WO2020170622A1

WO2020170622A1 - Boiler

Info

Publication number: WO2020170622A1
Application number: PCT/JP2020/000220
Authority: WO
Inventors: 貴澄寺原; 森　匡史; 龍太中村; 英輝天野
Original assignee: 三菱重工マリンマシナリ株式会社
Priority date: 2019-02-22
Filing date: 2020-01-08
Publication date: 2020-08-27
Also published as: JP2020134069A; KR20210114501A; CN113439180B; CN113439180A; KR102551979B1; EP3913283A1; JP7292898B2; EP3913283B1; DK3913283T3; EP3913283A4

Abstract

Provided is a boiler such that even if a large-capacity main burner is operating and a small-capacity sub-burner is not operating, it is possible to cool the sub-burner. The boiler comprises: a combustion vessel (11) that forms a combustion chamber (24); a main burner that is disposed in the combustion vessel (11); a sub-burner (13) that is disposed in the combustion vessel (11), disposed downstream of the flame formed by the main burner, and has a smaller capacity than the main burner; a sub-burner wind box (40) that accommodates the sub-burner (13) and is attached to the combustion vessel (11); a sub-burner air fan (44) that supplies air to the sub-burner wind box (40); and a control unit that controls the sub-burner air fan (44). The control unit 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), when the main burner is operating and the sub burner (13) is not operating.

Description

boiler

The present invention relates to a boiler.

ㆍ It is known that the burner creates a flame in the combustion chamber and produces steam. The following Patent Document 1 discloses a marine boiler mounted on a marine vessel. The boiler disclosed in the same document can cope with a large capacity to a small capacity by providing a small capacity burner in addition to the large capacity burner.

Japanese Utility Model Publication No. 57-81999

As a boiler mounted on a ship, there is a main engine boiler used as a power source for driving a propeller for propulsion. As a boiler having a smaller capacity than the main engine boiler, there is an auxiliary boiler used as an auxiliary power source for operating various devices mounted on a ship and driving a lightning generator.

The auxiliary boiler may require one for generating high-pressure steam for high-load equipment and another for generating low-pressure steam for low-load equipment. As a result, the number of facilities on the ship is increased. Further, since the auxiliary boiler requires time for pressurization, it is necessary to keep warm-up operation in order to quickly supply steam to the equipment. For this reason, an increase in fuel consumption by warming up the auxiliary boiler that generates high-pressure steam is an issue.

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

However, when operating a large capacity burner, the small capacity burner is stopped, and the radiant heat of the flame of the large capacity main burner may damage the small capacity sub-burner.

The present disclosure has been made in view of such circumstances, and an object thereof is to provide a boiler that can cool a small capacity burner when a large capacity main burner is operating.

A boiler according to an aspect of the present disclosure includes a combustion container that forms a combustion chamber, a main burner that is provided in the combustion container, and a downstream side of a flame that is provided in the combustion container and that is formed by the main burner. And a sub-burner having a smaller capacity than the main burner, a sub-burner wind box that accommodates the sub-burner and is attached to the combustion container, and an air supply that supplies air to the sub-burner wind box. Means and a control unit for controlling the air supply unit, the control unit driving the air supply unit when the main burner is operating and when the sub-burner is not operating.

　A secondary burner is provided downstream of the flame formed by the main burner. Therefore, when the main burner is operating and the sub-burner is not operating, if the combustion air is not supplied to the sub-burner, the sub-burner may be damaged by the radiant heat due to the flame of the main burner. Therefore, even when the sub-burner is not operating, the sub-burner is cooled by supplying air from the sub-burner air fan. Further, since the air is supplied so that the pressure in the sub-burner wind box is higher than the pressure in the combustion container, the sub-burner and the sub-burner wind box are provided for the combustion chamber in the pressurized state. Can be sealed.

The control unit controls the air supply unit so that the pressure in the auxiliary burner air box is higher than the pressure in the combustion container when the main burner is operating and the sub-burner is not operating. You may do it.

A boiler according to an aspect of the present disclosure includes a cooling steam supply unit that supplies cooling steam that cools the sub-burner.

Since it is decided to supply cooling steam, damage to the sub-burner due to radiant heat can be suppressed.

In the boiler according to one aspect of the present disclosure, the sub-burner includes an oil injection nozzle that injects oil fuel as combustion fuel into the combustion chamber, and the oil injection nozzle is a part of the cooling steam supply unit. It is said that.

　The oil injection nozzle of the sub-burner does not supply oil when it is not operating, so we decided to make the oil injection nozzle part of the cooling steam supply part and supply cooling steam from the oil injection nozzle. Since the oil injection nozzle injects the cooling steam from the tip of the sub-burner toward the combustion chamber, the sub-burner can be effectively protected from radiant heat.

In the boiler according to an aspect of the present disclosure, a steam supply nozzle is provided as a part of the cooling steam supply unit in the auxiliary burner air box.

It was decided to install a steam supply nozzle as part of the cooling steam supply unit in the auxiliary burner air box. As a result, the sub-burner housed in the sub-burner air box can be cooled. Further, since a path for supplying the cooling steam can be provided separately from the fuel nozzle of the auxiliary burner, the cooling steam can be supplied regardless of the operation of the auxiliary burner.
As the steam supply nozzle, for example, a steam ring nozzle that is a ring-shaped nozzle surrounding the sub-burner can be used.

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

◇The sub-burner is equipped with a gas injection nozzle so that gas fuel can be used in addition to oil fuel. The gas injection nozzle is part of the cooling steam supply unit, and the cooling steam is supplied from the gas injection nozzle. Since the gas injection nozzle injects the cooling steam from the tip of the sub-burner toward the combustion chamber, the sub-burner can be effectively protected from radiant heat.

In the boiler according to the aspect of the present disclosure, the cooling steam supply unit supplies the 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, it is possible to lower the flame temperature and reduce thermal NOx.

In a boiler according to an aspect of the present disclosure, a main burner air box that houses the main burner and is attached to the combustion container, a main burner air fan that supplies air to the main burner air box, and An air supply pipe for supplying air from the main burner air fan to the sub-burner air box.

It was decided to supply air from the main burner air fan to the auxiliary burner air box. Thus, even if the sub-burner air fan fails, cooling air can be supplied to the sub-burner air box.
The air supply from the main burner air fan to the auxiliary burner air box is controlled by the controller. That is, when the sub-burner air fan has not failed, the control unit controls the on-off valve and the like to stop the air flow. When the sub-burner air fan fails, the control unit controls the on-off valve and the like so that the air flows. Not only the failure of the sub-burner air fan, but also 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. ..

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

　It was decided to install a damper 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 via the air supply pipe from flowing back to the air supply means side.

Even if the sub-burner is not operating when the main burner is operating, the air is supplied from the air supply means, so the sub-burner can be cooled.

It is a longitudinal section showing the boiler concerning a 1st embodiment. FIG. 2 is a transverse sectional view taken along the line AA of FIG. 1. It is a cross-sectional view showing a schematic configuration of a sub-burner. It is the side view which showed the state which connected the air fan with respect to the boiler. It is the schematic block diagram which showed the fuel oil path and steam path of the auxiliary burner applied to the boiler which concerns on 2nd Embodiment. It is a transverse cross section showing the boiler concerning a 3rd embodiment. FIG. 7 is a front view showing the steam ring nozzle of FIG. 6.

Embodiments according to the present disclosure will be described below with reference to the drawings.
[First Embodiment]
Hereinafter, the first embodiment of the present disclosure will be described.
The boiler of the present embodiment is described as a marine boiler mounted on a ship. Specifically, it is explained as a case where the boiler is used as an auxiliary boiler that generates miscellaneous steam for driving a steam turbine or the like for a cargo oil pump, for example. However, the boiler is not limited to the auxiliary boiler, and in the case of a ship, for example, it can be used as a main engine boiler that serves as a power source during navigation or an auxiliary boiler that operates a machine mounted on the ship. The boiler is not limited to the one for marine vessels, and can be used for boilers for various purposes.

<Overall structure of boiler>
As shown in FIG. 1, the boiler 10 includes a combustion container 11, a main burner 12, a sub-burner 13, an evaporator 14, and a control unit 15.

The combustion container 11 has a box shape and has a combustion chamber 24 formed therein. The combustion chamber 24 is pressurized when the main burner 12 or the sub-burner 13 is operating. The operation of the

burners

12 and 13 means that a flame is being formed, and the non-operation of the

burners

12 and 13 means that a flame is not being formed.

The combustion container 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 so as 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. The ceiling portion 11a, the bottom portion 11b, the front wall portion 11c, the rear wall portion 11d, and the side wall portion 11e form a combustion chamber 24. The combustion chamber 24 is configured by being partitioned 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 described later. The main burner 12 and the sub-burner 13 face the combustion chamber 24.

The combustion container 11 is provided with an exhaust chamber 33 defined 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 evaporation pipe 25 described later. The gas outlet 22 communicates with the exhaust chamber 33. The combustion container 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 the combustion gas G that mainly flows from the combustion chamber 24 to the exhaust chamber 33.

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

As shown in FIG. 2, one sub-burner 13 is provided on the front wall 11c. Although the number of the sub-burners 13 is one in this embodiment, it may be plural. The sub-burner 13 is connected to a fuel supply line and an air supply line different from the main burner 12. The sub-burner 13 has an igniter (not shown) different from the main burner 12. The sub-burner 13 burns fuel oil and/or fuel gas in the combustion chamber 24 to form a flame F2 extending 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. In the present embodiment, the capacity of the sub-burner 13 is, for example, 1/5 times or more and 1/3 times or less that of the main burner 12.

The sub-burner 13 is housed in an air box 40 for the sub-burner as shown in FIG. The sub-burner wind box 40 is provided so as to project outward from the front wall portion 11c. The sub-burner air box 40 is supplied with the sub-burner air AR1. The sub-burner air AR1 is used as combustion air for the sub-burner 13, and is also used as sealing air and cooling air as described later.

As shown in FIG. 3, the sub-burner 13 includes an oil injection nozzle 13a for injecting oil fuel and a gas injection nozzle 13b for injecting gas fuel. The oil injection nozzle 13 a is located at the center of the cross section of the auxiliary burner 13. A plurality of gas injection nozzles 13b are provided at predetermined angular intervals centered on the oil injection nozzle 13a. Around the oil injection nozzle 13a and the gas injection nozzle 13b is a flow path through which the sub-burner air AR1 (see FIG. 2) flows. The numbers of the oil injection nozzles 13a and the gas injection nozzles 13b are not limited to those shown in FIG. 3, and a plurality of oil injection nozzles 13a may be provided, or 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 11c on the bottom 11b side of the combustion container 11 with respect to the main burner 12. As shown in FIG. 1, the sub-burner 13 is provided at a position near the lower end which is the downstream side of the flame F1 formed by the main burner 12, and is capable of supplying air to the lower end of the flame F1. More specifically, as an example, the sub-burner 13 is provided in the center portion of the front bank tube 28 and the wall tube (not shown) provided in the side wall portion 11e in the width direction of the combustion chamber 24 (left-right direction in FIG. 1). Has been. As an example, the sub-burner 13 is provided 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 sub-burner 13 may be provided near the center of the wall bank (not shown) provided on the side wall 11e and the front bank tube 28, or may be provided near the center of the gas outlet side passage 23. ..

The evaporator 14 is laterally composed of an evaporation tube group in which a plurality of evaporation tubes 25 are bundled. The plurality of evaporation tubes 25 are arranged in the combustion container 11 along the fuel gas ejection direction of the main burner 12. The lower ends of the plurality of evaporation pipes 25 are connected to a water drum 26 supported by the bottom 11b, and the upper ends thereof are connected to a steam drum 27 supported by the ceiling 11a. The evaporator 14 is arranged as a front bank tube 28 by arranging a part of the evaporation pipes 25 so as to be bent toward the front wall portion 11c.

In the boiler 10, the combustion chamber 24, the front bank tube 28, the evaporator 14, and the exhaust chamber 33 are arranged in this order from the main burner 12 and the sub-burner 13 toward the gas outlet 22. A plurality of wall tubes (furnace wall tubes) (not shown) as heat exchangers are provided on each wall surface of the combustion container 11. 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 for combustion to form a flame F1 or a flame F2, and a combustion gas G is generated. The generated combustion gas G flows from the side wall 11e side of the combustion container 11 to the side wall 11f side. At this time, the combustion gas G sequentially passes through the region where the front bank tube 28 is arranged and the region where the evaporator 14 is arranged from the combustion chamber 24 to the exhaust chamber 33. The combustion gas G passes through the front bank tube 28 and the evaporator 14 mainly through the lower region in FIG. 1 partitioned by the partition plate 29, that is, the gas outlet side passage 23. Then, the combustion gas G mainly changes its direction to flow into the upper region in FIG. 1 partitioned 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, respectively, that perform heat exchange with the combustion gas G when the combustion gas G passes through, recover the heat of the combustion gas G, and store it inside. Raises the temperature of circulating water or steam (heat medium).

The front bank tube 28 is arranged on the main burner 12 side and the sub-burner 13 side of the combustion container 11, that is, in a region where the temperature inside the combustion container 11 is high. The front bank tube 28 is connected to the water drum 26 and the steam drum 27, and water and steam circulate inside. The front bank tube 28 recovers the heat of the combustion gas G by exchanging heat between the combustion gas G and water or steam to raise the temperature of the water or steam and lower the temperature of the combustion gas G.

The evaporator 14 has a plurality of evaporation pipes 25 and is arranged closer to the gas outlet 22 than the front bank tube 28 in the combustion container 11. The combustion gas G that has passed through the nodule in which the front bank tube 28 is arranged passes through the evaporator 14. In the evaporator 14, a water drum 26 and a steam drum 27 are connected to respective ends of a plurality of evaporation pipes 25, and water and steam are circulated in each evaporation pipe 25. The evaporator 14 collects the heat of the combustion gas G by exchanging heat with the combustion gas G and water or steam when flowing from the water drum 26 through each evaporation pipe 25 to the steam drum 27. 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 evaporation pipe 25, so that only the steam rises and reaches the steam drum 27.

The heat of the combustion gas G that has passed through the evaporator 14 is recovered, the temperature of the combustion gas G drops, and the temperature of the combustion gas G reaches the exhaust chamber 33.

A pressure sensor (not shown) is provided in each of the combustion container 11 and the wind box 40. The output of each pressure sensor is transmitted to the control unit 15.

The control unit 15 controls the operation of the boiler 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), and a computer-readable storage medium. A series of processes for implementing various functions are stored in a storage medium or the like in the form of a program as an example, and the CPU reads the program into a RAM or the like to execute information processing/arithmetic processing. As a result, various functions are realized. The program is installed in a ROM or other storage medium in advance, provided in a state of being stored in a computer-readable storage medium, or delivered via a wired or wireless communication unit. Etc. may be applied. The computer-readable storage medium is a magnetic disk, a magneto-optical disk, a CD-ROM, a DVD-ROM, a semiconductor memory, or the like.

<Cooling structure of the 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. The sub-burner air fan 44 supplies the sub-burner air AR1 (see FIG. 2) into the sub-burner air box 40. Starting and stopping of the sub-burner air fan 44 are controlled by the control unit 15 (see FIG. 1). Further, the control unit 15 may control the rotation speed of the sub-burner air fan 44 to adjust the air flow rate.

A damper 46 that opens and closes the flow path is provided at the outlet of the sub-burner air fan 44. The opening and closing of the damper 46 is controlled by a command from the control unit 15. One end of an air supply pipe 48 is connected to the downstream side of the damper 46 and at an intermediate position of the auxiliary 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. The air supply pipe 48 is provided with an open/close valve 49. 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. The start and stop of the main burner air fan 52 is controlled by the control unit 15 (see FIG. 1). Further, the control unit 15 may control the rotation speed 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 housed in the main burner wind box 54. The air supplied to the main burner wind box 54 is used as combustion air for the main burner 12.

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

The control unit 15 does not operate the main burner 12 and does not operate when a low load less than a predetermined value is required, for example, 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 controller 15 operates only the sub-burner 13 to burn the fuel oil and/or the 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 to suppress the fuel consumption, and when the steam turbine needs to be driven, for example, By operating the burner 12, steam can be quickly supplied from the boiler 10.

The control unit 15 increases the load of the steam turbine (when the steam turbine for the cargo oil pump needs to be driven at a high load of a predetermined value or more, for example, 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 the increase in load. As described above, when the 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. At this time, fuel oil and fuel gas are not supplied to the sub-burner 13. The control unit 15 controls the sub-burner air fan 44 so that the pressure in the sub-burner wind box 40 is higher than the pressure in the combustion container 11.

The air supplied to the auxiliary burner wind box 40 is supplied to the vicinity of the lower end of the flame F1 formed by the main burner 12 after cooling the auxiliary burner 13. 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 combustion by the main burner 12 is reduced.

<Operation when the auxiliary burner air fan 44 fails>
When the auxiliary burner air fan 44 fails and air cannot be supplied to the auxiliary burner air box 40, the following operation is performed.
When the control unit 15 detects the failure of the auxiliary burner air fan 44, the control unit 15 operates the opening/closing valve 49 provided in the air supply pipe 48 from the fully closed state to the fully opened state. As a result, a part of the air supplied from the main burner air fan 52 is supplied to the auxiliary burner wind box 40 via the air supply pipe 48 and the auxiliary 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 auxiliary burner air fan 44. The failure of the sub-burner air fan 44 can be detected by monitoring the fan rotation speed.

According to this embodiment, the following operational effects are exhibited.
An auxiliary burner 13 is provided on the downstream side of the flame F1 formed by the main burner 12. Therefore, when the main burner 12 is operating and the sub-burner 13 is not operating, if the combustion air is not supplied to the sub-burner 13, the sub-burner 13 may be damaged by the radiant heat from the flame F1 of the main burner 12. is there. Therefore, even when the sub-burner 13 is not operating, the sub-burner 13 is cooled by supplying air from the sub-burner air fan 44. Further, since the air is supplied so that the pressure in the auxiliary burner wind box 40 is higher than the pressure in the combustion container 11, the auxiliary burner 13 and the auxiliary burner are supplied to the combustion chamber 24 in the pressurized state. The air duct 40 can be sealed. As a result, when the pressure in the auxiliary burner wind box 40 is lower than the pressure in the combustion container 11, it is possible to avoid the possibility that the combustion gas of the main burner 12 enters the auxiliary burner 13 (backflow).

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

A damper 46 has been installed at the outlet of the sub-burner air fan 44. Thus, by closing the damper 46 when the sub-burner air fan 44 is stopped, the air introduced from the main-burner air fan 52 via 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 present invention will be described. The present embodiment is different from the first embodiment in that the sub-burner 13 is cooled using steam. Therefore, the configuration different from that of 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 in the sub burner 13. 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 control unit 15.

A steam source (not shown) is connected to the upstream side of the steam supply path 62. The steam supply path 62 is branched 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 controller 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 the fuel oil. However, in the present embodiment, it can be used as cooling steam.

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

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

According to this embodiment, the following operational effects are exhibited.
Oil is not supplied to the oil injection nozzle 13a of the sub-burner 13 when it is not operating. Therefore, the oil injection nozzle 13a is made a part of the cooling steam supply unit and the cooling steam is supplied from the oil injection nozzle 13a. .. Since the oil injection nozzle 13a injects the cooling steam from the tip of the sub-burner 13 toward the inside of the combustion chamber 24, the sub-burner 13 can be effectively protected from the radiant heat.

By injecting steam from the oil injection nozzle 13a of the sub-burner 13, steam can be supplied to the downstream side of the flame F1 of the main burner 12. As a result, the temperature of the flame F1 can be lowered to reduce the thermal NOx. Further, if steam is supplied to the root of the flame F1, the mixture of fuel and air is hindered and combustion becomes unstable. On the downstream side of the flame F1 (the tip of the flame F1), the combustion reaction is near the end, and since much air is not required, there is no risk of unstable combustion.

Instead of injecting steam from the oil injection nozzle 13a, or in addition to injecting steam from the oil injection nozzle 13a, the gas is injected from the gas injection nozzle 13b (see FIG. 3) of the sub-burner 13. You can Accordingly, the gas injection nozzle 13b can be part of the cooling steam supply unit, and the cooling steam can be supplied from the gas injection nozzle 13b. Since the gas injection nozzle 13b injects the cooling steam from the tip of the auxiliary burner 13 toward the inside of the combustion chamber 24, the auxiliary burner 13 can be effectively protected from radiant heat. Further, the gas injection nozzle 13b protruding into the combustion chamber 24 can be effectively cooled.

[Third Embodiment]
Next, a third embodiment of the present invention will be described. The present embodiment is different from the first embodiment in that the sub-burner 13 is cooled using steam. Therefore, the configuration different from that of the first embodiment will be described below.

As shown in FIG. 6, a steam ring nozzle (steam supply nozzle) 72 is provided in the wind box 40 for the sub-burner. The steam ring nozzle 72 is connected to a steam source (not shown), and injects the steam from the auxiliary 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 the pipe at predetermined intervals. The steam ring nozzle 72 is installed so as to surround the base end portion of the auxiliary burner 13.

According to this embodiment, the following operational effects are exhibited.
A steam ring nozzle 72 is provided in the sub-burner wind box 40 as a part of the cooling steam supply unit. As a result, the sub-burner 13 housed in the sub-burner wind box 40 can be cooled.
Further, since the 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 the like, which are easily damaged by the flame of the main burner 12. Further, the flame cooling effect due to the steam injection is wide, and NOx can be reduced.
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 steam during the operation of the sub-burner 13, it is possible to reduce the NOx of the sub-burner 13 itself.

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

10 Boiler 11 Combustion Container 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 Sub Burner Wind Box 42 Secondary burner air duct 44 Secondary burner air fan (air supply means)
46 Damper 48 Air Supply Pipe 49 Opening/Closing Valve 50 Main Burner Air Duct 52 Main Burner Air Fan 54 Main Burner Air 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 auxiliary burner air F1, F2 flame G combustion gas

Claims

A combustion vessel forming a combustion chamber,
A main burner provided in the combustion vessel,
A sub-burner provided in the combustion container, provided on the downstream side of the flame formed by the main burner, and having a smaller capacity than the main burner,
An air box for the sub-burner that is attached to the combustion container while accommodating the sub-burner,
Air supply means for supplying air to the auxiliary burner wind box,
A control unit for controlling the air supply unit,
Equipped with
The said control part is a boiler which drives the said air supply means when the said main burner is operating, and when the said sub-burner is non-operating.
The boiler according to claim 1, wherein the control unit controls the air supply unit so that the pressure in the auxiliary burner air box is higher than the pressure in the combustion container.
The boiler according to claim 1, further comprising a cooling steam supply unit that supplies cooling steam for cooling the sub-burner.
The sub-burner includes an oil injection nozzle that injects oil fuel into the combustion chamber as combustion fuel,
The boiler according to claim 3, wherein the oil injection nozzle is a part of the cooling steam supply unit.
The boiler according to claim 3, wherein a steam supply nozzle is provided as a part of the cooling steam supply unit in the air box for the sub-burner.
The sub-burner includes a gas injection nozzle that injects gas fuel into the combustion chamber as combustion fuel,
The boiler according to claim 3 or 4, wherein the gas injection nozzle is part of the cooling steam supply unit.
The boiler according to claim 3, wherein the cooling steam supply unit supplies the cooling steam toward a downstream side of a flame formed by the main burner.
An air box for the main burner that accommodates the main burner and is attached to the combustion container,
An air fan for the main burner that supplies air to the wind box for the main burner,
An air supply pipe for supplying air from the main burner air fan to the sub-burner wind box,
The boiler according to claim 1 or 2, further comprising:
The boiler according to claim 8, wherein a damper that opens and closes the flow path is provided at the outlet of the air supply means.