WO2005080611A1

WO2005080611A1 - Suction hood for a liquid metal ladle and suction method

Info

Publication number: WO2005080611A1
Application number: PCT/EP2005/050062
Authority: WO
Inventors: Emile Lonardi; Jeff Mersch; Bernard Gramczewski; Dominique Rocchi
Original assignee: Paul Wurth S.A.
Priority date: 2004-02-24
Filing date: 2005-01-07
Publication date: 2005-09-01
Also published as: EP1568789A1

Abstract

A suction hood (10) for a metallurgical vessel (12), including a lid construction (16) having a size such that it extends over the opening in the metallurgical vessel (12), and provided with a channel (28). Means (26) are provided on the lid construction for drawing gases and/or dust from the metallurgical vessel. A movable lid portion (30) is associated with and adjustable in the channel (28) in the lid construction (16). The movable lid portion (30) includes an opening for a metal treatment device (15) in the metallurgical vessel (12). Means (42) for diverting gases and/or dust are provided in a recovery area between the channel (28) and the movable lid portion (30) for diverting any gases and/or dust that escape through the gap (36) defined by the movable lid portion (30).

Description

SUCTION HOOD FOR LIQUID METAL POCKET AND SUCTION METHOD

Technical area

The present invention generally relates to an extractor hood for a pocket of liquid metal and to a method for extracting gas and dust during the treatment of liquid metal in a pocket.

State of the art

In liquid metal treatment processes, metal, e.g. steel, is commonly treated in a pocket, by means of a bell or a tube immersed in the liquid metal. In this type of process, the liquid metal contained in the bag is subjected to various treatments in a confined area, delimited by the bell plunging into the liquid metal. Below the bell, a bubbling gas is injected into the liquid metal to homogenize it during the treatment. In such processes, it is often desirable to collect the gases and dust from the bag. For this reason, the treatment of the metal in the pocket by means of the bell is generally carried out under an extractor hood. One type of known extractor hood includes a cover structure sized to extend above the pocket opening. Suction means are associated with the cover structure to extract the gases from the metallurgical container out of the cover. The hood includes a movable cover part mounted in a substantially vertical passage arranged in the cover structure, and is vertically adjustable in this passage. The movable cover part has an opening through which the bell passes through the hood cover to reach the metal bath contained in the pocket. This movable cover part is lowered towards the pocket when the bell is immersed in the bath. To ensure easy movement of the movable cover, a clearance is provided between the movable cover portion and the passage of the structure forming the cover. Given the dimensions of such an installation and the severe conditions of use, a relatively large clearance is necessary, typically of the order of several centimeters. Unfortunately, this play cannot be obstructed by a conventional seal, because of the very high temperatures which prevail when the pocket is present under the hood and the large amount of dust which would quickly foul such a seal. This is why, in such extractor hoods, attempts are made to minimize gas and dust leaks at the clearance of the movable cover part by increasing the suction power under the hood.

Subject of the invention

The object of the present invention is to provide an improved extractor hood for a metallurgical container such as a pocket, having a minimum of gas and dust leaks by the play of the movable cover gasket. According to the invention, this objective is achieved by an extractor hood according to claim 1.

General description of the invention In order to solve the problem mentioned above, the extractor hood according to the invention comprises, at the level of an overlap zone between the passage and the movable cover part, means for deflecting the gases and / or dust in order to deflect the gases and / or dust liable to escape by the play of the movable cover part. Thus, in the extractor hood according to the invention, gas and / or dust leaks are considerably reduced, or even eliminated, by creating a deflection of the gases at the same place through which they could escape. This allows not to obstruct the play of the movable cover part, while minimizing gas and dust leaks to the outside. Another advantage of the present invention is that it makes it possible to reduce the suction power required. Indeed, it is no longer necessary to establish a depression as high as in conventional extractor hoods to avoid leaks by the play of the movable cover part. By reducing the vacuum under the hood, the volume of air circulating over the liquid metal in the pocket is reduced, and the risk of nitriding the metal bath is thus reduced. This deflection of gases and dust is preferably done by means of gas and / or dust suction arranged at the level of the overlap zone. Gases and dust entering the space due to the play of the movable cover part are therefore sucked in and thus diverted from their path in this space, and do not escape into the atmosphere. Alternatively, it is possible to deflect the gases and dust coming from the metallurgical container by gas blowing means. By blowing a gas (for example air) at the level of the overlap zone, a gas curtain is created which prevents the rise of gases and dust by the play of the movable cover part. In order to limit the amount of gas or dust which can engage in the clearance of the movable cover, the deflection means are preferably provided in the lower part of the passage in the structure forming a cover. In a preferred embodiment, the passage in the cover structure is defined by substantially vertical walls extending over a predetermined height. The movable cover part comprises walls cooperating with the walls of the passage to define the clearance. This variant is designed so that whatever the position of the movable cover part in the passage, there is an overlap between a lower part of the passage walls and the walls of the movable part. The means for blowing or suction then comprise a series of orifices opening into this lower part of the walls of said passage to ensure the deflection of gases and / or dust by suction or blowing. It will be noted that, due to the overlap, the peripheral walls of the movable cover part are always find opposite holes in the lower part of the passage. This allows greater efficiency of the deflection means which therefore act in the space of the game. In the case of suction, the orifices are connected to suction means. Preferably, the orifices are connected to the means associated with the structure forming a cover for sucking up the gases and / or dust. In the case of supply air, the channels are connected to a compressed gas supply, e.g. compressed air. Preferably, the cover-forming structure extends over a surface corresponding at least to that of the opening of the metallurgical container. The evacuation of gases and dust out of the cover structure is preferably done by at least one suction pipe opening into the collection volume defined by the cover structure and connected to suction means. The present extractor hood can be used in a variety of bagged liquid metal processing applications, and in particular with a liquid metal processing device comprising a fixed or rotating bell, or a tube. The opening in the movable cover part is therefore advantageously provided for the passage of such a device. According to another aspect of the invention, a method of suctioning gas and / or dust is proposed during the treatment of liquid metal in a metallurgical container such as a ladle, in which the metallurgical container is placed under an extractor hood. The extractor hood comprises a structure forming a cover dimensioned so as to extend above the opening of the metallurgical container and provided with a passage. A movable cover part is associated with the passage and is adjustable therein, a clearance being provided between the movable cover part and the passage of the cover structure. The movable cover portion further has an opening for a metal processing device in the metallurgical container. According to the present method, the gases and / or dust from the metallurgical container are sucked out of the structure forming a cover. In addition, it will be appreciated that at the level an area of the passage which overlaps with the movable cover part, a deviation of the gases and / or dust from the metallurgical container is created. This deflection of gases and / or dust, which is preferably carried out by suction or blowing, considerably reduces, or even eliminates, leaks by the play of the movable cover part.

Description of the drawings

Other features and characteristics of the invention will emerge from the detailed description of some advantageous embodiments presented below, by way of illustration, with reference to the accompanying drawings. These show:

FIG.1: a schematic sectional view of a preferred embodiment of an extractor hood according to the invention, under which is installed a pocket of liquid metal to be treated;

FIG.2: an exploded perspective view of a preferred embodiment of a cover structure and of a movable cover part; and

FIG.3: a perspective view from below of the structure forming the cover of Fig.2.

Detailed description of some preferred embodiments

In Fig.1 is shown schematically a preferred embodiment of an extractor hood 10 according to the invention. A pocket 12 comprising a refractory lining is filled with liquid steel 14 and is placed under the extractor hood 10 to treat the liquid metal 14 by means of a refractory bell

15 and suck up the gases, fumes and dust which emanate from the bag 12. The extractor hood 10 comprises a structure forming a cover 16, which is for example fixed to a support structure (not shown). The cover structure 16 is designed so as to extend above the opening of the pocket 12. In the present variant, the cover 16 extends over the entire opening of the pocket 12 up to beyond the edges of the latter, and is kept at a certain distance above the upper edges of the pocket 12 leaving an annular space 18. As illustrated in FIG. 1, the cover 16 comprises a substantially horizontal wall 20 bordered by a vertical peripheral wall 22, thus defining a collection volume 24. Two pipes 26 associated with the cover 16, opening under that -this by the peripheral walls 22 and connected to suction means (not shown), make it possible to evacuate the gases and dust collected under the cover 12, as illustrated by the arrows. The cover 16 includes a passage 28 with which is associated a movable cover portion 30 which is vertically adjustable in this passage 28. The passage 28 is defined by substantially vertical walls 29, which extend over a predetermined height. The movable cover part 30 is provided with an opening 32 through which the supply duct 34 of the bell 15 passes, through which the combustible materials, alloying elements or other materials for the treatment of liquid steel pass. 14. Depending on the filling level of the pocket 12, the bell 15 must be more or less lowered in the pocket 12 under the extractor hood 10, so that the lower edge of the bell 15 plunges into the liquid steel 14 (as illustrated in Fig. 1). In the bell 15 positioning maneuver, the position of the movable cover part 30 is also adjusted, which typically follows the vertical movement of the bell 15. To guarantee easy vertical movement of the movable cover part 30 in the passage 28, a relatively large clearance 36 is provided, of the order of a few centimeters, at the periphery of the movable cover part 30. It will be appreciated that in order to avoid gas or smoke leaks through the clearance

36 of the movable cover part 30, the extractor hood 10 comprises a gas deflection means, at a level of overlap between the movable cover part 30 and the passage 28, which here corresponds to the lower part of the passage 28. This deflection of the gases is preferably carried out by suction at the level of the overlap zone. In the present variant, the movable cover 30 comprises a wall substantially horizontal 38 whose surface corresponds to that of the section of the passage 28, and which is bordered by vertical peripheral walls 40. In Fig.1, the movable cover portion 30 is shown in its lower position; in the high position, the horizontal walls 20, respectively 38, of the mobile 30 and fixed 16 parts are at the same level. It will therefore be understood that, whatever the position of the movable part 30 in the passage 28, there is an overlap between the lower part of the passage 28 and a portion of the peripheral wall of the movable cover 30. Preferably, the suction is carried out by a series of orifices 42 provided in the lower part of the passage 28 where there is overlap. These orifices 42 open into the passage 28 and are connected by a suction pipe 44 which can be in communication with the same suction means as those used for suction by the pipes 26. Thus, the gases, fumes or dust which could engage in the clearance 36 of the movable cover part 30 are deflected and discharged through the orifices 42, thus preventing them from escaping into the atmosphere. Figs. 2 and 3 illustrate in detail a preferred embodiment of a cover structure 100. The cover structure 100 comprises a horizontal wall 102 and vertical peripheral walls 104. In these peripheral walls 104 of the cover 100 are provided openings 106 for sucking gases and dust out of the cover 100. These openings are connected by auxiliary pipes 105, themselves connected to a main suction pipe 107. The structure forming the cover 100 comprises a passage 108 defined by vertical walls 110 , with which the movable cover part 112 is associated, illustrated diagrammatically outside the passage 108 in FIG. 2. The movable cover portion 112 comprises a horizontal wall 114 provided with vertical peripheral walls 116 which cooperate with the walls 1 10 of the passage 108 to define a set of movable cover 112. The movable part is vertically adjustable in the passage 108 between a high position , in which the horizontal walls 102 and 114 of the fixed and mobile parts 100 and 112 are at same level, and a low position, in which the movable cover part 112 is lowered in the fixed part 100, in the collection space defined by the horizontal wall 102 and the walls 104. It will be noted that in operation, there are always an overlap between the lower part of the passage 108 and the walls of the movable cover part 112, whatever the position of the latter relative to the passage 108. In order to prevent the escape of gas and / or fumes and / or dust, the lower part of the passage 108 is provided with a series of orifices 118 which open into the passage 108. Outside the passage, all of its openings are connected by a pipe 120, which is itself connected to the pipe main suction 107. This series of orifices therefore allows a deflection of the gases by suction at the lower part of the passage 108, an area where there is overlap with the movable cover part 112, whatever the position of this head last.

LIST OF REFERENCE SIGNS

10 extractor hood

12 pocket

14 liquid steel

15 refractory bell

16 cover

18 annular space

20 horizontal cover wall

22 peripheral wall of the cover

24 collection volumes

26 pipes

28 passage

29 vertical walls of the passage

30 movable cover 32 opening

34 supply line clearance horizontal wall of the movable cover peripheral walls of the movable cover orifices suction pipe structure forming a cover horizontal wall peripheral walls openings auxiliary pipes main suction pipe passage vertical walls movable cover horizontal wall vertical peripheral walls vertical orifices duct

Claims

claims

1. Extractor hood for a metallurgical container comprising: a cover structure dimensioned so as to extend above the opening of the metallurgical container and provided with a passage; means associated with the cover structure for sucking up the gases and / or dust from the metallurgical container; a movable cover part associated with said passage of the cover structure and adjustable therein, a clearance being provided between the mobile cover part and the passage of the cover structure, the movable cover part having an opening for a device for treating the metal in the metallurgical container; and means for deflecting the gases and / or dust at a covering zone between the passage and the movable cover part, in order to deflect the gases and / or dust liable to escape by the play of the ^{i *} movable cover part. ^

2. Extractor hood according to claim 1, wherein the means for deflecting the gases and / or dust comprise means for blowing gas or for sucking gas and / or dust.

3. Extractor hood according to claim 1 or 2, wherein said passage in the cover structure is defined by substantially vertical walls extending over a predetermined height; the movable cover portion comprises walls cooperating with the walls of the passage to define the clearance; and in which, whatever the position of the movable cover part in the passage, there is an overlap between a lower part of the walls of the passage and the walls of the movable part; and the means allowing blowing or suction comprise a series of orifices arranged in this lower part of the walls of said passage.

4. Extractor hood according to claim 3, wherein said series of orifices is connected to the means associated with the cover-forming structure for sucking up the gases and / or dust.

5. Extractor hood according to claim 3, wherein said series of orifices is connected to a supply of compressed gas.

6. Extractor hood according to any one of the preceding claims, in which the cover-forming structure extends over a surface corresponding at least to that of the opening of the metallurgical container.

7. Extractor hood according to any one of the preceding claims, in which the cover-forming structure defines a gas and / or dust collection volume above the metallurgical container, into which opens at least one suction line connected to means of aspiration.

8. Extractor hood according to any one of the preceding claims, in which the opening in the movable cover part is provided for the passage of a liquid metal treatment device comprising a fixed or rotary bell, or a tube.

9. A method of sucking gas and / or dust during the treatment of liquid metal in a metallurgical container such as a ladle, in which the metallurgical container is placed under an extractor hood comprising: a cover structure dimensioned so to extend above the opening of the metallurgical container and provided with a passage; and a movable cover portion associated with and adjustable in said passage, a clearance being provided between the movable cover portion and the passage of the cover structure, the movable cover portion having an opening for a metal processing device in the metallurgical vessel; in which the gases and / or dust from the metallurgical container are sucked out of the cover structure; and at a zone of the passage which overlaps with the movable cover part, a deviation of the gases and / or dust from the metallurgical container is created.

10. The method of claim 9, wherein the deflection of gases and / or dust at the overlap zone is done by suction or blowing.

11. The method of claim 10, wherein the suction or blowing is done by a series of orifices arranged in the wall of the passage at the overlap zone.

12. The method of claim 9, 10 or 11, wherein the treatment of the liquid metal in the metallurgical container is done by a bath treatment device comprising a fixed or rotating bell, or a tube immersed in the liquid metal through the opening in the movable cover part.