Operation method of heating furnace and heating furnace

Abstract

The invention provides a method for operating a heating furnace and a heating furnace, which can effectively generate ammonia gas capable of suppressing emission of carbon dioxide as fuel gas of the heating furnace. A method for operating a heating furnace for controlling the temperature in a furnace of a heating furnace by alternately performing a combustion operation and a suction operation in a pair of facing combustion parts using a heat storage type combustion device in which combustion parts having heat storage parts are provided facing each other, the heat storage part is used for recovering sensible heat of suction gas sucked from the inside of the heating furnace, and in the combustion operation, combustion air passes through the heat storage part, so that the temperature of the combustion air is increased, and the combustion air is ejected towards the inside of the heating furnace. And liquid ammonia is sprayed from a fuel supply nozzle toward the ejection flow path of the combustion air passing through the heat storage unit.

Description

TECHNICAL FIELD

[0001] The present application relates to an operation method of a heating furnace that heats an object and a heating furnace. BACKGROUND

[0002] In a steel integrated ironworks, as a representative of a blast furnace gas discharged from a top of a blast furnace that manufactures molten iron by reducing iron ore, a by-product gas generated in a converter or a coke oven is effectively utilized (recycled) as a fuel gas. However, with a request for reduction of carbon dioxide emission in recent years, a combustion technology for reducing the usage amount of these by-product gases is required. For example, even in a heating furnace in which steel is heated in a hot rolling line, a heavy plate rolling line, or the like of a steel integrated ironworks, reduction of the usage amount of by-product gases and reduction of carbon dioxide emission are required. In this case, a technology of using ammonia as a fuel gas of a heating furnace is attracting attention. Ammonia that does not contain a carbon element mainly generates only water and nitrogen even if it is burned, so the reduction effect of carbon dioxide emission is large. Therefore, development of a technology for applying ammonia as a fuel gas of a heating furnace is desired.

[0003] Ammonia used as a fuel for combustion is transported and stored in a liquid state. If liquid ammonia (liquid state ammonia) is directly burned, the latent heat of evaporation of ammonia is high, so it cannot be sufficiently evaporated at the time of combustion, and there is a problem that the conversion efficiency to heat energy is reduced. Therefore, in order to obtain a prescribed combustion energy, it is necessary to excessively supply liquid state ammonia as a fuel, and the consumption amount of ammonia increases. On the other hand, in the case of pre-vaporizing before burning liquid state ammonia, prior heating for vaporizing ammonia is required, and additional energy is required.

[0004] In this regard, in Patent Literature 1, as a combustion device such as a gas turbine, a device using an ammonia vaporizer that vaporizes liquid ammonia using the heat of combustion exhaust gas is disclosed. The combustion exhaust gas of the combustor maintains a temperature of about 800°C, for example, so by heat exchange with the gas of the exhaust system passing through the combustor, liquid ammonia can be easily vaporized.

[0005] In addition, in Patent Literature 2, as a combustion device such as a gas turbine, a device that generates water vapor using the exhaust gas of a gas turbine, and sprays liquid ammonia to a flow path of the generated water vapor, thereby generating ammonia vapor is disclosed. In this case, by heat exchange of the high-temperature water vapor and the liquid state ammonia, liquid ammonia can be vaporized.

[0006] PRIOR ART DOCUMENTS

[0007] PATENT LITERATURE

[0008] Patent Literature 1: Japanese Patent Application Laid-Open No. 2015-190466

[0009] Patent Literature 2: Japanese Patent Application Laid-Open No. 2020-165603

[0010] Non-patent literature

[0011] Non-patent literature 1: Zheng et al., "Effect of atmosphere velocity on evaporation rate constant of free droplet", Journal of the Japan Institute of Energy, vol. 74, 1995, p. 39-p. 45 SUMMARY

[0012] PROBLEMS TO BE SOLVED BY THE INVENTION

[0013] However, if the above-described prior art is applied to a heating device such as a heating furnace, the following problems arise.

[0014] The technology described in Patent Literature 1 can be applied to a case where a large amount of gas is discharged as exhaust gas and the sensible heat possessed by the exhaust gas is also large, like a gas turbine. However, in a heating device such as an industrial heating furnace, the sensible heat possessed by the exhaust gas is used for preheating of combustion air, and thus, does not have the amount of heat to achieve vaporization of liquid ammonia. In addition, in the case of being applied to an existing heating furnace, a heat exchanger for performing heat exchange between the exhaust gas and the liquid ammonia needs to be newly added, and the equipment cost increases.

[0015] Regarding the technology described in Patent Literature 2, in the case where water vapor is generated using the exhaust gas discharged from the heating furnace, the exhaust gas does not have the amount of heat to vaporize the amount of ammonia gas required for combustion of the heating furnace. In addition, since water vapor is supplied to the inside of the heating furnace, oxidation of the heated material (object material) such as steel is promoted, and there is a problem that the product yield of the heated material decreases.

[0016] The present application was completed in view of the above-described circumstances, and aims to provide a heating furnace operation method and a heating furnace capable of efficiently generating ammonia gas capable of suppressing discharge of carbon dioxide as fuel gas of the heating furnace using the sensible heat recovered by a heat storage portion.

[0017] MEANS FOR SOLVING THE PROBLEMS

[0018] [1] A heating furnace operation method that controls a temperature in a furnace of a heating furnace by alternately performing a combustion operation and a suction operation in a pair of combustion portions that are disposed opposite to each other using a regenerative combustion device having a heat storage portion, wherein in the suction operation, sensible heat possessed by suction gas suctioned from the furnace of the heating furnace is recovered by the heat storage portion, in the combustion operation, combustion air is warmed by passing through the heat storage portion and is ejected toward the furnace of the heating furnace, and liquid ammonia is sprayed toward an ejection flow path of the combustion air after passing through the heat storage portion from a fuel supply nozzle.

[0019] [2] The method for operating a heating furnace according to [1], wherein the sprayed liquid ammonia is droplets having a Sauter mean diameter of 5 to 3000 μm.

[0020] [3] The method for operating a heating furnace according to [1] or [2], wherein the Sauter mean diameter d0 (mm) of the sprayed liquid ammonia is set as the distance L (mm) from the ejection outlet of the ejection flow path to the connection position to the fuel supply nozzle, and the average speed of the speed of the combustion air passing through the heat storage unit and the speed of the sprayed liquid ammonia in the direction of the ejection flow path is set as V. M (mm / s), the following formula (1) is satisfied:

[0021] [Mathematical formula 1]

[0022]

[0023] Here, K e The evaporation rate constant of liquid ammonia (mm 2 / s).

[0024] [4] The method for operating a heating furnace according to any one of [1] to [3], wherein the liquid ammonia is sprayed toward the ejection flow path of the combustion air passing through the heat storage unit and at least one gas fuel selected from coal gas and hydrocarbon gas is supplied.

[0025] [5] A heating furnace comprising a heat storage combustion device with combustion sections arranged opposite to each other, wherein the temperature in the furnace is controlled by alternately performing combustion and suction actions in a pair of the opposite combustion sections, wherein an alternating combustion control section is provided for controlling the pair of the combustion sections so as to alternately switch between performing the combustion and suction actions, wherein the combustion sections comprise: a heat storage section for recovering sensible heat of the suctioned gas sucked from the furnace of the heating furnace during the suction action; an ejection flow path for heating the combustion air by passing the combustion air through the heat storage section during the combustion action and ejecting the combustion air toward the furnace of the heating furnace; and a fuel supply nozzle for spraying liquid ammonia toward the ejection flow path during the combustion action.

[0026] Effects of the Invention

[0027] According to the present invention, sensible heat recovered by the heat storage unit can be used to efficiently generate ammonia gas capable of suppressing emission of carbon dioxide as fuel gas for a heating furnace. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic side view showing an example of a heating furnace.

[0029] Figure 2 It is a schematic cross-sectional view showing an example of a heating furnace.

[0030] Figure 3 This is a diagram showing the structure of flow paths involved in the supply and suction of combustion air, suction gas, and liquid ammonia in the regenerative combustion device.

[0031] Figure 4 This is a diagram showing a configuration related to the supply of combustion air and fuel to the first combustion nozzle.

[0032] Figure 5 This is a diagram schematically showing the positional relationship of the first fuel supply nozzle with respect to the first combustion nozzle.

[0033] Figure 6 It is a diagram schematically showing the structure of the first combustion unit according to the second embodiment.

[0034] Figure 7 It is a diagram schematically showing the structure of the first combustion unit according to the third embodiment.

[0035] Figure 8 It is a diagram schematically showing the structure of the first combustion unit according to the fourth embodiment. DETAILED DESCRIPTION

[0036] <First embodiment>

[0037] Hereinafter, a first embodiment of the present invention will be described in detail. Figure 1 and Figure 2 The structure of the heating furnace 10 of this embodiment is shown. Figure 1 A schematic side view is shown as an example of the heating furnace 10 . Figure 2 A schematic cross-sectional view of an example of a heating furnace 10 is shown. The heating furnace 10 includes a loading section 11, a combustion device 12, a conveyor 15, an extraction section 16, and a flue 17. The heating furnace 10 heats a target material S, serving as a heated object, to a temperature of 500 to 1400°C. Furthermore, when used in a hot rolling line, for example, the heating furnace 10 is used to heat target material S, such as cast slabs, to a predetermined temperature (approximately 1100 to 1300°C). The target material S is primarily metal, but may also be ferrous or non-ferrous metal.

[0038] The charging section 11 charges (carries in) the object material S into the furnace of the heating furnace 10. The discharging section 16 discharges (carries out) the heated object material S to the outside of the heating furnace 10. For example, a slab or the like of steel (object material S) manufactured by a continuous casting line is transported to a yard on the charging side of the heating furnace 10, and is charged into the furnace of the heating furnace 10 from the charging section 11 in accordance with a production plan of a hot rolling line or the like. The furnace of the heating furnace 10 is divided into a plurality of zones, and a heating zone divided into 2 to 8 zones is provided on the upstream side, and 1 to 3 soaking zones are provided on the downstream side.

[0039] In the operation of the heating furnace 10, the temperature of the atmosphere is controlled to be different for each zone of the furnace, and the average temperature of the object material S charged into the heating furnace 10 is controlled to gradually increase to a prescribed target heating temperature (target temperature of the object material S at the time of discharge from the heating furnace 10). The object material S heated to the target heating temperature is used for hot rolling by the discharging section 16.

[0040] A fixed type conveying section 15a such as a fixed carriage on which the object material S is placed and a moving type conveying section 15b such as a moving carriage that conveys the object material S are provided in the furnace of the heating furnace 10. The heating furnace 10 provided with the fixed type conveying section 15a and the moving type conveying section 15b is called a walking beam type continuous heating furnace.

[0041] The heating furnace 10 has a plurality of combustion devices 12 such as burners in the furnace along the conveying direction D of the object material S. The combustion device 12 heats the furnace by combustion. When the furnace is heated by combustion of the combustion device 12, the temperature of the object material S rises due to radiation from the wall portion 19 of the heating furnace 10. In addition, a flow of atmosphere gas is generated in the furnace, and the object material S is heated by convection of the atmosphere gas. Furthermore, the object material S can be heated by contact with the combustion flame F of the combustion device 12. That is, the combustion device 12 heats the furnace of the heating furnace 10 by combusting fuel gas as a heat source for heating, and heats the object material S placed in the furnace.

[0042] In the present embodiment, a regenerative combustion device 13 in which combustion sections having a heat storage portion are provided opposite at least a part of the combustion devices 12 of the heating furnace 10 is used. The regenerative combustion device 13 alternately performs a combustion operation and a suction operation in the pair of combustion sections opposite each other, to control the temperature of the furnace of the heating furnace 10. The regenerative combustion device 13 is also called a regenerative burner, and is widely used for industrial heating furnaces.

[0043] As Figure 1As shown, the combustion device 12 is arranged on the upper surface side and the lower surface side of the object material S in a manner that makes it difficult to generate a temperature difference between the upper surface and the lower surface of the object material S in the furnace of the heating furnace 10. The regenerative combustion device 13 has a structure in which a pair of first combustion section 13a and second combustion section 13n are arranged in opposition in the furnace. The pair of first combustion section 13a and second combustion section 13n in opposition are connected to the alternate combustion control section 14d in a controllable manner in order to perform alternate combustion in which the combustion operation and the suction operation are alternately switched and executed. A plurality of regenerative combustion devices 13 can be arranged in the heating furnace 10. In this case, a plurality of pairs of first combustion section 13a and second combustion section 13n in opposition can be arranged in the heating furnace 10, and the alternate combustion control section 14d can be connected in a manner that controls the alternate combustion of the plurality of pairs of first combustion section 13a and second combustion section 13n.

[0044] Next, the structure related to the supply of combustion air, the suction of suction gas, and the supply of liquid ammonia in the regenerative combustion device 13 will be described. Figure 3 The structure related to the supply and suction of combustion air, suction gas, and liquid ammonia will be described. Figure 3 (a) of FIG. 1 is a view that shows a state in which the combustion operation is performed in the first combustion section 13a and the suction operation is performed in the second combustion section 13n. Figure 3 (b) of FIG. 1 is a view that shows a state in which the combustion operation is performed in the second combustion section 13n and the suction operation is performed in the first combustion section 13a. Figure 3 (b) of FIG. 1 is a view that shows a state in which the combustion operation is performed in the second combustion section 13n and the suction operation is performed in the first combustion section 13a.

[0045] The regenerative combustion device 13 has a first combustion section 13a, a second combustion section 13n, a supply air blower 14a, a suction pump 14b, a four-way valve 14c, and an alternate combustion control section 14d. That is, the regenerative combustion device 13 has a pair of combustion sections (the first combustion section 13a and the second combustion section 13n).

[0046] The first combustion section 13a has a first combustion nozzle 13b, a first regenerative section 13c, a first gas flow path 13d, a first gas ejection flow path 13g, a first gas ejection port 13h, a first fuel supply nozzle 13i, a first fuel spray section 13j, and a first fuel flow path 13k. The first gas flow path 13d has a first gas flow meter 13e and a first gas flow adjustment valve 13f. The first fuel flow path 13k has a first fuel flow meter 13l and a first fuel flow adjustment valve 13m.

[0047] The second combustion section 13n has the same structure as the first combustion section 13a described above. Specifically, the second combustion section 13n includes a second combustion nozzle 13o, a second heat storage section 13p, a second gas flow path 13q, a second gas ejection flow path 13t, a second gas ejection port 13u, a second fuel supply nozzle 13v, a second fuel sprayer 13w, and a second fuel flow path 13x. The second gas flow path 13q includes a second gas flow meter 13r and a second gas flow control valve 13s. The second fuel flow path 13x includes a second fuel flow meter 13y and a second fuel flow control valve 13z.

[0048] Here, use Figure 3 (a) describes a state in which combustion is being performed in the first combustion section 13a and suction is being performed in the second combustion section 13n. The air supply blower 14a supplies combustion air O to the first combustion nozzle 13b via the first gas flow path 13d. The first gas flow control valve 13f adjusts the flow rate of combustion air O in the first gas flow path 13d. The combustion air O passes through the first heat storage section 13c, where it is heated by the sensible heat of the first heat storage section 13c and supplied to the first combustion nozzle 13b. In other words, the heated combustion air O is supplied to the first combustion nozzle 13b, generating a combustion flame F therein. This improves the thermal efficiency in the first combustion section 13a. The speed of the combustion air O supplied to the first combustion nozzle 13b is preferably between 1 and 10 m / s.

[0049] Combustion air O is not limited to air collected from the atmosphere. Gas containing more oxygen than atmospheric air can also be used, for example by removing nitrogen from the air or adding pure oxygen. This not only effectively promotes the oxidation reaction of the fuel, but also reduces the flow rate of the supplied combustion air O. Consequently, the power consumption of the air supply blower 14a and other components can be reduced. Alternatively, the oxygen content of the combustion air O can be reduced by mixing the exhaust gas (exhaust gas Q) from the heating furnace 10 with the combustion air O. This facilitates creating a reducing atmosphere within the heating furnace 10 and reduces the nitrogen oxides generated during combustion.

[0050] The first combustion nozzle 13b is connected to the first fuel flow path 13k for supplying fuel. Therefore, the fuel supplied from the first fuel flow path 13k is supplied to the first combustion nozzle 13b, mixed with the combustion air O to form a combustible gas, and then a combustion flame F is ejected into the heating furnace 10.

[0051] The suction pump 14b suctions the gas in the furnace (hereinafter, referred to as "furnace combustion gas") from the second combustion nozzle 13o in the non-combustion state as the suction gas Q via the second gas flow path 13q. The suction pump 14b discharges the suction gas Q suctioned and recovered to the outside of the heating furnace 10 as the exhaust gas. The furnace combustion gas becomes a high-temperature state at the time of the operation of the heating furnace 10, and thus the suction gas Q suctioned from the second combustion nozzle 13o also becomes high-temperature. Therefore, when the suction gas Q is suctioned by the suction pump 14b toward the second gas flow path 13q, heat is accumulated in the second regenerative portion 13p by the second regenerative portion 13p.

[0052] The second regenerative portion 13p can use a publicly known structure such as a silicon carbide ceramic, an alumina ceramic, a cordierite ceramic, a mullite ceramic, or the like as the regenerative portion of the regenerative combustion device 13. The second regenerative portion 13p can be configured by a structure in which a large number of ceramic balls are filled, or the like, or can be configured by a honeycomb structure. The velocity of the suction gas Q passing through the second regenerative portion 13p is preferably 1 m / s to 10 m / s. These structures in the second regenerative portion 13p are the same as those in the first regenerative portion 13c.

[0053] In the first combustion portion 13a and the second combustion portion 13n, the combustion with the air O and the suction with the suction gas Q are alternately performed by reversing the flow of the air O and the suction gas Q as indicated by (a). Figure 3 Specifically, a four-way valve 14c that switches the flow paths is provided for the first gas flow path 13d and the second gas flow path 13q connected to the air supply blower 14a and the suction pump 14b. By switching the first gas flow path 13d and the second gas flow path 13q in the four-way valve 14c, the flow direction of the gas flowing in the first gas flow path 13d and the second gas flow path 13q can be reversed.

[0054] Thus, the first gas flow path 13d functions to supply the air O at the time of the combustion in the first combustion portion 13a (at the time of combustion), and on the other hand, functions to suction the suction gas Q at the time of the suction in the first combustion portion 13a (at the time of non-combustion). The second gas flow path 13q also similarly functions to suction the suction gas Q at the time of the suction in the second combustion portion 13n (at the time of non-combustion), and on the other hand, functions to supply the air O at the time of the combustion in the second combustion portion 13n (at the time of combustion).

[0055] Here, in the case where the combustion is performed in the second combustion portion 13n, as indicated by (b), the air O is supplied to the second combustion portion 13n via the first gas flow path 13d and the second gas flow path 13q. Figure 3The combustion air O supplied from the air supply blower 14a is supplied toward the second combustion nozzle 13o via the second gas flow path 13q as shown in (b). Also, in the second combustion section 13n, the combustion air O supplied from the second gas flow path 13q is heated by passing through the second heat storage section 13p, mixes with the fuel supplied from the second fuel flow path 13x to generate a flammable gas, and is injected toward the inside of the furnace as a combustion flame F. At this time, in the first combustion section 13a in which the suction operation is performed, the inside of the furnace is sucked as the suction gas Q via the first gas flow path 13d by the suction pump 14b.

[0056] The fuel supplied to the first combustion nozzle 13b and the second combustion nozzle 13o can be supplied by opening and closing the opening degree of the first fuel flow rate adjustment valve 13m and the second fuel flow rate adjustment valve 13z provided in the first fuel flow path 13k and the second fuel flow path 13x in accordance with the timing of the combustion operation or the suction operation.

[0057] The alternate combustion control section 14d performs switching control of the combustion operation and the suction operation in the first combustion section 13a and the second combustion section 13n. The alternate combustion control section 14d controls the first combustion section 13a and the second combustion section 13n to perform either of the combustion operation and the suction operation. The alternate combustion control section 14d controls the first combustion section 13a and the second combustion section 13n such that the suction operation is performed in the combustion section on the other side when the combustion operation is performed in the combustion section on either side. The alternate combustion control section 14d can control the combustion operation and the suction operation to be switched at a prescribed time. The switching period of the combustion operation and the suction operation in the first combustion section 13a and the second combustion section 13n is preferably 20 seconds to 120 seconds. In the case where the period of switching of the combustion operation and the suction operation is less than 20 seconds, the frequency of switching of the first gas flow path 13d and the second gas flow path 13q increases, and thus it is possible to cause the equipment such as the four-way valve 14c to deteriorate early. Also, in the case where the period of switching of the combustion operation and the suction operation exceeds 120 seconds, the amount of heat accumulated in the first heat storage section 13c and the second heat storage section 13p becomes large, and thus it is necessary to make the first heat storage section 13c and the second heat storage section 13p large, and there is a problem in that the cost of the equipment becomes high.

[0058] As described above, in the regenerative combustion device 13, the supply of the combustion air O and the suction of the suction gas Q are alternately performed by alternately switching the combustion operation and the suction operation in the pair of combustion sections (the first combustion section 13a and the second combustion section 13n). Thus, in the suction operation, the sensible heat possessed by the suction gas Q is accumulated in the heat storage sections (the first heat storage section 13c and the second heat storage section 13p), and in the combustion operation, the combustion air O is heated by the heat storage sections (the first heat storage section 13c and the second heat storage section 13p), and thus it is possible to effectively use the heat of the suction gas Q.

[0059] Next, the structure related to the supply of the combustion air O and the fuel to the first combustion nozzle 13b in the combustion operation in the first combustion section 13a will be described. Figure 4 Figure 4 is a view showing the structure related to the supply of the combustion air O and the fuel to the first combustion nozzle 13b. In the following description of the embodiments, the structure related to the supply of the combustion air O and the fuel will be described taking the first combustion section 13a as an example, but the supply of the combustion air O and the fuel in the second combustion section 13n is the same, and thus the description related to the second combustion section 13n will be omitted.

[0060] As shown in Figure 4 , the first combustion nozzle 13b has a first heat storage section 13c inside. The first gas ejection flow path 13g is a flow path in the first combustion nozzle 13b in which the combustion air O warmed up by the first heat storage section 13c and passed through the first heat storage section 13c moves to the boundary with the furnace, i.e., the first gas ejection port 13h. The first fuel supply nozzle 13i has a first fuel spray section 13j inside. The first fuel supply nozzle 13i is connected to the first fuel flow path 13k.

[0061] In the combustion operation, liquid ammonia Al is supplied as the fuel to the first combustion nozzle 13b via the first fuel flow path 13k. The liquid ammonia Al is sprayed by the first fuel spray section 13j and supplied to the first combustion nozzle 13b through the first fuel supply nozzle 13i. In the combustion operation, the combustion air O is supplied to the first combustion nozzle 13b via the first gas flow path 13d. The combustion air O is warmed up by heat exchange when passing through the first heat storage section 13c. The combustion air O passed through the first heat storage section 13c is warmed up to a temperature of, for example, 500 to 1400°C. The liquid ammonia Al supplied from the first fuel supply nozzle 13i to the first combustion nozzle 13b is gasified by heat exchange with the combustion air O. Thus, the liquid ammonia Al is mixed with the combustion air O as ammonia gas Ag to form a flammable gas, and the combustion flame F is ejected toward the furnace from the first gas ejection port 13h.

[0062] The liquid ammonia Al used as the fuel is supplied from a liquid ammonia storage section 50. The liquid ammonia storage section 50 is a tank or the like container that stores a prescribed amount of liquid ammonia Al. Ammonia can be liquefied at around 8 atm at normal temperature, and thus can be easily stored in a liquid state. If ammonia is in a liquefied state, the volume of the container that stores the fuel can be reduced, and the transportability and storability are improved.

[0063] ​Liquid ammonia A1 stored in the liquid ammonia storage unit 50 is supplied to the first fuel flow path 13k using a supply pump (not shown). A first fuel flow meter 13l and a first fuel flow control valve 13m can be disposed between the supply pump and the first fuel spray unit 13j in the first fuel flow path 13k. The first fuel flow meter 13l measures the flow rate of liquid ammonia A1 supplied to the first fuel spray unit 13j. The first fuel flow control valve 13m adjusts the flow rate of liquid ammonia A1 supplied to the first fuel spray unit 13j. In this case, the first fuel flow control valve 13m can be configured as a solenoid valve to control the flow rate of liquid ammonia A1 supplied to the first fuel spray unit 13j.

[0064] The first fuel spray unit 13j sprays liquid ammonia Al toward the first gas ejection flow path 13g of the combustion air O that has passed through the first heat storage unit 13c. Spraying means spraying a liquid in a mist form. A known nozzle for spraying a liquid in a mist form can be used for the first fuel spray unit 13j.

[0065] The liquid ammonia A1 sprayed from the first fuel spray portion 13j passes through the first fuel supply nozzle 13i and merges with the flow of the combustion air O in the first combustion nozzle 13b. Thus, the liquid ammonia A1 sprayed from the first fuel spray portion 13j and passed through the first fuel supply nozzle 13i is mixed with the combustion air O flowing in the first combustion nozzle 13b, and heat exchange is performed between the liquid ammonia A1 and the combustion air O.

[0066] The first fuel supply nozzle 13i used in the first fuel spray section 13j can be a single-fluid nozzle that only sprays liquid ammonia Al, or a two-fluid nozzle that uses compressed air to spray liquid ammonia Al. The structure of the single-fluid nozzle is simple and not easily restricted by the installation space. The two-fluid nozzle can reduce the particle size of the spray and can control the particle size of the spray by adjusting the pressure and flow rate of the compressed air. In this case, in order to pressurize the air, a pump, a blower, a compressor, etc. can be used. In addition, when using a two-fluid nozzle, the liquid ammonia Al can also be pressurized. By pressurizing the liquid ammonia Al, the particle size of the spray can be reduced, and the particle size of the liquid ammonia Al can be adjusted by the pressure.

[0067] Here, from the viewpoint of uniform mixing with the combustion air O, the Sauter mean diameter of the liquid ammonia Al sprayed by the first fuel spray section 13j is preferably 5 μm to 3000 μm, more preferably 10 μm to 800 μm, and further preferably 50 μm to 300 μm. The Sauter mean diameter (D32) is also called the area mean diameter, and is used as a representative diameter of liquid droplets in a heat and mass transfer process. The Sauter mean diameter refers to an average diameter obtained by weighting the ratio of the surface area of a liquid droplet having a liquid droplet diameter d to the sum of the surface areas of all liquid droplets. Specifically, for a liquid droplet group having nd liquid droplets each having a liquid droplet diameter d, the Sauter mean diameter is calculated by the following equation (2).

[0068] [Mathematical equation 2]

[0069]

[0070] In the case where the Sauter mean diameter of the liquid ammonia Al is less than 5 μm, the momentum of the combustion air O ejected to the first combustion nozzle 13b at the time of combustion operation becomes excessively large compared to the momentum of the liquid ammonia Al, and the mixing of the combustion air O with the liquid ammonia Al becomes insufficient. Also, the temperature distribution of the combustion flame F generated from the tip end of the first combustion nozzle 13b, that is, the first gas ejection port 13h, becomes non-uniform, and the generation of nitrogen oxides becomes excessive, and thus is not preferable. On the other hand, if the Sauter mean diameter of the liquid ammonia Al exceeds 3000 μm, a time for gasifying the liquid ammonia Al is required. Therefore, at the time of injection of the combustion flame F from the tip end of the first combustion nozzle 13b, that is, the first gas ejection port 13h, by mixing the liquid ammonia Al with the combustion air O, the concentration distribution of ammonia becomes non-uniform, and unburned ammonia remains, and thus is not preferable.

[0071] The first fuel supply nozzle 13i has the first fuel spray section 13j at one end, and forms a flow path of the liquid ammonia Al sprayed from the first fuel spray section 13j. The other end of the first fuel supply nozzle 13i is connected to the first combustion nozzle 13b, and is configured to mix the liquid ammonia Al passing through the first fuel supply nozzle 13i with the combustion air O flowing in the first gas ejection flow path 13g. The first fuel supply nozzle 13i can be inclined with respect to the first gas ejection flow path 13g extending in the flow direction of the combustion air O along the first combustion nozzle 13b. Also, with respect to the speed of the spray direction of the liquid ammonia Al passing through the first fuel supply nozzle 13i, by having the same speed component as the flow direction of the combustion air O, the liquid ammonia Al is easily mixed with the combustion air O.

[0072] Here, the following equation (3) is used. Figure 5 The positional relationship of the first fuel supply nozzle 13i with respect to the first combustion nozzle 13b will be described. Figure 5is a view schematically showing a positional relationship of the first fuel supply nozzle 13i with respect to the first combustion nozzle 13b.

[0073] As shown in Figure 5 , the first fuel supply nozzle 13i is configured to have an inclination of an angle Θ with respect to the first gas ejection flow path 13g extending in a flow direction of the combustion air O flowing in the first combustion nozzle 13b. The connecting position M of the first fuel supply nozzle 13i with respect to the first combustion nozzle 13b is a position apart from the first gas ejection port 13h by a distance L (mm).

[0074] Here, a velocity of the combustion air O that has passed through the first heat storage portion 13c is set to V0 (mm / s), and a velocity of the liquid ammonia Al sprayed from the first fuel supply nozzle 13i toward the first gas ejection flow path 13g is set to V1 (mm / s). In this case, the first fuel supply nozzle 13i has an inclination of an angle Θ with respect to the first gas ejection flow path 13g extending in a flow direction of the combustion air O. Therefore, a velocity V F (mm / s) of a component in the direction of the first gas ejection flow path 13g (flow direction of the combustion air O) in the velocity of the sprayed liquid ammonia Al is V1 · cos Θ. In this case, the velocity of the combustion air O that has passed through the first heat storage portion 13c sometimes has a velocity distribution within a cross section of the first gas ejection flow path 13g, but the velocity V0 refers to an average velocity within the cross section of the first gas ejection flow path 13g. In addition, sizes of droplets of the liquid ammonia Al sprayed from the first fuel supply nozzle 13i toward the first gas ejection flow path 13g include various sizes, so there is a velocity distribution within the first fuel supply nozzle 13i depending on the droplet diameter. Therefore, the velocity V1 refers to an average velocity of the droplets of the liquid ammonia Al.

[0075] The liquid ammonia Al that has passed through the first fuel supply nozzle 13i reaches the first gas ejection port 13h while exchanging momentum with the combustion air O. Therefore, the liquid ammonia Al sprayed to the first combustion nozzle 13b can be regarded as passing through the first gas ejection flow path 13g at an average velocity V F (mm / s) of V0 and V M . Therefore, a time tT (s) of the liquid ammonia Al sprayed to the first combustion nozzle 13b until reaching the first gas ejection port 13h is represented by the following (3).

[0076] [Mathematical Expression 3]

[0077]

[0078] In addition, when the droplet diameter of the liquid ammonia Al sprayed from the first fuel supply nozzle 13i to the first combustion nozzle 13b is set to do (mm), the droplet diameter d (mm) at the time tT is expressed by the following equation (4) using the evaporation speed constant Ke (mm / s). 2

[0079] [Equation 4]

[0080]

[0081] Here, the evaporation speed constant Ke refers to a reduction rate of the square of the droplet diameter with respect to time during a stable evaporation period generated when the fuel droplet is introduced into a high-temperature atmosphere. That is, at the initial stage when the droplet is introduced into the high-temperature atmosphere, most of the heat flowing into the droplet is consumed by heating of the droplet itself, and thus the droplet does not evaporate much, and the reduction amount of the droplet diameter is small. However, in a state (stable evaporation period) where the droplet temperature reaches the wet-bulb temperature (temperature at which the heat flowing into the droplet is entirely used for evaporation of the droplet), the square of the droplet diameter linearly decreases with respect to time, and thus the reduction rate thereof is referred to as the evaporation constant.

[0082] The evaporation speed constant Ke can be determined by experiment using the droplet of the liquid ammonia. However, for example, it can also be determined using the following equation (5) described in Non-Patent Literature 1. In addition, Ke0 is the evaporation speed constant when Vo and V F Re represents the Reynolds number.

[0083] [Equation 5]

[0084]

[0085] At this time, based on the condition (d = 0) of the droplet gasification of the liquid ammonia Al at the time tT, the following equation (6) is derived using equation (4).

[0086] [Equation 6]

[0087]

[0088] Based on the above equations (3) and (6), the condition for gasifying the droplet of the liquid ammonia Al that has passed through the first fuel supply nozzle 13i during the period until the leading end of the first combustion nozzle 13b, that is, the first gas ejection port 13h, is expressed by the following equation (1). That is, if the droplet diameter of the liquid ammonia Al that has passed through the first fuel supply nozzle 13i is smaller than the droplet diameter calculated by equation (6), the liquid ammonia Al can be gasified during the period until the first gas ejection port 13h is reached.

[0089] [Equation 1]

[0090] ​

[0091] The droplet d0 of the liquid ammonia Al can be represented by the Sauter mean diameter of the liquid ammonia Al. Therefore, if the Sauter mean diameter d0 of the liquid ammonia Al sprayed from the first fuel supply nozzle 13i to the first combustion nozzle 13b satisfies the formula (1), the liquid ammonia Al sprayed from the first fuel supply nozzle 13i is considered to become the ammonia gas when the combustion flame F is injected from the first gas injection port 13h. In addition, the Sauter mean diameter of the liquid ammonia Al sprayed from the first fuel spray portion 13j is the same as the Sauter mean diameter of the liquid ammonia Al supplied from the first fuel supply nozzle 13i to the first combustion nozzle 13b, or the droplet diameter of the liquid ammonia Al sprayed from the first fuel spray portion 13j is slightly larger. Therefore, if the Sauter mean diameter of the liquid ammonia Al sprayed from the first fuel spray portion 13j satisfies the formula (1), the liquid ammonia Al becomes the ammonia gas Ag when the combustion flame F is injected from the first gas injection port 13h, that is, the front end of the first combustion nozzle 13b.

[0092] Specifically, in the case where the distance L between the connection position M of the first fuel supply nozzle 13i and the first gas injection port 13h is 100 mm, the evaporation velocity constant Ke is 0.1 mm / s, and the average velocity V is 5000 mm / s, the Reynolds number Re is approximately 16000. In this case, by making the Sauter mean diameter d0 of the sprayed liquid ammonia Al less than 0.84 mm, the liquid ammonia Al becomes the ammonia gas Ag when the combustion flame F is generated at the first gas injection port 13h. 2 M

[0093] ​​As described above, in the present embodiment, as the operation method of the heating furnace 10 using the regenerative combustion device 13, the combustion air O supplied to the first combustion nozzle 13b at the time of combustion operation is warmed up by the first regenerative portion 13c, and liquid ammonia Al is sprayed from the first fuel spray portion 13j toward the first gas ejection flow path 13g of the combustion air O passing through the first regenerative portion 13c and the first combustion nozzle 13b as a combustion fuel. Also, since the liquid ammonia Al exchanges heat while mixing with the warmed combustion air O, the liquid ammonia Al is vaporized to generate ammonia gas Ag in the first combustion nozzle 13b. The generated ammonia gas Ag is mixed with the combustion air O as a flammable gas, and the combustion flame F is ejected toward the furnace interior of the heating furnace 10. That is, by performing the combustion operation in the combustion device 12 using the liquid ammonia Al as a fuel, it is possible to reduce the carbon dioxide discharged from the heating furnace 10, and it is possible to omit the supply of external energy required for vaporization of the liquid ammonia Al. Also, in the first combustion nozzle 13b, heat exchange of the ammonia gas Al and the combustion air O is performed, so the temperature of the ammonia gas Ag rises. That is, as the fuel gas of the heating furnace 10, it is possible to efficiently generate ammonia gas using the sensible heat recovered by the regenerative portion. Also, the ammonia gas Ag has a property of thermally decomposing into nitrogen and hydrogen when it becomes a high-temperature state, so the combustion speed of ammonia as a fire-retardant fuel increases, and the stability of the burner combustion improves.

[0094] Here, the "regenerative portion" of the present application corresponds to the first regenerative portion 13c and the second regenerative portion 13p. The "combustion portion" of the present application corresponds to the first combustion portion 13a and the second combustion portion 13n. The "ejection flow path" of the present application corresponds to the first gas ejection flow path 13g and the second gas ejection flow path 13t. The "fuel supply nozzle" of the present application corresponds to the first fuel supply nozzle 13i and the second fuel supply nozzle 13v. The "ejection port" of the present application corresponds to the first gas ejection port 13h and the second gas ejection port 13u.

[0095] <Second Embodiment>

[0096] Next, the second embodiment of the present application will be described in detail. Figure 6 The structure of the first combustion portion 23a of the second embodiment is schematically shown. Figure 6 A first example of a fuel supply method when another gaseous fuel R is used as a fuel is shown. Figure 6 The structure shown is a structure provided with a plurality of supply nozzles for supplying fuel to the first combustion nozzle 23b, and is an example of a separate fuel injection method in which different kinds of fuel are separately supplied.

[0097] In the second embodiment, in addition to the first fuel supply nozzle 23i that supplies the liquid ammonia Al to the first combustion nozzle 23b, there is a gas fuel supply nozzle 20 that supplies the gas fuel R. In the case where there are a plurality of supply nozzles that supply fuel to the first combustion nozzle 23b, it is sufficient that one of them is the first fuel supply nozzle 23i that supplies the liquid ammonia Al. In this case, the combustion air O that is warmed by the first heat accumulating portion 23c, the liquid ammonia Al that is made into droplets by the first fuel spray portion 23j, and the gas fuel R that is supplied from the gas fuel supply nozzle 20 are mixed in the first combustion nozzle 23b, and heat exchange is performed. Also, the ammonia gas Ag is generated from the liquid ammonia Al that is supplied to the first combustion nozzle 23b, and the mixed fuel that is formed by mixing the ammonia gas Ag and the gas fuel R is combusted, and the combustion flame F is generated from the first gas ejection port 23h. The gas fuel R that is supplied from the gas fuel supply nozzle 20 is also warmed by the combustion air O, so the combustibility of the gas fuel R is also improved, and further energy saving is achieved.

[0098] In the present embodiment (second embodiment), it is possible to spray the liquid ammonia Al as a fuel for combustion toward the first gas ejection flow path 23g in which the combustion air O that has passed through the first heat accumulating portion 23c is ejected, and to use other gas fuel R as a fuel for combustion. The ammonia gas Ag is a fuel that is resistant to combustion, so by being used in combination with other gas fuel R, it is possible to promote the combustion of the ammonia gas Ag, and to improve the stability of the combustion flame F that is generated by the first combustion nozzle 23b.

[0099] As the other gas fuel R that promotes the combustion of the ammonia gas Ag, it is possible to use coal gas Cg. Here, the coal gas Cg refers to a gas that is obtained from coal. The coal gas Cg preferably includes any one of coke oven gas, blast furnace gas, converter gas, and electric furnace gas. These gases are byproduct gases that are generated at ironworks, and have the effect of stabilizing the combustion of the ammonia gas Ag. The blast furnace gas is a byproduct gas that is generated when pig iron is manufactured by reducing iron ore in a blast furnace. The coke oven gas is a byproduct gas that is generated by dry distillation of coal at a high temperature in order to manufacture coke. The converter gas is a byproduct gas that is generated in a steelmaking process in a converter. The electric furnace gas is a gas that is generated by incomplete combustion of an auxiliary fuel (carbon material) in an electric furnace. The coal gas Cg can be a mixed gas that includes these byproduct gases. The coal gas that constitutes the mixed gas can use a gas that is appropriately mixed with the blast furnace gas, the coke oven gas, and the converter gas (hereinafter, also referred to as "M gas"). By mixing the coal gas Cg that has a different calorific value than the ammonia gas Ag, it is possible to supply the heat that is required for heating the object material S in the heating furnace 10, and it is possible to perform stable operation of the heating furnace 10.

[0100] As the other gas fuel R for promoting combustion of the ammonia gas Ag, a hydrocarbon-based gas Hg can also be used. Here, the hydrocarbon-based gas Hg refers to a fuel gas vaporized from a hydrocarbon. The hydrocarbon-based gas Hg can use methane (CH4), ethane (C2H6), propane (C3H8), butane (C4H 10 ), ethylene (C2H4), propylene (C3H6), butylene (C4H8) as paraffin-based hydrocarbons, and these gases have an effect of stabilizing combustion of the ammonia gas Ag. In addition, compared with coal gas, emission of nitrogen oxides and sulfur oxides can be suppressed. By mixing the hydrocarbon-based gas Hg having a different calorific value compared with the ammonia gas Ag, it is possible to supply heat required for heating of the object material S in the heating furnace 10, and it is possible to perform stable operation of the heating furnace 10. In the present embodiment, at least one gas fuel selected from the coal gas Cg and the hydrocarbon-based gas Hg can be used as the other gas fuel R for promoting combustion of the ammonia gas Ag.

[0101] <Third Embodiment>

[0102] Next, the third embodiment of the present application will be described in detail. Figure 7 The structure of the first combustion section 33a of the third embodiment is schematically shown. Figure 7 A second example of the fuel supply method when using the other gas fuel R as the fuel is shown. Figure 7 The structure shown is a structure in which the liquid ammonia Al is supplied from the first fuel flow path 33k, after generating droplets of the liquid ammonia Al by the first fuel spray section 33j, a mixed fuel with the gas fuel R is generated, and the mixed fuel is supplied from the first fuel supply nozzle 33i to the first combustion nozzle 33b. Figure 7 The structure shown is an example of a post-spray mixed fuel generation method. In the present embodiment, as in the second embodiment, as the other gas fuel R for promoting combustion of the ammonia gas Ag, the coal gas Cg can be used.

[0103] In the third embodiment, liquid ammonia Al is sprayed by the first fuel spray section 33j, and the flow of the liquid droplets of the liquid ammonia Al moving inside the first fuel supply nozzle 33i toward the first combustion nozzle 33b is supplied with the gas fuel R from the gas fuel supply nozzle 30. Thereby, the mixed fuel of the liquid ammonia Al and the gas fuel R is supplied from the first fuel supply nozzle 33i toward the first combustion nozzle 33b. The first fuel spray section 33j can also apply a dual fluid nozzle using compressed air. By the injection of the compressed air, the flow speed of the liquid droplets of the liquid ammonia Al inside the first fuel supply nozzle 33i increases, and thus the mixing of the liquid ammonia Al and the gas fuel R is promoted. In this case, heat exchange is performed between the combustion air O warmed by the first heat accumulation section 33c and the liquid ammonia Al in the mixed fuel supplied from the first fuel supply nozzle 33i, and ammonia gas Ag is generated. Then, the mixed gas of the ammonia gas Ag and the gas fuel R becomes the fuel gas, and the combustion flame F is injected from the first gas injection port 33h. In this case, the gas fuel R supplied from the first fuel supply nozzle 33i is also heated by the combustion air O, and thus the combustibility of the gas fuel R is also improved.

[0104] <Fourth Embodiment>

[0105] Next, the fourth embodiment of the present application will be described in detail. Figure 8 The structure of the first combustion section 43a of the fourth embodiment is schematically shown. Figure 8 A third example of the fuel supply method when using other gas fuel R as the fuel is shown. Figure 8 The structure shown is a structure in which the liquid ammonia Al is supplied from the first fuel flow path 43k, and a mixed fuel with the gas fuel R is generated before the liquid droplets of the liquid ammonia Al are generated by the fluid spray section 42, and the mixed fuel is supplied from the gas fuel supply nozzle 40 toward the first combustion nozzle 43b. Figure 8 The structure shown is an example of the pre-spray mixed fuel generation method. In the present embodiment, as with the second and third embodiments, as the other gas fuel R that promotes the combustion of the ammonia gas Ag, coal gas Cg can be used.

[0106] In the fourth embodiment, liquid ammonia Al supplied from the first fuel flow path 43k is mixed with gaseous fuel R supplied from the gaseous fuel flow path 41, and then sprayed through the fluid spray section 42. The gaseous fuel R supplied from the gaseous fuel flow path 41 can be supplied as compressed gas compressed by a pump or compressor, and mixed with the liquid ammonia Al. Furthermore, due to the pressure generated within the supply piping, the Sauter mean diameter of the liquid ammonia Al sprayed from the fluid spray section 42 decreases, facilitating the vaporization of the liquid ammonia Al. In this case, heat exchange also occurs between the combustion air O heated by the first heat storage section 43c and the liquid ammonia Al in the mixed fuel supplied from the gaseous fuel supply nozzle 40, generating ammonia gas Ag. The mixed gas of ammonia gas Ag and gaseous fuel R becomes fuel gas, and a combustion flame F is ejected from the first gas outlet 43h.

[0107] Example

[0108] Next, the results of a combustion experiment conducted on the operating method of the heating furnace of the present invention are described. Figure 6 The first combustion unit 23a (second embodiment) shown is implemented. Figure 6 The first combustion unit 23a shown is an example of a single fuel injection system, and includes a first gas flow path 23d, a first heat storage unit 23c, a gas fuel supply nozzle 20, a first fuel supply nozzle 23i, a first fuel spray unit 23j, and a first combustion nozzle 23b.

[0109] In this embodiment, a combustible gas selected from methane (hydrocarbon-based gas Hg) and coke oven gas (coal gas Cg) is used as the gas fuel R. The gas fuel R, selected from methane and coke oven gas, is supplied to the gas fuel supply nozzle 20 via a gas fuel flow path (not shown). Liquid ammonia Al is supplied to the first fuel spray unit 23j via the first fuel flow path 23k, and the liquid ammonia Al sprayed by the first fuel spray unit 23j is supplied to the first fuel supply nozzle 23i. Flow control valves are provided in the gas fuel flow path and the first fuel flow path 23k to adjust the mixing ratio of the liquid ammonia Al and gas fuel R supplied to the first combustion nozzle 23b. A flow control valve is also provided in the first gas flow path 23d to adjust the air ratio of the fuel gas (liquid ammonia Al and gas fuel R) to 0.9 relative to the theoretical air ratio.

[0110] The rated capacity of the first combustion section 23a is 800,000 kcal / hr. The distance L between the connection position M of the first fuel supply nozzle 23i and the first gas outlet 23h, the front end of the first combustion nozzle 23b, is 100 mm. Regarding the flow rate of the fuel gas supplied during the combustion operation, when using a mixed fuel with ammonia as 40% calorific value and methane as 60% calorific value, the flow rate of ammonia Ag is 79 Nm3 The flow rate of liquid ammonia A1 is set at 100 N / hr. In addition, the flow rate of methane when only methane is used as the gas fuel R is set at 51 N / hr. 3 When coke oven gas is used as the gas fuel R, the flow rate of the coke oven gas is set to a calorific value substantially the same as that when a mixed fuel containing 40% ammonia and 60% methane is used.

[0111] On the other hand, as a conventional example, Figure 6 In the first combustion section 23a shown, liquid ammonia Al is not supplied from the first fuel flow path 23k, but methane is supplied to the gas fuel supply nozzle 20 as the gas fuel R. At this time, the flow rate of methane as the fuel gas is 84 Nm 3 / hr.

[0112] In this embodiment, combustion experiments were conducted by varying the mixture ratio of the combustion gas during the combustion operation of the first combustion unit 23a and the spray diameter of the liquid ammonia Al sprayed by the first fuel spray unit 23j. The Sauter mean diameter was used as the spray diameter of the liquid ammonia Al.

[0113] In the comparative example, the Figure 6 In the illustrated first combustion section 23a, liquid ammonia Al is not supplied via the first fuel flow path 23k, but rather a mixed gas of methane and ammonia Ag is supplied from the gas fuel supply nozzle 20 as the gaseous fuel. In this case, the ammonia Ag is pre-evaporated using an electric heater-type evaporator and then mixed with methane via a mixer before being supplied. The energy required to vaporize the liquid ammonia Al using the evaporator (the vaporization energy) is 1942 kJ per kg of liquid ammonia Al. It should be noted that the theoretical latent heat of vaporization of ammonia (0°C, 1 atm) is 1262 kJ / kg, so the efficiency of the evaporator used is 65%. That is, the high calorific value of ammonia Ag is 22.5 MJ / kg, so the ratio of the energy required to vaporize the liquid ammonia Al to the high calorific value of ammonia Ag is 8.63%.

[0114] Further, the concentration of carbon dioxide (CO2) and the concentration of nitrogen oxides (NOx) contained in the combustion gas in the furnace 10 were measured. Further, the state of the combustion flame F emitted from the first combustion nozzle 23b was captured by a video camera, and the stability of the flame was evaluated by visual observation. That is, the case where the combustion flame F was stably formed was evaluated as "O", the case where the combustion flame F continued to burn although it had fluctuations was evaluated as "Δ", and the case where the combustion flame F disappeared due to blowout was evaluated as "X". The evaluation results in the examples are shown in Table 1. Note that the amount of carbon dioxide (CO2) contained in the combustion gas in the furnace was taken as a reference (1.0) for the amount of carbon dioxide (CO2) contained in the combustion gas in the furnace in the existing example, and the ratio under each condition was shown.

[0115]

[0116] The existing example used only methane as the gas fuel as the fuel for the combustion operation in the first combustion section 23a. Further, the amount of carbon dioxide generated by combustion was the largest among the examples.

[0117] In Comparative Examples 1 to 3, a mixed gas, which was generated by mixing ammonia gas Ag, which was obtained by previously vaporizing liquid ammonia Al, with methane, was combusted as the fuel for the combustion operation in the first combustion section 23a. Further, since vaporization energy for vaporizing the liquid ammonia Al was required in advance, the greater the mixing ratio of the ammonia gas Ag in the gas fuel, the more additional energy was required.

[0118] In Inventive Examples 1 to 3, the Sauter mean diameter of the liquid ammonia Al sprayed from the first fuel spraying section 23j was set to 200 μm. Further, the amount of carbon dioxide contained in the combustion gas in the furnace was reduced compared to the existing example. In addition, in Inventive Examples 1 to 3, no additional vaporization energy as shown as a result of Comparative Examples 1 to 3 was required, and therefore ammonia gas could be efficiently generated using the sensible heat recovered by the first heat storage section 23c.

[0119] In Inventive Examples 4 to 6, a mixed fuel in which ammonia was set to 35% of the heat and methane was set to 65% of the heat was used. Further, compared to Inventive Examples 1 to 3, the Sauter mean diameter of the liquid ammonia Al sprayed from the first fuel spraying section 23j was changed. In Inventive Examples 4 to 6, the amount of carbon dioxide contained in the combustion gas in the furnace was reduced compared to the existing example. In addition, since no additional vaporization energy as shown as a result of Comparative Examples 1 to 3 was required, ammonia gas could be efficiently generated using the sensible heat recovered by the first heat storage section 23c.

[0120] In Inventive Examples 4 to 6, it is considered that the reason why the concentration of nitrogen oxides (NOx) is reduced compared with the result of Comparative Example 3 is that a part of the liquid ammonia Al remains in the form of unburned ammonia in the in-furnace combustion gas, and the nitrogen oxides generated due to the combustion of ammonia are reduced, and the concentration of nitrogen oxides in the in-furnace combustion gas is reduced. On the other hand, Inventive Examples 5 and 6 mean that, since the condition of the formula (1) is not satisfied, a part of the liquid ammonia Al is not vaporized during the period from the connection position M of the first fuel supply nozzle 23i to the front end portion of the first combustion nozzle 23b, that is, the first gas injection port 23h, and therefore the combustion flame F is fluctuated.

[0121] In Inventive Example 7, a mixed fuel of 35% heat of ammonia and 65% heat of coke oven gas is used. Further, the Sauter mean diameter of the liquid ammonia Al sprayed from the first fuel spray portion 23j is set to 200 μm. Also, the amount of carbon dioxide contained in the in-furnace combustion gas is reduced compared with the prior example. In addition, in Inventive Example 7, the additional vaporization energy shown as the result of Comparative Examples 1 to 3 is not required, and therefore ammonia gas can be efficiently generated using the sensible heat recovered by the first heat storage portion 23c.

[0122] BRIEF DESCRIPTION OF DRAWINGS

[0123] 10 heating furnace

[0124] 11 charging portion

[0125] 12 combustion device

[0126] 13 regenerative combustion device

[0127] 13a first combustion portion

[0128] 13n second combustion portion

[0129] 14a gas supply blower

[0130] 14b suction pump

[0131] 14c four-way valve

[0132] 14d alternate combustion control portion

[0133] 15 conveying device

[0134] 16 extraction portion

[0135] 17 flue portion

[0136] L distance

[0137] D conveying direction

[0138] S object material

[0139] F combustion flame

[0140] O combustion air

[0141] Q suction gas

[0142] M connection position

[0143] Al liquid ammonia

[0144] Ag ammonia gas

[0145] Cg coal gas

[0146] Hg hydrocarbon gas

Claims

1. A method for operating a heating furnace, comprising: utilizing a regenerative combustion device having combustion units having heat storage units disposed opposite to each other, and alternately performing combustion and suction operations in a pair of the opposing combustion units to control the temperature within the heating furnace, wherein: In the suction operation, the heat storage unit recovers the sensible heat of the suction gas sucked from the furnace of the heating furnace. During the combustion operation, combustion air is heated by passing through the heat storage unit and ejected into the heating furnace, and liquid ammonia is sprayed from a fuel supply nozzle toward an ejection flow path of the combustion air that has passed through the heat storage unit.

2. The method for operating a heating furnace according to claim 1, wherein: The liquid ammonia sprayed out is droplets with a Sauter mean diameter of 5 to 3000 μm.

3. The method for operating a heating furnace according to claim 1 or 2, wherein: The Sauter mean diameter d0 (mm) of the sprayed liquid ammonia is calculated by assuming that the distance from the ejection outlet of the ejection flow path to the connection position with the fuel supply nozzle is L (mm) and the average speed of the speed of the combustion air passing through the heat storage unit and the speed of the sprayed liquid ammonia in the direction of the ejection flow path is V. M (mm / s), the following formula (1) is satisfied: [Mathematical formula 1] Here, K e The evaporation rate constant of liquid ammonia (mm 2 / s).

4. The method for operating a heating furnace according to any one of claims 1 to 3, wherein: The liquid ammonia is sprayed toward the ejection flow path of the combustion air that has passed through the heat storage unit, and at least one gaseous fuel selected from coal gas and hydrocarbon-based gas is supplied.

5. A heating furnace comprising a regenerative combustion device with combustion units arranged opposite to each other, wherein the temperature inside the furnace is controlled by alternately performing combustion and suction operations in a pair of the opposite combustion units, wherein: The apparatus comprises an alternating combustion control unit configured to control a pair of the combustion units so as to alternately switch between performing the combustion operation and the suction operation. The combustion section includes: a heat storage section that recovers sensible heat of the suction gas sucked from the furnace of the heating furnace during the suction action; an ejection flow path that heats the combustion air by passing it through the heat storage section during the combustion action and ejects the combustion air toward the furnace of the heating furnace; and a fuel supply nozzle that sprays liquid ammonia toward the ejection flow path during the combustion action.

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