TWI858471B - Burners and boilers - Google Patents

Abstract

The burner comprises: a first nozzle, which is cylindrical and extends in an axial direction and has a front end opening for ejecting a mixed fluid of primary air and pulverized coal; and a second nozzle, which is arranged in the first nozzle to extend in the axial direction and has a front end portion located on the upstream side of the mixed fluid than the front end opening of the first nozzle and can eject ammonia.

Description

Burners and boilers

The present invention relates to a burner and a boiler.

Large boilers such as power generation boilers have a hollow furnace arranged in the vertical direction, and a plurality of burners are arranged on the furnace wall along the circumference of the furnace. In addition, a large boiler is connected to a flue above the vertical direction of the furnace, and a heat exchanger for generating steam is arranged in the flue. Then, the burner sprays a mixed gas of fuel and air (oxidizing gas) into the furnace to form a flame, and the generated combustion gas flows into the flue. A heat exchanger is set in the area where the combustion gas flows, and the water or steam flowing in the heat transfer tube constituting the heat exchanger is heated to generate superheated steam.

In recent years, research and development of burners that use ammonia as fuel in addition to conventional fossil fuels has been progressing. As a specific example of a boiler that uses such a burner, the one described in the following patent document 1 is known. In this boiler, a plurality of burners that burn fossil fuels and burn ammonia are independently provided. [Prior art document] [Patent document]

[Patent Document 1] Japanese Patent Application Publication No. 2019-178823

[The problem the invention is trying to solve]

However, the total number of burners that can be installed in a boiler is limited, so when burners that use ammonia as fuel are installed as described above, the number of burners that use fossil fuels will decrease. As a result, if ammonia is not available, for example, there is a problem that the output of the entire burner will decrease by that amount.

The present invention is completed to solve the above-mentioned problem, and its purpose is to provide a burner and a boiler that can efficiently use ammonia and fossil fuels as fuels. [Technical means for solving the problem]

In order to solve the above-mentioned problem, the burner of the present invention comprises: a first nozzle, which is cylindrical and extends in the axial direction, and has a front end opening for spraying a mixed fluid of primary air and pulverized coal; and a second nozzle, which is arranged in the aforementioned first nozzle to extend along the aforementioned axial direction, has a front end portion located on the upstream side of the aforementioned mixed fluid than the front end opening of the aforementioned first nozzle and can spray ammonia.

The boiler of the present invention comprises the burner and a furnace equipped with the burner. [Effects of the invention]

According to the present invention, a burner and a boiler that can efficiently use ammonia and fossil fuel as fuel can be provided.

Hereinafter, one embodiment of the present invention will be described with reference to the drawings. Furthermore, the present invention is not limited to the embodiment, and when there are multiple embodiments, the invention also includes a structure combining the embodiments. In the following description, "up" or "above" indicates the upper side in the lead vertical direction, and "down" or "below" indicates the lower side in the lead vertical direction. This lead vertical direction is not strict and contains errors.

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

(Structure of boiler) The boiler 10 of this embodiment burns the fine powder fuel after crushing the solid fuel through a burner, and the heat generated by the combustion can be used to exchange heat with water or steam to generate superheated steam. Biomass fuel or coal, etc. are used as solid fuel.

The boiler 10 comprises a furnace 11, a combustion device 20, and a combustion gas passage 12. The furnace 11 is in the shape of a square tube and is arranged along the lead vertical direction. The furnace wall 101 constituting the inner wall surface of the furnace 11 is composed of a plurality of heat transfer tubes and connecting tube segments connecting the heat transfer tubes to each other, and the heat generated by the combustion of the pulverized fuel is exchanged with water or steam flowing inside the heat transfer tubes to recover the heat, and the temperature rise of the furnace wall 101 is suppressed.

The combustion device 20 is installed in the lower area of the furnace 11. In the present embodiment, the combustion device 20 has a plurality of burners 21A, 21B, 21C, 21D, 21E, and 21F (hereinafter collectively referred to as "burners 21") installed on the furnace wall 101. The burners 21 are arranged at equal intervals along the circumference of the furnace 11 (for example, four burners are arranged at each corner of the quadrilateral furnace 11) as a group, and a plurality of sections are arranged along the vertical direction. In FIG. 1, for the convenience of illustration, only two burners in a group are shown, and each group is marked with the symbols 21A, 21B, 21C, 21D, 21E, and 21F. The shape of the furnace, the number of burner stages, the number of burners per stage, the arrangement of the burners, etc. are not limited to this embodiment.

The burners 21A, 21B, 21C, 21D, 21E, and 21F are connected to a plurality of grinders (crushers) 31A, 31B, 31C, 31D, 31E, and 31F (hereinafter collectively referred to as "crushers 31") through a plurality of powder fuel supply pipes 22A, 22B, 22C, 22D, 22E, and 22F (hereinafter collectively referred to as "powder fuel supply pipes 22"). The grinder 31 is, for example, a vertical roller grinder that supports a grinding platform (not shown) internally so as to be rotatable and supports a plurality of grinding rollers (not shown) above the grinding platform so as to be rotatable in conjunction with the rotation of the grinding platform. The solid fuel crushed by the coordinated operation of the crushing roller and the crushing platform is transported to the classifier (not shown) provided in the grinder 31 by the primary air (transportation gas, oxidizing gas) supplied to the grinder 31. In the classifier, the fuel is classified into fine powder fuel with a particle size below that suitable for combustion in the burner 21 and agglomerate fuel with a particle size larger than the particle size. The fine powder fuel is supplied to the burner 21 through the fine powder fuel supply pipe 22 together with the primary air through the classifier. The agglomerate fuel that has not passed through the classifier falls onto the crushing platform due to its own weight inside the grinder 31 and is crushed again.

In addition, the burners 21A, 21B, 21C, 21D, 21E, and 21F are connected to an ammonia supply source 52 through an ammonia fuel supply pipe 51. The ammonia fuel supply pipe 51 is independent of the powder fuel supply pipe 22 and is provided separately. 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 in each ammonia fuel supply pipe 51. The detailed structure of the burner 21 will be described later.

A wind box (air regulator) 23 is provided outside the furnace 11 where the burner 21 is installed, and one end of an air duct (air passage) 24 is connected to the wind box 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 provided in the air duct 24 (details to be described later), and is supplied to the burner 21 as secondary air (combustion air, oxidizing gas) through the wind box 23, and then guided to the inside of the furnace 11.

The combustion gas passage 12 is connected to the upper part of the furnace 11 in the vertical direction. In the combustion gas passage 12, as heat exchangers for recovering the heat of the combustion gas, superheaters 102A, 102B, 102C (hereinafter, collectively referred to as "superheaters 102"), reheaters 103A, 103B (hereinafter, collectively referred to as "reheaters 103"), and an economizer 104 are provided, so that heat is exchanged between the combustion gas generated in the furnace 11 and the feed water or steam flowing inside each heat exchanger. In addition, the arrangement and shape of each heat exchanger are not limited to the form described in FIG. 1.

A flue 13 is connected to the downstream side of the combustion gas passage 12 to discharge the combustion gas that has been overheated in the heat exchanger. The flue 13 is provided with an air preheater (air heater) 42 between the flue 13 and the air duct 24, and heat is exchanged between the air flowing in the air duct 24 and the combustion gas flowing in the flue 13, thereby heating the primary air supplied to the grinder 31 or the secondary air supplied to the burner 21, thereby further recovering heat from the combustion gas after the heat exchange with water or steam.

Furthermore, 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 having the function of reducing nitrogen oxides such as ammonia and urea water to the combustion gas flowing in the flue 13, so that the reaction between nitrogen oxides (NOx) in the combustion gas supplied with the reducing agent and the reducing agent is promoted by the catalytic action of the denitrification catalyst provided in the denitrification device 43, thereby removing and reducing nitrogen oxides in the combustion gas. A gas channel 41 is connected to the flue 13 at a position downstream of the air preheater 42. In the gas passage 41, there is a dust collecting device 44 such as an electric dust collector for removing ash from the combustion gas, or an environmental device such as a desulfurization device 46 for removing sulfur oxides, or an induced draft fan (IDF: Induced Draft Fan) 45 for guiding the exhaust gas to such environmental devices. The downstream end of the gas passage 41 is connected to the chimney 47, and the combustion gas treated by the environmental device is discharged out of the system as exhaust gas.

(Structure of burner) Next, the structure of the burner 21 is explained with reference to FIG. 2 and FIG. 3. As shown in the figures, the burner 21 has a first nozzle 61 and a second nozzle 62. The first nozzle 61 is cylindrical with the axis O as the center. More specifically, the first nozzle 61 has a rectangular ring-shaped cross-sectional shape when viewed from the axis O direction. The axis O is, for example, a virtual line extending in a substantial horizontal direction. The opening of the first nozzle 61 on one side of the axis O direction is a front end opening 63. The area on the other side of the axis O direction than the front opening 63 (i.e., the area inside the front opening 63) is the first flow path 64 for the mixed fluid of primary air and pulverized coal to flow.

The first flow path 64 is connected to the powder fuel supply pipe 22. The mixed fluid flowing into the first flow path 64 is ejected into the furnace 11 through the front end opening 63. Thereafter, the mixed fluid is ignited by an ignition device (not shown) to form a flame extending from the front end opening 63 toward the furnace 11. In the following description, the upstream side of the flow direction of the mixed fluid will be referred to as the "upstream side", and the opposite side will be referred to as the "downstream side".

An opening serving as a secondary air ejection port 66 is formed on the downstream end face (downstream end face 65) of the first nozzle 61. The upstream region of the secondary air ejection port 66 is a second flow path 68 for the flow of secondary air. The secondary air ejection port 66 is in the shape of a rectangular ring centered on the axis O. The secondary air ejection port 66 is connected to the above-mentioned wind box 23. The secondary air pressed from the wind box 23 is ejected from the secondary air ejection port 66. The secondary air is mixed with the flame, thereby appropriately adjusting the properties of the flame (flame temperature or flame length).

The second nozzle 62 is provided in the first flow path 64 of the first nozzle 61. The second nozzle 62 extends in the direction of the axis O. When viewed from the direction of the axis O, the second nozzle 62 is arranged at a position overlapping with the center of gravity of the rectangular front end opening 63 (i.e., on the axis O). The upstream end of the second nozzle 62 is connected to the ammonia fuel supply pipe 51. Thus, gaseous ammonia as a fuel is ejected from the second nozzle 62. Alternatively, the second nozzle 62 may be configured to eject liquid ammonia.

The front end portion 67 on the downstream side of the second nozzle 62 is located upstream of the front end opening 63 of the first nozzle 61 in the axis O direction. In other words, the front end portion 67 of the second nozzle 62 does not protrude from the front end opening 63 toward the furnace 11. In addition, the front end portion 67 is arranged at a position that does not overlap with the front end opening 63 in the axis O direction.

The cross-sectional shape of the second nozzle 62 is circular in the example of Fig. 3. However, the cross-sectional shape of the second nozzle 62 may be rectangular, polygonal, or elliptical.

(Effect) In the boiler 10, if the plurality of grinders 31 are driven, the crushed and classified fine powder fuel is supplied to the burner 21 through the fine powder fuel supply pipe 22 together with the primary air. In addition, the secondary air heated by the air preheater 42 is supplied to the burner 21 from the air duct 24 through the wind box 23. The burner 21 blows the fine powder fuel mixed gas formed by mixing the fine powder fuel and the primary air into the furnace 11, and blows the secondary air into the furnace 11. The fine powder fuel mixed gas blown into the furnace 11 is ignited and reacts with the secondary air to form a flame. A flame is formed in the lower area of the furnace 11, causing the high-temperature combustion gas to rise in the furnace 11 and flow into the combustion gas passage 12. In this embodiment, air is used as the oxidizing gas (primary air, secondary air), but the oxygen ratio may be more or less than that of air, and the ratio of the oxygen amount to the supplied fuel amount is adjusted to an appropriate range, thereby achieving stable combustion in the furnace 11.

The combustion gas flowing into the combustion gas passage 12 exchanges heat with water or steam through the superheater 102, the reheater 103, and the economizer 104 disposed inside the combustion gas passage 12, and then is discharged to the flue 13, and then nitrogen oxides are removed through the denitrification device 43, and then heat is exchanged with the primary air and the secondary air through the air preheater 42, and then further discharged to the gas passage 41, and then ash and the like are removed through the dust collecting device 44, and sulfur oxides are removed through the desulfurization device 46, and then discharged to the outside of the system from the chimney 47. In addition, the arrangement of each heat exchanger in the combustion gas passage 12 and each device in the flue 13 to the gas passage 41 does not necessarily have to be arranged in the above-described order with respect to the flow of the combustion gas.

Here, the burner 21 of this embodiment can use ammonia ejected from the second nozzle 62 as fuel in addition to the mixed fluid of pulverized coal and primary air ejected from the first nozzle 61. Conventionally, a plurality of burners for burning pulverized coal and ammonia are independently provided.

However, the total number of burners that can be installed in the furnace 11 is limited, so when burners using ammonia as fuel are installed as described above, the number of burners using pulverized coal as fuel will decrease. As a result, for example, when ammonia is not available, there is a problem that the output of the entire burner will be reduced by that amount. Therefore, in the burner 21 of this embodiment, the first nozzle 61 and the second nozzle 62 are provided in a manner that pulverized coal and ammonia can be used in common as fuel. In this way, not only can ammonia be used as fuel, but also when all the burners 21 are operated using only pulverized coal as fuel, the total output of the burners 21 can be avoided from being reduced.

Furthermore, according to the above-mentioned structure, the second nozzle 62 is located on the upstream side of the front end opening 63 of the first nozzle 61. Thus, it is possible to avoid the situation where the cross-sectional area of the front end opening 63 is reduced due to the second nozzle 62. Therefore, when using pulverized coal as fuel, at the same flow rate of primary air flow, it is possible to avoid the situation where the jet speed becomes faster and the ignition becomes unstable. As a result, ammonia can be used as fuel, and when using pulverized coal as fuel, it is possible to avoid the situation where the second nozzle 62 hinders the flow of the pulverized coal. Thus, it is possible to suppress the reduction in the output of the burner 21 when using pulverized coal as fuel. In other words, the same flame temperature and flame length as those in the case where the second nozzle 62 is not provided can be achieved.

Furthermore, according to the above structure, the secondary air ejected from the secondary air ejection port 66 is supplied to the flame formed by the mixed fluid, thereby adjusting the combustion efficiency and the flame temperature. In particular, the secondary air ejection port 66 is formed so as to surround the front end opening 63, so that the secondary air can be completely supplied from the periphery of the flame. In this way, the flame temperature distribution is made uniform, and a high-temperature combustion gas can be generated more stably.

Furthermore, according to the above-mentioned structure, the second nozzle 62 is arranged at the center of gravity (the position of the axis O) of the cross section of the first nozzle 61. Thereby, when ammonia is used as a fuel, the secondary air ejected from the secondary air ejection port 66 surrounds the flame formed by the ammonia. As a result, the shape and temperature of the flame can be stabilized when ammonia is used as a fuel.

In addition, according to the above structure, the pulverized fuel supply pipe 22 and the ammonia fuel supply pipe 51 are independently provided. Thus, the operation using only pulverized coal as fuel, the operation using only ammonia as fuel, and the operation using both as fuel can be smoothly performed. Moreover, the three operation states can be smoothly and instantly switched.

(Other embodiments) The embodiments of the present invention are described in detail with reference to the drawings above, but the specific structure is not limited to the embodiments, and design changes that do not exceed the scope of the present invention are also included. For example, in the above embodiments, an example of only providing a second nozzle 62 is described. However, as shown in Figures 4 and 5, a plurality of second nozzles 62 may be arranged in a grid along the sides of the front end opening 63 and occupying the inner side thereof.

According to the above structure, the plurality of second nozzles 62 are arranged in a grid pattern, thereby making the concentration distribution of ammonia at the front end opening 63 more uniform. Thereby, the flame can be formed more stably.

Furthermore, in the above-mentioned embodiment, it is explained that the boiler of the present invention is a boiler that uses solid fuel as fuel. As solid fuel used in the boiler 10, coal, biomass fuel, petroleum coke (PC: Petroleum Coke) fuel, petroleum residue, etc. are used. In addition, as the fuel of the boiler 10, it is not limited to solid fuel, and petroleum such as heavy oil, light oil, heavy oil, etc. or liquid fuel such as factory waste liquid can also be used. Moreover, gas fuels such as natural gas or various petroleum gases, by-product gas generated by steelmaking processes, etc. can also be used. In addition, it can also be applied to a mixed combustion boiler that uses a combination of these various fuels.

[Note] The burner 21 and boiler 10 described in each embodiment are, for example, understood as follows.

(1) A burner 21 of the first embodiment comprises: a first nozzle 61 which is cylindrical and extends in the direction of an axis O and has a front end opening 63 for ejecting a mixed fluid of primary air and pulverized coal; and a second nozzle 62 which is arranged in the first nozzle 61 to extend in the direction of the axis O and has a front end portion 67 which is located on the upstream side of the mixed fluid than the front end opening 63 of the first nozzle 61 and can eject ammonia.

According to the above structure, the second nozzle 62 is located upstream of the front opening 63 of the first nozzle 61. This can avoid the situation where the cross-sectional area of the front opening 63 is reduced due to the second nozzle 62. Therefore, when using pulverized coal as fuel, the increase in the flow rate of primary air at the same flow rate can be suppressed, avoiding ignition instability.

(2) The burner 21 of the second embodiment is the burner 21 of (1), wherein it may further have a secondary air injection port 66 which is provided around the aforementioned front end opening 63 of the aforementioned first nozzle 61 and is annular and capable of injecting secondary air.

According to the above structure, secondary air is supplied to the flame formed by the mixed fluid, thereby adjusting the combustion efficiency and the flame temperature.

(3) The burner 21 of the third aspect is the burner 21 of (1) or (2), wherein the second nozzle 62 may be arranged at the center of gravity of the cross section of the first nozzle 61.

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

(4) A fourth embodiment of the burner 21 is a burner 21 of any one of the embodiments (1) to (3), wherein the front end opening 63 of the first nozzle 61 is rectangular when viewed from the direction of the axis O, and the second nozzle 62 may be arranged in a lattice shape with spaces between the sides of the front end opening 63.

According to the above structure, the plurality of second nozzles 62 are arranged in a grid pattern, thereby making the concentration distribution of ammonia at the front end opening 63 uniform. Thereby, the flame can be formed more stably.

(5) The burner 21 of the fifth embodiment is a burner 21 of any one of the embodiments (1) to (4), wherein the first nozzle 61 is connected to a pulverized fuel supply pipe 22 extending from a grinder 31 for supplying pulverized coal, and the second nozzle 62 is connected to an ammonia fuel supply pipe 51 which is separately provided from the pulverized fuel supply pipe 22 and for supplying ammonia.

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

(6) A sixth embodiment of the boiler 10 includes the burner 21 of any one of the embodiments (1) to (5) and a furnace 11 provided with the burner 21.

According to the above structure, a boiler 10 can be provided which can use ammonia as a fuel and does not reduce the output when only pulverized coal is used as a fuel. [Industrial Applicability]

According to the present invention, a burner and a boiler that can efficiently use ammonia and fossil fuel as fuel can be provided.

10: Boiler 11: Furnace 12: Combustion gas passage 13: Flue 20: Combustion device 21,21A,21B,21C,21D,21E,21F: Burner 22,22A,22B,22C,22D,22E,22F: Micro-powder fuel supply pipe 23: Bellows (air regulator) 24: Air duct (air duct) 31: Grinding mill (crusher) 32: Injection fan (FDF) 41: Gas duct 42: Air preheater 43: Denitrification device 44: Dust collector 45: Induction fan (IDF) 46: Desulfurization device 47: Chimney 51: Ammonia fuel supply pipe 52: Ammonia supply source 61: First nozzle 62: Second nozzle 63: Front opening 64: First flow path 65: Downstream side surface 66: Secondary air injection port 67: Front end 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: Economizer

[Fig. 1] A schematic diagram showing the structure of a boiler according to an embodiment of the present invention. [Fig. 2] A cross-sectional view showing the structure of a burner according to an embodiment of the present invention. [Fig. 3] A view showing the burner according to an embodiment of the present invention as viewed from the axial direction. [Fig. 4] A cross-sectional view showing a variation of the burner according to an embodiment of the present invention. [Fig. 5] A view showing a variation of the burner according to an embodiment of the present invention as viewed from the axial direction.

21: Burner

61: No. 1 nozzle

62: No. 2 nozzle

63: Front opening

64: Flow path 1

65: Downstream end face

66: Secondary air outlet

67: Front end

68: Second flow path

O: Axis

Claims (8)

A burner comprises: a first nozzle, which is cylindrical and extends in an axial direction, and has a front opening for ejecting a mixed fluid of primary air and coal powder; and a second nozzle, which is arranged in the first nozzle to extend along the axial direction, has a front end portion located upstream of the front opening of the first nozzle and can eject ammonia, and further has a secondary air ejection port, which is arranged around the front opening of the first nozzle, is annular and can eject secondary air, and the second nozzle is arranged at the center of gravity of the cross section of the first nozzle. The burner as described in claim 1, wherein the front end opening of the first nozzle is rectangular when viewed from the axis direction, and the second nozzles are arranged in a grid pattern with spaces between them along each side of the front end opening. The burner as described in claim 1, wherein the front end opening of the first nozzle is rectangular when viewed from the axis direction, and the second nozzles are arranged in a grid pattern with spaces between them along each side of the front end opening. The burner as described in claim 1, wherein the first nozzle is connected to a pulverized fuel supply pipe extending from a pulverizer for supplying pulverized coal, and the second nozzle is connected to an ammonia fuel supply pipe which is separately provided from the pulverized fuel supply pipe and can supply ammonia. The burner as described in claim 1, wherein the first nozzle is connected to a pulverized fuel supply pipe extending from a pulverizer for supplying pulverized coal, and the second nozzle is connected to an ammonia fuel supply pipe which is separately provided from the pulverized fuel supply pipe and can supply ammonia. The burner as described in claim 2, wherein the first nozzle is connected to a pulverized fuel supply pipe extending from a pulverizer for supplying pulverized coal, and the second nozzle is connected to an ammonia fuel supply pipe which is separately provided from the pulverized fuel supply pipe and can supply ammonia. The burner as described in claim 3, wherein the first nozzle is connected to a pulverized fuel supply pipe extending from a pulverizer for supplying pulverized coal, and the second nozzle is connected to an ammonia fuel supply pipe which is separately provided from the pulverized fuel supply pipe and can supply ammonia. A boiler comprising: a burner as described in any one of claims 1 to 7, and a furnace equipped with the burner.

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