Method for operating heating furnace, and heating furnace

Abstract

The invention provides a method for operating a heating furnace and a heating furnace, which can use ammonia capable of suppressing emission of carbon dioxide as a fuel for combustion of the heating furnace and can reduce the amount of nitrogen oxide and unburned ammonia discharged to the outside of the heating furnace. The method for operating a heating furnace includes: a first burner heating step in which a first fuel gas containing ammonia is subjected to burner heating with combustion air having an air ratio of 0.9-1.0 with respect to the theoretical air amount of the first fuel gas; a second burner heating step in which a second fuel gas containing ammonia is subjected to burner heating with combustion air in which the air ratio with respect to the theoretical air amount of the second fuel gas is lower than the air ratio with respect to the theoretical air amount of the first fuel gas; and an air injection step of injecting air into a mixed exhaust gas of the exhaust gas generated by heating of the first burner and the exhaust gas generated by heating of the second burner.

Description

Technical Field

[0001] This invention relates to a method for operating a heating furnace and to a heating furnace itself. Background Technology

[0002] In integrated steel mills, blast furnace gas, emitted from the top of blast furnaces used to reduce iron ore to produce molten iron, is a prime example of the effective use of byproduct gases generated in converters and coke ovens as fuel gases. However, in recent years, with increasing demands for reducing carbon dioxide emissions, there is a growing need for combustion technologies that reduce the use of these byproduct gases. For example, even in steel heating furnaces used to heat steel in hot rolling lines and plate rolling lines of integrated steel mills, there is a growing need to reduce the use of byproduct gases and decrease carbon dioxide emissions. In this context, the focus is on technologies utilizing ammonia as fuel gas for steel heating furnaces. That is, ammonia, which contains no carbon, primarily produces water and nitrogen when burned, thus resulting in a significant reduction in carbon dioxide emissions. There is a desire to develop technologies for use in steel heating furnaces.

[0003] On the other hand, if ammonia is used as fuel for the heating furnace, the generation of nitrogen oxides (NOx) becomes a problem. Nitrogen oxides are harmful to human health and are a cause of photochemical smog and acid rain, thus making them subject to legal emission restrictions.

[0004] Therefore, heating technology was proposed to solve these problems.

[0005] Patent Document 1 discloses a boiler that includes a combustion device capable of burning ammonia as fuel in a furnace; a flue for guiding combustion gases generated from the combustion of fuel; and an injection unit disposed in at least one of the furnace and the flue downstream of the combustion device from the combustion gases, which injects ammonia as a reducing agent toward the central portion of the furnace or the flue when viewed from above.

[0006] Therefore, ammonia can be supplied to the center of the furnace, and even a small amount of ammonia can act as a reducing agent to reduce nitrogen oxides.

[0007] In addition, Patent Document 2 discloses a boiler comprising a burner for burning fossil fuels in a furnace; an additional air supply unit disposed downstream of the burner in the direction of combustion gas flow in the furnace; and an ammonia fuel supply unit that supplies ammonia fuel to the furnace upstream of the additional air supply unit in the direction of fuel gas flow.

[0008] Therefore, in a two-stage combustion boiler equipped with an additional air supply section, if ammonia fuel is introduced at a position upstream of the additional air supply section, the nitrogen component of the ammonia fuel is reduced to N2 in the reducing atmosphere zone of the furnace, which can suppress the generation of nitrogen oxides.

[0009] Existing technical documents

[0010] Patent documents

[0011] Patent Document 1: Japanese Patent Application Publication No. 2019-086191

[0012] Patent Document 2: Japanese Patent Application Publication No. 2018-076985 Summary of the Invention

[0013] However, if the aforementioned conventional technology is applied to heating furnaces used for heating steel and other materials, the following problems arise.

[0014] Patent Document 1 discloses a technique that targets combustion devices such as boilers, injecting ammonia downstream of the flow direction of the combustion gases to reduce nitrogen oxides generated in the combustion device. In this case, the amount of ammonia injected for reducing nitrogen oxides is extremely small compared to the flow rate of the combustion gases generated in the combustion device. Therefore, even when ammonia is injected towards the center of the furnace, it sometimes fails to mix evenly with the nitrogen oxides contained in the combustion gases. As a result, the nitrogen oxides contained in the combustion gases are sometimes not effectively reduced. Consequently, the ammonia, acting as a reducing agent, is left unburned and directly discharged to the outside of the furnace. In heating furnaces used to heat materials such as steel, unlike combustion devices such as boilers, there are generally opening and closing doors for loading or unloading the heated material into or from the furnace.

[0015] In this situation, the following problem arises: when the furnace door is opened and closed, toxic unburned ammonia (also known as "unburned ammonia") is discharged to the outside of the furnace, deteriorating the environment outside the furnace.

[0016] Patent Document 2 also targets combustion devices such as boilers, utilizing ammonia to reduce nitrogen oxides within a reducing atmosphere zone inside the furnace. Patent Document 2 discloses that, in order to create a reducing atmosphere zone within the furnace, the primary air supplied to the burner is less than the amount of air required for the complete combustion of fossil fuels. The technology disclosed in Patent Document 2 requires a certain space within the furnace and a certain reaction time for the reduction reaction of nitrogen oxides.

[0017] On the other hand, in a heating furnace used to heat materials such as steel, not only is a combustion device (e.g., a burner) required inside the furnace, but also space is needed to hold the heated material. In contrast, in a furnace such as a boiler, only the space required for the combustion reaction of fuel and combustion air is needed.

[0018] Therefore, if the technology disclosed in Patent Document 2 is applied to a heating furnace for heating the heated body, the space of the reducing atmosphere zone is expanded, resulting in the following problem: the reduction reaction of nitrogen oxides cannot proceed uniformly inside the reducing atmosphere zone, and unburned ammonia is discharged to the outside of the heating furnace.

[0019] Furthermore, Patent Document 2 discloses that when the amount of air supplied for ammonia combustion varies between 0.6 and 1.0 relative to the theoretical air amount, the leakage rate of unburned ammonia at the furnace outlet has the opposite characteristic to the conversion rate to NOx. Therefore, in order to reduce both nitrogen oxides (NOx) and unburned ammonia, the primary air ratio must be controlled within a narrow range, as nitrogen oxides and unburned ammonia are easily discharged to the outside due to changes in the operating conditions inside the heating furnace.

[0020] The present invention was made to solve the above-mentioned problems existing in the prior art. Its purpose is to provide an operating method and a heating furnace that can use ammonia, which can suppress the emission of carbon dioxide, as the combustion fuel for the heating furnace, and can reduce the amount of nitrogen oxides and unburned ammonia emitted to the outside of the heating furnace.

[0021] The operating method of the heating furnace of the present invention, which advantageously solves the above problems, is configured as follows.

[0022] [1] An operating method of a heating furnace includes a first burner heating step, wherein a first fuel gas containing ammonia is heated by a burner using combustion air with an air ratio of 0.9 to 1.0 relative to the theoretical air volume of the first fuel gas; a second burner heating step, wherein a second fuel gas containing ammonia is heated by a burner using combustion air with an air ratio that is lower than the theoretical air volume of the first fuel gas; and an air injection step, wherein air is injected.

[0023] [2] In the operation method of the heating furnace described in [1] above, the air injection step injects air into the mixed exhaust gas formed by the mixture of the exhaust gas generated by the first burner heating step and the exhaust gas generated by the second burner heating step.

[0024] [3] In the operation method of the heating furnace described in [1] or [2] above, in the heating step of the second burner, the air ratio relative to the theoretical air volume of the second fuel gas is less than 0.9.

[0025] [4] In the operation method of the heating furnace described in [1] or [2] above, at least one of the first fuel gas and the second fuel gas is heated by a mixture of ammonia and coal gas in the burner.

[0026] [5] In the operation method of the heating furnace described in [3] above, at least one of the first fuel gas and the second fuel gas is heated by a burner using a mixture of ammonia and coal gas.

[0027] The heating furnace of the present invention, which advantageously solves the above-mentioned problems, is configured as follows.

[0028] [6] A heating furnace includes two or more burner devices that use fuel gas containing ammonia to perform burner heating; an air ratio adjustment unit that adjusts the air ratio of combustion air supplied to the two or more burner devices relative to the theoretical air quantity of the fuel gas; a control unit that controls the air ratio of combustion air supplied to at least one of the two or more burner devices to be different from the air ratio of combustion air supplied to the other burner devices; and an air injection device that injects air into the mixed exhaust gas discharged from the two or more burner devices.

[0029] [7] In the heating furnace described above [6], the burner equipment includes a first burner equipment that uses combustion air with an air ratio of 0.9 to 1.0 relative to the theoretical air volume of the first fuel gas to heat the first fuel gas containing ammonia, the air ratio of which has been adjusted by the air ratio adjustment unit; and a second burner equipment that uses combustion air with an air ratio lower than the theoretical air volume of the first fuel gas to heat the second fuel gas containing ammonia; the first burner equipment, the second burner equipment, and the air injection equipment are arranged sequentially from the upstream side of the airflow along the airflow inside the heating furnace.

[0030] [8] In the heating furnace described above [6], the heating furnace has an opening for discharging the mixed exhaust gas, and the air injection device is positioned closer to the opening than the first burner device and the second burner device.

[0031] According to the present invention, carbon dioxide emissions can be suppressed by using ammonia as the combustion fuel for the heating furnace, and the emissions of nitrogen oxides and unburned ammonia generated by the combustion of ammonia into the heating furnace can be reduced. Attached Figure Description

[0032] Figure 1 This is a schematic diagram showing the basic structure of the heating furnace.

[0033] Figure 2 It means from Figure 1 A diagram showing the configuration of the burner equipment in the heating furnace, viewed from the front, in the direction of steel movement.

[0034] Figure 3 This is a configuration diagram of a heating furnace in this embodiment, which includes burner equipment and air injection equipment arranged in parallel.

[0035] Figure 4 This is a schematic diagram illustrating the chemical reactions within a heating furnace. A) Contains nitrogen oxides and unburned ammonia in the exhaust gas produced by the first burner. B) Contains nitrogen oxides and unburned ammonia in the exhaust gas produced by the second burner. C) Represents the chemical reaction between nitrogen oxides and unburned ammonia in the mixed exhaust gas.

[0036] Figure 5 This is a configuration diagram of a heating furnace with a burner device and an air injection device arranged in a relatively balanced manner according to this embodiment.

[0037] Figure 6 This is a configuration diagram of the heating furnace equipped with a burner device and an air injection device according to this embodiment, and a schematic diagram for illustrating the chemical reaction within the heating furnace. A) Nitrogen oxides and unburned ammonia are present in the exhaust gas generated by the heating of the first burner. B) Nitrogen oxides and unburned ammonia are present in the exhaust gas generated by the heating of the second burner.

[0038] Figure 7 This is a schematic diagram showing the configuration of the heating furnace according to this embodiment.

[0039] Figure 8 This is a configuration diagram of a heating furnace having a burner device with an air ratio adjustment unit, a control unit, and an air injection device, according to another embodiment. Detailed Implementation

[0040] The heating furnace of this embodiment will be described below.

[0041] <Heating Furnace>

[0042] The heating furnace according to embodiments of the present invention is a device comprising a burner for igniting fuel gas, which serves as a heat source, and a heated object housed within it, which is then heated to a predetermined temperature. The heated object is primarily a metal, which may be a ferrous metal or a non-ferrous metal. The heating temperature of the heated object is 700–1400°C.

[0043] Figure 1 , 2 This describes an example of a heating furnace in this embodiment where the material to be heated is steel. For example, a heating furnace used in a hot rolling mill for steel is used to heat cast slabs to a specified heating temperature (around 1100 to 1300°C).

[0044] Figure 1The heating furnace 1 shown includes a loading section 30 for loading steel S (slabs) as the heated material and a removal section 31 for removing (extracting) the heated steel S. For example, steel S manufactured using a continuous casting line is transported to the loading side of the heating furnace and loaded into the heating furnace 1 from the loading section 30 according to the production schedule of a hot rolling line, etc. The interior of the heating furnace 1 is divided into multiple zones, and on the upstream side, it is mostly composed of heating zones divided into 2 to 8 zones and 1 to 3 heat exchange zones. The interior of the heating furnace 1 generally includes a fixed slide 33 for holding the steel S and a moving slide 32 for conveying the steel S. A heating furnace equipped with a fixed slide 33 and a moving slide 32 is called a walking beam continuous heating furnace.

[0045] During the operation of the heating furnace, each zone inside the furnace is controlled to a different atmosphere temperature, and the average temperature of the steel S charged into the heating furnace 1 gradually increases. Thus, the steel S is controlled to a predetermined target heating temperature (the target temperature of the slab when it is removed from the heating furnace). The steel S, having reached the target temperature, is then supplied for hot rolling via the discharge section 31.

[0046] Inside the heating furnace 1, multiple burners are provided along the conveying direction of the steel S (steel movement direction 100). Burners B are configured to heat the interior of the heating furnace through combustion. When the interior of the heating furnace is heated by the burners, the temperature of the steel rises through radiation from the furnace wall. Additionally, sometimes an atmospheric gas flow occurs inside the heating furnace, heating the steel through convection. Furthermore, the steel can also be heated by direct contact between the burner flame and the steel. In either case, the burners heat the interior of the heating furnace by burning the fuel gas, which serves as a heat source, thereby heating the material inside the furnace.

[0047] The heating furnace 1, in addition to the space for emitting flames from the burner, also has a space for holding and conveying the material to be heated. Therefore, it is characterized by having a larger internal volume relative to the combustion energy input into the furnace compared to boilers and the like, which are designed to generate a combustion reaction internally. The internal volume of the furnace per unit combustion energy in a gas turbine, pulverized coal boiler, or oil / gas boiler (m³) 3 For example, a representative value of / MW is: 2m for a gas turbine. 3 / MW, pulverized coal boiler is 6m 3 / MW, oil and gas boiler is 2m 3 / MW. In contrast, the heating furnace is as large as 10-16m². 3 Around / MW, for example, 11-13m³ in the heating furnace used in hot rolling mills of steel. 3 Around / MW.

[0048] During the operation of the heating furnace 1, the doors (open / closed doors) of the loading section 30 and the unloading section 31 are closed, creating an internal pressure higher than atmospheric pressure. The doors are temporarily opened when steel S is loaded and unloaded. When the doors are open, a pressure difference is created between the pressure inside the furnace and the area near the door, causing the combustion gases inside the furnace to flow from the area of ​​higher pressure to the area of ​​lower pressure. With the doors of the heating furnace 1 open, the flow of combustion gases is mostly along the direction in which they are discharged from the furnace through the openings to the outside of the furnace 1.

[0049] Figure 2 This is a diagram showing a cross-section of the heating furnace 1. Burners B are mostly located inside the heating furnace 1, positioned on the upper and lower surfaces of the steel S respectively, so as not to create a temperature difference between the upper and lower surfaces of the steel S. Furthermore, they are mostly positioned on both sides of the steel S's conveying direction so as not to create a temperature difference between the front end S1 and the rear end S2 of the steel S.

[0050] The heating furnace 1 of this embodiment is a heating furnace comprising: two or more burner devices that use fuel gas containing ammonia for burner heating; an air ratio adjustment unit that adjusts the air ratio of the combustion air supplied to the two or more burner devices relative to the theoretical air quantity of the fuel gas; a control unit that controls the air ratio of the combustion air supplied to at least one of the two or more burner devices to be different from the air ratio of the combustion air supplied to the other burner devices; and an air injection device that injects air into the mixed exhaust gas discharged from the two or more burner devices.

[0051] <Burner Equipment>

[0052] Preferably, the device includes a first burner device that heats the first fuel gas containing ammonia using combustion air with an air ratio of 0.9 to 1.0 relative to the theoretical air volume of the first fuel gas; and a second burner device that heats the second fuel gas containing ammonia using combustion air with an air ratio that is lower than the theoretical air volume of the first fuel gas.

[0053] In addition, in the heating furnace 1 of this embodiment, at least one of the burners B disposed inside is a first burner device that uses combustion air to heat a first fuel gas containing ammonia, and at least one of the other burners B is a second burner device that uses combustion air to heat a second fuel gas containing ammonia.

[0054] use Figure 3 Describe the first burner equipment and the second burner equipment. Figure 3 It contains the location located Figure 1The diagram shows a portion of the furnace wall 35 on one side of the heating furnace 1, and an observation from above of the configuration of the first burner device 2, the second burner device 3, and the air injection device 4 of the heating furnace 1.

[0055] The first burner device 2 uses a first fuel gas 5 containing ammonia as fuel gas and combustion air 12 to perform first burner heating by injecting a flame into the furnace. The first burner device 2 includes a first burner nozzle 7 for injecting a flame into the furnace, a first fuel gas supply system 14 for supplying the first fuel gas 5 to the first burner nozzle 7, and a combustion air supply system 18 for supplying the combustion air 12 to the first burner nozzle 7. The first burner nozzle 7 is, for example, a double-tube nozzle, injecting the first fuel gas 5 into the furnace from the inside and supplying combustion air 12 from the outside. As a result, a combustible mixture of the first fuel gas 5 and combustion air 12 is formed, and a flame is injected into the heating furnace 1 from the front end of the first burner nozzle 7.

[0056] The second burner device 3 can be configured with the same structure as the first burner device 2. The second burner device 3 uses a second fuel gas 6 containing ammonia as fuel gas and combustion air 12 to perform second burner heating by injecting a flame into the furnace. The second burner device 3 includes a second burner nozzle 8 for injecting a flame into the furnace, a second fuel gas supply system 15 for supplying the second fuel gas 6 to the second burner nozzle 8, and a combustion air supply system 19 for supplying the combustion air 12 to the second burner nozzle 8. The second burner nozzle 8 may also be, for example, a double-tube nozzle, injecting the second fuel gas 6 into the furnace from the inner tube and supplying combustion air 12 from the outer tube. This forms a combustible mixture of the second fuel gas 6 and combustion air 12, which is then injected into the furnace 1 from the front end of the second burner nozzle 8.

[0057] In addition, the first burner device 2 and the second burner device 3 may use a vortex burner that has the function of stirring the fuel gas injected from the burner nozzle, or a tubular flame burner that blows the fuel gas and combustion air tangentially into the combustion tube to form a swirling flow in the combustion tube for combustion.

[0058] Both the first fuel gas 5 and the second fuel gas 6 use fuel gases containing ammonia. Ammonia can be used alone as a fuel gas, or a mixture of ammonia and other fuels can be used. The mixing ratio of ammonia in the first fuel gas 5 and the second fuel gas 6 can be different or the same. Furthermore, the other fuels constituting the mixture can be different or the same in the first fuel gas 5 and the second fuel gas 6. However, since there is a possibility that the equipment for supplying fuel gases to the heating furnace 1 becomes more complex and the equipment cost increases, it is economical to use the same fuel gas containing ammonia for both the first fuel gas 5 and the second fuel gas 6.

[0059] Ammonia is a flame-retardant fuel, more difficult to ignite and burning more slowly than ordinary fuels. To improve combustion stability, a mixed gas with other fuels can be used. Coal gas is the preferred fuel for mixing with ammonia. Coal gas refers to the gas obtained from coal. Preferably, the coal gas includes any one of coke oven gas, blast furnace gas, converter gas, or electric furnace gas. These are byproduct gases generated in steel mills and have the effect of stabilizing the combustion of ammonia. Blast furnace gas is a byproduct gas produced during the reduction of iron ore in a blast furnace to produce molten iron. Coke oven gas is a byproduct gas generated by the high-temperature dry distillation of coal to produce coke. Converter gas is a byproduct gas produced during the steelmaking process in a converter. Electric furnace gas is a gas generated due to the incomplete combustion of auxiliary fuels (carburizing agents) in an electric furnace. As the coal gas constituting the mixed gas, a gas appropriately mixed with blast furnace gas, coke oven gas, and converter gas (sometimes called M gas) can be used. This is because by mixing gases with different calorific values, the heat required for heating the object being heated is supplied, thus ensuring stable operation of the heating furnace.

[0060] Is to make Figure 3 The first fuel gas 5 used in the first burner device 2 and the second fuel gas 6 used in the second burner device 3 shown are both examples of a mixture of ammonia and coal gas.

[0061] The first fuel gas supply system 14 is connected to an ammonia supply system 25 and a coal gas supply system 27. Ammonia 10 and coal gas 11 are mixed in a mixing section 16 and supplied to the first burner nozzle 7. A flow regulating valve 53 for adjusting the supply amount of each gas to the mixing section 16 and a flow meter 52 for measuring the supply flow rate can be provided midway between the ammonia supply system 25 and the coal gas supply system 27. This allows adjustment of the mixing ratio of ammonia and coal gas in the mixed gas.

[0062] The second fuel gas supply system 15 is also connected to the ammonia supply system 26 and the coal gas supply system 28. Ammonia 10 and coal gas 11 are mixed in the mixing section 17 and supplied to the second burner nozzle 8. The second burner device 3 may also be equipped with a flow regulating valve 53 for adjusting the supply amount of ammonia 10 and coal gas 11 to the mixing section 17 and a flow meter 52 for measuring the supply flow rate, midway between the ammonia supply system 26 and the coal gas supply system 28.

[0063] The mixing section (16, 17) refers to the section where the supply piping of the coal gas supply system (27, 28) and the supply piping of the ammonia supply system (25, 26) merge. Ammonia 10 and coal gas 11 are supplied from their respective supply piping and then merged, thus mixing occurs even without a special stirring mechanism. The mixing section (16, 17) only needs to be formed into a defined space where these supply piping exchanges. However, the mixing section (16, 17) can also be equipped with static mixing equipment such as a static mixer, or a dynamic mixer with stirring function. This is preferable from the viewpoint of generating a more uniformly mixed gas mixture of coal gas and ammonia.

[0064] Midway between the combustion air supply system 18 of the first burner device 2 and the combustion air supply system 19 of the second burner device 3, a flow regulating valve 53 for adjusting the flow rate of the combustion air 12 supplied to the first burner nozzle 7 and the second burner nozzle 8, and a flow meter 52 for measuring the supply flow rate may also be provided. By adjusting the amount of combustion air in the first burner device 2 and the second burner device 3, the air ratio in the burner heating of each of the first burner device 2 and the second burner device 3 can be easily adjusted.

[0065] The combustion air used in the first burner device 2 and the combustion air used in the second burner device 3 can be supplied from the atmosphere via a combustion air supply system. However, air modified by removing nitrogen or adding pure oxygen can also be used for the combustion air 12. Increasing the oxygen content of the combustion air promotes the oxidation reaction of the fuel gas, reduces the flow rate of the combustion air supplied from the combustion air supply system, and thus reduces the power consumption of pumps, etc. Furthermore, reducing the oxygen content of the combustion air creates a reducing atmosphere inside the furnace, promoting the reduction of nitrogen oxides.

[0066] <Air jet equipment>

[0067] In addition to the first burner device 2 and the second burner device 3 described above, the heating furnace 1 of this embodiment also includes an air injection device 4, which injects air into the mixed exhaust gas 23 formed by the mixture of exhaust gas 21 discharged from the first burner device 2 and exhaust gas 22 discharged from the second burner device 3.

[0068] The air injection device 4 is connected to the air supply system 29, and injects air 13 from the air injection nozzle 9 into the furnace. Midway through the air supply system 29, a flow regulating valve 53 for adjusting the flow rate of the air 13 supplied to the air injection nozzle 9 and a flow meter 52 for measuring the supply flow rate can be provided. This allows adjustment of the amount of air injected into the mixed exhaust gas of the first burner device 2 and the second burner device 3, promoting the reduction reaction of nitrogen oxides contained in the mixed exhaust gas.

[0069] The air injected from the air injection device 4 can be air collected from the atmosphere. However, air modified by removing nitrogen or adding pure oxygen can also be supplied to the air injection nozzle 9 via the air supply system 29. By increasing the oxygen content of the air 13, the reduction reaction of nitrogen oxides contained in the mixed exhaust gas 23 is promoted.

[0070] <Configuration of burner equipment for heating furnace>

[0071] The configuration of the burner equipment in the heating furnace will be described. In this embodiment, along the airflow inside the heating furnace, a first burner device that heats the burner with an air ratio of 0.9 to 1.0 relative to the first fuel gas, a second burner device that heats the burner with an air ratio of less than that of the first fuel gas relative to the second fuel gas, and an air injection device that injects air into the mixture of exhaust gas discharged from the first burner device and exhaust gas discharged from the second burner device.

[0072] This is because it is believed that by injecting oxygen into the mixture of NOx and unburned ammonia, the reduction reaction of ammonia to NOx can be promoted, thereby reducing the amount of NOx and unburned ammonia discharged from the heating furnace.

[0073] Furthermore, when the furnace is equipped with an opening for discharging combustion gases, the air injection device is preferably positioned closer to the opening than the first burner device or the second burner device.

[0074] Figure 7 This is an example of the configuration of the heating furnace in this embodiment. Figure 7 The heating furnace shown includes a loading section 30 for loading the heated object into the heating furnace, a removal section 31 for removing the heated object, and a flue 34 for discharging exhaust gas (combustion gas) from inside the heating furnace to the outside of the heating furnace. The loading section 30 is a temporary opening when the heated object is loaded into the heating furnace. The removal section 31 is also a temporary opening when the heated object is removed from the heating furnace.

[0075] On the other hand, flue 34 is designed to discharge exhaust gas from the interior of the heating furnace 1 and to adjust the pressure inside the furnace so as not to be too high. It is partially open to the outside of the furnace, thus becoming an always-open opening. Therefore, in Figure 7 Inside the furnace 1 shown, at least an airflow of combustion gases is generated from inside the furnace toward the flue 34.

[0076] In this embodiment, a first burner device 2, a second burner device 3, and an air injection device 4 are sequentially arranged upstream of the combustion gas flow toward the flue 34. Figure 7 In the example shown, near the center of the conveying direction of the heating furnace 1, a first burner device 2 is arranged above and below the heated body. Downstream of the combustion gas flow of the first burner device 2, a second burner device 3 is arranged above the heated body, and two second burner devices 3 are arranged below it. Furthermore, along the combustion gas flow F, an air injection device 4 is arranged downstream of the second burner devices 3.

[0077] Should Figure 7 In this process, the first burner device 2 heats the burner with an air ratio of 0.9 to 1.0 relative to the first fuel gas, while the second burner device 3 heats the burner with an air ratio of less than that relative to the first fuel gas. As a result, exhaust gas 21, containing more nitrogen oxides, moves along the combustion gas flow F within the furnace and mixes with exhaust gas 22, containing more unburned ammonia, to generate mixed exhaust gas 23. Mixed exhaust gas 23 moves along the combustion gas flow F within the furnace and further moves toward the flue 34, which serves as an opening. The air injection device 4 is positioned downstream of the airflow than the first and second heating devices 2 and 3, thus injecting air 13 into the mixed exhaust gas 23 before it is discharged from the opening. As a result, the oxygen in the air 13 promotes the reduction of nitrogen oxides by ammonia, thereby reducing the concentration of nitrogen oxides and ammonia in the exhaust gas discharged to the outside of the furnace through the flue 34.

[0078] It should be noted that burner devices other than the first burner device 2 and the second burner device 3 can be used as burners within the heating furnace 1. However, the burner device other than the first burner device 2 and the second burner device 3 (referred to as the third burner device) is a device that uses fuel that does not contain ammonia for burner heating. The third burner device does not emit nitrogen oxides and unburned ammonia, or even if it does, as long as the emission amounts of nitrogen oxides and unburned ammonia are lower than those of the first burner device and the second burner device (e.g., less than 1 / 10), it will not cause external interference to the reduction reaction of nitrogen oxides in the mixed exhaust gas. The third burner device can, for example, perform burner heating using coal gas as fuel gas.

[0079] Figure 8 This describes the configuration of the heating furnace in this embodiment. Figure 8 The furnace shown is equipped with two burner devices (44A, 44B) and an air injection device 4. The two burner devices (44A, 44B) can be burner devices with the same structure, and the fuel gas 45 supplied to the burner devices 44 can also be the same fuel gas.

[0080] The burner unit 44 is provided with an air ratio adjustment unit 40, and the air ratio adjustment unit 40 corresponding to the two burner units (44A, 44B) is connected to the control unit 42. The air ratio adjustment unit 40 has the function of adjusting the air ratio of combustion air to fuel gas 45 for each burner unit 44.

[0081] For example, the air ratio adjustment unit 40 measures the flow rate of the fuel gas 45 supplied to the burner nozzle as fuel gas 45, and calculates the theoretical amount of air needed to completely combust the fuel gas 45 based on the measured flow rate of the fuel gas 45 and the fuel composition of the fuel gas 45. Then, based on the air ratio set for each burner device (44A, 44B), the opening of the flow adjustment valve configured in the combustion air supply system is adjusted, thereby setting the air ratio for burner heating for each burner device (44A, 44B).

[0082] The control unit 42 provides the air ratio setting value to the air ratio adjustment unit 40 of each burner device (44A, 44B). The control unit 42 provides the air ratio setting value to the air ratio adjustment unit 40 with an air ratio of 0.9 to 1.0 for one burner device 44A. The control unit 42 provides the air ratio setting value to the air ratio adjustment unit 40 with another burner device 44B heating the burner with an air ratio lower than that of the aforementioned burner device 44A.

[0083] In this case, such as Figure 8 As shown in the configuration relationship of each device, the control unit 42 can set the air ratio of the burner device 44A, which is located far away from the air injection device 4, to 0.9 to 1.0, and set the air ratio of the burner device 44B, which is located close to the air injection device 4, to be less than the air ratio of the burner device 44A, which is located far away from the air injection device 4.

[0084] The burner device 44A, which is located away from the air injection device 4 and whose air ratio is set to 0.9 to 1.0, functions as the first burner device 2, while the burner device 44B, which is located close to the air injection device 4, functions as the second burner device 3.

[0085] Therefore, by including two burner devices (44A, 44B) equipped with an air ratio adjustment unit 40 and a control unit 42 that sets their air ratio, a mixed exhaust gas 23 containing nitrogen oxides and unburned ammonia can be generated, and the reduction reaction of ammonia to nitrogen oxides can be promoted by the air injection device 4.

[0086] Next, the operation method of the heating furnace in this embodiment will be described.

[0087] <Operating Procedures for the Heating Furnace>

[0088] This embodiment is an operating method for a heating furnace, comprising a first burner heating step, wherein a first fuel gas containing ammonia is heated by a burner using combustion air with an air ratio of 0.9 to 1.0 relative to the theoretical air volume of the first fuel gas; a second burner heating step, wherein a second fuel gas containing ammonia is heated by a burner using combustion air with an air ratio lower than that relative to the theoretical air volume of the first fuel gas; and an air injection step, wherein air is injected.

[0089] In the heating furnace, nitrogen oxides are produced by burning fuel gas containing ammonia, generating a mixed waste gas containing both nitrogen oxides and ammonia. Oxygen-rich air is then injected into this mixed waste gas. This process promotes the reduction reaction of nitrogen oxides by ammonia. The ammonia is oxidized by the oxygen in the air, and the oxidized ammonia decomposes the nitrogen oxides. Thus, ammonia, along with the nitrogen oxides in the mixed waste gas, is also decomposed and rendered harmless.

[0090] The first burner and the second burner are combined because the exhaust gas heated by the first burner contains more nitrogen oxides, while the exhaust gas heated by the second burner contains more unburned ammonia. By mixing them, a mixed exhaust gas containing both nitrogen oxides and ammonia is generated.

[0091] use Figure 3 The operation method of the heating furnace is explained by the first burner heating device 2, the second burner device 3, and the air injection device 4 shown.

[0092] In this embodiment, the first burner is heated, that is, the first fuel gas 5 containing ammonia is heated by combustion air 12 with an air ratio (sometimes simply referred to as air ratio) of 0.9 to 1.0 relative to the theoretical air volume of the first fuel gas 5. Here, the theoretical air volume refers to the amount of air required for complete combustion of the fuel gas. In addition, the air ratio relative to the theoretical air volume refers to the ratio of the amount of air supplied to the burner device as combustion air to the amount of air required for complete combustion of the fuel gas.

[0093] The air-to-fuel ratio for heating the first burner is set to 0.9–1.0 to ensure that the exhaust gas 21 heated by the first burner contains nitrogen oxides. When the air-to-fuel ratio is less than 0.9, ammonia combustion is suppressed, and the amount of unburned ammonia in the exhaust gas 21 generated by the first burner increases compared to nitrogen oxides. On the other hand, if the air-to-fuel ratio exceeds 1.0, the combustion of ammonia contained in the first fuel gas is promoted, resulting in an excessive amount of nitrogen oxides in the exhaust gas 21, making it difficult to fully reduce the nitrogen oxides in the mixed exhaust gas 23.

[0094] It should be noted that the concentration of nitrogen oxides in the exhaust gas 21 generated by heating the first burner with an air ratio of 0.9 to 1.0 is approximately 400 to 5000 ppm. The exhaust gas 21 heated by the first burner sometimes also contains unburned ammonia, but its concentration is below 5 ppm when the air ratio is 0.9, and approximately zero when the air ratio is 0.95 to 1.0. Therefore, the exhaust gas 21 generated by heating the first burner contains a relatively high amount of nitrogen oxides.

[0095] On the other hand, in this embodiment, the second burner is heated, that is, the second fuel gas containing ammonia is heated by combustion air with an air ratio that is lower than the theoretical air ratio of the second fuel gas relative to the theoretical air ratio of the first fuel gas.

[0096] This is to ensure that the exhaust gas 22 heated by the second burner contains a higher proportion of unburned ammonia. When the air ratio heated by the second burner is higher than that heated by the first burner, the effectiveness of using the unburned ammonia contained in the exhaust gas 22 to reduce nitrogen oxides in the exhaust gas 21 is reduced.

[0097] The air ratio for the second burner heating is preferably less than 0.9 relative to the theoretical air volume of the second fuel gas. This is because the increased amount of unburned ammonia in the exhaust gas 22 heated by the second burner promotes the reduction reaction of nitrogen oxides in the mixed exhaust gas 23. The lower limit for the air ratio for the second burner heating is 0.7. When the air ratio for the second burner heating is less than 0.7, the combustion in the second burner heating becomes unstable.

[0098] It should be noted that the exhaust gas 22 heated by the second burner sometimes contains both nitrogen oxides and unburned ammonia. However, by making the air ratio for heating the second burner lower than that for heating the first burner, the exhaust gas 22 contains more unburned ammonia than the exhaust gas 21. Furthermore, by making the air ratio for heating the second burner 0.7 or higher and less than 0.9, the concentration of unburned ammonia in the exhaust gas 22 can be between 10 and 24,000 ppm. The concentration of unburned ammonia in the exhaust gas 22 increases as the air ratio for heating the second burner decreases, reaching approximately 1200 ppm when the air ratio is 0.85 and approximately 6400 ppm when the air ratio is 0.8. In this case, although the exhaust gas 22 also contains nitrogen oxides, its concentration is below 400 ppm, decreasing to approximately 15 ppm when the air ratio is 0.85. That is, the exhaust gas 22 produced by heating the second burner can contain a relatively large amount of unburned ammonia.

[0099] When the flame is injected into the heating furnace through the first burner, the exhaust gas 21 diffuses within the furnace. At this time, as... Figure 3 As shown, when an airflow of combustion gas (exhaust gas) is generated in the heating furnace, the exhaust gas 21 moves along the airflow in the heating furnace toward the second burner device 3. Similarly, when the flame is injected into the heating furnace by heating with the second burner, the exhaust gas 22 generated by the second burner also moves along the airflow in the heating furnace. As a result, the exhaust gas 21, which contains more nitrogen oxides, and the exhaust gas 22, which contains more unburned ammonia, mix in the heating furnace to generate a mixed exhaust gas 23 containing both nitrogen oxides and unburned ammonia. The balance of the amounts of nitrogen oxides and unburned ammonia contained in the mixed exhaust gas 23 can be changed by setting the air ratio for heating with the first burner and the air ratio for heating with the second burner. In addition, the ratio of the flow rate of the first fuel gas 5 used for heating with the first burner to the flow rate of the second fuel gas 6 used for heating with the second burner can be set and changed.

[0100] In this embodiment, an air injection device 4 is used to inject air 13 into the mixed exhaust gas 23 containing both nitrogen oxides and unburned ammonia. This is based on the understanding that the reduction reaction of ammonia with nitrogen oxides is promoted by the presence of a certain amount of oxygen.

[0101] That is, by injecting air 13 into the mixed exhaust gas 23 containing both nitrogen oxides and ammonia, the oxygen contained in the air 13 promotes the reduction reaction of nitrogen oxides by ammonia. This reduces the nitrogen oxides and ammonia in the mixed exhaust gas 23. The gas injected using the air injection device 4 can be any oxygen-containing gas; air modified by removing nitrogen or adding pure oxygen can also be injected.

[0102] Figure 4This is a schematic diagram illustrating the chemical reaction when air is injected into the mixed exhaust gas 23. The exhaust gas 21 heated by the first burner contains more nitrogen oxides generated from the combustion of ammonia than unburned ammonia. The exhaust gas 22 heated by the second burner contains more ammonia remaining in an unburned state from the fuel gas than nitrogen oxides. Furthermore, the mixed exhaust gas 23 is in a state of mixing these nitrogen oxides and unburned ammonia when oxygen is injected into the mixed exhaust gas.

[0103] This promotes the following reaction: ammonia (NH3) is oxidized by oxygen to generate NH radicals and HO2 radicals. On the other hand, among the nitrogen oxides contained in the mixed waste gas 23, nitric oxide (NO) is the main component. Nitric oxide (NO) is reduced by NH radicals to generate nitrogen gas and OH radicals. Thus, the nitrogen oxides in the mixed waste gas 23 are reduced.

[0104] On the other hand, the oxygen contained in the air 13 injected from the air injection device 4 decomposes ammonia in the mixed exhaust gas 23 containing unburned ammonia, generating NH free radicals.

[0105] In other words, if sufficient oxygen is injected into the mixed exhaust gas 23, unburned ammonia will be decomposed. Furthermore, as long as NH radicals are sufficiently generated, nitrogen oxides in the mixed exhaust gas 23 can be reduced. Thus, both nitrogen oxides and ammonia in the mixed exhaust gas 23 can be reduced.

[0106] As described above, in this embodiment, by injecting air into the mixture of exhaust gas generated from heating the first burner and exhaust gas generated from heating the second burner, nitrogen oxides and unburned ammonia can be effectively decomposed. This prevents nitrogen oxides and unburned ammonia from being discharged outside the furnace 1. In contrast, the technology disclosed in Patent Document 2, due to the pre-set air-to-ammonia ratio for ammonia combustion, makes it difficult for nitrogen oxides and ammonia to coexist. Furthermore, even if nitrogen oxides and ammonia coexist, it is difficult to adjust their balance. Therefore, there is a problem that even if an additional air supply unit is provided downstream of the burner in the direction of combustion gas flow within the furnace to supply oxygen, the reduction reaction of ammonia on nitrogen oxides cannot be effectively promoted. Therefore, in order to promote the reduction reaction of ammonia on nitrogen oxides, a certain space such as a reducing atmosphere zone must be provided.

[0107] On the other hand, according to the above embodiment, the burner is heated in such a way that the air ratio of the first burner to the second burner is in a predetermined relationship, so that nitrogen oxides and unburned ammonia can coexist in a balanced manner, and the reduction reaction of ammonia to nitrogen oxides can be effectively promoted.

[0108] In this case, the temperature of the mixed exhaust gas 23, formed by the mixture of the exhaust gas 21 generated by the first burner and the exhaust gas 22 generated by the second burner, is preferably 700–1450°C. This is because the generation of NH radicals promotes the reduction reaction of nitrogen oxides.

[0109] The injection of air 13 into the mixed exhaust gas 23 is preferably performed on the mixed exhaust gas 23 formed by mixing the exhaust gas 21 generated by heating the first burner with the exhaust gas 22 generated by heating the second burner. That is, the exhaust gas 21 generated by heating the first burner can be generated first, and then the generated exhaust gas 21 can be mixed with the exhaust gas 22 generated by heating the second burner. Figure 3 and Figure 5 The burner devices shown are all relative to the airflow of combustion gas in the heating furnace, and the second burner heating device 3 is arranged downstream of the first burner device 2.

[0110] In contrast, Figure 6 This example illustrates a second burner heating device 3 positioned upstream of a first burner device 2. In this case, exhaust gas 22 containing a significant amount of unburned ammonia is generated from the second burner device 3 upstream of the combustion gas flow. However, as the exhaust gas 22 approaches the first burner device 2 along the combustion gas flow, it sometimes approaches the area of ​​the flame ejected from the first burner device 2. Particularly when the combustion gas flow is fast, the exhaust gas 22 from the second burner device 3 moves downstream near the furnace wall. In this case, sometimes a portion of the unburned ammonia contained in the exhaust gas 22 is burned by the flame from the first burner device 2, reducing the amount of unburned ammonia in the exhaust gas 22, and some of it becomes nitrogen oxides.

[0111] As a result, the amount of unburned ammonia contained in the mixed exhaust gas 23 formed downstream of the first burner device 2 is reduced, which sometimes hinders the reduction reaction of ammonia to nitrogen oxides.

[0112] In summary, a mixed exhaust gas 23 is formed by mixing the exhaust gas 21 generated by heating the first burner with the exhaust gas 22 generated by heating the second burner, and air is injected into it.

[0113] Therefore, within the heating furnace 1, along the airflow inside the heating furnace, the first burner is heated, the second burner is heated, and air is injected from the upstream side of the airflow.

[0114] Example

[0115] The effects of this embodiment will be specifically described below based on examples, but the present invention is not limited to these examples.

[0116] As an embodiment of the present invention, the following examples will be described, namely, using Figure 3The burner device shown collects exhaust gas downstream of the combustion gas flow and measures the concentrations of nitrogen oxides and unburned ammonia contained in the exhaust gas.

[0117] The burner device is internally positioned along the flow of combustion gases F (from... Figure 3 (The flow generated from the left to the right) is arranged with a first burner device and a second burner device from the upstream side of the airflow. Then, an air injection device is provided on the downstream side of the airflow along the second burner device.

[0118] The fuel gas used in both the first and second burner devices is a mixture of ammonia and methane (CH4). Figure 3 In the process, ammonia is supplied from ammonia supply systems 25 and 26 to mixing sections 16 and 17, and methane is supplied from coal gas supply systems 27 and 28 to mixing sections 16 and 17, generating a mixed gas of ammonia and methane, which is then supplied to the burner nozzle as the first fuel gas 5 and the second fuel gas 6.

[0119] The ammonia supply systems 25 and 26 and the coal gas supply systems 27 and 28 are equipped with flow regulating valves to adjust the mixing ratio of the mixed gases. Additionally, the combustion air supply systems 18 and 19 are also equipped with flow regulating valves to adjust the air ratio relative to the theoretical air volume of the first fuel gas 5 and the second fuel gas 6.

[0120] On the other hand, the mixture consists of oxygen-containing air injected from the air injection device 4 into the exhaust gas mixture, which is formed by the exhaust gas discharged from the first burner and the exhaust gas discharged from the second burner. Furthermore, the air supply system 29 is equipped with a flow regulating valve, which can change the presence or absence (ON / OFF) of the air injected into the mixed exhaust gas.

[0121] The first and second burners are devices capable of outputting a rated capacity of 800,000 kcal / hr of heat. The first and second burners are positioned 2 m apart in the direction of combustion gas flow, and an air injection device is further positioned 2 m downstream of each other.

[0122] For the flow rates of ammonia and methane supplied to the first and second burner devices, with a heat ratio of ammonia to methane of 40% and 60%, respectively, the ammonia flow rate is 79 Nm³. 3 / hr, methane flow rate is 51 Nm 3 Combustion is carried out at a rate of / hr. Additionally, if only methane is used without ammonia as fuel gas, the methane flow rate is 84 Nm³. 3 / hr. The air flow rate ejected from the air jet device is 0.1 Nm. 3 / hr.

[0123] In this embodiment, a combustion experiment is conducted by changing the mixing ratio and air ratio of the mixed gas in the first burner heating device and the second burner heating device. Exhaust gas is collected downstream of the combustion gas flow F using the air injection device 4. Then, the concentrations of nitrogen oxides (NOx), unburned ammonia (NH3), and carbon dioxide (CO2) contained in the exhaust gas are measured.

[0124] Table 1 summarizes the inventive examples and comparative examples. It should be noted that the carbon dioxide (CO2) emission in the exhaust gas is based on a conventional example (Manufacturing No. 3) that does not use ammonia as fuel gas (1.0), and the ratios under each condition are shown in the table.

[0125] This embodiment is a combustion experiment using a small number of burners. Therefore, the more numerous the burners, such as in a heating furnace, the more likely it is to prevent the emission of nitrogen oxides and unburned ammonia. Thus, the baseline values ​​for nitrogen oxide and unburned ammonia concentrations are set more stringent than those for a typical heating furnace, with a baseline value of 100 ppm for nitrogen oxide concentration and 20 ppm for unburned ammonia concentration. Any nitrogen oxide or unburned ammonia concentration exceeding the baseline value is considered unacceptable, while both are below the baseline value and are considered acceptable.

[0126] The previous example (Manufacturing No. 3) was an example in which ammonia was not used as fuel gas in the heating of the first and second burners. In this case, the emission of nitrogen oxides and unburned ammonia was suppressed. However, the problem of high carbon dioxide emissions still existed, just like with conventional burner equipment.

[0127] The comparative example (Manufacturing No. 4) is an example in which a mixture of ammonia and methane is used only for heating in the second burner, but air injection from the air injection device 4 is not performed. By using ammonia in the fuel gas, the concentration of carbon dioxide is reduced compared to the previous example, but the emissions of nitrogen oxides and unburned ammonia are higher.

[0128] Comparative Example (Manufacture No. 5) is an example in which a mixture of ammonia and methane is used only for heating in the first burner, but air injection from the air injection device 4 is not performed. In Comparative Example (Manufacture No. 5), since the exhaust gas heated in the second burner does not contain unburned ammonia, the nitrogen oxides contained in the exhaust gas generated in the first burner are not reduced. Furthermore, the exhaust gas heated in the first burner sometimes contains a small amount of unburned ammonia, but this unburned ammonia is oxidized by heating in the second burner, promoting the formation of nitrogen oxides. Therefore, unburned ammonia is not detected in the exhaust gas, but the concentration of nitrogen oxides increases.

[0129] The comparative example (Manufacturing No. 6) is an example in which the mixture of ammonia and methane is burned in both the first burner heating and the second burner heating, but no air is injected from the air injection device 4. In this case, since oxygen is not supplied to the mixed exhaust gas generated by the first burner heating and the second burner heating, the reduction reaction of unburned ammonia to nitrogen oxides is not promoted, resulting in both nitrogen oxides and unburned ammonia exceeding the reference values.

[0130] The comparative example (Manufacturing No. 7) involves burning a mixture of ammonia and methane in both the first and second burner heating processes, and injecting air from the air injection device 4. However, since the air-to-gas ratio exceeds 1.0 in the first burner heating process, it is assumed that a large amount of nitrogen oxides are generated in the exhaust gas from the first burner heating process. Therefore, even if unburned ammonia is generated in the exhaust gas from the second burner heating process, the concentration of nitrogen oxides in the mixed exhaust gas is high, and thus it is assumed that residual nitrogen oxides remain in the exhaust gas.

[0131] In contrast, the invention example (Manufacturer No. 1) involves burning the ammonia-methane mixture in both the first and second burner heating processes, with the air ratio in the first burner heating process ranging from 0.9 to 1.0, and the air ratio in the second burner heating process being lower than that in the first burner heating process. Furthermore, air is injected into the mixture of the exhaust gas heated by the first and second burners using an air injection device 4. This significantly reduces the amount of carbon dioxide in the exhaust gas compared to conventional examples, and also reduces the concentration of nitrogen oxides and unburned ammonia in the exhaust gas.

[0132] Furthermore, in the invention example (manufacturing No. 2), by making the air ratio in the second burner heating less than 0.9, the concentration of nitrogen oxides can be reduced while maintaining the same concentration of unburned ammonia as in invention example 1.

[0133]

[0134] Symbol Explanation

[0135] 1 Heating Furnace

[0136] B Burner

[0137] F is the airflow of combustion gases.

[0138] S steel

[0139] S1 steel front end

[0140] S2 steel tail end

[0141] 2 First burner equipment

[0142] 3 Second burner equipment

[0143] 4. Air jet equipment

[0144] 5. First fuel gas

[0145] 6 Second fuel gas

[0146] 7 First burner nozzle

[0147] 8 Second burner nozzle

[0148] 9. Air jet nozzle

[0149] 10 Ammonia

[0150] 11 Gas

[0151] 12. Combustion air

[0152] 13 Air

[0153] 14 First fuel gas supply system

[0154] 15 Second fuel gas supply system 16, 17 Mixing section

[0155] 18, 19 Combustion air supply system; 21, 22 Exhaust gas

[0156] 23 Mixed exhaust gas

[0157] 24 Air jet

[0158] 25, 26 Ammonia Supply System

[0159] 27 and 28 Gas supply systems

[0160] 29. Air supply system

[0161] 30 Loading side

[0162] 31 Moving out department

[0163] 32 Moving slides

[0164] 33 Fixed Slide

[0165] 34. Flue

[0166] 35 Furnace wall

[0167] 36 Furnace

[0168] 40 Air ratio adjustment section

[0169] 41 Air jet

[0170] 42 Control Department

[0171] 44. Burner Equipment

[0172] 45 Fuel Gas

[0173] 50NOx concentration meter

[0174] 51 Ammonia Concentration Meter

[0175] 52 Flow Meter

[0176] 53 Flow regulating valve

[0177] 54 First Air Ratio Adjustment Section

[0178] 55 Second Air Ratio Adjustment Section

[0179] 100 Steel movement direction

Claims

1. A method for operating a heating furnace, comprising: In the first burner heating step, the first fuel gas containing ammonia is heated by combustion air with an air ratio of 0.9 to 1.0 relative to the theoretical air volume of the first fuel gas. The second burner heating step involves heating the second fuel gas containing ammonia using combustion air with an air ratio lower than the theoretical air ratio relative to the first fuel gas; and Air injection step: Inject air.

2. The method of operating the heating furnace according to claim 1, wherein, The air injection step injects air into the mixed exhaust gas formed by the mixture of exhaust gas generated by the first burner heating step and exhaust gas generated by the second burner heating step.

3. The method of operating the heating furnace according to claim 1 or 2, wherein, In the second burner heating step, the air ratio relative to the theoretical air quantity of the second fuel gas is less than 0.

9.

4. The method of operating the heating furnace according to claim 1 or 2, wherein, At least one of the first fuel gas and the second fuel gas is heated by a burner using a mixture of ammonia and coal gas.

5. The method of operating the heating furnace according to claim 3, wherein, At least one of the first fuel gas and the second fuel gas is heated by a burner using a mixture of ammonia and coal gas.

6. A heating furnace, comprising: Two or more burner devices, using fuel gas containing ammonia for burner heating; An air ratio adjustment unit adjusts the air ratio of the combustion air supplied to the two or more burner devices relative to the theoretical air quantity of the fuel gas. The control unit controls the air ratio of the combustion air supplied to at least one of the two or more burner devices to be different from the air ratio of the combustion air supplied to the other burner devices. as well as An air injection device that injects air into the mixed exhaust gas discharged from the two or more burner devices.

7. The heating furnace according to claim 6, wherein, The burner device has: The first burner device heats the first fuel gas containing ammonia, whose air ratio has been adjusted by the air ratio adjustment unit, using combustion air with an air ratio of 0.9 to 1.0 relative to the theoretical air volume of the first fuel gas. The second burner device heats the second fuel gas containing ammonia by using combustion air with an air ratio that is lower than the theoretical air ratio of the second fuel gas relative to the theoretical air ratio of the first fuel gas. Along the airflow inside the heating furnace, the first burner device, the second burner device, and the air injection device are sequentially arranged from the upstream side of the airflow.

8. The heating furnace according to claim 6, wherein, The heating furnace has an opening for discharging the mixed waste gas. The air injection device is positioned closer to the opening than the first burner device and the second burner device.

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