Boiler, and method of purging hydrogen gas

Abstract

To provide a boiler capable of suppressing a consumption of an inert gas for purging a hydrogen gas, and a method of purging the hydrogen gas.SOLUTION: A boiler that injects a fossil fuel gas supplied from a fossil fuel gas line and a hydrogen gas supplied from a hydrogen gas line into a combustion chamber to burn them is equipped with bypass block valves, and has a fossil fuel gas bypass line for connecting the fossil fuel gas line and the hydrogen gas line. The bypass block valves are set to be a closed state in a normal operation, and are set to be an open state when purging the hydrogen gas remaining in the hydrogen gas line, to send the fossil fuel gas into the hydrogen gas line.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a boiler and a method for purging hydrogen gas. [Background technology]

[0002] Patent Document 1 below discloses a hydrogen-fired boiler that can more efficiently purge a hydrogen supply line. This hydrogen-fired boiler is a small-scale once-through boiler or a small-scale once-through boiler that has a burner that burns hydrogen and performs combustion control, including starting and stopping boiler combustion, to generate steam according to fluctuations in the amount of steam required on the load side, and is equipped with a boiler body, a blower, a hydrogen supply line connected to the burner and supplying hydrogen gas to the burner, a shutoff valve disposed in the hydrogen supply line and opening and closing the flow path of the hydrogen supply line, a purge line connected downstream of and near the shutoff valve and supplying inert gas to the hydrogen supply line, a first supply valve disposed in the purge line and adjusting the amount of inert gas supplied, and a controller that controls the opening and closing of the shutoff valve and the first supply valve.

[0003] In this hydrogen-fired boiler, when stopping the combustion of hydrogen gas in the burner, the control unit first closes the shutoff valve, and opens the first supply valve only when the shutoff valve is closed and the boiler body is being ventilated by the blower, thereby diluting the hydrogen gas remaining in the hydrogen supply line from the burner outlet to the shutoff valve.With this hydrogen-fired boiler, inert gas is supplied from immediately adjacent to the shutoff valve, making it possible to efficiently purge the hydrogen gas remaining in the hydrogen supply line from the burner to the shutoff valve. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6939705 Summary of the Invention [Problem to be solved by the invention]

[0005] The background art uses an inert gas as a replacement gas to purge (remove) hydrogen gas. Therefore, when the inert gas is used up, it becomes impossible to purge (remove) hydrogen gas, which poses a problem that, for example, the operation of a hydrogen-fired boiler must be stopped. For example, when a hydrogen-fired boiler is operated with frequent start / stop cycles, the consumption of inert gas increases, which is a serious problem.

[0006] The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide a boiler and a hydrogen gas purging method that do not require the separate preparation of an inert gas for purging hydrogen gas, or that can reduce the amount of inert gas consumed for purging hydrogen gas. [Means for solving the problem]

[0007] In order to achieve the above object, the present invention employs, as a first solution relating to a boiler, a boiler that injects fossil fuel gas supplied from a fossil fuel gas line and hydrogen gas supplied from a hydrogen gas line into a combustion chamber and burns them, and is provided with a bypass shut-off valve and a fossil fuel gas bypass line that connects the fossil fuel gas line and the hydrogen gas line, and the bypass shut-off valve is set to a closed state during normal operation, and is set to an open state when purging the hydrogen gas remaining in the hydrogen gas line, so that the fossil fuel gas is sent to the hydrogen gas line.

[0008] The present invention employs, as a second solution related to a boiler, the first solution described above, in which only the fossil fuel gas is injected into the combustion chamber and burned during low-load combustion operation, and when the steam pressure reaches a set pressure value for switching to the low-load combustion operation during normal operation, the bypass shutoff valve is set to an open state for a predetermined time.

[0009] The present invention employs, as a third solution relating to a boiler, the first or second solution described above, wherein an inert gas shut-off valve is provided and an inert gas line connected to the hydrogen gas line is further provided, and the inert gas shut-off valve is set to an open state before an abnormal shutdown and / or the start of maintenance to send inert gas into the hydrogen gas line.

[0010] The present invention employs, as a fourth solution relating to a boiler, any one of the first to third solution means, further comprising a control device that controls the bypass cutoff valve.

[0011] In the present invention, as a solution to the problem of a method for purging a combustible gas supply pipe, a method for purging hydrogen gas when fossil fuel gas supplied from a fossil fuel gas line and hydrogen gas supplied from a hydrogen gas line are injected into a combustion chamber and combusted, employing the following means: the fossil fuel gas line and the hydrogen gas line are connected by a fossil fuel gas bypass line provided with a bypass shut-off valve; during normal operation, the bypass shut-off valve is set to a closed state; and when purging the hydrogen gas remaining in the hydrogen gas line, the bypass shut-off valve is set to an open state and the fossil fuel gas is sent to the hydrogen gas line. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a boiler and a hydrogen gas purging method that do not require the separate preparation of a replacement gas for purging hydrogen gas, or that can reduce the amount of inert gas consumed for purging hydrogen gas. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a system diagram showing the configuration of a main part of a boiler according to an embodiment of the present invention. [Figure 2] 1 is a first flowchart showing the operation of a boiler A according to one embodiment of the present invention. [Figure 3]4 is a second flowchart showing the operation of the boiler A according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The boiler A according to this embodiment is a boiler specified in the "Boiler and Pressure Vessel Safety Regulations" of the Ministry of Health, Labor and Welfare, and includes small-scale boilers, simple boilers, and compact boilers. As shown in Fig. 1, the boiler A is equipped with a fossil fuel gas tank T1, a hydrogen gas tank T2, and an inert gas tank T3.

[0015] In addition, this once-through boiler A is equipped with a fossil fuel gas line L1, a hydrogen gas line L2, an inert gas line L3, a fossil fuel gas bypass line L4, a first fossil fuel gas shut-off valve V11, a second fossil fuel gas shut-off valve V12, a first hydrogen gas shut-off valve V21, a second hydrogen gas shut-off valve V22, an inert gas shut-off valve V31, a first bypass shut-off valve V41, a second bypass shut-off valve V42, and a flame arrester F.

[0016] This once-through boiler A also includes a blower S, an air supply duct L5, a boiler body BH, and a control device C. Of the above-mentioned components, the boiler body BH includes at least a burner B, a boiler body CB, and a steam pressure sensor PS, as shown in the figure.

[0017] The fossil fuel gas tank T1 is a container of a predetermined capacity that stores fossil fuel gas G1, which is one of the fuels, and is equipped with a gas supply port. One end (rear end) of a fossil fuel gas line L1 is connected to this fossil fuel gas supply port. Such a fossil fuel gas tank T1 supplies the fossil fuel gas G1 from the fossil fuel gas supply port to one end (rear end) of the fossil fuel gas line L1.

[0018] The hydrogen gas tank T2 is a container of a predetermined capacity that stores hydrogen gas G2, the other fuel, and is equipped with a hydrogen gas supply port. One end (rear end) of the hydrogen gas line L2 is connected to this hydrogen gas supply port. The hydrogen gas tank T2 supplies hydrogen gas G2 from the hydrogen gas supply port to one end (rear end) of the hydrogen gas line L2.

[0019] The inert gas tank T3 is a container with a predetermined capacity for storing the inert gas G3 and is equipped with an inert gas supply port. One end (rear end) of the inert gas line L3 is connected to this inert gas supply port. The inert gas tank T3 supplies the inert gas G3 from the inert gas supply port to one end (rear end) of the inert gas line L3.

[0020] The fossil fuel gas G1 is a gas fuel derived from fossil fuels excavated from underground. This fossil fuel gas G1 is, for example, LNG (liquefied natural gas), LPG (liquefied petroleum gas), or city gas. This fossil fuel gas G1 is not limited to LNG (liquefied natural gas), LPG (liquefied petroleum gas), or city gas, but in a broad sense is a gas fuel derived from fossil fuels and having a slower flame propagation speed than hydrogen gas G2.

[0021] Hydrogen gas G2 is a gas fuel whose main component is hydrogen (H2). This hydrogen gas G2 does not contain carbon (C), which is recognized as a greenhouse gas, and has an extremely fast burning speed among known gas fuels. Inert gas G3 is known as a gas that is chemically stable and does not easily react with other elements or compounds, such as nitrogen gas.

[0022] The fossil fuel gas line L1 is a gas supply pipe that connects the fossil fuel gas tank T1 and the boiler body BH. That is, one end (rear end) of the fossil fuel gas line L1 is connected to the gas supply port of the fossil fuel gas tank T1, and the other end (front end) is connected to the first fuel receiving port of the boiler body BH. Such a fossil fuel gas line L1 supplies the fossil fuel gas G1 that flows in from the fossil fuel gas tank T1 to the boiler body BH.

[0023] The hydrogen gas line L2 is a gas pipe that connects the hydrogen gas tank T2 and the boiler body BH. That is, one end (rear end) of the hydrogen gas line L2 is connected to the gas supply port of the hydrogen gas tank T2, and the other end (front end) is connected to the second fuel receiving port of the boiler body BH. Such a hydrogen gas line L2 supplies the hydrogen gas G2 flowing in from the hydrogen gas tank T2 to the boiler body BH.

[0024] The inert gas line L3 is a gas pipe that connects the inert gas tank T3 and a midpoint of the hydrogen gas line L2. That is, one end (rear end) of the inert gas line L3 is connected to the gas supply port of the inert gas tank T3, and the other end (front end) is connected to the first connection point P of the hydrogen gas line L2. Such an inert gas line L3 supplies the inert gas G3 flowing in from the inert gas tank T3 to the hydrogen gas line L2.

[0025] The fossil fuel gas bypass line L4 is a gas pipe that connects an intermediate portion of the fossil fuel gas line L1 and an intermediate portion of the hydrogen gas line L2. That is, one end (rear end) of the fossil fuel gas bypass line L4 is connected to the second connection point Q of the fossil fuel gas line L1, and the other end (front end) is connected to the third connection point R of the hydrogen gas line L2. The fossil fuel gas bypass line L4 supplies the fossil fuel gas G1 flowing in from the fossil fuel gas line L1 to the hydrogen gas line L2.

[0026] The first fossil fuel gas shutoff valve V11 is a control valve that is provided in the fossil fuel gas line L1 and controlled by the control device C. As shown in the figure, the first fossil fuel gas shutoff valve V11 is provided in the fossil fuel gas line L1 between one end (rear end) and the second connection point Q. When set to an open state by the control device C, the first fossil fuel gas shutoff valve V11 allows the flow of the fossil fuel gas G1 in the fossil fuel gas line L1, and when set to a closed state by the control device C, shuts off the flow of the fossil fuel gas G1 in the fossil fuel gas line L1.

[0027] The second fossil fuel gas shutoff valve V12 is a control valve that is provided in the fossil fuel gas line L1, similar to the first fossil fuel gas shutoff valve V11, and is controlled by the control device C. As shown in the figure, the second fossil fuel gas shutoff valve V12 is provided in the fossil fuel gas line L1 between the first fossil fuel gas shutoff valve V11 and the second connection point Q.

[0028] Like the first fossil fuel gas shut-off valve V11 described above, when the second fossil fuel gas shut-off valve V12 is set to an open state by the control device C, it allows the flow of fossil fuel gas G1 in the fossil fuel gas line L1, and when it is set to a closed state by the control device C, it blocks the flow of fossil fuel gas G1 in the fossil fuel gas line L1.

[0029] The first hydrogen gas shutoff valve V21 is a control valve that is provided in the hydrogen gas line L2 and controlled by the control device C. As shown in the figure, the first hydrogen gas shutoff valve V21 is provided in the hydrogen gas line L2 between one end (rear end) and the first connection point P. When set to an open state by the control device C, this first hydrogen gas shutoff valve V21 allows the flow of hydrogen gas G2 in the hydrogen gas line L2, and when set to a closed state by the control device C, it shuts off the flow of hydrogen gas G2 in the hydrogen gas line L2.

[0030] The second hydrogen gas shutoff valve V22 is a control valve that is provided in the hydrogen gas line L2, similar to the first hydrogen gas shutoff valve V21, and is controlled by the control device C. As shown in the figure, this second hydrogen gas shutoff valve V22 is provided in the hydrogen gas line L2 between the first connection point P and the third connection point R. When set to an open state by the control device C, the second hydrogen gas shutoff valve V22 allows the flow of hydrogen gas G2 between the first connection point P and the third connection point R, and when set to a closed state by the control device C, the second hydrogen gas shutoff valve V22 blocks the flow of hydrogen gas G2 between the first connection point P and the third connection point R.

[0031] The inert gas shutoff valve V31 is a control valve that is provided in the inert gas line L3 and is controlled by the control device C. When the inert gas shutoff valve V31 is set to an open state by the control device C, it allows the inert gas G3 to flow through the inert gas line L3, and when the inert gas shutoff valve V31 is set to a closed state by the control device C, it shuts off the flow of the inert gas G3 through the inert gas line L3.

[0032] The first bypass cutoff valve V41 is a control valve that is provided in the fossil fuel gas bypass line L4 and is controlled by the control device C. The first bypass cutoff valve V41 is provided in the fossil fuel gas bypass line L4 upstream of the second bypass cutoff valve V42, i.e., on the second connection point Q side.

[0033] When such a first bypass shut-off valve V41 is set to an open state by the control device C, it allows the flow of fossil fuel gas G1 in the fossil fuel gas bypass line L4, and when it is set to a closed state by the control device C, it blocks the flow of fossil fuel gas G1 in the fossil fuel gas bypass line L4.

[0034] The second bypass cutoff valve V42 is a control valve that is provided in the fossil fuel gas bypass line L4, similar to the first bypass cutoff valve V41, and is controlled by the control device C. This second bypass cutoff valve V42 is provided in the fossil fuel gas bypass line L4 downstream of the first bypass cutoff valve V41, i.e., on the third connection point R side.

[0035] When such a second bypass shut-off valve V42 is set to an open state by the control device C, it allows the flow of fossil fuel gas G1 in the fossil fuel gas bypass line L4, and when it is set to a closed state by the control device C, it shuts off the flow of fossil fuel gas G1 in the fossil fuel gas bypass line L4.

[0036] The flame arrester F is a backfire prevention device provided in the hydrogen gas line L2 as shown in the figure. This flame arrester F is provided in the hydrogen gas line L2 between the third connection point R and the boiler body BH as shown in the figure. This flame arrester F prevents a flame generated in the boiler body BH from propagating through the hydrogen gas line L2 to the third connection point R.

[0037] The blower S has an air discharge port and is a device that blows combustion air G into the boiler body BH under the control of the control device C. One end (rear end) of the air supply duct L5 is connected to the air discharge port. The blower S sends out combustion air G4 into the air supply duct L5 under the control of the control device C.

[0038] The air supply duct L5 is an air flow passage that connects the blower S and the boiler body BH. One end (rear end) of this air supply duct L5 is connected to the air discharge port of the blower S, and the other end (front end) is connected to the air inlet of the boiler body BH. This air supply duct L5 supplies combustion air G4 that flows in from the blower S to the boiler body BH.

[0039] The boiler body BH is the main body of the boiler A and is equipped with the first fuel receiving port, the second fuel receiving port, and the air receiving port described above. This boiler body BH generates steam by burning the fossil fuel gas G1 flowing into the first fuel receiving port and the hydrogen gas G2 flowing into the second fuel receiving port using the combustion air G4 flowing into the air receiving port.

[0040] As shown in the figure, this boiler body BH includes a boiler body CB, a burner B, and a steam pressure sensor PS. The boiler body CB is a substantially cylindrical hollow body with a combustion chamber provided therein. This combustion chamber is provided with a combustion gas flow path B1 and multiple water tubes (not shown) through which boiler water flows. In this boiler body CB, a flame is generated by the combustion of fossil fuel gas G1 and / or hydrogen gas G2. The boiler water flowing through the water tubes is heated by the heat of the flame and becomes steam.

[0041] Burner B is a device that injects fossil fuel gas G1 and / or hydrogen gas G2 and combustion air G4 into the combustion chamber of the can body CB to burn them. That is, burner B is equipped with a first fuel nozzle that injects fossil fuel gas G1 into the combustion chamber, a second fuel nozzle that injects hydrogen gas G2 into the combustion chamber, an air injection nozzle that injects combustion air G4, and an ignition device.

[0042] The steam pressure sensor PS is a pressure sensor that detects the pressure (steam pressure) of the steam supplied to the demand destination from the boiler A (main body BH). This steam pressure sensor PS outputs the detected steam pressure value to the control device C as a pressure detection signal.

[0043] The control device C is a control device that controls the first fossil fuel gas shut-off valve V11, the second fossil fuel gas shut-off valve V12, the first hydrogen gas shut-off valve V21, the second hydrogen gas shut-off valve V22, the inert gas shut-off valve V31, the first bypass shut-off valve V41, the second bypass shut-off valve V42, the blower S, and the burner B based on pressure detection signals input from the steam pressure sensor PS, etc.

[0044] This control device C is equipped with an operation panel, and controls the first fossil fuel gas shutoff valve V11, the second fossil fuel gas shutoff valve V12, the first hydrogen gas shutoff valve V21, the second hydrogen gas shutoff valve V22, the inert gas shutoff valve V31, the first bypass shutoff valve V41, the second bypass shutoff valve V42, the blower S, and the burner B in a preset procedure based on the pressure detection signal described above and operation instructions input to the operation panel, thereby controlling the operation of the boiler A in accordance with the steam demand and operation instructions.

[0045] Next, the operation of the boiler A according to this embodiment, that is, the hydrogen gas purging method according to this embodiment, will be described in detail with reference to the flowcharts shown in FIGS.

[0046] 2, the control device C first starts up the boiler A (step S1). That is, when an operator operates the start switch on the control panel, the control device C starts up the boiler A. When starting up the boiler A, the control device C sets the first hydrogen gas shutoff valve V21, the second hydrogen gas shutoff valve V22, the inert gas shutoff valve V31, the first bypass shutoff valve V41, and the second bypass shutoff valve V42 to a closed state.

[0047] Then, the control device C starts up the boiler A and performs pre-purging (step S2). That is, the control device C sets all the shutoff valves, that is, the first fossil fuel gas shutoff valve V11, the second fossil fuel gas shutoff valve V12, the first hydrogen gas shutoff valve V21, the second hydrogen gas shutoff valve V22, the inert gas shutoff valve V31, the first bypass shutoff valve V41, and the second bypass shutoff valve V42, to a closed state.

[0048] The control device C then supplies combustion air G4 to the combustion chamber and combustion gas passage B1 of the can body CB by setting the above-mentioned shutoff valves and operating the blower S. By supplying the combustion air G4 to the combustion chamber and combustion gas passage B1 in this manner, the gas remaining in the combustion chamber and combustion gas passage B1 of the can body CB is pre-purged by the combustion air G4.

[0049] When the pre-purge is completed in this manner, the control device C operates the boiler A in low load combustion mode (step S3). That is, the control device C sets the first fossil fuel gas shutoff valve V11 and the second fossil fuel gas shutoff valve V12 to an open state and activates the blower S and the ignition device of the burner B, thereby injecting only the fossil fuel gas G1 from the burner B into the combustion chamber and burning it.

[0050] After the control device C has operated the boiler A in low-load combustion mode for a predetermined period of time, it switches the boiler A from low-load combustion mode to normal operation (step S4). That is, the control device C changes the setting of the first hydrogen gas shutoff valve V21 and the second hydrogen gas shutoff valve V22 from a closed state to an open state in response to an increase in steam demand, i.e., an increase in load.

[0051] As a result, burner B injects hydrogen gas G2 in addition to fossil fuel gas G1 into the combustion chamber of boiler body CB. Boiler A switches from low-load combustion operation to normal operation by co-burning fossil fuel gas G1 and hydrogen gas G2 in the combustion chamber of boiler body CB. This normal operation is a high-load combustion operation that can handle a higher output load than the low-load combustion operation.

[0052] Here, an operation switching pressure set value Xb is preset for the steam pressure of the steam supplied to the demand destination from boiler A (boiler body BH). This operation switching pressure set value Xb is a pressure threshold value for switching from normal operation (high load combustion operation) to low load combustion operation.

[0053] The control device C receives a pressure detection signal from the steam pressure sensor PS and determines whether the steam pressure of the water vapor has risen to the operation switching pressure set value Xb (step S5). If the determination in step S5 is "No," the control device C continues the normal operation in step S4.

[0054] On the other hand, if the determination in step S5 is "Yes," the control device C switches the boiler A from normal operation (high-load combustion operation) to low-load combustion operation, and causes the boiler A to operate in low-load combustion (step S6).

[0055] That is, the control device C switches the boiler A from normal operation (high-load combustion operation) to low-load combustion operation by maintaining the first fossil fuel gas shut-off valve V11 and the second fossil fuel gas shut-off valve V12 in an open state and changing the settings of the first hydrogen gas shut-off valve V21 and the second hydrogen gas shut-off valve V22 to a closed state.

[0056] Then, during this low-load combustion operation, the control device C performs purging (hydrogen purging) of the hydrogen gas line L2 using the fossil fuel gas G1 (step S7). That is, the control device C changes the settings of the first bypass shutoff valve V41 and the second bypass shutoff valve V42 from a closed state to an open state for a predetermined time (hydrogen purge time). As a result, the fossil fuel gas G1 flows into the hydrogen gas line L2 for the hydrogen purge time. Thereafter, the control device C closes the first bypass shutoff valve V41 and the second bypass shutoff valve V42.

[0057] The fossil fuel gas G1 flows from the second connection point Q into the fossil fuel gas bypass line L4 and also flows into the hydrogen gas line L2 via the third connection point R. The hydrogen gas G2 remaining in the hydrogen gas line L2 is purged by the fossil fuel gas G1 flowing into the hydrogen gas line L2 in this way, and is injected from the other end (tip) of the hydrogen gas line L2 through the second fuel nozzle of the burner B into the combustion chamber of the boiler body CB.

[0058] The hydrogen gas G2 purged from the hydrogen gas line L2 in this way is burned in the combustion chamber of the boiler body CB together with the fossil fuel gas G1 injected into the combustion chamber of the boiler body CB from the second fuel nozzle.Then, the vapor pressure of the water vapor generated in the boiler body CB gradually increases as the supply load decreases.

[0059] The control device C determines whether the steam pressure of the steam has risen to a preset combustion stop pressure Xa based on the pressure detection signal input from the steam pressure sensor PS (step S8). If the determination in step S8 is "No," the control device C operates the boiler A at low load combustion (step S9).

[0060] The low-load combustion operation in step S9 is equivalent to the low-load combustion operation in step S3 described above. While the low-load combustion operation in step S9 continues, the control device C repeats the determination process in step S8 described above to determine whether the vapor pressure of the water vapor has increased to the combustion stop pressure Xa.

[0061] On the other hand, if the determination in step S8 is "Yes," the control device C stops combustion in the boiler A (step S10). That is, the control device C changes the setting of the first fossil fuel gas shutoff valve V11 and the second fossil fuel gas shutoff valve V12 from an open state to a closed state, thereby stopping the supply of fuel to the burner B. As a result, the boiler A enters a combustion-stopped state.

[0062] After the boiler A is stopped in this manner, the control device C performs post-purging of the combustion chamber of the boiler body CB and the combustion gas passage B1 (step S11). That is, the control device C increases the air flow rate of the blower S, thereby post-purging the residual gas in the combustion chamber of the boiler body CB and the combustion gas passage B1 using the combustion air G4.

[0063] When this post-purging is completed, the control device C completely stops the boiler A (step S12). If the determination in step S8 is "No," the control device C repeats the determination process in step S8. That is, when the hydrogen purging in step S7 is completed, the control device C stops the combustion in the boiler A after the steam pressure of the water vapor has risen to the combustion stop pressure Xa.

[0064] Next, the operation when an abnormality occurs in boiler A will be described with reference to the flowchart in Figure 3. Various abnormalities can occur during operation of boiler A. When an abnormality occurs in boiler A, control device C performs hydrogen purging using inert gas G3 (step S1a).

[0065] That is, the control device C changes the settings of the first fossil fuel gas cutoff valve V11, the second fossil fuel gas cutoff valve V12, and the first hydrogen gas cutoff valve V21 from an open state to a closed state to stop combustion (step S2a). Also, the control device C maintains the second hydrogen gas cutoff valve V22 in an open state, and further changes the setting of the inert gas cutoff valve V31 from a closed state to an open state.

[0066] As a result, the inert gas G3 flows into the hydrogen gas line L2 via the inert gas line L3 and the first connection point P. This inert gas G3 flows from the first connection point P to the third connection point R, and further passes through the flame arrestor F and the other end (tip) of the hydrogen gas line L2, and is injected into the combustion chamber of the can body CB from the second fuel nozzle of the burner B for a predetermined time.

[0067] That is, the hydrogen gas G2 remaining in the hydrogen gas line L2 is purged by the inert gas G3 flowing into the hydrogen gas line L2 in this manner, and is then injected from the other end (tip) of the hydrogen gas line L2 through the second fuel nozzle of the burner B into the combustion chamber of the boiler body CB. In this way, the hydrogen purging of the hydrogen gas line L2 using the inert gas G3 is completed.

[0068] The control device C post-purges the combustion chamber and combustion gas passage B1 of the boiler body CB (step S3a). That is, the control device C increases the air flow rate of the blower S to post-purge the residual gas in the combustion chamber and combustion gas passage B1 of the boiler body CB using combustion air G4. Then, when the post-purge is completed, the control device C completely stops the boiler A (step S4a).

[0069] The boiler A of this embodiment injects fossil fuel gas G1 supplied from a fossil fuel gas line L1 and hydrogen gas G2 supplied from a hydrogen gas line L2 into a boiler body CB (combustion chamber) and burns them, and is provided with a first bypass shut-off valve V41 and a second bypass shut-off valve V42, and a fossil fuel gas bypass line L4 connecting the fossil fuel gas line L1 and the hydrogen gas line L2, and the first bypass shut-off valve V41 and the second bypass shut-off valve V42 are set to a closed state during normal operation, and are set to an open state when purging (hydrogen purging) the hydrogen gas G2 remaining in the hydrogen gas line L2, and send the fossil fuel gas G1 to the hydrogen gas line L2.

[0070] According to this embodiment, the fossil fuel gas G1 is used to purge (hydrogen purge) the hydrogen gas G2 remaining in the hydrogen gas line L2, so it is possible to provide a boiler A that does not require the separate preparation of an inert gas for purging the hydrogen gas.

[0071] Furthermore, in the boiler A of this embodiment, when operating in low-load combustion, only fossil fuel gas G1 is injected into the combustion chamber and burned, and when the steam pressure of the water vapor reaches the operation switching pressure set value Xb from normal operation (high-load combustion operation) to low-load combustion operation during normal operation, the first bypass shut-off valve V41 and the second bypass shut-off valve V42 are set to an open state for a preset hydrogen purge time (predetermined time).

[0072] According to this embodiment, the hydrogen gas G2 remaining in the hydrogen gas line L2 is purged (hydrogen purged) during low load combustion operation, so that the hydrogen gas G2 can be purged (hydrogen purged) effectively.

[0073] In addition, the boiler A of this embodiment is provided with an inert gas shut-off valve V31 and further includes an inert gas line L3 connected to the hydrogen gas line L2, and the inert gas shut-off valve V31 is set to an open state in the event of an abnormal or emergency shutdown or before maintenance begins to send inert gas G3 into the hydrogen gas line L2.

[0074] According to this embodiment, hydrogen purging using the inert gas G3 is performed only in the event of an abnormal or emergency shutdown or before the start of maintenance, so that the consumption of the inert gas G3 can be suppressed.

[0075] In addition, the boiler A of this embodiment further includes a control device C that controls the first fossil fuel gas shut-off valve V11, the second fossil fuel gas shut-off valve V12, the first hydrogen gas shut-off valve V21, the second hydrogen gas shut-off valve V22, and the inert gas shut-off valve V3.

[0076] According to this embodiment, non-hydrogen purging can be performed more quickly than when the first fossil fuel gas shutoff valve V11, the second fossil fuel gas shutoff valve V12, the first hydrogen gas shutoff valve V21, the second hydrogen gas shutoff valve V22, and the inert gas shutoff valve V3 are manually operated.

[0077] Furthermore, the method for purging hydrogen gas G2 according to this embodiment is a method for purging hydrogen gas G2 when fossil fuel gas G1 supplied from a fossil fuel gas line L1 and hydrogen gas G2 supplied from a hydrogen gas line L2 are injected into a can body CB (combustion chamber) and burned, in which the fossil fuel gas line L1 and the hydrogen gas line L2 are connected by a fossil fuel gas bypass line L4 provided with a first bypass shutoff valve V41 and a second bypass shutoff valve V42, and in normal operation, the first bypass shutoff valve V41 and the second bypass shutoff valve V42 are set to a closed state, and when purging hydrogen gas G2 remaining in the hydrogen gas line L2, the first bypass shutoff valve V41 and the second bypass shutoff valve V42 are set to an open state, and the fossil fuel gas G1 is sent to the hydrogen gas line L2.

[0078] According to this method for purging hydrogen gas G2, the hydrogen gas G2 in the hydrogen gas line L2 is purged (hydrogen purged) using fossil fuel gas G1, so it is possible to provide a method for purging hydrogen gas G2 that does not require the separate preparation of inert gas G3 for purging (hydrogen purging) the hydrogen gas G2.

[0079] The present invention is not limited to the above-described embodiments, and the following modifications are possible, for example: In the above-described embodiments, the first connection point P, the second connection point Q, and the third connection point R are set as shown in Fig. 1, and the first fossil fuel gas cutoff valve V11, the second fossil fuel gas cutoff valve V12, the first hydrogen gas cutoff valve V21, the second hydrogen gas cutoff valve V22, the inert gas cutoff valve V31, the first bypass cutoff valve V41, and the second bypass cutoff valve V42 are arranged as shown in Fig. 1.

[0080] However, the present invention is not limited to this. That is, the positions of the first connection point P, the second connection point Q, and the third connection point R and the manner in which the first fossil fuel gas shutoff valve V11, the second fossil fuel gas shutoff valve V12, the first hydrogen gas shutoff valve V21, the second hydrogen gas shutoff valve V22, the inert gas shutoff valve V31, the first bypass shutoff valve V41, and the second bypass shutoff valve V42 are provided such that the hydrogen gas G2 in the hydrogen gas line L2 can be purged (hydrogen purged) using the fossil fuel gas G1.

[0081] In addition, in each of the above embodiments, the first fossil fuel gas shut-off valve V11, the second fossil fuel gas shut-off valve V12, the first hydrogen gas shut-off valve V21, the second hydrogen gas shut-off valve V22, the inert gas shut-off valve V31, the first bypass shut-off valve V41 and the second bypass shut-off valve V42 are control valves controlled by the control device C, but the present invention is not limited to this.

[0082] All or some of the first fossil fuel gas shutoff valve V11, the second fossil fuel gas shutoff valve V12, the first hydrogen gas shutoff valve V21, the second hydrogen gas shutoff valve V22, the inert gas shutoff valve V31, the first bypass shutoff valve V41 and the second bypass shutoff valve V42 may be manual valves. [Explanation of symbols]

[0083] A Boiler B burner BH boiler body C Control device CB can body (combustion chamber) F Flame arrester G1 Fossil fuel gas G2 Hydrogen Gas G3 Inert Gas L1 Fossil fuel gas line L2 Hydrogen gas line L3 inert gas line L4 Fossil fuel gas bypass line L5 Air supply duct PS Steam Pressure Sensor S blower T1 Fossil Fuel Gas Tank T2 Hydrogen Gas Tank T3 Inert Gas Tank V11 First fossil fuel gas shutoff valve V12 Second fossil fuel gas shutoff valve V21 First hydrogen gas shutoff valve V22 Second hydrogen gas shutoff valve V31 Inert Gas Shut-Off Valve V41 First bypass shutoff valve V42 Second bypass shutoff valve

Claims

1. A boiler that injects fossil fuel gas supplied from a fossil fuel gas line and hydrogen gas supplied from a hydrogen gas line into a combustion chamber and combusts them, a fossil fuel gas bypass line that is provided with a bypass shutoff valve and connects the fossil fuel gas line and the hydrogen gas line; The bypass shutoff valve is set to a closed state during normal operation, and is set to an open state when purging the hydrogen gas remaining in the hydrogen gas line, thereby sending the fossil fuel gas into the hydrogen gas line.

2. 2. The boiler according to claim 1, wherein during low-load combustion operation, only the fossil fuel gas is injected into the combustion chamber and burned, and when the steam pressure during normal operation reaches a set pressure value for switching to the low-load combustion operation, the bypass shutoff valve is set to an open state for a predetermined time.

3. an inert gas line provided with an inert gas shutoff valve and connected to the hydrogen gas line; 3. The boiler according to claim 1, wherein the inert gas shutoff valve is set to an open state before an abnormal shutdown or / and before the start of maintenance, to feed the inert gas into the hydrogen gas line.

4. The boiler according to claim 1 or 2, further comprising a control device that controls the bypass shutoff valve.

5. A method for purging hydrogen gas when fossil fuel gas supplied from a fossil fuel gas line and hydrogen gas supplied from a hydrogen gas line are injected into a combustion chamber and combusted, comprising: a fossil fuel gas bypass line provided with a bypass shutoff valve connecting the fossil fuel gas line and the hydrogen gas line; A method for purging hydrogen gas, in which the bypass shutoff valve is set to a closed state during normal operation, and when purging the hydrogen gas remaining in the hydrogen gas line, the bypass shutoff valve is set to an open state and the fossil fuel gas is sent into the hydrogen gas line.

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