WO2022058317A1

WO2022058317A1 - Charging system for a metallurgical furnace

Info

Publication number: WO2022058317A1
Application number: PCT/EP2021/075251
Authority: WO
Inventors: Patrick Hutmacher; Claude Thinnes; Charles STEICHEN
Original assignee: Paul Wurth S.A.
Priority date: 2020-09-18
Filing date: 2021-09-14
Publication date: 2022-03-24
Also published as: AU2021342670A9; BR112023004609A2; AU2021342670A1; LU102071B1; TW202223315A

Abstract

The invention relates to a charging system (1) for a metallurgical furnace (100) that is elongate along a horizontal length direction (X) in that it has a longer dimension in the length direction (X) than in a horizontal width direction (Y) perpendicular thereto, the charging system (1) being adapted for feeding a plurality of materials to the metallurgical furnace (100). In order to provide a space-saving, simplified charging system for a furnace with an elongate cross-section, the invention provides that the charging system comprises: - a lock hopper (10) for receiving material, having an inlet sealing element (11) and an outlet sealing element (12), the lock hopper (10) being adapted to receive material through the inlet sealing element (11) when the inlet sealing element (11) is open, and being adapted to discharge material through the outlet sealing element (12) when the outlet sealing element (12) is open, the sealing elements (11, 12) being adapted to gas-tightly seal the lock hopper (10) when they are closed; - at least one process hopper (30) having a plurality of material chambers (31, 32, 33); - a transfer system (20) connecting the lock hopper (10) to each material chamber (31, 32, 33) and adapted to receive material from the lock hopper (10) through the outlet sealing element (12) and selectively transfer the received material from the lock hopper (10) to at least one selected material chamber (31, 32, 33) whereby different materials are transferable to different selected material chambers (31, 32, 33); and - a feeder system (40) connecting each material chamber (31, 32, 33) to the furnace (100), wherein the sealing elements (11, 12) are adapted to be opened alternatingly, so that the at least one process hopper (30) and the transfer system (20), downstream of the lock hopper (10), are separated by the sealing elements (11, 12) from an outside atmosphere, upstream of the lock hopper (10).

Description

Charging System for a Metallurgical Furnace

Technical Field

[0001] The invention relates to a charging system for a metallurgical furnace.

Background Art

[0002] Metallurgical furnaces are used for various applications, in particular for steelmaking. Apart from metallurgical furnaces (like blast furnaces) with a circular crosssection, there are furnaces with a rectangular, elongate cross-section. In such a furnace, the different charge materials, like iron ore and reduction materials, are normally not distributed evenly over the cross-section of the furnace. Rather, it is known to feed the different materials at different locations, e.g. feeding the iron ore near the centre of the furnace while other material is fed laterally. At least in the upper part of the furnace, the different materials form more or less distinct vertical columns. The currently employed method for distributing and feeding various materials to a furnace with a rectangular cross-section is to use at least one material hopper for each material. Moreover, there may be more than one charging point for each material. For example, if the furnace is operated with three different types of material, there may be a central charging point for the first material and two charging points for each of the second and the third material, which are disposed symmetrically on either side of the central charging point. In this example, it is common to use a total of five material hoppers. However, since blast furnaces operate under an elevated process pressure which is normally between 0,5 bar and 2 bar above atmospheric pressure, each of the material hoppers needs to be pressurized and depressurized during the charging sequence. A sealing element, such as a seal valve, is required above and below each material hopper. Furthermore, material gates below the material hoppers are required to control the discharge flowrate. In this example, feeding three different materials to the furnace requires a total of five material hoppers with ten sealing elements and five material gates. Therefore, the conventional method leads to a complex and huge layout arrangement, a complex charging and automation system as well as high investment costs. Technical Problem

[0003] It is thus an object of the present invention to provide a space-saving, simplified charging system for a furnace with an elongate cross-section. This object is solved by a charging system according to claim 1.

General Description of the Invention

[0004] The invention provides a charging system for a metallurgical furnace that is elongate along a horizontal length direction in that it has a longer dimension in the length direction than in a horizontal width direction perpendicular thereto. The metallurgical furnace may in particular be a shaft furnace, more specifically a blast furnace. It has an elongate cross-section that is longer along a length direction (or first direction) than along a width direction (or second direction). Normally, the cross-section can be described as rectangular, while it is understood that minor deviations from an exactly rectangular shape are possible.

[0005] The charging system is adapted for feeding a plurality of materials to the metallurgical furnace. More specifically, it is normally adapted to discharge different materials at different locations within the cross-section of the metallurgical furnace. Each of the materials, which may also be referred to as raw materials or charge materials, is a particulate bulk material which may comprise particles of various sizes. It should be understood that each material may also comprise particles of varying chemical compositions. Therefore, strictly speaking, such a material could be referred to as a material mixture. For sake of simplicity and brevity, the term “material” is used in the context of this invention. The system is adapted for feeding at least two, normally three, different materials, but may also be adapted for a higher number of different materials. A first material may e.g. be iron ore or another iron-bearing material, while a second material may be a fuel or a reducing material like coal, coke, carbonaceous material, wood, charcoal, or a mixture thereof.

[0006] The charging system comprises a lock hopper for receiving material, having an inlet sealing element and an outlet sealing element, the lock hopper being adapted to receive material through the inlet sealing element when the inlet sealing element is open, and being adapted to discharge material through the outlet sealing element when the outlet sealing element is open, the sealing elements being adapted to gas-tightly seal the lock hopper when they are closed. The lock hopper is normally disposed at or near the top of the charging system. According to the invention, the lock hopper is intended to receive and temporarily contain any of the different materials. It is adapted to receive material through an inlet sealing element. A funnel-shaped charge vessel may be disposed above the inlet sealing element. Any new material that is put into the vessel falls and/or slides into the lock hopper by force of gravity if the inlet sealing element is open. Any material inside the lock hopper can be discharged through the outlet sealing element. Both sealing elements may in particular be seal valves. They are adapted to provide a gas-tight seal for the lock hopper so that when both sealing elements are closed, the pressure inside the lock hopper can be regarded as independent of any outside pressure. It will be understood that the inlet sealing element is normally disposed at the top of the lock hopper, while the outlet sealing element is normally disposed at the bottom of the lock hopper. The lock hopper may comprise means for adjusting its internal pressure before one of the sealing elements is opened. It is understood that during operation, normally at least one sealing element is closed at any time.

[0007] The charging system further comprises at least one process hopper having a plurality of material chambers. Each material chamber is adapted and designed to at least temporarily contain one kind of material. Particularly, a specific material chamber is intended to contain a specific material. The material chambers can be regarded as compartments within the process hopper. The process hopper may comprise a housing that surrounds all material chambers. However, it is also possible that each material chamber has a dedicated housing and is separate from the other material chambers, in which case the term “process hopper” may simply refer to the group of material chambers. While the material chambers are separated from each other to prevent material exchange, they may be connected for gas exchange and have the same pressure at any time.

[0008] Also, the charging system comprises a transfer system that connects the lock hopper to each material chamber and is adapted to receive material from the lock hopper through the outlet sealing element and selectively transfer the received material from the lock hopper to at least one selected material chamber, whereby different materials are transferable to different selected material chambers. As will be explained further below, the transfer system normally comprises a plurality of pipes or channels that are adapted for guiding material. As far as possible, material transfer in the transfer system is preferably driven by gravity so that the material falls or slides through the transfer system. Therefore, with respect to the vertical axis, the transfer system is preferably disposed between the lock hopper and the material chambers of the process hopper. The transfer system can receive material from the lock hopper through the outlet sealing device and transfer the material to each material chamber. The transfer does not occur in a random manner, but at least one material chamber can be selected, and the transfer system is adapted to transfer the material only to the selected material chamber(s). Therefore, although any type of material is initially received in the (single) lock hopper, the different types of material can be directed to one or more dedicated material chambers. E.g. a first material can be transferred to at least one first material chamber, whereas a second material can be transferred to at least one second material chamber etc.

[0009] The charging system further comprises a feeder system connecting each material chamber to the furnace. Like the transfer system, the feeder system normally comprises a plurality of pipes or channels that are adapted for guiding material. Also, it is highly preferred that material transfer in the feeder system is entirely driven by gravity. Therefore, with respect to the vertical axis, the feeder system is preferably disposed between the material chambers and the furnace. It will be understood that the connection of one material chamber to the furnace is normally completely separate from the connections of any other material chamber to the furnace. However, if two material chambers are intended to hold the same type of material, they may partially be connected to the furnace by the same connection means (pipes, channels etc.).

[0010] The sealing elements are adapted to be opened alternatingly, so that the at least one process hopper and the transfer system, downstream of the lock hopper, are separated by the sealing elements from an outside atmosphere, upstream of the lock hopper. In other words, the sealing elements are adapted so that only one of them is opened at a time, i.e., they can be opened alternatingly. Accordingly, at least one sealing element is closed at any time. Accordingly, the transfer system and the process hopper(s), which are located downstream with respect to the material flow through the charging system, are separated from an outside atmosphere upstream of the lock hopper (e.g., in the abovementioned charge vessel). The sealing elements prevent direct pressure exchange between the outside atmosphere on the one hand and the charging system and the at least one process hopper on the other hand. In general, the “outside atmosphere” is the atmosphere upstream of the inlet element, but normally this is ambient atmosphere, corresponding to ambient pressure.

[0011] The inventive charging system brings about several advantages. Firstly, the number of sealing devices can be greatly reduced. There is normally one single lock hopper with two sealing devices, irrespective of the number of different materials that need to be supplied to the furnace. The separation of these materials is maintained by the different material chambers of the at least one process hopper. The lock hopper serves as an airlock through which any raw material is introduced into the charging system. It is not intended for long-time storage of raw material. Consequently, it can be designed relatively small in volume. In particular, its (internal) volume may be smaller than the combined volume of the material chambers of the process hopper. In some embodiments, its volume could be even smaller than the volume of a single material chamber. The material chambers of the process hopper, on the other hand, are separated from the outside atmosphere by the sealing devices of the lock hopper and therefore need no dedicated pressure regulation. The same applies to the charging system. During a receiving-and-discharging cycle of raw material, the lock hopper is subjected to a varying pressure. Its geometry can be designed specifically to withstand such cyclic pressure differences. For instance, it may have a circular cross-section. Apart from such a pressure-resistant shape, a relatively small size of the lock hopper can also enhance its resistance to (changing) internal pressure. The small size is made possible by the fact that the lock hopper is only intended to temporarily contain raw material that is afterwards transferred to one of the material chambers.

[0012] Although some kind of air-tight sealing element between the process hopper and the furnace is not ruled out by the concept of the invention, it is preferred that the feeder system is open for pressure exchange between the process hopper and the furnace. Since pressure exchange is possible between the furnace and the material chambers of the process hopper, the internal pressure of these chambers normally corresponds, at least approximately, to the internal pressure of the furnace. This pressure exchange in principle allows for a gas exchange between the furnace and the material chambers. However, gas transfer from the furnace to the chambers should be prevented in order to reduce heat transfer from the furnace to the process hopper. This can be achieved e.g. by injecting a gas like nitrogen into the material chambers, thereby creating a slight overpressure with respect to the furnace. During operation, the furnace pressure is largely constant. Therefore, the material chambers are subjected to a mostly constant, i.e. static pressure, which may differ from the furnace pressure by the abovementioned overpressure. This enables the design of the material chambers to be focused less on (cyclic) pressure resistance and more on other aspects, in particular optimum reception of raw material from the transfer system and optimum discharge of raw material to the feeder system. This refers to the general shape of the material chambers as well as their size. It should be noted that even if the feeder system is open to pressure exchange, it may comprise at least one device (e.g. a material gate) adapted to regulate or prevent material flow from the material chambers to the furnace.

[0013] It is also preferred that the transfer system is open for pressure exchange with the at least one process hopper. Accordingly, since the pressure in the process hopper (or any of its material chambers) can be relatively constant, the same applies to the pressure in the transfer system. This, in turn, may be beneficial for the transfer system, since it is not subjected to significant pressure changes.

[0014] According to a preferred embodiment, the charge system comprises means for detecting a charging level of each material chamber. The charging level or material level indicates to which extent the respective material chamber is filled with material. The charging level may be detected by any suitable sensor known in the art, e.g. an ultrasound sensor. Generally, the sensor needs to be adapted for continuous level measurement. In this context, the feeder system is preferably permanently open for material transfer from each material chamber to the furnace. In other words, if there is any material in the material chamber, it can be assumed that the entire feeder system (or the part of the feeder system that connects this material chamber to the furnace) is filled with material. Then, by measuring the charging level of the material chamber, a permanent material supply to the furnace can be secured. This is advantageous since although the material chamber is connected for pressure exchange with the furnace, the temperatures and other atmospheric conditions in the material chamber are normally much less severe, since it is separated from the furnace by the feeder system in between. This protection can be improved by creating a slight overpressure in the material chamber, as mentioned above. Accordingly, there is less need for special protection of the respective sensors.

[0015] According to one embodiment, the transfer system comprises a plurality of transfer subsystems having at least one transfer inlet at least indirectly connected to the lock hopper and at least one transfer outlet connected to a material chamber, the transfer outlets of different transfer subsystems in one material chamber being spaced apart along the length direction. Each transfer subsystem has at least one transfer inlet which is either directly or indirectly connected to the lock hopper, i.e. during operation, the transfer subsystem receives material from the lock hopper through the transfer inlet. On the other hand, the transfer subsystem has at least one transfer outlet that is connected to a material chamber, so that during operation, material is discharged through the transfer outlet into this material chamber. In this embodiment, the transfer outlets of different transfer subsystems are spaced apart along the length direction. One could also say that there are several discharge points in the material chamber that are distributed along the length direction. Accordingly, material can be distributed in the material chamber in a more uniform way, which is relevant especially in case of elongate material chamber. Preferably, the transfer inlets are also spaced apart along the length direction. The same applies to the transfer subsystems as a whole. Alternatively, the transfer system may only comprise a single transfer subsystem having at least one transfer inlet and at least one transfer outlet as described above. Thus, more generally, the transfer system may comprise at least one transfer subsystem.

[0016] In case of several spaced-apart transfer outlets, it can be difficult to realise a material transfer that is entirely gravity-driven. Accordingly, the transfer system may comprise a conveyor for conveying material along the length direction and a plurality of transfer inlets maybe connected to the conveyor. The conveyor may be arranged horizontally, i.e. it may be arranged parallel to the length direction. It could be a chain conveyor or any other conveyor suitable for transporting the raw materials. Although it would be possible to transfer material from the lock hopper to several transfer outlets by gravity only, this would also increase the height of the entire charging system, due to limitations of the angle of a channel or pipe with respect to the direction of gravity.

[0017] Preferably, at least one transfer subsystem comprises a plurality of transfer channels, each transfer channel being connected to a transfer inlet via a diverting device and to a transfer outlet, the diverting device being adapted to selectively direct a material from the transfer inlet to one of the transfer channels. As explained above, the lock hopper is used to temporarily store any type of material, which is afterwards selectively transferred to at least one selected material chamber. According to this embodiment, any type of material enters the transfer subsystem through a transfer inlet to which the diverting device is connected. Then, depending on the type of material, it is directed by the diverting device into one of the transfer channels, namely the transfer channel that leads to the material chamber for which the material is intended.

[0018] Preferably, the feeder system comprises, for each material chamber, at least one feeder subsystem having at least one feeder inlet at the respective material chamber and at least one feeder outlet at the furnace. The feeder subsystem can be regarded as a part of the feeder system that is associated with a respective material chamber. It is connected to the material chamber by at least one feeder inlet comprising at least one, normally a plurality of pipes or channels through which the material is transferred - preferably by gravity - to the feeder outlet, which serves as a discharge point into the furnace. The arrangement of the feeder outlets at the furnace mainly determines the distribution of the materials within the cross-section of the furnace. It is understood that the feeder subsystems for different materials are separate from each other. According to one embodiment, the feeder outlets of feeder subsystems that are connected to different material chambers are offset along the width direction. Thus, different materials can be disposed as columns or stacks that are offset along the width direction.

[0019] Oftentimes it is required to provide a certain type of material at two different locations in the furnace. For example, a first material could be provided at a central position within the furnace, while a second material could be provided on two opposite sides of the central position. The one hand, this could be achieved with two material chambers for the second material, each of which comprises a dedicated feeder subsystem. In a preferred embodiment, requirements like this can be fulfilled if at least one feeder subsystem comprises two feeder branches with feeder outlets spaced apart along the width direction. The two feeder branches may each have a dedicated feeder inlet or they could be connected to a single feeder inlet. Either way, each feeder branch has at least one feeder outlet and the at least one feeder outlet of the first feeder branch is spaced apart along the width direction from the at least one feeder outlet of the second feeder branch. Therefore, the two feeder branches discharge material at different positions that are spaced apart along the width direction. In particular, the feeder outlets could be disposed symmetrically with respect to a sensor plane of the furnace along the length direction. Alternatively, a feeder subsystem may only comprise a single feeder branch, which may be arranged centrally with respect to the furnace.

[0020] As mentioned above, the material chambers are normally not subjected to greater pressure differences, wherefore their design does not need to be focused on pressure resistance. In particular, the material chambers do not need to have a round cross-section as is preferred for the lock hopper. According to one embodiment, the material chambers of a process hopper are elongate along the length direction and are offset along the width direction. In other words, the material chambers are elongate along the same direction as the process hopper. They are offset with respect to each other along the width direction and may be disposed next to each other. The elongate design facilitates the routing of the different parts of the feeder system, in particular of the different feeder subsystems. The dimension of the material chambers along the length direction may correspond to between 80% and 120% of the dimension of the furnace. [0021] A specific, more uniform distribution of a raw material within the furnace can be realised if the feeder system comprises, for at least one material chamber, a plurality of feeder subsystems with feeder inlets that are offset along the length direction. This is of course preferably combined with the above-mentioned embodiment in which the respective material chambers elongate along the length direction. Normally, not only the feeder inlets, but the feeder subsystems in their entirety are offset along the length direction. Accordingly, one feeder subsystem can be associated with a specific region of the furnace with respect to the length direction.

[0022] Preferably, each feeder inlet is connected to a funnel-shaped outlet portion of a material chamber. It is understood that the outlet portion is disposed in the lower part or at the bottom of the material chamber. The funnel shape serves to direct the material into the feeder inlet as it moves downwards by force of gravity. The cross-section of the outlet portion tapers from top to bottom. In particular, the cross-section of all outlet portions can correspond to the entire cross-section of the material chamber so that any material within the material chamber is collected by one outlet portion and therefore is guided into a feeder inlet.

[0023] Preferably, the feeder inlets of different material chambers are offset along the length direction. This is preferred even if the material chambers are offset along the width direction, since it facilitates a simpler routing of the various feeder subsystems. In particular, if a feeder subsystem comprises two feeder branches, having the feeder inlets of different material chambers offset along the length direction greatly facilitates routing of the feeder branches that are associated with different material chambers. Different feeder subsystems can be kept separate more easily without the need of a large number of curved portions. Such curved portions should be reduced to a minimum since they impede the material transfer by gravity. If the feeder inlets are offset as described herein, corresponding outlet portions are normally not symmetrical but have offset or eccentric shape.

[0024] A desirable distribution of the material within the furnace can normally not be achieved with a single, unbranched pipe or channel. Preferably, at least one feeder branch comprises an upper channel connected to a feeder inlet and a plurality of lower channels, each lower channel being connected to the upper channel and to a feeder outlet. In other words, the feeder branch as such has a branching structure. An upper channel is connected to a feeder inlet and a plurality of lower channels are connected to the upper channel. One could also say that the lower channels branch off the upper channel. Each of the lower channels is connected to a feeder outlet. During operation, a material flow through the upper channel branches into material flows through each lower channel. Since the entire material transfer in the feeder system is preferably gravity driven, the upper channel is normally disposed entirely above the lower channels.

[0025] In order to facilitate the branching of the material flow, each lower channel is preferably connected to the upper channel via a diffuser device adapted to distribute material from the upper channel among the lower channels. Normally, the diffuser device is a passive device without movable parts, although it could be adapted to actively influence the material flow into the lower channels. According to one design, the diffuser device comprises an upper opening for the upper channel and a plurality of lower openings, one for each lower channel, that are disposed symmetrically with respect to the centre of the opening.

[0026] As mentioned above, the material chambers are preferably elongate along the same direction as the furnace. If the dimension of the furnace along the length direction is too great, it may be detrimental to use a single elongate material chamber for each material. One reason can be that the structural stability of a material chamber with an extreme length-to-width ratio is not enough to withstand the (static) internal pressure. In such a case, the charging system may comprise a plurality of process hoppers offset along the length direction. It will be understood that normally, each process hopper has at least one material chamber for each type of material. Accordingly, the charging system comprises, for each type of material, a plurality of material chambers that are offset along the length direction.

Brief Description of the Drawings

[0027] Preferred embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which:

Fig.1 is side view of a first blast furnace with a first embodiment of an inventive charging system along a width direction;

Fig.2 is side view of the blast furnace with the charging system from Fig.1 along a length direction;

Fig.3 is a perspective view of a diffuser device of the charging system from Fig.1 ; Fig.4 is a top view of the diffuser device from Fig.3;

Fig.5 is a side view of the diffuser device from Fig.3;

Fig.6 is a sectional view according to the line Vl-Vi in Fig.5; and

Fig.7 is side view of a second blast furnace with a second embodiment of an inventive charging system along the width direction.

Description of Preferred Embodiments

[0028] Figs 1 and 2 show a first embodiment of an inventive charging system 1 for a metallurgical furnace, e.g. for a blast furnace 100. The blast furnace 100 has a rectangular cross-section and is elongate along a length direction X, which corresponds to an X-axis. Its dimension (length) along the length direction X is about three times greater than its dimension (width) along a width direction Y, which corresponds to a Y- axis. The height direction Z corresponds to a Z-axis. The blast furnace 100 is operated with three different types of raw material, e.g. one iron-bearing material and two fuel materials. These raw materials are fed into the blast furnace 100 by the charging system 1.

[0029] The charging system 1 comprises a lock hopper 10 that is connected to a funnel- shaped charging vessel 5 via an inlet valve 11. When the inlet valve 11 is open, any raw material that is put into the charging vessel 5 can enter the lock hopper 10 and is temporarily contained therein. When the inlet valve 11 is open, an outlet valve 12 below the lock hopper 10 is closed. When the lock hopper 10 has received a charge of raw material, the inlet valve 11 is closed to provide a gas-tight seal with respect to the outside of the charging system 1. Afterwards, the outlet valve 12 is opened so that the raw material is discharged from the lock hopper 10 onto a conveyor 21 of a transfer system 20. The conveyor 21 may e.g. be a chain conveyor and is horizontally arranged along the length direction X.

[0030] Two transfer subsystems 22 of the transfer system 20 are connected to the conveyor 21. More specifically, each transfer subsystem 22 comprises a transfer inlet 23 that is connected to the conveyor 21 and three transfer channels 25 are connected to the transfer inlet 23 via a diverting device 24. The diverting device 24 is adapted to direct a material flow from the conveyor 21 selectively to one of the transfer channels 25. Each transfer channel 25 is connected via a transfer outlet 26 to a material chamber 31 , 32, 33 of a process hopper 30. A first material chamber 31 is intended for a first material, e.g. a first fuel material, while a second material chamber 32 is intended for a second material, e.g. an iron-bearing material and a third material chamber 33 is intended for a third material, e.g. a second fuel material. The first and second fuel material may or may not be the same. The lock hopper 10 is filled with a charge of one of these materials at a time, which is then transferred via the conveyor 21 , the diverting device 24 and the respective transfer channel 25 to a dedicated material chamber 31 , 32, 33. Each material chamber 31 , 32, 33 is elongate along the length direction X and has about the same length as the blast furnace 100. In contrast to this, the lock hopper 10 has a circular cross-section with the same dimensions along the length direction X and the width direction Y.

[0031] At each material chamber 31 , 32, 33, the transfer outlets 26 of the two transfer subsystems 22 are spaced apart along the length direction. This configuration enables an optimum distribution of the raw material in the respective material chamber 31 , 32, 33. The material chamber 31 , 32, 33 serves as a reservoir for the respective material and a charging level of the material chamber 31 , 32, 33 can be detected during operation by a suitable sensor (not shown), e.g. an ultrasonic sensor. Each material chamber 31 , 32, 33 is connected to the blast furnace 100 by a feeder system 40 which will be discussed below. By monitoring the charging level and replenishing the material if the charging level is below a certain threshold, it can be assured that the feeder system 40 is always filled with material, thereby ensuring optimum operation of the blast furnace 100. Although the feeder system 40 enables pressure exchange between the material chambers 31 , 32, 33 and the blast furnace 100, the temperature in the material chambers

31 , 32, 33 is considerably lower than inside or near the blast furnace 100 and the atmosphere is less aggressive. Therefore, the sensors need no or only minor protection and the measurement is facilitated. Also, a slight overpressure can be created in the material chambers 31 , 32, 33 with respect to the pressure in the blast furnace 100, e.g. by injecting a gas like nitrogen, whereby an gas flow from the blast furnace 100 to the material chambers 31 , 32, 33 is prevented.

[0032] Each material chamber 31 , 32, 33 comprises a plurality of funnel-shaped outlet portions 34, 35, 36 at its bottom. Feeder inlets 43, 53, 63 are connected to each outlet portion 34, 35, 36. Each feeder inlet 43, 53, 63 is part of a feeder subsystem 41 , 51 , 61 that is dedicated for transferring one kind of raw material from a material chamber 31 ,

32, 33 to the blast furnace 100. As can be seen in fig. 1 , the outlet portions 34, 35, 36 are non-symmetric and the feeder inlets 43, 53, 63 of different feeder subsystems 41 , 51 , 61 are offset along the length direction X. This design facilitates routing of the individual feeder subsystems 41 , 51 , 61 and helps reduce the complexity and the size of the charging system 1.

[0033] A first feeder subsystem 41 comprises two feeder branches 42 that originate from the same outlet portion 34 but are spaced apart along the width direction Y and lead to two separate feeder outlets 47 disposed on opposite sides of the blast furnace 100 with respect to the width direction Y. Each feeder branch 42 comprises an upper channel 44 connected to a feeder inlet 43 and three lower channels 46. The lower channels 46 are connected to the blast furnace 100 via individual feeder outlets 47 that are spaced apart along the length direction X and are connected to the upper channel 44 via a material gate 48 and a diffuser device 45. Figs 3 to 6 show the diffuser device 45 individually. It has an upper opening 45.1 that is connected to the upper channel 44 and three legs 45.3, each of which is connected to one lower channel 46. As can be seen by the top view of Fig.4 and the sectional view of Fig.6, each leg 45.3 communicates with a lower opening 45.2 and the lower openings 45.2 are symmetrically arranged underneath the upper opening 45.1. Therefore, as material enters the diffuser device 45 through the upper opening 45.1 , this material is evenly distributed among the three legs 45.3 and also among the lower channels 46.

[0034] A second feeder subsystem 51 has a similar setup as the first feeder subsystem 41 . However, it only has a single feeder branch 42 that is centrally arranged with respect to the blast furnace 100. An upper channel 54 is connected to an outlet portion 35 via a feeder inlet 53 and a material gate 58, and three lower channels 56 are connected to the upper channel 54 via a diffuser device 55 that has a similar design as the diffuser device 45 and will not be discussed in detail. Each lower channel 56 is connected to the blast furnace 100 via a feeder outlet 57.

[0035] A third feeder subsystem 61 has a similar setup as the first feeder subsystem 41 and also comprises two feeder branches 62 that are offset along the width direction Y. An upper channel 64 of each feeder branch 62 is connected to an outlet portion 36 via a feeder inlet 63 and three lower channels 66 are connected to the upper channel 64 via a material gate 68 and a diffuser device 65 that also has a similar design as the diffuser device 45. Each lower channel 66 is connected to the blast furnace 100 via a feeder outlet 67. As can be seen in Fig.2, the feeder outlets 67 of the two feeder branches 62 are offset along the width direction Y and are symmetrically disposed with respect to the centre of the blast furnace 100. [0036] According to the configuration of the feeder outlets 47, 57, 67, the material that is received in the first material chamber 31 is discharged symmetrically on opposite sides of the blast furnace 100. The material that is received in the second material chamber 32 is discharged centrally at the top of the blast furnace 100, while the material that is received in the third material chamber 33 is discharged symmetrically on opposite sides of the centre of the blast furnace 100 near its top.

[0037] It should be noted that although the charging system 1 is designed to feed three different materials to the blast furnace 100 at a total of 45 different feeder outlets 47, 57, 67, it requires only two gas-tight seal valves 11 , 12. The only component of the feeder system 1 that is subjected to considerable pressure changes during operation is the lock hopper 10. The transfer system 20, the process hopper 30 and the feeder system 40 are connected for pressure exchange with the blast furnace 100 and therefore have an almost constant internal pressure during operation, which may differ from the pressure in the blast furnace 100 by the abovementioned slight overpressure.

[0038] The material gates 48, 58, 68 can be opened or closed in order to prevent or enable material flow through the diffuser device 45, 55, 65 below. However, even when they are closed, they do not prevent pressure exchange, i.e. they are not gas-tight like the seal valves 11 , 12. There are several possible operation modes. In a gravity filling mode, the material gates 48, 58, 68 remain open all the time during normal operation. They are only closed during an initial filling process or during a shut-down of the plant. In a batch-filling mode, the material gates 48, 58, 68 regulate the discharge flow rate during normal operation, i.e. that they are opening and closing in every batch cycle.

[0039] Fig.7 shows a side view of a second blast furnace 100 with a second embodiment of an inventive charging system 1. This blast furnace 100 is considerably longer along the length direction X than the one shown in Figs 1 and 2. In order to achieve an adequate, uniform distribution of raw material inside the blast furnace 100, the feeder system 1 comprises two process hoppers 30, each of which is designed like the process hopper 30 of the first embodiment. The components of the feeder system 40 are the same as in the first embodiment, except that the number of components is doubled. In order to enable material transfer from the lock hopper 10 to the two process hoppers 30, the transfer system comprises a total of four transfer subsystems 22 (two for each process hopper 30) and the length of the conveyor 21 is increased with respect to the first embodiment. It should be noted that although the total number of feeder outlets 47, 57, 67 is now increased to 90, there is still only a single lock hopper 10 with two gas-tight seal valves 11 , 12.

Legend of Reference Numbers:

1 charging system 41 , 51 , 61 feeder subsystem

5 charging vessel 42, 52, 62 feeder branch

10 lock hopper 43, 53, 63 feeder inlet

11 , 12 seal valve 44, 54, 64 upper channel

20 transfer system 45, 55, 65 diffuser device

21 conveyor 45.1 upper opening

22 transfer subsystem 45.2 lower opening

23 transfer inlet 45.3 leg

24 diverting device 46, 56, 66 lower channel

25 transfer channel 47, 57, 67 feeder outlet

26 transfer outlet 48, 58, 68 material gate

30 process hopper 100 blast furnace

31-33 material chamber X length direction

34-36 outlet portion Y width direction

40 feeder system Z height direction

Claims

CLAIMS A charging system (1) for a metallurgical furnace (100) that is elongate along a horizontal length direction (X) in that it has a longer dimension in the length direction (X) than in a horizontal width direction (Y) perpendicular thereto, the charging system (1) being adapted for feeding a plurality of materials to the metallurgical furnace (100) and comprising:

- a lock hopper (10) for receiving material, having an inlet sealing element (11) and an outlet sealing element (12), the lock hopper (10) being adapted to receive material through the inlet sealing element (11) when the inlet sealing element (11) is open, and being adapted to discharge material through the outlet sealing element (12) when the outlet sealing element (12) is open, the sealing elements (11 , 12) being adapted to gas-tightly seal the lock hopper (10) when they are closed;

- at least one process hopper (30) having a plurality of material chambers (31 , 32, 33);

- a transfer system (20) connecting the lock hopper (10) to each material chamber (31 , 32, 33) and adapted to receive material from the lock hopper (10) through the outlet sealing element (12) and selectively transfer the received material from the lock hopper (10) to at least one selected material chamber (31 , 32, 33), whereby different materials are transferable to different selected material chambers (31 , 32, 33); and

- a feeder system (40) connecting each material chamber (31 , 32, 33) to the furnace (100), wherein the sealing elements (11 , 12) are adapted to be opened alternatingly, so that the at least one process hopper (30) and the transfer system (20), downstream of the lock hopper (10), are separated by the sealing elements (11 , 12) from an outside atmosphere, upstream of the lock hopper (10). The charging system according to claim 1 , characterised in that the feeder system (40) is open for pressure exchange between the process hopper (30) and the furnace (100).

3. The charging system according to any of the preceding claims, characterised in that it comprises means for detecting a charging level of each material chamber (31 , 32, 33).

4. The charging system according to any of the preceding claims, characterised in that the transfer system (20) comprises a plurality of transfer subsystems (22) having at least one transfer inlet (23) at least indirectly connected to the lock hopper (10) and at least one transfer outlet (26) connected to a material chamber (31 , 32, 33), the transfer outlets (26) of different transfer subsystems (22) in one material chamber (31 , 32, 33) being spaced apart along the length direction (X).

5. The charging system according to any of the preceding claims, characterised in that the transfer system (20) comprises a conveyor (21) for conveying material along the length direction (X) and a plurality of transfer inlets (23) is connected to the conveyor (21).

6. The charging system according to any of the preceding claims, characterised in that at least one transfer subsystem (22) comprises a plurality of transfer channels (25), each transfer channel (25) being connected to a transfer inlet (23) via a diverting device (24) and to a transfer outlet (26), the diverting device (24) being adapted to selectively direct a material from the transfer inlet (23) to one of the transfer channels (25).

7. The charging system according to any of the preceding claims, characterised in that the feeder system (40) comprises, for each material chamber (31 , 32, 33), at least one feeder subsystem (41 , 51 , 61) having at least one feeder inlet (43, 53, 63) at the respective material chamber (31 , 32, 33) and at least one feeder outlet (47, 57, 67) at the furnace.

8. The charging system according to any of the preceding claims, characterised in that at least one feeder subsystem (41 , 51 , 61) comprises two feeder branches (42, 52, 62) with feeder outlets (47, 57, 67) spaced apart along the width direction (Y). 18

9. The charging system according to any of the preceding claims, characterised in that the material chambers (31 , 32, 33) of a process hopper (30) are elongate along the length direction (X) and are offset along the width direction (Y).

10. The charging system according to any of the preceding claims, characterised in that the feeder system (40) comprises, for at least one material chamber (31 , 32, 33), a plurality of feeder subsystems (41 , 51 , 61) with feeder inlets (43, 53, 63) that are offset along the length direction (X).

11 . The charging system according to any of the preceding claims, characterised in that each feeder inlet (43, 53, 63) is connected to a funnel-shaped outlet portion (34, 35, 36) of a material chamber (31 , 32, 33).

12. The charging system according to any of the preceding claims, characterised in that the feeder inlets (43, 53, 63) of different material chambers (31 , 32, 33) are offset along the length direction (X).

13. The charging system according to any of the preceding claims, characterised in that at least one feeder branch (42, 52, 62) comprises an upper channel (44, 54, 64) connected to a feeder inlet (43, 53, 63) and a plurality of lower channels (46, 56, 66), each lower channel (46, 56, 66) being connected to the upper channel (44, 54, 64) and to a feeder outlet (47, 57, 67).

14. The charging system according to any of the preceding claims, characterised in that each lower channel (46, 56, 66) is connected to the upper channel (44, 54, 64) via a diffuser device (45, 55, 65) adapted to distribute material from the upper channel (44, 54, 64) among the lower channels (46, 56, 66).

15. The charging system according to any of the preceding claims, characterised in that it comprises a plurality of process hoppers (30) offset along the length direction (X).