Method for treating molten metals and/or slags in metallurgical baths and metallurgical plant for treating molten metals

Abstract

A method for treating molten metals (4) and/or slags in metallurgical baths comprises the introduction of a process gas into a melt bath. The process gas is accelerated to supersonic speed and is introduced below the melt bath surface (5) by means of at least one supersonic nozzle (6) with supersonic speed into the liquid phase of the molten metal (4) and/or into the slag and/or into the region of a phase boundary between molten metal and slag. The disclosure further relates to a metallurgical plant for treating molten metals.

Claims

1.-12. (canceled)

13. A method for treating molten metals (4) and/or slags in metallurgical baths, comprising: introducing a process gas into a melt bath, including accelerating the process gas to supersonic speed and introducing the process gas below a melt bath surface (5) by at least one supersonic nozzle (6) with supersonic speed into a liquid phase of a molten metal (4) and/or into a slag (13) and/or into a region of a phase boundary (14) between molten metal and slag (13), wherein the process gas is introduced at several locations of the melt bath using a plurality of supersonic nozzles (6), and wherein at least one of the plurality of supersonic nozzles (6) is operated outside its gas-dynamic design point.

14. The method according to claim 13, wherein the process gas is introduced into the molten metal (4) at different heights relative to the melt bath surface (5).

15. The method according to claim 13, wherein at least one of the plurality of supersonic nozzles (6) comprises a convergent nozzle part (10) and a divergent nozzle part (11).

16. The method according to claim 13, wherein the gas-dynamic design point of at least one of the plurality of supersonic nozzles (6) is selected such that a gas pressure of the process gas at an outlet cross-section (8) of the supersonic nozzle (6) corresponds to an ambient pressure within the molten metal (4).

17. The method according to claim 13, wherein at least one of the plurality of supersonic nozzles (6) is subjected to volume flows and/or pressures changes of the process gas during operation.

18. The method according to claim 13, wherein the process gas is introduced into a metallurgical vessel (1) vertically from below and/or laterally.

19. The method according to claim 13, comprising using a metallurgical vessel (1) having the plurality of supersonic nozzles (6) passing through a wall and/or a bottom of the metallurgical vessel (1).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0039] FIG. 1 is a schematic illustration of the arrangement of a supersonic nozzle in a side wall of a metallurgical vessel.

[0040] FIG. 2 is a schematic illustration of a metallurgical vessel designed as a Pierce Smith converter.

[0041] FIG. 3 is an illustration showing the speed profile of the process gas exiting from a supersonic nozzle operated at the design point.

[0042] FIG. 4 is an image corresponding to FIG. 2, wherein the wave patterns generated by the exiting process gas within the molten metal during the over-expanding mode of the supersonic nozzle are shown.

[0043] FIG. 5 is an image corresponding to FIG. 2, wherein the wave patterns generated by the exiting process gas within the molten metal during the under-expanding mode of the supersonic nozzle are shown.

DETAILED DESCRIPTION

[0044] FIG. 1 shows a metallurgical vessel 1 of a plant for treating molten metals, comprising a bottom 2 and a side wall 3, which are lined with a refractory material. The metallurgical vessel 1 is filled with a molten metal 4 into which a process gas, for example in the form of pure oxygen, is introduced below a melt bath surface 5 in the lower bath. For this purpose, a supersonic nozzle 6 with a certain outlet diameter D is provided in the side wall 3 of the metallurgical vessel 1. The metallurgical vessel 1 is shown only in simplified form for illustrative purposes. This can comprise a plurality of supersonic nozzles 6 recessed at different locations in the side wall 3 or bottom 2 of the metallurgical vessel 1 (side wall flusher and/or bottom flusher). The gas jet 7 introduced by the supersonic nozzle 6 into the metallurgical vessel 1 exits the supersonic nozzle 6 at a gas pressure corresponding to the ambient pressure prevailing in the molten metal 4. The gas jet 7 has a penetration depth J, which, because of the supersonic speed of the gas, is significantly higher than the penetration depth of gas jets with subsonic speed.

[0045] The supersonic nozzle 6, which is used in accordance with the disclosure, can be designed as a Laval supersonic nozzle with a bell-shaped convergent nozzle part 10 and a correspondingly bell-shaped divergent nozzle part 11, wherein the convergent nozzle part 10 merges continuously into the divergent nozzle part 11 in the region of a nozzle throat 12. The largest diameter of the convergent nozzle part 10 determines the inlet cross-section 9 of the supersonic nozzle 6, whereas the largest diameter of the divergent nozzle part 11 determines the outlet cross-section 8 of the supersonic nozzle 6.

[0046] FIG. 2 shows a variant of metallurgical vessel 1 for carrying out the method, which is designed as a Pierce Smith converter. The metallurgical vessel is designed as a cylinder rotatable about the longitudinal axis, the side wall 3 of which is penetrated by at least one supersonic nozzle 6, wherein the supersonic nozzle 6 is arranged in the side wall 3 in such a manner that the gas jet 7 can be introduced into the liquid at supersonic speed either into the liquid phase of the molten metal 4 or into the slag 13 or into the region of a phase boundary 14 between the molten metal 4 and the slag 13 below the surface 5 of the melt bath. With the variant of the metallurgical vessel 1 shown in FIG. 2, the reference signs used in FIG. 1 are used for corresponding features, wherein, in contrast to the metallurgical vessel 1 in accordance with FIG. 1, the side wall does not comprise a distinguished bottom, since the metallurgical vessel comprises a cylindrical shell surface and end faces, wherein the shell surface is designated above as side wall 3.

[0047] FIGS. 3 to 5 illustrate various modes of operation of the metallurgical plant for treating molten metals.

[0048] FIG. 3 shows the speed profile of the gas jet 7 at a supersonic nozzle 6 operated at the design point. With such mode of operation, the pressure p1 at the outlet cross-section 8 of the supersonic nozzle 6 corresponds to the pressure p in the molten metal. The upstream pressure p0 corresponds to the upstream pressure p0 in accordance with the design. A uniform, homogeneous speed profile is established at the outlet cross-section 8 of the supersonic nozzle.

[0049] With the variant of operation of the supersonic nozzle 6 illustrated in FIG. 4, the upstream pressure p0 of the process gas is selected to be lower than the upstream pressure p0 in accordance with the design. At the outlet cross-section 8 of the supersonic nozzle 6, there is a correspondingly lower pressure p1 of the process gas, which is lower than the ambient pressure poo in the molten metal 4. As a result, a sequence of compression waves and expansion waves is generated in the molten metal 4, which generates the disturbance pattern shown in the form of compression shocks and expansion waves. The variant of operation of the supersonic nozzle 6 shown in FIG. 3 is referred to as over-expanding mode.

[0050] Finally, FIG. 5 shows the disturbance pattern of the gas flow within the molten metal 4 generated at the supersonic nozzle 6 during under-expanding mode. In this mode of operation of the supersonic nozzle 6, the upstream pressure p0 of the process gas is greater than the upstream pressure p0 in accordance with the design. This results in a greater pressure p1 of the process gas at the outlet cross-section 8 of the supersonic nozzle, which is greater than the ambient pressure poo within the molten metal 4. This causes a post-expansion of the process gas within the molten metal 4.

LIST OF REFERENCE SIGNS

[0051] 1 Metallurgical vessel [0052] 2 Bottom of the metallurgical vessel [0053] 3 Side wall of the metallurgical vessel [0054] 4 Molten metal [0055] 5 Melt bath surface [0056] 6 Supersonic nozzle [0057] 7 Gas jet [0058] 8 Outlet cross-section of the supersonic nozzle [0059] 9 Inlet cross-section of the supersonic nozzle [0060] 10 Convergent part of the supersonic nozzle [0061] 11 Divergent part of the supersonic nozzle [0062] 12 Nozzle throat [0063] 13 Slag [0064] 14 Phase limit [0065] J Penetration depth of the gas jet [0066] p0 Upstream pressure of the process gas [0067] p1 Pressure of the process gas at the outlet cross-section of the supersonic nozzle [0068] p Pressure in the molten metal