Degasser snorkel with serpentine flow path cooling

Abstract

A snorkel (10) having a double shell core (16, 26) that defines an annular gap (40) between the shells and that has an array of baffles (66) arranged in the annular gap to define a serpentine flow path for cooling gases that pass through the annular gap. In an embodiment, a snorkel includes a flange (12) that defines an internal passageway (84) such that the fluid pathway through annular gap (40) includes passage of cooling medium through internal passageway (84).

Claims

1. A snorkel for use with a reaction vessel for degassing molten metal, said snorkel comprising: a first shell having an upper edge and a lower edge, said first shell defining a closed an outer surface and a closed an inner surface between said upper and lower edges; a second shell having an upper edge and a lower edge, said second shell defining a closed an outer surface and a closed an inner surface between said upper and lower edges, said second shell being oriented outside said first shell with the outer surface of said first shell opposing the inner surface of said second shell to define an annular gap therebetween, said second shell having an inlet opening and an outlet opening that are in fluid communication with said annual gap; a first refractory lining that is secured to the interior surface of said first shell; a second refractory lining that is secured to the outer surface of said second shell; an array of baffles, each baffle in said array of baffles being located in said annular gap between the outer surface of said first shell and the inner surface of said second shell and being located at a different respective longitudinal position of said annular gap, longitudinally adjacent baffles in said array cooperating with the outer surface of said first shell and the inner surface of said second shell to define at least first and second passageways, said inlet opening being in fluid communication with said outlet opening through said first passageway in series with said second passageway, at least one of said baffles having a free end; at least one member that is longitudinally oriented in said annular gap and that is connected to the ends of at least two baffles that are positioned longitudinally adjacent to said baffle, having a free end such that said longitudinal member cooperates with the free end of said baffle and with the outer surface of said inner shell and the inner surface of said outer shell to define a vertical opening between said first passageway and said second passageway such that there is a serpentine flow path through said first and second passageways; a fluid inlet that is in communication with said passageways; and a fluid outlet that is in communication with said passageways.

2. The snorkel of claim 1 further comprising a flange that is connected to said first shell.

3. The snorkel of claim 2 wherein said fluid inlet and said fluid outlet are in communication with said annular gap.

4. The snorkel of claim 3 wherein said flange includes a first internal passageway that is in fluid communication with an input port and that connects to said fluid inlet, said flange also including a second internal passageway that is in fluid communication with an output port and that connects to said fluid outlet such that cooling media that flows through said input port passes through said first internal passageway and exits said flange through said second internal passageway and said output port.

5. The snorkel of claim 4 wherein a barrier is located in the internal passageway of said flange between said inlet port and said output port such that cooling media flows from said internal passageway through said fluid inlet and into said annular gap, said cooling medium then flowing past the baffles of said array of baffles and through said fluid outlet back into the internal passageway.

6. The snorkel of claim 1 further comprising: a plurality of pipes that are secured to said first shell, each of said pipes having an inlet for receiving a fluid and having a diffused outlet for percolating said fluid from the pipe and radially inward from the inner surface of the refractory lining that is secured to the inner surface of said first shell.

7. A snorkel for use with a reaction vessel for degassing molten metal by holding a partial vacuum on the molten metal, said snorkel being connectable to said reaction vessel and comprising: a flange that is connectable to the reaction vessel, said flange including a first internal passageway that is in fluid communication with an input port, said flange also including a second internal passageway that is in fluid communication with an output port such that cooling media that flows through said input port passes through said first internal passageway and exits said flange through said second internal passageway and said output port; a first shell that has an upper edge and a lower edge, said first shell defining a closed outer surface and a closed inner surface between said upper and lower edges, the upper edge of said first shell defining a first circular edge and the lower edge of said first shell defining a second circular edge; a second shell with an upper edge and a lower edge, said second shell defining a closed outer surface and a closed inner surface between said upper and lower edges, the upper edge of said second shell defining a first circular edge and the lower edge of said second shell defining a second circular edge, said second shell being oriented concentrically with respect to said first shell with the outer surface of said first shell opposing the inner surface of said second shell and defining an annular gap between the outer surface of said first shell and the inner surface of said second shell; a refractory lining that is secured to the inner surface of said first shell, said refractory lining having an inner surface that defines a passageway along a longitudinal axis that intersects the centerpoints of the first and second circular edges of said first shell; a refractory lining that is secured to the external surface of said second shell; an array of arcuate-shaped baffles that is located in the annular gap between the outer surface of said first shell and the inner surface of said second shell, each of said arcuate-shaped baffles being located at a different longitudinal position of said annular gap, said arcuate-shaped baffles cooperating with the outer surface of said first shell and the inner surface of said second shell to define at least two arcuate passageways for conveying cooling medium through said annular gap, said arcuate-shaped baffles having one end that is a free end and also have a second end that is oppositely disposed from said free end; at least one primary baffle that cooperates with the free end of at least one of said arcuate-shaped baffles, the inside of the second shell, and the outside of the first shell to define an opening in the longitudinal direction between longitudinally adjacent arcuate passageways, said primary baffle also connected to the second end of at least one of said arcuate-shaped baffles to block the flow of cooling medium longitudinally past said arcuate baffle, said arcuate-shaped baffles being longitudinally adjacent to each other in said array so as to define a serpentine flow path through said passageways; a fluid inlet that is in communication with the at least one passageway for conveying cooling medium longitudinally through said annular gap, said fluid inlet also being in communication with said first internal passageway; and a fluid outlet that is in communication with one of said arcuate passageways for conveying cooling medium angularly with respect to the longitudinal axis of the passageway between the first and second openings of said first shell, said fluid outlet also being in communication with said second internal passageway of said flange.

8. The snorkel of claim 7 wherein said flange includes an internal passageway that is in communication with an input port and said fluid inlet and an internal passageway that is in communication with a fluid outlet and an output port such that cooling media that flows through said input port passes through said internal passageway, said fluid inlet, past said array of baffles, through said fluid outlet and said internal passageway, and exits said flange through said output port.

9. The snorkel of claim 8 wherein a barrier is located in the internal passageway of said flange between said inlet port and said output port such that cooling media flows from said internal passageway and through the fluid inlet into the annular gap, through the annular gap around said baffle array, and through said fluid outlet and back to said internal passageway.

10. The snorkel of claim 9 further comprising: a second fluid inlet that is in communication with the passageway for conveying cooling medium longitudinally through said annular gap; and a second fluid outlet that is in communication with one of said passageways for conveying cooling medium angularly with respect to the longitudinally axis of the passageway between the first and second openings of said first shell; a second input port in communication with said internal passageway and the annular gap; a second output port in communication with said internal passageway and the annular gap; and a second a barrier that is located in the internal passageway of said flange between said second inlet port and said second output port such that cooling media flows from said internal passageway and through the second fluid inlet into the annular gap, through the annular gap around said baffle array, and through said second fluid outlet and back to said internal passageway.

11. The snorkel of claim 7 further comprising: a plurality of pipes that are secured to said first shell, each of said pipes having an inlet for receiving a fluid and having a diffused outlet for percolating said fluid from the pipe and radially inward from the inner surface of the refractory lining that is secured to the inner surface of said first shell.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) A presently preferred embodiment of the disclosed invention is further described herein in connection with the accompanying drawings in which:

(2) FIG. 1 is an elevation view of the snorkel in accordance the disclosed invention in which the baffle array of the snorkel is vertically bisected and opened along one side of the outer shell show two parallel circuits of a serpentine flow path for conveying cooling medium through the annular gap defined between the first and second shells of the snorkel;

(3) FIG. 2 is a plan view of the snorkel shown in FIG. 1, but with the snorkel in its normal, non-bisected position;

(4) FIG. 3 is an elevation cross-section of the snorkel shown in FIGS. 1 and 2 with the first and second shells of the snorkel shown in cross-section;

(5) FIG. 4 is an elevation view of an alternative embodiment of the snorkel shown in FIGS. 1-3 wherein the flow path for conveying cooling medium extends from two parallel circuits for serpentine air flow into the flange that secures the nozzle to the reaction vessel;

(6) FIG. 5 is a plan view of the alternative embodiment of the snorkel shown in FIG. 4;

(7) FIG. 6 is an enlarged portion of the cross-section of FIG. 3 detailing the passage of pipes through a shell of the snorkel for the injection of inert gas into steel in the internal passageway of the nozzle; and

(8) FIG. 7 is a cross-section of the inner and outer shells of the nozzle shown in FIG. 3 that illustrates the location and nominal dimension of the shells in connection with tables that are included in the specification.

(9) FIG. 8 is graph showing temperature measurements set forth in Tables 3 and 4.

(10) FIG. 9 is a graph showing the effect of air-cooled system on snorkel temperature.

(11) FIG. 10 is a graph showing the increase of snorkel temperature for a snorkel with the disclosed air cooling structure as it remains in a molten bath.

DESCRIPTION OF A PRESENTLY PREFERRED EMBODIMENT OF THE DISCLOSED INVENTION

(12) As shown in FIGS. 1-3, a snorkel generally indicated as 10 is arranged for use with a reaction vessel (not shown) in a metal degassing process. The snorkel provides two parallel air flow circuits, each circuit having a serpentine flow path for cooling medium. The serpentine flow path allows improved cooling of the snorkel at times when it is exposed to molten metal. Snorkel 10 includes a flange 12 that is used to connect the snorkel to the reaction vessel. Flange 12 has a top surface 12a, an inner surface 12b, and a lower surface 12c. The interior of snorkel 10 defines a passageway 14 that is in communication with the interior of the reaction vessel.

(13) Snorkel 10 further includes a first shell 16 that is secured to flange 12 by fillet weld 17. First shell 16 defines a circular upper edge 18 and a circular lower edge 20 such that the first shell further defines a closed inner surface 22 between upper edge 18 and lower edge 20. First shell 16 also defines a closed outer surface 24 between upper edge 18 and lower edge 20.

(14) Snorkel 10 also includes a second shell 26 that defines a circular upper edge 28 and a circular lower edge 30 such that the second shell further defines a closed inner surface 32 and a closed outer surface 34 between the circular upper and lower edges 28 and 30.

(15) Second shell 26 is located concentrically with respect to the first shell 16 with the outer surface 24 of first shell 16 opposing the inner surface 32 of second shell 26 to define an annular gap 40 between surfaces 24 and 32.

(16) In the example of the preferred embodiment, first shell 16 has a first section 46 that is in the general shape of a cylinder and a second section 48 that is in the general shape of a truncated cone with the largest diameter, or base, 48a of the truncated cone being joined with a longitudinal end 48b of first section 46. Similarly, in the preferred embodiment second shell 26 has a first section 50 that is in the general shape of a cylinder and a second section 52 that is in the general shape of a truncated cone with the largest diameter, or base, 54 of the truncated cone being joined with a longitudinal end 56 of first section 50. First section 50 of second shell 26 is oriented concentrically outside of first section 46 of the first shell 16 and second section 52 of second shell 26 is oriented concentrically outside the second section 48 of the first shell 16. Correspondingly, annular gap 40 includes upper region 42 between first section 46 of the first shell and first section 50 of the second shell. Annular gap 40 also includes a lower region 44 between the second section 48 of said first shell and the second section 52 of the second shell.

(17) Alternatively some snorkels do not include a truncated cone section with the full shell being a right circular cylinder. The truncated cone shape at the lower, or distal, end of the first and second shells 16, 26 is sometimes used to compensate for thermal expansion of the lower distal, ends of the first shell 16 and the second shell 26 (which are remote from flange 12) at times when snorkel 10 is immersed in molten metal. It is thought that this shape sometimes compensates for a trumpeting effect of the distal ends of first shell 16 and second shell 26 caused by thermal expansion of the shells while the snorkel is immersed in molten metal.

(18) However, an alternative embodiment of the presently disclosed invention can include first shell 16 and second shell 26 in which the shells are only generally cylindrical as in section 46 of first shell 16 and section 50 of second shell 26. In that embodiment, the first and second shells have sections in the shape of a right circular cylinder. This alternative embodiment is possible in accordance with the presently disclosed invention because the serpentine air flow pathway that is subsequently described herein is effective to control thermal expansion of the distal portion of first shell 16 and second shell 26 so as to avoid trumpeting.

(19) Referring again to the embodiment of FIGS. 1-3, refractory lining 58 is secured to the inner surface 22 of the first shell 16 by a layer of refractory concrete 59. Refractory lining 58 extends longitudinally from a position that is substantially the same as the longitudinal position of top surface 12a of flange 12 to a position that is substantially the same longitudinal position as retainer 59a that is secured to first shell 16 adjacent lower edge 20. Refractory lining 58 has an inner surface 60 that defines a longitudinal passageway 62 through snorkel 10. Preferably, longitudinal passageway 62 is aligned with a center axis 62a that intersects the center points of the circular upper edge 18 and the circular lower edge 20 of the first shell 16.

(20) Refractory concrete layer 59 extends longitudinally past the upper edge 18 of first shell 16 and covers upper edge 18 and fillet weld 17 and contacts the inner surface 12b of flange 12. Refractory concrete layer 59 thus cooperates with refractory lining 58 and the top surface of flange 12 to provide a smooth planar surface for contacting and sealing the snorkel against the reactor vessel.

(21) A second refractory lining 64 is secured to the outer surface 34 of the second shell 26. Lining 64 extends in a radial direction away from the outer surface 34 of the second shell 26 by a sufficient dimension so that lining 64 is sufficient to protect the outer shell 26 from overheating at times when the snorkel 10 is immersed in molten metal. Lining 64 extends from a longitudinal position that is substantially the same as the position of the lower surface 12c of flange 12 to a position longitudinally beyond the lower edge 30 of the second shell 26. Additionally, at longitudinal positions beyond the longitudinal position of the retainer 59a and refractory lining 58, lining 64 extends radially inwardly from outer shell 26 to contact retainer 59a and the longitudinal end position of refractory lining 58. This refractory structure protects the distal ends of first shell 16 and second shell 26 from overheating at times when the snorkel 10 is immersed in molten metal.

(22) In accordance with the presently disclosed embodiment, two arrays of baffles 66 are located in the annular gap 40 between outer surface 24 of first shell 16 and the inner surface 32 of the second shell 26. In the presently preferred embodiment, one array of baffles 66 is located in each opposite half of annular gap 40 that are defined by longitudinal members such as walls 67 and 67a that extend longitudinally through annular gap 40 and divide annular gap 40 into two separate chambers 67b and 67c. Each chamber 67b and 67c includes at least one primary baffle 68 and an array of baffles 66. Primary baffles 68 are located at different angular positions within annular gap 40 which angular positions are approximately 180 apart. Also, longitudinal members such as primary baffles 68 are longitudinally oriented in the direction of the longitudinal center axis 62a of passageway 62.

(23) Primary baffles 68 cooperate with wall 67 or 67a, the outer surface 24 of the first shell 16, and the inner surface 32 of the second shell 26 to define a passageway 70 for conveying air or other cooling medium longitudinally through annular gap 40 from the upper region 42 of annular gap 40 to the lower region 44 of annular gap 40. Passageway 70 is generally aligned with the direction of passageway 62 between upper edge 18 and lower edge 20 of first shell 16.

(24) The array of baffles 66 further includes at least two arcuate baffles 72 that are located in annular gap 40 at respective longitudinal positions along snorkel 10. Each arcuate baffle 72 has opposite ends 74 and 76 that are located in annular gap 40 at different angular positions about axis 62a so that arcuate baffles 72 define an arc between the ends 74 and 76. Arcuate baffles 72 in the array of baffles 66 are respectively located at different longitudinal positions of said annular gap. At least three longitudinally adjacent arcuate baffles cooperate with the outer surface 24 of the first shell 16 and the inner surface 32 of the second shell 26 to define at least two arcuate passageways 78 that are longitudinally adjacent to each other for conveying air or another cooling medium though annular gap 40 in an angular direction with respect to the longitudinal axis 62a of passageway 62.

(25) Collectively, passageways 78 also convey the cooling medium in a longitudinal direction from the lower edge 20 of first shell 16 toward the upper edge 18 of first shell 16. One of ends 74, 76 of each arcuate baffle 72 is connected to one of the primary baffles 68 or to one of walls 67, 67a. The other of end 74, 76 of arcuate baffles 72 is a free end that is spaced apart from a primary baffle 68 and walls 67, 67a. Thus, a separate circuit or flow path is defined for each chamber 67b, 67c.

(26) In the longitudinal direction through annular gap 40, each flow path passes through an opening between passageways that are located longitudinally adjacent to each other. The opening is defined by one of free ends 76 of arcuate baffle 72, one of the primary baffles 68 or walls 67, 67a, the outer surface 24 of the first shell 16, and the inner surface 32 of the second shell 26. At least one of the longitudinally oriented members 68, 67 or 67a are connected to the ends 74 of baffles 72 that are located longitudinally adjacent to and on opposite sides of a baffle 72 with a free end 76 that is spaced apart from the same longitudinal member 68, 67 or 67a. In this way, the longitudinal member 68, 67 or 67a cooperates with free end 76 of baffle 72 and with the outer surface 24 of first shell 16 and the inner surface 32 of the second shell 26 to define a vertical opening between two longitudinally adjacent passageways 78 to create a serpentine flow path through the passageways. The flow path through passageways 78 is thus in series because the flow is first through one passageway 78, then through the opening at one end of the passageway, and then through the second longitudinally adjacent passageway 78.

(27) Stated differently, alternate baffles 72 in baffle array 66 have an end 74 that is connected to a longitudinally oriented member 68, 67 or 67a. The same longitudinal member 68, 67 or 67a also cooperates with the free end 76 of the other baffles in the baffle array 66, outer surface 24 of first shell 16, and inner surface 32 of second shell 26 to define openings between longitudinally adjacent passageways 78 to define a serpentine flow path between a passageway 78 at one longitudinal position of annular gap 40 and another passageway 78 at a second longitudinal position of annular gap 40.

(28) The flow path thus established communicates through openings between vertically adjacent arcuate passageways 78. One end 74 of each of vertically adjacent arcuate baffles 72 is connected to a different longitudinally oriented member such as primary baffle 68 or wall 67, 67a so that the flow path through annular gap 40 follows a serpentine pathway from the lower region 44 of the annular gap 40 to the upper region 42 of the annular gap 40 as illustrated in FIGS. 1-3.

(29) It has been found that location of the baffles is important to limit air flow restriction through annular gap 40. Preferably, the pattern for baffles is machined into the inner surface 32 of second shell 26 and the outer surface 20 of first shell 16 prior to forming shells 16 and 26. Appropriate spacing of the baffles will allow a flow of cooling air in the range of 100 to 800 scfm. Achievable minimum flow rates have been found to be three hundred scfm at ninety psi.

(30) In some embodiments, snorkel shells without the disclosed air cooling have been found to reach temperatures of approximated 2000 F. In contrast, the air-cooling structure has been found to maintain shelf temperatures at about the exit temperature of exhausted air. In the test results shown in Table 1 below, this was 350 F. A typical heat removal for the presently disclosed multi-circuit air flow has been found to be 3,222 BTUM at conditions specified in Table 1.

(31) TABLE-US-00001 TABLE 1 Temperature Temperature Flow at Exit inlet outlet Specific Weight ACFM Exit Heat Removal SCFM F. F. (lb/ft3) acf/1-Lb/ F. BTUM 600 60 350 0.0759 20.53 3,222

(32) Tables 3 and 4 show certain temperature measurements of a snorkel with the disclosed air-cooling system in contrast to a snorkel without such air-cooling. More specifically, Table 3 shows the temperature drop of a snorkel without air cooling after it has been immersed in a molten bath, heated to temperature, and then withdrawn from the bath. The temperature is measured over time as shown in Table 3 at two locations on the snorkelone location at the slag line and the other location about eight inches from the bottom of the snorkel.

(33) Using the temperature measurements of Table 3 as a benchmark, the snorkel with the disclosed air cooling structure was similarly immersed in a molten bath, heated to temperature, and then withdrawn from the bath. The snorkel temperature was measured at the same two corresponding locations that were used in the case of Table 3. However, in the case of Table 4, the air cooling system for the snorkel was operating.

(34) TABLE-US-00002 TABLES 3 and 4 Measurement Point Sp2 Sp3 Time Temp. Drop Temp. Drop (sec.) ( F.) ( F.) ( F.) ( F.) Without Air Cooling 0 1355.2 1420.3 89 1334 21.2 1349.8 70.5 210 1299.4 55.8 1296.3 124 333 1247.1 108.1 1259.3 161 457 1206.7 148.5 1237.8 182.5 572 1173.3 181.9 1217.1 203.2 683 1139.4 215.8 1174.7 245.6 With Air Cooling 0 1462.4 1494.9 132 1308.7 153.7 1230.4 264.5 252 1194.4 268 1049.4 445.5 370 1183.6 278.8 1057.6 437.3 490 1099.6 362.8 926.2 568.7 610 993.5 468.9 886.4 608.5 730 904.7 557.7 690.8 804.1

(35) The tabular results of Tables 3 and 4 are shown in FIG. 8. There it is clearly shown that the magnitude and rate of the temperature drop over the same time span is far greater in the case of the disclosed air-cooled snorkel.

(36) Table 5 discloses temperature measurements that were taken on air-cooled snorkels as herein disclosed that was used through 23 separate heats. Again in Table 5, the snorkel temperature was measured at two separate locationsat the slagline and approximately eight inches from the bottom of the snorkel. For each heat, the snorkel temperature was measured over a five minute period following the time that it was withdrawn from the molten bath.

(37) TABLE-US-00003 TABLE 5 Slagline - Port A approx. 8 from bottom - Point B Passage/Temp Drop Passage/Temp Drop Heat 1 min 2 min 3 min 4 min 5 min 1 min 2 min 3 min 4 min 5 min 2 500 570 565 727 3 350 327 342 503 4 514 655 373 568 5 375 396 322 445 6 138 345 520 352 357 291 445 677 562 757 7 337 294 453 401 255 378 458 559 8 324 245 243 162 298 2 228 420 543 596 9 62 403 133 270 362 485 601 10 199 127 266 187 238 257 11 253 186 179 304 260 375 432 484 12 98 183 136 207 13 18 350 453 110 229 322 14 124 279 324 119 212 273 15 138 40 497 287 467 0 356 550 494 570 16 154 386 220 265 417 613 758 835 0 17 213 250 277 350 483 283 394 429 604 665 18 287 392 456 324 460 338 509 604 659 706 19 317 320 401 504 578 317 477 562 677 757 20 145 418 604 703 694 138 316 440 529 604 21 22 64 161 492 656 23 109 269 404 420 568 456 594 699 777 453 Ave 235 293 235 351 453 248 400 482 614 665

(38) The serpentine pathway herein disclosed maximizes the cross-sectional area of the flow path through annular gap 40 for the cooling medium. It has been found that the presently disclosed apparatus affords approximately 20 times greater cross-sectional area flow for the cooling medium than cooling pipes known in the prior art. This has resulted in a rate of heat transfer away from first shell 16 and second shell 26 that is substantially 10 times the rate of heat transfer of cooling apparatus known in the prior art.

(39) As also shown in FIGS. 1-3, a fluid inlet 80 is in fluid communication with each passageway 70 in annular gap 40. When cooling medium is received at fluid inlet 80, it flows to the upper region 42 of annular gap 40. From upper region 42 the cooling medium flows through passageway 70 to the lower region 44 of annular gap 40, and then through the serpentine

(40) The tabular results of Table 5 are shown in FIG. 9 where it is clearly shown that the air-cooled system rapidly and diametrically reduced the snorkel temperature.

(41) FIG. 10 shows the increase of snorkel temperature (again at the same two locations) for a snorkel with the disclosed air cooling structure as it remains in a molten bath. FIG. 10 shows that the temperature increase of the snorkel is relatively limited and at a relatively slow rate.

(42) The serpentine pathway herein disclosed maximizes the cross-sectional area of the flow path through annular gap 40 for the cooling medium. It has been found that the presently disclosed apparatus affords approximately 20 times greater cross-sectional area flow for the cooling medium than cooling pipes known in the prior art. This has resulted in a rate of heat transfer away from first shell 16 and second shell 26 that is substantially 10 times the rate of heat transfer of cooling apparatus known in the prior art.

(43) As also shown in FIGS. 1-3, a fluid inlet 80 is in fluid communication with each passageway 70 in annular gap 40. When cooling medium is received at fluid inlet 80, it flows to the upper region 42 of annular gap 40. From upper region 42 the cooling medium flows through passageway 70 to the lower region 44 of annular gap 40, and then through the serpentine pathway of passageways 78 as previously explained. In each chamber 67b, 67c, a fluid outlet 82 is in fluid communication with one of the passageways 78 in annular gap 40 that convey cooling medium angularly with respect to the longitudinal axis of passageway 62 such that cooling medium is exhausted through fluid outlet 82. In this way, inlet 80 is in fluid communication with outlet 82 through at least two passageways 78 that are arranged for fluid flow through the passageways in series-one after the other.

(44) Cooling media flows simultaneously to fluid inlets 80 for each of the chambers of annular gap 40 such that cooling medium flows concurrently through the first and second chambers of the annular gap. This parallel flow of cooling medium through separate chambers or circuits of annular gap 40 increases the flow rate of the cooling medium to increase the rate of heat transfer away from the steel shells 16, 26 in comparison to apparatus in which the internal passageway includes only a single fluid inlet and a single fluid outlet. In alternative embodiments more than two parallel circuits could be used as will be apparent to those skilled in the art.

(45) To assure against air leakage in the cooling circuits, it is preferable to submit the cooling circuit to a pressure test. In an embodiment, the pressure test includes a gauge that is linked to a computer. A typical standard for passage of such testing is zero leakage over a thirty minute period at ninety psi.

(46) Alternatively to the embodiment of FIGS. 1-3, FIGS. 4 and 5 show an embodiment wherein flange 12 includes an internal passageway 84. Internal passageway 84 extends between a flange input ports 86 and 87 and a flange output ports 88 and 89. Cooling media passes through input port 87 through internal passageway 84 of flange 12 and exits the flange through the output port 88.

(47) Internal passageway 84 of flange 12 is in communication with fluid inlets 80, 81 and fluid outlets 82, 83 such that the fluid pathway through annular gap 40 also includes passage of the cooling medium through the internal passageway 84 of flange 12. Preferably, the internal passageway 84 of flange 12 includes baffles 90, 90a, 91, and 91a that are located in the internal passageway 84 between input ports 86, 87 and output ports 88, 89. More specifically, baffle 90 is located between fluid inlet 80 and fluid outlet 82, baffle 90a is located between fluid inlet 81 and fluid outlet 83, baffle 91 is located between fluid inlet 81 and fluid outlet 82, and baffle 91a is located between fluid inlet 80 and fluid outlet 83.

(48) Cooling media flows from the input port 86 to internal passageway 84 and from internal passageway through fluid inlet 81 to passageway 70 in the annular gap that is defined between the primary baffles 68. The cooling media then flows around arcuate baffles 72 in the first chamber and through fluid outlet 83 to internal passageway 84 and output port 89. Cooling media also flows from the second input port 87 to internal passageway 84 and from internal passageway 84 through fluid inlet 80 to a second passageway 70 of the annular gap that is defined between the primary baffles 68. The cooling media then flows around arcuate baffles 72 and through a second fluid outlet 82 to internal passageway 84 and second output port 88. In this way, cooling media flows from the internal passageway 84 and concurrently through the first and second chambers of the annular gap. This increases the flow rate of the cooling medium to increase the rate of heat transfer away from the steel shells 16, 26 in comparison to apparatus in which the internal passageway includes only a single fluid inlet and a single fluid outlet.

(49) It has been found that the structure of the embodiment of FIG. 4 allows for more convenient connections to the relatively large air supply pipes such as approximately 1.5 in. because such pipes won't fit immediately adjacent and below the flange as in some embodiments. Also, the embodiment of FIG. 4 is advantageous because it cools the flange as well as the other portions of the snorkel. This is more protective of the flange because the flange is exposed to the cooler air. Also, this embodiment avoids connection to multiple inlets when the air cooled system incorporates multiple cooling circuits. Also, according to this embodiment, the inlets are located further from the molten bath than embodiments in which the supply air is provided below the flange and directly to the snorkel shells.

(50) When the snorkel serves as the up snorkel, it further includes a plurality of pipes 92. Pipes 92 are secured in the layer of refractory concrete 59a. Each of pipes 92 has a respective inlet 94 for receiving an inert gas that can be injected into molten metal flowing in passageway 62. The inert gas supports the upward movement of steel from the ladle to the degasser vessel, and creates a turbulent condition inside the vessel that significantly increases the rate of carbon reduction during the RH process. Each of said pipes 92 further includes an outlet 96 for discharging the inert gas from the pipe 92 in a direction that is generally radially inward with respect to passageway 62. The inert gas passes into molten metal in the snorkel passageway from the inner surface 60 of the refractory lining 58.

(51) As shown in greater detail in FIG. 6, pipes 92 are sealed at first shell 16. Typically, first shell 16 may be Corten B grade steel of a to 1 thickness. In contrast, pipes 92 are typically OD 310 stainless steel tubing with a wall thickness of only 0.065 in. The dissimilarity of the materials and thickness of pipes 92 and first shell 16 complicates the welding of these two ports to form an air-tight seal.

(52) Accordingly, the presently disclosed invention includes a preliminary step of welding schedule 80 stainless pipes 93 to the argon shell plenum plate 93a for each pipe. The OD 0.065 in. wall thickness tubes are then threaded through each pipe 93 after which the plenum plate 93a is seal welded to first shell 16. An air seal is then created by tig welding the OD tubes 92 to the pipes 93 on the outside.

(53) It has been found that the horizontally oriented serpentine path herein disclosed obtains superior results in comparison to snorkel cooling mechanisms known in the prior art. As specifically shown in FIG. 7, the change in diameter of a snorkel shell having a diameter of 950-1000 mm is not more than 3 to 5 mm.

(54) More specifically, Tables 6 and 7 below show dimensions of an air cold snorkel as herein disclosed at the locations illustrated in FIG. 7. Table 6 corresponds to dimension (1) and Table 7 corresponds to dimension (2). Tables 6 and 7 are based on an air cooled snorkel that was used in 170 heats. It is shown then that after 170 heats, the air cooled snorkel charged only 5 mm (0.5%) at the outside diameter of the outer shell and that there was no measurable change in the inside diameter of the inner shell.

(55) TABLE-US-00004 TABLE 6 (1) Dimension Original 972 mm After usage 977 mm Change 5 mm (0.5%)

(56) TABLE-US-00005 TABLE 7 (2) Dimension Original 975 mm After usage 975 mm Change No change

(57) TABLE-US-00006 TABLE 8 (1) Dimension Original 926.3 mm After usage 965 mm Change 38.7 mm (4.2%)

(58) TABLE-US-00007 TABLE 9 (2) Dimension Original 975 mm After usage 980 mm Change 5 mm (0.5%)

(59) As basis for comparison, Tables 8 and 9 show change in diameter of a conventional snorkel without the disclosed air cooling. Tables 8 and 9 are based on the diameter changes in the conventional snorkel after only 130 heats. In that case, the outside diameter of the outer shell (Table 8) increased 387.7 mm (4.2%) and the inside diameter of the inner hell (Table 9) increased 5 mm (0.5%).

(60) This comparison shows that heat deformation of prior art snorkels causes the shells to trumpet outwardly at the distal end. This trumpeting phenomenon can be significant. In some cases it amounts to a change in diameter of the shell of as much as 150 mm. Such dramatic deformation causes substantial destruction of the refractory layers and premature failure of the snorkel.

(61) From the forgoing description, other embodiments of the invention that is herein disclosed also will become apparent to those skilled in the art. Such embodiments are also included within the scope of the following claims.