Industrial furnace and fuel supply method for industrial furnace

Abstract

To provide an industrial furnace for efficiently burning ammonia by using a simple facility and a fuel supply method for the industrial furnace.SOLUTION: In an industrial furnace, a burner 10 provided on a furnace wall 3 is supplied with ammonia via first piping 11 with a first on-off valve 31, gas fuel via second piping 12 with a second on-off valve 32 and combustion air via air piping 13 with an air on-off valve 33, so as to burn the ammonia and the gas in a mixed manner. Third piping 15 with a third on-off valve 35 is branched from the second piping 12, and the third piping 15 is connected to a portion between the burner 10 and the first on-off valve 31 provided in the first piping 11. Before fire is extinguished in the burner 10, the first on-off valve 31 is turned off and the second on-off valve 32 and the third on-off valve 35 are turned on to replace the ammonia between the burner 10 and the first on-off valve 31 in the first piping 11 with the gas fuel so as to discharge the ammonia into the furnace.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an industrial furnace for co-firing ammonia and gas, and a method for supplying fuel to the industrial furnace. [Background technology]

[0002] In recent years, ammonia has been attracting attention as a new fuel from the perspective of curbing global warming, as it does not produce carbon dioxide when burned. However, when ammonia is mixed with fossil fuels or burned alone, nitrogen oxides (NO X It is known that the amount of emissions of ) increases (see, for example, Patent Document 1).

[0003] The combustion device described in Patent Document 1 solves the problem of increased nitrogen oxides when coal is burned with ammonia added.

[0004] Generally, as shown in Fig. 4, ammonia (NH), gas fuel, and combustion air are supplied to a burner 10 provided on a side wall 3 of a furnace body 2 of an industrial furnace 1. Ammonia (NH) is sent from an ammonia supply device 21 to the burner 10 via a first pipe 11, which is provided with a first on-off valve (solenoid valve) 31 along the way. The gas fuel, consisting of an existing gas (conventional fuel) such as city gas or propane gas, is sent from a gas supply device 22 to the burner 10 via a second pipe 12, which is provided with a second on-off valve (solenoid valve) 32 along the way. As for combustion air, outside air is sent by a blower 23 to the burner 10 via an air pipe 13, which is provided with an air on-off valve (solenoid valve) 33 along the way.

[0005] In this way, when the combustion of ammonia is stopped and the fire is extinguished in an industrial furnace that handles ammonia, ammonia remains in the piping (here, the first piping 11). In particular, since ammonia is toxic, if it leaks, there is a risk of adverse effects on the human body.

[0006] Therefore, as shown in FIG. 5, a method is known in which the ammonia in the first pipe 11 is replaced with nitrogen. In this case, the end of the nitrogen piping 14, which supplies nitrogen (N2) from the nitrogen supply device 24, is connected between the burner 10 and the first on-off valve 31 of the first piping 11, and when the combustion of ammonia is stopped and the fire is extinguished, the first on-off valve 31 is turned off (closed) and the nitrogen on-off valve 34 provided on the nitrogen piping 14 is turned on (opened), and nitrogen (N2) is filled from the first on-off valve 31 of the first piping 11 to the burner 10 side, thereby replacing the ammonia with nitrogen. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 7020759 Summary of the Invention [Problem to be solved by the invention]

[0008] However, in the method of replacing ammonia with nitrogen, it is necessary to newly provide nitrogen together with the nitrogen supply device 24 . Furthermore, when the combustion of ammonia is restarted, it is necessary to first discharge the nitrogen filled in the first pipe 11, which poses the problem that it takes time to ignite the ammonia.

[0009] Therefore, an object of the present invention is to provide an industrial furnace that can efficiently burn ammonia using simple equipment and a fuel supply method for the industrial furnace. [Means for solving the problem]

[0010] In order to achieve the above object, the present invention provides an industrial furnace (1) for co-firing ammonia and gas by supplying ammonia through a first pipe (11) equipped with a first on-off valve (31), gas fuel through a second pipe (12) equipped with a second on-off valve (32), and combustion air through an air pipe (13) equipped with an air on-off valve (33) to a burner (10) provided on a furnace wall (3), A third pipe (15) with a third on-off valve (35) is branched from the second pipe (12), and the third pipe (15) is connected between the burner (10) and a first on-off valve (31) provided on the first pipe (11).

[0011] The present invention also provides a fuel supply method for an industrial furnace (1) for co-firing ammonia and gas by supplying ammonia through a first pipe (11) equipped with a first on-off valve (31), gas fuel through a second pipe (12) equipped with a second on-off valve (32), and combustion air through an air pipe (13) equipped with an air on-off valve (33) to a burner (10) provided on a furnace wall (3), the method comprising: a third pipe (15) with a third on-off valve (35) branched from the second pipe (12), and the third pipe (15) connected between the burner (10) and a first on-off valve (31) provided on the first pipe (11); Before the burner (10) is extinguished, the first on-off valve (31) is turned off, and the second on-off valve (32) and the third on-off valve (35) are turned on, so that ammonia in the first pipe (11) between the burner (10) and the first on-off valve (31) is replaced with gas fuel and the ammonia is discharged into the furnace. Note that turning on the second on-off valve (32) here includes not only turning on from off but also maintaining the on state. Normally, the second on-off valve (32) is in the on state during combustion before extinguishing.

[0012] Furthermore, the present invention is characterized in that, after the ammonia is replaced with the gas fuel, the second on-off valve (32) and the third on-off valve (35) are turned off to extinguish the fire.

[0013] Furthermore, the present invention is characterized in that, before ignition of the burner (10), the first on-off valve (31) is turned off, the air on-off valve (33) is turned on, and the second on-off valve (32) and the third on-off valve (35) are turned on, so that only gas fuel flows through the first pipe (11) between the burner (10) and the first on-off valve (31), and after ignition, the first on-off valve (31) is turned on and the third on-off valve (35) is turned off to supply ammonia into the furnace. Here, turning off the first on-off valve (31) includes not only turning off the on-off valve but also maintaining the off state. The first on-off valve (31) is turned off during fire extinguishing, and is therefore normally in the off state.

[0014] The present invention also provides a fuel supply method for an industrial furnace (1) for co-firing ammonia and gas by supplying ammonia through a first pipe (11) equipped with a first on-off valve (31), gas fuel through a second pipe (12) equipped with a second on-off valve (32), and combustion air through an air pipe (13) equipped with an air on-off valve (33) to a burner (10) provided on a furnace wall (3), the method comprising: a third pipe (15) with a third on-off valve (35) branched from the second pipe (12), and the third pipe (15) connected between the burner (10) and a first on-off valve (31) provided on the first pipe (11); Before ignition of the burner (10), the first on-off valve (31) is turned off, the air on-off valve (33) is turned on, and the second on-off valve (32) and the third on-off valve (35) are turned on, so that only gas fuel flows through the first pipe (11) between the burner (10) and the first on-off valve (31), and after ignition, the first on-off valve (31) is turned on and the third on-off valve (35) is turned off to supply ammonia into the furnace. Here, turning off the first on-off valve (31) includes not only turning off the on-off valve but also maintaining the off state. The first on-off valve (31) is turned off during fire extinguishing, and is therefore normally in the off state.

[0015] The symbols in parentheses above indicate corresponding elements or items described in the drawings and in the detailed description of the invention to be described later. [Effects of the Invention]

[0016] The industrial furnace of the present invention is an industrial furnace in which ammonia and gas are mixed and burned by supplying ammonia to a burner via a first pipe equipped with a first on-off valve, gas fuel via a second pipe equipped with a second on-off valve, and combustion air via an air pipe equipped with an air on-off valve, and a third pipe equipped with a third on-off valve branches off from the second pipe and is connected between the burner and the first on-off valve provided on the first pipe.Therefore, by turning off (closing) the first on-off valve and turning on (opening) the third on-off valve, ammonia between the burner and the first on-off valve in the first pipe can be easily replaced with gas fuel. That is, when ammonia is replaced with nitrogen as in the conventional method, it is necessary to install a new nitrogen supply device and a new pipe for nitrogen. However, in the present invention, it is only necessary to modify the existing gas fuel second pipe so that a third pipe branched off from the second pipe is connected to the first pipe, thereby reducing equipment costs. Furthermore, by replacing ammonia with existing gas fuel, leakage of toxic ammonia is prevented, providing peace of mind. Furthermore, the gas fuel that replaces ammonia is less toxic and less corrosive than ammonia, and has been used for a long time. Therefore, even if it leaks from the piping, it will have less impact on the human body and can be handled more safely.

[0017] Furthermore, according to the fuel supply method for an industrial furnace of the present invention, before the burner is extinguished, the first on-off valve is turned off and the second and third on-off valves are turned on, so that the ammonia between the burner and the first on-off valve in the first piping is replaced with gas fuel and the ammonia is discharged into the furnace. Therefore, after the fire is extinguished, i.e., when the industrial furnace is not in operation, ammonia, which is toxic to humans, does not remain in the first piping or the furnace, making it safe.

[0018] Furthermore, according to the fuel supply method for an industrial furnace of the present invention, before the burner is ignited, the first on-off valve is turned off, the air on-off valve is turned on, and the second on-off valve and the third on-off valve are turned on, so that only gas fuel is present between the burner and the first on-off valve in the first piping. Therefore, ammonia, which is difficult to burn, is not sent to the burner before ignition, and there is no need to worry about toxic ammonia leaking. After ignition, the first on-off valve is turned on and the third on-off valve is turned off to supply ammonia into the furnace. As the ammonia is sent to the burner side, the gas fuel filled in the first piping is gradually pushed out toward the burner, and the inside of the first piping is replaced with ammonia, making it possible to easily control combustion. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a partial cross-sectional view showing a main part and a fuel supply system of an industrial furnace according to an embodiment of the present invention. [Figure 2] 2 is a flowchart showing a fuel supply method during a fire extinguishing operation in the industrial furnace shown in FIG. [Figure 3] 2 is a flowchart showing a fuel supply method during an ignition operation in the industrial furnace shown in FIG. [Figure 4] FIG. 10 is a partial cross-sectional view showing the main parts and fuel supply system of a conventional industrial furnace. [Figure 5] FIG. 10 is a partial cross-sectional view showing a main part of an industrial furnace according to a conventional example and another fuel supply system. DETAILED DESCRIPTION OF THE INVENTION

[0020] An industrial furnace 1 according to an embodiment of the present invention will be described with reference to Fig. 1. Note that the same components as those in the conventional example are given the same reference numerals.

[0021] As shown in FIG. 1, an industrial furnace 1 according to this embodiment (here, a metal heating furnace will be described as an example) has a generally rectangular cross section, and is a furnace 1 in which burners 10 are provided on furnace walls 3 that constitute a furnace body 2, and ammonia (NH3) is mixed and burned with gas fuel by flames from the burners 10.

[0022] Ammonia (NH3) is sent from an ammonia supply device 21 to the burner 10 via a first pipe 11, which is provided with a first on-off valve (solenoid valve) 31. The gas fuel is made up of existing gases such as city gas or propane gas, and is sent from a gas supply device 22 to the burner 10 via a second pipe 12, which is provided with a second on-off valve (solenoid valve) 32. As combustion air, outside air is sent by a blower 23 to the burner 10 via an air pipe 13, which is provided with an air on-off valve (solenoid valve) 33.

[0023] A third pipe 15 equipped with a third on-off valve 35 is branched from the second pipe 12 that sends fuel gas, and the third pipe 15 is connected between the burner 10 and the first on-off valve 31 that is provided on the first pipe 11 that sends ammonia. The third on-off valve 35 is a solenoid valve, and a check valve 25 is provided between the third on-off valve 35 and the first on-off valve to prevent ammonia or gas fuel from flowing from the first pipe 11 side to the second pipe 12 side. Here, the third pipe 15 branches off between the second on-off valve 32 provided on the second pipe 12 and the gas supply device 22, but it may also branch off between the second on-off valve 32 and the burner 10. The first pipe 11, the second pipe 12 and the air pipe 13 are provided with throttle valves capable of changing the flow rate in addition to the on-off valves 31, 32 and 33, but are not shown in the drawings.

[0024] The opening and closing of each of the on-off valves (solenoid valves) 31, 32, 33, and 35 is controlled by a control device 500 that controls the entire electrical system of the industrial furnace 1. The control device 500 has a CPU which is a control unit, a memory unit consisting of a ROM in which a control program is stored and a RAM for writing and retrieving data, and is connected to a timer T. Here, an external timer T is shown, but an internal timer may also be used.

[0025] During combustion, the control device 500 keeps the first on-off valve 31, the second on-off valve 32, and the air on-off valve 33 in an on state (open state) and the third on-off valve 35 in an off state (closed state), but during extinguishing, it executes the operation shown in Figure 2.

[0026] More specifically, before extinguishing the burner 10, the CPU of the control device 500 first turns off the first on-off valve 31 (i.e., closes it) (step S101: hereinafter, the word "step" will be omitted). This prevents ammonia from flowing into the burner 10 from the ammonia supply device 21.

[0027] Next, the CPU of the control device 500 sets a timer T for a certain time and then turns it on (S102), and turns on the second on-off valve 32 and the third on-off valve 35 (i.e., opens them) (S103). Note that turning on the second on-off valve 32 here includes not only turning it from off to on, but also maintaining it in the on state. During combustion before extinguishing, the second on-off valve 32 is in the on state. As a result, the ammonia remaining between the burner 10 and the first on-off valve 31 in the first pipe 11 is discharged into the furnace, and the ammonia is completely replaced with gas fuel.

[0028] Thereafter, when the timer T is up (S104), the second on-off valve 32 and the third on-off valve 35 are turned off (i.e., closed) (S105), and the inflow of gas fuel to the burner 10 side is cut off to extinguish the flame (S106).

[0029] This provides peace of mind since ammonia is replaced with gas fuel, preventing the leakage of toxic ammonia. Furthermore, the gas fuel that replaces ammonia is less toxic and less corrosive than ammonia, and has been used for a long time. Therefore, even if it leaks from the piping, it will have less impact on the human body and can be handled more safely.

[0030] Furthermore, the control device 500 executes the operation shown in FIG. 3 at the time of ignition.

[0031] More specifically, before igniting the burner 10, the CPU of the control device 500 first turns off the first on-off valve 31 (i.e., closes it) (step S201: hereinafter, the word "step" will be omitted). Note that turning off the first on-off valve 31 here includes not only turning it off from on to off, but also maintaining the off state. The first on-off valve 31 is turned off during extinguishing, and is therefore normally in the off state. Next, after setting the timer T to a certain time, it is turned on (S202), and the air on-off valve 33 is turned on (that is, opened) (S203). As a result, combustion air flows to the burner 10.

[0032] Next, when the timer T expires (S204), the CPU of the control device 500 turns on the second on-off valve 32 and the third on-off valve 35 (i.e., opens them) (S205, S206). As a result, gas fuel is sent to the burner 10, and the first pipe 11 on the burner 10 side from the first on-off valve 31, the second pipe 12, and the third pipe 15 are filled with gas fuel.

[0033] Then, the CPU of the control device 500 commands ignition (spark) without delay (S207), and when ignition is completed (S208), it turns on the first on-off valve 31 (i.e., opens it) and turns off the third on-off valve 35 (i.e., closes it) to supply ammonia into the furnace (S209, S210).

[0034] Thereafter, the CPU of the control device 500 performs temperature control (S211) and starts combustion in the industrial furnace 1.

[0035] According to this, ammonia is not sent to the burner 10 before ignition, but is sent to the burner 10 side after the gas fuel has been sent and reliably ignited. As ammonia is sent to the burner 10 side in this way, the gas fuel filled in the first pipe 11 is gradually pushed out toward the burner 10 side and the inside of the first pipe 11 is replaced with ammonia, so that combustion can be easily controlled.

[0036] In this embodiment, an example has been described in which the industrial furnace 1 is applied to a metal heating furnace, but it can be widely used in combustion-type thermal equipment such as heat treatment furnaces, forging furnaces, melting furnaces, and ladle preheaters. [Explanation of symbols]

[0037] 1. Industrial furnace 2 Furnace body 3 side wall 10 Burner 11 First piping 12 Second piping 13 Air piping 14 Nitrogen piping 15 Third piping 21 Ammonia supply device 22 Gas supply equipment 23 Blois 24 Nitrogen supply device 25 Check valve 31 First shut-off valve 32 Second shut-off valve 33 Air on-off valve 34 Nitrogen on-off valve 35 Third shut-off valve 500 control device T-Timer

Claims

1. An industrial furnace in which ammonia and gas are mixed and burned by supplying ammonia through a first pipe having a first on-off valve, gas fuel through a second pipe having a second on-off valve, and combustion air through an air pipe having an air on-off valve to a burner provided on a furnace wall, an industrial furnace, characterized in that a third pipe equipped with a third on-off valve is branched from the second pipe, and the third pipe is connected between the burner and the first on-off valve provided on the first pipe.

2. A fuel supply method for an industrial furnace for co-firing ammonia and gas by supplying ammonia through a first pipe having a first on-off valve, gas fuel through a second pipe having a second on-off valve, and combustion air through an air pipe having an air on-off valve to a burner provided on a furnace wall, the method comprising: a third pipe having a third on-off valve branched from the second pipe, and the third pipe connected between the burner and the first on-off valve provided on the first pipe; ammonia in the first piping between the burner and the first on-off valve is replaced with gas fuel and the ammonia is discharged into the furnace.

3. 3. The fuel supply method for an industrial furnace according to claim 2, wherein after the ammonia is replaced with the gas fuel, the second and third on-off valves are turned off to extinguish the fire.

4. 4. The fuel supply method for an industrial furnace according to claim 2, wherein before ignition of the burner, the first on-off valve is turned off, the air on-off valve is turned on, and the second and third on-off valves are turned on to supply only gas fuel to the first piping between the burner and the first on-off valve, and after ignition, the first on-off valve is turned on and the third on-off valve is turned off to supply ammonia into the furnace.

5. A fuel supply method for an industrial furnace for co-firing ammonia and gas by supplying ammonia through a first pipe having a first on-off valve, gas fuel through a second pipe having a second on-off valve, and combustion air through an air pipe having an air on-off valve to a burner provided on a furnace wall, the method comprising: a third pipe having a third on-off valve branched from the second pipe, and the third pipe connected between the burner and the first on-off valve provided on the first pipe; ammonia is supplied into the furnace by turning on the first on-off valve and turning on the air on-off valve before ignition of the burner, and by turning on the second on-off valve and the third on-off valve, so that only gas fuel flows through the first piping between the burner and the first on-off valve, and by turning on the first on-off valve and turning off the third on-off valve after ignition.

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