LU502500B1

LU502500B1 - Tuyere for a metallurgical furnace

Info

Publication number: LU502500B1
Application number: LU502500A
Authority: LU
Inventors: Nicolas Maggioli
Original assignee: Wurth Paul Sa
Priority date: 2022-07-13
Filing date: 2022-07-13
Publication date: 2024-01-18
Also published as: WO2024013268A1

Abstract

The invention provides a tuyere that comprises a conical hollow tuyere body with an inner surface and an outer surface, the tuyere extending along a first axis from an inlet end to an opposite outlet end, the tuyere body having a tuyere tip at the outlet end and a conical connection surface at the inlet end. The conical connection surface is configured for engaging a conical seat of a tuyere holder or tuyere cooler. Advantageously, the tuyere further comprises a corrugated portion on the outer surface of the tuyere. The corrugated portion comprises at least one recess having an open curved profile and a surface enclosing the at least of recess. The corrugated portion is arranged and configured for, during operation of the metallurgical furnace, supporting burden material and forming a scaffold of the burden material.

Description

TUYERE FOR A METALLURGICAL FURNACE

Technical field

[0001] The present invention generally relates to the field of metallurgical furnaces, and in particular to a tuyere for blowing gas into a metallurgical furnace having an improved lifetime.

Background of the Invention

[0001] Tuyeres are essential parts of metallurgical furnaces, such as blast furnaces, as they enable to blow gases into the furnace away from the wall and thus prevent damages to this wall. Modern blast furnaces commonly comprise more than twenty such tuyeres around the furnace wall. The tuyeres are usually inserted into a tuyere cooler comprising a circuit for a cooling fluid. Tuyere and tuyere cooler are tightly pressed into an opening of the furnace wall, called tuyere cooler holder.

Moreover, the tuyeres themselves also generally comprise at least one circuit for a cooling fluid.

[0002] Because of the very harsh conditions in the tuyere breast, the tuyere and often the tuyere cooler can be damaged and require replacing after some time. The tuyere parts are often burnt or worn out by abrasion, impeding the normal functioning of the furnace. Their damage may also provoke gas or water leakages outside of the furnace with high risks for the health and safety of the workers around the furnace. Currently, a tuyere with a cooling circuit of a single chamber design, which is getting worn by abrasion or smelting and starts leaking into the furnace, is bypassed, leading to its complete failure. This implies an unscheduled outage of the metallurgical furnace to replace the defective tuyere. The lifetime of a tuyere varies from several days to several months, depending on the tuyere design and productivity of the furnace, which demands recurrent maintenance operation in relatively short intervals of time. Unscheduled outage of the metallurgical furnace to replace a defective tuyere lasts minimum 4 to 8 hours. The loss of production of such an outage financially exceeds the cost of the whole set of tuyeres installed in the furnace. Development of tuyere parts, in particular tuyeres, of a metallurgical furnace presenting an improved resistance to heat and impacts from liquid metal droplets, raceway material or descending burden, is hence important in the operation of blast furnaces itself.

[0003] Solutions have been developed to improve the design of the tuyeres and increase their resistance to abrasion. Most of these improvements involve either coating the outer surface with a wear resistant layer or providing the tuyere with more cooling pipes.

[0004] Amongst the solutions known in the art, CN 207793315 U discloses the coating of the tuyere tip and outer surface of the tuyere with an abrasion resistant alloy which comprises both a wear-resisting transition layer to enhance adherence with the tuyere material and a wear-resisting operational layer on top of the wear- resisting transition layer to provide for the increased resistance to abrasion. While the use of such an abrasion resistant alloy does enhance the resistance of the tuyere to abrasion, it will not protect the tuyere from damage caused by liquid metal droplets, raceway material or falling burden. Tuyere failure is thus merely delayed but not completely prevented.

[0005] Another solution is disclosed in EP 2 669 388 A1. The tuyere comprises two nose pipes and three different cooling pipes arranged above each other to form a stack between the inner and outer surface of the tuyere. According to

EP 2 669 388 A1, wear of the outer surface of the tuyere leading to a leaking of the outermost cooling pipe would only require this pipe to be bypassed, instead of the whole tuyere, as the two remaining cooling pipes would still provide enough cooling.

However, such tuyeres are time-consuming and expensive to produce, and do not resolve the problem of excessive wear of the tuyere outer surface.

Object of the invention

[0002] Itis thus an object of the present invention to provide an improved design of a tuyere for a metallurgical furnace having an extended lifetime without the afore mentioned drawbacks.

[0003] This object is solved by a tuyere according to claim 1.

General Description of the Invention

[0004] The invention overcomes the above discussed deficiencies and disadvantages by providing a tuyere for a metallurgical furnace, the tuyere comprising a conical hollow tuyere body with an inner surface and an outer surface.

The tuyere extends along a first axis from an inlet end to an opposite outlet end, and the tuyere body has a tuyere tip at the outlet end and a conical connection surface at the inlet end. The conical connection surface is configured for engaging a conical seat of a tuyere holder or tuyere cooler.

[0005] The tuyere further comprises a corrugated portion on the outer surface of the tuyere, the corrugated portion comprising at least one recess having an open curved profile and a surface enclosing the at least of recess, and said corrugated portion being arranged and configured for, during operation of the metallurgical furnace, supporting burden material and forming a scaffold of said burden material.

In other words, falling burden material is retained inside the recess and will aggregate both in the recess and on the surface of the corrugated portion. The corrugated portion thus promotes the formation of a scaffold of burden material and holds this scaffold in place. This scaffold not only protects the tuyere from liquid metal droplets and from the wear caused by impacts from raceway material but also from falling burden.

[0006] The corrugated portion is preferably arranged on an upper outer surface of the tuyere, i.e. on the portion of the outer surface which is proximal to falling burden material and on which falling material may aggregate.

[0007] “Corrugated” means in the context of the present application a series of preferably parallel ridges and recesses. In other words, in the present text, a corrugated portion is a surface that looks like a series of waves when seen from one end of the tuyere. In the context of the present application, the term “recess” means a space set back in a surface and is meant as a synonym of furrow, groove or corrugation.

[0008] A main advantage of the tuyere is that it boosts, promotes and increases the formation of a scaffold thereon, and thereby the formation of a protective layer.

Such a protective layer of burden material behaves like an insulation layer and decreases the heat load of the tuyere resulting in attenuated heat load picks.

[0009] Moreover, during operation of the metallurgical furnace, falling burden, raceway material and liquid metal droplets advantageously aggregate into and reinforce the scaffold. The heat and/or abrasion may damage the scaffold but not the tuyere. In other words, the scaffold may continuously be consumed and regenerated during operation of the metallurgical furnace so that the outer surface of the tuyere is not exposed to the harsh conditions of the furnace but protected therefrom by the scaffold. Thermal and/or wear damages mostly occur to the scaffold of burden material and damages to the tuyere are therefore strongly limited which dramatically improves the lifetime of the tuyere.

[0010] Advantageously, the tuyere comprising a corrugated portion will be resistant enough to ensure a continuous operation of the tuyere even with some loss of tuyere forming material under heat radiation due to the scaffold of burden material, which will be constantly formed and renewed.

[0011] In other words, such a tuyere that enables and promotes the creation, renewal and regeneration of a scaffold of burden material on top of the tuyere is protected against excessive heat load and abrasion/erosion wear, without having to change the process parameters of a furnace (such as e.g. blast and burden composition).

[0012] Retaining burden materials and forming a self-protection accretion layer such as a scaffold of burden material corresponds to a so-called stone box effect.

[0013] Another advantage of such a tuyere is that the at least one recess of the corrugated portion has an open curved profile. The recess can present any kind of profile, such as e.g. round, square or triangular, as long as the profile widens when seen from the inner surface toward the outer surface of the tuyere.

[0014] Such an open curved profile is easier to manufacture than a close curved profile, such as e.g. a dovetail design. Indeed, a recess presenting an open curved profile can be directly cast-in during production of the tuyere and does not require any subsequent manufacturing step, contrary to a close curved profile which requires machining or milling of a tuyere to remove material corresponding to the recess.

[0015] In embodiments, the corrugated portion may be made of an alloy of nickel, chromium, zirconium, titanium and/or tungsten, which further protects the corrugated portion from falling droplets and abrasion.

[0016] A recess being coated with a layer of protective material, such as e.g. a refractive material is still within the scope of the present disclosure. It is however a preferred embodiment that the recess is not filled to the rim with the protective material, so as to accommodate and retain falling burden material to form a scaffold during operation of the blast furnace.

[0017] Another advantage is that the modifications of the tuyere design involve / comprise the formation of the corrugated portion on the outer surface. These modifications are directly embedded into the manufacturing process of the tuyere, i.e. they are made at the same time as the tuyere.

[0018] The costs related to these modifications are virtually non-existent, or at least strongly reduced, as there is no need to manufacture additional protective parts such as e.g. additional protective layers on the outer surface of a conventional tuyere.

[0019] Yet another advantage of tuyere is that it will not require any design changes in the overall assembly. These tuyeres can be easily be used in new metallurgical furnaces or can be used to retrofit existing furnaces during a maintenance operation, such as e.g. replacement of a damaged tuyere.

[0020] In preferred embodiments, the corrugated portion comprises a plurality of recesses, each recess of the plurality of recesses having an open curved profile.

Preferably, the corrugated portion comprises between three and eleven recesses, more preferably the corrugated portion comprises between five and nine recesses.

[0021] In embodiments, the surface of the corrugated portion encloses the plurality of recesses. It may extend between each recess of the plurality of recesses.

[0022] Advantageously, a corrugated surface comprising a plurality of recesses retains any falling burden material easily, thereby improving the formation of the scaffold and the resulting stone box effect.

[0023] In the same or alternative embodiments, each recess of the corrugated portion may be discontinuous. The resulting stone box effect is maximized because of the accretions of burden material in the recesses and on top of the tuyere.

[0024] Advantageously, the thickness of the tuyere measured from the inner surface to the outer surface comprises a thicker portion and the recesses of the corrugated portion are provided in the thicker portion. In other words, the tuyere has an eccentric shape which creates an extra thickness of tuyere forming material on a portion of the outer surface of the tuyere. The recesses of the corrugated portion are formed in this extra thickness so as not to weaken other thinner portions of the tuyere. The extra thickness provides for the necessary stability and support to form the corrugated portion.

[0025] In preferred embodiments, the recesses are parallel to each other and essentially extend along a second axis.

[0026] Advantageously, the second axis is not co-axial with the first axis. The second axis not being co-axial with the first axis means that the recesses are arranged and oriented so as to form an angle with respect to the axis of the tuyere.

The higher the angle is, the better the retention of burden material would be inside the recesses, thus improving the formation of a scaffold protecting the upper outer surface of the tuyere. If the first and second were co-axial, burden material would not be retained by the recesses as the recesses would be oriented alongside the flow of falling material.

[0027] Preferably, the second axis is perpendicular to the first axis. If the recesses are arranged so as to be perpendicular to the direction of the flow of burden material, the retention of falling burden material, the formation of the scaffold and the resulting stone box effect is thereby maximized. This specific orientation of the recesses enhances the protection of the tuyere against excessive heat load and abrasion wear, thus enhancing its lifetime. However, orientation can be in chevron.

[0028] Recesses may have any shape, but preferably all recesses have a similar shape. In embodiments, the recesses may have a linear shape, i.e. the recesses are formed as straight lines presenting an open curved profile. Alternatively, the recesses may have a wavy shape or an angular shape.

[0029] Advantageously, the tuyere can be made of any metallic material or an alloy of any metallic material to ensure its resistance to heat and abrasion. However, the tuyere is preferably made of copper, copper alloy, steel or steel alloy.

[0030] In embodiments, the surface of each recess forming the corrugated portion is covered with a layer of a metallic material or an alloy of a metallic material, to further enhance its wear resistance to heat and abrasion. Such an additional layer provides an additional protection against wear due to falling burden material and liquid metallic (mostly iron) droplets. Preferably the surface of each recess is covered with a layer of copper, copper alloy, nickel, nickel alloy, steel or steel alloy.

[0031] According to the same or alternative embodiments, the surface of the corrugated portion and/or the tuyere tip are covered with a layer of a hardfacing material, such as e.g. Cr/Fe alloys and/or Cr/Ni alloys like Inconel 625. Hardfacing is the deposition of thick coatings of hard, wear-resistant materials on a worn or new component surface that is subject to wear in service. It is usually welded to the base material, and generally takes the form of specialized electrodes for arc welding or filler rod for oxyacetylene and gas tungsten arc welding. Surfaces covered with hardfacing material are the surfaces which are the most exposed to heat or abrasion. Covering them with hardfacing material improves their thermal and wear- resistance.

[0032] The tuyere can be of any kind. In particular, the tuyere may comprise a single chamber, a double chamber and/or a spiral chamber. In preferred embodiments, the tuyere further comprises a cast-in nose pipe and a double chamber, wherein the double chamber may preferably be made of an internal chamber and a spiral serpentine pipe. Advantageously, due to the internal chamber and the serpentine pipe, the nose pipe would not leak even if the tip of the tuyere get worn out. The second chamber (the internal chamber or the serpentine pipe) of the double chamber design provides for back-up cooling, should the first chamber (the serpentine pipe or the internal chamber) not be enough to ensure a sufficient cooling of the tuyere and/or should suffer damages.

[0033] Preferably, the pipe of the nose pipe is made of a metallic material or an alloy of a metallic material. More preferably, the pipe is made of copper, copper alloy, nickel, nickel alloy, steel or steel alloy. Such materials have a high smelting temperature, thereby providing the pipes with a protection against wear and liquid iron droplets once the outer surface of the tuyere has been worn out.

[0034] In embodiments, the tuyere further comprises injection channels arranged and configured for, during operation of the metallurgical furnace, directly injecting burden material above the tuyere. Advantageously, such injection channels promote the formation of the scaffold in and above the recesses of the corrugated portion, and thereby improves the thermal and wear protection of the tuyere.

[0035] According to the same or other embodiments, the tuyere further comprises straight channels arranged and configured for, during operation of the metallurgical furnace, using an electronic thickness measurement device.

[0036] It is another object of the present invention to provide a method for manufacturing a tuyere according to the invention. In embodiments, the tuyere is manufactured by machining, casting, welding, forging or any combination of these manufacturing methods. Preferably, the recesses of the corrugated portion are manufactured by casting.

[0037] It is yet another aspect of the invention to provide a metallurgical furnace comprising a tuyere arranged for feeding hot gas inside the metallurgical furnace, wherein the tuyere is a tuyere according to the invention.

[0038] The method according to the invention and the metallurgical furnace according to the invention retain all the advantages of the tuyere according to the invention.

Brief Description of the Drawings

[0039] Further details and advantages of the present invention will be apparent from the following detailed description of not limiting embodiments with reference to the attached drawing, wherein:

Fig.1 is a schematic view of a general arrangement of a tuyere;

Fig.2 is a schematic view of a tuyere according to the invention;

Fig.3 is a schematic sectional perspective view of the tuyere of Fig.2 along the axis A-A; and

Fig.4 is a schematic sectional view of the tuyere of Fig.2 along the axis A-A.

Description of Preferred Embodiments

[0040] In a metallurgical furnace, a number of tuyeres 10 are generally located inside the furnace wall 12 in order to feed hot gas into the furnace. As displayed on

Fig.1, a tuyere 10 is arranged in a furnace wall 12, usually within a tuyere cooler 14, which is, in turn arranged in a tuyere holder 16. The tuyere 10, tuyere cooler 14 and tuyere holder 16 are securely wedged into each other by means of conical surfaces narrowing in the direction of the interior of the furnace.

[0041] The tuyere 10 has a conical hollow tuyere body 18 with an inner surface and an outer surface 22. The tuyere body 18 extends along a first axis A-A from an outlet end 24 opening into the interior of the furnace to an inlet end 26 receiving the tip of a blowpipe 28.

[0042] The outer surface of the tuyere comprises a corrugated portion 34 as displayed on Fig.2. The corrugated portion 34 is formed on the upper portion 30 of the outer surface 22 of the tuyere 10. In the present text, the adjectives upper and lower must be considered as referring to the relative orientation of the tuyere in an operational position, i.e. as referring to the orientation of the tuyere as installed in the metallurgical furnace. The upper portion 30 of the outer surface 22 is therefore the portion of the outer surface facing the top of the furnace, and the lower portion 32 of the outer surface 22 is the portion of the outer surface facing the bottom of the furnace.

[0043] As displayed on the embodiment of Fig.2, the corrugated portion 34 comprises seven recesses 36 arranged and configured for, during operation of the metallurgical furnace, supporting burden material and forming a scaffold of burden material on top of the tuyere 10. The corrugated portion 34 must comprise at least one recess 36 to retain and support falling burden material. However, the corrugated portion 34 might comprise any suitable number of recesses 36 to obtain the desired effect, depending on the characteristics of the tuyere such as its length, and on the operating conditions of the metallurgical furnace, so that the embodiment of Fig.2 is only an illustrative, non-limiting embodiment.

[0044] The recesses 36 are equally distributed along a length of the corrugated portion 34. In alternative embodiments, the space between two adjacent recesses might vary from one group of two recesses to a neighbouring one (not shown). For example, the space between two adjacent recesses might be bigger near the inlet end of the tuyere. Alternatively, the space might be bigger near the outlet end of the tuyere.

[0045] Recesses 36 are not formed as one continuous recess but are formed as parallel recesses 36, discontinuous from each other. As displayed on Fig.2 to Fig.4, the recesses 36 have a linear shape and round open-curved profile 38 promoting the retention and support of falling burden material to form a scaffold thereof on the upper portion 30 of the outer surface 22 of the tuyere 10. Recesses 36 might present any suitable shape, such as e.g. a wavy or angular shape, and any kind of open curved profile, such as e.g. square or triangular (not shown).

[0046] The parallel recesses 36 essentially extend along a second axis B-B. The second axis B-B is perpendicular to the first axis A-A of the conical hollow tuyere body 18. In other words, the recesses 36 are perpendicular to the axis of the tuyere body 18. Such an orientation of the recesses maximizes the retention of falling burden material, the formation of the scaffold and the resulting stone box effect.

[0047] Every alternative embodiment, even if not explicitly displayed, wherein the second axis B-B is neither perpendicular nor co-axial to the axis A-A of the tuyere body is also part of the present disclosure and still within the scope of the present invention.

[0048] According to the embodiments displayed on the sectional views of Fig.3 and Fig.4, the tuyere 10 comprises a cast-in nose pipe 40, a spiral serpentine pipe 42 and an internal chamber 44. Each one of the spiral serpentine pipe 42 and the internal chamber 44 are formed between the inner surface 20 and the outer surface 22 of the tuyere body 18. The spiral serpentine pipe 42 is nearer to the outer surface 22 than the internal chamber 44 and the internal chamber 44 is nearer to the inner surface 20 than the spiral serpentine pipe 42. The skilled person will be aware of suitable dimensions for the various pipes, according to the design of the tuyere.

However suitable pipes may be selected from pipes having an inside diameter comprised between 74” and 2”.

[0049] According to the embodiment displayed on Fig.4, the tuyere body 18 is made of copper while a surface of each of the recesses 36 is coated with a layer 46 of copper, copper alloy, nickel, nickel alloy, steel or steel alloy. The upper 30 outer surface 22 of the tuyere 10 comprising the corrugated portion 34 and thus the surface of the corrugated portion 34 enclosing the recesses 36 and extending between the recesses 36 is covered with a hardfacing material 48. The tip of the tuyere is covered with the same hardfacing material 48. In embodiments, two different hardfacing materials might be used to cover the tip of the tuyere and the upper outer surface of the surface. The pipes of the nose pipe 40 and the spiral serpentine pipe 42 are made of copper, copper alloy, nickel, nickel alloy, steel or steel alloy.

[0050] While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiments.

List of Reference Symbols tuyere 12 furnace wall 14 tuyere cooler 16 tuyere holder 18 tuyere body inner surface 22 outer surface 24 outlet end 26 inlet end 28 blowpipe upper portion 32 lower portion 34 corrugated portion 36 recess 38 open-curved profile cast-in nose pipe 42 spiral serpentine pipe 44 internal chamber 46 recess coating layer 48 hardfacing material

A-A axis of the tuyere

B-B axis of the recesses

Claims

1. A tuyere for a metallurgical furnace, the tuyere comprising a conical hollow tuyere body with an inner surface and an outer surface, the tuyere extending along a first axis from an inlet end to an opposite outlet end, the tuyere body having a tuyere tip at the outlet end and a conical connection surface at the inlet end, said conical connection surface being configured for engaging a conical seat of a tuyere holder or tuyere cooler, characterized in that the tuyere further comprises a corrugated portion on the outer surface of the tuyere, said corrugated portion comprising at least one recess having an open curved profile and a surface enclosing the at least of recess, and said corrugated portion being arranged and configured for, during operation of the metallurgical furnace, supporting burden material and forming a scaffold of said burden material.

2. The tuyere as claimed in claim 1, wherein the corrugated portion comprises a plurality of recesses, each recess of the plurality of recesses having an open curved profile, preferably the corrugated portion comprises between three and eleven recesses, more preferably the corrugated portion comprises between five and nine recesses, and wherein the surface of the corrugated portion encloses the plurality of recesses and extends between each recess of the plurality of recesses.

3. The tuyere as claimed in claim 1 or 2, wherein each recess of the corrugated portion is discontinuous.

4. The tuyere as claimed in any one of the preceding claims, wherein a thickness of the tuyere from the inner surface to the outer surface comprises a thicker portion and wherein the recesses of the corrugated portion are provided in the thicker portion.

5. The tuyere as claimed in any one of the preceding claims, wherein the recesses are parallel to each other and essentially extend along a second axis, and wherein the second axis is not co-axial with the first axis.

6. The tuyere as claimed in claim 5, wherein the second axis is perpendicular to the first axis.

7. The tuyere as claimed in any one of the preceding claims, wherein the recesses have a linear shape.

8. The tuyere as claimed in any one of claims 1 to 6, wherein the recesses have a wavy shape or an angular shape.

9. The tuyere as claimed in any one of the preceding claims, wherein the tuyere is made of a metallic material or an alloy of a metallic material, preferably the tuyere is made of copper, copper alloy, steel or steel alloy.

10. The tuyere as claimed in any one of the preceding claims, wherein the surface of each recess forming the corrugated portion is covered with a layer of a metallic material or an alloy of a metallic material, preferably the surface of each recess is covered with a layer of copper, copper alloy, nickel, nickel alloy, steel or steel alloy.

11. The tuyere as claimed in any one of the preceding claims, wherein the surface of the corrugated portion and the tuyere tip are covered with a layer of a hardfacing material.

12. The tuyere as claimed in any one of the preceding claims, wherein the tuyere comprises a single chamber, a double chamber and/or a spiral chamber.

13. The tuyere as claimed in any one of the preceding claims, wherein the tuyere further comprises a cast-in nose pipe.

14. The tuyere as claimed in claim 13, wherein the pipe of the nose pipe is made of a metallic material or an alloy of a metallic material, preferably the pipe is made of copper, copper alloy, nickel, nickel alloy, steel or steel alloy.

15. The tuyere as claim in any one of the preceding claims, the tuyere further comprising injection channels arranged and configured for, during operation of the metallurgical furnace, directly injecting burden material above the tuyere.

16. The tuyere as claim in any one of the preceding claims, wherein the tuyere further comprises straight channels arranged and configured for, during operation of the metallurgical furnace, using an electronic thickness measurement device.

17.A method for manufacturing a tuyere as claimed in any one of the preceding claims.

18. The method as claimed in claim 17, wherein the tuyere is manufactured by machining, casting, welding, forging or any combination thereof.

19. The method as claimed in claim 17 or 18, wherein the recesses of the corrugated portion are manufactured by casting.

20. A metallurgical furnace comprising a tuyere arranged for feeding hot gas inside the metallurgical furnace, wherein the tuyere is a tuyere according to any one the claims 1 to 16.