Method for estimating unburned ammonia concentration, method for operating heating furnace, method for operating burner equipment, and device for controlling heating furnace

Abstract

The invention provides a method for estimating unburned ammonia, which can measure the concentration of ammonia contained in the exhaust gas of a heating furnace (1) on line by a simple method, wherein the ammonia is used as a fuel gas, and the emission of carbon dioxide can be suppressed. Also provided are a method for operating a heating furnace, a method for operating a burner facility, and a control device for a heating furnace, whereby unburned ammonia, which is the exhaust gas of the heating furnace (1), can be prevented from being discharged to the outside of the furnace. A method for estimating the concentration of unburned ammonia, which estimates the concentration of unburned ammonia contained in an exhaust gas discharged from a heating furnace that performs burner heating using a fuel gas containing ammonia and a carbon-containing fuel, comprises: a determination step for determining the concentration of unburned ammonia contained in the exhaust gas; determining the correlation between the concentration of carbon monoxide contained in the exhaust gas of the heating furnace and the concentration of unburned ammonia; a measurement step for measuring the concentration of carbon monoxide contained in the exhaust gas of the heating furnace during the operation of the heating furnace; and an estimation step for estimating the concentration of unburned ammonia contained in the exhaust gas of the heating furnace on the basis of the carbon monoxide concentration measured in the measurement step and the correlation between the carbon monoxide concentration and the unburned ammonia concentration determined in the determination step.

Description

Technical Field

[0001] This invention relates to a method for estimating the concentration of unburned ammonia, a method for operating a heating furnace, a method for operating a burner device, and a control device for a heating furnace. Background Technology

[0002] In integrated iron and steel plants, byproduct gases such as blast furnace gas discharged from the top of the blast furnace to produce molten iron from reduced iron ore, converter gas, and coking oven gas are effectively utilized as fuel gases. However, in recent years, the requirements for reducing carbon dioxide emissions have increased, necessitating combustion technologies to reduce the use of these byproduct gases. Even in heating furnaces used to heat slabs before rolling, such as those in hot rolling lines and heavy plate rolling lines in integrated iron and steel plants, there are requirements to reduce the use of byproduct gases and decrease carbon dioxide emissions.

[0003] Therefore, the focus is on technologies that use ammonia as a fuel gas in furnaces. Since ammonia, which contains no carbon, primarily produces water and nitrogen upon combustion, it significantly reduces carbon dioxide emissions. Therefore, the development of technologies for using ammonia as a fuel gas in furnaces is anticipated.

[0004] However, because ammonia is toxic, if unburned ammonia (also known as "unburned ammonia") is discharged outside the furnace, it will deteriorate the external environment of the furnace. Therefore, when using ammonia as the fuel gas for the furnace, it is necessary to measure the concentration of unburned ammonia in the furnace exhaust gas in order to suppress the discharge of unburned ammonia to the outside of the furnace.

[0005] In response, Patent Document 1 discloses a method for analyzing ammonia gas discharged from the outlet of a denitrification device for treating boiler exhaust gas. Specifically, when analyzing ammonia gas containing sulfur dioxide using the indophenol method, SO3 in the absorbent is removed by distillation. 2- Ions are added to improve analytical accuracy. The indophenol method, also known as the indophenol blue spectrophotometric method, involves absorbing ammonia from a gas with boric acid solution, then adding sodium phenolpentocyanonitrosoferric(III) solution and sodium hypochlorite solution to generate indophenol blue. The concentration of ammonia in the gas is calculated by measuring the absorbance (640 nm).

[0006] Besides the indophenol method, ion chromatography is another known method for analyzing ammonia in waste gas. Ion chromatography involves absorbing ammonia from the gas with boric acid solution, injecting the analytical sample solution into an ion chromatograph, obtaining a chromatogram of ammonium ions, and calculating the ammonia concentration in the gas based on the ammonium ion concentration.

[0007] Furthermore, Patent Document 2 discloses analytical methods for ammonia nitrogen, nitric acid / nitrite nitrogen, and total nitrogen. Specifically, the method describes a method in which ammonia gas is oxidized into NO gas using an oxidizing catalyst disposed in the combustion section of a heated reaction tube, and the NO gas is then sent to a chemiluminescent NO detector for analysis of ammonia nitrogen.

[0008] Furthermore, Non-Patent Document 1 discloses a dry gas measurement method for determining ammonia concentration using an infrared analyzer. Specifically, it discloses a method of installing a cooler in the piping that supplies the gas to be measured to the infrared analyzer, and supplying the dehumidified gas to the infrared analyzer therefrom.

[0009] Existing technical documents

[0010] Patent documents

[0011] Patent Document 1: Japanese Patent Application Publication No. 61-17955

[0012] Patent Document 2: Japanese Patent Application Publication No. 2001-21546

[0013] Non-patent literature

[0014] Non-Patent Literature 1: Toshio Miyamoto, "Implementation Status of Infrared Gas Analyzers", Industrial Chemical Journal, Chemical Society of Japan, November 1963, Vol. 66, No. 11, pp. 1561-1563 Summary of the Invention

[0015] The problem that the invention aims to solve

[0016] However, if the above-mentioned existing technology is applied to the determination of the concentration of unburned ammonia in the exhaust gas of a heating furnace, the following problems will arise.

[0017] First, to determine ammonia concentration using the method disclosed in Patent Document 1, the process involves steps such as absorption of ammonia gas into an absorption liquid, reaction with reagents, and analysis. That is, batch processing is required for ammonia concentration determination, and obtaining the results takes a certain amount of time (e.g., more than 10 minutes). Therefore, it is difficult to continuously determine ammonia concentration. This is also true when using ion chromatography to determine ammonia concentration.

[0018] Furthermore, if the method disclosed in Patent Document 2 is to be applied to the determination of the concentration of unburned ammonia in the exhaust gas of a heating furnace, it is necessary to pipe the ammonia-containing exhaust gas to the component measuring device. However, ammonia is highly soluble in water, so the temperature inside the pipes transporting the exhaust gas must be maintained above the dew point of the exhaust gas to prevent the ammonia in the exhaust gas from being removed by the moisture in the pipes. Therefore, the auxiliary equipment for measuring ammonia concentration becomes larger, increasing equipment costs. In addition, because ammonia is corrosive, corrosion of the pipes and pumps transporting the exhaust gas is likely to occur, posing a risk of leakage of ammonia-containing exhaust gas due to pipe corrosion. Therefore, the overall maintenance burden of the measuring device for measuring the ammonia concentration in exhaust gas is relatively large.

[0019] Furthermore, if the method disclosed in Non-Patent Document 1 is to be applied to the determination of the concentration of unburned ammonia in the exhaust gas of a heating furnace, dehumidification of the exhaust gas is required as a pretreatment for the component analysis. However, ammonia is highly soluble in water, and therefore dissolves in the moisture condensed during the dehumidification process. Consequently, a portion of the ammonia in the exhaust gas is removed before it is introduced into the component analysis device, leading to a decrease in the accuracy of the ammonia concentration determination.

[0020] This invention was made to address the aforementioned problems of the prior art. Its objective is to provide a method for estimating the concentration of unburned ammonia, enabling a simple online determination of the ammonia concentration in the exhaust gas of a furnace using ammonia as fuel gas, which suppresses carbon dioxide emissions. Furthermore, another objective of this invention is to provide an operating method for a furnace, an operating method for a burner device, and a control device for a furnace that suppresses the discharge of unburned ammonia as exhaust gas from the furnace.

[0021] Methods for solving problems

[0022] [1] A method for estimating the concentration of unburned ammonia, wherein the concentration of unburned ammonia contained in exhaust gas from a furnace heated by a burner using fuel gas containing ammonia and carbon-containing fuel is estimated, wherein the method for estimating the concentration of unburned ammonia includes: a determination step of determining a correlation between a carbon monoxide concentration in the exhaust gas of the furnace and an unburned ammonia concentration; a measurement step of measuring a carbon monoxide concentration in the exhaust gas of the furnace during operation of the furnace; and an estimation step of estimating the concentration of unburned ammonia contained in the exhaust gas of the furnace based on the carbon monoxide concentration measured in the measurement step and the correlation between the carbon monoxide concentration and the unburned ammonia concentration determined in the determination step.

[0023] [2] According to the method for estimating the concentration of unburned ammonia described in [1], in the determination step, for each of the multiple categories into which the operating conditions of the heating furnace are classified, the correlation between the concentration of carbon monoxide in the exhaust gas of the heating furnace and the concentration of unburned ammonia is determined.

[0024] [3] According to the method for estimating the concentration of unburned ammonia as described in [1] or [2], wherein the heating furnace is a conveying heating furnace that heats the material to be heated while conveying it from the loading section to the unloading section, and in the measurement step, the concentration of carbon monoxide contained in the exhaust gas of the heating furnace is measured at at least one of the flue from which the exhaust gas is discharged from the heating furnace, the loading section and the unloading section.

[0025] [4] A method for estimating the concentration of unburned ammonia, wherein the concentration of unburned ammonia contained in the exhaust gas of a burner device that performs burner heating using fuel gas containing ammonia and carbon-containing fuel is estimated, wherein the method for estimating the concentration of unburned ammonia includes: a determination step of determining a correlation between the concentration of carbon monoxide contained in the exhaust gas of the burner device and the concentration of unburned ammonia; a measurement step of measuring the concentration of carbon monoxide contained in the exhaust gas of the burner device when burner heating is performed by the burner device; and an estimation step of estimating the concentration of unburned ammonia contained in the exhaust gas of the burner device based on the concentration of carbon monoxide measured in the measurement step and the correlation between the concentration of carbon monoxide and the concentration of unburned ammonia determined in the determination step.

[0026] [5] According to the method for estimating the concentration of unburned ammonia described in [4], wherein, in the determination step, for each of the multiple categories into which the operating conditions of the burner equipment are classified, the correlation between the concentration of carbon monoxide in the exhaust gas of the burner equipment and the concentration of unburned ammonia is determined.

[0027] [6] A method of operating a heating furnace includes an operating step in which the operating conditions of the heating furnace are operated such that the concentration of unburned ammonia contained in the exhaust gas discharged from the heating furnace is reduced when the estimated value of the unburned ammonia concentration obtained by the estimation method of the unburned ammonia concentration described in [3] is above a predetermined value.

[0028] [7] According to the method of operating the heating furnace described in [6], the operating conditions of the heating furnace that are changed in the operation steps include at least one of the flow rate of combustion air for heating the burner, the flow rate of the fuel gas, the air ratio of the fuel gas to the theoretical air volume, and the mixing ratio of the ammonia to the carbon-containing fuel.

[0029] [8] A method of operating a burner device includes an operating step in which the operating conditions of the burner device are operated such that the concentration of unburned ammonia contained in the exhaust gas discharged from the burner device is reduced when the estimated value of the unburned ammonia concentration obtained by the estimation method for the unburned ammonia concentration described in [4] is above a predetermined value.

[0030] [9] According to the method of operating the burner device described in [8], wherein the operating conditions of the burner device that are changed in the operation steps include at least one of the flow rate of combustion air for heating the burner, the flow rate of the fuel gas, the air ratio of the fuel gas to the theoretical air volume, and the mixing ratio of the ammonia to the carbon-containing fuel.

[0031]

[10] A control device for a heating furnace, the heating furnace using a fuel gas containing ammonia and carbon-containing fuel to perform burner heating, wherein the control device for the heating furnace includes: a storage unit for storing a correlation between the concentration of carbon monoxide contained in the exhaust gas of the heating furnace and the concentration of unburned ammonia; an acquisition unit for acquiring the concentration of carbon monoxide contained in the exhaust gas of the heating furnace as measured during the operation of the heating furnace; an estimation unit for estimating the concentration of unburned ammonia contained in the exhaust gas of the heating furnace based on the carbon monoxide concentration acquired by the acquisition unit and the correlation between the carbon monoxide concentration stored in the storage unit and the concentration of unburned ammonia; and an operation amount calculation unit for calculating an operation amount for operating conditions of the heating furnace to make the estimated value less than the predetermined value when the estimated value of the unburned ammonia concentration estimated by the estimation unit is above a predetermined value.

[0032] Invention Effects

[0033] According to the method for estimating the concentration of unburned ammonia of the present invention, the concentration of ammonia contained in the exhaust gas of a furnace using ammonia that can suppress the emission of carbon dioxide as fuel gas can be measured online in a simple way. Furthermore, according to the furnace operation method, burner equipment operation method, and furnace control device of the present invention, ammonia that can suppress the emission of carbon dioxide can be used, and the emission of unburned ammonia as exhaust gas from the furnace can be suppressed. Attached Figure Description

[0034] [ Figure 1 ] Figure 1 This is a longitudinal sectional view of a heating furnace schematically illustrating one embodiment of the method for estimating the concentration of unburned ammonia, the operation method of the heating furnace, the operation method of the burner equipment, and the control device of the heating furnace to which the present invention is applied.

[0035] [ Figure 2 ] Figure 2This is a cross-sectional view of a heating furnace schematically illustrating one embodiment of the method for estimating the concentration of unburned ammonia, the method for operating the heating furnace, the method for operating the burner equipment, and the control device for the heating furnace to which the present invention is applied.

[0036] [ Figure 3 ] Figure 3 (a) and Figure 3 (b) is a side view or front view showing the details of a burner device that uses ammonia as fuel gas.

[0037] [ Figure 4 ] Figure 4 (a) and Figure 4 (b) in the diagram is a side view or front view showing the details of a burner device that does not use ammonia as a fuel gas.

[0038] [ Figure 5 ] Figure 5 This is a graph showing the correlation between the concentration of carbon monoxide and the concentration of unburned ammonia in the exhaust gas from a burner when the combustion rate of carbon-containing fuels in the fuel gas is faster than that of ammonia.

[0039] [ Figure 6 ] Figure 6 (a) and Figure 6 (b) shows the correlation between carbon monoxide concentration and unburned ammonia concentration in the exhaust gas from the burner equipment when the combustion rate of ammonia in the fuel gas is equal to that of carbon-containing fuel, and when the combustion rate of ammonia in the fuel gas is faster than that of carbon-containing fuel.

[0040] [ Figure 7 ] Figure 7 This is a schematic diagram illustrating an example of the configuration of a CO concentration meter in a heating furnace, representing one embodiment of the method for estimating the concentration of unburned ammonia, the operation method of the heating furnace, the operation method of the burner equipment, and the control device for the heating furnace according to the present invention.

[0041] [ Figure 8 ] Figure 8 It is a graph showing the correlation between the concentration of carbon monoxide and the concentration of unburned ammonia in the exhaust gas discharged from the flue of the heating furnace.

[0042] [ Figure 9 ] Figure 9 This is a diagram schematically illustrating a heating furnace in which the method for estimating the concentration of unburned ammonia according to the present invention is applied in another manner.

[0043] [ Figure 10 ] Figure 10 This is a block diagram illustrating an example of the structure of the control device for the heating furnace of the present invention.

[0044] [ Figure 11 ] Figure 11 This is a diagram schematically illustrating a test furnace used to determine the correlation between the concentration of carbon monoxide and the concentration of unburned ammonia in the exhaust gas of a heating furnace in the method for estimating the concentration of unburned ammonia of the present invention.

[0045] [ Figure 12 ] Figure 12 This is a diagram illustrating an example of the steps for determining the correlation between the concentration of carbon monoxide in the exhaust gas of a heating furnace and the concentration of unburned ammonia in the method for estimating the concentration of unburned ammonia of the present invention.

[0046] [ Figure 13 ] Figure 13 This is a graph showing an example of the estimated value of unburned ammonia concentration based on the estimation method of the present invention. Detailed Implementation

[0047] Hereinafter, with reference to the accompanying drawings, the embodiments of the method for estimating the concentration of unburned ammonia, the method for operating the heating furnace, the method for operating the burner equipment, and the control device for the heating furnace of the present invention will be described in detail.

[0048] <Heating Furnace>

[0049] Figure 1 A longitudinal sectional view of a heating furnace 1, illustrating a method for estimating unburned ammonia concentration, a method for operating a heating furnace, a method for operating a burner device, and a control device for the heating furnace, is shown schematically according to one embodiment of the present invention. Additionally, Figure 2 A schematic cross-sectional view of the heating furnace 1 is shown.

[0050] The heating furnace 1 is equipped with a first burner device 20a-20d and a second burner device 30a-30f for igniting fuel gas. These devices serve as heat sources to raise the temperature of the material S, which is placed inside the heating furnace 1, to a predetermined temperature. Details regarding the first burner device 20a-20d and the second burner device 30a-30f will be described later. The material S to be heated in the heating furnace 1 is primarily a metal, and can be any type of ferrous or non-ferrous metal. The heating temperature of the material S by the heating furnace 1 is, for example, 700-1400°C.

[0051] In this embodiment, the example is described where a slab before rolling, supplied to a hot rolling production line or a thick plate rolling production line for steel, is used as the material to be heated, and is heated using a heating furnace 1. For example, when heating a slab supplied to a hot rolling production line for steel using a heating furnace 1, the slab cast by a continuous casting device or the like is heated to a predetermined heating temperature (e.g., around 1100~1300°C).

[0052] like Figure 1 and Figure 2 As shown, the heating furnace 1 includes a loading section 11 for loading steel (slab) S, which is the material to be heated, and a discharging section 12 for removing (extracting) the heated steel S. For example, steel S manufactured by a continuous casting production line is transported to the loading side of the heating furnace 1 and loaded into the heating furnace 1 from the loading section 11 according to the production plan of a hot rolling production line or the like. The interior of the heating furnace 1 is divided into multiple sections, mostly consisting of a heating section consisting of 2 to 8 sections on the upstream side and a soaking section consisting of 1 to 3 sections on the downstream side. The interior of the heating furnace 1 is usually equipped with a fixed slide rail 13f for placing the steel S and a moving slide rail 13m for conveying the steel S. The heating furnace 1 equipped with the fixed slide rail 13f and the moving slide rail 13m is called a walking beam continuous heating furnace. Walking beam continuous heating furnaces are classified as conveyor heating furnaces that heat the material while conveying it from the loading section to the discharging section.

[0053] In the operation of heating furnace 1, the average temperature of the steel S charged into heating furnace 1 is gradually increased by controlling the internal atmosphere temperature of each section of heating furnace 1 to be different, so that the steel S reaches the specified target heating temperature (the target temperature of the slab removed from heating furnace 1). The steel S heated to the target heating temperature is supplied to the hot rolling line through the discharge section 12.

[0054] like Figure 1 As shown, inside the heating furnace 1, multiple first burner devices 20a-20d and second burner devices 30a-30f are provided along the conveying direction TD of the steel S. If the fuel gas is burned by the first burner devices 20a-20d and the second burner devices 30a-30f, the internal temperature of the heating furnace 1 rises, and the temperature of the steel S increases due to radiation from the furnace wall of the heating furnace 1. Additionally, the temperature of the steel S also rises due to convection of the atmospheric gas generated inside the heating furnace 1. Alternatively, the temperature of the steel S can also rise by direct contact between the flames from the first burner devices 20a-20d and the second burner devices 30a-30f and the steel S.

[0055] Inside the heating furnace 1, in addition to the space for emitting flames from the first burner devices 20a-20d and the second burner devices 30a-30f, space is also needed for placing and conveying the steel S. Therefore, the heating furnace is characterized by having a larger internal volume relative to the combustion energy input into the furnace compared to turbines, boilers, etc., which are designed for combustion reactions to occur internally.

[0056] Furnace internal volume per unit of combustion energy (m³) 3 The representative value of / MW, for example, is 2m in a gas turbine. 3Around / MW, in pulverized coal boilers, it is 6m 3 Around / MW, 2m in gas / oil boilers 3 Around / MW, in contrast, it is 10~16m in the heating furnace. 3 The capacity is around 11-13 m³ / MW, which is relatively large. In heating furnaces used in hot rolling mills for steel production lines, this is typically 11-13 m³ / MW. 3 Around / MW.

[0057] During the operation of the heating furnace 1, the doors (opening and closing doors) of the loading section 11 and the unloading section 12 are closed, and the internal pressure of the heating furnace 1 is higher than atmospheric pressure. Furthermore, if the doors of the loading section 11 and the unloading section 12 are temporarily opened during the loading and unloading of steel S, a pressure difference is generated between the central part of the heating furnace 1 and the vicinity of the doors. Therefore, the gas generated inside the heating furnace 1 by heating with the burner (hereinafter referred to as exhaust gas) flows from the high-pressure area to the low-pressure area. When the doors of the heating furnace 1 are open, exhaust gas flow is more likely to occur in the direction of discharge from the furnace 1 through the openings.

[0058] like Figure 1 and Figure 2 As shown, the heating furnace 1 includes a flue 14 for discharging exhaust gas generated inside the furnace through heating by a burner. The flue 14 is connected to an exhaust gas treatment device 15 for removing nitrogen oxides and unburned ammonia from the exhaust gas. The exhaust gas treatment device 15 reduces the concentration of nitrogen oxides and unburned ammonia in the exhaust gas to meet prescribed emission standards. Therefore, even if the exhaust gas contains nitrogen oxides and unburned ammonia, the concentration of nitrogen oxides and unburned ammonia can be reduced by the exhaust gas treatment device 15 connected to the flue 14, suppressing the emission of nitrogen oxides and unburned ammonia to the outside of the heating furnace 1. It should be noted that, in the following description, "suppressed" means that the concentration of nitrogen oxides and unburned ammonia in the exhaust gas decreases to, for example, below a predetermined upper limit value for the concentration of nitrogen oxides and unburned ammonia, in a manner not exceeding legal or other restrictions.

[0059] The flue 14 only needs to be able to discharge the exhaust gas generated by the heating furnace 1 to the outside of the furnace, and can be configured at any position in the heating furnace 1, but if Figure 1 and Figure 2 As shown, it is preferably positioned close to the loading section 11 of the heating furnace 1. In this way, the slabs transported to the loading side of the heating furnace 1 are preheated by the exhaust gas from the heating furnace 1, which is advantageous in terms of thermal efficiency. In addition, the flue 14 may also be equipped with a heat recovery device (not shown) for recovering the sensible heat of the exhaust gas.

[0060] like Figure 1 and Figure 2As shown, in the heating furnace 1, in order to prevent a temperature difference between the upper and lower surfaces of the steel S, the first burner devices 20a-20d and the second burner devices 30a-30f are mostly arranged on the upper and lower surface sides of the steel S, respectively. Furthermore, as... Figure 2 As shown, they are mostly arranged on both sides of the conveying direction TD of the steel S in a way that does not generate a temperature difference between the front end S1 and the rear end S2 of the steel S.

[0061] like Figure 1 As shown, the heating furnace 1 is equipped with a control computer 10 for controlling the operating status of the heating furnace 1. The control computer 10 calculates the operating conditions of the first burner equipment 20a to 20d and the second burner equipment 30a to 30f of the heating furnace 1 to heat the steel S to a predetermined target heating temperature. In addition, the control computer 10 controls the various actions of loading the steel S into the heating furnace 1, conveying it into the heating furnace 1, and removing it from the heating furnace 1, namely the opening and closing of the doors of the loading section 11 and the unloading section 12, and the movement of the moving slide rail 13m.

[0062] The furnace employing the method for estimating unburned ammonia concentration, the furnace operation method, the burner equipment operation method, and the furnace control device of the present invention includes, inside the furnace, one or more burner devices that use fuel gas F1, comprising ammonia and carbon-containing fuel, to perform burner heating. Furthermore, the furnace employing the method for estimating unburned ammonia concentration, the furnace operation method, the burner equipment operation method, and the furnace control device of the present invention preferably also includes a burner device that uses fuel gas F2, which does not contain ammonia, to perform burner heating. Hereinafter, the ammonia contained in the fuel gas refers to ammonia in a vaporized state.

[0063] In this embodiment, the first burner devices 20a-20d and the second burner devices 30a-30f are respectively equivalent to burner devices that use fuel gas F1 containing ammonia F11 and carbon-containing fuel F12 to perform burner heating. The second burner devices 30a-30f are respectively equivalent to burner devices that use fuel gas F2 that does not contain ammonia to perform burner heating.

[0064] like Figure 1 and Figure 2As shown, in the heating furnace 1, two of the four first burner devices 20a and 20b, located on the upper side of the central portion of the heating furnace 1 in the conveying direction TD, are arranged. The remaining two first burner devices 20c and 20d are located on the lower side of the central portion of the heating furnace 1 in the conveying direction TD. Additionally, two of the six second burner devices 30a and 30d are arranged on the upper and lower sides of the upstream portion of the heating furnace 1 in the conveying direction TD. The remaining four second burner devices 30b, 30c, 30e, and 30f are arranged on the upper and lower sides of the downstream portion of the heating furnace 1 in the conveying direction TD.

[0065] <First Burner Equipment>

[0066] Figure 3 (a) and Figure 3 (b) shows details of a burner device, namely the first burner device 20a to 20d, which uses fuel gas F1 including ammonia F11 and carbon-containing fuel F12 to carry out burner heating. Figure 3 (a) in the figure is a side view of the first burner device 20a-20d. Figure 3 (b) in the diagram is the front view.

[0067] like Figure 3 (a) and Figure 3 As shown in (b), the first burner devices 20a-20d use fuel gas F1 containing ammonia F11 and carbon-containing fuel F12 and combustion air A to perform burner heating by injecting flames into the furnace of the heating furnace 1. The first burner devices 20a-20d include: a burner nozzle 21 for injecting flames into the furnace of the heating furnace 1; a fuel gas supply system 22 for supplying fuel gas F1 to the burner nozzle 21; and a combustion air supply system 26 for supplying combustion air A to the burner nozzle 21. The first burner devices 20a-20d preferably include an air ratio control unit 27, which controls the air ratio (also simply referred to as air ratio) of the fuel gas F1 supplied to the burner nozzle 21 relative to the theoretical air volume.

[0068] The fuel gas supply system 22 is a piping that supplies fuel gas F1, which contains ammonia F11 and carbon-containing fuel F12, to the burner nozzle 21. The combustion air supply system 26 is a piping that supplies combustion air A to the burner nozzle 21.

[0069] The burner nozzle 21 is, for example, a double-tube nozzle, from which fuel gas F1 is injected into the furnace through the inner tube and combustion air A is injected into the furnace through the outer tube. As a result, a combustible mixture of fuel gas F1 and combustion air A is formed in front of the burner nozzle 21, and a flame is injected into the interior of the heating furnace 1 from the front end of the burner nozzle 21.

[0070] As in the first embodiment, when the heating furnace 1 has multiple first burner devices 20a to 20d, the mixing ratio of ammonia F11 and carbon-containing fuel F12 supplied to each of them, and the type of carbon-containing fuel F12, can be different or the same. However, setting the carbon-containing fuel F12 used for the fuel gas F1 supplied to the multiple first burner devices 20 to be of the same type can avoid complicating the supply equipment for supplying fuel gas F1 to the heating furnace 1 and increasing equipment costs, thus making it more economical.

[0071] Ammonia F11 is a flame-retardant fuel that is more difficult to ignite than ordinary fuels and burns more slowly. Therefore, in the first burner equipment 20a to 20d, by using fuel gas F1 mixed with carbon-containing fuel F12 in ammonia F11, the combustion stability can be improved compared to using ammonia F11 alone.

[0072] Carbon-containing fuel F12 refers to fuels that contain carbon as a constituent element. Because carbon is present in carbon, carbon-containing fuel F12 is burned when heated in a burner, producing carbon monoxide and carbon dioxide. Preferred carbon-containing fuels for F12 include methane, ethane, ethylene, acetylene, propane, propylene, butane, benzene, and carbon monoxide. Fossil fuels can be primarily used as carbon-containing fuel F12, but city gas, natural gas, and propane gas are also acceptable. Carbon-containing fuel F12 is not limited to fuels obtained from natural gas, but is preferably a synthetically produced fuel. It is preferable to use a fuel that is a proper blend of these fuels.

[0073] In the first embodiment, coal gas is used as the carbonaceous fuel F12. Coal gas is a gas obtained from coal. Preferably, the coal gas includes by-product gases generated in iron and steel plants, specifically, any one of coke oven gas, blast furnace gas, converter gas, or electric furnace gas. This is because they have the effect of stabilizing the combustion of ammonia F11.

[0074] Coke oven gas is a byproduct of the high-temperature dry distillation of coal used to produce coke. Blast furnace gas is a byproduct of the reduction of iron ore in a blast furnace to produce pig iron. Converter gas is a byproduct of the steelmaking process in a converter. Electric furnace gas is generated through the incomplete combustion of auxiliary fuels (carbon raisers) in an electric furnace.

[0075] Furthermore, as the gas, a mixture of blast furnace gas, coke oven gas, and converter gas (also known as M gas) is preferred. This is because by mixing gases with different calorific values, the heat required for heating the steel S can be supplied, and the operation of the heating furnace 1 can be carried out stably.

[0076] Furthermore, the fuel gas F1 used in the first burner device 20 may also be a fuel gas containing a third fuel gas in addition to ammonia F11 and carbon-containing fuel F12. The third fuel gas is a fuel that does not contain ammonia F11 and carbon-containing fuel F12. Hydrogen is preferably used as the third fuel gas, for example.

[0077] exist Figure 3 (a) and Figure 3 In (b), the case of using a mixture of ammonia F11 and coal gas F12 as fuel gas F1 in the first burner device 20 is illustrated.

[0078] Ammonia supply system 23 and coal gas supply system 24 are connected to fuel gas supply system 22. Ammonia F11 supplied from ammonia supply system 23 and coal gas F12 supplied from coal gas supply system 24 are mixed in mixing section 25 and supplied to burner nozzle 21 through fuel gas supply system 22.

[0079] For example, ammonia F11 is supplied from a tank storing ammonia F11 to an ammonia supply system 23, and the ammonia F11 is sent to a burner nozzle 21. For example, coal gas F12 is supplied from a tank storing coal gas to a coal gas supply system 24, and the coal gas F12 is sent to a burner nozzle 21.

[0080] In the middle of the ammonia supply system 23 and the coal gas supply system 24, it is preferable to have flow regulating valves 23v and 24v for adjusting the supply amount of each gas to the mixing section 25, and flow meters 23m and 24m for measuring the supply flow rate. In this way, the mixing ratio of ammonia F11 and coal gas F12 contained in fuel gas F1 can be adjusted.

[0081] It should be noted that flow meters 23m and 24m can estimate the flow rate of ammonia F11 or coal gas F12 by measuring the pressure of the gas supplied by ammonia supply system 23 or coal gas supply system 24. In this way, the flow rate can be easily estimated using a pressure gauge.

[0082] The mixing section 25 refers to the part where the supply pipes of the coal gas supply system 24 and the ammonia supply system 23 merge. Ammonia F11 and coal gas F12 are supplied from their respective supply pipes and then merge, thus allowing mixing even without a special stirring mechanism. The mixing section 25 only needs to be configured as a space with an appropriate volume at the point where these supply pipes merge. However, it is further preferable to include static mixing equipment such as a static mixer or a dynamic mixer with stirring function in the mixing section 25. In this way, fuel gas F1, which is a more uniform mixture of coal gas F12 and ammonia F11, can be generated.

[0083] Preferably, a flow regulating valve 26v for adjusting the flow rate of combustion air A supplied to the burner nozzle 21 and a flow meter 26m for measuring the supply flow rate are provided midway through the combustion air supply system 26 of the first burner device 20. This allows adjustment of the amount of combustion air A in the first burner device 20, thereby adjusting the air ratio during burner heating in the first burner device 20. For the flow meter 26m of the combustion air supply system 26, it is also preferable to estimate the flow rate by measuring the pressure of the supplied combustion air.

[0084] The air ratio control unit 27 controls the air ratio of fuel gas F1 to the stoichiometric air volume in the first burner devices 20a to 20d. The air ratio control unit 27 has the function of adjusting the air ratio of combustion air A to fuel gas F1 for each of the first burner devices 20a to 20d. Specifically, the air ratio control unit 27 uses flow meters 23m and 24m provided in the ammonia supply system 23 and the coal gas supply system 24 to measure the flow rate of fuel gas F1 supplied to the burner nozzle 21. Furthermore, the air ratio control unit 27 calculates the stoichiometric air volume required for complete combustion of fuel gas F1 based on the measured flow rate and fuel composition of fuel gas F1. Then, the air ratio control unit 27 adjusts the opening of the flow regulating valve 26v provided in the combustion air supply system 26 to control the air ratio of combustion air A to fuel gas F1 in the first burner devices 20a to 20d to a target air ratio set by the control computer 10, etc.

[0085] <Second Burner Equipment>

[0086] Figure 4 (a) and Figure 4 (b) in the text indicates the details of the burner equipment, namely the second burner equipment 30a to 30f, which uses fuel gas F2 that does not contain ammonia for burner heating. Figure 4 (a) in the figure is a side view of the second burner device 30a-30f. Figure 4 (b) in the diagram is the front view.

[0087] The second burner equipment 30a-30f has the following features: Figure 3 (a) and Figure 3 In the first burner devices 20a-20d shown in (b), the ammonia supply system 23, and the flow meter 23m and flow regulating valve 23v disposed in the ammonia supply system 23 are omitted. Furthermore, in the second burner devices 30a-30f, the mixing unit 25 for mixing ammonia F11 and coal gas F12 is not required. In other respects, the second burner devices 30a-30f can be constructed in the same manner as the first burner devices 20a-20d.

[0088] like Figure 4 (a) and Figure 4 As shown in (b), the second burner devices 30a-30f use fuel gas F2 composed of coal gas and combustion air A to perform burner heating by injecting flames into the furnace of the heating furnace 1. The second burner devices 30a-30f include a burner nozzle 31 for injecting flames into the furnace of the heating furnace 1, a fuel gas supply system 32 for supplying fuel gas F2 to the burner nozzle 31, and a combustion air supply system 36 for supplying combustion air A to the burner nozzle 31. The second burner devices 30a-30f preferably include an air ratio control unit 37, which controls the air ratio (also simply referred to as air ratio) of the fuel gas F2 supplied to the burner nozzle 31 relative to the theoretical air volume.

[0089] The fuel gas supply system 32 is a piping system that supplies fuel gas F2 to the burner nozzle 31. The combustion air supply system 36 is a piping system that supplies combustion air A to the burner nozzle 31.

[0090] The burner nozzle 31 is, for example, a double-tube nozzle, from which fuel gas F2 is injected into the furnace through the inner tube and combustion air A is injected into the furnace through the outer tube. As a result, a combustible mixture of fuel gas F2 and combustion air A is formed in front of the burner nozzle 31, and a flame is injected into the interior of the heating furnace 1 from the front end of the burner nozzle 31.

[0091] The coal gas used as fuel gas F2 in the second burner devices 30a to 30f can be the same as or different from the coal gas containing carbon-containing gas F11 in the fuel gas F1 used in the first burner device 20. Furthermore, the fuel gas F2 in the second burner devices 30a to 30f is not limited to coal gas. As fuel gas F2 in the second burner devices 30a to 30f, one or more of city gas, natural gas, and propane gas can be used, or a fuel gas mixture of two or more of these can be used. Additionally, as fuel gas F2 in the second burner device 30, carbon monoxide gas and methane (including methane extracted from natural gas and synthetically produced methane) can also be used.

[0092] <Correlation between carbon monoxide concentration and unburned ammonia concentration in exhaust gas>

[0093] As described above, in the first burner equipment 20a to 20d, a burner heating process is performed using fuel gas F1 containing ammonia F11 and carbon-containing fuel F12, and combustion air A, to inject a flame into the furnace. It is known that the combustion rates of ammonia F11 and carbon-containing fuel F12 are different. The combustion rate refers to the speed at which the fuel gas F1 enters the flame face at a right angle when the flame generated during burner heating unfolds. The combustion rate depends on the rate of chemical reaction between the unburned fuel gas F1 and the fuel air A, and the thermal conductivity.

[0094] Table 1 shows the combustion rates of ammonia and representative carbon-containing fuels. In Table 1, the combustion rate is expressed by the Weaver combustion rate coefficient (an index representing the relative value of the maximum combustion rate in the fuel gas and combustion air mixture when the maximum combustion rate of hydrogen is set to 100).

[0095] [Table 1]

[0096] As shown in Table 1, there is a difference in the combustion rate between ammonia and carbon-containing fuels. Therefore, although the fuel gas F1 injected from the burner nozzle 21 of the first burner devices 20a to 20d generates a mixture with the combustion air A and undergoes a combustion reaction, the combustion rate of the ammonia F11 contained in the fuel gas F1 differs from that of the carbon-containing fuel F12.

[0097] For example, if the combustion rate of carbon-containing fuel F12 in fuel gas F1 is faster than that of ammonia F11, the carbon-containing fuel F12 in fuel gas F1 combines with oxygen in the combustion air A, thus the combustion reaction of carbon-containing fuel F12 proceeds first. Furthermore, through the combustion of carbon-containing fuel F12, the oxygen in the combustion air A is consumed first, resulting in insufficient oxygen during the combustion of ammonia F11 in fuel gas F1. At this time, through the combustion reaction of carbon-containing fuel F12, the carbon atoms contained in carbon-containing fuel F12 are oxidized through complete combustion to generate carbon dioxide, making it difficult to generate carbon monoxide through incomplete combustion. In contrast, during the combustion of ammonia F11, the oxygen required for the combustion reaction of ammonia F11 is insufficient, resulting in unburned ammonia residue. Therefore, unburned ammonia remains in the exhaust gas of the first burner equipment from 20a to 20d, while on the other hand, the generation of carbon monoxide can be suppressed.

[0098] Next, if the air ratio of fuel gas F1 to the theoretical air volume decreases, the amount of oxygen in the combustion air A becomes insufficient relative to the combustion reaction of the preceding carbon-containing fuel F12. Therefore, the combustion of carbon-containing fuel F12 becomes incomplete combustion, producing carbon monoxide together with carbon dioxide.

[0099] In contrast, when the combustion rate of ammonia F11 is slower than that of carbonaceous fuel F12, the oxygen in the combustion air A is consumed first through the combustion reaction of the carbonaceous fuel F12. Therefore, the combustion of ammonia F11 becomes more incomplete, promoting the formation of unburned ammonia. This results in the following correlation: the more carbon monoxide contained in the exhaust gas discharged from the first burner equipment 20a–20d, the greater the increase in unburned ammonia.

[0100] As described above, this invention is based on the insight that when a burner is heated using fuel gas F1 containing ammonia F11 and carbon-containing fuel F12, there is a correlation between the concentration of unburned ammonia and the concentration of carbon monoxide in the exhaust gas discharged from the burner. Specifically, this invention estimates the concentration of unburned ammonia in the exhaust gas based on the correlation between the concentration of unburned ammonia and the concentration of carbon monoxide in the exhaust gas discharged from the first burner device 20a to 20d, using measured values ​​of the carbon monoxide concentration in the exhaust gas.

[0101] Figure 5 The correlation between carbon monoxide concentration and unburned ammonia concentration in the exhaust gas from the first burner device 20a–20d is shown when the combustion rate of carbon-containing fuel F12 contained in fuel gas F1 is faster than that of ammonia F11.

[0102] like Figure 5As shown, when the combustion rate of carbon-containing fuel F12 in fuel gas F1 is faster than that of ammonia F11, the rate of complete combustion of carbon-containing fuel F12 is faster than that of ammonia F11. Therefore, under the conditions of complete combustion of carbon-containing fuel F12 (in... Figure 5 The chart shown indicates that, under the condition that "CO concentration" becomes zero, the exhaust gas contains unburned ammonia. The greater the difference between the combustion rate of ammonia F11 and the combustion rate of carbon-containing fuel F12, the higher the concentration of unburned ammonia when the CO concentration becomes zero. Figure 5 The larger the value of the intercept on the vertical axis of the coordinate graph shown, the better.

[0103] Furthermore, when the air ratio of fuel gas F1 to the theoretical air volume is reduced from 1.0, the carbon monoxide concentration in the exhaust gas increases, and the oxygen required for the combustion reaction of ammonia F11 becomes even less sufficient, leading to an increase in the concentration of unburned ammonia. At this time, the correlation between the concentration of unburned ammonia and the carbon monoxide concentration in the exhaust gas discharged from the first burner unit from 20a to 20d is linear or approximately linear. Additionally, in Figure 5 In the coordinate graph shown, the slope of the unburned ammonia concentration relative to the carbon monoxide concentration varies depending on the combustion rates of the ammonia F11 contained in the fuel gas F1 and the carbon-containing fuel F12. Specifically, the combustion rate of the carbon-containing fuel F12 is greater than that of the ammonia F11, and the greater the difference, the greater the slope.

[0104] Figure 6 (a) shows the correlation between carbon monoxide concentration and unburned ammonia concentration in the exhaust gas when the combustion rate of ammonia F11 contained in fuel gas F1 is equal to that of carbon-containing fuel F12. Additionally, Figure 6 (b) shows the correlation between the concentration of carbon monoxide in the exhaust gas and the concentration of unburned ammonia when the combustion rate of ammonia F11 contained in fuel gas F1 is faster than that of carbon-containing fuel F12.

[0105] like Figure 6 As shown in (a), when the combustion rate of ammonia F11 contained in fuel gas F1 is equal to the combustion rate of carbon-containing fuel F12, the rate of complete combustion of ammonia F11 is equal to the rate of complete combustion of carbon-containing fuel F12. Therefore, under the condition of complete combustion of carbon-containing fuel F12 (in... Figure 6 Under the condition that "CO concentration" becomes zero in the chart shown in (a), no unburned ammonia remains in the exhaust gas. That is, both ammonia F11 and carbon-containing fuel F12 are completely burned.

[0106] Moreover, when the air ratio of fuel gas F1 to theoretical air volume is reduced from 1.0, both ammonia F11 and carbon-containing fuel F12 become oxygen-deficient in the combustion reaction, resulting in an increase in carbon monoxide concentration in the exhaust gas, as well as an increase in unburned ammonia concentration.

[0107] In addition, such as Figure 6 As shown in (b), when the combustion rate of ammonia F11 contained in fuel gas F1 is faster than the combustion rate of carbon-containing fuel F12, the rate of complete combustion of ammonia F11 is faster than the rate of complete combustion of carbon-containing fuel F12. Therefore, under the condition of complete combustion of ammonia F11 ( Figure 6 Under the condition that the "unburned ammonia concentration" is zero in the coordinate graph shown in (b), the exhaust gas contains carbon monoxide.

[0108] In addition, when the air ratio of fuel gas F1 to theoretical air volume is reduced from 1.0, the concentration of unburned ammonia in the exhaust gas increases, and the oxygen required for the combustion reaction of carbon-containing fuel F12 becomes even less, resulting in an increase in carbon monoxide concentration.

[0109] Thus, in the first burner equipment 20a to 20d that uses fuel gas F1 containing ammonia F11 and carbon-containing fuel F12 and combustion air A to heat the burner by injecting flames into the furnace, there is a correlation between the carbon monoxide concentration and the unburned ammonia concentration in the exhaust gas discharged from the first burner equipment 20 which is used for burner heating, based on the difference between the combustion rate of ammonia F11 and the combustion rate of carbon-containing fuel F12.

[0110] <Estimation Methods for Unburned Ammonia Concentration - First Approach>

[0111] As embodiments of the method for estimating the concentration of unburned ammonia according to the present invention, the first and second embodiments are described below.

[0112] In the methods for estimating the concentration of unburned ammonia in the first and second methods, the concentration of unburned ammonia contained in the exhaust gas discharged from a burner device that uses fuel gas containing ammonia and carbon-containing fuel for burner heating is estimated.

[0113] In the first method for estimating the concentration of unburned ammonia, firstly, a determination step is performed to pre-determine the correlation between the concentration of carbon monoxide contained in the exhaust gas of the heating furnace 1 and the concentration of unburned ammonia. Next, during the operation of the heating furnace 1, when the furnace is heated by the first burner device 20a to 20d, a measurement step is performed to determine the concentration of carbon monoxide contained in the exhaust gas of the heating furnace 1. Further, an estimation step is performed, based on the correlation between the carbon monoxide concentration measured in the measurement step and the concentration of unburned ammonia determined in the determination step, to estimate the concentration of unburned ammonia contained in the exhaust gas of the heating furnace 1.

[0114] Regarding these determination, measurement, and estimation steps, the first and second methods are explained in detail below.

[0115] First, in the determination step, the correlation between the carbon monoxide concentration and the unburned ammonia concentration in the exhaust gas of the first burner device 20a-20d is determined in advance. To determine the correlation between the carbon monoxide concentration and the unburned ammonia concentration in the exhaust gas of the first burner device 20a-20d, the following method can be applied, for example.

[0116] Figure 7 This describes the flow of exhaust gas generated by the flames injected from the first burner devices 20a to 20d within the heating furnace 1 and an example of the configuration of the CO concentration meter 18.

[0117] like Figure 7 As shown, since airflow is generated within the heating furnace 1, the exhaust gas generated by the flames injected from the first burner devices 20a to 20d flows downstream of the airflow within the furnace. Therefore, in the first embodiment, a CO concentration meter 18 is installed downstream of the airflow within the first burner devices 20a to 20d to measure the carbon monoxide concentration contained in the exhaust gas discharged from the first burner devices 20a to 20d. This allows for online measurement of the carbon monoxide concentration contained in the exhaust gas discharged from the first burner devices 20a to 20d.

[0118] Additionally, downstream of the gas flow within the furnace of the first burner equipment 20a-20d, exhaust gas discharged from the first burner equipment 20a-20d is collected, and actual data on the concentration of unburned ammonia contained in the exhaust gas are collected using a gas composition measuring device (not shown). The gas composition measuring device can be any device capable of measuring the concentration of unburned ammonia in wet gases; devices utilizing methods such as indophenol method or ion chromatography can be used. The measurement of the unburned ammonia concentration using the gas composition measuring device is preferably performed offline.

[0119] In this way, the measured values ​​of carbon monoxide concentration in the exhaust gas emitted from the first burner equipment 20a-20d, determined online by the CO concentration meter 18, and the actual values ​​of unburned ammonia concentration obtained offline by sampling the exhaust gas can be obtained as actual data. Furthermore, by changing the air ratio in the first burner equipment 20a-20d, multiple sets of actual data are obtained to determine the correlation between the carbon monoxide concentration and the unburned ammonia concentration in the exhaust gas from the first burner equipment 20a-20d.

[0120] Furthermore, the aforementioned determination step does not necessarily need to be performed during the operation of the heating furnace 1. For example, the correlation between the carbon monoxide concentration and the unburned ammonia concentration can be determined by injecting flames from the first burner devices 20a to 20d while the heating furnace 1 is stopped, and using the measured values ​​of the carbon monoxide concentration and the unburned ammonia concentration obtained therefrom. That is, the determination step can also be performed without heating the steel S in the heating furnace 1.

[0121] In the determination step, it is preferable to determine the correlation between the carbon monoxide concentration and the unburned ammonia concentration in the exhaust gas of the first burner equipment 20 for each type of operating condition of the first burner equipment 20a to 20d. Here, the type of operating condition refers to classifying the burner heating conditions and combustion state indicators representing the first burner equipment 20a to 20d into two or more categories. Then, in the determination step, the correlation between the carbon monoxide concentration and the unburned ammonia concentration is determined according to these categories. That is, as the operating conditions for burner heating of the first burner equipment 20a to 20d, the composition, type, and mixing ratio of ammonia F11 and carbon-containing fuel F12 used for burner heating are selected. Moreover, it is preferable to classify these operating conditions into, for example, 2 to 10 types, and for each of the classified types, determine the correlation between the carbon monoxide concentration and the unburned ammonia concentration in the exhaust gas of the first burner equipment 20a to 20d.

[0122] In determining the correlation between carbon monoxide concentration and unburned ammonia concentration, a table can be constructed for each type of operating condition. Alternatively, the correlation between carbon monoxide concentration and unburned ammonia concentration can be approximated using functions such as linear regression, with the function derived for each type of operating condition.

[0123] In the measurement step, when the burner is heated using the first burner equipment 20a to 20d, the concentration of carbon monoxide contained in the exhaust gas of the first burner equipment 20a to 20d is measured.

[0124] like Figure 7 As shown, in the first burner devices 20a to 20d, a CO concentration meter 18 disposed downstream of the airflow inside the furnace of the first burner devices 20a to 20d can be used to measure the carbon monoxide concentration in the exhaust gas online. The carbon monoxide concentration in the exhaust gas discharged from the first burner device 20 is preferably measured continuously using the CO concentration meter 18 at a period of, for example, 1 second to 60 seconds.

[0125] In the estimation step, the concentration of unburned ammonia in the exhaust gas of the first burner equipment 20a-20d is estimated based on the correlation between the carbon monoxide concentration measured in the determination step and the carbon monoxide and unburned ammonia concentrations predetermined in the determination step. Since the correlation between the carbon monoxide concentration and the unburned ammonia concentration in the exhaust gas of the first burner equipment 20a-20d is predetermined in the determination step, the concentration of unburned ammonia in the exhaust gas of the first burner equipment 20a-20d can be estimated by using the carbon monoxide concentration measured by the CO concentration meter 18. When the correlation between the carbon monoxide concentration and the unburned ammonia concentration is determined by a function, the unburned ammonia concentration can be calculated by inputting the carbon monoxide concentration measured by the CO concentration meter 18 into the function, thereby enabling continuous online estimation of the unburned ammonia concentration.

[0126] <Estimation Methods for Unburned Ammonia Concentration - Second Approach>

[0127] In the first aspect of the above-mentioned method for estimating unburned ammonia concentration, in the determination step, the correlation between the concentration of unburned ammonia and the concentration of carbon monoxide contained in the exhaust gas discharged from the first burner equipment 20a to 20d is determined.

[0128] Here, as Figure 1 As shown, when the heating furnace 1 is equipped with a second burner device 30a to 30f in addition to the first burner device 20a to 20d, a certain correlation is also established between the carbon monoxide concentration and the unburned ammonia concentration in the exhaust gas discharged from the loading section 11, unloading section 12 and flue 14 of the heating furnace 1.

[0129] For example, when coal gas (F2) is used as fuel gas in the second burner devices 30a-30f, the concentration of carbon monoxide in the exhaust gas from the second burner devices 30a-30f increases when the burners of the second burner devices 30a-30f are heated to an oxygen-deficient state. However, since the fuel gas F2 used in the second burner devices 30a-30f does not contain ammonia, no unburned ammonia is generated in the second burner devices 30a-30f. Although ammonia may sometimes be present in the coal gas F2, its content is trace. Therefore, the amount of unburned ammonia generated from the second burner devices 30a-30f is very small compared to the amount of unburned ammonia discharged from the first burner devices 20a-20d, and the concentration of unburned ammonia generated from the second burner devices 30a-30f can be ignored.

[0130] Therefore, when the exhaust gas discharged from the first burner devices 20a to 20d merges with the exhaust gas discharged from the second burner devices 30a to 30f, the merged exhaust gas contains a total amount of carbon monoxide, including unburned ammonia generated by the first burner devices 20a to 20d, carbon monoxide generated by the first burner devices 20a to 20d, and carbon monoxide generated by the second burner devices 30a to 30f.

[0131] Therefore, if the exhaust gas discharged from the first burner equipment 20a-20d merges with the exhaust gas discharged from the second burner equipment 30a-30f, the overall volume of the exhaust gas changes, and thus the gas concentration changes. However, if... Figure 8 As shown, the correlation between the concentration of carbon monoxide and the concentration of unburned ammonia in the exhaust gas of the first burner equipment is maintained for 20a to 20d.

[0132] Thus, even when the second burner devices 30a to 30f are provided, since the exhaust gas discharged from the loading section 11, unloading section 12, and flue 14 of the heating furnace 1 is formed by the merging of the exhaust gas discharged from the first burner devices 20a to 20d and the exhaust gas discharged from the second burner devices 30a to 30f, a certain correlation exists between the carbon monoxide concentration and the unburned ammonia concentration contained in the exhaust gas of the heating furnace 1.

[0133] Based on this principle, in the second method for estimating the concentration of unburned ammonia, the correlation between the concentration of carbon monoxide and the concentration of unburned ammonia in the exhaust gas discharged from the entire heating furnace 1 is predetermined in the determination step of the first method. This will be explained below.

[0134] Figure 9 The image shows a longitudinal sectional view of a second-mode heating furnace 1, schematically illustrating the application of a method for estimating the concentration of unburned ammonia.

[0135] When the loading section 11 and unloading section 12 of the heating furnace 1 are open, the exhaust gas generated inside the heating furnace 1 is discharged from the loading section 11 and unloading section 12 of the heating furnace 1 along with the airflow inside the heating furnace 1. In addition, when the loading section 11 and unloading section 12 of the heating furnace 1 are closed, the exhaust gas is discharged from the flue 14.

[0136] Therefore, as Figure 9As shown, CO concentration meters 18a and 18b, used to measure the carbon monoxide concentration in the exhaust gas, are respectively installed at the openings of the loading section 11 and the unloading section 12 of the heating furnace 1. Additionally, a CO concentration meter 18c is installed at the location where the airflow from the heating furnace 1 to the exhaust gas treatment device 15 is generated, for the exhaust gas discharged from the flue 14. Furthermore, to estimate the concentration of unburned ammonia in the exhaust gas treated by the exhaust gas treatment device 15, a CO concentration meter 18d can be further installed downstream of the exhaust gas treatment device 15 in the airflow direction. Thus, the carbon monoxide concentration contained in the exhaust gas discharged from the loading section 11 and the unloading section 12 of the heating furnace 1, as well as the exhaust gas discharged from the flue 14, can be measured online.

[0137] It is not necessary to install all of the aforementioned CO concentration meters 18a to 18d. Preferably, at least one of the CO concentration meter 18a in the loading section 11 and the CO concentration meter 18b in the unloading section 12 of the heating furnace 1 is installed. The exhaust gas discharged to the outside of the heating furnace 1 through the flue 14 is treated by the exhaust gas treatment device 15, thereby suppressing the concentration of unburned ammonia contained in the exhaust gas discharged to the outside of the heating furnace 1. In contrast, the loading section 11 and the unloading section 12 of the heating furnace 1 are temporarily open when the steel S is loaded into the heating furnace 1 and when it is unloaded from the heating furnace 1, making it difficult to treat the exhaust gas discharged from the openings by the exhaust gas treatment device. Therefore, it may be necessary to detect the unburned ammonia in the exhaust gas.

[0138] In the second method for estimating the concentration of unburned ammonia, the determination steps in the first method for estimating the concentration of unburned ammonia are modified as follows.

[0139] That is, in the second method for estimating the concentration of unburned ammonia, in the determination step, waste gas discharged from the heating furnace 1 is collected in the loading section 11 equipped with CO concentration meter 18a, the unloading section 12 equipped with CO concentration meter 18b, and the flue 14 equipped with CO concentration meters 18c and 18d. Actual data on the concentration of unburned ammonia contained in the waste gas are collected using a gas composition measuring device (not shown). The gas composition measuring device can be any device capable of measuring the concentration of unburned ammonia in wet gas; a component measuring device utilizing the indophenol method, ion chromatography, etc., can be used. The measurement of the concentration of unburned ammonia using the gas composition measuring device can be performed offline.

[0140] In this way, as actual data, it is possible to obtain the measured values ​​of carbon monoxide concentration in the exhaust gas discharged from the loading section 11 and unloading section 12 of the heating furnace 1 and the flue 14, which were measured online by the CO concentration meter from 18a to 18d, and the actual value of unburned ammonia concentration obtained offline by sampling the exhaust gas. Then, by changing the air ratio in the first burner equipment from 20a to 20d, multiple sets of actual data are obtained, thereby determining the correlation between the carbon monoxide concentration and the unburned ammonia concentration in the exhaust gas discharged from the heating furnace 1.

[0141] In the second method for estimating the concentration of unburned ammonia, it is preferable that, in the determination step, the correlation between the concentration of carbon monoxide and the concentration of unburned ammonia in the exhaust gas of the heating furnace 1 is determined according to each type of operating condition of the heating furnace 1. Here, the type of operating condition of the heating furnace 1 refers to dividing the conditions for heating the burners of the first burner devices 20a to 20d installed in the heating furnace 1 or the indicators representing the combustion state into two or more categories. Further, the type of operating condition of the heating furnace 1 can be divided into two or more categories representing the conditions and combustion state of the burners of the first burner devices 20a to 20d installed in the heating furnace 1 and the indicators representing the conditions and combustion state of the burners of the second burner devices 30a to 30f installed in the heating furnace 1. Then, in the determination step, the correlation between the concentration of carbon monoxide and the concentration of unburned ammonia is determined according to each category. Specifically, as the operating conditions for heating the burners of the first burner devices 20a to 20d, the composition, type, and mixing ratio of ammonia F11 and carbon-containing fuel F12 used for burner heating are selected. Furthermore, it is preferable to classify these operating conditions into, for example, 2 to 10 types, and for each type, determine the correlation between the carbon monoxide concentration and the unburned ammonia concentration in the exhaust gas discharged from the heating furnace 1. Additionally, for the burner heating operating conditions of the second burner devices 30a to 30f, the composition or type of fuel gas F2, air ratio, etc., are selected. Then, these operating conditions are classified into, for example, 2 to 10 types, and for each type, the correlation between the carbon monoxide concentration and the unburned ammonia concentration in the exhaust gas discharged from the heating furnace 1 is determined.

[0142] In the second method for estimating the concentration of unburned ammonia, the measurement step is performed by online measurement of the carbon monoxide concentration contained in the overall exhaust gas of the heating furnace 1 during its operation. For example... Figure 9 As shown, in the heating furnace 1, the carbon monoxide concentration in the exhaust gas can be continuously measured using CO concentration meters 18a to 18d. The carbon monoxide concentration in the exhaust gas discharged from the heating furnace 1 is preferably measured continuously using CO concentration meters 18a to 18d at a period of, for example, 1 to 60 seconds. It should be noted that for the CO concentration meters 18a and 18b installed in the loading section 11 and the unloading section 12 of the heating furnace 1, it is preferable to continuously measure the carbon monoxide concentration in the exhaust gas at least during the period when the loading section 11 and the unloading section 12 are open.

[0143] In the estimation step, the concentration of unburned ammonia in the exhaust gas of furnace 1 is estimated based on the correlation between the carbon monoxide concentration measured in the determination step and the carbon monoxide and unburned ammonia concentrations determined in the determination step. At this time, the correlation between the carbon monoxide concentration and the unburned ammonia concentration in the exhaust gas of furnace 1 is predetermined in the determination step. Therefore, in addition, the concentration of unburned ammonia in the exhaust gas of furnace 1 can be estimated by using the carbon monoxide concentration continuously measured by a CO concentration meter from 18a to 18d.

[0144] In addition, in the second method for estimating the concentration of unburned ammonia, such as Figure 9 As shown, an ammonia concentration meter 17 for measuring ammonia concentration is installed in the flue 14 of the heating furnace 1. Furthermore, the measured value of the unburned ammonia concentration in the exhaust gas is obtained using the ammonia concentration meter 17, and the measured value of the carbon monoxide concentration in the exhaust gas is obtained using a CO concentration meter 18c installed in the flue 14. Then, preferably, the correlation between the carbon monoxide concentration and the unburned ammonia concentration in the exhaust gas of the heating furnace 1 is determined based on these measured values.

[0145] The measurement of unburned ammonia concentration by ammonia concentration meter 17 is often difficult to perform continuously, therefore the acquisition of the measured value of unburned ammonia concentration by ammonia concentration meter 17 can also be performed discontinuously. In this case, for example, it is preferable to acquire the measured value of unburned ammonia concentration in exhaust gas by ammonia concentration meter 17, for example, every 10 to 60 minutes, and establish a correspondence with the measured value of carbon monoxide concentration based on CO concentration meter 18c installed in flue 14.

[0146] The correlation between the carbon monoxide concentration and the unburned ammonia concentration in the exhaust gas of the heating furnace 1, obtained by the ammonia concentration meter 17 and the CO concentration meter 18c installed in the flue 14, can be considered as the correlation of the entire heating furnace 1, which is formed by the mixture of exhaust gases from all the first burner devices 20a-20d and the second burner devices 30a-30f that are heated by burners inside the heating furnace 1. That is, the correlation between the carbon monoxide concentration and the unburned ammonia concentration determined in the determination step can be applied not only to the exhaust gas discharged from the flue 14 of the heating furnace 1, but also to the exhaust gas discharged through the loading section 11 and the unloading section 12 of the heating furnace 1. Therefore, as described above, the correlation between the carbon monoxide concentration and the unburned ammonia concentration in the exhaust gas of the heating furnace 1, determined by installing the ammonia concentration meter 17 in the flue 14 of the heating furnace 1 and performing the determination step, can also be used to estimate the unburned ammonia concentration in the exhaust gas discharged from the loading section 11 and the unloading section 12 of the heating furnace 1, without the need to install multiple ammonia concentration meters 17.

[0147] Regarding aspects other than those mentioned above, the method for estimating the unburned ammonia concentration in the second method is the same as that in the first method.

[0148] Operating methods for heating furnaces and burner equipment

[0149] The following describes the implementation methods of the heating furnace and the burner equipment of the present invention.

[0150] The operating method of the heating furnace in this embodiment includes the following operating steps: when the estimated value of the unburned ammonia concentration obtained by the above-described method for estimating the unburned ammonia concentration is above a predetermined value, the operating conditions of the heating furnace 1 are adjusted so that the concentration of unburned ammonia contained in the exhaust gas discharged from the heating furnace 1 is reduced.

[0151] Furthermore, in the above-described method of operating the heating furnace, the method of operating the burner equipment in this embodiment is achieved by setting the operation object of the operation steps to the operating conditions of the first burner equipment 20a to 20d rather than the operating conditions of the heating furnace 1 as a whole.

[0152] When the operation method of the heating furnace or the operation method of the burner equipment of this embodiment is carried out based on the estimation method of unburned ammonia concentration in the first manner described above, the process is as follows.

[0153] First, the concentration of unburned ammonia in the exhaust gas discharged from at least one of the first burner devices 20a to 20d in the heating furnace 1 is estimated using the method described in the first approach. Then, based on the estimated concentration of unburned ammonia, the operating conditions of the first burner devices 20a to 20d are adjusted to reduce the concentration of unburned ammonia in the exhaust gas discharged from the first burner devices 20a to 20d.

[0154] By operating the first burner equipment under the conditions 20a to 20d, the concentration of unburned ammonia in the exhaust gas discharged from the first burner equipment 20a to 20d decreases, and the concentration of unburned ammonia in the exhaust gas discharged from the entire heating furnace 1 also decreases. Thus, the operating conditions of the heating furnace 1 are operated in such a way that the concentration of unburned ammonia in the exhaust gas discharged from the heating furnace 1 decreases.

[0155] At this time, the operating conditions of the first burner devices 20a-20d, which are operated in the operation steps in such a way as reducing the concentration of unburned ammonia in the exhaust gas discharged from the first burner devices 20a-20d, preferably include at least one of the following: the flow rate of combustion air A used for burner heating of the first burner devices 20a-20d, the flow rate of fuel gas F1, the air ratio of fuel gas F1 to the theoretical air volume, and the mixing ratio of ammonia F11 to carbon-containing fuel F12.

[0156] For example, under the operating conditions of the first burner equipment 20a to 20d in the operating steps, increasing the amount of combustion air A promotes the combustion of unburned ammonia, making it difficult for unburned ammonia to remain. Alternatively, decreasing the flow rate of fuel gas F1 relatively increases the flow rate of combustion air A, thus achieving the same effect. The same applies when increasing the air ratio of fuel gas F1 relative to the stoichiometric air volume. Furthermore, adjusting the mixing ratio of ammonia F11 and coal gas F12 to reduce the flow rate of ammonia F11 also makes it difficult for unburned ammonia to remain.

[0157] Furthermore, when the operation method of the heating furnace or the operation method of the burner equipment in this embodiment are carried out based on the estimation method of unburned ammonia concentration in the second manner described above, the process is as follows.

[0158] First, the concentration of unburned ammonia in the exhaust gas discharged from the heater 1 is estimated using the second method described above. Then, based on the estimated concentration of unburned ammonia, the operating conditions of the heater 1 are adjusted to reduce the concentration of unburned ammonia in the exhaust gas discharged from the heater 1.

[0159] At this time, the operating conditions for the heater 1, which operate in the operation step to reduce the concentration of unburned ammonia in the exhaust gas discharged from the heater 1, preferably include at least one of the following: the flow rate of combustion air A used for burner heating in the first burner equipment 20a to 20d; the flow rate of fuel gas F1; the air ratio of fuel gas F1 to the theoretical air volume; and the mixing ratio of ammonia F11 to carbon-containing fuel F12. Furthermore, when estimating the concentration of unburned ammonia in the exhaust gas discharged from the heater 1 using the second method for estimating the concentration of unburned ammonia, the atmosphere temperature inside the heater 1 can also be selected as the operating condition for the heater 1 operating in the operation step. By increasing the atmosphere temperature inside the heater 1, the combustion of ammonia F11 is promoted, thus reducing the concentration of unburned ammonia contained in the exhaust gas discharged from the heater 1.

[0160] <Control device for heating furnace>

[0161] The following describes an embodiment of the control device for the heating furnace of the present invention.

[0162] Figure 10 This describes the structure of the control device 40 for the heating furnace in this embodiment.

[0163] The control device 40 for the heating furnace in this embodiment is a device for executing the above-described heating furnace operation method. For example... Figure 10 As shown, the control device 40 for the heating furnace includes a storage unit 41, an acquisition unit 42, an estimation unit 43, an operation quantity calculation unit 44, and an output unit 45.

[0164] Storage unit 41 stores a predetermined correlation between the carbon monoxide concentration and the unburned ammonia concentration in the exhaust gas of the heater 1. Specifically, storage unit 41 stores, for example, the correlation between the carbon monoxide concentration and the unburned ammonia concentration in the exhaust gas of the heater 1, which is predetermined through the determination step of the aforementioned method for estimating the unburned ammonia concentration. The correlation between the carbon monoxide concentration and the unburned ammonia concentration stored in storage unit 41 can be stored in tabular form or in function form. Furthermore, it is preferable that storage unit 41 obtains and stores a predetermined upper limit value for the unburned ammonia concentration from the control computer 10 of the heater 1.

[0165] The acquisition unit 42 acquires the carbon monoxide concentration in the exhaust gas of the heating furnace 1 as measured during operation of the heating furnace 1. Specifically, the acquisition unit 42 acquires the carbon monoxide concentration in the exhaust gas of the heating furnace 1 as measured during operation of the heating furnace 1 by CO concentration meters 18a to 18d installed in the heating furnace 1. As described above, CO concentration meters 18a to 18d are, for example, installed in the loading section 11 (CO concentration meter 18a), the unloading section 12 (CO concentration meter 18b), and the flue 14 (CO concentration meters 18c and 18d) of the heating furnace 1. The acquisition of the carbon monoxide concentration measurement value by the acquisition unit 42 is preferably performed via the control computer 10 or other operation data server.

[0166] The estimation unit 43 estimates the concentration of unburned ammonia in the exhaust gas of the heater 1 based on the correlation between the carbon monoxide concentration obtained by the acquisition unit 42 and the carbon monoxide concentration stored in the storage unit 41 and the unburned ammonia concentration. When the correlation between the carbon monoxide concentration stored in the storage unit 41 and the unburned ammonia concentration is in tabular form, the estimation unit 43 calculates the estimated value of the unburned ammonia concentration by referring to the tabular value corresponding to the carbon monoxide concentration obtained by the acquisition unit 42. Alternatively, when the correlation between the carbon monoxide concentration stored in the storage unit 41 and the unburned ammonia concentration is in functional form, the estimation unit 43 calculates the estimated value of the unburned ammonia concentration by inputting the measured value of the carbon monoxide concentration obtained by the acquisition unit 42 into the function.

[0167] When the estimated value of the unburned ammonia concentration estimated by the estimation unit 43 is above a specified value, that is, above the upper limit value of the pre-set unburned ammonia concentration, the operation quantity calculation unit 44 calculates the operation quantity for the heating furnace 1 to make the estimated value less than the specified value.

[0168] The output unit 45 outputs the operating conditions of the heating furnace 1 calculated by the operation quantity calculation unit 44 to the control computer 10 of the heating furnace 1, or outputs them to the display unit 46 as guidance operation quantities for the operator to refer to when operating the heating furnace 1. When the destination of the operation quantity of the heating furnace 1's operating conditions from the output unit 45 is the control computer 10, it is preferable to automatically update the operating conditions of the heating furnace 1 in the control computer 10. Furthermore, when the destination of the operation quantity of the heating furnace 1's operating conditions from the output unit 45 is the display unit 46, it is preferable for the operator to operate the heating furnace 1's operating conditions based on the guidance operation quantities displayed on the display unit 46.

[0169] The control device 40 for the heating furnace can be configured, for example, using a general-purpose computer equipped with an auxiliary storage device such as a memory, hard disk drive, or solid-state drive, and a CPU (central processing unit). The program for controlling the heating furnace control device 40 is stored in the auxiliary storage device, and read from the auxiliary storage device into the memory when the CPU executes the program. Furthermore, data generated during CPU processing is continuously stored in the memory and, as needed, stored in the auxiliary storage device.

[0170] The storage unit 41 is preferably implemented using the auxiliary storage device described above. Furthermore, the acquisition unit 42, estimation unit 43, operation quantity calculation unit 44, and output unit 45 are preferably implemented using the CPU described above to read and execute programs. The display unit 46 can be configured as a display device such as a liquid crystal display or an organic EL panel. Alternatively, the display unit 46 can also be configured as the display of a terminal device such as a smartphone or tablet computer. In this case, the terminal device equipped with the display unit 46 can communicate with the control device 40 of the heating furnace via a network.

[0171] The above describes the implementation methods of the method for estimating the concentration of unburned ammonia, the operation method of the heating furnace, the operation method of the burner equipment, and the control device of the heating furnace according to the present invention, but the present invention is not limited to these implementation methods.

[0172] Example

[0173] To verify the effectiveness of the method for estimating the concentration of unburned ammonia, the operation method of the heating furnace, the operation method of the burner equipment, and the control device of the heating furnace of the present invention, an experiment was conducted using a test heating furnace to estimate the concentration of ammonia contained in the exhaust gas of the heating furnace. The results are described below.

[0174] Figure 11 The diagram schematically shows a longitudinal sectional view of the 1T experimental heating furnace.

[0175] like Figure 11As shown, the experimental heating furnace 1T includes a flue 14 and an exhaust gas treatment device 15. The exhaust gas treatment device 15 is configured to include an oxidation catalyst, a denitrification device, and an ammonia removal device. In the flue 14, an openable and closable gas collection port 14a is provided upstream of the exhaust gas treatment device 15 in the direction of exhaust gas flow, which can collect samples of the exhaust gas flowing in the flue 14 as needed.

[0176] In addition, such as Figure 11 As shown, the experimental furnace 1T has 10 first burner devices 20a-20j as the heat source. These first burner devices 20a-20j use fuel gas F1 containing ammonia F11 and carbon-containing fuel F12 for burner heating. Five of the ten first burner devices 20a-20j are positioned above the steel S being transported in the furnace, and the remaining five first burner devices 20f-20j are positioned below the steel S being transported in the furnace. The experimental furnace 1T does not have a second burner device that uses fuel gas F2 without ammonia for burner heating. The first burner devices 20a-20j are all of the same model, and each of the first burner devices 20a-20j has a rated capacity of 800,000 kcal / hr.

[0177] The exhaust gas discharged from the flue 14 of the 1T experimental heating furnace is treated by the exhaust gas treatment device 15, thereby reducing the concentration of nitrogen oxides, unburned ammonia, and carbon monoxide in the exhaust gas and releasing it into the atmosphere.

[0178] The fuel gas F1 supplied to the first burner equipment 20a-20j uses ammonia F11 and coal gas F12, i.e., gas M. Specifically, gas M is a mixture of blast furnace gas, coke oven gas, and converter gas, adjusted to a lower calorific value of 2000 kcal / Nm³. 3 The gas. Table 2 shows the results of the preliminary analysis of the composition of gas M used by gas chromatography.

[0179] [Table 2]

[0180] In this embodiment, from Figure 3 The first burner device 20 shown is supplied with ammonia F11 by an ammonia supply system 23 and M gas by a coal gas supply system 24. Furthermore, the mixing ratio of ammonia F11 and M gas is adjusted by flow regulating valves 23v and 24v, respectively, provided in the ammonia supply system 23 and the coal gas supply system 24. It should be noted that the mixing ratio referred to here is the calorific value ratio of ammonia F11 to M gas. When the mixing ratio of ammonia F11 to M gas is 50%:50%, the flow rate of ammonia F11 is 119 Nm³. 3 / hr, the flow rate of gas M is 200 Nm 3 / hr.

[0181] In addition, the air ratio of fuel gas F1 to the theoretical air volume is adjusted by the flow regulating valve 26v of the combustion air supply system 26.

[0182] First, as a determining step, the correlation between the carbon monoxide concentration and the unburned ammonia concentration in the exhaust gas of the 1T experimental heating furnace was determined in advance.

[0183] In the determination process, combustion was performed using only the first burner device 20a, which is located on the upper side of the test furnace 1T and closest to the loading section 11, from burner devices 20a to 20j of the test furnace 1T. Regarding the combustion using the first burner device 20a, the mixing ratio of ammonia F11 to M gas was set to 50%:50%, and the air ratio was adjusted by adjusting the flow rate of combustion air A.

[0184] Specifically, after adjusting the flow rate of combustion air A to make the air ratio in the first burner device 20a reach the specified set value, the system is left idle for 10 minutes to allow the combustion state to stabilize and the atmosphere inside the test furnace 1T to become uniform. Then, the concentration of carbon monoxide in the exhaust gas is measured using a CO concentration meter 18c located in the flue 14, and a sample of the exhaust gas is collected from the gas collection port 14a.

[0185] For the exhaust gas sample collected from gas collection port 14a, the concentrations of unburned ammonia (NH3), carbon monoxide (CO), and carbon dioxide (CO2) in the exhaust gas were measured using an offline measuring device. The concentration of unburned ammonia in the exhaust gas was determined using boric acid absorption ion chromatography as specified in Japanese Industrial Standard JIS K0099:2020 "Method for Analysis of Ammonia in Exhaust Gas". Specifically, a boric acid absorbent solution was used to pass 20 L of exhaust gas at an average exhaust gas flow rate of 1.5 L / min. Furthermore, the concentration of carbon monoxide (CO) in the exhaust gas was measured offline using a low-potential electrolysis method, and the result was confirmed to be approximately consistent with the value measured by the CO concentration meter 18c located in flue 14. Further, the concentration of carbon dioxide in the exhaust gas was measured using a non-dispersive infrared method.

[0186] Figure 12 The diagram shows the correlation between the concentration of carbon monoxide (CO) in the exhaust gas and the concentration of unburned ammonia (NH3) when the air ratio in the first burner device 20a is changed and the above-mentioned preliminary test is performed multiple times.

[0187] like Figure 12As shown, there is a correlation between the carbon monoxide (CO) concentration and the unburned ammonia (NH3) concentration in the exhaust gas discharged from the first burner device 20a, indicating that the two are approximately linearly related. Furthermore, the correlation can be approximated by a straight line passing through the origin, suggesting that the combustion rates of ammonia F11 contained in fuel gas F1 and gas M are approximately equal. Based on... Figure 12 The results of the preliminary test shown, if expressed as a regression equation to represent the correlation between carbon monoxide concentration ΦCO (ppm) and unburned ammonia concentration ΦNH3 (ppm), become the following equation (1).

[0188] ΦNH3=0.1436×ΦCO……(1)

[0189] In this way, as a determining step, the correlation between the carbon monoxide concentration and the unburned ammonia concentration in the exhaust gas of the 1T experimental heating furnace can be determined.

[0190] Next, in the operation of the test furnace 1T, experiments were conducted on the determination steps for measuring the carbon monoxide concentration in the exhaust gas of the test furnace 1T, and the estimation steps for estimating the concentration of unburned ammonia in the exhaust gas of the test furnace 1T based on the correlation between the carbon monoxide concentration measured in the determination steps and the carbon monoxide concentration determined in the determination steps and the concentration of unburned ammonia.

[0191] In the measurement procedure, the operation of the test furnace 1T was carried out under the same combustion conditions as the first burner devices 20a to 20j. That is, the mixing ratio of fuel gas F1, the flow rate of fuel gas F1, and the air ratio of the first burner devices 20a to 20j were set to the same conditions when operating the test furnace 1T. In addition, the mixing ratio of ammonia F11 to M gas was set to 50%:50%, the same as the mixing ratio in the preliminary test mentioned above.

[0192] The measurement procedure is performed online by continuously measuring the carbon monoxide concentration in the exhaust gas passing through the flue 14 using a CO concentration meter 18c configured in the flue 14.

[0193] Next, as an estimation step, the estimated value of the unburned ammonia concentration is calculated by inputting the measured value of the online carbon monoxide concentration into the above equation (1) determined by the determination step. Thus, the unburned ammonia concentration of the exhaust gas is continuously estimated.

[0194] Figure 13 This represents the estimated value of the unburned ammonia concentration using the method for estimating the unburned ammonia concentration in this embodiment. Figure 13 The changes in the air ratio set for the first burner device 20, the carbon monoxide concentration measured by the measurement procedure, and the estimated values ​​of unburned ammonia concentration are indicated relative to the elapsed operating time of the test heating furnace 1T.

[0195] like Figure 13 As shown, under conditions where the air-to-gas ratio exceeds 1.0, the measured carbon monoxide concentration is 0 ppm. Based on this, the estimated value of the unburned ammonia concentration using equation (1) is also 0 ppm. This indicates that under conditions where the air-to-gas ratio exceeds 1.0, fuel gas F1 is almost completely burned, and the M gas contained in fuel gas F1 is completely burned. At this time, it is presumed that the ammonia F11 contained in fuel gas F1 is also completely burned.

[0196] In contrast, under conditions where the air ratio is below 1.0, a portion of the M gas contained in fuel gas F1 undergoes incomplete combustion, generating carbon monoxide gas. Based on this, the estimated value of the unburned ammonia concentration using equation (1) is also greater than 0 ppm.

[0197] To verify the accuracy of the estimated unburned ammonia concentration as described above, in the aforementioned operation, a sample of exhaust gas was collected from gas collection port 14a, and the unburned ammonia concentration was measured offline. The exhaust gas sample collection from gas collection port 14a was performed four times in the test furnace 1T, and the unburned ammonia concentration was measured for each sample. These are referred to as batch determination 1 to batch determination 4.

[0198] Figure 13 This indicates the time at which the waste gas sample was collected from gas collection port 14a. Then, using the waste gas samples collected from batch determination 1 to batch determination 4, the concentration of unburned ammonia was determined using boric acid absorption-ion chromatography.

[0199] Table 3 shows the correlation between the unburned ammonia concentration estimated online through the estimation step and the measured value of the unburned ammonia concentration determined offline through batch determination.

[0200] [Table 3]

[0201] As shown in Table 3, it can be confirmed that the online estimated value of unburned ammonia concentration using the method of the present invention is very close to the offline measured value. Specifically, it can be confirmed that the difference between the online estimated value and the offline measured value of unburned ammonia concentration is within ±7 ppm.

[0202] Explanation of reference numerals in the attached figures

[0203] 1 Heating Furnace

[0204] 1T experimental heating furnace

[0205] 10. Control computer

[0206] 11 Loading section

[0207] 12 Moving out department

[0208] 13f Fixed slide rail

[0209] 13m movable slide rail

[0210] 14. Flue

[0211] 14a Gas sampling port

[0212] 15. Waste gas treatment device

[0213] 16 NO X Concentration meter

[0214] 17 Ammonia Concentration Meter

[0215] 18. CO concentration meter (18a-18d)

[0216] 20, 20a~20j First burner equipment

[0217] 30, 30a~30f Second Burner Equipment

[0218] 21, 31 Burner Nozzles

[0219] 22, 32 Fuel gas supply system

[0220] 23 Ammonia Supply System

[0221] 24 Gas Supply System

[0222] 25 Mixing section

[0223] 26, 36 Combustion air supply system

[0224] Flow meters of 23m, 24m, 26m, 32m, and 36m

[0225] 23V, 24V, 26V, 32V, 36V flow regulating valves

[0226] 27, 37 Air Ratio Control Section

[0227] 40. Control device for heating furnace

[0228] 41 Storage Department

[0229] 42 Acquisition Department

[0230] 43. Estimation Department

[0231] 44 Operation Quantity Calculation Department

[0232] 45 Output Section

[0233] 46 Display Section

[0234] A. Combustion air

[0235] F1 and F2 fuel gases

[0236] F11 Ammonia

[0237] F12 coal gas (carbon-containing fuel)

[0238] S - Steel (the material being heated)

Claims

1. A method for estimating the concentration of unburned ammonia, comprising estimating the concentration of unburned ammonia contained in exhaust gas from a heating furnace, said heating furnace using a fuel gas containing ammonia and carbon-containing fuel for burner heating, wherein, The methods for estimating the concentration of unburned ammonia include: The steps involve determining the correlation between the concentration of carbon monoxide and the concentration of unburned ammonia in the exhaust gas from the heating furnace. The measurement step involves measuring the concentration of carbon monoxide in the exhaust gas from the heating furnace during its operation; and The estimation step estimates the concentration of unburned ammonia in the exhaust gas of the heating furnace based on the correlation between the carbon monoxide concentration determined in the determination step and the carbon monoxide concentration determined in the determination step and the concentration of unburned ammonia.

2. The method for estimating the concentration of unburned ammonia according to claim 1, wherein, In the determination step, for each of the multiple categories into which the operating conditions of the heating furnace are classified, the correlation between the concentration of carbon monoxide and the concentration of unburned ammonia in the exhaust gas of the heating furnace is determined.

3. The method for estimating the concentration of unburned ammonia according to claim 1 or 2, wherein, The heating furnace is a conveyor-type heating furnace that heats the material while it is being transported from the loading section to the unloading section. In the measurement step, the concentration of carbon monoxide contained in the exhaust gas of the heating furnace is measured at at least one of the flue from which the exhaust gas is discharged from the heating furnace, the loading section, and the unloading section.

4. A method for estimating the concentration of unburned ammonia, comprising estimating the concentration of unburned ammonia contained in exhaust gas from a burner device, said burner device using a fuel gas containing ammonia and carbon-containing fuel for burner heating, wherein, The methods for estimating the concentration of unburned ammonia include: The steps include determining the correlation between the concentration of carbon monoxide in the exhaust gas of the burner equipment and the concentration of unburned ammonia. The measurement steps include measuring the concentration of carbon monoxide in the exhaust gas of the burner device during burner heating; and... The estimation step estimates the concentration of unburned ammonia in the exhaust gas of the burner equipment based on the carbon monoxide concentration determined in the determination step and the correlation between the carbon monoxide concentration and the unburned ammonia concentration determined in the determination step.

5. The method for estimating the concentration of unburned ammonia according to claim 4, wherein, In the determination step, for each of the multiple categories into which the operating conditions of the burner equipment are classified, the correlation between the concentration of carbon monoxide and the concentration of unburned ammonia in the exhaust gas of the burner equipment is determined.

6. A method of operating a heating furnace, comprising the following steps, wherein the operating conditions of the heating furnace are adjusted such that the concentration of unburned ammonia contained in the exhaust gas discharged from the heating furnace is reduced when the estimated value of the unburned ammonia concentration obtained by the method of estimating the unburned ammonia concentration according to claim 3 is above a predetermined value.

7. The method of operating the heating furnace according to claim 6, wherein, The operating conditions of the heating furnace that are changed in the operation steps include at least one of the following: the flow rate of combustion air for heating the burner, the flow rate of the fuel gas, the air ratio of the fuel gas to the stoichiometric air volume, and the mixing ratio of the ammonia to the carbonaceous fuel.

8. A method of operating a burner device, comprising the following steps: when the estimated value of the unburned ammonia concentration obtained by the method for estimating the unburned ammonia concentration according to claim 4 is above a predetermined value, the operating conditions of the burner device are operated in such a way as to reduce the concentration of unburned ammonia contained in the exhaust gas discharged from the burner device.

9. The method of operating the burner equipment according to claim 8, wherein, The operating conditions of the burner equipment that are changed in the operation steps include at least one of the following: the flow rate of combustion air for heating the burner, the flow rate of the fuel gas, the air ratio of the fuel gas to the stoichiometric air volume, and the mixing ratio of the ammonia to the carbonaceous fuel.

10. A control device for a heating furnace, said heating furnace using a fuel gas containing ammonia and carbon-containing fuel to perform burner heating, wherein, The control device for the heating furnace includes: The storage unit stores the correlation between the concentration of carbon monoxide and the concentration of unburned ammonia in the exhaust gas from the heating furnace. The acquisition unit acquires the concentration of carbon monoxide contained in the exhaust gas of the heating furnace, as measured during the operation of the heating furnace; The estimation unit estimates the concentration of unburned ammonia in the exhaust gas of the heating furnace based on the correlation between the carbon monoxide concentration obtained by the acquisition unit and the carbon monoxide concentration stored in the storage unit and the concentration of unburned ammonia; and The operation quantity calculation unit calculates the operation quantity of the heating furnace to make the estimated value less than the specified value when the estimated value of the unburned ammonia concentration is above a predetermined value.

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