Top submerged injection lance for enhanced submerged combustion

Abstract

A lance for top submerged lancing injection in a pyro-metallurgical operation, wherein the lance has at least two substantially concentric pipes, with an annular passage for oxygen-containing gas defined between an outermost one of the pipes and a next adjacent pipe and a further passage for fuel defined within an innermost one of the pipes; the outermost pipe has a lower part of its length, from a submergible lower outlet end of the lance, by which the outermost pipe extends beyond an outlet end of the or each other pipe to define between the outlet end of the outermost pipe and the outlet end of the or each other pipe a chamber with which the passage for oxygen-containing gas communicates; and the lance further includes a defined gas flow-modifying device that is disposed in a lower end section of the passage for oxygen-containing gas.

Claims

1. A lance for top submerged lancing (TSL) injection in a pyro-metallurgical operation, wherein the lance has at least two substantially concentric pipes, with an annular passage for oxygen-containing gas defined between an outermost one of the pipes and a next adjacent pipe and a further passage for fuel defined within an innermost one of the pipes; the outermost pipe has a lower part of its length, from a submergible lower outlet end of the lance, by which the outermost pipe extends beyond an outlet end of the or each other pipe to define between an outlet end of the outermost pipe and the outlet end of the or each other pipe a chamber with which the passage for oxygen-containing gas communicates; and the lance further includes a gas flow-modifying device that is disposed in a lower end section of the passage for oxygen-containing gas, adjacent to the chamber, and that is operable to impart an inward flow component, away from the inner surface of the outermost pipe, to oxygen-containing gas passing into and longitudinally within the chamber towards the outlet end of the lance and thereby enhance mixing of the oxygen-containing gas with fuel passing into the chamber from the passage for fuel, the flow-modifying device having at least one inner component of helical form, and an outer component that extends around the at least one inner component, such that the flow-modifying device constrains gas flowing through to the lower end section of the annular passage to a helical flow path, of decreasing cross-section, around the outer surface of the next adjacent pipe, and said at least one inner component of helical form is provided in the lower end section of the annular passage that is of decreasing cross-section.

2. The lance of claim 1, wherein the flow-modifying device functions by imparting to the gas flowing longitudinally towards the chamber through the lower end section of the annular passage for oxygen-containing gas, a flow component away from the inner surface of the outermost pipe that in effect is substantially radial or radial and longitudinal.

3. The lance of claim 1, wherein the or each inner component is a helical vane, such that the flow-modifying device is a single or multi-start helical arrangement.

4. The lance of claim 3, wherein the vane of the inner component is secured at intervals, or continuously, along an inner helical edge, to the outer surface of the next innermost pipe.

5. The lance of claim 3, wherein the at least one vane decreases in width, radially relative to the next innermost pipe, from a maximum width at or nearer to an upper end of the vane.

6. The lance of 1, wherein the outer component closes the outer periphery of the helical flow path outwardly from and around the next innermost pipe.

7. The lance of claim 6, wherein the outer component bridges around and across successive flights of the or each vane.

8. The lance of claim 7, wherein the outer component has a frusto-conical inner surface, while its outer surface also is frusto-conical or of cylindrical.

9. The lance of claim 1, wherein the or each vane of the flow-modifying device is secured to the outer surface of the next adjacent pipe along a length of each vane.

10. The lance of claim 1, wherein the outer component of the flow-modifying device may comprise a sleeve or annular housing, and the or each vane is secured to the inner surface of the sleeve or housing.

11. The lance of claim 1, wherein the flow-modifying device includes at least four vanes.

12. The lance of claim 1, wherein the flow-modifying device is adapted to impart an inward flow component to a major proportion of gas flowing down the annular passage for oxygen-containing gas, but defines with the outermost pipe an annular gap through which a minor proportion of the gas is able to pass for flow over the inner surface of the outermost pipe.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) The present invention will now be described with reference to the figures of the accompanying drawings, which illustrate particular preferred embodiments of the present invention, wherein:

(2) FIG. 1 is a schematic perspective view, partly broken away, depicting a top submerged lancing (TSL) injection reactor;

(3) FIG. 2 illustrates one form of TSL lance according to the invention, suitable for use in a TSL reactor such as depicted in FIG. 1;

(4) FIG. 3 is an enlarged sectional view of components similar to those of FIG. 2; and

(5) FIG. 4 is a top plan view of a modified form of the components shown in FIG. 3, taken on a line corresponding to line A-A of FIG. 3.

DETAILED DESCRIPTION

(6) Before directly addressing the drawings, it is pertinent to note that a TSL lance according to the invention, as with TSL lances in general, necessarily is of large dimensions. At a location remote from the outlet end, such as adjacent to an upper or inlet end, the lance has a structure by which it can be suspended so as to hang down vertically within a TSL reactor. The lance may have a length as short as about 7.5 metres, such as for a small special purpose TSL reactor. The lance may be up to about 25 metres in length, or even greater, for a special purpose large TSL reactor. More usually, the lance ranges from about 10 to 20 metres in length. These dimensions relate to the overall length of the lance and the outermost pipe through to the outlet end. The next adjacent pipe, and the innermost and any other pipe for a lance with at least three substantially concentric pipes, may extend to the outlet end and therefore be of substantially the same overall length as the outermost pipe. However, each pipe other than the outermost pipe may terminate a short distance from the outlet end of the outermost pipe by, for example, up to about 1000 mm. The lance typically has a large diameter, such as set by an internal diameter for the outermost pipe of from about 100 to 650 mm, preferably about 200 to 650 mm, and an overall diameter of from 150 to 700 mm, preferably about 250 to 550 mm.

(7) Turning now to FIG. 1, there is shown a TSL reactor or furnace 10 suitable for use in conducting a pyro-metallurgical operation, using top submerged lancing (TSL) injection with a TSL lance according to the present invention. The furnace 10 is shown partly cut-away to reveal its interior, as if in the course of conducting a pyro-metallurgical operation. The furnace 10 has a tall cylindrical base section 12 for containing a molten bath 14 comprising, or having an upper layer, of slag. Extending from the upper extent of the base section 12, the furnace 10 has an asymmetrical, frusto-conical roof 16 and, above roof 16, an off-take flue 18. The section 12 and roof 16 of furnace 10 typically have an outer shell 20 of steel that is lined with suitable refractory 22. A vertically suspended lance 24, shown in more detail in FIG. 2, extends down into the base section 12 of furnace 10, through the roof 16 and close to the axis of section 12. The lance 24 passes through the roof portion 16 and is able to be raised or lowered by a carriage (not shown) to which the upper end of lance 24 is adapted to be connected. The carriage is moveable vertically on a guide structure (not shown). By means of lance 24, an oxygen-containing gas and a suitable fuel can be injected into the bath 14. The fuel may be entrained in a carrier gas, and typically is so entrained if it is a solid such as fine particulate coal. However, the fuel also may be a suitable hydrocarbon gas or liquid. Also, at least part of feed material to be smelted can be charged to the furnace 10, to fall into the bath 14, via inlet port 26. Additionally or alternatively, such feed material, if in particulate fines, can be injected into the bath via an appropriate passage of lance 24. Sealing (not shown) is provided for substantially sealing around the opening in furnace portion 16 through which lance 24 passes, and at port 26. Also, furnace 10 is kept below atmospheric pressure to prevent gases from exiting from the furnace 10 other than via flue 18.

(8) The lance 24 shown in the axial, sectional view of FIG. 2 has a concentric arrangement of an outer pipe 28 and an inner pipe 30. The lance 24 extends concentrically through a shroud tube 32 that terminates a substantial distance above the lower, tip end of lance 24 so that, in use of the lance, tube 32 also terminates a sufficient level above the bath 14. For some pyro-metallurgical operations, the pipes 28 and 30 may be of substantially the same length. However, for many pyro-metallurgical operations, the inner pipe 30 terminates above the tip end of the lance, as seen in FIG. 2, to provide a mixing and combustion chamber 34 within pipe 28, below the end of pipe 30, as required in lances in accordance with the present invention. As shown by the mid-region break in pipes 28 and 30, their length can vary according to the requirements for a process in which it is used. Process gas that provides external cooling for the outer pipe 28 is supplied via a conduit 36 to an annular space 38 between shroud device 32 and lance 24. Also, internal cooling of pipe 28 is achieved by an oxygen containing gas that is supplied via a conduit 40 for flow of the oxygen containing gas down an annular passage 42 defined between pipes 28 and 30 and communicating with chamber 34. Fuel can be supplied via a conduit 44 for flow into and down a passage 46 comprising the bore of pipe 30.

(9) Axially spaced swirlers 48 are provided in the passage between pipes 28 and 30, above the lower end of pipe 30 of lance 24. Each swirler 48 may be in the form of a single helical ribbon, as shown, or a system of multi-start helical ribbons. Swirling helical flow is imparted by swirlers 48 to the oxygen-containing gas passing down passage 42, and this forces the gas outwardly against the inner surface of pipe 28 and enhances cooling of pipe 28. The swirling also achieves a degree of mixing of that gas and the fuel in the mixing and combustion chamber 34. The swirlers 48 are mounted on the outer surface of pipe 30, such as by welding, after which pipe 28 is received as a sleeve along pipe 30 and along the swirlers 48 provided on pipe 30. The swirlers 48 have a width such that each has an outer helical edge closely adjacent to the inner surface of outer pips 28. Thus, substantially all gas passing down passage 42 is constrained to a helical flow path in passage 42 prior to entering chamber 34, and this is able to achieve a degree of mixing, in chamber 34, of the gas from passage 42 and fuel passing into chamber 34 from passage 46. A resultant gas/fuel mixture is fired to generate a combustion flame issuing from chamber 34 that is sufficient for the purpose of some TSL pyro-metallurgical operations. Not all material to comprise fuel need be combusted, as injection of some of the material into the molten bath may be required to provide a reducing agent or reductant. Where reducing agent is required in the molten bath, it is usual to designate the material as fuel/reductant, with that part not combusted as fuel being injected within the bath and able to function as reductant.

(10) While lance 24 has only two pipes 28 and 30, there can be more than two pipes. Thus, in one arrangement, passage 42 and swirler device 48 may be provided between pipe 28 and an intermediate pipe that is located between pipes 28 and 30. In that arrangement, a further annular passage for particulate feed material will be defined between the intermediate pipe and pipe 30.

(11) On start-up with furnace 10, the lance 24 is lowered to a position in which its lower tip end is above the initially quiescent bath 14. When oxygen-containing gas via conduit 40 and fuel via conduit 44 are injected through the lance 24, the fuel is combusted by igniting the resultant mixture of oxygen-containing gas and fuel formed in the chamber 34 before issuing from the lower, tip-end of the lance 24. The materials supplied through the lance for this combustion of the fuel are supplied at a high velocity resulting in generation of a very strong combustion jet or flame that impinges on the slag surface of bath 14, thereby causing strong splashing of the slag. The external surface of pipe 28 below the lower end of shroud tube 32 becomes covered with molten slag droplets that are solidified by the cooling effect of the gases passing down pipe 28, along and beyond passage 42. The accumulating slag forms a protective coating layer 50 (see enlarged insert A) over the outer surface of pipe 28. If not previously commenced, a flow of the cooling gas via conduit 38 is started, with that gas issuing from the lower end of shroud tube 32 to further cool the pipe 28. The lance 24 then is lowered so that the lower, tip end is submerged in the slag, to provide submerged injection and form a combustion zone within the slag by the combustion of fuel in the submerged combustion flame. The top-submerged injection generates substantial turbulence in the slag such that splashing of the slag continues, and intimate mixing of feed material with the slag can be achieved. The furnace 10 then is in a condition enabling a required pyro-metallurgical process to be conducted. In the course of that process, a cooling gas can be supplied via conduit 36 to the passage 38 between shroud tube 32 and outer pipe 28 of lance 24 so as to issue into a gas space 52 above the bath 14. The cooling gas further assists in cooling of the outer surface of pipe 28 of lance 24 and maintenance of the coating layer 52 of solidified slag. The cooling gas may be an oxygen-containing gas such as air or oxygen-enriched air to enable recovery of heat energy to the bath 14 by post-combustion of gases, such as carbon monoxide and hydrogen, evolved from bath 14 during the pyro-metallurgical operation. Alternatively, the cooling gas may be a non-oxidising gas such as nitrogen or an essentially non-oxidising, cooled process gas recovered from the flue gases.

(12) With the lance 24 of FIGS. 1 and 2, the lower part of the length of passage 42 is provided with a gas flow-modifying device 60. As can be seen, device 60 is disposed above chamber 34, between the outer pipe 28 and the inner pipe 30. The device 60 is operable to impart an inward flow component, away from the inner surface of pipe 28, to oxygen-containing gas flowing down passage 42, prior to the gas passing longitudinally into the chamber 34 and towards the lower, outlet end of lance 24. In imparting such flow component to the gas, the device is able to enhance mixing of the gas with fuel passing into chamber 34 from passage 46 of pipe 30, relative to mixing able to be achieved solely by swirlers 48 (i.e. without device 60).

(13) In FIG. 2, the device 60 comprises an inner component 82 which includes a three-start arrangement of circumferentially spaced helical vanes 62, and an outer component 80 which includes a frusto-conical sleeve or cone ring 64 that extends around and seals against the outer periphery of each vane 62. The three vanes 62 extend longitudinally to the junction between passage 42 and the upper end of chamber 34. The vanes 62, in addition to extending longitudinally, also extend circumferentially around the outer surface of pipe 30, so as to be of helical form. Each vane 62 is of narrow strip form, and secured, such as by welding, along one of its side edges to the outer surface of pipe 30, so that its width projects from that surface. While only schematically illustrated, each of the vanes 62 narrows in width along its length from a maximum width at or nearer to its upper end. Additionally, while the vanes 62 shown are substantially flat in transverse cross-sections and perpendicular to the longitudinal axis of lance 24, as is preferred, they may be inclined or curved in such cross-sections so their upper surface faces towards that axis. However, in each arrangement for lance 24 the vanes 62, in combination with the sleeve or cone ring 64, are to assist in imparting an inward flow component, away from pipe 28, to the gas flowing through the lower part of the length of passage 42, thereby enhancing mixing of the gas with fuel received into chamber 34 from passage 46, improving fuel combustion and strengthening the flame strength. These factors also result in spacing of the flame from the inner surface of pipe 28 and thereby minimise heating of pipe 28 by the flame.

(14) In the arrangement of FIG. 2, device 60 has a solid annular cone ring 64 having a frusto-conical inner surface 66. With inner pipe 30, surface 66 defines an annular passage 68 that decreases in radial width from a maximum at the upper end 68a to a minimum at the lower end 68b. The arrangement is such that ring 64, vanes 62 and pipe 30 together define a respective helical flow path of decreasing cross-section between each successive pair of vanes 62, with each flow path not only constraining the gas to helical flow paths imparting a flow component away from outer pipe 28, but also increasing the flow velocity of the gas to a maximum at lower end 68b.

(15) In the arrangement of FIG. 2, the solid cone ring 64 has a substantially cylindrical outer surface 70 that may contact or be closely adjacent to the inner surface of outer pipe 28. However, as shown in the enlarged insert B in FIG. 2, outer surface 70 of ring 64 may be spaced sufficiently from the inner surface of pipe 28 to define a narrow annular gap 72 between. The gap 72 preferably is sufficient to enable a minor proportion of the gas passing down passage 42 to pass between device 60 and pipe 28, thereby cooling the latter. For substantial uniformity of cooling of pipe 28, gap 72 most preferably enables passage of an annular curtain of gas. Back pressure resulting from the decreasing cross-section of gas flow paths through device 60 acts to increase the flow velocity of gas passing through gap 72, further assisting with cooling of pipe 28.

(16) As indicated, the vanes 62 of device 60 are secured at their inner edges to pipe 30. Also, cone ring 64 may be secured at its inner surface 66 to the radially-outer edges of vanes 62, such as by welding. Alternatively, or additionally, ring 64 may be secured at intervals around its outer surface 70 to outer pipe 28, such as by fasteners, or by fastening straps bridging across passage 42 to locations on inner pipe 30 above device 60.

(17) In the similar arrangements of FIGS. 3 and 4, parts corresponding to those of FIG. 2 have the same reference numeral, plus 100 and 200, respectively. In FIG. 3, the flow-modifying device 160 has two vanes 162 in a two-start arrangement, while device 260 of FIG. 4 has eight vanes 262. Also, instead of a solid cone ring 64 as in device 60 of FIG. 2, devices 160 and 260 have a frusto-conical sleeve 164, 264. While each of sleeves 164, 264 has a frusto-conical inner surface 166, 266, the sleeves are formed of sheet metal and have a respective outer surface 170 in the case of device 160, but not shown for device 260, which is of the same form as the surface 166, 266.

(18) In the device 160 of FIG. 3, the arrangement is shown as having device 160 installed in the passage 142 between an outer pipe 128 having an inner diameter P.sub.1 and an inner pipe 130 having an outer diameter P.sub.2. The device 160 has an overall height H.sub.1, with the sleeve 164 having a height H.sub.2, with an upper diameter D.sub.1 and a lower diameter D.sub.2. The upper diameter D.sub.1 of sleeve 164 is less than the inner diameter P.sub.1 of outer pipe 128 to leave a small annular gap G.sub.1 at the top of sleeve 164, and a relatively large annular spacing W.sub.1 between the upper end of sleeve 164 and pipe 130. The frusto-conical form of sleeve 164 results in a much larger annular gap G.sub.2 between the lower end of sleeve 164 and the inner surface of outer pipe 128 and a correspondingly lesser spacing W.sub.2 between the lower end of sleeve 164 and the outer surface of pipe 130. The radial width of gap G.sub.1 enables a minor proportion of gas passing down passage 142 to flow down over, and cool, the inner surface of pipe 128. The major part of the gas passes down through device 160, along flow paths between each successive pair of vanes 162. However, the downward tapering of the components of device 160 results in those flow paths decreasing in cross-section to the lower, outlet end of device 160, so gas flowing into chamber 134 issues at an increased flow velocity and directed towards the axis of lance 124, below the lower, outlet end of inner pipe 130. As a result, efficient, substantially complete, mixing is achieved between the gas entering the chamber 134 from passage 142 and device 160 and fuel entering chamber 134 from pipe 130. This enhanced mixing enables more efficient, substantially complete combustion of the fuel when the mixture is fired, generating a strong combustion flame that is localised below pipe 130 and laterally spaced from the surface of pipe 128.

(19) While devices 60 of FIG. 2 and device 160 of FIG. 3 have multi-start arrays of vanes 62, 162, the showing of three and two vanes, respectively, is for simplicity of illustration. There preferably are at least four vanes, such as from seven to twelve.

(20) Those skilled in the art will appreciate that the invention described herein is susceptible to variations and modifications other than those specifically described. It is understood that the invention includes all such variations and modifications which fall within the spirit and scope.

(21) Throughout the description and claims of the specification the word comprise and variation of the word, such as comprising and comprises, is not intended to exclude other additives, components, integers or steps.