TWI848285B - Combustion device, boiler, and combustion method - Google Patents

Abstract

[Topic] A combustion device capable of reducing the generation of greenhouse gases is provided. [Solution] A CFB boiler (circulating fluidized bed boiler) that supplies fuel to a furnace (11) in which a fluidized material flows and burns the fuel is provided with a carbon-free fuel supply section (16A to 16D). The carbon-free fuel supply section (16A to 16D) supplies ammonia and hydrogen as carbon-free fuels that do not contain carbon into the furnace (11). The carbon-free fuel supply section (16A) supplies carbon-free fuel to the wind box (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 surface of the fluidized bed (A), and the carbon-free fuel supply section (16D) supplies carbon-free fuel to the freeboard (B).

Description

Combustion device, boiler, and combustion method

The present invention relates to a combustion device and a boiler for burning fuel.

This application claims priority based on Japanese Patent Application No. 2021-080186 filed on May 11, 2021. The entire contents of the Japanese application are incorporated herein by reference.

As a boiler that generates steam from water by heat generated by burning fuel, a bubbling fluidized bed (BFB) boiler and a circulating fluidized bed (CFB) boiler that burn fuel using a fluidized bed or fluidized bed formed by a fluidized material such as silica sand flowing in a combustion chamber as a medium are widely known. A CFB boiler is disclosed in Patent Document 1.

[Prior Art Literature]

[Patent Document 1] Japanese Patent Publication No. 2012-255612

BFB boilers and CFB boilers can achieve high combustion efficiency by using a high-temperature fluid material flowing in the combustion chamber as a medium. Therefore, they are suitable for the combustion of unstable quality fuels and flame-retardant fuels such as biomass (biomass fuel), sludge (sludge), and waste (waste paper, waste plastic, waste tires, etc.). However, these fuels all have carbon as the main component, so they produce greenhouse gases such as carbon dioxide during combustion, which may further worsen global warming. In the recent decarbonization trend, in the long run, the demand for biomass fuels that can be called carbon-neutral is increasing, and it is difficult to prepare biomass fuels with stable quality at a low price and stably. Until now, in BFB boilers and CFB boilers, which are mainly used to burn flame-retardant carbon-containing fuels such as coal and waste fuels, in addition to the application of biomass fuels, the corresponding combustion methods that do not emit greenhouse gases such as carbon dioxide have also become a topic.

The present invention was developed in view of this situation, and its purpose is to provide a combustion device and boiler that can reduce the generation of greenhouse gases.

In order to solve the above-mentioned problem, a combustion device of one form of the present invention supplies fuel into a combustion chamber where a fluid material flows and causes it to burn. The combustion device is equipped with a carbon-free fuel supply unit, and the carbon-free fuel supply unit supplies carbon-free fuel (carbon-free fuel) that does not contain carbon into the combustion chamber.

Another aspect of the present invention is a boiler. The boiler comprises: a combustion section that supplies fuel to a combustion chamber where a fluid material flows and causes the fuel to burn; a carbon-free fuel supply section that supplies carbon-free fuel that does not contain carbon to the combustion chamber; and a steam generation section that generates steam from water using the heat generated in the combustion section.

In addition, any combination of the above constituent elements and the expression of the present invention converted between methods, devices, systems, recording media, computer programs, etc. are also valid as aspects of the present invention.

According to the present invention, the generation of greenhouse gases can be reduced by supplying carbon-free fuel.

A: Fluidized bed

B: Freeboard

1: Combustion section

2: Steam generation unit

3: Flowing material circulation department

4: Heat conduction part

5: Dust collection device

6: Chimney

11: Furnace

13: External circulation mechanism

14: Flow material supply department

15: Solid fuel supply unit

16,16A,16B,16C,16D: Carbon-free fuel supply department

16C: Start burner

21: Roller

22: Water supply pipe

23: Water pipes

24: Steam pipe

31: Cyclone separator

32: Sealed can

71: No. 1 blower

71A: No. 1 flow control valve

72: 2nd blower

72A: Second flow control valve

121: porous plate

122: Bellows

131: Extraction tube

132: Open/Close Valve

133: Flowing material conveyor

134: Cylindrical warehouse for flowing materials

135: Flowing material re-injection department

141: Flowing material hopper

142: Flow material feeder

151: Solid fuel hopper

152:Solid fuel feeder

161A, 161B, 161C, 161D: Storage Department

162A, 162B, 162C, 162D: Spraying device

163C: Carbon-containing fuel storage unit

164C: Carbon-free fuel control valve

165C: Carbon fuel control valve

166C: Mode switching unit

167C: Carbon-free fuel receiving unit

168C: Carbon-containing fuel receiving unit

[Figure 1] shows the overall structure of a CFB boiler (circulating fluidized bed boiler).

[Figure 2] schematically shows an example of the configuration of a starter burner as an integrated fuel supply unit.

Below, referring to the drawings, the form used to implement the present invention is described in detail. In the description and drawings, the same or equivalent components, components, and processes are marked with the same symbols, and repeated descriptions are appropriately omitted. For the convenience of explanation, the scale and shape of each part of the diagram are appropriately set, and no restrictive interpretation is made unless otherwise specified. The implementation form is an example and does not limit the scope of the present invention in any way. All features and their combinations described in the implementation form are not necessarily limited to the essence of the invention.

The combustion device of the present invention is any device that supplies fuel to a combustion chamber where a fluid material flows and burns the fuel. For example, when the combustion device is configured as a boiler, the combustion device can be configured as a BFB boiler or a CFB boiler that uses a fluidized bed or a fluidized bed formed by a fluid material such as silica sand flowing in the combustion chamber as a medium to burn the fuel. In this embodiment, the example of configuring the combustion device as a CFB boiler is mainly described.

FIG1 shows the overall structure of a CFB boiler (circulating fluidized bed boiler) as a combustion device. The CFB boiler is equipped with: a combustion section 1, which supplies fuel to a furnace 11 where fluid materials such as silica sand flow and burns it; a steam generating section 2, which generates steam from water by using the heat generated in the combustion section 1; a fluid material circulation section 3, which captures the fluid materials discharged outside the furnace 11 and returns them to the furnace 11; a heat transfer section 4, which heats the air supplied to the combustion section 1, the water supplied to the steam generating section 2, and the steam generated in the steam generating section 2 by using the high-temperature exhaust gas from the combustion section 1; a dust collecting device 5, which separates and captures soot and dust in the exhaust gas from the heat collecting device 4; and a chimney 6, which discharges the exhaust gas purified by the dust collecting device 5 into the atmosphere.

The combustion section 1 has a furnace 11 as a combustion chamber. The furnace 11 is a vertically elongated cylindrical shape, and the bottom is a constricted shape to increase the density of solid fuel and fluid material for efficient combustion. In addition, the bottom of the furnace 11 may not be a constricted shape, and the furnace 11 may be formed into a cylindrical shape with a substantially constant cross-sectional shape from the top to the bottom. The area indicated by A at the bottom of the furnace 11 represents a fluidized bed (also referred to as a fluidized bed or sand layer) formed by a high-density fluid material. In the fluidized bed A, powdered or granular fluid material such as silica sand flows by air supplied as a fluid fluid from the bottom of the furnace 11. The fuel introduced into the fluidized bed A burns efficiently by repeatedly contacting the high-temperature fluidized material and air while being stirred therein.

In addition, the fluidized material rises in the furnace 11 due to the rising airflow generated by combustion, so there is also fluidized material in the space above the fluidized bed A, that is, in the freeboard B. The density of the fluidized material in the freeboard B is smaller than the density of the fluidized material in the fluidized bed A, and becomes smaller as it approaches the top of the furnace 11. In the freeboard B, the fuel that is not completely burned in the fluidized bed A contacts the floating fluidized material and is burned. In addition, silica sand is exemplified as the fluidized material, but any material that does not burn in the high-temperature furnace 11 but maintains a solid state and flows and transfers heat to the fuel can be used, such as other sand, limestone and other stones, and dust.

A porous plate (also called a dispersion plate) 121 as a fluid permeation portion made of a porous material through which a fluid containing air passes is provided at the bottom of the furnace 11. The space directly below the porous plate 121, namely the wind box 122, constitutes a fluid supply portion (air supply portion), and the fluid supply portion supplies pressurized air supplied from the first blower 71 as a blower through the first flow control valve 71A into the furnace 11 through the porous plate 121. The pressurized air supplied to the bottom of the furnace 11 by the wind box 122 causes the fluid material to flow to form a fluidized bed A, and is used for combustion of fuel in the fluidized bed A or the freeboard B. In addition, in order to promote the combustion of fuel in the freeboard B and suppress the generation of harmful substances such as dioxin and carbon monoxide due to incomplete combustion, the second blower 72 as a blower supplies pressurized air to the freeboard B through the second flow control valve 72A. In addition, in this embodiment, the perforated plate 121 is used as an example to illustrate the fluid passing part, but the fluid passing part is not limited to this embodiment as long as it can make the fluid material flow in the fluidized bed A. For example, it can be formed by a plurality of plates with slits for supplying the fluid to the furnace 11.

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 connected to the bottom of the furnace 11 and capable of extracting a portion of the fluidized material in the fluidized bed A; an on-off valve 132, which controls the extraction pipe 131 to open and close and can adjust the flow rate of the fluidized material, that is, the amount of fluidized material extracted using the extraction pipe 131; a fluidized material conveyor 133 such as a bucket conveyor, which conveys the fluidized material extracted from the extraction pipe 131 to the upper side; a fluidized material cylindrical bin 134, which is arranged on the outer periphery of the furnace 11 corresponding to the upper part of the fluidized bed A and receives the fluidized material conveyed by the fluidized material conveyor 133; and a fluidized material re-injection section 135, which re-injects the fluidized material stored in the fluidized material cylindrical bin 134 into the furnace 11.

The extraction pipe 131, the on-off valve 132, the fluid material conveyor 133, the fluid material cylindrical bin 134, and the fluid material re-injection unit 135 constitute a circulation path of the fluid material connecting the bottom and the side of the furnace 11 outside the furnace 11. That is, the fluid material extracted from the bottom of the furnace 11 through the extraction pipe 131 passes through the on-off valve 132, the fluid material conveyor 133, the fluid material cylindrical bin 134, and is re-injected into the fluidized bed A from the side of the furnace 11 through the fluid material re-injection unit 135.

A fluid material supply unit 14 and a solid fuel supply unit 15 are provided on the furnace wall serving as the side wall of the furnace 11. The fluid material supply unit 14 supplies fluid material for forming a fluidized bed A into the furnace 11 when the CFB boiler is started, and the solid fuel supply unit 15 mainly supplies solid fuel for combustion in the fluidized bed A into the furnace 11. The fluid material supply unit 14 includes a funnel-shaped fluid material hopper 141 for storing fluid material, and a fluid material feeder 142 for supplying fluid material discharged from the bottom of the fluid material hopper 141 into the furnace 11. By controlling the rotation speed of the fluid material feeder 142, a desired amount of fluid material can be fed into the furnace 11. The solid fuel supply unit 15 includes: a funnel-shaped solid fuel hopper 151 for storing solid fuel; and a solid fuel feeder 152 for feeding the solid fuel discharged from the bottom of the solid fuel hopper 151 into the furnace 11. By controlling the rotation speed of the solid fuel feeder 152, the desired amount of solid fuel is fed into the furnace 11.

The solid fuel supplied by the solid fuel supply unit 15 to the furnace 11 is not particularly limited, but various types of coal such as anthracite, flue gas, and lignite, biomass, sludge, and waste materials can be cited. In a CFB boiler, high combustion efficiency can be achieved by using a high-temperature fluid material flowing in the furnace 11 as a medium, so that low-quality fuel and flame-retardant fuel can be efficiently burned. In addition, the solid fuel cited above is a carbon-containing fuel containing carbon, and the solid fuel supply unit 15 constitutes a carbon-containing fuel supply unit that supplies the carbon-containing fuel to the furnace 11. Furthermore, although there is no specific example at present, when solid fuel that does not contain carbon can be used, the solid fuel supply part 15 that supplies such carbon-free fuel to the furnace 11 constitutes a carbon-free fuel supply part.

In addition to or in place of the solid fuel supply unit 15, a carbon-free fuel supply unit 16 for supplying a non-solid or fluid (liquid or gaseous) carbon-free fuel to the furnace 11 is provided in each part of the combustion unit 1. Four examples of the carbon-free fuel supply unit 16 are shown below, but the location and pattern of the carbon-free fuel supply unit 16 are not limited thereto. The number of carbon-free fuel supply units 16 is not limited to four, and the effect of the present embodiment such as suppressing greenhouse gases described later can be exerted as long as there is at least one. The carbon-free fuel supply unit 16 may be provided in five or more locations. In addition, ammonia is used as an example of a non-solid carbon-free fuel in the following description, but other fuels such as hydrogen may also be used.

The carbon-free fuel supply unit 16A of the first configuration supplies ammonia as a carbon-free fuel to the wind box 122. The ammonia supplied to the wind box 122 is mixed with the pressurized air supplied into the wind box 122 from the first blower 71, and then supplied from the bottom to the fluidized bed A through the porous plate 121. Ammonia as a non-solid fuel is supplied together with the pressurized air that stirs the fluidized material and the solid fuel in the fluidized bed A, and thereby the fluidized material, the solid fuel, the pressurized air, and the ammonia are mixed, so that the ammonia, which is known to be flame retardant, can be efficiently burned. The carbon-free fuel supply unit 16A includes: a storage unit 161A for storing ammonia in a non-solid state of gas or liquid; and an injection device 162A for injecting the ammonia stored in the storage unit 161A into the bellows 122 in a non-solid state of gas or liquid.

The carbon-free fuel supply section 16B of the second configuration supplies ammonia as a carbon-free fuel from the side of the fluidized bed A (the fluidized material at the bottom of the furnace 11) on the perforated plate 121 into the fluidized bed A. The ammonia directly supplied into the fluidized bed A is mixed with the fluidized material, solid fuel, and pressurized air in the fluidized bed A and burns efficiently. The carbon-free fuel supply section 16B includes: a storage section 161B for storing ammonia in a non-solid state of gas or liquid; and a spray device 162B for spraying the ammonia stored in the storage section 161B into the fluidized bed A in a non-solid state of gas or liquid. Here, the front end of the injection device 162B is arranged to be inserted into the fluidized bed A from the side, thereby being able to efficiently inject ammonia into the fluidized bed A. In addition, the injection device 162B can be configured as a burner that mixes ammonia and air and burns them. At this time, the front end of the injection device 162B serves as a burner nozzle of the burner to eject the flame caused by the combustion of ammonia into the fluidized bed A. The burner of such a carbon-free fuel supply unit 16B can be configured as a jet burner or a nozzle, for example, to burn a carbon-free fuel such as ammonia on the side of the fluidized material (i.e., the fluidized bed A) at the bottom of the furnace 11.

The position of the injection port at the front end of the injection device 162B of the carbon-free fuel supply unit 16B may be any position 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 injection port of the injection device 162B is preferably less than about 1.5 m from the bottom surface of the furnace 11, and specifically, it is set to 0.5 m or the like. Furthermore, if expressed as a percentage relative to the height of the furnace 11, the typical height of the fluidized bed A, 1.5 m, is equivalent to 5.0% of 30 m. Therefore, the height of the injection port of the injection device 162B is preferably set in the range of 1.0% to 4.0%, and more preferably in the range of 1.5% to 2.5% (the above 0.5 m is equivalent to 1.7% of 30 m).

In addition, the injection port of the injection device 162B of the carbon-free fuel supply part 16B composed of a burner or the like is located at a height of less than 1.5 m from the bottom surface of the furnace 11, thereby confirming the effect of reducing the generation and emission of nitrous oxide ( _N2O : also called laughing gas or nitrous oxide) due to the combustion of ammonia. This is believed to be because the nitrous oxide generated near the injection port of the carbon-free fuel supply part 16B is reduced and converted into nitrogen when passing through the main combustion zone above it. In order to improve the reduction effect of nitrous oxide, it is only necessary to further lower the position of the injection port of the carbon-free fuel supply part 16B. For example, it is best to set it at a height less than 1.0m from the bottom surface of the furnace 11, and it is more preferable to set it at a height less than 0.5m from the bottom surface of the furnace 11.

Similarly, the injection port at the front end of the injection device 162B of the carbon-free fuel supply unit 16B composed of a burner or the like was set at a height of more than 1.5 m from the bottom surface of the furnace 11 (and preferably below the top of the fluidized bed A), thereby confirming the effect of reducing nitrogen oxides (NOx) generated and discharged due to ammonia combustion. This is believed to be because the nitrogen oxides generated at the bottom of the furnace 11 react with ammonia or the like supplied by the burner and are reduced to nitrogen. In order to obtain the reduction effect of nitrogen oxides while maintaining complete combustion of the supplied ammonia, the second blower 72 is usually installed at a height of about 3.0m to 4.0m from the bottom of the furnace 11, and it is preferable to set the injection port of the carbon-free fuel supply part 16B below the supply port of the pressurized air from the second blower 72 (in Figure 1, the pressurized air is supplied from above the fluidized bed A, but in practice, the pressurized air can be supplied from the side of the fluidized bed A). In order to achieve the effects of complete combustion of ammonia and reduction of nitrogen oxides at the same time, the ejector of the carbon-free fuel supply part 16B can be arranged below the pressurized air supply port. For example, for the typical pressurized air supply port (3.0m to 4.0m high) mentioned above, the ejector of the carbon-free fuel supply part 16B can be at a height of more than 2.0m from the bottom surface of the furnace 11, or at a height of more than 3.0m from the bottom surface of the furnace 11.

In order to effectively reduce the emission of _N2O and NOx, it is recommended to install the burner of the carbon-free fuel supply part 16B with a height of less than 1.5m (or less than 1.0m or less than 0.5m) and the burner of the carbon-free fuel supply part 16B with a height of more than 1.5m (or more than 2.0m or more than 3.0). The supply amount and combustion amount of the carbon-free fuel such as ammonia in each burner are individually adjusted, thereby minimizing or optimizing the emission of _N2O and NOx in the furnace 11.

The carbon-free fuel supply unit 16C of the third configuration is integrated with a start-up burner described later, and supplies ammonia as a carbon-free fuel downward from above the fluidized bed A 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 flowing on the surface of the fluidized bed A, the solid fuel, and the pressurized air, and is efficiently burned. Here, by using at least two combinations of a carbon-free fuel supply unit 16A that supplies ammonia from the bottom of the fluidized bed A, a carbon-free fuel supply unit 16B that supplies ammonia from the side of the fluidized bed A, and a carbon-free fuel supply unit 16C that supplies ammonia from the top of the fluidized bed A, the fluidized material, solid fuel, and pressurized air flowing in each part of the fluidized bed A can be efficiently mixed by spraying ammonia from different directions, so that ammonia, which is known to be flame-retardant, can be efficiently burned in each part of the fluidized bed A.

The carbon-free fuel supply unit 16C includes a storage unit 161C for storing ammonia in a non-solid state of gas or liquid, and an injection device 162C for injecting the ammonia stored in the storage unit 161C in a non-solid state of gas or liquid into the furnace 11. The injection device 162C also functions as a start-up burner described later, and is arranged to be tilted downward so that the surface of the fluidized bed A can be directly heated by the flame injected from its front end. The specific structure will be described later, but a starter burner is usually installed in a CFB boiler for starting. In this embodiment, the existing starter burner can also be used as a carbon-free fuel supply unit 16C for ammonia supply.

The position of the injection port at the front end of the injection device 162C as the carbon-free fuel supply unit 16C is determined according to the position of the existing start-up burner. For example, when the height of the furnace 11 is about 30m, the typical height of the start-up burner is about 2.0m, and it is located above the fluidized bed A with a height of about 1.5m. In addition, the carbon-free fuel supply unit 16C can be provided separately from the start-up burner, and the height of the injection port of the injection device 162C can be freely set. For example, it is preferable to set the injection port of the injection device 162C at a height of 6.0% or more (1.8m or more) of the height of the furnace 11 so that ammonia can be effectively injected to the surface of the fluidized bed A at a height of 5.0% (1.5m) of the height of the furnace 11 (30m). In addition, if the downward tilt angle of the injection device 162C is increased, ammonia can be injected to the surface of the fluidized bed A even if the installation height is large.

The carbon-free fuel supply unit 16D of the fourth setting pattern supplies ammonia as a carbon-free fuel to the freeboard B at the top of the furnace 11. The ammonia supplied to the freeboard B causes unburned materials such as solid fuel that are not completely burned in the fluidized bed A to burn, thereby suppressing the generation of harmful substances such as dioxin and carbon monoxide due to incomplete combustion. In particular, it is important to maintain a temperature of about 800°C or more so that dioxin is not generated in the freeboard B. Even in the freeboard B separated from the fluidized bed A where the main combustion is caused by burning ammonia from the carbon-free fuel supply unit 16D, a high temperature of about 800°C or more can be maintained.

In addition, ammonia also acts as a reducing agent, reducing nitrogen oxides (NOx) that may be generated as air pollutants during 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 before the exhaust gas after combustion in the lower part of the furnace 11 is discharged outside the furnace 11, nitrogen oxides in the exhaust gas can be effectively removed.

The carbon-free fuel supply unit 16D includes: a storage unit 161D for storing ammonia in a non-solid state of gas or liquid; and an injection device 162D for injecting the ammonia stored in the storage unit 161D into the freeboard B in a non-solid state of gas or liquid. In addition, the injection device 162D can be configured as a burner that mixes ammonia with air and burns it. At this time, the front end of the injection device 162D serves as a burner nozzle of the burner to inject the flame caused by the combustion of ammonia into the freeboard B.

The position of the injection port at the front end of the injection device 162D as the carbon-free fuel supply unit 16D may be any position as long as it faces the freeboard B. For example, when the height of the furnace 11 is about 30m, the freeboard B is formed above the fluidized bed A of about 1.5m. However, in the portion close to the surface of the fluidized bed A, the powdered or granular fluidized material and the solid fuel move violently and burn, so in order to exert the above-mentioned effect of removing dioxin and nitrogen oxides, it is preferable that the injection port of the injection device 162D is sufficiently separated from the surface of the fluidized bed A. On the other hand, if the position of the injection port of the injection device 162D is too high, the exhaust gas before the dioxin and nitrogen oxides are sufficiently removed by ammonia is discharged to the outside of the furnace 11, which is not good. Considering these viewpoints, it is preferable that the height of the ejection port of the ejection device 162D is set within the range of 50% (15m) to 70% (21m) of the height (30m) of the furnace 11.

As described above, by providing carbon-free fuel supply parts 16A to 16D at different multiple positions in the height direction of the furnace 11, that is, in the vertical direction, the combustion position of ammonia, which is known to be flame retardant, can be dispersed to achieve overall high combustion efficiency. Also, as described above, by gradually burning ammonia in each part of the furnace 11, it is possible to maintain high combustion efficiency and increase the overall ammonia supply. In other words, most of the previous carbon-containing fuels such as coal with carbon as the main component can be replaced by carbon-free fuels such as ammonia and hydrogen. Carbon-free fuels do not produce greenhouse gases containing carbon such as carbon dioxide when burned, so they can reduce the adverse effects of global warming on the global environment.

Next, the starter burner (referred to as the starter burner 16C) formed integrally with the carbon-free fuel supply unit 16C is described. In the starter burner 16C, a carbon-containing fuel storage unit 163C storing heavy oil as a carbon-containing fuel is provided in parallel with a storage unit 161C storing ammonia as a carbon-free fuel. A carbon-free fuel control valve 164C for controlling the amount of ammonia supplied from the storage section 161C to the injection device 162C is provided between the storage section 161C and the injection device 162C, and a carbon-containing fuel control valve 165C for controlling the amount of heavy oil supplied from the carbon-containing fuel storage section 163C to the injection device 162C is provided between the carbon-containing fuel storage section 163C and the injection device 162C.

The mode switching unit 166C controls the carbon-free fuel control valve 164C and the carbon-containing fuel control valve 165C to switch the open and closed states thereof complementarily. In the first mode in which the carbon-free fuel control valve 164C is in the open state and the carbon-containing fuel control valve 165C is in the closed state, the injection device 162C supplies ammonia from the storage unit 161C to the furnace 11. In the second mode in which the carbon-free fuel control valve 164C is in the closed state and the carbon-containing fuel control valve 165C is in the open state, the injection device 162C supplies heavy oil from the carbon-containing fuel storage unit 163C to the furnace 11. Specifically, the heavy oil mixed with air in the injector 162C constituting the burner will burn, and the front end of the injector 162C serves as the burner nozzle to eject the flame caused by the combustion of the heavy oil into the furnace 11.

The mode switching unit 166C switches to the second mode when the CFB boiler is started, and switches to the first mode after the CFB boiler is started. When the CFB boiler is started, a fluid material such as silica sand for forming a fluidized bed A is supplied from the fluid material supply unit 14 to the furnace 11. At this time, a solid fuel such as coal can be supplied from the solid fuel supply unit 15 to the furnace 11, and a carbon-free fuel such as ammonia and hydrogen can be supplied from the carbon-free fuel supply units 16A, 16B, and 16D other than the carbon-free fuel supply unit 16C to the furnace 11. The ejector 162C, which operates in the second mode when the CFB boiler is started, heats the fluidized material supplied from the fluidized material supply section 14 using the flame caused by the combustion of heavy oil. Here, the ejector 162C is set downwardly inclined, so the surface of the fluidized bed A formed by the fluidized material is directly heated, and the fluidized bed A and the furnace 11 are efficiently heated. As described above, the startup burner 16C heats the sand-like fluidized bed A from above, so it is also called a sand-like burner.

After the CFB boiler with the fluidized bed A and the furnace 11 sufficiently heated is started, that is, after the solid fuel can be burned in the fluidized bed A, the mode switching unit 166C switches to the first mode. The spray device 162C operating in the first mode sprays ammonia, hydrogen, or other carbon-free fuel from its front end to the surface of the fluidized bed A. As described above, the startup burner 16C is a combined fuel supply unit, which functions as a carbon-containing fuel supply unit for supplying heavy oil as a carbon-containing fuel in the second mode at the time of startup, and functions as a carbon-free fuel supply unit for supplying ammonia, hydrogen, or other carbon-free fuel in the first mode after startup. In the past, the startup burner was stopped after the temperature was raised during startup by heavy oil, etc. However, according to this embodiment, the startup burner can be effectively used as a carbon-free fuel supply unit even after startup.

FIG2 schematically shows an example of the configuration of the starter burner 16C as a combined fuel supply unit. The injection device 162C of the starter burner 16C includes a carbon-free fuel receiving unit 167C for receiving ammonia as a carbon-free fuel from a storage unit 161C and a carbon-containing fuel receiving unit 168C for receiving heavy oil as a carbon-containing fuel from a carbon-containing fuel storage unit 163C.

The combustion section 1 of the CFB boiler has been described in detail above. Next, the components other than the combustion section 1 of the CFB boiler will be described. The steam generating section 2 includes: a drum 21 for storing water for generating steam; a water supply pipe 22 for supplying water to the drum 21; a water pipe 23 for guiding the water in the drum 21 to the high-temperature furnace 11 for heating; and a steam pipe 24 for discharging the steam generated from the water heated by the water pipe 23 from the drum 21 as the output of the CFB boiler. The water supply pipe 22 constitutes an economizer that preheats the water supply by running through the heat transfer section 4 through which the high-temperature exhaust gas of the combustion section 1 passes, and the steam pipe 24 constitutes a superheater that superheats the steam by running through the heat transfer section 4 through which the high-temperature exhaust gas of the combustion section 1 passes. Similarly, the pressurized air supplied to the furnace 11 by the first blower 71 and the second blower 72 is also preheated by the high-temperature exhaust gas in the heat transfer section 4.

The fluid material circulation section 3 includes: a cyclone separator 31 for separating and capturing fluid material from the exhaust gas discharged from the upper part of the furnace 11; and a sealing tank 32 for returning the fluid material captured by the cyclone separator 31 to the furnace 11. The cyclone separator 31 is a cyclone-type powder separator with an upper portion formed in a substantially cylindrical shape and a lower portion formed in a substantially conical shape, and generates an airflow that descends in a spiral along the inner wall. The fluid material contained in the exhaust gas from the furnace 11 is captured by falling down by contacting the inner wall of the cyclone separator 31 while descending in a spiral along the airflow. In addition, the exhaust gas contains not only fluid material but also ammonia supplied from the carbon-free fuel supply section 16A to 16D. Therefore, even if nitrogen oxides remain in the exhaust gas, they can be efficiently removed by the ammonia that moves vigorously in the cyclone separator 31. Furthermore, by promoting the contact between the carbon-free fuel ammonia remaining in the exhaust gas as an unburned component and the fluid material in the cyclone separator 31, in other words, the cyclone separator 31 functions as an ammonia mixer or a carbon-free fuel mixer, and the complete combustion of ammonia as an unburned component can be expected. In addition, from the perspective of making the cyclone separator 31 function as an ammonia mixer, it is preferable that the carbon-free fuel supply section 16A~16D is arranged on the upstream side of the cyclone separator 31 in the exhaust gas flow.

The sealing tank 32 disposed below the cyclone separator 31 is filled with fluid material to prevent the backflow of unburned gas, etc. from the furnace 11 to the cyclone separator 31. The fluid material filled in the sealing tank 32 is gradually returned to the furnace 11 in the form of being pushed out by the weight of the fluid material newly captured by the cyclone separator 31.

The present invention has been described above based on the implementation form. Those skilled in the art should understand that the implementation form is an example, and various modifications can be applied to the combination of the various components and the various processing processes, and such modifications are also within the scope of the present invention.

In the embodiment, a CFB boiler is described as an example of a boiler, but the present invention can also be applied to a BFB boiler (bubble fluidized bed boiler). The structure of a BFB boiler is the same as that of a CFB boiler except that it does not have a fluid material circulation section 3 that captures the fluid material discharged outside the furnace 11 and returns it to the furnace 11.

In addition, the functional configuration of each device described in the implementation form can be realized by hardware resources or software resources, or by the coordinated operation of hardware resources and software resources. As hardware resources, processors, ROM, RAM, and other LSIs can be used. As software resources, operating systems, applications, and other programs can be used.

The present invention relates to a combustion system and a boiler for burning fuel.

1: Combustion section

2: Steam generation unit

3: Flowing material circulation department

4: Heat conduction part

5: Dust collection device

6: Chimney

11: Furnace

13: External circulation mechanism

14: Flow material supply department

15: Solid fuel supply unit

16A, 16B, 16C, 16D: Carbon-free fuel supply department

21: Roller

22: Water supply pipe

23: Water pipes

24: Steam pipe

31: Cyclone separator

32: Sealed can

71: 1st blower

71A: No. 1 flow control valve

72: 2nd blower

72A: Second flow control valve

121: porous plate

122: Bellows

131: Extraction tube

132: Open/Close Valve

133: Flowing material conveyor

134: Cylindrical warehouse for flowing materials

135: Flowing material re-injection department

141: Flowing material hopper

142: Flow material feeder

151:Solid fuel hopper

152:Solid fuel feeder

161A, 161B, 161C, 161D: Storage Department

162A, 162B, 162C, 162D: Spraying device

163C: Carbon-containing fuel storage unit

164C: Carbon-free fuel control valve

165C: Carbon fuel control valve

166C: Mode switching unit

A: Fluidized bed

B: Freeboard

Claims (16)

A circulating fluidized bed boiler supplies fuel to a combustion chamber where fluidized material flows and burns the fuel. The circulating fluidized bed boiler is provided with a carbon-free fuel supply section, and the carbon-free fuel supply section supplies carbon-free fuel that does not contain carbon into the combustion chamber. The circulating fluidized bed boiler as described in claim 1 further comprises a carbon-containing fuel supply section, which supplies the carbon-containing fuel containing carbon into the combustion chamber. The circulating fluidized bed boiler as described in claim 2, wherein the aforementioned carbon-free fuel supply section and the aforementioned carbon-containing fuel supply section constitute a combined fuel supply section, and the combined fuel supply section has a carbon-free fuel receiving section for receiving the aforementioned carbon-free fuel and a carbon-containing fuel receiving section for receiving the aforementioned carbon-containing fuel. The circulating fluidized bed boiler as described in claim 3, wherein the combined fuel supply unit further comprises a mode switching unit, the mode switching unit switching between a first mode of supplying the carbon-free fuel to the combustion chamber and a second mode of supplying the carbon-containing fuel to the combustion chamber. A circulating fluidized bed boiler as described in claim 4, wherein the mode switching unit switches to the second mode when the circulating fluidized bed boiler is started, and switches to the first mode after the circulating fluidized bed boiler is started. A circulating fluidized bed boiler as described in any one of claim 1 to claim 5, comprising: a fluid permeation section for allowing the fluid disposed at the bottom of the combustion chamber to permeate; and a flowing fluid supply section for supplying air that causes the flowing material to flow through the fluid permeation section into the combustion chamber, the carbon-free fuel supply section for supplying the carbon-free fuel to the flowing material on the fluid permeation section, and supplying the carbon-free fuel as a fluid together with the air into the combustion chamber through the fluid permeation section. A circulating fluidized bed boiler as described in any one of claim 1 to claim 5, wherein the carbon-free fuel supply section supplies the carbon-free fuel to the fluid material at the bottom of the combustion chamber from the side. A circulating fluidized bed boiler as described in claim 7, wherein the aforementioned carbon-free fuel supply section is a burner that burns the aforementioned carbon-free fuel on the side of the aforementioned fluidized material at the bottom of the aforementioned combustion chamber. A circulating fluidized bed boiler as described in claim 8, wherein the burner is installed at a height of less than 1.5m from the bottom of the combustion chamber. A circulating fluidized bed boiler as described in claim 8, wherein the burner is installed at a height of more than 1.5 m from the bottom of the combustion chamber. A circulating fluidized bed boiler as described in any one of claim 1 to claim 5, wherein the carbon-free fuel supply unit supplies the carbon-free fuel to a plurality of locations at different heights in the combustion chamber. A circulating fluidized bed boiler as described in any one of claim 1 to claim 5, wherein the aforementioned carbon-free fuel is a non-solid fuel. A circulating fluidized bed boiler as described in claim 12, wherein the aforementioned non-solid fuel is at least one of ammonia and hydrogen. The circulating fluidized bed boiler as described in any one of claim 1 to claim 5 further comprises a fluid material circulation section, wherein the fluid material circulation section captures the fluid material discharged out of the combustion chamber and returns it to the combustion chamber. A circulating fluidized bed boiler comprises: a combustion section for supplying fuel into a combustion chamber in which a fluid material flows and causing the fuel to burn; a carbon-free fuel supply section for supplying carbon-free fuel that does not contain carbon into the combustion chamber; and a steam generation section for generating steam from water by using the heat generated in the combustion section. A combustion method for a circulating fluidized bed boiler is to supply fuel to a combustion chamber in which a fluid material flows and burn the fuel. The combustion method includes a carbon-free fuel supply step, wherein the carbon-free fuel supply step supplies the carbon-free fuel that does not contain carbon to the combustion chamber.

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