Carbon pellet furnace and electro-thermal cupola furnace system provided with same

Abstract

The invention provides a carbon particle furnace and an electrothermal cupola furnace system provided with the same, which can ensure the soaking property of a granular carbon particle area. A furnace body refractory material (3) is provided inside a cylindrical furnace shell (2), three power supply terminal parts (4) are disposed inside the furnace shell (2) at 120 DEG intervals, and the inner sides of the furnace body refractory material (3) and the power supply terminal parts (4) are filled with granular carbon particles to form a granular carbon particle region (5). The molten raw material (M) is charged from above the center of the granular carbon particle region (5). The power supply terminal section (4) is provided with: an electrode plate (10) having an arc-shaped cross-section, the electrode plate (10) being in contact with the outer periphery of the granular carbon particle region (5); and a power supply rod (11), one end of which is coupled to the electrode plate (10) and the other end of which protrudes to the outside of the furnace case (2). Also provided is a carrier gas supply device that supplies a carrier gas using a power supply rod (11) such that the carrier gas passes through the granular carbon particle region (5) and is discharged upward toward the molten raw material (M).

Description

Technical Field

[0001] The invention relates to a carbon particle furnace and an electric heating cupola system having the same. Background Art

[0002] In the past, both at home and abroad, as melting furnaces for the production of cast iron castings, cupolas were mainly used as continuous melting furnaces, and arc furnaces and induction furnaces were mainly used as batch melting furnaces. Among these furnaces, cupolas use coke as a heat source for melting raw materials, so when the coke is burned, a large amount of CO2 gas, which is a cause of global warming, is generated. This is strongly pointed out as a major factor hindering the de-CO2 gasification action in production activities, which is currently the goal of the world.

[0003] For this reason, the casting industry is moving toward replacing cupola furnaces with induction electric furnaces. However, due to differences in raw materials and production methods from melting to casting between cupola furnaces and induction furnaces, it is necessary not only to replace the melting furnace but also to change the equipment before and after the melting furnace, which requires a lot of money and time.

[0004] However, in addition to arc furnaces and induction furnaces, there is also known a single-phase kryptol furnace using single-phase current, which passes alternating current through an aggregate of granular carbon particles using carbon and graphite as raw materials, and generates high heat by Joule heat based on the contact resistance of the granular carbon particles. In addition, a three-phase kryptol furnace using three-phase alternating current has been developed to improve such a single-phase kryptol furnace (for example, see Patent Document 1).

[0005] In addition, the inventors further studied the above-mentioned carbon particle furnace and developed a three-phase carbon particle furnace that can ensure the thermal uniformity of the granular carbon particle bed by supplying gas to the granular carbon particle bed as a heat energy transport medium, and have previously applied for a patent (Japanese Patent Application No. 2022-180233). Prior art literature Patent Literature

[0006] Patent document 1: Japanese Patent Publication No. 59-225283 Summary of the invention Technical Problems to be Solved by the Invention

[0007] The inventor of the present application has further studied the carbon pellet furnace and developed a carbon pellet furnace that can ensure the uniformity of the granular carbon particle bed by supplying gas as a heat transfer medium to the granular carbon particle bed. One object of the present invention is to provide a carbon pellet furnace that can ensure the uniformity of the granular carbon particle area.

[0008] In addition, as described above, conventional cupola furnaces generate a large amount of CO 2 when burning coke. In addition, when replacing conventional cupola furnaces with induction electric furnaces, it is also necessary to change the equipment, which requires a large amount of money and time.

[0009] In order to solve this problem, a new type of cupola furnace, an electric heating cupola furnace, which can significantly reduce the amount of coke used by partially modifying the basic structure of the conventional cupola furnace, can be considered.

[0010] Furthermore, the inventors believe that these problems can be solved by applying the principle of the above-mentioned carbon pellet furnace to a cupola furnace.

[0011] That is, it is believed that in the previous cupola furnace, there is a part at the bottom of the furnace that is filled with only a large amount of coke called bottom coke. When air is blown into this part and the coke is burned to melt the raw material, the principle of the above-mentioned carbon particle furnace is utilized. By using gas as a heat energy transport medium, the uniformity of the granular carbon particle area can be ensured, the CO2 generated by combustion can be suppressed, and the raw material can be melted efficiently.

[0012] The electric cupola system using the carbon particle furnace of the present invention aims to provide an electric cupola system, which has a basic structure in which electric thermal energy is input into the bottom coke, and the energy melts the molten raw materials existing on the top of the bottom coke along with the carrier gas, thereby suppressing the generation of CO2 gas. Technical solutions for solving technical problems

[0013] A carbon particle furnace in one embodiment of the present invention has a furnace body refractory material arranged inside a cylindrical furnace shell, a power supply terminal portion arranged on the inner side of the furnace shell, granular carbon particles are filled on the inner side of the furnace body refractory material and the power supply terminal portion to form a granular carbon particle area, and a raw material loading portion for loading molten raw materials is arranged above the granular carbon particle area, the power supply terminal portion comprises: an electrode plate in contact with the outer periphery of the granular carbon particle area; and a power supply rod, one end of which is connected to the electrode plate and the other end protrudes to the outside of the furnace shell, and a gas supply device is also provided, the gas supply device uses the power supply rod to supply gas so that the gas is discharged upward through the granular carbon particle area.

[0014] If this is done, a gas (carrier gas) serving as a transport medium for heat energy is supplied to the granular carbon particle area using a power rod, thereby ensuring thermal uniformity of the granular carbon particle area. The carrier gas is used to transport the heat energy generated in the granular carbon particle area upward, thereby efficiently heating the molten raw material loaded above the granular carbon particle area.

[0015] In addition, it is preferred that the carbon granule furnace has a plurality of the power supply terminals, which are arranged at predetermined angle intervals on the inner side of the furnace shell. In this way, power can be supplied to the granular carbon particles in the furnace shell from multiple directions, so that the electric heat energy in the furnace shell is more uniform, and the efficiency of heating the molten raw materials is improved.

[0016] In addition, the three power supply terminals of the carbon granule furnace are arranged at intervals of 120° inside the furnace shell. If so, for example, when three power supply terminals are arranged, the uniformity of power supply to the granular carbon particles in the furnace shell is improved by arranging them at intervals of 120°.

[0017] In addition, in the carbon particle furnace, preferably, the gas supply device comprises: a support frame, which is arranged on the power supply terminal portion and forms a gap portion between the furnace shell and the electrode plate; a gas channel, which is arranged on the power supply rod and supplies gas to the gap portion; and a plurality of small holes, which are arranged on the electrode plate and supply the gas from the gap portion to the granular carbon particle area.

[0018] In addition, in the carbon pellet furnace, it is preferred that the gas other than the oxidizing gas, i.e., the non-oxidizing gas, is preferably an inert gas or a reducing gas. As the inert gas, for example, nitrogen, argon, helium, etc. can be considered, and as the reducing gas, for example, hydrogen, etc. can be considered. In addition, it is considered that the gas used here can be used as long as it is a non-oxidizing gas.

[0019] In addition, in the carbon particle furnace, it is preferred that, when observed from vertically above, the granular carbon particle area has a central circular particle area and three fan-shaped particle areas radially arranged at intervals of 120° around the circular particle area, and the electrode plate has a circular arc cross-section, and the electrode plate contacts the radially outer end face of each fan-shaped particle area.

[0020] In addition, in the carbon particle furnace, it is preferred that a molten metal container is provided at the lower side of the granular carbon particle area, and the molten metal container comprises: a main body receiving portion, which is arranged at the lower side of the central part of the granular carbon particle area and holds the granular carbon particles; and a liquid discharge trough portion, which extends radially outward from the main body receiving portion and discharges the molten material to the outside, and a grounding electrode is provided through the main body receiving portion of the molten metal container.

[0021] In the carbon pellet furnace, it is more preferable that the electrode plates are provided with respect to the radially outer end faces of the respective fan-shaped pellet regions so as to cover the entire end faces.

[0022] In addition, in the carbon particle furnace, it is preferred that the main body receiving part is in the shape of a disk having a surrounding wall part having a through hole, the liquid outlet trough part is in the shape of a groove having a channel, and the interior of the surrounding wall part of the main body receiving part is connected to the channel of the liquid outlet trough part through the through hole.

[0023] In addition, in the carbon pellet furnace, it is preferred that the granular carbon particles include any one of granular carbon particles composed of coke and granular carbon particles composed of graphite. That is, it is preferred to use granular carbon particles composed of a raw material having electrical conductivity, and it is more preferred to use a raw material having high electrical conductivity. In addition, if it has electrical conductivity, it is also conceivable to use materials other than coke and graphite, such as silicon carbide.

[0024] In addition, in the carbon pellet furnace, it is preferred that, in the granular carbon particle region, the circular particle region contains granular carbon particles composed of coke, and the fan-shaped particle region contains granular carbon particles composed of graphite. If so, the fan-shaped particle region using graphite particles with low resistivity can have a low calorific value, and the circular particle region using coke particles with high resistivity can have a high heat generation force, so that a heat generating particle region with high efficiency can be formed as a whole.

[0025] An electric cupola furnace system according to one embodiment of the present invention is characterized in that it is an electric cupola furnace system comprising: a granular carbon particle bed located at the lower part of a melting furnace; and a gas supply device that supplies a carrier gas to the granular carbon particle bed so that electric heat energy is input along with the carrier gas to melt the molten raw material present on the granular carbon particle bed.

[0026] If this is done, a gas (carrier gas) serving as a transport medium for thermal energy is supplied to the granular carbon particle bed, thereby ensuring the thermal uniformity of the granular carbon particle bed. The carrier gas is utilized to transport the thermal energy generated in the granular carbon particle bed upward, thereby efficiently heating the molten raw material loaded above the granular carbon particle bed.

[0027] In addition, the electric heating cupola system is characterized by further comprising a gas circulation device for collecting the carrier gas exhausted from the melting furnace and circulating the carrier gas.

[0028] If this is done, the gas circulation device can be used to recover the used carrier gas and circulate it again as the carrier gas. Thus, the heat energy remaining in the carrier gas after use can be used without waste, and the cost can be suppressed and the environment can be taken care of.

[0029] Furthermore, in the electric cupola system, if the gas circulation device has a blower having a dust filter at the inlet side and circulating the carrier gas, the dust filter prevents gas containing a large amount of dust from directly passing through the inlet side of the blower.

[0030] In addition, in this electric cupola system, if the blower is a Roots blower and a gas cooler is provided on the upstream side of the dust filter, a certain air volume can be ensured and cooled by the gas cooler, so even high-temperature gas can be used.

[0031] In the conventional cupola, since the molten raw materials are continuously introduced, the furnace top is open, so the circulating carrier gas blown in from the coke bed contacts the outside air at the furnace top, and the outside air containing oxygen is mixed into the carrier gas.

[0032] In order to prevent this, it is preferred that a granular carbon particle bed is provided at the lower part of the melting furnace, electric heat energy is input along with the carrier gas, and the melting raw material existing on the granular carbon particle bed is melted, and a raw material charging device is provided, the raw material charging device is provided in the melting furnace, and the melting raw material is charged on the granular carbon particle bed, and the raw material charging device is of an intermittent charging type capable of charging in a state where the mixing of external air is blocked. If this is done, it is possible to prevent external air containing oxygen from mixing into the carrier gas.

[0033] In this case, if the raw material loading device includes: a raw material input chute, which is provided with a cover that can be opened and closed, and the raw materials are input; a partition valve, which divides the interior of the raw material input chute into an upper chamber of the chute and a lower chamber of the chute; an exhaust pump, which exhausts the upper chamber of the chute; and an electromagnetic valve device, which switches between exhausting the gas from the upper chamber of the chute and introducing circulating gas into the upper chamber of the chute, then a simple structure can be achieved. Effects of the Invention

[0034] According to the carbon pellet furnace of one embodiment of the present invention, it is possible to ensure thermal uniformity in the granular carbon particle region and to efficiently heat and melt the raw material.

[0035] In addition, according to the electric heating cupola system of one embodiment of the present invention, the generation of CO 2 gas can be suppressed. In another embodiment, by providing a gas circulation device, the used carrier gas can be recovered and circulated and used again as the carrier gas. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a cross-sectional view showing a schematic structure of a three-phase carbon particle furnace according to one embodiment of the present invention. Figure 2 yes Figure 1 Cross-sectional view along line AA. Figure 3 The electrode terminal portion is shown, where (a) is a front view, (b) is a top view, and (c) is a side view. Figure 4 is a circuit diagram of the electrical system of the three-phase carbon pellet furnace. Figure 5 This is a diagram showing another example of the connection method of the load resistor for three-phase AC. Figure 6 (a) and (b) are explanatory diagrams for calculating the resistance value of the fan-shaped particle region (granular carbon particle region) in a state where the fan-shaped particle region is sandwiched by two electrode terminal plates. Figure 7 This is a diagram of the granular carbon particle area viewed from vertically above. Figure 8 This is an explanatory diagram for calculating the resistance value. Fig. 9 It is a schematic diagram showing the granular carbon particle region of one phase. Fig.10 This is a schematic diagram showing a schematic configuration of an electric heating cupola system according to one embodiment of the present invention. Fig.11 This is a schematic diagram showing a raw material charging device. DETAILED DESCRIPTION

[0037] Hereinafter, an embodiment of the present invention will be described, but the present invention is not limited to the following embodiment. The following embodiment is described by taking a three-phase carbon pellet furnace as an example, but the present invention can also be applied to a multi-phase carbon pellet furnace other than a three-phase carbon pellet furnace, and can also be applied to a single-phase carbon pellet furnace.

[0038] <1. Carbon pellet furnace> Figure 1 is a cross-sectional view showing a schematic structure of a three-phase carbon particle furnace of the present invention, Figure 2 yes Figure 1 Cross-sectional view along line AA.

[0039] like Figure 1 As shown, in the three-phase carbon particle furnace 1, heat insulation plates 7A, 7B and furnace body refractory material 3 are arranged inside the cylindrical furnace shell 2, and three power supply terminals 4 are arranged at 120° intervals inside the furnace shell 2 and close to the furnace bed.

[0040] Granular carbon particles are filled inside the furnace refractory 3 and the power supply terminal 4 to form a granular carbon particle area 5, and an exhaust pipe 6 is provided on their upper side. An insulating board 7C and an exhaust pipe refractory 8 (refractory insulation bricks) are provided inside the exhaust pipe 6, and a raw material loading port 9A for loading the molten raw material M is provided in the center.

[0041] In addition, in the present embodiment, as an example, granular carbon particles using graphite as a raw material are used, but granular carbon particles using coke or silicon carbide as a raw material may also be used. For example, coke is cheaper than graphite, and has a great cost advantage when the equipment is large-scaled. In addition, by using silicon carbide in a round particle area, etc., when the melting raw material is steel, etc., it is possible to prevent carbon addition to the molten steel.

[0042] When viewed from the vertical top, the granular carbon particle region 5 has a central circular particle region 5A and three fan-shaped particle regions 5B radially arranged at intervals of 120° around the circular particle region 5A and gradually narrowing in width toward the center. In addition, fan-shaped furnace body refractory materials 3 are arranged between the fan-shaped particle regions 5B, and furnace body refractory materials 3 are also arranged on the upper side of the fan-shaped particle region 5B to the upper end of the furnace shell 2.

[0043] In addition, a raw material inlet 9B is provided corresponding to the upper center of the circular particle area 5A. The diameter of the raw material inlet 9B is substantially the same as the diameter of the circular particle area 5A, and is larger than the diameter of the raw material inlet 9A.

[0044] Each power supply terminal 4 includes: an arc-shaped electrode plate 10 (inner diameter R, height H, radius angle 60°) in cross section in contact with the outer periphery of the granular carbon particle area 5; and a power supply rod 11 having one end connected to the electrode plate 10 and the other end protruding to the outside of the furnace shell 2. In addition, the electrode plate 10 is respectively provided with respect to the radially outer end surface of each fan-shaped particle area 5B so as to cover the entire end surface and contact the entire end surface.

[0045] Granular carbon particles are filled inside the furnace refractory material 3 and each power supply terminal portion 4 to a height substantially equal to the height of the electrode plate 10, forming a granular carbon particle region 5. In addition, the power supply rod 11 is installed in the opening provided in the furnace shell 2 via an insulator 14. In addition, the heat insulation plate 7A has a thickness extending radially inward to the vicinity of the electrode plate 10.

[0046] In addition, a molten metal container 12 is provided below the granular carbon particle area 5. The molten metal container 12 is made of high temperature refractory material and comprises: a disk-shaped main body receiving portion 12A disposed below the circular particle area 5A which is the central portion of the granular carbon particle area 5; and a groove-shaped liquid outlet trough portion 12B extending radially outward from the main body receiving portion 12A to discharge the molten material to the outside.

[0047] The surrounding wall 12Aa of the main body receiving part 12A is provided with a through hole 12Ab, through which the interior of the main body receiving part 12A is connected to the channel portion of the liquid outlet tank 12B. Granular carbon particles are also filled in the main body receiving part 12A, forming a part of the circular particle area 5A. And, it is formed into a disk shape having an outer diameter substantially the same as that of the circular particle area 5A and including a cylindrical portion protruding downward, so that the molten metal dripping in the granular carbon particle area 5 can be easily collected.

[0048] Thus, the molten metal dripping in the granular carbon particle area 5 is received by the main body receiving portion 12A and discharged to the outside through the liquid discharge groove portion 12B.

[0049] A grounding electrode 13 made of graphite is provided through the main body receiving portion 12A of the molten metal container 12, and the three-phase current is stabilized. 13a is a grounding electrode terminal.

[0050] like Figure 1 as well as Figure 3 As shown, each power supply terminal 4 includes, in addition to the electrode plate 10 and the power supply rod 11, a support frame 15 that forms a gap S as a closed space between the furnace shell 2 and the electrode plate 10; a gas channel 11a that is provided in the power supply rod 11 and supplies a gas (carrier gas) as a transport medium of thermal energy to the gap S; and a plurality of small holes 10a that are provided in the electrode plate 10 and supply the carrier gas from the gap S to the granular carbon particle area 5. 16 is a power supply cable.

[0051] In each power supply terminal portion 4, a carrier gas is supplied from the power supply rod 11 through the gas passage 11a into the gap S of the support frame 15, and the carrier gas is supplied from the plurality of small holes 10a provided in the electrode plate 10 to the fan-shaped particle area 5B. Thereafter, the carrier gas flows toward the central circular particle area 5A and collides with each other, then flows upward and is discharged through the exhaust pipe 6.

[0052] In this way, a carrier gas supply device is configured to supply a carrier gas using the power supply rod 11 (gas passage 11 a ) so as to discharge the carrier gas upward toward the molten raw material M through the granular carbon particle area 5 .

[0053] The circuit of the three-phase carbon particle furnace 1 is as follows Figure 4 As shown in the figure, the power receiving cabinet 21 is connected to each power supply terminal 4 via a single-phase transformer 22. If a three-phase low-voltage, high-current AC current is supplied to the furnace 1, the granular carbon particles (granular carbon particle area 5) filled inside are heated and generate high temperature. In addition, the load resistor T1 of the three-phase AC is connected in star shape, but if Figure 5 As shown, the load resistor T2 may also be set to be connected in a triangle.

[0054] In the furnace of the present invention, the volume of the granular carbon particle area can be increased compared with the conventional furnace (refer to Japanese Patent Publication No. 59-225283), so if the input power is the same, the temperature of the high-temperature body generated becomes lower. This is suitable for melting metals with low melting points such as iron, copper, and aluminum alloys, and can be easily applied to general production furnaces.

[0055] In addition, since it is used as a production furnace, a large transformer of 500kVA or more is used. However, the resistance value of granular carbon particles is very small, so the output voltage of the secondary side of the transformer is small and the secondary current becomes large. If the secondary current becomes 30kVA or more, it is necessary to reduce the AC impedance of the secondary side conductor of the transformer as much as possible, and the secondary side conductor length must be reduced as much as possible. Therefore, the transformer is divided into three single-phase transformers and arranged very close to the electrode terminal.

[0056] (About the resistance value of the fan-shaped granular carbon particle area sandwiched by two electrode terminal plates) Next, the electrical resistance of the granular carbon particle region 5 will be described. like Figure 6 As shown in (a) and (b), metal electrode plates 52 and 53 are provided inside and outside the fan-shaped particle region 51 of height H. If an AC voltage is applied between the electrode plates 52 and 53, an AC current flows between the electrode plates 52 and 53, and the AC resistance between the electrode plates 52 and 53 at this time is calculated. If an arc portion with a thickness Δa from the center point O of the fan-shaped particle region 51 to a position at a radius a is assumed, the resistance value ΔR of the arc portion can be expressed by the following mathematical formula 1.

[0057] [Mathematical formula 1] (ρ: resistivity of granular carbon particles)

[0058] If ΔR when Δa is reduced to the limit is dR, the following mathematical formula 2 is obtained.

[0059] [Mathematical formula 2]

[0060] Therefore, the total resistance R between the electrode plates 52 and 53 is obtained by integrating dR from a1 to a2, and thus becomes the following mathematical formula 3.

[0061] [Mathematical formula 3]

[0062] The supplied carrier gas absorbs the Joule heat generated in the granular carbon particle region 5 (the circular particle region 5A and the fan-shaped particle region 5B) and becomes high temperature. The temperature at this time is given by the following mathematical formula 4.

[0063] [Formula 4] ΔTg=heating temperature of gas ℃ Eg = input power kW η = heat absorption efficiency of the gas Vg = gas flow rate Nm 3 / hr γg=Specific gravity of gas kg / Nm 3 Cp = constant pressure specific heat of gas kJ / kg℃

[0064] For example, if the carrier gas is argon, and the values ​​are: Eg = 30 kW, η = 0.8, Vg = 60 Nm 3 / h,γg=1.784kg / Nm 3 , Cp = 0.522 kJ / kg℃, which becomes the following mathematical formula 5.

[0065] [Mathematical formula 5]

[0066] The retained heat of the high-temperature gas is used to heat and melt the molten raw material placed on the upper part of the circular particle area 5A. That is, the inert gas supplied from the power supply terminal 4 becomes a transport medium (carrier gas) for the heat energy generated in the granular carbon particle area 5. In addition, after the carrier gas is used for heating and melting the raw material, if it is recovered through a gas cooler and a dust collector, it can be reused as the carrier gas supplied from the power supply terminal 4, which is very economical.

[0067] (About the resistance value when three-phase AC electricity flows in the circular particle area of ​​height H) like Figure 7 As shown in FIG. 6 , if the diameter of the circular particle region 5A of the granular carbon particle region 5 is set to D, the other dimensions are expressed by the following mathematical formula 6.

[0068] [Mathematical formula 6] r2=0.7D

[0069] The value of r2 can be determined arbitrarily, and is set to 0.7D here.

[0070] Furthermore, since it is a three-phase furnace, a three-phase alternating current flows from the three electrode plates 10 into the fan-shaped particle region 5B of the granular carbon particle region 5, and the granular carbon particle region 5 (thickness H) becomes a three-phase load resistor.

[0071] exist Figure 8 In the figure, three regions are assumed, namely, the R1 region, the R3 region, and the R2 region between them. The region where these three regions are combined basically overlaps with the region of the granular carbon particles surrounded by the thick line. Therefore, if the regional resistance values ​​of R1, R2, and R3 are obtained, the resistance value R of the region of the granular carbon particles can be approximated by the resistance value obtained by adding the three resistance values, so the three resistance values ​​are obtained. Furthermore, if the formula of the above-mentioned mathematical formula 3 is applied to R1, it can be expressed by the following mathematical formula 7.

[0072] [Formula 7] θ. : H: Height of the granular carbon particle area

[0073] If R3 is expressed similarly, it becomes the following mathematical formula 8.

[0074] [Mathematical formula 8]

[0075] As for the R2 portion, it is difficult to obtain the resistance value in its original shape, so the resistance value is obtained by replacing it with a rectangular region of 0.8L×0.8B (see Fig. 9 ).

[0076] [Mathematical formula 9]

[0077] In the above formula, θ1=60°=π / 3, θ2=90°=π / 2. Substituting these into the above formula, the equation becomes Mathematical Formula 10, and R can be calculated.

[0078] [Formula 10]

[0079] In this formula, attention should be paid to the value that does not include D. The diameter D of the circular granular carbon particle area is the reference circle diameter that becomes the basis for determining the size of the furnace, but it is found that the three-phase AC load resistance R has nothing to do with the size of D and is determined by the height H of the granular carbon particle area and the resistivity ρ of the granular carbon particles.

[0080] According to the above furnace, the granular carbon particle area in the central part is made circular, and the three-phase electrode current from the power supply terminal part 4 diffusely flows through the fan-shaped particle area 5B to the circular particle area 5A, so that the particle area as a whole becomes a heating area. Since the high temperature generated by supplying a current commensurate with the size of the granular carbon particle area 5 can be freely set, there is no limit to the size of the equipment, and it can be a high-temperature generating furnace of any size. Therefore, it is suitable for the production furnace of metals and metal oxides with a melting temperature of about 1000°C to 1800°C.

[0081] As the electrode terminal, a metal electrode plate 10 with a circular arc cross section is used instead of a graphite electrode rod, and a granular carbon particle area 5 (fan-shaped particle area 5B) is provided inside the electrode plate 10, thereby increasing the contact area between the electrode plate 10 and the granular carbon particle area 5 (fan-shaped particle area 5B), and reducing the heat generated by the contact resistance in this part as much as possible. The power loss of the power supply terminal 4 can be reduced, and the enlargement of the furnace equipment becomes easy.

[0082] Thus, the power supply terminal portion 4 does not tend to reach a high temperature, so water cooling is not required, and cooling using a carrier gas (air cooling) can be used. Therefore, the three-phase carbon particle furnace of the present invention has the following effects.

[0083] (i) Ensure thermal uniformity in the central granular carbon particle region. An inert gas such as argon or nitrogen is supplied as a carrier gas from the power supply terminal 4 toward the granular carbon particle area 5, thereby averaging the local uneven heat generation generated in the granular carbon particle area 5, ensuring the uniformity of heat throughout the entire granular carbon particle area 5, and efficiently heating and melting the raw material M.

[0084] (ii) The outlet temperature of the carrier gas can be freely changed by balancing the power input to the granular carbon particle area 5 and the carrier gas. In addition to the heat loss from the furnace structure, most of the heat energy of the power input to the granular carbon particle area 5 is absorbed by the carrier gas. Therefore, when the power input is constant, the outlet temperature of the gas changes inversely proportional to the gas flow rate, so the outlet temperature of the gas can be freely controlled by the gas flow rate.

[0085] (iii) No CO2 gas will be generated due to combustion. Since CO2 gas is not generated due to combustion, it is a production equipment that can achieve decarburization. In the past, in the vertical continuous melting furnace (such as cupola furnace, etc.) used in the production site, coke combustion was used to obtain high temperature, so a large amount of CO2 gas was generated. However, if it is an electric heating cupola furnace of the present invention, it can make a greater contribution to the degasification of CO2 at the production site of castings.

[0086] (iv) Easy to start and stop. Since only electricity is used as a heat source, the furnace can be easily started and stopped like a general electric furnace. When starting a continuous melting furnace using fossil fuels such as coke, heavy oil, and gas, it often takes time for the furnace condition to stabilize, but when starting the furnace of the present invention, a high temperature stable state can be obtained by simply supplying a starting current to the granular carbon particle area for a short time, so the workability at the production site becomes very good.

[0087] <2. Electric Heating Cupola System> Next, an electric heating cupola system including the three-phase carbon granule furnace as a melting furnace will be described. Fig.10 This is a schematic diagram showing an electric heating cupola system as one embodiment of the present invention.

[0088] like Fig.10 As shown, the electric heating cupola system 100 utilizes the above Figure 1 The three-phase carbon granule furnace 1 shown is used as a melting furnace. In addition, a granular carbon granule area 5 serving as a granular carbon granule bed is provided at the lower portion of the three-phase carbon granule furnace 1, and electric heat energy is introduced into the granular carbon granule area 5 along with a carrier gas to melt the melting raw material M present on the granular carbon granule area 5.

[0089] In addition, a space for storing gas is provided at the top of the three-phase carbon granule furnace 1, and a raw material loading device 103 for loading the molten raw material is provided on the granular carbon particle area 5. In addition, a circulating gas outlet 112 is provided in the space located at the top of the three-phase carbon granule furnace 1, and a gas circulation device 104 for collecting and recycling the carrier gas discharged from the circulating gas outlet 112 is provided.

[0090] The gas circulation device 104 connects the circulating gas outlet 112 and the power supply terminal 4, and has a blower 104a for circulating the carrier gas in the middle, and a dust filter 104b is provided at the inlet side of the blower 104a. The blower 104a is a Roots blower driven by a motor 104c, and a gas cooler 104d is provided at the upstream side of the dust filter 104b.

[0091] Here, the gas circulation blower 104a is the center of the gas circulation device 104. As the blower, a Roots blower that can easily ensure a certain air volume is the most suitable in this system. However, a general Roots blower has a relatively fine structure and cannot allow gas containing a large amount of dust to pass directly, so a dust filter 104b is provided on the inlet side of the blower 104a.

[0092] Depending on the structural material of the dust filter 104b, it may not be applicable to high-temperature gas, so the carrier gas discharged from the top of the three-phase carbon particle furnace 1 is cooled by the gas cooler 104d. There are many types of gas coolers such as air cooling and water cooling, and the most suitable cooler can be selected for this system.

[0093] The raw material charging device 103 is of an intermittent charging type capable of charging (putting in) in a state where the mixing of external air is blocked. Fig.11 As shown, the raw material loading device 103 comprises: a raw material feeding chute 106, which is equipped with a cover 105 and is arranged on the top of the furnace; a shut-off valve 107, which divides the interior of the raw material feeding chute into an upper chute chamber 106A and a lower chute chamber 106B; an exhaust pump 108, which exhausts the upper chute chamber 106A; and an electromagnetic valve device 109, which switches between exhausting the chute upper chamber 106A and introducing circulating gas into the chute upper chamber 106A.

[0094] The upper portion of the raw material input chute 106 is formed into a mortar shape for inputting raw materials, while the lower portion is cylindrical, and its lower end is inserted into the raw material loading port 9A which is the hollow portion in the center of the exhaust pipe 6. In addition, the cover 105 is opened and closed by the first cylinder 110A, and the shutoff valve 107 is opened and closed by the second cylinder 110B.

[0095] In addition, the electromagnetic valve device 109 includes: a first electromagnetic switch valve 109A, which is provided on a first passage 111A connecting the exhaust pump 108 and the chute upper chamber 106A; and a second electromagnetic switch valve 109B, which is provided on a second passage 111B connecting the circulating gas exhaust port 112 and the first passage 111A.

[0096] When the molten raw material is introduced, first, the lid 105 of the raw material introduction chute 106 is opened, and a certain amount of raw material is introduced into the chute upper chamber 106A while the isolation valve 107 is closed. Then, the lid 105 is closed, the second electromagnetic valve 109B is closed, and the first electromagnetic valve 109A is opened, so that the chute upper chamber 106A is sealed.

[0097] Then, the exhaust pump 108 is operated to exhaust the outside air in the chute upper chamber 106A until the pressure reaches 100 kPa, for example. Then, the first electromagnetic valve 109A is closed, the second electromagnetic valve 109B is opened, and the circulating gas is introduced into the chute upper chamber 106A from the circulating gas outlet 112. Then, the shutoff valve 107 is opened to charge the raw material into the furnace.

[0098] Such a series of operations are repeated intermittently at regular intervals, and the raw materials are intermittently charged into the furnace while preventing the mixing of external air. That is, it becomes an intermittent charging type that can charge in a state where the mixing of external air is blocked.

[0099] like Figure 1 As shown, the three-phase carbon particle furnace 1 is provided with heat insulation plates 7A, 7B and furnace body refractory material 3 inside a cylindrical furnace shell 2, and three power supply terminals 4 are arranged at intervals of 120 degrees in a portion which is the inner side of the furnace shell 2 and close to the furnace bed.

[0100] The inner side of the furnace body refractory material 3 and the power supply terminal part 4 is filled with granular carbon particles, forming a granular carbon particle area 5 that becomes a granular carbon particle bed, and an exhaust pipe 6 is provided on the upper side thereof. An insulating plate 7C and an exhaust pipe refractory material 8 (refractory insulation bricks) are provided inside the exhaust pipe 6, and a raw material loading port 9A for loading the molten raw material M is provided in the center.

[0101] like Figure 2 As shown in the figure, when viewed from vertically above, the granular carbon particle region 5 has a central circular particle region 5A and three fan-shaped particle regions 5B which are radially arranged around it at intervals of 120° and whose widths gradually narrow toward the center. In addition, fan-shaped furnace body refractory materials 3 are respectively arranged between the fan-shaped particle regions 5B, and furnace body refractory materials 3 are also arranged on the upper side of the fan-shaped particle region 5B to the upper end of the furnace shell 2.

[0102] In addition, a raw material inlet 9B is provided corresponding to the upper center of the circular particle area 5A. The diameter of the raw material inlet 9B is substantially the same as the diameter of the circular particle area 5A, and is larger than the diameter of the raw material inlet 9A.

[0103] Each power supply terminal portion 4 includes an arc-shaped electrode plate 10 (inner diameter R, height H, radius angle 60°) in cross section that contacts the outer periphery of the granular carbon particle area 5, and a power supply rod 11 whose one end is connected to the electrode plate 10 and the other end protrudes to the outside of the furnace shell 2. In addition, the electrode plate 10 is respectively provided with respect to the radially outer end surface of each fan-shaped particle area 5B so as to cover the entire end surface and contact the entire end surface.

[0104] The inner side of the furnace body refractory material 3 and each power supply terminal part 4 is filled with granular carbon particles to a height substantially the same as the height of the electrode plate 10, forming a granular carbon particle area 5 as a granular carbon particle bed. In addition, the power supply rod 11 is installed in the opening provided in the furnace shell 2 via an insulator 14. In addition, the heat insulation plate 7A has a thickness extending inward in the radial direction to the vicinity of the electrode plate 10.

[0105] In addition, a molten metal container 12 is provided below the granular carbon particle area 5. The molten metal container 12 is made of high temperature refractory material and comprises: a disk-shaped main body receiving portion 12A disposed below the circular particle area 5A which is the central portion of the granular carbon particle area 5; and a groove-shaped liquid outlet trough portion 12B extending radially outward from the main body receiving portion 12A to discharge the molten material to the outside.

[0106] The surrounding wall 12Aa of the main body receiving part 12A is provided with a through hole 12Ab, through which the interior of the main body receiving part 12A is connected to the channel portion of the liquid outlet tank 12B. Granular carbon particles are also filled in the main body receiving part 12A, forming a part of the circular particle area 5A. And, it is formed into a disk shape having an outer diameter substantially the same as that of the circular particle area 5A and including a cylindrical portion protruding downward, so that the molten metal dripping in the granular carbon particle area 5 can be easily collected.

[0107] Thus, the molten metal dripping in the granular carbon particle area 5 is received by the main body receiving portion 12A and discharged to the outside through the liquid discharge groove portion 12B.

[0108] A graphite grounding electrode 13 is provided through the main body receiving portion 12A of the molten metal container 12 to stabilize the three-phase current. 13a is a grounding electrode terminal, and 16 is a power supply cable.

[0109] like Figure 3 As shown, each power supply terminal portion 4, in addition to the electrode plate 10 and the power supply rod 11, also includes: a support frame 15, which forms a gap portion S as a closed space between the furnace shell 2 and the electrode plate 10; a gas channel 11a, which is arranged on the power supply rod 11 and supplies a carrier gas as a transport medium for thermal energy to the gap portion S; and a plurality of small holes 10a, which are arranged on the electrode plate 10 and supply a carrier gas from the gap portion S to the granular carbon particle area 5.

[0110] In each power supply terminal portion 4, a carrier gas is supplied from the power supply rod 11 through the gas passage 11a into the gap S of the support frame 15, and the carrier gas is supplied from the plurality of small holes 10a provided in the electrode plate 10 to the fan-shaped particle area 5B. Thereafter, the carrier gas flows toward the central circular particle area 5A and collides with each other, then flows upward and is discharged through the exhaust pipe 6.

[0111] In this way, a carrier gas supply device is configured to supply a carrier gas using the power supply rod 11 (gas passage 11 a ) so as to discharge the carrier gas upward toward the molten raw material M through the granular carbon particle area 5 .

[0112] Here, as a method of converting electrical energy into thermal energy inside the electric heating cupola, the contact resistance of carbon granules is used. In order to prevent the carbon granules from being digested, the carrier gas used as a transport medium for transferring the thermal energy to the raw material must absolutely not contain non-oxidizing gases. In addition, the carrier gas also needs to have high temperature stability such as not decomposing or ionizing at a high temperature of several thousand degrees.

[0113] As the gas that meets these requirements, argon or nitrogen is used, for example. These gases are easily available at common production sites and are most suitable as carrier gases, but because they are relatively expensive, they are circulated in the system and a carrier gas supply device is provided.

[0114] In addition, if Fig.10 As shown, the three-phase carbon granule furnace 1 is configured to be connected to each power supply terminal 4 from the power receiving cabinet 121 via the single-phase transformer 122. If a three-phase low-voltage, high-current AC current is supplied to the furnace 1, the granular carbon particles (granular carbon particle area 5) filled inside are heated and generate high temperature. In addition, the load resistor of the three-phase AC is connected in star shape, but it can also be connected in triangle shape.

[0115] Such a three-phase carbon particle furnace 1 can increase the volume of the granular carbon particle area compared with the conventional furnace (refer to Japanese Patent Publication No. 59-225283), so if the input power is the same, the temperature of the high-temperature body generated is lower. This is suitable for melting metals with low melting points such as iron, copper, and aluminum alloys, and can be easily applied to general production furnaces.

[0116] In addition, since it is used as a production furnace, a large transformer of 500kVA or more is used. However, since the resistance value of the granular carbon particles is very small, the secondary output voltage of the transformer is small and the secondary current becomes large. If the secondary current becomes 30kVA or more, it is necessary to reduce the AC impedance of the secondary conductor of the transformer as much as possible, and the secondary conductor length must be reduced as much as possible. Therefore, the transformer is divided into three single-phase transformers and arranged very close to the power supply terminal 4.

[0117] Furthermore, the central part of the furnace shell 2 is made circular, and the three-phase electrode current from the power supply terminal 4 diffuses and flows through the fan-shaped particle area 5B to the circular particle area 5A, so that the particle area portion as a whole becomes a heat generation area. The high temperature generated by supplying a current commensurate with the size of the granular carbon particle area 5 can be freely set, so there is no limit to the size of the equipment, and it can be a high-temperature generating furnace of any size. Therefore, it is suitable for the production furnace of metals and metal oxides with a melting temperature of about 1000°C to 1800°C.

[0118] As the electrode terminal, a metal electrode plate 10 with an arc-shaped cross section is used instead of a graphite electrode rod, and a granular carbon particle area 5 (fan-shaped particle area 5B) is provided inside the electrode plate 10, so that the contact area between the electrode plate 10 and the granular carbon particle area (fan-shaped particle area 5B) is increased, and the heat generated by the contact resistance in this part can be reduced as much as possible. The power loss of the power supply terminal 4 can be reduced, and the enlargement of the furnace equipment becomes easy.

[0119] In this way, since the power supply terminal portion 4 will not become too high a temperature, water cooling is not required, and it can be handled by cooling (air cooling) based on a carrier gas. Therefore, such a three-phase carbon particle furnace 1 (i) can ensure the uniformity of the granular carbon particle area in the central part. That is, since an inert gas such as argon gas and nitrogen gas is supplied as a carrier gas from the power supply terminal portion 4 toward the granular carbon particle area 5, the local uneven heat generation generated in the granular carbon particle area 5 is averaged, and the uniformity of the entire granular carbon particle area 5 can be ensured, and the raw material M can be efficiently heated and melted.

[0120] (ii) The outlet temperature of the carrier gas can be freely changed by the balance between the power input to the granular carbon particle area 5 and the carrier gas. That is, the power input to the granular carbon particle area 5, in addition to the heat loss from the furnace structure, most of the heat energy is absorbed by the carrier gas. Therefore, when the input power is constant, the outlet temperature of the gas changes inversely proportional to the gas flow rate, so the outlet temperature of the gas can be freely controlled by the gas flow rate.

[0121] (iii) Since no CO2 gas is generated by combustion, it is a production facility that achieves decarburization. In the past, in the vertical continuous melting furnace (such as a cupola furnace, etc.) used in the production site, coke combustion was used to obtain high temperatures, so a large amount of CO2 gas was generated. However, if it is an electric heating cupola furnace of the present invention, it can make a greater contribution to the degasification of CO2 at the production site of castings.

[0122] According to the above-mentioned structure, when only materials with a high carbon content such as pig iron or cast iron return scraps are used as raw materials for melting, CO 2 gas is not generated in principle.

[0123] However, when using iron scraps to reduce the cost of raw materials, coke must be used as a carburizing material in the raw materials, and a part of the coke combines with the oxygen of the iron oxide contained in the raw materials to generate CO2 gas, which is mixed into the carrier gas. However, the proportion is very small compared to the conventional cupola, so it can be solved by installing a CO2 gas removal device in the gas circulation device.

[0124] In an electric heating cupola, the melting temperature can be freely controlled within a certain range by balancing the input power and the carrier gas flow rate.

[0125] The electric cupola is also a type of electric furnace. Therefore, the furnace is easy to start and stop, which is a characteristic of all electric furnaces, and the length of the furnace operation time can be freely set.

[0126] As a method of converting electrical energy into thermal energy inside the cupola, the principle of a three-phase carbon granule furnace (see Japanese Patent Application No. 2022-180233) is adopted, but the application of this principle has nothing to do with the size of the furnace. Therefore, when applied to an electric heating cupola, it can be implemented in furnaces of any size regardless of the size of the equipment.

[0127] <3. Other Implementation Methods> As mentioned above, although the preferred embodiment of the present invention has been described with reference to the drawings, various additions and changes can be made without departing from the gist of the present invention.

[0128] In the above embodiment, argon or nitrogen, which are inert gases, are used as carrier gases, but inert gases or reducing gases other than these may also be used. By using reducing gases such as hydrogen, when the raw material to be melted is a metal oxide such as iron ore, reduction melting of the raw material can also be performed. In addition, as a carrier gas, it is considered that any gas other than an oxidizing gas or a non-oxidizing gas can be used.

[0129] In addition, in the above-mentioned embodiment, as an example, granular carbon particles using graphite as a raw material are used, but granular carbon particles using coke or silicon carbide as a raw material can also be used. For example, in the granular carbon particle area 5, granular carbon particles composed of coke can be included in the circular particle area 5A, and granular carbon particles composed of graphite can be included in the fan-shaped particle area 5B. The price of coke is lower than that of graphite, and it has a great cost advantage in the case of large-scale equipment. In addition, by using silicon carbide in the circular particle area, etc., when the melting raw material is steel, etc., it is possible to prevent carbon addition to molten steel. Therefore, such a method is also included in the scope of the present invention. Description of reference numerals:

[0130] 1: three-phase carbon particle furnace; 2: furnace shell; 3: furnace body refractory material; 4: power supply terminal; 5: granular carbon particle area; 5A: circular particle area; 5B: fan-shaped particle area; 6: exhaust pipe; 7A, 7B: insulation board; 8: exhaust pipe refractory material; 9A, 9B: raw material loading port; 10: electrode plate; 10a: small hole; 11: power supply rod; 11a: gas channel; 12: molten metal container; 12A: main body receiving part; 12Aa: surrounding wall; 12Ab: through hole; 12B: liquid outlet trough; 13: grounding electrode; 13a: grounding electrode terminal; 14: insulation ; 15: Support frame; 16: Power supply cable; 100: Electric cupola system; 103: Raw material loading device; 104: Gas circulation device; 104a: Blower; 104b: Dust filter; 104c: Motor; 104d: Gas cooler; 105: Cover; 106: Raw material feeding chute; 106A: Upper chamber of chute; 106B: Lower chamber of chute; 107: Shutoff valve; 108: Exhaust pump; 109: Solenoid valve device; 110A, 110B: Cylinder; 111A, 111B: Passage; 112: Circulating gas exhaust port; M: Melting raw material; S: Gap portion.

Claims

1. A carbon pellet furnace, characterized in that: A furnace body refractory material is arranged inside the cylindrical furnace shell, a power supply terminal portion is arranged inside the furnace shell, and granular carbon particles are filled inside the furnace body refractory material and the power supply terminal portion to form a granular carbon particle area. A raw material loading portion for loading a molten raw material is arranged above the granular carbon particle area. The power supply terminal portion includes: an electrode plate in contact with the outer periphery of the granular carbon particle area; and a power supply rod, one end of which is connected to the electrode plate and the other end of which protrudes to the outside of the furnace shell. A gas supply device is further provided, and the gas supply device supplies gas using the power supply rod so that the gas passes through the granular carbon particle area and is discharged upward.

2. The carbon pellet furnace according to claim 1, characterized in that: The carbon pellet furnace includes a plurality of the power supply terminal portions. The plurality of power supply terminal portions are arranged inside the furnace shell at predetermined angular intervals.

3. The carbon pellet furnace according to claim 1, characterized in that: The carbon pellet furnace includes three power supply terminal portions. The three power supply terminal portions are arranged inside the furnace shell at intervals of 120°.

4. The carbon pellet furnace according to claim 1, characterized in that: The gas supply device comprises: A support frame is provided at the power supply terminal portion to form a gap portion between the furnace shell and the electrode plate; a gas channel, provided on the power supply rod, for supplying gas to the gap; and A plurality of small holes are provided in the electrode plate to supply the gas from the gap portion to the granular carbon particle region.

5. The carbon particle furnace according to claim 1, characterized in that: The gas is a gas other than an oxidizing gas.

6. The carbon pellet furnace according to claim 1, characterized in that: The gas is an inert gas such as nitrogen and argon or a reducing gas such as hydrogen.

7. The carbon particle furnace according to claim 3, characterized in that: When viewed from vertically above, the granular carbon particle region includes a central circular particle region and three fan-shaped particle regions radially arranged around the circular particle region at intervals of 120°. The electrode plate has a circular arc cross section. The electrode plate is in contact with the radially outer end surface of each of the sector-shaped particle regions.

8. The carbon pellet furnace according to claim 1, characterized in that: A molten metal container is provided below the granular carbon particle area. The molten metal container comprises: a main body receiving portion arranged below the central portion of the granular carbon particle area to hold the granular carbon particles; and a liquid discharge groove portion extending radially outward from the main body receiving portion to discharge the molten material to the outside.

9. The carbon particle furnace according to claim 8, characterized in that: A ground electrode is provided through the center of the main body receiving portion of the molten metal container.

10. The carbon particle furnace according to claim 7, characterized in that: The electrode plates are respectively disposed with respect to the radially outer end surfaces of the sector-shaped particle regions so as to cover the entire end surfaces.

11. The carbon particle furnace according to claim 8, characterized in that: The main body receiving portion is in the shape of a disk provided with a surrounding wall portion having a through hole, The liquid outlet groove is in the shape of a groove having a channel. The interior of the surrounding wall portion of the main body receiving portion is connected to the channel of the liquid outlet groove portion through the through hole.

12. The carbon pellet furnace according to claim 1, characterized in that: The granular carbon particles include either granular carbon particles consisting of coke or granular carbon particles consisting of graphite.

13. The carbon particle furnace according to claim 7, characterized in that: In the granular carbon particle region, The circular particle region contains granular carbon particles composed of coke. The sector-shaped particle region contains granular carbon particles composed of graphite.

14. An electric heating cupola system, which is an electric heating cupola system, characterized in that: The electric heating cupola system comprises the carbon granule furnace according to any one of claims 1 to 13 as a melting furnace, The electrothermal cupola system has: a bed of granulated carbon particles located in a lower portion of the smelting furnace; and A gas supply device supplies a carrier gas to the granular carbon particle bed. The electric heat energy is introduced along with the carrier gas to melt the melting raw material existing on the granular carbon particle bed.

15. The electric cupola system according to claim 14, characterized in that: The electric cupola system further includes a gas circulation device that collects the carrier gas exhausted from the melting furnace and circulates the carrier gas for use.

16. The electric cupola system according to claim 15, characterized in that: The gas circulation device includes a blower having a dust filter at an inlet side and circulating the carrier gas.

17. The electric cupola system according to claim 16, characterized in that: The blower is a Roots blower, and a gas cooler is provided on the upstream side of the dust filter.

18. The electric cupola system according to claim 14, characterized in that: The electrothermal cupola system further comprises a raw material charging device, which is disposed in the melting furnace and charges the melting raw material onto the granular carbon particle bed. The raw material charging device is of an intermittent charging type capable of charging in a state where mixing of external air is blocked.

19. The electric cupola system according to claim 18, characterized in that: The raw material charging device comprises: The raw material is put into the chute, which is provided with a cover which can be opened and closed, and the raw material is put into the chute; A cut-off valve is used to divide the raw material input into the chute into an upper chamber and a lower chamber of the chute; An exhaust pump for exhausting the upper chamber of the chute; as well as The electromagnetic valve device switches between exhausting the gas from the upper chamber of the chute and introducing the circulating gas into the upper chamber of the chute.

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