WO1996041023A1

WO1996041023A1 - Appartus for self-sealing a submerged inlet tuyere of a molten metal reactor

Info

Publication number: WO1996041023A1
Application number: PCT/US1996/008530
Authority: WO
Inventors: Mark A. Wilkinson; Rick M. Rauenzahn; Christopher J. Nagel
Original assignee: Molten Metal Technology Inc
Current assignee: Molten Metal Technology Inc
Priority date: 1995-06-07
Filing date: 1996-06-04
Publication date: 1996-12-19
Anticipated expiration: 1997-12-07
Also published as: AU5974396A; TW323246B; ZA964736B

Abstract

An apparatus seals a submerged inlet (24) of a molten metal reactor (12) having a refractory lining (19). The apparatus includes a tuyere (20) at the submerged inlet and extending through a refractory lining (19). A plate (54) is embedded within the refractory lining (19), whereby feed, which is directed through the tuyere (20) and which seeps between the tuyere (20) and the refractory lining (19), is diverted by the plate (54) away from the tuyere (20) into the refractory lining (19) to seal the submerged inlet (24).

Description

APPARATUS FOR SELF-SEALING A SUBMERGED INLET TUYERE OF A MOLTEN METAL REACTOR

Background of the Invention

Tuyeres are commonly used for injecting various 5 feed materials, such as organic compositions, into a molten metal bath or molten salt bath. Tuyeres are typically embedded in the refractory wall that lines the reactor interior. In one embodiment, a tuyere is a pipe that extends through the refractory wall to the 0 interior surface of the refractory wall and is flush with the surface. The opening of the tuyere is usually located below the surface of the molten bath, either on the side or the bottom of the reactor wall. As the feed material is directed into the molten bath, a 5 portion of the feed material can be deflected back toward the wall. Consequently, the feed material that is directed into the molten bath is subject to a significant amount of static pressure and forms an accretion of feed and partially decomposed feed at the 0 opening of the tuyere.

Often, because of the high temperatures encountered in the reactor, expansion occurs diffentially in the refractory material and the tuyere, thereby causing a void space to form between the tuyere 5 and the refractory material. Also, the tuyere typically does not reach the temperature of the refractory material, because the feed material is not preheated to the temperature of the bath. Therefore, feed material can seep from the reactor between the 0 tuyere and the refractory lining to the exterior of the reactor. One attempt to avoid seepage of the feed material from the molten bath includes employing refractory bricks constructed to very narrow dimensional tolerances. However, this is typically very difficult and time consuming. Another option is to use a submerged lance for injection of feed into the molten bath. However, some lances are not very durable and are consumed quickly by the molten bath.

Therefore, a need exists for an apparatus to eliminate or minimize the problems described above.

Summary of the Invention

The present invention relates to an apparatus for self-sealing a submerged feed inlet of molten metal reactor. The apparatus includes a tuyere at the submerged inlet and extending through a refractory lining of the reactor. A plate projects from the tuyere and is embedded within the refractory lining, whereby feed, which is directed through the tuyere and which seeps between the tuyere and the refractory lining, is diverted by the plate away from the tuyere into the refractory lining to seal the submerged inlet.

In another embodiment, the apparatus includes a tuyere at the submerged inlet and extending through the refractory lining. An assembly lining surrounds the tuyere and a portion of the refractory lining and is embedded within the refractory lining, whereby feed, which is directed through the tuyere and which seeps into the refractory lining, is diverted by the assembly lining toward the molten bath to seal the submerged inlet.

In a further embodiment, the apparatus includes a tuyere at the submerged inlet and extending through the refractory lining. A plate projects transversely from the tuyere and is embedded within the refractory lining, whereby feed, which is directed through the tuyere and which seeps into the refractory lining is diverted by the plate toward the molten bath to at least partially seal the submerged inlet. An assembly lining surrounds the tuyere, plate and a portion of the refractory lining and embedded within the refractory lining, whereby feed, which is directed through the tuyere and which seeps into the refractory lining, is further diverted by the assembly lining toward the molten bath to seal the submerged inlet.

This invention provides several advantages. One advantage is that the plate provides a means for inhibiting the seepage of feed material from the reactor. Another advantage is that feed material that escapes into the void space is directed away from the tuyere into a portion of the refractory material that has a temperature sufficiently high to cause at least a portion of the feed material to dissociate. An additional advantage is that the plate is relatively easy to fabricate and to place within the refractory wall. Another advantage is that liquid and gas accumulation within the refractory are inhibited and are directed back into the bath. Brief Description of the Drawings

Figure 1 is a cut-away side elevational view of one embodiment of the apparatus of the present invention in a molten bath of a reactor. Figure 1A is a cut-away side elevational view of the submerged portion of the tuyere and plate shown in Figure 1.

Figure 2 is a cut-away side elevational view of a second embodiment of the tuyere and plate shown in Figures 1 and 1A.

Figure 3 is a cut-away side elevational view of a third embodiment of the tuyere and plate shown in Figures 1 and 1A.

Figure 4 is a cut-away side elevational view of a fourth embodiment of the apparatus including a tuyere and tuyere assembly lining.

Detailed Description of the Invention

The features and other details of the apparatus of the invention will now be more particularly described with reference to the accompanying drawings and pointed out in the claims. The same numeral present in different figures represents the same item. It will be understood that the particular embodiments of the invention are shown by way of illustration and not as limitations of the invention. The principle features of this invention can be employed in various embodiments without departing from the scope of the invention. All parts and percentages are by weight unless otherwise specified. The present invention relates generally to an apparatus for sealing a submerged inlet of a molten metal reactor having a refractory lining. A process and apparatus for dissociating waste in molten baths are disclosed in U.S. Patents 4,574,714 and 4,602,574, issued to Bach et al. The method and apparatus described by these patents can destroy polychlorinated biphenyls and other organic wastes, optionally together with inorganic wastes. Another apparatus and method for dissociating waste in a molten bath and for forming gaseous, vitreous and molten metal product streams from the waste are disclosed in U.S. Patent 5,301,620, issued to Nagel et al.

One embodiment of the invention is illustrated in Figure 1. Therein, system 10 includes reactor 12 for containing a molten bath suitable for dissociating a feed material. Examples of suitable reactors includes appropriately modified steel aking vessels known in the art, such as K-BOP, Q-BOP, argon-oxygen decarbonization furnace (AOD) , BOF, etc. Also, another suitable reactor is disclosed in U.S. Patent 5,301,620. Reactor 12 includes upper portion 14 and lower portion 16. Off-gas outlet 18 extends from upper portion 14 and is suitable for conducting an off-gas composition out of reactor 12. Reactor 12 has metal shell 17 and is lined with refractory lining 19. Refractory lining 19 can be bricks composed of aluminum oxide (A1₂0₃) , silicon dioxide (Si0₂) , thorium dioxide (Th0₂) , magnesium oxide ( gO) , zirconium dioxide (Zr0₂) , or other suitable material, such as a ceramic. The refractory lining can be coated with a gas impermeable coating, such as sputtered aluminum oxide.

Tuyere 20 is located at lower portion 16 of reactor 12 and can be a multiple concentric tuyere, in particular, a triple concentric tuyere. Tuyere 20, which is a concentric tuyere, includes feed material tube 22 for injection of a feed material at feed material inlet 24. Line 26 extends between feed material tube 22 and feed material source 28 for conducting feed material from feed material source 28.. by pump 30 to feed material tube 22. Oxidizing agent tube 32 of tuyere 20 is disposed concentrically about feed material tube 22 at tuyere inlet 24. Line 35 extends between oxidizing agent source 36 and oxidizing agent tube 34 for conducting a suitable oxidizing agent to oxidizing agent tube 34. Oxidizing agent can be oxygen or air which can oxidize a portion of the waste to form a dissociation product, such as carbon monoxide or carbon dioxide. Shroud gas tube 38 of tuyere 20 is disposed concentrically about oxidizing agent tube 32 at inlet 24. Line 40 extends between shroud gas tube 38 and shroud gas ■ source 42 for conducting a suitable shroud gas through the concentric opening between oxidizing agent tube 32 and shroud gas tube 38 to inlet 24. Shroud gas can be an inert gas, such as argon or nitrogen, or a hydrocarbon, such as propane.

Bottom tapping spout 44 extends from lower portion 16 of reactor 12 and is suitable for removal of molten metal from reactor 12. Induction coil 46 is located at lower portion 16 for heating molten bath 48 in reactor 12. It is to be understood that, alternatively, reactor 12 can be heated by other suitable means, such as by oxyfuel burners, electric arcs, etc.

Molten bath 48 is formed within reactor 12. Molten bath 48 can include at least one metal or molten salt thereof. Examples of suitable metals include iron, copper, nickel, zinc, etc. Examples of suitable salts include sodium chloride, potassium chloride, etc. Molten bath 48 can also include more than one metal. For example, molten bath 48 can include a solution of miscible metals, such as iron and nickel. In one embodiment, molten bath 48 can be formed substantially of elemental metal. Alternatively, molten bath 48 can be formed substantially of metal salts. Molten bath 48 is formed by at least partially filling reactor 12 with a suitable metal or salt. In another embodiment, molten bath 48 is formed of immiscible metals. These immiscible metals can include first metal 50, such as iron, and second metal 52, such as copper. Molten bath 48 is then heated by a suitable means, such as an induction coil or oxyfuel burner, not shown.

Suitable operating conditions of system 10 include, for example, a temperature which is sufficient to at least partially convert carbonaceous feed by dissociation to elemental carbon and other elemental constituents. Generally, a temperature in the range of between about 1,300° and 1,700°C is suitable.

Vitreous layer 54 is formed on molten bath 48. Vitreous layer 54 is substantially immiscible with molten bath 48. Vitreous layer 54 can have a lower thermal conductivity than that of molten bath 48.

Radiant heat loss from molten bath 48 can thereby be reduced to significantly below the radiant heat loss from molten bath 48 where no vitreous layer is present. Typically, vitreous layer 54 includes at least one metal oxide. Vitreous layer 54 can contain a suitable compound for scrubbing halogens, such as chlorine or fluorine, to prevent formation of hydrogen halide gases, such as hydrogen chloride. In one embodiment, vitreous layer 54 comprises a metal oxide having a free energy of oxidation, at the operating conditions of system 10, which is less than that from the oxidation of. atomic carbon to carbon monoxide, such as calcium ' oxide (CaO) .

As can be seen in Figure 1A, a self-sealing submerged feed inlet includes tuyere 20 and plate 54, positioned about shroud gas tube 38 in refractory lining 19. Plate 54 has an interior radius about equal to the outside diameter of tuyere 20. An outside edge of plate 54 extends into zone 56 within refractory lining 19. Zone 56 is at conditions sufficient to dissociate a substantial portion of the feed material present therein.

Void space 58 extends between refractory lining 19 and tuyere 20 from the interior surface 21 of refractory lining 19 to plate 54. Void space 58 can form as a result of the differences in the thermal expansion of the refractory material 19 and tuyere 20 at the operating temperature of the reactor.

Plate 54 extends from the outside circumference of tuyere 20 into the refractory lining 19. In one embodiment, annular plate has a radius of about 8.0 centimeters and a thickness of 0.1 centimeters. Plate 54 is about 10.0 centimeters from surface 21 of refractory lining 19. In another embodiment, plate 54 is corrugated. At the operating conditions of reactor 12, the temperature at the outside edge of the plate is in the range of between about 800 and 1,100°C. In addition to being heated by molten metal bath, plate 54 can be heated by other suitable means, such as resistant heating by conducting an electrical current though the plate. Annular plate is considered thin so that the ratio ( (K_r/L_r) / (K_r/L_f) ) / (__,/-_-) is greater than about one. K_r and K, represent the thermal conductivity of the refractory lining and the annular plate, respectively. L_r represents the distance from refractory surface 21 to plate 54. L_f represents the distance from shroud gas tube 38 to outer edge 55 of plate 54. δ_{ represents the thickness of plate 54.

Plate 54 is constructed of a material that can withstand the temperature and conditions of the molten bath 46 and feed material at the operating temperature of reactor 12. In one embodiment, plate 54 is constructed of a metal selected from the group consisting of stainless steel, titanium, tungsten, tantalum and zirconium. Also, a ceramic can be used. Plate 54 is attached to tuyere 20 in a manner to form seal 53 between plate 54 and tuyere 20 which prevents substantial passage of the feed material therethrough. For example, plate 54 can be welded to tuyere 20. Thermocouples 62 can be positioned at points on plate 54 to monitor the temperature of annular plate 54. Tuyere 24 and plate 54 can be in tuyere assembly 69. Tuyere assembly 69 can be formed of a refractory brick with tuyere assembly lining 70 or "can" surrounding tuyere assembly 69. Tuyere assembly lining 70 can be formed of a metal, ceramic or plasma coating. A suitable material includes one that has a melting point higher than the operating conditions of the molten bath and is resistive to chemical attack. This material includes tungsten, zirconium oxide and sputtered alumina. In one embodiment, tuyere assembly lining 70 is formed of a metal or plasma coating to prevent gas egress through the sides of tuyere assembly 69. The plasma coating is material applied by a plasma spraying process, as is known in the art.

Feed material, such as a suitable gaseous, liquid or solid feed, is directed into molten bath 48 from feed material source 28 through line 26 to feed material tube 22 in tuyere 20. Feed material enters molten bath 48 at inlet 24. Oxygen or another oxidizing agent is directed from oxidizing agent source 35 through line 34 to oxidizing agent tube 38. A suitable shroud gas, such as a hydrocarbon or inert gas, is directed from shroud gas source 42 through line 40 to shroud gas tube 38.

As the feed material is directed into molten bath 48, a portion of the feed material is deflected by accretion 63 formed at tuyere opening 24 and the static pressure of molten bath 48 toward refractory lining 19 and void space 58 which is adjacent to refractory lining 19. The feed material travels along the outside of the tuyere 20 in direction 64 toward the exterior of reactor 12. Plate 54 deflects at least a portion of feed material escaping from molten bath 48 in a direction transverse of the axis extending the length of tuyere 20. The feed material can be directed into zone 56 which can have conditions to dissociate the feed material into dissociated products, such as carbon oxide gas. The dissociated products can remain within refractory lining during the remainder of the operating run of reactor 12 blocking further escape of feed materials and dissociation products, thereby self- sealing the submerged feed inlet. A portion of the dissociation products can seep through refractory lining 19 to molten bath 48.

In Figure 2, a second embodiment of the invention is shown. Conical plate 66 is positioned about tuyere 20. Outer edge 68 extends toward molten bath 48 to direct escaping feed material transversely of the axis of the tuyere and coward molten bath 48. The feed material can be directed into zone 56 which can have conditions to dissociate the feed material into dissociated products. These products can remain within the refractory lining to further block further escape of feed materials and dissociation products. In another embodiment, the plate extends perpendicularly from the tuyere and then conically toward the molten metal bath. In Figure 3, a third embodiment of the invention is shown. A series of plates can be used. For instance, second plate 90 is positioned about tuyere 20. Second plate 90 deflects at least an additional portion of feed material escaping from molten bath 48. Second plate 90 can be parallel to plate 54. In one embodiment, second plate 90 has a diameter greater than plate 54. Preferably, plate 54 is positioned so that the temperature on plate 54 is above the dissociation temperature of the feed material, and second plate 90 is positioned at a temperature above the vaporization temperature of the dissociated products. In other embodiments, multiple plates are used, such as three plates. Also, the plates can be formed of different materials, such as one plate is formed of a metal, and a second plate is formed of ceramic. Further, each plate can be individually heated by suitable heating means.

In Figure 4, a fourth embodiment of the invention is shown. Tuyere assembly 69 has tuyere assembly lining 70 without a plate. Tuyere assembly lining 70 allows the gaseous products of dissociations and liquids to be contained in tuyere assembly 70 and directed into molten bath in region 92. Tuyere assembly, lining 70 can be connected to tuyere 20 by means similar to seal 53 which connects plate 54 to tuyere 20.

Equivalents

Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to specific embodiments of the invention described specifically herein. Such equivalents are intended to be encompassed in the scope of the following claims.

Claims

1. An apparatus for sealing a submerged inlet of a and molten metal reactor having a refractory lining a molten bath, comprising: a) a tuyere at said submerged inlet and extending through the refractory lining; and b) a plate projecting transversely from the tuyere and embedded within the refractory lining, whereby feed, which is directed through the tuyere and which seeps into the refractory lining, is diverted by said plate toward the molten bath to seal the submerged- inlet.

2. The apparatus of Claim 1 wherein the plate is normal to the axis of said tuyere.

3. The apparatus of Claim 1 wherein the plate is conically disposed about said tuyere.

4. The apparatus of Claim 2 wherein the tuyere is a multiple concentric tuyere.

5. The apparatus of Claim 4 wherein the tuyere is a triple concentric tuyere.

6. The apparatus of Claim 1 wherein the refractory lining includes refractory bricks.

7. The apparatus of Claim 1 wherein the refractory lining includes a ceramic.

8. The apparatus of Claim 6 wherein the refractory bricks include aluminum oxide.

9. The apparatus of Claim 6 wherein the refractory bricks include thorium dioxide.

10. The apparatus of Claim 6 wherein the refractory bricks include magnesium oxide.

11. The apparatus of Claim 6 wherein the refractory bricks include zirconium oxide.

12. The apparatus of Claim 6 wherein the refractory bricks include silicon oxide.

13. The apparatus of Claim 1 wherein the plate includes a metal.

14. The apparatus of Claim 13 wherein the metal is selected from the group consisting of stainless steel, titanium and zirconium.

15. The apparatus of Claim 14 wherein the plate includes a ceramic.

16. The apparatus of Claim 1 wherein the plate includes means for heating said plate.

17. The apparatus of Claim 16 wherein means for heating said plate can heat the plate to the temperature of vaporization of a feed material.

18. The apparatus of Claim 16 wherein means for heating said plate can heat the plate to the temperature of dissociation of a feed material.

19. The apparatus of Claim 1 wherein multiple plates are disposed about said tuyere.

20. The apparatus of Claim 19 wherein each of the multiple plates include means for heating a plate.

21. The apparatus of Claim 1 wherein a second plate is disposed about said tuyere.

22. The apparatus of Claim 21 wherein the first plate is formed of a ceramic and the second plate is formed of a metal.

23. A tuyere assembly which includes the apparatus of Claim 1.

24. The tuyere assembly of Claim 23 which includes a tuyere assembly lining.

25. The tuyere assembly of Claim 24 which includes a tuyere assembly lining that surrounds the tuyere and a portion of the refractory lining.

26. The tuyere assembly of Claim 25 wherein said tuyere assembly lining includes a metal.

27. The tuyere assembly of Claim 26 wherein said metal is gas impermeable.

28. The tuyere assembly of Claim 25 wherein said tuyere assembly lining includes a ceramic material.

29. The tuyere assembly of Claim 25 wherein said tuyere assembly lining includes a coating material applied by a plasma spraying process.

30. The tuyere assembly of Claim 29 wherein said coating material is gas impermeable.

31. An apparatus for self-sealing a submerged inlet of a molten metal reactor having a refractory lining, comprising: a) a tuyere at said submerged inlet and extending through the refractory lining; and b) a plate embedded within the refractory lining and positioned annularly about the tuyere in a direction parallel to an interior surface of the refractory lining proximate to the tuyere, whereby feed, which is directed through the tuyere and which seeps into the refractory lining, is diverted by said plate in a direction toward the interior surface of the refractory lining to seal the submerged inlet.

32. In a tuyere contained in a refractory lining in a molten metal reactor for directing a feed material into a molten metal reactor having a molten bath:

The improvement comprising a plate embedded within the refractory lining and extending transversely from the tuyere, whereby feed material seeping into the refractory lining from the molten bath is diverted by said plate toward the molten bath into the refractory lining to seal the tuyere.

33. An apparatus for sealing a submerged inlet of a molten metal reactor having a refractory lining and a molten bath, comprising: a) a tuyere at said submerged inlet and extending through the refractory lining; b) a first plate projecting transversely from the tuyere and embedded within the refractory lining; and c) a second plate projecting transversely from the tuyere and embedded within the refractory lining, whereby feed, which is directed through the tuyere and which seeps into the refractory lining, is diverted by said first plate and said second plate toward the molten bath to seal the submerged inlet.

34. A tuyere assembly for sealing a submerged inlet of a molten metal reactor having a refractory lining and a molten bath, comprising: a) a tuyere at said submerged inlet and extending through the refractory lining; and b) an assembly lining that surrounds the tuyere and a portion of the refractory lining and embedded within the refractory lining, whereby feed, which is directed through the tuyere and which seeps into the refractory .. lining, is diverted by said assembly lining toward the molten bath to seal the submerged inlet.

35. A tuyere assembly for sealing a submerged inlet of a molten metal reactor having a refractory lining and a molten bath, comprising: a) a tuyere at said submerged inlet and extending through the refractory lining; b) a plate projecting transversely from the tuyere and embedded within the refractory lining, whereby feed, which is directed through the tuyere and which seeps into the refractory lining is diverted by said plate toward the molten bath to at least partially seal the submerged inlet; and

c) an assembly lining that surrounds the tuyere, plate and a portion of the refractory lining and embedded within the refractory lining, whereby feed, which is directed through the tuyere and which seeps into the refractory lining, is further diverted by said assembly lining toward the molten bath to seal the submerged inlet.

36. A tuyere assembly for sealing a submerged inlet of a molten metal reactor having a refractory lining and a molten bath, comprising: a) a tuyere at said submerged inlet and extending through the refractory lining; b) a plurality of plates projecting transversely from the tuyere and embedded within the refractory lining, whereby feed, which is directed through the tuyere and which seeps into the refractory lining is diverted by said plate toward the molten bath to at least partially seal the submerged inlet; and c) an assembly lining that surrounds the tuyere, said plates and a portion of the refractory lining and embedded within the refractory lining, whereby feed, which is directed through the tuyere and which seeps into the refractory lining, is further diverted by said assembly lining toward the molten bath to seal the submerged inlet.