FR2676799A1 - PARTIAL SEALING DEVICE BETWEEN THE INTERIOR AND EXTERIOR OF AN ARC FURNACE. - Google Patents

Abstract

The device, according to the invention, for partial sealing between the interior (16) and the exterior (18) of an electric arc furnace comprising an arch (2) having at least one opening (4), an electrode (10) axially passing through the opening (4), a relatively large passage (14) existing between the wall of the opening (4) and the electrode (10), comprises a hollow element (20) placed on an outer surface horizontal plane of the furnace perpendicular to the axis (XX) of the electrode (10) and constituting the outer end of the opening, the hollow element surrounding the electrode with an annular clearance (22). When the furnace is of the tilting type, the device comprises stops 24 limiting the movement of the hollow element (20) during tilting of the furnace.

Description

The present invention relates to a device ensuring a seal

  partial improvement between an electrode of an electric arc furnace and the roof of the furnace. Electric arc furnaces, used in particular in the steel industry, have a vault

  provided with passages each crossed by an electrode.

  For the proper functioning of the oven, in particular the adjustment of the length of the electric arc, the electrodes are mounted movable longitudinally

in the passages.

  The electrodes being relatively fragile and subjected to uncontrolled transverse vibrations, the walls delimiting the passages are relatively distant from the external surface of the associated electrode to avoid any contact between the electrode and

  said walls, contact which deteriorates the electrode.

  Such a spacing between the walls of the passage and the electrode constitutes an important area of communication between the interior of the furnace and the ambient atmosphere. It turns out that such communication is harmful. In fact, when the oven is overpressure relative to the atmosphere, the gases contained in the

  oven escape through the communication area.

  When, on the contrary, the oven is under vacuum by

  air enters the furnace.

  When these exchanges between the inside and the outside of the oven are significant, they represent a nuisance

  important for the proper functioning of the oven.

  This is why different devices having

  to reduce these exchanges have been studied.

  It should be noted that devices ensuring total tightness by contact with the electrode cannot be used because they would cause rapid deterioration of the latter, therefore high costs, when the electrode is subjected to radial vibrations inherent in the passage. of a current

  high intensity electric current in the electrode.

  A device ensuring the protection of the electrodes of an electric arc furnace and limiting the gas exchanges between the inside and the outside of the

  oven, is for example described in the Certificate of use

FR 2 360 858.

  This protective device comprises a circular water box fixed to the roof of the oven around the electrode, a gas box constituted by an upper compartment, integral with the water box and comprising a gas inlet and exhaust orifices. gas which are located in the upper part of the gas box, moving parts in the form of an arc sector placed on the upper wall of the gas box and cooperating

  between them to form a crown surrounding the elect

  trode, each part comprising at its base a recess forming a chamber in which the gas is spread, and a lateral duct connected to the recess and opening laterally opposite the electrode to direct towards

this one a stream of gas.

  It turns out that such a device is relati-

  highly complex and difficult to implement.

  To remedy these drawbacks, the pre-

  sente invention aims to provide a device providing a partial seal between the inside and the outside of an electric arc furnace, the structure of which is simple and which is easy to implement. To this end, the present invention relates to a device for reducing gas exchanges between the inside and the outside of an arc furnace comprising a vault having at least one opening, an electrode axially passing through the opening, a passage delimited between the wall of the opening and the electrode, characterized in that it comprises a hollow element placed on a flat outer surface

  oven horizontal perpendicular to the axis of the

  electrode and constituting the outer end of the opening, the hollow element surrounding the electrode with

a determined ring clearance.

  According to other characteristics When the device is used on an oven

  - tilting, it includes stops limiting the displacement

  cementing of the hollow element on said external surface during the tilting of the furnace, to avoid contact between the hollow element and the external surface of the electrode. The hollow element has an open face located in

opposite the electrode.

  The hollow element comprises compartments separated by substantially radial partitions and having a

  open side facing the electrode.

  The partitions are angularly distributed, preferably evenly inside the body

hollow.

  The partitions have a short inner end

  dial spaced from the open face of the hollow body in

  direction of the outer periphery of the hollow body.

  The partitions have a blade-shaped profile.

  The hollow element has an open outer periphery putting the compartments in communication with

  a hollow crown supplied with pressurized gas.

  The side walls of the crown came from

  material with the side walls of the hollow element.

  The opening is delimited by an orifice arranged at

  across a roof having a horizontal exterior surface

  flat zontale, a sleeve being fixed coaxially to the orifice outside the vault and having at its end opposite the vault an annular plate with an internal diameter substantially equal to the diameter of the orifice to form between the vault and the annular plate zone in which a

gas under pressure.

  The hollow element is in sliding support on the face

outside of the annular plate.

  The hollow element is in sliding support on the roof.

The blown gas is a neutral gas.

  The invention will be better understood on reading

  of the description which will follow made only at

  by way of example, with reference to the accompanying drawings in which: FIG. 1 is a schematic sectional view of a

  opening of an electric arc furnace equipped with a provision

  sitive according to a first embodiment of the invention.

  FIG. 2 is a view in axial section, along II-

  II of FIG. 3, of a hollow element visible at more

small scale in Figure 1.

  Figure 3 is a top view of the hollow member

shown in figure 2.

  Figure 4 is a top view of a second mode of

  realization of the device according to the invention.

  Figure 5 is a sectional view along line 5-5

in Figure 4.

  Figure 6 is a schematic sectional view represented

  feeling a third embodiment of a provision

  sitive according to the invention on an electric arc furnace.

  Figure 7 is a view similar to Figure 6 showing an alternative embodiment of the device

Figure 6.

  In Figure 1 there is shown the upper part of the roof 2 of an electric arc furnace of the

  tilting type, commonly used in the steel industry.

  The vault 2 has an opening 4 with a vertical axis X-X delimited by a part of the vault forming a vault 6 having a flat horizontal upper face 8, forming an outer end face of

opening 4.

  An electrode 10 having an outer surface

  12 cylindrical crosses coaxially the opening 4.

  The electrode 10 is mounted so that it can

  see move axially by means known in

  itself, to ensure proper operation of the oven.

  The diameter of the external surface 12 of the electrode 10 is much smaller than the diameter of the opening 4, and delimits with the latter a

  relatively large annular passage 14.

  The annular passage 14 must be such that when the electrode 12 is subjected to radial vibrations, the electrode does not come into contact with the wall delimiting the opening 4, which would deteriorate it

or even break it.

  The annular passage 14 being relatively large allows the flow of a high gas flow between the interior 16 and the exterior 18 of the oven, flow which it is necessary to reduce to ensure the proper functioning of the oven.

  To this end, the oven is equipped with 1

  partial sealant which has an element

annular hollow 20.

  The annular hollow element 20 is placed in freely sliding support on the upper face 8 of the roof, coaxially with the electrode 10, with between

  the latter and the element 20 a reduced annular clearance 22.

  On the external surface 8 are fixed stops 24, intended to limit the displacement of the hollow element 20 on the surface 8 during tilting

  electric oven to extract the liquid metal.

  This avoids contact between the hollow element 20 and the electrode 10 which, on the one hand, could damage the latter by the shear due to impact, and on the other hand, could cause the initiation of an arc between the hollow element and the electrode, which

  would lead to the rapid destruction of the hollow element.

  Referring to Figures 2 and 3, we see that the hollow element 20 comprises two radial annular plates 26 and 28 which are parallel and axially spaced apart from each other, the externally radial peripheries of the plates 26 and

  28 being connected by a sleeve 30 of axis X-X.

  The internally radial peripheries 32 and 34 of the plates 26 and 28 respectively have the same diameter, the latter being slightly greater than the diameter of the outer surface 12 of the 1 electrode 10, and significantly smaller than that of the opening 4 of the oven. The space existing between the plates 26 and 28 comprises radial partitions 36 regularly distributed on the inner surface 38 of the sleeve 30. The partitions 36 are fixed by welding to the surface

inside 38 of sleeve 30.

  It should be noted that the partitions 36 can also be welded to one of the plates 26 or 28,

or both.

  The internally radial end 40 of the partitions 36 is located between the plates 26 and 28, that is to say axially set back towards the sleeve 30 relative to the peripheries 32 and 34 of the plates 26 and 28 respectively, so that that the partitions do not

  are not damaged in the event of contact between the

  hollow and the electrode in the absence of the stops 24 or when handling the elements before

their establishment.

  The partitions 36 thus delimit com

  compartments 42 open on their face intended to be in

opposite the electrode 10.

  The compartments 42 thus constitute a baffle creating pressure losses in the flow of gases entering or leaving the oven, which, added to the small annular clearance 22, will considerably reduce the gas exchange between the interior 16 and the exterior. 18

from the oven.

  Furthermore, the hollow element 20 being of light construction and simply placed on the surface 8, will slide on the latter when the electrode 10

  is subjected to radial vibrations.

  Indeed, the gas contained in the hollow element and the annular space 22 is compressed in the direction of the radial vibration of the electrode and repels the hollow element 20, so that the annular space 22 remains substantially constant , thus avoiding contact of the electrode 10 with

the hollow element 20.

  The hollow element 20 is made, preferably of metal, for example of non-magnetic stainless steel so as to limit the creation within it of

  Eddy currents due to intense magnetic fields

  ques created in the vicinity of the electrodes These eddy currents would heat it and lead to its rapid deterioration. In FIGS. 4 and 5 another embodiment of a hollow element 20 is shown, in which the externally radial periphery of the latter is open and opens into a crown.

ring finger 50.

  The annular ring 50 consists of two annular plates 52 and 54 arranged in the

  extension of the annular plates 26 and 28 respectively

  the externally radial periphery of the plat-

  ques 52 and 54 being closed by a cylindrical wall

  56, coaxial with the hollow element 20.

  The annular plates 52 and 54 of the cou-

  may have come in one piece with the plates

  26 and 28 respectively of the hollow element 20.

  The cylindrical wall 56 is pierced with an orifice 58 connected to a supply line 60 with pressurized gas This gas can therefore circulate in the compartments in the direction of the electrode 10 Its role is to improve the insulation between the oven and air

  outside, and cooling the hollow element 20.

  More simply, the gas can be blown directly into each or at least several of the compartments 42 by nozzles passing through the sleeve 30. Preferably the gas under pressure is a neutral gas. Furthermore, with reference to FIG. 4, it can be seen that the partitions 36 of the hollow element 20 are profiled so as to form blades, for directing the neutral gas entering the ring 50, through the compartments 42, so such that these gas flows are inclined on the axis XX along the arrow F Of course, the partitions 36 can also

  be straight as in the example previously described.

  Similarly, partitions profiled in blades can also be used when gas is not blown into the hollow element. They offer a larger contact surface than straight partitions.

  and therefore create more pressure drop.

  Figures 6 and 7 show the a-

  arrangement of a hollow element 20 on an oven, the opening through which extends the electrode 10 is constituted on the one hand by an orifice 62 of the roof

  6 and on the other hand by an annular plate 64.

  The annular plate 64 is arranged parallel

  along the outer surface 8 of the roof 6 and

removed from the latter.

  The annular plate 64 has an internal diameter substantially equal to the diameter of the orifice 62, and its periphery is fixed to the oven using

of a sleeve 66 of axis X-X.

  The annular plate 64, the sleeve 66, and the wall of the furnace delimit an area in which can

  be blown gas under pressure.

  In a first arrangement (see FIG. 6) the hollow element 20 is placed on the outer face 8 of the

vault 6.

  In a second arrangement (Figure 7), the hollow element 20 is placed on the outer surface

of the annular plate 64.

  The hollow element 20 according to the invention makes it possible to significantly reduce the communication between the interior and exterior of the oven, between which is

  thus ensured a relative seal.

  Indeed, the possibility of communication is reduced due to the fact that the annular space 22 is reduced relative to the passage 14, which is possible by the fact that the hollow element is placed on a flat wall

on which he can slide.

  Thus, in a 150-ton electric arc furnace, of the tilting type, comprising an electrode of 610 mm in diameter, the gas exchanges were reduced using a hollow element, arranged according to FIGS. 1 and 2, the diameter of the internally radial periphery (32, 34) of

622 mm.

  The use of a neutral gas in the

  positive described with reference to Figures 4 and 5 or in the area between the plate 64 and the roof top 6 of the arrangements shown in Figures 6 and 7 reduces gas exchange by adjusting the pressure of the blown gas according to the prevailing pressure at

inside the oven.

he

Claims (11)

  1 device for reducing gas exchange between the interior (16) and the exterior (18) of an electric arc furnace comprising a vault (2) having at least one opening (4), a through electrode (10) axially the opening (4), a passage (14) delimited between the wall of the opening (4) and the electrode (10), characterized in that it comprises a hollow element (20) placed on an external surface horizontal plane of the oven perpendicular to the axis (XX) of the electrode (10) and constituting the outer end of the opening, the hollow element surrounding the electrode with a clearance annular (22) determined.   2 Device according to claim 1, characterized in that it comprises stops (24) limiting the movement of the hollow element (20) on said outer surface (8; 70) during tilting from the oven.   3 Device according to claim 1 or 2, characterized in that the hollow element (20) has an inner face open radially opposite the electrode (10).   4 Device according to claim 3, characterized in that the hollow element (20) comprises compartments (42) separated by partitions (36) substantially radial, the compartments being open   facing the electrode (10).   Device according to claim 4,   characterized in that the partitions (36) are angular-   evenly distributed around the periphery of the hollow element (20).   6 Device according to claims 4 or   , characterized in that the partitions have a radial inner end (40) spaced from the open face of the hollow element (20) in the direction of the   outer periphery of the hollow element (20).   7 Device according to any one of   claims 4 to 6, characterized in that the   partitions have a blade-shaped profile (36).   8 Device according to any one of   Claims 1 to 7, characterized in that it comprises   means for blowing a gas into at least several of the compartments (42).   9 Device according to claim 7, characterized in that the radially outer periphery of the hollow element (20) is open and communicates with a hollow crown (50) supplied with gas under pressure.   Device according to claim 9, characterized in that the crown (50) and the hollow element (20) have lateral faces formed from one material. 11 Device according to any one of   Claims 1 to 7, characterized in that the opening   (4) of the oven is delimited by an orifice arranged in a roof (6) having a horizontal exterior surface   substantially planar, a sleeve (66) being fixed coaxially   at the orifice outside the roof and behaves   both at its end opposite the latter an annular plate (64) of internal diameter substantially equal to the diameter of the orifice (62), constituting the upper end of the opening, forming with the cap and the sleeve an area in which can be injected a gas under pressure.   12 Device according to claim 10, characterized in that the hollow element (20) is placed on   the outer face (70) of the annular plate (64).   13 Device according to claim 10, characterized in that the hollow element (20) is supported   sliding on the outer face (8) of the roof (6).   14 Device according to claim 8, ca-   characterized in that the gas supplied is a neutral gas.   Device according to any one of   claims 1 to 14 characterized in that the element   hollow 20 is made of non-magnetic stainless steel.