EP0730666B1 - Device for loading a shaft furnace - Google Patents

Abstract

A device for loading a shaft furnace having a lower cone (20). The device includes lower sealing members (48, 60) for sealing off an upper hopper (34) from a lower hopper (14) and collecting a load material. When opened, said lower sealing members (48, 60) are arranged to define a clear central material flow channel (50). The material flow forms a compact and focused flow. Members (28, 30, 24, 26) for moving the lower cone are arranged so that they do not hinder focusing of said flow. A deflecting surface (66) is arranged above the lower cone (20) to split the focused flow into a flow having rotational symmetry, whereby, inter alia, an improved filling symmetry in the lower hopper (14) is achieved.

Description

The invention relates to a device for loading a shaft furnace. It relates more particularly to a device for loading a shaft furnace comprising two superimposed hoppers, the lower hopper of which is provided with a bell which is capable of closing, in the closed position, the discharge opening from the lower hopper towards the shaft furnace and, in the open position, to distribute the loading material on the loading surface.

Conventional loading devices of a shaft furnace, in particular of a blast furnace, generally comprise a lower bell of large diameter and an upper bell of smaller diameter. The two bells are fitted to a lower hopper which forms an airlock for loading the shaft furnace. The large bell seals against the shaft furnace and distributes the loading material over the loading surface. The small bell seals against an upper hopper which is directly in communication with the atmosphere.

This upper hopper, which is fed by skip elevators, is normally a rotary hopper in order to ensure a more symmetrical supply of the loading airlock. Indeed, it is known that the loading of a static hopper by skip elevators, offset from the axis of the blast furnace, produces very asymmetrical loading profiles in this hopper, which results in asymmetrical loading of the airlock loading, hence an asymmetrical distribution of the loading material by the large bell on the loading surface of the shaft furnace. However, it is known that defects in symmetry in the load of the shaft furnace have harmful repercussions on the operation of the latter.

These conventional loading devices have the disadvantage that the lower bell insufficient its function as a lower sealing member of the loading airlock. Indeed, given the large diameter of the lower bell and the abrasion by the loading material flowing along the lower bell, it is hardly possible to ensure a lasting seal between the lower bell and its seat formed by the lower edge of the loading hatch.

To remedy this lack of tightness, it has been proposed to double the loading airlock. In other words, it has been proposed to produce the rotary upper hopper in the form of a closed enclosure, which can be isolated from the atmosphere by means of upper sealing valves. A device of this kind is for example described in the patent specifications US-A-4,878,655 and US-A-4,881,869. According to these two US patent specifications, the lower bell is suspended from a rod arranged in the axis of the shaft furnace. The upper hopper is suspended above the lower hopper so that it can be rotated around the axis of the shaft furnace. A first sealed rotary joint is provided for this purpose between the lower hopper and the upper hopper. At its upper end, the upper rotary hopper is connected in leaktight manner, using a second rotary seal, to a fixed cap provided with two supply boxes for skip elevators. These supply boxes are fitted with upper sealing valves. The lower closure means of the rotary hopper essentially comprise a bell which is movable in the axis of the oven below the rotary hopper, between an upper position closing a discharge opening and a lower position, in which it releases an annular discharge opening and is directly located in the material flow. To this end, the upper bell is suspended from a sleeve surrounding the suspension rod of the lower bell. It simultaneously fulfills a function material retaining member and sealing member between the upper rotary hopper and the lower fixed hopper and further constitutes, in the open position, at the discharge opening, a kind of radial expansion device the flow of material flowing from the upper hopper into the lower hopper.

The loading device described above naturally allows, thanks to its upper rotary hopper, to avoid significant symmetry defects in the loading of the shaft furnace. However, it does not make it possible to satisfactorily resolve the sealing problems, especially if the shaft furnace works at high pressures.

The object of the present invention is to provide a device for loading a shaft furnace, with two superimposed hoppers and lower bell (or large bell), which makes it possible to attenuate the influence of an asymmetrical loading of the upper hopper. on the distribution of the loading material by the lower bell, while creating more favorable premises for the execution of a sealing with high sealing between the upper hopper and the lower hopper.

In accordance with the present invention this object is achieved by a device according to the first claim.

It is important to note that the lower sealing means, connected between the lower hopper and the upper hopper, are arranged so that they release, in their open position, a central free passage substantially coaxial with the axis of the oven. to tank, so the material flow is established in the form of a compact and focused flow of material below the upper hopper. In addition, the means for vertically moving the lower bell are arranged outside the space occupied by this compact flow of material. In the trajectory of the compact material flow is arranged, above the lower bell at a place where the focusing of the material flow is finished or almost finished, a surface of deflection This deflection surface causes the focused flow above the lower bell to diverge or explode.

In the loading device according to the invention, the lower closure means release, in their open position, a central free passage substantially coaxial with the axis of the furnace. A compact flow of material is thus established between the upper hopper and the lower hopper, which is less influenced by asymmetries in the loading profile in the upper hopper than a radially expanded flow. It will indeed be appreciated that this central flow from the upper hopper converges the trajectories of the particles of matter around the axis of the shaft furnace and tends by this focusing of the trajectories of the particles to weaken the initial asymmetries in the spatial distribution of matter particles. The smaller the angle at the top of the flow cone of the upper hopper, the better the focusing result obtained.

It is recalled that in the previous devices, the sealing bell, which is located directly below a discharge opening, on the other hand causes an immediate expansion of the material flow and thus causes the trajectories of the material particles to diverge as soon as their first acceleration by gravity. A focusing of the trajectories around the central axis cannot occur and the immediate expansion of the flow tends to accentuate the initial asymmetries in the spatial distribution of these particles of matter around the central axis.

It will also be appreciated that a discharge section for a compact central flow has a smaller perimeter than a discharge section for an expanded annular flow. However, the perimeter of this discharge section directly determines the minimum length of the joint between the upper hopper and the lower sealed closure element. In other words, the joint whose sealing must be ensured may be shorter in the case of a central discharge opening, only in the case of an annular discharge opening. In this context, it should be noted more particularly that the smallest possible dimension of a discharge opening must necessarily be a multiple (k) of the largest dimension of the particles of material to be discharged (DMAX). In the case of an annular discharge opening, for example between a sealing bell and the lower edge of the upper hopper, it is the width of this annular space which must be at least equal to (k * DMAX). In the case of a central discharge opening, for example circular, it is the diameter of this central discharge opening which must be at least equal to (k * DMAX). It follows that the solid passage section can be much smaller than the annular passage section; which means that the perimeter of the solid passage section may be considerably less than the perimeter of the annular passage section. Hence a better mastery of the sealing problems at the level of communication between the lower hopper and the upper hopper.

Another advantage of the device according to the invention is that, in their respective open position, the lower sealing means are located outside said axial passage in which the flow of material is established in the form of a compact flow. matter. It follows that these sealing means, and in particular the sealing surfaces on these sealing means, are not subjected to abrasion work by the compact flow of material flowing from the upper hopper.

Since the means for vertically moving the lower bell are also arranged outside the space occupied by the compact flow of material, the convergence of the trajectories of the particles around the axis of the shaft furnace is not disturbed by any element of the proposed loading device, before hitting the deflection surface. It is therefore a focused compact flow which strikes the deflection surface located above the lower bell. The essential function of this deflection surface is to burst or diverge the focused compact flow of material above the bell and to distribute the material with symmetry of revolution on the lower bell. This deflection surface can therefore be specially designed for this function, ignoring any additional constraints. The geometry of this surface can thus be chosen so as to favor, for example, a burst with symmetry of revolution of the compact flow of material. In addition, the mechanical structure supporting this surface and the materials used for its construction can be adapted to the specific requirements resulting exclusively from its function as a deflection surface, without having to find compromises with regard to additional functions (such as for example sealing and sealing functions).

The lower closure means connected between the lower hopper and the upper hopper could naturally comprise a single closure member, which ensures both the retention of the material in the upper hopper and the seal between the lower hopper and the hopper superior. Most often, however, it is preferable that these lower sealing means comprise a sealing member located downstream of a material retaining member. To unload the upper hopper into the lower hopper, the sealing member is first moved to its open position, outside said central free passage for the compact flow of material, before moving the material retaining member. in its respective open position. It follows that the sealing member is already in its open position when the material flow begins to flow. The sealing member is therefore never in contact with the material flowing from the upper hopper.

The sealing member advantageously comprises a flexible seal. With such a flexible joint seal member, a seal is obtained which is far superior to that obtained with a conventional bell, which necessarily involves a seal of the metal on metal type. This improved seal allows working at higher pressures in the shaft furnace, without increasing leakage at the loading device. It will be appreciated that this creates a loading device with a lower bell which includes for the first time a loading airlock which can be truly qualified as waterproof with respect to the shaft furnace. This high tightness of the upper hopper relative to the shaft furnace allows in particular a controlled purging of the gases from the latter, when the lower and upper sealing members are closed. This is a considerable advantage given the increasingly stringent requirements with regard to environmental pollution.

The sealing member is preferably, but not necessarily, a sealing valve installed below the upper hopper. Such a valve has, among other things, the advantage of being more easily accessible and removable.

• un organe obturateur,
• un siège associé à cet organe obturateur, ce siège étant connecté de façon étanche à ladite trémie supérieure et entourant , en périphérie, l'espace occupé par ledit flux plein de matière,
• des moyens pour déplacer l'organe obturateur entre une position latérale dans laquelle il se trouve en-dehors dudit espace occupé par le flux compact de matière, et une position d'obturation, dans lequel il est situé en face de son siège, et
• des moyens pour appliquer l'organe obturateur dans sa position d'obturation fermement sur son siège.

This sealing valve advantageously comprises:

• a shutter member,
• a seat associated with this shutter member, this seat being tightly connected to said upper hopper and surrounding, at the periphery, the space occupied by said flow full of material,
• means for moving the shutter member between a lateral position in which it is outside said space occupied by the compact flow of material, and a shutter position, in which it is located opposite its seat, and
• means for applying the shutter member in its closed position firmly on its seat.

In a first preferred embodiment, said material retaining member comprises several shutter members symmetrical with respect to the axis of the furnace and means for moving these shutter elements symmetrically with respect to the axis of the furnace, so as to create a central opening around the axis of the oven. It follows that the material flow in the form of a compact flow is from the start coaxial with the axis of the furnace and that the passage section for the material can be modified.

The material retaining member may however also include a closure bell which is movable inside the hopper between a lower position for closing a discharge opening and an upper raised position, in which it releases the said opening. discharge opening. In the raised position, this bell advantageously influences the homogeneity of the flow of the material inside the hopper. In particular, in this raised position, it reduces the phenomenon of segregation of solid particles according to their particle size.

The deflection surface advantageously forms a cone of revolution, the apex of which is directed towards the upper hopper and the axis of which is coaxial with the axis of the flow of solid material. This shape of the deflection surface causes a gradual bursting of the compact flow and promotes the establishment of a symmetry of revolution with regard to all of the trajectories of the deflected particles.

To further promote the establishment of this symmetry of revolution, the cone of revolution is advantageously provided with guide fins which extend from the top towards the base of the cone, so as to define flow channels for the material along this last.

In order to correct residual asymmetries in the loading of the lower hopper, the deflection surface can be supported above the lower bell so as to be able to modify from the outside of the oven its arrangement in the compact material flow. Thus one can use for example a cone of revolution which is supported so as to be able to impose on it a horizontal displacement. One could however also use a cone of revolution which is supported so as to be able to impose on it from the outside of the oven a variable inclination. In pursuit of the same goal, it is of course also possible to use a deflection surface which is supported above the lower bell so as to be able to rotate around the axis of the furnace.

• les Figures 1 et 2 sont deux coupes longitudinales à travers un dispositif de chargement d'un four à cuve selon l'invention; les deux plans de coupes font entre eux un angle de 90°;
• les Figures 3A et 3B sont deux représentations schématiques de l'écoulement de la matière de la trémie supérieure dans la trémie inférieure, dans un dispositif de chargement d'un four à cuve selon l'invention;
• les Figures 4A et 4B sont deux représentations schématiques de l'écoulement de la matière de la trémie supérieure dans la trémie inférieure, dans un dispositif selon l'état de la technique;
• la Figure 5 est une coupe à travers un montage particulier d'une surface de déflexion selon l'invention;
• la Figure 6 est une représentation schématique de l'écoulement de la matière de la trémie supérieure dans la trémie inférieure, dans un dispositif selon l'invention équipé d'une surface de déflexion selon la Figure 5;
• la Figure 7 est une coupe longitudinales à travers un dispositif de chargement d'un four à cuve selon l'invention, qui est équipé d'une surface de déflexion qui peut être entraînée en rotation autour de l'axe central de la cloche inférieure.

Additional advantages and characteristics will emerge from the detailed description of advantageous embodiments of the invention, presented below by way of illustration, with reference to the appended drawings, in which:

• Figures 1 and 2 are two longitudinal sections through a loading device of a shaft furnace according to the invention; the two section planes make an angle of 90 ° between them;
• Figures 3A and 3B are two schematic representations of the flow of material from the upper hopper into the lower hopper, in a device for loading a shaft furnace according to the invention;
• Figures 4A and 4B are two schematic representations of the flow of material from the upper hopper into the lower hopper, in a device according to the prior art;
• Figure 5 is a section through a particular arrangement of a deflection surface according to the invention;
• Figure 6 is a schematic representation of the flow of material from the upper hopper into the lower hopper, in a device according to the invention equipped with a deflection surface according to Figure 5;
• Figure 7 is a longitudinal section through a loading device of a shaft furnace according to the invention, which is equipped with a deflection surface which can be rotated about the central axis of the lower bell.

In Figures 1 and 2 is shown a loading device 10 according to the invention, which is mounted above a tank furnace, for example a blast furnace, identified by the reference 12. This loading device 10 comprises a lower closed hopper 14. The lower hopper 14 defines a discharge opening 16 of large diameter, which is centered on the axis 18 of the shaft furnace 12. This discharge opening 16 is closable by a large bell 20 (or lower bell 20 ), which is shown in the closed position resting on a peripheral edge 22 of the discharge opening 16 of the lower hopper 14. To discharge the material contained in the lower hopper 14, the large bell 20 is lowered vertically, so define with the peripheral edge 22 an annular space with symmetry of revolution through which the lower hopper 14 can be unloaded on the loading surface of the shaft furnace (not shown). It will therefore be understood that to have a symmetrical distribution of the material on the loading surface of the shaft furnace, it is necessary to have a filling with symmetry of revolution of the lower hopper 14. In other words, the profile of loading into the lower hopper 14 directly influences the spatial composition of the load from the shaft furnace 12.

The large bell 20 is provided at its upper part with two lateral support arms 24, 26 by means of which it is supported by two jacks 28, 30. These jacks 28, 30 are mounted on an upper carcass 32 of the lower hopper 14. Their actuator rod enters the hopper 14, so as to be able to move the large bell 20 axially from its closed position to its open position and vice versa.

Above the lower hopper 14 is an upper hopper 34, which has a much smaller angle at the top than the lower hopper 14. This upper hopper 34 is supplied in a known manner by two skip elevators 36 and 36 '. To this end the upper hopper 34 is provided at its upper part with two open supply boxes 38 and 38 'which are each equipped with a sealing valve 40 and 40', hereinafter called upper sealing valves 40 and 40 '. In Figure 2 the upper sealing valve 40 is shown in the closed position in which it isolates the upper closed hopper 34 in a sealed manner from the supply boxes 38 and 38 '; while the sealing valve 40 'is shown in the open position in front of an inspection opening 42' in the upper hopper 34. The reference 44 in FIG. 1 identifies an actuation mechanism which makes it possible to pivot the valve d 'upper seal 40 from its open position to its closed position and apply it firmly against its seat.

At its lower end, the upper closed hopper 34 is connected by a sealed sleeve 46 to the lower hopper 14. In this sealed sleeve 46 is installed a sealing valve 48, below a discharge opening 50 which is defined, in the axis 18 of the shaft furnace, through the lower end of the hopper flow cone 34. This sealing valve 48 comprises: a seat 52, surrounding the discharge opening 50 and defining a surface of sealing directed towards the hopper 14; a shutter member 54, preferably provided with a flexible seal; a support arm 55 of the shutter member 54; and an actuating mechanism 56 of the shutter member 54. In Figure 2 we see the shutter member 54 in the lateral position relative to the discharge opening 50. It will be noted that in this lateral position the shutter member and its support arm 56 completely free the space located below the opening of discharge 50 and that the shutter member 54 is located opposite a visit opening 58 in the sealed sleeve 46. The actuation mechanism 56 allows the shutter member 54 to be pivoted, in the absence of a flow of material naturally, below the discharge opening 50 and to apply it along the axis 18 firmly with its flexible seal on the sealing surface of the seat 52.

Inside the upper hopper 34 is installed a material retaining bell 60 which closes, in the lowered position, a passage section of the flow cone of the upper hopper 34 upstream of the seat 52. In Figures 1 and 2 the bell 60 is shown in dotted lines in the raised position in which it entirely frees the passage section 50. It will be noted that in this raised position the bell 60 only influences the flow of the material inside the hopper 34 upstream of the discharge opening 50. In addition, it contributes to reducing the phenomenon of segregation of the material as a function of its particle size. The bell 60 is integral with a sleeve 62 which is suspended from a jack 64 mounted axially above the upper hopper 34.

Below the discharge opening 50, at a distance h from it, which is preferably at least of the same order of magnitude as the diameter of the passage section 50, a deflection surface is arranged, for example a deflection cone 66. This cone 66 is oriented with its apex in the direction of the discharge opening 50 and is, at least in its normal position, coaxial with the central axis 18 of the shaft furnace. The function is to burst the compact flow of material flowing from the upper hopper 34. The deflection cone 66, which is also easily removable and replaceable, is therefore manufactured using materials having good impact resistance and abrasion.

Normally, the bursting of the compact material flow is required with a symmetry of revolution as perfect as possible. For this purpose, the deflection cone can for example be provided with guide fins which stretch from the top towards its base, defining between them material flow channels. In addition, the cone can advantageously be rotated about the axis 18 of the shaft furnace.

In some cases it may however be advantageous to load a particular angular sector of the lower hopper 14 more or to rectify residual asymmetries. In this case, it is then sufficient to slightly move the deflection cone 66 outside of its alignment with the axis 18, symmetrically with respect to the angular sector that one wants to load more. To this end, the deflection cone 66 can for example be moved in a plane perpendicular to the axis 18. Alternatively, the axis of the deflector cone 66 could also be inclined relative to the central axis 18 of the shaft furnace. An orientable deflection surface therefore offers possibilities of influencing, almost at will, the distribution of the loading material on the loading surface of the shaft furnace 12.

Figures 3A, 3B and 4A, 4B compare a loading device according to the invention, shown in Figures 3A, 3B, to a conventional loading device, without rotary hopper, shown in Figures 4A, 4B. Unlike the device according to the invention, the conventional device comprises a small bell 80 (or upper bell) which can be moved below the discharge opening 82 of the upper hopper 84.

It will first be noted that in the conventional device of Figures 4A, 4B, the diameter of the discharge opening 82 is much larger than the diameter D of the discharge opening 50 in the device according to the invention of the Figures 3A, 3B. This is due to the fact that the width E of the annular space between the bell 80 and the lower edge of the hopper 84 must have a minimum value in order to avoid clogging by large particles of material.

Figures 3A and 4A show the beginning of the discharge of the two hoppers 34 and 84. The loading profile in the hoppers 34 and 84 is highly asymmetrical. This asymmetry results from the loading by the skips 36, 36 '. In the case of FIG. 4A, the bell 80, which serves both as a sealing member and as a material retaining member, deflects the paths of the particles of material already inside the hopper 84 to make them diverge radially with respect to the axis 18. In the case of FIG. 3A, the flow cone defined by the upper hopper 34, on the other hand converges the trajectories of the particles towards the axis 18, so that it s' establish at the outlet of the discharge section 50 a compact and homogenized flow, having an almost perfect symmetry of revolution. It is only at a distance h from the discharge opening 50, that is to say when the compact flux has already been established, that the focused flux is burst by the deflection surface 66.

The difference between the two devices becomes striking when analyzing Figures 3B and 4B, in which the upper hopper 34, 84 is only slightly filled. In the case of FIG. 3B the symmetry of revolution of the material flow is saved thanks to the focusing of the material flow at the outlet of the hopper 34. In FIG. 4B there is no longer any symmetry of revolution in the material flow. It will be noted that the volume of residual material contained in the hopper 84 (cf. FIG. 4B) is still very large when the material flow begins to lose its symmetry of revolution. In the case of FIG. 3B, the volume of residual material contained in the hopper 34 is on the other hand very small when the material flow begins to finally lose its symmetry of revolution.

In Figure 5 we see a mechanism which allows to modify the arrangement of the deflection cone 66 relative to the lower bell. The deflection cone 66 is guided in translation along the support arms 24, 26. A set of rods 100 connects the deflection cone 66 to a rod 102 which passes axially through the jack 30. If the rod 102 is pushed further into the oven, it causes the pivoting piece 104 to tilt about its suspension axis 106 on the support arm 26. This tilting of the piece 104 takes place in the direction of the arrow 108 and causes, by means of a rod 110, a displacement of the deflection cone 66 in the direction of the arrow 112. A displacement in the opposite direction of the arrow 112 is obtained by further withdrawing the rod 102 from the oven. An identical mechanism can be used to pivot, if necessary, the deflection cone 66 about a pivot axis perpendicular to the plane of the drawing.

The effect caused by a horizontal offset of the deflection cone 66 is described with the aid of Figure 6. In this Figure 6 we see that the deflection cone 66 is shifted to the right to direct more material to the left. It will be noted that the displacement of the deflection cone 66 takes place in the vertical plane which contains the axes of the two loading openings of the upper hopper (= plane of Figure 2). Indeed, it has been observed that the residual asymmetries of the loading surface in the hopper 14 are maximum in the plane of FIG. 2 and minimum in the plane of FIG. 1. The offset of the deflection cone 66 can be adjusted continuously during of the discharge from the upper hopper 34. This adjustment can for example be carried out on the basis of tests obtained for different filling profiles of the upper hopper 34 and different loading materials.

Figure 7 shows another alternative embodiment of the deflection surface according to the invention. In this embodiment, the deflection surface 66 'does not have any symmetry of revolution, but it is suspended above the lower bell 20 so as to be able to rotate around the axis 18. The suspension of this deflection surface 66 'comprises for example a rolling ring 120 and a toothing of gear on this rolling ring which meshes with a pinion 124 of a drive motor 122. The motor 122 is located outside the oven. This drive mechanism is particularly simple and can be easily protected against the heat prevailing inside the oven. It will be appreciated that the execution with a rotating deflection surface makes it possible to distribute the focused material flow with an almost perfect symmetry of revolution on the lower bell 20.

Claims (14)

1. Charging device for a shaft furnace comprising

   a lower hopper (14) defining a discharge opening (16) above a surface of the charge in the shaft furnace,

   a lower bell (20) having a blocking position in which it blocks off said discharge opening (16) of the lower hopper (14) and an open position in which it is located vertically below said discharge opening (16),

   means (24, 26, 28, 30) for vertically displacing the lower bell (20) from its blocking position to its open position and vice versa,

   an upper hopper (34) installed above said lower hopper (14) and connected in a sealed manner to the latter,

   lower means of blockage (48, 60) connected between the lower hopper (14) and the upper hopper (34) and having a blocking position, in which they isolate the upper hopper (34) in a sealed manner from the lower hopper (14) and retain the charging material in the upper hopper (34), and an open position, in which they allow communications between the upper hopper (34) and the lower hopper (14) and unblock a flux of material flowing from the upper hopper (34) to the lower hopper (14),

   at least one material feeding device (38, 38') for the upper hopper (34) mounted above the latter, this feeding device being in communication on one side with the atmosphere and on the other side with said upper hopper (34),

   at least one upper sealing device (40, 40') connected between said feeding devices and the upper hopper (34), in order to be able to isolate the latter in a sealed manner from the atmosphere, characterised

   in that, in their open position, said lower means of blockage (48, 60) connected between the lower hopper (14) and the upper hopper (34) are positioned in such a way that they unblock a free central passage (50) substantially coaxial with the axis (18) of the shaft furnace for the flux of material, so that this flux is established below the upper hopper (34) in the form of a compact flux of material,

   in that said means (28, 30, 24, 26) for vertically displacing the lower bell are positioned outside the space occupied by said compact flux of material, and

   in that, positioned above the lower bell, is a surface for deflecting (66) the compact flux of material so as to make the latter diverge above the lower bell.
2. Device according to Claim 1, characterised in that said means of blockage (48, 60) connected between the lower hopper (14) and the upper hopper (34) comprise a sealing device (52, 48) and a material retention device (60), said sealing device (52, 48) being located downstream from said material retention device (60).
3. Device according to Claim 2, characterised in that the sealing device (48) comprises a flexible sealing joint.
4. Device according to Claim 2 or 3, characterised in that the sealing device (48) is a sealing valve installed below the upper hopper (34).
5. Device according to Claim 4, characterised in that the sealing valve comprises

   a blocking device (54),

   a seating (52) associated with the blocking device (54), this seating being connected in a sealed manner to said upper hopper (34) and surrounding said space occupied by said compact flux of material,

   means (56) for moving the blocking device between a lateral position in which it is located outside said space occupied by said compact flux of material, and a blocking position, in which it is located opposite its seating (52), and

   means for applying the blocking device (54) in its blocking position firmly on to its seating (52).
6. Device according to any one of Claims 2 to 5, characterised in that said material retention device comprises several movable blocking devices so as to create a symmetrical discharge opening around the pouring axis.
7. Device according to Claim 4, characterised in that said material retention device comprises a bell (60) which can be moved in the upper hopper (34) between a lower position blocking a discharge opening (50) and an upper raised position, in which it unblocks said discharge opening (50).
8. Device according to any one of Claims 1 to 7, characterised in that said deflecting surface (66) forms a cone of revolution whose apex is directed towards the upper hopper (34) and whose axis is coaxial with the axis of the compact flux of material.
9. Device according to Claim 8, characterised in that the cone of revolution (66) is fitted with guide fins extending from the apex to the base of the cone so as to define flow channels for the material.
10. Device according to any one of Claims 1 to 9, characterised by a mechanism (100, 102) capable of varying the positioning of said deflecting surface (66) above said lower bell.
11. Device according to Claim 10, characterised in that said mechanism comprises a set of rods (100) capable of moving the deflecting surface (66) in a substantially horizontal plane.
12. Device according to Claim 10, characterised in that said mechanism comprises a set of rods (100) capable of pivoting the deflecting surface around a substantially horizontal axis.
13. Device according to any one of Claims 1 to 9, characterised by

    a mechanism (120) for suspending said deflecting surface (66') above said lower bell (20), which is designed in such a way that said deflecting surface (66') can be driven in rotation around the central axis of the lower bell (20), and

    a driving mechanism (124, 126) capable of driving said deflecting surface (66') in rotation.
14. Device according to Claim 13, characterised in that said suspension mechanism comprises a roller ring (120), and said driving mechanism comprises a set of gear teeth on the roller ring and a pinion (124), located inside the furnace, and a drive motor (122) for the pinion (124), located outside the furnace.

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