Ammonia combustion method for industrial furnace, and ammonia combustion industrial furnace

Abstract

To provide a combustion method and an industrial furnace that do not generate unburned ammonia even when ammonia fuel is used singly.SOLUTION: An ammonia combustion industrial furnace 1 for performing an ammonia combustion method includes: an ammonia fuel passage 3 for supplying ammonia fuel to a burner 2; an ammonia fuel on-off valve 4 for opening and closing the passage; a hydrocarbon fuel passage 5 for supplying hydrocarbon fuel to the burner 2; a hydrocarbon fuel on-off valve 6 for opening and closing the passage; a temperature sensor 7 for measuring an in-furnace temperature; and a control section 8 for transmitting an opening / closing signal to the ammonia fuel on-off valve 4 and the hydrocarbon fuel on-off valve 6. When the in-furnace temperature rises, only hydrocarbon fuel is combusted until the in-furnace temperature rises close to 1,000°C, and only ammonia fuel is combusted when the in-furnace temperature rises to 1,000°C. When the in-furnace temperature drops, only ammonia fuel is combusted until the furnace temperature drops close to 1,000°C. When the in-furnace temperature has dropped to less than 1,000°C, only hydrocarbon fuel is combusted.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for completely burning ammonia alone as a fuel in an industrial furnace, and an industrial furnace capable of completely burning ammonia alone as a fuel.

Background Art

[0002] In industrial furnaces for heat-treating metals and non-ferrous metals, many burn hydrocarbons such as natural gas as fuel. Although hydrocarbons are relatively environmentally friendly gases because they do not contain impurities such as carbon monoxide, there is a problem that they generate so-called greenhouse gases such as carbon dioxide when burned.

[0003] From this point of view, recently, in the field of industrial furnaces, a technology using ammonia, which does not generate carbon dioxide or the like even when burned, as fuel is known (see, for example, Patent Document 1). The invention described in this Patent Document 1 is a mechanism for facilitating the combustion of ammonia fuel by supplying hydrocarbon fuel into the furnace by a burner (a burner dedicated to hydrocarbon fuel) when burning ammonia fuel in the furnace by a burner (a burner dedicated to ammonia fuel). That is, the combustion of ammonia fuel is promoted by utilizing the combustion of hydrocarbon fuel.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the field of industrial furnaces, effective technologies for using ammonia as a sole fuel have not been established. Ammonia fuel has poor combustibility compared to hydrocarbon fuels and is difficult to burn completely. Further, when ammonia fuel is burned, a large amount of nitrogen oxides (NOx) is generated. If the amount of combustion air is reduced to suppress this, so-called unburned ammonia and nitrous oxide (N2O), which is a greenhouse gas, are generated. When ammonia fuel is burned in a furnace, these unburned ammonia and the like are generated in large quantities when the combustion temperature is less than 1000°C (for example, in the range of 450°C to 1000°C). This unburned ammonia is not preferable because it nitriding heat-treated materials such as metals and non-ferrous metals.

[0006] In the invention described in Patent Document 1, since ammonia fuel is burned even during the temperature increase in the furnace (for example, until the combustion temperature reaches 1000°C), theoretically, unburned ammonia and the like are generated. Further, the invention described in this document does not use ammonia as a sole fuel. Furthermore, when burning ammonia fuel with a burner dedicated to ammonia fuel, it is necessary to burn hydrocarbon fuel with a burner dedicated to hydrocarbons. Therefore, since a plurality of burners and associated on-off valves and the like are required, the configuration as an industrial furnace becomes complicated and large-scale.

[0007] Therefore, an object of the present invention is to provide an ammonia combustion method that does not generate unburned ammonia and the like even when ammonia fuel is used alone in an industrial furnace for heat-treating metals and non-ferrous metals, and an ammonia combustion industrial furnace with a simple configuration capable of burning ammonia as a sole fuel.

Means for Solving the Problems

[0008] To achieve the above object, the ammonia combustion method of the industrial furnace of the present invention is A method of burning ammonia as fuel in an industrial furnace for heating metals and non-ferrous metals with a burner for heat treatment, When raising the temperature inside the industrial furnace, hydrocarbon fuel is used alone until the temperature inside the furnace rises to nearly 1000°C. When the temperature inside the furnace reaches 1000°C, thereafter, ammonia fuel is used alone or in combination with hydrocarbon fuel.

[0009] Moreover, the ammonia combustion method for the industrial furnace of the present invention is In an industrial furnace for heat-treating metals and non-ferrous metals by heating with a burner, a method of burning ammonia as fuel, When lowering the temperature inside the industrial furnace, ammonia fuel is used alone or in combination with hydrocarbon fuel until the temperature inside the furnace drops to nearly 1000°C. When the temperature inside the furnace drops below 1000°C, thereafter, hydrocarbon fuel is used alone.

[0010] Moreover, the ammonia combustion method for the industrial furnace of the present invention is In an industrial furnace for heat-treating metals and non-ferrous metals by heating with a burner, a method of burning ammonia as fuel, When raising the temperature inside the industrial furnace, hydrocarbon fuel is used alone until the temperature inside the furnace rises to nearly 800°C. When the temperature inside the furnace reaches 800°C, thereafter, ammonia fuel is used alone or in combination with hydrocarbon fuel.

[0011] Moreover, the ammonia combustion method for the industrial furnace of the present invention is In an industrial furnace for heat-treating metals and non-ferrous metals by heating with a burner, a method of burning ammonia as fuel, When lowering the temperature inside the industrial furnace, ammonia fuel is used alone or in combination with hydrocarbon fuel until the temperature inside the furnace drops to nearly 800°C. When the temperature inside the furnace drops below 800°C, thereafter, hydrocarbon fuel is used alone.

[0012] In addition, the ammonia combustion method for an industrial furnace of the present invention is as follows. In an industrial furnace for heating and heat-treating metals or non-ferrous metals with a burner, a method of burning ammonia as fuel, when raising the temperature inside the industrial furnace, hydrocarbon fuel is used alone until the temperature inside the furnace rises near the set temperature of 800°C or higher and 1000°C or lower. When the temperature inside the furnace rises to the set temperature, thereafter, ammonia fuel is used alone, or hydrocarbon fuel and ammonia fuel are used in combination. It is characterized by this.

[0013] In addition, the ammonia combustion method for an industrial furnace of the present invention is as follows. In an industrial furnace for heating and heat-treating metals or non-ferrous metals with a burner, a method of burning ammonia as fuel, when lowering the temperature inside the industrial furnace, ammonia fuel is used alone, or hydrocarbon fuel and ammonia fuel are used in combination until the temperature inside the furnace drops near the set temperature of 800°C or higher and 1000°C or lower. When the temperature inside the furnace drops below the set temperature, thereafter, hydrocarbon fuel is used alone. It is characterized by this.

[0014] Furthermore, the ammonia combustion method for an industrial furnace of the present invention is characterized by using hydrogen fuel instead of the hydrocarbon fuel.

[0015] The ammonia combustion industrial furnace (1) of the present invention is an industrial furnace for heating and heat-treating metals or non-ferrous metals with a burner using ammonia as fuel, an ammonia fuel passage (3) for supplying the ammonia fuel to the burner (2), an ammonia fuel on-off valve (4) for opening and closing the ammonia fuel passage (3), a hydrocarbon fuel passage (5) for supplying hydrocarbon fuel to the burner (2), a hydrocarbon fuel on-off valve (6) for opening and closing the hydrocarbon fuel passage (5), a temperature sensor (7) for measuring the temperature inside the furnace, A control unit (8) that sends an opening / closing signal to the ammonia fuel on-off valve (4) and the hydrocarbon fuel on-off valve (6) according to the measured temperature of the temperature sensor (7). When raising the temperature inside the industrial furnace (1), until the temperature inside the furnace rises to nearly 1000 °C, according to the signal from the control unit (8), the hydrocarbon fuel on-off valve (6) is opened and the ammonia fuel on-off valve (4) is closed, and only the hydrocarbon fuel is burned by the burner (2) to heat the inside of the furnace. When the temperature inside the furnace rises to 1000 °C, according to the signal from the control unit (8), the hydrocarbon fuel on-off valve (6) is closed and the ammonia fuel on-off valve (4) is opened, and only the ammonia fuel is burned by the burner (2), or according to the signal from the control unit (8), the hydrocarbon fuel on-off valve (6) is opened and the ammonia fuel on-off valve (4) is opened, and both the ammonia fuel and the hydrocarbon fuel are burned by the burner (2) to heat the inside of the furnace. When lowering the temperature inside the industrial furnace (1), until the temperature inside the furnace drops to nearly 1000 °C, according to the signal from the control unit (8), the ammonia fuel on-off valve (4) is opened and the hydrocarbon fuel on-off valve (6) is closed, and only the ammonia fuel is burned by the burner (2), or according to the signal from the control unit (8), the ammonia fuel on-off valve (4) is opened and the hydrocarbon fuel on-off valve (6) is also opened, and both the ammonia fuel and the hydrocarbon fuel are burned by the burner (2) to heat the inside of the furnace. When the temperature inside the furnace drops below 1000 °C, according to the signal from the control unit (8), the ammonia fuel on-off valve (4) is closed and the hydrocarbon fuel on-off valve (6) is opened, and only the hydrocarbon fuel is burned by the burner (2) to heat the inside of the furnace. This is the characteristic.

[0016] The ammonia combustion industrial furnace (1) of the present invention is an industrial furnace for heat-treating metals and non-ferrous metals by heating with a burner (2) using ammonia as fuel. The burner (2) consists of a first burner (2a) and a second burner (2b). An ammonia fuel passage (3) for supplying the ammonia fuel to the first burner (2a); An ammonia fuel on-off valve (4) for opening and closing the ammonia fuel passage (3); A hydrocarbon fuel passage (5) for supplying the hydrocarbon fuel to the second burner (2b); A hydrocarbon fuel on-off valve (6) for opening and closing the hydrocarbon fuel; A temperature sensor (7) for measuring the temperature inside the furnace; A control unit (8) for sending an opening / closing signal to the ammonia fuel on-off valve (4) and the hydrocarbon fuel on-off valve (6) according to the measured temperature of the temperature sensor (7); When raising the temperature inside the industrial furnace (1), until the temperature inside the furnace rises to nearly 1000 °C, according to the signal from the control unit (8), the hydrocarbon fuel on-off valve (6) is opened and the ammonia fuel on-off valve (4) is closed, and only the hydrocarbon fuel is burned by the second burner (2b) to heat the inside of the furnace. When the temperature inside the furnace rises to 1000 °C, according to the signal from the control unit (8), the hydrocarbon fuel on-off valve (6) is closed and the ammonia fuel on-off valve (4) is opened, and only the ammonia fuel is burned by the first burner (2a), or according to the signal from the control unit (8), the hydrocarbon fuel on-off valve (6) is opened and burned by the second burner (2b), and the ammonia fuel on-off valve (4) is opened, and only the ammonia fuel is burned by the first burner (2a) to heat the inside of the furnace. When the temperature inside the industrial furnace (1) is decreased, until the temperature inside the furnace drops to nearly 1000°C, the ammonia fuel on-off valve (4) is opened by a signal from the control unit (8), and at the same time, the hydrocarbon fuel on-off valve (6) is closed, and only the ammonia fuel is burned by the first burner (2a), or by a signal from the control unit (8), the ammonia fuel on-off valve (4) is opened and the first burner (2a) is burned, and at the same time, the hydrocarbon fuel on-off valve (6) is also opened, and the hydrocarbon fuel is burned by the second burner (2b) to heat the inside of the furnace. When the temperature inside the furnace drops to less than 1000°C, the ammonia fuel on-off valve (4) is closed by a signal from the control unit (8), and at the same time, the hydrocarbon fuel on-off valve (6) is opened, and only the hydrocarbon fuel is burned by the second burner (2b) to heat the inside of the furnace. This is the feature.

[0017] Further, the ammonia combustion industrial furnace (1) of the present invention is an industrial furnace for heat-treating metals and non-ferrous metals by heating with a burner (2) using ammonia as fuel. An ammonia fuel passage (3) for supplying the ammonia fuel to the burner (2); An ammonia fuel on-off valve (4) for opening and closing the ammonia fuel passage (3); A hydrocarbon fuel passage (5) for supplying hydrocarbon fuel to the burner (2); A hydrocarbon fuel on-off valve (6) for opening and closing the hydrocarbon fuel passage (5); A temperature sensor (7) for measuring the temperature inside the furnace; And a control unit (8) that sends an opening and closing signal to the ammonia fuel on-off valve (4) and the hydrocarbon fuel on-off valve (6) according to the measured temperature of the temperature sensor (7). When increasing the temperature inside the industrial furnace (1), until the temperature inside the furnace rises near the set temperature of 800°C or more and 1000°C or less, according to the signal from the control unit (8), the hydrocarbon fuel on-off valve (6) is opened, and the ammonia fuel on-off valve (4) is closed, and only the hydrocarbon fuel is burned by the burner (2) to heat the inside of the furnace. When the temperature inside the furnace rises to the set temperature, according to the signal from the control unit (8), the hydrocarbon fuel on-off valve (6) is closed, and the ammonia fuel on-off valve (4) is opened, and only the ammonia fuel is burned by the burner (2), or according to the signal from the control unit (8), the hydrocarbon fuel on-off valve (6) is opened, and the ammonia fuel on-off valve (4) is opened, and both the ammonia fuel and the hydrocarbon fuel are burned by the burner (2) to heat the inside of the furnace. When decreasing the temperature inside the industrial furnace (1), until the temperature inside the furnace drops near the set temperature, according to the signal from the control unit (8), the ammonia fuel on-off valve (4) is opened, and the hydrocarbon fuel on-off valve (6) is closed, and only the ammonia fuel is burned by the burner (2), or according to the signal from the control unit (8), the ammonia fuel on-off valve (4) is opened, and the hydrocarbon fuel on-off valve (6) is also opened, and both the ammonia fuel and the hydrocarbon fuel are burned by the burner (2) to heat the inside of the furnace. When the temperature inside the furnace drops below the set temperature, according to the signal from the control unit (8), the ammonia fuel on-off valve (4) is closed, and the hydrocarbon fuel on-off valve (6) is opened, and only the hydrocarbon fuel is burned by the burner (2) to heat the inside of the furnace, which is characterized by this.

[0018] Also, the ammonia combustion industrial furnace (1) of the present invention is an industrial furnace for heat-treating metals and non-ferrous metals by heating with a burner (2) using ammonia as fuel. The burner (2) consists of a first burner (2a) and a second burner (2b). An ammonia fuel passage (3) for supplying the ammonia fuel to the first burner (2a). an ammonia fuel on-off valve (4) for opening and closing the ammonia fuel passage (3); a hydrocarbon fuel passage (5) for supplying hydrocarbon fuel to the second burner (2b); a hydrocarbon fuel on-off valve (6) for opening and closing the hydrocarbon fuel; a temperature sensor (7) for measuring the temperature inside the furnace; a control unit (8) for sending an opening and closing signal to the ammonia fuel on-off valve (4) and the hydrocarbon fuel on-off valve (6) according to the measured temperature of the temperature sensor (7); When raising the temperature inside the industrial furnace (1), until the temperature inside the furnace rises to near the set temperature of 800 °C or more and 1000 °C or less, the hydrocarbon fuel on-off valve (6) is opened and the ammonia fuel on-off valve (4) is closed by a signal from the control unit (8), and only the hydrocarbon fuel is burned by the second burner (2b) to heat the inside of the furnace. When the temperature inside the furnace rises to the set temperature, the hydrocarbon fuel on-off valve (6) is closed and the ammonia fuel on-off valve (4) is opened by a signal from the control unit (8), and only the ammonia fuel is burned by the first burner (2a), or the hydrocarbon fuel on-off valve (6) is opened and burned by the second burner (2b) and the ammonia fuel on-off valve (4) is opened by a signal from the control unit (8), and only the ammonia fuel is burned by the first burner (2a) to heat the inside of the furnace. When the temperature inside the industrial furnace (1) is decreased, until the temperature inside the furnace decreases to near the set temperature, the ammonia fuel on-off valve (4) is opened by a signal from the control unit (8), and at the same time, the hydrocarbon fuel on-off valve (6) is closed, and only the ammonia fuel is burned by the first burner (2a), or by a signal from the control unit (8), the ammonia fuel on-off valve (4) is opened and the first burner (2a) is burned, and at the same time, the hydrocarbon fuel on-off valve (6) is also opened, and the hydrocarbon fuel is burned by the second burner (2b) as well to heat the inside of the furnace. When the temperature inside the furnace decreases to less than the set temperature, the ammonia fuel on-off valve (4) is closed by a signal from the control unit (8), and at the same time, the hydrocarbon fuel on-off valve (6) is opened, and only the hydrocarbon fuel is burned by the second burner (2b) to heat the inside of the furnace. This is the gist of the invention.

[0019] In addition, the burner used in the ammonia combustion method and the ammonia combustion industrial furnace of the present invention may be any type of burner as long as it is generally used in industrial furnaces, including the first burner and the second burner. For example, it may be a radiant tube burner.

[0020] Here, the symbols in the parentheses indicate the corresponding elements or corresponding matters shown in the drawings and the embodiments for carrying out the invention described later.

Advantages of the Invention

[0021] According to the ammonia combustion method of the industrial furnace of the present invention, when the temperature inside the furnace is increased, the hydrocarbon fuel is used alone until the temperature inside the furnace increases to near 1000°C. When the temperature inside the furnace increases to 1000°C, thereafter, the ammonia fuel is used alone, or the hydrocarbon fuel and the ammonia fuel are used in combination for co-combustion. Therefore, unburned ammonia, nitrous oxide (N2O), etc. are not generated. That is, since the ammonia fuel is used after the temperature in the furnace has risen to 1000°C, it is possible to completely burn the ammonia fuel, which has poor combustibility compared to hydrocarbon fuels and the like. By completely burning the ammonia fuel, as described in the above prior art, it is possible to prevent the generation of unburned ammonia and the like that are generated in large quantities when the combustion temperature is less than 1000°C (for example, in the range of 450°C to 1000°C), and to heat and maintain the temperature in the furnace at 1000°C or higher.

[0022] Note that when the temperature in the furnace rises to 1000°C, the hydrocarbon fuel is not used thereafter, or the ammonia fuel and the hydrocarbon fuel are used in combination. As a result, the amount of hydrocarbon fuel used (combustion amount) can be reduced. Thereby, it is possible to suppress the generation of greenhouse gases such as carbon dioxide generated by the combustion of the hydrocarbon fuel.

[0023] Further, in the ammonia combustion method of the industrial furnace of the present invention, when the temperature in the furnace of the industrial furnace is decreased, until the temperature in the furnace decreases to near 1000°C, the ammonia fuel is used alone or the ammonia fuel and the hydrocarbon fuel are used in combination. When the temperature in the furnace decreases to less than 1000°C, the hydrocarbon fuel is used alone thereafter, so that unburned ammonia and the like are not generated. That is, the ammonia fuel is only used until the temperature in the furnace decreases to near 1000°C and is not used below 1000°C, so that it is possible to completely burn the ammonia fuel with poor combustibility. By completely burning the ammonia fuel, it is possible to lower the temperature in the furnace while preventing the generation of unburned ammonia and the like.

[0024] Note that since the hydrocarbon fuel is used after the temperature in the furnace has decreased to less than 1000°C, the amount of the hydrocarbon fuel used (combustion amount) can be reduced. Thereby, it is possible to suppress the generation of greenhouse gases generated by the combustion of the hydrocarbon fuel.

[0025] In the present invention, the switching from hydrocarbon fuel to ammonia fuel and vice versa from ammonia fuel to hydrocarbon fuel was based on a furnace temperature of 1000°C. However, it can also be based on 800°C, or on a set temperature between 800°C and 1000°C. At this time, as the reference approaches 1000°C from 800°C, the amounts of unburned ammonia and nitrous oxide (N2O) etc. decrease, so it is more preferable to use 1000°C as the reference.

[0026] Furthermore, according to the ammonia combustion method of the industrial furnace of the present invention, since hydrogen fuel can be used instead of hydrocarbon, generation of greenhouse gases such as carbon dioxide can be prevented. This is because hydrogen fuel does not generate greenhouse gases even when burned.

[0027] According to the ammonia combustion industrial furnace (one with a single burner) of the present invention, when raising the temperature inside the industrial furnace, until the temperature inside the furnace rises close to 1000°C according to a signal from the control unit, only the hydrocarbon fuel on-off valve is opened and only the hydrocarbon fuel is burned by the burner. When the temperature inside the furnace rises to 1000°C, only the ammonia fuel on-off valve is opened and only the ammonia fuel, or both the hydrocarbon fuel on-off valve and the ammonia fuel on-off valve are opened and burned by the burner. Therefore, it is possible to completely burn the ammonia fuel and prevent the generation of unburned ammonia etc. That is, since the ammonia fuel is used after the temperature inside the furnace has risen to 1000°C, it is possible to completely burn the ammonia fuel with poor combustibility. Therefore, unburned ammonia is not generated. Also, since the hydrocarbon fuel is not used after the temperature inside the furnace has risen to 1000°C, or the hydrocarbon fuel and the ammonia fuel are used simultaneously, the usage amount (combustion amount) of the hydrocarbon fuel can be reduced. Therefore, generation of greenhouse gases such as carbon dioxide can be suppressed.

[0028] When the temperature inside the industrial furnace is decreased, the control unit opens only the ammonia fuel on-off valve until the temperature inside the furnace drops to nearly 1000°C, and only burns ammonia fuel with the burner, or simultaneously opens the ammonia fuel on-off valve and the hydrocarbon fuel on-off valve to burn them together with the burner. When the temperature inside the furnace drops below 1000°C, only the hydrocarbon fuel on-off valve is opened to burn only the hydrocarbon fuel with the burner. Therefore, it is possible to completely burn the ammonia fuel and prevent the generation of unburned ammonia and the like. That is, since the use of ammonia fuel is limited until the temperature inside the furnace drops to nearly 1000°C, it is possible to completely burn the ammonia fuel with poor combustibility. Therefore, unburned ammonia is not generated. Also, since hydrocarbon fuel is not used after the temperature inside the furnace rises to 1000°C, or since ammonia fuel and hydrocarbon fuel are used simultaneously, the amount of hydrocarbon fuel used (combustion amount) can be reduced. Therefore, it is possible to suppress the generation of greenhouse gases such as carbon dioxide.

[0029] According to the ammonia combustion industrial furnace of the present invention (using two burners), when the temperature inside the industrial furnace is increased, the control unit opens only the hydrocarbon fuel on-off valve until the temperature inside the furnace rises to nearly 1000°C, and only burns the hydrocarbon fuel with the second burner. When the temperature inside the furnace rises to 1000°C, only the ammonia fuel on-off valve is opened to burn only the ammonia fuel with the first burner, or only the hydrocarbon fuel on-off valve is opened to burn only the hydrocarbon fuel with the second burner and only the ammonia fuel on-off valve is opened to simultaneously burn only the ammonia fuel with the first burner. Therefore, it is possible to completely burn the ammonia fuel and prevent the generation of unburned ammonia and the like. That is, since the ammonia fuel is used after the temperature in the furnace has risen to 1000°C, the ammonia fuel with poor combustibility can be completely burned, and as a result, the generation of unburned ammonia can be prevented. Also, since the hydrocarbon fuel is not used after the temperature in the furnace has risen to 1000°C, or the hydrocarbon fuel and the ammonia fuel are used simultaneously, the usage amount (combustion amount) of the hydrocarbon fuel can be reduced, and as a result, the generation of greenhouse gases such as carbon dioxide can be suppressed.

[0030] Also, when the temperature in the industrial furnace is decreased, the control unit opens only the ammonia fuel on-off valve until the temperature in the furnace drops to near 1000°C, and burns the ammonia fuel with the first burner, or opens only the ammonia fuel on-off valve to burn the ammonia fuel with the first burner while opening only the hydrocarbon fuel on-off valve to burn the hydrocarbon fuel with the second burner. When the temperature in the furnace drops below 1000°C, only the hydrocarbon fuel on-off valve is opened to burn the hydrocarbon fuel with the second burner, so that the ammonia fuel can be completely burned to prevent the generation of unburned ammonia and the like. That is, since the use of the ammonia fuel is limited until the temperature in the furnace drops to near 1000°C, the ammonia fuel with poor combustibility can be completely burned, and unburned ammonia is not generated. Also, since the hydrocarbon fuel is not used after the temperature in the furnace has dropped to 1000°C, its usage amount (combustion amount) can be reduced. Therefore, the generation of greenhouse gases such as carbon dioxide can be suppressed.

[0031] In the present invention, the switching from the hydrocarbon fuel to the ammonia fuel and vice versa is based on the furnace temperature of 1000°C, but it can also be based on the set temperature between 800°C and 1000°C. At this time, as the reference approaches 1000°C from 800°C, the amounts of unburned ammonia, nitrous oxide (N2O), etc. decrease, so it is more preferable to use 1000°C as the reference.

[0032] Note that since the two ammonia combustion industrial furnaces of the present invention described above burn both ammonia fuel and hydrocarbon fuel with one burner, the configuration is simpler compared to the above prior art that burns each with a dedicated burner.

Brief Description of the Drawings

[0033]

Figure 1

Figure 2

Modes for Carrying Out the Invention

[0034] Referring to FIG. 1, an ammonia combustion industrial furnace 1 (using one burner) according to a first embodiment of the present invention will be described together with an ammonia combustion method.

[0035] The ammonia combustion industrial furnace 1 according to the first embodiment of the present invention is an industrial furnace for heating and heat-treating metals and non-ferrous metals with a burner 2 that uses ammonia as fuel, and includes an ammonia fuel passage 3, an ammonia fuel on-off valve 4, a hydrocarbon fuel passage 5, a hydrocarbon fuel on-off valve 6, a combustion air passage 9, a combustion air on-off valve 10, a temperature sensor 7, and a control unit 8. The burner 2 is provided on a furnace wall 1a that forms the furnace body of the industrial furnace 1.

[0036] The ammonia fuel passage 3 supplies ammonia fuel to the burner 2 from an ammonia fuel supply section (not shown), and the ammonia fuel on-off valve 4 is provided in a part of this ammonia fuel passage 3 and opens and closes it. The hydrocarbon fuel passage 5 supplies hydrocarbon fuel (such as natural gas) to the burner 2 from a hydrocarbon fuel supply section (not shown), and the hydrocarbon fuel on-off valve 6 is provided in a part of this hydrocarbon fuel passage 5 and opens and closes it. The combustion air passage 9 supplies combustion air (outside air) to the burner 2, and the combustion air on-off valve 10 is provided in a part of this combustion air passage 9 and opens and closes it.

[0037] The temperature sensor 7 is a thermocouple type provided inside the furnace (inside the furnace body) for measuring the temperature inside the furnace. The control unit 8 is provided outside the furnace body and sends a signal (opening signal) to open each of the ammonia fuel on-off valve 4 and the hydrocarbon fuel on-off valve 6 and a signal (closing signal) to close each on-off valve according to the measured temperature of the temperature sensor 7. Note that the combustion air on-off valve 10 is opened by an opening signal from the control unit 8 when burning ammonia fuel and hydrocarbon fuel, and combustion air is continuously sent to the burner 2 through the combustion air passage 9. The control unit 8 has a storage unit such as a CPU, RAM, and ROM for controlling the whole, and can send a signal for determining the amounts of ammonia fuel, hydrocarbon fuel, and combustion air, in addition to the opening and closing signals, to the ammonia fuel on-off valve 4, the hydrocarbon fuel on-off valve 6, and the combustion air on-off valve 10.

[0038] The ammonia combustion industrial furnace 1 according to the first embodiment of the present invention operates as follows. First, when heat-treating non-ferrous metals or the like, the temperature inside the industrial furnace 1 is raised to a predetermined temperature (1000 °C or higher). At this time, until the temperature inside the furnace reaches nearly 1000 °C, the hydrocarbon fuel on-off valve 6 is opened by an opening signal from the control unit 8, and the ammonia fuel on-off valve 4 is closed by a closing signal from the same control unit 8. At this time, the combustion air on-off valve 10 is opened by an opening signal from the same control unit 8, and combustion air is supplied from the combustion air passage 9 to the burner 2. Thereby, only the hydrocarbon fuel is burned by the burner 2 to heat the inside of the furnace. Note that the temperature inside the furnace is measured at any time by the temperature sensor 7, and the measurement result is sent to the control unit 8.

[0039] When the temperature inside the furnace rises to 1000 °C due to the combustion of hydrocarbon fuel, based on the measurement result of the temperature sensor 7 that measures it, a closing signal is sent from the control unit 8 to the hydrocarbon fuel on-off valve 6, and an opening signal is sent to the ammonia fuel on-off valve 4. Due to this closing signal, the hydrocarbon fuel on-off valve 6 is closed, and due to the opening signal, the ammonia fuel on-off valve 4 is opened. Or, when the temperature inside the furnace rises to 1000 °C due to the combustion of hydrocarbon fuel, based on the measurement result of the temperature sensor 7 that measures it, a blocking signal is sent from the control unit 8 to the hydrocarbon fuel on-off valve 6 and an opening signal is sent to the ammonia fuel on-off valve 4. Or an opening signal is sent from the control unit 8 to the hydrocarbon fuel on-off valve 6 and the ammonia fuel on-off valve 4. Due to this opening signal, the hydrocarbon fuel on-off valve 6 and the ammonia fuel on-off valve 4 are opened. Thereby, only ammonia fuel is burned by the burner 2, or hydrocarbon fuel is co-burned by the burner 1 and ammonia fuel is burned by the burner 2 to heat and maintain the inside of the furnace at a temperature required for heat treatment of non-ferrous metals and the like.

[0040] When raising the temperature inside the furnace, this ammonia combustion industrial furnace 1 burns ammonia fuel after the temperature inside the furnace has risen to 1000 °C, so that ammonia fuel with poor combustibility can be completely burned. Therefore, unburned ammonia is not generated. Also, since hydrocarbon fuel is not used after the temperature inside the furnace has risen to 1000 °C, or hydrocarbon fuel and ammonia fuel are used simultaneously, the usage amount (combustion amount) of hydrocarbon fuel can be suppressed. Therefore, the generation of greenhouse gases such as carbon dioxide can be suppressed.

[0041] When the temperature inside the industrial furnace 1 is decreased for reasons such as the completion of heat treatment of non-ferrous metals or the like, until the temperature inside the furnace drops to nearly 1000 °C, the combustion of ammonia fuel or co-combustion while using a hydrocarbon fuel and an ammonia fuel in combination is continued, and the temperature is decreased by reducing the combustion amount or the like. Then, when the temperature drops to nearly 1000 °C, based on the measurement result from the temperature sensor 7, a closing signal is sent from the control unit 8 to the ammonia fuel on-off valve 4, and an opening signal is sent to the hydrocarbon fuel on-off valve 6. By this closing signal, the ammonia fuel on-off valve 4 is closed, and by the opening signal, the hydrocarbon fuel on-off valve 6 is opened. Thereby, only the hydrocarbon fuel is burned by the burner 2 to heat the inside of the furnace, and the temperature inside the furnace is decreased by gradually reducing its usage amount (combustion amount).

[0042] When this ammonia combustion industrial furnace 1 decreases the temperature inside the furnace, the use of ammonia fuel is limited only until the temperature inside the furnace drops to nearly 1000 °C, so the ammonia fuel with poor combustibility can be completely burned. Therefore, unburned ammonia is not generated. Further, since the hydrocarbon fuel is used after the temperature inside the furnace drops to 1000 °C, its usage amount can be reduced. Therefore, the generation of greenhouse gases such as carbon dioxide can be suppressed.

[0043] Next, with reference to FIG. 2, the ammonia combustion industrial furnace 1 (using two burners) according to the second embodiment of the present invention will be described together with the ammonia combustion method. This ammonia combustion industrial furnace 1 is an industrial furnace that heats and uses non-ferrous metals or the like with a burner 2 that uses ammonia as fuel, similar to the first embodiment. Different from the first embodiment, the burner 2 is composed of a first burner 2a and a second burner 2b. Note that both the first burner 2a and the second burner 2b are provided on the furnace wall 1a that forms the furnace body of the industrial furnace 1.

[0044] The ammonia combustion industrial furnace 1 according to the second embodiment includes an ammonia fuel passage 3, an ammonia fuel on-off valve 4, a hydrocarbon fuel passage 5, a hydrocarbon fuel on-off valve 6, two combustion air passages 9 (a first combustion air passage 9a and a second combustion air passage 9b), two combustion air on-off valves 10 (a first combustion air on-off valve 10a and a second combustion air on-off valve 10b), a temperature sensor 7, and a control unit 8.

[0045] The ammonia fuel passage 3 supplies ammonia fuel from an ammonia fuel supply unit (not shown) to the first burner 2a. The ammonia fuel on-off valve 4 is provided in a part of the ammonia fuel passage 3 and opens and closes it. The hydrocarbon fuel passage 5 supplies hydrocarbon fuel from a hydrocarbon fuel supply unit (not shown) to the second burner 2b. The hydrocarbon fuel on-off valve 6 is provided in a part of the hydrocarbon fuel passage 5 and opens and closes it.

[0046] The first combustion air passage 9a supplies air (outside air) for burning ammonia fuel to the first burner 2a. The first combustion air on-off valve 10a is provided in a part of the first combustion air passage 9a and opens and closes it. The second combustion air passage 9b supplies air (outside air) for burning hydrocarbon fuel to the second burner 2b. The second combustion air on-off valve 10b is provided in a part of the second combustion air passage 9b and opens and closes it.

[0047] The temperature sensor 7 is provided inside the furnace and measures the temperature inside the furnace. The control unit 8 sends opening and closing signals to both the ammonia fuel on-off valve 4 and the hydrocarbon fuel on-off valve 6 according to the measured temperature of the temperature sensor 7. Also, opening and closing signals are sent to the first combustion air on-off valve 10a and the second combustion air on-off valve 10b to control their opening and closing and adjust the air volume.

[0048] The operation of the ammonia combustion industrial furnace 1 according to the second embodiment will be described below. First, when raising the temperature inside the industrial furnace 1, until the temperature rises to nearly 1000°C, the hydrocarbon fuel is burned by the second burner 2b. In this state, the temperature inside the furnace is measured by the temperature sensor 7, and based on the opening / closing signal from the control unit 8 according to the measurement result, the hydrocarbon fuel on-off valve 6 and the second combustion air on-off valve 10b are opened, and the ammonia fuel on-off valve 4 and the first combustion air on-off valve 10a are closed.

[0049] When the temperature inside the furnace rises to 1000°C due to the combustion of the hydrocarbon fuel, the ammonia fuel is burned by the first burner 2a. Even in this state, the temperature inside the furnace is measured by the temperature sensor 7, and based on the opening / closing signal from the control unit 8 according to the measurement result, the ammonia fuel on-off valve 4 and the first combustion air on-off valve 10a are opened, the hydrocarbon fuel on-off valve 6 and the second combustion air on-off valve 10b are closed, and it becomes exclusive combustion of ammonia fuel. Or, according to the opening / closing signal from the control unit 8, the ammonia fuel on-off valve 4 and the first combustion air on-off valve 10a are opened, the hydrocarbon fuel on-off valve 6 and the second combustion air on-off valve 10b are opened, and it becomes co-combustion of hydrocarbon fuel and ammonia fuel. By burning this ammonia fuel with the first burner 2a, or by burning the ammonia fuel with the first burner 2a and the hydrocarbon fuel with the second burner 2b simultaneously, the temperature inside the furnace is heated to 1000°C or higher and maintained.

[0050] Also in the second embodiment, similar to the first embodiment, when raising the temperature inside the furnace, since the ammonia fuel is used after the temperature inside the furnace rises to 1000°C, the ammonia fuel with poor combustibility can be completely burned. Therefore, the generation of unburned ammonia can be prevented. Also, since the hydrocarbon fuel is not used after the temperature inside the furnace rises to 1000°C, or since the hydrocarbon fuel and the ammonia fuel are used simultaneously, the usage amount (combustion amount) can be reduced, and therefore, the generation of greenhouse gases such as carbon dioxide can be suppressed.

[0051] When gradually lowering the temperature in the furnace for reasons such as finishing the heat treatment of non-ferrous metals, etc., first, gradually reduce the combustion amount of ammonia fuel or the combustion amounts of hydrocarbon fuel and ammonia fuel, and lower the temperature in the furnace to near 1000 °C. In this state, stop the combustion of ammonia fuel at the first burner 2a, and start the combustion of hydrocarbon fuel at the second burner 2b. This is achieved by sending a closing signal from the control unit 8 to the ammonia fuel on-off valve 4 and the first combustion air on-off valve 10a, and a opening signal to the hydrocarbon fuel on-off valve 6 and the second combustion air on-off valve 10b based on the temperature measurement result of the temperature sensor 7. Thereby, only the hydrocarbon fuel is combusted, and by gradually reducing the combustion amount thereof, the temperature in the furnace is gradually lowered.

[0052] Also in this embodiment, when lowering the temperature in the furnace, the use of ammonia fuel is limited until the temperature in the furnace drops to near 1000 °C. Therefore, the poorly combustible ammonia fuel can be completely combusted, and unburned ammonia is not generated. Further, since the hydrocarbon fuel is used only after the temperature in the furnace has dropped to 1000 °C, its usage amount (combustion amount) can be reduced. Therefore, the generation of greenhouse gases such as carbon dioxide can be suppressed.

[0053] Note that the ammonia combustion industrial furnace 1 according to the above first and second embodiments can use hydrogen fuel instead of hydrocarbon fuel. Since hydrogen fuel does not generate greenhouse gases such as carbon dioxide even when combusted, its use is preferable.

[0054] Also, the ammonia combustion industrial furnaces according to the above two embodiments both combust both ammonia fuel and hydrocarbon fuel with one burner, so the configuration is simpler compared to the above prior art in which each is combusted with a dedicated burner. Therefore, the manufacturing cost is reduced and maintenance is also easy.

[0055] In this embodiment, the switching from hydrocarbon fuel to ammonia fuel and vice versa, i.e., the switching from ammonia fuel to hydrocarbon fuel, was based on a furnace temperature of 1000°C. However, it can also be based on 800°C, or on a set temperature between 800°C and 1000°C. At this time, as the reference approaches 1000°C from 800°C, the amounts of unburned ammonia and nitrous oxide (N2O) decrease, so it is more preferable to use 1000°C as the reference.

[0056] Also, the burner used in the ammonia combustion industrial furnace of this embodiment may be of any type as long as it is generally used in industrial furnaces, including the first burner and the second burner. For example, it may be a radiant tube burner.

[0057] In this way, the ammonia combustion method and the ammonia combustion industrial furnace for burning ammonia fuel alone or burning ammonia fuel and hydrocarbon fuel together simultaneously when the temperature in the furnace reaches 1000°C or higher are not described at all in the above-mentioned patent documents.

Explanation of Reference Numerals

[0058] 1 Industrial furnace 1a Furnace wall 2 Burner 2a First burner 2b Second burner 3 Ammonia fuel passage 4 Ammonia fuel on-off valve 5 Hydrocarbon fuel passage 6 Hydrocarbon fuel on-off valve 7 Temperature sensor 8 Control unit 9 Combustion air passage 9a First combustion air passage 9b Second combustion air passage 10 Combustion air on-off valve 10a First combustion air on-off valve 10b Second combustion air on-off valve

Claims

1. A method for burning ammonia as fuel in an industrial furnace for heat treatment of metals and non-ferrous metals by heating with a burner, comprising the steps of: A method for burning ammonia in an industrial furnace, characterized in that, when increasing the temperature inside the industrial furnace, a hydrocarbon fuel is used alone until the temperature inside the furnace reaches nearly 1000°C, and when the temperature inside the furnace reaches 1000°C, an ammonia fuel is used alone or a combination of a hydrocarbon fuel and an ammonia fuel is used thereafter.

2. A method for burning ammonia as fuel in an industrial furnace for heat treatment of metals and non-ferrous metals by heating with a burner, comprising the steps of: A method for burning ammonia in an industrial furnace, characterized in that, when lowering the temperature inside the industrial furnace, ammonia fuel is used alone or a hydrocarbon fuel and an ammonia fuel are used in combination until the temperature inside the furnace drops to near 1000°C, and when the temperature inside the furnace drops to less than 1000°C, the hydrocarbon fuel is used alone thereafter.

3. A method for burning ammonia as fuel in an industrial furnace for heat treatment of metals and non-ferrous metals by heating with a burner, comprising the steps of: A method for burning ammonia in an industrial furnace, characterized in that, when increasing the temperature inside the industrial furnace, a hydrocarbon fuel is used alone until the temperature inside the furnace reaches nearly 800°C, and when the temperature inside the furnace reaches 800°C, an ammonia fuel is used alone or a combination of a hydrocarbon fuel and an ammonia fuel is used thereafter.

4. A method for burning ammonia as fuel in an industrial furnace for heat treatment of metals or non-ferrous metals by heating with a burner, comprising the steps of: A method for burning ammonia in an industrial furnace, characterized in that, when lowering the temperature inside the industrial furnace, ammonia fuel is used alone or a hydrocarbon fuel and an ammonia fuel are used in combination until the temperature inside the furnace drops to near 800°C, and when the temperature inside the furnace drops to less than 800°C, the hydrocarbon fuel is used alone thereafter.

5. A method for burning ammonia as fuel in an industrial furnace for heat treatment of metals or non-ferrous metals by heating with a burner, comprising the steps of: A method for burning ammonia in an industrial furnace, characterized in that, when increasing the temperature inside the industrial furnace, a hydrocarbon fuel is used alone until the temperature inside the furnace rises to near a set temperature of 800°C or more and 1000°C or less, and, once the temperature inside the furnace has risen to the set temperature, ammonia fuel is used alone or ammonia fuel is used in combination therewith.

6. A method for burning ammonia as fuel in an industrial furnace for heat treatment of metals or non-ferrous metals by heating with a burner, comprising the steps of: A method for burning ammonia in an industrial furnace, characterized in that, when lowering the temperature inside the industrial furnace, ammonia fuel is used alone or a hydrocarbon fuel and ammonia fuel are used in combination until the temperature inside the furnace falls near a set temperature of 800°C or more and 1000°C or less, and when the temperature inside the furnace falls below the set temperature, hydrocarbon fuel is used alone thereafter.

7. 7. The method for burning ammonia in an industrial furnace according to claim 1, wherein hydrogen fuel is used instead of the hydrocarbon fuel.

8. An industrial furnace for heat-treating metals and non-ferrous metals by using a burner that uses ammonia as fuel, an ammonia fuel passage for supplying the ammonia fuel to the burner; an ammonia fuel on-off valve that opens and closes the ammonia fuel passage; a hydrocarbon fuel passage for supplying a hydrocarbon fuel to the burner; a hydrocarbon fuel on-off valve that opens and closes the hydrocarbon fuel passage; A temperature sensor for measuring a temperature inside the furnace; a control unit that sends an opening / closing signal to the ammonia fuel on-off valve and the hydrocarbon fuel on-off valve based on the temperature measured by the temperature sensor; When increasing the temperature inside the industrial furnace, until the temperature inside the furnace rises to near 1000°C, the hydrocarbon fuel on-off valve is opened and the ammonia fuel on-off valve is closed in response to a signal from the control unit, and only the hydrocarbon fuel is burned by the burner to heat the inside of the furnace, and when the temperature inside the furnace rises to 1000°C, the hydrocarbon fuel on-off valve is closed and the ammonia fuel on-off valve is opened in response to a signal from the control unit, and only the ammonia fuel is burned by the burner, or the hydrocarbon fuel on-off valve is opened and the ammonia fuel on-off valve is opened in response to a signal from the control unit, and both the ammonia fuel and the hydrocarbon fuel are burned by the burner to heat the inside of the furnace, an ammonia combustion industrial furnace, characterized in that, when lowering a temperature inside the industrial furnace, until the temperature inside the furnace drops to near 1000°C, the ammonia fuel on-off valve is opened and the hydrocarbon fuel on-off valve is closed in response to a signal from the control unit, and only the ammonia fuel is burned by the burner, or the ammonia fuel on-off valve is opened and the hydrocarbon fuel on-off valve is also opened in response to a signal from the control unit, and the ammonia fuel and the hydrocarbon fuel are also burned by the burner to heat the inside of the furnace, and when the temperature inside the furnace drops to less than 1000°C, the ammonia fuel on-off valve is closed and the hydrocarbon fuel on-off valve is opened in response to a signal from the control unit, and only the hydrocarbon fuel is burned by the burner to heat the inside of the furnace.

9. An industrial furnace for heat-treating metals and non-ferrous metals by using a burner that uses ammonia as fuel, The burner includes a first burner and a second burner, an ammonia fuel passage for supplying the ammonia fuel to the first burner; an ammonia fuel on-off valve that opens and closes the ammonia fuel passage; a hydrocarbon fuel passage for supplying a hydrocarbon fuel to the second burner; a hydrocarbon fuel on-off valve that opens and closes the hydrocarbon fuel; A temperature sensor for measuring a temperature inside the furnace; a control unit that sends an opening / closing signal to the ammonia fuel on-off valve and the hydrocarbon fuel on-off valve based on the temperature measured by the temperature sensor; When increasing the temperature inside the industrial furnace, until the temperature inside the furnace rises to near 1000°C, the hydrocarbon fuel on-off valve is opened and the ammonia fuel on-off valve is closed in response to a signal from the control unit, and only the hydrocarbon fuel is burned by the second burner to heat the inside of the furnace, and when the temperature inside the furnace rises to 1000°C, the hydrocarbon fuel on-off valve is closed and the ammonia fuel on-off valve is opened in response to a signal from the control unit, and only the ammonia fuel is burned by the first burner, or the hydrocarbon fuel on-off valve is opened and the ammonia fuel on-off valve is opened in response to a signal from the control unit, and only the ammonia fuel is burned by the first burner to heat the inside of the furnace, an ammonia combustion industrial furnace, characterized in that, when lowering a temperature inside the industrial furnace, until the temperature inside the furnace drops to near 1000°C, the ammonia fuel on-off valve is opened and the hydrocarbon fuel on-off valve is closed in response to a signal from the control unit, and only the ammonia fuel is burned by the first burner, or, in response to a signal from the control unit, the ammonia fuel on-off valve is opened and the first burner is burned, and the hydrocarbon fuel on-off valve is also opened in response to a signal from the control unit, and the hydrocarbon fuel is also burned by the second burner to heat the inside of the furnace, and when the temperature inside the furnace drops to less than 1000°C, the ammonia fuel on-off valve is closed and the hydrocarbon fuel on-off valve is opened in response to a signal from the control unit, and only the hydrocarbon fuel is burned by the second burner to heat the inside of the furnace.

10. An industrial furnace for heat-treating metals and non-ferrous metals by using a burner that uses ammonia as fuel, an ammonia fuel passage for supplying the ammonia fuel to the burner; an ammonia fuel on-off valve that opens and closes the ammonia fuel passage; a hydrocarbon fuel passage for supplying a hydrocarbon fuel to the burner; a hydrocarbon fuel on-off valve that opens and closes the hydrocarbon fuel passage; A temperature sensor for measuring a temperature inside the furnace; a control unit that sends an opening / closing signal to the ammonia fuel on-off valve and the hydrocarbon fuel on-off valve based on the temperature measured by the temperature sensor; When increasing the temperature inside the industrial furnace, until the temperature inside the furnace rises to near a set temperature of 800° C. or more and 1000° C. or less, the hydrocarbon fuel on-off valve is opened and the ammonia fuel on-off valve is closed in response to a signal from the control unit, and only the hydrocarbon fuel is burned by the burner to heat the inside of the furnace, and when the temperature inside the furnace rises to the set temperature, the hydrocarbon fuel on-off valve is closed and the ammonia fuel on-off valve is opened in response to a signal from the control unit, and only the ammonia fuel is burned by the burner, or the hydrocarbon fuel on-off valve is opened and the ammonia fuel on-off valve is opened in response to a signal from the control unit, and both the ammonia fuel and the hydrocarbon fuel are burned by the burner to heat the inside of the furnace, wherein, when lowering a temperature inside the industrial furnace, the ammonia fuel on-off valve is opened and the hydrocarbon fuel on-off valve is closed in response to a signal from the control unit, and only the ammonia fuel is burned by the burner, until the temperature inside the furnace drops to near the set temperature, or the ammonia fuel on-off valve is opened and the hydrocarbon fuel on-off valve is also opened in response to a signal from the control unit, and the ammonia fuel and the hydrocarbon fuel are also burned by the burner to heat the inside of the furnace, and when the temperature inside the furnace drops to below the set temperature, the ammonia fuel on-off valve is closed and the hydrocarbon fuel on-off valve is opened in response to a signal from the control unit, and only the hydrocarbon fuel is burned by the burner to heat the inside of the furnace.

11. An industrial furnace for heat-treating metals and non-ferrous metals by using a burner that uses ammonia as fuel, The burner includes a first burner and a second burner, an ammonia fuel passage for supplying the ammonia fuel to the first burner; an ammonia fuel on-off valve that opens and closes the ammonia fuel passage; a hydrocarbon fuel passage for supplying a hydrocarbon fuel to the second burner; a hydrocarbon fuel on-off valve that opens and closes the hydrocarbon fuel; A temperature sensor for measuring a temperature inside the furnace; a control unit that sends an opening / closing signal to the ammonia fuel on-off valve and the hydrocarbon fuel on-off valve based on the temperature measured by the temperature sensor; When increasing the temperature inside the industrial furnace, until the temperature inside the furnace rises close to a set temperature of 800° C. or more and 1000° C. or less, the hydrocarbon fuel on-off valve is opened and the ammonia fuel on-off valve is closed in response to a signal from the control unit, and only the hydrocarbon fuel is burned by the second burner to heat the inside of the furnace, and when the temperature inside the furnace rises to the set temperature, the hydrocarbon fuel on-off valve is closed and the ammonia fuel on-off valve is opened in response to a signal from the control unit, and only the ammonia fuel is burned by the first burner, or the hydrocarbon fuel on-off valve is opened and the ammonia fuel on-off valve is opened in response to a signal from the control unit, and only the ammonia fuel is burned by the first burner to heat the inside of the furnace, an ammonia combustion industrial furnace, characterized in that, when lowering a temperature inside the industrial furnace, until the temperature inside the furnace drops to near the set temperature, the ammonia fuel on-off valve is opened and the hydrocarbon fuel on-off valve is closed in response to a signal from the control unit to combust only the ammonia fuel by the first burner, or the ammonia fuel on-off valve is opened and the first burner is combusted in response to a signal from the control unit, and the hydrocarbon fuel on-off valve is also opened in response to a signal from the control unit to combust the hydrocarbon fuel also by the second burner to heat the inside of the furnace, and when the temperature inside the furnace drops to below the set temperature, the ammonia fuel on-off valve is closed and the hydrocarbon fuel on-off valve is opened in response to a signal from the control unit to combust only the hydrocarbon fuel by the second burner to heat the inside of the furnace.

Images