JP7253857B1 - three-phase kryptol furnace - Google Patents

Abstract

An object of the present invention is to ensure uniform heating in a kryptol grain region. SOLUTION: A furnace body refractory 3 is provided inside a cylindrical furnace shell 2, three power supply terminal portions 4 are arranged inside the furnace shell 2 at intervals of 120°, and the furnace body refractory 3 and the power supply terminal portion are arranged. Kryptol grains are filled inside 4 to form a kryptol grain region 5 . The melted raw material M is charged from above the center of the kryptol grain region 5 . The power supply terminal portion 4 includes an electrode plate 10 having an arcuate cross section that contacts the outer periphery of the kryptor grain region 5, and a power supply rod 11 having one end coupled to the electrode plate 10 and the other end projecting outside the furnace shell 2. have Furthermore, a carrier gas supply means is provided for supplying a carrier gas using a power supply rod 11 so as to be discharged upwardly through the kryptol grain region 5 toward the raw material M to be melted. [Selection diagram] Fig. 1

Description

The present invention relates to a three-phase kryptol furnace.

A single-phase kryptor furnace using a single-phase current is known, which utilizes high heat generated by Joule heat due to the contact resistance of the kryptol grains by passing an alternating current through an aggregate of kryptol grains made of carbon or graphite.

Therefore, such a single-phase kryptol furnace has been improved to develop a kryptol furnace using a three-phase alternating current, and a small ultra-high temperature melting furnace for research laboratories has been previously proposed (see, for example, Patent Document 1).

JP-A-59-225283

The inventor has further advanced the research and developed a three-phase kryptal furnace that can ensure uniform heating in the kryptol grain region by supplying gas as a thermal energy carrier medium to the kryptol grain region.

The present invention provides a three-phase kryptol furnace capable of ensuring uniform heating in the kryptol grain region.

A three-phase kryptol furnace according to one aspect of the present invention includes a furnace body refractory provided inside a cylindrical furnace shell, three power supply terminal portions arranged at intervals of 120° inside the furnace shell, and the furnace A three-phase kryptol furnace in which kryptol grains are filled inside the body refractory and the power supply terminal portion to form a kryptol grain region, and a raw material charging portion for charging the molten raw material is arranged above the kryptol grain region. , the power supply terminal portion has an electrode plate in contact with the outer periphery of the kryptor grain region, and a power supply rod having one end coupled to the electrode plate and the other end protruding outside the furnace shell, and A gas supply means is provided for supplying gas using the power supply rod so as to be discharged upward through the kryptor grain region.

In this way, a gas (carrier gas) as a medium for transporting thermal energy is supplied to the kryptol grain domains using the power supply rod, and the thermal uniformity of the kryptol grain domains is ensured. The generated thermal energy is transported upwards and efficiently heats the charged melted raw material above the kryptol grain area.

The gas supply means includes a support frame provided in the power supply terminal portion and forming a gap between the furnace shell and the electrode plate, and a gas passage provided in the power supply rod for supplying gas to the gap. and a plurality of small holes provided in the electrode plate for supplying the gas from the void to the kryptor grain region.

Moreover, the gas is preferably a gas other than an oxidizing gas, that is, a non-oxidizing gas, and is preferably an inert gas or a reducing gas. Examples of the inert gas include nitrogen, argon, and helium, and examples of the reducing gas include hydrogen. In addition, it is thought that the gas used for this can be utilized if it is non-oxidizing gas.

The kryptoll grain region has a central circular grain region and three fan-shaped grain regions radially provided around it at intervals of 120°, and the electrode plate has a circular cross section. It is desirable that the electrode plate is in arcuate shape, and that the electrode plate is in contact with the radially outer end face of each sector-shaped grain region.

Further, a molten metal receiver is provided below the cryptotol grain region, and the molten metal receiver is arranged below the central portion of the cryptotol grain region and holds the cryptotol grains. It is desirable that the molten metal receiver has a discharge gutter portion that extends radially outward and discharges the molten metal to the outside, and that a ground electrode is provided through the body receiving portion of the molten metal receiver.

Further, it is preferable that the electrode plate is provided so as to cover the entire end surface of each of the fan-shaped grain regions on the radially outer side.

The main body receiving portion has a dish shape provided with a surrounding wall portion having a through hole, the hot water discharge gutter portion has a gutter shape having a passage, and the inside of the surrounding wall portion of the main body receiving portion is It is desirable to be connected to the passage of the hot water outlet gutter portion through the through hole.

In addition, it is preferable that the Kryptol grains include either Kryptol grains made of coke or Kryptol grains made of graphite. That is, it is preferable to use kryptol grains made of a conductive raw material, and it is more preferable to use a highly conductive raw material. It should be noted that materials other than coke and graphite, such as silicon carbide, may be used as long as they have electrical conductivity.

In the kryptol grain region, it is preferable that the circular grain region contain kryptol grains made of coke, and the fan-shaped grain region contain kryptol grains made of graphite. In this way, the calorific value of the fan-shaped grain regions using graphite grains with a low specific resistance can be reduced, and the heating power of the circular grain regions using coke grains with a high specific resistance can be increased. It is possible to configure an efficient heat generating grain region as

The present invention can ensure uniform heating in the kryptol grain region, freely change the outlet temperature of the gas by adjusting the balance between the power supplied to the kryptol grains and the gas, and efficiently heat the raw material to be dissolved. And it does not generate _CO2 gas and is easy to start and stop.

1 is a cross-sectional view showing a schematic structure of a three-phase kryptor furnace according to the present invention; FIG. FIG. 2 is a cross-sectional view taken along line AA of FIG. 1; An electrode terminal part is shown, (a) is a front view, (b) is a top view, (c) is a side view. It is a circuit diagram of the electrical system of the three-phase Kryptor furnace. FIG. 5 is a diagram showing another example of connection of load resistors for three-phase alternating current; (a) and (b) are explanatory diagrams for calculating the resistance value of a fan-shaped grain region (cryptol grain region) sandwiched between two electrode terminal plates. It is the figure which looked at the kryptol grain region from the perpendicular upper part. FIG. 3 is a schematic diagram showing a kryptol grain region for one phase. FIG. 4 is an explanatory diagram for calculating a resistance value;

An embodiment according to the present invention will be described below, but the present invention is not limited to the following embodiment. FIG. 1 is a cross-sectional view showing the schematic structure of a three-phase kryptol furnace according to the present invention, and FIG. 2 is a cross-sectional view taken along line AA of FIG.

As shown in FIG. 1, a three-phase kryptol furnace 1 is provided with heat insulating boards 7A and 7B and a furnace body refractory 3 inside a cylindrical furnace shell 2. Three power supply terminal portions 4 are arranged at intervals of 120° in the portion.

The inside of the furnace body refractory 3 and the power supply terminal portion 4 is filled with kryptol grains to form a kryptol grain region 5, and an exhaust pipe 6 is provided above them. An insulating board 7C and an exhaust stack refractory 8 (refractory heat insulating brick) are provided inside the exhaust stack 6, and a raw material charging port 9A for charging the molten raw material M is provided in the center.

In the present embodiment, as an example, kryptol grains made from graphite are used, but kryptol grains made from coke or silicon carbide can also be used. For example, coke is cheaper than graphite, and it has a great cost advantage when the equipment is enlarged. In addition, by using silicon carbide in the circular grain regions and the like, it is possible to prevent recarburization of molten steel when the raw material for melting is steel.

The cryptol grain region 5 is composed of a circular grain region 5A in the center and three fan-shaped grain regions 5B radially provided around the circular grain region 5A at intervals of 120° and gradually narrowing toward the center when viewed from the vertical direction. have Fan-shaped furnace refractories 3 are arranged between the fan-shaped grain regions 5B, and the furnace refractory 3 is provided to the upper end of the furnace shell 2 above the fan-shaped grain regions 5B.

A raw material charging port 9B is provided corresponding to the upper center of the circular grain region 5A. The raw material charging port 9B has substantially the same diameter as the circular grain region 5A and has a larger diameter than the raw material charging port 9A.

Each power supply terminal portion 4 includes an electrode plate 10 having an arcuate cross section (inner diameter R, height H, radius angle 60°) in contact with the outer periphery of the kryptor grain region 5, and one end connected to the electrode plate 10 and the other end has a power supply rod 11 protruding outside the furnace shell 2 . The electrode plate 10 is provided so as to cover the entire end surface of each fan-shaped grain region 5B on the radially outer side, and is in contact with the entire end surface.

The inside of the furnace body refractory 3 and each power supply terminal portion 4 is filled with kryptor grains up to a height approximately equal to the height of the electrode plate 10 to form a kryptol grain region 5 . The power supply rod 11 is attached to an opening provided in the furnace shell 2 via an insulator 14 . Moreover, the heat insulation board 7A has a thickness extending radially inward to the vicinity of the electrode plate 10 .

In addition, a molten metal receiver 12 is provided below the cryptotol grain region 5 . The molten metal receiver 12 is made of a high-temperature refractory, and has a dish-shaped body receiving portion 12A disposed below the circular grain region 5A, which is the central portion of the kryptol grain region 5, and a body receiving portion 12A radially outward from the body receiving portion 12A. It has a gutter-shaped hot water discharge gutter portion 12B that extends to the outside and discharges the melted material to the outside.

A through hole 12Ab is provided in the peripheral wall portion 12Aa of the main body receiving portion 12A, and the interior of the main body receiving portion 12A and the passage portion of the outlet gutter portion 12B communicate through the through hole 12Ab. The body receiving portion 12A is also filled with kryptol grains and forms part of the circular grain region 5A. It has approximately the same outer diameter as the circular grain region 5A so as to easily collect the molten metal that drips inside the kryptol grain region 5, and has a dish shape including a downwardly protruding cylindrical portion.

As a result, the molten metal dripping inside the kryptol grain region 5 is received by the body receiving portion 12A and is discharged to the outside through the molten metal discharge gutter portion 12B.

A ground electrode 13 made of graphite is provided through the body receiving portion 12A of the molten metal receiver 12 to stabilize the three-phase current. 13a is a ground electrode terminal.

As shown in FIGS. 1 and 3, each power supply terminal portion 4 includes an electrode plate 10, a power supply rod 11, and a support that forms a closed space S between the furnace shell 2 and the electrode plate 10. a frame 15, a gas passage 11a provided in the power supply rod 11 to supply a gas (carrier gas) as a medium for transporting thermal energy to the space S, and a plurality of small holes 10a for supplying gas. 16 is a power supply cable.

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 space S of the support frame 15, and the carrier gas is supplied from a large number of small holes 10a provided in the electrode plate 10 into a sector shape. It is supplied to grain region 5B. The carrier gas then flows toward the central circular grain area 5A, collides with each other, and then flows upward and is discharged through the exhaust stack 6. FIG.

In this manner, the carrier gas supply means is configured to supply the carrier gas using the power supply rod 11 (gas passage 11a) so as to pass through the kryptol grain region 5 and be discharged upward toward the molten raw material M. .

The circuit of the three-phase kryptor furnace 1 is configured as shown in FIG. When supplied to the furnace 1, the kryptol grains (kryptol grain regions 5) filled therein generate heat, generating a high temperature. Note that the three-phase alternating current load resistor T1 uses a star connection, but as shown in FIG. 5, it is also possible to use a delta connection load resistor T2.

In such a furnace according to the present invention, the volume of the kryptol grain region can be increased compared to the conventional furnace (see Japanese Patent Laid-Open No. 59-225283), so if the power supplied is the same, , the temperature of the generated hot body 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.

In addition, since it is used as a production furnace, a large transformer of 500 kVA or more is used. current increases. When the secondary current is 30 kVA or more, it is necessary to minimize the AC impedance of the secondary conductor of the transformer, and to minimize the length of the secondary conductor. For this reason, the transformers are divided into three single-phase voltage generators and arranged in close proximity to the electrode terminals.

(Regarding the resistance value of the fan-shaped kryptol grain region sandwiched between two electrode terminal plates)
Next, the electrical resistance of the kryptoll grain domains 5 will be described.
As shown in FIGS. 6A and 6B, metal electrode plates 102 and 103 are provided inside and outside the fan-shaped grain region 101 having a height H, and an AC voltage is applied between the electrode plates 102 and 103. , AC current flows between the electrode plates 102 and 103, and the AC resistance between the electrode plates 102 and 103 at that time is obtained. Assuming an arcuate portion having a thickness Δa located at a radius a from the center point O of the fan-shaped grain region 101, the resistance value ΔR of this arcuate portion can be expressed by Equation 1 below.

If dR is ΔR when Δa is made as small as possible, then Equation 2 below is obtained.

Therefore, since the total resistance R between the electrode plates 102 and 103 is obtained by integrating dR from _a1 to _a2 , it is given by Equation 3 below.

The supplied carrier gas absorbs the Joule heat generated in the kryptol grain regions 5 (circular grain regions 5A and fan-shaped grain regions 5B) and reaches a high temperature.

For example, if the carrier gas is Ar gas and the respective values are Eg = 30 kW, η = 0.8, Vg = 60 Nm ³ /h, γg = 1.784 kg/Nm ³ , Cp = 0.522 kJ/kg°C, Formula 5 below is obtained.

The material to be melted placed above the circular grain region 5A is heated and melted by the amount of heat possessed by this high-temperature gas. In other words, the inert gas supplied from the power supply terminal portion 4 serves as a carrier gas for the thermal energy generated in the kryptor grain regions 5 . After the carrier gas is used to heat and melt the raw material, it can be reused as the carrier gas supplied from the power supply terminal portion 4 by recovering it through a gas cooler or a dust collector, which is very economical. .

(Regarding the resistance value when three-phase alternating current is applied to a circular grain area of height H)
As shown in FIG. 7, if the diameter of the circular grain region 5A of the kryptol grain region 5 is D, the other dimensions are given by the following Equation 6.

Although the value of r ₂ may be determined in any way, it is set to 0.7D here.

Since it is a three-phase furnace, the three-phase alternating current flows from the three electrode plates 10 into the fan-shaped grain regions 5B of the kryptor grain regions 5, and the kryptor grain regions 5 (thickness H) become three-phase. load resistance.

In FIG. 8, three zones are assumed: part R ₁ , part R ₃ and part R ₂ therebetween. The sum of these three zones almost overlaps with the kryptoll granulosphere bounded by the thick line. Therefore, if the zone resistance values of R ₁ , R ₂ , and R ₃ are obtained, the resistance value R of the kryptor grain region can be approximated by adding the three resistance values. to Then, by applying the above formula 3 to R ₁ , it can be represented by the following formula 7.

If R ₃ is expressed in the same way, the following formula 8 is obtained.

Since it is difficult to determine the resistance value of the R ₂ portion as it is, the resistance value is determined by replacing it with a rectangular zone of 0.8L×0.8B (see FIG. 9).

In the above equations, θ ₁ =60°=π/3 and θ ₂ =90°=π/2.

Note that this formula does not include the value of D. The diameter D of the circular kryptol grain region is the reference circle diameter that is the basis for determining the size of the furnace. It can be seen that it is determined by the specific resistance ρ of the grain.

According to the above furnace, the central kryptol grain region is made circular, and the three-phase electrode current from the power supply terminal portion 4 diffuses into the circular grain region 5A through the fan-shaped grain region 5B and flows to the entire grain region. is the exothermic region. Since the high temperature generated by supplying an electric current corresponding to the size of the kryptol grain region 5 can be freely set, there is no limit to the size of the equipment, and the high temperature generating furnace can be made as large as desired. Therefore, it is suitable for production furnaces of metals and metal oxides whose melting temperature is about 1000.degree. C. to 1800.degree.

By using a metal electrode plate 10 with an arc-shaped cross section as an electrode terminal instead of a graphite electrode rod and providing a cryptotal grain region 5 (fan-shaped grain region 5B) inside the electrode plate 10, the electrode plate By increasing the area of the contact portion between 10 and the cryptol grain region 5 (fan-shaped grain region 5B), heat generation due to contact resistance generated in that portion is made as small as possible. The power loss of the power supply terminal portion 4 can be reduced, and the size of the furnace equipment can be easily increased.

Since the power supply terminal portion 4 does not reach a very high temperature in this way, there is no need for water cooling, and cooling by carrier gas (air cooling) can be used. Therefore, the three-phase kryptol furnace according to the present invention exhibits the following effects.

(i) Ensure uniform heating in the central kryptol grain region.
Since an inert gas such as Ar gas or N ₂ gas is supplied as a carrier gas from the power supply terminal portion 4 toward the kryptol grain regions 5, the local non-uniform heat generated in the kryptol grain regions 5 is leveled. Therefore, uniform heating is ensured over the entire kryptol grain region 5, and the molten raw material M is efficiently heated.

(ii) The outlet temperature of the carrier gas can be freely changed by adjusting the balance between the electric power supplied to the kryptol grain region 5 and the carrier gas.
Most of the heat energy of the electric power supplied to the kryptor grain region 5 is absorbed by the carrier gas, except for the heat loss due to the structure of the furnace body. Therefore, when the input electric power is constant, the outlet temperature of the gas changes in inverse proportion to the flow rate of the gas, so the outlet temperature of the gas can be freely controlled by the flow rate of the gas.

(iii) no CO ₂ gas is generated;
Since CO ₂ gas is not generated, it will be a production facility that realizes decarbonization. Conventionally, vertical continuous melting furnaces (for example, cupolas) used at production sites use coke combustion to obtain high temperatures, so a large amount of CO ₂ gas is generated. Using an electrothermal cupola can greatly contribute to the elimination of CO ₂ gasification at casting production sites.

(iv) It is easy to start and stop.
Since only electric power is used as a heat source, it is easy to start and stop the furnace like a general electric furnace. Continuous melting furnaces that use petroleum fuels such as coke, heavy oil, and gas often take time to stabilize the furnace conditions at startup. Since a high-temperature stable state can be obtained only by supplying kryptoll to the grain region, the workability at the production site is greatly improved.

As described above, the preferred embodiments of the present invention have been described with reference to the drawings, but various additions, changes, or deletions can be made without departing from the scope of the present invention.

For example, in the above-described embodiments, the inert Ar gas was used as the carrier gas, but other inert gas or reducing gas can also be used. Further, by using a reducing gas such as H ₂ gas, it is possible to reduce and melt the raw material when the raw material to be melted is a metal oxide such as iron ore.

In addition, in the above-described embodiment, as an example, Kryptol grains made from graphite are used, but Kryptol grains made from coke or silicon carbide can also be used. Accordingly, such are also included in the scope of the present invention.

1 Three-phase Kryptol furnace 2 Furnace shell 3 Furnace refractory 4 Power supply terminal 5 Kryptol grain region 5A Circular grain region 5B Fan-shaped grain region 6 Exhaust stack 7A, 7B Insulation board 8 Exhaust stack refractories 9A, 9B Raw material charging port 10 Electrode plate 10a Small hole 11 Power supply rod 11a Gas passage 12 Molten metal receiver 12A Body receiver 12Aa Surrounding wall 12Ab Penetration hole 12B Outlet gutter 13 Earth electrode 13a Earth electrode terminal 14 Insulator 15 Support frame 16 Power supply cable M Raw material S void

Claims (11)

A furnace refractory is provided inside a cylindrical furnace shell, three power supply terminal portions are arranged inside the furnace shell at intervals of 120°, and kryptor grains are placed inside the furnace refractory and the power supply terminal portion. A three-phase kryptol furnace filled to form a kryptol grain region,
A raw material charging unit for charging the raw material to be dissolved is arranged above the kryptol grain region,
The power supply terminal portion has an electrode plate in contact with the outer circumference of the kryptor grain region, and a power supply rod having one end coupled to the electrode plate and the other end protruding outside the furnace shell,
Furthermore, a gas supply means is provided for supplying gas using the power supply rod so as to be discharged upward through the kryptol grain region,
Three-phase Kryptol furnace. The gas supply means is
a support frame provided at the power supply terminal portion and forming a gap between the furnace shell and the electrode plate;
a gas passage provided in the power supply rod for supplying gas to the gap;
a plurality of small holes provided in the electrode plate for supplying the gas from the void to the kryptor grain region;
A three-phase kryptor furnace according to claim 1. The gas is a gas other than an oxidizing gas,
A three-phase kryptor furnace according to claim 1. The gas is an inert gas such as _N2 or Ar gas, or a reducing gas such as _H2 gas.
A three-phase kryptor furnace according to claim 1. The kryptoll grain region has a central circular grain region and three fan-shaped grain regions radially provided at 120° intervals around it,
The electrode plate has an arcuate cross section,
the electrode plate is in contact with a radially outer end surface of each sector-shaped grain region;
A three-phase kryptor furnace according to claim 1. A molten metal receiver is provided below the cryptotol grain region,
The molten metal receiver comprises a main body receiving portion that is arranged below the central portion of the kryptol grain area and holds the kryptol grains, and a pouring gutter portion that extends radially outward from the main body receiving portion and discharges the molten material to the outside. has a
A three-phase kryptor furnace according to claim 1. A ground electrode is provided through the body receiving portion of the molten metal receiver,
A three-phase kryptor furnace according to claim 6. The electrode plate is provided so as to cover the entire end surface of each of the fan-shaped grain regions, with respect to the radially outer end surface.
A three-phase kryptoll furnace according to claim 5. The main body receiving portion has a dish shape provided with a peripheral wall portion having a through hole,
The hot water outlet gutter portion has a gutter shape having a passage,
The inside of the surrounding wall portion of the main body receiving portion is connected to the passage of the hot water outlet gutter portion through the through hole,
A three-phase kryptor furnace according to claim 6. In the Kryptol grains,
Contains either kryptol grains made of coke or kryptol grains made of graphite,
A three-phase kryptor furnace according to claim 1. In the cryptotol grain region,
The circular grain region contains kryptol grains made of coke,
The fan-shaped grain regions contain cryptotal grains made of graphite,
A three-phase kryptoll furnace according to claim 5.

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