Combustion system, method of purging ammonia gas in combustion system, and method of supplying ammonia gas in combustion system

Abstract

To maintain sealing of piping by gas after purging when ammonia gas is used as fuel.SOLUTION: A combustion system 100 includes a control device 90 which is configured to execute, in order to purge ammonia gas ga from a fuel conduit L1, processes of: closing a fuel valve V2 and stopping supply of the ammonia gas ga to a burner 12; opening a first gas valve V4 and supplying first gas g1 inert to the ammonia gas ga to the fuel conduit L1; and opening a second gas valve V5 and supplying second gas g2 inert to the first gas g1 to the fuel conduit L1 after concentration of the ammonia gas ga in the gas in the fuel conduit L1 decreases to a first threshold or below.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to combustion systems. [Background technology]

[0002] In combustion systems such as boilers, ammonia may be used as fuel. For example, Patent Document 1 discloses a power generation facility including a boiler that uses ammonia as fuel. When combustion stops and the boiler is not used for a long period of time, ammonia gas in the ammonia gas fuel piping facility is replaced with nitrogen gas, and the ammonia gas is sent to an ammonia gas absorption unit. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6319526 Summary of the Invention [Problem to be solved by the invention]

[0004] To purge ammonia gas from the piping, a gas inert to ammonia gas, such as nitrogen, is used. Furthermore, to maintain the gas seal of the piping after purging, it is necessary to continue supplying gas to prevent a drop in pressure within the piping. For example, when co-firing ammonia and fossil fuel, sealing the piping with gas is necessary to prevent ash from accumulating in the nozzle injection holes after purging. However, when nitrogen is used for purging as in Patent Document 1, costs increase.

[0005] The present disclosure aims to provide a combustion system that, when ammonia gas is used as fuel, can maintain gas sealing of piping after purging. The present disclosure also aims to provide a method for purging ammonia gas in a combustion system and a method for supplying ammonia gas in a combustion system. [Means for solving the problem]

[0006] A combustion system according to one aspect of the present disclosure includes a burner, a fuel conduit connected to the burner and supplying ammonia gas to the burner, a fuel valve provided in the fuel conduit and opening and closing the fuel conduit, a first gas conduit fluidly connected to the fuel conduit between the burner and the fuel valve and supplying a first gas inert to the ammonia gas to the fuel conduit, a second gas conduit fluidly connected to the fuel conduit between the burner and the fuel valve and supplying a second gas inert to the first gas to the fuel conduit, a first gas valve provided in the first gas conduit and opening and closing the first gas conduit, and a valve provided in the second gas conduit and a control device that controls the fuel valve, the first gas valve, and the second gas valve, the control device being configured to: close the fuel valve to stop the supply of ammonia gas to the burner in order to purge the ammonia gas from the fuel conduit; open the first gas valve to supply the first gas to the fuel conduit; and open the second gas valve to supply the second gas to the fuel conduit after the concentration of ammonia gas in the gas in the fuel conduit has fallen below a first threshold.

[0007] The control device may store a second threshold value for purging, and the control device may determine that the concentration of ammonia gas in the gas in the fuel conduit has fallen below the first threshold value when the elapsed time since the first gas valve was opened exceeds the second threshold value.

[0008] The combustion system may include a first sensor that detects the concentration of ammonia gas in the gas in the fuel conduit, the control device may store a first threshold value, and the control device may determine whether the concentration of ammonia gas received from the first sensor is less than or equal to the first threshold value.

[0009] The first gas may be nitrogen and the second gas may be air.

[0010] The first gas may include exhaust gas.

[0011] The first gas may be a mixture of nitrogen and exhaust gas.

[0012] The first gas may be exhaust gas.

[0013] A combustion system according to another aspect of the present disclosure includes a burner, a fuel conduit connected to the burner and supplying ammonia gas to the burner, a fuel valve provided in the fuel conduit and opening and closing the fuel conduit, a first gas conduit fluidly connected to the fuel conduit between the burner and the fuel valve and supplying a first gas inert to the ammonia gas to the fuel conduit, a second gas conduit fluidly connected to the fuel conduit between the burner and the fuel valve and supplying a second gas inert to the first gas to the fuel conduit, a first gas valve provided in the first gas conduit and opening and closing the first gas conduit, and a valve provided in the second gas conduit. a second gas valve that opens and closes the second gas conduit; and a control device that controls the fuel valve, the first gas valve, and the second gas valve, the control device being configured to: close the second gas valve to stop the supply of the second gas to the fuel conduit in order to supply ammonia gas to the burner; open the first gas valve to supply the first gas to the fuel conduit; and open the fuel valve to supply the ammonia gas to the burner after the concentration of a predetermined component in the second gas in the gas in the fuel conduit has fallen below a third threshold.

[0014] The control device may store a fourth threshold value for purging, and the control device may determine that the concentration of a predetermined component in the second gas in the gas in the fuel conduit has fallen below a third threshold value when the elapsed time since the first gas valve was opened exceeds the fourth threshold value.

[0015] The second gas may be air, and the combustion system may include a second sensor that detects the concentration of oxygen in the gas in the fuel conduit, a third threshold value may be set for the concentration of oxygen, the control device may store the third threshold value, and the control device may determine whether the concentration of oxygen received from the second sensor is less than or equal to the third threshold value.

[0016] The first gas may be nitrogen and the second gas may be air.

[0017] The first gas may include exhaust gas.

[0018] The first gas may be a mixture of nitrogen and exhaust gas.

[0019] The first gas may be exhaust gas.

[0020] Yet another aspect of the present disclosure is a method for purging ammonia gas in a combustion system, the combustion system including a burner, a fuel conduit connected to the burner and supplying ammonia gas to the burner, a fuel valve provided in the fuel conduit and configured to open and close the fuel conduit, a first gas conduit in fluid communication with the fuel conduit between the burner and the fuel valve and supplying a first gas inert to the ammonia gas to the fuel conduit, and a second gas conduit in fluid communication with the fuel conduit between the burner and the fuel valve and supplying a second gas inert to the first gas to the fuel conduit. a second gas conduit that supplies ammonia gas to the burner; a first gas valve provided in the first gas conduit that opens and closes the first gas conduit; and a second gas valve provided in the second gas conduit that opens and closes the second gas conduit, and the method includes closing a fuel valve to stop the supply of ammonia gas to the burner, opening the first gas valve to supply the first gas to the fuel conduit, and after the concentration of ammonia gas in the gas in the fuel conduit drops below a first threshold, opening the second gas valve to supply the second gas to the fuel conduit.

[0021] Yet another aspect of the present disclosure is a method for supplying ammonia gas in a combustion system, the combustion system including a burner, a fuel conduit connected to the burner and supplying ammonia gas to the burner, a fuel valve provided in the fuel conduit and configured to open and close the fuel conduit, a first gas conduit in fluid communication with the fuel conduit between the burner and the fuel valve and configured to supply a first gas inert to the ammonia gas to the fuel conduit, and a second gas inert to the first gas conduit between the burner and the fuel valve and configured to supply a second gas inert to the fuel conduit. a second gas conduit for supplying ammonia gas to the burner; a first gas valve provided in the first gas conduit for opening and closing the first gas conduit; and a second gas valve provided in the second gas conduit for opening and closing the second gas conduit, the method including: closing the second gas valve to stop the supply of the second gas to the fuel conduit; opening the first gas valve to supply the first gas to the fuel conduit; and, after a concentration of a predetermined component in the second gas in the gas in the fuel conduit falls below a third threshold, opening the fuel valve to supply ammonia gas to the burner. [Effects of the Invention]

[0022] According to the present disclosure, when ammonia is used as fuel, the gas can maintain a seal on the piping after purging. [Brief explanation of the drawings]

[0023] [Figure 1] FIG. 1 is a schematic diagram of a combustion system according to a first embodiment. [Figure 2] FIG. 2 is a flow chart illustrating a method for purging ammonia gas. [Figure 3] FIG. 3 is a flow chart showing a method for supplying ammonia gas. [Figure 4] FIG. 4 is a schematic diagram of a combustion system according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0024] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Specific dimensions, materials, numerical values, etc. shown in the embodiments are merely examples for ease of understanding and do not limit the present disclosure unless otherwise specified. In this specification and drawings, elements having substantially the same functions and configurations are designated by the same reference numerals to avoid redundant explanation, and elements not directly related to the present disclosure are not shown.

[0025] 1 is a schematic diagram of a combustion system 100 according to a first embodiment. For example, in this embodiment, the combustion system 100 is applied to a boiler 1 of a thermal power plant. In other embodiments, the combustion system 100 may be applied to other facilities. For example, the combustion system 100 includes the boiler 1 and a control device 90.

[0026] The boiler 1 includes a furnace 11. The furnace 11 defines a combustion space S. In the present disclosure, combustion space means the space in which fuel is combusted.

[0027] The boiler 1 includes at least one burner 12. In this embodiment, the boiler 1 includes a plurality of burners 12. For example, a burner 12 is provided on each of the opposing front and rear walls of the furnace 11. For example, the plurality of burners 12 are arranged in a single row or multiple rows along the horizontal direction.

[0028] The burner 12 injects fuel containing ammonia gas ga into the combustion space S. For example, the burner 12 may inject only ammonia gas ga into the combustion space S. Alternatively, for example, the burner 12 may inject a mixed fuel of ammonia gas ga and other fuel such as a fossil fuel into the combustion space S. Alternatively, for example, some of the multiple burners 12 may inject ammonia gas ga into the combustion space S, and the remaining multiple burners 12 may inject other fuel into the combustion space S. Alternatively, the burner 12 may inject only other fuel into the combustion space S as needed. The fuel is combusted in the combustion space S. The boiler 1 is connected to a flue 2. The flue 2 is fluidly connected to a chimney (not shown). Exhaust gas Ex generated by combustion is guided from the combustion space S to the chimney via the flue 2.

[0029] The burner 12 is connected to a first fuel conduit (fuel conduit) L1. The first fuel conduit L1 supplies ammonia gas ga to the burner 12. For example, the first fuel conduit L1 is connected to an ammonia supply source (not shown), such as a tank or an ammonia manufacturing apparatus. For example, the ammonia supply source may be a tank that stores liquid ammonia. In this case, for example, the first fuel conduit L1 may be provided with a vaporizer (not shown), and ammonia gas ga may be supplied from the vaporizer to the burner 12. Note that if a portion of the liquid ammonia is not vaporized in the vaporizer, the ammonia gas ga may contain liquid ammonia. The ammonia supply source is not limited to a tank.

[0030] A first fuel valve V1 is provided in the first fuel conduit L1. The first fuel valve V1 opens and closes the first fuel conduit L1. The first fuel valve V1 is communicatively connected to the control device 90 via wire or wirelessly and is controlled by the control device 90. For example, the first fuel valve V1 may be a ball valve. The first fuel valve V1 is not limited to a ball valve and may include any mechanism that can open and close the first fuel conduit L1.

[0031] A second fuel valve V2 is provided in the first fuel conduit L1. The second fuel valve V2 is provided in the first fuel conduit L1 between the first fuel valve V1 and the burner 12. The second fuel valve V2 is provided in the first fuel conduit L1 downstream of the first fuel valve V1. The second fuel valve V2 opens and closes the first fuel conduit L1. The second fuel valve V2 is connected to the control device 90 so as to be able to communicate with the control device 90 via wire or wirelessly, and is controlled by the control device 90. For example, the second fuel valve V2 may be a ball valve. The second fuel valve V2 is not limited to a ball valve and may include any mechanism capable of opening and closing the first fuel conduit L1.

[0032] A vent pipe L2 is connected to the first fuel conduit L1 between the first fuel valve V1 and the second fuel valve V2. For example, the vent pipe L2 is connected to an ammonia disposal device (not shown), such as a water abatement tank or a flare stack.

[0033] A vent valve V3 is provided in the vent pipe L2. The vent valve V3 opens and closes the vent pipe L2. The vent valve V3 is communicatively connected to the control device 90 via wire or wirelessly and is controlled by the control device 90. For example, in this embodiment, the second fuel valve V2 and the vent valve V3 may be operated simultaneously by a single driving device. In other embodiments, the second fuel valve V2 and the vent valve V3 may be operated by separate driving devices. For example, the vent valve V3 may be a ball valve. The vent valve V3 is not limited to a ball valve and may include any mechanism capable of opening and closing the vent pipe L2.

[0034] The first fuel conduit L1 is fluidly connected to the first gas conduit L3. The first gas conduit L3 supplies the first gas g1 to the first fuel conduit L1. The first gas conduit L3 is connected to the first fuel conduit L1 at a position downstream of the second fuel valve V2. In this embodiment, the first gas conduit L3 is connected to a junction pipe L5 and is connected to the first fuel conduit L1 via the junction pipe L5. In other embodiments, the first gas conduit L3 may be connected directly to the first fuel conduit L1.

[0035] The first gas g1 is a gas inert to ammonia. For example, the first gas g1 may be nitrogen. The first gas g1 is not limited to nitrogen. For example, the first gas conduit L3 may be connected to a first gas supply source (not shown), such as a tank or a nitrogen production device. For example, the first gas supply source may be a tank that stores gaseous nitrogen. The first gas supply source is not limited to a tank.

[0036] A first gas valve V4 is provided in the first gas conduit L3. The first gas valve V4 opens and closes the first gas conduit L3. The first gas valve V4 is communicably connected to the control device 90 via wire or wirelessly and is controlled by the control device 90. For example, the first gas valve V4 may be a ball valve. The first gas valve V4 is not limited to a ball valve and may include any mechanism capable of opening and closing the first gas conduit L3.

[0037] The first fuel conduit L1 is in fluid communication with the second gas conduit L4. The second gas conduit L4 supplies the first fuel conduit L1 with a second gas g2. The second gas conduit L4 is connected to the first fuel conduit L1 at a position downstream of the second fuel valve V2. In this embodiment, the second gas conduit L4 is connected to a junction pipe L5 and is connected to the first fuel conduit L1 via the junction pipe L5. In other embodiments, the second gas conduit L4 may be connected directly to the first fuel conduit L1.

[0038] The second gas g2 is a gas inert to the first gas g1. For example, the second gas g2 may be a gas that is less expensive than the first gas g1. For example, the second gas g2 may be air, specifically, ambient air. The second gas is not limited to air. For example, the second gas conduit L4 may be connected to a second gas supply source such as a compressor (not shown). For example, the compressor may draw in ambient air and deliver the drawn air to the second gas conduit L4. The second gas supply source is not limited to a compressor and may be, for example, a fan or a blower. For example, when an existing combustion system equipped with fans such as an FDF (forced draft fan) and a PAF (primary air fan) is retrofitted to the combustion system 100, the second gas conduit L4 may be in fluid communication with one of these fans and receive air therefrom. Alternatively, a fan may be newly installed in the combustion system to deliver air to the second gas conduit L4.

[0039] A second gas valve V5 is provided in the second gas conduit L4. The second gas valve V5 opens and closes the second gas conduit L4. The second gas valve V5 is communicably connected to the control device 90 via wire or wirelessly and is controlled by the control device 90. For example, the second gas valve V5 may be a ball valve. The second gas valve V5 is not limited to a ball valve and may include any mechanism capable of opening and closing the second gas conduit L4.

[0040] The first fuel conduit L1 may be provided with a first sensor Se1 that measures the concentration of ammonia gas in the gas in the first fuel conduit L1. For example, the first sensor Se1 may be provided in the first fuel conduit L1 in a section between the second fuel valve V2 and the burner 12. In this embodiment, the first sensor Se1 is provided at a position P1 where the first fuel conduit L1 branches off to the multiple burners 12. The location of the first sensor Se1 is not limited thereto. The first sensor Se1 is connected to the control device 90 so as to be able to communicate with the control device 90 via wire or wirelessly, and transmits measurement data to the control device 90.

[0041] A second sensor Se2 that measures the concentration of oxygen in the gas in the first fuel conduit L1 may be provided in the first fuel conduit L1. For example, the second sensor Se2 may be provided in a section of the first fuel conduit L1 between the second fuel valve V2 and the burner 12. In this embodiment, the second sensor Se2 is provided at position P1, similar to the first sensor Se1. Note that in FIG. 1 , the second sensor Se2 is shown separated from position P1 to avoid overlap with the first sensor Se1. The position of the second sensor Se2 is not limited thereto. The second sensor Se2 is communicatively connected to the control device 90 via wire or wirelessly and transmits measurement data to the control device 90.

[0042] The first fuel conduit L1 may be provided with a third sensor Se3 that measures the pressure inside the first fuel conduit L1. For example, the third sensor Se3 may be provided in the first fuel conduit L1 in a section between the second fuel valve V2 and the burner 12. The third sensor Se3 is communicably connected to the control device 90 by wire or wirelessly and transmits measurement data to the control device 90.

[0043] A flame arrester (not shown) for preventing flashback may be provided at least at one position on the first fuel conduit L1.

[0044] In this embodiment, the burner 12 is connected to a second fuel conduit L6. The second fuel conduit L6 supplies other fuel, such as fossil fuel, to the burner 12. The second fuel conduit L6 is connected to a supply source of other fuel (not shown). If the boiler 1 uses only ammonia gas ga as fuel, the second fuel conduit L6 is not essential.

[0045] The control device 90 controls the combustion system 100. The control device 90 includes components such as a processor 90a, a storage device 90b, and a connector 90c, which are connected to one another via a bus. For example, the processor 90a includes a central processing unit (CPU). For example, the storage device 90b includes a hard disk, a read-only memory (ROM) in which programs and the like are stored, and a random access memory (RAM) as a work area. The control device 90 is connected to each component of the combustion system 100 via the connector 90c so as to be able to communicate with them via a wired or wireless connection. For example, the control device 90 may further include other components such as a display device such as a liquid crystal display or a touch panel, and an input device such as a keyboard, buttons, or a touch panel. For example, the operation of the control device 90 may be realized by the processor 90a executing a program stored in the storage device 90b.

[0046] Next, the operation of the combustion system 100 while the ammonia gas ga is being combusted will be described.

[0047] During operation of the boiler 1 (burner 12), the processor 90a opens the first fuel valve V1 and the second fuel valve V2 and closes the vent valve V3, the first gas valve V4, and the second gas valve V5. The first fuel conduit L1 supplies ammonia gas ga to the burner 12. The burner 12 injects the ammonia gas ga into the combustion space S, where the ammonia gas ga is burned. For example, the combustion gas may be used to heat water to steam. The boiler 1 may burn only ammonia gas ga, or may burn ammonia gas ga and other fuels together.

[0048] Next, the operation of the combustion system 100 when stopping the combustion of the ammonia gas ga will be described.

[0049] Fig. 2 is a flowchart showing a method for purging ammonia gas (ga). For example, the operation shown in Fig. 2 may be started when a command to stop combustion of ammonia gas (ga) is input to the control device 90. Referring to Fig. 1, before the operation shown in Fig. 2, the first fuel valve V1 and the second fuel valve V2 are open, and the vent valve V3, the first gas valve V4, and the second gas valve V5 are closed. Before the operation shown in Fig. 2, the boiler 1 may be burning only ammonia gas (ga), or may be burning ammonia gas (ga) and another fuel together.

[0050] 2, the processor 90a closes the second fuel valve V2 to stop the supply of ammonia gas ga to the burner 12 (step S100). At the same time, in step S100, the vent valve V3 is opened.

[0051] Next, the processor 90a opens the first gas valve V4 to supply the first gas g1 to the first fuel conduit L1 (step S102).

[0052] 1, the first gas g1 pushes the ammonia gas ga remaining in the section of the first fuel conduit L1 downstream of the second fuel valve V2 into the combustion space S via the burner 12. When the ammonia gas ga is no longer pushed out from the burner 12, combustion stops. Note that the combustion may be stopped by any fire extinguishing means before the operation shown in FIG.

[0053] Referring to FIG. 2, the processor 90a then determines whether the concentration of ammonia gas ga in the gas inside the first fuel conduit L1 has fallen to or below a first threshold value (step S104).

[0054] 1, for example, the length of time (second threshold) required to replace the ammonia gas ga in the first fuel conduit L1 with the first gas g1 until the concentration of the ammonia gas ga in the gas in the first fuel conduit L1 falls below the first threshold may be determined in advance by experiment or analysis and stored in the memory device 90b. For example, the first threshold may be determined so that the remaining ammonia gas ga does not burn when the second gas g2 is supplied. For example, the first threshold is 15%. For example, the second threshold is determined depending on factors such as the size of the first fuel conduit L1, the flow rate of the first gas g1, and the first threshold. In step S104, if the elapsed time since the first gas valve V4 was opened exceeds the second threshold stored in the memory device 90b, the processor 90a may determine that the concentration of the ammonia gas ga in the gas in the first fuel conduit L1 has fallen below the first threshold.

[0055] Alternatively or additionally, in step S104, the control device 90 may receive the concentration of ammonia gas ga from the first sensor Se1. The memory device 90b may store a first threshold value instead of or in addition to the second threshold value. In step S104, the processor 90a may determine whether the concentration of ammonia gas ga received from the first sensor Se1 is equal to or less than the first threshold value.

[0056] 2, if it is determined in step S104 that the concentration of ammonia gas ga in the gas in the first fuel conduit L1 has not decreased to or below the first threshold value (NO), the processor 90a returns to step S104. For example, step S104 may be repeated at predetermined intervals.

[0057] In step S104, if it is determined that the concentration of ammonia gas ga in the gas in the first fuel conduit L1 has fallen below the first threshold (YES), the processor 90a closes the first gas valve V4 to stop the supply of the first gas g1 to the first fuel conduit L1 (step S106).

[0058] Subsequently, the processor 90a opens the second gas valve V5 to supply the second gas g2 to the first fuel conduit L1 (S108), and ends the operation. If the ammonia gas ga and another fuel are mixed and combusted before the operation shown in FIG. 2, the boiler 1 may continue to combust the other fuel.

[0059] 1, the second gas g2 pushes the first gas g1 remaining in the section of the first fuel conduit L1 downstream of the second fuel valve V2 into the combustion space S via the burner 12. Therefore, the first gas g1 in the first fuel conduit L1 is replaced with the second gas g2.

[0060] Through the above operation, ammonia gas ga is purged from the first fuel conduit L1. While the boiler 1 stops burning ammonia gas ga, the second gas conduit L4 continues to supply the second gas g2 to the first fuel conduit L1. This seals the burner 12 and the first fuel conduit L1, protecting them from unburned fuel and foreign matter from the combustion space S. While the boiler 1 stops burning ammonia gas ga, the processor 90a closes the first fuel valve V1.

[0061] Next, the operation of the combustion system 100 when starting combustion of the ammonia gas ga will be described.

[0062] Fig. 3 is a flowchart showing a method for supplying ammonia gas (ga). For example, the operation shown in Fig. 3 may be initiated when a command to start combustion of ammonia gas (ga) is input to the control device 90. Referring to Fig. 1, before the operation shown in Fig. 3, the first fuel valve V1, the second fuel valve V2, and the first gas valve V4 are closed, and the vent valve V3 and the second gas valve V5 are open. Before the operation shown in Fig. 3, the boiler 1 may be burning another fuel or may be stopped from operating.

[0063] Referring to FIG. 3, the processor 90a closes the second gas valve V5 to stop the supply of the second gas g2 to the first fuel conduit L1 (step S200).

[0064] Referring to FIG. 3, the processor 90a then opens the first gas valve V4 to supply the first gas g1 to the first fuel conduit L1 (step S202).

[0065] Referring to FIG. 1, the first gas g1 pushes the second gas g2, which remains in the section of the first fuel conduit L1 downstream of the second fuel valve V2, into the combustion space S via the burner 12.

[0066] Referring to FIG. 3, the processor 90a then determines whether the concentration of a predetermined component (for example, oxygen) in the second gas g2 in the gas inside the first fuel conduit L1 has fallen below a third threshold value (step S204).

[0067] 1 , for example, the length of time (fourth threshold) required to replace the second gas g2 in the first fuel conduit L1 with the first gas g1 until the concentration of oxygen in the gas in the first fuel conduit L1 drops below the third threshold may be determined in advance by experiment or analysis and stored in the memory device 90b. For example, the third threshold may be determined so that the ammonia gas g1 does not burn in the first fuel conduit L1 when the ammonia gas g2 is supplied. For example, if the predetermined component in the second gas g2 is oxygen, the third threshold is 10%. For example, the fourth threshold is determined depending on factors such as the size of the first fuel conduit L1, the flow rate of the first gas g1, and the third threshold. In step S204, if the elapsed time since the first gas valve V4 was opened exceeds the fourth threshold stored in the memory device 90b, the processor 90a may determine that the concentration of oxygen in the gas in the first fuel conduit L1 has dropped below the third threshold.

[0068] Alternatively or additionally, in step S204, the control device 90 may receive the oxygen concentration from the second sensor Se2. The memory device 90b may store a third threshold value instead of or in addition to the fourth threshold value. In step 204, the processor 90a may determine whether the oxygen concentration received from the second sensor Se2 is equal to or less than the third threshold value.

[0069] 3, if it is determined in step S204 that the concentration of oxygen in the gas in the first fuel conduit L1 has not decreased to or below the third threshold (NO), the processor 90a returns to step S204. For example, step S204 may be repeated at predetermined intervals.

[0070] In step S204, if it is determined that the concentration of oxygen in the gas in the first fuel conduit L1 has fallen below the third threshold (YES), the processor 90a closes the first gas valve V4 and stops the supply of the first gas g1 to the first fuel conduit L1 (step S206).

[0071] Next, the processor 90a opens the second fuel valve V2 to supply ammonia gas ga to the burner 12 (S208), and ends the operation. Also, in step S208, the vent valve V3 is simultaneously closed. Also, in step S208, the processor 90a opens the first fuel valve V1.

[0072] According to the above operation, ammonia gas ga is supplied to the burner 12. With reference to Fig. 1, the ammonia gas ga injected from the burner 12 into the combustion space S is combusted in the combustion space S.

[0073] As described above, the combustion system 100 according to this embodiment includes the burner 12, the first fuel conduit L1 connected to the burner 12 and supplying ammonia gas ga to the burner 12, the fuel valve V2 provided in the first fuel conduit L1 and opening and closing the first fuel conduit L1, the first gas conduit L3 fluidly communicating with the first fuel conduit L1 between the burner 12 and the fuel valve V2 and supplying the first gas g1, which is inactive with respect to ammonia gas ga, to the first fuel conduit L1, and the burner 12. and a fuel valve V2, and supplies a second gas conduit L4, which is inert to the first gas conduit L1, with a second gas g2, which is inert to the first gas g1, to the first fuel conduit L1; a first gas valve V4, which is provided in the first gas conduit L3 and opens and closes the first gas conduit L3; a second gas valve V5, which is provided in the second gas conduit L4 and opens and closes the second gas conduit L4; and a control device 90, which controls the fuel valve V2, the first gas valve V4, and the second gas valve V5. To purge ammonia gas from the first fuel conduit L1, the control device 90 is configured to close the fuel valve V2 to stop the supply of ammonia gas ga to the burner 12, open the first gas valve V4 to supply a first gas g1 to the first fuel conduit L1, and, after the concentration of ammonia gas ga in the gas in the first fuel conduit L1 drops below a first threshold, open the second gas valve V5 to supply a second gas g2 to the first fuel conduit L1. With this configuration, first, the ammonia gas ga remaining in the first fuel conduit L1 is purged with the first gas g1, and then the first gas g1 remaining in the first fuel conduit L1 is purged with the second gas g2. These operations can be automatically performed by the control device 90. After the first gas g1 is purged, the supply of the second gas g2 to the first fuel conduit L1 is continued, thereby sealing the burner 12 and the first fuel conduit L1. Therefore, when ammonia gas (GA) is used as fuel, the gas seal of the piping can be maintained after purging. Therefore, for example, when ammonia and fossil fuel are mixed and burned, ash deposition in the nozzle injection hole can be prevented after purging. Furthermore, by using a gas that is cheaper than the first gas (G1) as the second gas (G2), the cost of sealing can be reduced.

[0074] Furthermore, in the combustion system 100, for example, the control device 90 stores a second threshold value for purging, and when the elapsed time since the first gas valve V4 was opened exceeds the second threshold value, the control device 90 determines that the concentration of ammonia gas g in the gas in the first fuel conduit L1 has fallen to or below the first threshold value. As described above, the second threshold value for purging can be determined depending on factors such as the size of the first fuel conduit L1, the flow rate of the first gas g1, and the first threshold value. Therefore, with this configuration, a sensor for measuring the concentration of ammonia gas g can be omitted.

[0075] Alternatively or additionally, the combustion system 100 may include a first sensor Se1 that detects the concentration of ammonia gas ga in the gas in the first fuel conduit L1, the control device 90 may store a first threshold value, and the control device 90 may determine whether the concentration of ammonia gas ga received from the first sensor Se1 is equal to or less than the first threshold value. With this configuration, the concentration of ammonia gas ga in the gas in the first fuel conduit L1 can be accurately measured.

[0076] Furthermore, in the combustion system 100 according to this embodiment, the control device 90 is configured to execute the following operations in order to supply ammonia gas ga to the burner 12: close the second gas valve V5 to stop the supply of the second gas g2 to the first fuel conduit L1, open the first gas valve V4 to supply the first gas g1 to the first fuel conduit L1, and, after the concentration of a predetermined component (e.g., oxygen) in the second gas g2 in the gas in the first fuel conduit L1 has fallen to a third threshold or less, open the fuel valve V2 to supply ammonia gas ga to the burner 12. With this configuration, in addition to executing purging and sealing when the combustion of ammonia gas ga is stopped, the control device 90 can automatically release the seal and supply ammonia gas ga when the combustion of ammonia gas ga is started.

[0077] Furthermore, in the combustion system 100, the control device 90 stores a fourth threshold value for purging, and when the elapsed time since the first gas valve V4 was opened exceeds the fourth threshold value, the control device 90 determines that the concentration of a predetermined component in the second gas g2 in the gas in the first fuel conduit L1 has fallen to or below the third threshold value. As described above, the fourth threshold value for purging can be determined depending on factors such as the size of the first fuel conduit L1, the flow rate of the first gas g1, and the third threshold value. Therefore, with this configuration, a sensor for measuring the concentration of the predetermined component can be omitted.

[0078] In addition, in the combustion system 100, the second gas g2 is air. In this case, alternatively or additionally, the combustion system 100 may include a second sensor Se2 that detects the concentration of oxygen in the gas in the first fuel conduit L1, a third threshold value may be set for the concentration of oxygen, the control device 90 may store the third threshold value, and the control device 90 may determine whether the concentration of oxygen received from the second sensor Se2 is equal to or less than the third threshold value. With this configuration, the concentration of oxygen in the gas in the first fuel conduit L1 can be accurately measured.

[0079] Furthermore, in the combustion system 100, the first gas g1 is nitrogen and the second gas g2 is air. With this configuration, the second gas g2 can be obtained at low cost.

[0080] Furthermore, a method for purging ammonia gas (ga) in the combustion system 100 according to this embodiment includes closing the fuel valve V2 to stop the supply of ammonia gas (ga) to the burner 12, opening the first gas valve V4 to supply a first gas (g1) to the first fuel conduit L1, and, after the concentration of ammonia gas (ga) in the gas in the first fuel conduit L1 falls below a first threshold, opening the second gas valve V5 to supply a second gas (g2) to the first fuel conduit L1. With this configuration, purging and sealing can be performed when the combustion of ammonia gas (ga) is stopped.

[0081] Furthermore, a method for supplying ammonia gas g in the combustion system 100 according to this embodiment includes closing the second gas valve V5 to stop the supply of the second gas g2 to the first fuel conduit L1, opening the first gas valve V4 to supply the first gas g1 to the first fuel conduit L1, and, after the concentration of a predetermined component (e.g., oxygen) in the second gas g2 in the gas in the first fuel conduit L1 has fallen to a third threshold or less, opening the fuel valve V2 to supply ammonia gas g to the burner 12. With this configuration, in addition to performing purging and sealing when the combustion of ammonia gas g is stopped, it is possible to release the seal and supply ammonia gas g when the combustion of ammonia gas g is started.

[0082] Next, other embodiments will be described.

[0083] 4 is a schematic diagram of a combustion system 100A according to the second embodiment. The combustion system 100A differs from the combustion system 100 according to the first embodiment in that the first gas g1 includes the exhaust gas Ex. In other respects, the combustion system 100A may be the same as the combustion system 100.

[0084] For example, in this embodiment, the first gas conduit L3 is in fluid communication with the flue 2. Specifically, in this embodiment, a recirculation conduit L7 branches off from the flue 2. The recirculation conduit L7 is connected to the first gas conduit L3. The recirculation conduit L7 supplies the exhaust gas Ex from the flue 2 to the first gas conduit L3.

[0085] In this embodiment, the first gas conduit L3 is connected to both a nitrogen supply source, such as a tank or a nitrogen production device, and the flue 2. That is, in this embodiment, the first gas g1 is a mixed gas of nitrogen and exhaust gas Ex. In other embodiments, the first gas conduit L3 may not be connected to a nitrogen supply source, but may be connected only to the recirculation conduit L7. In this case, the first gas g1 is exhaust gas Ex.

[0086] For example, a fan 3 may be provided in the recirculation conduit L7. The fan 3 adjusts the flow rate of the flue gas Ex drawn into the recirculation conduit L7 from the flue 2. Furthermore, for example, a damper 4 may be provided in the recirculation conduit L7. The damper 4 adjusts the flow rate of the flue gas Ex flowing through the recirculation conduit L7. The fan 3 and the damper 4 may be communicatively connected to the control device 90 via wire or wirelessly and controlled by the control device 90. For example, the control device 90 may adjust the flow rate of the flue gas Ex supplied from the flue 2 to the first gas conduit L3 by controlling the fan 3 and the damper 4. Note that at least one of the fan 3 and the damper 4 does not necessarily have to be provided in the recirculation conduit L7. Furthermore, a compressor or a blower may be provided in the recirculation conduit L7 instead of the fan 3, and a valve may be provided in place of the damper 4.

[0087] The exhaust gas Ex has a lower oxygen concentration than ambient air. Therefore, the exhaust gas Ex may be used as the first gas g1 instead of or in addition to nitrogen. In this case, the cost of the first gas g1 can be reduced.

[0088] Next, the operation of the combustion system 100A when stopping the combustion of the ammonia gas ga will be described.

[0089] Description of the same operations as those of the combustion system 100 according to the first embodiment will be omitted. Before operation, the first fuel valve V1 and the second fuel valve V2 are open, and the vent valve V3, the first gas valve V4, the second gas valve V5, and the damper 4 are closed. Also, the fan 3 is stopped.

[0090] 2, in step S102, the processor 90a opens the first gas valve V4 and the damper 4 and starts the operation of the fan 3 to supply a mixed gas of nitrogen and the exhaust gas Ex as the first gas g1 to the first fuel conduit L1. Alternatively, when the first gas conduit L3 is connected only to the recirculation conduit L7, the exhaust gas Ex may be supplied to the first fuel conduit L1 as the first gas g1.

[0091] In step S106, the processor 90a closes the first gas valve V4 and the damper 4, and stops the operation of the fan 3 to stop the supply of the first gas g1 to the first fuel conduit L1.

[0092] Next, the operation of the combustion system 100A when starting combustion of the ammonia gas ga will be described.

[0093] Description of the same operations as those of the combustion system 100 according to the first embodiment will be omitted. Before the operation, the first fuel valve V1, the second fuel valve V2, the first gas valve V4, and the damper 4 are closed, and the vent valve V3 and the second gas valve V5 are open. The fan 3 is stopped. Furthermore, before the operation shown in FIG. 3, the boiler 1 is burning another fuel.

[0094] 3, in step S202, the processor 90a opens the first gas valve V4 and the damper 4 and starts the operation of the fan 3 to supply a mixed gas of nitrogen and the exhaust gas Ex as the first gas g1 to the first fuel conduit L1. Alternatively, when the first gas conduit L3 is connected only to the recirculation conduit L7, the exhaust gas Ex may be supplied to the first fuel conduit L1 as the first gas g1.

[0095] In step S206, the processor 90a closes the first gas valve V4 and the damper 4, and stops the operation of the fan 3 to stop the supply of the first gas g1 to the first fuel conduit L1.

[0096] The combustion system 100A according to the second embodiment as described above has the same effects as the combustion system 100 according to the first embodiment. In particular, in the combustion system 100A, the first gas g1 includes the exhaust gas Ex. For example, the first gas g1 may be a mixed gas of nitrogen and the exhaust gas Ex. Furthermore, for example, the first gas g1 may be the exhaust gas Ex. These configurations enable the cost of the first gas g1 to be reduced.

[0097] Although the embodiments have been described above with reference to the accompanying drawings, the present disclosure is not limited to the above embodiments. It is clear that a person skilled in the art can conceive of various modifications or alterations within the scope of the claims, and it is understood that these also fall within the technical scope of the present disclosure. Furthermore, the steps of the method of the above embodiments do not have to be performed in the order described above, and may be performed in a different order as long as no technical contradiction occurs.

[0098] For example, referring to Figure 2, in the above embodiment, step S102 is started after step S100. In other embodiments, for example, step S102 may be started simultaneously with step S100.

[0099] Similarly, in the above embodiment, step S108 is started after step S106. In other embodiments, for example, step S108 may be started simultaneously with step S106.

[0100] 3, in the above embodiment, step S202 is started after step S200. In other embodiments, for example, step S202 may be started simultaneously with step S200.

[0101] Similarly, in the above embodiment, step S208 is started after step S206. In other embodiments, for example, step S208 may be started simultaneously with step S206.

[0102] Additionally, the combustion system 100, 100A includes the first sensor Se1, the second sensor Se2, and the third sensor Se3. In other embodiments, the combustion system 100, 100A does not need to include at least one of the first sensor Se1, the second sensor Se2, and the third sensor Se3.

[0103] The disclosure can promote the use of ammonia, which leads to reduced CO2 emissions, and thereby contribute, for example, to Sustainable Development Goals (SDGs) Goal 7 "Ensure access to affordable, reliable, sustainable and modern energy" and Goal 13 "Take urgent action to combat climate change and its impacts." [Explanation of symbols]

[0104] 12 Burner 90 Control device 100 Combustion System 100A Combustion System Ex exhaust gas g1 First gas g2 Second gas ga ammonia gas L1 1st fuel conduit (fuel conduit) L3 First gas pipeline L4 Second gas pipeline Se1 First sensor Se2 Second sensor V2 Second fuel valve (fuel valve) V4 1st gas valve V5 Second gas valve

Claims

1. Burner and a fuel conduit connected to the burner for supplying ammonia gas to the burner; a fuel valve provided in the fuel conduit for opening and closing the fuel conduit; a first gas conduit in fluid communication with the fuel conduit between the burner and the fuel valve, the first gas conduit supplying a first gas inert to ammonia gas to the fuel conduit; a second gas conduit in fluid communication with the fuel conduit between the burner and the fuel valve, the second gas conduit supplying a second gas to the fuel conduit, the second gas being inert to the first gas; a first gas valve provided in the first gas conduit for opening and closing the first gas conduit; a second gas valve provided in the second gas conduit for opening and closing the second gas conduit; a control device for controlling the fuel valve, the first gas valve, and the second gas valve, The control device includes: closing the fuel valve to stop the supply of ammonia gas to the burner; opening the first gas valve to supply the first gas to the fuel conduit; After the concentration of ammonia gas in the gas in the fuel conduit falls below a first threshold, opening the second gas valve to supply the second gas to the fuel conduit; configured to perform a control device; A combustion system comprising:

2. the control device stores a second threshold for purging; the control device determines that the concentration of ammonia gas in the gas inside the fuel conduit has decreased to or below the first threshold value when the elapsed time since the first gas valve was opened exceeds the second threshold value; The combustion system of claim 1 .

3. the combustion system includes a first sensor for detecting a concentration of ammonia gas in the gas within the fuel conduit; The control device stores the first threshold value; the control device determines whether the concentration of ammonia gas received from the first sensor is equal to or less than the first threshold value; The combustion system of claim 1 .

4. The first gas is nitrogen and the second gas is air. A combustion system according to any one of claims 1 to 3.

5. The first gas includes exhaust gas. A combustion system according to any one of claims 1 to 3.

6. The first gas is a mixture of nitrogen and exhaust gas. The combustion system of claim 5 .

7. The first gas is exhaust gas. The combustion system of claim 5 .

8. Burner and a fuel conduit connected to the burner for supplying ammonia gas to the burner; a fuel valve provided in the fuel conduit for opening and closing the fuel conduit; a first gas conduit in fluid communication with the fuel conduit between the burner and the fuel valve, the first gas conduit supplying a first gas inert to ammonia gas to the fuel conduit; a second gas conduit in fluid communication with the fuel conduit between the burner and the fuel valve, the second gas conduit supplying a second gas to the fuel conduit, the second gas being inert to the first gas; a first gas valve provided in the first gas conduit for opening and closing the first gas conduit; a second gas valve provided in the second gas conduit for opening and closing the second gas conduit; a control device for controlling the fuel valve, the first gas valve, and the second gas valve, The control device controls the supply of ammonia gas to the burner. closing the second gas valve to stop the supply of the second gas to the fuel conduit; opening the first gas valve to supply the first gas to the fuel conduit; After the concentration of the predetermined component in the second gas in the gas in the fuel conduit falls below a third threshold, opening the fuel valve to supply ammonia gas to the burner; configured to perform a control device; A combustion system comprising:

9. the control device stores a fourth threshold for purging; the control device determines that the concentration of the predetermined component in the second gas in the gas inside the fuel conduit has decreased to or below the third threshold value when the elapsed time since the first gas valve was opened exceeds the fourth threshold value; The combustion system of claim 8 .

10. the second gas is air; the combustion system includes a second sensor for detecting a concentration of oxygen in the gas in the fuel conduit; the third threshold is set for a concentration of oxygen, the control device stores the third threshold value; the control device determines whether the concentration of oxygen received from the second sensor is equal to or less than the third threshold value; The combustion system of claim 8 .

11. The first gas is nitrogen and the second gas is air. A combustion system according to any one of claims 8 to 10.

12. The first gas includes exhaust gas. A combustion system according to any one of claims 8 to 10.

13. The first gas is a mixture of nitrogen and exhaust gas. The combustion system of claim 12.

14. The first gas is exhaust gas. The combustion system of claim 12.

15. 1. A method of purging ammonia gas in a combustion system, comprising: The combustion system includes: Burner and a fuel conduit connected to the burner for supplying ammonia gas to the burner; a fuel valve provided in the fuel conduit for opening and closing the fuel conduit; a first gas conduit in fluid communication with the fuel conduit between the burner and the fuel valve, the first gas conduit supplying a first gas inert to ammonia gas to the fuel conduit; a second gas conduit in fluid communication with the fuel conduit between the burner and the fuel valve, the second gas conduit supplying a second gas to the fuel conduit, the second gas being inert to the first gas; a first gas valve provided in the first gas conduit for opening and closing the first gas conduit; a second gas valve provided in the second gas conduit for opening and closing the second gas conduit; The method comprises: closing the fuel valve to stop the supply of ammonia gas to the burner; opening the first gas valve to supply the first gas to the fuel conduit; After the concentration of ammonia gas in the gas in the fuel conduit falls below a first threshold, opening the second gas valve to supply the second gas to the fuel conduit; A method comprising:

16. 1. A method for supplying ammonia gas in a combustion system, comprising: The combustion system includes: Burner and a fuel conduit connected to the burner for supplying ammonia gas to the burner; a fuel valve provided in the fuel conduit for opening and closing the fuel conduit; a first gas conduit in fluid communication with the fuel conduit between the burner and the fuel valve, the first gas conduit supplying a first gas inert to ammonia gas to the fuel conduit; a second gas conduit in fluid communication with the fuel conduit between the burner and the fuel valve, the second gas conduit supplying a second gas to the fuel conduit, the second gas being inert to the first gas; a first gas valve provided in the first gas conduit for opening and closing the first gas conduit; a second gas valve provided in the second gas conduit for opening and closing the second gas conduit; The method comprises: closing the second gas valve to stop the supply of the second gas to the fuel conduit; opening the first gas valve to supply the first gas to the fuel conduit; After the concentration of the predetermined component in the second gas in the gas in the fuel conduit falls below a third threshold, opening the fuel valve to supply ammonia gas to the burner; A method comprising:

Images