DE19529924C1 - Arc furnace with simple arc spot displacement mechanism - Google Patents

Abstract

The invention concerns an arc furnace, in particular a d.c. arc furnace, comprising a vessel and a cover which lies thereon and has an opening for at least one electrode provided with a movement unit for vertical displacement. According to the invention, the movement unit comprises a movement device (51) for moving the base point of the arc substantially horizontally. The furnace cover (12) has a central opening (13) with a central cover part (14) which is movable independently of the furnace cover. Provided between the furnace cover and the central cover part lying thereon are seals (16). The invention further concerns a process for operating an arc furnace of this type.

Description

The invention relates to an arc furnace and a method for avoiding Overheating of the furnace wall, with an upper vessel and an overlying one Oven cover, which has a passage opening for at least one electrode supported independently of the furnace lid and with a movement unit for vertical Shift is provided, and with a sealing unit provided for horizontal and vertical sealing of the surfaces between the electrode and the Passage opening.

DC arc furnaces are designed so that the arc is axially in the furnace chamber runs, in particular around the substances to be melted in the furnace chamber Metal scrap, heat and melt as evenly as possible. The distraction of the arc, for example, by randomly existing magnetic fields by the in Furnace space existing flow conditions and / or uneven Scrap distribution often leads to local overheating of the water-cooled Furnace wall so that there is excessive premature wear or even too melting of the furnace wall can occur.

One tries to avoid local overheating by scrap load as evenly as possible into the scrap basket and / or by placing the Bottom electrode and the high-current leads in the furnace chamber are accordingly cheap orders. When the arc furnace is operating, it turns out that the selected one Arrangement of the bottom electrode and the high current leads including the Scrap distribution is unfavorable, e.g. B. if in an area of the furnace  accidentally there are several heavy pieces of scrap, so there is a local one Overheating the furnace wall, there is a possibility of local overheating of the Remove the furnace wall by removing the electrode from the furnace pull out, i.e. the distance between the melting material and the Enlarge electrode tip, which makes the arc stronger at the same time is pulled apart (DE 22 04 882 B2). The disadvantage of this method is that the Energy input into the melt and thus the melting performance of the furnace is reduced. A second known method is to overheat the oven wall to cool more intensively, for example by adding more coolant locally through the corresponding cooling lines is pumped (DE 30 27 465 C1). With this method, too Energy input into the melt is reduced as part of the introduced Thermal energy is dissipated to the outside via the coolant. A third known method, the arc is generated with the help of in the furnace room Magnetic fields changed in their spatial position (DE 43 38 551 C1). This method is very technical complex and also has the disadvantage that the oven is not at the maximum installed power can be operated if the magnetic field due to change the current through the solenoids is to be changed.

To prevent hot gases and dusts from escaping from the furnace. Arc furnaces are usually designed with a furnace lid that can be closed and additionally with a sealing device between the electrode and the passage opening of the electrode. From DE-OS 24 55 202 such is Arc furnace known to have a furnace roof made of refractory material with a walled lid heart, in which filled with excess Passage openings are provided for the electrodes. The electrodes are with a Sealing device for horizontal and vertical sealing of the surfaces between the electrodes and the passage openings. Here is the Sealing device, which is a ring seal over and independent of the fireproof furnace ceiling supported by a supporting structure. To do this pivotable connecting links used, which has a slight lateral Allow the ring seal to move and move relative to the furnace ceiling. In addition, the ring seal to the furnace ceiling is adjustable cylindrically shaped part sealable. There is a ring on the furnace roof Ceiling seal provided, which is dimensioned so that it is opposite the lower cylindrical part in a narrow system telescopically by an amount that is clear  is smaller than the electrode diameter, can be moved, whereby the system through an elastic element is further improved.

Allowing for slight sideways movement and displacement compared to the ring seal, this arc furnace essentially serves pulling out and inserting the electrode through the ceiling opening facilitate, which must be done every time the furnace roof (the Lid) is lifted and swiveled to the side, for example around the oven refill. In particular, this ring seal enables the electrode in to pull a piece out of the oven vertically when on during operation local overheating of the water-cooled furnace wall occurs.

A disadvantage of this arc furnace is that the occurrence of a local Overheating the water-cooled furnace wall and thus the heat load on it Use the known methods only to reduce the price of the Energy input into the melt and thus the melting performance can be prevented can.

From DE-OS 29 05 752 an electrode remelting system is also with Electrode holder body and mold known, in which with the help of a special Electrode adjustment device changes the angular position of the electrode holding body can be, the adjusting device having two defined pivot axes, which are perpendicular to each other and which can be operated independently of one another Actuators are assigned. The purpose of the adjustment device is when retracting make an electrode position correction of the electrode within the mold, so that the arrangement of mold and electrode is as concentric as possible, so that The slag bath has the same possible spacing on the contour of the electrode.

The pivoting of the electrode axis is not the same in the genus belonging electrode remelting plant possible in a relatively uncomplicated manner these do not have a lined brick cover. Furthermore, only relatively small swiveling movements are provided since the swiveling device serves in particular the influence of an obliquely welded electrode rod to compensate for the concentricity of the arrangement, so one if possible to achieve a concentric arrangement of the electrode within the mold. A  However, a particularly concentric electrode arrangement is the case with an arc furnace Generic type not at all suitable for overheating the furnace wall avoid or eliminate.

The invention has set itself the goal of using simple constructive means Arc furnace of the generic type and a method for avoiding To create overheating of the furnace wall, in which local overheating of the water-cooled furnace wall is effectively prevented by simple means, so that it no excessive premature wear caused by overheating Oven wall comes. In addition, in the arc furnace to be created Energy input largely go into the melt and the melting performance through the Overheating the water-cooled furnace wall does not experience an unnecessary reduction.

The invention achieves the aim through the characterizing features of Device claim 1 and the process claim. According to the invention proposed that the movement unit also a movement device for im essential horizontal process of the arc base, which is in the area the electrode tip has. Furthermore, the furnace cover is with a central opening and an overlying lid heart provided in the Interact with those between the furnace lid and the lid heart provided seals movable independently, d. H. essentially horizontal is displaceable and the arc furnace gas and even during moving keeps dust-proof. The passage opening for the electrode can be in the sliding lid heart concentrically for a single electrode Main electrode axis can be arranged. A movement of the arc base with a horizontal motion component is usually with a corresponding displacement of the lid heart relative to the fixed Oven cover connected.

In the simplest case, the movement device for the horizontal movement of the Arc base designed as a shifting device, the horizontal Allows displacement of the entire electrode.

Another advantageous embodiment of the movement device for horizontal Movement of the arc base includes an angular position adjustment device for  Swiveling the electrode around at least one swivel axis. A pan Movement of the electrode in any direction is already done by two independent Swivel axes possible. Swiveling the electrode has the advantage of one reduced relative movement of the lid heart relative to the horizontal Movement stroke of the electrode tip. There is also a swivel in the upper Very easy to implement the electrode.

To implement two independent swivel axes, the Angle position adjustment device at least one separately controllable Adjustment drive on.

To prevent overheating of the furnace wall due to asymmetrical arcing due to an uneven consumption of the electrode tips and due to the Correct cracks forming the electrode tip with minimal electrode movement, it is proposed that the movement device be a rotary device for axial Rotation of the electrodes around the electrode axis includes.

Since the electrode tip in the area of the opening usually around several electrodes diameter must be moved horizontally, the central opening in the Oven cover a multiple of the electrode diameter. The The passage opening in the furnace cover expediently has a diameter between 500 mm and 1500 mm.

To ensure problem-free movement of the electrode, the Sealing unit on a sealing frame that the electrode as a closed Ring engages, being coaxial between the sealing frame and the electrode this a sealing sleeve is provided, the outer surface of which is machined and is slidably applied against the inner surfaces of the sealing frame, so that the Even in a tilted position, the electrode is light and does not leak Can cause passage opening to slide in the sealing frame.

To regulate the optimal electrode position, be sleeve-shaped around the furnace chamber Temperature sensors are arranged around the upper vessel, which the local Record the temperature of the furnace wall. In particular, the temperature sensors be arranged in a ring in a cross-sectional plane of the upper vessel.  

If the temperature of the furnace wall exceeds a predetermined value, the Arc foot point on the electrode tip automatically in particular Swivel or axial rotation moved away from this point.

A method for operating an arc furnace according to the invention provides that when temperature rises occur in a local area of Furnace wall the arc base of the electrode in particular from this area is moved radially away. For this purpose, the furnace wall temperatures are sleeve-shaped temperature sensors arranged around the upper vessel of the arc furnace recorded locally and by moving the electrodes overheating the wall of the Upper vessel controlled by a dedicated control device prevented.

Overheating of the furnace wall due to asymmetrical arcing uneven consumption of the electrode tips as well as during operation Forming cracks are advantageously avoided by the Overheating area facing side of the electrode tip to the Side facing away from the overheating region is rotated axially. The rotation can also be done continuously, e.g. B. if the asymmetry of the arc in remains essentially and only the position of the axial rotation Arc in the furnace room changed

An example of the invention is set out in the accompanying drawing. The shows only figure shows a section of an arc furnace with an electrode support device.

The arc furnace has a vessel 11 , which can be closed with a lid 12 , the lid 12 in turn being attached to a lifting and driving unit 60 . Above a lid opening 13 of the lid 12 , a lid heart 14 is arranged on the lid 12 with the interposition of seals, in particular sliding seals 16 . An electrode 31 projects into the vessel 11 through a lid heart opening 15 .

In the area of the lid heart opening 15 there is a sealing unit which is provided with a sealing frame 21 and a sealing sleeve 22 . In this case, the sealing frame 21 is connected to a flange 23 guided parallel to the lid opening 15 , with elastically deformable material 24 being provided between the two.

In the exemplary embodiment, the sealing frame 21 encompasses the sealing sleeve 22 ; however, the sealing frame 21 can also grip the electrode 31 directly. The use of a sealing sleeve 22 has the advantage that defined conditions of the contact surfaces are created here by mechanical processing of the outer surface. This ensures a tight and secure sliding of the electrode unit, particularly when the angular position of the electrode 31 changes. The electrode unit, including the electrode 31 and the electrode holder 32, is held by an electrode support device, consisting of a support arm 41 and support column 42 , which is fixedly arranged outside the arc furnace. The mounting and movement of the electrode 31 takes place by a movement unit arranged at the free end of the support arm 41 , which in particular has an angular position adjustment device 51 . The angular position adjustment device 51 , which encompasses the electrode above the electrode unit, enables the electrode 31 to be pivoted independently of one another about the two pivot axes A1 and A2 lying perpendicular to one another in a horizontal plane, including the units arranged on the electrode. At a pivoting of the electrode 31 through the Winkellageverstelleinrichtung 51 is also a horizontal displacement of the electrode 31 within the lid opening 13 takes place. The horizontal movement of the electrode 31 is transmitted to the cover heart 14 , which, when lying on the sliding seals 16, moves correspondingly horizontally relative to the cover 12 . The sliding seals 16 are preferably circular and close the lid opening 13 in a gas and dust-tight manner even during the horizontal movement of the lid heart 14 .

To cool the walls of the vessel 11 above the melt (upper vessel), cooling tubes 71 of a cooling device are provided in the wall, through which a cooling liquid flows during operation of the arc furnace. The temperature is recorded by a temperature measuring device which is connected to temperature sensors 81 which are also provided in the wall of the vessel, the temperature sensors being able to be arranged, for example, just below the inside of the wall of the vessel 11 above the melt. The temperature sensors 81 are preferably provided in the form of a sleeve around the upper vessel 11 of the arc furnace. This enables detection of the furnace wall temperature of the vessel 11 in a local area around the temperature sensors 81 . The temperature measuring device is connected to a control device (not shown), which is connected to a control device (also not shown) of the angular position adjusting device 51 , and if a predetermined temperature value is exceeded in a local area of the wall of the vessel 11, the tip of the electrode 31 by pivoting the entire electrode 31 moved away from this point about one of the pivot axes A1, A2; moving the tip of the electrode 31 pulls the base of the arc and thus the arc itself away from the overheating point of the vessel wall. The pivoting of the electrode has the advantage that the lid heart 14 experiences a significantly smaller horizontal displacement than the tip of the electrode.

Of course, the tip of the electrode 31 can also be moved away from the overheating point in that the electrode 31 is displaced parallel to the electrode axis by a correspondingly attached displacement device 41 . In addition to these refinements of the invention, a rotating device for rotating the electrode about the electrode axis can be provided on the free support arm 41 , since such a rotation of the electrode is sufficient to avoid overheating points in the wall of the vessel 11 whenever the base point of the arc due to uneven removal of the electrode or due to cracks in the electrode tip at an unfavorable location e.g. B. forms laterally in the lower region of the electrode. In these cases, an axial rotation of the electrode is sufficient to move the arc base away from the overheating point with minimal electrode movement.

Reference list

11 upper vessel
12 lids
13 lid opening
14 lid heart
15 lid heart opening
16 sliding seal
21 sealing frame
22 sealing sleeve
23 flange
24 elastic material
31 electrode
32 electrode holder
41 support arm
42 support column
51 movement device
60 lifting and driving unit
71 cooling pipes
81 temperature sensors

Claims (12)

1. Arc furnace with an upper vessel ( 11 ) and an overlying furnace lid, which has a passage opening for at least one electrode, which is supported independently of the furnace lid and is provided with a movement unit for vertical displacement, and with a sealing unit provided for horizontal and vertical sealing of the surfaces between the electrode and the passage opening, characterized in that the movement unit also has a movement device ( 51 ) for essentially horizontally moving the arc base, that the furnace cover ( 12 ) has a central opening ( 13 ) with a movable one independently of the furnace cover ( 12 ) Cover heart ( 14 ) is formed and that seals ( 16 ) are provided between the furnace lid ( 12 ) and the overlying lid heart ( 14 ). 2. Arc furnace according to claim 1, characterized in that the movement device ( 51 ) for horizontally displacing the electrode ( 31 ) is provided. 3. Arc furnace according to claim 1, characterized in that an angular position adjusting device for pivoting the electrode ( 31 ) around at least one pivot axis (A1, A2) is provided as the movement device ( 51 ). 4. arc furnace according to claim 3, characterized, that angular position adjustment device at least one each separately controllable adjustment drive. 5. Arc furnace according to claim 1, characterized in that a rotating device for rotating the electrode ( 31 ) around the electrode axis is provided as the movement device ( 51 ). 6. Arc furnace according to one of claims 1 to 3, characterized in that the central opening ( 13 ) in the furnace cover ( 12 ) is a multiple of the electrode diameter. 7. arc furnace according to claim 6, characterized, that the central opening in the furnace cover has a diameter between 500 mm and 1500 mm. 8. Arc furnace according to one of claims 1 to 5, characterized in that the sealing unit has a sealing frame ( 21 ) which engages around the electrode ( 31 ) as a closed ring and that between the sealing frame ( 21 ) and the electrode ( 31 ) coaxially a sealing sleeve ( 22 ) is provided, the outer surface of which is machined and can be slidably fitted against the inner surfaces of the sealing frame ( 21 ). 9. Arc furnace according to claim 1, characterized in that temperature sensors are arranged sleeve-shaped around the furnace space of the upper vessel ( 11 ). 10. A method of operating an arc furnace according to claim 1, wherein the Furnace wall temperatures by means of the upper vessel of the arc furnace arranged temperature sensors detected locally and the electrodes moved become, characterized, that when a predetermined temperature value is exceeded in a local Area of the furnace wall the arc base of the electrode automatically by this area is moved away.   11. The method according to claim 10, characterized, that the arc base moves radially away from this overheating area becomes. 12. The method according to claim 10 or 11, characterized, that the side of the electrode tip facing the overheating area the side facing away from the overheating area is rotated axially.