 where a fluid material such as silica sand flows and burns it, a steam generation section 2, which generates steam from water using heat generated in the combustion section 1, a fluid material circulation section 3, which collects the fluid material that leaves the furnace 11 and returns it to the furnace 11, a heat transfer section 4, which uses the high-temperature exhaust gas from the combustion section 1 to heat the air supplied to the combustion section 1, the water supplied to the steam generation section 2, and the steam generated in the steam generation section 2, a dust collector 5, which separates and collects soot and dust in the exhaust gas from the heat transfer section 4, and a chimney 6, which releases the exhaust gas purified by the dust collector 5 into the atmosphere.

[0014] The combustion section 1 includes a furnace 11 as a combustion chamber. The furnace 11 is a vertically elongated cylinder with a tapered bottom to increase the density of the solid fuel and fluidized material, enabling efficient combustion. The bottom of the furnace 11 does not have to be tapered, and the furnace 11 may be formed as a cylinder with a substantially constant cross-sectional shape from top to bottom. The area indicated by A at the bottom of the furnace 11 is a fluidized bed (also called a fluidized bed or sand layer) formed by a high-density fluidized material. In the fluidized bed A, powdered or granular fluidized material such as silica sand is fluidized by air supplied from the bottom of the furnace 11 as a fluidizing fluid. The fuel introduced into the fluidized bed A is efficiently combusted by repeatedly coming into contact with the high-temperature fluidized material and air while being stirred therein.

[0015] Note that because the fluidized material rises within the furnace 11 due to the updrafts generated by combustion, fluidized material also exists in the freeboard B, which is the space above the fluidized bed A. The density of the fluidized material in the freeboard B is smaller than that in the fluidized bed A, and decreases the further up the furnace 11 it goes. In the freeboard B, fuel that was not completely combusted in the fluidized bed A comes into contact with the floating fluidized material and is combusted. Note that although silica sand is exemplified as the fluidized material, any material may be used as long as it remains in a solid state without being combusted even in the high-temperature furnace 11 and functions as a medium for transferring heat to the fuel while fluidizing, and for example, other types of sand, stone such as limestone, or ash may also be used.

[0016] A perforated plate (also called a dispersion plate) 121, which serves as a fluid permeable section and is made of a porous material that allows fluids, including air, to pass through, is provided at the bottom of the furnace 11. The air box 122, which is the space directly below the perforated plate 121, constitutes a fluid supply section (air supply section) that supplies pressurized air, supplied from a first blower 71 (as a blower) via a first flow control valve 71A, into the furnace 11 via the perforated plate 121. The pressurized air supplied to the bottom of the furnace 11 by the air box 122 fluidizes the fluidized material to form a fluidized bed A and is also used for fuel combustion in the fluidized bed A or the freeboard B. To promote fuel combustion in the freeboard B and suppress the generation of harmful substances such as dioxins and carbon monoxide due to incomplete combustion, a second blower 72 (as a blower) supplies pressurized air to the freeboard B via a second flow control valve 72A. In this embodiment, the fluid permeable portion has been described using the perforated plate 121 as an example, but the fluid permeable portion is not limited to this embodiment as long as it can cause the fluid material to flow in the fluidized bed A, and may be formed, for example, from a number of plates formed with slits that supply the flowing fluid into the furnace 11.

[0017] In order to circulate the fluidized material in the fluidized bed A, an external circulation mechanism 13 having a circulation path outside the furnace 11 is provided. The external circulation mechanism 13 includes an extraction pipe 131 that communicates with the bottom of the furnace 11 and is capable of extracting a portion of the fluidized material in the fluidized bed A, an on-off valve 132 that controls the opening and closing of the extraction pipe 131 to adjust the flow rate of the fluidized material, i.e., the amount of fluidized material extracted by the extraction pipe 131, a fluidized material conveyor 133 such as a bucket conveyor that transports the fluidized material extracted by the extraction pipe 131 upward, a fluidized material silo 134 that is provided on the outer periphery of the furnace 11 corresponding to the upper part of the fluidized bed A and receives the fluidized material transported by the fluidized material conveyor 133, and a fluidized material re-introduction section 135 that re-introduces the fluidized material stored in the fluidized material silo 134 into the furnace 11.

[0018] The withdrawal pipe 131, on-off valve 132, fluidized material conveyor 133, fluidized material silo 134, and fluidized material re-introduction section 135 constitute a fluidized material circulation path that connects the bottom and side of furnace 11 outside of furnace 11. In other words, the fluidized material withdrawn from the bottom of furnace 11 by withdrawal pipe 131 passes through on-off valve 132, fluidized material conveyor 133, and fluidized material silo 134, and is re-introduced into fluidized bed A from the side of furnace 11 by fluidized material re-introduction section 135.

[0019] The furnace wall, which is the side wall of the furnace 11, is provided with a fluidized material supply unit 14 that supplies fluidized material for forming fluidized bed A into the furnace 11 when the CFB boiler is started up, and a solid fuel supply unit 15 that supplies solid fuel, mainly for combustion in the fluidized bed A, into the furnace 11. The fluidized material supply unit 14 includes a funnel-shaped fluidized material hopper 141 that stores the fluidized material, and a fluidized material feeder 142 that supplies the fluidized material discharged from the bottom of the fluidized material hopper 141 into the furnace 11. A desired amount of fluidized material is fed into the furnace 11 by controlling the rotation speed of the fluidized material feeder 142. The solid fuel supply unit 15 includes a funnel-shaped solid fuel hopper 151 that stores solid fuel, and a solid fuel feeder 152 that supplies the solid fuel discharged from the bottom of the solid fuel hopper 151 into the furnace 11. A desired amount of solid fuel is fed into the furnace 11 by controlling the rotation speed of the solid fuel feeder 152.

[0020] The solid fuel supplied by the solid fuel supply unit 15 into the furnace 11 is not particularly limited, and examples thereof include various types of coal, such as anthracite, bituminous coal, and lignite, as well as biomass, sludge, and waste materials. In a CFB boiler, high combustion efficiency is achieved by using a high-temperature fluid material flowing within the furnace 11 as a medium, so that low-quality fuels and non-flammable fuels can also be efficiently burned. Note that the solid fuels listed above are carbon-containing fuels, and the solid fuel supply unit 15 constitutes a carbon-containing fuel supply unit that supplies the carbon-containing fuel into the furnace 11. Furthermore, although there are few specific examples at present, if carbon-free solid fuels become available, the solid fuel supply unit 15 that supplies such carbon-free fuels into the furnace 11 will constitute a carbon-free fuel supply unit.

[0021] In addition to or instead of the solid fuel supply unit 15, a carbon-free fuel supply unit 16 that supplies a non-solid or fluid (liquid or gas) carbon-free fuel into the furnace 11 is provided in each part of the combustion unit 1. Four installation examples of the carbon-free fuel supply unit 16 are shown below, but the installation location and installation manner of the carbon-free fuel supply unit 16 are not limited to these. The number of carbon-free fuel supply units 16 is also not limited to four; as long as there is at least one, the effects of this embodiment, such as greenhouse gas suppression, described below, can be achieved. The carbon-free fuel supply units 16 may be provided in five or more locations. Furthermore, in the following description, ammonia is used as an example of a non-solid carbon-free fuel, but other fuels, such as hydrogen, may also be used.

[0022] The carbon-free fuel supply unit 16A according to the first installation embodiment supplies ammonia as a carbon-free fuel to the wind box 122. The ammonia supplied to the wind box 122 is mixed with pressurized air supplied from the first blower 71 into the wind box 122 and passes through the perforated plate 121 to be supplied into the fluidized bed A from below. By supplying ammonia as a non-solid fuel together with the pressurized air that agitates the fluidized material and solid fuel in the fluidized bed A, the fluidized material, solid fuel, pressurized air, and ammonia are mixed together, allowing ammonia, which is known to be flame-retardant, to be efficiently burned. The carbon-free fuel supply unit 16A includes a storage unit 161A that stores ammonia in a non-solid gaseous or liquid state, and an injection device 162A that injects the ammonia stored in the storage unit 161A into the wind box 122 in a non-solid gaseous or liquid state.

[0023] The carbon-free fuel supply unit 16B according to the second installation embodiment supplies ammonia as a carbon-free fuel into fluidized bed A from the side of fluidized bed A (fluidized material at the bottom of the furnace 11) on the perforated plate 121. The ammonia supplied directly into fluidized bed A is mixed with the fluidized material, solid fuel, and compressed air in fluidized bed A and is burned efficiently. The carbon-free fuel supply unit 16B includes a storage unit 161B that stores ammonia in a gaseous or liquid non-solid state, and an injection device 162B that injects the ammonia stored in storage unit 161B into fluidized bed A in a gaseous or liquid non-solid state. Here, by arranging the tip of the injection device 162B so that it is inserted into fluidized bed A from the side, ammonia can be efficiently injected into fluidized bed A. The injector 162B may be configured as a burner that mixes ammonia with air and burns the mixture, and in this case the tip of the injector 162B serves as a burner nozzle that ejects a flame resulting from the combustion of ammonia into the fluidized bed A. Such a burner as the carbon-free fuel supply unit 16B can be configured as, for example, a lance burner or a burner lance, and burns a carbon-free fuel such as ammonia at the side of the fluidized material (i.e., fluidized bed A) at the bottom of the furnace 11.

[0024] The position of the nozzle at the tip of the injector 162B of the carbon-free fuel supply unit 16B may be anywhere as long as it faces the fluidized bed A. For example, when the height of the furnace 11 is about 30 m, the typical height of the fluidized bed A is about 1.5 m, so the height of the nozzle of the injector 162B is preferably less than about 1.5 m from the bottom surface of the furnace 11, specifically 0.5 m. Furthermore, expressed as a percentage of the height of the furnace 11, the typical height of the fluidized bed A, 1.5 m, corresponds to 5.0% of 30 m. In contrast, the height of the nozzle of the injector 162B is preferably within a range of 1.0%-4.0%, more preferably within a range of 1.5%-2.5% (the above 0.5 m corresponds to 1.7% of 30 m).

[0025] Furthermore, it has been confirmed that the generation and emission of nitrous oxide (NO, also known as nitrous oxide or dinitrogen monoxide) due to the combustion of ammonia can be reduced by positioning the nozzle at the tip of the injector 162B of the carbon-free fuel supply unit 16B, which is composed of a burner or the like, at a height of less than 1.5 m from the bottom surface of the furnace 11. This is thought to be because nitrous oxide generated near the nozzle of the carbon-free fuel supply unit 16B is reduced and converted to nitrogen as it passes through the main combustion zone above it. To enhance the reduction effect of nitrous oxide reduction, the nozzle of the carbon-free fuel supply unit 16B can be positioned even lower, preferably at a height of less than 1.0 m from the bottom surface of the furnace 11, and even more preferably at a height of less than 0.5 m from the bottom surface of the furnace 11.

[0026] Similarly, it has been confirmed that the generation and emission of nitrogen oxides (NOx) due to the combustion of ammonia can be reduced by positioning the nozzle, which serves as the tip of the injector 162B of the carbon-free fuel supply unit 16B, which is composed of a burner or the like, at a height of 1.5 m or more above the bottom surface of the furnace 11 (and preferably below the top surface of the fluidized bed A). This is thought to be because nitrogen oxides generated at the bottom of the furnace 11 react with ammonia supplied by the burner or the like and are reduced to nitrogen. In order to obtain the effect of reducing nitrogen oxides while maintaining complete combustion of the supplied ammonia, it is preferable to install the nozzle of the carbon-free fuel supply unit 16B below the supply port of pressurized air from the second blower 72, which is typically located at a height of about 3.0 m to 4.0 m above the bottom surface of the furnace 11 (although in FIG. 1 the pressurized air is supplied above the fluidized bed A, in practice the pressurized air may be supplied from the side of the fluidized bed A). In order to simultaneously obtain such complete combustion of ammonia and the effect of reducing nitrogen oxides, the injection port of the carbon-free fuel supply unit 16B can be located below the pressurized air supply port. For example, compared to the typical pressurized air supply port described above (at a height of approximately 3.0 m to 4.0 m), the injection port of the carbon-free fuel supply unit 16B can be located at a height of, for example, 2.0 m or more from the bottom surface of the furnace 11, or at a height of 3.0 m or more from the bottom surface of the furnace 11.

[0027] To effectively reduce NO and NO emissions, it is preferable to install a burner of the carbon-free fuel supply unit 16B with a height of less than 1.5 m (or less than 1.0 m, or less than 0.5 m) and a burner of the carbon-free fuel supply unit 16B with a height of 1.5 m or more (or 2.0 m or more, or 3.0 m or more). By individually adjusting the supply amount and combustion amount of the carbon-free fuel such as ammonia in each burner, it is possible to minimize or optimize the NO and NO emissions in the furnace 11.

[0028] The carbon-free fuel supply unit 16C according to the third installation embodiment is integral with a startup burner, which will be described later, and supplies ammonia as a carbon-free fuel from above the fluidized bed A downward toward the surface (upper surface) of the fluidized bed A. The ammonia supplied from the carbon-free fuel supply unit 16C is mixed with the fluidized material, solid fuel, and compressed air flowing on the surface of the fluidized bed A and is efficiently burned. By combining at least two of the carbon-free fuel supply unit 16A that supplies ammonia from below the fluidized bed A, the carbon-free fuel supply unit 16B that supplies ammonia from the side of the fluidized bed A, and the carbon-free fuel supply unit 16C that supplies ammonia from above the fluidized bed A, ammonia can be injected from different directions into the fluidized material, solid fuel, and compressed air flowing in each part of the fluidized bed A and efficiently mixed therewith, thereby enabling ammonia, which is known to be flame-retardant, to be efficiently burned in each part of the fluidized bed A.

[0029] The carbon-free fuel supply unit 16C includes a storage unit 161C that stores ammonia in a non-solid state, such as gas or liquid, and an injection device 162C that injects the ammonia stored in the storage unit 161C into the furnace 11 in a non-solid state, such as gas or liquid. The injection device 162C also functions as a startup burner, which will be described later, and is provided at a downward incline so that the flame ejected from its tip can directly heat the surface of the fluidized bed A. Although the specific configuration will be described later, a startup burner is generally provided in a CFB boiler for startup, and in this embodiment, an existing startup burner can also be used as the carbon-free fuel supply unit 16C for supplying ammonia.

[0030] The position of the nozzle at the tip of the injector 162C of the carbon-free fuel supply unit 16C is determined by the position of the existing startup burner. For example, if the height of the furnace 11 is approximately 30 m, the typical height of the startup burner is approximately 2.0 m, which is located above the fluidized bed A, which is approximately 1.5 m high. The carbon-free fuel supply unit 16C may be provided separately from the startup burner, in which case the height of the nozzle of the injector 162C can be freely set. For example, it is preferable to provide the nozzle of the injector 162C at a height of 6.0% or more (1.8 m or more) of the height of the furnace 11 so that ammonia can be effectively injected onto the surface of the fluidized bed A, which is 5.0% (1.5 m) of the height of the furnace 11 (30 m). Note that by increasing the downward inclination angle of the injector 162C, ammonia can be injected onto the surface of the fluidized bed A even if the installation height is large.

[0031] The carbon-free fuel supply unit 16D according to the fourth installation embodiment supplies ammonia as a carbon-free fuel into the freeboard B at the top of the furnace 11. The ammonia supplied into the freeboard B burns unburned materials derived from solid fuels that were not completely combusted in the fluidized bed A, thereby suppressing the generation of harmful substances such as dioxins and carbon monoxide due to incomplete combustion. In particular, it is important to maintain a temperature of approximately 800°C or higher in the freeboard B to prevent the generation of dioxins. By burning ammonia from the carbon-free fuel supply unit 16D, a high temperature of approximately 800°C or higher can be maintained even in the freeboard B, which is separated from the fluidized bed A where the main combustion occurs.

[0032] Ammonia also functions as a reducing agent, reducing nitrogen oxides (NOx), an air pollutant that may be generated by combustion in the furnace 11, into harmless nitrogen and water. By supplying ammonia from the carbon-free fuel supply unit 16D to the freeboard B at the bottom of the furnace 11, where the exhaust gas after combustion is located before it leaves the furnace 11, nitrogen oxides in the exhaust gas can be effectively removed.

[0033] The carbon-free fuel supply unit 16D includes a storage unit 161D that stores ammonia in a non-solid state, such as gas or liquid, and an injection device 162D that injects the ammonia stored in the storage unit 161D in a non-solid state, such as gas or liquid, into the freeboard B. The injection device 162D may be configured as a burner that mixes ammonia with air and burns it, and in this case, the tip of the injection device 162D serves as the burner nozzle and ejects a flame generated by the combustion of ammonia into the freeboard B.

[0034] The nozzle of the injector 162D of the carbon-free fuel supply unit 16D can be located anywhere facing the freeboard B. For example, if the height of the furnace 11 is approximately 30 m, the freeboard B is approximately 1.5 m above the fluidized bed A. However, because powdered or granular fluidized material and solid fuel burn vigorously near the surface of the fluidized bed A, it is preferable to position the nozzle of the injector 162D sufficiently away from the surface of the fluidized bed A to achieve the above-mentioned effect of removing dioxins and nitrogen oxides. On the other hand, if the nozzle of the injector 162D is located too high, the exhaust gas will exit the furnace 11 before the dioxins and nitrogen oxides have been sufficiently removed by the ammonia. Taking these points into consideration, the height of the nozzle of the injector 162D is preferably within a range of, for example, 50% (15 m) to 70% (21 m) of the height of the furnace 11 (30 m).

[0035] As described above, by providing the carbon-free fuel supply units 16A-16D at multiple different positions in the vertical direction (i.e., the height direction) of the furnace 11, it is possible to distribute the combustion locations of ammonia, which is known to be flame-retardant, thereby achieving high overall combustion efficiency. Furthermore, by configuring the furnace 11 to burn ammonia little by little in each section, it is possible to increase the overall supply of ammonia while maintaining high combustion efficiency. In other words, many conventional carbon-containing fuels, such as coal, which is primarily composed of carbon, can be replaced with carbon-free fuels, such as ammonia and hydrogen. Carbon-free fuels do not generate carbon-containing greenhouse gases, such as carbon dioxide, when burned, thereby reducing the adverse impact on the global environment, which is experiencing increasing global warming.

[0036] Next, a startup burner (referred to as startup burner 16C) configured integrally with the carbon-free fuel supply unit 16C will be described. The startup burner 16C is provided with a carbon-containing fuel storage unit 163C for storing heavy oil as a carbon-containing fuel, in parallel with a carbon-free fuel storage unit 161C for storing ammonia as a carbon-free fuel. A carbon-free fuel control valve 164C is provided between the carbon-free fuel storage unit 161C and the injector 162C to control the amount of ammonia supplied from the carbon-free fuel storage unit 161C to the injector 162C, and a carbon-containing fuel control valve 165C is provided between the carbon-containing fuel storage unit 163C and the injector 162C to control the amount of heavy oil supplied from the carbon-containing fuel storage unit 163C to the injector 162C.

[0037] The mode switching unit 166C controls the carbon-free fuel control valve 164C and the carbon-containing fuel control valve 165C, switching their open / closed states in a complementary manner. In a first mode in which the carbon-free fuel control valve 164C is open and the carbon-containing fuel control valve 165C is closed, the injector 162C supplies ammonia from the carbon-free fuel storage unit 161C into the furnace 11. In a second mode in which the carbon-free fuel control valve 164C is closed and the carbon-containing fuel control valve 165C is open, the injector 162C supplies heavy oil from the carbon-containing fuel storage unit 163C into the furnace 11. Specifically, heavy oil mixed with air is combusted in the injector 162C configured as a burner, and the tip of the injector 162C serves as the burner nozzle and ejects a flame resulting from the combustion of the heavy oil into the furnace 11.

[0038] The mode switching unit 166C switches to the second mode when the CFB boiler is started up, and switches to the first mode after the CFB boiler is started up. During the start-up of the CFB boiler, a fluidizing material such as silica sand for forming a fluidized bed A is supplied from the fluidizing material supply unit 14 into the furnace 11. At this time, a solid fuel such as coal may also be supplied from the solid fuel supply unit 15 into the furnace 11, or a carbon-free fuel such as ammonia or hydrogen may also be supplied from the carbon-free fuel supply units 16A, 16B, and 16D other than the carbon-free fuel supply unit 16C into the furnace 11. The injector 162C, which operates in the second mode during the start-up of the CFB boiler, heats the fluidizing material supplied from the fluidizing material supply unit 14 with a flame generated by the combustion of heavy oil. Here, because the injector 162C is installed at a downward incline, the surface of the fluidized bed A formed by the fluidizing material is directly heated, thereby efficiently raising the temperature of the fluidized bed A and the inside of the furnace 11. In this way, the startup burner 16C heats the sandy fluidized bed A from above, and is therefore also called an above-sand burner.

[0039] After the CFB boiler is started and the fluidized bed A and the furnace 11 are sufficiently heated, i.e., after solid fuel combustion becomes possible in the fluidized bed A, the mode switching unit 166C switches to the first mode. The injector 162C operating in the first mode injects a carbon-free fuel, such as ammonia or hydrogen, from its tip onto the surface of the fluidized bed A. As described above, the startup burner 16C is a hybrid fuel supply unit that functions as a carbon-containing fuel supply unit that supplies heavy oil as a carbon-containing fuel in the second mode at startup, and functions as a carbon-free fuel supply unit that supplies ammonia, hydrogen, or the like as a carbon-free fuel in the first mode after startup. Conventional startup burners are shut down after heating up the CFB boiler with heavy oil or the like at startup, but according to this embodiment, the startup burner can be effectively used as a carbon-free fuel supply unit even after startup.

[0040] 2 is a schematic diagram illustrating a configuration example of a startup burner 16C as a hybrid fuel supply unit. The injection device 162C of the startup burner 16C includes a carbon-free fuel receiving section 167C that receives ammonia as a carbon-free fuel from a carbon-free fuel storage section 161C, and a carbon-containing fuel receiving section 168C that receives heavy oil as a carbon-containing fuel from a carbon-containing fuel storage section 163C.

[0041] The combustion section 1 of the CFB boiler has been described in detail above. Next, the configuration of the CFB boiler other than the combustion section 1 will be described. The steam generation section 2 includes a drum 21 that stores water for generating steam, a water feed pipe 22 that supplies water to the drum 21, a water pipe 23 that guides the water in the drum 21 into the high-temperature furnace 11 to heat it, and a steam pipe 24 that discharges steam generated from the water heated in the water pipe 23 from the drum 21 as the output of the CFB boiler. The water feed pipe 22 snakes through the heat transfer section 4 through which the high-temperature exhaust gas from the combustion section 1 passes, thereby forming an economizer that preheats the feed water. The steam pipe 24 snakes through the heat transfer section 4 through which the high-temperature exhaust gas from the combustion section 1 passes, thereby forming a superheater that superheats the steam. Similarly, the pressurized air supplied to the furnace 11 by the first blower 71 and the second blower 72 is preheated by the high-temperature exhaust gas from the heat transfer section 4.

[0042] The fluidized material circulation unit 3 includes a cyclone 31 that separates and collects fluidized material from the exhaust gas discharged from the top of the furnace 11, and a seal pot 32 that returns the fluidized material collected by the cyclone 31 to the furnace 11. The cyclone 31 is a cyclone-type powder separator with a generally cylindrical upper portion and a generally conical lower portion, and generates an airflow that spirals down along the inner wall. The fluidized material contained in the exhaust gas from the furnace 11 is collected by falling into contact with the inner wall of the cyclone 31 as it spirals down along the airflow. Note that the exhaust gas contains not only fluidized material but also ammonia supplied from the carbon-free fuel supply units 16A-16D. Therefore, even if nitrogen oxides remain in the exhaust gas, they can be efficiently removed by the ammonia moving vigorously within the cyclone 31. Furthermore, the cyclone 31 promotes contact between the fluidized material and the carbon-free fuel ammonia as unburned matter remaining in the exhaust gas, in other words, the cyclone 31 functions as an ammonia mixer or a carbon-free fuel agitator, and this is expected to result in complete combustion of the ammonia as unburned matter. From the viewpoint of having the cyclone 31 function as an ammonia mixer, it is preferable to install the carbon-free fuel supply units 16A to 16D upstream of the cyclone 31 in the flow of the exhaust gas.

[0043] The seal pot 32 provided below the cyclone 31 is filled with fluidizing material to prevent backflow of unburned gas and the like from the furnace 11 to the cyclone 31. The fluidizing material filled in the seal pot 32 is gradually returned to the furnace 11 by being pushed out by the weight of the fluidizing material newly collected by the cyclone 31.

[0044] The present invention has been described above based on the embodiments. The embodiments are merely examples, and it will be understood by those skilled in the art that various modifications are possible in the combination of the respective components and treatment processes, and that such modifications are also within the scope of the present invention.

[0045] Although the embodiment has been described using a CFB boiler as an example of a boiler, the present invention can also be applied to a BFB boiler (bubbling fluidized bed boiler). The configuration of a BFB boiler is similar to that of a CFB boiler, except that it does not include a fluid material circulation unit 3 that collects the fluid material that has left the furnace 11 and returns it to the furnace 11.

[0046] The functional configuration of each device described in the embodiments can be realized by hardware resources, software resources, or a combination of hardware and software resources. Examples of hardware resources include processors, ROMs, RAMs, and other LSIs. Examples of software resources include operating systems, applications, and other programs. [Explanation of symbols]

[0047] 1 combustion section, 2 steam generation section, 3 fluid material circulation section, 4 heat transfer section, 11 furnace, 13 external circulation mechanism, 14 fluid material supply section, 15 solid fuel supply section, 16 carbon-free fuel supply section, 16C start-up burner, 31 cyclone, 32 seal pot, 121 perforated plate, 122 wind box, 166C mode switching section, 167C carbon-free fuel receiving section, 168C carbon-containing fuel receiving section.

Claims

[Claim 1] A combustion device that supplies fuel into a combustion chamber in which a fluid material flows and burns the fuel, A carbon-free fuel supply unit is provided to supply carbon-free fuel into the combustion chamber. Combustion device.

Images