Hydrogen combustion furnace and method for operating the same

Abstract

To provide a hydrogen combustion furnace capable of reducing NOx emissions.SOLUTION: A selected hydrogen combustion furnace 1 includes: a combustion furnace body 2 having a burner 3; a first passage L1 for supplying hydrogen to the burner 3; a second passage L2 for supplying combustion supporting gas containing oxygen to the burner 3; a third passage L3 for deriving exhaust gas from the combustion furnace body 2; a first control device 7 that controls a supply amount of hydrogen; a second control device 8 that controls a supply amount of combustion supporting gas; a gas analysis device 5 that analyzes constituents in exhaust gas; and a control device 6. The control device 6 controls the first control device 7 and the second control device 8 on the basis of an analysis value obtained from the gas analysis device 5 so as to cause incomplete combustion of the hydrogen in the combustion furnace body 2.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a hydrogen-fueled furnace and a method for operating a hydrogen-fueled furnace. [Background technology]

[0002] Toward the realization of the demand for carbon neutrality, there is growing interest in the development of technologies to reduce CO2 gas emissions. Industrial furnaces used in the manufacturing process of metals, glass, etc. emit large amounts of CO2 gas, and reducing this amount is recognized as an important issue.

[0003] Oxyfuel combustion has long been known as an effective means of reducing CO2 gas emissions and saving energy. Oxyfuel combustion is a combustion method that uses oxygen or oxygen-enriched air, which is air enriched with oxygen, as the oxidant, and is widely used in industrial furnaces. Oxyfuel combustion reduces the amount of nitrogen in the oxidant that does not contribute to combustion, resulting in benefits such as an increase in flame temperature and reduced exhaust gas heat loss, and as a result, improved thermal efficiency makes it possible to reduce fuel consumption. In other words, the reduction in the amount of hydrocarbon fuel used significantly contributes to reducing CO2 gas emissions.

[0004] In addition to conventional energy-saving technologies, conversion of hydrocarbon fuels to hydrogen energy is expected. Patent Document 1 discloses a technology that uses a combustion burner (hydrogen burner) that uses hydrogen gas as fuel in an industrial combustion furnace. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2020-094740 Summary of the Invention [Problem to be solved by the invention]

[0006] In furnace combustion using a combustion burner and a combustion furnace, the input energy is divided into two types: heat that is effectively utilized within the furnace and heat that is lost by being discharged to the outside as exhaust gas. For example, when the oxygen ratio is 1.05 and the exhaust gas temperature is 1300°C, it is known that the higher the oxygen concentration in the oxidizer, the smaller the proportion of exhaust gas heat loss (i.e., the higher the proportion of heat that is effectively utilized within the furnace, meaning higher heating efficiency) in both cases where a hydrocarbon fuel (e.g., methane) is used as the fuel and where hydrogen is used. The higher the heating efficiency, the smaller the amount of fuel required to heat and maintain the furnace at a given temperature. Therefore, applying oxyfuel combustion to hydrogen burners that use hydrogen as fuel can be expected to reduce fuel costs.

[0007] However, it is generally believed that hydrogen combustion increases NOx emissions, primarily thermal NOx, due to its higher flame temperature compared to hydrocarbon fuels. Oxygen combustion also increases NOx emissions, particularly in oxygen-rich environments, due to its higher flame temperature. Therefore, there are concerns that combining hydrogen combustion with oxygen combustion will further increase NOx emissions.

[0008] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a hydrogen combustion furnace that is capable of reducing NOx emissions, and a method for operating a hydrogen combustion furnace. [Means for solving the problem]

[0009] In order to solve the above problems, the present invention has the following configuration. [1] A combustion furnace body having a burner; a first path for supplying hydrogen to the burner; a second passage for supplying a combustion-supporting gas containing oxygen to the burner; a third passage for discharging exhaust gas from the combustion furnace body; a first control device located in the first path and adjusting the amount of hydrogen supplied; a second control device located in the second path and configured to adjust the supply amount of the combustion supporting gas; a gas analyzer located in the third path and analyzing components in the exhaust gas; a control device that transmits and receives electrical signals between the first control device, the second control device, and the gas analyzer, A hydrogen combustion furnace, wherein the control device controls the first control device and the second control device based on the analysis value obtained from the gas analyzer so that the hydrogen is incompletely combusted in the combustion furnace body. [2] The hydrogen combustion furnace according to [1], further comprising a moisture removal device located in the third path and removing moisture from the exhaust gas. [3] The hydrogen combustion furnace according to [1] or [2], wherein the moisture removal device is located on the primary side of the gas analyzer. [4] The hydrogen combustion furnace according to any one of [1] to [3], further comprising a combustion device connected to the third path and using the exhaust gas as at least a part of the fuel. [5] The hydrogen combustion furnace according to any one of [1] to [4], wherein the combustion device is a heat exchanger provided across at least one or both of the first path and the second path. [6] A hydrogen combustion furnace according to any one of [1] to [5], wherein the combustion furnace body is a heating furnace that heats an object to be heated housed in an inner space. [7] A method for operating a hydrogen combustion furnace having a combustion furnace body with a burner that burns hydrogen and a combustion-supporting gas containing oxygen, comprising: A method for operating a hydrogen combustion furnace, comprising incompletely combusting the hydrogen in the combustion furnace body. [8] The method for operating a hydrogen combustion furnace according to [7], wherein in the combustion furnace body, incomplete combustion is carried out at an oxygen ratio of 0.98 or less. [9] The method for operating a hydrogen combustion furnace according to [7] or [8], wherein the combustion-supporting gas has an oxygen concentration of 90% by volume or more. [Effects of the Invention]

[0010] According to the hydrogen combustion furnace and the method for operating the hydrogen combustion furnace of the present invention, it is possible to reduce NOx emissions. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a system diagram showing an example of the configuration of a hydrogen combustion furnace applicable to this embodiment. [Figure 2] FIG. 10 is a system diagram showing another example of the configuration of a hydrogen combustion furnace applicable to this embodiment. [Figure 3] FIG. 1 is a diagram showing the results of a verification test of the present invention. [Figure 4] FIG. 1 is a diagram showing the results of a verification test of the present invention. [Figure 5] FIG. 1 is a diagram showing the results of a verification test of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0012] A hydrogen combustion furnace and an operating method of the hydrogen combustion furnace according to an embodiment of the present invention will be described in detail below with reference to the drawings. Note that the drawings used in the following description may show characteristic parts enlarged for the sake of clarity, and the dimensional proportions of the components may not necessarily be the same as those in reality.

[0013] The meanings and definitions of terms used in this specification are as follows. "Heating efficiency" refers to the value calculated by calculating the amount of heat carried away by the exhaust gas outside the furnace (exhaust gas heat loss) and assuming that the value obtained by subtracting the exhaust gas heat loss from the input energy is used to heat the furnace. "Oxygen ratio" refers to the ratio of the amount of oxygen contained in the combustion-supporting gas to the amount of oxygen required for complete combustion of the fuel. A numerical range expressed by "to" means that the numerical values ​​before and after "to" are the lower and upper limits of the numerical range.

[0014] <Hydrogen combustion furnace> First, the configuration of a hydrogen combustion furnace according to one embodiment of the present invention will be described. Figure 1 is a system diagram showing the configuration of a hydrogen combustion furnace according to this embodiment. Note that the solid arrows in Figure 1 indicate the direction of gas flow, and the dotted arrows indicate the direction of electrical signal transmission. As shown in FIG. 1, the hydrogen combustion furnace 1 of this embodiment is roughly configured to include a combustion furnace body 2, a burner 3, a moisture removal device 4, a gas analyzer 5, a control device 6, a flow control valve (first control device) 7, a flow control valve (second control device) 8, a combustor (combustion device) 9, and paths L1 to L6.

[0015] In the hydrogen combustion furnace 1 of this embodiment, hydrogen as fuel and oxygen contained in a combustion-supporting gas are supplied to a burner 3, and when they are combusted (in-furnace combustion) within the combustion furnace body 2, the hydrogen is burned at a low oxygen ratio (i.e., incomplete combustion), thereby reducing NOx emissions.

[0016] The combustion furnace body 2 is not particularly limited as long as it has an internal space and can burn the flame of the burner 3 inside the furnace. A heating furnace that heats an object to be heated (not shown) housed in the internal space can be used as the combustion furnace body 2. As a specific configuration, a conventionally known configuration (for example, a configuration described in patent documents such as JP 2020-148426 A and JP 2021-042102 A) can be applied.

[0017] When the hydrogen combustion furnace 1 of this embodiment is used as a heating furnace, examples of the object to be heated include steel, molten metal, and glass. Because the hydrogen combustion furnace 1 of this embodiment uses hydrogen gas as fuel, the exhaust gas produced during incomplete combustion is primarily composed of H, H2O, and N2, and does not emit carbon monoxide (CO), carbon dioxide (CO2), or soot, which are generated when hydrocarbon fuels are used. This is therefore preferable because there is no risk of adversely affecting the quality of the object to be heated.

[0018] The burner 3 is connected to the combustion furnace body 2 so that the flame nozzle communicates with the space inside the combustion furnace body 2. The burner 3 is not particularly limited as long as it burns hydrogen, which is the fuel, and oxygen contained in the combustion-supporting gas within the combustion furnace body 2 (in-furnace combustion). As a specific configuration, a conventionally known configuration (for example, a configuration described in patent documents such as JP-A-09-243028, JP-A-2013-079753, and JP-A-2021-124212) can be applied.

[0019] The path (first path) L1 is located between a hydrogen gas supply source (not shown) and the burner 3. The path L1 is a gas supply line that supplies hydrogen gas (H2) as fuel from the hydrogen gas supply source to the burner 3. A flow control valve (first control device) 7 is provided on the path L1.

[0020] The path (second path) L2 is located between a combustion-supporting gas supply source (not shown) and the burner 3. The path L2 is a gas supply line that supplies combustion-supporting gas from the combustion-supporting gas supply source to the burner 3. A flow control valve (second control device) 8 is provided on the path L2.

[0021] The flow control valves 7 and 8 are control devices that adjust the supply amount of gas flowing through the gas supply line either manually or in response to a control signal from the control device 6. Examples of the flow control valves 7 and 8 include a control valve, a mass flow controller, and a manual needle valve.

[0022] The combustion-supporting gas is a gas (oxidizing agent) containing oxygen, and oxygen gas (O2), oxygen-enriched air in which air is enriched with oxygen, or air can be used. The oxygen concentration in the combustion-supporting gas (oxidizing agent) is preferably 21% by volume or more, more preferably 40% by volume or more, and even more preferably 90% by volume or more. The higher the oxygen concentration in the combustion-supporting gas, the lower the nitrogen concentration in the combustion-supporting gas, which reduces NOx emissions when incomplete combustion occurs in the hydrogen combustion furnace 1. Furthermore, when the oxygen concentration in the combustion-supporting gas is 90% by volume or more, the hydrogen concentration in the exhaust gas increases, allowing the unreacted hydrogen gas contained in the exhaust gas to be effectively used as fuel.

[0023] The path (third path) L3 is located between the combustion furnace body 2 and the combustor 9. The path L3 is a gas supply line that supplies hydrogen gas in the exhaust gas discharged from the combustion furnace body 2 to the combustor 9 as part of the fuel. A moisture remover 4 and a gas analyzer 5 are provided on the path L3 in this order from the primary side.

[0024] The moisture removal device 4 is located on the upstream side of the gas analyzer 5 in the path L3. The moisture removal device 4 removes moisture (H2O) from the exhaust gas flowing through the path L3. The moisture removal device 4 is also connected to a path L4, which discharges the moisture removed from the exhaust gas to the outside of the system. The moisture removal device 4 is not particularly limited as long as it can remove moisture from the mixed gas. Examples of the moisture removal device 4 include a mist separator, a water wash bubbler, and a chiller.

[0025] The gas analyzer 5 is located on the downstream side of the moisture remover 4 on path L3. The gas analyzer 5 is a device having an analyzer that analyzes components in the exhaust gas that is led out from the combustion furnace main body 2 on path L3 and from which moisture has been removed by the moisture remover 4. The gas analyzer 5 has one or more analyzers that can confirm that incomplete combustion has occurred in the combustion furnace main body 2. That is, the gas analyzer 5 has at least one of a hydrogen analyzer that confirms whether or not hydrogen is contained in the exhaust gas and an oxygen analyzer that confirms whether or not oxygen is contained in the exhaust gas. The gas analyzer 5 may also have one or more analyzers that can detect nitrogen, NOx, and moisture, among the components in the exhaust gas that is led out on path L3.

[0026] The combustor (combustion device) 9 is a combustion device that uses unreacted hydrogen gas contained in the exhaust gas discharged from the combustion furnace main body 2 as at least a part of the fuel. The combustor 9 is not particularly limited as long as it can use the hydrogen gas contained in the exhaust gas as fuel. Examples of the combustor 9 include a boiler and other combustion furnaces. Furthermore, it is more preferable that the combustor 9 does not increase the NOx contained in the exhaust gas discharged from the combustion furnace main body 2.

[0027] Paths L3, L5, and L6 are connected to the combustor 9. Path L5 is a gas supply line that supplies fuel and combustion-supporting gas to the combustor 9. Path L6 is a gas discharge line that discharges exhaust gas from the combustor 9 to the outside of the system.

[0028] The control device 6 transmits and receives electrical signals via wire or wirelessly between the flow control valve (first control device) 7, the flow control valve (second control device) 8, and the gas analyzer 5. The control device 6 has a function of controlling the flow control valve 7 and the flow control valve 8 based on the gas analysis values ​​obtained from the gas analyzer 5 so that hydrogen is incompletely combusted in the combustion furnace main body 2.

[0029] The control device 6 is not particularly limited as long as it has the above-mentioned functions. The control device 6 may be configured to include a central processing unit (CPU), a memory, and a hard disk drive. The control device 6 may be provided independently (separately) from the flow control valve 7, the flow control valve 8, and the gas analyzer 5, or may be provided as an attachment to any of the flow control valve 7, the flow control valve 8, and the gas analyzer 5.

[0030] <How to operate a hydrogen combustion furnace> Next, a method of operating a hydrogen combustion furnace according to one embodiment of the present invention will be described. The method for operating a hydrogen combustion furnace according to this embodiment is a method for operating a hydrogen combustion furnace 1 including a combustion furnace body 2 having a burner 3 for burning hydrogen and a combustion-supporting gas containing oxygen. Hereinafter, a method of operating a hydrogen combustion furnace according to one embodiment of the present invention will be specifically described, taking as an example a case where oxygen-enriched air is used as the combustion-supporting gas in the above-described hydrogen combustion furnace 1.

[0031] 1, hydrogen gas (H2) is supplied from a path L1 to a burner 3, and oxygen-enriched air (N2, O2) as a combustion-supporting gas is supplied from a path L2 to a burner 3, and they are combusted in the combustion furnace body 2. In this embodiment, hydrogen is incompletely combusted in the combustion furnace body 2. A mixed gas containing unreacted hydrogen gas (H2), nitrogen gas (N2), water (H2O), and NOx is discharged as exhaust gas from the combustion furnace body 2 to a path L3.

[0032] Next, water is removed from the exhaust gas led to the path L3 in the moisture removal device 4. Here, a mixed gas containing hydrogen gas (H2), nitrogen gas (N2), and NOx flows through the path L3 on the secondary side of the moisture removal device 4.

[0033] Next, the gas components in the mixed gas flowing through path L3 are analyzed by the gas analyzer 5. Specifically, the gas analyzer 5 confirms that hydrogen has been incompletely combusted in the combustion furnace body 2, that is, that hydrogen gas is contained in the mixed gas, and that oxygen gas is not contained in the mixed gas.

[0034] The analysis results from the gas analyzer 5 are transmitted to the control device 6 via an electric signal. If the mixed gas does not contain hydrogen gas, the control device 6 transmits a control signal to the flow control valve (first control device) 7 to increase the opening. This increases the amount of hydrogen gas supplied to the burner 3 via the path L1.

[0035] On the other hand, when oxygen gas is contained in the mixed gas, the control device 6 sends a control signal to the flow control valve (second control device) 8 to reduce the opening degree, thereby reducing the combustion supporting gas supplied to the burner 3 via the path L2.

[0036] In the method for operating a hydrogen combustion furnace according to this embodiment, the control device 6 controls the oxygen ratio in the combustion furnace body 2 to be less than 1. By setting the upper limit of the oxygen ratio to less than 1, an incomplete combustion state is achieved, thereby suppressing the amount of NOx emissions in the exhaust gas. The upper limit of the oxygen ratio is preferably 0.98 or less, and more preferably 0.97 or less. By setting the oxygen ratio to 0.98 or less, a further effect of reducing NOx emissions can be obtained. The lower limit of the oxygen ratio is preferably 0.90 or more, and more preferably 0.95 or more. By setting the oxygen ratio to 0.90 or more, it is possible to effectively reduce NOx emissions while suppressing a decrease in heating efficiency.

[0037] Next, the gas components are analyzed by the gas analyzer 5, and the mixed gas flowing through the path L3 is introduced into the combustor 9. The combustor 9 uses hydrogen contained in the mixed gas as part of the fuel due to incomplete combustion in the combustion furnace body 2. As a result, according to the method for operating the hydrogen combustion furnace 1 of this embodiment, it is possible to suppress a decrease in the heating efficiency of the entire hydrogen combustion furnace 1 including the combustor 9.

[0038] In addition, when normal fuel and combustion-supporting gas are supplied to the combustor 9 via path L5 and combusted, if a small amount of hydrogen is supplied to the existing fuel, the combustion conditions do not change significantly, so NOx emissions remain low and are discharged via path L6. According to the method for operating the hydrogen combustion furnace 1 of this embodiment, the exhaust gas discharged from the combustion furnace body 2 can be reused without increasing the amount of NOx emissions.

[0039] As described above, according to the hydrogen combustion furnace 1 and its operating method of this embodiment, hydrogen gas is used as fuel for the burner 3, and when hydrogen is combusted in the combustion furnace main body 2, the hydrogen is burned at a low oxygen ratio (i.e., incomplete combustion), thereby reducing the amount of NOx emissions in the exhaust gas discharged from the combustion furnace main body 2.

[0040] Furthermore, according to the hydrogen combustion furnace 1 and its operating method of this embodiment, due to incomplete combustion of hydrogen gas in the combustion furnace body 2, the hydrogen contained in the mixed gas is used as part of the fuel for the combustor 9, so that the deterioration of heating efficiency of the entire hydrogen combustion furnace 1 including the combustor 9 can be suppressed.

[0041] The technical scope of the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. According to the hydrogen combustion furnace 1 and its operating method described above, a configuration using a combustor 9 as a combustion device has been described as an example, but the present invention is not limited to this. For example, a configuration using a heat exchanger 29 (see the following embodiment) instead of the combustor 9 as a combustion device may also be used.

[0042] FIG. 2 is a system diagram showing another example of the configuration of a hydrogen combustion furnace that can be applied to this embodiment. 2, a hydrogen combustion furnace 21 of another embodiment differs in configuration from the above-described hydrogen combustion furnace 1 in that a heat exchanger 29 is used as the combustion device instead of the combustor 9, and paths L25 and L26 are used instead of paths L5 and L6. Therefore, in the hydrogen combustion furnace 21, the same components as those of the hydrogen combustion furnace 1 are denoted by the same reference numerals, and their description will be omitted.

[0043] The heat exchanger (combustion device) 29 is provided across the path L1 and the path L2, and uses unreacted hydrogen gas contained in the exhaust gas discharged from the combustion furnace body 2 as at least a part of the fuel.

[0044] Paths L3, L25, and L26 are connected to the heat exchanger 29. Path L25 is a gas supply line that supplies a combustion-supporting gas (oxygen gas (O2) is exemplified in the figure) to the heat exchanger 29. Path L26 is a gas discharge line that discharges the exhaust gas derived from the heat exchanger 29 to the outside of the system.

[0045] In addition, in the method of operating the hydrogen combustion furnace 21, the gas components are analyzed by the gas analyzer 5, and then the mixed gas flowing through the path L3 is introduced into the heat exchanger 29. The heat exchanger 29 uses as fuel hydrogen contained in the mixed gas due to incomplete combustion in the combustion furnace body 2. This allows the heat generated by burning the hydrogen gas in the heat exchanger 29 to heat (preheat) the hydrogen gas flowing through the path L1 and the combustion-supporting gas flowing through the path L2.

[0046] As explained above, the hydrogen combustion furnace 21 and its operating method enable heat recovery in proportion to the efficiency of the heat exchanger 29. Furthermore, by controlling the temperature of the heat exchanger 29 to 1000°C or less, the heating efficiency of the entire hydrogen combustion furnace 21, including the heat exchanger 29, can be improved without increasing the amount of NOx emissions in the exhaust gas.

[0047] In the above-described hydrogen combustion furnace 21, the heat exchanger 29 is provided across the path L1 and the path L2 as an example, but the present invention is not limited to this. The heat exchanger 29 may be provided across at least one of the path L1 and the path L2. [Example]

[0048] The effects of the present invention will be explained below by means of verification tests, but the present invention is not limited to the contents of the following verification tests.

[0049] <Verification Test 1> In verification test 1, the hydrogen combustion furnace 1 shown in FIG. 1 was used to verify the relationship between the oxygen ratio and the NOx emission concentration when hydrogen gas was used as fuel for the burner 3, that is, during hydrogen combustion. [Simulation conditions] (1) Simulation software (calculation software): Chemikin Pro: manufactured by Ansys (2) Fuel gas: hydrogen (3) Combustion-supporting gas: oxygen or oxygen-enriched air (4) Reaction model: GRI Mech 3.0 http: / / www.me.berkeley.edu / gri_mech

[0050] Figure 3 shows the relationship between the oxygen ratio during hydrogen combustion and NOx emission concentration, showing (A) when the oxygen concentration in the combustion-supporting gas is 90% by volume, (B) when the oxygen concentration in the combustion-supporting gas is 40% by volume, and (c) when the oxygen concentration in the combustion-supporting gas is 21% by volume. 3(A) to 3(C), the horizontal axis indicates the oxygen ratio (Oxygen ratio [-]) and the vertical axis indicates the NOx emission concentration (NOx [ppm-wet]). Also, in all of Figures 3(A) to 3(C), the results were confirmed for furnace temperatures in the combustion furnace body 2 of 1300°C, 1400°C, 1500°C, and 1600°C. The NOx emission concentration is the NOx concentration in the exhaust gas that is discharged from the combustion furnace body 2 and contains water vapor (H2O).

[0051] As shown in Figures 3(A) to (C), when the oxygen ratio on the horizontal axis is less than 1, incomplete combustion occurs. However, during incomplete combustion, the NOx emission concentration decreases dramatically and gradually approaches zero.

[0052] Therefore, it was confirmed that, from the viewpoint of reducing the concentration of NOx emissions, regardless of the oxygen concentration in the combustion-supporting gas, the upper limit of the oxygen ratio is preferably 0.98 or less, and more preferably 0.97 or less.

[0053] <Verification Test 2> In verification test 2, the hydrogen combustion furnace 1 shown in FIG. 1 was used to verify the relationship between the oxygen ratio and heating efficiency during hydrogen combustion using hydrogen gas as fuel for the burner 3.

[0054] Figure 4 shows the relationship between the oxygen ratio and heating efficiency during hydrogen combustion, showing (A) when the oxygen concentration in the combustion-supporting gas is 90% by volume, (B) when the oxygen concentration in the combustion-supporting gas is 40% by volume, and (c) when the oxygen concentration in the combustion-supporting gas is 21% by volume. 4(A) to 4(C), the horizontal axis indicates the oxygen ratio (Oxygen ratio [-]) and the vertical axis indicates the heating efficiency (Heat Efficiency [%]). In addition, in all of Figures 4(A) to 4(C), the results were confirmed when the furnace temperatures in the combustion furnace body 2 were 1300°C, 1400°C, 1500°C, and 1600°C. The heating efficiency was calculated by calculating the amount of heat carried away by the exhaust gas outside the furnace (exhaust gas heat loss) and assuming that the value obtained by subtracting the exhaust gas heat loss from the input energy is used to heat the furnace.

[0055] As shown in Figures 4(A) to (C), regardless of the oxygen concentration in the combustion-supporting gas, the heating efficiency was maximized when the oxygen ratio was 1, and it was confirmed that the heating efficiency decreased as the difference between the oxygen ratio and 1 increased. Normally, burners are operated so that the oxygen ratio is 1 or higher to prevent incomplete combustion, and so that excess oxygen is supplied to the burner. However, when the oxygen ratio is significantly lowered to cause incomplete combustion, it was confirmed that the heating efficiency is clearly lower compared to regions where the oxygen ratio is 1 or higher.

[0056] Therefore, it was confirmed that, from the viewpoint of maintaining heating efficiency, it is preferable to set the lower limit of the oxygen ratio to 0.95 or more, regardless of the oxygen concentration in the combustion-supporting gas.

[0057] <Verification Test 3> In Verification Test 3, the hydrogen combustion furnace 1 shown in Figure 1 was used to verify the relationship between the oxygen ratio and the hydrogen concentration in the exhaust gas during hydrogen combustion using hydrogen gas as fuel for the burner 3.

[0058] Figure 5 shows the relationship between the oxygen ratio during hydrogen combustion and the hydrogen concentration in the exhaust gas, with (A) the oxygen concentration in the combustion-supporting gas being 90% by volume, (B) the oxygen concentration in the combustion-supporting gas being 40% by volume, and (c) the oxygen concentration in the combustion-supporting gas being 21% by volume. 5(A) to (C), the horizontal axis indicates the oxygen ratio (Oxygen ratio [-]) and the vertical axis indicates the hydrogen concentration (H2 [vol% dry]). In addition, in all of Figures 5(A) to (C), the results were confirmed when the furnace temperatures in the combustion furnace body 2 were 1300°C, 1400°C, 1500°C, and 1600°C. The hydrogen concentration is the hydrogen concentration in the dry gas from which water vapor (H2O) discharged from the combustion furnace body 2 has been removed by the moisture remover 4.

[0059] As shown in Figures 5(A) to (C), the oxygen ratio on the horizontal axis is less than 1. It was confirmed that the smaller the oxygen ratio value, the more hydrogen is emitted unburned, and therefore the hydrogen concentration in the exhaust gas also increases.

[0060] Therefore, from the perspective of reusing hydrogen in exhaust gas, it was suggested that regardless of the oxygen concentration in the combustion-supporting gas, the smaller the oxygen ratio, the higher the hydrogen concentration in the exhaust gas and the easier it is to combust, and therefore it may be possible to reuse it as fuel in other combustion devices.

[0061] As shown in Figures 5(A) to (C), it was confirmed that the higher the oxygen concentration in the combustion-supporting gas, the more hydrogen is discharged unburned, and therefore the hydrogen concentration in the exhaust gas also increases, when the oxygen ratio is less than 1.

[0062] Therefore, from the perspective of reusing hydrogen in exhaust gas, the higher the oxygen concentration in the combustion-supporting gas, the higher the hydrogen concentration in the exhaust gas when the oxygen ratio is less than 1, making it easier to combust, suggesting that it may be possible to reuse it as fuel in other combustion devices. [Explanation of symbols]

[0063] 1,21 Hydrogen combustion furnace 2. Combustion furnace body 3 Burner 4 Moisture removal device 5 Gas analyzer 6. Control device 7. Flow control valve (first control device) 8. Flow control valve (second control device) 9 Combustor (combustion device) 29 Heat exchanger (combustion device) L1 pathway (first pathway) L2 pathway (second pathway) L3 pathway (third pathway)

Claims

1. a combustion furnace body having a burner; a first path for supplying hydrogen to the burner; a second passage for supplying a combustion-supporting gas containing oxygen to the burner; a third passage for discharging exhaust gas from the combustion furnace body; a first control device located in the first path and configured to adjust the amount of hydrogen supplied; a second control device located in the second path and configured to adjust the supply amount of the combustion supporting gas; a gas analyzer located on the third path and analyzing components in the exhaust gas; a control device that transmits and receives electrical signals between the first control device, the second control device, and the gas analyzer; a moisture removal device located in the third path and removing moisture from the exhaust gas; Equipped with A hydrogen combustion furnace, wherein the control device controls the first control device and the second control device based on the analysis value obtained from the gas analyzer so that the hydrogen is incompletely combusted in the combustion furnace body.

2. 2. The hydrogen-fired furnace of claim 1, wherein the moisture removal device is located on the upstream side of the gas analyzer.

3. The hydrogen-combustion furnace according to claim 1 , further comprising a combustion device connected to the third path and using the exhaust gas as at least a portion of a fuel.

4. 4. The hydrogen combustion furnace according to claim 3, wherein the combustion device is a heat exchanger provided across at least one or both of the first path and the second path.

5. 5. The hydrogen combustion furnace according to claim 1, wherein the combustion furnace body is a heating furnace that heats an object to be heated housed in an inner space.

6. A method for operating a hydrogen combustion furnace having a combustion furnace body with a burner that combusts hydrogen and a combustion-supporting gas containing oxygen, comprising: In the combustion furnace body, the hydrogen is incompletely combusted, A method for operating a hydrogen combustion furnace using the combustion-supporting gas having an oxygen concentration of 90% by volume or more.

7. 7. The method for operating a hydrogen combustion furnace according to claim 6, wherein incomplete combustion is performed in the combustion furnace body with an oxygen ratio of 0.98 or less.

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