Processing system and boiler

Abstract

To provide a processing system capable of properly handling gaseous fuels. [Solution] A processing system 200 for a boiler 10 comprising a burner 21, an air supply line 26 for supplying combustion air, a gaseous fuel supply line 160 for supplying gaseous fuel to the burner 21, and a discharge line 170 for discharging gaseous fuel from the gaseous fuel supply line 160 to the outside of the system, wherein a communication line 210 connects the discharge line 170 and the intake duct 25 (air supply line 26).

Description

Technical Field

[0005]

[0001] The present disclosure relates to a processing system and a boiler.

Background Art

[0002] A boiler provided in a power generation plant such as a thermal power plant is configured to generate steam by heating and superheating boiler feed water with combustion gas. Combustion gas can be generated by burning a fuel containing, for example, pulverized fuel or gaseous fuel with a burner (Patent Document 1).

[0003] A discharge line for discharging gaseous fuel to the outside of the system as needed is connected to a fuel supply line that supplies gaseous fuel to the burner (Patent Document 2).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] Although the gaseous fuel discharged to the outside of the system (for example, the atmosphere) is a small amount, its impact on the environment is a concern. Since gaseous fuel is a flammable gas and may further have toxicity or odor, it is necessary to take measures such as installing an incinerator or a recovery device in the plant, or providing the gas discharge location at a high place to promote atmospheric diffusion.

[0006] The present disclosure has been made in view of such circumstances, and an object thereof is to provide a processing system and a boiler capable of appropriately processing gaseous fuel.

Means for Solving the Problems

[0007] To solve the above problems, the processing system and boiler disclosed herein employ the following means.

[0008] A processing system according to one aspect of the present disclosure is a processing system for a boiler comprising a burner, an air supply line for supplying combustion air, a fuel supply line for supplying gaseous fuel to the burner, and an exhaust line for discharging gaseous fuel from the fuel supply line to the outside of the system, wherein the system comprises a communication line connecting the exhaust line and the air supply line.

[0009] A boiler according to one aspect of the present disclosure comprises the processing system, the burner, the air supply line, the fuel supply line, and the discharge line. [Effects of the Invention]

[0010] According to this disclosure, it is possible to properly process gaseous fuels. [Brief explanation of the drawing]

[0011] [Figure 1] This is a schematic diagram of a boiler according to one embodiment of the present disclosure. [Figure 2] This is a schematic diagram of a processing system according to one embodiment of the present disclosure. [Figure 3] This is a diagram showing a steam system (water system) of a power plant equipped with a boiler according to one embodiment of the present disclosure. [Figure 4] This is a schematic diagram of a processing system according to one embodiment of the present disclosure (during depressurization). [Figure 5] This is a schematic diagram of a processing system according to one embodiment of the present disclosure (when leak check is completed). [Figure 6] This is a schematic diagram of a processing system according to one embodiment of the present disclosure (during the discharge of gaseous fuel between burner valves). [Modes for carrying out the invention]

[0012] Hereinafter, a processing system and a boiler according to an embodiment of the present disclosure will be described with reference to the drawings.

[0013] Note that the present disclosure is not limited by this embodiment. Also, when there are a plurality of embodiments, examples, and modifications, they may be combined and configured. Also, "up" and "above" indicate above in the vertical direction, and "down" and "below" indicate below in the vertical direction. However, the vertical direction may include errors.

[0014] [Regarding the configuration of the power generation plant] FIG. 1 is a schematic configuration diagram showing a boiler 10 included in a power generation plant 1. The boiler 10 is a facility that burns pulverized fuel obtained by pulverizing solid fuel and / or gaseous fuel with a plurality of burners 21 and generates steam (superheated steam) by heating boiler feed water or steam with the heat of the combustion gas generated by the combustion.

[0015] Examples of the solid fuel include biomass fuel and coal. Examples of the gaseous fuel include ammonia.

[0016] The boiler 10 of the present embodiment includes a furnace 11, a combustion device 20, and a combustion gas passage 12.

[0017] The furnace 11 has a hollow square column shape and is installed so as to stand along the vertical direction. The inner wall surface of the furnace 11 is constituted by a furnace wall 101. The furnace wall 101 has a plurality of heat transfer tubes and fins connecting the heat transfer tubes to each other, and is configured to recover heat by exchanging heat between the heat generated by the combustion of pulverized fuel and / or gaseous fuel and the boiler feed water or steam flowing inside each heat transfer tube. The furnace wall 101 is sometimes referred to as a "water-cooled wall".

[0018] The combustion device 20 is installed in the lower region of the furnace 11. The combustion device 20 has a plurality of burners 21A, 21B, 21C, 21D, 21E, 21F (sometimes collectively referred to as "burner 21") mounted on the furnace wall 101, and a wind box 23. The burners 21 are arranged in sets, with each set being placed at equal intervals along the circumferential direction of the furnace 11. Multiple sets of these burners are arranged in a vertical direction. In the case of Figure 1, for example, four burners 21 are placed at each corner of the rectangular furnace 11, and six sets of these burners are arranged in a vertical direction.

[0019] Note that in Figure 1, for illustrative purposes, only two of the multiple burners 21 included in one set are shown, and each set is labeled with the symbols 21A, 21B, 21C, 21D, 21E, and 21F. Furthermore, the shape of the furnace 11, the number of burner stages 21, the number of burners 21 in each stage, and the arrangement of the burners 21 are not limited to the above configuration.

[0020] Burners 21A, 21B, 21C, 21D, 21E, and 21F are connected to multiple mills 31A, 31B, 31C, 31D, 31E, and 31F (sometimes collectively referred to as "mill 31") via fine fuel supply pipes 22A, 22B, 22C, 22D, 22E, and 22F (sometimes collectively referred to as "fine fuel supply pipe 22").

[0021] As shown in Figures 1 and 2, the burners 21A, 21B, 21C, 21D, 21E, and 21F are connected to a gaseous fuel supply source (not shown) via a gaseous fuel supply line (fuel supply line) 160. As shown in Figure 2, the gaseous fuel supply line 160 includes, for example, a supply pipe 161, a ring header 162, a plurality of riser pipes 163, and a plurality of burner supply pipes 164.

[0022] The supply pipe 161 is a pipe that connects the gaseous fuel supply source to the ring header 162. In other words, the supply pipe 161 is a pipe that guides the gaseous fuel from the gaseous fuel supply source to the ring header 162. The supply pipe 161 is equipped with a shut-off valve 166 and a flow control valve 167, in order from upstream in the direction of gaseous fuel flow. The positions of the shut-off valve 166 and the flow control valve 167 can be swapped. A ring header 162 is connected to the end of the supply pipe 161.

[0023] The ring header 162 is a piping system that connects the supply pipe 161 to multiple riser pipes 163. In other words, the ring header 162 is a piping system for guiding gaseous fuel from the supply pipe 161 to each of the riser pipes 163. The ring header 162 is, for example, an endless ring-shaped pipe surrounding the furnace 11. This equalizes the pressure of the gaseous fuel supplied to each riser pipe 163. Multiple predetermined locations on the ring header 162 are connected to a single riser pipe 163. These predetermined locations correspond to each corner of the furnace 11 (where the burner 21 is installed).

[0024] Each riser pipe 163 is a pipe that connects the ring header 162 to a plurality of burner supply pipes 164. In other words, each riser pipe 163 is a pipe that guides gaseous fuel from the ring header 162 to each burner supply pipe 164. Each riser pipe 163 is, for example, a pipe extending upward from a predetermined location on the ring header 162. Multiple burner supply pipes 164 are connected to each riser pipe 163. Note that Figure 2 shows a riser pipe 163 connected to one burner supply pipe 164 connected to burner 21A, and the burner supply pipes 164 connected to the other burners 21B, 21C, 21D, 21E, and 21F are omitted.

[0025] Each burner supply pipe 164 is a pipe that connects the riser pipe 163 to the burner 21. In other words, each burner supply pipe 164 is a pipe that guides gaseous fuel from the riser pipe 163 to the burner 21. Each burner supply pipe 164 is equipped with a first burner valve (burner valve) 168 and a second burner valve (burner valve) 169, in order from upstream in the direction of gaseous fuel flow.

[0026] Furthermore, a second discharge pipe 172 (bleed line) equipped with a bleed valve 176 is connected to the burner supply pipe 164 between the first burner valve 168 and the second burner valve 169. This constitutes a double block and bleed system.

[0027] The boiler 10 is equipped with a discharge line 170. The discharge line 170 is a line for discharging gaseous fuel from the gaseous fuel supply line 160 to the outside of the system (outside the boiler 10). The discharge line 170 is used, for example, to divert some or all of the gaseous fuel flowing through the gaseous fuel supply line 160 to a location other than the boiler 10 (specifically, the burner 21). Examples of locations other than the boiler 10 include outside the system and the communication line 210. Further details will be described later.

[0028] The discharge line 170 includes, for example, a plurality of first discharge pipes 171, a plurality of second discharge pipes 172, and a discharge header pipe 173.

[0029] Each first discharge pipe 171 is a pipe that connects multiple riser pipes 163 to the discharge header pipe 173. In other words, each first discharge pipe 171 is a pipe that guides gaseous fuel from each riser pipe 163 to the discharge header pipe 173. Each first discharge pipe 171 is provided with a depressurization valve 175. The depressurization valve 175 is, for example, an ON-OFF valve.

[0030] Furthermore, as shown in Figure 2, in a configuration where the riser pipe 163 included in the gaseous fuel supply line 160 is directly connected to the discharge header pipe 173, the portion of the riser pipe 163 from the connection point of the burner supply pipe 164, which is located furthest downstream in the gaseous fuel flow direction, to the discharge header pipe 173 becomes the first discharge pipe 171.

[0031] Each second discharge pipe 172 is a pipe that connects the burner supply pipe 164 between the first burner valve 168 and the second burner valve 169 to the discharge header pipe 173. In other words, each second discharge pipe 172 is a pipe that guides gaseous fuel from the burner supply pipe 164 between the first burner valve 168 and the second burner valve 169 to the discharge header pipe 173. Each second discharge pipe 172 is provided with a bleed valve 176. The bleed valve 176 is, for example, an ON-OFF valve.

[0032] The discharge header pipe 173 is a pipe for collecting gaseous fuels led from each first discharge pipe 171 and / or each second discharge pipe 172 and guiding them to the outside of the system or to the communication line 210. The discharge header pipe 173 is equipped with a discharge valve 177. The discharge valve 177 is, for example, an ON-OFF valve. The discharge valve 177 is located downstream of the connection point of the first discharge pipe 171, which is the furthest downstream in the gaseous fuel flow direction.

[0033] Each burner 21 is supplied with pulverized fuel and / or gaseous fuel. In other words, each burner 21 is a device capable of exclusively burning pulverized fuel, exclusively burning gaseous fuel, or co-burning pulverized fuel and gaseous fuel. Furthermore, each burner 21 may be configured such that a burner for pulverized fuel and a burner for gaseous fuel are installed separately.

[0034] As shown in Figure 1, the mill 31 is a vertical roller mill configured such that, for example, a grinding table (not shown) is supported inside so as to be rotatable, and a plurality of grinding rollers (not shown) are supported above the grinding table so as to be rotatable in conjunction with the rotation of the grinding table. The solid fuel, crushed by the workings of the crushing rollers and the crushing table, is transported to the mill 31 by primary air (conveying gas, oxidizing gas) supplied to the mill 31 to a classifier (not shown) provided in the mill 31. In the classifier, the fuel is classified into fine pulverized fuel with a particle size suitable for combustion in the burner 21 and coarse pulverized fuel with a particle size larger than that. The fine pulverized fuel passes through the classifier and is supplied to the burner 21 via the fine pulverized fuel supply pipe 22 along with primary air. The coarse pulverized fuel that does not pass through the classifier falls onto the grinding table inside the mill 31 by its own weight and is ground again.

[0035] Outside the furnace 11 at the mounting position of the burner 21, a wind box 23 is provided, and one end of an air duct 24 is connected to this wind box 23. A forced draft fan (FDF) is provided at the other end of the air duct 24. The other end of the air duct 24 is connected to the outlet of the forced draft fan 32. On the other hand, a suction duct 25 is connected to the intake of the forced draft fan 32, and is configured to draw in air from the outside. In this embodiment, the air duct 24 and the suction duct 25 are considered as a series of lines (air supply line 26). In other words, the forced draft fan 32 is provided in the air supply line 26, the air supply line 26 upstream of the forced draft fan 32 is the suction duct 25, and the air supply line 26 downstream of the forced draft fan 32 is the air duct 24. The air supplied from the forced draft fan 32 is heated in an air preheater 42 installed in the air duct 24 (details will be described later), and then supplied to the boiler 10 as secondary air (combustion air, oxidizing gas) via the wind box 23 and burner 21, and introduced into the furnace 11.

[0036] Above the mounting position of the burner 21, a number of additional air ports (AA ports) 25 are provided to supply additional combustion air (AA) into the furnace 11. The end of an additional air duct (AA duct) 28, which branches off from the air duct 24, is connected to the additional air port 27, and a portion of the combustion air supplied from the forced draft fan 32 can be supplied to the additional air port 27 as additional combustion air via the additional air duct 28. In this embodiment, the additional air duct 28 is also considered to be part of the air supply line 26, in addition to the air duct 24 and the intake duct 25. In other words, the air supply line 26 is a line for guiding secondary air (including additional combustion air) to the boiler 10 (inside the furnace 11), and includes the air duct 24, the intake duct 25, and the additional air duct 28.

[0037] The combustion gas passage 12 is connected to the vertical upper part of the furnace 11. The combustion gas passage 12 is equipped with superheaters 102A, 102B, 102C (sometimes collectively referred to as "superheater 102"), reheaters 103A, 103B (sometimes collectively referred to as "reheater 103"), and an economizer 104 as heat exchangers for recovering heat from the combustion gas. Heat exchange takes place between the combustion gas generated in the furnace 11 and the boiler feedwater or steam flowing inside each heat exchanger. Note that the number, arrangement, and shape of each heat exchanger are not limited to the configuration shown in Figure 1.

[0038] Downstream of the combustion gas passage 12, a flue 13 is connected to which the combustion gas from which heat has been recovered in each heat exchanger is discharged. The flue 13 is equipped with an air preheater 42 (air heater), which is configured to exchange heat between the air flowing through the air duct 24 and the combustion gas flowing through the flue 13. The air preheater 42 heats the secondary air supplied to the burner 21 and the additional air port 27, thereby allowing for further heat recovery from the combustion gas after heat exchange with the boiler feedwater or steam.

[0039] Furthermore, a denitrification device 43 may be provided in the flue 13 at a position upstream of the air preheater 42. The denitrification device 43 supplies a reducing agent, such as ammonia or urea solution, which has the effect of reducing nitrogen oxides, to the combustion gas flowing through the flue 13. The reaction between the nitrogen oxides (NOx) in the combustion gas to which the reducing agent has been supplied is promoted by the catalytic action of a denitrification catalyst installed in the denitrification device 43, thereby removing and reducing nitrogen oxides in the combustion gas.

[0040] A gas duct 41 is connected to the flue 13 downstream of the air preheater 42. The gas duct 41 is equipped with dust collection devices 44 such as an electrostatic precipitator to remove ash and other particles from the combustion gas, environmental devices such as a desulfurization device 46 to remove sulfur oxides, and an induced draft fan (IDF) 45 to guide the exhaust gas to these environmental devices. The downstream end of the gas duct 41 is connected to a chimney 47, and the combustion gas treated by the environmental devices is discharged outside the system as exhaust gas.

[0041] In the boiler 10, when multiple mills 31 are driven, the crushed and classified pulverized fuel is supplied to the burner 21 via the pulverized fuel supply pipe 22 along with primary air. Secondary air heated by the air preheater 42 is also supplied to the burner 21 via the air duct 24 and wind box 23. Furthermore, when exclusively burning gaseous fuel or co-firing pulverized fuel and gaseous fuel is performed, the gaseous fuel is supplied to the burner 21 via the gaseous fuel supply line 160.

[0042] Burner 21 injects a mixture of pulverized fuel and primary air into the furnace 11, along with secondary air. In addition, when burning only gaseous fuel or when burning a mixture of pulverized fuel and gaseous fuel, burner 21 injects the gaseous fuel into the furnace 11. The fine fuel mixture and / or gaseous fuel blown into the furnace 11 is ignited and reacts with secondary air to form a flame. In the lower region of the furnace 11, flames are formed, and high-temperature combustion gases rise inside the furnace 11 and flow into the combustion gas passage 12. In this embodiment, air is used as the oxidizing gas (primary air, secondary air), but a gas with a higher or lower oxygen content than air may also be used. By adjusting the ratio of oxygen to the supplied fuel to an appropriate range, stable combustion can be achieved in the furnace 11.

[0043] The combustion gas flowing into the combustion gas passage 12 undergoes heat exchange with water and steam in the superheater 102, reheater 103, and economizer 104 located inside the combustion gas passage 12, before being discharged into the flue 13. There, nitrogen oxides are removed in the denitrification device 43, and heat exchange is performed with primary and secondary air in the air preheater 42. After further discharge into the gas duct 41, ash and other contaminants are removed in the dust collector 44, and sulfur oxides are removed in the desulfurization device 46 before being discharged out of the system through the chimney 47. Furthermore, the arrangement of each heat exchanger in the combustion gas passage 12 and each device in the flue 13 to the gas duct 41 does not necessarily have to be in the order described above with respect to the combustion gas flow.

[0044] Next, we will describe in detail the superheater 102, reheater 103, and economizer 104, which are installed in the combustion gas passage 12 as heat exchangers. Figure 3 is a diagram showing the steam system (water system) of the power plant 1. Note that Figure 1 does not accurately show the positions of each heat exchanger (superheaters 102A, 102B, 102C, reheaters 103A, 103B, economizer 104) within the combustion gas passage 12, and the arrangement order of each heat exchanger relative to the combustion gas flow is not limited to that shown in Figure 1.

[0045] As shown in Figure 3, the power plant 1 comprises heat exchangers installed in the boiler 10, a steam turbine 111 that is rotationally driven by the steam generated in the boiler 10, and a generator 113 connected to the steam turbine 111 that generates electricity using the rotational force of the steam turbine 111.

[0046] The steam turbine 111 includes, for example, a high-pressure turbine 111A, an intermediate-pressure turbine 111B, and a low-pressure turbine 111C. The steam heated in the superheater 102 of the boiler 10 rotates the high-pressure turbine 111A. The steam that has passed through the high-pressure turbine 111A is reheated in the reheater 103 of the boiler 10 and rotates the intermediate-pressure turbine 111B. The steam that has passed through the intermediate-pressure turbine 111B drives the low-pressure turbine 111C to rotate.

[0047] A condenser 112 is connected to the low-pressure turbine 111C, and the steam that rotates the low-pressure turbine 111C condenses in the condenser 112 through heat exchange with cooling water (for example, seawater, river water, or the returned heating feedwater described later) to become condensate (boiler feedwater). The condenser 112 is connected to the economizer 104 via the boiler feedwater line L1.

[0048] The boiler feedwater line L1 is equipped with, for example, a condensate pump 121 (CP), a low-pressure feedwater heater 122, a boiler feedwater pump 123 (BFP), and a high-pressure feedwater heater 124. The low-pressure feedwater heater 122 and the high-pressure feedwater heater 124 are devices that heat the boiler feedwater supplied to the economizer 104.

[0049] For example, if boiler 10 is a once-through boiler, the economizer 104 is connected to the heat transfer tubes that make up the furnace wall 101. The boiler feedwater, heated in the economizer 104 via the boiler feedwater line L1, is heated by radiation from the flames in the furnace 11 as it passes through the heat transfer tubes that make up the furnace wall 101, and is then guided to the steam-water separator 125. The steam separated in the steam separator 125 is supplied to the superheater 102. Meanwhile, the drain water separated in the steam separator 125 flows into the steam separator drain tank 126 and is led to the condenser 112 via the drain water line L2.

[0050] Furthermore, during startup or low-load operation of a once-through boiler, the boiler feedwater supplied from the economizer 104 may not evaporate completely as it passes through the heat transfer tubes constituting the furnace wall 101, resulting in an operating condition (wet operation condition) where water remains in the steam-water separator 125. In this wet operation condition, the drain water separated in the steam-water separator 125 and guided to the steam-water separator drain tank 126 may be recirculated and supplied from the economizer 104 to the heat transfer tubes constituting the furnace wall 101 by using the boiler circulation pump 127 (BCP) to merge it into the middle of the boiler feedwater line L1 via the circulation line L7.

[0051] As the combustion gas flows through the combustion gas passage 12, heat is recovered from the combustion gas in the superheater 102, reheater 103, and economizer 104. Meanwhile, the boiler feedwater supplied from the boiler feedwater pump 123 (BFP) is preheated in the economizer 104, then heated to steam as it passes through the heat transfer tubes that make up the furnace wall 101, and is led to the steam-water separator 125. The steam separated in the steam-water separator 125 is introduced into the first superheater 102A, the second superheater 102B, and the third superheater 102C, where it is superheated by the combustion gas. The superheated steam generated in the superheater 102 is supplied to the high-pressure turbine 111A via the steam line L3, which rotates the high-pressure turbine 111A. The steam discharged from the high-pressure turbine 111A is introduced into the first reheater 103A and the second reheater 103B via the steam line L4 and reheated. The steam reheated in each reheater is supplied to the intermediate-pressure turbine 111B via the steam line L5, which drives the intermediate-pressure turbine 111B to rotate. The steam discharged from the intermediate-pressure turbine 111B is supplied to the low-pressure turbine 111C via the steam line L6, and drives the low-pressure turbine 111C to rotate. The rotating shaft of the steam turbine 111 rotates the generator 113 to generate electricity. The steam discharged from the low-pressure turbine 111C is cooled in the condenser 112 to become condensate, which is then sent to the economizer 104 as boiler feedwater via the boiler feedwater line L1.

[0052] [About the processing system] The processing system 200 is a system that can guide gaseous fuel from the discharge header pipe 173 of the discharge line 170 to the air supply line 26. The processing system 200 is equipped with a communication line 210.

[0053] The communication line 210 is a pipe that connects the discharge header pipe 173 and the air supply line 26. In other words, the communication line 210 is a pipe that guides gaseous fuel (gaseous fuel flowing through the discharge header pipe 173) from the discharge header pipe 173 to the air supply line 26. A communication valve 214 is provided in the communication line 210. The communication valve 214 is, for example, an ON-OFF valve.

[0054] The starting end of the communication line 210 is connected to the discharge header pipe 173, which is located between the connection point of the first discharge pipe 171, which is the furthest downstream in the gaseous fuel flow direction, and the discharge valve 177.

[0055] On the other hand, the end of the communication line 210 is connected to the air supply line 26. As mentioned above, within the internal flow path of the air supply line 26, a flow of secondary air (including additional combustion air) toward the boiler 10 is formed by the forced draft fan 32. Therefore, when the end of the communication line 210 is connected to the air supply line 26, gaseous fuel is drawn into the air supply line 26 via the communication line 210. The gaseous fuel drawn into the air supply line 26 is supplied along with secondary air to the burner 21 (where combustion of pulverized fuel and / or gaseous fuel takes place) and the additional air port 27, and is incinerated in the boiler 10.

[0056] From the viewpoint of efficiently drawing in gaseous fuel, it is preferable that the communication line 210 is connected to the air supply line 26 (i.e., the suction duct 25) upstream of the forced draft fan 32 in the direction of secondary airflow. This is because the flow path formed inside the suction duct 25 becomes a negative pressure region.

[0057] The processing system 200 is further equipped with a gas detector 251. The gas detector 251 is a device that measures the concentration of gaseous fuels. The gas detector 251 is installed at a location where it can measure the concentration of gaseous fuel present inside the air supply line 26 (the region downstream of the connection point with the communication line 210). In this embodiment, the gas detector 251 is configured to measure the concentration of gaseous fuel present inside the suction duct 25.

[0058] The processing system 200 further includes a control unit 250. The control unit 250 is configured to communicate with each valve and instrument (such as the gas detector 251), and can control each valve.

[0059] [Regarding the flow of gaseous fuels] The flow of gaseous fuels will be explained by dividing it into several cases.

[0060] <During normal operation> As shown in Figure 2, during normal operation of the boiler 10, gaseous fuel is supplied to at least one burner 21 via the gaseous fuel supply line 160.

[0061] In this context, "normal operation" means a state in which gaseous fuel is being supplied to at least one burner 21.

[0062] During normal operation, the shut-off valve 166, the first burner valve 168, and the second burner valve 169 are in the open state. In addition, the depressurization valve 175, the bleed valve 176, the discharge valve 177, and the communication valve 214 are in the closed state. As a result, all gaseous fuel is supplied to at least one burner 21. At this time, the gaseous fuel is not released outside the system and is not introduced into the air supply line 26.

[0063] <When introducing gaseous fuel into an air supply line> When the boiler 10 is operating in a state where gaseous fuel can be introduced into the furnace 11, the gaseous fuel may be guided from the gaseous fuel supply line 160 to the air supply line 26. This allows the gaseous fuel, which would conventionally be discharged outside the system, to be incinerated in the boiler 10. In this context, "the operating state of the boiler 10 being in a state where gaseous fuel can be introduced into the furnace 11" means, for example, that some fuel is being supplied to one of the burners 21 and combustion is taking place, and that the boiler 10 is not in a total combustion shutoff state (MFT; Master Fuel Trip). Examples of cases in which gaseous fuel is introduced from the gaseous fuel supply line 160 to the air supply line 26 include the following: <<Depressurization after extinguishing a gaseous fuel fire>> As shown in Figure 4, during depressurization after extinguishing the gaseous fuel, the gaseous fuel is guided from the gaseous fuel supply line 160 to the air supply line 26 via the discharge line 170 and the communication line 210.

[0064] In this context, "depressurization after extinguishing gaseous fuel" refers to the process of discharging the gaseous fuel that was filled in the gaseous fuel supply line 160 downstream of the shut-off valve 166 after the combustion of gaseous fuel in all burners 21 has ended and the supply of gaseous fuel has been stopped (i.e., after the shut-off valve 166 has been closed). By depressurizing, leakage of gaseous fuel from the gaseous fuel supply line 160 is prevented.

[0065] During depressurization, the shut-off valve 166 is closed. The first burner valve 168 and the second burner valve 169 are also closed. The depressurization valve 175 is open. The bleed valve 176 and the discharge valve 177 are closed. The communication valve 214 is open. As a result, the gaseous fuel is guided from the gaseous fuel supply line 160 to the air supply line 26 (suction duct 25) via the discharge line 170 (part of the first discharge pipe 171 and discharge header pipe 173) and the communication line 210. As mentioned above, the gaseous fuel guided to the air supply line 26 is incinerated in the boiler 10 (it can be incinerated because combustion of other fuels is continuing).

[0066] <<Depressurization after leak check is complete>> As shown in Figure 5, after the leak check is completed, the gaseous fuel is guided from the gaseous fuel supply line 160 to the air supply line 26 via the discharge line 170 and the communication line 210.

[0067] In this context, "leak check" refers to the process of filling the gaseous fuel supply line 160 from the shut-off valve 166 to the first burner valve 168 with gaseous fuel before starting combustion of the gaseous fuel in the burner 21 (before igniting the burner 21) to confirm that there is no leakage of gaseous fuel. Specifically, the procedure is carried out in the following manner. First, the first burner valve 168 and the second burner valve 169 are closed, then the shut-off valve 166 is opened, and the flow control valve 167 is opened to a specified degree. Once the gaseous fuel supply line 160 from the shut-off valve 166 to the first burner valve 168 is filled with gaseous fuel, the shut-off valve 166 is closed. At this time, the pressure of the filled gaseous fuel (leak check pressure) is set to be approximately the same as the maximum pressure that can be expected during normal operation of the boiler 10. This is greater than the pressure when igniting the burner 21.

[0068] If the burner 21 is ignited while maintaining the leak check pressure after the leak check is complete, an excessive amount of gaseous fuel may be supplied to the burner 21, potentially causing ignition failure or an abnormal increase in pressure inside the furnace 11. Therefore, after the leak check is completed and before ignition, a portion of the gaseous fuel that was filled in the gaseous fuel supply line 160 from the shut-off valve 166 to the first burner valve 168 is guided to the air supply line 26 (suction duct 25), thereby reducing the pressure of the gaseous fuel from the leak check pressure to a pressure suitable for ignition.

[0069] During the period between the completion of the leak check and the ignition of burner 21, the shut-off valve 166 is in the closed state. Also, the first burner valve 168 and the second burner valve 169 are in the closed state. The depressurization valve 175 is in the open state. Also, the bleed valve 176 and the discharge valve 177 are in the closed state. Also, the communication valve 214 is in the open state. As a result, the gaseous fuel is guided from the gaseous fuel supply line 160 to the air supply line 26 (suction duct 25) via the discharge line 170 (first discharge pipe 171, part of the discharge header pipe 173) and the communication line 210. As mentioned above, the gaseous fuel guided to the air supply line 26 is incinerated in the boiler 10.

[0070] <<Discharge of gaseous fuel between burner valves>> As shown in Figure 6, when gaseous fuel is discharged between burner valves 168 and 169, the gaseous fuel is guided from the gaseous fuel supply line 160 to the air supply line 26 via the discharge line 170 and the communication line 210.

[0071] In this context, "discharge of gaseous fuel between burner valves 168 and 169" refers to the operation of discharging the gaseous fuel that was filled in the gaseous fuel supply line 160 (burner supply pipe 164) between the first burner valve 168 and the second burner valve 169 after the combustion of gaseous fuel in the designated burner 21 has been terminated and the supply of gaseous fuel has been stopped. By discharging the gaseous fuel between burner valves 168 and 169, a fuel-free space is created in the burner supply pipe 164, preventing gaseous fuel from leaking into the furnace 11.

[0072] When gaseous fuel is discharged between burner valves 168 and 169, the first burner valve 168 and the second burner valve 169 are closed. The depressurization valve 175 is also closed. The bleed valve 176 is open. The discharge valve 177 is closed. The communication valve 214 is open. The shut-off valve 166 is opened or closed as appropriate depending on the operating status of the other burners 21. For example, it is opened when the combustion of gaseous fuel continues in the other burners 21. As a result, the gaseous fuel is guided from the gaseous fuel supply line 160 to the air supply line 26 (suction duct 25) via the discharge line 170 (second discharge pipe 172, part of the discharge header pipe 173) and the communication line 210. As mentioned above, the gaseous fuel guided to the air supply line 26 is incinerated in the boiler 10.

[0073] In this case, the term "burner" includes an ignition burner installed for the purpose of igniting the main burner. Furthermore, the first burner valve 168, the second burner valve 169, and the bleed valve 176 may be configured as a single unit and operate in conjunction with each other (a coupled valve).

[0074] <If gaseous fuel is not supplied to the air duct> During depressurization, after leak checks are completed, and when discharging gaseous fuel between burner valves, the gaseous fuel was to be guided from the gaseous fuel supply line 160 to the air supply line 26. However, if it is not possible to introduce gaseous fuel into the reactor, the gaseous fuel is not to be guided from the gaseous fuel supply line 160 to the air supply line 26. Examples of situations in which gaseous fuel cannot be introduced into the reactor include the following:

[0075] <<When the concentration of gaseous fuel exceeds a predetermined value>> If the concentration of gaseous fuel in the air supply line 26 (the portion downstream of the connection point with the communication line 210) increases and approaches the lower explosive limit concentration, no further gaseous fuel should be introduced into the air supply line 26. This is because the risk of explosion increases. Therefore, to eliminate the risk of explosion, if the concentration of gaseous fuel present in the air supply line 26 exceeds a predetermined value (threshold), the communication valve 214 provided in the communication line 210 is closed to prevent gaseous fuel from being introduced into the air supply line 26.

[0076] The concentration of the gaseous fuel is continuously measured by the gas detector 251. Furthermore, the predetermined value (threshold) is set to a value less than the lower explosive limit concentration of the gaseous fuel (for example, about 1 / 10 of the lower explosive limit concentration).

[0077] <<When all fuel is shut off>> As mentioned above, when boiler 10 is in a state of complete fuel shutoff, gaseous fuel cannot be supplied to burner 21. Therefore, in the event that the boiler 10 is completely shut off of fuel, the communication valve 214 provided in the communication line 210 is closed to prevent gaseous fuel from being supplied to the air supply line 26.

[0078] <<In case of malfunction of the forced-air ventilator>> If a malfunction occurs in the forced-air fan 32, the necessary and sufficient secondary air may not flow (the flow rate may not be secured), which may cause gaseous fuel to accumulate in the air supply line 26 or prevent the gaseous fuel from being properly supplied to the burner 21. Therefore, if an abnormality occurs in the forced-air fan 32, the communication valve 214 provided in the communication line 210 is closed to prevent gaseous fuel from being introduced into the air supply line 26. Here, an abnormality in the forced-air fan 32 refers to a condition in which sufficient negative pressure cannot be secured in the suction duct 25 due to, for example, a decrease in output due to a malfunction (including stopping due to a malfunction).

[0079] <<When the shut-off valve is open>> If the shut-off valve 166 is open and a malfunction occurs in the control of the flow control valve 167, an excessive amount of gaseous fuel may be supplied to the gaseous fuel supply line 160. In this case, if the gaseous fuel is introduced into the air supply line 26, the concentration of gaseous fuel present in the air supply line 26 may exceed a predetermined value. Therefore, when the shut-off valve 166 is open, the communication valve 214 provided in the communication line 210 is closed to prevent gaseous fuel from being introduced into the air supply line 26. However, when gaseous fuel is discharged between burner valves 168 and 169, if there is another burner 21 that is continuing to burn gaseous fuel, the shut-off valve 166 is opened in order to supply gaseous fuel to that burner 21.

[0080] Conversely, if the shut-off valve 166 is closed, no new gaseous fuel will be supplied to the gaseous fuel supply line 160. In this case, the communication valve 214 provided in the communication line 210 may be opened to allow gaseous fuel to be guided to the air supply line 26. In this case, the purpose of introducing the gaseous fuel into the air supply line 26 is, for example, to discharge and incinerate the gaseous fuel filled in at least one part of the gaseous fuel supply line 160 (see the example above for "Introducing gaseous fuel into the air supply line").

[0081] [Regarding ammonia as a gaseous fuel] Ammonia (ammonia gas) is an odorous gas, and depending on the amount emitted, it may not be possible to disperse it into the atmosphere. Therefore, as in this embodiment, the gaseous fuel can be properly treated by incinerating it in the boiler 10 in predetermined cases.

[0082] Furthermore, since ammonia gas has a higher lower limit of its explosive range than other gases (e.g., hydrogen (H2), methane (CH4), propane (C3H8), etc.), a relatively large amount can be incinerated in boiler 10.

[0083] Furthermore, ammonia gas is low-flammability and is often intended for co-combustion with other fuels (for example, solid fuels such as biomass or coal) (i.e., boiler 10 is a co-combustion boiler, and ammonia gas as a gaseous fuel is an auxiliary fuel). Therefore, even when starting or ending use of the gaseous fuel, burner 21 is often burning other fuels, and even if the gaseous fuel is guided from the gaseous fuel supply line 160 to the air supply line 26, the gaseous fuel can be incinerated in boiler 10.

[0084] [Differentiation] The gaseous fuel is not limited to ammonia; for example, it could be natural gas or petroleum gas. Furthermore, this embodiment is particularly effective when the gaseous fuel is an odorous or toxic gas. Examples of odorous or toxic gases include CO (carbon monoxide), COG (coke oven gas), BFG (blast furnace gas), and waste decomposition gases (such as methane gas generated from garbage and livestock manure).

[0085] [effect] This embodiment provides the following effects.

[0086] Since the system is equipped with a communication line 210 that connects the discharge line 170 and the air supply line 26, gaseous fuel that is heading out of the system via the discharge line 170 can be guided to the air supply line 26 without being discharged out of the system. This allows gaseous fuel, which was previously discharged outside the system, to be incinerated in the boiler 10.

[0087] Since the communication line 210 connects the discharge line 170 to the portion of the air supply line 26 (suction duct 25) that is upstream of the forced draft fan 32 in the direction of combustion air flow, gaseous fuel can be efficiently guided to the air supply line 26.

[0088] The control unit 250 opens the communication valve 214 when the shut-off valve 166 is closed, so that when gaseous fuel filled in at least one part of the gaseous fuel supply line 160 is discharged, the discharged gaseous fuel can be guided to the air supply line 26.

[0089] The control unit 250 opens the communication valve 214 when combustion with gaseous fuel is not occurring in all burners 21, the shut-off valve 166 is closed, and all burner valves 168 are closed. This allows the gaseous fuel that has been filled into the gaseous fuel supply line 160 downstream of the shut-off valve 166 to be discharged for depressurization to be guided to the air supply line 26. Furthermore, when the gaseous fuel supplied to the gaseous fuel supply line 160 from the shut-off valve 166 to the burner valve 168 is discharged for leak checking, the discharged gaseous fuel can be guided to the air supply line 26.

[0090] The control unit 250 opens the communication valve 214 when combustion with gaseous fuel does not occur in a predetermined burner 21 and the two burner valves 168 and 169 corresponding to the predetermined burner 21 are closed. Therefore, when the gaseous fuel filled in the gaseous fuel supply line 160 between the two burner valves 168 and 169 is discharged to create a space in the fuel supply line where gaseous fuel is not present, the discharged gaseous fuel can be guided to the air supply line 26.

[0091] The control unit 250 closes the communication valve 214 when the concentration of gaseous fuel present in the air supply line 26 exceeds a predetermined value, thereby shutting off the supply of gaseous fuel to the air supply line 26 before the concentration of gaseous fuel in the combustion air flowing through the air supply line 26 reaches the lower explosive limit. This can reduce the risk of explosion.

[0092] The control unit 250 closes the communication valve 214 when the boiler 10 is in a completely fuel-shut-off state, so that when the boiler 10 is in a completely fuel-shut-off state, the gaseous fuel supplied to the air supply line 26 can be shut off.

[0093] The control unit 250 closes the communication valve 214 when it detects an abnormality in the forced draft fan 32. Therefore, in situations where gaseous fuel may not be properly supplied to the burner 21 via the air supply line 26, the gaseous fuel supplied to the air supply line 26 can be shut off.

[0094] The control unit 250 closes the communication valve 214 when the shut-off valve 166 is open. Therefore, even if a malfunction occurs in the control of the flow control valve 167 located downstream of the shut-off valve 166, gaseous fuel will not be supplied to the air supply line 26.

[0095] [Note] The processing system and boiler according to this embodiment, as described above, can be understood, for example, as follows.

[0096] A processing system (200) according to a first aspect of the present disclosure is a processing system (200) for a boiler (10) comprising: a burner (21); an air supply line (26) for supplying combustion air to the burner (21); a fuel supply line (160) for supplying gaseous fuel to the burner (21); and an exhaust line (170) for discharging gaseous fuel from the fuel supply line (160) to the outside of the system, wherein the system comprises a communication line (210) connecting the exhaust line (170) and the air supply line (26).

[0097] Since the system is equipped with a communication line (210) that connects the discharge line (170) and the air supply line (26), gaseous fuel that is heading out of the system via the discharge line (170) can be guided to the air supply line (26) without being discharged out of the system. This allows gaseous fuel, which was previously discharged outside the system, to be incinerated in the boiler (10).

[0098] In the processing system (200) according to a second aspect of the present disclosure, in the first aspect, the air supply line (26) is provided with a push fan (32) that generates a flow of combustion air toward the boiler (10), and the communication line (210) connects the discharge line (170) with a portion of the air supply line (26) that is upstream of the push fan (32) in the direction of the combustion air flow.

[0099] The communication line (210) connects the discharge line (170) to the portion of the air supply line (26) that is upstream of the forced-air fan (32) in the direction of combustion air flow, thereby enabling efficient guidance of gaseous fuel to the air supply line (26).

[0100] A processing system (200) according to a third aspect of the present disclosure, in the first or second aspect, comprises a control unit (250), a communication line (210) is provided with a communication valve (214), and a fuel supply line (160) is provided with a shut-off valve (166). The control unit (250) opens the communication valve (214) when the shut-off valve (166) is closed.

[0101] The control unit (250) opens the communication valve (214) when the shut-off valve (166) is closed, so that when gaseous fuel filled in at least one part of the fuel supply line (160) is discharged, the discharged gaseous fuel can be guided to the air supply line (26).

[0102] In the processing system (200) according to the fourth aspect of this disclosure, in the first or second aspect, the fuel supply line (160) is provided with a burner valve (168) located downstream of the shut-off valve (166), the discharge line (170) connects the portion of the fuel supply line (160) between the shut-off valve (166) and the burner valve (168) to the outside of the system, and the control unit (250) opens the communication valve (214) when combustion of gaseous fuel is not occurring in all of the burners (21), the shut-off valve (166) is closed, and the burner valve (168) is closed.

[0103] The control unit (250) opens the communication valve (214) when combustion with gaseous fuel is not occurring in all burners (21), the shut-off valve (166) is closed, and the burner valve (168) is also closed. This allows the gaseous fuel filled in the fuel supply line (160) downstream of the shut-off valve (166) to be discharged for depressurization, and the discharged gaseous fuel to be guided to the air supply line (26). Additionally, when the gaseous fuel filled in the fuel supply line (160) from the shut-off valve (166) to the burner valve (168) is discharged for leak checking, the discharged gaseous fuel can be guided to the air supply line (26).

[0104] In a fourth embodiment, the processing system (200) according to a fifth aspect of the present disclosure, the control unit (250) opens the communication valve (214) to discharge the gaseous fuel that was filled in the fuel supply line (160) downstream of the shut-off valve (166) after the combustion of gaseous fuel in all the burners (21) has been terminated.

[0105] The control unit (250) opens the communication valve (214) to discharge the gaseous fuel that was filled in the fuel supply line (160) downstream of the shut-off valve (166) after the combustion of gaseous fuel in all the burners (21) has ended. Therefore, when the gaseous fuel filled in the fuel supply line (160) downstream of the shut-off valve (166) is discharged to relieve pressure, the discharged gaseous fuel can be guided to the air supply line (26).

[0106] In the processing system (200) according to the sixth aspect of the present disclosure, in the fourth aspect, the control unit (250) fills the fuel supply line (160) from the shut-off valve (166) to the burner valve (168) with gaseous fuel and confirms that there is no leakage of gaseous fuel, and then opens the communication valve (214) to discharge the gaseous fuel that had been filled in the fuel supply line (160) from the shut-off valve (166) to the burner valve (168).

[0107] The control unit (250) fills the fuel supply line (160) from the shut-off valve (166) to the burner valve (168) with gaseous fuel and confirms that there is no leakage of gaseous fuel. Then, it opens the communication valve (214) to discharge the gaseous fuel that was filled in the fuel supply line (160) from the shut-off valve (166) to the burner valve (168). When the gaseous fuel that was filled in the fuel supply line (160) from the shut-off valve (166) to the burner valve (168) is discharged for leak checking, the discharged gaseous fuel can be guided to the air supply line (26).

[0108] The control unit (250) opens the communication valve (214) when combustion with gaseous fuel is not occurring in all burners (21), the shut-off valve (166) is closed, and the burner valve (168) is also closed. This allows the gaseous fuel that has been filled into the fuel supply line (160) from the shut-off valve (166) to the burner valve (168) to be discharged for leak checking to be guided to the air supply line (26).

[0109] A processing system (200) according to a seventh aspect of the present disclosure, in the first or second aspect, comprises a control unit (250), a communication line (210) is provided with a communication valve (214), a fuel supply line (160) is provided with a shut-off valve (166), the fuel supply line (160) is provided with two burner valves (168, 169) located downstream of the shut-off valve (166), the discharge line (170) connects the portion of the fuel supply line (160) between the two burner valves (168, 169) to the outside of the system, and the control unit (250) opens the communication valve (214) when combustion of gaseous fuel is not occurring in a predetermined burner (21) and the two burner valves (168, 169) corresponding to the predetermined burner (21) are closed.

[0110] The control unit (250) opens the communication valve (214) when combustion of gaseous fuel is not occurring in a predetermined burner (21) and the two burner valves (168, 169) corresponding to the predetermined burner (21) are closed. This allows the gaseous fuel filled in the fuel supply line (160) between the two burner valves (168, 169) to be discharged in order to create a space in the fuel supply line (160) where gaseous fuel is not present, and to be guided to the air supply line (26).

[0111] A processing system (200) according to the eighth aspect of this disclosure, in the first or second aspect, comprises a gas detector (251) for measuring the concentration of gaseous fuel present in the air supply line (26), and a control unit (250), wherein a communication valve (214) is provided in the communication line (210), and the control unit (250) closes the communication valve (214) when the concentration of gaseous fuel present in the air supply line (26) exceeds a predetermined value.

[0112] The control unit (250) closes the communication valve (214) when the concentration of gaseous fuel present in the air supply line (26) exceeds a predetermined value. This allows the supply of gaseous fuel to the air supply line (26) to be shut off before the concentration of gaseous fuel in the combustion air flowing through the air supply line (26) reaches the explosion range. This reduces the risk of explosion.

[0113] A processing system (200) according to a ninth aspect of the present disclosure comprises a control unit (250) in the first or second aspect, a communication line (210) is provided with a communication valve (214), and the control unit (250) closes the communication valve (214) when the boiler is in a state of complete fuel shutoff.

[0114] The control unit (250) closes the communication valve (214) when the boiler is in a state of complete fuel shutoff, so that when the boiler is in a state of complete fuel shutoff, the gaseous fuel supplied to the air supply line (26) can be shut off.

[0115] In a second embodiment, the processing system (200) according to the tenth aspect of this disclosure includes a control unit (250), and the communication line (210) is provided with a communication valve (214). The control unit (250) closes the communication valve (214) when it detects an abnormality in the push-in fan (32).

[0116] The control unit (250) closes the communication valve (214) when it detects an abnormality in the forced-air fan (32). This allows the gaseous fuel supplied to the air supply line (26) to be shut off in situations where gaseous fuel may not be properly supplied to the burner (21) via the air supply line (26).

[0117] A processing system (200) according to an eleventh aspect of the present disclosure, in the first or second aspect, comprises a control unit (250), a communication line (210) is provided with a communication valve (214), and a fuel supply line (160) is provided with a shut-off valve (166), and the control unit (250) closes the communication valve (214) when the shut-off valve (166) is open.

[0118] The control unit (250) closes the communication valve (214) when the shut-off valve (166) is open. Therefore, even if there is a malfunction in the control of the flow control valve (167) located downstream of the shut-off valve (166), gaseous fuel will not be supplied to the air supply line (26).

[0119] A processing system (200) according to a twelfth aspect of the present disclosure, in any of the first to eleventh aspects, is a co-firing boiler in which a gaseous fuel and other fuels can be burned in the burner, wherein the gaseous fuel is an auxiliary fuel supplied to the burner only when the other fuel is burning.

[0120] In the processing system (200) according to the thirteenth aspect of this disclosure, in any of the first to eleventh aspects, the gaseous fuel is an odorous or toxic gas.

[0121] In the processing system (200) according to the 14th aspect of this disclosure, in any of the 1st to 11th aspects, the gaseous fuel is a gas containing ammonia.

[0122] A boiler (10) according to a 15th aspect of this disclosure comprises a processing system (200) described in any of the 1st to 14th aspects, a plurality of burners (21), an air supply line (26), a fuel supply line (160), and a discharge line (170). [Explanation of Symbols]

[0123] 1. Power plant 10 Boilers 11 Furnace 12 Combustion gas passage 13 Flue 20 Combustion device 21 (21A~21F) Burner 22(22A~22F) Fine fuel supply pipe 23 Wind Box 24 Air duct 25 Intake duct 26 Air supply line 27 Additional Air Ports 28 Additional Air Ducts 31 (31A~31F) Mill (Grinder) 32. Forced ventilation fan (FDF) 41 Gas duct 42 Air preheater 43 Denitration equipment 44 Dust collection device 45. Induced Draft Fan (IDF) 46 Desulfurization equipment 47 Chimney 101 Furnace wall 102 Superheater 102A 1st superheater 102B 2nd superheater 102C 3rd superheater 103 Reheater 103A 1st reheater 103B 2nd reheater 104 Economizer 111 Steam Turbine 111A High-Pressure Turbine 111B Intermediate Pressure Turbine 111C Low-Pressure Turbine 160 Gas fuel supply line (fuel supply line) 161 Supply pipe 162 Ring Header 163 Riser pipe 164 Burner supply pipe 166 Shut-off valve 167 Flow control valve 168 First burner valve (burner valve) 169 Second burner valve (burner valve) 170 Discharge Line 171 1st discharge pipe 172 2nd discharge pipe 173 Discharge Header Pipe 175 Depressurization valve 176 Bleed valve 177 Discharge valve 200 processing systems 210 Connecting Line 214 Communicating valve 250 Control Unit 251 Gas detector

Claims

1. A processing system for a boiler comprising a burner, an air supply line for supplying combustion air, a fuel supply line for supplying gaseous fuel to the burner, and a discharge line for discharging the gaseous fuel from the fuel supply line to the outside of the system, The system includes a communication line connecting the aforementioned discharge line and the aforementioned air supply line. Processing system.

2. The aforementioned air supply line is equipped with a forced-air fan that generates a flow of combustion air toward the boiler. The aforementioned communication line connects the discharge line to a portion of the air supply line that is upstream of the push fan in the direction of combustion air flow. The processing system according to claim 1.

3. Equipped with a control unit, A communication valve is provided in the aforementioned communication line. The fuel supply line is equipped with a shut-off valve. The control unit opens the communication valve when the shut-off valve is closed. The processing system according to claim 1.

4. The fuel supply line is provided with a burner valve located downstream of the shut-off valve. The aforementioned discharge line connects the portion of the fuel supply line located between the shut-off valve and the burner valve to the outside of the system. The control unit opens the communication valve when combustion of gaseous fuel is not occurring in all of the burners, the shut-off valve is closed, and all of the burner valves are closed. The processing system according to claim 3.

5. After the control unit has terminated the combustion of gaseous fuel in all the burners, it opens the communication valve to discharge the gaseous fuel that was filled in the fuel supply line downstream of the shut-off valve. The processing system according to claim 4.

6. The control unit fills the fuel supply line from the shut-off valve to the burner valve with gaseous fuel and confirms that there is no leakage of gaseous fuel. After that, it opens the communication valve to discharge the gaseous fuel that had been filled into the fuel supply line from the shut-off valve to the burner valve. The processing system according to claim 4.

7. Equipped with a control unit, A communication valve is provided in the aforementioned communication line. The fuel supply line is equipped with a shut-off valve. The fuel supply line is provided with two burner valves located downstream of the shut-off valve. The aforementioned discharge line connects the portion of the fuel supply line located between the two burner valves to the outside of the system. The control unit opens the communication valve when combustion of gaseous fuel is not occurring in a predetermined burner and the two burner valves corresponding to the predetermined burner are closed. The processing system according to claim 1.

8. A gas detector for measuring the concentration of gaseous fuel present in the aforementioned air supply line, Control unit and Equipped with, A communication valve is provided in the aforementioned communication line. The control unit closes the communication valve when the concentration of gaseous fuel present in the air supply line exceeds a predetermined value. The processing system according to claim 1.

9. Equipped with a control unit, A communication valve is provided in the aforementioned communication line. The control unit closes the communication valve when the boiler is in a state of complete fuel shutoff. The processing system according to claim 1.

10. Equipped with a control unit, A communication valve is provided in the aforementioned communication line. The control unit closes the communication valve when it detects an abnormality in the push-in fan. The processing system according to claim 2.

11. Equipped with a control unit, A communication valve is provided in the aforementioned communication line. The fuel supply line is equipped with a shut-off valve. The control unit closes the communication valve when the shut-off valve is open. The processing system according to claim 1.

12. The boiler is a co-firing boiler in which gaseous fuel and other fuels can be burned in the burner. The gaseous fuel is an auxiliary fuel supplied to the burner only when other fuels are burning. The processing system according to claim 1.

13. Gaseous fuels are gases that have an odor or are toxic. The processing system according to claim 1.

14. Gaseous fuels are gases containing ammonia. The processing system according to claim 1.

15. A processing system according to any one of claims 1 to 14, The aforementioned burner, The aforementioned air supply line, The aforementioned fuel supply line, The aforementioned discharge line, It is equipped with Boiler.

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