JP7292898B2 - boiler - Google Patents

Description

The present invention relates to boilers.

Boilers are known in which a burner forms a flame in a combustion chamber to produce steam. Patent Literature 1 listed below discloses a marine boiler to be mounted on a ship. The boiler disclosed in the document is equipped with a small-capacity burner in addition to a large-capacity burner, so that it can handle both large-capacity and small-capacity boilers.

Japanese Utility Model Laid-Open No. 57-81999

Boilers mounted on ships include a main boiler used as a power source for driving a propulsion propeller. Further, as a boiler having a capacity smaller than that of the main boiler, there is an auxiliary boiler used as an auxiliary power source for operating various devices mounted on a ship or driving a lightning generator.

Auxiliary boilers may be required, one for generating high pressure steam for high load equipment and the other for generating low pressure steam for low load equipment. As a result, an increase in the number of equipment items on the ship is caused. In addition, since the auxiliary boiler takes time to pressurize, it is necessary to continue warm-up operation in order to quickly supply steam to the equipment. For this reason, an increase in fuel consumption due to the warm-up operation of the auxiliary boiler that generates high-pressure steam, in particular, becomes a problem.

Therefore, by providing burners with different capacities as in Patent Document 1, it is conceivable to achieve a high turndown by corresponding to a large capacity to a small capacity.

However, when the large-capacity burner is in operation, the small-capacity burner is stopped, and there is a risk that the small-capacity auxiliary burner will be damaged by the radiant heat of the flame of the large-capacity main burner.

The present disclosure has been made in view of such circumstances, and an object thereof is to provide a boiler capable of cooling a small-capacity burner while a large-capacity main burner is operating.

A boiler according to an aspect of the present disclosure includes a combustion vessel that forms a combustion chamber, a main burner provided in the combustion vessel, and a flame that is provided in the combustion vessel and formed downstream of the main burner. a sub-burner having a capacity smaller than that of the main burner, a sub-burner wind box accommodating the sub-burner and attached to the combustion vessel, and an air supply for supplying air to the sub-burner wind box. means, and a control section for controlling the air supply means, wherein the control section drives the air supply means when the main burner is in operation and the sub burner is not in operation.

A secondary burner is provided downstream of the flame formed by the primary burner. Therefore, when the main burner is in operation and the sub burner is not in operation, if combustion air is not supplied to the sub burner, the sub burner may be damaged by radiant heat from the flame of the main burner. Therefore, even when the sub burner is not in operation, the sub burner is cooled by supplying air from the sub burner air fan. In addition, since the air is supplied so that the pressure in the sub-burner wind box becomes higher than the pressure in the combustion chamber, the sub-burner and the sub-burner wind box are placed in the combustion chamber in a pressurized state. can be sealed.

Further, the control unit controls the air supply means so that the pressure in the sub-burner wind box is higher than the pressure in the combustion vessel when the main burner is in operation and the sub-burner is not in operation. You may make it control.

Further, the boiler according to one aspect of the present disclosure includes a cooling steam supply unit that supplies cooling steam for cooling the sub burner.

Furthermore, since cooling steam is supplied, damage to the sub burner due to radiant heat can be suppressed.

Further, in the boiler according to one aspect of the present disclosure, the auxiliary burner includes an oil injection nozzle that injects oil fuel as a combustion fuel into the combustion chamber, and the oil injection nozzle is provided for the cooling steam supply unit. It is considered part.

Since oil is not supplied to the oil injection nozzle of the auxiliary burner when it is not in operation, the oil injection nozzle is used as a part of the cooling steam supply section, and cooling steam is supplied from the oil injection nozzle. Since the oil injection nozzle injects cooling steam from the tip of the sub-burner into the combustion chamber, it is possible to effectively protect the sub-burner from radiant heat.

Further, in the boiler according to the aspect of the present disclosure, a steam supply nozzle is provided as part of the cooling steam supply section inside the sub-burner wind box.

A steam supply nozzle was provided as part of the cooling steam supply section in the wind box for the sub burner. Thereby, the sub-burner housed in the sub-burner wind box can be cooled. Further, since a path for supplying cooling steam can be provided separately from the fuel nozzle of the sub burner, cooling steam can be supplied regardless of the operation of the sub burner.
The steam supply nozzle may be, for example, a steam ring nozzle that is a ring-shaped nozzle surrounding the sub burner.

Further, in the boiler according to one aspect of the present disclosure, the sub burner includes a gas injection nozzle that injects gas fuel as a combustion fuel into the combustion chamber, and the gas injection nozzle is the cooling steam supply unit. It is considered part.

The auxiliary burners are equipped with gas injection nozzles so that gas fuel can be used in addition to oil fuel. The gas injection nozzle is used as a part of the cooling steam supply unit, and the cooling steam is supplied from the gas injection nozzle. Since the gas injection nozzle injects cooling steam from the tip of the sub burner into the combustion chamber, it is possible to effectively protect the sub burner from radiant heat.

Furthermore, in the boiler according to the aspect of the present disclosure, the cooling steam supply unit supplies cooling steam toward the downstream side of the flame formed by the main burner.

By supplying steam to the downstream side of the flame of the main burner, the flame temperature can be lowered to reduce thermal NOx.

Further, in the boiler according to an aspect of the present disclosure, a main burner wind box that accommodates the main burner and is attached to the combustion vessel, and a main burner air fan that supplies air to the main burner wind box and an air supply pipe for supplying air from the main burner air fan to the sub burner wind box.

Air was supplied from the air fan for the main burner to the wind box for the sub burner. As a result, even if the sub-burner air fan should fail, cooling air can be supplied to the sub-burner wind box.
The supply of air from the main burner air fan to the sub burner wind box is controlled by the controller. In other words, when the auxiliary burner air fan is not out of order, the controller controls the on-off valve and the like so as to stop the flow of air. If the sub-burner air fan fails, the controller controls the on-off valve and the like so that the air flows. Incidentally, not only when the sub-burner air fan fails, but when the amount of air supplied from the sub-burner air fan is insufficient, air may be supplied from the main burner fan to the sub-burner wind box. .

Furthermore, in the boiler according to one aspect of the present disclosure, a damper that opens and closes the flow path is provided at the outlet of the air supply means.

A damper is provided at the outlet of the air supply means. Thus, by closing the damper when the air supply means is stopped, it is possible to prevent the air guided from the main burner air fan through the air supply pipe from flowing back to the air supply means side.

Even if the sub-burner is inactive while the main burner is operating, the sub-burner can be cooled because air is supplied from the air supply means.

BRIEF DESCRIPTION OF THE DRAWINGS It is the longitudinal cross-sectional view which showed the boiler which concerns on 1st Embodiment. FIG. 2 is a cross-sectional view taken along line AA of FIG. 1; FIG. 3 is a cross-sectional view showing a schematic configuration of a sub-burner; FIG. 4 is a side view showing a state in which the air fan is connected to the boiler; FIG. 7 is a schematic configuration diagram showing a fuel oil path and a steam path of a sub burner applied to the boiler according to the second embodiment; It is a cross-sectional view showing a boiler according to a third embodiment. Figure 7 is a front view of the steam ring nozzle of Figure 6;

Embodiments according to the present disclosure will be described below with reference to the drawings.
[First embodiment]
A first embodiment of the present disclosure will be described below.
The boiler of this embodiment is described as a marine boiler mounted on a ship. Specifically, the boiler will be described as an auxiliary boiler for generating service steam for driving a steam turbine for a cargo oil pump, for example. However, the boiler is not limited to an auxiliary boiler. For example, in the case of a ship, it can be used as a main boiler that serves as a power source during navigation, or as an auxiliary boiler that operates machinery mounted on the ship. Moreover, the boiler is not limited to marine use, and can be used for boilers for various purposes.

<Overall configuration of boiler>
As shown in FIG. 1, the boiler 10 includes a combustion vessel 11, a main burner 12, a sub burner 13, an evaporator 14, and a controller 15.

The combustion vessel 11 has a box-like shape and forms a combustion chamber 24 inside. Combustion chamber 24 is pressurized during operation of main burner 12 or auxiliary burner 13 . It should be noted that the operating state of the burners 12 and 13 means a state in which flames are formed, and the non-operating state means a state in which flames are not formed.

The combustion vessel 11 has a ceiling portion 11a, a bottom portion 11b, a front wall portion 11c (see FIG. 2), a rear wall portion 11d (see FIG. 2), and a pair of side wall portions 11e and 11f. A gas outlet 22 is formed in the ceiling portion 11a. The bottom portion 11b is provided to face the ceiling portion 11a. The front wall portion 11c, the rear wall portion 11d, and the pair of side wall portions 11e and 11f extend so as to connect the ceiling portion 11a and the bottom portion 11b. A combustion chamber 24 is formed by the ceiling portion 11a, the bottom portion 11b, the front wall portion 11c, the rear wall portion 11d, and the side wall portion 11e. The combustion chamber 24 is defined by a ceiling portion 11a, a bottom portion 11b, a front wall portion 11c, a rear wall portion 11d, a side wall portion 11e, and a front bank tube 28, which will be described later. A main burner 12 and a sub burner 13 face the combustion chamber 24 .

The combustion vessel 11 is provided with an exhaust chamber 33 partitioned by a ceiling portion 11a, a bottom portion 11b, a front wall portion 11c, a rear wall portion 11d, a side wall portion 11f, and an evaporator pipe 25, which will be described later. A gas outlet 22 communicates with the exhaust chamber 33 . In addition, the combustion vessel 11 is provided with a partition plate 29 near the center of the evaporator 14 and the front bank tube 28 in the height direction (vertical direction in FIG. 1). The partition plate 29 forms the gas outlet side passage 23 with the bottom portion 11b in the region where the evaporator 14 and the front bank tube 28 are arranged. The gas outlet side passage 23 is a passage for combustion gas G that mainly flows from the combustion chamber 24 to the exhaust chamber 33 .

One main burner 12 is provided at a position spaced apart from the gas outlet 22 on the side wall portion 11e of the ceiling portion 11a. In addition, although the number of the main burners 12 is one in this embodiment, a plurality of them may be provided. The main burner 12 is connected to a fuel supply line and an air supply line. The main burner 12 also has an igniter (not shown). The main burner 12 burns fuel gas in a combustion chamber 24 surrounded by a ceiling portion 11a, a bottom portion 11b, and a side wall portion 11e to form a flame F1 directed toward the bottom portion 11b.

As shown in FIG. 2, one sub burner 13 is provided on the front wall portion 11c. In addition, although the number of sub burners 13 is one in this embodiment, a plurality of sub burners may be provided. The auxiliary burner 13 is connected to different fuel and air supply lines than the main burner 12 . Also, the sub burner 13 has an igniter (not shown) different from the main burner 12 . The auxiliary burner 13 burns fuel oil and/or fuel gas in the combustion chamber 24 to form a flame F2 directed from the front wall portion 11c to the rear wall portion 11d as shown in FIG. The sub burner 13 has a smaller capacity than the main burner 12. - 特許庁In this embodiment, the capacity of the sub burner 13 is, for example, ⅕ times or more and ⅓ times or less the capacity of the main burner 12 .

The sub-burner 13 is accommodated in the sub-burner wind box 40, as shown in FIG. The sub-burner wind box 40 is provided so as to protrude outward from the front wall portion 11c. Sub-burner air AR1 is supplied into the sub-burner wind box 40 . The sub-burner air AR1 is used as combustion air for the sub-burner 13, and is also used as seal air and cooling air, as will be described later.

The auxiliary burner 13, as shown in FIG. 3, includes an oil injection nozzle 13a for injecting oil fuel and a gas injection nozzle 13b for injecting gas fuel. The oil injection nozzle 13a is positioned at the center of the cross section of the sub burner 13. As shown in FIG. A plurality of gas injection nozzles 13b are provided at predetermined angular intervals around the oil injection nozzle 13a. The periphery of the oil injection nozzle 13a and the gas injection nozzle 13b forms a flow path through which the sub-burner air AR1 (see FIG. 2) flows. The number of oil injection nozzles 13a and gas injection nozzles 13b is not limited to that shown in FIG. 3, and a plurality of oil injection nozzles 13a may be provided, and more gas injection nozzles 13b may be provided.

As shown in FIGS. 1 and 2 , the sub burner 13 is provided on the front wall portion 11 c of the combustion vessel 11 on the bottom portion 11 b side of the main burner 12 . As shown in FIG. 1, the sub-burner 13 is provided at a position near the lower end of the flame F1 formed by the main burner 12 on the downstream side, and is capable of supplying air to the lower end of the flame F1. More specifically, as an example, the auxiliary burner 13 is provided at a central portion between a wall tube (not shown) provided on the side wall portion 11e and the front bank tube 28 in the width direction of the combustion chamber 24 (horizontal direction in FIG. 1). It is In addition, the auxiliary burner 13 is provided, as an example, in the central portion of the gas outlet side passage 23 in the height direction of the combustion chamber 24 (vertical direction in FIG. 1). The auxiliary burner 13 may be provided in the vicinity of the central portion between the wall tube (not shown) provided in the side wall portion 11e and the front bank tube 28, or may be provided in the vicinity of the central portion of the gas outlet side passage 23. .

The evaporator 14 is horizontally formed by a group of evaporator tubes in which a plurality of evaporator tubes 25 are bundled. A plurality of evaporator tubes 25 are arranged along the fuel gas ejection direction of the main burner 12 within the combustion vessel 11 . The plurality of evaporating tubes 25 are connected at their lower ends to a water drum 26 supported by the bottom portion 11b, and are connected at their upper ends to a steam drum 27 supported by the ceiling portion 11a. Also, the evaporator 14 is arranged as a front bank tube 28 by arranging a part of the evaporator tube 25 to be bent toward the front wall portion 11c.

The boiler 10 has a combustion chamber 24 , a front bank tube 28 , an evaporator 14 and an exhaust chamber 33 arranged in this order from the main burner 12 and the sub burner 13 toward the gas outlet 22 . Each wall surface of the combustion vessel 11 is provided with a plurality of wall tubes (furnace wall tubes), not shown, as heat exchangers. A superheater may be provided between the evaporator 14 and the front bank tube 28 to superheat the steam in the steam drum 27 to generate superheated steam.

In the boiler 10, the main burner 12 or the sub burner 13 injects fuel into the combustion chamber 24 and burns it, thereby forming the flame F1 or the flame F2 and generating the combustion gas G. The generated combustion gas G flows from the side wall portion 11e of the combustion vessel 11 to the side wall portion 11f. At this time, the combustion gas G passes from the combustion chamber 24 to the exhaust chamber 33 through the area where the front bank tube 28 is arranged and the area where the evaporator 14 is arranged. The combustion gas G passes through the front bank tube 28 and the evaporator 14 mainly through the lower region in FIG. 1 separated by the partition plate 29 in the exhaust chamber 33 , passes through the evaporator 14 again, and reaches the gas outlet 22 . The front bank tube 28 and the evaporator 14 are heat exchangers, and exchange heat with the combustion gas G when the combustion gas G passes through. It raises the temperature of the water or steam (heat medium) that flows through it.

The front bank tube 28 is arranged on the side of the main burner 12 and the sub-burner 13 in the combustion vessel 11 , that is, in a region where the temperature inside the combustion vessel 11 is high. The front bank tube 28 is connected to the water drum 26 and the steam drum 27, and water and steam flow inside. The front bank tube 28 recovers the heat of the combustion gas G through heat exchange between the combustion gas G and water or steam, thereby raising the temperature of the water or steam and lowering the temperature of the combustion gas G.

The evaporator 14 has a plurality of evaporator tubes 25 and is arranged closer to the gas outlet 22 than the front bank tube 28 in the combustion vessel 11 . The evaporator 14 passes the combustion gas G that has passed through the area where the front bank tube 28 is arranged. The evaporator 14 has a water drum 26 and a steam drum 27 connected to each end of a plurality of evaporating tubes 25 , and water and steam flow through each evaporating tube 25 . When the evaporator 14 flows from the water drum 26 through each evaporating tube 25 to the steam drum 27, the heat of the combustion gas G is recovered by heat exchange between the combustion gas G and water or steam. The temperature of the steam is raised and the temperature of the combustion gas G is lowered. That is, the combustion gas G heats the water and steam in each evaporating tube 25 , so that only the steam rises and reaches the steam drum 27 .

After passing through the evaporator 14 , the combustion gas G recovers heat, lowers in temperature, reaches the exhaust chamber 33 , becomes exhaust gas (combustion gas G), and is discharged to the outside from the gas outlet 22 .

The combustion vessel 11 and the wind box 40 are each provided with a pressure sensor (not shown). The output of each pressure sensor is transmitted to the control section 15 .

The control unit 15 controls the operations of the boilers such as the main burner 12 and the sub burner 13 described above. The control unit includes, for example, a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), a computer-readable storage medium, and the like. A series of processes for realizing various functions are stored in a storage medium or the like in the form of a program, for example, and the CPU reads out this program to a RAM or the like, and executes information processing and arithmetic processing. As a result, various functions are realized. The program may be pre-installed in a ROM or other storage medium, provided in a state stored in a computer-readable storage medium, or delivered via wired or wireless communication means. etc. may be applied. Computer-readable storage media include magnetic disks, magneto-optical disks, CD-ROMs, DVD-ROMs, semiconductor memories, and the like.

<Cooling structure of sub burner 13>
Next, the cooling structure of the sub burner 13 will be described with reference to FIG.
A sub-burner air fan 44 is connected to the sub-burner wind box 40 via a sub-burner air duct 42 . A sub-burner air fan 44 supplies sub-burner air AR<b>1 (see FIG. 2 ) into the sub-burner wind box 40 . Starting and stopping of the sub-burner air fan 44 are controlled by the controller 15 (see FIG. 1). Alternatively, the air flow rate may be adjusted by controlling the rotation speed of the sub-burner air fan 44 by the control section 15 .

A damper 46 for opening and closing the flow path is provided at the outlet of the sub-burner air fan 44 . Opening and closing of the damper 46 is controlled by commands from the control unit 15 . One end of an air supply pipe 48 is connected downstream of the damper 46 and in the middle of the sub-burner air duct 42 . The other end of the air supply pipe 48 is connected to an intermediate position of the main burner air duct 50 . An on-off valve 49 is provided on the air supply pipe 48 . The on-off valve 49 is controlled by the controller 15 .

A main burner air fan 52 is connected to the upstream end of the main burner air duct 50 . Starting and stopping of the main burner air fan 52 are controlled by the control unit 15 (see FIG. 1). Alternatively, the controller 15 may control the number of rotations of the main burner air fan 52 to adjust the air flow rate.
A main burner wind box 54 is connected to the downstream end of the main burner air duct 50 . The main burner 12 (see FIG. 1) is accommodated in the main burner wind box 54 . Air supplied to the main burner wind box 54 is used as combustion air for the main burners 12 .

<How to operate the boiler 10>
Next, the operation method of the boiler 10 will be explained. The control unit 15 adjusts the combustion by the main burner 12 and the sub burner 13 according to the load of the steam generated by the boiler 10 and adjusts the operating load of the boiler 10 .

The control unit 15 does not operate the main burner 12 when a low load of less than a predetermined value is required, such as when the steam turbine for the cargo oil pump is not driven. That is, combustion by the main burner 12 is not performed. At this time, the boiler 10 is warmed up by the auxiliary burner 13 . The control unit 15 operates only the auxiliary burner 13 to burn fuel oil and/or fuel gas. As a result, the boiler 10 is warmed up by the small-capacity auxiliary burner 13 without using the high-capacity main burner 12, thereby suppressing fuel consumption. Steam can be quickly supplied from the boiler 10 by operating the burner 12 .

The control unit 15 increases the load of the steam turbine (the operation required of the boiler 10) when a high load of a predetermined value or more is required, such as when the steam turbine for the cargo oil pump needs to be driven. The amount of fuel oil and/or fuel gas supplied to the main burner 12 is gradually increased according to load increase). Thus, when combustion is performed using only the main burner 12, the control unit 15 causes the sub-burner air fan 44 to supply air so as to cool the sub-burner 13. FIG. At this time, fuel oil and fuel gas are not supplied to the auxiliary burner 13 . The control unit 15 controls the sub-burner air fan 44 so that the pressure in the sub-burner wind box 40 becomes higher than the pressure in the combustion vessel 11 .

The air supplied to the sub-burner wind box 40 cools the sub-burner 13 and then is supplied to the vicinity of the lower end of the flame F1 formed by the main burner 12 . As a result, the flame is cooled in the vicinity of the lower end of the flame F1, and the amount of NOx produced by the combustion by the main burner 12 is reduced.

<Operation when sub-burner air fan 44 fails>
When the sub-burner air fan 44 fails and air cannot be supplied to the sub-burner wind box 40, the following operations are performed.
When the control unit 15 detects a failure of the sub-burner air fan 44, the control unit 15 operates the on-off valve 49 provided in the air supply pipe 48 from fully closed to fully open. As a result, part of the air supplied from the main burner air fan 52 is supplied to the sub burner wind box 40 via the air supply pipe 48 and the sub burner air duct 42 . At this time, the control unit 15 operates the damper 46 from fully open to fully closed. This prevents the air from flowing back to the sub-burner air fan 44 . A failure of the auxiliary burner air fan 44 can be detected by monitoring the number of revolutions of the fan.

According to this embodiment, the following effects are obtained.
A sub burner 13 is provided downstream of the flame F1 formed by the main burner 12 . Therefore, when the main burner 12 is in operation and the sub burner 13 is not in operation, if combustion air is not supplied to the sub burner 13, the sub burner 13 may be damaged by radiant heat from the flame F1 of the main burner 12. be. Therefore, the sub burner 13 is cooled by supplying air from the sub burner air fan 44 even when the sub burner 13 is not in operation. Further, since the air is supplied so that the pressure in the sub-burner wind box 40 becomes higher than the pressure in the combustion chamber 11, the sub-burner 13 and the sub-burner are supplied to the combustion chamber 24 in the pressurized state. The wind box 40 can be sealed. As a result, when the pressure inside the sub-burner wind box 40 is lower than the pressure inside the combustion vessel 11 , it is possible to prevent the combustion gas from the main burner 12 from entering (backflowing) into the sub-burner 13 .

The air supply pipe 48 is used to supply air from the main burner air fan 52 to the sub burner wind box 40 . As a result, cooling air can be supplied to the sub-burner wind box 40 even if the sub-burner air fan 44 fails.
Incidentally, not only when the sub-burner air fan 44 fails, but when the amount of air supplied from the sub-burner air fan 44 is insufficient, air is supplied from the main burner air fan 52 to the sub-burner wind box 40. You can do it.

A damper 46 is provided at the outlet of the sub-burner air fan 44 . As a result, by closing the damper 46 when the sub-burner air fan 44 is stopped, the air guided from the main burner air fan 52 through the air supply pipe 48 is directed to the sub-burner air fan 44 side. Backflow can be prevented.

[Second embodiment]
Next, a second embodiment of the invention will be described. This embodiment differs from the first embodiment in that it has a configuration for cooling the sub burner 13 using steam. Therefore, the configuration that is different from the first embodiment will be described below.

FIG. 5 shows a system for supplying fuel oil to the oil injection nozzle 13a (see FIG. 3) provided on the auxiliary burner 13. As shown in FIG. A fuel oil supply path 60 and a steam supply path (cooling steam supply section) 62 are connected to the oil injection nozzle 13a.

An oil tank and an oil supply pump (not shown) are connected to the upstream side of the fuel oil supply path 60 . A control valve 64 is provided in the fuel oil supply path 60 . The control valve 64 is controlled by the controller 15 .

A steam source (not shown) is connected to the upstream side of the steam supply path 62 . The steam supply path 62 branches into an atomized steam supply path 62a and a purge steam supply path 62b.

The atomized steam supply path 62a is connected to the oil injection nozzle 13a. A control valve 66 and a check valve 67 controlled by the control unit 15 are provided in the atomized steam supply path 62a. The steam supplied from the atomizing steam supply path 62a is originally used for atomizing fuel oil. However, in this embodiment, it can be used as cooling steam.

A downstream end of the purge steam supply path 62 b is connected to the fuel oil supply path 60 . A control valve 68 and a check valve 69 controlled by the controller 15 are provided in the purge steam supply path 62b. The steam supplied from the purge steam supply path 62b is originally used to purge the path through which the fuel oil flows. However, in this embodiment, it can be used as cooling steam.

Steam cooling of the sub burner 13 according to this embodiment is performed as follows.
When the control valve 64 of the fuel oil supply path 60 is closed to stop the supply of fuel oil, the auxiliary burner 13 is deactivated. At this time, when the main burner 12 is operating, the control unit 15 uses the steam supply path 62 to cause the oil injection nozzle 13a to inject steam. Specifically, the control valve 66 of the atomized steam supply path 62a is opened and the control valve 68 of the purged steam supply path 62b is opened to guide the steam to the oil injection nozzle 13a. By spraying steam from the oil injection nozzle 13a, the auxiliary burner 13 is protected from the radiant heat radiated from the flame F1 formed within the combustion chamber 24.
By spraying cooling steam radially (shade-like) from the tip of the oil injection nozzle 13a, the swirler and gas nozzle attached to the oil injection nozzle 13a are cooled by the radiant heat of the flame of the main burner 12. It can be blocked by steam, and the sub burner 13 can be protected more effectively.

According to this embodiment, the following effects are obtained.
Oil is not supplied to the oil injection nozzle 13a of the auxiliary burner 13 when it is not in operation. . Since the oil injection nozzle 13a injects cooling steam from the tip of the sub burner 13 into the combustion chamber 24, the sub burner 13 can be effectively protected from radiant heat.

Steam can be supplied to the downstream side of the flame F1 of the main burner 12 by injecting the steam from the oil injection nozzle 13a of the sub burner 13 . As a result, the temperature of the flame F1 can be lowered to reduce thermal NOx. Also, if steam is supplied to the base of the flame F1, the mixing of fuel and air is inhibited, resulting in unstable combustion. If it is on the downstream side of the flame F1 (the tip of the flame F1), the combustion reaction is nearing the end and there is no need for much air, so there is no possibility that the combustion will become unstable.

Instead of injecting steam from the oil injection nozzle 13a, or in addition to injecting steam from the oil injection nozzle 13a, steam is supplied from the gas injection nozzle 13b (see FIG. 3) of the sub burner 13. You can do it. As a result, the gas injection nozzle 13b can be used as a part of the cooling steam supply section, and the cooling steam can be supplied from the gas injection nozzle 13b. Since the gas injection nozzle 13b injects cooling steam from the tip of the sub burner 13 into the combustion chamber 24, the sub burner 13 can be effectively protected from radiant heat. Also, the gas injection nozzle 13b projecting into the combustion chamber 24 can be effectively cooled.

[Third embodiment]
Next, a third embodiment of the invention will be described. This embodiment differs from the first embodiment in that it has a configuration for cooling the sub burner 13 using steam. Therefore, the configuration that is different from the first embodiment will be described below.

As shown in FIG. 6, a steam ring nozzle (steam supply nozzle) 72 is provided in the sub-burner wind box 40 . The steam ring nozzle 72 is connected to a steam source (not shown) and injects steam from the sub-burner wind box 40 into the combustion chamber 24 . As shown in FIG. 7, the steam ring nozzle 72 has a ring-shaped pipe, and a plurality of injection holes 72a are formed in this pipe at predetermined intervals. The steam ring nozzle 72 is installed so as to surround the base end of the sub burner 13 .

According to this embodiment, the following effects are obtained.
A steam ring nozzle 72 is provided in the auxiliary burner wind box 40 as part of the cooling steam supply section. Thereby, the sub burner 13 accommodated in the sub burner wind box 40 can be cooled.
In addition, since cooling steam can be supplied to the entire sub burner 13 by the steam ring nozzle 72, it is possible to effectively cool the swirler, the gas injection nozzle 13b, and other parts that are likely to be damaged by the flame of the main burner 12. In addition, the flame cooling effect of steam blowing extends over a wide range, making it possible to reduce NOx.
Further, since a path for supplying cooling steam can be provided separately from the oil injection nozzle 13a and the gas injection nozzle 13b of the sub burner 13, the cooling steam can be supplied regardless of the operation of the sub burner 13. By blowing in steam when the sub burner 13 is in operation, it is possible to reduce NOx from the sub burner 13 itself.

Moreover, by supplying steam from the steam ring nozzle 72 toward the inside of the combustion chamber 24 , steam can be supplied to the downstream side of the flame F<b>1 of the main burner 12 . As a result, the temperature of the flame F1 can be lowered to reduce thermal NOx.

10 Boiler 11 Combustion vessel 12 Main burner 13 Sub burner 13a Oil injection nozzle 13b Gas injection nozzle 14 Evaporator 15 Control unit 22 Gas outlet 24 Combustion chamber 26 Water drum 27 Steam drum 29 Partition plate 33 Exhaust chamber 40 Air box 42 for sub burner Sub-burner air duct 44 Sub-burner air fan (air supply means)
46 damper 48 air supply pipe 49 on-off valve 50 main burner air duct 52 main burner air fan 54 main burner wind box 60 fuel oil supply path 62 steam supply path 62a atomized steam supply path 62b purge steam supply path 64 control valve 66 Control valve 67 Check valve 68 Control valve 69 Check valve 72 Steam ring nozzle (steam supply nozzle)
AR1 Sub-burner air F1, F2 Flame G Combustion gas

Claims (7)

a combustion vessel forming a combustion chamber;
a main burner provided in the combustion vessel;
a sub-burner provided in the combustion vessel, downstream of the flame formed by the main burner and having a smaller capacity than the main burner;
a sub-burner wind box that houses the sub-burner and is attached to the combustion vessel;
air supply means for supplying air to the sub burner wind box;
a control unit that controls the air supply means;
with
The control unit drives the air supply means when the main burner is in operation and when the sub burner is not in operation ,
A cooling steam supply unit for supplying cooling steam for cooling the sub burner,
The cooling steam supply unit is a boiler that supplies cooling steam toward the downstream side of the flame formed by the main burner . 2. The boiler according to claim 1, wherein the controller controls the air supply means so that the pressure in the sub-burner wind box is higher than the pressure in the combustion vessel. The auxiliary burner includes an oil injection nozzle for injecting oil fuel as combustion fuel into the combustion chamber,
3. The boiler according to claim 1 , wherein said oil injection nozzle is part of said cooling steam supply. 2. The boiler according to claim 1 , wherein a steam supply nozzle is provided as part of the cooling steam supply section within the sub burner wind box. The auxiliary burner includes a gas injection nozzle for injecting gas fuel as combustion fuel into the combustion chamber,
2. A boiler according to claim 1 , wherein said gas injection nozzle is part of said cooling steam supply. a main burner windbox housing the main burner and attached to the combustion vessel;
a main burner air fan that supplies air to the main burner wind box;
an air supply pipe for supplying air from the main burner air fan to the sub burner wind box;
2. The boiler of claim 1 , comprising: 7. The boiler according to claim 6 , wherein the outlet of said air supply means is provided with a damper for opening and closing a flow path.

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