WO2003014646A1

WO2003014646A1 - Method, apparatus and carriage for tapping of molten metal

Info

Publication number: WO2003014646A1
Application number: PCT/NO2002/000269
Authority: WO
Inventors: Per-Arne Klingenberg
Original assignee: Hmr Hydeq As
Priority date: 2001-08-10
Filing date: 2002-07-22
Publication date: 2003-02-20
Also published as: ATE295954T1; DE60204228D1; NO20013908D0; EP1425545A1; EP1425545B1; CN100400998C; CN1541325A; NO20013908A; DE60204228T2; NO312501B1

Abstract

Molten metal is tapped from an aluminium electrolytic furnace to a crucible (10) having a substantially circular cross-section supported in a transporting device with the axis (20) of the crucible (10) substantially horizontal. The crucible (10) has end walls (24) provided with means (44) for horizontal suspension of the crucible in the transporting device via a support structure (12) comprising two parallel, spaced guides (58) to be mounted in the transporting device displaceable along a ramp, and two crucible-support members (54) displaceably accomodated in a respective one of the two guides. A carriage for use in tapping molten metal from aluminium electrolytic furnaces comprises a crucible (10) and a support structure (12) as described above.

Description

METHOD, APPARATUS AND CARRIAGE FOR TAPPING OF MOLTEN METAL

The invention relates to tapping of molten metal from aluminium electrolytic furnaces or the like.

Factories for producing aluminium comprise a large number of electrolytic furnaces or cells placed side by side in the furnace houses. The spacing between the cells is at a minimum in order to save space. The tapping is brought about by drawing the molten metal from the electrolytic cells via a tapping tube up into a tapping crucible that is successively brought to a tapping position in between the furnaces by means of a transporting device which, upon completed tapping operation, carries the crucible to a foundry or other location as required for discharging the molten metal from the crucible. The transporting device could be a crane, truck or the like, but currently specially designed tapping carriages are normally used, such as described in NO 132 774 and WO 8604839. In all cases the tapping crucible, which normally has a circular-cylindrical cross section, is supported in the transporting device with its longitudinal axis vertical. The upper end wall of the crucible is in the form of a cover which can be removed from the underlying part of the crucible, permitting the latter to be lifted from the carriage, e.g. for rak- ing out slag which is normally removed from the wall of the crucible by means of a special milling tool.

There is a steadily increasing demand for larger tapping capacity in modern aluminium works. By tapping capacity as used herein is meant attainable volume of molten metal in the crucible, also called effective tapping volume. However, the possibility of expanding the capacity in such works is very limited. Owing to the narrow spacing between the electrolytic cells the width of the crucible, for example, and thus the diameter of the tapping crucible, is a limiting factor. In practice, therefore, the outer diameter of the crucible should not exceed 2 meter.

Another limiting factor is the height of the metal column in the crucible. The metal is drawn into the crucible by means of a vacuum at a pressure of about 0,3 bar absolute, giving a maximum static suction head of about 3 meter. Because of these limitations the crucible capacity of conventional tapping carriage/crucible structures of the above type can hardly be increased beyond about 3m³. In con- ventional designs of tapping carriages for different smelting works, the crucible diameter and crucible height has to be adapted to each individual work, requiring corresponding changes in the design of crucible, crucible cover, crucible support and the tapping carriage itself. The present invention solves the above capacity problem in a new and surprisingly simple way, namely by adapting the cylindrical tapping crucible with accessories in a manner permitting the crucible to be supported in the transporting device with the longitudinal axis of the crucible extending horizontally, such as stated in the appending patent claims in which the various aspects of the invention are defined. The length of the tapping carriage is not a critical dimension like height and width. Consequently, based on the inventive principle, the length of the crucible and thus its effective tapping volume, can be extended beyond that which is practically feasible with conventional tapping carriages. It is a realistic possibility to double the maximum crucible capacity by using the solution accord- ing to the present invention. In the manufacture of tapping carriages for smelting works having different capacity demands, the respective tapping carriages can easily be adapted to these demands, by scaling the lengths of the carriage and crucible correspondingly, without the necessity of special adaption of the remaining parts of the tapping carriage. Preferably, the crucible is divided radially in two parts that are releasably interconnected by means of a sealed flange connection, permitting the crucible, in disassembled condition with separated crucible parts, to be freed from slag with essentially the same tool that is used for conventional crucibles.

The invention also comprises an improved support structure in which the crucible is horizontally supported in a manner to permit the crucible to be displaced, together with the tapping tube, along a ramp, parallelly with the longitudinal axis of the tapping tube, while preferably also being capable of horizontal displacement. This permits rapid positioning of the tapping carriage and tapping tube into tapping position relative to the furnace more easily and snugly than permitted when using conventional technique.

These and other features and advantages of the invention will appear from the following description with reference to the appending drawings in which some structural parts have been omitted in the respective figures for the sake clarity, while some other, hidden or displaced parts are merely indicated with thin contour lines, and in which:

Figure 1 is a lateral view of a tapping carriage according to the invention,

Figure 2 is a partly sectional elevational view of a crucible according to the invention,

Figure 3 is an end view of the same crucible,

Figure 4 is an elevational view of the crucible according to the invention suspended in a support structure,

Figure 5 is an end view of the same, Figure 6 is a rear view of the tapping carriage with crucible during positioning to permit tapping from an electrolytic cell, and

Figures 7 and 8 are views like figures 4 and 6, respectively, but with the crucible supported in a modified support structure associated with a crane.

The invention is intended to be used primarily in connection with a trans- porting device in the form of a specially constructed tapping carriage of substantially the same type as that disclosed in the above NO 132 744 and WO 8604839, and it will therefore be described in such connection. It should be appreciated, however, that the invention is also relevant in connection with other transporting devices, as more fully explained below. The tapping carriage shown in figure 1 is in the form of an automotive vehicle generally comprising a main frame 2 with front wheels 4, rear wheels 6, driver cab 8, and a tapping crucible or ladle 10 having a substantially circular cross- section, supported in a support structure 12 which is rigidly connected to the main frame 2, between the front and rear wheels of the carriage. Pivotably supported on the carriage is also a tapping tube 14 adapted to be connected to a substantially bell-shaped tapping head 16. The tapping and discharge operations are carried out in a well-known manner by means of under-pressure (vacuum) and overpressure in crucible 10. Means for operating the tapping and discharge operations will normally be located in the driver cab together with operating means for controlling the movements of the tapping carriage. So far, the tapping carriage is generally in accordance with conventional tapping carriages of the introductorily mentioned type. What primarily distinguishes the carriage according to the invention from the prior art, is the fact that the circular-cylindrical crucible 10 is supported with its axis 20 (fig. 2) extending horizontally in the longitudinal direction of the carriage, rather than vertically upright, resulting in the introductorily mentioned advantages. A favourable embodiment of a crucible 10 intended for being horizontally supported in accordance with the inventive principle, is shown in figures 2 and 3, the former figure also including an encircled detail.

The crucible 10 consists of an elongate, substantially circular-cylindrical sidewall 22 having two preferably substantially flat end walls 24. According to an advantageous feature of the invention, the crucible 10 is divided into two parts 10a, 10b, along a radial plane through sidewall 22, in which the two crucible parts 10a, 10b are sealingly interconnected, preferably by means of a bolted flange connection 26, 28, provided with seals 30, 32 which, upon tightening of the flange bolts 36, are tightly compressed between the flange parts 26, 28 and opposing surfaces of the refractory lining 34 of the crucible. The seals 30, 32 could generally be of the standard heat-resistant type as used in conventional casting structures. Should a fracture occur in these seals, then the long tortuous leak passage from the interior of the crucible to its exterior, together with the cooling effect from the massive steel flange, will obviously cause the initial seepage of the molten metal to cool down and harden, thus preventing further seepage. The flange is made sufficiently massive and rigid to permit a few (6 - 8) strong bolts 36 to hold the crucible parts together.

One of the crucible parts, preferably the foremost one (with reference to the tapping vehicle) 10a has a tapping opening or hatch 38 near the top of the cylinder wall 22, adapted to cooperate with the tapping head 16, as detailed below. An additional opening 40 is formed near the end wall of crucible part 10a, for mounting a socket 18 (fig. 1) communicating with a discharge tube (not shown) internally of the crucible.

As previously mentioned, according to the invention the required maximum crucible capacity can be achieved by providing the horizontally disposed crucible with an effective length enabling the designer to satisfy even very high capacity requirements, in spite of the previously discussed limitations on crucible diameter. Thus, in accordance with the inventive idea it will be possible to provide tapping carriages having crucible capacities varying within a range from about 3m³ to 6m³ or more, based on a 2m maximum crucible diameter.

In manufacturing crucibles of different capacities, it will normally be the length (or depth) of the rear crucible part 10b, with unbroken cylinder wall 22, which is adapted to the required capacity, such as indicated with arrow A in figure 4, while the front crucible part 10a, with tapping and discharge openings, preferably will have a substantially fixed or "standard" length. This standard length could be about half the length of a crucible in the upper area of the capacity range, for example, to give a crucible having two crucible halves 10a, 10b of substantially equal lengths. In figure 2, however, the rear crucible part 10b is shown with a shorter length than the front crucible part 10a, which means that this crucible part is intended for a crucible belonging to the lower area of the capacity range.

For supporting the crucible 10 in the tapping carriage, each of its end walls 24 is provided with a pair of protruding, downward-directed journals 44 adapted to be received in corresponding journal seats 46 (figure 5) in the crucible 10 support structure. Further, the end walls 24 are formed with bracing ribs 48 distributing the supporting forces across the end walls. Preferably, the journals 44 are positioned at the upper part of the end walls, equally horizontally and vertically spaced, as shown in figure 3. An advantageous embodiment of the crucible support structure 12 is shown in figure 4. Here the seats 46 for the journals 44 in each end of the crucible 10 are disposed in respective suspension members 50 spaced in accordance with the spacing between the journal pairs in the crucible end walls 24 and resting horizontally displaceable, via wheels 52, on respective support members 54 which, in their turn, are slidingly supported in a respective one of two parallel guides 58 which, at their top and bottom ends, are secured to the main frame 2 of the tapping carriage. Horizontal movement of the suspension members 50 is accomplished by respective actuating rams 59, while movement of the support members 54 along the guides 58 is accomplished by means of respective actuating rams 61 (figure 6).

Load sensing means, such as weighing cells 60, can conveniently be provided in connection with the crucible suspension, for easy determination of tapped molten metal weight. As previously mentioned, the crucible tapping opening 38 is adapted to cooperate with a tapping head 16. The tapping head 16 has a somewhat elongate shape adapted to the shape of the tapping opening 38 and is, near one end portion thereof, at 61 connected to a superjacent bridge 62 extending horizontally longitudinally of the crucible 10 and, near each end thereof, connected to the upper end of a swivel arm 64 which, at its lower end, is pivotably connected to the upper end of the suspension member 50 of the support structure 12. The bridge 62 is also, at each outer end thereof, connected to the piston rod of an actuating ram 66 which, at its lower end, is rotatably supported in a respective one of the support members 50. By means of the rams 66, the bridge 62 with tapping head 16 can be swung from a tapping position in which the rim of the tapping head is urged into tight engagement with the rim of the tapping opening 38, to a raised position as indicated with thin contour lines in fig. 5, in which the crucible 10 is free to be disassembled for replacement, e.g. in connection with slag removal. The tapping tube 14 is adapted to swing out, as indicated with arrows B in fig. 4, from its position as shown in figure 1 where it is resting on the crucible 10 parallel to its longitudinal axis, into a downwardly and outwardly inclined position laterally of the carriage as shown in figure 6, substantially in the same manner as the tapping tube of the tapping carriage according to the previously mentioned NO 132 774. Thus, the tapping tube 14 is joumalled, via a cradle 70, on a tilted pivot 68 on a bracket 69 secured to the tapping head. Bracket 69 also carries a tilted actuating ram 71 (indicated in fig. 4 merely by its centre line) for pivoting the tapping tube. Tapping head 16, in its end wall 68 opposite its end connection 61 to bridge 62, has an opening surrounded by an annular seat tightly cooperating with a correspondingly shaped end portion of the tapping tube 14 when the latter has been swung down to its tapping position. These details of the connection between the tapping tube and the tapping head are not fully shown and described here, since they clearly appear from NO 132 774.

In figure 6 the tapping carriage according to the invention is shown in a position beside an electrolytic cell 80, with its tapping tube 14 swung out into tapping position. It is seen from the figure that the crucible 10, for easy and quick positioning of the tapping tube 14 relative to the electrolytic furnace, can be manoeuvred horizontally as indicated with arrows C, between two extreme positions by horizontal displacement of the suspension members 50 on the support members 54 transversally of the carriage, while the support members can slide up and down along the inclined guides parallel to the longitudinal axis of the tapping tube, as indicated by arrows C. In the figure, the crucible 10 with accessories is shown in its upper, "rear" (i.e. remote from the electrolytic furnace) extreme position, while the other extreme position of the crucible 10 and tapping tube 14, respectively, are indicated with contour lines. With the crucible in its upper, retracted position, the tapping carriage can be brought about 1m closer to the electro- lytic cell than what is possible with conventional tapping carriages with extended tapping tube. This solution gives opportunities for a valuable reduction of the spacing between the electrolytic cells and facilitates positioning of the tapping tube into the furnace by permitting the crucible with its tapping tube to be lowered parallelly with the longitudinal axis of the tapping tube. When the crucible is to be removed from its support structure in the transporting device, it can easily be released from the tapping head and tapping tube by swinging the tapping tube and head up from their position in connection with the crucible tapping opening 38 by way of the support structure bridge 62 and rams 66, whereupon the crucible can be lifted free of the support structure. Although the support structure 12 has been shown and described in connection with a transporting device in the form a tapping carriage, it can easily be adapted for use in connection with other forms of suitable transporting device. Figures 7 - 8 illustrate a modified support structure 112 intended for use in connection with a crane as transporting device. Support structure 112 is in the form of a yoke with support arms 154 connected to a hook-shaped lower suspension portion 150 provided with seats 146 for journals 44 of the crucible 10. In the embodiment shown the yoke 112 is connected via a telescopic length-adjustable connection 113 and turnrim 115 to a subjacent transporting device indicated by line 117, such as the carriage of a travelling crane. If desireable, however, yoke 112 can easily be adapted for suspension in a crane hook or the like.

Like the above described support structure 112, support structure or yoke 112 according to figs. 7 - 8 is provided with a tapping head 16 connected to bridge 62, swivel arm 64 and rams 66 connected to yoke suspension portion 150. However, support structure 112 is not provided with means, such as guides 58 in support structure 12, for positioning the tapping tube in the melting furnace, because the required positioning movements are accomplished by the crane and possibly the telescopic connection.

Claims

PATENT CLAIMS:

1. A method for use in tapping molten metal from aluminium electrolytic furnaces or the like to a tapping crucible having a substantially circular-cylindrical cross-section, said crucible (10) supported in a transporting device during the tapping operation, characterized in that the tapping crucible (10) is supported in the transporting device with its axis (20) substantially horizontal.

2. A crucible for tapping molten metal from aluminium electrolytic furnaces or the like to a crucible (10) via a tapping tube (14) and tapping head (16), with the crucible supported in a transporting device (12; 112), said crucible comprising a substantially circular-cylindrical sidewall (22) with tapping opening (38) and end walls (24), characterized in that the crucible (10) is adapted to be supported in the transporting device with its axis (20) substantially horizontal.

3. A crucible according to claim 2, characterized in that the end walls (24) of the crucible are provided with means (44) for suspending the crucible in the transporting device via a support structure (12; 112).

4. A crucible according to claims 2 or 3, characterized in that the crucible (10) is divided along a radial plane into two parts (10a, 10b) tightly interconnected by means of a flange connection (26, 28) with seals (30, 32).

5. A support structure for supporting a tapping crucible (10) having a substan- tially circular-cylindrical sidewall (22) and end walls (24), for use in tapping molten metal from aluminium electrolytic furnaces or the like to the crucible by means of a tapping tube (14) which during a tapping operation communicates via a tapping head (16) with a tapping opening (38) in the sidewall (22) of the crucible (10), characterized in that the support structure is adapted to support the cru- cible (10) with its axis (20) substantially horizontal, and that the tapping tube (14) and tapping head (16) are rotatably supported on the support structure, for displacement between a raised position above the crucible, in which the tapping tube and head do not communicate with the tapping opening (38) of the crucible, to a tapping position in which the tapping tube communicates with the tapping head and the tapping head communicates with the tapping opening (38) of the crucible.

6. A support structure according to claim 5, characterized in that it 5 comprises suspension members (50; 150) formed with seat means (46; 146) adapted to cooperate with respective bearing means (44) in each end wall (24) of the crucible (10).

7. A support structure according to claim 6, characterized in that the o tapping tube (14) and tapping head (16) are associated with a bridge (62) swing- ably connected to the suspension members (50; 150).

8. A support structure according to claim 5, characterized in that it comprises two parallel, spaced guides (58) adapted to be mounted in a crucible- 5 transporting device moveable along a ramp having and angle substantially equal to that of the tapping tube (14) during a tapping operation, and two crucible- support members (54) displaceably accomodated in a respective one of the two guides.

o 9. A support structure according to claims 6-8, characterized in that the suspension members (50) are disposed horizontal displaceable on the support members (54).

10. A support structure according to claim 7, characterized in that it is 5 in the form of a yoke (112) with support arms (154) connected to the suspension members (150).

11. A carriage for use in tapping molten metal from aluminium electrolytic furnaces or the like, characterized in that it comprises a crucible (10) as o defined in claims 2-4 supported with its axis substantially horizontal in a support structure (12) as defined in claim 5-9.