EP1325161A1

EP1325161A1 - Blowing lance nozzle

Info

Publication number: EP1325161A1
Application number: EP01969081A
Authority: EP
Inventors: Jacques Thomas
Original assignee: Individual
Current assignee: Individual
Priority date: 2000-09-15
Filing date: 2001-09-11
Publication date: 2003-07-09
Anticipated expiration: 2021-09-11
Also published as: US6849228B2; EP1325161B1; US20030178186A1; DE60110446D1; KR20030046454A; CN1457368A; AU2001289429A1; WO2002022892A1; BE1013686A3; CN1201024C; JP2004524437A; ATE294245T1; BR0113900A

Abstract

A blowing lance nozzle (1) having: a central tube (2) supplying stirring gas, an inner tube (5) for intake of a cooling liquid, an outer tube (10) for evacuation of the cooling liquid, a heat exchanging space (13), and an outlet conduit (15) for the stirring gas exiting from each orifice (4) in the front wall (3). The front wall (12) has a central recess (16) which is oriented towards the central orifice (8) and has a recess height/recess base ratio not less than 0.35. The heat exchanging space has a section for allowing passage of the cooling liquid through the space at a speed which is substantially constant, so as to obtain a cooling liquid passage speed, through the space, which is more or less constant.

Description

"Blowing lance nose".

The present invention relates to a blowing lance nose, intended for the mixing of baths, comprising a central tube for supplying mixing gas, closed at one end facing the bath by a first front wall provided with at least one opening, an internal tube forming with the central tube a first annular cavity for the passage of a coolant and closed at one end facing the bath by a second front wall having a central opening and an opening for passage provided in said first front wall, an external tube forming with the internal tube a second annular cavity for the passage of coolant and closed at one end facing the bath by a third front wall having an outlet orifice by opening provided in said first wall front, a heat exchange space which is located between, on the one hand, said second fron wall tale and said third front wall and, on the other hand, said central opening and said second annular cavity, and in which the coolant flows, and an outlet conduit for the stirring gas leaving each opening in said first front wall and going to a corresponding aforesaid outlet orifice passing through a said aforesaid orifice in a sealed manner to the coolant. This type of blowing lance nose has been known for a long time. By way of example, mention may be made of the blowing lance noses described in EP-A-0 340207, WO-97/000973, and US-A-4,432,534. To brew with oxygen jets baths of steel converters, the lance noses work at a distance from the bath of 1 to 2.5 m, while the bath has a temperature of the order of 1400 ° C. Under these operating conditions, the temperature of the nose can rapidly increase to 400 ° C., and must remain in this environment for approximately 20 minutes. Then, when the lance is removed, the nose quickly returns to room temperature, that is to say at 20 ° C.

It is therefore planned to build the front walls of the lance noses in a very good conductive material of heat, for example copper, to allow a heat exchange as efficient as possible with a coolant which flows at high speed the along this wall, inside the nose. However, the already known lance noses have the drawback of offering cooling which is not uniform over the entire surface of this wall exposed to variations in extremely critical thermal conditions. This results in mechanical tensions between the different zones of the wall.

In addition, cavitation phenomena are frequently observed in the coolant as a result of local depressions therein. This cavitation has the effect of causing poor cooling between the coolant and the wall to be cooled, the heat exchanges being much less good between a gas phase and a solid phase than between a liquid phase and a solid phase.

Many attempts have been made to soften the flow of coolant inside the lance nose, for example by making slight depressions in the front wall external of the nose (see for example US-A-4,432,534 and WO 96/23082). However, these arrangements have the disadvantage of not providing a sufficient heat exchange surface, in particular in the central region of the nose. It is also provided, in the central area of the lance nose described in EP-A-0340207, a significant depression on which are directed secondary jets of coolant, which has the effect of causing a swirl in the liquid flow. The object of the present invention is to provide a lance nose which is capable of undergoing the significant stresses to which it is subjected, during a significant number of successive uses, while providing a lance nose which is simple to manufacture and of defensible cost.

This problem is solved, according to the invention, by a blowing lance nose, as described at the start, in which said third front wall has a central depression which is directed towards said central opening and which has a relationship between depression height and vacuum base equal to or greater than 0.35, and the aforementioned heat exchange space has a section for the passage of the coolant which is substantially constant, so as to obtain a speed of passage of the coolant through this space which is approximately constant, in the presence of said depression.

By such a depression, the heat exchange surface greatly increases with respect to the same surface of the heat front coming from the bath, and this without causing either swirling or cavitation in the liquid. Advantageously, said central depression has a ratio between height and base equal to or greater than 0.4, in particular 0.5, and preferably even 0.8. By the expression "section for the passage of coolant", it is meant that the intended sections are taken perpendicular to the direction of flow of the coolant in the heat exchange space. In this way, at constant flow, the flow / section ratio remains constant and therefore the speed of passage of the liquid also remains constant. It can thus be ensured that at a given speed of passage, and at the critical temperature of the front wall to be cooled, no cavitation phenomenon is likely to occur in the coolant, which in general is of the water. Advantageously, for the front wall temperatures indicated above, a speed of passage of the flow liquid will be provided between 8 and 12 m / sec.

By substantially constant section, it should be understood, according to the invention, that the area of this section cannot vary within limits greater than 10%.

According to one embodiment of the invention, the lance nose comprises several said passage conduits arranged around a central axis and in that said central depression extends from said outlet orifices of these conduits. The base of the depression is thus advantageously maximum and allows an improved efficiency of the heat exchange in the depression. In an improved manner, the third front wall has an external diameter and the base of said depression is a circle having a diameter equal to at least 0.25 x said external diameter, preferably to at least 0.33 x this external diameter . The central depression is thus according to the invention in no way a small central recess arranged in the wall of the nose to reinforce the rigidity of the latter. According to an advantageous embodiment of the invention, said third front wall has a central depression in the shape of a cone.

According to an improved embodiment of the invention, said second front wall has, around the central opening, a central deformation in the form of a truncated cone, which is directed towards said first front wall. Preferably, said cone and said truncated cone have a common axis and the central depression in the form of a cone forms with this axis an angle greater than the angle formed between this axis and the central deformation in the form of a truncated cone. In this way, even in the heat exchange space located between the central depression of the third front wall and the central deformation of the second front wall, the section can remain constant and the speed of passage of the flow liquid remains there. also equivalent to that obtained along the entire third front wall.

According to a particular embodiment of the invention, the central depression is covered at least partially with a protective screen made of a material with high thermal resistance. It can be a disc-shaped plate which is carried by the central depression or pressed against it and which therefore does not require any welding for its fixing. The heat exchange between the coolant and the third front wall remains unchanged, while a large part of the area of the third front wall is protected from excessive overheating. Other embodiments of the lance nose according to the invention are indicated in the appended claims.

Other details and particularities of the invention will emerge from the description given below, without implied limitation, of embodiments of the invention, and with reference to the attached drawings. Figure 1 shows an axial sectional view of a blowing lance nose according to the invention.

Figure 2 shows an axial sectional view of an alternative embodiment. FIG. 3 shows a detail of a lance nose according to the invention, to illustrate the method of measuring the parameters necessary for the invention.

In the various drawings, identical or analogous elements are designated by the same references. In Figure 1, there is shown a nose 1 of blowing lance. This nose includes a central tube 2 for supplying stirring gas. This central tube 2 is closed by a front wall 3 which, in the example illustrated, is provided with several openings 4.

An internal tube 5 is arranged coaxially around the central tube 2 and these tubes form between them an annular cavity 6 which, in the example illustrated, is used for the supply of cooling water in the direction of the arrow F ^ Ce inner tube 5 is closed by a front wall 7 which is called a separator. This front wall 7 is provided with a central opening 8 and an orifice 9 in alignment with each opening 4 in the central tube 2.

An external tube 10 is arranged coaxially around the central tube 2. This external tube is generally made of steel and it forms with the internal tube 5 an annular cavity 11 which, in the example illustrated, is used for the outlet of water from cooling in the direction of arrow F ₂ . This external tube 10 is closed by a front wall 12 which faces the brewing bath and which is therefore subjected to critical thermal stresses, as explained above. Advantageously, this front wall is made of a material which is a good conductor of heat, for example copper, to allow a heat exchange as efficient as possible between the front wall 12 heated and the cooling water passing through the heat exchange space 13 which is located between the front wall 7 of the inner tube 5 and the front wall 12 of the outer tube 10. In the illustrated embodiment, the cooling water coming from the cavity 6 passes through the central opening 8 in the heat exchange zone 13. There it flows in the direction of the arrow F ₃ towards the outside, that is to say towards the cavity 11.

The front wall 12 is also provided with an outlet orifice 14 in alignment with each opening 4 provided in the front wall 3 and with each through orifice 9 provided in the front wall 7. In each of these aligned orifices and openings is arranged an outlet conduit 15 for the ejection of stirring gas outside the lance nose. These conduits are advantageously made of an erosion-resistant material, for example bronze, and are directed obliquely to the axis 19 of the lance nose. As is apparent from the illustrated embodiment, the outer front wall 12 is, according to the invention, provided in its center with a depression 16 in the form of a cone, which is directed towards the central opening. Preferably, this depression is sufficiently pronounced to present a ratio between the height of the internal wall of the cone (h) and the base diameter (B) equal to or greater than 0.35. In the illustrated case this ratio is equal to approximately 0.5. In this way, the heat exchange zone 13 is greatly increased for the same heat front undergone by the lance nose, hence an increased efficiency of the cooling of the front wall 12. It is entirely advantageous, as shown , that this depression 16 extends from the outlet conduits 15 and therefore forms a cone whose base is maximum. In the example illustrated, the ratio between the base B of the depression and the external diameter D of the front wall 12 is approximately 0.33. In addition, by the deep depression, the central area of the front wall outer 12, which is the most stressed thermally, is separated as far as possible from the surface of the bath.

FIG. 3 illustrates how the parameters h and B of the lance nose according to the invention must be measured. The height h is calculated between, on the one hand, the lower tangent plane 30 of the lance nose perpendicular to the axis 19 and the parallel plane 31 tangent to the top of the depression. If an element foreign to the depression is provided at the top thereof, such as for example the tie 20 in FIG. 2, the plane 31 remains in the position it would have if this foreign element did not exist. The summit of the depression must then be considered as a virtual point to be taken into account in the measurement.

The base B is located in the lower tangent plane 30. It is circumscribed by the line 32 resulting from the crossing between this plane 30 and the extension 33 of the internal faces 34 of the depression. Rounding is therefore not taken into account.

As can be seen in Figure 1, the outer diameter of the front wall 12 is taken where its value is maximum.

The front wall 7, serving as a separator between the water supply and the water outlet, also has a central deformation 17 directed towards the front wall 3. This deformation 17 has the shape of a truncated cone open towards the high through the central opening 8.

This truncated cone 17 is coaxial with the cone formed by the depression 16, their common axis being the axis 19 of the lance nose. The cone of the depression 16 forms with the axis 19 an angle greater than the angle formed between this axis and the imaginary extension of the truncated cone 17 to this axis.

As a result, the truncated cone 17 is further away from the cone

16 at its top than at its base. However, at its top, the truncated cone is narrower. So the section of the heat exchange space between the front walls 7 and 12, which is measured in a plane perpendicular to the direction of flow of the coolant, remains constant even in the presence of the central depression 16 provided in the embodiment illustrated in FIG. 1. Furthermore, at the outlet conduits 15, the coolant can only pass through the interstices situated circumferentially between these conduits in the heat exchange space 13. Consequently, to maintain a constant passage section for the liquid at this location cooling and therefore a constant passage speed at a given flow rate, an inward bulge 18 in the front wall 7 serving as a separator is provided in each of the aforementioned interstices.

The lance nose according to the invention is therefore arranged so as to provide over the entire extent of the heat exchange zone 13 a constant passage section for the coolant. At a determined flow rate of the water supply, a ratio is obtained between this flow rate (d) and the section (S) which remains constant during the operation of the lance, this ratio corresponding to a speed of passage of the flow liquid expressed in m / sec. Advantageously, the flow rate and the section will be determined to obtain an approximately constant speed of passage of between 8 and 12 m / sec. The cavitation phenomenon can thus be avoided as much as possible, which greatly improves the efficiency of the heat exchange obtained in the nose. In the embodiment illustrated in Figure 2, there is shown a lance nose which differs from that shown in Figure 1 in that the depression 16 is more pronounced. The top of the depression 16 projects through the opening 8 and therefore even opens into the space between the front walls 3 and 7, which makes it possible to obtain a ratio between h and B equal to or greater than 0.8. For better ensuring the mechanical resistance of the depression 16, a retaining element can be provided, for example a tie rod 20, between the top of the depression and a nut arranged on or in the front wall 3 of the central tube 2. Furthermore, the depression central 16 is, in this embodiment, completely covered by a thermally resistant plate 21. In this way, while allowing an unchanged heat exchange between the cooling water and the cone formed by the depression 16, the central part of the lance nose is thermally insulated from the heat of the bath, which reinforces the efficiency of the heat exchange and allows a longer life of the lance nose.

In the embodiment illustrated in FIG. 2, the plate 21 is composite, that is to say that it has an outer layer of a refractory material, for example ceramic, or of refractory steel and an inner layer in a thermally insulating material, such as for example fibrous alumina.

In the example illustrated, this plate is simply clamped between the head 22 of a threaded rod 23 passing through the plate 21 and screwed into a thread provided in the head of the tie rod 20. Other methods of fixing this plate could of course be planned.

Comparative tests were carried out under the same conditions in baths of a steelworks.

The tests were carried out with conventional noses from 3 competing firms (tests I to III in the table below), noses manufactured by the applicant with a slight central depression whose h / B ratio = 0.15 and the ratio D / B = 0.15 (test IV) and noses according to the invention, the h / B ratio = 0.44 and the D / B ratio = 0.30 (test V). Board

The lifespan of a nose is calculated on the number of flows that could have been brewed before having to discard that nose. As can be seen from this table, the improvement in the average lifespan of the noses according to the invention is remarkable and completely unexpected.

It should be understood that the present invention is in no way limited to the embodiments described above and that many modifications can be made thereto without departing from the scope of the appended claims.

Claims

1. Nose (1) of blowing lance, intended for the mixing of baths, comprising: a central tube (2) for supplying mixing gas, closed at one end facing the bath by a first front wall (3) provided at least one opening (4), an internal tube (5) forming with the central tube a first annular cavity (6) for the passage of a coolant and closed at one end facing the bath by a second wall front (7) having a central opening (8) and a passage orifice (9) by opening (4) provided in said first front wall (3), an external tube (10) forming with the internal tube (5) a second annular cavity (11) for the passage of the coolant and closed at one end facing the bath by a third front wall (12) having an outlet orifice (14) by opening (4) provided in said first front wall (3 ), a heat exchange space (13) which is located e on the one hand, said second front wall (7) and said third front wall (12) and, on the other hand, said central opening (8) and said second annular cavity (11), and into which flows the coolant, and an outlet duct (15) for the stirring gas leaving each opening (4) in said first front wall (3) and going to a corresponding outlet outlet (14) above mentioned passing through an aforementioned passage orifice (9) corresponding in a sealed manner to the coolant, characterized in that said third front wall (12) has a central depression (16) which is directed towards said central opening (8) and which has a relationship between depression height and base vacuum equal to or greater than 0.35, and in that the aforementioned heat exchange space (13) has a section for the passage of the coolant which is substantially constant, so as to obtain a speed of passage of the coolant cooling through this space which is approximately constant, in the presence of said depression.

2. Lance nose according to claim 1, characterized in that it comprises several passage conduits (15) said above arranged around a central axis (19) and in that said central depression (16) extends from said outlet ports (14) for these conduits.

3. Lance nose according to claim 2, characterized in that the third front wall has an external diameter and in that the base of said depression is a circle having a diameter equal to at least 0.25 x said external diameter.

4. lance nose according to one of claims 1 to 3, characterized in that said second front wall (7) has, around the central opening (8), a central deformation (17) in the form of a truncated cone , which is directed towards said first front wall (3).

5. Nose lance according to claim 4, characterized in that the central depression (16) has a cone shape, in that said cone and said truncated cone have a common axis (19) and in that the central depression (16) in the form of a cone forms with this axis an angle greater than the angle formed between this axis and the central deformation (17) in the form of a truncated cone.

6. lance nose according to any one of claims 1 to 5, characterized in that the central depression (16) projects through the central opening (8), towards said first front wall (3).

7. Spear nose according to any one of claims 1 to 6, characterized in that it comprises an element of retainer (20) which fixes a top of the central depression (16) to said first front wall (3).

8. Lance nose according to any one of claims 1 to 7, characterized in that the central depression (16) is covered at least partially with a protective screen (21) of a material with high thermal resistance.

9. Lance nose according to claim 8, characterized in that the protective screen (21) is carried on a rod (23) fixed to the top of the central depression (16).

10. Nose lance according to any one of claims 1 to 9, characterized in that it comprises several passage conduits (15) above said circumferentially separated by interstices, and in that said second front wall has at each aforementioned interstice a bulge (18) directed inward.

11. lance nose according to any one of claims 1 to 10, characterized in that it has a ratio between height of depression and base of depression equal to or greater than 0.4, advantageously 0.5, preferably 0.8.

12. Lance nose according to any one of claims 1 to 11, characterized in that the heat exchange space (13) is supplied with water at a predetermined flow rate and in that it

presents a relationship between this flow and said section (-) giving rise to

a flow speed of the flow liquid between 8 and 12 m / sec.