Fluid cooled lances for top submerged injection

Abstract

A TSL lance has an outer shell of three substantially concentric lance pipes, at least one further lance pipe concentrically within the shell, and an annular end wall at an outlet end of the lance which joins ends of outermost and innermost lance pipes of the shell at an outlet end of the lance and is spaced from an outlet end of the intermediate lance pipe of the shell. Coolant fluid is able to be circulated through the shell, by flow to and away from the outlet end. The spacing between the end wall and the outlet end of the intermediate pipe provides a constriction to the flow of coolant fluid to increase coolant fluid flow velocity therebetween. The further lance pipe defines a central bore and is spaced from the innermost lance pipe of the shell to define an annular passage, whereby materials passing along the bore and the passage mix adjacent to the outlet end of the lance. The end wall and an adjacent minor part of the length of the shell comprise a replaceable lance tip assembly.

Claims

1. A top submergible injection lance for use in a top submerged lancing injection within a slag layer of a molten bath in a pyrometallurgical process, wherein the lance has an outer shell of three substantially concentric lance pipes comprising an outermost, an innermost and an intermediate pipe, the lance including at least one further lance pipe arranged substantially concentrically within the shell, and further including an annular end wall at an outlet end of the lance which joins a respective end of the outermost and innermost lance pipes of the shell at an outlet end of the lance and is spaced from an outlet end of the intermediate lance pipe of the shell, wherein, at a location remote from the outlet end, adjacent to an upper or inlet end, the lance has a structure by which it is suspendable so as to hang down vertically, and the shell is adapted to circulate coolant fluid through the shell, by flow between the innermost and intermediate lance pipes to the outlet end and then back along the lance, away from the outlet end, by flow between the intermediate and outermost lance pipes, or the converse of this flow, wherein the spacing between the end wall and the outlet end of the intermediate pipe provides a constriction to the flow of coolant fluid operable to cause an increase in coolant fluid flow velocity between the end wall and the outlet end of the intermediate pipe; wherein the at least one further lance pipe defines a central bore, whereby a mixing chamber is defined by the outer shell between the outlet ends of the outer shell and of the at least one further pipe, and the at least one further lance pipe is spaced from the innermost lance pipe of the shell to define therebetween an annular passage, whereby combustible material passing along the bore and oxygen containing gas passing along the annular passage are able to form a combustible mixture in the mixing chamber and adjacent to the outlet end of the lance for combustion of the mixture in being injected within the slag layer, and wherein the end wall and an adjacent minor part of the length of each of the three pipes of the shell comprise a replaceable lance tip assembly able to be cut from a major part of the length of the three pipes of the shell to enable replacement.

2. The lance of claim 1 wherein the constriction is operable to provide a flow of coolant fluid across the end wall in the form of a thin film or stream relative to flow before and after the constriction.

3. The lance of claim 1, wherein at the end of the intermediate lance pipe there is defined a bead which has a radially curved, convex surface which faces towards the end wall, due to the bead being of tear drop, or rounded form, with the end of complementary concave form.

4. The lance of claim 3, wherein the constriction between the outlet end of the intermediate pipe and the end wall is of located radially of the lance in planes containing an axis for the lance, with the bead and the end wail providing the constriction through an angle of up to about 180°.

5. The lance of claim 3, wherein the constriction continues from the bead, between the outer surface of the intermediate lance pipe and an inner surface of the outermost pipe, over at least part of the length of the lance along which the intermediate pipe is of increased wall thickness.

6. The lance of claim 1, wherein the constriction is defined at least in part from a rounding of the end of the intermediate pipe and between the outer surface of the intermediate pipe and the inner surface of the outermost pipe, over at least part of the length of the lance along which the intermediate pipe has an increased wall thickness, with the constriction extending through an angle of at least 90°.

7. The lance of claim 1, wherein the lance includes an annular shroud disposed concentrically around an upper extent of the shell spaced from the outlet end.

8. The lance of claim 7, wherein the shroud has an outer shell of three substantially concentric shroud pipes comprising an outermost, an innermost and an intermediate pipe, and further including an annular end wail at an outlet end of the shroud which joins a respective outlet end of the outermost and innermost shroud pipes of the shell and is spaced from an outlet end of the intermediate shroud pipe of the shell, whereby coolant fluid is able to be circulated through the shell, along the shell to the outlet end by flow between the innermost and intermediate shroud pipes and then back along the shroud, away from the outlet end, by flow between the intermediate and outermost shroud pipes, or the converse of this flow, and wherein the spacing between the end wail and the outlet end of the intermediate pipe provides a constriction to the flow of coolant fluid operable to cause an increase in coolant fluid flow velocity between the end wall and the outlet end of the intermediate pipe.

9. The lance of claim 8, wherein the constriction of the shroud is operable to provide a flow of coolant fluid across the end wall of the shroud in the form of a thin film or stream relative to flow before and after the constriction.

10. The lance of claim 8, wherein the end of the intermediate shroud pipe there is defined a bead which has a radially curved, convex surface which faces towards the end wail, due to the head being of tear drop, or rounded form, with the end of complementary concave form.

11. The lance of claim 10, wherein the constriction between the outlet end of the intermediate shroud pipe and the end wall is of located radially of the shroud in planes containing an axis for the shroud, with bead and the end wail are closely to provide the constriction through an angle of up to about 180°.

12. The lance of claim 11, wherein the constriction continues from the bead, between the outer surface of the intermediate shroud pipe and an inner surface of the outermost shroud pipe, over at least part of the length of the shroud along which the intermediate pipe is of increased wall thickness.

13. The lance of claim 9, wherein the constriction is defined at least in part from a rounding of the end of the intermediate shroud pipe and between the outer surface of the intermediate shroud pipe and the inner surface of the outermost shroud pipe, over at least part of the length of the shroud along which the intermediate pipe has an increased wall thickness, with the constriction extending through an angle of at least 90° up to about 120°.

14. The lance of claim 1, wherein the constriction results in a coolant fluid flow rate there-through which is higher than the flow rate upstream of the constriction by a factor of from about 6 to 20.

15. The lance of claim 1, wherein the lance is from about 7.5 to about 25 meters in length.

16. The lance of claim 1 wherein the shell of the lance has an internal diameter of from about 100 mm to 650 mm, and an external diameter of 150 mm to 700 mm.

17. The lance of claim 1, wherein the further lance pipe extends to the outlet end of the lance.

18. The lance of claim 1 wherein the further lance pipe terminates within the shell by up to 1000 mm from the outlet end.

19. The lance of claim 1, wherein the lance includes an annular shroud disposed concentrically around an upper extent of the shell and spaced from the upper end.

Description

DETAILED DESCRIPTION OF THE INVENTION

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

(2) FIG. 1 is a schematic representation of one form of a lance according to the present invention;

(3) FIG. 2 is a sectional view of the lower part of a shrouded lance assembly according to the present invention; and

(4) FIGS. 3 to 7 show respective perspective views of alternative forms for a component of the shrouded lance assembly of FIG. 2.

(5) FIG. 1 schematically illustrates a TSL lance L according to one embodiment of the present invention. The lance L has four concentric pipes P1 to P4 of which pipes P1 to P3 form the main part of a shell S which also includes an annular end wall W. In the illustrated arrangement the lance L enables top submerged injection within the slag layer of a molten bath, for a required pyrometallurgical process, by injection of fuel down the bore of pipe P4 and injection of air and/or oxygen down through the annular passageway A between pipes P3 and P4. As shown, the pipe P4 terminates above the lower, outlet end E of lance L, to provide a mixing chamber M in which the fuel and air and/or oxygen are able to mix for combustion of the fuel. The ratio of fuel to oxygen is controlled in order to generate required oxidising, reducing or neutral conditions within the slag. Any fuel which is not combusted is injected within the slag to form part of reductant requirements when reducing conditions are necessary.

(6) The end wall W of shell S joins the ends of pipes P1 and P3 around the full circumference of pipes P1 and P3 at the outlet end E of lance L. Also, the lower end of pipe P2 is spaced from end wall W. As shown, coolant fluid is able to be circulated through shell S. In FIG. 1, coolant fluid is shown as being supplied down between pipes P2 and P3 for flow around the lower end of pipe P2 and return up between pipes P1 and P2. However, the converse of this flow can be used if a lesser level of heat energy extraction from pipe P1, in particular, is appropriate.

(7) Except at the lower end E of lance L, shell S has a substantially constant horizontal cross-sections in the normal in-use orientation shown. However, at end E, a constriction C is provided by the form of the lower end of pipe P2 and its co-operation with pipe P3 and end wall W. As shown, the lower end of pipe P2 carries an enlarged bead B having substantially the form of a torus so as to be of tear-drop shape, or substantially circular, in radial cross-sections (i.e. in planes containing the longitudinal axis X of lance L). Also, the surface of annular end wall W of shell S which faces bead B is of complementary concave hemi-toroidal form and bead B is positioned so that its lower convex surface is closely adjacent to but not in contact with the concave surface of end wall W. The arrangement is such that the flow velocity of coolant fluid is substantially constant in flow down between pipes P2 and P3 until it reaches the upper convex surface of bead B, after which the flow velocity progressively increases. The increase occurs in flow through an angle of about 90°, around the upper part of bead B, to a maximum around the lower half of bead in flow between bead B and end wall W. The maximum flow velocity is maintained in the flow of coolant fluid through an angle of about 180°, around the lower half of bead B. Thereafter the flow velocity decreases as the coolant fluid passes over the upper half of bead B until it reduces to a minimum in flow up between pipes P1 and P2. The constriction C is defined mainly by the spacing between the lower half of bead B and the end wall W, but the constriction C starts with the 90° of flow in pipe P3 around the upper surface of bead B.

(8) The increase in coolant fluid flow velocity within constriction C increases the ratio of surface to surface contact, between the coolant fluid and each of bead B and end wall W, per unit mass flow rate of the coolant fluid. As a consequence, heat energy extraction from the outlet end E of lance L is enhanced. This is particularly beneficial as burn back and wear at the submerged lower end of the lance L tend to be greatest and sets the time interval between stoppages for lance repair.

(9) The sectional view of FIG. 2 shows a shrouded lance assembly 10 in an in-use orientation. As shown, assembly 10 includes a plurality of concentric tubular members. These consist of members of an annular shroud 12, and members of a lance 14 which extends through shroud 12 to define an annular passage 16 there-between. FIG. 2 shows only the lower part of assembly 10. However, as is evident from FIG. 2, lance 14 is longer than shroud 12 and projects beyond shroud 12 at the lower end of assembly 10. The extent to which lance 14 projects beyond shroud 12 is not evident from FIG. 2, due to a section of lance 14 below shroud 12 being omitted in the in-use orientation shown.

(10) The tubular members of lance 14 include an innermost pipe 18, and an outer shell 20 around pipe 18 which terminates at an annular tip assembly 22 at the lower end of shell 20. The pipe 18 is shorter than lance 14 so as to extends into and terminate within the annular tip assembly 22. Pipe 18 defines a central passage 24. Also an annular passage 26 is defined between pipe 18 and shell 20. The arrangement is such that carbonaceous fuel and oxygen-containing gas are able to be passed under pressure along respective passages 24 and 26, and mixed in a mixing chamber 27 at the end of pipe 18, within assembly 22, for combustion of the fuel and generation of a combustion region extending from chamber 27 and beyond assembly 22.

(11) The shell 20 of lance 14 is formed by an inner pipe 28, an outer pipe 30 and an intermediate pipe 32, and an annular end wall 40 which joins the ends of pipes 28 and 30 around the full circumference of tip assembly 22. An annular passage 42 is defined between the inner pipe 28 intermediate pipes 32 of shell 20. Also, an annular passage 44 is defined between the intermediate pipe 32 outer pipe 30 of shell 20. The passages 42 and 44 are in communication due to the spacing between end wall 40 and the adjacent end of intermediate pipe 32. Thus, coolant fluid is able to be passed along passage 42, through shell 20 and its assembly 22 and then back along passage 44.

(12) The intermediate pipe 32 of tip assembly 22 has a cylindrical outer surface which is closely adjacent to outer pipe 30. Thus passage 44 is relatively narrow in its radial extent, at least within assembly 22 but preferably also along the full extent of shell 20. While varying with the lance diameter, the spacing between the intermediate and outer pipes 32 and 30 within assembly 22, but preferably also along the full extent of shell 20, may be from about 5 mm to 10 mm, such as about 8 mm, and slightly greater a short distance above the bottom wall to at the lower end of the intermediate pipe 32. In contrast, passage 42 is relatively wide, such as between 15 to 30 mm between inner and intermediate pipe 28 and 32 of shell 20. However, the inner peripheral surface of intermediate pipe 32 within tip assembly 22 tapers frusto-conically so as to increase in thickness and decrease in internal diameter in a direction extending towards end wall 40. As a consequence, the radial extent of passage 42 progressively decreases within assembly 22. The decrease preferably is to a radial extent of passage 42 which is similar to that for passage 44. Also, the spacing between end wall 40 and the adjacent end of pipe 38 is similar to the radial extent of passage 44. Thus, coolant fluid supplied under pressure along passage 42 is caused to increase progressively in velocity in its flow between pipes 28 and 32, and to flow at a high flow velocity across end wall 40 and along passage 44. Accordingly, the coolant fluid is able to achieve a high level of heat energy extraction from external surfaces of lance 14, at its shell 20 and tip assembly 22 and, hence, safeguard against the effect of high temperatures to which the lance is exposed in use.

(13) The end of lance 14 defining tip assembly 22 is the region most exposed to wear and burn back. The arrangement is such that the lower ends of pipes 28, 30 and 32 can be cut-off and a replacement tip assembly 22 installed, such as by welding. The length of cut-off and replaced can vary, such as in relation to the depth to which the outlet of lance 14 is submerged.

(14) Intermediate pipe 32 of lance 14 may be maintained in a fixed relationship with pipes 28 and 30, and with end wall 40. This may be achieved by any convenient arrangement. A fixed relationship retains the flow path for cooling fluid along passage 42 and then back along passage 44 so that a required rate of heat energy extraction by the coolant fluid is able to be maintained, if necessary by varying the rate of supply of cooling fluid to passage 42. Establishing and maintaining the fixed relationship may be ensured by a few small dimples or other suitable form of spaced provided at locations around the upper surface of wall 40 or the end face of pipe 32. Such spacers also can assist in avoiding unwarranted development of vibrations in lance 14.

(15) Turning now to shroud 12, it will be noted that apart from larger respective diameters of the pipes of which it is formed and the length of shroud 12, its construction is the same as that of shell 20 and its tip assembly 22. Accordingly, components of shroud 12 have the same reference numeral as used for shell 20 and its assembly 22, plus 100. Thus, further description of shroud 12 therefore is not necessary, beyond noting that it has a shell 120 and a tip assembly 122.

(16) With use of lance assembly 10, the outer surface of lance 14 up to shroud 12 is provided with a coating of solidified slag, as described above, while such coating also may be formed on the lower extent of the outer surface of shroud 12. After this, the lower end of lance 14 is submerged to a required depth in a slag bath from which the coating was formed, but with the lower extent of shroud 12 spaced above the bath.

(17) Pyrometallurgical reactions conducted in a reactor containing the slag bath usually result in combustible gases, principally carbon monoxide and hydrogen, evolving from the slag to the reactor space above the bath. If required, these gases can be subjected to post-combustion from which heat energy is able to be recovered by the slag. For this, oxygen containing gas can be supplied to the reactor space by being supplied to and issuing from the lower end of passage 16.

(18) The principal cooling of shroud 12 is by coolant fluid circulated along passage 142 and back along passage 144, although some further cooling is achieved by the gas injected through passage 16, above the surface of the slag bath. With lance 14, substantial cooling is able to be achieved by the high velocity gas, sub-sonic injected through passage 26, while further substantial cooling is achieved by coolant fluid circulated along passage 42 and back along passage 44. The balance between the two cooling actions for lance 14 can be varied by changing the mass flow rate at which the coolant fluid is circulated. Again an increased flow rate of coolant fluid, relative to the flow rate in passage 42, caused by a constriction provided by the narrow extent of passage 44 (at least within assembly 22) enhances heat energy extraction from the assembly 22 and the lower extent of shell 20. As a consequence the operating life of the lance is increased by a resultant reduction in wear and burn back, particularly at assembly 22.

(19) The arrangement with lance L of FIG. 1 and lance 10 of FIG. 2 is such that coolant fluid is able to be circulated through the shell of the lance, such as along the shell to the outlet end by flow between the innermost and intermediate lance pipes of the shell and then back along the lance, away from the outlet end, by flow between the intermediate and outermost lance pipes of the shell, or the converse of this flow arrangement. The respective end wall W,40 and an adjacent minor part of the length of each of the three lance pipes of the shell S,20, comprises a replaceable lance tip assembly, whereby a burnt back or worn lance tip assembly is able to be cut from a major part of the length of each of the three lance pipes to enable a new or repaired lance tip assembly to be welded in place. The end wall W,40 of the shell S,20 is at and defines the outlet end of the lance. Also, the at least one further lance pipe P4,18 defines a central bore 24, and the at least one further lance pipe P4,18 is spaced from the innermost lance pipe of the shell S,20 to define therebetween an annular passage A,42, whereby materials passing along the bore and the passage are able to mix adjacent to the outlet end of the lance in being injected within the slag layer.

(20) The TSL lance L,10 necessarily is of large dimensions. Also, at a location remote from the outlet end, such as adjacent to an upper or inlet end, the lance has a structure (not shown) by which it is suspendable so as to hang down vertically within a TSL reactor. The lance L,10 has a minimum length of about 7.5 meters, but may be up to about 20 meters in length, or even greater, for a special purpose large TSL reactor. More usually, the lance ranges from about 10 to 15 meters in length. These dimensions relate to the overall length of the lance through to the outlet end defined by the end wall of the shell. The at least one further lance pipe P4,18 may extend to the outlet end and therefore be of similar overall length but, as shown, may terminate a short distance, inwardly of the outlet end, such as by up to about 1000 mm. The lance typically has a large diameter, such as set by an internal diameter for the shell of from about 100 to 650 mm, preferably about 200 to 500 mm, and an overall diameter of from 150 to 700 mm, preferably about 250 to 550 mm.

(21) Each of FIGS. 3 to 7 illustrates schematically a respective, alternative form for the baffle comprising pipe 38 of tip assembly 22 of lance 14 and/or pipe 138 of shroud 12, although the baffle employed in lance 14 need not be of the same type as that used in shroud 12. The pipe 60 of FIG. 3 differs from pipe 38 or pipe 138 of FIG. 2. Each of pipes 38 and 138 has a cylindrical outer surface which is at a substantially constant spacing from the respective outer pipe 36, 136, such that a substantially constant coolant fluid flow velocity is maintained there-between in passage 44. In contrast, the outer surface of pipe 60 is profiled such that, in flowing upwardly in passage 44, a progressively decreasing fluid flow velocity is enabled after the decrease in flow velocity resulting from the larger external diameter at the lower end of pipe 60. Subject to the decrease not proceeding below a level providing for required heat energy removal from the outer pipe 36 and/or 136, good energy removal from the lower end of tip assembly 22 and/or 122 is able to be achieved.

(22) The respective pipes 62 and 64 of FIGS. 4 and 5 also differ at the outer surface from the arrangement of pipes 38, 138. While pipes 62 and 64 show respective forms, they achieve a similar result. In the case of pipe 62, a raised spiral, bead or ridge 63 extends in a helical formation around the cylindrical outer surface and may be continuous or intermittent, such as when a vane arrangement is employed. In contrast, the outer surface of pipe 64 has a helical groove 65 formed therein. In each case, coolant fluid is constrained to flow helically in passage 44 and/or 144, at least within the tip assembly 22 and/or 122. The bead or ridge 63 around pipe 62 is shown as being of rounded cross-section and it may be provided by wire tack-welded to pipe 62. However bead or ridge 63 can have other cross-sectional forms, while groove 65 of tube 64 can have a cross-sectional form other than the rectangular form shown.

(23) The pipe 66 of FIG. 6 is similar in overall form to pipes 38 and 138. However, it differs in having a circumferential array of holes 67 there-through adjacent to its lower end. Coolant fluid is able to pass through holes 67, additional to the flow passing around the lower end of pipe 66. Thus heat energy is able to be more effectively removed from the lower end of a lance 14 and/or 114 provided with a pipe 66.

(24) The pipe 68 of FIG. 7 is provided on its outer surface with an array of longitudinal flutes or grooves 69, resulting in longitudinal ridges 70. In this instance, the extent of increase in coolant fluid flow velocity is less than if grooves 69 had not been formed. That is, the flow velocity is dependent on the average radius of the outer surface of pipe 68.

(25) The respective pipes 38 and 138 of the arrangement of FIG. 2, and the respective pipes 60, 62, 64, 66 and 68 of FIGS. 3 to 7, may be produced in any suitable way. For example, the pipes may be machined or forged from a billet of a suitable metal, or by casting a suitable metal substantially final form.

(26) The coolant fluid may be of any suitable liquid or gas. A liquid cooling agent is preferred, and liquid coolants able to be used include water, ionic liquids and suitable polymer materials, including organosilicon compounds such as siloxanes. Examples of specific silicone polymers able to be used include the heat transfer fluids available under the trade mark SYLTHERM, owned by the Dow Corning Corporation.

(27) 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.