WO2025046980A1 - Method for controlling scale generation amount of metal material in heating furnace, scale generation amount control device, and heating furnace operation method - Google Patents

Abstract

Provided are: a method for controlling a scale generation amount of a metal material to control the scale generation amount to within an appropriate range in a case where a carbon dioxide discharge amount is to be reduced by using hydrogen or ammonia as a fuel gas of a heating furnace for heating the metal material; a scale generation amount control device; and a heating furnace operation method. According to the method for controlling a scale generation amount of a metal material in a heating furnace, the metal material is burner-heated using, as a fuel, a hydrogen-based gas containing in full either one or both of hydrogen and ammonia, the flow rate of the hydrogen-based gas used as the burner heating fuel is set as a heating furnace operating parameter, and the scale generation amount generated on the surface of the metal material is controlled on the basis of the flow rate of the hydrogen-based gas thus set. At least one item selected from a heating time and a heating temperature of the metal material in the heating furnace is also preferably set as a heating furnace operating parameter.

Description

Method for controlling the amount of scale formation on metal materials in a heating furnace, device for controlling the amount of scale formation, and method for operating a heating furnace

The present invention relates to a method for controlling the amount of scale formation on metal materials in a heating furnace, a device for controlling the amount of scale formation, and a method for operating a heating furnace using the method for controlling the amount of scale formation.

In integrated steelworks, blast furnace gas discharged from the top of the blast furnace, which reduces iron ore to produce molten iron, and by-product gases generated in converters and coke ovens have been effectively used as fuel gas. However, in recent years, with the demand for reducing carbon dioxide emissions, combustion technology has been required to reduce the amount of by-product gas used. For example, in the heating furnaces that heat steel materials in the hot rolling lines of integrated steelworks, there is a demand to reduce the amount of by-product gas used and the amount of carbon dioxide emissions. In this case, technology that uses hydrogen and ammonia as fuel gas for heating furnaces is attracting attention. In other words, hydrogen and ammonia, which do not contain carbon elements, mainly produce water and nitrogen when burned, so they are effective in reducing carbon dioxide emissions, and their application to heating furnaces is desirable.

In the heating furnace, scale (also called oxide scale) forms on the surface of the steel material during the process of heating the steel material. The scale formed in the heating furnace is also called primary scale, and is removed by descaling equipment installed in hot rolling lines, etc. Therefore, if the scale formed in the heating furnace becomes too thick, the weight of the steel material to be made into steel plate products decreases, resulting in a problem of lower product yield.

On the other hand, impurities generated during casting and foreign matter caused by mold powder mixed in during casting may be present near the surface of the steel material fed into the heating furnace. If hot rolling is performed with impurities or foreign matter still present on the surface of the steel material extracted from the heating furnace, these will become caught between the steel material and the rolling rolls, causing defects on the surface of the steel plate. For this reason, the scale generated on the steel material in the heating furnace is allowed to grow to a certain thickness, and then the surface impurities and foreign matter are removed together with the scale by a descaling device before hot rolling is performed.

In other words, in steel heating furnaces, it is necessary to control the amount of scale generation to an appropriate level in order to prevent a decrease in product yield by preventing excessive scale generation, and to actively generate a specified amount of scale to prevent the occurrence of surface defects.

In order to solve these problems, techniques for controlling the formation of scale on the steel surface have been proposed.
Patent Document 1 discloses a non-oxidizing heating method for steel as a technology for suppressing excessive scale formation, in which high-temperature non-oxidizing gas that has been preheated to a temperature equal to or higher than the temperature of the steel being heated or approximately equal to the furnace temperature is supplied around the steel in a heating furnace.

Patent Document 2 discloses a steel heating furnace that is equipped with a plurality of regenerative heating devices that supply high-temperature inert gas into the furnace and a plurality of gas burners that supply combustion gas into the furnace, and that is controlled so that the supply of high-temperature inert gas and the supply of combustion gas are carried out independently.
It is said that this makes it possible to heat steel without oxidizing it by alternately supplying high-temperature inert gas from multiple regenerative heating devices.

On the other hand, as a technology for generating a predetermined amount of scale, Patent Document 3 discloses a method for heating steel in which, when steel to be subjected to hot rolling is heated in a heating furnace, moisture is supplied into the heating furnace to adjust the dew point inside the heating furnace. This promotes oxidation of the steel surface, and casting defects concentrated within a position of about 0.5 mm from the surface layer of the steel can be removed together with the scale, which is said to improve the surface quality of steel plate products.

As a technique for controlling the amount of scale generation within an appropriate range, Patent Document 4 discloses a method for heating a slab for hot rolling in which the scale thickness of the slab when removed from the heating furnace is predicted, and the heating temperature and heating time of the slab are set so that the scale thickness becomes a predetermined value.

Japanese Patent Application Publication No. 9-20919 JP 2000-248314 A Japanese Patent Application Publication No. 5-331532 Japanese Patent Application Publication No. 7-54036

However, when applying conventional technology to control the amount of scale formation on steel within an appropriate range in a heating furnace that uses hydrogen or ammonia as fuel gas, the following problems arise:

The technique described in Patent Document 1 supplies a high-temperature non-oxidizing gas into a heating furnace in order to create a localized non-oxidizing atmosphere around steel material charged in the heating furnace.
However, when hydrogen or ammonia is burned as fuel gas in a heating furnace, the hydrogen in the fuel gas combines with the oxygen in the combustion air to generate water vapor, which poses a problem that the generated water vapor promotes the growth of scale on the steel surface even if a non-oxidizing atmosphere is formed in the heating furnace.

The technology described in Patent Document 2 uses a regenerative heating device to recover the sensible heat contained in the exhaust gas produced by burning fuel gas using a heat storage body, and then passes an inert gas through the heat storage body to supply high-temperature inert gas into the heating furnace, thereby attempting to suppress scale growth on steel in the heating furnace.
However, when hydrogen or ammonia is used as the fuel gas, the heat storage body also recovers water vapor in the exhaust gas, so that the inert gas passing through the heat storage body is humidified before being supplied to the heating furnace. Therefore, as in the above, even if high-temperature inert gas is supplied to the heating furnace, there is a problem that the amount of scale generation cannot be controlled within an appropriate range because the water vapor promotes the generation of scale on the steel surface.

Patent Document 3 is expected to have the effect of promoting oxidation of the steel surface by supplying moisture into the heating furnace, thereby improving the surface quality of steel plate products. However, when hydrogen or ammonia is used as the fuel gas, the oxidation of the steel is further promoted, causing excessive scale growth, and the amount of scale generation cannot be controlled within an appropriate range.

Patent Document 4 describes a method for controlling the amount of scale generation by setting the heating temperature and heating time. However, because the internal volume of a steel heating furnace is large, it takes a long time to change the heating temperature. Also, changing the heating time may result in a longer heating time for the steel, and in either case, there is room for improvement in that the production efficiency of the heating furnace decreases.

The present invention has been made to solve the above problems, and its purpose is to provide a method for controlling the amount of scale formation on metal materials, a scale formation control device, and a method for operating a heating furnace, for controlling the amount of scale formation within an appropriate range when attempting to reduce carbon dioxide emissions by using hydrogen or ammonia as fuel gas in a heating furnace that heats metal materials.

The method for controlling the amount of scale generation according to the present invention, which advantageously solves the above problems, is configured as follows.

[1] A method for controlling the amount of scale formation on a metallic material in a heating furnace, comprising the steps of: burning-heating the metallic material using a hydrogen-based gas containing either hydrogen or ammonia or both as fuel; setting a flow rate of the hydrogen-based gas used as fuel for the burner heating as an operational parameter of the heating furnace; and controlling the amount of scale formation on the surface of the metallic material based on the set flow rate of the hydrogen-based gas.
[2] The method for controlling the amount of scale formation on a metallic material according to the above-mentioned [1], further comprising the step of heating the metallic material with a burner using a mixed gas as fuel, the mixed gas being a mixture of the hydrogen-based gas and one or more gases selected from coal gas and a hydrocarbon-based gas.
[3] In the above-mentioned [1] or [2], a method for controlling the amount of scale formation on a metallic material in a heating furnace further comprises setting at least one selected from a heating time and a heating temperature of the metallic material in the heating furnace as an operation parameter of the heating furnace, and controlling the amount of scale formation formed on the surface of the metallic material based on the set operation parameter.
[4] In the above-mentioned [1] or [2], the heating furnace includes a pre-heating zone, a heating zone, and a soaking zone, and a hydrogen-based gas is used as a fuel for burner heating in the soaking zone, and a flow rate of the hydrogen-based gas used as a fuel for burner heating in the soaking zone is set as an operation parameter of the heating furnace, and the amount of scale formation on the surface of the metal material is controlled based on the set flow rate of the hydrogen-based gas.
[5] In the above [1] or [2], a method for controlling the amount of scale formation on a metallic material in a heating furnace, the method controls the amount of scale formation on the metallic material based on the operation parameters of the heating furnace so that the amount of scale formation falls within a preset range.
[6] In the above [3], the method for controlling the amount of scale formation on a metallic material in a heating furnace controls the amount of scale formation on the metallic material based on the operational parameters of the heating furnace so that the amount of scale formation falls within a preset range.
[7] A method for controlling the amount of scale formation on a metallic material in a heating furnace according to the above-mentioned [4], wherein the amount of scale formation on the metallic material is controlled based on the operational parameters of the heating furnace so that the amount of scale formation falls within a preset range.

The scale formation amount control device and the heating furnace operation method according to the present invention, which advantageously solve the above problems, are configured as follows.
[8] A device for controlling the amount of scale formation on a metallic material in a heating furnace, the device comprising a control unit including an acquisition unit that acquires operating parameters of the heating furnace including a flow rate of a hydrogen-based gas, the total amount of which is either hydrogen or ammonia or both, used as fuel for burner heating, a prediction unit that predicts the amount of scale formation on the metallic material using the acquired operating parameters, a determination unit that determines whether the predicted amount of scale formation is within a predetermined range, and a setting unit that sets the operating parameters of the heating furnace if the predicted amount of scale formation is not within the predetermined range.
[9] In the above [8], the device for controlling the amount of scale formation on metal materials in a heating furnace includes an acquisition unit that acquires operation parameters of the heating furnace including a flow rate of a mixed gas obtained by mixing the hydrogen-based gas with one or more gases selected from coal gas and a hydrocarbon-based gas.
[10] A method for operating a heating furnace in which a steel material is heated using the method for controlling the amount of scale formation on a metallic material in a heating furnace according to [5] above.
[11] A method for operating a heating furnace in which a steel material is heated using the method for controlling the amount of scale formation on a metallic material in a heating furnace according to [6] above.
[12] A method for operating a heating furnace in which a steel material is heated using the method for controlling the amount of scale formation on a metallic material in a heating furnace according to [7] above.

According to the present invention, by using hydrogen or ammonia as the fuel gas for the heating furnace, it is possible to reduce carbon dioxide emissions, and by controlling the amount of scale generation within an appropriate range, it is possible to reduce the occurrence of surface defects in metal materials while suppressing deterioration of product yield.

FIG. 1 is a schematic diagram illustrating a heating furnace according to one embodiment. FIG. 2 is a configuration diagram showing the arrangement of burner equipment in a heating furnace. FIG. 1 is a configuration diagram of an example of a burner facility. 1 is a block diagram showing a schematic configuration of a hydrogen-based burner facility for a heating furnace according to one embodiment; FIG. 1 is a configuration diagram of an example of a hydrogen-based burner facility. 1 is a graph showing the relationship between the scale thickness on the surface of the steel material and the heating time when the amount of water vapor in the furnace is changed. FIG. 1 is a configuration diagram of a scale generation amount control device according to an embodiment. 1 is a graph showing the relationship between the scale thickness on the surface of the steel material and the water vapor concentration in the furnace when the surface temperature of the heated material in the furnace is changed.

The following describes the device for controlling the amount of scale formation on metal materials in a heating furnace according to this embodiment.

The scale generation amount control device according to this embodiment includes an acquisition unit that acquires operating parameters of the heating furnace, including the flow rate of hydrogen-based gas, the total amount of which is either hydrogen or ammonia or both, used as fuel for burner heating; a prediction unit that predicts the amount of scale generation of the metal material using the acquired operating parameters; a determination unit that determines whether the predicted amount of scale generation is within a preset range; and a setting unit that sets the operating parameters of the heating furnace if the predicted amount of scale generation is not within the preset range.

First, a heating furnace equipped with a burner system will be described.
<Heating equipment>
FIG. 1 is a schematic cross-sectional view of a heating facility for metal materials according to an embodiment of the present invention. The heating facility is a facility in which a material to be heated is placed inside and heated to a predetermined temperature. The material to be heated is a metal material, but it may be either an iron-based metal or a non-ferrous metal as long as it is a metal material that generates an oxide (hereinafter referred to as scale) on its surface due to oxidation. The heating temperature of the material to be heated is 500 to 1400° C. In the following, a heating facility for heating steel material will be described, taking steel material as the metal material.

1 is installed in a hot rolling line for producing steel plates or steel strips, for example, and heats cast steel material to a predetermined heating temperature (approximately 1100 to 1300° C.). However, the steel material to be heated is not limited to slabs that are used as steel plate materials, but includes billets, blooms, and other steel materials that are used as materials for shaped steel, wire rods, steel pipes, and the like.
The heating equipment 100 includes a heating furnace 1 that heats steel material by burner heating using a fuel gas containing a hydrogen-based gas whose total amount is either hydrogen or ammonia or both. The process of heating the metal material to be heated in the heating furnace 1 is called the heating process.
In addition, in the heating equipment 100, a control computer 101 is preferably installed for performing data analysis of various operational parameters in order to control the operation of the heating process.

<Heating furnace>
The heating furnace 1 includes a charging section 8 for charging (hereinafter also referred to as "carrying in") the steel material S, and an unloading section 9 for unloading (hereinafter also referred to as "extracting") the steel material S. For example, steel material (slabs) 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 8 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 from the upstream side in the conveying direction of the steel material, it is composed of a preheating zone 3 divided into 1 to 3 zones, a heating zone 4 divided into 2 to 8 zones, and a soaking zone 5 divided into 1 to 3 zones. A conveying device 10 is arranged in the heating furnace 1 to convey the steel material S sequentially from a charging section 8 to an unloading section 9.
Each zone of the heating furnace 1 is controlled to a different atmospheric temperature, and the conveying device 10 conveys the steel material S through the preheating zone 3, the heating zone 4, and the soaking zone 5 in that order, so that the average temperature of the steel material S charged into the heating furnace 1 gradually increases and the steel material S is heated to a predetermined heating temperature (target heating temperature) in the heating furnace 1.

The transport device 10 is equipped with a support mechanism for the steel material S called a skid, and includes a fixed skid 10a that supports the steel material S, and a movable skid 10b that lifts and moves the steel material S. The movable skid 10b transports the steel material S toward the discharge section 9 by repeatedly ascending and descending, moving forward, descending, and retreating within the heating furnace 1.

A plurality of burners 6 are provided inside the heating furnace 1 along the transport direction of the steel material S. The burners 6 are arranged to heat the inside of the heating furnace 1 by combustion. When the inside of the heating furnace 1 is heated by the burners 6, the temperature of the steel material S increases due to radiation from the furnace wall of the heating furnace 1.
Also, a flow of atmospheric gas may occur inside the heating furnace 1, and the temperature of the steel material S may be increased by convection. Furthermore, the temperature of the steel material S may be increased by the direct contact of the flame of the burner 6 with the steel material S. In any case, the burner 6 heats the steel material S inside the heating furnace 1 by increasing the temperature inside the heating furnace 1.

The burners 6 are arranged in each of several zones inside the heating furnace 1. However, the number of zones does not necessarily have to match the number of burners. In the heating furnace 1 shown in FIG. 1, upper burners 6a are arranged on the upper surface side of the steel material S from the loading section 8 toward the discharge section 9, and lower burners 6b are arranged on the lower surface side of the steel material S. Also, in the heating furnace 1 shown in FIG. 1, side burners that spray flames from one side wall surface in the conveying direction of the steel material S toward the opposing side wall surface are shown as a schematic, but axial burners that spray flames in the same direction as the conveying direction of the steel material S or roof burners that spray flames from the ceiling of the heating furnace into the interior may also be used.

FIG. 2 shows the piping system of the burner 6 arranged in the heating furnace 1, taking as an example some of the zones that make up the heating furnace 6. The burners 6 (upper burner 6a, lower burner 6b) arranged in the heating furnace 1 are connected to a fuel gas supply system 31 that supplies fuel gas G and a combustion air supply system 32 that supplies combustion air A. The fuel gas supply system 31 and the combustion air supply system 32 are connected to a blower (not shown) and the like, and supply the fuel gas G and the combustion air A to the burner 6. As a result, the fuel gas G and the combustion air A are sprayed from the burner 6, and the fuel gas G is burned by diffusing, and a flame is blown into the inside of the heating furnace. The combustion air A may be air collected from the atmosphere. However, air that has been reformed by removing nitrogen from the air or adding pure oxygen may be used as the combustion air. By increasing the oxygen content of the combustion air, the oxidation reaction of the fuel gas G can be promoted, and the flow rate of the combustion air supplied from the combustion air supply system 32 can be reduced, thereby reducing the power consumption of pumps and the like. In addition, a mixed gas of oxygen and combustion exhaust gas may be used as the combustion air A. By reducing the oxygen content of the combustion air, the atmosphere inside the heating furnace can be made reducing, which promotes the reduction of nitrogen oxides generated by the combustion of ammonia, etc.

Figure 3 shows a schematic diagram of burner equipment 60 that performs burner heating. Note that burner refers to equipment that injects a flame into the furnace, and specifically refers to the part that injects the flame into the furnace. Also, burner equipment refers to the entire device, including the ancillary equipment for injecting the flame.

The burner equipment 60 includes a burner nozzle 7 that forms a flow path for fuel gas G and combustion air A for spraying a flame by the burner 6, a fuel gas supply system 31 that supplies fuel gas G to the burner nozzle 7, and a combustion air supply system 32 that supplies combustion air A to the burner nozzle 7.
The burner nozzle 7 is, for example, a double-pipe nozzle, and fuel gas G is injected into the furnace from the inside, and combustion air A is supplied to the outside. As a result, a combustible mixture is formed by mixing the fuel gas G and the combustion air A, and a flame is injected from the burner 6 into the heating furnace 1.

The burner equipment 60 may include a fuel gas flow rate control valve 33 for adjusting the flow rate of the fuel gas G supplied from the fuel gas supply system 31 to the burner nozzle 7, and a fuel gas flow meter 34 for measuring the flow rate of the fuel gas G. This makes it possible to adjust the combustion energy supplied into the heating furnace 1.
The burner equipment 60 may further include a combustion air flow rate control valve 35 for adjusting the flow rate of the combustion air A supplied from the combustion air supply system 32 to the burner nozzle 7, and a combustion air flow meter 36 for measuring the flow rate of the combustion air A. This makes it possible to adjust the air ratio of the fuel gas to the theoretical air amount in the burner 6.

In addition to the nozzle using the double-tube nozzle described above, the burner equipment 60 may also use a nozzle mix type burner that mixes the fuel gas and the combustion air midway through the burner nozzle. In this case, the combustion air may be preheated using exhaust gas or the like before it is mixed with the fuel gas.

The burner equipment shown in FIG. 2 is provided with a combustion air supply system 32 that supplies combustion air to the burners 6, and includes a combustion air flow control valve 35 that adjusts the flow rate of the combustion air supplied to each burner 6, and a combustion air flow meter 36 that measures the flow rate of the combustion air. However, the combustion air flow control valve 35 and the combustion air flow meter 36 do not need to be provided for each burner 6, and multiple burners may be treated as one group, and the flow rate of the combustion air may be adjusted for each group.

<Burner heating using coal gas>
Conventional steel heating furnaces have used by-product gases generated in steelworks and other facilities as fuel gases to be supplied to the burner equipment. By-product gases are mainly derived from coal, and are also called coal gases because they are generated due to incomplete combustion of coal. Coal gases include coke oven gas, blast furnace gas, converter gas, and electric furnace gas. Blast furnace gas is a by-product gas generated when reducing iron ore in a blast furnace to produce pig iron. Coke oven gas is a by-product gas generated by high-temperature carbonization of coal to produce coke. Converter gas is a by-product gas generated during the steelmaking process in a converter. Electric furnace gas is a by-product gas generated by incomplete combustion of auxiliary fuel (recarburizer) used in an electric furnace. By-product gases have various component compositions depending on the process in which they are generated.

For example, the typical composition of blast furnace gas is 21-30 vol% of combustible carbon monoxide, 50-60 vol% of non-combustible nitrogen, and 10-22 vol% of carbon dioxide. The lower heating value of blast furnace gas is about 3.45 MJ/ ^Nm3 . The typical composition of coke oven gas is 46-60 vol% of hydrogen, 20-35 vol% of methane, 5-10 vol% of carbon monoxide, and 2-4 vol% of hydrocarbons such as ethylene. The lower heating value of coke oven gas is about 18.0 MJ/ ^Nm3 . The typical composition of converter gas is about 75 vol% of carbon monoxide, about 13 vol% of carbon dioxide, and also contains small amounts of oxygen, nitrogen, and hydrogen. The lower heating value of converter gas is about 8.2 MJ/ ^Nm3 . The typical composition of electric furnace gas is about 10 vol% of carbon monoxide, about 22 vol% of carbon dioxide, about 5 vol% of oxygen, and about 56 vol% of nitrogen. The lower heating value of electric furnace gas is about 2.8 MJ/ ^Nm3 . Coal gas also includes a suitable mixture of blast furnace gas, coke oven gas, and converter gas (sometimes called M gas). By mixing coal gases with different heating values, the amount of heat required to heat the material to be heated can be supplied, ensuring stable operation of the heating furnace.

<Hydrogen burner equipment>
In the heating equipment 100 of this embodiment, at least one of the burner equipments arranged in the heating furnace uses a hydrogen-based gas containing either or both of hydrogen and ammonia as a fuel gas. Hereinafter, among the burner equipments arranged in the heating furnace, the burner equipment using a fuel gas containing either or both of hydrogen and ammonia as a fuel gas is referred to as a hydrogen-based burner equipment.
Moreover, hydrogen and ammonia used as fuel gas are called hydrogen-based gases.

First, an embodiment will be described in which a hydrogen-based gas containing either hydrogen or ammonia or both in total is used as fuel.

Hydrogen is a colorless gas at room temperature, with an ignition point of 560°C and a lower heating value of about 10.5 MJ/ ^Nm3 . When hydrogen is burned, the flame temperature is high and the combustion speed is fast, so the tip of the burner nozzle is likely to become hot. For this reason, it is advisable to use a burner nozzle in which hydrogen is mixed with combustion air after being ejected. This allows for slow combustion and reduces the thermal load on the burner nozzle. In a hydrogen-based burner facility that uses hydrogen as fuel gas G, combustion is performed under operating conditions of, for example, a flow rate of hydrogen ejected from the burner of 185 ^Nm3 /hr and a flow rate of combustion air of 370 to 601 ^Nm3 /hr.

Ammonia is a colorless gas at room temperature with an ignition point of 651°C and a lower heating value of approximately 14.1 MJ/ ^Nm3 . When ammonia is burned, the flame temperature is relatively low and the combustion speed is slow, so the ammonia combustion reaction can be stabilized by using a burner nozzle that actively mixes ammonia with combustion air. In a hydrogen-based burner facility that uses ammonia as fuel gas G, combustion is performed under operating conditions of, for example, ammonia injected from the burner at a flow rate of 185 ^Nm3 /hr and combustion air at a flow rate of 370 to 601 ^Nm3 /hr.

The hydrogen-based burner equipment 70 applied to this embodiment can be the same as the burner equipment 60 shown in FIG. 3. In other words, the hydrogen-based burner equipment 70 is the same burner equipment as the burner equipment that uses coal gas as the fuel gas, and is a burner equipment that uses hydrogen-based gas HG as the fuel gas G. By using hydrogen-based gas as the fuel gas, the hydrogen-based burner equipment suppresses the generation of carbon dioxide, and therefore the amount of carbon dioxide emitted from the heating furnace can be reduced.

The configuration of the hydrogen-based burner equipment 70 applied to this embodiment will be described with reference to FIG. 3. The hydrogen-based burner equipment 70 performs burner heating by injecting a flame into the furnace using hydrogen-based gas HG as fuel gas G and combustion air A. The hydrogen-based burner equipment 70 includes a burner nozzle 7 for injecting a flame into the furnace, a fuel gas supply system 31 that supplies fuel gas G to the burner nozzle 7, and a combustion air supply system 32 that supplies combustion air A to the burner nozzle 7. The burner nozzle 7 is, for example, a double-tube nozzle, and fuel gas G is injected into the furnace from the inside, and combustion air A is supplied to the outside. As a result, a combustible mixture is formed in which hydrogen-based gas HG is used as fuel gas G and combustion air A is mixed, and a flame is injected from the burner 6 toward the inside of the heating furnace 1.

The hydrogen-based burner equipment 70 preferably includes a fuel gas flow rate adjustment valve 33 for adjusting the flow rate of fuel gas G supplied from the fuel gas supply system 31 to the burner nozzle 7, and a fuel gas flow meter 34 for measuring the flow rate of fuel gas G. The hydrogen-based burner equipment 70 also preferably includes a flow rate setting unit 47 for setting the flow rate of the hydrogen-based gas. The flow rate setting unit 47 is, for example, a control controller, and issues a control command to adjust the valve opening of the fuel gas flow rate adjustment valve 33 so that the actual flow rate measured by the fuel gas flow meter 34 matches the flow rate set value of the hydrogen-based gas HG that is set in advance. This makes it possible to control the combustion energy of the flame injected from the hydrogen-based burner equipment 70 into the heating furnace 1 and the amount of carbon dioxide exhausted from the heating furnace 1.

The hydrogen-based burner equipment 70 is preferably provided with a steam amount control unit 48 that controls the amount of steam in the heating furnace 1 within a preset range, in addition to the flow rate setting unit 47. The steam amount control unit 48 is configured by, for example, a computer.
The water vapor amount control unit 48 calculates the amount of water vapor in the heating furnace 1, and sends a command to the flow rate setting unit 47 for the flow rate setting value of the hydrogen-based gas HG to be supplied to the hydrogen-based burner equipment 70 so that the calculated amount of water vapor in the furnace falls within a predetermined target range for the water vapor amount (target water vapor range).
Since the amount of water vapor in the heating furnace 1 affects the scale formation behavior on the surface of the steel material S, the water vapor amount control unit 48 can control the scale formation behavior on the surface of the steel material S by sending a command for the flow rate setting value of the hydrogen-based gas HG to the flow rate setting unit 47.
In this case, it is preferable to install a dew point meter 49 in the heating furnace 1 and estimate the amount of water vapor in the heating furnace 1 based on dew point information acquired by the dew point meter 49. The method of estimating the amount of water vapor in the heating furnace 1 will be described later.

4 shows an example in which a burner equipment 60 using coal gas CG as fuel gas G and a hydrogen-based burner equipment 70 using hydrogen-based gas HG as fuel gas G are arranged in the furnace as the burners 6 of the heating furnace 1. In this case, a fuel gas supply system that supplies fuel gas G to the burner nozzle 7 of the burner equipment 60 is connected to a supply source of coal gas CG, and the burner equipment 60 injects a flame generated by combustion of coal gas into the inside of the heating furnace 1.
On the other hand, a fuel gas supply system that supplies fuel gas G to the burner nozzle 7 of the hydrogen-based burner equipment 70 is connected to a supply source of hydrogen-based gas HG, and the hydrogen-based burner equipment 70 injects a flame produced by combustion of the hydrogen-based gas into the heating furnace 1. In this case, the combustion air supply system that supplies combustion air A to the burner equipment 60 and the hydrogen-based burner equipment 70 may be shared by the burner equipment 60 and the hydrogen-based burner equipment 70.

The heating furnace shown in Figure 4 includes hydrogen-based burner equipment that uses hydrogen-based gas HG as fuel gas G, compared to conventional heating furnaces that use coal gas CG as fuel gas G, and therefore reduces the amount of carbon dioxide emissions emitted from the heating furnace.

<Another embodiment of the hydrogen burner equipment>
Another embodiment of the hydrogen-based burner equipment will be described, in which a mixed gas obtained by mixing hydrogen-based gas with one or more gases selected from coal gas and hydrocarbon-based gas is used as the fuel gas.
Here, the mixed gas refers to a case where a hydrogen-based gas containing either or both of hydrogen and ammonia is mixed with coal gas (containing hydrogen) or a hydrocarbon-based gas (methane, ethane, propane, etc.).

The hydrogen-based burner equipment may use a mixed gas containing hydrogen-based gas HG and other fuels as the fuel gas G. For example, a mixed gas of hydrogen-based gas and coal gas may be used as the fuel gas G.

FIG. 5 shows another example of a hydrogen-based burner equipment, a hydrogen-based burner equipment 71, which uses a mixed gas of hydrogen-based gas HG and coal gas CG as fuel gas G. The hydrogen-based burner equipment 71 shown in FIG. 5 is similar to the hydrogen-based burner equipment 70 shown in FIG. 3 in that it includes a burner nozzle 7 that emits a flame into the heating furnace, a fuel gas supply system 31 that supplies fuel gas G to the burner nozzle 7, and a combustion air supply system 32 that supplies combustion air A to the burner nozzle 7. It is also similar in that combustion air A is supplied from the combustion air supply system 32 to the burner nozzle 7, a combustible mixture is formed by mixing the fuel gas G and the combustion air A, and a flame is emitted from the burner 6 toward the inside of the heating furnace.

On the other hand, the fuel gas supply system 31 of the hydrogen-based burner equipment 71 shown in FIG. 5 is equipped with a mixing section 40 that mixes hydrogen-based gas HG supplied through a hydrogen-based gas supply system 45 and coal gas CG supplied through a coal gas supply system 46. The mixing section 40 generates fuel gas G by mixing the hydrogen-based gas HG and the coal gas CG. The fuel gas G generated in the mixing section 40 is further mixed with combustion air A to form a combustible mixture, which is sprayed as a flame from the burner 6 toward the inside of the heating furnace 1.

The mixing section 40 refers to the area where the hydrogen-based gas supply system 45, which supplies the hydrogen-based gas HG, and the coal gas supply system 46, which supplies the coal gas CG, join together. The hydrogen-based gas HG and the coal gas CG are supplied from their respective supply pipes, and by joining together, mixing is achieved without the need for a special stirring mechanism. Therefore, the mixing section 40 may be configured as a fixed space at the area where these supply pipes intersect.

However, the mixing section 40 may be equipped with a static mixing device such as a static mixer, or a dynamic mixer with a stirring function. This is preferable because it results in a more uniform mixed gas of the hydrogen-based gas HG and the coal gas CG.

The hydrogen-based burner equipment 71 may be provided with a hydrogen-based gas flow rate control valve 41 for adjusting the flow rate of the hydrogen-based gas HG supplied to the mixing section 40 through the hydrogen-based gas supply system 45, and a hydrogen-based gas flow meter 42 for measuring the flow rate of the hydrogen-based gas HG. The hydrogen-based burner equipment 71 may also be provided with a coal gas flow rate control valve 43 for adjusting the flow rate of the coal gas CG supplied from the coal gas supply system 46 to the mixing section 40, and a coal gas flow meter 44 for measuring the flow rate of the coal gas CG.

This allows the mixing ratio of hydrogen-based gas HG and coal gas CG contained in the fuel gas G to be adjusted. When the mixing ratio of hydrogen-based gas HG contained in the fuel gas G is increased, the effect of reducing carbon dioxide emissions from the heating furnace 1 becomes greater compared to conventional burner heating that uses only coal gas CG as fuel gas.

On the other hand, when ammonia is used as the hydrogen-based gas, ammonia is a flame-retardant fuel that is more difficult to ignite and burns slower than general fuel gases, so if the mixture ratio of ammonia contained in the fuel gas G becomes large, combustion in the burner 6 may become unstable. By adjusting the mixture ratio of ammonia and coal gas contained in the fuel gas G, it is possible to ensure the stability of burner heating while reducing carbon dioxide emissions.

The hydrogen-based burner equipment 71 preferably further includes a flow rate setting unit 47 that sets the flow rate of the hydrogen-based gas HG supplied to the mixing unit 40. The flow rate setting unit 47 is, for example, a control controller, and issues a control command to adjust the valve opening of the hydrogen-based gas flow rate adjustment valve 41 so that the actual flow rate measured by the hydrogen-based gas flowmeter 42 matches the flow rate set value for the hydrogen-based gas HG that is set in advance. This makes it possible to control the combustion energy of the flame sprayed from the hydrogen-based burner equipment 71 into the heating furnace 1 and the amount of carbon dioxide exhausted from the heating furnace 1.

Furthermore, the flow rate setting unit 47, in addition to the function of setting the flow rate of the hydrogen-based gas HG supplied to the mixing unit 40, may be configured to give a control command to adjust the valve opening of the coal gas flow rate adjustment valve 43 so that the actual flow rate measured by the coal gas flowmeter 44 matches the flow rate setting value of the coal gas CG, which is set in advance. This makes it possible to set the flow rates of the hydrogen-based gas HG and the coal gas CG supplied to the mixing unit 40 separately, and to adjust the amount of combustion energy supplied into the heating furnace 1 and the amount of carbon dioxide exhausted from the heating furnace 1.

The hydrogen-based burner equipment 71 may be provided with a steam amount control unit 48 that controls the amount of steam in the heating furnace 1 within a preset range, in addition to the flow rate setting unit 47. The function of the steam amount control unit 48 is the same as that of the steam amount control unit 48 described above in FIG. 3.

When M gas, which is coal gas, and hydrogen, which is a hydrogen-based gas, are mixed and burned, the hydrogen mixing ratio (the ratio of the hydrogen flow rate supplied through the hydrogen-based gas supply system 45 to the flow rate of hydrogen supplied through the M gas and hydrogen-based gas supply system 45) can be selected arbitrarily. As an example, when the hydrogen mixing ratio is 60%, combustion is performed under the operating conditions of the hydrogen flow rate injected from the burner of 111 Nm ³ /hr, the M gas flow rate of 74 Nm ³ /hr, and the combustion air flow rate of 370 to 601 Nm ³ /hr. The M gas composition is 20 vol% carbon monoxide, 13 vol% carbon dioxide, 24 vol% hydrogen, 13 vol% methane, 1.2 vol% hydrocarbons such as ethylene, and 28.8 vol% nitrogen.
When M gas and ammonia are mixed and burned, the combustion becomes unstable when the ammonia mixing ratio (the ratio of the ammonia flow rate supplied through the hydrogen-based gas supply system 45 to the flow rate of the M gas and ammonia supplied through the hydrogen-based gas supply system 45) becomes high, so the ammonia mixing ratio is about 50%.
As an example, when the mixture ratio of ammonia is 30%, combustion is performed under the operating conditions of an ammonia flow rate injected from the burner of 50 Nm ³ /hr, an M gas flow rate of 117 Nm ³ /hr, and a combustion air flow rate of 480 to 624 Nm ³ /hr.

Next, the scale formation amount control device according to this embodiment will be described.
<Scale generation amount control device>
The scale formation amount control device of this embodiment comprises a control unit including an acquisition unit that acquires operating parameters of the heating furnace including the flow rate of hydrogen-based gas, the total amount of which is either hydrogen or ammonia or both, used as fuel for burner heating, a prediction unit that predicts the scale formation amount of the metal material using the acquired operating parameters, a determination unit that determines whether the predicted scale formation amount is within a preset range, and a setting unit that sets the operating parameters of the heating furnace if the predicted scale formation amount is not within the preset range.
The acquisition unit can also acquire operation parameters of the heating furnace including a flow rate of a mixed gas obtained by mixing the hydrogen-based gas with one or more gases selected from coal gas and a hydrocarbon-based gas.

FIG. 7 shows the configuration of the scale generation amount control device according to this embodiment. The scale generation amount control device 51 shown in FIG. 7 is, for example, a general-purpose computer such as a workstation or a personal computer. The scale generation amount control device 51 has a control unit 52, an input unit 53, an output unit 54, and a memory unit 55. The control unit 52 is, for example, a CPU, and executes various programs stored in the memory unit 55, causing the control unit 52 to function as an acquisition unit 56, a prediction unit 57, a determination unit 58, and a setting unit 59.

The input unit 53 is, for example, a keyboard, a touch panel that is provided integrally with a display, or the like.
The output unit 54 is, for example, an LCD or CRT display, etc. The storage unit 55 is, for example, an information recording medium such as an updatable flash memory, a built-in hard disk or a memory card connected via a data communication terminal, and a read/write device for the same.
The storage unit 55 stores programs and data for implementing control of the amount of scale generation by the scale generation amount control device 51. The storage unit 55 also stores a scale thickness prediction model that has been generated in advance.

Next, a method for controlling the amount of scale generation on a metallic material in a heating furnace according to this embodiment will be described.
<Method for controlling the amount of scale generation>
In the method for controlling the amount of scale formation according to this embodiment, a hydrogen-based gas containing either or both of hydrogen and ammonia as a fuel is used to burner-heat a metal material, the flow rate of the hydrogen-based gas used as the fuel for burner heating is set as an operational parameter of the heating furnace, and the amount of scale formation formed on the surface of the metal material is controlled based on the set flow rate of the hydrogen-based gas.
It is also possible to heat metal materials with a burner by using as fuel a mixed gas obtained by mixing one or more gases selected from coal gas and hydrocarbon gas with a hydrogen-based gas.

Here, the amount of scale formed refers to the thickness or amount of scale formed on the surface of the metal material being heated. The operating parameters of the heating furnace refer to the operating conditions of the heating furnace that affect the heating state of the material being heated in the heating furnace.

In the heating furnace 1, burner heating using hydrogen-based gas HG is performed, and water vapor is generated by the combustion of hydrogen and ammonia contained in the fuel gas G. In this situation, water penetrates from the surface of the metal material in the heating furnace 1, and the oxygen constituting the water molecules oxidizes the metal material in the heating furnace 1 and releases hydrogen. The hydrogen diffuses inside the oxide layer formed on the surface of the metal material and combines with the oxygen in the oxide layer at the interface between the oxide layer and the base material to generate water vapor.
The generated water vapor further oxidizes the metal material, promoting the generation of an oxide layer.
Therefore, in heating furnaces that use hydrogen or ammonia as fuel gas, water vapor contained in the combustion gas penetrates the interface with the oxide layer of the metal material and promotes the oxidation of the metal material, making it difficult to suppress scale formation on the metal material even when the inside of the heating furnace is controlled to a non-oxidizing atmosphere.

On the other hand, if there are foreign matters on the surface of the metal material before it is loaded into the heating equipment 100, such as impurities generated during casting or mold powder mixed in during casting, the combustion of hydrogen-based gas can promote the formation of scale on the metal material. Therefore, after the metal material is removed from the heating equipment 100, the oxide layer can be removed using a descaling device or the like, thereby suppressing the occurrence of surface defects in the metal material.

In this embodiment, it is preferable to provide a flow rate setting unit 47 in the hydrogen-based burner equipment to control the flow rate of the hydrogen-based gas HG. By changing the flow rate of the hydrogen-based gas HG, the amount of water vapor generated in the heating furnace 1 changes, and this makes it possible to control the thickness of the oxide layer that forms on the surface of the metal material.

Furthermore, it is preferable to provide a water vapor amount control unit 48 that controls the amount of water vapor in the heating furnace 1 to a preset range, and to set the flow rate setting unit 47 to a flow rate setting value of the hydrogen-based gas HG to be supplied to the hydrogen-based burner equipment 70, 71 based on the amount of water vapor in the heating furnace 1 calculated by the water vapor amount control unit 48. In this case, it is preferable that the water vapor amount control unit 48 estimates the amount of water vapor in the heating furnace 1 based on dew point information acquired by a dew point meter 49 installed in the heating furnace 1, and sends a command to the flow rate setting unit 47 for the flow rate setting value of the hydrogen-based gas HG to be supplied to the hydrogen-based burner equipment 70, 71 so that the estimated amount of water vapor falls within a preset target range of water vapor amount (target water vapor range). This makes it possible to control the amount of scale generation on the surface of the metal material in the heating process.

A method for estimating the amount of water vapor in the heating furnace 1 performed by the water vapor amount control unit 48 will be described. First, the water vapor amount control unit 48 acquires a measured value of the dew point of the atmospheric gas acquired by the dew point meter 49. From the acquired measured value of the dew point, the water vapor pressure of the atmospheric gas is calculated using a known relationship between the amount of saturated water vapor and temperature. Then, the volume fraction of water vapor contained in the atmospheric gas is calculated from the calculated water vapor pressure and the pressure (total pressure) of the atmospheric gas, and the amount of water vapor in the heating furnace 1 can be calculated using the inner volume of the heating furnace 1. As the known relationship between the amount of saturated water vapor and temperature, for example, the Tenens equation or the Murray equation may be applied.
In this manner, the steam amount control unit 48 can estimate the amount of steam in the heating furnace 1 .

As an example of a method for controlling the amount of scale formation on a metallic material, an example in which a steel material is heated will be described.
In the method for controlling the amount of scale formation on a metallic material according to this embodiment, the steel material S is preferably heated in the heating step so that the surface temperature of the steel material S reaches 1000 to 1250° C. In the heating step, burner heating using hydrogen-based gas HG is performed in a furnace, and the oxidation of the steel material S is promoted by the water vapor contained in the combustion gas of the hydrogen-based gas HG, so that a predetermined scale thickness can be formed by the time the heating step is completed. As a result, even if the steel material before the heating step contains impurities generated during casting or foreign matter due to mold powder mixed in during casting, the occurrence of surface defects can be suppressed by removing the scale using a descaling device or the like after the heating step is completed.

However, if the heating temperature is less than 1000°C, scale of the appropriate thickness may not be generated, so the heating temperature must be 1000°C or higher. The heating temperature is more preferably 1050°C or higher. On the other hand, if the heating temperature exceeds 1250°C, the thickness of the scale generated in the heating process becomes too thick, resulting in a decrease in product yield, so the heating temperature must be 1250°C or lower. The heating temperature is more preferably 1200°C or lower.

　ここで、ξはスケール厚み（μｍ）、Ａは頻度因子（１／ｓ）、Ｑは活性化エネルギー（Ｊ／ｍｏｌ）、Ｔは鋼材の表面温度（Ｋ）、Ｒは気体定数（Ｊ／ｍｏｌＫ）、ｔは経過時間（ｓ）である。頻度因子とは、単位時間当りに反応分子同士が衝突する回数を表す数値である。
　頻度因子Ａおよび活性化エネルギーＱは、鋼材の成分組成によって変化するため、加熱工程を実行する鋼材の鋼種ごとに予め実験により決定しておく。 Here, it is known that the growth of scale on the steel material in the heating furnace 1 is diffusion-limited and increases exponentially with respect to the surface temperature, as shown in formula (1).

Here, ξ is the scale thickness (μm), A is the frequency factor (1/s), Q is the activation energy (J/mol), T is the surface temperature of the steel (K), R is the gas constant (J/molK), and t is the elapsed time (s). The frequency factor is a value that indicates the number of collisions between reactive molecules per unit time.
The frequency factor A and the activation energy Q vary depending on the component composition of the steel material, and are therefore determined in advance by experiment for each type of steel material to be subjected to the heating process.

It may be difficult to directly measure the temperature of the steel material S being transported inside the heating furnace 1, and it is preferable to estimate the surface temperature of the steel material S inside the heating furnace 1 using a temperature model that calculates the temperature of the steel material S, and to control the operating conditions of the heating process so that the estimated temperature becomes the target heating temperature.
In this case, a temperature model of the steel material in the heating furnace is used that takes into consideration the effect of radiant heat from the furnace wall to the steel material, and the surface temperature of the steel material is calculated based on the actual measured atmospheric temperature in the heating furnace, position information (tracking information) of the steel material in the heating furnace, etc. The temperature model of the steel material may be loaded into a control computer (process computer) 101 to execute temperature calculations.
The temperature calculation method is to replace the steel material with a mesh divided into finite parts in the thickness and width directions, and solve the heat conduction equation using the finite difference method or finite element method to calculate the temperature at the thickness and width directions. In this case, the surface temperature of the steel material is the temperature calculated for the mesh located at the outermost layer in the thickness direction.

In the heating process, it is preferable to further control the amount of water vapor in the heating furnace 1 to 10-30% by volume by setting the flow rate of the hydrogen-based gas HG used for burner heating. If the amount of water vapor in the heating furnace 1 where the heating process is carried out is less than 10% by volume, the thickness of the scale formed on the surface of the steel material may be insufficient. On the other hand, if the amount of water vapor in the heating furnace 1 exceeds 30% by volume, scale on the surface of the steel material is likely to grow, and excessive scale may be formed.

FIG. 6 shows an example in which the thickness of scale formed on the surface of the steel material S was investigated after the steel material S was heated for a specified time while the heating temperature was set to 1050° C. in the heating process and the water vapor in the furnace was controlled to 5 volume %, 15 volume %, and 25 volume %.
Here, if the target thickness of the scale formed on the surface of the steel material is set to 350 μm or more and the reference value of the heating time in the heating process is set to 60 minutes (3,600 seconds), it can be seen from Figure 6 that when the water vapor in the heating furnace is as low as 5 volume %, the thickness of the scale formed on the surface of the steel material does not reach the target thickness.
In this case, the operating conditions of the heating furnace require the heating time to be extended beyond the standard value, which causes a problem of reduced production efficiency of the heating equipment 100.
On the other hand, when the steam in the heating furnace is 15 or 25 volume %, the thickness of the scale formed on the surface of the steel material is equal to or greater than the target thickness, and it is considered that sufficient scale can be formed to remove casting defects, etc. present on the surface of the steel material.

In the burner heating of the above embodiment, in addition to setting the flow rate of the hydrogen-based gas used as the fuel for the burner heating, it is preferable to set at least one selected from the heating time and heating temperature of the metal material in the heating furnace as an operation parameter of the heating furnace, because, as shown in the above formula (1), the scale growth of the steel material in the heating furnace 1 is diffusion-limited and is affected by the heating time and heating temperature.
For example, by setting the flow rate of the hydrogen-based gas used as fuel for burner heating to a high value to promote scale formation in the heating furnace, while shortening the heating time of the metal material in the heating furnace to a time shorter than a preset time, it is possible to improve the production efficiency of the heating equipment while ensuring an appropriate amount of scale formation.
In addition, by setting the flow rate of the hydrogen-based gas used as fuel for burner heating to a large value to promote scale formation in the heating furnace, while setting the heating temperature of the metal material in the heating furnace lower than a preset temperature, it is possible to improve the fuel consumption rate of the heating equipment while ensuring an appropriate amount of scale formation.

Furthermore, when the heating furnace includes a preheating zone, a heating zone, and a soaking zone, it is preferable to control the amount of scale formation on the metal material by setting the flow rate of hydrogen-based gas used as fuel for burner heating in the soaking zone as an operation parameter of the heating furnace. The preheating zone 3, heating zone 4, and soaking zone 5 of the heating furnace 1 are often controlled to different atmospheric temperatures, with the soaking zone 5 having the highest atmospheric temperature.
Since the formation of scale on metallic materials is promoted under conditions of high atmospheric temperature, the amount of scale formed on metallic materials can be significantly changed by changing the flow rate of the hydrogen-based gas.

Another embodiment of the method for controlling the amount of scale formation sets the operating parameters of the heating furnace so that the amount of scale formation on the surface of the heated material is within a preset range. This makes it possible to prevent the occurrence of surface defects in the metal material and further suppress a decrease in product yield. Here, the amount of scale formation will be explained using the thickness of scale formed on the surface of the heated material as an example.

In another embodiment, a target thickness (hereinafter referred to as the target scale thickness) of the scale (oxide layer) formed on the surface of the metal material in the heating process is set in advance. The target scale thickness is preferably set to a thickness equivalent to the thickness from the surface where impurities generated during casting and foreign matter caused by mold powder mixed in during casting that are distributed near the surface of the metal material before the heating process is performed are distributed, which is specified in advance. For example, the target scale thickness of the metal material to be heated may be set to about 50 to 1000 μm. When the metal material is a steel material, the target scale thickness may be set to 300 to 600 μm. This is because impurities generated during casting and foreign matter caused by mold powder mixed in during casting are often present in the range of approximately 300 to 600 μm from the surface of the steel material.

　ただし、ｆは加熱炉内の酸素分圧ＰＯ_２および水蒸気分圧ＰＨ_２Ｏの関数として、予めオフラインの加熱実験により決定しておく。スケールの成長挙動に対して酸素分圧や水蒸気分圧が影響を与えることは知られているが、理論的に定式化することは難しい。そのため、酸素分圧と水蒸気分圧を変化させて金属材料を加熱する実験を予め行っておき、金属材料の表面に生成するスケール厚みが、上記式（２）を満足するように関数ｆを回帰分析により決定しておくとよい。 The thickness of the scale formed on the surface of the metal material in the heating process may be estimated using a mathematical model that models the growth behavior of oxides (hereinafter referred to as a scale thickness prediction model).
For example, the scale growth of a steel material can be estimated using the following equation (2).

where f is a function of the oxygen partial pressure _PO2 and the water vapor partial pressure _PH2O in the heating furnace, and is determined in advance by an offline heating experiment. It is known that the oxygen partial pressure and the water vapor partial pressure affect the growth behavior of scale, but it is difficult to formulate this theoretically. Therefore, it is advisable to carry out an experiment in advance in which the metal material is heated while changing the oxygen partial pressure and the water vapor partial pressure, and to determine the function f by regression analysis so that the thickness of the scale formed on the surface of the metal material satisfies the above formula (2).

The scale thickness prediction model determined in advance as described above is loaded into the control computer 101 that sets the operating conditions of the heating equipment 100, and the predicted value of the scale thickness that will form on the surface of the metal material is calculated based on the information that the control computer 101 acquires from the heating furnace 1.

Specifically, the operating parameters of the heating furnace 1 are acquired from the control computer 101 (acquisition step). Next, based on the acquired operating parameters of the heating furnace 1, the scale thickness at the stage when the heating process is completed is predicted (prediction step). Then, it is determined whether the predicted scale thickness (predicted scale thickness) is within a preset range of the target scale thickness (determination step). In the determination step, if the predicted scale thickness is within the range of the target scale thickness, a command is issued to the control computer 101 to maintain the current operating conditions of the heating furnace 1. On the other hand, in the determination step, if the predicted scale thickness is not within the range of the target scale thickness, a setting command is issued to the control computer 101 to change the operating parameters of the heating furnace 1 (setting step).

The operating parameters of the heating furnace 1, which send a setting command to the control computer 101 in the setting step, use the flow rate of the hydrogen-based gas used as fuel for burner heating. In addition to the flow rate of the hydrogen-based gas, the heating time and heating temperature of the heating process may be used. Changing the flow rate of the hydrogen-based gas HG used in the heating process changes the water vapor generated by the burner heating, which allows the amount of scale generated on the metal material to be controlled. Furthermore, changing the heating time of the heating process changes the thickness of the oxide layer of the metal material generated in the heating process. Also, changing the heating temperature of the heating process (ambient temperature in each zone inside the heating furnace) changes the thickness of the oxide layer of the metal material generated in the heating process. In this case, the heating temperature of the heating process may be changed by changing the ambient temperature of the soaking zone.

Next, the process of scale generation amount control by the scale generation amount control device 51 will be described. The acquisition unit 56 acquires the operation parameters of the heating furnace 1 from the control computer 101. The acquisition unit 56 acquires the flow rate of the hydrogen-based gas HG used as fuel for the hydrogen-based burner equipment 70, 71 of the heating furnace 1 as the operation parameters of the heating furnace 1. The acquisition unit 56 acquires the set values of the heating time and heating temperature of the metal material in the heating furnace 1 as the operation parameters of the heating furnace 1. The acquisition unit 56 may also acquire measured values of the temperature and dew point of the atmospheric gas in the heating furnace 1.

When the prediction unit 57 acquires the operating parameters of the heating furnace 1 from the acquisition unit 56, it reads out the scale thickness prediction model stored in the memory unit 55. The prediction unit 57 inputs the operating parameters of the heating furnace 1 into the scale thickness prediction model and outputs a predicted value of the scale thickness (predicted scale thickness), thereby predicting the amount of scale generation. The prediction unit 57 may display the predicted predicted scale thickness on the output unit 54. This allows the operator to confirm the predicted value of the amount of scale generation in the heating process by visually checking the output unit 54.

Next, the process of judging the predicted scale thickness by the scale generation amount control device 51 will be described. The prediction unit 57 outputs the predicted scale thickness to the judgment unit 58. The judgment unit 58 judges whether the predicted value of the scale thickness obtained from the prediction unit 57 is within the range of the target scale thickness. The target scale thickness may be obtained from the control computer 101 and stored in the memory unit 55. The target scale thickness may be input by the operator from the input unit 53, or may be input in advance by the operator and stored in the memory unit 55. The judgment unit 58 outputs the judgment result of whether the predicted value of the scale thickness is within the range of the target scale thickness to the setting unit 59.

When the setting unit 59 obtains a judgment result from the judgment unit 58 that the scale predicted thickness is within the range of the scale target thickness, the setting unit 59 outputs a command to maintain the current operating parameters of the heating furnace 1 to the control computer 101, since the operating parameters of the heating furnace 1 obtained by the acquisition unit 56 can be used to control the scale predicted thickness to a predetermined range of the scale target thickness. On the other hand, when the setting unit 59 obtains a judgment result from the judgment unit 58 that the scale predicted thickness is not within the range of the scale target thickness, the setting unit 59 changes the operating parameters of the heating furnace 1 obtained by the acquisition unit 56. In this case, the setting unit 59 assumes new setting values obtained by changing the operating parameters of the heating furnace 1 from the current setting values, and outputs the setting values to the prediction unit 57. The prediction unit 57 again inputs the new setting values into the scale thickness prediction model, predicts the scale thickness, and outputs the setting values to the judgment unit 58. The judgment unit 58 judges whether the newly acquired predicted value of the scale thickness is within the range of the scale target thickness. The prediction unit 57 and the judgment unit 58 repeat this process until the predicted value of the scale thickness is within the range of the scale target thickness. The setting unit 59 then identifies the operating parameters of the heating furnace 1 that will bring the predicted value of the scale thickness within the range of the target scale thickness, and outputs these to the control computer 101.

The control computer 101 controls the heating equipment 100 to realize the set operating parameters of the heating furnace 1 based on the information obtained from the setting unit 59.

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

As an example of the present invention, we will explain an example of controlling the amount of scale formation on steel using a test device that simulates the above heating process. The test device used in this example is a combustion gas heating furnace that performs burner heating.

The combustion gas heating furnace in which the heating process is carried out has internal dimensions of 800mm high x 500mm wide x 1000mm long. The combustion gas heating furnace has burners placed on the top and bottom of the test pieces to be placed inside the furnace, and is configured to supply a mixed gas of hydrogen-based gas and coal gas from a fuel gas supply system. The hydrogen-based gas used in the mixed gas was ammonia, and the coal gas used was M gas, a mixture of by-product gases generated in steelworks.

The combustion conditions used in the examples were as follows: ammonia flow rate supplied to the burner was 50 ^Nm3 /hr, M gas flow rate was 117 ^Nm3 /hr, ammonia volume ratio in the mixed gas was 30%, and M gas volume ratio was 70%. Note that the M gas used had a composition that would result in 13 volume % of carbon dioxide being discharged into the exhaust gas under complete combustion conditions.
On the other hand, in the embodiment, the mixture ratio of ammonia was adjusted to set the burner heating conditions so that the carbon dioxide concentration in the exhaust gas in the heating step was 9% by volume.

In the example, carbon steel with plate thickness of 220 mm x plate width of 300 mm x plate length of 500 mm was used as the metal material to be heated. The heated material was taken by machining from the slab after casting, and a Φ0.5 mm K-sheathed thermocouple was attached at a position 2 mm deep from the surface in the center of the plate width and length. This allowed the temperature rise behavior of the heated material during the heating process to be measured, and the surface temperature of the heated material was estimated based on the measurement results.

Here, the heating conditions in the combustion gas heating furnace were changed in advance to investigate the relationship between the heating temperature and the thickness of the scale that forms on the surface of the heated material. Figure 8 shows the relationship between the water vapor concentration in the combustion gas heating furnace and the thickness of the scale on the heated material for each heating temperature. The heating time was 60 minutes. Regarding the thickness of the scale, when the surface temperature set in the combustion gas heating furnace was reached, the heated material was removed from the combustion gas heating furnace and immediately cooled with water. This prevented further scale growth. An evaluation sample was then machined from the heated material, and the cross section of the heated material was observed under an optical microscope to determine the thickness of the scale.

Figure 8 shows that the scale thickness of the heated material can be controlled by changing the water vapor concentration in the combustion gas heating furnace according to the heating temperature.

Next, a scale thickness prediction model was generated based on the results of the preliminary experiment in Figure 8, as well as the results of an investigation in which the heating time was changed. For the scale thickness prediction model, a mathematical model was used that models the oxide growth behavior shown in formula (2). The generated scale thickness prediction model was stored in the memory unit 55 of the scale formation amount control device 51, and the amount of scale formation on the metal material was controlled by setting the flow rate of the hydrogen-based gas used as fuel for burner heating as an operating parameter of the heating furnace.

Here, the target scale thickness of the carbon steel used for the heated material was set to the range of 350 to 600 μm. The range in which the carbon steel used for the heated material contains impurities generated during casting and foreign matter caused by mold powder mixed in during casting was specified in advance, and the target scale thickness was set to this range.
That is, if the thickness of scale generated on the evaluation sample taken from the heated material is less than 350 μm, the thickness of the scale may be insufficient and surface defects may occur when the material is subjected to hot rolling, etc. On the other hand, if the thickness of the scale exceeds 600 μm, excessive scale generation may result in a decrease in product yield.
From the above, a case where the scale thickness formed on the evaluation sample taken from the heated material was within the range of the target scale thickness of 350 to 600 μm was judged as pass (◯). On the other hand, a case where the scale thickness formed on the evaluation sample taken from the heated material was outside the range of the target scale thickness of 350 to 600 μm was judged as fail (×).

The heating conditions and test results are shown in Table 1. In Table 1, "heating temperature,""hydrogen-basedgas," and "mixing ratio of hydrogen-based gas" represent initial conditions for the operation parameters of the heating furnace that were previously set. "Operation parameters of the heating furnace to be changed" indicates the operation parameters that are reset by the setting unit 59 when the determination unit 58 determines that the predicted value of the scale thickness is not within the range of the target scale thickness. In this case, conditions 5 and 6 mean that the heating time or the heating temperature is reset in addition to the hydrogen-based gas flow rate as the operation parameter to be reset by the setting unit 59.
On the other hand, the "water vapor amount" indicates the concentration of water vapor in the furnace after the operation parameters of the heating furnace are set by the setting unit 59. The "scale thickness" indicates the scale thickness obtained by taking an evaluation sample in the same manner as above and observing the cross section of the heated material with an optical microscope.

As can be seen from Table 1, in the conditions 1 to 8 of the invention, the scale thickness generated on the evaluation sample taken from the heated material was within the range of the target scale thickness of 350 to 600 μm, and therefore was judged to be pass (◯). In particular, in conditions 3 and 4, even though the heating temperature was set at a relatively high 1100° C., the amount of water vapor in the furnace was controlled to be low, so the scale thickness of the heated material was within the range of the target scale thickness.
On the other hand, under condition 8, the heating temperature was relatively low at 1,050°C and the mixture ratio of hydrogen-based gas was low, so the heating conditions were not conducive to promoting scale formation. However, by controlling the hydrogen-based gas flow rate, the scale thickness of the heated material was within the range of the target scale thickness.

In contrast, in conditions 9 and 10, which are comparative examples, even when the judgment unit 58 judged that the predicted value of the scale thickness was not within the range of the target scale thickness, heating was performed under the preset initial conditions, so the scale thickness of the heated material did not fall within the range of the target scale thickness.

From the above, it was found that this embodiment can reduce carbon dioxide emissions by using hydrogen or ammonia as fuel gas for the heating furnace, and can also control the amount of scale generation within an appropriate range, reducing the occurrence of surface defects in metal materials.

REFERENCE SIGNS LIST 100 Heating equipment 101 Control computer S Steel material D Steel material transport direction A Combustion air G Fuel gas CG Coal gas HG Hydrogen gas 1 Heating furnace 3 Preheating zone 4 Heating zone 5 Uniformity zone 6 Burner 6a Upper burner 6b Lower burner 7 Burner nozzle 8 Charging section 9 Discharge section 10 Transport device 10a Fixed skid 10b Mobile skid 13 Exhaust duct 31 Fuel gas supply system 32 Combustion air supply system 33 Fuel gas flow control valve 34 Fuel gas flow meter 35 Combustion air flow control valve 36 Combustion air flow meter 37 Furnace wall 38 Furnace interior 40 Mixing section 41 Hydrogen-based gas flow control valve 42 Hydrogen-based gas flow meter 43 Coal gas flow control valve 44 Coal gas flow meter 45 Hydrogen-based gas supply system 46 Coal gas supply system 47 Flow rate setting unit 48 Water vapor amount control unit 49 Dew point meter 51 Scale formation amount control device 52 Control unit 53 Input unit 54 Output unit 55 Memory unit 56 Acquisition unit 57 Prediction unit 58 Determination unit 59 Setting unit 60 Burner equipment 70, 71 Hydrogen-based burner equipment

Claims (12)

A method for controlling the amount of scale formation on a metal material in a heating furnace, comprising:
The metal material is heated with a burner using a hydrogen-based gas containing either or both of hydrogen and ammonia as fuel;
a flow rate of the hydrogen-based gas used as fuel for the burner heating is set as an operation parameter of the heating furnace, and the amount of scale formed on the surface of the metal material is controlled based on the set flow rate of the hydrogen-based gas.
A method for controlling the amount of scale formation on metallic materials in a heating furnace. the metal material is heated with a burner using a mixed gas obtained by mixing the hydrogen-based gas with one or more gases selected from coal gas and a hydrocarbon-based gas as fuel;
The method for controlling the amount of scale formation on a metallic material in a heating furnace according to claim 1. At least one selected from a heating time and a heating temperature of the metal material in the heating furnace is further set as an operation parameter of the heating furnace, and the amount of scale formed on the surface of the metal material is controlled based on the set operation parameter.
3. A method for controlling the amount of scale formation on a metallic material in a heating furnace according to claim 1 or 2. The heating furnace includes a preheating zone, a heating zone, and a soaking zone,
Using hydrogen-based gas as fuel, burner heating is performed in the soaking zone,
a flow rate of the hydrogen-based gas used as fuel for burner heating of the soaking zone is set as an operation parameter of the heating furnace, and an amount of scale formed on a surface of a metal material is controlled based on the set flow rate of the hydrogen-based gas.
3. A method for controlling the amount of scale formation on a metallic material in a heating furnace according to claim 1 or 2. A method for controlling the amount of scale formation on a metal material in a heating furnace according to claim 1 or 2, which controls the amount of scale formation on the metal material based on the operating parameters of the heating furnace so that the amount of scale formation on the metal material is within a preset range. A method for controlling the amount of scale formation on a metal material in a heating furnace as described in claim 3, which controls the amount of scale formation on the metal material based on the operating parameters of the heating furnace so that the amount of scale formation on the metal material is within a preset range. A method for controlling the amount of scale formation on a metal material in a heating furnace as described in claim 4, which controls the amount of scale formation on the metal material based on the operating parameters of the heating furnace so that the amount of scale formation on the metal material is within a preset range. An apparatus for controlling the amount of scale formation on a metal material in a heating furnace, comprising: an acquisition unit for acquiring operating parameters of the heating furnace including a flow rate of a hydrogen-based gas, the total amount of which is either hydrogen or ammonia or both, used as a fuel for burner heating;
a prediction unit that predicts the amount of scale generation on the metallic material using the acquired operational parameters;
a determining unit that determines whether the predicted amount of scale generation is within a preset range, and a setting unit that sets operation parameters of the heating furnace when the predicted amount of scale generation is not within the preset range;
A device for controlling the amount of scale formation on a metal material in a heating furnace, comprising a control unit including: an acquisition unit that acquires operation parameters of the heating furnace including a flow rate of a mixed gas obtained by mixing the hydrogen-based gas with one or more gases selected from a coal gas and a hydrocarbon-based gas;
The device for controlling the amount of scale formation on metal materials in a heating furnace according to claim 8. A method for operating a heating furnace that heats steel material using the method for controlling the amount of scale formation on metal materials in a heating furnace described in claim 5. A method for operating a heating furnace that heats steel material using the method for controlling the amount of scale formation on metal materials in a heating furnace described in claim 6. A method for operating a heating furnace for heating a steel material, using the method for controlling the amount of scale formation on a metallic material in a heating furnace according to claim 7.

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