Metallurgical installation with improved removal of deposits

Abstract

A metallurgical plant comprises a vacuum treatment unit (1) for a molten metal (3) located in a ladle (2) and a vacuum pump (6) connected to the vacuum treatment unit (1) via a base pipeline (7), so that gas (8) can be extracted from a treatment area (5) formed by the vacuum treatment unit (1) via the vacuum pump (6) and the base pipeline (7). A base valve assembly (10) is arranged in the base pipeline (7), by means of which the base pipeline (7) can be shut off. The metallurgical plant further comprises a dust extraction system (11) which is fluidically connected to a connecting section (13) of the base pipeline (7) via an auxiliary pipeline (12). The connecting section (13) is located upstream of the base valve assembly (10) from the vacuum treatment unit (1).An additional valve device (14) is arranged in the auxiliary pipeline (12), by means of which the auxiliary pipeline (12) can be shut off.

Description

Title of the invention

[0001] Metallurgical plant with improved deposit removal field of technology

[0002] The present invention is based on a metallurgical plant, wherein the metallurgical plant comprises a vacuum treatment plant for a metal melt located in a ladle, wherein the metallurgical plant comprises a vacuum pump which is connected to the vacuum treatment plant via a base pipeline, so that gas can be extracted from a treatment area formed by the vacuum treatment plant via the vacuum pump and the base pipeline, wherein a base valve device is arranged in the base pipeline by means of which the base pipeline can be shut off, wherein the metallurgical plant comprises a dust extraction system. State of the art

[0003] Such a metallurgical plant is generally known. Summary of the invention

[0004] In vacuum treatment systems, slag and metal splashes form on the surface of the molten metal during treatment and accumulate on the inside of the system. These deposits—commonly referred to as slag buildup—must be removed periodically. Various methods exist for removing these deposits.

[0005] For example, it is known that some molten metals reach such high temperatures during vacuum treatment that the deposits melt completely or at least partially. These molten metals are known in the field as "unkilled heat" or "unquenchable melt." Because a vacuum is maintained in the treatment area during the melting of the deposits, no gases can escape uncontrollably from the treatment area.

[0006] Furthermore, it is known, for example, in RH systems, to place a collection container in place of the pan during periods when no pan is present under the vacuum treatment system and to remove the deposits using a combined oxygen-burning lance lowered into the treatment area from above. Two different procedures are possible for this.

[0007] One method is used when a longer period is available for removing the deposits. In this case, the lance is operated as a combustion lance. Oxygen and a flammable gas are supplied to the lance and burned at the lance tip. The heat generated in this way gradually melts the deposits, causing them to exit the vacuum treatment unit at the bottom and drip or fall into the collection container. This method produces only a relatively small amount of dust-laden gas.

[0008] The alternative procedure is used when only a shorter time is available for removing the deposits. In this case, the lance is operated as a pure oxygen lance. However, since the vacuum treatment system is still very hot due to the immediately preceding vacuum treatment of molten metal, strongly exothermic oxidation reactions occur between the injected oxygen and the metal and slag deposits. This causes the deposits to melt and escape from the bottom of the vacuum treatment system, dripping or falling into the collection container. A disadvantage of this procedure is that it produces significant quantities of dust-laden gases. If no further measures are taken, these gases escape from the bottom of the vacuum treatment system and accumulate in the surrounding area, thus polluting the environment.

[0009] To avoid such deposits in the vicinity of the vacuum treatment system and also other environmental pollution, it is possible to operate the vacuum pump at reduced power during the period in which the deposits on the inside of the vacuum treatment system are removed, thus extracting the resulting dust-laden gases.

[0010] Vacuum pumps are known that can handle gases, including those containing dust. These are so-called steam jet pumps. In this type of vacuum pump, the gases are cleaned of dust within the steam jet pump, and the purified gases are discharged via an exhaust pipe. However, steam jet pumps are disadvantageous, particularly from an energy perspective. With mechanical vacuum pumps, such as rotary lobe pumps or screw pumps, extracting the dust-laden gases produced during the removal of deposits can damage the vacuum pump or an upstream dust filter unit. In this case, the escape of dust-laden gases from the vacuum treatment system must be accepted under current technology. Only a general extraction of air from the workshop is possible.

[0011] The object of the present invention is to further develop a metallurgical plant of the type mentioned above in such a way that it is possible to extract the dust-laden gas from the treatment area regardless of the type of vacuum pump used.

[0012] The problem is solved by a metallurgical plant with the features of claim 1. Advantageous embodiments of the metallurgical plant are the subject of dependent claims 2 to 9.

[0013] According to the invention, a metallurgical plant of the type mentioned above is designed by: that the dust removal system is fluidically connected to a connecting section of the base pipeline via an additional pipeline, that the connecting section is arranged upstream of the base valve device as seen from the vacuum treatment system, and that an additional valve device is arranged in the additional pipeline by means of which the additional pipeline can be shut off.

[0014] By connecting the dust extraction system to the treatment area via the auxiliary pipeline, it is possible to extract the dust-laden gases generated during deposit removal and feed them into the dust extraction system without having to use the vacuum pump for extraction. However, by connecting the auxiliary pipeline to the connecting section, it is possible to continue using the main pipeline as much as possible. In particular, the location of the connecting section can be chosen as needed, provided it is positioned upstream of the main valve assembly from the perspective of the vacuum treatment system.

[0015] The vacuum treatment system can be configured according to requirements. In many cases, the vacuum treatment system is configured as an RH system (RH = Ruhrstahl-Heraeus) or as a VD system (VD = vacuum degassing).

[0016] As a rule, the vacuum treatment system includes a combined oxygen-burning lance that can be inserted into the system from above. This combined oxygen-burning lance allows for the easy removal of deposits, particularly on the inside of the vacuum treatment system.

[0017] Preferably, the vacuum pump is designed as a dry pump. This design is particularly advantageous from an energy efficiency point of view. For example, the vacuum pump can be designed as a rotary lobe pump or as a screw pump.

[0018] As a rule, the metallurgical plant also includes a gas conveying system, by means of which, with the auxiliary valve open, a gas flow can be conveyed from the treatment area via the main pipeline and the auxiliary pipeline to the dust collection system and through the dust collection system. The gas conveying system can be arranged upstream or downstream of the dust collection system, as required, from the perspective of the vacuum treatment plant. An arrangement downstream of the dust collection system is preferred.

[0019] Preferably, a gas cooler is arranged in the base pipeline. This allows the gas conveyed in the base pipeline to be cooled. This reduces the load on the pump as well as on other equipment. Preferably, the gas cooler is also located upstream of the connection section when viewed from the vacuum treatment system. In this case, the gas is cooled not only during normal operation (i.e., when the vacuum pump is running) but also during cleaning operation (i.e., when deposits are being removed).

[0020] Preferably, other components of the metallurgical plant, in which dust-laden gases are generated, are connected to the dust collection system. In this case, the dust collection system is used more efficiently. These other components of the metallurgical plant can include, for example, an electric arc furnace and / or a converter and / or a ladle furnace and / or a ladle station. Brief description of the drawings

[0021] The properties, features, and advantages of this invention described above, as well as the manner in which they are achieved, will become clearer and more readily understandable in connection with the following description of an exemplary embodiment, which is explained in more detail in conjunction with the drawings. These drawings show: FIG 1 a metallurgical plant in normal operation of a vacuum treatment plant and FIG 2 the metallurgical plant of FIG 1 in a special operation of the vacuum treatment plant. Description of the embodiments

[0022] According to FIG 1 A metallurgical plant includes a vacuum treatment system 1 for a molten metal 3 located in a ladle 2. For example, the vacuum treatment system 1 can be configured as shown in FIG 1 The vacuum treatment system can be configured as a vacuum treatment unit (VTU). In this case, the vacuum treatment unit has two nozzles 4 on its underside, which are immersed in the molten metal 3 located in the ladle 2. Alternatively – not shown – the vacuum treatment unit 1 can be configured as a vacuum treatment unit (VTU). In any case, the vacuum treatment unit 1 forms a treatment area 5 for the molten metal 3.

[0023] The metallurgical plant further includes a vacuum pump 6. The vacuum pump 6 is connected to the vacuum treatment plant 1 via a pipeline 7. This allows gas 8 to be extracted from the treatment area 5 via the vacuum pump 6 and the pipeline 7. The vacuum pump 6 is preferably designed as a dry pump. The gas 8 can, for example, be a gas such as that described in FIG 1 The gas 8, indicated by arrow 9, is blown into the molten metal 3. The gas 8 can be, for example, nitrogen or argon. Additional gases can also be produced during the vacuum treatment of the molten metal 3. A valve assembly 10 is arranged in the pipeline 7. The pipeline 7 can be shut off by means of the valve assembly 10. The pipeline 7 is subsequently referred to as the base pipeline 7 to distinguish it linguistically from other pipelines. Similarly, the valve assembly 10 is also subsequently referred to as the base valve assembly 10 to distinguish it linguistically from other valve assemblies.

[0024] The metallurgical plant also includes a dust extraction system 11. The dust extraction system 11 is fluidically connected via a pipeline 12 to a connecting section 13 of the main pipeline 7. The connecting section 13 is located upstream of the main valve assembly 10, as viewed from the vacuum treatment plant 1. A valve assembly 14 is located in the pipeline 12. The pipeline 12 can be shut off by means of the valve assembly 14. The pipeline 12 is subsequently referred to as the auxiliary pipeline 12 to distinguish it linguistically from other pipelines – in particular the main pipeline 7. Similarly, the valve assembly 14 is also subsequently referred to as the auxiliary valve assembly 14 to distinguish it linguistically from other valve assemblies – in particular the main valve assembly 10.

[0025] In many cases, a gas cooler 15 is arranged in the base pipeline 7 to cool the gas 8. If present, the gas cooler 15 is preferably located upstream of the connection section 13, as viewed from the vacuum treatment system 1.

[0026] In normal operation of the vacuum treatment system 1, the base valve assembly 10 is open and the auxiliary valve assembly 14 is closed. The gas 8 therefore flows as in FIG 1 As indicated by arrows 16, from the vacuum treatment system 1 through the base pipeline 7 via the base valve assembly 10 through the vacuum pump 6. From there it is usually released into the open air.

[0027] During normal operation, deposits 17 form on the inner walls of the vacuum treatment system 1. These deposits 17 must be removed from time to time. The removal of the deposits 17 is generally carried out by following the procedure described below. FIG 2 A combined oxygen-burning lance 18 is inserted into the treatment area 5 from above, and the deposits 17 are melted. If the removal of the deposits 17 is carried out in this manner, the vacuum treatment system 1 must, of course, include the combined oxygen-burning lance 18. Furthermore, during the removal of the deposits 10, the vacuum treatment system 1 is not operating in its normal mode, in which the treatment of a molten metal 3 can take place, but rather in a special mode. For example, as shown in the illustration in FIG 2 In the case of an RH system, a collection container 19 is arranged under the vacuum treatment system 1 instead of a pan 2, into which the molten deposits can fall.

[0028] If the removal of the deposits 17 takes place shortly after the treatment of a metal melt 3, the vacuum treatment system 1 is still very hot. In this case, with an RH system, it is sufficient to blow only oxygen into the treatment area 5 via the lance 18. Particularly in this operating mode, during the removal of the deposits 17, according to FIG 2 Significant amounts of dust-laden gases are present. To prevent the release of these gases into the environment, the base valve 10 is closed and the auxiliary valve 14 is opened. Thus, the dust-laden gases flow as described in FIG 2 As indicated by arrows 20, the gases travel from the vacuum treatment system 1 or treatment area 5 first through the main pipeline 7, then from connection section 13 through the auxiliary pipeline 12, then via the auxiliary valve assembly 14 to the dust collection system 11 and through the dust collection system 11. From there, the previously dust-laden and now cleaned gases are generally released into the open air.

[0029] In a vacuum incineration (VD) system, the normal treatment process for a metal melt 3 is carried out in a similar manner. In this case, the VD system is operating normally. During special operation, large quantities of dust-laden gases can also be generated. In particular, in a VD system, it is possible to wind a wire into the melt after the treatment of a metal melt 3 has been completed, while the vacuum vessel is closed. Normal atmospheric pressure prevails in the treatment area 5 during this period. The resulting dust-laden gases can then be extracted in the same way as described above for a vacuum incineration (RH) system.

[0030] To convey the dust-laden gases, the metallurgical plant includes a gas conveying device 21. The gas conveying device 21 is only effective, with regard to the dust-laden gases in the vacuum treatment plant 1, when the auxiliary valve device 14 is open. The gas conveying device 21 is configured as shown in the FIG 1 and 2 The vacuum treatment system 1 is preferably located downstream of the dust removal system 11. The gas flowing through the gas conveying device 21 is therefore already cleaned and no longer contaminated with dust.

[0031] In individual cases, it is possible that the dust collection system 11 is a separate dust collection system for the vacuum treatment system 1. However, as a rule, further components 22 to 25 of the metallurgical plant, in which dust-laden gases are generated, are connected to the dust collection system 11. These further components 22 to 25 of the metallurgical plant may include, for example, an electric arc furnace 22 and / or a converter 23 and / or a ladle furnace 24 and / or a ladle trimming station 25.

[0032] The present invention offers many advantages. In particular, it enables environmentally friendly removal of deposits without the risk of damaging the vacuum pump 6. Furthermore, the dust extraction system 11 is already present in practice. The additional effort required to convert an existing prior art metallurgical plant to a metallurgical plant according to the invention therefore consists only of installing the additional pipeline 12 and the additional valve assembly 14 and connecting the additional pipeline 12 to the main pipeline 7.

[0033] Although the invention has been further illustrated and described in detail by the preferred embodiments, the invention is not limited by the disclosed examples and other variations can be derived by the person skilled in the art without leaving the scope of protection of the invention. Reference symbol list

[0034] 1 Vacuum treatment system 2 Ladle 3 Melting metal 4 Nozzle 5 Treatment area 6 Vacuum pump 7 Base pipeline 8 Gas 9 Arrow 10 Base valve assembly 11 Dust extraction system 12 Auxiliary pipeline 13 Connection section 14 Auxiliary valve assembly 15 Gas cooler 16 Arrows 17 Deposits 18 Combined oxygen-burning lance 19 Collection container 20 Arrows 21 Gas conveying system 22 Additional component / Arc furnace 23 Additional component / Converter 24 Additional component / Ladle furnace 25 Additional component / Ladle station

Claims

1. Metallurgical plant, - wherein the metallurgical plant comprises a vacuum treatment plant (1) for a metal melt (3) located in a ladle (2), - wherein the metallurgical plant comprises a vacuum pump (6) which is connected to the vacuum treatment plant (1) via a base pipeline (7) so that gas (8) can be extracted from a treatment area (5) formed by the vacuum treatment plant (1) via the vacuum pump (6) and the base pipeline (7), - wherein a base valve device (10) is arranged in the base pipeline (7) by means of which the base pipeline (7) can be shut off, - wherein the metallurgical plant comprises a dust extraction system (11), characterized by - that the dust extraction system (11) is fluidically connected to a connecting section (13) of the main pipeline (7) via an additional pipeline (12), - thatthe connection section (13) is arranged in front of the base valve device (10) as seen from the vacuum treatment system (1) and - that An additional valve device (14) is arranged in the additional pipeline (12), by means of which the additional pipeline (12) can be shut off.

2. Metallurgical plant according to claim 1, characterized by that The vacuum treatment system is designed as an RH system or as a VD system.

3. Metallurgical plant according to claim 1 or 2, characterized by that The vacuum treatment system includes a combined oxygen-burning lance (18) which can be inserted from above into the treatment area (5).

4. Metallurgical plant according to claim 1, 2 or 3, characterized by that the vacuum pump (6) is designed as a dry pump.

5. Metallurgical plant according to one of the above claims, characterized by thatthe metallurgical plant comprises a gas conveying device (21) by means of which, with the auxiliary valve device (14) open, a gas flow can be conveyed from the treatment area (5) via the base pipeline (7) and the auxiliary pipeline (12) to the dust extraction system (11) and through the dust extraction system (11), and that the gas conveying device (21) is arranged downstream of the dust extraction system (L) from the vacuum treatment plant (1).

6. Metallurgical plant according to one of the above claims, characterized by that A gas cooler (15) is arranged in the base pipeline (7).

7. Metallurgical plant according to claim 7, characterized by that The gas cooler (15) is located in front of the connection section (13) as seen from the vacuum treatment system (1).

8. Metallurgical plant according to one of the above claims, characterized by thatThe dust extraction system (11) is connected to further components (22 to 25) of the metallurgical plant in which dust-laden gases are generated.

9. Metallurgical plant according to claim 9, characterized by that the other components (22 to 25) of the metallurgical plant include an electric arc furnace (22) and / or a converter (23) and / or a ladle furnace (24) and / or a ladle station (25).

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