This invention concerns a device for charging a shaft furnace, especially a blast furnace, comprising at least one and in general several charging hoppers which normally act as airlock reservoirs and are connected by a connecting box to a material distribution device with a rotatable, pivotable chute for distributing the charge inside the shaft furnace.
There is a considerable number of charging devices of this type that equip blast furnaces around the world. For a blast furnace, charging normally takes place as follows: when a first hopper is being charged under atmospheric pressure, a second hopper, which is then under blast furnace pressure, discharges its load through the connecting box into a central feed channel of the material distribution device. Fed by this central channel, the rotatable, pivotable chute distributes the charge over the charging surface of the furnace. When the second hopper is empty, it is isolated from the furnace and reduced to atmospheric pressure for refilling. The first hopper or, as the case may be, a third hopper, which has been previously filled, is then put under blast furnace pressure ready to feed the material distribution device.
With these charging devices, the flow of material leaving the hoppers normally follows a trajectory off-centre with respect to the central axis of the furnace, due to the eccentric position of the hoppers. It follows that the zone of impact on the rotatable, pivotable chute is variable and asymmetrical, and when the chute is in its withdrawn, inactive position, the impact on the charging surface of the furnace will not be central. On the one hand, asymmetrical, variable impact on the chute complicates the distribution procedure, because the distance over which the material slides along the chute varies with the angular position of the chute and depends on the hopper that is used. On the other hand, the eccentric trajectory from the chute poses a problem, especially when it is desired to improve the performance of a blast furnace by forming a coke chimney in the furnace charge around the central axis of the blast furnace. Using the charging devices described above, it is barely possible to form such a chimney of coke, as the devices are incapable of directing their loads accurately towards the centre of the furnace. Various solutions to this problem have been proposed, for example in the Luxembourg patents LU 85879, LU 86336 and LU 86340 of the applicant. In classical charging installations, the material being charged flows along the inclined wall of the connecting box before it reaches the rotatable, pivotable chute. The solutions mentioned above consist essentially in providing an additional conical funnel inside the connecting box. The output from this funnel is controlled by a metering unit in order to form a retainment of material in the funnel. In this way, the asymmetrical outflow into the chute is reduced or eliminated. However, these solutions require the installation of an elaborate control procedure as well as substantial and complex modifications to the classical charging device.
The invention proposes a charging device for a shaft furnace that allows, by simple means, centring the trajectory of the charge on the central axis of the furnace.
The invention provides a shaft furnace charging device comprising at least one charging hopper with a discharge orifice arranged offset with respect to the central axis of the shaft furnace, and a material distribution device arranged below this hopper. The material distribution device comprises a feed channel coaxial with the central axis of the furnace and a rotatable, pivotable chute arranged below the feed channel designed for distributing a charge into the shaft furnace. The charging device also comprises a funnel-shaped connecting box arranged between the material distribution device and the charging hopper. This connecting box possesses a lower central outlet communicating with the feed channel and at least one upper inlet arranged offset, i.e. off-centre with respect to the central axis of the furnace and communicating with the discharge orifice of the hopper. According to an important aspect of the invention, the charging device comprises at least one dispersion means—a spreader—situated upstream of the above-mentioned distribution device and on the trajectory of material discharged from the discharge orifice, that allows dispersing a flow of material to both sides of the above-mentioned feed channel.
It is known that, due to the funnel shape of the box, horizontal components of velocity will inevitably be communicated to each flow of matter entering off-centre and passing through the box. Consequently, the flow leaving the feed channel becomes eccentric. On the rotatable, pivotable chute, when the latter rotates, such an eccentric flow travels variable sliding distances. In fact, the zone of impact on the chute depends on the relative rotational position of the chute when the incident flow is not coaxial. The sliding distance travelled on the chute governs the degree of deceleration of the material. The result is that the speed of the material leaving the chute also depends on the rotational position of the chute. Thus it is not easy to achieve a desired charge profile of concentric circular zones, and the profile obtained often tends to be rather elliptical. Furthermore, the formation of a coke chimney, if this is desired, is also hampered.
The spreader according to the invention makes it possible to divide a flow of material discharged from the hopper and to disperse it, in the form of at least two separate flows, on to opposite sides of the inclined surfaces of the connecting box, that is to say to both sides of the feed channel. When the flows thus previously separated by the spreader come together again, the collision between them is sufficient to reduce or eliminate their horizontal components of velocity, thus creating a flow which is essentially centred, that is to say, essentially coaxial with the central axis of the furnace. Considering such a spreader, it will be appreciated that it is mechanically simple and hence reliable, that it can easily be arranged inside the connecting box and that its installation requires only few modifications to known charging devices.
According to a simple embodiment, the spreader comprises a spreader plate arranged inside the connecting box. According to a first variant of the invention, this spreader plate is a fixed horizontal plate. According to a second variant of the invention, this spreader plate is a pivotable plate that can be pivoted between an operating position and a non-operating position. In operating position, the plate is generally positioned horizontally so as to constitute an obstacle transverse to the direction of flow. In non-operating position, the plate is withdrawn, for example along the vertical direction, so as not to impede the flow of material.
In the case of a pivotable plate, the spreader plate advantageously has a geometry enabling it to at least partially cover the feed channel when in operating position. A pivotable plate can be greater in area than a fixed plate. The fact that it can at least partially cover the feed channel when in operating position makes it possible to optimize the spreading of material across the whole channel.
In an advantageous embodiment, the spreader also comprises a retaining edge by means of which an accumulation of material can be retained on the spreader. Such an accumulation can, in particular, reduce the effects of abrasive wear of the spreader. For efficient division and diversion of the flow of material, the spreader preferably comprises two opposite sides arranged contiguous with the walls of the connecting box.
In an advantageous embodiment, the feed channel comprises a first upper tubular section and a second lower tubular section, the horizontal cross-section of the first and/or the second tubular section tapering along the direction of material flow. This enables further improvement of the degree of centring of the flow of material at the outlet of the feed channel.
It is evident that the invention lends itself particularly well to a charging device employing several hoppers and to use in blast furnaces. It will also be appreciated that the spreader as described can easily be incorporated into an existing charging device as an improvement. In a preferred embodiment, the charging device comprises three charging hoppers, each having a discharge orifice offset with respect to the central axis of the furnace and comprising three spreaders, each discharge orifice having its respective spreader associated with it.
Other features and characteristics of the invention will become apparent in the detailed description of two advantageous forms of embodiment presented below, with reference to the attached drawings, in which:
A charging device, generally identified by reference number 10, is shown as an example in
The charging device 10 comprises, in known manner, a first hopper 16, a second hopper 18 and a third hopper 20, which act as airlock reservoirs for the material to be charged. Only the lower parts 22, 24 of the first and second hoppers 16, 18 are shown in the drawings. Although the third hopper 20 and its lower part 25 are present, they are not visible in the cross-sections. In
The reference number 26 generally identifies a material distribution device arranged below the hoppers 16, 18, 20. This material distribution device 26 comprises, in known manner, a feed channel 28 coaxial with the central axis 15 of the blast furnace and a rotatable, pivotable chute 30. The latter is arranged below the feed channel 28 and can turn round the central axis 15 and pivot about an essentially horizontal axis of suspension, so as to be able to distribute the charge through the throat 12 on to the charging surface of the blast furnace (not shown).
A connecting box 32 is arranged vertically between the material distribution device 26 and the hoppers 16, 18, 20. The connecting box 32 is essentially funnel-shaped. It comprises, in known manner, a lower discharge outlet 34 which communicates with the feed channel 28 of the material distribution device 26, and three upper inputs 36, 38, 40 arranged symmetrically with respect to the central axis 15 and connected to the lower parts 22, 24, 25 of the hoppers 16, 18, 20. Only the inputs 36 and 38 of the first and second hoppers 16 and 18 are shown in
In known manner, for each of the hoppers 16, 18, 20, a material gate valve 48, 50, 52 respectively serves to interrupt and control the flow to be discharged alternatively via one of the discharge orifices 42, 44, 46. A lower sealing valve 56, 58, 60 is associated with each of the material gate valves 48, 50, 52 and serves to seal the hopper 16, 18, 20 with respect to the blast furnace. It should also be noted, that respective upper sealing valves, mounted at the upper end of the hopper 16, 18, 20 and serving to seal the latter with respect to the outer atmosphere, is not shown in the figures.
In charging phase, the spreaders 66, 68, 70 serve to spread the material flow and thus to divide it and divert it towards different sides of the inclined walls of the connecting box 32. In particular, as can be seen in
In the embodiment according to
As can be seen in
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Number | Date | Country | Kind |
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91 217 | Jan 2006 | LU | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/EP2006/069468 | 12/8/2006 | WO | 00 | 7/21/2008 |