BLAST FURNACE PLANT

Abstract

The invention relates to a blast furnace plant (1, 1a-1c) with a blast furnace (2) and a charging device (3) for the blast furnace (2). In order to provide an economical way of providing clean gas to the charging device, the invention provides that the blast furnace plant (1, 1a-1c) further comprises: at least one nozzle (6) for introducing a clean gas into said charging device (3); a cleaning device (7) which is connected for receiving gas from the blast furnace (2) and arranged for removing dust from the gas; at least one compressor (9) arranged for receiving gas from the cleaning device (7), compressing the gas and feeding the gas to the at least one nozzle (6); and at least one turbine (8) connected for receiving and being driven by gas from the blast furnace (2), the at least one turbine being mechanically coupled to drive the at least one compressor (9).

Claims

1. Blast furnace plant with a blast furnace and a charging device for the blast furnace, wherein the blast furnace plant further comprises: at least one nozzle for introducing a clean gas into the charging device; a cleaning device which is connected for receiving gas from the blast furnace and arranged for removing dust from the gas; at least one compressor arranged for receiving gas from the cleaning device, compressing the gas and feeding the gas to the at least one nozzle; and at least one turbine connected for receiving and being driven by gas from the blast furnace, the at least one turbine being mechanically coupled to drive the at least one compressor.

2. Blast furnace plant according to claim 1, wherein the charging device comprises a main casing with a stationary housing and a suspension rotor for a movable distribution chute, said suspension rotor being rotatably mounted with respect to the housing, wherein at least one of said nozzles is disposed for introducing the clean gas into the main casing.

3. Blast furnace plant according to claim 1, wherein the charging device comprises a hopper for raw materials to be fed into the blast furnace, wherein at least one of said nozzles is disposed for introducing gas into the hopper.

4. Blast furnace plant according to claim 1, wherein the cleaning device comprises a first cleaning stage and a second cleaning stage for sequentially cleaning the gas.

5. Blast furnace plant according to claim 4, wherein the turbine and/or compressor is/are connected to receive gas from the second cleaning stage.

6. Blast furnace plant according to claim 4, wherein the turbine and/or compressor is/are connected to receive gas from the first cleaning stage or another intermediate stage of the cleaning device.

7. Blast furnace plant according to claim 6, wherein a further cleaning unit is disposed between the first cleaning stage or intermediate stage and the turbine, respectively the compressor.

8. Blast furnace plant according to claim 5, wherein a heat exchanger is arranged between the second cleaning stage and the turbine, which heat exchanger is arranged to use heat from the blast furnace.

9. Blast furnace plant according to claim 1, wherein said at least one turbine and said at least one compressor are connected by a common shaft for concerted rotation.

10. Gas recirculation arrangement for a blast furnace plant with a blast furnace and a charging device for the blast furnace, which gas recirculation arrangement comprises: at least one nozzle for introducing a clean gas into the charging device; a cleaning device which is connectable for receiving gas from the blast furnace and arranged for removing dust from the gas; at least one compressor arranged for receiving gas from the cleaning device, compressing the gas and feeding the gas to the at least one nozzle; and at least one turbine connectable for receiving and being driven by gas from the blast furnace, the at least turbine being mechanically coupled to drive the at least one compressor.

11. Method for operating a blast furnace plant with a blast furnace and a charging device for the blast furnace, the method comprising: a cleaning device receiving gas from the blast furnace and removing dust from the gas; at least one compressor receiving gas from the cleaning device, compressing the gas and feeding the gas to at least one nozzle; the at least one nozzle introducing the clean gas into the charging device; and at least one turbine receiving and being driven by gas from the blast furnace, the at least turbine being mechanically coupled to and driving the at least one compressor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Preferred embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which:

[0035] FIG. 1 is a schematic representation of a first embodiment of a blast furnace plant according to the invention;

[0036] FIG. 2 is a schematic representation of a second embodiment of a blast furnace plant according to the invention;

[0037] FIG. 3 is a schematic representation of a third embodiment of a blast furnace plant according to the invention; and

[0038] FIG. 4 is a schematic representation of a fourth embodiment of a blast furnace plant according to the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0039] FIG. 1 shows a schematic representation of an inventive blast furnace plant 1. A charging installation 3 is placed on top of a blast furnace 2. In an upper part of the charging installation 3, raw materials are placed in material hoppers 5. From here, they are charged to the blast furnace by a rotational chute 4.1, which is suspended on a lower side of a main casing 4. The main casing 4 is formed by a stationary housing and a suspension rotor, as is known in the art (not shown in detail). To provide for a rotatability of the rotor with respect to the housing, there is a gap between the two elements, which is minor, but could be an entry path for gas and particles into the main casing 4. The chute 4.1 is pivotally suspended on the rotor so that it can be tilted around a horizontal axis. The rotor further allows rotating the chute 4.1 around the furnace axis.

[0040] To prevent dust-laden top gas from the blast furnace 2 from entering the main casing 4, an over-pressure cleaned gas is injected into the gear housing by at least one nozzle 6. Hereby the furnace gas is at least largely kept out of the main casing. The details of this process can be different. E.g. a plurality of nozzles 6 can create a curtain of clean gas which blocks a gap between two moving parts of the housing and/or the gas is just introduced into the casing 4 by one or more nozzles to create an overpressure therein.

[0041] The clean gas is obtained by means of a gas recirculation arrangement 30, which will now be described. High-temperature top gas is extracted from the blast furnace through a first pipe 11. This top gas is highly dust-laden and therefore is fed into a cleaning device 7, which performs a two-stage cleaning. The first pipe 11 is connected to a dust catcher 7.1 (or alternatively a cyclone), which in turn is connected by a second pipe 12 to a wet separator 7.2, which comprises a scrubber 7.3 and a demister 7.4. After the two cleaning steps, the gas has a residual dust content, which may e.g. be of less than 20 mg/m.sup.3. It may be noticed that cleaning of BF top gas is conventional in the art and the cleaning device 7 may be designed according to conventional practice.

[0042] In the following, the design of the gas recirculation arrangement will depend on the presence, or not, of a TRT (top gas recovery turbine) downstream of the cleaning device 7. As it is known in the art, the TRT turbine is generally driven by the cleaned top gas in order to drive itself an electric generator, while the expanded top gas is returned to the plant network and may be burned. Referring to FIG. 1, clean gas exits cleaning device 7 in a clean gas piping 32 connected to a TRT turbine indicated 34.

[0043] It shall be appreciated that a part of the cleaned top gas is fed from piping 32 through a third pipe 13 into a turbine 8, which is driven by the gas pressure. The expanded gas exits the turbine 8 through a fourth pipe 14, by which it is returned to the gas network 36 downstream of the TRT 34. Since the gas arriving at the network 36 still has a high content of combustible components, its energy content may be used to create heat by burning.

[0044] The turbine 8 is mechanically coupled to a compressor 9 by a transmission unit 10. The transmission unit 10 may simply be a common shaft which connects the compressor 9 to the turbine 8; accordingly a conventional turbocharger may be used. However, the transmission unit 10 may be more complex, e.g. it may comprise a gear for creating different rotation speeds for the turbine 8 and the compressor 9 etc.

[0045] The compressor 9 is fed with clean gas by a fifth pipe 15, which originates from clean gas piping 32. While the use of clean gas in the compressor is preferred for maintenance reasons, the use of top gas at a lower purity/cleanliness level is also possible, as will be explained further below. The gas is compressed and exits the compressor 9 via a sixth pipe 16, which ends at the nozzle 6. By way of this configuration, the energy required for driving the compressor 9 is exclusively obtained from the pressure of the gas fed the turbine 8, which pressure results from the energy of the top gas in the blast furnace 2. Therefore, the gas recirculation arrangement 30 works without external energy or external gas supply.

[0046] It remains to be noted that in a BF plant with TRT, the top gas pressure is mainly regulated via the TRT device. By picking up the top gas further upstream in the cleaning device, one can benefit from top gas at a higher pressure, however only partially cleaned. For example, mixed-line 15.1 indicates alternative piping possibilities for feeding top gas (partially cleaned) to compressor 9. The piping 15.1 leading to compressor 9 can be connected at its other end either to the outlet 15.2 of the first cleaning stage 7.1 or to the demister 7.3 or its outlet indicated 15.3 and 15.4. Also in some embodiments, the third piping 13 leading to turbine 8 could be connected further upstream in the cleaning device 7, e.g. after the first cleaning stage 7.1 or after the demister 7.3. In such cases using partially/semi cleaned top gas, a small cleaning unit may be arranged in the piping to the turbine or compressor, as e.g. indicated 15.5 in FIG. 1.

[0047] FIG. 2 shows a second embodiment of a blast furnace plant 1a with an alternative gas recirculation arrangement 30a. The components are largely identical to the embodiment shown in FIG. 1 and will insofar not be described again. In this embodiment, there is no TRT causing a pressure drop in the clean gas piping 32. The turbine 8 is therefore driven by semi-cleaned gas carried through a pipe 13.1 branching off from the connection pipe between the first 7.1 and second 7.2 cleaning stages. Reference 13.2 indicates an optional small gas cleaning unit.

[0048] Here again the mixed line 15.1 illustrates alternative piping options for feeding partially cleaned top gas to the compressor, which can be picked up at the desmister 7.3 or its outlet, as indicated 15.3 or 15.4. Reference sign 15.5 indicates an optional small cleaning unit.

[0049] FIG. 3 shows a third embodiment of a blast furnace plant 1b, which is also largely similar to the embodiment shown in FIG. 1. It comprises a gas recirculation arrangement 30b that differs from the one shown in FIG. 1 in that a tenth pipe 40 originates from the compressor 9, which pipe 40 ends in at least one nozzle 42 for injecting clean gas into one or more material hoppers 5. This allows for pressure equalization in the hoppers, which would otherwise be performed by injecting nitrogen gas. It is understood that it would be possible to have the tenth pipe 40 originate from the sixth pipe 16 of FIG. 1 and to inject clean gas into the hopper 5 and into the main casing 4 at the same time.

[0050] It may be noticed that in this embodiment, the compressed clean gas is preferably stored in a buffer hopper 44. If desired, a piping may be connected from the buffer hopper to the valve actuation unit 46 controlling the material discharging and metering from the hoppers 5.

[0051] FIG. 4 shows a fourth embodiment of a blast furnace plant 1c with another slightly different gas recirculation arrangement 30c. The components, which are simplified in this representation, are largely identical to the embodiment shown in FIG. 1 and will insofar not be described again. The difference to the embodiment shown in FIG. 1 is that the third pipe 13 leads through a heat exchanger 24. An eleventh pipe 21 also leads to the heat exchanger 24. This pipe 21 originates from the blast furnace and guides high-temperature top gas to the heat exchanger 24. There, the high-temperature gas heats up the cleaned gas in the third pipe 13, thereby increasing its enthalpy and pressure. The efficiency of the turbine 8 is therefore significantly enhanced.