Combustor

Abstract

To provide a combustor capable of improving economical efficiency and operational work efficiency while sufficiently reducing a discharge amount of ammonia to the outside, when using ammonia as fuel gas.SOLUTION: A combustor comprises a control device S capable of controlling valve openings of a first flow control valve V1 and a second flow control valve V2. A hydrocarbon gas flow pipe L2 is connected to a downstream pipe portion of an ammonia gas flow pipe L1 downstream of an installation position of the first flow control valve V1 in a state of allowing hydrocarbon gas to flow. Before combustion is stopped, the control device S closes the first flow control valve V1 and opens the second flow control valve V2, performing hydrocarbon gas purge control to purge ammonia gas in the downstream pipe portion of the ammonia gas flow pipe L1 with hydrocarbon gas.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a combustion device that mixes and burns a fuel gas and an oxidizer containing oxygen. [Background technology]

[0002] Conventionally, in order to address environmental issues such as global warming, ammonia burners and combustion furnaces that use ammonia gas as fuel gas and combustion air as an oxidizer have been known as decarbonization combustion technologies that do not emit carbon dioxide (see Patent Document 1). Ammonia has a relatively high minimum ignition energy of 170 mJ and a relatively slow burning speed of 7 cm / s, making it flame-retardant and difficult to ignite. It is also classified as a specific malodorous substance, for which emission standards are set by the Offensive Odor Control Act. For this reason, it is important that unburned ammonia does not leak outside the burner or combustion furnace, particularly when the burner combustion is stopped.

[0003] Therefore, a technique is known for preventing backfire in a fuel gas flow pipe by performing nitrogen purging by passing nitrogen gas through the fuel gas flow pipe (see Patent Document 2). The technique disclosed in Patent Document 2 is configured to connect a nitrogen gas flow pipe for purging to the fuel gas flow pipe in communication with the fuel gas flow pipe, and to provide an on-off valve for opening and closing the nitrogen gas flow pipe, and to open the on-off valve when purging is required, thereby enabling purge control to be performed by passing nitrogen gas through the fuel gas flow pipe. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2023-178082 [Patent Document 2] Japanese Patent Application Publication No. 2019-168205 Summary of the Invention [Problem to be solved by the invention]

[0005] For the burner disclosed in Patent Document 1, a configuration for executing purge control using nitrogen gas as disclosed in Patent Document 2 is conceivable, but when purging with nitrogen gas is performed, the nitrogen used for purging is consumed at least when the burner combustion is stopped, even though it does not contribute to combustion, so there is room for improvement from the standpoint of economy.Furthermore, since it is necessary to prepare nitrogen cylinders to supply nitrogen, and the cylinders must be replaced periodically, there is also room for improvement from the standpoint of operational efficiency.

[0006] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a combustion apparatus that can improve economic efficiency and operational efficiency while sufficiently reducing the amount of ammonia emitted to the outside when ammonia is used as fuel gas. [Means for solving the problem]

[0007] A combustion device for achieving the above object is a combustion device that burns a mixture of fuel gas and an oxidizer containing oxygen, and its characteristic configuration is as follows: a hydrocarbon gas flow pipe through which a hydrocarbon gas containing methane as a main component as the fuel gas flows; an ammonia gas flow pipe through which ammonia gas as the fuel gas flows; a first flow control valve capable of adjusting the flow rate of the ammonia gas flowing through the ammonia gas flow pipe; a second flow control valve capable of adjusting the flow rate of the hydrocarbon gas flowing through the hydrocarbon gas flow pipe; and a control device capable of controlling the valve openings of the first flow control valve and the second flow control valve, the hydrocarbon gas flow pipe is connected in communication with a downstream pipe portion of the ammonia gas flow pipe that is downstream of an installation position of the first flow control valve in a state that allows the hydrocarbon gas to flow therethrough, The control device executes hydrocarbon gas purge control to purge the ammonia gas in the downstream piping portion of the ammonia gas flow piping with the hydrocarbon gas by closing the first flow control valve and opening the second flow control valve before combustion is stopped.

[0008] According to the above characteristic configuration, the control device closes the first flow control valve and opens the second flow control valve before combustion is stopped, and executes hydrocarbon gas purge control to purge ammonia gas in the downstream piping portion of the ammonia gas flow piping with hydrocarbon gas. Therefore, for example, after combustion is stopped, ammonia can be prevented from remaining in the ammonia gas flow piping, and ammonia, as a specified malodorous substance, can be prevented from being emitted to the outside from the ammonia gas flow piping. In particular, the hydrocarbon gas purge control uses hydrocarbon gas such as city gas 13A that can be supplied through a general gas supply network to purge, so compared to purging with nitrogen supplied from a regular cylinder, work such as changing cylinders can be omitted, thereby improving operational efficiency and economy. As described above, when ammonia is used as fuel gas, it is possible to realize a combustion apparatus that can improve economic efficiency and operational efficiency while sufficiently reducing the amount of ammonia discharged to the outside.

[0009] Further characteristic features of the combustion device include: an ignition device that ignites the air-fuel mixture, The control device has a feature that, from before ignition by the ignition device until ignition, the control device keeps the first flow control valve in a closed state and the second flow control valve in an open state, and after ignition by the ignition device, executes ignition fuel flow control by gradually increasing the opening of the first flow control valve and gradually decreasing the opening of the second flow control valve.

[0010] As explained above, ammonia has a relatively large minimum ignition energy of 170 mJ and a relatively slow burning speed of 7 cm / s, making it flame-retardant and difficult to ignite. Therefore, when ammonia gas is used alone, there is a risk of misfires occurring or unstable combustion. As described above, by executing the fuel flow rate control at ignition, the first flow control valve is closed and the second flow control valve is open from before ignition until the time of ignition, so that the air-fuel mixture containing hydrocarbon gas as fuel gas can be ignited at the time of ignition. This makes it possible to prevent misfires and unstable combustion at the time of ignition. Furthermore, since the proportion of ammonia gas in the fuel gas is gradually increased after ignition, the risk of misfires and unstable combustion can be sufficiently reduced compared to when switching from hydrocarbon gas to hydrogen gas instantaneously.

[0011] Further characteristic features of the combustion device include: The control device, after executing the ignition fuel flow rate control, transitions to ammonia combustion control in which the first flow rate control valve is opened and the second flow rate control valve is closed.

[0012] According to the above characteristic configuration, after the fuel flow rate control at ignition is executed and ignition is properly performed, the control is switched to ammonia combustion control using ammonia gas as the fuel gas. Therefore, compared to the case where hydrocarbon gas is used as the fuel gas, a combustion device can be realized that can reduce CO2 emissions and contribute to decarbonization.

[0013] A further characteristic configuration of the combustion device is that the control device A first mixed-combustion ratio adjustment control is executed to increase the valve opening of the first flow control valve at a predetermined first reference change rate and decrease the valve opening of the second flow control valve at a predetermined second reference change rate, thereby increasing the mixed-combustion ratio of the ammonia gas to all of the fuel gas; and When the mixed-combustion ratio is 30% or more and 60% or less, the ignition-time fuel flow rate control executes second mixed-combustion ratio adjustment control, which increases the mixed-combustion ratio by increasing the rate of change of the valve opening of the first flow control valve at a first rate of change that is greater than the first reference rate of change and decreasing the valve opening of the second flow control valve at a second rate of change that is greater than the second reference rate of change.

[0014] As has been described so far, the combustion device according to the present invention executes the first fuel mix ratio adjustment control to decrease the calorific value proportion of hydrocarbon gas in the fuel gas and increase the calorific value proportion of ammonia gas, for example, immediately after ignition. Here, the inventors of the present invention have found that in the first co-combustion ratio adjustment control, the closer the ratio of the calorific value of hydrocarbon gas to the calorific value of ammonia gas in the fuel gas is to a predetermined ratio (for example, about 1:1), in other words, the closer the co-combustion ratio of ammonia gas to all fuel gas is to a predetermined ratio (for example, about 50%), the higher the total ratio of thermal NOx and fuel NOx contained in the exhaust gas will be. Therefore, in the above-described characteristic configuration, when the mixed combustion ratio is between 30% and 60%, the rate of change of the valve opening of the first flow control valve is increased at a first rate that is greater than the first reference rate of change, and the valve opening of the second flow control valve is decreased at a second rate that is greater than the second reference rate of change, thereby executing second mixed combustion ratio adjustment control in the ignition fuel flow control to increase the mixed combustion ratio. By doing so, the time it takes for the mixed combustion ratio to approach 50% can be shortened, and the amounts of thermal NOx and fuel NOx contained in the exhaust gas can be sufficiently reduced.

[0015] A further characteristic configuration of the combustion device is that the control device a stop flow rate control can be executed in which, before the hydrocarbon gas purge control, the opening degree of the second flow rate control valve is set to an opening degree equal to or greater than a lower limit combustion opening degree which is greater than zero, and the opening degree of the first flow rate control valve is gradually reduced to zero, A third mixed-combustion ratio adjustment control is executed to reduce the mixed-combustion ratio of the ammonia gas relative to all of the fuel gas by decreasing the valve opening of the first flow control valve at a third reference change rate and increasing the valve opening of the second flow control valve at a fourth reference change rate, and When the mixed-combustion ratio is 30% or more and 60% or less, a fourth mixed-combustion ratio adjustment control is executed in the stop-time flow control, which reduces the mixed-combustion ratio by decreasing the rate of change of the valve opening of the first flow control valve at a third rate of change larger than the third reference rate of change and increasing the valve opening of the second flow control valve at a fourth rate of change larger than the fourth reference rate.

[0016] The combustion device according to the present invention executes third co-firing ratio adjustment control to increase the calorific value proportion of hydrocarbon gas in the fuel gas and decrease the calorific value proportion of ammonia gas, for example, in the period before combustion is stopped. As described above, the inventors of the present invention have found that, in the third co-combustion ratio adjustment control, the closer the ratio of the calorific value of hydrocarbon gas to the calorific value of ammonia gas in the fuel gas is to 1:1, in other words, the closer the co-combustion ratio of ammonia gas to all fuel gas is to 50%, the higher the total proportion of thermal NOx and fuel NOx contained in the exhaust gas. Therefore, in the above-described characteristic configuration, when the mixed combustion ratio is 30% or more and 60% or less, the rate of change in the valve opening of the first flow control valve is reduced at a third rate that is greater than the third reference rate of change, and the valve opening of the second flow control valve is increased at a fourth rate that is greater than the fourth reference rate of change, thereby executing fourth mixed combustion ratio adjustment control in the stop-time flow control to reduce the mixed combustion ratio. This makes it possible to shorten the time it takes for the mixed combustion ratio to approach a predetermined rate (for example, around 50%), and therefore to sufficiently reduce the amounts of thermal NOx and fuel NOx contained in the exhaust gas. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a schematic diagram of a combustion device according to the present invention. [Figure 2]FIG. 4 is a control flow diagram relating to a combustion start process. [Figure 3] FIG. 4 is a control flow diagram relating to a combustion stop process. [Figure 4] 5 is a graph showing changes over time in the valve opening degrees of the first flow control valve and the second flow control valve during the combustion start process. FIG. [Figure 5] 10 is a graph showing changes over time in the valve opening degrees of the first flow control valve and the second flow control valve during the combustion stopping process. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0018] A combustion apparatus 100 according to an embodiment of the present invention relates to a combustion apparatus that can improve economic efficiency and operational efficiency while sufficiently reducing the amount of ammonia discharged to the outside when ammonia is used as fuel gas. The combustion apparatus 100 according to this embodiment will be described below with reference to FIGS.

[0019] The combustion device 100 according to this embodiment burns a mixture of fuel gas and combustion air (an example of an oxidizer containing oxygen), and employs an electronic linkage system using a flow control unit S2 as a control device S to control the flow rates of the fuel gas and combustion air and burn the mixture at a desired air ratio. As shown in FIG. 1, the combustion device 100 is configured by connecting, to a burner body BNa, a hydrocarbon gas flow pipe L2 through which a hydrocarbon gas (e.g., city gas 13A) containing a hydrocarbon (e.g., methane) as a main component as a fuel gas, an ammonia gas flow pipe L1 through which ammonia gas as a fuel gas flows, and a combustion air flow pipe L3 through which combustion air compressed by a blower B whose rotation speed is controlled by an inverter system, and forms a combustion flame by igniting the air-fuel mixture in the burner body BNa by an ignition device not shown.

[0020] The ammonia gas flow pipe L1 is provided with, in the order listed from the upstream side, a first flow meter F1 that measures the flow rate of the ammonia gas flowing therethrough, a first flow control valve V1 that controls the flow rate of the ammonia gas flowing therethrough, a first on-off valve SV1 and a second on-off valve SV2 that switch the flow path between an open state and a closed state, and a first check valve GV1 that prevents the flow of fluid from the downstream side to the upstream side. The hydrocarbon gas flow pipe L2 is provided with, in this order from the upstream side, a second flow meter F2 that measures the flow rate of the hydrocarbon gas flowing therethrough, a second flow control valve V2 that controls the flow rate of the hydrocarbon gas flowing therethrough, a third on-off valve SV3 and a fourth on-off valve SV4 that switch the flow path between an open state and a closed state, and a second check valve GV2 that prevents fluid from flowing from the downstream side to the upstream side.

[0021] The hydrocarbon gas flow pipe L2 is preferably connected in communication with at least a downstream pipe portion of the ammonia gas flow pipe L1 downstream of the installation position of the first flow control valve V1 in a state allowing the hydrocarbon gas to flow therethrough. In this embodiment, as shown in Fig. 1, the downstream portion of the second check valve GV2 of the hydrocarbon gas flow pipe L2 is connected to the downstream portion of the first check valve GV1 of the ammonia gas flow pipe L1 at a junction G, and a mixer (not shown) is provided at the junction G for mixing the hydrocarbon gas and the ammonia gas.

[0022] The combustion air flow pipe L3 is provided with a third flow meter F3 that measures the flow rate of the combustion air flowing through it, and a third flow control valve V3 that controls the flow rate of the combustion air flowing through it, in the order listed from the upstream side.

[0023] The control device S is configured so that various functions are performed by the cooperation of hardware and software. The flow rate control unit S2 serving as the control device S is configured to control the flow rates of the fuel gas and combustion air based on the measurement results of a temperature sensor ND that measures the temperature inside the combustion furnace R heated by the combustion flame formed in the burner body BNa. In other words, the flow rate control unit S2 controls the apertures of the first flow rate control valve V1, the second flow rate control valve V2, and the third flow rate control valve V3 based on the flow rates measured by the first flow meter F1, the second flow meter F2, and the third flow meter F3 so that the temperature measured by the temperature sensor ND becomes a target temperature stored in advance in the memory unit S1 serving as the control device S. Furthermore, the flow control unit S2 controls the opening degrees of the first flow control valve V1, the second flow control valve V2, and the third flow control valve V3 based on the flow rates measured by the first flow meter F1, the second flow meter F2, and the third flow meter F3 so that the air ratio of the mixture supplied to the burner body BNa becomes the desired air ratio stored in the memory unit S1.

[0024] As described above, the combustion device 100 according to this embodiment uses ammonia gas as fuel gas, but does not use gases such as nitrogen that do not contribute to combustion in order to purge the ammonia gas. That is, the combustion device 100 is configured to include only an ammonia gas flow pipe L1, a hydrocarbon gas flow pipe L2, and a combustion air flow pipe L3 as the piping and other components for supplying gas to the burner body BNa. The combustion device 100 according to the embodiment employs the above-described configuration, and when flame-retardant ammonia gas is used as the fuel gas, the combustion is controlled based on the flow charts relating to the combustion start process shown in FIG. 2 and the combustion stop process shown in FIG. 3 in order to effectively prevent misfires and unstable combustion at the time of ignition, and to prevent ammonia, which is a specified malodorous substance, from leaking to the outside when or after combustion is stopped. The following description will also be made with reference to FIGS. 4 and 5, which are graphs showing the changes over time in the opening degrees of the first flow control valve V1 and the second flow control valve V2 during the combustion start process.

[0025] In the combustion start process, as shown in FIG. 2, the flow control unit S2 first operates the blower B at a predetermined rotation speed and opens the third flow control valve V3 to a predetermined degree to allow combustion air to flow through the combustion air flow pipe L3 (#11).

[0026] Next, the flow rate control unit S2 opens the third on-off valve SV3 and the fourth on-off valve SV4 and opens the second flow control valve V2 to a predetermined opening degree (100% in FIG. 4), thereby flowing the hydrocarbon gas through the hydrocarbon gas flow pipe L2 to the burner body BNa (#12). The flow rate control unit S2 ignites the mixture of hydrocarbon gas and combustion air using an ignition device (not shown) (#13). During ignition, the second flow rate control valve V2 is maintained at a predetermined opening that is greater than zero and equal to or greater than the lower combustion limit opening (100% in the graph shown in FIG. 4).

[0027] Next, the flow rate control unit S2 closes the first flow rate control valve V1 and opens the second flow rate control valve V2 before and during ignition by the ignition device, but after ignition by the ignition device, gradually increases the aperture of the first flow rate control valve V1 to increase the flow rate of ammonia gas and gradually decreases the aperture of the second flow rate control valve V2 to decrease the flow rate of hydrocarbon gas (#14 to #17). This prevents flame-retardant ammonia gas from being contained in the fuel gas at ignition, preventing misfires and unstable combustion.

[0028] The inventors have found that when the above-mentioned fuel flow rate control at ignition is performed, the closer the ratio of the calorific value of hydrocarbon gas to the calorific value of ammonia gas in the fuel gas is to a predetermined ratio (for example, about 1:1), in other words, the closer the mixed combustion ratio of ammonia gas to all fuel gas is to a predetermined ratio (for example, about 50%), the higher the total ratio of thermal NOx and fuel NOx contained in the exhaust gas will be.

[0029] Therefore, in the combustion device 100 according to this embodiment, the following control steps #14 to #17 are executed to reduce the amount of NOx emitted as exhaust gas. That is, the processing of the following steps #14 to #17 is included in the ignition fuel flow rate control. If the ammonia gas co-combustion ratio for all fuel gases is not between 30% and 60% (No in #14), the flow rate control unit S2 increases the valve aperture of the first flow control valve V1 at a predetermined first reference rate (e.g., a rate of change of 2% / sec) and decreases the valve aperture of the second flow control valve V2 at a predetermined second reference rate (e.g., a rate of change of 2% / sec), thereby executing first co-combustion ratio adjustment control to increase the ammonia gas co-combustion ratio for all fuel gases (#15). On the other hand, if the mixed-combustion ratio is 30% or more and 60% or less (Yes in #14), the flow rate control unit S2 increases the rate of change of the valve opening of the first flow control valve V1 at a first rate of change that is greater than the first reference rate of change (e.g., a rate of change of 3% / sec), and decreases the valve opening of the second flow control valve V2 at a second rate of change that is greater than the second reference rate of change (e.g., a rate of change of 3% / sec), thereby executing second mixed-combustion ratio adjustment control to increase the mixed-combustion ratio (#16).

[0030] Incidentally, the first reference change rate, the second reference change rate, the first change rate, and the second change rate are values ​​that are predetermined and stored in the storage unit S1.

[0031] Furthermore, if the opening degree of the first flow control valve V1 is not 100% (No in #17), the flow control unit S2 repeatedly executes the control of steps #14 to #16 described above. On the other hand, if the opening degree of the first flow control valve V1 is 100% (Yes in #17), in other words, if the first flow control valve V1 is in an open state (opening degree: 100%) and the second flow control valve V2 is in a closed state (opening degree: 0%), the flow control unit S2 executes (continues) ammonia combustion control to achieve a mono-fuel state of ammonia gas.

[0032] Next, the combustion stop process will be described with reference to the control flow of FIG. 3 and the graph of FIG. When the combustion stop process is initiated, the flow control unit S2 executes stop flow control by gradually reducing the opening of the first flow control valve V1 to zero while maintaining the opening of the second flow control valve V2 at a lower combustion limit opening greater than zero (for example, the minimum opening at which no misfire occurs, Vα in FIG. 5).

[0033] As described above, the inventors have found that when the stop-time flow rate control is performed, the closer the ratio of the calorific value of hydrocarbon gas to the calorific value of ammonia gas in the fuel gas is to a predetermined ratio (for example, about 1:1), in other words, the closer the mixed combustion ratio of ammonia gas to all fuel gas is to a predetermined ratio (for example, about 50%), the higher the total proportion of thermal NOx and fuel NOx contained in the exhaust gas will be. Therefore, in the combustion device 100 according to this embodiment, the following control of steps #21 to #24 (control included in the stop-time flow rate control) is executed in order to reduce the amount of NOx emitted as exhaust gas.

[0034] If the ammonia gas co-combustion ratio for all fuel gases is not 30% or more and 60% or less (No in #21), the flow rate control unit S2 executes third co-combustion ratio adjustment control to reduce the ammonia gas co-combustion ratio for all fuel gases by decreasing the valve aperture of the first flow control valve V1 at a predetermined third reference change rate (e.g., a change rate of 2% / second) and increasing the valve aperture of the second flow control valve V2 at a predetermined fourth reference change rate (e.g., a change rate of 2% / second) (#22). On the other hand, if the mixed-combustion ratio is 30% or more and 60% or less (Yes in #21), the flow rate control unit S2 executes fourth mixed-combustion ratio adjustment control to increase the mixed-combustion ratio by decreasing the rate of change of the valve opening of the first flow control valve V1 at a third rate of change greater than the third reference rate of change (e.g., a rate of change of 3% / sec) and decreasing the valve opening of the second flow control valve V2 at a fourth rate of change greater than the fourth reference rate of change (e.g., a rate of change of 3% / sec) (#23).

[0035] Incidentally, the third reference change rate, the fourth reference change rate, the third change rate, and the fourth change rate are values ​​that are predetermined and stored in the storage unit S1.

[0036] Furthermore, if the opening degree of the first flow control valve V1 is not 0% (No in #24), the flow rate control unit S2 repeatedly executes the control of steps #21 to #23 described above. On the other hand, if the opening degree of the first flow control valve V1 is 0% (Yes in #24), in other words, if the first flow control valve V1 is in a closed state (opening degree: 0%) and the second flow control valve V2 is in an open state (for example, opening degree: 100%), the flow rate control unit S2 executes hydrocarbon gas purge control to flow hydrocarbon gas into the burner body BNa via the hydrocarbon gas flow pipe L2 and the ammonia gas flow pipe L1 downstream of the junction G for a predetermined first purge time before combustion is stopped, in order to purge the downstream side of the junction G of the ammonia gas flow pipe L1 with hydrocarbon gas as fuel gas (#25). In addition, in the hydrocarbon gas purge control, the flow control unit S2 maintains the first on-off valve SV1 and the second on-off valve SV2 in a closed state, and also closes the first flow control valve V1 to prohibit ammonia gas from being introduced into the burner body BNa.

[0037] The flow rate control unit S2 performs hydrocarbon gas purge control for a predetermined first purge time (a time during which hydrocarbon gas is allowed to flow at a flow rate equivalent to at least five times the piping volume downstream of the confluence G of the ammonia gas flow piping L1), and then stops combustion.

[0038] [Another embodiment] (1) In the above embodiment, when controlling the flow rates of hydrogen gas and hydrocarbon gas in the ignition flow rate control and the first combustion stop control, the flow rate control unit S2 controls the opening degrees of the various flow rate control valves so that the air ratio of the mixture becomes a predetermined value. The air ratio does not necessarily have to be a constant value, but may be controlled to fall within a range in which the air-fuel mixture can be stably combusted.

[0039] (2) In the above embodiment, the second fuel-mixing ratio adjustment control and the fourth fuel-mixing ratio adjustment control are executed as an example of control, but these controls do not necessarily have to be executed. In this case, in the combustion start process, only the first fuel mixture ratio adjustment control is executed in the ignition fuel flow rate control, and in the combustion stop process, only the third fuel mixture ratio adjustment control is executed in the stop-time flow rate control.

[0040] (3) In the above embodiment, a control example has been shown in which, when combustion is started in the combustion start process, the combustion transitions to ammonia-only combustion in which the fuel gas is only ammonia gas, and the ammonia-only combustion is maintained. The flow rate control unit S2 does not necessarily have to perform ammonia mono-fuel combustion, but may perform mixed combustion in which hydrocarbon gas and ammonia gas are mixed and burned at a predetermined ratio as fuel gas, and control the mixed combustion to maintain the mixed combustion.

[0041] Furthermore, the configurations disclosed in the above embodiments (including other embodiments, the same applies below) can be applied in combination with configurations disclosed in other embodiments, as long as no contradictions arise. Furthermore, the embodiments disclosed in this specification are examples, and the embodiments of the present invention are not limited to these, and can be modified as appropriate within the scope that does not deviate from the purpose of the present invention. [Industrial Applicability]

[0042] INDUSTRIAL APPLICABILITY The combustion apparatus of the present invention can be effectively used as a combustion apparatus that can improve economic efficiency and operational efficiency while sufficiently reducing the amount of ammonia discharged to the outside when ammonia is used as fuel gas. [Explanation of symbols]

[0043] 100: Combustion equipment BNa: Burner body L1: Ammonia gas flow piping L2: Hydrocarbon gas flow piping L3: Combustion air flow piping S: Control device S2:Flow control section V1: First flow control valve V2: Second flow control valve

Claims

1. A combustion device that burns a mixture of fuel gas and an oxidizer containing oxygen, a hydrocarbon gas flow pipe through which a hydrocarbon gas containing methane as a main component as the fuel gas flows; an ammonia gas flow pipe through which ammonia gas as the fuel gas flows; a first flow control valve capable of adjusting the flow rate of the ammonia gas flowing through the ammonia gas flow pipe; a second flow control valve capable of adjusting the flow rate of the hydrocarbon gas flowing through the hydrocarbon gas flow pipe; and a control device capable of controlling the valve openings of the first flow control valve and the second flow control valve, the hydrocarbon gas flow pipe is connected in communication with a downstream pipe portion of the ammonia gas flow pipe that is downstream of an installation position of the first flow control valve in a state that allows the hydrocarbon gas to flow therethrough, The control device performs hydrocarbon gas purge control to purge the ammonia gas in the downstream piping portion of the ammonia gas flow piping with the hydrocarbon gas by closing the first flow control valve and opening the second flow control valve before combustion is stopped.

2. an ignition device that ignites the air-fuel mixture, 2. The combustion device according to claim 1, wherein the control device closes the first flow control valve and opens the second flow control valve before ignition by the ignition device until ignition, and after ignition by the ignition device, executes ignition fuel flow control by gradually increasing an opening degree of the first flow control valve and gradually decreasing an opening degree of the second flow control valve.

3. 3. The combustion device according to claim 2, wherein, after executing the ignition fuel flow rate control, the control device transitions to ammonia combustion control in which the first flow rate control valve is opened and the second flow rate control valve is closed.

4. The control device A first mixed-combustion ratio adjustment control is executed to increase the valve opening of the first flow control valve at a predetermined first reference change rate and decrease the valve opening of the second flow control valve at a predetermined second reference change rate, thereby increasing the mixed-combustion ratio of the ammonia gas to all of the fuel gas; and 3. The combustion device according to claim 2, wherein, when the mixed-combustion ratio is 30% or more and 60% or less, the ignition-time fuel flow rate control executes second mixed-combustion ratio adjustment control, which increases the mixed-combustion ratio by increasing a rate of change of the valve aperture of the first flow control valve at a first rate of change greater than the first reference rate of change and decreasing the valve aperture of the second flow control valve at a second rate of change greater than the second reference rate of change.

5. The control device a stop flow rate control can be executed in which, before the hydrocarbon gas purge control, the opening degree of the second flow rate control valve is set to an opening degree equal to or greater than a lower limit combustion opening degree which is greater than zero, and the opening degree of the first flow rate control valve is gradually reduced to zero, A third mixed-combustion ratio adjustment control is executed to reduce the mixed-combustion ratio of the ammonia gas relative to all of the fuel gas by decreasing the valve aperture of the first flow control valve at a third reference change rate and increasing the valve aperture of the second flow control valve at a fourth reference change rate, and 3. The combustion device according to claim 1, wherein, when the mixed-combustion ratio is 30% or more and 60% or less, the stop-time flow rate control executes fourth mixed-combustion ratio adjustment control, which reduces the mixed-combustion ratio by decreasing a rate of change of the valve aperture of the first flow control valve at a third rate that is greater than the third reference rate of change and increasing the valve aperture of the second flow control valve at a fourth rate that is greater than the fourth reference rate of change.

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