GAS INJECTION SYSTEM, FURNACE PROVIDED WITH SUCH A SYSTEM AND USE THEREOF

Abstract

A gas injection system includes a tubular wall 3 capable of being thermally stressed and having a proximal extremity and a distal extremity 11, at the distal extremity, at least one extremity opening through which at least one gas is projected. A cooling is system located in the tubular wall including axial channels 12 which extend axially towards the distal extremity and in which a cooling fluid is circulated. Connecting channels 13 circumferentially join the axial channels to each other at the distal extremity of the tubular wall. The connecting channels, which circumferentially join the axial channels at the distal extremity of the tubular wall, have a rounded shape in the direction of the distal extremity.

Claims

1. Gas injection system comprising: a tubular wall capable of being thermally stressed and having a proximal extremity and a distal extremity, at the distal extremity, at least one extremity opening through which at least one gas is projected, and a cooling system located in said tubular wall and comprising axial channels which, between a proximal terminal and a distal terminal, extend axially towards said distal extremity of the tubular wall and in which a cooling fluid is circulated, connecting channels circumferentially joining the axial channels to each other at the distal terminal, the connecting channels having a rounded shape in the direction of the distal extremity of the tubular wall, wherein said tubular wall is monobloc, wherein said axial channels pass axially through this the monobloc tubular wall which has, at the distal terminal of the axial channels, a circumferential groove, a closing crown closing the circumferential groove of the monobloc tubular wall, wherein said rounded connecting channels are arranged between said circumferential groove and said closing crown.

2. Gas injection system according to claim 1, comprising a burner injector provided with said monobloc tubular wall in which said cooling system is located.

3. Gas injection system according to claim 1, comprising a sheath provided with said monobloc tubular wall in which said cooling system is located.

4. Gas injection system according to claim 3, wherein said sheath is arranged at one extremity of a burner injector, covering the burner injector at least partially.

5. Gas injection system according to claim 1, wherein the cooling system comprises passage channels which circumferentially join axial channels at a proximal terminal.

6. Gas injection system according to claim 5, wherein passage channels which circumferentially join axial channels have a rounded shape in the opposite direction to the distal extremity of the tubular wall.

7. Gas injection system according to any of claim 5, wherein the monobloc tubular wall is, between said proximal terminal of the axial channels and the proximal extremity of the tubular wall, in the shape of a thinner tip, wherein the injection system further comprises a flange fitted on said tip of the monobloc tubular wall and wherein said passage channels are arranged between said tip and said flange.

8. Gas injection system according to any of claim 5, wherein the monobloc tubular wall has, at said proximal terminal of the axial channels, an additional circumferential groove, wherein the injection system further comprises an additional closing crown, formed from at least two crown elements, which seals the additional circumferential groove of the monobloc tubular wall and said passage channels are arranged between said additional circumferential groove and said additional closing crown.

9. Gas injection system according to claim 5, wherein the cooling system is composed of comprises at least one cooling coil comprising a plurality of axial channels arranged parallel in succession in the tubular wall and joined to each other successively by a connecting channel, then by a passage channel in a repeating pattern.

10. Gas injection system according to claim 9, wherein each cooling coil comprises an inlet and an outlet for cooling fluid arranged in the tubular wall at a distance from the distal extremity thereof.

11. Gas injection system according to claim 5, wherein the axial channels, the joining channels and the passage channels have a substantially constant flow cross-section.

12. Gas injection system according to claim 9, wherein the cooling system comprises two cooling coils each covering half of the tubular wall of the injection system.

13. Gas injection system according to claim 1, wherein said at least one projected gas is chosen from the group consisting of oxygen, supersonic oxygen, air, carbon gases, nitrogen and mixtures thereof, the gases being in the form of a flame following combustion.

14. Gas injection system according to claim 1, wherein said closing crown comprises at least two crown elements.

15. Furnace equipped with at least one gas injection system according to claim 1.

16. Use A method using of at least one gas injection system according to claim 1, comprising processing metal material in a furnace.

17. A method according to claim 16, comprising melting scrap, refining steel in an electric furnace or reheating slabs.

Description

[0047] Other details and features of the invention will emerge from the description below, which is not limiting, of an exemplary embodiment of a gas injection system according to the invention, shown in the appended drawings.

[0048] FIG. 1 shows a profile view of a gas injection system according to the invention.

[0049] FIG. 2 shows a cross-sectional view along line II-II of the gas injection system of FIG. 1, on an enlarged scale.

[0050] FIG. 3 shows a cross-sectional view along line III-Ill of the gas injection system of FIG. 1, on an enlarged scale.

[0051] FIG. 4 shows a cross-sectional view along line IV-IV of the gas injection system of FIG. 1, on an enlarged scale and in exploded form.

[0052] FIG. 5 shows a front view of the extremity of the gas injection system according to FIG. 1, on an enlarged scale.

[0053] FIG. 6 shows a sectional view along line VI-VI of FIG. 5.

[0054] The gas injection system shown in the figures is a burner equipped with a sheath. It comprises a tubular injector 1 whose extremity opening is partially covered by a sheath generally referred to as 2. It has a monobloc tubular wall 3 which forms, around the injector, a jacket which, as shown in the figures, is cooled by a cooling system.

[0055] In FIG. 1, the vertical wall of the furnace, on which the burner is attached at an angle, is shown schematically by the dashed line 4.

[0056] The burner injector is supplied with fuel, e.g. natural gas, via the inlet 5 and with oxidant, e.g. technical oxygen, via the inlet 9. During operation, a flame is formed in the mixing chamber enclosed by the tubular wall 3 and exits by an opening 10 at the distal extremity 11 thereof. Supersonic oxygen may also be fed into the injector 1 by the supply duct 6.

[0057] In the example shown in these figures, the cooling system of the sheath 2 comprises a supply duct 7 for a cooling fluid and an exhaust duct 8 thereof.

[0058] As shown in FIGS. 2, 4 and 6, the cooling system comprises several axial channels 12 which extend axially towards the distal extremity 11 of the tubular wall. The cooling fluid, e.g. water, circulates in these channels, which comes from the supply duct 7 and then flows towards the exhaust duct 8. These channels are drilled into the body of the monobloc tubular wall.

[0059] Circumferentially adjacent axial channels are, at the distal extremity 11 of the tubular wall 3, joined by connecting channels 13 which have a rounded shape in the direction of this extremity. In the example shown in FIG. 6, the connecting channels 13 have a rounded shape and thus ensure a smooth transition between the axial channels they join.

[0060] At a distance from the distal extremity 11 of the tubular wall, i.e. closer to the wall of the furnace, circumferentially adjacent axial channels are joined by passage channels 14 which have a slightly rounded shape in the opposite direction to the aforementioned distal extremity 11.

[0061] In the example shown, the axial channels 12 arranged in succession at the periphery of the tubular wall 3 are joined to each other successively by a rounded connecting channel 13, then by a rounded passage channel 14, then again by a rounded connecting channel 13, and so on, to form at least one cooling coil in the tubular wall 3. Connection between the axial channels is carried out individually, step by step, without requiring co-axial channels which generate foaming, or meetings between several channels.

[0062] In the example shown, in particular when referring to FIGS. 3 and 6, it can be seen that the supply duct 7 for the cooling fluid opens opposite the inlet 15 of two axial channels 12 so that two cooling coils each covering half of the tubular wall 3 may be supplied in this way. In FIG. 5, the arrow indicates the location of the supply duct 7 at the back of the tubular wall. The two outlets 16 of these coils open into a peripheral channel 17 which ends opposite the exhaust duct 8 for the cooling fluid. The channels thus form two cooling circuits, divided into separate circumferential areas within the tubular wall. These circuits are supplied by the same fluid source, the duct 7, and end in the same outlet, the duct 8.

[0063] As shown in particular in FIGS. 1, 4 and 6, the tubular wall is monobloc and has, in the exemplary embodiment shown, a circumferential groove 19 at the distal terminal of the axial channels 12. This groove is sealed by a closing crown formed, in the example shown, of two half-crowns 20 and 21. The connecting channels 13 are, in the example shown, shaped partly in the bottom of the circumferential groove 19 and partly inside the half-crowns 20 and 21. Naturally, it would also be possible to arrange them only at the bottom of the groove or only inside the half-crowns.

[0064] This monobloc arrangement at the extremity of the gas injection system according to the invention, in the most mechanically and thermally stressed part thereof, makes it possible to reduce to a minimum metallic discontinuity and thus to produce an excellent ability to balance the temperature field in the metal alloy used, with rapid transfer of heat from the heat source to the cooling liquid. By radially incorporating the half-crowns 20 and 21 into the circumferential groove 19, i.e. in the solid material of the monobloc tubular wall 3, a highly crack-resistant arrangement is obtained, which simultaneously allows an optimised flow of the fluid in the cooling system.

[0065] While the furnace is in operation, the distal extremity 11 of the tubular wall 3 is particularly thermally stressed not only by heat sources from the furnace, e.g. the molten metal bath or the electric arcs, but also by the flame in the burner injector cavity. Due to the angled arrangement of the burner on the refractory wall of the furnace, part of the distal extremity of the tubular wall 3 of the sheath projects further into the furnace and is consequently more particularly thermally stressed.

[0066] In the example shown, the supply duct 7 for the cooling fluid is arranged to directly supply two axial channels 12 arranged in this projected part of the tubular wall 3. In this way, the two axial channels 12 each end directly in the most thermally stressed part of the distal extremity of the tubular wall. They form the start of two cooling coils and make it possible to locate the incoming and therefore “cold” cooling fluid at the most stressed points.

[0067] As shown in particular in FIGS. 1, 3 and 6, at its proximal extremity, the monobloc tubular wall is in the shape of a thinner tip 22. A flange 18 is fitted on this tip. In the example shown, the passage channels 14, as well as the inlet 15 and outlet 16 leading to the supply duct 7 and exhaust duct 8 are shaped partly on the surface of the tip 22 and partly inside the flange. Naturally, it would also be possible to arrange them only in the flange 18 or only inside the tip 22.

[0068] Another arrangement could also be considered, consisting of an additional groove 23 comparable to the groove 19 and a crown formed from two or more crown elements comparable to the half-crowns 20 and 21. The possible location of this additional groove is shown in dash-dot lines in FIG. 1.

[0069] It must be understood that the present invention is in no way limited to the embodiment described above and that it may be modified within the scope of the appended claims.

[0070] For example, it is possible to have one, three or more cooling coils.

[0071] By distributing a free number of cooling circuits, whose channel cross section may be freely sized, it is possible to adjust the fluid velocity for a very wide range of cooling fluid flows and thus a high Reynolds number to which the heat exchange coefficient is directly linked.