JP2025002654A - Burner, boiler and combustion method - Google Patents

Abstract

To provide a burner capable of suppressing combustion deterioration of pulverized fuel when pulverized fuel and ammonia are mixed and burned, a boiler, and a combustion method.SOLUTION: A burner comprises: a pulverized fuel supply pipe that guides pulverized fuel and primary air for transporting the pulverized fuel to a furnace; a first gaseous ammonia supply pipe that supplies gaseous ammonia to the pulverized fuel supply pipe; and a mixed fuel nozzle that ejects a mixture of the pulverized fuel, the gaseous ammonia, and the primary air from the pulverized fuel supply pipe into the furnace. The burner is configured such that a ratio of an amount of the gaseous ammonia to a total amount of the pulverized fuel and the gaseous ammonia supplied to the furnace through the mixed fuel nozzle is 10% or less on a calorific value basis.SELECTED DRAWING: Figure 3

Description

This disclosure relates to burners, boilers, and combustion methods.

A burner that mixes pulverized fuel such as pulverized coal with ammonia may be used.

Patent Document 1 discloses a boiler that injects a mixed fuel of pulverized coal and ammonia from a burner into a furnace for combustion.

JP 2021-165629 A

When pulverized fuel such as pulverized coal and gaseous ammonia are fed into the burner through the same supply pipe (i.e., when a mixture of pulverized fuel and gaseous ammonia is fed into the burner), the pulverized fuel burns through a process of increasing temperature and releasing volatile matter, whereas ammonia, being in a gaseous state, burns before the pulverized fuel ignites. When this happens, the air near the burner is consumed by the ammonia, causing a shortage of the air necessary for the pulverized fuel to burn, which can impede the combustion of the pulverized fuel.

In view of the above, at least one embodiment of the present invention provides a burner, boiler, and combustion method that can suppress deterioration of the combustibility of pulverized fuel when pulverized fuel and ammonia are mixed and burned.

The burner according to at least one embodiment of the present invention comprises:
A pulverized fuel supply pipe for introducing pulverized fuel and primary air for conveying the pulverized fuel into the furnace;
a first gaseous ammonia supply pipe for supplying gaseous ammonia to the pulverized fuel supply pipe;
a mixed fuel nozzle for injecting a mixture of the pulverized fuel, the primary air and the gaseous ammonia from the pulverized fuel supply pipe into the furnace;
Equipped with
The ratio of the amount of the gaseous ammonia to the total amount of the pulverized fuel and the gaseous ammonia supplied to the furnace through the mixed fuel nozzle is configured to be 10% or less on a calorific value basis.

Further, the boiler according to at least one embodiment of the present invention includes:
A burner as described above;
a furnace for combusting the pulverized fuel and the gaseous ammonia supplied to the burner through the pulverized fuel supply pipe;
Equipped with.

In addition, the combustion method according to at least one embodiment of the present invention includes:
A combustion method using a burner including a pulverized fuel supply pipe for introducing pulverized fuel and primary air for transporting the pulverized fuel into a furnace, a first gaseous ammonia supply pipe for mixing gaseous ammonia into the pulverized fuel supply pipe, and a mixed fuel nozzle for ejecting a mixture of the pulverized fuel, the primary air, and the gaseous ammonia from the pulverized fuel supply pipe into the furnace,
The method includes a step of adjusting the amount of gaseous ammonia supplied to the pulverized fuel supply pipe so that a ratio of the amount of ammonia to a total amount of pulverized fuel and ammonia supplied to the furnace through the mixed fuel nozzle on a calorific value basis is 10% or less.

According to at least one embodiment of the present invention, a burner, boiler, and combustion method are provided that can suppress deterioration of the combustibility of pulverized fuel when pulverized fuel and ammonia are mixed and burned.

1 is a schematic configuration diagram showing a boiler to which a burner according to an embodiment is applied; FIG. 2 is a schematic diagram of a burner constituting the boiler shown in FIG. 1 . FIG. 1 is a schematic diagram of a burner according to an embodiment. FIG. 1 is a schematic diagram of a burner according to an embodiment. 1 is a graph showing an example of the relationship between ammonia co-firing ratio (horizontal axis) and flame propagation frequency (vertical axis). 1 is a graph showing the relationship between the ammonia co-firing ratio (horizontal axis) and the coal (pulverized coal) combustion ratio (vertical axis). FIG. 2 is a schematic diagram showing a flame formed when fuel is combusted by a burner according to an embodiment.

Below, several embodiments of the present invention will be described with reference to the attached drawings. However, the dimensions, materials, shapes, relative positions, etc. of the components described as the embodiments or shown in the drawings are not intended to limit the scope of the present invention, but are merely illustrative examples. In the following explanation, top and upward refer to the upper side in the vertical direction, and bottom and downward refer to the lower side in the vertical direction, and the vertical direction is not precise and may include errors.

(Boiler and burner configuration)
FIG. 1 is a schematic configuration diagram showing a boiler to which a burner according to some embodiments is applied.

As shown in FIG. 1, a boiler 10 according to one embodiment is a boiler that can burn pulverized fuel made by pulverizing solid fuel with a burner and exchange the heat generated by this combustion with feed water or steam to generate superheated steam. Biomass fuel, coal, etc. are used as the solid fuel.

The boiler 10 has a furnace 11, a combustion device 20, and a combustion gas passage 12. The furnace 11 has a hollow rectangular cylinder shape and is installed vertically. The furnace wall 101 that constitutes the inner wall surface of the furnace 11 is composed of multiple heat transfer tubes and fins that connect the heat transfer tubes to each other, and recovers the heat generated by the combustion of pulverized fuel by heat exchange with water and steam flowing inside the heat transfer tube, while suppressing the temperature rise of the furnace wall 101.

The combustion device 20 is installed in the lower region of the furnace 11. In this embodiment, the combustion device 20 has a plurality of burners 21A, 21B, 21C, 21D, 21E, and 21F (hereinafter, may be collectively referred to as "burners 21") attached to the furnace wall 101. The burners 21 may be arranged in a plurality of vertical stages, with each set consisting of burners 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). Note that, 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, 21C, 21D, 21E, and 21F. 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.

For example, the combustion device 20 may be a swirl combustion type combustion device in which multiple burners 21 are evenly arranged around the circumferential direction of the furnace 11 and configured to eject fuel around a center line extending in the vertical direction of the furnace 11, as described above. Alternatively, the combustion device 20 may be an opposed combustion type combustion device in which the burners 21 are provided on each of a pair of opposed furnace walls 101 so as to face each other.

Burners 21A, 21B, 21C, 21D, 21E, and 21F are connected to a plurality of mills (pulverizers) 31A, 31B, 31C, 31D, 31E, and 31F (hereinafter, collectively referred to as "mills 31") via a plurality of pulverized fuel supply pipes 22A, 22B, 22C, 22D, 22E, and 22F (hereinafter, collectively referred to as "pulverized fuel supply pipes 22"). Mill 31 is, for example, a vertical roller mill in which a grinding table (not shown) is supported inside so as to be driven and rotatable, and a plurality of grinding rollers (not shown) are supported above the grinding table so as to be rotatable in conjunction with the rotation of the grinding table. The solid fuel pulverized by the cooperation of the grinding rollers and the grinding table is transported to a classifier (not shown) provided in mill 31 by primary air (conveyor gas, oxidizing gas) supplied to mill 31. In the classifier, the fuel is classified into fine pulverized fuel with a particle size smaller than that suitable for combustion in the burner 21, and coarse pulverized fuel with a larger particle size. The fine pulverized fuel passes through the classifier and is supplied to the burner 21 via the fine pulverized fuel supply pipe 22 together with the primary air. 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-ground.

An air register 23 is provided on the outside of the furnace 11 at the installation position of the burner 21, and one end of an air duct 24 is connected to the air register 23. A forced draft fan (FDF: Forced Draft Fan) 32 is connected to the other end of the air duct 24. The air supplied from the forced draft fan 32 is heated by an air preheater 42 installed in the air duct 24 (details will be described later), 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.

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 the 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.

The 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, and the primary air supplied to the mill 31 and the secondary air supplied to the burner 21 are heated, thereby recovering further heat from the combustion gas after heat exchange with water and steam.

In addition, 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 the effect of reducing nitrogen oxides, such as ammonia and urea water, to the combustion gas flowing in the flue 13, and promotes the reaction between the nitrogen oxides (NOx) in the combustion gas to which the reducing agent is supplied and the reducing agent by the catalytic action of a denitration catalyst installed in the denitration device 43, thereby removing and reducing the nitrogen oxides in the combustion gas. A gas duct 41 is connected downstream of the air preheater 42 of the flue 13. The gas duct 41 is provided with environmental devices such as a dust collector 44 such as an electric dust collector that removes ash from the combustion gas and a desulfurization device 46 that removes sulfur oxides, as well as an induced draft fan (IDF) 45 for directing the exhaust gas to these environmental devices. The downstream end of the gas duct 41 is connected to a chimney 47, and the combustion gas treated in the environmental device is discharged outside the system as exhaust gas.

In the boiler 10, when the multiple mills 31 are driven, the pulverized and classified pulverized fuel is supplied to the burner 21 together with the primary air through the pulverized fuel supply pipe 22. In addition, secondary air heated by the air preheater 42 is supplied to the burner 21 through the wind box 23 from the wind duct 24. The burner 21 blows a pulverized fuel 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. A flame is formed in the lower region of the furnace 11, and high-temperature combustion gas rises inside the furnace 11 and flows into the combustion gas passage 12. In this embodiment, air is used as the oxidizing gas (primary air, secondary air), but it may be a gas with a higher or lower oxygen content than air, and stable combustion in the furnace 11 is achieved by adjusting the ratio of the amount of oxygen to the amount of fuel supplied to an appropriate range.

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

In the above-mentioned embodiment, the boiler of the present invention 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) fuel, petroleum residue, etc.

Fuel for the boiler is not limited to solid fuels, and can also use petroleum such as heavy oil, light oil, and heavy oil, industrial wastewater, and liquid fuels such as liquefied ammonia. In addition, gaseous fuels such as natural gas, various petroleum gases, by-product gases generated in the steelmaking process, hydrogen gas, and ammonia gas can also be used.

Furthermore, it can also be applied to mixed-fuel boilers that use a combination of these various fuels.

Figure 2 is a schematic diagram of the burner 21 constituting the boiler 10 shown in Figure 1. As shown in Figure 2, the burner 21 (each of the burners 21A to 21F described above) is equipped with a central burner 60 located in the center in the vertical direction, and pulverized fuel burners 50A and 50B (hereinafter collectively referred to as pulverized fuel burners 50) located above and below the central burner 60. In addition, combustion air nozzles 56 are provided above and below these burner groups (the central burner 60 and the pulverized fuel burners 50A and 50B).

The pulverized fuel burner 50 includes a pulverized fuel nozzle 52 and an air nozzle 54. The pulverized fuel nozzle 52 is adapted to blow primary air supplied from the pulverized fuel supply pipe 22 and pulverized fuel (such as pulverized coal) carried by the primary air into the furnace 11. The air nozzle 54 is adapted to blow secondary air (heated air heated by the air heater 42) supplied from the air duct 24 into the furnace 11.

The central burner 60 is configured to blow fuel for diffusion combustion together with air into the furnace 11. In the exemplary embodiment shown in FIG. 2, the central burner 60 includes an oil fuel nozzle 62 configured to blow oil fuel into the furnace 11, and an air nozzle 66 arranged to surround the periphery of the oil fuel nozzle 62. The air nozzle 66 may be configured to blow secondary air (heated air heated by the air heater 42) supplied from the air duct 24 into the furnace 11.

The combustion air nozzle 56 may be configured to blow secondary air (heated air heated by the air heater 42) supplied from the air duct 24 into the furnace 11.

Next, the burner according to some embodiments will be described in more detail. Figures 3 and 4 are each a schematic diagram of a burner according to one embodiment.

As shown in Figures 3 and 4, the burner 21 according to one embodiment includes the above-mentioned pulverized fuel supply pipe 22, a first gaseous ammonia supply pipe 70, and a mixed fuel nozzle 68.

As described above, the pulverized fuel supply pipe 22 is configured to guide pulverized fuel (such as pulverized coal) and primary air for transporting the pulverized fuel to the furnace 11.

The first gaseous ammonia supply pipe 70 is connected to the pulverized fuel supply pipe 22 and is configured to supply gaseous ammonia to the pulverized fuel supply pipe 22.

The first gaseous ammonia supply pipe 70 may be configured so that ammonia from an ammonia tank 74 in which liquid ammonia is stored is vaporized and then supplied via an ammonia line 76. The ammonia line 76 may be provided with a vaporizer 78 for vaporizing the liquid ammonia from the ammonia tank 74. The ammonia line 76 may be provided with a first valve 80 for adjusting the amount of gaseous ammonia supplied from the first gaseous ammonia supply pipe 70 to the pulverized fuel supply pipe 22.

The first gaseous ammonia supply pipe 70 may be provided with a gate valve 72 for switching between supplying and not supplying gaseous ammonia from the first gaseous ammonia supply pipe 70 to the pulverized fuel supply pipe 22.

The mixed fuel nozzle 68 is configured to spray a mixture of pulverized fuel, primary air, and gaseous ammonia from the pulverized fuel supply pipe 22 into the furnace 11.

3 and 4, the pulverized fuel nozzle 52 of one of the pulverized fuel burners 50A and 50B constituting the burner 21 functions as the above-mentioned mixed fuel nozzle 68. In other embodiments, the pulverized fuel nozzle 52 of the other of the pulverized fuel burners 50A and 50B constituting the burner 21 may function as the above-mentioned mixed fuel nozzle 68, or both of the pulverized fuel nozzles 52 of the pulverized fuel burners 50A and 50B may function as the above-mentioned mixed fuel nozzle 68.

The burner 21 may also include a control device 90 for adjusting the amount of gaseous ammonia supplied from the first gaseous ammonia supply pipe 70 to the pulverized fuel supply pipe 22. The control device 90 may be configured to adjust the opening of the first valve 80 so that the amount of gaseous ammonia supplied to the pulverized fuel supply pipe 22 becomes a predetermined value.

In some embodiments, the burner 21 is configured so that the ratio of the amount of gaseous ammonia to the total amount of pulverized fuel and gaseous ammonia supplied to the furnace 11 through the mixed fuel nozzle 68 on a calorific value basis (hereinafter also referred to as the ammonia co-firing ratio) is 10% or less. In one embodiment, the control device 90 may adjust the opening of the first valve 80 so that the ammonia co-firing ratio is 10% or less.

Here, FIG. 5 is a graph showing the relationship between the ammonia co-firing ratio (horizontal axis) and the flame propagation frequency (vertical axis) when pulverized coal (pulverized fuel) and gaseous ammonia are co-firing using the burner 21 described above. FIG. 6 is a graph showing the relationship between the ammonia co-firing ratio (horizontal axis) and the coal (pulverized coal) combustion rate (vertical axis) when pulverized coal (pulverized fuel) and gaseous ammonia are co-firing using the burner 21 described above.

When pulverized fuel such as pulverized coal and gaseous ammonia are fed into the burner through the same supply pipe (i.e., when a mixture of pulverized fuel and gaseous ammonia is fed into the burner), the pulverized fuel burns through a process of increasing temperature and releasing volatile matter, whereas ammonia, being in gaseous form, burns before the pulverized fuel ignites. When this happens, the air near the burner is consumed by the ammonia, causing a shortage of the air necessary for the pulverized fuel to burn, which can impede the combustion of the pulverized fuel.

For example, as shown in Figure 5, when pulverized coal, gaseous ammonia, and primary air are mixed and combusted, the frequency of flame propagation, in which the pulverized coal ignites and burns in groups, decreases compared to coal-only combustion (ammonia co-firing rate 0%), and as shown in Figure 6, the ignition and combustibility of the pulverized coal deteriorates. In particular, when the ammonia co-firing rate exceeds 10%, the frequency of flame propagation decreases significantly, and it can be seen that the combustion rate of coal also tends to decrease accordingly.

In this regard, in the burner 21 according to the embodiment described above, the ammonia co-combustion ratio in the mixed fuel of pulverized fuel and gaseous ammonia supplied to the furnace 11 through the mixed fuel nozzle 68 is set to 10% or less, so that even if the ammonia burns before the pulverized fuel in the furnace 11, there is little shortage of air required for the combustion of the pulverized fuel. This makes it possible to suppress deterioration in the combustibility of the pulverized fuel.

In some embodiments, the burner 21 is configured so that the flow velocity of the gas containing primary air and gaseous ammonia at the outlet of the mixed fuel nozzle 68 is 35 m/s or less. In one embodiment, the control device 90 may adjust the opening of the first valve 80 so that the above-mentioned flow velocity (gas flow velocity at the outlet of the mixed fuel nozzle 68) is 35 m/s or less.

When gaseous ammonia is introduced into the pulverized fuel supply pipe 22, the gas flow rate in the pulverized fuel supply pipe 22 increases, which increases the ejection flow velocity at the outlet of the mixed fuel nozzle 68, which ejects fuel from the pulverized fuel supply pipe 22 into the furnace 11, and this may deteriorate the ignition ability of the pulverized fuel. In this regard, according to the above-mentioned embodiment, the gas flow velocity at the outlet of the mixed fuel nozzle 68 is set to 35 m/s or less, so that the gas flow velocity at the outlet of the mixed fuel nozzle 68 is not too fast, and deterioration of the combustibility of the pulverized fuel can be more effectively suppressed.

The upper limit of the gas flow velocity at the outlet of the mixed fuel nozzle 68 may differ depending on the type of furnace 11 (combustion device 20). For example, in the case of the combustion device 20 using the above-mentioned swirl combustion method, the flow velocity of the gas containing primary air and gaseous ammonia at the outlet of the mixed fuel nozzle 68 may be configured to be 35 m/s or less. In addition, in the case of the combustion device 20 using the above-mentioned opposed combustion method, the flow velocity of the gas containing primary air and gaseous ammonia at the outlet of the mixed fuel nozzle 68 may be configured to be 30 m/s or less.

In some embodiments, the burner 21 may be provided with a first adjustment unit configured to adjust the amount of gaseous ammonia supplied from the first gaseous ammonia supply pipe 70 to the pulverized fuel supply pipe 22 so that the amount of gaseous ammonia supplied from the first gaseous ammonia supply pipe 70 to the pulverized fuel supply pipe 22 is the smaller of the first supply amount and the second supply amount described below. Here, the first supply amount is a supply amount of gaseous ammonia such that the ratio of the amount of gaseous ammonia on a calorific value basis to the total amount of ammonia co-firing rate of the mixed fuel of the pulverized fuel and gaseous ammonia supplied to the furnace 11 through the mixed fuel nozzle 68 (ammonia co-firing rate) is 10% or less, and the second supply amount is a supply amount of gaseous ammonia such that the flow velocity of the gas containing primary air and gaseous ammonia at the outlet of the mixed fuel nozzle 68 is 35 m/s or less.

In one embodiment, the control device 90 may have the function of the first adjustment unit described above.

According to the above-described embodiment, the amount of gaseous ammonia supplied to the pulverized fuel supply pipe 22 is adjusted to the smaller of the first supply amount at which the calorific value-based ammonia co-combustion rate is 10% or less, and the second supply amount at which the gas flow velocity at the outlet of the mixed fuel nozzle 68 is 35 m/s, so that deterioration of the combustibility of the pulverized fuel can be more effectively suppressed.

In the exemplary embodiment shown in FIG. 4, the burner 21 further includes a second gaseous ammonia supply pipe 84 for supplying gaseous ammonia to the inside of the air nozzle 54 provided adjacent to the mixed fuel nozzle 68 (pulverized fuel nozzle 52). In the embodiment shown in FIG. 4, two second gaseous ammonia supply pipes 84 are provided inside the air nozzle 54, located above and below the mixed fuel nozzle 68.

The first gaseous ammonia supply pipe 70 is connected to the pulverized fuel supply pipe 22 and is configured to supply gaseous ammonia to the pulverized fuel supply pipe 22.

The first gaseous ammonia supply pipe 70 may be configured so that ammonia from an ammonia tank 74 in which liquid ammonia is stored is vaporized and then supplied via an ammonia line 76. The ammonia line 76 may be provided with a vaporizer 78 for vaporizing the liquid ammonia from the ammonia tank 74.

In the exemplary embodiment shown in FIG. 4, the ammonia line 76 includes an ammonia line 76A connected to the first gaseous ammonia supply pipe 70 and an ammonia line 76B connected to the second gaseous ammonia supply pipe 84.

As shown in FIG. 4, the ammonia line 76B (ammonia line 76) may be provided with a second valve 82 for adjusting the amount of gaseous ammonia supplied from the second gaseous ammonia supply pipe 84 to the air nozzle 54.

In some embodiments, the burner 21 is configured so that the flow rate of the gas containing the secondary air and gaseous ammonia at the outlet of the air nozzle 54 is 50 m/s or less. In one embodiment, the control device 90 may adjust the opening of the second valve 82 so that the flow rate of the gas at the outlet of the air nozzle 54 is 50 m/s or less.

Here, FIG. 7 is a schematic diagram showing a flame 110 formed by the combustion of a mixed fuel containing pulverized fuel ejected from the mixed fuel nozzle 68, and a flame 112 formed by the combustion of a premixed air-fuel ejected from the air nozzle 54. The reference numeral 114 indicates the flow of the premixed air-fuel containing secondary air from the air nozzle 54.

The premixed gas ejected from the air nozzle 54 into the furnace 11 has relatively good ignition and combustibility, and may actually hinder the ignition and combustion of the pulverized fuel supplied to the furnace 11 from the mixed fuel nozzle 68. In this regard, in the above-mentioned embodiment, the gas flow velocity at the outlet of the air nozzle 54 is about 50 m/s, which is faster than the gas flow velocity at the outlet of the mixed fuel nozzle 68, so that the ignition of the premixed gas ejected from the air nozzle 54 can be delayed compared to the ignition of the pulverized fuel, as shown in FIG. 7. In addition, the effect of preventing ammonia from consuming air ahead of the pulverized fuel is also obtained. On the other hand, by setting the gas flow velocity at the outlet of the air nozzle 54 to 50 m/s or less, the flow velocity is not too fast and it is difficult to hinder the ignition of the pulverized fuel. Therefore, according to the above-mentioned embodiment, the deterioration of the combustibility of the pulverized fuel can be more effectively suppressed.

As described above, by setting the gas flow velocity at the outlet of the air nozzle 54 to approximately 50 m/s, which is faster than the gas flow velocity at the outlet of the mixed fuel nozzle 68, it is expected that the effect of suppressing the increase in nitrogen oxides (NOx) can also be achieved.

In some embodiments, the burner 21 is configured so that the air ratio, which is the ratio of the total supply amount of primary air (primary air from the pulverized fuel supply pipe 22) and secondary air (secondary air from the air nozzle 54) to the theoretical amount of air required for combustion of the pulverized fuel and gaseous ammonia supplied to the furnace 11 through the mixed fuel nozzle 68 and the gaseous ammonia supplied to the furnace 11 through the air nozzle 54, is 0.28 or more. In one embodiment, the control device 90 may adjust the opening degree of the second valve 82 so that the above-mentioned air ratio is 0.28 or more.

According to the above embodiment, the air ratio is set to 0.28 or more, so there is little risk of a shortage of air used to burn the pulverized fuel. This makes it possible to more effectively suppress deterioration of the combustibility of the pulverized fuel.

In some embodiments, the burner 21 may be provided with a second adjustment unit configured to adjust the amount of gaseous ammonia supplied from the second gaseous ammonia supply pipe 84 to the air nozzle 54 so that the amount of gaseous ammonia supplied from the second gaseous ammonia supply pipe 84 to the air nozzle 54 is the smaller of the third supply amount and the fourth supply amount described below. Here, the third supply amount is the amount of gaseous ammonia supplied such that the flow velocity of the gas containing secondary air and gaseous ammonia at the outlet of the air nozzle 54 is 50 m/s or less, and the fourth supply amount is the amount of gaseous ammonia supplied such that the air ratio, which is the ratio of the total supply amount of primary air (primary air from the pulverized fuel supply pipe 22) and secondary air (secondary air from the air nozzle 54) to the theoretical air amount required for combustion of the pulverized fuel and gaseous ammonia supplied to the furnace 11 via the mixed fuel nozzle 68 and the gaseous ammonia supplied to the furnace 11 via the air nozzle 54, is 0.28 or more.

In one embodiment, the control device 90 may have the function of the second adjustment unit described above.

In addition to supplying gaseous ammonia to the pulverized fuel supply pipe 22, gaseous ammonia can be further supplied to the air nozzle 54 to supply a premixture of secondary air and gaseous ammonia to the furnace 11, thereby increasing the amount of ammonia input to the furnace 11. On the other hand, in this case, the gas flow velocity at the outlet of the air nozzle 54 adjacent to the mixed fuel nozzle 68 increases and the air ratio in the furnace 11 decreases, so that the ignition ability of the pulverized fuel supplied to the furnace 11 from the mixed fuel nozzle 68 may deteriorate.
In this regard, according to the above-described embodiment, the amount of gaseous ammonia supplied to the air nozzle 54 is adjusted to be the smaller of the third supply amount at which the gas flow velocity at the outlet of the air nozzle 54 is 50 m/s, and the fourth supply amount at which the above-described air ratio is 0.28 or more, so that the deterioration of the combustibility of the pulverized fuel can be more effectively suppressed.

The contents described in each of the above embodiments can be understood, for example, as follows:

[1] At least one embodiment of the burner (21) of the present invention comprises:
A pulverized fuel supply pipe (22) for introducing pulverized fuel and primary air for conveying the pulverized fuel into the furnace (11);
a first gaseous ammonia supply pipe (70) for supplying gaseous ammonia to the pulverized fuel supply pipe;
a mixed fuel nozzle (68) for ejecting a mixture of the pulverized fuel, the primary air and the gaseous ammonia from the pulverized fuel supply pipe into the furnace;
Equipped with
The ratio of the amount of the gaseous ammonia to the total amount of the pulverized fuel and the gaseous ammonia supplied to the furnace through the mixed fuel nozzle is configured to be 10% or less on a calorific value basis.

According to the configuration of [1] above, when pulverized fuel such as pulverized coal and gaseous ammonia are mixed and burned, the ratio of the amount of gaseous ammonia to the total amount of pulverized fuel and gaseous ammonia supplied to the furnace through the mixed fuel nozzle on a calorific value basis (hereinafter also referred to as the ammonia mixed combustion ratio) is set to 10% or less. Therefore, even if ammonia burns prior to the pulverized fuel in the furnace, there is little shortage of air required for combustion of the pulverized fuel. This makes it possible to suppress deterioration of the combustibility of the pulverized fuel.

[2] In some embodiments, in the configuration of [1] above,
The burner is
The flow velocity of the gas containing the primary air and the gaseous ammonia at the outlet of the mixed fuel nozzle is configured to be 35 m/s or less.

When gaseous ammonia is injected into the pulverized fuel supply pipe, the gas flow rate in the pulverized fuel supply pipe increases, which increases the ejection flow velocity at the outlet of the mixed fuel nozzle that ejects fuel from the pulverized fuel supply pipe into the furnace, and this may deteriorate the ignition characteristics of the pulverized fuel. In this regard, according to the configuration of [2] above, the gas flow velocity at the outlet of the mixed fuel nozzle is set to 35 m/s or less, so that the gas flow velocity at the outlet of the mixed fuel nozzle is not too fast, and deterioration of the combustibility of the pulverized fuel can be more effectively suppressed.

[3] In some embodiments, in the configuration of [1] or [2] above,
The burner is
A first adjusting unit (e.g., a control device 90) is provided for adjusting the amount of the gaseous ammonia supplied from the first gaseous ammonia supply pipe to the pulverized fuel supply pipe;
The first adjustment unit is configured to adjust the supply amount of the gaseous ammonia to the pulverized fuel supply pipe so that the supply amount is the smaller one of the first supply amount and the second supply amount of the gaseous ammonia,
the first supply amount is a supply amount of gaseous ammonia such that a ratio of the amount of gaseous ammonia to a total amount of the pulverized fuel and the gaseous ammonia supplied to the furnace through the mixed fuel nozzle is 10% or less on a calorific value basis;
The second supply amount is a supply amount of gaseous ammonia such that a flow velocity of the gas containing the primary air and the gaseous ammonia at an outlet of the mixed fuel nozzle is 35 m/s or less.

According to the configuration of [3] above, the amount of gaseous ammonia supplied to the pulverized fuel supply pipe is adjusted to the smaller of the first supply amount at which the ammonia co-combustion rate based on the calorific value is 10% or less, and the second supply amount at which the gas flow velocity at the mixed fuel nozzle outlet is 35 m/s, so that the deterioration of the combustibility of the pulverized fuel can be more effectively suppressed.

[4] In some embodiments, in any one of the configurations [1] to [3] above,
an air nozzle (54) adjacent to the mixed fuel nozzle for supplying secondary air to the furnace;
a second gaseous ammonia supply pipe (84) for supplying gaseous ammonia to the inside of the air nozzle;
A second adjusting unit (e.g., a control device 90) for adjusting the amount of the gaseous ammonia supplied from the second gaseous ammonia supply pipe to the air nozzle;
Equipped with
The second adjustment unit is configured to adjust the supply amount of the gaseous ammonia to the air nozzle so as to be a smaller one of a third supply amount and a fourth supply amount of the gaseous ammonia,
the third supply amount is a supply amount of gaseous ammonia such that a flow velocity of the gas containing the secondary air and the gaseous ammonia at an outlet of the air nozzle is 50 m/s or less;
The fourth supply amount is a supply amount of gaseous ammonia such that an air ratio, which is a ratio of the total supply amount of the primary air and the secondary air to the furnace to a theoretical amount of air required for combustion of the pulverized fuel and the gaseous ammonia supplied to the furnace via the mixed fuel nozzle, and the gaseous ammonia supplied to the furnace via the air nozzle, is 0.28 or more.

In addition to the configuration of [1] above, the amount of ammonia fed to the furnace can be increased by supplying gaseous ammonia to the air nozzle and supplying a premixed gas of secondary air and gaseous ammonia to the furnace. However, in this case, the gas flow velocity at the outlet of the air nozzle adjacent to the mixed fuel nozzle increases and the air ratio in the furnace decreases, which may deteriorate the ignition ability of the pulverized fuel fed to the furnace from the mixed fuel nozzle.
In this regard, according to the configuration [4] above, the amount of gaseous ammonia supplied to the air nozzle is adjusted to be the smaller of the third supply amount at which the gas flow velocity at the outlet of the air nozzle is 50 m/s, and the fourth supply amount at which the above-mentioned air ratio is 0.28 or more, so that the deterioration of the combustibility of the pulverized fuel can be more effectively suppressed.

[5] At least one embodiment of the boiler (10) of the present invention comprises:
A burner (21) according to any one of the above [1] to [4];
a furnace (11) for combusting the pulverized fuel and the gaseous ammonia supplied to the burner through the pulverized fuel supply pipe (22);
Equipped with.

According to the configuration of [5] above, when pulverized fuel such as pulverized coal and gaseous ammonia are mixed and burned, the ratio of the amount of gaseous ammonia to the total amount of pulverized fuel and gaseous ammonia supplied to the furnace through the mixed fuel nozzle on a calorific value basis (ammonia mixed combustion ratio) is set to 10% or less, so that even if ammonia burns before the pulverized fuel in the furnace, there is little shortage of air required for combustion of the pulverized fuel. This makes it possible to suppress deterioration of the combustibility of the pulverized fuel.

[6] At least one embodiment of the combustion method of the present invention comprises:
A combustion method using a burner (21) including a pulverized fuel supply pipe (22) for introducing pulverized fuel and primary air for transporting the pulverized fuel into a furnace, a first gaseous ammonia supply pipe (70) for mixing gaseous ammonia into the pulverized fuel supply pipe, and a mixed fuel nozzle (68) for ejecting a mixture of the pulverized fuel, the primary air, and the gaseous ammonia from the pulverized fuel supply pipe into the furnace, comprising:
The method includes a step of adjusting the amount of gaseous ammonia supplied to the pulverized fuel supply pipe so that a ratio of the amount of ammonia to a total amount of pulverized fuel and ammonia supplied to the furnace through the mixed fuel nozzle on a calorific value basis is 10% or less.

According to the method of [6] above, when pulverized fuel such as pulverized coal is mixed with gaseous ammonia, the ratio of the amount of gaseous ammonia to the total amount of pulverized fuel and gaseous ammonia supplied to the furnace through the mixed fuel nozzle on a calorific value basis (ammonia mixed combustion ratio) is set to 10% or less, so that even if ammonia burns before the pulverized fuel in the furnace, there is little shortage of air required for combustion of the pulverized fuel. This makes it possible to suppress deterioration of the combustibility of the pulverized fuel.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and also includes variations on the above-described embodiments and appropriate combinations of these embodiments.

In this specification, expressions expressing relative or absolute configuration, such as "in a certain direction,""along a certain direction,""parallel,""orthogonal,""center,""concentric," or "coaxial," do not only strictly represent such a configuration, but also represent 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.
Furthermore, in this specification, expressions describing shapes such as a rectangular shape or a cylindrical shape do not only refer to shapes such as a rectangular shape or a cylindrical shape 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.
In addition, in this specification, the expressions "comprise,""include," or "have" a certain element are not exclusive expressions that exclude the presence of other elements.

10 Boiler 11 Furnace 12 Combustion gas passage 13 Flue 20 Combustion device 21 (21A-21F) Burner 22 (22A-22F) Pulverized fuel supply pipe 23 Wind box 24 Wind duct (air duct)
31 Mill 32 Forced draft fan 41 Gas duct 42 Air preheater (air heater)
43 Denitrification device 44 Device 46 Desulfurization device 47 Chimney 50 Pulverized fuel burner 50A Pulverized fuel burner 50B Pulverized fuel burner 52 Pulverized fuel nozzle 54 Air nozzle 56 Combustion air nozzle 60 Central burner 62 Oil fuel nozzle 66 Air nozzle 68 Mixed fuel nozzle 70 First gaseous ammonia supply pipe 72 Gate valve 74 Ammonia tank 76 Ammonia line 76A Ammonia line 76B Ammonia line 78 Vaporizer 80 First valve 82 Second valve 84 Second gaseous ammonia supply pipe 90 Control device 101 Furnace wall 102 Superheater 102A Superheater 102B Superheater 102C Superheater 103 Reheater 103A Reheater 103B Reheater 104 Economizer 110 Flame 112 Flame

Claims (6)

A pulverized fuel supply pipe for introducing pulverized fuel and primary air for conveying the pulverized fuel into the furnace;
a first gaseous ammonia supply pipe for supplying gaseous ammonia to the pulverized fuel supply pipe;
a mixed fuel nozzle for injecting a mixture of the pulverized fuel, the gaseous ammonia, and the primary air from the pulverized fuel supply pipe into the furnace;
Equipped with
A burner configured such that a ratio of the amount of the gaseous ammonia to a total amount of the pulverized fuel and the gaseous ammonia supplied to the furnace through the mixed fuel nozzle is 10% or less on a calorific value basis. 2. The burner according to claim 1, wherein the flow velocity of the primary air and the gas containing gaseous ammonia at the outlet of the mixed fuel nozzle is 35 m/s or less. A first adjusting unit is provided for adjusting the amount of the gaseous ammonia supplied from the first gaseous ammonia supply pipe to the pulverized fuel supply pipe,
The first adjusting unit is configured to adjust the supply amount of the gaseous ammonia to the pulverized fuel supply pipe so that the supply amount is the smaller one of the first supply amount and the second supply amount of the gaseous ammonia,
the first supply amount is a supply amount of gaseous ammonia such that a ratio of the amount of gaseous ammonia to a total amount of the pulverized fuel and the gaseous ammonia supplied to the furnace through the mixed fuel nozzle is 10% or less on a calorific value basis;
3. The burner according to claim 1, wherein the second supply amount is a supply amount of gaseous ammonia such that a flow velocity of the gas containing the primary air and the gaseous ammonia at an outlet of the mixed fuel nozzle is 35 m/s or less. an air nozzle disposed adjacent to the mixed fuel nozzle for supplying secondary air to the furnace;
a second gaseous ammonia supply pipe for supplying gaseous ammonia to the inside of the air nozzle;
A second adjusting unit for adjusting the amount of the gaseous ammonia supplied from the second gaseous ammonia supply pipe to the air nozzle;
Equipped with
The second adjustment unit is configured to adjust the supply amount of the gaseous ammonia to the air nozzle so as to be a smaller one of a third supply amount and a fourth supply amount of the gaseous ammonia,
the third supply amount is a supply amount of gaseous ammonia such that a flow velocity of the gas containing the secondary air and the gaseous ammonia at an outlet of the air nozzle is 50 m/s or less;
3. The burner according to claim 1 or 2, wherein the fourth supply amount is a supply amount of gaseous ammonia such that an air ratio, which is a ratio of a total supply amount of the primary air and the secondary air to the furnace to a theoretical amount of air required for combustion of the pulverized fuel and the gaseous ammonia supplied to the furnace via the mixed fuel nozzle, and the gaseous ammonia supplied to the furnace via the air nozzle, is 0.28 or more. A burner according to claim 1 or 2;
a furnace for combusting the pulverized fuel and the gaseous ammonia supplied to the burner through the pulverized fuel supply pipe;
A boiler equipped with A combustion method using a burner including a pulverized fuel supply pipe for introducing pulverized fuel and primary air for transporting the pulverized fuel into a furnace, a first gaseous ammonia supply pipe for mixing gaseous ammonia into the pulverized fuel supply pipe, and a mixed fuel nozzle for ejecting a mixture of the pulverized fuel, the primary air, and the gaseous ammonia from the pulverized fuel supply pipe into the furnace,
A combustion method comprising a step of adjusting an amount of the gaseous ammonia supplied to the pulverized fuel supply pipe so that a ratio of an amount of ammonia to a total amount of the pulverized fuel and ammonia supplied to the furnace through the mixed fuel nozzle on a calorific value basis is 10% or less.

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