JP7515230B1 - Burner fuel control device and burner fuel control method - Google Patents

Abstract

A burner fuel control device and a burner fuel control method are provided that are capable of preventing flashback without using a flame arrester.
[Solution] A supply line L11 for supplying hydrogen gas or nitrogen gas is connected to a burner 5. A first valve device 2 and a second valve device 3 downstream of the first valve device 2 are arranged on the supply line L11. The first valve device 2 has a first input port 23 connected to a hydrogen gas supply source 7, a second input port 24 connected to a nitrogen gas supply source 8, and an output port 25, and is a three-way valve that can switch between a first state in which hydrogen gas is output from the output port 25 and a second state in which nitrogen gas is output from the output port 25. The second valve device 3 is an on-off valve that can switch between an open state in which the supply line L11 is opened and a closed state in which the supply line L11 is blocked.
[Selected Figure] Figure 1

Description

The present invention relates to a burner fuel control device and a burner fuel control method that selectively supplies fuel or inert gas to a burner that burns fuel.

Conventionally, natural gas, propane gas, etc. have been used as fuel for burners used in combustion facilities such as boilers and industrial furnaces. However, due to the growing environmental awareness in recent years, the use of hydrogen gas as fuel has been promoted in order to reduce _CO2 emissions.

However, because hydrogen gas has a faster burning speed than conventional fuels, when the burner starts or stops burning, the flame generated in the burner may flow back into the supply line that supplies fuel to the burner (hereinafter, this flame backflow phenomenon will be referred to as backfire). This backfire is prevented by using a backfire prevention device (flame arrester). For example, the invention disclosed in Patent Document 1 and the device disclosed in Figure 8 are known as such burner fuel control devices.

Here, a conventional burner fuel control device will be described in detail with reference to FIG. 8. FIG. 8 is a diagram illustrating the general configuration of a conventional burner fuel control device 100 (hereinafter simply referred to as fuel control device 100).

The fuel control device 100 is a device for supplying fuel for combustion to a burner 5 provided in a combustion furnace 4 such as a boiler.

The fuel control device 100 is equipped with a hydrogen supply line L21 extending from a hydrogen gas supply source 7. The hydrogen supply line L21 has the supply source 7 on the upstream side and is connected to the burner 5 on the downstream side. As a result, the hydrogen supply line L21 supplies the hydrogen gas supplied from the supply source 7 to the burner 5 as fuel. In addition, the hydrogen supply line L21 is provided with a first shutoff valve 51, a second shutoff valve 52, and a flame arrester 53, in that order from the upstream side.

The fuel control device 100 further includes a nitrogen gas supply line L22 extending from the nitrogen gas supply source 8. The nitrogen gas supply line L22 is upstream of the supply source 8 and merges with the hydrogen supply line L21 on the downstream side. Specifically, the nitrogen gas supply line L22 merges with the hydrogen supply line L21 on the downstream side of the second shutoff valve 52 and the upstream side of the flame arrestor 53 on the hydrogen supply line L21. In addition, a third shutoff valve 54 and a fourth shutoff valve 55 are provided on the nitrogen gas supply line L22 from the upstream side.

Furthermore, an air supply line L23 is connected to the burner 5, and air for combustion is supplied from the blower 6.

In the fuel control device 100 described above, when the burner 5 is burning, the first shutoff valve 51 and the second shutoff valve 52 are both open, and hydrogen gas continues to be supplied to the burner 5 through the flame arrestor 53. At this time, either or both of the third shutoff valve 54 and the fourth shutoff valve 55 are closed, and the supply of nitrogen is cut off.

When combustion in the burner 5 is stopped, the first shutoff valve 51 and the second shutoff valve 52 are closed to cut off the supply of hydrogen gas. After that, the fourth shutoff valve 55 is opened to purge the hydrogen gas downstream of the second shutoff valve 52 in the hydrogen supply line L21 (hereinafter referred to as the downstream side of the line) with nitrogen gas. This prevents the hydrogen remaining on the downstream side of the line from mixing with air to form a flammable gas mixture.

However, even if purging is performed as described above, it may not be possible to completely replace the hydrogen gas in the supply line L21 with nitrogen gas, making it difficult to completely prevent backfire. In such cases, a flame arrestor 53 is provided downstream of the hydrogen supply line L21 to prevent flames from flowing back upstream from the flame arrestor 53, even if backfire occurs.

JP 2018-200166 A

As described above, when the burner 5 is burning, hydrogen gas passes through the flame arrestor 53 and is supplied to the burner 5. However, due to the flame quenching structure inside the flame arrestor 53, the pressure loss increases when the hydrogen gas passes through the flame arrestor 53.

Therefore, in order to maintain the necessary hydrogen gas pressure in the burner 5, it is necessary to increase the supply pressure of the hydrogen gas supply source 7. For example, the supply pressure of the supply source 7 must be approximately twice the pressure required in the burner 5, which may not be possible with existing equipment.

Furthermore, flame arresters are large and expensive, and their installation requires securing installation space and is costly. Since one flame arrester is required for each burner, installing multiple burners is particularly costly. Furthermore, if the flame arrester deteriorates, such as by burning out due to flashback, it must be replaced, and the cost of maintaining the fuel control device is also high.

The present invention was made in consideration of the above problems, and aims to provide a burner fuel control device and a burner fuel control method that can prevent flashback without using a flame arrester.

In order to solve the above problems, the burner fuel control device and burner fuel control method according to one aspect of the present invention have the following configuration.

(1) A fuel control device for a burner that selectively supplies fuel or inert gas to a burner that burns fuel, the device being characterized in that a supply line that supplies the fuel or inert gas is connected to the burner, a first valve device and a second valve device downstream of the first valve device are disposed in the supply line, the first valve device is a three-way valve that includes a first input port connected to a supply source of the fuel, a second input port connected to a supply source of the inert gas, and an output port, and is capable of switching between a first state in which the fuel is output from the output port and a second state in which the inert gas is output from the output port, and the second valve device is an on-off valve that is capable of switching between an open state in which the supply line is opened and a closed state in which the supply line is shut off.

(2) In the burner fuel control device described in (1), it is preferable that the burner fuel control device further includes a control unit that stores a control program for controlling the first valve device and the second valve device, and the control program further includes a step of changing the second valve device from the closed state to the open state while maintaining the first valve device in the second state in order to start combustion in the burner, and a step of changing the first valve device from the second state to the first state after a first predetermined time has elapsed while maintaining the second valve device in the open state.

(3) In the burner fuel control device described in (1) or (2), it is preferable that the burner fuel control device further includes a control unit that stores a control program for controlling the first valve device and the second valve device, and the control program further includes a step of switching the first valve device from the first state to the second state while maintaining the second valve device in the open state in order to stop combustion of the burner, and a step of switching the second valve device from the open state to the closed state after a second predetermined time has elapsed while maintaining the first valve device in the second state.

(4) In the burner fuel control device described in any one of (1) to (3), it is preferable that the first valve device comprises a valve chamber communicating with the first input port, the second input port, and the output port, and a valve body arranged in the valve chamber, the valve chamber comprises a first valve port through which the fuel flows in from the first input port, and a second valve port located opposite the first valve port through which the inert gas flows in from the second input port, and the valve body is held in the valve chamber so as to be capable of reciprocating between a first position that blocks the first valve port and a second position that blocks the second valve port.

(5) In the burner fuel control device described in (4), it is preferable that the first valve device is provided with a drive rod connected to the valve body and reciprocating the valve body, the drive rod is provided with a pressure acting surface that receives the pressure of the fuel input from the first input port to the first valve device so that the drive rod moves in a direction in which the valve body approaches the first valve port, and the surface area of the pressure acting surface is larger than the surface area of the face of the valve body facing the first valve port.

(6) A method for controlling burner combustion using the burner fuel control device described in (1), characterized in that the method includes the steps of: changing the second valve device from the closed state to the open state while maintaining the first valve device in the second state in order to start combustion in the burner; and, after a first predetermined time has elapsed, changing the first valve device from the second state to the first state while maintaining the second valve device in the open state.

(7) A method for controlling a burner's combustion using the burner's fuel control device described in (1), characterized in that the method includes the steps of: switching the first valve device from the first state to the second state while maintaining the second valve device in the open state in order to stop the burner's combustion; and, after a second predetermined time has elapsed, switching the second valve device from the open state to the closed state while maintaining the first valve device in the second state.

According to the burner fuel control device, a supply line for supplying fuel or inert gas is connected to the burner, a first valve device and a second valve device downstream of the first valve device are arranged in the supply line, the first valve device is a three-way valve having a first input port connected to a fuel supply source, a second input port connected to a inert gas supply source, and an output port, and capable of switching between a first state in which fuel is output from the output port and a second state in which inert gas is output from the output port, and the second valve device is a three-way valve capable of switching between an open state in which the supply line is opened and a closed state in which the supply line is blocked. Since the valve is characterized by being an on-off valve that can be switched between and, for example, as described in (2) or (6) above, if the second valve device is switched from the closed state to the open state while maintaining the first valve device in the second state in order to start the combustion of the burner, and the first valve device is switched from the second state to the first state after the first predetermined time has elapsed while maintaining the second valve device in the open state, when the combustion of the burner is to be started (at the time of ignition), first, the supply line can be purged with an inert gas (e.g., nitrogen gas) in order to switch the second valve device from the closed state to the open state while maintaining the first valve device in the second state. Then, after the predetermined time has elapsed, fuel (e.g., hydrogen gas) is supplied to the supply line in order to switch the first valve device from the second state to the first state while maintaining the second valve device in the open state, and the burner can be ignited. The first predetermined time mentioned above refers to the time that the purge continues, and is adjusted appropriately to a time that allows sufficient purging with inert gas to be performed depending on the size of the combustion furnace, the capacity of the supply line, etc.

In this way, when the burner is ignited, the supply line is first purged, replacing the air in the supply line with inert gas. This makes it possible to prevent the generation of a flammable mixture of air and hydrogen in the supply line, and thus to prevent the occurrence of flashback. This allows the burner to be ignited safely.

Furthermore, for example, if the burner fuel control device is configured as described in (3) or (7) above, to stop combustion in the burner, the first valve device is switched from the first state to the second state while maintaining the second valve device in an open state, and after the elapse of a second predetermined time, the second valve device is switched from the open state to a closed state while maintaining the first valve device in the second state,
When the combustion is stopped (extinguishing), the supply line can be purged with the inert gas by first switching the first valve device from the first state to the second state while keeping the second valve device in the open state. In other words, the fuel that filled the supply line during the burner combustion can be replaced with the inert gas.
Then, after a predetermined time has elapsed, the second valve device is switched from the open state to the closed state while the first valve device is maintained in the second state, thereby cutting off the supply of the inert gas.

In this way, when the burner is turned off, the supply line is first purged and the fuel is replaced with inert gas, which prevents fuel from remaining in the supply line and thus prevents backfire. This allows the burner to be turned off safely. The second predetermined time means the time that the purging continues, and is appropriately set to a time that allows sufficient purging with inert gas to be performed based on the volume of the supply line, the flow rate of the inert gas being supplied, etc.

As described above, by reliably purging the supply line with inert gas both when the burner is ignited and when it is extinguished, it is possible to prevent the generation of a flammable mixture in the supply line, and thus prevent flashback from occurring without using a flame arrester. This prevents the occurrence of fuel pressure loss and increases in cost and installation space that would otherwise occur due to the use of a flame arrester. In addition, since the first valve device and the second valve device are sufficient as the valve devices used in the fuel control device, it is possible to prevent flashback from occurring with fewer valve devices than in the past (see Figure 8).

The burner fuel control device and burner fuel control method of the present invention make it possible to prevent flashback without using a flame arrester.

1 is a diagram illustrating a schematic configuration of a burner fuel control device according to an embodiment of the present invention; 3A and 3B are diagrams illustrating configurations of a first valve device and a second valve device. FIG. 4 is a diagram for explaining the process of fuel control, showing the states of the first valve device and the second valve device when the system is in a stopped state. FIG. 4 is a diagram for explaining the process of fuel control, showing the states of the first valve device and the second valve device when pre-purging is performed. FIG. 4 is a diagram for explaining the process of fuel control, showing the states of the first valve device and the second valve device when ignition is performed. FIG. 4 is a diagram for explaining the fuel control process, showing the states of the first valve device and the second valve device when the burner is burning. 4 is a diagram for explaining the fuel control process, showing the states of the first valve device and the second valve device when extinguishing the fire. FIG. FIG. 1 is a diagram illustrating a schematic configuration of a burner fuel control device according to a conventional technique.

The embodiment of the fuel control device for a burner according to the present invention will be described in detail with reference to the drawings. Fig. 1 is a diagram illustrating the general configuration of the fuel control device for a burner 1 (hereinafter simply referred to as the fuel control device 1) according to this embodiment. Fig. 2 is a diagram illustrating the configuration of the first valve device 2 and the second valve device 3.

(General configuration of the fuel control device)
First, a description will be given of a schematic configuration of a fuel control device 1 according to this embodiment. The fuel control device 1 is a device for supplying fuel for combustion to a burner 5 provided in a combustion furnace 4 such as a boiler.

As shown in FIG. 1, the fuel control device 1 includes a supply line L11 connected to the burner 5. The supply line L11 is a pipe for supplying hydrogen gas (an example of a fuel) or nitrogen gas (an example of an inert gas) to the burner 5.

A first valve device 2 is disposed in the supply line L11. The first valve device 2 is a three-way valve that can switch the internal flow path according to the operation of the internal valve body (details will be described later). The first valve device 2 has a first input port 23, a second input port 24, and an output port 25.

The first input port 23 is connected to a hydrogen gas supply source 7 via a hydrogen gas supply line L12. The supply pressure of the hydrogen gas at the supply source 7 is not particularly limited, but is, for example, 0.01-0.3 MPa. The hydrogen gas supply line L12 is a pipe for allowing the hydrogen gas supplied from the supply source 7 to flow into the first valve device 2.

The second input port 24 is connected to a nitrogen gas supply source 8 via a nitrogen gas supply line L13. The supply pressure of the nitrogen gas in the supply source 8 is set to be higher than the supply pressure of hydrogen, although not particularly limited thereto. The nitrogen gas supply line L13 is a pipe for allowing the nitrogen gas supplied from the supply source 8 to flow into the first valve device 2.

The output port 25 outputs from the first valve device 2 the hydrogen gas that has flowed into the first valve device 2 from the first input port 23, or the nitrogen gas that has flowed into the first valve device 2 from the second input port 24, in response to the operation of the valve body 223 (see FIG. 2) inside the first valve device 2. The state in which the first valve device 2 outputs hydrogen gas from the output port 25 is referred to as the first state, and the state in which the first valve device 2 outputs nitrogen gas from the output port 25 is referred to as the second state.

Furthermore, a second valve device 3 is disposed in the supply line L11 downstream of the first valve device 2. The second valve device 3 is an on-off valve that can be switched between an open state that opens the supply line L11 and a closed state that blocks the supply line L11 according to the operation of an internal valve body 321 (see FIG. 2) (details will be described later). The second valve device 3 has an input port 33 and an output port 34.

The input port 33 is connected to the output port 25 of the first valve device 2. The connection here means that the input port 33 may be directly connected to the output port 25 of the first valve device 2, or may be connected via a pipe. By connecting the input port 33 to the output port 25 of the first valve device 2, the hydrogen gas or nitrogen gas output from the first valve device 2 flows into the second valve device 3.

When the second valve device 3 is in an open state, the output port 34 outputs the hydrogen gas or nitrogen gas that flows into the second valve device 3 from the input port 33 from the second valve device 3. The hydrogen gas or nitrogen gas output from the second valve device 3 is then supplied to the burner 5 through the supply line L11.

Furthermore, an air supply line L14 is connected to the burner 5. A blower 6 is connected to the upstream side of the air supply line L14, and air for combustion is supplied from the blower 6 to the burner 5 through the air supply line L14.

The fuel control device 1 also includes a control unit 9 that controls the combustion of the burner 5. The control unit 9 is electrically connected to the first valve device 2, the second valve device 3, and the blower 6. The control unit 9 also stores a control program for controlling the first valve device 2, the second valve device 3, and the blower 6. In other words, the control unit 9 controls the combustion of the burner 5 by controlling the operation of the first valve device 2, the second valve device 3, and the blower 6 using the control program.

(Regarding the first valve device)
Next, the first valve device 2 (three-way valve) will be described in more detail. The first valve device 2 is an air-operated pilot valve. As shown in FIG. 2, the first valve device 2 includes a drive unit 21 and a valve unit 22, which are stacked vertically in the figure.

The drive unit 21 has a disk-shaped piston 211 loaded inside. The piston 211 is connected to a drive rod 215, which is made up of a first rod member 215a and a second rod member 215b. The drive rod 215 extends from the drive unit 21 toward the valve unit 22, and a valve body 223 (described later) is connected to the end of the drive rod 215 opposite the piston 211.

The inside of the drive unit 21 is divided into a first chamber 212a and a second chamber 212b in the vertical direction in the figure by the piston 211. Operating air can be introduced into the first chamber 212a from an operating port 213. Therefore, by introducing operating air into the first chamber 212a and increasing the pressure in the first chamber 212a, the piston 211 can be moved toward the second chamber 212b. An air vent hole 214 is provided in the second chamber 212b, and when the piston 211 moves toward the second chamber 212b, the air in the second chamber 212b is discharged to the outside through the air vent hole 214.

The drive unit 21 also includes a coil spring 216 in the second chamber 212b that applies a biasing force to the first chamber 212a side of the piston 211. Therefore, when operating air is introduced into the first chamber 212a, the piston 211 moves toward the second chamber 212b side (downward in FIG. 2) against the biasing force of the coil spring 216, and when the introduction of operating air into the first chamber 212a is stopped, the piston 211 moves toward the first chamber 212a side (upward in FIG. 2) due to the biasing force of the coil spring 216. As described above, the piston 211 moves up and down, and the drive rod 215 connected to the piston 211 also moves up and down in accordance with the up and down movement of the piston 211.

The valve section 22 includes a first input port 23, a second input port 24, an output port 25, a valve chamber 221, and a fluid chamber 222. The fluid chamber 222 is located upstream of the valve chamber 221 and communicates with the valve chamber 221 via the first valve port 221a. Furthermore, the fluid chamber 222 communicates with the first input port 23. Therefore, hydrogen gas flowing into the first valve device 2 from the first input port 23 can flow into the valve chamber 221 via the fluid chamber 222 and the first valve port 221a.

The valve chamber 221 also has a second valve port 221b that faces the first valve port 221a, and is connected to the second input port 24 via the second valve port 221b. Therefore, the nitrogen gas that flows into the first valve device 2 from the second input port 24 can flow into the valve chamber 221 via the second valve port 221b.

Furthermore, the valve chamber 221 is connected to the output port 25. Therefore, the hydrogen gas or nitrogen gas that flows into the valve chamber 221 can be output from the output port 25.

In addition, the valve chamber 221 is provided with an annular first valve seat 221c around the first valve port 221a. In addition, the valve chamber 221 is provided with an annular second valve seat 221d around the second valve port 221b. In addition, the valve chamber 221 is provided with a disk-shaped valve body 223 positioned coaxially with the first valve port 221a and the second valve port 221b. Since this valve body 223 is connected to the drive rod 215, it can reciprocate between a first position where it abuts against the first valve seat 221c to block the first valve port 221a and a second position where it abuts against the second valve seat 221d to block the second valve port 221b by the drive rod 215 moving up and down. More specifically, if the introduction of operating air into the first chamber 212a of the drive unit 21 is stopped, the piston 211 moves to the side of the first chamber 212a. As a result, the drive rod 215 moves upward in FIG. 2, and the valve body 223 connected to the drive rod 215 is located in the first position. On the other hand, if operating air is introduced into the first chamber 212a of the drive unit 21, the piston 211 moves toward the second chamber 212b. As a result, the drive rod 215 moves downward in FIG. 2, and the valve body 223 connected to the drive rod 215 is located in the second position.

When the valve body 223 is in the first position, hydrogen gas does not flow into the valve chamber 221, and nitrogen gas flows into the valve chamber 221. Thus, nitrogen gas is output from the output port 25 (second state of the first valve device 2). On the other hand, when the valve body 223 is in the second position, nitrogen gas does not flow into the valve chamber 221, and hydrogen gas flows into the valve chamber 221. Thus, hydrogen gas is output from the output port 25 (first state of the first valve device 2). For fail-safe purposes, when the supply of operating air is no longer possible due to a power outage or the like, the biasing force of the coil spring 216 causes the valve body 223 to be positioned in the first position, blocking the flow of hydrogen gas.

The valve unit 22 further includes a pressure application chamber 224 between the fluid chamber 222 and the drive unit 21. The pressure application chamber 224 is connected to the fluid chamber 222 by an internal flow path 226, so that hydrogen gas flowing into the fluid chamber 222 also flows into the pressure application chamber 224.

The driving rod 215 also includes a thin film member 225, which is fixed in the pressure chamber 224. The end face of the thin film member 225 facing the pressure chamber 224 is the pressure action surface 225a, which is subjected to the action of pressure from the hydrogen gas flowing into the pressure chamber 224. The thin film member 225 can also be elastically deformed in the same direction as the driving direction of the driving rod 215 (the up and down direction in the figure) according to the pressure acting on the pressure action surface 225a. In other words, if the pressure acting on the pressure action surface 225a increases, the thin film member 225 elastically deforms toward the driving unit 21, and accordingly moves the driving rod 215 upward. This causes the valve body 223 to move upward (toward the first valve port 221a).

The surface area of the pressure acting surface 225a is larger than the surface area of the surface (opposing surface 223a) of the valve body 223 facing the first valve port 221a. Therefore, the force received by the hydrogen gas flowing into the first valve device 2 is larger on the pressure acting surface 225a than on the opposing surface 223a. In other words, the force of the hydrogen gas flowing into the first valve device 2 elastically deforming the thin film member 225 toward the drive unit 21, i.e., the force that moves the valve body 223 in a direction toward the first valve port 221a, is larger than the force that moves the valve body 223 in a direction away from the first valve port 221a. Therefore, if the pressure value of the hydrogen gas flowing into the first input port 23 becomes unnecessarily high due to a malfunction of the supply source 7 or the like, the hydrogen gas flowing from the fluid chamber 222 into the pressure application chamber 224 through the internal flow path 226 causes the thin film member 225 to elastically deform toward the drive unit 21, positioning the valve body 223 in the first position. In other words, the flow of hydrogen gas is blocked, so the thin film member 225 functions as a fail-safe.

(Regarding the second valve device)
Next, the second valve device 3 (on-off valve) will be described in detail. The second valve device 3 is a normally closed type solenoid valve that is open when energized and closed when de-energized. As shown in Fig. 2, the second valve device 3 includes a drive unit 31 and a valve unit 32 stacked vertically in the figure.

The drive unit 31 has a cylindrical coil bobbin 311 inside. The coil bobbin 311 has a recess 311a on its outer periphery, and an excitation coil 312 is wound around the recess 311a. A fixed iron core 313 and a movable iron core 314 are inserted into the hollow portion 311b of the coil bobbin 311.

The fixed iron core 313 and the movable iron core 314 are arranged side by side on the same axis so that the lower end surface of the fixed iron core 313 in FIG. 2 faces the upper end surface of the movable iron core 314 in FIG. 2. The movable iron core 314 is movable up and down, and when a current is passed through the excitation coil 312, the fixed iron core 313 is magnetized and attracts the movable iron core 314. As a result, the movable iron core 314 moves toward the fixed iron core 313 (upward in FIG. 2). In addition, a rod 315 is inserted and fixed to the movable iron core 314. Therefore, when the fixed iron core 313 attracts the movable iron core 314, the rod 315 also moves in accordance with the movement of the movable iron core 314.

The valve section 32 includes an input port 33, an output port 34, and a valve chamber 322. The valve chamber 322 is connected to the input port 33. Therefore, hydrogen gas or nitrogen gas flowing into the second valve device 3 from the input port 33 can be made to flow into the valve chamber 322. Furthermore, the valve chamber 322 is connected to the output port 34 via the valve opening 322a. Therefore, the hydrogen gas or nitrogen gas flowing into the valve chamber 322 can be output from the output port 34.

The valve chamber 322 is provided with an annular valve seat 322b around the valve port 322a. In addition, the valve chamber 322 is provided with a disk-shaped valve body 321 positioned coaxially with the valve port 322a. This valve body 321 is connected to a rod 315 inserted into the valve chamber 322. Furthermore, one end of a coil spring 324 abuts against the end face of the valve body 321 on the drive unit 31 side. The other end of the coil spring 324 abuts against a flange member 323 provided at a distance from the end face of the valve body 321 on the drive unit 31 side, and the coil spring 324 is in a compressed state. Therefore, the valve body 321 is biased toward the valve seat 322b by the coil spring 324.

The valve body 321 as described above can move toward and away from the valve seat 322b due to the movement of the movable iron core 314 and the biasing force of the coil spring 324. More specifically, when no current is applied to the excitation coil 312, the valve body 321 is moved toward the valve seat 322b by the biasing force of the coil spring 324 and comes into contact with the valve seat 322b. On the other hand, when current is applied to the excitation coil 312, the fixed iron core 313 is magnetized and the movable iron core 314 moves toward the fixed iron core 313. This causes the rod 315 to move upward in FIG. 2, and the valve body 223 connected to the rod 315 moves away from the valve seat 322b.

When the valve body 321 is in contact with the valve seat 322b, the second valve device 3 is in a closed state, and hydrogen gas or nitrogen gas flowing into the second valve device 3 from the input port 33 is not output from the output port 34. When the valve body 321 is separated from the valve seat 322b, the second valve device 3 is in an open state, and hydrogen gas or nitrogen gas flowing into the second valve device 3 from the input port 33 is output from the output port 34. For fail-safe purposes, when power is cut off due to a power outage or the like and electricity is no longer flowing, the second valve device 3 is in a closed state due to the biasing force of the coil spring 324.

(Fuel control)
Next, the control of the supply state of hydrogen gas and nitrogen gas to the burner 5 using the fuel control device 1 (hereinafter, simply referred to as fuel control) will be described. Specifically, the fuel control from the system stopped state, when combustion of the burner 5 is started, to the state in which combustion of the burner 5 is being performed, to the state in which combustion of the burner 5 is stopped and the system stopped state again will be described. Note that the above "system stopped state" means a state in which the operation of the combustion furnace 4 is stopped. In addition, hereinafter, starting combustion of the burner 5 will be simply referred to as "ignition", and stopping combustion of the burner 5 will be simply referred to as "extinguishing".

Fuel control is performed by controlling the first valve device 2 and the second valve device 3 as shown in Figures 3 and 4 by a control program stored in the control unit 9. Figure 3 is a diagram explaining the fuel control process, and shows the state of the first valve device 2 and the second valve device 3 when the system is stopped. Figure 4 is a diagram explaining the fuel control process, and shows the state of the first valve device 2 and the second valve device 3 when pre-purging the supply line L11. Note that pre-purging the supply line L11 means purging the supply line L11 with nitrogen gas G12 before ignition. Figure 5 is a diagram explaining the fuel control process, and shows the state of the first valve device 2 and the second valve device 3 when ignition is performed. Figure 6 is a diagram explaining the fuel control process, and shows the state of the first valve device 2 and the second valve device 3 when combustion of the burner 5 is performed. Figure 7 is a diagram explaining the fuel control process, and shows the state of the first valve device 2 and the second valve device 3 when extinguishing. 3 to 7, the hydrogen gas G11 and nitrogen gas G12 flowing inside the first valve device 2, the second valve device 3, the supply line L11, the hydrogen gas supply line L12, and the nitrogen gas supply line L13 are represented by dots. Specifically, the dots with a relatively high density represent the hydrogen gas G11, and the dots with a relatively low density represent the nitrogen gas G12.

(System stopped)
First, the state of the system being stopped will be described. When the system is being stopped, as shown in Fig. 3, the first valve device 2 is in a state in which the valve body 223 is located at the first position, and the second valve device 3 is in a valve-closed state. That is, in the first valve device 2, the hydrogen gas G11 is blocked, while the nitrogen gas G12 is output from the output port 25 (second state). The nitrogen gas G12 output from the output port 25 is blocked by the second valve device 3. That is, neither the hydrogen gas G11 nor the nitrogen gas G12 flows through the supply line L11.

(Pre-purge step)
To ignite the burner 5 from the system stop state, first, a pre-purge is performed. As shown in FIG. 4, the pre-purge is performed by opening the second valve device 3 while maintaining the valve body 223 of the first valve device 2 in the first position (i.e., while maintaining the first valve device 2 in the second state). By opening the second valve device 3 while maintaining the valve body 223 of the first valve device 2 in the first position, the nitrogen gas G12 that had flowed into the second valve device 3 is output from the output port 34 of the second valve device 3 and flows through the supply line L11. In this way, by flowing the nitrogen gas into the supply line L11, the air in the supply line L11 is replaced with the nitrogen gas G12. This makes it possible to prevent the generation of a flammable mixture of air and hydrogen in the supply line L11, and therefore to prevent backfire during ignition. Therefore, the burner 5 can be ignited safely.

(Ignition step)
After a predetermined time (first predetermined time) has elapsed since the start of the pre-purge, the burner 5 is ignited. As shown in FIG. 5, the burner 5 is ignited by positioning the valve body 223 of the first valve device 2 in the second position (i.e., changing the first valve device 2 from the second state to the first state) while maintaining the second valve device 3 in the open state. By positioning the valve body 223 of the first valve device 2 in the second position, the nitrogen gas G12 is blocked and the hydrogen gas G11 is output from the output port 25 of the first valve device 2. When the hydrogen gas G11 output from the output port 25 of the first valve device 2 flows into the second valve device 3, the hydrogen gas G11 is output from the output port 34 of the second valve device 3 to the supply line L11 because the second valve device 3 is maintained in the open state. Thus, the nitrogen gas G12 that filled the supply line L11 during the pre-purge is replaced with the hydrogen gas G11. Then, when the hydrogen gas G11 reaches the burner 5, it is ignited, for example, by a pilot burner provided in the combustion furnace 4, and combustion of the hydrogen gas begins in the burner 5. Note that the above-mentioned predetermined time means the time for which pre-purging continues, and is appropriately set to a time that allows sufficient purging with the nitrogen gas G12 to be performed based on the volume of the supply line L11, the flow rate of the inert gas being supplied, etc.

(Continuation of combustion)
After ignition, while the burner 5 continues to burn, the valve body 223 of the first valve device 2 is maintained in the second position (i.e., the first valve device 2 is maintained in the first position), and the second valve device 3 is maintained in the open state, as shown in Fig. 6. This allows hydrogen gas G11 to continue to be supplied to the burner 5 through the supply line L11, and the burner 5 can continue to burn.

(Fire extinguishing steps)
As shown in FIG. 7, the burner 5 is extinguished by positioning the valve body 223 of the first valve device 2 in the first position (i.e., changing the first valve device 2 from the first state to the second state) while maintaining the second valve device 3 in the open state. By positioning the valve body 223 of the first valve device 2 in the first position, the hydrogen gas G11 is blocked and the nitrogen gas G12 is output from the output port 25 of the first valve device 2. When the nitrogen gas G12 output from the output port 25 of the first valve device 2 flows into the second valve device 3, the second valve device 3 is maintained in the open state, so that the nitrogen gas G12 is output from the output port 34 of the second valve device 3 to the supply line L11. Thus, the hydrogen gas G11 that filled the supply line L11 when the burner 5 was in the combustion state is post-purged. The post-purging of the supply line L11 means purging the supply line L11 with the nitrogen gas G12 when extinguishing the burner 5. More specifically, the hydrogen gas G11 in the supply line L11 is pushed from the upstream side to the downstream side (the burner 5 side) by the nitrogen gas G12, and the gas in the supply line L11 is replaced from the hydrogen gas G11 to the nitrogen gas G12. As the post-purge progresses, the concentration of the hydrogen gas G11 remaining in the supply line L11 decreases, and the burner 5 is naturally extinguished. Then, finally, the supply line L11 is filled with the nitrogen gas G12 (the state becomes the same as the state shown in FIG. 4). In this way, by replacing the gas in the supply line L11, the burner 5 is extinguished, so that the hydrogen gas G11 does not remain in the supply line L11 and the occurrence of backfire can be prevented. Therefore, the burner 5 can be safely extinguished.

(System shutdown step)
The system is stopped after a predetermined time (second predetermined time) has elapsed since the start of the post-purge. The system is stopped by closing the second valve device 3 while maintaining the valve body 223 of the first valve device 2 in the first position (i.e., while maintaining the first valve device 2 in the second state). That is, the system is stopped by setting the first valve device 2 and the second valve device 3 to the state shown in Fig. 3. The above-mentioned predetermined time means the time during which the post-purge continues, and is appropriately set to a time that allows sufficient purging with the nitrogen gas G12 to be performed based on the volume of the supply line L11, the flow rate of the inert gas to be supplied, etc.

(About the action and effect)
As described above, the burner fuel control device 1 according to this embodiment has the following features:
(1) A burner fuel control device 1 selectively supplies fuel (hydrogen gas) or inert gas (nitrogen gas) to a burner 5 that burns fuel (hydrogen gas), characterized in that a supply line L11 for supplying the fuel (hydrogen gas) or inert gas (nitrogen gas) is connected to the burner 5, a first valve device 2 and a second valve device 3 downstream of the first valve device 2 are arranged in the supply line L11, the first valve device 2 has a first input port 23 connected to a supply source 7 of the fuel (hydrogen gas), a second input port 24 connected to a supply source 8 of the inert gas (nitrogen gas), and an output port 25, and is a three-way valve that can switch between a first state in which the fuel (hydrogen gas) is output from the output port 25 and a second state in which the inert gas (nitrogen gas) is output from the output port 25, and the second valve device 3 is an on-off valve that can switch between an open state in which the supply line L11 is opened and a closed state in which the supply line L11 is blocked.

(2) In the burner fuel control device 1, it is preferable to include a control unit 9 that stores a control program for controlling the first valve device 2 and the second valve device 3, and the control program includes a step of changing the second valve device 3 from a closed state to an open state while maintaining the first valve device 2 in the second state in order to start combustion in the burner 5 (pre-purge step), and a step of changing the first valve device 2 from the second state to the first state after a first predetermined time has elapsed while maintaining the second valve device 3 in the open state (ignition step).

(3) In the burner fuel control device 1, it is preferable to include a control unit 9 that stores a control program for controlling the first valve device 2 and the second valve device 3, and the control program includes a step of switching the first valve device 2 from the first state to the second state while maintaining the second valve device 3 in an open state in order to stop combustion of the burner 5 (extinguishing step), and a step of switching the second valve device 3 from the open state to the closed state after a second predetermined time has elapsed while maintaining the first valve device 2 in the second state (system shutdown step).

(4) In the burner fuel control device 1, the first valve device 2 preferably includes a valve chamber 221 that is connected to the first input port 23, the second input port 24, and the output port 25, and a valve body 223 that is disposed within the valve chamber 221; the valve chamber 221 preferably includes a first valve port 221a through which fuel (hydrogen gas) flows in from the first input port 23, and a second valve port 221b that is positioned opposite the first valve port 221a and through which inert gas flows in from the second input port 24; and the valve body 223 preferably is held within the valve chamber 221 so as to be capable of reciprocating between a first position that blocks the first valve port 221a and a second position that blocks the second valve port 221b.

(5) In the burner fuel control device 1, the first valve device 2 is preferably provided with a drive rod 215 connected to the valve body 223 and reciprocating the valve body 223, the drive rod 215 is preferably provided with a pressure acting surface 225a that receives the pressure of the fuel (hydrogen) input from the first input port 23 to the first valve device 2 so that the drive rod 215 moves in a direction in which the valve body 223 approaches the first valve port 221a, and the surface area of the pressure acting surface 225a is preferably larger than the surface area of the surface (opposing surface 223a) of the valve body 223 that faces the first valve port 221a.

As described above, the burner fuel control method according to the present embodiment includes the following steps:
(6) A burner fuel control method for controlling combustion of a burner 5 using the above-mentioned burner fuel control device 1, characterized in that it includes a step of changing the second valve device 3 from a closed state to an open state while maintaining the first valve device 2 in a second state in order to start combustion of the burner 5 (a pre-purge step), and a step of changing the first valve device 2 from the second state to the first state after a first predetermined time has elapsed while maintaining the second valve device 3 in an open state (an ignition step).

(7) The burner fuel control method for controlling the combustion of the burner 5 using the burner fuel control device 1 is characterized by comprising a step of switching the first valve device 2 from the first state to the second state while maintaining the second valve device 3 in an open state in order to stop the combustion of the burner 5 (extinguishing step), and a step of switching the second valve device 3 from the open state to the closed state after a second predetermined time has elapsed while maintaining the first valve device 2 in the second state (system stopping step).

According to the above-mentioned fuel control device for burner 1, in the fuel control device for burner 1 that selectively supplies fuel (hydrogen gas) or inert gas (nitrogen gas) to the burner 5 that burns the fuel (hydrogen gas), a supply line L11 that supplies the fuel (hydrogen gas) or inert gas (nitrogen gas) is connected to the burner 5, a first valve device 2 and a second valve device 3 downstream of the first valve device 2 are arranged on the supply line L11, the first valve device 2 is provided with a first input port 23 connected to a supply source 7 of the fuel (hydrogen gas), a second input port 24 connected to a supply source 8 of the inert gas (nitrogen gas), and an output port 25, and is a three-way valve that can be switched between a first state in which the fuel (hydrogen gas) is output from the output port 25 and a second state in which the inert gas (nitrogen gas) is output from the output port 25. and the second valve device 3 is an on-off valve that can be switched between an open state in which the supply line L11 is opened and a closed state in which the supply line L11 is blocked. Therefore, for example, as described in (2) or (6) above, in order to start combustion in the burner 5, the second valve device 3 is changed from a closed state to an open state while maintaining the first valve device 2 in the second state (pre-purging step), and after a first predetermined time has elapsed, the first valve device 2 is changed from the second state to the first state while maintaining the second valve device 3 in the open state (ignition step). Then, when combustion in the burner 5 is to be started (at the time of ignition), first, the supply line can be purged (pre-purged) with an inert gas (e.g., nitrogen gas) to change the second valve device 3 from a closed state to an open state while maintaining the first valve device 2 in the second state. Then, after a predetermined time has elapsed, the first valve device 2 is changed from the second state to the first state while the second valve device 3 is maintained in an open state, so that fuel (hydrogen gas) is supplied to the supply line L11 and the burner 5 can be ignited.

In this way, by first purging the supply line L11 when igniting the burner 5, it is possible to prevent hydrogen gas from remaining in the supply line L11, and thus prevent backfire from occurring. Therefore, the burner 5 can be ignited safely.

For example, as described in (3) or (7) above, in order to stop the combustion of the burner 5, the first valve device 2 is switched from the first state to the second state while the second valve device 3 is maintained in the open state (extinguishing step), and after the second predetermined time has elapsed, the second valve device 3 is switched from the open state to the closed state while the first valve device 2 is maintained in the second state (system stop step). At the time of stopping the combustion (extinguishing), first, the first valve device 2 is switched from the first state to the second state while the second valve device 3 is maintained in the open state, so that the supply line L11 can be purged (post-purged) with nitrogen gas. In other words, the hydrogen gas that filled the supply line L11 during the combustion of the burner 5 can be replaced with nitrogen gas. Then, after the predetermined time has elapsed, the second valve device 3 is switched from the open state to the closed state while the first valve device 2 is maintained in the second state, thereby cutting off the supply of nitrogen gas.

In this way, when the burner 5 is extinguished, the supply line L11 is first purged and the hydrogen gas is replaced with an inert gas, which prevents hydrogen gas from remaining in the supply line L11 and thus prevents backfire. Therefore, the burner 5 can be extinguished safely.

As described above, by reliably purging the supply line L11 with nitrogen gas both when the burner 5 is ignited and when it is extinguished, it is possible to prevent the generation of a flammable mixture in the supply line L11, and thus prevent the occurrence of flashback without using a flame arrester. This prevents the occurrence of fuel pressure loss and increases in cost and installation space that would otherwise be caused by using a flame arrester. In addition, since the first valve device 2 and the second valve device 3 are sufficient as the valve devices used in the fuel control device, it is possible to prevent the occurrence of flashback with fewer valve devices than in the past (see Figure 8).

The above embodiment is merely an example and does not limit the present invention in any way. Therefore, the present invention can be improved and modified in various ways without departing from the scope of the present invention. For example, the first valve device 2 is described as an air-operated valve device, but it may be an electromagnetic valve. The first valve device 2 and the second valve device 3 may be directly connected or connected via a pipe. Although hydrogen gas is given as the fuel and nitrogen gas as the inert gas, they are not limited to these. For example, methane gas, propane gas, acetylene gas, etc. may be used as the fuel, and argon gas, helium gas, etc. may be used as the inert gas.

Reference Signs List 1 Burner fuel control device 2 First valve device 3 Second valve device 5 Burner 23 First input port 24 Second input port 25 Output port L11 Supply line

Claims (6)

A burner fuel control device that selectively supplies the fuel or an inert gas to a burner that burns the fuel,
A supply line for supplying the fuel or the inert gas is connected to the burner;
A first valve device and a second valve device downstream of the first valve device are disposed in the supply line;
The first valve device is
a first input port connected to a source of the fuel, a second input port connected to a source of the inert gas, and an output port;
a three-way valve that is switchable between a first state in which the fuel is output from the output port and a second state in which the inert gas is output from the output port;
The second valve device is
an on-off valve that is switchable between an open state in which the supply line is opened and a closed state in which the supply line is blocked;
a control unit that stores a control program for controlling the first valve device and the second valve device;
The control program includes:
for initiating combustion of the burner;
changing the second valve device from the closed state to the open state while maintaining the first valve device in the second state;
after a first predetermined time has elapsed, changing the first valve device from the second state to the first state while maintaining the second valve device in the open state;
To have
A fuel control device for a burner comprising: A burner fuel control device that selectively supplies the fuel or an inert gas to a burner that burns the fuel,
A supply line for supplying the fuel or the inert gas is connected to the burner;
A first valve device and a second valve device downstream of the first valve device are disposed in the supply line;
The first valve device is
a first input port connected to a source of the fuel, a second input port connected to a source of the inert gas, and an output port;
a three-way valve that is switchable between a first state in which the fuel is output from the output port and a second state in which the inert gas is output from the output port;
The second valve device is
an on-off valve that is switchable between an open state in which the supply line is opened and a closed state in which the supply line is blocked;
a control unit that stores a control program for controlling the first valve device and the second valve device;
The control program includes:
To stop the combustion of the burner,
switching the first valve device from the first state to the second state while maintaining the second valve device in the open state;
after a second predetermined time has elapsed, changing the second valve device from the open state to the closed state while maintaining the first valve device in the second state;
To have
A fuel control device for a burner comprising: 3. The burner fuel control device according to claim 1,
the first valve device includes a valve chamber communicating with the first input port, the second input port, and the output port, and a valve body disposed in the valve chamber;
The valve chamber is
a first valve port through which the fuel flows in from the first input port;
a second valve port located opposite the first valve port and configured to allow the inert gas to flow in from the second input port;
To have
the valve body is held in the valve chamber so as to be capable of reciprocating between a first position at which the valve body closes the first valve port and a second position at which the valve body closes the second valve port;
A fuel control device for a burner comprising: 4. The burner fuel control device according to claim 3 ,
the first valve device includes a drive rod connected to the valve body and causing the valve body to reciprocate;
the drive rod has a pressure acting surface that is acted upon by pressure of the fuel input from the first input port to the first valve device so that the drive rod moves in a direction in which the valve body approaches the first valve port;
a surface area of the pressure acting surface is larger than a surface area of a surface of the valve body facing the first valve port;
A fuel control device for a burner comprising: A burner fuel control device that selectively supplies fuel or an inert gas to a burner that burns fuel,
A supply line for supplying the fuel or the inert gas is connected to the burner;
A first valve device and a second valve device downstream of the first valve device are disposed in the supply line;
The first valve device is
a first input port connected to a source of the fuel, a second input port connected to a source of the inert gas, and an output port;
a three-way valve that is switchable between a first state in which the fuel is output from the output port and a second state in which the inert gas is output from the output port;
The second valve device is
an on-off valve that is switchable between an open state in which the supply line is opened and a closed state in which the supply line is blocked;
A burner fuel control method for controlling burner combustion using a burner fuel control device, comprising:
for initiating combustion of the burner;
changing the second valve device from the closed state to the open state while maintaining the first valve device in the second state;
after a first predetermined time has elapsed, changing the first valve device from the second state to the first state while maintaining the second valve device in the open state;
To have
A burner fuel control method comprising: A burner fuel control device that selectively supplies fuel or an inert gas to a burner that burns fuel,
A supply line for supplying the fuel or the inert gas is connected to the burner;
A first valve device and a second valve device downstream of the first valve device are disposed in the supply line;
The first valve device is
a first input port connected to a source of the fuel, a second input port connected to a source of the inert gas, and an output port;
a three-way valve that is switchable between a first state in which the fuel is output from the output port and a second state in which the inert gas is output from the output port;
The second valve device is
an on-off valve that is switchable between an open state in which the supply line is opened and a closed state in which the supply line is blocked;
A burner fuel control method for controlling burner combustion using a burner fuel control device, comprising:
To stop the combustion of the burner,
switching the first valve device from the first state to the second state while maintaining the second valve device in the open state;
after a second predetermined time has elapsed, changing the second valve device from the open state to the closed state while maintaining the first valve device in the second state;
To have
A burner fuel control method comprising:

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