NO312501B1 - Method and crucible for use in tapping molten metal from aluminum electrolysis furnaces and the like, as well as drill construction for storing the crucible - Google Patents

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

The invention relates to a method and crucible for use when tapping molten metal from aluminum electrolysis furnaces and the like, as well as a support structure for storing the crucible.

Furnace plants for the production of aluminum comprise a large number of electrolysis furnaces or cells which are located in rows next to each other in the furnace halls. To save space, the distance between the cells is kept to a minimum. Tapping takes place by the molten metal in the electrolysis cells being sucked up via a tapping pipe into a tapping crucible which, with the help of a transport device, is successively brought into a tapping position in the spaces between the furnaces, and which, after completing the tapping operation, brings the crucible to a foundry or other desired place for emptying the molten metal from the crucible. The transport device can be a crane, forklift or similar, but today, as a rule, specially designed tank wagons are used for this purpose, e.g. as described in NO patents no. 132 774 and 166 066. In all cases, the crucible, which normally has a circular-cylindrical cross-sectional shape, is stored in the transport device with its longitudinal axis in the vertical direction. The upper end wall of the crucible is in the form of a lid which can be removed from the underlying part of the crucible, so that it can be lifted freely from the carriage, for example for cleaning out slag which is normally released from the crucible wall with the help of a special milling tool.

There is an ever-increasing need for greater tapping capacity in modern aluminum works. By tapping capacity is meant here the achievable volume of molten metal in the crucible, hereinafter also called effective tapping volume. However, the possibility of expanding the capacity in such works is very limited. Because of. the narrow space between the ovens is, for example, the width of the bottling carriage, and thus the diameter of the bottling crucible a limiting factor. In practice, the outer diameter of the crucible cannot therefore exceed 2 metres. Another limiting factor is the height of the metal column in the crucible. The metal is sucked into the crucible using a vacuum at a pressure of approx. 0.3 bar absolute, which gives a maximum static suction height of approx. 3 meters. Due to such limitations, it is difficult to increase the crucible capacity beyond approx. 3m<3 > for conventional tap wagon/crucible constructions of the above-mentioned type. With traditional solutions for the construction of bottling wagons for different smelters, the crucible diameter and crucible height must be adapted to each individual work, with a corresponding need for changes in the construction of the crucible, crucible lid, crucible storage and the bottling wagon itself.

Through the present invention, the above-mentioned capacity problem is solved in a new and surprisingly simple way, namely by adapting the cylindrical tapping crucible and its accessories in such a way that the crucible is suitable to be stored with its axis horizontal in the transport device, as stated in the subsequent patent claims where the invention in its various aspects is defined. The length of the tap trolley is not a critical size in line with height and width. Based on the principle of the invention, the length of the crucible and thereby its effective bottling volume can be increased beyond what is practically possible with conventional bottling carts. It is realistically possible to double the maximum crucible capacity by using the solution according to the present invention. When producing bottling wagons for smelters with different capacity requirements, the respective bottling wagons can be easily adapted to these needs, by corresponding scaling of the wagon and crucible length, without the need for special adaptation of the bottling wagon's other parts.

The crucible is preferably divided radially into two parts which are releasably held together by means of a tight flange connection. Thereby, the crucible, in a disassembled state with separate crucible parts, can be cleaned of slag with essentially the same tools used for conventional crucibles.

The invention also includes an advantageous support structure where the crucible is stored horizontally in such a way that it, together with the tapping pipe, can be moved along an inclined plane parallel to the longitudinal axis of the tapping pipe, at the same time that it can preferably also be moved horizontally. Thereby, the bottling carriage and the bottling pipe can be quickly brought into the bottling position in relation to the oven in a simpler and more space-saving way than is possible with conventional bottling trolleys.

The above as well as further features and advantages of the invention will be apparent from the following description in connection with the accompanying drawings where, for the sake of clarity, certain structural parts are omitted in the respective figures, while certain other, hidden or displaced parts are only indicated with thin contour lines, and where : Figure 1 shows a bottling cart with a crucible according to the invention, seen from the side,

Figure 2 is an elevation, partly in section, of a crucible according to the invention,

Figure 3 is an end view of the same crucible,

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

Figure 5 is an end view of the same,

Figure 6 shows the bottling cart with crucible seen from the rear, during positioning for bottling from an electrolysis cell, and Figures 7 and 8 are views similar to Figures 4 and 6 respectively, but with the crucible stored in a modified support structure in connection with a crane.

The invention is primarily intended for use in connection with a transport device in the form of a specially constructed bottling trolley of essentially the same type as according to the aforementioned NO patents, and will therefore first be described in this context. However, it will be clear that the invention is also relevant in connection with other transport devices, as also explained in more detail below.

The tap wagon shown in Figure 1 is in the form of a self-propelled vehicle which essentially comprises a main frame 2 with front wheel 4, rear wheel 6 and cab 8, as well as a tap crucible 10 with a mainly circular cross-section which is stored in a support structure 12 which is rigidly connected with the main frame 2, between the cart's front and rear wheels. On the cart there is also a swing-out tapping pipe 14 arranged for connection to a mainly bell-shaped tapping head 16. The tapping and emptying operations take place in a known manner by means of negative pressure (vacuum) and overpressure in the crucible 10. Organs for operating the tapping and emptying operations will normally be arranged in the cab together with operating devices for controlling the carriage's movements. So far, the bottling wagon is essentially in accordance with conventional bottling wagons of the type mentioned at the outset.

What primarily distinguishes the tap wagon shown in fig. 1 from the state of the art, is that the circular-cylindrical crucible 10 is stored with its axis 20 (fig. 2) lying horizontally in the longitudinal direction of the carriage instead of vertically upright, with the initially mentioned advantages this entails.

A suitable embodiment of a crucible 10 intended for horizontal storage according to the principle of the invention is shown in figures 2 and 3, where the first-mentioned figure also includes a circled detail section.

The crucible 10 consists of an elongated, mainly circular cylindrical side wall 22 connected to two preferably mainly planar 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 the side wall 22, where the two crucible parts 10a, 10b are sealed together, preferably by means of a bolted flange connection 26, 28, with seals 30, 32 which, when the flange bolts 36 are tightened, are sealingly compressed between the flange parts 26, 28 and adjacent surfaces of the crucible's refractory lining 34. The seals 30, 32 can in mainly be in the form of standard heat-resistant gaskets that are used in known cast constructions. Should a break in the seals occur, the long labyrinth-like leakage channel from the inside of the crucible to its outside, together with the cooling effect from the massive steel flange, will ensure that the incipient outflow of molten metal immediately cools down and solidifies and thereby seals against further outflow. The flange is made massive and rigid enough that a few (6-8) strong bolts 36 hold the crucible parts together.

The one, preferably front (on the bottling carriage), crucible part 10a has a

tap opening or hatch 38 near the top of the cylinder wall 22 arranged to cooperate with the tap head 16, as further explained below. A further opening 40 is designed near the end wall of the crucible part 10a for mounting a pipe connection 18 (Fig. 1) in connection with an internal discharge pipe (not shown) in the crucible.

As previously mentioned, the desired maximum crucible capacity can be achieved according to the invention, by giving the horizontally lying crucible an effective length which, despite the aforementioned limitations on the crucible diameter, makes it possible to satisfy even very high capacity requirements. In line with the idea of the invention, it will thus be possible to use bottling wagons with crucible capacities that can be varied within a scale from approx. 3m<3> to 6m<3> or more, based on a maximum crucible diameter of 2m.

When producing crucibles with 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 desired capacity, as indicated by arrows A in Figure 4, while the front crucible part 10a, with the tap and drain openings will preferably have a largely fixed or "standard" length. This standard length can, for example, amount to approx. half the length of a crucible in the upper part of the capacity scale, so that the crucible will have two essentially equally long crucible halves 10a, 10b. In Figure 2, however, the rear crucible part 10b is shown with a shorter length than the front crucible part 10a, so that this crucible part is intended for a crucible which belongs in the lower part of the capacity scale.

For storage of the crucible 10 in the crucible carriage, each of its end walls 24 is equipped with a pair of protruding, downward-facing bearing pins 44 which are designed to be accommodated in corresponding bearing pin seats 46 (figure 5) in the crucible 10 support structure. The end walls 24 are further designed with stiffening ribs 48 for distribution of the storage force over the end walls. The bearing pins 44 are preferably arranged in the upper part of the end walls, with mutual horizontal and vertical distance, as shown in Figure 3.

An advantageous embodiment of the crucible support structure 12 can be seen in figure 4. Here the seats 46 for the bearing pins 44 at each end of the crucible 10 are arranged in respective suspension elements 50 which, with a mutual distance corresponding to the distance between the pairs of bearing pins in the end walls 24 of the crucible, via wheels 52 rests horizontally displaceably on its own support element 54 which in turn via wheels 56 is displaceably stored in each of two parallel inclined guides 58 which are attached at their upper and lower ends to the main frame 2 of the tap carriage. The horizontal movement of the suspension elements 50 is accomplished by respective power cylinders 59, while the movement of the support elements 54 along the guides 58 is accomplished with the help of respective power cylinders 61 (figure 6).

Load sensing means, such as weighing cells 60, can suitably be arranged in connection with the crucible suspension, for simple determination of the melted melt weight.

As mentioned above, the crucible's tapping opening 38 is arranged to cooperate with a tapping head 16. The tapping head 16 has a somewhat elongated shape adapted to the shape of the tapping opening 38 and is, near one end part, connected at 61 to an overlying, horizontally running in the longitudinal direction of the crucible 10 bridge 62 which near each end is connected to the upper end of a swing arm 64 which at its lower end is pivotally connected to the upper end of the suspension element 50 of the support structure 12. The bridge 62 is also connected at each extreme end to the piston rod of a power cylinder 66 which in its lower end is rotatably supported in each of the suspension elements 50. With the help of the cylinders 66, the bridge 62 with the tapping head 16 can be swung from a tapping position where the circumferential edge of the tapping head is pressed into sealing contact around the tapping opening 38, to an upturned position as indicated by thin contour lines in fig. 5, where the crucible 10 can be freely dismantled for replacement, e.g. in connection with stroke limitation.

The tapping tube 14 is designed to be pivoted, as indicated by arrows B in fig. 4, from its rest position shown in Figure 1 along the crucible 10 parallel to its longitudinal axis, to a downward and outwardly sloping position to the side of the cart, as shown in Figure 6, essentially in the same way as the tap pipe of the tap cart according to the aforementioned NO 132 774. The tap pipe 14 is thus, via a cradle 70, supported on an inclined pivot pin 68 in a bracket 69 which is attached to the tap head. The bracket 69 also carries an inclined power cylinder 71 (in Fig. 4 only indicated by its center line), for the pivoting movement of the tap tube. The tap head 16 has in its end wall 68, opposite its end connection 61 with the bridge 62, an opening surrounded by a seat ring which sealingly cooperates with a correspondingly designed end part of the tap pipe 14 when this is swung down to its tap position. These details of the tap pipe's connection to the tap head are not shown and described in more detail here, as they clearly appear in NO 132 774.

In Figure 6, the tapping carriage according to the invention is shown in position next to an electrolysis cell 80, with the tapping pipe 14 in a swinging tapping position. It is clear from the figure that the crucible 10, for easy and quick positioning of the tapping tube 14 in relation to the electrolysis furnace, can be maneuvered horizontally between two extreme positions as indicated by arrows C, by horizontal displacement of the suspension elements 50 on the support elements 54 in the transverse direction of the carriage, at the same time that the support elements can is moved up and down along the inclined guides parallel to the longitudinal axis of the tapping pipe, as indicated by arrows C. In the figure, the crucible 10 with accessories is shown in its upper, "rear" (i.e. furthest from the electrolysis furnace) outer position, while respectively the other outer positions of the crucible 10 and the tap tube 14 are indicated by contour lines. With the crucible in its upper, retracted position, the bottling trolley can be brought approx. 1m closer to the electrolysis furnace than is possible with conventional bottling wagons with a flared bottling tube. The solution thereby entails valuable space savings in the transverse direction between the electrolysis cells. At the same time, the positioning of the draw pipe in the oven is made easier by lowering the crucible with the draw pipe parallel to the draw pipe's longitudinal axis.

When the crucible is to be removed from the support structure in the transport device, it can be easily released from the tap head and the tap tube by swinging these, with the help of the support structure's bridge 62 and power cylinders 66, from their connection with the crucible tap opening 38, after which the crucible can be freely lifted out of the support device - the thing.

Although the support structure 12 is shown and described in connection with a transport device in the form of a tap trolley, it can be adapted by simple means for use in connection with other forms of suitable transport device. Figures 7 - 8 show a modified support structure 112 for use in connection with a crane as a transport device. The support structure 112 is here in the form of a yoke with support arms 154 connected to a hook-shaped, lower suspension part 150 equipped with seats 146 for the bearing pins 44 of the crucible 10. In the embodiment shown, the yoke 112 is connected via a telescopic length-adjustable connection 113 and slewing ring 115 to an overlying transport facility indicated by line 117, e.g. the running cat of a traveling crane. If desired, however, the yoke 112 can easily be adapted for suspension in a crane hook or similar.

Like the support structure 12 described above, the support structure or yoke 112 according to fig. 7-8 equipped with tap head 16 connected to bridge 62, swing arms 64 and power cylinders 66 connected to the yoke suspension part 150. The support structure 112 is not, however, equipped with organs for positioning the tap pipe in the melting furnace, such as the inclined guides 58 in the support structure 12, as the necessary positioning movements are taken care of by the crane and possibly the telescopic connection.

Claims (10)

1. Method for use when tapping molten metal from aluminum electrolysis furnaces and the like into a tapping crucible with a mainly circular-cylindrical cross-sectional shape, where the crucible (10) during a tapping operation is stored in a transport device, characterized in that the tapping crucible (10) is stored in the transport device lying with its axis (20) mainly horizontal. 2. Crucible for tapping molten metal from aluminum electrolysis furnaces and the like to the crucible (10) via a tapping pipe (14) and tapping head (16), with the crucible stored in a transport device (12; 112), which crucible comprises a substantially circular cylindrical side wall (22) with tapping opening (38) and end walls (24), characterized in that the crucible (10) is arranged to be stored in the transport device lying down with its axis (20) mainly horizontal. 3. Crucible according to claim 2, characterized in that the end walls (24) of the crucible are equipped with organs (44) for suspending the crucible in the transport device via a support structure (12; 112). 4. Crucible according to claim 2 or 3, characterized in that the crucible (10) along a radial plane is divided into two parts (10a, 10b) which are tightly joined together by means of a flange connection (26, 28) with seals (30, 32). 5. Support structure for storing a tapping crucible (10) with mainly circular cylindrical side wall (22) and end walls (24), for use when tapping molten metal from aluminum electrolysis furnaces and similar to the crucible by means of a tapping tube (14) which under a tapping operation via a tapping head (16) communicates with a tapping opening (38) in the side wall (22) of the crucible (10), characterized in that the support structure is arranged for storage of the crucible (10) lying with its axis (20) mainly horizontal, and in that the tapping pipe (14) and the tapping head (16) are pivotably supported on the support structure, for movement between a position lifted from the crucible where they do not communicate with the tapping opening (38) of the crucible (10), to a tapping position where the tapping pipe communicates with the tapping head and the tapping head communicates with the crucible tap opening (38). 6. Support structure according to claim 5, characterized in that it comprises suspension elements (50; 150) designed with seat members (46; 146) arranged to cooperate with respective bearing members (44) in each of the end walls (24) of the crucible (10). 7. Support structure according to claim 6, characterized in that the tap pipe (14) and the tap head (16) are connected by a bridge (62) which is pivotally connected to the suspension elements (50; 150). 8. Support structure according to claim 5, characterized in that it comprises two parallel, spaced apart guides (58) which are designed to be mounted in a crucible transport device along an inclined plane with essentially the same angle as the inclined angle of the tapping pipe (14) during the tapping operation, as well as two crucible support elements (54) which are displaceably engaged in each of the two guides. 9. Support structure according to claims 6-8. characterized in that the suspension elements (50) are arranged horizontally displaceably on the support elements (54). 10. Support structure according to claim 7, characterized in that it is in the form of a yoke (112) with support arms (154) connected to the suspension elements (150).