Lances for top submerged injection

Abstract

A lance (10), for conducting a pyrometallurgical operation by top submerged lancing (TSL) injection, wherein the lance (10) has at least an inner pipe (12) and outer pipe (14) which are substantially concentric. The lower outlet of the inner pipe (12) is set at a level relative to the lower, outlet end of the outer pipe (14) required for pyrometallurgical operation. The lance (10) further includes a shroud (22) through which the outer pipe (14) extends and which is mounted on and extends along an upper portion of the outer pipe (14) to define with the outer pipe (14) a passageway (28) along which gas is able to be supplied for flow towards the outlet end of the outer pipe (14) for discharge exteriorly of the lance (10). The shroud (22) is longitudinally adjustable relative to the outer pipe (14) to enable substantial maintenance of, or variation in, a longitudinal spacing between the outlet ends of the shroud (22) and the outer pipe (14).

Claims

1. A lance, for conducting a pyrometallurgical operation by top submerged lancing (TSL) injection, the lance having at least inner and outer substantially concentric pipes with a lower outlet end of the inner or at least the next innermost pipe set at a level higher relative to the lower outlet end of the outer pipe required for the pyrometallurgical operation; wherein the lance further includes a shroud through which the outer pipe extends and which is mounted on and extends along an upper portion of the outer pipe to define with the outer pipe a passageway along which gas is able to be supplied for flow towards the outlet end of the outer pipe for discharge exteriorly of the lance, and the shroud is adjustably mounted relative to the outer pipe for longitudinal adjustment relative to the outer pipe whilst the lance is in use during a pyrometallurgical operation to enable substantial maintenance of or variation in a longitudinal spacing between the outlet ends of the shroud and the outer pipe, and wherein the lance is suspended from an installation which is operable to raise or lower the lance as a whole relative to a TSL reactor and is operable to provide relative longitudinal movement between the shroud and the outer pipe, and the lance further includes a drive system by which the relative longitudinal movement between the shroud and the outer pipe is generated, and wherein the lance further includes a helical vane or other flow shaping device extending longitudinally in an annular space between the outer pipe and the inner pipe or, where the lance has at least three substantially concentric pipes, between the outer pipe and a next innermost pipe between the outer pipe and the inner pipe.

2. The lance of claim 1, wherein movement of the shroud relative to the outer pipe is enabled so as to maintain a substantially constant longitudinal spacing between the outlet ends of the shroud and the outer pipe to offset wearing and burning back of the lower end of the outer pipe in use of the lance in a pyrometallurgical operation such as to maintain/control chemical potentials in slag and offgas.

3. The lance of claim 2, wherein relative movement between the shroud and the outer pipe is continuous or stepwise in the course of the pyrometallurgical operation.

4. The lance of claim 3, wherein the shroud remains stationary relative to a reactor including the lance when the outer pipe is lowered through the shroud to offset wear and burning back of its lower end.

5. The lance of claim 3, wherein the lance enables movement of the shroud relative to the outer pipe to provide adjustment of the height of the shroud relative to a reactor including the lance by the shroud being adjustable to provide a substantially constant spacing between the lower end of the shroud and the top surface of the molten bath as the volume of the bath changes due to formation of slag and/or production of a molten or metal phase or as a phase is tapped from the reactor in the course of the pyrometallurgical operation.

6. The lance of claim 3, wherein the shroud is adjustable relative to the outer pipe for the purpose of moving the shroud between active and inactive positions or between positions either to adjust the intensity of the cooling effect of gas discharged from the lower end of the shroud or to adjust the rate of heat energy transfer to a molten bath where that gas is for the purpose of post-combustion.

7. The lance of claim 1, wherein the pipes are in a fixed relationship, with provision made for longitudinal adjustment of the shroud relative to each of the pipes.

8. The lance of claim 1, wherein the shroud is adjustably mounted on the outer pipe to enable the shroud as a whole to move along the outer pipe.

9. The lance of claim 1, wherein the shroud comprises at least two concentric sleeves, with one of the sleeves fixed in relation to the outer pipe and at least one other sleeve adjustable relative to the fixed sleeve and the outer pipe.

10. The lance of claim 1, wherein the relative positions of the inner and outer pipes are longitudinally adjustable to enable the length of a mixing chamber, defined between the lower end of the outer pipe and the lower end of the next pipe, to be maintained at a desired setting during a period of use to compensate for the lower end of the outer pipe wearing and burning back.

11. The lance of claim 10, wherein the lower end of the inner pipe has substantially zero offset from the lower end of the outer pipe.

12. The lance of claim 10, wherein the lower end of the inner pipe is set back from the lower end of the outer pipe so that a mixing chamber is defined between those ends.

13. The lance of claim 10, wherein the lance has at least three pipes, with the vane connected at one longitudinal edge to the outer surface of the pipe next innermost of the outer pipe, and with its other edge adjacent to the inner surface of the outer pipe.

14. The lance of claim 13, wherein the pipes other than the outer pipe are longitudinally fixed relative to each other.

15. The lance of claim 1, wherein the lance enables relative longitudinal movement between the inner and outer pipes by an installation lowering mounting by which the lance as a whole is supported as the inner pipe is raised relative to the mountings or the lance enables relative longitudinal movement between the inner and outer pipes by the outer pipe being lowered while the inner pipe is held stationary.

16. The lance of claim 1 wherein the level of the outlet end of the shroud relative to the lower end of the outer pipe is able to be maintained by relative movement between the shroud and outer pipe to be within ±25 mm of a required level for the inner pipe.

17. The lance of claim 1, wherein the drive system is operable to generate relative movement at a predetermined substantially constant rate.

18. The lance of claim 1, wherein the drive system is variable speed to accommodate a variation in operating conditions in which the lance is used.

19. The lance of claim 1, wherein the drive system is adjustable manually.

20. The lance of claim 1, wherein the drive system is adjustable by remote control.

21. The lance of claim 1, wherein the lance includes or has an associated sensor able to monitor at least one parameter of a pyrometallurgical operation and to provide an output by which the drive system is adjustable.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In order that the invention may more readily be understood, description now is directed to the accompanying drawings, in which:

(2) FIG. 1 schematically shows in side elevation a first form of lance in use in conducting a pyrometallurgical top submerged lancing operation;

(3) FIG. 2 corresponds to FIG. 1, but shows a second form of lance;

(4) FIG. 3 is a schematic representation of a sectional view of a third form of lance for TSL pyrometallurgical operations;

(5) FIG. 4 corresponds to FIG. 3, but shows a schematic representation of a fourth form of lance for such operations; and

(6) FIG. 5 corresponds to FIG. 3, but shows a schematic representation of a fifth form of lance for such operations.

DETAILED DESCRIPTION OF THE DRAWINGS

(7) FIG. 1 depicts a top submerged lance 11 which, schematically, is shown as in use. The lance 11 includes an outer pipe 13 through which at least an inner pipe (not shown) extends co-axially, and a shroud 15 which is concentric with an upper extent of the pipe 13. The lower end of the lance 11 is shown submerged in a layer of slag 17 of a molten bath contained in a top submerged lancing reactor (not shown). The extent of submergence is such that, while material passing down within outer pipe 13 is injected below the surface of slag 17, the lower end of shroud 15 is spaced above the upper surface of the slag 17.

(8) The injection within slag 17 generates turbulence and splashing of the slag. The splashes are schematically shown by the lines 19, to the right of pipe 13 but, in reality, splashes would be generated around the full circumference of pipe 13. The lance 11 is suspended from an installation (not shown) by which it is able to be raised or lowered as a whole, as depicted by arrow A. Prior to the lance 11 being positioned to submerge its lower end, the lance 11 is positioned so that the lower end is just above the surface of the slag 17. Air then is blown from the lance 11 down onto the slag 17, to agitate the slag and generate splashes 19. This results in molten slag droplets covering the lower extent of the outer surface of outer pipe 13. The gas being blown through the lance cools the pipe 13 and solidifies the slag splashes 19 to build up a solidified slag coating 21. The lance 11 then is lowered by the installation to submerge the lower end of the lance 11. Despite being partially submerged, the coating 21 is able to be maintained by the cooling effect of injected gas despite the solidified slag being in contact with molten slag 17.

(9) The height of the lower end of shroud 15 above the molten slag 17 may be such that, as shown, the outer surface of shroud 15 is not coated by splashes 19 to any significant extent. Gas, typically air or oxygen-enriched air, is able to be supplied through the annular space between shroud 15 and pipe 13 so as to flow down along pipe 13 and discharge into the reactor space above the surface of slag 17, as depicted by arrows 23. Despite the height of shroud 15, the gas flow 23 assists with keeping pipe 13 sufficiently cool for maintaining solid slag coating 21. Maintenance of coating 21 remains possible even when the gas of flow 23 is used for post-combustion of gases evolving from the molten bath to cause heat energy from post-combustion being taken up by slag splashes 19. The post-combustion may be of metal vapours, free sulphur, hydrogen and/or carbon monoxide, NO.sub.x and/or dioxins and other toxic organics.

(10) In known forms of shrouded lance the shroud is of fixed length, and the distance by which the outlet end of the shroud is spaced from the outlet end of the outer pipe can be varied only by cutting a section from the lower end of the shroud, or welding a further length to the existing shroud. Thus, the shroud is fixed and adjustment of the shroud essentially requires manual operation, not suited to relatively fine adjustment, while the lance is out of service.

(11) In contrast to the known form of shrouded lance, shroud 15 is adjustable on the upper end of pipe 13 to enable variation in the spacing X between the lower end of shroud 15 and the lower outlet end of pipe 13. There is a number of different arrangements by which the spacing X can be varied. In a first arrangement, shroud 15 is adjustably mounted on the upper end of pipe 13 so as to be reversibly movable as a whole along the pipe. In a second arrangement, the shroud 15 is fixed in relation to pipe 13, but with shroud 15 variable in length so that its lower end can be extended towards, or retracted from, the lower end of pipe 13, to decrease or increase, respectively, the distance X. In one form of the second arrangement, the shroud 15 may comprise at least two longitudinally overlapping telescopic sections of which one is fixed in relation to pipe 13 while the or each other section is longitudinally slidable relative to the fixed section.

(12) In another form of second arrangement, shroud 15 again comprises at least two longitudinally overlapping sections of which one is fixed or secured in relation to the outer pipe, with the sections being adjustable by screw threaded engagement by which at least one section can be extended or retracted.

(13) With the arrangement of FIG. 1 as illustrated the spacing X, for the depth of submergence of the pipe 13, is such that a slag coating has not formed on shroud 15. This, of course, could change for a greater depth of submergence, a rising level of slag in the course of a pyrometallurgical operation, or with either lowering of shroud 15 on pipe 13 or an increase in the length of shroud 15 lessening the spacing X. Also, some dust or other deposits could collect on the outer surface of shroud 15. In view of a possible slag or dust coating forming on shroud 15, it is preferred with each form of the second arrangement that the innermost section of shroud 15 is fixed in relation to pipe 13, so that it is not exposed over the range of variation in the length X, even when the outer section is fully retracted.

(14) FIG. 2 shows an alternative form of lance 11a. The arrangement of this will be readily understood from the description of lance 11 of FIG. 1. The features shown in FIG. 2 have the same reference numerals as in FIG. 1, but distinguished by the suffix “a”.

(15) The arrangement for lance 11a differs principally in that shroud 15a is longer, resulting in a distance Y between its lower end and the lower end of outer pipe 13a which is substantially less than the distance X for lance 11 of FIG. 1. As a consequence, the slag coating 25a has formed on shroud 15a in addition to the coating 21a on pipe 13a. As can be seen, the thickness of coating 21a on pipe 13a is not such as to block the lower end of the annular space between shroud 15a and pipe 13a when the shroud 15a is in the lower most position, that is, with the distance Y at a minimum value for the range obtainable with adjustment of shroud 15a relative to pipe 13a.

(16) The smaller spacing Y compared to spacing X results in shroud 15a providing increased protection for outer pipe 13a against radiant heat energy. Also, the gas supplied through the annular space between shroud 15a and pipe 13a is able to provide cooling over a greater length of pipe 13a. This assists in maintaining the solid slag coating 21a on pipe 13a, even over the submerged portion in contact with molten slag 17a. That added cooling can be beneficial in enabling maintenance of the solid slag coating 21a even where oxygen-containing gas discharging from the lower end of the shroud 15a is used for post-combustion close to the surface of the slag 17 so that there is a high take-up by the slag of heat energy generated by the post-combustion.

(17) The lances 11 and 11a of FIGS. 1 and 2 are able to be used with a drive system. This may be as described earlier herein, or as described with reference to FIGS. 3 and 4.

(18) The lance 10 of FIG. 3 has two concentric steel pipes of circular cross-section. These include an inner pipe 12 and an outer pipe 14. An annular passage 16 is defined between the pipes 12 and 14. Along the passage 16 helical vanes or baffles 20 may be used to enhance cooling. The or each section of the baffle is provided by a strip or ribbon which extends helically around pipe 12, and has one edge welded to the outer surface of pipe 12, while its other edge is closely adjacent to the inner surface of outer pipe 14. The form of the baffle may be similar to that of the swirler strips 14 shown in FIG. 2 of U.S. Pat. No. 4,251,271 to Floyd.

(19) The lance 10 also includes an annular shroud 22 concentric with pipes 12 and 14 and mounted on the upper end of outer pipe 14. The shroud 22 has two concentric sleeves comprising an inner sleeve 24 fixed in relation to pipes 12 and 14, and an outer sleeve 26 which is longitudinally adjustable on the inner sleeve 24. By lowering or raising outer sleeve 26 on inner sleeve 24, the spacing N, between the lower end of sleeve 26 and the lower outlet end of outer pipe 14, is able to be varied between a maximum, as illustrated, and a minimum.

(20) The sleeve 26 may be telescopically slidable on sleeve 24. In that case, one of the sleeves may have ridges or teeth which mesh with grooves defined in the other sleeve, to provide a spline coupling. The ridges or teeth and the grooves may extend parallel to the axis of lance 10, or helically around that axis, so that sleeve 26 may move linearly along sleeve 24 or rotate to move both longitudinally and circumferentially. In the latter case, the sleeves 24, 26 may have helical ridges and grooves, respectively, which define a threaded coupling between the sleeves.

(21) The lower end of inner pipe 12 is spaced above the lower end of outer pipe 14 by the distance L. This results in a chamber 18 in the extent of pipe 14 below pipe 12, which functions as a mixing chamber.

(22) In the simple arrangement illustrated, air, oxygen or oxygen-enriched air is supplied to the passage 16, at the upper end of lance 10. A suitable fuel with any required conveying medium is supplied into the upper end of pipe 12. The helical baffle in passage 16 imparts strong swirling action to the gas supplied to passage 16. Thus, the cooling effect of the gas is enhanced and the gas and fuel are intimately mixed together in chamber 18 with the mixture able to be fired to produce efficient combustion of the fuel and generation of a strong combustion flame issuing from the lower end of lance 10. The ratio of oxygen to fuel can be varied, depending on the strength of reducing or oxidising conditions to be generated at or below the lower end of the lance. Oxygen or fuel not consumed in the combustion flame is injected within the slag of the bath, with any component of the fuel which is not combusted in the combustion flame being available within the slag as reductant. For this reason it often is indicated in TSL injection that fuel/reductant is injected by the lance.

(23) In addition to the supply of oxygen or oxygen-enriched air being supplied to the passage 16, air, oxygen or oxygen-enriched air is supplied to the upper end of a passage 28 defined by shroud 22 and pipe 14. The gas supplied to passage 28 may be the same or differ from the gas supplied to passage 16. The length of passage 28 corresponds to the spacing between the upper end of sleeve 24 and the lower outlet end of sleeve 26 and varies with extension or retraction of sleeve 26 relative to sleeve 24. Gas supplied along passage 28 serves to cool outer pipe 14 and, on discharging at the lower end of shroud 22, enables post-combustion, such as of metal vapours, free sulphur, hydrogen, carbon monoxide, NO.sub.x and/or organics such as dioxins, which evolves from a molten bath in which lance 10 is used in conducting a pyrometallurgical process or operation.

(24) The arrangement for lance 30 shown in FIG. 4 will be understood from the description of FIG. 3. Corresponding parts have the reference as FIG. 3, plus 20. The difference in this instance is that the lance 30 has three concentric pipes, due to a third pipe 33 being positioned between inner and outer pipes 32 and 34. Thus, passage 36 and swirler 40 are between pipes 33 and 34. Also, then lower end of pipe 33 is set back from the lower end of pipe 34 by a distance (M-L), where M is the distance between the lower ends of pipes 33 and 34 and L is the distance between the lower ends of pipes 32 and 33. Thus, the mixing chamber 38 has an annular extension around the length of pipe 32 which is below the end of pipe 33.

(25) Again, a helical baffle (not shown) is provided. However, in this instance, the baffle is mounted on the outer surface of pipe 33 and extends across passage 36 so that its outer edge is close to the inner surface of pipe 34. Again, the lance 30 of FIG. 4 has a shroud 42 with a sleeve 44 secured to pipe 34 and a sleeve 46 adjustable on sleeve 44 to vary the distance P.

(26) In this embodiment of a lance 30, fuel is supplied at the upper end of pipe 32, while free-oxygen containing gas is supplied through pipe 34, along passage 36 between pipes 33 and 34 and along passage 48 between shroud 42 and pipe 34. Also, feed material, such as concentrate, granular slag or granular matte, plus flux, may be supplied through pipe 33, along the annular passage 37 between pipe 32 and pipe 33. The mixing of oxygen containing gas and feed commences before the end of pipe 32 and the gas/feed mixture then is mixed with fuel below the end of pipe 32. Again, the fuel is combusted in mixing chamber 36, while the feed can at least be pre-heated, possibly partly melted or reacted, before being injected within the slag layer of a reactor into which lance 30 extends.

(27) FIG. 5 shows a variant of the lance 10 of FIG. 3. A similar variant could be based on the lance 30 of FIG. 4. The parts of the lance of FIG. 5 which correspond to those of lance 10 have the same reference numeral, plus 40.

(28) The lance 50 of FIG. 5 readily will be understood from the description of lance 10. One difference is that a helical baffle is not provided, however they may be used. Also, the shroud 62 comprises only a single sleeve 25 which is adjustable as a whole along lance outer pipe 54. The adjustment may be such as described for adjustment of outer sleeve 26 on inner sleeve 24 of shroud 22 of lance 10.

(29) As one skilled in the art would appreciate, the indicated feed arrangements in FIGS. 3 to 5 are examples only of variations to the central concept. The injection annulus or passage chosen for the various gases and solids may be varied without affecting the nature of the invention, as may be the use or not of swirlers or baffles within.

(30) Each of lances 10, 30 and 50 is able to be used in a variety of pyrometallurgical operations, for the production of various metals from a range of primary and secondary feeds, and in the recovery of metals from a range of residues and wastes. The lances 10, 30 and 50 consist of concentric pipes and while two or three pipes are usual, there can be at least one further pipe in lances for some special applications. The lances can be used to inject feeds, fuel and process gases into a molten bath.

(31) In all cases, the pipes of the lance are of a fixed operating length below the roof of a TSL reactor in which the lance is to be used. More specifically, the lance position is relative to the bath, and the overall lance length is typically long enough to reach a fixed distance from the furnace hearth. However, each of lances 10, 30 and 50 preferably is adjustable for the purpose of maintaining a substantially constant length for the respective mixing chamber 16 and 36 required for a particular pyrometallurgical operation. In the case of lances 10 and 50, the arrangement enables the length L to be kept substantially constant, despite wear and burn back of the lower end of pipe 14 which otherwise would reduce the length L. Similarly, in lance 30, the arrangement enables each of the lengths L and M to be kept substantially constant, despite wear and burn back of the lower end of pipe 34 which otherwise would reduce the lengths L and M. Thus, the length L in lances 10 and 50, and the lengths L and M in the case of lance 30 can be maintained at settings providing optimum conditions for top submerged lancing injection of a required pyrometallurgical operation and for required operating conditions.

(32) In the case of lance 30, the passages 36 and 37 enable different materials to be isolated from each other until the materials discharge into chamber 38 and mix. The lance may have at least one further pipe, resulting in a further passage through which a still further material can pass. The at least one further pipe may have a set back distance corresponding to L or M or a distance other than L and M. Also, in lance 30, each of L and M, and the set back distance of any further pipe, may be adjustable to compensate for a required change in operating conditions.

(33) The lances 10 and 30 are shown as having a drive system D of any of a variety of different forms. While each system D is shown as spaced from the respective lance 10, 30 and operatively connected by a line or drive link 41, drive system D may be mounted on lance 10, 30, on an installation from which the lance is suspended, or on some adjacent structure, depending on the nature of system D. Thus, line or link 41 may be a direct mechanical drive by which the outer sleeve of the respective shroud 22, 42 is able to adjust longitudinally relative to the inner sleeve. The link also may enable one pipe to be moved longitudinally relative to another in order to compensate for wear or burn back of the lower end of the outer pipe. Alternatively, the line or link 41 may denote action of system D through a coupling to an installation by which the lance 10, 30 is suspended. In each case, the system D may be operable on a set time-controlled basis, to impart a fixed rate of relative movement between the lance sleeves and preferably between pipes of lance 10, 30. Alternatively, the drive may be operable in response to a signal generated by a control unit C. The arrangement may be such that the signal is adjustable in response to an output from a sensor S which is monitored by control unit C. The sensor may be positioned and operable to provide an output indicative of variation in the length L and M caused by wear and burn back of the lower end of the outer sleeve of lance 10 and 30.

(34) The drive system D and the sensor S may be operable or of a nature detailed earlier herein.

(35) The lance of the present invention is able to provide numerous benefits over conventional top submerged lances with a fixed shroud. These benefits include: (a) Where lance wear and burn back is unavoidable, the required spacing between the outlet ends of the shroud and the outer pipe is able to be substantially maintained. This enables an optimum setting be retained throughout a pyrometallurgical operation. (b) Where a pyrometallurgical operation is conducted in a sequence of stages requiring differing operating conditions, the shroud is able to be retracted if not required in a given stage or positioned as required for each stage. (c) Control of the process parameters including post combustion, offgas control and interaction of splashed slag with reactions occurring in the upper furnace region.

(36) Finally, it is to be understood that various alterations, modifications and/or additions may be introduced into the constructions and arrangements of parts previously described without departing from the spirit or ambit of the invention.