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

Abstract

The present invention provides a method for estimating unburned ammonia, which is capable of easily measuring the ammonia concentration contained in the exhaust gas from a heating furnace that uses ammonia as a fuel gas that can suppress carbon dioxide emissions, and a method for operating the heating furnace and a control device. [Solution] A method for estimating the concentration of unburned ammonia contained in exhaust gas discharged from a heating furnace that performs burner heating using fuel gas containing ammonia and a carbon-containing fuel, the method includes: a specifying step for specifying a correlation between the carbon monoxide concentration and the unburned ammonia concentration contained in the exhaust gas of the heating furnace; a measuring step for 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 for 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.

Description

[Technical field]

[0001] The present invention relates to a method for estimating an unburned ammonia concentration, a method for operating a heating furnace, a method for operating a burner facility, and a control device for a heating furnace. [Background technology]

[0002] In integrated steelworks, 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 are being sought to reduce the amount of by-product gas used. In hot rolling lines and plate rolling lines in integrated steelworks, there is also a demand to reduce the amount of by-product gas used and the amount of carbon dioxide emissions in the heating furnaces that heat slabs before rolling.

[0003] Therefore, technology that uses ammonia as fuel gas for heating furnaces has been attracting attention. When ammonia, which does not contain carbon elements, is burned, mainly water and nitrogen are generated, which has a large effect of reducing carbon dioxide emissions, and there is a demand for technological development that enables the use of ammonia as fuel gas for heating furnaces.

[0004] However, since ammonia is toxic, if unburned ammonia (also called "unburned ammonia") is discharged outside the heating furnace, it will deteriorate the environment outside the heating furnace. Therefore, when ammonia is used as the 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 denitrification device that treats boiler exhaust gas. Specifically, when analyzing ammonia gas in which sulfur dioxide coexists by the indophenol method, the absorption liquid is distilled to remove the SO32- The accuracy of the analysis is improved by removing ions. The indophenol method, also known as the indophenol blue spectrophotometric method, involves absorbing the ammonia in the gas into a boric acid solution, then adding a sodium phenolpentacyanonitrosylferrate (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 the ion chromatography method, 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 ammonia gas being oxidized to NO gas by an oxidation catalyst provided in the combustion section of a heated reaction tube, and the NO gas being sent to a chemiluminescence type 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. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Publication No. 17955 / 1983 [Patent Document 2] JP 2001-21546 A [Non-patent literature]

[0010] [Non-Patent Document 1] 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 Summary of the Invention [Problem to be solved by the invention]

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

[0012] First, to measure the ammonia concentration using the method disclosed in Patent Document 1, it is necessary to follow the steps of absorbing ammonia gas into an absorbing liquid, reacting with a reagent, and analyzing. In other words, it is necessary to measure the ammonia concentration 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. The same is true when measuring the ammonia concentration using ion chromatography.

[0013] In addition, when the method disclosed in Patent Document 2 is applied to the measurement of the concentration of unburned ammonia contained in the exhaust gas of a heating furnace, a pipe is required to transport the exhaust gas containing ammonia to a component measuring device. However, since ammonia is highly soluble in water, it is necessary to maintain the temperature in the pipe transporting the exhaust gas at or above the dew point of the exhaust gas so that the ammonia in the exhaust gas is not removed by the moisture in the pipe. This makes the auxiliary equipment for measuring the ammonia concentration larger, resulting in high equipment costs. In addition, since ammonia is corrosive, the pipes and pumps transporting the exhaust gas are prone to corrosion, and there is a risk of the exhaust gas containing ammonia leaking due to the corrosion of the pipes. Therefore, the load required for the maintenance of the entire measuring device for measuring the ammonia concentration in the exhaust gas is large.

[0014] Furthermore, when the method disclosed in Non-Patent Document 1 is applied to the measurement of the concentration of unburned ammonia contained in the exhaust gas of a heating furnace, the exhaust gas needs to be dehumidified as a pretreatment for the component analysis of the exhaust gas. However, since ammonia is highly soluble in water, ammonia dissolves in the moisture that condenses during the dehumidification process of the pretreatment. Therefore, before the exhaust gas is introduced into the component analysis device, a part of the ammonia in the exhaust gas is removed, 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, and an object of the present invention is to provide a method for estimating the concentration of unburned ammonia, which can measure the ammonia concentration contained in the exhaust gas of a heating furnace using ammonia as a fuel gas, which can suppress the emission of carbon dioxide, online by a simple method. Another object of the present invention is to provide a method for operating a heating furnace, a method for operating a burner facility, and a control device for a heating furnace, which can suppress the emission of unburned ammonia to the outside of the furnace as the exhaust gas of the heating furnace. [Means for solving the problem]

[0016] In order to solve the above problems, the present invention has the following features.

[0017] [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 determination step of determining a correlation between a carbon monoxide concentration and an unburned ammonia concentration contained in the exhaust gas of the heating furnace; a measurement step of measuring the carbon monoxide concentration contained in the exhaust gas of the heating furnace during operation of the heating furnace; 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 measurement step and the correlation between the carbon monoxide concentration and the unburned ammonia concentration determined in the determination step.

[0018] [2] The method for estimating unburned ammonia concentration described in [1], wherein the identification step identifies the 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.

[0019] [3] The method for estimating the concentration of unburned ammonia described in [1] or [2], wherein the heating furnace is a transporting type heating furnace which heats the material to be heated while transporting it from a loading section to a discharge section, and the measurement 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.

[0020] [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 determination step of determining a correlation between the carbon monoxide concentration and the unburned ammonia concentration contained in the exhaust gas from the burner equipment; a measurement 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 measurement step and the correlation between the carbon monoxide concentration and the unburned ammonia concentration determined in the determination step.

[0021] [5] The method for estimating unburned ammonia concentration described in [4], wherein the identification step identifies the 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.

[0022] [6] A method for operating a heating furnace, comprising an operating step of manipulating 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 described in [3] is equal to or greater than a predetermined value.

[0023] [7] The method for operating a heating furnace described in [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 mixing ratio of the ammonia and the carbon-containing fuel.

[0024] [8] A method for operating a burner equipment, comprising, when an estimated value of an unburned ammonia concentration estimated by the method for estimating an unburned ammonia concentration described in [4] is equal to or greater than a predetermined value, 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.

[0025] [9] The method for operating a burner equipment described in [8], wherein the operating conditions of the burner equipment 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.

[0026]

[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 the 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 calculates an operation amount of an operating condition of the heating furnace so that the estimated value of the unburned ammonia concentration estimated by the estimation unit is smaller than a predetermined value when the estimated value is equal to or greater than the predetermined value. Effect of the Invention

[0027] According to the method for estimating the unburned ammonia concentration of the present invention, the ammonia concentration contained in the exhaust gas of a heating furnace that uses ammonia capable of suppressing carbon dioxide emissions as a fuel gas can be measured online by a simple method. Also, according to 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, ammonia capable of suppressing carbon dioxide emissions is used, and it is possible to suppress the discharge of unburned ammonia to the outside of the furnace as the exhaust gas of the heating furnace. [Brief description of the drawings]

[0028] [Figure 1] FIG. 1 is a vertical cross-sectional view that typically shows a heating furnace to which an embodiment of a method for estimating an unburned ammonia concentration, a method for operating a heating furnace, a method for operating a burner facility, and a control device for a heating furnace according to the present invention is applied. [Diagram 2] FIG. 2 is a cross-sectional view that typically shows a heating furnace to which an embodiment of the method for estimating an 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 is applied. [Diagram 3] 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. [Figure 4] 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 a fuel gas. [Diagram 5] FIG. 5 is a graph showing the correlation between the carbon monoxide concentration and the unburned ammonia concentration in the exhaust gas from the burner equipment when the combustion speed of the carbon-containing fuel contained in the fuel gas is faster than the combustion speed of the ammonia. [Figure 6] Figures 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. [Figure 7]FIG. 7 is a diagram showing a schematic example of an arrangement of CO concentration meters in a heating furnace to which an embodiment of the method for estimating an 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 is applied. [Figure 8] 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. [Figure 9] FIG. 9 is a diagram showing a schematic diagram of a heating furnace to which another embodiment of the method for estimating the unburned ammonia concentration according to the present invention is applied. [Figure 10] FIG. 10 is a block diagram showing a configuration of an example of a heating furnace control device according to the present invention. [Figure 11] FIG. 11 is a diagram showing a schematic diagram of a test heating furnace for identifying the correlation between the carbon monoxide concentration and the unburned ammonia concentration contained in exhaust gas from the heating furnace in the method for estimating the unburned ammonia concentration according to the present invention. [Figure 12] FIG. 12 is a graph for explaining an example of a specifying step for specifying the correlation between the carbon monoxide concentration and the unburned ammonia concentration contained in the exhaust gas from the heating furnace in the method for estimating the unburned ammonia concentration according to the present invention. [Figure 13] FIG. 13 is a graph showing an example of an estimated value of the unburned ammonia concentration by the method for estimating the unburned ammonia concentration according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, with reference to the drawings, embodiments of a method for estimating an unburned ammonia concentration, a method for operating a heating furnace, a method for operating a burner facility, and a control device for a heating furnace according to the present invention will be described in detail. <Heating furnace> Fig. 1 is a schematic vertical cross-sectional view of a heating furnace 1 to which a method for estimating an unburned ammonia concentration, a method for operating a heating furnace, a method for operating a burner facility, and a control device for a heating furnace according to an embodiment of the present invention are applied. Fig. 2 is a schematic cross-sectional view of the heating furnace 1.

[0030] The heating furnace 1 is equipped with first burner equipment 20a-20d and second burner equipment 30a-30f that burn fuel gas, and is an equipment that uses these as a heat source to heat the material S charged inside the heating furnace 1 to a predetermined temperature. The first burner equipment 20a-20d and the second burner equipment 30a-30f will be described in detail later. The material S to be heated by the heating furnace 1 is mainly metal, and may be either ferrous metal or non-ferrous metal. The heating temperature of the material S by the heating furnace 1 is, for example, 700 to 1400°C.

[0031] In this embodiment, a case will be described in which a pre-rolled 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 device or the like is heated to a predetermined heating temperature (for example, about 1100 to 1300°C).

[0032] As shown in FIG. 1 and FIG. 2, the heating furnace 1 is provided with a charging section 11 for charging the steel material (slab) S, which is the material to be heated, and a discharge section 12 for discharging (extracting) the heated steel material S. 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 inside of the heating furnace 1 is divided into a plurality of 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 inside of the heating furnace 1 is generally provided with a fixed skid 13f for placing the steel material S and a movable skid 13m for transporting the steel material S. The heating furnace 1 provided with the fixed skid 13f and the movable skid 13m is called a walking beam type continuous heating furnace. Walking beam type continuous heating furnaces are classified as conveying type heating furnaces, which heat the material being heated while transporting it from the charging section to the unloading section.

[0033] In operation of the heating furnace 1, the inside of the heating furnace 1 is controlled to have different atmospheric temperatures for each zone, so that the average temperature of the steel material S charged into the heating furnace 1 is gradually increased and the steel material S is controlled 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.

[0034] As shown in Fig. 1, inside the heating furnace 1, a plurality of first burner equipment 20a-20d and second burner equipment 30a-30f are provided along the conveying direction TD of the steel material S. When the first burner equipment 20a-20d and the second burner equipment 30a-30f burn 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 the atmospheric gas generated inside the heating furnace 1. Alternatively, the temperature of the steel material S may rise due to the flames from the first burner equipment 20a-20d and the second burner equipment 30a-30f directly contacting the steel material S.

[0035] 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-20d and the second burner equipment 30a-30f. For this reason, a heating furnace is characterized by a large internal volume relative to the combustion energy input therein, compared to turbines, boilers, and the like that are intended to cause a combustion reaction inside the furnace.

[0036] Furnace volume per unit of combustion energy (m 3 / MW) is, for example, 2m for a gas turbine. 3 / MW, 6m for pulverized coal boiler 3 / MW, gas and oil boiler 2m 3 / MW, whereas a heating furnace has a capacity of 10 to 16 m 3 / MW. The heating furnaces used in hot rolling lines for steel products have a diameter of 11 to 13 m. 3 / MW.

[0037] 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, and gas (hereinafter referred to as exhaust gas) generated in the furnace by burner heating inside the heating furnace 1 flows from the area of ​​high pressure to the area 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.

[0038] As shown in FIG. 1 and FIG. 2, the heating furnace 1 is provided 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 in 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 as to meet a predetermined emission standard. 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, and the emission of nitrogen oxides and unburned ammonia to the outside of the heating furnace 1 is suppressed. 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 values ​​of the concentrations of nitrogen oxides and unburned ammonia that are preset so as not to exceed the regulatory values ​​set by laws and regulations, for example.

[0039] 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 to the outside of the furnace, but it is preferable to locate it 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.

[0040] 1 and 2, in a heating furnace 1, first burner equipment 20a-20d and second burner equipment 30a-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.

[0041] As shown in Fig. 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., opening and closing the doors of the charging section 11 and unloading section 12, and the operation of the moving skid 13m.

[0042] The heating furnace to which the method for estimating unburned ammonia concentration, the method for operating a heating furnace, the method for operating a burner equipment, and the control device for a heating furnace according to the present invention are applied is provided with at least one burner equipment inside the heating furnace, which performs burner heating using a fuel gas F1 containing ammonia and a carbon-containing fuel. In addition, the heating furnace to which the method for estimating unburned ammonia concentration, the method for operating a heating furnace, the method for operating a burner equipment, and the control device for a heating furnace according to the present invention are applied is preferably provided with a burner equipment that performs burner heating using a fuel gas F2 that does not contain ammonia. Hereinafter, the ammonia contained in the fuel gas means ammonia gas in a vaporized state.

[0043] In this embodiment, among the first burner equipment 20a-20d and the second burner equipment 30a-30f, the first burner equipment 20a-20d corresponds to the burner equipment that performs burner heating using the fuel gas F1 containing ammonia F11 and the carbon-containing fuel F12. Also, the second burner equipment 30a-30f corresponds to the burner equipment that performs burner heating using the fuel gas F2 that does not contain ammonia.

[0044] As shown in Figures 1 and 2, in the heating furnace 1, of the four first burner equipment 20a-20d, two first burner equipment 20a, 20b are provided on the upper side of the center of the heating furnace 1 in the conveying direction TD. The remaining two first burner equipment 20c, 20d are provided on the lower side of the center of the heating furnace 1 in the conveying direction TD. In addition, of the six second burner equipment 30a-30f, two second burner equipment 30a, 30d are provided on the upper and lower sides of 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 on the upper and lower sides of the downstream part of the heating furnace 1 in the conveying direction TD. <First burner equipment> 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, that is, the first burner equipment 20a-20d. Fig. 3(a) is a side view of the first burner equipment 20a-20d, and Fig. 3(b) is a front view.

[0045] As shown in Fig. 3(a) and Fig. 3(b), the first burner equipment 20a-20d performs burner heating by injecting a flame into the furnace of 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-20d includes a burner nozzle 21 for injecting a flame into the furnace of the heating furnace 1, a fuel gas supply system 22 for supplying the fuel gas F1 to the burner nozzle 21, and a combustion air supply system 26 for supplying the combustion air A to the burner nozzle 21. The first burner equipment 20a-20d preferably includes an air ratio control unit 27 for controlling the air ratio (also simply referred to as the air ratio) of the fuel gas F1 supplied to the burner nozzle 21 to the theoretical air amount.

[0046] 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.

[0047] The burner nozzle 21 is composed of, for example, a double-tube nozzle, and the fuel gas F1 is injected from the inner tube, and the combustion air A is injected from the outer tube, toward the inside of the furnace. As a result, a combustible gas mixture of the fuel gas F1 and the 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 inside of the heating furnace 1.

[0048] When the heating furnace 1 is provided with a plurality of first burner units 20a-20d as in the first embodiment, the mixing ratio of the ammonia F11 and the carbon-containing fuel F12 supplied to each of them 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 units 20, since this avoids the equipment for supplying the fuel gas F1 to the heating furnace 1 becoming complicated and the equipment cost increasing.

[0049] Ammonia F11 is a flame-retardant fuel, which is more difficult to ignite than general fuels and has a slower combustion speed. Therefore, in the first burner equipment 20a-20d, by using the fuel gas F1 in which ammonia F11 is mixed with a carbon-containing fuel F12, the stability of combustion can be improved compared to the case where only ammonia F11 is used.

[0050] The carbon-containing fuel F12 refers to a fuel that contains carbon as a constituent element. Since the carbon-containing fuel F12 contains carbon as a constituent element, carbon monoxide and carbon dioxide are generated by burning the fuel by burner heating. The carbon-containing fuel F12 is preferably methane, ethane, ethylene, acetylene, propane, propylene, butane, benzene, carbon monoxide, or the like. As the carbon-containing fuel F12, mainly fossil fuels can be used, including city gas, natural gas, propane gas, and the like. The carbon-containing fuel F12 is not limited to fuels extracted from natural gas, etc., and is preferably artificially synthesized. As the carbon-containing fuel F12, it is preferable to use a suitable mixture of these fuels.

[0051] 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.

[0052] Coke oven gas is a by-product gas produced during 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 during the steelmaking process in a converter. Electric furnace gas is a gas produced by the incomplete combustion of auxiliary fuel (recarburizer) in an electric furnace.

[0053] In addition, it is preferable to use a mixed gas (also called M gas) of blast furnace gas, coke oven gas, and converter gas as the coal gas. By mixing coal gases with different heating values, the amount of heat required for heating the steel material S can be supplied, and the operation of the heating furnace 1 can be stably performed.

[0054] In addition, the fuel gas F1 used in the first burner equipment 20 may contain a third fuel gas in addition to the 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. As the third fuel gas, it is preferable to use, for example, hydrogen.

[0055] 3(a) and 3(b) show 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. In FIG.

[0056] 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 mixer 25 and supplied to the burner nozzle 21 through the fuel gas supply system 22.

[0057] 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.

[0058] It is preferable that flow rate control valves 23v, 24v for adjusting the supply amount of each gas to the mixing section 25 and flow meters 23m, 24m for measuring the supply flow rate are provided in the ammonia gas supply system 23 and the coal gas supply system 24. In this way, the mixing ratio of ammonia F11 and coal gas F12 contained in the fuel gas F1 can be adjusted.

[0059] The flowmeters 23m and 24m may estimate the flow rate of the ammonia F11 or the coal gas F12 by measuring the pressure of the gas transported by the ammonia gas supply system 23 or the coal gas supply system 24. In this way, the flow rate can be easily estimated using the pressure gauge.

[0060] The mixing section 25 refers to a portion where the supply pipe of the coal gas supply system 24 and the supply pipe of the ammonia gas supply system 23 join together. Ammonia F11 and coal gas F12 are supplied from their respective supply pipes and joined together, so that mixing can be performed without providing 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 together. However, it is more preferable to provide 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, it is possible to generate fuel gas F1 in which coal gas F12 and ammonia F11 are mixed more uniformly.

[0061] It is preferable to provide a flow rate adjustment valve 26v for adjusting the flow rate of the combustion air A supplied to the burner nozzle 21 and a flow 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 the combustion air A of the first burner equipment 20 and adjust the air ratio in the burner heating of the first burner equipment 20. It is also preferable for the flow meter 26m of the combustion air supply system 26 to estimate the flow rate by measuring the pressure of the transported combustion air.

[0062] The air ratio control unit 27 controls the air ratio of the fuel gas F1 of the first burner equipment 20a-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 equipment 20a-20d. Specifically, the air ratio control unit 27 measures the flow rate of the fuel gas F1 supplied to the burner nozzle 21 using the flow meters 23m and 24m provided in the ammonia gas supply system 23 and the coal gas supply system 24, and calculates the theoretical air amount for completely combusting the fuel gas F1 from 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 arranged in the combustion air supply system 26 to control the air ratio of the combustion air A to the fuel gas F1 in the first burner equipment 20a-20d to a target air ratio set by the control computer 10 or the like. <Second burner equipment> 4(a) and 4(b) show details of the burner equipment that performs burner heating using the fuel gas F2 that does not contain ammonia, that is, the second burner equipment 30a-30f. Fig. 4(a) is a side view of the second burner equipment 30a-30f, and Fig. 4(b) is a front view.

[0063] The second burner equipment 30a to 30f has a configuration in which the ammonia gas supply system 23, and the flowmeter 23m and the flow rate 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). Also, the second burner equipment 30a to 30f does not need to be provided with the mixer 25 that mixes the ammonia F11 and the coal gas F12. In other respects, the second burner equipment 30a to 30f can be configured in the same manner as the first burner equipment 20a to 20d.

[0064] As shown in Fig. 4(a) and Fig. 4(b), the second burner equipment 30a-30f performs burner heating by injecting a flame into the furnace of the heating furnace 1 using fuel gas F2 made of coal gas and combustion air A. The second burner equipment 30a-30f includes a burner nozzle 31 for injecting a flame into the furnace of 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-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 to the theoretical air amount.

[0065] The fuel gas supply system 32 is a pipe that supplies the fuel gas F2 to the burner nozzle 31. The combustion air supply system 36 is a pipe that supplies the combustion air A to the burner nozzle 31.

[0066] The burner nozzle 31 is composed of, for example, a double-tube nozzle, and the fuel gas F2 is injected from the inner tube, and the combustion air A is injected from the outer tube, toward the inside of the furnace. As a result, a combustible gas mixture of the fuel gas F2 and the 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 inside of the heating furnace 1.

[0067] 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. In addition, the fuel gas F2 of the second burner equipment 30a-30f is not limited to coal gas. As the fuel gas F2 of the second burner equipment 30a-30f, one or more of city gas, natural gas, and propane gas may be used, or a fuel gas containing two or more of these gases may be used. In addition, carbon monoxide gas or methane (including both methane extracted from natural gas and methane artificially synthesized) may be used as the fuel gas F2 of the second burner equipment 30. <Correlation between carbon monoxide concentration and unburned ammonia concentration in exhaust gas> As described above, in the first burner equipment 20a-20d, burner heating is performed by injecting a flame into the furnace using the fuel gas F1 containing ammonia F11 and carbon-containing fuel F12, and the combustion air A. Here, it is known that the ammonia F11 and the carbon-containing fuel F12 have different combustion speeds. The combustion speed means the speed at which the fuel gas F1 enters the flame front at a right angle when the flame generated in the burner heating propagates. The combustion speed depends on the rate of chemical reaction and the thermal conductivity of the mixed gas of the unburned fuel gas F1 and the fuel air A.

[0068] The burning speeds of ammonia and typical carbon-containing fuels are shown in Table 1. In Table 1, the burning speeds are shown using Weaver's burning speed coefficient (an index showing the relative value of the maximum burning speed in a mixture of fuel gas and combustion air, with the maximum burning speed of hydrogen being taken as 100).

[0069] [Table 1]

[0070] 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 nozzle 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.

[0071] For example, when the combustion speed of the carbon-containing fuel F12 contained in the fuel gas F1 is faster than that of the ammonia F11, the carbon-containing fuel F12 in the fuel gas F1 combines with the oxygen in the combustion air A, and the combustion reaction of the carbon-containing fuel F12 precedes. Then, the oxygen in the combustion air A is consumed first by the combustion of the carbon-containing fuel F12, so that when the ammonia F11 in the fuel gas F1 burns, there is a shortage of oxygen. At this time, the carbon atoms contained in the carbon-containing fuel F12 are oxidized by complete combustion by the combustion reaction of the carbon-containing fuel F12 to generate carbon dioxide, so that carbon monoxide, which would be generated by incomplete combustion, is difficult to generate. On the other hand, when the ammonia F11 burns, there is a shortage of oxygen required for the combustion reaction of the ammonia F11, so that unburned ammonia remains. Therefore, while unburned ammonia remains in the exhaust gas of the first burner equipment 20a to 20d, the generation of carbon monoxide is suppressed.

[0072] 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 together with carbon dioxide.

[0073] On the other hand, when the combustion speed of the ammonia F11 is slower than that 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, so that the combustion state of the ammonia F11 becomes more incomplete, and the generation of unburned ammonia is promoted. In this way, a correlation is generated 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 increases.

[0074] As described above, the present invention is based on the finding that a correlation is found between the unburned ammonia concentration and the carbon monoxide concentration 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 unburned ammonia concentration contained in the exhaust gas from the measured value of the carbon monoxide concentration in the exhaust gas based on 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.

[0075] FIG. 5 shows the correlation between the carbon monoxide concentration and the unburned ammonia concentration in the exhaust gas from the first burner equipment 20a-20d when the combustion speed of the carbon-containing fuel F12 contained in the fuel gas F1 is faster than the combustion speed of the ammonia F11.

[0076] As shown in Fig. 5, when the combustion speed of the carbon-containing fuel F12 contained in the fuel gas F1 is faster than the combustion speed of the ammonia F11, the speed at which the carbon-containing fuel F12 completely burns is faster than the speed at which the ammonia F11 completely burns. Therefore, under the condition in which the carbon-containing fuel F12 completely burns (the condition in which the "CO concentration" is zero in the graph shown in Fig. 5), unburned ammonia is contained in the exhaust gas. The larger the difference between the combustion speed of the ammonia F11 and the combustion speed of the carbon-containing fuel F12, the larger the unburned ammonia concentration when the CO concentration is zero, that is, the value of the intercept of the vertical axis of the graph shown in Fig. 5, becomes.

[0077] Then, when the air ratio of the fuel gas F1 to the theoretical air amount is decreased from 1.0, the carbon monoxide concentration in the exhaust gas increases, and the oxygen required for the combustion reaction of the ammonia F11 becomes even more insufficient, so that the unburned ammonia concentration also increases. 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 almost linear. In addition, in the graph shown in FIG. 5, the slope of the unburned ammonia concentration with respect to the carbon monoxide concentration changes depending on the combustion speed of the ammonia F11 and the carbon-containing fuel F12 contained in the fuel gas F1. Specifically, the combustion speed of the carbon-containing fuel F12 is higher than the combustion speed of the ammonia F11, and the larger the difference between them, the larger the slope becomes.

[0078] Fig. 6(a) shows the correlation between the carbon monoxide concentration and the unburned ammonia concentration in the exhaust gas when the combustion speed of the ammonia F11 contained in the fuel gas F1 is equal to the combustion speed of the carbon-containing fuel F12. Fig. 6(b) shows the correlation between the carbon monoxide concentration and the unburned ammonia concentration in the exhaust gas when the combustion speed of the ammonia F11 contained in the fuel gas F1 is faster than the combustion speed of the carbon-containing fuel F12.

[0079] As shown in Fig. 6(a), when the combustion speed of the ammonia F11 contained in the fuel gas F1 is equal to the combustion speed of the carbon-containing fuel F12, the speed at which the ammonia F11 is completely burned is equal to the speed at which the carbon-containing fuel F12 is completely burned. Therefore, under the condition in which the carbon-containing fuel F12 is completely burned (the condition in which the "CO concentration" is zero in the graph shown in Fig. 6(a)), no unburned ammonia remains in the exhaust gas. In other words, both the ammonia F11 and the carbon-containing fuel F12 are completely burned.

[0080] 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.

[0081] 6(b), when the combustion speed of the ammonia F11 contained in the fuel gas F1 is faster than the combustion speed of the carbon-containing fuel F12, the speed at which the ammonia F11 is completely burned is faster than the speed at which the carbon-containing fuel F12 is completely burned. Therefore, under the condition that the ammonia F11 is completely burned (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.

[0082] 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 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.

[0083] In this way, in the first burner equipment 20a-20d that performs burner heating by injecting a flame into the furnace using fuel gas F1 containing ammonia F11 and carbon-containing fuel F12, and 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> As an embodiment of the method for estimating the concentration of unburned ammonia according to the present invention, a first aspect and a second aspect thereof will be described below.

[0084] The method for estimating an unburned ammonia concentration of the first and second aspects estimates 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.

[0085] In the first embodiment of the method for estimating the unburned ammonia concentration, first, a specifying step is performed to specify in advance a correlation between the carbon monoxide concentration and the unburned ammonia concentration contained in the exhaust gas of the heating furnace 1. Next, a measuring step is performed to measure the carbon monoxide concentration contained in the exhaust gas of the heating furnace 1 when burner heating is performed by the first burner equipment 20a-20d during operation of the heating furnace 1. Furthermore, an estimating step is performed to estimate the unburned ammonia concentration contained in the exhaust gas of the heating furnace 1 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.

[0086] The first and second aspects of the identifying step, measuring step, and estimating step will be specifically described below.

[0087] First, in the identification step, a correlation between the carbon monoxide concentration and the unburned ammonia concentration contained in the exhaust gas of 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 of the first burner equipment 20a to 20d, for example, the following method can be applied.

[0088] FIG. 7 shows the flow of exhaust gas generated by flames ejected 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. In FIG.

[0089] As shown in Fig. 7, since a gas flow occurs in the heating furnace 1, the exhaust gas generated by the flames ejected from the first burner equipment 20a-20d flows toward the downstream side of the gas flow in the furnace. Therefore, in the first embodiment, a CO concentration meter 18 for measuring the carbon monoxide concentration contained in the exhaust gas discharged from the first burner equipment 20a-20d is installed downstream of the gas flow in the furnace from the first burner equipment 20a-20d. This allows the carbon monoxide concentration contained in the exhaust gas discharged from the first burner equipment 20a-20d to be measured online.

[0090] Further, 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 of the unburned ammonia concentration contained in the exhaust gas is collected by a gas component measuring device (not shown). The gas component measuring device may be any device capable of measuring the unburned ammonia concentration in the wet gas, and a component measuring device using the indophenol method, ion chromatography method, or the like may be used. The measurement of the unburned ammonia concentration by the gas component measuring device is preferably performed offline.

[0091] In this way, the actual measured value of the carbon monoxide concentration contained in the exhaust gas discharged from the first burner equipment 20a-20d, measured online by the CO concentration meter 18, and the actual value of the unburned ammonia concentration, obtained offline by sampling the exhaust gas, can be obtained as actual data. Then, by changing the air ratio in the first burner equipment 20a-20d and obtaining a plurality of sets of actual data, a correlation between the carbon monoxide concentration and the unburned ammonia concentration in the exhaust gas of the first burner equipment 20a-20d can be identified.

[0092] The above-mentioned specifying step does not necessarily have to be performed during the 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-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 by this. In other words, the specifying step may be performed when the steel material S is not being heated in the heating furnace 1.

[0093] 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 of the first burner equipment 20 for each classification of the operating conditions of the first burner equipment 20a-20d. Here, the classification of the operating conditions means that the indexes representing the conditions and combustion state of the burner heating by the first burner equipment 20a-20d are divided 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, it is preferable to select the composition and type of the carbon-containing fuel F12 used for the burner heating, the mixing ratio of the ammonia F11 and the carbon-containing fuel F12, etc. as the operating conditions of the burner heating of the first burner equipment 20a-20d, 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 of the first burner equipment 20a-20d for each classification.

[0094] In the specifying step, the correlation between the carbon monoxide concentration and the unburned ammonia concentration can be configured as a table specified for each operating condition category. Alternatively, the correlation between the carbon monoxide concentration and the unburned ammonia concentration can be specified by function approximation such as a linear regression equation, and a function equation can be obtained for each operating condition category.

[0095] In the measuring step, when burner heating is performed by the first burner equipment 20a to 20d, the carbon monoxide concentration contained in the exhaust gas from the first burner equipment 20a to 20d is measured.

[0096] 7, in the first burner equipment 20a-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-20d. It is preferable that the carbon monoxide concentration contained in the exhaust gas discharged from the first burner equipment 20 is continuously measured using the CO concentration meter 18 at intervals of, for example, 1 to 60 seconds.

[0097] In the estimation step, the unburned ammonia concentration contained in the exhaust gas of the 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 of the first burner equipment 20a-20d is previously specified in the specification step, the unburned ammonia concentration contained in the exhaust gas of the first burner equipment 20a-20d can be estimated by using the carbon monoxide concentration measured by the CO concentration meter 18 in addition to this. When the correlation between the carbon monoxide concentration and the unburned ammonia concentration is specified by a function formula, the unburned ammonia concentration can be calculated by inputting the carbon monoxide concentration measured by the CO concentration meter 18 into the function formula, and the unburned ammonia concentration can be continuously estimated online. <Method for estimating unburned ammonia concentration - second aspect> In the first aspect of the method for estimating the 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.

[0098] Here, as shown in FIG. 1, when the heating furnace 1 is equipped with the second burner equipment 30a-30f in addition to the first burner equipment 20a-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.

[0099] 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 insufficient in oxygen, the carbon monoxide concentration in the exhaust gas from the second burner equipment 30a-30f increases. However, since the fuel gas F2 used in the second burner equipment 30a-30f does not contain ammonia gas, unburned ammonia is not generated in the second burner equipment 30a-30f. Although the coal gas F2 may contain ammonia, the amount of the ammonia is very small compared to the amount of the unburned ammonia discharged from the first burner equipment 20a-20d, and the concentration of the unburned ammonia generated in the second burner equipment 30a-30f can be ignored.

[0100] Therefore, when the exhaust gas discharged from the first burner equipment 20a-20d and the exhaust gas discharged from the second burner equipment 30a-30f are combined, the combined exhaust gas contains unburned ammonia generated in the first burner equipment 20a-20d and the total amount of carbon monoxide generated in the first burner equipment 20a-20d and the carbon monoxide generated in the second burner equipment 30a-30f.

[0101] Therefore, when the exhaust gas discharged from the first burner equipment 20a-20d and the exhaust gas discharged from the second burner equipment 30a-30f are combined, the total volume of the exhaust gas changes, and therefore the gas concentration value 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-20d is maintained.

[0102] In this way, even when the second burner equipment 30a-30f is provided, the exhaust gas discharged from the loading 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-20d and the exhaust gas discharged from the second burner equipment 30a-30f, so 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.

[0103] 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 identifying 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 identified in advance. This will be described below.

[0104] 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.

[0105] 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.

[0106] Therefore, as shown in Fig. 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. For the exhaust gas discharged from the flue 14, a CO concentration meter 18c is installed at a position where a gas flow occurs 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 further installed at a position downstream of the exhaust gas treatment device 15 in the gas flow direction of the flue 14. 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.

[0107] 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 discharged to the outside of the heating furnace 1 through the flue 14 is treated by the exhaust gas treatment device 15, so that the concentration of unburned ammonia contained in the exhaust gas discharged to the outside of the heating furnace 1 is suppressed. On the other hand, 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 opening by the exhaust gas treatment device, so that it may become necessary to detect the unburned ammonia in the exhaust gas.

[0108] In the method for estimating the unburned ammonia concentration of the second aspect, the specifying step in the method for estimating the unburned ammonia concentration of the first aspect is changed as follows.

[0109] That is, in the second embodiment of the method for estimating the unburned ammonia concentration, in the specific step, the exhaust gas discharged from the heating furnace 1 is sampled in the charging section 11 where the CO concentration meter 18a is provided, the discharge section 12 where the CO concentration meter 18b is provided, and the flue 14 where the CO concentration meters 18c and 18d are provided, and the actual data of the unburned ammonia concentration contained in the exhaust gas is collected by a gas component measuring device (not shown). The gas component measuring device may be any device that can measure the unburned ammonia concentration in the wet gas, and a component measuring device using the indophenol method, ion chromatography method, or the like can be used. The measurement of the unburned ammonia concentration by the gas component measuring device may be performed offline.

[0110] In this way, actual measured values ​​of 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, which are measured online by the CO concentration meters 18a-18d, and actual values ​​of the unburned ammonia concentration obtained offline by sampling the exhaust gas, can be obtained as actual data. Then, by changing the air ratio in the first burner equipment 20a-20d and obtaining multiple sets of actual 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.

[0111] In the second embodiment of the method for estimating the unburned ammonia concentration, it is preferable to specify the correlation between the carbon monoxide concentration and the unburned ammonia concentration contained in the exhaust gas of the heating furnace 1 for each classification of the operating conditions of the heating furnace 1 in the specifying step. Here, the classification of the operating conditions of the heating furnace 1 refers to dividing the indexes representing the burner heating conditions and the combustion state by the first burner equipment 20a-20d provided in the heating furnace 1 into two or more. Furthermore, the classification of the operating conditions of the heating furnace 1 may be such that the indexes representing the burner heating conditions and the combustion state by the first burner equipment 20a-20d provided in the heating furnace 1 and the burner heating conditions and the combustion state by the second burner equipment 30a-30f are divided into two or more. Then, in the specifying step, the correlation between the carbon monoxide concentration and the unburned ammonia concentration is specified for each classification. Specifically, it is preferable to select the composition and type of the carbon-containing fuel F12 used for the burner heating, the mixing ratio of the ammonia F11 and the carbon-containing fuel F12, etc. as the operating conditions for the burner heating of the first burner equipment 20a-20d, classify these operating conditions into, for example, 2 to 10 types, and specify the correlation between the carbon monoxide concentration and the unburned ammonia concentration contained in the exhaust gas discharged from the heating furnace 1 for each of the classified categories. Furthermore, it is preferable to select the composition and type of the fuel gas F2, the air ratio, etc. as the operating conditions for the burner heating of the second burner equipment 30a-30f, classify these operating conditions into, for example, 2 to 10 types, and specify the correlation between the carbon monoxide concentration and the unburned ammonia concentration contained in the exhaust gas discharged from the heating furnace 1 for each of the classified categories.

[0112] In the method for estimating the unburned ammonia concentration of the second embodiment, the measuring step is performed by measuring the carbon monoxide concentration contained in the exhaust gas of the entire heating furnace 1 online during the operation of the heating furnace 1. As shown in FIG. 9, in the heating furnace 1, the carbon monoxide concentration contained in the exhaust gas can be continuously measured by the CO concentration meters 18a to 18d. It is preferable that the carbon monoxide concentration contained in the exhaust gas discharged from the heating furnace 1 is continuously measured by the CO concentration meters 18a to 18d, for example, at a cycle of 1 to 60 seconds. It is preferable that the CO concentration meters 18a, 18b provided in the charging section 11 and the discharge section 12 of the heating furnace 1 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.

[0113] In the estimation step, 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. At this time, since 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, the unburned ammonia concentration contained in the exhaust gas from the heating furnace 1 can be estimated by using the carbon monoxide concentrations continuously measured by the CO concentration meters 18a to 18d in addition to this.

[0114] In the second embodiment of the method for estimating the unburned ammonia concentration, an ammonia concentration meter 17 for measuring the ammonia concentration is provided in the flue 14 of the heating furnace 1, as shown in Fig. 9. The ammonia concentration meter 17 obtains 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 obtains an actual measurement value of the carbon monoxide concentration contained in the exhaust gas. It is preferable to specify a correlation between the carbon monoxide concentration and the unburned ammonia concentration contained in the exhaust gas of the heating furnace 1 from these actual measurement values.

[0115] 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 measurement value of the unburned ammonia concentration using the ammonia concentration meter 17. In this case, it is preferable to obtain the actual measurement value of the unburned ammonia concentration contained in the exhaust gas using the ammonia concentration meter 17 every 10 to 60 minutes, for example, and correlate it with the actual measurement value of the carbon monoxide concentration using the CO concentration meter 18c installed in the flue 14.

[0116] 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 as being for the entire heating furnace 1, which is a mixture of exhaust gas from all of the first burner equipment 20a-20d and the second burner equipment 30a-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 discharged after passing through the charging section 11 and the discharge section 12 of the heating furnace 1. 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 an 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 of the exhaust gas discharged from the loading section 11 and the discharge section 12 of the heating furnace 1, and there is no need to install multiple ammonia concentration meters 17.

[0117] 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. <Operation method of heating furnace, operation method of burner equipment> DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for operating a heating furnace and a method for operating a burner system according to the present invention will be described below.

[0118] The method for operating a heating furnace in 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 is reduced 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.

[0119] Furthermore, the burner equipment operating method of this embodiment is realized by setting the operation target of the operation step to the operation conditions of the first burner equipment 20a to 20d rather than the operation conditions of the entire heating furnace 1 in the above-mentioned heating furnace operating method.

[0120] When the method for operating a heating furnace or a burner facility according to this embodiment is carried out based on the method for estimating the unburned ammonia concentration according to the first aspect described above, the flow is, for example, as follows.

[0121] First, the unburned ammonia concentration of the exhaust gas discharged from at least one of the first burner equipment 20a-20d provided in the heating furnace 1 is estimated by the above-mentioned first embodiment of the unburned ammonia concentration estimation method. Then, based on the estimated unburned ammonia concentration, the operating conditions of the first burner equipment 20a-20d are manipulated so that the unburned ammonia concentration contained in the exhaust gas discharged from the first burner equipment 20a-20d is reduced.

[0122] When the unburned ammonia concentration in the exhaust gas discharged from the first burner equipment 20a-20d is reduced by manipulating the operating conditions of the first burner equipment 20a-20d, the unburned ammonia concentration contained in the exhaust gas discharged from the entire heating furnace 1 is also reduced. In this manner, 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 is reduced.

[0123] In this case, the operating conditions of the first burner equipment 20a-20d, which are operated in an operation step so as to reduce the unburned ammonia concentration in the exhaust gas discharged from the first burner equipment 20a-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-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.

[0124] For example, by increasing the combustion air A as an operating condition of the first burner equipment 20a-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 the same effect can be 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 mixture ratio of the ammonia F11 and the coal gas F12 so as to reduce the flow rate of the ammonia F11, unburned ammonia is less likely to remain.

[0125] Moreover, when the method for operating a heating furnace or the method for operating a burner facility according to this embodiment is carried out based on the method for estimating the unburned ammonia concentration according to the second aspect described above, the flow is, for example, as follows.

[0126] First, the unburned ammonia concentration of 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 small.

[0127] At this time, the operation conditions of the heating furnace 1 operated in the operation step so as to reduce the unburned ammonia concentration of 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 the ammonia F11 and the carbon-containing fuel F12. In addition, when the unburned ammonia concentration of the exhaust gas discharged from the heating furnace 1 is estimated by the method for estimating the unburned ammonia concentration of the second aspect, the atmospheric temperature in the heating furnace 1 may be selected as the operation conditions of the heating furnace 1 operated in the operation step. By increasing the atmospheric temperature in the heating furnace 1, the combustion of the ammonia F11 is promoted, and the unburned ammonia concentration contained in the exhaust gas discharged from the heating furnace 1 decreases. <Heating furnace control device> DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a heating furnace control device according to the present invention will be described below.

[0128] FIG. 10 shows the configuration of a heating furnace control device 40 of this embodiment.

[0129] The heating furnace control device 40 of this embodiment is a device for executing the above-mentioned heating furnace operation method. As shown in Fig. 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.

[0130] The storage unit 41 stores a correlation between the carbon monoxide concentration and the unburned ammonia concentration contained in the exhaust gas of the heating furnace 1, which is specified in advance, for example, by the specifying step of the above-mentioned method for estimating the unburned ammonia concentration. The correlation between the carbon monoxide concentration and the unburned ammonia concentration stored in the storage unit 41 may be stored in the form of a table or a function. In addition, it is preferable that the storage unit 41 obtains a preset upper limit value of the unburned ammonia concentration from the control computer 10 of the heating furnace 1 and stores this.

[0131] The acquisition unit 42 acquires the carbon monoxide concentration contained in the exhaust gas of 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 of 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, 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.

[0132] The estimation unit 43 estimates the unburned ammonia concentration contained in the exhaust gas of 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 a table format, 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 a function format, 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.

[0133] 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.

[0134] The output unit 45 outputs the operation conditions of the heating furnace 1 calculated by the operation amount calculation unit 44 to the control computer 10 of the heating furnace 1, or outputs them to the display unit 46 as guidance operation amounts to be referred to when the operator operates the operation conditions of the heating furnace 1. When the output destination of the operation amounts of the operation conditions of the heating furnace 1 from the output unit 45 is the control computer 10, it is preferable that the operation conditions of the heating furnace 1 are automatically updated in the control computer 10. When the output destination of the operation amounts of the operation conditions of the heating furnace 1 from the output unit 45 is the display unit 46, it is preferable that the operator operates the operation conditions of the heating furnace 1 based on the guidance operation amounts shown on the display unit 46.

[0135] The heating furnace control device 40 can be configured using, for example, a general-purpose computer equipped with a memory, an auxiliary storage device such as a hard disk drive or solid state drive, a CPU (Central Processing Unit), etc. The auxiliary storage device stores a program for executing the 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 also stored in the memory at all times, and is stored in the auxiliary storage device as necessary.

[0136] The storage unit 41 is preferably realized by, for example, the auxiliary storage device described above. The acquisition unit 42, the estimation unit 43, the operation amount calculation unit 44, and the output unit 45 are preferably realized by the CPU described above reading and executing programs. The display unit 46 can be configured by a display device such as a liquid crystal display or an organic EL panel. Alternatively, the display unit 46 may be configured by a display of a terminal device such as a smartphone or a 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.

[0137] Although the embodiments of the method for estimating an 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. EXAMPLES

[0138] In order to verify the effects of the method for estimating the unburned ammonia concentration, the method for operating a heating furnace, the method for operating a burner equipment, and the control device for a heating furnace of the present invention, a test was conducted to estimate the ammonia concentration contained in the exhaust gas from the heating furnace using a test heating furnace, and the results are described below.

[0139] FIG. 11 is a schematic vertical cross-sectional view of the test heating furnace 1T.

[0140] As shown in Fig. 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 at a position upstream of the exhaust gas treatment device 15 in the exhaust gas flow direction, so that a sample of the exhaust gas flowing through the flue 14 can be collected as necessary.

[0141] As shown in FIG. 11, the test heating furnace 1T is configured to include ten first burner equipment 20a-20j as a heat source for heating. These first burner equipment 20a-20j are burner equipment that performs burner heating using fuel gas F1 containing ammonia F11 and carbon-containing fuel F12. Of the ten first burner equipment 20a-20j, five first burner equipment 20a-20e are arranged above the steel material S transported in the furnace, and the remaining five first burner equipment 20f-20j are arranged below the steel material S transported in the furnace. The test heating furnace 1T is configured not to include a second burner equipment that performs burner heating using fuel gas F2 that does not contain ammonia. The first burner equipment 20a-20j are of the same type, and the rated capacity of each of the first burner equipment 20a-20j is 800,000 kcal / hr.

[0142] 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.

[0143] As the fuel gas F1 to be supplied to the first burner units 20a to 20j, M gas consisting of ammonia F11 and coal gas F12 was used. 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 / Nm 3 Table 2 shows the results of a preliminary gas chromatographic analysis of the composition of the M gas used.

[0144] [Table 2]

[0145] In this embodiment, 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 the flow rate control valves 23v, 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 is 50%:50%, the flow rate of ammonia F11 is 119 Nm 3 / hr, M gas flow rate is 200Nm 3 / hr.

[0146] In addition, the air ratio of the fuel gas F1 to the theoretical air amount was adjusted by the flow rate adjustment valve 26v provided in the combustion air supply system 26.

[0147] First, as an 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.

[0148] In the identification step, among the burner equipment 20a to 20j of the test heating furnace 1T, only the first burner equipment 20a arranged on the upper side of the test heating furnace 1T and closest to the charging section 11 was used for combustion. The combustion test using the first burner equipment 20a was performed by adjusting the air ratio by adjusting the flow rate of the combustion air A, with the mixture ratio of ammonia F11 and M gas being 50%:50%.

[0149] Specifically, the flow rate of the combustion air A was adjusted so that the air ratio in the first burner equipment 20a was set to a predetermined setting value, and then the test furnace 1T was left on standby for 10 minutes so that the combustion state was stabilized and the atmosphere inside the furnace was made uniform. Thereafter, the carbon monoxide concentration in the exhaust gas was measured by 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.

[0150] The unburned ammonia (NH3) concentration, carbon monoxide (CO) concentration, and carbon dioxide (CO2) concentration of the exhaust gas were measured using an offline measuring device for the exhaust gas sample collected from the gas sampling port 14a. The unburned ammonia concentration of the exhaust gas was measured by the boric acid absorption-ion chromatography method specified in the Japanese Industrial Standard JIS K0099:2020 "Method for analyzing ammonia in exhaust gas". Specifically, a boric acid absorption solution was used through which 20 L of exhaust gas had been passed under conditions of an average exhaust gas flow rate of 1.5 L / min. In addition, the carbon monoxide (CO) concentration of the exhaust gas was measured offline using a low-potential electrolysis method, and it was confirmed that it was almost consistent with the measurement value measured by the CO concentration meter 18c placed in the flue 14. Furthermore, the carbon dioxide concentration of the exhaust gas was measured by a non-dispersive infrared method.

[0151] FIG. 12 shows the correlation between the carbon monoxide (CO) concentration and the unburned ammonia (NH3) concentration in the exhaust gas when the above-mentioned preliminary test was performed multiple times while changing the air ratio in the first burner equipment 20a.

[0152] As shown in Figure 12, a correlation is observed between the carbon monoxide (CO) concentration and the unburned ammonia (NH3) concentration of the exhaust gas discharged by the first burner equipment 20a, and it can be seen that the two are almost linearly related. 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 speeds of ammonia F11 contained in the fuel gas F1 and M gas are roughly equal. Based on the results of the preliminary test shown in Figure 12, the correlation between the carbon monoxide concentration φCO (ppm) and the unburned ammonia concentration φNH3 (ppm) is expressed by a regression equation as shown in the following equation (1).

[0153] φNH3=0.1436×φCO ……(1) In this manner, as an identification step, a correlation between the carbon monoxide concentration and the unburned ammonia concentration contained in the exhaust gas from the test heating furnace 1T was identified.

[0154] 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.

[0155] In the measurement step, the test furnace 1T was operated under the same combustion conditions for all of the first burner equipment 20a-20j. That is, the test furnace 1T was operated by setting the mixture ratio of the fuel gas F1, the flow rate of the fuel gas F1, and the air ratio for the first burner equipment 20a-20j under the same conditions. The mixture ratio of the ammonia F11 and the M gas was 50%:50%, which was the same as the mixture ratio in the above-mentioned preliminary test.

[0156] The measuring step was performed online by continuously measuring the carbon monoxide concentration contained in the exhaust gas passing through the flue 14 using the CO concentration meter 18c disposed in the flue 14.

[0157] Next, in the estimation step, the measured value of the carbon monoxide concentration measured online was input into the above formula (1) specified 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.

[0158] The estimated value of the unburned ammonia concentration by the estimation method of 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 operation time of the test heating furnace 1T.

[0159] As shown in Fig. 13, when the air ratio exceeds 1.0, the measured carbon monoxide concentration is 0 ppm, and based on this, the estimated value of the unburned ammonia concentration estimated using formula (1) is also 0 ppm. This indicates that when 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.

[0160] In contrast, when the air ratio was 1.0 or less, some of the M gas contained in the fuel gas F1 was incompletely burned, generating carbon monoxide gas. Based on this, the estimated value of the unburned ammonia concentration using equation (1) was also greater than 0 ppm.

[0161] 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 are referred to as batch measurement 1 to batch measurement 4.

[0162] 13 shows the timing of sampling of exhaust gas samples from the gas sampling port 14a. Using the exhaust gas samples collected in each of batch measurements 1 to 4, the unburned ammonia concentration was measured by boric acid absorption-ion chromatography.

[0163] Table 3 shows the correlation between the unburned ammonia concentration estimated online by the estimation step and the measured unburned ammonia concentration measured offline by batch measurement.

[0164] [Table 3]

[0165] As shown in Table 3, it was confirmed that the value of the unburned ammonia concentration estimated online by the method for estimating the unburned ammonia concentration of the present invention is 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 is within ±7 ppm. [Explanation of symbols]

[0166] 1 Furnace 1T Test furnace 10 Control computer 11 Charging section 12 Unloading section 13f Fixed Skid 13m moving skid 14 Flue 14a Gas sampling port 15 Exhaust gas treatment equipment 16 NO X concentration meter 17 Ammonia concentration meter 18, 18a~18d CO concentration meter 20, 20a~20j First burner equipment 30, 30a~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 adjustment valve 27, 37 Air ratio control unit 40 Heating furnace control device 41 Storage section 42 Acquisition Department 43 Estimation part 44 Operation amount calculation section 45 Output section 46 Display section A Combustion air F1, F2 fuel gas F11 Ammonia gas F12 Coal gas (carbon-containing fuel) S Steel material (heated material)

Claims

1. A method for estimating a concentration of unburned ammonia contained in an exhaust gas discharged from a heating furnace that performs burner heating using a fuel gas containing ammonia and a carbon-containing fuel, comprising: A step of identifying 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 a carbon monoxide concentration contained in an exhaust gas from the heating furnace during operation of the heating furnace; an estimation step of estimating an unburned ammonia concentration contained in the exhaust gas of the heating furnace based on the carbon monoxide concentration measured in the measurement step and the correlation between the carbon monoxide concentration and the unburned ammonia concentration identified in the identification step; A method for estimating an unburned ammonia concentration, comprising:

2. 2. The method for estimating an unburned ammonia concentration according to claim 1, wherein the identifying step identifies a correlation between a carbon monoxide concentration and an unburned ammonia concentration contained in an exhaust gas of the heating furnace for each of a plurality of classifications of operating conditions of the heating furnace.

3. The heating furnace is a conveying type heating furnace that conveys the material to be heated from a charging section to a discharge section while heating the material, 3. The method for estimating an unburned ammonia concentration according to claim 1 or 2, wherein the measuring step measures a 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 a concentration of unburned ammonia contained in an exhaust gas discharged from a burner facility that performs burner heating using a fuel gas containing ammonia and a carbon-containing fuel, comprising: A step of identifying a correlation between a carbon monoxide concentration and an unburned ammonia concentration contained in an exhaust gas from the burner equipment; a measuring step of measuring a carbon monoxide concentration contained in exhaust gas from the burner equipment when burner heating is performed by the burner equipment; an estimation step of estimating an unburned ammonia concentration contained in the exhaust gas from the burner equipment 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; A method for estimating an unburned ammonia concentration, comprising:

5. 5. The method for estimating an unburned ammonia concentration according to claim 4, wherein the specifying step specifies a correlation between a carbon monoxide concentration and an unburned ammonia concentration contained in an exhaust gas from the burner equipment for each of a plurality of classifications of operating conditions of the burner equipment.

6. 4. A method for operating a heating furnace, comprising the step of manipulating 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 an unburned ammonia concentration according to claim 3 is equal to or greater than a predetermined value.

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

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

9. 9. The burner equipment operation method according to claim 8, wherein the operating conditions of the burner equipment changed in the operation step include at least one of a flow rate of the combustion air used for heating the burner, a flow rate of the fuel gas, an air ratio of the fuel gas to a theoretical air amount, and a 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, A memory unit that stores a correlation between a carbon monoxide concentration and an unburned ammonia concentration contained in the exhaust gas from the heating furnace; an acquisition unit that acquires a carbon monoxide concentration contained in exhaust gas from the heating furnace measured during operation of the heating furnace; an estimation unit that estimates an unburned ammonia concentration contained in the exhaust gas of the heating furnace based on the carbon monoxide concentration acquired by the acquisition unit and a correlation between the carbon monoxide concentration and the unburned ammonia concentration stored in the memory unit; an operation amount calculation unit that calculates an operation amount of an operation condition of the heating furnace so that the estimated value of the unburned ammonia concentration estimated by the estimation unit becomes smaller than a predetermined value when the estimated value of the unburned ammonia concentration estimated by the estimation unit is equal to or larger than a predetermined value; A control device for a heating furnace comprising:

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