CN110088550B

CN110088550B - Spray gun tube

Info

Publication number: CN110088550B
Application number: CN201780080051.1A
Authority: CN
Inventors: 奥勒·埃里克松; 亨里克·哈尔
Original assignee: Sandvik Intellectual Property AB
Current assignee: Heruimai Pipe Co.,Ltd.; Alleima AB
Priority date: 2016-12-23
Filing date: 2017-12-22
Publication date: 2022-04-26
Anticipated expiration: 2037-12-22
Also published as: WO2018115503A1; EP3559578B1; ES2921231T3; EP3559578A1; CN110088550A

Abstract

The present disclosure relates to a lance tube (1) having a central through hole extending along a longitudinal axis (a). The lance tube has: a double-layered end portion (2) having an annular outer layer (4) made of a first alloy resistant to high temperature corrosion and an annular inner layer (5) made of a second alloy, and wherein the inner and outer layers are mechanically interlocked, and wherein a metallic bond has been formed between the inner and outer layers by hot working; and a main portion (3) of a single layer made of said second alloy. The lance tube is suitable for use in a lime kiln.

Description

Spray gun tube

Technical Field

The present disclosure relates to lance tubes. In particular, but not exclusively, the present disclosure relates to a lance tube intended for a lime kiln. The lance tube may also be intended for use in a pulverized coal injection lance, such as a blast furnace.

Background

In the production of quick lime (calcium oxide) from limestone (calcium carbonate), a lime kiln is used for the calcination process. The most common lime kiln is the Parallel Flow Regenerative (PFR) shaft kiln, which consists of two vertical shafts and a connecting cross channel. While the limestone is calcined in the combustion zone in one of the shafts, the other shaft preheats the limestone. Hot combustion gases are transferred from the calcination shaft through the crossover passages to the non-calcination shaft where they preheat limestone in the upper region of the shaft. The flow direction of the gas is reversed at regular intervals. This allows regenerative preheating of limestone and therefore this type of lime kiln is energy efficient. The fuel is conveyed into the calcination shaft via lances projecting into the combustion zone. Since the calcination process requires a high temperature of about 1000 ℃, the lance must be heat resistant.

The lance includes a lance tube which is subjected to severe high temperature corrosive conditions due to the high temperatures, corrosive elements in the fuel and erosion from limestone. The main corrosion mechanisms in lime kilns are oxidation, sulfidation and erosion corrosion. The most severe corrosion typically occurs about 50-100 centimeters from the lower end of the lance tube which delivers the fuel into the combustion zone. Corrosion may lead to breakage of the lance in this area and thereby shorten the blast. Since this shortening changes the kiln combustion parameters and reduces its efficiency, broken lances need to be replaced.

Common materials for lance tubes include: chromium oxide forming steel alloys (e.g., ferritic stainless steel alloy ASTM 446), and austenitic stainless steel alloys UNS S35315, UNS S30815, ASTM310, and ASTM 316. The life of the lance tube is typically about six months to two years.

Previous attempts have been made to use alumina forming alloys such as, for example, iron chromium aluminum (FeCrAl) in lance tube applications. This alloy forms a protective alumina scale and is known to be very resistant to corrosion at high temperatures. However, in addition to being relatively expensive, FeCrAl alloys are also brittle at low temperatures and also difficult to weld.

Disclosure of Invention

In view of the foregoing, it would be desirable to provide a barrel for a lance that is improved in at least some respects over known barrels. In particular, it is desirable to provide a lance tube for use in lime kilns or in lime furnace burners, in blast furnace coal injection and in sootblower elements, which has an improved lifetime compared to known lance tubes.

This is achieved by the initially defined lance tube comprising:

-a double-layered end portion having an annular outer layer made of a first alloy resistant to high temperature corrosion and an annular inner layer made of a second alloy, wherein the annular inner layer and the annular outer layer are mechanically interlocked, and wherein a metallic bond has been formed between the annular inner layer and the annular outer layer by hot working, and

-a major part of a single layer made of a second alloy.

At the end portion of the double layer intended to form the lower end of the lance tube, an annular outer layer made of a high temperature corrosion resistant alloy provides enhanced corrosion resistance at the critical portion of the lance tube. In a lime kiln, this part will be located at the bottom of the kiln, where the highest temperatures will be experienced. Improved corrosion resistance is achieved without having to compromise the mechanical properties and high temperature wear resistance of the lance tube. The metallic bond between the annular inner layer and the annular outer layer ensures that there are no air gaps between the layers, which may result in reduced thermal conductivity. Thus, although two different alloys (alloys with different compositions) are used, a good thermal conductivity of the lance tube is also obtained. The metallic bond between the layers should be formed in a major portion of the interface between the annular inner layer and the annular outer layer, but there may be a minor portion of the interface where no metallic bond is present. The metal bond is formed by a thermal process such as hot extrusion, hot drawing, hot rolling or hot punching or other suitable technique.

Mechanical interlocking is provided prior to hot working to achieve metal bonding. The mechanical interlock will form a seal preventing oxygen from entering between the layers during the hot working process, and the mechanical interlock will additionally hold the annular inner layer and the annular outer layer together, i.e. prevent them from slipping, during hot working. The mechanical interlocking thus makes it possible to realize the proposed lance tube without having to weld the base part and the outer part together before hot working. Thus, the lance tube can be made of two alloys, which are often difficult to join by welding. In addition, the combination of the mechanical interlock and the metallic bond between the layers facilitates the ability of the lance tube to withstand high forces.

According to one embodiment, the thermal processing described above or below is thermal extrusion.

According to one embodiment, the annular inner layer and the annular outer layer are mechanically interlocked by a helically extending thread formed in the interface between the annular inner layer and the annular outer layer. The helically extending threads form an effective interlock and also increase the interface area, which will therefore help to improve the distribution of forces applied to the barrel as compared to a barrel without such helically extending threads. Thus, the lance tube will be able to withstand higher loads in the interface between the layers.

According to one embodiment, a major portion of the monolayer extends along a major portion of the lance tube as measured along the longitudinal axis. The portion of the monolayer may extend along more than half of the length of the lance tube, or along more than 75% of the length of the lance tube. The double-layered portion is therefore relatively short and covers only the critical portion of the lance tube where additional high temperature corrosion resistance is required. If an expensive first alloy is used for the outer layer, this will reduce the overall cost of the lance tube without compromising its service life. The double-layered portion, which is intended to form the lower portion of the tube from which the fuel is delivered, may generally extend along the lance tube by at least 70cm to 150 cm. The length of the lance tube measured in the axial direction may be several meters.

According to one embodiment, the second alloy is selected from a stainless steel alloy or a carbon steel. Stainless steel alloys and carbon steels having the desired mechanical strength and high temperature wear resistance are suitable choices for the main portion and inner layer of the lance tube. An example of a suitable carbon steel is a carbon steel according to standard DIN 17135a, comprising 0.1 to 0.3C and 0.1 to 2.0 Mn, the balance being Fe and unavoidable impurities.

According to an embodiment, the second alloy is selected from a ferritic stainless steel alloy or an austenitic stainless steel alloy. Suitable alloys are not limited to, for example, ferritic stainless steel alloy ASTM 446-1 and austenitic stainless steel alloys UNS S35315, UNS S30815, UNS N08810/N08811, ASTM310, and ASTM 316/316H. These alloys will provide the desired mechanical properties as well as sufficient high temperature corrosion and wear resistance for the main part of the lance tube and are suitable choices in e.g. lime kiln applications.

According to one embodiment, the first alloy is an alumina forming alloy. The alumina forming alloy forms a protective alumina scale on the outer surface of the annular outer layer that will provide excellent high temperature corrosion resistance. Suitable alumina forming alloys include iron chromium aluminum (FeCrAl) alloys and other alumina forming alloys.

According to one embodiment, the alumina forming alloy is a ferro-chrome aluminum alloy. FeCrAl alloys, e.g. under the trade mark

APM and

FeCrAl alloys, marketed by APMT, have suitable high temperature corrosion resistance for use as the outer layer. To obtain an improved creep strength, oxide dispersion strengthened alloys produced by powder metallurgy may be used. However, the alloys can also be conventionally manufactured using melting and casting techniques.

According to one embodiment, the first alloy comprises:

9 to 25% by weight of Cr,

2.5 to 8% by weight of Al,

the balance being Fe and impurities normally present, and optionally also other intentionally added alloying elements. In one embodiment, the first alloy comprises 20 to 25 wt.% Cr and 5 to 7 wt.% Al, with the balance being Fe and impurities typically present. In another embodiment, the first alloy comprises 20 to 25 wt.% Cr, 5 to 7 wt.% Al, and 1 to 4Mo, with the balance being Fe and impurities typically present.

According to one embodiment, the first alloy is a cerium-containing stainless steel alloy, such as a chromium oxide-forming austenitic stainless steel alloy containing cerium. The addition of cerium stabilizes the chromium oxide at high temperatures and thus improves high temperature corrosion performance and provides good structural stability at high temperatures. Suitable alloys are for example UNS S30815 and UNS S35315, which comprise C0.04 to 0.10, Mn 1 to 2, Cr 20 to 26, Ni 10 to 12 or 34 to 36, N0.12 to 0.20, Ce 0.03 to 0.08, the balance being Fe and unavoidable impurities.

According to one embodiment, the thickness of the annular outer layer is in the interval 5% to 50% of the total wall thickness. The thickness should be sufficient to achieve the desired high temperature corrosion resistance without the risk of the annular outer layer cracking or otherwise breaking.

According to one embodiment, the thickness of the annular outer layer is in the interval of 10% to 40% of the total wall thickness, so that sufficient corrosion resistance is ensured at a reasonable cost.

According to one embodiment, the total wall thickness of the lance tube is in the interval 3mm to 20 mm. The wall thickness depends on, for example, the size of the lance tube. For example, for outer diameters of about 60mm, 50mm, 40mm, 30mm and 12mm, wall thicknesses of about 10mm, 9mm, 6mm and 3mm, respectively, may be suitable.

According to one embodiment, the outer diameter of the lance tube measured at each of the main portion of the single layer and the end portions of the double layer is the same or substantially the same.

According to one embodiment, the inner diameter of the lance tube measured at each of the main portion of the single layer and the end portions of the double layer is the same or substantially the same. This facilitates the flow characteristics of the lance tube.

The present disclosure also relates to the use of the proposed lance tube as a lance tube in a lime kiln. The proposed lance tube may also be used in other applications requiring a combination of high temperature corrosion resistance and mechanical strength, such as in lime furnace burners, in blast furnace coal injection and in sootblower elements.

Other advantageous features and advantages of the proposed barrel and method of manufacture will appear from the following description.

Definition of

Lance tubes are to be understood herein as tubes of relatively small diameter compared to their length, which are intended for use in lime kilns or lime furnace burners, in blast furnace coal dust injection and in sootblower elements. The lance tube is for delivering fuel from a first end of the lance tube to a second end of the lance tube, wherein the first end is connected to a fuel supply system and the second end is open. The lance tube is not pressurized.

Drawings

Embodiments of the proposed barrel and method of manufacture will be described hereinafter with reference to the accompanying drawings, which should not be construed as limiting, in which:

figure 1 schematically illustrates a perspective view of a lance tube according to one embodiment,

figure 2 schematically illustrates a cross-sectional view of a lance tube according to another embodiment,

figures 3a to 3c schematically show a base part and an outer part for the manufacture of a lance tube,

figure 4 schematically shows a longitudinal cross-sectional view of a part of the base part and the inner part for the manufacture of a lance tube,

FIG. 5 schematically shows a longitudinal cross-sectional view of a portion of a workpiece used to manufacture a lance tube, an

Fig. 6 shows a longitudinal sectional photograph of the interface in the lance tube.

Detailed Description

Fig. 1 shows schematically and not to scale a lance tube 1 according to one embodiment of the disclosure. The lance tube has a relatively short double-layered end portion 2 and a single-layered main portion 3. The double-layered end portion 2 has an annular outer layer 4 made of a first alloy and an annular inner layer 5 made of a second alloy. The main portion 3 of the single layer is entirely formed by the second alloy forming the inner layer 5 of the end portion 2 of the double layer.

Fig. 2 schematically shows a straight lance tube 1 in cross-section taken along the longitudinal axis a of the lance tube. As can be seen from the enlarged view of the marked region, a helically extending thread 6 extends in the interface between the annular outer layer 4 and the annular inner layer 5. The helically extending thread 6 serves to mechanically interlock the two

layers

4, 5. However, the

layers

4, 5 are also bonded by a metallic bond formed in the interface by thermal processing (e.g. hot extrusion).

A lance tube according to the present disclosure may be manufactured from the components shown in fig. 3a to 3 c. These components include a base component 301 made of the second alloy and an outer component 401 made of the first alloy, the base component 301 will form the inner layer 5 of the lance tube 1 and the outer component 401 will form the outer layer 4 of the lance tube 1.

The base member 301 is a tube having a circular cross-section with a central through hole extending along the longitudinal axis a. An external thread section 302 is provided, the external thread section 302 having a helical thread 306 (see fig. 3b) formed in an outer peripheral surface of an end portion of the base member 301. The base member 301 is shown having an unthreaded section 303 adjacent to the threaded section 302. The inner diameter D of the base member is constant or substantially constant along the longitudinal axis, but the outer diameter D1 of the unthreaded section 303 is greater than the outer diameter D2 of the threaded section 302.

The outer member 401 is also a tube with a circular cross-section having a central through hole extending along the longitudinal axis a. In the embodiment shown, the length of the outer member 401 in the longitudinal direction corresponds to the length of the threaded section 302 of the base member 301. The outer part 401 has an internal threaded section 402, which internal threaded section 402 extends in the embodiment shown along the entire length of the outer part 401. In other words, a helical thread 406 (see fig. 3c) is formed in the inner peripheral surface of the outer member 401. The outer member 401 is thereby configured for threaded engagement with the externally threaded section 302 of the base member 301. The outer diameter D3 of the outer member 401 is equal or substantially equal to the outer diameter D1 of the unthreaded section 303 of the base member 301, while the inner diameter D2 of the outer member 401 matches the outer diameter D2 of the threaded section 302 of the base member 301.

The tubular workpiece is formed by mounting the outer member 401 around the base member 301 such that the internally threaded section 402 of the outer member 401 engages with the externally threaded section 302 of the base member 301, i.e. by screwing the outer member 401 onto the threaded end portion of the base member 301. Thereby, a mechanical interlock is formed between the threaded

sections

302, 402.

The workpiece is then hot worked, for example by hot extrusion. During hot working (e.g., hot extrusion), a metallic bond is formed between the threaded

sections

302, 402 while maintaining the mechanical interlock. The outer diameter of the workpiece is also reduced and the length is increased. The straightening and/or pickling may be performed before the resulting lance tube 1 is cut to its final length and, if necessary, formed into the desired shape.

The

components

301, 401 shown in figure 3a are suitable for hot extrusion by pushing the workpiece through an extrusion die (leading end first through the extrusion die), where the leading end is the end where the outer component 401 is mounted. The transition surface 308 between the externally threaded section 302 and the unthreaded section 303 of the base member 301 is smooth, without sharp edges. The transition surface 308 is shown in more detail in fig. 3B, which shows an enlarged view of the circled area B of fig. 3 a. The cross-section of the transition surface is shaped as an inverted S-shape with the concave portion 304 closest to the threaded section 302 and the convex portion 305 closest to the unthreaded section 303. As shown in fig. 3C, which shows an enlarged view of the circled area C of fig. 3a, the outer part 401 has an end surface 408, which end surface 408 has a corresponding S-shape, wherein the male portion 404 is close to the internal thread 406 and the female portion 405 is close to the outer circumferential surface 407 of the outer part 401. Thus, the concave portion 405 of the end surface 408 will overlap the convex portion 305 of the transition surface 308, which prevents the penetration and separation of oxygen during the extrusion process.

Another option is to make the leading end the end without the external part mounted in the extrusion process. In this case, as shown in fig. 4, the base part 301 is formed with a C-shaped concave transition surface 308 such that it floats on a rounded annular end surface 408 of the outer part 401 and forms a seal during extrusion. Thus, when the

components

301, 401 are installed to form a workpiece, the outer peripheral surface 307 of the base component 301 overlaps the outer peripheral surface 407 of the outer component 401.

Fig. 5 shows a cross-sectional view of parts of a workpiece 501, the workpiece 501 being suitable for hot extrusion by pushing the workpiece 501 through an extrusion die (leading end 502 first passing through the extrusion die), wherein the leading end 502 is the end where the outer component 401 is mounted. The end on which the outer component 401 is mounted has been machined to form a rounded end surface 503. In this embodiment, the design of the transition surfaces 308, 408 of the base part 301 and the outer part 401, respectively, differs from the design shown in fig. 3a to 3 c. As can be seen in the cross-sectional view, the transition surface 308 of the base member 301 comprises a first straight portion 309 perpendicular to the longitudinal axis a and a second straight portion 310 inclined at an angle a of 30 ° with respect to the longitudinal axis a. The curved surface connects the two

straight portions

309, 310. Of course, the angle α may vary.

Transition surface 408 of outer member 401 is formed to engage and overlap transition surface 308 such that a seal is formed. The first straight portions 309 extend for a thickness h in the total wall thickness t of the outer part.

Examples of the invention

In a production test, ten lance tubes according to the embodiment shown in fig. 1 were manufactured. Ten outer parts made of the first alloy and ten base parts made of the second alloy are formed. In this case, the first alloy is a trademark

APM is a known iron-chromium-aluminum (FeCrAl) alloy. The composition of the first alloy, measured in weight percent (wt.%), is disclosed in table I.

C	Si	Mn	Al	Cr	Fe
						≤0.08	≤0.07	0.7	6	22	Balance of

TABLE I

The second alloy is a ferritic stainless steel according to ASTM 446-1 having the composition in weight% disclosed in table II.

C

Si

Mn

P

S

Cr

N

Fe

≤0.20

0.5

0.8

≤0.030

≤0.015

26.5

0.2

Balance of

TABLE II

Each base part has an overall length of 400mm, an outer diameter D1 of 164mm and an inner diameter D of 41 mm. An external thread section having a length of 95mm and an outer diameter D2 of 154mm was formed by cutting. The outer members each have a length of 95mm and an inner diameter d2 of 154mm and are provided with internal helical threads. These components have the transitional design shown in fig. 5. The wall thickness t of the outer part is 5mm and the thickness h is 1.8 mm. The helical thread has a pitch of 2 mm.

These parts were degreased using ethanol. Thereafter, the outer member 401 is screwed onto the base member 301 to form a workpiece as shown in fig. 5.

Thereafter, the workpiece was heated to 900 ℃ and hot extruded at the temperatures shown in table III. The workpiece is extruded with the end portion to which the external member is attached as a leading end.

Workpiece	Extrusion temperature (. degree.C.)
		S1	1120
S2	1120
		S3	1120
S4	1120
		S5	1120
S6	1090
		S7	1090
S8	1070
		S9	1070
S10	1050

TABLE III

After hot extrusion, the formed tubes were straightened and grit blasted with steel grit.

The length of the double-layered portion of the manufactured lance tube was found to be between 70cm and 120 cm. The thickness of the outer layer was measured in the test specimen using optical and electron microscopy and found to be between 600 μm and 900 μm.

Using energy dispersive X-ray spectroscopy, it was also investigated whether a protective alumina oxide scale had formed on the outer layer of the portion of the bilayer during heat treatment, and whether a metallic bond had formed between the inner and outer layers. It was found that alumina oxide scale had formed on the surface of the outer layer and aluminium nitride precipitates had formed in the outer layer, indicating that nitrogen diffused from the inner layer made of the second alloy ASTM 446-1 to that made of the second alloy by the trademark

In the outer layer made of the first alloy sold by APM, this in turn indicates the formation ofAnd (4) metal bonding.

Fig. 6 shows a cross-sectional photograph of a portion of the interface between the inner layer 5 and the outer layer 4 of a double layer portion of a lance tube made in accordance with an embodiment. The picture is taken at the foremost portion of the lance tube, which corresponds to the leading end of the workpiece. The helically extending thread 6 can be clearly seen. Thus, although a metallic bond has been formed in the interface, the inner and outer layers are still mechanically bonded together.

Of course, the dimensions of the components used may vary depending on the desired dimensions of the final lance tube as well as the alloys used and the parameters used during hot working (e.g., hot extrusion). Various other processing steps, such as preheating and cold rolling, may also be included. The design of the base member and the outer member may vary depending on the requirements for the final lance tube.

The proposed lance tube may be shaped to suit the requirements of a lime kiln or other application in which the proposed lance tube is used. The design of the lance tube may be varied, for example by having all or part of the double layer section have an outer diameter that is different from (e.g. smaller than) the outer diameter of the main section. The double layered end portion of the lance tube may also include a portion made entirely of the first alloy making up the outer layer such that the high temperature corrosion resistant first alloy covers the end of the lance tube.

The presented lance tube is not limited to the above described embodiments but many possibilities to modifications thereof will be apparent to a person skilled in the art without departing from the scope of the appended claims.

Claims

1. A lance tube (1), the lance tube (1) having a central through-hole extending along a longitudinal axis (A),

it is characterized in that

The lance tube (1) comprises:

-a double-layered end portion (2), the double-layered end portion (2) having an annular outer layer (4) made of a first alloy resistant to high temperature corrosion and an annular inner layer (5) made of a second alloy, wherein the annular inner layer (5) and the annular outer layer (4) are mechanically interlocked, and wherein a metallic bond has been formed between the annular inner layer (5) and the annular outer layer (4) by hot working, and

-a main part (3) of a single layer made of the second alloy, wherein the metallic bond has been formed between the annular inner layer (5) and the annular outer layer (4) by hot extrusion, the first and second alloys being typically difficult to join by welding, the hot extrusion being achieved by pushing the workpiece through an extrusion die, wherein the leading end is first passed through the extrusion die, wherein the leading end is the end where the annular outer layer is mounted, the transition surface between the external threaded section and the unthreaded section of the annular inner layer being smooth without sharp edges.

2. The lance tube of claim 1, wherein the annular inner layer (5) and the annular outer layer (4) are mechanically interlocked by helically extending threads (6), the helically extending threads (6) being formed in an interface between the annular inner layer (5) and the annular outer layer (4).

3. The lance tube of claim 1 or 2, wherein a major portion (3) of the monolayer extends along a major portion of the lance tube (1), the major portion of the lance tube (1) being measured along the longitudinal axis (a).

4. The lance tube of claim 1 or 2, wherein the second alloy is selected from a stainless steel alloy or carbon steel.

5. The lance tube of claim 1 or 2, wherein the second alloy is selected from a ferritic stainless steel alloy or an austenitic stainless steel alloy.

6. The lance tube of claim 1 or 2, wherein the first alloy is an alumina forming alloy.

7. The lance tube of claim 6, wherein the aluminum oxide forming alloy is an iron chromium aluminum alloy.

8. The lance tube of claim 1 or 2, wherein the first alloy comprises:

9 to 25% by weight of Cr,

2.5 to 8% by weight of Al,

the balance being Fe and impurities usually present, and optionally also other intentionally added alloying elements.

9. The lance tube according to claim 1 or 2, wherein the thickness of the annular outer layer (4) is in the interval of 5% to 50% of the total wall thickness.

10. The lance tube according to claim 1 or 2, wherein the thickness of the annular outer layer (4) is in the interval of 10% to 40% of the total wall thickness.

11. The lance tube of claim 1 or 2, wherein the lance tube (1) has a total wall thickness in the interval of 3mm to 20 mm.

12. The lance tube of claim 1 or 2, wherein the outer diameter of the lance tube (1) measured at each of the main portion (3) of the single tier and the end portions (2) of the double tier is the same.

13. The lance tube of claim 1 or 2, wherein the inner diameter of the lance tube measured at each of the main portion of the single tier and the end portions of the double tier is the same.

14. The lance tube (1) according to any one of the preceding claims for use as lance tube in lime kilns, in lime furnace burners, in blast furnace coal dust injection and in sootblower elements.