Deskulling lance

Abstract

A lance for discharging high velocity oxygen or other gases to remove skulls which form within the upper cone section of steelmaking vessels. The lance includes a lance tip having a plurality of sets of radially spaced nozzles whereby gas is directed generally laterally outwardly against the inner wall of the cone section to retard or remove the skulls.

Description

FIELD OF THE INVENTION

[0001] The present invention relates in general to steelmaking processes and, in particular, to basic oxygen furnace processes wherein oxygen is blown into the metal bath. More specifically, the invention relates to a lance designed to blow oxygen gas or other gases through the upper opening of a steelmaking vessel for the purpose of removing or retarding the formation of skull which generally is built up on the inner wall of the nose or cone section of the vessel.

BACKGROUND OF THE INVENTION

[0002] A basic oxygen furnace (hereinafter “BOF”) used to make steel includes an outer steel shell and a refractory lining inside the outer steel shell. Most basic oxygen furnaces are equipped with two lances, only one of which can be in an operative position above the furnace at a given time. One of the two lances is an idle-side auxiliary lance that is kept on standby outside the perimeter of the furnace. The other lance is a main oxygen blowing refining lance which, during the steelmaking process, is located in the furnace above the bath. In conventional BOF shops, a motorized lance transport and elevator system is used to manipulate the main and auxiliary lances.

[0003] Due to the violent agitation of the melt during refining of the molten metal into steel, a material commonly known as skull, a mixture of molten metal and oxides, is deposited on the working surface of the furnace and on the lances. The formation of skull at the cone of the BOF is undesirable because it restricts the ability to lower lances and to charge scrap into the cone of the furnace.

[0004] In addition, because of factors including wear, high temperature and the combustion of high velocity oxygen gas in the furnace, the refractory walls deteriorate and must be repaired or replaced. One way to maintain the refractory walls of the furnace is through a process known as slag splashing in which a lance is used to blow an inert gas toward the slag layer. This causes the slag to be splashed upwardly onto the refractory walls and to coat portions of the refractory walls that have been worn. The slag cools on the refractory walls, effectively repairing worn portions of the walls. However, the slag splashing process may increase the problem of skull build-up at the cone of the furnace.

[0005] In view of the problems of skulling at the cone of the furnace and deterioration of the refractory walls, some BOF shops employ an idle-side deskulling lance and a refining lance. Oxygen gas is typically blown from the deskulling lance to melt the skull at the furnace cone as the lance is moved vertically up and down near the location of the skull. Examples of deskulling lances are provided in U.S. Pat. Nos. 4,230,274 and 4,332,033. A disadvantage of these lances is that they cannot remove furnace skulls in selected areas. That is, they are useful for removing skulls that are generally uniformly deposited about the interior of the furnace cone, but they cannot be used to target skulls having relatively thicker and thinner zones of deposits.

[0006] If the deskulling process is not carefully monitored, the furnace refractory lining may be rapidly damaged by a deskulling lance. Thus, while beneficially removing thicker skull deposits in one area of the furnace cone, a conventional deskulling lance may have already melted thinner skulling in other areas and begun degrading the underlying refractory.

[0007] U.S. Pat. No. 5,865,867 discloses a multipurpose lance, one function of which is deskulling. When used in its deskulling mode, one or more auxiliary or deskulling nozzles may be selectively plugged to create desired deskulling gas patterns. However, because this lance, like those of U.S. Pat. Nos. 4,230,274, 4,332,033, possesses only a single set of radially disposed deskulling nozzles, it is prone to uneven skull removal such as undercutting of the skull if the vertical movement of the lance is not carefully controlled during a deskulling procedure.

[0008] An advantage exists, therefore, for a deskulling lance that can effectively perform removal of both uniform and non-uniform deposits of skull from the interior of a steelmaking furnace.

SUMMARY OF THE INVENTION

[0009] The present invention involves introducing a lance into the charging opening of a steelmaking vessel and placing it into position where gas is blown generally laterally outwardly against the inner surface of the vessel cone to prevent the buildup of skull or to remove the same. The lance includes a tip having a relatively large volume gas chamber and radial orifices or nozzles which extend generally in a direction to blow oxygen or other gases against the cone of the vessel. The lance is supported so that it can be moved by machinery in an up and down manner whereby the entire nose or cone portion of the vessel can be traversed and gases may be delivered to all portions of the vessel wherein the cone skull buildup exists.

[0010] Among the advantages of the deskulling lance according to the invention is that it effectively removes both uniform and non-uniform deposits of skull from the interior of a steelmaking furnace. This beneficial feature is the result of a lance tip having nozzles that may be selectively plugged. So constructed, when removal of generally uniformly deposited furnace skull is encountered, all of the lance tip nozzles are unplugged whereby deskulling gas such as oxygen is discharged uniformly from the periphery of the lance tip and skull is removed from the vessel at a uniform rate throughout the circumference of the vessel. Where uneven skull deposits are present, one or more of the tip nozzles may be plugged to avoid damage the vessel's refractory where little or no skull may be present while the remaining nozzles may remain unplugged to melt relatively thicker deposits of skull. As a consequence, vessel skull may be removed in a precise and minimally destructive manner.

[0011] In addition, the radially disposed tip nozzles according to the invention preferably comprise two or more sets of nozzles preferably arranged at differing orientations with respect to one another. In this way, the nozzles of the several rings can be selectively opened or plugged to enable variable gas flow patterns to be created that may be used to effectively remove uneven deposits of vessel skull. Further, multiple sets of differently oriented deskulling nozzles reduce the possibility of uneven skull removal such as undercutting that commonly occurs with conventional deskulling lance tips having a single ring of deskulling nozzles.

[0012] Other details, objects and advantages of the present invention will become apparent as the following description of the presently preferred embodiments and presently preferred methods of practicing the invention proceeds.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The invention will become more readily apparent from the following description of preferred embodiments thereof shown, by way of example only, in the accompanying drawings wherein:

[0014] FIG. 1 is a cross-sectional view of a steelmaking vessel showing a conventional deskulling lance inserted therein for removing skull;

[0015] FIG. 2 is an enlarged perspective view of a conventional deskulling lance tip attached to the lower end of a lance body;

[0016] FIG. 3 is a bottom plan view of the deskulling lance tip of FIG. 2;

[0017] FIG. 4 is an elevational cross-sectional view of the deskulling lance tip of FIG. 2 taken along the line 4-4 of FIG. 3;

[0018] FIG. 5 is an elevational cross-section view of a deskulling lance tip according to the present invention;

[0019] FIG. 6 is an enlarged elevational cross-section view of a first embodiment of a plug means inserted into a nozzle of a deskulling lance tip according to the present invention;

[0020] FIG. 7A is an enlarged elevational cross-section view of a further embodiment of a plug means that is insertable into a nozzle of a deskulling lance tip according to the present invention;

[0021] FIG. 7B illustrates the plug means of FIG. 7A inserted into a nozzle of a deskulling lance tip according to the present invention;

[0022] FIG. 8A is an enlarged elevational cross-section view of a further embodiment of a partially assembled plug means inserted into a nozzle of a deskulling lance tip according to the present invention; and

[0023] FIG. 8B is an enlarged elevational cross-section view of the fully assembled plug means of FIG. 8A inserted into a nozzle of a deskulling lance tip according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0024] Referring to the drawings wherein like or similar references indicate like or similar elements throughout the several views, there is shown in FIG. 1 a conventional BOF steelmaking vessel 10 which includes an outer steel shell 11 having a lower hearth section 12. The shell 11 is suitably lined by ceramic or other refractory material indicated at 13. The vessel 10 is so shaped at its upper end to provide an upwardly and inwardly tapering nose or cone section 14 provided with a charging opening 15. The steel bath 16 is contained within the hearth section 12 of the vessel 10. The schematic broken lines 17 at the upper end of the vessel or cone section 14 indicate a buildup of skull resulting from the steelmaking process. The present invention provides for equipment and a process to remove or to prevent the build up of undesirable skull that can interfere with the efficient operation of the steelmaking vessel. Support trunnions 18 of conventional design support vessel 10 during the steelmaking process.

[0025] A conventional deskulling lance 19 is inserted into the cone section 14 by means of an unillustrated crane, elevator or the like, which can be operated to move the lance upwardly and downwardly for removal of skull 17. The lower end of lance 19 is provided with a suitable porting tip 21 consisting of a single ring of radially disposed nozzles described hereinafter in connection with FIGS. 2-4. When moving lance 19 up and down in vessel 10 during a deskulling procedure, a plurality of radially spaced streams of oxygen or other effective media are blown or directed toward the inner wall of cone 14 of vessel 10 to remove the formation of skull 17 after it has been built up during the steelmaking process.

[0026] FIGS. 2, 3, and 4 reveal in greater detail the construction of conventional deskulling lance 19. The lance includes a lance body or piping structure 20 with tip 21 being connected to the piping structure by any suitable means such as welding or the like. Piping structure 20 includes an outer pipe assembly 25, and intermediate pipe assembly 26 and an inner pipe assembly 27. As best shown in FIG. 4, the intermediate pipe assembly 26 typically includes telescoping lower sections 28 and 29 which permit relative sliding movement to accommodate longitudinal thermal expansion. Certain pipes of the piping structure 20 also normally include suitable spacing members 30 to space the intermediate pipe assembly 26 from the outer pipe assembly 25.

[0027] Tip 21 is provided with a bottom wall 31, an annular converging portion 32 formed by an outer downwardly converging wall 33 and an inner downwardly converging wall 34. Ports or nozzles 35 are radially spaced about the lower end of the nozzle and extend substantially perpendicular to the inner and outer walls 34 and 33. Tip 21 is provided with a relatively wide gas chamber 38′ which is in alignment with and communicates with a gas conduit 38 formed by means of inner pipe assembly 27. With this construction, lance 19 thus can direct oxygen or other gases from the gas conduit 38 through the gas chamber 38′ and downwardly and outwardly through nozzles 35 against the inner walls of the cone section 14 of vessel 10 to remove or retard skull 17 occurring as a result of the steelmaking process.

[0028] As shown in FIG. 4, tip 21 also includes an inner skirt wall 36 which extends to and is connected to the lower end of the inner pipe assembly 27. Further, an outer skirt wall 37 is connected to the outer pipe assembly 25. Water outlet passages are designated at 39 and inlet passages at 40. The telescoping pipe section 29 is provided at its lower end with a projecting portion 41 which extends into a water by-pass chamber designated at 42.

[0029] While generally useful for removing uniform skull deposits, conventional deskulling lances of the type illustrated in FIGS. 1-4 are of limited use in removing skulls of non-uniform thicknesses and consistencies. This is because they discharge deskulling gas uniformly against the interior surface of the cone section 14 of vessel 10. In situations where skull is not uniformly deposited on the cone section, i.e., where the skull includes relatively thicker and thinner deposits, a conventional deskulling lance can cause damage to the refractory material 13 when the thinner skull deposits have been removed but the thicker skull deposits have not. Further, because conventional deskulling lance tips have a single ring of deskulling nozzles, great care must be taken when moving the lance upwardly and downwardly during a deskulling procedure. If vertical lance movement is not carefully controlled, uneven skull removal such as undercutting may occur if the lance resides too long at a particular elevation. The deskulling lances according to the present invention overcome these shortcomings.

[0030] FIG. 5 illustrates a deskulling lance tip 21′ constructed in accordance with the present invention. Tip 21′ is connectable by any suitable means such as welding or the like to a lance body or piping structure 20′ similar to piping structure 20 of lance 19 to create a deskulling lance 19′. In many respects, tip 21′ and lance body 20′ are constructed substantially similarly to tip 21 and lance body 20 described above. For brevity, therefore, only those features that are not present in FIGS. 2-4 or materially differ from their counterparts in FIGS. 2-4 or are whose descriptions are otherwise necessary for a proper understanding of the present invention will be described in detail herein.

[0031] According to the invention, deskulling tip 21′ includes a plurality of discrete sets of deskulling nozzles that are in some way differently oriented relative to one another in the tip. For example, one set of deskulling nozzles may be disposed above or below another set, one set may discharge deskulling gas at a relatively deeper or shallower angle than another set, one set may radiate from a common center point located along the longitudinal axis of the tip whereas another set may assume a quasi or fully tangential orientation or neither set may radiate from a common center point but each set may assume different tangential orientations. According to a presently preferred embodiment, tip 21′ includes a first set of radially spaced nozzles 35′ disposed at an angle α of at least about 30°, and preferably at least about 60°, with respect to the longitudinal axis 50 of the tip 21′ (which is coextensive with the longitudinal axis of the lance to which the tip is connected). Similarly, tip 21′ further preferably includes a second set of radially spaced nozzles 35″ disposed at an angle β of at least about 30°, and preferably at least about 60°, with respect to the longitudinal axis 50. Although not illustrated, additional sets of radially spaced nozzles may also be provided that may be disposed at angles of at least about 30°, and preferably at least about 60°, with respect to the longitudinal axis 50. Angle α of the first set of nozzles 35′, angle β of the second set of nozzles 35″ and the angles of any additional sets of nozzles with respect to the longitudinal axis 50 are preferably different form one another. By providing multiple sets of nozzles such as nozzles 35′, 35″ and any additional sets of nozzles at differing angles with respect to the longitudinal axis 50, deskulling gas such as oxygen is discharged at differing angles against the furnace skull. Consequently, the possibility of uneven skull removal (e.g., undercutting) as the lance is moved vertically relative to the steelmaking vessel is considerably reduced because the nozzles of one set of nozzles can operate to melt away undercuts or other imperfections in the skull that may be created by another set of nozzles during the deskulling procedure.

[0032] Another advantage of the present invention is the provision of plug means that may be selectively used to plug any one or more of the deskulling nozzles 35′, 35″ and/or the nozzles of any additional sets of deskulling nozzles in order to enable variable gas flow patterns to be created that may be used to effectively remove uneven deposits of vessel skull. FIGS. 6-8B illustrate presently preferred examples of such plug means.

[0033] Referring to FIG. 6, the plug means comprise threaded plugs 60 having external threads 62 provided about the circumference of the plugs which are adapted to matingly engage with internal threads 64 provided along a portion of the lengths of the nozzles 35′, 35″ and/or the nozzles of any additional sets of deskulling nozzles. To facilitate insertion within the nozzles, plugs 60 are desirably formed with a recess or projection 66, e.g., a socket or bolt head, that can be turned by a simple turning tool such as a wrench. The nozzles and the plugs 60 may taper outwardly in the direction of gas flow to facilitate removal of the plugs.

[0034] FIGS. 7A and 7B show another form of tip 21′ adapted to releasably receive a further embodiment of plug means of the present invention. According to this embodiment, nozzles 35′, 35″ and/or the nozzles of any additional sets of deskulling nozzles preferably include latch means 70 in the form of at least one pin, bolt or the like protruding inwardly into each of the nozzles. Latch pin 70 is adapted to releasably engage plug means 72 shown in FIG. 7A. More particularly, plug means 72 preferably comprises a body portion 74 and a head portion 76. Body portion 74 preferably includes at least one recessed, preferably generally L-shaped keyway or slot 78 corresponding in number and radial spacing to each latch pin 170. Each slot 78 further preferably includes a lip or ridge 80 for positively retaining the plug means 72 in engagement with the latch pin 70 during operation of the lance assembly.

[0035] To connect one of the plugs 72 in a deskulling nozzle, the body portion 74 of the plugs is aligned with the latch pin 70 such that the latch pin is received by a first leg portion of slot 78. The plug is then pressed into the nozzle to a point where it can be inserted no further. Thereafter, the plug is rotated through an angle of generally about 90° or less whereby the latch pin passes into a laterally extending second leg of slot 78 until ridge 80 fully passes the latch pin. The plug(s) 72 are then released. The plug(s) 72 remain in position in the nozzle(s) due to their weight, the pressure of gas exerted against them during operation of the lance, and the mechanical interference between the latch pin and the ridge 80. To remove plugs 72 the insertion procedure is simply reversed.

[0036] To minimize gas leakage through the deskulling nozzles during lance operation, the body portions of plugs 72 are preferably provided with an unillustrated annular slot or groove sized to receive an O-ring or similar sealing means 82. To facilitate insertion of the plugs 72, the head portions of the plugs are desirably formed with a recess or projection that is suitable for turning by a simple turning tool such as a wrench.

[0037] It will be understood that the relative dispositions of the latch pin and engagement slots may be reversed. That is, the plugs 72 may carry one or more outwardly projecting latches similar to the latch pin 70 which may engage correspondingly arranged recessed slots similar to slots 78 that may be formed in the interior walls of the nozzles 35′, 35″ or other deskulling nozzles.

[0038] FIGS. 8A and 8B show another form of tip 21′ adapted to releasably receive a further embodiment of plug means 90 of the present invention. According to this embodiment, nozzles 35′, 35″ and/or the nozzles of any additional sets of deskulling nozzles may be selectively plugged by plug means 90 comprising an expandable anchor member 92 and an expander member 94. Anchor member 92 may be fabricated from any material capable of withstanding the high temperatures and gas pressures encountered during a deskulling procedure. Suitable materials may include, without limitation, a metal or metal alloy such as stainless steel. To plug a nozzle, anchor member 92 is inserted into the nozzle and the expander member 94, which may assume the form of a bolt or the like, is inserted into the anchor member. In so doing, the anchor member is pressed into tight frictional engagement with the circumferential wall surface of the nozzle and the nozzle passageway becomes blocked by the presence of the anchor member and the expander member. Preferably, expander member 94 includes a recess or projection 96 that is suitable for turning by a simple turning tool such as a wrench.

[0039] Although the invention has been described in detail for the purpose of illustration, it is to be understood that such detail is solely for that purpose and that variations can be made therein by those skilled in the art without departing from the spirit and scope of the invention as claimed herein.

Claims

1. A deskulling lance tip comprising: a first set of deskulling nozzles; and at least one additional set of deskulling nozzles disposed at a different orientation in said tip relative to said first set of deskulling nozzles.

2. The deskulling lance tip of claim 1 wherein said tip has a longitudinal axis, said first set of deskulling nozzles are disposed at an angle with respect to said longitudinal axis, and said at least one additional set of deskulling nozzles are disposed at an angle with respect to said longitudinal axis.

3. The deskulling lance tip of claim 2 wherein said angles are at least about 30°.

4. The deskulling lance tip of claim 1 wherein said first set of deskulling nozzles is disposed at a first angle with respect to said longitudinal axis and said at least one additional set of deskulling nozzles is disposed at at least one additional angle with respect to said longitudinal axis.

5. The deskulling lance tip of claim 4 wherein said at least one additional angle is different from said first angle.

6. The deskulling lance tip of claim 1 further comprising means for plugging desired nozzles of at least one of said first set of deskulling nozzles and said at least one additional set of deskulling nozzles.

7. The deskulling lance tip of claim 6 wherein said plugging means comprise at least one threaded plug.

8. The deskulling lance tip of claim 6 wherein said plugging means comprise at least one slotted plug.

9. The deskulling lance tip of claim 6 wherein said plugging means comprise at least one friction plug.

10. A deskulling lance comprising: a lance body and a lance tip connected to said lance body, said lance tip comprising: a first set of deskulling nozzles; and at least one additional set of deskulling nozzles disposed at a different orientation in said tip relative to said first set of deskulling nozzles.

11. The deskulling lance of claim 10 wherein said tip has a longitudinal axis, said first set of deskulling nozzles are disposed at an angle with respect to said longitudinal axis, and said at least one additional set of deskulling nozzles are disposed at an angle with respect to said longitudinal axis.

12. The deskulling lance of claim 11 wherein said angles are at least about 30°.

13. The deskulling lance of claim 10 wherein said first set of deskulling nozzles is disposed at a first angle with respect to said longitudinal axis and said at least one additional set of deskulling nozzles is disposed at at least one additional angle with respect to said longitudinal axis.

14. The deskulling lance of claim 13 wherein said at least one additional angle is different from said first angle.

15. The deskulling lance of claim 10 further comprising means for plugging desired nozzles of at least one of said first set of deskulling nozzles and said at least one additional set of deskulling nozzles.

16. The deskulling lance of claim 15 wherein said plugging means comprise at least one threaded plug.

17. The deskulling lance of claim 15 wherein said plugging means comprise at least one slotted plug.

18. The deskulling lance of claim 15 wherein said plugging means comprise at least one friction plug.

19. A method of removing skull from a steelmaking vessel comprising the steps of: inserting a deskulling lance having a lance body and a lance tip into the vessel; discharging gas from the lance toward a skull deposit on the interior of the vessel, said discharging comprising: discharging gas from a first set of deskulling nozzles in the lance tip; and discharging gas from at least one additional set of deskulling nozzles disposed at a different orientation in the lance tip relative to the first set of deskulling nozzles.

20. The method of claim 19 further comprising selectively plugging at least one nozzle of the first set of deskulling nozzles and the at least one additional set of deskulling nozzles.