Unburned ammonia concentration estimation method, heating furnace operation method, burner facility operation method, and heating furnace control device

Abstract

Provided is an unburned ammonia estimation method with which the concentration of ammonia contained in exhaust gas of a heating furnace 1 that employs ammonia, with which carbon dioxide emissions can be suppressed, as a fuel gas can be measured online using a simple method. Also provided are a heating furnace operation method, a burner facility operation method, and a heating furnace control device with which it is possible to suppress the discharge of unburned ammonia to the outside of the heating furnace 1 as heating furnace exhaust gas.　Provided is an unburned ammonia concentration estimation method for estimating the concentration of unburned ammonia contained in exhaust gas discharged from a heating furnace that performs burner heating using a fuel gas containing ammonia and a carbon-containing fuel, the method including: an identification step for identifying a correlation between the concentration of carbon monoxide and the concentration of unburned ammonia contained in the heating furnace exhaust gas; a measurement step for measuring the concentration of carbon monoxide contained in the heating furnace exhaust gas during operation of the heating furnace; and an estimation step for estimating the concentration of unburned ammonia contained in the heating furnace exhaust gas on the basis of the carbon monoxide concentration measured in the measurement step and the correlation between the concentration of carbon monoxide and the concentration of unburned ammonia identified in the identification step.

Description

Method for estimating unburned ammonia concentration, method for operating a heating furnace, method for operating a burner facility, and control device for a heating furnace

[0001] The present 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 facility, and a control device for a heating furnace.

[0002] In integrated steel works, by-product gases such as blast furnace gas discharged from the top of the blast furnace, which reduces iron ore to produce molten iron, converter gas generated in the converter, and coke oven gas generated in the coke oven are effectively used as fuel gas. However, in recent years, there has been an increasing demand for reducing carbon dioxide emissions, and combustion technologies that can reduce the amount of by-product gas used are being sought. In hot rolling lines and plate rolling lines of integrated steel works, there is also a demand for reducing the amount of by-product gas used and carbon dioxide emissions in heating furnaces that heat slabs before rolling.

[0003] Therefore, technology using ammonia as fuel gas for heating furnaces has attracted attention. When ammonia, which does not contain carbon elements, is burned, it mainly produces water and nitrogen, which has a significant effect in reducing carbon dioxide emissions, and there is a need to develop technology to use ammonia as fuel gas for heating furnaces.

[0004] However, because ammonia is toxic, if unburned ammonia (also referred to as "unburned ammonia") is discharged outside the heating furnace, it will deteriorate the environment outside the heating furnace. Therefore, when ammonia is used as fuel gas for the heating furnace, it is necessary to measure the concentration of unburned ammonia contained in the exhaust gas from the heating furnace in order to prevent unburned ammonia from being discharged outside the heating furnace.

[0005] In this regard, Patent Document 1 discloses a method for analyzing ammonia gas in exhaust gas discharged from the outlet of a denitration device that treats boiler exhaust gas. Specifically, when analyzing ammonia gas coexisting with sulfur dioxide by the indophenol method, the absorption liquid is distilled to remove SO in the liquid. ３ ２－The indophenol method, also known as the indophenol blue absorptiometry, involves absorbing ammonia in a gas into a boric acid solution, then adding a phenolpentacyanonitrosyl sodium ferrate (III) solution and a sodium hypochlorite solution to generate indophenol blue, and measuring the absorbance (640 nm) to calculate the ammonia concentration in the gas.

[0006] In addition to the indophenol method, ion chromatography is also known as a method for analyzing ammonia in exhaust gas. In ion chromatography, the ammonia in the gas is absorbed in a boric acid solution, and then the analytical sample solution is injected into an ion chromatograph to obtain a chromatogram of ammonium ions, and the ammonia concentration in the gas is calculated from the ammonium ion concentration.

[0007] Patent Document 2 discloses a method for analyzing ammonia nitrogen, nitrate / nitrite nitrogen, and total nitrogen. Specifically, the method describes oxidizing ammonia gas to NO gas using an oxidation catalyst provided in the combustion section of a heated reaction tube, and sending this NO gas to a chemiluminescence NO detector to analyze ammonia nitrogen.

[0008] Furthermore, Non-Patent Document 1 discloses a dry gas measurement method for measuring the ammonia concentration using an infrared analyzer. Specifically, the method discloses a method in which a cooler is installed in a pipe that conveys the gas to be measured to the infrared analyzer, and the gas dehumidified by the cooler is supplied to the infrared analyzer.

[0009] Japanese Patent Application Laid-Open No. 61-17955 Japanese Patent Application Laid-Open No. 2001-21546

[0010] Toshio Miyamoto, "Current Status of Infrared Gas Analyzers," Journal of Industrial Chemistry, Chemical Society of Japan, November 1963, Vol. 66, No. 11, pp. 1561-1563

[0011] However, when the above-mentioned conventional technology is applied to measuring the concentration of unburned ammonia contained in the exhaust gas from a heating furnace, the following problems arise.

[0012] First, measuring the ammonia concentration using the method disclosed in Patent Document 1 requires steps such as absorbing ammonia gas into an absorption liquid, reacting with a reagent, and analyzing the result. In other words, the ammonia concentration needs to be measured by batch processing, and it takes a certain amount of time (e.g., 10 minutes or more) to obtain the measurement results. Therefore, it is difficult to measure the ammonia concentration continuously. This is also true when measuring the ammonia concentration using ion chromatography.

[0013] Furthermore, when applying the method disclosed in Patent Document 2 to measuring the concentration of unburned ammonia contained in exhaust gas from a heating furnace, piping is required to transport the ammonia-containing exhaust gas to a component measuring device. However, because ammonia is highly soluble in water, the temperature in the piping 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 moisture in the piping. This requires larger equipment for measuring the ammonia concentration, which increases the equipment cost. Furthermore, because ammonia is corrosive, the piping and pumps transporting the exhaust gas are prone to corrosion, and corrosion of the piping poses a risk of leakage of ammonia-containing exhaust gas. This results in a heavy burden on the maintenance of the entire measuring device for measuring the ammonia concentration in exhaust gas.

[0014] Furthermore, when applying the method disclosed in Non-Patent Document 1 to the measurement of the concentration of unburned ammonia contained in the exhaust gas of a heating furnace, it is necessary to dehumidify the exhaust gas as a pretreatment for the component analysis of the exhaust gas. However, because ammonia is highly soluble in water, ammonia dissolves in the moisture that condenses during the dehumidification process of the pretreatment. Therefore, some of the ammonia in the exhaust gas is removed before the exhaust gas is introduced into the component analyzer, which reduces the measurement accuracy of the ammonia concentration.

[0015] The present invention has been made to solve the above-mentioned problems of the prior art. An object of the present invention is to provide a method for estimating the concentration of unburned ammonia, which can easily measure the concentration of ammonia contained in the exhaust gas of a heating furnace that uses ammonia as a fuel gas and can suppress carbon dioxide emissions, online. Another object of the present invention is to provide a method for operating a heating furnace, a method for operating a burner system, and a heating furnace control device that can suppress the emission of unburned ammonia as exhaust gas from the heating furnace.

[0016] [1] A method for estimating the concentration of unburned ammonia contained in exhaust gas discharged from a heating furnace that performs burner heating using a fuel gas containing ammonia and a carbon-containing fuel, the method comprising: a specifying step of specifying a correlation between a carbon monoxide concentration and an unburned ammonia concentration in the exhaust gas of the heating furnace; a measuring step of measuring the carbon monoxide concentration in the exhaust gas of the heating furnace during operation of the heating furnace; and an estimating step of estimating the unburned ammonia concentration in the exhaust gas of the heating furnace based on the carbon monoxide concentration measured in the measuring step and the correlation between the carbon monoxide concentration and the unburned ammonia concentration specified in the specifying step. [2] The method for estimating the concentration of unburned ammonia described in [1], wherein the specifying step specifies the correlation between the carbon monoxide concentration and the unburned ammonia concentration in the exhaust gas of the heating furnace for each of a plurality of classifications of operating conditions of the heating furnace. [3] The method for estimating an unburned ammonia concentration according to [1] or [2], wherein the heating furnace is a conveying type heating furnace that heats the material to be heated while conveying it from a charging section to a discharge section, and the measuring step measures the carbon monoxide concentration contained in the exhaust gas from the heating furnace at at least one of a flue for discharging exhaust gas from the heating furnace, the charging section, and the discharge section. [4] A method for estimating the concentration of unburned ammonia contained in exhaust gas emitted from a burner equipment that performs burner heating using a fuel gas containing ammonia and a carbon-containing fuel, the method comprising: a specifying step of specifying a correlation between a carbon monoxide concentration and an unburned ammonia concentration in the exhaust gas from the burner equipment; a measuring step of measuring the carbon monoxide concentration in the exhaust gas from the burner equipment when burner heating is performed by the burner equipment; and an estimating step of estimating the unburned ammonia concentration in the exhaust gas from the burner equipment based on the carbon monoxide concentration measured in the measuring step and the correlation between the carbon monoxide concentration and the unburned ammonia concentration specified in the specifying step. [5] The method for estimating the concentration of unburned ammonia described in [4], wherein the specifying step specifies the correlation between the carbon monoxide concentration and the unburned ammonia concentration in the exhaust gas from the burner equipment for each of a plurality of classifications of operating conditions of the burner equipment.[6] A method for operating a heating furnace, comprising an operation step of manipulating the operating conditions of the heating furnace so as to reduce the unburned ammonia concentration contained in exhaust gas discharged from the heating furnace when an estimated value of the unburned ammonia concentration estimated by the method for estimating the unburned ammonia concentration according to [3] is equal to or greater than a predetermined value. [7] The method for operating a heating furnace according to [6], wherein the operating conditions of the heating furnace changed in the operation step include at least one of the flow rate of combustion air used for the burner heating, the flow rate of the fuel gas, the air ratio of the fuel gas to a theoretical air amount, and the mixing ratio of the ammonia and the carbon-containing fuel. [8] A method for operating a burner equipment, comprising an operation step of manipulating the operating conditions of the burner equipment so as to reduce the unburned ammonia concentration contained in exhaust gas discharged from the burner equipment when an estimated value of the unburned ammonia concentration estimated by the method for estimating the unburned ammonia concentration according to [4] is equal to or greater than a predetermined value. [9] The method for operating a burner facility according to [8], wherein the operating conditions of the burner facility that are changed in the operation step include at least one of the flow rate of the combustion air used for heating the burner, the flow rate of the fuel gas, the air ratio of the fuel gas to the theoretical air amount, and the mixing ratio of the ammonia and the carbon-containing fuel.

[10] A control device for a heating furnace that performs burner heating using a fuel gas containing ammonia and a carbon-containing fuel, the control device for a heating furnace including: a memory unit that stores a correlation between a carbon monoxide concentration and an unburned ammonia concentration contained in an exhaust gas of the heating furnace; an acquisition unit that acquires the carbon monoxide concentration contained in the exhaust gas of the heating furnace measured during operation of the heating furnace; an estimation unit that estimates the unburned ammonia concentration 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 and the unburned ammonia concentration stored in the memory unit; and an operation amount calculation unit that, when the estimated value of the unburned ammonia concentration estimated by the estimation unit is equal to or greater than a predetermined value, calculates an operation amount for an operating condition of the heating furnace so that the estimated value becomes smaller than the predetermined value.

[0017] 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 heating furnace that uses ammonia as a fuel gas, which can suppress carbon dioxide emissions, can be measured online by a simple method. Furthermore, according to the method for operating a heating furnace, the method for operating a burner facility, and the heating furnace control device of the present invention, ammonia that can suppress carbon dioxide emissions is used, and it is possible to suppress unburned ammonia from being emitted to the outside of the furnace as part of the exhaust gas of the heating furnace.

[0018]

[0023] Figure 1 is a longitudinal cross-sectional view schematically showing a heating furnace to which an embodiment of the method for estimating unburned ammonia concentration, a method for operating a heating furnace, a method for operating a burner facility, and a heating furnace control device according to the present invention is applied. Figure 2 is a transverse cross-sectional view schematically showing a heating furnace to which an embodiment of the method for estimating unburned ammonia concentration, a method for operating a heating furnace, a method for operating a burner facility, and a heating furnace control device according to the present invention is applied. Figures 3(a) and 3(b) are a side view and a front view showing details of a burner facility that uses ammonia as fuel gas. Figures 4(a) and 4(b) are a side view and a front view showing details of a burner facility that does not use ammonia as fuel gas. Figure 5 is a graph showing the correlation between the carbon monoxide concentration and the unburned ammonia concentration in the exhaust gas from the burner facility when the combustion rate of a carbon-containing fuel contained in the fuel gas is faster than the combustion rate of ammonia. 6(a) and 6(b) are graphs showing the correlation between the carbon monoxide concentration and the unburned ammonia concentration in the exhaust gas from the burner equipment when the combustion rates of the ammonia contained in the fuel gas and the carbon-containing fuel are equal and when the combustion rate of the ammonia contained in the fuel gas is faster than the combustion rate of the carbon-containing fuel, respectively. FIG. 7 is a diagram schematically showing an example of the arrangement of a CO concentration meter in a heating furnace to which an embodiment of the method for estimating an unburned ammonia concentration, a method for operating a heating furnace, a method for operating a burner equipment, and a heating furnace control device according to the present invention is applied. FIG. 8 is a graph showing the correlation between the carbon monoxide concentration and the unburned ammonia concentration in the exhaust gas discharged from the flue of the heating furnace. FIG. 9 is a diagram schematically showing a heating furnace to which another embodiment of the method for estimating an unburned ammonia concentration according to the present invention is applied. FIG. 10 is a block diagram showing the configuration of an example of a heating furnace control device according to the present invention. FIG. 11 is a diagram schematically showing a test heating furnace for identifying the correlation between the carbon monoxide concentration and the unburned ammonia concentration in the exhaust gas from the heating furnace, in the method for estimating an unburned ammonia concentration according to the present invention. Fig. 12 is a graph for explaining an example of a step of identifying a correlation between the carbon monoxide concentration and the unburned ammonia concentration contained in the exhaust gas of the heating furnace in the method for estimating the unburned ammonia concentration according to the present invention. Fig. 13 is a graph showing an example of an estimated value of the unburned ammonia concentration according to the method for estimating the unburned ammonia concentration according to the present invention.

[0019] Hereinafter, with reference to the drawings, embodiments of the method for estimating the unburned ammonia concentration, the method for operating a heating furnace, the method for operating a burner facility, and the heating furnace control device of the present invention will be described in detail. <Heating Furnace> Fig. 1 shows a schematic vertical cross-sectional view of a heating furnace 1 to which the method for estimating the unburned ammonia concentration, the method for operating a heating furnace, the method for operating a burner facility, and the heating furnace control device according to one embodiment of the present invention are applied. Fig. 2 shows a schematic cross-sectional view of the heating furnace 1.

[0020] The heating furnace 1 is equipped with first burner equipment 20a-20d and second burner equipment 30a-30f that combust fuel gas, and is an equipment that uses these as a heat source to heat the material S to be heated that is charged inside the heating furnace 1 to a predetermined temperature. Details of the first burner equipment 20a-20d and the second burner equipment 30a-30f will be described later. The material S to be heated by the heating furnace 1 is mainly metal, and may be either an ferrous metal or a non-ferrous metal. The heating temperature of the material S by the heating furnace 1 is, for example, 700-1400°C.

[0021] In this embodiment, an example will be described in which a pre-rolling slab supplied to a hot rolling line for steel or a thick plate rolling line is used as the material to be heated S, and this is heated by a heating furnace 1. For example, when a slab to be supplied to a hot rolling line for steel is heated by the heating furnace 1, a slab cast by a continuous casting machine or the like is heated to a predetermined heating temperature (for example, about 1100 to 1300°C).

[0022] As shown in Figures 1 and 2, the heating furnace 1 includes a charging section 11 into which the steel material (slab) S to be heated is charged, and an unloading section 12 into which the heated steel material S is unloaded (extracted). For example, the steel material S produced in a continuous casting line is transported to a yard on the charging side of the heating furnace 1 and is charged into the heating furnace 1 from the charging section 11 according to a production schedule of a hot rolling line or the like. The interior of the heating furnace 1 is divided into multiple zones, and is often composed of a heating zone consisting of 2 to 8 zones on the upstream side and a soaking zone consisting of 1 to 3 zones on the downstream side. The interior of the heating furnace 1 is generally equipped with a fixed skid 13f on which the steel material S is placed and a movable skid 13m for transporting the steel material S. A heating furnace 1 equipped with a fixed skid 13f and a movable skid 13m is called a walking beam continuous heating furnace. Walking beam continuous heating furnaces are classified as conveying furnaces, which heat materials while transporting them from the charging section to the unloading section.

[0023] In operation of the heating furnace 1, the interior of the heating furnace 1 is controlled to have different atmospheric temperatures in each zone, thereby gradually increasing the average temperature of the steel material S charged into the heating furnace 1 and controlling the steel material S to reach a predetermined target heating temperature (the target temperature of the slab discharged from the heating furnace 1). The steel material S heated to the target heating temperature passes through the discharge section 12 and is supplied to the hot rolling line.

[0024] As shown in Figure 1, the interior of the heating furnace 1 is provided with a plurality of first burner equipment 20a to 20d and second burner equipment 30a to 30f along the conveying direction TD of the steel material S. When the first burner equipment 20a to 20d and second burner equipment 30a to 30f combust fuel gas and the temperature inside the heating furnace 1 rises, the temperature of the steel material S rises due to radiation from the furnace wall of the heating furnace 1. The temperature of the steel material S also rises due to convection of atmospheric gas generated inside the heating furnace 1. Alternatively, the temperature rise of the steel material S may be caused by the flames from the first burner equipment 20a to 20d and second burner equipment 30a to 30f directly contacting the steel material S.

[0025] The interior of the heating furnace 1 requires a space for placing and transporting the steel material S, in addition to the space for emitting flames from the first burner equipment 20a to 20d and the second burner equipment 30a to 30f. For this reason, a heating furnace is characterized by a larger internal volume relative to the combustion energy input therein, compared to turbines, boilers, etc., which are intended to cause a combustion reaction inside the furnace.

[0026] Furnace volume per unit of combustion energy (m ３ / MW) is, for example, 2 m ３ / MW, 6m with pulverized coal boiler ３ / MW, 2m for gas and oil boilers ３ / MW, whereas in a heating furnace it is 10 to 16 m ３ / MW. In the heating furnaces used in hot rolling lines for steel, the ３ / MW.

[0027] During operation of the heating furnace 1, the doors (opening and closing doors) of the charging section 11 and the discharge section 12 are closed, and the internal pressure of the heating furnace 1 becomes higher than atmospheric pressure. When the doors of the charging section 11 and the discharge section 12 are temporarily opened during charging and unloading of the steel material S, a pressure difference occurs between the center of the heating furnace 1 and the vicinity of the doors. Therefore, gas generated in the furnace by burner heating inside the heating furnace 1 (hereinafter referred to as exhaust gas) flows from areas of high pressure to areas of low pressure. When the door of the heating furnace 1 is open, the exhaust gas often flows in the direction in which it is discharged outside the heating furnace 1 through the opening.

[0028] As shown in Figures 1 and 2, the heating furnace 1 is equipped with a flue 14 for exhausting exhaust gas generated in the furnace by burner heating. 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 concentrations of nitrogen oxides and unburned ammonia in the exhaust gas and treats the exhaust gas so that it meets specified emission standards. As a result, even if nitrogen oxides or unburned ammonia are contained in the exhaust gas, the concentrations of nitrogen oxides and unburned ammonia are reduced by the exhaust gas treatment device 15 connected to the flue 14, thereby suppressing the emission of nitrogen oxides and unburned ammonia to the outside of the heating furnace 1. In the following description, "suppressed" means that the concentrations of nitrogen oxides and unburned ammonia in the exhaust gas are reduced to or below the upper limit of the nitrogen oxide and unburned ammonia concentrations that are preset so as not to exceed, for example, legally regulated values.

[0029] The flue 14 may be located anywhere in the heating furnace 1 as long as it can discharge the exhaust gas generated in the heating furnace 1 outside the furnace, but it is preferably located near the charging section 11 of the heating furnace 1, as shown in Figures 1 and 2. In this way, the slabs transported to the yard on the charging 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. The flue 14 may also be equipped with a heat recovery device (not shown) that recovers the sensible heat of the exhaust gas.

[0030] 1 and 2, in the heating furnace 1, first burner equipment 20a to 20d and second burner equipment 30a to 30f are often arranged on the upper and lower sides, respectively, of the steel material S so as to prevent a temperature difference from occurring between the upper and lower surfaces of the steel material S. Also, as shown in Fig. 2, they are often arranged on both sides of the conveying direction TD of the steel material S so as to prevent a temperature difference from occurring between the leading end S1 and the trailing end S2 of the steel material S.

[0031] As shown in Figure 1, the heating furnace 1 is equipped with a control computer 10 for controlling the operating state of the heating furnace 1. The control computer 10 calculates the operating conditions of the first burner equipment 20a-20d and the second burner equipment 30a-30f provided in the heating furnace 1 so that the steel material S is heated to a predetermined target heating temperature. The control computer 10 also controls each operation of charging the steel material S into the heating furnace 1, transporting it within the heating furnace 1, and unloading it from the heating furnace 1, i.e., the opening and closing of the doors of the charging section 11 and the unloading section 12, the operation of the moving skid 13m, etc.

[0032] A heating furnace to which the method for estimating unburned ammonia concentration, method for operating a heating furnace, method for operating a burner equipment, and heating furnace control device of the present invention are applied is provided with one or more burner equipment inside the heating furnace that performs burner heating using a fuel gas F1 containing ammonia and a carbon-containing fuel. Furthermore, a heating furnace to which the method for estimating unburned ammonia concentration, method for operating a heating furnace, method for operating a burner equipment, and heating furnace control device of the present invention are applied preferably further includes burner equipment that performs burner heating using a fuel gas F2 that does not contain ammonia. Hereinafter, ammonia contained in the fuel gas refers to ammonia gas in a vaporized state.

[0033] In this embodiment, of the first burner equipment 20a to 20d and the second burner equipment 30a to 30f, the first burner equipment 20a to 20d corresponds to the burner equipment that performs burner heating using a fuel gas F1 containing ammonia F11 and a carbon-containing fuel F12, and the second burner equipment 30a to 30f corresponds to the burner equipment that performs burner heating using a fuel gas F2 that does not contain ammonia.

[0034] 1 and 2, of the four first burner equipment 20a to 20d in the heating furnace 1, two first burner equipment 20a, 20b are provided above the center of the heating furnace 1 in the conveying direction TD. The remaining two first burner equipment 20c, 20d are provided below the center of the heating furnace 1 in the conveying direction TD. Furthermore, of the six second burner equipment 30a to 30f, two second burner equipment 30a, 30d are provided above and below the upstream part of the heating furnace 1 in the conveying direction TD. The remaining four second burner equipment 30b, 30c, 30e, 30f are provided above and below the downstream part of the heating furnace 1 in the conveying direction TD. <First burner equipment> Figures 3(a) and 3(b) show details of the burner equipment that performs burner heating using fuel gas F1 containing ammonia F11 and carbon-containing fuel F12, i.e., the first burner equipment 20a to 20d. Figure 3(a) is a side view of the first burner equipment 20a to 20d, and Figure 3(b) is a front view.

[0035] 3(a) and 3(b), the first burner equipment 20a to 20d performs burner heating by injecting a flame into the heating furnace 1 using a fuel gas F1 containing ammonia F11 and a carbon-containing fuel F12, and combustion air A. The first burner equipment 20a to 20d includes a burner nozzle 21 for injecting a flame into the heating furnace 1, a fuel gas supply system 22 that supplies the fuel gas F1 to the burner nozzle 21, and a combustion air supply system 26 that supplies the combustion air A to the burner nozzle 21. The first burner equipment 20a to 20d preferably includes an air ratio control unit 27 that controls the air ratio (also simply referred to as the air ratio) of the fuel gas F1 supplied to the burner nozzle 21 relative to the theoretical air amount.

[0036] The fuel gas supply system 22 is a pipe that supplies a fuel gas F1 containing ammonia F11 and a carbon-containing fuel F12 to the burner nozzle 21. The combustion air supply system 26 is a pipe that supplies combustion air A to the burner nozzle 21.

[0037] The burner nozzle 21 is configured, for example, as a double-pipe nozzle, and fuel gas F1 is injected from the inner pipe and combustion air A from the outer pipe toward the furnace interior. As a result, a combustible gas mixture of fuel gas F1 and combustion air A is formed in front of the burner nozzle 21, and a flame is injected from the tip of the burner nozzle 21 toward the interior of the heating furnace 1.

[0038] When the heating furnace 1 is provided with a plurality of first burner equipment 20a to 20d as in the first embodiment, the mixing ratio of the ammonia F11 and the carbon-containing fuel F12 supplied to each of the first burner equipment 20a to 20d and the type of the carbon-containing fuel F12 may be different or the same. However, it is more economical to use the same type of carbon-containing fuel F12 for the fuel gas F1 supplied to the plurality of first burner equipment 20, because this avoids the need for a complex supply facility for the fuel gas F1 to the heating furnace 1 and an increase in facility costs.

[0039] Ammonia F11 is a flame-retardant fuel that is more difficult to ignite than general fuels and has a slower combustion rate. Therefore, in the first burner facilities 20a to 20d, by using fuel gas F1 in which ammonia F11 is mixed with carbon-containing fuel F12, it is possible to improve the stability of combustion compared to when only ammonia F11 is used.

[0040] The carbon-containing fuel F12 refers to a fuel that contains carbon as a constituent element. Because the carbon-containing fuel F12 contains carbon as a constituent element, carbon monoxide and carbon dioxide are produced when the fuel is burned by heating with a burner. The carbon-containing fuel F12 is preferably methane, ethane, ethylene, acetylene, propane, propylene, butane, benzene, carbon monoxide, or the like. Fossil fuels can be mainly used as the carbon-containing fuel F12, and include city gas, natural gas, propane gas, and the like. The carbon-containing fuel F12 is not limited to fuel extracted from natural gas or the like, and is preferably artificially synthesized. It is preferable to use an appropriate mixture of these fuels as the carbon-containing fuel F12.

[0041] In the first embodiment, coal gas is used as the carbon-containing fuel F12. Coal gas is a gas obtained from coal. The coal gas preferably contains any of by-product gases generated in steelworks, specifically, coke oven gas, blast furnace gas, converter gas, and electric furnace gas. This is because these have the effect of stabilizing the combustion of ammonia F11.

[0042] Coke oven gas is a by-product gas produced by high-temperature carbonization of coal to produce coke. Blast furnace gas is a by-product gas produced when iron ore is reduced in a blast furnace to produce pig iron. Converter furnace gas is a by-product gas produced in the steelmaking process in a converter furnace. Electric furnace gas is a gas produced by the incomplete combustion of auxiliary fuel (recarburizer) in an electric furnace.

[0043] It is also preferable to use a mixed gas (also called M gas) of blast furnace gas, coke oven gas, and converter gas as the coal gas, because by mixing coal gases with different calorific values, the amount of heat required to heat the steel material S can be supplied, and the operation of the heating furnace 1 can be stably carried out.

[0044] Furthermore, the fuel gas F1 used in the first burner equipment 20 may contain a third fuel gas in addition to ammonia F11 and the carbon-containing fuel F12. The third fuel gas is a fuel that does not contain ammonia F11 and does not contain the carbon-containing fuel F12. It is preferable to use, for example, hydrogen as the third fuel gas.

[0045] 3(a) and 3(b) illustrate a case where a mixed gas of ammonia F11 and coal gas F12 is used as the fuel gas F1 used in the first burner equipment 20.

[0046] An ammonia gas supply system 23 and a coal gas supply system 24 are connected to the fuel gas supply system 22. Ammonia F11 supplied from the ammonia gas supply system 23 and coal gas F12 supplied from the coal gas supply system 24 are mixed in a mixing section 25 and supplied to the burner nozzle 21 through the fuel gas supply system 22.

[0047] The ammonia gas supply system 23 is supplied with ammonia F11 from, for example, a tank that stores ammonia F11, and this ammonia F11 is sent to the burner nozzle 21. The coal gas supply system 24 is supplied with coal gas F12 from, for example, a tank that stores coal gas, and this coal gas F12 is sent to the burner nozzle 21.

[0048] It is preferable that flow rate control valves 23v and 24v for adjusting the amounts of the gases supplied to the mixing section 25 and flow meters 23m and 24m for measuring the supply flow rates are provided midway through the ammonia gas supply system 23 and the coal gas supply system 24. In this way, the mixing ratio of the ammonia F11 and the coal gas F12 contained in the fuel gas F1 can be adjusted.

[0049] The flow meters 23m and 24m may be configured to estimate the flow rates of ammonia F11 and coal gas F12 by measuring the pressure of the gas conveyed by the ammonia gas supply system 23 and the coal gas supply system 24. In this way, the flow rates can be easily estimated using the pressure meters.

[0050] The mixing section 25 refers to the portion where the supply pipe of the coal gas supply system 24 and the supply pipe of the ammonia gas supply system 23 join. Ammonia F11 and coal gas F12 are supplied from their respective supply pipes and joined together, so that mixing is achieved without the need for a special stirring mechanism. The mixing section 25 may be configured as a space having an appropriate volume at the position where these supply pipes join. However, it is more preferable to equip the mixing section 25 with a static mixing device such as a static mixer or a dynamic mixer with a stirring function. In this way, fuel gas F1 in which coal gas F12 and ammonia F11 are more uniformly mixed can be produced.

[0051] It is preferable to provide a flow rate adjustment valve 26v for adjusting the flow rate of combustion air A supplied to the burner nozzle 21 and a flow rate meter 26m for measuring the supply flow rate in the middle of the combustion air supply system 26 of the first burner equipment 20. This makes it possible to adjust the amount of combustion air A in the first burner equipment 20 and adjust the air ratio in burner heating of the first burner equipment 20. It is also preferable for the flow rate meter 26m of the combustion air supply system 26 to estimate the flow rate by measuring the pressure of the combustion air being transported.

[0052] The air ratio control unit 27 controls the air ratio of the fuel gas F1 of each of the first burner units 20a to 20d relative to the theoretical air amount. The air ratio control unit 27 has a function of adjusting the air ratio of the combustion air A to the fuel gas F1 for each of the first burner units 20a to 20d. Specifically, the air ratio control unit 27 measures the flow rate of the fuel gas F1 supplied to the burner nozzle 21 using flow meters 23m and 24m provided in the ammonia gas supply system 23 and the coal gas supply system 24. Furthermore, the air ratio control unit 27 calculates the theoretical air amount required for complete combustion of the fuel gas F1 based on the measured flow rate of the fuel gas F1 and the fuel composition of the fuel gas F1. The air ratio control unit 27 then adjusts the aperture of the flow rate control valve 26v provided in the combustion air supply system 26 to control the air ratio of the combustion air A to the fuel gas F1 in each of the first burner units 20a to 20d to a target air ratio set by the control computer 10 or the like. <Second burner equipment> Figures 4(a) and 4(b) show details of the burner equipment that performs burner heating using fuel gas F2 that does not contain ammonia, i.e., the second burner equipment 30a to 30f. Figure 4(a) is a side view of the second burner equipment 30a to 30f, and Figure 4(b) is a front view.

[0053] The second burner equipment 30a to 30f has a configuration in which the ammonia gas supply system 23, and the flow meter 23m and flow control valve 23v arranged in the ammonia gas supply system 23 are omitted from the first burner equipment 20a to 20d shown in Figures 3(a) and 3(b). Furthermore, the second burner equipment 30a to 30f does not need to be provided with a mixing section 25 that mixes ammonia F11 and coal gas F12. In other respects, the second burner equipment 30a to 30f can be configured in the same way as the first burner equipment 20a to 20d.

[0054] 4(a) and 4(b), the second burner equipment 30a to 30f performs burner heating by injecting a flame into the heating furnace 1 using fuel gas F2 made of coal gas and combustion air A. The second burner equipment 30a to 30f includes a burner nozzle 31 for injecting a flame into the heating furnace 1, a fuel gas supply system 32 for supplying the fuel gas F2 to the burner nozzle 31, and a combustion air supply system 36 for supplying the combustion air A to the burner nozzle 31. The second burner equipment 30a to 30f preferably includes an air ratio control unit 37 for controlling the air ratio (also simply referred to as the air ratio) of the fuel gas F2 supplied to the burner nozzle 31 relative to the theoretical air amount.

[0055] The fuel gas supply system 32 is a pipe that supplies fuel gas F2 to the burner nozzle 31. The combustion air supply system 36 is a pipe that supplies combustion air A to the burner nozzle 31.

[0056] The burner nozzle 31 is configured, for example, as a double-pipe nozzle, and fuel gas F2 is injected from the inner pipe and combustion air A from the outer pipe toward the furnace interior. As a result, a combustible gas mixture of fuel gas F2 and combustion air A is formed in front of the burner nozzle 31, and a flame is injected from the tip of the burner nozzle 31 toward the interior of the heating furnace 1.

[0057] The coal gas used as the fuel gas F2 of the second burner equipment 30a-30f may be the same as or different from the coal gas used as the carbon-containing gas F11 contained in the fuel gas F1 of the first burner equipment 20. Furthermore, the fuel gas F2 of the second burner equipment 30a-30f is not limited to coal gas. The fuel gas F2 of the second burner equipment 30a-30f may be one or more of city gas, natural gas, and propane gas, or a mixture of two or more of these. Furthermore, the fuel gas F2 of the second burner equipment 30 may be carbon monoxide gas or methane (including both methane extracted from natural gas and artificially synthesized methane). <Correlation between carbon monoxide concentration and unburned ammonia concentration in exhaust gas> As described above, the first burner equipment 20a-20d performs burner heating by injecting a flame into the furnace using a fuel gas F1 containing ammonia F11 and a carbon-containing fuel F12 and combustion air A. It is known that ammonia F11 and carbon-containing fuel F12 have different combustion speeds. The combustion speed refers to the speed at which fuel gas F1 enters the flame surface perpendicular to the flame when the flame generated by burner heating propagates. The combustion speed depends on the rate of chemical reaction and thermal conductivity of the mixture of unburned fuel gas F1 and fuel air A.

[0058] The burning rates of ammonia and typical carbon-containing fuels are shown in Table 1. In Table 1, the burning rates are shown using Weaver's burning rate coefficient (an index showing the relative value of the maximum burning rate in a mixture of fuel gas and combustion air, when the maximum burning rate of hydrogen is set to 100).

[0059]

[0060] As shown in Table 1, there is a difference in the combustion speed between ammonia and the carbon-containing fuel. Therefore, although the fuel gas F1 injected from the burner nozzles 21 of the first burner equipment 20a to 20d generates a mixed gas with the combustion air A and a combustion reaction occurs, there is a difference in the combustion speed between the ammonia F11 and the carbon-containing fuel F12 contained in the fuel gas F1.

[0061] For example, if the combustion rate of the carbon-containing fuel F12 contained in the fuel gas F1 is faster than the combustion rate of the ammonia F11, the carbon-containing fuel F12 in the fuel gas F1 combines with the oxygen in the combustion air A, causing the combustion reaction of the carbon-containing fuel F12 to proceed first. The oxygen in the combustion air A is consumed first by the combustion of the carbon-containing fuel F12, resulting in a shortage of oxygen when the ammonia F11 in the fuel gas F1 burns. At this time, the combustion reaction of the carbon-containing fuel F12 oxidizes the carbon atoms contained in the carbon-containing fuel F12 through complete combustion, producing carbon dioxide, making it difficult to produce carbon monoxide, which would otherwise be produced through incomplete combustion. In contrast, when the ammonia F11 burns, the oxygen required for the combustion reaction of the ammonia F11 is insufficient, leaving unburned ammonia. Therefore, while unburned ammonia remains in the exhaust gas from the first burner equipment 20a-20d, the production of carbon monoxide is suppressed.

[0062] Next, when the air ratio of the fuel gas F1 to the theoretical air amount becomes small, the amount of oxygen in the combustion air A becomes insufficient for the preceding combustion reaction of the carbon-containing fuel F12. As a result, the combustion of the carbon-containing fuel F12 becomes incomplete, and carbon monoxide is produced along with carbon dioxide.

[0063] On the other hand, when the combustion rate of the ammonia F11 is slower than the combustion rate of the carbon-containing fuel F12, the oxygen in the combustion air A is consumed first by the preceding combustion reaction of the carbon-containing fuel F12. As a result, the combustion state of the ammonia F11 becomes even more incomplete, and the production of unburned ammonia is promoted. In this way, a correlation is created in which the more carbon monoxide is contained in the exhaust gas discharged from the first burner equipment 20a to 20d, the more unburned ammonia also increases.

[0064] As described above, the present invention is based on the finding that a correlation is observed between the concentration of unburned ammonia and the concentration of carbon monoxide contained in the exhaust gas discharged from the burner equipment when burner heating is performed using fuel gas F1 containing ammonia F11 and carbon-containing fuel F12. That is, the present invention estimates the concentration of unburned ammonia contained in the exhaust gas from the measured value of the carbon monoxide concentration in the exhaust gas based on 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.

[0065] Figure 5 shows the correlation between the carbon monoxide concentration and the unburned ammonia concentration in the exhaust gas from the first burner equipment 20a to 20d when the combustion rate of the carbon-containing fuel F12 contained in the fuel gas F1 is faster than the combustion rate of the ammonia F11.

[0066] As shown in Fig. 5, when the combustion rate of the carbon-containing fuel F12 contained in the fuel gas F1 is faster than the combustion rate of the ammonia F11, the rate at which the carbon-containing fuel F12 completely burns is faster than the rate at which the ammonia F11 completely burns. Therefore, under conditions in which the carbon-containing fuel F12 completely burns (conditions in which the "CO concentration" is zero in the graph shown in Fig. 5), unburned ammonia is contained in the exhaust gas. The greater the difference between the combustion rate of the ammonia F11 and the combustion rate of the carbon-containing fuel F12, the greater the unburned ammonia concentration when the CO concentration is zero, i.e., the value of the intercept on the vertical axis of the graph shown in Fig. 5.

[0067] Then, as the air ratio of the fuel gas F1 to the theoretical air amount 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 more insufficient, causing the unburned ammonia concentration to also increase. At this time, the correlation between the unburned ammonia concentration and the carbon monoxide concentration contained in the exhaust gas discharged from the first burner equipment 20a to 20d becomes linear or approximately linear. Furthermore, in the graph shown in Figure 5, the slope of the unburned ammonia concentration versus the carbon monoxide concentration changes depending on the combustion rates of the ammonia F11 and the carbon-containing fuel F12 contained in the fuel gas F1. Specifically, the slope becomes steeper as the combustion rate of the carbon-containing fuel F12 is higher than the combustion rate of the ammonia F11, and the difference between them is greater.

[0068] 6(a) shows the correlation between the carbon monoxide concentration and the unburned ammonia concentration in the exhaust gas when the combustion rate of ammonia F11 contained in fuel gas F1 is equal to the combustion rate of carbon-containing fuel F12. Also, FIG. 6(b) shows the correlation between the carbon monoxide concentration and the unburned ammonia concentration in the exhaust gas when the combustion rate of ammonia F11 contained in fuel gas F1 is faster than the combustion rate of carbon-containing fuel F12.

[0069] As shown in Figure 6(a), when the combustion rate of ammonia F11 contained in the fuel gas F1 is equal to the combustion rate of the carbon-containing fuel F12, the rate at which ammonia F11 completely burns is also equal to the rate at which the carbon-containing fuel F12 completely burns. Therefore, under conditions in which the carbon-containing fuel F12 completely burns (conditions in which the "CO concentration" is zero in the graph shown in Figure 6(a)), no unburned ammonia remains in the exhaust gas. In other words, both the ammonia F11 and the carbon-containing fuel F12 completely burn.

[0070] Then, when the air ratio of the fuel gas F1 to the theoretical air amount is decreased from 1.0, both the ammonia F11 and the carbon-containing fuel F12 become oxygen-deficient in the combustion reaction, and the carbon monoxide concentration in the exhaust gas increases, and the unburned ammonia concentration also increases.

[0071] 6(b), when the combustion rate of ammonia F11 contained in the fuel gas F1 is faster than the combustion rate of the carbon-containing fuel F12, the rate at which ammonia F11 completely burns is faster than the rate at which the carbon-containing fuel F12 completely burns. Therefore, under the condition that ammonia F11 completely burns (the condition that the "unburned ammonia concentration" is zero in the graph shown in FIG. 6(b)), carbon monoxide is contained in the exhaust gas.

[0072] Furthermore, when the air ratio of the fuel gas F1 to the theoretical air amount is reduced from 1.0, the concentration of unburned ammonia contained in the exhaust gas increases, and the oxygen required for the combustion reaction of the carbon-containing fuel F12 becomes even more insufficient, causing the carbon monoxide concentration to increase.

[0073] In this way, in the first burner equipment 20a to 20d that performs burner heating by injecting a flame into the furnace using the fuel gas F1 containing ammonia F11 and the carbon-containing fuel F12 and the combustion air A, a correlation exists between the carbon monoxide concentration and the unburned ammonia concentration in the exhaust gas discharged from the first burner equipment 20 that performs burner heating, depending on the difference between the combustion rate of the ammonia F11 and the combustion rate of the carbon-containing fuel F12. <Method for estimating unburned ammonia concentration - First aspect> First and second aspects of the method for estimating unburned ammonia concentration according to the present invention will be described below.

[0074] The methods for estimating the unburned ammonia concentration of the first and second aspects estimate the concentration of unburned ammonia contained in exhaust gas discharged from a burner facility that performs burner heating using a fuel gas containing ammonia and a carbon-containing fuel.

[0075] In the method for estimating the unburned ammonia concentration of the first aspect, first, an identification step is performed in which a correlation between the carbon monoxide concentration and the unburned ammonia concentration contained in the exhaust gas from the heating furnace 1 is identified in advance. Next, a measurement step is performed in which the carbon monoxide concentration contained in the exhaust gas from the heating furnace 1 is measured when burner heating is performed by the first burner equipment 20a to 20d during operation of the heating furnace 1. Furthermore, an estimation step is performed in which the unburned ammonia concentration contained in the exhaust gas from the heating furnace 1 is estimated based on the carbon monoxide concentration measured in the measurement step and the correlation between the carbon monoxide concentration and the unburned ammonia concentration identified in the identification step.

[0076] The first and second aspects of the specifying step, measuring step, and estimating step will be specifically described below.

[0077] First, in the identification step, a correlation between the carbon monoxide concentration and the unburned ammonia concentration contained in the exhaust gas from the first burner equipment 20a to 20d is identified in advance. To identify the correlation between the carbon monoxide concentration and the unburned ammonia concentration contained in the exhaust gas from the first burner equipment 20a to 20d, for example, the following method can be applied.

[0078] FIG. 7 shows the flow of exhaust gas generated by the flames injected from the first burner units 20a to 20d within the heating furnace 1, and an example of the arrangement of the CO concentration meter 18.

[0079] 7, because a gas flow occurs within the heating furnace 1, the exhaust gas generated by the flames ejected from the first burner equipment 20a to 20d flows downstream in the gas flow within the furnace. Therefore, in the first embodiment, a CO concentration meter 18 that measures the carbon monoxide concentration contained in the exhaust gas discharged from the first burner equipment 20a to 20d is installed downstream in the gas flow within the furnace from the first burner equipment 20a to 20d. This makes it possible to measure the carbon monoxide concentration contained in the exhaust gas discharged from the first burner equipment 20a to 20d online.

[0080] Furthermore, downstream of the gas flow in the furnace of the first burner equipment 20a-20d, the exhaust gas discharged from the first burner equipment 20a-20d is sampled, and actual data on the concentration of unburned ammonia contained in the exhaust gas is collected using a gas component measuring device (not shown). The gas component measuring device may be any device that can measure the concentration of unburned ammonia in wet gas, and a component measuring device using the indophenol method, ion chromatography, or the like may be used. Measurement of the unburned ammonia concentration using the gas component measuring device is preferably performed offline.

[0081] In this way, the actual measured value of the carbon monoxide concentration contained in the exhaust gas discharged from the first burner equipment 20a to 20d, which is measured online by the CO concentration meter 18, and the actual value of the unburned ammonia concentration, which is obtained offline by sampling the exhaust gas, can be obtained as performance data. Then, by changing the air ratio in the first burner equipment 20a to 20d and obtaining multiple sets of performance data, the correlation between the carbon monoxide concentration and the unburned ammonia concentration in the exhaust gas from the first burner equipment 20a to 20d can be identified.

[0082] The above-mentioned specifying step does not necessarily have to be performed during operation of the heating furnace 1. For example, while the heating furnace 1 is stopped, a flame may be sprayed from the first burner equipment 20a to 20d, and the correlation between the carbon monoxide concentration and the unburned ammonia concentration may be specified using the actual measured values ​​of the carbon monoxide concentration and the unburned ammonia concentration obtained thereby. In other words, the specifying step may be performed when the steel material S is not being heated in the heating furnace 1.

[0083] In the identification step, it is preferable to identify the correlation between the carbon monoxide concentration and the unburned ammonia concentration contained in the exhaust gas from the first burner equipment 20 for each classification of the operating conditions of the first burner equipment 20a to 20d. Here, classification of operating conditions refers to dividing the indicators representing the burner heating conditions and combustion state of the first burner equipment 20a to 20d into two or more types. Then, in the identification step, the correlation between the carbon monoxide concentration and the unburned ammonia concentration is identified for each of these classifications. That is, the composition and type of the carbon-containing fuel F12 used for burner heating, the mixing ratio of ammonia F11 to the carbon-containing fuel F12, etc. are selected as the operating conditions for burner heating of the first burner equipment 20a to 20d. Then, it is preferable to classify these operating conditions into, for example, 2 to 10 types, and identify the correlation between the carbon monoxide concentration and the unburned ammonia concentration contained in the exhaust gas from the first burner equipment 20a to 20d for each of the classifications.

[0084] In the identifying step, the correlation between the carbon monoxide concentration and the unburned ammonia concentration can be configured as a table identified for each operating condition category. Alternatively, the correlation between the carbon monoxide concentration and the unburned ammonia concentration can be identified by function approximation such as a linear regression equation, and a function formula can be obtained for each operating condition category.

[0085] In the measuring step, the carbon monoxide concentration contained in the exhaust gas from the first burner equipment 20a to 20d is measured when burner heating is performed by the first burner equipment 20a to 20d.

[0086] 7, in the first burner equipment 20a to 20d, the carbon monoxide concentration contained in the exhaust gas can be measured online using a CO concentration meter 18 arranged downstream of the gas flow in the furnace of the first burner equipment 20a to 20d. The carbon monoxide concentration contained in the exhaust gas discharged from the first burner equipment 20 is preferably measured continuously using the CO concentration meter 18, for example, at intervals of 1 to 60 seconds.

[0087] In the estimation step, the concentration of unburned ammonia contained in the exhaust gas from first burner equipment 20a-20d is estimated based on the carbon monoxide concentration measured in the measurement step and the correlation between the carbon monoxide concentration and the unburned ammonia concentration previously specified in the specification step. At this time, since the correlation between the carbon monoxide concentration and the unburned ammonia concentration contained in the exhaust gas from first burner equipment 20a-20d is previously specified in the specification step, the concentration of unburned ammonia contained in the exhaust gas from first burner equipment 20a-20d can be estimated by using the carbon monoxide concentration measured by CO concentration meter 18 in addition to this. When the correlation between the carbon monoxide concentration and the unburned ammonia concentration is specified by a functional formula, the unburned ammonia concentration can be calculated by inputting the carbon monoxide concentration measured by CO concentration meter 18 into the functional formula, thereby allowing the unburned ammonia concentration to be continuously estimated online. <Method for estimating unburned ammonia concentration - Second aspect> In the first aspect of the method for estimating unburned ammonia concentration described above, in the identifying step, the correlation between the unburned ammonia concentration and the carbon monoxide concentration contained in the exhaust gas discharged from the first burner equipment 20a to 20d is identified.

[0088] Here, as shown in FIG. 1 , when the heating furnace 1 is equipped with second burner equipment 30a to 30f in addition to the first burner equipment 20a to 20d, a certain correlation is also established between the carbon monoxide concentration and the unburned ammonia concentration contained in the exhaust gas discharged from the charging section 11, the discharge section 12, and the flue 14 of the heating furnace 1.

[0089] For example, when coal gas is used as the fuel gas F2 in the second burner equipment 30a-30f, if the burner heating by the second burner equipment 30a-30f becomes oxygen-deficient, the carbon monoxide concentration in the exhaust gas from the second burner equipment 30a-30f increases. However, because the fuel gas F2 used by the second burner equipment 30a-30f does not contain ammonia gas, unburned ammonia is not generated in the second burner equipment 30a-30f. Although ammonia may be contained in the coal gas F2, the amount of ammonia contained is very small. Therefore, the amount of unburned ammonia generated from the second burner equipment 30a-30f is much smaller than the amount of unburned ammonia discharged from the first burner equipment 20a-20d, and the concentration of unburned ammonia generated in the second burner equipment 30a-30f can be ignored.

[0090] Therefore, when the exhaust gas discharged from the first burner equipment 20a to 20d and the exhaust gas discharged from the second burner equipment 30a to 30f are combined, the combined exhaust gas contains unburned ammonia produced in the first burner equipment 20a to 20d and the total amount of carbon monoxide produced in the first burner equipment 20a to 20d and the carbon monoxide produced in the second burner equipment 30a to 30f.

[0091] Therefore, when the exhaust gas discharged from the first burner equipment 20a to 20d and the exhaust gas discharged from the second burner equipment 30a to 30f join together, the volume of the entire exhaust gas changes, and therefore the value of the gas concentration changes. However, as shown in Figure 8, the correlation between the carbon monoxide concentration and the unburned ammonia concentration contained in the exhaust gas from the first burner equipment 20a to 20d is maintained.

[0092] In this way, even when the second burner equipment 30a to 30f is provided, the exhaust gas discharged from the charging section 11, the discharge section 12, and the flue 14 of the heating furnace 1 is a mixture of the exhaust gas discharged from the first burner equipment 20a to 20d and the exhaust gas discharged from the second burner equipment 30a to 30f, and therefore a certain correlation is established between the carbon monoxide concentration and the unburned ammonia concentration contained in the exhaust gas of the heating furnace 1.

[0093] Based on this principle, the second aspect of the method for estimating the unburned ammonia concentration is the same as the first aspect except that, in the specifying step, a correlation between the carbon monoxide concentration and the unburned ammonia concentration contained in the exhaust gas discharged from the entire heating furnace 1 is specified in advance. This will be described below.

[0094] FIG. 9 is a schematic vertical cross-sectional view of a heating furnace 1 to which the second embodiment of the method for estimating the unburned ammonia concentration is applied.

[0095] When the charging section 11 and the discharge section 12 of the heating furnace 1 are open, the exhaust gas generated inside the heating furnace 1 is discharged from the charging section 11 and the discharge section 12 of the heating furnace 1 according to the gas flow inside the heating furnace 1. When the charging section 11 and the discharge section 12 of the heating furnace 1 are closed, the exhaust gas is discharged from the flue 14.

[0096] 9, CO concentration meters 18a and 18b for measuring the carbon monoxide concentration contained in the exhaust gas are installed at the openings of the charging section 11 and the discharge section 12 of the heating furnace 1, respectively. Furthermore, for the exhaust gas discharged from the flue 14, a CO concentration meter 18c is installed at a position where gas flows from the heating furnace 1 to the exhaust gas treatment device 15. Furthermore, in order to estimate the unburned ammonia concentration of the exhaust gas treated by the exhaust gas treatment device 15, a CO concentration meter 18d may be installed in the flue 14 at a position downstream of the exhaust gas treatment device 15 in the gas flow direction. This allows the carbon monoxide concentration contained in the exhaust gas discharged from the charging section 11 and the discharge section 12 of the heating furnace 1 and the flue 14 to be measured online.

[0097] Although it is not necessary to install all of the above-mentioned CO concentration meters 18a to 18d, it is preferable to install at least one of the CO concentration meter 18a in the charging section 11 of the heating furnace 1 and the CO concentration meter 18b in the discharge section 12. The exhaust gas that passes through the flue 14 and is discharged to the outside of the heating furnace 1 is treated by the exhaust gas treatment device 15, so the concentration of unburned ammonia contained in the exhaust gas discharged to the outside of the heating furnace 1 is suppressed. In contrast, the charging section 11 and the discharge section 12 of the heating furnace 1 are temporarily opened when the steel material S is charged into the heating furnace 1 and when it is discharged from the heating furnace 1, and it is difficult to treat the exhaust gas discharged from the openings using the exhaust gas treatment device, so it may become necessary to detect unburned ammonia in the exhaust gas.

[0098] In the method for estimating the concentration of unburned ammonia according to the second aspect, the specifying step in the method for estimating the concentration of unburned ammonia according to the first aspect is changed as follows.

[0099] That is, in the second aspect of the method for estimating the unburned ammonia concentration, in the identifying step, exhaust gas discharged from the heating furnace 1 is sampled in the charging section 11 equipped with the CO concentration meter 18a, the discharge section 12 equipped with the CO concentration meter 18b, and the flue 14 equipped with the CO concentration meters 18c and 18d, and actual data on the unburned ammonia concentration contained in the exhaust gas is collected using a gas component measuring device (not shown). The gas component measuring device may be any device that can measure the unburned ammonia concentration in wet gas, and a component measuring device using the indophenol method, ion chromatography, or the like may be used. Measurement of the unburned ammonia concentration using the gas component measuring device may be performed offline.

[0100] In this way, actual measured values ​​of the carbon monoxide concentrations contained in the exhaust gas discharged from the charging section 11 and the discharge section 12 of the heating furnace 1 and the flue 14, which are measured online by the CO concentration meters 18a to 18d, and actual values ​​of the unburned ammonia concentrations obtained offline by sampling the exhaust gas, can be obtained as performance data. Then, by changing the air ratio in the first burner equipment 20a to 20d and obtaining multiple sets of performance data, a correlation between the carbon monoxide concentration and the unburned ammonia concentration in the exhaust gas discharged from the heating furnace 1 can be identified.

[0101] In the second aspect of the method for estimating the unburned ammonia concentration, the identifying step preferably identifies the correlation between the carbon monoxide concentration and the unburned ammonia concentration contained in the exhaust gas from the heating furnace 1 for each classification of the operating conditions of the heating furnace 1. Here, the classification of the operating conditions of the heating furnace 1 refers to dividing the indicators representing the burner heating conditions and combustion state by the first burner equipment 20a to 20d provided in the heating furnace 1 into two or more classifications. Furthermore, the classification of the operating conditions of the heating furnace 1 may be such that the indicators representing the burner heating conditions and combustion state by the first burner equipment 20a to 20d provided in the heating furnace 1 and the burner heating conditions and combustion state by the second burner equipment 30a to 30f are divided into two or more classifications. Then, in the identifying step, the correlation between the carbon monoxide concentration and the unburned ammonia concentration is identified for each classification. Specifically, the burner heating operating conditions for the first burner equipment 20a-20d include the composition and type of the carbon-containing fuel F12 used for burner heating, the mixing ratio of ammonia F11 and the carbon-containing fuel F12, etc. These operating conditions are then preferably classified into, for example, 2 to 10 types, and a correlation between the carbon monoxide concentration and the unburned ammonia concentration contained in the exhaust gas discharged from the heating furnace 1 is identified for each classification. Furthermore, the burner heating operating conditions for the second burner equipment 30a-30f include the composition and type of the fuel gas F2, the air ratio, etc. These operating conditions are then preferably classified into, for example, 2 to 10 types, and a correlation between the carbon monoxide concentration and the unburned ammonia concentration contained in the exhaust gas discharged from the heating furnace 1 is identified for each classification.

[0102] In the second embodiment of the method for estimating the concentration of unburned ammonia, the measuring step is performed by measuring the carbon monoxide concentration contained in the exhaust gas from the entire heating furnace 1 online during operation of the heating furnace 1. As shown in FIG. 9 , the heating furnace 1 can continuously measure the carbon monoxide concentration contained in the exhaust gas using CO concentration meters 18a to 18d. The carbon monoxide concentration contained in the exhaust gas discharged from the heating furnace 1 is preferably continuously measured using the CO concentration meters 18a to 18d at intervals of, for example, 1 to 60 seconds. Note that the CO concentration meters 18a, 18b provided in the charging section 11 and the discharge section 12 of the heating furnace 1 preferably continuously measure the carbon monoxide concentration contained in the exhaust gas at least while the charging section 11 and the discharge section 12 are open.

[0103] In the estimation step, the concentration of unburned ammonia contained in the exhaust gas from the heating furnace 1 is estimated based on the carbon monoxide concentration measured in the measurement step and the correlation between the carbon monoxide concentration and the unburned ammonia concentration identified in the identification step. At this time, the correlation between the carbon monoxide concentration and the unburned ammonia concentration contained in the exhaust gas from the heating furnace 1 is identified in advance in the identification step. Therefore, by using the carbon monoxide concentration continuously measured by the CO concentration meters 18a to 18d in addition to this, the concentration of unburned ammonia contained in the exhaust gas from the heating furnace 1 can be estimated.

[0104] 9, an ammonia concentration meter 17 for measuring ammonia concentration is provided in the flue 14 of the heating furnace 1. The ammonia concentration meter 17 acquires an actual measurement value of the unburned ammonia concentration contained in the exhaust gas, and a CO concentration meter 18c provided in the flue 14 acquires an actual measurement value of the carbon monoxide concentration contained in the exhaust gas. It is preferable to identify a correlation between the carbon monoxide concentration and the unburned ammonia concentration contained in the exhaust gas from the heating furnace 1 from these actual measurement values.

[0105] Since it is often difficult to continuously measure the unburned ammonia concentration using the ammonia concentration meter 17, it is not necessary to continuously obtain the actual measured value of the unburned ammonia concentration using the ammonia concentration meter 17. In this case, it is preferable to obtain the actual measured value of the unburned ammonia concentration contained in the exhaust gas using the ammonia concentration meter 17, for example, every 10 to 60 minutes, and correlate it with the actual measured value of the carbon monoxide concentration using the CO concentration meter 18c installed in the flue 14.

[0106] The correlation between the carbon monoxide concentration and the unburned ammonia concentration contained in the exhaust gas from the heating furnace 1, obtained by the ammonia concentration meter 17 and the CO concentration meter 18c provided in the flue 14, can be considered to apply to the entire heating furnace 1, which is a mixture of exhaust gas from all of the first burner equipment 20a to 20d and second burner equipment 30a to 30f that perform burner heating inside the heating furnace 1. In other words, the correlation between the carbon monoxide concentration and the unburned ammonia concentration identified in the identification 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 that passes through the charging section 11 and the discharge section 12 of the heating furnace 1 and is discharged. Therefore, as described above, the correlation between the carbon monoxide concentration and the unburned ammonia concentration contained in the exhaust gas from the heating furnace 1, which is identified by installing the ammonia concentration meter 17 in the flue 14 of the heating furnace 1 and executing the identification step, can also be used to estimate the unburned ammonia concentration in the exhaust gas discharged from the charging section 11 and the discharge section 12 of the heating furnace 1, and there is no need to install multiple ammonia concentration meters 17.

[0107] Except for the above points, the method for estimating the unburned ammonia concentration of the second aspect is performed in the same manner as the method for estimating the unburned ammonia concentration of the first aspect. <Method for operating a heating furnace and method for operating a burner facility> Embodiments of the method for operating a heating furnace and method for operating a burner facility according to the present invention will be described below.

[0108] The method for operating a heating furnace of this embodiment includes an operation step of manipulating the operating conditions of the heating furnace 1 so that the unburned ammonia concentration contained in the exhaust gas discharged from the heating furnace 1 becomes smaller when the estimated value of the unburned ammonia concentration estimated by the above-mentioned method for estimating the unburned ammonia concentration is equal to or greater than a predetermined value.

[0109] Furthermore, the burner equipment operating method of this embodiment is realized by setting the operation target of the operation step to the operating conditions of the first burner equipment 20a to 20d rather than the operating conditions of the entire heating furnace 1 in the above-described heating furnace operating method.

[0110] When the method for operating a heating furnace or a burner facility according to this embodiment is performed based on the method for estimating the unburned ammonia concentration according to the first aspect, the flow is, for example, as follows.

[0111] First, by the method for estimating the unburned ammonia concentration of the first aspect described above, the unburned ammonia concentration of the exhaust gas discharged from at least one of the first burner equipment 20a to 20d provided in the heating furnace 1 is estimated. Then, based on the estimated unburned ammonia concentration, the operating conditions of the first burner equipment 20a to 20d are manipulated so as to reduce the unburned ammonia concentration contained in the exhaust gas discharged from the first burner equipment 20a to 20d.

[0112] When the unburned ammonia concentration in the exhaust gas discharged from the first burner equipment 20a to 20d is reduced by manipulating the operating conditions of the first burner equipment 20a to 20d, the unburned ammonia concentration contained in the exhaust gas discharged from the entire heating furnace 1 is also reduced. In this way, the operating conditions of the heating furnace 1 are manipulated so as to reduce the unburned ammonia concentration contained in the exhaust gas discharged from the heating furnace 1.

[0113] In this case, the operating conditions of the first burner equipment 20a to 20d, which are operated in the operation step so as to reduce the unburned ammonia concentration in the exhaust gas discharged from the first burner equipment 20a to 20d, preferably include at least one of the flow rate of the combustion air A used for burner heating by the first burner equipment 20a to 20d, the flow rate of the fuel gas F1, the air ratio of the fuel gas F1 to the theoretical air amount, and the mixing ratio of the ammonia F11 and the carbon-containing fuel F12.

[0114] For example, by increasing the combustion air A as an operating condition of the first burner equipment 20a to 20d operated in the operation step, the combustion of unburned ammonia is promoted and unburned ammonia is less likely to remain. Furthermore, by reducing the flow rate of the fuel gas F1, the flow rate of the combustion air A increases relatively, and a similar effect is obtained. The same is true when the air ratio of the fuel gas F1 to the theoretical air amount is increased. Furthermore, by adjusting the mixing ratio of ammonia F11 and coal gas F12 so as to reduce the flow rate of ammonia F11, unburned ammonia is less likely to remain.

[0115] Furthermore, when the method for operating a heating furnace or the method for operating a burner facility according to this embodiment is performed based on the method for estimating the unburned ammonia concentration according to the second aspect, the flow is, for example, as follows.

[0116] First, the unburned ammonia concentration in the exhaust gas discharged from the heating furnace 1 is estimated by the method for estimating the unburned ammonia concentration of the second aspect described above. Then, based on the estimated unburned ammonia concentration, the operating conditions of the heating furnace 1 are manipulated so that the unburned ammonia concentration contained in the exhaust gas discharged from the heating furnace 1 becomes smaller.

[0117] In this case, the operating conditions of the heating furnace 1 operated in the operation step so as to reduce the unburned ammonia concentration in the exhaust gas discharged from the heating furnace 1 preferably include at least one of the flow rate of the combustion air A used for burner heating by the first burner equipment 20a-20d, the flow rate of the fuel gas F1, the air ratio of the fuel gas F1 to the theoretical air amount, and the mixing ratio of ammonia F11 and the carbon-containing fuel F12. Furthermore, when estimating the unburned ammonia concentration in the exhaust gas discharged from the heating furnace 1 using the method for estimating the unburned ammonia concentration of the second aspect, the ambient temperature within the heating furnace 1 may be selected as the operating condition of the heating furnace 1 operated in the operation step. Increasing the ambient temperature within the heating furnace 1 promotes combustion of ammonia F11, thereby reducing the unburned ammonia concentration in the exhaust gas discharged from the heating furnace 1. <Heating Furnace Control Device> An embodiment of a heating furnace control device according to the present invention will be described below.

[0118] FIG. 10 shows the configuration of the heating furnace control device 40 of this embodiment.

[0119] The heating furnace control device 40 of this embodiment is a device for executing the above-mentioned heating furnace operation method. As shown in Figure 10, the heating furnace control device 40 includes a memory unit 41, an acquisition unit 42, an estimation unit 43, an operation amount calculation unit 44, and an output unit 45.

[0120] The memory unit 41 stores a predetermined correlation between the carbon monoxide concentration and the unburned ammonia concentration contained in the exhaust gas from the heating furnace 1. Specifically, the memory unit 41 stores the correlation between the carbon monoxide concentration and the unburned ammonia concentration contained in the exhaust gas from the heating furnace 1, which correlation was previously determined, for example, by the determination step of the above-described method for estimating the unburned ammonia concentration. The correlation between the carbon monoxide concentration and the unburned ammonia concentration stored in the memory unit 41 may be stored in the form of a table or a function. Furthermore, the memory unit 41 preferably acquires a predetermined upper limit value for the unburned ammonia concentration from the control computer 10 of the heating furnace 1 and stores this.

[0121] The acquisition unit 42 acquires the carbon monoxide concentration contained in the exhaust gas from the heating furnace 1, measured during operation of the heating furnace 1. Specifically, the acquisition unit 42 acquires the carbon monoxide concentration contained in the exhaust gas from the heating furnace 1, measured during operation of the heating furnace 1 by the CO concentration meters 18a to 18d arranged in the heating furnace 1. As described above, the CO concentration meters 18a to 18d are arranged, for example, in the charging section 11 (CO concentration meter 18a), the discharge section 12 (CO concentration meter 18b), and the flue 14 (CO concentration meters 18c and 18d) of the heating furnace 1. It is preferable that the acquisition unit 42 acquires the measured values ​​of the carbon monoxide concentration via the control computer 10 or another operation data server.

[0122] The estimation unit 43 estimates the concentration of unburned ammonia contained in the exhaust gas from the heating furnace 1 based on the carbon monoxide concentration acquired by the acquisition unit 42 and the correlation between the carbon monoxide concentration and the unburned ammonia concentration stored in the memory unit 41. When the correlation between the carbon monoxide concentration and the unburned ammonia concentration stored in the memory unit 41 is in table form, the estimation unit 43 calculates an estimated value of the unburned ammonia concentration by referring to the table value corresponding to the carbon monoxide concentration acquired by the acquisition unit 42. When the correlation between the carbon monoxide concentration and the unburned ammonia concentration stored in the memory unit 41 is in function form, the estimation unit 43 calculates an estimated value of the unburned ammonia concentration by inputting the measured value of the carbon monoxide concentration acquired by the acquisition unit 42 into the function.

[0123] When the estimated value of the unburned ammonia concentration estimated by the estimation unit 43 is equal to or greater than a predetermined value, i.e., equal to or greater than a preset upper limit value of the unburned ammonia concentration, the operation amount calculation unit 44 calculates an operation amount for the operating conditions of the heating furnace 1 so that the estimated value becomes smaller than this predetermined value.

[0124] The output unit 45 outputs the operating conditions of the heating furnace 1 calculated by the operation variable calculation unit 44 to the control computer 10 of the heating furnace 1, or outputs them to the display unit 46 as guidance operation variables to be referred to when the operator operates the operating conditions of the heating furnace 1. When the output destination of the operation variables for the operating conditions of the heating furnace 1 from the output unit 45 is the control computer 10, it is preferable that the operating conditions of the heating furnace 1 are automatically updated in the control computer 10. When the output destination of the operation variables for the operating conditions of the heating furnace 1 from the output unit 45 is the display unit 46, it is preferable that the operator operates the operating conditions of the heating furnace 1 based on the guidance operation variables shown on the display unit 46.

[0125] The heating furnace control device 40 can be configured using a general-purpose computer including, for example, a memory, an auxiliary storage device such as a hard disk drive or solid state drive, and a CPU (Central Processing Unit). The auxiliary storage device stores a program that executes control by the heating furnace control device 40, and when the program is executed by the CPU, it is read from the auxiliary storage device to the memory. Data being processed by the CPU is stored in the memory as needed, and is also stored in the auxiliary storage device as needed.

[0126] The storage unit 41 is preferably realized by, for example, the auxiliary storage device described above. The acquisition unit 42, estimation unit 43, operation amount calculation unit 44, and output unit 45 are preferably realized by the CPU reading and executing 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 may be configured as a display of a terminal device such as a smartphone or tablet. In this case, the terminal device equipped with the display unit 46 is configured to be able to communicate with the heating furnace control device 40 via a network.

[0127] Although the embodiments of the method for estimating the unburned ammonia concentration, the method for operating a heating furnace, the method for operating a burner facility, and the control device for a heating furnace according to the present invention have been described above, the present invention is not limited to these embodiments.

[0128] In order to verify the effects of the method for estimating the concentration of unburned ammonia, the method for operating a heating furnace, the method for operating a burner facility, and the control device for a heating furnace of the present invention, a test was conducted to estimate the concentration of ammonia contained in the exhaust gas from the heating furnace using a test heating furnace. The results are described below.

[0129] FIG. 11 is a schematic vertical cross-sectional view of the test heating furnace 1T.

[0130] As shown in Figure 11, the test heating furnace 1T is equipped with a flue 14 and an exhaust gas treatment device 15. The exhaust gas treatment device 15 is configured to include an oxidation catalyst, a denitration device, and an ammonia removal device. The flue 14 is provided with an openable and closable gas sampling port 14a located upstream of the exhaust gas treatment device 15 in the exhaust gas flow direction, so that samples of the exhaust gas flowing through the flue 14 can be collected as needed.

[0131] As shown in FIG. 11 , the test heating furnace 1T was configured to include ten first burner equipment 20a-20j as heat sources. These first burner equipment 20a-20j were burner equipment that performed burner heating using a fuel gas F1 containing ammonia F11 and a carbon-containing fuel F12. Of the ten first burner equipment 20a-20j, five first burner equipment 20a-20e were positioned above the steel material S being transported through the furnace, and the remaining five first burner equipment 20f-20j were positioned below the steel material S being transported through the furnace. The test heating furnace 1T was not configured to include second burner equipment that performed burner heating using a fuel gas F2 that did not contain ammonia. The first burner equipment 20a-20j were of the same type, and each of the first burner equipment 20a-20j had a rated capacity of 800,000 kcal / hr.

[0132] The exhaust gas discharged from the flue 14 of the test heating furnace 1T was treated by an exhaust gas treatment device 15 to reduce the concentrations of nitrogen oxides, unburned ammonia, and carbon monoxide in the exhaust gas, and then released into the atmosphere.

[0133] The fuel gas F1 supplied to the first burner units 20a to 20j was an M gas consisting of ammonia F11 and coal gas F12. Specifically, the M gas was a mixture of blast furnace gas, coke oven gas, and converter gas, and had a lower heating value of 2000 kcal / Nm3. ３ Table 2 shows the results of a preliminary gas chromatographic analysis of the composition of the M gas used.

[0134]

[0135] In this example, ammonia F11 was supplied from the ammonia gas supply system 23 of the first burner equipment 20 shown in Fig. 3, and M gas was supplied from the coal gas supply system 24. The mixture ratio of ammonia F11 and M gas was adjusted by flow rate control valves 23v and 24v provided in the ammonia gas supply system 23 and the coal gas supply system 24, respectively. Note that the mixture ratio here means the calorific value ratio of ammonia F11 and M gas. When the mixture ratio of ammonia F11 and M gas was 50%:50%, the flow rate of ammonia F11 was 119 Nm ３ / hr, M gas flow rate is 200 Nm ３ / hr.

[0136] Furthermore, the air ratio of the fuel gas F1 to the theoretical air amount was adjusted by the flow rate adjusting valve 26v provided in the combustion air supply system 26.

[0137] First, in the identification step, the correlation between the carbon monoxide concentration and the unburned ammonia concentration contained in the exhaust gas from the test heating furnace 1T was identified in advance.

[0138] In the identification step, combustion was performed using only the first burner equipment 20a, which was located above the test heating furnace 1T and closest to the charging section 11, among the burner equipment 20a to 20j of the test heating furnace 1T. The combustion test using the first burner equipment 20a was performed with a mixture ratio of ammonia F11 and M gas set to 50%:50%, and the air ratio was adjusted by adjusting the flow rate of the combustion air A.

[0139] Specifically, the flow rate of the combustion air A was adjusted so that the air ratio in the first burner equipment 20a would be a predetermined set value, and then the test furnace 1T was left standing for 10 minutes until the combustion state stabilized and the atmosphere inside the furnace became uniform. Thereafter, the carbon monoxide concentration in the exhaust gas was measured using the CO concentration meter 18c disposed in the flue 14, and a sample of the exhaust gas was taken from the gas sampling port 14a.

[0140] The exhaust gas sample collected from the gas sampling port 14a was analyzed for unburned ammonia (NH ３ ) concentration, carbon monoxide (CO) concentration, and carbon dioxide (CO ２The unburned ammonia concentration in the exhaust gas was measured using boric acid absorption / ion chromatography as specified in the Japanese Industrial Standard JIS K0099:2020 "Method for Determining Ammonia in Exhaust Gas." Specifically, a boric acid absorption solution was used through which 20 L of exhaust gas was passed at an average exhaust gas flow rate of 1.5 L / min. The carbon monoxide (CO) concentration in the exhaust gas was measured offline using low-potential electrolysis, and it was confirmed that this closely matched the measurement value obtained by the CO concentration meter 18c installed in the flue 14. Furthermore, the carbon dioxide concentration in the exhaust gas was measured using a non-dispersive infrared method.

[0141] FIG. 12 shows the carbon monoxide (CO) concentration and unburned ammonia (NH ３ ) concentration.

[0142] As shown in FIG. 12, the carbon monoxide (CO) concentration and the unburned ammonia (NH ３ ) concentration, and it can be seen that the two are in an almost linear relationship. In addition, the correlation between the two can be approximated by a straight line passing through the origin, and it can be seen that the combustion rates of ammonia F11 contained in fuel gas F1 and M gas are roughly equal. Based on the results of the preliminary test shown in Figure 12, ３ The correlation with (ppm) can be expressed by a regression equation as shown in the following equation (1).

[0143] φNH ３ =0.1436×φCO 2 (1) In this way, in the identification step, the correlation between the carbon monoxide concentration and the unburned ammonia concentration contained in the exhaust gas from the test heating furnace 1T could be identified.

[0144] Next, tests were conducted on a measurement step of measuring the carbon monoxide concentration contained in the exhaust gas from the test heating furnace 1T during operation of the test heating furnace 1T, and an estimation step of estimating the unburned ammonia concentration contained in the exhaust gas from the test heating furnace 1T based on the carbon monoxide concentration measured in the measurement step and the correlation between the carbon monoxide concentration and the unburned ammonia concentration identified in the identification step.

[0145] In the measurement step, the test heating furnace 1T was operated under the same combustion conditions for all of the first burner equipment 20a to 20j. That is, the test heating furnace 1T was operated under the same conditions for the fuel gas F1 mixture ratio, fuel gas F1 flow rate, and air ratio for the first burner equipment 20a to 20j. The mixture ratio of ammonia F11 and M gas was 50%:50%, which was the same as the mixture ratio in the above-mentioned preliminary test.

[0146] The measuring step was performed online by continuously measuring the carbon monoxide concentration contained in the exhaust gas passing through the flue 14 using a CO concentration meter 18c disposed in the flue 14.

[0147] Next, in the estimation step, the measured value of the carbon monoxide concentration measured online was input into the above equation (1) identified in the identification step to calculate an estimated value of the unburned ammonia concentration. In this way, the unburned ammonia concentration of the exhaust gas was continuously estimated.

[0148] The estimated value of the unburned ammonia concentration by the method for estimating the unburned ammonia concentration of this embodiment is shown in Fig. 13. Fig. 13 shows the change in the air ratio set for the first burner equipment 20, the carbon monoxide concentration measured in the measurement step, and the estimated value of the unburned ammonia concentration over the course of the operation time of the test heating furnace 1T.

[0149] 13, under conditions where the air ratio exceeds 1.0, the measured carbon monoxide concentration was 0 ppm, and based on this, the estimated value of the unburned ammonia concentration estimated using equation (1) was also 0 ppm. This indicates that under conditions where the air ratio exceeds 1.0, the fuel gas F1 is almost completely combusted, and the M gas contained in the fuel gas F1 is completely combusted. At this time, it is estimated that the ammonia F11 contained in the fuel gas F1 is also completely combusted.

[0150] On the other hand, when the air ratio was 1.0 or less, the combustion of part of the M gas contained in the fuel gas F1 was incomplete, and carbon monoxide gas was generated. Based on this, the estimated value of the unburned ammonia concentration estimated using equation (1) was also greater than 0 ppm.

[0151] In order to confirm the accuracy of the estimated value of the unburned ammonia concentration estimated as described above, exhaust gas samples were taken from the gas sampling port 14a during the above-mentioned operation, and the unburned ammonia concentration was measured offline. Exhaust gas samples were taken from the gas sampling port 14a four times during the operation of the test heating furnace 1T, and the unburned ammonia concentration was measured for each sample. These samples will be referred to as batch measurement 1 to batch measurement 4.

[0152] 13 shows the timing of sampling the exhaust gas samples from the gas sampling port 14a. The exhaust gas samples collected in each of batch measurements 1 to 4 were used to measure the unburned ammonia concentration by boric acid absorption / ion chromatography.

[0153] Table 3 shows the correlation between the unburned ammonia concentration estimated online by the estimation step and the measured value of the unburned ammonia concentration measured offline by batch measurement.

[0154]

[0155] As shown in Table 3, it was confirmed that the unburned ammonia concentration value estimated online using the method for estimating the unburned ammonia concentration of the present invention was very close to the unburned ammonia concentration measured offline. Specifically, it was confirmed that the difference between the online estimated value of the unburned ammonia concentration and the offline measured value was within ±7 ppm.

[0156] REFERENCE SIGNS LIST 1 Heating furnace 1T Test heating furnace 10 Control computer 11 Charging section 12 Discharge section 13f Fixed skid 13m Moving skid 14 Flue 14a Gas sampling port 15 Exhaust gas treatment device 16 NO Ｘ Concentration meter 17 Ammonia concentration meter 18, 18a to 18d CO concentration meter 20, 20a to 20j First burner equipment 30, 30a to 30f Second burner equipment 21, 31 Burner nozzle 22, 32 Fuel gas supply system 23 Ammonia gas supply system 24 Coal gas supply system 25 Mixing section 26, 36 Combustion air supply system 23m, 24m, 26m, 32m, 36m Flowmeter 23v, 24v, 26v, 32v, 36v Flow rate adjustment valve 27, 37 Air ratio control unit 40 Heating furnace control device 41 Memory unit 42 Acquisition unit 43 Estimation unit 44 Operation amount calculation unit 45 Output unit 46 Display unit A Combustion air F1, F2 Fuel gas F11 Ammonia gas F12 Coal gas (carbon-containing fuel) S Steel material (material to be heated)

Claims

1. A method for estimating an unburned ammonia concentration, which estimates the concentration of unburned ammonia contained in exhaust gas discharged from a heating furnace that performs burner heating using a fuel gas containing ammonia and a carbon-containing fuel, comprising: a specifying step of specifying a correlation between a carbon monoxide concentration and an unburned ammonia concentration contained in the exhaust gas of the heating furnace; a measuring step of measuring the carbon monoxide concentration contained in the exhaust gas of the heating furnace while the heating furnace is in operation; and an estimation step of estimating the unburned ammonia concentration contained in the exhaust gas of the heating furnace based on the carbon monoxide concentration measured in the measuring step and the correlation between the carbon monoxide concentration and the unburned ammonia concentration specified in the specifying step.

2. A method for estimating unburned ammonia concentration as described in claim 1, wherein the identification step identifies a correlation between the carbon monoxide concentration and the unburned ammonia concentration contained in the exhaust gas of the heating furnace for each category into which the operating conditions of the heating furnace are classified into multiple types.

3. A method for estimating an unburned ammonia concentration as described in claim 1 or claim 2, wherein the heating furnace is a transport type heating furnace which heats the material to be heated while transporting it from a loading section to a discharge section, and the measuring step measures the carbon monoxide concentration contained in the exhaust gas from the heating furnace at at least one of a flue through which exhaust gas is discharged from the heating furnace, the loading section, and the discharge section.

4. A method for estimating an unburned ammonia concentration, which estimates the concentration of unburned ammonia contained in exhaust gas discharged from a burner equipment that performs burner heating using a fuel gas containing ammonia and a carbon-containing fuel, comprising: a specifying step of specifying a correlation between the carbon monoxide concentration and the unburned ammonia concentration contained in the exhaust gas from the burner equipment; a measuring step of measuring the carbon monoxide concentration contained in the exhaust gas from the burner equipment when burner heating is performed by the burner equipment; and an estimation step of estimating the unburned ammonia concentration contained in the exhaust gas from the burner equipment based on the carbon monoxide concentration measured in the measuring step and the correlation between the carbon monoxide concentration and the unburned ammonia concentration specified in the specifying step.

5. A method for estimating unburned ammonia concentration as described in claim 4, wherein the identification step identifies a correlation between the carbon monoxide concentration and the unburned ammonia concentration contained in the exhaust gas of the burner equipment for each category into which the operating conditions of the burner equipment are classified into multiple types.

6. A method for operating a heating furnace, comprising an operating step of manipulating the operating conditions of the heating furnace so as to reduce the unburned ammonia concentration contained in exhaust gas discharged from the heating furnace when the estimated value of the unburned ammonia concentration estimated by the method for estimating the unburned ammonia concentration described in claim 3 is equal to or greater than a predetermined value.

7. The method for operating a heating furnace according to claim 6, wherein the operating conditions of the heating furnace that are changed in the operation step include at least one of the flow rate of the combustion air used for the burner heating, the flow rate of the fuel gas, the air ratio of the fuel gas to the theoretical air amount, and the mixture ratio of the ammonia and the carbon-containing fuel.

8. A method for operating a burner equipment, comprising an operating step of manipulating the operating conditions of the burner equipment so as to reduce the unburned ammonia concentration contained in the exhaust gas discharged from the burner equipment when an estimated value of the unburned ammonia concentration estimated by the method for estimating the unburned ammonia concentration described in claim 4 is equal to or greater than a predetermined value.

9. The method for operating a burner facility according to claim 8, wherein the operating conditions of the burner facility that are changed in the operation step include at least one of the flow rate of the combustion air used for heating the burner, the flow rate of the fuel gas, the air ratio of the fuel gas to a theoretical air amount, and the mixture ratio of the ammonia and the carbon-containing fuel.

10. A control device for a heating furnace that performs burner heating using a fuel gas containing ammonia and a carbon-containing fuel, comprising: a memory unit that stores a correlation between a carbon monoxide concentration and an unburned ammonia concentration contained in an exhaust gas of the heating furnace; an acquisition unit that acquires the carbon monoxide concentration contained in the exhaust gas of the heating furnace measured during operation of the heating furnace; an estimation unit that estimates the unburned ammonia concentration 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 and the unburned ammonia concentration stored in the memory unit; and an operation amount calculation unit that, when the estimated value of the unburned ammonia concentration estimated by the estimation unit is equal to or greater than a predetermined value, calculates an operation amount for an operating condition of the heating furnace so that the estimated value becomes smaller than the predetermined value.

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