Heating apparatus

Abstract

To provide a technique for suppressing the generation of dross and the emission of carbon dioxide in a heating apparatus for holding a temperature of a molten metal in a crucible to the melting point of the molten metal or more.SOLUTION: A heating apparatus comprises a crucible, and is used for holding the temperature of a molten metal in the crucible to a melting point of the molten metal or more. The heating apparatus comprises: an enclosure which encloses the crucible and has a gas feed port for feeding a gas to the outside of the crucible; and a catalyst combustion device which is connected with the enclosure, generates a combustion gas of 1,000°C or less by the catalytic combustion of hydrogen, and feeds the combustion gas into the enclosure via the gas feed port.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a heating device for maintaining the temperature of a molten metal. [Background technology]

[0002] Conventionally, casting uses a melting furnace for melting metal and a holding furnace for storing the molten metal. A known holding furnace maintains the temperature of the molten metal by heating a crucible containing the molten metal using combustion gas from a burner (see, for example, Patent Documents 1 and 2).

[0003] Patent Document 1 discloses a heating furnace (melting furnace, holding furnace) that heats a crucible evenly by configuring the combustion gas supplied from a burner to a combustion space in a refractory furnace to swirl while raising the combustion space. Patent Document 2 discloses an aluminum melting and holding furnace that both melts aluminum and holds molten aluminum. In this molten aluminum holding furnace, two regeneration burners (hereinafter also referred to as regenerative burners) are arranged spaced apart in the height direction of the crucible, and the crucible is heated evenly by alternately switching between the two regenerative burners in a short period of time. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-216358 [Patent Document 2] Japanese Patent Application Publication No. 6-257951 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the technology described in the above patent document has a problem in that carbon dioxide is emitted because a gas burner is used. Also, the technology described in the above patent document 2 has a risk of excessively increasing the temperature inside the furnace due to regeneration, which may result in the generation of dross. Therefore, there is a need for another technology for heating the crucible.

[0006] Therefore, an object of the present disclosure is to provide a technology for suppressing the generation of dross and the emission of carbon dioxide in a heating device. [Means for solving the problem]

[0007] The present disclosure has been made to solve at least part of the above-mentioned problems, and can be realized in the following forms.

[0008] (1) According to one aspect of the present disclosure, there is provided a heating device including a crucible for maintaining the temperature of molten metal in the crucible at or above the melting point of the molten metal. The heating device includes a housing that contains the crucible and has a gas supply port for supplying gas to the outside of the crucible, and a catalytic combustion device connected to the housing that generates combustion gas at 1000°C or less by catalytic combustion of hydrogen and supplies the combustion gas into the housing via the gas supply port.

[0009] According to this configuration, the crucible is heated by combustion gas generated by catalytic combustion of hydrogen, thereby suppressing carbon dioxide emissions. Furthermore, since combustion gas of 1000°C or less is generated in the catalytic combustion device, the generation of dross caused by heating the crucible with gas of a temperature higher than 1000°C can be suppressed. Note that the melting point of metals used in casting is generally lower than 1000°C, so the molten state of the molten metal can be maintained by heating the crucible with combustion gas of 1000°C or less, which is higher than the melting point of the molten metal.

[0010] (2) The heating device of the above aspect may further include at least one heat accumulator, an exhaust gas supply passage that supplies the combustion gas discharged from the housing to the heat accumulator, a pre-heated oxygen-containing gas supply passage that supplies an oxygen-containing gas containing oxygen to the heat accumulator, and a preheated oxygen-containing gas supply passage that connects the heat accumulator and the catalytic combustor and supplies the oxygen-containing gas that has passed through the heat accumulator to the catalytic combustor. In this way, the sensible heat of the combustion gas discharged from the housing can be recovered by the heat accumulator to preheat the oxygen-containing gas, thereby improving energy efficiency.

[0011] (3) In the heating device of the above aspect, catalytic combustion of hydrogen in the catalytic combustor may be performed at an excess air ratio of 3 or more. In this way, combustion gas of 1000°C or less can be easily generated with a simple configuration, compared to when other gases (e.g., nitrogen) are supplied to the catalytic combustor to lower the temperature of the combustion gas.

[0012] (4) The heating device of the above aspect may further include a combustion gas control unit that controls the flow rate of the combustion gas so that the combustion gas impinges on the crucible, and the gas supply port of the housing may be provided so that the combustion gas impinges on the crucible. In this way, the combustion gas can be made to impinge on the crucible, thereby promoting heat transfer from the gas to the molten metal (promotion of heat transfer by an impinging jet).

[0013] (5) The catalytic combustion apparatus may further include a first temperature acquisition unit that measures the temperature of a high-temperature portion of the molten metal in the crucible, a second temperature acquisition unit that measures the temperature of a low-temperature portion of the molten metal in the crucible, and a control unit that controls the flow rates of hydrogen and oxygen-containing gas supplied to the catalytic combustion apparatus based on the temperature measurements by the first temperature acquisition unit and the second temperature acquisition unit. In this way, the temperature of the combustion gas can be controlled based on the temperature of the molten metal in the crucible, thereby more appropriately managing the temperature of the molten metal. As a result, energy efficiency can be improved.

[0014] The present disclosure can be realized in various forms, for example, in the form of a heating system equipped with a heating device, a control device for controlling the heating device, a control method for the heating device, a computer program for causing a computer to execute the control method, a server device for distributing the computer program, a non-transitory storage medium on which the computer program is stored, etc. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is an explanatory diagram conceptually showing the configuration of a heating device according to a first embodiment. [Figure 2] FIG. 2 is an explanatory diagram showing a schematic configuration of a main body of the heating device with a portion cut away. [Figure 3] FIG. 1 is a diagram showing the adiabatic flame temperature of hydrogen. [Figure 4] FIG. 10 is an explanatory diagram conceptually showing the configuration of a heating device according to a second embodiment. [Figure 5] FIG. 2 is an explanatory diagram conceptually showing the configuration of a holding furnace of a comparative example. [Figure 6] FIG. 10 is an explanatory diagram conceptually showing the configuration of a heating device according to a third embodiment. [Figure 7] FIG. 3 is an explanatory diagram of the arrangement of a first temperature acquisition unit and a second temperature acquisition unit. [Figure 8] 10 is a flowchart showing a flow of flow rate control. [Figure 9] FIG. 4 is an explanatory diagram showing the collision angle of combustion gas. DETAILED DESCRIPTION OF THE INVENTION

[0016] First Embodiment FIG. 1 is an explanatory diagram conceptually illustrating the configuration of a heating device 100 according to a first embodiment of the present disclosure. The heating device 100 is a device for maintaining the temperature of molten metal in a crucible at or above the melting point of the molten metal. As shown in the figure, the heating device 100 includes a crucible 10, a housing 20 that houses the crucible 10, and a catalytic combustion device 30 that is connected to the housing 20 and supplies hydrogen combustion gas into the housing 20. In the following description, the crucible 10 and the housing 20 are collectively referred to as a "main body 22." The heating device 100 is used to heat molten metals (such as aluminum, zinc, and magnesium) with melting points of 1000°C or less, or alloys thereof.

[0017] 2 is an explanatory diagram showing a schematic configuration of the heating device 100 of this embodiment, with a portion of the main body 22 cut away. In FIG. 2, the flow of combustion gas is indicated by arrows. The crucible 10 of this embodiment is a heat-resistant container that has a vessel shape (a cylindrical shape with a bottom in FIG. 2) that can store the molten metal M and is open at the top. The crucible 10 is made of a material that has high thermal conductivity and heat resistance and does not react with the molten metal M. When the molten metal M is aluminum (Al), the crucible 10 is made of alumina (Al2O3), for example. The shape of the crucible 10 is not limited to the example shown in FIG. 2, and various shapes can be adopted, such as a cylindrical shape with a curved bottom or a mortar shape.

[0018] As shown in Fig. 2, the housing 20 holds the crucible 10 with the top of the crucible 10 open. In this embodiment, the housing 20 also has a generally cylindrical shape with a bottom, with a gas supply port 12 formed on the bottom surface and a gas exhaust port 14 formed on the side surface. The housing 20 is made of a material that has high heat resistance and low hydrogen embrittlement (is not easily embrittled in a hydrogen environment). For example, stainless steel (SUS) can be used.

[0019] 1, a combustion gas supply passage R10 is connected to the gas supply port 12 of the housing 20, and combustion gas as high-temperature gas generated in the catalytic combustion device 30 is supplied into the housing 20 via the combustion gas supply passage R10 and the gas supply port 12. In addition, an exhaust gas flow passage R50 is connected to the gas exhaust port 14 of the housing 20, and the combustion gas exhausted from the housing 20 is released to the outside via the exhaust gas flow passage R50.

[0020] Gas supply port 12 is provided on the bottom surface of housing 20 so that the combustion gas collides with the bottom surface of crucible 10. As shown in Fig. 2, the combustion gas is supplied from gas supply port 12 into housing 20, collides with the bottom surface of crucible 10, passes outside crucible 10, and is discharged to the outside via gas discharge port 14. In this way, the high-temperature combustion gas flows outside crucible 10, thereby heating molten metal M in crucible 10 and maintaining the molten state of molten metal M.

[0021] 2, the combustion gas collides perpendicularly (at a collision angle of 90°) with the bottom surface of the crucible 10. Therefore, by applying a collision jet, heat transfer from the gas to the molten metal can be promoted.

[0022] The catalytic combustion device 30 catalytically combusts hydrogen to generate high-temperature combustion gas (high-temperature water vapor-containing gas). Titanium oxide (TiO2), alumina (Al2O3), etc. can be used as the catalyst support, and various shapes such as honeycomb, sphere, and pellet can be used. For example, ruthenium (Ru), iron (Fe), nickel (Ni), etc. can be used as the catalyst. A hydrogen supply passage R20 and an air supply passage R30 are connected to the catalytic combustion device 30, and hydrogen is supplied via the hydrogen supply passage R20, and air as an oxygen-containing gas is supplied via the air supply passage R30.

[0023] FIG. 3 shows the adiabatic flame temperature of hydrogen. This figure shows the simulation results under conditions of an initial temperature of 25°C and a pressure of 0 kPa. The air is 21% oxygen and the remainder nitrogen. Here, the excess air ratio is the mass of the supplied air divided by the theoretically required minimum air mass. As shown in the figure, the adiabatic flame temperature is 1000°C or less when the excess air ratio is 3 or more. In the heating device 100 of this embodiment, the flow rate ratio of hydrogen and air supplied to the catalytic combustion device 30 is preset so that the excess air ratio in the catalytic combustion device 30 is 3 or more. This allows the temperature of the combustion gas supplied to the housing 20 to be 1000°C or less. The flow rates of hydrogen and air supplied to the catalytic combustion device 30 are further set so that the combustion gas collides with the bottom surface of the crucible 10. For example, flow control valves installed at the air intake and the hydrogen supply port of the hydrogen tank storing hydrogen supply air and hydrogen at preset flow rates. These flow control valves function as the "combustion gas control unit."

[0024] The excess air ratio can be determined depending on the melting point of the metal of the molten metal M placed in the crucible 10. The main low-melting-point metals used in casting are aluminum, zinc, magnesium, tin, and lead. The melting point of aluminum is 660°C, that of zinc is 420°C, that of magnesium is 650°C, that of tin is 232°C, and that of lead is 327°C. When the molten metal M is molten aluminum, the amount of dross generated increases significantly at temperatures above 750°C. Therefore, it is preferable to maintain the temperature of the molten metal M at a temperature above 660°C (melting point) and below 750°C. In this case, if the combustion gas is set to 750°C, the temperature difference between the molten aluminum and the combustion gas may not be sufficient, resulting in insufficient heat transfer from the combustion gas to the molten aluminum. Therefore, high-temperature gas at approximately 1000°C is considered to be suitable for holding the molten aluminum. Therefore, when using molten aluminum, it is preferable to set the excess air ratio to 3.

[0025] As described above, the heating device 100 of this embodiment is equipped with a catalytic combustion device 30, and heats the crucible 10 using the combustion gas (high-temperature gas) generated by the catalytic combustion device 30. Therefore, compared to heating the crucible 10 by directly applying a burner flame to the crucible 10, it is possible to suppress the generation of dross that would otherwise be caused by excessive temperature rise due to localized heating. Furthermore, the generation of dross can be suppressed by setting the temperature of the combustion gas to 1000°C or less. Note that the melting points of metals used in casting are generally lower than 1000°C, and therefore the molten state of the molten metal can be maintained by heating the crucible using combustion gas that is higher than the melting point of the molten metal but is equal to or lower than 1000°C.

[0026] In a device for heating molten metal, if the amount of dross generated increases, the power required for post-processing (removal, metal separation, etc.) increases and the yield of the ingot decreases (dross consists of metal nitrides, oxides, etc.). As described above, the heating device 100 of this embodiment can suppress the generation of dross, thereby suppressing the increase in power required for the heating device and the yield of the ingot.

[0027] Furthermore, the heating device 100 does not emit carbon dioxide because it generates high-temperature combustion gas through catalytic combustion of hydrogen in the catalytic combustion device 30. Therefore, carbon dioxide emissions can be reduced compared to when a city gas burner is used, which contributes to measures against global warming.

[0028] Furthermore, since the heating device 100 is configured so that the combustion gas impinges on the bottom surface of the crucible 10, it is possible to apply an impingement jet to promote heat transfer from the combustion gas to the molten metal, thereby improving energy efficiency. Note that, when an impingement jet is used in the case of heating with a conventional burner, the temperature of the molten metal near the impingement point is excessively raised, which may result in the generation of a large amount of dross. Therefore, conventionally, the combustion gas or flame has been supplied / radiated in the tangential direction of the crucible (see, for example, Patent Document 1). In contrast, since the temperature of the combustion gas in the heating device 100 is 1000°C or less, there is no concern that a large amount of dross will be generated even if an impingement jet is used, and it is possible to apply an impingement jet to improve energy efficiency.

[0029] Second Embodiment 4 is an explanatory diagram conceptually illustrating the configuration of a heating device 100A according to a second embodiment of the present disclosure. The heating device 100A of this embodiment differs from the heating device 100 of the first embodiment in that it includes a first heat accumulator 40 and a second heat accumulator 50 that recover sensible heat from the combustion gas discharged from the housing 20, and preheats the air supplied to the catalytic combustion device 30 with the heat recovered in the first heat accumulator 40 and the second heat accumulator 50. In the embodiments described below, the same components as those of the heating device 100 of the first embodiment are designated by the same reference numerals, and reference is made to the preceding description.

[0030] In this embodiment, the first heat accumulator 40 and the second heat accumulator 50 have the same configuration. When there is no need to distinguish between the first heat accumulator 40 and the second heat accumulator 50, they are simply referred to as "heat accumulators." The heat accumulators are filled with, for example, ceramic balls as a heat storage material. As the ceramic, for example, zirconia (ZrO2), alumina (Al2O3), etc. can be used.

[0031] In the heating device 100A, the exhaust gas flow path R50 branches into a first exhaust gas supply path R51 and a second exhaust gas supply path R52. The first exhaust gas supply path R51 is connected to the first heat accumulator 40, and the second exhaust gas supply path R52 is connected to the second heat accumulator 50. A first exhaust gas discharge path R61 is connected to the first heat accumulator 40, and a second exhaust gas discharge path R62 is connected to the second heat accumulator 50. The first exhaust gas discharge path R61 and the second exhaust gas discharge path R62 are connected to the exhaust gas discharge path R60. The exhaust gas flow path R50, the first exhaust gas supply path R51, and the second exhaust gas supply path R52 in this embodiment are also referred to as "exhaust gas supply paths."

[0032] The first exhaust gas supply channel R51, the second exhaust gas supply channel R52, the first exhaust gas discharge channel R61, and the second exhaust gas discharge channel R62 are provided with valves V51, V52, V61, and V62, respectively. When the valves V51 and V61 are open and the valves V52 and V62 are closed, the combustion gas discharged from the gas discharge port 14 is supplied to the first heat accumulator 40 through the exhaust gas flow channel R50 and the first exhaust gas supply channel R51, and the low-temperature combustion gas from which sensible heat has been recovered in the first heat accumulator 40 is discharged to the outside through the first exhaust gas discharge channel R61 and the exhaust gas discharge channel R60.

[0033] On the other hand, when valves V51 and V61 are closed and valves V52 and V62 are open, the combustion gas discharged from the gas exhaust port 14 is supplied to the second heat accumulator 50 through the exhaust gas flow path R50 and the second exhaust gas supply path R52, and the low-temperature combustion gas from which sensible heat has been recovered in the second heat accumulator 50 is discharged to the outside through the second exhaust gas discharge path R62 and the exhaust gas discharge path R60.

[0034] The heating device 100A also includes a pre-preheated air supply channel R40, and a first pre-preheated air supply channel R41 and a second pre-preheated air supply channel R42 branching off from the pre-preheated air supply channel R40. The first pre-preheated air supply channel R41 is connected to the first heat accumulator 40, and the second pre-preheated air supply channel R42 is connected to the second heat accumulator 50. The heating device 100A also includes a first pre-heated air supply channel R31 and a second pre-heated air supply channel R32 joining the air supply channel R30. The first pre-heated air supply channel R31 is connected to the first heat accumulator 40, and the second pre-heated air supply channel R32 is connected to the second heat accumulator 50. The pre-preheated air supply channel R40, the first pre-preheated air supply channel R41, and the second pre-preheated air supply channel R42 in this embodiment are also referred to as "pre-preheated oxygen-containing gas supply channels." In addition, the first preheated air supply channel R31, the second preheated air supply channel R32, and the air supply channel R30 in this embodiment are also referred to as "preheated oxygen-containing gas supply channels."

[0035] The first pre-preheated air supply passage R41, the second pre-preheated air supply passage R42, the first pre-heated air supply passage R31, and the second pre-heated air supply passage R32 are provided with valves V41, V42, V31, and V32, respectively. When the valves V41 and V31 are open and the valves V42 and V32 are closed, air is supplied to the first heat accumulator 40 through the pre-preheated air supply passage R40 and the first pre-preheated air supply passage R41, and the air preheated in the first heat accumulator 40 is supplied to the catalytic combustion device 30 through the first pre-heated air supply passage R31 and the air supply passage R30.

[0036] On the other hand, when valves V41 and V31 are closed and valves V42 and V32 are open, air is supplied to the second heat accumulator 50 through the pre-preheated air supply passage R40 and the second pre-preheated air supply passage R42, and the air preheated in the second heat accumulator 50 is supplied to the catalytic combustion device 30 through the second preheated air supply passage R32 and the air supply passage R30.

[0037] In the heating device 100A, while exhaust gas is supplied to the first heat accumulator 40 and heat is stored in the first heat accumulator 40, air is supplied to the second heat accumulator 50 in which heat has been stored, and the supply air is preheated by the second heat accumulator 50 (mode 1). Similarly, while exhaust gas is supplied to the second heat accumulator 50 and heat is stored in the second heat accumulator 50, air is supplied to the first heat accumulator 40 in which heat has been stored, and the supply air is preheated by the first heat accumulator 40 (mode 2). In this way, heat storage and air preheating in the two heat accumulators, in other words, mode 1 and mode 2, are performed alternately (also referred to as alternating operation). The heating device 100A of this embodiment is configured to switch between mode 1 and mode 2 at predetermined time intervals. The time for each mode (heat storage and preheating time) is determined in advance based on, for example, experiments or simulations. Switching between mode 1 and mode 2 may be performed, for example, every several tens of seconds.

[0038] The effects of the heating device 100A of this embodiment will be explained in comparison with a conventional holding furnace shown in FIG. 5. FIG. 5 is an explanatory diagram conceptually illustrating the configuration of a comparative holding furnace 100P. As shown in the figure, the comparative holding furnace 100P includes a crucible 10, a housing 20P that houses the crucible 10, and a burner B that heats the crucible 10 with a flame. It also includes a heat exchanger 40P that exchanges heat between the exhaust gas discharged from the housing 20P and the air supplied to the burner B. Because melting is not required in the holding furnace 100P, heating is performed at the minimum necessary temperature. Therefore, the heat exchanger 40P recovers and reuses the sensible heat of the exhaust gas. Preheating using a heat exchanger has a lower heat recovery rate than preheating using heat storage material, so excessive increases in the furnace temperature can be avoided. However, due to the low heat recovery rate of the heat exchanger 40P, the energy efficiency of the holding furnace 100P is low.

[0039] In contrast to this, the heating device 100A of this embodiment uses a heat accumulator to recover sensible heat of the exhaust gas to preheat the air, thereby improving energy efficiency.

[0040] Furthermore, when combustion gas is generated by catalytic combustion of hydrogen, catalytic combustion of hydrogen is usually performed at an excess air ratio of 1, resulting in a higher combustion temperature compared to gas burners that use hydrocarbon fuels. If a regenerative burner is used to recover and reuse sensible heat using a heat accumulator to improve energy output, the combustion temperature will likely rise further, resulting in the generation of dross in the molten metal. To address this issue, the heating device 100A of this embodiment sets the excess air ratio in the catalytic combustion device 30 to 3 or more, thereby lowering the temperature of the combustion gas, thereby suppressing the generation of dross in the molten metal even when a regenerative burner is used. In other words, it is possible to achieve both dross suppression and improved energy efficiency.

[0041] <Third embodiment> 6 is an explanatory diagram conceptually illustrating the configuration of a heating device 100B according to a third embodiment of the present disclosure. In addition to the configuration of the heating device 100A according to the second embodiment, the heating device 100B of this embodiment includes a first temperature acquisition unit 72 and a second temperature acquisition unit 74 that measure the temperature of the molten metal in the crucible 10, and a control unit 90 that controls the flow rates of hydrogen and air supplied to the catalytic combustion device 30.

[0042] FIG. 7 is an explanatory diagram of the arrangement of the first temperature acquisition unit 72 and the second temperature acquisition unit 74. The first temperature acquisition unit 72 and the second temperature acquisition unit 74 are temperature sensors capable of measuring the temperature of the molten metal. For example, a thermocouple-type temperature sensor can be used as the temperature sensor. The first temperature acquisition unit 72 is arranged to measure the temperature of the high-temperature portion HA of the molten metal, and the second temperature acquisition unit 74 is arranged to measure the temperature of the low-temperature portion LA of the molten metal. In this embodiment, the first temperature acquisition unit 72 is arranged near the bottom surface of the crucible 10 where the combustion gas impinges, and the second temperature acquisition unit 74 is arranged near the top surface of the molten metal, which is away from the bottom surface of the crucible 10. In this embodiment, the high-temperature portion of the molten metal is located near the position where the combustion gas impinges (also referred to as the impingement portion), and the low-temperature portion of the molten metal is located away from the impingement portion. However, the high-temperature portion and the low-temperature portion of the molten metal may be investigated in advance through experiments or simulations, and the first temperature acquisition unit 72 may be arranged in the high-temperature portion and the second temperature acquisition unit 74 in the low-temperature portion. The first temperature acquisition unit 72 and the second temperature acquisition unit 74 input the temperature measurement results to the control unit 90. In Fig. 7, for ease of explanation, the high temperature area HA and the low temperature area LA are shown surrounded by layers, but this does not mean that the temperature in each area is constant, but rather shows the high temperature area and the low temperature area conceptually.

[0043] The control unit 90 is a computer including a ROM, a RAM, and a CPU, and controls the entire heating device 100B. The control unit 90 determines target values ​​for the supply hydrogen flow rate, the supply air flow rate, and the excess air ratio based on the temperature measurement results input from the first temperature acquisition unit 72 and the second temperature acquisition unit 74, and controls the apertures of valves V22, V31, V32, V41, and V42 (FIG. 6) to achieve the respective flow rates. Here, the computer includes a PLC (programmable logic controller), a PC (personal computer), or the like. The control unit 90 may further control the timing of switching between Mode 1 and Mode 2 described in the second embodiment. The control unit 90 in this embodiment is also referred to as a "flow rate control unit."

[0044] FIG. 8 is a flowchart showing the flow of flow rate control in this embodiment. In step S102, the first temperature acquisition unit 72 acquires a first temperature value T1, which is the temperature of the high-temperature portion HA of the molten metal M (Figure 7), and inputs it to the control unit 90, and the second temperature acquisition unit 74 acquires a second temperature value T2, which is the temperature of the low-temperature portion LA of the molten metal M, and inputs it to the control unit 90.

[0045] In step S104, the control unit 90 determines the target values ​​of the supply hydrogen flow rate, the supply air flow rate, and the excess air ratio using the following (Equations 1) to (Equations 3).

[0046]

number

[0047] The proportional constants k1 and k2 can be arbitrarily set by the user based on experiments, simulations, etc. The above (Equation 1) to (Equation 3) increase the supply hydrogen flow rate when the second temperature value T2 is lower than the target value, and on the other hand, increase the excess air ratio λ when the first temperature value T1 is lower than the target value. tar It is designed to lower the temperature of the combustion gas and increase the combustion gas temperature. tart ≧3.

[0048] In step S106, the control unit 90 controls the openings of the valves V22, V31, V32, V41, and V42 (FIG. 6) so that the supply hydrogen flow rate and supply air flow rate become equal to those determined in step S104. In the flow rate control of this embodiment, steps S102 to S106 are repeatedly executed at intervals of Δt. Δt can be set arbitrarily. For example, Δt may be set to 1 second.

[0049] As described above, according to the heating device 100B of this embodiment, the flow rate of supplied hydrogen and the flow rate of supplied air can be controlled in accordance with the temperature of the molten metal M, and the temperature of the combustion gas can be controlled, thereby improving the accuracy of managing the temperature of the molten metal M. As a result, the generation of dross can be further suppressed. For example, when the molten metal M is molten aluminum, the amount of dross generally increases significantly when the temperature of the molten metal reaches 750°C or higher. Therefore, by maintaining the temperatures of both the high-temperature portion and the low-temperature portion of the molten aluminum at a temperature above the melting point and below 750°C, the generation of dross can be appropriately suppressed.

[0050] <Modification of this embodiment> The present disclosure is not limited to the above-described embodiments, and can be implemented in various forms without departing from the spirit thereof. For example, the following modifications are also possible.

[0051] Although the above embodiment shows an example in which air is used as the oxygen-containing gas, various gases containing oxygen can be used. For example, a mixed gas of oxygen and nitrogen, or a mixed gas of oxygen and an inert gas such as argon, etc. may be used.

[0052] In the above embodiment, the catalytic combustion of hydrogen in the catalytic combustor is performed at an excess air ratio of 3 or more, thereby keeping the combustion gas temperature at 1000°C or less. However, the combustion gas temperature may be kept at 1000°C or less by other methods. For example, a gas other than air (e.g., nitrogen) may be supplied to the catalytic combustion device 30.

[0053] In the above embodiment, an example was shown in which the combustion gas impinges on the bottom surface of the crucible 10 perpendicularly (at 90°), but the angle at which the combustion gas impinges on the crucible 10 is not limited to that in the above embodiment. Fig. 9 is an explanatory diagram showing the collision angle θ of the combustion gas. In Fig. 9, the collision angle θ is shown as the angle between the bottom surface of the crucible 10 and the center line of the combustion gas discharge. The collision angle θ is not particularly limited, but is preferably 90°±45° in consideration of energy efficiency.

[0054] In the above embodiment, an example is shown in which the combustion gas is made to collide with the crucible 10, but the combustion gas may be supplied to the outside of the crucible 10 without colliding with the crucible 10. In this case, the molten metal M in the crucible 10 can also be heated by the high-temperature combustion gas.

[0055] In the above embodiment, an example was shown in which the combustion gas impinges on the bottom surface of the crucible 10, but the position at which the combustion gas impinges is not limited to the above embodiment. For example, the combustion gas may impinge on the side surface of the crucible 10. The combustion gas may also impinge on a plurality of positions. In other words, the number and arrangement of the gas supply ports 12 in the housing are not limited to the above embodiment.

[0056] In the above embodiment, Fig. 2 shows an example in which two gas exhaust ports 14 are formed on the side surface of the housing 20, but the number of gas exhaust ports 14 is not limited to the example in Fig. 2 and may be one, or three or more. In addition, the arrangement of the gas exhaust ports 14 is not limited to the above embodiment.

[0057] The present disclosure has been described above based on embodiments and modifications, but the embodiments of the above-described aspects are intended to facilitate understanding of the present disclosure and are not intended to limit the present disclosure. The present disclosure may be modified or improved without departing from the spirit and scope of the claims, and equivalents thereof are included in the present disclosure. Furthermore, if a technical feature is not described as essential in this specification, it may be deleted as appropriate.

[0058] The present disclosure can also be realized in the following forms. [Application example 1] A heating device having a crucible and configured to maintain a temperature of molten metal in the crucible at or above the melting point of the molten metal, a housing containing the crucible and having a gas supply port for supplying gas to the outside of the crucible; a catalytic combustion device connected to the housing, which generates a combustion gas of 1000°C or less by catalytic combustion of hydrogen, and supplies the combustion gas into the housing through the gas supply port; Equipped with heating device. [Application example 2] The heating device according to Application Example 1, moreover, at least one heat accumulator; an exhaust gas supply passage that supplies the combustion gas exhausted from the housing to the heat accumulator; a pre-preheated oxygen-containing gas supply passage for supplying an oxygen-containing gas containing oxygen to the heat accumulator; a preheated oxygen-containing gas supply passage connecting the heat accumulator and the catalytic combustor, for supplying the oxygen-containing gas that has passed through the heat accumulator to the catalytic combustor; heating device. [Application example 3] The heating device according to Application Example 1 or Application Example 2, The catalytic combustion of hydrogen in the catalytic combustor is carried out at an excess air ratio of 3 or more. heating device. [Application example 4] The heating device according to any one of Application Examples 1 to 3, a combustion gas control unit that controls the flow rate of the combustion gas so that the combustion gas collides with the crucible; The gas supply port of the housing is The combustion gas is arranged to impinge on the crucible. heating device. [Application example 5] The heating device according to any one of Application Examples 1 to 4, a first temperature acquisition unit that measures the temperature of a high-temperature portion of the molten metal in the crucible; a second temperature acquisition unit that measures the temperature of a low-temperature portion of the molten metal in the crucible; a control unit that controls the flow rates of hydrogen and oxygen-containing gas supplied to the catalytic combustion device based on the temperature measurement results obtained by the first temperature acquisition unit and the second temperature acquisition unit; Further provided with heating device. [Explanation of symbols]

[0059] 12...Gas supply port 14...Gas outlet 20, 20P... Cabinet 22...Main body 30...Catalytic combustion device 40...1st heat storage device 40P…Heat exchanger 50…Second heat storage device 72...First temperature acquisition section 74...Second temperature acquisition section 90...Control unit 100, 100A, 100B…Heating device 100P…Holding furnace B...Burner HA...High temperature section LA…Low temperature section M...molten metal R10: Combustion gas supply line R20: Hydrogen supply line R30...Air supply line R31: First preheated air supply line R32: Second preheated air supply line R40: Pre-heating air supply line R41: First preheating air supply line R42: Second pre-heating air supply line R50...Exhaust gas flow path R51…First exhaust gas supply line R52...Second exhaust gas supply line R60...Exhaust gas discharge duct R61...First exhaust gas discharge channel R62...Second exhaust gas discharge channel V22, V41, V42, V51, V52…valves

Claims

1. A heating device having a crucible and configured to maintain a temperature of molten metal in the crucible at or above the melting point of the molten metal, a housing containing the crucible and having a gas supply port for supplying gas to the outside of the crucible; a catalytic combustion device connected to the housing, which generates a combustion gas having a temperature of 1000°C or less by catalytic combustion of hydrogen, and supplies the combustion gas into the housing through the gas supply port; Equipped with heating device.

2. The heating device according to claim 1, moreover, at least one heat accumulator; an exhaust gas supply passage that supplies the combustion gas exhausted from the housing to the heat accumulator; a pre-preheated oxygen-containing gas supply passage for supplying an oxygen-containing gas containing oxygen to the heat accumulator; a preheated oxygen-containing gas supply passage connecting the heat accumulator and the catalytic combustor, for supplying the oxygen-containing gas that has passed through the heat accumulator to the catalytic combustor; heating device.

3. The heating device according to claim 1, The catalytic combustion of hydrogen in the catalytic combustor is carried out at an excess air ratio of 3 or more. heating device.

4. The heating device according to claim 1, a combustion gas control unit that controls the flow rate of the combustion gas so that the combustion gas collides with the crucible; The gas supply port of the housing is The combustion gas is arranged to impinge on the crucible. heating device.

5. The heating device according to any one of claims 1 to 4, a first temperature acquisition unit that measures the temperature of a high-temperature portion of the molten metal in the crucible; a second temperature acquisition unit that measures the temperature of a low-temperature portion of the molten metal in the crucible; a control unit that controls the flow rates of hydrogen and oxygen-containing gas supplied to the catalytic combustion device based on the temperature measurement results obtained by the first temperature acquisition unit and the second temperature acquisition unit; Further provided with heating device.

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