JP2011069527A - LOW NOx COMBUSTION DEVICE OF BOILER, COMBUSTION METHOD, AND BOILER - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a low NOx combustion device of a boiler, a combustion method, and the boiler, which surely suppress generation of NOx even when combustion conditions are changed. <P>SOLUTION: This low NOx combustion device 10 of the boiler 2 having a furnace 4 producing a combustion gas, and a combustion gas passage 5 in which the combustion gas flows, further includes a burner device 2 disposed in the furnace 4 and having a liquid fuel injection port and a gas fuel injection port, an inert gas supply line 11 for supplying an inert gas to at least one of the gas fuel injection portion and the liquid fuel injection port, an inert gas flow rate adjustment valve 12 for adjusting a supply amount of the inert gas, a NOx detecting means 51 for detecting an amount of NOx included in the combustion gas, a flame detecting means 52 for detecting a state of flame, and a control means 50 for controlling the inert gas flow rate adjustment valve 12 on the basis of the amount of NOx detected by the NOx detecting means 51 and the state of flame detected by the flame detecting means 52. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a low NOx combustion apparatus and combustion method for a boiler that selectively injects and burns at least one of liquid fuel or gaseous fuel from a burner apparatus, and a boiler equipped with the low NOx combustion apparatus.

  2. Description of the Related Art Conventionally, as a burner device provided in a boiler, a burner device for mixed combustion in which liquid fuel such as heavy oil fuel and gaseous fuel such as natural gas are injected at the same time or one of them is selectively injected and burned is known. In this burner apparatus, a low-quality liquid fuel, which is usually called C heavy oil fuel, is used, so that the amount of NOx emission is large. Even when C heavy oil fuel is not used, NOx is generated in the boilers that use fossil fuels such as other heavy oil fuels or natural gas as a result of combustion in the furnace or nitrogen contained in the air. To do. In particular, the above-mentioned burner device for mixed combustion is often used in a marine boiler mounted on a ship, and a marine boiler is more compact than a land boiler used in a power plant or the like because of a large installation space limitation. With such a structure, there was a problem that the furnace heat load was high and a large amount of NOx was generated. In recent years, NOx reduction is also required for marine boilers due to increasing environmental awareness and stricter exhaust gas regulations at ports.

  One method of suppressing NOx emissions in these boilers is a method of suppressing the generation of NOx using a low NOx burner. In Patent Document 1, an oil / gas-fired burner having an injection port for injecting oil fuel toward the downstream side at the center of an air passage for supplying combustion air is provided on the downstream side in the furnace of the air passage. There is disclosed a configuration in which a burner structure that forms a thin air region is used, and the generation of NOx is suppressed by slowly burning oil fuel injected into the thin air region.

Japanese Patent No. 4119853

  As described above, the oil / gas-fired burner described in Patent Document 1 suppresses the generation of NOx by forming a thin air region by the structure of the burner. However, the amount of NOx generated varies depending on the type of fuel and transient fluctuations in combustion conditions. For example, when heavy oil fuel is used as the fuel for the burner device, the amount of NOx generated is larger than when natural gas is used as fuel. Further, when the flame temperature partially increases, the amount of NOx generated increases. As described above, in the boiler, the type of fuel and the combustion condition of the flame change with time, but Patent Document 1 cannot cope with this change.

  Therefore, in view of the problems of the prior art, the present invention provides a low NOx combustion apparatus and combustion method for a boiler, and a boiler that can reliably suppress the generation of NOx even when the combustion conditions change. For the purpose.

  In order to solve the above problems, a low NOx combustion apparatus for a boiler according to the present invention includes a furnace for generating combustion gas, and a low NOx combustion for a boiler having a combustion gas passage connected to the furnace and through which the combustion gas flows. In the apparatus, a burner device provided in the furnace and having a liquid fuel injection port for injecting liquid fuel and a gas fuel supply injection port for injecting gaseous fuel, the gaseous fuel injection port of the burner device, and the liquid fuel injection An inert gas supply means for supplying an inert gas to at least one of the ports; an inert gas supply amount adjusting means for adjusting the supply amount of the inert gas provided in the inert gas supply means; and the combustion gas NOx detecting means provided in the passage for detecting the amount of NOx contained in the combustion gas, flame detecting means for detecting the state of a flame formed by the burner device, and the NO And a controlling means for controlling the inert gas supply amount adjusting means based on the state of the flame is detected at the detected NOx amount detecting means and said flame detecting means.

According to the present invention, by supplying an inert gas from at least one of the gas fuel injection port and the liquid fuel injection port of the burner device, the oxygen concentration in the region where the fuel is injected can be reduced and the fuel can be burnt slowly. It is possible to reliably suppress the generation of NOx. That is, the fuel is slowly burned by supplying the inert gas, the generation of NOx can be suppressed by lowering the combustion temperature, and the nitrogen content in the fuel is reduced in the reduction region having a low air-fuel ratio formed by supplying the inert gas. Is converted to N ₂ to prevent NOx formation reaction.
Even when the type of fuel and the combustion conditions change, the inert gas supply amount adjusting means is controlled based on the NOx amount detected by the NOx detecting means, so the amount of NOx generated by combustion is reduced. It can be reliably reduced. Furthermore, since the inert gas supply amount adjusting means is controlled based on the state of the flame detected by the flame detecting means, it is possible to prevent the flame from being misfired due to the unstable combustion state due to the supply of the inert gas.

The inert gas supply means preferably supplies the inert gas to the gaseous fuel injection port.
In this way, by supplying the inert gas to the gaseous fuel injection port, low NOx combustion can be achieved, and even when the gaseous fuel is being injected, the inert gas can be supplied by being mixed into the gaseous fuel.

The inert gas supply means preferably supplies the inert gas to the liquid fuel injection port.
Thus, by supplying the inert gas to the liquid fuel injection port, it is possible to achieve low NOx combustion and to prevent burning of the nozzle.

Furthermore, the control means is inactive when the amount of NOx detected by the NOx detection means is equal to or greater than a preset threshold value and the flame state detected by the flame detection means is stable. It is preferable to control the inert gas supply amount adjusting means so as to supply gas.
As described above, the inert gas is supplied only when the NOx amount is equal to or greater than the threshold value, and when the NOx amount in the combustion gas is small, the supply of the inert gas is stopped to use the inert gas. It is possible to reduce the amount. In addition, by supplying the inert gas only when the flame state is stable, it is possible to prevent the flame from becoming unstable when the inert gas is supplied and preventing the flame from being misfired.

  Further, a low NOx combustion method for a boiler according to the present invention includes a furnace, a burner device provided in the furnace, having a liquid fuel injection port for injecting liquid fuel and a gaseous fuel injection port for injecting gaseous fuel, In a low NOx combustion method for a boiler having a combustion gas passage connected to a furnace, a step of generating combustion gas by injecting and burning at least one of the liquid fuel and the gaseous fuel from the burner device into the furnace. Detecting the amount of NOx contained in the combustion gas flowing through the combustion gas passage, detecting the state of the flame formed by the burner device, and based on the NOx amount and the state of the flame Supplying an inert gas to at least one of the gaseous fuel injection port and the liquid fuel injection port of a burner device.

In the step of supplying the inert gas, the inert gas is preferably supplied to the gaseous fuel injection port.
In the step of supplying the inert gas, the inert gas is preferably supplied to the liquid fuel injection port.
Further, in the step of supplying the inert gas, it is preferable to supply the inert gas when the amount of NOx is equal to or greater than a preset threshold value and the flame state is stable.

  A boiler according to the present invention is provided in a furnace, a low NOx combustion apparatus that generates combustion gas in the furnace, a combustion gas passage connected to the furnace and through which the combustion gas flows, and the combustion gas passage. A boiler including a heat exchanger that generates steam from the combustion gas, wherein the low NOx combustion device is provided in the furnace, and a liquid fuel injection port for injecting liquid fuel and a gaseous fuel for injecting gaseous fuel A burner device having an injection port; an inert gas supply means for supplying an inert gas to at least one of the gaseous fuel injection port and the liquid fuel injection port of the burner device; and the inert gas supply unit. An inert gas supply amount adjusting means for adjusting the supply amount of the inert gas; a NOx detecting means provided in the combustion gas passage for detecting the amount of NOx contained in the combustion gas; Flame detection means for detecting the state of a flame formed by the burner device, the amount of inert gas supplied based on the amount of NOx detected by the NOx detection means and the state of the flame detected by the flame detection means Control means for controlling the adjusting means.

As described above, according to the present invention, by supplying an inert gas from at least one of the gas fuel injection port and the liquid fuel injection port of the burner device, the oxygen concentration in the region where the fuel is injected is reduced and the fuel is supplied. Slow combustion is possible, and generation of NOx can be reliably suppressed.
Even when the type of fuel and the combustion conditions change, the present invention detects the amount of NOx contained in the combustion gas and supplies the inert gas based on this, so that the amount of NOx can be reliably reduced. Furthermore, since the state of the flame formed by the burner device is detected and the inert gas supply amount adjusting means is controlled based on this, the combustion state becomes unstable due to the supply of the inert gas, and the flame is misfired. Can be prevented.

1 is an overall configuration diagram of a marine boiler provided with a low NOx combustion apparatus according to a first embodiment of the present invention. It is a longitudinal cross-sectional view of a burner apparatus. It is a front view of the burner apparatus seen from the furnace inner side of FIG. It is a flowchart which shows the low NOx combustion method which concerns on 1st Embodiment of this invention. 5 is a flowchart showing a modification of the low NOx combustion method shown in FIG. It is a figure explaining the combustion method of the boiler using a low NOx combustion apparatus, (a) is a graph which shows the change of NOx detection value, (b) is a graph which shows the opening degree of an inert gas amount adjustment valve. It is a whole block diagram of the marine boiler provided with the low NOx combustion apparatus which concerns on 2nd Embodiment of this invention. It is the graph which compared the NOx reduction effect in the low NOx combustion using the inert gas of this embodiment, and the low NOx combustion using the exhaust gas which is a comparative example.

  Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention unless otherwise specified, but are merely illustrative examples. Not too much.

(First embodiment)
FIG. 1 is an overall configuration diagram of a marine boiler including a low NOx combustion apparatus according to a first embodiment of the present invention.
The boiler 1 includes a furnace 4 that generates combustion gas, a combustion gas passage 5 that is connected to the furnace 4 and through which the combustion gas flows, a heat exchanger that is disposed in the combustion gas passage 5, and a low NOx fuel in the furnace 4. And a low NOx combustion device 10 for combustion.
The furnace 4 has a substantially box shape, and the furnace wall is formed of an evaporation tube. In the furnace 4, the fuel injected from the burner device 2 is burned to generate combustion gas.
The combustion gas passage 5 is connected to the furnace 4 so that the combustion gas generated in the furnace 4 flows and is discharged from the gas outlet 6.
The heat exchanger is composed of a bank tube 7, a superheater 8, and an evaporation tube group 9 arranged in order from the furnace side. In addition, the kind and arrangement | positioning of a heat exchanger are not limited to this.

  In the marine boiler 1 having the above-described configuration, combustion is performed by selectively injecting oil fuel or gas fuel from the burner device 2 into the furnace 4. Combustion gas generated by combustion flows out from the furnace 4 to the combustion gas passage 5 and passes through the bank tube 7, the superheater 8, and the evaporation tube group 9 disposed in the combustion gas passage 5 in order while exchanging heat. It is discharged from the outlet 6. The steam generated in the bank tube 7 and the evaporator tube group 9 is collected in the steam drum 3, and this steam is supplied to necessary equipment as a drive source.

  The low NOx combustion apparatus 10 includes a burner apparatus 2 provided in the furnace 4, an inert gas supply line 11 that supplies an inert gas to the burner apparatus 2, and an inert gas flow rate adjustment that is provided in the inert gas supply line. And a valve (hereinafter referred to as a first valve) 12. Further, the low NOx combustion apparatus 10 includes a NOx detection means 51 provided in the combustion gas passage 5, a flame detection means 52 for detecting the state of a flame formed by the burner device 2, a NOx detector means 51, and a flame detection. And a control device 50 that controls the first valve 12 based on the detection signal of the means 52.

2 and 3 are diagrams illustrating an example of the burner device 2.
The burner device 2 includes an oil fuel injection port 20 that injects oil fuel into the furnace 4, and a gas fuel injection port 23 that injects gas fuel into the furnace 2. In addition, although the fuel injected by the burner apparatus 2 used the oil fuel for the liquid fuel as an example, and used the gas fuel for the gaseous fuel, it is not limited to this.
The oil fuel injection port 20 is provided at the center of the tip of the burner device 2, and a plurality of gas fuel injection ports 23 are provided so as to surround the oil fuel injection port 20.

The oil fuel injection port 20 is located inside the furnace 4 and is connected to an oil fuel supply pipe 22 extending in the longitudinal direction at the center of the burner device 2. The oil fuel supply pipe 22 is connected to the oil fuel supply line 13 at the base of the burner device 2. The oil fuel supply pipe 22 is constituted by, for example, a burner gun. In this case, an oil fuel injection port 20 is formed at the tip inside the furnace of the tip 21 provided at the tip of the burner gun.
A swirler 32 is attached to the front end side of the oil fuel supply pipe 22 so as to surround the oil fuel injection port 20. The swirler 32 generates a swirling flow in the passing air and stabilizes the flame with a circulating flow generated by the negative pressure generated at that time.

The gas fuel injection port 23 is located inside the furnace 4 and is connected to a plurality of gas fuel supply pipes 24 arranged around the oil fuel supply pipe 22 in an annular shape. The gas fuel supply pipe 24 communicates with a gas supply chamber 25 provided on the burner base side. The oil fuel supply pipe 22 and the gas fuel supply pipe 24 are supported by a tip support plate 31 on the tip side of the burner device 2.
The burner device 2 having the above-described configuration is fixed to the furnace 4 by a base support plate 30 provided at the burner base.

  An air passage 26 is provided around the gas fuel supply pipe 24 so as to cover the gas fuel supply pipe 24. The air passage 26 communicates with an air box 27 provided on the base side of the burner device 2. An air blocking damper 28 is attached to the wind box 27, and the air flowing from the air blocking damper 28 is supplied into the furnace 4 through the air passage 26 via the wind box 27.

As shown in FIG. 1, the oil fuel supply pipe 22 (see FIG. 2) of the burner device 2 described above is connected to the oil fuel supply line 13. The oil fuel supply line 13 is provided with an oil fuel flow rate adjustment valve 14 (hereinafter referred to as a second valve) that adjusts the supply amount of the oil fuel by controlling the opening degree.
A gas fuel supply pipe 24 (see FIG. 2) of the burner device 2 is connected to the gas fuel supply line 15. The gas fuel supply line 15 is provided with a gas fuel adjustment valve (hereinafter referred to as a third valve) 16 that adjusts the supply amount of the gas fuel by controlling the opening degree.
The inert gas supply line 11 is connected to a gas fuel supply line 15.

The combustion method of the burner device 2 includes oil-only firing, gas-only firing, and oil / gas mixed firing, and the combustion method can be switched by opening and closing the second valve 14 and the third valve 16 respectively. Yes.
In the case of oil-only firing, the control device 50 controls the second valve 14 to open to supply oil fuel to the oil fuel supply pipe 22 of the burner device 2, and the third valve 16 to close to control the gas fuel supply pipe. The supply of gas fuel to 24 is cut off. At the same time, the air blocking damper 28 is opened to allow air to flow into the wind box 27, and the air that has flowed in is supplied into the furnace 4 through the air passage 26 via the wind box 27. At this time, the air passing through the swirler 32 flows into the furnace 4 as a swirling flow. The oil fuel supplied to the oil fuel supply pipe 22 is injected into the furnace 4 from the oil fuel injection port 20, and similarly, when mixed with the air flowing into the furnace 4, it is ignited to generate a flame.

In the case of gas-only firing, the control device 50 controls the second valve 14 to be closed to shut off the supply of oil fuel to the oil fuel supply pipe 22, and the third valve 16 is controlled to be opened to control the gas in the burner device 2. Gas fuel is supplied to the fuel supply pipe 24. At the same time, the air blocking damper 28 is opened to supply air into the furnace 4 from the air passage 26. The gas fuel supplied to the gas fuel supply pipe 24 is injected into the furnace 4 from the gas fuel injection port 23.
In the case of mixed combustion of oil and gas, the control device 50 controls the second valve 14 to open to supply oil fuel to the oil fuel supply pipe 22, and the third valve 16 to control to open the gas in the burner device 2. Gas fuel is supplied to the fuel supply pipe 24. At the same time, the air blocking damper 28 is opened to supply air into the furnace 4 from the air passage 26. The oil fuel supplied to the oil fuel supply pipe 22 is injected into the furnace 4 from the oil fuel injection port 20, and the gas fuel supplied to the gas fuel supply pipe 24 is injected into the furnace 4 from the gas fuel injection port 23. .

The NOx detection means 51 is provided in the vicinity of the gas passage outlet 6 of the combustion gas passage 5 and detects the amount of NOx contained in the combustion gas.
The flame detection means 52 is provided in the vicinity of the burner device 2 and detects the state of the flame formed by the burner device 2. As the flame detection means 52, an optical means or the like for determining the state of the flame by detecting light such as infrared rays or ultraviolet rays is used.

  The control device 50 controls the opening degree of the first valve 12 based on the NOx amount detected by the NOx detection means 51 and the flame state detected by the flame detection means 52. Specifically, the first valve 12 is controlled to open when the amount of NOx is equal to or greater than a preset threshold value and the flame state is stable. Thus, the inert gas is supplied to the gas fuel supply pipe 24 through the inert gas supply line 11 and is injected into the furnace 4 from the gas fuel injection port 23. In some cases, the control device 50 controls the combustion by the burner device 2 by controlling the second valve 14 and the third valve 16 together with the control of the first valve 12 based on the NOx detection means 51. You may do it.

Hereinafter, the combustion method of the boiler 1 using the low NOx combustion apparatus 10 which concerns on this embodiment is demonstrated.
In the boiler 1, at least one of oil fuel or gas fuel is injected from the burner device 2, the injected fuel is ignited and burned, and operation is started (S1). At this time, the combustion method may be any of oil-only firing, gas-only firing, or oil / gas mixed firing. During the operation of the boiler 1, the NOx amount contained in the combustion gas is detected by the NOx detecting means 51 continuously or intermittently (S2). The detected NOx amount is represented, for example, by a graph of NOx amount change over time as shown in FIG. As seen in this graph, the amount of NOx contained in the combustion gas varies depending on the type of fuel and the combustion conditions.

Have set up threshold _{X 0} in advance NOx amount to the controller 50, the detected NOx amount X is determined by the controller 50 whether a threshold value _{X 0} or more (S3). When the detected NOx amount X is determined to be the threshold value X ₀ or more, a flame detection sensor 52 detects the state of flame formed by the burner apparatus 2 (S4). The controller 50 determines whether or not the flame state is stable (S5). If it is determined that the flame is stable, the first valve 12 is controlled to be opened, and the inert gas is burned. 2 is supplied to the gas fuel supply pipe 24. The inert gas supplied to the gas fuel supply pipe 24 is injected into the furnace 4 from the inert gas injection port 23.

According to the present embodiment, by injecting the inert gas from the gas fuel supply pipe 24 into the furnace 4 together with the fuel injection, the oxygen concentration in the region where the fuel is injected from the burner device 2 can be reduced, The fuel can be burnt slowly and the generation of NOx can be suppressed.
In addition, even when the type of fuel and the combustion conditions change, the present embodiment detects the amount of NOx contained in the combustion gas and supplies the inert gas based on this, so the amount of NOx can be reliably reduced. . Furthermore, since the state of the flame formed by the burner device 2 is detected and the first valve 12 is controlled based on this, the combustion state becomes unstable due to the supply of the inert gas, and the flame is misfired. Can be prevented.

  Moreover, you may employ | adopt the combustion method shown in FIG. 5 as a modification of the combustion method of the boiler 1 shown in FIG. After starting the operation of the boiler, the flame detection means 52 first detects the state of the flame formed by the burner device 2, and then the NOx detection means 51 detects the amount of NOx contained in the combustion gas. It has become. The first valve 12 is controlled to open when the flame is stable and the detected amount of NOx is equal to or greater than the threshold value.

Further, based on the detected amount of NOx, it is preferable to control the opening degree of the first valve 12 while confirming the stable state of the flame. For example, as shown in FIGS. 6A and 6B, at time t ₁ when the NOx detection value X becomes equal to or greater than the threshold value X ₀ , the valve opening Y is controlled to the opening side to the opening Y _1. . Elapses further time, at the time the NOx detection value X becomes greater than _{X 1} threshold _{X 0 t 2,} the opening degree Y of the first valve 12, until the opening degree _{Y 1} is greater than the opening degree _{Y 2} Control to open side. Furthermore over time, NOx detection value X at time t ₃ when becomes less than the threshold value X _0, controls the first valve 12 closed.
Thus, by controlling the opening degree of the first valve 12 stepwise or proportionally in accordance with the detected amount of NOx, even if the combustion conditions fluctuate, the NOx concentration always follows a constant concentration. The occurrence can be suppressed so as to be as follows.

(Second Embodiment)
FIG. 7 is an overall configuration diagram of a marine boiler including a low NOx combustion apparatus according to a second embodiment of the present invention. In the description of the second embodiment, the detailed description of the same configuration as that of the first embodiment described above will be omitted.
A marine boiler 1 according to a second embodiment includes a furnace 4 that generates combustion gas, a combustion gas passage 5 that is connected to the furnace 4 and through which the combustion gas flows, a heat exchanger that is disposed in the combustion gas passage 5, and a furnace 4 and a low NOx combustion apparatus 10 for burning the fuel at low NOx.

  The low NOx combustion apparatus 10 includes a burner apparatus 2 provided in the furnace 4, an inert gas supply line 11 that supplies an inert gas to the burner apparatus 2, and a first valve 12 provided in the inert gas supply line. Is provided. Further, the low NOx combustion apparatus 10 includes a NOx detection means 51 provided in the combustion gas passage 5, a flame detection means 52 for detecting the state of a flame formed by the burner device 2, a NOx detector means 51, and a flame detection. And a control device 50 that controls the first valve 12 based on the detection signal of the means 52.

Since the burner apparatus 2 is the same structure as 1st Embodiment, FIG.2 and FIG.3 is used. The burner device 2 includes an oil fuel injection port 20 for injecting oil fuel into the furnace 4 and a gas fuel injection port 23 for injecting gas fuel.
In the first embodiment, the inert gas supply line 11 supplies gas fuel to the gas fuel injection port 23. In the second embodiment, the inert gas supply line 17 supplies gas to the oil fuel injection port 20. It is configured to supply fuel.

  The inert gas supply line 17 is connected to the oil fuel supply line 13. Then, the second valve 14 provided in the oil fuel supply line 13 and the first valve 18 provided in the inert gas supply line 17 are controlled to be opened / closed by the control device 50 to be supplied to the oil fuel injection port 20. Switch between oil fuel and inert gas.

  Specifically, when the second valve 14 is closed, the amount of NOx detected by the NOx detecting means 51 is equal to or greater than a threshold value, and the state of the flame detected by the flame detecting means 52 is stable, The control device 50 controls the first valve 18 to open. By this control, the inert gas is supplied to the oil fuel injection port 20 in a state where the supply of oil fuel to the oil fuel injection port 20 of the burner device 2 is interrupted. At this time, the third valve 16 is controlled to be opened, and gas fuel is supplied to the gas fuel injection port 23 of the burner device 2. A gas is injected from the gas fuel injection port 23 into the furnace 4 to generate a flame and burn, but an inert gas is supplied from the oil fuel injection port 20 to the region where the gas fuel is injected. Therefore, the oxygen concentration is low and slow combustion can be performed, and low NOx combustion becomes possible.

Here, FIG. 8 shows the results of an experiment for verifying the NOx reduction effect using the marine boiler 1 according to the present embodiment and a conventional marine boiler having a configuration for recirculating exhaust gas as a comparative example.
In this embodiment, the marine boiler 1 according to the first embodiment shown in FIG. 1 is used, and nitrogen gas is used as an inert gas supplied to the gas fuel injection port 23. On the other hand, the marine boiler of the comparative example is a marine boiler 1 similar to that of the first embodiment, and a boiler having a conventional oil / gas burning burner is used instead of the low NOx combustion apparatus 10. Further, in the comparative example, a part of the exhaust gas discharged from the gas outlet 6 is recirculated to the furnace 4.

As is clear from FIG. 8, the NOx reduction effect is higher when the inert gas is introduced from the burner device 2 into the flame center than when the exhaust gas is simply recirculated. In particular, it has been found that the NOx reduction effect increases as the gas mixing rate increases.
Therefore, according to the embodiment of the present invention, it is possible to increase the NOx generation suppressing effect as compared with the conventional low NOx combustion by exhaust gas recirculation.

  Embodiment of this invention is applicable to the boiler 1 generally provided with the burner apparatus 2 which selectively injects at least one of liquid fuel and gaseous fuel. For example, the present invention can be applied to a marine boiler, a power generation boiler, and the like, but is preferably applied to a marine boiler. Marine boilers are compact, have a high furnace load, and have a large amount of NOx emissions due to space limitations. Therefore, by applying the embodiment of the present invention, it is possible to reduce the NOx without adopting a two-stage combustion furnace, or without newly installing a denitration facility, and even for a marine boiler having a limited installation space. Is suitable.

In particular, the boiler according to the embodiment of the present invention is preferably mounted on an LNG ship. An LNG ship often employs an oil / gas burner so that boil-off gas generated from the LNG tank and inexpensive heavy oil can be burned. Conventionally, the gas fuel injection port is stopped at the time of heavy oil combustion, but by using the boiler according to the embodiment of the present invention, an inert gas such as nitrogen gas is supplied to the gas fuel injection port, and the base part of the oil flame By mixing an inert gas into the gas, low NOx combustion is possible.
Further, the embodiment of the present invention can be effectively used not only as a normal operation in a marine boiler, but also as a means for suppressing a temporary NOx peak during port operation or overload operation.
Furthermore, since the embodiment of the present invention can be easily attached to the existing boiler, it is also effective for remodeling the existing boiler for the purpose of low NOx.

DESCRIPTION OF SYMBOLS 1 Marine boiler 2 Burner apparatus 4 Furnace 5 Combustion gas passage 10 Low NOx combustion apparatus 11, 17 Inert gas supply line 12, 18 1st valve (inert gas flow control valve)
13 Oil fuel supply line 14 Second valve (Oil fuel flow control valve)
15 Gas fuel supply line 16 Third valve (Gas fuel flow adjustment valve)
20 Oil fuel injection port 22 Oil fuel supply pipe 23 Combustion gas injection port 24 Gas fuel supply pipe 26 Air passage 50 Control device 51 NOx detection means 52 Flame detection means

Claims (9)

In a low NOx combustion apparatus for a boiler having a furnace that generates combustion gas and a combustion gas passage that is connected to the furnace and through which the combustion gas flows,
A burner device provided in the furnace and having a liquid fuel injection port for injecting liquid fuel and a gaseous fuel supply injection port for injecting gaseous fuel;
An inert gas supply means for supplying an inert gas to at least one of the gaseous fuel injection port and the liquid fuel injection port of the burner device;
An inert gas supply amount adjusting means provided in the inert gas supply means for adjusting the supply amount of the inert gas;
NOx detection means provided in the combustion gas passage for detecting the amount of NOx contained in the combustion gas;
Flame detection means for detecting the state of the flame formed by the burner device;
And a control means for controlling the inert gas supply amount adjusting means based on a NOx amount detected by the NOx detecting means and a flame state detected by the flame detecting means. NOx combustion device.   The low NOx combustion apparatus for a boiler according to claim 1, wherein the inert gas supply means supplies the inert gas to the gaseous fuel injection port.   The low NOx combustion apparatus for a boiler according to claim 1, wherein the inert gas supply means supplies the inert gas to the liquid fuel injection port.   When the NOx amount detected by the NOx detecting means is greater than or equal to a preset threshold value and the flame state detected by the flame detecting means is stable, the control means The low NOx combustion apparatus for a boiler according to any one of claims 1 to 3, wherein the inert gas supply amount adjusting means is controlled to supply the boiler. A boiler having a furnace, a burner device provided in the furnace, having a liquid fuel injection port for injecting liquid fuel and a gas fuel injection port for injecting gaseous fuel, and a combustion gas passage connected to the furnace In the NOx combustion method,
Injecting and burning at least one of the liquid fuel and the gaseous fuel from the burner device into the furnace, and generating combustion gas;
Detecting the amount of NOx contained in the combustion gas flowing through the combustion gas passage;
Detecting a state of a flame formed by the burner device;
And a step of supplying an inert gas to at least one of the gaseous fuel injection port and the liquid fuel injection port of the burner device based on the amount of NOx and the state of the flame. Method.   6. The low NOx combustion method for a boiler according to claim 5, wherein in the step of supplying the inert gas, the inert gas is supplied to the gaseous fuel injection port.   6. The boiler low NOx combustion method according to claim 5, wherein the inert gas is supplied to the liquid fuel injection port in the step of supplying the inert gas.   The step of supplying the inert gas is characterized in that the inert gas is supplied when the amount of NOx is equal to or greater than a preset threshold value and the state of the flame is stable. The low NOx combustion method for a boiler according to any one of 5 to 7. A furnace,
A low NOx combustion device for generating combustion gas in the furnace;
A combustion gas passage connected to the furnace and through which the combustion gas flows;
A boiler provided in the combustion gas passage, and comprising a heat exchanger that generates steam by the combustion gas,
The low NOx combustion device comprises:
A burner device provided in the furnace and having a liquid fuel injection port for injecting liquid fuel and a gaseous fuel supply injection port for injecting gaseous fuel;
An inert gas supply means for supplying an inert gas to at least one of the gaseous fuel injection port and the liquid fuel injection port of the burner device;
An inert gas supply amount adjusting means provided in the inert gas supply means for adjusting the supply amount of the inert gas;
NOx detection means provided in the combustion gas passage for detecting the amount of NOx contained in the combustion gas;
Flame detection means for detecting the state of the flame formed by the burner device;
And a control means for controlling the inert gas supply amount adjusting means based on the NOx amount detected by the NOx detecting means and the flame state detected by the flame detecting means.

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