AU2006202305A8 - Inducing swirl in a gas flow - Google Patents

Abstract

The present invention relates to an apparatus for injecting gas into a vessel. The apparatus may include a 5 gas flow duct and a central body within a forward end region of the duct. The central body and the gas flow duct form an annular nozzle for the discharge of gas from the duct. A plurality of flow directing vanes are disposed about the central body to impart swirl to a gas flow 10 through the nozzle. The flow directing vanes have substantially straight leading end portions radiating outwardly from the central body and extending along the duct. The vanes also have substantially helical trailing end portions extending helically about the central body 15 toward the front end of the duct and transition portions joining the leading end portions to the trailing end portions. The transition portions are shaped so as to merge smoothly with both the leading end portions and the trailing end portions and to smoothly and progressively 20 change shape between them.

Description

AUSTRALIA Patents Act 1990 COMPLETE SPECIFICATION STANDARD PATENT Applicant: TECHNOLOGICAL RESOURCES PTY. LIMITED A.C.N. 002 183 557 Invention Title: INDUCING SWIRL IN A GAS FLOW The following statement is a full description of this invention, including the best method of performing it known to us: - 2 INDUCING SWIRL IN A GAS FLOW TECHNICAL FIELD This invention relates to swirl inducers for 5 inducing swirl in gas flows. It has particular but not exclusive application to apparatus for injecting a flow of gas with swirl into a metallurgical vessel under high temperature conditions. Such metallurgical vessel may for example be a smelting vessel in which molten metal is 10 produced by a direct smelting process. A known direct smelting process, which relies on a molten metal layer as a reaction medium, and is generally referred to as the HIsmelt process, is described 15 in International application PCT/AU96/00197 (WO 96/31627) in the name of the applicant. The HIsmelt process as described in the International application comprises: 20 (a) forming a bath of molten iron and slag in a vessel; (b) injecting into the bath: (i) a metalliferous feed material, typically metal oxides; and 25 (ii) a solid carbonaceous material, typically coal, which acts as a reductant of the metal oxides and a source of energy; and (c) smelting metalliferous feed material to 30 metal in the metal layer. The term "smelting" is herein understood to mean thermal processing wherein chemical reactions that reduce metal oxides take place to produce liquid metal. 35 The HIsmelt process also comprises post combusting reaction gases, such as CO and H 2 released from H:\rebeccas\keep\Speci folder Geoff - general\TRPL P206 complete.doc 30/05/06 - 3 the bath in the space above the bath with oxygen containing gas and transferring the heat generated by the post-combustion to the bath to contribute to the thermal energy required to smelt the metalliferous feed materials. 5 The HIsmelt process also comprises forming a transition zone above the nominal quiescent surface of the bath in which there is a favourable mass of ascending and thereafter descending droplets or splashes or streams of 10 molten metal and/or slag which provide an effective medium to transfer to the bath the thermal energy generated by post-combusting reaction gases above the bath. In the HIsmelt process the metalliferous feed 15 material and solid carbonaceous material is injected into the metal layer through a number of lances/tuyeres which are inclined to the vertical so as to extend downwardly and inwardly through the side wall of the smelting vessel and into the lower region of the vessel so as to deliver 20 the solids material into the metal layer in the bottom of the vessel. To promote the post combustion of reaction gases in the upper part of the vessel, a blast of hot air, which may be oxygen enriched, is injected into the upper region of the vessel through the downwardly extending hot 25 air injection lance. To promote effective post combustion of the gases in the upper part of the vessel, it is desirable that the incoming hot air blast exit the lance with a swirling motion. To achieve this, the outlet end of the lance may be fitted with internal flow guides to 30 impart an appropriate swirling motion. The upper regions of the vessel may reach temperatures of the order of 2000*C and the hot air may be delivered into the lance at temperatures of the order of 1100-1400 0 C. The lance must therefore be capable of withstanding extremely high 35 temperatures both internally and on the external walls, particularly at the delivery end of the lance which projects into the combustion zone of the vessel. H:\rebeccas\keep\Speci folder Geoff - general\TRPL P206 complete.doc 30/05/06 -4 A lance construction suitable for injecting gas into a metallurgical vessel for performing the HIsmelt process is disclosed in International Application 5 No. PCT/AU02/00458 (WO 02/083958) in the name of the applicant. In that apparatus the gas flows through a gas flow duct within which there is an elongate central tubular structure and a plurality of flow directing vanes disposed about the central tubular structure toward the 10 forward end of the duct to impart swirl to gas flowing through the duct. The swirl imparting vanes are disposed in a four-start helical formation with each vane being of helical form throughout its length and extending through a rotation of 180* to impart substantial swirl to the gas 15 flow. It has been found that vanes of this form also impart substantial turbulence to the flow which can actually detract from the amount of swirl induced. By the present invention, the shaping of the swirl vanes can be modified so as to enable swirl to be induced with reduced 20 turbulence. Moreover, modification of the shaping of the vanes in accordance with the invention can also facilitate their manufacture. For high temperature applications such as in the HIsmelt process, the vanes must be cast from high melting temperature material which can be difficult 25 to mould into complex shapes. DISCLOSURE OF THE INVENTION According to the invention, apparatus for injecting gas into a vessel may include: 30 a gas flow duct extending from a rear end to a forward end from which to discharge gas from the duct; a central body within a forward end region of the duct and co-acting therewith to form an annular nozzle for the discharge of gas from the duct; and 35 a plurality of flow directing vanes disposed about the central body to impart swirl to a gas flow through the nozzle; H:\rebeccas\keep\Speci folder Geoff - general\TRPL P206 complete.doc 30/05/06 - 5 wherein the flow directing vanes have substantially straight leading end portions radiating outwardly from the central body and extending along the 5 duct, substantially helical trailing end portions extending helically about the central body toward the front end of the duct, and transition portions joining the leading end portions to the trailing end portions and shaped so as to merge smoothly with both the leading end 10 portions and the trailing end portions and to smoothly and progressively change shape between them. The leading end portions of the vanes may taper in thickness in the longitudinal direction so as to 15 progressively increase in thickness from leading edges of the vanes to the transition portions of the vanes. The vanes may also progressively reduce in thickness radially outwards of the vanes. They may for 20 example be of generally trapezoidal cross-section and taper from their roots to tips which are thinner than the roots. The radial cross-sections of the vanes may be 25 generally constant throughout the transitional and trailing end portions. There may be four vanes spaced circumferentially about the central body so as to progress from the leading 30 end portions through the transition portions into a four-start helical formation. The straight leading end portions of the vanes may extend through less than 20% of the overall length of 35 the vanes measured longitudinally of the duct. The length of the leading end portions may be minimised so as to extend through only about 20mm which may be as little as 3 H:\rebeccaa\keep\Speci folder Geoff - general\TRPL P206 complete.doc 30/05/06 - 6 to 4% of the overall length of the vanes. The transition portions of the vanes may also extend through at least 20% of the overall length of the 5 vanes measured along the length of the duct. The straight leading end portions and the transition portions of the vanes may together extend through a length which is in the range 0.4-0.8 of the 10 outer diameter of the vanes. Each vane may rotate through an angle in the range 80*-120* between its leading edge and trailing edge. 15 The angle of rotation may be about 90* so that each vane extends through about one quarter of a full turn about the central body between its leading and trailing edges. Each vane may in its transition portion rotate through an angle in the range 10*-20* and through its 20 trailing end portion may rotate through a further angle in the range 60*-80*. More specifically, each vane may through its transition portion rotate through an angle of about 25 13*-14* and may through its trailing end portion rotate through a further angle of between 76* and 770*. The angle of the helical portions of the vanes relative to the longitudinal axis of the duct may be such 30 as to produce in the gas discharging from the duct a swirl in the range 0.3-0.7, preferably about 0.5. The central body may be formed by a leading end part of an elongate central tubular structure extending 35 within the gas flow duct from its rear end to its forward end and the vanes may be mounted thereon. H:\rebeccas\keep\Speci folder Geoff - general\TRPL P206 complete.doc 30/05/06 The vanes may be formed integrally with a mounting sleeve by which they are mounted on the central body. 5 The invention also extends to a gas swirl inducer for mounting in a gas flow duct for imparting swirl to gas flowing therethrough, comprising a central elongate portion and a plurality of swirl vanes disposed about and extending along the central portion, wherein the swirl 10 vanes have substantially straight leading end portions radiating out from the central portion and extending straight along it, substantially helical trailing end portions extending helically about the central portion, and transition portions joining the leading end portions 15 to the trailing end portions and shaped so as to merge smoothly with both the leading end portions and the trailing end portions and to smoothly and progressively change shape between them. 20 BRIEF DESCRIPTION OF THE DRAWINGS In order that the invention may be more fully explained one particular embodiment will be described in detail with reference to the accompanying drawings in which: 25 Figure 1 is a vertical section through a direct smelting vessel incorporating a pair of solids injection lances and a hot air blast injection lance incorporating a swirl inducer in accordance with the invention; Figure 2 is a longitudinal cross-section through 30 the hot air injection lance; Figure 3 is a longitudinal cross-section to an enlarged scale through a front part of a central structure of the lance; Figures 4 and 5 illustrate the construction of a 35 forward nose end of the central structure; Figure 6 is a longitudinal cross-section through the central structure; H:\rebeccas\keep\Speci folder Geoff - general\TRPL P206 complete.doc 30/05/06 - 8 Figure 7 shows a detail in the region 8 of Figure 6; Figure 8 is a cross-section on the line 8-8 in Figure 7; 5 Figure 9 is a cross-section on the line 9-9 in Figure 7; Figure 10 illustrates the swirl inducer incorporated in the hot air injection lance; Figures 11 and 12 are end views of the inducer 10 shown in Figure 10; Figure 13 is an enlarged detail of the inducer; Figure 14 is a cross-section through a swirl vane of the inducer; and Figure 15 illustrates the construction of the 15 swirl inducer in Figure 10. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Figure 1 illustrates a direct smelting vessel suitable for operation by the HIsmelt process as described 20 in International Patent Application PCT/AU96/00197. The metallurgical vessel is denoted generally as 11 and has a hearth that includes a base 12 and sides 13 formed from refractory bricks; side walls 14 which form a generally cylindrical barrel extending upwardly from the sides 13 of 25 the hearth and which includes an upper barrel section 15 and a lower barrel section 16; a roof 17; an outlet 18 for off-gases; a forehearth 19 for discharging molten metal continuously; and a tap-hole 21 for discharging molten slag. 30 In use, the vessel contains a molten bath of iron and slag which includes a layer 22 of molten metal and a layer 23 of molten slag on the metal layer 22. The arrow marked by the numeral 24 indicates the position of the 35 nominal quiescent surface of the metal layer 22 and the arrow marked by the numeral 25 indicates the position of the nominal quiescent surface of the slag layer 23. The term "quiescent surface" is understood to mean the surface H:\rebeccas\keep\Speci folder Geoff - general\TRPL P206 complete.doc 30/05/06 -9 when there is no injection of gas and solids into the vessel. The vessel is fitted with a downwardly extending 5 hot air injection lance 26 for delivering a hot air blast into an upper region of the vessel and two solids injection lances 27 extending downwardly and inwardly through the side walls 14 and into the slag layer 23 for injecting iron ore, solid carbonaceous material, and 10 fluxes entrained in an oxygen-deficient carrier gas into the metal layer 22. The position of the lances 27 is selected so that their outlet ends 28 are above the surface of the metal layer 22 during operation of the process. This position of the lances reduces the risk of 15 damage through contact with molten metal and also makes it possible to cool the lances by forced internal water cooling without significant risk of water coming into contact with the molten metal in the vessel. 20 The construction of the hot air injection lance 26 is illustrated in Figures 2-15. As shown in these figures lance 26 comprises an elongate duct 31 which receives hot gas through a gas inlet structure 32 and injects it into the upper region of vessel. The lance 25 includes an elongate central tubular structure 33 which extends within the gas flow duct 31 from its rear end to its forward end. Adjacent the forward end of the duct, central structure 33 carries a swirl inducer 90 comprising a series of four swirl imparting vanes 91 for imparting 30 swirl to the gas flow exiting the duct. The forward end of central structure 33 has a domed nose 35 which projects forwardly beyond the tip 36 of duct 31 so that the forward end of the central body and the duct tip co-act together to form an annular nozzle for divergent flow of gas from 35 the duct with swirl imparted by the vanes 91. The construction of swirl inducer 90 is H:\rebeccas\keep\Speci folder Geoff - general\TRPL P206 complete doc 30/05/06 - 10 illustrated in Figures 10-15. As shown in these figures, the inducer consists of the four vanes 91 that are formed integrally with a central tubular portion 93 which serves as a mounting sleeve by which the swirl inducer is mounted 5 on the forward end of central structure 33. The inducer may be moulded from a high melting temperature alloy material such as UMCO 50 which contains by weight 0.05-0.12% carbon, 0.5-1% silicon, a maximum of 0.5-1% manganese, 0.02% phosphorous, 0.02% sulphur, 10 27-29% chromium, 48-52% cobalt and the balance essentially of iron. Such material is available commercially from several manufacturers generally under the name UMCO 50. The swirl vanes 91 of inducer 90 have 15 substantially straight leading end portions 91A radiating outwardly from the central tubular body 93 and extending straight along that body, helical trailing end portions 91C extending helically about the central tubular body and transition portions 91B joining the leading end 20 portions 91A to the trailing end portions 91C and shaped so as to merge smoothly with both the leading end portions 91A and the trailing end portions 91C and to smoothly and progressively change shape between them. The taper in thickness in the longitudinal direction 25 throughout the transitions 91B so as to progressively increase in thickness from relatively narrow leading edges to develop full thickness at the beginning of the helical trailing end portions 91C. The vanes also taper in thickness so as to reduce in thickness in the radially 30 outward direction and to have a trapezoidal cross-section as seen in Figure 14. At the leading edge 94 of each vane the profile tapers from a root of 12mm thickness to a tip of 8mm thickness. Through the leading end portions the root thickness increases to 28mm and the tip thickness to 35 20mm. The radial cross-sections of the vanes remain constant throughout the transition and trailing end portions 91B, 91C. H:\rebeccas\keep\Speci folder Geoff - general\TRPL P206 complete.doc 30/05/06 - 11 Each vane 90 rotates through an angle of 90* between its leading edge 94 and its trailing edge 95. The length of the straight leading end portions 91A is 5 minimised to about 20mm which may be as little as 3-4% of the overall length of the vanes whereas the transition portions 91B extend through a significant part of the overall length of the vanes. Specifically, the transition portions may extend through at least 20% of the overall 10 length of the vanes as measured along the length of the tubular body 93. It has been found that the shaping of the vanes in this way enhances a uniform flow of gas to efficiently impart swirl while minimising turbulence. The extended straight leading end portions 91A of the vanes 15 partition the gas into quadrants about the central body 93 so that when the gas reaches the transition portions of the vanes any low pressure regions created by the changing gas flow direction cannot result in gas being drawn from an adjacent part of the flow (as can happen if the gas 20 enters helical swirl vanes without extended straight and transition sections). In a typical hot air injection lance used in operation of the HIsmelt process, the gas flow duct may 25 have a diameter of the order of 782mm with the swirl vanes 91 produced to a similar diameter so as to be a sliding fit within the duct. The central tubular body of the inducer 90 may have an outside diameter of the order of 334mm and the overall length of the inducer may 30 be 1215mm. The vanes may have an overall length of the order of 1053mm as measured axially of the tubular body 93 with the straight portions of the vanes 91 occupying a length of the order of 230mm and the transition portions 91B a length of the order of 240mm. The 35 transition portions 91B of the vanes may turn through an angle of 13.30 with the helical portions 91C rotating through the remaining 76.70 so as to produce the 90* H:\rebeccaB\keep\Speci folder Geoff - general\TRPL P206 complete.doc 30/05/06 - 12 rotation of the vanes between their leading and trailing edges. Computer modelling by the Applicant has indicated that with these dimensions a swirl within the range of 0.3-0.7 preferably of the order of 0.5 at a flow rate 5 of 140,OOONm 3 /h, at a temperature of 1200 0 C and at an axial velocity of 300m/s appears to be achievable. In this regard the anticipated swirl of the gas flow through the swirl inducer 90 was modelled using 10 FLUENT , a computational fluid dynamics (CFD) software package available from Fluent Inc, of New Hampshire, USA. The following formula was used to model the swirl: 1 Juwr2dr riance Jw 2 rdr 15 Where the variable 'S' is the swirl number of gas flow through the lance, the variable 'u' represents tangential velocity of the gas flow through the lance, the variable 'w' represents the axial velocity of the gas flow through 20 the lance and the variable 'r' is the outer diameter of the swirl vanes. The wall of the main part of duct 31 extending downstream from the gas inlet 32 is internally water 25 cooled. This section of the duct is comprised of a series of three concentric steel tubes 37, 38, 39 extending to the forward end part of the duct where they are connected to the duct tip 36. The duct tip 36 is of hollow annular formation and it is internally water cooled by cooling 30 water supplied and returned through passages in the wall of duct 31. Specifically, cooling water is supplied through an inlet 41 and annular inlet manifold 42 into an inner annular water flow passage 43 defined between the tubes 38, 39 of the duct through to the hollow interior of 35 the duct tip 36 through circumferentially spaced openings H:\rebeccas\keep\Speci folder Geoff - general\TRPL P206 complete.doc 30/05/06 - 13 in the tip. Water is returned from the tip through circumferentially spaced openings into an outer annular water return flow passage 44 defined between the tubes 37, 38 and backwardly to a water outlet 45 at the rear end of 5 the water cooled section of duct 31. The water cooled section of duct 31 is internally lined with an internal refractory lining 46 that fits within the innermost metal tube 39 of the duct and extends 10 through to the water cooled tip 36 of the duct. The inner periphery of duct tip 36 is generally flush with the inner surface of the refractory lining which defines the effective flow passage for gas through the duct. The forward end of the refractory lining has a slightly 15 reduced diameter section 47 which receives the swirl vanes 34 with a snug sliding fit. Rearwardly from section 47 the refractory lining is of slightly greater diameter to enable the central structure 33 to be inserted downwardly through the duct on assembly of the lance until the swirl 20 vanes 34 reach the forward end of the duct where they are guided into snug engagement with refractory section 47 by a tapered refractory land 48 which locates and guides the vanes into the refractory section 47. 25 The front end of central structure 33 which carries the swirl vanes 34 is internally water cooled by cooling water supplied forwardly through the central structure from the rear end to the forward end of the lance and then returned back along the central structure 30 to the rear end of the lance. This enables a very strong flow of cooling water directly to the forward end of the central structure and to the domed nose 35 in particular which is subjected to very high heat flux in operation of the lance. 35 Central structure 33 comprises inner and outer concentric steel tubes 50, 51 formed by tube segments, H:\rebeccas\keep\Speci folder Geoff - general\TRPL P206 complete.doc 30/05/06 - 14 disposed end to end and welded together. Inner tube 50 defines a central water flow passage 52 through which water flows forwardly through the central structure from a water inlet 53 at the rear end of the lance through to the 5 front end nose 35 of the central structure and an annular water return passage 54 defined between the two tubes through which the cooling water returns from nose 35 back through the central structure to a water outlet 55 at the rear end of the lance. 10 The nose end 35 of central structure 33 comprises an inner copper body 61 fitted within an outer domed nose shell 62 also formed of copper. The inner copper piece 61 is formed with a central water flow passage 63 to receive 15 water from the central passage 52 of structure 33 and direct it to the tip of the nose. Nose end 35 is formed with projecting ribs 64 which fit snugly within the nose shell 62 to define a single continuous cooling water flow passage 65 between the inner section 61 and the outer nose 20 shell 62. As seen particularly in Figures 4 and 5. The ribs 64 are shaped so that the single continuous passage 65 extends as annular passage segments 66 interconnected by passage segments 67 sloping from one annular segment to the next. Thus passage 65 extends from the tip of the 25 nose in a spiral which, although not of regular helical formation, does spiral around and back along the nose to exit at the rear end of the nose into the annular return passage formed between the tubes 51, 52 of central structure 33. 30 The forced flow of cooling water in a single coherent stream through spiral passage 65 extending around and back along the nose end 35 of central structure ensures efficient heat extraction and avoids the 35 development of "hot spots" on the nose which could occur if the cooling water is allowed to divide into separate streams at the nose. In the illustrated arrangement the H:\rebeccas\keep\Speci folder Geoff - general\TRPL P206 complete.doc 30/05/06 - 15 cooling water is constrained in a single stream from the time that it enters the nose end 35 to the time that it exits the nose end. 5 Inner structure 33 is provided with an external heat shield 69 to shield against heat transfer from the incoming hot gas flow in the duct 31 into the cooling water flowing within the central structure 33. If subjected to the very high temperatures and high gas flows 10 required in a large scale smelting installation, a solid refractory shield may provide only short service. In the illustrated construction the shield 69 is formed of tubular sleeves of high melting temperature alloy. These sleeves are arranged end to end to form a continuous 15 ceramic shield surrounding an air gap 70 between the shield and the outermost tube 51 of the central structure. In particular the shield may be made of tubular segments of the material UMCO 50 as described above. This material provides excellent heat shielding but it undergoes 20 significant thermal expansion at high temperatures. To deal with this problem the individual tubular segments of the heat shield are formed and mounted as shown in Figures 6 - 9 to enable them to expand longitudinally independently of one another while maintaining a 25 substantially continuous shield at all times. As illustrated in those figures the individual sleeves are mounted on location strips 71 and plate supports 72 fitted to the outer tube 51 of central structure 33, the rear end of each shield tube being stepped at 73 to fit over the 30 plate support with an end gap 74 to enable independent longitudinal thermal expansion of each strip. Anti rotation strips 75 may also be fitted to each sleeve to fit about one of the location strips 71 on tube 52 to prevent rotation of the shield sleeves. 35 Hot gas is delivered to duct 31 through the gas inlet section 32. The hot gas may be oxygen enriched air H:\rebeccas\keep\Speci folder Geoff - general\TRPL P206 complete.doc 30/05/06 - 16 provided through heating stoves at a temperature of the order of 1200 0 C. This air must be delivered through refractory lined ducting and it will pick up refractory grit which can cause severe erosion problems if delivered 5 at high speed directly into the main water cooled section of duct 31. Gas inlet 32 is designed to enable the duct to receive high volume hot air delivery with refractory particles while minimising damage of the water cooled section of the duct. Inlet 31 comprises a T-shaped 10 body 81 moulded as a unit in a hard wearing refractory material and located within a thin walled outer metal shell 82. Body 81 defines a first tubular passage 83 aligned with the central passage of duct 31 and a second tubular passage 84 normal to passage 83 to receive the hot 15 airflow delivered from stoves (not shown). Passage 83 is aligned with the gas flow passage of duct 31 and is connected to it through a central passage 85 in a refractory connecting piece 86 of inlet 32. 20 The hot air delivered to inlet 32 passes through tubular passage 84 of body 81 and impinges on the hard wearing refractory wall of the thick refractory body 82 which is resistant to erosion. The gas flow then changes direction to flow at right angles down through passage 83 25 of the T-shaped body 81 and the central passage 85 of transition piece 86 and into the main part of the duct. The wall of passage 83 may be tapered in the forward flow direction so as to accelerate the flow into the duct. It may for example be tapered to an included angle of the 30 order of 70*. The transition refractory body 86 is tapered in thickness to match the thick wall of refractory body 81 at one end and the much thinner refractory lining 48 of the main section of duct 31. It is accordingly also water cooled through an annular cooling water jacket 87 through 35 which cooling water is circulated through an inlet 88 and an outlet 89. The rear end of central structure 33 extends through the tubular passage 83 of gas inlet 32. H:\rebeccas\keep\Speci folder Geoff - general\TRPL P206 complete.doc 30/05/06 - 17 It is located within a refractory liner plug 91 which closes the rear end of passage 83, the rear end of central structure 33 extending back from gas inlet 32 to the water flow inlet 53 and outlet 55. 5 The illustrated apparatus is capable of injecting high volumes of hot gas into the smelting vessel 26 at high temperature. The central structure 33 is capable of delivering large volumes of cooling water quickly and 10 directly to the nose section of the central structure and the forced flow of that cooling water in an undivided cooling flow around the nose structure enables very efficient heat extraction from the front end of the central structure. The independent water flow to the tip 15 of the duct also enables efficient heat extraction from the other high heat flux components of the lance. Delivery of the hot air flow into an inlet in which it impacts with a thick wall of a refractory chamber or passage before flowing downwardly into the duct enables 20 high volumes of air contaminated with refractory grit to be handled without severe erosion of the refractory lining and heat shield in the main section of the lance. It has been found that the swirl inducer 90 25 having the swirl vanes 91 formed with the straight leading end portions 91A and transition portions 91B and with the helical portions terminated so that the vanes rotate through only one quarter of a turn rather than through 180* as in previous apparatus allows swirl to be imparted 30 with much reduced turbulence. Moreover, the vanes with the lesser turn are a less complex shape to cast and they can be much more readily manufactured from high melting temperature material such as UMCO 50. H:\rebeccas\keep\Speci folder Geoff - general\TRPL P206 complete.doc 30/05/06

Claims (32)

1. Apparatus for injecting gas into a vessel, comprising; 5 a gas flow duct extending from a rear end to a forward end from which to discharge gas from the duct; a central body within a forward end region of the duct and co-acting therewith to form an annular nozzle for the discharge of gas from the duct; and 10 a plurality of flow directing vanes disposed about the central body to impart swirl to a gas flow through the nozzle; wherein the flow directing vanes have substantially straight leading end portions radiating 15 outwardly from the central body and extending along the duct, substantially helical trailing end portions extending helically about the central body toward the front end of the duct, and transition portions joining the leading end portions to the trailing end portions and 20 shaped so as to merge smoothly with both the leading end portions and the trailing end portions and to smoothly and progressively change shape between them.

2. Apparatus as claimed in claim 1, wherein the 25 leading parts of the vanes taper in thickness in the longitudinal direction so as to progressively increase in thickness toward the helical trailing end portions of the vanes. 30

3. Apparatus as claimed in claim 2, wherein the vanes progressively increase in thickness throughout the transition portions.

4. Apparatus as claimed in any one of the preceding 35 claims, wherein the radial cross-sections of the vanes are generically constant throughout the helical trailing end portions. H:\rebeccas\keep\Speci folder Geoff - general\TRPL P206 complete.doc 30/05/06 - 19 5. Apparatus as claimed in any one of the preceding claims, wherein the vanes progressively reduce in thickness radially outwards of the vanes.

5

6. Apparatus as claimed in claim 5, wherein the vanes are of generally trapezoidal cross-section and taper from their roots to tips which are thinner than the roots. 10

7. Apparatus as claimed in any one of the preceding claims, wherein there are four vanes spaced circumferentially about the central body so as to progress from the leading end portions through the transition portions into a four-start helical formation. 15

8. Apparatus as claimed in any one of the preceding claims, wherein the straight leading end portions and the transition portions of the vanes together extend through a length which is in the range 0.4-0.8 of the outer diameter 20 of the vanes.

9. Apparatus as claimed in any one of the preceding claims, wherein each vane rotates through an angle in the range 80*-120" between its leading edge and trailing edge. 25

10. Apparatus as claimed in claim 9, wherein the angle of rotation of each vane is about 900 so that each vane extends through about one quarter of a full turn about the central body between its leading and trailing 30 edges.

11. Apparatus as claimed in claim 9 or claim 10, wherein each vane in its transition portion rotates through an angle in the range 10*-20* and through its 35 trailing end portion rotates through a further angle in the range 60*-80*. H:\rebeccaa\keep\Speci folder Geoff - general\TRPL P206 complete.doc 30/05/06 - 20

12. Apparatus as claimed in claim 11, wherein each vane through its transition portion rotates through an angle of about 13*-14* and through its trailing end portion rotates through a further angle of between 760 and 5 770.

13. Apparatus as claimed in any one of the preceding claims, wherein the straight leading end portions of the vanes extend through less than 20% of the overall length 10 of the vanes measured longitudinally of the duct.

14. Apparatus as claimed in claim 13, wherein the transition portions of the vanes extend through at least 20% of the overall length of the vanes measured along the 15 length of the duct.

15. Apparatus as claimed in any one of the preceding claims, wherein the angle of the helical portions of the vanes relative to the longitudinal axis of the duct is 20 such as to produce in the gas discharging from the duct a swirl in the range 0.3-0.7.

16. Apparatus as claimed in any one of the preceding claims, wherein the central body is formed by a leading 25 end part of an elongate central tubular structure extending within the gas flow duct from its rear end to its forward end and the vanes are mounted thereon.

17. Apparatus as claimed in claim 16, wherein the 30 vanes are formed integrally with a mounting sleeve by which they are mounted on the central body.

18. A gas swirl inducer for mounting in a gas flow duct for imparting swirl to gas flowing therethrough, 35 comprising a central elongate portion and a plurality of swirl vanes disposed about and extending along the central portion, wherein the swirl vanes have substantially H:\rebeccas\keep\Speci folder Geoff - general\TRPL P206 complete.doc 30/05/06 - 21 straight leading end portions radiating out from the central portion and extending straight along it, substantially helical trailing end portions extending helically about the central portion, and transition 5 portions joining the leading end portions to the trailing end portions and shaped so as to merge smoothly with both the leading end portions and the trailing end portions and to smoothly and progressively change shape between them. 10

19. A gas swirl inducer as claimed in claim 17, wherein the leading parts of the vanes taper in thickness in the longitudinal direction so as to progressively increase in thickness toward the helical trailing end portions of the vanes. 15

20. A gas swirl inducer as claimed in claim 19, wherein the vanes progressively increase in thickness throughout the transition portions. 20

21. A gas swirl inducer as claimed in any one of claims 18 to 20, wherein the radial cross-section of the vanes are generally constant throughout the helical trailing end portions. 25

22. A gas swirl inducer as claimed in any one of claims 18 to 21, wherein the vanes progressively reduce in thickness radially outwards of the vanes.

23. A gas swirl inducer as claimed in claim 22, 30 wherein the vanes are of generally trapezoidal cross section and taper from their roots to tips which are thinner than the roots.

24. A gas swirl inducer as claimed in any one of 35 claims 18 to 23, wherein there are four vanes spaced circumferentially about the central elongate position so as to progress from the leading end portions through the H:\rebeccas\keep\Speci folder Geoff - general\TRPL P206 complete.doc 30/05/06 - 22 transition portions into a four-start helical formation.

25. A gas swirl inducer as claimed in any one of claims 18 to 24, wherein the straight leading end portions 5 and the transition portions of the vanes together extend through a length which is in the range 0.4-0.8 of the outer diameter of the vanes.

26. A gas swirl inducer as claimed in any one of 10 claims 18 to 25, wherein each vane rotates through an angle in the range 80*-120* between its leading edge and trailing edge.

27. A gas swirl inducer as claimed in claim 26, 15 wherein the angle of rotation of each vane is about 90* so that each vane extends through about one quarter of a full turn about the central body between its leading and trailing edges. 20

28. A gas swirl inducer as claimed in claim 27, wherein each vane in its transition portion rotates through an angle in the range 10*-20* and through its trailing end portion rotates through a further angle in the range 60*-80*. 25

29. A gas swirl inducer as claimed in any one of claims 18 to 28, wherein the straight leading end portions of the vanes may extend through less than 20% of the overall length of the vanes measured longitudinally of the 30 central elongate position.

30. A gas swirl inducer as claimed in claim 23, wherein the transition portions of the vanes extend through at least 20% of the overall length of the vanes 35 measured along the central elongate potion. H:\rebeccas\keep\Speci folder Geoff - general\TRPL P206 complete.doc 30/05/06 - 23

31. A gas swirl inducer as claimed in any one of claims 18 to 30, wherein the vanes are formed integrally with the central elongate portion of the inducer. 5

32. A gas swirl inducer as claimed in any one of claims 18 to 31, wherein the central elongate portion is cylindrical. Dated this 30th day of May 2006 10 TECHNOLOGICAL RESOURCES PTY LIMITED By their Patent Attorneys GRIFFITH HACK Fellows Institute of Patent and Trade Mark Attorneys of Australia H:\rebeccas\keep\Speci folder Geoff - general\TRPL P206 complete.doc 30/05/06