TWI855471B - Burner, boiler equipped with the same, and burner operation method - Google Patents

Abstract

A burner is provided which can increase the mixed combustion rate of ammonia fuel when ammonia fuel and fine powder fuel are mixed and burned. The burner comprises: an inner cylinder nozzle (61) extending along a central axis (CL); an outer cylinder nozzle (62) extending along the central axis (CL) and arranged to cover the inner cylinder nozzle (61) and supply fine powder fuel and primary air into a furnace; a flame retainer (71) for fine powder fuel and maintaining the flame of the fine powder fuel supplied from the outer cylinder nozzle (62); and a concentrator (69) arranged inside the outer cylinder nozzle (62) and concentrating the fine powder fuel toward the flame retainer (71) for fine powder fuel and supplying the ammonia fuel to the inner cylinder nozzle (61).

Description

Burner, boiler equipped with the same, and burner operation method

The present invention, for example, relates to a burner, a boiler equipped with the same, and an operating method of the burner, which burns a fine powder fuel obtained by pulverizing a solid fuel and an ammonia fuel.

Large boilers such as power generation boilers have a hollow furnace that is set in the lead vertical direction, and a plurality of burners are arranged on the wall surface of the furnace. In addition, a large boiler is connected to a flue above the lead 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. The 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.

As a burner used in a boiler, there are studies on the method of burning a mixture of pulverized coal and ammonia fuel, or the method of burning pulverized coal exclusively and ammonia fuel exclusively (for example, Patent Document 1). [Prior Art Document] [Patent Document]

[Patent Document 1] Japanese Patent Application Publication No. 2020-41748

[The problem the invention is trying to solve]

However, although Patent Document 1 discloses that pulverized coal and ammonia fuel are coaxially mixed and burned, it does not examine the increase in the mixed combustion rate of ammonia fuel. For example, in the structure of Patent Document 1, if the mixed combustion rate of ammonia fuel is increased, there is a problem that the flammability of pulverized coal decreases and it cannot continue to be mixed and burned with ammonia fuel.

The present invention was completed in view of the above situation, and its purpose is to provide a burner that can increase the mixed combustion rate of ammonia fuel when mixing ammonia fuel and fine powder fuel for combustion, a boiler equipped with the burner, and an operating method of the burner. [Technical means for solving the problem]

A burner in one aspect of the present invention comprises: an inner cylinder nozzle extending along a central axis; an outer cylinder nozzle extending along the aforementioned central axis and arranged to cover the aforementioned inner cylinder nozzle, and supplying powdered fuel and primary air into a furnace; a flame retainer for powdered fuel, which retains the flame of the aforementioned powdered fuel supplied from the aforementioned outer cylinder nozzle; and a concentrator, which is arranged inside the aforementioned outer cylinder nozzle, concentrates the aforementioned powdered fuel toward the aforementioned flame retainer for powdered fuel, and supplies ammonia fuel to the aforementioned inner cylinder nozzle or the aforementioned outer cylinder nozzle.

The operating method of a burner in one aspect of the present invention comprises: an inner cylinder nozzle extending along the central axis; an outer cylinder nozzle extending along the aforementioned central axis and arranged to cover the aforementioned inner cylinder nozzle, supplying fine powder fuel and primary air into the furnace; a flame retainer for fine powder fuel, which retains the flame of the fine powder fuel supplied from the aforementioned outer cylinder nozzle; and a concentrator, which is arranged inside the aforementioned outer cylinder nozzle, concentrating the aforementioned fine powder fuel toward the aforementioned flame retainer for fine powder fuel. The operating method is to supply ammonia fuel to the aforementioned inner cylinder nozzle or the aforementioned outer cylinder nozzle. [Effect of the invention]

According to the burner of the present invention, the mixed combustion rate of ammonia fuel can be increased.

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.

[First embodiment] FIG1 shows a boiler 10 of this embodiment that uses pulverized fuel and/or ammonia (NH ₃ ) fuel as main fuel. The boiler 10 of this embodiment burns pulverized solid fuel and ammonia fuel by a burner, and the heat generated by the combustion is exchanged with feed water or steam to generate superheated steam. Biomass fuel or coal is 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 recovered by heat exchange with water or steam flowing inside the heat transfer tubes, 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 referred to as "burners 21" when the burners are not distinguished) installed on the furnace wall 101. The burners 21 are arranged at equal intervals along the furnace wall 101 in the circumferential direction (for example, in a manner of opposing combustion, the burners are arranged to face each other in the circumferential direction on the opposing furnace walls 101), and are arranged in a plurality of sections along the vertical direction. 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 those in 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 referred to as "crushers 31" when the grinders are not distinguished) through a plurality of powder fuel supply pipes 22A, 22B, 22C, 22D, 22E, and 22F, respectively (hereinafter referred to as "powder fuel supply pipes 22" when the powder fuel supply pipes are not distinguished). The grinder 31 is, for example, a vertical roller grinder that supports a grinding platform (not shown in the figure) internally so as to be driven and rotatable, and a plurality of grinding rollers (not shown in the figure) are supported above the grinding platform so as to be rotatable in conjunction with the rotation of the grinding platform. The solid fuel crushed by the cooperative 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.

A wind box (air regulator) 23 is provided outside the furnace 11 at the installation position of the burner 21, 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, and is supplied to the burner 21 as secondary air (combustion air, oxidizing gas) through the wind box 23, and then is injected into 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, there are provided: superheaters 102A, 102B, 102C (hereinafter referred to as "superheaters 102" when the superheaters are not distinguished), reheaters 103A, 103B (hereinafter referred to as "reheaters 103" when the reheaters are not distinguished), and economizer 104, 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 Figure 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 and the like 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 a chimney 47, and the combustion gas treated by the environmental device is discharged out of the system as exhaust gas.

In the case of mixed combustion of fine powder fuel and ammonia fuel in the boiler 10, if the plurality of grinders 31 are driven, the fine powder fuel that has been crushed and classified 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 air 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 air 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, and the high-temperature combustion gas rises in the furnace 11 and flows into the combustion gas passage 12. In the present embodiment, air is used as the oxidizing gas (primary air, secondary air), but a gas having a higher or lower oxygen ratio than air may be used, and the ratio of the amount of oxygen to the amount of fuel supplied is adjusted to an appropriate range, thereby achieving stable combustion in the furnace 11.

Furthermore, a plurality of additional air ports (AA ports) 25 for supplying additional air (AA: Additional Air) for combustion into the furnace 11 are provided above the installation position of the burner 21 of the furnace 11. The additional air ports 25 are connected to the ends of the additional air passages (AA passages) 26 branched from the air duct 24, and a part of the air supplied from the blower 32 is supplied to the additional air ports 25 through the additional air passages 26 as additional air for combustion.

In the region A (region corresponding to the installation range of the wind box 23 in the height direction) inside the furnace 11 shown in Fig. 1, a flame is formed by the combustion of the mixed air of the primary air and the pulverized fuel and the secondary air. Here, the air ratio of the region A is set to be 1 or less, specifically, the air amount (the total amount of the primary air and the secondary air) supplied to the burner 21 is set to be less than the theoretical air amount of the fuel amount supplied to the burner 21, so that the region A and the region B (the region from the uppermost part of the burner 21 to the lowermost part of the additional air port 25) inside the furnace 11 become a reducing environment, and the nitrogen oxides (NOx) generated by the combustion are reduced inside the furnace 11. Afterwards, zone C (the zone above the lowest part of the additional air port 25) supplies additional air for combustion from the additional air port 25 to the combustion gas after NOx reduction to complete the combustion, but the reduction effect of zones A and B reduces the amount of NOx generated.

The combustion gas flowing into the combustion gas passage 12 exchanges heat with water or steam through the superheater 102, reheater 103, and economizer 104 disposed inside the combustion gas passage 12, and is then discharged to the flue 13, and nitrogen oxides are removed through the denitrification device 43, and heat is exchanged with primary air and secondary air through the air preheater 42, and is further discharged to the gas passage 41, and 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.

The boiler 10 is provided with an ammonia supply source 50. Ammonia is stored in a gaseous or liquid state as an ammonia fuel in the ammonia supply source 50. The ammonia fuel is supplied from the ammonia supply source 50 to each burner 21. When the burner 21 uses ammonia gas, the ammonia fuel is stored as a gas in the ammonia supply source 50, or is stored as liquid ammonia and vaporized on the way to the burner 21. When the burner 21 uses liquid ammonia, it is preferable to store liquid ammonia in the ammonia supply source 50.

The switching between the micro powder fuel and the ammonia fuel can be performed manually by the operator or by the command of the control unit. The control unit is composed of, for example, a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), and a storage medium readable by a computer. Then, a series of processes used to realize various functions are stored in the form of a program in a storage medium, etc., and the CPU reads the program into the RAM, etc., and performs information processing and calculation processing to realize various functions. In addition, the program can also be applied to: the form of being pre-installed in ROM or other storage media, the form of being provided in a state of being stored in a storage medium readable by a computer, and the form of being transmitted through wired or wireless communication means, etc. Computer-readable storage media refers to magnetic disks, magneto-optical disks, CD-ROMs, DVD-ROMs, semiconductor memories, etc.

FIG2 shows a burner 21. The burner 21 can perform mixed combustion of fine powder fuel and ammonia (ammonia fuel). The burner 21 has an inner cylinder nozzle 61 extending along the center axis CL and an outer cylinder nozzle 62 arranged to cover the inner cylinder nozzle 61. An oil nozzle 63 is provided on the inner peripheral side of the inner cylinder nozzle 61. Each nozzle 61, 62, 63 has a common center axis CL, and has a circular cross-section, for example, and is made of metal.

The inner cylinder nozzle 61 is supplied with ammonia gas and air (combustion air), and the mixed gas thereof is ejected into the furnace 11. Ammonia gas is supplied from the ammonia supply source 50 of FIG.

An ammonia flame retainer 67 is provided at the front end of the inner cylinder nozzle 61 between the inner cylinder nozzle 63 and the oil nozzle 63. The ammonia flame retainer 67 is, for example, fan-shaped and imparts rotation about the central axis CL to the mixed gas of ammonia and air. The ammonia flame retainer 67 maintains the flame of the ammonia gas ejected from the inner cylinder nozzle 61.

The outer tube nozzle 62 is supplied with the fine powder fuel and primary air guided from the grinder 31 (see FIG. 1 ). The outer tube nozzle 62 is provided with a limiting reduction portion 68 and a concentrator 69 .

The constriction portion 68 is provided on the inner wall of the outer cylinder nozzle 62 in the circumferential direction, and is convex toward the inner circumference (center axis CL side) to constrict the flow path in the outer cylinder nozzle 62. For example, it includes an upstream side inclined portion 68a located on the upstream side and inclined toward the inner circumference, and a downstream side inclined portion 68b connected to the top of the upstream side inclined portion 68a and inclined toward the outer circumference toward the downstream side. The constriction portion 68 is used to impart a velocity component toward the center axis CL to the flow.

The concentrator 69 is located on the downstream side of the restricting portion 68, and is fixedly extended in the circumferential direction on the outer wall of the oil nozzle 63, and has a shape that bulges toward the outer circumference. For example, it has an upstream side inclined portion 69a located on the upstream side and inclined toward the inner circumference, a cylindrical portion 69c connected to the vertex of the upstream side inclined portion 68a and extending parallel to the central axis CL, and a downstream side inclined portion 69b connected to the downstream end of the cylindrical portion 69c and inclined toward the outer circumference toward the downstream side.

The concentrator 69 expands the flow path narrowed by the constriction 68, thereby imparting a velocity component in the direction (radius direction) toward the outer tube nozzle 62. The inertial force of the micro-powder fuel is greater than that of the primary air, so it is concentrated on the inner wall side of the outer tube nozzle 62 by the constriction 68 and the concentrator 69, forming a high concentration area of micro-powder fuel.

A flame retainer 71 for fine powder fuel serving as a baffle is provided at the front end and the outer peripheral side of the outer cylinder nozzle 62. The flame retainer 71 for fine powder fuel is in a ring shape when the outer cylinder nozzle 62 is viewed from the front. The flame retainer 71 for fine powder fuel partially blocks the flow of the secondary air flowing in the secondary air flow path 73, and forms a flame retaining area on the downstream side thereof. In this way, the flame of the fine powder fuel supplied from the outer cylinder nozzle 62 is retained.

The oil nozzle 63 is supplied with oil fuel from an oil fuel supply source (not shown). The oil fuel is used when the burner 21 is started. After the start, the supply of the oil fuel is stopped and a small amount of cooling air is supplied.

The secondary air flow path 73 is provided so as to cover the outer cylinder nozzle 62. A tertiary air flow path 74 is provided on the outer peripheral side of the secondary air flow path 73 so as to cover the secondary air flow path 73. In the tertiary air flow path 74, a rotator 74a for imparting rotation to the tertiary air is provided.

Next, the operation of the burner 21 of the above structure is explained. First, the burner 21 is started by supplying oil fuel from the oil nozzle 63. The oil fuel sprayed from the oil nozzle 63 into the furnace 11 forms a flame together with the air supplied from the inner cylinder nozzle 61, which heats up the furnace 11. The flame of the oil fuel is maintained by the ammonia flame retainer 67. That is, the ammonia flame retainer 67 is also used to maintain the flame of the oil fuel during startup.

Then, when the furnace 11 is heated to a predetermined temperature and the startup is terminated, the supply of the oil fuel is stopped. When the supply of the oil fuel is stopped, a small amount of air flows from the oil nozzle 63 for cooling the oil nozzle 63.

After a predetermined time has passed since the start of the burner, the supply of the fine powder fuel and ammonia gas is performed as follows.

The powder fuel is slowly supplied from the outer cylinder nozzle 62 together with the primary air, and a flame caused by the powder fuel is formed. The powder fuel forms a high concentration area on the inner wall side of the outer cylinder nozzle 62 by the restrictor 68 and the concentrator 69. The flame of the powder fuel is maintained by the powder fuel flame retainer 71 provided in the outer cylinder nozzle 62, and is burned in stages by the secondary air supplied from the secondary air flow path 73 and the tertiary air supplied from the tertiary air flow path 74.

Ammonia is slowly supplied from an ammonia supply source 50 (see FIG. 1 ) to the inner cylinder nozzle 61 together with air, and is guided to the ammonia flame retainer 67 in a pre-mixed state. The pre-mixed gas given a rotation by the ammonia flame retainer 67 moves straight along the central axis CL to form a pre-mixed flame of ammonia. In this way, the flame of ammonia is maintained by the ammonia flame retainer 67 and mixed and burned with the fine powder fuel supplied from the outer cylinder nozzle 62.

The effects of the present embodiment described above are as follows. The fine powder fuel is concentrated toward the inner wall of the fine powder fuel flame retainer 71 by the concentrator 69 provided inside the outer cylinder nozzle 62. Thus, the flame retaining effect of the fine powder fuel flame retainer 71 is made more stable. Furthermore, ammonia is supplied to the inner cylinder nozzle 61, thereby supplying ammonia to the vicinity of the flame of the fine powder fuel after flame retaining is enhanced by the concentrator 69 and the fine powder fuel flame retainer 71, more specifically, to the inner side, thereby stabilizing the combustion of ammonia and increasing the mixed combustion rate of ammonia fuel. For example, the mixed combustion rate of ammonia fuel can be increased to more than 50% when a single burner burns multiple fuels at the same time.

Ammonia and air are supplied to the inner cylinder nozzle 61 for premixed combustion, thereby stabilizing the flame. In addition, the flame of ammonia is further stabilized by the ammonia flame protector 67 provided at the front end of the inner cylinder nozzle 61. This increases the mixed combustion rate of ammonia fuel.

Furthermore, in the present embodiment, a control valve (not shown) is provided for controlling the air flow rate supplied to the inner cylinder nozzle 61, and the opening of the control valve may be controlled by the control unit. At this time, the control unit obtains ammonia, air, pulverized fuel and primary air flow rates from a sensor (not shown) and calculates the mixed combustion rate (current value) of ammonia fuel. Then, the control unit adjusts the opening of the control valve to reduce the air flow rate in response to the increase in the mixed combustion rate of ammonia fuel. By performing control in this way, even if the mixed combustion rate of ammonia fuel increases and there is a risk that the flame of the pulverized fuel will be difficult to maintain, the air flow rate can be reduced in response to the increase in ammonia fuel, thereby reducing the flow rate of the premixed fuel flowing out of the inner cylinder nozzle 61. In this way, the ignition hindrance of the fine powder fuel can be avoided as much as possible and the flame of the fine powder fuel can be maintained, which can increase the mixed combustion rate of the ammonia fuel.

[Second embodiment] Next, the second embodiment of the present invention is described using FIG. 3A and FIG. 3B. In this embodiment, in addition to omitting the oil nozzle 63 of the first embodiment, the ammonia gas ejection position is also different. In the following description, the same symbols are attached to the same structures as the first embodiment and their descriptions are omitted, and the description is mainly for the different structures.

As shown in FIG3A, the burner 21 of this embodiment is provided with an inner cylinder nozzle 61 at a position closest to the center axis CL. Therefore, the oil nozzle 63 of the first embodiment is not provided inside the inner cylinder nozzle 61. The end of the inner cylinder nozzle 61 on the furnace 11 side (the right end in FIG3A) is closed, and ammonia does not spray out from there. Ammonia is supplied to the inner cylinder nozzle 61 from the ammonia supply source 50 shown in FIG1. However, unlike the first embodiment, only ammonia is supplied to the inner cylinder nozzle 61, and air is not supplied.

As shown in FIG3B , a plurality of slits (ammonia gas ejection holes) 80 are formed in the concentrator 69. The slits 80 form the longitudinal flow path radially in the radial direction. In the present embodiment, there are four slits 80, but the number is not particularly limited, and may be two or more or three or more. Each slit 80 is connected to the inner tube nozzle 61 for ammonia gas to flow. Each slit 80, as shown in FIG3A , is formed in the downstream side inclined portion 68b of the concentrator 69, and as shown by the arrow, ammonia gas is ejected in the direction along the center axis CL. Ammonia gas is ejected into the outer tube nozzle 62 through the slit 80. The air used for combustion of ammonia is the primary air flowing in the outer tube nozzle 62.

According to this embodiment, the following effects are achieved. Ammonia gas is ejected from each slit 80 formed in the concentrator 69 into the outer tube nozzle 62, so that flames can be formed together with the fine powder fuel, and the mixed combustion rate of ammonia fuel can be increased.

Ammonia is ejected from the slit 80 along the central axis CL and is not diffused in the radial direction as much as possible, so that the mixing with the fine powder fuel concentrated by the concentrator 69 toward the inner wall side of the outer tube nozzle 62 is delayed, which can reduce NOx.

In the present embodiment, ammonia gas is ejected from the slit 80 along the central axis CL, but it may be changed as shown in Figs. 4A and 4B. Specifically, the ejection direction of ammonia gas is changed. The slit 80' is formed so that ammonia gas is ejected toward the outer peripheral side (radius direction) inclined with respect to the central axis CL as shown by the arrows in Figs. 4A and 4B.

The ammonia is made to be inclined from the slit 80' with respect to the central axis CL and sprayed toward the outer peripheral side, whereby the ammonia diffuses on the inner wall side of the outer tube nozzle 62 and mixes with the fine powder fuel concentrated on the inner wall side of the outer tube nozzle 62 by the concentrator 69, thereby promoting combustion.

[Third embodiment] Next, the third embodiment of the present invention will be described using FIG. 5. This embodiment differs from the second embodiment in that a distributor 82 is added. The other structures are the same, so the same symbols are attached and the description is omitted.

As shown in FIG5 , an annular distributor 82 is provided inside the front end of the outer tube nozzle 62. The distributor 82 is provided to surround the downstream end of the downstream inclined portion 69b of the concentrator 69. The distributor 82 divides the flow path inside the outer tube nozzle 62 into an inner flow path 62a and an outer flow path 62b.

The inner flow path 62a and the outer flow path 62b of the outer tube nozzle 62 are separated by the concentrator 69 to form the inner flow path 62a where the primary air mainly flows and the outer flow path 62b where the concentrated fine powder fuel mainly flows. In this way, the primary air flowing in the inner flow path 62a can be used for the combustion of ammonia, and the ignition of the fine powder fuel can be promoted by the concentrated fine powder fuel flowing in the outer flow path 62b.

In the present embodiment, as shown in Fig. 5, the ammonia gas is ejected in a direction inclined with respect to the central axis CL and ejected toward the outer peripheral side as shown in Fig. 4A, but the present invention is not limited thereto. For example, as shown in Fig. 3A, the ammonia gas may be ejected from the slit 80 along the central axis CL.

[Fourth embodiment] Next, the fourth embodiment of the present invention will be described using FIGS. 6A to 6C. In the second embodiment, the ammonia gas is blown out from the inner peripheral side of the outer cylinder nozzle 62, but this embodiment is different in that the ammonia gas is blown out from the inner wall side of the outer cylinder nozzle 62. In the following description, the same symbols are attached to the same structures as the second embodiment and their descriptions are omitted, and the description is mainly for the different structures.

As shown in Fig. 6A, ammonia gas is not supplied from the inner cylinder nozzle 61. The inner cylinder nozzle 61 basically flows a small amount of cooling air, but is used as an oil nozzle at the time of startup if necessary.

A plurality of circumferential concentrators 85 are provided on the inner wall of the outer cylinder nozzle 62. Each circumferential concentrator 85 is located on the outer circumferential side of the downstream inclined portion 69b of the concentrator 69.

As shown in Fig. 6B, each circumferential concentrator 85 is provided at predetermined intervals along the circumferential direction of the inner wall of the outer cylinder nozzle 62. The fine powder fuel concentrated by the concentrator 69 is confined between adjacent circumferential concentrators 85 to flow.

FIG6C shows two circumferential concentrators 85 as an example. In the same figure, the upper side shows the outer peripheral side of the outer cylinder nozzle 62, and the lower side shows the inner peripheral side of the outer cylinder nozzle 62. As shown in FIG6C, an ammonia gas ejection hole 85a for ejecting ammonia gas is provided at the front end (downstream end) of the circumferential concentrator 85. The circumferential concentrator 85 is connected to an ammonia gas supply pipe 87 (refer to FIG6A and FIG6B) through a tubular mounting portion 85b. Ammonia gas is supplied to the circumferential concentrator 85 from an ammonia supply source 50 (refer to FIG1) through the ammonia gas supply pipe 87.

As shown in FIG. 6C , the circumferential concentrator 85 is in a rhombus shape when viewed from the inner circumference of the outer cylinder nozzle 62, gradually widening from the upstream end 85c and gradually narrowing from the middle position 85d to the downstream end 85e. A plurality of ammonia gas ejection holes 85a are formed on the downstream side surface 85f from the middle position 85d to the downstream end 85e. In addition, the inner circumferential side surface of the circumferential concentrator 85, i.e., the bottom surface 85g, is closed.

According to this embodiment, the following effects are exerted. The concentrator 69 is arranged on the outer wall of the inner tube nozzle 61, thereby concentrating the fine powder fuel toward the inner wall side of the outer tube nozzle 62. Then, on the inner wall of the front end of the outer tube nozzle 62, a plurality of circumferential concentrators 85 are arranged at predetermined intervals in the circumferential direction, thereby partially reducing the width of the flow path in the circumferential direction and concentrating the fine powder fuel in the circumferential direction. Then, ammonia is ejected from the ammonia ejection hole 85a arranged in the circumferential concentrator 85, thereby mixing with the fine powder fuel concentrated in the circumferential direction to promote combustion.

[Fifth Implementation] Next, the fifth implementation of the present invention will be described using FIG. 7A and FIG. 7B. In the first implementation, ammonia gas is used, but this implementation is different in that liquid ammonia is used. In the following description, the same symbols are attached to the same structures as the first implementation, and their descriptions are omitted, and the description is mainly for the different structures.

As shown in FIG7A, a liquid ammonia supply pipe 90 for spraying liquid ammonia is provided in the inner cylinder nozzle 61. The liquid ammonia supply pipe 90 is provided in plurality at predetermined intervals around the central axis CL. Liquid ammonia is supplied to the liquid ammonia supply pipe 90 from the ammonia supply source 50 (see FIG1). Air is supplied to the inner cylinder nozzle 61.

A liquid ammonia injection nozzle 92 is provided in the liquid ammonia supply pipe 90 as shown in FIG. 7B . A liquid ammonia flow path is formed in the liquid ammonia injection nozzle 92 as shown in FIG. 7B , and atomized liquid ammonia fuel is injected into the inner cylinder nozzle 61 from a plurality of injection holes 92a. Liquid ammonia is injected by pressure spraying through the liquid ammonia injection nozzle 92. Liquid ammonia is injected from the liquid ammonia injection nozzle 92 of the liquid ammonia supply pipe 90 to the upstream side of the ammonia flame protector 67.

[Sixth embodiment] Next, the sixth embodiment of the present invention will be described using FIG8. In the fifth embodiment, a form of supplying liquid ammonia is shown, but as a burner for burning liquid ammonia, liquid ammonia can also be supplied to an oil nozzle 63 that sprays oil fuel, which is also liquid. In this case, if a large amount of liquid ammonia is supplied to the furnace 11 from the center axis CL side of the burner 21, the temperature near the outlet of the burner 21 will drop due to the heat of vaporization, and it is considered that ignition will be difficult. Therefore, in addition to the ammonia supplied from the oil nozzle 63, it is better to supply the necessary amount of ammonia from the outer peripheral side of the oil nozzle 63, that is, from the ammonia supply pipe 95 provided in the tertiary air flow path 74.

The ammonia supply pipe 95 is a cylindrical member, and is disposed in the tertiary air flow path 74 at appropriate intervals in the circumferential direction. However, the shape and number of the ammonia supply pipe 95 are not limited as long as the fuel can be stably ignited and burned. Furthermore, the ammonia supplied to the ammonia supply pipe 95 may be liquid or gas.

According to this embodiment, the following effects are exerted. Liquid ammonia is sprayed on the upstream side of the ammonia flame retardant 67 provided at the front end of the inner cylinder nozzle 61. As a result, liquid ammonia is mixed with the air supplied to the inner cylinder nozzle 61 on the upstream side of the ammonia flame retardant 67, and liquid ammonia is vaporized as much as possible in the ammonia flame retardant 67, and the flame retardant effect of the ammonia flame retardant 67 is more stable. As a result, the mixed combustion rate of ammonia fuel can be increased.

In the above-mentioned embodiments, the boiler of the present invention is described as a boiler using solid fuel as fuel. As the solid fuel used in the boiler, coal, biomass fuel, petroleum coke (PC: Petroleum Coke) fuel, petroleum residue, etc. are used.

The burner, the boiler equipped with the same, and the operating method of the burner described in each embodiment described above can be grasped as follows, for example.

A burner (21) according to one aspect of the present invention comprises: an inner cylinder nozzle (61) extending along a central axis (CL); an outer cylinder nozzle (62) extending along the aforementioned central axis and arranged to cover the aforementioned inner cylinder nozzle and supply powdered fuel and primary air into a furnace; a flame retainer (71) for powdered fuel and maintaining the flame of the aforementioned powdered fuel supplied from the aforementioned outer cylinder nozzle; and a concentrator (69) arranged inside the aforementioned outer cylinder nozzle and concentrating the aforementioned powdered fuel toward the aforementioned flame retainer for powdered fuel and supplying ammonia fuel to the aforementioned inner cylinder nozzle or the aforementioned outer cylinder nozzle.

The fine powder fuel is concentrated toward the fine powder fuel flame retainer by the concentrator provided inside the outer cylinder nozzle. Thus, the flame retaining effect of the fine powder fuel flame retainer is stabilized. Furthermore, the ammonia fuel is supplied to the inner cylinder nozzle or the outer cylinder nozzle, thereby supplying the ammonia fuel to the vicinity of the flame of the fine powder fuel after flame retaining is enhanced by the concentrator and the fine powder fuel flame retainer, thereby increasing the mixed combustion rate of the ammonia fuel.

In one aspect of the burner of the present invention, ammonia is used as the aforementioned ammonia fuel, ammonia and air are supplied to the aforementioned inner cylinder nozzle, and an ammonia flame retainer (67) is provided at the front end of the aforementioned inner cylinder nozzle, which is used to maintain the flame of the aforementioned ammonia supplied from the aforementioned inner cylinder nozzle.

Ammonia and air are supplied to the inner cylinder nozzle for premixed combustion, thereby stabilizing the flame. In addition, the ammonia flame protector installed at the front end of the inner cylinder nozzle makes the ammonia flame more stable. This can increase the mixed combustion rate of ammonia fuel.

In one aspect of the present invention, the burner comprises: a control valve for controlling the flow rate of air supplied to the inner tube nozzle, and a control unit for controlling the control valve. The control unit controls the control valve to reduce the flow rate of the air in response to an increase in the mixed combustion rate of the ammonia fuel.

If the mixed combustion rate of ammonia fuel increases, it may be difficult to maintain the flame of the fine powder fuel. Therefore, the air flow rate is reduced in response to the increase of ammonia fuel, thereby reducing the flow rate of the premixed fuel flowing out of the inner cylinder nozzle. In this way, the ignition hindrance of the fine powder fuel can be avoided as much as possible, the flame of the fine powder fuel can be maintained, and the mixed combustion rate of ammonia fuel can be increased.

In one aspect of the burner of the present invention, ammonia is used as the aforementioned ammonia fuel, ammonia is supplied to the aforementioned inner tube nozzle, the aforementioned concentrator is arranged on the outer wall of the aforementioned inner tube nozzle, and the aforementioned concentrator is provided with an ammonia ejection hole (80, 80') for ejecting the aforementioned ammonia guided out of the aforementioned inner tube nozzle into the aforementioned outer tube nozzle.

The concentrator is arranged on the outer wall of the inner tube nozzle, so that the fine powder fuel can be concentrated toward the inner wall of the outer tube nozzle. Ammonia is ejected from the ammonia ejection hole formed in the concentrator into the outer tube nozzle, so that flames can be formed together with the fine powder fuel, which can increase the mixed combustion rate of ammonia fuel.

In the burner according to one aspect of the present invention, the ammonia gas ejection hole is formed in a direction so that the ammonia gas is ejected along the central axis.

Ammonia is ejected from the ammonia ejection hole along the central axis, whereby the mixing with the micronized fuel that has been concentrated by the concentrator toward the inner wall side of the outer tube nozzle is delayed, thereby reducing NOx.

In the burner according to one aspect of the present invention, the ammonia gas ejection hole is formed in a direction in which the ammonia gas is ejected toward the outer peripheral side while being inclined with respect to the central axis.

Ammonia is sprayed out from the ammonia spray hole at an angle to the central axis and toward the periphery, whereby the ammonia diffuses on the inner wall of the outer tube nozzle and mixes with the fine powder fuel that has been concentrated by the concentrator toward the inner wall of the outer tube nozzle, thereby promoting combustion.

In a burner according to one aspect of the present invention, a distributor (82) is provided at the front end of the outer tube nozzle to separate the burner into an inner flow path and an outer flow path.

A distributor is provided at the front end of the outer tube nozzle to separate the inner flow path and the outer flow path of the outer tube nozzle, thereby forming an inner flow path where primary air mainly flows and an outer flow path where concentrated micro-powder fuel mainly flows. In this way, the primary air flowing in the inner flow path can be used for the combustion of ammonia, and the concentrated micro-powder fuel flowing in the outer flow path can be used to promote the ignition of the micro-powder fuel.

In one aspect of the burner of the present invention, ammonia is used as the aforementioned ammonia fuel. The aforementioned concentrator is arranged on the outer wall of the aforementioned inner tube nozzle. On the inner wall at the front end of the aforementioned outer tube nozzle, a plurality of circumferential concentrators (85) are arranged at predetermined intervals in the circumferential direction. Ammonia ejection holes (85a) for ejecting the aforementioned ammonia are formed in the aforementioned circumferential concentrators.

A concentrator is arranged on the outer wall of the inner tube nozzle, thereby concentrating the fine powder fuel toward the inner wall of the outer tube nozzle. Then, a plurality of circumferential direction concentrators are arranged at predetermined intervals in the circumferential direction on the inner wall at the front end of the outer tube nozzle, thereby partially reducing the width of the flow path in the circumferential direction and concentrating the fine powder fuel in the circumferential direction. Then, ammonia is ejected from the ammonia ejection holes arranged in the circumferential direction concentrators, thereby mixing with the fine powder fuel concentrated in the circumferential direction to promote combustion.

In one aspect of the burner of the present invention, liquid ammonia is used as the aforementioned ammonia fuel, air is supplied to the aforementioned inner cylinder nozzle, and an ammonia flame retainer (67) is provided at the front end of the aforementioned inner cylinder nozzle, which is used to maintain the flame of the ammonia supplied from the aforementioned inner cylinder nozzle. Inside the aforementioned inner cylinder nozzle, a liquid ammonia supply pipe (90) is provided, which sprays the aforementioned liquid ammonia on the upstream side of the aforementioned ammonia flame retainer.

Liquid ammonia is sprayed on the upstream side of the ammonia flame protector located at the front end of the inner cylinder nozzle. This will mix with the air supplied to the inner cylinder nozzle on the upstream side of the ammonia flame protector, and the liquid ammonia will be vaporized as much as possible in the flame protector, making the flame protection effect of the ammonia flame protector more stable. This can increase the mixed combustion rate of ammonia fuel.

In the burner of one aspect of the present invention, liquid ammonia fuel is supplied from the inner tube nozzle, and ammonia is sprayed from the ammonia supply pipe provided on the outer peripheral side of the outer tube nozzle.

Liquid ammonia is supplied from the inner tube nozzle, and ammonia is ejected from the ammonia supply pipe provided on the outer peripheral side of the outer tube nozzle, thereby increasing the mixed combustion rate of ammonia. Also, liquid ammonia is supplied from the inner tube nozzle, thereby lowering the temperature near the outlet of the burner by the heat of vaporization, which may make ignition difficult. However, by reducing the amount of liquid ammonia supplied from the inner tube nozzle by an amount equivalent to the amount of ammonia supplied from the ammonia supply pipe, ignition can be performed appropriately. Furthermore, the ammonia supplied from the ammonia supply pipe may be liquid or gaseous.

A boiler (10) according to one aspect of the present invention is provided with any one of the above-mentioned burners.

The operating method of a burner in one aspect of the present invention comprises: an inner cylinder nozzle extending along a central axis; an outer cylinder nozzle extending along the aforementioned central axis and arranged to cover the aforementioned inner cylinder nozzle, and supplying powdered fuel and primary air into a furnace; a flame retainer for powdered fuel, and maintaining the flame of the aforementioned powdered fuel supplied from the aforementioned outer cylinder nozzle; and a concentrator, which is arranged inside the aforementioned outer cylinder nozzle, and concentrates the aforementioned powdered fuel toward the aforementioned flame retainer for powdered fuel. The operating method comprises supplying ammonia fuel to the aforementioned inner cylinder nozzle or the aforementioned outer cylinder nozzle.

In addition, according to one aspect of the burner of the present invention, the following advantageous effects can be obtained. In a mixed combustion burner that burns pulverized fuel and ammonia fuel simultaneously with a single burner, especially in a load area lower than the rated output, the ignition and flame retention of the fuel become strict conditions, so the upper and lower limits of the mixed combustion rate tend to be narrowed.

Furthermore, in order to stably form and maintain the flames of a plurality of fuels having different combustion characteristics in a mixed combustion burner, the lower limit of the minimum load is likely to be higher than that of a dedicated combustion burner for a specific fuel.

In wall-fired boilers that use multiple stages and multiple rows of burners on the furnace wall, most burners in one stage are treated as a group for ignition, fire extinguishing, and output (load) adjustment. Some burners are stopped for preparation, and the load of other operating burner stages is adjusted, or the number of stopped burner stages is increased to reduce the load.

If the burner of the present invention is equipped in each section and each row of the wall-fired boiler, the mixed combustion rate of ammonia fuel can be improved. Even in the area where the boiler load is relatively low, the upper and lower limits of the mixed combustion rate are wide, and the lower limit of the minimum boiler load is also low. Therefore, the operability of the boiler plant and the flexibility to cope with the changes in the mixed combustion rate and load will be improved.

According to the burner of the present invention, the mixed combustion rate of ammonia fuel can be increased, that is, the upper limit of the mixed combustion rate is higher. Therefore, when a part of the burners of an existing boiler that only has a burner for burning micro-powder fuel is replaced with a burner that can burn ammonia and converted into a mixed combustion boiler, there is an advantage that compared with a burner with a lower upper limit of the mixed combustion rate, it is sufficient to replace a smaller number of burners.

According to the burner of the present invention, the range of the upper and lower limits of the mixed combustion rate of ammonia fuel is wider. Therefore, in a boiler plant that has both a burner for burning a specific type of fuel and a burner for burning a mixed ammonia and micro-powder fuel, there is a greater advantage in the selection of burners from use to shutdown or the adjustment range of the load than a burner with a narrower range of the upper and lower limits of the mixed combustion rate of ammonia fuel.

Furthermore, stable combustion can be achieved even at low loads, and the lower limit of the minimum load can be set lower.

In response to the fuel dispatching conditions of the boiler plant, the fuel supply ratio, that is, the mixed combustion rate, can be increased or decreased, making it easy to cope with flexible operation.

10: Boiler 11: Furnace 12: Combustion gas passage 13: Flue 20: Combustion device 21: Burner 22: Powder fuel supply pipe 23: Bellows (air regulator) 24: Air duct (air passage) 25: Additional air vent 26: Additional air passage 31: Grinding mill (crusher) 32: Injection fan (FDF) 41: Gas passage 42: Air preheater 43: Denitrification device 44: Dust collector 45: Induction fan (IDF) 46: Desulfurization device 47: Chimney 50: Ammonia supply source 61: Inner cylinder nozzle 62: outer cylinder nozzle 62a: inner flow path 62b: outer flow path 63: oil nozzle 67: flame protector for ammonia 68: constriction part 68a: upstream side inclined part 68b: downstream side inclined part 69: concentrator 69a: upstream side inclined part 69b: downstream side inclined part 69c: cylinder part 71: flame protector for micro powder fuel 73: secondary air flow path 74: tertiary air flow path 74a: rotator 80,80': gap (ammonia ejection hole) 82: distributor 85: circumferential direction concentrator 85a: ammonia ejection hole 85b: Mounting part 85c: Upstream end 85d: Middle position 85e: Downstream end 85f: Downstream side 85g: Bottom surface 87: Ammonia supply pipe 90: Liquid ammonia supply pipe 92: Liquid ammonia injection nozzle 92a: Injection hole 95: Liquid ammonia supply pipe 101: Furnace wall 102: Superheater 103: Reheater 104: Economizer

[Fig. 1] is a schematic structural diagram of a boiler according to the first embodiment of the present invention. [Fig. 2] is a longitudinal sectional view of the burner of Fig. 1. [Fig. 3A] is a longitudinal sectional view of the burner according to the second embodiment of the present invention. [Fig. 3B] is a front view of the inner tube nozzle and the outer tube nozzle of Fig. 3A. [Fig. 4A] is a longitudinal sectional view of a burner of a modified example of Fig. 3A. [Fig. 4B] is a front view of the inner tube nozzle and the outer tube nozzle of Fig. 4A. [Fig. 5] is a longitudinal sectional view of the burner according to the third embodiment of the present invention. [Fig. 6A] is a longitudinal sectional view of the burner according to the fourth embodiment of the present invention. [Fig. 6B] shows a front view of the inner cylinder nozzle and the outer cylinder nozzle of Fig. 6A. [Fig. 6C] shows a perspective view of the circumferential direction concentrator of Fig. 6A and Fig. 6B. [Fig. 7A] shows a longitudinal sectional view of the burner of the fifth embodiment of the present invention. [Fig. 7B] shows a longitudinal sectional view of the liquid ammonia injection nozzle. [Fig. 8] shows a longitudinal sectional view of the burner of the sixth embodiment of the present invention.

11: Fireplace

21: Burner

61: Inner tube nozzle

62: External nozzle

63: Oil spray nozzle

67: Flame protector for ammonia

68: Reduction section

68a: Upstream side slope

68b: Downstream side slope

69: Concentrator

69a: Upstream side slope

69b: Downstream side slope

69c: cylindrical part

71: Flame protector for micro powder fuel

73: Secondary air flow path

74: Tertiary air flow path

74a: Rotator

101: Fireplace wall

CL: Center axis

Claims (4)

A burner comprises: an inner cylinder nozzle extending along a central axis; an outer cylinder nozzle extending along the central axis and arranged to cover the inner cylinder nozzle, supplying pulverized fuel and primary air into a furnace; a flame retainer for pulverized fuel, which retains the flame of the pulverized fuel supplied from the outer cylinder nozzle; and a concentrator arranged inside the outer cylinder nozzle, concentrating the pulverized fuel toward the flame retainer for pulverized fuel, supplying ammonia fuel and air to the inner cylinder nozzle, and spraying ammonia fuel from an ammonia supply pipe arranged on the outer peripheral side of the outer cylinder nozzle. The burner as described in claim 1 comprises: a control valve for controlling the flow rate of air supplied to the inner tube nozzle, and a control unit for controlling the control valve, wherein the control unit controls the control valve to reduce the flow rate of the air in response to an increase in the mixed combustion rate of the ammonia fuel. A boiler having a burner as claimed in any one of claims 1 to 2. A method for operating a burner, wherein the burner comprises: an inner cylinder nozzle extending along a central axis; an outer cylinder nozzle extending along the central axis and arranged to cover the inner cylinder nozzle, supplying fine powder fuel and primary air into a furnace; a flame retainer for fine powder fuel, which retains the flame supplied from the outer cylinder nozzle to the fine powder fuel; and a concentrator arranged inside the outer cylinder nozzle. , the aforementioned fine powder fuel is concentrated on the side of the aforementioned fine powder fuel flame protector, ammonia fuel and air are supplied to the aforementioned inner cylinder nozzle, and ammonia fuel is sprayed from an ammonia supply pipe provided on the outer peripheral side of the aforementioned outer cylinder nozzle. The operation method of the aforementioned burner is to slowly supply the aforementioned fine powder fuel and primary air to the aforementioned outer cylinder nozzle and spray it, and slowly supply the aforementioned ammonia fuel and air to the aforementioned inner cylinder nozzle and spray it in a pre-mixed state.

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