JP2005337560A - Electric furnace - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric furnace including a small ceiling to be effectively cooled without requiring spacial machining cost and degrading strength and service life. <P>SOLUTION: The electric furnace such as a three-phase a.c. arc furnace F1 comprises a cylindrical furnace body 2 having a furnace bottom and a furnace wall, a furnace cover 4 having a dust collecting hole 8 for closing an opening portion of the furnace body, the small ceiling 6 arranged near the center of the furnace cover, having through-holes 7 through which a plurality of electrodes d1-d3 pass, and formed of a refractory product, and a cooling pipe 14 for supplying cooling water w downward to at least a position near the dust collecting hole of the furnace cover out of the small ceiling. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an electric furnace such as a direct current arc furnace or a three-phase alternating current arc furnace and capable of effectively cooling a small ceiling thereof.

A DC arc furnace or a three-phase AC arc furnace is a cylindrical furnace body including a furnace bottom and a furnace wall, a furnace lid that closes an opening of the furnace body, and a single or A small ceiling through which a plurality of electrodes can be moved up and down. Such a small ceiling is arranged for the purpose of insulation between the electrode made of graphite and the iron cover covering the surface of the furnace cover, and is composed of a substantially disk-shaped refractory part.
By the way, in the said arc furnace, since it contacts or adjoins high temperature molten steel and an arc, it is necessary to cool a furnace main body, a furnace cover, and a small ceiling effectively.

Therefore, in order to cool the refractory in the small lid located in the center of the furnace lid, in particular, in the refractory forming the small ceiling, a number of cooling holes along the vertical direction are drilled, A cooling method for a small ceiling refractory in a DC arc furnace is proposed in which cooling water sprinkled from outside the furnace is entered and the refractory on the small ceiling is cooled by the heat of vaporization of the cooling water (for example, Patent Document 1). reference).
However, while the above cooling method can effectively cool the refractory forming the small ceiling, it requires processing costs for drilling a large number of cooling holes, reducing the strength of the small ceiling, There was a problem that the lifetime was reduced due to thermal effects.

JP-A-9-126657 (Pages 1 to 4, FIGS. 2 to 5)

  The present invention solves the problems in the background art described above, and provides an electric furnace including a small ceiling that can be effectively cooled without requiring special processing costs and without reducing strength and life. Is an issue.

Means for Solving the Problems and Effects of the Invention

In order to solve the above-mentioned problems, the present invention intensively cools a portion of the small ceiling arranged at the center of the furnace lid of the electric furnace, which requires cooling, as a result of intensive studies and investigations by the inventors. , It was conceived.
That is, an electric furnace of the present invention (Claim 1) includes a furnace body having a cylindrical shape and having a furnace bottom and a furnace wall, a furnace lid that closes an opening of the furnace body and has a dust collection hole, and the furnace. A small ceiling made of a refractory and having a through-hole penetrating one or a plurality of electrodes disposed near the center of the lid, and at least the position of the small ceiling close to the dust collection hole of the furnace lid And a cooling pipe for supplying cooling water or cooling mist from.

According to this, among the refractories that form the small ceiling, in particular, close to the dust collection hole of the furnace lid, and intensively by the high temperature exhaust gas generated by arc heating flame or melting or refining of raw materials, etc. Since the melt damage of the exposed part can be effectively suppressed and the life of the small ceiling can be extended, the maintenance of the electric furnace including this can be facilitated.
The furnace body is composed of a metal water-cooled box or a furnace bottom and a furnace wall coated with an iron skin on the outside of the refractory. It consists of what coated. The small ceiling is made of a disk-shaped refractory. In a DC arc furnace, one through-hole for penetrating the electrode is drilled in the center, and in a three-phase AC arc furnace, three through-holes for penetrating the electrode are drilled. Has been. Further, the dust collection hole of the furnace lid is drilled at a position slightly away from the electrode and communicates with the dust collection duct.

Further, in the present invention, the injection hole or the spray hole in the cooling pipe opens toward the position near the dust collection hole of the furnace cover in the small ceiling, and in addition to the furnace cover near the dust collection hole. Also included is an electric furnace (Claim 2) that is also open toward.
According to this, in addition to the above-mentioned portion of the small ceiling close to the dust collection hole of the furnace lid, the furnace lid in the vicinity of the dust collection hole that is exposed to arc hot flame or high-temperature exhaust gas accompanying melting and refining of raw materials. This part can also be cooled together. For this reason, since the lifetime of a furnace lid can also be prolonged, the maintenance of the electric furnace containing these becomes still easier.

Further, according to the present invention, the cooling pipe is supported by a pair of suspension beams that support one end or both ends of the cooling pipe while raising and lowering the furnace lid and pivotable in the horizontal direction. ) Is also included.
According to this, a pair of cooling pipes are individually attached to a pair of suspension beams, or a single cooling pipe that is long in the axial direction is provided, without providing a cooling pipe for spraying or spraying cooling water or cooling mist independently. By installing between the pair of suspension beams, it is possible to provide a cooling pipe at a low cost. Therefore, the small free space above the electric furnace can be effectively used to reliably cool the small ceiling and the furnace lid close to the dust collection hole, and a water supply pipe for supplying cooling water etc. to the cooling pipe is provided. Thus, overheating of the pair of suspension beams can be prevented.

In addition, according to the present invention, the pair of suspension beams has one or a plurality of conductor support arms that support the electrode or the plurality of electrodes so as to be movable up and down, and can be swung in the horizontal direction together with the conductor support arms. An electric furnace (claim 4) is also included.
According to this, one or a plurality of conductor support arms that support one electrode in a DC arc furnace or three electrodes used in a three-phase AC arc furnace so as to be movable up and down are disposed between a pair of suspension beams. Yes. Therefore, a furnace including a small ceiling can be cooled by cooling water or cooling mist injected / sprayed from the cooling pipe, and the electrode is raised and positioned above the electric furnace. The lid can be swung to a position away from the electric furnace together with the electrode, and maintenance such as inspection of the small ceiling, the furnace lid, the electrode, and the cooling pipe can be performed simultaneously. During the turning, operations such as charging the raw material into the furnace main body and taking out the molten steel out of the furnace are performed.

A plurality of the cooling pipes protrude from the pair of suspension beams so that the cooling water or the cooling mist can be sprayed / sprayed even on the refractory in the small ceiling portion that is not close to the dust collection hole. You may arrange in.
Further, as will be described later, the DC arc furnace has a furnace bottom electrode disposed on the furnace bottom of the furnace body so as to face the lower end of the one electrode passing through the small ceiling of the furnace lid.

The best mode for carrying out the present invention will be described below.
FIG. 1 is a plan view of a three-phase AC arc furnace (electric furnace) F1 according to one embodiment of the present invention, and FIG. 2 is a vertical sectional view of the three-phase AC arc furnace F1.
As shown in FIGS. 1 and 2, the three-phase AC arc furnace (electric furnace) F <b> 1 includes a furnace body 2 having a substantially cylindrical shape and a furnace wall and a furnace bottom (not shown), and an opening above the furnace body 2. A substantially disc-shaped furnace lid 4 that is closed, and a small ceiling 6 that is circularly fit in a round hole 5 formed in the center of the furnace lid 4 in a plan view.

The furnace body 2 has a bottomed cylindrical shape as a whole, and has an unillustrated iron skin attached to the outside of a refractory made of, for example, magnesia or alumina. In addition, the furnace lid 4 is provided with a dust collection hole 8 on the outside (right side in FIGS. 1 and 2) of the round hole 5 located in the center. The dust collection hole 8 is heat-resistant and detachable. It communicates with the duct 9 for use.
As shown in FIGS. 1 and 2, the small ceiling 6 is made of the same fixed refractory as described above, which is divided into three by a Y-shaped partition line c in plan view, and in the vicinity of the center of each refractory having a fan shape in plan view. Are individually drilled with through-holes 7 that vertically penetrate the graphite electrodes d1 to d3.
The graphite electrodes d1 to d3 are individually supported by three conductor support arms b1 to b3 each having a holder h penetrating the graphite electrodes d1 to d3 by a known mechanism.

Furthermore, the furnace lid 4 including the small ceiling 6 is supported by a pair of suspension beams 10a and 10b through a hook or the like (not shown) so as to be movable up and down. And as shown by the one-dot chain line arrow in FIG. 1, when turning in the horizontal direction, the opening of the furnace body 2 is opened, and the raw material is charged and the molten steel is poured out.
The pair of suspension beams 10a and 10b are connected to each other on the left side of FIGS. 1 and 2, and the bases of the three conductor support arms b1 to b3 located between the suspension beams 10a and 10b with respect to the connection portion (not shown). The ends are connected individually. That is, the conductor support arms b1 to b3 are also turnable along the horizontal direction together with the pair of suspension beams 10a and 10b. However, prior to the turning, the electrodes d1 to d3 are raised above the through holes 7 of the small ceiling 6 in advance.
The conductor support arms b1 to b3 are wired with conductive cables (not shown) that conduct in parallel between the electrodes d1 to d3 and an AC power supply (not shown).

As shown on the right side of FIGS. 1 and 2, a pair of cooling pipes 12 and 14 are attached obliquely and laterally (tip) and symmetrically inside the pair of suspension beams 10 a and 10 b near the tip. The cooling pipes 12 and 14 are horizontally projected from the suspension beams 10a and 10b so as to approach a portion of the small ceiling 6 near the dust collection hole 8 of the furnace lid 4 and a plurality of injection holes s formed in them. Is opened toward the portion (position) of the small ceiling 6 near the dust collection hole 8.
A water spray nozzle or a mist spray nozzle may be attached to the spray hole s. Further, the tips of the cooling pipes 12 and 14 do not contact the elbow portion of the dust collection duct 9. Further, the suspension beams 10a and 10b are provided with a water supply pipe (not shown) for supplying cooling water to the cooling pipes 12 and 14, and in the form of spraying mist, the cooling water and air are mixed to form a mist. A vaporizer is further provided.

Here, an operation method of the three-phase AC arc furnace (electric furnace) F1 will be described.
A small ceiling 6 supported on suspended beams 10a and 10b horizontally swung as shown in FIGS. 1 and 2 after previously introducing raw materials (such as scrap iron, ingots, alloy components, etc.) into the furnace body 2 in advance. Is placed on the opening of the furnace body 2 to close it. At this time, the elbow part which is one end of the dust collection duct 9 is connected to the dust collection hole 8 of the furnace lid 4.
Next, as shown in FIG. 2, the graphite electrodes d <b> 1 to d <b> 3 supported by the holders h positioned at the ends of the conductor support arms b <b> 1 to b <b> 3 horizontally swiveled together with the suspension beams 10 a and 10 b are lowered, The through-hole 7 is penetrated and the front-end | tips are made to approach the said raw material.

In this state, when a predetermined alternating current is supplied to the graphite electrodes d1 to d3, the electrodes d1 to d3 are energized through the raw material, and as shown in FIG. ) To the raw material, arcs a are radiated to heat and melt the raw material.
As the melting of the raw material proceeds, as shown in FIG. 2, molten steel M, which is a metal component, starts to stay on the furnace bottom of the furnace body 2, and slag such as non-metallic inclusions (not shown) rises thereon. Moreover, the gas containing the dust discharged | emitted from the heated raw material by reaction at the time of the said melt | dissolution is discharged | emitted out of the furnace through the dust collection hole 8 through the dust collection duct 9. FIG.

During this time, of the refractory that forms the small ceiling 6, the portion (position) near the dust collection hole 8 of the furnace lid 4, that is, the portion near the right side of the small ceiling 6 in FIG. Since it is a gas flow path, it is exposed to a hot flame of arc a or a high-temperature exhaust gas generated as a result of melting of the raw material, resulting in a very high temperature.
In order to prevent melting of the small ceiling 6 due to such high temperature, the cooling water w is conically shaped from each injection hole s of the cooling pipes 12 and 14 as shown in FIGS. The refractory material of the small ceiling 6 forming the portion is cooled by spraying from above to the portion (position) near the right side of the small ceiling 6 close to the dust hole 8.

As a result, melting of the portion near the right side of the small ceiling 6 adjacent to the dust collection hole 8 can be prevented, stable melting operation can be performed, and the lifetime of the small ceiling 6 can be increased from about 1.3 times to about 1.5. Since it can be about twice as long, maintenance of the three-phase AC arc furnace F1 is also facilitated. Moreover, overheating of the pair of suspension beams 10a and 10b itself can be prevented.
3 and 4, the injection holes s are increased to the opposite side, and cooling water w is also injected from the cooling pipes 12 and 14 to the furnace lid 4 near the dust collection holes 8. Also good. Further, instead of the cooling water w, the cooling mist may be sprayed on each part.

5 and 6 are a plan view and a vertical cross section similar to the above, showing a three-phase AC arc furnace (electric furnace) F1 including cooling pipes 16 of different forms.
As shown in FIGS. 5 and 6, the three-phase AC arc furnace F1 is similar to the furnace body 2, the furnace lid 4, the small ceiling 6, the suspension beams 10a and 10b, the graphite electrodes d1 to d3, and the conductor support arm b1. The cooling pipe 16 having a substantially square shape in plan view is installed substantially horizontally near the tip between the suspension beams 10a and 10b.
A water supply pipe passing through one or both of the suspension beams 10a and 10b is connected to both ends or one end of the cooling pipe 16. In the cooling pipe 16, the intermediate bent portion does not contact the elbow portion of the dust collection duct 9, and the plurality of injection holes s are directed toward the portion (position) near the dust collection hole 8 of the furnace lid 4 in the small ceiling 6. It is open.
In order to avoid contact with the dust collection duct 9, the cross section near the bent portion located in the middle of the cooling pipe 16 may have a flat shape along the vertical direction.

In the same manner as described above, the raw material is charged into the furnace main body 2, and as shown in FIGS. 5 and 6, the suspension beams 10a and 10b are horizontally swirled together with the graphite electrodes d1 to d3 and the conductor support arms b1 to b3. The opening of the main body 2 is closed with a furnace lid 4 including a small ceiling 6. Further, the graphite electrodes d1 to d3 are lowered from the tips of the conductor support arms b1 to b3, and the through holes 7 of the small ceiling 6 are passed through so that the tips approach the raw material.
In this state, when a predetermined alternating current is supplied to the graphite electrodes d1 to d3, as shown in FIG. 6, arcs a are emitted from the tips of the electrodes d1 to d3 toward the raw material, respectively, and the raw material is heated. And dissolve.

As the melting of the raw material proceeds, as shown in FIG. 6, the molten steel M as a metal component starts to stay on the furnace bottom of the furnace body 2, and a slag (not shown) floats on the molten steel M. Dust-containing gas generated from the heated raw material is discharged from the dust collection hole 8 through the dust collection duct 9 to the outside of the furnace.
During this time, the portion of the refractory that forms the small ceiling 6 and close to the dust collection hole 8 of the furnace lid 4 (the position near the right side of the small ceiling 6 in FIG. 5) is accompanied by the arc a thermal flame and melting of the raw material. Exposed to a flow of high-temperature exhaust gas generated in the above manner, and the temperature becomes extremely high as described above.

In order to prevent melting of the small ceiling 6 due to the high temperature, the cooling water w is formed in a conical shape from each injection hole s of the cooling pipe 16 as shown in FIGS. The refractory of the small ceiling 6 that forms the portion is sprayed from above to the portion (position) near the right side of the small ceiling 6 that is close to 8.
As a result, it is possible to prevent melting of the portion near the right side of the small ceiling 6 adjacent to the dust collection hole 8, perform stable melting operation, and prolong the life of the small ceiling 6 in the same manner as described above. Maintenance of the AC arc furnace F1 is also facilitated, and overheating of the pair of suspension beams 10a and 10b itself can be prevented.
5 and 6, the injection holes s are increased to the opposite side, and the cooling water w is similarly injected from the cooling pipe 16 to the furnace lid 4 near the dust collection holes 8. Also good. Further, instead of the cooling water w, the cooling mist may be sprayed on the respective portions.

7 and 8 are a plan view and a vertical section showing a direct current (DC) arc furnace (electric furnace) F2 of the present invention. As shown in FIGS. 7 and 8, the DC arc furnace F2 has a substantially cylindrical shape and a furnace body 2 having a furnace wall and a furnace bottom 2a, and a substantially disk shape that closes the opening above the furnace body 2. A furnace lid 4 and a small ceiling 6 having a circular shape in plan view fitted into a round hole 5 formed in the center of the furnace lid 4 are provided.
At the center of the furnace bottom 2a of the furnace body 2, an upper end surface of a graphite-made vertical furnace bottom electrode d5 is exposed. The furnace bottom electrode d5 is connected to a DC power source (not shown).
Similarly to the above, the furnace lid 4 is provided with a dust collection hole 8 outside the round hole 5, and the dust collection hole 8 communicates with a heat-resistant and removable dust collection duct 9.

The small ceiling 6 is made of the same shaped refractory material as described above, and as shown in FIGS. 7 and 8, a single through hole 7 is formed in the center of the small ceiling 6 so as to vertically penetrate the graphite electrode d4. The graphite electrode d4 is supported by a single conductor support arm b having a holder h that penetrates the graphite electrode d4 so as to be movable up and down. Moreover, the graphite electrode d4 is arrange | positioned so that it may become coaxial with the furnace bottom electrode d5, as shown in FIG. 8, and both end surfaces oppose in the furnace main body 2. FIG.
Further, the furnace lid 4 including the small ceiling 6 is supported by the pair of suspension beams 10a and 10b so as to be movable up and down, as described above, and as indicated by the rising of the furnace lid 4 and the one-dot chain line arrow in FIG. When turning in the horizontal direction, the opening of the furnace body 2 is opened.

  The pair of suspension beams 10a and 10b are coupled to each other on the left side in FIGS. 7 and 8, and the base end portion of the conductor support arm b positioned between the suspension beams 10a and 10b is connected to the coupling portion (not shown). . The conductor support arm b can be turned along the horizontal direction together with the pair of suspension beams 10a and 10b. However, prior to the turning, the electrode d4 is raised above the through hole 7 of the small ceiling 6 in advance. Note that a conductive cable (not shown) that conducts electricity between the electrode d4 and a DC power source (not shown) is also wired to the conductor support arm b.

As shown on the right side of FIGS. 7 and 8, a pair of cooling pipes 12 and 14 are attached in the same manner as described above inside the pair of suspension beams 10 a and 10 b, and these are connected to the furnace cover 4 on the small ceiling 6. Is close to the portion (position) near the dust collection hole 8.
The plurality of injection holes s opened in the cooling pipes 12 and 14 are open toward the portion (position) of the small ceiling 6 near the dust collection hole 8.
Instead of the cooling pipes 12 and 14, one cooling pipe 16 may be installed between the suspension beams 10a and 10b. Further, a water spray nozzle or a mist spray nozzle may be attached to the spray hole s.

In the same manner as described above, the raw material is charged into the furnace body 2, and as shown in FIGS. 7 and 8, the suspension beams 10a and 10b are swung horizontally together with the graphite electrode d4 and the conductor support arm b to open the furnace body 2. The part is closed with a furnace lid 4 including a small ceiling 6. Next, the graphite electrode d4 is lowered from the tip of the conductor support arm b, and is passed through the through hole 7 of the small ceiling 6, so that the tip approaches the raw material and faces the furnace bottom electrode d5.
In this state, when a predetermined direct current is supplied to the graphite electrode d4 and the furnace bottom electrode d5, the electrodes d4 and d5 are energized through the raw material, and as shown in FIG. 8, from the tip of the graphite electrode d4 toward the raw material. Arc a is emitted, and the raw material is heated and melted.

As the melting of the raw material proceeds, as shown in FIG. 8, the molten steel M as a metal component starts to stay on the furnace bottom 2a of the furnace body 2, and a slag (not shown) floats on the molten steel M. The dust-containing gas discharged from the heated raw material is discharged out of the furnace through the dust collection hole 8 and the dust collection duct 9.
During this time, the portion of the refractory that forms the small ceiling 6 and close to the dust collection hole 8 of the furnace lid 4 (the position near the right side of the small ceiling 6 in FIG. 7) is accompanied by the melting of the hot flame of the arc a and the raw material. Exposed to the flow of high-temperature exhaust gas generated in the above manner, and the temperature becomes high as described above.

In order to prevent melting of the small ceiling 6 due to such high temperature, as shown in FIGS. 7 and 8, the cooling water w is formed in a conical shape from each injection hole s of the cooling pipes 12 and 14 to collect the furnace lid 4. The refractory material of the small ceiling 6 forming the portion is cooled by spraying from above onto the portion near the right side of the small ceiling 6 adjacent to the dust hole 8.
As a result, it is possible to prevent melting of the portion near the right side of the small ceiling 6 adjacent to the dust collection hole 8, perform stable melting operation, and prolong the life of the small ceiling 6 in the same manner as described above. Maintenance of F2 is also facilitated, and overheating of the suspension beams 10a and 10b themselves can be prevented.
7 and 8, the injection hole s is also opened on the opposite side, and the cooling water w is also injected from the cooling pipes 12 and 14 to the furnace lid 4 near the dust collection hole 8. May be. Further, instead of the cooling water w described above, cooling mist may be sprayed on the respective parts.

The present invention is not limited to the embodiments described above.
For example, the cooling pipes 12 and 14 and the cooling pipe 16 are cooled from an intermediate position between the suspension beams 10a and 10b in order to cool a refractory that forms a portion (position) other than the vicinity of the dust collection hole 8 in the small ceiling 6. Alternatively, the projection may be provided in the horizontal direction.
The cooling pipes 12 and 14 and the cooling pipe 16 may have a curved shape along the periphery of the small ceiling 6 in plan view.
Further, the cooling pipes 12 and 14 and the cooling pipe 16 can be sprayed or sprayed in parallel with the cooling water w and the cooling mist, and these can be applied to different parts of the small ceiling 6 and the furnace lid 4 from different positions. You may make it spray and spray.
In addition, the electric furnace of the present invention is not limited to the arc furnaces F1 and F2, but also includes, for example, an arc-type garbage melting furnace in which waste incineration ash is arc-melted into granulated slag.

The top view which shows the electric furnace of 1 form in this invention. FIG. 2 is a vertical sectional view taken along the line XX in FIG. The top view which shows the use condition of the said electric furnace. FIG. 4 is a vertical sectional view taken along line XX in FIG. 3. The top view which shows the electric furnace of a different form, and its use condition. FIG. 6 is a vertical sectional view taken along the line YY in FIG. Furthermore, the top view which shows the electric furnace of a different form, and its use condition. FIG. 8 is a vertical sectional view taken along the line ZZ in FIG. 7.

Explanation of symbols

2 ………………… Furnace body 2a ……………… Furnace bottom 4 ………………… Furnace lid 6 …………………… Small ceiling 7 ………………… Through hole 8 ………………… Dust collection hole 10a, 10b… Hanging beam 12,14,16… Cooling pipe F1 ……………… 3-phase AC arc furnace (electric furnace)
F2 ……………… DC arc furnace (electric furnace)
b, b1 to b3 ... conductor support arms d1 to d4 ... ... graphite electrode (electrode)
d5 ……………… Furnace bottom electrode (electrode)
s ………………… Injection hole w ………………… Cooling water

Claims (4)

A furnace body having a cylindrical shape and having a furnace bottom and a furnace wall;
A furnace lid that closes the opening of the furnace body and has a dust collection hole;
A small ceiling that is disposed near the center of the furnace lid, has a through-hole that penetrates one or more electrodes, and is made of a refractory;
A cooling pipe for supplying cooling water or cooling mist from above to at least a position near the dust collection hole of the furnace lid in the small ceiling,
An electric furnace characterized by that. In addition to opening toward the position near the dust collection hole of the furnace lid in the small ceiling, the injection hole or spray hole in the cooling pipe also opens toward the furnace lid near the dust collection hole. ,
The electric furnace according to claim 1. The cooling pipe is supported by a pair of suspension beams that support one end or both ends of the cooling pipe while raising and lowering the furnace lid and pivotable in the horizontal direction.
The electric furnace according to claim 1, wherein the electric furnace is provided. The pair of suspension beams have one or more conductor support arms that support the one or more electrodes so as to be able to move up and down, and can be turned in the horizontal direction together with the conductor support arms.
The electric furnace according to claim 3.

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