Heating device, control method, and control apparatus

Abstract

To provide a heating device, when being used for an aluminum melting furnace in particular, which can suppress carbon dioxide emissions and efficiently heat aluminum molten metal, and a control method and a control apparatus using the same.SOLUTION: A heating device 1 comprises: a ceramic heater 10 which holds a heating element and a temperature detection part at the inside of a ceramic body 11 made of ceramics; and a control part 20 which controls the heating state of the heater corresponding to a temperature detected in the temperature detection part. A control method is executed by using the heating device 1. A control apparatus includes the heating device 1.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a heating device, a control method, and a control device.

Background Art

[0002] In an aluminum melting furnace, there is a method for controlling the temperature of the molten aluminum by controlling the combustion amount of a burner based on an output signal emitted by a molten metal temperature regulator according to the deviation between the set value of the molten metal temperature and the detected molten metal temperature by a thermocouple. For example, Patent Document 1 describes a method for controlling the temperature of the molten aluminum in an aluminum melting furnace, in which the thermocouple is intermittently immersed in the molten metal, the temperature of the molten metal is controlled based on the detected molten metal temperature during this immersion, the output of the molten metal temperature regulator is held at the end of one temperature detection of the molten metal, and the hold is released at the start of the temperature control of the molten metal based on the detected molten metal temperature accompanying the next immersion of the thermocouple.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in recent years, the demand for suppressing carbon dioxide emissions has been increasing. In the aluminum melting furnace as well, although there is a movement to reduce carbon dioxide emissions as much as possible, there is still no effective means.

[0005] The present invention solves such problems, and an object of the present invention is to provide a heating device that can suppress carbon dioxide emissions and efficiently heat a metal melt when used in a metal melting furnace, particularly an aluminum melting furnace, a control method using the same, and a control device.

Means for Solving the Problem

[0006] The heating device of the present invention is characterized by comprising a ceramic heater that holds a heating element and a temperature detection unit inside a ceramic body made of ceramics, and a control unit that controls the heating state of the ceramic heater according to the temperature detected by the temperature detection unit. By using a ceramic heater whose heating state can be controlled in a metal melting furnace, particularly an aluminum melting furnace, it is possible to suppress carbon dioxide emissions more than when heating molten aluminum with a burner and efficiently heat the molten aluminum. It is preferable that the ceramic body is a plate-like body. Since the ceramic body is a plate-like body, the whole is small and compact, and it can be installed even in a narrow space.

[0007] The control method of the present invention is a control method for controlling the heating state of a discharge part of a metal melting furnace that melts the metal introduced from an inlet and discharges the melted metal at a discharge part with an open upper surface. A ceramic heater that holds a heating element and a temperature detection unit is fixed along the inner wall surface of the discharge part inside a ceramic body made of ceramics. When the temperature detected by the temperature detection unit falls below a first threshold value, the ceramic heater is operated to control the heating state of the discharge part. By installing a ceramic heater whose heating state can be controlled along the inner wall surface of the discharge part of a metal melting furnace, for example, an aluminum melting furnace, when the temperature detected by the temperature detection unit falls below the first threshold value, the ceramic heater can be operated to control the heating state of the discharge part. Thereby, it is possible to suppress carbon dioxide emissions more than when heating molten metal with a burner and efficiently heat the molten metal. Another temperature detection unit is further provided in the derivation unit. The heating state of the holding burner in the holding chamber communicating with the derivation unit is further controlled by the temperature detected by the another temperature detection unit. When the metal melting furnace is in an operating state, if the temperature detected by the another temperature detection unit is lower than a second threshold value, the holding burner is operated. It is preferable that the second threshold value is lower than the first threshold value. Since the second threshold value, which is the operating temperature of the holding burner, is low, the holding burner is configured to hardly operate, so that it is possible to suppress the emission of carbon dioxide. When the metal melting furnace is in a non-operating state, the setting of the second threshold value is cancelled, and if the temperature detected by the another temperature detection unit is lower than a third threshold value, the holding burner is operated. It is preferable that the third threshold value is lower than the second threshold value. In the non-operating state, if the third threshold value, which is the operating temperature of the holding burner, is set, the holding burner hardly operates. However, even if the ceramic heater fails during the non-operation, since it is configured so that the metal can maintain a liquid state, it is possible to hold high-quality molten aluminum. When the third threshold value is 580 to 600 °C, it is preferable because aluminum can maintain a liquid state when the metal furnace is an aluminum melting furnace.

[0008] The control device of the present invention is a control device that controls the heating state of the outlet part of an aluminum melting furnace that melts aluminum introduced from an inlet and discharges the melted aluminum at an outlet with an open upper surface. In the outlet part, a ceramic heater that holds a heating element and a temperature detection part is fixed along its inner wall surface inside a ceramic body made of ceramics. When the temperature detected by the temperature detection part falls below a first threshold value, a furnace temperature control part that operates the ceramic heater, and in the outlet part, another temperature detection part is further provided. When the temperature detected by the other temperature detection part falls below a second threshold value, a furnace temperature control part that operates a holding burner in a holding chamber communicating with the outlet part is provided, and the second threshold value is set lower than the first threshold value. By installing a ceramic heater capable of controlling the heating state along the inner wall surface of the outlet part of a metal melting furnace, particularly an aluminum melting furnace, when the temperature detected by the temperature detection part falls below the first threshold value, the ceramic heater can be operated to control the heating state of the outlet part. As a result, it is possible to suppress carbon dioxide emissions compared to heating the molten aluminum with a burner and efficiently heat the molten aluminum. Furthermore, since the second threshold value, which is the operating temperature of the holding burner, is low, the holding burner is configured to hardly operate, so it is possible to further suppress carbon dioxide emissions.

Advantages of the Invention

[0009] The heating device of the present invention can suppress carbon dioxide emissions and efficiently heat the molten metal when used in a metal melting furnace, particularly an aluminum melting furnace. And the control method and control device for controlling the heating state of the outlet part of an aluminum melting furnace using this can suppress carbon dioxide emissions from a metal melting furnace, particularly an aluminum melting furnace, and efficiently heat the molten aluminum.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Mode for Carrying Out the Invention

[0011] The heating device of the present invention will be described with reference to FIGS. 1 to 5. The heating device 1 of the present invention schematically shown in FIG. 1 includes a ceramic heater 10, a control device which is a control unit 20 for controlling the ceramic heater 10, and a connection line 30 for electrically connecting the ceramic heater 1 and the control unit 20. The details of the ceramic heater 10 will be described with reference to FIG. 2. In FIG. 2, each member provided inside the ceramic heater 10 is schematically shown so as to be visible. The ceramic heater 10 includes a ceramic body 11, a heating element 12 and a first temperature detection end 13 (temperature detection unit) embedded inside the ceramic body 11. The control unit 20 controls the heat generation state of the heating element 12 according to the temperature detected by the first temperature detection end 13. Although it will be described in detail later, in the heating device 1, the ceramic heater 10 is attached to the lead-out portion 54 of the aluminum melting furnace 5 (aluminum melting furnace in the present embodiment) as shown in FIG. 5, and the heating state of the lead-out portion 54 can be controlled by the control unit 20.

[0012] In this embodiment, the ceramic body 11 is rectangular plate-shaped when viewed from the front. Being plate-shaped, as shown in FIG. 4, it can be installed along the wall surface of the lead-out portion 54. Examples of the ceramics used for the ceramic body 11 include, among non-oxides, silicon carbide (SiC), silicon nitride (Si3N4), aluminum nitride (AlN), and among oxides, barium titanate (BaTiO3), lead zirconate titanate (Pb(Zr,Ti)O3), ferrite (M2+O·Fe2O3), alumina (Al2O3), forsterite (2MgO·SiO2), zirconia (ZrO2), zircon (ZrO2·SiO2), mullite (3Al2O3·2SiO2), steatite (MgO·SiO2), cordierite (2MgO·2Al2O3·5SiO2), etc. One or more of these components can be selected as the main component according to the application to meet the performance requirements. Preferably, it contains silicon carbide-based ceramics, but it may also be configured to ignite an additive containing silicon carbide in ceramics that do not contain silicon carbide. More preferably, it is a mixture of silicon carbide-based ceramics and refractory cement. As the refractory cement, for example, commercially available unshaped refractories and those mixed with castables can be used, such as those shown in Table 1 below. In the present invention, although not limited, those with a high content of silicon carbide (SiC) are preferred, and those containing 70% or more of silicon carbide as shown in Types 5 and 6 are preferred.

Table 1

[0013] In this embodiment, a heating element 12, which is a coiled nichrome wire, is provided inside the ceramic body 11. As the heating element 12, any type can be used. For example, a nichrome coil wire, a sheathed heater, a cartridge heater, a micro heater, etc. can be used. The sheathed heater is formed by inserting a coiled nichrome wire into an outer cylinder of heat-resistant steel and filling MgO insulator around it. If the melting point of the heat-resistant steel is 1300°C, it has a heat resistance of 1100°C. The micro heater is formed by inserting a linear nichrome wire into a thin tube of heat-resistant steel and filling MgO insulator around it. It is thinner than the sheathed heater and is intended for a fine object to be heated.

[0014] In this embodiment, six heating elements 12 are provided at intervals along the longitudinal direction (vertical direction during installation) of the ceramic body 11. However, the number and arrangement are not limited to this, and additional elements may be provided as appropriate.

[0015] A first temperature detection terminal 13, which is a temperature sensor, is provided on the ceramic body 11. The first temperature detection terminal 13 detects the temperature of the ceramic body 11 and the temperature of the molten aluminum. The temperature information detected by the first temperature detection terminal 13 is sent to the control unit 20, and the control unit 20 controls the ceramic heater 10 according to this temperature. The first temperature detection terminal 13 is provided between the heating elements 12 without contacting any of the heating elements 12 (see FIG. 3). As the first temperature detection terminal 13, anything can be used as long as it can be provided inside the ceramic body 11. For example, a thermocouple can be used.

[0016] Furthermore, a second temperature detection terminal 14, which is another temperature sensor, is provided on the ceramic body 11 so as to contact one of the heating elements 12. The second temperature detection terminal 14 detects the temperature of the heating element 12. The temperature information detected by the second temperature detection terminal 14 is sent to the control unit 20, and the control unit 20 detects an abnormality of the heating element 12 according to this temperature. As the second temperature detection terminal 14, for example, a thermocouple can be used.

[0017] Such a ceramic heater 10 is obtained as follows. That is, an appropriate number of heating elements 12 and the like are installed in a mold, temporarily fixed as appropriate, and then the ceramics prepared in a slurry state are poured into the mold from a feeder. In that state, it is left standing at room temperature or fired at a low temperature. Usually, a wooden mold is frequently used for the mold, but it is not limited thereto, and any other material, such as a paper material like cardboard, can also be used. If it is a combustible material, it burns and is removed during the subsequent firing process at a high temperature. Thereby, the ceramic heater 10 which is a cast-in heater can be obtained.

[0018] One end 41 of a mounting portion 40 which is L-shaped in a side view is fixed to the upper portion of the ceramic body 11. The mounting portion 40 is fixed to the upper portion of the ceramic body 11, and an internal connection wire (not shown) connected to the heating element 12, the first temperature detection end 13, and the second temperature detection end 14 is provided inside thereof. A connector 43 is provided on the lower surface 42 of the other end side of the mounting portion 40. The internal connection wire (not shown) is electrically connected to the connector 43. The flat portion 44 between the connector of the mounting portion 40 and the one end 41 is placed on the wall surface of the lead-out portion 54 when the ceramic heater 10 is attached to the lead-out portion 54. As shown in FIG. 4, a mounting portion 45 may be fixed on the wall surface of the lead-out portion 54, and the flat portion 44 may be placed on the mounting portion 45.

[0019] Furthermore, as shown in FIG. 4, a control unit 20 is electrically connected to the connector 43 via a connection wire 30. Thereby, the control unit 20 is electrically connected to the heating element 12, the first temperature detection end 13, and the second temperature detection end 14.

[0020] The control unit 20 includes a furnace temperature control unit 21, a thermal runaway prevention control unit 22, and a display unit 23. The furnace temperature control unit 21 performs control based on the temperature detected by the first temperature detection terminal 13. Further, when the temperature detected by the second temperature detection terminal 14 exceeds the threshold value, the thermal runaway prevention control unit 22 turns off the power supply of the ceramic heater 10. In addition, information such as the temperature detected by the furnace temperature control unit 21 and the thermal runaway prevention control unit 22 is configured to be displayed on the display unit 23. Note that in the present embodiment, one display unit 23 is provided in the control unit 20, but the present invention is not limited thereto, and a plurality of display units may be provided. Further, in the present embodiment, the control unit 20 is a control device, but the present invention is not limited thereto. For example, the control unit 20 may exist on a server.

[0021] The aluminum melting furnace 5 controlled using such a heating device 1 will be described with reference to FIG. 5. In the present invention, the “melting furnace” of the “metal melting furnace” includes not only a metal melting furnace but also a metal melting crucible furnace and a metal melting holding furnace. Further, although aluminum is shown as an example of the “metal” of the “metal melting furnace”, low melting point metals such as zinc are also included. The aluminum melting furnace 5 includes an introduction unit 51 for introducing aluminum, a melting chamber 52 for melting the aluminum introduced from the introduction unit 51, a holding chamber 53 that is continuous with the melting chamber 52 and holds the melted aluminum melt, and a lead-out unit 54 that is continuous with the holding chamber 53. An aluminum ingot is introduced through the opening of the introduction unit 51 and introduced into the melting chamber 52. The aluminum introduced by the melting burner 55 provided in the melting chamber 52 is melted into an aluminum melt. Since the bottom surface 56 of the melting chamber 52 is inclined, the aluminum melt moves to the holding chamber 53 through the bottom surface 56 of the melting chamber 52. A holding burner 58 is provided on the ceiling portion 57 of the holding chamber 53. The holding chamber 53 communicates with a lead-out unit 54 having an open upper surface.

[0022] The lead-out section 54 is provided with a ceramic heater 10. The first temperature detection end 13 of the ceramic heater 10 detects the temperature of the molten aluminum in the lead-out section 54, and the temperature information is sent to the control unit 20, and the control unit 20 controls the ceramic heater 10. Further, a third temperature detection section 59 is provided in the lead-out section 54. The third temperature detection section 59 is a thermocouple and transmits the detected temperature information to another control unit 50. Another control unit 50 controls the heating state of the holding burner 58 according to the temperature detected by the third temperature detection section 59.

[0023] Here, the conventional heating control of the aluminum melting furnace 5 will be described with reference to FIG. 6. The aluminum melting furnace 5 itself is the same as the aluminum melting furnace 5 of the present embodiment, but is different in that the ceramic heater 10 is not installed. Conventionally, the third temperature detection section 59 detects the temperature of the lead-out section 54, and according to the detected temperature, only the holding burner 58 is burned by another control unit 50 to increase the temperature of the lead-out section 54. In this way, in the conventional case, since the temperature of the lead-out section 54 was adjusted only by the holding burner 58 in the holding chamber 52, it took time for the temperature of the lead-out section 54 to actually reach the desired temperature, and the thermal efficiency was low, and the carbon dioxide emission was large. That is, when heating the lead-out section 54 by burning the holding burner 58, the molten aluminum in the lead-out section 54 is heated after the molten aluminum in the holding chamber is heated, so the reactivity is low and it takes time to heat. Further, the temperature of the holding chamber 53 becomes higher than the desired temperature due to the holding burner 58, and the quality of the molten aluminum has deteriorated. Furthermore, in the heating by the holding burner 58, the temperature of the molten aluminum varies. Also, when heating the lead-out section 54 using an electric heater with a tube-type silicon nitride protective tube in the lead-out section 54, the size cannot be increased due to the space problem of the lead-out section 54, so a plurality of electric heaters with tube-type silicon nitride protective tubes cannot be installed, it takes time to warm up, and there is a problem that the silicon nitride protective tube is easily broken.

[0024] In contrast, in the present invention, since the shape of the ceramic body 11 of the ceramic heater 10 is plate-shaped, it can be installed along the inner wall surface of the lead-out portion 54, without interfering with the member for sucking out the molten aluminum from the lead-out portion 54. Further, since it is plate-shaped, unlike tubular parts, it is less likely to crack. Furthermore, in the present embodiment, the ceramic heater 10 can be directly inserted into the lead-out portion 54 to directly heat only the molten aluminum in the lead-out portion 54, so it can be heated more efficiently than when using the holding burner 58. Also, since gas combustion is suppressed, it is possible to suppress the emission of carbon dioxide. Moreover, it can be easily attached to the aluminum melting furnace 5 that has been conventionally used, so the convenience is also high.

[0025] Using the heating device 1 shown in Embodiment 1, when melting 1 kg of an aluminum alloy at 20°C and raising the temperature to 720°C, the amount of heat required was 22621 kcal. On the other hand, when a third temperature detection unit 59 was installed in the lead-out portion 54 as in the conventional case and the holding burner 58 was burned while monitoring the temperature of the lead-out portion 54, when melting 1 kg of an aluminum alloy at 20°C and raising the temperature to 720°C, the amount of heat required was 37852 kcal. Therefore, by using the heating device 1 shown in the present Embodiment 1, the molten aluminum in the lead-out portion 54 can be directly heated, and carbon dioxide reduction can also be achieved.

[0026] (Control Method) A control method for an aluminum melting furnace using the heating device 1 of the present embodiment will be described. During the operation of the aluminum melting furnace 5, the heating state of the lead-out portion 54 of the aluminum melting furnace is controlled by controlling the operations of the holding burner 58 and the ceramic heater 10.

[0027] The holding burner 58 is brought into an operating state by a control device (not shown) based on the temperature information detected by the third temperature detection unit 59 when the control conditions are met (YES), and is brought into a stopped state when the control conditions are not met (NO). Further, the ceramic heater 10 is brought into an operating state by a control device (not shown) based on the temperature information detected by the first temperature detection end 13 by the control unit 20 when the control conditions are met (YES), and is brought into a stopped state when the control conditions are not met (NO). Here, the respective control conditions are as follows.

[0028] · Control condition of the holding burner 58: Whether the temperature of the derivation unit 54 is less than or equal to (target temperature - 5°C: second threshold value) · Control condition of the ceramic heater 10: Whether the temperature of the derivation unit 54 based on the temperature detected by the first temperature detection end 13 is less than or equal to the target temperature (first threshold value) Note that the "target temperature" is 650 to 720°C in the case of a general aluminum alloy (for example, ADC12).

[0029] By being controlled in this way, when the temperature becomes lower than the target temperature, the ceramic heater 10 is ignited, the heating of the derivation unit 54 immediately starts, and the time for the holding burner 58 to be in the operating state is short. Thereby, it is possible to suppress gas combustion and suppress the emission of carbon dioxide. Further, since the time for the holding burner 58 to be in the operating state is short, the molten aluminum is not overheated, not only the thermal efficiency is good, but also the quality of the molten aluminum can be improved.

[0030] On the other hand, when the aluminum melting furnace 5 is shut down, the second threshold value is released, and the control conditions are changed as follows.

[0031] · Control condition of the holding burner 58: Whether the temperature of the derivation unit 54 is less than or equal to the set temperature (third threshold value) · Control condition of the ceramic heater 10: Whether the temperature of the derivation unit 54 based on the temperature detected by the first temperature detection end 13 is less than or equal to the target temperature (first threshold value) However, the set temperature is 5°C or more lower than the target temperature, for example, it is 580 to 600°C. Note that the target temperature of the ceramic heater 10 during shutdown may be equal to or lower than the target temperature during operation.

[0032] By being controlled in this way, when the first temperature detection end 13 detects that the temperature of the lead-out part 54 has become lower than the target temperature, the control part 20 ignites the ceramic heater 10, and the heating of the lead-out part 54 immediately starts. On the other hand, since the set temperature (third threshold value) for the holding burner 58 to be in the operating state is very low compared to the target temperature, the ignition of the holding burner 58 is hardly performed compared to during operation. Thereby, it is possible to further suppress the emission of carbon dioxide. Note that the holding burner 58 may be configured not to operate during shutdown. However, when the molten aluminum becomes lower than 580 to 600°C, it cannot maintain the liquid phase, and it is necessary to maintain this temperature. In such a case where the temperature becomes lower than this, since there is a possibility that the ceramic heater 10 is malfunctioning, it is preferable to set the set temperature as in this embodiment.

[0033] In the present invention, the control part 20 is a control part different from another control part 50 that controls the ceramic heater 10 and controls the holding burner 58, but is not limited thereto, and both controls may be performed by the same control part.

[0034] The present invention is not limited to the above-described embodiments. For example, in the above-described embodiments, the output of the ceramic heater 10 is only in the operating state and the stopped state, but is not limited thereto, and the output may be configured to be finely controlled according to the detected temperature of the lead-out part 54. Further, in the above-described embodiments, the aluminum melting furnace is shown as an example of the metal melting furnace, but a heating device can be similarly installed in a zinc melting furnace, an aluminum melting crucible furnace, etc., and the control method can be implemented. Note that when a heating device is installed in the zinc melting furnace, the third threshold value may be set to the temperature at which zinc can maintain the liquid phase.

Explanation of Reference Numerals

[0035] 1 Heating device 5 Aluminum melting furnace 10 Ceramic heater 11 Ceramic body 12 Heating element 13 First temperature detection end 14 Second temperature detection end 20 Control unit 21 Furnace temperature control unit 22 Overheat prevention control unit 23 Display unit 30 Connection wire 40 Mounting part 41 One end 42 Bottom surface 43 Connector 44 Flat surface part 45 Mounting part 50 Another control unit 51 Introduction part 52 Melting chamber 53 Holding chamber 54 Outlet part 55 Melting burner 56 Bottom surface 57 Ceiling part 58 Holding burner 59 Third temperature detection part

Claims

1. A heating device comprising: a ceramic heater that holds a heating element and a temperature detection unit inside a ceramic body made of ceramics; and a control unit that controls the heating state of the ceramic heater according to the temperature detected by the temperature detection unit.

2. The heating device according to claim 1, wherein the ceramic body is a plate-like body.

3. A control method for controlling the heating state of a discharge part of a metal melting furnace that melts metal introduced from an inlet and discharges the melted metal at a discharge part with an open upper surface, A control method in which a ceramic heater that holds a heating element and a temperature detection unit is fixed along the inner wall surface of the discharge part inside a ceramic body made of ceramics, and when the temperature detected by the temperature detection unit falls below a first threshold value, the ceramic heater is operated to control the heating state of the discharge part.

4. Another temperature detection unit is further provided in the discharge part, and the heating state of a holding burner in a holding chamber communicating with the discharge part is further controlled by the temperature detected by the another temperature detection unit. When the metal melting furnace is in an operating state, The control method according to claim 3, wherein when the temperature detected by the another temperature detection unit falls below a second threshold value, the holding burner is operated, and the second threshold value is lower than the first threshold value.

5. When the metal melting furnace is in a non-operating state, the setting of the second threshold value is cancelled, The control method according to claim 4, wherein when the temperature detected by the another temperature detection unit falls below a third threshold value, the holding burner is operated, and the third threshold value is lower than the second threshold value.

6. The control method according to claim 3, wherein the metal melting furnace is an aluminum melting furnace.

7. The control method according to claim 5, wherein the metal melting furnace is an aluminum melting furnace, and the third threshold value is 580 to 600 °C.

8. A control device for controlling the heating state of a discharge part of an aluminum melting furnace that melts aluminum introduced from an inlet and discharges the melted aluminum at a discharge part with an open upper surface, In the discharge part, a ceramic heater that holds a heating element and a temperature detection unit is fixed along its inner wall surface inside a ceramic body made of ceramics. An in-furnace temperature control unit that operates the ceramic heater when the temperature detected by the temperature detection unit falls below a first threshold value. Another temperature detection unit is further provided in the derivation unit. When the temperature detected by the another temperature detection unit is lower than a second threshold value, a furnace temperature control unit for operating a holding burner in a holding chamber communicating with the derivation unit is provided. The control device is characterized in that the second threshold value is set lower than the first threshold value.

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