JP2023147929A - Burner and boiler - Google Patents

Abstract

To provide a burner which enables ammonia and a fossil fuel to be efficiently used as a fuel, and to provide a boiler.SOLUTION: A burner includes: a first nozzle forming a cylindrical shape extending in an axial direction and having a tip opening capable of jetting a fluid mixture of primary air and fine powdered coal; and a second nozzle disposed in the first nozzle so as to extend in the axial direction and having a tip part which is located at the upstream side of the fluid mixture relative to the tip opening of the first nozzle and capable of jetting ammonia.SELECTED DRAWING: Figure 2

Description

The present disclosure relates to burners and boilers.

A large boiler such as a power generation boiler has a hollow furnace installed vertically, and a plurality of burners are arranged along the circumferential direction of the furnace wall. Further, in a large boiler, a flue is connected vertically above the furnace, and a heat exchanger for generating steam is disposed in the flue. A flame is formed by the burner injecting a mixture of fuel and air (oxidizing gas) into the furnace, and combustion gas is generated and flows into the flue. A heat exchanger is installed in a region where combustion gas flows, and superheated steam is generated by heating water or steam flowing through heat transfer tubes that make up the heat exchanger.

In recent years, research and development has been progressing on burners that use ammonia as fuel in addition to conventional fossil fuels. As a specific example of a boiler to which this type of burner is applied, the one described in Patent Document 1 below is known. In this boiler, a plurality of burners for burning fossil fuel and a plurality of burners for burning ammonia are each independently provided.

JP 2019-178823 Publication

However, since the total number of burners that can be installed in a boiler is fixed, when burners that use ammonia as fuel are provided as described above, the number of burners that use fossil fuel as fuel decreases. As a result, there is a problem that, for example, in a situation where ammonia cannot be obtained, the overall output of the burner is reduced accordingly.

The present disclosure has been made to solve the above problems, and an object thereof is to provide a burner and a boiler that can efficiently use ammonia and fossil fuel as fuel.

In order to solve the above problems, a burner according to the present disclosure includes a first nozzle having a cylindrical shape extending in the axial direction and having a tip opening capable of ejecting a mixed fluid of primary air and pulverized coal; a second nozzle that is arranged to extend in the axial direction within the nozzle, is located upstream of the mixed fluid than the tip opening of the first nozzle, and has a tip that can eject ammonia.

A boiler according to the present disclosure includes the burner described above and a furnace provided with the burner.

According to the present disclosure, it is possible to provide a burner and a boiler that can efficiently use ammonia and fossil fuel as fuel.

FIG. 1 is a schematic diagram showing the configuration of a boiler according to an embodiment of the present disclosure. FIG. 1 is a cross-sectional view showing the configuration of a burner according to an embodiment of the present disclosure. FIG. 2 is a diagram of a burner according to an embodiment of the present disclosure viewed from an axial direction. FIG. 7 is a cross-sectional view showing a modification of the burner according to the embodiment of the present disclosure. FIG. 6 is a diagram of a modified example of the burner according to the embodiment of the present disclosure, viewed from the axial direction.

Hereinafter, one embodiment of the present disclosure will be described with reference to the drawings. It should be noted that the present invention is not limited to this embodiment, and if there are multiple embodiments, the present invention may be configured by combining each embodiment. In the following description, the term "above" or "upper" refers to the upper side in the vertical direction, and "lower" or "lower" refers to the lower side in the vertical direction, and the vertical direction is not exact and includes errors.

FIG. 1 is a schematic configuration diagram showing a boiler using solid fuel as the main fuel according to the present embodiment.

(Boiler configuration)
The boiler 10 of this embodiment is a boiler that can generate superheated steam by combusting pulverized fuel obtained by pulverizing solid fuel using a burner, and exchanging the heat generated by the combustion with feed water and steam. As the solid fuel, biomass fuel, coal, etc. are used.

The boiler 10 has a furnace 11, a combustion device 20, and a combustion gas passage 12. The furnace 11 has a hollow rectangular tube shape and is installed along the vertical direction. Furnace wall 101, which constitutes the inner wall surface of furnace 11, is composed of a plurality of heat exchanger tubes and fins that connect the heat exchanger tubes, and transfers heat generated by combustion of pulverized fuel to water or water flowing inside the heat exchanger tubes. In addition to recovering heat by exchanging heat with steam, the temperature rise of the furnace wall 101 is suppressed.

Combustion device 20 is installed in the lower region of furnace 11 . In the present embodiment, the combustion device 20 includes a plurality of burners 21A, 21B, 21C, 21D, 21E, and 21F (hereinafter sometimes collectively referred to as "burners 21") attached to the furnace wall 101. have. The burners 21 are arranged at equal intervals along the circumferential direction of the furnace 11 (for example, four burners installed at each corner of the rectangular furnace 11) as one set, and are arranged in multiple stages along the vertical direction. It is located. In addition, in FIG. 1, for convenience of illustration, only two of the burners in one set are shown, and each set is labeled with 21A, 21B, 21C, 21D, 21E, and 21F. The shape of the furnace, the number of stages of burners, the number of burners in one stage, the arrangement of burners, etc. are not limited to this embodiment.

The burners 21A, 21B, 21C, 21D, 21E, and 21F each have a plurality of pulverized fuel supply pipes 22A, 22B, 22C, 22D, 22E, and 22F (hereinafter collectively referred to as "pulverized fuel supply pipes 22") ) is connected to a plurality of mills (pulverizers) 31A, 31B, 31C, 31D, 31E, and 31F (hereinafter sometimes collectively referred to as "mill 31"). For example, the mill 31 has a crushing table (not shown) supported in the interior so as to be rotatable, and a plurality of crushing rollers (not shown) are supported above the crushing table so as to be rotatable in conjunction with the rotation of the crushing table. This is a vertical roller mill. The solid fuel pulverized by the cooperation of the pulverizing roller and the pulverizing table is conveyed to a classifier (not shown) provided in the mill 31 by primary air (conveying gas, oxidizing gas) supplied to the mill 31. . In the classifier, the fuel is classified into fine fuel having a particle size smaller than that suitable for combustion in the burner 21 and coarse fuel having a particle size larger than the particle size. The pulverized fuel passes through a classifier and is supplied together with primary air to the burner 21 via a pulverized fuel supply pipe 22. The coarse fuel that has not passed through the classifier falls onto the grinding table due to its own weight inside the mill 31 and is re-ground.

Furthermore, the burners 21A, 21B, 21C, 21D, 21E, and 21F are connected to an ammonia supply source 52 via an ammonia fuel supply pipe 51. The ammonia fuel supply pipe 51 is provided separately from the pulverized fuel supply pipe 22. Further, in the example of FIG. 1, a plurality of ammonia fuel supply pipes 51 extend from a single ammonia supply source 52, but an ammonia supply source 52 may be provided for each ammonia fuel supply pipe 51. The detailed configuration of the burner 21 will be described later.

A wind box (air register) 23 is provided on the outside of the furnace 11 at the mounting position of the burner 21, and one end portion of an air passage (air duct) 24 is connected to this wind box 23. A forced draft fan (FDF) 32 is connected to the other end of the air passage 24 . The air supplied from the forced draft fan 32 is heated by an air preheater 42 installed in the air passage 24 (details will be described later), and is supplied to the burner 21 via the wind box 23 as secondary air (combustion air, oxidizing air, etc.). gas) and thrown into the furnace 11.

The combustion gas passage 12 is connected to the upper part of the furnace 11 in the vertical direction. The combustion gas passage 12 includes superheaters 102A, 102B, and 102C (hereinafter sometimes collectively referred to as "superheaters 102"), reheaters as heat exchangers for recovering the heat of the combustion gas. 103A and 103B (hereinafter, may be collectively referred to as "reheater 103"), and an economizer 104 are provided, and the combustion gas generated in the furnace 11 and the inside of each heat exchanger are Heat exchange takes place with the circulating feed water and steam. Note that the arrangement and shape of each heat exchanger are not limited to the form shown in FIG. 1.

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

Further, a denitrification device 43 may be provided in the flue 13 at a position upstream of the air preheater 42. The denitrification device 43 supplies a reducing agent, such as ammonia or urea water, which has the effect of reducing nitrogen oxides to the combustion gas flowing through the flue 13, and removes nitrogen oxides from the combustion gas to which the reducing agent has been supplied. By promoting the reaction between (NOx) and the reducing agent by the catalytic action of the denitrification catalyst installed in the denitrification device 43, nitrogen oxides in the combustion gas are removed and reduced.
A gas duct 41 is connected to the flue 13 downstream of the air preheater 42 . The gas duct 41 includes environmental devices such as a dust collector 44 such as an electrostatic precipitator that removes ash from the combustion gas and a desulfurization device 46 that removes sulfur oxides, as well as environmental devices for guiding the exhaust gas to these environmental devices. An induced draft fan (IDF) 45 is provided. The downstream end of the gas duct 41 is connected to a chimney 47, and the combustion gas treated by the environmental device is discharged outside the system as exhaust gas.

(Burner configuration)
Next, the configuration of the burner 21 will be explained with reference to FIGS. 2 and 3. As shown in these figures, the burner 21 includes a first nozzle 61 and a second nozzle 62. The first nozzle 61 has a cylindrical shape centered on the axis O direction. More specifically, the first nozzle 61 has a rectangular annular cross-sectional shape when viewed from the axis O direction. The axis O is, for example, an imaginary line extending in a substantially horizontal direction. An opening on one side of the first nozzle 61 in the direction of the axis O is a tip opening 63 . The region on the other side of the tip opening 63 in the axis O direction (that is, the area inside the tip opening 63) is a first flow path 64 through which a mixed fluid of primary air and pulverized coal flows.

The first flow path 64 is connected to the pulverized fuel supply pipe 22 described above. The mixed fluid that has flowed into the first flow path 64 is ejected into the furnace 11 through the tip opening 63. Thereafter, the mixed fluid is ignited by an ignition device (not shown), and a flame extending from the tip opening 63 toward the inside of the furnace 11 is formed. In the following description, the upstream side in the flow direction of the mixed fluid may be simply referred to as the "upstream side," and the opposite side may simply be referred to as the "downstream side."

An opening as a secondary air jet port 66 is formed in the end face (downstream end face 65 ) of the first nozzle 61 facing downstream. An area on the upstream side of the secondary air outlet 66 is a second flow path 68 through which secondary air flows. The secondary air outlet 66 has a rectangular ring shape centered on the axis O. This secondary air outlet 66 communicates with the above-mentioned wind box 23. The secondary air force-fed from the wind box 23 is ejected from the secondary air ejection port 66. By mixing the secondary air with the flame, the properties of the flame (flame temperature and flame length) are optimized.

The second nozzle 62 is provided within the first flow path 64 of the first nozzle 61 . The second nozzle 62 extends in the direction of the axis O. Further, the second nozzle 62 is arranged at a position overlapping the center of gravity (that is, on the axis O) of the rectangular tip opening 63 when viewed from the axis O direction. The upstream end of the second nozzle 62 is connected to the ammonia fuel supply pipe 51. As a result, gaseous ammonia as fuel is ejected from the second nozzle 62. Note that the configuration may be such that liquid ammonia is ejected from the second nozzle 62.

The downstream tip portion 67 of the second nozzle 62 is located upstream of the tip opening 63 of the first nozzle 61 in the axis O direction. That is, the tip 67 of the second nozzle 62 does not protrude from the tip opening 63 toward the furnace 11 side. Further, the tip portion 67 is arranged at a position that does not overlap the tip opening 63 in the direction of the axis O.

The cross-sectional shape of the second nozzle 62 is circular in the example of FIG. However, it is also possible to make the cross-sectional shape of the second nozzle 62 rectangular, polygonal, or elliptical.

(effect)
In the boiler 10, when the plurality of mills 31 are driven, pulverized and classified pulverized fuel is supplied to the burner 21 through the pulverized fuel supply pipe 22 together with primary air. Further, secondary air heated by the air preheater 42 is supplied to the burner 21 from the air passage 24 via the air box 23. The burner 21 blows into the furnace 11 a pulverized fuel mixture in which pulverized fuel and primary air are mixed, and also blows secondary air into the furnace 11 . The pulverized fuel mixture blown into the furnace 11 ignites and reacts with secondary air to form a flame. A flame is formed in the lower region within the furnace 11 and hot combustion gases rise within the furnace 11 and flow into the combustion gas passage 12 . Note that in this embodiment, air is used as the oxidizing gas (primary air, secondary air), but it may have a higher or lower oxygen content than air, and the oxygen content relative to the amount of fuel supplied may be By adjusting the ratio of amounts within an appropriate range, stable combustion is achieved in the furnace 11.

The combustion gas flowing 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 then is discharged into the flue 13. Nitrogen oxides are removed in a denitrification device 43, and after heat exchange with primary air and secondary air in an air preheater 42, they are further discharged to a gas duct 41, ash etc. are removed in a dust collector 44, and a desulfurization device 46 After the sulfur oxides are removed, they are 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 arranged in the above-described order with respect to the combustion gas flow.

Here, in the burner 21 according to the present embodiment, in addition to using the mixed fluid of pulverized coal and primary air ejected from the first nozzle 61 as fuel, ammonia ejected from the second nozzle 62 can be used as the fuel. It is considered possible. Conventionally, a plurality of burners for burning pulverized coal and a plurality of burners for burning ammonia have been provided independently.

However, since the total number of burners that can be installed in the furnace 11 is fixed, if burners that use ammonia as fuel are provided as described above, the number of burners that use pulverized coal as fuel will decrease. As a result, there is a problem that, for example, in a situation where ammonia cannot be obtained, the overall output of the burner is reduced accordingly. Therefore, the burner 21 according to the present embodiment includes a first nozzle 61 and a second nozzle 62 so that pulverized coal and ammonia can be used as fuel. Thereby, although ammonia can be used as fuel, when all the burners 21 are operated using only pulverized coal as fuel, it is possible to avoid a decrease in the total output of these burners 21.

Furthermore, according to the above configuration, the second nozzle 62 is located upstream of the tip opening 63 of the first nozzle 61. Thereby, it is possible to avoid a reduction in the cross-sectional area of the tip opening 63 due to the second nozzle 62. Therefore, when using pulverized coal as a fuel, if the primary air flow rate is the same, the ejection speed becomes faster, and it is possible to avoid unstable ignition. As a result, while it is possible to use ammonia as a fuel, when pulverized coal is used as a fuel, it is possible to avoid the second nozzle 62 interfering with the flow of the pulverized coal. Thereby, it is possible to suppress a decrease in the output of the burner 21 when using pulverized coal as fuel. In other words, the same flame temperature and flame length as in the case where the second nozzle 62 is not provided can be achieved.

Further, according to the above configuration, by supplying the secondary air ejected from the secondary air jet port 66 to the flame formed by the mixed fluid, it becomes possible to optimize the combustion efficiency and flame temperature. In particular, since the secondary air outlet 66 is formed so as to surround the tip opening 63, secondary air can be evenly supplied from around the flame. Thereby, the flame temperature distribution is made uniform, and it becomes possible to generate high-temperature combustion gas more stably.

Further, according to the above configuration, the second nozzle 62 is arranged at the center of gravity position (the position of the axis O) in the cross section of the first nozzle 61. As a result, when ammonia is used as a fuel, the flame formed by the ammonia is surrounded by the secondary air ejected from the secondary air outlet 66. As a result, even when ammonia is used as a fuel, the shape and temperature of the flame can be stabilized.

In addition, according to the above configuration, the pulverized fuel supply pipe 22 and the ammonia fuel supply pipe 51 are provided independently. Thereby, operation using only pulverized coal as fuel, operation using only ammonia as fuel, and operation using both as fuel can be performed smoothly. Furthermore, it is also possible to smoothly and immediately switch between these three operating states.

(Other embodiments)
Although the embodiment of the present disclosure has been described above in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and may include design changes without departing from the gist of the present disclosure. For example, in the embodiment described above, an example in which only one second nozzle 62 is provided has been described. However, as shown in FIGS. 4 and 5, the plurality of second nozzles 62 may be arranged in a grid along each side of the tip opening 63 and occupying the inside thereof.

According to the above configuration, since the plurality of second nozzles 62 are arranged in a grid pattern, the concentration distribution of ammonia in the tip opening 63 can be made more uniform. This makes it possible to form a flame more stably.

Furthermore, in the embodiments described above, 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 10 includes coal, biomass fuel, petroleum coke (PC) fuel, petroleum residue, and the like.
Note that the fuel for the boiler 10 is not limited to solid fuel, and petroleum such as heavy oil, light oil, and heavy oil, and liquid fuel such as factory waste liquid can also be used. Gaseous fuels such as natural gas, various petroleum gases, and by-product gases generated in steel manufacturing processes can also be used.
Furthermore, it can also be applied to a mixed combustion boiler that uses a combination of these various fuels.

<Additional notes>
The burner 21 and boiler 10 described in each embodiment are understood as follows, for example.

(1) The burner 21 according to the first aspect includes a first nozzle 61 having a cylindrical shape extending in the direction of the axis O and having a tip opening 63 capable of ejecting a mixed fluid of primary air and pulverized coal; A second nozzle 61 is disposed within the first nozzle 61 to extend in the direction of the axis O, is located upstream of the mixed fluid than the tip opening 63 of the first nozzle 61, and has a tip 67 capable of ejecting ammonia. A nozzle 62 is provided.

According to the above configuration, the second nozzle 62 is located upstream of the tip opening 63 of the first nozzle 61. Thereby, it is possible to avoid a reduction in the cross-sectional area of the tip opening 63 due to the second nozzle 62. Therefore, when using pulverized coal as a fuel, an increase in flow velocity is suppressed even with the same flow rate of primary air, and destabilization of ignition can be avoided.

(2) The burner 21 according to the second aspect is the burner 21 of (1), and is provided around the tip opening 63 of the first nozzle 61, has an annular shape, and is capable of ejecting secondary air. It further has a secondary air outlet 66.

According to the above configuration, by supplying secondary air to the flame formed by the mixed fluid, it is possible to optimize the combustion efficiency and flame temperature.

(3) The burner 21 according to the third aspect is the burner 21 of (1) or (2), in which the second nozzle 62 is arranged at the center of gravity in the cross section of the first nozzle 61.

According to the above configuration, since the second nozzle 62 is arranged at the center of gravity in the cross section of the first nozzle 61, the shape of the flame can be stabilized when ammonia is used as the fuel.

(4) The burner 21 according to the fourth aspect is the burner 21 according to any one of the aspects (1) to (3), in which the tip opening 63 of the first nozzle 61 is The second nozzles 62 have a rectangular shape, and a plurality of second nozzles 62 are arranged in a grid pattern along each side of the tip opening 63 at intervals.

According to the above configuration, since the plurality of second nozzles 62 are arranged in a grid pattern, the concentration distribution of ammonia in the tip opening 63 can be made uniform. This makes it possible to form a flame more stably.

(5) The burner 21 according to the fifth aspect is the burner 21 according to any one of the aspects (1) to (4), in which the first nozzle 61 extends from the mill 31 that can supply pulverized coal. The second nozzle 62 is connected to the pulverized fuel supply pipe 22 , and the second nozzle 62 is connected to an ammonia fuel supply pipe 51 that is provided separately from the pulverized fuel supply pipe 22 and is capable of supplying ammonia.

According to the above configuration, since the pulverized fuel supply pipe 22 and the ammonia fuel supply pipe 51 are provided independently, operation using only pulverized coal as fuel, operation using only ammonia as fuel, and operation using both as fuel are possible. Each fuel can be operated smoothly.

(6) The boiler 10 according to the sixth aspect includes the burner 21 according to any one of the aspects (1) to (5), and the furnace 11 in which the burner 21 is provided.

According to the above configuration, it is possible to provide a boiler 10 that can use ammonia as a fuel and does not reduce its output when only pulverized coal is used as a fuel.

10... Boiler 11... Furnace 12... Combustion gas passage 13... Flue 20... Combustion device 21... Burner 22... Pulverized fuel supply pipe 23... Wind box (air register)
24...Wind duct (air duct)
31...Mill (pulverizer)
32...Forced draft fan (FDF)
41... Gas duct 42... Air preheater 43... Denitrification device 44... Dust collector 45... Induced draft fan (IDF)
46...Desulfurizer 47...Chimney 51...Ammonia fuel supply pipe 52...Ammonia supply source 61...First nozzle 62...Second nozzle 63...Tip opening 64...First flow path 65...Downstream end surface 66...Secondary air jet port 67... Tip portion 68... Second flow path 101... Furnace wall 102... Superheater 102A... First superheater 102B... Second superheater 102C... Third superheater 103... Reheater 103A... First reheater 103B... Second reheater 104...Energy saver

Claims (6)

a first nozzle having a cylindrical shape extending in the axial direction and having a tip opening capable of ejecting a mixed fluid of primary air and pulverized coal;
a second nozzle that is arranged to extend in the axial direction within the first nozzle and has a tip portion that is located upstream of the mixed fluid than the tip opening of the first nozzle and is capable of ejecting ammonia;
A burner equipped with The burner according to claim 1, further comprising a secondary air ejection port provided around the tip opening of the first nozzle, which is annular and capable of ejecting secondary air. The burner according to claim 1 or 2, wherein the second nozzle is located at a center of gravity in a cross section of the first nozzle. The tip opening of the first nozzle has a rectangular shape when viewed from the axial direction, and a plurality of the second nozzles are arranged in a grid pattern at intervals along each side of the tip opening. The burner according to any one of 3 to 3. The first nozzle is connected to a pulverized fuel supply pipe extending from a mill capable of supplying pulverized coal, and the second nozzle is connected to an ammonia fuel supply pipe provided separately from the pulverized fuel supply pipe and capable of supplying ammonia. Burner according to any one of claims 1 to 4, which are connected. The burner according to any one of claims 1 to 5,
a furnace provided with the burner;
A boiler equipped with

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