JP2009198117A - Protection member of marine boiler overheater pipe - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a protection member of a marine boiler overheater pipe such as capable of preventing metallic corrosion by acceleration high temperature oxidation (a vanadium attack) with a simple constitution. <P>SOLUTION: This protection member is formed of a plate-like member for covering the periphery of the marine boiler overheater pipe with a plurality, with curvature for contacting in a surface with the marine boiler overheater pipe, by using an alloy of nickel Ni and a chrome Cr of adding molybdenum Mo, for preventing corrosion by combustion ash sticking including vanadium, by being arranged in a passing part of a burner flame in the marine boiler overheater pipe with heavy oil as main fuel. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a protection member for a marine boiler superheater tube, and more particularly to a protection member for a marine boiler superheater tube that can withstand thinning due to accelerated high-temperature oxidation (vanadium attack) accompanying fuel deterioration in a heavy oil cooking boiler. Is.

  The main boiler for ships has a superheater tube group called a so-called super heater, and liquefied natural gas (LNG) and heavy oil fuel have been generally used as fuels. Has increased. However, heavy oil fuels tend to be deteriorated, and due to this, thinning due to high temperature corrosion of boiler superheater tubes has become a problem.

That is, the crude heavy oil contains vanadium, sulfur, sodium and the like, but the ash of these vanadium compounds has a melting point of 535 ° C., 5Na ₂ O · V ₂ O ₄ , 5Na ₂ O · V ₂ O ₄ 11V. ₂ O _5, 565 ° C. for _{2Na 2 O · 3V 2 O 5} , etc., the melting point is low melting ash 600 ° C. or less, ash of a low melting point vanadium compounds are melted by the heat of the engine and the burner It adheres to the outer surface of the superheater tube in the state of molten soot, destroys the oxide film on the metal surface, and corrodes the metal by accelerated high temperature oxidation (vanadium attack). In addition, the outer surface of the superheater tube is oxidized and corroded by moisture due to the leakage of steam, or carbon contained in crude heavy oil rubs the superheater tube, which becomes a major factor in causing wear.

  For such problems, it is generally preferable to change the material of the boiler superheater tube. For example, a 2.25Cr material is applied to a high-temperature part, or 1Cr steel is used for a part below 500 ° C. Has been done. In addition, boilers adopting SUS347, SUS310, etc. are increasing in areas where the thinning due to corrosion at the highest temperature area is large. Further, in order to improve the corrosion resistance, it is preferable to use a nickel-based corrosion resistant alloy, but it is problematic in terms of cost to use all the superheater tubes as such a corrosion resistant alloy. There is also a need for short-term life extension measures by implementing emergency measures due to the construction period.

  As a technique for preventing corrosion due to the adhesion of such combustion ash, for example, Patent Document 1 describes the durability of a heat transfer tube with straight fins arranged in a combustion exhaust gas passage of a coal-fired boiler applied to a thermal power generation facility or the like. In order to improve the performance, the part where the joint with the straight fin is intermittently welded is continuously welded over the entire length of the protector to completely cover the heat transfer tube at the base of the straight fin, and the mounting range of the protector A heat transfer tube protector is disclosed which is limited to only the upstream side of the tube and reduces the gas flow rate between the heat transfer tubes to improve the wear resistance of the heat transfer tubes.

  Further, in Patent Document 2, a boiler tube protector that protects a boiler tube from a soot blower that ejects water vapor and removes soot is formed by a combination of a plurality of ceramic bodies each having a divided cylindrical shape. If it is attached to the split surfaces on both sides of the tube in a shape that suppresses displacement along the split surfaces, suppresses movement in the direction perpendicular to the split surfaces, or is installed in multiple stages on a boiler tube that extends vertically, A boiler tube protector and a method of mounting the same are disclosed in which a step portion is provided that is temporarily fixed by a stopper provided at a lower stage and hardens the mortar by heat generated during boiler operation.

JP-A-5-215302 Japanese Patent Laid-Open No. 10-227403

  However, in the protective member shown in Patent Document 1, selective wear occurs because the conventional protective member is intermittent welding, or the wear of the superheater tube is not constant due to the protective member, and wear proceeds. The superheater tube protective member disclosed in Patent Document 2 relates to a soot blower that ejects water vapor and removes soot, and is a metal by accelerated high-temperature oxidation (vanadium attack). It cannot cope with corrosion.

  Therefore, in this invention, it is a subject to provide the protection member of the marine boiler superheater pipe | tube which can prevent the metal corrosion by accelerated high temperature oxidation (vanadium attack) with a simple structure.

In order to solve the above problems, the protection member for a marine boiler superheater pipe according to the present invention is:
A protection member for a marine boiler superheater pipe that is provided at a site where combustion gas easily passes in a marine boiler superheater pipe using heavy oil as a main fuel and prevents corrosion due to vanadium-containing combustion ash adhesion,
The protective member uses a nickel (Ni) -chromium (Cr) alloy to which molybdenum (Mo) is added, has a curvature that makes surface contact with the marine boiler superheater tube, and has a plurality of surroundings of the marine boiler superheater tube. It is characterized by being formed as a covering plate member.

  In this way, the protection member for the marine boiler superheater pipe is formed so as to cover the marine boiler superheater pipe in surface contact with the nickel (Ni) -chromium (Cr) alloy to which molybdenum (Mo) is added. The vanadium compound ash can be prevented from adhering to the superheater tube, and has high corrosion resistance in the presence of nickel (Ni), chromium (Cr) and molybdenum (Mo), and accelerated high-temperature oxidation (vanadium). It is possible to provide a protective member that can effectively reduce the metal corrosion due to attack) and the thinning rate.

  The protective members made of the plurality of plate-like members each have a semicircular cross section so as to cover the marine boiler superheater tube, and a circumferential edge of one protective member is a circumferential edge of another protective member. The marine boiler superheater pipe is provided with an engaging hook on the one protective member side at a position in contact with the portion and an engaging protrusion on the other protective member side, and the engaging hook is engaged with the engaging protrusion. By attaching to, it can be set as the protection member which can be easily attached to a superheater pipe | tube, without performing special welding etc.

  In addition, the protective member of the part where the combustion gas easily passes becomes high temperature, and the temperature on the opposite side is relatively lower than the part, so that a difference in expansion coefficient occurs. There is a possibility of dropping out. Therefore, one plate-like member in the plate-like member forming the protection member is formed so that the axial length is shorter than the other plate-like members, and the region without the one plate-like member is defined as a circumferential end in the region. By covering with a sub-plate member that is welded separately to each of the other plate-like members where the portion is present and forms a gap at the opposite site, the difference in expansion coefficient between them is due to the presence of the gap at the opposite site. Further, since the auxiliary plate member and the plate member in position cover the whole superheated organ, even if the engagement is disengaged, the protective member is not detached from the superheater tube.

  As described above, the protection member for a marine boiler superheater tube according to the present invention can prevent the ash of the vanadium compound from adhering, and has high corrosion resistance due to the presence of nickel (Ni) chromium (Cr) and molybdenum (Mo). Therefore, it is possible to effectively reduce metal corrosion and thinning speed due to accelerated high-temperature oxidation (vanadium attack), and it can be easily attached by the engaging member and the expansion coefficient is achieved by the presence of the sub-plate member. It can be set as the protection member of the marine boiler superheater pipe | tube which can prevent the drop-off | omission by the difference of.

  Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention unless otherwise specified, but are merely illustrative examples. Not too much.

  First, the structure of a marine boiler incorporating a protection member for a marine boiler superheater tube according to the present invention will be described with reference to FIGS. FIG. 4 is a view showing an example of the structure of a marine boiler incorporating a protection member for a marine boiler superheater tube according to the present invention.

  The illustrated marine boiler is a sealed container comprising a furnace having a combustion device 1 for burning heavy oil and a combustion chamber 2, a water drum 3, and a steam drum 4 disposed above the water drum 3 and containing steam. It consists of a boiler body. Different combustion apparatuses are used depending on the type of fuel. In the illustrated boiler, the combustion apparatus 1 is composed of a burner that uses heavy oil or gaseous fuel as fuel.

  The burner 1 generates a flame by generating a flame, and in the combustion chamber 2, the gas almost burned by the burner is brought into contact with the hot air under high temperature and burned well. The boiler body has a front bank tube extending between the water drum 3 and the steam drum 4 or a front steam pipe 5 and a rear bank tube or rear steam pipes 6 to 10, and the drums 3, 4 and the front steam pipe. 5 and the rear steam pipes 6 to 10 are filled with water, and the water surface is set to a predetermined height of the steam drum 4.

  The combustion gas generated in the furnace flows toward the boiler body, and heat is transmitted to the boiler body by radiation or contact, and then discharged from the boiler body outlet 11. The steam generated by the combustion gas in the drum 3, the front steam pipe 5 and the rear steam pipes 6 to 10 is sent to the steam drum 4.

  The boiler body has precipitation pipes 12, 13, 14 extending between the drums 3, 4 outside the combustion chamber 2, and these precipitation pipes 12, 13, 14 are used to store steam collected in the steam drum 4. It is an unheated downcomer for returning water droplets condensed by staying in the water drum 3.

  The illustrated boiler further includes a superheater pipe 16 for converting the steam from the steam drum 4 into superheated steam, and the superheater pipe 16 is parallel to the first superheater pipe manifold 17 and the superheater pipe inlet / outlet header 17. A superheater tube intermediate header 18 that extends and a superheater tube 19 that extends in an inverted U shape when viewed between the superheater tube headers 17 and 18 in FIG. 4 are provided.

  FIG. 3 is a cross-sectional view (A) of a position indicated as AA ′ in a portion of the superheater pipe 19 incorporating the protection member for the marine boiler superheater pipe in FIG. 4 and a partially enlarged view (B) thereof. is there. The superheater pipe inlet / outlet header 17 is formed with an inlet 20 connected to the steam drum 4 via a saturated steam pipe 15 (see FIG. 4), and an outlet 21 connected to a steam turbine or the like (not shown). Has been. Note that FIG. 3B will be described later.

  A superheater tube 19 extends between the superheater tube intermediate header 18 and the superheater tube inlet / outlet header 17. Therefore, the steam from the steam drum 4 enters from the inlet 20 of the superheater pipe inlet / outlet header 17 via the saturated steam pipe 15, and the superheater pipe 19 passes between the superheater pipe inlet / outlet header 17 and the superheater pipe intermediate header 18. Then, it is superheated by flowing one after another, and is supplied from the outlet 21 of the superheater pipe inlet / outlet header 17 to a steam turbine or the like (not shown).

  In the marine boiler configured as described above, the superheater pipe 19 is generally formed of a heat-resistant and corrosion-resistant alloy such as 1Cr steel and 2.25Cr steel, and as described above, SUS347, SUS310, SUS304, SUS316, etc. It is preferable to use a heat-resistant and corrosion-resistant alloy containing nickel and chromium, such as typical stainless steel and nickel-base alloy, but it is costly to manufacture all the superheater tubes 19 with a heat-resistant and corrosion-resistant alloy containing nickel and chromium. It becomes a problem. For this reason, as described above, the combustion ash of heavy oil adheres and the metal is corroded by accelerated high temperature oxidation (vanadium attack). Therefore, in the present invention, the superheater pipe 19 is covered with a protective member, and the superheater pipe 19 is covered with the combustion ash. To prevent vanadium attack.

  FIG. 1 is a view showing a state in which a protection member for a marine boiler superheater pipe according to the present invention is attached at different angles, and FIG. 2 is a diagram for explaining a configuration of a protection member 30 for a marine boiler superheater pipe. Exploded views (A), (B) and (C) are a front view and a side view of the engaging protrusion (B) and the engaging hook (C) for engaging the first and second protective members 31 and 32, respectively. , And (D) are perspective views showing a state in which these members are assembled.

  The protective member of the marine boiler superheater tube 19 of the present invention has a thickness of 3 to 5 mm of nickel (Ni) -chromium (Cr) to which molybdenum (Mo) having a composition of Ni-45Cr-1Mo (mass%) is added. An alloy (trade name MC Alloy manufactured by Mitsubishi Materials Co., Ltd. is used) is formed into a semicircular cross-sectional shape by providing a surface contact curvature with the marine boiler superheater tube 19, and the marine boiler superheater tube 19. It consists of plate-shaped members 31, 32, 41, and 42 that cover the periphery of the plurality.

  As described above, crude heavy oil contains vanadium, sulfur, sodium, etc., and the ash of these vanadium compounds includes low-melting ash having a melting point of 600 ° C. or less, which melts and melts due to the heat of the engine or burner. It adheres to the outer surface of the superheater tube in a state like a cocoon, destroys the oxide film on the metal surface, and corrodes the metal by accelerated high-temperature oxidation (vanadium attack).

However, as shown in the graph showing the change in the corrosion rate accompanying the temperature change in the 3% HF + 17% HNO ₃ solution in FIG. Compared to the excellent nickel-based corrosion-resistant alloy MA276 (trade name, manufactured by Mitsubishi Materials Corporation), the extension alloy MA20Nb improved from the sulfuric acid-resistant casting alloy, it has excellent corrosion resistance. In FIG. 6, the horizontal axis represents the liquid temperature (unit: ° C.), the vertical axis represents the corrosion rate (unit: mm / year), MA20Nb is 5 mm / year, MA276 is 6.5 mm / year, and SUS304 is 40 mm / year. On the other hand, even when MC alloy exceeds 100 ° C., it shows excellent corrosion resistance of about 1.5 mm / year.

Further, MC alloy having a thickness of 3 to 5 mm, MA601 that can withstand a high-temperature oxidizing atmosphere, and excellent in carburization resistance, and SUS310 that is excellent in acid resistance and heat resistance are heated in air at 1150 ° C. for 24 hours and cooled to room temperature. as shown in the graph 7 showing the weight loss in the case of repeating the processing of, with respect to the MA601 30 tests the -90mg ^/ cm 3, SUS310 is 360 mg / cm ^3, the MC alloy - An excellent weight loss characteristic of about 50 mg / cm ³ is shown. In the graph of FIG. 7, the horizontal axis represents the number of times, and the vertical axis represents the decrease in weight change (unit: mg / cm ³ ).

  2A, the protective member 30 of the superheater tube 19 of the present invention has, for example, a first protective member 31 having a semicircular cross-sectional shape, and a first protective member 31 having the same semicircular cross-sectional shape. In order to cover the region where the superheater tube 19 cannot be covered because the height of the second protective member 32 and the second protective member 32 are lower than those of the first protective member 31. , A third protection member 41 as a sub-plate member having a ¼ circular cross-sectional shape, a sub-protection member 40 composed of a fourth protection member 42, and a first protection member 31 and a second protection member 32 includes an engaging projection 33 (B) and an engaging hook 34 (C).

  Of these, the third protection member 41 and the fourth protection member 42 that are sub-plate-like members can cover the superheater tube 19 because the height of the second protection member 32 is lower than that of the first protection member 31. In order to cover the incapable area, as shown in FIG. 2D, the first protective member 31 is welded separately to each of the circumferential ends facing this area. At the time of this welding, when the first protective member 31 and the second protective member 32 are engaged, a position where a gap is formed in a portion where the third protective member 41 and the fourth protective member 42 face each other. Welded in connection.

  This is to prevent the protective member 30 from coming off the superheater tube 19 because the expansion rate of the protective member differs depending on how the combustion gas from the burner 1 hits. In other words, the flame of the burner 1 flows from the combustion chamber 2 toward the boiler body, radiates heat to the boiler body, and communicates heat with the combustion gas, and is then discharged from the boiler body outlet 11. The protective member (the first protective member 31 in FIG. 2) of the portion directly exposed to the flame of the burner 1 becomes high temperature, and the opposite side (second protective member 32) has a temperature higher than that of the portion directly exposed to the combustion gas. This is because there is a possibility that the first protective member 31 and the second protective member are disengaged due to the difference in expansion rate, and the protective member may fall off.

  Therefore, the 3rd protection member 41 and the 4th protection member 42 which are subplate members are welded to the 1st protection member 31, and the 1st protection member 31 and the 2nd protection member 32 are engaged. When the third protective member 41 and the fourth protective member 42 face each other, a gap is provided to compensate for the difference in expansion coefficient between the first protective member 31 and the first protective member 31. Even when the second protective member 32 is disengaged, it is possible to prevent the third protective member 41 and the fourth protective member 42 from being separated because they surround the superheater tube 19.

  Further, the engaging protrusion 33 shown in FIG. 2 (B) is provided with a slope portion so as to engage with a hook hole 35 provided in the center of the engaging hook 34 shown in FIG. The engaging hook 34 engages and pushes the hook hole 35 provided at the center of the engaging hook 34 into the inclined surface portion. Therefore, as shown in FIG. 2D, the engagement hook 34 is welded to a portion where the end of the first protection member 31 is opposed to the second protection member 32, and the engagement protrusion 33 is the second protection member. The first protection member 31 and the end of the member 32 are welded to a portion facing each other. This positional relationship may be reversed.

  The first protection member 31 and the second protection member 32 are disposed so as to surround the superheater tube 19, and the engagement protrusion 33 and the engagement hook 34 are engaged to engage the first protection member 31 and the first protection member 31. Two protective members 32 are attached around the superheater tube 19. Thereafter, the third protective member 41 and the fourth protective member 42 are welded to the first protective member 31 as shown in FIG.

  Returning to FIG. 1 again, FIG. 1 shows a partially broken view of the state where the first to fourth protective members are attached to the superheater tube 19 as described above, and 30 in the figure has been described above. The protective member 31 is a first protective member, 32 is a second protective member, 33 is an engaging protrusion, 34 is an engaging hook, 41 is a third protective member, and 42 is a fourth protective member. 1A and 1B show a part of a state in which the protective member 30 attached to the superheater pipe 19 is attached at different angles as shown in the front view shown in the upper part of the figure. (A) shows that the first protective member 31 is attached in a state of being rotated 30 degrees counterclockwise, and (B) is attached in the state of being rotated clockwise by 30 degrees. .

  The first protective member 31 and the second protective member 32 have a curvature that makes surface contact with the marine boiler superheater pipe 19 as described above, and a plurality of the surroundings of the marine boiler superheater pipe 19 (in this case) 2), and the engagement hook 34 is provided on the first protection member 31 side where the circumferential edge of the first protection member 31 is in contact with the circumferential edge of the second protection member 32. Since the engagement protrusions 33 are provided on the second protection member 32 side, and the engagement hooks 34 are engaged with the engagement protrusions 33 and attached to the marine boiler superheater pipe 19, the attachment and removal are very simple. be able to.

  Further, the second protective member 32 has an axial length shorter than that of the first protective member 31, and a region where the second protective member 32 is not provided is a first in which a circumferential end exists in this region. By covering with the third protective member 41 and the fourth protective member 42, which are sub-plate-like members that are welded separately to each of the protective members 31 and have gaps formed at the opposing portions, the combustion gas directly hits them. Even if a temperature difference occurs on the opposite side of the part and the engagement is disengaged, the protective member 30 can be prevented from falling off.

  In this way, a plate-like MC alloy having a thickness of 3 to 5 mm is used, and has a curvature that makes surface contact with the marine boiler superheater tube 19 and is formed into a semicircular or ¼ circular cross-sectional shape. By covering the periphery of the superheater tube 19 with the protective member 30 formed of the fourth protective member, vanadium attack is prevented by preventing combustion ash from adhering to the superheater tube 19.

  Returning to FIG. 3 again, FIG. 3B is an enlarged view of the state in which the protective member 30 is attached to the superheater tube 19 as viewed from above. FIG. 3B is an enlarged view of one row of the superheater tube 19 in the portion indicated by 25 in FIG. 3A, and a protective member 30 is provided on the superheater tube 19 as shown in FIGS. ) Indicates that it is attached at an angle as shown in the upper part. This attachment angle is set to an angle at which the vanadium-based combustion ash existing on the upper part of the protective member melts and falls and hardly enters the gap between the superheater tube and the protective member, for example, 30 ° in the example of the figure.

  The above is a protection member for a marine boiler superheater pipe according to the present invention, but a graph showing the change in thickness over time by attaching a protection member (protector) made with this MC alloy to an actual superheater pipe is shown in the figure. 5. In FIG. 5, (A) and (B) are the results of examination of different superheater tubes. In each graph, the horizontal axis indicates the year and the vertical axis indicates the thickness of the superheater tube (unit: mm). In the graph of (A), the protective member described above was attached in July 2001, about 7 years after the service was launched in August 1994, and the graph of (B) entered service in August 1994. In October 2001, about 7 years after the installation, the protective member described above was attached, and the thicknesses at the heights 550, 600, 700, and 800 from the furnace bottom were examined.

  As can be seen from this graph, the wall thickness decreased in proportion to the time before the protective member (protector) was attached, whereas after the protective member (protector) was attached, the graph in (A) clearly shows the meat. In the graph of (B), the rate of decrease in thickness decreased, and at the initial stage, the decrease rate slightly increased at any height, but the one with a height of 550 clearly decreased in rate after that and had a certain effect. I understand that.

  As described above, the protection member for a marine boiler superheater tube according to the present invention prevents adhesion of vanadium compound ash, and is high in the presence of nickel (Ni) chromium (Cr) and molybdenum (Mo). Because it has corrosion resistance, it can effectively reduce metal corrosion and thinning speed due to accelerated high temperature oxidation (vanadium attack), and it can be easily attached by the engaging member and expands in the presence of the sub-plate member. It can be set as the protection member of the marine boiler superheater pipe | tube which can also prevent the drop-off | omission by the difference in a rate.

  ADVANTAGE OF THE INVENTION According to this invention, the thickness reduction of a marine boiler superheater pipe | tube can be prevented effectively, and a big effect can be acquired using it for a marine boiler superheater pipe | tube.

It is the figure which showed the state which attached the protection member of the marine boiler superheater pipe | tube used by this invention to the superheater pipe | tube at a different angle. The exploded view (A) for demonstrating the structure of the protection member of the marine boiler superheater tube which becomes this invention, the engagement protrusion (B) which engages the 1st, 2nd protection members 31 and 32, engagement It is the perspective view which showed the combined hook (C) and the state (D) which assembled these members. It is the figure (A) which showed the site | part of the superheater pipe | tube incorporating the protection member of the marine boiler superheater pipe | tube which becomes this invention, and its partially enlarged view (B). It is a figure which shows the structure of the marine boiler incorporating the protection member of the marine boiler superheater tube which becomes this invention. It is the graph which incorporated the protection member of the marine boiler superheater pipe | tube used by this invention in a marine boiler superheater pipe | tube, and investigated the condition of the metal thinning. It is a graph of the change of the corrosion rate accompanying the temperature change in a 3% HF + 17% HNO3 solution. It is the graph which investigated the weight loss for every 24 hours in 1150 degreeC air | atmosphere.

Explanation of symbols

19 Overheating organ 30 Protection member 31 First protection member 32 Second protection member 33 Engagement protrusion 34 Engagement hook 35 Hook hole 41 Third protection member 42 Fourth protection member

Claims (3)

A protection member for a marine boiler superheater pipe that is provided at a site where combustion gas easily passes in a marine boiler superheater pipe using heavy oil as a main fuel and prevents corrosion due to vanadium-containing combustion ash adhesion,
The protective member uses a nickel (Ni) -chromium (Cr) alloy to which molybdenum (Mo) is added, has a curvature that makes surface contact with the marine boiler superheater tube, and has a plurality of surroundings of the marine boiler superheater tube. A protective member for a marine boiler superheater tube, characterized in that the protective member is formed as a covering plate-like member.   The protective members made of the plurality of plate-shaped members are each formed in a semicircular cross section to cover the marine boiler superheater tube, and the circumferential edge of one protective member is the circumferential edge of another protective member. An engagement hook is provided on the one protective member side of the contact position, and an engagement protrusion is provided on the other protection member side, and the engagement hook is engaged with the engagement protrusion and attached to the marine boiler superheater tube. The protection member in the marine boiler superheater pipe according to claim 1, wherein the protection member is used.   One plate-like member in the plate-like member forming the protective member is formed so that the axial length is shorter than the other plate-like members, and an area where the one plate-like member is not present is a circumferential end portion in the area. The protection of a marine boiler superheater pipe according to claim 1 or 2, characterized in that it is covered with a sub-plate-like member that is welded separately to each of the other plate-like members that are present to form a gap in the opposite part. Element.

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