Furnace system comprising an electric arc furnace with a supply of liquid metal through a closable opening

Abstract

An electric arc furnace has a lower vessel (1). The top of the lower vessel (1) has a cross-section which has a main region (3) surrounded by a vertically upwardly projecting upper vessel (7) such that the main region (3) forms a vertical central axis (4), and the top also has a projecting region (6) which adjoins the main region (3) and extends over a limited angular range (α), as seen from the central axis (4). The electric arc furnace has a furnace cover (8) which covers the top of the upper vessel (7), and the electric arc furnace also has a horizontal cover (9) by means of which the projecting region (6) is covered. An opening which can be closed by means of a closure (10) is provided in the upper vessel (7) within the limited angular range (α), as seen from the central axis (4), and a protective cover (11) is provided above the horizontal cover (9) in the region of the opening, said protective cover being used to protect the horizontal cover (9) against metal and slag splashes which occur when liquid metal is supplied to the lower vessel (1) via the door (10).

Description

[0001] Description

[0002] Title of the invention

[0003] Furnace system with electric arc furnace and liquid metal feed through a closable opening

[0004] field of technology

[0005] The present invention relates to an electric arc furnace,

[0006] - wherein the electric arc furnace has a lower vessel,

[0007] - wherein the lower vessel has a cross-section on its upper side which has a main area surrounded by a vertically upward-projecting upper vessel, such that the main area forms a vertical central axis,

[0008] - wherein the upper surface continues to have a bay window area adjacent to the main area and extending over a limited angular range when viewed from the central axis,

[0009] - wherein the electric arc furnace has a furnace lid that covers the upper vessel at its top,

[0010] - wherein the electric arc furnace has a horizontal cover through which the bay window area is covered.

[0011] State of the art

[0012] Such an electric arc furnace is generally known.

[0013] Summary of the invention

[0014] In many cases, molten metal is charged into an electric arc furnace through the slag door. On an electric arc furnace of the type described above, the slag door is located at an angle opposite the limited angular range. In other cases, charging molten metal through the slag door is not possible. This is particularly true if the ladle containing the molten metal is delivered within the limited angular range, where the tap hole of the lower vessel is also located.

[0015] In the prior art, it is known to remove the furnace lid and pour the molten metal into the lower vessel from above. This procedure is possible if a crane – especially one located at the tapping end – can travel directly over the lower vessel. However, this procedure has disadvantages. In particular, it poses a safety risk and, in some cases, even a risk of explosion. Furthermore, it results in significant time delays and energy losses.

[0016] In cases where the ladle containing the molten metal is delivered within a limited angular range, making it impossible to charge the molten metal through the slag door, a hopper is often permanently installed on the lower vessel through which the molten metal can be introduced. This method also has its disadvantages. In particular, the trough through which the molten metal is fed into the lower vessel cannot be preheated. As a result, residues, known as deposits, accumulate there. These residues must be removed manually. Furthermore, a foamy slag forms on the molten metal during operation of the electric arc furnace. This foamy slag can rise to the point where the hopper opens into the lower vessel, potentially clogging the opening. Here, too, only manual cleaning is possible. In both cases, manual cleaning requires the electric arc furnace to be shut down.

[0017] The object of the present invention is to create possibilities by means of which a reliable and efficient operation of an electric arc furnace of the type mentioned above is possible even when the ladle containing the liquid metal is delivered in the limited angular range.

[0018] The problem is solved by a furnace system with the features of claim 1. Advantageous embodiments of the furnace system are the subject of dependent claims 2 to 14.

[0019] According to the invention, a furnace system of the type mentioned above is designed by:

[0020] - that, viewed from the central axis, an opening which can be closed by means of a closure is arranged in the upper vessel within the limited angular range and

[0021] - that a protective cover is arranged above the horizontal cover in the area of ​​the opening, by means of which the horizontal cover is protected from splashes of metal and slag that occur when liquid metal is supplied to the lower vessel via the opening.

[0022] This provides an opening through which the molten metal can be fed into the lower vessel. This opening can then be closed. The protective cover also adequately protects the horizontal cover. The protective cover is therefore not a channel through which the metal is intended to flow, but purely a protective cover. While a channel for the molten metal is still required, this channel is not, within the scope of the present invention, a fixed element of the electric arc furnace. Rather, the channel can, for example, be part of a transport device by means of which the ladle containing the molten metal is transported. A cover for the channel and a funnel positioned upstream of the channel can also be components of the transport device.

[0023] The limited angular range is usually less than 90°. For example, it can be approximately 60° (+ / - 10). 0The horizontal cover is typically water-cooled on its upper surface. A hydraulic cylinder unit may be associated with the closure for opening and closing the opening.

[0024] The upper vessel typically has a water cooling system on its inner side. Therefore, the protective cover preferably has a projection that extends beyond the water cooling system and into the furnace chamber. This ensures that the protective cover not only protects the horizontal cover but also the area of ​​the upper vessel below the opening or the protective cover itself.

[0025] Preferably, when closed, the closure is flush with the inside of the upper vessel and also features a refractory reinforcement on its inner surface that becomes thicker towards the bottom. This protects the protective cover from the scrap during the initial loading of the container. This is especially true if the refractory reinforcement of the closure extends inwards beyond the protective cover.

[0026] Preferably, the closure has a cleaning edge on its underside for removing slag and / or metal residue from the top of the protective cover when the closure is closed. This prevents contamination of the protective cover as much as possible.

[0027] Preferably, the opening is positioned off-center with respect to the limited angular range. This particularly simplifies access to the tapping area of ​​the lower vessel, which is usually also located in the bay window area.

[0028] Preferably, the protective cover is arranged in a retaining frame that is detachably attached to the upper vessel, in particular by being hooked onto the upper vessel. This allows the protective cover to be easily attached to and detached from the upper vessel, so that the protective cover can be serviced and possibly repaired independently of the operation of the electric arc furnace. In particular, it is possible to continue operating the electric arc furnace if, during this time, the removed protective cover is replaced with another protective cover.

[0029] Preferably, the protective cover is designed as a sheet metal tray with a fire-resistant lining on its upper surface. This design is simple, robust, reliable, and cost-effective.

[0030] Preferably, the protective cover is inclined towards the lower vessel so that any metal or slag striking the protective cover is directed into the lower vessel. This minimizes contamination of the protective cover. The angle of inclination relative to the horizontal is preferably at least 0.5° and at most 10°. Typically, the angle of inclination is between 2° and 5°.

[0031] Preferably, the closure is designed as a pivoting flap whose pivot axis runs horizontally and is located at the upper edge of the flap. This design has proven to be particularly advantageous in tests.

[0032] Preferably, the closure is made of copper. This facilitates cooling of the closure. Furthermore, the closure is preferably water-cooled. This allows for particularly good heat dissipation.

[0033] The supply of liquid metal to the electric arc furnace is usually accomplished by means of a ladle carriage with a tilting ladle that can be moved to the arc furnace. Such a ladle carriage is also present in this invention. Within the scope of the present invention, a pouring trough can be arranged on the ladle carriage, the end of which can be moved through the opening into the interior of the electric arc furnace as the ladle carriage is moved. This allows liquid metal in the ladle to flow from the ladle into the lower vessel via the pouring trough. The trough can, in particular, be heated.

[0034] Brief description of the drawings

[0035] The properties, features, and advantages of this invention described above, as well as the manner in which they are achieved, will become clearer and more readily understandable in connection with the following description of an exemplary embodiment, which is explained in more detail in conjunction with the drawings. Figure 1 shows a section through an electric arc furnace with a closed partition.

[0036] FIG 2 shows a section through the electric arc furnace of FIG 1 with the opening open,

[0037] FIG 3 shows the electric arc furnace of FIG 2 with a so-called launder,

[0038] FIG 4 shows the electric arc furnace of FIG 1 from above,

[0039] FIG 5 shows a section of an upper vessel of the electric arc furnace and FIG 6 shows a section through a protective cover.

[0040] Description of the embodiments

[0041] FIGS. 1 to 4 show the same electric arc furnace and are therefore explained together below.

[0042] According to FIGS. 1 to 4, the electric arc furnace has a lower vessel 1. The lower vessel 1 is supported in a base 2 (usually referred to as a cradle). The lower vessel 1 has – see especially FIG. 4 – a cross-section on its upper side that includes a main section 3. Often, the main section 3 forms a vertical central axis 4. In particular, the electrodes 5 of the electric arc furnace are arranged exactly or at least approximately uniformly around the central axis 4. The upper side of the lower vessel 1 also has a bay section 6 adjacent to the main section 3. The bay section 6 extends from the central axis 4 over a limited angular range a.

[0043] The electric arc furnace further comprises a vertically projecting upper vessel 7, which extends upwards from the top of the lower vessel 1 and surrounds the main chamber 3. The upper vessel 7 typically has water cooling on its inside, as indicated in FIGS. 1 to 3 by the cooling water pipes. A furnace lid 8 of the electric arc furnace covers the furnace vessel 7 at its top. The electric arc furnace also has a horizontal cover 9 (bay panel) that covers the bay area 6.

[0044] Viewed from the central axis 4, an opening is arranged in the upper vessel 7 within the limited angular range a. The opening is closed by a closure 10. The closure 10 is preferably made of copper. Furthermore, the closure 10 is preferably water-cooled. In the closed state (see FIG. 1), the closure 10 is generally flush with the inside of the upper vessel 7. Furthermore, the closure 10 is preferably designed as a pivotable flap, the pivot axis 10' of which is horizontal and is located at the upper edge of the flap or closure 10. A protective cover 11 is arranged above the horizontal cover 9 in the area of ​​the closure 10. By means of the protective cover 11, the horizontal cover 9 is protected from splashes of metal and slag that occur when liquid metal is fed into the lower vessel 1 via the opening.The opening is preferably arranged off-center with respect to the limited angular range a. This is particularly evident from FIG. 4, because the off-center protective cover 11, which is located below the opening, can be seen in FIG. 4.

[0045] The supply of liquid metal to the lower vessel 1 via the opening is carried out according to the following procedure:

[0046] A ladle car 12 with a ladle 13 containing liquid metal 14 is moved to the electric arc furnace. A feed trough 15, usually called a launder, is also arranged on the ladle car 12. Before the end of the feed trough 15 reaches the lower vessel 1, the opening is opened (i.e., the closure 10 is moved accordingly) so that the end of the feed trough 15 can be moved through the opening into the interior of the electric arc furnace. The ladle 13 is then tilted so that the liquid metal 14 flows from the ladle 13, via the feed trough 15, into the lower vessel 1. The ladle car 12 is then moved away from the electric arc furnace so that the opening can be closed again. Before the liquid metal 14 is tilted into the feed trough 15, the feed trough 15 is preferably heated, for example, by means of gas burners.

[0047] As can be seen particularly clearly in FIGS. 1 and 2, the protective cover 11 has a projection 11' that extends inwards beyond the water cooling (cooling water pipes) into the furnace chamber. In the closed position, the closure 10 is flush with the inner surface of the upper vessel 7. Furthermore, according to these two FIGS., the closure 10 preferably has a refractory reinforcement 10" on its inner surface, which becomes thicker towards the bottom. The refractory reinforcement 10" can, in particular, extend inwards beyond the protective cover 11 – including its projection 11'.

[0048] The protective cover 11 is preferably arranged in a retaining frame 16, which in turn is detachably attached to the upper vessel 7. The retaining frame 16 can, in particular, be hooked onto the upper vessel 7. As can also be seen from the schematic representation in FIG. 5, the protective cover 11 is inclined towards the lower vessel 1. The angle of inclination β relative to the horizontal is usually at least 0.5°, in particular at least 1° or at least 2°. This ensures that any metal 14 or slag (not shown) striking the protective cover 11 is directed into the lower vessel 1. Furthermore, according to FIG. 6, the protective cover 7 is usually designed as a sheet metal tray 17, which is provided on its upper side with a refractory lining 18.

[0049] The closure 10, as shown in FIG. 6, preferably has a cleaning edge 19 on its underside. This makes it possible to remove slag and / or metal residues from the top of the protective cover 11 when closing the closure 10.

[0050] The present invention has many advantages. One advantage lies in the arrangement of the opening. Because of the off-center arrangement of the opening, it is possible to ensure that the opening does not obscure an area of ​​the bay window 6 located above a tap hole of the lower vessel 1, nor does it impede access to this area of ​​the bay window 6. A further advantage is that the feed trough 15 is not a fixed component of the electric arc furnace and can therefore be maintained and preheated independently of the electric arc furnace.

[0051] Although the invention has been further illustrated and described in detail by the preferred embodiments, the invention is not limited by the disclosed examples and other variations can be derived from them by the person skilled in the art without leaving the scope of protection of the invention.

[0052] Reference symbol list

[0053] 1 lower container

[0054] 2 Substructure

[0055] 3 Main Area

[0056] 4 Central axis

[0057] 5 electrodes

[0058] 6 Bay window area

[0059] 7 Upper vessel

[0060] 8 Oven lids

[0061] 9 Cover

[0062] 10 Closure

[0063] 10' swivel axis

[0064] 10" reinforcement

[0065] 11 Protective cover

[0066] 11' lead

[0067] 12 pan trolleys

[0068] 13 pans

[0069] 14 Metal

[0070] 15 Pouring trough

[0071] 16 mounting frames

[0072] 17 sheet metal tubs

[0073] 18. Brickwork

[0074] 19 Clearing edge a Angle range ß Inclination angle

Claims

Patent claims 1. Furnace system with an electric arc furnace, - wherein the electric arc furnace has a lower vessel (1), - wherein the lower vessel (1) has a cross-section on its upper side which has a main area (3) surrounded by a vertically upwardly projecting upper vessel (7), such that the main area (3) forms a vertical central axis (4), - wherein the upper surface continues to have a bay window area (6) adjacent to the main area (3) and extending over a limited angular range (a) as seen from the central axis (4), - wherein the electric arc furnace has a furnace lid (8) which covers the upper vessel (7) at its top, - wherein the electric arc furnace has a horizontal cover (9) through which the bay window area (6) is covered, characterized by , - that in the upper vessel (7) viewed from the central axis (4) within the limited angular range (a) an opening which can be closed by means of a closure (10) is arranged and - that a protective cover (11) is arranged above the horizontal cover (9) in the area of ​​the opening, by means of which the horizontal cover (9) is protected from metal and slag splashes that occur when liquid metal is supplied to the lower vessel (1) via the opening.

2. Furnace system according to claim 1, characterized in that the upper vessel (7) has a water cooling system on its inside and that the protective cover (11) has a projection (11') which extends beyond the water cooling system inwards into the furnace chamber.

3. Furnace system according to claim 1 or 2, characterized in that the closure (10) is flush with the upper vessel (7) on the inside when closed and that the closure (10) has a refractory reinforcement (10") on its inside which becomes thicker towards the bottom.

4. Oven system according to claim 3, characterized by , that the fire-resistant reinforcement (10") of the closure (10) extends inwards beyond the protective cover (11).

5. Furnace system according to one of the above claims, characterized in that the closure (10) has a clearing edge (19) on its underside for removing slag and / or metal residues from the top of the protective cover (11) when closing the closure (10).

6. Oven system according to one of the above claims, characterized in that the closure (10) is arranged off-center with respect to the limited angular range (a).

7. Oven system according to one of the above claims, characterized in that the protective cover (11) is arranged in a retaining frame (16) which is detachably attached to the upper vessel (7), in particular hooked onto the upper vessel (7).

8. Oven system according to one of the above claims, characterized in that the protective cover (11) is designed as a sheet metal tray (17) which is provided on its upper side with a refractory lining (18).

9. Furnace system according to one of the above claims, characterized in that the protective cover (11) is inclined towards the lower vessel (1) so that metal (14) or slag impacting the protective cover (11) is directed into the lower vessel (1).

10. Oven system according to one of the above claims, characterized in that the closure (10) is designed as a pivotable flap, the pivot axis (10') of which runs horizontally and is arranged at the upper edge of the flap.

11. Furnace system according to one of the above claims, characterized in that the closure (10) is made of copper.

12. Oven system according to one of the above claims, characterized in that the closure (10) is water-cooled.

13. Furnace system according to one of the above claims, characterized in that the furnace system comprises a ladle carriage (12) movable to the electric arc furnace with a tiltable ladle (13) and that a feed trough (15) is arranged on the ladle carriage (12), the end of which can be moved through the opening into the interior of the electric arc furnace when the ladle carriage (12) is moved, so that liquid metal (14) located in the ladle (13) can flow from the ladle (13) into the lower vessel (1) via the feed trough (15).

14. Furnace system according to claim 13, characterized in that the feed trough (15) is heatable.

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