Furnace

Abstract

This furnace comprises: a burner (10) that selectively injects, into a combustion space (S), a first fuel that is more readily combustible than ammonia and a second fuel that contains ammonia; a first temperature sensor (T1) that measures the temperature of a wall (16) defining the combustion space (S); a second temperature sensor (T2) that measures the temperature of the combustion space (S); a third temperature sensor (T3) that measures the temperature of the burner (10); and a control device. The control device stores a reference temperature for each of the temperature sensors (T1, T2, T3). The control device executes first control for controlling the burner (10) so as to inject the first fuel when each of the measured temperatures of the temperature sensors (T1, T2, T3) is lower than the respective reference temperatures, and executes second control for controlling the burner (10) so as to inject the second fuel when at least one of the measured temperatures of the temperature sensors (T1, T2, T3) reaches the corresponding reference temperature.

Description

furnace

[0001] This application claims the benefit of priority from Japanese Patent Application No. 2024-11637, filed on January 30, 2024, the contents of which are incorporated herein by reference.

[0002] Ammonia may be used as fuel in a furnace. For example, Patent Document 1 discloses a boiler that uses ammonia and oil fuel. For example, when ammonia fuel is used exclusively, oil fuel is first injected into the furnace to form a flame. When the temperature inside the furnace is raised to a predetermined temperature and startup is completed, the supply of oil fuel is stopped and liquid ammonia is supplied. After startup, only a flame using liquid ammonia is formed.

[0003] International Publication No. 2023 / 120700

[0004] Ammonia is CO ２ Ammonia is known as a fuel that does not emit CO2. However, ammonia is difficult to ignite compared to other fuels such as fossil fuels. Furthermore, metal components inside the furnace may be deteriorated by ammonia. Thus, when ammonia is used as a fuel, the furnace may have various problems.

[0005] The present disclosure aims to provide a furnace that addresses the challenges of ignition when ammonia is used as a fuel.

[0006] A furnace according to one aspect of the present disclosure includes at least one burner that selectively injects into a combustion space a first fuel that is more flammable than ammonia and a second fuel that contains ammonia; a first temperature sensor that measures the temperature of a wall that defines the combustion space; a second temperature sensor that measures the temperature of the combustion space; a third temperature sensor that measures the temperature of the at least one burner; and a control device that controls the at least one burner, wherein the control device stores a reference temperature for each of the first temperature sensor, the second temperature sensor, and the third temperature sensor, and the control device executes a first control that controls the at least one burner to inject the first fuel when each of the temperatures measured by the first temperature sensor, the second temperature sensor, and the third temperature sensor is lower than the respective reference temperature, and starts a second control that controls the at least one burner to inject the second fuel when at least one of the temperatures measured by the first temperature sensor, the second temperature sensor, and the third temperature sensor reaches a corresponding reference temperature.

[0007] The control device may initiate the second control when the temperature measured by at least the second temperature sensor reaches a corresponding reference temperature.

[0008] The control device may start the second control when the temperatures measured by the first temperature sensor, the second temperature sensor, and the third temperature sensor each reach a respective reference temperature.

[0009] The reference temperature of the third temperature sensor may be lower than the reference temperature of the first temperature sensor and the reference temperature of the second temperature sensor.

[0010] The at least one burner may include a plurality of burners arranged vertically, and the control device may control the plurality of burners so that the second fuel is first injected from the lowest burner when starting the second control.

[0011] The at least one burner may include a plurality of burners arranged along a horizontal direction, and the plurality of burners may include at least a first section including a central burner among the plurality of burners, a second section including a burner at one end of the plurality of burners, and a third section including a burner at the other end of the plurality of burners, and when starting the second control, the control device may control the plurality of burners so that the second fuel is first injected from the burner in the first section.

[0012] The at least one burner may include a plurality of burners arranged horizontally, and the plurality of burners may be divided into first burners and second burners arranged alternately with each other in the horizontal direction, and the control device may control the plurality of burners so that the second fuel is first injected from the first burner when starting the second control.

[0013] The present disclosure addresses the challenges of ignition when ammonia is used as a fuel in a furnace.

[0014] Fig. 1 is a schematic cross-sectional view of a boiler equipped with a furnace according to an embodiment. Fig. 2 is a schematic cross-sectional view showing an example of a burner. Fig. 3 is a schematic cross-sectional view taken along line III-III in Fig. 1. Fig. 4 is a flowchart showing an example of the operation of the furnace. Fig. 5 is a schematic cross-sectional view showing another example of a burner.

[0015] 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.

[0016] 1 is a schematic cross-sectional view of a boiler 100 including a furnace 1 according to an embodiment. In this embodiment, the furnace 1 is applied to the boiler 100. In other embodiments, the furnace 1 may be applied to other equipment, such as a naphtha cracking furnace. For example, the boiler 100 includes the furnace 1 and a flue 2. The furnace 1 includes a plurality of burners 10 and a control device 90. The boiler 100 and the furnace 1 may further include other components.

[0017] The furnace 1 extends vertically. The furnace 1 defines a combustion space S. In this disclosure, the combustion space refers to a space in which fuel is combusted. In this embodiment, the furnace 1 has a rectangular shape when viewed from above. For example, an exhaust port is provided at the bottom of the furnace 1. The exhaust port discharges ash generated by combustion to the outside.

[0018] The furnace 1 burns a first fuel F1 and a second fuel F2. The furnace 1 is connected to a first supply source 3 that supplies the first fuel F1 and a second supply source 4 that supplies the second fuel F2. For example, the first supply source 3 may include a tank that stores the first fuel F1, a compressor, etc. The second supply source 4 may include a tank that stores the second fuel F2, a compressor, etc.

[0019] The first fuel F1 is more flammable than ammonia. For example, the first fuel F1 may include a fossil fuel. For example, in this embodiment, the first fuel F1 is methane or propane (CnHm). The first fuel F1 is not limited to these.

[0020] The second fuel F2 includes ammonia. For example, the second fuel F2 may be gaseous ammonia or liquid ammonia. For example, the second supply source 4 may store liquid ammonia. When gaseous ammonia is used as the second fuel F2, a vaporizer (not shown) may be provided on a pipe connecting the second supply source 4 to the plurality of burners 10. In another embodiment, an ammonia manufacturing apparatus may be used as the second supply source 4.

[0021] In the combustion space S, a flame FL is generated by combustion. For example, the boiler 100 includes a superheater (not shown) installed on the upper part of the furnace 1. The superheater exchanges heat between the combustion gas generated in the furnace 1 and water, thereby generating steam. Furthermore, for example, the boiler 100 may further include components (not shown), such as a reheater, a coal economizer, or an air preheater.

[0022] The flue 2 is a passage that guides the exhaust gas generated in the furnace 1 to the outside. The flue 2 is connected to the upper part of the furnace 1. For example, the flue 2 includes a first flue 2a and a second flue 2b. The first flue 2a extends horizontally from the upper part of the furnace 1. The second flue 2b extends downward from the end of the first flue 2a. For example, the second flue 2b is connected to a pipe (not shown) that guides the exhaust gas to the outside.

[0023] The burners 10 are provided on the side walls of the furnace 1. In this embodiment, the furnace 1 includes four side walls, including a front wall 1A, a rear wall 1B, a right wall, and a left wall. Each of the side walls extends vertically and horizontally. The cross-sectional view of FIG. 1 shows the front wall 1A and the rear wall 1B, and multiple burners 10 are arranged on each of the front wall 1A and the rear wall 1B. The right wall and the left wall are not shown. The arrangement of the multiple burners 10 will be described in detail below.

[0024] The burners 10 selectively inject a first fuel F1 and a second fuel F2 into the combustion space S. Each burner 10 is connected to a first supply source 3 and a second supply source 4.

[0025] A valve V1 that adjusts the flow rate of the first fuel F1 is provided in the pipe P1 that connects each burner 10 to the first supply source 3. For example, the valve V1 may be a control valve. The valve V1 is connected to a 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. The control device 90 adjusts the flow rate of the first fuel F1 supplied to the burner 10 by controlling the opening degree of the valve V1.

[0026] A valve V2 that adjusts the flow rate of the second fuel F2 is provided in the pipe P2 that connects each burner 10 to the second supply source 4. For example, the valve V2 may be a control valve. The valve V2 is connected to a 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. The control device 90 adjusts the flow rate of the second fuel F2 supplied to the burner 10 by controlling the opening degree of the valve V2.

[0027] In this embodiment, the pipe P1 merges with the pipe P2. For example, the pipe P2 is provided with a valve V3 that prevents backflow from the burner 10. For example, the valve V3 may be a gate valve or a check valve. The valve V3 may be connected to the control device 90 so as to be able to communicate with the control device 90 via wire or wirelessly, and may be opened and closed by the control device 90.

[0028] Each burner 10 is connected to an air supply 5, such as a compressor. For example, ambient air around the furnace 1 may be supplied to the burners 10.

[0029] A valve V4 that adjusts the flow rate of air is provided in the pipe P3 that connects each burner 10 to the air supply source 5. For example, the valve V4 may be a control valve. The valve V4 may be connected to the control device 90 so as to be able to communicate with it via wire or wirelessly, and may be controlled by the control device 90. For example, the control device 90 may adjust the flow rate of air supplied to the burners 10 by controlling the opening degree of the valve V4.

[0030] In this embodiment, the pipe P3 joins the pipe P2. Therefore, in this embodiment, the fuel and air are premixed (premixed combustion). In other embodiments, the fuel and air may be injected separately into the combustion space S (diffusion combustion).

[0031] In each burner 10, the fuel is switched between the first fuel F1 and the second fuel F2. In other words, when looking at a single burner 10, the first fuel F1 and the second fuel F2 are not mixed and burned.

[0032] 2 is a schematic cross-sectional view showing an example of the burner 10. For example, the burner 10 may be a radiant burner. The radiant burner heats the surface 16 of the burner tile 11 by burning fuel, and heats an object (not shown) located at a distance from the radiant burner by radiant heat from the heated surface 16. In this case, the burner 10 includes the burner tile 11 and a nozzle 12. The burner 10 may further include other components.

[0033] The burner tile 11 is formed of a refractory material, such as a molded product containing ceramic. In this embodiment, the burner tile 11 has a roughly rectangular parallelepiped shape. However, the burner tile 11 is not limited to this shape and may have other shapes. The burner tile 11 includes a front surface 13 that is arranged to face the object to be heated, and a back surface 14 opposite the front surface 13.

[0034] In this embodiment, the burner tile 11 includes a recess 15 on the front surface 13. The recess 15 is formed from the front surface 13 toward the back surface 14. The recess 15 is defined by a surface 16. The recess 15 is used as a combustion space S. In this embodiment, the recess 15 has a hemispherical shape. In other embodiments, the recess 15 may have other shapes, such as a cylindrical shape or a polygonal prism shape. In this embodiment, the burner tile 11 is also referred to as a "radiant cup." Also, in this embodiment, the burner 10 is also referred to as a "radiant cup burner." In other embodiments, the burner tile 11 may not include the recess 15.

[0035] The nozzle 12 protrudes from the burner tile 11 toward the combustion space S. When viewed from a direction perpendicular to the front surface 13, the nozzle 12 is located in the center of the recess 15.

[0036] The nozzle 12 includes at least one injection hole 12a. In the present embodiment, the nozzle 12 includes a single injection hole 12a. In other embodiments, the nozzle 12 may include multiple injection holes 12a. The injection hole 12a faces the combustion space S. For example, the injection hole 12a may face the combustion space S in a direction parallel to the axis of the nozzle 12, or may face the combustion space S in a direction perpendicular to the axis. Each injection hole 12a is fluidly connected to the pipe P2 and selectively injects the first fuel F1 or the second fuel F2 into the combustion space S. In the present embodiment, each injection hole 12a selectively injects a first mixed gas of the first fuel F1 and air or a second mixed gas of the second fuel F2 and air into the combustion space S.

[0037] The furnace 1 is equipped with a first temperature sensor T1, a second temperature sensor T2, and a third temperature sensor T3.

[0038] The first temperature sensor T1 measures the temperature of a wall that defines the combustion space S. In this embodiment, the first temperature sensor T1 measures the temperature of a burner tile 11 that defines the combustion space S of the burner 10. In this embodiment, the first temperature sensor T1 is disposed inside the burner tile 11 so as to measure the temperature of the surface 16 or the temperature in the vicinity of the surface 16. The first temperature sensor T1 is connected to the control device 90 so as to be able to communicate with the control device 90 by wire or wirelessly, and transmits the measured temperature to the control device 90.

[0039] The second temperature sensor T2 measures the temperature of the combustion space S, specifically, the temperature of the gas in the combustion space S. In this embodiment, the second temperature sensor T2 is attached to the burner tile 11 so as to protrude from the front surface 13. The second temperature sensor T2 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 the measured temperature to the control device 90.

[0040] The third temperature sensor T3 measures the temperature of the burner 10, specifically, the temperature of the nozzle 12. In this embodiment, the third temperature sensor T3 measures the temperature of a portion of the nozzle 12 that protrudes from the surface 16 into the combustion space S. For example, the third temperature sensor T3 may be attached to the surface of the nozzle 12. The third temperature sensor T3 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 the measured temperature to the control device 90.

[0041] For example, the first temperature sensor T1, the second temperature sensor T2, and the third temperature sensor T3 may be provided only for a representative burner 10 among the plurality of burners 10.

[0042] Returning to FIG. 1 , the control device 90 controls the furnace 1. The control device 90 may also control at least some of the other components of the boiler 100. For example, the control device 90 may control the entire boiler 100. The control device 90 includes components such as a processor 90a, a storage device 90b, and a connector 90c, which are connected to each other 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) for storing programs, and a random access memory (RAM) as a work area. The control device 90 is connected to each component of the furnace 1 via the connector 90c so as to be able to communicate with them via wired or wireless communication. 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.

[0043] Next, the arrangement of the plurality of burners 10 will be described.

[0044] Figure 3 is a schematic cross-sectional view taken along line III-III in Figure 1. The upper diagram in Figure 3 shows the front wall 1A and multiple burners 10 arranged on the front wall 1A. The lower diagram in Figure 3 shows a schematic graph showing the temperature distribution along the front wall 1A in the region of the combustion space S that faces the front wall 1A. Note that multiple burners 10 may also be arranged on the rear wall 1B (not shown), similar to the front wall 1A.

[0045] 3, the burners 10 are arranged in a plurality of vertical rows and a plurality of horizontal rows on the front wall 1A. In this embodiment, the burners 10 are arranged in three vertical rows and 12 horizontal rows. The number of rows and the number of columns are not limited to these.

[0046] Each stage includes a plurality of burners 10. In this embodiment, each stage includes 12 burners 10. Each stage also includes a first section D1, a second section D2, and a third section D3. In other words, the plurality of rows are divided into a first section D1, a second section D2, and a third section D3.

[0047] In each stage, the first section D1 includes a central burner 10 among the plurality of burners 10. Also, each first section D1 includes a plurality of burners 10. In this embodiment, the first section D1 includes four burners 10.

[0048] In each stage, the second section D2 includes a burner 10 at one end of the plurality of burners 10. Also, each second section D2 includes a plurality of burners 10. In this embodiment, the second section D2 includes four burners 10.

[0049] In each stage, the third section D3 includes the burner 10 at the other end of the plurality of burners 10. Also, each third section D3 includes a plurality of burners 10. In this embodiment, the third section D3 includes four burners 10.

[0050] In other embodiments, a further section may be set between the first section D1 and the second section D2, or a further section may be set between the first section D1 and the third section D3.

[0051] Next, the operation of the furnace 1 will be described.

[0052] Figure 4 is a flow chart illustrating an example of the operation of furnace 1. For example, the operations shown in Figure 4 may begin when controller 90 receives a command from an operator to start operation of furnace 1.

[0053] The processor 90a of the control device 90 controls the plurality of burners 10 to inject a first fuel F1 from each burner 10 into the combustion space S (first control) (step S100). Specifically, the processor 90a controls the valves V1 to V4 to supply a first mixed gas of the first fuel F1 and air to each burner 10. For example, the first mixed gas injected from the burner 10 may be ignited by an ignition device (not shown).

[0054] The processor 90a determines whether the first measured temperature received from the first temperature sensor T1 is equal to or higher than a first reference temperature (step S102).

[0055] Referring to FIG. 2 , in a radiant burner, the fuel injected from the injection hole 12a is heated by heat from the surface 16. Ammonia is more difficult to ignite than other fuels, such as fossil fuels. Therefore, if the temperature of the surface 16 is lower than a certain temperature, the second fuel F2 containing ammonia cannot be ignited. Therefore, the processor 90a determines whether the first measured temperature received from the first temperature sensor T1, i.e., the temperature of the surface 16, is equal to or higher than a first reference temperature. For example, the first reference temperature may be set in advance by calculation, analysis, experiment, or the like. For example, the first reference temperature may be approximately 1000° C. For example, the first reference temperature may be higher or lower than the second reference temperature. The first reference temperature is not limited to this. The first reference temperature may be stored in the storage device 90b.

[0056] Referring to FIG. 4, if the first measured temperature is equal to or higher than the first reference temperature in step S102 (YES), the processor 90a determines whether the second measured temperature received from the second temperature sensor T2 is equal to or higher than the second reference temperature (step S104).

[0057] Referring to FIG. 2 , in the radiant burner, fuel injected from the injection hole 12a is ignited in the combustion space S. As described above, ammonia is more difficult to ignite than other fuels such as fossil fuels. Therefore, if the temperature of the gas in the combustion space S is lower than a certain temperature, the second fuel F2 containing ammonia cannot be ignited. Therefore, the processor 90a determines whether the second measured temperature received from the second temperature sensor T2, i.e., the temperature of the gas in the combustion space S, is equal to or higher than a second reference temperature. For example, the second reference temperature may be the ignition temperature of ammonia or may be set based on the ignition temperature of ammonia. For example, the second reference temperature may be approximately 900° C. The second reference temperature is not limited to this. The second reference temperature may be stored in the storage device 90b.

[0058] Referring to FIG. 4, if the second measured temperature is equal to or higher than the second reference temperature in step S104 (YES), the processor 90a determines whether the third measured temperature received from the third temperature sensor T3 is equal to or higher than the third reference temperature (step S106).

[0059] Referring to FIG. 2 , in this embodiment, the nozzle 12 of the burner 10 is made of metal. Generally, some metals are susceptible to degradation by ammonia within a certain temperature range. Therefore, if the temperature of the nozzle 12 is lower than the upper limit of a certain temperature range, the second fuel F2 containing ammonia accelerates degradation of the nozzle 12. Therefore, the processor 90a determines whether the third measured temperature received from the third temperature sensor T3, i.e., the temperature of the nozzle 12, is equal to or higher than a third reference temperature. For example, the third reference temperature may be the upper limit temperature of degradation by ammonia of the material forming the nozzle 12, or may be preset based on this upper limit temperature. Furthermore, the upper limit temperature of degradation by ammonia of some metal materials is lower than the ignition temperature of ammonia. Therefore, the third reference temperature may be lower than the first reference temperature and the second reference temperature. For example, the third reference temperature may be approximately 700° C. The third reference temperature is not limited to this. The third reference temperature may be stored in the storage device 90b.

[0060] 4, if the third measured temperature is equal to or higher than the third reference temperature in step S106 (YES), the processor 90a injects the second fuel F2 from some of the plurality of burners 10 into the combustion space S (second control) (step S108). When the first fuel F1 has been switched to the second fuel F2 in all of the burners 10, the operation shown in FIG. 4 ends.

[0061] 3, in this embodiment, the burners 10 are arranged in multiple stages along the vertical direction. Combustion gas from the burner 10 in the lowest stage flows upward and passes through a region in front of the burners 10 in the upper stages. Therefore, if a portion of the fuel injected from the burner 10 in the lowest stage is unburned, the unburned fuel can be combusted while passing through a region in front of the burners 10 in the upper stages.

[0062] For this reason, in the present embodiment, the processor 90a controls the plurality of burners 10 so that the second fuel F2 is first injected from the burner 10 in the lowest stage. With such a configuration, it is possible to extend the residence time of the second fuel F2 in the combustion space S, and to reduce unburned ammonia.

[0063] Furthermore, in the horizontal direction, the edges of the front wall 1A are more exposed to the ambient air than the center of the front wall 1A. Therefore, the temperature at the edges of the combustion space S is less likely to increase than the temperature at the center of the combustion space S. For this reason, as shown in the lower diagram of Figure 3, the temperature of the combustion space S is highest at the center in the horizontal direction. In other words, the second fuel F2 containing ammonia is more likely to be ignited at the center of the combustion space S in the horizontal direction.

[0064] For this reason, in this embodiment, the processor 90a controls the plurality of burners 10 so that the second fuel F2 is first injected from the burner 10 in the first section D1 among the burners 10 in the lowest stage. With this configuration, it is possible to improve the ignition ability of the second fuel F2 containing ammonia and reduce unburned ammonia.

[0065] Furthermore, if the second fuel F2 containing ammonia is injected simultaneously from the adjacent burners 10, there is a possibility that misfires may occur.

[0066] For this reason, in this embodiment, the multiple burners 10 in each of the sections D1, D2, and D3 are divided into two groups. The first group includes multiple first burners 10A. In FIG. 3, the first burners 10A are indicated by black circles. The second group includes multiple second burners 10B. In FIG. 3, the second burners 10B are indicated by white circles. The first burners 10A and the second burners 10B are arranged alternately in the horizontal direction. Note that the first burners 10A and the second burners 10B have the same configuration. The processor 90a controls the multiple burners 10 in each of the sections D1, D2, and D3 so that the second fuel F2 is injected first from the first burner 10A.

[0067] In summary, the processor 90a first controls the burners 10 to inject the second fuel F2 into the combustion space S from the first burner 10A in the first section D1 of the lowest stage.

[0068] Subsequently, the processor 90a controls the burners 10 to inject the second fuel F2 from the first burners 10A in the second and third sections D2 and D3 of the lowest stage, respectively. There may be a predetermined interval between the first and second injections.

[0069] Subsequently, the processor 90a thirdly controls the burners 10 so that the second burners 10B in all the compartments D1, D2, and D3 in the lowest stage inject the second fuel F2 into the combustion space S. There may be a predetermined interval between the second injection and the third injection.

[0070] Next, the processor 90a repeats the above operation for the burners 10 in the compartments D1, D2, and D3 in the second row from the bottom. Furthermore, the processor 90a repeats the above operation for the burners 10 in the compartments D1, D2, and D3 in the uppermost row. In this way, the first fuel F1 is switched to the second fuel F2 in all the burners 10. While some of the burners 10 are injecting the first fuel F1, the first fuel F1 and the second fuel F2 are mixed and burned in the furnace 1 as a whole. After the first fuel F1 has been switched to the second fuel F2 in all the burners 10, the second fuel F2 is exclusively burned in the furnace 1.

[0071] The order in which the burners 10 start injecting the second fuel F2 is not limited to the above order.

[0072] 4 , if the first measured temperature is lower than the first reference temperature in step S102 (NO), if the second measured temperature is lower than the second reference temperature in step S104 (NO), or if the third measured temperature is lower than the third reference temperature in step S106 (NO), the processor 90a repeats steps S102 to S106. For example, the processor 90a may repeat steps S102 to S106 at predetermined intervals. In other words, in this embodiment, the injection of the second fuel F2 is started when all of the temperatures measured by the first temperature sensor T1, the second temperature sensor T2, and the third temperature sensor T3 have reached the reference temperatures.

[0073] In another embodiment, the injection of the second fuel F2 may be started when at least one of the temperatures measured by the first temperature sensor T1, the second temperature sensor T2, and the third temperature sensor T3 reaches a corresponding reference temperature. In other words, when any one of steps S102, S104, and S106 is satisfied first (YES), the processor 90a may proceed to step S108.

[0074] In addition, for example, in still another embodiment, the injection of the second fuel F2 may be started when at least the second measured temperature of the second temperature sensor T2 reaches the second reference temperature. In other words, in another embodiment, the processor 90a may execute only step S104 among steps S102 to S106, and may omit steps S102 and S106.

[0075] The furnace 1 as described above comprises at least one burner 10 that selectively injects into a combustion space S one of a first fuel F1 that is more flammable than ammonia and a second fuel F2 that contains ammonia, a first temperature sensor T1 that measures the temperature of a surface 16 that defines the combustion space S, a second temperature sensor T2 that measures the temperature of the combustion space S, a third temperature sensor T3 that measures the temperature of the at least one burner 10, and a control device 90 that controls the at least one burner 10. The control device 90 stores a reference temperature for each of the first temperature sensor T1, the second temperature sensor T2, and the third temperature sensor T3. The control device 90 executes a first control to control at least one burner 10 to inject a first fuel F1 when each of the temperatures measured by the first temperature sensor T1, the second temperature sensor T2, and the third temperature sensor T3 is lower than a corresponding reference temperature, and starts a second control to control at least one burner 10 to inject a second fuel F2 when at least one of the temperatures measured by the first temperature sensor T1, the second temperature sensor T2, and the third temperature sensor T3 reaches a corresponding reference temperature. This configuration can address at least one of the ignition issues, including the low ignition property of ammonia and the degradation of components of the furnace 1 due to ammonia. Therefore, the ignition issues when ammonia is used as a fuel can be addressed.

[0076] In the furnace 1, the control device 90 may start the second control when at least the second measured temperature of the second temperature sensor T2 reaches the second reference temperature. In this case, the ignition ability of the second fuel F2 containing ammonia can be improved, and misfire can be prevented.

[0077] Furthermore, in the furnace 1, the second control is started when the temperatures measured by the first temperature sensor T1, the second temperature sensor T2, and the third temperature sensor T3 reach their respective reference temperatures. With this configuration, it is possible to improve the ignition ability of the second fuel F2 and prevent deterioration of the burner 10 due to ammonia.

[0078] Furthermore, in the furnace 1, the third reference temperature of the third temperature sensor T3 is lower than the first reference temperature of the first temperature sensor T1 and the first reference temperature of the second temperature sensor T2. As described above, the upper limit temperature of deterioration of some metal materials due to ammonia is lower than the ignition temperature of ammonia. Therefore, this configuration can prevent deterioration of the burner 10 due to ammonia.

[0079] Furthermore, in the furnace 1, the at least one burner 10 includes a plurality of burners 10 arranged along the vertical direction, and when starting the second control, the control device 90 controls the plurality of burners 10 so that the second fuel F2 is first injected from the lowest burner 10. With this configuration, it is possible to extend the residence time of the second fuel F2 in the combustion space S and reduce unburned ammonia.

[0080] Furthermore, in the furnace 1, the at least one burner 10 includes a plurality of burners 10 arranged along the horizontal direction, and the plurality of burners 10 includes at least a first section D1 including a central burner 10 among the plurality of burners 10, a second section D2 including a burner 10 at one end of the plurality of burners 10, and a third section D3 including a burner 10 at the other end of the plurality of burners 10. When starting the second control, the control device 90 controls the plurality of burners 10 so that the second fuel F2 is first injected from the burner in the first section D1. As described above, the temperature of the combustion space S is highest at the center in the horizontal direction. Therefore, with this configuration, it is possible to improve the ignition ability of the second fuel F2 containing ammonia and reduce unburned ammonia.

[0081] Furthermore, in the furnace 1, at least one burner 10 includes a plurality of burners 10 arranged horizontally, and the plurality of burners 10 are divided into first burners 10A and second burners 10B arranged alternately in the horizontal direction. When starting the second control, the control device 90 controls the plurality of burners 10 so that the first burner 10A injects the second fuel F2 first. As described above, if the second fuel F2 containing ammonia is injected simultaneously from adjacent burners 10, misfires are likely to occur. With this configuration, misfires can be prevented.

[0082] Although the embodiments have been described above with reference to the accompanying drawings, the present disclosure is not limited to the above-described 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 such modifications also fall within the technical scope of the present disclosure.

[0083] For example, in the above embodiment, the burner 10 is a radiant cup burner. However, the burner 10 is not limited to a radiant cup burner.

[0084] Fig. 5 is a schematic cross-sectional view showing another example of the burner 20. For example, as shown in Fig. 5, the burner 20 may be a radiant wall burner. Specifically, in the burner 20, the burner tile 11 does not include the recess 15 and the surface 16. In the burner 20, the first temperature sensor T1 is disposed inside the burner tile 11 so as to measure the temperature of the front surface 13 or the temperature near the front surface 13. In other configurations, the burner 20 may be the same as the burner 10.

[0085] The present disclosure provides ２ It can promote the use of ammonia, which leads to reduced emissions, thereby contributing, for example, to Sustainable Development Goal (SDG) 7 "Ensure access to affordable, reliable, sustainable and modern energy" and SDG 13 "Take urgent action to combat climate change and its impacts".

[0086] REFERENCE SIGNS LIST 1 Furnace 1A Front wall 1B Rear wall 10 Burner 10A First burner 10B Second burner 13 Front surface (wall defining combustion space) 16 Surface (wall defining combustion space) 20 Burner 90 Control device D1 First compartment D2 Second compartment D3 Third compartment F1 First fuel F2 Second fuel S Combustion space T1 First temperature sensor T2 Second temperature sensor T3 Third temperature sensor

Claims

1. A furnace comprising: at least one burner that selectively injects into a combustion space a first fuel that is more flammable than ammonia and a second fuel that contains ammonia; a first temperature sensor that measures the temperature of a wall that defines the combustion space; a second temperature sensor that measures the temperature of the combustion space; a third temperature sensor that measures the temperature of the at least one burner; and a control device that controls the at least one burner, the control device storing a reference temperature for each of the first temperature sensor, the second temperature sensor, and the third temperature sensor, the control device executing a first control that controls the at least one burner to inject the first fuel when each of the temperatures measured by the first temperature sensor, the second temperature sensor, and the third temperature sensor is lower than a respective reference temperature, and initiating a second control that controls the at least one burner to inject the second fuel when at least one of the temperatures measured by the first temperature sensor, the second temperature sensor, and the third temperature sensor reaches a corresponding reference temperature.

2. The furnace according to claim 1, wherein the control device starts the second control when the temperature measured by at least the second temperature sensor reaches a corresponding reference temperature.

3. The furnace according to claim 2, wherein the control device initiates the second control when the temperatures measured by the first temperature sensor, the second temperature sensor, and the third temperature sensor each reach a respective reference temperature.

4. The furnace of claim 1, wherein the reference temperature of the third temperature sensor is lower than the reference temperature of the first temperature sensor and the reference temperature of the second temperature sensor.

5. The furnace according to claim 1, wherein the at least one burner includes a plurality of burners arranged along a vertical direction, and the control device controls the plurality of burners so that the second fuel is first injected from the lowest burner when starting the second control.

6. The furnace according to claim 1, wherein the at least one burner includes a plurality of burners arranged along a horizontal direction, the plurality of burners including at least a first section including a central burner of the plurality of burners, a second section including a burner at one end of the plurality of burners, and a third section including a burner at the other end of the plurality of burners, and wherein the control device, when starting the second control, controls the plurality of burners so that the second fuel is first injected from the burner in the first section.

7. The furnace according to claim 1, wherein the at least one burner includes a plurality of burners arranged along a horizontal direction, the plurality of burners are divided into first burners and second burners arranged alternately in the horizontal direction, and the control device controls the plurality of burners so that the second fuel is first injected from the first burner when starting the second control.

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